US20120001105A1 - Valve control apparatus and electric driving apparatus - Google Patents

Abstract

A valve control apparatus is provided with a valve, a shaft supporting the valve, an end-gear of an actuator driving the valve. The shaft is press-inserted into the end-gear. A stopper disposed on the shaft regulates a valve operation range. The end-gear can engage with the middle gear of the reduction-gears mechanism even in out of the gear-operation-angle range. When a rotation angle sensor detects a rotation angle of the end-gear in out of the gear-operation-angle range, it is determined that a malfunction occurs in a rotation-force-transmitting path.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• This application is based on Japanese Patent Applications No. 2010-149284 filed on Jun. 30, 2010, and No. 2010-160184 filed on Jul. 15, 2010, the disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTION
• The present invention relates to a valve control apparatus including a valve and an actuator. The valve opens/closes a fluid-passage and the actuator drives the valve. Especially, the valve control apparatus is used for opening/closing an intake passage communicating with a combustion chamber of an internal combustion engine. Further, the present invention relates to an electric driving apparatus which drives a driven member by use of a driving force of an electric motor.
BACKGROUND OF THE INVENTION
• Conventionally, a valve control apparatus has a valve which opens/closes an intake passage communicating with a combustion chamber of an internal combustion engine, a shaft supporting the valve, and an actuator driving the valve in order to control an intake air flow rate. The actuator has an end-gear receiving a driving force from an electric motor (driving source). The end-gear is connected to the shaft, so that the valve and the actuator are connected to each other. Refer to JP-2004-124933A (GB-2393218A) and JP-2009-013934A (US-2009/0007875A1).
• FIG. 6 shows avalve control apparatus100 shown in JP-2004-124933A. Anactuator101 is provided with an end-gear103 which is made of resin material and receives a driving force from an electric motor (driving source). Ashaft104 made of metallic material is press-inserted into ahole106 of the end-gear103, whereby theshaft104 is connected with the end-gear103. A rotation of the end-gear103 is transmitted to thevalve107 through theshaft104.
• Ahousing109 has a stopper (not shown) to which a stopper-portion (not shown) of the end-gear103 confronts so that an operation range of thevalve107 is regulated. That is, the stopper regulates an angular operation range of the end-gear103 so that the operation range of thevalve107 is restricted. Further, thevalve control apparatus100 is provided with a sensor (not shown) which detects a rotational angle of the end-gear103, so that a position of thevalve107 is detected.
• In thisvalve control apparatus100, since thevalve107 is connected to theactuator101 by press-inserting theshaft104 into the end-gear103, its manufacturing cost is relatively low.
• However, in thisvalve control apparatus100, if a press-inserting portion between theshaft104 and the end-gear103 is damaged, the sensor detecting the rotational angle of the end-gear103 can not detect this malfunction. That is, a malfunction in a driving-force-transmitting path can not be detected.
• If the press-inserting portion is broken, it is likely that the rotation of the end-gear103 is restricted by the stopper and only theshaft104 may spin free. In such a case, even though the end-gear103 is restricted by the stopper, thevalve107 rotates over a restricted range. Since the sensor detects only the rotational angle of the end-gear103, it can not be detected that thevalve107 rotates over the normal range.
• In order to detect the above malfunction, it is conceivable that another sensor directly detecting a rotational angle of theshaft104 is necessary. However, another sensor increases the manufacturing cost.
• FIG. 7 shows avalve control apparatus200 shown in JP-2009-013934A. Asensor201 directly detects a rotational angle of ashaft202 so that an opening degree of thevalve203 is detected. theshaft202 rotates over a normal rotational range of thevalve203 due to a breakage in a connection portion between ashaft202 and an end-gear204, thesensor201 outputs a detection value which indicates that the rotational angle of theshaft202 is abnormal. Thus, it can be detected that thevalve203 has a malfunction.
• However, in thisvalve control apparatus200, a configuration of connecting portion between thevalve203 and theactuator205 becomes complicated. Further, a gear-holding member206 for connecting the end-gear204 to theshaft202 and a sensor-holding member208 for holding amagnet207 on theshaft202 are necessary, which increase the number of parts and increase the manufacturing cost. Thus, even in thevalve control apparatus200, a malfunction in a connecting portion between theshaft202 and the end-gear204 is not detected with low cost.
• It is well known that an electric driving apparatus drives a valve, which corresponds to a driven member, by use of a driving force of an electric motor. The electric driving apparatus is applied to a valve control apparatus for an internal combustion engine, which adjusts an intake air quantity or an exhaust gas quantity.
• The electric driving apparatus is provided with a mechanism which holds a mechanical position of the driven member. For example, in a case that the electric driving apparatus is applied to a tumble-control-valve (TCV) apparatus, a reduction-gears mechanism is provided with a stopper so that the driven member is mechanically held at a full-open position or a full-close position.
• In such an electric driving apparatus, when the driven member is mechanically held, the electric current supplied to the electric motor is stepwise increased. For example, when the TCV-apparatus rotates a tumble-control valve toward the full-close position, the electric current supplied to the electric motor varies as shown inFIG. 17. That is, when the electric motor is energized, the electric current is temporarily rapidly increased due to an inrush current, and then the electric current is decreased. When the unheld driven member is mechanically held, the electric current supplied to the electric motor is stepwise increased. When the driven member is not mechanically held, the condition of the driven member is referred to as an unhold condition, hereinafter. Also, when the driven member is mechanically held, the condition of the driven member is referred to as a hold condition, hereinafter.
• It has been needed to correctly determines whether the condition of the driven member is normally changed from the unhold condition to the hold condition without respect to the stepwise increase in the electric current.
• JP-8-19172A and JP-2005-151766A show an electric circuit configuration in which it is determined that a malfunction occurs when the electric current supplied to the electric motor exceeds a specified threshold. However, in this electric circuit, the change from the unhold condition to the hold condition is not determined as a normal change.
• JP-2001-4674A shows an electric circuit configuration in which the supplied electric current is integrated so that an over-current due to a short circuit is distinguished from a normal electric current increase due to the condition change from the unhold condition to the hold condition. However, in this electric circuit, it is likely determined that no malfunction occurs even if a malfunction other than over-current occurs.
SUMMARY OF THE INVENTION
• The present invention is made in view of the above matters, and it is an object of the present invention to provide a valve control apparatus which enables to detect a malfunction with low cost.
• Also, the present invention is made in view of the above matters, and it is another object of the present invention to provide an electric driving apparatus which is able to determine whether a driven member is surely moved from the unhold condition to the hold condition.
• According to the present invention, a valve control apparatus has a valve opening/closing a fluid passage, a shaft supporting the valve and an actuator driving the valve. The shaft is press-inserted into a press-insert hole formed in an end-gear of the actuator.
• Since the valve is connected to the actuator by press-inserting the shaft into the end-gear, its manufacturing cost can be made lower.
• Further, the shaft has an exposed portion which is out of the press-insert hole. A stopper radially extending from the exposed portion is provided to the shaft. A housing has a stopper surface with which the stopper is brought into contact, so that a valve operation range is regulated. Still further, the valve control apparatus has a sensor detecting a rotation angle of the actuator, and a malfunction detecting means for detecting a malfunction in a rotation-force-transmitting path to the shaft.
• The end-gear has gear teeth comprised of inside gear teeth and outside gear teeth. The inside gear teeth engages with the gear of the motor in a gear-operation-angle range of the end-gear which corresponds to the valve operation range. The outside gear teeth engage with the gear of the motor in out of the gear-operation-angle range. The end-gear can engage with a gear of a motor even in out of the gear-operation-angle range.
• The malfunction detecting means determines that a malfunction occurs when the end-gear rotates over the gear-operation-angle range and the detection value of the sensor is out of the normal detection values corresponding to the valve operation range.
• According to the above, by detecting the rotation angle of the actuator, a malfunction in a rotation-force-transmitting path can be detected. Thus, it is unnecessary to directly detect the rotation angle of the shaft in order to find a malfunction. The manufacturing cost is not increased. A damage of a connecting portion of the shaft and the end-gear can be detected with low cost.
• According to the present invention, an electric driving apparatus includes an electric motor generating a driving force while receiving an electric current; an electric current detecting means for detecting the electric current supplied to the electric motor; and a control means for controlling an energization to the electric motor so that the driving force is transmitted to a driven member in order to vary a displacement magnitude which represents at least one of a variation in position of the driven member and a variation in posture of the driven member.
• The displacement magnitude includes a hold value at which the driven member is mechanically held and the displacement magnitude does not vary even though the driving force is continued to be transmitted from the electric motor to the driven member so as to vary the displacement magnitude in one direction. The electric current supplied to the electric motor is stepwise increased when the displacement magnitude reaches the hold value after the displacement magnitude has been varied in one direction.
• The control means stores a threshold regarding the electric current supplied to the electric motor for determining whether the displacement magnitude normally reaches the hold value in a case that the electric motor is controlled in such a manner that the displacement magnitude reaches the hold value after the displacement magnitude has been varied in one direction. After the electric motor is energized, the electric current exceeds the threshold temporarily due to the inrush current. Then, the electric current is lowered than the threshold. After that, when the electric current excesses the threshold again, it is determined that the displacement magnitude normally reach the hold value.
• Thereby, it can be able to determine whether the driven member is normally moved from the unhold condition to the hold condition.
BRIEF DESCRIPTION OF THE DRAWINGS
• Other objects, features and advantages of the present invention will become more apparent from the following description made with reference to the accompanying drawings, in which like parts are designated by like reference numbers and in which:
• FIG. 1 is a fragmentally sectional view showing a tumble-control-valve control apparatus according to a first embodiment;
• FIG. 2 is an enlarged cross sectional view showing an essential portion of the tumble-control-valve control apparatus according to the first embodiment;
• FIG. 3A is a cross sectional view showing a stopper;
• FIG. 3B is a plain view of an end-gear according to the first embodiment;
• FIG. 4A is a cross sectional view showing a stopper;
• FIG. 4B is a plain view of an end-gear according to a second embodiment;
• FIG. 5 is a cross sectional view showing a stopper according to a third embodiment;
• FIG. 6 is a cross sectional view showing a conventional valve control apparatus; and
• FIG. 7 is a cross sectional view showing a conventional valve control apparatus.
• FIG. 8A is a cross sectional view showing an essential part of a TCV apparatus according to a fourth embodiment;
• FIG. 8B is a cross sectional view showing a stopper configuration of the TCV apparatus according to the fourth embodiment;
• FIG. 9A is a chart showing a circuit configuration of an electric driving apparatus;
• FIG. 9B is a graph showing an electric current supplied to the electric motor;
• FIG. 10A is a chart for explaining a lock-current in a case that both brushes are in contact with a single commutator;
• FIG. 10B is a chart for explaining a lock-current in a case a single brush is in contact with two brushed;
• FIG. 11 is a main flowchart for operating an electric driving apparatus according to the fourth embodiment;
• FIG. 12 is a sub-flowchart for operating an electric driving apparatus according to the fourth embodiment;
• FIG. 13 is another sub-flowchart for operating an electric driving apparatus according to the fourth embodiment;
• FIG. 14 is a chart showing a circuit configuration of an electric driving apparatus according to a fifth embodiment;
• FIG. 15A is a chart showing a table data according to the fifth embodiment;
• FIG. 15B is a chart for explaining an update of the table data according to the fifth embodiment;
• FIG. 16A is a graph showing an electric current supplied to the electric motor according to a sixth embodiment;
• FIG. 16B is a graph showing a relationship between a frequency of PWM-signal and a sampling frequency; and
• FIG. 17 is a graph showing an electric current for explaining a conventional driving apparatus.
DETAILED DESCRIPTION OF EMBODIMENTSFirst Embodiment
• [Structure of first embodiment]
• Referring toFIGS. 1 to 3, a first embodiment of the present invention will be described. In this embodiment, the present invention is applied to a tumble-control-valve control apparatus, which is referred to as a TCV control apparatus, hereinafter. The TCV control apparatus adjusts flow passage areas ofintake passages2 each of which communicates with a combustion chamber of each cylinder of an internal combustion engine, whereby tumble flow is generated in each combustion chamber.
• The TCV control apparatus is provided with an intake manifold (housing)3 defining anintake passages2 therein, avalve4 opening/closing theintake passage2, ashaft5 supporting thevalve4, anelectronic actuator6 driving thevalve4 through theshaft5, arotation angle sensor7 detecting an opening degree of thevalve4, and an electronic control unit (ECU: not shown) receiving detection signals from therotation angle sensor7.
• Theintake manifold3 is a casing which forms a plurality ofintake passages2 and is made of polyamide resin. Each ofintake passages2 has rectangular cross section and communicates with each intake port (not shown) of a cylinder head.
• A tumble control valve, which is referred to as TCV hereinafter, is provided in theintake manifold3 in order to generate tumble flow in the combustion chamber.
• The TCV is comprised of avalve housing11 accommodated in ahousing storage chamber10 of theintake manifold3 and thevalve4 which is rotatably accommodated in thevalve housing11. The number of thehousing storage chamber10 is equal to the number of the cylinders. Each of thevalve housings11 is held in eachhousing storage chamber10.
• Theintake manifold3 and thevalve housing11 respectively have penetratingholes13,14 through which theshaft5 is rotatably inserted.
• Theshaft5 supports thevalve4 and its end portion is connected to theactuator6. Theshaft5 is made of metallic material and has polygonal cross section.
• Further, theintake manifold3 has anaccommodation chamber17 which accommodates a part of theactuator6. Theintake passage2 communicates with theaccommodation chamber17 through the penetratingholes13,14.
• Thevalve4 is made of polyamide resin. A rotation axis of thevalve4 extends in a direction perpendicular to an air flow direction in theintake passage2. Thevalve4 has apolygonal hole19 through which theshaft5 is inserted. Thevalve4 and theshaft5 rotate together. The cross section of thepolygonal hole19 is substantially the same as the cross section of theshaft5, whereby a relative rotation between theshaft5 and thevalve4 is prevented.
• Thevalve4 is rotated in thevalve housing11 to vary the flow passage area of theintake passage2. When the flow passage area of the intake passage is reduced, the tumble flow is generated in the combustion chamber. Such a tumble flow improves a combustion efficiency and fuel economy, and reduces emissions.
• As shown inFIG. 1, thevalve4 has anotch portion20. When thevalve4 fully closes theintake passage2, a rectangular aperture is defined between thevalve4 and thevalve housing11 by thenotch portion20. The intake air flows through this rectangular aperture, so that the tumble flow is generated in the combustion chamber.
• When thevalve4 is fully opened in its operational range, the flow passage area of theintake passage2 becomes maximum.
• When thevalve4 is fully closed in its operational range, the flow passage area of theintake passage2 becomes minimum.
• It should be noted that the valve operational range represents a rotational angle range within which thevalve4 can be rotated.
• The rotational angle range of thevalve4 is defined by stoppers (not shown). When thevalve4 is fully closed, one of stoppers is in contact with thevalve4. When thevalve4 is fully opened, the other stopper is in contact with thevalve4.
• Theactuator6 is provided with an electric motor (not shown), a reduction-gears mechanism and anactuator case21 which accommodates the reduction-gears mechanism.
• The reduction-gears mechanism includes a motor gear connected to an output shaft of the electric motor, a middle gear engaging with the motor gear, and an end-gear25 engaging with the middle gear.
• The end-gear25 made of polyamide resin has an engagingportion27 and agear portion28. The engagingportion27 defines a press-insert hole26 therein. Thegear portion28 is engaged with the middle gear (not shown). The engagingportion27 extends from thegear portion28, and has a middle-diameter portion31 and a small-diameter portion32. The diameter of the middle-diameter portion31 is smaller than that of thegear portion28, and the diameter of the small-diameter portion32 is smaller than that of the middle-diameter portion31.
• The press-insert hole26 extends along a center axis of the small-diameter portion32 and the middle-diameter portion31. Anend portion33 of theshaft5 is press-inserted into the press-insert hole26, whereby the shaft is concentrically connected to the end-gear25. Theshaft5 and the end-gear25 rotate together. Thisend portion33 of theshaft5 is referred to as a press-insert portion33. The cross section of the press-insert hole26 is substantially the same as the cross section of theshaft5, whereby a relative rotation between theshaft5 and the end-gear25 is prevented.
• The other portion of theshaft5, which is not press-inserted into thehole26, is referred to as an exposedportion34. The exposedportion34 is provided with astopper35 which radially extends. As shown inFIG. 3A, thestopper35 is comprised of adisc portion37 and a stopper-contactingportion38 which radially outward protrudes from thedisc portion37.
• Theaccommodation chamber17 is comprised of alarge chamber40, amiddle chamber41, and asmall chamber42. The penetratinghole13 communicates with thesmall chamber42.
• The middle-diameter portion31 of the end-gear25 is accommodated in thelarge chamber40, and the small-diameter portion32 is accommodated in such a manner as to extend from thelarge chamber40 to thesmall chamber42. Thegear portion28 is accommodated in theactuator case21. The exposedportion34 and thestopper35 are accommodated in thesmall chamber42.
• As shown inFIG. 3A, theintake manifold3 has twostopper walls44,45. The stopper-contactingportion38 comes into contact with one of thestopper walls44,45, whereby the rotation of theshaft5 is regulated and the operation range of thevalve4 is also regulated.
• Thestopper wall44 corresponds to a full-close position of thevalve4 and theother stopper wall45 corresponds to a full-open position of thevalve4. Thesmall chamber42 is comprised of a firstsmall chamber46 and a secondsmall chamber47. Thedisc portion37 is accommodated in the firstsmall chamber46, and the stopper-contactingportion38 is accommodated in the secondsmall chamber47. The stepped surfaces between the firstsmall chamber46 and the secondsmall chamber47 respectively correspond to the full-close stopper wall44 and the full-open stopper wall45.
• When the stopper-contactingportion38 is brought into a contact with the full-close stopper wall44, thevalve4 is positioned at a full-close position. When the stopper-contactingportion38 is brought into a contact with the full-open stopper wall45, thevalve4 is positioned at a full-open position. The valve operation range is from the full-close position to the full-open position.
• Further, since the end-gear25 rotates along with theshaft5 and thevalve4, an operation range of the end-gear25 is also restricted as shown inFIG. 3B. That is, the operation range of the end-gear25 is identical to the valve operation range. When thevalve4 is at the full-close position, the end-gear25 is positioned at a full-close gear position. When thevalve4 is at the full-open position, the end-gear25 is positioned at a full-close gear position.
• Thegear portion28 has gear teeth which are able to engage with the middle gear of the reduction-gears mechanism even if the end-gear25 rotates over the operation range. That is, thegear portion28 has gear teeth which are comprised ofinside gear teeth49 engaging with the middle gear in the gear-operation-angle range andoutside gear teeth50 engaging with the middle gear in out of the gear-operation-angle range, as shown inFIG. 3B.
• In the present embodiment, thegear portion28 has thegear teeth49,50 along its entire circumferential periphery. The end-gear25 can engage with the middle gear of the reduction-gears mechanism even in out of the gear-operation-angle range.
• Aconcave portion51 is formed on an end surface of thegear portion28. Theactuator case21 has aprotrusion52 which is inserted into theconcave portion51, whereby the end-gear25 is connected to theactuator case21, as shown inFIG. 2.
• The TCV control apparatus is provided with a seal member53 (for example, an oil seal or an X-ring) between the engagingportion27 and theaccommodation chamber17. An outer surface of theseal member53 is in contact with an inner surface of themiddle chamber41, and an inner surface of theseal member53 is in contact with an outer surface of the small-diameter portion32. Thereby, theseal member53 prevents an air-leakage from theintake passage2 toward theactuator case21. The maximum diameter of thestopper35 is greater than that of theseal member53.
• Therotation angle sensor7 includes amagnet54 fixed in the end-gear25 and aHall element55 detecting magnetic flux generated by themagnet54. Specifically, themagnet54 is fixed in the end-gear25 by insert-molding, and theHall element55 is disposed on theactuator case21.
• Themagnet54 and theHall element55 are arranged in such a manner as to perform a relative movement to each other. When the end-gear25 rotates, a relative position between themagnet54 and theHall element55 is varied. The magnetic flux density passing through theHall element55 is also varied. Based on this variation in magnetic flux density, therotation angle sensor7 detects the rotation angle of the end-gear25. Instead of theHall element55, a Hall IC or a magnetic resistance element can be used.
• In the present embodiment, since the rotation angle of theshaft5 holding thevalve4 is identical to the rotation angle of the end-gear25, the opening degree of thevalve4 can be detected by obtaining the rotation angle of the end-gear25.
• The ECU has a microcomputer including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), an input circuit, an output circuit and a timer.
• The ECU functions as a valve position computing means for computing an opening degree of thevalve4 based on the detection value of therotation angle sensor7.
• Also, the ECU functions as a malfunction detecting means for detecting a malfunction in a driving force transmitting path to theshaft5.
• The ECU stores the detection values detected by therotation angle sensor7, which correspond to the valve operation range, as normal detection values. That is, the ECU stores the detection value detected by therotation angle sensor7 in a case that the end-gear25 rotates in the gear-operation-angle range.
• The malfunction detecting means determines that a malfunction occurs when the end-gear25 rotates over the gear-operation-angle range and the detection value of therotation angle sensor7 is out of the normal detection values. A specific way of detecting a malfunction will be described hereinafter.
[Operation of First Embodiment]
• (i) Normal condition
• In a case that the end-gear25 and theshaft5 are normally connected to each other, the end-gear25 rotates from the full-open gear position to the full-close gear position. Also, thevalve4 rotates from full-open position to the full-close position. When the stopper-contactingportion38 is brought into contact with the full-close stopper wall44, thevalve4 stops rotating at the full-close position. The end-gear25 also stops at the full-close gear position.
• Therotation angle sensor7 outputs detection signals which indicate the rotation angle of the end-gear25 is within the gear-operation-angle range. Thus, the malfunction detecting means determines that no malfunction occurs.
• (ii) Abnormal condition
• If the connecting portion between the end-gear25 and theshaft5 is broken, the end-gear25 rotates over the full-close gear position. The end-gear25 rotates free without respect to the full-close stopper wall44. That is, the end-gear25 rotates out of the gear-operation-angle range. At this moment, therotation angle sensor7 outputs detection signals which indicate the rotation angle of the end-gear25 is out of the gear-operation-angle range. Thus, the malfunction detecting means determines that a malfunction occurs in a driving power transmitting path from the end-gear25 to theshaft5. Then, a warning lump is turned on to notify a passenger of the malfunction.
• Besides, in a case that the detection value of therotation angle sensor7 is proportional to the opening degree of the valve, a lower limit value and an upper limit value of the detection value, which respectively correspond to the full-close position and the full-open position, are stored in a memory as a normal detection value of therotation angle sensor7 corresponding to the valve operation range. When the actual detection value becomes lower than the lower limit value, or when the actual detection value becomes higher than the upper limit value, it is determined that a malfunction occurs.
[Advantages of First Embodiment]
• In the first embodiment, since thevalve4 is connected to theactuator6 by press-inserting theshaft5 into the end-gear25, its manufacturing cost can be made lower.
• The end-gear25 can engage with the middle gear of the reduction-gears mechanism even in out of the gear-operation-angle range. The malfunction detecting means determines that a malfunction occurs when the end-gear25 rotates over the gear-operation-angle range and the detection value of therotation angle sensor7 is out of the normal detection values corresponding to the valve operation range.
• When the driving force is not transmitted from the end-gear25 to theshaft5 due to a malfunction, this malfunction can be detected by detecting the rotation angle of the end-gear25. Thus, it is unnecessary to directly detect the rotation angle of theshaft5 in order to find a malfunction. The manufacturing cost is not increased. A damage of a connecting portion of theshaft5 and the end-gear25 can be detected with low cost.
• Further, according to the present embodiment, the maximum diameter of thestopper35 is smaller than the diameter of theseal member53. That is, the diameter of thestopper35 is smaller than the inner diameter of themiddle chamber41. Thus, the end-gear25, theshaft5, and theseal member53 are easily assembled in theaccommodation chamber17. Specifically, after thestopper35 is arranged in thesmall chamber42 through themiddle chamber41, theseal member53 is assembled in themiddle chamber41. It is less likely that thestopper35 conflicts with theseal member53.
Second Embodiment
• Referring toFIGS. 4A and 4B, a second embodiment will be described. In the second and the successive embodiments, the same parts and components as those in the first embodiment are indicated with the same reference numerals and the same descriptions will not be reiterated.
• The second embodiment is different from the first embodiment in the configuration of the stopper. That is, stop-screws58 are provided on step-surfaces57 between the firstsmall chamber46 and the secondsmall chamber47. A tip end of the stop-screw58 functions as a full-close position stopper44, and a tip end of the other stop-screw58 functions as a full-open position stopper45.
• In the second embodiment, thegear portion28 has gear teeth partially along its circumferential periphery, as shown inFIG. 4B. That is, theinside gear teeth49 are provided in the gear-operation-angle range, and theoutside gear teeth50 are provided at both sides of theinside gear teeth49. The second embodiment has the same advantages as the first embodiment.
Third Embodiment
• Referring toFIG. 5, a third embodiment will be described. The third embodiment is different from the first embodiment in the configuration of the stopper and thestopper portion35. Thestopper portion35 is comprised of adisc portion37 and aconcave portion59. At circumferential both ends of theconcave portion59,step portions60 are formed.
• The inner diameter of thesmall chamber42 is slightly larger than the outer diameter of thedisc portion37. Aprojection61 is formed on an inner wall surface of thesmall chamber42 in such a manner as to project toward theconcave portion59. One side surface of theprojection61 functions as the full-open position stopper45, and the other side surface of theprojection61 functions as the full-close position stopper44. Thesestep portions60 andstoppers44,45 regulate the operation angle range of theshaft5. The third embodiment has the same advantages as the first embodiment.
[Modification]
• Therotation angle sensor7 can be arranged in such a manner as to detect the rotation angle of theactuator6. That is, therotation angle sensor7 may detect the rotation angle of the output shaft of the electric motor, the motor gear, or the middle gear.
• The detection value of therotation angle sensor7 may be ON-OFF signal. A switching position between ON-signal and OFF signal is previously stored. If the detection value is switched at improper switching position, it is determined that a malfunction occurs.
• The present invention can be applied to a swirl-control-valve control apparatus, a throttle-valve control apparatus, or an EGR-valve control apparatus.
Fourth Embodiment
• Referring toFIGS. 8A to 10B, a configuration of an electric driving apparatus will be described.
• Theelectric drive apparatus301 includes anelectric motor302. Theelectric drive apparatus301 is applied to a tumble-control-valve (TCV)apparatus304 which drives atumble control valve304.
• That is, theTCV apparatus304 is provided with thetumble control valve303 and theelectric motor302. Thetumble control valve303 is rotatably supported in anintake manifold306 to adjust the flow passage area of anintake passage307.
• Thevalve303 is fixed on avalve shaft308. Thevalve303 has rectangular shape. Thevalve303 has anotch portion309.
• Thedrive apparatus301 is provided with theelectric motor302 and an electric current detecting means311 which detects the electric current supplied to theelectric motor302. Further, thedrive apparatus301 is provided with a control means312 which controls the energization of theelectric motor302 and adriving circuit314 which turns on/off theelectric motor302 according to a control signal from the control means312.
• Theelectric motors302 is a well-known DC motor which is comprised of arotor318 having a plurality ofcoils316 and a plurality ofcommutator317, astator320 having a plurality ofmagnets319, and twobrushes321a,321b.
• The electric current detecting means311 is a well-known electric current detecting circuit which detects electric current supplied to theelectric motor302 based on voltage drop in ashunt resistance324.
• The control means312 is a microcomputer having a CPU, a ROM, a RAM, an input device and an output device.
• The drivingcircuit314 has four switchingelements325 to rotate theelectric motor302 in the normal direction or the reverse direction.
• The rotation torque generated by theelectric motor302 is transmitted to thevalve shaft308 thorough a reduction-gears mechanism. Thevalve shaft308 is concentrically connected to an end-gear326 of the reduction-gears mechanism. Anend portion326aof the end-gear326 is supported by theintake manifold306 through an oil-seal327.
• Astopper329 is provided to thevalve shaft308.
• Thestopper329 is comprised of adisc portion330 and a stopper-contactingportion331 which radially outward protrudes from thedisc portion330. Thestopper329 is rotatably accommodated in achamber332.
• Thechamber332 is comprised of afirst chamber333 and a second chamber334. Thedisc portion330 is accommodated in thefirst chamber333 and the stopper-contactingportion331 is accommodated in the second chamber334. Both end walls of the second chamber334 definestopper walls335,336.
• When the stopper-contactingportion331 is in contact with thestopper wall335 or theother stopper wall336, thevalve303 is mechanically held. When thevalve303 is full-closed, the stopper-contactingpotion331 is in contact with the full-close stopper wall335. When thevalve303 is full-opened, the stopper-contactingportion331 is in contact with the full-open stopper wall336.
• Thus, even if thevalve303 receives the rotation torque from theelectric motor302, thevalve303 does not rotate over the full-close stopper wall335 or the full-open stopper wall336.
• When the stopper-contactingportion331 is brought into contact with one of thestopper walls335,336 (hold condition), the electric current supplied to theelectric motor302 is stepwise increased.
• When thevalve303 rotates to the full-open position or the full-close position, the electric current supplied to theelectric motor302 varies as shown inFIG. 9B. That is, when theelectric motor302 is energized, the electric current is temporarily rapidly increased due to an inrush current, and then the electric current is decreased. When thevalve303 is mechanically held, the electric current supplied to theelectric motor302 is stepwise increased. The unhold condition is comprised of an initial condition and a rotation condition. In the initial condition, the electric current supplied to theelectric motor302 is steeply varied due to the inrush current. In the rotation condition, the electric current supplied to themotor302 is constant and thevalve303 rotates in a constant speed. It should be noted that the electric current of the time when thevalve303 is mechanically held is referred to as a lock-current.
• The control means312 stores a threshold “Ithr” with respect to the electric current supplied to themotor302. When the electric current is temporarily increased and decreased due to the inrush current, and then exceeds the threshold “Ithr”, the control means312 determines that thevalve303 is normally brought into the hold condition.
• That is, after theelectric motor302 is energized, the electric current exceeds the threshold “Ithr” temporarily due to the inrush current. Then, the electric current is lowered than the threshold “Ithr”. After that, when the electric current excesses the threshold “Ithr” again, it is determined that thevalve303 is normally full-closed or full-opened.
• With respect to the temporal increase and decrease in electric current due to the inrush current, after the electric current is lowered than the threshold “Ithr”, when the absolute value of the temporal variation rate of the electric current is lowered than a specified convergence value, the control means312 determines that a temporal increase and decrease in electric current due to the inrush current has been converged.
• Further, the control means312 functions as a lock-current estimating means which estimates the lock-current. When thevalve303 is in the hold condition, therotor318 stops, and each of thebrushes321a,321bis in contact with asingle commutator317, the lock-current is denoted by “Ia”. When at least one ofbrushes321a,321bis in contact with twocommutators317, the lock-current is denoted by “Ib”. The control means312 stores a lock-current ratio “Ia/Ib”. The estimated lock-current is denoted by “Iss”. The threshold “Ithr” is defined in such a manner as not to exceed an upper value which is obtained by multiplying “Iss” by “Ia/Ib”.
• For example, as shown inFIGS. 10A and 10B, theelectric motor302 has three-phase coils316a-316cin delta connection. Each ofcommutators317A-317C is connected to thecoils316a-316c.The resistance value of thecoils316a-316cis denoted by “r”.
• FIG. 10A shows a case in which each ofbrushes321a,321bis in contact with only thecorresponding commutator317B,317C. The lock-current is denoted by “Ia”.FIG. 10B shows a case in which thebrush321ais in contact with thecommutators317A,317B and thebrush321bis in contact with only thecommutator317C. The lock-current is denoted by “Ib”.
• In a case shown in FIG,10A, the combined resistance between thebrushes321a,321bis expressed by “r×(⅔)”. In a case shown inFIG. 10B, the combined resistance between thebrushes321a,321bis expressed by “r×(½)”. Thus, the ratio “Ia/Ib” is 0.75 and the threshold “Ithr” is defined so as to be smaller than an upper value (=Iss×0.75).
• In a case that theelectric motor302 has (2N+1)-phase coils316, the ratio “Ia/Ib” can be expressed by (2N+1)/(2 (N+1)). In a case that theelectric motor302 has 2N-phase coils316, the ratio “Ia/Ib” can be expressed by (2N-1)/(2 (N-1)).
• After it is determined that thevalve303 is normally brought into the hold condition, the lock-current estimating means defines an average of a plurality of detection current detected by the electric current detecting means311 as an estimation value “Iss” of the lock-current.
• When thevalve303 is rotated to the hold condition next time, the control means312 defines the threshold “Ithr” smaller than the upper value (=Iss×(Ia/Ib)), and determines whether thevalve303 is normally full-closed or full-opened.
• Further, the control means312 integrates the electric current from when theelectric motor302 is energized until when the electric current is stepwise increased. Based on the integrated value, the control means312 determines whether the rotational position of thevalve303 is normal. That is, in a case that theelectric motor302 is a DC motor, a rotation speed N(t) [rad/s] of themotor302 and the electric current I(t) has a linear relation as expressed by following formula (1).
• 
  N(t)=a−b·I(t)  (1)
• In a case that a time period and a rotation angle of themotor302 from when theelectric motor302 is energized until when the electric current is stepwise increased are respectively expressed by T1 [s] and θ [rad], the rotation angle θ can be computed by definite-integrating the rotation speed N(t) from 0 to T1 with respect to time “t”. Thus, the rotation angle θ can be expressed by following formula (2).
• 
  θ=a·T1+·b·∫₀^T1I(t)dt  (2)
• As above, since the rotational position of thevalve303 corresponds to the rotational angle of theelectric motor302, it can be determined whether the rotational position of thevalve303 is normal based on the above integrated value.
[Control Processing of Fourth Embodiment]
• Referring toFIGS. 11 to 13, a control processing of the drivingapparatus301 will be described hereinafter.
• FIG. 11 is a main flowchart of a processing in which it is determined whether the rotational position of thevalve303 normally reaches the full-close position in a case that thevalve303 rotates from the full-open position toward the full-close position. This flowchart starts when theelectric motor302 is energized.
• In step S1, the computer determines whether thevalve303 has moved from the initial condition to the rotation condition. When the answer is NO, the procedure proceeds to step S2. When the answer is YES, the procedure proceeds to step S3.
• The determination of whether thevalve303 has moved from the initial condition to the rotation condition is conducted by executing a sub-flowchart shown inFIG. 12.
• In step S101, the computer determines whether an absolute value “ABVR” of a temporal variation ratio of the electric current is lower than or equal to a specified convergent value “COV”. An absolute value of a difference value between the currently detected electric current and the previously detected electric current is defined as the absolute value of the temporal variation ratio of the electric current.
• When the answer is YES in step S101, the procedure proceeds to step S102. When the answer is NO in step S101, the procedure proceeds to step S103. In step S103, the computer determines that thevalve303 has not moved to the rotation condition. The procedure goes back to step S1 of the main flowchart. The answer in step S1 is NO.
• In step S102, the computer determines whether the electric current is less than the threshold “Ithr”. When the answer is YES in step S102, the procedure proceeds to step S104. When the answer is NO in step S102, the procedure proceeds to step S103. In step S103, the computer determines that thevalve303 has not moved to the rotation condition. The procedure goes back to step S1 of the main flowchart. The answer in step S1 is NO.
• In step S104, the computer determines that thevalve303 has moved to the rotation condition. The procedure goes back to step S1 of the main flowchart. The answer in step S1 is YES.
• In step S2, the computer determines whether an elapsed time “Telp1” from energization of themotor302 exceeds an upper limit time of the initial condition. When the answer is NO in step S2, the procedure goes back to step S1. When the answer is YES in step S2, the procedure proceeds to step S4 in which the computer determines that thevalve303 is stuck. The upper limit time of the initial condition is defined based on a time period which is required to converge the temporal increase/closed in electric current due to the inrush current.
• In step S3, the computer determines whether thevalve303 has moved from the rotation condition to the hold condition. When the answer is NO, the procedure proceeds to step S5. When the answer is YES, the procedure proceeds to step S6.
• The determination of whether thevalve303 has moved from the rotation condition to the hold condition is conducted by executing a sub-flowchart shown inFIG. 13.
• In step S301, the computer determines whether the electric current is greater than the threshold “Ithr”. When the answer is YES in step S301, the procedure proceeds to step S302. When the answer is NO in step5301, the procedure proceeds to step S303.
• In step S302, the computer determines that thevalve303 has moved to the hold condition. The procedure goes back to step S3 of the main flowchart. The answer in step S3 is YES. In step S303, the computer determines that thevalve303 has not moved to the hold condition. The procedure goes back to step S3 of the main flowchart. The answer in step S3 is NO.
• In step S5, the computer determines whether an elapsed time “Telp2” after thevalve303 has moved to the rotation condition exceeds a specified upper limit time. When the answer is NO, the procedure goes back to step S3. When the answer is YES, the procedure proceeds to step S7.
• In step S6, the computer determines whether an elapsed time “Telp3” after thevalve303 has moved to the rotation condition exceeds a specified lower limit time. When the answer is NO in step S6, the procedure proceeds to step S8 in which the computer determines that a malfunction exists in the rotation position of thevalve303.
• The upper limit time and the lower limit time of the rotation condition are defined based on a time period which is necessary for thevalve303 to rotate from the full-open position to the full-close position. It should be noted that when the rotation quantity of thevalve303 from the full-open position is excessively small, it is determined that a malfunction exists in the rotation position of thevalve303.
• In step S7, the computer determines whether the electric current is smaller than a break-wire value. The break-wire value is a reference value for determining whether a breaking of wire occurs in theelectric motor302. When the answer is YES in step S7, the procedure proceeds to step S9 in which the computer determines that a breaking of wire occurs. When the answer is NO in step S7, the procedure proceeds to step S10 in which the computer determines that a disengage malfunction occurs.
• The disengage malfunction represents that a disengagement occurs in a torque transmitting path between theelectric motor302 and thevalve shaft308. For example, when a connecting portion between thevalve shaft308 and the end-gear326 is broken, the end-gear326 is disengaged from thevalve shaft308. Such a breakage is referred to as a disengage malfunction.
• When the answer is NO in step S6, the procedure proceeds to step S11 in which thevalve303 is normally rotated form the full-open position to the full-close position. Then, the procedure proceeds to step S12 in which the lock-current is estimated to end the main flowchart.
• The control means312 functions as a lock-current estimating means by executing step S12.
[Advantages of Fourth Embodiment]
• In a case that thevalve303 rotates from the full-open position to the full-close position, the control means312 stores the threshold “Ithr” for determining whether thevalve303 is normally full-closed. After theelectric motor302 is energized, the electric current exceeds the threshold “Ithr” temporarily due to the inrush current. Then, the electric current is lowered than the threshold “Ithr”. After that, when the electric current excesses the threshold “Ithr” again, it is determined that thevalve303 is normally full-closed.
• Thereby, based on the appropriately established threshold “Ithr”, it is able to correctly determine whether thevalve303 is surely moved from the rotation condition to the hold condition.
• If thevalve303 has not moved from the rotation condition to the hold condition, the computer determines that thevalve303 is stuck in step S4, a malfunction exists in the rotation position of thevalve303 in step S8, a breaking of wire occurs in step S9, or the disengage malfunction occurs in step S10.
• Also, after the electric current is lowered than the threshold “Ithr”, when the absolute value of the temporal variation rate of the electric current is lowered than the specified convergence value, the control means312 determines that the inrush current has been converged and thevalve303 has moved from the initial condition to the rotation condition. Thereby, even though the time period required to converge the inrush current fluctuates, the convergence of the inrush current can be surely detected.
• The control means312 stores the ratio “Ia/Ib” and the threshold “Ithr” is defined in such a manner as not to exceed an upper value which is obtained by multiplying “Iss” by “Ia/Ib”. Thereby, without respect to a contact condition between thebrushes321a,321band thecommutators317A-317C, it is surely determined whether thevalve303 has normally moved from the unhold condition to the hold condition.
• Further, the control means312 integrates the electric current from when theelectric motor302 is energized until when the electric current is stepwise increased. Based on the integrated value, the control means312 determines whether the rotational position of thevalve303 is normal. Since the electric current supplied to theelectric motor302 and the rotation speed of themotor302 has a liner correlation, the above integrated value and the rotation angle of themotor302 has also liner correlation. The rotation angle of themotor302 corresponds to the rotational position of thevalve303 one-on-one. Therefore, it can be determined whether the rotational position of thevalve303 is normal based on the integrated value with high accuracy.
Fifth Embodiment
• As shown inFIG. 14, the drivingapparatus301 is provided with a temperature estimating means340 which estimates ambient temperature around theelectric motor302, and a voltage detecting means341 which detects voltage ofelectric power source313. Theelectric motor302 receives electricity from theelectric power source313. The voltage detecting means341 is a well-known voltage detecting circuit which outputs detection signal to the control means312. The temperature estimating means340 is a water-temperature sensor which detects engine coolant temperature. The ambient temperature around themotor302 is estimated based on the engine coolant temperature.
• Also, the control means312 stores a ratio between the lock-current and the power source voltage as a function P(T) of the ambient temperature T. This ratio is referred to as hold-condition conductance. More specifically, as shown inFIG. 15A, the control means312 stores the ambient temperature and the hold-condition conductance as a table data of “T” and “P(T)”.
• The control means312 applies the estimation value of the ambient temperature to the function P(T) to compute the hold-condition conductance. The control means312 computes an estimation value “Iss” of the lock-current by multiplying the hold-condition conductance and the detection value of the power source voltage.
• The threshold “Ithr” is defined in such a manner as not to exceed an upper value which is obtained by multiplying “Iss” and “Ia/Ib”.
• Furthermore, the control means312 corrects the function P(T) based on the detected electric current, the estimated ambient temperature around themotor302, and the detected power source voltage. Specifically, the detected value of the lock-current is divided by the detected value of the power source voltage so that the actual measured value “P” of the hold-condition conductance is computed. Based on the actual measured value “P”, the table data of the function P(T) is updated.
• For example, in a case that the estimated value of the ambient temperature around themotor302 is Ts° C. (0° C.<Ts<20° C.), a ratio between a difference (Ts−0) and a difference (20−Ts) is defined as “s:(1−s)” (0<s<1), the hold-condition conductance obtained based on not-updated P(0) and P(20) is denoted by P(Ts), and the difference between “P” and “P(Ts)” is denoted by “ΔP(Ts)”.
• In this case, after a weighting is performed with respect to not-updated P(0) and P(20) according to Ts° C., the updated P(0) and P(20) are expressed as follows:
• 
  UpdatedP(0)=not-updatedP(0)+k·(1−s)·ΔP(Ts)
• 
  UpdatedP(20)=not-updatedP(20)+k·s·ΔP(Ts)
• 
  whereink=1/(2s²−2s+1).
[Advantages of Fifth Embodiment]
• According to the fifth embodiment, the drivingapparatus301 is provided with a temperature estimating means340 which estimates the ambient temperature around theelectric motor302, a voltage detecting means341 which detects the power source voltage. The control means312 computes the hold-condition conductance based on the table data which shows a relation between the ambient temperature around themotor302 and the hold-condition conductance. Further, the estimation value “Iss” of the lock-current is computed by multiplying the hold-condition conductance and the detection value of the power source voltage. Thereby, the estimation value “Iss” of the lock-current can be computed in view of the thermal characteristic.
• Further, the control means312 corrects the table data based on the detected value of the electric current supplied to themotor302, the estimation value of the ambient temperature around themotor302 and the detection value of the power source voltage. Thereby, even if the characteristics of theelectric motor302 are varied with age, the hold-condition conductance in the table data can be updated with high accuracy. Even if the characteristics of theelectric motor302 are varied with age, the lock-current can be estimated with high accuracy.
Sixth Embodiment
• According to a sixth embodiment, as shown inFIGS. 16A and 16B, the control means312 outputs PWM-signals to four switchingelements325 of adriving circuit314 so that the energization of themotor302 is controlled. A sampling frequency at which the control means312 obtains the detection values from the current detecting means311 is greater than a value which is obtained by dividing the frequency of the PWM-signals by a duty ratio of the PWM-signals. Thereby, since the detection value of the electric current is surely obtained during ON-period of the PWM-signals, it can be avoided that the detection value of the electric current is obtained only during OFF-period of the PWM-signals.
• The control means312 does not use detection value which is lower than a reference value, when executing processings shown inFIGS. 4-6. Thus, erroneous determinations can be avoided.
[Modification]
• The drivingapparatus301 is not limited to the above embodiments. For example, it can be determined whether the rotational position of thevalve303 normally reaches the full-open position in a case that thevalve303 rotates from the full-close position toward the full-open position.
• The hold condition can be generated at a middle position between the fuel-open position and the full-close position. The driving apparatus can be applied to a throttle valve control apparatus or an EGR gas control apparatus.
• In the above embodiments, thevalve303 is a butterfly valve. Alternatively, thevalve303 may be a poppet valve or a needle valve.
• In a case that thevalve303 is a poppet valve, the drivingapparatus301 controls a linear movement of the poppet valve.

Claims (16)

1. A valve control apparatus comprising:

a valve opening/closing a fluid passage;

a shaft supporting the valve;

a housing accommodating the valve and the shaft therein;

an actuator having a reduction-gears mechanism which transmits a decelerated rotational force of a motor to the shaft;

a sensor detecting a rotation angle of the actuator; and

a malfunction detecting means for detecting a malfunction in a rotational-force-transmitting path to the shaft, wherein

the reduction-gears mechanism includes an end-gear engaging with a gear of the motor to transmit the rotational force of the motor to the shaft,

the end-gear is provided with a connecting portion and gear teeth engaging with the gear of the motor, the connecting portion is made of resin material and is provided with a press-insert hole,

the shaft has a press-insert portion which is press-inserted into the press-insert hole, an exposed portion which is out of the press-insert hole, and a stopper which radially extends from the exposed portion,

the housing has a stopper surface with which the stopper is brought into contact, so that a valve operation range is regulated,

the gear teeth is comprised of inside gear teeth and outside gear teeth, the inside gear teeth engages with the gear of the motor in a gear-operation-angle range of the end-gear which corresponds to the valve operation range, the outside gear teeth engages with the gear of the motor in out of the gear-operation-angle range, and

the malfunction detecting means determines that a malfunction occurs when the end-gear rotates over the gear-operation-angle range and the detection value of the rotation angle sensor is out of normal detection values which correspond to the valve operation range.

2. A valve control apparatus according toclaim 1, wherein

the end-gear has the gear teeth along an entire circumferential periphery.

3. A valve control apparatus according toclaim 1, wherein

the end-gear has the gear teeth partially along a circumferential periphery.

4. A valve control apparatus according toclaim 1, wherein

the sensor includes a magnet fixed to the end-gear and an element detecting magnetic flux generated by the magnet.

5. A valve control apparatus according toclaim 1, wherein

the fluid passage is an intake passage communicating with a combustion chamber of an internal combustion engine.

6. A valve control apparatus according toclaim 1, wherein

the fluid passage is an intake passage communicating with a combustion chamber of an internal combustion engine,

the housing defines the intake passage and an accommodation chamber which accommodates the end-gear.

7. A valve control apparatus according toclaim 6, further comprising

a seal member which air-tightly seals between the connecting portion and an inner wall of the accommodation chamber.

8. A valve control apparatus according toclaim 7, wherein

a maximum diameter of the stopper is smaller than an outer diameter of the seal member.

9. An electric driving apparatus comprising:

an electric motor generating a driving force while receiving an electric current;

an electric current detecting means for detecting the electric current supplied to the electric motor, and

a control means for controlling an energization to the electric motor so that the driving force is transmitted to a driven member in order to vary a displacement magnitude which represents at least one of a variation in position of the driven member and a variation in posture of the driven member, wherein

the displacement magnitude includes a hold value at which the driven member is mechanically held and the displacement magnitude does not vary even though the driving force is continued to be transmitted from the electric motor to the driven member so as to vary the displacement magnitude in one direction,

the electric current supplied to the electric motor is stepwise increased when the displacement magnitude reaches the hold value after the displacement magnitude has been varied in one direction,

the control means stores a threshold regarding the electric current supplied to the electric motor for determining whether the displacement magnitude normally reaches the hold value in a case that the electric motor is controlled in such a manner that the displacement magnitude reaches the hold value after the displacement magnitude has been varied in one direction, and

after the electric motor is energized, the electric current exceeds the threshold temporarily due to the inrush current, then the electric current is lowered than the threshold, and when the electric current excesses the threshold again, the control means determines that the displacement magnitude has normally reached the hold value.

10. An electric driving apparatus according toclaim 9, wherein

after the electric current is lowered than the threshold, when an absolute value of a temporal variation rate of the electric current is lowered than a specified convergence value, the control means determines that a temporal increase and decrease in electric current due to the inrush current has been converged.

11. An electric driving apparatus according toclaim 9, wherein

the electric motor includes a rotor having a plurality of coils and a plurality of commutators, a stator having a plurality of magnets, and two brushes being in contact with the commutators to supply the electric current to the coils,

the electric motor generates a rotational torque,

the control means includes a lock-current estimating means for estimating a lock-current which is supplied to the electric motor after the displacement magnitude has reached the hold value,

when the displacement magnitude reaches the hold value, the rotor stops and each of the brushes is in contact with the single commutator, the lock-current is denoted by “Ia”,

when at least one of brushes is in contact with the multiple commutators, the lock-current is denoted by “Ib”,

the control means stores a lock-current ratio “Ia/Ib”, and

the threshold is defined in such a manner as not to exceed an upper value which is obtained by multiplying the estimated lock-current and the lock-current ratio “Ia/Ib”.

12. An electric driving apparatus according toclaim 11, wherein

the lock-current estimating means defines an average value of a plurality of electric current values detected by the electric current detecting means as the estimation value of the lock-current after it is determined that the displacement magnitude normally reaches the hold value.

13. An electric driving apparatus according toclaim 11, further comprising:

a temperature estimating means for estimating an ambient temperature around the electric motor;

a power source voltage detecting means for detecting a voltage of a power source which supplies an electricity to the electric motor, wherein

the lock-current estimating means stores a ratio between the lock-current and the power source voltage as a function of the ambient temperature around the electric motor,

the lock-current estimating means computes said ratio between the lock-current and the power source voltage by applying the estimated value of the ambient temperature to the function, and

the lock-current estimating means computes an estimation value of the lock-current by multiplying said ratio and the power source voltage.

14. An electric driving apparatus according toclaim 13, wherein

after it is determined that the displacement magnitude normally reaches the hold value, the lock-current estimating means corrects the function based on a detection value of the electric current detected by the electric current detecting means, an estimate value of the ambient temperature around the electric motor estimated by the temperature estimating means, and a detection value of the power source voltage detected by the power source voltage detecting means.

15. An electric driving apparatus according toclaim 9, wherein

the control means integrates the electric current supplied to the electric motor from when the electric motor is energized until when the electric current is stepwise increased, and

the control means determines whether the displacement value is normal based on the integrated value.

16. An electric driving apparatus according toclaim 9, further comprising

a driving circuit which turns on/off the electric motor according to a control signal from the control means, wherein

the control means outputs a PWM-signal as the control signal to the driving circuit to control an energization of the electric motor, and

a sampling frequency at which the control means obtains the detection values from the current detecting means is greater than a value which is obtained by dividing the frequency of the PWM-signal by a duty ratio of the PWM-signal.

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