Two-speed transmission and electric vehicle drive device

Abstract

The present invention realizes a structure of a two-speed transmission that can switch the speed reduction ratio between an input side and an output side in two levels, and that can be easily miniaturized. A two-speed transmission 1 comprises: a speed reduction unit 6 having a carrier 19 that rotates integrally with a transmission input element 4, a first sun element 20, a second sun element 21 that rotates integrally with a transmission output element 5, a first intermediate element 22 that is rotatably supported on the carrier 19 and engages with the first sun element 20 so as to transmit torque, and a plurality of second intermediate elements 23 that rotate integrally with the first intermediate element 22 and engage with the second sun element 21 so as to transmit torque; a first shift mechanism 7 that switches between a cutting mode in which the carrier 19 and the first sun element 20 are relatively rotatable and a connection mode in which the carrier 19 and the first sun element 20 are not relatively rotatable; and a second shift mechanism 8 that switches between a free mode in which the first sun element 20 is rotatable relative to a structure element 28 and a lock mode in which the first sun element 20 is not rotatable.

Description

Two-speed transmission and electric vehicle drive unit

[0001] The present disclosure relates to a two-speed transmission capable of switching the reduction ratio between the input side and the output side in two stages, and a drive unit for an electric vehicle equipped with 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 sources 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. 17 .

[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 17. That is, 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 17. That is, the electric vehicle will be able to drive at high speeds, but will have poor acceleration performance at low speeds. 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, shown by the dashed line c in Figure 17, 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] Japanese Patent Application Laid-Open Publication No. 2006-022879 discloses a drive system for an electric vehicle in which rotation of a motor output shaft is reduced by a two-stage transmission before being transmitted to a differential. The two-stage transmission includes first and second reduction units, each of which is formed by a parallel-shaft gear reducer and has a different reduction ratio, as well as first and second switching means. The two-stage transmission switches between the mode of the first switching means and the mode of the second switching means, enabling power transmission through only one of the first and second reduction units. This allows the reduction ratio between the motor output shaft and the differential input element to be switched between large and small.

[0005] Japanese Patent Application Laid-Open No. 2006-022879

[0006] In the two-speed transmission described in JP 2006-022879 A, ​​a first reduction section and a second reduction section, each of which is constituted by a parallel shaft gear reducer, are provided between the motor output shaft and the differential input element, which poses a problem that the two-speed transmission tends to become large.

[0007] The present disclosure aims to realize a two-speed transmission structure that can switch the reduction ratio between the input side and the output side in two stages and that can be easily made compact.

[0008] A two-speed transmission according to one aspect of the present disclosure includes a transmission input element, a transmission output element, a reduction gear unit, 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 deceleration section includes a carrier, a first solar element, a second solar element, a plurality of first intermediate elements, and a plurality of second intermediate elements.

[0012] The carrier rotates integrally with the transmission input element.

[0013] The first solar 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.

[0014] The second solar element rotates integrally with the transmission output element.

[0015] The plurality of first intermediate elements are supported by the carrier so as to be rotatable (spinning) about their respective central axes, and are engaged with the first solar element so as to be able to transmit torque.

[0016] The plurality of second intermediate elements are configured to rotate integrally (rotate on their axes) with the plurality of first intermediate elements and are engaged with the second solar element so as to be able to transmit torque, and the number of the plurality of second intermediate elements is the same as the number of the plurality of first intermediate elements.

[0017] The first shift mechanism is provided between the carrier and the first solar element, and switches the carrier and the first solar 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 the structural element, which does not rotate even during use, and the first solar element, and switches the first solar element between a free mode in which it can rotate relative to the structural element, and a locked mode in which it cannot rotate.

[0019] In one aspect of the two-speed transmission of the present disclosure, at least a portion of at least one of the first solar element, the second solar element, the plurality of first intermediate elements, or the plurality of second intermediate elements can be positioned radially inward of the transmission input element.

[0020] In one aspect of the two-speed transmission of the present disclosure, the first sun element can be constituted by a first sun gear, the second sun element can be constituted by a second sun gear, the plurality of first intermediate elements can be constituted by a plurality of first intermediate gears, and the plurality of second intermediate elements can be constituted by a plurality of second intermediate gears.

[0021] In one aspect of the two-speed transmission of the present disclosure, the first solar element can be constituted by a first solar roller, the second solar element can be constituted by a second solar roller, the plurality of first intermediate elements can be constituted by a plurality of first intermediate rollers, and the plurality of second intermediate elements can be constituted by a plurality of second intermediate rollers.

[0022] 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.

[0023] An electric vehicle drive system according to one aspect of the present disclosure includes: a two-speed transmission having a transmission input element; and an electric motor for rotationally driving the transmission input element.

[0024] In particular, in the electric vehicle drive device according to one aspect of the present disclosure, the two-speed transmission is configured by the two-speed transmission according to one aspect of the present disclosure.

[0025] 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 and distributes the rotation input to the differential input element to a plurality of drive wheels.

[0026] According to one aspect of the two-speed transmission of the present disclosure, the reduction ratio between the transmission input element on the input side and the transmission output element on the output side can be switched between two stages, and miniaturization can be easily achieved.

[0027] 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, partially simplified, of the electric vehicle drive system according to the first embodiment. FIG. 4 is a side view, partially simplified, of the electric vehicle drive system according to the first embodiment. FIG. 5 is a bottom view, viewed from below, of FIG. 4. FIG. 6 is an end view, viewed from the left, of FIG. 4. FIG. 7 is a cross-sectional view taken along A-A in FIG. 4. FIG. 8 is a cross-sectional view taken along B-B in FIG. 4. FIG. 9 is a cross-sectional view taken along C-C in FIG. 4. FIG. 10 is a cross-sectional view taken along D-D in FIG. 4. FIG. 11 is a cross-sectional view taken along E-E in FIG. 4. FIG. 12 is a cross-sectional view schematically illustrating an electric vehicle drive system according to a second embodiment of the present disclosure. Fig. 13 is a partially simplified perspective view of a second example of an electric vehicle drive device. Fig. 14 is a partially simplified side view of the second example of an electric vehicle drive device. Fig. 15 is a bottom view seen from below in Fig. 14. Fig. 16 is a cross-sectional view taken along line F-F in Fig. 14. Fig. 17 is a diagram illustrating the effect of incorporating a transmission into a drive device using an electric motor as a drive source.

[0028] First Example A first example of an embodiment of the present disclosure will be described with reference to FIGS. 1 to 11. FIG.

[0029] <Two-Speed ​​Transmission> The two-speed transmission 1 constitutes a drive device for an electric vehicle together with the electric motor 2. The two-speed transmission 1 reduces the rotation of the electric motor 2 and transmits it to a plurality of drive wheels.

[0030] The two-speed transmission 1 includes a transmission input element 4, a transmission output element 5, a reduction gear unit 6, a first shift mechanism 7, and a second shift mechanism 8. The two-speed transmission 1 can switch the reduction ratio between the transmission input element 4 and the transmission output element 5 between two levels, high and low, by switching between the mode of the first shift mechanism 7 and the mode of the second shift mechanism 8 and switching the torque transmission path that passes through the reduction gear unit 6.

[0031] In the following description, unless otherwise specified, the axial direction of the two-speed transmission 1 refers to the axial direction of the rotation shafts of the elements 4 to 8 that make up the two-speed transmission 1. The terms one axial side and the other axial side are used only to indicate the relative positions of the elements. For convenience of explanation, in this specification, 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.

[0032] The transmission input element 4 is rotatably supported. That is, the transmission input element 4 is arranged to be rotatable relative to a structural element 28 such as a housing or a frame that does not rotate even during use. The transmission input element 4 is rotationally driven by the electric motor 2 directly or via a reducer, and transmits torque to the reduction unit 6.

[0033] The transmission output element 5 is supported coaxially with the transmission input element 4 and capable of relative rotation with respect to the transmission input element 4. Therefore, one of the transmission input element 4 and the transmission output element 5 is located on one axial side, and the other is located on the other axial side. In this example, for convenience, the description will be given assuming that the transmission output element 5 is located on one axial side and the transmission input element 4 is located on the other axial side. The transmission output element 5 is also located so as to be rotatable with respect to the structural element 28. The transmission output element 5 receives torque from the reduction gear unit 6 and transmits the torque to the multiple drive wheels.

[0034] The speed reducer 6 includes a carrier 19, a first solar element 20, a second solar element 21, a plurality of first intermediate elements 22, and a plurality of second intermediate elements 23. The speed reducer 6 can be configured by a gear reducer or a friction roller reducer.

[0035] The carrier 19 is configured to rotate integrally with the transmission input element 4. The carrier 19 supports the plurality of first intermediate elements 22 and the plurality of second intermediate elements 23 so that they can rotate (spin) about their respective central axes and rotate (revolve) about the central axis of the carrier 19.

[0036] The positional relationship between the transmission input element 4 and the carrier 19 can be any configuration depending on the respective structures, as long as they can rotate integrally. For example, a configuration in which the transmission input element 4 and the carrier 19 are connected in the axial direction, a configuration in which the transmission input element 4 and the carrier 19 are connected in the radial direction, or a configuration in which the transmission input element 4 is directly formed on the outer circumferential surface of the carrier tubular portion 27 can be used.

[0037] The first sun element 20 is supported coaxially with the transmission input element 4 and capable of rotating relative to the transmission input element 4 and the transmission output element 5. The first sun element 20 is disposed on the other axial side, which is the input side of the reduction gear unit 6.

[0038] The second sun element 21 rotates integrally with the transmission output element 5. The second sun element 21 is disposed on one axial side of the reduction gear unit 6, which is the output side.

[0039] The first intermediate elements 22 are supported by the carrier 19 so as to be rotatable (spinning) about their respective central axes, and are engaged with the first solar elements 20 so as to be able to transmit torque. Therefore, the first intermediate elements 22 are arranged on the other axial side, which is the input side, of the reduction gear unit 6.

[0040] The plurality of second intermediate elements 23 are configured to rotate (spin on their axes) integrally with the plurality of first intermediate elements 22, and are engaged with the second solar elements 21 so as to be able to transmit torque. Therefore, the plurality of second intermediate elements 23 are arranged on one axial side, which is the output side, of the speed reducer 6. The number of the plurality of second intermediate elements 23 is the same as the number of the plurality of first intermediate elements 22.

[0041] The first shift mechanism 7 is provided between the carrier 19 and the first solar element 20, and switches the carrier 19 and the first solar element 20 between a disconnection mode in which they are rotatable relative to each other and a connection mode in which they are not rotatable relative to each other.

[0042] The configuration of the first shift mechanism 7 is not particularly limited as long as it can switch between a disconnection mode in which the carrier 19 and the first solar element 20 are rotatable relative to each other and a connection mode in which they are not rotatable relative to each other. For example, the first shift mechanism 7 can be configured with a meshing or friction clutch. The first shift mechanism 7 can be controlled based on the operation of a drive device such as an actuator (not shown).

[0043] The second shift mechanism 8 is provided between the structural element 28, which does not rotate even when in use, and the first solar element 20, and switches between a free mode in which the first solar element 20 can rotate relative to the structural element 28, and a locked mode in which it cannot rotate.

[0044] The configuration of the second shift mechanism 8 is not particularly limited as long as it can switch between a free mode in which the first solar element 20 is rotatable and a locked mode in which it is not rotatable relative to the structural element 28. For example, the second shift mechanism 8 can be configured with a meshing or friction brake. The second shift mechanism 8 can be controlled based on the operation of a drive device such as an actuator (not shown).

[0045] In addition to the free mode and the lock mode, the second shift mechanism 8 can have a one-way clutch mode that allows rotation of the first solar element 20 in a predetermined direction and prevents rotation in the opposite direction to the predetermined direction. In this case, the second shift mechanism 8 is configured by a brake (torque selectable device).

[0046] By switching between the mode of the first shift mechanism 7 and the mode of the second shift mechanism 8, the two-speed transmission 1 can switch between a low reduction ratio mode in which the reduction ratio between the transmission input element 4 and the transmission output element 5 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.

[0047] (Low Reduction Ratio Mode) To switch the two-speed transmission 1 to the low reduction ratio mode, the first shift mechanism 7 is switched to a connected mode in which the carrier 19 and the first sun element 20 are unable to rotate relative to each other, and the second shift mechanism 8 is switched to a free mode in which the first sun element 20 is rotatable relative to the structural element 28. This makes it impossible for the carrier 19 and the first sun element 20 to rotate relative to each other, and allows the first sun element 20 to rotate relative to the structural element 28.

[0048] In this low reduction ratio mode, the carrier 19, the first solar element 20, and the second solar element 21 rotate in the same direction and at the same speed, and the entire reduction gear unit 6 rotates as a unit, in a so-called glued state. Therefore, the rotation input to the transmission input element 4 passes through the path shown by the thick line in Figure 2(A) and is transmitted directly to the transmission output element 5 without being reduced in speed. That is, in the low reduction ratio mode, the reduction ratio between the transmission input element 4 and the transmission output element 5 is 1.

[0049] (High Reduction Ratio Mode) To switch the two-speed transmission 1 to the high reduction ratio mode, the first shift mechanism 7 is switched to a disconnection mode in which the carrier 19 and the first sun element 20 are rotatable relative to each other, and the second shift mechanism 8 is switched to a lock mode in which the first sun element 20 is unable to rotate relative to the structural element 28. This allows the carrier 19 and the first sun element 20 to rotate relative to each other, and prevents the first sun element 20 from rotating relative to the structural element 28.

[0050] In such a high reduction ratio mode, the rotation input to the transmission input element 4 is transmitted to the transmission output element 5 by passing through the path shown by the thick line in Fig. 2(B) . Specifically, the rotation input to the transmission input element 4 is transmitted in the following order: the rotational motion of the carrier 19, the revolutionary motion of the first intermediate element 22 and the second intermediate element 23, the rotational motion of the first intermediate element 22 based on engagement with the first sun element 20, the rotational motion of the second intermediate element 23, the rotational motion of the second sun element 21, and the rotational motion of the transmission output element 5.

[0051] In the high reduction ratio mode, the reduction ratio between the transmission input element 4 and the transmission output element 5 is determined by the gear ratio between the first sun element 20 and the first intermediate element 22 and the gear ratio between the second sun element 21 and the second intermediate element 23. The gear ratio means the gear ratio in the case of a gear reducer, or the outer diameter ratio (or circumferential length ratio) in the case of a friction roller reducer.

[0052] The two-speed transmission 1 can switch the reduction ratio between the transmission input element 4 and the transmission output element 5 between two stages: high and low. Specifically, in a region where the rotation input to the transmission input element 4 is low speed and high torque, the two-speed transmission 1 switches to a high reduction ratio mode, and in a region where the rotation input to the transmission input element 4 is high speed and low torque, the two-speed transmission 1 switches to a low reduction ratio mode. Therefore, when the two-speed transmission 1 is applied to a drive system for an electric vehicle, the acceleration performance and high-speed performance of an electric vehicle using only the electric motor 2 as a drive source can be made similar to those of a gasoline engine vehicle.

[0053] In the two-speed transmission 1, in the high reduction ratio mode, the power input to the transmission input element 4 and transmitted to the carrier 19 can be distributed and transmitted to the plurality of first intermediate elements 22 and the plurality of second intermediate elements 23. For this reason, in the two-speed transmission 1, it is easier to reduce the size of the reduction unit 6 compared to the two-speed transmission described in JP 2006-22879 A, ​​in which the first reduction unit and the second reduction unit are each configured using parallel shaft gear reducers.

[0054] The two-speed transmission 1 may have any overall structure and any structure for each of its components, as long as the reduction ratio between the transmission input element 4 and the transmission output element 5 can be switched between two levels, high and low, via the reduction unit 6. Specific configurations of the two-speed transmission 1 of this example, which are advantageous from the perspective of downsizing the two-speed transmission 1, will be described in detail below, although the invention is not limited thereto.

[0055] The transmission input element 4 is rotationally driven by the electric motor 2 directly or via a reducer. When the transmission input element 4 is directly connected to the electric motor 2, the transmission input element 4 can be formed on or externally fitted and fixed to the motor output shaft 10. When the transmission input element 4 is rotationally driven via a reducer, the transmission input element 4 is configured by gears, pulleys, sprockets, and the like, which are components of the reducer, depending on the type of the reducer.

[0056] The transmission input element 4 is preferably connected radially to the carrier 19. In this case, the transmission input element 4 can be provided directly on the carrier 19. Alternatively, the transmission input element 4 can be provided on an input member 16 that is configured separately from the carrier 19 and supported and fixed to the carrier 19 so as to rotate integrally with the carrier 19.

[0057] In this example, the transmission input element 4 is configured by a gear (input gear) and is provided integrally with the carrier 19. The carrier 19 has a substantially cylindrical carrier tubular portion 27. The transmission input element 4 is configured by providing a plurality of teeth on the outer peripheral surface of the substantially cylindrical input member 16 that is fitted and fixed to the outside of the carrier tubular portion 27.

[0058] Although the structure of the carrier 19 is not limited to this, in this example, the carrier 19 has a pair of rim portions 24a, 24b spaced apart in the axial direction, and a plurality of connecting portions 25 connecting the pair of rim portions 24a, 24b to each other.

[0059] Of the pair of rim portions 24a, 24b, the rim portion 24a on one axial side has a hollow circular plate shape.

[0060] Of the pair of rim portions 24a, 24b, the rim portion 24b on the other axial side includes a side plate portion 26 having a hollow circular plate shape, and a carrier tubular portion 27 extending to the other axial side from the radially outer end of the side plate portion 26. The input member 16 of the transmission input element 4 is fitted and fixed to the outer peripheral surface of the carrier tubular portion 27 so as not to rotate relative to the carrier 19. This connects the transmission input element 4 and the carrier 19 so as to rotate integrally.

[0061] The multiple connection portions 25 axially connect multiple circumferential locations on the radially outer end of the rim portion 24a on one axial side to multiple circumferential locations on the radially middle portion of the side plate portion 26 of the rim portion 24b on the other axial side.

[0062] Of the deceleration section 6, the first solar element 20, the second solar element 21, the plurality of first intermediate elements 22, and the plurality of second intermediate elements 23, excluding the carrier 19, are arranged between a pair of rim portions 24a, 24b.

[0063] In the reduction gear section 6, the first solar element 20, the second solar element 21, the plurality of first intermediate elements 22, and the plurality of second intermediate elements 23 can be arranged in a portion axially offset from the transmission input element 4. Alternatively, at least a portion of at least one of the first solar element 20, the second solar element 21, the plurality of first intermediate elements 22, or the plurality of second intermediate elements 23 can be arranged radially inward of the transmission input element 4. In this example, the first solar element 20, the second solar element 21, the plurality of first intermediate elements 22, and the plurality of second intermediate elements 23 are arranged in a portion axially offset from the input member 16.

[0064] The plurality of first intermediate elements 22 and the plurality of second intermediate elements 23 are respectively arranged in the portions between two of the plurality of connecting portions 25 that are adjacent in the circumferential direction.

[0065] The first sun element 20 is supported coaxially with the transmission input element 4 and capable of relative rotation with respect to the transmission input element 4 and the transmission output element 5. Therefore, the first sun element 20 is also arranged coaxially with the transmission output element 5 and the carrier 19. The carrier 19 and the first sun element 20 can be switched by the first shift mechanism 7 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. The first sun element 20 is also supported by the structural element 28 so that the second shift mechanism 8 can switch between a free mode in which it is rotatable relative to the structural element 28, in which it does not rotate even during use, and a locked mode in which it is not rotatable relative to the structural element 28.

[0066] The second solar element 21 is disposed at the other axial end of the shaft member 18 on which the transmission output element 5 is provided. The second solar element 21 can be configured to rotate integrally with the transmission output element 5 by being provided directly on the shaft member 18. Alternatively, the second solar element 21 can be connected to the transmission output element 5 by providing the second solar element 21 on the outer circumferential surface of a substantially cylindrical tubular body and externally fitting and fixing the tubular body to the shaft member 18 so as not to rotate relative to the shaft member 18.

[0067] The plurality of first intermediate elements 22 are supported by the carrier 19 so as to be rotatable (spinning) about their respective central axes, and are engaged with the first solar elements 20 so as to be able to transmit torque. The first intermediate elements 22 are arranged at a plurality of locations on the carrier 19 in the circumferential direction around the first solar element 20. The central axes of the first intermediate elements 22 are arranged parallel to the central axis of the carrier 19.

[0068] The plurality of second intermediate elements 23 are configured to rotate integrally with the plurality of first intermediate elements 22, and are engaged with the second solar elements 21 so as to be able to transmit torque. The second intermediate elements 23 are arranged at a plurality of locations in the circumferential direction around the second solar element 21 of the carrier 19. The central axis of each of the second intermediate elements 23 is arranged parallel to the central axis of the carrier 19.

[0069] The number of the plurality of second intermediate elements 23 is the same as the number of the plurality of first intermediate elements 22. The number of the first intermediate elements 22 and the number of the second intermediate elements 23 can each be any number equal to or greater than 2. In this example, the number of the first intermediate elements 22 and the number of the second intermediate elements 23 is three.

[0070] Any structure applicable to a planetary reduction mechanism can be employed for supporting the first intermediate element 22 and the second intermediate element 23 on the carrier 19 so that they can rotate (spin) about their respective central axes and rotate integrally. For example, the first intermediate element 22 is provided on a cylindrical body having a substantially cylindrical shape, and the second intermediate element 23 is provided on a large-diameter portion provided on one axial side of the intermediate shaft 30 having a stepped cylindrical shape. The cylindrical body constituting the first intermediate element 22 is externally fitted and fixed to a small-diameter portion provided on the other axial side of the intermediate shaft 30 so as not to rotate relative to the small-diameter portion, thereby forming a connection between the first intermediate element 22 and the second intermediate element 23. The connection between the first intermediate element 22 and the second intermediate element 23 can then be supported on the carrier 19 via a support shaft 31 and a radial bearing 32 so as to be rotatable (spin) about its central axis.

[0071] Alternatively, the first intermediate element 22 and the second intermediate element 23 can be provided on a cylindrical body, and these cylindrical bodies can be connected so that they cannot rotate relative to each other, and then supported on the support shaft 31 via a radial bearing 32, or the first intermediate element 22 and the second intermediate element 23 can be provided integrally with the intermediate shaft 30.

[0072] When the reduction unit 6 is configured with a gear reducer, the first sun element 20, the second sun element 21, the plurality of first intermediate elements 22, and the plurality of second intermediate elements 23 are each configured with gears (first sun gear, second sun gear, first intermediate gear, and second intermediate gear). In this case, torque is transmitted between the first sun gear constituting the first sun element 20 and the plurality of first intermediate elements 22 by meshing between the first sun gear constituting the first sun element 20 and the plurality of first intermediate elements 22, and torque is transmitted between the second sun gear constituting the second sun element 21 and the plurality of second intermediate elements 23 by meshing between the second sun gear constituting the second sun element 21 and the plurality of second intermediate elements 23.

[0073] In this case, the gears constituting the first solar element 20, the second solar element 21, the plurality of first intermediate elements 22, and the plurality of second intermediate elements 23 are not particularly limited as long as they can transmit torque by meshing with each other. For example, these gears may be spur gears, helical gears, etc.

[0074] When the speed reducer 6 is configured with a friction roller reducer, the first sun element 20, the second sun element 21, the plurality of first intermediate elements 22, and the plurality of second intermediate elements 23 are each configured with a friction roller (first sun roller, second sun roller, first intermediate roller, and second intermediate roller). In this case, torque is transmitted between the first sun element 20 and the plurality of first intermediate elements 22 by rolling contact between the first sun roller that constitutes the first sun element 20 and the first intermediate rollers that constitute the plurality of first intermediate elements 22, and torque is transmitted between the second sun element 21 and the plurality of second intermediate elements 23 by rolling contact between the second sun roller that constitutes the second sun element 21 and the second intermediate rollers that constitute the plurality of second intermediate elements 23.

[0075] The specifications of the first solar element 20, the second solar element 21, the plurality of first intermediate elements 22, and the plurality of second intermediate elements 23 are set so that in the high reduction ratio mode of the two-speed transmission 1, in which relative rotation between the carrier 19 and the first solar element 20 is possible and rotation of the first solar element 20 relative to the structural element 28 is prevented, the rotation input to the transmission input element 4 is decelerated in the reduction section 6.

[0076] Specifically, when the reduction unit 6 is configured with a gear reducer, the number of teeth of the first intermediate gear that constitutes the first intermediate element 22 is equal to or greater than the number of teeth of the first sun gear that constitutes the first sun element 20, and is greater than the number of teeth of the second intermediate gear that constitutes the second intermediate element 23. When the reduction unit 6 is configured with a friction roller reducer, the outer diameter of the first intermediate roller that constitutes the first intermediate element 22 is equal to or greater than the outer diameter of the first sun roller that constitutes the first sun element 20, and is greater than the outer diameter of each of the second intermediate rollers of the second intermediate element 23.

[0077] In this example, the speed reducer 6 is configured by a gear reducer. Specifically, the gears constituting the first solar element 20, the second solar element 21, the plurality of first intermediate elements 22, and the plurality of second intermediate elements 23 that constitute the speed reducer 6 are configured by helical gears.

[0078] The first sun gear constituting the first sun element 20 is configured by providing a plurality of teeth on the outer peripheral surface of one axial end of a sun shaft 29 having a stepped cylindrical shape.

[0079] The second sun gear constituting the second sun element 21 is configured by providing a plurality of teeth on the outer peripheral surface of a cylindrical body fitted and fixed to the other axial end of the shaft member 18 .

[0080] The number of teeth of the first intermediate gear that constitutes the first intermediate element 22 is greater than the number of teeth of the first sun gear that constitutes the first sun element 20, and is also greater than the number of teeth of the second intermediate gear that constitutes the second intermediate element 23. As a result, in the high reduction ratio mode of the two-speed transmission 1, where relative rotation between the carrier 19 and the first sun element 20 is possible and rotation of the first sun element 20 relative to the structural element 28 is prevented, the rotation input to the transmission input element 4 is reduced in the reduction unit 6.

[0081] In this example, the first intermediate gear constituting the first intermediate element 22 is configured by providing a plurality of teeth on the outer peripheral surface of a cylindrical body fitted and fixed to the other axial side portion of the intermediate shaft 30. The second intermediate gear constituting the second intermediate element 23 is configured by providing a plurality of teeth on the outer peripheral surface of one axial side portion of the intermediate shaft 30.

[0082] The connection between the first intermediate element 22 and the second intermediate element 23 is supported by the carrier 19 via a support shaft 31 and a radial bearing 32 so as to be rotatable (spinning) about its central axis.

[0083] The support shaft 31 is supported so as to span between the pair of rim portions 24a, 24b, with its central axis arranged parallel to the central axis of the carrier 19. Specifically, the end portion of the support shaft 31 on one axial side is supported and fixed to a radially intermediate portion of the rim portion 24a on one axial side, and the end portion of the support shaft 31 on the other axial side is supported and fixed to a radially intermediate portion of the side plate portion 26 of the rim portion 24b on the other axial side.

[0084] In this example, the radial bearing 32 is disposed between the inner peripheral surface of the intermediate shaft 30 and the outer peripheral surface of the support shaft 31. The radial bearing 32 is configured as a radial rolling bearing having a plurality of rolling elements such as needles, or a cylindrical radial sliding bearing. In this example, the radial bearing 32 is configured by arranging a plurality of needles in double rows between an outer ring raceway provided on the inner peripheral surface of the intermediate shaft 30 and an inner ring raceway provided on the outer peripheral surface of the support shaft 31.

[0085] When the reduction unit 6 is configured by a gear reducer as in this example, the pitches of the gears that make up the first sun element 20, the second sun element 21, the multiple first intermediate elements 22, and the multiple second intermediate elements 23 can be made approximately the same. In this case, in accordance with the relative magnitudes of the numbers of teeth of these elements (gears), the pitch diameter of the first intermediate gear that makes up the first intermediate element 22 is larger than the pitch diameter of the second intermediate gear that makes up the second intermediate element 23. Therefore, the pitch diameter of the first sun gear that makes up the first sun element 20 is smaller than the pitch diameter of the second sun gear that makes up the second sun element 21, and the number of teeth of the first sun gear is smaller than the number of teeth of the second sun gear.

[0086] Furthermore, in this example, the pitch diameter of the second intermediate gear that constitutes the second intermediate element 23 is smaller than the pitch diameter of the second sun gear that constitutes the second sun element 21, and the number of teeth of each of the second intermediate gears is smaller than the number of teeth of the second sun gear.

[0087] However, as long as the rotation input to the first sun element 20 can be slowed down by the reduction unit 6 in the high reduction ratio mode of the two-speed transmission 1, the pitch circle diameter of the second intermediate gear constituting the second intermediate element 23 can be made equal to or greater than the pitch circle diameter of the second sun gear constituting the second sun element 21, and the number of teeth of the second intermediate gear can be made equal to or greater than the number of teeth of the second sun gear.

[0088] When the reduction unit 6 is configured with a friction roller reducer, the relationship in size between the outer diameters of the friction rollers is as follows: That is, the outer diameter of the first intermediate roller that constitutes the first intermediate element 22 is equal to or greater than the outer diameter of the first sun roller that constitutes the first sun element 20, preferably greater than the outer diameter of the first sun roller, and is equal to or greater than the outer diameter of the second intermediate roller that constitutes the second intermediate element 23, preferably greater than the outer diameter of the second intermediate roller. The outer diameter of the first sun roller is smaller than the outer diameter of the second sun roller that constitutes the second sun element 21. Furthermore, the outer diameter of the second intermediate roller is smaller than the outer diameter of the second sun roller. However, similarly, the outer diameter of the second intermediate roller can be equal to or greater than the outer diameter of the second sun roller, as long as the rotation input to the first sun element 20 can be decelerated by the reduction unit 6 in the high reduction ratio mode of the two-speed transmission 1.

[0089] In this example, the first shift mechanism 7 has an actuator (not shown), and based on the operation of the actuator, switches between a disconnection mode in which the carrier 19 and the first solar element 20 can rotate relative to each other, and a connection mode in which they cannot rotate relative to each other.

[0090] The first shift mechanism 7 is provided between the carrier cylindrical portion 27 of the carrier 19 and the axially intermediate portion of the sun shaft 29 .

[0091] In this example, the second shift mechanism 8 has an actuator, and switches between a free mode in which the first solar element 20 is rotatable relative to the structural element 28 and a locked mode in which it is not rotatable, based on the operation of the actuator.

[0092] The second shift mechanism 8 is provided between the structural element 28 and the axially intermediate portion and / or the axially other side portion of the sun shaft 29 .

[0093] The actuators constituting the first shift mechanism 7 and the second shift mechanism 8 can be electric actuators such as electric motors and solenoids, or hydraulic cylinders that are operated by hydraulic pressure. However, in electric vehicles, in order to reduce costs or improve fuel economy by simplifying the system and thereby eliminate the need for a hydraulic system or to make the system smaller, it is preferable to use electric actuators as the actuators constituting the first shift mechanism 7 and the second shift mechanism 8.

[0094] The actuators constituting the first shift mechanism 7 and the second shift mechanism 8 may be the same actuator or different actuators.

[0095] At least a portion of the first shift mechanism 7, the second shift mechanism 8, or both, can be disposed radially inward of the transmission input element 4. In this example, one axial side portion of the first shift mechanism 7 is disposed radially inward of the input member 16 of the transmission input element 4. However, the first shift mechanism 7 and the second shift mechanism 8 can also be disposed at a position offset from the transmission input element 4 in the axial direction.

[0096] The transmission output element 5 is provided on the outer peripheral surface of a shaft member 18 that is rotatably supported by a bearing 17 relative to a structural element 28, for example. In this example, the shaft member 18 has a stepped cylindrical shape and includes a large-diameter portion provided in an axially intermediate portion and small-diameter portions provided on both sides of the axially intermediate portion, and is rotatably supported relative to the structural element 28 by bearings 17 fitted onto the outside of the small-diameter portions. The transmission output element 5 is configured by providing a plurality of teeth on the outer peripheral surface of the large-diameter portion of the shaft member 18. In this example, fitting the bearing 17 onto the outside of the small-diameter portion of the shaft member 18 contributes to the miniaturization of the structure including the transmission output element 5.

[0097] <Driving device for electric vehicle> The driving device for electric vehicle of this example includes the two-speed transmission 1 of this example and an electric motor 2, and has the function of transmitting the rotation of the electric motor 2 to a plurality of driving wheels after reducing the speed by the two-speed transmission 1. In the two-speed transmission 1 of this example, the reduction unit 6 is made compact, so that the entire driving device for electric vehicle of this example can be made compact.

[0098] The electric vehicle drive system of this example can further include a differential mechanism 3 as an optional element. In this case, the electric vehicle drive system is configured so that the rotation of the electric motor 2 is reduced in speed by the two-speed transmission 1, input to the differential mechanism 3, and distributed to a plurality of drive wheels (not shown) by the differential mechanism 3. In this example, although not limited to this, the electric motor 2 is disposed on one side in the axial direction of the two-speed transmission 1. This makes it easier to achieve size reduction compared to a structure in which the electric motor 2 is disposed radially outward of the two-speed transmission 1.

[0099] The electric motor 2 includes a motor housing 9 , a motor output shaft 10 , a rotor 11 , and a stator 12 .

[0100] The motor output shaft 10 is rotatably supported inside the motor housing 9 via a plurality of bearings 33. In this example, the motor output shaft 10 extends from the motor housing 9 to the other axial side.

[0101] The rotor 11 is fitted and fixed around the motor output shaft 10 so as to rotate integrally with the motor output shaft 10. The rotor 11 can have any of various conventionally known structures, such as a squirrel-cage type, a wound type, or a permanent magnet type.

[0102] The stator 12 is disposed coaxially around the rotor 11 and is supported and fixed inside the motor housing 9. Specifically, the inner peripheral surface of the stator 12 faces the outer peripheral surface of the rotor 11 via a small radial gap, and the outer peripheral surface of the stator 12 is fitted and fixed inside the motor housing 9. The stator 12 can have any of various conventionally known structures, such as a wound type or a permanent magnet type.

[0103] The structure for rotationally driving the transmission input element 4 by the electric motor 2 is not particularly limited, and the transmission input element 4 can be rotationally driven directly by the electric motor 2 or via a reducer.

[0104] When the electric motor 2 is configured to directly rotate the transmission input element 4 , the transmission input element 4 can be formed directly on the motor output shaft 10 or can be fitted and fixed to the outside of the motor output shaft 10 .

[0105] When the transmission input element 4 is configured to be rotationally driven by the electric motor 2 via a reducer, for example, the transmission input element 4 may be configured as a gear (input gear), and the gear may be meshed with a drive gear 13 provided on the motor output shaft 10 directly or via one or more gears. Alternatively, the transmission input element 4 may be configured as a pulley, and a belt may be stretched between the pulley and a drive pulley provided on the motor output shaft 10. Alternatively, the transmission input element 4 may be configured as a sprocket, and a chain may be stretched between the sprocket and a drive sprocket provided on the motor output shaft 10.

[0106] In this example, the transmission input element 4 of the two-speed transmission 1 is configured by a gear (input gear), and a drive gear 13 provided at the tip of the motor output shaft 10 is meshed with the input gear.

[0107] The transmission input element (input gear) 4 and the drive gear 13 are not particularly limited as long as they can mesh with each other and transmit torque. For example, the transmission input element 4 and the drive gear 13 may be configured as spur gears, helical gears, etc. In this example, the transmission input element 4 and the drive gear 13 are configured as helical gears.

[0108] The differential mechanism 3 has a differential input element 14 that is rotationally driven based on the rotation of the transmission output element 5, and distributes the rotation input to the differential input element 14 to a plurality of drive wheels.

[0109] The structure of the differential mechanism 3 is not particularly limited as long as it can distribute the rotation input to the differential input element 14 to a plurality of drive wheels. Specifically, the differential mechanism 3 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.

[0110] Examples of differentials having a mechanism for limiting differential include, but are not limited to, a differential lock that has a mechanism for forcibly locking 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 3, 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.

[0111] In this example, the differential mechanism 3 is composed of an open differential that distributes the rotation input to the differential input element 14 to a pair of drive shafts 15a, 15b, each connected via a constant velocity joint so that torque can be transmitted to the drive wheels.

[0112] The structure for transmitting the rotation of the transmission output element 5 to the differential input element 14 is not particularly limited. For example, the transmission output element 5 and the differential input element 14 can each be configured with gears, and these gears can be meshed directly or via one or more intermediate gears. Alternatively, the transmission output element 5 and the differential input element 14 can each be configured with pulleys, and a belt can be stretched between these pulleys. Alternatively, the transmission output element 5 and the differential input element 14 can each be configured with sprockets, and a chain can be stretched between these sprockets.

[0113] In this example, the transmission output element 5 of the two-speed transmission 1 is configured by a gear (output gear), and the output gear is directly meshed with the gear that constitutes the differential input element 14 .

[0114] In this case, the transmission output element (output gear) 5 and the differential input element 14 are not particularly limited as long as they can mesh with each other and transmit torque. For example, the transmission output element 5 and the differential input element 14 may be configured as spur gears, helical gears, etc. In this example, the transmission output element 5 and the differential input element 14 are configured as helical gears.

[0115] In the electric vehicle drive system of this example, the two-speed transmission 1 and the electric motor 2, and further the differential mechanism 3, may be disposed in any position. That is, the electric motor 2 may be disposed on the other axial side of the two-speed transmission 1.

[0116] [Second Example] A second example of the embodiment of the present disclosure will be described with reference to Figures 12 to 16. In this example, components having the same functions as those in the first example are denoted by the same reference numerals, and detailed descriptions thereof will be omitted.

[0117] In this example, at least a portion of at least one of the first solar element 20, the second solar element 21, the plurality of first intermediate elements 22, or the plurality of second intermediate elements 23 of the reduction section 6 is arranged radially inside the transmission input element 4a.

[0118] More specifically, one axial side portion of the first solar element 20 and one axial side portion of the multiple first intermediate elements 22, and the other axial side portion of the second solar element 21 and the other axial side portions of the multiple second intermediate elements 23 are arranged radially inside the input member 16a of the transmission input element 4a.

[0119] For this reason, the rim portion 24c on the other axial side of the carrier 19a includes a side plate portion 26 having a hollow circular plate shape, and a cylindrical carrier portion 27a that extends axially to one side from the radially outer end of the side plate portion 26. The input member 16a of the transmission input element 4a is externally fitted and fixed to the outer peripheral surface of the carrier portion 27a so as not to rotate relative to it.

[0120] According to this example, the axial dimension of the speed reducer portion 6a can be made even shorter than the axial dimension of the speed reducer portion 6 of the first example.

[0121] The other configurations and effects of the second example are the same as those of the first example.

[0122] DESCRIPTION OF SYMBOLS 1 Two-speed transmission 2 Electric motor 3 Differential mechanism 4, 4a Transmission input element 5 Transmission output element 6, 6a Reduction section 7 First shift mechanism 8 Second shift mechanism 9 Motor housing 10 Motor output shaft 11 Rotor 12 Stator 13 Drive gear 14 Differential input element 15a, 15b Drive shaft 16, 16a Input member 17 Bearing 18 Shaft member 19, 19a Carrier 20 First sun element 21 Second sun element 22 First intermediate element 23 Second intermediate element 24a, 24b, 24c Rim portion 25 Connection portion 26 Side plate portion 27, 27a Carrier cylinder portion 28 Structural element 29 Sun shaft 30 Intermediate shaft 31 Support shaft 32 Radial bearing 33 Bearing

Claims

1. A reduction gear unit having a rotatably supported transmission input element, a transmission output element supported coaxially with the transmission input element and capable of relative rotation with respect to the transmission input element, a carrier, a first sun element, a second sun element, a plurality of first intermediate elements, and a plurality of second intermediate elements, wherein the carrier rotates integrally with the transmission input element, the first sun element is supported coaxially with the transmission input element and capable of relative rotation with respect to the transmission input element and the transmission output element, the second sun element rotates integrally with the transmission output element, the plurality of first intermediate elements are supported on the carrier to be rotatable about their respective central axes and are each engaged with the first sun element so as to be able to transmit torque, and the plurality of second intermediate elements are each configured to rotate integrally with the plurality of first intermediate elements and are each engaged with the second sun element so as to be able to transmit torque. a first shift mechanism provided between the carrier and the first solar element, for switching between a disconnected mode in which the carrier and the first solar element are rotatable relative to each other and a connected mode in which the carrier and the first solar element are not rotatable relative to each other; and a second shift mechanism provided between the first solar element and a structural element that does not rotate even when in use, for switching between a free mode in which the first solar element is rotatable relative to the structural element and a locked mode in which the first solar element is not rotatable.

2. A two-speed transmission as described in claim 1, wherein at least a portion of at least one of the first sun element, the second sun element, the plurality of first intermediate elements, or the plurality of second intermediate elements of the reduction section is arranged radially inward of the transmission input element.

3. A two-speed transmission as set forth in claim 1 or 2, wherein the first sun element is constituted by a first sun gear, the second sun element is constituted by a second sun gear, the plurality of first intermediate elements are constituted by a plurality of first intermediate gears, and the plurality of second intermediate elements are constituted by a plurality of second intermediate gears.

4. A two-speed transmission according to any one of claims 1 to 3, wherein the transmission input element, the transmission output element, or both, are constituted by gears.

5. A drive device for an electric vehicle, comprising: a two-speed transmission having a transmission input element; and an electric motor for rotationally driving the transmission input element, wherein the two-speed transmission is configured as the two-speed transmission according to any one of claims 1 to 4.

6. The electric vehicle drive device according to claim 5, further comprising a differential mechanism having a differential input element that is rotationally driven based on the rotation of the transmission output element, and distributing the rotation input to the differential input element to a plurality of drive wheels.

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