JPH0958454A - Vacuum booster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an output of a vacuum booster from being lowered rapidly after a brake operation is canceled while a solenoid is being driven by making a drive circuit to receive a detecting signal of a release switch which detects the cancellation of the brake operation and to make the solenoid to perform a duty operation so as to cancel the booster operation while the solenoid is under operation. SOLUTION: When a release switch is sending an ON signal according to a treadle operation of a brake pedal, if a treadle speed of the brake pedal is larger than the predetermined value Sa, it is judged by a detecting means whether or not a pedal stroke is larger than the predetermined value Sb. If the pedal stroke is larger than the predetermined value Sb, the brake pedal operation is judged to be a quick service so that a solenoid is driven to apply a brake to a vehicle. When the release switch is sending an OFF signal according to the cancellation of treadle of the brake pedal, the solenoid is switched to a duty operation. If a duty operation time is equal to or larger than the predetermined value t α, an output of a vacuum booster device is judged to be null so that the drive of the solenoid is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum booster used as a component of a vehicle brake system.

[0002]

2. Description of the Related Art As a conventional vacuum booster, SAE9
The one disclosed in No. 50761 is known. This vacuum booster includes a movable wall that is movably installed in a housing and divides the housing into a constant pressure chamber and a variable pressure chamber, a power piston connected to the movable wall, and an outer end opening of the power piston. From the same power piston to the outside of the power piston and connected to a brake pedal and movable in a substantially input / output axis direction by a brake operation; The valve plunger member that is slidable along and engages with the input rod; and the first state that engages with the valve plunger member and the second state that disengages the valve plunger member selectively cause the A control valve that communicates the variable pressure chamber with the atmosphere, a solenoid that is connected to a power source and operates the valve plunger member by receiving power supply, and the solenoid. In a vacuum booster having a driving circuit for driving, an extension portion is formed so as to project radially outward of the valve plunger member, and the extension portion is moved near a portion of the power piston facing the input side of the extension portion. Eventually, a detection means for detecting the movement of the input rod is provided, and the drive circuit receives the detection signal of the detection means at least when the solenoid is driven to release the drive of the solenoid and release the boosting action of the vacuum booster. It is characterized by doing.

The operation of this vacuum booster will be described with reference to FIG. FIG. 4 is a characteristic diagram of the output of this vacuum booster, in which the vertical axis represents the output of the vacuum booster, the horizontal axis represents the depression force of the brake pedal, and the solid line is the characteristic diagram during normal operation. And the broken line shows the characteristic diagram when the solenoid is driven.
Further, the valve plunger member of the vacuum booster includes a first valve plunger member that is engaged with each other and interlocks with the input rod, and a second valve plunger that is actuated by driving a solenoid. In this vacuum booster, the input rod moves into the power piston in response to the brake operation of the depression force F of the brake pedal, and the valve plunger member also moves with the movement of the input rod, and the valve plunger member and the control valve. With and disengaged,
Atmosphere is introduced into the variable pressure chamber to generate propulsive force in the movable wall, and thus in the power piston, and an output at point a is passed along the solid line to cut off the communication between the variable pressure chamber and the atmospheric pressure, and However, if some detection means needs to drive the solenoid by this brake operation, for example, the brake pedal depressing speed detecting means detects that the brake pedal depressing speed is A value equal to or greater than a predetermined value is determined, and it is determined that this braking operation is a sudden braking, and a signal is transmitted to the drive circuit to drive the solenoid, and the drive circuit receiving the signal drives the solenoid and is in a non-operating state. Actuating a second valve plunger, which is part of the valve plunger member, to engage the second valve plunger and the control valve. Ri further into the variable pressure chamber to generate a propulsion force to the movable wall and thus the power piston by introducing the atmosphere, forms an output at point b.

When the brake operation is released, the output decreases along the dotted line, the extension member also moves to the input side as the input rod moves to the initial position, and the extension member moves to the input side. That is, the detection means detects the reduction of the pedaling force of the brake pedal to the pedaling force at point c, and thus the release of the brake operation, sends a detection signal to the drive circuit, and the drive circuit which receives the detection signal receives the detection signal at point c. Since the drive of the solenoid is stopped, the second valve plunger moves to the initial position, disengages from the control valve, and the pressure difference between the variable pressure chamber and the constant pressure chamber is eliminated by connecting the variable pressure chamber and the constant pressure chamber. The movable wall and thus the power piston also return to the initial position, and the boosting action of the vacuum booster is completed.

[0005]

However, in the above-described vacuum booster, the drive circuit instantaneously stops the drive of the solenoid at the point c in response to the detection signal of the detection means that detects the release of the brake operation. , The atmosphere in the variable pressure chamber suddenly flows into the constant pressure chamber, and the output of the vacuum booster decreases rapidly, that is, the output at point c decreases to the output at point d. There was a problem such as a bad ring.

According to the present invention, it is possible to prevent the output of the vacuum booster from rapidly lowering after the brake operation is released when the solenoid is driven, and to improve the pedal feeling by smoothing the brake release operation. , That is the technical issue.

[0007]

In order to solve the above technical problems, a movable wall that is movably installed in a housing and divides the housing into a constant pressure chamber and a variable pressure chamber, and is connected to the movable wall. A power piston, an input rod that extends from the outer end opening of the power piston to the outside of the power piston, is connected to a brake pedal, and is movable in the substantially input / output axis direction by a brake operation, and the power piston in the power piston. A valve plunger member that is housed substantially coaxially therein and that is slidable along a substantially input / output shaft and that engages with the input rod; and a first state that engages with the valve plunger member is disengaged. A control valve that selectively communicates the variable pressure chamber with the atmosphere by adopting the second state, and the valve plunger part that is connected to a power source and receives power supply. In a vacuum booster having a solenoid for activating the solenoid and a drive circuit for driving the solenoid, a release switch for detecting release of a brake operation is provided, and the drive circuit detects the release switch detection signal at least when the solenoid is driven. In response to this, a vacuum booster characterized by performing a duty operation for intermittently driving the solenoid to release the boosting action is constructed.

Preferably, the release switch detects the release of the brake operation by the relative movement of the input rod and the housing or the load applied to the input rod and the brake pedal. Boosters are desirable.

Further, it is preferable that the drive circuit terminates the drive of the solenoid after the solenoid is duty-operated for a predetermined time.

According to another aspect of the vacuum booster of the present invention, when a brake operation is performed and some detecting means needs to drive the solenoid by this brake operation, for example, the depression speed detecting means of the brake pedal detects the brake operation. The accompanying pedal speed of the brake pedal is above a specified value,
When it judges that this braking operation is a sudden braking, it sends a signal to the drive circuit to drive the solenoid, and the drive circuit that receives the signal drives the solenoid to operate the valve plunger member, and the valve plunger member and the control valve When is disengaged, the atmosphere is introduced into the variable pressure chamber to generate a propulsive force on the movable wall, and thus on the power piston, thereby providing a boosting action.

When the brake operation is released, the release switch detects the release of the brake operation and sends a detection signal to the drive circuit, and the drive circuit which receives the detection signal performs duty operation for intermittently driving the solenoid. The valve plunger member and the control valve intermittently engage with each other to intermittently communicate the variable pressure chamber and the constant pressure chamber,
Since the pressure difference between the transformer chamber and the constant pressure chamber gradually disappears,
The movable wall, and thus the power piston, gradually returns to the initial position, and the boosting action of the vacuum booster is completed.

According to another aspect of the vacuum booster of the present invention, when a brake operation is performed and some detecting means needs to drive the solenoid by the brake operation, for example, the brake pedal depressing speed detecting means performs the brake operation. The accompanying pedal speed of the brake pedal is above a specified value,
When it judges that this braking operation is a sudden braking, it sends a signal to the drive circuit to drive the solenoid, and the drive circuit that receives the signal drives the solenoid to operate the valve plunger member, and the valve plunger member and the control valve When is disengaged, the atmosphere is introduced into the variable pressure chamber to generate a propulsive force on the movable wall, and thus on the power piston, thereby providing a boosting action.

When the brake operation is released, the input rod moves to the initial position, that is, the input rod relatively moves with respect to the housing, and the relative movement of the input rod with respect to the housing causes the release switch to move. The movement of the input rod to the input side, that is, the release of the brake operation is detected, a detection signal is sent to the drive circuit, or the load applied to the input rod or the brake pedal is reduced, that is,
The release switch detects the release of the brake operation, sends a detection signal to the drive circuit, and the drive circuit that receives the detection signal intermittently drives the solenoid to perform duty operation, so that the valve plunger member and the control valve are intermittently connected. The pressure difference between the variable pressure chamber and the constant pressure chamber gradually disappears, and the movable wall, and thus the power piston, gradually returns to the initial position. The boosting action of the vacuum booster is terminated.

According to the third aspect of the present invention, in addition to the functions of the first and second aspects, the drive circuit receiving the detection signal causes the solenoid valve to intermittently drive the solenoid for a predetermined period of time so that the valve is operated. The plunger member and the control valve are intermittently engaged to intermittently communicate the variable pressure chamber and the constant pressure chamber, and the pressure difference between the variable pressure chamber and the constant pressure chamber gradually disappears. At the same time, it returns to the initial position and ends the boosting action of the vacuum booster.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments.

(First Embodiment) As shown in FIG. 1, a housing 10 includes a third shell 11, a second shell 12, and a first shell.
It is composed of the shell 13. The housing 10 has a second shell 12 and a first shell 13 airtightly fitted inside a third shell 11.

A closed space Rb is formed between the first shell 13 and the second shell 12.

A movable wall 15 is arranged in the space Rb. The interior of the space Rb is further divided by the movable wall 15 into a variable pressure chamber Rb1 and a constant pressure chamber Rb2. Movable wall 15
Includes an annular plate 151 and a diaphragm 152. The inner peripheral portion of the annular plate 151 is engaged with the outer peripheral portion of the power piston 16. Also, the diaphragm 1
The inner peripheral portion of 52 is supported by the outer periphery of the power piston 16 and is clamped by a clamping member, and the outer peripheral portion of the first piston 13 is
And is hermetically sandwiched by the second shell 12.

A sealed space Ra is formed between the third shell 11 and the second shell 12. A movable wall 14 is provided in the space Ra. The interior of the space Ra is further divided by a movable wall 14 into a variable pressure chamber Ra1 and a constant pressure chamber Ra2. The movable wall 14 includes an annular plate 141 and a diaphragm 142. Annular plate 141
Is supported on the outer periphery of the power piston 16.
The outer peripheral end of the diaphragm 142 is airtightly sandwiched between the second shell 12 and the third shell 11, and the inner peripheral end is sandwiched by the power piston 16, the annular plate 141, and the sandwiching member.

A communication passage 16 is provided inside the power piston 16.
a and 16b are formed. The communication path 16a connects the constant pressure chamber Ra2 and the constant pressure chamber Rb2. Communication passage 16b
Connects the transformer room Ra1 and the transformer room Rb1.

A plurality of bolts are fixed to the first shell 13. The first shell 13 is attached to a dashboard (not shown) by bolts.

A connector 17 for fixing the space Ra2 to a negative pressure source (not shown) such as an internal combustion engine is fixed to the third shell 11.

An annular seal fixed to the second shell 12 is provided between the second shell 12 and the power piston 16.
A bush is provided. Further, between the first shell 13 and the power piston 16, there is provided an annular seal and a bush clamped and fixed to the first shell 13. The power piston 16 is supported by respective seals and bushes, and can slide in the axial direction of the housing 10.

Inside the power piston 16, an air cleaner 18, an input rod 19, a control valve 20,
The valve plunger member 21, the solenoid 22, and the output rod 34 are inserted.

FIG. 2 shows the valve plunger member 21 of FIG.
It is an expanded sectional view of the peripheral part of. In FIG. 2, the valve plunger member 21 includes a first valve plunger 23 that supports the input rod 19 and a second valve plunger 24. The first valve plunger 23 includes a transmission rod 23a on the output side and the input rod 23a. An atmosphere control seat portion 23b is provided at a side end portion, movement of which in the input / output direction is regulated by a key 36, and the second valve plunger 24 includes a movable core 241 and a slider valve 242 which are engaged with each other. The slider valve 242 is provided with a negative pressure control seat portion 242a at the input end. Further, a spring 27 for urging the second valve plunger 24 to the output side is interposed between the first valve plunger 23 and the second valve plunger 24.

A ball joint 191 is formed at one end of the input rod 19. Ball joint 19
1 is inserted into the first valve plunger 23 and fixed by caulking, and the input rod 19 is slidably supported by the first valve plunger 23. The other end of the input rod 19 is connected to a brake pedal (not shown).

Input rod 19 and valve plunger member 2
A control valve is formed between the control valve 1 and the control valve 1. The control valve is a seat portion 20 a of the control valve 20 urged toward the valve plunger 21 by a spring 25.
A negative pressure control seat 16 a provided on the power piston 16, an atmospheric control seat 23 b provided on the first valve plunger 23, and a negative pressure control seat 242 a provided on the slider valve 242. It consists of. The control valve 20 is interposed between the outer circumference of the input rod 19 and the inner circumference of the power piston 16.
One end of a spring 26 for urging the input rod 19 toward the initial position is in contact with the spring. The other end of the spring 26 is in contact with the flange of the input rod 19.

Outer periphery of movable core 241 and power piston 1
A solenoid 22 is disposed between the inner circumference of the solenoid 6 and the solenoid 22 and is attached to a case 28 that covers the solenoid 22 and the movable core 241. The case 28 is engaged with the transmission rod 23a, and the case 28 including the solenoid 22 also moves in the input / output axis direction in accordance with the movement of the input rod 19 along the input / output axis.

The solenoid 22 is electrically connected to a solenoid drive circuit 29 (in FIG. 1) arranged outside the housing 10.

Outer circumference of solenoid 22 and power piston 1
A release switch 30 is attached to the case 28 and between the inner circumference of the case 6. The release switch 30 is means for detecting the axial position of the input rod 19 with respect to the housing 10.

The release switch 30 is provided with a substantially rod-shaped sensor 30a which is movable (slidable) in parallel to the substantially input / output axis, and the sensor 30a is substantially parallel to the input / output axis in the housing 1.
0 extends along the inner wall to the input side and faces the detection surface of the housing 10 facing the output side. In the initial state, the sensor 30a is in contact with the detection surface. The release switch 30 is also electrically connected to the solenoid drive circuit 29 (in FIG. 1) and sends an OFF signal to the drive circuit 29 in the initial state.

A reaction disk 31 is provided on the output side of the transmission rod 23a. The reaction disk 31 is provided on a reaction disk retainer 32,
The reaction disc retainer 32 is in contact with the output-side end face of the power piston 16.

In FIG. 1, a spring 33 is interposed between the power piston 16 and the housing 10, and the spring 33 urges the power piston 16 toward the input side via a reaction disc retainer 32.

An output rod 34 is arranged in contact with the output side end surface of the reaction disc 31. A master cylinder 37 and an ABS (anti-lock brake system) 35 are arranged on the output side of the output rod 34 outside the housing 10. Master cylinder 3
7 and ABS (antilock brake system) 35 normally act on the brakes via hydraulic pressure according to the output from the output rod 34, and when the speed difference between the vehicle body speed and the drive wheels becomes large, Temporarily reduce the braking force,
This is a system that prevents slipping of the drive wheels. next,
The operation of the vacuum booster according to the present embodiment will be described with reference to FIGS. 1 to 3 and 5. FIG. 3 is a flowchart for driving the solenoid of the vacuum booster according to the present embodiment.
FIG. 4 is a characteristic diagram of the output of the vacuum booster of the present embodiment when the brake pedal operation is released, where the vertical axis represents the output of the vacuum booster and the horizontal axis represents time.

First, the normal operation will be described. When a brake pedal (not shown) is depressed, the input rod 19
Moves toward the inside of the power piston 16, the valve plunger member 21 and the case 28 also slide inside the power piston 16 as the input rod 19 moves, and the seal portion 20a of the control valve 20 is moved to the output side by the spring 25. The seal portion 20a contacts the negative pressure control seat portion 16a to block the communication between the constant pressure chambers Ra2 and Rb2 and the variable pressure chambers Ra1 and Rb1 by being urged by the valve plunger member 21. After the contact with the negative pressure control seat 16a, the atmosphere control seat portion 23b of the first valve plunger 23 separates from the seal portion 20a and the variable pressure chamber Ra1,
Atmosphere is introduced into Rb1 to cause a pressure difference between the constant pressure chambers Ra2 and Rb2 and the variable pressure chambers Ra1 and Rb1 to generate a propulsive force in the power piston 16.

When the power piston 16 moves to the output side, the output rod 34 moves via the reaction disc retainer 32 and the reaction disc 31, and the movement of the output rod 34 causes the master cylinder 37 to move.
Increases hydraulic pressure and brakes the vehicle drive wheels.

When the depression of the brake pedal is released, the input rod 19 moves toward the outside of the power piston 16, and as the input rod 19 moves, the valve plunger member 21 also slides inside the power piston 16 to control the atmosphere. The seat portion 23b comes into contact with the seal portion 20a so that the transformation chamber Ra
1, the communication between Rb1 and the atmosphere is cut off, and further movement of the valve plunger member 21 causes the seal portion 20a to interlock with the valve plunger member 21 so that the seal portion 20a is separated from the negative pressure control seat portion 16a and the constant pressure is maintained. Room Ra2, R
b2 and the transformer rooms Ra1 and Rb1 are communicated with each other, and the transformer room Ra1
1, the atmosphere in Rb1 flows into the constant pressure chambers Ra2 and Rb2, the pressure difference between the constant pressure chambers Ra2 and Rb2 and the variable pressure chambers Ra1 and Rb1 disappears, and the power piston 16 returns to the initial position.

With the return of the power piston 16 to the initial position, the output rod 34 also returns to the initial position, so that the master cylinder 37 lowers the hydraulic pressure and releases the brakes on the drive wheels of the vehicle.

Next, the operation when the solenoid 22 is driven will be described. When the brake pedal is depressed,
When the valve plunger member 21, the case 28 and the release switch 30 are integrally moved to the output side, step 1
At 01, the movement of the release switch 30 separates the sensor 30a from the detection surface of the housing 10 facing the output side, and it is determined whether or not the release switch 30 has transmitted an ON signal to the drive circuit 29. If the release switch 30 does not transmit the ON signal to the drive circuit 29, that is, the sensor 30a is not separated from the detection surface facing the output side of the housing 10, and the release switch 30 outputs the OFF signal to the drive circuit 29. If the call continues to be sent to, return to step 101. Release switch 30 is O
When the N signal is transmitted, in step 102,
Whether or not the brake pedal depression speed is higher than a predetermined value Sa is determined by a brake pedal depression speed detection means (not shown). If the speed of depression of the brake pedal is less than the predetermined value Sa, the process returns to step 101, and if it is greater than the predetermined value Sa, in step 103, the pedal stroke associated with the depression of the brake pedal is not shown. The stroke detection means determines whether or not the value is larger than the predetermined value Sb. If the pedal stroke accompanying the depression of the brake pedal is less than the predetermined value Sb, step 1
Returning to 01, if it is larger than the predetermined value Sb, it is determined from the pedal speed in step 102 and the pedal stroke determination in step 103 that this brake pedal operation is a sudden braking, and in step 104, the drive circuit 29 The solenoid 22 is driven by. Solenoid 2
2 is driven, the movable core 241 moves to the input side, and the slider valve 2 moves as the movable core 241 moves.
42 also moves to the input side, the negative pressure control seat portion 242a of the slider valve 242 contacts the seal portion 20a, and cuts off the communication between the constant pressure chambers Ra2 and Rb2 and the variable pressure chambers Ra1 and Rb1. The movement of 242 causes the seal portion 20a to move to the input side so that the seal portion 20a moves to the first position.
The air is introduced from the atmosphere control seat portion 23b of the valve plunger 23 into the variable pressure chambers Ra1 and Rb1, and a pressure difference is generated between the constant pressure chambers Ra2 and Rb2 and the variable pressure chambers Ra1 and Rb1. Generate propulsion. When the power piston 16 moves to the output side, the output rod 34 moves via the reaction disc retainer 32 and the reaction disc 31, and the movement of the output rod 34 raises the hydraulic pressure in the master cylinder 37 and the drive wheels of the vehicle. Brake on.

When the depression of the brake pedal is released, the input rod 19 moves toward the outside of the power piston 16, and as the input rod 19 moves, the first valve plunger 23 and the case 28 move inside the power piston 16. The slide switch 30 slides and the release switch 30 attached to the case 28 also moves to the input side as the case 28 moves. The release switch 30 contacts the facing detection surface and the release switch 30 is OF.
It is determined whether or not the F signal is transmitted to the drive circuit 22. If the sensor 30a is not in contact with the detection surface facing the output side of the housing 10 and the release switch 30 is transmitting an ON signal, the process returns to step 104 to continue driving the solenoid 22 to release the release signal. If the switch 30 is transmitting the OFF signal, in step 106, the operation of the solenoid 22 is switched to duty driving for intermittently driving. For example, assuming that the time required for the second valve plunger 24 to make one reciprocation in the power piston 16 by switching the driving of the solenoid 22 to a fixed duty driving at a duty ratio of 0.3 is 1 , The solenoid 22 is driven, the second valve plunger 24 moves to the input side,
The time period during which the negative pressure control seat portion 242a of the slider valve 242 is in contact with the seal portion 20a and introduces the atmosphere into the variable pressure chambers Ra1 and Rb1 is 0.3.
The driving of the solenoid 22 is temporarily stopped, the second valve plunger 24 returns to the initial position, and the negative pressure control seat portion 2
42a is separated from the seal portion 20a, and the seal portion 20a
Is in contact with the atmospheric control seat portion 23b of the first valve plunger, and the negative pressure control seat portion 1 of the power piston is
6a is not in contact, the constant pressure chambers Ra2, Rb2 are in communication with the variable pressure chambers Ra1, Rb1, and the time during which the atmosphere in the variable pressure chambers Ra1, Rb1 is flowing into the constant pressure chambers Ra2, Rb2 is 0.7, By repeating the reciprocating motion of the power piston 16 of the second valve plunger 24, the atmosphere in the variable pressure chambers Ra1 and Rb1 is intermittently changed to the constant pressure chambers Ra2 and Rb.
b2 into the constant pressure chambers Ra2, Rb2 and the variable pressure chamber Ra.
1, the pressure difference between Rb1 and Rb1 gradually disappears. That is, in FIG. 5, the output gradually decreases to the right from point c to point e, and point c in FIG. 5 indicates point c in FIG. In step 107, it is judged whether or not the duty driving time is equal to or longer than the predetermined value tα shown in FIG. 5, that is, the time required for the output at the point c to decrease to 0, and if it is less than the predetermined value tα, Returning to step 106, duty driving is continued, and if it is equal to or greater than the predetermined value tα, it is determined that the output of the vacuum booster has reached 0, and driving of the solenoid 22 is stopped in step 108. Constant pressure chambers Ra2 and Rb2 and variable pressure chambers Ra1 and R
Due to the disappearance of the pressure difference between the power piston 16 and b1, the power piston 16 returns to the initial position, and as the power piston 16 returns to the initial position, the output rod 34 also returns to the initial position. Lowers the hydraulic pressure and releases the brakes on the vehicle drive wheels.

As described above, according to the vacuum booster of the present embodiment, when the brake operation is released while the solenoid 22 is driven, the drive of the solenoid 22 is switched to the duty drive. Since the output of the vacuum booster gradually decreases, it is possible to prevent the output of the vacuum booster from rapidly decreasing, the brake release operation becomes smooth, and the pedal feel can be improved.

Further, since the release switch 30 detects the release of the brake operation from the relative movement of the input rod 19 interlocked with the brake pedal with respect to the housing 10, the release of the brake operation can be instantly detected without delay. it can.

Further, the solenoid 22 is operated for a predetermined time tα.
Since the output of the vacuum booster is set to 0 by driving the duty ratio of, and the drive of the solenoid 22 is terminated after the elapse of a predetermined time tα, that is, when the output of the vacuum booster becomes 0, for example, A means for detecting the output of the vacuum booster is provided, the detecting means detects that the output of the vacuum booster has reached 0, transmits a signal to the drive circuit, and the drive circuit receiving the signal detects that the solenoid There is no need to take a complicated and expensive structure such as stopping driving. Further, the inclination from the point c to the point e in FIG. 5 can be changed by appropriately setting the predetermined time ta and the duty ratio of the duty driving of the solenoid 22.

In the present embodiment, the release switch 30 detects the release of the brake operation from the relative movement between the input rod 19 and the housing 10. However, the load applied to the input rod 19 or the brake pedal is detected. Also in the vacuum booster of the present invention provided with the release switch for detecting the release of the brake operation, the same operational effect as the vacuum booster of the present embodiment can be obtained.

Further, in the present embodiment, the solenoid 22 is driven by the duty driving in which the duty ratio is fixed at 0.3. However, the vacuum driving of the present invention in which the duty driving is performed by varying the duty ratio is performed. Even in force devices
The same effect as the vacuum booster of this embodiment can be obtained. For example, in the case of the duty ratio variation type duty driving in which the duty driving with the duty ratio 0.4 is performed until a certain time within the set time tα and thereafter the duty driving with the duty ratio 0.1 is performed, Figure 5
The inclination from the point c to the point e in the middle is a gradual inclination when the duty ratio is 0.4 and a steep inclination when the duty ratio is 0.1. On the contrary, in the case of the duty ratio variation type duty driving in which the duty driving with the duty ratio 0.1 is performed until a certain time within the set time tα and thereafter the duty driving with the duty ratio 0.4 is performed. ,
The slope from point c to point e in FIG. 5 has a steep slope when the duty ratio is 0.1 and a gentle slope when the duty ratio is 0.4. Therefore, the output of the vacuum booster gradually decreases even when the duty ratio variation type duty driving is performed.

Although the present invention has been described with reference to the above-described embodiments, the present invention is not limited to the above-mentioned aspects, but includes various aspects according to the principle of the present invention.

[0047]

As described above, according to the invention of claim 1, when the brake operation is released during the driving of the solenoid, the driving of the solenoid is switched to the duty driving which is intermittent driving. As a result, the output of the vacuum booster gradually decreases, so that the output of the vacuum booster is prevented from rapidly decreasing, the brake release operation becomes smooth, and the pedal feeling can be improved.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, the release of the brake operation is performed by the relative movement of the input rod interlocking with the brake pedal with respect to the housing, or by the input rod or By detecting the release switch from the load of the brake pedal, it is possible to instantly detect the release of the brake operation without delay.

According to the third aspect of the invention, in addition to the effect of the first or second aspect of the invention, the vacuum booster of the vacuum booster is driven by driving the solenoid duty-cycled for a predetermined time. The output is set to 0, and the driving of the solenoid is terminated after the elapse of a predetermined time, that is, when the output of the vacuum booster becomes 0. Therefore, for example, a means for detecting the output of the vacuum booster is provided, The detection means detects that the output of the vacuum booster has reached 0, transmits a signal to the drive circuit, and the drive circuit that receives the signal stops the driving of the solenoid, which requires a complicated and expensive structure. Nor. Further, by appropriately setting the predetermined time and the duty ratio of the duty driving of the solenoid, it is possible to change the reduction rate of the output of the vacuum booster.

[Brief description of drawings]

FIG. 1 is a sectional view of a vacuum booster according to a first embodiment.

FIG. 2 is a partially enlarged sectional view of FIG.

FIG. 3 is a flowchart of driving a solenoid according to the first embodiment.

FIG. 4 is a characteristic diagram of a conventional vacuum booster.

FIG. 5 is a characteristic diagram of the vacuum booster according to the first embodiment.

[Explanation of symbols]

 10 Housing 14, 15 Movable Wall 16 Power Piston 19 Input Rod 20 Control Valve 21 Valve Plunger Member 22 Solenoid 29 Drive Circuit 30 Release Switch Ra1, Rb1 Transformer Chamber Ra2, Rb2 Constant Pressure Chamber

Claims (3)

[Claims] 1. A movable wall that is movably installed in the housing and divides the housing into a constant pressure chamber and a variable pressure chamber, a power piston connected to the movable wall, and an outer end opening of the power piston. An input rod that extends out of the power piston and is connected to a brake pedal and is movable in a substantially input / output axis direction by a brake operation; and an input rod that is housed in the power piston substantially coaxially and along the substantially input / output shaft. By selectively sliding the valve plunger member that is slidable and engages the input rod, and the first state that engages with the valve plunger member and the second state that disengages the valve plunger member. Control valve for communicating with the atmosphere, a solenoid connected to an electric power source to actuate the valve plunger member by receiving supply of electric power, and a solenoid for driving the solenoid. A vacuum booster having a drive circuit for operating the solenoid, the release circuit detecting release of a brake operation is provided, and the drive circuit receives the detection signal of the release switch at least when the solenoid is driven, and intermittently drives the solenoid. A vacuum booster characterized by performing a duty operation to release a boosting action. 2. The release switch detects release of a brake operation by relative movement between the input rod and the housing or a load applied to the input rod or the brake pedal. 1 vacuum booster. 3. The vacuum booster according to claim 1, wherein the drive circuit terminates driving of the solenoid after the solenoid is duty-operated for a predetermined time.