JPH089305B2 - Automotive slip control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention controls a torque applied to a drive wheel to prevent an excessive slip of the drive wheel from 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.

As a slip control of this type, there is a conventional one disclosed in JP-A-58-16948 or JP-A-60-56662. Both of the technologies disclosed in these publications utilize the application of a braking force to the drive wheels by a brake and the reduction of the torque generated by the engine itself as a power source in order to reduce the torque applied to the drive wheels. It is supposed to be done. More specifically, JP-A-58-16
In the 948 publication, when the slip of the drive wheels is small, only the drive wheels are braked, while when the slip of the drive wheels is large, in addition to the braking of the drive wheels,
It is designed to reduce the torque generated by the engine.
Further, in JP-A-60-56662, when the slip on only one side of the left and right drive wheels is large, braking is performed only on the drive wheel on one side having a large slip, while the left and right drive wheels are When both the slips of the drive wheels are large, the drive wheels on both sides are braked and the torque generated by the engine is reduced. As described above, the systems disclosed in both of the above publications mainly utilize the braking of the drive wheel by the brake, and supplementarily reduce the torque generated by the engine.

(Problems to be Solved by the Invention) The slip control by adjusting the braking force and the slip control by adjusting the generated torque have advantages and disadvantages. That is, when the braking force is used, it is excellent in responsiveness, but on the other hand, shock is likely to occur and there is a problem in driving feeling. In addition, effective use of energy or ensuring reliability of the brake are required. Will be at a disadvantage. On the other hand, the slip control by adjusting the generated torque is advantageous in terms of driving feeling due to smooth torque fluctuation and in energy efficiency by not generating unnecessary torque, but has a problem in responsiveness. is there.

From the above viewpoint, when at least the slip of the driving wheels is large, it is necessary to perform the slip control by both applying the braking force by the brake and decreasing the torque generated from the engine in order to obtain a quick convergence of the slip. Is extremely preferable, and in addition to this, it is possible to appropriately balance the responsiveness, the driving falling, the energy efficiency, and the reliability of the brake.

In this way, when slip control is performed by both applying braking force and decreasing generated torque, the control ratio, that is, the proportion of the decrease in applied torque to the drive wheels accompanying slip control, It becomes one problem. In particular, when the driver makes a request for acceleration, it is desired that the request for acceleration can be promptly dealt with. That is, while preventing excessive slip of the drive wheels by slip control,
It is desired to be able to quickly respond to the demand for acceleration. In particular, when the above control ratio is set from the viewpoint of avoiding the use of the brake as much as possible, the torque generated by the engine as the power source is greatly reduced. The problem is how to prevent (response delay of increase in generated torque for coping with acceleration request).

The present invention has been made in consideration of the above circumstances, and performs slip control of drive wheels by appropriately using both application of braking force to drive wheels and reduction of torque generated by a power source itself such as an engine. Based on the above, it is an object of the present invention to provide a slip control device for an automobile capable of promptly responding to a request for acceleration.

(Means and Actions for Solving Problems) In order to achieve the above-mentioned object, in the present invention, when acceleration is requested, correction is performed so as to increase the ratio of slip control by the brake. is there. That is, increasing the ratio of slip control by the brake increases the degree to which the torque generated by the power source is suppressed by the brake, in other words, the power source generates torque with a considerable margin during slip control. This means that when the slip is converged and the brake is released, the above-mentioned margin torque is used to obtain quick acceleration. When acceleration is not requested, the control ratio by the brake is reduced to ensure driving feeling, energy efficiency, and reliability of the brake. It should be noted that whether or not the acceleration request is made can be detected by observing the rate of change of the accelerator, etc. as is usually done, but the acceleration by using a switch manually operated by the driver can be used. It may be a request.

Specifically, as shown in Fig. 19, in the slip control device of an automobile, the torque applied to the drive wheels is controlled to prevent excessive slip of the drive wheels from the road surface. Generated torque adjusting means for adjusting the generated torque of the power source, braking force adjusting means for adjusting the braking force of the driving wheel brake, slip detecting means for detecting the slip state of the driving wheel with respect to the road surface, and the slip When the output from the detection means is received and the slip of the drive wheels is equal to or greater than a predetermined value, the generated torque of the power source is reduced and the braking force is applied to the drive wheels by operating the generated torque adjusting means and the braking force adjusting means. Slip control means for performing slip control by means of the above, acceleration detection means for detecting the driver's request for acceleration, and when there is a request for acceleration, The slip control by the lip control unit, a configuration equipped with a correction means for correcting the direction of the increasing number of the slip control by the brake.

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

1. Outline of Overall Structure In FIG. 1, an automobile 1 includes four wheels, left and right front wheels 2 and 3 that are drive wheels and left and right rear wheels 4 and 5 that are driven wheels. An engine 6 as a power source is mounted on the front part of the automobile 1, and the torque generated by the engine 6 passes through a clutch 7, a transmission 8 and a differential gear 9 and then through left and right drive shafts 10 and 11. Is transmitted to the left and right front wheels 2 and 3 as driving wheels. In this way, the automobile 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. The throttle actuator 14 may be composed of a DC motor, a step motor, an electromagnetically driven control driven by a fluid pressure such as a hydraulic pressure, or the like.

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 is branched 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 and 29a for the front wheels brakes 21 and 22 serving as drive wheels are provided with electromagnetic hydraulic pressure control valves 30 or braking force adjusting means or
31 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 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 a brake fluid pressure for the brake 21 (22), and the generated brake fluid pressure can be increased or decreased or held. You 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 to the brake 21 (2
It acts only on the 2) 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 brake fluid pressure for slip control is not generated in 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, 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 the valves SV1 to SV4 as described above, based on the command signal from the control unit Us. 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 are input to the control unit Us. The sensor 61 has a throttle valve 13
The opening degree of is detected. The sensor 62 detects whether or not the clutch 7 is engaged. Sensor 63
Is for detecting the gear stage of the transmission 8. Sensor 64,
Reference numeral 65 is for detecting the number of rotations of the left and right front wheels 2, 3 as driving wheels. The sensor 66 detects the rotation speed of the left rear wheel 4 as a driven wheel, that is, the vehicle speed. The sensor 67 detects the operation amount of the accelerator 69, that is, the accelerator opening degree. The sensor 68 detects an operation amount of the steering wheel 70, that is, a steering angle. The sensors 64, 65, 66 are each configured by using, for example, a pickup, and the sensors 61, 6
3, 67 and 68 are configured by using, for example, a potentiometer, and the sensor 62 is configured by a switch that operates ON and OFF, for example. In addition to the above, when the driver manually inputs an acceleration request, a signal from a switch (travel mode selection switch) 71 for this purpose is input to the control unit Us.

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 driving wheels (2, 3) WL: Number of rotations of driven wheels (4) (vehicle speed) The throttle control control unit UT feeds back the throttle valve 13 (throttle actuator 14) so that the target throttle opening is achieved. It is controlled.
When slip control is not performed during this throttle control, the operation amount of the accelerator 69 operated by the driver D is set.
FIG. 12 shows an example of the correspondence relationship between the accelerator opening and the throttle opening at this time, which is controlled so that the target throttle opening corresponds to 1: 1. Further, the control unit UT does not follow the characteristics shown in FIG.
Throttle control is performed so that the target throttle opening Tn calculated in step S3 is reached.

Throttle valve 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: Number of rotations of driven wheel (4) WD: Number of rotations of driving wheel (2, 3) KP: Proportional constant KI: Integral constant FP: Proportional constant FD: Differential constant SET: Target slip rate (for throttle control) Above formula As in (2), the rotational speed of the drive wheels is feedback-controlled so that the throttle opening degree Tn becomes a predetermined target slip rate 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 Controlled to be.

PI-PD control using the above-mentioned control unit UT is shown in FIG. 3 as a block diagram, and “S ′” shown in FIG. 3 is an “operator”. The suffixes "n" and "n-1" indicate the values of the respective signals at the present time and at the time of sampling one time before.

Brake control During slip control, the control unit U
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).

The target slip rate SBT of this brake is set to be larger than the target slip rate SET of the engine in this embodiment, as will be 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 Note that the above values are actually ice-burn spike tires. It is shown based on the data obtained by driving by. Then, S = 0.01 and 0.02 for performing the buffer control A / S, and the slip rate S = 0 when the slip control by the brake is stopped.
09 are unchanged in the examples. 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 are changed depending on the road surface condition,
In FIG. 5, "0.17", "0.06" or "0.2" is shown as an example. The slip rate S = 0.2 at the start of slip control uses the slip rate at the time of maximum grip force generation obtained when using a spike tire (see the solid line in FIG. 13). 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.

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.

t _{2 to} t ₄ (recovery control) The throttle valve 13 is held at a predetermined opening for a predetermined time (for example, 170 msec) after the slip has converged (S <0.2) (open loop control). At this time, S = 0/2
The maximum acceleration GMAX at time (t ₂ ) is calculated and
The maximum μ on the road surface (maximum driving force of the driving wheels) 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 wheels. This control is performed in order to prevent the vehicle body acceleration G from dropping immediately after the slip is converged because the response does not meet the deadline in the feedback control because the slip converges rapidly. Therefore, when the slip convergence is predicted (lower than S = 0.2), the predetermined torque is secured in advance as described above, and the acceleration performance is improved.

The optimum throttle opening TVo for realizing the torque applied to the drive wheels that can generate the maximum grip force is
Although it can be theoretically obtained from the torque curve and the gear ratio of the engine 6, in the embodiment, it is determined based on the map as shown in FIG. 15, for example. This map is prepared 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. The map shown in FIG. 12 is premised at a certain shift speed (for example, the first speed), and the optimum throttle opening TVo is corrected at the other shift speeds.

t _{4 to} t ₇ (backup control, buffer control) In order to deal with the case where the slip ratio S is abnormally reduced,
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. Then, when the slip ratio is between 0.01 and 0.02, buffer control is performed (t _{4 to} t ₅ and t _{6 to} t ₇ ) in order to smoothly shift to the next feedback control. This backup control is performed when the feedback control and the recovery control cannot handle it. Of course, the backup control has a sufficiently higher response speed than the feedback control.

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

Further, in the above-mentioned buffer control, as shown in FIG. 16, the throttle opening T ₂ obtained by the feedback control calculation and the throttle opening T ₁ obtained by the backup control calculation are changed by the current slip ratio S ₀ . The throttle opening T ₀ is obtained by proportional distribution.

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

Since the accelerator 69 is fully closed by t ₈ after 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. Incidentally, in the embodiment, the slip control is stopped by fully closing the accelerator as well as the target throttle opening by the slip control from the throttle opening determined by FIG. 12 corresponding to the accelerator opening operated by the driver. I also try to do it when it gets smaller.

Here, when there is a request for acceleration, in order to increase the ratio of brake control, in the embodiment, as shown in FIG.
The target slip ratio SBT of the brake control is corrected so as to be reduced. That is, between t ₁ and t ₂ and t ₃ and t ₄ in FIG. 18 is the time of request for acceleration in which the accelerator pedal depression speed is equal to or higher than a predetermined value, and at this time, the target slip rate SBT of the brake control is Corrected to be lowered. By reducing SBT in this way, the "difference" between SBT and SET is reduced. As a result, even if the current slip rate is the same, the braking force by the brake at that time is large, and this control is great. The surplus torque generated in the engine 6 increases as the power increases. Therefore, when the slip is reduced and the brake is released, the engine 6 is quickly accelerated by the above-mentioned surplus torque. Of course, in order to increase the ratio of this brake control, it is sufficient to reduce the “difference” between SBT and SET as described above. Therefore, either or both of reducing SBT and increasing SET can be performed. It may be performed.

Details of Slip Control (Flowchart) Next, details of the slip control will be described with reference to the flowcharts of FIGS. 6 to 11, but in the embodiment, in the stack in which the automobile 1 is stuck in a mud or the like, Brake control is also used to perform stack control for escaping from the mud or the like. In the following description, P indicates a step.

FIG. 6 (Main) After the system is initialized in P1, it is determined in P2 whether or not it is currently in a stack (a state in which it is stuck in a muddy or the like and cannot move). This determination is made by checking whether or not a stack flag described later is set. If NO in P2, it is determined in P3 whether or not the accelerator 69 is fully closed. When 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 observing whether or not slip flags for left and right front wheels 2 and 3 which will be described later are set. 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, at P9, the initial value of the target slip ratio SET for the engine (throttle) (0.06 in the embodiment) is set, and at P10, the initial value of the target slip ratio SBT for the brake (in the embodiment,
0.17) is set. Thereafter, as will be described later, brake control at P11 and engine control at P12 are performed for slip control. The initial values are set in P9 and P11 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 at P16 is performed. 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.

If YES is determined in P2, the processes after P15 are 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, the signals from the sensors 61 to 68 are input for data processing. Next, after the slip detection process which will be described later is performed at P22, the throttle control at P23 is performed.

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 that is the target of slip control has occurred, and whether or not there is a stack.

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

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, at P35, it is judged if 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 at P34 to the predetermined reference value 0.2. If YES in the determination in P35, the slip flag is set because the left front wheel 2 is in the slip state. 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 only by the rotational 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, left front wheel 2 is determined in P42.
The slip flag of is set. On the contrary, when NO is determined in P41, the slip flag of the left front wheel 2 is reset in P43.

After P42 and P43, at 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). At this time, move to P51,
It is determined whether or not the average value of the number of rotations of the left and right front wheels 2 and 3 as driving wheels is small (for example, 2 km / h converted to vehicle speed
It is determined whether or not the following). When 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. If YES is determined in 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, move to P56, and if NO in P55, move to P32.

After P56, it is determined in P57 whether the vehicle speed is higher than 6.3 km / h. If YES in 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). If NO in P57, in P59, the front wheels 2,
The target speed of 3 is uniformly set to 10 km / h. P51
If YES, the brake is slowly released at P60.

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

In P61, it is determined whether or not the slip has transitioned to the convergent state (whether or not the time point t _{2 in} FIG. 5 has passed). 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 rate S of the right front wheel 3 is larger than 0.2. When 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 or not it 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). On the contrary, when P64 is NO, the current slip ratio is calculated according to the drive wheel having the larger slip ratio of 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 described above makes it possible to further avoid the use of the brake by calculating the current slip ratio so as to suppress the slip of the drive wheel that is more slippery. 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 rate S
It is determined whether it is greater than 0.02. If YES in P67, the throttle valve 13 is feedback-controlled in S68 for slip control. Of course, at this time, the target throttle opening (T
n) is set so as 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 rate S in P69
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. If NO in P72, the process after P73 is performed to perform 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 this, in P76, P73
Estimate the friction coefficient of the road surface from GMAX in step 1 and change both the target slip ratios SET and SBT for slip control by the engine (throttle) and brake. How to change the target slip rates SET and SBT will be described later.

If YES in P72, it means that the recovery control is completed, and thus the processes in and after P62 described above are performed.

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

First, at P79, it is judged if acceleration is currently requested. In the embodiment, this determination is performed by checking whether or not the stepping speed of the accelerator 69 is equal to or higher than a predetermined value as described above. If YES in the determination in P79, the target slip rate SBT of the brake control is corrected in P80 so as to decrease, and the process proceeds to P81. Conversely, P
If NO at 79, proceed to P81 without decreasing P80. When the acceleration request is selected by the switch 71 (see FIG. 1), the determination of the acceleration request in P79 is made by observing the operation state of the switch 71.

In P81, it is determined whether or not the stack is currently in progress. When NO in P81, response speed Bn of the brake in P82 (corresponding to the duty ratio for opening / closing control of SV1 to SV4)
The limit value (maximum value) is set as a function corresponding to the vehicle speed (the higher the vehicle speed, the larger). On the contrary, YES in P81
In this case, the limit value BLM is set in P83 as a fixed value smaller than that in P82. In addition, this P8
Processes 2 and 83 are performed in consideration of the fact that the brake fluid pressure increase / decrease speed is too fast and causes vibrations, etc., when Bn as it is calculated by the equation (5) is used. It In addition to this, in P83, it is not particularly preferable that the braking force on the drive wheels suddenly changes due to escape from the stack, so the limit value is set to a small constant value.

After P82 or P83, the slip rate S at P84
Is determined to be greater than 0.09 which is the brake control stop point. If YES in P84, the operating 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 the Bn is larger 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.
After setting to, the pressure of the right brake 22 is increased at P89. When P87 is NO, 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. These P91 to P93 are when the pressure of the right brake 22 is reduced, and correspond to the processes of P87, P88, and P89.

After P89 and P93, the process shifts to P94, where the left brake 21 is also subjected to pressure increase or pressure reduction processing in the same manner as 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 reduce the value, it is preferable for preventing deterioration of acceleration and engine stall due to excessive braking.

Change of target slip ratios SET and SBT (P76) The target slip ratios 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 clear from FIG. 17, in principle, the larger the maximum acceleration GMAX, the target slip ratios SET and SBT.
Is designed to be large. And the target slip rate S
Limit values are set for ET and SBT respectively.

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

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 in the increasing direction up to the 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 following range.

Acceleration sensation The acceleration sensation changes as described above by changing the “difference” between SET and SBT, and since this point has already been described in detail, duplicate description thereof will be omitted.

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 SET is made smaller, ie SET is relatively smaller than SBT. As is clear from FIG. 13, this is the slip rate S = 0.2 when the maximum grip force is generated.
In the range of up to 0.3, the target slip ratio is reduced to reduce the grip force of the driving wheel, while increasing the lateral force as much as possible and increasing the bending force.

The characteristics (modes) (1) to (3) described above can be selected manually according to the preference of the driving vehicle D (mode selection using the switch 71).

In the above-described embodiment, the target slip ratio of the brake SBT is set to be larger than that of the engine SET, so that the brake control is not performed in a small slip state, so that the frequency of use thereof is reduced. In addition, the load on the brake control is reduced even when a large slip occurs. In addition, SBT and S
Since a point (SBC) for stopping the slip control by the brake is provided between the ET and the ET, the brake pressure is sufficiently reduced when the brake control is stopped, so that abrupt torque fluctuation is unlikely to occur. Of course, in the present invention, the target slip rates of the engine and the brake can be set to the same value.

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

The acceleration request is detected by checking the accelerator pedal depression speed, the operating state of the mode selection switch 71, the accelerator pedal depression amount, the downshift operation of the transmission 8, the vehicle body acceleration, the vehicle speed pattern (particularly the degree of increase in vehicle speed), etc. This can be done by looking at the appropriate parameters.

It is also possible to detect a request for acceleration before the slip control is entered, and make a correction to increase the ratio of the brake control after starting the slip control in accordance with the request for acceleration. In this case, the target slip ratios SBT and SE at P9 and P10 are set in order to make the correction to increase the brake control ratio faster.
The "difference" from T can be set to be smaller from the stage of the initial value. Of course, the degree of reducing the "difference" between SBT and SET can be adjusted according to the degree of acceleration demand.

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 to adjust the generated torque by so-called load control. In an Otto type engine (for example, a gasoline engine), the air-fuel mixture amount is adjusted, and in a diesel engine, the fuel injection amount 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 high and low atmospheric temperature, rain, snow, ice burn etc.
Can be automatically detected or manually input to make the prediction of the slip state of the drive wheels even more appropriate.

Brake hydraulic circuit and sensors 64, 65, 66 of FIG.
Can use the existing SBA (anti-brake lock system).

To increase the control ratio by the brake, you may stop the slip control by the engine,
If slip control is performed with a certain target value,
This may be performed by changing the control amount for the deviation from the target value or by changing the target value itself (the control amount or the target value may be changed for at least one of the brake and the engine). . In short, an appropriate method can be used as long as it is possible to change the ratio of the amount of decrease in the torque generated by the engine that contributes to the reduction of the rotational torque of the drive wheels and the amount of braking of the brake when there is an acceleration request and when it does not Can be adopted.

(Effects of the Invention) As is apparent from the above description, the present invention is effective when slip control of drive wheels is performed using both braking force application by a brake and reduction of torque generated from a power source. It is possible to obtain a good acceleration response while optimally setting the balance.

[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. 6 to 11 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 the buffer control is performed. FIG. 17 is a graph showing an example of a map used to determine the target slip rate. FIG. 18 is a graph showing a state where a correction for increasing the ratio of the brake control when there is a request for acceleration (correction of the target slip ratio SBT of the brake control) is being performed. FIG. 19 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: Acceleration request selection mode switch SV1 to SV4: Electromagnetic opening / closing valve U: Control unit

Claims (3)

[Claims] Claim: What is claimed is: 1. A slip control device for a vehicle, wherein a slip applied to a road surface of a drive wheel is prevented from becoming excessive by controlling a torque applied to the drive wheel. Generated torque adjusting means, adjusting braking force of the driving wheel brake, braking force adjusting means, slip detecting means for detecting a slip state of the driving wheel with respect to the road surface, and output from the slip detecting means, When the slip of the driving wheels is equal to or more than a predetermined value, slip control means for performing slip control by reducing the generated torque of the power source by operating the generated torque adjusting means and the braking force adjusting means and applying the braking force to the driving wheels Acceleration detection means for detecting a driver's request for acceleration, and when there is an acceleration request, the slip control means The slip control, the slip control device of a motor vehicle, characterized by comprising a correction means for correcting the direction of the increasing number of the slip control by the brake. 2. The slip control means according to claim 1, wherein the slip control means controls the slip by reducing the generated torque and applying the braking force only when the slip of the drive wheel is large, and the slip of the drive wheel is small. In this case, slip control is performed only by adjusting the generated torque without applying the braking force. 3. The slip control means according to claim 1 or 2, wherein the slip control means performs a slip control so that the magnitude of the slip of the drive wheels reaches a target value, and the correction means accelerates. The target value of the slip control by the brake is reduced when there is a request for.