JP3704751B2 - Fluid pressure generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluid pressure generating device that generates a predetermined fluid pressure such as a master cylinder.
[0002]
[Prior art]
Recently, there is an increasing demand for automated gear shifting in large vehicles such as buses and trucks. These vehicles generally have a large weight and load capacity, and using a fluid torque converter such as that adopted for passenger cars as a clutch type is disadvantageous in terms of fuel consumption and loss, so the friction clutch is intermittently operated by automatic operation, In parallel with this, a transmission (manual transmission) is automatically operated by an actuator to achieve automatic shifting. As a clutch on / off device that automatically operates the clutch, a booster (clutch booster) that performs on / off operation of the friction clutch by air pressure is generally used.
[0003]
On the other hand, when starting a vehicle, the operation of the clutch becomes delicate, and if it is attempted to perform the operation with automatic control, the device becomes complicated and expensive, so only in this case a manual operation using the clutch pedal (manual operation) In order to simplify the apparatus and to reduce the price, there has been proposed (for example, Japanese Utility Model Publication No. 4-8023). That is, the hydraulic pressure is applied from the master cylinder to the booster by operating the clutch pedal, and this is driven.
[0004]
[Problems to be solved by the invention]
By the way, in this type of auto clutch system, when automatic gear shifting is being performed, pneumatic pressure is supplied to the booster, the internal power piston is pushed, and the clutch is operated in the dividing direction. However, in the conventional configuration, the passage for sending the hydraulic pressure from the master cylinder communicates with the hydraulic cylinder of the booster whose volume changes according to the movement of the power piston, and when the hydraulic cylinder volume increases due to the pushing of the power piston. There is a possibility that negative pressure is generated in the hydraulic passage and air is sucked.
[0005]
In order to prevent the occurrence of such negative pressure, it is necessary to provide a manual operation and automatic operation canceling mechanism in the hydraulic output part of the booster as disclosed in Japanese Utility Model Publication No. 4-8023. The mechanism is complicated and reliability is also a problem. Therefore, in order to prevent the generation of negative pressure without changing the booster, the master cylinder can be driven not only by the clutch pedal but also by the control system (pneumatic pressure supply circuit) and without interfering with each other. It is desirable to do. Further, in order to improve the followability of the clutch pedal and the clutch, it is necessary to reduce the friction of the master cylinder as much as possible, but there has not been a fluid pressure generator applicable to such a master cylinder.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a cylinder body having a first fluid chamber that contains a working fluid, and is slidably provided in the cylinder body so as to face the first fluid chamber. A first piston for pressurizing the working fluid in the chamber, and provided at the end of the first piston opposite to the first fluid chamber so as to be detachable, and slidably accommodated in the cylinder body The second piston is partitioned by the second piston and the cylinder body, and is supplied with pressure fluid to move the second piston to push the first piston in the working fluid pressurizing direction. Two fluid chambers, a supply means for supplying pressure fluid to the second fluid chamber, and an insertion hole formed in the second piston are provided so that only the first piston is pressurized with the working fluid. Push in the direction Rod and, above the atmospheric pressure chamber that first piston and the second fluid chamber of the pressure fluid when the said second piston is spaced is opened to the atmosphere through the through hole, the first and second pistons for each provided them is obtained and a spring for urging the opposite side of the working fluid pressure direction. Accordingly, by sliding the first piston by the operation of the rod, the working fluid can be appropriately boosted to generate a predetermined fluid pressure. At this time, since the second piston is biased in the opposite direction by the spring, it is disconnected from the first piston, and the rod operates only the first piston. Further, by supplying pressure fluid to the second fluid chamber, the second piston is operated in the cylinder body and the second piston is pressed against the first piston, so that the space between the second piston and the first piston is self-sealed. The Accordingly, the working fluid can be pressurized by receiving the pressure of the fluid supplied integrally with the second piston and the first piston. That is, the desired fluid pressure can be generated without interfering with each other and without significantly increasing the friction of the master cylinder by the mechanical operation and the fluid supply control.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
When the present invention is applied to a master cylinder of a vehicle clutch interrupting device, a hydraulic piston is configured as a first piston and a pneumatic piston is configured as a second piston. Then, when the clutch pedal is depressed, the rod is operated to push only the hydraulic piston. Further, the pneumatic pressure supply system is controlled by a controller to supply air pressure to the second fluid chamber at the time of shifting, thereby moving the pneumatic piston and pushing the hydraulic piston. The actuator of the clutch such as a booster is appropriately driven by the hydraulic pressure generated by pushing the hydraulic piston. The pneumatic piston has a larger diameter than that of the hydraulic piston so that a high operating hydraulic pressure can be obtained even at a low air pressure. It is preferable to provide an atmospheric pressure chamber between the pneumatic piston and the hydraulic piston.
[0008]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0009]
FIG. 1 shows a first embodiment of the fluid pressure generator of the present invention. This fluid pressure generator is configured to generate a predetermined oil pressure using oil as a working fluid and high pressure air as a pressure fluid, and has a cylinder body 12 having a first fluid chamber 11 for containing oil. A hydraulic piston 13 as a first piston for pressurizing oil, a first push rod 14 and a second push rod 15 for pushing the hydraulic piston 13 in the pressurizing direction P, and a second push rod 15 A pneumatic piston 16 as a second piston that is inserted and operated by air pressure, a second fluid chamber 17 that is partitioned by the pneumatic piston 16 and the cylinder body 12 to introduce high-pressure air, a hydraulic piston 13 and a pneumatic piston 16 are provided. The first spring 18 and the second spring 19 that are biased in the opposite direction to the pressing direction P are mainly configured. .
[0010]
The cylinder body 12 is formed with a hydraulic cylinder portion 20 for sliding the hydraulic piston 13 on the distal end side and a pneumatic cylinder portion 21 for sliding the pneumatic piston 16 on the proximal end side. The hydraulic cylinder section 20 has a first fluid chamber 11 defined therein, and a hydraulic outlet 23 is formed in the tip wall 22. An oil supply path 25 with an orifice for supplementing oil at a low pressure from a reservoir tank (not shown) is formed in the peripheral wall 24 of the hydraulic cylinder section 20. The pneumatic cylinder portion 21 is formed with a larger diameter than the hydraulic cylinder portion 20, and an atmospheric pressure chamber 26 is partitioned in addition to the second fluid chamber 17 inside thereof. An air introduction port 28 for introducing high-pressure air into the second fluid chamber 17 is formed in the peripheral wall 27 of the pneumatic cylinder portion 21. The atmospheric pressure chamber 26 is partitioned between a step wall 29 serving as a boundary with the hydraulic cylinder unit 20 and the pneumatic piston 16 and is opened to the outside (open to the atmosphere) by a communication hole 30 formed in the peripheral wall 27. Yes. Further, the base end side of the pneumatic cylinder portion 21 is provided by a shaft end plate 53 that is stopped and fitted to the end portion of the peripheral wall 27 by a snap ring 52, and a seal wall member 31 that is provided so as to overlap with the shaft end plate 53. It is partitioned. The seal wall member 31 has a bottomed cylindrical shape extending toward the distal end side, and the flange portion 32 on the proximal end side thereof is in contact with the inner wall of the pneumatic cylinder portion 21 via the seal 33. An insertion hole 35 for inserting the second push rod 15 is formed at the position of the cylinder axis of the front surface portion 34 of the seal wall member 31. A seal 36 is provided in the insertion hole 35.
[0011]
The hydraulic piston 13 is a substantially cylindrical solid member having an outer diameter substantially equal to the inner diameter of the hydraulic cylinder portion 20 and having a length substantially equal to the cylinder length of the hydraulic cylinder portion 20. An enlarged flange 37 is formed. That is, the rear end side of the hydraulic piston 13 protrudes into the atmospheric pressure chamber 26. A tip 38 of the hydraulic piston 13 faces the first fluid chamber 11, and a first spring 18 is provided between the piston tip 38 and the tip wall 22 of the cylinder body 12. The piston tip 38 is provided with a primary cup 39 for appropriately holding the end of the first spring 18. Further, a slightly reduced diameter portion 40 is formed over an appropriate section at a position slightly proximal to the piston tip 38, and between the reduced diameter portion 40 and the inner wall of the hydraulic cylinder portion 20. A branch path 41 of the oil supply path 25 is communicated with the gap so that oil is appropriately supplied. A seal 42 is provided in the vicinity of the proximal end side of the reduced diameter portion 40.
[0012]
The first push rod 14 and the second push rod 15 are provided along the axial center of the cylinder body 12, and the distal end of the first push rod 14 abuts on the base end portion 43 of the second push rod 15 and pressurizes. A force in the direction P is transmitted. The base end portion 43 of the second push rod 15 is formed in a bowl shape, and the movement in the backward direction is restricted by contacting the inner surface of the shaft end plate 53. And the base end part 43 slides inward of the cylindrical part 44 of the seal wall member 31, and stroke movement is guided. The tip of the second push rod 15 is formed in a hemispherical shape and comes into contact with a receiving seat 45 formed on the flange portion 37 of the hydraulic piston 13.
[0013]
The pneumatic piston 16 has a bottomed cylindrical shape surrounding the seal wall member 31, and its peripheral portion 46 is appropriately formed smaller than the inner diameter of the pneumatic cylinder portion 21, and the peripheral edge of the surface portion 47 has a seal 48. And is in sliding contact with the inner wall of the pneumatic cylinder portion 21. An insertion hole 49 for inserting the second push rod 15 is formed at the axial center position of the surface portion 47. The second spring 19 is provided between the surface portion 47 and the step wall 29. Due to the urging force of the second spring 19, the base end of the peripheral portion 46 of the pneumatic piston 16 is in contact with the front side of the flange portion 32 of the seal wall member 31 in a state where no air pressure is supplied. Further, a communication hole 50 is formed in the peripheral portion 46 of the pneumatic piston 16 for guiding the supplied high-pressure air to the inside thereof. Therefore, the second fluid chamber 17 includes a space surrounded by the inner wall of the pneumatic cylinder portion 21 and the peripheral edge 46 and the edge of the surface portion 47 of the pneumatic piston 16 as well as the air pressure piston 16 and the seal wall member 31. It is substantially formed by the space between them. Further, when the hydraulic piston 13 is not pushed by the push rods 14 and 15, the flange portion 37 is surface-bonded to the pneumatic piston 16 by the biasing force of the first spring 18, and the seal provided on the flange portion 37. 80 prevents high-pressure air from flowing into the atmospheric pressure chamber 26 from the insertion hole ( sliding hole ) 49. In addition, the step wall 29 is provided with a stroke stopper 51 that contacts the front surface of the outer periphery of the pneumatic piston 16 to restrict the movement range of the pneumatic piston 16 in the pressurizing direction P.
[0014]
When the mechanical force is applied to the first push rod 14 to move in the right direction in the figure, the second push rod 15 pushed by the hydraulic pressure generating device configured as described above is The hydraulic piston 13 is pushed against the urging force of the first spring 18 through the insertion hole 49 of the pneumatic piston 16 in contact with the portion 37. The hydraulic piston 13 slides in the hydraulic cylinder portion 20 to increase the pressure by an amount corresponding to the amount of movement, and drives the hydraulic drive system connected to the hydraulic outlet 23. In addition, when high pressure air is introduced into the second fluid chamber 17 in a state where the push rods 14 and 15 are not operated, the pneumatic piston 16 overcomes the urging force of the second spring 19 and air supply amount (air pressure). The hydraulic cylinder 13 is slid with a stroke corresponding to the pressure, and the hydraulic piston 13 is integrally pushed to increase the pressure of the oil in the first fluid chamber 11. At this time, the second push rod 15 and the hydraulic piston 13 are separated from each other, and the pneumatic piston 16 and the hydraulic piston 13 are self-sealed at their contact surfaces.
[0015]
In this way, the hydraulic piston 13 and the pneumatic piston 16 are provided in series in the cylinder body 12, and the hydraulic piston 13 is driven by the push rods 14 and 15 or the operation of the pneumatic piston 16 by supplying air pressure. As a result, the desired hydraulic pressure can be generated without interfering with each other. When the second push rod 15 is actuated, the hydraulic piston 13 is pushed directly, and the dedicated springs 18 and 19 are provided on both pistons 13 and 16, respectively, so that sliding resistance (friction) can be reduced. That is, the followability between the push rods 14 and 15 and the generation of hydraulic pressure can be improved. Further, since the number of sliding seals of the hydraulic piston 13 is small and the diameter is small, the pushing reaction force can be further reduced. When the first push rod 14 is operated in a state where the pneumatic piston 16 is pushed by air, the second push rod 15 causes air to flow backward from the air introduction port 28 while the pneumatic pressure is increased. It penetrates the piston 16 and hits the hydraulic piston 13. For this reason, the pressure of the air supply source (in the air tank) slightly increases, but if the capacity is sufficiently large, this pressure increase can be ignored. Therefore, even if the push rods 14 and 15 are operated by overcoming the air reaction force, the air supply system is not adversely affected.
[0016]
Furthermore, in this embodiment, since the diameter of the surface portion 47 of the pneumatic piston 16 is larger than the diameter of the piston tip 38 of the hydraulic piston 13, a high operating oil pressure can be generated even with a relatively small air pressure. Further, when the pneumatic piston 16 is pushed by the supply of air pressure, the space between the pneumatic piston 16 and the hydraulic piston 13 is self-sealed, so that high-pressure air does not flow out from the insertion hole 49 and is surely empty. The pressure piston 16 can be driven. Since the atmospheric pressure chamber 26 is interposed between the pneumatic piston 16 and the hydraulic piston 13, in other words, between the first fluid chamber 11 and the second fluid chamber 17, high pressure air flows into the first fluid chamber 11. Thus, it can be surely prevented from being mixed into the oil. That is, it is not necessary to make the seal structure of the pistons 13 and 16 heavy. Further, since the seal wall member 31 that defines the base end side of the second fluid chamber 17 is shaped like a bottomed cylinder, the second push rod 15 is guided inward thereof, so that stable rod slot along the axial center is achieved. Is secured. If the stroke of the second push rod 15 is made larger than the stroke of the pneumatic piston 16, the seal between the pneumatic piston 16 and the hydraulic piston 13 can be opened with the push rod 14 and 15 side full stroke. In addition, control when switching from driving by air pressure to driving by push rods 14 and 15 is facilitated. That is, it becomes easy to take the timing of air pressure OFF.
[0017]
Next, a second embodiment of the present invention will be described with reference to FIG. In this hydraulic pressure generator, the hydraulic piston 55 is formed with such a length and outer diameter that the entire hydraulic piston 55 slides in the hydraulic cylinder portion 56, and the tip of the second push rod 57 is the head of the hydraulic piston 55. The hydraulic cylinder portion 56 is extended so as to abut against the hydraulic cylinder 60. The pneumatic piston 61 includes a surface portion 68 whose outer edge slides on the inner wall of the pneumatic cylinder portion 65, and a cylindrical shaft portion 69 extending from the axial center position of the surface portion 68 to the distal end side. A second push rod 57 is inserted into the portion 69. The tip 79 of the cylindrical shaft portion 69 is in contact with the shaft end surface of the head 60 of the hydraulic piston 55, and a seal 80 is provided on the joint surface. A wear ring 81 is provided on the inner peripheral wall on the distal end side of the cylindrical shaft portion 69. The substantially bottomed cylindrical sealing wall member 89 is formed up to the position of the air introduction port 28, between the peripheral wall 90 and the inner wall of the pneumatic cylinder portion 65, and between the face wall 91 and the pneumatic piston 61. The second fluid chamber 92 is partitioned.
[0018]
In the second embodiment, since the hydraulic piston 55 slides in the hydraulic cylinder portion 56 over the entire length, the hydraulic piston 55 is deformed by the pushing of the second push rod 57. And a stable stroke is ensured. Other configurations and operations are the same as those in the first embodiment.
[0019]
Next, referring to FIG. 3, a third embodiment in which the fluid pressure generating device of the present invention is applied to the master cylinder 10 of the clutch engaging / disengaging device 1 will be described. The clutch disengagement device 1 includes an air pressure supply means 2 for supplying air pressure, a booster device 7 that operates the friction clutch 8 to the disengagement side (right side) A by the air pressure, operation of the clutch pedal 9 and A master cylinder 10 for supplying pilot pressure (working hydraulic pressure) to the booster 7 by air pressure by the air pressure supply means 2, and a controller (computer-type control device) 72 for appropriately controlling the air pressure to the master cylinder 10. It is mainly comprised by. As the master cylinder 10, the hydraulic pressure generator of the first embodiment (or the second embodiment) is used, and a reservoir tank 58 connected to the oil supply path 25 is provided in the first fluid chamber 11, and A supply pipe 59 is provided.
[0020]
The air pressure supply unit 2 is driven by an engine (not shown) and generates a relatively high pressure air pressure, an air dryer 4 that dries high-pressure air from the compressor 3, and an air dryer 4. The air tank 5 mainly stores high-pressure air and a check valve 6 provided on the inlet side of the air tank 5. A pneumatic pipe 62 is connected to the outlet side of the air tank 5, and a pneumatic pipe 67 branched from a branch point 63 on the upstream side is connected to the control valve portion 7 a of the booster 7. That is, a first air pressure supply path a for supplying driving air pressure to the booster 7 is formed by these air pressure pipes 62 and 67. The end of the pneumatic pipe 62 extends to the master cylinder 10 and is connected to the air inlet 28. That is, the pneumatic piping 62 forms a second pneumatic supply path b for supplying high-pressure air to the master cylinder 10.
[0021]
When the air pressure is introduced through the first pneumatic supply passage a and the pilot pressure is supplied through the hydraulic pipe 54, the booster 7 moves the piston plate (not shown) to the clutch 8 side (right side in the figure). The clutch lever 8a is swung in the dividing direction. The control valve portion 7a controls the swing amount of the clutch lever 8a according to the magnitude of the supplied hydraulic pressure. When the hydraulic pressure is released, the air pressure is released to the atmosphere, and the clutch lever 8a is operated to the connection side (left side) B.
[0022]
Two electromagnetic switching valves 78 and 79 are provided in the middle of the second pneumatic supply path b. These electromagnetic switching valves 78 and 79 are operated by the controller 72 so that they are opened when they are turned on to enter the air pressure supply state, and when they are turned off, the air pressure supply is stopped and the downstream air pressure is released to the atmosphere. It has become. In particular, the upstream electromagnetic switching valve 78 is configured to release the downstream air pressure to the atmosphere while appropriately restricting. That is, by the combination of ON / OFF of the electromagnetic switching valves 78 and 79, the air pressure can be supplied to the master cylinder 10 at one stage speed and the air pressure can be discharged at two stages speed. Therefore, since the clutch engagement speed can be selected in two stages, the clutch engagement shock can be reduced by selecting the optimum combination.
[0023]
The controller 72 is connected to a stroke sensor 82 and an idle switch 83 provided in the accelerator pedal 75, and a vehicle speed sensor 85 provided near the output shaft of the transmission 71 to detect the vehicle speed. The electromagnetic switching valves 78 and 79 are operated based on the engine speed and the like, and the transmission 71 is operated by an actuator (not shown) for automatic control. In addition, the controller 72 includes a shift lever switch 84 that detects the position of a shift lever (not shown), a pressure switch 86 that detects the pressure of the air tank 5, and a pedal switch 87 that detects the operation of the clutch pedal 9. A clutch stroke sensor 88 that detects the operation of the clutch lever 8a is connected.
[0024]
When shifting is performed in the clutch connecting / disconnecting device configured as described above, when a shift signal generated by a driver's shift operation is input to the controller 72 during normal vehicle travel, the controller 72 sets both the electromagnetic switching valves 78 and 79 to each other. The air pressure is supplied to the master cylinder 10 through the second air pressure supply path b. By this pneumatic pressure supply, the pneumatic piston 16 (61) and the hydraulic piston 13 (55) of the master cylinder 10 are driven, the pilot pressure is supplied to the booster 7, and the clutch 8 is disconnected. Subsequently, the transmission 71 is operated by the drive signal of the controller 72, and the shift is executed. When this speed change operation is completed, the electromagnetic switching valves 78 and 79 are turned OFF, the air pressure of the master cylinder 10 is released at a predetermined speed, the air pressure piston 16 (61) and the hydraulic piston 13 (55) are returned, and the pilot pressure is reduced. Lower. Thus, the booster 7 performs the engagement operation of the clutch 8 and completes the shift.
[0025]
When the vehicle starts, the driver depresses the clutch pedal 9 to operate the shift lever. By depressing the clutch pedal 9, the push rods 14, 15 (57) push the hydraulic piston 13 (55) and supply the pilot pressure to the booster 7 in the same manner, thereby separating the friction clutch 8. Is done. Then, the controller 72 that senses the operation of the shift lever drives the transmission 71 to set the starting shift stage. Subsequently, when the clutch pedal 9 is released, the push rods 14 and 15 (57) retreat, and the pistons 13 (55) and 16 (61) are returned to the original positions by the urging forces of the springs 18 and 19, When the pilot pressure decreases, the booster 7 connects the friction clutch 8 and starts.
[0026]
In this way, the booster 7 for switching the friction clutch 8 by air pressure is controlled only by the pilot pressure of the master cylinder 10, so that the booster 7 can be controlled by another conventional pneumatic pressure supply path. Compared with the configuration for controlling the pneumatic circuit, there is no possibility that a negative pressure is generated in the hydraulic pipe 54, and no vaporization of the oil is caused. That is, it is possible to prevent trouble without causing a situation in which the clutch operation becomes impossible. Further, there is no change in the booster 7 and its pneumatic supply system, etc., the entire configuration is simplified, and reliability and maintainability can be ensured. In particular, the master cylinder 10 of the present invention has a configuration in which the friction does not increase excessively, so that the followability between the clutch pedal 9 and the friction clutch 8 can be improved.
[0027]
Further, in this embodiment, when the clutch pedal 9 is depressed during automatic control, a signal is sent from the pedal switch 87 at that moment, and both the electromagnetic switching valves 78 and 79 are turned OFF, and a master operation by manual operation is performed. The pistons 13 (55) and 16 (61) of the cylinder 10 are allowed to move. Further, since the push rods 14 and 15 (57) pass through the pneumatic piston 16 (61) and push only the hydraulic piston 13 (55), the pneumatic piston 16 ( Even if 61) becomes inoperable, there is no problem in driving the hydraulic piston 13 (55), and the clutch can be engaged and disengaged by manual operation.
[0028]
In the third embodiment, the case where the fluid pressure generating device of the present invention is applied to the master cylinder 10 of the clutch engaging / disconnecting device 1 is shown. However, the present invention is applied to manual (push rod operation) and automatic control such as a brake. The present invention can be widely applied to a mechanism that achieves both (air pressure supply). In addition the above embodiments have been using the oil and the air as the working fluid and the pressure fluid, the present invention is not limited to this combination, etc. Luna to use oil for example both fluids, various combinations Is possible.
[0029]
【The invention's effect】
In short, according to the present invention, a desired fluid pressure can be generated without interfering with each other by mechanical drive and fluid supply control by the operation of the rod. In addition, the friction when driven by the operation of the rod is not excessively increased.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing a first embodiment of a fluid pressure generating apparatus of the present invention.
FIG. 2 is a side sectional view showing a second embodiment of the fluid pressure generating apparatus of the present invention.
FIG. 3 is a block diagram showing a third embodiment of the fluid pressure generator of the present invention.
[Explanation of symbols]
11 First fluid chamber 12 Cylinder body 13, 55 Hydraulic piston (first piston)
14 First push rod (rod)
15, 57 Second push rod (rod)
16, 61 Pneumatic piston (second piston)
17 Second fluid chamber 18 First spring (spring)
19 Second spring (spring)
20, 56 Hydraulic cylinder part 21, 65 Pneumatic cylinder part 26 Atmospheric pressure chamber
49 insertion hole P Fluid pressure direction (working fluid pressure direction)

Claims (1)

A cylinder body having a first fluid chamber for containing a working fluid; and a first cylinder for slidably provided in the cylinder body facing the first fluid chamber and pressurizing the working fluid in the first fluid chamber. A first piston, a second piston that is slidably accommodated in an end of the first piston opposite to the first fluid chamber, and is slidably accommodated in the cylinder body; the second piston; A second fluid chamber that is partitioned by the cylinder body and moves the second piston when the pressure fluid is supplied to push the first piston in the working fluid pressurizing direction; and the second fluid chamber A supply means for supplying pressure fluid to the rod, a rod provided through an insertion hole formed in the second piston, and for pushing only the first piston in the working fluid pressurizing direction; First piss above And the atmospheric pressure chamber that the second fluid chamber of the pressure fluid is opened to the atmosphere through the through hole when the emissions and the said second piston is spaced, the operation of these respectively provided on the first and second piston A fluid pressure generating device, comprising: a spring for urging in the direction opposite to the fluid pressurizing direction.

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