JPH0891195A - Motional characteristics control device for vehicle - Google Patents

Abstract

PURPOSE: To fulfil more effectively both a slip restricting function and an LSD function by providing a driving wheel brake control means, which controls braking torque given to each driving wheel, corresponding to a driving wheel condition and a difference in the driving wheel condition. CONSTITUTION: A motional characteristics control device for a vehicle independently gives braking torque to right and left driving wheels FR, FL, a driving wheel condition detecting means detects the condition of each driving wheel, and a driving-condition-difference-detecting-means detects the difference in the condition between the right and left driving wheels. A driving wheel brake control means 30 controls braking torque given to each driving wheel, corresponding to both driving wheel condition and the difference in the driving wheel condition. When a driver attaches importance to slip restriction, a mean select ratio (K) is made larger (approach 1.0), thereby realizing a setting in which an acceleration quantity acquires a great importance. Meanwhile, when the accelerating performance is of the great importance although a little slip is allowed, the mean select ratio is made smaller (approach zero), thereby giving importance to an LSD function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided with a braking mechanism capable of independently applying a braking torque to left and right driving wheels, and controlling the braking torque applied to each driving wheel, for example, traction control during acceleration slip. The present invention relates to a vehicle motion characteristic control device for improving vehicle motion characteristics by performing the above.

[0002]

2. Description of the Related Art Conventionally, a braking mechanism that can independently apply a braking torque to left and right driving wheels is provided, and the braking torque applied to each driving wheel is controlled to perform, for example, traction control during acceleration slip. 2. Description of the Related Art There is known a vehicle motion characteristic control device that attempts to improve the vehicle motion characteristics. When controlling the braking force of the driving wheels, there are two types, a function of braking both wheels of the left and right driving wheels and a function of braking only one wheel. In the case of two-wheel braking, slip due to excessive driving force The effect of the slip suppression function to suppress the vehicle stability and ensure the stability of the vehicle is great.On the other hand, in the case of one-wheel braking, in order to ensure the acceleration of the vehicle, the one-wheel slip due to the difference in the road surface μ is suppressed. The effect of the differential limiting (LSD) function that transmits the driving force to the other wheels is large.

Here, the following inconvenience occurs during one-wheel braking. That is, when the braking torque is applied only to the driving wheels on the low μ road side while traveling on a traveling road (hereinafter referred to as a split road) in which the frictional states of the left and right wheels are different from each other,
Due to the LSD function, a drive torque corresponding to the applied braking torque is generated in the drive wheels on the high μ road side due to the differential effect. Therefore, the total driving force of the high-μ road-side drive wheels becomes large and a cornering force is generated, and as a result, vehicle deflection such as tail swing occurs and the vehicle behavior becomes unstable.

[0004] Then, as a thing made paying attention to this, there is one disclosed in Japanese Patent Laid-Open No. 3-92462. This is because when a braking torque is applied to one wheel on the low μ road side while traveling on a split road, the driving force generated on the driving wheels on the high μ road side is canceled in response to the braking torque. A relatively small braking torque is also applied to the roadside drive wheels.

[0005]

However, in the above-mentioned Japanese Patent Laid-Open No. 3-92462, since the braking torque is always applied to the high μ road side drive wheels during traveling on the split road, the following problems occur. No slip or small slip High μ
Applying the braking torque to the road side basically acts on the vehicle stall side. For example, when the vehicle acceleration is large, such as on a split road of a high μ road and a medium μ road, the vehicle deflection is small and the above high μ
Applying braking torque to the roadside does not make any sense.

As described above, it is not always optimum to uniformly apply the braking torque to the high-μ road-side drive wheels during traveling on the split road, depending on the road surface condition or the vehicle control condition, and the braking torque acts on the minus side. Sometimes it ends up. That is, which of the slip suppression effect and the LSD effect is to be emphasized obviously differs depending on the vehicle control environment including the road surface condition, and it is expected that optimal control will be performed in consideration of them as well.

Therefore, in the present invention, the slip suppressing function for suppressing the slip due to the excessive driving force to ensure the stability of the vehicle and the slip for one wheel due to the difference in the road surface μ to transmit the driving force to the other wheels. The degree of control with the LSD function,
It is an object of the present invention to provide a vehicle motion characteristic control device capable of exhibiting both functions more effectively by appropriately changing the road surface condition and the vehicle control condition.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the invention according to claim 1 is a vehicle dynamic characteristic control having a braking mechanism capable of independently applying a braking torque to the left and right driving wheels. The device is a drive wheel state detecting means for detecting the state of each drive wheel, a drive wheel state difference detecting means for detecting a state difference between the left and right drive wheels, and the drive wheel state and the drive wheel state difference. In accordance with the above, there is provided a drive wheel braking control means for controlling the braking torque applied to each drive wheel, and the vehicle motion characteristic control device.

The invention according to claim 2 is characterized in that an acceleration slip amount is used as the driving wheel state and a driving speed difference is used as the driving wheel state difference. The invention according to claim 3 uses drive torque as the drive wheel state,
A driving torque difference is used as the driving wheel state difference, and the invention according to claim 4 uses a braking torque as the driving wheel state and a braking torque difference as the driving wheel state difference. Is characterized by.

According to a fifth aspect of the present invention, there is provided the vehicle motion characteristic control device according to the first aspect, wherein the braking torque control is changed according to the vehicle control environment. On the other hand, the invention according to claim 6 is a vehicle motion characteristic control device including a braking mechanism capable of independently applying a braking torque to the left and right driving wheels, wherein the rolling wheel speed detection detects the speed of the rolling wheels. Means, a drive wheel speed detecting means for detecting the speed of the drive wheels, and an acceleration slip control means for controlling the acceleration slip by using an acceleration slip amount obtained from the rolling wheel speed and the drive wheel speed as a control deviation. And a drive wheel speed difference control means for controlling the left and right drive wheel speed differences as a control deviation, and the acceleration slip control and the drive wheel speed difference control according to the vehicle control environment. And a drive wheel braking control means for changing the above.

As the vehicle control environment according to claim 5 or 6, the vehicle speed is taken into consideration as shown in claim 7, the road surface μ is taken into consideration as shown in claim 8, or the vehicle control environment is taken into consideration. The turning state of the vehicle is taken into consideration, the braking system load state is taken into consideration as shown in claim 10, and the brake hydraulic pressure increasing ability in the braking system is taken into consideration as shown in claim 11. It is possible to do it. Of course, a plurality or all of the vehicle speed, the road surface μ, the turning state of the vehicle, the braking system load state, and the brake hydraulic pressure increasing ability in the braking system described in claims 7 to 11 may be considered.

[0012]

In the vehicle motion characteristic control device according to the first aspect, the braking torque can be independently applied to the left and right drive wheels, and the drive wheel state detection means detects the state of each drive wheel. The drive wheel state difference detection means detects the state difference between the left and right drive wheels. Then, the drive wheel braking control means controls the braking torque applied to each drive wheel in accordance with the drive wheel state and the drive wheel state difference. As the drive wheel state and the drive wheel state difference, the acceleration slip and the drive speed difference may be used as in claim 2, or the drive torque and the drive torque difference may be used as in claim 3. Alternatively, the braking torque and the braking torque difference may be used.

Then, as described in claim 5, it is preferable to change the braking torque control according to the vehicle control environment. The point that the braking torque control is changed according to the vehicle control environment will be described in detail later. On the other hand, according to the invention described in claim 6, the braking torque can be independently applied to the left and right driving wheels, the rolling wheel speed detecting means detects the speed of the rolling wheels, and the driving wheel speed detecting means detects the driving wheels. Detect the speed of. Then, the acceleration slip control means, as the control deviation, the acceleration slip amount obtained from the rolling wheel speed and the driving wheel speed,
The control for suppressing the acceleration slip is performed, and the drive wheel speed difference control means performs the control for suppressing the left and right drive wheel speed difference by using the left and right drive wheel speed difference as a control deviation. Further, the drive wheel braking control means changes the acceleration slip control and the drive wheel speed difference control according to the vehicle control environment.

The vehicle control environment is defined by claim 7.
As shown in FIG. 11, more appropriate control can be performed in consideration of the vehicle speed, the road surface μ, the turning state of the vehicle, the braking system load state, and the brake fluid pressure increasing capability in the braking system. Next, the effect exerted from the above-mentioned action will be described.

First, the basic technical idea of the present invention will be described. If the control for suppressing the acceleration slip is performed using the acceleration slip amount, which is one of the driving wheel states, as the control deviation, the slip suppression effect naturally increases. In addition, if the left and right drive wheel speed difference, which is one of the drive wheel state differences, is used as a control deviation to control the left and right drive wheel speed differences, the so-called LSD effect is enhanced. In the past, there was no idea to control them by fusing them, but as shown in claim 1,
Based on both the drive wheel state and the drive wheel state difference, it is possible to perform either drive wheel braking control that emphasizes the slip suppression effect or drive wheel braking control that emphasizes the LSD effect.

In order to make this point clearer, claim 6
The case will be described as an example. In this case, the acceleration slip control means controls the acceleration slip by using the acceleration slip obtained from the rolling wheel speed and the driving wheel speed as a control deviation, and the driving wheel speed difference control means controls the left and right driving wheel speed differences. As a control deviation, control is performed to suppress the difference between the left and right driving wheel speeds. For example, the acceleration slip obtained from the difference between the smaller one of the left and right driving wheel speeds and the rolling wheel speed naturally reflects how much the acceleration slip is, and also the speed between the driving wheels. The difference reflects the influence of the difference in the road surface μ on the split road, for example.

Then, the drive wheel braking control means changes the acceleration slip control and the drive wheel speed difference control according to the vehicle control environment. Therefore, if you want to emphasize slip suppression, set the acceleration slip amount to be important, allow some slip, and if acceleration is required, set the drive wheel speed difference to be more important to achieve more appropriate motion. Characteristic control is realized.

Next, as a vehicle control environment,
~ 11, the vehicle speed, the road surface μ, the turning state of the vehicle,
The braking system load state and the ability to increase the brake fluid pressure in the braking system have been described, but they will be explained together with their effects. First, the following can be considered regarding the vehicle speed. For example, when traveling at a relatively low speed, considering that the possibility of so-called spin is low and it is possible to easily correct even if spinning, it is better to emphasize acceleration performance as a general vehicle motion characteristic. It is advantageous above. Therefore, control that emphasizes the LSD function for one-wheel braking is preferable. On the other hand, when traveling at medium to high speed,
On the contrary, considering that there is a high possibility of spinning and it is difficult to correct if it spins, it is better to emphasize stability rather than acceleration in terms of overall vehicle motion characteristics (especially safety aspects). Is advantageous. Therefore, it is preferable to attach importance to the acceleration slip control that is the braking of both wheels.

Next, regarding the road surface μ, the following consideration can be made. Since the vehicle behavior change due to a slight slip is smaller on a high μ road, in such a case, the control with emphasis on the LSD function is preferable. On the other hand, since the vehicle behavior change is large on a low μ road even with a small amount of slip, it is preferable to emphasize acceleration slip control in that case.

Regarding the turning state of the vehicle, the following consideration can be made. The larger the turning radius (including the straight traveling state), the smaller the change in vehicle behavior due to a slight slip. In that case, therefore, the control emphasizing the LSD function is preferable.
On the other hand, the smaller the turning radius, the greater the change in vehicle behavior even with a small amount of slip. Therefore, in that case, it is preferable to prioritize acceleration slip control.

Since the above three elements are elements that change frequently even during normal running, it is desirable to consider them together if possible. Next, the braking system load state will be described. For example, the magnitude of the load in the braking system is detected based on the control time or control frequency of the brake control, the brake fluid temperature, or the like. When the load is large, the acceleration slip control is gradually stopped, and the LSD with a small load is detected.
It is possible to shift to control. By doing so, the braking system can be protected.

Next, the ability of the brake system to increase the brake fluid pressure will be described. For example, even if the braking system is controlled in the same way as at normal temperature due to an increase in the viscous resistance of the brake fluid due to low temperature, or a decrease in the pump discharge capacity, the brake fluid pressure increase gradient in the actual wheel cylinders In some cases, the pressure boosting ability may be reduced such that In such a case, when both wheels do not have the ability to increase the desired pressure at the same time, both the slip suppression function and the LSD function can be performed by performing the control with more emphasis on the LSD function, which is one-wheel braking. You can avoid the worst situation that would reduce it.

A mechanical differential limiting device (for example, a friction type device such as Torsen differential, or a rotation speed sensitive type device such as viscous coupling)
When the present invention is applied to a vehicle equipped with, the left and right drive wheel speed difference is unlikely to occur (the drive wheel state difference is unlikely to occur) due to the mechanical differential limiting device. Therefore, in that case, only the degree of slip control is automatically changed according to the "vehicle control environment", which does not depart from the gist of the present invention.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is a schematic configuration diagram showing the configuration of the entire control system of a vehicle to which the present invention is applied. In this embodiment, the present invention is applied to a front engine / front drive (FF) four-wheel vehicle, and brake oil is sucked from a master cylinder (hereinafter referred to as M / C) as a hydraulic pump to brake the M / C. This is an example of using a self-priming pump that returns oil.

As shown in FIG. 1, each wheel of the vehicle (left front wheel F
L, right front wheel FR, left rear wheel RL, right rear wheel RR), wheel cylinders (hereinafter referred to as W / C) 2FL, 2FR, 2RL, 2RR for applying a braking force to each wheel FL to RR, and Speed sensor 4FL for detecting the rotation speed of each wheel FL to RR,
4FR, 4RL and 4RR are provided respectively. In addition, front left and right wheels (hereinafter simply referred to as drive wheels) FL and FR that are drive wheels
Is rotated by receiving a driving force from an internal combustion engine 10 connected via a transmission 6 and a differential gear 8. The internal combustion engine 10 serving as a power source has its rotational speed and intake air. A sensor group 12 is provided to detect operating conditions such as the amount, cooling water temperature, and throttle valve opening (throttle opening). And these sensor groups 1
The detection signal from the engine 2 is sent to the engine (E / G) control device 20.
And is used by the E / G control device 20 to control the fuel injection amount and ignition timing of the internal combustion engine 10 based on the detection signal.

Further, the detection signals from the speed sensors 4FL to 4RR provided on the wheels FL to RR are input to the braking control device 30. The braking control device 30 includes a brake pedal 32.
By controlling various solenoid valves in the hydraulic circuit 40 provided in the hydraulic path from the M / C 34 that discharges brake fluid by stepping on the vehicle to the W / C 2FL to 2RR of each wheel FL to RR, the vehicle is braked and the vehicle is braked. This is for executing an acceleration slip control for suppressing a slip generated on a wheel at the time of acceleration, and is in an ON state when the brake pedal 32 is operated in addition to the detection signals from the speed sensors 4FL to 4RR. Brake switch (hereinafter referred to as brake SW) 36
And the W of the drive wheels FL, FR provided in the hydraulic circuit 40.
/ C2FL, 2FR operates by receiving a detection signal from a pressure sensor or the like (not shown) that detects the hydraulic pressure inside.

The E / G control device 20 and the braking control device 30 are each composed of a microcomputer mainly composed of a CPU, a ROM, a RAM and the like, and each of these control devices 20 and 30 is formed by a sensor. It is equipped with a communication device that sends and receives detection data and control data.

Next, the hydraulic circuit 40 will be described. As shown in FIG. 2, the hydraulic circuit 40 supplies the brake fluid that is pressure-fed from the two oil passages of the M / C 34 to the left front wheel FL and the right rear wheel R.
R, right front wheel FR and left rear wheel RL are provided with two hydraulic paths 42 and 44 respectively. Of these hydraulic paths 44, 42, the hydraulic paths 44R, 42R leading to the W / C2RL, 2RR of the left and right rear wheels (hereinafter simply referred to as driven wheels) RL, RR that are driven wheels are the paths 44R, 42R. Four
Holding valves (pressure increasing control valves) 46RL and 46RR that can be switched between a pressure increasing position that communicates the 2Rs and a holding position that blocks the path.
And pressure reducing valves (pressure reducing control valves) 48RL and 48RR for discharging the brake fluid in the respective W / Cs 2RL and 2RR.

The pressure-increasing control valves 46RL and 46RR are normally in the pressure-increasing position, and are switched to the holding position by energization from the braking control device 30. Further, the pressure reducing control valves 48RL and 48RR are normally in a shut-off state, and are brought into a communication state by energization from the braking control device 30 so that the W / C
Drain the brake fluid in 2RL and 2RR.

On the other hand, among the hydraulic paths 42, 44, the hydraulic paths 42F, 44F reaching the W / C2FL, 2FR of the left and right front wheels FL, FR, which are the drive wheels, include the hydraulic path 4 on the driven wheel side.
Similar to 4R and 42R, the pressure increasing control valves 46FL and 46FR and the pressure reducing control valves 48FL and 48FR as the above-described control valves are provided, and the pressure increasing control valves 46FL and 46FR provide M / C3.
The master cylinder cut valve (SM, which serves as the above-mentioned switching valve that connects and disconnects the passages 42F and 44F to the fourth side
Valve) 50FL, 50FR are provided.

The shut-off position of each of the SM valves 50FL and 50FR means that the hydraulic pressure on the pressure increasing control valves 46FL and 46FR side is M /
Relief valves 52FL, 5 which communicate with each other when the hydraulic pressure on the C34 side is higher than a predetermined value and become equal to or higher than the upper limit value to limit the hydraulic pressure on the pressure increase control valves 46FL, 46FR to the upper limit value or less.
This is the position set to 2FR.

The SM valves 50FL and 50FR communicate with each other when the hydraulic pressure on the M / C 34 side becomes greater than the hydraulic pressure on the pressure increase control valves 46FL and 46FR, and the brake output from the M / C 34 is output. Relief valves 54FL and 54FR that supply oil to the pressure increasing control valves 46FL and 46FR are connected in parallel. The SM valves 50FL and 50FR are normally in a communication state, and are switched to a cutoff state by energization from the braking control device 30.

Further, the hydraulic pressure paths 42 and 44 are provided with reservoirs 56 and 58 for temporarily storing the brake fluid discharged from the pressure reducing control valves 48FL to 48RR, and the brake fluid is added to the SM valve 50FL. Hydraulic path 42Fa between pressure control valve 46FL, SM valve 50FR and pressure increase control valve 46FR
A pump 6 for pressure-feeding to a hydraulic path 44Fa between
0,62 are provided. In addition, each pump 60, 62
Accumulators 64 and 66 that suppress the pulsation of the internal hydraulic pressure are provided in the discharge path of the brake fluid from the.

Further, in each of the hydraulic paths 42 and 44, when the brake TRC control described later is executed, the M / C 34
From the reservoir 68 provided on the upper part of C34 to the pump 6
0 and 62 are provided with oil supply paths 42P and 44P for directly supplying brake oil.
The P and 44P are provided with reservoir cut valves (SR valves) 70FL and 70FR for communicating and blocking the paths.

The SR valves 70FL and 70FR are normally in a shut-off state and are switched to a communication state by energization from the braking control device 30. In addition, each pump 60, 6
2 is driven via the pump motor 80 when ABS control or TRC control described later is executed.

Next, the calculation processing executed in the braking control device 30 of the present embodiment will be described with reference to FIGS. As shown in FIG. 3, when an ignition switch (not shown) is turned on, first, initialization processing such as memory clear and flag reset is performed (step 100). Next, the detection signals from the speed sensors 4FL, 4FR, 4RL, 4RR, that is, the rolling wheel speed VWF and the driving wheel speed VWD are input (step 110). In order to distinguish between the left and right wheels, the left driving wheel speed VWDL and the right driving wheel speed VWDR are used.

Then, the acceleration slip control target speed VTS is calculated (step 120). The acceleration slip control target speed VTS is obtained, for example, by adding a predetermined offset value to the rolling wheel speed VWF. This offset value may be a fixed value or may be calculated from the target slip ratio. Further, the target slip ratio itself may be used. The acceleration slip control target speed VTS may be set as a common value for the left and right driving wheels, or may be set for each wheel independently.

Subsequently, at step 130, a control deviation (hereinafter referred to as acceleration slip control deviation) εS for suppressing the acceleration slip is calculated. The acceleration slip control deviation εS may be set as a common value for the left and right driving wheels, or may be set for each wheel independently. Also, step 140
Then, a control deviation (hereinafter, referred to as LSD control deviation) εL for the LSD function is calculated. Below, these two control deviations ε
S and εL will be described.

First, the acceleration slip control deviation εS is calculated as a difference between the smaller one of the left and right driving wheel speeds VWDR and VWDL and the acceleration slip control target speed VTS as shown in the following equation. .epsilon.S = min (VWDR, VWDL) -VTS On the other hand, the LSD control deviation .epsilon.L is calculated as the difference between the larger speed and the smaller speed of the left and right driving wheel speeds VWDR and VWDL as shown in the following equation. .

ΕL = max (VWDR, VWDL) -min
(VWDR, VWDL) Then, εS → 0 and εL → 0 are control targets, respectively. In the above formula, in order to obtain the acceleration slip control deviation εS, the smaller one of the left and right driving wheel speeds VWDR and VWDL is used to obtain the difference from the acceleration slip control target speed VTS. Average speed of driving wheels [VDM = (V
WDR + VWDL) / 2] may be used. In that case,
Acceleration slip control deviation εS and LSD control deviation εL
Are respectively expressed by the following equations.

ΕS = VDM−VTS εL = max (VWDR, VWDL) −VDM The control deviation ε calculated in these steps 130 and 140.
Using S and εL, and using the mean select ratio K calculated in step 150, the control deviation εW for the wheel whose drive wheel speed is max and the wheel whose drive wheel speed is min.
MAX and εWMIN are calculated (step 160). Details of the calculation of the mean select ratio K will be described later with reference to FIGS.
The value of 0 ≦ K ≦ 1 and the K
The control deviations εWMAX and εWMIN with respect to the driving wheels are calculated by using the following equation.

ΕWMAX = K · εS + (1−K) · εL εWMIN = K · εS And, as described above, the mean select ratio K is 0 ≦ K.
When ≦ 1, and K = 0, the control is for the LSD function only, and when K = 1, the control is for the acceleration slip only. Further, in the range of 0 <K <1, it is possible to shift to control in which the function of suppressing the acceleration slip is emphasized as K is increased. What factor causes the value of K to change will be described later with reference to FIGS. 4 and 5, and the description of the process in FIG. 3 will proceed.

When the control deviations .epsilon.WMAX and .epsilon.WMIN for the drive wheels are determined in step 160, the processing for actual hydraulic control is started. First, in step 170, it is determined whether or not control is in progress. If not in control, it is determined in step 180 whether or not the control start condition is satisfied. To supplement the determination as to whether or not this control start condition is satisfied, it is determined whether or not the control deviations εWMAX and εWMIN exceed a predetermined control start determination value εSTART. For example, if the control deviation corresponding to one wheel exceeds the control start determination value ε START, control is started.

When the control start condition is not satisfied,
The process returns to step 110 as it is and the following processing is repeated. However, when the control start condition is satisfied, the target hydraulic pressure PBre is reached.
f is calculated (step 190), the actuator is driven (step 200), the estimated hydraulic pressure PB is calculated (step 210), and the process returns to step 110.

Target hydraulic pressure PBref in step 190
Is the control deviation εWMAX calculated in step 160,
Using εWMIN, a predetermined arithmetic expression f (εWMAX), f
It is calculated according to (εWMIN). The predetermined arithmetic expressions f (εWMAX) and f (εWMIN) are control deviations εW
This is based on so-called PID control that performs proportional / integral / derivative according to MAX and εWMIN. This PID control is a well-known one that has been widely adopted as a vehicle control system, and therefore its detailed description is omitted.

While the hydraulic control for driving the actuator in accordance with the target hydraulic pressure PBref is being executed in this way, it is judged in step 170 that the control is being executed.
In step 220, it is determined whether the control end condition is satisfied. To supplement the determination of whether the control end condition is satisfied, it is determined whether or not the control deviations εWMAX and εWMIN have fallen below a predetermined control end determination value εEND for a predetermined time and whether or not the estimated hydraulic pressure PB = 0. For example, both control deviations ε
When WMAX and εWMIN are below the control end determination value εEND, it is determined that the control end condition is satisfied.

While this control termination condition is not satisfied,
If the control ending condition is satisfied by proceeding to step 190 and continuing the PID control, the process returns to step 110 without performing steps 190 to 210. Next, the mean select ratio K calculation processing in step 150 will be described with reference to the flowchart in FIG.

The outline of the processing will be described. Step 151
To 155, the factor values K1 to K5 for determining the mean select ratio K are calculated, respectively, and step 15
In No. 6, the mean select ratio K is calculated by summing the weighting factors a1 to a5 set for each of the factor values K1 to K5 and multiplying the respective factor values K1 to K5.

Next, the factor values K1 to K5 will be described with reference to FIG. As described above, as the mean select ratio K is increased (approaching 1), the control shifts to the function that emphasizes the function of suppressing the acceleration slip.
As for each of the factor values K1 to K5, the larger the respective values, the more important the acceleration slip control becomes. With this in mind, the explanation of each factor value K1 to K5 will be made.

K1 calculated in step 151 is calculated based on the rolling wheel speed VWF. For example, K1 is calculated based on the map as shown in FIG. The map shown in FIG. 5 (A) is a map in which the value of K1 increases as the rolling wheel speed VWF increases, and when a certain predetermined value is exceeded, K1 = 1 is fixed. The estimated vehicle body speed VBD calculated from the rolling wheel speed VWF may be used instead of the rolling wheel speed VWF.

This K1 determines whether the priority control is prioritized between the acceleration slip control and the LSD control.
This is due to the influence of vehicle speed. As described above, when traveling at a relatively low speed, the so-called spin is less likely to occur and can be easily corrected by spinning, while when traveling at a medium speed to a high speed. Is more likely to spin on the contrary, and is difficult to fix if it spins. Therefore, at low speeds, control that emphasizes the LSD function that improves acceleration is preferred, and at high speeds, acceleration slip control that improves stability is more important than acceleration.

Next, K2 calculated in step 152 is calculated on the basis of the road surface μ.
K2 is calculated based on the map shown in FIG.
In the example shown in FIG. 5B, the value of K2 decreases as the road surface μ increases, and K2 = 0 when the value exceeds a certain value.
It is a map fixed by.

Regarding the road surface μ, the change in vehicle behavior due to a slight slip is smaller on a road with a higher μ, so in that case L
Control that emphasizes the SD function is preferable, and on the other hand, the vehicle behavior change is large even on a small slip on a low μ road. In that case, therefore, it is preferable to emphasize acceleration slip control. This is a map that takes these things into consideration.

Next, K3 calculated in step 153 is calculated based on the turning state of the vehicle. For example, K3 is calculated based on the map shown in FIG. 5 (C). The one shown in FIG. 5 (C) adopts a turning radius as a control deviation indicating a turning state of the vehicle. The value of K3 becomes smaller as the turning radius becomes larger, and K3 = 0 when a certain predetermined value is exceeded. It is a map fixed by.

Considering the influence of the turning state of the vehicle, the larger the turning radius (including the straight running state), the smaller the change in vehicle behavior due to a slight slip.
Control that emphasizes the function is preferable. On the other hand, the smaller the turning radius, the greater the change in vehicle behavior even with a small amount of slip. Therefore, in that case, it is preferable to emphasize the acceleration slip control. The turning radius is calculated based on the speed difference of the rolling wheels, the steering angle, or the detection value from the lateral G (yaw rate) sensor.

Next, K4 calculated in step 154 is calculated based on the brake load of the vehicle.
For example, K4 is calculated based on the map as shown in FIG. The map shown in FIG. 5 (D) is a map in which the value of K4 decreases as the brake load of the vehicle increases, and is fixed at K4 = 0 when the value exceeds a predetermined value.

Considering the influence of the load state of the brake, it is conceivable that when the load is large, the acceleration slip control is gradually stopped and the LSD control with a small load is started. By doing so, the braking system can be protected. The brake load is calculated based on the control time or control frequency of brake control, the brake fluid temperature, or the like.

K5 calculated in step 155 is calculated based on the actuator characteristics of the hydraulic control mechanism. For example, K5 is calculated based on the map as shown in FIG. What is shown in FIG. 5 (E) is
The value of K5 increases as the discharge capacity of the pump increases, and when it exceeds a certain value, the map is fixed at K5 = 1.

For example, the viscosity of the brake fluid increases due to the low temperature, or the discharge capacity of the pump decreases, so that the brake fluid pressure in the actual wheel cylinder increases even if the hydraulic control is performed in the same manner as at normal temperature. There is a case where the pressure boosting ability is lowered such that the pressure gradient becomes small. In such a case, when both wheels do not have the ability to increase the desired pressure at the same time, both the slip suppression function and the LSD function can be performed by performing the control with more emphasis on the LSD function, which is one-wheel braking. You can avoid the worst situation that would reduce it.

The factor values K1 to K calculated in this way
5, the mean select ratio K is calculated in step 156. In this case, the factor values K1 to
The weighting factors a1 to a5 set for each K5 are also changed depending on the characteristics of the vehicle, various actuator characteristics, and the like. Some examples of this are given below.

For example, the straight running stability of the vehicle varies depending on the suspension characteristics, the vehicle load distribution, or the structure of the vehicle such as so-called FF (front engine / front drive) or FR (front engine / rear drive). For example, in the case of FR, spinning is easier than in the case of FF, so this point may be taken into consideration. Further, when turning, FF has an understeer characteristic and FR has an oversteer characteristic, so it is advisable to reflect these differences in the weighting coefficient a3 for K3.

Further, regarding K4 calculated based on the brake load and K5 calculated based on the actuator characteristic, the solenoid diameter of the actuator and the cooling characteristic, or the temperature of the pump discharge capacity and the wheel linder capacity (pressure increasing characteristic) are also included. It is better to consider the dependency on.

As described above, according to this embodiment,
Based on both the acceleration slip as the driving wheel state and the driving wheel speed difference as the driving wheel state difference, both the driving wheel braking control emphasizing the slip suppression effect and the driving wheel braking control emphasizing the LSD effect are performed. You can Then, the “degree” of the acceleration slip control and the LSD control is changed according to the vehicle control environment (vehicle characteristics, road surface μ, etc.). That is, when it is desired to emphasize slip suppression, the mean select ratio K is increased (close to 1).
Then, the acceleration slip amount is set to be important, and when some slip is allowed and acceleration is required, the mean select ratio K is made small (close to 0) and the LSD function is set to be important.

As described above, the slip suppressing function for suppressing the slip due to the excessive driving force to ensure the stability of the vehicle and the LSD function for suppressing the slip of one wheel due to the difference in the road surface μ and transmitting the driving force to the other wheels. By appropriately changing the control degree of the above according to the road surface condition or the vehicle control condition, both functions can be more effectively exerted, and more appropriate vehicle motion characteristic control can be performed.

As described above, the present invention is not limited to such embodiments, and various embodiments can be carried out without departing from the scope of the present invention. For example, although the FF vehicle is taken as an example in the above embodiment, it may be an FR vehicle or a four-wheel drive (4WD) vehicle. Slip detection in the case of a 4WD vehicle can be realized by using the difference between the wheel speed and the vehicle body speed estimated from the acceleration sensor.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an overall configuration of a vehicle control system to which a motion characteristic control device of the present invention is applied.

FIG. 2 is a configuration explanatory view centering on a hydraulic system of the braking control device according to the embodiment.

FIG. 3 is a flowchart showing a calculation process executed in the braking control device of the embodiment.

FIG. 4 is a flowchart showing a mean select ratio K calculation process according to the embodiment.

FIG. 5 is an explanatory diagram of a map used when calculating factor values K1 to K5 for determining the mean select ratio K.

[Explanation of symbols]

4 ... Speed sensor 6 ... Transmission 8 ... Differential gear 10 ... Internal combustion engine 12 ... Sensor group 20 ... E / G control device 30 ... Braking control device 32 ... Brake pedal 40 ... Hydraulic circuit 46 ... Pressure increase control valve 48 ... Pressure reduction control 50 ... SM valve 52, 54 ... Relief valve 60 ... Pump 70 ... SR valve 80 ... Pump motor FL ... Left front wheel FR ... Right front wheel RL ... Left rear wheel RR ... Right rear wheel

Claims (11)

[Claims] 1. A vehicle motion characteristic control device comprising a braking mechanism capable of independently applying a braking torque to the left and right drive wheels, the drive wheel state detecting means detecting a state of each of the drive wheels. Drive wheel state difference detection means for detecting the state difference between the left and right drive wheels, and drive wheel braking control means for controlling the braking torque applied to each drive wheel in accordance with the drive wheel state and the drive wheel state difference. And a motion characteristic control device for a vehicle, comprising: 2. The vehicle motion characteristic control device according to claim 1, wherein an acceleration slip is used as the drive wheel state, and a drive speed difference is used as the drive wheel state difference. 3. The vehicle motion characteristic control device according to claim 1, wherein a drive torque is used as the drive wheel state, and a drive torque difference is used as the drive wheel state difference. 4. The vehicle motion characteristic control device according to claim 1, wherein a braking torque is used as the driving wheel state, and a braking torque difference is used as the driving wheel state difference. 5. The vehicle motion characteristic control device according to claim 1, wherein the braking torque control is changed according to a vehicle control environment. 6. A vehicle motion characteristic control device having a braking mechanism capable of independently applying a braking torque to the left and right driving wheels, the rolling wheel speed detecting means for detecting a speed of the rolling wheels, and the above drive. Drive wheel speed detection means for detecting wheel speeds, acceleration slip control means for controlling acceleration slip by using acceleration slip obtained from the rolling wheel speed and drive wheel speed as a control deviation, and left and right drive wheels Drive wheel speed difference control means for controlling the left and right drive wheel speed differences by using the speed difference as a control deviation, and drive wheel braking for changing the acceleration slip control and the drive wheel speed difference control according to the vehicle control environment. A vehicle motion characteristic control device comprising: a control unit. 7. The vehicle motion characteristic control device according to claim 5, wherein a vehicle speed is considered as the vehicle control environment. 8. The vehicle motion characteristic control device according to claim 5, wherein the road surface μ is taken into consideration as the vehicle control environment. 9. The vehicle motion characteristic control device according to claim 5, wherein a turning state of the vehicle is considered as the vehicle control environment. 10. The vehicle motion characteristic control device according to claim 5, wherein a braking system load state is considered as the vehicle control environment. 11. The vehicle motion characteristic control device according to claim 5, wherein the vehicle control environment takes into consideration the brake fluid pressure increasing ability of the braking system.