JPH053926Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to a dustproof mechanism for a length measuring device.

[Prior Art] As shown in FIGS. 4 and 5, a conventional length measuring device has a base portion 21 on which a linear scale 2 is mounted.
and an edge 22 forming an opening surface 23 extending upward from the edge of the base 21 and opening along the longitudinal extension direction of the linear scale 2; A reading mechanism section (including a light emitting section 3 and a light receiving section 4) 3 and 4 for reading the linear scale 2 and a reading mechanism section (including a light emitting section 3 and a light receiving section 4), which is housed in It has a holding part 5 and a column part 10 that passes through an opening surface 23 and connects the holding part 5 and the reading mechanism parts 3 and 4.

At this time, a sliding gap is provided between the column 10 and the edge 22 to allow the column 10 to slide. Therefore, there is a possibility that oil, moisture, metal powder, etc. may enter the reading mechanism sections 3 and 4 from between them.

Therefore, conventionally, an elastic seal 6 made of rubber or the like is provided between the column 10 and the edge 22 in order to prevent dust from reading the reading mechanisms 3 and 4. This prevents oil, moisture, metal powder, etc. from entering.

[Problems to be solved by the invention] However, in the conventional dust-proof mechanism for length measuring devices, because the relative movement for length measurement is repeated between the linear scale and the reading mechanism, the edge of the column and frame It was impossible to completely seal the space between them. Moreover, the sliding movement of the pillar portion generates abrasion powder of the elastic seal, which contaminates the light receiving portion of the reading mechanism and causes reading errors.

On the other hand, the patent application filed in 1983 by the same applicant as the present application
According to Publication No. 180102 (filed on July 21, 1962), by providing a magnetic fluid seal between the column and the edge at a position below the elastic seal,
A mechanism is disclosed that completely prevents the intrusion of oil, moisture, metal powder, etc., and the abrasion powder of the above-mentioned elastic seal.

Specifically, as shown in FIGS. 6 and 7, in addition to the elastic seal 6 described above, a pair of elastic seals 6 that extend along the entire length of the linear scale 2 in the longitudinal direction and face each other at a constant distance are provided. A pair of unit magnetic circuits comprising soft magnetic pole piece (yoke) plates 8, 8 and a permanent magnet plate 7 tightly sandwiched between the pair of yokes 8, 8 are connected to the column part 10. A magnetic fluid is provided on the opposing edges 22 and is magnetically filled and held over the entire length of the hollow portion 24 formed between the pair of yoke plates 8 in each unit magnetic circuit. By injecting the seal 9, a film of the magnetic fluid seal 9 is formed between the column 10 and the edge 22, and thereby the sliding gap of the column 10 is covered by the film of the magnetic fluid seal 9. Then seal it.
As a result, the elastic seal 6 and the magnetic fluid seal 9 work together to prevent oil from entering the reading mechanisms 3 and 4.
A multilayered dustproof mechanism that completely prevents moisture, metal powder, etc. from entering has been disclosed.

However, in the case of the magnetic fluid seal in such a multilayer dustproof mechanism, if the scale is arranged so that the longitudinal direction is along the vertical direction, the magnetic fluid seal on the upper side will flow downward due to gravity. The drawback was that the magnetic fluid seal membrane on the side was torn and the dustproof performance deteriorated.

In view of the above drawbacks, the technical problem of the present invention is to completely prevent oil, moisture, metal powder, etc. from entering the reading mechanism, and to ensure that the longitudinal direction of the linear scale is parallel to the vertical direction. It is an object of the present invention to provide a dustproof mechanism for a length measuring device that does not cause film breakage of a magnetic fluid seal even when the magnetic fluid seal is installed.

[Means for Solving the Problems] According to the present invention, there is provided a frame body defining a storage space containing a linear scale and a reading mechanism for reading the linear scale, and a frame body provided on one end surface of the frame body. An edge forming an opening surface opened along the longitudinal extension direction of the linear scale, a holding section movable relative to the frame body, and connecting the holding section and the reading mechanism section through the opening surface. , a dustproof mechanism for a length measuring device used in a length measuring device having a column movable along the longitudinal extension direction of the linear scale, wherein a magnetic fluid for sealing the opening surface is magnetically applied to the length measuring device; There is obtained a dustproof mechanism for a length measuring device, characterized in that it includes a magnetic circuit section that holds the linear scale and increases the magnetic strength along the longitudinal extension direction of the linear scale.

Further, according to the present invention, the magnetic circuit section is comprised of a pair of unit magnetic circuits facing each other with a predetermined distance between them, and the pair of unit magnetic circuits is configured to supply the magnetic fluid with a predetermined distance. A dustproof mechanism for a length measuring device that is magnetically held is obtained.

Further, according to the present invention, each of the pair of unit magnetic circuits has a permanent magnet body and a pair of soft magnetic plate members facing each other while sandwiching both poles of the permanent magnet body, and in one unit magnetic circuit, The ends of the pair of soft magnetic plate members face the ends of the pair of soft magnetic plate members in the other unit magnetic circuit with the predetermined distance apart, and the permanent magnet bodies have different magnetic intensities. Consisting of multiple permanent magnets,
A dustproof mechanism for a length measuring device is obtained, wherein the plurality of permanent magnets are arranged along the longitudinal extension direction of the linear scale.

Further, according to the present invention, each of the pair of unit magnetic circuits has a permanent magnet body and a pair of soft magnetic plate members facing each other while sandwiching both poles of the permanent magnet body, and one unit magnetic circuit The ends of the pair of soft magnetic plate members in the other unit magnetic circuit face the ends of the pair of soft magnetic plate members in the other unit magnetic circuit with the predetermined distance
There is provided a dustproof mechanism for a length measuring device, characterized in that the linear scale is gradually narrowed along the longitudinal direction of the linear scale.

Further, according to the present invention, there is obtained a dustproof mechanism for a length measuring device, characterized in that an elastic sealing member for sealing between the edge and the column is provided on the edge.

More specifically, even when the longitudinal extension direction of the linear scale of a length measuring device is parallel to the vertical direction, the magnetic fluid film of the present invention can be used, for example, in a pair of units facing each other. If the distance between the magnetic circuits is gradually narrowed from the lower end to the upper end in the longitudinal direction of the linear scale, the magnetic resistance at the distance is an increasing function of the distance, so the distance between the magnetic circuits becomes The magnetic field strength at will gradually increase from the bottom to the top. For this reason, the magnetic fluid film is magnetized by the magnetic field (magnetic field strength) between the pair of unit magnetic circuits, so that the magnetic energy (negative energy) gradually increases from the lower end to the upper end. Therefore, the gravitational (potential) energy (positive energy) of the magnetic fluid that is magnetically held between
Even if it gradually increases in proportion to the height in the vertical direction, the magnetic energy (negative energy) also increases, so as a result, the increase in potential energy is canceled out.

Therefore, even if the magnetic fluid on the upper side of the magnetic fluid film increases in potential energy due to gravity, magnetic energy is supplied to cancel it, so it does not flow to the lower side, and as a result, the magnetic fluid increases. This can prevent the upper membrane from tearing.

It goes without saying that in the magnetic fluid seal to which the present invention relates, the distance between the lower end and the upper end is specified within a range in which the column that moves within the distance can move smoothly. It is.

Furthermore, although it is less economical, it is possible to reduce the magnetic field strength between the magnetic fluids by replacing the permanent magnets that make up the unit magnetic circuit with ones that have higher magnetic properties, or by increasing the volume of the permanent magnets. Strengthen it,
It is also possible to prevent the film from breaking.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

In addition, this embodiment employs the same structure as the conventional dustproof mechanism shown in FIGS. 6 to 8, except for the structure of the seal structure.

In FIGS. 1a and 1b, the present seal structure according to the first embodiment includes two soft magnetic pole pieces 8 extending in the longitudinal direction of a linear scale (not shown),
8 and a first unit magnetic circuit 12 consisting of a plate-shaped permanent magnet 7 that is closely attached between the pole pieces 8, 8 with an adhesive or the like, and two soft magnetic pole pieces 8' having a similar configuration. . 8) are placed facing each other with a distance between them, and the ends of the pole pieces 8, 8 of the first unit magnetic circuit 12 and the second
The magnetic fluid film 9 is magnetically filled and held between the ends of the pole pieces 8' and 8' of the unit magnetic circuit 12'. It is provided so that it gradually decreases from the side to the upper end side. In addition, the first and second
Both ends of the unit magnetic circuits 12, 12' in the longitudinal direction are tightly fixed to a non-magnetic packing 11 (made of fluorocarbon rubber, a resin made from a fluorocarbon coating, or a non-magnetic metal such as A1).

Therefore, in this configuration, the distance between the pole pieces in the first and second unit magnetic circuits is 30
Since the magnetic resistance is arranged to gradually decrease from the lower end to the upper end along the vertical direction, the magnetic resistance at the interval 30 also decreases. Conversely, the magnetic field strength in the interval 30 increases from the bottom to the top. Therefore, the gravitational potential energy (positive energy) applied to the magnetic fluid film 9, which increases from the lower end to the upper end, is reduced by the magnetization energy (negative energy) of the magnetic fluid, and preferably between 30
By appropriately adjusting the distance between the two, they can cancel each other out, so that it is possible to prevent the magnetic fluid from flowing downward.

Note that both ends of the pair of unit magnetic circuits 12, 12' are in close contact with the non-magnetic packing 11. This is because there is a magnetic circuit discontinuity at the end of the unit magnetic circuits 12, 12', and due to the leakage magnetic field due to the magnetic discontinuity, the magnetic fluid of the magnetic fluid film 9 is magnetically dispersed in each unit. This is to prevent leakage to the outside through the magnetic circuits 12, 12'. Also,
The reason why a fluorocarbon-based material such as volatile fluorocarbon rubber is used for the material of the non-magnetic packing 11 is that since the magnetic fluid itself is oil-based, it is possible to prevent the magnetic fluid from flowing out due to wetting.

Next, Fig. 2 a, b, and c show the second embodiment of the present invention.
An example is shown below.

In the second embodiment, the permanent magnets 7 and 7' shown in the first embodiment are made into a permanent magnet group consisting of four permanent magnets A, B, C, and D each having different magnetic properties. This is a characteristic feature.
The magnitude of the magnetic flux density in a cross section perpendicular to the magnetization direction of the permanent magnet group is set to be in the order of A<B<C<D. Therefore, the magnetic field strength in the interval 30 increases sequentially in four steps from the lower end to the upper end. Therefore, effects similar to those obtained in the first embodiment can be obtained. In addition,
Although the number of such permanent magnet groups is four in this embodiment, it is clear that the gist of the present invention is not limited to these four.

Next, a third embodiment of the present invention is shown in FIGS. 3a, 3b, and 3c.

In this embodiment, each pole piece 8 of each pole piece on the reading mechanism side, It is characterized in that a yoke plate 13 made of a soft magnetic material is attached so that the yoke plates 8' are connected to each other so as to be integrated. That is, by attaching this yoke plate 13 to a part of the upper end portion of the first and second unit magnetic circuits 12, 12' on the reading mechanism side, unit magnetic circuit 1
2, 12', each pole piece 8 on the holding part side,
The vertical magnetic field strength between 8' increases from the lower end to the upper end. Therefore, effects similar to those of the first embodiment can be obtained.

[Effect of the invention] As explained above, according to the invention, even if the longitudinal extension direction of the built-in linear scale is installed parallel to the vertical direction, the magnetic fluid provided in the dust-proof mechanism can be By controlling the strength of the magnetic field held in the magnetic field, it is possible to effectively prevent the downward flow of the magnetic fluid due to gravity, resulting in highly reliable dustproof performance that does not cause the magnetic fluid film to break. A dustproof mechanism for a length measuring device is obtained.

[Brief explanation of drawings]

Figures 1a and 1b are schematic diagrams of the first embodiment of the present invention, where a is a top view and b is an A-A diagram of the first embodiment.
2 is a schematic view of a second embodiment of the present invention, a is a top view thereof, b is a side view thereof, and c is a BB sectional view thereof; FIG. 3 is a schematic view of the third embodiment of the present invention, in which a is a top view, b is a side view, c is a sectional view taken along line C-C, and FIGS. A perspective view and a cross-sectional view of a dust-proof mechanism for a length-measuring device, and FIGS. 6 to 8 are a perspective view, a cross-sectional view, and a partial cutaway of the sealing mechanism of a dust-proof mechanism for a length-measuring device that has already been filed by the applicant. FIG. 1...Frame, 2...Linear scale, 3...
... Light emitting section, 4 ... Light receiving section, 5 ... Holding section, 6 ...
Elastic sealing member, 7, 7'...Permanent magnet, 8,
8'...Permanent magnet plate, 9...Magnetic fluid, 10...
Column part, 11...Non-magnetic packing, 12...First
and a second unit magnetic circuit, 13...yoke plate, 2
1... Base portion, 22... Edge portion, 23... Opening surface.

Claims (1)

[Claims for Utility Model Registration] 1. A frame body defining a storage space containing a linear scale and a reading mechanism for reading the linear scale, and a longitudinal extension of the linear scale provided on one end surface of the frame body. an edge forming an opening surface opened along the direction; a holding section movable relative to the frame body; connecting the holding section and the reading mechanism section through the opening surface; A dustproof mechanism for a length measuring device used in a length measuring device having a column movable along an extension direction, which magnetically holds a magnetic fluid for sealing the opening surface, and A dustproof mechanism for a length measuring device, comprising a magnetic circuit portion whose strength increases along the longitudinal direction of the linear scale. 2. In the dustproof mechanism for a length measuring device according to claim 1, the magnetic circuit section is composed of a pair of unit magnetic circuits facing each other with a predetermined distance apart,
The pair of unit magnetic circuits, during the predetermined period,
A dustproof mechanism for a length measuring device, characterized in that the magnetic fluid is held magnetically. 3. In the dustproof mechanism for a length measuring device according to claim 2, the pair of unit magnetic circuits each include a permanent magnet body and a pair of soft magnetic plate members facing each other with both poles of the permanent magnet body sandwiched therebetween. The ends of the pair of soft magnetic plate members in one unit magnetic circuit are connected to the ends of the pair of soft magnetic plate members in the other unit magnetic circuit for the predetermined distance.
The permanent magnet body is composed of a plurality of permanent magnets having mutually different magnetic strengths,
A dustproof mechanism for a length measuring device, wherein the plurality of permanent magnets are arranged along the longitudinal direction of the linear scale. 4. In the dustproof mechanism for a length measuring device according to claim 2 or 3, the pair of unit magnetic circuits includes a permanent magnet body and a pair of soft magnetic plate members facing each other with the poles of the permanent magnet body sandwiched therebetween. and the ends of the pair of soft magnetic plate members in one unit magnetic circuit face the ends of the pair of soft magnetic plate members in the other unit magnetic circuit with the predetermined distance 〓. The dustproof mechanism for a length measuring device is further characterized in that the predetermined distance is gradually narrowed along the longitudinal direction of the linear scale. 5. The dustproof mechanism for a length measuring device according to any one of claims 1 to 4, characterized in that an elastic sealing member for sealing between the edge and the column is provided on the edge. Dust-proof mechanism for length measuring devices.