JPH053927Y2 - - 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. 9 and 10, 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, between the column part 10 and the edge part 22,
In order to make the column part 10 slidable, a sliding space is provided.
is provided. 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.

[Problem to be solved by the invention] However, in the conventional dust-proof mechanism for length measuring devices, the relative movement for length measurement is repeated between the linear scale and the reading mechanism, so the edge of the column and frame It was impossible to completely seal the space between them. Furthermore, 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. 11 and 12, 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 certain 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 constructed by connecting the pillar portion 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 pillar portion 10 and the edge 22, and thereby the sliding gap of the pillar portion 10 is covered by the film of the magnetic fluid seal 9. Then seal it. As a result, a multi-layered dustproof mechanism is disclosed in which the elastic seal 6 and the magnetic fluid seal 9 work together to completely prevent oil, moisture, metal powder, etc. from entering the reading mechanism sections 3 and 4. has been done.

However, in the magnetic fluid seal 9 in such a multiple-structure dustproof mechanism, when the moving speed of the column portion 10 increases, the magnetic fluid in the forward direction of the column portion overflows onto the yoke plate 8, causing the magnetic fluid seal 9 behind the column portion 10 to undergo pressure breakdown, resulting in a deterioration of the dustproof performance.

Here, a detailed explanation will be given using FIG. 7 and FIGS. 8a, b, and c. When the pillar part 10 moves at high speed, the hollow part 24, which is sealed by the magnetic fluid seal 9, the pole pieces 8, 8', and the permanent magnet plate 7, is moved by the pillar part 10, as shown in FIG. 8a. As a partition, the column part 10 is divided into an empty part in the forward direction shown by the arrow in FIG. 7 and an empty part in the backward direction,
It will essentially be divided into two parts.

At this time, as shown in FIG. 8b, the faster the moving speed of the column 10, the more the air in the direction in which the column 10 moves forward is compressed by the column 10 itself, increasing the pressure. , the magnetic fluid seal 9 in front of the column 10 is also pushed out in the same way, and both effects combine to cause the magnetic fluid seal 9 to overflow onto the yoke plate 8.

On the other hand, similarly, the faster the movement speed of the column 10, the more the empty space in the direction in which the column 10 retreats.
As shown in FIG. 8c, the column 10 expands and reduces the pressure, and the magnetic fluid seal 9 itself behind the column 10 is also depleted, so that the film pressure of the magnetic fluid seals 9 and 9' is reduced. The magnetic fluid seal 9 becomes thinner, the seal pressure resistance decreases, and both effects combine to cause the magnetic fluid seal 9 at the rear of the column 10 to break, degrading the dustproof performance.

Therefore, in view of the above-mentioned drawbacks, the technical problem of the present invention is to completely prevent oil, moisture, metal powder, etc. from entering the reading mechanism, and to completely prevent the intrusion of oil, moisture, metal powder, etc. It is an object of the present invention to provide a dustproof mechanism for a length measuring device that prevents liquid leakage from a magnetic fluid seal and seal pressure breakdown.

[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 dust-proof mechanism for a length measuring device used in a length measuring device having a pillar section movably provided along the longitudinal extension direction of the linear scale,
For a length measuring device, comprising: a magnetic circuit section that magnetically holds a magnetic fluid for sealing the opening surface, and has a magnetic fluid sealing film made of the magnetic fluid as a substantially single layer. A dustproof mechanism is provided.

Further, according to the present invention, the magnetic circuit section is composed of a pair of unit magnetic circuits facing each other with a predetermined distance between them, and the pair of unit magnetic circuits are arranged so that the magnetic fluid is preferably held magnetically.

Further, according to the present invention, each of the pair of unit magnetic circuits includes a permanent magnet body and a pair of soft magnetic plate members facing each other while sandwiching both poles of the permanent magnet body, The ends of the pair of soft magnetic plate members in the circuit face the ends of the pair of soft magnetic plate members in the other unit magnetic circuit with the predetermined distance apart, and the magnetic fluid flows in the predetermined distance. It is preferable that the soft magnetic plate member is magnetically held between one of the ends of the pair of soft magnetic plate members facing each other with a square.

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 moving speed of the column of the length measuring device increases, the magnetic fluid seal membrane of the present invention is made of one layer, so the sealed space created by the magnetic fluid seal is better than that of the conventional one. Since it is much larger than the space sealed inside the two-layer magnetic fluid seal, pressure fluctuations in the sealed space due to the movement of the column are caused. In other words, if the width is made smaller than the width of the cavity filled with liquid, it will be compressed by the movement of the column,
Alternatively, since the amount of liquid that is deficient is reduced, the effects of the present invention can be further enhanced.

Further, it is desirable that the cross-sectional shape of the pillar portion is streamlined. Additionally, the magnetization of the ferrofluid seal is high;
It is desirable that the viscosity is low, and the strength of the magnetic field holding the magnetic fluid is also preferably high.

In addition, 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, the separation of the magnetic fluid can be reduced.
The magnetic field strength may be increased to prevent film breakage.

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

In this embodiment, except for the structure of the seal structure, the structure is similar to that of the conventional dustproof mechanism shown in FIGS. 11 to 13.

-First Embodiment- In Fig. 1a, this seal structure includes two soft magnetic pole pieces 8A, 8B extending in the longitudinal direction of a linear scale (not shown), and the pole pieces 8A, 8B. A first unit magnetic circuit 12 consisting of a plate-shaped permanent magnet 7 that is closely attached with an adhesive or the like.
With a similar configuration, two soft magnetic pole pieces 8A', 8B' and a plate-shaped permanent magnet 7' are closely attached between the pole pieces 8A', 8B' with an adhesive or the like.
A second unit magnetic circuit 12' consisting of a pole piece 8A of the first unit magnetic circuit 12 is arranged on the edge 22 of the frame 1 (see FIG. 13) facing each other at a distance. Between the end and the end of the pole piece 8A' of the second unit magnetic circuit 12'
In addition, the magnetic fluid film 9 is magnetically filled and held, thereby forming a single-layer magnetic fluid seal.

Therefore, even if the moving speed of the column part 10 (see FIG. 13) becomes faster, the sealed space by the magnetic fluid seal 9 is smaller than the conventional two-layer magnetic fluid seal (first
Since it is much larger than the sealed space (see Figure 3), pressure fluctuations in the sealed space due to movement of the column 10 are reduced, and liquid leakage and pressure breakdown can be prevented.

As shown in FIG. 1b, the condition is such that the distance l between the two opposing soft magnetic pole pieces 8A and 8B is greater than the distance g between the soft magnetic pole pieces 8A' and 8A'. (g<l) will make the single-layer ferrofluid seal more stable. On the other hand, if g>l, there is a possibility that the magnetic fluid will flow between the soft magnetic pole pieces 8A and 8B due to the relationship of magnetic resistance, resulting in the formation of the conventional two-layer magnetic fluid seal. There is sex.

-Second Embodiment- As shown in FIG. 2, in the second embodiment, the soft magnetic pole piece 8B of the first unit magnetic circuit 12 and the soft magnetic pole piece 8B of the second unit magnetic circuit 12' In order to further reduce the magnetic resistance between the pole pieces 8B', the ends of the pole pieces 8B and 8B' are bent to face each other while maintaining a predetermined distance g, thereby increasing the opposing area. The strength of the magnetic field that holds the magnetic fluid can be improved. Note that the same effect can be obtained even if the distance g between the ends of the pole pieces 8B and 8B' is reduced.

-Third Embodiment- As shown in FIG. 3a, in the third embodiment, the soft magnetic pole piece 8B of the first unit magnetic circuit 12 and the soft magnetic pole piece 8B of the second unit magnetic circuit 12' In order to substantially eliminate magnetic resistance between the body pole pieces 8B and 8B', one end of each of the pole pieces 8B and 8B' is opposed to each other with a predetermined separation distance g, and , each of the other end portions is lowered along the inner wall of the frame body 1 and magnetically short-circuited on the bottom surface of the frame body 1, and compared to the second embodiment,
The strength of the magnetic field that holds the magnetic fluid can be further improved. In addition, FIG. 3b shows a case in which the other end of each of the pole pieces 8B and 8B' is arranged around the inner wall of the frame body 1 and magnetically short-circuited.

-Fourth Embodiment- As shown in FIG. 4, the fourth embodiment has a structure that is a further modification of the third embodiment.

-Fifth Embodiment- As shown in FIG. 5, in the fifth embodiment, the first and second unit magnetic circuits 12, 12' face each other at a predetermined distance, and the permanent magnet 7 ，
7' are arranged with the same polarity. As a result, a magnetic loop is formed between the pole pieces of each of the first and second unit magnetic circuits. Pole piece 8 of first unit magnetic circuit 12
A and 8B are the opposing second unit magnetic circuits 12'
The second unit magnetic circuit 12' extends in the direction facing the magnetic field and is connected via the non-magnetic material 20 to form an independent magnetic loop. Similarly, the second unit magnetic circuit 12' also forms a magnetic loop. Therefore, the magnetic fluid constitutes a single-layer magnetic fluid seal 9 that is held in each magnetic loop, and is not dispersed into two or four magnetic paths.

-Sixth Embodiment- The configuration shown in FIG. 6 is different from the above embodiment, but shows a two-layer magnetic fluid seal having substantially the same effect as a single-layer magnetic fluid seal. It is. That is, the inner spacer section 24 surrounded between the first and second unit magnetic circuits, and the inner spacer section 2
This shows a configuration in which through holes 31 and 32 opening facing the magnet 4 are formed in the permanent magnet 7' or the pole piece 8B, respectively, to reduce pressure fluctuations in the internal gap 24. In addition, in the through holes 31 and 32,
Preferably, an air filter (not shown) is provided.

[Effects of the invention] As explained above, according to the present invention, even when the moving speed of the linear scale pillar becomes high, the magnetic fluid seal provided in the dust-proof mechanism is made into a layered structure, so that the pillar can be easily moved. It is possible to suppress pressure fluctuations on the magnetic fluid due to movement and prevent liquid leakage from the magnetic fluid seal and destruction of the magnetic fluid seal, making it possible to provide a dustproof mechanism for length measuring devices with highly reliable dustproof performance. It will be done.

[Brief explanation of the drawing]

Figures 1a and b are schematic diagrams of a first embodiment of the invention, Figure 2 is a schematic diagram of a second embodiment of the invention, and Figures 3a and b are diagrams of a second embodiment of the invention. A schematic diagram of the third embodiment, FIG. 4 is a schematic diagram of the fourth embodiment according to the present invention, FIG. 5 is a schematic diagram of the fifth embodiment according to the present invention, and FIG. 6 is a schematic diagram of the fifth embodiment according to the present invention. A schematic diagram of another embodiment having a similar effect; FIG. 7 is a schematic diagram showing a part of a conventional magnetic fluid seal; FIG. 8a,
b, c are conceptual diagrams showing the pressure fluctuation state of a conventional two-layered magnetic fluid seal when the column advances and retreats; Fig. 9 is a perspective view of a conventional dust-proof mechanism for a length measuring device; Fig. 10 is a conventional A sectional view of a dustproof mechanism for a length measuring device, and FIGS. 11 to 13 are a perspective view, a sectional view, and a partially cutaway sectional view of a sealing mechanism of a dustproof mechanism for a length measuring device that has already been filed by the applicant. be. 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
0...Nonmagnetic material, 21...Base portion, 22...Edge portion, 23...Opening surface, 24...Inner space.

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 that is locked to the edge; the holding section and the reading mechanism section are connected through the opening surface; In a dustproof mechanism for a length measuring device, which is used in a length measuring device having a column movable along the longitudinal direction, the magnetic fluid for sealing the opening surface is magnetically held, and the magnetic fluid for sealing the opening surface is held magnetically. A dustproof mechanism for a length measuring device, comprising a magnetic circuit section having a magnetic fluid sealing film made of magnetic fluid as substantially one layer. 2. In the dust-proof 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, and the pair of unit magnetic circuits are arranged in the predetermined direction. A dustproof mechanism for a length measuring device, characterized in that the magnetic fluid is magnetically held between the parts. 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.
between the ends of the pair of soft magnetic plate members facing each other with the predetermined distance
A dustproof mechanism for a length measuring device characterized by being held magnetically. 4. The dustproof mechanism for a length measuring device according to any one of claims 1 to 3, 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.