JP2537807B2 - Automotive slip control system - 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 becoming too large on a road surface. The present invention relates to a control device.

(Prior Art) Preventing excessive slip of the drive wheels from the road surface is effective for effectively obtaining the propulsive force of the vehicle and for safety such as preventing spin. And to prevent excessive slip of the driving wheels,
It is only necessary to reduce the torque applied to the drive wheels that causes slip.

A conventional control for this type of slip control is disclosed in JP-A-58-16948. The technology disclosed in this publication is designed to reduce the torque applied to the drive wheels by utilizing the braking force applied to the drive wheels by a brake and the torque generated by the engine itself. . More specifically, when the slip of the driving wheel is small, only the braking of the driving wheel is performed, while when the slip of the driving wheel becomes large, in addition to the braking of the driving wheel,
It is designed to reduce the torque generated by the engine.
In other words, the braking of the drive wheel by the brake is mainly used, and the torque generated by the engine is supplementarily reduced.

In the publication, the case of cornering is mentioned as a case where the slip control of the drive wheels is performed. That is, the load on the drive wheel on the inner side in the turning direction is reduced, while the torque applied to the drive wheel on the outer side is increased by the action of the differential device to increase the slip. Therefore, slip control may be performed on the outer drive wheel. It is shown. Then, the slip control of the outer drive wheel should be performed with reference to the inner drive wheel with less slip (so-called select low).
Is also disclosed.

(Problems to be Solved by the Invention) However, as described in the above publication, if the slip control at the time of cornering is simply performed on the basis of the slip of the inner drive wheels, the stability at the time of cornering can be secured. However, it becomes difficult to secure sufficient propulsive force when traveling straight ahead. In other words, in order to improve stability during cornering, the slip should be made small in order to increase the lateral force (side force) of the drive wheel. However, if this slip is made small, the propulsion force (grip force of the drive wheel) Will be reduced. In other words, there is a limit to the sum of the propulsive force (grip force) and lateral force of the drive wheels, and there is a limit when one is increased, and the other is decreased. Is set to a large value, lateral force is insufficient during cornering, which hinders stability during cornering, and conversely, if the drive wheel slip is set to a small value to ensure stability during cornering, straight driving Will be impaired.

The present invention has been made in consideration of the circumstances as described above, and slip control of a vehicle that can sufficiently secure both a sufficient propulsive force during straight running and stability during cornering is achieved. To provide a device.

(Means and Actions for Solving Problems) In order to achieve the above-mentioned object, in the present invention, the target value at the time of slip control, that is, what value the slip of the driving wheels is set to, It is designed to be different between straight running and cornering. That is, during cornering, the target value is set (changed compared to when traveling straight ahead) so that the slip of the driving wheels becomes smaller in order to increase the lateral force of the drive wheels than when traveling straight ahead.

Specifically, as shown in FIG. 23, in a slip control device for an automobile, which controls the torque applied to the drive wheels to prevent the drive wheels from slipping excessively on the road surface, Torque adjusting means for adjusting the applied torque to the driving wheel, slip detecting means for detecting the slip state of the driving wheel with respect to the road surface, and output from the slip detecting means so that the slip of the driving wheel becomes a predetermined target value. Slip control means for controlling the torque adjusting means, cornering means for detecting that the vehicle is cornering, and during cornering, the slip of the drive wheels is smaller than when traveling straight ahead, and the steeper the cornering is. And a target value setting means for setting the target value so that the slip of the driving wheels becomes small.

Embodiments Embodiments of the present invention will be described below with reference to the accompanying drawings.

1. Overview of Overall Configuration In FIG. 1, an automobile 1 includes four wheels, that is, left and right front wheels 2 and 3 serving as driving wheels and left and right rear wheels 4 and 5 serving as driven wheels. An engine 6 as a power source is mounted on a front portion of the vehicle 1. The torque generated by the engine 6 is transmitted through a clutch 7, a transmission 8, and a differential gear 9, and then transmitted to right and left drive shafts 10 and 11. Through the transmission, the driving force is transmitted to left and right front wheels 2 and 3 as driving wheels. Thus, the vehicle 1 is of the FF type (front engine / front drive).

The engine 6 as a power source has its intake passage 12
Load control, that is, control of generated torque is performed by the throttle valve 13 disposed in the.
More specifically, the engine 6 is a gasoline engine, and the generated torque is changed by the change of the intake air amount, and the intake air amount is adjusted by the throttle valve 13. And the throttle valve 13
The throttle actuator 14 is electromagnetically controlled to be opened and closed. It should be noted that the throttle actuator 14 may be constituted by an appropriate device such as a DC motor, a step motor, and a device driven and electromagnetically driven 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, and each of the brakes 21 to 24 is a disc brake. This disc brake is
As is known, it comprises a disc 25 which rotates with the wheels and a caliper 26. The caliper 26 holds a 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 according to the magnitude of the brake fluid pressure supplied to the wheel cylinder. .

The master cylinder 27 as a brake fluid pressure generation source has two
It is of a tandem type having two discharge ports 27a and 27b.
The brake pipe 28 extending from the discharge port 27a is branched into two branch pipes 28a and 28b on the way, and the branch pipe 28a is connected to (the wheel cylinder of) the brake 22 for the right front wheel.
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. In this way, the brake piping system is of the so-called two-system X type. The branch pipes 28a, 29a for the front wheel brakes 21, 22 serving as drive wheels are provided with electromagnetic hydraulic 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 (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 are
Each has a cylinder 41 and a piston 42 slidably fitted in the cylinder 41. The interior of the cylinder 41 is divided into a variable volume chamber 43 and a control chamber 44 by the piston 42. The variable volume chamber 43 serves as a passage system for the brake fluid pressure from the master cylinder 27 to the brake 21 (22). Therefore, by adjusting the displacement position of the piston 42, the volume of the variable volume chamber 43 can be changed to generate brake fluid pressure for the brake 21 (22), and increase or decrease or maintain the generated brake fluid pressure. Will be able to do it.

The piston 42 is constantly urged by a 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. The check valve 46 closes the inlet side of the variable volume chamber 43 when the piston 42 is displaced in the direction of reducing the volume of the variable volume chamber 43. As a result, the brake fluid pressure generated in the variable volume chamber 43 is reduced by the brake 21 (2
2) It acts only on the side and does not act on the brakes 23, 24 of the rear wheels 4, 5 as driven wheels.

The displacement position of the piston 42 is adjusted by adjusting the control hydraulic pressure for the control chamber 44. Explaining this point in detail, the supply pipe 48 extending from the reservoir 47 is branched into two in the middle, and one branch pipe 48R is connected to the control chamber 44 of the valve 30.
And the other branch pipe 48L is connected to the control room 4 of the valve 31.
Connected to 4. A pump 49 and a relief valve 50 are connected to the supply pipe 48, and a supply valve SV3 (SV2) which is an electromagnetic on-off valve is connected to a branch pipe 48L (48R) of the supply pipe 48. Each control chamber 44 is further connected to a reservoir 47 via a discharge pipe 51R or 51L, and a discharge valve SV4 (SV1), which is 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 check valve 46 basically prevents the brake pedal 32 from operating. However, the hydraulic pressure control valve 30
When the brake fluid pressure generated in (31) is small (for example, during pressure reduction), the brake is operated by operating the brake pedal 32. 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 21 (22) 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, which will be described later. Brake 2
The state of the brake fluid pressure to Nos. 1 and 22 and the operation relationship between the valves SV1 to SV4 are summarized in the following table.

Control Unit Configuration Overview 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 the command signal from the control unit Us.

The slip control unit U S is composed of a digital computer, more specifically, a microcomputer. Signals from the sensors (or switches) 61 to 68 and 71 are input to the control unit Us. The sensor 61 detects the opening degree of the throttle valve 13. The sensor 62 detects whether or not the clutch 7 is engaged.
The sensor 63 detects a gear position of the transmission 8. The sensors 64 and 65 detect the number of rotations of the left and right front wheels 2 and 3 as driving wheels. The sensor 66 detects the rotational speed of the rear left wheel 4 as a driven wheel, that is, the vehicle speed. Sensor
Reference numeral 67 detects the operation amount of the accelerator 69, that is, the accelerator opening. The sensor 68 detects an operation amount of the steering wheel 70, that is, a steering angle. Sensor (switch) 71
Is for inputting (selecting) a target value (target slip ratio) of slip of the drive wheels by a manual operation performed by the driver D. The above-mentioned sensors 64, 65, 66 are each configured by using, for example, a pickup, and the sensors 61, 63, 67, 68
Is configured using a potentiometer, for example
The reference numeral 62 is composed of, for example, a switch that operates ON and OFF. Further, the switch 71 can select the target slip rate from large (hard) to small (soft) stepwise or steplessly by using a slide type lever 71a as shown in FIG. 21, for example. (See also Fig. 13).

The control unit Us is basically a CPU, RO
Equipped with M, RAM, CLOCK, and other input / output interfaces, and A / D according to input and output signals.
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 thereof will be omitted. The maps and the like in the following description are 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 (2, 3) WL: Number of rotations of driven wheel (4) (vehicle speed) Throttle control The control unit UT feeds back the throttle valve 13 (throttle actuator 14) so that the target throttle opening is achieved. It is controlled.
In the throttle control, when the slip control is not performed, the operation amount of the accelerator 69 operated by the driver D is
FIG. 12 shows an example of the correspondence relationship between the access opening and the throttle opening at this time, which is controlled so that the target throttle opening corresponds to 1: 1. 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 barba 1 with control unit UT
In the embodiment, the feedback control 3 is performed by PI-PD control in order to compensate the variation in the response speed of the engine 6. That is, during slip control of the drive wheels, PI-PD control is performed on the opening of the throttle valve 13 so that the current slip rate matches the target slip rate. More specifically, the target throttle opening Tn during slip control
Is calculated by the following equation (2).

WL: Revolution of driven wheel (4) WD: Revolution of drive wheel (2, 3) 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 equation (1), the throttle opening is calculated by the following equation (3) when the target drive wheel rotation speed WET is Is controlled so that

PL-PD control using the above-mentioned control unit UT is shown in FIG. 3 as a block diagram, and “S ′” shown in this FIG. 3 is an “operator”. The suffixes “n” and “n−1” indicate the value of each signal at the current time and at the time of the previous sampling.

Brake control During slip control, the control unit U
The rotation (slip) of the left and right drive wheels 2, 3 using B
Feedback control is performed independently on the left and right sides so that a predetermined target slip rate SBT is achieved. In other words, in the brake control, feedback control is performed so that the drive wheel rotation 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 SBT 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 as to increase the SBT (WBT) larger than the predetermined SET (WET). It is used less frequently. Then, in this embodiment, the feedback control satisfying the expression (4) is performed by the I-PD control having excellent stability. More specifically, the brake operation amount (valves 30, 31
The operation amount Bn of the piston 44 in is calculated by the following equation (5).

KI: Integral coefficient KD: Proportional coefficient FD: Differential coefficient When Bn is larger than 0 (when "positive"), the brake fluid pressure is increased, and when it is 0 or less, the pressure is reduced. This increase / decrease in brake fluid pressure is dependent on the valves SV1 to SV4 as described above.
It is done by opening and closing. Further, the increase / decrease speed of the brake fluid pressure is adjusted by adjusting the ratio (duty ratio) of the opening / closing times of the valves SV1 to SV4 (duty control), which is obtained by the above equation (5).
The duty control is proportional to the absolute value of Bn. Therefore, the absolute value of Bn is proportional to the changing speed of the brake fluid pressure, and conversely the duty ratio that determines the increasing / decreasing speed is
It also indicates Bn.

The I-PD control by the control unit UB described above is shown as a block diagram in FIG.
“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 symbols and numerical values shown in FIG. 5 are as follows.

S / C: Slip control area E / G: Engine slip control B / R: Brake slip control F / B: Feedback control O / R: Open loop control R / Y: Recovery control B / A: Backup control A / S: Buffer control S = 0.2: Slip rate at the start of slip control (SS S = 0.17: Target slip rate by brake (SBT) S = 0.09: Slip rate when slip control by brake is stopped (SBC) S = 0.06 : Target slip rate (SET) by engine S = 0.01 to 0.02: Slip rate in the range where buffer control is performed S = 0.01 or less: Slip rate in the range where backup control is performed Based on the data obtained, S = 0.01 and 0.02 for performing the cushioning control A / S, and the slip ratio S = 0.09 at the time when the slip control by the brake is stopped are not changed in the embodiment. On the other hand, the target slip rate SBT by the brake, the target slip rate SET by the engine, and the slip rate SS at the start of slip control
Is changed depending on the road surface condition, etc., and in FIG. 5, as an example, “0.17”, “0.06” or “0.
2 ”is shown. For the slip rate S = 0.2 at the start of slip control, the slip rate at the time when the maximum grip force is obtained, which is obtained when the spike tire is used, is used.
(See Figure 13 solid line). In this way, the slip ratio at the start of slip control is increased to 0.2 in order to obtain the actual slip ratio when this maximum grip force is obtained. The target slip ratios SET and SBT by the engine and the brake are corrected according to the slip ratio.

The solid line in FIG. 13 shows how the magnitude of the grip force and the lateral force (shown as a friction coefficient with respect to the road surface) in the case of a spike tire changes in relation to the slip rate. Further, the broken line in FIG. 13 shows the relationship between the grip force and the lateral force in the case of a normal tire. And the
As shown in FIG. 13, the target slip ratio SD that can be manually selected by the switch 71 is slightly larger than the value (hard) at which the maximum grip force is generated in the state where the spike tire is running on the ice burn, A value (soft) that is sufficiently smaller than when this maximum grip force occurs
It is set as the range of and.

Based on the above, FIG. 5 will be described over time.

Since the slip ratio S from t _{0 to} t ₁ does not exceed S = 0.2 which is the slip control start condition, slip control is not performed. That is, when the slip of the driving wheels is small, the acceleration performance can be improved by not performing the slip control (traveling 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 with ~t ₂ slip control is started, the slip rate 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. Also, since the target slip rate of the brake (S = 0.17) is larger than the target slip rate of the engine (S = 0.06), the brake is pressed during a large slip (S> 0.17), but during a small slip. At (S <0.17), the brake is not pressurized, and the slip is controlled by the control of only the engine.

between t ₂ ~t ₄ (Recovery Control) slip convergence (S <0.2) and a predetermined time after (e.g. 170 msec), the throttle valve 13 is held at a predetermined opening (open loop control). At this time, S = 0/2
The maximum acceleration GMAX at the time (t ₂ ) is obtained, and this GM
The maximum μ of the road surface (the maximum grip force of the driving wheel) is estimated from AX. Then, the throttle valve 13 is held for a predetermined time as described above so as to generate the maximum grip force of the drive wheel. This control is performed in order to prevent the body acceleration G from dropping immediately after the convergence of the slip because the response is not enough in the feedback control because the convergence of the slip occurs rapidly. Therefore, when the convergence of the slip is predicted (lower than S = 0.2), the predetermined torque is secured in advance as described above, and the acceleration is improved.

Optimal throttle opening TV for realizing the torque applied to the drive wheels that can generate the maximum grip force
₀ is theoretically obtained from the torque curve and the gear ratio of the engine 6, but in the embodiment, it is determined based on a map as shown in FIG. 15, for example. This map is created by an experimental method, and when GMAX is 0.15 or less and 0.4 or more, it is set to a predetermined constant value in consideration of the measurement error of GMAX. It should be noted that the map shown in FIG. 12 is based on a certain speed (for example, first speed), and that the optimum throttle opening TV ₀ is set at another speed.
Is corrected.

t _{4 to} t ₇ (backup control, buffer control) To cope with the slip rate S abnormally decreasing,
Backup control is performed (open loop control).
That is, when S <0.01, the feedback control is stopped and the throttle valve 13 is opened stepwise. When the slip ratio is between 0.01 and 0.02, in order to smoothly transition to the next feedback control, buffer control is performed (t ₄ ~t ₅ and t ₆ ~t _7). This backup control is performed when the feedback control and the recovery control cannot cope. Of course, the backup control has a sufficiently high response speed than the feedback control.

In this embodiment, the rate of increase of the throttle opening in the backup control is 0.5% with respect to the previous throttle opening every 14 msec of the throttle opening sampling time.
It is assumed to be added by the opening.

Further, in the above buffer control, as shown in FIG. 16, a throttle opening T ₂ obtained by the feedback control calculation, and a throttle opening T ₁ obtained by the backup control operation, the current slip ratio S ₀ It is set as the throttle opening T ₀ obtained by proportional distribution.

By controlling the up t ₇ ~t ₈ t _7, a smooth transition to only by the slip control engine.

After t ₈ 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 intention of the driver D, there is no risk of re-slip because the torque is sufficiently reduced. In addition, in the embodiment, the slip control is stopped by fully closing the access and the target throttle opening by the slip control from the throttle opening determined by FIG. 12 corresponding to the access opening operated by the driver. I also try to do it when it gets smaller.

Here, during cornering, the target slip ratio SET under engine control is set to be smaller than that during straight running. The target slip rate S for engine control is
The reason why only ET is made small is because the target slip ratio SBT itself in brake control is sufficiently larger than the suitable slip ratio at the time of cornering, but this SBT can be made small at the time of cornering. It should be noted that whether or not it is during cornering is checked according to the operating state of the handle 70 in the embodiment, but in addition to this, it is conventionally adopted to detect cornering such as lateral force acting on the vehicle body. Various methods can be adopted.

Details of Slip Control (Flowchart) Next, the details of the slip control will be described with reference to the flowcharts of FIGS. 6 to 11. In the embodiment, in the stack in which the vehicle 1 is stuck in muddy or the like, A stack control for getting out of the mud or the like is also performed by using the brake control. In the following description, P indicates a step.

FIG. 6 (Main) After the system has been initialized in P1, it is determined in P2 whether or not the vehicle is currently in a stack state (a state in which it cannot be stuck in a muddy area or the like). This determination is made by checking whether or not a stack flag described later is set. If the determination in P2 is NO, it is determined in P3 whether the accelerator 69 is fully closed. If NO is determined in P3, it is determined in P4 whether the current throttle opening is larger than the accelerator opening. When NO is determined in P4, it is determined in P5 whether or not slip control is currently being performed. This determination is made by checking whether or not the slip control flag is set. this
When NO is determined in P5, it is determined in P6 whether or not slip for performing slip control has occurred. This determination is made by checking whether a slip flag has been set for the left and right front wheels 2 and 3 described below. When NO is determined in P6, the process shifts to P7 and the slip control is stopped (normal traveling).

When YES is determined in P6, the process shifts to P8, and the slip control flag is set. Subsequently, in P9, the initial value (0.06 in the embodiment) of the target slip ratio SET for the engine (throttle) is set, and then in P9.2, the target slip ratio SET in P9 is corrected as will be described later. Further, at P10, the initial value (0.17 in the embodiment) of the target slip rate SBT for braking is set. After this,
As described below, for slip control, P11
Brake control at P12 and engine control at P12 are performed. The initial values are set in P9 and P10 based on the maximum acceleration GMAX obtained in the previous slip control from the same viewpoint as in P76 described later.

If YES is determined in P5, the above P11
Then, the slip control is continued.

If YES is determined in P4, it means that slip control is not needed, and the process proceeds to P14. At P14, the slip control flag is reset. Next, the engine control is stopped at P15, and the brake control is performed at P16. Note that the brake control in P16 is performed as a countermeasure during the stack.

If YES is determined in P3, the brake is released in P13, and then the processes from P14 are performed.

When YES is determined in P2, the processing after P15 is performed.

The flowcharts of FIGS. 7 and 8 are 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 to 68 is input for data processing. Next, after the process of slip detection described later is performed in P22, the throttle control is performed in P23.

The throttle control in P23 is performed according to the flowchart shown in FIG. First, in P24, it is determined whether or not the slip control flag is set, that is, whether or not slip control is currently being performed. this
When YES in P24, the control of the throttle valve 13 is selected for slip control, that is, control that realizes a predetermined target slip ratio SET without following the characteristics shown in FIG. When NO is determined in P24, the opening / closing control of the throttle valve 13 is performed in P26.
It is selected as subject to the will of the driver D (according to the characteristics shown in FIG. 12). After P25 and P26, control for achieving the target throttle opening degree is performed in P27 (control according to P68, P70, P71 described later or the 12th control).
Control according to the characteristics of the figure).

FIG. 9 (slip detection process) The flowchart of FIG. 9 corresponds to P22 of FIG. This flowchart is for detecting whether or not a slip which is a target of the slip control has occurred and whether or not the vehicle is stuck.

First, at P31, it is determined whether or not the clutch 7 is completely connected. If YES is determined in this P31,
The stack flag is reset in P32 as if it was not in the stack. Next, in P33, it is determined whether or not the current vehicle speed is low, that is, for example, smaller than 6.3 km / h.

When NO is determined in P33, the correction value α for slip determination is calculated in P34 according to the steering angle of the steering wheel (see FIG. 14). Thereafter, in P35, it is determined whether or not the slip ratio of the left front wheel 2 as the left driving wheel is larger than a value (0.2 + α) obtained by adding α in P34 to the predetermined reference value 0.2. If the determination in P35 is YES, it is determined that the left front wheel 2 is in the slip state, and the slip flag is set. Conversely, when it is determined to be NO in P35, the left front wheel 3
The slip flag of is reset. The correction value α is set in consideration of the rotation difference between the inner and outer wheels (particularly the rotation difference between the driving wheel and the driven wheel) during turning.

After P36 or P37, in P38, P39, and P40, the slip flag for the right front wheel 3 is set or reset in the same manner as in P35, P36, and P37.

When YES is determined in P33, it means that the vehicle is running at low speed, and the error in the calculation of the slip ratio based on the equation (1) becomes large.
The detection is made based only on the rotation speed of the drive wheels.
That is, in P41, the rotation speed of the left front wheel 2 is 10 kV.
It is determined whether or not it is higher than the number of revolutions corresponding to m / h. If YES is determined in P41, the left front wheel 2
Is set. Conversely, if NO is determined in P41, the slip flag of the left front wheel 2 is reset in P43.

After P42 and P43, in P44, P45 and P46, the right front wheel 3
The slip flag for is set or reset in the same manner as in the case of P41 to P43.

When it is determined to be NO in P31, it is considered that the vehicle may be in the stack (during the stack, the driver D tries to escape from the mud or the like while using the half clutch). In this case, shift to P51,
It is determined whether or not the average value of the rotational speeds of the left and right front wheels 2 and 3 as drive wheels is small (for example, 2 km / h in terms of vehicle speed).
It is determined whether or not the following). If NO is determined in P51, it is determined in P52 whether or not the stack control is currently being performed. When it is determined to be NO in P52, it is determined in P53 whether or not the rotation speed of the right front wheel 3 is higher than the rotation speed of the left front wheel 2. When YES is determined in P53, it is determined whether or not the rotation speed of the right front wheel 3 is larger than 1.5 times the rotation speed of the left front wheel 2. When YES is determined in this P54, the stack flag is set in P56. Conversely, P
If NO is determined in 54, it is determined that the stack is not in the stack, and the above-described processing from P32 is performed.

When it is determined to be NO in P53, it is determined in P55 whether the rotational speed of the left front wheel 2 is greater than 1.5 times the rotational speed of the right front wheel 3. If YES in P55, the process proceeds to P56, and if NO, the process proceeds to P32.

After P56, it is determined in P57 whether the vehicle speed is higher than 6.3 km / h. If YES in this P57,
The target rotation speeds of the front wheels 2 and 3 are determined by the following
It is set to be 1.25 times (equivalent to a slip rate of 0.2). When NO in P57, in P59, the front wheel 2,
The target speed of 3 is set uniformly to 10 km / h.

Furthermore, if YES in P51, the brake is slowly released in P60.

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

In P61, whether the transition slip to a converged state (whether the time that has passed through t ₂ time points of FIG. 5) is determined. When NO in P61, it is determined in P62 whether the slip ratio S of the left front wheel 2 is larger than 0.2. At P62
If NO, it is determined in P63 whether the slip ratio S of the right front wheel 3 is greater than 0.2. If NO in P63, it is determined in P64 whether only one of the left and right front wheels 2, 3 is under brake control, that is, whether the vehicle is traveling on a split road. If YES in P64, in P65,
The current slip ratio is calculated according to the drive wheel having the lower slip ratio among the left and right front wheels 2 and 3 (select low). Conversely, when the answer is NO in P64, the current slip ratio is calculated according to the drive wheel having the larger slip ratio among the left and right front wheels 2 and 3 (select high). Even if NO in P62 and P63, the process shifts to P66.

The select high in P65 allows the use of the brake to be further avoided by calculating the current slip ratio in order to suppress the slip of the drive wheel that is more likely to slip. On the other hand, the select low in P65 described above suppresses slippage of the drive wheel that is more slippery by the brake when traveling on a split road where the road surface on which the left and right drive wheels are in contact has different friction coefficients 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 limiting the select time, for example, or for stopping the select low when the brake is overheated.

After P65 and P66, at P67, the current slip ratio S
It is determined whether it is greater than 0.02. If YES in P67, in P68, the throttle valve 13 is feedback-controlled for slip control. Of course, at this time, the target throttle opening (T
n) is set to realize the target slip ratio SET set in P65 and P66 or changed in P76 described later.

If NO in P67, the current slip ratio S is
It is determined whether it is greater than 0.01. If YES in P69, the above-described buffer control is performed in P70. If NO in P69, the backup control described above is performed in P71.

On the other hand, if YES in P61, the flow shifts to P72, where it is determined whether or not a predetermined time (the time for performing recovery control, 170 msec in the embodiment as described above) has elapsed after slip convergence. When the answer is NO in P72, the processing after P73 is performed to perform the recovery control. That is, first, at P73, the maximum acceleration GMAX is measured of the automobile 1 (FIG. 5 t ₂ time).
Then, in P74, the optimum throttle opening Tv ₀ as this GMAX is obtained is set (see FIG. 15). Further, at P75, according to the current gear position of the transmission 8, P
The optimal throttle opening Tv ₀ at 74 is corrected. That is, since the applied torque to the drive wheels also differs depending on the shift speed, the optimal throttle opening Tv ₀ for a certain reference shift speed is set in P74, and the difference in the shift speed is corrected in P75. It is. After that, in P76, the friction coefficient of the road surface is estimated from GMAX in P73, and the target slip ratios SET and SBT of the slip control by the engine (throttle) and brake are both changed. In addition, this target slip rate S
How to change ET and SBT will be described later.
Then, in P77, the target slip ratio SET in the engine control is corrected, and this point will also be described later.

If YES in P72, it means that the recovery control is to be ended, and the above-described processing from P62 is performed.

FIG. 11 (Brake control) The flowchart shown in FIG. 11 corresponds to P11 and P16 in FIG.

First, in P81, it is determined whether or not the stack is currently being stacked. When NO in P81, in P82, the limit value (maximum value) of the response speed Bn (corresponding to the opening / closing control duty ratio of SV1 to SV4) of the brake is a function according to the vehicle speed (the higher the vehicle speed, the greater) Set as. Conversely, P81
If the answer is YES in P83, the limit value BLM is
Set as a constant value smaller than 82. Note that the processing in P82 and P83 takes into account that, when Bn is calculated as in the above equation (5), the rate of increase and decrease of the brake fluid pressure is too fast, which may cause vibration or the like. Done. In addition, in P83, since it is not particularly preferable that the braking force applied to the drive wheels suddenly changes due to escape from the stack, the limit value is set to a small constant value.

After P82 or P83, the slip rate S at P84
Is greater than 0.09, which is the stop point of the brake control. If YES in P84, the operation speed Bn of the right front wheel brake 22 is calculated in P85 (corresponding to Bn in the I-PD control in FIG. 4). Thereafter, in P86, it is determined whether or not Bn is greater than “0”. This determination is a determination as to whether or not the pressure increasing direction of the brake is positive and the pressure reducing direction is negative.
If YES in P86, it is determined in P87 whether Bn> BLM. If YES in P87, set Bn to the limit value BLM
, The pressure of the right brake 22 is increased in P89. When NO in P87, the pressure is increased in P89 with the value of Bn set in P85.

When P86 is NO, Bn is "negative" or "0". Therefore, after Pn is absolute valued in P90, the processes of P91 to 93 are performed. Steps P91 to P93 are for depressurizing the right brake 22, and correspond to the processing of P87, P88, and P89.

After P89 and P93, the process shifts to P94, and pressure increase or pressure reduction processing is performed for the left brake 21 in the same manner as for the right brake 22 (processing corresponding to P84 to P93).

On the other hand, if NO in P84, it means that the brake control is to be stopped, so the brake is released in P95.

When there is a large difference between the actual rotational speed of the drive wheels and the target rotational speed (actual slip ratio and target slip ratio) between P85 and P86, for example, the integration constant KI in the above equation (5) is set to By performing the correction so as to make it small, it is preferable in order to prevent the deterioration and the engine stall due to the excessive braking.

Change of target slip rates SET and SBT (P76) The target slip rates SET and SBT of the engine and the brake changed in P76 are based on the maximum acceleration GMAX measured in P73, for example, as shown in FIG. Be changed. As is apparent from FIG. 17, in principle, as the maximum acceleration GMAX increases, the target slip rates SET and SBT increase.
Is designed to be large. And the target slip rate S
Limit values are set for ET and SBT respectively.

Correction of target slip ratio SET (Fig. 22) This is correction of SET in P9-2 and P77. First, P
At 101, each correction coefficient a, b, c is read from a map created in advance. The correction factors a and b are the 18th
As shown in the figure or FIG. 19, the value is set according to the selection of the mode switch 71 manually operated. Further, the correction coefficient c is set according to the steering angle of the steering wheel (the tightness of the curve during cornering), as shown in FIG.

After P101, it is determined in P102 whether GMAX in P73 is smaller than a predetermined value. If YES in P102, it means that the road surface on which the vehicle is currently traveling is low μ, so the target slip ratio SET is corrected by the correction coefficient b for low μ and the correction coefficient c for cornering. When NO in P102, the road surface on which the vehicle is currently traveling has a high μ, so in P104, the correction coefficient a for high μ and the correction coefficient c for cornering are
The target slip rate SET is corrected by and.

Thus, during cornering, the target slip ratio SET is corrected in the direction of decreasing. That is, as is clear from FIG. 13, the lateral force of the drive wheels is increased by decreasing the slip ratio to ensure stability.Slip control is the slip ratio in the vicinity where the maximum grip force is generated. (Slip rate S = near 0.2 in FIG. 13) Since the range is equal to or less than the target slip rate, the grip force is changed to be reduced.

Here, for example, when the hardware is selected by the mode switch 71 (the selection in FIG. 13 is SD) and the target slip ratio is larger than the maximum grip force generation time, this manual selection is prohibited. Then, the target slip ratio may be changed so that the maximum grip force is generated.

By the way, next, the setting relationship between the target slip rate SET and SBT is
A description will be given of how it affects the driving sensation of the automobile 1.

Driving wheel grip force SET and SBT are offset in the vertical direction in FIG. 17 as a whole. Then, in order to increase the grip force, offset in the upward direction is performed. That is, as a characteristic of the spiked tire, as shown in FIG. 13, since the coefficient of friction μ is increasing up to a slip rate of 0.2 to 0.3, the slip rate of 0.2 to 0.3
The above can be said as long as it is used in the range of 0.3 or less.

Acceleration feeling The acceleration feeling changes by changing the "difference" between SET and SBT. The smaller the "difference", the greater the acceleration feeling. That is, when SET is set to a value smaller than SBT as in the embodiment, 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 braking control and the engine control are approaching a direction in which they are distributed with almost the same distribution.
In other words, the torque generated by the engine is squeezed by the brake to drive the drive wheels, and when the torque is rapidly increased for acceleration, the torque to the drive wheels increases without delay by simply loosening the brake. To do.

Smoothness of acceleration Increase SBT, that is, make it relatively larger than SET. This means that by increasing the priority of engine control, smooth torque change, which is an advantage of engine control, can be more effectively generated.

Stability during cornering As described above.

The above-described characteristics (1) to (3) can be selected manually in accordance with the preference of the driver D, similarly to the mode switch for adjusting the characteristics (1).

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

The torque applied to the drive wheels can be adjusted by adjusting the engagement state of the clutch 7 in addition to engine control and brake control, or by changing the gear ratio of the transmission 8 (especially effective in the case of a continuously variable transmission). For example, any one of the appropriate constituent elements that can adjust the torque applied to the drive wheels or a combination thereof can be used.

For adjusting the torque generated by the engine 6, it is preferable to change and control a 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, and in the case of a diesel engine, the amount of fuel injection is adjusted. Is preferred. However, the load control is not limited to this, and may be performed by adjusting the ignition timing in the Otto type engine or by adjusting the fuel injection timing in the diesel engine. Further, in an engine that performs supercharging, the supercharging pressure may be adjusted. Of course, the power source is not limited to the internal combustion engine, and may be an electric motor. In this case, the generated torque may be adjusted by adjusting the electric power supplied to the motor.

In the automobile 1, the front wheels 2 and 3 are not limited to drive wheels, and the rear wheels 4 and 5 may be drive wheels, or all four wheels may be drive wheels.

In order to detect the slip state of the drive wheels, it may be detected directly like the rotational speed of the drive wheels as in the embodiment, but in addition to this, the slip state is predicted according to the state of the vehicle, that is, You may make it detect indirectly. Examples of such a vehicle state include an increase in torque generated by a power source or an increase in rotational speed, a change in accelerator opening, a change in drive shaft rotation, a steering state (cornering), and a floating state of a 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.

Brake fluid pressure circuit and sensors 64, 64, 66 of FIG.
Can use the existing ABS (anti-brake lock system).

(Effects of the Invention) As is apparent from the above description, the present invention can satisfy both sufficient securing of propulsive force during straight traveling and stability of stability during cornering.

[Brief description of drawings]

FIG. 1 is an overall system diagram showing an embodiment of the present invention. FIG. 2 is a diagram showing an example of a brake hydraulic pressure control circuit. FIG. 3 is a block diagram when feedback controlling the throttle valve. FIG. 4 is a block diagram when feedback control of the brake is performed. FIG. 5 is a graph schematically showing a control example of the present invention. FIG. 6 to FIG. 11 and FIG. 22 are flowcharts showing a control example of the present invention. FIG. 12 is a graph showing characteristics of throttle opening with respect to accelerator opening when slip control is not performed. FIG. 13 is a graph showing the relationship between the grip force of the driving wheel and the lateral force as a relationship between the slip ratio and the coefficient of friction with the road surface. FIG. 14 is a graph showing correction values when the slip ratio at the start of slip control is corrected according to the steering angle of the steering wheel. FIG. 15 is a graph showing the optimum throttle opening corresponding to the maximum acceleration during recovery control. FIG. 16 is a graph showing the relationship between the slip ratio and the throttle opening when performing the buffer control. FIG. 17 is a graph showing an example of a map used for determining a target slip ratio. 18 and 19 are graphs showing the correction coefficient of the target slip ratio according to the operating state of the manual switch. FIG. 20 is a graph showing the correction coefficient of the target slip rate according to the steering angle of the steering wheel. FIG. 21 is a diagram showing an example of a mode switch for manually selecting a target slip rate. FIG. 23 is an overall configuration diagram of the present invention. 1: Automobile 2, 3: Front wheel (driving wheel) 4, 5: Rear wheel (driven wheel) 6: Engine (power source) 7: Clutch 8: Transmission 13: Throttle valve 14: Throttle actuator 21 to 24: Brake 27 : Master cylinder 30, 31: Fluid pressure control valve 32: Brake pedal 61: Sensor (throttle opening) 62: Sensor (clutch) 63: Sensor (gear stage) 64, 65: Sensor (driving wheel speed) 66: Sensor (Driven wheel speed) 67: Sensor (accelerator opening) 68: Sensor (steering wheel steering angle) 69: Accelerator 70: Handle 71: Switch for changing target slip ratio SV1 to SV4: Electromagnetic on-off valve U: Control unit

Claims (1)

(57) [Claims] Claim: What is claimed is: 1. A vehicle slip control device for preventing excessive slip of a drive wheel on a road surface by controlling the torque applied to the drive wheel, the torque adjusting the torque applied to the drive wheel. Adjusting means, slip detecting means for detecting a slip state of the driving wheel with respect to the road surface, and slip for controlling the torque adjusting means so that the slip of the driving wheel reaches a predetermined target value by receiving an output from the slip detecting means. The control means, the cornering detection means for detecting that the vehicle is cornering, the drive wheel slip is smaller during cornering than when traveling straight ahead, and the steerer the cornering is, the smaller the slip of the drive wheel is. And a target value setting means for setting the target value as described above. Loop control system.