JPH08183438A - Braking pressure control device for vehicle - Google Patents

Abstract

PURPOSE: To suppress wheel lock immediately after the start of normal braking following braking operation by boosting braking pressure gradually toward the supply pressure of a master cylinder based on braking operation in the case of braking operation being detected when braking pressure is supplied to wheel cylinders. CONSTITUTION: Wheels FL-RR are provided with wheel cylinders (W/C) 6FL-6RR and wheel speed sensors 7FL-7RR. A braking control device 20 to which each wheel speed signal is inputted executes anti-skid control for suppressing wheel lock at the braking time of a vehicle and traction control (TRC control) for suppressing the accelerating slip of the wheels at the accelerating time of the vehicle. TRC control is continued in the case of an acceleration demand being larger than a deceleration demand and terminated in the case of the deceleration demand being larger than the acceleration demand. When braking operation is detected during TRC control, it is so controlled that braking oil pressure gradually rises after equalizing driving wheel oil pressure and driven wheel oil pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle brake pressure control device used, for example, for traction control during acceleration slip of a vehicle.

[0002]

2. Description of the Related Art In a brake pressure control device of this type, when an acceleration slip of a vehicle occurs, for example, a braking force is applied to a wheel cylinder of driving wheels by a brake pressure fed from a high pressure source (hydraulic pump). So-called traction control (hereinafter referred to as TRC control) is performed.

[0003]

However, in the above-mentioned conventional control device, various problems are likely to occur when the TRC control is ended as described above. That is, when the driver performs the braking operation during the TRC control, the deceleration lock occurs immediately after the start of the normal braking (including the ABS processing) due to the increase in the brake hydraulic pressure. Further, since a large amount of brake fluid used for TRC control is normally discharged to the outside, the balance of the brake pressure of each wheel may be lost at that time, which may hinder the brake pressure control.

The present invention has been made in view of the above problems, and an object thereof is to eliminate various problems that have occurred in the past and always execute appropriate brake pressure control. (EN) Provided is a vehicle brake pressure control device.

[0005]

In order to achieve the above object, the invention as set forth in claim 1 is a wheel of a master cylinder and a wheel for optimizing the motion characteristics of the vehicle except when the driver performs a braking operation. A brake pressure control unit that cuts off a path connecting the cylinder and applies a brake pressure from a high pressure source to the wheel cylinder, a braking operation detection unit that detects a braking operation by a driver, and the brake pressure control unit. When a braking operation of the driver is detected by the braking operation detection means when the brake pressure is applied to the wheel cylinder,
The gist is that it is provided with a control ending means for gradually increasing the brake pressure toward the supply pressure of the master cylinder based on the braking operation.

According to a second aspect of the present invention, in the first aspect of the present invention, the control termination means, before gradually increasing the brake pressure of the wheel cylinder, the wheel cylinder and the wheel of another wheel. The cylinders are communicated with each other so that the brake pressures of both wheel cylinders are equalized.

According to the invention described in claim 3, in the invention described in claim 1 or 2, based on the braking operation by the driver,
First determining means for determining the degree of the driver's deceleration request,
A second determination means for determining the degree of the driver's acceleration request based on the driver's acceleration request, wherein the control termination means is: when the driver's braking operation and acceleration operation occur simultaneously,
If the degree of acceleration request is greater than the degree of deceleration request,
It is configured to prohibit the control end of the brake pressure.

According to the invention described in claim 4, claims 1 to 3 are provided.
In any one of the inventions, the vehicle body speed detecting means for detecting or estimating the vehicle body speed, and the upper limit value of the brake pressure controlled by the brake pressure control means are set according to the vehicle body speed detected by the vehicle body speed detecting means. Pressure upper limit value setting means.

According to a fifth aspect of the invention, in the invention of the fourth aspect, the pressure upper limit value setting means is configured to set the upper limit value larger as the vehicle body speed becomes lower.

[0010]

According to the first aspect of the present invention, the brake pressure control means sets the path connecting the master cylinder and the wheel cylinder of the wheel to optimize the motion characteristics of the vehicle except when the driver performs a braking operation. At the same time as shutting off, brake pressure from a high pressure source is applied to the wheel cylinder. The braking operation detecting means detects a braking operation by the driver. The control ending means supplies the master cylinder based on the braking operation when the braking operation detecting means detects the braking operation of the driver while the brake pressure is being applied to the wheel cylinders by the braking pressure control means. The brake pressure is gradually increased toward the pressure.
In this case, the wheel lock immediately after the start of the normal braking accompanying the braking operation is suppressed, and the stable vehicle operation after the end of the TRC control is secured.

According to the second aspect of the present invention, the control termination means connects the wheel cylinder to the wheel cylinders of other wheels before gradually increasing the brake pressure of the wheel cylinders so that both wheels can communicate with each other. Make the cylinder brake pressure equal. In other words, in a vehicle that performs TRC control, the brake pressure is started to increase after the brake pressure of the drive wheels of the vehicle and the brake pressure of the driven wheels of the vehicle become equal, so that the balance of the brake pressure is good. Held in a state. Further, the time until the pressure increase is started is shortened as compared with the normal method of starting the pressure increase after discharging all the brake oil used during the TRC control (after setting the drive wheel hydraulic pressure = 0).

According to the third aspect of the present invention, the first determining means determines the degree of the driver's deceleration request based on the driver's braking operation, and the second determining means determines the driver's deceleration request. The degree of the driver's acceleration request is judged based on the acceleration request. Specifically, the degree of the acceleration request is detected from the accelerator opening, the shift position of the transmission, the vehicle speed, etc., and the degree of the deceleration is detected from the supply pressure of the master cylinder, the depression amount of the brake pedal, and the like. Then, the control ending means prohibits the control end of the brake pressure when the degree of the acceleration request is larger than the degree of the deceleration request when the driver performs the braking operation and the acceleration operation at the same time.

That is, for example, both the acceleration request and the deceleration request are detected when performing both pedal depressing operations (both the accelerator pedal and the brake pedal) when starting on a slope.
Further, on a low μ road, the driver may perform a brake operation (deceleration request) during TRC control (acceleration request). In these cases, if the acceleration request> the deceleration request, the brake pressure control (TRC control) is continued, and if the acceleration request <the deceleration request, the brake pressure control (TRC control) can be ended. According to this processing, even though the TRC control is necessary (that is, contrary to the driving state of the vehicle and the driver's intention), the TRC control is not terminated.

According to the invention described in claim 4, the vehicle body speed detecting means detects or estimates the vehicle body speed, and the pressure upper limit value setting means controls the brake by the brake pressure control means according to the vehicle body speed. Set the upper pressure limit. That is, for example, the occurrence situation of the acceleration slip of the vehicle changes depending on the vehicle body speed, so that the brake pressure required during the TRC control also changes depending on the vehicle body speed. Therefore, by setting the upper limit value of the brake pressure according to the vehicle body speed as in this configuration, it becomes possible to control the brake pressure that reflects the vehicle body speed.

According to the fifth aspect of the present invention, the pressure upper limit setting means sets the upper limit to be larger as the vehicle body speed is lower. That is, a sudden initial slip is likely to occur in a low speed range such as when the vehicle starts and it is preferable to set the upper limit value of the brake pressure to be high. Moreover, the possibility of sudden slippage in the high-speed range is small, and by setting the upper limit value of the brake pressure to a lower value, the TRC control is completed even when the TRC control ends.
The control oil is discharged quickly.

[0016]

【Example】

(First Embodiment) A first embodiment in which the present invention is embodied in a traction control device for a front wheel drive type four-wheel vehicle will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the outline of a traction control device according to this embodiment. That is, in this embodiment, the left and right front wheels FL and FR are set as the driving wheels, and the left and right rear wheels R are
L and RR are driven wheels. This device realizes traction control by brake pressure control by applying a braking force to the drive wheels even when the driver is not operating the brake. In this embodiment, a so-called master self-priming master return pump is used as the hydraulic pump.

As shown in FIG. 1, the wheels FL to R of the vehicle are shown.
R is a wheel cylinder (hereinafter referred to as W / C) 6FL, 6FR, 6R for giving a braking force to each wheel FL to RR.
L, 6RR and wheel speed sensors 7FL, 7FR, 7RL, 7RR for detecting the rotation speed of the wheels are provided, respectively.
As the wheel speed sensors 7FL to 7RR, electromagnetic pickup type sensors or photoelectric conversion type sensors are used. In addition, the left and right front wheels that are drive wheels (hereinafter, simply referred to as drive wheels)
FL and FR rotate by receiving driving force from an internal combustion engine 1 connected via a transmission 2 and a differential gear 3. The internal combustion engine 1 is provided with a sensor group 4 for detecting operating conditions such as engine speed, intake air amount, cooling water temperature, throttle valve opening (throttle opening) and the like. The detection signals from these sensor groups 4 are input to the E / G control device 10, and the E / G control device 10 controls the fuel injection amount and ignition timing of the internal combustion engine 1 based on the detection signals.

Further, the detection signals from the wheel speed sensors 7FL to 7RR provided on the wheels FL to RR are input to the braking control device 20. The braking control device 20 includes an anti-skid control (hereinafter, referred to as ABS control) that suppresses a wheel lock generated during vehicle braking, and a traction control (hereinafter, referred to as an ABS control) that suppresses an acceleration slip of a wheel generated during vehicle acceleration.
TRC control) is executed. In this case, the braking control device 20 provides a hydraulic path from a master cylinder (hereinafter referred to as M / C) 22 that discharges brake fluid in accordance with a depression operation of a brake pedal 21 to W / C6FL to 6RR of each wheel FL to RR. It controls various solenoid valves in the provided hydraulic circuit 30. In addition to the detection signals from the wheel speed sensors 7FL to 7RR, the braking control device 20 has a brake switch 23 that is turned on when the brake pedal 21 is operated.
Or W / of the drive wheels FL, FR provided in the hydraulic circuit 30
It operates by receiving a detection signal from a pressure sensor or the like (not shown) that detects the hydraulic pressures of C6FL and 6FR.

The E / G control device 10 and the braking control device 20 are each composed of a microcomputer mainly composed of a CPU, a ROM, a RAM and the like. A communication device for transmitting and receiving control data is provided. In this embodiment, T
The RC control corresponds to the brake pressure control, and the braking control device 2
0 constitutes a brake pressure control means, a control termination means, a first judgment means, a second judgment means, a vehicle body speed detection means, and a pressure upper limit value setting means. The brake switch 23 constitutes a braking operation detecting means.

Next, the hydraulic circuit 30 will be described with reference to FIG. In FIG. 2, the hydraulic port 22a of the M / C22,
Brake fluid pressure-fed from the same M / C 22 is supplied to the left front wheel FL and the right rear wheel RR, and the right front wheel FR and the left rear wheel RL.
Two hydraulic paths 31 and 32 for supplying the respective oil pressures to each of them are connected. The hydraulic circuit 30 is configured by a so-called four-wheel independent control system (four-channel system) that controls the brake pressure of each wheel for each four wheels. M / C
22 and the hydraulic path between each W / C6FL to 6RR,
Pressure increase control valve 33FL, 33FR, 33 consisting of 2-position solenoid valve
Pressure reducing control valve 34F consisting of RL, 33RR and 2-position solenoid valve
L, 34FR, 34RL, 34RR and pressure reducing control valves 34FL-3
Reservoirs 35 and 36 for temporarily storing the brake fluid discharged from the 4RR are provided. Each of the control valves is in the illustrated state during normal braking, and during ABS control or TRC control, the control valve is controlled to either the pressure increasing / holding / pressure reducing state in accordance with the control mode set by the braking control device 20. To be done.

That is, in the pressure increasing mode, the pressure increasing control valve 3
3FL to 33RR are controlled to the communicating position (the position shown), and the pressure reducing control valves 34FL to 34RR are controlled to the shut-off position (the position shown),
Brake fluid is supplied to each W / C 6FL to 6RR. Also,
In the holding mode, the pressure increase control valves 33FL to 33RR and the pressure reduction control valves 34FL to 34RR are both controlled to the shutoff position, and the W / C6
The supply of brake fluid to FL-6RR is stopped. further,
In the pressure reduction mode, the pressure increase control valves 33FL to 33RR are controlled to the shutoff position, and the pressure reduction control valves 34FL to 34RR are controlled to the communication position,
Brake fluid from W / C6FL to 6RR reservoirs 35, 36
Is discharged to.

The reservoirs 35, 36 have the same reservoir 35,
Hydraulic pump 3 for sucking up brake fluid in 36
7, 38 (high-pressure supply source) are connected, and the hydraulic pumps 37, 38 are driven by a pump motor 39. Accumulators 40, 41 that suppress the pulsation of the internal hydraulic pressure are provided on the discharge sides of the hydraulic pumps 37, 38. The accumulators 40, 41 serve as hydraulic paths on the drive wheel side (M of the pressure increase control valves 33FL, 33FR). / C22 side). The hydraulic pumps 37 and 38 are brake TRCs described later.
It is driven via the pump motor 39 when the control is executed.

Further, on the drive wheels FL, FR side of the hydraulic circuit 30, the master cylinder cut for connecting or disconnecting the hydraulic paths between the M / C 22 and the pressure increasing control valves 33FL, 33FR. Valves (hereinafter referred to as SM valves) 42 and 43 are provided. The shut-off positions of the SM valves 42 and 43 are the pressure increasing control valves 33FL and 33FR.
When the hydraulic pressure on the side of the M / C 22 becomes equal to or higher than the upper limit of the hydraulic pressure on the side of the M / C 22 by a predetermined value, the hydraulic pressure is communicated to increase the pressure of the control valve 33
This is the position set by the relief valves 44 and 45 that limit the hydraulic pressures on the FL and 33FR sides to below their upper limit values.

In the hydraulic path that bypasses the SM valves 42 and 43, the hydraulic pressure on the M / C 22 side is increased by the pressure increasing control valves 33FL and 33FL.
When it becomes larger than the hydraulic pressure on the FR side, it is connected to M / C2.
Relief valves 46 and 47 are arranged to supply the pressure oil discharged from No. 2 to the pressure increase control valves 33FL and 33FR. SM
The valves 42 and 43 are two-position solenoid valves, and are switched from a communication position (position shown in the figure) to a cutoff position by an ON (energization) signal from the braking control device 20 during TRC control.

In the hydraulic paths 31 and 32, when the brake TRC control is executed, the hydraulic pump 3 is transferred from the reservoir tank 50 provided above the M / C 22 via the M / C 22.
Oil supply paths 31a and 32a for directly supplying brake oil to 7, 38 are provided. These oil supply routes 3
Reservoir cut valves (hereinafter, referred to as SR valves) 48 and 49 that connect or block the paths are arranged on the 1a and 32a. The SR valves 48, 49 are two-position solenoid valves, which are switched from the cut-off position (position shown in the figure) to the communication position in response to an ON (energization) signal from the braking control device 20 during TRC control.

When a slip (acceleration slip) occurs on the drive wheels FL, FR during vehicle acceleration, the braking control device 20 starts TRC control as brake pressure control described later in order to suppress the acceleration slip. That is, the SM valves 42 and 43 and the SR valves 48 and 49 in the hydraulic circuit 30 are turned on (energized), and the pressure increase control valves 33FL to 33RR and the pressure reduction control valves 34FL to 34RR are turned on and off (energized / non-energized). By doing so, braking force is applied to the drive wheels FL, FR. Also, the braking control device 20 suppresses the output torque of the internal combustion engine 1 by outputting a fuel injection amount reduction or ignition timing retard command to the E / G control device 10 when an acceleration slip occurs. E / G / TRC
The control is executed (the details are omitted in this description, and the following T
Speaking of RC control, it means brake TRC control).

Next, the operation and effect peculiar to this embodiment will be described with reference to the drawings. Here, FIG. 3 and FIG. 4 are flowcharts showing a TRC control routine executed by the braking control device 20, and the specific contents of the TRC control will be described below with reference to the flowchart (in the following description, the control will be described. Braking control device 20 as a main body
Will be omitted).

Now, when the TRC control routine is started, first in step 100 of FIG.
Wheel speed VWFL, VW of each wheel from the detection results of FL to 7RR
Calculate FR, VWRL, VWRR (hereinafter VWFL, VWFR
Is the driving wheel speed, and VWRL and VWRR are the driven wheel speeds).
In the following step 101, the left and right driven wheel speeds VWRL, V
Calculate the estimated vehicle speed VT0 from the average of WRR (VT0 =
(VWRL + VWRR) / 2). Further, in step 102, the actual acceleration slip amounts SFL, SFR of the drive wheels FL, FR are calculated from the estimated vehicle body speed VT0 and the drive wheel speeds VWFL, VWFR.
Is calculated, and in step 103, the estimated vehicle body speed V is also calculated.
Target slip amount S from T0 and drive wheel speeds VWFL and VWFR
Calculate tFL and StFR.

Thereafter, in step 104, the acceleration request χA
Is calculated, and in the subsequent step 105, the deceleration request χB is calculated. Here, the acceleration request χ A is calculated according to the accelerator opening at that time, for example, using the relationship of FIG. Further, the deceleration request χ B is calculated according to the M / C oil pressure at that time using the relationship of FIG. 6, for example. Here, the M / C oil pressure is M / C2
It may be detected by the M / C pressure sensor provided in the second discharge side path, or may be estimated by using an arithmetic expression that approximates the rising curve of the M / C oil pressure. Alternatively, it may be estimated from the estimated vehicle deceleration (one-time differential value of the estimated vehicle speed VT0). That is, since the hydraulic pressure acts on the driven wheels, the M / C hydraulic pressure can be detected from the deceleration.

Then, in step 106, it is determined whether the ABS control is permitted or prohibited based on the estimated vehicle speed VT0. Specifically, the estimated vehicle speed VT0 is 9 km
When the value changes from less than / h to 9 km / h or more, the ABS control flag FABS is set to "1" to allow the ABS control. Further, when the estimated vehicle speed VT0 changes from more than 5 km / h to less than 5 km / h, the ABS control flag FABS is reset to "0" in order to prohibit the ABS control. In other words, in the extremely low speed range of the vehicle, for example, the detection accuracy of the wheel speed sensors 7FL to 7RR may be significantly reduced, which may lead to erroneous control of the ABS control.
Prohibit BS control.

After that, in step 107, it is judged whether or not the TRC control is being performed. If the TRC control is not being performed, the process proceeds to step 108, and if the TRC control is being performed, the step 10 is performed.
Proceed to 9. When the process proceeds to step 108 without being in the TRC control, it is determined whether or not the start condition of the TRC control is satisfied in the step 108, and when the process is in the TRC control and the process proceeds to step 109, the step 109 is performed. It is determined whether or not the condition for ending the TRC control is satisfied.

Here, the determination of the start condition of the TRC control is as follows.
It is determined by determining whether the actual acceleration slip amounts SFL, SFR are larger than a predetermined control start determination value SS (SFL> S).
If S or SFR> SS, the condition is satisfied). Further, the determination of the termination condition of the TRC control is performed by determining whether or not the acceleration slip amounts SFL, SFR are smaller than a predetermined control termination determination value SE, and the drive wheels FL. The determination is made by determining whether the W / C oil pressures PBFL and PBFR on the FR side are "0" (if SFL <SE and SFR <SE, and if PBFL = 0 and PBFR = 0,
Satisfaction of conditions). It should be noted that the condition for ending the TRC control may include that the above conditions continue for a predetermined time.

If step 108 is answered in the negative, T
RC control is deemed unnecessary, and the process returns to step 100. Then, thereafter, the above processing is repeatedly executed until the TRC control start condition (step 108) is satisfied.

When step 108 is positively determined or when step 109 is negatively determined, the routine proceeds to step 110, where the acceleration request χ of step 104 is requested.
A is compared with the deceleration demand χB in step 105.
In this case, if acceleration demand χ A ≤ deceleration demand χ B, then TR
In order to permit the end of the C control (brake pressure control), the routine proceeds to step 111, and if the acceleration request χ A> the deceleration request χ B, the routine proceeds to step 112 of FIG. 4 in order to continue the TRC control (brake pressure control).

That is, step 109 or step 11
If 0 is affirmatively determined, the process proceeds to step 111, and TR
The C control end processing is executed. In step 111, the SM valves 42, 43 and the SR valves 48, 49 are turned off (non-energized) and the driving of the hydraulic pumps 37, 38 is stopped.

When the determination at step 110 is negative, the TRC control according to the acceleration slip state of the vehicle is executed at subsequent steps 112 to 119 of FIG. For more information,
At step 112, it is judged if the ABS control flag FABS is "0". At this time, FABS =
If it is 0, the upper limit value PRMAX of the brake hydraulic pressure at that time is set to "80 atm" in step 113, and if FABS = 1, the hydraulic pressure upper limit value PRMAX is set to "20 atm" in step 114. That is, a sudden initial slip is likely to occur in an extremely low speed range (ABS control prohibition range) such as when the vehicle starts, and the hydraulic pressure upper limit P is set to prevent this initial slip.
RMAX is set higher. Further, in a vehicle speed range higher than that (ABS control permission range), since the vehicle is running in high gear, the possibility of sudden slippage is small, and the hydraulic pressure upper limit PRMAX is set to be low.

Then, in step 115, the target slip amounts StFL, StFR and the actual acceleration slip amounts SFL, SFR are
Deviations ΔSFL (= StFL-SFL), ΔSFR (= StFR
-SFR) is calculated, and the target hydraulic pressure P of the left and right drive wheels FL, FR is controlled by PI control based on the deviations ΔSFL, ΔSFR.
Calculate RFL and PRFR.

Then, at step 116, it is judged if the sum of the target hydraulic pressures PRFL, PRFR of the left and right driving wheels FL, FR is larger than the hydraulic pressure upper limit value PRMAX calculated at steps 113, 114. In this case, PRFL + PRFR>
If PRMAX is reached and step 116 is affirmatively determined, the sum of the drive wheel hydraulic pressures (PRFL + PRFR) is the hydraulic pressure upper limit value PRMAX.
In step 117, the following equation (1),
The target hydraulic pressures PRFL and PRFR are changed using the equation (2).

PRFL = PRMAX.PRFL / (PRFL + PRFR) (1) PRFR = PRMAX.PRFR / (PRFL + PRFR) (2) On the other hand, PRFL + PRFR ≦ PRMAX and step 117
If NO is determined, the process directly proceeds to step 118.
In step 118, the SM valves 42, 43 and the SR valves 48, 49 are turned on (energized) and the pressure is increased in order to control the W / C oil pressures of the left and right drive wheels FL, FR to the target oil pressures PRFL, PRFR. The control valves 33FL, 33FR and the pressure reducing control valves 34FL, 34FR are operated to either the pressure increasing / holding / pressure reducing state. Then, in step 119, the actual W /
The C hydraulic pressures PBFL and PBFR are detected, and this routine ends. Here, in the present embodiment, the W / C oil pressures PBFL and PBFR are obtained using the detection result of a pressure sensor (not shown).
It is also possible to estimate using an arithmetic expression that approximates the W / C oil pressure rise curve.

Next, the operation of the above routine will be described more specifically with reference to the timing chart of FIG.
Note that FIG. 7 shows an example when the vehicle starts. In FIG. 7, when the vehicle starts at time t1, the drive wheel speed VWFL,
VWFR sharply increases with respect to the estimated vehicle speed VT0. As a result, the acceleration slip amount suddenly increases, and the TRC control is started at time t2 when the acceleration slip amount exceeds the control start determination value SS (YES in step 108 of FIG. 3).

Further, during the time t1 to t3 when the estimated wheel speed VT0 is 9 km / h or less, the ABS control flag FABS
Is maintained at "0" and the hydraulic pressure upper limit PRMAX is set to "80".
"atm". Therefore, the sum of the target hydraulic pressure (PRFL
+ PRFR) is kept below "80 atm". In this case, the initial slip that occurs when the vehicle starts is suppressed within the range of the hydraulic pressure upper limit value PRMAX (= 80 atm).

At time t3, the estimated wheel speed VT0 exceeds 9 km / h, the ABS control flag FABS is set to "1", and the hydraulic pressure upper limit PRMAX is switched to "20 atm". Therefore, after time t3, the sum of the target hydraulic pressures (PRFL + PRFR) is “20 atm”.
It becomes the following. In this case, the acceleration slip is suppressed within the range of the hydraulic pressure upper limit value PRMAX (= 20 atm).

On the other hand, in the period from time t1 to t3,
Even if the brake switch 23 is stepped on and a deceleration request is made, the ABS control is prohibited. In this case, the drive wheel hydraulic pressure due to the TRC control becomes high, but switching to the ABS control is prohibited, so that the M / C 22 is damaged when pumping back a large amount of brake fluid used in the TRC control. There is no such thing.

Further, after the time t3, the brake switch 2
When 3 is stepped on to generate a deceleration request, switching from TRC control to ABS control is permitted. At that time, TRC
Drive wheel hydraulic pressure due to control is relatively low (20 atm or less)
Since the amount of brake oil is pumped back at the end of TRC control, damage to the M / C 22 is prevented, and the brake oil is quickly discharged.

As described above, in the brake pressure control system of the present embodiment, the degree of acceleration request and the degree of deceleration request are compared,
When the acceleration request is larger, the switching from the TRC control to the ABS control is prohibited, and when the deceleration request is larger, T
Switching from RC control to ABS control is permitted (step 110 in FIG. 3). If the above switching is permitted (YES in step 110), TR
The C control termination process is executed (step 111 in FIG. 3).

In short, for example, both pedal depressing operations (both accelerator pedal and brake pedal depressing) when starting on a slope.
When performing, the acceleration request and the deceleration request are both detected. In this case, if TRC control or ABS control is not performed according to the degree of these demands, excessive brake fluid will flow into the hydraulic circuit (including W / C6FL to 6RR), causing damage to the M / C22 and reducing braking performance. There is a risk of lowering. However, in the present embodiment, if the acceleration request> the deceleration request, the TRC control is continued, and if the acceleration request <the deceleration request, the TRC control is terminated and the normal brake (ABS control) is switched to. As a result, it is possible to realize the brake pressure control that suits the driver's wishes, and it is possible to prevent problems such as deterioration in braking performance and damage to the M / C 22.

Further, in the present control device, the permission / prohibition of the ABS control is determined according to the vehicle speed (step 10 in FIG. 3).
6) In the extremely low speed range where the ABS control is prohibited, the upper limit value of the brake pressure of the TRC control is set high, and in the areas other than the extremely low speed range where the ABS control is permitted, the upper limit value of the brake pressure of the TRC control is set lower ( Steps 113 and 11 of FIG.
4). That is, when the vehicle body speed changes, the occurrence state of acceleration slip changes, and the brake pressure required for the TRC control at that time also changes. Therefore, by setting the upper limit value of the brake pressure according to the vehicle speed as in this configuration, it is possible to realize the brake pressure control that reflects the vehicle speed.

Next, T accompanying the brake operation by the driver
The RC control end processing will be described. This corresponds to the content of step 111 in FIG. 3 described above. First, a specific operation of the process will be described with reference to the timing chart of FIG. It should be noted that FIG. 9 is a timing chart showing an ending operation of TRC control which is generally used conventionally.

That is, before time t11 in FIG.
The C control is being executed, and the pressure increasing control valves 33FL, 33FR and the pressure reducing control valves 34FL, 34FR on the drive wheels FL, FR side are
It is controlled in one of the pressure increasing / holding / pressure reducing control modes according to the acceleration slip amount at each moment. Therefore, before time t11, the W / C hydraulic pressure of the drive wheels FL and FR (hereinafter, referred to as drive wheel hydraulic pressure) is the control hydraulic pressure by the TRC control. Also, since there is no brake operation, the driven wheel R
The W / C oil pressures of L and RR (hereinafter referred to as driven wheel oil pressures) are "0".

Then, at time t11, the brake pedal 21
When is depressed (STP =
(Indicated by ON), the control mode of the drive wheels FL, FR is set to the pressure reduction mode, and the control mode of the driven wheels RL, RR is set to the pressure reduction mode. That is, the drive wheels FL, F
R and driven wheels RL, RR control valves 33FL to 33RR, 3
4FL to 34RR are all turned on (energized), and at this time, W / C6FL of the drive wheel FL and W / C of the driven wheel RR of one hydraulic system
The drive wheel F of the other hydraulic system is connected with the C6RR communicating.
The R W / C6FR and the driven wheel RL W / C6RL are communicated. Therefore, in both systems, the drive wheel hydraulic pressure and the driven wheel hydraulic pressure instantly become equal pressures.

When the drive wheel hydraulic pressure and the driven wheel hydraulic pressure become equal at time t12, the SM valve 42 (43) that has been on (energized) until then is turned off (energized). Further, the hydraulic pressure is maintained for a predetermined time on both the drive wheels FL and FR sides and the driven wheels RL and RR sides, and thereafter the control mode of each wheel is set so as to gradually increase each hydraulic pressure. In this case, the drive wheel hydraulic pressure (front wheel hydraulic pressure) is the driven wheel hydraulic pressure (rear wheel hydraulic pressure).
The brake hydraulic pressure is controlled to be higher than the above.

On the other hand, in FIG. 9, STP = O at time t21.
When it becomes N, the pressure reducing process for making the drive wheel oil pressure "0" is performed thereafter, and the drive wheel oil pressure is "0" at time t22.
become. At this time, the driven wheel hydraulic pressure increases as the hydraulic pressure of the M / C 22 increases. Then, at time t22, the control mode of the drive wheels is fixed to the pressure increasing mode, and the drive wheel hydraulic pressure rises from "0". After that, when a predetermined deceleration slip occurs on the drive wheels, the ABS control is started. That is, in the conventional general TRC control termination process, the brake fluid on the drive wheel side used for TRC control is completely discharged to the outside, and the drive wheel hydraulic pressure becomes "0", and then the hydraulic pressure from the M / C 22 is reached. Is added.

According to the processing shown in FIG. 8, the problem of the conventional processing shown in FIG. 9 is solved. That is,
In the conventional termination process shown in FIG. 9, when the TRC control is terminated, the braking force is increased after the drive wheel hydraulic pressure is reduced to “0”, so the period until the drive wheel hydraulic pressure is reduced (time t21 in FIG. 9). There is a problem in that the braking performance is deteriorated from t22 to t22). However, in the termination process of the present embodiment shown in FIG. 8, the drive wheel hydraulic pressure is not reduced to "0", so that the reduction in braking performance can be minimized. Further, in FIG. 9, the hydraulic pressure of each wheel suddenly rises while the pressure increasing mode is fixed, so that the wheel lock is likely to occur immediately after the start of braking, but according to FIG. 8, the hydraulic pressure gradually rises.
The occurrence of wheel lock is prevented. Further, in FIG. 9, the difference between the driving wheel hydraulic pressure and the driven wheel hydraulic pressure is large at any timing, and the vehicle may be unstable due to disturbance in the front-rear distribution of the braking force. However, according to FIG. 8, the difference in hydraulic pressure is suppressed, and the front-rear distribution of the braking force is maintained in a desired state.

FIG. 10 shows a processing routine executed to realize the above processing, and this routine is executed by the braking control device 20 at a predetermined interrupt timing. FIG.
0, in step 200, it is determined whether or not STP = ON, and only when STP = ON, the subsequent steps 210 to 240 are executed. In this case, step 21
At 0, pressure reduction on the drive wheel side and the driven wheel side is performed, and then,
Until the next step 220 is established, that is, until the drive wheel hydraulic pressure and the driven wheel hydraulic pressure become equal to each other, the above step 210 is performed.
To continue. Here, as described above, STP =
When the drive wheels FL, FR and the driven wheels RL, RR are both in the pressure reducing mode when turned on, the drive wheel hydraulic pressure and the driven wheel hydraulic pressure become equal pressures instantaneously, so when a predetermined minute time elapses after STP = ON, step 220 is affirmatively determined.

Then, in step 230, the drive wheels F
The control duty of the actuators (each control valve, SM valve, etc.) on the L, FR side and the driven wheels RL, RR side is calculated. Specifically, using the map of FIG. 11, it is calculated according to the elapsed time from the establishment of step 220 (the elapsed time from time t2). Here, the control duty is set so that the hydraulic pressure on the front wheel (driving wheel) side is higher than the hydraulic pressure on the rear wheel (driven wheel) side. The brake pressure with a duty ratio of 100% corresponds to the M / C hydraulic pressure. Then, in step 240, it is determined whether the duty ratio has reached 100%,
When the duty ratio = 100%, the termination process is terminated. According to the processing of steps 230 and 240, the brake pressure gradually increases as the control duty increases.

As described above, according to the above-described TRC control ending process, the wheel lock is suppressed immediately after the start of the normal brake due to the braking operation, and the balance of the brake pressure of each wheel is maintained in a good state. . As a result, proper brake pressure control can always be executed.

The present invention can be embodied in the following modes other than the above embodiment. (1) In the above embodiment, the TRC control is prioritized over the normal braking (ABS control) when the acceleration request is greater than the deceleration request.
The vehicle braking direction may be controlled by the E / G / TRC control while continuing the control. In this case, the braking performance of the vehicle can be sufficiently secured.

(2) In the above embodiment, the operation of FIG.
Although it is described as a part of the routine (step 111), the end determination of the TRC control as shown in FIG.
It is also possible to embody the operation of FIG. 8 in a device without 0). In this case, even if the device permits the termination of the TRC control simply by the ON signal of the brake switch, the conventional problems at the start of the normal braking can be solved.

(3) In the above embodiment, the brake pressure control is embodied by the TRC control that suppresses the acceleration slip of the driving wheels, but this can be changed. For example, it may be embodied in a brake pressure control configured to apply a braking force to a wheel different from the driving wheel when the vehicle is driven (other than during braking).

(4) In the above embodiment, the hydraulic circuit is embodied using the master self-priming master return hydraulic pump, but it may be embodied using the reservoir self-priming reservoir return hydraulic pump.

[0062]

According to the invention described in claim 1, it is possible to suppress the wheel lock immediately after the start of the normal brake due to the braking operation, and to secure a stable vehicle operation after the TRC control is completed. As a result, it is possible to eliminate various problems that have occurred in the past and always perform appropriate brake pressure control.

According to the second aspect of the invention, the balance of the brake pressure can be maintained in a good state.
According to the third aspect of the invention, the brake pressure control can be executed according to the result of comparison between the degree of the acceleration request and the degree of the deceleration request, and the control that is more in line with the driver's intention can be realized. You can

According to the invention described in claims 4 and 5, it is possible to realize the brake pressure control adapted to the vehicle speed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a traction control device according to an embodiment.

FIG. 2 is a configuration diagram of a hydraulic circuit.

FIG. 3 is a flowchart showing a TRC control routine.

FIG. 4 is a flowchart showing a TRC control routine following FIG.

FIG. 5 is a diagram for calculating an acceleration request.

FIG. 6 is a diagram for calculating a deceleration request.

FIG. 7 is a timing chart corresponding to the routines of FIGS. 3 and 4.

FIG. 8 is a timing chart showing an operation at the end of TRC control.

FIG. 9 is a timing chart showing the operation of a general device.

FIG. 10 is a flowchart showing TRC control termination processing.

FIG. 11 is a diagram for calculating a duty ratio.

[Explanation of symbols]

6FL to 6RR ... Wheel cylinders, 20 ... Brake pressure control means, control termination means, first determination means, second determination means, vehicle body speed detection means, braking control device as pressure upper limit setting means, 22 ... Master cylinder , 23 ... Brake switches as braking operation detecting means, 37, 38 ... Hydraulic pumps as high-pressure generation sources, FR, FL ... Left and right front wheels (driving wheels), RR, RL ... Left and right rear wheels (driven wheels).

Claims (5)

[Claims] 1. Except during braking operation by a driver,
In order to optimize the motion characteristics of the vehicle, a path connecting the master cylinder and the wheel cylinder of the wheel is cut off, and a brake pressure control means for applying a brake pressure from a high pressure source to the wheel cylinder, and a braking operation by a driver And a braking operation detecting means for detecting the braking pressure applied to the wheel cylinder by the brake pressure control means, if the braking operation of the driver is detected by the braking operation detection means, A brake pressure control device for a vehicle, comprising: a control ending means for gradually increasing a brake pressure toward a supply pressure of a master cylinder based on an operation. 2. The control ending means communicates the wheel cylinder of another wheel with the wheel cylinders of other wheels before gradually increasing the brake pressure of the wheel cylinder to equalize the brake pressure of both wheel cylinders. The brake pressure control device for a vehicle according to claim 1. 3. A first judging means for judging the degree of deceleration request of the driver based on the braking operation of the driver, and a second judging means for judging the degree of acceleration request of the driver based on the acceleration request of the driver. When the driver's braking operation and acceleration operation occur at the same time, the control termination means prohibits termination of the brake pressure control if the degree of acceleration request is greater than the degree of deceleration request. The vehicle brake pressure control device according to claim 1 or 2. 4. A vehicle body speed detecting means for detecting or estimating a vehicle body speed, and a pressure upper limit value for setting an upper limit value of the brake pressure controlled by the brake pressure control means in accordance with the vehicle body speed detected by the vehicle body speed detecting means. A setting means is provided.
4. The vehicle brake pressure control device according to any one of 3 to 3. 5. The vehicle brake pressure control device according to claim 4, wherein the pressure upper limit setting means sets the upper limit to be larger as the vehicle body speed is lower.