JP4354592B2 - Fluid pressure pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluid pressure drive pump, and more particularly, to an improvement in a mechanism for switching a drive fluid pumping direction of a two-position direction switching valve when supplying and exhausting a drive fluid to the drive pump through a two-position direction switching valve.
[0002]
[Prior art]
FIG. 7 shows an example of a bellows pump which is one of the conventional fluid pressure driven pumps. The basic structure of the pump is that the left and right cylinder cases 1 and 2, the pump head 15 forming the inlets 8 and 9, the cylinder cases 1 and 2, the pump head 15 with the pump head 15 mounted on the open end side. The bellows 3 and 4 disposed in the cylinder formed between the two, the shaft 5 having both ends connected to the free end face side of the bellows 3 and 4, and the switching fluid supplied and exhausted to the drive chambers on both sides A two-position direction switching valve 6 for alternately pumping the driving fluid to the cases 1 and 2 and a switching means for switching the driving fluid pumping direction of the two-position direction switching valve 6 are provided. The cylinder cases 1 and 2 are assembled to the apparatus main body 13 while being connected to the pump heads 15. The fixed side open ends of the bellows 3 and 4 communicate with the inlets 8 and 9 of the pump head 15 and communicate with the liquid feed pipe 14 with the check valve 10. The switching means includes a switching lever 12 and pilot valves 11A and 11B, which are connected to the shaft 5 and reciprocate in conjunction with each other. The switching lever 12 operates the pilot valves 11A and 11B alternately. The switching fluid is sequentially applied to the corresponding side of the two-position direction switching valve 6 to switch the operation direction of the two-position direction switching valve 6. Thereby, the two-position direction switching valve 6 alternately supplies the driving fluid pressure-fed via the three-way valve 7A into the cylinder cases 1 and 2 and exhausts it from the other cylinder case. In conjunction with this, the bellows 3 and 4 are alternately expanded and contracted to suck and discharge liquid from the entrances 8 and 9.
[0004]
As shown in FIG. 4, the two-position direction switching valve 6 is provided with a valve box 19 forming ports P1 to P5, a spool 20 disposed in the valve box 19, and both sides of the spool 20. The drive chambers 21a and 22a are provided, and the fluid pressure of the switching fluid supplied and exhausted from the three-way valve 7B to the drive chambers 21a and 22a via the pilot valves 11A and 11B is applied to the drive pistons 23a and 23b, and the spool 20 Reciprocate to switch communication between ports. In FIG. 6, pipes 16a, 16b and 16c indicated by solid lines are on the driving fluid side, and pipes 17a, 17b and 17c indicated by broken lines are on the switching fluid side.
FIG. 4A shows a state in which the switching fluid is supplied to the drive chamber 21a. At this time, the input port P1 and the output port P3 communicate with each other, and the output port P2 and the discharge port P4 communicate with each other. In relation to the pump, the driving fluid is pumped to one side of the cylinder cases 1 and 2 and the driving fluid is exhausted from the other side. Conversely, FIG. 4B shows a state in which the switching fluid is supplied to the drive chamber 22a. At this time, the input port P1 and the output port P2 communicate with each other, and the output port P3 and the discharge port P5 communicate with each other. In relation to the pump side, the driving fluid is pumped to the other side of the cylinder cases 1 and 2 and the driving fluid is exhausted from one side. In this way, the two-position direction switching valve 6 moves the spool 20 between two positions by the switching fluid that is alternately pumped to the drive chambers 21a and 22a to switch the communication between the ports.
[0005]
[Problems to be solved by the invention]
In the above bellows pump, the two-position direction switching valve 6 alternately presses the switching lever 12 interlocked with the reciprocating motion of the shaft 5 against the contact portions of both pilot valves 11A and 11B, thereby the pilot valve 11A on the side pressed. , 11B are operated only while they are pressed and sequentially switched. However, the switching means of the two-position direction switching valve 6 is compact because the structure of the pilot valves 11A and 11B is complicated, the failure rate is high, the cost is short, the life is short, and a relatively long switching lever 12 is used. However, the pipes 17a, 17b, and 17c are complicated. As the switching means, a proximity switch or the like may be used instead of the pilot valves 11A and 11B and the switching lever 12. However, the sensor sensitivity becomes unstable depending on the atmosphere and temperature, the service life is shortened, and the replacement frequency is increased. In many cases, it cannot be adopted from the viewpoint of reliability.
[0006]
From such a background, the present inventors have developed a structure that can solve the above problems as disclosed in JP-A-11-22646. The object of the present invention is to further improve it, simplify the switching means of the two-position direction switching valve while maintaining accuracy, enable cost reduction, and increase the operating rate by reducing the frequency of parts replacement. Is to be able to. Other purposes will be made clear with the following description.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has left and right cylinder cases 1 and 2, a pump head 15 having outlets 8 and 9, and an opening end side attached to the pump head 15 as illustrated in FIGS. 1 to 5. Expansion and contraction members 3 and 4 disposed in each cylinder formed by the cylinder cases 1 and 2 and the pump head 15 in a state, and a shaft 5 having both ends connected to the free end sides of the respective expansion and contraction members 3 and 4, A two-position direction switching valve 6 that alternately pumps driving fluid into the cylinders by switching fluid supplied to and discharged from the driving chambers 21a and 22a on both sides, and switching means that switches the driving fluid pumping direction of the two-position direction switching valve 6 In the fluid pressure driven pump that draws liquid from the inlet 9 and discharges it from the outlet 8 by expanding and contracting the expansion members 3 and 4 with reciprocation of the shaft 5, the switching means The valve body 49 is normally closed with respect to the valve body 46, and is opened when the valve body 49 is pushed on the free end side of the expandable expansion / contraction member among the expansion / contraction members 3 and 4. The introduced switching fluid is constituted by pressure-reducing switching valves 42A and 42B for discharging the cylinder fluid into the cylinder cases 1 and 2, and the pressure-reducing switching valves 42A and 42B are freely attached to the cylinder cases 1 and 2, respectively. Each is mounted opposite to the end side, and the inlet 46a of both pressure-reducing switching valves 42A and 42B is connected to the corresponding drive chambers 21a and 22a of the two-position direction switching valve 6, respectively. A pressure difference is generated in each of the drive chambers 21a and 22a of the two-position direction switching valve 6 by the pressure-reducing switching valve side that is opened and the pressure-reducing switching valve side that is kept closed by contraction of the expansion member 4 or 3. To form.
[0008]
In the present invention described above, examples of the fluid pressure driven pump include a bellows pump illustrated in FIGS. 1 and 6 and a diaphragm pump in which the bellows portion of the bellows pump is a diaphragm. The pressure-reducing switching valves 42A and 42B are, for example, simple ones in which the valve body 49 is urged to the valve body 46 by the urging means 50 in the closing direction. The valve body 46 can be composed of a main body 47 having an inlet 46a and a cylindrical portion 48 having an outlet 48a. The valve body 49 should just have the front-end | tip shaft part 49b projected outside from the exit 48a. Here, the pressure-reducing switching valves 42A and 42B are such that the distal end shaft portion 49b of the valve body 49 is opposed to the free end side of the telescopic members 3 and 4 with respect to the cylinder cases 1 and 2, It is attached so that it can be pushed and switched to the open state. The inlets 46a of the pressure-reducing switching valves 42A and 42B are respectively connected to the corresponding piping sides of the two drive chambers 21a and 22a of the two-position direction switching valve 6 (where switching fluid is supplied simultaneously via the pipings 18a and 18b). Connected.
[0009]
In this configuration, the switching fluid is simultaneously applied to both the drive chambers 21 a and 22 a of the two-position direction switching valve 6. Thereafter, when the driving fluid is supplied to the two-position direction switching valve 6, the driving fluid is applied to the one cylinder chamber, the corresponding expansion / contraction member contracts, and the connecting shaft 5 also moves in conjunction with it. The other expansion / contraction member is expanded by the movement of the shaft 5, and when the pressure-reducing switching valve facing the expansion / contraction member is pushed by the expansion / contraction member, the expansion / contraction member is activated and switched to the open state. Exhaust into the chamber. As a result, the two-position direction switching valve 6 creates a pressure difference between the drive chambers 21a and 22a, and the spool 20 is pushed to the opposite side by the pressure difference to switch the position of the port. Apply to the chamber. By repeating this operation, the two-position direction switching valve 6 can alternately switch the operating direction of the spool 20.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS. In the description of the embodiments, various technically preferable limitations are given because they are preferable examples of the present invention, but the technical scope of the present invention is not limited.
[0011]
FIG. 1 schematically shows the structure of an entire pump including a drive system in which the present invention is applied to a bellows pump, FIG. 2 is a schematic sectional view showing the structure of a pump body, and FIG. 3 shows a structural example of a pressure-reducing switching valve. FIG. 4 is a sectional view, FIG. 4 shows a configuration example of a two-position direction switching valve, and FIG. 5 is a schematic operation diagram of the pressure-reducing switching valve. In FIG. 1, the same reference numerals are used for the same parts or members as those shown in FIG.
The bellows pump is disposed in a cylinder formed between the cylinder cases 1 and 2 and the pump head 15 and the pump head 15 forming the left and right cylinder cases 1 and 2, the inlets 8 and 9. Bellows 3, 4, shaft 5 having both ends connected to the free end surfaces of the bellows 3, 4, two-position direction switching valve 6 for alternately pumping drive fluid into cylinder cases 1, 2, and switching thereof And pressure reducing switching valves 42A and 42B as means. The two-position direction switching valve 6 alternately supplies the pumped driving fluid into the cylinder cases 1 and 2, and conversely exhausts the bellows 3 and 4 from the other cylinder case. By alternately expanding and contracting, liquid is sucked and discharged from the liquid inlets 8 and 9 of the pump head 15.
[0012]
The cylinder cases 1 and 2 include substantially cylindrical case bodies 31 and 32 and cap-shaped covers 34 and 35 that close rear openings of the case bodies 31 and 32. The front sides of the case bodies 31 and 32 are joined and arranged on the corresponding end face sides of the pump head 15, and the rear sides are closed by covers 34 and 35. The cover 34, 35 is provided with nozzles 36, 37 for introducing or discharging a driving fluid such as air into the cylinder cases 1, 2 and mounting holes provided on the end face side for attaching pressure reducing switching valves 42A, 42B described later. 34a, 35a, leg portions 34b, 35b projecting on the lower surface side, and a leak sensor for detecting liquid leakage from the bellows 3, 4 (not shown).
[0013]
The bellows 3 and 4 are made of plastic, have a cylindrical shape that can be expanded and contracted in the horizontal direction, have one end opened, and the other end closed. The open ends of the bellows 3 and 4 are arranged in mounting grooves provided on the corresponding side surfaces of the pump head 15, and a part thereof is pressed by the corresponding portions of the case main bodies 31 and 32. On the other end side of the bellows 3, 4, that is, the free end side, a large-diameter disk-shaped connecting plate 40 is mounted. The connecting plates 40 of the bellows 3 and 4 are connected by a plurality of shafts 5 that are slidably disposed through the case main bodies 31 and 32 and the pump head 15, and when one bellows contracts, the other bellows The shaft 5 extends in conjunction with the shaft 5.
[0014]
The pump head 15 has a disk shape substantially the same diameter as the case main bodies 31 and 32, and includes a suction passage 36 leading to the inlet 9 and a discharge passage 37 leading to the outlet 8, and a pair of through holes 38 respectively communicating with one of them. , 39 are formed. The through holes 38 and 39 are located above and below the pump head 15, and the through hole 38 communicating with the suction passage 36 is located on the lower side, and the through hole 39 communicating with the discharge passage 37 is located on the upper side. The through hole 38 is a hole for introducing the liquid into the bellows 3 and 4 from the inlet 9 and the suction passage 36, and the through hole 39 is a hole for sending the liquid in the bellows 3 and 4 to the discharge passage 37 and the outlet 8. The suction passage 36 communicates with the through hole 38 from the front side or the rear side of the pump head 15, and a joint pipe (not shown) is attached to introduce the target liquid. The discharge passage 37 communicates with the through hole 39 from the upper side of the pump head 15 and supplies the liquid from the outlet 8 such as a joint pipe to the target location. Reference numeral 41 denotes a plurality of connecting bolts for connecting the pump head 15 and the cylinder cases 1 and 2. Reference numeral 43a denotes a seal member interposed between the pump head 15 and the case bodies 31, 32, and reference numeral 43b denotes a seal member interposed between the case bodies 31, 32 and the covers 34, 35.
[0015]
A check valve 44 for suction is disposed on both sides of the through hole 38, and a check valve 45 for discharge is disposed on both sides of the through hole 39. Each of these check valves 44 and 45 has a spring check structure in which the valve body is urged by a spring which is a spring member in the attached state of the valve body, and the opening and closing operation is different from the corresponding valve seat of the valve body. Open and close in the direction. That is, the check valves 44 and 45 are operated in the state shown in FIG. 2 in which the right check valve 44a is closed by spring pressure and the left check valve 44b is opened against discharge and discharged. Of these, the right check valve 45b is opened and the left check valve 45a is closed. At this time, the internal pressure of the bellows 4 is maximized in a process in which the liquid is sucked and then contracted by the pressure of the supplied driving fluid to discharge the liquid. The driving fluid at that time requires, for example, a pressure proportional to the spring pressure Vs of the corresponding check valve in addition to the internal pressure V0 of the discharge side bellows. The check valves 44 and 45 may be those disclosed in Japanese Patent Application Laid-Open No. 11-11377.
[0016]
The pressure-reducing switching valves 42A and 42B have the same structure, and are composed of a valve body 46, a valve body 49, and an urging means 50. The valve body 46 includes a main body 47 that forms an inlet 46 a for introducing a switching fluid, and a cylindrical portion 48 that is disposed to face the free end face side of the bellows 3 and 4. The main body 47 has a substantially concave shape in the lateral direction, and is formed as a deeper recess 47 a at the center of the recess. A nozzle 51 serving as an inlet 46 a is attached to the radial hole of the recess 47 a, and the switching fluid is recessed through the nozzle 51. 47a can be introduced. The cylindrical portion 48 has an outlet 48a that penetrates through the distal end surface serving as a valve seat, a mounting male screw 48b formed on the outer periphery, and a large-diameter rear portion 48c that engages with the concave portion. The valve body 49 includes a barrel portion 49a that is slidably disposed inside the cylindrical portion 48, and a shaft portion 49b that projects from the distal end surface of the barrel portion 49a and projects outward from the outlet 48a. The body portion 49a is in contact with the inner periphery of the cylinder portion 48 via a plurality of protrusions 49c whose outer periphery on the rear side that is cylindrical is protruded in the horizontal direction, and the outer periphery on the front end side that is closed at the end surface is slightly smaller in diameter. A gap L is formed between the inner periphery of the cylindrical portion 48. The urging means 50 is a coil spring and is disposed in the cylindrical portion 48 from the recess 47a. Then, the cylindrical portion 48 is engaged with the concave shape of the main body 47 while the valve body 49 is put in the cylindrical portion 48 as shown in FIG. After joining, the plurality of mounting screws 52 are fixed. In this assembled state, the valve body 49 is slid by the pressure of the urging means 50 in the direction of protruding the shaft portion 49b from the outlet 48a, so that the introduced switching fluid is not released from the outlet 48a. Reference numeral 53a denotes a seal member interposed between the main body 47 and the cylindrical portion 48, reference numeral 53b denotes a seal member attached to a front end surface serving as an attachment reference surface of the large diameter rear portion 48c, and 53c denotes a front end of the trunk portion 49a. It is a seal member mounted on a surface (a surface facing the front end surface of the cylindrical portion 48 serving as a valve seat).
[0017]
Next, the configuration related to the two-position direction switching valve will be outlined. The two-position direction switching valve 6 includes a valve box 19 having a plurality of ports P1, P2, P3, P4, and P5, a spool 20 disposed in the valve box 19, and screws or the like on both sides of the valve box 19. Cover members 21 and 22 that are attached, and a drive chamber 21a that is provided inside each cover member 21 and 22 and in which the drive piston 23a is disposed and a drive chamber 22a in which the drive piston 23b is disposed. The drive pistons 23a and 23b are actuated by the fluid pressure of the switching fluid supplied alternately to the drive chambers 21a and 22a via the cylinder mechanism 30 to move the spool 20 between the two switching positions. Switch communication. Reference numeral 24a denotes a packing attached to both sides of the spool 20, and reference numeral 24b denotes a packing attached to the drive pistons 23a and 23b. Further, the cover members 21 and 22 can escape to the outside when the switching fluid applied to the drive chambers 21a and 22a becomes a predetermined pressure or more as in the conventional case.
[0018]
The above-described two-position direction switching valve 6 is connected to a pipe for flowing a driving fluid that expands and contracts the bellows 3 and 4 and a pipe for flowing a switching fluid for switching the operation direction of the two-position direction switching valve 6. In FIG. 1, the solid line indicates a pipe for flowing the driving fluid, and the broken line indicates a pipe for flowing the switching fluid. Among these, the piping for the driving fluid includes the piping 16a leading from the driving fluid source to the input port P1 of the two-position direction switching valve 6 through the three-way valve 7A, the output ports P2, P3 of the two-position direction switching valve 6 and the cylinder. The pipes 16b and 16c connect the nozzles 36 and 37 of the cases 1 and 2, respectively. Reference numerals 16d and 16e are pipes for exhausting the driving fluid in the cylinder cases 1 and 2 from the exhaust ports P4 and P5 of the two-position direction switching valve 6 in the process of reducing the bellows 3 and 4, respectively. On the other hand, the switching fluid piping includes piping 18a and 18b for simultaneously supplying switching fluid from the switching fluid source to the drive chambers 21a and 22a via the three-way valve 7B, and inlets 46a of the pressure-reducing switching valves 42A and 42B. And pipes 18c and 18d connecting the drive chambers 21a and 22a. Orifices OR1 and OR2 are interposed in the pipe 18a and the pipe 18b, respectively. Of these, in this example, the ORIFES OR1 has a diameter of 0.8 mm and the ORIFES OR2 has a diameter of 1.0 mm. In this case, the orifices OR1 and OR2 having different diameters are attached to facilitate the formation of a difference in the internal pressures of both drive chambers 21a and 22a, which will be described later, but may be omitted.
[0019]
Next, the pump drive incorporating the pressure-reducing switching valves 42A and 42B will be described with reference to FIGS. Note that, in the two-position direction switching valve 6 before the pump is operated, the position of the spool 20 is maintained in a stopped state. FIG. 4B assumes that state. First, the three-way valve 7B on the switching fluid source side is turned on, and switching fluid (for example, ^{2 to 3} kg / cm ² ) is simultaneously applied to both drive chambers 21a and 22a of the two-position direction switching valve 6. The spool 20 is held at the initial position because both the drive chambers 21a and 22a have the same pressure. Next, when the three-way valve 7A on the driving fluid source side is turned on and driving fluid (for example, 4 to 5 kg / cm ² ) is supplied to the input port P1 of the two-position direction switching valve 6, the driving fluid is input to the input port. From P1, it is applied to the right cylinder chamber through the output port P2, the pipe 16b, and the nozzle 36, the expandable member 3 contracts (liquid discharge mode) as shown in FIG. 1, and the connecting shaft 5 moves to the left in conjunction with it. The bellows 4 expands and expands (liquid suction mode) by the movement of the shaft 5. The pressure-reducing switching valve 42B on the left side is operated and switched to open by pressing the tip shaft portion 49b of the valve body 49 through the connecting plate 40 when the bellows 4 is extended to the design value. The upper part of FIG. 5 shows the state at that time. Then, the pressure reducing switching valve 42 </ b> B exhausts the supplied switching fluid into the cylinder case 2. This exhaust gas lowers the switching fluid pressure in the drive chamber 22a connected via the pipe 18d, and forms a pressure difference between the drive chambers 21a and 22a. Due to this pressure difference, the spool 20 loses its balance and is pushed from the drive chamber 21a, which is relatively high in pressure, to be switched to the state shown in FIG. 4A, and the output ports communicating with the input port P1 are changed from P2 to P3. Switch to. Then, the driving fluid is applied from the input port P1 to the left cylinder chamber through the output port P3, the pipe 16c, and the nozzle 37, the bellows 4 contracts (liquid discharge mode), and the connecting shaft 5 is also interlocked with the right side. Move to. The bellows 3 expands and expands (liquid suction mode) by the movement of the shaft 5. The right pressure-reducing switching valve 42A is operated and switched to open by pressing the tip shaft portion 49b of the valve body 49 through the connecting plate 30 when the bellows 3 is extended to the design value. The lower part of FIG. 5 shows the state at that time.
[0020]
In this way, the pressure-reducing switching valves 42A and 42B regularly communicate between the ports of the two-way switching valve 6 by breaking the pressure balance between the drive chambers 21a and 22a in synchronization with the bellows 3 and 4. It is switched to. Therefore, in the structure of the present invention, the whole apparatus can be further simplified by the simple pressure-reducing switching valves 42A and 42B. In other words, according to the present invention, the conventional pilot valves 11A and 11B and the switching lever 12 can be eliminated by the simple pressure-reducing switching valves 42A and 42B. Further, since the pressure-reducing switching valves 42A and 42B use the switching fluid used in the two-position direction switching valve 6 and are interlocked with the expansion / contraction state of the expansion / contraction members 3 and 4, simplification of the piping system, The life of the switching valve can be maintained, and the cost is reduced and the performance is excellent.
[0021]
FIG. 6 shows a modification in which the present invention is applied to the conventional pump of FIG. In FIG. 6, the same reference numerals are used for the same parts or members as those shown in FIGS. 7 and 1 to 5. In this modification, pressure-reducing switching valves 42A and 42B are attached to cylinder cases 1 and 2 and piping 18a to 18d on the switching fluid side is attached as described above with respect to the structure of FIG. Therefore, the switching operation of the two-position direction switching valve 6 is the same as that described with reference to FIGS. As described above, the present invention can be variously modified in terms of the pump structure as long as the constituent elements of claim 1 are provided.
[0022]
【The invention's effect】
As described above, the fluid pressure driven pump according to the present invention is simpler than the structure in which the pressure reducing switching valve, which is the switching means of the two-position direction switching valve, uses the conventional pilot valve and the switching lever, reducing the cost and reducing the space. And simplification are achieved. In addition, the switching operation of the pressure-reducing switching valve with respect to the two-position direction switching valve is linked to the expansion and contraction of both expansion and contraction members, so that the performance is excellent and mechanical wear unlike conventional ones is difficult to occur and the operating life is extended. Can be maintained and reliability can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an entire drive pump to which the present invention is applied.
FIG. 2 is an enlarged cross-sectional view showing a main part of the pump body of FIG.
3 is a cross-sectional view showing the configuration of the pressure-reducing switching valve of FIG.
4 is an enlarged cross-sectional view showing the operation of the example of the two-position direction switching valve in FIG. 1. FIG.
FIG. 5 is a reference diagram for explaining the operation of the drive pump of FIG. 1;
6 is a schematic configuration diagram showing another example of the drive pump corresponding to FIG. 1. FIG.
FIG. 7 is a diagram showing a structure of a conventional bellows pump drive system.
[Explanation of symbols]
1 and 2 are cylinder cases 3 and 4 are bellows (expandable members)
5 is shaft 6 is 2-position direction switching valve 15 is pump head 15
8 and 9 are pump head inlets and outlets 42A and 42B.

Claims (4)

Left and right cylinder cases; a pump head forming an inlet / outlet; and a telescopic member disposed in each cylinder formed by the cylinder case and the pump head in a state where the opening end side is mounted on the pump head; A shaft having both ends connected to the free ends of the telescopic members, a two-position direction switching valve for alternately pumping the driving fluid into the cylinders by switching fluid supplied to and discharged from the driving chambers on both sides, and the two-position A fluid pressure drive pump that includes a switching unit that switches a driving fluid pumping direction of the direction switching valve, and draws liquid from the inlet and discharges it from the outlet by expanding and contracting the expansion members with the reciprocation of the shaft. In the switching means, the valve body is normally closed with respect to the valve body, and is pushed on the free end side of the expansion member that is inflated among the two expansion members. In the open state can constitute the switching fluids under reduced selector valve for reducing the pressure by discharging the switching fluids to be introduced into the valve body in the cylinder casing,
The pressure-reducing switching valve is mounted on each cylinder case so as to face the free end of the telescopic member, and the inlet of each pressure-reducing switching valve is connected to the corresponding drive chamber side of the two-position direction switching valve. A pressure difference is generated between the drive chambers of the two-position direction switching valve by the pressure-reducing switching valve side that is opened by expansion of the telescopic member and the pressure-reducing switching valve side that is maintained closed by contraction of the telescopic member. A fluid pressure driven pump characterized by forming. A cylinder part in which the valve body of the pressure-reducing switching valve is arranged opposite to the free end side of the telescopic member, an outlet penetrating the end face of the cylinder part , and a valve formed inside the end face corresponding to the valve body A barrel having a seat , the valve body being slidably disposed in the cylindrical portion, and a shaft portion that protrudes outward from the outlet at the tip of the barrel and can contact the free end of the expansion member. The fluid pressure pump according to claim 1.   The fluid pressure drive pump according to claim 1, further comprising a biasing unit that is built in the valve body and constantly biases the valve body in a closed state.   The fluid pressure driven pump according to any one of claims 1 to 3, wherein the expandable member is a bellows.

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