Brake control device improving driver's brake feeling

Abstract

A lower limit of a target value of a wheel cylinder pressure generated by a wheel cylinder is set as a first value PT1. Specifically, the first value PT1 is determined based on the application pressure generated by the wheel cylinder during an automatic brake control. Accordingly, the actual application pressure generated can be set to be equal to or more than the first value PT1. Thus, it is possible to prevent the application pressure from being decreased unintentionally when the automatic brake control is switched to a manual brake control, and thus, it is possible to maintain a deceleration speed of a vehicle at the level of a vehicle body deceleration generated during the automatic brake control. Accordingly, it is less likely that the driver will be caused to feel a sense of unease by weakening of the braking force.

Description

CROSS REFERENCE TO RELATED APPLICATION This application is based upon and claims the benefit of Japanese Patent Application No. 2003-319817 filed on Sep. 11, 2003, the content of which are incorporated herein by reference. FIELD OF THE INVENTION The present invention relates to a vehicular brake control device that improves the brake feeling of a driver by adjusting deceleration generated by an automatic brake and a manual brake. BACKGROUND OF THE INVENTION Japanese Patent Publication No. 2000-313322 discloses a related vehicular brake control device that aims to achieve a good brake feeling when a manual brake is operated during automatic braking. The brake control device has a relief valve for releasing brake fluid, and is thus able to release brake fluid pressure applied to a wheel cylinder by the manual brake. When a brake pedal is operated during automatic braking, the opening of the relief valve is controlled in accordance with a release time. This release time is determine...

AI Technical Summary

Benefits of technology

A main object of the present invention is to provide a vehicular brake control device that can perform a brake control so as to generate a brake feeling that accords with a driver's expectations by adjusting a deceleration speed when an automatic brake is switched to a manual brake.

Another object of the present invention is to provide a brake control device that can inhibit sudden increase in a vehicle body deceleration, and inhibit the driver from being caused to feel a sense of unease when a braking force is applied suddenly.

According to a first aspect of the present invention, a lower limit of a target value of an application pressure generated by a braking force generating unit is set. The lower limit is determined based on a pressure generated by a wheel cylinder during automatic brake control. Accordingly, it is possible to make sure that the actual application pressure generated is equal to or more than the first value. Thus, it is possible to prevent the application pressure from being decreased unintentionally when the automatic brake control is switched to a brake assist control, and thus, it is possible to maintain a deceleration speed of a vehicle at the level of a vehicle body deceleration generated during the automatic brake control. Accordingly, it is less likely that the driver will be caused to feel a sense of unease by weakening of the braking force. Accordingly, the brake control can be performed such that a brake feeling is generated that accords with a driver's expectations.

In this configuration, the upper limit value for the application pressure generated by the braking force generating unit is set. Further, a value that is obtained by adding the first value to an upper limit value of the change in the application pressure is adopted as this upper limit value. Accordingly, it is possible to make sure that the actual application pressure generated does not increase suddenly.

With the above described configuration, it is possible to prevent the application pressure from being increased rapidly when the automatic brake control is switched to the manual brake control. Thus, it is less likely that the driver will be caused to feel a sense of unease resulting from sudden application of braking force. Accordingly, the brake control can be performed such that a brake feeling is generated that accords with the driver's expectations.

Problems solved by technology

However, according to the disclosure of Japanese Patent Publication No. 2000-313322, when the brake fluid pressure applied to the wheel cylinder is released by the operation of the manual brake, the deceleration speed generated by the automatic brake is temporarily reduced, and deceleration speed inconsistency, namely, a fall in the deceleration speed, may result.

As a result of this reduction, the driver feels a sense of unease, i.e., feels that the braking force is weakened, and is not able to obtain a brake feeling that meets with the driver's expectations.

In this case, the vehicle body deceleration is increased, and the driver may feel a sense of unease due to the sudden braking force.

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