JP2587041B2 - 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 a drive wheel with respect to a road surface is effective in effectively obtaining a propulsive force of an automobile and in terms of safety such as preventing spin. Then, to prevent the driving wheel slip from becoming excessive,
That is, it is only necessary to reduce the applied torque to the drive wheels that causes the slip.

Conventionally, such a type of slip control is disclosed in JP-A-58-16948 or JP-A-60-56662. Both of the techniques disclosed in these publications reduce the torque applied to the drive wheels by using a braking force applied to the drive wheels by a brake and reducing the generated torque of the engine itself. Has become. More specifically, in Japanese Patent Application Laid-Open No. 58-16948, when the slip of the drive wheel is small, only the braking of the drive wheel is performed, while when the slip of the drive wheel is large, In addition to braking, the torque generated by the engine is reduced. Also, JP-A-60-56
In the device disclosed in Japanese Patent No. 662, when only one of the left and right driving wheels has a large slip, braking is performed on only one of the driving wheels having a large slip, while both the left and right driving wheels have a large slip. In some cases, braking is performed on the drive wheels on both sides, and the generated torque of the engine is reduced.

(Problems to be Solved by the Invention) Such a system in which the slip control is performed by using the engine also has the following problems due to the characteristics of the engine control.

That is, there is a problem of response delay of the control as a characteristic of the engine control. Therefore, when the generated torque of the engine is greatly narrowed down for the slip control, it takes time to recover the generated torque. Causes a response delay.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vehicle slip control device capable of performing an increase control of an engine generated torque with good response.

(Means and Action for Solving the Problems) In order to achieve the above object, the present invention has the following configuration. That is, as shown in the block diagram of FIG. 19, in a vehicle slip control device that controls the applied torque to the drive wheels to prevent the slip of the drive wheels on the road surface from becoming excessive, Generated torque adjusting means for adjusting the generated torque of the engine; slip detecting means for detecting a slip state of the drive wheel with respect to the road surface; and controlling the generated torque adjusting means when the slip detected by the slip detecting means increases. An engine slip control means for reducing the generated torque of the engine, and when the control amount of the engine slip control means becomes a value such that the generated torque of the engine falls below a predetermined lower limit, the control is performed. Lower limit value setting means for forcibly setting the amount to the lower limit value; vehicle speed detecting means for detecting vehicle speed; Lower limit value changing means for changing the lower limit value such that the lower limit value becomes larger as the vehicle speed detected at the step becomes higher, braking force adjusting means for adjusting a braking force applied to driving wheels, at least the lower limit value A brake slip control unit that is activated when the setting unit is activated, and controls the braking force adjustment unit to prevent the slip detected by the slip detection unit from becoming excessive. is there.

(Effect of the Invention) According to the present invention, by setting the lower limit value of the engine generated torque, it is possible to prevent a situation in which the engine generated torque is excessively reduced. In particular, since the lower limit is variably set so as to increase as the vehicle speed increases, the engine stall when the vehicle speed is low while preventing a decrease in stability due to stall when the vehicle speed is high. Can be prevented. Of course, when the lower limit value is set for the engine generated torque, the slip control by the brake is performed, so that there is no problem in preventing excessive slip of the drive wheels.

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

1. Overview of Overall Configuration In FIG. 1, an automobile 1 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
The load control, that is, the control of the generated torque, is performed by the throttle valve 13 disposed in the first position.
More specifically, the engine 6 is a gasoline engine, and the generated torque is changed by a change in the intake air amount. The intake air amount is adjusted by the throttle valve 13. And the throttle valve 13
Is controlled to be electromagnetically opened and closed by a throttle actuator 14. It should be noted that the throttle actuator 14 may be constituted by 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, respectively, and each of the brakes 21 to 24 is a disc brake. This disc brake is
As is known, it has a disk 25 that rotates with the wheels and a caliper 26. The caliper 26 holds the brake pad and includes a wheel cylinder, and a braking force is generated by pressing the brake pad against the disc 25 with a force corresponding to the magnitude of the brake fluid pressure supplied to the wheel cylinder. .

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

Brake Hydraulic Pressure Control Circuit As shown in FIG. 2, each of the hydraulic pressure control valves 30 and 31 has a cylinder 41 and a piston 42 slidably fitted in the cylinder 41. The inside of the cylinder 41 is defined by the piston 42 into a variable volume chamber 43 and a control chamber 44. The variable volume chamber 43 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 the return spring 45 in a direction in which the volume of the variable volume chamber 43 increases. A check valve 46 is integrated with the piston 42. The check valve 46 closes the inlet side of the variable volume chamber 43 when the piston 42 is displaced in a direction to reduce 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 (22).
It acts only on the side and does not act on the brakes 23, 24 of the rear wheels 4, 5 as driven wheels.

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

At the time of braking using the hydraulic pressure control valve 30 (31) (during slip control), the brake by the operation of the brake pedal 32 basically does not work due to the action of the check valve 46. However, the hydraulic pressure control valve 30
When the brake fluid pressure generated in (31) is small (for example, during pressure reduction), the brake by operating the brake pedal 32 operates. Of course, when the brake fluid pressure for slip control is not generated by the fluid pressure control valve 30 (31), the master cylinder 27 and the brake 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 described later. Brake 2
The following table summarizes the relationship between the state of the brake fluid pressure to the valves 1 and 22 and the operation relationship between the valves SV1 to SV4.

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

The control unit US for slip control is constituted by a digital computer, more specifically, a microcomputer. Signals from the sensors (or switches) 61 to 68 are input to the control unit US. The sensor 61 is connected to the throttle valve 13
This is for detecting the opening degree. The sensor 62 detects whether the clutch 7 is engaged. Sensor 63
Is for detecting the gear position of the transmission 8. Sensor 64,
Reference numeral 65 indicates the number of rotations of the left and right front wheels 2 and 3 as drive wheels. The sensor 66 detects the rotational speed of the rear left 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. The sensor 68 detects the operation amount of the steering wheel 70, that is, the steering angle. The sensors 64, 65, and 66 are each configured using, for example, a pickup, and the sensors 61, 6
3, 67, 68 are configured using, for example, a potentiometer, and the sensor 62 is configured, for example, by a switch that operates ON and OFF.

Note that 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 signals and output signals.
Alternatively, a D / A converter is also provided, but since these points are the same as those in the case of using a microcomputer, detailed description thereof is omitted. The maps and the like in the following description are those stored in the ROM of the control unit US.

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

WD: Number of rotations of drive wheels (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.
If the slip control is not performed during the throttle control, the amount of operation of the accelerator 69 operated by the driver D is limited to
FIG. 12 shows an example of a correspondence relationship between the accelerator opening and the throttle opening at this time so that the target throttle opening corresponds to 1: 1. Further, the control unit UT performs the throttle control so that the target throttle opening degree Tn calculated by the control unit US is basically obtained without following the characteristics shown in FIG. 12 during the slip control. Has become. Then, a lower limit value TL is provided for the target throttle opening Tn, and when the target throttle opening Tn is smaller than the lower limit TL, the slip control is performed based on the lower limit TL by changing to the target throttle opening Tu. The lower limit value TL is variable according to the vehicle speed in the present embodiment (see FIG. 18).

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

The PI-PD control using the above-described control unit UT is shown in FIG. 3 as a block diagram, and “S ′” shown in FIG. 3 is an “operator”. 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 so that a predetermined target slip ratio SBT is obtained independently for the left and right sides. In other words, in the brake control, feedback control is performed so that the driving wheel rotational speed WBT is set by the following equation (4).

In this embodiment, the brake target slip ratio SBT is set to be larger than the target slip ratio SET of the engine as described later. In other words, the slip control of the present embodiment
The frequency of use of the brake is reduced by increasing / decreasing the engine output so as to attain a predetermined SET (WET) and performing a torque increasing / decreasing action by the brake so as to attain a larger SBT (WBT). And in this embodiment,
Feedback control that satisfies the above equation (4)
The control is performed by I-PD control having excellent stability. More specifically, the brake operation amount (the operation amount of the piston 44 in the valves 30, 31) Bn is calculated by the following equation (5).

KI: Integral constant KD: Proportional constant FD: Differential constant When Bn is greater than 0 (when "positive"), brake fluid pressure is increased, and when Bn is 0 or less, pressure is reduced. The increase and decrease of the brake fluid pressure is controlled by the valves SV1 to SV4 as described above.
Is performed by opening and closing. The rate of increase and decrease of the brake fluid pressure is adjusted by adjusting the duty ratio of the valves SV1 to SV4 (duty ratio).
Duty control is performed in proportion to the absolute value of Bn. Therefore, the absolute value of Bn is proportional to the change speed of the brake fluid pressure, and conversely, the duty ratio that determines the increase / decrease speed is
It also indicates Bn.

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

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

S / C: Slip control area E / G: Slip control by engine B / R: Slip control by brake F / B: Feedback control O / R: Open loop control R / Y: Recovery control B / A: Backup control A / S: Buffering 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 at stop of slip control by brake (SBC) S = 0.06: Target slip ratio by engine (SET) S = 0.01 to 0.02: Slip ratio in the range where buffer control is performed S = 0.01 or less: Slip ratio in the range where backup control is performed Are shown based on the data obtained by traveling. Then, S = 0.01 and 0.02 for performing the buffer control A / S, and the slip ratio S = 0 when the slip control by the brake is stopped.
09 is unchanged in each 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 the slip control are changed by road surface conditions and the like.
FIG. 5 shows “0.17”, “0.06” or “0.2” as an example. The slip ratio S = 0.2 at the start of the slip control uses the slip ratio at the time of generation of the maximum grip force obtained when the spike tire is used (see the solid line in FIG. 13). In this way, the slip ratio at the start of the slip control is increased to 0.2 in order to obtain the actual slip ratio when the maximum grip force is obtained. The target slip rates SET and SBT due to the engine and the brake are corrected in accordance with the slip rate. The solid line in FIG. 13 shows how the magnitude of a grip force and a lateral force (shown as a coefficient of friction with respect to a road surface) at the time of a spike tire changes in relation to a slip ratio. 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 with the passage of time.

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

t ₁ 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. In addition, since the target slip ratio of the brake (S = 0.17) is larger than the target slip ratio of the engine (S = 0.06), the brake is pressurized during a large slip (S> 0.17), but when the slip is small. In (S <0.17), the brake is not pressurized, and the control is performed only by the engine so that the slip is converged.

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 applied torque to the driving wheels that can generate the maximum grip force
_{Although 0} is theoretically obtained from the torque curve and the gear ratio of the engine 6, in the embodiment, it is determined based on, for example, a map as shown in FIG. 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 step by step. 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 increase rate of the throttle opening in the backup control is, in the embodiment, added by 0.5% to the previous throttle opening as shown in the following equation every 14 msec of the throttle opening sampling time. It is.

Formula: T = T _n-1 + 0.5% where T _n : target throttle opening T _n-1 : previous throttle opening In the above buffer control, as shown in FIG. a throttle opening T ₂ obtained by the calculation, the throttle opening T ₁ obtained by the backup control operation, are to calculate the target throttle opening Tn by prorating by the current slip ratio S _0.

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 will of the driver D, there is no danger of re-slip because the torque is sufficiently reduced. In the embodiment, in addition to the full closing of the accelerator, the target throttle opening by the slip control is determined from the throttle opening determined by FIG. 12 corresponding to the accelerator opening operated by the driver. Is also performed when it becomes smaller.

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. If NO is determined in P4, it is determined in P5 whether the slip control is currently being performed. This determination is made by checking whether the slip control flag is set. this
If NO is determined in P5, it is determined in P6 whether or not a slip has occurred to perform slip control. 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 proceeds to P7, and the slip control is stopped (normal traveling).

When YES is determined in P6, the flow shifts to P8, where a slip control flag is set. Subsequently, in P9, the initial value of the target slip ratio SET for the engine (throttle) (0.06 in the embodiment) is set, and in P10, the initial value of the target slip ratio SBT for the brake (0.07 in the embodiment) is set. Is done. Thereafter, as described later, brake control at P11 and engine control at P12 are performed for slip control. Note that P9, P10
Is set based on the maximum acceleration GMAX obtained in the previous slip control from the same viewpoint as in P76 described later.

If the slip control flag is determined to be YES in P5, the process proceeds to P11 described above, and the slip control is continuously performed.

When YES is determined in P4, it means that the slip control has become unnecessary, and the routine shifts to P14. In this P14, the slip control flag is reset. Next, the engine control is stopped at P15, and the brake control is performed at P16. The brake control in P16 is performed as a countermeasure during stacking.

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

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

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

First, in P21, each signal from each of the sensors 61 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 at P23 is performed according to the flowchart shown in FIG. First, in P24, it is determined whether the slip control flag is set, that is, whether the slip control is currently being performed. this
When YES in P24, control for controlling 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 control of opening and closing the throttle valve 13 is performed in P26.
It is selected according to the will of the driver D (according to the characteristics shown in FIG. 12). After P25 and P26, control for realizing the target throttle opening is performed at P27 (control according to P68, P70 and P71 described later or twelfth control).
Control according to the characteristics in the figure).

FIG. 9 (slip detection process) The flowchart in FIG. 9 corresponds to P22 in 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, a correction value α for slip determination is calculated in P34 according to the steering angle (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, if NO is determined in P35, the left front wheel 2
Is reset. The correction value α is set in consideration of a rotation difference between the inner and outer wheels during turning (particularly, a rotation difference between a driving wheel and a driven wheel).

After P36 or P37, setting or resetting of the slip flag for the right front wheel 3 as the right driving wheel is performed in P38, P39, and P40 in the same manner as in P35, P36, and P37.

When YES is determined in P33, the vehicle is at low speed, and the vehicle speed is used, that is, the error in the calculation of the slip rate 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 increased to the vehicle speed of 10 k
It is determined whether or not the rotation speed is higher than 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
Is set or reset in the same manner as in the above P41 to P43.

In P31, when it is determined to be NO, it is considered that there is a possibility that the vehicle is in a stuck state. (During the stuck period, the driver D tries to escape from a mud or the like while using a 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: If NO is determined in P51, it is determined in P52 whether or not the stack control is currently being performed. If NO is determined in P52, it is determined in P53 whether 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
When NO is determined in 54, it is determined that the vehicle is not in the stack, and the above-described processing after P32 is performed.

If NO in P53, it is determined in P55 whether the rotation speed of the left front wheel 2 is larger than 1.5 times the rotation speed of the right front wheel 3 or not. If YES in this P55
The process proceeds to P56 and, if NO, 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 speed of the front wheels 2 and 3 is set to 1.
It is set to be 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. P51
If the answer is YES, the brake is released slowly in P60.

FIG. 10 (brake control) The flowchart shown in FIG. 10 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 brake response speed Bn (corresponding to the duty ratio for opening / closing control of SV1 to SV4) is set to a function corresponding to the vehicle speed (the larger the vehicle speed, the larger the value) 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, in the processing of P82 and P83, it is considered that, when Bn calculated as in the above equation (5) is used, 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 to determine whether the brake pressure increasing direction is the pressure increasing direction when the pressure decreasing direction is considered negative. P8
If YES in 6, it is determined in P87 whether Bn> BLM. If YES in P87, Bn is set to the limit value BLM, and then in P89, the pressure of the right brake 22 is increased. When NO in P87, the pressure is increased in P89 with the value of Bn set in P85.

When NO in P86, Bn is "negative" or "0", so that the absolute value ratio of Bn in P90 is followed by the processing of P91 to P93. 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 the difference between the actual rotation speed of the drive wheel and the target rotation speed (actual slip ratio and target slip ratio) is large between P85 and P86, for example, the integration constant KI in the above equation (5) is calculated. Performing the correction to reduce the value is preferable in preventing acceleration deterioration and engine stall due to excessive braking.

FIG. 11 (engine control) The flowchart shown in FIG. 11 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. If NO in P61, it is determined in P62 whether the slip ratio S of the left front wheel 2 is greater 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 at P64, at P65
The current slip ratio is calculated based on 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). In P62 and P63
If NO, the program shifts to P66.

The select high in P66 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. Conversely, when the vehicle is traveling on a split road in which the friction coefficient of the road surface on which the left and right drive wheels contact the ground is different, for example, the select low in P65 suppresses the slip of the drive wheel that is more likely to slip by the brake, This makes it possible to run with the grip of the driving wheel on the difficult side.
In the case of this select row, in order to avoid overuse of the brake, it is preferable to limit the time to, for example, a predetermined time, or to provide a backup means for stopping the select row 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, the target throttle opening Tn based on the feedback control is calculated in P68. Of course, at this time,
The target throttle opening (Tn) of the throttle valve 13 is P6
5. The target slip ratio SET set in P66 or changed in P76 described later is set to realize the target slip ratio SET.

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 target throttle opening Tn in the above-described buffer control is calculated in P70. If NO in P69, the target throttle opening Tn in the backup control described above is calculated in P71.

The target throttle opening degree Tn obtained in P68 or P70 or P71 in this way is compared with the throttle lower limit value TL as described later, and is finally set (P72, P73, P74). On the other hand, if YES in P61, it is determined that the large slip of the drive wheel is converging, and the flow shifts in P75, and after shifting to the slip convergence direction, a predetermined time (time for performing the recovery control. As described above, it is determined whether or not 170 msec has elapsed. If the answer is NO in P75, the processes in and after P76 are performed to perform the recovery control. That is,
First, at P76, the maximum acceleration GMAX of the car 1 is measured (FIG. 5 t ₂ time). Then, in P77, the optimum throttle opening Tv ₀ as this GMAX is obtained is set (see FIG. 15). Further, in P78, the optimum throttle opening Tv _{0 in} P77 is corrected according to the current gear position of the transmission 8. That is, since the applied torque to the drive wheels also varies depending on the shift speed, the optimum throttle opening Tv ₀ for a certain reference shift speed is set in P77, and the difference in the shift speed is corrected in P78. It is. Thereafter, in P79, the friction coefficient of the road surface is estimated from GMAX in P76, and the target slip rates SET and SBT of the subsequent slip control by the engine (throttle) and the brake are changed.

If YES in P75, it means that the recovery control is to be ended, and the above-described processing from P62 is performed.

The target slip rates SET and SBT of the engine and the brake, which are changed in P76, are changed based on the maximum acceleration GMAX measured in P73, for example, as shown in FIGS. 17 and 18. FIG. 17 shows a case of a straight road, and FIG.
The figure shows the case of a curved course. As apparent from FIGS. 17 and 18, in principle, the target slip rates SET and SBT are set to increase as the maximum acceleration GMAX increases. The target slip rates SET and SBT are each provided with a limit value.

Throttle lower limit (TL) setting (P72, P73, P74) In P72, the lower limit TL of the target throttle opening is
Based on the map shown in FIG. 18, the value is set according to the current vehicle speed and gear position. That is, in the present embodiment, the throttle opening required to maintain the current vehicle speed is set as the lower limit value TL. Then, in the next P73, the target throttle opening Tn obtained in the above P87 or P74, P71 is compared with the throttle lower limit value TL, and when the target throttle opening Tn is smaller than the lower limit value TL, in P74, This lower limit value TL is set as the target throttle opening Tn. As a result, the throttle opening during the slip control is not reduced until the throttle valve 13 is fully closed, and at a minimum, the throttle opening required to maintain the current vehicle speed is suppressed. Will stand up well. Of course, the surplus generated torque of the engine corresponding to the convergence of the slip is absorbed by the brake control as shown in FIG.

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

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

The vehicle 1 is not limited to the front wheels 2 and 3 having 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 wheel, the slip state may be directly detected like the rotation speed of the drive wheel as in the embodiment, but in addition, the slip state is predicted according to the state of the vehicle, that is, You may make it detect indirectly. Such vehicle states include, for example, an increase in the generated torque or the number of revolutions of the power source, a change in the accelerator opening, a change in the rotation of the drive shaft, a steering state (cornering), and a floating state of the vehicle body (acceleration). , Load capacity, and the like. In addition to this, the road surface μ such as atmospheric temperature, rain, snow, ice burn, etc.
Can be automatically detected or input manually to make the prediction of the slip state of the drive wheels even more appropriate.

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

[Brief description of the drawings]

FIG. 1 is an overall system diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing an example of a control circuit for a brake fluid pressure. FIG. 3 is a block diagram when the feedback control of the throttle valve is performed. FIG. 4 is a block diagram when the brake is feedback controlled. FIG. 5 is a graph schematically showing a control example of the present invention. 6 to 11 are flowcharts showing control examples of the present invention. FIG. 12 is a graph showing characteristics of the throttle opening with respect to the accelerator opening when the slip control is not performed. FIG. 13 is a graph showing the relationship between the grip force of the drive wheels and the lateral force by the relationship between the slip ratio and the coefficient of friction on the road surface. FIG. 14 is a graph showing a correction value when the slip ratio at the start of the slip control is corrected according to the steering angle. FIG. 15 is a graph showing the optimal throttle opening corresponding to the maximum acceleration during the 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. FIG. 18 is a graph showing the relationship between the lower limit value TL of the throttle opening and the vehicle speed. FIG. 19 is an overall configuration diagram of the present invention. 1: Automobile 2, 3: Front wheel (drive wheel) 4, 5: Rear wheel (driven wheel) 6: Engine (power source) 13: Throttle valve 14: Throttle actuator 21 to 24: Brake 27: Master cylinder 30, 31: Hydraulic pressure control valve 32: Brake pedal 61: Sensor (throttle opening) 63: Sensor (gear position) 64, 65: Sensor (driving wheel speed) 66: Sensor (driven wheel speed) 67: Sensor (accelerator speed) 69: Accelerator SV1 to SV4: Electromagnetic open / close valve U: Control unit

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiro Matsuoka 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Corporation (56) References JP-A-62-29461 (JP, A) JP-A-60 -99757 (JP, A) JP-A-61-16136 (JP, A)

Claims (1)

(57) [Claims] In a slip control apparatus for an automobile, wherein a torque applied to a drive wheel is controlled to prevent an excessive slip of a drive wheel on a road surface, a generated torque adjustment for adjusting a generated torque of an engine. Means, a slip detecting means for detecting a slip state of the drive wheel with respect to the road surface, and a control for reducing the generated torque of the engine by controlling the generated torque adjusting means when the slip detected by the slip detecting means becomes large. When the control amount by the engine slip control means to be performed and the control amount by the engine slip control means become a value such that the torque generated by the engine falls below a predetermined lower limit value, the control amount is forcibly set to the lower limit value. Lower limit value setting means, vehicle speed detecting means for detecting vehicle speed, and the lower the vehicle speed detected by the vehicle speed detecting means, the lower the lower Lower limit value changing means for changing the lower limit value so that the value becomes a large value; braking force adjusting means for adjusting the braking force applied to the drive wheels; and actuated when at least the lower limit value setting means is actuated. And a brake slip control means for controlling the braking force adjusting means to prevent the slip detected by the slip detecting means from becoming excessive. A slip control apparatus for an automobile, comprising: