JPH1130201A - Piston position detecting device for piston type accumulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston position detecting device which eliminates the need for installing springs in the device, and further, has an outer end of a detection rod exposed to the outside of a cylinder, thereby enabling the use of a signal transmission means other than magnetism. SOLUTION: This device is provided with a detection rod 15 which is pushed by a piston and changes its position, an inside pressure face 25 which receives the pressure inside a cylinder 1 in a direction as to push the detection rod 15 toward the outside of the cylinder 1, an outside pressure face 26 which receives the pressure inside the cylinder 1 in a direction as to push the detection rod 15 toward the inside of the cylinder 1 and is provided with a pressure receiving area set larger than that of the inside pressure face 25, a pressure introduction passage 22 which introduces pressure so that the pressure inside the cylinder 1 is applied to the outside pressure face 26, and seal sections 17, 20 which seal the pressure inside the cylinder 1 from leaking to the outside of the cylinder 1, and an outer end 15e of the detection rod 15 is exposed to the outside of the cylinder 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston position detecting device attached to a piston type accumulator for detecting the position of a piston.

[0002]

2. Description of the Related Art A piston position detecting device disclosed in Japanese Patent Application Laid-Open No. Hei 7-139502 uses a load of a spring installed inside the device to hold a detecting rod. However, since the length or diameter of the spring is regulated by the mounting space, there is a problem that the space of the rod is restricted. Further, when utilizing the load of the spring as described above, there is a disadvantage that the load (spring force) of the spring must be adjusted according to the level of the pressure in the cylinder.

In the piston position detecting device disclosed in Japanese Patent Application Laid-Open No. 2-186102, the outer end of the detecting rod is covered by a pressure cover fixed outside the end wall of the cylinder. Therefore, since the outer end of the detection rod is not directly exposed to the outside of the cylinder, the operation of the detection rod displaced by being pushed by the piston must be transmitted to the outside by the magnetism of the magnet sensor penetrating the pressure cover. Therefore, there is a disadvantage that mechanical signal transmission means other than magnetism cannot be used, for example, detection is performed by the outer end of the detection rod directly pressing the limit switch.

[0004]

In view of the above, the present invention does not require the installation of a spring inside the device, and furthermore, the outer end of the detection rod is exposed to the outside of the cylinder, and signals other than magnetic signals are detected. It is an object of the present invention to provide a piston position detecting device capable of utilizing a transmitting means.

[0005]

To achieve the above object, a piston position detecting device according to claim 1 of the present invention comprises:
A piston that separates an oil chamber and a gas chamber is attached to a piston-type accumulator that is slidably arranged in a cylinder,
A piston position detection device that detects the position of the piston, wherein the detection rod is slidably disposed in a hole provided in an end wall of the cylinder, and is displaced by being pressed by the piston. An inner pressure receiving portion that receives the pressure in the cylinder so as to press the cylinder toward the outside, and receives the pressure in the cylinder so as to press the detection rod toward the inside of the cylinder; An outer pressure receiving portion set to be larger than the pressure receiving portion, a pressure conduit for guiding the pressure so that the pressure in the cylinder acts on the outer pressure receiving portion, and a pressure in the cylinder so as not to leak outside the cylinder. An annular seal portion disposed on the outer peripheral side of the detection rod to seal the pressure, and the outer end of the detection rod is exposed outside the cylinder. It was.

According to a second aspect of the present invention, there is provided a piston position detecting device according to the first aspect of the present invention, wherein the piston is provided on the detecting rod even if the piston comes into contact with the inner end surface of the detecting rod. The pressure guide is opened at a position other than the inner end surface of the detection rod so that the pressure guide is not closed.

In the piston position detecting device according to the first aspect of the present invention, a hole is provided in an end wall of a cylinder in which a piston is slidably inserted, and a detecting rod is formed in the hole. It is slidably inserted. The pressure in the cylinder acts on the inner pressure-receiving part of the detection rod, and the pressure in the cylinder also acts on the outer pressure-receiving part via the pressure passage, but the pressure-receiving area of the outer pressure-receiving part is smaller than the pressure-receiving area of the inner pressure-receiving part. Due to the large setting, the detection rod is always located at the inner end of the cylinder in its stroke range.

That is, even if a spring is not installed in the device, the detection rod is urged inward of the cylinder by a difference in pressing force due to a difference in pressure receiving area between the inner pressure receiving portion and the outer pressure receiving portion. Only when pressed by the piston, it is displaced toward the outside of the cylinder against this urging force.

The pressure in the cylinder guided to act on the outer pressure receiving portion via the pressure conduit is leaked to the outside by being sealed by an annular seal portion arranged on the outer peripheral side of the detection rod. Is prevented. Specifically, the pressure in the cylinder is hydraulic when the device is installed on the oil chamber side of the piston type accumulator, and is gas pressure when it is installed on the gas chamber side.

In any case, the pressure in the cylinder is sealed by a seal portion disposed on the outer peripheral side of the detection rod, so that the detection rod has a structure in which the outer end is exposed to the outside of the cylinder. It is possible to do.
Therefore, for example, by setting the outer end of the detection rod so as to directly press the limit switch, it is possible to detect the position of the piston using signal transmission means other than magnetism.

In addition to this, as in the piston position detecting device according to the second aspect of the present invention having the above structure, even if the piston comes into contact with the inner end surface of the detecting rod, the pressure applied to the detecting rod is increased. If the pressure conduit is opened at a position other than the inner end surface of the detection rod so that the conduit is not blocked, the pressure conduit will not be blocked even if the piston comes into contact with the inner end surface of the detection rod. Even if the detection rod moves by being pushed by the piston after the contact, the pressure in the device does not become abnormally high.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic cross section of a piston type accumulator provided with a piston position detecting device according to the present embodiment, and shows a cylinder 1 vertically arranged in the figure.
A piston 4 for partitioning the inside of the cylinder 1 into an oil chamber 2 on the upper and lower sides in the figure and a gas chamber 3 on the upper side in the figure is slidably disposed inside the cylinder.

In the cylinder 1, a bottom cover 6 is connected to one end of a cylinder tube 5 and fixed with a lock nut 7, and a top cover 8 is connected to the other end of the cylinder tube 5 and this is connected with a lock nut 9. It is fixed. A gas port flange 10 is further connected to the top cover 8.

A piston position detecting device 11 is provided on each of the bottom cover 6 and the top cover 8.

The piston position detecting device 11 on the side of the oil chamber 2 installed on the bottom cover 6 has the following configuration.

That is, as shown in an enlarged manner in FIG. 2, first, the bottom cover 6 is provided with a hole 12 having a circular cross section penetrating the bottom cover 6 in the thickness direction.
A cylindrical guide 13 is inserted and fixed in the hole 12 over the entire length thereof. On the inner peripheral surface of the guide 13, the inner diameter of the guide 13 is made relatively small inside the cylinder 1 (upper side in the figure) and outside the cylinder 1 (upper and lower sides in the figure).
An annular step 13a is provided so as to have a relatively large diameter. The guide 1 is located between the bottom cover 6 and the guide 13.
3 is sealed by a seal portion 14 made of an O-ring fitted to the outer periphery of the third member 3.

A detection rod (also referred to as a piston rod or free piston) 15 having a circular cross section is inserted through the guide 13 so as to be slidable in the axial direction. The detection rod 15 has an axial length longer than the guide 13, and has a relatively large diameter
5c is provided integrally. Therefore, detection rod 1
5 is the piston portion 15c and the inner shaft portion 1 inside the piston portion 15c.
5b and an outer shaft portion 15d on the outside thereof are coaxially and integrally provided. The tip of the inner shaft portion 15b is the inner end portion 15a of the entire detection rod 15, and the tip of the outer shaft portion 15d is the detection rod. The entire outer end 15 is an outer end 15e.

The guide 1 is located on the outer peripheral side of the outer shaft portion 15d.
A cylindrical guide bush 16 is provided on the inner peripheral side of
It is interpolated so as to be fixed to the side. Guide 13
The space between the guide bush 16 and the guide bush 16 is sealed by a seal portion 17 formed of an O-ring fitted on the outer periphery of the guide bush 16. Since the guide bush 16 is fixed to the inner peripheral side of the guide 13, the detection rod 15
The piston 15c can reciprocate in the axial direction with a stroke in a range where the piston portion 15c contacts the step portion 13a on its inner end surface and contacts the guide bush 16 on its outer end surface. The figure shows a state in which the piston portion 15c is in contact with the step portion 13a at its inner end face, and the detection rod 15 is located at the upper end of the stroke in the drawing. At this time, the inner end 15a of the detection rod 15 projects into the oil chamber 2.

The gap between the guide 13 and the inner shaft 15b is sealed by a seal 18 made of an O-ring fitted on the outer periphery of the inner shaft 15b. The gap between the guide 13 and the piston portion 15c is sealed by a seal portion 19 formed of an O-ring fitted on the outer periphery of the piston portion 15c. Also, between the guide bush 16 and the outer shaft portion 15d,
The outer shaft 15d is sealed by a seal portion 20 made of an O-ring fitted to the outer periphery of the outer shaft 15d.

The detection rod 15 is provided with a pressure passage 22 so that the oil pressure in the oil chamber 2 is guided to the annular pressure chamber 21 between the piston 15c and the guide bush 16. The pressure conduit 22 has a vertical hole portion 22a having a circular cross section provided along the central axis of the inner shaft portion 15b and the piston portion 15c, and an outer shaft portion communicating with the vertical hole portion 22a in a substantially T-shape. A portion 15d is provided with a horizontal hole portion 22b having a circular cross-section provided along the radial direction thereof. It is opened at two symmetrical locations on the outer peripheral surface of 15d.

An annular space 23 between the piston portion 15c and the step portion 13a on the opposite side of the pressure chamber 21 with the piston portion 15c interposed between the piston portion 15c and the step portion 13a so that the oil pressure beyond the seal portion 18 does not stay there. Open part (also called vent)
24 is open to the atmosphere. The open-to-atmosphere portion 24 is provided on the guide 13 so as to communicate with the space 23 along a radial direction of the guide 13 and on the outer peripheral surface of the guide 13 so as to communicate with the transverse hole 24a. Annular groove 24b, and a longitudinal groove 24c provided along the axial direction on the outer peripheral surface of the guide 13 so as to communicate with the groove 24b.
And

The detection rod 15 is provided with an inner pressure receiving portion 25 so as to be pressed by the hydraulic pressure toward the outside of the cylinder 1, and the outer pressure receiving portion 25 is pressed by the oil pressure toward the inside of the cylinder 1 in the opposite direction. The pressure receiving area of the latter is set larger than the pressure receiving area of the former. The specifications are as follows.

[0024]

(Equation 1)

D ₁ : the outer diameter of the piston portion 15 c D ₂ : the outer diameter of the outer shaft 15 d D ₃ : the outer diameter of the inner shaft 15 b D ₄ : the diameter of the vertical hole 22 a, where (1) In the formula,
Since the received pressure and the atmospheric pressure in the lateral hole 22b are relatively small numerically, they are omitted.

A piston position detecting device 1 having the above configuration
1, since the pressure receiving area of the outer pressure receiving portion 26 of the detection rod 15 is set to be larger than the pressure receiving area of the inner pressure receiving portion 25, the detection rod 15 is always inside the cylinder 1 in its stroke range as shown in the drawing. And the inner end 15a of the detection rod 15 projects into the oil chamber 2. That is, even if the device does not include a spring as in the related art, the detection rod 15 is urged inward of the cylinder 1 by the difference in the pressing force due to the difference in the pressure receiving area between the inner pressure receiving portion 25 and the outer pressure receiving portion 26. I have. Further, the hydraulic pressure guided to the pressure chamber 21 via the pressure conduit 22 so as to act on the outer pressure receiving portion 26 is sealed by the annular seal portions 17 and 20 arranged on the outer peripheral side of the detection rod 15. It is prevented from leaking outside. The outer end 15 e of the detection rod 15 is exposed outside the cylinder 1.

Therefore, when the piston 4 moves and presses the detection rod 15 in the vertical direction in the figure with respect to the apparatus in the posture shown in FIG.
And the outer end 15e of the cylinder 1
Project outside. Therefore, for example, the outer end 15e
Can directly detect the position of the piston 4 by directly pressing a limit switch (not shown), whereby the piston 4 can be detected using signal transmission means other than magnetism.
Can be detected.

The piston position detecting device 11 on the side of the gas chamber 3 installed on the top cover 8 has the following configuration. The detection device 11 on the gas chamber 3 side is provided with the oil chamber 2 described above.
The upper and lower detectors 11 are substantially symmetrical with respect to the upper and lower sides and have substantially the same configuration.
7 is fixed.

That is, as shown in an enlarged manner in FIG. 3, first, the top cover 8 is provided with a hole 12 having a circular cross section penetrating the top cover 8 in the thickness direction.
A cylindrical guide 13 is inserted and fixed in the hole 12 over the entire length thereof. On the inner peripheral surface of the guide 13, the inside diameter of the guide 13 is made relatively small inside the cylinder 1 (upper side in the figure) and outside the cylinder 1 (upper side in the figure).
An annular step 13a is provided so as to have a relatively large diameter. The guide 1 is located between the bottom cover 6 and the guide 13.
3 is sealed by a seal portion 14 made of an O-ring fitted to the outer periphery of the third member 3.

A detection rod (also referred to as a piston rod) 15 having a circular cross section is inserted through the guide 13 and a set flange 27 disposed coaxially with the guide 13 so as to be slidable in the axial direction. . The detection rod 15 has a longer axial length than the guide 13, and a relatively large-diameter piston portion 15c is integrally provided substantially at the center in the axial direction. Therefore, the detection rod 15 includes the piston portion 15c, the inner shaft portion 15b inside the piston portion 15c, and the outer shaft portion 15d outside the same coaxially and integrally. Inner end 15a of
And the tip of the outer shaft portion 15d is the detection rod 1
5 as the outer end 15e.

The guide 1 is located on the outer peripheral side of the outer shaft portion 15d.
A cylindrical guide bush 16 is provided on the inner peripheral side of
It is interpolated so as to be fixed to the side. Guide 13
The space between the guide bush 16 and the guide bush 16 is sealed by a seal portion 17 formed of an O-ring fitted on the outer periphery of the guide bush 16. Since the guide bush 16 is fixed to the inner peripheral side of the guide 13, the detection rod 15
The piston 15c can reciprocate in the axial direction with a stroke in a range where the piston portion 15c contacts the step portion 13a on its inner end surface and contacts the guide bush 16 on its outer end surface. The figure shows a state in which the piston portion 15c is in contact with the step portion 13a at its inner end face, and thus the detection rod 15 is located at the upper and lower ends of the stroke. At this time, the inner end 15a of the detection rod 15 projects into the gas chamber 3.

The gap between the guide 13 and the inner shaft portion 15b is sealed by a seal portion 18 formed of an O-ring fitted on the outer periphery of the inner shaft portion 15b. The gap between the guide 13 and the piston portion 15c is sealed by a seal portion 19 formed of an O-ring fitted on the outer periphery of the piston portion 15c. Also, between the guide bush 16 and the outer shaft portion 15d,
The outer shaft 15d is sealed by a seal portion 20 made of an O-ring fitted to the outer periphery of the outer shaft 15d.

A pressure conduit 22 is provided in the detection rod 15 so that the gas pressure in the gas chamber 3 is guided to the annular pressure chamber 21 between the piston 15c and the guide bush 16. The pressure conduit 22 has a vertical hole portion 22a having a circular cross section provided along the central axis of the inner shaft portion 15b and the piston portion 15c, and an outer side communicating with the vertical hole portion 22a in a substantially T-shape. The shaft portion 15d is provided with a horizontal hole portion 22b having a circular cross section provided along the radial direction thereof. The vertical hole portion 22a is opened at the tip end surface of the inner shaft portion 15b, and the horizontal hole portion 22b is formed on the outer shaft portion. It is open at two symmetrical locations on the outer peripheral surface of the portion 15d.

The annular space 23 between the piston portion 15c and the step portion 13a opposite to the pressure chamber 21 with the piston portion 15c interposed therebetween prevents gas pressure exceeding the seal portion 18 from staying there. It is open to the atmosphere by an open-to-atmosphere section (also referred to as a vent section) 24. This atmosphere opening part 2
4 is a lateral hole 24a provided in the guide 13 along the radial direction so as to communicate with the space 23, and an annular hole provided on the outer peripheral surface of the guide 13 so as to communicate with the lateral hole 24a. A groove 24b, a vertical groove 24c provided along the axial direction on the outer peripheral surface of the guide 13 so as to communicate with the groove 24b, and a radial direction on the inner end face of the set flange 27 so as to communicate with the vertical groove 24c. And a shaft hole 24e of a set flange 27 communicating with the lateral groove 24d.

The detection rod 15 has an inner pressure receiving portion 25 so as to be pressed toward the outside of the cylinder 1 by gas pressure, and has an outer pressure receiving portion 25 to be pressed toward the inside of the cylinder 1 in the opposite direction. A pressure receiving section 26,
The pressure receiving area of the latter is set larger than the pressure receiving area of the former. The specifications are as follows.

[0036]

(Equation 1)

D ₁ : outer diameter of the piston portion 15 c D ₂ : outer diameter of the outer shaft 15 d D ₃ : outer diameter of the inner shaft 15 b D ₄ : diameter of the vertical hole portion 22 a In equation (1), the pressure and atmospheric pressure in the lateral hole 22b are numerically relatively small, and therefore are omitted.

The piston position detecting device 1 having the above configuration
1, since the pressure receiving area of the outer pressure receiving portion 26 of the detection rod 15 is set to be larger than the pressure receiving area of the inner pressure receiving portion 25, the detection rod 15 is always inside the cylinder 1 in its stroke range as shown in the drawing. And the inner end 15a of the detection rod 15 is
It protrudes into. That is, even if the device does not include a spring as in the related art, the detection rod 15 is urged inward of the cylinder 1 by the difference in the pressing force due to the difference in the pressure receiving area between the inner pressure receiving portion 25 and the outer pressure receiving portion 26. I have. Further, the gas pressure guided to the pressure chamber 21 via the pressure conduit 22 so as to act on the outer pressure receiving portion 26 is sealed by the annular seal portions 17 and 20 disposed on the outer peripheral side of the detection rod 15. Prevents leakage to the outside. The outer end 15 e of the detection rod 15 is exposed outside the cylinder 1.

Therefore, when the piston 4 moves and presses the detection rod 15 upward in the figure with respect to the device in the posture shown in FIG.
And the outer end 15e of the cylinder 1
Project outside. Therefore, for example, the outer end 15e
Can directly detect the position of the piston 4 by directly pressing a limit switch (not shown), whereby the piston 4 can be detected using signal transmission means other than magnetism.
Can be detected.

As described above, the present invention does not require the installation of a spring inside the device 11 and the outer end portion 15e of the detection rod 15 is exposed to the outside of the cylinder 1 in comparison with the above-mentioned prior art. The main object and effect of the present invention is to make it possible to use signal transmission means other than magnetism, but this is not to exclude magnetism as signal transmission means, but to expand the range of choice. . Therefore, the detection rod 15
A magnet may be used in combination with the magnet sensor. Whatever type of signal transmission means is used, it is possible to detect an arbitrary position by lengthening the rod 15 and using a plurality of sensors or switches.

In the above embodiment, the piston 4
Is moved, and its end face is the inner end 1 of the detection rod 15.
5a, the pressure conduit 22 opened at the inner end 15a is closed by the end face of the piston 4. After the abutment and closing, the pressure conduit 22 is pushed by the piston 4 to detect the detection rod 15a.
Moves, the pressure in the pressure chamber 21 becomes abnormally high, and an excessive load is applied to the seal portions 17, 19, 20.
There is a concern that the seal portions 17, 19, 20 may be damaged early.

Therefore, in order to avoid this, even if the piston 4 abuts on the end face of the inner end 15a of the detection rod 15, the pressure conduit 22 opened on the end face of this inner end 15a is prevented from being blocked. It is effective to open the conduit 22 at a position other than the end surface of the inner end 15a of the detection rod 15, and specifically, the following configuration is conceivable.

First, as shown in FIG. 4 or FIG. 5, the pressure conduit 22 is opened at the inner end 15a of the detection rod 15, and a required number of slits 22c are provided around this opening. Pressure conduit 2 through slit 22c
2 is also opened to the peripheral surface of the detection rod 15. The slits 22c are evenly arranged on the figure. FIG. 4 corresponds to FIG. 2, and FIG. 5 corresponds to FIG.

As shown in FIG. 6 or FIG. 7, the pressure guide path 22 is not opened at the inner end 15a of the detection rod 15, but is formed into a pointed shape. The pressure conduit 22 is opened to the peripheral surface of the detection rod 15 via the portion 22d. The side hole 22d is connected to the detection rod 15
Are provided along the radial direction, and are opened 180 degrees symmetrically to the peripheral surface at two locations. Further, in this case, since the inner end 15a end face of the detection rod 15 has no flat surface due to any irregularities due to openings or slits, the piston 4 that comes into contact with the inner end 15a has a flat surface. There is an effect that is hard to be damaged. FIG. 6 corresponds to FIG. 2, and FIG. 7 corresponds to FIG.

[0045]

The present invention has the following effects.

That is, in the piston position detecting device according to the first aspect of the present invention having the above-described structure, first, an urging force toward the inside of the cylinder due to a difference in pressure receiving area between the inner pressure receiving portion and the outer pressure receiving portion is set. Therefore, the detection rod is urged toward the inside of the cylinder even when the spring is not installed. That is, the detection rod is always positioned at the inner end of the stroke even if not biased by the spring, and is displaced outward against the biasing force only when pressed by the piston, and when the piston separates. Automatic return operation by the urging force. Therefore, the number of parts can be reduced by the omission of the spring, and it is not necessary to adjust the magnitude of the force for protruding the detection rod into the cylinder in accordance with the level of the pressure in the cylinder.

In addition, in the piston position detecting device having the above configuration, since the outer end of the detecting rod is exposed outside the cylinder, it is possible to use signal transmitting means other than magnetism. Thus, the range of selection of the signal transmission means including the magnetic means can be expanded.

In addition to the above, in the piston position detecting device according to the second aspect of the present invention having the above structure,
Even if the piston abuts on the inner end surface of the detection rod, the pressure conduit is opened at a position other than the inner end surface of the detection rod so that the pressure conduit provided on the detection rod is not closed. Even if the piston comes into contact with the inner end surface of the detection rod, the pressure conduit is not closed. Therefore, even if the detection rod moves by being pushed by the piston after the contact, the pressure in the device does not become abnormally high, and the seal portion for sealing this pressure is prevented from being damaged at an early stage due to the high pressure. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a piston type accumulator provided with a piston position detecting device according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is an enlarged view of a portion B in FIG. 1;

FIG. 4 is a sectional view of a piston position detecting device according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a piston position detecting device according to another embodiment of the present invention.

FIG. 6 is a sectional view of a piston position detecting device according to another embodiment of the present invention.

FIG. 7 is a sectional view of a piston position detecting device according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Oil chamber 3 Gas chamber 4 Piston 5 Cylinder tube 6 Bottom cover 7, 9 Lock nut 8 Top cover 10 Gas port flange 11 Piston position detector 12 Hole 13 Guide 13a Step 14, 14, 18, 19, 20 Seal part 15 Detection rod 15a Inner end part 15b Inner shaft part 15c Piston part 15d Outer shaft part 15e Outer end part 16 Guide bush 21 Pressure chamber 22 Pressure passage 22a Vertical hole part 22b, 22d, 24a Horizontal hole part 22c Slit 23 Space 24 Atmospheric release part 24b Groove part 24c Vertical groove part 24d Horizontal groove part 24e Shaft hole part 25 Inside pressure receiving part 26 Outside pressure receiving part 27 Set flange

Claims (2)

[Claims] 1. A piston type accumulator in which a piston (4) for partitioning an oil chamber (2) and a gas chamber (3) is slidably disposed in a cylinder (1). Piston position detecting device for detecting position (11)
A detection rod (15) slidably disposed in a hole (12) provided in an end wall of the cylinder (1) and displaced by being pressed by the piston (4); 15) an inner pressure receiving portion (25) for receiving the pressure in the cylinder (1) so as to press the cylinder (1) toward the outside, and the detection rod (15) inside the cylinder (1). An outer pressure receiving portion (26) having a pressure receiving area set to be larger than that of the inner pressure receiving portion (25), and a pressure in the cylinder (1) is set such that the pressure in the cylinder (1) is increased. Outer pressure receiving part (26)
A pressure conduit (22) for guiding the pressure so as to act on the outer periphery of the detection rod (15) so that the pressure in the cylinder (1) does not leak outside the cylinder (1). Annular seal part (1)
7) and (20), wherein the outer end (15e) of the detection rod (15) is exposed outside the cylinder (1). 2. The piston position detecting device according to claim 1, wherein the piston (4) is connected to an inner end (15) of the detecting rod (15).
a) The pressure conduit (22) is connected to the inner end (15) of the detection rod (15) so that the pressure conduit (22) provided in the detection rod (15) is not closed even when the pressure rod (15) abuts on the end face.
a) A piston position detecting device of a piston type accumulator, which is open at a position other than the end surface.