JPH0452964Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention is a ring-shaped magnet that can be attached to a cylinder shaft in order to position the expanding and contracting cylinder shaft using magnetic detection means in air cylinders, oil cylinders, etc. Regarding the improvement of

[Conventional technology]

Air cylinders and oil cylinders are often used as actuators in various industrial machines. As a positioning means for the cylinder shaft (hereinafter simply referred to as shaft) in these cylinders, as shown in FIG. By arranging the magnetic sensor e close to the outer surface of the cylinder a, the magnetic sensor e detects the position of the ring-shaped magnet c, which moves with the movement of the shaft b, and uses the data. It is known to control the extension/contraction distance of shaft b based on this.

As shown in FIG. 8, the ring-shaped magnet c is externally fitted into the annular groove f of the holder d, which is H-shaped in side view. A plastic magnet c1 that is integrally molded with the magnet c1 or a rubber magnet c2 that has a notch g for expansion in the radial direction as shown in FIG. 9b is used.

[The problem that the idea aims to solve]

Plastic magnets have (BH)max≒2.0 and have a strong magnetic force, so they have the advantage of being easy to detect magnetic fields.
As shown in Figures A and B, by using a holder d with a two-member structure such as a two-piece structure, and connecting the two halves of the holder d by sandwiching the plastic magnet c1 between the holder d, the plastic magnet c1 can be placed in the annular groove f of the holder d. It is necessary to position the
Holder d has a two-member structure and requires a structure to connect the two split holders, which not only complicates the holder but also requires time and effort to install.
This was a cause of high costs.

In addition, since the rubber magnet c2 has flexibility, the 11th
By enlarging the cut as shown in the figure, it is possible to attach the rubber magnet c2 to the annular groove of the holder.Therefore, there is no need to make the holder a two-member structure, which reduces the manufacturing cost of the holder and the rubber magnet. Although it has the advantage of reducing the cost of installing it on the shaft, rubber magnets have a weak magnetic force of about (BH) max ≒ 1.6, making magnetic detection difficult. Also, the rubber magnet c2 has a notch g for expansion.
However, since the opposing end faces h and h of the cross section cut by the cut g are magnetically the same polarity, they will repel, and since the rubber magnet is flexible, it will not be possible to join. As a result of the magnetic force separating the end faces h and h, there was a problem that the mounting could not be done tightly.

The present invention was developed in view of the current situation, and provides a ring-shaped magnet that can obtain sufficient magnetic force, can be attached to the shaft with a simple holder, and reduces the manufacturing and installation costs of the holder. The purpose is to provide.

[Means to solve problems]

The gist of the present invention, which solves these problems, is to form a plurality of arc-shaped plastic magnets that form a ring shape when combined using plastic magnets made by dispersing and mixing a magnetic material into a synthetic resin, and to connect each of the plastic magnets to form a ring shape. The opposing joining end surfaces of the arc-shaped plastic magnets are made to have the same polarity so as to magnetically repel each other, and the joining end surface has an engaging portion having a force-fitting structure with a concave-convex relationship for connecting adjacent arc-shaped plastic magnets. The present invention is characterized in that these arc-shaped plastic magnets are connected by the engaging portion of the forced fitting structure by utilizing elastic deformation of the plastic magnets against magnetic repulsion.

[Operation] In order to attach the ring-shaped magnets having such a configuration to the shaft, each arc-shaped plastic magnet is fitted into the annular groove of the holder, which is H-shaped in side view and is fixed to the shaft in advance with screws or other means, and Each arcuate plastic magnet is connected to an engaging portion formed on its respective joint end surface. In this way, with the ring-shaped magnet of the present invention, when attaching the ring-shaped magnet to the shaft, there is no need to sandwich the ring-shaped magnet from both sides between the divided holders, so the structure of the holder can be simplified, and the holder can be attached to the shaft in advance. It can be fixed to the shaft, and installation is as simple as connecting an arc-shaped plastic magnet to the engaging part, so there is no need to insert the magnet from one end of the shaft like with conventional plastic magnets, and the installation time is reduced. The effort can also be greatly simplified.

In addition, the engaging parts that connect each arc-shaped plastic magnet have a force-fitting structure based on a concave-convex relationship, and by simply pressing the arc-shaped plastic magnet in a predetermined direction, the arc-shaped plastic magnet can be firmly fixed by utilizing the elastic deformation of the plastic magnet. Can be connected to. Since the opposing joint end surfaces of the arc-shaped plastic magnets to be connected are magnetized with the same polarity, the magnets are connected against the repulsive magnetic force, but once they are connected by the force-fitting structure, it becomes difficult to separate them. , the ring shape is maintained. Since the bonded portions have the same polarity, there is almost no decrease in the magnetic field strength at the bonded portions, and a ring-shaped magnet with excellent characteristics can be obtained.

〔Example〕

Next, details of the present invention will be explained based on illustrated embodiments. FIG. 1 is an explanatory diagram showing one embodiment of the ring-shaped magnet of the present invention. The ring-shaped magnet 1 is composed of arc-shaped plastic magnets 1a and 1b bisected by a line passing through the diameter. A convex portion 4a for engagement is formed on one of the joining end surfaces 2a, 3a of the arc-shaped plastic magnet 1a, and a recessed portion 5a is formed on the other side. The joint end surface 2b of the other circular arc plastic magnet 1b facing the circular arc plastic magnet 1a has a concave portion 5b for receiving the convex portion 4a, and the joint end surface 3b has a convex portion that can be fitted into the concave portion 5a. A portion 4b is formed. The convex portions 4a and 4b both have a bulging portion formed on the tip side, and the concave portions 5a and 5b respectively.
The structure is such that the elastic deformation of the plastic magnet is used to forcibly fit them into each other, making it difficult to separate them once they are fitted. Then, the opposing joint end surface 2
a and 3b and joining end surfaces 2b and 3a are each magnetized to the same polarity and are joined and connected against repulsive magnetic force. In the illustrated example, an arc-shaped plastic magnet 1a
Although a convex portion was formed on one of the bonding end surfaces 2a, 3a and a concave portion was formed on the other, a convex portion was formed on both the bonding end surfaces 2a, 3a, and the arc-shaped plastic magnet 1
It is also optional to form concave portions for receiving the convex portions on both of the bonding end surfaces 2b and 3b of the arc-shaped plastic magnet 1b facing a.

The arc-shaped plastic magnet can be divided into three parts as shown in FIG. 2, or it can be divided into four or more parts. However, when the plastic magnet has high hardness and poor flexibility, it is expected that it will be somewhat difficult to connect arc-shaped plastic magnets that are divided into three or more parts because the deformation of the engaging portion is small. However, even in such a case, if the number of divisions is an even number, each arc-shaped plastic magnet is assembled in advance and two semi-circular arc-shaped plastic magnets are assembled into the holder. If it is prepared in advance, the subsequent assembly work can be done in exactly the same way as when assembling a ring-shaped magnet divided into two parts.

Further, in the illustrated example, each arc-shaped plastic magnet is equally divided, but it may also be a combination of large arcs and small arcs.

3A and 4B and 4A and 4B show other embodiments of the engaging portion, and FIG. 3A is a case in which a water droplet-shaped convex portion 6 having a bulge at the tip is formed. , B is a case in which an engaging portion having a tapered notch that engages with each other is formed on the opposing end surfaces of the arc-shaped plastic magnet, and FIG. This is a case in which a rod-shaped projection 8 having a shape formed therein is provided, a hole 9 capable of receiving the rod-shaped projection 8 is formed on the other joint end surface, and both of these form an engaging portion. It is up to you which of these aspects to adopt, but generally speaking, plastic magnets have low flexibility, so
The one shown as FIG. 3B is advantageous. The illustrated example has a structure in which the joint end surfaces of arc-shaped plastic magnets are pressed together and forcedly fitted together, but this does not preclude the use of other force-fitted structures having a concave-convex relationship.

The material of each arc-shaped plastic magnet constituting the ring-shaped magnet is appropriately selected depending on the orientation of the magnetic poles and the magnetic field strength. It is preferable to use designed barium ferrite or strontium ferrite powder, and the synthetic resin used as the binder is one or two selected from nylon 6, nylon 12, polypropylene, polybutene, or polyphenylene sulfide. It is preferable to use a mixture of more than one species. These synthetic resins have excellent dispersibility of the magnetic material and excellent corrosion resistance, so it is possible to provide a ring-shaped magnet that does not change much over time and does not require maintenance.

To manufacture a ring-shaped magnet, a synthetic resin containing the magnetic material dispersed and mixed is injected into a mold to integrally mold a ring-shaped member, and after the ring-shaped member is taken out, it is magnetized using a separate device. Alternatively, it is also possible to place a magnetizing magnet made of a sintered magnet or an electromagnet in the mold for molding the ring-shaped member, to form a magnetic field within the mold, and to magnetize the ring-shaped member at the same time as molding. . Various orientations of the magnetic poles can be considered, such as polar anisotropic orientation, radial anisotropic orientation, and axial anisotropic orientation.

There are various methods for manufacturing the ring-shaped magnet of the present invention, but as a method for manufacturing a ring-shaped magnet with a magnetization mode as shown in FIG. 5A, for example, as shown in FIG. There is a method of dividing and cutting a plurality of arc-shaped plastic magnets 1a and 1b so that an engaging part with a force-fit structure is formed by unevenness at the part. The opposing end faces of the two will have the same polarity and will repel each other. However, in the present invention, the engagement portion formed on the joint end faces is a forced fit structure due to the uneven relationship, so after the joint is connected against the repulsive magnetic force, the joint end faces firmly maintain the ring shape even if they repel each other. Moreover, a strong magnetic field can be exerted even at the joint portion without decreasing the magnetic force at the engaging portion.

As shown in FIG. 6, the ring-shaped magnet having such a structure is externally fitted into a holder d which is fixed in advance to the shaft b by screws or the like. The holder d is an annular member having an annular groove f and is H-shaped in side view,
It is integrally molded from magnetic materials such as iron and nickel.

To fit the ring-shaped magnet into the annular groove f of the holder d, use the arc-shaped plastic magnets 1a and 1b.
are placed opposite each other with the holder d in between so that their joining end surfaces face each other, and then both arc-shaped plastic magnets are pushed from both sides against the repulsive magnetic force to form the convex portion 4.
a, 4b are forcibly fitted into the recesses 5a, 5b, and the inner peripheral edge 11 thereof is brought into contact with the bottom of the annular groove f to complete the installation.

The shaft b to which the ring-shaped magnet is attached in this way is inserted into a cylinder a made of a non-magnetic material such as stainless steel, as shown in FIG. A magnetic sensor e is placed nearby. The position of the ring-shaped magnet that moves within the cylinder as the shaft moves is detected by using a magnetic sensor to detect the magnetic field generated by the ring-shaped magnet.

As the magnetic sensor, it is also possible to use something other than the semiconductor magnetic sensor described above. For example, by providing an iron piece that moves up and down in response to the magnetic attraction force of a ring-shaped magnet, and providing contacts at the top and bottom of the iron piece. It is also possible to create a non-contact relay-like structure that detects the proximity of a ring magnet by, for example, an iron piece coming into contact with a lower contact when the ring magnet approaches, and use this as a magnetic sensor. Adopted.

As described above, the ring-shaped magnet according to the present invention is
The opposing joining end surfaces of the connected arcuate plastic magnets are magnetized to the same polarity, and an engaging portion having a force-fitting structure having a concave and convex relationship is formed on the joining end surface,
In addition to arranging the end faces that repel each other,
Since the ring-shaped magnet is constructed by force-fitting the engaging part using the elastic deformation of the plastic magnet, the separate type holder with the two-member structure can be attached to the shaft like a conventional ring-shaped magnet. It has the basic effect of being able to use an integrated holder with a simple structure without the need for a The shape can be firmly maintained. Moreover, since the joints of the arcuate plastic magnets have the same polarity, the magnetic field strength at the joints does not decrease, and a ring-shaped magnet with excellent characteristics can be obtained. Moreover, since this ring-shaped magnet is made of plastic magnet, the magnetic field is strong and can be easily detected by a magnetic sensor.

Furthermore, when barium ferrite or strontium ferrite, which is structurally designed to be suitable for anisotropy, is selected as the magnetic material for the plastic magnet, the magnetic poles can be oriented freely and a strong magnetic field can be obtained. or,
When one or a mixture of two or more selected from nylon 6, nylon 12, polypropylene, polybutene, or polyphenylene sulfide is used as the synthetic resin for the binder, these synthetic resins disperse the magnetic material. This makes it possible to obtain ring-shaped magnets of uniform quality and excellent durability.

[Effect of idea]

The ring-shaped magnet according to the present invention is produced by molding a plurality of circular arc-shaped plastic magnets that become a ring-shaped magnet when combined, and magnetizing the opposing joint end surfaces of the connected circular arc-shaped plastic magnets to have the same polarity. A ring is formed by forming an engaging part with a force-fitting structure consisting of unevenness on the joint end face, arranging the mutually repelling end faces facing each other, and force-fitting the engaging part by utilizing the elastic deformation of the plastic magnet. Because the magnet is configured as a magnet, unlike conventional ring-shaped magnets, there is no need for a separate holder consisting of two parts when attaching it to the shaft, and a simple integrated holder can be used. In addition to having the basic effect of being extremely easy to use, since it is a force-fitting structure, the ring shape can be firmly maintained by exerting a retaining effect after connection. Moreover, since the joints of each arc-shaped plastic magnet are joined with the same polarity, the magnetic field strength at the joint does not decrease, and the excellent magnetic properties of the plastic magnet itself can be utilized to the maximum. In this way, since a ring-shaped magnet capable of generating a strong magnetic field is obtained, detection by a magnetic sensor placed outside the cylinder becomes easy.

[Brief explanation of the drawing]

1A and 1B are explanatory diagrams showing one embodiment of the ring-shaped magnet according to the present invention, FIG. 2 is an explanatory diagram showing another embodiment of the ring-shaped magnet according to the present invention, and FIGS.
Figures A and B are explanatory diagrams showing various aspects of the engaging part;
Figures A and B are explanatory diagrams showing the orientation of the magnetic poles when joining arc-shaped plastic magnets. Figure 6 A and B are explanatory diagrams showing how to attach the arc-shaped plastic magnet to the holder. Figure 7 is a ring-shaped plastic magnet. An explanatory diagram showing the state in which the magnet is attached to the shaft and inserted into the cylinder. Figure 8 (a) is a front view of the holder, Figure 8 (b) is a side view of the same, Figure 9 (a) and (b) are conventional ring-shaped magnets, FIGS. 10A and 10B and FIG. 11 are explanatory diagrams showing a conventional method of attaching a ring-shaped magnet. a... Cylinder, b... Shaft, c... Ring-shaped magnet, d... Holder, e... Magnetic sensor, f... Annular groove, g... Notch, h... End face, 1... Ring-shaped magnet , 1a, 1b...Circular plastic magnet, 2a, 2b...Joining end surface, 3
a, 3b...joint end surface, 4a, 4b...convex portion, 5
a, 5b...Concave portion, 6...Water droplet-shaped protrusion, 7...Engaging portion, 8...Bar-shaped protrusion, 9...Hole, 11...Inner peripheral edge.

Claims (1)

[Scope of Claim for Utility Model Registration] A ring-shaped magnet for position detection that is externally fixed to the cylinder shaft of an air cylinder or oil cylinder, etc. with a holder interposed therebetween, in which a magnetic material is dispersed and mixed in a synthetic resin. A plurality of arc-shaped plastic magnets are formed into a ring shape when combined, and the opposite joining end surfaces of the connected arc-shaped plastic magnets are made with the same polarity so as to magnetically repel each other. At the same time, the joint end face is provided with an engaging portion having a force-fitting structure due to a concave-convex relationship for connecting adjacent arc-shaped plastic magnets, and these arc-shaped plastic magnets are connected to each other by resisting magnetic repulsion. A ring-shaped magnet configured by being connected by the engaging portion of the forcible fitting structure using the elastic deformation of the ring.