Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1998-12-03
2001-04-03
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C137S596170, C137S627500
Reexamination Certificate
active
06209970
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority of Japanese Patent Applications No.9-336044 filed Dec. 5, 1997, No.9-353527 filed Dec. 22, 1997, No.10-3931 filed Jan. 12, 1998, No.10-20074 filed Jan. 30, 1998, and No.10-266708 filed Sep. 21, 1998, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic valve and a brake control system adopting the electromagnetic valve as a hydraulic pressure control valve for increasing or decreasing brake hydraulic pressure.
2. Description of Related Art
Conventionally, in a brake control device for carrying out traction control or turn trace control (vehicle yaw control), an SR valve which is an electromagnetic valve is provided as a hydraulic pressure control valve for adjusting wheel cylinder pressure by opening and closing a conduit from a master cylinder to a pump. As shown in
FIG. 12
, the SR valve closes the hydraulic path by a valve body
111
biased in an arrow mark A direction by a spring
112
.
However, according to the SR valve having such a structure, in the case where a brake pedal
113
is depressed and hydraulic pressure (master cylinder pressure) on the side of a master cylinder
114
is increased, the master cylinder pressure acts to the valve body
111
so that the valve body
111
is moved in a valve closing direction (arrow mark A direction). Accordingly, even when electricity is supplied to a solenoid
115
, attracting force in an arrow mark B direction caused by electromagnetic force of the solenoid
115
may become deficient and the SR valve may not be opened.
Accordingly, when the SR valve is used in, for example, a brake control device for carrying out power assist brake control (PAB control), that is, a brake control device for carrying out pressure increase control in which when the brake pedal
113
is depressed, a pump
116
is operated and the wheel cylinder pressure is increased more than normal to thereby enhance wheel braking force, pressure increase control may not be carried out preferably.
Although as a measure therefor, there is conceivable a method of enlarging the size (performance) of the solenoid, then, the SR valve becomes large-sized. Hence, for example, there has been proposed an SR valve using a main valve and an auxiliary valve.
Such an SR valve has an auxiliary valve comprising a magnetic body for alternatively opening and closing an auxiliary path by supplying electricity to a solenoid. When the auxiliary path is opened in accordance with operation of the auxiliary valve, pressure difference applied on a main valve comprising a nonmagnetic body is alleviated, thereby assisting the main valve to open a main path (refer to DE19529363).
However, according to such an SR valve having the main valve and the auxiliary valve, it is difficult to carry out precise control.
In recent years, there has been intensified a tendency of carrying out power assist brake control for promoting braking performance by increasing wheel cylinder pressure when a brake pedal is depressed in addition to, for example, normal brake operation, antiskid control, traction control and turn trace control (vehicle yaw control) in a single brake control device. Therefore, with the above-described conventional SR valve which only carries out simple opening and closing operation, it is difficult to preferably carry out various control while clearing problems of pedal feeling, operational sound and so on.
Further, even when a constitution capable of carrying out complicated operation is added to the SR valve, with the complicated structure, the device is large-sized and the cost is increased which is not preferable.
The present invention has been carried out in order to solve the above-mentioned problems and it is an object of the present invention to provide an electromagnetic valve capable of preferably carrying out various control and a brake control device adopting the electromagnetic valve.
SUMMARY OF THE INVENTION
In order to achieve such an object, according to the present invention, there is provided an electromagnetic valve which is arranged in a conduit between a brake hydraulic pressure generating device (for example, a master cylinder) for generating brake hydraulic pressure in braking a vehicle and an intake side of a pump for supplying brake fluid to a wheel braking force generating device (for example, a wheel cylinder) for generating wheel braking force. In the electromagnetic valve, a main communication path and a restricted communication path are formed. The electromagnetic valve comprises a main valve having a main valve body capable of opening and closing the main communication path connected to the conduit except the restricted communication path by moving in a predetermined direction (for example, axial direction). In particular, the restricted communication path is formed in the main valve body. The electromagnetic valve further comprises an auxiliary valve having an auxiliary valve body capable of opening and closing the restricted communication path of the main valve body by moving in the predetermined direction the same as the main valve moving direction. A main valve body biasing device (for example, assist spring) biases the main valve body in a direction of closing the main communication path. An auxiliary valve body biasing device (for example, return spring) biases the auxiliary valve body in a direction of closing the restricted communication path. A magnetic force applying device (for example, solenoid) applies electromagnetic force to bias the auxiliary valve body in a direction of opening the restricted communication path against the biasing force of the auxiliary valve body biasing device.
Particularly, the auxiliary valve is provided with an engaging portion for engaging with the main valve body after opening the restricted communication path when moving in the predetermined direction. Therefore, the main valve body is also moved in accordance with further movement of the auxiliary valve body, by which the main valve can be opened. The electromagnetic force applying device can adjust electromagnetic force applied to the auxiliary valve body so that only the auxiliary valve is opened by movement of the auxiliary valve body or both the auxiliary valve and the main valve are opened by movement of the auxiliary valve body and the main valve body.
Here, as means for adjusting the electromagnetic force applied on the auxiliary valve body, for example, there can be used a device for adjusting the magnitude of current conducted to the solenoid (or voltage value thereof) or a device for adjusting the duty ratio of current conducted to the solenoid (or the duty ratio of voltage applied thereto).
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Kamiya Masahiko
Majima Yozo
Denso Corporation
Kramer Devon
Oberleitner Robert J.
Pillsbury & Winthrop LLP
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