JPH0532722Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fluid pressure cylinder equipped with a position detection device that detects the position of a piston using a magnetic sensor. This relates to a fluid pressure cylinder equipped with a piston position detection device.

[Prior Art] The position detection of a piston in a fluid pressure cylinder is used to brake and lock the piston when it reaches a desired position, or to drive or stop another working machine in synchronization with the fluid pressure cylinder. It is already known to use a magnetic sensor to detect the position of the piston.

A piston position detection device using a magnetic sensor has the advantage of being usable for a long period of time, but it may malfunction due to strong magnetic fields generated by large currents near electric welding machines, electroplating devices, etc.

In order to prevent the above-mentioned malfunction, a fluid pressure cylinder has been proposed in which the head cover of the fluid pressure cylinder is formed of a ferromagnetic material and a magnetic sensor is installed within the head cover.

However, since the cylinder tube in a fluid pressure cylinder is usually made of thin-walled aluminum alloy to reduce weight, the previously proposed fluid pressure cylinders are prone to malfunction due to leakage magnetic fields from the cylinder tube side. be.

Further, in the previously proposed fluid pressure cylinder, the head cover is formed of a ferromagnetic material, so there is a problem in that existing fluid pressure cylinders cannot be used.

[Problem to be solved by the invention] The problem to be solved by the invention is to provide a fluid pressure cylinder with a piston position detection device that does not malfunction even in a strong magnetic field and can use an existing fluid pressure cylinder. There is a particular thing.

[Means for Solving the Problems] In order to solve the above problems, the present invention includes a cylinder, a sliding member having a piston and a piston rod that slide within the cylinder, and a magnetic sensor that detects the position of the piston. In the fluid pressure cylinder with a piston position detection device, a cylindrical sensor holder having a bottom wall on the piston side is installed in the cylinder parallel to the sliding direction of the sliding member, and the sensor holder is made of a magnetic material. and providing the magnetic sensor in the sensor holder,
The above problem has been solved by providing a magnet in the hollow part formed in the sliding member into which the sensor holder is loosely fitted, which operates the magnetic sensor placed in the opposing position from outside the sensor holder. be.

[Function] A magnetic sensor installed in a sensor holder made of magnetic material is magnetically shielded by the sensor holder, and in particular, the bottom wall provided on the piston side also shields leakage magnetic fields from the cylinder tube side. , will not malfunction even in strong magnetic fields.

When the cylinder is driven, the magnet provided in the hollow part of the sliding member slides to a position facing the magnetic sensor, and the magnet operates the magnetic sensor from outside the sensor holder, making it possible to detect the position of the piston. can.

In this case, since the sensor holder loosely fits into the hollow part of the sliding member, the magnet can be opposed to the magnetic sensor without changing the stroke length of the piston.

[Embodiment] FIGS. 1 and 2 show an embodiment of the present invention. This fluid pressure cylinder 1 includes a tube cover 3 having a cylinder tube 2, a head cover 4, and a rod cover 5. , 5 are made of non-magnetic material such as aluminum alloy and are integrated by appropriate means, and the piston 7 sliding inside the cylinder tube 2 is connected to a reduced diameter part formed at one end of the piston rod 8. It is screwed on, and cushion rings 9a and 9b are provided on both sides thereof. The rod cover 5 also has mounting parts 10 and 1 for mounting the fluid pressure cylinder on a suitable machine, etc.
It is equipped with 0.

A cylindrical magnet holder 12 has one end screwed onto the cushion ring 9a, and a magnet assembly 13 consisting of a plurality of ring-shaped magnets is attached to the enlarged diameter portion of the other end. 14, a magnetic holder 12, a magnetic assembly 13
The inner circumferential surface of the annular hollow part of the magnetic holder 14 has the same cylindrical surface in the sliding direction of the rod 8, and the tip of the magnetic holder 12 has the same cylindrical surface as shown in FIG. When in the terminal position, the recess 1 formed in the head cover 4 passes through the through hole 15 of the tube cover 3.
It extends to the position where it is inserted into 6.

The covers 3 and 5 have high-pressure air supply and discharge ports 18a and 18b opened in the radial direction of the covers, and through holes 15 communicating with the ports 18a and 18b.
Cushion rings 9a and 9b are provided at the opening edge of the recess 19 formed in the rod cover 5 on the piston side.
cushion packing 20 into which the
a and 20b are attached.

A cup-shaped sensor cover 22 is attached to the protrusion formed on the head cover 4 by an appropriate means, and a support member 23 attached to the sensor cover 22 with screws is attached to a bottomed cylindrical and strong support member 23. The tip of a sensor holder 24 made of a magnetic material is screwed, and the sensor holder 24 is connected to the magnetic holder 12,
Magnet assembly 13 and magnetic presser foot 1
The cushion ring 9a has an outer diameter that fits loosely into the annular hollow portion of the cushion ring 9a, and the cushion ring 9a has an outer diameter that fits loosely into the annular hollow portion of the cushion ring 9a.
It has been extended nearby.

Inside the sensor holder 24, a magnetic sensor 25 made of a magnetic sensing element such as a reed switch, a magnetoresistive element, a Hall element, etc. is fixed by appropriate means, and a lead wire 26 of the magnetic sensor 25 is fixed.
is the printed circuit board 2 attached to the support member 23
7 to the outside of the sensor cover 22 (see FIG. 2). The magnet assembly 13 has a magnetic field larger than that which saturates the magnetic shield of the sensor holder 24 when it slides to a position facing the magnetic sensor 25.
generates a piston position detection signal using the magnetic field leaked through the sensor holder 24.

Reference numeral 20 in FIG. 1 is an indicator light, and the printed circuit board 2
7.

Note that the fluid pressure cylinder of the above embodiment has cushion rings 9a, 9 that generate cushion pressure.
Although the hydraulic cylinder of the present invention is not limited to the above-mentioned embodiment, it is of course possible to omit the cushion mechanism. be.

The magnetic sensor 25 incorporated in the fluid pressure cylinder 1 of the above embodiment is not only magnetically shielded by the sensor holder 24, but also protected against leakage magnetic fields from the cylinder tube side by the bottom wall provided on the piston side. Since the magnetic sensor 25 is also shielded, the magnetic sensor 25 will not malfunction even if the fluid pressure cylinder 1 is installed near a machine or the like that generates a strong magnetic field.

When the piston 7 reaches near the end of the head side stroke by supplying and discharging pressure fluid, the magnetic sensor 2
5 operates the magnetic sensor 25 from outside the sensor holder 24 with a magnetic field greater than the magnetic field that saturates the magnetic shield of the sensor holder 24. Even if the piston 7 is installed in the sensor holder 24, the position of the piston 7 can be accurately detected.

Further, since the sensor holder 24 is loosely fitted into the hollow portion of the sliding member, the magnetic sensor 25 can be operated by the magnet assembly 13 without changing the stroke length of the piston.

Note that, as shown by the two-dot chain line in FIG. 1, if a cylinder cover 30 made of a ferromagnetic material is installed, which covers from the sensor cover 22 side to the middle of the tube cover 3, the fluid pressure cylinder 1 can be made more completely magnetic. can be shielded.

[Effects of the invention] The fluid pressure cylinder of the invention installs a magnetic sensor in a cylindrical sensor holder made of magnetic material, magnetically shields the magnetic sensor from a strong magnetic field outside the cylinder, and The piston side, where strong magnetic fields tend to leak, is bottomed, and leakage magnetic fields from the cylinder tube side are also shielded, so the magnetic sensor will not malfunction even in strong magnetic fields.

In addition, since the magnetic sensor is operated by the magnetic field of the magnet that is slid to the opposing position, it is not possible to detect the position of the piston even if the magnetic sensor is installed in a magnetically shielded sensor holder. Can be done.

Further, since the sensor holder loosely fits into the hollow portion formed in the sliding member, the magnet can be slid to a position facing the magnetic sensor without changing the stroke length of the piston.

Furthermore, since the head cover does not need to be made of ferromagnetic material, an existing fluid pressure cylinder can be used.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional front view of a main part of an embodiment of the present invention, and FIG. 2 is a side view of the same. 3...Tube cover, 4...Head cover,
5... Rod cover, 7... Piston, 8... Piston rod, 13... Magnet assembly,
24...sensor holder, 25...magnetic sensor.

Claims (1)

[Claims for Utility Model Registration] A fluid pressure cylinder equipped with a piston position detection device comprising a cylinder, a sliding member having a piston and a piston rod that slide in the cylinder, and a magnetic sensor for detecting the position of the piston, the above-mentioned A cylindrical sensor holder having a bottom wall on the piston side is installed in the cylinder parallel to the sliding direction of the sliding member, the sensor holder is made of a magnetic material, and the magnetic sensor is installed in the sensor holder. A piston position detection device characterized in that a magnet is provided in a hollow portion formed in the sliding member into which the sensor holder is loosely fitted, and that operates the magnetic sensor that has come to an opposing position from outside the sensor holder. Fluid pressure cylinder with.