Motors: expansible chamber type – Working member position feedback to motive fluid control – Plural input signal means for single motor valve
Reexamination Certificate
1999-04-15
2002-01-01
Ryznic, John E. (Department: 3745)
Motors: expansible chamber type
Working member position feedback to motive fluid control
Plural input signal means for single motor valve
Reexamination Certificate
active
06334383
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a brake booster. More particularly, the present invention pertains to a vacuum type servo system to be applied to an automobile.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,483,866 discloses a vacuum type servo system that includes a housing in which is formed at least one pressure chamber, a movable wall disposed in the housing to move forward and backward with respect to the housing for partitioning the pressure chamber into a front chamber communicating with a vacuum source and a rear chamber for selectively communicating with the front chamber and the atmosphere, a power piston jointed to the movable wall, an input member arranged in the power piston to move forward and backward with respect to the power piston, and a valve plunger member arranged in the power piston for moving forward and backward integrally with the input member. An atmospheric valve seat is arranged in the valve plunger member and a vacuum valve seat is arranged in the power piston. A control valve is defined by an atmospheric seal portion capable of moving into and out of engagement with the atmospheric valve seat to cut off communication with the rear chamber and the atmosphere upon engaging the atmospheric valve seat and to establish communication of the rear chamber with the atmosphere upon being out of engagement with the atmospheric valve seat, and a vacuum seal portion capable of moving into and out of engagement with the vacuum valve seat to cut off communication between the front chamber and the rear chamber upon engagement with the vacuum valve seat and to establish communication of the rear chamber with the front chamber upon being out of engagement with the vacuum valve seat. An output member outputs to the outside the forward force of the power piston in accordance with the movement of the movable wall. A reaction member transmits member to the output member the forward force of the power piston and an input applied to the input, and applies a reaction of a magnitude corresponding to the output of the output member to move the input member backward. An actuator brings the valve plunger member forward to move the atmospheric valve seat away from the atmospheric seal portion to thereby establish communication between the rear chamber and the atmosphere.
In this known vacuum type servo system, the valve plunger member is moved by activating the actuator separately of the operation of the input member so that the atmospheric valve seat is moved away from the atmospheric seal portion to establish communication between the rear chamber and the atmosphere and accordingly a pressure difference between the front chamber and the rear chamber. When this pressure difference is established between the front chamber and the rear chamber by the activation of the actuator, forward forces are generated at the movable wall and the power piston, and the output member outputs the forward force of the power piston to the outside.
In this vacuum type servo system, however, the flow of atmospheric air into the rear chamber by the activation of the actuator continues until the rear chamber receives the atmospheric pressure so that the output of the vacuum type servo system to be outputted from the output member in accordance with the activation of the actuator reaches a maximum.
It is conceivable that this vacuum type servo system for generating an output by activation of the actuator independently of the operation of the input member can be applied to an automatic braking system that is designed to maintain the vehicle distance, for example, at a predetermined value.
This automatic braking system is typically designed so that when the distance between a running vehicle and a proceeding vehicle becomes shorter than a predetermined distance, for example, braking action in the vehicle is achieved by activating the system without any braking operation of the driver so that the vehicle distance may be kept at a predetermined value. The automatic braking action of this automatic braking system has a tendency not to require a high braking force.
When the aforementioned vacuum type servo system is applied to an automatic braking system such as described above, the actuator is activated when the vehicle distance becomes shorter than the predetermined value. The output is thus generated in the vacuum type servo system to effect the automatic braking operation without any braking operation of the driver, i.e., without any operation of the input member.
However, the braking force to be generated at this time is based on the maximum output that is established in the vacuum type servo system and this rather strong braking force may not be well suited for the automatic braking operation in the automatic braking system. In other words, the known vacuum type servo system described above is not well suited for braking systems which do not require the generation of the maximum output of the vacuum type servo system.
In light of the foregoing, a need exists for a vacuum type servo system that is capable of regulating the output accompanying the activation of an actuator to the maximum output or less than the maximum output.
A need also exists for a vacuum type servo system which is able to control the output accompanying the activation of the actuator within a range lower than the jumping output of the performance of an ordinary brake.
SUMMARY OF THE INVENTION
A vacuum type servo system according to one aspect of the invention includes: a housing having at least one pressure chamber formed therein; a movable wall so disposed in the housing as to move forward and backward with respect to the housing for partitioning the pressure chamber into a front chamber communicating with a vacuum source and a rear chamber selected to communicate with the front chamber and the atmosphere; a power piston jointed to the movable wall; an input member so arranged in the power piston as to move forward and backward with respect to the power piston; an atmospheric valve seat arranged in the power piston for moving forward and backward integrally with the input member; a vacuum valve seat arranged in the power piston; a control valve including an atmospheric seal portion capable of coming into and going out of abutment against the atmospheric valve seat for cutting off the communication with the rear chamber and the atmosphere when it comes into abutment against the atmospheric valve seat and for establishing the communication of the rear chamber with the atmosphere when it goes out of abutment against the atmospheric valve seat, and a vacuum seal portion capable of coming into and going out of abutment against the vacuum valve seat for cutting off t-e communication between the front chamber and the rear chamber when it comes into abutment against the vacuum valve seat and for establishing the communication of the rear chamber with the front chamber when it goes out of abutment against the vacuum valve seat; an output member for outputting the forward force of the power piston in accordance with the movement of the movable wall to the outside of the system; a reaction member for transmitting the forward force of the power piston and an input fed to the input member, to the output member and for applying a reaction of a magnitude corresponding to an output of the output member, to move the input member backward; and an actuator for bringing the atmospheric valve seat and the atmospheric seal portion away from each other to establish the communication between the rear chamber and the atmosphere, wherein the input member includes: a front member for coming into abutment against the reaction member; and a rear member capable of moving integrally with the atmospheric valve seat, so that when a predetermined input is fed to the input member, the rear member moves forward by a predetermined stroke with respect to the front member, and so that when the input member is moved backward by a reaction of the reaction member in accordance with the activation of the actuator, the atmospheric valve seat
Miwa Akihiko
Tsubouchi Kaoru
Aisin Seiki Kabushiki Kaisha
Ryznic John E.
LandOfFree
Vacuum servo apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vacuum servo apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vacuum servo apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2835137