JP3425610B2 - Piston type accumulator piston position detector - Google Patents

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 for a piston type accumulator, and more specifically, it detects displacement of the piston position that occurs when the pressure liquid in a hydraulic circuit enters and leaves the liquid chamber of the accumulator. However, the present invention relates to a piston position detection device that detects the presence or absence of leakage of gas in the gas chamber of the accumulator based on the detected position.

[0002]

2. Description of the Related Art The following is a conventional piston position detecting device for a piston type accumulator. A cylinder forms a closed space by the head cover and the bottom cover is defined by the piston, and in the gas chamber on the head cover side, in order to restore the position of the piston displaced by the volume change of the hydraulic pressure on the bottom cover side connected to the hydraulic circuit. In the piston type accumulator in which the gas of (1) is filled, a non-magnetic material that vertically penetrates through the center of the piston and has a closed lower end while the upper end projects from the head cover and is open to the atmosphere outside the cylinder. Guide pipes are fixed at the upper and lower ends of the cylinder,
A center seal that enables liquid-tight sliding of the piston, which is displaced along the guide pipe, is arranged at a deep end of a recess provided in a central portion of the piston, and prevents deviation of the center seal. And a permanent magnet close to the outer surface of the guide pipe is disposed on the cover that closes the recess, and a magnetism sensitive body that is sensitive to the permanent magnet is disposed inside the guide pipe. A piston position detecting device for a piston type accumulator, which is provided with a displacement detector which is taken out from the upper end of the pipe and detects the position of the piston.

[0003]

In the conventional example, a non-magnetic guide pipe that vertically penetrates the center of the piston is fixed at the upper and lower ends of the cylinder. The axial center of the pipe and the shaft of the piston are fixed. It is difficult to fix at both ends to match the heart, which causes misalignment.

When this misalignment occurs, a large resistance of the guide pipe is applied when the piston slides, so that the piston cannot slide smoothly. Therefore, it is difficult to accurately detect the piston position that corresponds to the pressure fluctuation. Further, since the guide pulp penetrates the piston, it is necessary to seal between the two. However, since the seal between the two is a seal of the sliding portion, one side is worn due to eccentricity of the seal member, the seal is damaged in a short time, and seal leakage occurs. Therefore, it is necessary to disassemble and assemble the accumulator in a short time and replace worn metal parts and seal members,
A lot of labor and cost are required for maintenance.

In view of the above circumstances, an object of the present invention is to detect a piston position that accurately corresponds to pressure fluctuation. Another purpose is to create maintenance-free products.

[0006]

According to the present invention, a cylinder whose both ends are closed by a head cover and a bottom cover, a piston for partitioning the inside of the cylinder into a liquid chamber and a gas chamber, and one end fixed to the inner surface of the head cover are provided. And the other end is a free end, a non-magnetic guide pipe for guiding the magnetism sensitive body, a permanent magnet for operating the magnetism sensitive body, and the piston position from the sensing operation of the magnetism sensitive body. A piston type accumulator comprising: a displacement detector for detecting
The guide pipe has one end fixed to said piston Sareso
The protrusions are blocked, a free end and the other end is exposed to the gas chamber, the permanent magnet is fixed to the guide pipe, before
Note that the head cover and bottom cover have the above
It is characterized by having a recess for accommodating the end of the id pipe .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Both ends of a cylinder containing a piston are closed by a head cover and a bottom cover. One end of the magnetic sensitive body is fixed to the inner surface of the head cover, and the other end of the magnetic sensitive body is inserted into the free end of the non-magnetic guide pipe. The fixed end of this guide pipe is fixed to the piston. The guide pipe is provided with a permanent magnet for operating the magnetic sensitive body.

When the fluid pressure fluctuates, the piston slides while being guided by the cylinder, and when the magnetic sensitive body is sensitive to the approach of the permanent magnet, the sensitive motion is taken out from the upper end of the guide pipe and transmitted to the displacement detector. It The displacement detector detects the piston position based on the sensitive movement.

A probe rod is used as the magnetic sensitive body, and a magnetostrictive linear displacement detector is used as a displacement detector for detecting the torsional strain generated by the proximity of the permanent magnet to the magnetostrictive line given to the probe rod.

Further, a proximity switch sensitive to a permanent magnet or a magnetic iron piece may be used as the magnetic sensitive body. When using this magnetism sensitive iron piece, the displacement detector may be a potentiometer which detects an electric resistor according to the repeated length of the cable suspending the magnetism sensitive iron piece.

[0011]

First Embodiment A first embodiment of the present invention will be described with reference to FIGS. The piston type accumulator 1 has a piston 2
A cylinder 3 fitted with the cylinder 3 and a head cover 5 and a bottom cover 6 for closing both ends of the cylinder 3 are provided.

The piston 2 has a concave cross section and divides the inside of the accumulator 1 into a liquid chamber 10 and a gas chamber 15. At the center of the bottom portion 2a of the piston, the guide pipe 2
0 is provided so as to penetrate therethrough. In order to prevent the liquid in the liquid chamber 10 from being exposed in the gas chamber 15, the protruding end portion 20b of the guide pipe 20 is closed, and a packing or the like is provided between the bottom portion 2a of the piston and the guide pipe 20. The seal member 25 is provided.

At the free end 20a of this guide pipe,
A permanent magnet 30 is provided. This guide pipe 20
Is a non-magnetic material made of stainless steel or a plastic material. The non-magnetic material is used to prevent the permanent magnet 30 from being magnetized so as not to interfere with the sensitive operation of the magnetic sensitive body 40. This is because The fixed end portion 20b of the pipe 20 is fixed to the piston 2 by a step portion 21 and a nut 23.

The installation position of the permanent magnet 30, the diameter D of the guide pipe 20, the protruding amount l, and the entire length are appropriately selected as necessary.

A pipe insertion portion 6 is provided on the inner surface 5a of the head cover 5, and the insertion portion 6 is the pipe 2
The free end portion 20a of 0 is formed into a size that can be inserted. In this pipe insertion portion 6, a magnetic sensitive body 40 is provided so as to project,
The free end 40a is loosely fitted in the guide pipe 20.

The magnetism sensitive body 40 is a probe rod having a length substantially equal to the piston stroke, and a receive coil 42 is wound around the probe lot 40 over the entire length. This probe rod 40 has four lead wires.
It is connected to the displacement detector 50 via 1.

This displacement detector 50 is a magnetostrictive linear displacement detector, and the piston 2 is connected to the magnetostrictive line of the probe rod 40.
The position of the piston 2 can be detected by generating a torsional strain due to the approach of the permanent magnet 30 which is displaced due to the movement. Therefore, torsional strain can be generated regardless of the position of the permanent magnet 30, and the position of the piston 2 can be continuously detected.

A gas supply / discharge port 7 is provided in the head cover 5, and gas is supplied / discharged to / from the gas chamber 15 via the gas supply / discharge port 7.

The bottom cover 6 is provided with a liquid supply / discharge port 8, through which the liquid in the hydraulic circuit 9 flows into the liquid chamber 10 or the liquid supply / discharge port 8 is provided. The liquid flows out into the hydraulic circuit 9.

The operation of this embodiment will be described. The pressure of the hydraulic circuit rises due to the locking of the actuator (not shown), the pressure liquid flows into the liquid chamber 10 through the liquid supply / discharge port 8, and the piston 2 compresses the enclosed gas in the gas chamber 15 by the liquid pressure. While displacing.

When the lock of the operating element is released, the hydraulic pressure is lowered, and the piston 2 is displaced in the opposite direction due to the enclosed gas pressure.

With the displacement of the piston 2, the permanent magnet 4
0 is also displaced. At this time, current pulses are applied from the magnetostrictive linear displacement detector 50 to the probe rod 40 forming the magnetostrictive line at regular intervals. By applying this current pulse, a circumferential magnetic field is instantaneously generated in the entire axial region of the magnetostrictive line.

The permanent magnet 30 is attached to the magnetism sensitive member 40 at the position shown.
When a magnetic force is applied to, an axial magnetic field is applied in its vicinity,
A gradient magnetic field is generated by combining the axial magnetic field and the circumferential magnetic field, and the magnetostrictive line is distorted in the gradient direction. This torsional strain occurs only at the moment when the current pulse is applied, and this becomes a mechanical elastic wave and propagates on the magnetostrictive line toward both ends thereof.

When a current pulse is generated at a certain momentary interval, an induced signal due to the current pulse appears, and after t seconds, a distorted signal indicating arrival of an ultrasonic wave, which is a mechanical elastic wave, is generated.
It is detected by the strain detector. By performing a predetermined calculation based on the detected value, how far the permanent magnet 30 is from the strain detector 50 is measured, and the distance is displayed on a display device such as a CRT (not shown). With this device, the position of the permanent magnet 30 can be continuously detected each time a current pulse is applied, and the position of the piston 2 can be constantly monitored.

[0025]

[Second Embodiment] A second embodiment of the present invention will be described with reference to FIG. The difference between this embodiment and the first embodiment is that the proximity switch 7 is used instead of using a probe rod (magnetostriction line) as the magnetic sensitive body.
It means 0. The number of the proximity switches 70 is appropriately selected according to need, and for example, a plurality or a single switch is used.

When the permanent magnet 30 is in the position shown in the figure, the contact of only the proximity switch to which the permanent magnet 30 is close is turned on, and which proximity switch has operated can be detected by a displacement detector (not shown).

[0027]

Third Embodiment A third embodiment of the present invention will be described with reference to FIG. 4, but the difference from the first embodiment is that a potentiometer 80 is used as a displacement detector. In this potentiometer 80, a magnetic sensitive iron piece 81 is used as a magnetic sensitive body, the magnetic sensitive iron piece 81 is moved up and down by the displacement of the permanent magnet 30, and the length of the cable 83 in which the magnetic sensitive iron piece 81 is suspended in the guide pipe 20. Is converted into an electric resistance value and detected.

Although not shown in the figure, a potentiometer 80 is provided with a pulley capable of winding the cable 83 by utilizing the elastic force of a spiral spring. When the magnetic sensitive iron piece 81 is lowered by the permanent magnet 30,
The cable 83 is wound up from the pulley. The rotation of the pulley that winds up the cable 83 is converted into one rotation or less by the planetary gear mechanism, and the output voltage corresponding to the electric resistance value obtained at the rotation angle can be obtained. Therefore, it is possible to know the position of the piston 2 through the magnetism sensitive iron piece 81.

[0029]

Fourth Embodiment A fourth embodiment of the present invention will be described with reference to FIG. The difference between this embodiment and the first embodiment is that a stopper 100 for restricting the rising range of the piston is attached between the inner surface 5a of the head cover and the piston 2. The stopper 100 is fixed to the inner surface 5a of the head cover, but it is not always necessary to do so.
For example, the tip 2u of the piston 2 or the free end 20a of the guide pipe may be extended so that the tip 2u or the free end 20a contacts the inner surface 5a of the head cover 5 when the piston 2 moves up.

[0030]

As described above, according to the present invention, one end of the guide pipe is fixed to the piston and the other end is a free end.
Since the permanent magnet is fixed to the guide pipe, the piston can slide smoothly without being obstructed by the magnetic sensitive body. Therefore, an accurate piston position corresponding to the hydraulic pressure can be detected, and there is no fear of seal leakage.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a displacement detector.

FIG. 3 is a longitudinal sectional view of a main part showing a second embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a main part showing a third embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a main part showing a fourth embodiment of the present invention.

[Explanation of symbols]

1 Piston type accumulator 2 pistons 3 cylinders 5 head cover 6 Bottom cover 10 Liquid chamber 15 gas chamber 20 Guide pipe 30 permanent magnets 40 Magnetosensitive 50 displacement detector

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-269503 (JP, A) JP-A-5-18406 (JP, A) JP-A-4-331802 (JP, A) Actual development Sho-60- 162702 (JP, U) Actual Kaihei 2-75498 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F15B 1/00-1/26 F15B 15/00-15/28 G01B 7/00 G01D 5/18

Claims (2)

(57) [Claims] 1. A cylinder whose both ends are closed by a head cover and a bottom cover, a piston for partitioning the inside of the cylinder into a liquid chamber and a gas chamber, one end fixed to the inner surface of the head cover, and the other end free. A magnetic sensitive body, a non-magnetic guide pipe for guiding the magnetic sensitive body, a permanent magnet for operating the magnetic sensitive body, a displacement detector for detecting the piston position from the sensitive operation of the magnetic sensitive body, a piston type accumulator with a; the guide pipe has one end fixed to said piston Sareso
Is a closed end, the other end is a free end exposed to the gas chamber, the permanent magnet is fixed to the guide pipe, the head cover and the bottom cover are the inner surface of the
A piston type accumulator having a recess for accommodating the end of the guide pipe . 2. The piston type accumulator according to claim 1, wherein the piston and the guide pipe are integrally molded .