control device

Abstract

The present application relates to a control device that stabilizes the behavior of a vehicle body. A control device (100) of a vehicle (1) includes a control section that, in the event of slippage of front wheels (11a, 11b) of the vehicle (1), performs torque adjustment control that reduces the drive torque of the front wheels (11a, 11b) and sets the drive torque of rear wheels (11c, 11d) of the vehicle (1) to be lower than the drive torque of the front wheels (11a, 11b).

Description

TECHNICAL FIELD

[0001] The present application relates to a control device. BACKGROUND

[0002] Technology of individually controlling a driving torque of a front wheel and a driving torque of a rear wheel in a vehicle. For example, technology of using at least one of an engine and a front motor as a driving source of a front wheel, using a rear motor as a driving source of a rear wheel, thereby individually controlling a driving torque of a front wheel and a driving torque of a rear wheel is disclosed in Patent Literature 1.

[0003] Patent Literature 1: Japanese Patent Application Laid-Open No. 2007-314099 SUMMARY

[0004] However, in a vehicle capable of individually controlling a driving torque of a front wheel and a driving torque of a rear wheel, there is a case where, when the vehicle enters a low μ road (for example, a frozen travel road) or the like, in a situation where the front wheel slips, the driving torque of the front wheel is reduced, and the rear wheel generates a driving torque of the same degree as the reduction amount of the driving torque of the front wheel to compensate. Thereby, the slip of the front wheel is eliminated on the basis of the total torque generated on the vehicle being maintained. However, since the driving torque of the rear wheel is increased, the rear wheel can slip. In this case, the vehicle body behavior becomes an oversteer behavior, and instability is caused.

[0005] Therefore, the present application aims to provide a control device capable of stabilizing a vehicle body behavior.

[0006] To solve the above problem, the control device of the present application is provided with a control section that, in a situation where a front wheel of a vehicle slips, executes torque adjustment control of reducing a driving torque of the front wheel and making a driving torque of a rear wheel of the vehicle a torque lower than the driving torque of the front wheel.

[0007] It can be that the control section is capable of switching a driving mode of the vehicle between a front wheel drive mode of driving the front wheel without driving the rear wheel and a four wheel drive mode of driving the front wheel and the rear wheel, and in execution of the front wheel drive mode, in a situation where the front wheel slips, the control section switches the driving mode to the four wheel drive mode and executes the torque adjustment control.

[0008] It can be that the control section controls the driving torque of the front wheel in the torque adjustment control in such a way that a slip rate of the front wheel approaches a target slip rate larger than 0%.

[0009] It can be that the control section controls the driving torque of the rear wheel in the torque adjustment control in such a way that a slip rate of the rear wheel approaches 0%.

[0010] It can be that the control section controls the driving torque of the rear wheel in the torque adjustment control in such a way as to satisfy the following expression (1),

[0011] TR = TF / (1 + ST / 100)... (1)

[0012] wherein,

[0013] TF: driving torque of the front wheels [N / m]

[0014] TR: driving torque of the rear wheels [N / m]

[0015] ST: target slip rate [%].

[0016] It can be that, in the execution of the torque adjustment control, in a case where the vehicle enters a high-μ road having a friction coefficient larger than the reference friction coefficient, the control portion stops the torque adjustment control.

[0017] According to the present application, it is possible to stabilize the behavior of the vehicle body. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic view showing the outline structure of a vehicle in which the control device of the embodiment of the present application is installed.

[0019] Figure 2 is a block diagram showing one example of the functional structure of the control device of the embodiment of the present application.

[0020] Figure 3 is a flowchart showing one example of the flow of the processing for stabilizing the behavior of the vehicle body performed by the control device of the embodiment of the present application.

[0021] Figure 4 is a graph showing one example of the changes in various state quantities in a case where the front wheels slip and the drive mode is switched to the four-wheel drive mode in the comparative example.

[0022] Figure 5 is a graph showing one example of the changes in various state quantities in a case where the front wheels slip and the drive mode is switched to the four-wheel drive mode in the embodiment of the present application.

[0023] Figure 6 is a schematic view showing the relationship between the slip rate and the grip.

[0024] (LEGEND OF REFERENCE NUMERALS)

[0025] 1 vehicle

[0026] 11a, 11b front wheels

[0027] 11c, 11d rear wheels

[0028] 13f front differential device

[0029] 13r rear differential device

[0030] 15f front-wheel drive motor

[0031] 15r rear-wheel drive motor

[0032] 17f inverter

[0033] 17r inverter

[0034] 19 storage battery

[0035] 21f front-wheel motor rotation speed sensor

[0036] 21r rear-wheel motor rotation speed sensor

[0037] 23 vehicle speed sensor

[0038] 25 accelerator operation amount sensor

[0039] 100 control device

[0040] 110 acquisition section

[0041] 120 control section

[0042] 121 motor control section DETAILED DESCRIPTION

[0043] Hereinafter, a preferred embodiment of the present application will be described in detail with reference to the accompanying drawings. The dimensions, materials, other specific numerical values and the like shown in the present embodiment are merely examples for easy understanding of the application, and the present application is not limited to them except for the cases where specifically explained. Further, in the present specification and drawings, the same reference numerals are assigned to the components having substantially the same function and structure, and the repeated description is omitted, and the components not directly related to the present application are omitted from the illustration.

[0044] <Structure of vehicle>

[0045] Referring to Figure 1 and Figure 2 , the structure of a vehicle 1 in which a control device 100 of the embodiment of the present application is installed will be described.

[0046] Figure 1 is a schematic view showing the outline structure of the vehicle 1. In Figure 1 , the advancing direction of the vehicle 1 is set as the front direction, the retreating direction opposite to the advancing direction is set as the rear direction, and the left side and the right side in the state facing the front direction are set as the left direction and the right direction, respectively, whereby the vehicle 1 is shown.

[0047] The vehicle 1 is an electric vehicle provided with drive motors (specifically, front-wheel drive motors 15f and rear-wheel drive motors 15r described later) as drive sources and travels using the torque output from the drive motors.

[0048] Furthermore, the vehicle 1 described below is merely an example of a vehicle equipped with the control device of the present invention, and as will be described later, the structure of a vehicle equipped with the control device of the present invention is not particularly limited to the structure of vehicle 1.

[0049] like Figure 1 As shown, vehicle 1 includes front wheels 11a and 11b, rear wheels 11c and 11d, a front differential 13f, a rear differential 13r, a front-wheel drive motor 15f, a rear-wheel drive motor 15r, an inverter 17f and 17r, a battery 19, a front-wheel motor speed sensor 21f, a rear-wheel motor speed sensor 21r, a vehicle speed sensor 23, a throttle operation sensor 25, and a control device 100.

[0050] Hereinafter, without distinguishing between the front wheels 11a, 11b, 11c, and 11d, these wheels will be referred to simply as wheels 11. Similarly, without distinguishing between the front-wheel drive motor 15f and the rear-wheel drive motor 15r, these motors will be referred to simply as drive motors 15. Furthermore, without distinguishing between inverters 17f and 17r, these inverters will be referred to simply as inverters 17. Finally, without distinguishing between the front-wheel motor speed sensor 21f and the rear-wheel motor speed sensor 21r, these sensors will be referred to simply as motor speed sensors 21.

[0051] The front-wheel drive motor 15f is a drive motor that outputs the torque that drives the front wheels 11a and 11b (that is, the drive torque of the front wheels 11a and 11b). Furthermore, the front wheel 11a is equivalent to the left front wheel, and the front wheel 11b is equivalent to the right front wheel.

[0052] The front-wheel drive motor 15f is driven by electricity supplied from the battery 19. The front-wheel drive motor 15f is connected to the front differential 13f. The front differential 13f is connected to the front wheels 11a and 11b via drive shafts. The torque output from the front-wheel drive motor 15f is transmitted to the front differential 13f, and then distributed and transmitted to the front wheels 11a and 11b by the front differential 13f.

[0053] The front-wheel drive motor 15f is, for example, a multiphase AC motor, connected to the battery 19 via an inverter 17f. The DC power supplied from the battery 19 is converted into AC power by the inverter 17f and supplied to the front-wheel drive motor 15f.

[0054] The front-wheel drive motor 15f can have a function of a generator that generates electric power using kinetic energy of the front wheels 11a, 11b, in addition to a function of outputting driving torque of the front wheels 11a, 11b. In a case where the front-wheel drive motor 15f functions as a generator, electric power is generated by the front-wheel drive motor 15f, and a braking force generated by regenerative braking is applied to the vehicle 1. The alternating-current electric power generated by the front-wheel drive motor 15f is converted into direct-current electric power by the inverter 17f, and is supplied to the battery 19. Thus, the battery 19 is charged.

[0055] The rear-wheel drive motor 15r is a drive motor that outputs torque for driving the rear wheels 11c, 11d, that is, driving torque of the rear wheels 11c, 11d. In addition, the rear wheel 11c corresponds to a left rear wheel, and the rear wheel 11d corresponds to a right rear wheel.

[0056] The rear-wheel drive motor 15r is driven using electric power supplied from the battery 19. The rear-wheel drive motor 15r is connected to the rear differential 13r. The rear differential 13r is coupled to the rear wheels 11c, 11d via drive shafts, respectively. Torque output from the rear-wheel drive motor 15r is distributed by the rear differential 13r and transmitted to the rear wheels 11c, 11d after being transmitted to the rear differential 13r.

[0057] The rear-wheel drive motor 15r is, for example, a multiphase alternating-current motor, and is connected to the battery 19 via the inverter 17r. Direct-current electric power supplied from the battery 19 is converted into alternating-current electric power by the inverter 17r, and is supplied to the rear-wheel drive motor 15r.

[0058] The rear-wheel drive motor 15r can have a function of a generator that generates electric power using kinetic energy of the rear wheels 11c, 11d, in addition to a function of outputting driving torque of the rear wheels 11c, 11d. In a case where the rear-wheel drive motor 15r functions as a generator, electric power is generated by the rear-wheel drive motor 15r, and a braking force generated by regenerative braking is applied to the vehicle 1. The alternating-current electric power generated by the rear-wheel drive motor 15r is converted into direct-current electric power by the inverter 17r, and is supplied to the battery 19. Thus, the battery 19 is charged.

[0059] The front-wheel motor rotation speed sensor 21f detects a rotation speed of the front-wheel drive motor 15f, and outputs a detection result. The rotation speed of the front-wheel drive motor 15f detected by the front-wheel motor rotation speed sensor 21f is used as information indicating wheel speeds of the front wheels 11a, 11b in processing performed by the control device 100, which will be described later.

[0060] The rear wheel motor rotation speed sensor 21r detects the rotation speed of the rear wheel drive motor 15r and outputs the detection result. The rotation speed of the rear wheel drive motor 15r detected by the rear wheel motor rotation speed sensor 21r is used as information indicating the wheel speed of the rear wheels 11c, 11d in the processing described later by the control device 100.

[0061] The vehicle speed sensor 23 detects the vehicle speed (that is, the vehicle body speed) of the vehicle 1 and outputs the detection result.

[0062] The accelerator operation amount sensor 25 detects the operation amount of the accelerator operation (specifically, the operation of stepping on the accelerator pedal (omitted from illustration)) by the driver, that is, the accelerator operation amount, and outputs the detection result.

[0063] The control device 100 includes an arithmetic processing device, that is, a CPU (Central Processing Unit), a storage element, that is, a ROM (Read Only Memory) that stores programs, arithmetic parameters, and the like for use by the CPU, and a storage element, that is, a RAM (Random Access Memory) that temporarily stores parameters and the like that appropriately change in the execution of the CPU.

[0064] The control device 100 communicates with each device mounted to the vehicle 1 (for example, the inverter 17, the front wheel motor rotation speed sensor 21f, the rear wheel motor rotation speed sensor 21r, the vehicle speed sensor 23, the accelerator operation amount sensor 25, and the like). The communication of the control device 100 with each device is achieved using, for example, CAN (Controller Area Network) communication.

[0065] Furthermore, the functions possessed by the control device 100 of the present embodiment can be shared by a plurality of control devices, or a plurality of functions can be implemented by one control device. In the case where the functions possessed by the control device 100 are shared by a plurality of control devices, the plurality of control devices can be connected to each other via a communication bus such as a CAN.

[0066] Figure 2 is a block diagram showing one example of the functional structure of the control device 100.

[0067] For example, as shown in Figure 2 , the control device 100 has an acquisition section 110 and a control section 120.

[0068] The acquisition section 110 acquires various information used in the processing by the control section 120 and outputs to the control section 120. For example, the acquisition section 110 acquires various information output from the front wheel motor rotation speed sensor 21f, the rear wheel motor rotation speed sensor 21r, the vehicle speed sensor 23, and the accelerator operation amount sensor 25.

[0069] The control portion 120 controls the running of the vehicle 1 by controlling the operation of each device in the vehicle 1. For example, the control portion 120 includes a motor control portion 121.

[0070] The motor control portion 121 controls the operation of each drive motor 15 by controlling the operation of each inverter 17. Specifically, the motor control portion 121 controls the supply of electric power between the battery 19 and the front-wheel drive motor 15f by controlling the operation of the switching element of the inverter 17f. Thereby, the motor control portion 121 controls the drive torque of the front wheels 11a, 11b output by the front-wheel drive motor 15f. In addition, the motor control portion 121 controls the supply of electric power between the battery 19 and the rear-wheel drive motor 15r by controlling the operation of the switching element of the inverter 17r. Thereby, the motor control portion 121 controls the drive torque of the rear wheels 11c, 11d output by the rear-wheel drive motor 15r. As described above, the motor control portion 121 can individually control the drive torque of the front wheels 11a, 11b and the drive torque of the rear wheels 11c, 11d.

[0071] Here, the control portion 120 can switch the drive mode of the vehicle 1 between a front-wheel drive mode and a four-wheel drive mode. The front-wheel drive mode is a drive mode in which the front wheels 11a, 11b are driven and the rear wheels 11c, 11d are not driven. The four-wheel drive mode is a drive mode in which the front wheels 11a, 11b and the rear wheels 11c, 11d are driven.

[0072] At ordinary times (specifically, when the vehicle 1 runs in a state in which the wheels 11 do not slip), the control portion 120 sets the drive mode to the front-wheel drive mode. In the front-wheel drive mode, the number of components operating for transmitting torque in the vehicle 1 is reduced compared to the four-wheel drive mode, so the electric power consumption is reduced.

[0073] On the other hand, in the case where the front wheels 11a, 11b slip, the control portion 120 sets the drive mode to the four-wheel drive mode. The slip means a phenomenon in which the slip rate of the wheels 11 (specifically, a value obtained by dividing the difference between the wheel speed and the vehicle speed by the vehicle speed) is excessively large and the wheels 11 spin. The slip occurs, for example, when the vehicle 1 enters a low-μ road. The low-μ road is a running road having a friction coefficient lower than a reference friction coefficient. Specifically, the low-μ road is a running road (for example, a frozen running road) in which the occurrence of the slip of the wheels 11 is highly likely.

[0074] In the present embodiment, in a case where the front wheels 11a, 11b slip and the drive mode is switched to the four-wheel drive mode, the control section 120 of the control device 100 executes the torque adjustment control that reduces the drive torque of the front wheels 11a, 11b and makes the drive torque of the rear wheels 11c, 11d be lower than the drive torque of the front wheels 11a, 11b. Thereby, it is possible to stabilize the vehicle body behavior. Further, the detailed contents of the processing for stabilizing the vehicle body behavior by the control device 100 are described later.

[0075] <Operation of Control Device>

[0076] Next, the operation of the control device 100 of the embodiment of the present application is described with reference to Figures 3-6

[0077] Figure 3 is a flowchart showing one example of the flow of the processing for stabilizing the vehicle body behavior by the control device 100. Specifically, Figure 3 the control flow shown in Figure 3 the control flow shown in

[0078] If the control flow shown in Figure 3 is started, first in step S101, the control section 120 determines whether the front wheels 11a, 11b slip. In a case where it is determined that the front wheels 11a, 11b slip (step S101 / Yes), the control section 120 switches the drive mode of the vehicle 1 to the four-wheel drive mode and executes the torque adjustment control in step S102. On the other hand, in a case where it is determined that the front wheels 11a, 11b do not slip (step S101 / No), the control flow shown in Figure 3 is ended.

[0079] In the determination processing of step S101, the control section 120 determines the slip rate of the front wheels 11a, 11b, for example, and determines that the front wheels 11a, 11b slip in a case where the slip rate of the front wheels 11a, 11b is equal to or higher than a reference slip rate. Further, the control section 120 can determine the slip rate of the front wheels 11a, 11b using the detection results of the front motor rotation speed sensor 21f and the vehicle speed sensor 23. The reference slip rate is a value set so as to be able to appropriately determine whether the wheels 11 slip, and can be appropriately set in accordance with the specifications of the vehicle 1.

[0080] ​In a case where the drive mode is switched to the four-wheel drive mode in step S102, as described above, the control portion 120 executes the torque adjustment control (specifically, control to reduce the drive torque of the front wheels 11a, 11b and to make the drive torque of the rear wheels 11c, 11d lower than the drive torque of the front wheels 11a, 11b). Further, details of the torque adjustment control executed in conjunction with the switching to the four-wheel drive mode will be described later.

[0081] Subsequent to step S102, in step S103, the control portion 120 determines whether the vehicle 1 has entered a high-μ road. In a case where it is determined that the vehicle 1 has entered a high-μ road (step S103 / YES), the processing proceeds to step S104, and the control portion 120 switches the drive mode of the vehicle 1 to the front-wheel drive mode, Figure 3 The control routine shown in FIG. 6 ends in this case. In this case, the torque adjustment control is stopped in conjunction with the switching to the front-wheel drive mode. On the other hand, in a case where it is determined that the vehicle 1 has not entered a high-μ road (step S103 / NO), the determination processing of step S103 is repeated.

[0082] A high-μ road is a travel road having a friction coefficient larger than the reference friction coefficient. Specifically, unlike a low-μ road, a high-μ road is a travel road in which wheel slip is less likely to occur (for example, a travel road paved with asphalt and dry).

[0083] In the determination processing of step S103, for example, in a case where both the slip rates of the front wheels 11a, 11b and the slip rates of the rear wheels 11c, 11d decrease to values around 0%, the control portion 120 determines that the vehicle 1 has entered a high-μ road. Further, the control portion 120 can determine the slip rates of the rear wheels 11c, 11d using the detection results of the rear wheel motor rotation speed sensor 21r and the vehicle speed sensor 23.

[0084] Further, the determination processing of step S103 is not limited to the example described above (that is, an example in which the slip rate is used as a determination parameter). For example, the control portion 120 can determine whether the vehicle 1 has entered a high-μ road based on the slip rates of the front wheels 11a, 11b and various parameters related to the rear wheels 11c, 11d (for example, a time change rate of the slip rate, a grip force of the tire, a time change rate of the grip force of the tire, and the like).

[0085] Next, with respect to changes in various state quantities in a case where the drive mode is switched to the four-wheel drive mode due to the slip of the front wheels 11a, 11b, reference is made to Figure 4 and Figure 5 A comparison is made between the comparative example and each case of the present embodiment. In the comparative example, as in the present embodiment, in a case where the front wheels 11a, 11b slip, the drive mode is switched to the four-wheel drive mode. However, in the comparative example, unlike the present embodiment, the torque adjustment control is not executed in the execution of the four-wheel drive mode.

[0086] Figure 4 is a graph showing one example of the changes in various state quantities in the case where the front wheels 11a, 11b slip and the drive mode is switched to the four-wheel drive mode in the comparative example. Specifically, in Figure 4 , as the various state quantities, the four-wheel drive flag, the respective drive torques (the drive torque TF [N / m] of the front wheels 11a, 11b, the drive torque TR [N / m] of the rear wheels 11c, 11d, the total torque TT [N / m] which is the sum of the drive torque TF and the drive torque TR, and the torque TD [N / m] which is the torque required to generate the drive torque in the vehicle 1), the yaw angular velocity [deg / s] of the vehicle 1, and the steering angle [deg] are shown. Further, in the comparative example, the total torque TT coincides with the required torque TD.

[0087] In Figure 4 , the positive direction of the yaw angular velocity and the steering angle corresponds to the direction in which the vehicle 1 turns to the right side (specifically, to the right side in the state of the traveling direction). On the other hand, the negative direction of the yaw angular velocity and the steering angle corresponds to the direction in which the vehicle 1 turns to the left side (specifically, to the left side in the state of the traveling direction). The four-wheel drive flag becomes 1 in the case where the drive mode is switched to the four-wheel drive mode, and becomes 0 in the case where the drive mode is not switched to the four-wheel drive mode (that is, in the case of the front-wheel drive mode). The four-wheel drive flag is rewritten and stored by the control device of the comparative example.

[0088] In the example shown in Figure 4 , the vehicle 1 which turns to the right side in the front-wheel drive mode enters the low μ road at time t11, and the front wheels 11a, 11b slip. Therefore, before time t11, the yaw angular velocity and the steering angle are positive values. In addition, before time t11, the drive torque TF of the front wheels 11a, 11b coincides with the required torque TD. Here, at time t11, the four-wheel drive flag is switched from 0 to 1 in conjunction with the slip of the front wheels 11a, 11b, and the drive mode is switched to the four-wheel drive mode.

[0089] In the comparative example, in the four-wheel drive mode, the torque is distributed to the front and rear wheels in such a manner that the total torque TT which is the sum of the drive torque TF of the front wheels 11a, 11b and the drive torque TR of the rear wheels 11c, 11d becomes the required torque TD. That is, the drive torque TF of the front wheels 11a, 11b is reduced, and the rear wheels 11c, 11d generate a drive torque which is the same degree as the amount of reduction in the drive torque TF of the front wheels 11a, 11b to compensate. Therefore, after time t11, the drive torque TF of the front wheels 11a, 11b is reduced, and thus the slip of the front wheels 11a, 11b is eliminated.

[0090] However, in Figure 4In the example shown, after time t11, the rear wheels 11c and 11d slip due to the increased driving torque TR. Therefore, after time t11, the vehicle's movement becomes an oversteer, with a significant increase in yaw rate. Consequently, the driver needs to steer to drastically change the steering angle. For example, between time t12 and time t13, the negative steering angle indicates that a steering wheel turn is being performed in the opposite direction to the turning direction of vehicle 1.

[0091] Figure 5 This is a diagram illustrating an example of the changes in various state quantities when the front wheels 11a and 11b slip and the drive mode switches to four-wheel drive mode in this embodiment. Specifically, in Figure 5 In the diagram, various state variables are shown in relation to... Figure 4 The state quantities shown are of the same type as those in the diagram. Furthermore, in this embodiment, the four-wheel drive indicator is stored in the storage element of the control device 100 and is rewritten by the control unit 120.

[0092] exist Figure 5 In the example shown, with Figure 6 Similarly, in the example shown, vehicle 1, which is turning right in front-wheel drive mode, enters the low μ path at time t21, and the front wheels 11a and 11b slip. Therefore, at time t21, as the front wheels 11a and 11b slip, the four-wheel drive flag changes from 0 to 1, and the drive mode changes to four-wheel drive mode.

[0093] In this embodiment, torque adjustment control is performed in four-wheel drive mode. As a result, the drive torque TF of the front wheels 11a and 11b is reduced, and the drive torque TR of the rear wheels 11c and 11d is controlled to be below the drive torque TF of the front wheels 11a and 11b. Therefore, after time t21, the drive torque TF of the front wheels 11a and 11b decreases, thereby eliminating slippage of the front wheels 11a and 11b.

[0094] Preferably, the control unit 120 controls the drive torque TF of the front wheels 11a and 11b under torque adjustment control in a manner that makes the slip rate of the front wheels 11a and 11b close to a target slip rate greater than 0%. Here, the target slip rate is set to a value within the effective recovery range of the grip force of the tires of the front wheels 11a and 11b (that is, the friction force generated between the tires and the road surface).

[0095] Figure 6 This is a schematic diagram illustrating the relationship between slippage rate and grip. For example... Figure 6As shown, generally, the component of the road adhesion force in the advancing direction, i.e., the longitudinal road adhesion force, increases in a process in which the slip ratio of the wheel 11 increases from 0% to about 20%, and then decreases in a process in which the slip ratio of the wheel 11 increases. In addition, generally, the component of the road adhesion force perpendicular to the advancing direction, i.e., the lateral road adhesion force, decreases as the slip ratio of the wheel increases. Therefore, in order to make both the longitudinal road adhesion force and the lateral road adhesion force high, it is preferable to adjust the slip ratio of the wheel 11 to a target region from about 10% to about 20%. Therefore, the target slip ratio under the torque adjustment control is set to a value within the target region in which the road adhesion forces of the tires of the front wheels 11a, 11b are effectively recovered, for example.

[0096] In addition, in the present embodiment, the drive torque TR of the rear wheels 11c, 11d is controlled to be lower than the drive torque TF of the front wheels 11a, 11b by the torque adjustment control, so the excessive increase in the drive torque TR of the rear wheels 11c, 11d accompanying the switching to the four-wheel drive mode is suppressed. Therefore, in the example shown in FIG. 21, the slip of the rear wheels 11c, 11d is avoided after the time t21. Therefore, the vehicle body behavior is suppressed from becoming an oversteer behavior after the time t21, so the vehicle body behavior is stabilized. Therefore, compared with the example shown in FIG. 20, the yaw rate is suppressed from increasing, and the steering to substantially correct the steering angle is not required. For example, it is known from the fact that the steering angle is maintained at a positive value after the time t21 that the steering to turn the steering wheel in the direction opposite to the turning direction of the vehicle 1 is not required. Figure 5 Figure 4 In the example shown in FIG. 21, the slip of the rear wheels 11c, 11d is avoided after the time t21. Therefore, the vehicle body behavior is suppressed from becoming an oversteer behavior after the time t21, so the vehicle body behavior is stabilized. Therefore, compared with the example shown in FIG. 20, the yaw rate is suppressed from increasing, and the steering to substantially correct the steering angle is not required. For example, it is known from the fact that the steering angle is maintained at a positive value after the time t21 that the steering to turn the steering wheel in the direction opposite to the turning direction of the vehicle 1 is not required.

[0097] Here, under the torque adjustment control, from the viewpoint of appropriately avoiding the slip of the rear wheels 11c, 11d, it is preferable that the control portion 120 control the drive torque TR of the rear wheels 11c, 11d in such a manner that the slip ratio of the rear wheels 11c, 11d approaches 0%. For example, it is preferable that the control portion 120 control the drive torque TR of the rear wheels 11c, 11d under the torque adjustment control in such a manner that the following equation (1) is satisfied.

[0098] TR = TF / (1 + ST / 100)... (1)

[0099] In equation (1), ST is the target slip ratio of the front wheels 11a, 11b under the torque adjustment control. For example, in the case where the target slip ratio ST is 10%, the drive torque TR of the rear wheels 11c, 11d becomes a value obtained by dividing the drive torque TF of the front wheels 11a, 11b by 1.1. By controlling the drive torque TR of the rear wheels 11c, 11d in such a manner that equation (1) is satisfied, it is possible to appropriately make the slip ratio of the rear wheels 11c, 11d approach 0%.

[0100] In addition, in the example shown in FIG. 21, the slip of the rear wheels 11c, 11d is avoided after the time t21. Therefore, the vehicle body behavior is suppressed from becoming an oversteer behavior after the time t21, so the vehicle body behavior is stabilized. Therefore, compared with the example shown in FIG. 20, the yaw rate is suppressed from increasing, and the steering to substantially correct the steering angle is not required. For example, it is known from the fact that the steering angle is maintained at a positive value after the time t21 that the steering to turn the steering wheel in the direction opposite to the turning direction of the vehicle 1 is not required. Figure 5 ​In the example shown in FIG. 21, the total torque TT is lower than the required torque TD after time t21 as a result of the execution of the torque adjustment control, but the total torque TT can coincide with the required torque TD in the execution of the torque adjustment control. For example, sometimes the drive torque TF of the front wheels 11a, 11b is determined in such a manner that the slip ratio of the front wheels 11a, 11b becomes the target slip ratio ST under the torque adjustment control, and the value obtained by subtracting the determined drive torque TF from the required torque TD is smaller than the value of the drive torque TR of the rear wheels 11c, 11d determined by equation (1). In this case, if the drive torque TR is controlled to the value determined by equation (1), the total torque TT exceeds the required torque TD, so the control section 120 controls the drive torque TR to the value obtained by subtracting the drive torque TF from the required torque TD. Thus, the total torque TT coincides with the required torque TD. Further, the control section 120 can determine the required torque, for example, using the accelerator operation amount and the vehicle speed.

[0101] <Effects of the control device>

[0102] Next, the effects of the control device 100 of the embodiment of the application will be described.

[0103] In the control device 100 of the embodiment, the control section 120 executes the torque adjustment control that reduces the drive torque TF of the front wheels 11a, 11b and makes the drive torque TR of the rear wheels 11c, 11d of the vehicle 1 be lower than the drive torque TF of the front wheels 11a, 11b in the case where the front wheels 11a, 11b of the vehicle 1 slip. Thus, in the case where the front wheels 11a, 11b slip, the drive torque TF of the front wheels 11a, 11b is reduced, so the slip of the front wheels 11a, 11b is eliminated. Also, by controlling the drive torque TR of the rear wheels 11c, 11d to be lower than the drive torque TF of the front wheels 11a, 11b, the drive torque TR of the rear wheels 11c, 11d is suppressed from becoming excessively large. Thus, the slip of the rear wheels 11c, 11d is avoided, so the vehicle body behavior is suppressed from becoming the oversteer behavior. Thus, it is possible to stabilize the vehicle body behavior.

[0104] Further, in the control device 100 of the embodiment, it is preferable that the control section 120 be capable of switching the drive mode of the vehicle 1 between a front-wheel drive mode that drives the front wheels 11a, 11b and does not drive the rear wheels 11c, 11d and a four-wheel drive mode that drives the front wheels 11a, 11b and the rear wheels 11c, 11d, and in the execution of the front-wheel drive mode, the drive mode is switched to the four-wheel drive mode in the case where the front wheels 11a, 11b slip, and the torque adjustment control is executed. Thus, at ordinary times, the electric power consumption is reduced by the front-wheel drive mode, and in the case where the front wheels 11a, 11b slip, the four-wheel drive mode is switched, so it is possible to stabilize the vehicle body behavior.

[0105] Further, in the control device 100 of the present embodiment, it is preferable that the control section 120 control the drive torque TR of the rear wheels 11c, 11d in such a manner as to make the slip rates of the rear wheels 11c, 11d approach 0% under the torque adjustment control. Thereby, it is possible to properly avoid the slip of the rear wheels 11c, 11d.

[0106] Further, in the control device 100 of the present embodiment, it is preferable that the control section 120 control the drive torque TR of the rear wheels 11c, 11d in such a manner as to make the slip rates of the rear wheels 11c, 11d approach 0% under the torque adjustment control. Thereby, it is possible to properly avoid the slip of the rear wheels 11c, 11d.

[0107] Further, in the control device 100 of the present embodiment, it is preferable that the control section 120 control the drive torque TR of the rear wheels 11c, 11d in such a manner as to make the slip rates of the rear wheels 11c, 11d approach 0% under the torque adjustment control. Thereby, it is possible to properly avoid the slip of the rear wheels 11c, 11d.

[0108] Further, in the control device 100 of the present embodiment, it is preferable that the control section 120 stop the torque adjustment control in the execution of the torque adjustment control in a case where the vehicle 1 enters a high-μ road having a friction coefficient larger than the reference friction coefficient. Thereby, it is possible to suppress the unnecessary continuation of the torque adjustment control in a situation where there is little possibility of the slip of the wheels 11 even if the torque adjustment control is not executed.

[0109] The preferred embodiments of the present application are explained above with reference to the accompanying drawings, but the present application is of course not limited to the above-described embodiments, and various modifications or changes within the scope of the claims naturally belong to the technical scope of the present application.

[0110] For example, the above-described Figure 1 The structure of the vehicle 1 is explained, but the structure of the vehicle of the present application is not limited to such an example. The vehicle of the present application can be, for example, a vehicle in which a part of the constituent elements shown in the above-described Figure 1 are deleted, added, or changed. Further, the vehicle of the present application can be, for example, a vehicle in which a drive motor is provided for each wheel (that is, four drive motors are provided). Furthermore, a part or all of the drive sources in the vehicle of the present application can be drive sources other than the drive motor (for example, an engine or the like).

[0111] Further, for example, the processes explained in the present specification using the flowcharts are not necessarily executed in the order shown in the flowcharts. Further, either additional processing steps can be adopted or a part of the processing steps can be omitted.

[0112] Industrial applicability The present application can be used in a control device.

Claims

1. A control device provided with a control section that, in a case where a front wheel of a vehicle slips, executes torque adjustment control that reduces a drive torque of the front wheel and makes a drive torque of a rear wheel of the vehicle lower than the drive torque of the front wheel, the control section being capable of switching a drive mode of the vehicle between a front wheel drive mode in which the front wheel is driven and the rear wheel is not driven, and a four wheel drive mode in which the front wheel and the rear wheel are driven, in the execution of the front wheel drive mode, in a case where the front wheel slips, the control section switches the drive mode to the four wheel drive mode and executes the torque adjustment control, the control section controls the drive torque of the front wheel in the torque adjustment control in such a way that a slip rate of the front wheel approaches a target slip rate that is greater than 0%, the control section controls the drive torque of the rear wheel in the torque adjustment control in such a way that a slip rate of the rear wheel approaches 0%, the control section controls the drive torque of the rear wheel in the torque adjustment control in such a way that the following expression (1) is satisfied, TR = TF / (1 + ST / 100)... (1) where, TF: the drive torque of the front wheel [N / m] TR: the drive torque of the rear wheel [N / m] ST: the target slip rate [%].

2. The control device according to claim 1, wherein, in the execution of the torque adjustment control, in a case where the vehicle enters a high μ road having a friction coefficient that is greater than a reference friction coefficient, the control section stops the torque adjustment control.

3. The control device according to claim 1, wherein, the control section determines a required torque using an accelerator operation amount and a vehicle speed, the control section determines the drive torque of the front wheel in such a way that the slip rate of the front wheel becomes the target slip rate, and when a value obtained by subtracting the determined drive torque of the front wheel from the required torque is smaller than a value of the drive torque of the rear wheel obtained by the expression (1), controls the drive torque of the rear wheel to a value obtained by subtracting the drive torque of the front wheel from the required torque. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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