Dual-motor electric transmission and control method

Abstract

This invention relates to a dual-motor electric transmission for electric vehicles and a control method for the dual-motor electric transmission. The transmission includes a first motor and a second motor for driving the vehicle, a first gear arrangement, a second gear arrangement, and a manifold. The first gear arrangement includes a first gear arrangement first shaft and at least one first gear and a second gear. Each of the first and second gears can selectively engage and disengage from the first gear arrangement first shaft via a first clutch element and a second clutch element. The first gear arrangement is configured to supply a first torque from the first motor to the manifold via one of the first and second gears. The second gear arrangement includes a second gear arrangement first shaft and at least one second gear arrangement first gear. The second gear arrangement first gear can engage and disengage from the second gear arrangement first shaft via a second gear arrangement first clutch element. The second gear arrangement is configured to supply a second torque from the second motor to the manifold.

Description

Technical Field

[0001] This invention relates to a dual-motor electric transmission for electric vehicles and a control method for controlling the dual-motor electric transmission. Background Technology

[0002] A primary goal in improving the drive unit of electric vehicles is to increase the efficiency of the electric transmission. For the electric motor to operate at optimal efficiency, multiple gear ratios are needed to output to the transmission. Power shifting is also required for optimal performance. Power shifting enables gear changes (gear shifting) without reducing output torque. Especially in off-highway markets or other high-performance applications, power shifting and functional safety design are crucial. Summary of the Invention

[0003] Therefore, the object of the present invention is to provide a dual-motor electric transmission with improved efficiency and functional safety design.

[0004] This objective is achieved by a dual-motor electric transmission device according to independent claim 1 and a control method for the dual-motor electric transmission device according to claim 10. Advantageous embodiments of the dual-motor electric transmission device are mentioned in the dependent claims.

[0005] The dual-motor electric transmission for electric vehicles according to the present invention includes: a first electric motor and a second electric motor for driving the vehicle, a first gear arrangement, a second gear arrangement, and a consolidation box, wherein the first gear arrangement includes a first gear arrangement first shaft and at least one first gear and a second gear, wherein each of the first gear and the second gear is selectively engaged and disengaged from the first gear arrangement first shaft via a first clutch element or a second clutch element, and the first gear arrangement is configured to supply a first torque from the first electric motor to the consolidation box via one of the first gear and the second gear; the second gear arrangement includes a second gear arrangement first shaft and at least one second gear arrangement first gear, wherein the second gear arrangement first gear is engageable and disengaged from the second gear arrangement first shaft via a second gear arrangement first clutch element, and the second gear arrangement is configured to supply a second torque from the second electric motor to the consolidation box; and the consolidation box is configured to combine the first torque and the second torque and to output a combined output torque.

[0006] By having two electric motors on the input side and a combined output torque on the output side of the transmission, the first and second electric motors can be driven substantially independently of each other and according to the separately connected gear arrangements, thereby maximizing the efficiency of the dual-motor electric transmission. Furthermore, the transmission according to the invention is capable of power switching, meaning that the combined output torque can be maintained during gear switching (shifting).

[0007] According to the simplest configuration of the invention, the second gear arrangement can be either direct drive or a single constant gear ratio.

[0008] According to an advantageous embodiment of the present invention, the first gear arrangement may further include a first gear arrangement second shaft and a first gear arrangement fixed gear set, wherein the first gear arrangement first shaft is connected to the first gear arrangement second shaft via the first gear arrangement fixed gear set.

[0009] According to another advantageous embodiment, the second gear arrangement may further include a second gear arrangement second gear, which can engage or disengage from the first shaft of the second gear arrangement via a second clutch element of the second gear arrangement.

[0010] According to another advantageous embodiment, the second gear arrangement may further include a second gear arrangement second shaft and a second gear arrangement fixed gear set, wherein the second gear arrangement first shaft is connected to the second gear arrangement second shaft via the second gear arrangement fixed gear set.

[0011] According to another advantageous embodiment, the second gear arrangement may further include a second gear arrangement second shaft and at least two additional gears fixedly engaged with the second gear arrangement second shaft, wherein one of the two additional gears meshes with a first gear of the second gear arrangement on the first shaft of the second gear arrangement, and the other of the two additional gears is connected to a collection box.

[0012] According to another advantageous embodiment, the clutch element may be spring-loaded and / or automatically disengaged in the event of loss of actuation. This makes the mechanical system of the transmission functionally safe, meaning that no power can be transmitted from the electric motor to the wheels unless the clutches of the first and second gear arrangements are hydraulically, electrically, or otherwise activated.

[0013] According to another advantageous embodiment, the clutch element may include a toothed clutch or a synchronizing clutch, or may consist of a toothed clutch or a synchronizing clutch.

[0014] According to another advantageous embodiment, the second motor can be connected to the power take-off and / or the charging pump. In particular, the second motor can be selectively disconnected from the collection box so as to power only the power take-off and / or the charging pump.

[0015] According to another advantageous embodiment, the combined output torque can be output to the front output yoke (fork) and / or the rear output yoke (fork).

[0016] According to another advantageous embodiment, a third gear arrangement may be added between the summing box and the rear and front output yokes. This third gear arrangement may include two gear sets that can engage and disengage via a first and a second clutch element of the third gear arrangement. These clutch elements may consist of or be configured as wet clutches. Wet clutches enable power switching.

[0017] According to another advantageous embodiment, an inter-axle differential may be arranged between the front output yoke and the rear output yoke, optionally including a locking function and / or a disengagement clutch to disengage the front output yoke from the rear output yoke or vice versa. Alternatively, the front output yoke and the rear output yoke are rigidly connected or otherwise connected.

[0018] According to another advantageous embodiment, the dual-motor electric transmission may include a first control unit adapted to control a second motor to provide an increased second torque during gear switching of the first gear arrangement, such that the combined output torque remains substantially constant during gear switching.

[0019] According to another advantageous embodiment, the dual-motor electric transmission may include a second control unit adapted to control the first motor to provide an increased first torque during gear switching of the second gear arrangement, such that the combined output torque remains substantially constant during gear switching.

[0020] The first control unit and the second control unit can be parts of a common control unit, or they can be separate components and / or connected to the main control unit. The first control unit and the second control unit can be inverter control units and can be adapted to control the first motor and the second motor respectively to achieve the speed-torque setpoint provided by the main control unit.

[0021] According to another advantageous embodiment, the increased first torque or second torque may be the peak torque of the first motor or the second motor, wherein the peak torque may be approximately twice the continuous torque of the first motor or the second motor.

[0022] The present invention also includes a control method for controlling a dual-motor electric transmission as described above to perform gear switching from a first gear to a second gear in a first gear arrangement. The control method includes: controlling a second motor to synchronize with a first gear in the second gear arrangement; controlling a first clutch element in the second gear arrangement to engage with a first shaft in the second gear arrangement; controlling the first motor to reduce a first torque to zero and simultaneously controlling the second motor to increase a second torque, such that the engaged output torque is substantially constant; controlling the first clutch element to disengage from the first shaft in the first gear arrangement; controlling the first motor to synchronize with the second gear in the first gear arrangement; controlling the second clutch element to engage with the first shaft in the first gear arrangement; controlling the second motor to reduce the second torque and simultaneously controlling the first motor to increase the first torque, such that the engaged output torque is substantially constant.

[0023] According to an advantageous embodiment of the above control method, if the first gear (gear) is lower than the second gear (gear), the gear switching process in the first gear arrangement can be an upshifting process.

[0024] According to another advantageous embodiment of the above control method, if the first gear (gear) is higher than the second gear (gear), the gear switching process in the first gear arrangement can be a downshifting process.

[0025] The present invention also includes a dual-motor electric transmission for controlling a second gear arrangement having at least two gears as described above, to perform gear switching from a first gear to a second gear in the second gear arrangement, the control method comprising: controlling a first motor to synchronize with a first gear of the first gear arrangement; controlling a first clutch element to engage with a first shaft of the first gear arrangement; controlling a second motor to reduce a second torque to zero and simultaneously controlling the first motor to increase a first torque such that the engaged output torque is substantially constant; controlling the first clutch element to disengage from the first shaft of the second gear arrangement; controlling the second motor to synchronize with a second gear of the second gear arrangement; controlling a second clutch element of the second gear arrangement to engage with the first shaft of the second gear arrangement; controlling the first motor to reduce the first torque and simultaneously controlling the second motor to increase the second torque such that the engaged output torque is substantially constant.

[0026] According to an advantageous embodiment of the above control method, if the first gear (gear) of the second gear arrangement is lower than the second gear (gear) of the second gear arrangement, then the gear switching process in the second gear arrangement can be an upshifting process.

[0027] According to another advantageous embodiment of the present invention, if the second gear arrangement of the first gear (gear) is higher than the second gear arrangement of the second gear (gear), then the gear switching process in the second gear arrangement can be a downshifting process.

[0028] The advantage of the control method according to the invention is that the output torque is a continuous curve without a drop in the torque curve. Although the first gear arrangement is the simplest construction, a two-speed gear arrangement with a toothed clutch, the output torque will be maintained during gear shifts. This is achieved by increasing the torque of one electric motor while another electric motor synchronizes the open toothed clutch at zero power. For full power switching, an electric motor can be selected where the peak power during gear shifts is at least twice the continuous power. Power switching is required for many high-performance applications, such as off-highway applications. However, electric power systems require high efficiency to reduce energy storage, such as battery size. Therefore, a highly efficient toothed clutch is preferred. Attached Figure Description

[0029] In the following description, some preferred embodiments of the dual-motor electric transmission and control method according to the present invention are described in more detail with reference to the accompanying drawings. The described features are conceivable not only in combinations of the disclosed embodiments but also in specific embodiments independent of various other combinations.

[0030] Figure 1 The transmission layout according to a first embodiment of the present invention is schematically shown.

[0031] Figure 2 The transmission layout according to a second embodiment of the present invention is schematically shown.

[0032] Figure 3 The transmission layout according to a third embodiment of the present invention is schematically shown.

[0033] Figure 4 The diagram shows the transmission output torque curves for different transmission output speeds, and...

[0034] Figure 5 The output power curves of the transmission are shown for different transmission output speeds. Detailed Implementation

[0035] Figure 1 A transmission layout according to a first embodiment of the present invention is schematically shown. According to the first embodiment, a dual-motor electric transmission device for an electric vehicle includes a first motor 1 controlled by a first inverter controller 1a, and a second motor 2 controlled by a second inverter controller 2a. The first motor and the second motors 1 and 2 are configured to drive the electric vehicle. The transmission also includes a first gear arrangement 10, a second gear arrangement 20, and a summation box 30.

[0036] The first gear arrangement 10 includes a first gear arrangement first shaft 10a, a first gear 11, and a second gear 12, wherein each of the first gear and the second gear 11, 12 can selectively engage and disengage from the first gear arrangement first shaft 10a via a first toothed clutch or a second toothed clutch (dog clutch) 11a, 12a. The first gear arrangement 10 also includes a first gear arrangement second shaft 13 and a first gear arrangement fixed gear set with gears 14, 15. Gear 14 is permanently engaged with the first gear arrangement second shaft, and gear 15 is permanently engaged with the first gear arrangement first shaft 10a, and gears 14, 15 mesh with each other, such that the first gear arrangement first shaft 10a is connected to the first gear arrangement second shaft 13 via the first gear arrangement fixed gear set 14, 15.

[0037] The second gear arrangement 20 includes a second gear arrangement first shaft 20a and a second gear arrangement first gear 22, wherein the second gear arrangement first gear 22 can engage and disengage from the second gear arrangement first shaft 20a via a second gear arrangement first toothed clutch 22a. The second gear arrangement 20 also includes a second gear arrangement second shaft 23 and two additional gears 24 and 25 fixedly engaged with the second gear arrangement second shaft 23, wherein one of the two additional gears 24 and 25 meshes with the second gear arrangement first gear 22 on the second gear arrangement first shaft 20a, while the other of the two additional gears 24 and 25 is connected to the collection box 30. Furthermore, the second gear arrangement first shaft 20a is connected to a power take-off (PTO). In this case, the toothed clutch 22a disengages from the second gear arrangement first shaft 20a, and only the PTO is powered by the second electric motor 2.

[0038] The concentrator includes a shaft 30a, a first concentrator gear 32, and a second concentrator gear 31, which are permanently engaged with the shaft 30a. The shaft 30a is also connected to a front output yoke 34 and a rear output yoke 33. The front output yoke and the rear output yokes 33 and 34 are configured to deliver combined output torque to the wheels of the vehicle.

[0039] The first gear 11 of the first gear arrangement 10 meshes with the first gear 32 of the collection box. Each of the second gear 12 of the first gear arrangement 10 and the gear 25 of the second gear arrangement 20 meshes with the second gear 32 of the collection box.

[0040] The first gear arrangement 10 is configured to supply a first torque from the first electric motor 1 to the concentrator 30 via one of the first and second gears 11 and 12. The second gear arrangement 20 is configured to supply a second torque from the second electric motor 2 to the concentrator 30. The concentrator 30 is configured to combine the first and second torques and output the combined output torque to the front output yoke and the rear output yoke 34 and 33.

[0041] In this embodiment, the second gear 12 of the first gear arrangement 10 and the first gear 22 of the second gear arrangement 10 have the same dimensions and form the second gear of the transmission. The first gear 11 of the first gear arrangement 10 is smaller than gears 12 and 22 and forms the first gear of the transmission. In other words, when the transmission is in the first gear, only the electric motor 1 can be driven by engaging the first toothed clutch 11a. In the second gear, the electric motor 1 can be driven independently by engaging clutch 12a or the electric motor 2 can be driven jointly by engaging both clutches 12a and 22a. Therefore, in the second gear, both the electric motors 1 and 2 can contribute to the output torque, and the load can be symmetrically distributed between the two motors to improve the performance of the transmission.

[0042] Figure 2 A transmission layout according to a second embodiment of the present invention is schematically illustrated. In the second embodiment, the first gear arrangement 10 and the collection box 30 are designed as in the first embodiment. The difference between the second embodiment and the first embodiment lies in the design of the second gear arrangement 20. The second gear arrangement 20 in the second embodiment is designed to be similar to the first gear arrangement 10.

[0043] The second gear arrangement 20 includes a second gear arrangement first shaft 20a and a second gear arrangement first gear 21, wherein the second gear arrangement first gear 21 can engage and disengage from the second gear arrangement first shaft 20a via a second gear arrangement first toothed clutch 21a. The second gear arrangement 20 may also include a second gear arrangement second gear 22, which can engage or disengage from the second gear arrangement first shaft 20a via a second gear arrangement second toothed clutch 22a. The second gear arrangement 20 further includes a second gear arrangement second shaft 23 and a second gear arrangement fixed gear set with gears 26 and 27. Gear 26 is permanently engaged with the second shaft 23, while gear 27 is permanently engaged with the first shaft 20a. Gears 26 and 27 mesh with each other, such that the second gear arrangement first shaft 20a is connected to the second gear arrangement second shaft 23 via the second gear arrangement fixed gear set 26 and 27.

[0044] Each of the first gear arrangement first gear 11 and the second gear arrangement first gear 21 meshes with the gear 32 of the collection box 30. Furthermore, each of the first gear arrangement second gear 21 and the second gear arrangement second gear 22 meshes with the gear 31 of the collection box 30.

[0045] In this embodiment, the first gear 11 and the first gear 21 of the first gear arrangement 10 have the same dimensions and form the first gear of the transmission. The second gear 12 and the first gear 22 of the first gear arrangement 10 have the same dimensions, are larger than gears 11 and 21, and form the second gear of the transmission. In other words, in the first gear of the transmission, motor 1 can be driven independently by engaging clutch 11a or motor 2 by engaging clutch 21a, or both motors 1 and 2 can be driven together by engaging both clutches 11a and 21a. Similarly, in the second gear of the transmission, motor 1 can be driven independently by engaging clutch 12a or motor 2 by engaging clutch 22a, or both motors 1 and 2 can be driven together by engaging both clutches 12a and 22a. Therefore, in both the first and second gears of the transmission, both motors 1 and 2 can contribute to the output torque, and the load can be symmetrically distributed between motors 1 and 2 to improve the efficiency of the transmission. When both motors 1 and 2 are configured to drive in the first gear, the maximum output torque of the transmission can be increased.

[0046] Figure 3 A transmission layout according to a third embodiment of the present invention is schematically shown. The third embodiment is similar to the second embodiment. However, the third embodiment differs from the second embodiment in that it includes a third gear arrangement 50 and an inter-axle differential 60, the third gear arrangement 50 being connected to the shaft 30a of the central storage box 30.

[0047] Each of the first gear arrangement 11 and the second gear arrangement 21 meshes with the gear 32 of the collection box 30. Furthermore, each of the first gear arrangement 12 and the second gear arrangement 22 meshes with the gear 31 of the collection box 30. In the first to third embodiments, the collection box gear 31 is smaller than the collection box gear 32.

[0048] In this embodiment, the first gear 11 of the first gear arrangement 10 and the first gear 21 of the second gear arrangement 10 have the same dimensions and form the first gear of the transmission. The second gear 12 of the first gear arrangement 10 and the second gear 22 of the second gear arrangement 10 have the same dimensions, are larger than gears 11 and 21, and form the second gear of the transmission. In other words, in the first gear of the transmission, motor 1 can be driven independently by engaging clutch 11a and via the master gear 32, or motor 2 can be driven independently by engaging clutch 21a and via the master gear 32, or both motors 1 and 2 can be driven by engaging clutches 11a and 21a and via the master gear 32. In the second gear of the transmission, motor 1 can be driven independently by engaging clutch 12a and via the master gear 31, or motor 2 can be driven independently by engaging clutch 22a and via the master gear 31, or both motors 1 and 2 can be driven by engaging clutches 12a and 22a and via the master gear 31. Therefore, in both the first and second gears of the transmission, both motors 1 and 2 can contribute to the output torque. Because the transmission is connected to different summing gears in the first and second gears, the load can be distributed between motors 1 and 2, which can improve the efficiency of the transmission.

[0049] The third gear arrangement is a two-speed gear arrangement with a wet clutch. The other two gears 51 and 52 can be selectively engaged and disengaged from the shaft 30a of the collection box 30 via wet clutches 51a and 52a. Gear ratios 51 and 52 are suitable for the two electric motors 1 and 2. For some applications, these additional speed ratios can help achieve higher speeds or torques. Wet clutches 51a and 52a allow power switching in the additional gears 51 and 52. However, if the application allows some gear switching to occur with a decrease in output torque, a toothed clutch, synchronizer, or other type of clutch can also be used here alternatively. As a further alternative, the third gear arrangement can be a single gear ratio in a basic configuration without a clutch.

[0050] The junction box is connected to the inter-axle differential 60 via the third gear arrangement 50. The inter-axle differential 60 has a locking function provided by a wet clutch. Alternatively, other clutches, such as a gear clutch, can be selected.

[0051] The following describes a control method for controlling a dual-motor electric transmission according to a first embodiment to perform gear shifting from the first gear 11 to the second gear 12 in the first gear arrangement 1 without a drop in output torque. The second gear arrangement 2 has only one output-direction gear ratio, while the first gear arrangement 1 has two output-direction gear ratios. This vehicle application allows one electric motor to be used in the first gear and two electric motors to be used in the second gear. In the first gear, the first electric motor 1 is used to drive the vehicle, while the second electric motor 2 is turned off to supply power to the power take-off / charge pump at a sufficiently high speed. In the second gear, both the first electric motor 1 and the second electric motor 2 drive the vehicle. At the start of the gear shifting (gear changing) process, the first electric motor 1 is controlled to drive via the first toothed clutch 11a. Then, the second electric motor 2 is controlled to synchronize with the first gear 22 of the second gear arrangement. Then, the first toothed clutch 22a of the second gear arrangement is controlled to engage with the first shaft 20a of the second gear arrangement. Next, the first motor 1 is controlled to reduce the first torque to zero, while the second motor 2 is simultaneously controlled to increase the second torque, so that the combined output torque is substantially constant. Then, the first geared clutch 11a is controlled to disengage from the first shaft 10a of the first gear arrangement. Next, the second motor 1 is controlled to synchronize with the first gear 12 of the second gear arrangement. Then, the second geared clutch 12a is controlled to engage with the first shaft 10a of the first gear arrangement. Next, the second motor 21 is controlled to reduce the second torque, while the first motor 1 is simultaneously controlled to increase the first torque, so that the combined output torque is substantially constant.

[0052] Figure 4 The diagram shows the transmission output torque curves for different transmission output speeds. Continuous curves 71, 72, and 74 represent the continuous torque with one electric motor in second gear, two electric motors in second gear, and one electric motor in first gear, respectively. Dashed curves 73, 75, and 76 represent the peak torque with one electric motor in second gear, two electric motors in second gear, and one electric motor in first gear, respectively. Figure 5The diagram illustrates the different transmission output power curves based on the transmission output speed. Continuous curves 81, 82, and 84 represent the continuous power outputs of one electric motor in second gear, two electric motors in second gear, and one electric motor in first gear, respectively. Dashed curves 83, 85, and 86 represent the peak power outputs of one electric motor in second gear, two electric motors in second gear, and one electric motor in first gear, respectively. The continuous torque in first gear is represented by continuous curve 74, and the continuous torque in second gear is represented by continuous curve 72. During gear shifts, the torque of one electric motor increases to compensate for the zero torque of the other electric motor. This is represented by dashed curve 73. Since dashed curve 73 lies above curves 74 and 72 in the shift region, no torque drop is observed during gear shifts. Therefore, the output torque to the wheels is maintained throughout the vehicle speed range without any torque drop. In other words, gear changes are achieved through power shifting.

[0053] For functional safety reasons, automatic shifting to neutral is required in unsafe vehicle conditions. While the gear clutch is preferably a normally open clutch for the first and second gear arrangements 10 and 20, other technologies can also be used. One example is a spring-loaded synchronizing clutch. One advantage of using a synchronizing clutch is that the synchronization of the electric motor can be less precise, which simplifies the control of the electric motor.

Claims

1. A dual-motor electric transmission for an electric vehicle, the transmission comprising: The first and second electric motors are used to drive the car. The system comprises a first gear arrangement, a second gear arrangement, a junction box, and a control unit. The first gear arrangement includes a first gear arrangement first shaft and at least a first gear and a second gear, wherein each of the first gear and the second gear is selectively engaged and disengaged from the first gear arrangement first shaft via a first clutch element and a second clutch element, and the first gear arrangement is configured to supply a first torque from the first electric motor to the collection box via one of the first gear and the second gear. The second gear arrangement includes a second gear arrangement first shaft and at least a second gear arrangement first gear, wherein the second gear arrangement first gear is engageable and disengageable from the second gear arrangement first shaft via a second gear arrangement first clutch element, and the second gear arrangement is configured to supply a second torque from the second electric motor to the collection box. The summing box is configured to combine the first torque and the second torque, and is configured to output the combined output torque, and The control unit is adapted to control the second motor to provide an increased second torque during gear switching of the first gear arrangement, such that the combined output torque remains substantially constant during gear switching.

2. The dual-motor electric vehicle transmission of claim 1, wherein, The first gear arrangement further includes a first gear arrangement second shaft and a first gear arrangement fixed gear set, wherein the first gear arrangement first shaft is connected to the first gear arrangement second shaft via the first gear arrangement fixed gear set.

3. The dual-motor electric variable transmission of any preceding claim, wherein, The second gear arrangement further includes a second gear, which can engage or disengage with the first shaft of the second gear arrangement via a second clutch element.

4. The dual-motor electric vehicle transmission of claim 3, wherein, The second gear arrangement further includes a second gear arrangement second shaft and a second gear arrangement fixed gear set, wherein the second gear arrangement first shaft is connected to the second gear arrangement second shaft via the second gear arrangement fixed gear set.

5. The dual-motor electric vehicle transmission of Claim 1 or 2, wherein, The second gear arrangement further includes a second gear arrangement second shaft and at least two additional gears fixedly engaged with the second gear arrangement second shaft, wherein one of the two additional gears meshes with a first gear of the second gear arrangement on the first shaft of the second gear arrangement, and the other of the two additional gears is connected to the collection box.

6. The dual-motor electric vehicle transmission of claim 1, wherein, The clutch element is spring-loaded and / or disengages automatically upon loss of actuation.

7. The dual-motor electric transmission according to claim 1, characterized in that, The clutch element includes a toothed clutch or a synchronous clutch.

8. The dual-motor electric transmission according to claim 1, characterized in that, The second motor is connected to the power take-off and / or the charging pump.

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