JP3607975B2 - Brake control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brake control device that performs braking force control during vehicle braking.
[0002]
[Prior art]
Conventionally, as described in JP-A-8-276842, as a brake control device, when a certain condition is satisfied after the antilock control is started, the antilock control is terminated even during braking. In addition, it is known that the anti-lock control is resumed when a certain condition is satisfied even if the anti-lock control is once ended. This device is intended to ensure the running stability of the vehicle being braked by appropriately terminating or restarting the antilock control even during braking.
[0003]
[Problems to be solved by the invention]
However, the above-described conventional brake control device has a problem that the antilock control may be started when the vehicle passes a step during braking. For example, when the vehicle being braked passes a road surface step, the brake control device cannot specify whether the road surface changes or the braking force changes, and antilock control is started. In terms of braking force control, it is desirable to avoid the start of antilock control when the road surface is stepped.
[0004]
Accordingly, the present invention has been made to solve such problems, and an object of the present invention is to provide a brake control device that can perform appropriate braking force control.
[0005]
[Means for Solving the Problems]
That is, the brake control device according to the present invention is a brake control device that performs braking force control based on the slip amount of the wheel during braking of the vehicle, and the rate of change of the brake operation amount of the driver of the vehicle is smaller than the first set value. Brake operation determining means for determining whether or not, wheel acceleration change rate determining means for determining whether or not the wheel acceleration change rate of the wheel is smaller than the second set value, and the rate of change of the brake operation amount by the brake operation determining means Control prohibiting means for prohibiting the start of braking force control when the wheel acceleration change rate is smaller than the second set value by the wheel acceleration change rate determining means. To do.
[0006]
According to this invention, even when the slip amount of the wheel during vehicle braking exceeds a predetermined value, the brake operation amount of the driver is smaller than the first set value and the wheel acceleration change rate is smaller than the second set value. In such a case, the start of antilock control is prohibited. Accordingly, it is possible to prohibit the start of the antilock control when the vehicle passes through the stepped portion of the road surface during braking. Accordingly, it is possible to avoid the start of the antilock control when the antilock control is unnecessary, such as when the vehicle is stepped, and to perform the appropriate antilock control.
[0007]
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.
(First embodiment)
FIG. 1 shows a configuration of a brake control device according to the present embodiment. As shown in FIG. 1, the brake control device 1 includes an ECU 2. The ECU 2 is mainly configured by a computer including a CPU, a ROM, and a RAM. Various control routines including a braking force control routine are stored in the ROM.
[0008]
A wheel speed sensor 3 for detecting the rotational speed of the wheel is provided on the input side of the ECU 2. The wheel speed sensor 3 is provided for each wheel of the vehicle, and outputs a signal corresponding to the rotational speed of each wheel to the ECU 2. A master cylinder hydraulic pressure sensor 6 is connected to the input side of the ECU 2. The master cylinder hydraulic pressure sensor 6 detects the hydraulic pressure generated in the master cylinder, and detects the brake operation amount of the driver. The master cylinder hydraulic pressure sensor 6 need not be provided for each of the two rake systems provided in the vehicle, and may be provided for only one of them. Note that the means for detecting the brake operation amount is not limited to the master cylinder hydraulic pressure sensor 6, and a brake stroke sensor or a brake pedal force detection sensor may be used alone or in combination.
[0009]
On the other hand, a brake actuator 7 is connected to the output side of the ECU 2 for each brake system. Each brake actuator 7 includes two holding valves 9 and two pressure reducing valves 10. Of these, the two holding valves 9 and the two pressure reducing valves 10 constitute a brake hydraulic pressure control valve device 11 in the sense of controlling the hydraulic pressure of the wheel cylinder.
[0010]
A pump motor 12 for driving the pump is connected to the output side of the ECU 2. By driving the pump motor 12, the hydraulic pressure in the reservoir is reduced. A brake system to be subjected to brake control is obtained by dividing a brake system into two systems using, for example, a tandem master cylinder.
[0011]
FIG. 2 shows an example of a brake system to be subjected to brake control.
[0012]
As shown in FIG. 2, the depression force of the brake pedal 24 is transmitted to the master cylinder 20 via the booster 22. The main passage 40 of the first brake system for the left front wheel FL and the right rear wheel RR is connected to one of the two pressure chambers provided in the master cylinder 20, and the right front wheel FR is connected to the other pressure chamber. The main passage 41 of the second brake system for the left rear wheel RL is connected. That is, in the brake system, the output passage from the master cylinder 20 is constituted by two diagonal passage systems. Since these brake systems have the same configuration, only the first brake system will be representatively described below, and description of the second brake system will be omitted.
[0013]
In the first brake system, the master cylinder 20 is connected by a main passage 40 to a wheel cylinder 50 that operates the brake 42 of the left front wheel FL and a wheel cylinder 50 that operates the brake 44 of the right rear wheel RR. Yes. The main passage 40 extends from the master cylinder 20 and then branches into a bifurcated shape. One of the branched passages becomes a main passage 54, and the main passage 54 also branches into a forked shape into two branch passages 56. It is lined up. Wheel cylinders 50 are connected to the downstream side of each branch passage 56. A master cylinder hydraulic pressure sensor 6 is connected to the downstream side of the other branch passage of the main passage 40.
[0014]
In the middle of each branch passage 56, a holding valve 60, which is an electromagnetic normally open valve, is disposed. The holding valve 60 allows a bidirectional flow of brake fluid between the master cylinder 20 and the wheel cylinder 50 when the solenoid is in an off state, that is, an open state, and blocks the flow when the solenoid is in an on state, that is, a closed state. Each branch passage 56 is provided with a check valve 64 that bypasses each holding valve 60. A proportioning valve 65 is provided in the middle of the two branch passages 56 corresponding to the right rear wheel RR.
[0015]
Each reservoir passage 66 extends from a portion of each branch passage 56 between the holding valve 60 and the wheel cylinder 50 and reaches the reservoir 72. In the middle of each reservoir passage 66, a pressure reducing valve 70, which is an electromagnetic normally closed valve, is provided. The pressure reducing valve 70 prevents the flow of brake fluid from the wheel cylinder 50 toward the reservoir 72 when the solenoid is off, ie, closed, and allows the flow when the solenoid is on, ie, opened.
[0016]
The reservoir 72 is configured by fitting a reservoir piston 74 to a reservoir housing 73 so as to be airtight and slidable, and accommodates brake fluid in a reservoir chamber 76 formed by the fitting. The reservoir piston 74 is always urged by a spring 78, which is a resilient member, so that the volume of the reservoir chamber 76 decreases.
[0017]
A pump 82 is disposed between the upstream side of the holding valve 60 in each branch passage 56 and the reservoir 72. The pump 82 operates by driving the pump motor 12 and decreases the hydraulic pressure in the reservoir 72. Further, check valves 84 and 86 for restricting the flow of the brake fluid are disposed on the upstream side and the downstream side of the pump 82.
[0018]
The brake system shown in FIG. 2 may be a system capable of brake assist control. For example, a three-way valve is provided in the middle of the main passage 54, and the master cylinder 20 is held by the holding valve 60 by the operation of the three-way valve. Alternatively, it may communicate with any of the reservoirs 72 as appropriate.
[0019]
Next, the operation of the brake control device will be described.
[0020]
FIG. 3 is a flowchart showing the operation of the brake control device. In FIG. 3, the control is started when the driver depresses the brake pedal 24. First, in step S <b> 10 (hereinafter simply referred to as “S <b> 10”, the same applies to other steps), the wheel speed sensor 3. The wheel speed Vw detected by is read. Then, the process proceeds to S12, and the master pressure Pm of the master cylinder 20 detected by the master cylinder hydraulic pressure sensor 6 is read. Next, the process proceeds to S14, where the vehicle body speed Vso of the vehicle is estimated based on the wheel speed Vw, and the process proceeds to S16, where the wheel acceleration Vw ′ is calculated based on the wheel speed Vw.
[0021]
Then, the process proceeds to S18, where a master pressure change rate Pm ′, which is a temporal change rate of the master pressure, is calculated based on the master pressure Pm. The change rate Vw ″ is calculated.
[0022]
Next, the process proceeds to S22, in which it is determined whether or not the calculated wheel acceleration Vw ′ is smaller than the set value G1. Here, the set value G1 is a value stored in advance in the RAM or the like of the ECU 2 and is a comparison value with the deceleration, and thus is set as a negative value. When it is determined in S22 that the wheel acceleration Vw ′ is not smaller than G1, the process returns to S10. On the other hand, when it is determined that the wheel acceleration Vw ′ is smaller than G1, the process proceeds to S24, and the wheel speed deviation ΔVs is calculated. The wheel speed deviation ΔVs is calculated by the following equation (1).
[0023]
ΔVs = Vso−Vw−ΔVr (1)
Here, ΔVr in the equation (1) is a set value stored in advance in the RAM or the like of the ECU 2, and for example, the wheel speed Vw is subtracted from the vehicle body speed Vso when the wheel acceleration Vw ′ is the set value G1. Value is set.
[0024]
Then, the process proceeds to S26, where it is determined whether or not the wheel speed deviation ΔVs is larger than the set value S. The set value S is a set slip amount value stored in advance in the RAM of the ECU 2 or the like. When it is determined in S26 that the wheel speed deviation ΔVs is not larger than the slip amount S, the process returns to S10. On the other hand, when it is determined that the wheel speed deviation ΔVs is larger than the set value S, the routine proceeds to S28, where it is determined whether or not the master pressure change rate Pm ′ is smaller than the set value P1. Here, the set value P1 is a set value stored in advance in the RAM or the like of the ECU 2, and is set to a value in the range of about 0 to 20 MPa / sec, and more preferably a value of about 3 MPa / sec. Set to
[0025]
When it is determined in S28 that the master pressure change rate Pm ′ is not smaller than the set value P1, the process proceeds to S32 and antilock control is started. On the other hand, when it is determined in S28 that the master pressure change rate Pm ′ is smaller than the set value P1, the process proceeds to S30, where it is determined whether or not the wheel acceleration change rate Vw ″ is smaller than the set value J. The set value J is a set value stored in advance in the RAM or the like of the ECU 2, and is set to a value in the range of about −1000 to −6000 m / s ² / s, and more preferably about − It is set to a value of 1500m ^{/ s} 2 ^{/ s.}
[0026]
When it is determined in S30 that the wheel acceleration change rate Vw ″ is not smaller than the set value J, the process proceeds to S32 and antilock control is started. On the other hand, in S30, the wheel acceleration change rate Vw ″ is set. When it is determined that the value is smaller than the value J, the process proceeds to S34, and the start of the antilock control is prohibited.
[0027]
As described above, according to the brake control device of the present embodiment, even when the slip amount of the wheel during vehicle braking exceeds a predetermined value, the master pressure change rate Pm ′ is smaller than the set value P1, and the wheel When the acceleration change rate Vw ″ is smaller than the set value J, the start of antilock control is prohibited. Thus, when the vehicle passes through the stepped portion of the road surface during braking, the antilock control is started. Can be prohibited.
[0028]
That is, by determining whether or not the master pressure change rate Pm ′ is smaller than the set value P1, it is possible to identify whether the wheel slip is caused by a road surface change or a braking force change. Further, by determining whether or not the wheel acceleration change rate Vw ″ is smaller than the set value J, it is possible to identify whether the road surface change is due to the passage of a step or the passage of a low μ road such as ice or fresh snow. For this reason, it is possible to identify whether or not the wheel slip is caused by the passage of the step, and to reliably prohibit the start of the antilock control when the slip of the wheel is caused by the passage of the step.
[0029]
Therefore, it is possible to avoid the start of the antilock control when the antilock control is unnecessary, such as when the vehicle is stepped, and appropriate antilock control is possible.
[0030]
【The invention's effect】
As described above, according to the present invention, when antilock control is unnecessary, such as when the vehicle is stepped, it is possible to avoid the start of antilock control and perform appropriate antilock control.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a brake control device according to an embodiment.
FIG. 2 is an explanatory diagram of a brake system to be controlled by the brake control device according to the embodiment.
FIG. 3 is a flowchart showing the operation of the brake control device according to the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Brake control apparatus, 2 ... ECU, 3 ... Wheel speed sensor, 5 ... Brake sensor, 6 ... Master cylinder hydraulic pressure sensor, 9 ... Holding valve, 10 ... Pressure reducing valve, 50 ... Wheel cylinder.

Claims (1)

In a brake control device that performs braking force control based on a slip amount of a wheel during braking of a vehicle,
Brake operation determining means for determining whether the rate of change of the brake operation amount of the driver of the vehicle is smaller than a first set value;
Wheel acceleration change rate determination means for determining whether the wheel acceleration change rate of the wheel is smaller than a second set value;
Small the brake operation amount change rate is higher than the first set value by the brake operation determining means, and, when the wheel acceleration change rate is smaller than the second set value by the wheel acceleration change rate determining means, said system Control prohibiting means for prohibiting the start of power control;
A brake control device comprising:

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