Vehicle drive device

Abstract

The present application provides a vehicle drive device capable of suppressing a decrease in a driver's predictability on driving performance. A vehicle drive device (50) includes a main power source (40) including a first motor (MGl), a center differential (20) that distributes input torque (Tin) input from the main power source (40) to front wheels (28) and rear wheels (38), a sub power source (42) including a second motor (MG2) that adds additional torque (Tadd) to a rear drive shaft (32), and an electronic control device (90) that controls the input torque (Tin) and the additional torque (Tadd). The electronic control device (90) appropriately sets an input torque sharing ratio (k) to maintain a distribution ratio (β) of drive torque transmitted to the front wheels (28), i.e., front wheel drive torque (Trf), relative to total drive torque (Tr) at a prescribed constant value (= k x γf) if the front wheel side distribution ratio (γf) is a fixed value in a case where the first motor (MGl) and the second motor (MG2) are operating and the total drive torque (Tr) is being changed.

Description

Technical Field

[0001] The present invention relates to a drive device for a vehicle, comprising: a primary power source including a first electric motor that inputs drive torque to a central differential; a secondary power source including a second electric motor that adds drive torque to the rear power transmission path between the central differential and the rear wheels; and a control device for controlling the drive torque output from the primary power source and the secondary power source respectively. Background Technology

[0002] A known vehicle drive system comprises: an engine that inputs drive torque to a central differential, the central differential distributing drive torque to the front and rear wheels; an electric motor that adds drive torque to the rearward power transmission path between the central differential and the rear wheels; and a control device that controls the drive torque output from the engine and the electric motor respectively. For example, this is the case as described in Patent Document 1.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-36808 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] Here, the driving torque transmitted to the front wheels is referred to as the "front wheel driving torque," and the sum of the driving torques transmitted to the front and rear wheels is referred to as the total driving torque. In the vehicle drive system disclosed in Patent Document 1, for example, if the ratio of the front wheel driving torque to the total driving torque, i.e., the distribution ratio, changes according to the vehicle's ground load without the driver's intention, the driver may experience a sense of incoordination in driving performance. That is, the driver's predictability in driving performance decreases.

[0008] The present invention was made against the background described above, and its object is to provide a vehicle drive device that can suppress the decline in the driver's predictability of driving performance.

[0009] means for solving problems

[0010] The essence of the present invention is a vehicle drive system comprising: a primary power source including a first electric motor; a central differential for distributing input torque from the primary power source to the front wheels and the rear wheels; an auxiliary power source including a second electric motor for adding additional torque to the rear power transmission path between the central differential and the rear wheels; and a control device for controlling the input torque and the additional torque, the control device being configured to maintain the distribution ratio of the drive torque transmitted to the front wheels, i.e., the front wheel drive torque, relative to the total drive torque at a predetermined constant value when the primary power source and the auxiliary power source are operating and the total drive torque transmitted to the front wheels and the rear wheels varies.

[0011] The effects of the invention

[0012] According to the vehicle drive system of the present invention, the control device is configured to maintain the distribution ratio of the driving torque transmitted to the front wheels (i.e., the front wheel driving torque) relative to the total driving torque at a predetermined constant value when the active power source and the auxiliary power source are operating and the total driving torque transmitted to the front wheels and the rear wheels changes. Thus, the control device is configured to maintain the distribution ratio of the front wheel driving torque relative to the total driving torque at a predetermined constant value. That is, since the distribution ratio of the driving torque to the front wheels and the rear wheels remains unchanged, there is no situation where the driver unconsciously changes the distribution ratio of the driving torque, suppressing a decrease in the driver's predictability of driving performance, i.e., the driver's perception of a lack of coordination in driving performance. Attached Figure Description

[0013] Figure 1 This is a schematic structural diagram of a vehicle equipped with the drive unit of Embodiment 1, and a functional block diagram showing the main parts of the control functions used for various controls of the vehicle.

[0014] Figure 2 This is an explanation Figure 1 An example of a flowchart illustrating the control operation of an electronic control device.

[0015] Figure 3 This is a schematic structural diagram of a vehicle equipped with the drive unit of Embodiment 2, and a functional block diagram showing the main parts of the control functions used for various controls of the vehicle.

[0016] Figure 4 This is an explanation Figure 3 An example of a flowchart illustrating the control operation of an electronic control device. Detailed Implementation

[0017] Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, in each embodiment, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the parts may not be accurately depicted.

[0018]

Example

[0019] Figure 1 This is a schematic structural diagram of a vehicle 10 equipped with the vehicle drive unit 50 of Embodiment 1, and a functional block diagram showing the main parts of the control functions for various controls of the vehicle 10.

[0020] The vehicle drive unit 50 is a four-wheel drive vehicle, equipped with an engine 12 as a power source for driving, a first electric motor MG1 and a second electric motor MG2, and a center differential 20, which are known structures. Hereinafter, "center differential 20" will be abbreviated as "center differential 20".

[0021] Engine 12 is a known internal combustion engine. The first electric motor MG1 and the second electric motor MG2 are so-called electric generators, such as a known three-phase synchronous electric generator. The first electric motor MG1 is connected to the output shaft of engine 12 to transmit power. Engine 12 and the first electric motor MG1 constitute the main power source 40.

[0022] The vehicle drive unit 50 has an automatic transmission 16 on the input-side power transmission path PTi between the power source 40 and the center differential 20. The power source 40 and the automatic transmission 16 are connected via a transmission input shaft 14. The automatic transmission 16 and the center differential 20 are connected via a transmission output shaft 18. The automatic transmission 16 is a known structure that changes the rotation of the transmission input shaft 14 and outputs to the transmission output shaft 18. The automatic transmission 16 is controlled by an electronic control unit 90 (described later) to form a desired gear ratio α from different gear ratios α. The transmission input shaft 14 is also the output shaft of the power source 40, and the transmission output shaft 18 is also the input shaft of the center differential 20. The gear ratio α is the ratio of the rotational speed N1 [rpm] of the transmission input shaft 14 to the rotational speed N2 [rpm] of the transmission output shaft 18 [=N1 / N2]. Through the automatic transmission 16, the rotational speed N2 of the transmission output shaft 18 is changed to 1 / α times the rotational speed N1 of the transmission input shaft 14. The drive torque input from the transmission output shaft 18 to the central differential 20 becomes α times the drive torque input from the transmission input shaft 14 to the automatic transmission 16. The drive torque input from the transmission output shaft 18 to the central differential 20 is called the "input torque Tin [N·m]".

[0023] In the vehicle drive system 50, on the front power transmission path PTf between the central differential 20 and the pair of front wheels 28, a front drive shaft 22, a front differential gear 24, and a pair of front drive shafts 26 are sequentially arranged from the central differential 20 side; these are known structures. Hereinafter, "the pair of front wheels 28" will be abbreviated as "front wheels 28". The front wheels 28 are equivalent to "front wheels" in this invention. In the vehicle drive system 50, on the rear power transmission path PTR between the central differential 20 and the pair of rear wheels 38, a rear drive shaft 32, a rear differential gear 34, and a pair of rear drive shafts 36 are sequentially arranged from the central differential 20 side; these are known structures. Hereinafter, "the pair of rear wheels 38" will be abbreviated as "rear wheels 38". The rear wheels 38 are equivalent to "rear wheels" in this invention. The second electric motor MG2 is capable of transmitting power to the rear drive shaft 32. The second electric motor MG2 forms a structure that adds driving torque to the rear power transmission path PTR between the central differential 20 and the rear wheel 38. The second electric motor MG2 constitutes the auxiliary power source 42.

[0024] The power source 40 outputs input torque Tin to the center differential 20 via the automatic transmission 16. The center differential 20 is a known structure that distributes the input torque Tin to the front wheels 28 and the rear wheels 38 respectively. The center differential 20 distributes the input torque Tin to the front drive shaft 22 side as the product of the front wheel distribution rate γf (=Tin×γf), and distributes the input torque Tin to the rear drive shaft 32 side as the product of the rear wheel distribution rate γr (=Tin×γr). The front wheel distribution rate γf is the ratio of the input torque Tin transmitted by the center differential 20 to the front wheels 28, and the rear wheel distribution rate γr is the ratio of the input torque Tin transmitted by the center differential 20 to the rear wheels 38. The front wheel distribution rate γf is equivalent to the "distribution rate" in this invention. Both the front wheel distribution rate γf and the rear wheel distribution rate γr are values ​​between 0 and 1, and their sum (=γf+γr) is "1". In this embodiment, the front wheel distribution ratio γf and the rear wheel distribution ratio γr of the center differential 20 are fixed values. The center differential 20 is, for example, a planetary gear type center differential with fixed front wheel distribution ratio γf and rear wheel distribution ratio γr.

[0025] The vehicle drive unit 50 includes an inverter 60, a battery 62, and an electronic control unit 90. The inverter 60 is a known power supply circuit that converts direct current (DC) to alternating current (AC) or vice versa. A first motor MG1 and a second motor MG2 are connected to the battery 62 via the inverter 60, respectively. The first motor MG1 and the second motor MG2 control their respective output torques by controlling the inverter 60 through the electronic control unit 90. The drive torque output from the first motor MG1, i.e., the shaft torque on the transmission input shaft 14, is called the first motor torque Tmg1 [N·m]. The drive torque output from the second motor MG2, i.e., the shaft torque on the rear drive shaft 32, is called the second motor torque Tmg2 [N·m]. The second motor torque Tmg2 is an additional torque Tadd that adds the drive torque to the rear drive shaft 32. When the first motor MG1 and the second motor MG2 function as motors, the first motor torque Tmg1 and the second motor torque Tmg2 constitute the operating torque; when the first motor MG1 and the second motor MG2 function as generators, the first motor torque Tmg1 and the second motor torque Tmg2 constitute the regenerative torque. Battery 62 is an energy storage device that supplies power to the first motor MG1 and the second motor MG2 and receives power from the first motor MG1 and the second motor MG2 respectively.

[0026] In vehicle 10, a driving mode can be selected from multiple driving modes. For example, the driving modes include normal driving mode, off-road driving mode, and sport driving mode. Normal driving mode is, for example, a driving mode for paved roads. Compared with off-road driving mode and sport driving mode, normal driving mode is a driving mode that is predetermined to be able to drive under conditions of good fuel efficiency and electricity consumption. Off-road driving mode is, for example, a driving mode for unpaved roads. Compared with normal driving mode and sport driving mode, off-road driving mode is a driving mode that is predetermined to be suitable for off-road driving, and is a driving mode selected, for example, when the required drive torque Trdem [N·m] is large. "Required drive torque Trdem" is calculated and determined, for example, by applying the throttle opening θacc [%] operated by the driver and the actual vehicle speed V [km / h] in the required drive torque mapping. Required drive torque Trdem is the total drive torque Tr [N·m] requested by the driver for vehicle 10, that is, the sum of the drive torque transmitted to the front wheels 28 and the rear wheels 38, and is the drive torque required by vehicle 10. The required drive torque mapping is, for example, an experimentally or design-based pre-set and stored mapping relating the throttle opening θacc and vehicle speed V to the required drive torque Trdem. The sport driving mode is, for example, a driving mode for paved roads. Compared to the normal driving mode, this is a driving mode pre-determined to allow for good power performance, selected when it is desired to reduce the drive torque distributed to the front wheels 28, which act as steering wheels. Switching between driving modes is, for example, performed manually by the driver using a driving mode selection switch 80. The driving mode selection switch 80 is, for example, a momentary push-button switch. Each time the driver presses the driving mode selection switch 80, the selected driving mode sequentially switches from the normal driving mode to the off-road driving mode, from the off-road mode to the sport driving mode, and from the sport mode back to the normal mode.

[0027] The electronic control unit 90 is configured, for example, to include a so-called microcomputer, and performs various controls of the vehicle 10 by processing signals according to a pre-stored program. The electronic control unit 90 is equivalent to the "control device" in this invention. Various signals are input to the electronic control unit 90, for example, based on the detection values ​​of various sensors (e.g., speed sensor 70, speed sensor 72, speed sensor 74, vehicle speed sensor 76, throttle opening sensor 78, driving mode selection switch 80, etc.). These signals include, for example, the engine speed Ne [rpm] of the engine 12, the speed Nmg1 [rpm] of the first electric motor MG1 converted to the speed on the transmission input shaft 14, the speed Nmg2 [rpm] of the second electric motor MG2 converted to the speed on the rear drive shaft 32, the vehicle speed V, the throttle opening θacc, which indicates the magnitude of the driver's acceleration operation, and the mode selection signal Smode, which indicates the driving mode selected by the driver through manual operation of the driving mode selection switch 80. The electronic control unit 90 outputs various control signals to various components of the vehicle 10 (engine 12, inverter 60, automatic transmission 16, etc.). These signals include engine control signal Se for controlling the operating state of engine 12, first motor control signals Smg1 and Smg2 for controlling the operating states of first motor MG1 and second motor MG2, and shift control signal Sat for shifting the automatic transmission 16. Thus, the engine speed Ne and engine torque Te [N·m], the first motor speed Nmg1 and first motor torque Tmg1, and the second motor speed Nmg2 and second motor torque Tmg2 are controlled by the electronic control unit 90. The engine torque Te is the output torque of engine 12.

[0028] Next, the control function of the electronic control unit 90 will be explained when the engine 12, the first electric motor MG1 and the second electric motor MG2 are working and the total drive torque Tr changes.

[0029] The electronic control unit 90 functionally includes a necessary drive torque determination unit 92, a driving mode switching unit 94, a distribution determination unit 96, and a drive unit control unit 98.

[0030] The required drive torque determination unit 92 determines the required drive torque Trdem based on the actual throttle opening θacc and vehicle speed V. The driving mode switching unit 94 switches to the driving mode selected manually by the driver via the driving mode selection switch 80.

[0031] When the allocation decision unit 96 determines that the driving mode switched by the driving mode switching unit 94 is the normal driving mode, it determines the input torque sharing ratio k as a sharing ratio value k0. The input torque sharing ratio k is the ratio of the input torque Tin to the required drive torque Trdem (=Tin / Trdem). The input torque sharing ratio k is equivalent to the "sharing ratio" in this invention. When the allocation decision unit 96 determines that the driving mode switched by the driving mode switching unit 94 is the off-road driving mode, it determines the input torque sharing ratio k as a sharing ratio value k1 (>k0). When the allocation decision unit 96 determines that the driving mode switched by the driving mode switching unit 94 is the sport driving mode, it determines the input torque sharing ratio k as a sharing ratio value k2 (<k0). The sharing ratio values ​​k0, k1, and k2 are constant values ​​that are experimentally or intentionally predetermined according to each driving mode, equivalent to the "prescribed constant values" in this invention. The allocation decision unit 96 determines whether to perform the transmission control of the automatic transmission 16. The allocation decision unit 96 uses, for example, a shift mapping to determine the shift of the automatic transmission 16. The shift mapping is a predetermined and well-known relationship in which a shift line for determining the shift of the automatic transmission 16 is provided on a two-dimensional coordinate system, for example, with vehicle speed V and required drive torque Trdem as variables. The allocation decision unit 96 calculates and determines the input torque Tin based on equation (1).

[0032] Tin = k × Trdem…(1)

[0033] Next, the situation where the allocation decision unit 96 determines that transmission control will not be executed will be explained.

[0034] The allocation decision unit 96 obtains the current gear ratio α0. Since equation (2) holds, it calculates and determines the first motor torque Tmg1 based on equation (3) according to equations (1) and (2). In addition, the output torque Tmain is the output torque of the power source 40, and is the sum of the engine torque Te and the first motor torque Tmg1. The allocation decision unit 96 calculates and determines the second motor torque Tmg2 based on equation (4).

[0035] Tin=Tmain / α0=(Te+Tmg1) / α0…(2)

[0036] Tmg1=(k×Trdem)×α0-Te…(3)

[0037] Tmg2=(1-k)×Trdem…(4)

[0038] The drive unit control unit 98 performs output control of the main power source 40 and the auxiliary power source 42 respectively, so that the first motor torque Tmg1 and the second motor torque Tmg2 are determined by the distribution determination unit 96. In addition, the engine torque Te is less likely to change in a short time compared with the first motor torque Tmg1. Therefore, it is preferable to not change the engine torque Te, but to change the first motor torque Tmg1, so that equation (3) holds.

[0039] In the output control of the drive unit control unit 98 when the distribution decision unit 96 determines that transmission control will not be performed, the front wheel drive torque Trf [N·m] and the rear wheel drive torque Trr [N·m] are represented by equations (5) and (6). The input torque sharing ratio k is any constant value among the sharing ratio values ​​k0 to k2 determined according to the driving mode selected by the driver, and the front wheel side distribution ratio γf is also a fixed value. Thus, the ratio of the front wheel drive torque Trf to the rear wheel drive torque Trr is controlled to be a constant ratio (k×γf): (1-k×γf). That is, the electronic control unit 90 is configured to maintain the distribution ratio β (=Trf / Tr) of the front wheel drive torque Trf to the total drive torque Tr at a predetermined constant value (=k×γf). The sum of the front wheel drive torque Trf and the rear wheel drive torque Trr is the required drive torque Trdem. Furthermore, the predetermined constant value (=k×γf) is equivalent to the "predetermined constant value" in this invention.

[0040] Trf=Tin×γf

[0041] =(k×Trdem)×γf

[0042] =(k×γf)×Trdem…(5)

[0043] Trr = Tin × γr + Tmg2

[0044] =(k×Trdem)×(1-γf)+(1-k)×Trdem

[0045] =(1-k×γf)×Trdem…(6)

[0046] Next, the situation where the allocation decision unit 96 determines that transmission control should be executed will be explained.

[0047] After the gear shift control is executed, i.e., the gear ratio α1 after the gear shift, the allocation decision unit 96 calculates and determines the first motor torque Tmg1 after the gear shift based on equation (8) according to equation (1) and equation (7). The allocation decision unit 96 calculates and determines the second motor torque Tmg2 after the gear shift based on the aforementioned equation (4).

[0048] Tin=Tmain / α1=(Te+Tmg1) / α1…(7)

[0049] Tmg1=(k×Trdem)×α1-Te…(8)

[0050] The drive unit control unit 98 performs the gear shift control of the automatic transmission 16 and performs the output control of the main power source 40 and the auxiliary power source 42 respectively, so as to become the first motor torque Tmg1 and the second motor torque Tmg2 after gear shift determined by the distribution determination unit 96.

[0051] In the output control following the gear shift control performed by the drive unit control unit 98 when the distribution decision unit 96 determines that gear shift control is to be executed, the front wheel drive torque Trf and the rear wheel drive torque Trr are expressed by the aforementioned equations (5) and (6). Therefore, the electronic control unit 90 is configured to maintain the distribution ratio β at a predetermined constant value (=k×γf). In addition, the sum of the front wheel drive torque Trf and the rear wheel drive torque Trr is the required drive torque Trdem.

[0052] Figure 2 This is an explanation Figure 1 An example of a flowchart illustrating the control operation of the electronic control device 90. Figure 2 The flowchart is repeated when the engine 12, the first electric motor MG1, and the second electric motor MG2 are operating and causing the total drive torque Tr to change.

[0053] First, in step S10 (hereinafter referred to as "step"), the required drive torque Trdem is determined, and in S20, the driving mode is determined. If the driving mode is determined to be normal driving mode in S20, the torque sharing ratio k is determined to be k0 in S30. If the driving mode is determined to be off-road driving mode in S20, the torque sharing ratio k is determined to be k1 in S32. If the driving mode is determined to be sport driving mode in S20, the torque sharing ratio k is determined to be k2 in S34. After executing S30 to S34, in S40, it is determined whether to perform transmission control of the automatic transmission 16.

[0054] If the determination in S40 is negative (i.e., no speed change control is performed), the current gear ratio α0 is obtained in S50a. After executing S50a, the output torque Tmain [N·m] of the main power source 40 is determined in S60a, the first motor torque Tmg1 is determined in S70a, and the second motor torque Tmg2 is determined in S80a. After executing S80a, the output control of the main power source 40 and the auxiliary power source 42 is performed in S90a to obtain the first motor torque Tmg1 and the second motor torque Tmg2 determined in S70a and S80a, respectively. If the determination in S40 is positive (i.e., speed change control is performed), the gear ratio α1 after speed change is obtained in S50b. After executing S50b, the output torque Tmain of the main power source 40 after speed change is determined in S60b, the first motor torque Tmg1 after speed change is determined in S70b, and the second motor torque Tmg2 after speed change is determined in S80b. After executing S80b, in S90b, the automatic transmission 16 undergoes gear shift control, and the output control of the primary power source 40 and the secondary power source 42 is executed respectively, to achieve the gear shifted first motor torque Tmg1 and gear shifted second motor torque Tmg2 determined in S70b and S80b. The process returns after executing S90a and S90b.

[0055] According to this embodiment, an automatic transmission 16 is provided on the input-side power transmission path PTi between the main power source 40 and the central differential 20. The electronic control unit 90 is configured such that, when performing gear shift control of the automatic transmission 16, even if the gear ratio α of the automatic transmission 16 changes, the distribution ratio β is maintained at a predetermined constant value (=k×γf). That is, since the distribution ratio of the drive torque between the front wheels 28 and the rear wheels 38 remains unchanged, there will be no situation where the driver unconsciously changes the distribution ratio of the drive torque, thus suppressing the decrease in the driver's predictability of driving performance, i.e., the driver's feeling of uncoordinated driving performance.

[0056] According to this embodiment, (a) the front wheel distribution ratio γf, which distributes the input torque Tin to the front wheels 28 by the central differential 20, is constant; and (b) the electronic control unit 90, while maintaining the distribution ratio β at a predetermined constant value, configures the input torque sharing ratio k to be maintained at a predetermined constant value, i.e., any one of the sharing ratio values ​​k0 to k2. With the front wheel distribution ratio γf constant, the electronic control unit 90 is simply configured to maintain the input torque sharing ratio k at any one of the sharing ratio values ​​k0 to k2, which are predetermined constant values, thereby maintaining the distribution ratio β at a predetermined constant value. This suppresses the driver's perception of incoordination in driving performance.

[0057] According to this embodiment, the electronic control device 90 is configured to maintain the distribution ratio β at a predetermined constant value (=k×γf) by switching the input torque distribution ratio k according to the driving mode selected by the driver. By maintaining the predetermined constant value (=k×γf) of the distribution ratio β according to the driving mode switch, a distribution ratio of the driving torque suitable for the driving mode selected by the driver is achieved between the front wheel driving torque Trf and the rear wheel driving torque Trr. For example, in an off-road driving mode where a relatively large required driving torque Trdem is needed, by making the distribution ratio β (=Trf / Tr) larger than in the normal driving mode, the tire grip can be maximized in the so-called friction circle. For example, in a sport driving mode, by making the distribution ratio β smaller than in the normal driving mode, the spare tire grip on the friction circle on the front wheel 28 side is increased, thereby improving the steering performance of the vehicle 10.

[0058]

Example 2

[0059] Figure 3 This is a schematic structural diagram of a vehicle 110 equipped with the vehicle drive unit 150 of Embodiment 2, and a functional block diagram showing the main parts of the control functions used for various controls of the vehicle 110. The vehicle drive unit 150 has a structure that is substantially the same as that of the vehicle drive unit 50 of Embodiment 1 described above, but the main differences are: (a) a power source 140 is provided instead of a power source 40; (b) a central differential 120 is provided instead of a central differential 20; (c) an automatic transmission 16 is not provided between the power source 140 and the central differential 120; (d) a secondary power source 142 is provided instead of a secondary power source 42; and (e) an electronic control unit 190 is provided instead of an electronic control unit 90. Therefore, in this embodiment, the description focuses on the parts that are different from those in Embodiment 1, and the same reference numerals are used to mark the parts that are substantially common in function with those in Embodiment 1, and descriptions are omitted where appropriate. Hereinafter, "central differential 120" will be abbreviated as "central differential 120".

[0060] The main power source 140 has a structure substantially the same as the aforementioned main power source 40, but differs in that it is constituted only by the first electric motor MG1 and does not include the engine 12. The output torque Tmain has the same value as the first electric motor torque Tmg1, and is also the input torque Tin. The center differential 120 has a structure substantially the same as the aforementioned center differential 20, but differs in that the front wheel side distribution ratio γf is variable. The center differential 120 is, for example, an electronically controlled center differential or the like that makes the front wheel side distribution ratio γf and the rear wheel side distribution ratio γr variable, is provided with a differential limiting mechanism, and has electronically controlled differential limiting. The auxiliary power source 142 has a structure substantially the same as the aforementioned auxiliary power source 42, but differs in that the second electric motor MG2 is connected to the differential case 34c of the rear differential gear 34 so as to be capable of transmitting power. Accordingly, similarly to the aforementioned first embodiment, the second electric motor MG2 is structured to apply drive torque to the rear power transmission path PTr between the center differential 120 and the rear wheels 38.

[0061] Next, the control function of the electronic control device 190 in a state where the engine 12, the first electric motor MG1, and the second electric motor MG2 are in operation and the total drive torque Tr is varied will be described.

[0062] The electronic control device 190 functionally includes a required drive torque determination unit 92, a travel mode switching unit 94, a distribution determination unit 196, and a drive device control unit 198.

[0063] When the distribution determination unit 196 determines that the travel mode switched by the travel mode switching unit 94 is the normal travel mode, the distribution determination unit 196 determines the product R (=k×γf) of the input torque share ratio k and the front wheel side distribution ratio γf as a constant value R0, and determines the input torque share ratio k as R0 / γf. When the distribution determination unit 196 determines that the travel mode switched by the travel mode switching unit 94 is the off-road travel mode, the distribution determination unit 196 determines the product R as a constant value R1 (>R0), and determines the input torque share ratio k as R1 / γf. When the distribution determination unit 196 determines that the travel mode switched by the travel mode switching unit 94 is the sport travel mode, the distribution determination unit 196 determines the product R as a constant value R2 (<R0), and determines the input torque share ratio k as R2 / γf. In this way, the distribution determination unit 196 varies the front wheel side distribution ratio γf and the input torque share ratio k respectively, without varying the product R (=k×γf), in accordance with the travel mode selected by the driver. In addition, the constant values R0, R1, and R2 are constant values experimentally or design-wise determined in advance in accordance with the respective travel modes, and correspond to the "predetermined constant values" in the present invention.

[0064] Since the torque Tmg1 of the first motor is the same as the input torque Tin, the allocation decision unit 196 calculates and determines the torque Tmg1 of the first motor based on equation (9). The allocation decision unit 196 calculates and determines the torque Tmg2 of the second motor based on the aforementioned equation (4).

[0065] Tmg1=Tin=(k×Trdem)…(9)

[0066] The drive unit control unit 198 performs output control of the main power source 140 and the auxiliary power source 142 respectively, so as to become the first motor torque Tmg1 and the second motor torque Tmg2 determined by the allocation decision unit 196.

[0067] In the output control of the drive unit control unit 198, as in Embodiment 1, the front wheel drive torque Trf and the rear wheel drive torque Trr are represented by equations (5) and (6). The product R (=k×γf) is any one of the constant values ​​R0 to R2. Thus, the ratio of the front wheel drive torque Trf to the rear wheel drive torque Trr is controlled to be a constant ratio (k×γf): (1-k×γf). That is, the electronic control unit 190 is configured to maintain the distribution ratio β at a predetermined constant value (=k×γf).

[0068] Figure 4 This is an explanation Figure 3 An example of a flowchart illustrating the control operation of the electronic control device 190. Figure 4 The flowchart is repeated under the condition that the first motor MG1 and the second motor MG2 are working and the total drive torque Tr changes.

[0069] Figure 4 The flowchart is the same as that in the aforementioned embodiment 1. Figure 2 The flowcharts have roughly the same structure, but the differences are: S130 to S134 are replaced by S30 to S34 respectively; and S170 to S190 are executed after S130 to S134 without the decision step of S40.

[0070] When it is determined in S20 that the travel mode is the normal travel mode, in S130, the product R (=k×γf) is determined as a constant value R0, and the input torque distribution ratio k is determined as R0 / γf. When it is determined in S20 that the travel mode is the off-road travel mode, in S132, the product R is determined as a constant value R1 (>R0), and the input torque distribution ratio k is determined as R1 / γf. When it is determined in S20 that the travel mode is the sport travel mode, in S134, the product R is determined as a constant value R2 (<R0), and the input torque distribution ratio k is determined as R2 / γf. After executing S130 to S134, the first motor torque Tmg1 is determined in S170, and the second motor torque Tmg2 is determined in S180. After executing S180, output control of the main power source 140 and the auxiliary power source 142 is executed in S190 so as to achieve the first motor torque Tmg1 and the second motor torque Tmg2 determined in S170 and S180. After executing S190, the process returns.

[0071] According to the present embodiment, the electronic control device 190 maintains the product R (=k×γf) at any one of the constant values R0 to R2 determined according to the travel mode selected by the driver, while maintaining the distribution ratio β at a predetermined constant value. Since the product R is configured to be maintained at a constant value, the distribution ratio of the drive torque to the front wheels 28 and the rear wheels 38 does not change. Therefore, the driver will not unconsciously change the distribution ratio of the drive torque, and the reduction in the driver's predictability in driving performance is suppressed.

[0072] In addition, the above are the respective embodiments of the present invention, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art without departing from the gist thereof.

[0073] In the aforementioned Embodiments 1 and 2, there are three travel modes: the normal travel mode, the off-road travel mode, and the sport travel mode, but the present invention is not limited thereto. The number of travel modes may be four or more, or two or one.

[0074] For example, in the aforementioned Embodiment 1, the center differential 20 may also be a torque-sensitive type or the like with a differential limiting function. In this case, the stability of the vehicle during turning is improved.

[0075] The present invention can also be applied to the configuration in which the automatic transmission 16 is not provided in the aforementioned Embodiment 1, and can also be applied to the configuration in which the automatic transmission is provided on the input-side power transmission path PTin in the aforementioned Embodiment 2. When no automatic transmission is provided, this is synonymous with virtually providing an automatic transmission with a speed ratio α of "1". Further, the present invention can also be applied to a configuration in which a gear pair with a fixed speed ratio (=gear ratio) is provided instead of the automatic transmission 16.

[0076] The present invention can be applied to the configuration in Embodiment 1 where the main power source 40 does not include the engine 12 but only includes the first electric motor MG1, and it can also be applied to the configuration in Embodiment 2 where the main power source 140 includes the engine 12. Furthermore, the present invention can also be applied to the configurations in Embodiments 1 and 2 where the auxiliary power sources 42 and 142 include power sources other than the second electric motor MG2.

[0077] Explanation of reference numerals in the attached figures

[0078] 16: Automatic transmission; 20, 120: Central differential; 28: Front wheel pair; 38: Rear wheel pair; 40, 140: Main power source; 42, 142: Secondary power source; 50, 150: Vehicle drive unit; 90, 190: Electronic control unit; k: Input torque sharing ratio; k0, k1, k2: Sharing ratio values ​​(specified constant values); MG1: First electric motor; MG2: Second electric motor; PTi: Input side power transmission path; PTr: Rear side power transmission path; R: Product; R0, R1, R2: Constant values ​​(specified constant values); Tin: Input torque; Tmg2: Second electric motor torque (additional torque); Tr: Total drive torque; Trdem: Required drive torque; Trf: Front wheel drive torque; Tsum: Total torque; α: Gear ratio; β: Distribution ratio; γf: Front wheel side distribution rate (distribution rate).

Claims

1. A vehicle drive unit (50, 150), comprising: The main power source (40, 140) includes the first electric motor (MG1); The central differential (20, 120) distributes the input torque (Tin) from the power source to the front wheel (28) and the rear wheel (38); The auxiliary power source (42, 142) includes a second electric motor (MG2) that applies additional torque (Tmg2) to the rear power transmission path (PTr) between the center differential and the rear wheels; and The control devices (90, 190) control the input torque and the additional torque, and the vehicle drive unit (50, 150) is characterized in that... The control device is configured to maintain the distribution ratio (β) of the driving torque transmitted to the front wheels, i.e., the front wheel driving torque (Trf), relative to the total driving torque, at a predetermined constant value when the active power source and the auxiliary power source are operating and the total driving torque (Tr) transmitted to the front wheels and the rear wheels changes.

2. The vehicle drive device according to claim 1, characterized in that, The control device is configured to maintain the product of the distribution rate (γf) of the input torque to the front wheels and the sharing ratio (k) of the input torque relative to the required drive torque (Trdem) necessary for the vehicle at the predetermined constant value while maintaining the distribution ratio at the predetermined constant value, and to make the additional torque the product of the value obtained by subtracting the sharing ratio from 1 and the required drive torque.

3. The vehicle drive unit according to claim 2, characterized in that, The central differential distributes the input torque to the front wheels at a constant rate. The control device is configured to maintain the sharing ratio at a predetermined constant value while maintaining the allocation ratio at the predetermined constant value.

4. The vehicle drive unit according to any one of claims 1 to 3, characterized in that, The control device is configured to switch the specified constant value according to the driving mode selected by the driver.

5. The vehicle drive unit according to any one of claims 1 to 3, characterized in that, An automatic transmission (16) is provided on the input-side power transmission path between the active power source and the central differential. The control device is configured to maintain the distribution ratio at the predetermined constant value even if the gear ratio of the automatic transmission changes when performing the gear shift control of the automatic transmission.

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