vehicle

Abstract

The present disclosure relates to a vehicle capable of suppressing the output power of a front wheel motor or a rear wheel motor from being limited. The vehicle (1) comprises: a front wheel motor (12) for driving a front wheel (10); a rear wheel motor (16) for driving a rear wheel (14); a temperature detection unit (36, 38) for detecting the temperature of the front wheel motor (12) and the temperature of the rear wheel motor (16); and a distribution ratio control unit (50) for reducing the torque of the motor with a relatively high temperature and increasing the torque of the motor with a relatively low temperature when either the temperature of the front wheel motor (12) or the temperature of the rear wheel motor (16) is higher than a second temperature, wherein the second temperature is set to a value lower than a first temperature, and the first temperature is a threshold value for determining whether to limit the output power of the front wheel motor (12) and the rear wheel motor (16).

Description

Technical Field

[0001] The present disclosure relates to a vehicle. Background Art

[0002] There is a technology for controlling the distribution ratio of the torque of a drive device that drives the front wheels and the torque of a drive device that drives the rear wheels (for example, Patent Document 1).

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-178053 Summary of the invention

[0006] The higher the torque allocated to the front wheel motor driving the front wheels and the rear wheel motor driving the rear wheels, the higher the temperature. When the temperature of the front wheel motor and the rear wheel motor becomes too high, the output power is limited to prevent failure. If the output power of any of the front wheel motor and the rear wheel motor is limited, the vehicle is forced to become front wheel drive or rear wheel drive (so-called 2WD). In this case, the vehicle cannot become all-wheel drive (so-called AWD), and the driving efficiency and stability may be reduced.

[0007] Therefore, an object of the present disclosure is to provide a vehicle capable of suppressing the output power of a front wheel motor or a rear wheel motor from being limited.

[0008] In order to solve the above-mentioned problems, the vehicle disclosed in the present invention comprises: a front-wheel motor for driving the front wheels; a rear-wheel motor for driving the rear wheels; a temperature detection unit for detecting the temperature of the front-wheel motor and the temperature of the rear-wheel motor; and a distribution ratio control unit for making the torque of the motor with a relatively higher temperature between the front-wheel motor and the rear-wheel motor low and making the torque of the motor with a relatively lower temperature high when either the temperature of the front-wheel motor or the temperature of the rear-wheel motor is higher than a second temperature, wherein the second temperature is set to a value lower than the first temperature, and the first temperature is a threshold value for whether to limit the output power of the front-wheel motor and the rear-wheel motor.

[0009] In addition, it may be that, when either the temperature of the front wheel motor or the temperature of the rear wheel motor is higher than the second temperature, the distribution ratio control unit derives the distribution ratio of the torque of the front wheel motor to the torque of the rear wheel motor according to the temperature difference ratio of the front wheel side temperature difference to the rear wheel side temperature difference, the front wheel side temperature difference being the difference between the first temperature and the temperature of the front wheel motor, and the rear wheel side temperature difference being the difference between the first temperature and the temperature of the rear wheel motor.

[0010] Alternatively, the distribution ratio control unit may set the time variation of the command value when the pedal receiving the acceleration operation is depressed to be smaller than the time variation of the command value when the pedal is not depressed, and the time variation of the command value is used to control the distribution ratio to become the target value.

[0011] Furthermore, the distribution ratio control unit may make the second temperature different depending on the driving method of the front wheels and the rear wheels.

[0012] Public Effect

[0013] According to the present disclosure, it is possible to suppress the output power of the front wheel motor or the rear wheel motor from being limited. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram showing the structure of a vehicle according to the present embodiment.

[0015] Figure 2 This is a diagram showing an example of the temperature of the front wheel motor and the temperature of the rear wheel motor.

[0016] Figure 3 This is a state transition diagram for explaining the transition of the control state of the distribution ratio in the distribution ratio control unit.

[0017] Figure 4 It is a diagram for explaining the time change of the distribution ratio.

[0018] Figure 5 It is a flowchart explaining the operation flow of the distribution ratio control unit.

[0019] Figure 6 This is a flowchart illustrating the flow of the travel priority control.

[0020] Figure 7 This is a flowchart illustrating the flow of uniform temperature control.

[0021] Figure 8 1 is a flowchart illustrating the flow of output power limit control.

[0022] Fig. 9 It is a flowchart explaining the flow of temporary AWD control.

[0023] Description of Reference Numerals

[0024] 1 vehicle;

[0025] 10 front wheels;

[0026] 12 front wheel motor;

[0027] 14 rear wheels;

[0028] 16 rear wheel motor;

[0029] 36, 38 temperature detection unit;

[0030] 50 Distribution ratio control unit. DETAILED DESCRIPTION

[0031] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present disclosure unless otherwise specifically excluded. In addition, in the present specification and the accompanying drawings, the same reference numerals are marked on the elements having substantially the same functions and structures, and repeated descriptions are omitted. In addition, the elements that are not directly related to the present disclosure are omitted from the drawings.

[0032] Figure 1 A schematic diagram showing the structure of the vehicle 1 according to the present embodiment is shown. Figure 1 In FIG. 1 , the flow of control signals is indicated by dashed arrows. The configuration and processing related to this embodiment are described in detail below, and the configuration and processing not related to this embodiment are omitted.

[0033] The vehicle 1 includes: a front wheel 10, a front wheel motor 12, a rear wheel 14, a rear wheel motor 16, a front differential gear 18, a front drive shaft 20, a rear differential gear 22, a rear drive shaft 24, a battery 26, inverters 28, 32, a central control unit 30, a cooling mechanism 34, temperature detection units 36, 38, a pedaling amount sensor 40 and a drive switching switch 42.

[0034] The vehicle 1 is an electric vehicle that uses a front wheel motor 12 for driving the front wheel 10 and a rear wheel motor 16 for driving the rear wheel 14 as drive sources. The front wheel motor 12 and the rear wheel motor 16 are, for example, permanent magnet synchronous motors, but are not limited thereto and may be induction motors or the like. In addition, the front wheel motor 12 and the rear wheel motor 16 may have different specifications (for example, rated output power, etc.) or the same specifications. In the following, the front wheel motor 12 and the rear wheel motor 16 may be collectively referred to as simply a motor.

[0035] The rotation shaft of the front wheel motor 12 is connected to the front differential gear 18. The front differential gear 18 is connected to the front wheel 10 via the front drive shaft 20. The rotation shaft of the rear wheel motor 16 is connected to the rear differential gear 22. The rear differential gear 22 is connected to the rear wheel 14 via the rear drive shaft 24.

[0036] The battery 26 is a secondary battery such as a lithium-ion battery. The inverter 28 is connected to the battery 26 and the front wheel motor 12. The inverter 28 converts the DC power of the battery 26 into AC power corresponding to the torque command sent from the central control unit 30 and supplies it to the front wheel motor 12. The front wheel motor 12 consumes the AC power supplied by the inverter 28 to drive the rotating shaft. As a result, the front wheel motor 12 drives the front wheel 10 with a torque corresponding to the torque command through the front differential gear 18 and the front drive shaft 20.

[0037] The front wheel motor 12 described above may function as a generator in accordance with the rotation of the front wheel 10 . In this case, the AC power generated by the front wheel motor 12 is converted into DC power by the inverter 28 and regenerated in the battery 26 .

[0038] The inverter 32 is connected to the battery 26 and the rear wheel motor 16. The inverter 32 converts the DC power of the battery 26 into AC power corresponding to the torque command sent from the central control unit 30 and supplies it to the rear wheel motor 16. The rear wheel motor 16 consumes the AC power supplied by the inverter 32 to drive the rotating shaft. As a result, the rear wheel motor 16 drives the rear wheel 14 with a torque corresponding to the torque command through the rear differential gear 22 and the rear drive shaft 24.

[0039] The rear wheel motor 16 described above can function as a generator in accordance with the rotation of the rear wheel 14 . In this case, the AC power generated by the rear wheel motor 16 is converted into DC power by the inverter 32 and regenerated in the battery 26 .

[0040] The cooling mechanism 34 includes a cooling pump (not shown) and a heat exchanger (not shown) driven by consuming the power of the battery 26. The cooling pump circulates cooling water between the front wheel motor 12 and the heat exchanger and between the rear wheel motor 16 and the heat exchanger. As a result, the cooling mechanism 34 cools the front wheel motor 12 and the rear wheel motor 16.

[0041] The temperature detection unit 36 ​​detects the temperature of the front wheel motor 12 (hereinafter, sometimes referred to as the front wheel motor temperature), and the temperature detection unit 38 detects the temperature of the rear wheel motor 16 (hereinafter, sometimes referred to as the rear wheel motor temperature). The temperature detection units 36 and 38 may be provided inside the motor housing or on the outer side of the motor housing.

[0042] The depression amount sensor 40 detects the depression amount of a pedal (accelerator pedal) (not shown) that receives the acceleration operation of the driver. In other words, the depression amount sensor 40 detects the acceleration operation of the driver.

[0043] The drive switch 42 receives a driver's operation to switch the drive method (hereinafter sometimes referred to as a drive mode) of the front wheels 10 and the rear wheels 14. Specifically, the drive switch 42 receives a switch operation between a power consumption priority drive mode and a normal all-wheel drive mode.

[0044] In the power consumption priority driving mode, the front wheels 10 and the rear wheels 14 are driven and controlled so that the power consumption (efficiency with respect to the power consumption of the battery 26) becomes high. In the power consumption priority driving mode, for example, the driving control is such that during acceleration, the torque of the rear wheels 14 is made larger than that of the front wheels 10, and during high-speed driving, the torque of the front wheels 10 is made larger than that of the rear wheels 14. In this way, in the power consumption priority driving mode, the torque distribution to the front wheels 10 and the rear wheels 14 is controlled in detail according to the current driving mode (for example, acceleration, constant speed, deceleration, turning, etc.), so that the vehicle 1 can travel efficiently.

[0045] In the normal all-wheel drive mode, the drive control is such that the torque is distributed approximately equally to the front wheels 10 and the rear wheels 14 regardless of the current driving mode. Thus, in the normal all-wheel drive mode, the vehicle 1 can be driven stably. In the following, all-wheel drive that drives all the front wheels 10 and the rear wheels 14 is sometimes expressed as AWD.

[0046] In the normal all-wheel drive mode, all-wheel drive (AWD) is always used, but in the power consumption priority drive mode, all-wheel drive (AWD) may be used, and front-wheel drive or rear-wheel drive (so-called 2WD) may be used.

[0047] The central control unit 30 is composed of a semiconductor integrated circuit including a central processing unit (CPU), a ROM (read only memory) storing programs, a RAM (random access memory) used as a work area, etc. The central control unit 30 functions as the distribution ratio control unit 50 by executing the programs.

[0048] The distribution ratio control unit 50 derives a required torque (hereinafter, sometimes simply referred to as torque) required by the vehicle 1 based on the pedaling amount acquired from the pedaling amount sensor 40. The distribution ratio control unit 50 distributes the derived required torque into a torque borne by the front wheel motor 12 and a torque borne by the rear wheel motor 16. In other words, the distribution ratio control unit 50 distributes the required torque between the front wheel motor 12 and the rear wheel motor 16 in proportion.

[0049] The distribution ratio control unit 50 controls the distribution ratio of the torque between the front wheel motor 12 and the rear wheel motor 16 , that is, the torque distribution ratio (hereinafter, sometimes simply referred to as the distribution ratio).

[0050] The distribution ratio control unit 50 basically controls the distribution ratio of the torque in a manner that gives priority to the running of the vehicle 1. For example, when the drive switching switch 42 is set to the power consumption priority driving mode, the distribution ratio control unit 50 controls the distribution ratio by giving priority to running the vehicle 1 in a manner that increases the power consumption. In addition, when the drive switching switch 42 is set to the normal all-wheel drive mode, the distribution ratio control unit 50 controls the distribution ratio by giving priority to stable running of the vehicle 1. Hereinafter, the distribution ratio control that gives priority to the running of the vehicle 1 is sometimes referred to as running priority control.

[0051] In addition, here, an example of setting the drive mode by the drive switching switch 42 is given, but the setting of the drive mode is not limited to the method performed by the drive switching switch 42. For example, the distribution ratio control unit 50 may also set the drive mode (power consumption priority drive mode or normal all-wheel drive mode) in consideration of the driving mode, the SOC (State Of Charge) of the battery 26, and the like.

[0052] Here, to increase the torque of the motor, a larger amount of current (q-axis current Iq) that contributes to the torque must flow to the motor. Therefore, as the torque of the motor increases (that is, as more torque is distributed), the temperature of the motor gradually increases.

[0053] In addition, if the torque distribution ratio is controlled by giving priority to the driving of the vehicle 1, there is a situation where the torque of one of the motors is high and continues to be high. For example, if the vehicle is driven at high speed for a long time in the power consumption priority driving mode, there is a situation where the torque of the rear wheel motor 16 is low and the torque of the front wheel motor 12 is high and continues to be high. In this case, there is a situation where the temperature of the front wheel motor 12 with relatively high torque becomes relatively higher than the temperature of the rear wheel motor 16 with relatively low torque. That is, in the vehicle 1, a bias occurs between the temperature of the front wheel motor 12 and the temperature of the rear wheel motor 16, and the temperature of either motor may become too high.

[0054] If the temperature of the motor becomes too high, the motor may fail. Therefore, when the temperature of the motor becomes too high, the driving of the motor is stopped, and only the motor whose temperature is not too high is used to drive the vehicle 1. In this case, the vehicle 1 cannot be driven by both the front wheels 10 and the rear wheels 14, and the efficiency and stability of the vehicle 1 may be reduced.

[0055] Therefore, the distribution ratio control unit 50 controls the distribution ratio according to the temperature of the motors before the temperature of the motors becomes too high so as to suppress the temperature deviation of the front wheel motors 12 and the rear wheel motors 16. Hereinafter, the control of the distribution ratio in a manner of suppressing the temperature deviation of the front wheel motors 12 and the rear wheel motors 16 is sometimes referred to as temperature control.

[0056] Figure 2: is a diagram showing an example of the temperature of the front wheel motor 12 and the temperature of the rear wheel motor 16. Figure 2 In FIG. 6 , the upper limit temperature is indicated by a solid line 60 , the first temperature is indicated by a dashed line 62 , and the second temperature is indicated by a dashed double-dashed line 64 .

[0057] The upper limit temperature indicated by a solid line 60 is the upper limit value of the temperature at which the motor can be driven without limiting the output power. The upper limit temperature is, for example, the rated temperature of the motor and is determined by the specifications of the motor.

[0058] The first temperature indicated by the single-dot chain line 62 is set to a value lower than the upper limit temperature. The first temperature is a threshold value for determining whether to actually limit the output power of the front wheel motor 12 and the rear wheel motor 16. Although described in detail later, when the temperature of the motor is higher than the first temperature, the output power of the motor having the temperature higher than the first temperature is limited.

[0059] The second temperature indicated by the double-dashed line 64 is set to a value lower than the first temperature. The second temperature is a threshold value for determining whether to perform the driving priority control or the average temperature control. Although described in detail later, when the temperature of the motor is below the second temperature, the driving priority control is performed, and when the temperature of the motor is higher than the second temperature, the average temperature control is performed. That is, in order to shift from the driving priority control to the average temperature control before reaching the first temperature at which the output power of the motor is limited, the second temperature is set to be lower than the first temperature.

[0060] In addition, Figure 2 In FIG. 1 , a case is exemplified in which the temperature of the front-wheel motor 12 is higher than the second temperature and is equal to or lower than the first temperature, and the temperature of the rear-wheel motor 16 is equal to or lower than the second temperature.

[0061] In addition, Figure 2 In the example, the upper limit temperature, the first temperature, and the second temperature are equal in the front wheel motor 12 and the rear wheel motor 16 , but the upper limit temperature, the first temperature, and the second temperature may be different in the front wheel motor 12 and the rear wheel motor 16 .

[0062] When both the front wheel motor temperature and the rear wheel motor temperature are equal to or lower than the second temperature, the distribution ratio control unit 50 performs the running priority control corresponding to the set electric power consumption priority drive mode or the normal all-wheel drive mode.

[0063] In addition, when at least one of the front wheel motor temperature and the rear wheel motor temperature is higher than the second temperature, the distribution ratio control unit 50 performs the temperature control. Figure 2 In the embodiment, the front wheel motor temperature is higher than the second temperature, so the temperature uniformity control is performed.

[0064] Under the uniform temperature control, the distribution ratio control unit 50 makes the torque of the motor with a relatively high temperature, among the front wheel motor 12 and the rear wheel motor 16, low, and makes the torque of the motor with a relatively low temperature high. Figure 2 As shown, when the front wheel motor temperature is higher than the rear wheel motor temperature, the distribution ratio control unit 50 controls the distribution ratio so that the torque of the front wheel motor 12 becomes relatively low and the torque of the rear wheel motor 16 becomes relatively high.

[0065] More specifically, under the uniform temperature control, the distribution ratio control unit 50 derives the front wheel side temperature difference (ΔT1) which is the difference between the first temperature and the temperature of the front wheel motor 12, and the rear wheel side temperature difference (ΔT2) which is the difference between the first temperature and the temperature of the rear wheel motor 16. The distribution ratio control unit 50 derives the temperature difference ratio (for example, ΔT1 / ΔT2) which is the ratio of the front wheel side temperature difference (ΔT1) to the rear wheel side temperature difference (ΔT2). The distribution ratio control unit 50 derives the distribution ratio (for example, TQf / TQr) of the torque (TQf) of the front wheel motor 12 and the torque (TQr) of the rear wheel motor 16 according to the derived temperature difference ratio. For example, if the temperature difference ratio between the temperature difference on the front wheel side (ΔT1) and the temperature difference on the rear wheel side (ΔT2) is 1 to 5 (ΔT1 / ΔT2=1 / 5), the distribution ratio control unit 50 sets the distribution ratio of the torque (TQf) of the front wheel motor 12 and the torque (TQr) of the rear wheel motor 16 to 1 to 5 (TQf / TQr=1 / 5).

[0066] As a result, the temperature of the rear wheel motor tends to rise due to the increase in torque, but the temperature of the front wheel motor is suppressed from rising due to the decrease in torque. Furthermore, the temperature of the front wheel motor 12 is gradually reduced by cooling the cooling mechanism 34. As a result, the distribution ratio control unit 50 can return the temperature of the front wheel motor to below the second temperature, thereby making the temperature of the front wheel motor and the temperature of the rear wheel motor approximately equal.

[0067] In addition, although the example of the temperature difference ratio being the same as the distribution ratio (1 to 5) is given, the specific value of the distribution ratio is not limited to the same value as the temperature difference ratio. At least, the magnitude relationship between the temperature difference on the front wheel side and the temperature difference on the rear wheel side is the same as the magnitude relationship between the torque of the front wheel motor 12 and the torque of the rear wheel motor 16. For example, when the temperature difference on the rear wheel side is large, such as the temperature difference ratio between the temperature difference on the front wheel side and the temperature difference on the rear wheel side is 1 to 5, the distribution ratio of the torque of the front wheel motor 12 and the torque of the rear wheel motor 16 is, for example, 1 to 2, 2 to 3, etc., as long as the torque of the rear wheel motor 16 is large.

[0068] In addition, the allocation ratio control unit 50 can make the second temperature different in the power consumption priority drive mode or the normal all-wheel drive mode. For example, when the normal all-wheel drive mode is set, the torque is always distributed to the front wheel motor 12 and the rear wheel motor 16, so the bias between the front wheel motor temperature and the rear wheel motor temperature tends to become relatively small. Therefore, in the case of the normal all-wheel drive mode, the allocation ratio control unit 50 can set the second temperature to be relatively low. In addition, when the power consumption priority drive mode is set, there is also a situation where the torque is distributed to only one of the front wheel motor 12 and the rear wheel motor 16, so the bias between the front wheel motor temperature and the rear wheel motor temperature tends to become relatively large. Therefore, in the case of the power consumption priority drive mode, the allocation ratio control unit 50 can set the second temperature to be relatively high.

[0069] In this way, the distribution ratio control unit 50 can make the second temperature different according to the driving mode of the front wheel 10 and the rear wheel 14 (i.e., the type of driving mode such as the power consumption priority driving mode or the normal all-wheel drive mode). If the second temperature is set to a fixed value, the driving priority control and the temperature control are frequently switched according to the driving mode, which may cause discomfort to the driver or increase the processing load. In the vehicle 1, by making the second temperature different according to the driving mode, it is possible to suppress the increase of the processing load or the discomfort to the driver.

[0070] Furthermore, when at least one of the front wheel motor temperature and the rear wheel motor temperature is higher than the first temperature, the allocation ratio control unit 50 performs output power limiting control for limiting the output power of the motor.

[0071] When the front wheel motor temperature is higher than the first temperature, the distribution ratio control unit 50 sets the torque of the front wheel motor 12 to zero under the output power limit control, and drives the vehicle 1 only with the rear wheel motor 16. When the temperature of the rear wheel motor 16 is higher than the first temperature, the distribution ratio control unit 50 sets the torque of the rear wheel motor 16 to zero under the output power limit control, and drives the vehicle 1 only with the front wheel motor 12. That is, under the output power limit control, the all-wheel drive is stopped and the front wheel drive or the rear wheel drive is performed.

[0072] Thus, by limiting the output of the motor with a high temperature (specifically, setting the torque to zero), the temperature rise of the motor with limited output can be suppressed. Furthermore, the motor with limited output is cooled by the cooling mechanism 34, so that the temperature can be returned to below the first temperature.

[0073] Thus, in the vehicle 1, the failure of the motor whose temperature rises can be prevented beforehand by the output power limit control. In addition, the distribution ratio control unit 50 performs the output power limit control at the time when the temperature of the motor exceeds the first temperature before the temperature of the motor exceeds the upper limit temperature. Therefore, in the vehicle 1, the failure of the motor can be prevented more reliably.

[0074] In addition, even if the temperature of the motor is higher than the first temperature, as long as the temperature of the motor is below the upper limit temperature, the motor can be driven from the perspective of the motor specification. Therefore, even if the output power limit control is performed, when the temperature of the motor is below the upper limit temperature and all-wheel drive (AWD) is temporarily required, the distribution ratio control unit 50 stops the output power limit control and controls the distribution ratio to temporarily achieve all-wheel drive. Hereinafter, controlling the distribution ratio to temporarily achieve all-wheel drive is sometimes referred to as temporary AWD control.

[0075] The so-called temporary need for all-wheel drive is, for example, the occurrence of slip. For example, when the left-right speed difference between any one of the front wheel 10 and the rear wheel 14 is greater than a predetermined speed difference, it is considered that slip has occurred, and the distribution ratio control unit 50 determines that all-wheel drive is temporarily required. For example, in a state where the output power of the front wheel motor 12 is limited to achieve rear-wheel drive, when the rear wheel 14 slips, the distribution ratio control unit 50 relatively reduces the torque of the rear wheel motor 16 and increases the torque of the front wheel motor 12 from zero, thereby temporarily achieving all-wheel drive.

[0076] Thus, in the vehicle 1, by allowing temporary all-wheel drive, unexpected situations can be dealt with, thereby preventing accidents, etc. In other words, in the vehicle 1, by setting the first temperature to be lower than the upper limit temperature, such temporary AWD control can be performed, thereby enabling the vehicle 1 to be controlled more flexibly.

[0077] Figure 3 1 is a state transition diagram for explaining the transition of the control state of the distribution ratio in the distribution ratio control unit 50. The distribution ratio control unit 50 transitions the control states of the above-mentioned running priority control, temperature equalization control, output power limitation control, and temporary AWD control according to the temperature of the motor.

[0078] When the front wheel motor temperature is lower than the second temperature and the rear wheel motor temperature is lower than the second temperature, the allocation ratio control unit 50 enters the driving priority control state. In the driving priority control state, if at least one of the front wheel motor temperature and the rear wheel motor temperature is higher than the second temperature, the allocation ratio control unit 50 changes from the driving priority control to the uniform temperature control state. In addition, in the uniform temperature control state, if at least one of the front wheel motor temperature and the rear wheel motor temperature is higher than the first temperature, the allocation ratio control unit 50 changes from the uniform temperature control to the output power limit control state. In addition, in the output power limit control state, if the front wheel motor temperature is lower than the upper limit temperature and the rear wheel motor temperature is lower than the upper limit temperature, and AWD is temporarily required, the allocation ratio control unit 50 changes from the output power limit control to the temporary AWD control state.

[0079] In addition, in the state of temporary AWD control, if the front wheel motor temperature is higher than the upper limit temperature, or the rear wheel motor temperature is higher than the upper limit temperature, or temporary AWD is not required, the distribution ratio control unit 50 changes from the temporary AWD control to the output power limit control state. In addition, in the state of output power limit control, if the front wheel motor temperature is lower than the first temperature and the rear wheel motor temperature is lower than the first temperature, the distribution ratio control unit 50 changes from the output power limit control to the uniform temperature control state. In addition, if the front wheel motor temperature is lower than the second temperature and the rear wheel motor temperature is lower than the second temperature from the uniform temperature control state, the distribution ratio control unit 50 changes from the uniform temperature control to the driving priority control state.

[0080] Here, when the driving priority control is changed to the temperature control and when the temperature control is changed to the driving priority control, the target value of the torque distribution ratio changes abruptly. If the actual torque distribution ratio changes abruptly according to the target value when the driver steps on the accelerator pedal, the behavior of the vehicle 1 is disturbed, which may cause discomfort to the driver. For example, when accelerating in a state where the torque of the rear wheel motor 16 is distributed more, if the torque of the rear wheel motor 16 is suddenly reduced when the vehicle is changed to the temperature control, the driver may feel uncomfortable as if the vehicle suddenly stalls.

[0081] Therefore, when the control state is switched between the travel priority control and the temperature equalization control, if the pedal (accelerator pedal) receiving the acceleration operation is depressed, the distribution ratio control unit 50 suppresses the time variation of the actual torque distribution ratio from becoming larger.

[0082] Figure 4 is a graph illustrating the time variation of the distribution ratio. Figure 4 In FIG. 1 , a single-dot chain line 70 indicates a target value of the distribution ratio, and a solid line 72 indicates a command value of the distribution ratio for controlling the distribution ratio to the target value. Figure 4In FIG. 1 , the distribution ratio is expressed by the ratio of the torque of the rear wheel motor 16 to the total torque of the torque of the front wheel motor 12 and the torque of the rear wheel motor 16 . That is, Figure 4 The lower area of ​​the dashed line 70 or the solid line 72 represents the ratio of the torque of the rear wheel motor 16, and the upper area represents the ratio of the torque of the front wheel motor 12. In addition, the throttle-on indicates that the accelerator pedal is depressed (the depression amount is greater than zero), and the throttle-off indicates that the accelerator pedal is not depressed (the depression amount is zero).

[0083] like Figure 4 As shown, for example, the accelerator is on during the period from time T0 to time T1, and the torque of the front wheel motor 12 is higher than the torque of the rear wheel motor 16. During this period, the command value of the distribution ratio is approximately consistent with the target value of the distribution ratio. Moreover, at time T1, the temperature of the front wheel motor is higher than the second temperature, and the distribution ratio control unit 50 is set to switch from the driving priority control to the uniform temperature control.

[0084] In this case, the distribution ratio control unit 50 derives a target value of the distribution ratio such that the torque of the front wheel motor 12 is low and the torque of the rear wheel motor 16 is high, as indicated by the dashed line 70, according to the front wheel side temperature difference and the rear wheel side temperature difference. In this case, the target value of the distribution ratio changes rapidly around time T1, as indicated by the dashed line 70.

[0085] However, at time T1, the accelerator is on, so the distribution ratio control unit 50 makes the time change of the command value of the distribution ratio small. Specifically, the distribution ratio control unit 50 changes the command value of the distribution ratio slowly (for example, about 2% to 3% per second) toward the target value from time T1 to time T2 when the accelerator is continuously on.

[0086] After the accelerator is turned off at time T2, the distribution ratio control unit 50 changes the distribution ratio command value toward the target value quickly (for example, about 10% per second). As shown between time T2 and time T3, the distribution ratio command value becomes approximately equal to the target value.

[0087] In addition, at time T3, the accelerator is turned on. In addition, at time T4, both the front wheel motor temperature and the rear wheel motor temperature become below the second temperature, and the distribution ratio control unit 50 changes from the average temperature control to the driving priority control. In addition, just before reaching time T4, the torque of the rear wheel motor 16 is higher than the torque of the front wheel motor 12. In addition, at time T4, the distribution ratio control unit 50 derives a target value of the distribution ratio such that the torque of the rear wheel motor 16 is low and the torque of the front wheel motor 12 is high in the power consumption priority driving mode. In this case, around time T4, the target value of the distribution ratio changes sharply as shown by the single-dot chain line 70.

[0088] However, at time T4, the accelerator is on, so the distribution ratio control unit 50 makes the time change of the command value of the distribution ratio small. Specifically, the distribution ratio control unit 50 changes the command value of the distribution ratio slowly (for example, about 2% to 3% per second) toward the target value from time T4 to time T5 when the accelerator is continuously on.

[0089] After the accelerator is turned off at time T5, the distribution ratio control unit 50 changes the distribution ratio command value toward the target value quickly (for example, about 10% per second). As shown in the period from time T5 to time T6, the distribution ratio command value becomes approximately equal to the target value.

[0090] In this way, the distribution ratio control unit 50 makes the time change amount of the distribution ratio command value when the accelerator pedal (pedal receiving the acceleration operation) is depressed smaller than the time change amount of the distribution ratio command value when the accelerator pedal is not depressed.

[0091] As a result, in the vehicle 1, the time variation of the torque distribution ratio during the period of torque application becomes small, and it is possible to suppress abrupt changes in the behavior of the vehicle 1. As a result, in the vehicle 1, when the accelerator pedal is depressed, even if the control state changes between the travel priority control and the temperature equalization control, it is possible to avoid causing discomfort to the driver.

[0092] Figure 5 1 is a flowchart for explaining the operation flow of the distribution ratio control unit 50. The distribution ratio control unit 50 repeatedly performs embedded control in a predetermined control cycle. Figure 5 A series of processing.

[0093] When the start time of the embedded control is reached, the allocation ratio control unit 50 determines whether the power consumption priority driving mode is selected by the drive switching switch 42 (S100). When the power consumption priority driving mode is selected by the drive switching switch 42 ("Yes" in S100), the allocation ratio control unit 50 sets the driving mode to the power consumption priority driving mode (S110) and enters the process of step S130.

[0094] When the power consumption priority drive mode is not selected by the drive changeover switch 42 (ie, the normal all-wheel drive mode is selected) (No in S100), the distribution ratio control unit 50 sets the drive mode to the normal all-wheel drive mode (S120) and proceeds to step S130.

[0095] After the drive mode is set (S110, S120), the allocation ratio control unit 50 sets the second temperature according to the type of the set drive mode (S130). Specifically, the allocation ratio control unit 50 sets the second temperature relatively high when the power consumption priority drive mode is set, and sets the second temperature relatively low when the normal all-wheel drive mode is set.

[0096] Next, the distribution ratio control unit 50 acquires the front wheel motor temperature from the temperature detection unit 36 ​​and acquires the rear wheel motor temperature from the temperature detection unit 38 (S140). That is, the distribution ratio control unit 50 acquires the motor temperature from the temperature detection unit.

[0097] Next, the distribution ratio control unit 50 determines whether the acquired front wheel motor temperature is equal to or lower than the first temperature (S150). If the front wheel motor temperature is not equal to or lower than the first temperature (No in S150), the distribution ratio control unit 50 proceeds to step S210.

[0098] When the front wheel motor temperature is lower than the first temperature (Yes in S150), the distribution ratio control unit 50 determines whether the rear wheel motor temperature is lower than the first temperature (S160). When the rear wheel motor temperature is not lower than the first temperature (No in S160), the distribution ratio control unit 50 proceeds to step S210.

[0099] When the rear wheel motor temperature is lower than the first temperature ("Yes" in S160), the distribution ratio control unit 50 proceeds to the process of step S170. That is, when both the front wheel motor temperature and the rear wheel motor temperature are lower than the first temperature, the distribution ratio control unit 50 proceeds to the process of step S170, and when at least one of the front wheel motor temperature and the rear wheel motor temperature is higher than the first temperature, the distribution ratio control unit 50 proceeds to the process of step S210.

[0100] In step S170, the distribution ratio control unit 50 determines whether the front wheel motor temperature is lower than the second temperature (S170). If the front wheel motor temperature is lower than the second temperature (Yes in S170), the distribution ratio control unit 50 determines whether the rear wheel motor temperature is lower than the second temperature (S180).

[0101] When the rear wheel motor temperature is lower than the second temperature (Yes in S180), the distribution ratio control unit 50 performs the running priority control corresponding to the power consumption priority drive mode or the normal all-wheel drive mode (S190), and ends the series of processing. The flow of the running priority control will be described later.

[0102] When the front wheel motor temperature is not lower than the second temperature (No in S170), or when the rear wheel motor temperature is not lower than the second temperature (No in S180), the distribution ratio control unit 50 performs temperature control corresponding to the temperature of the motor (S200), and ends a series of processing. The flow of temperature control will be described later.

[0103] In addition, in step S210, the allocation ratio control unit 50 determines whether the temperature of the front wheel motor is higher than the upper limit temperature (S210). When the temperature of the front wheel motor is not higher than the upper limit temperature ("No" in S210), the allocation ratio control unit 50 determines whether the temperature of the rear wheel motor is higher than the upper limit temperature (S220). When the temperature of the rear wheel motor is not higher than the upper limit temperature ("No" in S220), the allocation ratio control unit 50 determines whether it is necessary to temporarily set it to all-wheel drive (AWD) (S230). For example, when the speed difference between the left and right wheels is greater than a predetermined speed difference, it is considered to be slipping, and the allocation ratio control unit 50 determines that it is necessary to temporarily set it to all-wheel drive.

[0104] When the front wheel motor temperature is higher than the upper limit temperature ("Yes" in S210), when the rear wheel motor temperature is higher than the upper limit temperature ("Yes" in S220), or when it is not necessary to temporarily set to all-wheel drive ("No" in S230), the distribution ratio control unit 50 performs output power limitation control (S240), and ends a series of processing. The flow of output power limitation control will be described later.

[0105] If temporary all-wheel drive is required (YES in S230 ), the distribution ratio control unit 50 performs temporary AWD control ( S250 ) and ends a series of processing. The flow of the temporary AWD control will be described later.

[0106] Figure 6 1 is a flowchart for explaining the flow of the driving priority control. The distribution ratio control unit 50 first acquires the depression amount of the accelerator pedal from the depression amount sensor 40 (S300). Next, the distribution ratio control unit 50 derives the required torque based on the acquired depression amount (S310).

[0107] Next, the distribution ratio control unit 50 derives a target value of the torque distribution ratio according to the current driving mode (power consumption priority driving mode or normal all-wheel drive mode) (S320). For example, when the current driving mode is the power consumption priority driving mode, the distribution ratio control unit 50 derives a target value of the distribution ratio that increases power consumption based on the current driving mode and the power consumption of each motor.

[0108] Next, the distribution ratio control unit 50 derives the command value of the distribution ratio based on the target value of the distribution ratio (S330). At this time, when the pedaling amount continues to be non-zero from the point when the control state changes from the temperature control to the driving priority control, the distribution ratio control unit 50 derives the current command value of the distribution ratio in a manner that reduces the change in the command value.

[0109] Next, the distribution ratio control unit 50 derives a torque command value for the front wheel motor 12 and a torque command value for the rear wheel motor 16 based on the command value of the distribution ratio and the required torque ( S340 ).

[0110] Next, the distribution ratio control unit 50 sends the torque command value for the front wheel motor 12 to the inverter 28 and sends the torque command value for the rear wheel motor 16 to the inverter 32 ( S350 ), and ends the series of processing.

[0111] Figure 7 1 is a flowchart for explaining the flow of the uniform temperature control. The distribution ratio control unit 50 first obtains the depression amount of the accelerator pedal from the depression amount sensor 40 (S400). Next, the distribution ratio control unit 50 derives the required torque based on the obtained depression amount (S410).

[0112] Next, the distribution ratio control unit 50 derives the front wheel side temperature difference based on the front wheel motor temperature and the first temperature (S420), and derives the rear wheel side temperature difference based on the rear wheel motor temperature and the first temperature (S430). Next, the distribution ratio control unit 50 derives the temperature difference ratio based on the front wheel side temperature difference and the rear wheel side temperature difference (S440).

[0113] Next, the distribution ratio control unit 50 derives a target value of the torque distribution ratio based on the temperature difference ratio (S450). For example, the distribution ratio control unit 50 derives a target value of the distribution ratio in which the torque of the wheel with a relatively large temperature difference between the front wheel 10 and the rear wheel 14 is relatively high and the torque of the wheel with a relatively small temperature difference is relatively low.

[0114] Next, the distribution ratio control unit 50 derives the command value of the distribution ratio based on the target value of the distribution ratio (S460). At this time, when the pedaling amount continues to be non-zero from the point when the control state changes from the driving priority control to the uniform temperature control, the distribution ratio control unit 50 derives the current command value of the distribution ratio in a manner that minimizes the change in the command value.

[0115] Next, the distribution ratio control unit 50 derives a torque command value for the front wheel motor 12 and a torque command value for the rear wheel motor based on the command value of the distribution ratio and the required torque ( S470 ).

[0116] Next, the distribution ratio control unit 50 sends the torque command value for the front wheel motor 12 to the inverter 28 and sends the torque command value for the rear wheel motor 16 to the inverter 32 ( S480 ), and ends the series of processing.

[0117] Figure 8 1 is a flowchart for explaining the flow of the output power limitation control. The distribution ratio control unit 50 first obtains the depression amount of the accelerator pedal from the depression amount sensor 40 (S500). Next, the distribution ratio control unit 50 derives the required torque based on the obtained depression amount (S510).

[0118] Next, the allocation ratio control unit 50 determines whether the front wheel motor 12 is output-limited among the front wheel motor 12 and the rear wheel motor 16 (S520). That is, when the temperature of the front wheel motor is higher than the first temperature ( Figure 5 The output power limit control ( Figure 5 In the case of S240 of FIG. 1 , the distribution ratio control unit 50 determines that the front wheel motor 12 is output-limited. In addition, when the rear wheel motor temperature is higher than the first temperature ( Figure 5 The output power limit control ( Figure 5 In the case of S240), the distribution ratio control unit 50 determines that the rear wheel motor 16 becomes output-power-limited.

[0119] When it is determined that the front wheel motor 12 is output-power-limited (Yes in S520), the distribution ratio control unit 50 sets the torque command value of the front wheel motor 12 to zero (S530), and sets the torque command value of the rear wheel motor 16 to the value of the required torque (S540). Furthermore, the distribution ratio control unit 50 sends the torque command value indicating zero to the inverter 28 on the front wheel motor 12 side, and sends the torque command value indicating the required torque to the inverter 32 on the rear wheel motor 16 side (S570), and ends a series of processing.

[0120] When it is determined that the front wheel motor 12 is not output-limited (No in S520), the rear wheel motor 16 is deemed to be output-limited, and the distribution ratio control unit 50 sets the torque command value of the rear wheel motor 16 to zero (S550) and sets the torque command value of the front wheel motor 12 to the value of the required torque (S560). Furthermore, the distribution ratio control unit 50 sends the torque command value indicating the required torque to the inverter 28 on the front wheel motor 12 side, and sends the torque command value indicating zero to the inverter 32 on the rear wheel motor 16 side (S570), and ends a series of processing.

[0121] Fig. 9 2 is a flowchart for explaining the flow of temporary AWD control. In the temporary AWD control, basically, the same flow of processing as that of the driving priority control is performed.

[0122] Specifically, the distribution ratio control unit 50 obtains the amount of depression of the accelerator pedal from the depression amount sensor 40 (S600), and derives the required torque based on the obtained depression amount (S610). Next, the distribution ratio control unit 50 derives the target value of the torque distribution ratio based on the state of the vehicle 1 that requires AWD, such as slipping (S620). Next, the distribution ratio control unit 50 derives the command value of the distribution ratio based on the target value of the distribution ratio (S630). Next, the distribution ratio control unit 50 derives the torque command value for the front wheel motor 12 and the torque command value for the rear wheel motor 16 based on the command value of the distribution ratio and the required torque (S640). Next, the distribution ratio control unit 50 sends the torque command value for the front wheel motor 12 to the inverter 28, and sends the torque command value for the rear wheel motor 16 to the inverter 32 (S650), and ends a series of processing.

[0123] As described above, the distribution ratio control unit 50 of the vehicle 1 of the present embodiment makes the torque of the motor with relatively higher temperature among the front wheel motor 12 and the rear wheel motor 16 low, and makes the torque of the motor with relatively lower temperature high, when either the front wheel motor temperature or the rear wheel motor temperature becomes higher than the second temperature, wherein the second temperature is set to a value lower than the first temperature, and the first temperature is a threshold value for whether to limit the output power of the front wheel motor 12 and the rear wheel motor 16.

[0124] Specifically, when either the temperature of the front wheel motor 12 or the temperature of the rear wheel motor 16 is higher than the second temperature, the distribution ratio control unit 50 derives the distribution ratio of the torque of the front wheel motor 12 to the torque of the rear wheel motor 16 according to the temperature difference ratio of the front wheel side temperature difference to the rear wheel side temperature difference, wherein the front wheel side temperature difference is the difference between the first temperature and the temperature of the front wheel motor 12, and the rear wheel side temperature difference is the difference between the first temperature and the temperature of the rear wheel motor 16.

[0125] Thus, in the vehicle 1 of the present embodiment, the temperature rise of the relatively high-temperature motor can be suppressed before the output power of the front wheel motor 12 or the rear wheel motor 16 is limited. In the vehicle 1 of the present embodiment, by suppressing the temperature rise of the relatively high-temperature motor, the time for the temperature of the motor to reach the first temperature or the upper limit temperature can be prolonged.

[0126] Therefore, according to the vehicle 1 of the present embodiment, it is possible to suppress the output power of the front wheel motor 12 or the rear wheel motor 16 from being limited. As a result, in the vehicle 1 of the present embodiment, it is possible to suppress the vehicle 1 from being forced to be front wheel drive or rear wheel drive (2WD).

[0127] In addition, in the present embodiment, an example is given in which the first temperature is set to be lower than the upper limit temperature. However, when the temporary AWD control is omitted, the distribution ratio control unit 50 may also set the first temperature to the upper limit temperature. In this manner, the output power of the front wheel motor 12 or the rear wheel motor 16 can also be suppressed from being limited.

[0128] The above, while referring to the attached Figure 1 Although the embodiments of the present disclosure are described, it is self-evident that the present disclosure is not limited to the embodiments. For those skilled in the art, it is obvious that various changes or modifications can be thought of within the scope of the claims, and it should be understood that these also naturally belong to the technical scope of the present disclosure.

Claims

1. A vehicle, wherein: have: Front wheel motor, driving the front wheel; A rear wheel motor drives the rear wheel; a temperature detection unit that detects the temperature of the front wheel motor and the temperature of the rear wheel motor; and The distribution ratio control unit is configured to lower the torque of the motor with a relatively higher temperature among the front wheel motor and the rear wheel motor and to increase the torque of the motor with a relatively lower temperature when either the temperature of the front wheel motor or the rear wheel motor is higher than a second temperature, wherein the second temperature is set to a value lower than a first temperature, and the first temperature is a threshold value for determining whether to limit the output power of the front wheel motor and the rear wheel motor. When either the temperature of the front wheel motor or the temperature of the rear wheel motor is higher than the second temperature, the distribution ratio control unit controls the distribution ratio of the torque of the front wheel motor to the torque of the rear wheel motor according to the temperature difference ratio of the front wheel side temperature difference to the rear wheel side temperature difference, the front wheel side temperature difference being the difference between the first temperature and the temperature of the front wheel motor, and the rear wheel side temperature difference being the difference between the first temperature and the temperature of the rear wheel motor.

2. The vehicle according to claim 1, wherein: The distribution ratio control unit sets the time variation of the command value when the pedal receiving the acceleration operation is stepped on to be smaller than the time variation of the command value when the pedal is not stepped on. The time variation of the command value is used to control the distribution ratio to a target value.

3. The vehicle according to claim 1 or 2, wherein: The distribution ratio control unit makes the second temperature different according to the driving method of the front wheels and the rear wheels.

4. The vehicle according to claim 1, wherein: When either the temperature of the front wheel motor or the temperature of the rear wheel motor is higher than the first temperature, and the temperature of the front wheel motor and the temperature of the rear wheel motor are respectively lower than their respective drive upper limit temperatures, and when it is determined that temporary all-wheel drive is required, the distribution ratio control unit controls the distribution ratio of the torque of the front wheel motor to the torque of the rear wheel motor in such a way that all-wheel drive is temporarily achieved.

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