Driving force control device of electric vehicle

Abstract

To provide a driving force control device of an electric vehicle suppressing a temperature of a motor as a driving force source from reaching a restrictive temperature and suppressing travelling stability from being reduced when reaching the restrictive temperature.SOLUTION: A driving force control device of an electric vehicle is constituted of: an upper limit torque setting part 26 setting a torque at a time of reaching a first prescribed temperature as an upper limit torque of a first motor when a temperature of the first motor is a first prescribed temperature or higher and also lower than a first restrictive temperature; a limit torque setting part 27 setting a first limit torque smaller than the torque set by the upper limit torque setting part 26 as the upper limit torque of the first motor, when the temperature of the first motor is the first restrictive temperature or higher; a target torque setting part 28 setting a torque of a second motor on the basis of the upper limit torque of the first motor, a target torque distribution ratio as a target value of a ratio of the torque transmitted to front wheels and rear wheels, or a driving torque required by the electric vehicle.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a driving force control device for an electric vehicle including a motor as a driving force source for either the front wheel or the rear wheel, and another driving force source such as an engine or a motor as a driving force source for the other wheel.

Background Art

[0002] Patent Document 1 describes a control device for a four-wheel drive vehicle including a front motor as a driving force source for a pair of front wheels and a rear motor as a driving force source for a pair of rear wheels. When the operation of the rear motor is restricted according to the temperature of the rear motor or the temperature of the power storage device, this control device sets the output torque of the rear motor to a limit torque determined based on the temperature of the rear motor, subtracts a torque corresponding to the limit torque of the rear motor from the driving torque required for the vehicle, and sets the subtracted torque as the output torque of the front motor. That is, when the torque of the rear motor is restricted, it is configured to satisfy the driving torque required for the vehicle by reducing the torque of the rear motor to the limit torque and increasing the torque of the front motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The control device described in Patent Document 1 outputs a limit torque according to the temperature of the rear motor. Therefore, for example, when driving by outputting torque from the rear motor and the front motor based on the target torque distribution ratio of the front and rear wheels, when the temperature of the rear motor reaches a predetermined temperature, the torque of the rear motor is decreased, while the torque of the front motor is increased by a torque amount corresponding to the decrease in the torque of the rear motor. As a result, the distribution ratio of the torque between the front and rear wheels may deviate greatly from the target torque distribution ratio suddenly, and the driving stability may be deteriorated.

[0005] The present invention has been made paying attention to the above technical problem, and an object thereof is to provide a driving force control device for an electric vehicle that can suppress the temperature of a motor as a driving force source from reaching a limit temperature and can suppress a decrease in driving stability when the limit temperature is reached.

Means for Solving the Problem

[0006] To achieve the above object, the present invention provides a driving force control device for an electric vehicle capable of setting a four-wheel drive running mode in which a first driving wheel, which is one of a front wheel and a rear wheel, is driven by a first motor, and another driving force source different from the first motor that drives a second driving wheel, which is the other of the front wheel and the rear wheel. The driving force control device includes a controller that controls the first motor. When the temperature of the first motor is equal to or higher than a predetermined first temperature and lower than a predetermined first limit temperature for protecting the first motor, the controller sets the torque at the time when the first predetermined temperature is reached as the upper limit torque of the first motor. The controller includes an upper limit torque setting unit, a limit torque setting unit, and a target torque setting unit. When the temperature of the first motor is equal to or higher than the first limit temperature, the limit torque setting unit sets a first limit torque, which is smaller than the torque set by the upper limit torque setting unit and is determined according to the temperature of the first motor, as the upper limit torque of the first motor. The target torque setting unit sets the torque of the other driving force source based on the upper limit torque of the first motor, a target torque distribution ratio that is a target value of the ratio of the torque transmitted to the front wheel and the rear wheel, or the driving torque required for the electric vehicle.

[0007] In the present invention, the other driving force source includes a second motor, the controller is configured to control the second motor, the upper limit torque setting unit sets the torque at the time when the second predetermined temperature is reached as the upper limit torque of the second motor when the temperature of the second motor is equal to or higher than a predetermined second temperature and lower than a predetermined second limit temperature for protecting the second motor, and the target torque setting unit sets the torque at the time when the first predetermined temperature is reached as the upper limit torque of the first motor and the torque at the time when the second predetermined temperature is reached as the upper limit torque of the second motor when the temperature of the first motor is equal to or higher than the first predetermined temperature and lower than the first limit temperature, and the temperature of the second motor is equal to or higher than the second predetermined temperature and lower than the second limit temperature.

[0008] In the present invention, the other drive power source includes a second motor, the controller is configured to control the second motor, the limit torque setting unit sets, when the temperature of the second motor is equal to or higher than a second limit temperature predetermined to protect the second motor, a second limit torque determined according to the temperature of the second motor as the upper limit torque of the second motor, and the target torque setting unit may set, when the temperature of the first motor is equal to or higher than the first limit temperature and the temperature of the second motor is equal to or higher than the second limit temperature, the first limit torque as the upper limit torque of the first motor and the second limit torque as the upper limit torque of the second motor.

[0009] In the present invention, the other drive power source includes a second motor, the controller is configured to control the second motor, and is configured to be able to set a manual range mode for determining a required drive torque of the electric vehicle based on a plurality of drive characteristics, and includes a shift device for changing drive characteristics in the manual range mode by a driver's shift operation. The controller may prohibit the change of the drive characteristics in which the required drive torque in the manual range mode increases when the temperature of the first motor is equal to or higher than the first predetermined temperature and the temperature of the second motor is equal to or higher than a second predetermined temperature lower than a second limit temperature predetermined to protect the second motor.

Advantages of the Invention

[0010] According to the present invention, when the temperature of a first motor that drives a first drive wheel, which is one of a front wheel and a rear wheel, is equal to or higher than a first predetermined temperature and lower than a first limit temperature, the torque at the time when the first predetermined temperature is reached is set as the upper limit torque of the first motor. Therefore, it is possible to suppress the temperature of the first motor from rising to equal to or higher than the first predetermined temperature, or to reduce the rate of increase in its temperature. As a result, it is possible to suppress the temperature of the first motor from reaching the first limit temperature.

[0011] Also, when the required drive torque continues to increase from a state where the temperature of the first motor is lower than the first predetermined temperature, the torque at the time when the temperature of the first motor exceeds the first predetermined temperature is defined as the upper limit torque of the first motor, and the torque of the first motor is fixed to the upper limit torque, and the torque of other drive power sources gradually increases. Then, thereafter, when the temperature of the first motor becomes equal to or higher than the first limit temperature, the torque of the first motor is reduced to the limit torque, and the torque of other drive power sources is continuously increased. That is, the torque distribution ratio gradually deviates from the target torque distribution ratio after reaching the first predetermined temperature, and after reaching the first limit temperature, the change rate of the deviation amount increases. Therefore, it is possible to suppress a sudden change in the torque distribution ratio and suppress a decrease in running stability.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0013] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the embodiments described below are merely examples of implementing the present invention and do not limit the present invention.

[0014] The electric vehicle targeted by the present invention is a vehicle with a total of four wheels, two front wheels and two rear wheels. A motor is provided as a driving force source for at least one of the front two wheels and the rear two wheels, and an engine, a motor, or the like is provided as a driving force source for the other wheels. It is an electric vehicle that can drive each of the front two wheels and the rear two wheels independently of each other. Note that the front two wheels may be connected to the driving force source for the front wheels via an appropriate differential mechanism, and the rear two wheels may be connected to the driving force source for the rear wheels via an appropriate other differential mechanism. Furthermore, the electric vehicle targeted by the present invention may be an electric vehicle configured to be provided with a motor as a driving force source corresponding to each of the four front and rear wheels so that the driving torque and the regenerative braking torque (regenerative torque) of each of the four wheels can be controlled independently of each other.

[0015] FIG. 1 schematically shows an example of a four-wheel independent drive vehicle configured to be able to drive all four wheels independently of each other in addition to being able to control the driving torque or the regenerative braking torque of the front wheels and the rear wheels independently of each other. The electric vehicle (hereinafter simply referred to as the vehicle) Ve shown here includes the left and right front wheels 1r, 1l and the left and right rear wheels 2r, 2l, and 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 units Pf, Pr are each mainly composed of a motor and a gear reduction mechanism (transmission mechanism).

[0016] Fig. 2 shows an example of the drive unit Pr on the rear wheel 2r, 2l side in a skeleton diagram. This drive unit Pr is composed of a pair of drive systems that control the left and right rear wheels 2r, 2l independently of each other. Since these drive systems have a symmetric configuration, they will be described together without particularly specifying "right" or "left". In the following description, when the suffix of a reference numeral has one character, "f" indicates for the front wheel, "l" indicates for the left wheel, "r" indicates for the right wheel or the rear wheel. When the suffix has 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.

[0017] In the drive unit Pr for the rear wheels 2r, 2l, motors Mrr, Mrl are mounted with their rotation center axes oriented in the longitudinal direction of the vehicle Ve. Drive gears 3rr, 3rl are attached to the rotor shafts of these motors, and these drive gears 3rr, 3rl are meshed with counter drive gears 4rr, 4rl. The counter drive gears 4rr, 4rl have a larger diameter than the drive gears 3rr, 3rl. Therefore, these gear pairs constitute a speed reduction mechanism. Counter drive gears 5rr, 5rl, which are bevel gears, are provided so as to rotate integrally on the same axis as the counter drive gears 4rr, 4rl. These counter drive gears 5rr, 5rl are meshed with driven gears 7rr, 7rl, which are bevel gears integral with drive shafts 6rr, 6rl connected to the rear wheels 2r, 2l. By making the driven gears 7rr, 7rl have a larger diameter than the counter drive gears 5rr, 5rl, these gear pairs can be used as a speed reduction mechanism.

[0018] These motors Mrr, Mrl, the reduction gear mechanism, and each bevel gear are housed in a liquid-tight manner inside the casing 8. For the motors Mrr, Mrl inside this casing 8, electric oil pumps OPrr, OPrl for supplying oil for cooling and lubrication are provided. These oil pumps OPrr, OPrl are configured to rotate at a rotational speed based on the output torque, rotational speed, or temperature of the motors Mrr, Mrl and discharge oil. Note that the oil pumps OPrr, OPrl on the rear wheel 2r, 2l sides 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 on the outside of the casing 8 of the vehicle Ve, configured to suck up the oil 10r from the oil reservoir 9r and supply the oil 10r to the motors Mrr, Mrl via the cooling oil passages 11rr, 11rl provided through the casing 8.

[0019] Note that although not particularly shown in the drawings, it is configured such that the oil 10r refluxes from the inside of the casing 8 to the oil reservoir 9r. Also, an oil cooler may be provided in the middle of the cooling oil passages 11rr, 11rl.

[0020] Fig. 3 shows an example of the drive unit Pf on the front wheel 1r, 1l sides in a skeleton diagram. Since this drive unit Pf has a symmetric configuration, it will be described collectively without particularly specifying "right" or "left". Motors Mfr, Mfl are mounted with their rotation center axes oriented in the width direction (lateral direction) of the vehicle Ve, and drive gears 12fr, 12fl are attached to their rotor shafts. These drive gears 12fr, 12fl are meshed with idle gears 13r, 13l. Counter shafts 14r, 14l are provided parallel to the rotation center axes of these idle gears 13r, 13l, and the idle gears 13r, 13l are meshed with counter driven gears 15fr, 15fl attached to these counter shafts 14r, 14l.

[0021] Since the counter drive gears 15fr and 15fl attached to the motors Mfr and Mrl have a larger diameter than the drive gears 12fr and 12fl, a reduction mechanism is constituted by these gear pairs. Counter drive gears 16fr and 16fl are attached to the counter shafts 14r and 14l, and these counter drive gears 16fr and 16fl mesh with the driven gears 18fr and 18fl which are integral with the drive shafts 17fr and 17fl connected to the front wheels 1r and 1l. Since the driven gears 18fr and 18fl have a larger diameter than these counter drive gears 16fr and 16fl, a reduction mechanism is constituted by these gear pairs.

[0022] The motors Mfr and Mfl on the front wheel 1r and 1l sides are configured to be cooled by the oil 10f in the same manner as the motors Mrr and Mrl on the rear wheel 2r and 2l sides. That is, electric oil pumps OPfr and OPfl are provided corresponding to the motors Mfr and Mfl on the front wheel 1r and 1l sides, and these oil pumps OPfr and OPfl are configured to pump up the oil 10f from the oil sump 9f and supply the oil 10f to the motors Mfr and Mfl via the cooling oil passages 19fr and 19fl. These oil pumps OPfr and OPfl are configured to rotate at a rotational speed based on the output torque, rotational speed, or temperature of the motors Mfr and Mfl and discharge the oil.

[0023] Although not particularly shown in the figure, the oil that has cooled the motors Mfr and Mfl is configured to flow back to the oil sump 9f. Also, an oil cooler may be provided in the middle of the cooling oil passages 19fr and 19fl. In addition, the oil pumps on the front wheel 1r and 1l sides may be a single oil pump that supplies the oil 10f to the left and right motors Mfr and Mfl together in the same manner as the oil pumps on the rear wheel 2r and 2l sides described above.

[0024] An oil pump OPm for pumping oil for lubrication is provided. 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 when the vehicle Ve is running, pumps up the oil 10f from the oil sump 9f, and is configured to supply the oil 10f to predetermined lubrication locations such as gears and bearings provided in the drive units Pf on the front wheel 1r, 1l sides.

[0025] A power storage device (Bat) 20 for exchanging electric power with each of the above motors Mfr, Mfl, Mrr, Mrl and oil pumps OPfr, OPfl, OPrr, OPrl is provided. This power storage device 20 is mainly composed of a secondary battery such as a lithium ion battery or an all-solid-state battery. Each of the motors Mfr, Mfl, Mrr, Mrl is, for example, a permanent magnet type synchronous motor, and these motors Mfr, Mfl, Mrr, Mrl are connected to the power storage device 20 via power controllers PCfr, PCfl, PCrr, PCrl mainly composed of inverters. Therefore, each of the motors Mfr, Mfl, Mrr, Mrl has its output torque and braking torque during energy regeneration individually controlled independently of each other. Note that the power controllers PCfr, PCfl, PCrr, PCrl only need to have independent functions and may be configured as a single unit as a whole.

[0026] The vehicle Ve configured as described above can control the output torques of the motors Mfr, Mfl, Mrr, Mrl independently of each other. Therefore, for example, it is possible to switch between a two-wheel drive running mode in which the motors Mrr, Mrl are controlled as drive power sources and the energization of the motors Mfr, Mfl is stopped, and a four-wheel drive running mode in which each of the motors Mfr, Mfl, Mrr, Mrl is controlled as a drive power source. Further, when running in the four-wheel drive running mode, the ratio of the output torques of the front and rear motors can be appropriately changed based on the running characteristics required by the driver and the like.

[0027] A mode selection switch (mode selection unit) 21 for such a driver to select a driving characteristic (driving mode) is provided in the vehicle Ve. Specifically, the driving mode is mainly a control form for controlling the driving torque based on a predetermined standard, such as a track mode for improving the turning performance by controlling the driving torque and the regenerative torque (braking torque) of each motor Mfr, Mfl, Mrr, Mrl, or a drift mode for individually controlling the torque of each of the four wheels to eliminate understeer or control it to optimal traction to improve the agility and driving accuracy during turning, or a manual sports mode for ensuring a large driving torque up to a high vehicle speed to improve the acceleration performance or power performance.

[0028] In addition, this vehicle Ve is provided with a shift device such as a shift lever or paddle shift (not shown), the operation of the shift device is detected by a shift position sensor 22, and a manual range mode for changing the driving characteristic (shift range), which is the relationship between the accelerator operation amount and the required driving torque, can be set according to the signal of the shift position sensor 22. These driving modes (including the manual range mode) control the torque balance between the front and rear wheels or output a large driving torque, so they correspond to a four-wheel drive running mode in which all the motors Mfr, Mfl, Mrr, Mrl are driven to run.

[0029] And it is configured to select any of these driving modes or cancel the selection to select the normal normal mode by the above mode selection switch 21 and shift device. Note that a plurality of mode selection switches 21 may be provided corresponding to the driving modes, or one mode selection switch may be provided and configured to sequentially switch the driving mode to be selected according to the number of operations.

[0030] A controller 23 is provided for controlling each motor Mfr, Mfl, Mrr, Mrl and each electric oil pump OPfl, OPfr, OPrl, OPrr based on the above-described driving mode, shift range, etc. The controller 23 is mainly composed of a microcomputer, and uses the input data and the data stored in advance to perform calculations according to a predetermined program or with reference to a predetermined map, and outputs the result of the calculation to each of the above-described motors Mfr, Mfl, Mrr, Mrl and the electric oil pump OPfl, OPfr, OPrl, OPrr as a control command signal.

[0031] Examples of the input signals and output signals for performing such control are shown in FIG. 4. Examples of the input signals are a vehicle speed signal, an accelerator opening signal, a shift position signal, a mode selection switch signal, a shift up (+) signal, a shift down (-) signal, a track mode signal, a drift mode signal, and the like. Examples of the command signals to be output are the torque of the motor Mrl for the left rear wheel 2l, the torque of the motor Mrr for the right rear wheel 2r, the control signal of the oil pump OPrl for the left rear wheel 2l, the control signal of the oil pump OPrr for the right rear wheel 2r, the torque of the motor Mfl for the left front wheel 1l, the torque of the motor Mfr for the right front wheel 1r, the control signal of the oil pump OPfl for the left front wheel 1l, the control signal of the oil pump OPfr for the right front wheel 1r, and the like.

[0032] FIG. 5 shows an example of a drive torque map stored in the controller 23 for determining the drive torque required for the vehicle Ve. This drive torque map determines the drive torque required for the vehicle Ve based on the vehicle speed and the accelerator opening. The vehicle speed is taken on the horizontal axis, the required drive torque is taken on the vertical axis, and each accelerator opening is shown by a curve. When the manual range mode is set, it may be configured to change and determine the required drive torque according to the accelerator opening according to the driving mode and the selected shift range, such as determining that the greater the low range is selected, the greater the magnitude of the required drive torque with respect to the accelerator opening becomes.

[0033] Furthermore, when the controller 23 has a track mode, a drift mode, a manual sports mode, a manual range mode, etc. set or selected and the vehicle travels in four-wheel drive, a temperature region map for determining the torque relationship between the motors Mfr, Mfl and the motors Mrr, Mrl according to the temperature conditions of each motor Mfr, Mfl, Mrr, Mrl is stored. FIG. 6 shows an example of the temperature region map, where the temperature of the motors Mfr, Mfl is taken on the horizontal axis and the temperature of the motors Mrr, Mrl is taken on the vertical axis. When the temperatures of the motors Mfr, Mfl are different, the temperature of the higher-temperature motor Mfr (Mfl) is adopted to refer to the temperature region map in FIG. 6. Similarly, when the temperatures of the motors Mrr, Mrl are different, the temperature of the higher-temperature motor Mrr (Mrl) can be adopted to refer to the map in FIG. 6. In the following description, the motors Mfr, Mfl are collectively referred to as the front motor Mf, and the motors Mrr, Mrl are collectively referred to as the rear motor Mr.

[0034] In the region (region A) where the temperature of the front motor Mf in the temperature region map shown in FIG. 6 is less than the first predetermined temperature T1 and the temperature of the rear motor Mr is less than the second predetermined temperature T2, the distribution ratio of the output torque of the front motor Mf (that is, the torque transmitted to the front wheels 1r, 1l) and the output torque of the rear motor Mr (that is, the torque transmitted to the rear wheels 2r, 2l) is determined based on the set or selected driving mode and the like.

[0035] In the region (region B) where the temperature of the front motor Mf is equal to or higher than the first predetermined temperature T1 and less than the first limit temperature T3 and the temperature of the rear motor Mr is less than the second predetermined temperature T2, the upper limit torque of the front motor Mf is set to the torque at the time when it reaches region B, and the output torque of the rear motor Mr is set so as to satisfy the torque required for the vehicle Ve. Here, the first limit temperature T3 may be a temperature (for example, the rated temperature) determined to protect the front motor Mf.

[0036] Note that, in this case, the front motor Mf corresponds to the "first motor" in the embodiment of the present invention, the front wheels 1r, 1l correspond to the "first drive wheels" in the embodiment of the present invention, the rear motor Mr corresponds to the "other driving force source" or "second motor" in the embodiment of the present invention, and the rear wheels 2r, 2l correspond to the "second drive wheels" in the embodiment of the present invention.

[0037] Therefore, for example, when the temperature conditions of the front motor Mf and the rear motor Mr are in the B region and the driving torque required for the vehicle Ve increases, the torque of the front motor Mf is fixed to the torque at the time when the temperature of the front motor Mf reaches the B region, and the torque transmitted to the front wheels 1r, 1l obtained by multiplying the torque of the front motor Mf by the gear ratio of the drive unit Pf is subtracted from the required driving torque, and the torque of the rear motor Mr is set to the resulting torque. That is, only the output torque of the rear motor Mr is increased to satisfy the required driving torque.

[0038] Also, when the torques of the front motor Mf and the rear motor Mr are continuously maintained constant from the time when the temperature conditions of the front motor Mf and the rear motor Mr reach the B region, the torques of the front motor Mf and the rear motor Mr are maintained at the torques at the time when they reached the B region. Further, when the temperature conditions of the front motor Mf and the rear motor Mr are in the B region and the driving torque required for the vehicle Ve decreases, the torque of at least one of the motors Mr (Mf) of the front motor Mf and the rear motor Mr is decreased so that the difference between the target value (target torque distribution ratio) of the torque distribution ratio determined according to the driving mode or the like and the actual torque distribution ratio decreases.

[0039] In the region (C region) where the temperature of the rear motor Mr is equal to or higher than the second predetermined temperature T2 and lower than the second limit temperature T4, and the temperature of the front motor Mf is lower than the first predetermined temperature T1, the upper limit torque of the rear motor Mr is set to the torque at the time when the C region is reached, and the output torque of the front motor Mf is set so as to satisfy the torque required for the vehicle Ve. Here, the second limit temperature T4 may be a temperature (for example, the rated temperature) determined to protect the rear motor Mr.

[0040] In this case, the rear motor Mr corresponds to the "first motor" in the embodiment of the present invention, the rear wheels 2r, 2l correspond to the "first drive wheels" in the embodiment of the present invention, the front motor Mf corresponds to the "other drive power source" or "second motor" in the embodiment of the present invention, and the front wheels 1r, 1l correspond to the "second drive wheels" in the embodiment of the present invention.

[0041] Therefore, for example, when the temperature conditions of the front motor Mf and the rear motor Mr are in the C region, if the drive torque required for the vehicle Ve increases, the torque of the rear motor Mr is fixed to the torque at the time when the temperature of the rear motor Mr enters the C region, and the torque of the front motor Mf is set to the torque obtained by subtracting the torque transmitted to the rear wheels 2r, 2l, which is obtained by multiplying the gear ratio of the drive unit Pr by the torque of the rear motor Mr, from the required drive torque. That is, only the output torque of the front motor Mf is increased to satisfy the required drive torque.

[0042] Also, when the torques of the front motor Mf and the rear motor Mr are continuously maintained constant from the time when the temperature conditions of the front motor Mf and the rear motor Mr reach the C region, the torques of the front motor Mf and the rear motor Mr are maintained at the torques at the time when the C region is reached. Further, when the temperature conditions of the front motor Mf and the rear motor Mr are in the C region and the drive torque required for the vehicle Ve decreases, the torque of at least one of the front motor Mf and the rear motor Mr, i.e., the motor Mf (Mr), is decreased so that the difference between the target torque distribution ratio and the actual torque distribution ratio according to the driving mode or the like decreases.

[0043] Also, in a region (D region) where the temperature of the front motor Mf is equal to or higher than the first limit temperature T3 and the temperature of the rear motor Mr is lower than the second limit temperature T4, the output torque of the front motor Mf is set to be less than a predetermined first limit torque, and the output torque of the rear motor Mr is set so as to satisfy the torque required for the vehicle Ve. This first limit torque is a torque determined according to the temperature of the front motor Mf. For example, it may be a torque determined such that the heat generation amount of the front motor Mf is less than the cooling amount by the oil pumps OPfr and OPfl, or may be a torque (zero) at which the power controllers PCfr and PCfl are shut down. That is, the first limit torque is smaller than the upper limit torque set when the temperature of the front motor Mf reaches the first predetermined temperature T1.

[0044] Note that in this case, the front motor Mf corresponds to the "first motor" in the embodiment of the present invention, the front wheels 1r and 1l correspond to the "first drive wheels" in the embodiment of the present invention, the rear motor Mr corresponds to the "other driving force source" or "second motor" in the embodiment of the present invention, and the rear wheels 2r and 2l correspond to the "second drive wheels" in the embodiment of the present invention.

[0045] Therefore, for example, when the torque of the front motor Mf at the time when the temperature conditions of the front motor Mf and the rear motor Mr enter the D region are equal to or higher than the first limit torque, the torque of the front motor Mf is reduced to be less than the first limit torque, and based on the torque obtained by subtracting the torque transmitted to the front wheels 1r and 1l, which is obtained by multiplying the torque of the front motor Mf by the gear ratio of the drive unit Pf, from the required drive torque, the torque of the rear motor Mr is set.

[0046] Also, when the temperature conditions of the front motor Mf and the rear motor Mr are in the D region, if the drive torque required for the vehicle Ve increases, the torque of the front motor Mf is set to less than the first limit torque, and the torque transmitted to the front wheels 1r, 1l obtained by multiplying the torque of the front motor Mf by the gear ratio of the drive unit Pf is subtracted from the required drive torque, and based on this torque, the torque of the rear motor Mr is set.

[0047] In addition, when the torque of the front motor Mf at the time when the temperature conditions of the front motor Mf and the rear motor Mr enter the D region is less than the first limit torque, or when the temperature conditions of the front motor Mf and the rear motor Mr are in the D region and the required drive torque is maintained or decreased, the torques of the front motor Mf and the rear motor Mr are maintained, or the torque of at least one of the motors Mr (Mf) of the front motor Mf and the rear motor Mr is decreased so that the difference between the target torque distribution ratio and the actual torque distribution ratio becomes small.

[0048] The region (E region) where the temperature of the rear motor Mr is equal to or higher than the second limit temperature T4 and the temperature of the front motor Mf is lower than the first limit temperature T3 is a region where the output torque of the rear motor Mr is set to less than a predetermined second limit torque, and the output torque of the front motor Mf is set so as to satisfy the torque required for the vehicle Ve. This second limit torque is a torque determined according to the temperature of the rear motor Mr. For example, it may be a torque determined so that the heat generation amount of the rear motor Mr is less than the cooling amount by the oil pumps OPrr, OPrl, or it may be a torque (zero) at which the power controllers PCrr, PCrl are shut down. That is, the second limit torque is smaller than the upper limit torque set when the temperature of the rear motor Mr reaches the second predetermined temperature T2.

[0049] Note that in this case, the rear motor Mr corresponds to the "first motor" in the embodiment of the present invention, the rear wheels 2r, 2l correspond to the "first drive wheels" in the embodiment of the present invention, the front motor Mf corresponds to the "other drive power source" or "second motor" in the embodiment of the present invention, and the front wheels 1r, 1l correspond to the "second drive wheels" in the embodiment of the present invention.

[0050] Therefore, for example, when the torque of the rear motor Mr at the time when the temperature conditions of the front motor Mf and the rear motor Mr enter the E region is equal to or higher than the second limit torque, the torque of the rear motor Mr is reduced to less than the second limit torque, and the torque transmitted to the rear wheels 2r, 2l obtained by multiplying the torque of the rear motor Mr by the gear ratio of the drive unit Pr is subtracted from the required drive torque, and the torque of the front motor Mf is set based on the resulting torque.

[0051] Also, when the temperature conditions of the front motor Mf and the rear motor Mr are in the E region and the drive torque required for the vehicle Ve increases, the torque of the rear motor Mr is set to less than the second limit torque, and the torque of the front motor Mf is set based on the torque transmitted to the rear wheels 2r, 2l obtained by multiplying the torque of the rear motor Mr by the gear ratio of the drive unit Pr and subtracted from the required drive torque.

[0052] Note that when the torque of the rear motor Mr at the time when the temperature conditions of the front motor Mf and the rear motor Mr enter the E region is less than the second limit torque, or when the temperature conditions of the front motor Mf and the rear motor Mr are in the E region and the required drive torque is maintained or reduced, the torques of the front motor Mf and the rear motor Mr are maintained, or the torque of at least one of the motors Mf (Mr) of the front motor Mf and the rear motor Mr is reduced so that the difference between the target torque distribution ratio and the actual torque distribution ratio becomes small.

[0053] Furthermore, in a region (F region) where the temperature of the front motor Mf is equal to or higher than the first predetermined temperature T1 and lower than the first limit temperature T3, and the temperature of the rear motor Mr is equal to or higher than the second predetermined temperature T2 and lower than the second limit temperature T4, the upper limit torque of the front motor Mf and the upper limit torque of the rear motor Mr are set to the torque at the time when the F region is reached. Therefore, for example, when the temperature conditions of the front motor Mf and the rear motor Mr are in the F region, if the drive torque required for the vehicle Ve increases, the torque of the front motor Mf and the torque of the rear motor Mr are fixed to the torque at the time when the temperature conditions become the F region. That is, the vehicle runs at a torque equal to or lower than the required drive torque. When the required drive torque is maintained constant when the temperature conditions are in the F region, the torques of the front motor Mf and the rear motor Mr are maintained constant. When the required drive torque decreases, the torque of at least one of the front motor Mf and the rear motor Mr (Mf (Mr)) is decreased so that the difference between the target torque distribution ratio and the actual torque distribution ratio becomes smaller.

[0054] Note that the front motor Mf and the rear motor Mr in this case correspond to the "first motor" and the "other drive power source" or "second motor" in the embodiment of the present invention, and the front wheels 1r, 1l and the rear wheels 2r, 2l correspond to the "first drive wheels" and the "second drive wheels" in the embodiment of the present invention.

[0055] In the region (G region) where the temperature of the front motor Mf is equal to or higher than the first limit temperature T3 and the temperature of the rear motor Mr is equal to or higher than the second limit temperature T4, it is necessary to cool the front motor Mf and the rear motor Mr in order to suppress a decrease in their durability. Therefore, the G region is a region where the output torque of the front motor Mf is set to be equal to or lower than the first limit torque and the output torque of the rear motor Mr is set to be equal to or lower than the second limit torque. That is, when the temperature condition is the G region, until the required drive torque decreases to be equal to or lower than the drive torque generated by outputting the first limit torque from the front motor Mf and the second limit torque from the rear motor Mr, the first limit torque is output from the front motor Mf and the second limit torque is output from the rear motor Mr. Further, when the required drive torque decreases to be equal to or lower than the drive torque generated by outputting the first limit torque from the front motor Mf and the second limit torque from the rear motor Mr, the torque of at least one of the front motor Mf and the rear motor Mr (Mf (Mr)) is decreased so that the difference between the target torque distribution ratio and the actual torque distribution ratio becomes small.

[0056] Note that the front motor Mf and the rear motor Mr in this case correspond to the "first motor" and the "other driving power source" or the "second motor" in the embodiment of the present invention, and the front wheels 1r, 1l and the rear wheels 2r, 2l correspond to the "first driving wheels" and the "second driving wheels" in the embodiment of the present invention.

[0057] FIG. 7 shows an example of a functional configuration for controlling the motors Mfr, Mfl, Mrr, and Mrl in the controller 23. The controller 23 shown in FIG. 7 includes a required drive torque calculation unit 24, a temperature region determination unit 25, an upper limit torque setting unit 26, a limit torque setting unit 27, and a target torque setting unit 28. The required drive torque calculation unit 24 calculates the drive torque required for the electric vehicle Ve with reference to the above drive torque map. That is, the required drive torque is calculated based on the vehicle speed signal input to the controller 23, the accelerator opening signal, and the drive torque map stored in the controller 23.

[0058] The temperature range determination unit 25 determines in which region of the temperature range map the temperature conditions of the front motor Mf and the rear motor Mr are. That is, it reads the temperature signal of the front motor Mf and the temperature signal of the rear motor Mr, and determines the region based on these signals and the temperature range map.

[0059] When the temperature conditions of the front motor Mf and the rear motor Mr shift to any of the B region, C region, or F region, the upper limit torque setting unit 26 sets the torque at that time as the upper limit torque of the front motor Mf or the rear motor Mr.

[0060] When the temperature conditions of the front motor Mf and the rear motor Mr shift to any of the D region, E region, or G region, the limit torque setting unit 27 sets the limit torque of the front motor Mf or the rear motor Mr as the upper limit torque of the front motor Mf or the rear motor Mr.

[0061] Based on the upper limit torque of at least one of the front motor Mf and the rear motor Mr set by the upper limit torque setting unit 26 and the limit torque setting unit 27 described above, the drive torque required for the vehicle Ve, and the target torque distribution ratio, the target torque setting unit 28 sets the torque of the other motor.

[0062] An example of the control by this controller 23 will be described with reference to the flowchart shown in FIG. 8. In the control example shown in FIG. 8, first, input data is acquired in step S1. The input data acquired here is the accelerator opening, vehicle speed, motor temperature, oil temperature, shift range, driving mode, etc. Next, the required drive torque is calculated (step S2). This step S2 is executed by the above-described required drive torque calculation unit 24, which calls the drive torque map and obtains the required drive torque based on the accelerator opening signal and the vehicle speed signal input to the controller 23.

[0063] Subsequently, it is calculated which region of the temperature region map the temperature conditions of the front motor Mf and the rear motor Mr are in (step S3). That is, the region is determined based on the temperature signal of the front motor Mf and the temperature signal of the rear motor Mr input to the controller 23. Specifically, the temperature region determination unit 25 determines whether the temperature of the front motor Mf is equal to or higher than the first predetermined temperature T1, whether it is equal to or higher than the first limit temperature T3, whether the temperature of the rear motor Mr is equal to or higher than the second predetermined temperature T2, and whether it is equal to or higher than the second limit temperature T4, and determines the region based on the determination result.

[0064] Next, based on the region calculated in step S3, the target torque of each motor Mf, Mr is set (step S4). Specifically, when the region calculated in step S3 is the A region, the target torque of each motor Mf, Mr is set based on the target torque distribution ratio as described above. When the region calculated in step S3 is any of the B region, C region, and F region, the upper limit torque setting unit 26 sets the upper limit torque of at least one of the front motor Mf and the rear motor Mr, i.e., Mf (Mr), based on the temperature condition to the torque at the time when it reaches that region, and the target torque setting unit 28 sets the target torque of each motor Mf (Mr) based on the required drive torque and the upper limit torque. Further, when the region calculated in step S3 is any of the D region, E region, and G region, the limit torque setting unit 27 sets the upper limit torque of at least one of the front motor Mf and the rear motor Mr, i.e., Mf (Mr), based on the temperature condition to the limit torque, and the target torque setting unit 28 sets the target torque of each motor Mf, Mr based on the required drive torque and the upper limit torque.

[0065] Then, based on the target torque of each motor Mf, Mr set in step S4, the power controllers PCfr, PCfl, PCrr, PCrl are controlled to output torque from each motor Mf, Mr (step S5).

[0066] In addition, the above-described vehicle Ve can set a manual range mode, and this manual range mode is configured to set a shift range according to a shift operation by the driver. Since the shift range changes the required drive torque with respect to the accelerator opening, when a shift operation (downshift operation) that sets a relatively large required drive torque is performed, the required drive torque changes stepwise. On the other hand, when the temperature condition is the F region, the upper limit torques of the front motor Mf and the rear motor Mr are set to the torques at the time when the F region is reached, and when it is the G region, the upper limit torques of the front motor Mf and the rear motor Mr are set to the limit torques determined according to the temperatures of those motors Mf, Mr. That is, in the F region or the G region of the temperature condition, since the torque of each motor Mf, Mr cannot be increased above the torque at the time when those regions are reached, the drive torque of the vehicle Ve cannot be increased.

[0067] Therefore, in the control example shown in FIG. 8, following step S5, it is determined whether the temperature condition is the F region or the G region (step S6). When it is affirmatively determined in step S6 because the temperature condition is the F region or the G region, the change of the shift range by the downshift operation in the manual range mode is prohibited (step S7), and this routine is terminated. On the contrary, when it is negatively determined in step S6 because the temperature condition is not the F region or the G region, this routine is terminated as it is. In addition to step S7, a signal for notifying the driver that the change of the shift range is prohibited may be output.

[0068] When the temperature of the front motor Mf exceeds the first predetermined temperature T1 or the temperature of the rear motor Mr exceeds the second predetermined temperature T2 as described above, by setting the torque at that time as the upper limit torque of the front motor Mf or the rear motor Mr, it is possible to suppress the temperature of the front motor Mf or the rear motor Mr from rising above the first predetermined temperature T1 or the second predetermined temperature T2, or to reduce the rate of increase in the temperature of the front motor Mf or the rear motor Mr. As a result, it is possible to suppress the temperature of the front motor Mf or the rear motor Mr from reaching the first limit temperature T3 or the second limit temperature T4.

[0069] Also, the torque at the time when the temperature of the front motor Mf exceeds the first predetermined temperature T3 or the temperature of the rear motor Mr exceeds the second predetermined temperature T4 is defined as the upper limit torque of the torque of the front motor Mf or the rear motor Mr. Therefore, when the temperature of either the front motor Mf or the rear motor Mr of the motors Mf (Mr) gradually increases as the required driving torque increases, when the temperature of the front motor Mf exceeds the first predetermined temperature T1 or the temperature of the rear motor Mr exceeds the second predetermined temperature T4, the torque of that motor Mf (Mr) is fixed and the torque of the other motor Mr (Mf) gradually increases. Then, thereafter, when the temperature of the front motor Mf exceeds the first limit temperature T3 or the temperature of the rear motor Mr exceeds the second limit temperature T4, the torque of one motor Mf (Mr) is reduced to the limit torque and the torque of the other motor Mr (Mf) is continuously increased. That is, the torque distribution ratio gradually deviates from the target torque distribution ratio after reaching the first predetermined temperature T1 or the second predetermined temperature T2, and after reaching the first limit temperature T3 or the second limit temperature T4, the rate of change of the deviation amount increases. Therefore, it is possible to suppress a sudden change in the torque distribution ratio and suppress a decrease in running stability.

[0070] In addition, the driving force control device for an electric vehicle in the embodiment of the present invention is not limited to the case where the front motor Mf and the rear motor Mr are heated when the vehicle is traveling in the four-wheel drive mode. For example, when the vehicle is traveling in the two-wheel drive mode with the rear motor Mr as the driving force source and the temperature of the rear motor Mr rises to the second predetermined temperature T2, the torque of the rear motor Mr at that time is set as the upper limit torque. When the required driving torque of the vehicle Ve increases and the required driving torque cannot be output only by the rear motor Mr, the vehicle may be configured to switch to the four-wheel drive mode and output the insufficient torque from the front motor Mf.

[0071] Further, the front motor Mf and the rear motor Mr are heated due to copper loss, iron loss, etc. Even when the regenerative braking torque is output, they are heated in the same manner as when the driving torque is output. Therefore, the driving force control device for an electric vehicle in the embodiment of the present invention may be configured to execute during regenerative braking travel and set the upper limit value of the regenerative torque of the front motor Mf and the rear motor Mr according to the temperature of the front motor Mf and the rear motor Mr.

[0072] Furthermore, the electric vehicle in the embodiment of the present invention is not limited to a vehicle equipped with a motor as the driving force source for the front wheels and a motor as the driving force source for the rear wheels. It may be a so-called hybrid vehicle equipped with a motor as the driving force source for either the front wheels or the rear wheels and an engine as the driving force source for the other wheels. In this case, when the temperature of the motor becomes equal to or higher than the predetermined temperature, the torque at that time is set as the upper limit torque of the motor, and when the required driving torque increases, the insufficient torque may be configured to be output from the engine.

Explanation of Reference Numerals

[0073] 1r, 1l Front wheels 2r, 2l Rear wheels 21 Mode selection switch 22 Shift position sensor 23 Controller 24 Required driving torque calculation unit 25 Temperature region determination unit 26 Upper limit torque setting unit 27 Limit torque setting unit 28 Target torque setting unit Mfr, Mfl, Mrr, Mrl Motors Mf Front motor Mr Rear motor Ve Electric vehicle

Claims

1. A first motor that drives a first drive wheel which is one of a front wheel and a rear wheel, and another drive power source different from the first motor that drives a second drive wheel which is the other of the front wheel and the rear wheel, and a drive force control device for an electric vehicle capable of setting a four-wheel drive running mode in which the vehicle runs by the first motor and the other drive power source, comprising a controller that controls the first motor, wherein the controller, when the temperature of the first motor is equal to or higher than a predetermined first temperature and lower than a predetermined first limit temperature for protecting the first motor, sets the torque at the time when the first predetermined temperature is reached as the upper limit torque of the first motor, an upper limit torque setting unit; when the temperature of the first motor is equal to or higher than the first limit temperature, sets a first limit torque determined according to the temperature of the first motor, which is smaller than the torque set by the upper limit torque setting unit, as the upper limit torque of the first motor, a limit torque setting unit; and is configured by a target torque setting unit that sets the torque of the other drive power source based on the upper limit torque of the first motor, a target torque distribution ratio that is a target value of the ratio of the torque transmitted to the front wheel and the rear wheel, or the drive torque required for the electric vehicle. A drive force control device for an electric vehicle, characterized in that.

2. A drive force control device for an electric vehicle according to Claim 1, wherein the other drive power source includes a second motor, the controller is configured to control the second motor, the upper limit torque setting unit sets the torque at the time when the second predetermined temperature is reached as the upper limit torque of the second motor when the temperature of the second motor is equal to or higher than a predetermined second temperature and lower than a predetermined second limit temperature for protecting the second motor, the target torque setting unit sets the torque at the time when the first predetermined temperature is reached as the upper limit torque of the first motor and the torque at the time when the second predetermined temperature is reached as the upper limit torque of the second motor when the temperature of the first motor is equal to or higher than the first predetermined temperature and lower than the first limit temperature, and the temperature of the second motor is equal to or higher than the second predetermined temperature and lower than the second limit temperature. A drive force control device for an electric vehicle, characterized in that.

3. A drive force control device for an electric vehicle according to Claim 1, wherein the other drive power source includes a second motor, The controller is configured to control the second motor. When the temperature of the second motor is equal to or higher than a second limit temperature predetermined to protect the second motor, the limit torque setting unit sets, as the upper limit torque of the second motor, a second limit torque determined according to the temperature of the second motor. When the temperature of the first motor is equal to or higher than the first limit temperature and the temperature of the second motor is equal to or higher than the second limit temperature, the target torque setting unit sets the first limit torque as the upper limit torque of the first motor and sets the second limit torque as the upper limit torque of the second motor. A driving force control device for an electric vehicle, characterized in that.

4. A driving force control device for an electric vehicle according to claim 1, wherein the other drive power source includes a second motor, the controller is configured to control the second motor, configured to be able to set a manual range mode for determining a required drive torque of the electric vehicle based on a plurality of drive characteristics, equipped with a shift device for changing the drive characteristics in the manual range mode by a driver's shift operation, the controller, when the temperature of the first motor is equal to or higher than the first predetermined temperature and the temperature of the second motor is equal to or higher than a second predetermined temperature lower than the second limit temperature predetermined to protect the second motor, prohibits the change of the drive characteristics in which the required drive torque in the manual range mode increases. A driving force control device for an electric vehicle, characterized in that.

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