JPS6239966Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a brake booster that uses fluid pressure to boost the operating force of a brake device, and is particularly applicable to brake boosters where the brake operation sensation changes gradually near the assist limit point. It concerns boosters.

Generally, a brake booster includes a power piston that operates according to a pressure difference on both sides, and a large diameter plunger that is fitted into a large diameter part of a stepped hole formed in the power piston and transmits force to an output member. A small-diameter plunger connected to the input member and fitted into the small-diameter portion of the stepped hole, and a reaction force from the large-diameter plunger disposed in the large-diameter portion between the large-diameter plunger and the small-diameter plunger. and a reaction member made of a soft elastic body that distributes the input power to the small-diameter plunger and the power piston, and receives the input applied to the input member at a multiplication factor according to the pressure-receiving area ratio of the large-diameter plunger and the small-diameter plunger to the reaction member. It is configured to boost the power and transmit it to the output member.

However, in such a conventional brake booster, near the assisting limit point where the assisting force of the power piston reaches its limit, the force output from the output member to the brake device relative to the brake pedal operating force applied to the input member increases. Since the boost factor suddenly decreases, this has the disadvantage that it tends to give the driver the impression that the brake pedal is bottoming (a phenomenon in which it hits the floor). Particularly, in brake boosters that have a large boost factor in the normal use range, such as those used in recent large luxury vehicles, such drawbacks are significant, resulting in poor brake operation feel.

On the other hand, in order to alleviate such drawbacks, it is possible to set the boost factor small in the normal range or to set the tire so that it locks before the power piston assists the limit point. In the latter case, the original purpose of the brake booster is lost as the brake operability is impaired, and in the latter case, a disadvantage arises in that delicate brake operation near the lock is difficult.

The present invention was developed against the background of the above-mentioned circumstances, and its purpose is to minimize and gradually change the feel of brake operation near the assist limit point without reducing the boost factor in the normal use range. Our goal is to provide a brake booster with the highest quality.

In order to achieve such an objective, the gist of the present invention is to form a plurality of stepped end faces of a small diameter plunger, and to form a plurality of reaction members overlapping each other in a stepped shape that can be pressed against each of the end faces. The space between each end face of the small-diameter plunger and each layer of the reaction member facing the small-diameter plunger is set such that as the small-diameter plunger moves forward, the pressure receiving area of the small-diameter plunger against the reaction member increases in stages. To,
The reason is that the differences have been made step by step.

In this way, as the small-diameter plunger is moved forward, the pressure receiving area of the small-diameter plunger with respect to the reaction member is increased in stages, and the output member is transferred to the brake device in response to the input applied to the input member. Since the boosting factor of the output force can be reduced in stages before reaching the assisting limit point of the power piston, the braking operation feeling can be changed near the assisting limit point without lowering the boosting factor in the normal use range. is small and gradual.

Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

In FIG. 1, a brake booster 10 boosts the operating force applied from a brake pedal 11 to an input rod 12, which is an input member, and outputs it from an output rod 13, which is an output member, to a master cylinder 14. . The brake booster 10 has an airtight chamber consisting of a front shell 16 and a rear shell 18, and the chamber is divided into a constant pressure chamber 22 and a variable pressure chamber 24 by a diaphragm type power piston 20. The constant pressure chamber 22 is connected to a negative pressure source 28 such as an engine intake manifold or a vacuum pump via a pipe joint 26, and is always kept under negative pressure.The variable pressure chamber 24 is connected to the constant pressure chamber 22 or The internal pressure is controlled by selectively communicating with the atmosphere.

The power piston 20 includes a bowl-shaped diaphragm plate 30, a diaphragm rubber 32 which is stacked on the diaphragm plate 30 and whose periphery is fixed in a cavity, and a power piston main body which is fixed to the center of the diaphragm plate 30 by a claw. 34, and is driven in the axial direction based on the pressure difference between the constant pressure chamber 22 and the variable pressure chamber 24.

The power piston body 34 is provided with a control valve 36 and a relay mechanism 38. The control valve 36 has a first valve seat 4 formed in the power piston body 34.
0, a second valve seat 46 formed on a valve plunger 44 slidably fitted to the power piston body 34 and connected to the input rod 12, and both valve seats 4.
0 and 46, and a valve element 48, which is an elastic body, provided in common with the valve elements 0 and 46. The power piston body 34 has air flow passages 50 and 5 communicating with the constant pressure chamber 22 and the variable pressure chamber 24.
2 is formed. Therefore, when the valve element 48 is seated on the second valve seat 46, the constant pressure chamber 22 and the variable pressure chamber 24 are communicated through the air flow passages 50 and 52, but the input rod 12 is advanced. When the valve element 48 and the second valve seat 46 are separated and the valve element 48 is seated on the first valve seat 40, the air flow passage 50 is closed and the atmosphere is connected to the variable pressure chamber 24 through the air flow passage 52. It is now possible to communicate.

Further, the notch hole provided in the power piston body 34 engages with a circumferential groove formed in the middle part of the valve plunger 44, and the valve plunger 4
A bifurcated stopper key 54 that regulates the forward end and reverse end of 4 is inserted, and the stopper key 54
4 is prevented from being pulled out by an annular stopper ring 56 provided around the power piston body 34. The portion of the power piston body 34 that protrudes from the rear shell 18 is covered by a boot 58, and the rear end of the boot 58 has a variable pressure chamber 2.
An air inlet (not shown) for supplying atmospheric air is provided to 4.

On the other hand, the output rod 13 is disposed so as to be freely movable in the axial direction while passing through the center of the front shell 16. The auxiliary force is transmitted to the output rod 13 via the relay mechanism 38. That is, as shown in detail in FIG. 2, the relay mechanism 38 is fitted into a small diameter portion 60 of a stepped hole formed in the center of the power piston body 34 so as to be slidable in the axial direction, and is connected to the valve plunger. A small diameter plunger portion 62 formed at the front end of 44 and a large diameter portion 6 of its stepped hole.
A large diameter plunger part 66 is fitted to the output rod 4 so as to be slidable in the axial direction and is integrally provided at the rear end of the output rod 13, and between the small diameter plunger part 62 and the large diameter plunger part 66. It is composed of a first reaction member 68 and a second reaction member 70, which are disposed in the large diameter portion 64 of. The small diameter plunger part 62 is formed in a stepped shape and includes a circular end face 72 facing the large diameter plunger part 66 and an annular end face 74 located on the rear side thereof. The first reaction member 68 has a disk shape with the same diameter as the large-diameter plunger portion 66, and the second reaction member 70 has a hole into which the front step of the small-diameter plunger portion 62 is slidably inserted. And the first
It has an annular shape with the same diameter as the reaction member 68, and is overlapped with a similar annular spacer 76 interposed therebetween. When the brake booster 10 is in the non-operating state, the gap A between the end surface 72 and the first reaction member 68 is set to be larger than the gap B between the end surface 74 and the second reaction member 70. These different gaps gradually increase the pressure receiving area of the small diameter plunger portion 62 as the small diameter plunger portion 62 moves forward with respect to the power piston main body 34 . Note that the first reaction member 68 and the second reaction member 7
0 is made of a soft elastic material such as natural rubber or nitrile rubber, and the first reaction member 68 is harder than the second reaction member 70.

Returning to FIG. 1, a coil-shaped return spring 78 is inserted between the front shell 16 and the power piston body 34, and a spring receiver 80 is arranged between the return spring 78 and the power piston body 34. The power piston body 34 and the output rod 13 are always urged rearward (toward the input rod 12 side).

The operation of this embodiment will be explained below.

When the brake pedal 11 is not depressed, the valve element 48 is attached to the second valve seat 46.
Since the first valve seat 40 and the valve element 48 are separated from each other while the power piston 20 is seated, the variable pressure chamber 24 and the constant pressure chamber 22 are communicated with each other.
There is no pressure difference on either side. Therefore, the power piston body 34 and the output rod 13 are positioned at the rearmost position according to the biasing force of the return spring 78. FIGS. 1 and 2 show this state.

When the brake pedal 11 is operated in this state and the input rod 12 is moved forward, the valve plunger 44 is moved forward relative to the power piston body 34, so that the first valve seat 40
At the same time, the second valve seat 46 and the valve element 48 are separated from each other. Therefore, the atmosphere is caused to flow into the variable pressure chamber 24 according to the opening degree of the control valve 36, and a pressure difference is generated on both sides of the power piston 20.
As the power piston 20 is advanced together with the valve plunger 44, the movement of the power piston 20 is transmitted to the output rod 13 through the second reaction member 70, the spacer 76 and the first reaction member 68, and the output rod 13 is pushed out. As a result, the master cylinder 14
The brake fluid inside is supplied to a brake system (not shown), the brake clearance disappears, and a braking effect begins to appear. At this time, the brake reaction force applied to the output rod 13 eliminates the gap B, and the annular end surface 74 and the second reaction member 70
The brake reaction force is distributed between the power piston body 34 and the valve plunger 44 according to the pressure receiving area ratio with respect to the second reaction member 70. That is, for example, the area of the end face 74 is C,
Assuming that the area where the stepped portion between the large diameter portion 64 and the small diameter portion 60 in the stepped hole contacts the end surface of the second reaction member 70 is D, the operating force applied to the input rod 12 assists the power piston 20. It is transmitted to the output rod 13 at a high multiplication factor of (C+D)/C. A straight line X in FIG. 3 shows such a relationship in the commonly used range.

Next, when the operating force of the brake pedal 11 is further strengthened, the brake reaction force applied to the output rod 13 increases, so that the first reaction member 68
is deformed, and its first reaction member 6
8 comes into contact with the circular end surface 72, resulting in the state shown in FIG. Therefore, the valve plunger 44
As the pressure-receiving area increases, the power factor is lowered by one step, making brake operation feel a little heavier. Straight line Y in FIG. 3 shows such a relationship. That is, for example, if the area of the circular end surface 72 is E,
The operating force applied to the input rod 12 is (C+D+
It is transmitted to the output rod 13 at a multiplication factor of E)/(D+E). Furthermore, its area (C+D+E)
is equal to the area of the large diameter plunger portion 66.

Furthermore, when the operating force of the brake pedal 11 is increased, the pressure difference between both sides of the power piston 20 reaches its limit, and from then on, changes in the operating force applied to the brake pedal 11 are directly transmitted as changes in the output of the output rod 13. . That is, the auxiliary force of the power piston 20 reaches its limit point, and thereafter the power piston 20 will be in a state of transmitting a constant auxiliary force to the output rod 13 regardless of changes in the operating force, so that the force output from the output rod 13 will be reduced. is the operating force applied to the input rod 12 plus the constant assisting force. Therefore, the multiplication rate (rate of change) of the output relative to the input in this state is:
The value becomes "1", and the straight line Z in FIG. 3 shows this state.

In this way, according to the conventional brake booster, as shown by the broken line in Fig. 3, the boosting factor rapidly decreases near the assist limit point of the power piston (the break point in the broken line), so the brake operation becomes difficult. In contrast to the sudden change in feeling that can easily give the driver the impression that the brake pedal has bottomed out, in this embodiment, the pressure-receiving area of the valve plunger 44 relative to the reaction members 68 and 70 is similar to that of the valve. The boosting factor is increased in stages as the plunger 44 moves forward, and the boosting factor is reduced in two steps before the power piston 20 reaches its boosting limit point (the corner point between the straight line Y and the straight line Z). The change in the feel of the brake operation near the limit point becomes small and gradual. Therefore, especially in a brake booster such as a large luxury vehicle where the boost factor in the normal range before the assist limit point is increased, it is possible to perform an operation where the brake pedal bottoms without reducing the boost factor in the normal range. The sensation is greatly relieved.

Next, another embodiment of the present invention will be described. In the following description, parts common to those in the above-mentioned embodiments are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 5, the small-diameter plunger part 62 is formed in a three-stage stepped shape and includes a circular end face 82 facing the large-diameter plunger part 66 and annular end faces 84 and 86 located behind the circular end face 82, respectively. ing. As in the above-described embodiment, an annular second reaction member 88 and a third reaction member 90 are superimposed on the first reaction member 68 via spacers 92 and 94, respectively. A gap F between the reaction member 68 and the end face 84 and the second reaction member 88
The gap H between the end face 86 and the third reaction member 90 is set smaller than the gap G between the end face 86 and the third reaction member 90.

Therefore, as the valve plunger 44 moves forward, the pressure receiving area of the small diameter plunger portion 62 relative to the reaction members 68, 88, 90 increases stepwise, and the characteristics shown in FIG. 6 are obtained. That is, if the areas of the end faces 86, 84, and 82 are J, K, and L, respectively, and the area of the step between the large diameter portion 64 and the small diameter portion 60 is D, as in the previous embodiment, then the gap H is At the initial stage of extinction, the power factor is (J+D)/J, as shown by the straight line U.
At the stage when the gap G disappears, the power factor is (J+K+D)/(J+K) as shown by the straight line V, and at the stage when the gap F disappears, the power factor becomes (J+K+L+D)/( as shown by the straight line W). J+K+L),
The operating force applied to the input rod 12 is output from the output rod 13.

As described above, according to the present embodiment, the assisting limit point of the power piston 20 (the breaking point of the straight line W and the straight line Z)
Since the boost factor is reduced in three steps before reaching the assist limit point, there is an advantage that changes in the feeling of brake operation near the assist limit point are further alleviated.

Although the embodiment of the present invention has been described above based on the drawings, the present invention can also be applied to other aspects.

For example, although the large diameter plunger portion 66 in the above-described embodiment is provided integrally with the output rod 13, the large diameter plunger portion 66 and the output rod 13
The brake booster is provided so as to be relatively movable in the axial direction, and the output is transmitted to the output rod 13 via a lever mounted between the large diameter plunger part 66 and the power piston 20. It's also good.

In the embodiment described above, the small diameter plunger portion 62
In order to gradually change the pressure receiving area of
Although the gap A is set larger than the gap B, there is no problem even if the gap A is set smaller than the gap B.

The above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

As detailed above, according to the brake booster of the present invention, as the small-diameter plunger moves forward, the pressure receiving area of the small-diameter plunger with respect to the reaction member increases in stages, and the operation applied to the input member Since the multiplication factor of the force output from the output member to the brake device is reduced in stages before reaching the assisting limit point of the power piston, the boosting factor in the normal use range can be reduced without decreasing the assisting limit point. Changes in the feel of braking in the vicinity become smaller and more gradual.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view showing the configuration of an embodiment of the present invention. FIG. 2 is a partial sectional view showing the main part of FIG. 1. 3 and 4 are graphs and diagrams illustrating the operation of the embodiment of FIG. 1. FIGS. 5 and 6 are views corresponding to FIGS. 2 and 3 in other embodiments of the present invention. 12: Input rod, 13: Output rod, 20:
Power piston, 60: Small diameter part, 62: Small diameter plunger part (small diameter plunger), 64: Large diameter part, 6
6: Large diameter plunger part (large diameter plunger), {6
8: first reaction member, 70, 88: second reaction member, 90: third reaction member}
(reaction member), 72, 74, 82, 84,
86: End face.

Claims (1)

[Claims for Utility Model Registration] A power piston that operates according to the pressure difference on both sides, and a large diameter plunger that is fitted into the large diameter part of a stepped hole formed in the power piston and transmits force to an output member. and a small-diameter plunger connected to the input member and fitted into the small-diameter portion of the stepped hole;
a reaction member made of a soft elastic body, which is disposed in a large diameter portion between the large diameter plunger and the small diameter plunger, and distributes reaction force from the large diameter plunger to the small diameter plunger and the power piston; In a brake booster that boosts the input applied to the input member and transmits it to the output member at a boosting factor according to the pressure receiving area ratio of the large-diameter plunger and the small-diameter plunger to the reaction member, the small-diameter plunger has a stepped shape. A plurality of end faces of the small diameter plunger are formed, and the reaction member is stacked in a stepwise manner such that the reaction member can be pressed against the end face, respectively, and each end face of the small diameter plunger and each layer of the reaction member opposing thereto are formed in a plurality of layers. A brake booster characterized in that the gap is made to vary in stages so that as the small diameter plunger advances, the pressure receiving area of the small diameter plunger with respect to the reaction member increases in stages.