Control device for power transmission device, vehicle, and control method for power transmission device

Abstract

The present invention provides a control device for a power transmission device, a vehicle, and a control method for a power transmission device. In the control device for the power transmission device, the power transmission device includes a first input shaft, a second input shaft for inputting power from a motor, a rear-wheel side output shaft for outputting power to a first drive wheel, a front-wheel side output shaft for outputting power to a second drive wheel, and a planetary gear device. The planetary gear device includes a sun gear connected to the second input shaft, a gear carrier connected to the front-wheel side output shaft, and a ring gear connected to the first input shaft and the rear-wheel side output shaft as three rotating elements. When the torque of the rear-wheel side output shaft becomes equal to or less than a threshold value in a state where the motor outputs power, the control device engages a engaging device.

Description

Technical Field

[0001] The present invention relates to a control device for a power transmission device, a vehicle, and a control method for a power transmission device. Background Art

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

[0003] International Publication No. 2010 / 141682 discloses that in a transfer case having a sub-power source (second power source) in the transfer case housing, the power output from the second power source is transmitted to the front wheels and the 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 can function as a transmission, and the rotation of the first power source is speeded up 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 in a state where the differential device is in a differential operation state, since the torque of the second power source acts on the first output shaft and the second output shaft, the torque of each output shaft may become reverse.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a control device for a power transmission device, a vehicle, and a control method for a power transmission device that can suppress the torque of each output shaft from becoming reverse when power is transmitted via a differential device.

[0006] In the control device of the power transmission device of the present invention, the power transmission device includes: a first input shaft that inputs power from a first power source; a second input shaft that inputs power from a second power source; a first output shaft that outputs power to a first drive wheel; a second output shaft that outputs power to a second drive wheel; and a differential device that has three rotating elements, namely, 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 control device of the power transmission device is characterized in that when the torque of the first output shaft is below a threshold value in a state where the second power source outputs power, the differential action of the differential device is restricted as compared with the case where the torque of the first output shaft is larger than the threshold value.

[0007] According to this structure, when the torque of the first output shaft is below the threshold value when the power of the second power source is transmitted through the differential device, the differential action of the differential device can be restricted as compared with the case where the torque of the first output shaft is larger than the threshold value. Thus, by restricting the differential action of the differential device according to the torque of the first output shaft, it is possible to prevent the torques of the respective output shafts from becoming reverse.

[0008] Alternatively, the power transmission device may further include an engaging device that selectively connects any two of the three rotating elements. When the differential device can perform differential action and the torque of the first output shaft is below the threshold value in a state where the second power source outputs power, the engaging device is engaged.

[0009] According to this structure, the differential action of the differential device can be restricted by controlling the engaging device.

[0010] Alternatively, based on the torque input from the first input shaft to the first output shaft, the torque output by the second power source, the gear ratio between the second power source and the second input shaft, and the gear ratio of the differential device, the torque of the first output shaft is calculated, and the calculated torque of the first output shaft is compared with the threshold value.

[0011] According to this structure, the torque of the first output shaft can be calculated for comparison with the threshold value.

[0012] Alternatively, the second power source is a rotating electric machine, and when regeneration is performed by the rotating electric machine, the engaging device is engaged.

[0013] According to this structure, when regeneration is performed using the rotating electric machine, the engaging device can be engaged to restrict the differential action of the differential device.

[0014] Furthermore, the engagement device may be engaged when only the second power source is driven without driving the first power source.

[0015] According to this configuration, when power running is performed by the second power source, the engagement device can be engaged to limit the differential action of the differential device.

[0016] Furthermore, the engagement device may be a friction engagement device that switches between an engaged state, a semi-engaged state, and a released state.

[0017] According to this configuration, the friction engagement device can be controlled to an engaged state, a semi-engaged state, and a released state.

[0018] In addition, the first drive wheel and the second drive wheel may be wheels of a vehicle, and when the torque of the first output shaft is below a threshold value in a state where the differential device is capable of differential and the second power source outputs power, when the turning degree (Japanese: 转回度合い) of the vehicle is large, the engagement degree of the friction engagement device is reduced compared to a case where the turning degree of the vehicle is small.

[0019] According to this configuration, the degree of engagement of the friction engagement device can be controlled according to the turning condition of the vehicle. Thus, the differential device is allowed to operate differentially during turning, thereby allowing the first output shaft and the second output shaft to operate differentially.

[0020] Furthermore, when the torque of the first output shaft is equal to or less than a threshold value while the differential device is capable of differential operation and the second power source is outputting power, the friction engagement device may be placed in a semi-engaged state during cornering of the vehicle.

[0021] According to this configuration, by placing the friction engagement device in the semi-engaged state during cornering, it is possible to allow differential movement of the differential device.

[0022] Furthermore, the engagement device may selectively couple the second rotation element and the third rotation element.

[0023] According to this configuration, the differential action of the differential device can be limited by coupling the second rotating element and the third rotating element via the engagement device. In addition, since power is not transmitted through the gears of the differential device, the differential device can be miniaturized.

[0024] Furthermore, the engagement device may selectively couple the first rotation element and the third rotation element.

[0025] According to this structure, the differential action of the differential device can be restricted by connecting the first rotating element and the third rotating element by the engaging device. In addition, since the rotational speed difference between the engaging elements can be increased, miniaturization of the engaging device can be achieved.

[0026] The vehicle of the present invention includes a control device for the power transmission device of the above invention.

[0027] According to this structure, in a vehicle, when the torque of the first output shaft is below a threshold value when the power of the second power source is transmitted via the differential device, the differential action of the differential device can be restricted compared to the case where the torque of the first output shaft is larger than the threshold value. Thus, by restricting the differential action of the differential device according to the torque of the first output shaft, it is possible to prevent the torques of the respective output shafts from becoming reverse.

[0028] In addition, in the control method of the power transmission device of the present invention, the power transmission device includes: a first input shaft that inputs power from a first power source; a second input shaft that inputs power from a second power source; a first output shaft that outputs power to a first drive wheel; a second output shaft that outputs power to a second drive wheel; and a differential device that 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 control method of the power transmission device is characterized in that the control method includes the following steps: when the torque of the first output shaft is below a threshold value in a state where the second power source outputs power, the differential action of the differential device is restricted compared to the case where the torque of the first output shaft is larger than the threshold value.

[0029] According to this structure, when the torque of the first output shaft is below a threshold value when the power of the second power source is transmitted via the differential device, the differential action of the differential device can be restricted compared to the case where the torque of the first output shaft is larger than the threshold value. Thus, by restricting the differential action of the differential device according to the torque of the first output shaft, it is possible to prevent the torques of the respective output shafts from becoming reverse.

[0030] Alternatively, the power transmission device may further include an engaging device that selectively connects any two of the three rotating elements, and the control method may further include the following steps: when the differential device can perform differential and the torque of the first output shaft is below a threshold value in a state where the second power source outputs power, the engaging device is engaged.

[0031] According to this structure, the differential action of the differential device can be restricted by controlling the engaging device.

[0032] Alternatively, it may also be that the control method further includes: a step of calculating the torque of the first output shaft based on the torque input from the first input shaft to the first output shaft, the torque output by the second power source, the gear ratio between the second power source and the second input shaft, and the gear ratio of the differential device; and a step of comparing the calculated torque of the first output shaft with the threshold value.

[0033] According to this structure, it is possible to calculate the torque of the first output shaft for comparison with the threshold value.

[0034] Alternatively, it may also be that the second power source is a rotating electric machine, and the control method further includes the following step: when regeneration is performed by the rotating electric machine, engaging the engaging device.

[0035] According to this structure, when regeneration is performed using the rotating electric machine, it is possible to engage the engaging device to limit the differential action of the differential device.

[0036] In addition, the control method further includes the following step: when the first power source is not driven and only the second power source is driven, engaging the engaging device.

[0037] According to this structure, when power running is performed by the second power source, it is possible to engage the engaging device to limit the differential action of the differential device.

[0038] Alternatively, it may also be that the engaging device is a friction engaging device that switches to an engaged state, a semi-engaged state, and a released state, the first drive wheel and the second drive wheel are wheels of a vehicle, and the control method further includes the following step: when the torque of the first output shaft is below the threshold value in a state where the differential device can perform differential and the second power source outputs power, when the turning degree of the vehicle is large, compared with the case where the turning degree of the vehicle is small, reducing the engagement degree of the friction engaging device.

[0039] According to this structure, it is possible to control the engagement degree of the friction engaging device according to the turning condition of the vehicle. Thus, during turning, the differential of the differential device is allowed, and thus the differential between the first output shaft and the second output shaft is allowed.

[0040] Alternatively, it may also be that the control method further includes the following step: when the torque of the first output shaft is below the threshold value in a state where the differential device can perform differential and the second power source outputs power, during the turning of the vehicle, making the friction engaging device in a semi-engaged state.

[0041] According to this structure, by making the friction engaging device in a semi-engaged state during turning, it is possible to allow the differential of the differential device.

[0042] In the present invention, when the torque of the first output shaft is below the threshold value when the power of the second power source is transmitted via the differential device, the differential action of the differential device can be restricted as compared with the case where the torque of the first output shaft is larger than the threshold value. Thus, by restricting the differential action of the differential device according to the torque of the first output shaft, it is possible to suppress the torque of each output shaft from becoming reverse. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Hereinafter, the features, advantages, and technical and industrial significance of the exemplary embodiments of the present invention will be described with reference to the drawings, in which like reference numerals denote like elements, and in the drawings:

[0044] Figure 1 is a schematic diagram schematically showing a vehicle according to an embodiment.

[0045] Figure 2 is a schematic diagram schematically showing the structure of a transfer case according to an embodiment.

[0046] Figure 3 is a schematic diagram for explaining the transfer case during the torque distribution 4WD mode.

[0047] Figure 4 is a collinear diagram showing the state of the rotating elements in the planetary gear device during the torque distribution 4WD mode.

[0048] Figure 5 is a collinear diagram showing another state of the rotating elements in the planetary gear device during the torque distribution 4WD mode.

[0049] Figure 6 is a flowchart showing a clutch control process.

[0050] Figure 7 is a collinear diagram showing the state of the rotating elements in the planetary gear device according to the first modification.

[0051] Figure 8 is a collinear diagram showing the state of the rotating elements in the planetary gear device according to the second modification.

[0052] Figure 9 is a schematic diagram schematically showing the structure of a transfer case according to the third modification.

[0053] Figure 10 is a flowchart showing the clutch control process according to the third modification.

[0054] Figure 11 is a schematic diagram schematically showing the structure of a transfer case according to the fourth modification. DETAILED DESCRIPTION OF THE INVENTION

[0055] Hereinafter, with reference to the drawings, a control device for a power transmission device, a vehicle, and a control method for a power transmission device in an embodiment of the present invention will be specifically described. In addition, the present invention is not limited to the embodiments described below.

[0056] Figure 1 is a schematic diagram schematically showing the vehicle of the embodiment. The vehicle 1 includes an engine 2 as a power source, left and right front wheels 3L, 3R, left and right rear wheels 4L, 4R, and a power transmission device 10 that transmits the power of the engine ② to the front wheels 3 and the rear wheels 4 respectively. This vehicle 1 is a four-wheel drive vehicle based on front-engine rear-wheel drive. The rear wheels 4 are main drive wheels that become drive wheels during both two-wheel drive travel and four-wheel drive travel. On the other hand, the front wheels 3 are auxiliary drive wheels that become driven wheels during two-wheel drive travel and drive wheels during four-wheel drive travel. In addition, in the present embodiment, the engine 2 is the "first power source", the rear wheels 4 are the "first drive wheels", and the front wheels 3 are the "second drive wheels".

[0057] The power transmission device 10 includes: a transmission 11 connected to the engine 2, a transfer case 12 as a front and rear wheel power distribution device connected to the transmission 11, a front propeller shaft 13 and a rear propeller shaft 14 respectively 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, 17R connected to the front-wheel differential gear mechanism 15, and left and right rear-wheel axles 18L, 18R connected to the rear-wheel differential gear mechanism 16. In addition, when there is no special distinction between the left and right of the wheels and axles, the reference numerals L and R are omitted, and they are described as the front wheels 3, the rear wheels 4, the front-wheel axle 17, and the rear-wheel axle 18.

[0058] The power output from the engine 2 is transmitted to the transfer case 12 via the transmission 11. And the power transmitted to the transfer case 12 is transmitted from the transfer case 12 to the rear wheels 4 in sequence via the rear propeller shaft 14, the rear-wheel differential gear mechanism 16, and the rear-wheel side power transmission path of the rear-wheel axle 18. In addition, a part of the power transmitted to the rear-wheel 4 side is distributed by the transfer case 12 to the front-wheel 3 side, and is transmitted to the front wheels 3 in sequence via the front propeller shaft 13, the front-wheel differential gear mechanism 15, and the front-wheel side power transmission path of the front-wheel axle 17.

[0059] In addition, the vehicle 1 includes an electronic control device 100 that controls the vehicle 1. For example, the electronic control device 100 is configured to include a microcomputer having a CPU, a RAM, a ROM, an input / output interface, etc. The CPU performs signal processing by using the temporary storage function of the RAM while executing various controls of the vehicle 1 according to a program pre-stored in the ROM.

[0060] Signals from various sensors mounted on the vehicle 1 are input to the electronic control unit 100. For example, sensor signals from an engine speed sensor, a motor rotation angle sensor, a vehicle speed sensor, an accelerator opening sensor, a 4WD selection switch for selecting a four-wheel drive state by the driver's operation, etc. are input to the electronic control unit 100. The electronic control unit 100 performs drive control of the vehicle 1 based on the input sensor signals. Further, a command signal for controlling the engine 2, a command signal for controlling the transmission 11, a command signal for controlling the transfer case 12, etc. are output from the electronic control unit 100. That is, the electronic control unit 100 is a control unit of the power transmission device 10.

[0061] Figure 2 It is a schematic diagram schematically showing the structure of the transfer case in the embodiment. The transfer case 12 includes a transfer case housing 20 as a non-rotating member. Further, the transfer case 12 includes a first input shaft 21, a second input shaft 22, a rear wheel side output shaft 23, a front wheel side output shaft 24, a planetary gear device 25, a transmission device 26, a motor 30, and an engagement device 40 inside the transfer case housing 20. Further, in the present embodiment, the rear wheel side output shaft 23 is the "first output shaft", the front wheel side output shaft 24 is the "second output shaft", the planetary gear device 25 is the "differential device", the transmission device 26 is the "first transmission device", and the motor 30 is the "second power source".

[0062] The first input shaft 21 is an input member that inputs the 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 the output member of the transmission 11.

[0063] The second input shaft 22 is an input member that inputs the power from the motor 30 to the planetary gear device 25. The power from the motor 30 is directly transmitted to the second input shaft 22. For example, the second input shaft 22 is spline-fitted to the output member (rotor shaft 33) of the motor 30 and rotates integrally with the rotor shaft 33.

[0064] The rear wheel side output shaft 23 is an output member that outputs power from the transfer case 12 to the rear wheels 4. The rear wheel side output shaft 23 is a main drive shaft that is arranged on the same axis as the first input shaft 21 and is connected to the rear drive shaft 14.

[0065] The front-wheel-side output shaft 24 is an output member that transmits power from the transfer case 12 to the front wheels 3. The front-wheel-side output shaft 24 is a sub-drive shaft that is arranged on an axis different from that of the first input shaft 21 and the rear-wheel-side output shaft 23 and is connected to the front drive shaft 13. The front-wheel-side output shaft 24 is arranged in parallel with the rear-wheel-side output shaft 23 and is connected to the planetary gear device 25 via a transmission device 26 so as to be able to transmit power.

[0066] The planetary gear device 25 is a differential device having three rotating elements and functions as a power distribution mechanism that distributes the power of the power source to the front wheels 3 and the rear wheels 4. Figure 2 The illustrated planetary gear device 25 is a single-pinion type planetary gear device. The planetary gear device 25 includes a sun gear S, a carrier C that supports a plurality of pairs of meshing pinions so as to be able to rotate self and revolve, and a ring gear R that meshes with the sun gear S via the pinions as three rotating elements. In the present 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".

[0067] The second input shaft 22 is connected to the sun gear S so as to rotate integrally. That is, a motor 30 is connected to the sun gear S.

[0068] The first rotating member 51 is connected to the carrier C so as to rotate integrally. That is, the front-wheel-side output shaft 24 is connected to the carrier C. The first rotating member 51 is a member that rotates integrally with the carrier C and has gear teeth 51a as an engaging element. Further, the first rotating member 51 forms a power transmission path between the planetary gear device 25 and the front-wheel-side output shaft 24.

[0069] The second rotating member 52 is connected to the ring gear R so as to rotate integrally. The second rotating member 52 is a member that rotates integrally with the ring gear R and has gear teeth 52a as an engaging element. The first input shaft 21 and the rear-wheel-side output shaft 23 are connected to the second rotating member 52 so as to rotate integrally. That is, the first input shaft 21 and the rear-wheel-side output shaft 23 are connected to the ring gear R.

[0070] 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 29.

[0071] The drive gear 27 is a rotating member that functions as an output section on the front wheel side, and is an output gear that transmits power to the front wheel side output shaft 24. The drive gear 27 is arranged on the same axis as the first input shaft 21 and the rear wheel side output shaft 23 so as to be rotatable relative to the rear wheel side output shaft 23. Further, the first rotating member 51 and the gear carrier C are integrally rotatably connected to the drive gear 27. That is, in the transfer case 12, each rotating element of the drive gear 27 and the planetary gear device 25 is arranged at the same rotation center as the first input shaft 21 and the rear wheel side output shaft 23.

[0072] The driven gear 28 is a gear provided integrally with the front wheel side output shaft 24. The chain 29 is a drive chain for the front wheels that connects between the drive gear 27 and the driven gear 28. When the drive gear 27 rotates, the driven gear 28 rotates, and the driven gear 28 rotates integrally with the front wheel side output shaft 24.

[0073] The motor 30 is a rotary electric machine (motor generator) that can function as a 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 has a stator core and a stator coil wound around the stator core. The second input shaft 22 is rotatably connected to the rotor shaft 33.

[0074] The engagement device 40 is a clutch that switches between an engaged state and a released state, and is a device that switches the state of the planetary gear device 25. In the transfer case 12, when the engagement device 40 switches between the engaged state and the released state, the state of the planetary gear device 25 switches between an integrated state and a differential state.

[0075] For example, when the engagement device 40 is in the engaged state, the planetary gear device 25 becomes a state in which differential action is restricted (integrated state). The engaged state is a state in which two of the three rotating elements included in the planetary gear device 25 are connected to each other. The integrated state is a state in which the differential of the planetary gear device 25 is restricted. Further, when the engagement device 40 is in the released state, the planetary gear device 25 becomes a state in which differential action is permitted (differential state). The released state is a state in which the two rotating elements to be connected are released so as to be rotatable relative to each other. The differential state is a state in which the three rotating elements included in the planetary gear device 25 can perform differential action.

[0076] The engaging device 40 is a dog clutch that selectively connects the carrier C and the ring gear R. Therefore, the engaging device 40 switches the state of the planetary gear device 25 between an integrated state in which the carrier C and the ring gear R can rotate integrally and a differential state in which the carrier C and the ring gear R can rotate relative to each other. And the engaging device 40 has a switching sleeve 41.

[0077] The switching sleeve 41 has gear teeth 41a as engaging elements. The gear teeth 41a mesh with the gear teeth 51a of the first rotating member 51 that rotates integrally with the carrier C and the gear teeth 52a of the second rotating member 52 that rotates integrally with the ring gear R. The switching sleeve 41 moves axially by an actuator of the engaging device 40. And the switching sleeve 41 switches between an engaged state in which the carrier C and the ring gear R are connected to be able to rotate integrally and a released state in which the three rotating elements can perform differential action.

[0078] When the gear teeth 41a of the switching sleeve 41 mesh with both the gear teeth 51a and the gear teeth 52a, the engaging device 40 becomes the engaged state. On the other hand, when the gear teeth 41a of the switching sleeve 41 do not mesh with either the gear teeth 51a or the gear teeth 52a, the engaging device 40 becomes the released state.

[0079] And in the vehicle 1, in the four-wheel drive state where the front wheels 3 and the rear wheels 4 are driven, the power of the power source is transmitted to the front wheels 3 and the rear wheels 4 via the planetary gear device 25. At this time, the planetary gear device 25 can be switched between the integrated state and the differential state. That is, the transfer case 12 can switch between a differential state in which the rotational differential between the rear drive shaft 14 and the front drive shaft 13 is not restricted and a non-differential state in which the rotational differential between them is restricted by switching the state of the planetary gear device 25 when it becomes the four-wheel drive state. That is, the transfer case 12 can switch between a case where the rear wheel side output shaft 23 and the drive gear 27 become a state where they can perform differential action and a case where the rear wheel side output shaft 23 and the drive gear 27 become a non-differential state in the four-wheel drive state. In this way, the transfer case 12 can be switched to multiple drive states by using the planetary gear device 25 and the engaging device 40.

[0080] Therefore, when controlling the driving state of the transfer case 12, the electronic control device 100 controls the operation of the motor 30 and the state of the engagement device 40, thereby controlling the state of the planetary gear device 25. The command signal for controlling the transfer case 12 includes a command signal for controlling the motor 30 and a command signal for controlling the engagement device 40. The electronic control device 100 outputs a command signal to the actuator that operates the engagement device 40 to control the operation of the engagement device 40. That is, the electronic control device 100 is a control device that controls the engagement device 40. Moreover, by the electronic control device 100 performing the switching control of the engagement device 40, the planetary gear device 25 can be switched between the first mode (integrated mode) and the second mode (power distribution mode).

[0081] The integrated mode is a state (integrated state) in which two of the three rotating elements included in the planetary gear device 25 are connected to each other. The power distribution mode is a state (differential state) in which the three rotating elements included in the planetary gear device 25 are differentially driven in a state where they are respectively connected to the motor 30, the rear wheel side output shaft 23, and the front wheel side output shaft 24. In addition, in the transfer case 12, regardless of the state of the planetary gear device 25, the motor 30, the engine 2, the rear wheel side output shaft 23, and the front wheel side output shaft 24 are respectively connected to the three rotating elements. Therefore, the power distribution mode is synonymous with the differential state.

[0082] In addition, the transfer case 12 can be switched to multiple driving states based on the states of the engine 2 and the motor 30 in addition to the state of the planetary gear device 25. For example, the transfer case 12 can set a first driving state (fixed distribution 4WD mode) and a second driving state (torque distribution 4WD mode).

[0083] Here, refer to Figures 2 to 5 for an explanation of the first to second driving states. In addition, in Figures 4 to 5 , a collinear diagram showing the rotational state of the planetary gear device 25 is shown. The motor 30 is recorded as "MG", the engine 2 is recorded as "ENG", the sun gear S is recorded as "S", the carrier C is recorded as "C", the ring gear R is recorded as "R", the torque of the first input shaft 21 is recorded as "Te", the torque of the second input shaft 22 is recorded as "Tm", the torque of the rear wheel side output shaft 23 is recorded as "T1", the torque of the front wheel side output shaft 24 is recorded as "T2", the reaction torque is recorded as "T3", and the gear ratio of the planetary gear device 25 is recorded as "ρ". In addition, in the relationship between the vertical axes of the collinear diagram, when the interval corresponding to "1" is formed between the sun gear S and the carrier C, the interval corresponding to the gear ratio ρ of the planetary gear device 25 (=the number of teeth of the sun gear S / the number of teeth of the ring gear R) is formed between the carrier C and the ring gear R.

[0084] First, with reference to Figure 2 the first driving state (fixed distribution 4WD mode) will be described. The first driving state is a four-wheel drive state in which power is transmitted to the front wheels 3 and the rear wheels 4, and is a case where the engaging device 40 is in an engaged state and the planetary gear device 25 is in an integrated state. The first driving state is a so-called fixed distribution 4WD mode.

[0085] The fixed distribution 4WD mode is a mode in which the power distribution to the rear wheel side output shaft 23 and the front wheel side output shaft 24 is mechanically fixed. In the fixed distribution 4WD mode, when the power of the engine 2 is distributed to the rear wheel side output shaft 23 and the front wheel side output shaft 24, the engaging device 40 engages to restrict the differential action of the planetary gear device 25, so that the three rotating elements have the same rotational speed.

[0086] Next, with reference to Figures 3 to 5 , the second driving state (torque distribution 4WD mode) will be described. The second driving state is a four-wheel drive state in which power is transmitted to the front wheels 3 and the rear wheels 4, and is a case where the engaging device 40 is in a released state and the planetary gear device 25 is in a differential state. In the second driving state, the front-rear distribution control can be performed using the motor torque output from the motor 30. The second driving state is a so-called torque distribution 4WD mode. The purpose of the torque distribution mode is to generate a driving force on the front wheels 3 using the power of the motor 30 and change the power distribution transmitted to the drive gear 27 and the rear wheel side output shaft 23.

[0087] As Figure 3 shown, when the transfer case 12 is in the torque distribution 4WD mode, the engaging device 40 is in a released state, and the switching sleeve 41 is not engaged with the first rotating member 51. And the planetary gear device 25 in the differential state functions as a power distribution mechanism.

[0088] Thus, in the torque distribution 4WD mode, since the planetary gear device 25 is in the power distribution mode (differential state), the torque Te transmitted from the engine 2 to the first input shaft 21 is transmitted to the rear wheel side output shaft 23, and the torque Tm transmitted from the motor 30 to the second input shaft 22 is transmitted to the front wheel side output shaft 24 via the planetary gear device 25. At this time, as Figure 4 shown, the distribution of the power transmitted to the front wheel side and the rear wheel side can be controlled using the torque output from the motor 30.

[0089] In Figure 4In the example shown, when the motor 30 applies a positive-direction torque T2 to the front-wheel-side output shaft 24, a negative-direction torque acts on the rear-wheel-side output shaft 23 as a reaction force. Therefore, the positive-direction torque Te from the engine 2 and the negative-direction reaction torque T3 generated by the torque reaction act on the rear-wheel-side output shaft 23. Also, since the torque Te of the first input shaft 21 acting in the positive direction is greater than the reaction torque T3 acting in the negative direction, the torque T1 of the rear-wheel-side output shaft 23 becomes a positive-direction torque.

[0090] In addition, a positive-direction torque refers to a torque acting in the direction of increasing the rotational speed in the positive direction (i.e., the direction of making the rotational speed in the negative direction approach 0). A negative-direction torque refers to a torque acting in the direction of decreasing the rotational speed in the positive direction (i.e., the direction of making the rotational speed in the negative direction move away from 0). In Figure 4 the collinear diagram shown, the positive-direction torque is represented by an upward arrow, and the negative-direction torque is represented by a downward arrow. Also, in the collinear diagram, the positive-direction rotational speed is represented above "0", and the negative-direction rotational speed is represented below "0".

[0091] Here, the torque Tm of the second input shaft 22 is obtained by multiplying the gear ratio between the motor 30 and the second input shaft 22 and the motor torque. Since the rotor shaft 33 of the motor 30 is connected to the second input shaft 22 and the sun gear S so as to rotate integrally, the gear ratio between the motor 30 and the sun gear S is "1". Therefore, the torque output from the motor 30 acts directly on the second input shaft 22. As a result, the torque Tm of the second input shaft 22 becomes the same magnitude as the motor torque.

[0092] The torque T2 of the front-wheel-side output shaft 24 is represented by T2 = {(1 + ρ) / ρ} × Tm. The reaction torque T3 is represented by T3 = (1 / ρ) × Tm. And the torque T1 of the rear-wheel-side output shaft 23 is represented by T1 = Te - T3 = Te - (1 / ρ) × Tm.

[0093] The torque Te of the first input shaft 21 is the torque transmitted from the engine 2 to the first input shaft 21. Since the first input shaft 21 is directly connected to the rear-wheel-side output shaft 23 and is connected to the rear-wheel-side output shaft 23 and the ring gear R so as to rotate integrally, the gear ratio between the first input shaft 21 and the ring gear R becomes "1". Therefore, the torque Te of the first input shaft 21 acts directly on the rear-wheel-side output shaft 23.

[0094] Also, in the torque distribution 4WD mode (the planetary gear device 25 is in the power distribution mode), by increasing the torque output from the motor 30, the torque T2 of the front-wheel-side output shaft 24 can be increased. However, when the motor torque becomes too large in order to increase the torque T2 of the front-wheel-side output shaft 24, the reaction torque T3 also becomes large. Therefore, asFigure 5 As shown, the reaction torque T3 is larger than the torque Te of the first input shaft 21, and the torque T1 of the rear-wheel side output shaft 23 may become a torque in the negative direction.

[0095] Therefore, the vehicle 1 is configured to suppress the torques T2 of the front-wheel side output shaft 24 and T1 of the rear-wheel side output shaft 23 from becoming reverse when power is transmitted via the planetary gear device 25. The electronic control unit 100 can perform control to switch from the torque distribution 4WD mode to the fixed distribution 4WD mode by executing the engagement control of the engagement device 40 and switching the planetary gear device 25 to the integrated state. In the fixed distribution 4WD mode, if a positive-direction motor torque acts on the front-wheel side output shaft 24, both the torque T2 of the front-wheel side output shaft 24 and the torque T1 of the rear-wheel side output shaft 23 become torques in the positive direction.

[0096] Figure 6 It is a flowchart showing the engagement control process. In addition, Figure 6 the control shown is repeatedly executed by the electronic control unit 100.

[0097] The electronic control unit 100 determines whether the planetary gear device 25 is in the power distribution mode period (step S1). In step S1, it is determined whether the planetary gear device 25 is in the power distribution mode (differential state). That is, it is determined whether the engagement device 40 is in the released state (non-engaged). In addition, the released state is synonymous with non-engaged.

[0098] When the planetary gear device 25 is not in the power distribution mode period (step S1: No), this control routine ends.

[0099] When the planetary gear device 25 is in the power distribution mode period (step S1: Yes), the electronic control unit 100 determines whether there is a motion requirement for the motor 30 (step S2). In step S2, based on the required driving force, vehicle speed, slope, selection state of the 4WD selection switch, etc., it is determined whether there is a motion requirement for the motor 30.

[0100] For example, in step S2, the electronic control unit 100 calculates the required driving force based on the vehicle speed and the accelerator opening. When the required driving force is larger than a predetermined value, it is determined that there is a motion requirement for the motor 30. This electronic control unit 100 can detect the vehicle speed based on the signal input from the vehicle speed sensor and can detect the accelerator opening based on the signal input from the accelerator opening sensor. In addition, the electronic control unit 100 can also determine that there is a motion requirement for the motor 30 when the slope corresponding to the state of the road surface on which the vehicle 1 is traveling is larger than a predetermined value. Moreover, the electronic control unit 100 determines whether a selection operation of the 4WD selection switch to the four-wheel drive state has been accepted.

[0101] When there is a requirement for the operation of the motor 30 (Step S2: Yes), the electronic control unit 100 determines whether the torque T1 of the rear wheel side output shaft 23 is equal to or less than a threshold value (Step S3). In Step S3, the electronic control unit 100 calculates the torque T1 of the rear wheel side output shaft 23 and determines whether the calculated torque T1 is equal to or less than the threshold value. This threshold value is a pre-set value. The threshold value can be set to a value representing the torque in the positive direction or a value representing the torque in the negative direction. For example, in order to determine the situation where the torque T1 of the rear wheel side output shaft 23 is about to reverse, the threshold value can be set to the torque in the positive direction or zero. Alternatively, in order to determine the situation where the torque T1 of the rear wheel side output shaft 23 has reversed, the threshold value can also be set to the torque in the negative direction.

[0102] In this Step S3, the electronic control unit 100 calculates the torque T1 of the rear wheel side output shaft 23 based on the torque Te input from the first input shaft 21 to the rear wheel side output shaft 23, the torque output by the motor 30, the gear ratio from the motor 30 to the second input shaft 22, and the gear ratio ρ of the planetary gear unit 25. That is to say, the torque T1 of the rear wheel side output shaft 23 is calculated using the formula T1 = Te - (1 / ρ) × Tm. The calculated torque T1 is compared with the threshold value.

[0103] Moreover, when the torque T1 of the rear wheel side output shaft 23 is equal to or less than the threshold value (Step S3: Yes), the electronic control unit 100 engages the engaging device 40 (Step S4). In Step S4, a command signal for engaging the engaging device 40 is output from the electronic control unit 100, and the engaging device 40 is switched from the released state to the engaged state. After the process of this Step S4 is implemented, this control routine ends.

[0104] When the torque T1 of the rear wheel side output shaft 23 is greater than the threshold value (Step S3: No), the engaging device 40 is maintained in the released state (Step S5). In Step S5, the planetary gear unit 25 is maintained in the differential state. After the process of this Step S5 is implemented, this control routine ends.

[0105] In addition, when a negative determination is made in Step S2 because there is no requirement for the operation of the motor 30 (Step S2: No), this control routine proceeds to Step S5. That is to say, when there is no requirement for the operation of the motor 30, the planetary gear unit 25 is also maintained in the differential state.

[0106] As described above, according to the embodiment, when the motor 30 outputs torque during the power distribution mode, when the torque T1 of the rear wheel side output shaft 23 is smaller than the threshold value, the control to engage the engaging device 40 is executed. Thus, when the torque of the motor 30 becomes excessive and the torque T1 of the rear wheel side output shaft 23 is about to reverse (when the torques of the respective output shafts become opposite), the differential action of the planetary gear device 25 is restricted by the engaging device 40, so that the torque input from the motor 30 to the planetary gear device 25 can be output to the rear wheel side output shaft 23 and the front wheel side output shaft 24 in the same direction.

[0107] In addition, as a modification example of the above-described embodiment, it can be configured to be applied to the case where regeneration is performed by the motor 30 (the first modification example), and the case of the EV mode in which only the motor 30 performs power running (the second modification example).

[0108] First, as the first modification example, the case where regeneration is performed by the motor 30 will be described. In the first modification example, in Figure 6 the shown step S3, it is determined whether regeneration is performed by the motor 30. That is, in the case where the torque T1 of the rear wheel side output shaft 23 is below the threshold value, it includes the case where regeneration is performed by the motor 30. In step S3 of the first modification example, during the running of the vehicle 1, in a state where the output of the engine 2 is stopped, it is determined whether regeneration is performed by the motor 30.

[0109] For example, during the forward running of the vehicle 1, the rear wheels 4 and the front wheels 3 rotate in the positive direction, and the rear wheel side output shaft 23 and the front wheel side output shaft 24 rotate in the positive direction. Therefore, even if the planetary gear device 25 is in a differential state, the second input shaft 22 and the motor 30 rotate in the positive direction by the rotation of the drive wheels. And if it is detected during forward running that the depression of the accelerator pedal has been released (accelerator off), the electronic control device 100 determines that there is a regeneration requirement. In the case where the depression of the accelerator pedal has been released, the torque Te transmitted from the engine 2 to the first input shaft 21 becomes zero, so that the torque T1 of the rear wheel side output shaft 23 is smaller than the threshold value. That is, as the vehicle state in the case of making an affirmative determination in step S2 (step S2: Yes) and making an affirmative determination in step S3 (step S3: Yes), the case where regeneration is performed by the motor 30 can be cited. Figure 7 An example of the collinearity diagram during this regeneration is shown. In addition, Figure 7 the "CL" shown represents the engaging device 40.

[0110] As Figure 7As shown, when performing regeneration using the external force from the drive wheels during the travel of the vehicle 1, the motor 30 outputs a torque in the negative direction while rotating in the positive direction. Therefore, the torque Tm of the second input shaft 22 is in the negative direction. At this time, since the engaging device 40 is in the engaged state and the planetary gear device 25 is in an integrated state, during regeneration, the torques T1 of the rear-wheel side output shaft 23 and T2 of the front-wheel side output shaft 24 both become regeneration torques in the negative direction.

[0111] Thus, according to the first modification example, by restricting the differential of the planetary gear device 25 using the engaging device 40 during regeneration, it is possible to cause the rear-wheel side output shaft 23 and the front-wheel side output shaft 24 to generate regeneration torques in the same direction. In addition, since the planetary gear device 25 is in an integrated state during regeneration, the rear-wheel side output shaft 23 is directly connected to the motor 30, so the limit of the regeneration torque based on the direct transmission of the motor 30 can be increased and the regeneration efficiency is improved.

[0112] Next, as a second modification example, the case of the EV mode in which only the motor 30 performs power running will be described. In the second modification example, in Figure 6 step S3 shown, it is determined whether it is the EV mode in which only the motor 30 performs power running. That is, in the case where the torque T1 of the rear-wheel side output shaft 23 is below the threshold value, it includes the case where only the motor 30 performs power running.In step S3 of the second modification example, it is determined whether the motor 30 performs power running during the travel of the vehicle 1 and in a state where the output of the engine 2 has stopped.

[0113] When the vehicle 1 performs EV travel, the torque Te transmitted from the engine 2 to the first input shaft 21 becomes zero, so the torque T1 of the rear-wheel side output shaft 23 becomes smaller. That is, as the vehicle state in the case of making an affirmative determination in step S2 (step S2: Yes) and making an affirmative determination in step S3 (step S3: Yes), the case where only the motor 30 performs power running (EV mode) can be cited. Figure 8 An example of a collinearity diagram when performing this EV travel is shown. In addition, Figure 8 "CL" shown represents the engaging device 40.

[0114] As Figure 8 shown, when the vehicle 1 performs EV travel, the power of the motor 30 is transmitted to each output shaft via the planetary gear device 25. At this time, by engaging the engaging device 40 to make the planetary gear device 25 in an integrated state, the torques T1 of the rear-wheel side output shaft 23 and T2 of the front-wheel side output shaft 24 both become power running torques in the positive direction.

[0115] Thus, according to the second modification example, by restricting the differential action of the planetary gear device 25 using the engagement device 40 during EV travel, it is possible to cause the rear-wheel side output shaft 23 and the front-wheel side output shaft 24 to generate driving torques in the same direction. In addition, since the planetary gear device 25 is in an integrated state during EV travel, the motor 30 is directly connected to the rear-wheel side output shaft 23, so it is possible to increase the limit of the driving torque directly transmitted by the motor 30 and improve the driving efficiency. That is, it is possible to achieve an expansion of the range in which EV travel can be performed.

[0116] In addition, as another modification example, it can be configured to be applied to the case where the vehicle 1 turns (third modification example). In the third modification example, the engagement determination of the engagement device 40 can be made based on the turning state of the vehicle 1. Here, refer to Figure 9 and Figure 10 to describe the third modification example.

[0117] Figure 9 is a schematic diagram schematically showing the structure of the transfer case in the third modification example. The transfer case 12 of the third modification example includes a friction engagement device 60 that selectively connects the gear carrier C and the ring gear R. That is, instead of the engagement device 40 constituted by a dog clutch, a friction engagement device 60 as a friction clutch is provided.

[0118] The friction engagement device 60 has 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. And the friction engagement device 60 operates using a hydraulic actuator.

[0119] The electronic control device 100 can implement control to switch the friction engagement device 60 to an engaged state, a semi-engaged state, and a released state. And regarding the engagement degree of the friction engagement device 60, the engagement degree in the engaged state is relatively large, and the engagement degrees in the semi-engaged state and the released state are relatively small. Regarding this engagement degree, the engagement degree in the engaged state is larger than the engagement degree in the semi-engaged state, and the engagement degree in the semi-engaged state is larger than the engagement degree in the released state.

[0120] When the friction engagement device 60 is in the engaged state, the friction engagement elements are completely engaged with each other. The engaged state is complete engagement, and the gear carrier C and the ring gear R rotate integrally.

[0121] When the friction engagement device 60 is in a semi-engaged state, the friction engagement elements are in contact with each other, allowing for sliding movement. The semi-engaged state allows for sliding movement of the friction engagement elements while maintaining the torque transfer capacity of the friction engagement device 60. In other words, this allows for differential movement between the carrier C and the ring gear R. Therefore, when the friction engagement device 60 is in a semi-engaged state, the rear wheel output shaft 23 and the drive gear 27 are in a state where differential movement is possible.

[0122] When the friction engagement device 60 is in the released state, the friction engagement elements do not contact each other. In the released state, no transfer torque capacity is generated, and no slippage occurs between the friction engagement elements.

[0123] Furthermore, because the planetary gear unit 25 functions as a differential device (center differential) between the front and rear wheels, if the friction engagement device 60 is fully engaged while the vehicle 1 is turning, the rotational difference between the front and rear wheels cannot be absorbed, potentially causing a tight corner braking phenomenon. Therefore, the electronic control unit 100 of the third modified example is configured to execute control to cause the friction engagement device 60 to slip according to the degree of turning of the vehicle 1.

[0124] Furthermore, the electronic control unit 100 can detect that the vehicle 1 is turning based on signals input from the steering angle sensor. Furthermore, the electronic control unit 100 partially engages the friction engagement device 60 while the vehicle 1 is turning, thereby allowing differential movement of the planetary gear unit 25. This allows differential movement between the rear propeller shaft 14 and the front propeller shaft 13. This allows for a rotational differential between the front wheels 3 and 4, thereby suppressing sudden braking.

[0125] Figure 10 : is a flowchart showing the engagement control process of the third modified example. Figure 10 The control shown is repeatedly executed by the electronic control device 100. Figure 10 Steps S11 to S13 and S19 are shown in FIG. Figure 6 Since the processes in steps S1 to S3 and S5 are the same, their description is omitted.

[0126] If the torque T1 of the rear wheel output shaft 23 is less than or equal to the threshold (step S13: YES), the electronic control unit 100 determines whether the vehicle 1 is turning (step S14). In step S14, based on the signal from the steering angle sensor, it can be determined that the vehicle is turning if the steering angle is greater than a predetermined value. Furthermore, turning can be indicated as a large degree of turning, while non-turning can be indicated as a small degree of turning.

[0127] When the vehicle 1 is not in the turning period (step S14: No), the electronic control device 100 fully engages the friction engagement device 60 (step S15). In step S15, under the control of the electronic control device 100, the friction engagement device 60 is switched from the released state to the engaged state. After the process of step S15 is implemented, this control routine ends.

[0128] When the vehicle 1 is in the turning period (step S14: Yes), the electronic control device 100 makes the friction engagement device 60 in a semi-engaged state (step S16). In step S16, under the control of the electronic control device 100, the friction engagement device 60 is switched from the released state to the semi-engaged state. The engagement degree of the semi-engaged state is smaller than that of the engaged state. That is, when the turning degree of the vehicle 1 is large (step S14: Yes), the electronic control device 100 reduces the engagement degree of the friction engagement device 60 compared with the case where the turning degree of the vehicle 1 is small (step S14: No).

[0129] And, the friction engagement device 60 maintains the semi-engaged state, and the electronic control device 100 determines whether the torque T1 of the rear wheel side output shaft 23 is below the threshold value (step S17). In step S17, in the vehicle state where it is in the turning period and in the semi-engaged state, the torque T1 of the rear wheel side output shaft 23 is calculated again, and the calculated torque T1 is compared with the threshold value. This threshold value is the same as the threshold value used in step S13.

[0130] When an affirmative determination is made in step S17 because the torque T1 of the rear wheel side output shaft 23 is below the threshold value (step S17: Yes), the electronic control device 100 suppresses the torque output from the motor 30 (step S18). In step S18, the electronic control device 100 restricts the output of the motor 30 to make the motor torque smaller. When the engagement of the friction engagement device 60 is released, the torque T1 of the rear wheel side output shaft 23 may become below the threshold value. Therefore, the torque T1 of the rear wheel side output shaft 23 is determined again in the semi-engaged state, and the torque of the motor 30 is suppressed as needed. After the process of step S18 is implemented, this control routine ends.

[0131] When it is determined in the determination process of step S17 that the torque T1 of the rear wheel side output shaft 23 is not below the threshold value (step S17: No), this control routine ends.

[0132] In addition, when it is determined in the determination process of step S12 that there is no operation requirement for the motor 30 (step S12: No), this control routine proceeds to step S19. Moreover, when it is determined in the determination process of step S13 that the torque T1 of the rear wheel side output shaft 23 is greater than the threshold value (step S13: No), this control routine proceeds to step S19.

[0133] Thus, according to the third modification example, control for sliding the friction engagement device 60 can be performed according to the turning degree of the vehicle 1. Thereby, during turning, the differential of the planetary gear device 25 is allowed, and the sharp turn braking phenomenon can be suppressed.

[0134] In addition, as a further modification example (fourth modification example) of the third modification example, when integrating the three rotating elements to limit the differential action of the planetary gear device 25, it is not limited to the case where the gear carrier C and the ring gear R can be integrally rotatably connected. That is, the two rotating elements that can be integrally rotatably connected are not particularly limited, and any two of the three rotating elements in the planetary gear device 25 can be selectively connected. For example, as Figure 11 shown, the transfer case 12 of the fourth modification example includes a friction engagement device 61 that selectively connects the sun gear S (first rotating element) and the ring gear R (third rotating element).

[0135] The friction engagement device 61 selectively connects the third rotating member 53 that rotates integrally with the sun gear S and the second rotating member 52 that rotates integrally with the ring gear R. The friction engagement device 61 has 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. And, the friction engagement device 61 operates by a hydraulic actuator.

[0136] In addition, the engagement device included in the transfer case 12 may have a function of fixing any one of the rotating elements in the planetary gear device 25, a function of switching the power transmission path, etc., in addition to the function of switching the planetary gear device 25 between the integrated state and the differential state. That is, the engagement device only needs to have at least the function of switching the state of the planetary gear device 25 to the integrated state and the differential state.

[0137] In addition, the motor 30 is not limited to the structure arranged on the same axis as the first input shaft 21 and the rear wheel side output shaft 23, and may be arranged on an axis different from the first input shaft 21 and the rear wheel side output shaft 23. Moreover, the power output from the motor 30 can also be transmitted to the second input shaft 22 via a reduction gear train in which a plurality of gears are meshed. At this time, the rotation of the motor 30 is speeded up (reduced) and transmitted to the sun gear S. In this case, when calculating the torque T1 of the rear wheel side output shaft 23, the electronic control device 100 can use this reduction ratio (gear transmission ratio).

[0138] In addition, since the motor 30 is composed of a rotating electric machine (motor generator), power can be generated using the power from the engine 2. The power generated by the motor 30 is stored in the battery. Moreover, the first power source is not limited to the engine, and may also be a rotating electric machine.

Claims

1. A control device for a power transmission device, the power transmission device comprising: A first input shaft that inputs power from a first power source; A second input shaft that inputs power from a second power source; A first output shaft that outputs power to a first driving wheel; A second output shaft that outputs power to a second driving wheel; and A differential device that has three rotating elements, namely, 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 control device is characterized in that When the torque of the first output shaft is below a threshold value in a state where the second power source outputs power, the differential action of the differential device is restricted as compared with the case where the torque of the first output shaft is larger than the threshold value, The power transmission device further comprises an engaging device that selectively connects any two of the three rotating elements, When the torque of the first output shaft is below a threshold value in a state where the differential device can perform differential operation and the second power source outputs power, the engaging device is engaged, Based on the torque input from the first input shaft to the first output shaft, the torque output by the second power source, the gear ratio between the second power source and the second input shaft, and the gear ratio of the differential device, the torque of the first output shaft is calculated, The calculated torque of the first output shaft is compared with the threshold value.

2. The control device for a power transmission device according to claim 1, characterized in that The second power source is a rotating electric machine, When regeneration is performed by the rotating electric machine, the engaging device is engaged.

3. The control device for a power transmission device according to claim 1 or 2, characterized in that When only the second power source is driven without driving the first power source, the engaging device is engaged.

4. The control device for a power transmission device according to claim 1 or 2, characterized in that The engaging device is a friction engaging device that can be switched to an engaged state, a semi-engaged state, and a released state.

5. The control device for a power transmission device according to claim 4, characterized in that The first driving wheel and the second driving wheel are wheels of a vehicle, When the torque of the first output shaft is below a threshold value in a state where the differential device can perform differential operation and the second power source outputs power, when the turning degree of the vehicle is large, the engagement degree of the friction engaging device is reduced as compared with the case where the turning degree of the vehicle is small.

6. The control device for a power transmission device according to claim 5, characterized in that When the torque of the first output shaft is below a threshold value in a state where the differential device can perform differential operation and the second power source outputs power, during the turning of the vehicle, the friction engaging device is in a semi-engaged state.

7. The control device of the power transmission device according to claim 4, wherein the engaging device selectively connects the second rotating element and the third rotating element.

8. The control device of the power transmission device according to claim 4, wherein the engaging device selectively connects the first rotating element and the third rotating element.

9. A vehicle, characterized in that the vehicle is equipped with the control device of the power transmission device according to any one of claims 1 to 8.

10. A control method for a power transmission device, the power transmission device comprising: a first input shaft that inputs power from a first power source; a second input shaft that inputs power from a second power source; a first output shaft that outputs power to a first drive wheel; a second output shaft that outputs power to a second drive wheel; and a differential device that has three rotating elements including 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 control method is characterized in that the control method includes the following steps: when the torque of the first output shaft is below a threshold value in a state where the second power source outputs power, compared with the case where the torque of the first output shaft is larger than the threshold value, the differential action of the differential device is restricted, the power transmission device further includes an engaging device that selectively connects any two of the three rotating elements, the control method further includes the following steps: when the torque of the first output shaft is below a threshold value in a state where the differential device can perform differential and the second power source outputs power, the engaging device is engaged, the engaging device is a friction engaging device that can be switched to an engaged state, a semi-engaged state, and a released state, the first drive wheel and the second drive wheel are wheels of the vehicle, the control method further includes the following steps: when the torque of the first output shaft is below a threshold value in a state where the differential device can perform differential and the second power source outputs power, when the turning degree of the vehicle is large, compared with the case where the turning degree of the vehicle is small, the engagement degree of the friction engaging device is reduced.

11. The control method for a power transmission device according to claim 10, wherein the control method further includes: a step of calculating the torque of the first output shaft based on the torque input from the first input shaft to the first output shaft, the torque output by the second power source, the gear ratio between the second power source and the second input shaft, and the gear ratio of the differential device; and a step of comparing the calculated torque of the first output shaft with the threshold value.

12. The control method for a power transmission device according to claim 10 or 11, wherein the second power source is a rotary electric machine. The control method further includes the following steps: when regeneration is performed by the rotary electric machine, engage the engaging device.

13. The control method of the power transmission device according to claim 10 or 11, wherein: The control method further includes the following steps: when only the second power source is driven without driving the first power source, engage the engaging device.

14. The control method of the power transmission device according to claim 10, wherein: The control method further includes the following steps: when the torque of the first output shaft is below a threshold value in a state where the differential device can perform differential and the second power source outputs power, during a turn of the vehicle, bring the friction engaging device into a semi-engaged state.

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