JP2859733B2 - Brake booster - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake booster for reducing the operation force of a brake pedal, and more particularly to a brake booster that can be used for a traction control system or the like. Related to power devices.

[Related Art] In recent years, the need for improving the safety of automatic workers has increased, and various proposals have been made accordingly. Among them, in order to prevent the tire from spinning at the time of starting acceleration etc., the engine output is forcibly controlled by the car separately from the operation of the accelerator pedal,
In addition, a traction control system or the like that forcibly controls the brakes on the tires that are idling on the vehicle side has been adopted in various vehicles.

In the traction control system as described above, it is necessary to perform brake control separately from operation by a brake pedal. For this reason, a device for performing this control using a brake booster has already been disclosed (JP-A-Hei. 1-127446).

This device has a constant pressure chamber communicating with a negative pressure source, a negative pressure passage having a vacuum valve, and an operating pressure communicating with the atmosphere through an atmosphere passage having an atmosphere valve communicating with the negative pressure source through a constant pressure chamber. A power piston that partitions the space between the constant pressure chamber and the working pressure chamber and is arranged and moves according to the pressure difference between the constant pressure chamber and the working pressure chamber to drive the output shaft;
A return spring for urging the power piston toward the working pressure chamber, wherein a communication between the negative pressure source and the vacuum valve and a vacuum valve are provided between the negative pressure source and the vacuum valve in the negative pressure passage. An electromagnetic valve is provided to switch between communication with the atmosphere.

In a brake booster having such a structure, when there is no input from a normal brake pedal, the above-mentioned vacuum valve is open and the atmospheric valve is closed, and the constant pressure chamber and the working chamber are reduced to substantially the same negative pressure. Is kept. Then, when there is an input from the brake pedal, the vacuum valve is closed, then the atmosphere valve is opened, and the atmosphere flows into the working pressure chamber while maintaining the negative pressure in the constant pressure chamber. Then, a pressure difference is generated between the constant pressure chamber and the working pressure chamber, and the power piston moves, and the output shaft is driven to generate the brake hydraulic pressure in the master cylinder. When traction control or the like is performed using this brake booster, the electromagnetic valve is switched to send air toward the vacuum valve. Then, since the vacuum valve is open, the air flows into the working pressure chamber as it is, whereby the power piston moves.

However, when the brake is applied by the brake pedal with the brake booster having the above structure, the closing of the vacuum valve and the opening of the atmospheric valve are performed by the stroke of the operating rod that moves by pressing the brake pedal. Therefore, an invalid stroke was required from the closing of the vacuum valve to the opening of the atmospheric valve, and the response of the brake was poor. The brake booster, which has excellent brake responsiveness, balances the pressure between the constant pressure chamber and the working pressure chamber so that the vacuum valve and the atmospheric valve are closed when the operating rod is not operated. When there is an input from the brake pedal, the air valve opens immediately because both valves are closed, and the air pressure flows into the working pressure chamber while the negative pressure in the constant-pressure chamber remains unchanged, causing the power piston to operate. There is a so-called short travel type of moving structure. However, when this is used for traction control or the like, since the vacuum valve is closed, there is a problem that air cannot flow into the working pressure chamber by switching the switching valve as described above.

Among the so-called short travel types, in addition to the one in which both the vacuum valve and the atmospheric valve are closed, the one in which the opening amount of the vacuum valve is minimized is also known. Can be used for traction control, but there is a problem that the response during traction control is poor because the opening amount of the vacuum valve is small.

In addition, the above-described brake booster cannot forcibly introduce air into the working pressure chamber in a booster operating state in which both the atmospheric valve and the vacuum valve are closed (when the brake pedal is held down). Therefore, control for forcibly increasing the braking force in such a booster operating state cannot be performed. For this reason, there is also a problem that it cannot be applied to a brake device that increases the braking force beyond the input of the brake pedal when needed under any circumstances.

Accordingly, an object of the present invention is to provide a brake device which has excellent brake responsiveness even when used for traction control, and which increases the braking force beyond the input of a brake pedal when required under any circumstances. An object of the present invention is to provide a brake booster that can also be used for applications.

[Means for Solving the Problems] In order to achieve the above object, a brake booster of the present invention includes a casing, and a power dividing a casing into a constant pressure chamber and an operating pressure chamber communicating with a negative pressure source. A piston, an atmospheric valve provided on the power piston, operated by an operating rod, opened by relative advance of the operating rod, and introducing air into the working pressure chamber; and a relative retreat of the operating rod. A vacuum valve that opens the valve and communicates the working pressure chamber with the negative pressure source; a negative pressure passage that connects the vacuum valve with the negative pressure source; and a power piston that faces the working pressure chamber. An output shaft connected to the power piston, the output shaft being configured to output a thrust generated in the power piston by a differential pressure generated between the constant pressure chamber and the working pressure chamber; A switching valve that is provided in the middle of the negative pressure passage, interrupts communication between the negative pressure source and the vacuum valve, and introduces air into the vacuum valve, and a negative pressure passage between the switching valve and the vacuum valve. And a check valve provided in the bypass and extending in a forward direction from the switching valve side toward the working pressure chamber.

[Operation] According to the present invention, when brake control is performed by traction control or the like, the switching valve is switched so that the vacuum valve in the negative pressure passage that has communicated with the negative pressure source communicates with the atmosphere. Then, since the vacuum valve is closed or only slightly open, the air branches off from the negative pressure passage between the switching valve and the working pressure chamber and passes through the bypass communicating with the working pressure chamber to the negative pressure. It flows into the working pressure chamber. When the balance between the pressure in the working pressure chamber and the pressure in the constant pressure chamber, which is negative pressure, is lost, the power piston that separates the constant pressure chamber and the working pressure chamber moves toward the constant pressure chamber and opens the vacuum valve. Will be. Therefore, the air further flows into the working pressure chamber through both the negative pressure passage and the bypass, and the power piston moves further to the constant pressure chamber side to drive the output shaft. That is, when the vacuum valve is closed, the brake operation is enabled, and when the vacuum valve is open, the air is supplied from the bypass, so that the brake operation is performed quickly. When the brake control is completed, the switching valve is switched so that the vacuum valve in the negative pressure passage that has been in communication with the atmosphere is in communication with the negative pressure source. Then the vacuum valve is open,
The air flows out to the negative pressure source via the negative pressure passage. And
When the pressure in the working pressure chamber and the pressure in the constant pressure chamber balance, the power piston moves to the working pressure chamber side and closes the vacuum valve. At this time, the bypass is provided with a check valve for moving air only from the switching valve side to the working pressure chamber side, so that there is no outflow of air from the working pressure chamber to the bypass. Then, it waits for the next brake control by traction control or the input from the brake pedal.

Embodiment A brake booster according to an embodiment of the present invention will be described below with reference to FIG. In this embodiment, a tandem brake booster (having two constant pressure chambers and two working pressure chambers) will be described as an example.
A single-type brake booster (having a structure having one constant-pressure chamber and one working-pressure chamber) may of course have the same structure. The basic structure of the brake booster shown below is of the short travel type described above.

Reference numeral 1 denotes an operating rod that moves in response to an input from a brake pedal (not shown), reference numeral 2 denotes a casing of a brake booster, reference numeral 2a denotes a front shell that forms the casing 2, and reference numeral 2b denotes a casing that also forms the casing 2. Reference numeral 3 denotes a bracket provided on the front shell 2a, and reference numeral 4 denotes a negative pressure source. Further, the casing 2 is divided into two parts by a center plate 5 that slidably supports the outer periphery of a valve body described later while maintaining airtightness. Each of the casings 2 is further connected to a negative pressure source 4 by a power piston described later. Constant pressure chamber 6
A first constant pressure chamber 8 communicating with the second constant pressure chamber 6 via a constant pressure passage 7; and a negative pressure source 4 via a negative pressure passage (described later) and an atmospheric valve (described later). Atmospheric passage 9
And a first working pressure chamber 11 communicating with the atmosphere via a filter silencer 10 therein, and a first working pressure chamber 11 and a working pressure passage.
The second working pressure chamber 13 is substantially divided into a second working pressure chamber 13 communicating with the second working pressure chamber 13 via the second working pressure chamber 13.
The inner periphery of the center plate 5 is a seal / sliding member.
The seal / sliding member 14 slides on the outer periphery of a valve body (described later).

In addition, as described above, the first constant pressure chamber 8 and the first working pressure chamber 11
And the first constant pressure chamber 8 and the first working pressure chamber.
1st diaphragm plate part 15 which receives pressure difference with the inside 15
A second diaphragm plate portion 16 which partitions between the second constant pressure chamber 6 and the second working pressure chamber 13 and receives a pressure difference between the inside of the second constant pressure chamber 6 and the inside of the second working pressure chamber 13; The power piston 18 is constituted by the valve body 17 to which the plate portions 15 and 16 are fixed. Power piston 18
Is formed so as to be movable in the left-right direction in FIG. 1 because the thrust generated therein drives an output shaft 19 that presses a piston of a master cylinder (not shown). The first diaphragm plate part 15 is composed of a diaphragm plate 15a and a diaphragm 20, the second diaphragm plate part 16 is composed of a diaphragm plate 16a and a diaphragm 21, and the outer peripheral side thereof is a casing 2
The inner peripheral side is fixed to the valve body 17. Thus, the second constant pressure chamber 6 and the second working pressure chamber 13 are movable with respect to the casing 2 while maintaining the airtightness. A boot 22 that is deformable with the movement of the valve body 17 is attached between the tip of the valve body 17 and the rear shell 2b.

Then, as the power piston 18 moves, the volumes of the first constant pressure chamber 8, the first working pressure chamber 11, the second constant pressure chamber 6, and the second working pressure chamber 13 change. A return spring 23 for urging the power piston 18 toward the first working pressure chamber is provided in the second constant pressure chamber 6.

The negative pressure passage 24 extends from the negative pressure source 4 to the entrance 25 of the bracket 3.
Into the bracket 3, pass through the inside of the bracket 3, and the pipe 26 fixed to the center of the bracket 3 and the output shaft 19 of the power piston 18
Through the inside of the power piston 18 and to a vacuum valve (to be described later). Where the power piston 18
The valve body 17 has a valve seat 17 and a spring seat 27 airtightly provided on the inner periphery of the valve body 17. A fitting sealing member 28 is provided. Because of this, the pipe
Although the seal member 28 slides on the upper surface 26 in accordance with the movement of the power piston 18, airtightness in the negative pressure passage 24 is not impaired.

An atmospheric valve 30 and a vacuum valve 31 are provided in the small-diameter cylindrical portion 29 of the valve body 17 of the power piston 18. The atmosphere valve 30 is operated by the operating rod 1 and is opened by the relative advance of the operating rod 1 (movement to the left as shown in FIG. 1) to introduce the atmosphere into the first working pressure chamber 8. And a seat surface 32a at the tip of the poppet 32 and an annular projection 33a of a valve plunger 33 (described later). Further, the vacuum valve 31 provided at the boundary of the negative pressure passage 24 with the first working pressure chamber 11 is opened by the relative retreat of the operating rod 1 (moving rightward as shown in FIG. 1),
The first working pressure chamber 11 communicates with the negative pressure source 4, and includes a convex portion 18 a of the power piston 18 and a seat surface 32 a at the tip of the poppet 32. The valve plunger 33 closes the atmosphere valve 30 and the vacuum valve 31 by balancing the power piston 18 in a state where the first constant pressure chamber 8 and the second constant pressure chamber 6 are set to the negative pressure by the negative pressure source 4. The short travel mechanism 34 includes a valve plunger 33 and a key 35 attached to the valve plunger 33 so as to be able to slide slightly in the axial direction.
A groove 36 provided in the valve body 17 so that the key 35 can move in the axial direction of the valve body 17, and a stopper plate 37 for stopping the right movement of the key 35 in FIG. It is.

Here, as described above, the atmosphere valve 30 is connected to the tip of the poppet 32.
32a and a projection 33a of the valve plunger 33. When an input is made from a brake pedal (not shown), the valve rod plunger is operated by the operating rod 1.
33 is pressed and opened. The operating rod 1 is constantly urged rightward by a return spring 39 or the like. The reaction disk 38 is provided between the output shaft 19 and the valve body 17 and transmits a reaction force from the output shaft 19 to the operating rod 1 via the valve plunger 33. Further, as described above, the vacuum valve 31 at the boundary of the negative pressure passage 24 with the first working pressure chamber 11 is used.
Is constituted by a convex portion 18a of the power piston 18 and a tip portion 32a of a poppet 32 that operates via the operating rod 1 when an input is made from a brake pedal (not shown). When the brake is released from the brake pedal (not shown) when the brake is released during the normal brake operation, the operating rod 1 retreats relatively to the valve body 17 by the return spring 39 or the like ( (Moving rightward in FIG. 1). As a result, the vacuum valve 31 opens, the pressures in the first working pressure chamber 11 and the second working pressure chamber 13 decrease, and the power piston 18
Return to the right direction in the figure. And the key 35 is the stopper plate 37
In this state, the valve plunger 33 is released, and in this state, the valve body 17 also gradually moves rightward in FIG. The pressure in the pressure chamber 13 balances and closes to the vacuum valve 31. When the valve body 17 further moves to the right in FIG. 1 during the above operation, the atmospheric valve 30 opens, the valve body 17 moves to the left, and the atmospheric valve 30 and the vacuum valve 31 are closed to balance the pressure. By the way, it stops.

Further, the vacuum valve 31 is connected to the inside of the first constant-pressure chamber 8 and the second constant-pressure chamber 6 without operation from a brake pedal (not shown).
When the pressure balance between the inside and the first working pressure chamber 11 and the inside of the second working pressure chamber 13 is lost, the power piston 18 moves toward the second constant pressure chamber 6 (to the left in FIG. 1). The vacuum valve 31 will open. Further, the vacuum valve 31 closes when the pressures in the first working pressure chamber 11 and the second working pressure chamber 13 and the pressures in the first constant pressure chamber 11 and the second constant pressure chamber 13 are balanced as described above. (The state shown in FIG. 1).

Further, in the present embodiment, the communication between the negative pressure source 4 and the vacuum valve 31 is cut off at a portion between the negative pressure source 4 and the vacuum valve 31 in the negative pressure passage 24 to introduce the atmosphere into the vacuum valve 31. A switching valve 40 is provided, and the switching valve 40 is provided with a controller 41 for controlling the operation thereof. Also, the switching valve 41 and the first working pressure chamber
Between the first working pressure chamber 11 and the first working pressure chamber 11
A bypass 42 is provided which communicates with the
A check valve 42 has a forward direction from the switching valve 40 side toward the first working pressure chamber 11 side, and allows only the forward air movement.
43 are provided.

The operation of the brake booster having such a structure when the brake control is performed by traction control or the like without depending on the input from the brake pedal will be described below.

In the brake booster having the above-described structure, the switching valve 40 connects the negative pressure source 4 and the vacuum valve 31 in a state of waiting for an input from a brake pedal and a brake control by traction control or the like. , The negative pressure passage 24, the first constant pressure chamber 8, the second constant pressure chamber 6
Inside, the inside of the first working pressure chamber 11 and the inside of the second working pressure chamber 13 are all maintained at a negative pressure. The atmosphere valve 30 and the vacuum valve 31 are closed.

Here, when it becomes necessary to generate the brake oil pressure due to traction control or the like, the switching valve 40 is switched by a signal from the controller 41 to switch the negative pressure source 4
A portion from the switching valve 40 to the vacuum valve 31 of the negative pressure passage 24, which has been in communication with the vacuum passage 31, is communicated with the atmosphere 44. Then, since the vacuum valve 31 is closed, the air flows into the first working pressure chamber 11 of negative pressure via the bypass 42 and further flows into the second working pressure chamber 13 via the working pressure passage 12. . Then, the balance between the pressures in the first working pressure chamber 11 and the second working pressure chamber 13 and the negative pressures in the first constant pressure chamber 8 and the second constant pressure chamber 6 is lost, and the power piston 18 is moved. The second constant pressure chamber 6 side (left direction in FIG. 1)
And the vacuum valve 31 is opened. Therefore, air flows into the first working pressure chamber 11 and the second working pressure chamber 13 through both the negative pressure passage 24 and the bypass 42, and the power piston
18 further moves to the second constant pressure chamber 6 side to drive the output shaft 19, and the tip of the output shaft 19 presses the piston of the master cylinder (not shown) to generate brake hydraulic pressure. .

Next, when the brake control such as the traction control is completed, the switching valve 40 is switched by the signal of the controller 41, and the vacuum valve 31 that has been in communication with the atmosphere 44 is in communication with the negative pressure source 4. Then, since the vacuum valve 31 is open, the air in the first working pressure chamber 11 and the air in the second working pressure chamber 13 flow out to the negative pressure source 4 via the negative pressure passage 24. The pressures in the first working pressure chamber 11 and the second working pressure chamber 13 and the first constant pressure chamber 8
When the pressures in the inside and the second constant pressure chamber 6 are balanced, the power piston 18 moves to the first working pressure chamber 11 side (to the right in FIG. 1) to close the vacuum valve 31. At this time, bypass
Since the check valve 43 is provided on the switching valve 40 and allows the movement of air only from the switching valve 40 side to the first working pressure chamber 11 side, air does not flow from the first working pressure chamber 11 to the bypass 42. Absent. Then, inside the negative pressure passage 24, inside the first constant pressure chamber 8,
Inside the second constant pressure chamber 6, inside the first working pressure chamber 11, and inside the second working pressure chamber 13
The interior is kept at a negative pressure, the atmospheric valve 30 and the vacuum valve 31 are closed, and the next brake control by the traction control or the like or the input from the brake pedal waits.

Here, the switching valve 40 is switched even when performing control such that the braking force is forcibly increased from the booster operating state in which one of the atmospheric valve 30 and the vacuum valve 31 is closed (when the brake pedal is held down). , Switching valve 40 of negative pressure passage 24
If the portion from to the vacuum valve 31 is communicated with the atmosphere 44, the same operation as described above is performed to drive the output shaft 19 and increase the brake oil pressure.

In the above description, the communication between the negative pressure source and the switching valve can of course be indirectly connected to the negative pressure source via, for example, a constant pressure chamber or the like.

In the embodiment described above, the power piston is balanced and the vacuum valve is closed.However, the power piston abuts on the key or the rear shell before the vacuum valve closes or with the vacuum valve closed. As described above, a short travel mechanism for regulating the position of the power piston may be used.

The basic structure of the brake booster shown above is a short travel type brake booster as described above, and the operation and the like by the input of the brake pedal are the same as those of the conventional short travel type brake booster. is there.

[Effects of the Invention] As described in detail above, according to the present invention, traction and braking can be performed using a short travel type brake booster.
Brake control such as control can be performed quickly. Therefore, there is no delay in braking response during normal braking. Further, since it can be constituted by one switching valve and one check valve, an inexpensive and lightweight brake booster for traction control or the like can be provided.

In addition, since the atmosphere can be forcibly introduced into the working pressure chamber even in a booster operating state in which both the atmosphere valve and the vacuum valve are closed, the brake pedal can be used in any situation under any circumstances. Can be applied to a brake device that increases the braking force beyond the input of the braking force.

[Brief description of the drawings]

FIG. 1 is a main sectional view showing a brake booster according to an embodiment of the present invention. 1 ... operating rod, 2 ... casing, 4
...... Negative pressure source, 6 ... second constant pressure chamber (constant pressure chamber), 8 ... first constant pressure chamber (constant pressure chamber), 11 ... first working pressure chamber (working pressure chamber),
13 ... second working pressure chamber (working pressure chamber), 18 ... power piston, 19 ... output shaft, 23 ... return spring, 24 ...
Negative pressure passage, 30 ... Atmospheric valve, 31 ... Vacuum valve, 34 ... Short travel mechanism, 40 ... Switching valve, 42 ... Bypass, 43 ...
… Check valve, 44 …… atmosphere.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B60T 13/52-13/577

Claims (1)

(57) [Claims] 1. A casing, a power piston that divides the casing into a constant pressure chamber and a working pressure chamber communicating with a negative pressure source, and a power piston provided in the power piston and operated by an operating rod to move relative to the operating rod. An atmospheric valve, which is opened by a typical forward movement and introduces air into the working pressure chamber, and a vacuum valve, which is opened by a relative retreat of the operating rod and communicates the working pressure chamber and the negative pressure source. A negative pressure passage communicating the vacuum valve with a negative pressure source; a return spring biasing the power piston toward the working pressure chamber; and a constant pressure chamber and a working pressure chamber connected to the power piston. An output shaft that outputs a thrust generated in a power piston by a differential pressure generated between the negative pressure source and a vacuum valve. A switching valve for introducing air to the valve side; a bypass branched from a negative pressure passage between the switching valve and the vacuum valve to communicate with the working pressure chamber; provided on the bypass; And a check valve for directing a forward direction toward the working pressure chamber.