CN107763153B - Planetary gear type two-speed transmission for electric vehicle - Google Patents

Abstract

A two speed transmission for an electric vehicle comprising: a planetary gear train including a sun gear, a ring gear, a planetary gear, and a carrier, the sun gear being connected to a driving motor of the electric vehicle, the rotational motion of the driving motor being output through the carrier; a first clutch device including a first electric actuator and a first clutch assembly axially driven by the first electric actuator via a first drive spring into an engaged state in which the ring gear is locked against rotation via the first clutch assembly; and a second clutch device including a second electric actuator and a second clutch assembly axially driven by the second electric actuator via a second drive spring to enter an engaged state, wherein the ring gear is coupled to the carrier via the second clutch assembly in the engaged state of the second clutch assembly.

Description

Planetary gear type two-speed transmission for electric vehicle

Technical Field

The present application relates to a two-speed transmission for use in an electric vehicle that shifts gears using an electric actuator.

Background

Electric vehicles use a drive motor as a vehicle power source. The output rotational motion and torque of the drive motor are transmitted to the wheels of the vehicle via a transmission. There are two speed transmissions for electric vehicle transmissions. Transmissions of electric vehicles may be classified into a fixed shaft type transmission and a planetary gear type transmission from the viewpoint of the gear train type of the transmission; in terms of the shift pattern, the transmission of the electric vehicle may be classified into a DCT (dual clutch transmission) and an AMT (automated mechanical transmission). With the DCT, the whole gear shifting process can be smoothly realized in a non-power-interruption mode, and the axial size and the gear shifting impact are small. However, the DCT structure is complex, costly, and requires high manufacturing process requirements and high control accuracy. By adopting the AMT, the relatively smooth gear shifting process can be realized, and the gear shifting time can be shortened. However, it is difficult to avoid a shift power interruption, thereby affecting shifting comfort.

Accordingly, it is desirable to provide a two speed transmission having a simple structure and good shifting performance.

Disclosure of Invention

The object of the present application is to provide a two-speed transmission for an electric vehicle which can provide good shifting performance and high-efficiency transmission in a simple manner.

To achieve the object, the present application provides in one aspect a two speed transmission for an electric vehicle, the transmission comprising: a planetary gear train including a sun gear rotatable about a central axis, a ring gear coaxially arranged around the sun gear, at least one planetary gear meshed between the sun gear and the ring gear, and a carrier carrying the at least one planetary gear and rotatable about a central axis of the sun gear, the sun gear being connected to a drive motor of an electric vehicle, rotational motion of the drive motor being output through the carrier; a first clutch device including a first electric actuator and a first clutch assembly axially driven by the first electric actuator via a first drive spring into an engaged state in which the ring gear is locked against rotation via the first clutch assembly; and a second clutch device including a second electric actuator and a second clutch assembly axially driven by the second electric actuator via a second drive spring to enter an engaged state, wherein the ring gear is coupled to the carrier via the second clutch assembly in the engaged state of the second clutch assembly.

According to one possible embodiment, each of the first and second clutch assemblies comprises a first friction plate adapted to be axially urged by the respective first or second drive spring and a second friction plate arranged facing the first friction plate and adapted to be axially pressed by the first friction plate.

According to one possible embodiment, the first electric actuator and the second electric actuator each include an actuator motor and a motion conversion mechanism that converts a rotational motion output by the actuator motor into a linear motion.

According to a possible embodiment, the motion conversion mechanism is a ball screw mechanism comprising a ball screw driven by the actuator motor and a ball nut arranged around the ball screw and axially movable along the ball screw.

According to one possible embodiment, the ball nut drives the first or the second drive spring via a driver.

According to one possible embodiment, the lever is a lever pivoted about a pivot.

According to a possible embodiment, the first clutch means further comprise a first slide which is able to be driven in axial movement, but not in rotation, by a first electric actuator, the first drive spring being mounted on the first slide.

According to one possible embodiment, the second clutch device further comprises: a second slide block which is driven by a second electric actuator to move axially but not rotate; and a drive sleeve disposed around the second slider and axially movable and rotatable, the drive sleeve being urged by the second drive spring in a direction toward the second clutch assembly.

According to one possible embodiment, a spacer is arranged between the second slide and the drive sleeve, a ring of balls is arranged between the spacer and the second slide, and a return spring is arranged between the spacer and the drive sleeve, which return spring pushes the drive sleeve in a direction away from the second coupling unit on the one hand and pushes the second slide in a direction towards the second coupling unit via the spacer and the ring of balls on the other hand.

According to one possible embodiment, the first clutch assembly and the second clutch assembly each also have a disengaged state, and the first electric actuator and the second electric actuator have a self-locking function, such that when the first or second clutch assembly is in its engaged or disengaged state, the respective first or second electric actuator is de-energized and the engaged or disengaged state of the first or second clutch assembly is maintained by the self-locking function.

According to one possible embodiment, the transmission is in first gear when the first clutch assembly is in an engaged state and the second clutch assembly is in a disengaged state; the transmission is in second gear when the first clutch assembly is in the disengaged state and the second clutch assembly is in the engaged state.

According to one possible embodiment, the two-speed transmission further comprises a transmission housing on which the first and second electric actuators are mounted.

According to one possible embodiment, the first and second drive springs are disk springs, respectively.

The application provides a two-gear transmission especially suitable for an electric vehicle, belongs to an AMT (automated mechanical transmission), and realizes effective control of gear selection and shifting by utilizing pressure generated by an electric actuating mechanism at a driving spring (especially a disc spring) end. Compared with various actuating mechanisms (electric, hydraulic and the like) in the conventional AMT, the gear shifting loss is small, the gear shifting process is smooth, and the power interruption can be effectively avoided. Compared with DCT, the structure is simple and compact, the cost is reduced, and the method is beneficial to market promotion. Therefore, the transmission of the application can have the advantages of the double clutch and the motor-driven actuator.

Drawings

The present application may be further understood by reading the following detailed description with reference to the drawings, in which:

FIG. 1 is a schematic diagram of a drive system of an electric vehicle according to one possible embodiment of the present application;

FIG. 2 is a schematic cross-sectional view of one type of electric actuator that may be used in the transmission in the drive system of FIG. 1;

fig. 3 is a schematic diagram of a modification of the second clutch device that may be used in the transmission in the drive system of fig. 1.

Detailed Description

The two speed transmission of the present application is described below with reference to the accompanying drawings.

Fig. 1 schematically shows a drive system for an electric vehicle according to one possible embodiment of the present application, which includes atransmission case 1 on which adrive motor 2 as a vehicle power source is assembled. During normal running of the vehicle, thedrive motor 2 is powered by an on-vehicle battery pack and outputs rotational motion and torque. Thedrive motor 2 may also function as a generator during a vehicle braking operation for achieving regenerative braking power generation.

The operation of thedrive motor 2 is controlled by a controller. The controller may be a vehicle ECU (electronic control unit), a sub-module in the vehicle ECU, a separate controller in communication with the vehicle ECU, or the like. The controller controls thedrive motor 2 to rotate in a desired direction at a desired speed. The speed of thedrive motor 2 depends on various factors such as the intensity of current supplied from the battery pack, the running resistance of the vehicle, and the like.

A motor shaft 3 of thedrive motor 2 extends into thetransmission housing 1 and is connected to a planetary gear train. The planetary gear train essentially comprises a sun gear 4, one ormore planet gears 6 carried by aplanet carrier 5, and a ring gear 7. The sun gear 4 is fixedly connected to the motor shaft 3 and rotates with the motor shaft 3, the ring gear 7 is coaxially arranged around the sun gear 4, and theplanetary gears 6 are engaged between the sun gear 4 and the ring gear 7. A plurality ofplanetary gears 6 are typically employed, primarily for load sharing and to provide better balance.

Anoutput shaft 8 is fixedly connected to thecarrier 5, and theoutput shaft 8 extends outside thetransmission housing 1. The motor shaft 3 is coaxial with theoutput shaft 8, both defining the central axis of the transmission.

Theoutput shaft 8 is kinematically connected to a differential 9, for example via a gear set (not shown) between them. Differential 9 may be any differential available in the art, such as an integrated bevel gear differential. The differential 9 drives the two wheels via a pair of half shafts.

Two speed ratios of the transmission, i.e. two gears, are achieved by the planetary gear train described above. Specifically, a first speed ratio (first gear) can be achieved by locking the ring gear 7 to thetransmission case 1, and a second speed ratio (second gear) can be achieved by coupling the ring gear 7 to thecarrier 5. These two gears are realized by a first clutch device and a second clutch device, as described in detail below.

As shown in fig. 1, the first clutch device includes anelectric actuator 10 disposed outside thetransmission case 1 on the side close to the axial direction of thedrive motor 2, and is controlled by the controller to drive ashift lever 11. Theshift lever 11 extends into thetransmission housing 1 and is pivotable about apivot axis 12 which is arranged fixedly in thetransmission housing 1, i.e. theshift lever 11 is in the form of a lever. Afirst end 11a of theshift lever 11 is driven by theactuator 10 to reciprocate along the axial direction of the transmission, and a secondopposite end 11b of theshift lever 11 is movably connected to theslider 13, for example, hooked in a groove on theslider 13. Theslider 13 is fitted over asleeve 14 fixed in thetransmission case 1 around the motor shaft 3 and is axially slidable along thesleeve 14. When thefirst end 11a of theshift lever 11 is driven by theactuator 10 to move axially, thesecond end 11b of theshift lever 11 drives theslider 13 to slide axially on thesleeve 14. Theslide 13 is non-rotatable relative to thetransmission housing 1.

Theslider 13 is arranged in the axial direction on the side of the planetary gear train facing thedrive motor 2, and includes asleeve portion 13a surrounding theboss 14 and aflange portion 13b radially protruding from thesleeve portion 13a, theflange portion 13b facing the planetary gear train in the axial direction. Adrive spring 15 is fixed to theflange portion 13b, and thedrive spring 15 is in the form of a disc spring in the illustrated example.

Furthermore, the ring gear 7 is provided at its axial side facing thedrive motor 2 with a first clutch assembly, which is a multiple-disc clutch assembly including a plurality offirst friction plates 16 axially movable relative to the ring gear 7 and a plurality ofsecond friction plates 17 arranged alternately axially opposite to the respectivefirst friction plates 16 and axially fixed relative to the ring gear 7. Thedrive spring 15 is located between theflange portion 13b and thefirst friction plate 16 in the axial direction. Thedrive spring 15 is provided or formed with a pressure plate (not shown) at its axial end facing the first clutch pack.

The first clutch assembly has a disengaged state and an engaged state. In particular, theactuator 10 holds theslide 13 by means of theshift lever 11 in a position in which thedrive spring 15 does not axially push thefirst friction plates 16, with thefirst friction plates 16 in their home position and axially separated from thesecond friction plates 17, with the first clutch assembly in the disengaged state and with the ring gear 7 in the unlocked state relative to thetransmission housing 1, i.e. with the ring gear 7 rotatable in thetransmission housing 1. When theactuator 10 drives theslider 13 to axially advance toward the first clutch assembly by means of theshift lever 11, thedrive spring 15 axially pushes thefirst friction plate 16 axially adjacent thereto through the pressure plate thereof to press each of thefirst friction plate 16 and thesecond friction plate 17 against each other, the first clutch assembly is shifted to the engaged state, and the ring gear 7 is fixed together with thefirst friction plate 16 and theslider 13 to thereby be in the locked state with respect to thetransmission case 1. At this time, since theslider 13 is not rotatable with respect to thetransmission case 1, the ring gear 7 is also not rotatable with respect to thetransmission case 1, and it can be considered that the ring gear 7 is locked with respect to thetransmission case 1 and is not rotatable. Thedrive spring 15 should have a sufficient spring rate to ensure that the ring gear 7 is locked relative to thetransmission housing 1 in the engaged state of the first clutch assembly.

First friction disk 16 and/orsecond friction disk 17 are equipped with a return mechanism, such as a return spring. When theshift lever 11 drives theslider 13 to move backward, the return mechanism returns each of thefirst friction plate 16 and thesecond friction plate 17 to their original positions and to be separated from each other, and the first clutch assembly returns to its disengaged state.

Since the first clutch device serves to lock the ring gear 7, i.e. to thestationary transmission housing 1, it can be referred to as a locking device (or locking clutch).

It will be appreciated that the first andsecond friction plates 16 and 17 of the first clutch assembly may each be a single plate.

One exemplary construction of theactuator 10 is shown in fig. 2, wherein theactuator 10 is formed by a motor-driven ball screw mechanism, which basically comprises: anactuator housing 41 fixed to thetransmission housing 1; aball screw 43 rotatably mounted in theactuator housing 41 through abearing 42; alarge gear 45 mounted on oneend 44 of theball screw 43 extending outside theactuator housing 41; anactuator motor 46 that outputs a rotational motion; apinion 47 mounted on a motor shaft of theactuator motor 46 and engaged with thelarge gear 45; aball nut 48 fitted around theball screw 43 and axially movable along theball screw 43;balls 49 disposed between theball screw 43 and theball nut 48 to drive theball nut 48 to move axially when theball screw 43 rotates; aguide rod 50 fixed in theactuator housing 41 and passing through theball nut 48 to guide the axial movement of theball nut 48.

Theball nut 48 has aprotrusion 48a disposed on an outer periphery thereof, and theprotrusion 48a is received in a receiving groove in thefirst end 11a of theshift lever 11 such that thefirst end 11a of theshift lever 11 can pivot about theprotrusion 48a and can be moved axially by theprotrusion 48 a. Of course, it will be appreciated that other forms of pivotable engagement between theball nut 48 and thefirst end 11a of theshift lever 11 are possible.

Since the ball screw mechanism has a self-locking function, theactuator motor 46 can be de-energized after theactuator 10 brings the first clutch assembly into the disengaged state or the engaged state, thereby maintaining the first clutch assembly in the disengaged state or the engaged state by means of the self-locking function of the ball screw mechanism.

With respect to thetoggle lever 11, it will be appreciated that thesecond end 11b thereof may be fitted with aninsert 11c for hooking into a groove on theslider 13. Preferably, theshift lever 11 includes a bifurcated portion so as to create a pair ofsecond ends 11b located on both radial sides of theslider 13. The pair of second ends 11b each have aninsert 11c, the twoinserts 11c being hooked in diametrically opposite grooves in theslide 13, so that thedriver 11 can axially drive theslide 13 by means of the pair ofinserts 11 c.

It will also be appreciated that theshift lever 11 in the example shown is in the form of a lever pivoted about thepivot 12, so that the displacement of the two ends of theshift lever 11 can be made different, in particular the displacement of thesecond end 11b is greater than the displacement of thefirst end 11 a. However, it is also possible to design theshift lever 11 in an axially translating manner (i.e. not in a pivoting manner, with thepivot 12 eliminated), which is driven by theactuator 10 at thefirst end 11a to move theentire shift lever 11 axially instead of pivoting, also enabling the axial shifting of theslider 13 at thesecond end 11 b.

Other forms ofdial 11 that can be driven by theactuator 10 to axially dial theslider 13 may also be used in the transmission of the present application.

Further, with regard to theactuator 10, it is understood that it is disposed outside thetransmission case 1 in the illustrated example to facilitate the layout inside thetransmission case 1. However, theactuator 10 can also be arranged inside thetransmission housing 1, where the layout allows, which is particularly advantageous for the translation-type shifter lever 11 (with a short distance from theslider 13, for ease of operation).

With regard to theactuator 10, it will also be appreciated that in the illustrated example, which is an electric actuator with a motor providing a driving force, a ball screw is used as the motion conversion mechanism, enabling precise control of the stroke of theslider 13. However, it will be appreciated that other forms of electric actuators, including different types of motors and different types of motion conversion mechanisms, may be used with the transmission of the present application. For example, a worm gear mechanism may be used in place of the ball screw mechanism described above. As another example, the combination of the rotary-type motor 46 and the ball screw mechanism described above may simply be replaced with a linear motor; furthermore, even the linear motor can be arranged directly in thetransmission housing 1, if the space in thetransmission housing 1 permits, so that it directly drives theslider 13, without the aid of thedriver 11.

With regard to thedrive spring 15, it will be appreciated that in the illustrated example it is in the form of a disc spring, but other forms of compression spring may be employed in the transmission of the present application. It is even possible to use a tension spring for thedrive spring 15, based on the axial position of theslide 13 and the first clutch pack.

Returning to fig. 1, the second clutch device includes anelectric actuator 20 disposed outside thetransmission housing 1 on the side away from the axial direction of thedrive motor 2, which is controlled by the controller to drive ashift lever 21. Theshift lever 21 extends into thetransmission housing 1 and is pivotable about apivot 22 which is fixedly arranged in thetransmission housing 1, i.e. theshift lever 21 is in the form of a lever. Afirst end 21a of theshift lever 21 is driven by theactuator 10 to reciprocate in the axial direction of the transmission, and an oppositesecond end 21b of theshift lever 21 is movably connected to aslide 23, for example, hooked in a groove on theslide 23. Theslider 23 is fitted over asleeve 24 fixed in thetransmission case 1 around theoutput shaft 8, and is axially slidable along thesleeve 24. When thefirst end 21a of theshift lever 21 is driven by theactuator 20 to move axially, thesecond end 21b of theshift lever 21 drives theslider 23 to slide axially on thebushing 24. Theslide 23 is non-rotatable relative to thetransmission housing 1.

Theslider 23 is arranged in the axial direction on the side of the planetary gear train facing away from thedrive motor 2, and includes asleeve portion 23a surrounding theboss 24 and aflange portion 23b radially protruding from thesleeve portion 23a, theflange portion 23b facing the planetary gear train in the axial direction.

Thedrive sleeve 25 is arranged around theslide 23 and is rotatable and axially displaceable relative to theslide 23. Thedrive sleeve 25 includes: acylindrical portion 25a surrounding a part of thesleeve portion 23a of theslider 23, wherein theflange portion 23b faces an inner wall of thecylindrical portion 25 a; aninner flange 25b extending radially inward toward thesleeve portion 23a at an axial end of thecylindrical portion 25a facing away from the planetary gear train; anouter flange 25c extending radially outward at one end of thecylindrical portion 25a in the axial direction facing the planetary gear train.

Between thesleeve portion 23a and theflange portion 23b of theslider 23 and thecylindrical portion 25a and theinner flange 25b of thedrive sleeve 25, a substantially annular accommodation space is defined in which a substantiallyannular partition plate 26 is disposed. Thespacer 26 extends radially between thesleeve portion 23a and thecylindrical portion 25a, and between thespacer 26 and theflange portion 23b, a ring ofballs 27 is arranged so that thespacer 26 is rotatable relative to theslider 23. Between thespacing plate 26 and theinner flange 25b, areturn spring 28 is arranged for urging thespacing plate 26 toward the planetary gear train (i.e., toward theflange portion 23b) so that thespacing plate 26 is always urged axially against theflange portion 23b by means of theballs 27.

In the illustrated example, thereturn spring 28 is in the form of a disc spring, although other forms of compression springs or other resilient return elements may be used herein.

Adrive spring 29 is arranged between a fixed point relative to the ring gear 7 (for example, an axial extension of the ring gear 7 itself) and theouter flange 25c of thedrive sleeve 25 for axially biasing thedrive sleeve 25 towards the planetary gear train. In the example shown, thedrive spring 29 is in the form of a disc spring, but as with thedrive spring 15, other forms of compression springs, even tension springs, may be used herein.

Thedrive spring 29 is axially compressed between the region fixed relative to the ring gear 7 and theouter flange 25c of thedrive sleeve 25, and thereturn spring 28 is axially compressed between thespacer plate 26 and theinner flange 25b of thedrive sleeve 25, so that thedrive spring 29, thedrive sleeve 25, thereturn spring 28 and thespacer plate 26 are non-rotatable relative to the ring gear 7, but thedrive sleeve 25 and thespacer plate 26 are axially movable relative to the ring gear 7.

Furthermore, a second clutch assembly is provided between theoutput shaft 8 and the ring gear 7, which is a multi-disc clutch assembly, comprising a plurality offirst friction plates 30 axially movable relative to the ring gear 7 but non-rotatable relative to the ring gear 7 (i.e. thefirst friction plates 30 always rotate with the ring gear 7 when the ring gear 7 rotates) and a plurality ofsecond friction plates 31 arranged staggered axially opposite thefirst friction plates 30 and axially fixed relative to theoutput shaft 8. Theouter flange 25c of thedrive sleeve 25 faces axially toward the second clutch pack.

The second clutch assembly has a disengaged state and an engaged state for effecting disengagement and engagement between the ring gear 7 and the output shaft 8 (carrier 5). Specifically, theactuator 20 holds theslider 23 by means of theshift lever 21 in a position such that theouter flange 25c of thedrive sleeve 25 is axially spaced from the adjacentfirst friction plate 30, with both thereturn spring 28 and thedrive spring 29 axially compressed to their respective maximum compression states, the second clutch assembly being disengaged and the ring gear 7 being disengaged from the output shaft 8 (the carrier 5).

When theactuator 20 drives theslider 23 axially forward toward the second clutch assembly by means of theshift lever 21, thereturn spring 28 and thedrive spring 29 are both axially extended, thedrive sleeve 25 is moved toward the second clutch assembly under the action of thedrive spring 29 to contact thefirst friction plates 30 axially adjacent thereto, and thefirst friction plates 30 and thesecond friction plates 31 are pushed against each other, so that the second clutch assembly is shifted to the engaged state. At this time, the ring gear 7 is coupled to theoutput shaft 8 via thedrive spring 29, thedrive sleeve 25, and the second clutch assembly, that is, the ring gear 7 is coupled to thecarrier 5, so that the ring gear 7 and thecarrier 5 can rotate in synchronization.

It should be noted that the axial compression force in thereturn spring 28 is counteracting the spring force exerted by thedrive spring 29 on thefirst friction plate 30. To eliminate or reduce this counteracting effect as much as possible, after thefirst friction plate 30 has contacted thesecond friction plate 31, theactuator 20 can drive theslide 23 via theshift lever 21a short distance further toward the second clutch pack, so that the axial compression force in thereturn spring 28 is reduced to a small extent, so that thedrive spring 29 exerts as much spring force as possible on thefirst friction plate 30.

Thedrive spring 29 should have a sufficient spring rate to ensure that the ring gear 7 is locked to theplanet carrier 5 in the engaged state of the second clutch assembly. Furthermore, the spring rate of thereturn spring 28 is preferably lower than the spring rate of thedrive spring 29, so that the spring force of thedrive spring 29 is not counteracted by thereturn spring 28 so that thedrive spring 29 can apply a sufficiently large spring force to thefirst friction plates 30; at the same time, it is ensured that theslide 23 is not axially displaced into contact with the first friction lining 30 axially adjacent thereto when theactuator 20 drives theslide 23 axially towards the second clutch partner by means of theshift lever 21. To further prevent accidental contact between theslider 23 and thefirst friction plate 30, a radially inwardly extendingprojection 25d, such as an inner flange, may be provided at an axial end of thecylindrical portion 25a facing the planetary gear train.

In the engaged state of the second clutch partner, if it is intended to return to its disengaged state, theactuator 20 drives theslide 23 back in the direction away from the second clutch partner by means of thedriver 21, so that thereturn spring 28 is initially compressed axially. When the axial compression force in thereturn spring 28 becomes greater than the axial compression force of thedrive spring 29, thedrive spring 29 also begins to be compressed axially, causing thedrive sleeve 25 to be pulled away from thefirst friction plates 30. Thefirst friction plate 30 and/or thesecond friction plate 31 are equipped with a return mechanism, such as a return spring. When theshift lever 21 drives theslider 23 to move backward, the return mechanism returns thefirst friction plates 30 and thesecond friction plates 31 to their original positions and separates from each other, and the second clutch assembly returns to its disengaged state. Thus, the lock between the ring gear 7 and thecarrier 5 is released.

It will be appreciated that thefirst friction plate 30 and thesecond friction plate 31 of the second clutch assembly may also be a single plate.

It is noted that theactuator 20 has the same or similar structure as theactuator 10, and therefore, the various structures and modifications thereof described above with reference to theactuator 10 are equally applicable to theactuator 20, and the description of theactuator 20 will not be repeated here.

Likewise, theshift lever 21 has the same or similar structure as theshift lever 11, and therefore, the various structures and modifications thereof described above with reference to theshift lever 11 are also applicable to theshift lever 21, and a description of theshift lever 21 will not be repeated here.

Further, in the example of the second clutch device described above, thereturn spring 28, thepartition plate 26, and theballs 27 are employed to achieve relative axial movement and relative rotational movement between the rotatable portion (thedrive sleeve 25, etc.) and the non-rotatable portion (theslider 23, etc.) in the second clutch device. However, it is understood that the above-describedreturn spring 28,partition plate 26 andballs 27 may be eliminated in the second clutch device as long as relative rotation between the rotatable portion and the non-rotatable portion in the second clutch device is enabled.

For example, in an alternative embodiment shown in fig. 3, the second clutch device includes adrive sleeve 60 axially movable but not relatively rotatable with respect to the output shaft 8 (the carrier 5), aslider 61 fitted over thedrive sleeve 60, a ring ofballs 62 provided between thedrive sleeve 60 and theslider 61 so that thedrive sleeve 60 can rotate with respect to theslider 61, adrive spring 63 supported by thedrive sleeve 60 for urging thefirst friction plates 30 axially adjacent thereto so that thefirst friction plates 30 are engaged with and pressed against thesecond friction plates 31, and an axial end of thedrive spring 63 facing the second clutch assembly is provided with or formed with a pressure plate (not shown). In such an embodiment, theslider 61 is axially movable but non-rotatable relative to thetransmission housing 1, thedrive sleeve 60 is axially movable and rotatable relative to thetransmission housing 1, and thedrive sleeve 60 is rotatable relative to theslider 61 and axially movable with theslider 61. In this way, theactuator 20 drives theslider 61 via theshift lever 21, so that the second clutch assembly can be switched between its disengaged and engaged states.

Other forms of second clutch devices suitable for use in the transmission of the present application are also contemplated.

The combination of the disengaged state and the engaged state of the first and second clutch assemblies by the first and second clutch devices enables two gears of the transmission.

First, in the first gear state, the first clutch assembly is brought into or kept in an engaged state by the first clutch device, and the second clutch assembly is brought into or kept in a disengaged state by the second clutch device. At this time, the ring gear 7 is locked to thetransmission case 1 so as not to rotate, the sun gear 4, theplanetary gears 6, and thecarrier 5 rotate relative to each other, and the output motion of thedrive motor 2 is transmitted to the sun gear 4 through the motor shaft 3, transmitted to thecarrier 5 by the sun gear 4 via theplanetary gears 6 rotating between the ring gear 7 and the sun gear 4, and transmitted from the transmission output to the differential gear 9 through theoutput shaft 8 connected to thecarrier 5. At this time, the speed ratio between the motor shaft 3 and theoutput shaft 8 is greater than 1.

If the first gear is required to be switched to the second gear, the first clutch device can be controlled to act to enable the first clutch assembly to return to the separation state, and the second clutch device can be controlled to act to enable the second clutch assembly to reach the engagement state. At this time, the ring gear 7 is locked to thecarrier 5, so that the sun gear 4, thecarrier 5, the pinion gears 6, and the ring gear 7 cannot rotate relative to each other, the entire planetary gear train is formed as a locked unit, and the output motion of thedrive motor 2 is transmitted to the differential 9 through the motor shaft 3 directly via the sun gear 4 and thecarrier 5 from theoutput shaft 8 from the transmission. At this time, the speed ratio between the motor shaft 3 and theoutput shaft 8 is 1.

The two-speed transmission of the present application is essentially an AMT that locks a ring gear of a planetary gear train in the transmission to a transmission housing or a carrier by operation of a first clutch device and a second clutch device to realize two speeds of the transmission. The first clutch device and the second clutch device are both used for realizing the engagement of the clutch assembly through the spring force of the driving spring. The spring force exerted by the drive spring on the clutch pack is gradually increased, so that no component impact occurs during shifting.

In addition, first clutch and the second clutch of this application have all adopted electric actuator, realize first clutch and second clutch's coordinated control easily, compare with the traditional AMT that adopts hydraulic actuator or the electric actuator of other forms to realize shifting gears, shift the loss little, keep away the power of shifting gears interrupt more easily, the process of shifting gears more smoothly, and the efficiency of whole derailleur can improve.

In addition, compared with the traditional DCT, the transmission has the advantages of simpler structure, lower cost and easier market acceptance.

Although the present application has been described herein with reference to particular embodiments, the scope of the present application is not intended to be limited to the details shown. Various modifications may be made to these details without departing from the underlying principles of the application.

Claims (10)

1. A two speed transmission for an electric vehicle comprising:

a planetary gear train including a sun gear (4) rotatable about a central axis, a ring gear (7) coaxially arranged around the sun gear, at least one planetary gear (6) engaged between the sun gear and the ring gear, and a carrier (5) carrying the at least one planetary gear and rotatable about the central axis of the sun gear, the sun gear being connected to a drive motor of an electric vehicle, rotational motion of the drive motor being output through the carrier;

a first clutch device including a first electric actuator (10) and a first clutch assembly (16, 17) axially driven by the first electric actuator via a first drive spring (15) into an engaged state in which the ring gear is locked against rotation via the first clutch assembly; the first clutch device further comprises a first slider (13) which is driven by a first electric actuator to move axially but not rotate, the first drive spring being mounted on the first slider; and

a second clutch device including a second electric actuator (20) and a second clutch assembly (30, 31) axially driven by the second electric actuator via a second drive spring (29) into an engaged state in which the ring gear is coupled to the carrier via the second clutch assembly; the second clutch device further includes: a second slide (23) which is axially movable but not rotatable by a second electric actuator; and a drive sleeve (25) arranged around the second slider and axially movable and rotatable, the drive sleeve being urged by the second drive spring in a direction towards the second clutch pack.

2. The two speed transmission of claim 1, wherein the first and second clutch assemblies each include a first friction plate adapted to be axially biased by the respective first or second drive spring and a second friction plate disposed opposite the first friction plate and adapted to be axially compressed by the first friction plate.

3. The two speed transmission of claim 1, wherein the first and second electric actuators each include an actuator motor (46) and a motion conversion mechanism that converts rotary motion output by the actuator motor into linear motion.

4. A two speed transmission according to claim 3, wherein the motion conversion mechanism is a ball screw mechanism comprising a ball screw (43) driven by the actuator motor and a ball nut (48) arranged around the ball screw and axially movable along the ball screw.

5. The two speed transmission according to claim 4, wherein the ball nut drives the first or second drive spring via a shift lever (11), which is a lever pivoted about a pivot axis.

6. Two-speed transmission according to claim 1, wherein a spacer plate (26) is arranged between the second slide and the drive sleeve, a ring of balls (27) being arranged between the spacer plate and the second slide, and a return spring (28) being arranged between the spacer plate and the drive sleeve, the return spring on the one hand urging the drive sleeve in a direction away from the second clutch pack and on the other hand urging the second slide via the spacer plate and the ring of balls in a direction towards the second clutch pack.

7. A two speed transmission according to any one of claims 1 to 6 wherein the first and second clutch assemblies each also have a disengaged condition, the first and second electric actuators having a self locking function whereby when the first or second clutch assembly is in its engaged or disengaged condition the respective first or second electric actuator is de-energised to maintain the engaged or disengaged condition of the first or second clutch assembly by the self locking function.

8. The two speed transmission of claim 7, wherein when the first clutch assembly is in an engaged state and the second clutch assembly is in a disengaged state, the transmission is in first gear; the transmission is in second gear when the first clutch assembly is in the disengaged state and the second clutch assembly is in the engaged state.

9. A two speed transmission according to any one of claims 1 to 6 further comprising a transmission housing, the first and second electric actuators being mounted on the transmission housing.

10. The two speed transmission of any one of claims 1 to 6, wherein the first and second drive springs are each disc springs.

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