Two-stage transmission and electric vehicle drive device

Abstract

[Problem] To provide a structure facilitating miniaturization of a drive device for an electric vehicle incorporating a two-stage transmission. [Solution] A two-stage transmission 2 is provided with a transmission input element 5, a transmission output element 6, a planetary reduction mechanism 7, a first shift mechanism 8, and a second shift mechanism 9. The planetary reduction mechanism 7 is disposed between the transmission input element 5 and the transmission output element 6 in the axial direction of the transmission input element 5.

Description

Two-speed transmission and electric vehicle drive unit

[0001] The present disclosure relates to a two-speed transmission that can change the reduction ratio between a transmission input element and a transmission output element in two stages, and to a drive system for an electric vehicle that includes the two-speed transmission.

[0002] In response to the recent trend toward reducing fossil fuel consumption, research into electric vehicles and hybrid vehicles has progressed, and some have been implemented. Unlike internal combustion engines (engines) that operate by directly burning fossil fuels, electric motors, which are the power source of electric vehicles and hybrid vehicles, generally generate maximum torque at startup and have desirable torque and rotational speed characteristics for automotive applications. Therefore, unlike typical automobiles powered by internal combustion engines, electric motors do not necessarily require a transmission. However, even when an electric motor is used as the power source, the inclusion of a transmission can improve acceleration and high-speed performance. Specifically, the inclusion of a transmission can smooth the relationship between the vehicle's running speed and acceleration, similar to that of an automobile equipped with an internal combustion engine and a transmission in its power transmission system. This point will be explained with reference to FIG. 16 .

[0003] For example, if a power transmission device with a large reduction ratio is placed between the motor output shaft of an electric motor and the differential input element of a differential gear connected to the drive wheels, the relationship between the acceleration (G) and driving speed (km / h) of the electric vehicle will conceptually be as shown by the solid line a in Figure 16. In other words, the electric vehicle will have excellent acceleration performance at low speeds, but will not be able to drive at high speeds. In contrast, if a power transmission device with a small reduction ratio is placed between the motor output shaft and the differential input element, the relationship will be as shown by the dotted line b in Figure 16. In other words, the electric vehicle will be able to drive at high speeds, but its acceleration performance at low speeds will be impaired. In contrast, if a transmission is placed between the motor output shaft and the differential input element and the reduction ratio of this transmission is changed according to the vehicle speed, a characteristic will be obtained in which the portion of the solid line a to the left of point P and the portion of the dotted line b to the right of point P are continuous. This characteristic is almost the same as that of an engine vehicle with a similar output, as shown by the dashed line c in Figure 16, and it can be seen that in terms of acceleration performance and high-speed performance, it is possible to obtain performance equivalent to that of an engine vehicle with a transmission in its power transmission system.

[0004] International Publication No. 2016 / 150411 discloses a drive system for an electric vehicle that uses a two-stage transmission to increase the output torque of an electric motor and transmit it to an axle. The two-stage transmission includes an input gear, an output gear, a double-pinion planetary gear reducer, a first shift mechanism, and a second shift mechanism. The two-stage transmission can switch the reduction ratio between the input gear and the output gear between two levels, high and low, by switching between the modes of the first shift mechanism and the second shift mechanism.

[0005] International Publication No. 2016 / 150411

[0006] In the two-speed transmission described in WO 2016 / 150411, the output gear is disposed between the input gear and the planetary gear reducer in the axial direction of the input gear. Therefore, the electric motor must be disposed close to the input gear, which has a larger outer diameter than the output gear. This limits the installation position of the electric motor, restricting design freedom and potentially increasing the overall size of the electric vehicle drive system.

[0007] The present disclosure aims to realize a structure that facilitates miniaturization of an electric vehicle drive unit incorporating a two-speed transmission that can change the reduction ratio between a transmission input element and a transmission output element in stages.

[0008] A two-speed transmission according to one aspect of the present disclosure includes a transmission input element, a transmission output element, a planetary reduction mechanism, a first shift mechanism, and a second shift mechanism.

[0009] The transmission input element is rotatably supported.

[0010] The transmission output element is supported coaxially with the transmission input element and capable of relative rotation with respect to the transmission input element.

[0011] The planetary reduction mechanism includes a sun element, a ring element, a carrier, and a plurality of planet elements.

[0012] The sun element is supported coaxially with the transmission input element and for relative rotation with respect to the transmission input element and the transmission output element.

[0013] The ring element is disposed around the sun element and coaxially with the sun element.

[0014] The carrier is arranged coaxially with the solar element.

[0015] The plurality of planetary elements are engaged with the sun element and the ring element so as to be able to transmit torque, and are supported by the carrier so as to be able to rotate about their respective central axes.

[0016] A first element of the sun element, the ring element, or the carrier is connected to rotate integrally with the transmission input element, and a second element of the sun element, the ring element, or the carrier other than the first element is connected to rotate integrally with the transmission output element.

[0017] The first shift mechanism is provided between the first element and a third element other than the first element and the second element among the sun element, the ring element, or the carrier, and switches the first element and the third element between a disconnection mode in which they can rotate relative to each other and a connection mode in which they cannot rotate relative to each other.

[0018] The second shift mechanism is provided between a structural element such as a housing or a frame that does not rotate even when in use and the third element, and switches between a free mode in which the third element can rotate relative to the structural element, and a locked mode in which the third element cannot rotate.

[0019] In particular, in a two-speed transmission according to one aspect of the present disclosure, the planetary reduction mechanism is disposed between the transmission input element and the transmission output element in the axial direction of the transmission input element.

[0020] In one aspect of the two-speed transmission of the present disclosure, the transmission input element can have an input tubular portion, and at least a portion of the first shift mechanism, the second shift mechanism, or both can be positioned radially inward of the input tubular portion.

[0021] In a two-speed transmission according to one aspect of the present disclosure, the plurality of planetary elements may include a plurality of first planetary elements that are engaged with the sun element so as to be able to transmit torque, and a plurality of second planetary elements that are engaged with the ring element so as to be able to transmit torque and that are engaged with the plurality of first planetary elements so as to be able to transmit torque. That is, the planetary reduction mechanism may be configured as a double-pinion planetary reduction mechanism.

[0022] In this case, the first element may be constituted by the carrier, the second element may be constituted by the ring element, and the third element may be constituted by the sun element.

[0023] Alternatively, the first element can be constituted by the sun element, the second element can be constituted by the ring element, and the third element can be constituted by the carrier.

[0024] Alternatively, in a two-speed transmission according to one aspect of the present disclosure, each of the plurality of planetary elements can be engaged with both the sun element and the ring element so as to be able to transmit torque. That is, the planetary reduction mechanism can be configured as a single-pinion planetary reduction mechanism.

[0025] In this case, the first element may be constituted by the ring element, the second element may be constituted by the carrier, and the third element may be constituted by the sun element.

[0026] Alternatively, the first element can be constituted by the sun element, the second element can be constituted by the carrier, and the third element can be constituted by the ring element.

[0027] In the two-speed transmission according to one aspect of the present disclosure, the sun element can be configured by a sun gear, the ring element can be configured by a ring gear, and the plurality of planetary elements can be configured by a plurality of planetary gears. That is, the planetary reduction mechanism can be configured by a planetary gear reducer.

[0028] Alternatively, the sun element can be a sun roller, the ring element can be a ring roller, and the plurality of planetary elements can be a plurality of planetary rollers. That is, the planetary reduction mechanism can be a planetary friction roller reducer.

[0029] In a two-speed transmission according to one aspect of the present disclosure, the transmission input element, the transmission output element, or both may be configured by gears.

[0030] An electric vehicle drive system according to one aspect of the present disclosure includes: a two-speed transmission; and an electric motor for rotationally driving a transmission input element of the two-speed transmission.

[0031] In particular, in an electric vehicle drive system according to an aspect of the present disclosure, the two-speed transmission is configured as the two-speed transmission according to an aspect of the present disclosure, so that the electric motor or its motor output element (such as the motor output shaft or the reducer) can be disposed in close proximity to a transmission output element having an outer diameter smaller than that of a transmission input element.

[0032] An electric vehicle drive device according to one aspect of the present disclosure can further include a differential mechanism that has a differential input element that is rotationally driven based on the rotation of the transmission output element of the two-speed transmission and distributes the rotation input to the differential input element to a plurality of drive wheels.

[0033] According to the two-speed transmission of one aspect of the present disclosure, it is possible to easily reduce the size of an electric vehicle drive unit incorporating the two-speed transmission.

[0034] FIG. 1 is a cross-sectional view schematically illustrating an electric vehicle drive system according to a first embodiment of the present disclosure. FIG. 2A is a diagram illustrating a torque transmission path in a low reduction ratio mode, and FIG. 2B is a diagram illustrating a torque transmission path in a high reduction ratio mode. FIG. 3 is a perspective view illustrating the electric vehicle drive system according to the first embodiment. FIG. 4 is a side view illustrating the electric vehicle drive system according to the first embodiment. FIG. 5 is a bottom view viewed from below in FIG. 4. FIG. 6 is an end view viewed from the left in FIG. 4. FIG. 7 is a cross-sectional view taken along line A-A in FIG. 4. FIG. 8 is a cross-sectional view taken along line B-B in FIG. 4. FIG. 9 is a cross-sectional view taken along line C-C in FIG. 4. FIG. 10 is a cross-sectional view taken along line D-D in FIG. 4. FIG. 11A is a schematic diagram corresponding to the cross-section A-A in FIG. 4 for a first modified example of the electric vehicle drive system according to the first embodiment, and FIG. 11B is a schematic diagram corresponding to the cross-section A-A in FIG. 4 for a second modified example of the electric vehicle drive system according to the first embodiment. Fig. 12 is a cross-sectional view showing an electric vehicle drive device according to a second example of an embodiment of the present disclosure. Fig. 13 is a cross-sectional view schematically showing an electric vehicle drive device according to a third example of an embodiment of the present disclosure. Fig. 14 is a cross-sectional view schematically showing an electric vehicle drive device according to a fourth example of an embodiment of the present disclosure. Fig. 15 is a cross-sectional view schematically showing an electric vehicle drive device according to a fifth example of an embodiment of the present disclosure. Fig. 16 is a diagram for explaining the effect of incorporating a transmission into a drive device using an electric motor as a drive source.

[0035] First Example A first example of an embodiment of the present disclosure will be described with reference to FIGS. 1 to 10. FIG.

[0036] <Overall Structure of Electric Vehicle Drive Device> The electric vehicle drive device 1 includes a two-speed transmission 2 and an electric motor 3 for rotationally driving a transmission input element 5 of the two-speed transmission 2. The electric vehicle drive device 1 may further include a differential mechanism 4. The differential mechanism 4 has a differential input element 15 that is rotationally driven based on the rotation of a transmission output element 6 of the two-speed transmission 2, and distributes the rotation input to the differential input element 15 to a plurality of drive wheels.

[0037] The electric vehicle drive system 1 of this example includes a two-speed transmission 2, an electric motor 3, and a differential mechanism 4, and is configured so that the output torque of the electric motor 3 is increased by the two-speed transmission 2, input to the differential mechanism 4, and distributed to a plurality of drive wheels by the differential mechanism 4. However, the electric vehicle drive system 1 can also omit the differential mechanism 4 and transmit the rotation of the transmission output element of the two-speed transmission to the drive wheels without going through the differential mechanism 4.

[0038] The two-speed transmission 2 includes a transmission input element 5, a transmission output element 6, a planetary reduction mechanism 7, a first shift mechanism 8, and a second shift mechanism 9. The two-speed transmission 2 is configured to be able to switch the reduction ratio between the transmission input element 5 and the transmission output element 6 between two levels, high and low, by switching between the mode of the first shift mechanism 8 and the mode of the second shift mechanism 9 and switching the torque transmission path that passes through the planetary reduction mechanism 7.

[0039] The electric motor 3 drives the transmission input element 5 to rotate.

[0040] The electric motor 3 includes a motor housing 10 , a motor output shaft 11 , a rotor 12 , and a stator 13 .

[0041] The motor output shaft 11 is rotatably supported inside the motor housing 10 via a plurality of bearings (not shown).

[0042] The rotor 12 is fitted and fixed around the motor output shaft 11 so as to rotate integrally with the motor output shaft 11. The rotor 12 may have any of various conventionally known structures, such as a squirrel-cage type, a wound type, or a permanent magnet type.

[0043] The stator 13 is disposed coaxially around the rotor 12 and is supported and fixed inside the motor housing 10. Specifically, the inner peripheral surface of the stator 13 faces the outer peripheral surface of the rotor 12 via a small radial gap, and the outer peripheral surface of the stator 13 is fitted and fixed inside the motor housing 10. The stator 13 can have any of various conventionally known structures, such as a wound type or a permanent magnet type.

[0044] The structure for rotationally driving the transmission input element 5 by the electric motor 3 is not particularly limited, and the transmission input element 5 can be rotationally driven directly by the electric motor 3 or via a reducer.

[0045] When the electric motor 3 is configured to directly rotate the transmission input element 5, the transmission input element 5 can be formed directly on or externally fitted and fixed to the motor output shaft 11. In this case, the motor output shaft 11 constitutes the motor output element 14 of the electric motor 3.

[0046] When the electric motor 3 is configured to rotate the transmission input element 5 via a reducer, for example, a drive gear provided on the motor output shaft 11 can be meshed with the transmission input element 5 formed of a gear directly or via one or more intermediate gears. Alternatively, a belt can be stretched between a drive pulley provided on the motor output shaft 11 and the transmission input element 5 formed of a pulley. Alternatively, a chain can be stretched between a drive sprocket provided on the motor output shaft 11 and the transmission input element 5 formed of a sprocket. In these cases, the drive gear, drive pulley, or drive sprocket constitutes the motor output element 14 of the electric motor 3.

[0047] In this example, a drive gear 14, which is a motor output element 14 provided at the tip of a motor output shaft 11, is meshed with an input gear 5, which is a transmission input element 5 made up of gears.

[0048] The drive gear 14 is not particularly limited as long as it can mesh with the input gear 5 and transmit torque between the input gear 5. For example, the drive gear 14 may be a spur gear, a helical gear, etc. In this example, the drive gear 14 is a helical gear.

[0049] By including the differential mechanism 4, the electric vehicle drive system 1 can distribute the rotation input from the transmission output element 6 to the differential input element 15 to a plurality of drive wheels.

[0050] The structure of the differential mechanism 4 is not particularly limited as long as it can distribute the rotation input to the differential input element 15 to a plurality of drive wheels. Specifically, the differential mechanism 4 can be configured as an open differential that does not have a mechanism for limiting differential movement, or a differential that has a mechanism for limiting differential movement.

[0051] Examples of differentials having a mechanism for limiting differential include, but are not limited to, a differential lock having a mechanism for forcibly fixing differential, a limited slip differential that can limit differential depending on conditions, and a torque vectoring differential that can independently control torque to each drive wheel.When a limited slip differential is used as the differential mechanism 4, any of the following structures may be adopted: a rotation-sensitive type that limits differential depending on the difference in rotation speed of the drive wheels, a torque-sensitive type that limits differential depending on the difference in torque of the drive wheels, or an electronically controlled type that controls differential limiting electronically.

[0052] In this example, the differential mechanism 4 is composed of an open differential that distributes the rotation input to the differential input element 15 to a pair of drive shafts 16a, 16b, each connected via a constant velocity joint so that torque can be transmitted to the drive wheels.

[0053] The structure for transmitting the rotation of the transmission output element 6 to the differential input element 15 is not particularly limited. For example, the transmission output element 6 formed of a gear can be meshed with the differential input element 15 formed of a gear directly or via one or more intermediate gears. Alternatively, a belt can be stretched between the transmission output element 6 formed of a pulley and the differential input element 15 also formed of a pulley. Alternatively, a chain can be stretched between the transmission output element 6 formed of a sprocket and the differential input element 15 also formed of a sprocket.

[0054] In this example, a transmission output element (output gear) 6 formed of a gear is directly meshed with a differential input element 15 formed of a gear.

[0055] <Detailed Structure of Two-Speed ​​Transmission> The specific structure of the two-speed transmission 2 will now be described.

[0056] Unless otherwise specified, the axial direction of the two-speed transmission 2 refers to the axial direction of the transmission input element 5. In the following description, one axial side corresponds to the right side in Figures 1, 4, 5, and 7, and the other axial side corresponds to the left side in Figures 1, 4, 5, and 7.

[0057] The transmission input element 5 is rotatably supported by a structural element such as a housing or a frame that does not rotate even during use. The transmission input element 5 is configured to be rotatably driven by the electric motor 3. Specifically, the transmission input element 5 is configured by gears, pulleys, sprockets, etc. In this example, the transmission input element 5 is configured by an input gear 5.

[0058] When an input gear 5 is used as the transmission input element 5, the structure of the input gear 5 is not particularly limited as long as the input gear 5 is able to mesh with the drive gear 14 that is rotationally driven by the electric motor 3 and transmit torque between the input gear 5 and the drive gear 14. For example, the input gear 5 may be configured as a spur gear, a helical gear, or the like. In this example, the input gear 5 is configured as a helical gear.

[0059] The transmission input element 5 may have an input tubular portion 17. The input tubular portion 17 has a substantially cylindrical shape. When the transmission input element 5 is formed by the input gear 5 as in this example, the input gear 5 is formed by providing a plurality of teeth on the outer peripheral surface of the input tubular portion 17.

[0060] The transmission output element 6 is supported coaxially with the transmission input element 5 and capable of relative rotation with respect to the transmission input element 5. The transmission output element 6 has an outer diameter smaller than that of the transmission input element 5. The transmission output element 6 is configured to be able to rotationally drive the differential input element 15 of the differential mechanism 4. Specifically, the transmission output element 6 is configured by a gear, a pulley, a sprocket, etc. In this example, the transmission output element 6 is configured by an output gear 6.

[0061] The output gear 6 is not particularly limited as long as it can mesh with the differential input element 15 of the differential mechanism 4 and transmit torque between the differential input element 15. For example, the output gear 6 may be configured as a spur gear, a helical gear, etc. In this example, the output gear 6 is configured as a helical gear.

[0062] The transmission output element 6 has a shaft member 19, which is rotatably supported relative to the structural element via a bearing 18. When the transmission output element 6 is constituted by an output gear 6 as in this example, the output gear 6 is constituted by providing a plurality of teeth on the outer peripheral surface of the axially middle portion of the shaft member 19 having a stepped cylindrical shape.

[0063] The planetary reduction mechanism 7 comprises a sun element 20 supported coaxially with the transmission input element 5 and capable of relative rotation with respect to the transmission input element 5 and the transmission output element 6, a ring element 21 arranged coaxially around the sun element 20, a carrier 22 arranged coaxially with the sun element 20, and a plurality of planetary elements 23 engaged with the sun element 20 and the ring element 21 so as to be able to transmit torque and supported on the carrier 22 so as to be able to rotate around their respective central axes.

[0064] A first element among the sun element 20, the ring element 21, or the carrier 22 is connected to rotate integrally with the transmission input element 5, and a second element other than the first element among the sun element 20, the ring element 21, and the carrier 22 is connected to rotate integrally with the transmission output element 6.

[0065] A first shift mechanism 8 is provided between the first element and a third element other than the first element and the second element, which is a sun element 20, a ring element 21, or a carrier 22, and a second shift mechanism 9 is provided between the third element and a structural element 24 that does not rotate even when in use, such as a housing or a frame.

[0066] The first shift mechanism 8 is provided between the solar element 20 and the carrier 22, and switches between a disconnection mode in which the solar element 20 and the carrier 22 are rotatable relative to each other and a connection mode in which they are not rotatable relative to each other. The first shift mechanism 8 has an actuator (not shown), and switches between the disconnection mode in which the solar element 20 and the carrier 22 are rotatable relative to each other and a connection mode in which they are not rotatable relative to each other based on the operation of the actuator.

[0067] The configuration of the first shift mechanism 8 is not particularly limited as long as the actuator can switch between a disconnection mode in which the solar element 20 and the carrier 22 are rotatable relative to each other and a connection mode in which the solar element 20 and the carrier 22 are not rotatable relative to each other. For example, the first shift mechanism 8 can be configured by a meshing or friction clutch.

[0068] The second shift mechanism 9 is provided between the solar element 20 and a structural element 24 that does not rotate even when the housing or the like is in use, and switches between a free mode in which the solar element 20 is rotatable relative to the structural element 24 and a locked mode in which the solar element 20 is not rotatable. The second shift mechanism 9 has an actuator, and switches between a free mode in which the solar element 20 is rotatable relative to the structural element 24 and a locked mode in which the solar element 20 is not rotatable based on the operation of the actuator.

[0069] The configuration of the second shift mechanism 9 is not particularly limited as long as it can be switched by an actuator between a free mode in which the solar element 20 is rotatable relative to the structural element 24 and a locked mode in which it is not rotatable. For example, the second shift mechanism 9 can be configured with a meshing or friction brake. Alternatively, the second shift mechanism 9 can be configured with a brake (torque selectable device) that has a one-way clutch mode that allows rotation of the solar element 20 in a predetermined direction and prevents rotation in the opposite direction to the predetermined direction, in addition to the free mode and locked mode.

[0070] The actuators constituting the first shift mechanism 8 and the second shift mechanism 9 can be electric motors, electric actuators such as solenoids, hydraulic cylinders that are operated by hydraulic pressure, etc. However, in an electric vehicle, in order to reduce costs by simplifying the system, improve fuel economy, or both, it is preferable to use an electric actuator as the actuator constituting the second shift mechanism 9 in order to eliminate the need for a hydraulic system or to make the system smaller.

[0071] The actuators constituting the first shift mechanism 8 and the second shift mechanism 9 may be the same actuator or different actuators.

[0072] In the electric vehicle drive device 1 of this example, the planetary reduction mechanism 7 is disposed axially between the transmission input element 5 and the transmission output element 6. In other words, the transmission input element 5 is disposed on the other axial side of the planetary reduction mechanism 7, and the transmission output element 6 is disposed on one axial side of the planetary reduction mechanism 7.

[0073] For this reason, in the two-speed transmission 2 of this example, the electric motor 3 or its motor output element 14 (such as the motor output shaft, drive gear, drive pulley, or drive sprocket) can be disposed in proximity to the transmission output element 6, which has an outer diameter smaller than that of the transmission input element 5. For example, as shown in FIG. 3 , the motor housing 10 of the electric motor 3 that rotates the transmission input element 5, and the bearings 37 that rotatably support the motor output shaft 11 relative to a structural element such as a housing or frame, can be disposed in proximity to the transmission output element 6, which has an outer diameter smaller than that of the transmission input element 5. Therefore, the two-speed transmission 2 of this example allows for greater freedom in the installation position of the electric motor 3, making it easier to reduce the size of the electric vehicle drive system 1 incorporating the two-speed transmission 2, compared to the two-speed transmission described in WO 2016 / 150411, which has a structure in which the output gear is disposed between the input gear and the planetary gear reducer and the electric motor must be disposed in proximity to the input gear.

[0074] The planetary reduction mechanism 7 is configured as a double-pinion type planetary reduction mechanism or a single-pinion type planetary reduction mechanism.

[0075] In the double-pinion planetary reduction mechanism 7, the multiple planetary elements 23 include multiple first planetary elements 23a that engage with the sun element 20 so as to be able to transmit torque, and multiple second planetary elements 23b that engage with the ring element 21 so as to be able to transmit torque and that engage with the multiple first planetary elements 23a so as to be able to transmit torque.

[0076] When the planetary reduction mechanism 7 is configured as a double-pinion type planetary reduction mechanism, the first element can be configured as a carrier 22, the second element can be configured as a ring element 21, and the third element can be configured as a sun element 20. Alternatively, the first element can be configured as a sun element 20, the second element can be configured as a ring element 21, and the third element can be configured as a carrier 22.

[0077] In the single-pinion type planetary reduction mechanism 7, each of the plurality of planetary elements 23 is engaged with both the sun element 20 and the ring element 21 so as to be able to transmit torque.

[0078] When the planetary reduction mechanism 7 is configured as a double-pinion type planetary reduction mechanism, the first element can be configured as a ring element 21, the second element can be configured as a carrier 22, and the third element can be configured as a sun element 20. Alternatively, the first element can be configured as a sun element 20, the second element can be configured as a carrier 22, and the third element can be configured as a ring element 21.

[0079] The planetary reduction mechanism 7 is composed of a planetary gear reducer or a planetary friction roller reducer. The planetary reduction mechanism 7 can be either a double-pinion type or a single-pinion type. In the double-pinion type planetary reduction mechanism 7, the multiple planetary elements 23 include multiple first planetary elements 23a that engage with the sun element 20 and multiple second planetary elements 23b that engage with the ring element 21 and also engage with the multiple first planetary elements 23a. In the single-pinion type planetary reduction mechanism 7, each of the multiple planetary elements 23 engages with both the sun element 20 and the ring element 21.

[0080] In the planetary gear type planetary reduction mechanism 7, the sun element 20, the ring element 21, and the multiple planetary elements 23 are each composed of gears, and torque is transmitted by meshing between the sun gear 20 and the multiple planetary gears 23, and by meshing between the ring gear 21 and the multiple planetary gears 23.

[0081] When the planetary reduction mechanism 7 is configured as a double-pinion planetary gear reducer, the plurality of planetary gears 23 includes a plurality of first planetary gears 23a that mesh with the sun gear 20, and a plurality of second planetary gears 23b that mesh with the ring gear 21 and also mesh with the plurality of first planetary gears 23a. The carrier 22 supports the plurality of first planetary gears 23a and the plurality of second planetary gears 23b so that they can rotate (spin) about their respective central axes and rotate (revolve) about the central axis of the carrier 22.

[0082] When the planetary reduction mechanism 7 is configured as a single-pinion planetary gear reducer, each of the multiple planet gears 23 meshes with both the sun gear 20 and the ring gear 21. The carrier 22 supports the multiple planet gears 23 so that they can rotate about their respective central axes (spin) and rotate about the central axis of the carrier 22 (revolution).

[0083] In the planetary friction roller type planetary reduction mechanism 7, the sun element 20, the ring element 21, and the multiple planet elements 23 are each composed of a friction roller, and torque is transmitted by rolling contact between the sun roller 20 and the multiple planet rollers 23, and by rolling contact between the ring roller 21 and the multiple planet rollers 23.

[0084] When the planetary reduction mechanism 7 is configured as a double-pinion planetary friction roller reducer, the multiple planetary rollers 23 include multiple first planetary rollers 23a that are in rolling contact with the sun roller 20, and multiple second planetary rollers 23b that are in rolling contact with the ring roller 21 and also in rolling contact with the multiple first planetary rollers 23a. The carrier 22 supports the multiple first planetary rollers 23a and the multiple second planetary rollers 23b so that they can rotate (spin) about their respective central axes and rotate (revolve) about the central axis of the carrier 22.

[0085] When the planetary reduction mechanism 7 is configured by a single-pinion planetary friction roller reducer, each of the multiple planetary rollers 23 is in rolling contact with both the sun roller 20 and the ring roller 21. The carrier 22 supports the multiple planetary rollers 23 so that they can rotate around their respective central axes (spin) and rotate around the central axis of the carrier 22 (revolution).

[0086] In this example, the planetary reduction mechanism 7 is configured by a double-pinion planetary gear reducer. Specifically, the planetary reduction mechanism 7 has a sun gear 20, a ring gear 21, a carrier 22, a plurality of first planetary gears 23 a, and a plurality of second planetary gears 23 b.

[0087] In addition, the first element connected to the transmission input element (input gear) 5 so as to rotate integrally therewith is constituted by a carrier 22, the second element connected to the transmission output element (output gear) 6 so as to rotate integrally therewith is constituted by a ring gear 21, and the third element is constituted by a sun gear 20.

[0088] The sun gear 20 is disposed coaxially with the input gear 5, and is supported to be rotatable relative to the input gear 5 and the output gear 6. The sun gear 20 is supported relative to the structural element 24 so that the first shift mechanism 8 can switch between a disconnection mode in which the sun gear 20 is rotatable relative to the carrier 22 and a connection mode in which the sun gear 20 is not rotatable relative to the carrier 22, and the second shift mechanism 9 can switch between a free mode in which the sun gear 20 is rotatable relative to the structural element 24 and a lock mode in which the sun gear 20 is not rotatable relative to the structural element 24.

[0089] The sun gear 20 is configured by providing a plurality of teeth on the outer peripheral surface of one axial end of a sun shaft 25 having a stepped cylindrical shape.

[0090] The ring gear 21 is disposed around the sun gear 20 and coaxially with the sun gear 20, and is connected to the output gear 6 so as to rotate integrally with the sun gear 20.

[0091] The ring gear 21 includes a main body 26 having a substantially cylindrical shape and a gear housing 27 having a crank-shaped cross section.

[0092] A plurality of teeth are provided on the inner peripheral surface of the main body 26 that faces the sun gear 20 .

[0093] The gear housing 27 has a small-diameter cylindrical portion 28 on one axial side, a large-diameter cylindrical portion 29 on the other axial side, and a hollow, circular side plate portion 30 connecting the small-diameter cylindrical portion 28 and the large-diameter cylindrical portion 29. The main body portion 26 is fitted and fixed to the large-diameter cylindrical portion 29 so as not to rotate relative to each other, and the end portion of the shaft member 19 on the other axial side is fitted and fixed to the small-diameter cylindrical portion 28 so as not to rotate relative to each other. This connects the output gear 6 and the ring gear 21 so as to rotate integrally.

[0094] The carrier 22 is connected to the input gear 5 so as to rotate integrally with the input gear 5. The carrier 22 supports the plurality of first planetary gears 23 a and the plurality of second planetary gears 23 b so that they can rotate (spin) about their respective central axes and rotate (revolve) about the central axis of the carrier 22.

[0095] The carrier 22 has a pair of rim portions 31a, 31b spaced apart in the axial direction, and a plurality of connection portions 32 connecting the pair of rim portions 31a, 31b together.

[0096] Of the pair of rim portions 31a, 31b, the rim portion 31a on one axial side has a hollow circular plate shape.

[0097] Of the pair of rim portions 31a, 31b, the rim portion 31b on the other axial side includes a side plate portion 33 having a hollow circular plate shape, and a cylindrical carrier tubular portion 34 that extends axially from the radially outer end of the side plate portion 33. The input tubular portion 17 of the input gear 5 is fitted and fixed to the other axial end of the carrier tubular portion 34 so as not to rotate relative to it. This connects the input gear 5 and the carrier 22 so as to rotate integrally.

[0098] The multiple connection portions 32 axially connect multiple circumferential locations on the radially outer end of the rim portion 31a on one axial side to multiple circumferential locations on the radially middle portion of the side plate portion 33 of the rim portion 31b on the other axial side.

[0099] The plurality of first planetary gears 23a and the plurality of second planetary gears 23b are supported by the carrier 22 so as to be rotatable (spinning) around their respective central axes which are arranged parallel to the central axis of the carrier 22, and are arranged at a plurality of locations in the circumferential direction between the sun gear 20 and the ring gear 21. The plurality of first planetary gears 23a mesh with the sun gear 20. The plurality of second planetary gears 23b mesh with the plurality of first planetary gears 23a and also with the ring gear 21. In other words, the plurality of first planetary gears 23a and the plurality of second planetary gears 23b mesh with each other to form pairs.

[0100] The number of first planetary gears 23a can be any number equal to or greater than two. The number of second planetary gears 23b is the same as the number of first planetary gears 23a. In this example, the number of first planetary gears 23a and the number of second planetary gears 23b are both three.

[0101] Each of the first planetary gears 23 a and the second planetary gears 23 b is configured by providing a plurality of teeth on the outer peripheral surface of a generally cylindrical body, and is supported by the carrier 22 via a support shaft 35 and a radial bearing 36 so as to be rotatable about its central axis (spinning).

[0102] The support shaft 35 is supported so as to span between the pair of rim portions 31 a, 31 b, with its central axis arranged parallel to the central axis of the carrier 22. Specifically, one axial end of the support shaft 35 is supported and fixed to a radially intermediate portion of the rim portion 31 a on one axial side, and the other axial end of the support shaft 35 is supported and fixed to a radially intermediate portion of the side plate portion 33 of the rim portion 31 b on the other axial side.

[0103] The radial bearing 36 is disposed between the inner peripheral surface of the first planetary gear 23 a or the second planetary gear 23 b and the outer peripheral surface of the support shaft 35 .

[0104] The radial bearing 36 is configured as a radial rolling bearing having a plurality of rolling elements such as needles, or a radial sliding bearing having a cylindrical shape.

[0105] In the two-speed transmission 2 , at least a portion of the first shift mechanism 8 , the second shift mechanism 9 , or both, can be disposed radially inside the input tubular portion 17 .

[0106] In this example, the other axial side portion of the second shift mechanism 9 is disposed radially inside the input cylindrical portion 17. In other words, the input cylindrical portion 17 is disposed radially outside the other axial side portion of the second shift mechanism 9.

[0107] More specifically, the first shift mechanism 8 is disposed radially inside one axial side portion of the carrier tubular portion 34, and is provided between the one axial side portion of the carrier tubular portion 34 and an axial middle portion of the sun shaft 25. The second shift mechanism 9 is disposed radially inside the other axial side portion of the carrier tubular portion 34, and is provided between the other axial side portion of the carrier tubular portion 34 and the structural element 24. The input tubular portion 17 is fitted and fixed to the end portion on the other axial side of the carrier tubular portion 34. As a result, the other axial side portion of the second shift mechanism 9 is disposed radially inside the input tubular portion 17.

[0108] 11A , in the two-speed transmission 2, the input tubular portion 17 can also be fitted and fixed to the outside of the axially intermediate portion of the carrier tubular portion 34. In this case, the other axial side portion of the first shift mechanism 8 and the one axial side portion of the second shift mechanism 9 are disposed radially inside the input tubular portion 17.

[0109] 11B , the input tubular portion 17 can be fitted and fixed to one axial end of the carrier tubular portion 34. In this case, the one axial end portion of the first shift mechanism 8 is disposed radially inside the input tubular portion 17.

[0110] In this way, in the two-speed transmission 2, it is possible to arrange at least a portion of the first shift mechanism 8, the second shift mechanism 9, or both, radially inside the input tubular portion 17. Therefore, in the two-speed transmission 2, the axial dimension can be reduced compared to a structure in which the input gear, output gear, planetary gear reducer, first shift mechanism, and second shift mechanism are arranged in series in the axial direction, such as the two-speed transmission described in WO 2016 / 150411, making it easier to achieve miniaturization.

[0111] In this example, the entire first shift mechanism 8 and the entire second shift mechanism 9 are disposed radially inside the carrier tube portion 34 .

[0112] However, a portion of the first shift mechanism 8, the second shift mechanism 9, or both may be disposed at a position axially offset from the radially inner side of the carrier tubular portion 34. For example, in the first modified example shown in Fig. 11(A) or the second modified example shown in Fig. 11(B), the portion of the carrier tubular portion 34 that protrudes further axially than the input tubular portion 17 may be omitted.

[0113] When a portion of the first shift mechanism 8, the second shift mechanism 9, or both, is positioned axially away from the radial inner side of the carrier tube portion 34, the outer diameter of the portion positioned axially away from the radial inner side of the carrier tube portion 34 can be made larger than the inner diameter of the carrier tube portion 34.

[0114] By switching between the mode of the first shift mechanism 8 and the mode of the second shift mechanism 9, the two-speed transmission 2 can switch between a low reduction ratio mode in which the reduction ratio between the transmission input element 5 and the transmission output element 6 is small (reduction ratio is 1), and a high reduction ratio mode in which the reduction ratio is larger than that in the low reduction ratio mode.

[0115] (Low reduction ratio mode) To switch the two-speed transmission 2 to the low reduction ratio mode, the first shift mechanism 8 is switched to a connected mode in which the solar element 20 and the carrier 22 cannot rotate relative to each other, and the second shift mechanism 9 is switched to a free mode in which the solar element 20 can rotate relative to the structural element 24. This causes the solar element 20 and the carrier 22 to rotate integrally, and allows the solar element 20 to rotate relative to the structural element 24.

[0116] In such a low reduction ratio mode, the sun element 20, the ring element 21, and the carrier 22 rotate in the same direction and at the same speed, and the entire planetary reduction mechanism 7 rotates as a unit, in a so-called glued state. Therefore, the rotation input from the electric motor 3 to the transmission input element 5 via the motor output element 14 is transmitted directly to the transmission output element 6 without being reduced in speed, via the path shown by the thick line in Figure 2(A). That is, in the low reduction ratio mode, the reduction ratio between the transmission input element 5 and the transmission output element 6 is 1.

[0117] (High Reduction Ratio Mode) To switch the two-speed transmission 2 to the high reduction ratio mode, the first shift mechanism 8 is switched to a disconnection mode in which the sun element 20 and the carrier 22 are rotatable relative to each other, and the second shift mechanism 9 is switched to a lock mode in which the sun element 20 is not rotatable relative to the structural element 24. This allows the sun element 20 and the carrier 22 to rotate relative to each other, and prevents the sun element 20 from rotating relative to the structural element 24.

[0118] In such a high reduction ratio mode, the rotation input from the electric motor 3 via the motor output element 14 to the transmission input element 5 is reduced in speed and transmitted to the transmission output element 6 by passing through the path shown by the thick line in Fig. 2(B) . Specifically, the rotation input to the transmission input element 5 is transmitted in the following order: the rotational motion of the carrier 22, the orbital motion of the first planetary element 23a and the second planetary element 23b, the rotational motion of the first planetary element 23a based on meshing with the sun element 20, the rotational motion of the second planetary element 23b, the rotational motion of the ring element 21, and the rotational motion of the transmission output element 6.

[0119] In the high reduction ratio mode, the reduction ratio between the transmission input element 5 and the transmission output element 6 is determined by the gear ratio between the ring element 21 and the sun element 20. In this example, the reduction ratio between the input gear 5 and the output gear 6 is determined by the number of teeth of the ring gear 21 relative to the number of teeth of the sun gear 20 (number of teeth of the ring gear 21 / number of teeth of the sun gear 20).

[0120] The two-speed transmission 2 can switch the reduction ratio between the transmission input element 5 and the transmission output element 6 between two levels: high and low. Specifically, in a region where the rotation input from the electric motor 3 to the transmission input element 5 via the motor output element 14 is low speed and high torque, the two-speed transmission 2 switches to a high reduction ratio mode, and in a region where the rotation input to the transmission input element 5 is high speed and low torque, the two-speed transmission 2 switches to a low reduction ratio mode. As a result, an electric vehicle using the electric motor 3 as its only drive source can have acceleration performance and high-speed performance similar to those of a gasoline engine vehicle.

[0121] [Second Example] A second example of the embodiment of the present disclosure will be described with reference to Fig. 12. In this example, components having the same functions as those in the first example are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0122] In this example, the first shift mechanism 8a is configured by a normally open type friction clutch, and the second shift mechanism 9a is configured by a mesh type brake.

[0123] The first shift mechanism 8 a includes a friction engagement portion 38 , an elastic biasing means 39 , a cam device 40 , and an electric actuator 41 .

[0124] The frictional engagement unit 38 has at least one first friction plate 42 and at least one second friction plate 43 supported to allow relative axial displacement, and is provided between the solar element 20 and the carrier 22. The frictional engagement unit 38 switches to a connection mode in which the solar element 20 and the carrier 22 rotate integrally by pressing the first friction plate 42 and the second friction plate 43 against each other. On the other hand, when the force pressing the first friction plate 42 and the second friction plate 43 against each other is released, the frictional engagement unit 38 switches to a disconnection mode in which the solar element 20 and the carrier 22 are capable of relative rotation.

[0125] In this example, the friction engagement unit 38 has a plurality of first friction plates 42 and a plurality of second friction plates 43. The friction engagement unit 38 is configured as a multi-plate clutch in which a plurality of first friction plates 42 supported so as to be capable of relative axial displacement relative to the solar element 20 and a plurality of second friction plates 43 supported so as to be capable of relative axial displacement relative to the carrier 22 are alternately stacked. A return spring (not shown) is provided between the first friction plates 42 and the second friction plates 43, elastically biasing the first friction plates 42 and the second friction plates 43 in a direction widening the gap between them. The elastic force of the return spring is smaller than the elastic restoring force of the elastic member 47 of the elastic biasing means 39.

[0126] The multiple first friction plates 42 are supported on the outer surface of the cylindrical portion 45 of a flange member 44 having a crank-shaped cross-sectional shape, which is externally fitted and fixed to the sun shaft 25a so that relative axial displacement and relative rotation are not possible, allowing axial displacement but not relative rotation.

[0127] The plurality of second friction plates 43 are supported on the inner peripheral surface of the other axial side portion of the carrier cylindrical portion 34a so as to be capable of axial displacement but not capable of relative rotation.

[0128] The elastic biasing means 39 elastically biases the first friction plate 42 and the second friction plate 43 in a direction in which they press against each other. In this example, the elastic biasing means 39 has a piston 46 and an elastic member 47.

[0129] The piston 46 is supported so as to be movable in the axial direction relative to the sun shaft 25a. In this example, the piston 46 has a circular ring portion 68 fitted onto the outside of the circular ring portion 68 so as to be movable in the axial direction relative to the sun shaft 25a, and a cylindrical portion 69 extending from the radially outer end of the circular ring portion 68 toward the other axial side. The end face on the other axial side of the cylindrical portion 69 faces the side face on the one axial side of the first friction plate 42 that is located furthest to the one axial side among the plurality of first friction plates 42.

[0130] The elastic member 47 is provided between the sun shaft 25a and the piston 46. In this example, the elastic member 47 is sandwiched in an elastically compressed state between an annular member 71 that is fitted onto the sun shaft 25a and is prevented from displacing in one axial direction by a retaining ring 70, and a side surface on one axial side of the piston 46. In other words, the elastic biasing means 39 elastically biases the first friction plate 42, which is closest to one axial side, toward the other axial side via the piston 46 by the force of the elastic member 47 attempting to elastically restore its original shape, thereby elastically biasing the first friction plate 42 and the second friction plate 43 in a direction in which they are pressed against each other.

[0131] The elastic member 47 is formed of a spring such as a disc spring, a compression coil spring, or an extension coil spring. The elastic member 47 can be formed of one spring or multiple springs. In this example, the elastic member 47 is formed by combining two disc springs in series in two stages, overlapping each other in opposite axial directions so that their large-diameter ends face each other.

[0132] The cam device 40 has a drive cam 49, a driven cam 50, and a plurality of rolling elements 51. As the drive cam 49 rotates, the cam device 40 moves the driven cam 50 in a direction that widens the axial distance between the drive cam 49 and the driven cam 50, thereby pressing the elastic biasing means 39 in a direction that releases the force pressing the first friction plate 42 and the second friction plate 43 against each other.

[0133] The drive cam 49 is supported by a support bearing 54 to allow relative rotation and relative axial displacement relative to a fixed member 52, which is supported and fixed to a component such as a housing or a frame that does not rotate or displace during use. The drive cam 49 has a drive cam surface 53 on the radially inner part of its side surface on one axial side, where the drive cam surface 53 has an equal number of recesses and protrusions arranged alternately in the circumferential direction. The drive cam 49 is configured to be rotatable by the electric actuator 41.

[0134] The driven cam 50 is disposed around the fixed member 52 so as to be capable of relative axial displacement with respect to the fixed member 52. Specifically, a female spline portion 66 provided on the inner peripheral surface of the driven cam 50 is spline-engaged with a male spline portion provided on the outer peripheral surface of one axial side portion of the fixed member 52, thereby supporting the driven cam 50 so as to be capable of relative axial displacement with respect to the fixed member 52.

[0135] The driven cam 50 faces the piston 46 of the elastically biasing means 39 via the release bearing 55 and the pressing member 56. In other words, the release bearing 55 and the pressing member 56 are provided between the driven cam 50 and the elastically biasing means 39.

[0136] Release bearing 55 is provided between a pressing member 56 opposing piston 46 of elastic biasing means 39 and driven cam 50 of cam device 40. Release bearing 55 has a pair of raceways 57 a, 57 b and a plurality of rolling elements 58 arranged to roll freely between the pair of raceways 57 a, 57 b. Of the pair of raceways 57 a, 57 b, the raceway 57 b on the other axial side is supported and fixed relative to driven cam 50.

[0137] In this example, a preload applying means 59 for applying a preload to the release bearing 55 is provided between the release bearing 55 and the sun shaft 25a. The preload applying means 59 is sandwiched in an elastically compressed state between one axial side surface of the axially one bearing ring 57a of a pair of bearing rings 57a, 57b constituting the release bearing 55 and the other axial side surface of the inner circular ring portion 48 of the flange member 44. This applies a preload to the release bearing 55 and prevents the release bearing 55 from falling out from between the elastic biasing means 39 and the cam device 40 even when the piston 46 is pressed axially toward one side against the elastic restoring force of the elastic member 47. The elastic force of the preload applying means 59 is smaller than the elastic restoring force of the elastic member 47. The preload applying means 59 can be formed, for example, by one or more disc springs or one or more coil springs.

[0138] The pressing member 56 has a cylindrical base and protruding portions that protrude toward one axial direction from multiple circumferential positions on one axial end of the base. One axially facing raceway 57a of a pair of raceways 57a, 57b of the release bearing 55 is supported and fixed to the other axial end of the base. The protruding portions are inserted into a through-hole provided in the inner circular ring portion 48 of the flange member 44, and the tip end (the one axial end) of the protruding portions faces a radially intermediate portion of the other axial side surface of the piston 46.

[0139] Each of the plurality of rolling elements 51 has its central axis (axis of rotation) oriented in a radial direction around the central axis of the driven cam 50, and is supported by the driven cam 50 so as to be able to rotate (spin) around that central axis. The outer circumferential surface of each of the plurality of rolling elements 51 is in rolling contact with the drive cam surface 53 of the drive cam 49.

[0140] In the cam device 40, as the driving cam 49 rotates, the amount by which the rolling element 51 rides up from the bottom of the recess that forms the driving cam surface 53 increases or decreases, causing the driven cam 50 to move in the axial direction.

[0141] That is, when the driving cam 49 is rotated in a predetermined direction, the amount by which the rolling element 51 rides up from the bottom of the recess that constitutes the driving cam surface 53 increases, and the driven cam 50 moves to one axial direction. When the driven cam 50 moves to one axial direction, the piston 46 of the elastic biasing means 39 is pressed toward one axial direction via the release bearing 55 and the pressing member 56, and the elastic member 47 is elastically compressed. This reduces and ultimately eliminates the force pressing the first friction plate 42 and the second friction plate 43 against each other. Then, due to the action of the return spring, the gap between the first friction plate 42 and the second friction plate 43 widens, and the mode switches to a cutting mode in which the solar element 20 and the carrier 22 can rotate relative to each other.

[0142] In contrast, when the driving cam 49 is rotated in the direction opposite to the predetermined direction, the amount by which the rolling elements 51 climb up from the bottom of the recess that constitutes the driving cam surface 53 decreases, and the driven cam 50 moves to the other axial side. When the driven cam 50 moves to the other axial side, the force of the elastic biasing means 39 pressing the piston 46 toward one axial side decreases via the release bearing 55 and the pressing member 56. When the force pressing the piston 46 toward one axial side decreases, the piston 46, the release bearing 55, and the pressing member 56 are pressed toward the other axial side mainly by the elastic restoring force of the elastic member 47, and the second friction plate 43, which is closest to one axial side, is pressed toward the other axial side by the piston 46. As a result, the first friction plate 42 and the second friction plate 43 are pressed against each other, and the connection mode is switched to one in which relative rotation between the solar element 20 and the carrier 22 is disabled.

[0143] Electric actuator 41 has a shift motor and a reducer 67, and the shift motor drives and rotates drive cam 49 of cam device 40 via reducer 67. In this example, reducer 67 is formed by meshing worm teeth provided on the outer peripheral surface of worm 60, which is driven and rotated by the shift motor, with wheel teeth provided on the outer peripheral surface of drive cam 49.

[0144] The second shift mechanism 9 a includes an outer diameter side member 61 , an inner diameter side member 62 , an engagement pin (not shown), and a select plate 63 .

[0145] The outer diameter side member 61 has a substantially cylindrical shape, and is supported and fixed to a structural element that does not rotate or displace during use.

[0146] The inner diameter side member 62 has a substantially cylindrical shape and is fixed to the outside of an outer circular ring portion 64 of the flange member 44, which extends radially outward from the other axial end of the cylindrical portion 45. Therefore, the inner diameter side member 62 rotates integrally with the solar element 20.

[0147] The engagement pin is releasably bridged between the outer diameter side member 61 and the inner diameter side member 62. Specifically, for example, the engagement pin protrudes radially inward from the inner peripheral surface of the outer diameter side member 61 and is supported in a state in which it is given an elastic force directed radially inward. The inner diameter side member 62 has an engagement recess on its outer peripheral surface that can engage with the tip of the engagement pin.

[0148] The select plate 63 has a mode select portion that is a concave and convex portion in the circumferential direction. A plurality of pins 65 are hung between the select plate 63 and the drive cam 49. This allows the drive cam 49 and the select plate 63 to rotate integrally (in the same direction at the same speed).

[0149] The second shift mechanism 9a switches between a state in which the outer diameter side member 61 and the inner diameter side member 62 are rotatable relative to each other and a state in which they are not, based on the rotation of the selector plate 63. That is, based on the rotation of the selector plate 63, the convex portion constituting the mode selector pushes the engagement pin radially outward, thereby disengaging the engagement pin from the engagement recess. This allows rotation of the inner diameter side member 62 relative to the outer diameter side member 61, thereby allowing rotation of the sun gear 20 relative to the structural element. In contrast, based on the rotation of the selector plate 63, the convex portion constituting the mode selector moves to a position circumferentially offset from the tip of the engagement pin, thereby engaging the engagement pin with the engagement recess. This prevents rotation of the inner diameter side member 62 relative to the outer diameter side member 61, thereby preventing rotation of the sun gear 20 relative to the structural element.

[0150] In the two-speed transmission 2a of this example, a portion of the first shift mechanism 8a is disposed radially inside the input tubular portion 17. Specifically, one axial side portion of the first shift mechanism 8a is disposed radially inside the carrier tubular portion 34a. More specifically, the friction engagement portion 38, the elastic biasing means 39, the pressing member 56, and the preload applying means 59 of the first shift mechanism 8a are disposed radially inside the carrier tubular portion 34a. The input tubular portion 17 is fitted and fixed to the outer end of one axial side of the carrier tubular portion 34a. As a result, the elastic biasing means 39 of the first shift mechanism 8a is disposed radially inside the input tubular portion 17.

[0151] In this example as well, a portion of the first shift mechanism 8a is disposed radially inside the input cylindrical portion 17, so that the axial dimension can be reduced, making it easier to achieve miniaturization.

[0152] In this example, the other axial side portion of the first shift mechanism 8a and the second shift mechanism 9a are disposed at positions axially offset from the radially inner side of the carrier cylindrical portion 34a. The outer diameter of the other axial side portion of the first shift mechanism 8a is larger than the inner diameter of the carrier cylindrical portion 34a, and the outer diameter of the second shift mechanism 9a is larger than the inner diameter of the carrier cylindrical portion 34a.

[0153] In the two-speed transmission 2a of this example, the drive cam 49 is driven to rotate by one shift motor, and the mode of the first shift mechanism 8a can be switched by adjusting the circumferential phase of the drive cam 49, and the mode of the second shift mechanism 9a can be switched by adjusting the circumferential phase of the select plate 63.

[0154] The other configurations and effects of the second example are the same as those of the first example.

[0155] [Third Example] A third example of the embodiment of the present disclosure will be described with reference to Fig. 13. In this example, components having the same functions as those in the first example are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0156] In this example, the planetary reduction mechanism 7 is configured as a double-pinion type planetary reduction mechanism.

[0157] The first element connected to the transmission input element 5 for integral rotation is constituted by a sun element 20, the second element connected to the transmission output element 6 for integral rotation is constituted by a ring element 21, and the third element is constituted by a carrier 22. That is, the first shift mechanism 8 is provided between the sun element 20 and the carrier 22, and the second shift mechanism 9 is provided between the structural element 24 and the carrier 22.

[0158] In the two-speed transmission 2 of this example, the reduction ratio between the transmission input element 5 and the transmission output element 6 can also be switched between high and low by switching the mode of the first shift mechanism 8 and the mode of the second shift mechanism 9.

[0159] To switch the two-speed transmission 2 to the low reduction ratio mode, the first shift mechanism 8 is switched to a connected mode in which the solar element 20 and the carrier 22 cannot rotate relative to each other, and the second shift mechanism 9 is switched to a free mode in which the carrier 22 can rotate relative to the structural element 24.

[0160] In the low reduction ratio mode, the sun element 20, the ring element 21, and the carrier 22 rotate in the same direction and at the same speed, and the entire planetary reduction mechanism 7 rotates as a unit, in a so-called glued state. As a result, the rotation input to the transmission input element 5 is transmitted to the transmission output element 6 as is without being reduced in speed.

[0161] To switch the two-speed transmission 2 to the high reduction ratio mode, the first shift mechanism 8 is switched to a disconnection mode in which the solar element 20 and the carrier 22 can rotate relative to each other, and the second shift mechanism 9 is switched to a lock mode in which the carrier 22 cannot rotate relative to the structural element 24.

[0162] In the high reduction ratio mode, the rotation input to the transmission input element 5 is transmitted in the following order: rotational motion of the sun element 20, rotational motion of the first planetary element 23a, rotational motion of the second planetary element 23b, rotational motion of the ring element 21, and rotational motion of the transmission output element 6.

[0163] The configuration and effects of other parts of the third example are the same as those of the first example.

[0164] [Fourth Example] A fourth example of the embodiment of the present disclosure will be described with reference to Fig. 14. In this example, components having the same functions as those in the first example are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0165] In this example, the planetary reduction mechanism 7 is configured as a single-pinion planetary reduction mechanism. That is, each of the plurality of planetary elements 23 that configure the planetary reduction mechanism 7 is engaged with both the sun element 20 and the ring element 21 so as to be able to transmit torque.

[0166] The first element connected to the transmission input element 5 for integral rotation is constituted by a ring element 21, the second element connected to the transmission output element 6 for integral rotation is constituted by a carrier 22, and the third element is constituted by a sun element 20. That is, the first shift mechanism 8 is provided between the ring element 21 and the sun element 20, and the second shift mechanism 9 is provided between the structural element 24 and the sun element 20.

[0167] In the two-speed transmission 2 of this example, the reduction ratio between the transmission input element 5 and the transmission output element 6 can also be switched between high and low by switching the mode of the first shift mechanism 8 and the mode of the second shift mechanism 9.

[0168] To switch the two-speed transmission 2 to the low reduction ratio mode, the first shift mechanism 8 is switched to a connection mode in which the ring element 21 and the sun element 20 cannot rotate relative to each other, and the second shift mechanism 9 is switched to a free mode in which the sun element 20 can rotate relative to the structural element 24.

[0169] In the low reduction ratio mode, the sun element 20, the ring element 21, and the carrier 22 rotate in the same direction and at the same speed, and the entire planetary reduction mechanism 7 rotates as a unit, in a so-called glued state. As a result, the rotation input to the transmission input element 5 is transmitted to the transmission output element 6 as is without being reduced in speed.

[0170] To switch the two-speed transmission 2 to the high reduction ratio mode, the first shift mechanism 8 is switched to a disconnection mode in which the ring element 21 and the sun element 20 are rotatable relative to each other, and the second shift mechanism 9 is switched to a lock mode in which the sun element 20 cannot rotate relative to the structural element 24.

[0171] In the high reduction ratio mode, the rotation input to the transmission input element 5 is transmitted in the following order: rotational motion of the ring element 21, rotational motion of the planetary element 23, orbital motion of the planetary element 23 based on engagement with the sun element 20, rotational motion of the carrier 22, and rotational motion of the transmission output element 6.

[0172] The remaining configurations and effects of the fourth example are the same as those of the first example.

[0173] Fifth Example A fifth example of the embodiment of the present disclosure will be described with reference to Fig. 15. In this example, components having the same functions as those in the first example are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0174] In this example, the planetary reduction mechanism 7 is configured as a single-pinion type planetary reduction mechanism.

[0175] The first element connected to the transmission input element 5 for integral rotation is constituted by the sun element 20, the second element connected to the transmission output element 6 for integral rotation is constituted by the carrier 22, and the third element is constituted by the ring element 21. That is, the first shift mechanism 8 is provided between the sun element 20 and the ring element 21, and the second shift mechanism 9 is provided between the structural element 24 and the ring element 21.

[0176] In the two-speed transmission 2 of this example, the reduction ratio between the transmission input element 5 and the transmission output element 6 can also be switched between high and low by switching the mode of the first shift mechanism 8 and the mode of the second shift mechanism 9.

[0177] To switch the two-speed transmission 2 to the low reduction ratio mode, the first shift mechanism 8 is switched to a connection mode in which the sun element 20 and the ring element 21 cannot rotate relative to each other, and the second shift mechanism 9 is switched to a free mode in which the ring element 21 can rotate relative to the structural element 24.

[0178] In the low reduction ratio mode, the sun element 20, the ring element 21, and the carrier 22 rotate in the same direction and at the same speed, and the entire planetary reduction mechanism 7 rotates as a unit, in a so-called glued state. As a result, the rotation input to the transmission input element 5 is transmitted to the transmission output element 6 as is without being reduced in speed.

[0179] To switch the two-speed transmission 2 to the high reduction ratio mode, the first shift mechanism 8 is switched to a disconnection mode in which the sun element 20 and the ring element 21 are rotatable relative to each other, and the second shift mechanism 9 is switched to a lock mode in which the ring element 21 cannot rotate relative to the structural element 24.

[0180] In the high reduction ratio mode, the rotation input to the transmission input element 5 is transmitted in the following order: rotational motion of the sun element 20, rotational motion of the planetary element 23, orbital motion of the planetary element 23 based on engagement with the ring element 21, rotational motion of the carrier 22, and rotational motion of the transmission output element 6.

[0181] The remaining configurations and effects of the fifth example are similar to those of the first and fourth examples.

[0182] REFERENCE SIGNS LIST 1 Electric vehicle drive device 2, 2a Two-speed transmission 3 Electric motor 4 Differential mechanism 5 Transmission input element (input gear) 6 Transmission output element (output gear) 7 Planetary reduction mechanism 8, 8a First shift mechanism 9, 9a Second shift mechanism 10 Motor housing 11 Motor output shaft 12 Rotor 13 Stator 14 Drive gear 15 Differential input element 16a, 16b Drive shaft 17 Input cylinder portion 18 Bearing 19 Shaft member 20 Sun element (sun gear) 21 Ring element (ring gear) 22 Carrier 23 Planetary element (planetary gear) 23a First planetary element (first planetary gear) 23b Second planetary element (second planetary gear) 24 Structural element 25, 25a Sun shaft 26 Main body 27 Gear housing 28 Small diameter cylindrical portion 29 Large diameter cylindrical portion 30 Side plate portions 31a, 31b Rim portion 32 Connecting portion 33 Side plate portions 34, 34a Carrier cylindrical portion 35 Support shaft 36 Radial bearing 37 Bearing 38 Friction engagement portion 39 Elastic biasing means 40 Cam device 41 Electric actuator 42 First friction plate 43 Second friction plate 44 Flange member 45 Cylindrical portion 46 Piston 47 Elastic member 48 Inner circular ring portion 49 Drive cam 50 Driven cam 51 Rolling element 52 Fixed member 53 Drive cam surface 54 Support bearing 55 Release bearing 56 Pressing member 57a, 57b Raceway ring 58 Rolling element 59 Preload applying means 60 Worm 61 Outer diameter side member 62 Inner diameter side member 63 Select plate 64 Outer circular ring portion 65 Pin 66 Female spline portion 67 Reducer 68 Circular ring portion 69 Cylindrical portion 70 Retaining ring 71 Annular member

Claims

1. A planetary reduction mechanism comprising: a rotatably supported transmission input element; a transmission output element supported coaxially with the transmission input element and rotatable relative to the transmission input element; a sun element supported coaxially with the transmission input element and rotatable relative to the transmission input element and the transmission output element; a ring element arranged coaxially around the sun element; a carrier arranged coaxially with the sun element; and a plurality of planetary elements engaged with the sun element and the ring element so as to be able to transmit torque and supported by the carrier so as to be rotatable about their respective central axes, wherein a first element of the sun element, the ring element, or the carrier is connected to rotate integrally with the transmission input element, and a second element other than the first element of the sun element, the ring element, or the carrier is connected to rotate integrally with the transmission output element. a first shift mechanism provided between the first element and a third element other than the first element and the second element among the sun element, the ring element, or the carrier, and switching the first element and the third element between a disconnected mode in which they are rotatable relative to each other and a connected mode in which they are not rotatable relative to each other; and a second shift mechanism provided between the third element and a structural element that does not rotate even when in use, and switching between a free mode in which the third element is rotatable relative to the structural element and a locked mode in which it is not rotatable, wherein the planetary reduction mechanism is disposed between the transmission input element and the transmission output element in the axial direction of the transmission input element.

2. The two-speed transmission according to claim 1, wherein the transmission input element has an input tubular portion, and at least a portion of the first shift mechanism, the second shift mechanism, or both, is disposed radially inward of the input tubular portion.

3. A two-speed transmission according to claim 1 or 2, wherein said plurality of planetary elements comprises a plurality of first planetary elements that are engaged with said sun element so as to be able to transmit torque, and a plurality of second planetary elements that are engaged with said ring element so as to be able to transmit torque and that are engaged with said plurality of first planetary elements so as to be able to transmit torque.

4. A two-speed transmission according to claim 3, wherein said first element is constituted by said carrier, said second element is constituted by said ring element, and said third element is constituted by said sun element.

5. A two-speed transmission according to claim 3, wherein said first element is constituted by said sun element, said second element is constituted by said ring element, and said third element is constituted by said carrier.

6. A two-speed transmission according to claim 1 or 2, wherein each of said plurality of planetary elements is engaged with both said sun element and said ring element so as to be able to transmit torque.

7. A two-speed transmission according to claim 6, wherein said first element is constituted by said ring element, said second element is constituted by said carrier, and said third element is constituted by said sun element.

8. A two-speed transmission according to claim 6, wherein the first element is constituted by the sun element, the second element is constituted by the carrier, and the third element is constituted by the ring element.

9. A two-speed transmission according to any one of claims 1 to 8, wherein the sun element is constituted by a sun gear, the ring element is constituted by a ring gear, and the plurality of planetary elements are constituted by a plurality of planetary gears.

10. A two-speed transmission according to any one of claims 1 to 9, wherein the transmission input element, the transmission output element, or both, are constituted by gears.

11. A drive device for an electric vehicle, comprising: a two-speed transmission; and an electric motor for rotationally driving a transmission input element of the two-speed transmission, wherein the two-speed transmission is configured by the two-speed transmission according to any one of claims 1 to 10.

12. The electric vehicle drive device according to claim 11, further comprising a differential mechanism having a differential input element that is rotationally driven based on the rotation of the transmission output element of the two-speed transmission, and distributing the rotation input to the differential input element to a plurality of drive wheels.

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