JPH02258431A - Slip control device for automobile - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention controls the drive torque based on the detected value of the drive wheel slip amount detection means to make the drive wheel slip amount follow a target value. This invention relates to a slip control device for an automobile.

[Prior Art] In general, in automobiles, when the drive torque of the drive wheels becomes too large relative to the road resistance, the amount of slip of the drive wheels becomes excessive, resulting in poor running stability. However, if the drive wheels are allowed to slip moderately, a large grip force is obtained on the drive wheels, which increases the propulsive force and improves acceleration. Therefore, a slip control device has been proposed that controls the drive torque to optimize the amount of slip of the drive wheels when the drive wheels start to slip, thereby achieving running stability or good acceleration.

In such conventional slip control devices, a slip amount detection means for detecting the amount of slip of the drive wheels is generally provided, and the drive torque is feedback-controlled based on the detected value of the slip amount detection means, thereby controlling the amount of slip of the drive wheels. The slip amount is made to follow a predetermined target value.

Furthermore, in order to improve driving characteristics such as driving stability and acceleration, it is possible to change the control characteristics of slip control according to the road surface condition or the driving condition of the vehicle. Japanese Patent Publication No. 63-31859 discloses a slip control device that sets a slip control target value such that the amount of slip of the driving wheels is smaller during cornering than when driving straight. In automobiles equipped with such slip control devices,
When cornering, the amount of slip on the drive wheels is prevented from becoming excessive, improving driving stability, and when driving straight, the grip force of the drive wheels is increased, improving acceleration performance, which improves driving performance, especially on winding roads. This has the advantage of improving the quality.

[Problems to be Solved by the Invention] However, in conventional automobiles that perform slip control in consideration of road surface conditions or driving conditions,
Both assume that the road is flat. However, when driving on a slope, the load distribution between the front and rear wheels changes depending on the inclination angle. The problem is that the rear wheels (drive wheels) tend to slip when going downhill, and conventional slip control characteristics that are set assuming a flat road cannot perform proper slip control.

The present invention has been made in view of the above-mentioned conventional problems, and can perform appropriate slip control on both flat roads and sloped roads, and improves driving characteristics such as driving stability and acceleration. It is an object of the present invention to provide an automobile slip control device that can improve the slip control system.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a slip amount detection means for detecting the slip amount of the drive wheels, and controls the drive torque based on the detected value of the slip amount detection means. In the slip control device for an automobile, the amount of slip of the driving wheels is made to follow a target value by means of a vehicle body tilt angle detection means for detecting the tilt angle of the vehicle body, and the slip amount is controlled according to the detected value of the vehicle body tilt angle detection means. Provided is a slip control device for an automobile, characterized in that the control characteristics of the control are changed.

[Operations and Effects of the Invention] According to the present invention, the amount of slip at which slip control should be started, the slip control target value, etc. are determined according to the inclination angle of the vehicle body detected by the vehicle inclination angle detection means, that is, the inclination angle of the road. The control characteristics of the vehicle can be changed in a direction that cancels the change in the vehicle's load distribution due to the slope. For example, F
In F cars, by setting the amount of slip at which slip control should be started on uphill slopes and the slip control target value to be smaller than on flat roads, the front wheels (drive wheels) have a reduced load distribution.
The slip amount is suppressed and the amount of slip is prevented from becoming excessive. Conversely, in FR vehicles, by setting the slip amount at which slip control should be started and the slip control target value small on downhill slopes, the slip of the rear wheels (drive wheels) whose load distribution has decreased is suppressed, and the slip amount is reduced. is prevented from becoming excessive. In this way, stable slip control can always be performed on both flat roads and slopes.

[Embodiment 1] Hereinafter, embodiments of the present invention will be described based on the attached drawings.

Overview of overall configuration In Fig. 1, a car l has left and right front wheels 2 which are drive wheels.
．． 3 and left and right rear wheels 4.5 serving as driven wheels. An engine 6 as a power source is mounted on the front of the automobile 1, and the torque generated by the engine 6 passes through a clutch 7, a transmission 8, and a differential gear 9, and then through the left and right drive shafts 7NO111. The power is transmitted to the left and right front wheels 2.3 as driving wheels. In this way, the automobile 1 is of the FF type (front engine, front drive).

The engine 6 as a power source has its intake passage 12
Load control, that is, control of generated torque is performed by a throttle valve 13 disposed in the engine. More specifically, the engine 6 is a gasoline engine, and the generated torque changes depending on the change in the intake air amount, and the intake air amount is adjusted by the throttle valve 13. The throttle valve 13 is electromagnetically controlled to open and close 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, or one driven by fluid pressure such as oil pressure and electromagnetically controlled.

Each wheel 2 to 5 has a brake 21122.23.
Alternatively, 24 are provided, and each of the brakes 21 to 24 is a disc brake. As is known, this disc brake includes a disc 25 that rotates together with the wheel and a caliper 26. This caliper 2
6 holds the brake pad and includes a wheel cylinder, and the brake pad is moved to the disc 25 with a force corresponding to the magnitude of the brake fluid pressure supplied to the wheel cylinder.
Braking force is generated by pressing against the

The mask cylinder 27 as a brake fluid pressure generation source is 2
It is of 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 in the middle, and the branch pipe 28a is connected to the right front wheel brake 22 (wheel cylinder).
The branch pipe 28b is connected to the left rear wheel brake 23.

Further, the brake pipe 29 extending from the discharge port 27b is branched into two branch pipes 29a and 29b in the middle, and the branch pipe 29a is connected to the left front wheel brake 21.
b is connected to the right rear wheel brake 24. In this way, the brake piping system is of the so-called two-system X type. Brakes 21 and 22 for the front wheels, which are the driving wheels.
An electromagnetic hydraulic pressure control valve 30 or 31 as a braking force adjusting means is connected to the branch pipes 28a and 29a. Of course, the brake fluid pressure generated in the mask cylinder 27 depends on the amount (depression force) of the brake pedal 32 by the driver.

Brake Hydraulic Pressure Control Circuit As shown in FIG. 2, each of the hydraulic pressure control valves 30, 31 has a cylinder 41 and a piston 42 slidably inserted into the cylinder 41. The piston 42 defines the inside of the cylinder 41 into a variable volume chamber 43 and a control chamber 44 . This variable volume chamber 43 serves as a passageway for brake fluid pressure from the mask 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 is changed, and the brake 21 (22
), and the generated brake fluid pressure can be increased, decreased or maintained.

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. Further, a check valve 46 is integrated into the piston 42. This check valve 46 is connected to the piston 4.
2 is displaced in the direction of decreasing the volume of the variable volume chamber 43, the inlet side to the variable volume chamber 43 is closed.

As a result, the brake fluid pressure generated in the variable volume chamber 43 acts only on the brake 21 (22) side, and does not act on the brake 23, 24 of the rear wheel 4.5 as a driven wheel. There is.

The displacement position of the piston 42 is adjusted by adjusting the control hydraulic pressure to the control chamber 44. To explain 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 valve 30.
The other branch pipe 48L is connected to the control chamber 44 of the valve 31. A pump 49 and a relief valve 50 are connected to the supply pipe 48, and a supply valve 5V3 (SV2) consisting of an electromagnetic on-off valve is connected to the branch pipe 48L (48R).

Each control chamber 44 is further connected to a reservoir 47 via a discharge pipe 51R or 5IL, and is connected to a reservoir 47 via a discharge pipe 51L (51L).
R) is equipped with a discharge valve 5V4 (SV
I) is connected.

During braking (slip control) using this hydraulic pressure control valve 30 (31), the check valve 46 basically prevents the brake pedal 32 from being applied.

However, when the brake fluid pressure generated by the fluid pressure control valve 30 (31) is small (for example, during pressure reduction), the brake is applied by operating the brake pedal 32. Of course, when brake fluid pressure for slip control is not generated by the fluid pressure control valve 30 (31), the mask cylinder 27
Since the brake 21 (22) is in communication with the brake 21 (22), a normal braking action is performed due to the operation of the brake pedal 27.

Each of the valves SVI to SV4 is controlled to open and close by a brake control unit UB, which will be described later. Condition of brake fluid pressure to brake 2122 and each valve SVI
~The operational relationship with SV4 is summarized and shown on the vestibule.

(The following is a blank space.) In FIG. 1, U is a control unit, which is broadly divided into the aforementioned 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 SVI to SV4, as described above, based on command signals from the control unit US. Also,
The throttle control unit UT performs drive control of the throttle actuator 14 based on a command signal from the control unit US.

The slip control control unit US is constituted by a digital computer, more specifically a microcomputer. This control unit US includes each sensor (or switch) 61 to 68.
Signals from 71 and 100 are input. sensor 61
Detects the opening degree of the throttle valve 13. The sensor 62 detects whether the clutch 7 is engaged. The sensor 63 detects the gear position of the transmission 8. Sensors 64 and 65 detect the rotational speed of the left and right front wheels 2.3 as driving wheels. The sensor 66 detects the rotational speed of the left rear wheel 4 as a driven wheel, that is, the vehicle speed. The sensor 67 detects the amount of operation of the accelerator 69, that is, the opening degree of the accelerator. The sensor 68 detects the amount of operation of the steering wheel 70, that is, the steering angle. The sensor (switch) 71 is used to input (select) a target slip value (target slip rate) of the driving wheels by manual operation by the driver.

Further, the sensor 100 is a tilt angle sensor that detects the tilt angle of the automobile l. The sensors 64, 65, and 66 are each configured using a pickup, for example, and the sensors 61.
63, 67, and 68 are configured by using, for example, potentiometers, and the sensor 62 is configured by, for example, a switch that operates in an ON/OFF manner. Furthermore, switch 71
For example, as shown in FIG. 21, the target slip rate can be selected from large (hard) to small (soft) in a stepwise or stepless manner using a sliding lever 71a. (See also Figure 13).

The control unit US basically consists of a CPU,
It is equipped with ROM, RAM% CLOCK, and also has an input/output interface 7/8 and an A/D or D/A converter depending on the input signal and output signal.
Since these points are the same as usual when using a microcomputer, a detailed explanation thereof will be omitted. Note that 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 explained in order, and the slip rate S used in the following explanation shall be defined by the following equation (1).

WD WD: Rotation speed WL of driving wheels (2, 3) 2 Rotation speed (vehicle speed) of driven wheels (4) The throttle control control unit UT operates the throttle valve 13 (throttle actuator 14) so that the target throttle opening is achieved. It is controlled by feedback. During this throttle control, when slip control is not performed, control is performed so that the target throttle opening corresponds to the operation amount of the accelerator 69 operated by the driver (1=1), and the accelerator opening at this time is FIG. 12 shows an example of the correspondence relationship between and the throttle opening degree. Furthermore, during the slip rough' control, the control unit UT performs throttle control so as to achieve the target throttle opening degree Tn calculated by the control unit IJs, without following the characteristics shown in FIG.

Throttle valve 1 using control unit UT
In the embodiment, the feedback control No. 3 is performed by Pl-PD control in order to compensate for fluctuations in the response speed of the engine 6. That is, during drive slip control, the opening degree of the throttle valve 13 is controlled by PI-PD so that the current slip rate matches the target slip rate. More specifically, the target throttle opening degree Tn during slip control is calculated by the following equation (2).

Tn=Tn-1 -3ET -FP (WDn-WDn-1) -FD (WDn-2XWDn-1+WDn-2)・
...(2) WL: Rotation speed of driven wheels (4) WD: Rotation speed of driving wheels (2, 3) KP; 1 for proportional constant: Integral constant FP: Proportional constant FD: Differential constant 5 ETJI base slip rate (throttle For control) the above formula (2
), the throttle opening degree Tn is feedback-controlled to the rotational speed of the drive wheels so that it reaches a predetermined target slip rate SET. In other words, as is clear from the above equation (1), the throttle opening degree is controlled so that the target driving wheel rotation speed WET is expressed by the following equation (3).

Pr-PD using the control unit UT described above
The control is shown in FIG. 3 as a block diagram, and [S'] shown in FIG. 3 is an "operator". Further, each suffix rn'' and rn-IJ indicate the value of each signal at the current time and at the time of sampling one time before.

During brake control slip control, the control unit UB
The rotation (slip) of the left and right drive wheels 2.3 is feedback-controlled independently to a predetermined target slip rate SBT. In other words, brake control is expressed by the following equation (
Feedback control is performed so that the driving wheel rotational speed WBT set in step 4) is achieved.

In this embodiment, the target rate SBT of the brake is set to be larger than the target slip rate SET of the engine, as will be described later. In other words, the slip control of this embodiment increases or decreases the engine output to a predetermined value of 5ET (~VET), and also increases or decreases the torque by the brake to achieve a larger 5BT (WBT). is used less frequently. In this embodiment, feedback control is performed by I-PD control, which has excellent stability, so as to satisfy the above equation (4). More specifically, the brake operation amount (operation amount of the piston 44 in the valve 30, 31) Bn is calculated by the following equation (5).

Bn-Bn-1 +KI (WLnX -WDn)-
3BT -FP (WDn-WDn-1) -FD (WDn -2XWDn -1+WDn -
2)...(5) K: Integral coefficient KD: Proportional coefficient FD: Derivative coefficient When Bn above is greater than 0 (positive), it is an increase in brake fluid pressure, and when it is less than 0, it is an increase in brake fluid pressure. The pressure will be reduced. This increase/decrease in brake fluid pressure is controlled by the valve SVI~
This is done by opening and closing SV4. In addition, the adjustment of the increase/decrease speed of brake fluid pressure is performed using the valves 5VI-SV mentioned above.
This is done by adjusting (duty control) the ratio of the opening/closing time (duty ratio) of No. 4, and the duty control is proportional to the absolute value of Bn determined by the above equation (5). Therefore, the absolute value of Bn is proportional to the rate of change in brake pressure reduction, and conversely, the duty ratio that determines the rate of increase/deceleration indicates Bn.

The IPD control by the control unit UB described above is shown in FIG. 4 as a block diagram, and "S'' shown in FIG. 4 is an "operator."

Overall outline of slip control The overall outline of slip control by the control unit U will be described with reference to FIG. 5. The meanings of the symbols 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 0/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 (
S BT) S=0.09: Slip rate when stopping slip control by brake (S BC) S=0°06: Target slip rate by engine (S
ET) S-0,01-0,02: Slip rate in the range where buffer control is performed S = 0.01 or less 2. Slip rate in the range where backup control is performed The results are shown based on the data obtained. Then, S-O performs buffer control A/S.

01 and 0.02, and the slip rate S=0.09 at the time when the slip control by the brake is stopped are left unchanged in the embodiment. On the other hand, the target slip rate SB due to the brake
T and the target slip rate SET by the engine, as well as the slip rate SS at the start of slip control, change depending on the road surface conditions such as the slope angle. , +, rO,06'' or ro,2''. The slip rate S=0.2 at the start of the slip control is the slip rate at the time when the maximum grip force is generated when using spiked tires (see the solid line in FIG. 13). In this way, the reason why the slip rate at the start of slip control is set at 062 (of course, it changes depending on the slope angle of the road) is that the actual slip rate when this maximum grip force is obtained can be calculated. This is to correct the target slip ratios SET and SBT for the engine and brake according to the slip ratio at the time when the maximum grip force occurs.

In addition, the solid line in FIG. 13 shows how the magnitude of grip force and lateral force (shown as a friction coefficient with respect to the road surface) when using a spiked tire changes in relation to the slip rate. Moreover, the broken line in FIG. 13 shows the relationship between grip force and lateral force when using normal tires. and,
As shown in FIG. 13, the target slip rate SD, which can be manually selected by the switch 71, ranges from a value slightly larger (hard) than the point at which the maximum grip force is generated when driving on an ice slope with spiked tires. ,
This value is one tenth smaller than the point at which the maximum grip force is generated (
software) and is set as a range.

On the premise of the above, FIG. 5 will be explained with the passage of time.

(2) t0-1° Since the slip rate S does not exceed S-0,2, which is the condition for starting slip control, slip control is not performed. That is, when the slip of the driving wheels is small, acceleration performance can be improved by not controlling the slip (driving using a large grip force). Of course, at this time,
The characteristics of the throttle opening with respect to the accelerator opening are the 12th
It is uniformly determined as shown in the figure. It goes without saying that the slip control start slip rate (SS) changes depending on the inclination angle.

■L1~t! This is when slip control is started and the slip rate is equal to or higher than the brake-based slip control stop point (S-0, 09). At this time, since the slip rate is relatively large, slip control is performed by reducing the torque generated by the engine and braking by the brake. In addition, the target slip rate of the brake (S = 0.17) is larger than the target slip rate of the engine (S = 0.06), so the brake is not pressurized when there is a large slip (S > 0.17). However,
When the slip is small (s>0.17), the brake is not pressurized and the slip is controlled only by the engine.

[2 to 14 (Recovery Control) The throttle valve 13 is maintained at a predetermined opening degree for a predetermined time (for example, 170 m5ec) after the slip converges (S<0.2) (oven loose control). At this time, the maximum acceleration GMAX at the time s-o, 2Qz) is determined, and the maximum μ (maximum grip force of the driving wheels) of the road surface is estimated from this GMAX. Then, the throttle valve 13 is held for a predetermined period of time as described above so as to generate the maximum grip force for the driving wheels. This control is performed to prevent the vehicle body acceleration G from dropping immediately after the slip converges because feedback control cannot respond in time because the convergence of the slip occurs rapidly. When the convergence of the slip is predicted (S=decreased from 0.2), a predetermined torque is secured in advance as described above, and acceleration performance is improved.

The optimal throttle opening TVo to achieve the torque applied to the drive wheels that can generate the maximum grip force mentioned above is:
Although it can be determined theoretically from the torque curve and gear ratio of the engine 6, in the embodiment, it is determined based on a map as shown in FIG. 15, for example. This map was created using an experimental method, and G MAX is 0.15.
Above and when it is 0, 4 or more, it is set to a predetermined constant value in consideration of the measurement error of G MAX. The map shown in FIG. 15 is based on the assumption that the vehicle is at a certain gear position (for example, L speed), and the optimum throttle opening degree TV is corrected at other gear positions.

(2) t, ~ty (backup control, buffer control) In order to cope with an abnormal decrease in the slip rate S, backup control is performed (oven loop control). That is,
When s<0.01, the feedback control is stopped and the throttle valve 13 is opened in stages. And the slip rate is 0. When the value is between Ol and 0.02, buffer control is performed to smoothly transition to the next feedback control (11 to L, and 11 to 11).
). This backup control is performed when neither feedback control nor recovery control can cope with the problem. Of course, this backup control is assumed to have a sufficiently faster response speed than feedback control.

In this embodiment, the increase rate of the throttle opening in this backup control is set to 0 for every 14m5ec of throttle opening with respect to the previous throttle opening.
, 5% opening is added.

Further, in the buffer control, as shown in FIG. 16, the throttle opening degree T2 obtained by the feedback control calculation and the throttle opening degree T obtained by the backup control calculation are set to the current slip rate S. The throttle opening degree T0 is obtained by proportionally distributing the opening amount T0.

■By performing control from L7 to t@L7, there is a smooth transition to slip control using only the engine.

■Since accelerator 69 was fully closed by the driver after L8, Nuri Z
control is aborted. At this time, the throttle valve 13
Even if the opening degree is left to the driver's will, there is no risk of slipping again because the torque has been sufficiently reduced. In addition to fully closing the accelerator, in the embodiment, the slip control is canceled when the target throttle opening due to the slip control is lower than the throttle opening determined by FIG. 12, which corresponds to the accelerator opening operated by the driver. I also try to do this when it gets smaller.

Here, when driving on a slope, the slip rate SS at the start of slip control and the target slip rate SET by engine control are set to be smaller than when driving on a flat surface when climbing, and vice versa when descending. These are set larger than when driving on flat ground. In addition, for FR cars, SS
The characteristics with respect to the inclination angle of SET and SET need to be set inversely in terms of magnitude. In addition, the target slip rate SET for engine control
The reason for reducing only is to take into consideration that the target slip rate SBT itself in brake control is sufficiently larger than the slip rate suitable for uphill running.
This SBT can also be reduced when traveling uphill.

Details of slip control (flow chart) Next, Figure 6~
The details of the slip control will be explained with reference to the flowchart in FIG. It also controls the stack. In addition, in the following explanation, P
indicates a step.

FIG. 6 (Main) After the system is initialized at Pl, it is determined at P2 whether or not the system is currently stuck (such as stuck in mud or the like and unable to move). This determination is made by checking whether a stack flag, which will be described later, is set. When the determination in P2 is NO, it is determined in P3 whether or not the accelerator 69 is fully closed. When the determination in P3 is NO, it is determined in P4 whether or not the current throttle opening is greater than the accelerator opening.

If the determination in P4 is No, it is determined in P5 whether or not slip control is currently being performed. This determination is made by checking whether the slip control flag is set.

When the determination is No in P5, the skid rate SS at which slip control should be started is calculated in P6. This SS is a linear function of the inclination angle θ of the vehicle l (that is, the inclination angle of the road) detected by the vehicle inclination angle sensor 100, and as shown in FIG. 20, the larger the inclination angle θ, the smaller the SS. It looks like this. In addition, in the case of FR cars, excessive slip occurs in the rear wheels when going downhill, so
Conversely, the larger the inclination angle θ, the larger the SS needs to be set.

Next, at Pl, it is determined whether the current slip rate S exceeds the above-mentioned SS, that is, whether a slip that requires slip control has occurred. NO with this Pl
When it is determined that this is the case, the process moves to P8, where the slip control is stopped and normal driving is performed.

If YES is determined in P7, slip control is started, so the process moves to Plo and the slip control flag is set. Subsequently, in Pll, the initial value of the target slippage rate SET for the engine (throttle) is calculated. This SET is a linear function of the inclination angle θ of the vehicle l (that is, the inclination angle of the road) detected by the vehicle inclination angle sensor 100, and as shown in FIG.
The larger the value, the smaller the SS becomes.

Note that in the case of an FR vehicle, excessive slip occurs in the rear wheels on downhill slopes, so conversely, the larger the inclination angle θ, the greater the need to set SET.

Next, in PI3, the target slip rate SET at pH is corrected as described later. In addition, in PI3, the initial value of the target slip rate SBT for the brake (0.17 in the example)
is set. After this, as described later,
For slip control, brake control is performed at PI3 and engine control is performed at PI3. In addition, pH, PI
The setting of the target slip rate SET in step 3 is performed based on the maximum acceleration G MAX obtained in the previous slip control from the same viewpoint as in P76 described later.

(The following is a blank space) When the determination is YES in the above P5, the process moves to the above-mentioned PI3, and the slip control is continued.

If YES is determined in P4, slip control is no longer necessary, and the process moves to PI3. This PI
At step 7, the slip control flag is reset. Then,
Engine control is stopped at PI3, and brake control is performed at PI3. In addition, in brake control with this PI3,
It is done as if it were dealt with while stacked.

If YES is determined in P3, the brake is released in PI6, and then the processes from P17 onwards are performed.

When the determination in P2 is YES, the processes from P18 onwards are performed.

7 and 8 The 70-chart in FIG. 7 interrupts the main 70-chart in FIG. 6, for example, every 14 m5ec.

First, in P21, each signal from each sensor 61 to 68 is input for data processing. Next, after slip detection processing, which will be described later, is performed in P22, 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 slip control is currently being performed. When YES in P24, 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 Figure @12. Also, in P24, No.
When it is determined that this is the case, at P2O, the opening/closing control of the throttle valve 13 is selected to be left to the driver's will (according to the characteristics shown in FIG. 12). This P2
5. After P2O, control is performed in P27 to achieve the target throttle opening (P68, which will be described later).
, P2O, P71, or control according to the characteristics shown in FIG. 12).

FIG. 9 (Slip Detection Process) The flowchart in FIG. 9 corresponds to P22 in FIG. 7. This flowchart is for detecting whether a slip that is subject to slip control has occurred and whether or not the vehicle is stuck.

First, in P31, it is determined whether the clutch 7 is completely connected. If YES is determined in P31, it is assumed that the stack is not in progress, and the stacking lug is reset in P32. Then P3
3, the current vehicle speed is low, for example, 5.3 km.
It is determined whether or not the value is smaller than /h.

When the determination in P33 is No, a correction value α for slip determination is calculated in P34 according to the steering angle of the steering wheel (see FIG. 14). After this, at P35, the slip rate of the left front wheel 2 as the left driving wheel is set to a predetermined reference value of 0.
It is determined whether or not the value is larger than the value (0, 2+α) obtained by adding the elongation in P34 above to 2. With this P35 determination, Y
In the case of ES, it is assumed that the left front wheel 2 is in a slip state, and the slip flag is set. On the other hand, NO on P35
When it is determined that this is the case, the slip flag for the left front wheel 3 is reset. Note that the correction value σ is set in consideration of the rotational difference between the inner and outer wheels (particularly the rotational difference between the driving wheel and the driven wheel) during turning.

After P36 or P37, P38, P39, P2O
In , the slip flag for the right front wheel 3 is set or reset in the same manner as in P35 and P37.

If YES is determined in P33, the vehicle speed is low, and there will be a large error in calculating the slip rate using the vehicle speed, that is, based on equation (1). It is intended to be detected only by That is, at P41, the rotation speed of the left front wheel 2 is
It is determined whether the rotational speed is greater than the rotational speed equivalent to a vehicle speed of 10 km/h. When it is determined as YES in this P41, P
At 42, the slip flag for the left front wheel 2 is set.

Conversely, if the determination is NO at P4.1, the slip flag for the left front wheel 2 is reset at P43.

After P42 and P43, the slip flag for the right front wheel 3 is set or reset in P44, P45, and P4O in the same manner as in P41 to P43 described above.

If the determination in P31 is No, there is a possibility that the vehicle is stuck (when the driver is stuck, the driver tries to escape from the mud etc. while using the clutch in a partially engaged state). In this case, the process moves to P51, and it is determined whether the average value of the rotation speed of the left and right front wheels 2 and 3 as driving wheels is small (for example, 2 kph in terms of vehicle speed).
m/h or less). No on P51
When it is determined that this is the case, it is determined in P52 whether or not stack control is currently being performed. When the determination is No in P52, it is determined in P53 whether the rotation speed of the right front wheel 3 is greater than the rotation speed of the left front wheel 2. P5
If the determination is YES in step 3, it is determined whether the rotation speed of the right front wheel 3 is greater than 1.5 times the rotation speed of the left front wheel 2. If YES is determined in this P54, P56
The stack flag is set. Conversely, when the determination in P54 is No, it is assumed that the stack is not in progress, and the processes from P32 onwards are performed.

In addition, when the determination in P53 is No, P55j
Here, the rotation speed of the left front wheel 2 is 1 of the rotation speed of the right front wheel 3.
．． It is determined whether or not it is larger than five times. Y with this P55
If ES, the process moves to P56, and if No, the process moves to P32.

After P56, the vehicle speed is 6.3km/h at P57.
It is determined whether or not it is larger than . YES on this P57
When this is determined, the target rotation speed of the front wheels 2.3 is set to be 1.25 times the driven wheel rotation speed indicating the vehicle speed (corresponding to a slip ratio of 0.2).

Also, if P57 is NO, then in P59, the front wheel 2
．． The target rotation speed of No. 3 is uniformly set to lQkm/h.

Further, if YES in P51, the brake is slowly released in P2O.

Figure 1O (engine control) The flowchart shown in Figure 10 is based on the PI3 of Figure 6.
It corresponds to

At P61, it is determined whether the slip has transitioned to a convergence state (whether it has passed time t2 in FIG. 5). If NO in P61, it is determined in PO2 whether the slip rate S of the left front wheel 2 is greater than SS. If NO in PO2, it is determined in P63 whether the slip rate S of the right front wheel 3 is greater than SS. This P6
If No in 3, it is determined at PO4 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 PO4, at P65, left and right front wheels 2
．． The current slip rate is calculated according to the drive wheel with the lower slip rate among the three wheels (select low). On the contrary, PO4
If NO, the current slip rate is calculated according to the drive wheel with the larger slip rate among the left and right front wheels 2.3 (select high). It should be noted that when the result in PO2 and P63 is NO, the process also moves to P66.

The selection high in P65 allows the use of the brake to be further avoided by calculating the current slip rate in order to suppress the slip of the slippery drive wheel. On the other hand, the select low in P65 above is effective when driving on a split road where the friction coefficients of the road surface on which the left and right drive wheels touch the ground are different, while controlling the slip of the drive wheel that is more likely to slip using the brake. This makes it possible to drive by taking advantage of the grip of the drive wheel on the weaker side.

In the case of this select low, in order to avoid overusing the brakes, it is advisable to limit the select low to a certain period of time, for example, or to take backup measures to stop the select low if the brakes overheat.

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

If No in P67, it is determined in P2O whether the current slip rate S is greater than 0.01. If YES at P2O, the buffer control described above is performed at P2O. Also, if P2O is NO, P71
In this step, the backup control described above is performed.

On the other hand, if YES in P61, the process moves to P72, where it is determined whether a predetermined time (time for performing recovery control, 1.70 msec as described above in the embodiment) has elapsed after the slip convergence. N at P72.

In this case, the processing from P73 onward is performed to perform recovery control. That is, first, in P73, the maximum acceleration GMAX of the automobile 1 is measured (at time L2 in FIG. 5). Next, in PI4, the optimum throttle opening degree Tvo for obtaining this G MAX is set (see FIG. 15). Further, in PI5, the optimum throttle opening degree Tvo in PI4 is corrected according to the current gear position of the transmission 8. That is, since the torque applied to the drive wheels differs depending on the gear position, PI4 sets the optimum throttle opening Tvo for a certain standard gear position,
PI5 is designed to correct this difference in gear position.

After this, in P76, the friction coefficient of the road surface is estimated from GMAX in P73, and the target slip rate for slip control by the engine (throttle) and brake is set.

Change SBT together. Note that this target slip rate SET
, how to change SBT will be described later. Then, in PI7, the target slip ratio SET in engine control is corrected according to the inclination angle θ of the automobile 1, and this point will also be described later.

If YES in the previous λP72, this means that the recovery control has ended, and the processes from P62 described above are performed.

Prisoner 11 (Brake control) The flowchart shown in FIG.
and P1. It corresponds to 9.

First, in P81, it is determined whether or not the stack is currently in progress. If NO at P81, at P82,
A limit value (maximum value) BLM of the brake response speed Bn (corresponding to the duty ratio for opening/closing control of SVI to SV4) is set as a function according to the vehicle speed (the higher the vehicle speed, the larger the value). Conversely, if YES in P81, the limit value BLM is set as a constant value smaller than that in P82 in P83. In addition, this P82, 83
This process is performed in consideration of the fact that if the Bn calculated by the equation (5) is used as it is, the rate of increase/decrease in brake fluid pressure will be too fast and cause vibrations. In addition, in P83, it is particularly undesirable for the braking force applied to the drive wheels to change suddenly in order to escape from the stuck state, so a small constant value is set as the limit value.

After P82 or P83, it is determined in P84 whether the slip ratio S is larger than 0.09, which is the point at which brake control is stopped. When 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 system in FIG. 4). After this, in P86, the above Bn is “
It is determined whether or not the value is greater than 0. This determination determines whether or not the brake pressure is increasing, assuming that the brake pressure increasing direction is positive and the pressure decreasing direction is negative. When YES in P86, it is determined in P87 whether Bn>BLM. If YES on P87, set Bn to limit value B.
After setting to L M, on P89, set the right brake 2.
2 pressure increases are made. Also, if P87 is NO, P
The pressure is increased at P89 using the Bn value set at P85.

If No in P86, Bn is "negative" or "0".
”, so after converting Bn into an absolute value in P2O, the process of ~93 is performed in P9. These P91 to P93 are when depressurizing the right brake 22, and P87, P88, and P89
It corresponds to the processing of

After P89 and P93, the program moves to P94J, where the left brake 21 is increased or decreased in pressure in the same way as the right brake 22 (processing corresponding to P84 to P93).

On the other hand, if No in P84, it is time to cancel the brake control, so the brake is released in P95.

In addition, between P85 and P86, the actual rotation speed and target rotation speed (actual slip rate and target slip rate) of the driving wheels
When the difference is large, it is preferable to correct the integral constant in equation (5) by reducing 1, for example, in order to prevent deterioration of acceleration and engine stalling due to excessive braking.

Change target slip rate SET, SBT (P76) above P
The target slip rate SET and SBT between the engine and brake changed in P76 is based on the maximum acceleration G MAX measured in P73, for example, in the case of 5S=0.2, as shown in FIG. Modified as shown.

As is clear from FIG. 17, in principle, the larger the maximum acceleration G MAX, the higher the target slip rate SET,
The idea is to increase the SBT. Limit values are set for each of the target slip rates SET and SBT.

Correction of target slip ratio SET (FIG. 22) This is correction of SET at P12 and P77.

As mentioned above, SET is the inclination angle θ(
In other words, it is determined according to the gradient of the road (see Fig. 20). In other words, when driving uphill, keep the front wheels 2.
Since the drive wheels 3 (driving wheels) tend to slip more easily, the target slip rate SET is made smaller as the inclination angle θ becomes larger. Also, when driving downhill, the front wheels
, 3 increases, conversely, the target slip rate SE
T is increased.

Note that in the case of an FR vehicle, the rear wheels 4.5 (driving wheels) tend to slip when traveling downhill, so conversely, the larger the inclination angle θ, the higher the target slip rate SET needs to be.

First, in PIOI, each correction coefficient a, b is read from a map created in advance. correction coefficient a,
As shown in FIG. 18 or FIG. 19, b has a value corresponding to the selection of the manually operated mode switch 71, respectively.

After Plol, GM at P73 in P2O3
It is determined whether AX is smaller than a predetermined value.

When P 1.02 is YES, the road surface on which the vehicle is currently traveling is low μ, so the target slip rate SET is low μ.
It is corrected by a correction coefficient for Also, Plf)2
If the answer is NO, the road surface you are currently driving on has a high μ.
At P2O3, the target slip rate SET is corrected by the correction coefficient a for high μ.

Even with this correction, when driving uphill, the target slip rate SET is set smaller than when driving on flat ground, and by lowering the slip rate, the lateral force of the drive wheels is increased and stability is ensured. Ru.

Note that slip control is performed within the range of the slip rate around which the maximum grip force is generated (slip rate S-〇, around 2 in Figure 13), so by lowering the target slip rate, the grip force can be reduced. will be moved in the direction of

Here, if, for example, Hard is selected by Mode Switch 1 (the selection shown in SD in Figure 13) and the target slip rate is greater than the point at which the maximum grip force is generated, this manual selection is required. may be prohibited, and the target slip rate may be changed to a slip rate at which the maximum grip force is generated.

Next, we will explain how the setting relationship between the target slip rate SET and SBT affects the feeling of driving a car.

■The grip force SET and SBT of the drive wheels are offset in the vertical direction in FIG. 17 as a whole. Then, to increase the grip force, perform an upward offset. In other words, as shown in Fig. 13, the characteristics of spiked tires include a slip rate of 0.2.
Since the friction coefficient μ is in an increasing direction up to about 0.3, the above can be said as long as the slip ratio is used in the range of 0.2 to 0.3 or less.

■Acceleration feeling The acceleration feeling changes by changing the "difference" between SET and SBT, and the smaller this "difference" is, the greater the acceleration feeling becomes. That is, when SET is set to a value smaller than SBT as in the embodiment, brake control mainly acts when the slip rate is large, and engine control acts mainly when the slip rate is small. therefore,
When the "difference" between SET and SBT is made smaller, brake control and engine control come closer to working with almost the same distribution. In other words, the brakes are used to reduce the torque generated by the engine to drive the drive wheels, and if the torque is rapidly increased for acceleration, simply loosening the brakes will increase the torque to the drive wheels without delay in response. do.

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

Although the embodiments have been described above, the present invention is not limited thereto, and includes, for example, the following cases.

■In addition to engine control and brake control, the torque applied to the drive wheels can be adjusted by adjusting the engagement state of the clutch 7 or by changing the gear ratio of the transmission 8 (especially effective in the case of a continuously variable transmission) This can be done by any one or a combination of appropriate components that can adjust the torque applied to the drive wheels.

(2) It is preferable to adjust the generated torque of the engine 6 by changing and controlling the factors that most affect the output generated by the engine. In other words, it is preferable to adjust the generated torque by so-called load control, and in the case of an automatic engine (for example, a gasoline engine), by adjusting the mixture amount, and in the case of a diesel engine, by adjusting the amount of fuel injection. is preferred. However, the load control is not limited to this, and may be performed by adjusting the ignition timing in an Otto type engine, or by adjusting the fuel injection timing in a diesel engine.

Furthermore, in engines that require supercharging, this may be done by adjusting the supercharging pressure.

Of course, the power source is not limited to an internal combustion engine, but may also be an electric motor, and in this case, the generated torque may be adjusted by adjusting the power supplied to the motor.

(2) In the automobile I, the front wheels 2.3 are not limited to driving wheels, but the rear wheels 4.5 may be driving wheels, or all four wheels may be driving wheels.

■In order to detect the slip state of the drive wheels, it is possible to directly detect the rotation speed of the drive wheels as in the embodiment, but it is also possible to predict the slip state according to the state of the vehicle. In other words, it may be detected indirectly. Such vehicle conditions include, for example, an increase in the generated torque or rotational speed of the power source, a change in the degree of accelerator opening, a change in the rotation of the drive shaft, the steering condition (cornering), and the floating condition of the vehicle body (acceleration). , loading capacity, etc. In addition to this, atmospheric temperature fluctuations, rain, snow, ice burns, etc.
It is also possible to predict the slip state of the driving wheels even more appropriately by automatically detecting one or inputting it manually.

■Brake hydraulic pressure circuit and sensor 64.64. in Figure 2.
66 may use an existing ABS (anti-brake lock system).

[Brief explanation of 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 brake fluid pressure control circuit. FIG. 3 is a block diagram when performing feedback control of the throttle valve. FIG. 4 is a block diagram when feedback controlling the brakes. FIG. 5 is a graph schematically showing a control example of the present invention. 6 to 11 and 22 are flowcharts showing examples of gradient control according to the present invention.) FIG. 12 is a graph showing the characteristics of throttle opening relative to accelerator opening when slip control is not performed. FIG. 13 is a graph showing the relationship between the grip force of the driving wheels and the lateral force in terms of the relationship between the slip rate and the friction coefficient with respect to the road surface. FIG. 14 is a graph showing correction values when the slip rate 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 slip rate and throttle opening when performing buffer control. FIG. 17 is a graph showing correction coefficients for the target slip rate depending on the operating state of the manual switch, and FIGS. 18 and 19 are graphs used when determining the target slip rate. FIG. 20 is a graph showing the characteristics of the target slip rate and the slip rate at which slip control should be started, with respect to the inclination angle of the vehicle. FIG. 21 is a diagram showing an example of a mode switch for manually selecting a target slip rate. l: Car 2.3: Front wheel (driving wheel) 4.5: Rear wheel (driven wheel) 6: Engine (power source) 7 Co-clutch 8: Transmission 3: Throttle valve 4: Throttle actuator 1 to 24 Nibrake 7: Mask Cylinder 0.31: Hydraulic pressure control valve 2 Brake pedal l: Sensor (throttle opening) 2: Sensor (clutch) 3: Sensor (gear) 4.65: Sensor (driving wheel rotation speed) 6: Sensor (driving wheel rotation speed) 7: Sensor (accelerator opening) 8: Sensor (handle steering angle) 69 Near accelerator 0: Handle 71: Target slip rate change switch 100: Tilt angle sensor 5VI-3V4: Electromagnetic opening/closing valve LI: Control unit patent Applicant Mazda Co., Ltd. Chief Master Masato
Patent attorney Aohaku Haka 1 person Fig. 2 Fig. 7 Fig. 8 Fig. 16 Fig. 17 Fig. 12 Figure 15 MAX Figure 18 Figure 2o Figure 19

Claims (1)

[Claims] (1) A vehicle that is provided with a slip amount detection means for detecting the amount of slip of the drive wheels, and controls the drive torque based on the detected value of the slip amount detection means to make the amount of slip of the drive wheels follow a target value. A slip control device for an automobile, characterized in that a vehicle body inclination angle detection means for detecting a vehicle body inclination angle is provided, and control characteristics of the slip control are changed according to a detected value of the vehicle body inclination angle detection means. slip control device