Power transmission device

Abstract

A power transmission device comprises: a first input shaft, which inputs power from a first power source; a second input shaft, which inputs power from a second power source; a first output shaft, which outputs power to a first drive wheel; a second output shaft, which outputs power to a second drive wheel; and a differential device, the differential device having a first rotating element connected to the second input shaft, a second rotating element connected to the second output shaft, and a third rotating element connected to the first input shaft and the first output shaft as three rotating elements, the power transmission device having a coupling device for selectively connecting any two of the three rotating elements.

Description

Technical Field

[0001] The present invention relates to a power transmission device. Background Art

[0002] A transfer case is a known power transmission device mounted on a vehicle, which distributes power from the engine (first power source) and transmits it to the front and rear wheels. The output side of the transfer case is connected to the front and rear wheel propeller shafts. Furthermore, the transfer case can switch between a two-wheel drive mode, in which power is output to only one propeller shaft, and a four-wheel drive mode, in which power is output to both propeller shafts.

[0003] International Publication No. 2010 / 141682 discloses a transfer case having an auxiliary power source (second power source) within the transfer case housing, wherein power output from the second power source is transmitted to the front and rear wheels via a differential device. In the structure described in International Publication No. 2010 / 141682, by fixing one of the three rotating elements included in the differential device to the transfer case housing, the differential device functions as a transmission, and the rotation of the first power source is shifted by the differential device and transmitted to the output member. Summary of the Invention

[0004] In the structure described in International Publication No. 2010 / 141682, when four-wheel drive is performed with the differential device performing differential action, the torque of the second power source acts on the first and second output shafts, and the torques of the output shafts may be in opposite directions.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power transmission device capable of suppressing the torque of each output shaft from being in the reverse direction when power is transmitted via a differential device.

[0006] The present invention is a power transmission device, which includes: a first input shaft, which inputs power from a first power source; a second input shaft, which inputs power from a second power source; a first output shaft, which outputs power to a first drive wheel; a second output shaft, which outputs power to a second drive wheel; and a differential device, which has a first rotating element connected to the second input shaft, a second rotating element connected to the second output shaft, and a third rotating element connected to the first input shaft and the first output shaft as three rotating elements. The power transmission device is characterized in that it has a coupling device for selectively connecting any two of the three rotating elements.

[0007] According to this configuration, the differential action of the differential can be limited by coupling any two of the three rotating elements included in the differential using the engagement device. Therefore, by limiting the differential action of the differential using the engagement device during power transmission through the differential, the torque of each output shaft can be prevented from being reversed.

[0008] Furthermore, the engagement device may switch between an engaged state in which the three rotation elements are allowed to rotate integrally and a released state in which the three rotation elements are allowed to perform differential motion.

[0009] According to this configuration, by switching the engagement device between the engaged state and the released state, it is possible to switch between a state in which the differential action of the differential device is restricted and a state in which the differential action of the differential device is not restricted.

[0010] Furthermore, the engagement device may selectively couple the second rotation element and the third rotation element.

[0011] According to this structure, when the second rotating element and the third rotating element are connected by the engagement device, the three rotating elements can rotate integrally. This can limit the differential action of the differential device and prevent the torques of the first output shaft and the second output shaft from being in opposite directions even when the torque of the second power source acts.

[0012] Furthermore, the engagement device may be a friction engagement device.

[0013] According to this configuration, the engagement device can be configured using the friction engagement device.

[0014] Furthermore, the engagement device may selectively couple the first rotation element and the second rotation element.

[0015] According to this structure, when the first rotating element and the second rotating element are connected by the engagement device, the three rotating elements can rotate integrally. This can limit the differential action of the differential device, and even if the torque of the second power source acts, it can also prevent the torque of the first output shaft and the second output shaft from being in opposite directions.

[0016] Furthermore, the differential device may be a planetary gear device.

[0017] According to this configuration, a differential device can be configured using the planetary gear device.

[0018] In addition, the power transmission device may also include a first transmission device, which is arranged in the power transmission path between the differential device and the second output shaft, the first output shaft and the first input shaft are arranged on the same axis, and the second output shaft is arranged parallel to the first output shaft and is connected to the differential device via the first transmission device so as to transmit power.

[0019] According to this configuration, power can be transmitted to the second output shaft and the second drive wheel via the differential device and the first transmission device.

[0020] Furthermore, the first transmission device may be configured to include a chain belt.

[0021] According to this configuration, the first transmission device can be configured as a mechanism including a chain belt.

[0022] Furthermore, the first transmission device and the differential device may be arranged coaxially with the first output shaft in order from the first power source side, and the second output shaft may extend axially from the first transmission device toward the first power source side.

[0023] According to this configuration, the second output shaft can be shortened by positioning the first transmission device closer to the first power source than the differential device.

[0024] Furthermore, the first transmission device and the engagement device may be arranged coaxially with the first output shaft in order from the first power source side, and the second output shaft may extend axially from the first transmission device toward the first power source side.

[0025] According to this configuration, the second output shaft can be shortened by positioning the first transmission device closer to the first power source than the engagement device.

[0026] In addition, the differential device and the second power source may be arranged in sequence from the first power source side on the same axis as the first output shaft, and the second output shaft may extend axially from a position between the differential device and the second power source toward the first power source side.

[0027] According to this configuration, the second output shaft can be shortened by extending the second output shaft from the axial position between the differential device and the second power source toward the first power source.

[0028] In addition, the power transmission device may also include a second transmission device, which is arranged in the power transmission path between the second power source and the differential device, and the second power source is arranged on a shaft other than the first output shaft and the second output shaft, and is connected to the differential device via the second transmission device so as to transmit power.

[0029] According to this configuration, it is possible to obtain a degree of freedom in the arrangement of the second power source or the arrangement of the differential device.

[0030] Furthermore, the second transmission device may be a speed reducer.

[0031] According to this configuration, the rotation of the second power source can be decelerated and transmitted to the second input shaft.

[0032] In the present invention, the differential action of the differential is limited by coupling any two of the three rotating elements included in the differential with a coupling device. Therefore, when power is transmitted through the differential, limiting the differential action of the differential by the coupling device prevents the torque of each output shaft from being reversed. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0034] Figure 1 It is a schematic diagram schematically showing a vehicle equipped with the power transmission device according to the embodiment.

[0035] Figure 2 It is a schematic diagram schematically showing the structure of a transfer case in the embodiment.

[0036] Figure 3 It is a collinear diagram showing the state of the rotating elements in the planetary gear device in the integrated state.

[0037] Figure 4 This is a schematic diagram schematically showing the structure of a transfer case in a first modified example.

[0038] Figure 5 It is a schematic diagram schematically showing the structure of a transfer case in a second modified example.

[0039] Figure 6 This is a schematic diagram schematically showing the structure of a transfer case in a third modified example.

[0040] Figure 7 This is a schematic diagram schematically showing the structure of a transfer case in a fourth modified example.

[0041] Figure 8 It is a schematic diagram schematically showing the structure of a transfer case in a fifth modification.

[0042] Figure 9 This is a schematic diagram schematically showing the structure of a transfer case in a sixth modified example. DETAILED DESCRIPTION

[0043] Hereinafter, the power transmission device in the embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiment described below.

[0044] Figure 1 This is a schematic diagram schematically illustrating a vehicle equipped with a power transmission device according to an embodiment. Vehicle 1 includes an engine 2 as a power source, left and right front wheels 3L and 3R, left and right rear wheels 4L and 4R, and a power transmission device 10 that transmits power from engine 2 to the front wheels 3 and rear wheels 4, respectively. Vehicle 1 is a four-wheel drive vehicle based on front-engine rear-wheel drive. The rear wheels 4 are the main drive wheels that serve as drive wheels during both two-wheel drive and four-wheel drive. On the other hand, the front wheels 3 are auxiliary drive wheels that serve as driven wheels during two-wheel drive and as drive wheels during four-wheel drive. In this embodiment, the rear wheels 4 serve as the first drive wheels, and the front wheels 3 serve as the second drive wheels.

[0045] The power transmission device 10 includes a transmission 11 connected to the engine 2, a transfer case 12 connected to the transmission 11 as a front and rear wheel power distribution device, a front propeller shaft 13 and a rear propeller shaft 14 connected to the transfer case 12, a front wheel differential gear mechanism 15 connected to the front propeller shaft 13, a rear wheel differential gear mechanism 16 connected to the rear propeller shaft 14, left and right front wheel axles 17L and 17R connected to the front wheel differential gear mechanism 15, and left and right rear wheel axles 18L and 18R connected to the rear wheel differential gear mechanism 16. In the absence of a particular distinction between wheels and axles, L and R are omitted in the reference numerals and are referred to as the front wheel 3, the rear wheel 4, the front wheel axle 17, and the rear wheel axle 18.

[0046] The power output from the engine 2 is transmitted to the transfer case 12 via the transmission 11. The power transmitted to the transfer case 12 is then transmitted from the transfer case 12 to the rear wheels 4 via a power transmission path on the rear wheel side, which includes a rear propeller shaft 14, a rear wheel differential gear mechanism 16, and a rear axle 18. Furthermore, a portion of the power transmitted to the rear wheels 4 is distributed by the transfer case 12 to the front wheels 3 and then transmitted to the front wheels 3 via a power transmission path on the front wheel side, which includes a front propeller shaft 13, a front wheel differential gear mechanism 15, and a front axle 17.

[0047] Figure 2This is a schematic diagram schematically illustrating the structure of a transfer case in an embodiment. The transfer case 12 includes a transfer case housing 20 as a non-rotating member. Furthermore, the transfer case 12 includes a first input shaft 21, a second input shaft 22, a rear wheel output shaft 23, a front wheel output shaft 24, a planetary gear unit 25, a transmission unit 26, a motor 30, and a coupling device 40 within the transfer case housing 20.

[0048] The first input shaft 21 is an input member that inputs power from the engine 2 to the transfer case 12. The power from the engine 2 is transmitted to the first input shaft 21 via the transmission 11. For example, the first input shaft 21 is spline-fitted to an output member of the transmission 11.

[0049] The second input shaft 22 is an input member that inputs power from the motor 30 to the planetary gear device 25. The power from the motor 30 is directly input to the second input shaft 22. For example, the second input shaft 22 is spline-fitted with the output member (rotor shaft 33) of the motor 30 and rotates integrally with the rotor shaft 33.

[0050] The rear wheel output shaft 23 is an output member that outputs power from the transfer case 12 to the rear wheels 4. This rear wheel output shaft 23 is a main drive shaft that is coaxially arranged with the first input shaft 21 and is connected to the rear propeller shaft 14. In the transfer case 12, the rear wheel output shaft 23 is the first output shaft.

[0051] The front-wheel output shaft 24 is a second output shaft that outputs power from the transfer case 12 to the front wheels 3. This front-wheel output shaft 24 is a secondary drive shaft that is arranged on a separate axis from the first input shaft 21 and the rear-wheel output shaft 23 and is connected to the front propeller shaft 13. In the transfer case 12, the front-wheel output shaft 24 is a second output shaft that is arranged parallel to the first output shaft and is connected to the planetary gear unit 25 via a transmission device 26 for power transmission.

[0052] The planetary gear device 25 is a differential device having three rotation elements and is composed of a single pinion type planetary gear device. The planetary gear device 25 functions as a power distribution mechanism that distributes power from a power source to the front wheels 3 and the rear wheels 4 .

[0053] like Figure 2 As shown, the planetary gear device 25 includes three rotating elements: a sun gear S, a carrier C that supports multiple pairs of mutually meshing pinion gears so that they can rotate and revolve, and a ring gear R that meshes with the sun gear S via the pinion gears. In this embodiment, the sun gear S is the first rotating element, the carrier C is the second rotating element, and the ring gear R is the third rotating element.

[0054] The second input shaft 22 is coupled to the sun gear S so as to rotate integrally therewith. In other words, the sun gear S is coupled to the motor 30 .

[0055] A first rotating member 51 is connected to the gear carrier C so as to rotate integrally therewith. The first rotating member 51 is a member that rotates integrally with the gear carrier C and has gear teeth 51a as engaging elements. The drive gear 27 of the transmission device 26 is connected to the first rotating member 51 so as to rotate integrally therewith. The transmission device 26 forms a power transmission path between the planetary gear device 25 and the front wheel output shaft 24. In other words, the front wheel output shaft 24 is connected to the gear carrier C.

[0056] A second rotating member 52 is coupled to the ring gear R for integral rotation. The second rotating member 52 rotates integrally with the ring gear R and includes gear teeth 52a as engaging elements. The first input shaft 21 and the rear wheel-side output shaft 23 are coupled to the second rotating member 52 for integral rotation. In other words, the ring gear R is coupled to the first input shaft 21 and the rear wheel-side output shaft 23.

[0057] The transmission device 26 is a mechanism that forms a power transmission path on the front wheel side, and is provided in the power transmission path between the planetary gear device 25 and the front wheel side output shaft 24. The transmission device 26 includes a drive gear 27, a driven gear 28, and a chain belt 29.

[0058] The drive gear 27 is a rotating member that functions as an output portion for the front wheels and is the output gear that transmits power to the front-wheel output shaft 24. The drive gear 27 is coaxially arranged with the first input shaft 21 and the rear-wheel output shaft 23 so as to be rotatable relative to these shafts, and is coupled to the carrier C for integral rotation. In the transfer case 12, the drive gear 27 and the rotating elements of the planetary gear set 25 are arranged coaxially with the rear-wheel output shaft 23.

[0059] The driven gear 28 is a gear integrally provided with the front wheel output shaft 24. The chain belt 29 is a front wheel drive chain connecting the drive gear 27 and the driven gear 28. Furthermore, the rotation of the drive gear 27 rotates the driven gear 28, and the driven gear 28 rotates integrally with the front wheel output shaft 24. In this embodiment, the transmission device 26 is the first transmission device.

[0060] The motor 30 is a rotating electrical machine (motor generator) capable of functioning as both an electric motor and a generator. The motor 30 is electrically connected to a battery via an inverter. The motor 30 includes a rotor 31, a stator 32, and a rotor shaft 33. The rotor 31 rotates integrally with the rotor shaft 33. The stator 32 includes a stator core and stator coils wound around the stator core. The second input shaft 22 is coupled to the rotor shaft 33 for integral rotation.

[0061] The engagement device 40 is a clutch that switches the state of the planetary gear set 25, switching between an engaged state and a released state. The engagement device 40 connects the carrier C and the ring gear R so that they rotate integrally. Furthermore, the engagement device 40 switches between an integrated state, in which the carrier C and the ring gear R rotate integrally, and a differential state, in which the carrier C and the ring gear R rotate relative to each other. In other words, the engagement device 40 switches between an engaged state that restricts the differential action of the planetary gear set 25 and a released state that does not restrict the differential action of the planetary gear set 25.

[0062] The coupling device 40 is composed of a dog clutch and has a switching sleeve 41. The switching sleeve 41 has gear teeth 41a as a coupling element. The gear teeth 41a mesh with the gear teeth 51a of the first rotating member 51 that rotates integrally with the gear frame C and the gear teeth 52a of the second rotating member 52 that rotates integrally with the ring gear R. In addition, the switching sleeve 41 is moved in the axial direction by the actuator of the coupling device 40. And the switching sleeve 41 switches between an integrated state in which the gear frame C and the ring gear R are connected in a manner that can rotate integrally and a differential state in which the three rotating elements act differentially. That is, the coupling device 40 becomes an engaged state by the gear teeth 41a of the switching sleeve 41 meshing with both the gear teeth 51a and the gear teeth 52a, and becomes a released state by the gear teeth 41a of the switching sleeve 41 meshing with only one of the gear teeth 51a and the gear teeth 52a.

[0063] Inside the transfer case 20, a motor 30, a transmission 26, and a planetary gear 25 are arranged in this order from the engine side in the axial direction, coaxially with the rear wheel output shaft 23. Furthermore, the front wheel output shaft 24 extends axially from the transmission 26 toward the engine side.

[0064] Furthermore, when the transfer case 12 is in the four-wheel drive state, it switches between a differential state in which the rotational differential between the rear propeller shaft 14 and the front propeller shaft 13 is not restricted, and a non-differential state in which the rotational differential between them is restricted. That is, in the power distribution state, the transfer case 12 can switch between a state in which the rear wheel output shaft 23 and the drive gear 27 are in a differential state, and a state in which the rear wheel output shaft 23 and the drive gear 27 are in a non-differential state.

[0065] In addition, if Figure 1As shown, vehicle 1 includes an electronic control unit 100 for controlling vehicle 1. Electronic control unit 100 outputs command signals to the actuators that operate engagement device 40, thereby controlling the operation of engagement device 40. For example, electronic control unit 100 is configured as a microcomputer including a CPU, RAM, ROM, and input / output interfaces. The CPU executes various controls for vehicle 1 by performing signal processing according to programs pre-stored in ROM while utilizing the RAM's temporary storage function.

[0066] Signals from various sensors mounted on the vehicle 1 are input to the electronic control unit 100. For example, sensor signals from the engine speed sensor, the motor rotation angle sensor, the vehicle speed sensor, the accelerator position sensor, and the 4WD select switch used by the driver to select the four-wheel drive state are input to the electronic control unit 100. Based on the input sensor signals, the electronic control unit 100 performs drive control of the vehicle 1, etc. Furthermore, the electronic control unit 100 outputs command signals for controlling the engine 2, the transmission 11, and the transfer case 12. The command signals for controlling the transfer case 12 include command signals for controlling the motor 30 and the clutch device 40.

[0067] Therefore, the electronic control unit 100 controls the state of the planetary gear unit 25 by controlling the operation of the motor 30 and the state of the coupling device 40 when controlling the drive state of the transfer case 12. By having the electronic control unit 100 perform switching control of the coupling device 40, the planetary gear unit 25 can switch between an integrated state and a differential state. The integrated state is a state in which two of the three rotating elements included in the planetary gear unit 25 are connected to each other. The differential state is a state in which the three rotating elements included in the planetary gear unit 25 can perform a differential action. Moreover, in the transfer case 12, regardless of the state of the planetary gear unit 25, the three rotating elements are respectively connected to the motor 30, the engine 2, the rear wheel side output shaft 23, and the front wheel side output shaft 24.

[0068] Figure 3 is a collinear diagram showing the state of the rotating elements in the planetary gear device in an integrated state. Figure 3 , the motor 30 is described as “MG”, the engine 2 is described as “ENG”, the sun gear S is described as “S”, the carrier C is described as “C”, the ring gear R is described as “R”, and the clutch device 40 is described as “CL”.

[0069] In the transfer case 12, as Figure 3As shown, with the engagement device 40 engaged, the planetary gear unit 25 is integrated. In this integrated state, a fixed-displacement 4WD mode is possible, which transmits power to the front wheels 3 and rear wheels 4. Specifically, when the transfer case 12 is in the fixed-displacement 4WD mode, the switching sleeve 41 meshes with the first rotating element 51 and the second rotating element 52.

[0070] In this fixed-displacement 4WD mode, power transmitted from the engine 2 to the first input shaft 21 is transmitted to the rear-wheel output shaft 23 and then to the front-wheel output shaft 24 via the integrated planetary gear set 25. Specifically, in this fixed-displacement 4WD mode, when distributing the engine 2's power to the front-wheel output shaft 24, the differential action of the planetary gear set 25 is limited by engaging the engagement device 40, allowing the three rotating elements to rotate at the same speed. Therefore, when torque Tm from the motor 30 acts on the front-wheel output shaft 24, torque T2 acting on the front-wheel output shaft 24 and torque T1 acting on the rear-wheel output shaft 23 can both be positive torques. Consequently, when torque Tm from the motor 30 is transmitted to the front-wheel output shaft 24 via the planetary gear set 25, torques T1 and T2 on each output shaft can be prevented from rotating in the opposite directions. Furthermore, the fact that the torques of the respective output shafts are in opposite directions indicates that when the motor 30 outputs torque such that positive torque acts on the front-wheel output shaft 24, the reaction force of this torque acts on the rear-wheel output shaft 23. As a result, the torque of the front-wheel output shaft 24 is in the positive direction, while the torque of the rear-wheel output shaft 23 is in the negative direction. In other words, the directions of the torques of the front-wheel output shaft 24 and the rear-wheel output shaft 23 are in opposite directions. In this embodiment, the motor 30 outputs positive torque so that positive torque acts on the front-wheel output shaft 24.

[0071] In addition, in the transfer case 12, the planetary gear device 25 is put into a differential state by making the coupling device 40 into a released state. In this differential state, as a four-wheel drive state in which power is transmitted to the front wheels 3 and the rear wheels 4, a so-called torque distribution 4WD mode can be performed. The purpose of the torque distribution 4WD mode is to use the power of the motor 30 to generate a driving force for the front wheels 3, so as to change the distribution of power transmitted to the rear wheel side output shaft 23 and the front wheel side output shaft 24. That is, in the torque distribution 4WD mode, the motor torque output from the motor 30 can be used to perform front and rear distribution control. When the transfer case 12 is in the torque distribution 4WD mode, the switching sleeve 41 is engaged with only one of the first rotating member 51 and the second rotating member 52.

[0072] In this torque-split 4WD mode, power transmitted from the engine 2 to the first input shaft 21 is transmitted to the rear-wheel output shaft 23, while power transmitted from the motor 30 to the second input shaft 22 is transmitted to the front-wheel output shaft 24 via the planetary gear set 25 in a differential state. Specifically, in the torque-split 4WD mode, when distributing power from the power source between the front wheels 3 and the rear wheels 4, the planetary gear set 25 is enabled to perform differential operation by disengaging the engagement device 40. Therefore, in the torque-split 4WD mode, the distribution of power transmitted to the front and rear wheels can be controlled using the torque output from the motor 30. In this case, since the differential action of the planetary gear set 25 is not restricted, when positive torque is applied to the front-wheel output shaft 24 by the motor 30, negative torque is applied to the rear-wheel output shaft 23 by the reaction force of this torque. In other words, positive torque due to the torque from the engine 2 and negative torque due to the reaction force of the motor torque act on the rear-wheel output shaft 23.

[0073] As described above, according to the embodiment, by switching the engagement device 40 between the engaged state and the released state, the differential action of the planetary gear device 25 can be selectively limited. Therefore, when the differential action of the planetary gear device 25 is limited, even if the torque of the motor 30 causes a positive torque to act on the front wheel-side output shaft 24, the direction of the torque of each output shaft can be prevented from being reversed.

[0074] Furthermore, motor 30 is comprised of a rotating electrical machine (motor generator), and thus can generate electricity using the power from engine 2 or regenerate electricity using the power input from the drive wheels. The electricity generated by motor 30 is stored in a battery. Furthermore, the first and second power sources may be either an engine or a rotating electrical machine. For example, the first power source may be a rotating electrical machine, and the second power source may be an engine.

[0075] In addition, as a modification of the above embodiment, a friction type engagement device may be provided instead of the meshing type engagement device 40. Figure 4 As shown, the transfer case 12 of the first modified example includes a friction engagement device 60 that selectively couples the carrier C and the ring gear R.

[0076] The friction engagement device 60 selectively connects the first rotating member 51 that rotates integrally with the gear carrier C and the second rotating member 52 that rotates integrally with the ring gear R. The friction engagement device 60 includes a first friction engagement element that rotates integrally with the first rotating member 51 and a second friction engagement element that rotates integrally with the second rotating member 52. The friction engagement device 60 is operated by a hydraulic actuator. In addition, in this first modified example, the motor 30, the transmission device 26, the friction engagement device 60, and the planetary gear device 25 are arranged in order from the engine side in the axial direction on the same axis as the rear wheel side output shaft 23. By locating the friction engagement device 60 at a position farther rearward than the transmission device 26, the front wheel side output shaft 24 can be shortened.

[0077] Furthermore, when the three rotating elements are integrated in order to limit the differential action of the planetary gear device 25, it is not limited to the case where the carrier C and the ring gear R are connected so as to be able to rotate integrally. In other words, the two rotating elements connected so as to be able to rotate integrally are not particularly limited, and any two rotating elements among the three rotating elements in the planetary gear device 25 can be selectively connected. For example, Figure 5 As shown, the transfer case 12 of the second modified example includes a friction engagement device 61 that selectively couples the sun gear S and the ring gear R.

[0078] The friction engagement device 61 selectively connects the third rotating member 53, which rotates integrally with the sun gear S, and the second rotating member 52, which rotates integrally with the ring gear R. The friction engagement device 61 includes a first friction engagement element that rotates integrally with the third rotating member 53 and a second friction engagement element that rotates integrally with the second rotating member 52. Furthermore, the friction engagement device 61 is operated by a hydraulic actuator. Furthermore, in this second modified example, the motor 30, the transmission device 26, the planetary gear device 25, and the friction engagement device 61 are arranged in this order, axially from the engine side, on the same axis as the rear wheel output shaft 23. By positioning the friction engagement device 61 further rearward than the transmission device 26, the front wheel output shaft 24 can be shortened.

[0079] In addition, as a further modification of the second modification, the motor 30, the transmission device 26, the planetary gear device 25 and the friction engagement device 61 may be arranged in the same manner as in the axial direction. Figure 5 The configurations shown are different. Figure 6 As shown, the transfer case 12 of the third modification is provided with the friction engagement device 61, the planetary gear unit 25, the transmission device 26, and the motor 30 in the order from the engine side in the axial direction.

[0080] As another modification, the motor 30 is not limited to being arranged on the same axis as the first input shaft 21 and the rear wheel output shaft 23 , but may be arranged on an axis different from the first input shaft 21 and the rear wheel output shaft 23 . Figure 7 and Figure 8 An example of this modification will be described below.

[0081] For example, Figure 7 As shown, the transfer case 12 of the fourth modification includes a motor 30 arranged on a different axis from the first input shaft 21 and the second input shaft 22; and a second transmission device 70 provided in the power transmission path between the motor 30 and the second input shaft 22. This fourth modification is a further modification of the second modification. Furthermore, in the transfer case 12, arranged in this order in the axial direction from the engine side are the second transmission device 70, the transmission device 26, the friction engagement device 60, and the planetary gear device 25.

[0082] The second transmission device 70 includes a reduction gear 71, an intermediate gear (English: counter gear) 72, and an input gear 73. The reduction gear 71 is provided on the rotor shaft 33 of the motor 30. The reduction gear 71 meshes with the intermediate gear 72. The intermediate gear 72 meshes with the input gear 73. The input gear 73 is mounted on the second input shaft 22 and rotates integrally with the second input shaft 22. The reduction gear 71, the intermediate gear 72, and the input gear 73 form a reduction gear train. Therefore, in the fourth modified example, when the power output from the motor 30 is transmitted to the second input shaft 22 via the second transmission device 70, the rotation of the motor 30 is shifted (reduced) and transmitted to the sun gear S. Furthermore, because the motor 30 is arranged on a different axis from the first input shaft 21 and the rear-wheel output shaft 23, it can be arranged in a position that axially overlaps with the transmission device 26, thereby reducing the axial size of the transfer case 12. This provides greater flexibility in the placement of the motor 30 and the planetary gear device 25.

[0083] For example, Figure 8 As shown, the transfer case 12 of the fifth modification includes a motor 30 arranged on a different axis from the first input shaft 21 and the second input shaft 22; and a second transmission device 80 provided in the power transmission path between the motor 30 and the second input shaft 22. This fifth modification is a further modification of the third modification. Furthermore, in the transfer case 12, arranged in the order of the friction engagement device 61, the planetary gear device 25, the transmission device 26, the second transmission device 80, and the motor 30 in the axial direction from the engine side.

[0084] The second transmission device 80 has a reduction gear 81 and an input gear 82. The reduction gear 81 is provided on the rotor shaft 33 of the motor 30. The reduction gear 81 is engaged with the input gear 82. The input gear 82 is mounted on the second input shaft 22 and rotates integrally with the second input shaft 22. The reduction gear 81 is a gear having a smaller diameter than the input gear 82, so the reduction gear train is formed by the reduction gear 81 and the input gear 82. In other words, the second transmission device 80 is a reducer. Therefore, in the fifth variant, when the power output from the motor 30 is transmitted to the second input shaft 22 via the second transmission device 80, the rotation of the motor 30 is changed in speed (reduced) and transmitted to the sun gear S.

[0085] In addition, as another modification, Figure 9 As shown, in the transfer case 12 of the sixth modification, in the planetary gear device 25, the motor 30 is connected to the sun gear S, the first input shaft 21 and the rear wheel output shaft 23 are connected to the carrier C, and the front wheel output shaft 24 is connected to the ring gear R. In this sixth modification, the sun gear S is the first rotating element, the ring gear R is the second rotating element, and the carrier C is the third rotating element.

[0086] In the torque distribution 4WD mode of this sixth modified example, the motor 30 outputs negative torque to apply positive torque to the front-wheel output shaft 24. Specifically, when the motor 30 outputs negative torque, causing positive torque to act on the front-wheel output shaft 24 (ring gear R), this torque reaction force causes negative torque to act on the rear-wheel output shaft 23 (carrier C). Thus, positive torque from the torque of the engine 2 and negative torque from the torque reaction force of the motor torque act on the rear-wheel output shaft 23.

Claims

1. A power transmission device, comprising: a first input shaft, the first input shaft inputting power from a first power source; a second input shaft, the second input shaft inputting power from a second power source; a first output shaft, the first output shaft outputting power to the first drive wheel; a second output shaft, the second output shaft outputting power to the second drive wheel; and a differential device having three rotating elements: a first rotating element connected to the second input shaft, a second rotating element connected to the second output shaft, and a third rotating element connected to the first input shaft and the first output shaft; The power transmission device is characterized in that: The power transmission device includes a coupling device for selectively coupling any two of the three rotating elements. The power transmission device further includes a first transmission device provided in a power transmission path between the differential device and the second output shaft. The first output shaft and the first input shaft are arranged on the same axis. The second output shaft is arranged in parallel with the first output shaft and is connected to the differential device via the first transmission device so as to be capable of transmitting power. The first transmission device and the differential device are arranged on the same axis as the first output shaft in order from the first power source side to the first output shaft. The second output shaft extends axially from the first transmission device toward the first power source.

2. A power transmission device comprising: a first input shaft, the first input shaft inputting power from a first power source; a second input shaft, the second input shaft inputting power from a second power source; a first output shaft, the first output shaft outputting power to the first drive wheel; a second output shaft, the second output shaft outputting power to the second drive wheel; and a differential device having three rotating elements: a first rotating element connected to the second input shaft, a second rotating element connected to the second output shaft, and a third rotating element connected to the first input shaft and the first output shaft; The power transmission device is characterized in that: The power transmission device includes a coupling device for selectively coupling any two of the three rotating elements. The power transmission device further includes a first transmission device provided in a power transmission path between the differential device and the second output shaft. The first output shaft and the first input shaft are arranged on the same axis. The second output shaft is arranged in parallel with the first output shaft and is connected to the differential device via the first transmission device so as to be capable of transmitting power. The first transmission device and the engagement device are arranged on the same axis as the first output shaft in order from the first power source side to the first output shaft. The second output shaft extends axially from the first transmission device toward the first power source.

3. The power transmission device according to claim 1 or 2, characterized in that: The engagement device switches between an engaged state in which the three rotation elements can rotate integrally and a released state in which the three rotation elements can perform differential motion.

4. The power transmission device according to claim 1 or 2, characterized in that: The engagement device selectively couples the second rotation element and the third rotation element.

5. The power transmission device according to claim 1 or 2, characterized in that: The engagement device is a friction engagement device.

6. The power transmission device according to claim 5, characterized in that: The engagement device selectively couples the first rotation element and the second rotation element.

7. The power transmission device according to claim 1 or 2, characterized in that: The differential device is a planetary gear device.

8. The power transmission device according to claim 1 or 2, characterized in that: The first transmission device is configured to include a chain belt.

9. The power transmission device according to claim 1 or 2, characterized in that: The power transmission device further includes a second transmission device provided in a power transmission path between the second power source and the differential device. The second power source is disposed on a shaft other than the first output shaft and the second output shaft, and is connected to the differential device via the second transmission device so as to be capable of transmitting power.

10. The power transmission device according to claim 9, characterized in that: The second transmission device is a speed reducer.

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