JPH037255Y2 - - 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 varies depending on the hydraulic 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, a hydraulic booster that uses oil pressure can be connected in parallel to the power steering hydraulic system, for example.
Attachment 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. That is, 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 greater braking force is required when the vehicle is loaded than when the vehicle is lightly loaded, so the input, i.e. It also requires a lot of pedaling force. In this way, when the weight of the vehicle is large, a large amount of force is required to press the pedal, so if the brake pedal is pressed with a large cargo load, the legs are likely to become fatigued, which inconveniences the brake operability. .

An object of the present invention is to provide a hydraulic variable booster that can increase the boost ratio when a light vehicle is loaded than when the vehicle is loaded, thereby reducing the difference in pedal force when the vehicle is lightly loaded and when the vehicle is 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. It has a main hydraulic pressure receiving surface that generates a pressing force to press in the direction, and a piston part that is provided integrally with the output shaft and moves in accordance with the movement of the input shaft, and a piston part 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 passage and adjusts the hydraulic pressure supplied to the main hydraulic pressure receiving surface according to the movement of the input shaft. An auxiliary oil pressure receiving surface that generates a pressing force to assist the output shaft pressing force of the piston part, an auxiliary oil path that is branched from the oil passage and applies hydraulic pressure to the auxiliary oil pressure receiving surface, and an auxiliary oil passage that is arranged in the auxiliary oil passage and that is the same. It consists of a switching valve that opens and closes the auxiliary oil passage, and a controller that sends an open signal to the switching valve when the cargo load is greater than a predetermined value based on a signal from a sensor installed on the vehicle body that detects the cargo load. It is characterized by

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 cargo load of the vehicle body is below a predetermined value, and applies the hydraulic pressure to the main hydraulic pressure receiving surface of the piston part. This piston part transmits the increased pressing force to the output shaft, and on the other hand,
When the load amount of the vehicle body exceeds a predetermined value, the hydraulic pressure on the oil path side is received by the main hydraulic pressure receiving surface and the auxiliary hydraulic pressure receiving surface of the piston section, and the piston section acts to transmit the increased pressing force to the output shaft. do.

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 installed in parallel with an oil pump 5 and an accumulator (a diverter valve may be added between the pump element and the not shown) 6 used in the power steering 4. Connected. 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.

The hydraulic variable booster 3, as shown in FIG.
An input shaft 10 connected to the brake pedal 2 in the frame 9 and an output shaft 11 disposed on the same line as the input shaft 10 and applying a pressing force to a piston (not shown) in the master cylinder 1 are slidably connected to each other. To support.
A piston portion 12 is integrally formed at one end of the output shaft 11, and is moved to a stop position by a return spring 20.
Pressed and supported by P0. The end face of the piston portion 12 is formed as a main hydraulic pressure receiving surface 14, and this is projected into a main hydraulic pressure chamber 15. On this main hydraulic pressure receiving surface, one end of the lever 13 is connected to a spool valve 16, which will be described later.
connected via. 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 body 9 in a non-rotatable but slidable manner, and the return spring 2
1, the main body side of the input shaft 10 is pressed in the return direction A, and supported at the stop position (the position shown by the solid line in FIG. 3) P1. Note that the main pressing end 101 of the input shaft 10 protrudes from inside the connecting member 18, and is arranged so as to be able to abut between both pins 17 and 19 of the lever 13.

The piston portion 12 is formed in two stages along its longitudinal direction, has a main hydraulic pressure receiving surface 14, and has an outer diameter.
The first piston part 121 of D1 and the outer diameter D2 extending stepwise from the other end of this first piston part (D2>D1)
It has a second piston part 122. The connecting portion between the inner wall on the frame body 9 side where the first piston portion 121 comes into sliding contact and the inner wall where the second piston portion 122 comes into sliding contact is formed as a tapered stopper wall 901. An annular hydraulic pressure receiving surface 123 as a step-shaped auxiliary hydraulic pressure receiving surface comes into contact with and separates (see FIG. 4). An opening 902 is formed in the frame body in a stopper wall 901 that can come into contact with this annular hydraulic pressure receiving surface. be done. As shown in FIG. 3, the auxiliary oil passage 22 is provided with a switching valve 23 that functions as a three-way valve in the middle thereof, and when this switching valve is turned on, the auxiliary oil passage 22 is communicated with, and when it is turned off, the auxiliary oil passage 22 is cut off. The oil on the opening 902 side is guided to the reservoir 24 side. Note that, as shown in FIG. 2, this switching valve is connected to a controller 25. 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, a long guide hole 38 is formed in the frame 9 in a direction parallel to the output shaft 11, into which the spool valve 16 is slidably fitted. Spool valve 16
A connecting hole 161 is formed in the center over almost the entire length, thereby almost eliminating the pressure difference between both ends. This spool valve has one end protruded into the main hydraulic chamber 15 and is engaged with a U-shaped groove at the upper end of the lever 13 via a pin 27. In this case, spool valve 1
6 receives the pressure in the main hydraulic chamber 15 at both ends, and therefore operates only by the pressing force from the lever 13 as the input shaft moves and the pressing force from the return spring 26. An annular recess 162 is provided in the body of this spool valve.
is formed, and a horizontal hole 163 communicating with the connecting hole 161 is opened here. Input shaft 10 is at stop position
When in P1, the lever 13 moves the spool valve 16 to the third position.
It is supported at the stop position P2 shown by the solid line in the figure. In this case, of the two openings following the guide hole 38, the outlet 2
8 faces the annular recess 162, and the inlet 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 amount of cargo load is small, the controller 25 does not issue an on signal. When the brake pedal 2 is depressed in this state, the input shaft 10 receives the input pedal force F1 and is initially operated, and this operation is transmitted to the connecting member 18 via the return spring 21. Furthermore, this operation rotates the lever 13 counterclockwise using the pin 17 as a fulcrum, and moves the spool valve 16 to the stop position.
It is slid from P2 toward the operating position P3 shown in FIG. 5 by an amount corresponding to the value of the pedal force F1. Then, the outlet 2
8 is closed, the inlet 29 faces the annular recess 162 by a predetermined amount, and pressure oil of a value corresponding to the opening amount of this inlet flows into the main hydraulic chamber 15. At this point, the step F1 from the input shaft 10 is applied directly to the piston portion 12 from the main pressing end 101 via the lever 13. As shown in Fig. 4, in addition to this pressing force from the input shaft side, the main hydraulic pressure receiving surface 14 of area S1 (=π・D1 ² /4) receives hydraulic pressure F2 based on the hydraulic pressure, and the resultant force is the output. It acts on the shaft 11 as a first stage output F3. The output shaft 11 is actuated by the 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 the 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 opening 902 communicate with each other. When the brake pedal 2 is depressed in this state, the spool valve 16 is first switched by an amount corresponding to the value of the pedal force F1, and a predetermined level of pressure oil is supplied to the main hydraulic chamber 15. Then, this pressure oil passes through the auxiliary oil passage 22 and acts on the annular hydraulic pressure receiving surface 123 as well. Therefore, the piston 12 is connected to the main hydraulic pressure receiving surface 1.
In addition to 4, the annular hydraulic pressure receiving surface 123 also receives pressure oil, and a circular surface of diameter D2 and area S2 (=π・D2 ² /4) receives hydraulic pressure F4, resulting in the resultant force of hydraulic pressure F4 and pedal force F1. is applied to the master cylinder 1 side as the second stage output F5. The second stage output F5 is larger than the first stage output F3,
Based on this, the braking force of each wheel cylinder 7 also becomes sufficiently large. In addition, the change in output for each input during the above-mentioned light loading and loading is shown in the sixth column.
Shown in the figure.

As is clear from FIG. 6, according to the hydraulic variable booster 3, even if the input pedal force F1 is constant,
Since the boost ratio changes according to the change in the area of the piston part 12, the single-stage output of c (indicated by a broken line) when lightly loaded
Compared to F3, the two-stage output of d (shown by the solid line) is always larger when loading a car, and it applies a relatively large braking force even if you do not press the brake pedal 2 strongly when loading a car. It can reduce fatigue of people's feet. In this case, in particular, if the difference in the required braking force between when the vehicle is loaded and when the vehicle is lightly loaded is detected in advance and the annular hydraulic pressure receiving surface 123 is formed that can obtain an output corresponding to this difference, It is possible to apply the brakes on the vehicle at the same time with the same pedal force, almost regardless of the weight of the cargo.

The hydraulic variable booster 3 shown in FIG.
The piston part 12, which is integral with the piston part 1, was formed as first and second piston parts 121 and 122 by having two different outer diameters along its longitudinal direction, but instead, as shown in FIG. In addition, the outer diameter of the piston part 30 is varied in three stages along its longitudinal direction, and the first, second and third piston parts 301, 302,
303. The stepped portion between the first and second piston portions 301 and 302 and the stepped portion of the second and third piston portions 302 and 303 are formed as annular hydraulic pressure receiving surfaces 31 and 32, respectively.
The main hydraulic chamber 15 is connected to both of these hydraulic pressure receiving surfaces via an auxiliary oil passage 34 having a switching valve 33 and an auxiliary oil passage 36 having a switching valve 35. Both the switching valves 33 and 35 may be connected to a controller 37, and the controller may sequentially turn on the switching valves depending on the degree of cargo load. In this case, it is possible to respond appropriately and sequentially to the three stages of changes in the amount of cargo load, and the driver operates the brakes of the vehicle to the same extent as when the cargo is lightly loaded, using the same pedal force as when the cargo is lightly loaded, even when the cargo weight changes. can.

[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 variable hydraulic booster as an embodiment of the present invention, and Figure 3 is a cross-section of the main parts of the same device. 4 is an explanatory diagram of the operation of the piston part of the above device, FIG. 5 is an explanatory diagram of the operation of the spool valve of the above device, FIG. 6 is an input-output characteristic diagram of the same device, and FIG. 7 is an explanatory diagram of the operation of the spool valve of the same device. 3A and 3B each show schematic cross-sectional views of piston portions used in other embodiments. 1... Master cylinder, 2... Brake pedal, 3... Hydraulic variable booster, 10... Input shaft,
11... Output shaft, 12... Piston part, 123...
...Annular hydraulic pressure receiving surface, 13...Lever, 14...Main hydraulic pressure receiving surface, 15...Main hydraulic pressure chamber, 16...Spool valve, 22...Sub-oil passage, 23...Switching valve.

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 piston part has a hydraulic pressure receiving surface and is provided integrally with the output shaft and moves according to the movement of the input shaft, and a piston part is provided in an oil passage that sends oil from the hydraulic source to the main hydraulic pressure receiving surface of the input shaft. A spool valve that adjusts the hydraulic pressure supplied to the main hydraulic pressure receiving surface according to the movement, and a pressing force that is formed on the piston and receives hydraulic pressure to assist the output shaft pressing force of the piston part. An auxiliary oil pressure receiving surface that generates hydraulic pressure, an auxiliary oil path that is branched from the oil path and applies hydraulic pressure to the auxiliary oil pressure receiving surface, a switching valve that is disposed in the auxiliary oil path and opens and closes the auxiliary oil path, and a A hydraulic variable booster comprising: a controller that sends an open signal to the switching valve when the load amount exceeds a predetermined value based on a signal from a sensor that detects the load amount.