JPH10293004A - Magnetic scale device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an ideal circuit drive positioning by mounting a magnetic scale to either a reciprocating member or its fixed position and a magnetic displacement element to the other. SOLUTION: When a lever 6 rotates around a rotary shaft 5 of a lever 6, a lever operation tip 7 speedily reciprocates between a position where an object to be worked is located and a position away from it. A drive force required for the rotary movement of the lever 6 is given by a voice coil motor 1 and a thin-plate-shaped scale 2 is mounted to the lever 6. The scale 2 reciprocates relatively for a magnetic resistance element 3 when the lever 6 rotates around a rotary shaft 5. The magnetic resistance element 3 is mounted to a sensor holder 4, for example, by adhesion to read a scale for detecting a position being magnetically recorded at the scale 2, and the sensor holder 4 is mounted to other members for forming a fixing part, thus ideally detecting the amount of travel of the reciprocating operation of the scale 2 and the positioning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic scale device used for detecting a rotational position (relative position detection) of a rotating member in a machine tool, an industrial machine, or the like.

[0002]

2. Description of the Related Art In a system, such as a wire bonding machine, which has a rotating shaft and whose rotation driving force is determined by a voice coil motor using a magnet, the rotation of the tip of a rotating system is determined. Therefore, an optical encoder was used.

[0003]

However, in the case of an optical encoder, since a scale with a scale for position detection is made of glass, it is difficult to form the scale in an arc shape. Therefore, it was difficult to attach the scale according to the radius of rotation. In addition, the scale part becomes large, and a gravitational load is applied to the rotating part, which hinders a good operation.

In order to avoid this disadvantage, it is conceivable to use a magnetic scale. However, a conventional detection method using a magnetic scale is a method in which the detection head and the scale move relative to each other while contacting to read the scale. Therefore, there are drawbacks such as that smooth rotation is hindered by friction between the detection head and the scale, and that the contact portion is worn.

[0005] Further, whether the optical scale device is used or the magnetic scale device is used, there are cases where it is desired to detect the reference position (origin detection) using the scale device. In such a case, even if a member for detecting the reference position is provided separately, or if one scale device is used, the device itself becomes large.

Overcoming the above shortcomings and reducing the size of the scale device introduces new problems. For example, a magnetic scale for position detection is recorded on the magnetic medium of the magnetic encoder, but this scale is invisible and small, so there is no space for writing characters or symbols for identification. When a user attaches an encoder to a device such as a machine tool, the user may not be able to discriminate the front and back, and may attach it erroneously.

When a plurality of tracks are provided, each track must be arranged so as to face the corresponding magnetoresistive element. However, if the shape of the magnetic medium is, for example, a quadrangle, it is difficult to determine the direction of the scale. ,
Similarly, it may be mistakenly attached. In particular, when the shape is a square, it is completely lost.

An object of the present invention is to overcome the above-mentioned drawbacks of the conventional magnetic scale apparatus, and to apply the present invention to an apparatus having a rotary shaft such as a wire bonding machine and the rotary drive of which is performed by a motor using a magnet. And

[0009]

In order to solve the above-mentioned problem, the present invention provides a magnetic scale device using the following means.

[0010] Of the scale and the detection head necessary for detecting the movement (rotation) position, the scale is attached to the movable part (rotary system) of the application device (for example, a wire bonding machine), and the detection head is attached to the fixed part. By doing so, the lead wire of the detection head does not hinder the movement of the movable portion, does not require a lead wire, and reduces the influence on the movable portion by attaching a relatively light scale to the movable portion. be able to.

A magnetoelectric conversion element is used as a detection head for performing the position detection, and the detection head is installed on a fixed side with respect to a rotating system. A magnetic shield is provided to block the detection head and the scale from an external magnetic field generated from a motor or the like and affecting the detection head and / or the scale made of a magnetic medium. -The shape of the magnetic medium (scale) is asymmetric.

[0012]

Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 11 shows a magnetic scale device according to an embodiment of the present invention. As shown in the drawing, a magnetic scale device is attached to a swing type rotary drive device using a voice coil motor. Lever 6
Is rotatable in a limited arc around the rotation axis 5, and when the lever 6 rotates around the rotation axis 5, the lever working tip 7 moves the position of the object to be machined and High-speed reciprocation can be performed between the separated positions.

The driving force required for the lever 6 to make a rotational movement is provided by the voice coil motor 1. The thin scale 2 is attached to the lever 6.
The scale 2 reciprocates relative to the magnetoresistive element 3 when the lever 6 rotates around the rotation shaft 5.

The magneto-resistive element 3 is provided for reading a scale for position detection magnetically recorded on the thin scale 2. The magneto-resistive element 3 includes a sensor holder 4.
Is attached to the panel by bonding or caulking by fitting. The sensor holder 4 is further attached to another member forming a fixing portion. Thus, the movement amount of the reciprocating operation of the thin scale 2 can be detected and positioned.

FIG. 1 is a schematic view showing another embodiment in which the magnetic scale device of the present invention is applied to a machine tool. 1 is the same as the scale device described above with reference to FIG. 11 except for the portion where the magnetic scale device is formed, and therefore detailed description is omitted.

As shown in the figure, a place for attaching the scale 2 is provided at the end (free end) of the lever 6 opposite to the tip (working end) 7 facing the workpiece. The sensor 3 is disposed so as to face the scale 2 with an appropriate clearance (gap).

The sensor 3 uses a magnetoresistive element (MR element) or the like, and is attached to the sensor holder 4. The sensor holder 4 is mounted on a fixed (immobile) location on or near the machine tool.

The scale 2 and the sensor 3 are magnetically shielded by a shield plate 8 so as not to be affected by an external magnetic field. The magnetic shield will be described below with reference to the accompanying drawings by way of example.

FIGS. 2 and 3 are perspective views showing a detailed structure when the shield plate 8 (see FIG. 1) is attached to the fixed side of the magnetoresistive element 2. FIG. FIG. 2A shows the sensor holder 4.
A sensor is mounted on the sensor holder 4, and the sensor portion is covered with a magnetic shield plate so as to be shielded from an external magnetic field.

The tip of the lever 6 described in FIG. 1 is inserted between the sensor and the magnetic shield plate 8 so as to move relatively to the sensor. In the example of FIG. 2, the lever is formed in a U-shape so that the movement of the tip of the lever is not hindered by the magnetic shield plate 8. On the surface of the tip of the lever facing the sensor, as shown at the top of FIG.
Scale 2 is attached. The shape of the magnetic shield is not limited to the shape shown in FIG. 2A, but can be various shapes. FIG. 2A shows the sensor holder 4.
It is structured to be attached to the rear surface of
FIG. 2B shows a structure in which the sensor holder is attached to the fixed portion from the side.

FIG. 3 shows another shape of the lever 6 and the shield plate 8. In this example, a slit-like passage is formed in the shield plate 8 so that the movement of the lever 6 is not hindered. Other structures are almost the same as those shown in FIG.

As shown in FIGS. 2 and 3, the magnetic shield plate 8 is attached so as to cover the magnetoresistive element 3 constituting the sensor. Then, it is possible to cut off a magnetic field that enters from the outside in the vicinity of the detection unit.

In the example described with reference to FIGS. 2 and 3, the shield plate is arranged on the side where the sensor is placed. In the example described below, the shield plate 8 is a scale. Is on the side where it is located.

FIG. 4 shows the rear end (free end) of the lever 6 in detail. As shown in the figure, a scale fixing base 9 is attached to the tip, and the scale 2 is mounted on the fixing base. The side of the scale 2 is covered with a shield plate 8 so that the portion of the scale 2 is not affected by an external magnetic field, particularly a magnetic field generated from the voice coil motor 1.

Next, a method of attaching a scale made of a magnetic medium to a lever will be described. In FIG.
(A) shows the surface on which the magnetic medium is mounted, and the lower part shows a cross section in the thickness direction.

As shown in the figure, the scale is directly mounted on the mounting table by fixing screws or the like. Further, as another example, the scale is mounted on a mounting table using a member for holding the scale as shown in (b) and (c). In the above example, the scale is mounted on a flat surface. However, since the thin plate-shaped scale can be bent in the thickness direction, it can be mounted on a curved surface.

Next, the positional relationship between the detection head and the scale will be described. As shown in FIGS. 1 to 4 and FIGS. 6 to 7, when the scale 2 is mounted on an arc which is a locus of a rotational motion, a thin plate-shaped magnetic scale is used. Can be bent to the arc, so that when the lever rotates around the rotation axis, the distance between the scale surface and the detection head can be constant.

Thus, even if the gap between the scale and the detection head is narrowed, there is no fear that the scale and the detection head come into contact with each other. Also, while the lever is rotating around the rotation axis, the distance (clearance) CL between the scale and the detection head is kept constant, and good positioning detection can be performed.

FIG. 6 shows the relationship between a scale made of a magnetic medium and a detection head made of a magnetoresistive element. The left side of FIG. 6 shows the relationship between the scale and the detection head as viewed from the longitudinal direction of the lever, and the right side shows the relationship between the scale and the detection head as viewed from the scale surface direction.

FIG. 7 similarly shows the relationship between the scale and the detection head (magnetoresistive element). The difference from FIG. 6 is that the direction of the detection head with respect to the scale surface is different. In this arrangement, the clearance can be made smaller than in the arrangement of FIG. 6 by arranging the attachment part of the lead wire drawn out of the magnetoresistive element outside the scale, so that the wavelength can be further shortened. , High accuracy and high resolution can be realized. .

FIG. 8 shows still another embodiment in which a scale is attached to a side surface near the rear end of a lever. The upper side of the figure shows a side view, and the lower side shows a top view. It shows the place. Such a structure is also possible by recording a magnetic scale for position detection in accordance with the radius of rotation R.

As described above, various combinations are conceivable for the manner of attaching the scale to the lever and the manner of disposing the detection head on the surface of the scale. Therefore, it is necessary to arrange in an appropriate combination in each case.

However, when a thin plate scale made of a magnetic medium is used as the scale, it is difficult to distinguish the front and back of the scale because the magnetic scale recorded on the scale cannot be seen. .

Further, when a plurality of tracks are recorded, such as when an increment track and an origin track are recorded on one thin plate-shaped magnetic medium, it is necessary to detect them separately. Therefore, it is necessary to know the track direction.

In the case of having a plurality of tracks, each track must be arranged so as to face the corresponding magnetoresistive element. May be attached. In particular, when the shape or the shape is a square, it is completely lost.

FIG. 9 exemplifies a thin plate-shaped magnetic scale, a magnetoresistive element, and a mount for the magnetoresistive element.
Since the magnetoresistive element has a tape-shaped lead wire (flexible substrate), the direction can be determined by this. The use state of the magnetoresistive element is such that the side with the lead wire is opposed to the scale, so that the front and the back can be distinguished.

As shown on the right side of FIG. 10, when viewed in the Y-axis direction, it is symmetrical in the left-right direction.
When viewed in the X-axis direction, one side has a lead wire but the other side has no lead wire (that is, it is asymmetric), so that left and right can be identified.

As shown in FIG. 10, the scale can be identified by cutting off one corner of the square. If the scale illustrated on the left side of FIG. 10 is based on this state and is set as a table, if the scale is inverted in the Y direction, the cut-off corner becomes the third quadrant. In the case of turning over, the cut corner comes to the second quadrant and the fourth quadrant. Therefore, the front and back can be distinguished.

When the scale and the detection head (sensor) are combined using each asymmetric portion, the front and back of the scale and the orientation of the scale and the sensor 3 can be uniquely determined.

As described above, the magnetic scale is formed in a small size, mounted without mistake in the mounting direction, and if necessary, the range of the effective length of the scale (the length actually used for detection) is shielded by the shield plate. Thus, the use of the magnetic scale, which has been difficult in the past, has been facilitated by not being affected by the external magnetic field.

The embodiments of the present invention have been described with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various modifications and changes can be made without departing from the technical idea of the present invention. Of course, there are modifications.

For example, the magnetoelectric conversion element is not limited to the MR element (magnetic resistance element), but may be a Hall element, a magnetic impedance element, or the like. The magnetic scale portion can be appropriately changed according to the structure of the apparatus to be applied and the installation environment. In the above embodiment, the scale and the detection head are separately mounted, but they may be combined into one unit.

[0044]

The magnetic scale of the present invention has the following effects by having the above configuration. That is, since a lightweight thin plate-shaped scale can be attached to the rotary drive unit, the weight increase is small, and an ideal rotary drive positioning device can be configured.

The use of the magnetoresistive element and the thin plate-shaped magnetic medium provides a non-contact magnetic encoder, and the use of a magnetic shield enables installation in a place where a magnetic field such as a voice coil motor is generated. It is also very effective for high-speed positioning using a linear motor or the like.

Also, by using a magnetoresistive element and a thin plate scale, a position detecting device having a plurality of tracks can be manufactured at low cost. In this case, since the thin scale can be made very light, it does not affect its operation even if it is attached to the rotary drive.

Because of the magnetic type, the detection position of the origin serving as the reference position may be recorded on a scale according to the environment in which it is used. In addition, since the processing of the outer shape of the thin plate-shaped magnetic medium is simple, the built-in rotation Since a design suitable for the drive unit can be made, the assemblability can be improved and the cost can be reduced.

By arranging the magnetic shield between the magnet motor and the thin plate scale, it can be easily protected from an external magnetic field. Further, by arranging the magnetic shield on the fixed side, it is possible to easily protect the rotary drive unit from an external magnetic field without imposing a weight burden.

If the detection head has a shape having at least an asymmetric portion with respect to the center of the detection portion, and if the shape of the magnetic medium is asymmetric, the front and back and the direction of the detection head and the magnetic medium are determined, the mounting may be mistaken. Absent.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of a machine tool to which a magnetic scale device according to an embodiment of the present invention is attached.

FIG. 2 is a perspective view of a shield plate used in the magnetic scale device of the present invention.

FIG. 3 is a perspective view of a shield plate used in the magnetic scale device of the present invention.

FIG. 4 is a perspective view of a shield plate used in the magnetic scale device of the present invention.

FIG. 5 is a schematic diagram of a scale mounting structure.

FIG. 6 is a schematic diagram illustrating a positional relationship between a scale and a detection head (magnetic resistance element).

FIG. 7 is a schematic diagram showing a positional relationship between a scale and a detection head (magnetic resistance element).

FIG. 8 is a schematic diagram showing a positional relationship between a scale and a detection head (magnetic resistance element).

FIG. 9 is a schematic diagram illustrating a positional relationship between a scale and a detection head (magnetic resistance element).

FIG. 10 is a diagram for explaining the asymmetry of the scale and the detection head.

FIG. 11 is a schematic diagram of a main part of a machine tool to which a magnetic scale device is attached.

[Explanation of symbols]

1 voice coil motor, 2 scales, 3 sensors,
4 Sensor holder, 5 rotation shaft, 6 lever, 7 lever working tip, 8 shield plate, 9 free end of lever

Claims (5)

[Claims] 1. A magnetic scale device for detecting the position of a reciprocating member in a rotary drive mechanism having a member that reciprocates about a rotation axis when a rotational driving force is applied by a motor using a magnet. A magnetic scale device comprising a displacement detection unit having a magnetic scale attached to one of the reciprocating member and a fixed position outside the member, and a magnetoelectric conversion element attached to the other. 2. The magnetic scale device according to claim 1, further comprising: a shield member for shielding at least an effective length portion of the magnetic scale from the external magnetic field. . 3. The magnetic scale device according to claim 2, wherein the reciprocating member is a lever having a working end and a free end located on both sides of a fulcrum, and the magnetic scale is attached to the free end. A magnetic scale device comprising a thin plate-shaped magnetic medium, wherein the magnetoelectric conversion element is mounted at the fixed position, and wherein the shield member is mounted at a fixed position on the magnetoelectric conversion element side. 4. The magnetic scale device according to claim 2, wherein the reciprocating member is a lever having a working end and a free end located on both sides of a fulcrum, and the magnetic scale is attached to the free end. A magnetic scale device comprising a thin plate-shaped magnetic medium, wherein the magnetoelectric conversion element is attached to the fixed position, and wherein the shield member is attached to the free end so as to cover an effective length of the thin plate-shaped magnetic medium. 5. The magnetic scale device according to claim 1, wherein the magnetic scale has an asymmetric shape.