JPH0147340B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brake booster, and more specifically to a brake booster that improves brake feeling by reducing the invalid stroke of the brake booster during brake operation.

A brake booster controls the opening and closing of a valve mechanism via an operating lever that is linked to the brake pedal.
When the brake is operated, atmospheric pressure is introduced into the variable pressure chamber, and the pressure difference between the variable pressure chamber and the negative pressure chamber is applied to the power piston to obtain a boost function, and when the brake is released, communication between the variable pressure chamber and the atmosphere is cut off. At the same time, the variable pressure chamber is communicated with the negative pressure chamber, and a return spring returns the power piston to the non-operating position. In order to improve the responsiveness of the brake booster, it is preferable to increase the flow area between the variable pressure chamber and the atmosphere and between the variable pressure chamber and the negative pressure chamber, that is, to increase the lift amount of the valve mechanism. When the lift amount of the valve mechanism is increased in order to increase the flow path area between the variable pressure chamber and the negative pressure chamber, the brake pedal is depressed from an inactive state and the valve mechanism blocks communication between the variable pressure chamber and the negative pressure chamber. The disadvantage is that the amount of invalid stroke of the brake pedal required to reach this point increases, resulting in poor brake feeling.

In order to eliminate such drawbacks, conventionally, a stopper member is attached to the valve plunger that constitutes the above-mentioned valve mechanism and is connected to the tip of the operating rod, and when the brake booster is not in operation, this stopper member is attached to the inner surface of the shell, etc. to control the retreating position of the valve plunger by making contact with it,
Accordingly, a device has been proposed which reduces the amount of invalid stroke of the brake pedal when the brake pedal is depressed.

However, with this configuration, the shape of the stopper member is complicated, making it difficult to manufacture, and there is also a problem in that abnormal noise is generated due to contact between the stopper member and the shell.

In view of the above points, the present invention provides a brake booster capable of suppressing the invalid stroke amount of the brake pedal without providing a special stopper member. A second valve mechanism is provided to open and close the second passage in conjunction with the brake pedal, and the second passage is opened when the power piston retreats. It is said that

The present invention will be explained below with reference to illustrated embodiments. 1st
In the figure, a shell 1 is constructed by abutting a front shell 2 and a rear shell 3, and the outer peripheral edge of a diaphragm 4 is held between the abutting portions. The power piston 5 is supported in the shell 1 so as to be able to move forward and backward, and the inner peripheral edge of the diaphragm 4 is fitted to the outer periphery of the tip thereof, and a diaphragm plate 6 that supports the front surface of the diaphragm 4 is attached. Further, the rear cylinder portion 7 is slidably projected from the opening of the rear shell 3 via a seal 8. On the other hand, a base end fitting portion 11 of a driven rod 10 is slidably fitted into a fitting hole 9 formed in the center of the front surface of the power piston 5. This driven rod 1
The tip end of the front shell 2 passes through the end wall of the front shell 2 through a seal 12 in an airtight manner to transmit output to a master cylinder (not shown).

The inside of the shell is divided into a negative pressure chamber 13 and a variable pressure chamber 14 by the power piston 5, diaphragm 4, and diaphragm plate 6. The inside of the negative pressure chamber 13 communicates with a negative pressure source such as an engine intake pipe through a negative pressure pipe 15, and is always under negative pressure. Atmospheric air is introduced in conjunction with the above-mentioned chambers 13 and 14, and the power piston 5, etc.
In response to the pressure difference between the front shell 2 and the end wall, the return spring 16 elastically mounted between the front shell 2 and the end wall is deflected and moved forward, and brake hydraulic pressure is generated in the master cylinder via the driven rod 10.

The power piston 5 is provided with a passage that allows communication between the negative pressure chamber 13 and the variable pressure chamber 14, and a valve mechanism that opens and closes this passage and introduces atmospheric air into the variable pressure chamber 14. That is, passage 17
penetrates the inside of the power piston 5 and opens into the internal chamber 18 in the cylindrical portion 7, while a passage 19 is formed at the base of the cylindrical portion 7 to constantly communicate the internal chamber 18 and the variable pressure chamber 14, Thereby, the negative pressure chamber 13 and the variable pressure chamber 14 can communicate with each other via the internal chamber 18. Further, a second passage 20 is formed at the tip of the power piston 5 so that the negative pressure chamber 13 and the variable pressure chamber 14 can be directly communicated with each other. Passage 17, 19
A valve mechanism for cutting off communication between the two and opening and closing the second passage 20 is provided on the operating rod 21 as described below.

The operating lever 21 protrudes from the rear opening of the cylindrical portion 7 through the air cleaner 36, is connected to the brake pedal at its protruding portion, and transmits the pedal force acting thereon to the master cylinder. A valve plunger 23 which is caulked to the tip spherical portion 22 of the operating rod 21 is connected to the power piston 5.
It is slidably fitted into the shaft hole 24 of the lever, and faces the reaction disk 25 fitted into the driven rod fitting portion 11 in the illustrated non-operating state, but when the operating rod 21 is advanced, The driven rod 10 comes into contact with this reaction disk 25, and the driven rod 10
Press. Thus, a key 26 is engaged with the central small diameter portion 23a of the valve plunger 23 so as to be relatively movable, and this key 26 is connected to the power piston 5.
It loosely fits into the through hole 27 of the valve plunger 23.
is movable relative to the power piston 5 in the front-back direction within an allowable range of relative displacement with the key 26 and relative displacement of the key 26 with respect to the power piston 5. The protruding portion of the key 26 from the through hole 27 faces the opening of the second passage 20,
This relative movement opens and closes this passage 20.

Behind the spherical part 22 of the operating rod 21 is a passage 1.
A valve member 28 is provided to cut off communication between 7 and 19. The valve member 28 has a structure in which an annular plate member 29 is covered with an elastic member such as rubber, and has a substantially cylindrical shape. It has been fixed. A valve return spring 33 is provided between the enlarged portion 30 of the valve member 28 and the receiving portion 32 attached to the intermediate flange portion 31 of the operating rod 21. A valve biasing spring 34 is mounted between the valve biasing spring 34 and the valve biasing spring 34. Therefore, in the non-operating state, the valve plunger 23 receives the biasing force of the valve return spring 33 and is biased to the right in FIG. The valve member 28 is brought into contact with the valve member 28 and the second passage 20 is opened.
is energized by the valve biasing spring 34 and the valve plunger 23
The inside of the shell 1 is shut off from the atmosphere by closely contacting the valve seat 35 of the shell 1.

However, in the non-operating state of the lever, the power piston 5 is moved to the right side in FIG. However, when the brake pedal is depressed from this state and the operating rod 21 moves forward against the valve return spring 33, the valve member 28 moves toward the power piston 5.
It comes into elastic contact with a valve seat 38 formed therein to cut off communication between the passage 17 and the internal chamber 18 (see FIG. 2). When the operating rod 21 further moves forward, the valve plunger 23 moves forward and comes into elastic contact with the reaction disk 25, but since the valve member 28 is locked to the valve seat 38, the valve seat 35 of the valve plunger 23 Air is separated from the member 28 and enters the variable pressure chamber 14 through the passage 19 (see FIG. 3). As a result, the key 26 is moved into the second passage 20 by the atmospheric pressure acting from behind.
closes the passage 20 by closely contacting the seal 39 of the
Communication between the negative pressure chamber 13 and the variable pressure chamber 14 is completely cut off. Further, the power piston 5 is energized by the atmospheric pressure introduced into the variable pressure chamber 14 and moves forward against the return spring 16, and the driven rod 10 operates the master cylinder to supply braking fluid pressure to the brake cylinder.

When the pedal force is removed from the brake pedal, the valve plunger 23 is moved to the right relative to the power piston 5 together with the operating rod 21 by the valve return spring 33. Then, the valve seat 35 of the valve plunger 23 comes into close contact with the valve member 28 to isolate the inside of the shell 1 from the atmosphere, and then, as the valve plunger 23 retreats,
The valve member 28 separates from the valve seat 35 to communicate the variable pressure chamber 14 with the negative pressure chamber 13, and the key 26 separates from the seal 39 to open the second passage 20.
As a result, the variable pressure chamber 14 communicates with the negative pressure chamber 13 via a flow path with a large flow area, and the pressure within the variable pressure chamber 14 quickly becomes the same as that of the negative pressure chamber 13, so that the power piston 5 Return spring 16
It quickly retreats due to its explosive force. Note that when the key 26 opens the second passage 20, the air in the variable pressure chamber 14 is sucked into the negative pressure chamber 13 along arrow A, but in order to make the flow of this air smooth, A portion 40 of the outer periphery of the seal 39 facing the end of the key 26 is slightly more concave than the other portions (see FIG. 5).

4, the power piston 5 is displaced to the right by the elastic force of the return spring 16, and the annular protrusion 37 of the diaphragm 4 comes into elastic contact with the inside of the rear shell 3. The backward movement of is completed and the state shown in FIG. 1 is reached. That is, the relative positional relationship of the valve plunger 23, key 26, valve member 28, etc. within the power piston 5 is determined by comparing FIG. 1 with FIG. It's exactly the same over time.

Now, when the operating rod 21 is moved forward again from the non-operating position via the brake pedal, the valve member 28 is seated on the valve seat 38, and the valve seat 35 of the valve plunger 23 is separated from the valve member 28, so that the variable pressure chamber Atmospheric air is introduced into 14. In other words, switching the flow path in the power piston 5 requires at least a lift amount δ ₀ until the valve member 28 comes into contact with the valve seat 38.
This becomes an invalid stroke, but in this embodiment, this lift amount δ ₀ is set to the minimum necessary value. This is because when the power piston 5 retreats,
The variable pressure chamber 14 and the negative pressure chamber 13 communicate with each other through a second passage 20, and the pressure in the variable pressure chamber 14 is quickly transferred to the negative pressure chamber 1.
This is because the pressure is the same as 3. Therefore, the above-mentioned invalid stroke is very small, and the responsiveness in brake operation is extremely good.Furthermore, since the second passage 20 is provided, the brake can be released quickly.

Note that the gap δ ₁ between the key 26 and the seal 39 is set to be approximately the same size as the above-mentioned lift amount δ ₀ or slightly smaller, and the facing distance δ _{2 between the valve plunger 23 and the reaction disk 25 is set to be equal to or slightly smaller than the lift amount δ 0} . It is approximately the same as the quantity δ ₀ .

FIG. 6 shows a second embodiment of the present invention.
Unlike the first embodiment described above, a spring seat 42 is attached inside the inner peripheral bead portion 41 of the diaphragm 4, and a spring 42 is mounted between the spring seat 42 and the key 26.
3. According to this configuration, the key 26 closes the second passage 20 by the elastic force of the spring 43 when the power piston 5 moves forward,
Even when the pressure difference between the negative pressure chamber 13 and the variable pressure chamber 14 is small, this passage 2 can be reliably blocked.

As described above, in each of the above embodiments, the second passage 2 is moved by the relative movement of the key 26 with respect to the power piston 5.
0 is opened and closed to cut off communication between the negative pressure chamber 13 and the variable pressure chamber 14. Therefore, in order to determine the response performance of the brake booster, the thickness of the key 26, the size of the through hole 27, and the length of the central small diameter portion 23a of the valve plunger 23 can be appropriately selected, and the degree of freedom is big.

Note that a poppet valve or the like may be provided at the entrance of the second passage 20, and this valve may be opened and closed by interference with the key 26, or the second passage 20 may be opened and closed by the plunger 23. be.

As described above, according to the present invention, with a simple configuration,
It is possible to obtain a brake booster that minimizes invalid stroke and has good operating characteristics.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the first embodiment of the present invention, Fig. 2 is a sectional view of the main part immediately after the valve member closes the passage, and Fig. 3 is a state in which the valve plunger is separated from the valve member. , FIG. 4 is a sectional view of the main part when the power piston is retracted, FIG. 5 is a sectional view taken along the - line in FIG. 1, and FIG. 6 is a sectional view of the main part. FIG. 2 is a sectional view showing a second embodiment of the present invention. 1: Ciel, 5: Power piston, 13: Pressure chamber (negative pressure chamber), 14: Pressure chamber (variable pressure chamber), 17,1
9: passage, 20: second passage, 26: second valve mechanism (key), 28: valve mechanism (valve member).

Claims (1)

[Claims] 1. A shell that is partitioned into a plurality of pressure chambers, a power piston that is provided within the shell so as to be able to move forward and backward, and a passage between the pressure chambers that opens and closes in conjunction with the brake pedal. The brake booster includes a valve mechanism that causes a pressure difference, and the power piston moves back and forth within the shell in response to the pressure difference. A second valve mechanism is provided that opens and closes the second passage in conjunction with the brake pedal, and this second valve mechanism closes the second passage when the power piston moves forward, and closes the second passage when the power piston moves back. A brake booster characterized by opening a passage.