Vehicle with independently driven left and right wheels

Abstract

The invention relates to a left and right wheel independent drive type vehicle provided with a controller. The controller is provided with: a temperature detection unit that detects the temperature of the left motor and the temperature of the right motor; a temperature determination unit that determines whether one of the detected temperatures deviates from a predetermined temperature range; a driving force limiting unit that, when it is determined that the temperature of one of the left motor and the right motor deviates from the temperature range, reduces the driving torque of the other motor that does not deviate from the temperature range; and a drive torque increasing unit that, when the drive torque of the other motor is reduced, increases the drive torque of the other one of the first drive device and the second drive device, which does not include the one motor deviating from the temperature range.

Description

Technical Field

[0001] The present invention relates to a vehicle configured to independently drive left and right wheels, and particularly to a vehicle provided with electric motors for each of the left and right wheels. Background Art

[0002] In order to improve the driving performance, running stability, etc. of a vehicle, it is preferable to separately control the driving force (driving torque) generated at each wheel. For example, a vehicle described in Japanese Patent Application Laid-Open No. 2001-112114 is configured such that an engine and a first electric motor are provided as driving force sources for the front wheels, and the driving torque output from the driving force sources is transmitted to the left and right front wheels in a state allowing differential via a differential mechanism (differential gear). On the other hand, a second electric motor is provided as a driving force source for the rear wheels, and the driving torque output from the second electric motor is transmitted to the left and right rear wheels via a differential gear. In the vehicle described in Japanese Patent Application Laid-Open No. 2001-112114, for example, by making the thermal rating of the first electric motor higher than the thermal rating of the second electric motor, running stability is maintained even when the operation of any one of the electric motors is restricted.

[0003] An electric motor used as a driving force source for a vehicle inevitably generates heat during operation. If its temperature reaches the upper limit, the torque that can be output is restricted, and in addition, durability is reduced, etc., and normal operation is restricted. In the vehicle described in Japanese Patent Application Laid-Open No. 2001-112114, the thermal ratings of the front and rear electric motors used as driving force sources are set in a specific relationship, so even if the operation of either the front or rear electric motor is restricted, the operation of the other electric motor can be ensured and running stability can be maintained.

[0004] However, a vehicle performs various maneuvers such as acceleration, deceleration, turning, uphill and downhill driving, and the load applied to each wheel or the driving torque required for each wheel is different each time. Therefore, if running stability or power performance is to be maintained in any of such various driving states, it is desirable to drive all wheels (e.g., the front and rear four wheels) or at least a pair of left and right wheels using separately provided individual electric motors. In the vehicle described in Japanese Patent Application Laid-Open No. 2001-112114, even if the balance of power distribution between the front and rear wheels can be maintained, it is difficult to independently control the driving torques of the left and right wheels separately. In addition, in the vehicle described in Japanese Patent Application Laid-Open No. 2001-112114, if the differential limit of each of the front and rear differentials is appropriately configured, the driving torques of the left and right wheels can be controlled to some extent. However, for this purpose, a new differential limit mechanism and its control device must be provided, which causes other problems such as an increase in the size and weight of the vehicle. In addition, in order to avoid restrictions on operation caused by the heat of the electric motor, a cooling device with sufficient capacity or size can be provided, but in this case, other problems such as an increase in the size and weight of the vehicle also occur.

[0005] On the other hand, conventionally, there has been known a vehicle configured to be provided with motors corresponding to all wheels, such as a in-wheel motor vehicle, and to drive all wheels individually by these motors. In such a vehicle, there are sometimes restrictions on operation caused by the heat of the motors. However, if the cooling device is made large-capacity in order to reduce the restrictions on operation caused by heat, problems such as the enlargement of the device will occur. In addition, in a vehicle configured to drive all wheels individually, it is also considered that the driving force balance between the left and right wheels may be impaired due to the heat characteristics of the motors and the like. However, such problems have not been particularly focused on in the past, and in addition, no preferable countermeasures or devices in such a case have been proposed. Summary of the Invention

[0006] The present invention has been completed in view of the above circumstances, and an object thereof is to provide a vehicle that can maintain necessary and sufficient driving performance without causing enlargement of the cooling device or the like even when there is a restriction on driving in either of the left and right wheels.

[0007] To achieve the above object, the present invention is a vehicle with independent left and right wheel drive, the vehicle with independent left and right wheel drive comprising: a first drive device that drives the left and right front wheels; and a second drive device that drives the left and right rear wheels, at least one of the first drive device and the second drive device comprising: a left motor that drives a left wheel; and a right motor that drives a right wheel paired with the left wheel, the vehicle with independent left and right wheel drive being characterized by comprising a controller that controls the first drive device and the second drive device, the controller comprising: a temperature detection unit that detects the temperature of the left motor and the temperature of the right motor; a temperature determination unit that determines a case where the temperature of either of the temperatures detected by the temperature detection unit deviates from a predetermined temperature range; a driving force limitation unit that reduces the driving torque of the other motor whose temperature has not deviated from the temperature range when it is determined by the temperature determination unit that the temperature of either the left motor or the right motor has deviated from the temperature range; and a driving torque increase unit that increases the driving torque of the other drive device of the first drive device and the second drive device that does not include the motor whose temperature has deviated from the temperature range when the driving torque of the other motor is reduced by the driving force limitation unit.

[0008] In the present invention, alternatively, the other driving device of the first driving device and the second driving device includes a traveling electric motor as a driving force source, the temperature detection unit further has a function of detecting the temperature of the traveling electric motor, and the controller further includes: a stability determination unit that determines a case where the temperature of the traveling electric motor enters a predetermined stable range; and a drive torque increase prohibition unit that prohibits an increase in the drive torque by the drive torque increase unit when the temperature of the traveling electric motor does not enter the stable range.

[0009] In the present invention, alternatively, the controller further includes a four-wheel drive determination unit that determines four-wheel drive traveling in which the first driving device and the second driving device output drive torque to travel, and the driving force limitation unit is configured to reduce the drive torque of the other motor when it is determined that the four-wheel drive traveling is in progress, and the drive torque increase unit is configured to increase the drive torque of the other driving device when it is determined that the four-wheel drive traveling is in progress.

[0010] In the present invention, alternatively, the controller further includes: a turning detection unit that detects a case where the vehicle turns and travels; and a drive limitation prohibition unit that prohibits a reduction in the drive torque of the other motor by the driving force limitation unit when the turning and traveling of the vehicle is detected.

[0011] In the present invention, alternatively, the temperature range is either a range that only determines the upper limit temperature or a range determined by the upper limit temperature and the lower limit temperature.

[0012] According to the present invention, in the first driving device that drives the front wheels or the second driving device that drives the rear wheels, when the temperature of either the left or right motor is too high or too low, the drive torque of the other motor is reduced. Therefore, the drive torque of the other motor is reduced in accordance with the motor whose drive torque is restricted by the temperature condition, so that it is possible to avoid or suppress the disruption of the torque balance between the left and right wheels. At the same time, the drive torque of the other driving device is increased, so that the drive torque reduced due to the temperature condition is compensated by the increase in the drive torque of the other driving device. Therefore, it is possible to maintain the drive torque of the vehicle as a whole and avoid or suppress the deterioration of the power performance and driving stability. In addition, when the temperature of any motor becomes high, the motor is not actively cooled further in order to maintain the drive torque of the vehicle as a whole. Therefore, it is not necessary to increase the size or capacity of the cooling device, etc., and it is possible to avoid the increase in size and weight of the driving device or the vehicle.

[0013] Further, in the present invention, when the temperature of the other driving device does not enter the stable range, the driving torque of the other driving device is not increased, so that damage to the other driving device, reduction in durability, etc. can be prevented or suppressed.

[0014] In the present invention, control for reducing the driving torque of the other motor and increasing the driving torque of the other driving device is performed only in the four-wheel drive state. Therefore, compared with the two-wheel drive state, the change in the driving torque borne by the wheels is small, so that discomfort caused by impact or the like or a change in riding comfort can be avoided or suppressed.

[0015] Moreover, in the present invention, when the vehicle is turning, control for reducing the driving torque of the other motor and increasing the driving torque of the other driving device is prohibited, so that it is possible to avoid or suppress the turning driving from becoming unstable or the control from becoming complicated. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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 components, and in the drawings:

[0017] Figure 1 is a block diagram schematically showing a drive system of a four-wheel independent drive vehicle as an example of a vehicle in an embodiment of the present invention.

[0018] Figure 2 is a schematic diagram showing an example of a drive unit on the rear wheel side of the drive system.

[0019] Figure 3 is a schematic diagram showing an example of a drive unit on the front wheel side of the drive system.

[0020] Figure 4 is a schematic diagram for explaining various mechanisms for driving, stopping, and turning of a vehicle.

[0021] Figure 5 is a block diagram illustrating a functional configuration of a controller and input signals.

[0022] Figure 6 is a flowchart showing an example of control executed in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] Next, embodiments of the present invention will be described with reference to the drawings. In addition, the embodiments described below are merely examples of the cases where the present invention is implemented, and do not limit the present invention.

[0024] In the present invention, the vehicle as the object is a four-wheel vehicle with two front wheels and two rear wheels. The vehicle is configured such that drive devices are provided respectively for the two front wheels and the two rear wheels, and the two front wheels and the two rear wheels can be driven independently of each other. Moreover, the vehicle is configured such that electric motors (electric motors or motor generators, hereinafter referred to as electric motors) as power sources are provided corresponding to the left front wheel and the right front wheel, or the left rear wheel and the right rear wheel, which are in a paired relationship with each other, and the left and right wheels can be driven independently. In addition, the wheels with electric motors provided individually can be only the front wheels, or only the rear wheels. In this case, it can also be configured such that the left and right wheels without electric motors provided individually are connected to a single electric motor via a differential gear.

[0025] In Figure 1 FIG. 5 schematically shows an example of a left and right wheel independent drive type vehicle configured to be able to independently drive all four wheels in addition to being able to independently control the drive torque or regenerative braking torque of the front and rear wheels. The vehicle Ve shown here includes left and right front wheels 1r, 1l and left and right rear wheels 2r, 2l, and drive devices (drive units) Pf, Pr as driving force sources are provided corresponding to the front wheels 1r, 1l and the rear wheels 2r, 2l respectively. These drive devices Pf, Pr are each mainly composed of an electric motor and a gear reduction mechanism (transmission mechanism).

[0026] In Figure 2 FIG. 6 schematically shows an example of the drive device Pr on the rear wheel 2r, 2l side. The drive device Pr is composed of a pair of drive systems that independently control the left and right rear wheels 2r, 2l. Since these drive systems have a left-right symmetric structure, they are described together without specifically indicating "right" or "left". In addition, in the following description, when the suffix in the reference numeral is one character, "f" indicates for the front wheel, "l" indicates for the left wheel, "r" indicates for the right wheel or the rear wheel, and when it is two characters, the first character "f" indicates for the front wheel, "r" indicates for the rear wheel, the second character "r" indicates for the right wheel, and "l" indicates for the left wheel.

[0027] In the drive devices Pr for the rear wheels 2r and 2l, traveling motors Mrr and Mrl are mounted such that their rotational center axes face the front-rear direction of the vehicle Ve. Drive gears 3rr and 3rl are mounted on their rotor shafts, and these drive gears 3rr and 3rl mesh with reverse driven gears 4rr and 4rl. The reverse driven gears 4rr and 4rl have a larger diameter than these drive gears 3rr and 3rl, so these gear pairs constitute a speed reduction mechanism. Bevel gears 5rr and 5rl as reverse drive gears are provided on the same axis as the reverse driven gears 4rr and 4rl to rotate integrally, and these reverse drive gears 5rr and 5rl mesh with driven gears 7rr and 7rl, which are bevel gears integral with the drive shafts 6rr and 6rl connected to the rear wheels 2r and 2l. By making the driven gears 7rr and 7rl have a larger diameter than the reverse drive gears 5rr and 5rl, these gear pairs can be used as a speed reduction mechanism.

[0028] These motors Mrr and Mrl, the speed reduction mechanism, and each bevel gear are housed inside the housing 8 in a liquid-tight state. Electric oil pumps OPrr and OPrl are provided for supplying oil for cooling and lubrication to the motors Mrr and Mrl inside the housing 8. In addition, the oil pumps on the rear wheel 2r and 2l sides can also be a single oil pump that supplies oil 10r to the left and right motors Mrr and Mrl together. These oil pumps OPrr and OPrl are provided at appropriate positions on the vehicle Ve outside the housing 8, and are configured to draw oil 10r from the oil storage section 9r and supply the oil 10r to the motors Mrr and Mrl via cooling oil passages 11rr and 11rl provided through the housing 8. In addition, although not particularly shown, it is configured that the oil 10r flows back from the inside of the housing 8 to the oil storage section 9r. Additionally, an oil cooler can also be provided in the middle of the cooling oil passages 11rr and 11rl.

[0029] In Figure 3An example of the drive device Pf on the front wheel 1r, 1l side is schematically shown. Since this drive device Pf has a bilaterally symmetric structure, it will be described in a unified manner without specifically indicating "right" or "left". The traveling motors Mfr and Mfl are mounted such that their rotation center axes face the width direction (lateral direction) of the vehicle Ve, and drive gears 12fr and 12fl are mounted on their rotor shafts. These drive gears 12fr and 12fl mesh with the idle gears 13r and 13l. Countershafts 14r and 14l are provided parallel to the rotation center axes of the idle gears 13r and 13l, and the idle gears 13r and 13l mesh with reverse driven gears 15fr and 15fl mounted on the countershafts 14r and 14l. By making the reverse driven gears 15fr and 15fl have a larger diameter than the drive gears 12fr and 12fl mounted on the motors Mfr and Mrl, a reduction mechanism is constituted by these gear pairs. Reverse drive gears 16fr and 16fl are mounted on the countershafts 14r and 14l, and these reverse drive gears 16fr and 16fl mesh with driven gears 18fr and 18fl which are gears integral with the drive shafts 17fr and 17fl connected to the front wheels 1r and 1l. By making the driven gears 18fr and 18fl have a larger diameter than the reverse drive gears 16fr and 16fl, a reduction mechanism is constituted by these gear pairs.

[0030] The motors Mfr and Mfl on the front wheel 1r, 1l side are configured to be cooled by oil 10f in the same manner as the motors Mrr and Mrl on the rear wheel 2r, 2l side. That is, electric oil pumps OPfr and OPfl are provided corresponding to the motors Mfr and Mfl on the front wheel 1r, 1l side. These oil pumps OPfr and OPfl are configured to draw the oil 10f from the oil storage part 9f and supply the oil 10f to the motors Mfr and Mfl via the cooling oil passages 19fr and 19fl. In addition, although not specifically shown, the oil after cooling the motors Mfr and Mfl is configured to flow back to the oil storage part 9r. Also, an oil cooler may be provided in the middle of the cooling oil passages 19fr and 19fl. Further, the oil pumps on the front wheel 1r, 1l side may be the same as the oil pumps on the aforementioned rear wheel 2r, 2l side and be one oil pump that supplies the oil 10f to the left and right motors Mfr and Mfl together.

[0031] An oil pump OPm for drawing oil for lubrication is provided. This oil pump OPm is a mechanical pump and, in the example shown, Figure 3 is connected to the countershaft 14l on the left front wheel 1l side. Therefore, this oil pump OPm is configured to be driven when the vehicle Ve is traveling, draw the oil 10f from the oil storage part 9f, and supply the oil 10f to predetermined lubrication parts such as gears and bearings.

[0032] A power storage device (Bat) 20 is provided for power transfer between the above-described motors Mfr, Mfl, Mrr, Mrl, oil pumps OPfr, OPfl, OPrr, and OPrl (refer to Figure 1 ). The power storage device 20 is mainly composed of a secondary battery such as a lithium-ion battery or a all-solid-state battery. Each of the motors Mfr, Mfl, Mrr, and Mrl is, for example, a permanent magnet synchronous motor, and these motors Mfr, Mfl, Mrr, and Mrl are connected to the power storage device 20 via power controllers PCf and PCr mainly composed of inverters. Therefore, each of the motors Mfr, Mfl, Mrr, and Mrl independently controls its output torque and braking torque during energy regeneration. In addition, the functions of the power controllers PCf and PCr only need to be independent of each other, and they can also be integrally formed as a single unit.

[0033] The vehicle Ve is equipped with various mechanisms for traveling, stopping, and turning in the same manner as a normal vehicle. In Figure 4 its main structure is schematically described. Braking mechanisms Bfr, Bfl, Brr, and Brl are provided for each of the wheels 1r, 1l, 2r, and 2l. These braking mechanisms Bfr, Bfl, Brr, and Brl are configured to generate braking force not only by operating the brake pedal 21 but also by being electronically controlled. As a system for electronically controlling this braking force, a vehicle stability control system (VSC) 22 is provided. The VSC 22 can have the same structure as a conventionally known structure. For example, it is a system that combines a traction control system (TCS) 23 that operates the braking mechanisms Bfr, Bfl, Brr, and Brl in a manner that limits the driving force of each wheel and an anti-lock braking system (ABS) 24 that reduces or releases the braking force of the braking mechanisms Bfr, Bfl, Brr, and Brl in a manner that avoids locking of each wheel. Therefore, when the control based on the VSC 22 is executed, acceleration or deceleration is generated in the vehicle Ve.

[0034] In Figure 4 the vehicle Ve shown, the front wheels 1r and 1l are steering wheels, and a power steering mechanism (PS or EPS) composed of a steering wheel 25, a steering linkage 26, an actuator 27 for assisting the steering operation force, etc. is provided.

[0035] Moreover, in the vehicle Ve, there are provided an accelerator pedal 28 for performing acceleration and deceleration operations, a shift device 29 for selecting a gear shift or a driving gear, a mode selection switch 30 for selecting a driving mode, etc. These shift devices 29 and mode selection switches 30 can be structures that select a gear shift (gear ratio) through a lever provided on the floor, a center console, etc., structures that select a shift gear, or structures that sequentially switch the gear shift by performing an upshift operation or a downshift operation in a manual position, or can also be structures that sequentially switch the shift gear or sequentially switch the gear shift (gear ratio) by operating a push button switch provided on the instrument panel, a steering wheel, a steering column, etc.

[0036] In addition, the driving mode is mainly a control method for controlling the drive torque based on a predetermined reference, and is a normal mode in which acceleration performance and energy efficiency (electric power economy) are standard values, an economic mode that preferentially controls electric power economy compared to acceleration performance, a manual sport mode with improved acceleration performance or power performance, a tracking mode with improved cornering performance, a drift mode that further improves driving accuracy, etc. These driving modes are selected by operating the above-mentioned shift device 29 and mode selection switch 30. In addition, driving modes other than the normal mode and the economic mode are generally selected by the driver when a greater driving force or braking force is required, so a four-wheel drive state in which the front and rear wheels 1r, 1l, 2r, and 2l are driving wheels is set. In addition, even in the normal mode, a four-wheel drive state is sometimes set when an emergency acceleration operation or an emergency deceleration operation is performed.

[0037] Various operation states or driving requirement states including the vehicle speed of the vehicle Ve are detected by sensors. When listing examples of such sensors, although not particularly illustrated, they are, for example, a vehicle speed sensor, an accelerator opening sensor, an oil temperature sensor, a steering operation angle sensor, a shift position sensor, a brake sensor, a driving mode sensor, a motor rotation speed sensor, a motor temperature sensor, etc.

[0038] A controller 31 is provided for controlling the drive torque, rotation speed, or regeneration torque of the above-mentioned motors Mfr, Mfl, Mrr, and Mrl, the rotation speed of the electric oil pumps OPfr, OPfl, OPrr, and OPrl, or the discharge amount of these oil pumps OPfr, OPfl, OPrr, and OPrl based on the operation states and driving requirement states detected by these sensors. The controller 31 is mainly composed of a microcomputer composed of an arithmetic element (CPU), a storage element (RAM, ROM), an interface, etc., and is configured to perform arithmetic operations using the input data and the pre-stored data according to a predetermined program, and output the result of the arithmetic operation as a control command signal to the aforementioned power controllers PCf, PCr, etc.

[0039] In particular, the controller 31 is configured to control the distribution of the driving torque to maintain the driving performance or driving stability of the vehicle Ve when the driving torque of either the left or right motor Mfr, Mfl in the driving device Pf on the front wheel 1r, 11 side or the driving torque of the motor Mrr, Mrl in the driving device Pr on the rear wheel 2r, 21 side is limited due to the influence of heat. Specifically, when the driving torque of the left motor Mfl (or Mrl) or the right motor Mfr (or Mrr) is limited due to excessively high or low temperature, the driving torque of the other motor paired with the motor Mfl (or Mrl or Mfr or Mrr) in the left and right direction (vehicle width direction) of the vehicle Ve is reduced. Therefore, for example, when the temperature becomes too high, the temperature rise is prevented or suppressed by reducing the driving torque instead of promoting cooling by the increase in the amount of oil 10f, 10r. The driving torque of the other driving device Pr (or Pl) is increased to compensate for the reduction in the driving torque of the vehicle Ve as a whole that is caused by this. When such control is performed, the driving torque of the front, rear, left, and right wheels may slightly change and affect the steering characteristics or turning characteristics. Therefore, the control of the driving torque or torque distribution is appropriately executed or prohibited according to the turning state of the vehicle Ve. In order to perform such control, the controller 31 has Figure 5 The illustrated functional structures (or functional units).

[0040] The controller 31 is provided with a temperature detection unit 31a for detecting the temperature of the motors Mfr, Mfl, Mrr, and Mrl. The temperature detection can be performed based on data obtained by a temperature sensor not shown in the figure provided for each motor Mfr, Mfl, Mrr, and Mrl, or can be performed based on data obtained by an oil temperature sensor. The controller 31 is provided with a temperature determination unit 31b for determining whether the detected temperature enters a predetermined temperature range. The motors Mfr, Mfl, Mrr, and Mrl are determined as specifications according to the temperature range in which the motors Mfr, Mfl, Mrr, and Mrl are designed to output the driving torque. When the motors Mfr, Mfl, Mrr, and Mrl are operated in a state exceeding the upper limit temperature, the desired driving torque cannot be output, or damage such as sintering occurs, or the durability is reduced. In addition, when the motors are operated in a state below the lower limit temperature, abnormalities or damage occur to related components including bearings, and the durability is reduced. Therefore, the temperature range is pre-set for the motors Mfr, Mfl, Mrr, and Mrl so that the motors can operate normally or as expected. This temperature range may not be in accordance with the specifications of the motors Mfr, Mfl, Mrr, and Mrl, but may be a temperature range determined by upper and lower temperature limits determined as specifications or by adding a predetermined margin to the upper and lower temperature limits. Furthermore, it may be a temperature range that specifies only the upper temperature limit according to the environment in which the vehicle Ve is expected to be used.

[0041] The controller 31 is provided with a driving force limiting unit 31c. When the temperature of either the left or right motor Mfr, Mrr (or Mfl, Mrl) deviates from a predetermined temperature range, the driving force limiting unit 31c reduces the driving torque of the other motor that is paired with the motor deviating from the temperature range in the left - right direction (vehicle width direction) of the vehicle Ve and whose temperature enters the above - mentioned temperature range. This control is for making the balance of the left - right driving torques or the torque distribution ratio suitable for the driving state at that moment. When the driving torque of one of the left - right motors is limited, the driving torque of the other motor is reduced so as to match the limited driving torque. Therefore, the reduced torque of the other motor only needs to be a torque that matches the torque of the limited motor. When the torque of one motor is reduced to avoid thermal influence, the driving torque of the other motor can also be reduced to match the reduced driving torque. In addition, in this case, even if the driving torque of one motor is restricted due to thermal influence, the torques of the left - right motors that are paired with each other do not become zero and are maintained at a predetermined torque. This is to maintain the four - wheel drive state.

[0042] The controller 31 is provided with a driving torque increasing unit 31d. As described above, when the temperature deviates from the predetermined temperature range and the driving torque is limited, the driving torque of the driving device Pf, Pr on the front or rear side of the motor including the motor deviating from the temperature range is reduced. Therefore, the driving torque of the other driving device Pr, Pf is increased to compensate for the reduction in the driving torque, in order to maintain the driving performance or driving stability of the vehicle Ve and maintain the driving torque of the vehicle Ve as a whole. The driving torque increasing unit 31d performs the increasing control of the driving torque for this purpose.

[0043] If the driving torque of any motor is increased, the temperature of that motor will inevitably rise. Therefore, the increasing control of the driving torque based on the driving torque increasing unit 31d preferably makes the temperature of the driving devices Pr, Pf that execute this control enter a predetermined stable range. Here, the stable range is a range of temperatures at which the motor can operate without hindrance, and it can be the same as the above - mentioned predetermined temperature range, or it can be a range set differently from the predetermined temperature range. The temperature of the driving devices Pr, Pf (especially their motors) can be detected by the above - mentioned temperature detection unit 31a, and a stable determination unit 31e for determining whether the temperature enters the stable range is provided in the controller 31. In addition, a driving torque increasing prohibition unit 31f is provided in the controller 31, and the driving torque increasing prohibition unit 31f prohibits the above - mentioned driving torque increasing control when the temperature of the driving devices Pr, Pf does not enter the stable range.

[0044] In the above control in which the drive torque changes due to the temperature of any motor being so-called abnormal, the drive torque of either the front wheel 1r, 1l side or the rear wheel 2r, 2l side, which is so-called 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 the four-wheel drive state of the four wheels before and after driving. Therefore, the controller 31 includes a four-wheel drive determination unit 31g to determine the preconditions for the execution of the control. Since the driving state maintaining the four-wheel drive state can be determined based on the driving mode, the four-wheel drive state can be determined not only based on the output state of the control signals output to the respective motors Mfr, Mfl, Mrr, Mrl, but also based on the selected driving mode.

[0045] The turning performance and steering characteristics change according to the magnitudes of the drive torques of the left and right wheels. Therefore, when controlling the drive torques of the left and right wheels as described above, it is possible to affect the turning performance or handling stability, etc. Therefore, a turning detection unit 31h for detecting the turning driving of the vehicle Ve is provided in the controller 31. In addition, it is preferable to avoid or suppress changes in the turning performance or driving state due to changes in the drive torques of the left and right wheels. Therefore, a drive restriction prohibition unit 31i is provided in the controller 31, and the drive restriction prohibition unit 31i prohibits the control of reducing the drive torque of the other motor by the above-described driving force restriction unit 31c when detecting turning driving.

[0046] As data for performing the above control, various data are input to the controller 31. If examples of the input signals are listed, they are as follows. The motor temperatures obtained by the temperature sensors of the respective motors Mfr, Mfl, Mrr, Mrl or the oil temperature sensor, the driving mode for determining the four-wheel drive state, the steering angle for determining turning driving, the rotational speeds of the respective wheels obtained by the wheel speed sensors, etc. are input to the controller 31. In addition, if examples of the data pre-stored in the controller 31 are listed, a temperature range for determining whether the detected temperature is too high or too low, a drive torque reduction amplitude or the distribution ratio of the left and right drive torques for reducing the drive torque of the paired other motor when the temperature of any motor deviates from the predetermined temperature range, a drive torque increase amount or the front and rear drive torque distribution ratio for increasing the drive torque of the drive device including the motor that has not deviated from the above temperature range, the stable range of the temperature of the drive device for increasing the drive torque, etc. are pre-stored in the controller 31.

[0047] In Figure 6 a flowchart shows an example of the control executed by the above-described controller 31. Figure 6The routine shown is repeatedly executed by the controller 31 at every predetermined short time when the vehicle Ve is running. First, it is determined whether the vehicle Ve is in a four-wheel drive state (4WD) where all four wheels are driven and is going straight (S1). If the determination result of S1 is "No" because it is not in either four-wheel drive or going straight, no special control is performed and the process returns. That is, the routine shown is temporarily ended. Figure 6 The function for making the determination of S1 is the function of the aforementioned four-wheel drive determination unit 31g and the turning detection unit 31h. In addition, in the case where the determination result of S1 is "No" because the vehicle Ve is turning, the steps for controlling the drive torque described later are skipped and the control of the drive torque is not performed. Therefore, the function of avoiding such control of the drive torque is equivalent to the function of the aforementioned drive limit prohibition unit 31i.

[0048] On the contrary, in the case where the determination result of S1 is "Yes" because the drive state of the vehicle Ve is four-wheel drive and the vehicle Ve is going straight, it is determined whether there is a motor Mfr, Mfl, Mrr, or Mrl with a temperature exceeding a pre-determined temperature range. Figure 6 In the example shown, it is determined whether there is a motor whose motor temperature deviates to the high-temperature side within a predetermined temperature range, that is, a so-called high-temperature motor (high-temperature motor) above the upper limit temperature of the temperature range (S2). In the case where the determination result of S2 is "No" because no excessively high-temperature motor is detected, it is determined whether there is a motor whose motor temperature deviates to the low-temperature side within a predetermined temperature range, that is, a so-called low-temperature motor (low-temperature motor) below the lower limit temperature of the temperature range (S3). The function for making the determination of S2 and the function for making the determination of S3 are equivalent to the functions of the aforementioned temperature detection unit 31a and the temperature determination unit 31b. When the determination result is "No" in both S2 and S3, all four motors Mfr, Mfl, Mrr, and Mrl can operate normally, so no special control is performed and the process returns.

[0049] On the contrary, when the judgment result in either S2 or S3 is "Yes", output control is performed on the motors Mfr, Mfl, Mrr, and Mrl. First, when the judgment result in S2 is "Yes" because a motor whose detected temperature deviates to the high-temperature side within a predetermined temperature range is detected, it is judged whether the other motor is stable (S4). Here, regarding "the other motor", when the so-called temperature-abnormal motor with excessive high temperature is the motor Mfr, Mfl on the front-wheel 1r, 1l side, it refers to the motors Mrr, Mrl on the rear-wheel 2r, 2l side; when the so-called temperature-abnormal motor with excessive high temperature is the motor Mrr, Mrl on the rear-wheel 2r, 2l side, it refers to the motors Mfr, Mfl on the front-wheel 1r, 1l side. In addition, "stable" means that no abnormality is detected including the temperature. Therefore, the function of making this judgment in S4 is equivalent to the function of the aforementioned stability determination unit 31e.

[0050] When the judgment result in S4 is "Yes", the torque of the other motor can be increased. Therefore, the torque of the left and right pair of motors including the motor with an abnormality in terms of temperature is reduced, and the torque of the other left and right pair of motors for which stability determination has been made is increased (S5), and then the process returns. In Figure 6 the control in S5 is described as "reduction of the torque of the abnormal motor pair and increase of the torque of the stable motor pair".

[0051] Specifically, when the motor Mfr (or Mfl) on either the front right wheel 1r or front left wheel 1l side is at a high temperature, the torque of the other motor Mfl (or Mfr) paired with the motor Mfr (or Mfl) in the left-right direction is reduced. This torque control can be a control that matches the torque of the other motor Mfl (or Mfr) with the torque of the motor Mfr (or Mfl) whose output is restricted due to temperature, or it can also be a control that reduces the torques of the left and right motors Mfr and Mfl in a balanced manner. Similarly, when the motor Mrr (or Mrl) on either the rear right wheel 2r or rear left wheel 2l side is at a high temperature, the torque of the other motor Mrl (or Mrr) paired with the motor Mrr (or Mrl) in the left-right direction is reduced. This torque control can be a control that matches the torque of the other motor Mrl (or Mrr) with the torque of the motor Mrr (or Mrl) whose output is restricted due to temperature, or it can also be a control that reduces the torques of the left and right motors Mrr and Mrl in a balanced manner. In addition, the control of "increasing the torque of the stable motor pair" is a control that increases the torque of the other pair of motors Mrr and Mrl (or Mfr and Mfl) in the front-rear direction when reducing the torque of a pair of motors Mfr and Mfl (or Mrr and Mrl) on either the front or rear side. The increased amount can be an amount equivalent to the reduced amount of the torque of a pair of motors Mfr and Mfl (or Mrr and Mrl) on either the front or rear side. This is to maintain the driving torque of the vehicle Ve as a whole.

[0052] In this way, in S5, the torque of the other motor paired with the motor with a so-called abnormality due to temperature in the left-right direction is reduced, and in addition, the driving torque of the other pair of motors separated from the pair of motors whose driving torque has been reduced in the front-rear direction of the vehicle Ve is increased. Therefore, the control or function performed in S5 is equivalent to the functions of the aforementioned driving force limiting unit 31c and the driving torque increasing unit 31d. In addition, when the determination result in the above S4 is "no", the control in the above S5 is avoided. Therefore, the function of avoiding the control in S5 is equivalent to the function of the aforementioned driving torque increase prohibition unit 31f.

[0053] On the other hand, when the determination result in the above S4 is "no", the driving torque of the motor is reduced (S6), and then it returns. Here, the motor whose driving torque is reduced is the motor whose temperature exceeds a predetermined upper limit temperature. Therefore, the driving torques of the other motors paired with this motor in the left-right direction are also reduced in order to achieve balance of the left and right driving torques.

[0054] By performing the control of reducing and increasing the driving torque in S5 above, it is possible to suppress the heat generation of the motor with an excessively high temperature and reduce its temperature. In this case, it is not particularly necessary to increase the supply amount of the oil 10f, 10r supplied by the aforementioned oil pumps OPfr, OPfl, OPrr, OPrl. Therefore, it is possible to avoid the necessity of making the mechanism for cooling the motors Mfr, Mfl, Mrr, Mrl particularly large-sized, and in addition, it is possible to avoid or suppress damage to and reduction in durability of the motors Mfr, Mfl, Mrr, Mrl. Moreover, even if the driving torque is reduced on either the front or rear side of the vehicle Ve, the reduction in torque can be compensated by the driving torque on the other side (front or rear), so that the driving performance or power performance of the vehicle Ve can be maintained in a good state.

[0055] Even in the case of a motor in which a temperature lower than a predetermined temperature range is detected (present), the above-described control of reducing or limiting and increasing the driving torque is similarly performed. That is, if the determination result in S3 is "Yes" because the temperature of any motor is lower than the lower limit temperature that determines the predetermined temperature range, it is determined whether the other motor is stable (S7). The control of S7 is the same as the control of S4 described above. Therefore, regarding the "other motor", when the temperature abnormally low so-called temperature abnormal motor is the motor Mfr, Mfl on the front wheel 1r, 1l side, it refers to the motor Mrr, Mrl on the rear wheel 2r, 2l side, and when the temperature abnormally low so-called temperature abnormal motor is the motor Mrr, Mrl on the rear wheel 2r, 2l side, it refers to the motor Mfr, Mfl on the front wheel 1r, 1l side. In addition, "stable" means that no abnormality is detected including the temperature. Therefore, the function of making this determination in S7 is equivalent to the function of the aforementioned stability determination unit 31e.

[0056] When the determination result in 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 for which stability determination has been made is increased (S8), and then the process returns. The control of S8 is the same as the control of S5 described above, and Figure 6 it is described as "reduction of torque of abnormal motor pair, increase of torque of stable motor pair" in it. In addition, the content of the specific control in S8 is the same as the control in S5 described above. Moreover, the above-described driving torque control is performed even when the temperature is low because components such as the motor and its associated bearings and lubricating oil may operate abnormally, and if a large driving torque is output in this state, some damage may occur. In other words, it is possible to avoid or suppress such damage and reduction in durability.

[0057] In addition, the present invention is not limited to the above-described embodiments. The left and right wheels each provided with a driving motor individually can be any two of the front wheels and the rear wheels, and the present invention can also be applied to a vehicle configured such that the other two wheels are driven by a single power source. Further, the present invention can also be such that a predetermined temperature range is a range defined only by the upper limit temperature, and when the temperature of any motor exceeds this upper limit temperature, the control of reducing and increasing the aforementioned driving torque is performed.

Claims

1. A left-right wheel independent drive type vehicle, the left-right wheel independent drive type vehicle comprising: a first drive device, the first drive device drives the left and right front wheels; and a second drive device, the second drive device drives the left and right rear wheels, at least one of the first drive device and the second drive device comprises: a left motor, the left motor drives the left wheel; and a right motor, the right motor drives the right wheel paired with the left wheel, wherein: The left and right wheel independent drive type vehicle includes a controller for controlling the first drive device and the second drive device. The controller has: a temperature detection unit configured to detect a temperature of the left motor and a temperature of the right motor; a temperature determination unit configured to determine whether any one of the temperatures detected by the temperature detection unit deviates from a predetermined temperature range; a driving force limiting unit that, when the temperature determining unit determines that the temperature of one of the left motor and the right motor deviates from the temperature range, reduces the driving torque of the other motor whose temperature does not deviate from the temperature range; as well as A driving torque increasing unit increases the driving torque of the other driving device of the first driving device and the second driving device, excluding the one motor whose temperature deviates from the temperature range, when the driving torque of the other motor is reduced by the driving force limiting unit.

2. The left and right wheel independent drive type vehicle according to claim 1, wherein: The other of the first drive device and the second drive device includes a travel electric motor as a drive force source. The temperature detection unit further has a function of detecting the temperature of the driving motor. The controller also has: a stability determination unit that determines that the temperature of the travel motor has entered a predetermined stable range; and A drive torque increase prohibition unit prohibits the drive torque increase unit from increasing the drive torque when the temperature of the electric motor for traveling has not entered the stable range.

3. The left and right wheel independent drive type vehicle according to claim 1 or 2, wherein: The controller further includes a four-wheel drive determination unit configured to determine that the first drive device and the second drive device output drive torque to drive the vehicle in four-wheel drive mode. The driving force limiting unit is configured to reduce the driving torque of the other electric motor when the four-wheel drive is determined, and the driving torque increasing unit is configured to increase the driving torque of the other driving device when the four-wheel drive is determined.

4. The left and right wheel independent drive type vehicle according to claim 1 or 2, wherein: The controller also has: a turning detection unit, the turning detection unit detecting a turning situation of the vehicle; and A drive restriction prohibition unit prohibits the drive force restriction unit from reducing the drive torque of the other electric motor when a turning of the vehicle is detected.

5. The left and right wheel independent drive type vehicle according to claim 1 or 2, wherein: The temperature range is any one of a range in which only the upper limit temperature is determined and a range determined by the upper limit temperature and the lower limit temperature.

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