JP4185791B2 - Braking control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a braking control device that controls braking of a vehicle.
[0002]
[Prior art]
Conventionally, as described in JP-A-8-34331, as a braking control device that controls braking of a vehicle, a brake system that independently applies a braking force by a wheel cylinder installed on each wheel is provided, It is known that when the supply hydraulic pressure of the wheel cylinder in one of the two driving wheels connected by the differential device is being reduced, the pressure increase to the other wheel cylinder is delayed. This device is intended to prevent the occurrence of vibration due to the mutual interference of torque between the drive wheels to ensure a stable braking operation.
[0003]
[Patent Document 1]
JP-A-8-34331
[Problems to be solved by the invention]
By the way, in such an apparatus, when the wheel acceleration is large, there is a case where erroneous decompression suppression control is performed to reduce a decompression point at which the fluid pressure is decompressed. This erroneous decompression suppression control is control that suppresses entry into the decompression mode by lowering the decompression start set value that starts the decompression mode when the wheel acceleration exceeds a predetermined value or more.
[0005]
However, if braking control is performed under such an erroneous decompression suppression control, the acceleration of the own wheel increases due to the torque circulation of the other drive wheels when the speed of the other drive wheels drops, and an erroneous decompression is caused by the erroneous decompression suppression control. There is a risk that the points will be lowered and proper braking control cannot be performed.
[0006]
Accordingly, the present invention has been made to solve such a problem, and provides a braking control device capable of performing appropriate braking control on driving wheels connected via a differential device. Objective.
[0007]
[Means for Solving the Problems]
That is, the braking control device according to the present invention controls braking by reducing, holding, or increasing the brake fluid pressure according to the wheel acceleration with respect to a plurality of wheels transmitted by distributing the driving force via the differential device. A braking control device that performs an erroneous decompression suppression means for reducing a decompression reference value for setting the brake fluid pressure to a decompression mode when the wheel acceleration at the wheel exceeds a predetermined value. When the torque circulation by the other wheels connected to each other is greater than or equal to a predetermined value, the reduction of the pressure reduction reference value by the erroneous pressure reduction suppression means is prohibited.
[0008]
Further, the braking control device according to the present invention prohibits the reduction of the decompression reference value by the erroneous decompression suppression means when the wheel acceleration of the other wheels is smaller than the predetermined acceleration and the other wheels are depressurizing. It is characterized by.
[0009]
According to these inventions, when the torque circulation by the other wheels connected via the differential gear is equal to or greater than a predetermined value, the erroneous decompression suppression process is prohibited by prohibiting the reduction of the decompression reference value by the erroneous decompression suppression means. This prevents delay in reducing the brake fluid pressure, can suppress the mutual interference of torque, and perform appropriate braking control.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.
[0011]
FIG. 1 shows a configuration of a braking control apparatus according to the present embodiment.
[0012]
As shown in FIG. 1, the braking control device 1 is installed in a vehicle of a four-wheel drive vehicle, and applies braking force applied to a right front wheel FR, a left front wheel FL, a right rear wheel RR, and a left rear wheel RL serving as driving wheels. It is something to control. The vehicle is provided with a front differential 3 that connects the right front wheel FR and the left front wheel FL via the drive shaft 2, and connects the right rear wheel RR and the left rear wheel RL via the drive shaft 4. A rear differential 5 is provided.
[0013]
The front differential 3 functions as a differential device that distributes the driving force transmitted through the propeller shaft 6 to the right front wheel FR and the left front wheel FL and absorbs the rotational speed difference between the right front wheel FR and the left front wheel FL.
[0014]
The rear differential 5 functions as a differential device that distributes the driving force transmitted through the propeller shaft 6 to the right rear wheel RR and the left rear wheel RL, and absorbs the rotational speed difference between the right rear wheel RR and the left rear wheel RL. To do.
[0015]
Further, the vehicle is provided with a center differential 7 that connects the front differential 3 and the rear differential 5 via the propeller shaft 6. The center differential 7 functions as a differential device that distributes the driving force transmitted through the engine 8 and the transmission 9 to the front wheel side and the rear wheel side, and absorbs the rotational speed difference between the front wheel side and the rear wheel side.
[0016]
The braking control device 1 is provided with an ECU 10. The ECU 10 is mainly configured by a computer including a CPU, a ROM, and a RAM. The ROM stores various control routines including a braking control routine.
[0017]
The braking control device 1 is provided with a wheel speed sensor 11. The wheel speed sensor 11 is a wheel speed detecting means for detecting the rotational speed of each wheel of the vehicle, and is installed on each of the right front wheel FR, the left front wheel FL, the right rear wheel RR, and the left rear wheel RL. Each wheel speed sensor 11 is connected to the ECU 10 and outputs a detection signal to the ECU 10.
[0018]
The braking control device 1 is provided with a brake actuator 20. The brake actuator 20 is for adjusting the hydraulic pressure applied to the wheel cylinder of each wheel. For example, the brake actuator 20 includes a plurality of solenoid valves, a pump motor, and the like, and operates according to a control signal from the ECU 10.
[0019]
FIG. 2 shows a brake hydraulic system in the braking control device.
[0020]
As shown in FIG. 2, the brake hydraulic system is, for example, a front-rear piping system that is divided into a front-wheel hydraulic control system and a rear-wheel hydraulic control system. The brake fluid pressure system includes a master cylinder 31 as fluid pressure generating means. The master cylinder 31 operates according to the pedaling force applied to the brake pedal 33 and generates a hydraulic pressure. The master cylinder 31 has a booster function. A reservoir 34 is connected to the master cylinder 31, and a pump 35 serving as an auxiliary hydraulic pressure source is connected via an accumulator 36.
[0021]
The pump 35 is driven by a motor 37, boosts and outputs the brake fluid in the reservoir 34, and accumulates pressure on the accumulator 36 via a check valve 38. The motor 37 is driven in response to the hydraulic pressure in the accumulator 36 falling below a predetermined lower limit value, and stops in response to the hydraulic pressure in the accumulator 36 exceeding a predetermined upper limit value. As a result, a predetermined hydraulic pressure is appropriately supplied from the accumulator 36 to the master cylinder 31 and also supplied to the liquid path 81 extending to the wheel cylinder side.
[0022]
The master cylinder 31 receives the hydraulic pressure from the accumulator 36 and generates a hydraulic pressure proportional to the pilot pressure as the hydraulic pressure generated when the brake pedal 33 is depressed.
[0023]
The master cylinder 31 and the wheel cylinder 41FR of the right front wheel FR are connected by a liquid passage. In the middle of the liquid passage 42, a switching valve SA1 and a holding valve 43 are provided. The switching valve SA1 is a three-port, two-position electromagnetic switching valve, which communicates the master cylinder 31 and the wheel cylinder 41FR when not in operation, and shuts off the master cylinder 31 and the wheel cylinder 41FR when operating and connects the accumulator 36 through the liquid path 81. The wheel cylinder 41FR is communicated. The switching valve SA1 operates in response to a control signal from the ECU 10.
[0024]
The holding valve 43 is a two-port, two-position normally-open electromagnetic on-off valve that operates in response to a control signal from the ECU 10, communicates the master cylinder 31 and the wheel cylinder 41 FR when not in operation, The wheel cylinder 41FR is shut off. Further, a check valve 45 that bypasses the holding valve 43 is provided in the liquid passage 42.
[0025]
A liquid path 46 connected to the reservoir 34 is connected to a portion of the liquid path 42 between the holding valve 43 and the wheel cylinder 41FR. A pressure reducing valve 44 is disposed in the middle of the liquid path 46. The pressure reducing valve 44 is a 2-port 2-position normally-closed electromagnetic on-off valve that operates in response to a control signal from the ECU 10, shuts off the wheel cylinder 41FR and the reservoir 34 when not in operation, and operates the wheel cylinder 41FR and reservoir at the time of operation. 34 is communicated.
[0026]
The master cylinder 31 and the wheel cylinder 41FL of the left front wheel FL are connected by a liquid passage 52. In the middle of the liquid passage 52, a switching valve SA2 and a holding valve 53 are provided. The switching valve SA2 is a three-port 2-position electromagnetic switching valve. When the valve is not operated, the master cylinder 31 and the wheel cylinder 41FL are communicated with each other. When the valve is operated, the master cylinder 31 and the wheel cylinder 41FL are cut off and the accumulator 36 is connected to the accumulator 36. The wheel cylinder 41FL is connected. This switching valve SA2 operates in response to a control signal from the ECU 10.
[0027]
The holding valve 53 is a two-port two-position normally-open electromagnetic on-off valve that operates in response to a control signal from the ECU 10, communicates the master cylinder 31 and the wheel cylinder 41 FL when not in operation, The wheel cylinder 41FL is shut off. Further, the liquid passage 52 is provided with a check valve 55 that bypasses the holding valve 53.
[0028]
A liquid path 56 connected to the reservoir 34 is connected to a portion of the liquid path 52 between the holding valve 53 and the wheel cylinder 41FL. A pressure reducing valve 54 is disposed in the middle of the liquid path 56. The pressure reducing valve 54 is a 2-port 2-position normally-closed electromagnetic on-off valve that operates in response to a control signal from the ECU 10 and shuts off the wheel cylinder 41FL and the reservoir 34 when not operated, and the wheel cylinder 41FL and reservoir when operated. 34 is communicated.
[0029]
A liquid path 61 is provided between the master cylinder 31 and the middle of the liquid path 81. In the middle of the liquid path 61, a switching valve SA3 is provided. The switching valve SA3 is a two-port two-position normally-open electromagnetic on-off valve that operates in response to a control signal from the ECU 10 and sets the liquid path 61 in a communicating state when not operated and shuts the liquid path 61 in an operating state. To do. The liquid path 61 is provided with a check valve 67 that bypasses the switching valve SA3. The liquid path 61 intersects with the liquid path 81 and extends further toward the wheel cylinder of the rear wheel, and is branched into two liquid paths: a liquid path 62 and a liquid path 72.
[0030]
The liquid path 62 is connected to the wheel cylinder 41RR of the right rear wheel RR, and a holding valve 63 is disposed in the middle thereof. The holding valve 63 is a two-port two-position normally-open electromagnetic on-off valve that operates in response to a control signal from the ECU 10, communicates the master cylinder 31 and the wheel cylinder 41 RR when not in operation, The wheel cylinder 41RR is shut off. Further, the liquid passage 62 is provided with a check valve 65 that bypasses the holding valve 63.
[0031]
Further, a liquid path 66 connected to the reservoir 34 is connected to the liquid path 62 between the holding valve 63 and the wheel cylinder 41RR. A pressure reducing valve 64 is disposed in the middle of the liquid path 66. The pressure reducing valve 64 is a 2-port 2-position normally-closed electromagnetic on-off valve that operates in response to a control signal from the ECU 10, shuts off the wheel cylinder 41 RR and the reservoir 34 when not in operation, and turns off the wheel cylinder 41 RR and reservoir during operation. 34 is communicated.
[0032]
On the other hand, the liquid passage 72 is connected to the wheel cylinder 41RL of the left rear wheel RL, and a holding valve 73 is disposed in the middle thereof. The holding valve 73 is a two-port two-position normally-open electromagnetic on-off valve that operates in response to a control signal from the ECU 10, communicates the master cylinder 31 and the wheel cylinder 41 RL when not in operation, The wheel cylinder 41RL is shut off. The liquid passage 72 is provided with a check valve 75 that bypasses the holding valve 73.
[0033]
A liquid path 76 connected to the reservoir 34 is connected to the liquid path 72 between the holding valve 73 and the wheel cylinder 41RL. A pressure reducing valve 74 is disposed in the middle of the liquid path 76. The pressure reducing valve 74 is a 2-port 2-position normally-closed electromagnetic on-off valve that operates in response to a control signal from the ECU 10, shuts off the wheel cylinder 41RL and the reservoir 34 when not in operation, and turns off the wheel cylinder 41RL and reservoir when in operation. 34 is communicated.
[0034]
A switching valve STR is disposed in the middle of the liquid path 81 and at a position closer to the accumulator 36 than the position intersecting the liquid path 61. The switching valve STR is a 2-port 2-position normally-closed electromagnetic on-off valve that operates in response to a control signal from the ECU 10, shuts off the fluid path 81 when not activated, and allows the fluid path 81 to communicate when activated.
[0035]
According to such a brake fluid pressure system, the switching valve SA1, the switching valve SA2, the switching valve SA3, and the switching valve STR are controlled by a control signal from the ECU 10 during normal times (when forced braking control is not performed). Are switched off, the switching valve SA1 communicates with the master cylinder 31 and the wheel cylinder 41FR, the switching valve SA2 communicates with the master cylinder 32 and the wheel cylinder 41FL, and the switching valve SA3 opens. The switching valve STR is closed.
[0036]
Further, at normal times, all the holding valves 43, 53, 63 and 73 and the pressure reducing valves 44, 54, 64 and 74 are all inactive, and all the holding valves 43, 53, 63 and 73 are all opened. Thus, the pressure reducing valves 44, 54, 64 and 74 are all closed.
[0037]
Accordingly, the hydraulic pressure of the master cylinder 31 is transmitted to the wheel cylinders 41RR and 41RL through the liquid passage 61, the liquid passage 62, and the liquid passage 72, and the hydraulic pressure of the master cylinder 31 is transmitted through the liquid passage 42 and the liquid passage 52 to the wheel cylinder. It is transmitted to 41FR and 41FL, and the braking force according to a driver | operator's brake operation will be obtained.
[0038]
On the other hand, according to this brake hydraulic system, ABS control (anti-lock brake control) is started under the condition that the driver performs a braking operation and the wheel speed is below a certain value with respect to the vehicle body speed. The In this case, by switching the switching valve STR, closing the switching valve SA1 and the switching valve SA2 (operating state), and opening only the switching valve SA3 (non-operating state), the liquid path 61 Thus, a high hydraulic pressure is transmitted from the master cylinder 31 to the wheel cylinders 41 of all the wheels of the right front wheel FR, the left front wheel FL, the right rear wheel RR, and the left rear wheel RL. At the same time, the holding valves 43, 53, 63 and 73 and the pressure reducing valves 44, 54, 64 and 74 are appropriately opened and closed to adjust the hydraulic pressure of the wheel cylinders 41, and the braking force of each wheel is adjusted. Be controlled. Detailed control contents will be described later.
[0039]
Next, the operation of the braking control device according to this embodiment will be described.
[0040]
FIG. 5 is a flowchart of the braking control process in the braking control device 1.
[0041]
In S100 of FIG. 5, the ECU 10 is initialized, and various calculation values such as a CPU and a RAM built in the ECU 10 are appropriately cleared. Then, the wheel speed Vw of each wheel is read (S102), the wheel acceleration DVw is calculated based on the wheel speed Vw at each wheel (S104), and the vehicle body speed Vso is calculated (S106).
[0042]
And it is judged whether the control start conditions of each wheel are satisfy | filled (S108). For example, the control start condition is that the difference between the vehicle body speed Vso and the wheel speed Vw is equal to or greater than a set value. When it is determined that this control start condition is not satisfied, the control process is terminated. On the other hand, when it is determined that the control start condition is satisfied, it is determined whether or not the decompression mode is set based on the relationship among the wheel speed Vw, the vehicle body speed Vso, and the wheel acceleration DVw (S110).
[0043]
When it is determined that the pressure reduction mode is selected, a pressure reduction output process is performed (S112). That is, in FIG. 2, from the ECU 10, the switching valve STR, the switching valve SA1, the switching valve SA2, the switching valve SA3, the holding valve 43, 53, 63 or 73 (hereinafter referred to as “holding valve” as appropriate) and the pressure reducing valves 44, 54, A control signal is output to 64 or 74 (hereinafter referred to as “pressure reducing valve” as appropriate). Then, by the control signal, the switching valve STR is closed, the switching valve SA1 and the switching valve SA2 are closed, and the switching valve SA3 is opened. Further, the holding valve is closed and the pressure reducing valve is opened and closed. As a result, the hydraulic pressure in the wheel cylinder 41 is released to the reservoir through the pressure reducing valve, and the hydraulic pressure in the wheel cylinder 41 is reduced.
[0044]
On the other hand, when it is determined in S110 of FIG. 3 that the pressure reduction mode is not set, it is determined whether or not the pulse increase mode is set based on the relationship between the wheel speed Vw, the vehicle body speed Vso, and the wheel acceleration DVw (S114). When it is determined that the pulse increase mode is not selected, a holding output process is performed (S116). That is, a control signal is output to each of the holding valve and the pressure reducing valve, the holding valve is closed, and the pressure reducing valve is also closed. Thereby, the hydraulic pressure of the wheel cylinder 41 is maintained.
[0045]
On the other hand, when it is determined in S114 that the pulse increase mode is set, a pulse increase output process is performed (S118). That is, a control signal is output from the ECU 10 to the holding valve and the pressure reducing valve, the holding valve is opened and closed, and the pressure reducing valve is closed. Thereby, the hydraulic pressure is transmitted from the master cylinder 31 to the wheel cylinder 41, and the hydraulic pressure of the wheel cylinder is increased. Then, the control process ends.
[0046]
Next, the brake fluid pressure mode setting in the braking control process will be described in detail.
[0047]
In the braking control process described above, whether or not the hydraulic pressure in the wheel cylinder 41 is set to any one of the pressure reduction mode, the pressure increase mode (pulse increase mode), and the holding mode is, for example, as shown in FIG. It is determined based on the wheel acceleration DVw. That is, the depressurization mode is set from when the wheel acceleration DVw becomes equal to or lower than the first depressurization start set value A1 to the hold start set value B (B> A1) or higher, and the hold mode is set while the wheel acceleration DVw is equal to or higher than the hold start set value B. The pressure increasing mode is set from when the holding start set value B or less is reached until the first pressure reduction starting set value A1 or less.
[0048]
As described above, when the braking control is repeatedly performed in the pressure-reducing mode, the holding mode, and the pressure-increasing mode, or when the wheel acceleration DVw becomes equal to or higher than the upper limit C (C> B) in the stage before the braking control, a predetermined condition is satisfied. Thus, the depressurization start reference value is switched from the first depressurization start set value A1 to the second depressurization start set value A2 for a predetermined time. The second decompression start set value A2 is set to a value lower than the first decompression start set value A1. The predetermined condition is a condition that whether or not the torque circulation by the other driving wheel connected via the differential device is greater than or equal to a predetermined value in the driving wheel to be brake controlled.
[0049]
FIG. 5 shows a flowchart of the switching process of the decompression start set value.
[0050]
As shown in S200 of FIG. 5, it is determined whether or not the torque circulation by the other driving wheels connected via the differential device in the driving wheels to be brake controlled is greater than or equal to a predetermined value. This determination is made, for example, based on whether or not the wheel acceleration of the other driving wheel is lower than a predetermined value and the other driving wheel is in the pressure reduction mode. That is, when the wheel acceleration of the other driving wheel is lower than the predetermined value and the other driving wheel is in the decompression mode, it is determined that the torque circulation by the other driving wheel is not less than the predetermined value, and the wheel of the other driving wheel is When the acceleration is not lower than a predetermined value or when the other driving wheel is not in the decompression mode, it is determined that the torque circulation by the other driving wheel is not greater than or equal to the predetermined value.
[0051]
When it is determined in S200 that the torque circulation by the other driving wheels is not equal to or greater than the predetermined value, switching of the reference value for starting the pressure reduction is permitted. That is, as shown in FIG. 4, when the wheel acceleration DVw becomes equal to or higher than the upper limit value C, the reference value for the pressure reduction start is switched from the first pressure reduction start set value A1 to the second pressure reduction start set value A2 for a predetermined time. .
[0052]
On the other hand, when it is determined in S200 that the torque circulation by the other driving wheels is equal to or greater than the predetermined value, switching of the reference value for starting the pressure reduction is prohibited. That is, as shown in FIG. 4, even when the wheel acceleration DVw becomes equal to or higher than the upper limit value C, the reference value for the start of decompression is not switched from the first decompression start set value A1 to the second decompression start set value A2, One decompression start set value A1 is maintained (two-dot chain line in FIG. 4).
[0053]
As described above, according to the braking control device according to the present embodiment, the reference value of the decompression start by the erroneous decompression suppression control when the torque circulation by the other wheels connected via the differential device is greater than or equal to the predetermined value. By prohibiting the decrease, delay in reducing the brake fluid pressure is prevented from being delayed by the erroneous decompression suppression control, the mutual interference of torque suppression can be suppressed, and appropriate braking control can be performed.
[0054]
In this embodiment, the case of braking control in a four-wheel drive vehicle has been described. However, the braking control device according to the present invention is not limited to such a case, and the driving force is distributed via a differential device. As long as the braking control is performed on the plurality of wheels transmitted in this manner, the braking control may be performed by another vehicle.
[0055]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a braking control device that can perform appropriate braking control on the drive wheels connected via the differential device.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a braking control device according to an embodiment of the present invention.
2 is an explanatory diagram of a brake hydraulic system of the braking control device of FIG. 1. FIG.
FIG. 3 is a flowchart of a braking control process in the braking control device of FIG. 1;
4 is an explanatory diagram of brake fluid pressure mode setting in the braking control process of FIG. 3; FIG.
5 is a flowchart of switching processing of a pressure reduction start set value in the braking control device of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Braking control apparatus, 3 ... Front differential, 5 ... Rear differential, 7 ... Center differential, 10 ... ECU, 11 ... Wheel speed sensor, 41 ... Wheel cylinder.

Claims (2)

A braking control device that performs braking control by reducing, holding, and increasing the brake fluid pressure according to wheel acceleration with respect to a plurality of wheels that are transmitted by distributing driving force through a differential device,
An erroneous depressurization suppressing means for lowering a depressurization reference value for setting the brake fluid pressure in a depressurization mode when the wheel acceleration in the wheel becomes a predetermined value or more;
Prohibiting a reduction in the decompression reference value by the erroneous decompression suppression means when the torque circulation by the other wheels connected via the differential device is greater than or equal to a predetermined value,
A braking control device characterized by the above. Prohibiting lowering of the decompression reference value by the erroneous decompression suppression means when the wheel acceleration of the other wheel is smaller than a predetermined acceleration and the other wheel is decompressing,
The braking control device according to claim 1.

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