JPH0344946B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tandem brake booster that doubles the pedal effort applied to the brake pedal so that a large braking force can be obtained with a light pedal effort, and more particularly relates to a tandem brake booster that boosts the pedal force applied to the brake pedal, and more particularly relates to a tandem brake booster that boosts the pedal force applied to the brake pedal so that a large braking force can be obtained with a light pedal force. The present invention relates to a safety device for a tandem brake booster that allows a substantially normal boost function to be obtained even when the brake booster is in use.

In recent years, as a tandem brake booster, one booster mechanism is configured in the same way as a normal single brake booster, and the other booster mechanism has an external control that controls the supply and discharge of pressure fluid to it. A device is provided, and this control device detects the input value applied to the input shaft and the output value outputted to the output shaft, and supplies and discharges pressure fluid so that the output value corresponds to the input value. A method has been proposed that controls the

According to the tandem brake booster having such a configuration, even if the output ratio of one booster mechanism is constant, the output ratio of the other booster mechanism is determined by the correspondence between the input value and the output value in the control device. Since it can be changed freely by simply changing it, it is now possible to freely change the total output from both boosting mechanisms. It also has the advantage of being easily adaptable.

In addition, even if one of the booster mechanisms loses its function due to a failure in the control device, the other booster mechanism is constructed in the same way as a normal single brake booster as described above. It has the advantage of providing a boosting function and ensuring safety.

However, even if the boosting function can be obtained when the above-mentioned control device fails, its capacity will basically be halved, so a fairly large pedal force is usually required to perform the same braking action as in normal conditions. This causes the driver to feel uneasy.

In view of such circumstances, the present invention is designed so that when the above-mentioned control device etc. is abnormal, pressure fluid can be supplied from the normal boosting mechanism side to the faulty boosting mechanism, so that the normal boosting mechanism is substantially restored. The present invention provides a safety device for a tandem brake booster that can ensure a strong boost function.

The present invention will be described below with reference to the illustrated embodiments.
In FIG. 1, 1 is a shell consisting of a front shell 1a, a center shell 1b, and a rear shell 1c.The inside of this shell 1 is divided into two chambers by a center plate 2 provided on the center shell 1b, and That is, the left side chamber is formed into a constant pressure chamber 5 and a variable pressure chamber 6 by the front diaphragm 3 and the front power piston 4, and the rear or right side chamber is formed into a constant pressure chamber 9 and a variable pressure chamber 10 by the rear diaphragm 7 and the rear power piston 8.
It is divided into

The front power piston 4 and the rear power piston 8 are each slidably provided in the shell 1, and an output shaft 12 is slidably passed through the center plate 2 while keeping airtight with a seal member 11. The two are integrally connected. The base of the output shaft 12 is slidably fitted to the shaft of the rear power piston 8 via the reaction disk 13, and the intermediate part is fitted to the shaft of the rear power piston 8 via the reaction disk 13.
The above-mentioned front power piston 4 is
It is fixed at The tip of this output shaft 12 is connected to the seal member 1 from the shaft of the front shell 1a.
5, it is kept airtight and protrudes to the outside, and is interlocked with a piston of a master cylinder (not shown). In addition, 16 is the front power piston 4 mentioned above.
This is a return spring that biases and holds the rear power piston 8 and the rear power piston 8 in the non-operating position shown in the figure.

A valve body 20 integrally provided on the shaft portion of the rear power piston 8 projects outwardly from the rear shell 1c via a seal member 21, and a conventionally well-known valve mechanism 22 is provided on the shaft portion. This valve mechanism 22 includes a valve plunger 23 that is slidably fitted into the valve body 20 and has a distal end surface facing the reaction disk 13, a distal end spherical portion is pivotally supported on the valve plunger 23, and a distal end An input shaft 24 that is linked to a brake pedal (not shown)
and a valve body 27 that can be seated on valve seats 25 and 26 provided on the valve body 20 and valve plunger 23, respectively.

In the non-operating state shown in the figure in which the valve body 27 and the valve seat 26 are seated and the valve body 27 and the valve seat 25 are unseated, the space between the constant pressure chamber 9 and the variable pressure chamber 10 before and after the rear power piston 8 is 20, a gap between the valve body 27 and the valve seat 25, and a radial passage 29 formed in the valve body 20. In the operating state in which the valve body 27 and the valve seat 26 are seated apart, the seating blocks communication between the constant pressure chamber 9 and the variable pressure chamber 10, and
In this embodiment, a pressure fluid supplied from a fluid pressure source 30 such as a compressed air source is supplied through a conduit 31, an axial passage 32 formed at the end of the shaft portion of the valve body 20, and a gap between the valve body 27 and the valve seat 26. , and can be introduced into the variable pressure chamber 10 via the radial passage 29.

Further, the constant pressure chamber 5 in front of the front power piston 4 is always communicated with the atmosphere through a passage 35 and an air cleaner (not shown), and the constant pressure chamber 5 and the constant pressure chamber 9 on the rear power piston 8 side are connected through a passage 36. and is in constant communication. On the other hand, the variable pressure chambers 6 and 10 at the rear of each power piston 4 and 8 are communicated via a communication passage 37 and an electromagnetic on-off valve 38, and this on-off valve 38 opens the communication passage 37 when deenergized, that is, in a natural state. The communication path 37 is opened and the communication path 37 is cut off when the control device 39 is excited.

Therefore, when the communicating passage 37 is opened, the pressure fluid introduced into the variable pressure chamber 10 on the rear power piston 8 side by the valve mechanism 22 flows through the communicating passage 37 into the variable pressure chamber 6 on the front power piston 4 side. In this state, the structure is similar to that of a conventional tandem brake booster. On the other hand, when the communication path 37 is shut off, even if pressure fluid is introduced into the variable pressure chamber 10 on the rear power piston 8 side, the pressure fluid will not be introduced into the variable pressure chamber 6 on the front power piston 4 side. Therefore, the rear power piston 8 side functions in the same manner as a conventional single brake booster.

The variable pressure chamber 6 on the side of the front power piston 4 has a passage 40 and an electromagnetic three-way control valve 41.
The three-way control valve 41 can selectively communicate with the above-mentioned fluid pressure source 30 or the atmosphere through the three-way control valve 41, and its flow path can be switched and controlled by the control device 39. . Further, contrary to the on-off valve 38, the three-way control valve 41 closes the passage 40 when deenergized, that is, in a natural state. Furthermore, each of the above-mentioned transformation chambers 6, 1
Pressure detectors 42 and 43 for detecting zero pressure are provided, and detection signals from each pressure detector 42 and 43 are input to the control device 39.

This control device 39 is connected to the pressure detector 4 which detects the pressure inside the variable pressure chamber 6 on the side of the rear power piston 8.
3, and indirectly detects the magnitude of the pedal force applied to the input shaft 24 based on the magnitude of the detection signal, and outputs based on the magnitude of the detection signal and the input/output characteristics stored in advance in the memory circuit. The three-way control valve 41 receives a detection signal from the pressure detector 42 that detects the pressure in the variable pressure chamber 6 on the side of the front power piston 4 so that the detected value corresponds to the calculated output. This allows the flow path to be controlled.

In the above configuration, during normal operation, the on-off valve 38 is excited by the control device 39, and the normally communicating passage 3
7 is closed. Therefore, as described above, even if the input shaft 24 is actuated and pressure fluid is introduced into the variable pressure chamber 10 on the rear power piston 8 side, the pressure fluid is introduced into the variable pressure chamber 6 on the front power piston 4 side. The booster mechanism on the front power piston 4 side is separated from the booster mechanism on the rear power piston 8 side.

During normal operation, when the brake pedal is not in operation, that is, when no pedal force is applied to the brake pedal, the valve mechanism 22 communicates between the constant pressure chamber 9 on the rear power piston 8 side and the variable pressure chamber 10. No fluid pressure difference occurs before and after the power piston 8. On the other hand, the control device 39 detects the non-operating state by the pressure detector 43, controls the three-way control valve 41 to cut off communication between the variable pressure chamber 6 and the fluid pressure source 30, and also closes the variable pressure chamber 6 to the fluid pressure source 30. 6
Since the constant pressure chamber 5 and the variable pressure chamber 6 are introduced into the constant pressure chamber 5 and the variable pressure chamber 6 by communicating with the atmosphere, no fluid pressure difference occurs before and after the front power piston 4. Therefore, each of the power pistons 4, 8 is held in the operating position shown by the return spring 16. In this state, when the brake pedal is depressed and the input shaft 24 is moved forward, the flow path of the valve mechanism 22 is switched, cutting off communication between the constant pressure chamber 9 and the variable pressure chamber 10, and also blocking the communication from the fluid pressure source 30. Pressure fluid is supplied into the variable pressure chamber 10. As a result, as is conventionally known, a fluid pressure difference is generated before and after the rear power piston 8 according to the pedal force applied to the input shaft 24, and the rear power piston 8 is moved forward by this fluid pressure difference. become.

At the same time, the pressure of the pressure fluid supplied into the variable pressure chamber 10 is detected by the pressure detector 43, so the control device 39 controls the three-way control valve 41.
The fluid circuit of the variable pressure chamber 6 and the atmosphere is switched, and the communication between the variable pressure chamber 6 and the fluid pressure source 3 is switched.
0 to introduce fluid pressure into the variable pressure chamber 6. Then, the control device 39 detects the pressure introduced into the variable pressure chamber 6 using the pressure detector 42,
An output corresponding to the input is calculated from the magnitude of the input detected by the pressure detector 43 and predetermined input/output characteristics, and the pressure detected by the pressure detector 42 corresponds to the calculated output. The flow path of the three-way control valve 41 is switched and controlled so that

In this way, when a fluid pressure difference is created between the front and rear of each power piston 4, 8 according to the input, each power piston 4, 8 is moved forward against the elastic force of the return spring 16, and this Accordingly, an output shaft 12 integrated with each power piston 4, 8
When the motor is moved forward with an output corresponding to the input, brake fluid pressure is generated in a master cylinder (not shown) linked to the output shaft 12, and a braking action is performed.

On the other hand, when the pedal force applied to the input shaft 24 is released when the brake action is released, the valve mechanism 22 switches its flow path to reduce the fluid pressure difference before and after the rear power piston 8. At the same time, the control device 39 detects a decrease in the pedal force using the pressure detector 43, and the three-way control valve 4
The pressure fluid in the variable pressure chamber 6 is discharged to the atmosphere through the three-way control valve 41 by switching the passage 1, thereby reducing the fluid pressure difference before and after the front power piston 4. As a result, each power piston 4, 8 is retracted by the return spring 16, and is finally returned to the non-operating position shown in the figure.

As understood from the above explanation, the control device 3
By changing the input/output characteristics stored in the memory circuit 9, you can easily change the input/output characteristics of the front power piston 4 side without changing the dimensions of any mechanical parts, and therefore increase the tandem brake boost. The input/output characteristics of the device as a whole can be changed, and compared to the past, parts of various tandem brake boosters can be shared, resulting in cost reduction. Furthermore, the input/output characteristics described above can be freely set by storing them in the memory circuit of the control device 39, so that input/output characteristics including a curve for obtaining the optimum braking action can be easily obtained. Become.

In this embodiment, an on-off valve 38 that opens the communication passage 37 and a three-way control valve 41 that closes the passage 40 are provided in the natural state, so that if the control device 39 malfunctions or the like, each control valve 38, 41 is no longer excited, the on-off valve 38 maintains its natural state and opens the communication passage 37, and at the same time, the three-way control valve 41 closes the passage 40 and opens the communication passage 37. The variable pressure chamber 6 is now sealed.

In this state, the configuration is similar to that of a conventionally known tandem brake booster. Therefore, like such a conventional tandem brake booster, the valve mechanism 22 controls the flow of fluid pressure in response to the forward and backward movement of the input shaft 24. By controlling the opening and closing of the passage, pressure fluid of the same pressure is introduced into both variable pressure chambers 10 and 6 through the communication passage 37. Therefore, although the input/output characteristics of the tandem brake booster in this case are uniquely determined, it is possible to ensure a boost function substantially equivalent to that in normal conditions.

FIG. 2 shows another embodiment of the present invention,
In this embodiment, the on-off valve 38 and the three-way control valve 41
and are constructed from one flow path switching valve 50.

The flow path switching valve 50 includes a pair of passages 52 and 53 formed in a housing 51, a valve seat 54 formed between the passages, and a valve body 55 seated on the valve seat 54. By communicating the passages 52 and 53 with the communication passage 37, the pair of variable pressure chambers 6 and 10 are communicated via an on-off valve constituted by the valve body 55 and the valve seat 54.

A plunger 56 is slidably fitted into the housing 51, and the plunger 56 is brought into elastic contact with the valve body 55 by a spring 57, and the valve body 55 is normally placed at a position separated from the valve seat 54. The force is maintained. Therefore, similarly to the embodiment described above, in the natural state, the variable pressure chambers 6 and 10 communicate with each other. The valve body 55 also has a through hole 58.
This through hole 58 is provided with a plunger 56.
The through hole 58 is connected to the fluid pressure source 30 through a passage 59 on the opposite side thereof, and the through hole 58 can be closed when the plunger 56 is in elastic contact with the valve body 55.

However, the plunger 56 constitutes a part of a conventionally known proportional solenoid valve 60, and this proportional solenoid valve 60 receives a signal from the control device 39 and adjusts the pressure of the pressure fluid from the fluid pressure source 30. Input shaft 2
It is possible to control and circulate the pressure according to the pedal force of Step 4. The other configurations are similar to those of the above embodiment.

In such a configuration, when the proportional solenoid valve 60 is not in operation and no signal is input from the control device 39, or when a failure occurs, the plunger 56 uses the elastic force of the spring 57 to push the valve body 55 into the housing 51. In this state, the valve body 55 is separated from the valve seat 54 to communicate between the variable pressure chambers 6 and 10, and closes the through hole 58 of the valve body 55. Therefore, in the event of a failure, the pressure fluid introduced into the variable pressure chamber 10 on the rear power piston 8 side is introduced into the variable pressure chamber 6 on the front power piston 4 side via the communication passage 37, so that normally the tandem brake booster is not activated. It will operate in the same way as the device.

On the other hand, under normal conditions, when the control device 39 detects that a pedal force is applied to the input shaft 24 by the pressure detector 43, it outputs a signal corresponding to the pedal force to the proportional solenoid valve 60. As a result, when the plunger 56 is moved to the left against the spring 57, the valve body 55 is moved to the left by the fluid pressure and seats on the valve seat 54, cutting off communication between the variable pressure chambers 6 and 10, and further When the plunger 56 is moved to the left, the through hole 58 is opened and pressure fluid is introduced into the variable pressure chamber 6 through the passage 59 and the through hole 58.

The proportional solenoid valve 60 detects the pressure within the passage 52, that is, within the variable pressure chamber 6, and when the pressure reaches a level corresponding to the signal from the control device 39, it moves the plunger 56 to the right and opens the through hole 58. Close it now.
The pressure inside the variable pressure chamber 6 is maintained at a predetermined pressure. Then, when the pedal force applied to the input shaft 24 decreases, the proportional solenoid valve 60 is activated by the plunger 5.
6 to the right, the valve body 55 is removed from the valve seat 54, the pressure fluid in the variable pressure chamber 6 is discharged into the rear variable pressure chamber 10 via the communication path 37, and the pressure in the variable pressure chamber 6 is input. The pressure is maintained at a level corresponding to the pedaling force on the shaft 24.

In this embodiment, it is necessary to set the pressure in the variable pressure chamber 6 controlled by the control device 39 to be higher than the pressure in the variable pressure chamber 10 controlled by the valve mechanism 22. Of course, if this condition is satisfied, the output ratio of the booster mechanism on the control device 39 side can be freely set.

Further, in the above embodiment, even if the boosting function cannot be obtained at all, the input shaft 24
Since the output shaft 12 and the output shaft 12 are mechanically interlocked, brake fluid pressure can be generated in the master cylinder. Further, in the above embodiment, the passage 35 is communicated with the atmosphere, but it may also be communicated with a negative pressure source such as an intake manifold, and in that case, it goes without saying that the atmosphere can be used as the fluid pressure source 30. be. Furthermore, the opening/closing valve 38 is turned off by the communication passage 3 only when pedal force is applied to the input shaft 24.
7 may be closed, and the three-way control valve 41 may be composed of an electromagnetic on-off valve.

Further, in the above embodiment, the pedal force applied to the input shaft 24 is indirectly detected by the pressure detector 43, and the output generated on the output shaft 12 is indirectly detected by the pressure detector 42, but this is not always necessary. It is not limited to this. For example, as the input detection means for detecting the pedal force applied to the input shaft 24, a load detector such as a load cell can be used to directly detect the magnitude of the pedal force applied to the input shaft, and also detect the output applied to the output shaft. Similarly, a load detector may be used as the output detection means, or the brake fluid pressure generated within the master cylinder may be detected.

As described above, the present invention configures one boosting mechanism of a tandem brake booster in the same manner as a normal single brake booster during normal operation, and configures the other boosting mechanism according to the magnitude of the pedal force. By configuring the brake booster as having a control device that controls the supply and discharge of pressure fluid, it is possible to freely change the total output ratio of both booster mechanisms, and at the same time, the above-mentioned control device, etc. In the event of a failure, the on-off valve that shuts off the passage between the two booster mechanisms is automatically opened, allowing pressurized fluid to be supplied to both booster mechanisms. This provides the effect of ensuring a boosting function similar to that of a brake booster and safely performing braking.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is a system diagram of main parts showing another embodiment of the present invention. 1... Ciel, 2... Center plate, 4,
8... Power piston, 5, 9... Constant pressure chamber, 6,
DESCRIPTION OF SYMBOLS 10... Pressure change chamber, 12... Output shaft, 20... Valve body, 22... Valve mechanism, 24... Input shaft, 2
8, 29, 32... passage, 37... communicating passage, 30
... Fluid pressure source, 38 ... Opening/closing valve, 39 ... Control device, 41 ... Three-way control valve, 42, 43 ... Pressure detector, 50 ... Channel switching valve, 55 ... Valve body,
56...Plunger, 60...Proportional solenoid valve.

Claims (1)

[Claims] 1 A pair of power pistons are provided in the shell to move forward and backward, and together with a center plate provided in the shell, define a constant pressure chamber and a variable pressure chamber at the front and rear of each. A valve mechanism that switches and controls a flow path between a constant pressure chamber, a variable pressure chamber, and a fluid pressure source before and after the power piston, and introduces pressure fluid into the variable pressure chamber behind the power piston in accordance with the input applied to the input shaft. is provided outside the shell, detects that an input is applied to the input shaft, switches and controls the flow path between the variable pressure chamber behind the other power piston and the fluid pressure source, and controls the flow path between the variable pressure chamber and the fluid pressure source behind the other power piston. The tandem brake booster is equipped with a control device that introduces pressurized fluid according to the input applied to the input shaft into a rear variable pressure chamber, and further includes a communication path between the variable pressure chambers at the rear of the pair of power pistons. and communicate with the communication path, and leave the communication path open in a natural state, and
A safety device for a tandem brake booster, comprising an on-off valve that closes a communication path at least when the tandem brake booster is in normal operation.