Vehicle motion control method and vehicle motion control device

Abstract

To stabilize a vehicle behavior by suppressing a slip of a primary drive wheel before the vehicle behavior changes greatly in a vehicle that has one of front wheel and rear wheel as the primary drive wheel and the other thereof as a secondary drive wheel.SOLUTION: A vehicle motion control method includes: calculating a first inner-outer wheel speed difference D1 being a difference in wheel speed between a right wheel and a left wheel, of a primary wheel of front and rear wheels (S1); determining whether the first inner-outer wheel speed difference is equal to or more than a first threshold (S2); and increasing, in the case of determining that the first inner-outer wheel speed difference is equal to or more than the first threshold, decreasing drive force of the primary drive wheel and increasing drive force of the secondary drive wheel, of the front and rear wheels (S3, S12).SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a vehicle motion control method and a vehicle motion control device. [Background technology]

[0002] Patent Document 1 describes a vehicle motion control device that stabilizes vehicle behavior by controlling the distribution of driving force between front and rear wheels depending on whether the lateral acceleration or sideslip angle of the vehicle is equal to or greater than a predetermined value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-349887 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the vehicle motion control device described in Patent Document 1 has a problem in that it is not possible to stabilize the vehicle behavior before the lateral acceleration or sideslip angle reaches or exceeds a predetermined value. The present invention aims to stabilize vehicle behavior in a vehicle in which one of the front and rear wheels is a main drive wheel and the other is a secondary drive wheel by suppressing slip of the main drive wheel before the vehicle behavior changes significantly. [Means for solving the problem]

[0005] In one embodiment of the vehicle motion control method of the present invention, a first inner / outer wheel speed difference, which is the difference between the wheel speed of the right wheel and the wheel speed of the left wheel, which are the main drive wheels among the front wheels and rear wheels, is determined to be greater than or equal to a first threshold value, and if it is determined that the first inner / outer wheel speed difference is greater than or equal to the first threshold value, the driving force of the main drive wheel is reduced and the driving force of the secondary drive wheel, which is one of the front wheels and rear wheels, is increased. [Effects of the Invention]

[0006] According to the present invention, in a vehicle in which one of the front and rear wheels is a main drive wheel and the other is a secondary drive wheel, slip of the main drive wheel can be suppressed before the vehicle behavior changes significantly, thereby stabilizing the vehicle behavior. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram illustrating an example of a vehicle equipped with a vehicle motion control device according to an embodiment; [Figure 2] 2 is a block diagram showing an example of a functional configuration of a braking / driving force controller shown in FIG. 1. FIG. [Figure 3] 10(a) to 10(c) are time charts illustrating an example of the reduction amount of driving force due to the wheel speed difference between the inner and outer main driving wheels in the first embodiment. [Figure 4] 6(a) to 6(c) are time charts illustrating an example of the reduction amount of driving force due to the wheel speed difference between the inner and outer wheels of the subordinate driving wheels in the first embodiment. [Figure 5] 6(a) to 6(c) are time charts illustrating an example of the reduction amount of driving force due to the main and slave drive wheel speed difference in the first embodiment. [Figure 6] 3 is a flowchart illustrating an example of a vehicle motion control method according to the first embodiment. [Figure 7] FIG. 10 is a block diagram illustrating an example of a functional configuration of a reduction amount calculation unit in the second embodiment. [Figure 8] 10(a) to 10(d) are time charts illustrating an example of the reduction amount of driving force due to the inner / outer wheel speed difference in the second embodiment. [Figure 9] 10 is a flowchart illustrating an example of a vehicle motion control method according to a second embodiment. [Figure 10] 10(a) to 10(d) are time charts illustrating an example of the reduction amount of driving force due to the inner / outer wheel speed difference in the third embodiment. [Figure 11] 10 is a flowchart illustrating an example of a vehicle motion control method according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, identical or similar parts are designated by identical or similar reference numerals, and redundant explanations will be omitted. Each drawing is a schematic diagram and may differ from the actual product. The embodiments shown below exemplify devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention is not limited to the devices and methods exemplified in the following embodiments. The technical concept of the present invention can be modified in various ways within the technical scope of the claims.

[0009] (First embodiment) (composition) 1 is a schematic diagram of an example of a vehicle equipped with a vehicle motion control device according to an embodiment. The vehicle motion control device 1 includes an accelerator sensor 2, a brake sensor 3, wheel speed sensors 4FR, 4FL, 4RR, and 4RL, and a braking / driving force controller 5. These wheel speed sensors 4FR, 4FL, 4RR, and 4RL may be referred to as "wheel speed sensors 4." The vehicle motion control device 1 also includes a brake controller 10, a hydraulic circuit 11, and a right front wheel brake caliper 12FR, a left front wheel brake caliper 12FL, a right rear wheel brake caliper 12RR, and a left rear wheel brake caliper 12RL, which are arranged on the right front wheel WFR, the left front wheel WFL, the right rear wheel WRR, and the left rear wheel WRL, respectively. These brake calipers 12FR, 12FL, 12RR, and 12RL may be collectively referred to as "brake calipers 12." The hydraulic circuit 11 and the brake calipers 12 may be collectively referred to as the "braking device."

[0010] The vehicle motion control device 1 also includes a power controller 13, a first driving force source 14f that generates driving force to the front wheels WFR and WFL, and a second driving force source 14r that generates driving force to the rear wheels WRR and WRL. The second driving force source 14r may be separate driving force sources that generate driving force for the right rear wheel WRR and the left rear wheel WRL, respectively. In this case, instead of using the wheel speed sensors 4RR and 4RL, the rotational speed of the rotary shaft of the driving force source may be measured to detect the wheel speeds of the right rear wheel WRR and the left rear wheel WRL. The rear wheels WRR and WRL may be driven by a single second driving force source 14r.

[0011] The first driving power source 14f and the second driving power source 14r may be, for example, electric motors, or instead of the first driving power source 14f and the second driving power source 14r, a single engine or a hybrid drive system combining an engine and an electric motor may be used to apply driving force to the front wheels WFR and WFL and the rear wheels WRR and WRL. In this case, a clutch may be provided in the driving power transmission path from the engine to the rear wheels WRR and WRL, and the driving force generated at the rear wheels WRR and WRL may be increased or decreased by changing the engagement force of the clutch. In the following description, the front wheels WFR and WFL may be referred to as "front wheels WF," and the rear wheels WRR and WRL may be referred to as "rear wheels WR."

[0012] The accelerator sensor 2 detects an accelerator stroke amount Ac, which is the stroke amount (depression amount) of an accelerator pedal 15 that can be operated by a driver. The accelerator sensor 2 outputs an information signal of the accelerator stroke amount Ac to the braking / driving force controller 5. The brake sensor 3 detects a brake stroke amount Br, which is a stroke amount (depression amount) of a brake pedal 16 that can be operated by a driver. The brake sensor 3 outputs an information signal of the brake stroke amount Br to the braking / driving force controller 5. Wheel speed sensors 4FR, 4FL, 4RR, and 4RL detect wheel speeds (rotational speeds) VFR, VFL, VRR, and VRL of the front right wheel WFR, front left wheel WFL, rear right wheel WRR, and rear left wheel WRL. Wheel speed sensor 4 outputs information signals of the wheel speeds VFR, VFL, VRR, and VRL to braking / driving force controller 5.

[0013] The braking / driving force controller 5 is an electronic control unit (ECU) that controls the braking force and driving force generated in the vehicle based on the accelerator stroke amount Ac and the brake stroke amount Br. The braking / driving force controller 5 includes a processor and peripheral components such as a storage device. The functions of the braking / driving force controller 5 described below are realized by the processor executing a computer program stored in the storage device. The braking / driving force controller 5 may also be formed by dedicated hardware. For example, the braking / driving force controller 5 may include a functional logic circuit (such as an FPGA or ASIC) set in a general-purpose semiconductor integrated circuit.

[0014] The braking / driving force controller 5 uses the various input information signals to generate a driving force command signal that controls the driving force Fdf generated in the front wheels WF and the driving force Fdr generated in the rear wheels WR, and outputs it to the power controller 13. In response to the driving force command signal output from the braking / driving force controller 5, the power controller 13 controls the driving torques generated by the first driving force source 14f and the second driving force source 14r.

[0015] Furthermore, the braking / driving force controller 5 uses the various input information signals to generate braking force command signals for controlling the braking force Fbf of the front wheels WF and the braking force Fbr of the rear wheels WR, and outputs them to the brake controller 10. The brake controller 10 controls the hydraulic pressure of the brake fluid supplied to the brake calipers 12FR and 12FL of the front wheels WF and the hydraulic pressure of the brake fluid supplied to the brake calipers 12RR and 12RL of the rear wheels WR by the hydraulic circuit 11 in accordance with the braking force command signal output from the braking / driving force controller 5. The brake controller 10 may generate braking forces for the front wheels WF and the rear wheels WR by regenerative braking of the first driving power source 14f and the second driving power source 14r. Hereinafter, the regenerative braking of the first driving power source 14f and the second driving power source 14r may be simply referred to as "regenerative braking."

[0016] With the above configuration, the vehicle motion control device 1 of the embodiment can generate a driving force for each of the front wheels WF and the rear wheels WR. The drive force controller 5 can change the distribution of the driving force (driving force distribution) generated in the front wheels WF and the rear wheels WR by controlling the driving torque generated by the first driving force source 14f and the second driving force source 14r. When generating driving torque by a single engine or a hybrid drive device instead of the first driving force source 14f and the second driving force source 14r, the driving force distribution between the front wheels WF and the rear wheels WR can be changed by controlling the engagement force of the clutch between the driving force source and the rear wheels WR.

[0017] The ratio of the driving force distribution between the front wheels WF and the rear wheels WR can be appropriately set according to the situation and purpose, but is usually set in the range from 7:3 to 3:7. In the following description, among the front wheels WF and the rear wheels WR, the wheel with a large driving force is referred to as the "main driving wheel", and the wheel with a small driving force is referred to as the "sub-driving wheel". For example, in a state where the control is such that the driving force Fdf > Fdr, the front wheels WF become the main driving wheels and the rear wheels WR become the sub-driving wheels. In a state where the control is such that the driving force Fdf < Fdr, the front wheels WF become the sub-driving wheels and the rear wheels WR become the main driving wheels.

[0018] By changing the driving force distribution between the front wheels WF and the rear wheels WR, the vehicle motion control device 1 can control the vehicle behavior. For example, in the vehicle motion control device described in Patent Document 1 above, the driving force distribution between the front and rear wheels is controlled according to whether the lateral acceleration or the sideslip angle of the vehicle is greater than or equal to a predetermined value to stabilize the vehicle behavior. However, for example, in a driving scene where turning while accelerating, the wheels may slip before the lateral acceleration or the sideslip angle becomes greater than or equal to a predetermined value. When the wheels slip before the lateral acceleration or the sideslip angle becomes greater than or equal to a predetermined value as described above, in the vehicle motion control device described in Patent Document 1, the control of the driving force distribution may not be in time, so there is a possibility that the vehicle behavior cannot be stabilized.

[0019] Therefore, the braking / driving force controller 5 of this embodiment calculates a first inner / outer wheel speed difference D1, which is the difference between the wheel speed of the right wheel and the wheel speed of the left wheel, of the main drive wheels, and determines whether the first inner / outer wheel speed difference D1 is equal to or greater than a first threshold value T1m.When it is determined that the first inner / outer wheel speed difference D1 is equal to or greater than the first threshold value T1m, the braking / driving force controller 5 reduces the driving force of the main drive wheels. This makes it possible to suppress slippage of the main drive wheels before the vehicle behavior changes significantly, thereby suppressing sudden changes in vehicle behavior.

[0020] However, when the front wheels WF are the main drive wheels, if the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m and the drive force of the main drive wheels (i.e., the front wheels WF) is reduced, hunting may occur in the reduction amount fm of the drive force of the main drive wheels. The reason for this is as follows. First, when the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m and the driving force of the main drive wheels is reduced, the load on the vehicle body moves forward, and the load on the front wheels WF increases.

[0021] When the load on the front wheels WF, which are the main drive wheels, increases, the grip force of the main drive wheels increases. This causes the first inner / outer wheel speed difference D1 to decrease. As a result, if the reduction amount fm of the drive force of the main drive wheels is reduced, the load transfer on the vehicle body decreases, and the grip force of the main drive wheels decreases. If this causes the main drive wheels to slip again, the first inner / outer wheel speed difference D1 increases, so the reduction amount fm of the drive force of the main drive wheels is increased. In this way, hunting occurs, in which the reduction amount fm of the driving force of the main drive wheels repeatedly increases and decreases. When hunting occurs, the longitudinal acceleration oscillates, making the vehicle behavior unstable.

[0022] On the other hand, if the main drive wheels are rear WR wheels, reducing the drive force of the main drive wheels will cause the load of the vehicle body to shift forward, reducing the grip of the main drive wheels (rear WR wheels), which will hinder the slip suppression effect of reducing the drive force of the main drive wheels. Therefore, when the braking / driving force controller 5 of this embodiment determines that the first inner / outer wheel speed difference D1 is equal to or greater than the first threshold value T1m, it reduces the driving force of the main driving wheels and increases the driving force of the subordinate driving wheels. In other words, the reduction in driving force of the main driving wheels is compensated for by the increase in driving force of the subordinate driving wheels.

[0023] This suppresses the load shift of the vehicle body due to the reduction in drive force of the main drive wheels, thereby suppressing hunting in the reduction amount fm of drive force of the main drive wheels when the front wheels WF are the main drive wheels. Also, when the rear wheels WR are the main drive wheels, the effect of suppressing slip caused by the reduction in drive force of the main drive wheels is prevented from being impaired by load shift. As a result, vehicle behavior can be stabilized. Furthermore, the driving force can be maintained by compensating for the reduction in the driving force of the main driving wheels with an increase in the driving force of the secondary driving wheels, so that even if the driving force of the main driving wheels is reduced, the loss of acceleration performance can be suppressed.

[0024] The braking / driving force controller 5 will be described in more detail below. Figure 2 is a block diagram showing an example of the functional configuration of the braking / driving force controller 5. The braking / driving force controller 5 includes a reduction amount calculation unit 30, a vehicle speed calculation unit 31, a driving force setting unit 32, and a braking force setting unit 33. The vehicle speed calculation unit 31 calculates the vehicle speed Vv of the vehicle based on the wheel speeds VFR, VFL, VRR, and VRL. For example, the vehicle speed calculation unit 31 may calculate the average value of the wheel speeds VFR, VFL, VRR, and VRL as the vehicle speed Vv.

[0025] The driving force setting unit 32 receives the vehicle speed Vv calculated by the vehicle speed calculation unit 31, the accelerator stroke amount Ac, and the driving source driving force reduction amounts tm and ts output from the reduction amount calculation unit 30. The drive source driving force reduction amount tm is the reduction amount of the drive force command value that one of the first drive power source 14f or the second drive power source 14r generates in the main drive wheels, and the drive source driving force reduction amount ts is the reduction amount of the drive force command value that the other drive power source generates in the secondary drive wheels.

[0026] The driving force setting unit 32 sets basic driving forces Fdf0 and Fdr0 to be generated at the front wheels WF and rear wheels WR based on the vehicle speed Vv and the accelerator stroke amount Ac. Further, the driving force setting unit 32 determines whether the front wheels WF or the rear wheels WR are the main driving wheels. For example, the driving force setting unit 32 may determine whether the front wheels WF or the rear wheels WR are the main driving wheels based on the basic driving forces Fdf0 and Fdr0.

[0027] For example, if the basic driving force Fdf0 is greater than the basic driving force Fdr0, it may be determined that the front wheels WF are the main drive wheels and the rear wheels WR are the secondary drive wheels, and if the basic driving force Fdr0 is greater than the basic driving force Fdf0, it may be determined that the front wheels WF are the secondary drive wheels and the rear wheels WR are the main drive wheels. The driving force setting unit 32 may also output a determination result signal indicating which of the front wheels WF and the rear wheels WR is the main drive wheel to the reduction amount calculation unit 30 and the braking force setting unit 33.

[0028] Furthermore, the driving force setting unit 32 reduces the basic driving force of the main drive wheels, of the basic driving forces Fdf0 and Fdr0, by the driving force reduction amount tm of the driving source, and reduces the basic driving force of the subordinate drive wheels by the driving force reduction amount ts of the driving source, thereby setting the driving forces Fdf and Fdr of the front wheels WF and rear wheels WR reduced by these reduction amounts tm and ts. The driving force setting unit 32 outputs a driving force command signal including command values ​​for the driving forces Fdf and Fdr to the power controller 13.

[0029] On the other hand, the braking force setting unit 33 receives the brake stroke amount Br and the braking force increase amounts bm and bs output from the reduction amount calculation unit 30. The braking force increase amount bm is the increase amount of the braking force command value for the main drive wheels, and the braking force increase amount bs is the increase amount of the braking force command value for the slave drive wheels. The braking force increase amounts bm and bs may be the increase amounts of braking force by the braking device or the increase amounts of braking force by the regenerative brake. The braking force setting unit 33 sets basic braking forces Fbf0 and Fbr0 of the front wheels WF and rear wheels WR by the braking device or regenerative brake based on the brake stroke amount Br.

[0030] The braking force setting unit 33 increases the basic braking force of the main drive wheels by the braking force increase amount bm, and reduces the basic braking force of the secondary drive wheels by the braking force increase amount bs, thereby setting braking forces Fbf and Fbr of the front wheels WF and rear wheels WR increased by these increase amounts. The braking force setting unit 33 outputs a braking force command signal including command values ​​of the braking forces Fbf and Fbr to the brake controller 10.

[0031] The reduction amount calculation unit 30 receives wheel speeds VFR, VFL, VRR, and VRL of the front right wheel WFR, front left wheel WFL, rear right wheel WRR, and rear left wheel WRL detected by wheel speed sensors 4FR, 4FL, 4RR, and 4RL, respectively. The reduction amount calculation unit 30 calculates the drive source driving force reduction amounts tm and ts and the braking force increase amounts bm and bs based on the wheel speed differences among the wheel speeds VFR, VFL, VRR, and VRL.

[0032] The reduction amount calculation unit 30 includes a first inner / outer wheel speed difference calculation unit 40, a first driving force reduction amount setting unit 41, a second inner / outer wheel speed difference calculation unit 42, a second driving force reduction amount setting unit 43, a main / subordinate driving wheel speed difference calculation unit 44, a third driving force reduction amount setting unit 45, adders 46 and 49, subtractors 47 and 48, a first distribution unit 50, and a second distribution unit 51. The first inner / outer wheel speed difference calculation unit 40 calculates the absolute value of the difference between the wheel speed of the right wheel and the wheel speed of the left wheel, which are the main drive wheels, among the wheel speeds VFR, VFL, VRR, and VRL as the first inner / outer wheel speed difference D1.

[0033] The first driving force reduction amount setting unit 41 determines whether the first inner / outer wheel speed difference D1 is equal to or greater than a first threshold value T1m. When it is determined that the first inner / outer wheel speed difference D1 is greater than or equal to the first threshold value T1m, the first driving force reduction amount setting unit 41 sets a first main driving wheel driving force reduction amount fm1 greater than 0 as the reduction amount of the driving force of the main driving wheels. In this case, for example, when the first inner / outer wheel speed difference D1 is large, the first driving force reduction amount setting unit 41 may set a larger first main driving wheel driving force reduction amount fm1 than when the first inner / outer wheel speed difference D1 is small.

[0034] For example, when the first inner / outer wheel speed difference D1 is less than a predetermined value, the first main drive wheel driving force reduction amount fm1 may be set to a relatively small value, and when the first inner / outer wheel speed difference D1 is equal to or greater than the predetermined value, the first main drive wheel driving force reduction amount fm1 may be set to a relatively large value. Also, for example, the first driving force reduction amount setting unit 41 may set a larger first main-drive-wheel driving force reduction amount fm1 as the first inner-outer wheel speed difference D1 increases.

[0035] For example, the first driving force reduction amount setting unit 41 may set the product obtained by multiplying the first inner / outer wheel speed difference D1 by a coefficient as the first main drive wheel driving force reduction amount fm1. Alternatively, for example, the first driving force reduction amount setting unit 41 may set the first main drive wheel driving force reduction amount fm1 in accordance with a map that defines the relationship between the first inner / outer wheel speed difference D1 and the first main drive wheel driving force reduction amount fm1. On the other hand, when the first inner / outer wheel speed difference D1 is less than the first threshold value T1m, the first driving force reduction amount setting unit 41 sets the value of the first main driving wheel driving force reduction amount fm1 to zero.

[0036] The second inner / outer wheel speed difference calculation unit 42 calculates the absolute value of the difference between the wheel speed of the right wheel and the wheel speed of the left wheel, which are the subordinate drive wheels, among the wheel speeds VFR, VFL, VRR, and VRL as the second inner / outer wheel speed difference D2. The second driving force reduction amount setting unit 43 determines whether the second inner / outer wheel speed difference D2 is equal to or greater than the first threshold value T1s. The first threshold value T1s may be set to a value equal to or different from the first threshold value T1m of the first inner / outer wheel speed difference D1.

[0037] When it is determined that the second inner / outer wheel speed difference D2 is greater than or equal to the first threshold value T1s, the second driving force reduction amount setting unit 43 sets the first driven wheel driving force reduction amount fs1 that is greater than 0 as the reduction amount of the driving force of the driven wheel. In this case, for example, when the second inner / outer wheel speed difference D2 is large, the second driving force reduction amount setting unit 43 may set a larger first slave drive wheel driving force reduction amount fs1 than when the second inner / outer wheel speed difference D2 is small.

[0038] For example, if the second inner / outer wheel speed difference D2 is less than a predetermined value, the first subordinate drive wheel driving force reduction amount fs1 may be set to a relatively small value, and if the second inner / outer wheel speed difference D2 is greater than or equal to the predetermined value, the first subordinate drive wheel driving force reduction amount fs1 may be set to a relatively large value. Also, for example, the second driving force reduction amount setting unit 43 may set a larger first driven wheel driving force reduction amount fs1 as the second inner / outer wheel speed difference D2 increases.

[0039] For example, the second driving force reduction amount setting unit 43 may set the product obtained by multiplying the second inner / outer wheel speed difference D2 by a coefficient as the first driven wheel driving force reduction amount fs1. Alternatively, for example, the second driving force reduction amount setting unit 43 may set the first driven wheel driving force reduction amount fs1 in accordance with a map that defines the relationship between the second inner / outer wheel speed difference D2 and the first driven wheel driving force reduction amount fs1. On the other hand, when the second inner / outer wheel speed difference D2 is less than the first threshold value T1s, the second driving force reduction amount setting unit 43 sets the value of the first driven-drive-wheel driving force reduction amount fs1 to zero.

[0040] The main / subordinate drive wheel wheel speed difference calculation unit 44 calculates the absolute value of the difference between the wheel speeds of the main drive wheels and the subordinate drive wheels among the wheel speeds VFR, VFL, VRR, and VRL as the main / subordinate drive wheel wheel speed difference D3. The main / subordinate drive wheel wheel speed difference calculation unit 44 may calculate the absolute value of the difference between the average value of the wheel speeds of the right and left main drive wheels and the average value of the wheel speeds of the right and left subordinate drive wheels as the main / subordinate drive wheel wheel speed difference D3. The main / subordinate drive wheel wheel speed difference D3 may also be the difference between the maximum values ​​of the wheel speeds of the right and left wheels or the difference between the minimum values ​​of the wheel speeds of the right and left wheels. The third driving force reduction amount setting unit 45 determines whether the primary / subordinate driving wheel speed difference D3 is equal to or greater than a predetermined threshold value T2.

[0041] When it is determined that the main / subordinate drive wheel speed difference D3 is equal to or greater than a predetermined threshold value T2, the third drive force reduction amount setting unit 45 sets a second main drive wheel drive force reduction amount fm2 and a second subordinate drive wheel drive force reduction amount fs2 that are greater than 0 as the reduction amounts of the drive forces of the main drive wheels and the subordinate drive wheels, respectively. In this case, for example, when the main / subordinate drive wheel wheel speed difference D3 is large, the third drive force reduction amount setting unit 45 may set a larger second main drive wheel drive force reduction amount fm2 and a larger second subordinate drive wheel drive force reduction amount fs2 than when the main / subordinate drive wheel wheel speed difference D3 is small.

[0042] For example, when the main / subordinate drive wheel speed difference D3 is less than a predetermined value, the second main drive wheel driving force reduction amount fm2 and the second subordinate drive wheel driving force reduction amount fs2 may be set to relatively small values, and when the main / subordinate drive wheel speed difference D3 is equal to or greater than the predetermined value, the second main drive wheel driving force reduction amount fm2 and the second subordinate drive wheel driving force reduction amount fs2 may be set to relatively large values. Further, for example, the third driving force reduction amount setting unit 45 may set larger second main driving wheel driving force reduction amounts fm2 and fs2 as the main / subordinate driving wheel speed difference D3 increases.

[0043] For example, the second drive force reduction amount setting unit 43 may set the product obtained by multiplying the main-subordinate drive wheel speed difference D3 by a coefficient as the second main drive wheel drive force reduction amount fm2 and the second subordinate drive wheel drive force reduction amount fs2. Alternatively, for example, the second drive force reduction amount setting unit 43 may set the second main drive wheel drive force reduction amount fm2 in accordance with a map that defines the relationship between the main-subordinate drive wheel speed difference D3 and the second main drive wheel drive force reduction amount fm2, and may set the second subordinate drive wheel drive force reduction amount fs2 in accordance with a map that defines the relationship between the main-subordinate drive wheel speed difference D3 and the second subordinate drive wheel drive force reduction amount fs2. On the other hand, when the main / subordinate drive wheel speed difference D3 is less than the predetermined threshold T2, the third drive force reduction amount setting unit 45 sets the values ​​of the second main drive wheel drive force reduction amount fm2 and the second subordinate drive wheel drive force reduction amount fs2 to 0.

[0044] The adder 46 calculates the sum (fm1+fm2) of the first main drive wheel drive force reduction amount fm1 and the second main drive wheel drive force reduction amount fm2 as the main drive wheel drive force reduction amount fm. Subtractors 47 and 48 and adder 49 calculate the difference (fs1+fs2-fm1+fm2) obtained by subtracting the sum of the first main drive wheel drive force reduction amount fm1 and the second main drive wheel drive force reduction amount fm2 from the sum of the first subordinate drive wheel drive force reduction amount fs1 and the second subordinate drive wheel drive force reduction amount fs2 as the subordinate drive wheel drive force reduction amount fs. Therefore, when the first inner / outer wheel speed difference D1 is equal to or greater than the first threshold value T1m, the driving force of the main driving wheels is reduced by the first main driving wheel driving force reduction amount fm1. Also, the driving force reduction amount fs of the secondary driving wheels is reduced by the first main driving wheel driving force reduction amount fm1, so the driving force of the secondary driving wheels increases. Similarly, when the main / subordinate drive wheel speed difference D3 is equal to or greater than the predetermined threshold T2, the drive force of the main drive wheels is reduced by the second main drive wheel drive force reduction amount fm2. Also, the drive force reduction amount fs of the subordinate drive wheels is reduced by the second main drive wheel drive force reduction amount fm2, so the drive force of the subordinate drive wheels increases.

[0045] The first distribution unit 50 distributes the main drive wheel driving force reduction amount fm into a driving source driving force reduction amount tm by the driving force source and a braking force increase amount bm by the braking device or regenerative brake, and outputs the driving source driving force reduction amount tm to the driving force setting unit 32 and outputs the braking force increase amount bm to the braking force setting unit 33. The second distribution unit 51 distributes the subordinate drive wheel driving force reduction amount fs into a driving source driving force reduction amount ts by the driving force source and a braking force increase amount bs by the braking device or regenerative brake, and outputs the driving source driving force reduction amount ts to the driving force setting unit 32 and outputs the braking force increase amount bs to the braking force setting unit 33.

[0046] (action) An example of the operation of the reduction amount calculation unit 30 will be described below. Figures 3(a) to 3(c) are time charts illustrating an example of the reduction amount of driving force due to the first inner / outer wheel speed difference D1 of the main drive wheels. For simplicity of explanation, the influence of the second inner / outer wheel speed difference D2 of the subordinate drive wheels and the main / subordinate drive wheel speed difference D3 will be omitted here. The solid line in Figure 3(a) shows the wheel speed of the left main drive wheel, and the dashed line shows the time change in the wheel speed of the right wheel. Figure 3(b) shows the time change in the main drive wheel driving force reduction amount fm, and Figure 3(c) shows the time change in the secondary drive wheel driving force reduction amount fs.

[0047] As shown in Figure 3(a), when the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m due to slippage of the main drive wheels at time t1, the first main drive wheel driving force reduction amount fm1 is set to a larger value as the first inner / outer wheel speed difference D1 increases. Therefore, as shown in Figure 3(b), the main drive wheel driving force reduction amount fm = fm1 + fm2 increases. This reduces the driving force of the main drive wheels. Thereafter, when the slip of the main drive wheels converges and the first inner / outer wheel speed difference D1 becomes less than the predetermined threshold at time t2, the first drive force reduction amount setting unit 41 sets the value of the first main drive wheel drive force reduction amount fm1 to 0. This threshold may be equal to or different from the first threshold T1m. When the first main drive wheel drive force reduction amount fm1 becomes 0, the main drive wheel drive force reduction amount fm also becomes 0, and the reduction in drive force of the main drive wheels ends.

[0048] On the other hand, when the first main drive wheel drive force reduction amount fm1 becomes greater than 0 at time t1, the subordinate drive wheel drive force reduction amount fs=fs1+fs2-fm1-fm2 decreases as shown in Figure 3(c). In other words, the drive force of the subordinate drive wheels increases. As a result, when the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m, the driving force of the main driving wheels is reduced and the driving force of the subordinate driving wheels is increased.

[0049] 4(a) to 4(c) are time charts illustrating an example of the reduction in drive force due to the second inner / outer wheel speed difference D2 of the subordinate drive wheels. For simplicity of explanation, the effects of the first inner / outer wheel speed difference D1 and the main / subordinate drive wheel speed difference D3 are omitted here. The solid line in Figure 4(a) shows the wheel speed of the left driven wheel, and the dashed line shows the time change in the wheel speed of the right wheel. Figure 4(b) shows the time change in the driving force reduction amount fm of the main drive wheels, and Figure 4(c) shows the time change in the driving force reduction amount fs of the driven drive wheels.

[0050] As shown in Figure 4(a), when the second inner-outer wheel speed difference D2 becomes equal to or greater than the first threshold value T1s due to slippage of the subordinate drive wheels at time t1, the larger the second inner-outer wheel speed difference D2, the larger the first subordinate drive wheel driving force reduction amount fs1 is set to. Therefore, as shown in Figure 4(c), the subordinate drive wheel driving force reduction amount fs = fs1 + fs2 - fm1 - fm2 becomes larger. This reduces the driving force of the subordinate drive wheels. On the other hand, the main drive wheel driving force reduction amount fm is the sum (fm1 + fm2) of the first main drive wheel driving force reduction amount fm1 and the second main drive wheel driving force reduction amount fm2. Therefore, as shown in FIG. 4(c), it is not affected by the first subordinate drive wheel driving force reduction amount fs1. In this way, even if the driving force of the subordinate drive wheels is reduced, the driving force of the main drive wheels does not increase. In other words, the reduction in driving force of the subordinate drive wheels is not compensated for by an increase in driving force of the main drive wheels. Thereafter, when the slip of the driven wheels converges and the second inner / outer wheel speed difference D2 becomes less than the predetermined threshold value at time t2, the second driving force reduction amount setting unit 43 sets the value of the first driven wheel driving force reduction amount fs1 to 0. This threshold value may be equal to or different from the first threshold value T1s. When the first driven wheel driving force reduction amount fs1 becomes 0, the driven wheel driving force reduction amount fs also becomes 0.

[0051] 5(a) to 5(c) are time charts illustrating an example of the reduction in drive force due to the main-subordinate drive wheel speed difference D3. For simplicity of explanation, the effects of the first inner-outer wheel speed difference D1 and the second inner-outer wheel speed difference D2 are omitted here. The solid line in Figure 5(a) shows the wheel speed of the main drive wheels, and the dashed line shows the time change in the wheel speed of the slave drive wheels. Figure 5(b) shows the time change in the drive force reduction amount fm of the main drive wheels, and Figure 5(c) shows the time change in the drive force reduction amount fs of the slave drive wheels.

[0052] As shown in Figure 5(a), when the main / subordinate drive wheel speed difference D3 becomes equal to or greater than a predetermined threshold value T2, the larger the main / subordinate drive wheel speed difference D3 becomes, the larger the second main drive wheel driving force reduction amount fm2 and the second subordinate drive wheel driving force reduction amount fs2 are set to. Therefore, the main drive wheel driving force reduction amount fm=fm1+fm2 becomes large as shown in Fig. 5(b), thereby reducing the driving force of the main drive wheels.

[0053] On the other hand, the driven wheel driving force reduction amount fs = fs1 + fs2 - fm1 - fm2 increases as the second driven wheel driving force reduction amount fs2 increases, but decreases as the second main drive wheel driving force reduction amount fm2 increases. Therefore, when the third driving force reduction amount setting unit 45 sets the second main drive wheel driving force reduction amount fm2 greater than the second driven wheel driving force reduction amount fs2, the driven drive wheel driving force reduction amount fs decreases as shown in Figure 5(c). In other words, the driving force of the driven wheels increases. As a result, when the main drive wheel speed difference D3 becomes equal to or greater than the predetermined threshold value T2, the drive force of the main drive wheel is reduced and the drive force of the subordinate drive wheel is increased.

[0054] (Vehicle motion control method) FIG. 6 is a flowchart of an example of the vehicle motion control method according to the first embodiment. In step S1, the first inner / outer wheel speed difference calculation unit 40 and the second inner / outer wheel speed difference calculation unit 42 calculate the first inner / outer wheel speed difference D1 and the second inner / outer wheel speed difference D2. In step S2, the first driving force reduction amount setting unit 41 determines whether the first inner / outer wheel speed difference D1 is equal to or greater than the first threshold value T1m. If the first inner / outer wheel speed difference D1 is equal to or greater than the first threshold value T1m (step S2: Y), the process proceeds to step S3. If the first inner / outer wheel speed difference D1 is not equal to or greater than the first threshold value T1m (step S2: N), the process proceeds to step S4.

[0055] In step S3, the first driving force reduction amount setting unit 41 sets the first main driving wheel driving force reduction amount fm1 greater than 0 in accordance with the first inner / outer wheel speed difference D1. Thereafter, the process proceeds to step S5. In step S4, the first driving force reduction amount setting unit 41 sets the value of the first main driving wheel driving force reduction amount fm1 to 0. Thereafter, the process proceeds to step S5.

[0056] In step S5, the second driving force reduction amount setting unit 43 determines whether the second inner / outer wheel speed difference D2 is equal to or greater than the first threshold value T1s. If the second inner / outer wheel speed difference D2 is equal to or greater than the first threshold value T1s (step S5: Y), the process proceeds to step S6. If the second inner / outer wheel speed difference D2 is not equal to or greater than the first threshold value T1s (step S5: N), the process proceeds to step S7. In step S6, the second driving force reduction amount setting unit 43 sets the first driven-drive-wheel driving force reduction amount fs1 greater than 0 in accordance with the second inner / outer wheel speed difference D2. Thereafter, the process proceeds to step S8.

[0057] In step S7, the second driving force reduction amount setting unit 43 sets the value of the first driven wheel driving force reduction amount fs1 to 0. Thereafter, the process proceeds to step S8. In step S8, the primary / subordinate drive wheel speed difference calculation unit 44 calculates the primary / subordinate drive wheel speed difference D3. In step S9, the third driving force reduction amount setting unit 45 determines whether the primary / subordinate drive wheel speed difference D3 is equal to or greater than the predetermined threshold value T2. If the primary / subordinate drive wheel speed difference D3 is equal to or greater than the predetermined threshold value T2 (step S9: Y), the process proceeds to step S10. If the primary / subordinate drive wheel speed difference D3 is not equal to or greater than the predetermined threshold value T2 (step S9: N), the process proceeds to step S11.

[0058] In step S10, the third driving force reduction amount setting unit 45 sets the second main driving wheel driving force reduction amount fm2 greater than 0 and the second slave driving wheel driving force reduction amount fs2 greater than 0 in accordance with the main / slave driving wheel speed difference D3. Then, the process proceeds to step S12. In step S11, the third driving force reduction amount setting unit 45 sets the values ​​of the second main-drive-wheel driving force reduction amount fm2 and the second slave-drive-wheel driving force reduction amount fs2 to 0. After that, the process proceeds to step S12.

[0059] In step S12, adder 46 calculates the sum (fm1+fm2) of the first main drive wheel drive force reduction amount fm1 and the second main drive wheel drive force reduction amount fm2 as the main drive wheel drive force reduction amount fm. Subtractors 47 and 48 and adder 49 calculate the difference (fs1+fs2-fm1+fm2) obtained by subtracting the sum of the first main drive wheel drive force reduction amount fm1 and the second main drive wheel drive force reduction amount fm2 from the sum of the first subordinate drive wheel drive force reduction amount fs1 and the second subordinate drive wheel drive force reduction amount fs2 as the subordinate drive wheel drive force reduction amount fs. Then, the process ends.

[0060] (Second embodiment) In a situation where the main drive wheels are slipping, the secondary drive wheels may also be slipping. Therefore, if the drive force of the secondary drive wheels is increased in conjunction with a reduction in the drive force of the main drive wheels, this may exacerbate the slip of the secondary drive wheels. Therefore, in the second embodiment, the reduction amount calculation unit 30 determines whether the second inner / outer wheel speed difference D2 is greater than or equal to the second threshold value T3, and if it determines that the first inner / outer wheel speed difference D1 is greater than or equal to the first threshold value T1m and the second inner / outer wheel speed difference D2 is greater than or equal to the second threshold value T3, it does not increase the driving force of the secondary drive wheels (for example, it prohibits an increase in the driving force of the secondary drive wheels). This suppresses an increase in the drive force of the driven wheels and prevents the driven wheels from slipping, thereby stabilizing the vehicle behavior.

[0061] 7 is a block diagram showing an example of the functional configuration of the reduction amount calculation unit 30 in the second embodiment. The same components as those of the reduction amount calculation unit 30 in the first embodiment are given the same reference numerals. The reduction amount calculation unit 30 in the second embodiment includes a slave drive wheel slip suppression unit 52. The slave drive wheel slip suppression unit 52 determines whether the second inner / outer wheel speed difference D2 is equal to or greater than a second threshold value T3. If it is determined that the second inner / outer wheel speed difference D2 is less than the second threshold value T3, the slave drive wheel slip suppression unit 52 inputs the first main drive wheel drive force reduction amount fm1 set by the first drive force reduction amount setting unit 41 directly to the subtractor 47, and inputs the second main drive wheel drive force reduction amount fm2 set by the third drive force reduction amount setting unit 45 directly to the subtractor 48.

[0062] Therefore, when the first main drive wheel driving force reduction amount fm1 is a positive value other than 0 (i.e., when the first inner / outer wheel speed difference D1 is equal to or greater than the first threshold value T1m), the first main drive wheel driving force reduction amount fm1 reduces the driven drive wheel driving force reduction amount fs. In other words, the driving force of the driven wheels increases. Also, when the second main drive wheel driving force reduction amount fm2 is a positive value other than 0 (i.e., when the main / subordinate drive wheel speed difference D3 is equal to or greater than the predetermined threshold value T2), the second main drive wheel driving force reduction amount fm2 reduces the driven drive wheel driving force reduction amount fs. In other words, the driving force of the driven wheels increases.

[0063] On the other hand, when it is determined that the second inner / outer wheel speed difference D2 is greater than or equal to the second threshold value T3, the secondary drive wheel slip suppression unit 52 inputs the value 0 to the subtractors 47 and 48 instead of the first and second main drive wheel drive force reduction amounts fm1 and fm2. As a result, even if the first inner / outer wheel speed difference D1 is equal to or greater than the first threshold value T1m, the driving force of the subordinate drive wheel does not increase due to the first main drive wheel driving force reduction amount fm1, and even if the main / subordinate drive wheel speed difference D3 is equal to or greater than the predetermined threshold value T2, the driving force of the subordinate drive wheel does not increase due to the second main drive wheel driving force reduction amount fm2.

[0064] The solid line in Figure 8(a) shows the wheel speed of the left wheel, which is the main drive wheel, and the dashed line shows the time change in the wheel speed of the right wheel. The solid line in Figure 8(b) shows the wheel speed of the left wheel, which is the slave drive wheel, and the dashed line shows the time change in the wheel speed of the right wheel. Figure 8(c) shows the time change in the main drive wheel driving force reduction amount fm, and Figure 8(d) shows the time change in the slave drive wheel driving force reduction amount fs. As shown in FIG. 8(a), when the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m due to slippage of the main drive wheels at time t1, the larger the first inner / outer wheel speed difference D1 becomes, as shown in FIG. 8(c), the larger the main drive wheel driving force reduction amount fm becomes. This reduces the driving force of the main drive wheels. Also, as shown in FIG. 8(d), the secondary drive wheel driving force reduction amount fs decreases. In other words, the driving force of the secondary drive wheels increases.

[0065] After that, at time t2, the slip of the main drive wheels converges. Then, at time t3, slip of the slave drive wheels occurs, and the second inner / outer wheel speed difference D2 becomes equal to or greater than the second threshold value T3, as shown in FIG. 8(a). In this case, even if the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m due to slippage of the main drive wheels at time t4, the first main drive wheel drive force reduction amount fm1 does not reduce the subordinate drive wheel drive force reduction amount fs. In other words, the reduction in drive force of the main drive wheels is not compensated for by an increase in drive force of the subordinate drive wheels. This makes it possible to prevent the subordinate drive wheels from slipping.

[0066] In the above explanation, the slave drive wheel slip suppression unit 52 is configured not to increase the drive force of the slave drive wheels by the first main drive wheel drive force reduction amount fm1 and the second main drive wheel drive force reduction amount fm2 when it determines that the second inner / outer wheel speed difference D2 is greater than the second threshold value T3, but it may also be configured not to increase the drive force of the slave drive wheels by the first main drive wheel drive force reduction amount fm1 and the second main drive wheel drive force reduction amount fm2 when it determines that the second inner / outer wheel speed difference D2 is greater than the first inner / outer wheel speed difference D1.

[0067] 9 is a flowchart of an example of a vehicle motion control method according to the second embodiment. The processing of steps S21 to S31 in FIG. 9 is the same as the processing of steps S1 to S11 described with reference to FIG. In step S32, the driven wheel slip suppression unit 52 determines whether the second inner / outer wheel speed difference D2 is equal to or greater than the second threshold value T3 or whether the second inner / outer wheel speed difference D2 is greater than the first inner / outer wheel speed difference D1. If the second inner / outer wheel speed difference D2 is equal to or greater than the second threshold value T3 or greater than the first inner / outer wheel speed difference D1 (step S32: Y), the process proceeds to step S33.

[0068] If the second inner / outer wheel speed difference D2 is less than the second threshold value T3 and is equal to or less than the first inner / outer wheel speed difference D1 (step S32: N), the process proceeds to step S34. In step S33, the slave drive wheel slip suppression unit 52 inputs a value of 0 to the subtractors 47 and 48 instead of the first and second main drive wheel drive force reduction amounts fm1 and fm2. The adder 46 calculates the main drive wheel drive force reduction amount fm = (fm1 + fm2). The subtractors 47 and 48 and the adder 49 calculate the slave drive wheel drive force reduction amount fs = fs1 + fs2. The process then ends. In step S34, the slave drive wheel slip suppression unit 52 inputs the first and second main drive wheel drive force reduction amounts fm1 and fm2 to the subtractors 47 and 48. The adder 46 calculates the main drive wheel drive force reduction amount fm = (fm1 + fm2). The subtractors 47 and 48 and the adder 49 calculate the slave drive wheel drive force reduction amount fs = fs1 + fs2 - fm1 - fm2. The process then ends.

[0069] (Third embodiment) As described above with reference to the time charts of Figures 3(a) to 3(c), when slippage occurs in the main drive wheels and the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m, the drive force of the main drive wheels is reduced. After that, when the slippage of the main drive wheels subsides, the reduction in the drive force of the main drive wheels is stopped. Therefore, if the first inner / outer wheel speed difference D1 repeatedly increases and decreases, causing the reduction and stopping of the driving force of the main driving wheels to be repeated, there is a risk that the occupants will feel the acceleration fluctuations due to the fluctuations in driving force and feel uncomfortable.

[0070] In particular, the control resolution of the braking devices, such as the hydraulic circuit 11 and the brake caliper 12, is lower than the control resolution of the first driving force source 14f and the second driving force source 14r, which are electric motors. Therefore, when the driving force of the driving wheels is reduced by the braking force of the braking devices, the fluctuations in the driving force tend to become larger, and the acceleration fluctuations felt by the occupants also tend to become larger. Therefore, in the third embodiment, after the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m and the driving force of the main driving wheels is reduced, the reduction amount calculation unit 30 limits the increase or decrease in the driving force of the main driving wheels for a predetermined time in accordance with fluctuations in the first inner / outer wheel speed difference D1. This suppresses fluctuations in driving force even if the first inner / outer wheel speed difference D1 repeatedly increases and decreases after the driving force of the main drive wheels is reduced. As a result, fluctuations in driving force can be suppressed, and acceleration fluctuations felt by the occupants can also be suppressed.

[0071] The solid line in Fig. 10(a) shows the wheel speed of the left main drive wheel, and the dashed line shows the change in wheel speed of the right wheel over time. Fig. 10(b) shows the change in the main drive wheel driving force reduction amount fm over time, Fig. 10(c) shows the change in the motor command of the driving force source that generates driving force to the main drive wheels over time, and Fig. 10(d) shows the change in the braking force increase amount bm, which is the increase in the braking force of the main drive wheels applied by the braking device, over time. At time t1, when slippage occurs in the main drive wheels and the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m as shown in Figure 10(a), the main drive wheel driving force reduction amount fm increases as shown in Figure 10(b).

[0072] 3 and 7 distributes the main drive wheel drive force reduction amount fm to a drive source drive force reduction amount tm, which is a reduction amount of the drive force command value for the main drive wheels, and a braking force increase amount bm, which is an increase amount of the braking force command value for the main drive wheels. As a result, the motor command of the drive force source for the main drive wheels is reduced as shown in FIG. 10(c). Also, the braking force increase amount bm increases as shown in FIG. 10(d) (i.e., the braking force of the main drive wheels by the brake device increases). Thereafter, when the slip of the main drive wheels converges and the first inner / outer wheel speed difference D1 becomes less than the predetermined threshold at time t2, the first drive force reduction amount setting unit 41 sets the value of the first main drive wheel drive force reduction amount fm1 to 0. This causes the motor command of the drive force source to return to normal as shown in FIG. 10(c).

[0073] On the other hand, the first distributor 50 limits the change in the braking force increase amount bm for only a predetermined time TD after the slip has subsided. This limits the decrease or increase in the driving force of the main drive wheels due to changes in the braking force of the brake device for only the predetermined time TD. As a result, the braking force of the main drive wheels by the brake device is maintained, and changes in vehicle behavior are suppressed. Then, at time t3, when slippage occurs in the main drive wheels and the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m as shown in Figure 10(a), the main drive wheel driving force reduction amount fm increases as shown in Figure 10(b).

[0074] As a result, the motor command for the drive force source of the main drive wheels is reduced as shown in Figure 10(c). At time t4, the slip of the main drive wheels converges, and the reduction in the motor command for the drive force source stops as shown in Figure 10(c). During this time, fluctuations in the braking force increase amount bm are suppressed and maintained at a constant value. When the time t5 arrives after a predetermined time TD has elapsed since the slip convergence, the first distribution unit 50 gradually changes the braking force increase amount bm to zero.

[0075] In the above description, the first distributing unit 50 limited the change in the braking force increase amount bm, but it may also limit the change in the drive source drive force reduction amount tm. That is, after the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m and the drive force of the main drive wheels is reduced, the first distributing unit 50 may limit, for a predetermined time, the increase or decrease of the motor command for the drive force source in accordance with fluctuations in the first inner / outer wheel speed difference D1. Furthermore, after the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m and the driving force of the main drive wheels is reduced, the second allocator 51 may also limit, for a predetermined time, the increase or decrease of the driving source driving force reduction amount ts and / or the braking force increase amount bs in accordance with fluctuations in the first inner / outer wheel speed difference D1. In other words, the increase or decrease of the driving force of the slave drive wheels may be limited for a predetermined time.

[0076] 11 is a flowchart of an example of a vehicle motion control method according to the third embodiment. The processing of steps S41 to S54 in FIG. 11 is the same as the processing of steps S21 to S34 described with reference to FIG. In step S55, the first distribution unit 50 distributes the main drive wheel drive force reduction amount fm to the drive source drive force reduction amount tm and the braking force increase amount bm, and distributes the slave drive wheel drive force reduction amount fs to the drive source drive force reduction amount ts and the braking force increase amount bs. In step S56, the first allocating unit 50 limits changes in the drive source driving force reduction amount tm and the braking force increase amount bm until a predetermined time has elapsed after the first inner / outer wheel speed difference D1 becomes equal to or greater than the first threshold value T1m. The second allocating unit 51 may also similarly limit changes in the drive source driving force reduction amount ts and the braking force increase amount bs. Then, the process ends.

[0077] (Effects of the embodiment) (1) The braking / driving force controller 5 calculates a first inner / outer wheel speed difference, which is the difference between the wheel speed of the right wheel and the wheel speed of the left wheel, which are the main drive wheels among the front wheels and rear wheels, determines whether the first inner / outer wheel speed difference is equal to or greater than a first threshold value, and if it determines that the first inner / outer wheel speed difference is equal to or greater than the first threshold value, reduces the drive force of the main drive wheel and increases the drive force of the secondary drive wheel, which is one of the front wheels and rear wheels. This suppresses slippage of the main drive wheels before significant changes in vehicle behavior occur, thereby preventing sudden changes in vehicle behavior. Furthermore, by suppressing the shift in vehicle body load caused by a reduction in the drive force of the main drive wheels, vehicle behavior can be stabilized. Furthermore, since the drive force can be maintained by compensating for the reduction in drive force of the main drive wheels with an increase in drive force of the secondary drive wheels, loss of acceleration performance can be prevented even when the drive force of the main drive wheels is reduced.

[0078] (2) When the first inner / outer wheel speed difference is large, the braking / driving force controller 5 may increase the amount of reduction in the driving force of the main driving wheels and the amount of increase in the driving force of the secondary driving wheels compared to when the first inner / outer wheel speed difference is small. This allows the amount of reduction to be determined according to the first inner / outer wheel speed difference, thereby mitigating changes in vehicle behavior when slippage occurs at the main drive wheels. Also, when the first inner / outer wheel speed difference is large, the amount of reduction in drive force at the main drive wheels can be increased, allowing slippage at the main drive wheels to be quickly contained, and the amount of increase in drive force at the slave drive wheels can also be increased, preventing unnecessary reductions in drive force.

[0079] (3) The braking / driving force controller 5 may calculate a second inner / outer wheel speed difference, which is the difference between the wheel speed of the right wheel and the wheel speed of the left wheel, of the subordinate driving wheels, determine whether the second inner / outer wheel speed difference is greater than or equal to a second threshold value, and not increase the driving force of the subordinate driving wheels if it is determined that the first inner / outer wheel speed difference is greater than or equal to the first threshold value and the second inner / outer wheel speed difference is greater than or equal to the second threshold value. The braking / driving force controller 5 may be configured not to increase the driving force of the secondary drive wheel when it determines that the first inner / outer wheel speed difference is equal to or greater than a first threshold value and that the second inner / outer wheel speed difference is greater than the first inner / outer wheel speed difference. This suppresses an increase in the drive force of the driven wheels and prevents the driven wheels from slipping, thereby stabilizing the vehicle behavior.

[0080] (4) After the first inner / outer wheel speed difference becomes equal to or greater than the first threshold value and the driving force of the main driving wheels is reduced, the braking / driving force controller 5 may limit, for a predetermined period of time, the increase or decrease in the driving force of the main driving wheels in accordance with fluctuations in the first inner / outer wheel speed difference. As a result, even if the first inner / outer wheel speed difference repeatedly becomes equal to or greater than the first threshold value and becomes less than the first threshold value, fluctuations in driving force can be suppressed, and fluctuations in acceleration felt by the occupants can be suppressed. (5) The braking / driving force controller 5 may reduce the driving force of the main drive wheels by reducing the driving force generated by the driving force source on the main drive wheels, or by increasing the braking force of the main drive wheels by regenerative braking of the braking device or the driving force source. This allows a reduction in the driving force of the main drive wheels.

[0081] (6) The main drive wheels may be front wheels and the secondary drive wheels may be rear wheels. In this case, it is possible to suppress hunting in the reduction of the drive force of the main drive wheels, which occurs due to a shift in the load of the vehicle body caused by a reduction in the drive force of the main drive wheels. (7) The main drive wheels may be rear wheels and the secondary drive wheels may be front wheels. This prevents the effect of reducing the driving force of the main drive wheels to prevent slippage from being impaired by load shift. [Explanation of symbols]

[0082] 1...Vehicle motion control device, 4FR, 4FL, 4RR, 4RL...Wheel speed sensors, 11...Hydraulic pressure circuit, 12FR, 12FL, 12RR, 12RL...Brake calipers, WFR...Right front wheel, WFL...Left front wheel, WRR...Right rear wheel, WRL...Left rear wheel

Claims

1. calculating a first inner / outer wheel speed difference which is a difference between the wheel speed of the right wheel and the wheel speed of the left wheel, which are main drive wheels among the front wheels and the rear wheels; determining whether the first inner / outer wheel speed difference is equal to or greater than a first threshold value; When it is determined that the first inner / outer wheel speed difference is equal to or greater than a first threshold value, the driving force of the main driving wheels is reduced and the driving force of the subordinate driving wheels of the front wheels and the rear wheels is increased; determining whether a second inner / outer wheel speed difference, which is a difference between the wheel speed of the right wheel and the wheel speed of the left wheel, of the subordinate drive wheels, is equal to or greater than a second threshold value; not increasing the driving force of the slave drive wheels when it is determined that the first inner and outer wheel speed difference is equal to or greater than a first threshold value and the second inner and outer wheel speed difference is equal to or greater than a second threshold value; A vehicle motion control method comprising:

2. Calculating a first inner / outer wheel speed difference, which is the difference between the wheel speed of the right wheel and the wheel speed of the left wheel, which are the main drive wheels of the front and rear wheels; determining whether the first inner / outer wheel speed difference is equal to or greater than a first threshold value; When it is determined that the first inner / outer wheel speed difference is equal to or greater than a first threshold value, the driving force of the main driving wheels is reduced and the driving force of the subordinate driving wheels of the front wheels and the rear wheels is increased; determining which of a second inner / outer wheel speed difference, which is a difference between the wheel speed of the right wheel and the wheel speed of the left wheel, of the subordinate drive wheels, or the first inner / outer wheel speed difference is larger; not increasing the driving force of the slave drive wheels when it is determined that the first inner and outer wheel speed difference is equal to or greater than a first threshold value and the second inner and outer wheel speed difference is greater than the first inner and outer wheel speed difference; A vehicle motion control method comprising:

3. Calculating a first inner / outer wheel speed difference, which is the difference between the wheel speed of the right wheel and the wheel speed of the left wheel, which are the main drive wheels of the front and rear wheels; determining whether the first inner / outer wheel speed difference is equal to or greater than a first threshold value; When it is determined that the first inner / outer wheel speed difference is equal to or greater than a first threshold value, the driving force of the main driving wheels is reduced and the driving force of the subordinate driving wheels of the front wheels and the rear wheels is increased; A vehicle motion control method characterized by limiting, for a predetermined time, the increase or decrease in the driving force of the main drive wheels in accordance with fluctuations in the first inner / outer wheel speed difference after the first inner / outer wheel speed difference becomes equal to or greater than a first threshold value and the driving force of the main drive wheels is reduced.

4. Calculating a first inner / outer wheel speed difference, which is the difference between the wheel speed of the right wheel and the wheel speed of the left wheel, which are the main drive wheels of the front and rear wheels; determining whether the first inner / outer wheel speed difference is equal to or greater than a first threshold value; When it is determined that the first inner / outer wheel speed difference is equal to or greater than a first threshold value, the driving force of the main driving wheels is reduced and the driving force of the subordinate driving wheels of the front wheels and the rear wheels is increased; A vehicle motion control method comprising: reducing the driving force generated by a driving force source at the main drive wheels; or increasing the braking force of the main drive wheels by a braking device or regenerative braking of the driving force source, thereby reducing the driving force of the main drive wheels.

5. A vehicle motion control method described in any one of claims 1 to 4, characterized in that when the first inner / outer wheel speed difference is large, the reduction in driving force of the main drive wheel and the increase in driving force of the secondary drive wheel are made larger than when the first inner / outer wheel speed difference is small.

6. 6. The vehicle motion control method according to claim 1, wherein the main drive wheels are front wheels, and the secondary drive wheels are rear wheels.

7. 6. The vehicle motion control method according to claim 1, wherein the main drive wheels are rear wheels, and the secondary drive wheels are front wheels.

8. At least one driving force source that generates driving force on the main driving wheels and the secondary driving wheels among the front wheels and the rear wheels; a first wheel speed sensor for detecting a wheel speed of the right wheel of the main drive wheels; a second wheel speed sensor for detecting the wheel speed of the left wheel of the main drive wheel; a controller that calculates a first inner / outer wheel speed difference, which is a difference between the wheel speed of the right wheel detected by the first wheel speed sensor and the wheel speed of the left wheel detected by the first wheel speed sensor, determines whether the first inner / outer wheel speed difference is equal to or greater than a first threshold value, and reduces the driving force of the main driving wheels and increases the driving force of the slave driving wheels when it is determined that the first inner / outer wheel speed difference is equal to or greater than the first threshold value; Equipped with The vehicle motion control device is characterized in that the controller reduces the driving force of the main drive wheels by reducing the driving force generated by a driving force source on the main drive wheels, or by increasing the braking force of the main drive wheels by a braking device or regenerative braking of the driving force source.

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