JP2973660B2 - Moving distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving distance measuring apparatus, and more particularly to a moving distance measuring apparatus which improves the resolution of reading a magnetic scale by a magnetic detection sensor to improve the measuring accuracy of the moving distance of a moving object.

[0002]

2. Description of the Related Art As a device for measuring a moving distance of a moving object such as an XY table of a wire bonder, there is a moving distance measuring device generally called a magnetic encoder. This device generally includes a magnetic scale attached to a moving object, and a magnetic detection sensor attached to an external member so as to face the magnetic scale and reads a magnetic scale of the scale. When the body moves, the magnetic scale also moves. The magnetic detection sensor reads the scale of the movement of the scale, and measures the moving distance of the moving body.

[0003]

By the way, a gap having a predetermined width is provided between the magnetic scale and the magnetic detection sensor so as not to hinder the movement of the scale.
Since the resolution of the magnetic detection sensor decreases in inverse proportion to the distance, the narrower the gap, the higher the measurement accuracy. Therefore, it is conceivable to reduce this gap as much as possible in order to increase the measurement accuracy. However, if the surface accuracy of the magnetic scale is rough, the magnetic detection sensor may come into contact with the magnetic scale during the measurement and damage the sensor. Therefore, conventionally, when mounting the magnetic scale and the magnetic encoder, the positioning of each mounting position was adjusted with a gap as far as possible without the tip end surface of the magnetic detection sensor coming into contact with the surface of the magnetic scale.
As described above, when the surface accuracy of the magnetic scale is rough, for example, there is a place where a relatively large gap is formed during the movement of the moving object, and there is a limit in narrowing the gap.

Accordingly, an object of the present invention is to provide a moving distance measuring device capable of improving the resolution of reading a magnetic scale by a magnetic detection sensor and improving the accuracy of measuring the moving distance of a moving object.

[0005]

For this purpose, the present invention provides a magnetic scale made of a magnetic material, a magnetic detection sensor facing the magnetic scale and reading a magnetic scale of the scale, and a magnetic detection sensor mounted on the magnetic scale. Block, a bracket to which the block is attached, an elastic member interposed between the block and the bracket to urge the block toward the magnetic scale, and an air member provided in the block to allow air to flow through the magnetic scale. A moving distance measuring device is composed of an air pad for ejecting air and air blowing means for communicating with the air pad and ejecting air from the air pad to secure a minimal gap between the magnetic scale and the magnetic detection sensor. And the magnetic scale or bracket is relatively moved with respect to the moving object or the external member. It is those that are Attach.

[0006]

According to the above construction, the air blowing means is driven,
When air is jetted from the air pad to the magnetic scale, the block is pushed by air pressure and the elastic member contracts, thereby forming a very small gap between the magnetic scale and the magnetic detection sensor.

Next, when the moving object is moved while maintaining this state, the magnetic scale or the magnetic detection sensor attached to the moving object also moves on the surface of the magnetic detecting sensor or the magnetic scale while securing the gap. The magnetic detection sensor reads the scale of the magnetic scale corresponding to the movement, and measures the moving distance of the moving object.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a use state of the moving distance measuring device. 1 is a moving table as a moving object, 2 is a nut provided at the lower part of the table 1, 3
Is a ball screw screwed into the nut 2, and M is a motor. When the motor M is driven, the ball screw 3 rotates and the moving table 1 moves in the direction of the arrow.

Reference numeral 4 denotes a long magnetic scale made of a magnetic material, which is attached to a side surface of the moving table 1 with its length direction aligned with the moving direction of the moving table 1. Reference numeral 4a denotes a magnetic scale formed on the surface of the magnetic scale 4, and is formed in a vertical stripe shape at a pitch of, for example, 100 to 500 μm.

In FIGS. 2 and 3, reference numeral 5 denotes a magnetic detection sensor which faces the magnetic scale 4 and reads a magnetic scale 4a of the scale 4. Reference numeral 6 denotes a block to which the magnetic detection sensor 5 is attached. As shown in FIG. 4, a surface 6a of the block 6 facing the magnetic scale 4 is provided.
A projection 6b, to which the magnetic detection sensor 5 is attached, protrudes from the center of the projection. 7 is an air pad 18 (described later)
, And formed through the front and back surfaces of both ends of the block 6.

In FIG. 1, reference numeral 8 denotes a bracket to which the block 6 is attached, which is attached to an external member 10 via a plate 9. In this bracket 8,
A cross beam 8a is provided horizontally, and is divided into a front space portion 12 and a rear space portion 13 by the cross beam 8a. The block 6 is housed in the front space 12. In FIG. 4, reference numerals 8b protrude inward from the distal ends of the brackets 8, respectively, to form elastic members 14 (described later).
And a pair of left and right stoppers 11 for preventing the block 6 from protruding to the outside due to the urging force, and 11 is a through hole formed at both ends of the cross beam 8a.

In FIG. 4, reference numeral 14 denotes an elastic member for urging the block 6 toward the magnetic scale 4, and a front space portion 12 is provided.
Between the block 6 and the bracket 8.
In this embodiment, two sets of arched leaf springs are employed as the elastic members 14, but other springs such as coil springs and resin springs can be employed. Reference numeral 15 denotes a bolt for attaching the elastic member 14 to the block 6.
Reference numeral 6 denotes a bolt hole formed at the center of the elastic member 14 for inserting a bolt 15, and reference numeral 17 denotes a pair of through holes formed at both ends of the elastic member 14.

In FIG. 4, reference numeral 18 denotes a pair of air pads for injecting air to the magnetic scale 4 to secure a minimum gap G between the magnetic scale 4 and the magnetic detection sensor 5. The air pad 18 is screwed into the left and right screw holes 7 of the block 6. Reference numeral 18a denotes a hollow portion formed inside the air pad 18, and the ejection port side of the hollow portion 18a is an orifice-shaped ejection portion 18b.

The height of the tip surface of the air pad 18 is substantially equal to the height of the tip surface of the magnetic detection sensor 5. This is for minimizing the gap G to about the air film thickness obtained by a constant air injection pressure. At this time, the height of the air pad 18 is adjusted by adjusting the screwing depth of the air pad 18 into the screw hole 7 or by fixing screws 25 which are screwed onto both ends of the block 6 to fix the air pad 18 to the block 6. This is done by adjusting

In FIG. 2, reference numeral 18c denotes a pair of connecting portions (see also FIG. 4) protruding from the base end of the air pad 18, and is a tuning fork-shaped tube 2 disposed in the rear space 13.
0 are connected to each other through through-holes 11 and 17 in the forked side end. Reference numeral 21 denotes an air passage formed inside the plate 9, the other end of the tube 20 is connected to one opening 21a, and a plug 22 is fitted into the other opening 21b.

In FIG. 1, reference numeral 23 denotes an air blowing means such as an external blower device, which is connected to a plug 22 via a tube 24 to indirectly communicate the air blowing means 23 with the air pad 18. State. Pressurized air generated by driving the air blowing means 23 passes through a tube 24, a plug 22, an air passage 21, and a tube 20, and reaches the air pad 18 as shown in FIG. As shown in FIG. 4, the air that has reached the air pad 18 blows out from the orifice 18b to the magnetic scale surface 4 to form an air bearing.

Due to the reaction force of this air bearing, the block 6 is pushed into the cross beam 8a, and the elastic member 14 contracts,
Thereby, a minimal gap G is provided between the magnetic scale 4 and the magnetic detection sensor 5. That is, an air bearing is provided between the magnetic scale 4 and the air pad 18. The gap G is maintained even during the movement of the moving table 1 by continuing to drive the air blowing means 23.

By the way, as described in the section of the prior art, it is known that the resolution of the magnetic detection sensor 5 decreases in inverse proportion to the distance (gap). It means that the resolution of reading the magnetic scale 4 by the magnetic detection sensor 5 increases as the value of. Although this was a well-known fact in the past, in the conventional means, since the gap was fixed in advance at the interval where the magnetic scale and the magnetic detection sensor did not contact during measurement, as described above, for example, the surface of the magnetic scale In the case where the accuracy is rough, there is a place where a relatively large gap is formed depending on the position during the movement of the moving object. Therefore, this method has a limit in narrowing the gap.

On the other hand, in this apparatus, the magnetic scale 4
By providing an air bearing between the air pad 18 and the air pad 18, even if the magnetic scale 4 has a rough surface accuracy, the elastic member 14 expands and contracts in accordance with the rough surface. Can be measured,
Thereby, the accuracy of measuring the moving distance of the moving table 1 can be improved.

The present apparatus has the above-described configuration, and the operation will be described next. As shown in FIG.
Generated by the driving of the tube 24, the air passage 2
1. The air passes through the tube 20 to reach the air pad 18, and is jetted onto the surface of the magnetic scale 4 by the jetting portion 18b.
Due to the reaction force of the air bearing, the block 6 is pushed in, the elastic member 14 contracts, and a very small gap G is secured between the magnetic scale 4 and the magnetic detection sensor 5.

Next, when the moving table 1 is moved while maintaining this state, the magnetic scale 4 attached to the moving table 1 also moves, and the amount of the magnetic scale 4a of the magnetic scale 4 for this movement is magnetically detected. The sensor 5 reads and measures the moving distance of the moving table 1.

As described above, the air bearing is provided between the magnetic scale 4 and the air pad 18 to secure a very small gap G between the magnetic scale 4 and the magnetic detection sensor 5 at which the distance does not change during the measurement. As a result, the magnetic detection sensor 5
, The resolution of the reading of the magnetic scale 4 can be increased, and the accuracy of measuring the moving distance of the moving table 1 can be improved.

The present invention is not limited to the above embodiment. For example, the magnetic detection sensor 5 may be attached to the moving table 1 and the magnetic scale 4 may be attached to the external member 10.

Further, in the embodiment, the moving table 1 which moves only in one direction is adopted as the moving object. However, a moving table which moves in the XY directions such as an XY table of a wire bonder may be adopted. In this case, it is preferable to apply this means to both the X table and the Y table,
It may be applied to only one table.

[0025]

As described above, the present invention provides a magnetic scale made of a magnetic material, a magnetic detection sensor facing the magnetic scale and reading a magnetic scale of the scale, and a block to which the magnetic detection sensor is attached. When,
A bracket to which the block is attached, an elastic member interposed between the block and the bracket to urge the block toward the magnetic scale, and an air pad provided on the block to inject air to the magnetic scale And a moving distance measuring device comprising: air blowing means for communicating with the air pad and injecting air from the air pad to secure a minimal gap between the magnetic scale and the magnetic detection sensor; and By attaching the magnetic scale or bracket relatively to the moving object or the external member, a very small gap is provided between the magnetic scale and the magnetic detection sensor that does not change during measurement. Increase the resolution of reading the magnetic scale by the sensor and measure the moving distance of the moving table It can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a moving distance measuring device according to the present invention.

FIG. 2 is a plan view of the main part.

FIG. 3 is a front view of the main part.

FIG. 4 is a plan view of the main part.

[Description of Signs] 1 Moved object 4 Magnetic scale 4a Magnetic scale 5 Magnetic detection sensor 6 Block 8 Bracket 10 External member 14 Elastic member 18 Air pad 23 Air blowing means G Minimal gap

Claims (1)

(57) [Claims] 1. A magnetic scale made of a magnetic material, a magnetic detection sensor facing the magnetic scale and reading a magnetic scale of the scale, a block to which the magnetic detection sensor is mounted, and a bracket to which the block is mounted. An elastic member interposed between the block and the bracket to urge the block toward the magnetic scale; an air pad provided on the block to inject air to the magnetic scale; and an air pad communicating with the air pad. Air blowing means for securing a minimal gap between the magnetic scale and the magnetic detection sensor by injecting air from the air pad, wherein the magnetic scale or bracket is attached to the moving object or an external member. A moving distance measuring device which is relatively attached.