JP3577088B2 - Driving / braking force distribution control device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a driving / braking force distribution control device for a vehicle, and more particularly to a technique for eliminating unnecessary operation thereof.
[0002]
[Prior art]
It has already been proposed to mount a drive / braking force distribution control device on a vehicle. This device is generally provided in a vehicle having a plurality of wheels, and controls distribution of at least one of a driving force and a braking force to each wheel. (A) Acquiring the actual turning state amount of the vehicle And (b) distribution control means for controlling distribution so that the acquired actual turning state quantity follows the target turning state quantity. The yawing moment generated in the vehicle body is controlled so as to always match the driver's intention (ie, the amount of operation).
[0003]
One conventional example of this device is described in Japanese Patent Application Laid-Open No. 60-248466. This is because the distribution control means starts the braking force distribution control when the difference between the obtained actual turning state quantity and the target turning state quantity becomes larger than a non-zero reference value. Is a braking force distribution control device that controls the distribution of the braking force so as to follow the target turning state quantity.
[0004]
[Problems to be solved by the invention]
In this conventional device, the distribution control is not started unless the difference between the actual value and the target value of the turning state quantity becomes larger than the reference value. The distribution control is not started to the extent that the error occurs, and unnecessary distribution control is avoided.
[0005]
However, research conducted by the present applicant has revealed the following facts regarding this conventional device. That is, in this conventional device, the reference value is not changed regardless of the vehicle speed. However, when the vehicle speed is low, the reference value is not changed even if the behavior of the vehicle becomes unstable as compared with the case where the vehicle speed is high. Since it can be easily corrected, the necessity of distribution control is not high.Therefore, if the reference value is made variable according to the vehicle speed, and is larger when the vehicle speed is low than when it is high, the reference value is limited only when it is really necessary. Thus, the fact that the distribution control is performed and unnecessary distribution control is omitted has been found out.
[0006]
Thus, the fact that the control start condition is made variable and the control start condition becomes stricter as the necessity of the distribution control becomes lower, the wasteful distribution control can be further omitted, has been found. The present invention has been made to solve the problem of further eliminating unnecessary distribution control.
[0007]
[Means for Solving the Problems]
In order to solve this problem, the invention according to claim 1 includes a driving / braking force distribution control device, as shown in FIG. 1, comprising: (a) an actual turning state amount obtaining means 1 for obtaining an actual turning state amount of a vehicle; (B) when a deviation of the actual turning state quantity acquired by the actual turning state quantity acquisition means from a target turning state quantity determined based on the vehicle speed and the steering angle is obtained, and the deviation is larger than a reference value. (C) distribution control means 2 for starting the driving / braking force distribution control and controlling the distribution so that the actual turning state quantity follows the target turning state quantity, and (c) increasing the reference value when the vehicle speed is low. Control start reference value determining means 3 for determining a value larger than the case.
According to a second aspect of the present invention, the driving / braking force distribution control device is obtained by (d) an actual turning state amount obtaining unit that obtains an actual turning state amount of the vehicle, and (e) the actual turning state amount obtaining unit. The deviation of the actual turning state amount from the target turning state amount is acquired, and when the deviation becomes larger than the reference value, the drive / braking force distribution control is started, and the actual turning state amount follows the target turning state amount. And (f) control start reference value determining means for determining the reference value to be a value other than 0 and a larger value when the vehicle speed is higher when the vehicle speed is lower. It is characterized by that.
According to a third aspect of the present invention, the actual turning state quantity obtaining means obtains a yaw rate of the vehicle.includingCharacterized in thatThe invention according to claim 4 is characterized in that the actual turning state amount obtaining means includes a means for obtaining a lateral acceleration of the vehicle,The invention according to claim 5 is characterized in that the control start reference value determining means further determines the reference value to be a larger value when the absolute value of the steering angle is large and smaller when the absolute value of the steering angle is small.
[0008]
One aspect of the "distribution control means 2" is to start the drive / braking force distribution control when the difference between the actual turning state quantity and the target turning state quantity becomes larger than the reference value, When the difference between the amount and the target turning state amount becomes equal to or less than the reference value, the drive / braking force distribution control can be terminated. That is, the drive / braking force distribution control can be performed only during a period in which the difference between the actual turning state amount and the target turning state amount is larger than the reference value (however, the control start determination reference value And the reference value for judging the control end may be different from each other.) In another aspect, the drive / braking force distribution control is started when the difference between the actual turning state amount and the target turning state amount becomes larger than the reference value. The driving / braking force distribution control may not be terminated until the difference becomes zero.
[0009]
[Action]
In the driving / braking force control device according to the present invention, the control start reference value determining means 3 determines that the reference value is larger when the vehicle speed is low than when it is high. Then, the distribution control is not easily started, and the distribution control is started only when it is really necessary.
[0010]
【The invention's effect】
As described above, according to the present invention, the distribution control is started only when it is really necessary, so that not only the load on the driving / braking force distribution control device itself but also the driving / braking force control device is controlled. Can reduce the load on a device (for example, a center differential clutch, a brake, etc.) used for distribution control.
[0011]
【Example】
Hereinafter, a braking force distribution control device according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0012]
This braking force distribution control device is provided in a four-wheel vehicle in which wheels are arranged in front, rear, left and right, and controls left, right, front and rear distribution of a braking force. This braking force distribution control device is provided in the electrically controlled brake system shown in FIG. In this brake system, as shown in FIG. 1, a master cylinder 10 and an electric control hydraulic pressure source 12 are connected to a wheel cylinder 20 of each of the four wheels FR, FL, RR, RL via a two-position valve 14. It is constituted by being done. The two-position valve 14 enables either the master cylinder 10 or the electric control hydraulic pressure source 12 to be selected as the hydraulic pressure source for the wheel cylinder 20.
[0013]
The master cylinder 10 is of a tandem type in which two pressurizing chambers are arranged in series with each other, and mechanically generates a hydraulic pressure in the pressurizing chambers at a height corresponding to the depression force F of the brake pedal 24. One pressurizing chamber is connected to the wheel cylinders 20 of the left and right front wheels FL, FR, and the other pressurizing chamber is connected to the wheel cylinders 20 of the left and right rear wheels RL, RR.
[0014]
The electric control hydraulic pressure source 12 mainly includes an accumulator 30, a pump 34 for pumping hydraulic fluid from a reservoir 32 and storing it in the accumulator 30, a linear hydraulic pressure control valve 40 for controlling the hydraulic pressure to a height proportional to the exciting current, and the like. The linear hydraulic pressure control valve 40 reduces the high hydraulic pressure accumulated in the accumulator 30 to an appropriate level and outputs the reduced hydraulic pressure. The linear hydraulic pressure control valve 40 changes the level of the hydraulic pressure linearly with respect to the magnetic force by balancing the magnetic force and the hydraulic pressure acting on the spool in opposite directions by the spool itself. The linear hydraulic pressure control valves 40 are provided individually for each wheel cylinder 20 and control the brake pressure of each wheel cylinder 20 independently of each other.
[0015]
The two-position valve 14 is also provided individually for each wheel cylinder 20. In the non-energized state, the two-position valve 14 is at a position where the master cylinder 10 is communicated with the wheel cylinder 20 and the linear hydraulic pressure control valve 40 is shut off from the wheel cylinder 20. A direction switching valve that allows the master cylinder 10 to be disconnected from the wheel cylinder 20 while communicating the wheel 40 with the wheel cylinder 20.
[0016]
The linear hydraulic pressure control valve 40 and the two-position valve 14 are connected to the output side of an ECU (Electronic Controlled Unit) 60 via drive circuits 50 and 52 as shown in FIG. On the other hand, an input side of the ECU 60 is connected to a pedaling force sensor 70, a yaw rate sensor 72, a vehicle speed sensor 74, a steering angle sensor 76, a front wheel load sensor 78, a rear wheel load sensor 80, a pressure sensor 86, and the like. Hereinafter, each of these sensors will be briefly described.
[0017]
The pedal force sensor 70 detects the pedal force F of the brake pedal 24. The yaw rate sensor 72 detects a yaw rate actually generated in the vehicle body, that is, an actual yaw rate γ, and detects a counterclockwise yaw rate as positive and a clockwise yaw rate as negative. The vehicle speed sensor 74 detects a vehicle speed V that is the traveling speed of the vehicle. The steering angle sensor 76 detects the steering angle θ of the steering wheel. The front wheel load sensor 78 and the rear wheel load sensor 80 respectively provide a ground load W acting on the left / right front wheel and the left / right rear wheel, respectively._FL, W_FR, W_RL, W_RRIs to be detected. The pressure sensor 86 is provided individually for each wheel cylinder 20 and detects the brake pressure P thereof.
[0018]
The ECU 60 mainly includes a computer including a CPU, a ROM, and a RAM. The ECU 60 executes a program stored in advance based on various input signals to determine whether the electric control hydraulic pressure source 12 is normal. Then, if it is normal, the pedaling force-brake pressure control is executed, and the left / right / front / rear distribution control is executed regardless of whether the vehicle is braking.
[0019]
Here, the "pedal force-brake pressure control" means the total braking force B suitable for realizing the vehicle deceleration having a magnitude corresponding to the pedal force F of the brake pedal 24._TOTAnd the total braking force B_TOTIs the ground load W on each wheel._FL, W_FR, W_RL, W_RRIs to control the brake pressure via the linear hydraulic pressure control valve 40 so that the brake pressure is distributed according to the ratio. That is, the reference front wheel braking force B of the left front wheel_FL0Is
(W_FL/ (W_FL+ W_FR+ W_RL+ W_RR)) ・ B_TOT
And the reference braking force B for the right front wheel_FR0Is
(W_FR/ (W_FL+ W_FR+ W_RL+ W_RR)) ・ B_TOT
And the reference braking force B for the left rear wheel_RL0Is
(W_RL/ (W_FL+ W_FR+ W_RL+ W_RR)) ・ B_TOT
And the reference rear wheel braking force B of the right rear wheel_RR0Is
(W_RR/ (W_FL+ W_FR+ W_RL+ W_RR)) ・ B_TOT
It is said that.
[0020]
On the other hand, the "right / left / front / rear distribution control" is a control in which the left / right distribution control and the front / rear distribution control are executed together, and they are executed simultaneously with the pedaling force-brake pressure control. Then, the actual yaw rate γ of the vehicle body is detected, and the target yaw rate γ of the vehicle body is obtained from the vehicle speed V and the steering angle θ.^*Is determined, and the reference wheel braking force B in the pedaling force-brake pressure control is determined.₀The actual yaw rate γ is the target yaw rate γ^*(This is one aspect of “distribution” in the present invention) so as to follow the braking force. That is, as shown in FIG. 4, the left / right and front / rear distribution control is performed by a control method in which the actual vehicle follows the virtual model in which the steering response characteristic of the actual yaw rate γ is set in advance, that is, the reference model. And the actual yaw rate γ is the target yaw rate γ which is the output of the reference model.^*This is a model-following control of the yaw rate that controls the left / right and front / rear distribution by following the vehicle, and the vehicle's actual steering characteristics are close to neutral, ensuring the vehicle's steering stability regardless of whether the vehicle is braking. That is, the difference between the left and right and front and rear braking forces is controlled. Details of this control will be described later.
[0021]
When the electric control hydraulic pressure source 12 is enabled, the discharge of the hydraulic fluid from the master cylinder 20, that is, the displacement of the brake pedal 24 is prevented by the two-position valve 14, so that the brake operation feeling is considerably hard. It will be. Therefore, even when the electric control hydraulic pressure source 12 is enabled, a brake operation feeling similar to that when the master cylinder 10 is enabled is obtained, as shown in FIG. In addition, a stroke simulator 92 is connected to the pressurizing chamber of the master cylinder 10 via a two-position valve 90 which is a normally closed electromagnetic on-off valve. While the electric control hydraulic pressure source 12 is enabled, the two-position valve 90 is energized and is kept open, so that the hydraulic fluid discharged from the master cylinder 10 is accumulated under pressure. The displacement of the brake pedal 24 is realized in a pseudo manner.
[0022]
On the other hand, when the electric control hydraulic pressure source 12 is not normal, the ECU 60 sets the two-position valve 14 to a non-energized state to enable the master cylinder 10, and the brake of the wheel cylinder 20 is operated in accordance with the operation of the brake pedal 24. The pressure is changed mechanically.
[0023]
Here, the left / right / front / rear distribution control will be described in detail.
[0024]
In this control, first, the reference wheel braking force B related to the pedaling force-brake pressure control.₀(That is, the total braking force B)_TOTIs substantially maintained), the braking force left / right difference ΔB related to the left / right distribution control is calculated. This braking force left-right difference ΔB is
K ・ (γ^*-Γ)
Is calculated as Here, “K” is a control gain that increases as the vehicle speed V increases and decreases as the absolute value of the steering angle θ increases.
[0025]
The control gain K is increased as the vehicle speed V increases, that is, when the vehicle speed V is low, the yaw rate deviation Δγ (= γ) of the braking force left-right difference ΔB is larger than when the vehicle speed V is large.^*-Γ) is determined to be sensitive because the driver can more easily perform the operation for correcting the behavior of the vehicle when the vehicle speed V is low than when the vehicle speed V is high. This is because the nature is not high. Also, the reason why the control gain K is determined to decrease as the absolute value of the steering angle θ increases is that the driver is sensitive to the occurrence of the yaw rate deviation Δγ while the steering wheel is near the neutral position, This is because it is not sensitive in a state where the steering angle θ deviates from the neutral position, and therefore, it is not necessary to execute the distribution control when the absolute value of the steering angle θ is large than when the absolute value of the steering angle θ is small. By determining the control gain K with such characteristics, useless distribution control is omitted, and useless brake operation is also omitted, and as a result, the load on the brake (for example, the amount of wear) is reduced. It is.
[0026]
In the present embodiment, in order for the control gain K to be obtained with the above characteristics, the control gain K is specifically set to the partial control gain K₁And K₂And the partial control gain K₁Is a variable value that changes as shown in the graph of FIG. 5 according to the vehicle speed V, while the partial control gain K₂Is a variable value that changes as shown in the graph of FIG. 6 according to the steering angle θ. The control gain K can be determined by any other method. For example, the relationship between the vehicle speed V, the steering angle θ, and the control gain K is stored in advance in the form of a map, a functional expression, or the like. May be employed.
[0027]
When the braking force left / right difference ΔB is calculated in this manner, the braking force left / right difference ΔB is distributed to the front wheels and the rear wheels according to the wheel load distribution between the front and rear wheels. The total braking force B in the pedaling force-brake pressure control_TOTIs distributed to the front and rear wheels, and the braking force left / right difference ΔB is distributed. However, in this embodiment, a yawing moment for correcting the direction of the vehicle body is generated by increasing the brake pressure P of one of the left and right wheels, and specifically, If it is necessary to increase the turning yaw moment, the braking force is increased for both the right front wheel and the right rear wheel, and conversely, if it is necessary to increase the counterclockwise yawing moment of the vehicle body, It is designed to increase the braking force for both the left front wheel and the left rear wheel.
[0028]
Therefore, in the left-right distribution control, the actual yaw rate γ is equal to the target yaw rate γ.^*(The yaw rate is positive in the counterclockwise direction), the target yaw rate γ^*If the yaw rate deviation Δγ, which is a value obtained by subtracting the actual yaw rate γ from the above, is equal to or less than 0, the final braking force B of the right front wheel is increased in order to increase the clockwise yawing moment._FRIs
B_FR0+ ((W_FR/ (W_FR+ W_RR)) ・ | ΔB |
And the final braking force B on the right rear wheel_RRIs
B_RR0+ ((W_RR/ (W_FR+ W_RR)) ・ | ΔB |
And the final braking force B of the front left wheel_FLIs
B_FL0
And the final braking force B of the left rear wheel_RLIs
B_RL0
It becomes.
[0029]
On the other hand, the actual yaw rate γ is the target yaw rate γ^*If the yaw rate deviation Δγ is larger than 0 due to the smaller value, the final braking force B of the right front wheel is increased to increase the counterclockwise yawing moment._FRIs
B_FR0
And the final braking force B on the right rear wheel_RRIs
B_RR0
And the final braking force B of the front left wheel_FLIs
B_FL0+ ((W_FL/ (W_FL+ W_RL)) ・ ΔB
And the final braking force B of the left rear wheel_RLIs
B_RL0+ ((W_RL/ (W_FL+ W_RL)) ・ ΔB
It becomes.
[0030]
When the left / right distribution control is executed because the yaw rate deviation Δγ is not 0, the sum of the final braking force B of each wheel becomes the total braking force B in the pedaling force-brake pressure control._TOTAs a result, the braking force left / right difference ΔB is increased. That is, in the present embodiment, the influence of the left / right distribution control affects the pedaling force-brake pressure control, but it is considered that such an effect does not cause a problem for vehicle braking. However, it goes without saying that the present invention can be implemented such that the influence of the left / right distribution control does not affect the pedaling force-brake pressure control at all.
[0031]
On the other hand, in the front-rear distribution control, the turning characteristic value Δγ_CIs used. Turning characteristic value Δγ_CIs the target yaw rate γ from the actual yaw rate γ^*Is multiplied by the actual yaw rate γ, and has the following characteristics. That is, the sign is positive when the vehicle exhibits the oversteer characteristic, becomes negative when the vehicle exhibits the understeer characteristic, and the absolute value increases as the oversteer characteristic or the understeer characteristic increases. Moreover, the turning characteristic value Δγ_CIs not affected by whether the turning direction of the vehicle is left or right.
[0032]
In this front-rear distribution control, when the vehicle exhibits the oversteer characteristic, that is, the turning characteristic value Δγ_cIs positive, the front wheel braking force is increased and the front wheel lateral force is reduced, while the rear wheel braking force is reduced and the rear wheel lateral force is increased, thereby suppressing the oversteer characteristic. The yawing moment in the direction of movement is increased. On the other hand, when the vehicle exhibits understeer characteristics, that is, the turning characteristic value Δγ_cIs negative, the front wheel braking force is reduced and the front wheel lateral force is increased, while the rear wheel braking force is increased and the rear wheel lateral force is reduced, thereby suppressing the understeer characteristics. The yawing moment in the direction of movement is increased.
[0033]
In this front-rear distribution control, the front wheel braking force and the rear wheel braking force are increased or decreased by the same amount Δb in directions opposite to each other. The increase / decrease amount Δb is equal to the turning characteristic value Δγ_CIs determined so as to increase as the absolute value of the yaw moment increases. As a result, the yawing moment based on the front-rear distribution control becomes the turning characteristic value Δγ_CWill increase as the absolute value of increases.
[0034]
The increase / decrease amount Δb has a characteristic that it takes a positive value when the vehicle exhibits the oversteer characteristic, and takes a negative value when the vehicle exhibits the understeer characteristic. Therefore, in this front-rear distribution control, the front wheel braking force is calculated as the sum of each wheel braking force related to the left / right distribution control and Δb, and the rear wheel braking force is calculated from each wheel braking force related to the left / right distribution control. It is calculated as a value obtained by subtracting Δb.
[0035]
The amount of increase / decrease Δb is specifically calculated as the product of the absolute value of the braking force left / right difference ΔB and a coefficient R, and the coefficient R is calculated as shown in FIG. When the characteristic is indicated, the value is "0". When the oversteer characteristic (represented by "OS" in the figure) is indicated, the value is "larger than 0". When the understeer characteristic (represented by "US" in the figure) is indicated. Is a variable value that is “a value smaller than 0”. As a result, the increase / decrease amount Δb is obtained with the above characteristics.
[0036]
Therefore, in the left / right / front / rear distribution control, the final wheel braking force B is determined as follows. That is, when the yaw rate deviation Δγ is equal to or less than 0 (that is, when the left / right braking force difference ΔB is equal to or less than 0), the final braking force B of the right front wheel is reduced._FRIs
B_FR0+ ((W_FR/ (W_FR+ W_RR)) + R) · | ΔB |
And the final braking force B on the right rear wheel_RRIs
B_RR0+ ((W_RR/ (W_FR+ W_RR))-R) · | ΔB |
And the final braking force B of the front left wheel_FLIs
B_FL0
And the final braking force B of the left rear wheel_RLIs
B_RL0
It is determined to be.
[0037]
On the other hand, when the yaw rate deviation Δγ is larger than 0 (that is, when the braking force left-right difference ΔB is larger than 0), the final right wheel braking force B_FRIs
B_FR0
And the final braking force B on the right rear wheel_RRIs
B_RR0
And the final braking force B of the front left wheel_FLIs
B_FL0+ ((W_FL/ (W_FL+ W_RL)) + R) · ΔB
And the final braking force B of the left rear wheel_RLIs
B_RL0+ ((W_RL/ (W_FL+ W_RL))-R) · ΔB
It is determined to be.
[0038]
However, in the present embodiment, as long as the absolute value of the braking force left / right difference ΔB does not exceed the non-zero reference value H, the left / right / front / rear distribution control is not executed, and only the pedaling force-brake pressure control is executed. ing. In addition, the reference value H is determined so as to decrease as the vehicle speed V increases and to increase as the absolute value of the steering angle θ increases. As described above, when the vehicle speed V is low, the necessity of distribution control is not higher than when it is high, and when the absolute value of the steering angle θ is large, the necessity of distribution control is not higher than when it is low. is there.
[0039]
In this embodiment, in order to obtain the reference value H with the above characteristics, the reference value H is specifically set to the partial reference value H.₁And H₂And the partial reference value H₁Is a variable value that changes according to the vehicle speed V as shown in the graph of FIG.₂Is a variable value that changes as shown in the graph of FIG. 9 according to the steering angle θ. The reference value H can be determined by any other method. For example, the relationship between the vehicle speed V, the steering angle θ, and the reference value H is stored in advance in the form of a map, a functional expression, or the like. May be employed.
[0040]
Further, in the present embodiment, when the left / right / front / rear distribution control is started because the absolute value of the braking force left / right difference ΔB exceeds the reference value H, the control is performed using the value of the braking force left / right difference ΔB as it is. Instead, the control is performed using a value obtained by subtracting the reference value H from the braking force left-right difference ΔB. One measure has been taken to suppress a sudden change in the behavior of the vehicle due to the setting of the reference value H. In order to give priority to improving the initial response of the control, it is desirable not to take such measures.
[0041]
As described above, the pedaling force-brake pressure control and the left / right / front / rear distribution control have been described individually, and the relationship between the controls has also been described. Will be described with reference to the flowchart of FIG.
[0042]
First, in step S1 (hereinafter simply referred to as S1; the same applies to other steps), the pedaling force F, the actual yaw rate γ, the vehicle speed V, the steering angle θ, and the wheel load W are obtained from various sensors._FR, W_FL, W_RR, W_RLIs taken in. Next, in S2, according to the pedaling force F, the total braking force B related to the pedaling force-brake pressure control._TOTIs determined. Then, in S3, the wheel load W_FR, W_FL, W_RR, W_RLBase wheel braking force B related to pedaling force-brake pressure control according to the wheel load distribution based on_FR0, B_FL0, B_RR0, B_RL0Is determined.
[0043]
Subsequently, in S4, the target yaw rate γ is calculated from the steering angle θ and the vehicle speed V.^*Is determined. The relationship between these parameters is stored in advance in the ROM of the computer, and the target yaw rate γ^*Is determined.
[0044]
Then, in S5, the partial control gain K according to the vehicle speed V₁Is determined, and the partial control gain K is determined according to the steering angle θ.₂Is determined. Partial control gain K₁(Represented graphically in FIG. 5) and the partial control gain K₂(Represented by a graph in FIG. 6) is stored in advance in the ROM of the computer, and the partial control gain K is calculated using these relationships.₁, K₂Is determined this time. Subsequently, in S6, these partial control gains K₁, K₂Is determined as the current value of the control gain K. Then, in S7, the control gain K and the target yaw rate γ^*From the actual yaw rate γ, the target value of the braking force left / right difference ΔB is determined.
[0045]
Subsequently, in S8, the actual yaw rate γ and the target yaw rate γ^*From the turning characteristic value Δγ_CIs calculated, and the turning characteristic value Δγ is further calculated._C, The current value of the coefficient R is determined. These turning characteristic values Δγ_CThe relationship between the coefficient R and the coefficient R (shown in a graph in FIG. 7) is stored in advance in the ROM of the computer, and the current value of the coefficient R is determined using the relationship.
[0046]
Then, in S9, the partial reference value H is set according to the vehicle speed V.₁Is determined, and further, the partial reference value H is determined according to the steering angle θ.₂Is determined. Partial reference value H₁And the vehicle speed V (shown graphically in FIG. 8), and the partial reference value H₂(Represented by a graph in FIG. 9) is stored in advance in the ROM of the computer, and the partial reference value H is obtained by using these relationships.₁, H₂Is determined this time. Subsequently, in S10, these partial reference values H₁, H₂Is determined as the current value of the reference value H.
[0047]
Thereafter, in S11, it is determined whether or not the absolute value of the braking force left / right difference ΔB is larger than a reference value H. Assuming that this time is not larger than the reference value H, the determination is NO, and in S12, the reference wheel braking force B_FR0Etc. as they are, the final braking force B for each wheel_FRSubsequently, in S13, the final braking force B of each wheel is obtained._FRThe linear hydraulic pressure control valve 40 is controlled while monitoring the brake pressure by the pressure sensor 86 so that the above-described operations are realized. Thus, one execution of this routine ends.
[0048]
Thereafter, if it is assumed that the absolute value of the braking force left-right difference ΔB has become larger than the reference value H while the execution of S1 to S13, that is, the execution of only the pedaling force-brake pressure control, is repeated, the determination in S11 becomes YES, and the determination in S14 is made. The following steps are executed, whereby not only the pedaling force-brake pressure control but also the right / left / front / rear distribution control is executed.
[0049]
Specifically, in S14, it is determined whether or not the braking force left-right difference ΔB is greater than zero. It is determined whether it is necessary to increase the counterclockwise yaw moment or the clockwise yaw moment. In this case, assuming that the braking force left / right difference ΔB is greater than 0, the determination becomes YES, and in S15, the braking force left / right difference ΔB is changed by subtracting the reference value H from the braking force left / right difference ΔB. By executing S16, S17, and S13, the brake pressure is controlled so that the changed braking force left / right difference ΔB is realized.
[0050]
On the other hand, this time, if it is assumed that the braking force left / right difference ΔB is equal to or less than 0, the determination in S14 is NO, and in S18, the braking force is added by adding the reference value H to the braking force left / right difference ΔB. The left / right difference ΔB is changed, and thereafter, by executing S19, 20, and 13, the brake pressure is controlled such that the changed braking force left / right difference ΔB is realized.
[0051]
As is clear from the above description, in the present embodiment, the start condition of the distribution control is made stricter when the vehicle speed V is low than when it is high, and more strict when the absolute value of the steering angle θ is large. Therefore, the distribution control is executed only when it is really necessary, and the effect that unnecessary distribution control is omitted and the load on the brake or the like is reduced is obtained.
[0052]
Further, in the present embodiment, the control characteristic of the distribution control is less sensitive when the vehicle speed V is low than when it is large, and is less sensitive when the absolute value of the steering angle θ is large than when it is small. The distribution control is avoided, which also has the effect of eliminating unnecessary distribution control and reducing the load on the brake and the like.
[0053]
As is apparent from the above description, in the present embodiment, the yaw rate sensor 72 constitutes one aspect of the “actual turning state amount acquiring means 1” of the present invention, and the ECU 60 performs S1 to S4, S7, and S8 in FIG. , 11 to 20 constitute one embodiment of the “distribution control means 2” in the present invention, and the part of the ECU 60 that executes S5, 6, 9 and 10 in FIG. Together with the sensor 76, it constitutes one aspect of the "control start reference value determining means 3" of the present invention.
[0054]
As mentioned above, although one Example of this invention was described in detail based on drawing, this invention can be implemented in another aspect.
[0055]
For example, in the above embodiment, the distribution control is not executed unless the yaw rate deviation Δγ becomes larger than a certain value. Specifically, each distribution control becomes larger than the certain value. It started and ended when it fell below that value. However, the distribution control of each time is not started unless the yaw rate deviation Δγ becomes larger than a certain value, but once the distribution control is started, the yaw rate deviation Δγ becomes 0, not when the yaw rate deviation Δγ becomes smaller than a certain value. The present invention can be implemented such that the distribution control is sometimes terminated. That is, in the above embodiment, the dead zone is provided not only in the start condition but also in the end condition of the distribution control. However, the present invention can be implemented without providing the start condition but not in the end condition. You can.
[0056]
In the above-described embodiment, the reference value H is determined so as not to become 0. For example, when the vehicle speed V and the steering angle θ are sufficiently large, the reference value H becomes 0. You can also decide.
[0057]
Further, in the above-described embodiment, the yaw rate of the vehicle body is selected as the "turning motion state amount" in the present invention. However, for example, the lateral acceleration of the vehicle body may be selected.
[0058]
In the above embodiment, the braking force distribution is directly controlled by controlling the brake pressure of each wheel cylinder 20. For example, the slip ratio of each wheel in the antilock control is controlled. By doing so, the braking force distribution can also be controlled indirectly.
[0059]
Further, the present invention is applicable not only to a driving / braking force distribution control device for an automobile using an internal combustion engine as a driving source, but also to a driving / braking force distribution control device for a so-called electric vehicle using an electric motor as a driving source. It can also be applied to
[0060]
Without departing from the scope of the claims, various modifications and improvements can be made to the present invention based on the knowledge of those skilled in the art.
[Brief description of the drawings]
FIG. 1 is a block diagram conceptually showing a configuration of the present invention.
FIG. 2 is a system diagram showing an electrically controlled brake system including a braking force distribution control device according to one embodiment of the present invention.
FIG. 3 is a block diagram showing an electrical configuration of the electrically controlled brake system.
FIG. 4 is a block diagram showing a control model used by the braking force distribution control device.
FIG. 5 shows a vehicle speed V and a partial control gain K used by the braking force distribution control device.₁6 is a graph showing a relationship with the graph.
FIG. 6 shows a steering angle θ and a partial control gain K used by the braking force distribution control device.₂6 is a graph showing a relationship with the graph.
FIG. 7 is a turning characteristic value Δγ used by the braking force distribution control device._C6 is a graph showing the relationship between the coefficient R and the coefficient R.
FIG. 8 shows a vehicle speed V and a partial reference value H used by the braking force distribution control device.₁6 is a graph showing a relationship with the graph.
FIG. 9 shows a steering angle θ and a partial reference value H used by the braking force distribution control device.₂6 is a graph showing a relationship with the graph.
FIG. 10 is a flowchart showing a left / right / front / rear distribution control routine used by the braking force distribution control device.
[Explanation of symbols]
20 Wheel cylinder
40 Linear hydraulic pressure control valve
60 ECU
72 Yaw rate sensor
74 Vehicle speed sensor
76 Steering angle sensor

Claims (5)

A driving / braking force distribution control device that is provided in a vehicle having a plurality of wheels and controls distribution of at least one of a driving force and a braking force to each wheel.
An actual turning state amount obtaining means for obtaining an actual turning state amount of the vehicle,
A deviation of the actual turning state quantity acquired by the actual turning state quantity acquisition means from a target turning state quantity determined based on the vehicle speed and the steering angle is acquired, and when the deviation becomes larger than a reference value, the drive Distribution control means for starting braking force distribution control, controlling the distribution so that the actual turning state amount follows the target turning state amount,
A control start reference value determining means for determining the reference value to be larger when the vehicle speed is low and larger when the vehicle speed is high. A driving / braking force distribution control device that is provided in a vehicle having a plurality of wheels and controls distribution of at least one of a driving force and a braking force to each wheel.
An actual turning state amount obtaining means for obtaining an actual turning state amount of the vehicle,
A deviation of the actual turning state amount obtained by the actual turning state amount obtaining means from the target turning state amount is acquired, and when the deviation becomes larger than a reference value, the drive / braking force distribution control is started, and the actual turning state is started. Distribution control means for controlling the distribution so that the state quantity follows the target turning state quantity,
And a control start reference value determining means for determining the reference value to be a value other than 0 and a larger value when the vehicle speed is lower than when the vehicle speed is higher. The actual turning state quantity acquisition means, the driving and braking force distribution control apparatus according to means for obtaining the yaw rate of the vehicle including claim 1 or 2. The driving / braking force distribution control device according to claim 1, wherein the actual turning state quantity acquisition unit includes a unit that acquires a lateral acceleration of the vehicle. The driving / braking force according to any one of claims 1 to 4 , wherein the control start reference value determining means further determines the reference value to be a larger value when the absolute value of the steering angle is large and smaller when the absolute value of the steering angle is small. Distribution control device.

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