JP2677392B2 - Vehicle slip control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention controls a torque applied to a drive wheel to prevent the slip of the drive wheel from being excessively slipped on a road surface. The present invention relates to a control device.

(Prior Art) Preventing excessive slip of a drive wheel with respect to a road surface is effective in effectively obtaining a propulsive force of an automobile and in terms of safety such as preventing spin. Then, to prevent the driving wheel slip from becoming excessive,
That is, it is only necessary to reduce the applied torque to the drive wheels that causes the slip.

Conventionally, slip control of this type is performed by applying a braking force to a drive wheel by a brake, or is disclosed in, for example, JP-A-57-22948. According to the technology disclosed in this publication, in order to reduce the applied torque to the drive wheels, the application of a braking force to the drive wheels by a brake and the reduction of the generated torque of the engine itself are performed as appropriate. I have. Of course, such slip control is performed by detecting the slip of the drive wheels. That is, the slip of the drive wheel is a state in which the speed of the drive wheel is higher than the speed of the vehicle body, and therefore, the slip control requires detection of the vehicle body speed and the drive wheel speed.

(Problems to be Solved by the Invention) However, during running on a rough road such as an uneven road, a phenomenon occurs in which the drive wheels repeatedly accelerate and decelerate due to the influence of the unevenness of the road surface. For this reason, the speed detection value of the driving wheels may increase or decrease during traveling on a rough road, which may cause an erroneous slip determination. When such an erroneous determination is made, unnecessary slip control causes problems such as heating of the brake or deterioration of traveling performance, and an increase in electrical load due to repeated start and stop of slip control is a problem. Becomes

In consideration of the above-mentioned circumstances, it is conceivable to increase the start threshold value of slip control to make it difficult to start slip control when traveling on a rough road. However, in this case, after the slip control is started, the slip control is performed in the same way as the good road, so the slip control is sensitively performed in response to the increase / decrease in the speed detection of the drive wheels on the bad road. It's too much, and it's not entirely satisfactory.

Therefore, an object of the present invention is to provide a slip control device for a vehicle, which can optimize the slip control during traveling on a rough road.

(Means for Solving the Problems) In order to achieve the above object, the present invention has the following configuration. That is, as shown in a block diagram in FIG. 17, torque adjusting means for adjusting the torque applied to the drive wheels, and bad road detection for detecting that the wheel is traveling on a bad road where acceleration and deceleration are repeated Means, a wheel speed detecting means for detecting a wheel speed, and a slip control means for controlling the torque adjusting means based on the detection results of the rough road detecting means and the wheel speed detecting means, the slip control means However, when it is determined that the drive wheels are slipping based on the detection result of the wheel speed detecting means, while controlling the torque adjusting means to reduce the applied torque to the drive wheels by a predetermined amount, When the bad road running is detected by the bad road detecting means, the torque reduction amount applied to the drive wheels at the time of the slip determination is smaller than that when the bad road running is not detected. It is configured so as to control the Luk adjusting means.

(Advantages of the Invention) In the present invention, when traveling on a bad road, the control amount of slip control is made smaller than when traveling on a good road. A situation in which the slip control is performed by reaction is prevented, that is, the slip control on the rough road is smoothly performed, and the slip control on the rough road is more optimized.

Further, on a bad road, it is preferable to make the driving wheels slippery as compared with a good road, because good acceleration can be obtained, and this is preferable for improving running performance on the bad road.

(Example) Hereinafter, an example of the present invention will be described with reference to the attached drawings.

1. Overview of Overall Configuration In FIG. 1, an automobile 1 has four wheels, left and right front wheels 2 and 3 serving as driven wheels, and left and right rear wheels 4 and 5 serving as driving wheels. An engine 6 as a power source is mounted on a front portion of the automobile 1. The torque generated by the engine 6 passes through a clutch 7, a transmission 8, a propeller shaft 9, and a differential gear 10, and then to left and right drive shafts 11 </ b> L. , 11R to the left and right rear wheels 4, 5 as drive wheels. Thus, the automobile 1 is of the FR type (front engine / rear drive).

The engine 6 as a power source has its intake passage 12
The load control, that is, the control of the generated torque, is performed by the throttle valve 13 disposed in the first position.
More specifically, the engine 6 is a gasoline engine, and the generated torque is changed by a change in the intake air amount. The intake air amount is adjusted by the throttle valve 13. And the throttle valve 13
Is controlled to be electromagnetically opened and closed by a throttle actuator 14. It should be noted that the throttle actuator 14 may be constituted by a DC motor, a stepping motor, or an appropriate actuator driven and electromagnetically controlled by a fluid pressure such as a hydraulic pressure.

Each of the wheels 2 to 5 is provided with a brake 21, 22, 23 or 24, respectively, and each of the brakes 21 to 24 is a disc brake. This disc brake is
As is known, it has a disk 25 that rotates with the wheels and a caliper 26. The caliper 26 holds the brake pad and includes a wheel cylinder, and a braking force is generated by pressing the brake pad against the disc 25 with a force corresponding to the magnitude of the brake fluid pressure supplied to the wheel cylinder. .

The master cylinder 27 as a brake fluid pressure source
It is a tandem type having two discharge ports 27a and 27b.
The brake pipe 28 extending from the discharge port 27a branches into two branch pipes 28a and 28b on the way, and the branch pipe 28a is connected to (the wheel cylinder of) the right front wheel brake 22.
b is connected to the left rear wheel brake 23. A brake pipe 29 extending from the discharge port 27b branches into two branch pipes 29a and 29b on the way, the branch pipe 29a is connected to the left front wheel brake 21, and the branch pipe 29b is connected to the right rear wheel brake 24. It is connected to the. As described above, the brake piping system is a so-called two-system X type. The branch pipes 28b and 29b for the rear wheel brakes 23 and 24 serving as drive wheels are provided with electromagnetic hydraulic pressure control valves 30 or 31 as braking force adjusting means.
Is connected. Of course, the brake fluid pressure generated in the master cylinder 27 depends on the amount of depression (the depression force) of the brake pedal 32 by the driver D.

Brake hydraulic pressure control circuit As shown in FIG. 2, the hydraulic pressure control valves 30 and 31
Each has a cylinder 41 and a piston 42 slidably fitted in the cylinder 41. The inside of the cylinder 41 is defined by the piston 42 into a variable volume chamber 43 and a control chamber 44. The variable volume chamber 43 is a passage for the passage of the brake fluid pressure from the master cylinder 27 to the brake 23 (24). Therefore, by adjusting the displacement position of the piston 42, the volume of the variable volume chamber 43 can be changed to generate brake hydraulic pressure for the brake 23 (24), and increase or decrease or maintain the generated brake hydraulic pressure. Will be able to do it.

The piston 42 is constantly urged by the return spring 45 in a direction in which the volume of the variable volume chamber 43 increases. A check valve 46 is integrated with the piston 42. When the piston 42 is displaced in a direction to reduce the volume of the variable volume chamber 43, the check valve 46 closes the inflow side to the variable volume chamber 43. As a result, the brake fluid pressure generated in the variable volume chamber 43 is reduced by the brake 23 (2
4) It acts only on the side and does not act on the brakes 21, 22 of the front wheels 2, 3 as driven wheels.

Adjustment of the displacement position of the piston 42 is performed by adjusting the control hydraulic pressure with respect to the control chamber 44. To explain this point in detail, a supply pipe 48 extending from a reservoir 47 is branched into two parts on the way, and one branch pipe 48R is connected to the control chamber 44 of the valve 30.
To the control chamber 4 of the valve 31.
Connected to 4. The supply pipe 48 is connected to a pump 49 and a relief valve 50, and the branch pipe 48L (48R) is connected to a supply valve SV3 (SV2) composed of an electromagnetic on-off valve. Each control room 44 is further connected to a reservoir 47 via a discharge pipe 51R or 51L, and a discharge valve SV4 (SV1) composed of an electromagnetic on-off valve is connected to the discharge pipe 51L (51R).

At the time of braking using the hydraulic pressure control valve 30 (31) (during slip control), the brake by the operation of the brake pedal 32 basically does not work due to the action of the check valve 46. However, the hydraulic pressure control valve 30
When the brake fluid pressure generated in (31) is small (for example, during pressure reduction), the brake by operating the brake pedal 32 operates. Of course, when the brake fluid pressure for slip control is not generated by the fluid pressure control valve 30 (31), the master cylinder 27 and the brake 23 (24) are in communication with each other. As a result, a normal braking action is performed.

The valves SV1 to SV4 are controlled to open and close by a brake control unit UB described later. Brake 2
The following table summarizes the relationship between the state of the brake fluid pressure to 3, 24 and the operation relationship between each of the valves SV1 to SV4.

1. Outline of Configuration of Control Unit In FIG. 1, U is a control unit,
This is roughly divided into a brake control unit UB, a throttle control unit UT, and a slip control control unit US. The control unit UB controls the opening and closing of each of the valves SV1 to SV4 based on the command signal from the control unit US as described above. Further, the throttle control unit UT controls the drive of the throttle actuator 14 based on a command signal from the control unit US.

The control unit US for slip control is constituted by a digital computer, more specifically, a microcomputer. The control unit US includes sensors (or switches) 61, 62, 64
To 68 are input. The sensor 61 detects the opening of the throttle valve 13. The sensor 62 detects whether the clutch 7 is engaged.
The sensor 64 detects the rotation speed of the left front wheel 2 as a driven wheel, that is, the vehicle speed. The sensors 65 and 66 detect the rotational speeds of the left and right rear wheels 4 and 5 as drive wheels. The sensor 67 detects the operation amount of the accelerator 69, that is, the accelerator opening. The sensor 68 detects the operation amount of the steering wheel 70, that is, the steering angle. The above sensors 64, 65, 66
Are each configured using, for example, a pickup, the sensors 61, 67, and 68 are configured using, for example, a potentiometer, and the sensor 62 is configured by, for example, a switch that operates ON and OFF.

Note that the control unit US is basically a CPU, RO
Equipped with M, RAM, and CLOCK.In addition to having an input / output interface, A /
It also has a D or D / A converter, but since these points are the same as those in the case of using a microcomputer, detailed description is omitted. The maps and the like in the following description are those stored in the ROM of the control unit US.

Next, the control contents of the control unit U will be sequentially described. The slip ratio S used in the following description is
It is defined by the following equation (1).

WD: Number of rotations of drive wheels (4, 5) WL: Number of rotations of driven wheel (2) (vehicle speed) Throttle control The control unit UT feeds back the throttle valve 13 (throttle actuator 14) so as to reach the target throttle opening. It is controlled.
During the throttle control, when slip control is not performed, the operation amount of the accelerator 69 operated by the driver D is 1:
Control to reach the target throttle opening corresponding to 1,
An example of the correspondence between the accelerator opening and the throttle opening at this time is shown in FIG. Further, during slip control, the control unit UT does not follow the characteristics shown in FIG. 12, but performs throttle control such that the target throttle opening Tn calculated by the control unit Us is reached.

Throttle valve 1 using control unit UT
In the embodiment, the feedback control of 3 is performed by PI-PD control in order to compensate for the fluctuation of the response speed of the engine 6. That is, during the slip control of the drive wheels, the opening degree of the throttle valve 13 is controlled by PI-PD so that the current slip rate matches the target slip rate. More specifically, the target throttle opening Tn for slip control
Is calculated by the following equation (2).

WL: Revolution of driven wheel (2) WD: Revolution of drive wheel (4, 5) KP: Proportional constant KI: Integral constant FP: Proportional constant FD: Differential constant SET: Target slip ratio (for throttle control) As shown in (2), the throttle opening Tn is feedback-controlled on the rotation speed of the drive wheels so as to reach a predetermined target slip ratio SET. In other words, as is apparent from the above equation (1), the throttle opening is determined by the following equation (3) when the target drive wheel rotational speed WET is Is controlled so that

The PI-PD control using the above-described control unit UT is shown in FIG. 3 as a block diagram, and “S ′” shown in FIG. 3 is an “operator”. In addition, the values of each signal at the time of each baffle “n” and “n−1” baldness and at the time of sampling one time before are shown.

Brake control During slip control, the control unit U
The rotation (slip) of the left and right drive wheels 4, 5 using B
Feedback control is performed so that a predetermined target slip ratio SBT is obtained independently for the left and right sides. In other words, in the brake control, feedback control is performed so that the driving wheel rotational speed WBT is set by the following equation (4).

In this embodiment, the target slip rate SBT of the brake is set to be larger than the target slip rate SET of the engine as described later. In other words, in the slip control of the present embodiment, the engine output is increased / decreased to the predetermined SET (WET) and the torque is increased / decreased by the brake so that the SBT (WBT) is also increased to increase the brake output. It is used less frequently. In this embodiment, feedback control that satisfies the above equation (4) is performed by I-PD control having excellent stability. More specifically, the brake operation amount (valves 30, 31
Is calculated by the following equation (5).

KI: integral coefficient KD: proportional coefficient FD: differential coefficient When the above Bn is greater than 0 (when "positive"), the brake fluid pressure is increased, and when it is 0 or less, the pressure is reduced. The increase or decrease of the brake fluid pressure is performed by opening and closing the valves SV1 to SV4 as described above. The rate of increase or decrease of the brake fluid pressure is adjusted by adjusting (duty control) the ratio (duty ratio) of the opening and closing times of the valves SV1 to SV4.
Duty control proportional to the absolute value of Therefore, the absolute value of Bn is proportional to the change speed of the brake fluid pressure, and conversely, the duty ratio for determining the increase / decrease speed is Bn
Is also shown.

FIG. 4 is a block diagram showing the I-PD control by the control unit UB described above.
"S '" shown in the figure is an "operator".

Overall Outline of Slip Control An overall outline of slip control by the control unit U will be described with reference to FIG. In addition,
The meanings of the signs and numerical values shown in FIG. 5 are as follows.

S = 0.2: Slip rate at start of slip control on flat road (SS) S = 0.17: Target slip rate by braking on flat road
(SBT) S = 0.09: Slip rate when the brake slip control is stopped (SBC) S = 0.06: Target slip rate by the engine on a flat road
(SET) The above numerical values are shown based on the data obtained by actually running the ice barn with spiked tires. The slip ratio S = 0.09 at the time when the slip control by the brake is stopped is not changed in the embodiment. on the other hand,
The target slip rate SBT due to the brake, the target slip rate SET due to the engine, and the slip rate SS at the start of the slip control are changed depending on road surface conditions and the like. In FIG. 5, examples are "0.17", " 0.06 "or" 0.2 ". The slip ratio S = 0.2 at the start of the slip control uses the slip ratio at the time of generation of the maximum grip force obtained when the spike tire is used (see the solid line in FIG. 13). In this way, the slip ratio at the start of the slip control is increased to 0.2 in order to obtain the actual slip ratio when the maximum grip force is obtained. The target slip rates SET and SBT due to the engine and the brake are corrected in accordance with the slip rate. The solid line in FIG. 13 shows how the magnitude of a grip force and a lateral force (shown as a coefficient of friction with respect to a road surface) at the time of a spike tire changes in relation to a slip ratio. Also,
The broken line in FIG. 13 shows the relationship between the grip force and the lateral force when using a normal tire.

Slip control on a flat road Based on the above, FIG. 5 will be described with the passage of time.

Since t ₀ ~t ₁ slip ratio S does not exceed the S = 0.2 as the slip control starting condition, the slip control is not performed. That is, when the slip of the drive wheel is small, the acceleration can be improved by not performing the slip control (running using a large grip force). Of course, at this time,
The characteristic of the throttle opening with respect to the accelerator opening is uniformly determined as shown in FIG.

t ₁ ~t ₃ with the slip control is initiated, slip ratio is when the above slip control stop point by the brake (S = 0.09). At this time, since the slip ratio is relatively large, slip control is performed by reducing the torque generated by the engine and braking by the brake. In addition, since the target slip ratio of the brake (S = 0.17) is larger than the target slip ratio of the engine (S = 0.06), the brake is pressurized during a large slip (S> 0.17), but when the slip is small. In (S <0.17), the brake is not pressurized, and the control is performed only by the engine so that the slip is converged.

t ₃ ~t ₄ engine only by the slip control is performed.

After t ₄ Since the accelerator 69 is completely closed by the driver D, the slip control is stopped. At this time, even if the opening degree of the throttle valve 13 is left to the will of the driver D, there is no danger of re-slip because the torque is sufficiently reduced. In the embodiment, in addition to the full closing of the accelerator, the target throttle opening by the slip control is determined from the throttle opening determined by FIG. 12 corresponding to the accelerator opening operated by the driver. Is also performed when it becomes smaller.

Slip control on uneven road On a bad road where the drive wheels 4, 5 repeatedly accelerate and decelerate, the slip ratio SS at the start of slip control is changed to SS = 0.22. That is, the slip determination level is raised to cope with the increase / decrease in the detection speed of the drive wheels (the dead zone is increased). Along with this, the target slip rate SBT by the brake is changed to SBT = 0.19 and the target slip rate SET by the engine is changed to SET = 0.08. That is, the target value level of the slip control is raised to reduce the control amount of the slip control.

Details of Slip Control (Flowchart) Next, referring to the flowcharts of FIGS. 6 to 11,
Details of the slip control will be described.

The control at the time of failure will be described with reference to the case where the slip control system (throttle control system) by the engine has failed. In the following description, P indicates a step.

FIG. 6 (Main) After the system is initialized in P2, it is determined in P3 whether the accelerator 69 is fully closed. this
If NO is determined in P3, it is determined in P4 whether the current throttle opening is larger than the accelerator opening. If NO is determined in P4, it is determined in P5 whether the slip control is currently being performed. This determination is made by checking whether the slip control flag is set. When NO is determined in this P5, it is determined in P6 whether a slip has occurred to perform the slip control. This determination is made by checking whether at least one of the slip flags for the left and right rear wheels 4, 5 described later is set. When NO is determined in P6, the process proceeds to P7, and the slip control is stopped (normal traveling).

When YES is determined in P6, the flow shifts to P8, where a slip control flag is set. Subsequently, in P9, the initial value of the target slip rate SET for the engine (throttle) is set to 0.06 on a flat road and 0.08 on a rough road based on the presence / absence of a bad road running flag described later. The initial value of the target slip ratio SBT is set to 0.17 on a flat road and 0.19 on a bad road based on the presence / absence of a bad road running flag, which will be described later. Brake control and engine control on P12 are performed. The setting of the initial values in P9 and P10 is performed based on the maximum acceleration GMAX obtained in the previous slip control.

When YES is determined in P5, the above-described P11
Then, the slip control is continuously performed.

When YES is determined in P4, it means that the slip control has become unnecessary, and the routine shifts to P14. In this P14, after the slip control flag is reset, the flow shifts to P7, where the slip control is stopped.

When YES is determined in P3, the brake is released in P13, and then the processing after P14 is performed.

7 and 8 The flowchart of FIG. 7 is interrupted, for example, every 14 msec with respect to the main flowchart of FIG.

First, in P21, each signal from each of the sensors 61, 62, 64-68 is input for data processing. Next, as will be described later, the rough road detection in P22, the slip detection processing in P23, and the sroll control in P24 are performed.

The throttle control at P24 is performed according to the flowchart shown in FIG. First, in P26, it is determined whether or not the throttle control system is faulty. This P26
If the determination is NO (normal), the process proceeds to P27,
At 27, it is judged if the slip control flag is set, that is, if the slip control is currently performed. If YES in this P27, proceed to P28,
The control of the throttle valve 13 is used for slip control,
That is, a control that realizes the predetermined target slip ratio SET without selecting the characteristic shown in FIG. 12 is selected. Also,
When NO is determined in P27, in P29, it is selected (according to the characteristics shown in FIG. 12) so that the opening / closing control of the throttle valve 13 is left to the will of the driver D. After P28 and P29, control for realizing the target throttle opening is performed in P30.

On the other hand, when the determination in P26 is YES (throttle control system is faulty), the process proceeds to P31, the fail flag is set, and the warning lamp (attached to the driver's seat) is lit in P32. Then, proceed to P29. That is, when a failure of the throttle control system occurs, the slip control by the engine is stopped and the opening / closing control of the throttle is under the control of the driver.

FIG. 9 (Detection of rough road) The flowchart of FIG. 9 corresponds to P22 of FIG.

The rough road is detected here by the signals from the sensors 65 and 66 for detecting the rotational speeds of the drive wheels 4 and 5, and the operation of the accelerator 69 and the brake pedal 32. That is, when the acceleration / deceleration of the drive wheels 4 and 5 becomes a predetermined value G0 or more in a short time (P90, P92, P94),
After assuming that the acceleration / deceleration is repeated abnormally, the acceleration of the drive wheels 4, 5 is not based on the accelerator operation by the driving vehicle D (P91, 95) and the deceleration of the drive wheels 4, 5 is the driver D. It is not based on the brake operation by P. (P93), and when the two conditions are satisfied, it is determined that the vehicle is traveling on a rough road, and the rough road traveling flag is set at P96. On the contrary, when any of the above three conditions is missing, it is determined that the slip control for traveling on a rough road is unnecessary.
The rough road running flag is reset (P97).

FIG. 10 (slip detection process) The flowchart of FIG. 10 corresponds to P23 of FIG. This flowchart is for detecting whether or not a slip which is a target of the slip control has occurred.

First, at P33, it is determined whether or not the clutch 7 is completely connected. If YES is determined in this P33,
In P34, a correction value α for slip determination is calculated according to the steering angle of the steering wheel (see FIG. 14). After that, in P35, it is determined whether or not the vehicle is traveling on a bad road by the bad road traveling flag. When the result of the determination is NO (flat road), in P36, the slip of the left rear wheel 4 as the left driving wheel is performed. It is determined whether or not the rate is larger than a value (0.2 + α) obtained by adding α in P34 to the predetermined reference value 0.2. This P36
If YES in step S3, the slip flag is set because the left rear wheel 4 is in the slip state (P3
7). On the contrary, when NO is determined in P36, the slip flag of the left rear wheel 4 is reset (P38). The correction value α is set in consideration of a rotation difference between the inner and outer wheels during turning (particularly, a rotation difference between a driving wheel and a driven wheel).

After P37 or P38, setting or resetting of the slip flag for the right rear wheel 5 is performed in P39, P40 and P41 in the same manner as in P35, P36 and P37.

On the other hand, the determination is YES in P35 (while driving on a rough road).
In case of, S = 0.2, which is larger than the flat road setting reference value (S = 0.2) in P36, after the step after P42.
Based on 2, the presence or absence of the slip state is determined.
That is, when the vehicle is traveling on a rough road, the start level of the slip control is changed from S = 0.2 to a high level such as S = 0.22 through the determination of P42 and P45.

FIG. 11 (engine control) The flowchart shown in FIG. 10 corresponds to P12 in FIG.

First, in P60, it is determined whether or not a failure is occurring, and if NO, then in P61, it is determined whether or not the slip has transitioned to a convergent state (whether or not the time point t _{2 in} FIG. 5 has passed). Is determined. If NO in P61, it is determined in P62 whether the slip ratio S of the left rear wheel 4 is larger than the control start level SS. If NO in P62, P63
Then, it is determined whether or not the slip ratio S of the right rear wheel 5 is larger than SS. If NO in P63, it is determined in P64 whether only one of the left and right rear wheels 4, 5 is under brake control, that is, whether the vehicle is traveling on a split road. If YES at P64, at P65, left and right rear wheels 4, 5
The current slip ratio is calculated according to the driving wheel having the lower slip ratio (select low). Conversely, if the answer is NO in P64, the current slip ratio is calculated in P66 in accordance with the drive wheel having the larger slip ratio among the left and right rear wheels 4 and 5 (select high). It should be noted that also when the answer is NO in P62 and P63, the process shifts to P66.

The select high in P66 described above makes it possible to further avoid the use of the brake by calculating the current slip rate in order to control the slip of the drive wheel that is more slippery. On the other hand, the select low in p65 described above controls the slip of the drive wheel that is more slippery by the brake when driving on a split road where the friction coefficient of the road surface where the left and right drive wheels are in contact is different It will be possible to drive while making use of the grip of the drive wheels on the difficult side.
In the case of this select low, in order to avoid overuse of the brake, it is advisable to provide a backup means, for example, for a limited period of time, or to suspend this select low when the brake heats up.

After P65 and P66, the throttle valve 13
Target opening Tn of the slip control (feedback control)
Calculated for Of course, at this time, the target throttle opening (Tn) of the throttle valve 13 is set so as to realize the target slip ratio SET set in P6 and P66 or changed in P69 described later.

On the other hand, if YES in P61, the process shifts to P68 and automobile 1
Maximum acceleration GMAX is measured in (Figure 5 t ₂ time). Next, at P69, the friction coefficient of the road surface is estimated from GMAX at P68, and both the target slip rates SET and SBT of the slip control by the engine (throttle) and the brake are changed. How to change the target slip rates SET and SBT will be described later.

FIG. 12 (Brake control) The flowchart shown in FIG. 12 corresponds to P11 in FIG.

First, in P81, it is determined whether or not the slip ratio S of the right rear wheel 5 is larger than 0.09, which is a brake control stop point. If YES in P81, the operation speed Bn of the right rear wheel brake 24 is calculated in P82 (I in FIG. 4).
-Equivalent to Bn in PD control). After this, at P83,
It is determined whether or not Bn is greater than “0”. This determination is a determination as to whether the pressure increase direction of the gray is the positive pressure direction and the negative pressure direction is the negative pressure direction. If YES in P83, the pressure is increased in P84 with the value of Bn set in P85.

When NO in P83, Bn is "negative" or "0". Therefore, after Bn is converted to an absolute value in P85, the right brake is depressurized (Bn output) in P86.

On the other hand, if NO in P81, it means that the brake control is to be stopped, so the right brake is released in P87.

After P84, P86, P87, shift to P88, and left brake 23
Similarly to the right brake 24, pressure increase, pressure decrease, or brake release processing is performed.

Change of target slip rates SET and SBT (P69) The target slip rates SET and SBT of the engine and the brake changed in P69 are based on the maximum acceleration GMAX measured in P68, for example, as shown in FIG. Be changed. As is clear from FIG. 15, as the maximum acceleration GMAX increases, the target slip rates SET and SBT increase in principle.
Is to be increased. And the target slip rate S
ET and SBT are each provided with a limit value.

Here, how the setting relationship with the target slip rates SET and SBT affects the driving feeling of the automobile 1 will be described.

Driving wheel grip force SET and SBT are offset vertically in Fig. 15 as a whole. In order to increase the grip force, an upward offset is performed. That is, as a characteristic of the spike tire, as shown in FIG. 13, since the friction coefficient μ is in the increasing direction up to the slip rate of 0.2 to 0.3, the slip rate is 0.2 to 0.3.
The above can be said as long as it is used in the range of 0.3 or less.

The feeling of acceleration The feeling of acceleration changes by changing the "difference" between SET and SBT. The smaller the "difference", the greater the feeling of acceleration. That is, as in the embodiment, when SET is set to a value smaller than SBT, the brake control mainly works when the slip ratio is large, and the engine control mainly works when the slip ratio is small. Therefore, SET
When the "difference" between SBT and SBT is reduced, the direction in which the brake control and the engine control work in substantially the same distribution is approaching.
In other words, when the drive wheels are driven by squeezing the generated torque of the engine by the brake, and when the torque is rapidly increased for acceleration, the torque to the drive wheels increases without delay by simply releasing the brake. I do.

Acceleration smoothness SBT is large, that is, relatively large compared to SET. This means that by increasing the priority of the engine control, a smooth torque change, which is an advantage of the engine control, can be more effectively generated.

Stability during cornering SET is small, ie SET is relatively smaller than SBT. As is apparent from FIG. 13, this is because the slip ratio S at which the maximum grip force occurs is 0.2 to 0.2%.
In the range of 0.3 or less, by lowering the target slip ratio, the grip force of the drive wheel is reduced, while the lateral force is increased as much as possible to increase the bending force.

The above-mentioned characteristics (mode) can be selected manually according to the preference of the driving vehicle D (mode selection).

In the embodiment described above, the brake slip SBT is set larger than the engine SET as the target slip rate, so that the brake control in a small slip state is not performed, so that the use frequency is reduced. In addition to this, the load on the brake control can be reduced even when a large slip occurs. In addition, SBT and S
Since a point (SBC) at which the slip control by the brake is stopped is provided between the ET and the ET, the brake pressure is sufficiently reduced at the time of the stop of the brake control, so that a rapid torque change is unlikely to occur.

Although the embodiment has been described above, the present invention is not limited to this and includes, for example, the following case.

The magnitude relationship between the target slip ratios by the brake control and the engine control may be opposite to that in the embodiment, or may be the same.

As the adjustment of the generated torque of the engine 6, it is preferable to change and control the factor that most affects the generated output of the engine. That is, it is preferable that the generated torque is adjusted by so-called load control. In the case of an Otto type engine (for example, a gasoline engine), the amount of air-fuel mixture is adjusted. In the case of a diesel engine, the amount of fuel injection is adjusted. Is preferred. However, the present invention is not limited to this load control, and may be performed by adjusting the ignition timing in an Otto engine, or by adjusting the fuel injection timing in a diesel engine. Further, in the case of a supercharging engine, the supercharging may be performed by adjusting the supercharging pressure. Of course, the power source is not limited to the internal combustion engine, but may be an electric motor. In this case, the generated torque may be adjusted by adjusting the power supplied to the motor.

The vehicle 1 may have front wheels 2 and 3 as driving wheels (FF vehicles) or four wheels as driving wheels (4WD vehicles).

In order to detect the slip state of the drive wheel, the slip state may be directly detected like the rotation speed of the drive wheel as in the embodiment, but in addition, the slip state is predicted according to the state of the vehicle, that is, You may make it detect indirectly. Such vehicle states include, for example, an increase in torque generated by the power sole or an increase in the number of revolutions, a change in the accelerator opening, a change in the rotation of the drive shaft, a steering state (cornering), and a floating state of the vehicle body (acceleration) , Load capacity, etc. are considered. In addition to this, the road surface μ such as atmospheric temperature, rain, snow, ice burn, etc.
Can be automatically detected or input manually to make the prediction of the slip state of the drive wheels even more appropriate.

The brake fluid pressure control circuit and sensors 64 and 65 of FIG.
66 can use the thing of the existing ABS (anti-brake lock system).

In the above embodiment, as the control mode during running on a rough road, the slip rate SS at the slip control start time and the target slip rates SBT and SET of the brake and the engine are changed at the same time. However, only one of them may be performed.

(Effects of the Invention) As is clear from the above description, according to the present invention, it is possible to optimize the slip control during traveling on a rough road in which the drive wheels accelerate and decelerate.

[Brief description of the drawings]

FIG. 1 is an overall system diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing an example of a control circuit for a brake fluid pressure. FIG. 3 is a block diagram when the feedback control of the throttle valve is performed. FIG. 4 is a block diagram when the brake is feedback controlled. FIG. 5 is a graph schematically showing a control example of the present invention. 6 to 12 are flowcharts showing control examples of the present invention. FIG. 13 is a graph showing characteristics of the throttle opening with respect to the accelerator opening when the slip control is not performed. FIG. 14 is a graph showing the relationship between the grip force of the drive wheels and the lateral force by the relationship between the slip ratio and the coefficient of friction on the road surface. FIG. 15 is a graph showing a correction value when the slip ratio at the start of the slip control is corrected according to the steering angle of the steering wheel. FIG. 16 is a graph showing an example of a map used to determine the target slip rate. FIG. 17 is an overall configuration diagram of the present invention. 1: Automobile 2, 3: Front wheel (driven wheel) 4, 5: Rear wheel (driving wheel) 6: Engine (power source) 13: Throttle valve 14: Sroll actuator 21-24: Brake 27: Master cylinder 30, 31 : Hydraulic control valve 32: Brake pedal 61: Sensor (throttle opening) 64: Sensor (driven wheel speed) 65, 66: Sensor (driving wheel speed) 67: Sensor (accelerator opening) SV1 to SV4: Electromagnetic Open / close valve U: Control unit

Claims (1)

(57) [Claims] 1. A torque adjusting means for adjusting a torque applied to a driving wheel, a bad road detecting means for detecting that a wheel is traveling on a bad road where acceleration and deceleration are repeated, and a wheel for detecting a wheel speed. Speed detection means, and slip control means for controlling the torque adjustment means based on the detection results of the rough road detection means and the wheel speed detection means, wherein the slip control means detects the wheel speed detection means. When it is determined that the drive wheels are slipping based on the result, the torque adjusting means is controlled so as to reduce the applied torque to the drive wheels by a predetermined amount, and the bad road traveling means is operated by the bad road detecting means. Is set to control the torque adjusting means so that the amount of reduction in torque applied to the drive wheels at the time of slip determination is smaller than when no rough road running is detected. The vehicle slip control device is characterized in that: