Left-right wheel independently-driven type vehicle

Abstract

To maintain sufficient driving performance without requiring enlargement of a cooling device, even when a driving constraint occurs in any of left and right wheels.SOLUTION: A left-right wheel independently-driven type vehicle comprises: a temperature detection unit 31a that detects the temperature of a left motor and the temperature of a right motor; a temperature determination unit 31b that determines that one of the detected temperatures falls outside a predetermined temperature range; a drive force limiting unit 31c that, when it is determined that the one motor of the temperature of the left motor and the temperature of the right motor falls outside the temperature range, reduces the drive torque of the other motor that does not fall outside the temperature range; and a drive torque increase unit 31d that increases the drive torque of the other drive device not including the motor outside the temperature range in the first drive device and the second drive device, when reducing the drive torque of the other motor.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a vehicle configured to drive left and right wheels independently, and more particularly to a vehicle in which an electric motor is provided for each of the left and right wheels. [Background technology]

[0002] In order to improve the driving performance and running stability of a vehicle, it is preferable to individually control the driving force (driving torque) generated at each wheel. For example, the vehicle described in Patent Document 1 is configured to provide an engine and a first electric motor as a driving force source for the front wheels, and transmit the driving torque output from this driving force source to the left and right front wheels via a differential mechanism (differential), while allowing the differential, and provide a second electric motor as a driving force source for the rear wheels, and transmit the driving torque output from this second electric motor to the left and right rear wheels via the differential. In the vehicle described in Patent Document 1, for example, the thermal rating of the first electric motor is set higher than the thermal rating of the second electric motor, so that running stability is maintained even when the operation of one of the electric motors is restricted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-112114 A Summary of the Invention [Problem to be solved by the invention]

[0004] An electric motor used as a driving force source for a vehicle inevitably generates heat when it operates, and if the temperature reaches an upper limit, the torque that can be output is limited, durability is reduced, and normal operation is restricted. In the vehicle described in Patent Document 1, the thermal ratings of the front and rear electric motors used as driving force sources are set to have a specific relationship, so that even if the operation of one of the front or rear electric motors is restricted, the operation of the other electric motor is ensured, thereby maintaining driving stability.

[0005] However, a vehicle performs various driving operations such as acceleration / deceleration, turning, and climbing / descending slopes, and the load applied to each wheel or the drive torque required for each wheel is different each time. Therefore, in order to maintain driving stability or power performance in any of such various driving conditions, it is desirable to drive all wheels (for example, four wheels at the front and rear) or at least a pair of left and right wheels by individual electric motors provided corresponding to each wheel. In the vehicle described in Patent Document 1, even if the balance of the power distribution between the front and rear wheels can be maintained, it is difficult to control the drive torque of the left and right wheels independently of each other. In addition, if the vehicle described in Patent Document 1 is configured to appropriately perform differential limiting of each of the front and rear differentials, the drive torque of the left and right wheels can be controlled to some extent. However, in order to do so, a differential limiting mechanism and its control device must be newly provided, which results in other problems such as an increase in the size and weight of the vehicle. In addition, it is possible to provide a cooling device with sufficient capacity or size to avoid operational restrictions due to the heat of the electric motor, but even in that case, other problems such as an increase in the size and weight of the vehicle will occur.

[0006] On the other hand, conventionally, vehicles have been known in which motors are provided for all wheels, such as in-wheel motor vehicles, and all wheels are individually driven by the motors. Even in this type of vehicle, the operation may be restricted by the heat of the motor, but if the cooling device is increased in capacity to reduce the operation restriction due to heat, the above-mentioned problems such as the increase in size of the device arise. Also, even in a vehicle configured to drive all wheels individually, it is possible that the balance of the driving forces of the left and right wheels may be impaired due to the thermal characteristics of the motor, but conventionally, no particular attention has been paid to such problems, and no suitable means or devices have been proposed for dealing with such cases.

[0007] This invention has been made against the background of the above circumstances, and aims to provide a vehicle that can maintain necessary and sufficient driving performance even when driving restrictions arise on one of the left or right wheels, without incurring an increase in the size of the cooling device, etc. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a left and right wheel independent drive type vehicle, comprising a first drive unit for driving left and right front wheels and a second drive unit for driving left and right rear wheels, at least one of the first drive unit and the second drive unit comprising a left electric motor for driving a left wheel and a right electric motor for driving a right wheel paired with the left wheel, the vehicle further comprising a controller for controlling the first drive unit and the second drive unit, the controller further comprising a temperature detection unit for detecting a temperature of the left motor and a temperature of the right motor, and a controller for detecting whether one of the temperatures detected by the temperature detection unit is a temperature detection unit. a driving force limiting unit which, when it is determined by the temperature determination unit that the temperature of one of the left motor and the right motor is outside the temperature range, reduces the driving torque of the other motor whose temperature is not outside the temperature range; and a driving torque increasing unit which, when the driving torque of the other motor is reduced by the driving force limiting unit, increases the driving torque of the other driving unit, of the first driving device and the second driving device, that does not include the one of the motors whose temperature is outside the temperature range.

[0009] In this invention, the other of the first drive device and the second drive device may be equipped with a traction motor as a drive force source, the temperature detection unit may further have a function of detecting the temperature of the traction motor, and the controller may further include a steady-state determination unit that determines whether the temperature of the traction motor is within a predetermined steady-state range, and a drive torque increase prohibition unit that prohibits the drive torque increase unit from increasing the drive torque when the temperature of the traction motor is not within the steady-state range.

[0010] In this invention, the controller may further include a four-wheel drive determination unit that determines four-wheel drive driving in which the first drive unit and the second drive unit output drive torque to drive the vehicle, and the drive force limiting unit may be configured to reduce the drive torque of the other electric motor when four-wheel drive driving is determined, and the drive torque increasing unit may be configured to increase the drive torque by the other drive unit when four-wheel drive driving is determined.

[0011] In this invention, the controller may further include a turning detection unit that detects that the vehicle is turning, and a drive limiting prohibition unit that prohibits the drive force limiting unit from reducing the drive torque of the other electric motor when a turning motion of the vehicle is detected.

[0012] In the present invention, the temperature range may be either a range in which only an upper limit temperature is defined, or a range determined by an upper limit temperature and a lower limit temperature. Effect of the Invention

[0013] According to this invention, in the first drive unit for driving the front wheels or the second drive unit for driving the rear wheels, when the temperature of one of the left and right electric motors is excessively high or excessively low, the drive torque of the other electric motor is reduced. Therefore, since the drive torque of the other electric motor is reduced in accordance with the one electric motor whose drive torque is limited by the temperature condition, it is possible to avoid or suppress the imbalance of torque at the left and right wheels. In addition, since the drive torque of the other drive unit is increased, the drive torque reduced by the temperature condition is compensated for by the increase in the drive torque of the other drive unit, so that the drive torque of the entire vehicle can be maintained, and it is possible to avoid or suppress the loss of power performance and driving stability. In addition, when the temperature of one of the electric motors becomes high, the electric motor is not actively cooled further in order to maintain the drive torque of the entire vehicle, so there is no need to increase the size or capacity of the cooling device, and it is possible to avoid the size and weight of the drive unit or the vehicle.

[0014] In addition, in this invention, when the temperature of the other driving device is not within the steady range, the driving torque of the other driving device is not increased, thereby preventing or suppressing damage to the other driving device or a decrease in durability.

[0015] In this invention, control is executed to reduce the drive torque of the other electric motor and increase the drive torque of the other drive device only when the vehicle is in four-wheel drive mode. As a result, the change in drive torque borne by the wheels is smaller than in two-wheel drive mode, and therefore discomfort due to shocks or changes in ride comfort can be avoided or suppressed.

[0016] Furthermore, in this invention, when the vehicle is turning, control of the reduction in the driving torque of the other electric motor and the increase in the driving torque of the other drive unit are prohibited, thereby avoiding or suppressing unstable turning and complicated control. [Brief description of the drawings]

[0017] [Figure 1] 1 is a block diagram showing a schematic diagram of a drive system of a four-wheel independent drive vehicle as an example of a vehicle according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a skeleton diagram showing an example of a rear wheel side drive unit. [Diagram 3] FIG. 2 is a skeleton diagram showing an example of a front wheel drive unit. [Figure 4] 2 is a schematic diagram for explaining various mechanisms for driving, stopping, and turning a vehicle. FIG. [Diagram 5] 3 is a block diagram illustrating a functional configuration and input signals of a controller. FIG. [Figure 6] 4 is a flowchart illustrating an example of control executed in the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is merely an example of the case where the present invention is implemented, and is not intended to limit the present invention.

[0019] The vehicle targeted by the present invention is a vehicle with a total of four wheels, two front wheels and two rear wheels, in which a drive unit is provided for each of the two front wheels and the two rear wheels, so that the two front wheels and the two rear wheels can be driven independently of each other. Furthermore, the vehicle is configured so that an electric motor (motor or motor-generator, hereinafter referred to as motor) is provided as a power source corresponding to each of the paired left front wheel and right front wheel, or the left rear wheel and right rear wheel, so that the left wheel and the right wheel can be driven independently. Note that the wheels individually provided with a motor may be only the front wheels, or only the rear wheels. In that case, the left and right wheels not individually provided with a motor may be configured to be connected to a single electric motor via a differential gear.

[0020] Fig. 1 shows a schematic example of a left-right wheel independent drive vehicle that is configured so that all four wheels can be driven independently in addition to being able to control the drive torque or regenerative braking torque of the front and rear wheels independently. The vehicle Ve shown here has left and right front wheels 1r, 1l and left and right rear wheels 2r, 2l, and is provided with drive devices (drive units) Pf, Pr as drive force sources corresponding to the front wheels 1r, 1l and the rear wheels 2r, 2l, respectively. Each of these drive devices Pf, Pr is mainly composed of a motor and a gear reduction mechanism (transmission mechanism).

[0021] An example of a drive unit Pr for the rear wheels 2r, 2l is shown in a skeleton diagram in Fig. 2. This drive unit Pr is composed of a pair of drive systems that independently control the left and right rear wheels 2r, 2l, and since these drive systems are symmetrical, they will be described together without being specifically designated as "right" or "left". In the following description, when the suffix of a reference symbol is one letter, "f" indicates the front wheel, "l" indicates the left wheel, and "r" indicates the right wheel or the rear wheel, and when it is two letters, the first letter "f" indicates the front wheel, "r" indicates the rear wheel, and the second letter "r" indicates the right wheel, and "l" indicates the left wheel.

[0022] The driving device Pr of the rear wheels 2r, 2l is equipped with a motor Mrr, Mrl for driving, with its central axis of rotation directed in the front-rear direction of the vehicle Ve, and a drive gear 3rr, 3rl is attached to the rotor shaft, and this drive gear 3rr, 3rl is meshed with a counter driven gear 4rr, 4rl. The counter driven gear 4rr, 4rl has a larger diameter than the drive gear 3rr, 3rl, and therefore these gear pairs constitute a reduction mechanism. The counter driven gear 4rr, 4rl is provided on the same axis as the counter driven gear 4rr, 4rl so as to rotate integrally, and this counter drive gear 5rr, 5rl is meshed with a driven gear 7rr, 7rl which is a bevel gear integral with a drive shaft 6rr, 6rl connected to the rear wheels 2r, 2l. By making the driven gear 7rr, 7rl larger in diameter than the counter drive gear 5rr, 5rl, these gear pairs can be used as a reduction mechanism.

[0023] These motors Mrr, Mrl, the reduction mechanism, and each bevel gear are accommodated in a liquid-tight state inside the casing 8. Electric oil pumps OPrr, OPrl are provided to supply oil for cooling and lubrication to the motors Mrr, Mrl inside the casing 8. The oil pump on the rear wheel 2r, 2l side may be a single oil pump that supplies oil 10r to the left and right motors Mrr, Mrl collectively. These oil pumps OPrr, OPrl are provided at appropriate locations outside the casing 8 on the vehicle Ve, and are configured to pump up oil 10r from an oil reservoir 9r and supply the oil 10r to the motors Mrr, Mrl through cooling oil passages 11rr, 11rl provided through the casing 8. Although not particularly shown, the oil 10r is configured to flow back from inside the casing 8 to the oil reservoir 9r. An oil cooler may be provided midway through the cooling oil passages 11rr, 11rl.

[0024] FIG. 3 shows a skeleton diagram of an example of the drive unit Pf on the front wheels 1r, 1l side. Since the drive unit Pf has a symmetrical configuration, it will be described together without specifying "right" or "left". The motors Mfr, Mfl for driving are mounted with their rotation central axis facing the width direction (lateral direction) of the vehicle Ve, and drive gears 12fr, 12fl are attached to the rotor shafts, and the drive gears 12fr, 12fl mesh with the idle gears 13r, 13l. Countershafts 14r, 14l are provided parallel to the rotation central axis of the idle gears 13r, 13l, and the idle gears 13r, 13l mesh with the counter driven gears 15fr, 15fl attached to the countershafts 14r, 14l. The counter driven gears 15fr, 15fl have a larger diameter than the drive gears 12fr, 12fl attached to the motors Mfr, Mrl, and the gear pairs form a reduction mechanism. Counter drive gears 16fr, 16fl are attached to the counter shafts 14r, 14l, and these counter drive gears 16fr, 16fl mesh with driven gears 18fr, 18fl that are integral with drive shafts 17fr, 17fl that are connected to the front wheels 1r, 1l. The driven gears 18fr, 18fl have a larger diameter than the counter drive gears 16fr, 16fl, so that these gear pairs form a reduction mechanism.

[0025] The motors Mfr, Mfl on the front wheels 1r, 1l are configured to be cooled by the oil 10f in the same manner as the motors Mrr, Mrl on the rear wheels 2r, 2l. That is, electric oil pumps OPfr, OPfl are provided corresponding to the motors Mfr, Mfl on the front wheels 1r, 1l, and these oil pumps OPfr, OPfl are configured to pump up the oil 10f from the oil reservoir 9f and supply the oil 10f to the motors Mfr, Mfl through the cooling oil passages 19fr, 19fl. Although not shown in particular, the oil that has cooled the motors Mfr, Mfl is configured to return to the oil reservoir 9r. An oil cooler may be provided in the middle of the cooling oil passages 19fr, 19fl. The oil pump on the front wheels 1r, 1l may be a single oil pump that supplies the oil 10f to the left and right motors Mfr, Mfl collectively, similar to the oil pump on the rear wheels 2r, 2l described above.

[0026] An oil pump OPm is provided to pump up oil for lubrication. This oil pump OPm is a mechanical pump, and in the example shown in Fig. 3, is connected to the countershaft 14l on the left front wheel 1l side. Therefore, this oil pump OPm is driven while the vehicle Ve is running, and is configured to pump up oil 10f from an oil reservoir 9f and supply the oil 10f to predetermined lubrication points such as gears and bearings.

[0027] An electric storage device (Bat) 20 is provided for transferring electric power between each of the motors Mfr, Mfl, Mrr, Mrl and the oil pumps OPfr, OPfl, OPrr, OPrl (see FIG. 1). The electric storage device 20 is mainly composed of a secondary battery such as a lithium ion battery or a solid-state battery. Each of the motors Mfr, Mfl, Mrr, Mrl is, for example, a permanent magnet synchronous motor, and these motors Mfr, Mfl, Mrr, Mrl are connected to the electric storage device 20 via power controllers PCf, PCr mainly composed of inverters. Therefore, the output torque and the braking torque during energy regeneration of each of the motors Mfr, Mfl, Mrr, Mrl are individually controlled independently of each other. Note that the power controllers PCf, PCr only need to be independent of each other in function, and may be configured as an integrated unit as a whole.

[0028] The vehicle Ve is equipped with various mechanisms for running, stopping, and turning, just like a normal vehicle. The main components are shown in FIG. 4. The wheels 1r, 1l, 2r, and 2l are provided with brake mechanisms Bfr, ​​Bfl, Brr, and Brl. These brake mechanisms Bfr, ​​Bfl, Brr, and Brl are configured to generate braking forces by operating a brake pedal 21, and are also configured to generate braking forces by being electrically controlled. A vehicle stability control (VSC) 22 is provided as a system for electrically controlling the braking forces. The VSC 22 may have a configuration similar to that known in the art, and is, for example, a system that integrates a traction control system (TCS) 23 that operates the brake mechanisms Bfr, ​​Bfl, Brr, and Brl to limit the driving force of each wheel, and an anti-lock brake system (ABS) 24 that reduces or releases the braking force of the brake mechanisms Bfr, ​​Bfl, Brr, and Brl to avoid locking of each wheel. Therefore, when control by the VSC 22 is executed, acceleration and deceleration occur in the vehicle Ve.

[0029] A vehicle Ve shown in FIG. 4 has front wheels 1r, 1l that are steerable, and is provided with a power steering mechanism (PS or EPS) including a steering wheel 25, a steering linkage 26, and an actuator 27 that assists steering force.

[0030] Furthermore, the vehicle Ve is provided with an accelerator pedal 28 for accelerating and decelerating, a shift device 29 for selecting a gear stage or a driving range, a mode selection switch 30 for selecting a driving mode, etc. These shift devices 29 and mode selection switches 30 may be configured to select a gear stage (gear ratio) using a lever provided on the floor or center console, or to select a shift range, or may be configured to switch gear stages one by one by operating an up or down operation in a manual position, or may be configured to switch shift ranges in sequence or switch gear stages (gear ratios) one by one by operating a button switch provided on an instrument panel, a steering wheel, a steering column, etc.

[0031] The driving modes are mainly control modes that control the drive torque based on a predetermined standard, and include a normal mode in which acceleration and energy efficiency (electricity consumption) are standard values, an economy mode in which electricity consumption is controlled with priority over acceleration, a manual sports mode that improves acceleration or power performance, a track mode that improves cornering performance, and a drift mode that further improves driving accuracy. These driving modes are selected by operating the shift device 29 or the mode selection switch 30. In addition, driving modes other than the normal mode and the economy mode are generally selected by the driver in order to obtain a larger driving force or braking force, so that a four-wheel drive state is set with the front and rear wheels 1r, 1l, 2r, and 2l as drive wheels. Even in the normal mode, if a sudden acceleration operation or a sudden deceleration operation is performed, the four-wheel drive state may be set.

[0032] Various operating conditions or driving requirements of the vehicle Ve, including the vehicle speed, are detected by sensors, such as a vehicle speed sensor, an accelerator opening sensor, an oil temperature sensor, a steering angle sensor, a shift position sensor, a brake sensor, a driving mode sensor, a motor rotation speed sensor, and a motor temperature sensor (not shown).

[0033] A controller 31 is provided that controls the drive torque, rotation speed or regenerative torque of each of the motors Mfr, Mfl, Mrr, Mrl, the rotation speed of each of the electric oil pumps OPfr, OPfl, OPrr, OPrl, or the discharge amount of each of the oil pumps OPfr, OPfl, OPrr, OPrl, based on the operating conditions and driving requirements detected by these sensors. The controller 31 is mainly configured with a microcomputer that includes a calculation element (CPU), memory elements (RAM, ROM), an interface, etc., and is configured to perform calculations according to a predetermined program using input data and pre-stored data, and to output the results of the calculations as control command signals to the power controllers PCf, PCr, etc.

[0034] In particular, the controller 31 is configured to control the distribution of the drive torque so as to maintain the drive performance or running stability of the vehicle Ve when the drive torque of either the left or right motor Mfr, Mfl in the drive unit Pf on the front wheels 1r, 1l side, or the drive torque of the motor Mrr, Mrl in the drive unit Pr on the rear wheels 2r, 2l side, is limited due to the influence of heat. Specifically, when the drive torque of the left motor Mfl (or Mrl) or the right motor Mfr (or Mrr) is limited due to an excessively high or low temperature, the drive torque of the other motor paired with the motor Mfl (or Mrl, or Mfr or Mrr) in the left-right direction (vehicle width direction) of the vehicle Ve is reduced. Therefore, for example, when the temperature becomes excessively high, instead of promoting cooling by increasing the amount of oil 10f, 10r, the drive torque is reduced to prevent or suppress an increase in temperature. The resulting reduction in the overall drive torque of the vehicle Ve is compensated for by increasing the drive torque of the other drive unit Pr (or Pl). Since such control may cause slight changes in the drive torque of the front, rear, left and right wheels, affecting the steering characteristics or turning characteristics, the control of the drive torque or torque distribution is appropriately executed or prohibited according to the turning state of the vehicle Ve. The controller 31 has a functional configuration (or functional means) exemplified in Fig. 5 in order to execute such control.

[0035] The controller 31 is provided with a temperature detection unit 31a that detects the temperature of the motors Mfr, Mfl, Mrr, and Mrl. The temperature can be detected based on data obtained by a temperature sensor (not shown) provided for each of the motors Mfr, Mfl, Mrr, and Mrl, or based on data obtained by an oil temperature sensor. The controller 31 is provided with a temperature determination unit 31b that determines whether the detected temperature is within a predetermined temperature range. The temperature range in which the motors Mfr, Mfl, Mrr, and Mrl output driving torque as designed is determined as a specification (spec), and if the motors Mfr, Mfl, Mrr, and Mrl are operated at a temperature exceeding the upper limit temperature, the motors may not be able to output the desired driving torque, may be damaged by seizure, or may have a reduced durability. If the motors are operated at a temperature below the lower limit temperature, abnormalities or damage may occur in related parts such as bearings, or durability may be reduced. Therefore, temperature ranges are determined in advance for the motors Mfr, Mfl, Mrr, and Mrl so that they operate normally or as expected. The temperature range does not have to be exactly the same as the specifications of the motors Mfr, Mfl, Mrr, and Mrl, and may be the upper and lower limit temperatures defined in the specifications or a temperature range defined by adding a certain margin to the upper and lower limit temperatures. Furthermore, depending on the environment in which the vehicle Ve is expected to be used, the temperature range may be one that defines only the upper limit temperature.

[0036] When the temperature of one of the left and right motors Mfr, Mrr (or Mfl, Mrl) is outside a predetermined temperature range, the controller 31 is provided with a driving force limiting unit 31c that reduces the driving torque of the other motor that is paired with the motor that is outside the temperature range in the left-right direction (vehicle width direction) of the vehicle Ve and whose temperature is within the above-mentioned temperature range. This control is for making the balance of the left and right driving torques or the torque distribution ratio suitable for the driving state at that time, and when the driving torque of one of the left and right motors is limited, the driving torque of the other motor is reduced to match the limited driving torque. Therefore, the torque of the other motor to be reduced may be a torque that matches the torque of the one motor that is limited, and when the torque of one motor is reduced to avoid thermal effects, the driving torque of the other motor may be reduced to match the reduced driving torque. In this case, the torque of the left and right motors that are paired with each other is not made zero but is maintained at a predetermined torque even if the driving torque of one motor is restricted by thermal effects. This is to maintain four-wheel drive.

[0037] The controller 31 includes a drive torque increase unit 31d. As described above, when the temperature is out of a predetermined temperature range and the drive torque is limited, the drive torque in the front or rear drive unit Pf, Pr including the motor that is out of the temperature range decreases, so the drive torque of the other drive unit Pr, Pf is increased to compensate for the decrease in drive torque, thereby maintaining the overall drive torque of the vehicle Ve in order to maintain the drive performance or running stability of the vehicle Ve. The drive torque increase unit 31d executes the increase control of the drive torque for this purpose.

[0038] If the drive torque of any of the motors is increased, the temperature of that motor will inevitably rise. Therefore, it is preferable that the temperature of the drive devices Pr and Pf that execute the drive torque increase control by the drive torque increase unit 31d is within a predetermined steady range. Here, the steady range is a temperature range in which the motor can be operated without any problems, and may be the same as the above-mentioned predetermined temperature range, or may be a range set separately from the predetermined temperature range. The temperature of the drive devices Pr and Pf (particularly the motor) can be detected by the above-mentioned temperature detection unit 31a, and the controller 31 is provided with a steady state determination unit 31e that determines whether the temperature is within the steady state range. In addition, the controller 31 is provided with a drive torque increase prohibition unit 31f that prohibits the above-mentioned drive torque increase control when the temperature of the drive devices Pr and Pf is not within the steady state range.

[0039] In the above control in which the drive torque is changed due to the temperature of any one of the motors being abnormal, the drive torque of either the front wheels 1r, 1l side or the rear wheels 2r, 2l side, which are abnormal in terms of temperature, is reduced, and the drive torque of the other side is increased. Therefore, such control of the drive torque is executed in a four-wheel drive state in which the front and rear four wheels are driven. Therefore, the controller 31 includes a four-wheel drive determination unit 31g for determining the prerequisites for executing the control. Since the running state in which the four-wheel drive state is maintained can be determined based on the running mode, the four-wheel drive state can be determined not only based on the output state of the control signals to the motors Mfr, Mfl, Mrr, Mrl, but also based on the selected running mode.

[0040] Since the turning performance and steering characteristics change depending on the magnitude of the drive torque of the left and right wheels, there is a possibility that the turning performance or the driving stability may be affected when the drive torque of the left and right wheels is controlled. Therefore, the controller 31 is provided with a turning detection unit 31h that detects that the vehicle Ve is turning. In addition, it is preferable to avoid or suppress changes in the turning performance or the driving state caused by changes in the drive torque of the left and right wheels, and therefore the controller 31 is provided with a drive limiting prohibiting unit 31i that prohibits the drive force limiting unit 31c from controlling the other motor to reduce the drive torque when turning is detected.

[0041] Various data are input to the controller 31 as data for carrying out the above-mentioned control, and examples of the input signals are as follows: motor temperatures obtained by temperature sensors or oil temperature sensors of the motors Mfr, Mfl, Mrr, and Mrl, a driving mode for determining a four-wheel drive state, a steering angle for determining cornering, and the number of rotations of each wheel obtained by a wheel speed sensor or the like are input to the controller 31. Examples of data previously stored in the controller 31 include a temperature range for determining whether a detected temperature is excessively high or excessively low, a drive torque reduction width or a left / right drive torque distribution ratio for reducing the drive torque of a paired motor when the temperature of any one of the motors is outside a predetermined temperature range, a drive torque increase amount or a front / rear drive torque distribution ratio for increasing the drive torque of a drive unit including a motor that is not outside the above-mentioned temperature range, and a steady range for the temperature of the drive unit for increasing the drive torque.

[0042] An example of the control executed by the controller 31 is shown in a flow chart in FIG. 6. The routine shown in FIG. 6 is repeatedly executed by the controller 31 at predetermined short intervals when the vehicle Ve is traveling. First, it is determined whether the vehicle Ve is in a four-wheel drive state (4WD) in which all four wheels are driven and traveling straight (step S1). If the result of the determination in step S1 is "NO" because the vehicle is neither in four-wheel drive nor traveling straight, the process returns without performing any particular control. That is, the routine shown in FIG. 6 is temporarily terminated. The function of making the determination in step S1 is the function of the four-wheel drive determination unit 31g and the turning detection unit 31h described above. Also, if the result of the determination in step S1 is "NO" because the vehicle Ve is turning, the step of controlling the driving torque described below is bypassed and the driving torque is not controlled, so the function of avoiding such control of the driving torque corresponds to the function of the driving limiting and prohibiting unit 31i described above.

[0043] On the contrary, when the vehicle Ve is in four-wheel drive and traveling straight ahead, so that the result of the judgment in step S1 is "Yes", it is judged whether or not there are any motors Mfr, Mfl, Mrr, Mrl whose temperature exceeds the predetermined temperature range. In the example shown in FIG. 6, it is judged whether or not there are any motors whose motor temperature is outside the predetermined temperature range on the high side, that is, so-called high-temperature motors (high-temperature motors) whose motor temperature is equal to or higher than the upper limit of the temperature range (step S2). When the result of the judgment in step S2 is "No" because no excessively high-temperature motor is detected, it is judged whether or not there are any motors whose motor temperature is outside the predetermined temperature range on the low side, that is, so-called low-temperature motors (low-temperature motors) whose motor temperature is equal to or lower than the lower limit of the temperature range (step S3). The function of making the judgment in step S2 and the function of making the judgment in step S3 correspond to the functions of the temperature detection unit 31a and the temperature judgment unit 31b described above. If the determination results are "NO" in both steps S2 and S3, this means that the motors Mfr, Mfl, Mrr, and Mrl for all four wheels can be operated normally, so the process returns without carrying out any particular control.

[0044] On the other hand, if the result of the judgment in either step S2 or step S3 is "Yes", output control is executed for the motors Mfr, Mfl, Mrr, and Mrl. First, if the judgment result in step S2 is "Yes" because a motor whose temperature is outside the predetermined temperature range on the high side is detected, it is judged whether the other motor is steady or not (step S4). Here, "the other motor" refers to the motors Mrr, Mrl on the rear wheels 2r, 2l when the excessively high temperature, so-called temperature abnormal motor, is the motor Mfr, Mfl on the front wheels 1r, 1l, and to the motors Mfr, Mfl on the front wheels 1r, 1l when the excessively high temperature, so-called temperature abnormal motor, is the motor Mrr, Mrl on the rear wheels 2r, 2l. Also, "steady" means that no abnormality, including temperature, is detected. Therefore, the function of making the judgment in step S4 corresponds to the function of the steady state judgment unit 31e described above.

[0045] If the result of the determination in step S4 is "Yes", it is possible to increase the torque of the other motor. Therefore, the torque of the pair of left and right motors including the motor with an abnormality in terms of temperature is reduced, and the torque of the other pair of left and right motors that have been determined to be in a steady state is increased (step S5), and then the process returns. The control of this step S5 is shown in Figure 6 as "torque reduction of abnormal motor pair and torque increase of steady motor pair".

[0046] Specifically, when the temperature of one of the motors Mfr (or Mfl) on the front wheels 1r, 1l is high, the torque of the other motor Mfl (or Mfr) paired with that motor Mfr (or Mfl) in the left-right direction is reduced. This torque control may be a control that matches the torque of the other motor Mfl (or Mfr) to the torque of the one motor Mfr (or Mfl) whose output is limited in terms of temperature, or may be a control that reduces the torque of both the left and right motors Mfr, Mfl so as to balance each other. Similarly, when the temperature of one of the motors Mrr (or Mrl) on the rear wheels 2r, 2l is high, the torque of the other motor Mrl (or Mrl) paired with that motor Mrr (or Mrl) in the left-right direction is reduced. This torque control may be a control that adjusts the torque of the other motor Mrl (or Mrr) to the torque of one motor Mrr (or Mrl) whose output is limited in terms of temperature, or a control that reduces the torques of both the left and right motors Mrr, Mrl so as to balance each other. Furthermore, the control of "increasing the torque of the stationary motor pair" is a control that increases the torque of the other pair of motors Mrr, Mrl (or Mfr, Mfl) either front or rear when the torque of one pair of motors Mfr, Mfl (or Mrr, Mrl) is reduced. The amount of increase may be an amount equivalent to the amount of reduction in the torque of one pair of motors Mfr, Mfl (or Mrr, Mrl) either front or rear. This is to maintain the overall drive torque of the vehicle Ve.

[0047] In this way, in step S5, the torque of the other motor paired in the left-right direction with the motor having a so-called abnormality in terms of temperature is reduced, and the drive torque of the other pair of motors separated in the front-rear direction of the vehicle Ve from the pair of motors whose drive torque has been reduced is increased, so the control or function performed in step S5 corresponds to the function of the drive force limiting unit 31c and the function of the drive torque increasing unit 31d described above. Also, if the determination result in step S4 is "NO", the control of step S5 is avoided, and this function of avoiding the control of step S5 corresponds to the function of the drive torque increase prohibiting unit 31f described above.

[0048] On the other hand, if the result of the judgment in step S4 is "NO", the drive torque of the motor is reduced (step S6), and then the process returns. Here, the motor whose drive torque is reduced is the motor whose temperature exceeds a predetermined upper limit temperature, and therefore the drive torque of the other motor paired with that motor in the left and right direction is also reduced in order to balance the drive torques on the left and right.

[0049] By executing the control of the reduction and increase of the drive torque in step S5, the heat generation of the motor with an excessively high temperature can be suppressed and the temperature can be lowered. In this case, there is no particular need to increase the amount of oil 10f, 10r supplied by the oil pumps OPfr, OPfl, OPrr, OPrl described above. Therefore, it is possible to avoid the need to enlarge the mechanism for cooling the motors Mfr, Mfl, Mrr, Mrl, and to avoid or suppress damage to or deterioration of the durability of the motors Mfr, Mfl, Mrr, Mrl. Furthermore, even if the drive torque is reduced at either the front or rear of the vehicle Ve, the torque reduction is compensated for by the drive torque at the other of the front or rear, so that the running performance or power performance of the vehicle Ve can be maintained in a good state.

[0050] The above-mentioned control of the reduction or restriction and increase of the drive torque is executed in the same manner even if a motor with a temperature below the predetermined temperature range is detected (exists). That is, if the temperature of any one of the motors is below the lower limit temperature that determines the predetermined temperature range and the result of the judgment in step S3 is "Yes", it is judged whether the other motor is steady or not (step S7). The control in this step S7 is the same as the control in step S4 described above, and therefore, the "other motor" refers to the motors Mrr, Mrl on the rear wheels 2r, 2l when the motors Mfr, Mfl on the front wheels 1r, 1l are excessively cold, so-called temperature abnormal motors, and refers to the motors Mfr, Mfl on the front wheels 1r, 1l when the motors Mrr, Mrl on the rear wheels 2r, 2l are excessively cold, so-called temperature abnormal motors. In addition, "steady" means that no abnormality, including temperature, is detected. Therefore, the function of making the judgment in this step S7 corresponds to the function of the steady state judgment unit 31e described above.

[0051] If the result of the judgment in step S7 is "Yes", it is possible to increase the torque of the other motor. Therefore, the torque of the pair of left and right motors including the motor with an abnormality in terms of temperature is reduced, and the torque of the other pair of left and right motors that have been judged to be in a steady state is increased (step S8), and then the process returns. The control in step S8 is the same as the control in step S5 described above, which is shown in FIG. 6 as "torque reduction of abnormal motor pair / torque increase of steady motor pair". The specific control content in step S8 is also the same as the control in step S5 described above. The reason why the above-mentioned drive torque control is performed even when the temperature is low is that the motor and its related parts such as bearings and lubricating oil may not operate normally, and there is a concern that some damage may occur if a large drive torque is output in that state. In other words, such damage and deterioration of durability can be avoided or suppressed.

[0052] The present invention is not limited to the above-described embodiment, and the left and right wheels on which the drive motors are provided separately may be either the front wheels or the rear wheels, and the present invention can also be applied to a vehicle configured to drive the other two wheels with a single drive power source. Also, the present invention may be configured to set the predetermined temperature range as a range defined only by an upper limit temperature, and to perform the above-described control of reducing and increasing the drive torque when the temperature of any of the motors exceeds the upper limit temperature. [Explanation of symbols]

[0053] 1r,1l front wheel 2r,2l rear wheel 3rr, 3rl drive gear 4rr, 4rl counter driven gear 5rr, 5rl counter drive gear 6rr,6rl drive shaft 7rr,7rl Driven gear 8 Casing 9r,9f Oil reservoir 10f,10r Oil 11rr,11rl,19fr,19fl Cooling oil path 12fr,12fl drive gear 13r,13l idle gear 14l,14r countershaft 15fr,15fl Counter driven gear 16fr,16fl counter drive gear 17fr,17fl drive shaft 18fr,18fl Driven gear 20. Energy storage device 21 Brake pedal 22 Vehicle Stability Control (VSC) 23 Traction Control System (TCS) 24 Anti-lock Braking System (ABS) 25 Steering Wheel 26 Steering linkage 27 Actuator 28 Accelerator pedal 29 Shifting device 30 Mode selection switch 31 Controller 31a Temperature detection section 31b Temperature judgment section 31c Driving force limiting section 31d Drive torque increase section 31e Steady-state determination unit 31f Driving torque increase prohibition section 31g Four-wheel drive determination unit 31h Rotation detector 31i Drive restriction prohibition section Bfr, Bfl, Brr, Brl Brake mechanism Mfr, Mfl, Mrr, Mrl Motor (electric motor) OPfr, OPfl, OPrr, OPrl Oil pump PCf, PCr Power Controller Pf,Pr drive unit Vehicle

Claims

1. A left and right wheel independent drive vehicle comprising a first drive unit that drives left and right front wheels and a second drive unit that drives left and right rear wheels, at least one of the first drive unit and the second drive unit comprising a left electric motor that drives a left wheel and a right electric motor that drives a right wheel that is paired with the left wheel, a controller that controls the first drive device and the second drive device; The controller: a temperature detection unit that detects a temperature of the left motor and a temperature of the right motor; a temperature determination unit that determines whether one of the temperatures detected by the temperature detection unit is outside a predetermined temperature range; a driving force limiting unit that, when it is determined by the temperature determining unit that the temperature of one of the left motor and the right motor is outside the temperature range, reduces a driving torque of the other motor, the temperature of which is not outside the temperature range; a drive torque increasing unit that increases a drive torque by the other of the first and second drive units that does not include the one of the electric motors that is outside the temperature range when the drive torque of the other electric motor is reduced by the drive force limiting unit; Equipped with A vehicle with independent left and right wheel drive.

2. 2. The left and right wheel independent drive vehicle according to claim 1, the other of the first drive device and the second drive device includes a traveling electric motor as a drive power source, The temperature detection unit further has a function of detecting a temperature of the driving motor, The controller: a steady-state determination unit that determines whether the temperature of the driving motor is within a predetermined steady-state range; a drive torque increase prohibition unit that prohibits the drive torque increase unit from increasing the drive torque when the temperature of the electric motor for traveling is not within the steady range; It also has A vehicle with independent left and right wheel drive.

3. 3. The left and right wheel independent drive vehicle according to claim 1 or 2, The controller further includes a four-wheel drive determination unit that determines whether the vehicle is in four-wheel drive mode in which the first drive device and the second drive device are outputting drive torque to each other, the drive force limiting unit is configured to reduce a drive torque of the other electric motor when the four-wheel drive traveling is determined, and The drive torque increasing unit is configured to increase the drive torque by the other drive device when the four-wheel drive running is determined. A vehicle with independent left and right wheel drive.

4. 3. The left and right wheel independent drive vehicle according to claim 1 or 2, The controller: A turning detection unit that detects whether the vehicle is turning; a drive limiting prohibiting unit that prohibits the drive force limiting unit from reducing the drive torque of the other electric motor when a turning motion of the vehicle is detected; It also has A vehicle with independent left and right wheel drive.

5. 3. The left and right wheel independent drive vehicle according to claim 1 or 2, 2. A vehicle having independent drive for left and right wheels, wherein the temperature range is either a range in which only an upper limit temperature is defined, or a range determined by an upper limit temperature and a lower limit temperature.

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