JP2948361B2 - Vehicle slip control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slip control device for a vehicle, which prevents a drive wheel from slipping too much on a road surface.

[0002]

2. Description of the Related Art Various slip control devices (traction control devices) have been proposed which prevent the driving wheels from slipping on the road surface during acceleration of the vehicle or the like, thereby satisfying acceleration performance and vehicle stability. ing.

[0003] The slip control is performed by reducing the torque applied to the driving wheels. Therefore, the braking control for applying a braking force to the driving wheels and the engine for reducing the generated torque (output) of the engine are performed. Control is performed. In both of the brake control and the engine control, feedback control is generally performed so that the actual slip value of the drive wheels with respect to the road surface becomes a predetermined target value.

In slip control, since the road surface μ has a great influence, various methods for estimating the road surface μ have been proposed. Japanese Patent Application Laid-Open No. 60-197434 discloses that a road surface μ is estimated from driven wheel acceleration, that is, vehicle acceleration.

[0005] Incidentally, the start of the slip control is started when a large slip occurs in the driving wheel. However, the large slip of the driving wheel often occurs due to noise. A typical example of this noise is generated when the vehicle travels on a rough road, particularly on an uneven road, or when shifting up.

More specifically, when the vehicle is traveling on a rough road, the driving wheels repeatedly contact and separate from the road surface. However, this large slip is converged at the time of the next contact with the ground, and therefore, starting the slip control due to a temporary slip when the vehicle is separated from the road surface deteriorates the acceleration. Will be.

In addition, at the time of upshifting, the inertia energy of the driving system released due to the decrease in the engine speed acts on the driving wheels, and also at this time, a large slip occurs on the driving wheels. However, a large slip at the time of upshifting is also temporary, and performing the slip control in such a case leads to deterioration of acceleration.

Although it is conceivable to determine whether or not a spin requiring a slip control has occurred using the road surface μ as a parameter, it is difficult to accurately determine the road surface μ before the slip control. .

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vehicle slip control device capable of reliably preventing a situation in which slip control is unnecessarily started. I do.

[0010]

In order to achieve the above object, the present invention has the following configuration. That is, torque adjusting means for adjusting the applied torque to the drive wheels, first detecting means for detecting the vehicle body acceleration, second detecting means for detecting the rate of change of the engine speed, and detecting the rate of change of the drive wheel speed A third detecting means, a vehicle acceleration detected by the first detecting means, a rate of change of an engine speed detected by the second detecting means, and a driving wheel speed detected by the third detecting means. A spin determining means for determining whether or not a spin requiring the slip control of the driving wheel has occurred based on the change rate; and an operation is started when the determining means determines that a spin has occurred on the driving wheel. And a slip control means for controlling the torque adjusting means to reduce the torque applied to the drive wheels.

The above-mentioned spin judging means can be specifically constituted as follows. That is, first threshold value setting means for setting a first threshold value for the engine speed change rate based on the vehicle body acceleration detected by the first detection means;
Based on the vehicle body acceleration detected by the first detecting means,
Second threshold value setting means for setting a second threshold value for the driving wheel speed change rate, and whether an engine speed change rate detected by the second detection means is larger than the first threshold value or not. First determining means for determining whether the driving wheel speed change rate detected by the third detecting means is greater than the second threshold value; and What is necessary is just to have the structure provided with the 3rd determination means which determines whether the spin occurred in the drive wheel according to the determination result of a determination means and a 2nd determination means.

It is preferable that the slip control means be configured to perform feedback control of the torque adjusting means so that the actual slip value of the drive wheel becomes a predetermined target value.

[0013]

According to the present invention, it is possible to reliably prevent a situation in which the slip control is unnecessarily started when traveling on a rough road or when shifting up.

That is, spin can be regarded as occurring only when both the rate of change of the engine speed and the rate of change of the driving wheel speed are large. This is either a temporary slip during traveling or when no slip has occurred.

Incidentally, when the rate of change of the engine speed is large and the rate of change of the drive wheel speed is small, it can be considered that the slip is caused by upshifting, and the rate of change of the drive wheel speed is small. Is large, it can be considered that a temporary slip occurs during traveling on a rough road. When both the rates of change are small, it means that no slip has occurred, and thus it is originally a time when the slip control is unnecessary.

Further, the first rate of change of the engine speed is defined as follows.
Since the threshold value and the second threshold value for the driving wheel speed change rate are each set based on the vehicle body acceleration, the threshold value can always be set to an appropriate value and spin determination can be accurately performed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, 1FL is a left front wheel, 1FR is a right front wheel, 1RL is a left rear wheel, and 1RR is a right rear wheel. The engine 2 is mounted horizontally on the front of the vehicle body.
Torque generated by the clutch 3, the transmission 4, the differential gear 5,
Is transmitted to the left front wheel 1FL via the left drive shaft 6L and to the right front wheel 1FR via the right drive shaft 6R. As described above, the vehicle has the front wheels 1F
L, 1FR are drive wheels, and rear wheels 1RL, 1RR are front wheel drive vehicles that are driven wheels.

[0018] Brakes 7FR to 7R mounted on each wheel
R is a hydraulic disk brake.
Further, a master cylinder 8 as a brake hydraulic pressure generating source is provided.
Is a tandem type having two discharge ports 8a and 8b. A brake pipe 13 extending from one discharge port 8a of the master cylinder 8 is branched into two on the way.
The branch pipe 13F is connected to the left front wheel brake 7FL (a wheel cylinder mounted in the caliper), and the branch pipe 13R is connected to the right rear wheel brake 7RR.
The branch pipe 14 extending from the other discharge port 8b of the master cylinder 8 is also branched into two, the branch pipe 14F is connected to the right front wheel brake 7FR, and the branch pipe 14R is connected to the left rear wheel brake 7RL. It is connected.

Branch pipe 13 for front wheels, that is, for drive wheels
F and 14F are provided with an electromagnetic hydraulic pressure control valve 15L or 1F.
5R is connected, and an electromagnetic on-off valve 16L or 16R is connected to the branch pipes 13R and 14R for the rear wheels. The hydraulic pressure adjusting valves 15L and 15R are provided with a brake 7FL,
The brake fluid pressure supply from the master cylinder 8 to the 7FR and the brake fluid pressure of the brakes 7FL and 7FR
The mode of release to the reservoir tanks 22L and 22R via 1L and 21R is switched. The brake fluid in the reservoir tank 21L is returned to the pipe 13 via a pipe 25L to which a check valve 24L is connected by a pump 23L. Similarly, the brake fluid in the reservoir tank 22R is
By R, it is returned to the pipe 14 via the pipe 25R to which the check valve 24R is connected.

The stepping force on the brake pedal 12 is
The power is transmitted to the master cylinder 8 via a booster, that is, a brake booster 11. The booster 11 is basically the same as a known vacuum booster. However, in the case of slip control, as will be described later, the booster action is performed even if the brake pedal is not depressed. Is performed.

The booster 11 has a case 31 fixed to the vehicle body and the master cylinder 8, and the inside of the case 31 is formed by a diaphragm 32 and a valve body 33 fixed thereto. A chamber 34 and a second chamber 35 are defined. A negative pressure (for example, the negative pressure of the intake air of the engine 2) is always supplied to the first chamber 34. When the brake pedal is not depressed, the second chamber 35 is communicated with the first chamber 34, -The operation of the star 11 is stopped. When the brake pedal 12 is depressed,
Atmospheric pressure is supplied to the second chamber 35, whereby the diaphragm 32 is displaced forward together with the valve body 33 to perform a boosting function.

Switching between the negative pressure supply and the atmospheric pressure supply to the second chamber 35 is basically performed by a valve device provided in the valve body 33. This valve body 33
The portion will be described with reference to FIG.

First, the valve body 33 has a power piston 41 fixed to the diaphragm 32, and a reaction disk 42 and a base end of an output shaft 43 are provided in a recess 41 a formed in the power piston 41. Are fitted. This output shaft 43 serves as an input shaft of the master cylinder 8. A valve plunger 45 is mounted in the valve body 33 at the tip of the input shaft 44 connected to the brake pedal 12. Behind the valve plunger 45, a vacuum valve 46 is provided.

The power piston 41 has a pressure introducing passage 50.
The pressure introducing passage 50 is always in communication with a space X formed around the valve plunger 45. This space X is always in communication with the second chamber 35. A valve seat 47 on which the vacuum valve 46 is detached and seated is formed at an opening end of the pressure introducing passage 50 on the space X side. Further, the vacuum valve 46 includes a valve plunger 45.
The seat is also detached from and seated on a valve seat 45a formed at the rear end.

In the above configuration, it is assumed that a negative pressure is introduced into the pressure introducing passage 50. In this state, when the brake pedal 12 is not depressed, the vacuum valve 46 is seated on the valve seat 45a by the urging force of the springs 48 and 49 in the state of FIG. ing. Therefore, the pressure introduction passage 5
The negative pressure from 0 is introduced into the second chamber 35 via the space X, and no boosting action is performed.

When the brake pedal 12 is depressed,
The input shaft 44 and thus the valve plunger 45 are moved forward (to the left in the drawing). During this forward movement, the vacuum valve 46
Is first seated on the valve seat 47 and the space X and the pressure introduction passage 50 are
To the vacuum valve 46 and the valve seat 45
a are separated. When the vacuum valve 46 and the valve seat 45a are separated from each other, the atmospheric pressure from behind the valve body 33 is introduced into the space X, and the second chamber 35 becomes the atmospheric pressure. As a result, the diaphragm 32 is displaced forward together with the valve body 33, and as a result, the output shaft 43 moves forward and a boosting action is performed. The brake reaction force from the master cylinder 8 is transmitted via the reaction disk 42 to the valve plunger 45 and thus to the brake pedal 12.
When the brake pedal 12 is released, the return spring 36 (see FIG. 1) returns to the state shown in FIG. 2 to prepare for the next boosting action.

Although the parts described above are the same as those of the known vacuum booster, in this embodiment, the negative pressure of the first chamber 34 is introduced into the pressure introduction passage 50 for slip control. The state is switched to a state in which atmospheric pressure is introduced. That is, the first chamber 34 and the pressure introduction passage 5
0 is connected via a pipe 37, and a three-way electromagnetic switching valve 38 (see FIG. 1) is connected to the pipe 37. The switching valve 38 connects the pressure introduction passage 50 to the first chamber 34 during demagnetization, and introduces atmospheric pressure into the pressure introduction passage 50 during excitation. When the switching valve 38 is excited and atmospheric pressure is introduced into the pressure introducing passage 50, the space X and hence the second chamber 35
Thus, even if the brake pedal 12 is not depressed, the pressure becomes the atmospheric pressure. As a result, a boosting action is performed to generate a brake hydraulic pressure in the master cylinder 8.

FIG. 3 schematically shows a control system. In FIG. 3, U is a control unit constituted by using a microcomputer.
Signals from sensors or switches S1 to S8 are input. The sensors S1 to S4 detect rotation speeds of the wheels 1FL to 1RR. The switch S5 is an accelerator switch that is turned on when the accelerator pedal 10 is fully closed. Switches S6 and S7 are each
The switch is activated when the key pedal 12 is depressed, for example, one switch is normally open and the other is normally closed. The sensor S8 detects the engine speed.

The output from the control unit U to each device shown in FIG. 3 is indicated by reference numeral 9 which is a torque adjusting means for adjusting the torque generated by the engine 2. The torque adjusting means 9 adjusts the intake air amount, for example,
Alternatively, the generated torque is adjusted by a combination of the number of fuel cut cylinders and the ignition timing adjustment.

Next, an outline of the slip control will be described with reference to FIG.
Will be described with reference to FIG. In FIG. 4, the left driving wheel 1
An example is shown where no slip occurs in the FL and a large slip occurs in the right drive wheel 1FR.

Engine Control First, the engine control is started according to the result of the spin determination described later (at time t1 in FIG. 4). The engine control is performed by performing feedback control on the torque adjusting means 9 so that the actual slip value becomes the engine target value (first target value) STE. The engine control is stopped when the accelerator is fully closed, or when the time when the actual slip value has become the control continuation threshold SC (smaller than the first target value) has continued for a predetermined time or more (FIG. 4
From t6 to t7).

Brake Control The brake control is started when all of the following conditions are satisfied. The first start condition is that the engine is being controlled. The second start condition is that the left and right drive wheels 1FL, 1F
That is, the difference between the actual slip values of R is equal to or larger than a predetermined value (t2 in FIG. 4). The third start condition is that the vehicle speed is equal to or lower than a predetermined first vehicle speed V1. The fourth start condition is that a predetermined delay time described later has elapsed.

Prior to the start of the brake control, a switching delay 38 is set simultaneously with the start of the engine control in consideration of a response delay.
Is excited, the booster 11 is brought into a boosted state, the hydraulic pressure regulating valves 15L and 15R are at the relief position, and the on-off valves 16L and 16R are closed. Then, after the switching valve 38 is excited, when the actual slip value shows a predetermined deceleration (the time until the predetermined deceleration is shown is the delay time, and in FIG. 4, between t2 and t3). , Bra
Key control is started.

The brake control is performed on the left and right driving wheels 1FL, 1F.
By independently controlling the hydraulic pressure regulating valves 15L and 15R in such a manner that the actual slip value of each of R becomes the brake target value (second target value) STB (> STE). (Duty control).

The brake control is stopped when any one of the following conditions is satisfied. The first stop condition is when engine control is stopped. The second stop condition is when the vehicle speed becomes higher than a predetermined second vehicle speed V2 (V2> V1). The third stop condition is that the control signals for the left and right hydraulic pressure control valves 15L, 15R both indicate a pressure reduction and for a predetermined time (500 msec in the embodiment).
c) This is the time when the continuation is continued (t4 to t5 in FIG. 4).

The fourth stop condition is that the left and right brakes 7F
This is when the brake fluid pressures of L and 7FR are both zero. The fifth stop condition is when one of the switches S6 and S7 detects that the brake pedal 12 is depressed (the brake pedal 12 is depressed by the switches S6 and S7). Is detected, the start of the brake control is prohibited).

When the brake control is stopped, the switching valve 38 is operated as long as the engine control is performed, the hydraulic pressure regulating valves 15L and 15R are in the relief positions, and the on-off valve 1
6L and 16R are closed (the same state as the standby state until the start of the brake control). When the engine control is stopped or the brake pedal 12 is depressed, the switching valve 38 is demagnetized.

Next, a control example of the present invention will be described with reference to flowcharts shown in FIG. 5 and subsequent figures. In the following description, P indicates a step. FIG. 5 shows the overall flow. First, at P1, after the signals from the respective sensors and the like are input, at P2, the rotational speeds WSRL and WSRR of the left and right drive wheels 1FL, 1FR are averaged to obtain The vehicle speed VS is calculated.

At P3, a first target value STE for engine control and a second target value STB for brake control are determined in a known manner (STB> STE). In P4,
The slip value SFL of the left driving wheel 1FL is equal to its rotational speed W.
The vehicle speed VS is calculated by subtracting the vehicle speed VS from the SFL. Similarly, the slip value SFR of the right drive wheel 1FR is calculated by subtracting the vehicle speed VS from the rotation speed WSFR.

In the processing of P5 to P7, the larger one of the left and right drive wheel slip values SFL and SFR is set as the engine control slip value SA. In P8, it is determined whether the slip flag is 1 or not. When the slip flag is 1, it means that the slip control is being performed (at least the engine is being controlled). When the determination in P8 is NO, after the start determination of the engine control described later is made in P9, P1
At 0, an end determination described later is made.

If the determination in P8 is YES, the engine is controlled in P11, and then in P12,
It is determined whether the brake flag is "1". When the brake flag is "1", it means that the brake control is being performed. If the determination in P12 is NO, a brake start determination, which will be described later, is made in P13.
Move to. If the determination in P12 is YES, P
After the brake control is performed at 14, the program proceeds to P10.

FIG. 6 shows the contents of P9 in FIG. First,
In P21, by differentiating the vehicle speed, for example, the vehicle speed VS five times earlier than the current vehicle speed VS by sampling time.
By subtracting 5, 5, the vehicle body acceleration is calculated. Similarly, at P22, an engine speed change dRPM is calculated by differentiating the engine speed, and subsequently P
At 23, the drive wheel speed change rate dVWD is calculated by differentiating the drive wheel speed.

At P24, the first threshold value α for the engine speed change rate is determined based on the vehicle acceleration calculated at P21 while referring to Table 1.

[0044]

[Table 1]

At P25, the second threshold value β for the driving wheel speed change rate is determined based on the vehicle body acceleration calculated at P21 while referring to Table 2.

[0046]

[Table 2]

In P26, it is determined whether or not the engine speed change rate dRPM calculated in P22 is larger than a first threshold value α. If the determination in P26 is YES, in P27, it is determined whether the drive wheel speed change rate dVWD calculated in P22 is larger than the second threshold value β.

When the determination in P27 is YES, slip control is required (spin determination is performed). In this case, the slip flag is set to 1 in P28,
In P29, engine control is started, and in P30, preparation for starting brake control is made. Specifically, the preparation at P30 includes exciting the switching valve 38 to generate the brake hydraulic pressure in the master cylinder 8, and setting the hydraulic pressure adjusting valves 15L and 15R to the relief position. And closing the on-off valves 16L and 16R.

If the determination in P26 or P27 is NO, it means that the slip control is unnecessary (no spin), and the process returns to P1. Note that the control shown in FIG. 6 may be performed based on the drive wheel speed change rate of the left and right drive wheels that is larger (select high).

FIG. 7 shows the contents of P13 in FIG. First, at P31, it is determined whether the vehicle speed VS is equal to or lower than the first vehicle speed V1. If the determination in P31 is YES, the rotational speed difference DNL between the left and right drive wheels 1FL and 1FR is calculated in P32, and then in P33,
It is determined whether or not the difference DNL is equal to or greater than a predetermined value.
If the determination in P33 is YES, in P34,
It is determined whether or not a predetermined delay time has elapsed since the occurrence of the difference (t2 to t3 in FIG. 4). If the determination in P34 is YES, after the brake flag is set to 1 in P35, in P36, the hydraulic pressure adjusting valve 15L,
Brake control by controlling 15R is started. NO in any of the names P31, P33, and P34
In the case of, the process ends.

FIG. 8 shows the contents of P10 in FIG. First, in P41, it is determined whether or not the accelerator is fully closed. If the determination in P41 is YES, P42
After the slip control, that is, both the engine control and the brake control are stopped, the respective flags are reset to 0 in P43.

When the determination in P41 is NO, in P45, it is determined whether or not the actual slip value SA for engine control is equal to or smaller than the end threshold value SC. This P45
If the determination is YES, in P46, it is determined whether the state where SA is equal to or smaller than the end threshold value SC has continued for 1000 msec. YES in this determination of P46
In the case of, the program shifts to P42 and the slip control is stopped.

If the determination in P45 or P46 is NO, it is determined in P47 whether the vehicle speed VS is equal to or higher than the second vehicle speed V2. If the determination in P47 is YES, the process returns to P48. After stopping the brake control while gradually reducing the brake fluid pressure to prevent the occurrence of slip, the brake flag is reset to 0 in P49. The gradual suspension of the brake control is performed by reducing the pressure reduction signal to the hydraulic pressure regulating valves 15L and 15R at predetermined time intervals, but the degree of pressure reduction at one time increases. Restrictions are imposed.

If the determination in P47 is NO, it is determined in P50 whether the brake fluid pressures of the left and right drive wheel brakes 7FL and 7FR have both become zero. This P50
If the determination is YES, the brake control is stopped in P51, and then the flow shifts to P49. The estimation of the brake fluid pressure can be indirectly known by various methods already proposed, but a sensor for directly detecting the brake fluid pressure can also be used.

If the determination in P50 is NO, in P52, it is determined whether or not the control signals to the hydraulic pressure regulating valves 15L and 15R both indicate a pressure reduction.
If the determination is YES, it is determined whether or not the state where both the pressure reduction signals are 0 has continued for 500 msec. If the determination in P53 is YES, the brake control is stopped in P51. If the determination in P52 or P53 is NO, the process is terminated as it is (continuation of engine control and brake control).

Here, the brake switch S6 or S
7, if it is detected that the brake pedal 12 is depressed, the brake control is forcibly stopped by the interrupt processing for the flow chart.

Although the embodiment has been described above, the slip value is calculated not as the difference between the drive wheel and the driven wheel, but as a ratio, for example, as the drive wheel speed / driven wheel speed, or (drive wheel speed-driven wheel speed). ) / Driven wheel speed.
The brake fluid pressure for the brake control is the same as that of the booster 11.
Alternatively, it may be generated by a dedicated pump without using.

[Brief description of the drawings]

FIG. 1 is an overall system diagram showing an example of a vehicle to which the present invention is applied.

FIG. 2 is a sectional view showing a main part of the brake booster.

FIG. 3 is a diagram showing an input and output relationship with respect to a control unit.

FIG. 4 is a time chart schematically showing a control example of the present invention.

FIG. 5 is a flowchart showing a control example of the present invention.

FIG. 6 is a flowchart showing a control example of the present invention.

FIG. 7 is a flowchart showing a control example of the present invention.

FIG. 8 is a flowchart showing a control example of the present invention.

[Explanation of symbols]

 Reference Signs List 1FL, 1FR Front wheel (drive wheel) 1RL, 1RR Rear wheel (driven wheel) 2 Engine 7FL-7RR Brake 8 Master cylinder 9 Torque adjustment means 11 Brake booster (power booster) 12 Brake pedal 15L, 15R Hydraulic pressure adjusting valve 16L, 16R On-off valve 38 Switching valve (switching between negative pressure supply and atmospheric pressure supply) U Control unit S1 to S4 Wheel speed sensor S8 Engine speed sensor

Continuation of front page (72) Inventor Haruki Yata 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (72) Inventor Chizumi 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-2-151537 (JP, A) JP-A-1-186453 (JP, A) JP-A-60-197434 (JP, A) JP-A-63-113131 (JP, A) JP-A-1-170725 (JP, A) JP-A-3-70638 (JP, A) JP-A-60-215434 (JP, A) JP-A-63-263248 (JP, A) (58) (Int.Cl. ⁶ , DB name) B60K 41/20 F02D 29/02 311 F02D 45/00 314 F02D 45/00 345

Claims (3)

(57) [Claims] 1. A torque adjusting means for adjusting a torque applied to a driving wheel, a first detecting means for detecting a vehicle acceleration, a second detecting means for detecting a rate of change of an engine speed, and a change in a driving wheel speed. A third detecting means for detecting a rate, a vehicle body acceleration detected by the first detecting means, a change rate of an engine speed detected by the second detecting means, and a drive detected by the third detecting means. Based on the rate of change of the wheel speed, based on spin determination means for determining whether or not a spin that requires slip control of the drive wheel has occurred, and when the determination means has determined that a spin has occurred on the drive wheel. A slip control device that is activated and controls the torque adjusting device to reduce the torque applied to the drive wheels. 2. A first threshold value according to claim 1, wherein said spin determination means sets a first threshold value for an engine speed change rate based on a vehicle acceleration detected by said first detection means. Setting means, second threshold value setting means for setting a second threshold value for the drive wheel speed change rate based on the vehicle body acceleration detected by the first detection means, and detection by the second detection means. A first determining means for determining whether or not a change rate of the engine speed is greater than the first threshold value; and a drive wheel speed change rate detected by the third detecting means is a second threshold value. Second determination means for determining whether the value is greater than a value, and third determination for determining whether or not spin has occurred in the drive wheel according to the determination results of the first and second determination means. And means. 3. The method according to claim 2, wherein said slip control means controls the torque adjusting means so that an actual slip value of the drive wheel becomes a predetermined target value.