Abstract: A motor-driven parking brake apparatus includes a load sensor (pressure sensor) for detecting axial load of a screw shaft. The pressure sensor includes a transmission member which receives the axial load via a circular surface of a plate, and a casing which accommodates the transmission member and receives the axial load via the transmission member. This casing has a circular opening having an opening area smaller than the surface of the circular surface. The pressure sensor detects a pressure generated due to a load received from an exposed portion of the transmission member which is exposed from the circular opening. Due to characteristics of the transmission member, the load received from the exposed portion is a portion of the axial load and proportional to the axial load.

Abstract: To provide a negative pressure type booster device which has a high responsiveness even when a brake pedal is stepped on strongly and which is simplified and compact in construction. To this end, a passage 45 communicating directly with the atmosphere is provided between the internal surface of a sliding cylindrical portion 8b of a valve piston 8 and the external surface of a silencer 27, and the atmospheric air is enabled to be admitted from the passage 45 to a variable pressure chamber 6 directly without passing through the silencer 27 when an input member is advanced beyond a predetermined distance relative to the valve piston.

Abstract: In a vacuum type brake booster, the reaction of output transmitted from an output shaft to a reaction member is transmitted to a valve body, a plunger, and a stepped pin. A valve mechanism, which is assembled to an axial hole of the valve body, includes an atmospheric valve seat which advances and retreats together with the plunger, a vacuum valve seat assembled to the valve body to advance and retreat, and a valve member having an atmospheric valve portion which forms an atmospheric valve in cooperation with the atmospheric valve seat and a vacuum valve portion which forms a vacuum valve in cooperation with the vacuum valve seat. The stepped pin is pushed rearward when a corresponding portion of the rear surface of the reaction member deforms and bulges rearward, and pushes the vacuum valve seat rearward in relation to the valve body.

Abstract: A master cylinder includes a piston received in a cylinder body and formed with piston ports. An annular groove is formed in the inner periphery of the piston in its area where the piston ports are formed. An arcuate plate is received in the annular groove. A sleeve is inserted into the arcuate groove to retain the arcuate plate in the annular groove. A gap as a fluid passage is defined between the arcuate plate and the inner surface of the annular groove. A pressure chamber defined in the cylinder body communicates with a communication passage communicating with a reservoir through the above gap, cutouts of holes formed in the arcuate plate and holes formed in the sleeve. When hydraulic fluid flows rapidly from the pressure chamber toward the reservoir, the arcuate plate is adapted to elastically and radially expand, thus closing some of the piston ports.

Abstract: In a negative pressure type booster device, secondary passages 53 communicating directly with the atmosphere is formed between the internal surface of a sliding cylindrical portion 8b of a valve piston 8 and the external surface of a silencer 27, and communication means 60 is provided for being controlled to vary its path area in dependence on the advance amount of an input rod 23 when the same is moved beyond a predetermined distance relative to the valve piston 8. Thus, when a brake pedal 25 is stepped on strongly, the atmospheric air can be led from the secondary passages 53 through the communication means 60 to a variable pressure chamber 6, so that the property of the responsiveness in braking operation can be improved to a responsiveness enhancing property which varies in dependence on the manner of stepping the brake pedal 25.

Abstract: A master cylinder includes a cylinder body, primary cups supported on the inner periphery of the cylinder body, and a primary piston and a secondary piston inserted in the cylinder body so as to be in sliding contact with the respective primary cups. The cylinder body is integrally formed with annular walls behind the respective primary cups. The annular walls have a greater inner diameter than the inner diameter of the cylinder body to define annular passages between the annular walls and the respective pistons. Connecting passages having a greater radial dimension than the annular passage are defined between the inner periphery of the cylinder body and the respective pistons behind the respective annular walls so as to communicate with a reservoir. While the master cylinder is not actuated, piston ports formed in the respective pistons communicate with the reservoir through the respective annular passages and connecting passages.

Abstract: The housing of a motor-driven parking brake apparatus includes a pair of cable reaction-receiving portions for receiving reactions from cables generated due to tensions of the cables, and an axial load-receiving portion for receiving axial load from a screw shaft generated due to the tensions of the cables. These portions, which must be formed to have a large wall thickness, are provided on one side of the housing. This structure reduces the size of the housing. In addition, the axial load-receiving portion is provided between the paired cable reaction-receiving portions. This arrangement further reduces the size of the housing.

Abstract: A motor-driven parking brake apparatus includes a load sensor (pressure sensor) for detecting axial load of a screw shaft. The pressure sensor includes a transmission member which receives the axial load via a circular surface of a plate, and a casing which accommodates the transmission member and receives the axial load via the transmission member. This casing has a circular opening having an opening area smaller than the surface of the circular surface. The pressure sensor detects a pressure generated due to a load received from an exposed portion of the transmission member which is exposed from the circular opening. Due to characteristics of the transmission member, the load received from the exposed portion is a portion of the axial load and proportional to the axial load.

Abstract: A vacuum booster which moderates a retraction speed of a valve seat member to restrain a contact noise between a key member retracting in a unitary manner with the valve seat member and a flange surface of a plunger. The vacuum booster includes a noise restriction device.

Abstract: Reaction force from a reaction member is divided and transmitted to a front shaft portion of a plunger via abutment member and to a flange portion of the plunger via a spring unit. The spring unit includes a tubular first holding member assembled to the front shaft portion of the plunger and being engageable, at its front end portion, with the reaction member, a second holding ember assembled to a rear end portion of the first holding member and having a rear end portion which extends rearward from the first holding member for engagement with the flange portion, and Belleville springs held between the first and second holding members. When the reaction force transmitted from the reaction member to the first holding member exceeds the load of the springs, the first holding member moves while compressing the springs and engages with a stepped portion of a valve body.

Abstract: A master cylinder includes a piston received in a cylinder body and formed with piston ports. An annular groove is formed in the inner periphery of the piston in its area where the piston ports are formed. An arcuate plate is received in the annular groove. A sleeve is inserted into the arcuate groove to retain the arcuate plate in the annular groove. A gap as a fluid passage is defined between the arcuate plate and the inner surface of the annular groove. A pressure chamber defined in the cylinder body communicates with a communication passage communicating with a reservoir through the above gap, cutouts of holes formed in the arcuate plate and holes formed in the sleeve. When hydraulic fluid flows rapidly from the pressure chamber toward the reservoir, the arcuate plate is adapted to elastically and radially expand, thus closing some of the piston ports.

Abstract: In a vacuum type brake booster, the reaction of output transmitted from an output shaft to a reaction member is transmitted to a valve body, a plunger, and a stepped pin. A valve mechanism, which is assembled to an axial hole of the valve body, includes an atmospheric valve seat which advances and retreats together with the plunger, a vacuum valve seat assembled to the valve body to advance and retreat, and a valve member having an atmospheric valve portion which forms an atmospheric valve in cooperation with the atmospheric valve seat and a vacuum valve portion which forms a vacuum valve in cooperation with the vacuum valve seat. The stepped pin is pushed rearward when a corresponding portion of the rear surface of the reaction member deforms and bulges rearward, and pushes the vacuum valve seat rearward in relation to the valve body.

Abstract: In a negative pressure type booster device, secondary passages 53 communicating directly with the atmosphere is formed between the internal surface of a sliding cylindrical portion 8b of a valve piston 8 and the external surface of a silencer 27, and communication means 60 is provided for being controlled to vary its path area in dependence on the advance amount of an input rod 23 when the same is moved beyond a predetermined distance relative to the valve piston 8. Thus, when a brake pedal 25 is stepped on strongly, the atmospheric air can be led from the secondary passages 53 through the communication means 60 to a variable pressure chamber 6, so that the property of the responsiveness in braking operation can be improved to a responsiveness enhancing property which varies in dependence on the manner of stepping the brake pedal 25.

Abstract: A master cylinder includes a primary cup received in a groove formed in the inner wall of the cylinder body. Projections are formed on a radially inner portion of the cup so as to protrude forwardly from the front end of the radially inner portion. The projections are adapted to be pressed against the front end wall of the cup-receiving groove and elastically deformed under a pressure difference produced between the front and rear ends of the cup when the piston is returned quickly, allowing the cup to advance in the cup-receiving groove. When the cup advances in the groove, a fluid passage is defined between a base portion of the cup and the rear end wall of the groove.

Abstract: A negative pressure type booster device possesses a valve mechanism constructed to compensate for insufficient depressing force applied to a brake pedal upon emergency braking. Upon depression of the brake pedal, first negative pressure valves contact first negative pressure valve seats to block a variable pressure chamber from communication with a constant pressure chamber, and an atmosphere valve seat is separated from an atmosphere valve to communicate the variable pressure chamber with atmosphere. A partition member thus moves forwards depending on the pressure difference between the chambers to output a propelling force from an output rod. When the brake pedal is stepped on quickly, a valve member is urged backwards by a spring member causing second negative pressure valve seats to contact second negative pressure valves and move the valve member backwards. The atmosphere valve separates from the atmosphere valve seat, and the variable pressure chamber quickly communicates with atmosphere.

Abstract: A negative pressure type booster includes a power piston, a slide valve, and a holding mechanism, among others, and assists a driver during emergency braking. The holding mechanism is adapted to hold the slide valve at a predetermined frontward position, and includes a latch member that is mounted to the power piston in such a manner as to be linearly movable in a radial direction, and a garter spring for biasing the latch member radially inward. The latch member has a hook that can be engaged with and disengaged from a hook provided on the slide valve. When a plunger moves frontward relative to the power piston by a quantity greater than a predetermined value, a push slope provided on the plunger pushes a passive slope provided on the latch member radially outward, whereby the hook of the latch member is disengaged from the hook of the slide valve.

Abstract: A master cylinder includes a cylinder body and primary and secondary pistons slidably received in the cylinder body, thereby defining first and second pressure chambers in the cylinder body. The first and second pressure chambers communicate with a reservoir through first and second fluid passages, respectively. During automatic brake control such as traction control or vehicle stability control, hydraulic fluid is drawn from the reservoir through the first and second pressure chambers. A throttle valve is received in each of the first and second fluid passages. The throttle valves are adapted to open while the master cylinder is inoperative and to close under backflow pressure when hydraulic fluid flows from the pressure chambers toward the reservoir. The throttle valves each include a floating valve body and a valve seat.

Abstract: In a negative pressure type booster, an atmospheric valve seat is formed on an annular disk of an input member, which disk extends radially outward. The annular disk and an annular diaphragm located frontward of the annular disk and mounted to the input member define an annular atmospheric chamber. The atmospheric chamber communicates with the atmosphere via an air hole formed in the annular disk. The diaphragm is supported from the front by a power piston. The diaphragm is a flexible member. Inner and outer circumferential portions of the flexible member are formed into respective rolling portions for allowing frontward/rearward movement of the input member by means of curviform deformation. An atmospheric control valve portion, which is seated on and separated from the atmospheric valve seat, and a vacuum control valve portion, which is seated on and separated from a vacuum valve seat formed on the power piston, are axially separated.

Abstract: A master cylinder includes a primary piston and a secondary piston, each formed with piston ports which include two different kinds of ports, i.e. first ports for ensuring communication between a reservoir and a pressure chamber of the master cylinder, and second ports through which brake fluid is sucked from the reservoir during automatic break control. The second ports are greater in number than the first ports and are positioned forwardly of the first ports so that the second ports are closed by primary cups which are provided on the inner wall of the cylinder body so as to be in sliding contact with the respective pistons before the first ports when the respective pistons are advanced. An annular wall having a greater inner diameter than the outer diameter of the pistons is formed on the inner wall of the cylinder body to support the back of each of the primary cups. An annular groove is formed in each piston so as to communicate with the first ports.

Abstract: Reaction force from a reaction member is divided and transmitted to a front shaft portion of a plunger via abutment member and to a flange portion of the plunger via a spring unit. The spring unit includes a tubular first holding member assembled to the front shaft portion of the plunger and being engageable, at its front end portion, with the reaction member, a second holding ember assembled to a rear end portion of the first holding member and having a rear end portion which extends rearward from the first holding member for engagement with the flange portion, and Belleville springs held between the first and second holding members. When the reaction force transmitted from the reaction member to the first holding member exceeds the load of the springs, the first holding member moves while compressing the springs and engages with a stepped portion of a valve body.