JPH0352374B2 - - Google Patents

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a hydraulic booster used in a brake booster or a Kratz booster, and more specifically relates to a hydraulic booster that can change the boost ratio. The present invention relates to a boost ratio control device for a pressure booster.

"Prior Art" A hydraulic booster is normally operated in conjunction with a power piston that is slidably fitted into a housing, a power chamber formed at one end of the power piston, and an input shaft. The chamber is equipped with a control valve that advances the power piston by introducing hydraulic pressure corresponding to the input applied to the input shaft into the power chamber, and the small input is multiplied by the hydraulic pressure corresponding to the input introduced into the power chamber. It is now possible to output

``Problem to be solved by the invention'' This type of hydraulic booster is already well known, but the conventional hydraulic booster had a constant boost ratio and could not be changed. . Therefore,
For example, when a hydraulic booster is used as a brake booster for a truck, there is a difference in the driver's sense of control when the truck is empty and when the truck is loaded, and the driver may perceive that the braking force is low when the truck is loaded. It was a lot. Furthermore, even under the same braking condition, some drivers may perceive the braking force to be too large or too small, and there are individual differences in preferred braking sensations.

"Means and Effects for Solving the Problems" In view of the above-mentioned circumstances, the present invention provides at least two power pistons, a first power piston and a second power piston having different diameters, each of which is slidably fitted into a housing. The power chamber is formed at one end of the first power piston, the second power chamber is formed between the first power piston and the second power piston, and the second power chamber is formed between the first power piston and the second power piston. The power chamber is selectively communicated with the above-mentioned power chamber or the reservoir via a flow path switching valve to vary the pressure receiving area of the hydraulic pressure acting on the power piston as a whole, thereby changing the boost ratio. It was made so that it could be done.

In addition, since the power piston is configured as a stepped power piston from the separate first power piston and second power piston, each first power piston and the second power piston are simply connected to each other with respect to the stepped hole formed in the housing. Simply by slidably fitting the second power piston, smooth operation can be obtained even if both power pistons are not located on the same axis, thus making it easy to manufacture the power piston. In addition, the assembly can be made easier.

"Example" Hereinafter, an example in which the present invention is applied as a brake booster will be described. In FIG.
The housing 1 of the hydraulic booster includes a main body 2 and a cover 3.
Both are kept liquid-tight by a seal member 4 and connected by bolts or the like (not shown).

A stepped hole 5 is bored in the main body 2, and a stepped power piston 8 consisting of a first piston 6 and a second piston 7 is slidably fitted into the stepped hole 5, Further, a hole 9 is bored in the cover 3 on the same axis as the hole 5, and an input shaft 10 which is connected to a brake pedal (not shown) is slidably fitted therein.

The input shaft 10 is linked to the power piston 8 and also linked to a control valve 12, which will be described in detail later, via a lever 11.
0 is introduced into the first power chamber 13 formed between the main body 2 and the cover 3, and the power piston 8 is moved forward, that is, to the left by the hydraulic pressure. We are making it possible to do so.

The tip of the input shaft 10 is inserted into a seal member 2 in a bottomed hole 20 formed in the right end shaft portion of the power piston 8.
1, they are slidably fitted while maintaining liquid tightness.
The inside of the hole 20 is defined as a pressure chamber 22. The pressure chamber 2 is then
2 is communicated with the first power chamber 13, and the passage 23 is provided with a check valve 24 that only allows flow of pressure oil from the first power chamber 13 to the pressure chamber 22.

This check valve 24 is interlocked with one end of a pin 25 that is loosely fitted into the passage 23, and the other end of this pin 25 is brought into contact with a bracket 26 that is slidably fitted on the outer periphery of the input shaft 10. ing. This bracket 2
6 is a spring 27 loaded between this and the input shaft 10.
Therefore, the check valve 24 is normally positioned at the position shown in the figure in contact with a stepped portion formed on the input shaft 10. In this state, the check valve 24 is positioned at the open position by the pin 25, and the pressure chamber 22 and the 1 power chamber 13 are communicated with each other.

The bracket 26 has a base end 28 that slidably passes through the input shaft 10 and abuts the pin.
An axial portion 29 extends from the lower part of the base end portion 28 to the right side in the axial direction, and a U-shaped cross section portion 30 extends upward from both sides of the right end portion of the axial portion 29 across the input shaft 10. This U-shaped part 30
Long grooves 31 are formed on both sides of each. Pins 32 fixedly provided to the lever 11 described above are engaged in the long grooves 31, respectively.

The lever 11 interlocks the input shaft 10 and the control valve 12, as well as the power piston 8 and the control valve 12, and the lever 11 interlocks the input shaft 10 and the control valve 12, and the lever 11 interlocks the input shaft 10 and the control valve 12, and the power piston 8 and the control valve 12.
A U-shaped portion 30 extending upward from the axial portion 29 of 6
parallel parts 33 that are parallel to each other and both parallel parts 33
By engaging the pins 32 provided on the inner surfaces of both parallel parts 33 with the long grooves 31 of the bracket 26, the intermediate part of the lever 11 is connected to the input shaft 10. It is linked to.

One end of the lever 11 is connected to a long groove (not shown) provided therein in the longitudinal direction and to the control valve 12.
The lever 11 is interlocked with the spool 35 by engaging with a pin (not shown) provided on the spool 35 of the lever 11, and the other end of the lever 11 is connected to a bracket 36 integrally connected to the right end of the power piston 8 with the pin 3.
It is pivotally supported via the piston 7 and interlocked with the power piston 8.

Next, the control valve 12 has a hole 40 that penetrates the main body 2 and communicates with the first power chamber 13 at one end.
A sleeve 42 is fitted into the hole 40 with a plurality of seal members 41 sealed at required locations.
and a plug 43 that is screwed onto the main body 2 to fix the sleeve 42 to the housing 1 and seal the other end of the hole 40, so that the spool 35 can be slidably attached to the sleeve 42. They are mated. Also, this spool 35 and plug 4
A spring 44 is loaded between the spool 35 and the cover 3, so that the tip of the spool 35 is normally held in the non-operating position shown in the figure, where it comes into contact with the cover 3. At this time, the elastic force of the spring 44 is set smaller than the elastic force of the spring 27 that urges the bracket 26 described above.

A shaft passage 45 is formed in the shaft portion of the spool 35 passing through it, and this shaft passage 45 and the spool 3
The shaft passage 45 is always communicated with the first power chamber 13 by a radial passage 46 formed at the right end of the shaft passage 45 . A pair of radial passages 47 and 48 are formed at the intermediate portion of the spool 35 at a required interval, and a radial passage 47 of the spool 35 located in the non-operating position shown in the figure is formed in the sleeve 42. , 48, a supply passage 49 for supplying pressure oil and a discharge passage 50 for discharging pressure oil are formed, respectively.

Pressure oil is supplied to the supply passage 49 from a pump 52 or an accumulator 53. That is, the pressure oil discharged from the pump 52 passes through the check valve 54 to the accumulator 53.
The pressure oil accumulated in the accumulator 53 is transferred to a conduit 55, a passage 56 formed in the main body 2,
A passage 59 formed in a disk member 58 held by a plug 57 screwed onto the main body 2, and a filter 60
and is supplied to the supply passage 49 through a passage 61 formed in the main body 2. The filter 60 is formed of sintered metal into a cylindrical shape, and is fixed in the main body 2 by a plug 57 via the disk member 58.

On the other hand, the discharge passage 50 communicates with a reservoir 64 of the pump 52 via a passage 62 formed in the main body 2 and a conduit 63, and the discharge passage 50 communicates with a reservoir 64 of the pump 52.
is located in the non-operating position shown in the figure, the communication between the left radial passage 47 formed in the spool 35 and the supply passage 49 is cut off, and the right radial passage 48 formed in the spool 35 is disconnected from the supply passage 49. is communicated with the discharge passage 50, so that the first power chamber 13 is connected to the reservoir 6 in the non-operating state shown in the figure.
It is connected to 4.

However, the first component constituting the power piston 8
The piston 6 and the second piston 7 having a larger diameter than the first piston 6 are provided with seal members 65 and 66, respectively.
The small diameter portion formed at the right end of the second piston 7 is inserted into the hole 67 formed at the left end of the first piston 6. Both pistons 6 and 7 are brought into contact with each other by a loose fit.

A hole 68 formed at the left end of the second piston 7
Fit the right end of the output shaft 69 into the
9 and a retainer 70 fitted into the left end of the stepped hole 5. It is normally held in the non-operating position shown in the figure. The elastic force of the spring 71 is set to be larger than the elastic force of the spring 27 that urges the bracket 26, and the output shaft 69 is inserted through the retainer 70 and connected to the piston of the master cylinder (not shown). It is linked to.

Further, the second power chamber 75 defined by the stepped hole 5, the first piston 6, and the second piston 7 is connected to a passage 76 formed in the main body 2 and a conduit 7.
7, and communicates with an electromagnetic flow switching valve 78 provided in the conduit 77, and communicates the flow switching valve 78 with the first power chamber 13 via the conduit 79 and a passage 80 formed in the main body 2. , and communicates with the reservoir 64 via a conduit 81.

The electromagnetic flow path switching valve 78 is configured so that its flow path can be changed automatically by a detector (not shown) that detects the loading condition of the vehicle or by a manual switch. The second power chamber is connected to the first power chamber 13 or the reservoir 5.
It is possible to communicate with either one of the three.

In the above configuration, when the vehicle is in an empty state, the flow path switching valve 78 communicates the second power chamber 75 with the reservoir 64.
No hydraulic pressure is introduced into the power room.

In this state, when the brake pedal is depressed and the input shaft 10 moves to the left from the non-operating state shown in the figure, the bracket 26 fixed to the input shaft 10 by the spring 27 moves to the left together with the input shaft 10. will be done. Then, although the power piston 8 is held in the non-operating position shown in the figure by the spring 71 which has a larger elastic force than the elastic force of the spring 27, the elastic force of the spring 44 which biases the spool 35 of the control valve 12 Since the force is smaller than that of the spring 27, the lever 11 rotates counterclockwise about a pin 37 provided in a bracket 36 integral with the power piston 8, displacing the spool 35 to the left.

Then, the communication between the radial passage 48 provided in the spool 35 and the discharge passage 50 provided in the sleeve 42 is cut off, and the other radial passage 47 provided in the spool 35 is communicated with the supply passage 49. Therefore, the pressure oil introduced into the supply passage 49 flows into the radial passage 4 of the spool 35.
7, introduced into the first power chamber 13 via the axial passage 45 and the radial passage 46. At this time, the pressure oil is also supplied to the left end side of the spool 35 through the shaft passage 45, so the spool 35 is not moved to the left by the pressure oil introduced into the first power chamber 13. .

When pressure oil is introduced into the first power chamber 13, the pressure oil acts on the pressure receiving area _A1 of the power piston 8, causing the power piston 8 to move to the left against the spring 71, and at the same time, it moves the power piston 8 to the left against the spring 71. It acts on the cross-sectional area B and allows the driver to sense the brake reaction force. In the intermediate load state, the hydraulic pressure introduced into the first power chamber 13 is determined by the magnitude of the input applied to the input shaft 10, that is, the pressure of the brake pedal, as in the conventional brake fluid pressure booster of this type. The pressure is controlled in accordance with the pedal effort, thereby obtaining a constant boost ratio shown by the straight line a in FIG. The boost ratio is A ₁ /B
given by.

At this time, the spool 35 in the lever 11
Since the distance L between the connection point of the spool 35 and the power piston 8 is larger than the distance l between the connection point of the spool 35 and the input shaft 10, the amount of movement of the power piston 8 is greater than the amount of movement of the input shaft 10. As a result, the volume inside the pressure chamber 22 increases or decreases, but in this case, the pressure oil in the first power chamber 13 is reduced to pressure via the check valve 24, which is kept open by the pin 25. Since it is supplied and discharged into the chamber 22, the forward and backward movement of the power piston 8 and the forward and backward movement of the input shaft 10 are not hindered.

Next, when the magnitude of the input applied to the input shaft 10 exceeds the full load point (symbol b in Figure 2), the oil pressure in the first power chamber 13 reaches the maximum pressure and does not rise any further. The power piston 8 comes to rest at that position, and from this state the input shaft 1
0 is advanced, the lever 11 pivotally supported on the power piston 8 and the bracket 3 integrated therewith
Since the input shaft 10 is stationary integrally with the power piston 8, the input shaft 10 is
will be advanced. As a result, the check valve 24 interlocks with the bracket 30 via the pin 25.
closes and seals the pressure chamber 22, so the input shaft 10
and the power piston 8 are integrally connected to each other through oil sealed in the pressure chamber 22, and as the input applied to the input shaft 10 increases, the output increases at a ratio of 1:1. It becomes like this. (See line c in Figure 2).

Next, when the vehicle is in a loaded state, the flow path switching valve 78 switches the second power chamber 75 from the first power chamber 13.
The second power chamber 7
The same hydraulic pressure as that of the first power chamber 13 is also introduced into the first power chamber 13. In this case, the pressure receiving area of the power piston 8 is _A2 , so the boost ratio is _A2 /
B (A ₂ >A ₁ ), and it is clear that the boost ratio increases. (See line a' in Figure 2).

In the above embodiment, the portion of the stepped power piston 8 facing the first power chamber 13 is a small diameter portion, but that portion may be a large diameter portion. However, in that case, the second power chamber 75 is replaced by the first power chamber 1.
3 is in communication with the boost ratio, and the 2nd
A state in which the power chamber 75 is communicated with the reservoir 64 is a state in which the boost ratio is large.

Also, the stepped portion of the stepped power piston 8 is not necessarily 2
It is not necessary that the second power chamber 75 be one stage, that is, there is only one second power chamber 75, and it is also possible to form a large number of power chambers with three or more stages as necessary.

Further, although the above embodiment shows an example in which the present invention is applied to a hydraulic pressure booster using a closed circuit, it is of course applicable to a hydraulic pressure booster using an open circuit. It goes without saying that it can be applied not only as a brake booster but also as a clutch booster.

"Effects of the Invention" As described above, according to the present invention, it is possible to freely change the boost ratio of the hydraulic booster according to preferences, braking conditions, etc., and it is also possible to manufacture and assemble power pistons. The effect is that it can be easily attached.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is a characteristic diagram of the present invention. 1... Housing, 6... First piston, 7...
...Second piston, 8...Power piston, 10...
...Input shaft, 11...Lever, 12...Control valve, 1
3...First power chamber, 35...Spool, 49...
Supply passage, 50...Discharge passage, 52...Pump,
53...Accumulator, 64...Reservoir, 6
9...Output shaft, 75...Second power chamber, 78...Flow path switching valve, _A1 , _A2 , B...Pressure receiving area.

Claims (1)

[Claims] 1. A power piston slidably fitted into a housing, a first power chamber formed at one end of the power piston, and an input shaft that is operated in conjunction with an input shaft and that is applied to the first power chamber to the input shaft. and a control valve that advances the power piston by introducing hydraulic pressure according to the hydraulic pressure, at least two first power pistons having different diameters, each of which is slidably fitted into a housing. and a second power piston, and the two are in contact with each other, and the first power chamber is formed at one end of the first power piston, and the second power chamber is formed between the first power piston and the second power piston. death,
A boost ratio control device for a hydraulic booster, further comprising a flow path switching valve that selectively communicates the second power chamber with the first power chamber or the reservoir.