JP2018179012A - Transmission device for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a period of torque interruption while suppressing drop in transmission torque by torque interruption during switching of shift stages, in a transmission device for electric vehicle with a synchro mechanism.SOLUTION: A transmission device 10 is used for an electric vehicle driven by an electric motor EM. The transmission device 10 includes: an input shaft 1 in which power is inputted from the electric motor EM; an output shaft 2 arranged in parallel with the input shaft 1; a main transmission unit 3; and a transmission assist unit 4. The main transmission unit 3 includes a low speed side shift stage 3L and a high speed side shift stage 3H, and a synchro mechanism 8 for performing switching between these shift stages 3L, 3H, and it changes the rotational speed inputted in the input shaft 1 and transmits it to the output shaft 2. The transmission assist unit 4 has a transmission ratio smaller than the high speed side shift stage 3H, and transmits power from the input shaft 1 to the output shaft 2 when switching the shift stages of the main transmission unit 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a transmission used in an electric vehicle driven by an electric motor.

  Generally, in an electrically powered vehicle using a motor as a power source, a reduction gear is provided which decelerates the rotation of the motor and transmits it to the output side.

  Here, there is a need to travel (work) at a low speed and with a large torque in a powered SUV, that is, a SUEV (Suports Utility Electric Vehicle) or a light cargo electric powered vehicle. In such a case, the demand can not be met by merely providing the reduction gear. Therefore, a transmission is also required for an electric vehicle.

  It is shown by FIG. 2 of patent document 1 that a transmission is provided in the vehicle drive device provided with the electric motor as a driving force source for driving | running | working. The transmission of this patent document 1 is arrange | positioned between the one end part with the one end part of the output rotation member of an electric motor, and a front wheel. The transmission has a shift input shaft and a shift output shaft, and can change the transmission ratio between the shift input shaft and the shift output shaft. Specifically, the transmission is a two-speed automatic transmission, and can be switched between a first speed on the low speed side and a second speed on the high speed side.

Re-issued patent WO2013 / 042211 published gazette

  In a transmission for an electric vehicle, in order to simplify the configuration, it is conceivable to switch gears by using a dog clutch having a synchro mechanism. However, in a transmission using a dog clutch, torque interruption (breaking of torque transmission: so-called “torque loss”) occurs at the time of gear position switching.

  For example, in a SUEV or electric vehicle for light cargo, if torque interruption occurs under a load such as towing, the vehicle may stop and it may not be possible to restart the vehicle, or a large hesitation (at the time of restart) In some cases, the travelability may deteriorate due to a delay.

  SUMMARY OF THE INVENTION It is an object of the present invention to suppress torque interruption at the time of gear change, and to shorten the torque interruption period as much as possible, particularly in a transmission for an electric vehicle with a synchronization mechanism.

  (1) The transmission according to the present invention is used for an electric vehicle driven by an electric motor. The transmission includes a first shaft to which power is input from the electric motor, a second shaft disposed parallel to the first shaft, a main transmission unit, and a transmission assist unit. The main transmission unit has a plurality of shift speeds and at least one synchro mechanism for switching among the shift speeds, and changes the rotational speed input to the first axis to shift the second axis To communicate. The shift assist unit transmits power from the first shaft to the second shaft when switching the shift position of the main shift unit.

  When power is input from the electric motor to the first shaft, the power is transmitted to the second shaft via any shift speed of the main transmission unit. At this time, the rotational speed is changed by the shift speed. When the gear is switched, power is transmitted from the first shaft to the second shaft by the shift assist unit.

  Here, since power is transmitted through the shift assist unit at the time of gear shift switching in the main transmission unit, the reduction of the transmission torque due to torque interruption and the torque interruption period are shortened at gear shift switching. be able to.

  (2) Preferably, the shift assist unit transmits power from the first axis to the second axis in place of the main shift unit when switching the shift position of the main shift unit.

  Here, in the case where power is transmitted by the shift assist unit, if the power transmission is performed also in the shift gear on the main shift unit side, it is difficult for the synchro mechanism to be released from the shift that is transmitting power. Specifically, the synchronizer ring that constitutes the synchronization mechanism does not easily separate from the dog clutch portion of the power transmitting gear.

  Therefore, at the time of switching of the gear position of the main transmission unit, power transmission is not performed on the main transmission unit side, and the synchronization mechanism portion is synchronized by transmitting power only by the shift assist unit. For this reason, the synchro mechanism operates smoothly, and a smooth shift can be performed.

  (3) Preferably, the gear shift assist unit has a gear ratio smaller than the highest gear position with the smallest gear ratio among the plurality of gear positions of the main transmission unit.

  With such a configuration, when the shift assist unit is operated at the time of switching the shift position, power is always transmitted via the shift assist unit. Therefore, as described above, a smooth shift is possible.

  (4) Preferably, the shift assist unit has a first gear and a second gear for assist, a clutch input member, and a clutch portion. The first assist gear is rotatably supported by the first shaft. The assist input member is non-rotatably supported by the first shaft. The clutch portion performs transmission and disconnection of power between the first assist gear and the assist input member. The second assist gear is non-rotatably supported by the second shaft and meshes with the first assist gear.

  In this device, when the clutch unit is in the power transmission state, the power is transmitted in the path of the first axis → assist input member → first assist gear → second assist gear → second axis.

  Here, since the clutch portion constituting the shift assist unit is disposed on the first shaft, the clutch capacity can be reduced as compared with the case where the clutch portion is disposed on the second shaft on the output side. The assist unit can be made compact.

  (5) Preferably, the clutch portion has a plurality of clutch plates and a piston for pressing the plurality of clutch plates together.

  (6) Preferably, the main transmission unit has a first gear and a second gear for low speed, and a first gear and a second gear for high speed. The low speed first gear is rotatably supported on the first shaft. The low speed second gear is non-rotatably supported on the second shaft and meshes with the low speed first gear. The high speed first gear is rotatably supported on the first shaft. The second high speed gear is non-rotatably supported on the second shaft and meshes with the first high speed gear. Then, the synchro mechanism selectively connects either the low speed first gear or the high speed first gear to the first axis in the first axis. Also, the shift assist unit has a transmission gear ratio smaller than the transmission gear ratios of the first and second high-speed gears.

  Here, the main transmission unit has two shift speeds. In the low-speed gear, the power input to the first shaft is transmitted along the path of the first shaft → synchro mechanism → first gear for low speed → second gear for low speed → second axis. In the high-speed gear, the power input to the first shaft is transmitted along the path of the first shaft → synchro mechanism → first gear for high speed → second gear for high speed → second axis.

  And since the gear shift assist unit has a gear ratio smaller than the gear ratio of the high gear, the gear shift assist unit is operated when switching the gear, for example, the fastening force of the clutch portion provided in the gear shift unit The power is transmitted in a direction dependent on the shift assist unit, and the degree of dependence on the shift assist unit gradually increases. Then, with the increase of the transmission torque on the side of the shift assist unit, the transmission torque by the synchronization mechanism is reduced to be substantially "0", so that the smooth gear change becomes possible as described above.

  (7) Preferably, the shift assist unit transmits power from the first shaft to the second shaft before the start of switching of the shift position of the main shift unit.

  As a result, it is possible to further shorten the duration of the transmission torque drop due to torque interruption and the torque interruption.

  According to the present invention as described above, in the transmission for an electric vehicle with a synchronization mechanism, the torque interruption itself at the time of switching of the shift can be reduced and, at the same time, the torque interruption period can be shortened as much as possible. Further, in the case where the shift assist unit is provided to shorten the period of torque interruption, it is possible to prevent the problem that the shift gear can not be smoothly switched.

FIG. 1 is a schematic view showing a configuration of a transmission according to an embodiment of the present invention. FIG. 7 is a diagram showing a power transmission path of a low speed gear. FIG. 2 is a diagram showing a power transmission path of a high-speed gear. Flow chart at gear shift switching. FIG. 7 is a diagram showing a power transmission path at the time of gear shift switching.

[overall structure]
FIG. 1 shows a schematic configuration of a transmission 10 for an electric vehicle according to an embodiment of the present invention. The transmission 10 has two shift speeds, and shifts the rotational speed of the motor EM and outputs it to an axle.

  The transmission 10 includes an input shaft (first shaft) 1, an output shaft (second shaft) 2, a main transmission unit 3, and a transmission assist unit 4. The transmission 10 also has a final gear GF and a differential gear 5.

[Input axis 1]
The input shaft 1 is rotatably supported by a transmission case (not shown). The input shaft 1 is connected to the output shaft of the motor EM, and the power of the motor EM is directly input to the input shaft 1.

[Output axis 2]
The output shaft 2 is disposed parallel to the input shaft 1 and rotatably supported by a transmission case (not shown).

[Main transmission unit 3]
As described above, the main transmission unit 3 can perform two-speed shifting, and includes a low speed gear 3L, a high speed gear 3H, and a synchro mechanism 8. The low speed gear 3L is disposed on the motor EM side, and the high speed transmission 3H is disposed on the side away from the motor EM. Further, the synchronization mechanism 8 is disposed on the input shaft 1 axially between the low speed gear 3L and the high speed gear 3H.

  The low speed gear stage 3L has a low speed input gear (first low speed gear) GLi and an output gear (second low speed gear) GLo. The low speed input gear GLi is rotatably supported by the input shaft 1. The low speed output gear GLo is non-rotatably supported by the output shaft 2 and is constantly meshed with the low speed input gear GLi.

  The high-speed gear stage 3H has an input gear (first gear for high speed) GHi for high speed and an output gear (second gear for high speed) GHo. The high speed input gear GHi is rotatably supported by the input shaft 1. The high speed input gear GHi is disposed opposite to the low speed input gear GLi on the opposite side of the low speed input gear GLi to the electric motor EM. The high speed output gear GHo is non-rotatably supported by the output shaft 2 and is constantly meshed with the high speed input gear GHi.

  The synchronization mechanism 8 is disposed on the input shaft 1 as described above. The synchronization mechanism 8 is the same as a known structure including a synchronizer ring, a sleeve and the like, and the detailed description will be omitted here. The synchronization mechanism 8 is disposed axially between the low speed input gear GLi and the high speed input gear GHi, and selectively connects one of the low speed input gear GLi and the high speed input gear GHi to the input shaft 1, Also release the connection.

[Shift Assist Unit 4]
The shift assist unit 4 is disposed on the opposite side to the low speed gear 3L across the high speed gear 3H. The shift assist unit 4 transmits power from the input shaft 1 to the output shaft 2 when switching the shift position of the main shift unit 3. That is, the shift assist unit 4 transmits power from the input shaft 1 to the output shaft 2 instead of the main shift unit 3 when switching the shift position of the main shift unit 3.

  Specifically, the shift assist unit 4 includes an assist input gear (first assist gear) GAi, a clutch housing (assist input member) 12, a clutch portion 13, and an assist output gear (second assist). Gear) GAo, and.

  The assist input gear GAi is disposed on the input shaft 1 on the opposite side of the low speed input gear GLi across the high speed input gear GHi, and is rotatably supported on the input shaft 1.

  The clutch housing 12 is disposed on the opposite side of the high speed input gear GHi across the assist input gear GAi. The clutch housing 12 is formed in a tubular shape in which one end side (the assist input gear GAi side) opens. An inner peripheral portion on the other end side of the clutch housing 12 is fixed to the input shaft 1. That is, the clutch housing 12 can not rotate with respect to the input shaft 1.

  The clutch portion 13 is accommodated inside the clutch housing 12. The clutch unit 13 performs transmission and disconnection of power between the clutch housing 12 and the assist input gear GAi. The clutch portion 13 has a plurality of clutch plates 15 and a piston 16 for pressing the plurality of clutch plates 15 into contact with each other. The plurality of clutch plates 15 have a first clutch plate engaged non-rotatably with the clutch housing 12 and a second clutch plate engaged non-rotatably with the assist input gear GAi. The piston 16 is axially movable by hydraulic pressure.

  The assist output gear GAo is non-rotatably supported by the output shaft 2 and is constantly meshed with the assist input gear GAi.

[Final gear GF and differential gear 5]
The final gear GF is non-rotatably supported by the input shaft 18 of the differential gear 5, and is always meshed with the assist output gear GAo.

[Gear ratio]
In main transmission unit 3, gear ratio Rh of high speed gear 3H (number of teeth of high speed output gear GHo / number of teeth of high speed input gear GHi) is gear ratio R1 of low speed gear 3L (output for low speed) Number of teeth of gear GLo / number of teeth of input gear GLi for low speed)). Further, the gear ratio Ra (the number of teeth of the assist output gear GAo / the number of teeth of the assist input gear GAi) of the gear shift assist unit 4 is set to be smaller than the gear ratio Rh of the high speed gear 3H. For example, it is preferable to set the ratio (Ra / Rh) of the gear ratio Ra of the shift assist unit 4 to the gear ratio Rh of the high-speed gear 3H in the range of 1.2> (Ra / Rh)> 1.0 .

[Operation in each gear]
<Low speed gear 3L>
When traveling at the low speed gear 3 L, the low speed input gear GLi is connected to the input shaft 1 by the operation of the synchronization mechanism 8. In this case, the clutch unit 13 of the shift assist unit 4 is off (in a state where power transmission is canceled).

  When low speed gear 3L is selected, as shown in FIG. 2, the power from motor EM is input shaft 1 → synchro mechanism 8 → input gear GLi for low speed → output gear GLo for low speed → output shaft 2 → The power is transmitted to the axle along the path of assist output gear GAo → final gear GF → differential gear 5.

<High-speed gear 3H>
When traveling at the high speed gear, the high speed input gear GHi is connected to the input shaft 1 by the operation of the synchronization mechanism 8. In this case, the clutch unit 13 of the shift assist unit 4 is off (in a state where power transmission is canceled).

  When high speed gear 3H is selected, as shown in FIG. 3, the power from motor EM is input shaft 1 → synchro mechanism 8 → high speed input gear GHi → high speed output gear GHo → output axis 2 → The power is transmitted to the axle along the path of assist output gear GAo → final gear GF → differential gear 5.

[At shift]
When switching between the low speed gear 3L and the high speed gear 3H, as shown in the flowchart of FIG. 4, first, in step S1, the clutch 13 of the shift assist unit 4 is turned on (power transmission state ).

  Here, since the transmission ratio of the shift assist unit 4 is set smaller than the transmission ratios of the low speed gear 3L and the high speed gear 3H, the power from the electric motor EM is output via the transmission assist unit 4 Transmitted to That is, since the gear ratio of the shift assist unit 4 is set to be smaller than the gear ratios of the low speed gear 3L and the high speed gear 3H, the power is obtained by either the low speed gear 3L or the high speed gear 3H. Even in the state of being transmitted, when the clutch unit 13 of the shift assist unit 4 is turned on, the output shaft 2 will rotate at a higher rotational speed. Therefore, the power from the electric motor EM is transmitted to the output side only by the shift assist unit 4.

  The above operation will be described with step S2 and step S3.

  In step S2, the synchro mechanism 8 is operated, and the low-speed input gear GLi (or high-speed input gear GHi) previously connected to the input shaft 1 is replaced with the reverse high-speed input gear GHi (or low-speed input gear). Switch to GLi). That is, in step S2, an extraction force is applied to the sleeve of the synchronization mechanism 8. Then, in step S3, it is detected whether or not the synchronization mechanism 8 has been released (whether the connection of the low speed input gear GLi to the input shaft 1 has been released).

  At this time, when the clutch unit 13 is turned on and the fastening force of the clutch unit 13 is increased, the power is transmitted in the direction dependent on the shift assist unit 4 and the degree of dependency on the shift assist unit 4 gradually increases. Then, with the increase of the transmission torque on the side of the shift assist unit 4, the transmission torque by the synchronization mechanism 8 is reduced to almost “0”. For this reason, in the state where the hub and the sleeve are engaged in the synchronization mechanism 8, these engagements can be released.

  If it is determined in step S3 that the synchronization mechanism 8 has been released, the process proceeds from step S3 to step S4. In step S4, the transmission torque of the clutch unit 13 and the output torque of the motor EM are controlled to synchronize the input and output rotational speeds of the synchronization mechanism 8. That is, the transmission torque of the clutch unit 13 and the output torque of the electric motor EM are controlled so that the rotation speed of the input shaft 1 and the rotation speed of the high speed input gear GHi (or the low speed input gear GLi) are substantially synchronized.

  When the clutch unit 13 of the shift assist unit 4 is on at the time of the above gear shift switching, as shown in FIG. 5, the power from the motor EM is input shaft 1 → clutch housing 12 → clutch portion 13 → assist It is transmitted to the axle along the path of: input gear GAi → assist output gear GAo → final gear GF → differential gear 5

  Then, step S4 is executed until the input / output rotational speeds of the synchronization mechanism 8 are synchronized. If the input and output rotational speeds of the synchronization mechanism 8 are synchronized, the process proceeds from step S5 to step S6.

  In step S6, the synchro mechanism 8 is operated, and the high speed input gear GHi (or the low speed input gear GLi) is connected to the input shaft 1.

  If it is determined in step S7 that the engagement by the synchronization mechanism 8 is completed, that is, the connection of the high speed input gear GHi (or the low speed input gear GLi) to the input shaft 1 is completed, the process proceeds from step S7 to step S8. In step S8, the clutch unit 13 of the shift assist unit 4 is turned off. Thereby, the motive power from the electric motor EM is transmitted to the output side via the high-speed gear stage 3H (or the low-speed gear stage 3L).

  Since the power from the electric motor EM is transmitted to the output side by the shift assist unit 4 at the time of the change of the gear position as described above, the torque is not lost. Further, at the time of the switching operation of the synchronizing mechanism 8, since no torque is acting on the synchronizing mechanism 8, the synchronizing mechanism 8 can be operated smoothly.

[Other embodiments]
The present invention is not limited to the embodiments as described above, and various changes or modifications are possible without departing from the scope of the present invention.

  (A) In the above embodiment, the present invention is applied to a transmission having two shift speeds, but the present invention can be similarly applied to a transmission having three or more shift speeds.

  (B) The configuration of the shift assist unit 4 is an example, and various changes can be made.

  (C) In the above embodiment, the present invention is applied to a transmission having two shafts. However, for example, a counter shaft is provided between the output shaft and the final gear, and a gear set is provided on the counter shaft The invention is equally applicable to transmissions having.

  (D) The arrangement of the gears is not limited to the above embodiment.

Reference Signs List 1 input shaft 2 output shaft 3 main transmission unit 4 transmission assist unit 8 synchronization mechanism 10 transmission 12 clutch housing (input member for assist)
13 clutch part 15 clutch plate 16 piston GLi input gear for low speed (first gear for low speed)
GLo Low Speed Output Gear (Low Speed Second Gear)
GHi High-speed input gear (1st gear for high-speed)
GHo High Speed Output Gear (High Speed Second Gear)
GAi Assist Input Gear (First Gear for Assist)
Output gear for GAo assist (second gear for assist)

Claims (7)

A transmission used for an electric vehicle driven by an electric motor, comprising:
A first shaft to which power is input from the motor;
A second axis arranged parallel to the first axis;
A plurality of shift speeds and at least one synchro mechanism for switching among the shift speeds, and transmitting the rotation speed input to the first shaft to the second shaft The main transmission unit to
A shift assist unit that transmits power from the first shaft to the second shaft at the time of switching the shift position of the main transmission unit;
Transmission for an electrically powered vehicle comprising:   The transmission for an electric vehicle according to claim 1, wherein the shift assist unit transmits power from the first shaft to the second shaft instead of the main shift unit when switching the shift position of the main shift unit.   The transmission for an electric vehicle according to claim 2, wherein the shift assist unit has a gear ratio smaller than a highest gear position with the smallest gear ratio among the plurality of gear positions of the main transmission unit. The shift assist unit is
A first assist gear rotatably supported on the first shaft;
An assist input member supported non-rotatably on the first shaft;
A clutch unit for transmitting and disconnecting power between the first assist gear and the assist input member;
An assist second gear which is non-rotatably supported by the second shaft and meshes with the first assist gear;
Have
The transmission for an electric vehicle according to claim 3. The clutch unit is
With multiple clutch plates,
A piston for pressing the plurality of clutch plates together;
Have
The transmission for an electric vehicle according to claim 4. The main transmission unit is
A low speed first gear rotatably supported on the first shaft;
A second gear for low speed which is non-rotatably supported by the second shaft and engaged with the first gear for low speed;
A high speed first gear rotatably supported on the first shaft;
A second gear for high speed which is non-rotatably supported by the second shaft and engaged with the first gear for high speed;
Have
The synchro mechanism is disposed between the first low speed gear and the high speed first gear on the first shaft, and one of the low speed first gear and the high speed first gear is disposed on the first shaft. Selectively linked to
The shift assist unit has a gear ratio smaller than that of the first gear for high speed and the second high gear.
The transmission for an electric vehicle according to any one of claims 1 to 5.   The transmission for an electric vehicle according to any one of claims 1 to 6, wherein the shift assist unit transmits power from the first shaft to the second shaft before start of switching of the shift position of the main shift unit.

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