JPH037257Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for boosting braking force using hydraulic pressure, and particularly to a variable hydraulic booster that can vary the boost ratio.

The braking force of a vehicle changes depending on the oil pressure applied to each wheel cylinder. Pressure oil to this wheel cylinder is generated by the operation of a piston in a brake master cylinder. A known method is to directly apply pedal depression force as a pressing force to the piston, and to double the pressing force by using a power piston formed with a pressure receiving surface for pressurized fluid. Among these, hydraulic boosters that use oil pressure can be connected in parallel to, for example, the hydraulic system of power steering, and the installation rate is increasing. By the way, in a conventional brake hydraulic booster, the area of the hydraulic pressure receiving surface of the power piston that receives high hydraulic pressure is constant, and when the hydraulic pressure is constant, the boost ratio is constant. In other words, as shown in Fig. 1, when no boost is applied to the input transmitted from the brake pedal to the input shaft in the hydraulic booster (which almost matches the pedal force), the output corresponding to the broken line a is It is only transmitted to the master cylinder side, and when boosting is performed, an output corresponding to the solid line b relative to the input is transmitted to the master cylinder side, and a large braking force can be obtained. However, when operating such a conventional brake device equipped with a hydraulic booster, under the same road surface conditions, a larger braking force is required when the vehicle is loaded than when the vehicle is lightly loaded, so that the input, i.e., It also requires a lot of pedaling force. In this way, when the weight of the vehicle is large, it is necessary to apply a large amount of force to the pedal, so if you press the brake pedal when the cargo load is large, your feet will easily become fatigued and brake operability will deteriorate. .

An object of the present invention is to provide a hydraulic variable booster that can reduce the difference in pedal force when a vehicle is lightly loaded and when a vehicle is loaded by increasing the boost ratio when the vehicle is loaded than when the vehicle is lightly loaded.

The variable hydraulic booster according to the present invention has an input shaft that moves in the axial direction by the pedal force, an output shaft that applies pressing force to the brake master cylinder, and a hydraulic booster that moves the output shaft to the brake master cylinder by receiving hydraulic pressure. A main piston has a main hydraulic pressure receiving surface that generates a pressing force to press in a direction, and is provided integrally with the output shaft and moves in accordance with the movement of the input shaft, and a main piston that supplies oil from a hydraulic source to the main hydraulic pressure receiving surface. It consists of a spool valve that is installed in the sending oil path and adjusts the hydraulic pressure supplied to the main hydraulic pressure receiving surface according to the movement of the input shaft, and in particular, it is integrally connected to the main piston and receives hydraulic pressure. an auxiliary piston having an auxiliary hydraulic pressure receiving surface formed to generate a pressing force that assists the output shaft pressing force of the main piston; and an auxiliary oil path that is branched from the oil passage and applies hydraulic pressure to the auxiliary hydraulic pressure receiving surface. , a switching valve installed in the auxiliary oil passage that opens and closes the auxiliary oil passage, and a signal from a sensor installed on the vehicle body that detects the amount of cargo load. It is characterized by being comprised of a controller that sends signals.

Such a variable hydraulic booster guides pressurized oil to the main hydraulic chamber that continues to the oil passage side via the spool valve when the car body's cargo load is below a predetermined value, and applies the hydraulic pressure to the main hydraulic pressure receiving surface of the main piston. This main piston transmits the increased pressing force to the output shaft, and the other
When the load amount of the car body exceeds a predetermined value, the hydraulic pressure on the oil path side is received by the main hydraulic pressure receiving surface and the secondary hydraulic pressure receiving surface of both the main and sub pistons, and this piston part applies the increased pressing force to the output shaft. It acts to convey.

The present invention will be described below with reference to the accompanying drawings. Second
The figure shows a hydraulic variable booster 3 installed between a brake master cylinder 1 and a brake pedal 2.
showed that. This hydraulic variable booster 3 is connected in parallel with the power steering to an oil pump 5 and an accumulator (a diversion valve may be added between the pump element and the not shown) 6 used in the power steering 4. be done. The master cylinder 1 is connected to each wheel cylinder 7 via a hydraulic pipe, and is configured so that each wheel cylinder applies a braking force to each wheel 8 in conjunction with the pressurizing operation of the master cylinder.

As shown in FIG. 3, the hydraulic variable booster 3 includes an input shaft 1 connected to a brake pedal 2 within a frame 9.
0 and an output shaft 11 disposed on the same line as this and applying a pressing force to a piston (not shown) in the master cylinder 1, respectively, are slidably supported. A piston portion 12 is integrally formed at one end of the output shaft, and is pressed and supported by a return spring 20 to a stop position P0. As shown in FIG. 3, the piston section 12 integrally connects a first piston section 121 with a large diameter D1 and a second piston section 122 (see FIG. 4) with a small diameter D2 by an arm section 30 of a rigid body. It is formed by Both piston portions are fitted into a first cylinder 31 and a second cylinder 32 serving as a pressure regulating cylinder within the frame body 9, respectively, so that both piston portions can slide in the same direction.

As shown in FIG. 3, the first piston portion 121 is formed with its end surface as the main hydraulic pressure receiving surface 14,
This is made to rush into the main hydraulic chamber 15. The other end of a lever 13, one end of which is connected to a spool valve 16 to be described later, is connected to this main hydraulic pressure receiving surface via a pin 17 that faces perpendicular to the plane of the paper in FIG. The lever 13 similarly connects a hollow connecting member 18 on the input shaft 10 side with a pin 19 near the pin 17 side. This connecting member is fitted into the frame 9 in a non-rotatable but slidable manner, and is pressed in the return direction A toward the main body of the input shaft 10 via the return spring 21, and is pushed to the stop position (the position shown by the solid line in FIG. 3). ) Support P1. Note that the main pressing end 101 of the main pressing member 10 protrudes from the center of the connecting member 18, and this is connected to both pins 17 and 19 of the lever 13.
It is arranged so that it can come into contact between the two.

As shown in FIG. 4, the main body of the second piston portion 122 is fitted into the second cylinder 32, and the extending portion thereof is integrally connected to the arm portion 30 on the main hydraulic chamber 15 side. The second cylinder 32 is the second piston portion 122
It includes a variable hydraulic pressure chamber 321 and a low pressure chamber 322 that are divided into two. The low pressure chamber 322 always communicates with the reservoir 24, and the variable hydraulic pressure chamber 321 communicates with the reservoir 24 or the main hydraulic chamber 15 via the switching valve 23 forming a three-way valve.
is selectively connected to. That is, the main oil pressure chamber 15 and the variable oil pressure chamber 321, which are on the oil path leading to the oil pump 5 side, can communicate with each other through the auxiliary oil path 22 provided with the switching valve 23. When receiving power, sub-oil line 2
2 are in communication, and the second piston portion 122 of the variable hydraulic chamber 321 receives the same hydraulic pressure as the main hydraulic chamber 15. The controller 25 outputs an ON signal to the switching valve 23 based on the output of a load sensor 26 that detects the amount of cargo load of the vehicle, and when this exceeds a set value.

As shown in FIG. 3, an output shaft 11 is provided within the frame 9.
A long guide hole 33 is formed in a direction parallel to the guide hole 33, into which the spool valve 16 is slidably fitted. The spool valve 16 has a connecting hole 161 formed in its center over almost its entire length, thereby eliminating almost the pressure difference between both ends. This spool valve has one end protruding into the main hydraulic chamber 15 and engages with a U-shaped groove at the upper end of the lever 13 via a pin 27. In this case, since the spool valve 16 receives the pressure within the main hydraulic chamber 15 at both ends, it is operated only by the pressing force from the lever 13 and the pressing force from the return spring 26. An annular recess 162 is formed in the body of this spool valve,
A lateral hole 163 communicating with the connecting hole 161 is opened here. When the input shaft 10 is at the stop position P1, the lever 13 supports the spool valve 16 at the stop position P2 shown by the solid line in FIG. In this case, guide hole 3
Of the two openings following No. 3, the outflow port 28 faces the annular recess 162, and the inflow port 29 is blocked from the annular recess. Note that the inlet 29 communicates with the pump 5 side, and the outlet 28 communicates with the reservoir 24 side.

The operation of such variable hydraulic booster 3 will be explained. Hydraulic pump 5 is operated by the drive of an engine (not shown), and hydraulic variable booster 3 receives pressurized oil together with power steering device 4 via accumulator 6 . First, if the load amount is small, the controller 25 does not issue an on signal, so the low pressure chamber 322
Both the variable oil pressure chamber 321 and the variable oil pressure chamber 321 communicate with the reservoir 24 on the low pressure oil path side. When the brake pedal 2 is depressed in this state, the input shaft 1 receives the pedal force F1 as an input.
0 is initially activated, and this activation is transmitted to the connecting member 18 via the return spring 21. Furthermore, this operation is performed on pin 1
7 as a fulcrum, the lever 13 is rotated counterclockwise, which causes the spool valve 16 to slide from the stop position P2 toward the operating position P3 shown in FIG. 5 by an amount corresponding to the value of the pedal force F1. Then, the outflow port 28 is closed, the inflow port 29 faces the annular recess 162 by a predetermined amount, and pressure oil of a value corresponding to the opening amount of this inflow port flows into the main hydraulic chamber 15. As shown in FIG. 6, at this point, the pedal force F1 from the input shaft 10 is at the main pressing end 1.
01 directly onto the piston portion 12 via the lever 13. Moreover, the main hydraulic pressure receiving surface 14 with area S1 (=π・D1 ² /4) receives hydraulic pressure F2 based on hydraulic pressure,
The resultant force based on such boosting action acts on the output shaft 11 as the first stage output F3. The output shaft 11 is actuated by this first-stage output F3, and the master cylinder 1 is actuated, and each wheel cylinder 7 generates a braking force by the pressure oil from this master cylinder.
On the other hand, if the load amount exceeds the set value, the controller 25 outputs an on signal to the switching valve 23, so the main hydraulic chamber 15 and the variable hydraulic chamber 321 communicate with each other. If you press brake pedal 2 in this state, the pedal force will be
In response to F1, first, the spool valve 16 is switched by an amount corresponding to the value of the pedal force F1, and pressure oil at a predetermined level is supplied to the main hydraulic chamber 15 and the variable hydraulic chamber 321. Then, the piston part 12 has the first area S1.
The piston part 121 and the second piston part 122 having an area S2 (=π・D2 ² /4) receive hydraulic pressure F2,
Generate F4. Based on this force-supplying action, the resultant force of both hydraulic pressures F2 and F4 and pedal force F1 is a two-stage output.
Acts on the master cylinder 1 side as F5. This second stage output F5 is larger than the first stage output F3, and the braking force of each wheel cylinder 7 based on this also becomes larger by the output difference. Incidentally, FIG. 7 shows the changes in the output for each input when the vehicle is lightly loaded and when the vehicle is loaded.

As is clear from Fig. 7, the hydraulic variable booster 3
According to , even if the input pedal force F1 is constant, the boost ratio changes according to the change in the area of the piston part 12, so when the load is light, the single-stage output of c (indicated by the broken line)
From F3, two-stage output of d when loading (shown by solid line)
The F5 is always larger, and the braking force is relatively large even if you don't press the brake pedal hard when loading a truck, which reduces fatigue in the driver's legs when loading a truck. Moreover, since the second piston part 122 is arranged in parallel with the first piston part 121, the input shaft 10
This is particularly advantageous when arranging the output shaft 11 and the output shaft 11 in a line does not result in a relatively large overall length, and the installation space in the longitudinal direction is relatively short.

[Brief explanation of the drawing]

Figure 1 is an input-output characteristic diagram of a conventional hydraulic booster, Figure 2 is a schematic configuration diagram of a hydraulic booster as an embodiment of the present invention, and Figure 3 is a sectional view of the main parts of the same device. , FIG. 4 is a sectional view taken along the - line in FIG. 3,
FIG. 5 is an explanatory diagram of the operation of the spool valve of the same device, FIG. 6 is an explanatory diagram of the operation of the piston part of the same device, and FIG.
The figures each show an input-output characteristic diagram of the same device. 1... Master cylinder, 2... Brake pedal, 3... Hydraulic variable booster, 10... Input shaft,
11... Output shaft, 12... Piston part, 121...
...first piston part, 122...second piston part,
14... Main hydraulic pressure receiving surface, 15... Main hydraulic chamber, 16...
...Spool valve, 22...Auxiliary oil passage, 23...Switching valve, 30...Arm.

Claims (1)

[Scope of utility model registration request] An input shaft that moves in the axial direction according to the force of the pedal, an output shaft that applies a pressing force to the brake master cylinder, and a main shaft that generates a pressing force that presses the output shaft in the direction of the brake master cylinder by receiving hydraulic pressure. A main piston has a hydraulic pressure receiving surface and is provided integrally with the output shaft and moves in accordance with the movement of the input shaft, and a main piston is provided in an oil passage that sends oil from a hydraulic source to the main hydraulic pressure receiving surface of the input shaft. and a spool valve that adjusts the hydraulic pressure supplied to the main hydraulic pressure receiving surface according to the movement of the main piston. A sub-piston having a sub-hydraulic pressure receiving surface formed to generate pressure; a sub-oil passage branched from the oil passage and applying hydraulic pressure to the sub-hydraulic receiving surface; It is characterized by consisting of a switching valve that opens and closes the road, and a controller that sends an opening signal to the switching valve when the cargo load exceeds a predetermined value based on a signal from a sensor installed on the vehicle body that detects the cargo load. Hydraulic variable booster.