JPH0416004Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a piston position detection device used when controlling related equipment etc. as the piston of a fluid pressure cylinder moves.

Conventional technology Conventionally, such a piston position detection device for a fluid pressure cylinder has been disclosed in Japanese Patent Publication No. 46840 (1983) and Publication No. 46840 (1983),
No. 25671, Utility Model No. 55-97203, Utility Model No. 57-144604
According to these, N is applied to the piston sliding in the cylinder tube in the axial direction.
-It has a structure in which a single circular permanent magnet with an S pole (magnetic axis) is installed, and a magnetically sensitive switch such as a reed switch that is operated by the magnetic force generated by this circular permanent magnet is installed on the outside of the cylinder tube. .

Problems to be Solved by the Invention According to the above-mentioned conventional technology, when the piston speed is increased, the time during which the magnetically sensitive switch is activated by the magnetic force of the annular permanent magnet and is turned on becomes extremely short. If a control device (such as a relay) connected to a magnetically sensitive switch does not respond, increase the axial length of the annular permanent magnet and change the length of the piston so that the annular permanent magnet can be attached to it. Although the shape was changed to widen the spread of the magnetic field in the axial direction by the annular permanent magnet, there was a problem in that the specifications of these two members had to be changed. Also, for example,
51-28793, in which the piston is connected to a piston mount that extends outwardly through the cylinder wall and moves along a slot, and the slot is sealed with a sealing member. In this case, the piston mount and piston are connected at the center of the piston axis (this is convenient for mounting and operating at the center of the piston), so an annular permanent magnet is installed here. was difficult.

Means to Solve the Problem The present invention operates a magnetically sensitive switch on the outer periphery of the cylinder tube using the magnetic force of a magnet attached to a non-magnetic piston that is slidably fitted inside the cylinder tube. In the piston position detection device for a fluid pressure cylinder, the piston is provided with a pair of mounting holes arranged in parallel at a predetermined interval in the axial direction of the piston, and at least one rod-shaped permanent magnet is installed in each of the mounting holes. It is characterized in that it is fitted with one magnetic pole facing the inner circumferential surface of the cylinder tube, and the magnetism of the magnetic pole facing the inner circumferential surface of the cylinder tube is reversed.

Function Since a rod-shaped permanent magnet is fitted into each of the two mounting holes provided in the piston to form a magnetic field between these two rod-shaped permanent magnets, when increasing the axial spread of the magnetic field, This can be done by changing the positions of the two mounting holes on the piston, and only the specifications of one member need to be changed. Further, since a rod-shaped permanent magnet is attached to the piston, it can be easily applied to a piston of a rodless cylinder where it is difficult to attach an annular permanent magnet, and the piston position of a rodless cylinder can also be detected.

Embodiment Referring to FIGS. 1 to 3, a case will be described in which the present invention is applied to a rodless cylinder. A cylinder chamber 2 having a circular cross section is formed in a cylinder tube 1 having a rectangular cross section, and end caps 5 and 6 having ports 3 and 4 for supplying and discharging pressurized fluid are fixed to both ends of the cylinder tube 1, respectively. ing. A piston 7 made of a non-magnetic material such as an aluminum alloy is slidably fitted into the cylinder tube 1 . In this piston 7, mounting holes 10, 10 for bar magnets are arranged symmetrically on both sides from the center in the axial direction at a predetermined distance in the axial direction.
0, Alnico bar magnets (bar-shaped permanent magnets) 8 and 9,
The magnetic axis thereof is substantially orthogonal to the piston axial direction, and the respective magnetic poles 8a, 8b, 9a, 9b face the inner circumferential surface 1a of the cylinder tube 1, and the opposing 8a,
9a, 8b, and 9b are fitted so that their polarities are reversed and are integrated with an adhesive. Inner and outer seal bands 12 and 13, whose ends are fixed to the left and right end caps 5 and 6, are provided on the inside and outside of the slot 11, which is open over the entire length of the cylinder tube 1, so as to seal the slot 11. It's getting old. A piston yoke 14 that moves while pushing the inner and outer seal bands 12 and 13 inward and outward is connected to the center of the piston 7, and a piston mount 15 is connected to the protrusion 14a of the piston yoke 14. There is. Long grooves 16 in the axial direction are formed on the outer peripheral surfaces 2a, 2b, 2c of the cylinder tube 1.
a and 16b are formed over the entire length of the cylinder tube 1 with appropriate spacing. This long groove 1
Among 6a and 16b, the Alnico bar magnets 8 and 9
A pair of fittings 17A, 17B, 18A, 18 are provided in the long grooves 16a, 16b perpendicular to the magnetic axis direction of the
B, insert the reed switch 19 shown as a magnetically sensitive switch that comes into contact with the outer peripheral surfaces 2a and 2b between the fixtures 17A and 17B and 18A and 18B, respectively, and tighten the reed switch 19 with the setscrew. 20 and a nut 21, and is attached to a predetermined position in the axial direction of the rodless cylinder. As is well known, the reed switch 19 includes a reed piece that closes when a magnet approaches it within a vacuum glass tube 19b filled with an inert gas, and the outside of the reed switch 19 is covered with a magnetic shield cover 19a. Note that the reed switch 19 may be replaced by a magnetically sensitive switch incorporating a non-contact electronic element (such as a Hall element or a magnetoresistive element) that is sensitive to magnetic flux.

According to such a configuration, between the opposing magnetic poles 8a, 9a and 8b, 9b of the pair of Alnico bar magnets 8, 9 attached to the piston 7, the magnetic fields generated by each bar magnet alone are combined and strong. A magnetic field G is generated. Therefore, pressure fluid flows into and out of the cylinder chamber 2 from the ports 3 and 4, causing the piston 7 to move along the slot 11 together with the piston mount 15, and at the same time, the magnetic field G moves, so that the reed switch 19 is reliably activated by a strong magnetic field G to detect the piston position.

Now, when the piston speed becomes faster than normal,
Since the axial spread of the magnetic field G is constant, the time during which the reed switch 19 is activated by the magnetic field G is shorter than usual, and therefore, a switch (not shown) with a relatively slow response time connected to the reed switch 19 has a relatively slow response time. There are times when control devices such as relays cannot be fully controlled. The specifications of this rodless cylinder will be changed to accommodate this, but if you just want to expand the magnetic field a little, you can use alnico magnets 8 and 9.
The mounting hole 1 of the piston 7 remains the same.
It is only necessary to change the interval between 0 and 10, and the specifications can be easily changed.

In this application, the reed switch is installed on both sides of the cylinder tube 1, but of course it may be installed on one side.
Further, in this case, it is sufficient that the rod-shaped permanent magnets are attached to the wall 7a on one side of the piston, and each one of the magnetic poles faces the inner surface of the cylinder tube. Also,
The type of cylinder that can be installed does not have to be a rodless type as in the present application. For example, the piston rod is guided by a guide shaft that is integrally attached to the outside of the cylinder tube in parallel with the piston axis, and the piston and cylinder tube are connected to each other. may not rotate relative to each other. Further, in the present application, an alnico magnet that has a small diameter and a long length and generates a strong magnetic field is used, but a rod-shaped permanent magnet made of other magnetic materials may also be used.

Effects of the Invention As described above, according to the piston position detection device of the present invention, it is possible to generate a strong magnetic field over a relatively wide range in the piston axial direction between the two magnetic poles facing the inner peripheral surface of the cylinder tube. The magnetically sensitive switch can be operated reliably and the piston position can be detected accurately. Moreover, when trying to widen the spread of this magnetic field, the rod-shaped permanent magnet of this invention can be used to some extent by simply changing the mounting hole position of the piston without changing the specifications. Even when the piston speed is high, it is easy to extend the operation time of the magnetically sensitive switch by the time necessary to operate the control device by simply changing the specifications of one member (the piston). can be done. Even though it is easy to change the spread of the magnetic field in the axial direction of the piston, since a pair of rod-shaped permanent magnets are arranged side by side on the piston,
It can also be easily applied to rodless cylinders where it is difficult to attach a circular permanent magnet to a piston as in the past.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of the rodless cylinder, Figure 2 is a longitudinal sectional view of the rodless cylinder.
The diagram is the A-A diagram in Figure 1, and the diagram in Figure 3 is the B-B diagram in Figure 1.
It is a line diagram. 1... Cylinder tube, 1a... Cylinder tube inner peripheral surface, 7... Piston, 8, 9... Alnico bar magnet, 8a, 8b, 9a, 9b... Magnetic pole,
19...Reed switch.

Claims (1)

[Scope of utility model registration request] A piston of a fluid pressure cylinder that uses the magnetic force of a magnet attached to a non-magnetic piston that is slidably fitted in a non-magnetic cylinder tube to operate a magnetically sensitive switch on the outer circumference of the cylinder tube to detect the piston position. In the position detection device, a pair of mounting holes are arranged in parallel in the piston at a predetermined interval in the axial direction of the piston, and rod-shaped permanent magnets are installed in these mounting holes, with at least one magnetic pole facing the inner circumferential surface of the cylinder tube. What is claimed is: 1. A piston position detecting device, characterized in that the magnetic pole facing the inner circumferential surface of a cylinder tube has reverse magnetism.