JPH0743457Y2 - Cylinder magnetic shield device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a magnetic shield device for a cylinder equipped with a piston position detection sensor.

[Conventional technology]

Conventionally, there is a cylinder case in which a sensor mounting groove extending in the axial direction of the cylinder is formed on the outer peripheral surface of the cylinder case, and a detection switch having a sensor incorporated therein is mounted in the sensor mounting groove. Further, a magnet is provided on the outer circumference of the piston head, and the position of the piston head can be detected based on the detection of magnetism by the sensor. However, since the cylinder sensor of not only reacts to the magnetism of the piston head magnet but also to the magnetism from the outside, using the cylinder in a place where magnetism is generated around it may cause malfunction of the detection switch. There was a problem that there is.

In order to solve the above-mentioned problems, there is a method in which the detection switch is covered with a magnetic shield member so that the sensor in the detection switch is not affected by the magnetism around the cylinder.

[Problems to be solved by the device]

However, in a cylinder in which the detection switch is covered with a magnetic shield member, the shape of the detection switch is large as a whole, so it is necessary to make the sensor mounting groove of the cylinder large. There is a problem that it must be increased. Also, since the magnetic shield member only covers the detection switch, there is a risk that the magnet of the piston head will be demagnetized by the magnetic field from the outside. There is also a problem that may not work properly.

The present invention has been made in order to solve the above problems, and its purpose is to prevent malfunction of the detection switch due to magnetism without increasing the size of the detection switch and to reduce the magnet of the piston head. An object of the present invention is to provide a magnetic shield device capable of preventing magnetism.

[Means for Solving the Problems]

To achieve the above object, in the present invention, in a cylinder in which a sensor for detecting a piston position can be attached to the outer circumference of a cylinder case, a magnetic shield member for blocking magnetism from the outside of the cylinder is provided along the outer circumference surface of the cylinder case. And the magnetic shield member covers almost the entire outer peripheral surface of the cylinder case.

[Action]

Therefore, in this invention, the magnetism from the outside of the cylinder is absorbed by the magnetic shield member covering the cylinder case and does not affect the magnets of the detection switch and the piston head.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 4, a sensor mounting groove 3 extending in the axial direction of the piston rod 2, that is, the axial direction of the cylinder is formed on two outer peripheral surfaces of the cylinder case 1 which correspond to each other. The detection switch 4 is attached to the. A hooking portion 5 is formed opposite to the opening edge on the outer surface side of the sensor mounting groove 3, and projecting portions 6 are provided on both sides of the detection switch 4. Further, a downward housing hole 7 is formed in the detection switch 4, and a nut 8 is non-rotatably fitted in the housing hole 7. An insertion hole 9 is formed through the detection switch 4 so as to communicate with the screw hole of the nut 8, and a screw 10 that is inserted through the insertion hole 9 is screwed into the nut 8.

As shown in FIGS. 2 and 3, the detection switch 4 is internally provided with a sensor 12 for detecting the position of the piston head 11. The sensor 12 is a magnetic sensor. Further, as shown in FIG. 4, a pair of permanent magnets 13 are attached to the outer circumference of the piston head 11, and each permanent magnet 13 is arranged at a position closest to the sensor mounting groove 3. The piston position can be detected based on the magnetic sensing of the sensor 12 incorporated in the detection switch 4.

As shown in FIGS. 1 to 4, the cylinder case 1 is covered with a pair of magnetic shield plates 14 made of soft iron and having a function as a magnetic body. The magnetic shield plate 14 has a U-shaped cross section, and covers substantially the entire surface of the cylinder case 1 and has both edges extending to the vicinity of the sensor mounting groove 3. And the third
As shown in the figure, the portions of the magnetic shield plate 14 facing the both ends of the sensor mounting groove 3 are further extended to the sensor mounting groove 3 side so that the magnetism is prevented from entering from both ends of the sensor mounting groove 3. Has become. The magnetic shield plate 14 is fixed to the side surface of the cylinder case 1 by a fixing screw 15.

Next, the operation of the magnetic shield device configured as described above will be described.

Now, in order to fix the detection switch 4 in the sensor mounting groove 3 of this cylinder, the screw 10 is screwed into the nut 8 and the tip of the screw 10 is pressed against the bottom surface of the sensor mounting groove 3. The protrusion 6 of the detection switch 4 is pressed against the hooking portion 5 of the sensor mounting groove 3 by force, whereby the detection switch 4 is fixed in the sensor mounting groove 3.

When the magnetic shield plate 14 is attached to the outer surface of the cylinder on which the detection switch 4 is mounted as described above with the fixing screw 15, the magnetism from the outside of the cylinder is absorbed by the magnetic shield plate 14 that covers the cylinder case 1 and the detection switch 4 is attached. Also, the permanent magnet 13 of the piston head 11 is not affected. Therefore, as long as the magnetic shield plate 14 does not cause magnetic saturation, there is no risk that the detection switch 4 will malfunction or the permanent magnet 13 of the piston head 11 will be demagnetized due to external magnetism. Further, since the cylinder case 1 is simply covered with the plate-shaped magnetic shield plate 14, the cylinder case 1
The shape of is not so large.

The invention is not limited to the above embodiment,
For example, the magnetic shield plate 14 may be provided integrally with the cylinder case 1, and the configuration of each part may be arbitrarily modified and embodied without departing from the spirit of the invention.

[Effect of device]

As described above in detail, according to the present invention, it is possible to prevent malfunction of the detection switch due to external magnetism and prevent demagnetization of the permanent magnet of the piston head without increasing the size of the detection switch. It has the excellent effect of being able to

[Brief description of drawings]

1 is a side view showing an embodiment of a magnetic shield device embodying the present invention, FIG. 2 is a front view thereof, FIG. 3 is a plan view thereof, and FIG. 4 is a front sectional view thereof. Cylinder case 1, sensor mounting groove 3, piston head 1
1, sensor 12, permanent magnet (magnet) 13, magnetic shield plate (magnetic shield member) 14.

Claims (1)

[Scope of utility model registration request] 1. A cylinder in which a sensor (13) for detecting a piston position can be mounted on the outer periphery of a cylinder case (1), wherein a magnetic shield member (14) for blocking magnetism from the outside of the cylinder is provided in the cylinder case (1). A magnetic shield device, which is provided along the outer peripheral surface of a cylinder case (1) and substantially covers the entire outer peripheral surface of the cylinder case (1).