US3804558A - Electromagnetic pump - Google Patents

Abstract

An electromagnetic pump comprises a pump section including an inlet and outlet chambers adapted to receive fluid therein and separated from each other, and a pump means interconnecting said inlet and outlet chambers. Said pump means has a reciprocating piston so as to deliver the fluid from said inlet chamber to said outlet chamber by the reciprocating motion of said piston. A drive control circuit for actuating said piston to reciprocate is provided in said pump section, wherein said drive control circuit comprises a solenoid for actuating said piston, a feedback coil inductively coupled with said solenoid, a transistor having its collector-emitter circuit connected to a power supply in series with said solenoid and a series circuit of a diode and a voltage regulating unit. Said feedback coil is connected across the base and emitter of said transistor with the polarity such that said transistor is rendered more heavily conductive by a voltage induced across said feedback coil and applied across the base and emitter of said transistor when the current supply to said solenoid is increased. Said series circuit of a diode and a voltage regulating unit is connected in parallel with said solenoid to discharge a counter electromotive force induced in said solenoid.

Description

ELECTROMAGNETIC PUMP Inventor: Morikazu Naito, lnaz awa, Japan Nippondenso Co., Ltd., Aichi-ken, Japan Filed: Apr. 19, 1972 Appl. No; 245,554

Assignee:

Foreign Application Priority Data 1451 Apr. 16, 1974 Primary Examiner-C. J. Husar Attorney, Agent, or Firm-Cushman, Darby & Cushman '57 ABSTRACT An electromagnetic pump comprises a pump section including an inlet and outlet chambers adapted to receive fluid therein and separated from each other, and Apr. 30, 1971 Japan 46-29321 a pump means interconnecting said inlet and outlet June 18, 1971 Japan 46/52803 chambers. Said pump means has a reciprocating piston so as to deliver the fluid from said inlet chamber [,52] US. Cl. 417/417 to said outlet chamber by the reciprocating motion of [51] Int. Cl.F04b 17/04 said piston. A drive control circuit for actuating said '[58] Field of Search 307/265, 271, 275; piston to reciprocate is provided in said pump section, 4l7/415-4l7 wherein said drive control circuit comprises a solenoid for actuating said piston, a feedback coil inductively [56] References Cited coupled with said solenoid, a transistor having'its col- UNITED STATES PATENTS lector-emitter circuit connected to a powersupply in 2,989,651 6/1961 Smith 307 275 Series solenolfi and f Semis a 3.010932 [1961 Carney I u n 307/275 X and a voltage regulating unit. Sa d feedback co1l 1s 3.219344 11/1965 Martin h I I 307/265 X connected across the base and emitter of said transis- 3 225 2 7 9 5 v 307/265 X tor with the polarity such that said transistor is ren- 2,084,605 6/1937 Webb 417/417 X dered more heavily conductive by a voltage induced 3,556,684 l/1971 Rouquette 417/417 X across said feedback coil and applied across thebase 3,5 3,06 l /19 Wallace 4117/4115 X and emitter of said transistor when the current supply 3418583 H1964 f 417/417 X to said solenoid is increased. Said series circuit of a 313811616 5/1968 werthe'merm- 417M117 diode and a voltage regulating unit is connected in 3479531 11/1969 Gaud 307/275 X parallel with said solenoid to discharge a counter elec- 3,629,674 112/1971, Brown 4l7/4l5 X 1 1 tromotive force induced in sand solenoid. FOREIGN PATENTSOR APPLICATIONS l,l96,703 7/1965 Germany 307/275 2 Clam, 9 D'awmg Flgulles I 1 o o b I it] QATENTEBAPR 16 I974 SHEET & 0F 4 FIG, 8

DIODE 37 (m sec) ELECTROMAGNETIC PUMP BACKGROUND OF THEINVENTION 1. Field of the Invention The present invention relates to an electromagnetic pump operating on a DC power supply such as a battery and more particularly to a reciprocating piston type electromagnetic fuel feed pump.

2. Description of the Prior Art This type of electromagnetic pump operating on a DC power supply, particularly a reciprocating piston type electromagnetic fuel feed pump that has been used employs a mechanical construction in which a housing of a magnetic material formed into a cylindrical shape is provided with a solenoid and a feedback coil concentrically stacked in the central portion of the housing which is hermetically sealed by means of a cap mounted at each end thereof. An inlet chamber and outlet chamber are formed on the opposite sides of said solenoid. A cylinder of a non-magnetic material ex-.

tends through said solenoid and an inlet valve is disposed on the inlet chamber side of said cylinder. A hollow piston of a magnetic material is axially slidably mounted in said cylinder and the piston is opened toward the inlet chamber side. An outlet valve is mounted in the piston on the outlet chamber side thereof. The piston is normally biased by a spring into an output chamber side position in the cylinder so that the energization of said solenoid exerts a force on the piston urging it toward the inlet chamber side against the spring force. A self-excited blocking oscillator circuit is separately provided so that said oscillator circuit is self-excited into oscillation by the action of said feedback coil thereby energizing said solenoid periodically. Consequently, the piston reciprocates within the cylinder between the inlet chamber side and the outlet chamber side thereof. Thus, when the piston moves away from the inlet chamber side toward the outlet chamber side, the fuel in the inlet chamber is admitted into the cylinder and the hollowed portion of the piston by way of the inlet valve, and the fuel thus admitted into the cylinder and the hollowed portion of the piston is delivered into the outlet chamber through the outlet valve when the piston moves away from the outlet chamber side toward the inlet chamber side. In this manner, the electromagnetic pump operates as a fuel pump.

A disadvantage of the prior art devices of this type is that while the pumps output, i.e., the amount of fuel delivered is related to the bulk of the pump and the number of reciprocating motions of the piston, i.e., the oscillation frequency of the self-excited oscillator circuit, it is difficult to obtain a higher oscillation frequency and it is thus necessary to increase the bulk of the pump to increase the pumps output.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a piston type electromagnetic reciprocating pump whose output is markedly increased by increasing the number of reciprocating motion of its piston, but without any increase in the bulk of the pump.

It is another object of the present invention to provide a reciprocating piston type electromagnetic pump which is simple in construction and easy in assembling.

In accomplishing these and other equally desirable objects, the electromagnetic pump provided in accordance with the present invention comprises a pump section including fuel inlet and outlet chambers separated from each other and pump means interconnecting said fuel inlet and outlet chambers and having a reciprocating piston whereby the fuel in said inlet chamber is delivered into said outlet chamber by said pump means by virtue of the reciprocating motion of said piston, and a drive control circuit for controlling the reciprocating motion of said piston, and drive control cir cuit comprising a solenoid for actuating said piston, a feedback coil inductively coupled to said solenoid, a transistor having its collector-emitter circuit connected to a power supply in series with said solenoid, said feedback coil being connected across the base and emitter of said transistor with the polarity such that said transistor is rendered more conductive by a voltage induced across said feedback coil and applied across said base and emitter of said transistor when the current supply to said solenoid is increased, anda series circuit of a diode and a voltage regulating unit connected in parallel with said solenoid to discharge a counter electromotive force induced in said solenoid.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of the pump mechanism of an electromagnetic pump according to the present invention.

FIG. 2 is a side view of the pump mechanism of the electromagnetic pump shown'in FIG. 1.

FIG. 3 is a sectional view of FIG. 2.

FIG. 4 is a schematic diagram of the control circuit used with the electromagnetic pump of FIG. 1.

FIG. 5 is a graph showing the characteristics of the control circuit shown in FIG. 4.

FIG. 6 is a schematic diagram of a conventional control circuit.

FIG. 7 is a graph showing the characteristics of the control circuit shown in FIG. 6.

FIG. 8 is a graph showing l-V characteristic curves of diode and resistor.

FIG. 9 is a graph showing the attenuation time of electric current relative to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2 there is shown the pump section of an electromagnetic pump according to an embodiment of the present invention. In the figures,numeral 1 designates a housing of a magnetic material having a bottom wall and a cylindrical wall; 12 an inlet chamber casing of a non-magnetic material having an inlet port 1a and contiguously mounted on the bottom wall of thehousing 1; 13 an output chamber casing of a non-magnetic material having an outlet port 1b and contiguously mounted on thehousing 1 opposite to the housing bottom wall. Also mounted on the outside of the housing portion of the pump section is acircuit unit 1 1 incorporating the circuit elements of a drive control circuit which will be explained later in detail. A lead wire for supplying power to the drive control circuit extends from the circuit unit 11 to the outside thereof and is connected to apower supply 31 through aswitch 30. In the sectional view of FIG. 3 illustrating the pump mechanism in detail,numeral 5 designates a hollow cylinder of a non-magnetic material which extends axially through the bottom wall of thehousing 1 with its one end projecting to theinlet chamber 12 side and the other end to theoutlet chamber 13 side. Aninlet valve 20 is provided at the one end of the cylinder and an opening is provided at the other end of the cylinder. Anannular solenoid 2 and anannular feedback coil 35 surrounding thesolenoid 2 are provided in the central portion of thehousing 1 surrounding thecylinder 5. These coils will be explained later in detail. Numeral 3 designates a shielding plate of a magnetic material soldered to thecylinder 5 by a solder 6a. Theshielding plate 3 is formed with agroove 3a for receiving an O-ring in its surface contacting thehousing 1. Numeral 4 designates a shielding plate of a magnetic material; 16 a brass plate disposed on the bottom of thehousing 1 and soldered to thecylinder 5 by a solder 6b. A piston 21 of a magnetic material is axially slidably mounted within thecylinder 5 and a passage 21a extends axially therethrough with anoutlet valve 23 provided at one end of the passage 21a. A groove 12a for receiving an O-ring 26 is formed in the surface of theinlet chamber casing 12 contacting thebrass plate 16 and another groove 13a for receiving an O-ring 27 is formed in the surface of theoutlet chamber casing 13 contacting thehousing 1. Theinlet chamber casing 12 and theoutlet chamber casing 13 with thehousing 1 disposed therebetween are joined together by three marginal throughbolt connectors 17 at three points 120 degrees apart from one another. Thesolenoid 2,feedback coil 35 and circuit unit 11 are molded with a resin.

The pump section is assembled as follows: The magnetic shielding plate 4 and thesolenoid 2 are first mounted in thecylindrical housing 1 with a closed bottom and then the O-ring 15 is fitted in thering groove 3a in theshielding plate 3. After thecylinder 5 is inserted through and soldered by the solder 6b at an opening 16a of thebrass plate 16 mounted on the bottom of thehousing 1, theinlet valve 20,spring 22,outlet valve 23 and piston 21 are assembled in place to complete the pump section. Thereafter, the O-rings 26 and 27 are fitted in the ring grooves 120 and 13a of theinlet chamber casing 12 andoutlet chamber casing 13, respectively, and thecasings 12 and 13 are joined together with the marginal throughbolt connectors 17 thus providing a complete assemblage.

It should be noted that the inlet port la and outlet port 1b may be pointed in any desired direction and all that is required to do so is simply to join theinlet chamber casing 12,housing 1 andoutlet chamber casing 13 after the direction of the inlet andoutlet port 10 and 1b have been selected and the relative positions of thecasing 12,housing 1 andcasing 13 have been determined. It will be seen from FIG. 2 that the position of the inlet port 1a may be changed as shown by phantom lines.

It should also be noted that the present invention is not intended to be limited to the described embodiment, since various modifications and changes may be obvious to those skilled in the art. For example, any desired number of the marginal throughbolt connectors 17 may be used and they may also be placed at regular intervals.

The operation of the pump section will now be explained. As will be explained later in detail, when thesolenoid 2 is energized, its magnetic force causes the piston 21 to move within thecylinder 5 toward the inlet chamber side against the force of thespring 22. When this occurs, the inlet valve is closed and theoutlet valve 23 is opened so that the fuel in thecylinder 5 is delivered into the outlet chamber through theoutlet valve 23, passage 21a in the piston 21 and the open end of thecylinder 5. When thesolenoid 2 is eventually deenergized, the piston 21 is moved toward the outlet chamber side under the pressure of the spring'22. At this time, theinlet valve 20 is opened and the outlet valve 21 is closed so that the fuel in the inlet chamber is admitted into thecylinder 5 by means of the vacuum that exists in thecylinder 5. The repetitions of this process deliver the fuel in the inlet chamber into the outlet chamber. The fuel to the inlet chamber is supplied from the sump (not shown) through theinlet port 10 and the fuel in the outlet chamber is discharged to any desired destination (not shown) through the outlet port lb.

The drive control circuit which periodically energizes thesolenoid 2 to operate the pump comprises a socalled self-excited blocking oscillator. FIG. 6 illustrates a known type of control circuit in which thesolenoid 2 is connected in series with the collector-emitter circuit of atransistor 36 and to thepower supply 31 through theswitch 30. Thefeedback coil 35 is provided to surround thesolenoid 2 as previously mentioned and thus the two coils are closely inductively coupled with each other. Thefeedback coil 35 is connected across the base and emitter of thetransistor 36 with the polarity such that thetransistor 36 is biased so that when thetransistor 36 is conducted and thus the current supply to thesolenoid 2 gradually increases, the current supply thereto is increased still further.

As described above, in an electromagnetic pump of this type the reciprocating motion of the piston 21 is effected by the alternating operations of the energizing force of thesolenoid 2 and the force of thespring 22 to deliver fluid and thus the discharged volume Q (cc/min) per unit time is determined by the product of the sectional area S (cm) of the piston 21, the stroke l (cm) of the piston 21 and the number of reciprocating motion of the piston 21, i.e., the oscillation frequency f(I-I X 60 of the self-excited blocking oscillator circuit. Therefore, in order to increase the amount of fuel delivered with a limited bulk, the number of reciprocating motion of the piston 21 and hence the oscillation frequency of the self-excited blocking oscillator circuit must be increased.

The oscillation frequency of the self-excited blocking oscillator circuit depends on the sum of the conduction time and cutoff time of thetransistor 36, and in an attempt to increase the oscillation frequency of this selfexcited blocking oscillator circuit aresistor 34 is connected in series with a counter electromotiveforce absorbing diode 38 connected in parallel with thesolenoid 2, so that when thetransistor 36 is cut off, the counter electromotive force induced in thesolenoid 2 is quickly attenuated by means of theresistor 34 to decrease the cutoff time of thetransistor 36 and thus to increase the oscillation frequency. In other words, the attenuation time of the counter electromotive force induced in thesolenoid 2 depends on the value L/R, where R is the resistance value of a closed circuit comprising thesolenoid 2,diode 38 andresistor 34 and L is the inductance of thesolenoid 2. Consequently, this attenuation time will be decreased with the corresponding increase in the oscillation frequency as the resistance value of theresistor 34 is increased.

However, since the damped current I having a certain initial value flows in the closed circuit comprising thesoldnoid 2,diode 38 andresistor 34, the value of voltage e applied across thesolenoid 2 increases in proportion to an increase in the resistance value of theresistor 34 thus increasing the voltage applied across the emitter and collector of thetransistor 36.

In the circuit shown in FIG. 6, the oscillation frequency ful the voltage V (V) across the emitter and collector of thetransistor 36 and the delivered volume Q (cc/min) changed as shown in FIG. 7 with varia tions in the resistance value of theresistor 34.

The characteristic curves in FIG. 7 show the results obtained when the resistance Ra of theresistor 34 was varied from 0 to 30 ohms employing thesolenoid 2 whose'nu mber of turns 500 T, resistance value 1.9 ohms and inductance 25 mH, thefeedback coil 35 having the number of turns 450 T,resistance value 19 ohms andinductance 30 mH, thetransistor 36 having thecurrent amplification factor 40 and the lampere, l-volt diode 38 for absorbing counter electromotive force. The attenuation time of counter electromotive force (equal to the cutoff time of the transistor 36) T varied over the range from 50 to 18 ms and the oscillation frequency f changed in the range between 14 and 24 H and the delivered volume Q could vary over the range from 1,600 to 2,500 cc/min, whereas the voltage V across the emitter and collector of thetransistor 36 attained very high values ranging from 14 to 100 volts.

Consequently, if the voltage applied across the emitter and collector of thetransistor 36 increases extraordinarily as described above, from the reliability point of view or the like, thetransistor 36 must be such that it withstands a correspondingly higher voltage. There is thus a drawback in that the manufacturing cost of electromagnetic pumps employing high-voltage withstanding transistors tends to become very high, since such transistors are not readily available and at the same time they are very expensive.

According to the present invention, the control circuit is constructed as shown in FIG. 4. In the figure, thesolenoid 2 of the pump section is connected in series with the emitter and collector of thetransistor 36 and thefeedback coil 35 is connected across the emitter and base of thetransistor 36. Thefeedback coil 35 is closely coupled inductively with thesolenoid 2 with the polarity such that thetransistor 36 is rendered more conductive when the current supply to thesolenoid 2 is increased.

The series circuit of the counter electromotiveforce absorbing diode 38 and avoltage regulating unit 37 consisting of at least onediode 37a is connected in parallel with thesolenoid 2.

Numeral 3l designates a DC power supply such as a battery; 30 a power supply switch; 39 a starting resistor connected between the base of thetransistor 36 and the positive terminal side of thesolenoid 2; 40 a transistor protecting diode connected in parallel with thefeedback coil 35; 41 a diode for protecting thetransistor 36 from the external pulses.

With the construction described above, the operation of this control circuit will now be explained. When thepower supply switch 30 is closed, the base current flows into thetransistor 36 through the startingresistor 39. In consequence, the collector current starts flowing in thetransistor 36 producing a voltage across thesolenoid 2 and thus inducing a voltage across the feedback coil 35.-This voltage is then applied to thetransistor 36 in the form of positive feedback placing thetransistor 36 into a higher conduction state. In this case, if the value of this positive feedback is designated by A and the amplification degree of thetransistor 36 by B and if A and B are selected so that the condition A'B l holds, then the circuit comprising thesolenoid 2,feedback coil 35 andtransistor 36 satisfies the condition of oscillation so that it initiates and maintains self-excited blocking oscillations so long as thepower supply switch 30 remains closed, thereby supplying the interrupted current to thesolenoid 2.

In this case, if T and T are the conduction time and cutoff time of thetransistor 36, respectively, then the oscillation frequency f of the self-excited blocking oscillator circuit is given by f l/(I T and the oscillation frequency f can be increased by reducing the cutoff time T The cutoff time T of thetransistor 36 depends on the time it takes the counter electromotive force induced in thesolenoid 2 upon the cutting off of thetransistor 36 to dissipate, that is, the time during which the damped current having a certain initial value remains flowing in the closed circuit comprising the so lenoid 2, counter electromotiveforce absorbing diode 38. anddiode 37a. Consequently, as previously explained, the more the resistance value of the closed circuit is increased, the more the cutoff time T is decreased with the corresponding increase in the oscillation frequency f. t

Then, by connecting the counter electromotiveforce absorbing diode 38 and at least oneadditional diode 37a instead of the resistance (Ra) used in the prior art in series with thesolenoid 2, the oscillation frequency f can be increased and further the voltage applied across the emitter and collector of thetransistor 36 can be limited in low value compared with the circuit of FIG. 6 for reasons that will be explained hereunder. The maximum value I of a current through a closing circuit of thepower supply 31,switch 30,solenoid 2 and thetransistor 36 at the conductive state of thetransistor 36 is determined by the product of the base current I of thetransistor 36 and the amplification factor A, i.e., 1,, X A. Therefore, immediately after the transistor has been rendered non-conductive, the maximum current I which was carried through thetransistor 36 till then, is led through the series circuit of thediodes 37a and 38.

The diode has an I-V characteristic as shown in FIG. 8. Assuming that the maximum current I is 3 amperes, the voltage drop across the series circuit of the diodes is about 2 volts when the number of the diodes n is l, and about 14 volts whenn 9. In contrast, the voltage drop across the series circuit of thediode 38 and theresistor 34 in the prior art circuit as shown in FIG. 6 is about volts when the resistor Ra of 30 ohms is used, and about 3 volts when the resistor Ra of 1 ohm is used.

As mentioned previously, however, if the resistor Ra of a low resistance such as 1 ohm is used, the current 1 is hardly reduced and hence thetransistor 36 remains in a non-conductive state for a considerably long time.

In the circuit as shown in FIG. 4, the effective resistance of the series circuit of the diodes is relatively low for the initial period when the current through the series circuit is relatively large, but increases rapidly due to the non-linear I-V characteristic of the diodes with attenuation of the current through the closing circuit of the transistor and the diodes. Thus the increase of the effective resistance of the diodes contributes accumulatively to attenuation of the current through the closing circuit. Attenuation curves, i.e., ampere I to time 1 curves, of the current I through the closing circuit in FIG. 9 show this situation. The current I decreases first along a curve for a low resistance of the fixed resistor Ra, but decreases last along a curve for a high resistance of the resistor. This attenuation time of the current I if the number of the diodes is 9, in effect, is equivalent to the attenuation time for 30 ohms of the resistor Ra.

Consequently, the counter electromotive force induced in thesolenoid 2 is prevented from being increased excessively and the attenuation time of the current is small like as the fixed resistor of a high resistance inserted in the conventional circuit. Further, by the use of an integrating circuit of the diodes, the cir cuit can be manufactured economically.

With the embodiment described above, the oscillation frequency f(I-I the attenuation time of counter electromotive force (equal to the cutoff time of the transistor 36) T the voltage V (V) across the emitter and collector of thetransistor 36 and the delivered volume Q (cc/min) changed as shown in FIG. 5 when the number of thediodes 37a was increased progressively.

The characteristic curves shown in FIG. 5 indicate the results obtained when the l-ampere, l-volt diode 37a ranging in number from 0 to 9 were connected in series with the counter electromotiveforce absorbing diode 38 employing thesolenoid 2 whose number of turns 500 T, resistance 1.9 ohms and inductance 25 mI-I,feedback coil 35 whose number of turns 450 T, resistance 1.9 ohms andinductance 30 mH,transistors 36 whosecurrent amplification factor 40, and the l-ampere, l-volt diode 38 for absorbing counter electromotive force. The attenuation time T varied in the range from 50 to 18 ms. The oscillation frequency f changed in the range between 14 and 24 H and the delivered volume Q was increased in the range between 1,600 and 2,300 cc/min, while the variation of the voltage V across the emitter and collector of thetransistor 36 were very small ranging from 14 to 22 volts.

While in the embodiment described above thevoltage regulating unit 37 connected in series with the counter electromotiveforce absorbing diode 38 has been explained as employing ordinary diodes, other voltage regulating elements, such as, Zener diodes or varistors may of course be employed. If a Zener diode is employed, its anode (cathode) should be connected to the anode (cathode) of the counter electromotiveforce absorbing diode 38.

As explained hereinbefore, a novel feature of the electromagnetic pump according to the present invention is that since the series circuit of the counter electromotiveforce absorbing diode 38 and the .voltage regulating unit 37 is connected in parallel with thesolenoid 2 of the self-excited blocking oscillator circuit, by suitably selecting the resistance value of thevoltage regulating unit 37, the oscillation frequency of the selfexcited blocking oscillator circuit can be increased with the resultant increase in the amount of fuel delivered without considerably increasing the voltage across thesolenoid 2 and hence the voltage applied across the emitter and collector of thetransistor 36. Thus, in contrast to the conventional devices in which theresistor 34 is connected in series with the counter electromotiveforce absorbing diode 38, a low-voltage proof and inexpensive transistor may be employed for thetransistor 36 and moreover the construction of the electromagnetic pump is simplified. Thus, in accordance with the present invention, there is provided an electromagnetic pump which is small and compact, capable of providing a large output and inexpensive to manufacture.

I claim:

1. An electromagnetic pump comprising:

a pump section including an inlet chamber and an outlet chamber adapted to receive fluid therein and separated from each other,

pump means interconnecting said inlet and outlet chambers and having a reciprocating piston, said pump means having an inlet valve disposed on the inlet chamber side thereof, said reciprocating piston having an outlet disposed on the outlet chamber'side thereof, said reciprocating piston delivering the fluid from said inlet chamber to said outlet chamber through said inlet and outlet valves by the reciprocating motion of said piston, and

a drive control circuit for actuating said piston to reciprocate, said drive control circuit including a solenoid for actuating said piston, a feedback coil inductively coupled with said solenoid, a transistor having its collector-emitter circuit connected to a power supply in series with said solenoid, said feedback coil being connected across the base and emitter to said transistor with a plurality such that said transistor is rendered more deeply conductive by a voltage induced across said feedback coil and applied across the base and emitter of said transistor when current flowing through said solenoid is increased, and

a series circuit including a diode and a voltage regulating unit connected in parallel with said solenoid to discharge counter electromotive force induced in said solenoid, said voltage regulating unit having diodes connected in series with each other.

2. An electromagnetic pump according toclaim 1 wherein said pump section comprises:

an inlet chamber casing having said inlet chamber defined therein and an inlet port adapted to draw fuel into said inlet chamber,

an outlet chamber casing having said outlet chamber defined therein and on outlet port to deliver the fluid in said outlet chamber to the outside, and

a housing having said pump means mounted therein and accommodating said solenoid and said feedback coil to enclose said piston of said pump means,

said housing having at least one input terminal of said solenoid, said housing being clamped between said inlet chamber casing and said outlet chamber casing in alignment therewith by a plurality of marginal through bolt connectors which are arranged on the marginal edges of said inlet chamber casing and said outlet chamber casing at equal intervals.

Claims (2)

1. An electromagnetic pump comprising: a pump section including an inlet chamber and an outlet chamber adapted to receive fluid therein and separated from each other, pump means interconnecting said inlet and outlet chambers and having a reciprocating piston, said pump means having an inlet valve disposed on the inlet chamber side thereof, said reciprocating piston having an outlet disposed on the outlet chamber side thereof, said reciprocating piston deliveRing the fluid from said inlet chamber to said outlet chamber through said inlet and outlet valves by the reciprocating motion of said piston, and a drive control circuit for actuating said piston to reciprocate, said drive control circuit including a solenoid for actuating said piston, a feedback coil inductively coupled with said solenoid, a transistor having its collector-emitter circuit connected to a power supply in series with said solenoid, said feedback coil being connected across the base and emitter to said transistor with a plurality such that said transistor is rendered more deeply conductive by a voltage induced across said feedback coil and applied across the base and emitter of said transistor when current flowing through said solenoid is increased, and a series circuit including a diode and a voltage regulating unit connected in parallel with said solenoid to discharge counter electromotive force induced in said solenoid, said voltage regulating unit having diodes connected in series with each other.

2. An electromagnetic pump according to claim 1 wherein said pump section comprises: an inlet chamber casing having said inlet chamber defined therein and an inlet port adapted to draw fuel into said inlet chamber, an outlet chamber casing having said outlet chamber defined therein and on outlet port to deliver the fluid in said outlet chamber to the outside, and a housing having said pump means mounted therein and accommodating said solenoid and said feedback coil to enclose said piston of said pump means, said housing having at least one input terminal of said solenoid, said housing being clamped between said inlet chamber casing and said outlet chamber casing in alignment therewith by a plurality of marginal through bolt connectors which are arranged on the marginal edges of said inlet chamber casing and said outlet chamber casing at equal intervals.

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