JP2512720B2 - Automotive slip control system - Google Patents

Abstract

PURPOSE:To prevent the engine stall by varying the control speed or the control quantity for the brake power which acts onto a driving wheel according to the result of the detection of the load, etc. supplied into an engine, in the constitution in which the slip of the driving wheel is suppressed by controlling the brake power which acts onto the driving wheel. CONSTITUTION:When the brake power which acts onto a driving wheel is controlled by controlling a brake power adjusting means A by a slip control means B and the excessive increase of the slip for a road surface of the driving wheel is prevented, a load detecting means C for detecting the generated torque of an engine or the load supplied into the engine is installed. The output signal of the load detecting means C is input into a slip control adjusting means D, and when the generated torque of the engine is small, or the load supplied into the engine is large, the control speed or the control quantity of the brake power is adjusted to each small value. Therefore, the engine stall can be prevented, and the slip convergence performance can be improved.

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,
That is, it is only necessary to reduce the applied torque to the drive wheels that causes the 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 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. ing. More specifically, in JP-A-58-16948,
When the slip of the driving wheel is small, only the braking of the driving wheel is performed, and when the slip of the driving wheel is large, the generated torque of the engine is reduced in addition to the braking of the driving wheel. 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.

(Problems to be Solved by the Invention) By the way, when slip control is performed by applying a braking force to driving wheels such as a brake, it is necessary to consider engine stall (stop of the engine). That is, when the braking force is rapidly applied, the slip convergence is improved, but the risk of engine stall increases.

Therefore, an object of the present invention is to provide a slip control device for an automobile, which achieves both improvement of slip convergence and prevention of engine stall.

(Means and Actions for Solving Problems) In order to achieve the above-mentioned object, in the present invention, attention is paid to the difficulty of engine stall depending on the running state of the vehicle, for example, when the torque generated by the engine is small. As described above, when the engine stall is likely to occur, the control of the braking force application is performed gently to prevent the engine stall. On the other hand, when the engine stall is difficult to occur, such as when the engine generated torque is large, the control of the braking force application is performed relatively. The slip convergence is improved by suddenly performing this.

That is, as shown in FIG. 20, on the premise of an automobile slip control device which prevents excessive slip of the drive wheels from the road surface by controlling the braking force acting on the drive wheels, Braking force adjusting means for adjusting the power, load detecting means for detecting the torque generated by the engine or load on the engine, and a signal from the load detecting means, when the torque generated by the engine is small or the load on the engine is low. When it is large, a slip control adjusting means for reducing the control speed or control amount of the braking force is provided.

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

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

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

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

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

Brake Hydraulic Pressure Control Circuit As shown in FIG. 2, the hydraulic pressure control valves 30 and 31 are
Each has a cylinder 41 and a piston 42 slidably fitted in the cylinder 41. The interior of the cylinder 41 is divided into a variable volume chamber 43 and a control chamber 44 by the piston 42. The variable volume chamber 43 serves as a passage system for the brake fluid pressure from the master cylinder 27 to the brake 21 (22). Therefore, by adjusting the displacement position of the piston 42, the volume of the variable volume chamber 43 can be changed to generate brake fluid pressure for the brake 21 (22), and increase or decrease or maintain the generated brake fluid pressure. Will be able to do it.

The piston 42 is constantly urged by a return spring 45 in a direction in which the volume of the variable volume chamber 43 increases. A check valve 46 is integrated with the piston 42. The check valve 46 closes the inlet side of the variable volume chamber 43 when the piston 42 is displaced in the direction of reducing the volume of the variable volume chamber 43. As a result, the brake fluid pressure generated in the variable volume chamber 43 is reduced by the brake 21 (2
2) It acts only on the side and does not act on the brakes 23, 24 of the rear wheels 4, 5 as driven wheels.

The displacement position of the piston 42 is adjusted by adjusting the control hydraulic pressure for the control chamber 44. Explaining this point in detail, the supply pipe 48 extending from the reservoir 47 is branched into two in the middle, and one branch pipe 48R is connected to the control chamber 44 of the valve 30.
And the other branch pipe 48L is connected to the control room 4 of the valve 31.
Connected to 4. A pump 49 and a relief valve 50 are connected to the supply pipe 48, and a supply valve SV3 (SV2) which is an electromagnetic on-off valve is connected to a branch pipe 48L (48R) of the supply pipe 48. Each control chamber 44 is further connected to a reservoir 47 via a discharge pipe 51R or 51L, and a discharge valve SV4 (SV1), which is an electromagnetic on-off valve, is connected to the discharge pipe 51L (51R).

At the time of braking using the hydraulic pressure control valve 30 (31) (during slip control), the check valve 46 basically prevents the brake pedal 32 from operating. However, the hydraulic pressure control valve 30
When the brake fluid pressure generated in (31) is small (for example, during pressure reduction), the brake is operated by operating the brake pedal 32. Of course, when the brake fluid pressure for slip control is not generated by the fluid pressure control valve 30 (31), the master cylinder 27 and the brake 21 (22) are in communication with each other. As a result, a normal braking action is performed.

The valves SV1 to SV4 are controlled to be opened / closed by a brake control unit UB 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 control unit UB for throttle, a control unit UT for throttle, and a control unit US for slip control, in addition to the above-mentioned brake control unit UB. The control unit UB controls the opening / closing of each of the valves SV1 to SV4 based on the command signal from the control unit US, as described above. Further, the throttle control unit UT controls the drive of the throttle actuator 14 based on the command signal from the control unit US.

The slip control unit US is composed of a digital computer, more specifically, a microcomputer. This control unit
The signals from the sensors (or switches) 61 to 68 are input to the US. The sensor 61 detects the opening degree of the throttle valve 13. The sensor 62 detects whether or not the clutch 7 is engaged. The sensor 63 detects a gear position of the transmission 8. The sensors 64 and 65 detect the number of rotations of the left and right front wheels 2 and 3 as driving wheels. The sensor 66 detects the rotational speed of the rear left wheel 4 as a driven wheel, that is, the vehicle speed. 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. Each of the sensors 64, 65, 66 is configured by using, for example, a pickup, and each of the sensors 61, 63, 6
7, 68 are configured by using, for example, a potentiometer, and the sensor 62 is configured by, for example, a switch that operates ON and OFF.

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: Drive wheel (2, 3) rotation speed WL: Driven wheel (4) rotation speed (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. During the throttle control, when the slip control is not performed, the operation amount of the accelerator 69 operated by the driver D is
FIG. 12 shows an example of 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, during the slip control, the control unit UT performs throttle control such that the target throttle opening Tn calculated by the control unit US is reached without following the characteristics shown in FIG.

Throttle valve 13 with control unit UT
In the embodiment, the feedback control is performed by PI-PD control in order to compensate for the variation in the response speed of the engine 6. That is, during throttle 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 wheels (2, 3) KP: Proportional constant KI: Integral constant FP: Proportional constant FD: Differential constant SET: Target slip ratio (for throttle control) Above formula As in (2), the rotational speed of the drive wheels is feedback-controlled so that the throttle opening Tn becomes a predetermined target slip ratio SET. In other words, as is apparent from the equation (1), the throttle opening is the target drive wheel speed WE.
T is the following formula (3) Is controlled so that

PI-PD control using the control unit UT described above is shown in FIG. 3 as a block diagram.
“S ′” shown in the figure 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 UB
The rotational speed (slip) of the left and right drive wheels 2, 3 using
Feedback control is performed independently on the left and right sides so that the 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 ratio SBT of this brake is set to be larger than the target slip ratio SET of the engine in this embodiment, as will be described later. In other words, the slip control according to the present embodiment increases or decreases the engine output so as to achieve the predetermined SET (WET), and increases or decreases the torque by the brake so that the SBT (WBT) becomes larger than the predetermined SET (WET). 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 the above Bn is greater than 0 (“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 (duty control) the opening / closing time (duty ratio) of the valves SV1 to SV4, which is obtained by the above equation (5).
The duty control is proportional to the absolute value of Bn.

The I-PD control by the control unit UB described above is shown in FIG. 4 as a block diagram.
“S ′” shown in the figure is an “operator”.

Further, in this embodiment, a limit value (BLM) is provided for the braking speed, and this limit value (BLM) increases as the throttle opening increases as shown in FIG. It is supposed to be a value.
That is, the braking speed is stopped when the engine generated torque is large.

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 by engine (SET) 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 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 depending on the road surface condition and the like, and in FIG. 5, an example is “0.17”. , "0.06" or "0.2" are shown. 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 due to 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.

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 (t ₂ ) is calculated, and this GMAX
From this, the maximum μ of the road surface (maximum grip force of the driving wheels) is estimated. 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.

The optimum throttle opening TV ₀ for realizing the torque applied to the drive wheels that can generate the maximum grip force is
Although it 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. The map shown in FIG. 12 is premised at a certain shift speed (for example, the first speed), and at other shift speeds, the optimal throttle opening TV _o is corrected.

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

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

Further, in the above-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 calculated according to the current slip rate S _o . 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 t ₈ after the driver D accelerator 69 due is fully closed, 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. Note that the slip control is stopped in the embodiment in addition to fully closing the accelerator,
It is also performed when the target throttle opening degree by the slip control becomes smaller than the throttle opening degree determined by FIG. 12 corresponding to the accelerator opening degree operated by the driver.

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. With the determination of P2
If NO, it is determined in P3 whether or not the accelerator 69 is fully closed. If NO is determined in P3, it is determined in P4 whether the current throttle opening is larger than the accelerator opening. When NO is determined in P4, it is determined in P5 whether or not the slip control is currently being performed. This determination is performed by checking whether or not the slip control flag is set. . this
When NO is determined in P5, it is determined in P6 whether or not slip for performing slip control has occurred. This determination is made by checking whether a slip flag has been set for the left and right front wheels 2 and 3 described below. When NO is determined in P6, the process shifts to P7 and the slip control is stopped (normal traveling).

When YES is determined in P6, the process shifts to P8, and the slip control flag is set. Subsequently, at P9, the initial value of the target slip rate SET for the engine (throttle) (0.06 in the example) is set, and at P10, the initial value of the target slip rate SBT for the brake (in the example,
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 P10 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.

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

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

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

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

First, in P21, each signal from each of the sensors 61 to 68 is input for data processing. Next, after the process of slip detection described later is performed in P22, the throttle control is performed in P23.

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

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

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

When NO is determined in P33, the correction value α for slip determination is calculated in P34 according to the steering angle of the steering wheel (see FIG. 14). Thereafter, in P35, it is determined whether or not the slip ratio of the left front wheel 2 as the left driving wheel is larger than a value (0.2 + α) obtained by adding α in P34 to the predetermined reference value 0.2. If the determination in P35 is YES, it is determined that the left front wheel 2 is in the slip state, and the slip flag is set. Conversely, if NO is determined in P35, the left front wheel 2
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, 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, it means that the vehicle is running at low speed, and the error in the calculation of the slip ratio based on the equation (1) becomes large.
The detection is made based only on the rotation speed of the drive wheels.
That is, in P41, the rotation speed of the left front wheel 2 is 10 kV.
It is determined whether or not it is higher than the number of revolutions corresponding to m / h. If YES is determined in P41, the left front wheel 2
Is set. Conversely, if NO is determined in P41, the slip flag of the left front wheel 2 is reset in P43.

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

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

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

After P56, it is determined in P57 whether the vehicle speed is higher than 6.3 km / h. If YES in this P57,
The target rotation 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 (Engine control) The flowchart shown in FIG. 10 corresponds to P12 in FIG.

In P61, whether the transition slip to a converged state (whether the time that has passed through t ₂ time points of FIG. 5) is determined. When NO in P61, it is determined in P62 whether the slip ratio S of the left front wheel 2 is larger than 0.2. At P62
If NO, it is determined in P63 whether the slip ratio S of the right front wheel 3 is greater than 0.2. If NO in P63, it is determined in P64 whether only one of the left and right front wheels 2, 3 is under brake control, that is, whether the vehicle is traveling on a split road. If YES in P64, in P65,
The current slip ratio is calculated based on 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). In addition, P62, P63 NO
Also, shift to P66.

The select high in P66 described above makes it possible to further avoid the use of the brake by calculating the current slip ratio in order 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 ratio S
It is determined whether it is greater than 0.02. If YES in P67, in P68, the throttle valve 13 is feedback-controlled for slip control. Of course, at this time, the target throttle opening (T
n) is set to realize the target slip ratio SET set in P65 and P66 or changed in P76 described later.

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

On the other hand, if YES in P61, the process proceeds to P72 assuming that a large slip of the drive wheels is converging, and a predetermined time after the shift to the slip convergence direction (a time for performing the recovery control. As described above, it is determined whether or not 170 msec has elapsed. When the answer is NO in P72, the processing after P73 is performed to perform the recovery control. That is,
First, at P73, the maximum acceleration GMAX of the car 1 is measured (FIG. 5 t ₂ time). Next, at P74, the optimum throttle opening degree Tv ₀ is set so as to obtain this GMAX (see FIG. 15). Further, in P75, the optimum throttle opening Tv _{0 in} P74 is corrected according to the current gear position of the transmission 8. That is, since the applied torque to the drive wheels also differs depending on the shift speed, the optimal throttle opening Tv ₀ for a certain reference shift speed is set in P74, and the difference in the shift speed is corrected in P75. It is. After that, in P76, the friction coefficient of the road surface is estimated from GMAX in P73, and the target slip rate SET and SBT of the slip control by the engine (throttle) and brake after that are both changed. How to change the target slip ratios SET and SBT will be described later.

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

The target slip ratios SET and SBT of the engine and the brake changed in P76 are the maximum acceleration G measured in P73.
It is changed based on MAX, for example, as shown in FIG. As is clear from FIG. 17, in principle, the larger the maximum acceleration GMAX, the larger the target slip ratios SET and SBT. Then, the target slip ratio SET, SBT
Each has a limit value.

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

First, in P81, it is determined whether or not the stack is currently being stacked. If NO in P81, in P82, the limit value (BLM) of the pressure increase / decrease speed of the brake is set to a value (the larger the throttle opening is, the larger) according to the throttle opening based on the following formula. It

BLM = f (θ) θ: Throttle opening When YES at P81, at P83, above limit value BLM
Is set as a constant value smaller than that in the case of P82. It should be noted that the processes of P82 and P83 may cause vibration and the like because the increase / decrease speed of the brake fluid pressure is too fast when Bn as it is calculated by the equation (5) is used.
Also, it is performed in consideration of obtaining braking according to the throttle opening. 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 amount Bn of the right front wheel brake 22 is calculated in P85 (fourth operation).
This corresponds to Bn in the I-PD control in the figure). Thereafter, in P86, it is determined whether or not Bn is greater than “0”.
This determination is a determination as to whether or not the pressure increasing direction of the brake is positive and the pressure reducing direction is negative. P86
If YES, then in P87, it is determined whether or not Bn> BLM. If YES in P87, it is assumed that the brake operation amount Bn has exceeded the limit value BLM, and after setting Bn to the limit value BLM, the pressure in the right brake 22 is increased in P89. When NO in P87, the pressure is increased in P89 with the value of Bn set in P85. Through this series of steps, the brake speed is regulated to the limit value BLM, and is stopped as the throttle opening is increased (see FIG. 19).

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

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

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

When the difference between the actual rotation speed of the drive wheel and the target rotation speed (the actual slip ratio and the 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.

As described above, according to the present embodiment, the brake speed is regulated to the limit value (BLM), and according to the throttle opening,
The larger the throttle opening with less risk of engine stall, the faster the throttle opening. As a result, the slip convergence is improved.
In other words, when the throttle opening, which has a high risk of engine stall, is small, the braking speed is slowed,
Slip convergence is achieved while preventing engine stall.

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

Limit value (BL
M) was changed according to the throttle opening (11th
In the figure, P82), the control gain of each operation in the brake control, for example, the KI value (equation (5)) may be changed according to the throttle opening (P85 in FIG. 11).

A brake pressure sensor may be provided separately, and the brake pressure sensor may directly detect the brake pressure to regulate the brake pressure increasing speed. For example, the step of holding the brake pressure when the value detected by the brake pressure sensor is a predetermined value may be provided before P89 or P93 in the flowchart shown in FIG.

In the above and P82 (Fig. 11), the brake speed is changed by the throttle opening. However, instead of the throttle opening, the load on the engine is large depending on the magnitude of the load on the engine ( If the engine stalls easily), the braking speed may be reduced. In this case, the load on the engine may be detected based on the size of the loaded weight, the engagement and disengagement of the clutch, the shift speed, the slope of the slope, and the like.

Further, instead of the brake speed, the absolute value of the brake pressure, that is, the control amount may be changed.

The addition of the driving force acting on the driving wheels is not limited to the driving wheel brakes 21 and 22, and a braking means may be separately provided in the power plant system for the driving wheels.

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

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

(Effects of the Invention) As is apparent from the above, the present invention changes the control of the braking force that acts on the drive wheels according to the difficulty of occurrence of engine stall, and therefore prevents engine stall and improves slip convergence. It is possible to achieve both.

[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 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 throttle opening and the brake speed limit value (BLM). FIG. 19 shows an example of block control according to the throttle opening, and is a graph corresponding to FIG. FIG. 20 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 21-24: Brake 27 : Master cylinder 30, 31: Hydraulic 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) SV1 to SV4: Electromagnetic on-off valve U: Control unit

Claims (1)

(57) [Claims] 1. A slip control device for an automobile, wherein a slip force of a drive wheel on a road surface is prevented from becoming excessive by controlling a braking force acting on the drive wheel. Means, a load detection means for detecting a torque generated by the engine or a load on the engine, and a signal from the load detection means. When the torque generated by the engine is small or the load on the engine is large, the braking force A slip control device for an automobile, comprising: a slip control adjusting means for reducing a control speed or a control amount.