JPH08232909A - Generating method for reciprocating motion by fluid pressure and generating device thereof - Google Patents

Abstract

PURPOSE: To improve the durability by performing the reversing of an advancing and retracting motion of a piston stored in a cylinder so that it can freely slide back and forth, by the use of fluid pressure without using a spring. CONSTITUTION: A front plunger 20 and a rear plunger 21 are stored in a cylinder provided in a body 3 so that they can freely slide back and forth respectively. By supplying air the rear plunger 21 is slid forth or back in order for the passage of supply air to be switched, to switch the advancing direction of the rear plunger 21, and to switch the advancing direction of the front plunger 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid pressure reciprocating motion generating method and device which can be used as a driving device for a pneumatic automatic cutter tool or the like.

[0002]

2. Description of the Related Art FIG. 7 is a diagram schematically showing a sectional structure of a conventional pneumatic automatic cutter tool 100. As shown in FIG. In the pneumatic automatic cutter tool 100, a spindle 104 having pistons 105 and 106 at both front and rear ends is slidably housed in a cylinder 103 surrounded by a front wall 101 and a rear wall 102. A slider valve 116 having front, center, and rear annular ribs 111, 112, and 113 circumferentially in contact with the inner wall of the cylinder is slidably fitted in the middle of the spindle 104 so as to be slidable back and forth. The spindle 104 includes the front wall 101 of the cylinder 103 and the front piston 1.
05 and the cylinder 10
3 is stopped and held in a state in which the elasticity of the rear spring 108 provided between the rear wall 102 and the rear piston 106 is balanced. The front end of the spindle 104 penetrates the front wall 101 of the cylinder 103 and projects forward.
The cutter blade 120 is attached to this protruding end.

[0003] The slider valve 116 has a forward air supply passage 114 extending from a peripheral surface between a central annular rib 112 and a rear annular rib 113 to a front surface of the slider valve 116.
And a rearward air supply passage 115 that extends from the peripheral surface between the front annular rib 111 and the central annular rib 112 to the rear surface of the slider valve 116. In addition, cylinder 10
3, a main air supply passage 109 is formed so as to match the forward air supply passage 114 of the slider valve 116 in the neutral stop state. Reference numeral 110 denotes an exhaust path, which opens into the cylinder 103 at a predetermined position.

[0004] The conventional pneumatic automatic cutter tool 100 constructed as described above operates as follows. First, the forward air supply passage 114 of the slider valve 116 extends from the air supply main passage 109.
, When air is sent between the slider valve 116 and the front piston 105, the slider valve 116 reverses vigorously, hits the rear piston 106 on the rear surface, and moves the spindle 104 backward. At this time, the rearward supply passage 115 of the slider valve 116 is
And the air sent to the backward air supply passage 115 is sent between the slider valve 116 and the rear piston 106. Therefore, this time, the slider valve 116 moves forward vigorously and the front piston 10
Hitting 5 causes the spindle 104 to move forward.
At this time, the forward air supply passage 114 of the slider valve 116 comes into contact with the main air supply passage 109 again, so the above movement is repeated at high speed, and the cutter blade 120 reciprocates in the front-rear direction together with the spindle 104. It is like this.

[0005]

Each time the slider valve 116 repeatedly moves forward and backward, the front spring 107 and the rear spring 1
Since 08 is repeatedly shocked and instantaneously compressed and expanded, the front spring 107 and the rear spring 108 are easily deteriorated or damaged and need to be replaced relatively frequently. Further, the air supply flow path is switched by moving the slider valve 116 forward and backward. However, the balance of the resilience of the front spring 107 and the rear spring 108 is poor (including the case where the above-described deterioration occurs). ) Has a problem in that the stop position (reverse rotation position in the traveling direction) of the slider valve 116 varies, which adversely affects the forward / backward movement, and the reciprocating motion of the cutter blade 120 cannot be obtained smoothly. there were.

The present invention has been made in view of the above circumstances, and it is not necessary to frequently replace the front spring, the rear spring, and the like, and the cutter blade and the like can be smoothly reciprocated. An object of the present invention is to provide a method and an apparatus for generating reciprocating motion by fluid pressure.

[0007]

In order to achieve the above object, the present invention takes the following technical means. That is, in the method of generating reciprocation according to the present invention, the front plunger housed in the cylinder surrounded by the front wall and the rear wall is made to stand by at the rear stop position of the front and rear sliding area, and The rear plunger housed rearward of the front plunger is made to stand by at the front stop position in the front and rear sliding area, whereby the radial step portions formed on the peripheral wall of the rear plunger and the cylinder inner wall are mutually forward and backward. And the working fluid is supplied between the step portions to move the rear plunger backward, thereby forming a third chamber between the step portions, and the thrust of the rear plunger is used to move the rear portion. The working fluid filling the fourth chamber behind the plunger is circulated to the second chamber between the front and rear plungers, and the excess working fluid in the fourth chamber is discharged to the outside of the cylinder. After the rear plunger has moved backward by a predetermined amount, the working fluid supply path is switched from the third chamber to the second chamber to move the front plunger forward, and the forward thrust of the front plunger is used to advance the front of the front plunger. By discharging the working fluid filling the first chamber to the outside of the cylinder and switching the supply of the working fluid from the second chamber to the fourth chamber through the circulation passage opened after the rear plunger further moves backward by a predetermined amount. The rear plunger is moved forward, and the thrust of the rear plunger is used to discharge a part of the working fluid in the second chamber to the outside of the cylinder, and the rear plunger is moved through a circulation passage opened after moving forward by a predetermined amount. The front plunger is moved backward by switching the supply of fluid from the fourth chamber to the first chamber, and by repeating these operations, the front plunger is moved to the cylinder. It is characterized in that the drive take-out head provided so as to protrude through the front wall so as to reciprocate.

According to such a reciprocating motion generating method, by supplying the working fluid into the cylinder, the rear plunger housed in the cylinder is mainly slid forward and backward, thereby switching the flow path of the working fluid. Then, the front plunger is slid forward and backward relative to the rear plunger (that is, in such a manner that the mutual approach and mutual separation are repeated), and the reciprocating motion with respect to the cutter blade etc. is performed from the drive take-out head provided in the front plunger. I take it out. By doing so, the front spring and the rear spring are unnecessary. Further, the working fluid being supplied to the chamber that is being expanded when either one of the plungers moves forward or backward is predetermined by the circulation passage opened according to the positioning of the plunger during forward movement or backward movement. It is used as a driving force when the other plunger is moved forward or backward (when the traveling direction is reversed).

Further, in the reciprocating motion generating apparatus according to the present invention, the front plunger and the rear plunger are respectively housed in the cylinder surrounded by the front wall and the rear wall so as to be slidable back and forth.
Depending on the positioning of the front and rear plungers,
A first chamber in front of the front plunger, a second chamber between the front and rear plungers, and a third chamber formed between radial step portions formed on the peripheral wall of the rear plunger and the cylinder inner wall, respectively. , Is formed so as to be partitioned or not formed with the fourth chamber behind the rear plunger, and the first chamber to the fourth chamber have a supply passage and a discharge passage for the working fluid toward each of these chambers when they are formed. Opened or closed, the pressure receiving area of the front plunger facing the first chamber and the second chamber is formed as large as possible in the cylinder, and the front plunger penetrates the front wall of the cylinder. The drive take-out head is provided so as to project forward.

The discharge passages opened toward the respective chambers when the first to fourth chambers are formed include direct discharge passages which are discharged from the chamber side to the outside of the cylinder and are being reduced. It is preferable to form a circulation channel that is guided from a certain chamber side toward the chamber side to be expanded. Such a reciprocating motion generating device is a device for carrying out the reciprocating motion generating method of the present invention, and has the same operation, but a portion of the front plunger facing the first chamber (that is,
By forming the pressure receiving area of the portion facing the front wall of the cylinder) and the portion facing the second chamber (that is, the portion facing the rear plunger) as large as possible within the allowable range in the cylinder. As for the front-rear sliding force of the front plunger, a strong force necessary for work with a cutter blade or the like can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a pneumatic automatic cutter tool 2 in which a reciprocating motion generating device 1 according to the present invention is incorporated in a main body 3.
Fig. 4 is a side view showing a drive take-out head of the reciprocating motion generating device 1, a cutter blade 5 attached to the drive take-out head 4 to reciprocate, and 14 a main body cylinder 3 and an air supply unit. A hose joint for connecting a hose 6 having a system and an exhaust system, and 7 is an operation switch for connecting and disconnecting the supply air in the hose joint 14.

FIG. 2 is a side sectional view showing a reciprocating motion generating device 1 by enlarging and breaking the main body cylinder 3, and the reciprocating motion generating device 1 includes a front cylinder 10 having a front wall 11. The cylinder 15 is composed of a rear cylinder 12 connected to the rear of the front cylinder 10 and a rear wall 13 that closes the rear portion of the rear cylinder 12 as a part of the hose joint 14. Front cylinder 1
The front plunger 20 is housed in 0 so that it can slide back and forth,
A rear plunger 21 is housed in the rear cylinder 12 so as to be slidable back and forth. A cushioning material 17 for the rear plunger 21 is embedded in the rear wall 13 with its front portion exposed in the rear cylinder 12.

The front plunger 20 is formed so as to protrude to the full inner diameter of the front cylinder 10, and has a flange portion 20a whose front and rear surfaces are pressure receiving surfaces;
Oa is formed so as to have an H-shaped cross section by a cylindrical peripheral wall 20b provided to protrude forward and backward from the outer peripheral end of Oa. A drive shaft 22 that penetrates through the front wall 11 of the front cylinder 10 and protrudes forward from the main body body 3 is connected to the flange portion 20a. An ejection head 4 (see FIG. 1) is provided.

FIG. 3 is a side view showing the rear plunger 21. The rear plunger 21 has a small diameter portion 21a,
It has a middle diameter portion 21b and a large diameter portion 22c.
A is provided with a first constricted portion 24, and a middle constricted portion 21b is provided with a second constricted portion 25 and a third constricted portion 26. Front end portion of middle diameter portion 21b (step portion with small diameter portion 21a)
Is provided with a chamfer 27. And the small diameter portion 21
Inside a is formed an air passage 39 that communicates the outer peripheral surface of the first constricted portion 24 with the front end surface.

FIG. 4 shows the front cylinder 10, wherein (a) is a rear view, (b) is a sectional view taken along the line AA (in the same direction as in FIG. 2), and (c) is B. It is a -B line sectional view. The front cylinder 10 is provided with a guide cylinder 23 for holding the drive shaft 22 at the front of the front wall 11. In this guide cylinder 23, a bush or packing for bearing is mounted. Are formed. The inner diameter of the front cylinder 10 is formed so as to be able to slidably hold the outer peripheral surface of the above-mentioned front plunger 20 while contacting the outer peripheral surface of the front plunger 20 except for a partial area 10a near the front wall 11. , A partial area 10 near the front wall 11 with respect to this inner diameter.
The inner diameter of a is formed to be slightly larger. On the other hand, three air passages 30, 31, 32 are formed inside the peripheral wall (inside the thickness) of the front cylinder 10 so as to extend in the front-rear direction. Each of the air passages 30 to 31 has one end opened at a different position in the front-rear direction and the circumferential direction of the cylinder inner wall, and the other end opened at the rear end surface of the front cylinder 10.

For convenience of description below, each air passage 30 is provided.
To 32, the openings on the cylinder inner wall side are holes a, c, and e, and similarly, the front cylinder 1 in each of the air passages 30 to 32 is formed.
The openings on the rear end face side of 0 are holes b, d, and f. 5A and 5B show the rear cylinder 12, wherein FIG. 5A is a front view, FIG. 5B is a right side view, and FIG.
(D) is a sectional view taken along line DD, (e)
Is a sectional view taken along line EE. Of the outer peripheral portion of the rear cylinder 12, the portion near the front end portion is the front plunger 20 described above.
The diameter is reduced so as to be smaller than the inner diameter on the rear side of the cylindrical peripheral wall 20b. On the outer peripheral portion behind the reduced diameter portion, opposing peripheral surfaces are recessed in a semicircular groove along the front-rear direction, and their rear ends are opened but the front ends are not opened. The thus formed concave portion 38 is provided. Further, inside the rear cylinder 12, the small diameter portion 12a and the medium diameter portion 1 are arranged from the front to the rear.
2b and a large diameter portion 12c. These parts (1
The inner diameters of 2a, 12b, 12c) are such that the outer peripheral surfaces of the small-diameter portion 21a, the intermediate-diameter portion 21b, and the large-diameter portion 22c of the rear plunger 21 can be held in a slidable manner while being in airtight contact therewith. Is formed. In addition, medium diameter part 1
A boring portion 12d slightly larger than the inner diameter of the middle diameter portion 12b on the rear side is formed at the front end of the 2b (close to the step portion with the small diameter portion 12a). Then, in the half-moon groove-shaped recess 38, a hole u penetrating in the radial direction at a portion overlapping the small diameter portion 12a, a hole x, y penetrating in the radial direction at a portion overlapping the middle diameter portion 12b, and a large diameter portion. A hole z penetrating in the radial direction is formed at a portion overlapping with 12c. Five air passages 33 to 37 are formed inside the peripheral wall (inside the thickness) of the rear cylinder 12 along the front-rear direction. Among these, the ventilation passages 34 to 36 have one ends opened at different positions in the front-rear direction and the circumferential direction of the inner wall of the cylinder, and the other end is opened at the front end surface of the rear cylinder 12. In addition, of the two other passages, one of the ventilation passages 33 is opened at the front and rear in correspondence with the intermediate diameter portion 12b, and the other end is opened at the rear end surface of the rear cylinder 12. Has become. And the other air passage 37
Has both ends open to the inner wall of each cylinder so that the medium diameter portion 21b and the large diameter portion 22c communicate with each other. Of course, these ventilation passages 33 and 37 are also positioned differently from the above-mentioned ventilation passages 34 to 36 in the circumferential direction.

For the sake of convenience in the following description, each air passage 33
Through 37 are holes g, h, j,
n, p, s, and t; similarly, openings k, m, and r at the front end face side of the rear cylinder 12 in the ventilation paths 34 to 36, and openings at the rear end face side of the rear cylinder 12 in the ventilation path 33. Is a hole i. Between the front cylinder 10 and the rear cylinder 12, the ventilation paths 30 and 34 are in communication with the holes b and k, the ventilation paths 31 and 35 are in communication with the holes d and m, and the 36 are connected so that the holes f and r communicate with each other, and this connected state is held by positioning means (not shown) such as a knock pin. Each of these connected ventilation paths is sometimes used as a circulation path and sometimes as a supply path for switching. Also, as shown in FIG. 2, the front cylinder 10 and the rear cylinder 12 are housed in the main body 3,
When the hose joint 14 is connected to the hose joint 14, the hole i of the air passage 33 communicates with the air supply main passage 16 provided in the hose joint 14 to form a supply passage.
Further, the half-moon groove-shaped recess 38 forms a direct discharge passage for exhaust with the inner peripheral surface of the main body 3, and this direct discharge passage is connected to an exhaust system (not shown) in the hose joint 14. It is designed to communicate. In FIG. 2, the ventilation paths 31, 3
5 and the air passages 32 and 36 and the air passage 37 are drawn so as to deviate from the actual formation position, and the portions other than the air passage 37 are shown by broken lines to avoid confusion with others.
The holes u, x, y, and z are indicated by two-dot chain lines.

Next, a method for generating reciprocating motion according to the present invention will be described with reference to FIG.
A description will be given based on (a) to (c). As shown in FIG. 6A, the front plunger 20
Is made to stand by at the rear stop position of the front and rear sliding area, and the rear plunger 21 is made to stand by at the front stop position of the front and rear sliding area in the rear cylinder 12 (that is, in the mutual proximity state). The operation shall be started from the state.

After pressing the operation switch 7 (see FIG. 1), the supply air from the air supply main passage 16 and the ventilation passage 33 is first divided into the holes h and g. The air reaches the hole j via the second constricted portion 25 of the rear plunger 21, and is supplied from the hole a to the first chamber formed in front of the front plunger 20 through the ventilation paths 34 and 30. On the other hand, what flows into the hole g is provided between the small diameter portion 21a of the rear plunger 21 and the middle diameter portion 21b, and between the small diameter portion 12a and the middle diameter portion 12b of the rear cylinder 12. Both the raised step portion and the stepped portion are added to the portions in close contact with each other. In this portion, the chamfered portion 27 (see FIG. 3) of the rear plunger 21 and the boring portion 12d (see FIG. 5) of the rear cylinder 12 are in a matched state, so that air is divided between them. And acts to push open between the step portions. for that reason,
The rear plunger 21 is moved backward while forming the third chamber between the step portions. Then, due to the thrust generated by the rearward movement of the rear plunger 21, the air that has filled the fourth chamber formed at the rear of the rear plunger 21 up to that point passes through the air passages 35 and 31 from the hole n to the hole c. From the rear plunger 21 and the front plunger 2
It will be diverted to the 2nd chamber between 0. Also the fourth
Excess air in the room passes through the ventilation passage 37 from the hole s to the hole t, and further the third constricted portion 2 of the rear plunger 21.
After being discharged from the hole y to the concave portion 38 (direct discharge path) outside the hole y, the gas is exhausted to the hose joint 14 side.

As shown in FIG. 6B, the rear plunger 2
When 1 moves backward, the hole h is closed and the supply of air to the first chamber is cut off, and then the air flowing into the third chamber from the hole g is vented from the first constricted portion 24 of the rear plunger 21. It flows into the passage 39 and is supplied to the second chamber together with the air circulated from the fourth chamber as described above. As a result, the front plunger 20 is advanced. Then, the thrust that accompanies the forward movement of the front plunger 20 pushes the air filled in the first chamber up to that time from the hole e to the hole p through the ventilation paths 32 and 36 (see FIG. 6).
In (b), the front plunger 20 has been drawn so as to have advanced past the position of the hole e).
After passing through the second constricted portion 25 and the hole x of the rear plunger 21 which is in the state of conforming with the above, it is discharged to the concave portion 38 (direct discharge path) on the outside thereof and exhausted to the hose joint 14 side. At this time, part of the air being supplied to the second chamber reaches the hole n from the hole c through the ventilation paths 31 and 35, and is circulated into the fourth chamber. Therefore, when the rear plunger 21 collides with the cushioning material 17 by the reverse movement, the internal pressure in the fourth chamber starts to increase, and the rear plunger 2
Induces the force to move forward by reversing the traveling direction of 1.
After such operation, the front plunger 20 reaches the front stop position in the front and rear sliding area, and the rear plunger 21
Is reaching the rear stop position in the front and rear sliding area (that is, in a mutually separated state).

As shown in FIG. 6 (c), the rear plunger 2
1 starts to move forward by reversing the traveling direction, the first constricted portion 24 eventually becomes the small-diameter portion 12a of the rear cylinder 12.
And the air supply to the second chamber is cut off, and the hole h is opened instead. The air from the hole h passes through the second constricted portion 25 of the rear plunger 21 to the hole j, and is sent into the hole a through the ventilation paths 34 and 30. At this time, the front plunger 20 overlaps the hole a as shown in FIG. 6B, but a partial region 10a near the front wall 11 in the front cylinder 10 (see FIG. (See 4) has a large diameter, air flows into the first chamber through the hole a, and the front plunger 20 can be moved backward. On the other hand, the second chamber is reduced by the thrust when the front plunger 20 moves backward and the thrust of the rear plunger 21 that is moving forward as described above. The filled air reaches the hole n from the hole c via the ventilation paths 31 and 35 and is circulated to the fourth chamber, and flows from the fourth chamber into the hole s, passes through the ventilation path 37, and from the hole t. Further, at this time, the third constricted portion 26 and the hole y of the rear plunger 21 in the matching state are set.
After that, the air is discharged to the concave portion 38 (direct release path) on the outside thereof and is exhausted to the hose joint 14 side. Therefore, after this operation, the front plunger 20 reaches the rear stop position in the front and rear sliding range, and the rear plunger 21 reaches the front stop position in the front and rear sliding range.
After returning to the stage shown in (a), these operations are repeated at high speed. As a result, the drive take-out head 4 (see FIG. 1) reciprocates.

In the present invention, a liquid such as water can be used as the working fluid other than air. In addition, by appropriately replacing the items attached to the drive take-out head 4 (for example, saw teeth, hammers, ratchet wrench, etc.),
Its versatility can be enhanced.

[0023]

According to the reciprocating motion generating method of the present invention and the reciprocating motion generating device of the present invention, the working fluid is supplied into the cylinder to mainly slide the rear plunger housed in the cylinder back and forth. The front plunger is slid back and forth relative to the rear plunger (that is, in the manner of repeating mutual proximity and mutual separation), and the flow path of the working fluid is switched. The reciprocating motion with respect to the cutter blade is taken out from the drive take-out head. Therefore, the front spring and the rear spring, which have been conventionally required, can be eliminated, and maintenance due to deterioration and damage of the front spring and the rear spring can be eliminated.

Further, the working fluid supplied to the chamber which is being expanded when either one of the plungers moves forward or backward is circulated according to the position of the plunger during forward movement or backward movement. It is circulated to a predetermined chamber by a road, and is used as a driving force when the other plunger is moved forward or backward (when the traveling direction is reversed). Therefore, the operating efficiency is improved when the front and rear plungers reverse their traveling directions,
A smooth and stable reciprocating motion can be obtained in the drive take-out head.

In the reciprocating motion generating device of the present invention, by forming the pressure receiving area of the front plunger as large as possible, it is possible to obtain a sliding force required for various operations that is necessary and sufficient for various operations. I am doing it.

[Brief description of drawings]

FIG. 1 is a side view of a pneumatic automatic cutter tool incorporating a reciprocating motion generating device according to the present invention.

FIG. 2 is a side sectional view showing a reciprocating motion generator by enlarging and breaking a main part of FIG. 1;

FIG. 3 is a side sectional view of the rear plunger (slightly reduced from FIG. 2).

4A and 4B show a front cylinder, in which FIG. 4A is a rear view, FIG. 4B is a sectional view taken along line AA of FIG. 4A, and FIG. 4C is a sectional view taken along line BB of FIG. (Both are slightly reduced from FIG. 2).

FIG. 5 is a view showing a rear cylinder, in which (a) is a front view, (b) is a right side view of (a), and (c) is C of (a).
-C line sectional view, (d) DD line sectional view of (a),
(E) is a sectional view taken along line EE of (a) (both are shown in FIG.
Slightly smaller).

FIG. 6 is a schematic diagram for explaining a reciprocating motion generation method according to the present invention.

FIG. 7 is a diagram schematically showing a sectional structure of a conventional pneumatic automatic cutter tool.

[Explanation of symbols]

 1 Reciprocating Motion Generator 2 Pneumatic Automatic Cutter Device 4 Drive Extraction Head 5 Cutter Blade 10 Front Cylinder 11 Front Wall 12 Rear Cylinder 13 Rear Wall 15 Cylinder 20 Front Plunger 21 Rear Plunger

Claims (3)

[Claims] 1. A front plunger housed in a cylinder surrounded by a front wall and a rear wall is made to stand by at a rear stop position of a front and rear sliding area thereof, and is housed behind the front plunger in the cylinder. The rear plunger is made to stand by at the front stop position in the front-rear sliding area so that the radial step portions formed on the peripheral wall of the rear plunger and the inner wall of the cylinder are brought into close contact with each other in the front-rear direction. The third chamber is formed between the step portions by supplying the working fluid between the parts to move the rear plunger backward, and the fourth chamber behind the rear plunger is filled with the thrust of the rear plunger moving backward. The working fluid to be discharged is circulated to the second chamber between the front and rear plungers, and the excess working fluid in the fourth chamber is discharged to the outside of the cylinder. After advancing, the working fluid supply path is switched from the third chamber to the second chamber to advance the front plunger, and the thrust of the front plunger is used to fill the first chamber in front of the front plunger. The working fluid to be discharged to the outside of the cylinder, and the working fluid is supplied from the second chamber to the fourth chamber through a circulation passage opened after the rear plunger further moves backward by a predetermined amount.
The rear plunger is moved forward by switching to the chamber, the thrust of the rear plunger is used to discharge a part of the working fluid in the second chamber to the outside of the cylinder, and the flow is opened after the rear plunger moves forward by a predetermined amount. The front plunger is moved backward by switching the supply of the working fluid from the fourth chamber to the first chamber through the passage, and by repeating these operations, the front plunger is projected through the front wall of the cylinder. A method for generating reciprocation by fluid pressure, characterized in that the drive take-out head provided in the reciprocating part is reciprocated. 2. A front plunger and a rear plunger are respectively housed in a cylinder surrounded by a front wall and a rear wall so as to be slidable back and forth, and the inside of the cylinder is adjusted depending on the positions of the front and rear plungers.
A first chamber in front of the front plunger, a second chamber between the front and rear plungers, and a third chamber formed between radial step portions formed on the peripheral wall of the rear plunger and the cylinder inner wall, respectively. , Is formed so as to be partitioned or not formed in the fourth chamber behind the rear plunger, and the first chamber to the fourth chamber are provided with a working fluid supply path and a discharge path toward each of these chambers when they are formed. Opened or closed, the pressure receiving area of the front plunger facing the first chamber and the second chamber is formed as large as possible in the cylinder, and the front plunger penetrates the front wall of the cylinder. A reciprocating motion generating device by a fluid pressure, wherein a drive take-out head is provided so as to project forward. 3. The discharge passage, which is opened toward each chamber when the first to fourth chambers are formed, includes a direct discharge passage that is discharged from the side of the chamber that is being reduced to the outside of the cylinder, and a reduced discharge passage. 3. The reciprocating motion generating device by fluid pressure according to claim 2, wherein a circulation passage is formed to be guided from the chamber side toward the chamber side to be expanded.