JP2744621B2 - Tandem negative pressure booster - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a negative pressure booster used for a brake booster or the like, and in particular, a tandem type in which two power pistons are arranged in a skewered shape. And a negative pressure booster.

(Prior Art) Conventionally, in a brake booster using a negative pressure, in order to obtain a larger braking force with a small brake pedal depressing force, for example, Japanese Utility Model Laid-Open No. 63-53860 discloses A tandem type brake booster in which two power pistons as shown are arranged in a skewered shape is used.

In such a tandem type brake booster, when the brake pedal is depressed in performing braking, the control valve is switched, and the atmosphere is introduced into two transformer chambers partitioned by two respective power pistons. Two power pistons operate by the action of the introduced atmosphere. The master cylinder is operated by the operation of these power pistons to generate brake fluid pressure, and braking is performed. In this case, since the piston of the master cylinder is operated by the two power pistons, the maximum brake hydraulic pressure generated becomes larger as compared with a brake booster using a single power piston.

(Problems to be Solved by the Invention) However, in such a tandem type brake booster, two variable pressure chambers into which the atmosphere is introduced at the time of braking are provided, so that the total volume thereof is a single volume. It is much larger than that of the transformation chamber in the brake booster with the power piston. For this reason, when trying to use a control valve of the same size as a control valve in a brake booster with a single power piston,
It takes time for the pressure in the two transformer chambers to reach a pressure at which the two power pistons can be operated, which delays the operation of the power pistons. That is, the broken line c in FIG.
As shown by, the rise of the output of the brake booster in the early stage of operation is delayed. As described above, the conventional tandem brake booster has a lower response than a brake booster using a single power piston.

Therefore, in order to improve the responsiveness of the brake booster, it is conceivable to increase the opening amount of the control valve or increase the passage area of the atmosphere flowing into the variable pressure chamber. However, if the valve opening amount of the control valve is simply increased, the valve stroke must be set large, so that the loss stroke of the booster is increased. Further, simply increasing the area of the air passage would increase the radial dimension of the booster. For this reason, the design of the conventional tandem-type negative pressure booster must be largely changed, and the cost of the tandem-type negative pressure booster increases. Thus, in each case, new problems arise in the performance, size and cost of the booster.

The present invention has been made in view of such a problem, and an object of the present invention is to improve the responsiveness by speeding up the output rise at the beginning of operation without increasing the size of the booster as a whole, and to improve the responsiveness. A simple and inexpensive tandem-type negative pressure booster is provided.

(Means for Solving the Problems) In order to solve the above-mentioned problems, an invention according to claim (1) provides a tandem-type negative pressure booster in which a first communicating chamber and a second communicating chamber communicate with each other. Inside, an orifice is provided.

According to a second aspect of the present invention, in the first aspect of the present invention, when air flows from the control valve to the variable pressure chamber communicating with the orifice in the passage in which the orifice is provided, the air passes through the orifice. And a one-way valve that bypasses the orifice and facilitates the flow of air when the air flows in the opposite direction.

(Operation) In the tandem-type negative pressure booster according to the invention of claim (1) having such a configuration, when the control valve is switched via the input shaft to operate the booster, the first variable pressure chamber is operated. The second transformer chamber communicates with the atmosphere via a control valve and a passage. In that case, the atmospheric pressure air is quickly introduced into the second variable pressure chamber without any restriction. Further, the air introduced into the second transformer chamber is introduced into the first transformer chamber via the passage. At this time, the flow rate of the air introduced into the first transformer chamber is provided in the passage. Will be limited by the orifice. Therefore, air is not quickly introduced into the first transformation chamber.

For this reason, at the beginning of braking, most of the air flowing through the control valve is intensively introduced into the second transformer chamber.
The pressure in the second variable pressure chamber rises quickly in a state close to the pressure increase in the single variable pressure chamber in the booster with the single power piston. Therefore, in the early stage of the operation, the first power piston is not activated, but the second power piston receiving the pressure of the rapidly rising second transformer chamber is quickly activated, and the booster quickly outputs the power. I will be. That is, the rise of the output of the tandem type negative pressure booster is quickened.

Since the pressure in the first variable pressure chamber into which air is introduced via the orifice is not rapid but gradually increases, the power piston receiving the pressure in the first variable pressure chamber also delays the operation of the second power piston. It works. Thereby, the output of the booster is further increased, and a large output by the tandem type negative pressure booster can be obtained.

Further, in the tandem type negative pressure booster according to the invention of claim (2), the rise of the output is similarly accelerated during operation.

When the control valve is switched to release the operation, the first
The second pressure chamber and the second variable pressure chamber are both connected to the first and second constant pressure chambers via a control valve. For this reason, the air in the second variable pressure chamber quickly flows out to the first constant pressure chamber, while the air in the first variable pressure chamber on the side where air is introduced via the orifice bypasses the orifice by opening the one-way valve. Then as quickly as the first
It will flow out into the constant pressure chamber. Therefore, the power piston and the valve body can both return quickly, and the operation of the booster is quickly released.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment in which a tandem type negative pressure booster according to the present invention is applied to a brake booster.
The figure is an enlarged detail view of a portion A in FIG.

As shown in FIG. 1, the brake booster 1 includes a front shell 2 and a rear shell 3, and the front shell 2 and the rear shell 3 are formed such that a large space is formed therein. They are connected by bayonet connection or the like. The space inside the shells 2 and 3 is divided into a front room 5 and a rear room 6 by a center plate 4.

A valve body 7 is disposed so as to penetrate the rear shell 3 and the center plate 4. The valve body 7 is airtightly and slidably mounted on the rear shell 3 and the center plate 4 by a pair of seal members 8 and 9. It is supported by. A front power piston 10 and a rear power piston 11 housed in the front chamber 5 and the rear chamber 6, respectively, are connected to the valve body 7. A front diaphragm 12 and a rear diaphragm 13 are provided between the shells 2, 3 and the valve body 7 on the back of the power pistons 10, 11. The front power piston 10 and the front diaphragm 12 constitute a first power piston of the present invention, and the first power piston divides the front chamber 5 into a first constant pressure chamber 5a and a first variable pressure chamber 5b. Also, the rear power piston 11 and the rear diaphragm 13
Constitutes a second power piston according to the present invention, and the rear chamber 6 is connected to the second constant pressure chamber by the second power piston.
6a and a second transformer chamber 6b.

The valve body 7 is provided with a hole 7a opening to the first constant pressure chamber 5a, a hole 7b opening to the atmosphere, and a hole 7c communicating with the second variable pressure chamber 6b. Also, the valve body 7 has
An axial passage 14 communicating the holes 7a and 7b and a radial passage 15 communicating the passage 14 and the second constant pressure chamber 6a are formed. Further, the valve body 7 includes
Axial passage connecting the second transformer chamber 6b and the first transformer chamber 5b
16 and a passage 17 communicating the second transformer chamber 6b with the hole 7c are formed.

As shown in detail in FIG. 2, the passage 16 is provided with a one-way valve 19 having an orifice 18. The one-way valve 19 allows air to flow only through the closed orifice 18 when air flows from the second transformer chamber 6b toward the first transformer chamber 5b, and opens when the air flows in the opposite direction. It is made to flow by bypassing. A valve plunger is provided in the hole 7c of the valve body 7.
20 is slidably fitted. An input shaft 21 linked to a brake pedal (not shown) is connected to a right end of the valve plunger 20. The valve plunger 20 extends radially through the valve body 7 and projects into the hole 7c.
This prevents the valve body 7 from slipping out. The key member 22 is relatively movable in the axial direction by a predetermined distance with respect to the valve body 7, and is prevented from falling out of the valve body 7 by the retainer 23.

A control valve 24 is provided between the holes 7b and 7c of the valve body 7. The control valve 24 is attached to the valve body 7 and is constantly biased in the direction of the valve plunger 20 by the resilient force of a spring 25 provided between the control valve 24 and the input shaft 21.
A first valve seat 27 formed at the right end of the valve plunger 20;
And a second valve seat 28 formed in the valve body 7. When the valve body 26 is seated on the first valve seat 27 and is separated from the second valve seat 28, the control valve 24 operates in the first and second constant pressure chambers.
The first and second transformer chambers 5b and 6b communicate with the first and second transformer chambers 5b and 6b and the atmosphere, and the valve body 26 is moved from the first valve seat 27 to the first and second transformer chambers 5b and 6b. When the user is unseated and seated on the second valve seat 28, the communication between the first and second constant pressure chambers 5a, 6a and the first and second variable pressure chambers 5b, 6b is cut off and the first and second constant pressure chambers 5b, 6b are cut off.
Switching control is performed so that the transformation chambers 5b and 6b communicate with the atmosphere.

An output shaft 29 is provided in the hole 7a of the valve body 7, and the valve body 7 is slidably fitted in a hole formed in the right end large diameter portion of the output shaft 29. A reaction disc 30 is accommodated between the valve body 7 and the output shaft 29 in the hole at the right end of the large diameter portion. Therefore, the left end of the valve plunger 20 is
It is designed to face 30. The output shaft 29 is prevented from falling out of the valve body 7 by a retainer 32 urged rightward by a return spring 31 for returning the valve body 7 to the inoperative position. Further, the left end of the output shaft 29 is airtightly and slidably supported by a seal member 33 and protrudes out of the front shell 2, and its left end is interlocked with a piston of a master cylinder (not shown) attached to the front shell 2. Have been to be.

The valve body 7 and the front power piston 10 and the rear power piston 11 connected to the valve body 7 are normally held at the inoperative position shown by a return spring 31.
In this inoperative state, the key member 22 contacts the inner surface of the rear shell 3 so that the valve body 7 and the valve plunger
It regulates the right row with 20, holding them in the retreat position. In this case, the key member 22 is located at the most advanced position with respect to the valve body 7, so that the valve body 26 and the second valve seat 28
Is kept very small or zero. By doing in this way, at the time of braking, as soon as the valve plunger 20 is actuated via the input shaft 21, the valve element 26 and the first valve seat 27 are separated, and the first and second variable pressure chambers 5b, 6b communicates with the atmosphere.

The first constant pressure chamber 5a communicates with, for example, an intake manifold of an engine (not shown) through a negative pressure introducing pipe 34 attached to the front shell 2. Therefore, a negative pressure is always introduced into the first and second constant pressure chambers 5a, 6a.

 Next, the operation of this embodiment will be described.

When the brake booster 1 is in the inoperative position shown in the figure, the first and second variable pressure chambers 5b, 6b have first and second constant pressure chambers 5a, 5b.
The negative pressure is the same as that of 6a, or slightly higher than the first and second constant pressure chambers 5a and 6a, and is a pressure almost balanced with the elasticity of the return spring 31.

When the brake pedal is depressed for braking, the input shaft 21 moves forward toward the valve body 7 and the valve 26 of the control valve 24 is seated on the second valve seat 28 or immediately after the input shaft 21 moves forward. One valve seat 27 is separated from the valve body 26.
Therefore, air at atmospheric pressure flows into the second variable pressure chamber 6b through the gap between the valve body 26 and the first valve seat 27 and the passage 17. Second
The air that has flowed into the variable pressure chamber 6b also tries to flow into the first variable pressure chamber 5b through the passage 16 at the same time. However, since the orifice 18 is interposed in the passage 16, the flow rate of the air flowing to the first variable pressure chamber 5b is limited. Therefore, at this time, most of the air flowing through the control valve 24 flows intensively into the second variable pressure chamber 6b. As a result, the second
The pressure in the variable pressure chamber 6b sharply increases, and the rear power piston 11 starts operating relatively early. Therefore, the brake booster 1 outputs the force via the output shaft 29 to operate the piston of the master cylinder and start braking. As shown in FIG. 3, the output at this time is represented by a solid line b, and its rise is faster than that of a conventional tandem brake booster represented by a broken line c. Therefore, the responsiveness of the brake booster 1 in the early stage of operation is improved without increasing the opening amount of the control valve 24 or the passage of the air.

Then, the left end of the valve plunger 20 is in contact with the reaction disk 30, and the reaction force from the master cylinder is transmitted to the valve plunger 20 via the reaction disk 30, and this reaction force is further transmitted via the input shaft 21 and the brake pedal. To the driver.

After a lapse of a predetermined time, sufficient air flows into the first variable pressure chamber 5b, so that the front power piston 10 also operates, and the output increases.

As the load on the input shaft 21 increases with time as indicated by the dashed line a in FIG. 3, the output increases along the solid line b. In that case, this output is
Since the pressure in the transformation chamber 5b gradually becomes equal to the pressure in the second transformation chamber 6b, it becomes almost the same as the output of the conventional booster, that is, the lines b and c in FIG. Become almost the same.

When the brake pedal is released to release the braking, the input shaft 21 and the valve plunger 20 move rightward with respect to the valve body 7. For this reason, the first valve seat 27 abuts on the valve body 26 to shut off the first and second variable pressure chambers 5b and 6b from the atmosphere, and the valve body 26 separates from the second valve seat 28 and becomes first and second. The two variable pressure chambers 5b and 6b communicate with the first and second constant pressure chambers 5a and 6a. As a result, the air in the first and second variable pressure chambers 5b, 6b flows to the first constant pressure chamber 5a, and further flows to the intake manifold through the negative pressure introducing pipe. In this case, the key member 22 and the valve plunger 20 are at the most retracted position with respect to the valve body 7, and the gap between the valve body 26 and the second valve seat 28 is relatively large. Therefore, the air in the second transformation chamber 6b flows quickly. Further, since the one-way valve 19 is opened, the air in the first variable pressure chamber 5b also flows quickly. As a result, the valve body 7 and the front and rear power pistons 10, 11 are quickly retracted by the elastic force of the spring 31.

When the key member 22 comes into contact with the inner surface of the rear shell 3, the valve plunger 20 does not further retract, but the valve body 7 continues to retract further until the key member 20 reaches the most advanced position with respect to the valve body 7. When the key member 20 is at the most advanced position with respect to the valve body 7, the valve body 7 is not further retracted, and is at the retracted limit position.
Thus, the valve body 7 and the valve plunger 20 are in the initial inoperative position shown.

In this embodiment, the second transformation chamber 6b and the first transformation chamber 5b
In the passage 16 communicating with the valve, a one-way valve 19 having a simple structure having an orifice 18 may be simply provided, so that it is not necessary to largely change the design of the conventional tandem type negative pressure booster. Therefore, the tandem type negative pressure booster can be formed with a simple structure and at a low cost.

Although the one-way valve 19 is provided in the above-described embodiment, the present invention is not limited to this, and the one-way valve 19 is not necessarily required. Therefore, the one-way valve 19 may be omitted and only the orifice 18 may be provided. In that case, it is necessary to appropriately set the throttle amount of the orifice 18 so that the return of the front power piston 10 does not become too slow when the operation is released.

Further, in the above-described embodiment, the orifice 18 and the one-way valve 19 are used.
And the passage 16 communicating with the first transformer chamber 5b is connected to the valve body 7
Although it is assumed to be used for the booster formed in
Passage 16 to front shell 2 or rear shell 3
The present invention can also be applied to a booster formed by the center plate 4 and the booster.

Furthermore, the case where the negative pressure booster of the present invention is applied to a brake booster has been described, but the present invention can also be applied to other boosters such as a clutch booster.

(Effect of the Invention) As is apparent from the above description, the tandem-type negative pressure booster according to the invention of claim (1) restricts the flow of air from the control valve to the first variable pressure chamber via the orifice. hand,
Since the air from the control valve is mainly mainly introduced into the second variable pressure chamber, the output of the tandem type negative pressure booster at the beginning of operation can be quickly started.

In addition, in the invention of claim (2), in addition to this, the flow of air from the first variable pressure chamber into which the air is introduced by being restricted via the orifice by the one-way valve to the control valve is restricted by the orifice. The operation can be canceled quickly because the operation is free.

Moreover, since the one-way valve has the orifice, the one-way valve and the orifice can be formed integrally, and the structure of the one-way valve and the orifice can be simplified.

Further, in any of the inventions, it is not necessary to increase the opening amount of the control valve or the cross-sectional area of the air passage communicating with the variable pressure chamber. In addition, in the first aspect of the present invention, an orifice may be simply provided in a passage communicating the first and second variable pressure chambers, and in the second aspect of the invention, a simple structure having an orifice in one direction. Since it is only necessary to provide a valve, it is not necessary to largely change the design of the conventional tandem vacuum booster. Therefore, the tandem-type negative pressure booster can have a conventional size and excellent responsiveness, and the tandem-type negative pressure booster can have a simple structure and can be formed at low cost.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment in which a tandem type negative pressure booster according to the present invention is applied to a brake booster, FIG. 2 is an enlarged detailed view of a portion A in FIG. 1, and FIG. It is explanatory drawing which shows each output characteristic of this Example and the conventional tandem type negative pressure booster. 1 ... Brake booster (tandem type negative pressure booster),
2 front shell, 3 rear shell, 4 center plate, 5 front room, 5a first constant pressure chamber, 5b
... 1st variable pressure chamber, 6 ... rear chamber, 6a ... 2nd constant pressure chamber, 6b
... Second variable pressure chamber, 7... Valve body, 10... Front power piston (first power piston), 11... Rear power piston (second power piston), 12... Front diaphragm (first power piston) , 13… rear diaphragm (second power piston), 16… passage, 18…
Orifice, 19 ... one-way valve, 21 ... input shaft, 24 ... control valve

Claims (2)

(57) [Claims] 1. A center plate for partitioning a space formed by a front shell and a rear shell into a front chamber and a rear chamber, a valve body penetrating the center plate and the rear shell in an airtight and slidable manner. A first power piston connected to the valve body and dividing the front chamber into a first constant pressure chamber and a first variable pressure chamber into which a negative pressure is introduced; and a first power piston connected to the valve body, and the rear chamber is connected to the first power piston. A second power piston partitioned into a second constant-pressure chamber communicating with the first constant-pressure chamber, and a second variable-pressure chamber communicating with the first variable-pressure chamber; an input shaft disposed in the valve body so as to be movable forward and backward; The second variable pressure chamber is provided in a valve body, and when the input shaft is not operated, the second variable pressure chamber is cut off from the atmosphere and communicated with the first and second constant pressure chambers or cut off from these constant pressure chambers. A tandem-type negative pressure multiplier comprising: a control valve for controlling the switching so that the second variable pressure chamber communicates with the atmosphere when the input shaft advances toward the valve body and cuts off the first and second constant pressure chambers. In the power device, an orifice that restricts a flow of air from the second transformation chamber to the first transformation chamber is provided in a passage communicating the first transformation chamber and the second transformation chamber. A tandem type negative pressure booster characterized by the following. 2. A passage in which said orifice is disposed,
When air flows from the control valve toward the variable pressure chamber communicating with this passage, air flows only through the orifice, and when air flows in the opposite direction, air bypasses the orifice. The tandem type negative pressure booster according to claim 1, further comprising a one-way valve provided with the orifice for causing the fluid to flow.