JPS6114983B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brake booster that utilizes both negative pressure from an intake manifold and compressed air from an air pump.

Modern vehicles are equipped with many anti-pollution parts, which increases the weight of the vehicle and tends to lower the degree of vacuum in the intake negative pressure, so the brakes must be doubled to obtain the necessary braking force. The effective diameter of the pressure receiving member of the force device must be increased. On the other hand, the interior of the engine room is becoming increasingly narrow as many parts are installed for pollution control and safety measures.
It is desired to downsize brake boosters.

In order to meet these demands, a device was developed in JP-A-51-1 that introduced negative pressure and positive pressure higher than atmospheric pressure to the front and rear of the power piston to obtain strong braking force.
This method has been proposed in Japanese Patent Application Laid-open No. 51674 and Japanese Patent Application Laid-open No. 133773/1983.

However, in the former case, a pressure chamber that introduces pressure higher than atmospheric pressure is provided inside the front of the power piston, and a valve mechanism that shuts off the atmospheric pressure introduction side is provided at the rear of the brake operating lever, so that when the brake operating lever moves forward, After this shutoff valve mechanism is closed, a third valve mechanism formed at the tip of the plunger conducts the pressure chamber to the variable pressure chamber side of the power piston. A pressure higher than atmospheric pressure is always introduced, and an annular poppet valve communicating with the pressure is provided, and a valve seat is formed behind the bulbous part of the operating rod tip to sit on the annular poppet valve, so that when the brake operating rod moves forward, the annular poppet valve is connected to the annular poppet valve. After the valve is brought into contact with the rear surface of a well-known valve mechanism, the valve seat is opened, and pressure higher than atmospheric pressure is introduced into the variable pressure chamber side of the power piston.

Therefore, according to the above-mentioned known devices, since the brake operating rod is provided with a valve mechanism for shutting off the atmosphere, the shutoff valve mechanism is closed after the pressure in the variable pressure chamber reaches atmospheric pressure, and the pressure in the variable pressure chamber is closed. When switching the inlet side to the compressed air source, a loss stroke is added to the operating stroke of the brake operating lever, resulting in an undesirable effect on the brake feeling. Furthermore, since a separate valve mechanism is provided on the plunger and the brake operating rod, these operating members themselves require various modifications and additions, making the structure unavoidable.

The present invention has been made in view of the above-mentioned deficiencies, and, without making any particular modification to the conventional brake booster itself, a third pressure chamber communicating with the variable pressure chamber at the initial stage of braking, and a third pressure chamber connected to this pressure chamber An object of the present invention is to provide a brake booster that does not cause stroke loss during operation by simply adding a switching valve device that switches communication between the atmosphere side and the compressed air source side to a normal brake booster. The feature is that a power piston and a diaphragm divide the inside of the sealed shell into a negative pressure chamber that communicates with a negative pressure source and a variable pressure chamber, and that when the brake is operated, the negative pressure is controlled by a valve mechanism. In a brake booster that cuts off communication between a pressure chamber and a variable pressure chamber and generates a pressure difference between the two chambers to apply an auxiliary force to the power piston connected to the master cylinder,
A third pressure chamber is provided connected to the operating pressure introduction side of the valve mechanism, and this third pressure chamber is connected to a compressed air source via an air introduction pipe, and the third pressure chamber is connected to the operating pressure introduction side of the valve mechanism. The pressure chamber includes a first on-off valve that communicates the third pressure chamber with the atmosphere in response to a pressure drop in the third pressure chamber; and a second on-off valve that communicates the pressure chamber with the compressed air source.

According to this configuration, at the initial stage of braking, the first on-off valve of the switching valve device opens and the atmosphere is introduced into the transformation chamber via the third transformation chamber, and when the pressure in this transformation chamber rises to a predetermined level, The on-off valve responds and automatically switches the third variable pressure chamber to the compression chamber air source side, allowing strong working pressure to be applied to the variable pressure chamber, and during this time, smooth operation is achieved without adding any loss stroke to the braking operation. can be made to do so.

The illustrated embodiment will be described below. In FIG.
The power piston 3 and diaphragm 4 connect the inside of the sealed shell between the two shells 1 and 2 to the negative pressure chamber 5 and change pressure. It is divided into 6 rooms. Reference numeral 7 denotes a negative pressure introduction pipe that opens into the negative pressure chamber 5 and is connected to the intake manifold.

8 is a partition wall provided integrally with the rear shell 2, and 8 is a partition wall provided at the front bent part 2 of the rear shell 2.
A and a define a third pressure chamber 9, and a rear cylindrical body 3a of the power piston 3 is slidably disposed in the third pressure chamber 9 from the front thereof. A brake operating rod 10 is inserted into the rear cylindrical body 3a from behind the pressure chamber 9, and the tip of the brake operating rod 10 is connected to a valve mechanism 11.
The well-known valve mechanism 11 controls communication between the negative pressure chamber 5 and the variable pressure chamber 6 and between the variable pressure chamber 6 and the third pressure chamber 9 in response to the pushing operation of the brake operating rod 10. Note that reference numerals 12 and 13 indicate seal members provided on the sliding portions of the rear cylindrical body 3a and the brake operating rod 10, respectively.

An air introduction pipe 15 communicating with an air pump 14 opens into the third pressure chamber 9, and a switching valve device 16 is provided in the middle of this air introduction pipe 15. As is clear from FIG. 2, the switching valve device 16 includes a check valve 1 which is a first on-off valve that controls the introduction of atmospheric air.
7, and an on-off valve 18 which is a second on-off valve that controls the introduction of compressed air from the air pump 14. The check valve 17 consists of a valve body 17b that receives atmospheric pressure through an opening 17a, and a compression spring 17c that presses the valve body 17b toward the opening 17a, so that the pressure inside the air introduction pipe 15 is kept at a constant pressure below atmospheric pressure. Air inlet pipe 15 that opens when it gets hot and lets the atmosphere in
and into the third pressure chamber 9. Other on-off valve 18
consists of a valve body 18a, a compression spring 18c that presses the valve body 18a toward the valve seat 18b, a plunger 18d that presses the valve body 18a to open and close it, and a compression spring 18e that presses the valve body 18a toward the valve body 18a.
The pressure of the variable pressure chamber 6 acts on the lower surface of the member 8d through the hole 19. The strength of each compression spring of these valves is set so as to obtain the following operations.

That is, first, when the brake is not activated, the non-mechanism 11 connects the negative pressure chamber 5 and the variable pressure chamber 6, and the variable pressure chamber 6
The communication with the third pressure chamber 9 is cut off. Therefore, the negative pressure chamber 5 and the variable pressure chamber 6 are maintained at the same negative pressure by the negative pressure from the negative pressure introduction pipe 7, and the third force chamber 9 is maintained at atmospheric pressure or a pressure slightly higher than atmospheric pressure. ing. That is, at this time, the plunger 18d of the on-off valve 18 receives the pressure difference between the third pressure chamber 9 and the variable pressure chamber 6, bends the compression spring 18e, and is in a non-contact position with the valve body 18a. 18a is pressed against the valve seat 18b by a compression spring 18c to close the air introduction pipe 15. At this time, check valve 17
is of course closed.

When the brake operating lever 10 is pushed in from this state, the well-known valve mechanism 11 cuts off the communication between the negative pressure chamber 5 and the variable pressure chamber 6, and causes the variable pressure chamber 6 to communicate with the third pressure chamber 9. As a result, the pressure in the variable pressure chamber 6 increases and the pressure in the third pressure chamber 9 decreases.As a result, the check valve 17 is opened as the pressure in the third pressure chamber 9 is reduced, and the atmospheric pressure is reduced. It is introduced into the variable pressure chamber 6 via this third variable pressure chamber 9. Therefore, an auxiliary force is applied to the power piston 3 due to the pressure difference between the variable pressure chamber 6 and the negative pressure chamber 6, the driven rod 20 moves forward, and a braking hydraulic pressure is generated in a master cylinder (not shown). This is the initial braking operation.

If braking is continued further, the pressure in the variable pressure chamber 6 rises to atmospheric pressure or a value close to atmospheric pressure, and the on-off valve 1
8, the pressure approaches the pressure inside the air introduction pipe 15 downstream of the air intake pipe 8.
Therefore, the pressure difference acting on the plunger 18d of the on-off valve 18 becomes smaller, so that the compression spring 18d
8e, the valve body 18a is moved upward in FIG. It is led to the transformation chamber 6 (see Figure 2). Therefore, in this state, a pressure difference between the negative pressure in the negative pressure chamber 5 and the positive pressure of the compressed air from the air pump 14 acts on the power piston 3, and stronger braking is performed compared to the initial stage of braking. It can be done. Note that the check valve 17 closes after the third pressure chamber 9 approaches atmospheric pressure, cutting off communication between the third pressure chamber 9 and the atmosphere.

Note that when the brake is released in the above state, the valve mechanism 11 communicates the negative pressure chamber 5 with the variable pressure chamber 6, and as a result, the power piston 3 returns to the non-operating position, and at this time, the third pressure chamber 9 is filled with compressed air. Although it remains, this compressed air is introduced into the negative pressure chamber 6 and consumed at the beginning of the next brake operation, so it does not affect the braking operation.

Next, talking about the safety functions of this brake booster, first of all, if the vacuum source fails, both the negative pressure chamber 5 and the variable pressure chamber 6 will be at atmospheric pressure when the brake is not in operation, but when the brake is in operation, the on-off valve 18 and the third Since compressed air is introduced into the variable pressure chamber 6 via the pressure chamber 9, the power piston 3 operates due to the pressure difference between the compressed air and atmospheric pressure, thereby ensuring boost operation. In addition, if the compressed air source fails, the check valve 17 opens when the brake is applied and atmospheric air is introduced into the third pressure chamber 9 and the variable pressure chamber 6, so the booster operates based on the pressure difference between atmospheric pressure and negative pressure. is ensured.

In the illustrated embodiment, the check valve 17 and the on-off valve 18 constituting the switching valve device 16 are integrally provided, but it is possible to make the positions of both valves different. It can be provided on the wall of chamber 9.

As described above, according to the present invention, without making any particular modification to the structure itself of the conventional brake booster, the third variable pressure chamber connected to the working pressure introduction side of the variable voltage chamber and the third variable voltage chamber are connected to the third variable pressure chamber in the initial stage of braking. The simple configuration of adding a switching valve device that communicates with atmospheric pressure and switches the third pressure chamber to the compressed air source when the pressure in the variable pressure chamber rises allows smooth braking operation without the risk of loss stroke. You can get the effect you want.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of a brake booster according to the present invention, and FIG. 2 is a sectional view taken along the line - in FIG. 1: Front shell, 2: Back shell, 3: Power piston, 4: Diaphragm, 5: Negative pressure chamber, 6:
Variable pressure chamber, 8: Partition wall, 9: Third pressure chamber, 10:
Brake operating rod, 11: Valve mechanism, 14: Air pump, 15: Air introduction pipe, 16: Switching valve device, 1
7: Check valve, 18: Open/close valve.

Claims (1)

[Claims] 1. A power piston and a diaphragm divide the inside of the sealed shell into a negative pressure chamber communicating with a negative pressure source and a variable pressure chamber, and a valve mechanism separates the negative pressure chamber and variable pressure chamber when the brake is operated. In a brake booster that cuts off communication and generates a pressure difference between both chambers to apply an assisting force to the power piston connected to the master cylinder, the brake booster is connected to the operating pressure introduction side of the valve mechanism. A third pressure chamber is provided, and this third pressure chamber is connected to a compressed air source via an air introduction pipe, and the pressure of this third pressure chamber is connected to the air introduction pipe or the third pressure chamber. a first on-off valve that communicates the third pressure chamber with the atmosphere in response to a drop, and a second on-off valve that communicates the third pressure chamber with a source of compressed air in response to a desired pressure increase in the variable pressure chamber; A brake booster comprising a switching valve device comprising an on-off valve. 2. Claim 1, wherein the third pressure chamber is formed integrally with the sealed shell, and a portion of the power piston is slidably disposed within the third pressure chamber.
Brake booster described in section.