JP2000337852A - Position detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect, with high precision, the positions of two members in linear relative movement by decreasing both a dislocation error and return error at the same time. SOLUTION: In the position detecting device 1, a detecting head held by a head holder is held tiltably in the longitudinal direction of a scale 12 while being clamped under energization by a pair of clamping members provided coaxially with the center axis of the scale 12, for position detection of two members in relative linear movement. Here, the head holder is supported with sliding parts 52 and 53 which slide on a case 11 while energized by an energizing part 54 in the direction (X4 and X5) toward the sliding part, for position detection of the two members in relative linear movement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device used for controlling a moving position of a movable portion of a machine tool, an industrial machine, or the like, and more particularly to detecting a moving position of a movable portion performing a linear moving operation. The present invention relates to a position detecting device.

[0002]

2. Description of the Related Art Conventionally, in machine tools and industrial machines,
In order to control the position of the movable part that moves linearly, a so-called position detection device is used.

Hereinafter, a conventional position detecting device will be described with reference to the drawings.

FIG. 10 is a perspective view of a conventional position detecting device, FIG. 11 is a side view of the position detecting device, and FIG. 12 is a sectional view showing the internal structure of the position detecting device. Show.

[0005] The conventional position detecting device 101 includes a main body 10.
2 and a head slider 103 attached to the main body 102.

The position detecting device 101 is configured as a part of a machine tool, and detects a relative movement position of two members which move relatively linearly. For example, the position detection device 101 includes a reference unit 104 fixed at a predetermined position,
Detecting a relative movement position of the movable portion 105 to move linearly with respect to the reference portion 104 in the X ₁ direction and the X ₂ direction shown in FIG. 10. The position detecting device 101 includes a main body 102
Alternatively, one of the head sliders 103 is
04, and the other is attached to the movable part 105. 10 and 11, the main body 102 is attached to the reference portion 104, and the head slider 10 is attached to the movable portion 105.
3 shows an example in which 3 is attached.

The main body 102 is a housing 111 and a recording medium made of a long, high coercive force material such as a round bar, and a scale 112 provided inside the housing 111 and both ends of the scale 112. To fix the scale 112 at a predetermined position in the housing 111.
14. It should be noted that the brackets 113 and 114 are not shown in FIG.

The housing 111 has, for example, a rectangular cylindrical shape, and has a slit 115 formed by cutting out one side surface. The housing 111 is provided with the slit 11
At the longitudinal ends of the side surfaces 117 and 118 orthogonal to the side surface on which the base 5 is formed, substantially circular housing mounting holes 121 and 12 are formed.
2, 123 and 124 are formed.

The scale 112 includes brackets 113, 1
Both ends are held by 14 and fixed in the housing 111. The scale 112 is provided so as to be parallel to the longitudinal direction of the housing 111 and to be located on the center axis of the rectangular tube. A scale signal for detecting the relative position between the reference unit 104 and the movable unit 105 is magnetically recorded on the scale 112 as a position signal. This scale signal is a signal in which pits, marks, and the like, which are continuously repeated at predetermined intervals, are recorded in the longitudinal direction of the scale 112. For example, a magnetic signal whose polarity is inverted at a predetermined recording wavelength is a signal of the scale 112. This is a signal recorded continuously in the longitudinal direction.

The head slider 103 is provided in the main body 1.
02, a head carrier 132 provided outside the main body 102, and a connecting portion 133 connecting the head holding portion 131 and the head carrier 132. Is attached to the main body 102 so as to be movable in the longitudinal direction.

FIG. 13 is an exploded perspective view of a main part of the head holding section 131.

The head holder 131 includes a head holder 1.
34 are provided. In this head holder 134,
An insertion hole for the scale 112 is provided. The head holder 134 is attached to the scale 112 by inserting the scale 112 into the insertion hole,
The scale 112 can be moved linearly in the longitudinal direction.

The head holder 134 is covered by a head holder case 136 on the outside, and holds a signal detection head 135 inside. The signal detection head 135 detects a scale signal recorded on the scale 112. Since the signal detection head 135 is held by the head holder 134, the signal detection head 135 moves in parallel in the longitudinal direction of the scale 112 with the linear movement of the head holder 134.

The scale 112 of the head holder 134
A pair of sliding support members 137, 1
38 are attached. This sliding support member 137,
138 has a substantially cylindrical shape, and has an insertion hole through which the scale 112 is inserted at the center axis. The sliding support members 137 and 138 are slidably supported by the scale 112 by inserting the scale 112 into the insertion holes. The sliding support members 137 and 138 are slidably supported by the scale 112, so that the head holder 134
2, the head holder 134 is prevented from being displaced in a direction orthogonal to the moving direction.

The head holding portion 131 is provided with a pair of first spacers 139 and 140 and a pair of second spacers 141 and 142.

The pair of first spacers 139 and 140 have insertion holes through which the scale 112 is inserted. The pair of first spacers 139 and 140 are attached to the scale 112 when the scale 112 is inserted into the insertion holes, and are linearly movable in the longitudinal direction of the scale 112. Further, the pair of first spacers 139 and 140 are provided with sliding support members 137 and 13.
8 is provided on one end surface of the scale 112 to which the head holder 134 in the longitudinal direction is not attached.

Also, a pair of second spacers 141, 14
2 has an insertion hole through which the scale 112 is inserted. The pair of second spacers 141 and 142 are attached to the scale 112 by inserting the scale 112 into the insertion holes, and are capable of linearly moving in the longitudinal direction of the scale 112. Further, the pair of second spacers 141 and 142 form first spacers 139 and 1.
40 sliding support member 13 in the longitudinal direction of scale 112
7, 138 are attached to one end face not provided.

The head holding portion 131 is provided with a pair of head holder holding members 143 and 144 and a spring 145.

The head holder holding members 143 and 144 have insertion holes through which the scale 112 is inserted. The head holder holding members 143 and 144 are attached to the scale 112 by inserting the scale 112 into the insertion holes, and are capable of moving linearly in the longitudinal direction of the scale 112. The head holder holding members 143 and 144 are fixed to the connecting portion 133. The pair of head holder holding members 143, 144
The head holder 134 to which the sliding support members 137 and 138 are attached is moved to a pair of first spacers 139 and 139.
The scale 112 is sandwiched from both ends in a direction parallel to the longitudinal direction of the scale 112 via a pair of second spacers 141 and 142. A spring 145 is provided between the head holder holding member 143 and the second spacer 141. The spring 145 is connected to the head holder holding member 14.
3, the head holder 134 is urged in a direction toward the head holder holding member 144.

The head holder 134 is provided with a detent pin 146. This pin for stopping rotation 1
46 has one end in the longitudinal direction fixed to the head holder 134, and the other end inserted into a rotation regulating hole 147 provided in the connecting portion 133. Therefore, the head holder 13
The rotation about the 4th scale 112 as a central axis is regulated.

Each component of the head holding portion 131 has a coaxial configuration with the scale 112 as a central axis. Therefore, the detection error of the scale signal due to the movement of the head holding unit 131 is minimized, and highly accurate position detection can be performed.

In the head holding section 131, the first
Spacers 139, 140 and the second spacer 141, 1
42 has a spherical surface. In the head holding portion 131, the sliding support member 137 directly attached to the head holder 134,
138 slides with the scale 112, but other components include, for example, a pair of first spacers 139, 140,
The scale 112 is inserted into the pair of second spacers 141 and 142 and the head holder holding members 143 and 144 with a certain gap. Therefore, for example, when there is a subtle axis distortion in the scale 112 or when a force in a direction other than the moving direction is applied to the head carrier 132, the scale 112 is moved with respect to the head holder holding members 143 and 144. When a displacement occurs in a direction perpendicular to the longitudinal direction, the spherical contact surface allows the displacement of the center axis of the head holder 134 and the center axes of the head holding members 143 and 144 and gives the scale 112. It functions to reduce the bending moment.

The head holding section 131 having the above configuration
Is mounted on the scale 112 so as to be movable in a direction parallel to the longitudinal direction of the scale 112, and the signal detection head 35 detects a scale signal recorded on the scale 112 in accordance with the movement.

The head holding section 131 includes a connecting section 133.
Through the head carrier 132. One end of the connecting portion 133 in a direction orthogonal to the longitudinal direction of the scale 112 is fixed to the head holder holding members 143 and 144, and the other end is inserted through the slit 115 to
Is fixed to a head carrier 132 provided outside.

As described above, the head slider 103 includes the head holding portion 131, the head carrier 132, and the connecting portion 133, and is attached to the main body 102 so as to be movable in the longitudinal direction of the scale 112. The head slider 103 transmits the scale signal detected by the signal detection head 135 according to the relative movement with respect to the main body 102 to the signal cable 1 provided on the head carrier 132.
The control signal is supplied to a control device (not shown) via 48.

The position detecting device 101 having the above configuration
Is that the scale 112 is parallel to the relative movement direction of the reference portion 104 and the movable portion 105, and the slit 115 is
It is arranged so as to open to the fifth side. The main body 102 of the position detecting device 101 thus arranged is
One of the side surfaces 117 and 118 orthogonal to the side surface on which 5 is formed is the mounting surface. And the scale 11 of this mounting surface
2 at the positions of the housing mounting holes 121, 122, 123, and 124 provided at the ends in the direction parallel to the longitudinal direction of the main body 2 by fixing members such as body bolts 151, 152 and washers 155.
It is fixed to the reference part 104. Further, the head slider 103 of the position detecting device 101 arranged as described above is fixed to the movable part 5 by slider bolts 153 and 154.

Therefore, in the position detecting device 101, the relative position between the main body 102 and the head slider 103 changes according to the linear movement of the movable portion 105, and the signal detecting head 135 provided in the head slider 103 is moved. By detecting a scale signal that changes according to the change in the relative position, the moving position of the movable unit 105 can be detected.

[0028]

By the way, in such a conventional position detecting apparatus 101, how parallel the scale 112 is attached to the housing 111 is the movement of the reference section 104 and the movable section 105. Linearity, reference part 10
4 and the movable section 105, the main body 102 may be distorted or distorted by the scale 112 due to its own weight, manufacturing accuracy, etc., deflection or distortion of the scale 112 and the center axis of the head holding section 112, or the like. The attitude of the signal detection head 135 changes with the relative movement with the head slider 103 (the signal detection head 1 in a direction orthogonal to the longitudinal direction of the scale 112 with respect to the longitudinal direction of the scale 112).
35).

In the position detection device 101, an error occurs in the position detection accuracy due to the change in the attitude of the signal detection head 135.

For example, as shown in FIG.
When a distortion or the like occurs in the head 12, a posture change occurs in the head holder 136 (in which the signal detection head 135 is held), and the signal detection position of the signal detection head 135 changes to the scale 1.
12 is slightly displaced with respect to the longitudinal direction, causing an error. FIG. 14 shows the head holder 136, the scale 112, the sliding support member 137, the first spacer 139, and the second spacer 14 when the posture does not change.
1 is indicated by a solid line. FIG. 14 shows the head holder 136, the scale 112, the sliding support member 137, and the first spacer 1 when the posture has changed.
39 is indicated by a dotted line. As shown in FIG.
When the signal detection position of the signal detection head 135 is inclined, an error (δ) occurs in the longitudinal direction according to the inclination.

The error caused by the change in the attitude of the signal detection head 135 includes an error caused by a difference in the longitudinal position of the scale 112 of the signal detection head 135 and an error caused by a difference in the moving direction of the signal detection head 135. is there.
Hereinafter, the former will be referred to as a displacement error and the latter will be referred to as a return error, and the cause of the occurrence of both will be described.

A scale 11 having a predetermined amount of deflection
FIG. 15A shows a case where the signal detection head 135 moves from the one bracket 114 side to the other bracket 113 side on the flexure scale 112 (moving from the left end to the right end in the figure). FIG. 15B shows a posture change state in the case where the signal detection head 135 moves from the other bracket 113 side to the one bracket 114 side on the deflected scale 112 (FIG. 15B). FIG. 15C illustrates a posture change state in the case of moving from the right end to the left end).

First, the cause of the occurrence of the displacement error will be described.

First, the signal detection head 135 is moved to the scale 1
12 (the scale 11 on one bracket 114 side)
2), the attitude (inclination with respect to the moving direction) of the signal detection head 135 is substantially the same as the projection angle (θ ₁ ) of the scale 112 from the bracket 114. This is because the rigidity is high at the end of the scale 112, and the center axis of the head holder 136 holding the signal detection head 135 is parallel to the scale 112. Based). Subsequently, as the signal detection head 135 moves from the left end of the scale 112 toward the center, the inclination of the signal detection head 135 with respect to the moving direction becomes smaller, and the inclination becomes θ ₂ (θ ₁ > θ ₂ ) at the center of the scale 112. Where scale 1
The reason that the inclination of the signal detection head 135 in the moving direction at the center of the scale 12 is not parallel to the scale 112 is that the rigidity at the center of the scale 112 is lower than that at the end. And the spring 1 that urges the head holder 134 in the moving direction.
This is because the spring force of the scale 45 becomes relatively high with respect to the rigidity of the scale 112. Subsequently, the signal detection head 13
As 5 moves from the center of the scale 112 to the right end, the inclination of the signal detection head 135 with respect to the moving direction further decreases, and the inclination becomes 0 at a certain position. Subsequently, when the signal detection head 135 further moves to the right end from the position where the tilt becomes zero, the signal detection head 135 starts to tilt in the opposite direction. When the signal detection head 135 is located at the right end of the scale 112, the attitude of the signal detection head 135 is determined by the protrusion angle (θ) of the scale 112 from the bracket 113.
_It is almost the same as ₃ ).

As described above, in the signal detecting head 135, the head holder 134 has a spherical shape provided on the first spacers 139 and 140 and the second spacers 141 and 142, so that the center axis of the signal detecting head 135 and the head holding members 143 and 144 can be adjusted. Since the scale 112 is held while allowing the displacement, the posture of the scale 112 is different at each position in the longitudinal direction. Then, an error due to a difference in posture at each position in the longitudinal direction of the scale 112 appears as a position shift error.

Next, the cause of the return error will be described.

First, the signal detection head 135 is moved to the scale 1
When the signal detection head 135 is positioned at the right end (end on the other bracket 113 side) of the scale 12, the attitude (inclination with respect to the moving direction) of the signal detection head 135 is substantially the same as the protrusion angle (θ ₃ ) of the scale 112 from the bracket 114. . Subsequently, as the signal detection head 135 moves from the left end of the scale 112 toward the center, the inclination of the signal detection head 135 with respect to the moving direction becomes smaller.
It becomes ₄ . Subsequently, the signal detection head 135 is connected to the scale 1
12 from the center to the left end, the signal detection head 1
The inclination with respect to the moving direction of 35 further decreases, and the inclination becomes 0 at a certain position. Subsequently, the signal detection head 135
From the position where the inclination becomes 0 to the left end,
The signal detection head 135 starts to tilt in the reverse direction. And
When the signal detection head 135 is positioned at the right end of the scale 112, the posture of the signal detection head 135 is
Is substantially the same as the protrusion angle (θ ₁ ) from the bracket 114.

Here, the case where the signal detection head 135 moves from the left end to the right end as shown in FIG.
The attitude of the signal detection head 135 at the same position on the scale 112 is different from that when the signal detection head 135 moves from the right end to the left end as shown in FIG.
In particular, the attitude greatly differs at the center position of the scale 112, and the attitude difference becomes smaller toward the end of the scale 112.

As described above, in the signal detection head 135, the head holder 134 has a spherical shape provided on the first spacers 139 and 140 and the second spacers 141 and 142 so that the center axis of the head with the head holding members 143 and 144 can be adjusted. Since the detection head 135 is held while allowing the displacement, the posture at the same position on the scale 112 differs in the moving direction of the detection head 135 (the direction from the left end to the right end, or the direction from the right end to the left end). An error due to a difference in the moving direction of the detection head 135 appears as a return error.

More specifically, FIG. 16A shows the displacement error when the signal detection head 135 moves from the left end to the right end and the displacement error when the signal detection head 135 moves from the right end to the left end. 16B, the return error is that the signal detection head 135 moves from the right end to the left end due to the displacement error when the signal detection head 135 moves from the left end to the right end as shown in FIG. This is a value obtained by subtracting the positional deviation error in the case.

In the head holding section 131, the first
Spacers 139, 140 and the second spacer 141, 1
42 has a spherical surface. In the head holding portion 131, the sliding support member 137 directly attached to the head holder 134,
138 slides with the scale 112, but other components include, for example, a pair of first spacers 139, 140,
The scale 112 is inserted into the pair of second spacers 141 and 142 and the head holder holding members 143 and 144 with a certain gap. Therefore, the head holder holding members 143 and 144 are moved in the longitudinal direction of the scale 112, for example, when the scale 112 has slight axis distortion or when a force in a direction other than the moving direction is applied to the head carrier 132. When the head holder holding members 143, 144 are displaced in a direction perpendicular to the direction, the spherical contact surface allows the center axis of the head holder 134 and the center axis of the head holding members 143, 144 to be displaced. And
It functions to reduce the bending moment applied to the scale 112.

In the conventional position detecting apparatus 101, it is necessary to adjust, for example, the amount of the spring 145, the rigidity of the scale 112, and the like so as to reduce both the positional deviation error and the return error.

In order to reduce the displacement error, for example, the spring force of the spring 145 may be increased to increase the force holding the head holder 134 in the longitudinal direction of the scale 112. Further, in order to reduce the return error, the rigidity of the scale 112 may be increased.

However, the positional deviation error and the return error are trade-offs such that if the relationship between the amount of spring and frictional force and the scale rigidity is adjusted so as to reduce one error, the other error will increase. In the relationship
It was very difficult to reduce both at the same time.

In order to reduce both of them at the same time, it is necessary to further reduce the mounting error of the scale 111 with respect to the housing 111, and to further secure the linearity of movement between the reference portion 104 and the movable portion 105. A machine for increasing the mounting accuracy of the position detecting device 1 with respect to the reference portion 104 and the movable portion 105, and increasing the straightness of the scale 112 so as not to bend or warp due to its own weight or manufacturing accuracy. Performing such adjustments would increase the number of work steps and lead to a significant cost increase.

The present invention has been made in view of such circumstances, and simultaneously reduces both the positional deviation error and the return error to accurately determine the position of the two members that move relatively linearly. An object of the present invention is to provide a position detecting device capable of detecting the position.

[0047]

In order to solve the above-mentioned problems, a position detecting apparatus according to the present invention detects a relative movement position between a first member and a second member which move relatively linearly. A position detecting device, comprising: a long recording medium on which a position signal is recorded along a longitudinal direction; a housing fixed to the first member; and the housing and the recording medium fixed. A main body having a fixing member, a head holder slidably attached to the recording medium in a longitudinal direction of the recording medium, and a detection unit for detecting a position signal held by the head holder and recorded on the recording medium. A head, a pair of holding members movably attached to the recording medium in the longitudinal direction of the recording medium, and biasing the head holder in the longitudinal direction of the recording medium to clamp the head holder; and the housing fixed to the head holder. Sliding with the body A head holder supporting member for supporting the head holder, an urging means for urging the head holder in a direction perpendicular to a longitudinal direction of the recording medium, and fixed to the second member connected to the pair of holding members; And a head slider having a head carrier, wherein the pair of sandwiching members are provided with a center axis in the movement direction coaxial with the recording medium, and the head holder has a center axis in the movement direction. The pair of holding members can be tilted with respect to a center axis with respect to the moving direction, and are held between the pair of holding members. The urging means moves to a sliding portion between the head holder support member and the housing. It is characterized in that the head holder is biased in a direction toward the head.

In this position detecting device, the detecting head held by the head holder is held so as to be tiltable with respect to the longitudinal direction of the recording medium and a pair of holding members provided coaxially with the center axis of the recording medium. To detect the position of the two members that are biased and held and relatively linearly move.
Further, in this position detection device, the detection head held by the head holder is supported by the head holder supporting member that slides on the housing and is urged in the direction toward the sliding portion by the urging means, The position of the two members that relatively linearly move is detected.

In order to solve the above problem, a position detecting device according to the present invention is a position detecting device which detects a relative movement position between a first member and a second member which move relatively linearly. A long recording medium on which a position signal is recorded along the longitudinal direction, a housing fixed to the first member, and a fixing member fixing the housing and the recording medium. A main body, a head holder slidably attached to the recording medium in a longitudinal direction of the recording medium, a detection head held by the head holder and detecting a position signal recorded on the recording medium; A pair of holding members movably attached to the recording medium in the longitudinal direction of the medium and biasing the head holder in the longitudinal direction of the recording medium to hold the head holder, and fixed to the pair of holding members and the head holder; Automatic A head slider having a core means and a head carrier connected to the pair of holding members and fixed to the second member, wherein the pair of holding members have a center axis with respect to the moving direction of the recording medium, The head holder is provided coaxially, and the center axis of the head holder in the moving direction is tiltable with respect to the center axis of the pair of holding members in the moving direction, and the head holder is held by the pair of holding members. The centering means is characterized in that the center axes of the pair of holding members and the center axis of the head holder are matched with a predetermined elastic force.

In this position detecting device, the detecting head held by the head holder is held so as to be tiltable with respect to the longitudinal direction of the recording medium and a pair of holding members provided coaxially with the center axis of the recording medium. To detect the position of the two members that are biased and held and relatively linearly move.
Further, in this position detecting device, the center axis of the head holder holding the detection head is moved by the centering means fixed to the pair of holding members and the head holder with a predetermined elastic force to the center of the pair of holding members. Coincides with the axis.

[0051]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a position detecting device according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of a position detecting device according to a first embodiment of the present invention, FIG. 2 is a side view of the position detecting device, and FIG. 1 is a cross-sectional view illustrating the internal structure of FIG.

The position detecting device 1 according to the first embodiment of the present invention comprises a main body 2 and a head slider 3 attached to the main body 2.

The position detecting device 1 is configured as a part of a machine tool, and is a device for detecting a relative movement position of two members which move relatively linearly. For example, the position detection device 1
Is a reference part 4 fixed at a predetermined position,
Detecting a relative movement position of the movable portion 5 to move linearly in the direction X ₁ and X ₂ direction shown in FIG. 1 for. In the position detecting device 1, one of the main body 2 and the head slider 3 is attached to the reference portion 4, and the other is attached to the movable portion 5. FIG. 1 shows an example in which the main body 2 is attached to the reference portion 4 and the head slider 3 is attached to the movable portion 5.

The main body 2 is a casing 11 and a recording medium made of a long, high coercive force material such as a round bar.
And a bracket 13, 14 for holding both ends of the scale 12 and fixing the scale 12 at a predetermined position in the housing 11.
The brackets 13 and 14 are not shown in FIG. 1 for the sake of clarification of the drawings.

The housing 11 has, for example, a rectangular cylindrical shape, and has a slit 15 formed by cutting out one side surface. The housing 11 has substantially circular housing mounting holes 21, 22, 23, 24 formed at longitudinal ends of side surfaces 17, 18 orthogonal to the side surface on which the slit 15 is formed. . The side surface of the housing 11 where the slit is formed is referred to as a bottom surface 19, and the other surface parallel to the bottom surface 19 is referred to as an upper surface 20.

The scale 12 has its both ends held by brackets 13 and 14 and is fixed in the housing 11. The scale 12 is provided so as to be parallel to the longitudinal direction of the housing 11 and to be positioned on the central axis of the rectangular tube. A scale signal for detecting the relative position between the reference unit 4 and the movable unit 5 is magnetically recorded on the scale 12 as a position signal. This scale signal is a signal in which pits, marks, and the like, which are continuously repeated at predetermined intervals, are recorded in the longitudinal direction of the scale 12. For example, a magnetic signal whose polarity is inverted at a predetermined recording wavelength is a signal of the scale 12. This is a signal recorded continuously in the longitudinal direction.

The head slider 3 includes a head holding section 31 provided inside the main body 2, a head carrier 32 provided outside the main body 2, and a head holding section 3.
1 and a connecting portion 33 for connecting the head carrier 32 to the main body 2 so as to be movable in the longitudinal direction of the scale 12.

FIG. 4 is an exploded perspective view of a main part of the head holding unit 31.

The head holder 31 has a head holder 34
Is provided. The head holder 34 has an insertion hole for the scale 12. Head holder 34
The scale 12 is attached to the scale 12 by passing the scale 12 through the insertion hole, and is linearly movable in the longitudinal direction of the scale 12.

The outside of the head holder 34 is covered by a head holder case 36, and the inside thereof is
The signal detection head 35 is held. Signal detection head 3
5 detects the scale signal recorded on the scale 12. Since the signal detection head 35 is held by the head holder 34, the signal detection head 35 moves in parallel in the longitudinal direction of the scale 12 with the linear movement of the head holder 34.

A pair of sliding support members 37 and 38 are attached to both ends of the scale 12 of the head holder 34 in the longitudinal direction. The sliding support members 37 and 38 have a substantially columnar shape, and an insertion hole through which the scale 12 is inserted is provided in the center axis. The sliding support members 37 and 38 are slidably supported by the scale 12 by inserting the scale 12 into the insertion holes. The sliding support members 37 and 38 are slidably supported by the scale 12 so that when the head holder 34 moves parallel to the longitudinal direction of the scale 12,
The head holder 34 is prevented from being displaced in a direction perpendicular to the moving direction.

The head holding portion 31 has a pair of first
, And a pair of second spacers 41,
42 are provided.

The pair of first spacers 39 and 40 have insertion holes through which the scale 12 is inserted. The pair of first spacers 39 and 40 are attached to the scale 12 by inserting the scale 12 into the insertion holes, and are capable of linearly moving in the longitudinal direction of the scale 12. In addition, the pair of first spacers 39, 40
Is attached to one end face of the sliding support members 37, 38 to which the head holder 34 in the longitudinal direction of the scale 12 is not attached.

A pair of second spacers 41 and 42
Is provided with an insertion hole through which the scale 12 is inserted.
The pair of second spacers 41 and 42 are attached to the scale 12 by inserting the scale 12 into the insertion holes, and are linearly movable in the longitudinal direction of the scale 12. Also, the pair of second spacers 41,
Reference numeral 42 is provided on one end face of the scale 12 of the first spacers 39, 40 where the sliding support members 37, 38 in the longitudinal direction are not provided.

The head holding section 31 is provided with a pair of head holder holding members 43 and 44 and a spring 45.

The head holder holding members 43 and 44 are provided with insertion holes through which the scale 12 is inserted. The head holder holding members 43 and 44 are provided with a scale 1 in this insertion hole.
By being inserted, 2 is attached to the scale 12 and can be moved linearly in the longitudinal direction of the scale 12. The head holder holding members 43 and 44 are fixed to the connecting portion 33. The pair of head holder holding members 43 and 44 are used to connect the head holder 34 to which the sliding support members 37 and 38 are attached to the pair of first spacers 3.
9, 40 and a pair of second spacers 41, 42,
The scale 12 is sandwiched from both ends in a direction parallel to the longitudinal direction. A spring 45 is provided between the head holder holding member 43 and the second spacer 41. The spring 45 moves the head holder 34 from the head holder holding member 43 toward the head holder holding member 44.
Is energizing.

The head holder 34 is provided with a detent pin 46. This detent pin 46
Has one end in the longitudinal direction fixed to the head holder 34, and the other end inserted into a rotation regulating hole 147 provided in the connecting portion 33. Therefore, rotation of the head holder 34 about the scale 12 as a central axis is restricted.

Each component of such a head holding portion 31 has a coaxial configuration with the scale 12 as a central axis.
Therefore, the detection error of the scale signal due to the movement of the head holding unit 31 is minimized, and highly accurate position detection can be performed.

Further, in the head holding portion 31, each of the attachment surfaces on which the first spacers 39 and 40 and the second spacers 41 and 42 are attached has a spherical shape. In the head holding unit 31, the sliding support members 37 and 38 directly attached to the head holder 34 are used for the scale 1.
2, but the other components are, for example, a pair of first spacers 39 and 40 and a pair of second spacers 4.
The scale 12 is inserted into the head holder members 1 and 42 and the head holder holding members 43 and 44 with a certain gap. Therefore, for example, when the scale 12 has slight axis distortion or when a force in a direction other than the moving direction is applied to the head carrier 32, the head holder holding member 4
When a positional shift occurs in a direction perpendicular to the longitudinal direction of the scale 12 with respect to the center axes of the head holder 34 and the head holding members 43 and 44, when the position shift occurs in the direction orthogonal to the longitudinal direction of the scale 12. The function is to allow displacement and to reduce the bending moment applied to the scale 12.

The head holding unit 31 having the above configuration is
The scale 12 is attached to the scale 12 so as to be movable in a direction parallel to the longitudinal direction of the scale 12, and the signal detection head 35 detects a scale signal recorded on the scale 12 according to the movement.

The head holding unit 31 having such a structure is also provided.
Is provided with a guide mechanism 50. FIG. 5 is a perspective view of a main part of the head holding unit 31 provided with the guide mechanism 50.

The guide mechanism 50 is used for the head holder 34
, A first sliding portion 52 and a second sliding portion 53 attached to the guide pedestal 51, and a biasing portion 54 attached to the guide pedestal 51. Consists of

The guide pedestal 51 is made of a thin plate bent in a substantially U-shape. The guide pedestal 51 is attached to the head holder 34 such that three surfaces bent in a substantially U-shape are parallel to each surface of the housing 11 other than the bottom surface 19 in which the slit 15 is formed. I have. That is, the guide pedestal 51 is configured such that each surface of the thin plate bent in a substantially U shape is formed by the side surface 17 and the side surface 18 of the rectangular cylindrical housing 11.
And the upper surface 20 so as to be parallel. Here, a surface parallel to the side surface 17 is referred to as a first surface 51a, a surface parallel to the upper surface 20 is referred to as a second surface 51b, and a surface parallel to the side surface 18 is referred to as a third surface 51c. The guide pedestal 51
May not necessarily be parallel to the respective surfaces of the side surfaces 17 and 18 and the upper surface 20 of the housing 11.

The first sliding part 52 is a long carriage supporting part 5 attached to the first surface 51 a of the guide base 51.
5 and a pair of trolleys 56 and 57 provided at both ends of the trolley support portion 55. The carriage support portion 55 is attached in a direction in which the longitudinal direction is parallel to the scale 12. The pair of trolleys 56 and 57 are provided such that the wheels roll on the side surface 17 of the housing 11 in accordance with the movement of the head holding unit 31. Therefore, the first sliding portion 52 is fixed to the head holder 34 as a whole, and moves in parallel with the longitudinal direction of the scale 12 with the movement of the head holding portion 31.
It slides on the side surface 17 of the housing 11.

The second sliding portion 53 is a long carriage supporting portion 5 attached to the second surface 51b of the guide base 51.
8 and a pair of carriages 59 and 60 provided at both ends of the carriage support portion 58. The carriage supporting portion 58 is attached in a direction in which the longitudinal direction is parallel to the scale 12. The pair of trolleys 59 and 60 are provided such that the wheels roll on the upper surface 20 of the housing 11 in accordance with the movement of the head holding unit 31. Therefore, the second sliding portion 53 is fixed to the head holder 34 as a whole, and moves in parallel in the longitudinal direction of the scale 12 with the movement of the head holding portion 31.
It slides on the upper surface 20 of the housing 11.

Although the bogies 56, 57, 59 and 60 are shown in FIG. 5 as having a pair of two wheels, the number of wheels is not limited. For example, the number of wheels is one. It may be configured. In addition, carts 56, 57,
One of the wheels 59 and 60 may be configured with one wheel, and the other may be configured with a pair of two wheels.

The biasing portion 54 includes a leaf spring 61 provided continuously on the third surface 51 c of the guide base 51, and a pressing sliding portion 62 provided at an end of the leaf spring 61. .
One end of the leaf spring 61 is continuously provided in parallel with the third surface 51c of the guide base 51, and the other end is bent by about 45 degrees. The pressing sliding portion 62 is provided at a bent portion at the other end of the leaf spring 61, and is provided on the side surface 18 of the housing 11.
And the bottom part 19 provided with the slit 15 is abutted against the corner part 18a of the casing 11 on the rectangular tube, which is the connection part between the two. The pressing and sliding portion 62 slides on a corner portion 18 a which is a connection portion between the side surface 18 of the housing 11 and the bottom surface 19 provided with the slit 15 in accordance with the movement of the head holding portion 31. Therefore, the pressing and sliding portion 62 is fixed to the head holder 34 as a whole, urges the head holder 34 in the direction from the corner portion 18a toward the scale 12, and the side surface 18 of the housing 11 and the slit 15 are provided. Slides at the connection with the given surface.

[0079] In such a guide mechanism 50, as shown in FIG. 6, the direction from the corner portion 18a to the center of the housing 11 (the X ₃ direction in FIG. 6), the urging portion 54 of the head holder 34 It is energizing. Therefore, the guide mechanism 50
In, from the center of the housing 11 in the direction toward perpendicular to the side surface 17 (the X ₄ direction in FIG. 6), the force for pressing the side surfaces 17 of the housing 11 is applied to the first sliding portion 52. Further, in the guide mechanism 50, from the center of the housing 11 in the direction toward perpendicular to the top surface 20 (in FIG. 6 to X ₅ direction), the force for pressing the upper surface 20 of the housing 11 is a second sliding portion 53 Join.
Therefore, in the guide mechanism 50, the head holder 34
Of the scale 12 in accordance with the longitudinal movement of the scale 12 can be suppressed.

The head holding section 31 is connected to the connecting section 3
3 and a head carrier 32. The connecting portion 33 has one end in a direction orthogonal to the longitudinal direction of the scale 12 fixed to the head holder holding members 43 and 44, and the other end inserted through the slit 15 and provided outside the main body 2. Fixed to

As described above, the head slider 3 is constituted by the head holding portion 31, the head carrier 32, and the connecting portion 33, and is movably movable in the longitudinal direction of the scale 12.
Attached to. And this head slider 3
Is a signal detection head 35 according to relative movement with respect to the main body 2.
Supplies the detected scale signal to a control device (not shown) via a signal cable 63 provided on the head carrier 32.

The position detecting device 1 having the above configuration is arranged such that the scale 12 is parallel to the direction of relative movement between the reference portion 4 and the movable portion 5, and the slit 15 is opened to the movable portion 5 side. In the main body 2 of the position detecting device 1 arranged as described above, one of the side surfaces 17 and 18 orthogonal to the side surface on which the slit 15 is formed serves as a mounting surface. At the positions of the housing mounting holes 21, 22, 23, 24 provided at the end of the mounting surface in the direction parallel to the longitudinal direction of the scale 12, the reference portion is fixed by a fixing member such as a body bolt or a washer. Fixed to 4. Further, the head slider 3 of the position detecting device 1 arranged as described above is fixed to the movable portion 5 by bolts.

Accordingly, in the position detecting device 1, the main body 2 and the head slider 3 are moved in accordance with the linear movement of the movable portion 5.
And a signal detection head 35 provided in the head slider 3 detects a scale signal that changes in accordance with the change in the relative position, thereby detecting the moving position of the movable portion 5. Can be.

Further, in the position detecting device 1, the head holder 34 holding the signal detecting head 35 is slid and moved in the housing 11 by the guide mechanism 50. for that reason,
This change in the attitude of the signal detection head 35 is reduced, and a position error, which is an error due to a difference in the position of the signal detection head 35 on the scale 12, and a return error, which is an error due to a difference in the moving direction of the signal detection head 35. Can be reduced without significantly increasing the cost, and the positions of the two members that move relatively linearly can be detected with high accuracy.

In the position detecting device 1, the housing 11
The means for urging the first sliding portion 52 and the second sliding portion 53 in the direction from the center of the housing to the side surface 17 and the upper surface 20 is the same as the housing 11 in the position detecting device 1 of this embodiment. By moving the head holder 3, the housing 11 is used as a fulcrum.
Although the urging portion 54 for urging the fourth member 4 is used, the present invention is not limited to such means. For example, the biasing means may be fixed to the pair of head holder holding portions 43 and 44 and the connecting portion 33, and may bias the head holder 34 with the pair of head holder holding portions 43 and 44 and the connecting portion 33 as a fulcrum. Further, the urging portion 54 urges the head holder 34 by the spring force of the leaf spring 61. However, without using such a spring force, for example, the compressed air is blown out to the housing 11 side and the head holder 34 is urged. 34 may be energized.

As shown in FIG. 7, in the position detecting device 1, the bogie supporting portions 55 (58) of the first sliding portion 52 and the second sliding portion 53 are attached from the center of the housing 11. Side 17
Elastic part 6 elastically displaced in a direction toward (or upper surface 20).
4 may be provided.

Next, a position detecting device according to a second embodiment of the present invention will be described with reference to the drawings.

FIG. 8 is a sectional view showing the internal structure of a position detecting device according to a second embodiment of the present invention. Note that the appearance of the position detecting device of the second embodiment is the same as that of the position detecting device 1 of the first embodiment, so that the perspective view and the side view are omitted here. Also,
In describing the position detecting device of the second embodiment, the same components as those of the position detecting device 1 of the first embodiment are denoted by the same reference numerals in the drawings, and detailed description thereof will be omitted. I do.

The position detecting device 71 according to the second embodiment of the present invention comprises a main body 2 and a head slider 3 attached to the main body 2.

The position detecting device 71 is configured as a part of a machine tool, and detects a relative movement position of two members which move relatively linearly.

The main body 2 holds the housing 11, the scale 12 provided inside the housing 11, and both ends of the scale 12, and fixes the scale 12 at a predetermined position in the housing 11. And brackets 13 and 14 to be used.

The housing 11 has, for example, a rectangular cylindrical shape, and has a slit 15 formed by cutting out one side surface. The housing 11 has substantially circular housing mounting holes 21, 22, 23, 24 formed at longitudinal ends of side surfaces 17, 18 orthogonal to the side surface on which the slit 15 is formed. .

The scale 12 has its both ends held by brackets 13 and 14 and is fixed in the housing 11. The scale 12 is provided so as to be parallel to the longitudinal direction of the housing 11 and to be positioned on the central axis of the rectangular tube. A scale signal for detecting the relative position between the reference unit 4 and the movable unit 5 is magnetically recorded on the scale 12 as a position signal.

The head slider 3 includes a head holding portion 72 provided inside the main body 2, a head carrier 32 provided outside the main body 2, and a head holding portion 7.
The scale 12 has a connecting portion 33 connecting the head carrier 32 to the main body 2, and is attached to the main body 2 movably in the longitudinal direction of the scale 12.

The head holder 34 includes a head holder 34.
Is provided. The outside of the head holder 34 is covered by a head holder case 36, and a signal detection head 35 is held therein. The signal detection head 35 detects a scale signal recorded on the scale 12.

A pair of sliding support members 37 and 38 are attached to both ends of the scale 12 of the head holder 34 in the longitudinal direction.

The head holding portion 72 is provided with a pair of first spacers 39 and 40 and a pair of second spacers 41 and 42. This pair of first spacers 39, 4
Numeral 0 is provided on one end surface of the sliding support members 37, 38 to which the head holder 34 in the longitudinal direction of the scale 12 is not attached. Also, the pair of second spacers 41,
Reference numeral 42 is provided on one end face of the scale 12 of the first spacers 39, 40 where the sliding support members 37, 38 in the longitudinal direction are not provided.

The head holding section 72 is provided with a pair of head holder holding members 43 and 44 and a spring 45.

The head holder 34 is provided with a pin 46 for preventing rotation.

Each component of the head holding portion 72 has a coaxial configuration with the scale 12 as a central axis.
Therefore, the detection error of the scale signal due to the movement of the head holding unit 72 is minimized, and highly accurate position detection can be performed.

In the head holding section 72, the respective surfaces on which the first spacers 39 and 40 and the second spacers 41 and 42 are provided have a spherical shape. In the head holding unit 72, the sliding support members 37 and 38 directly attached to the head holder 34 are used for the scale 1.
2, but the other components are, for example, a pair of first spacers 39 and 40 and a pair of second spacers 4.
The scale 12 is inserted into the head holder members 1 and 42 and the head holder holding members 43 and 44 with a certain gap. Therefore, for example, when the scale 12 has slight axis distortion or when a force in a direction other than the moving direction is applied to the head carrier 32, the head holder holding member 4
When a positional shift occurs in a direction perpendicular to the longitudinal direction of the scale 12 with respect to the center axes of the head holder 34 and the head holding members 43 and 44, when the position shift occurs in the direction orthogonal to the longitudinal direction of the scale 12. The function is to allow displacement and to reduce the bending moment applied to the scale 12.

The head holding section 72 having the above structure is
The scale 12 is attached to the scale 12 so as to be movable in a direction parallel to the longitudinal direction of the scale 12, and the signal detection head 35 detects a scale signal recorded on the scale 12 according to the movement.

The head holding section 72 having such a structure is also provided.
Are provided with a plurality of self-aligning springs 73. FIG. 9 is a perspective view of a main part of the head holding unit 72 provided with the plurality of self-aligning springs 73.

Each of the self-aligning springs 73 has a substantially elongated shape, and is provided so that its longitudinal direction is parallel to the scale 12. Each self-aligning spring 7
3 has a central portion fixed to the head holder 34.
Both ends of each self-aligning spring 73 are fixed to a pair of head holder holding members 43 and 44, respectively. The self-aligning spring 73 has an elastic portion 74 formed between the pair of head holder holding members 43 and 44 and the center.

For example, when the attitude of the head holder 34 changes due to the movement of the scale 12 in the longitudinal direction, the plurality of self-aligning springs 73 are generated by the elastic force of the elastic portion 74. It works so that the holder 34 is located at the ideal center. In other words, the self-centering spring 73 is configured by the pair of head holder holding members 43 and 44 and the head holder 3.
It works to make the central axis coincide with 4.

The head holding section 72 is connected to the connecting section 3
3 and a head carrier 32. The connecting portion 33 has one end in a direction orthogonal to the longitudinal direction of the scale 12 fixed to the head holder holding members 43 and 44, and the other end inserted through the slit 15 and provided outside the main body 2. Fixed to

As described above, the head slider 3 comprises the head holding portion 72, the head carrier 32, and the connecting portion 33, and is movably movable in the longitudinal direction of the scale 12.
Attached to. And this head slider 3
Is a signal detection head 35 according to relative movement with respect to the main body 2.
Supplies the detected scale signal to a control device (not shown) via a signal cable 63 provided on the head carrier 32.

The position detecting device 71 having the above configuration is
The scale 12 is arranged so as to be parallel to the direction of relative movement between the reference part 4 and the movable part 5, and the slit 15 is opened to the movable part 5 side. In the main body 2 of the position detecting device 71 arranged as described above, one of the side surfaces 17 and 18 orthogonal to the side surface on which the slit 15 is formed serves as a mounting surface. Then, at the positions of the housing mounting holes 21, 22, 23, 24 provided at the end of the mounting surface in the direction parallel to the longitudinal direction of the scale 12,
It is fixed to the reference part 4 by fixing members such as body bolts and washers. In addition, the position detecting device 7 thus arranged
The first head slider 3 is fixed to the movable portion 5 by bolts.

Accordingly, in the position detecting device 71, the relative position between the main body 2 and the head slider 3 changes according to the linear movement of the movable portion 5, and the signal detecting head 35 provided in the head slider 3 By detecting the scale signal that changes according to the change in the relative position, the moving position of the movable unit 5 can be detected.

In the position detecting device 71, the center position of the head holder 34 holding the signal detecting head 35 is held by the self-aligning spring 73. Therefore, the change in the attitude of the signal detection head 35 is reduced, and a positional deviation error, which is an error due to a difference in the position of the signal detection head 35 on the scale 12, and a return, which is an error due to a difference in the moving direction of the signal detection head 35. Both the error and the error can be reduced without significantly increasing the cost, and the positions of the two members relatively linearly moving can be detected with high accuracy.

The self-aligning spring 73 is not limited to a self-aligning spring using a spring force, but may be a spring having a liquid self-aligning structure using air or oil.

[0112]

In the position detecting apparatus according to the present invention, the detecting head held by the head holder is held so as to be tiltable with respect to the longitudinal direction of the recording medium and is provided coaxially with the center axis of the recording medium. The position of the two members which are urged and held by the pair of holding members and relatively linearly moved is detected. As a result, in this position detection device, the recording medium and the holding mechanism of the detection head have a coaxial structure, and a deviation from the center axis of the recording medium is allowed. The bending moment applied to the medium can be reduced.

Further, in this position detecting device, the detection head held by the head holder is supported by the head holder supporting member that slides on the housing, and is urged in the direction toward the sliding portion by the urging means. Then, the positions of the two members that relatively linearly move are detected. As a result, this position detection device can reduce both the detection error due to the difference in the position of the detection head on the recording medium and the error due to the difference in the moving direction of the detection head, and perform position detection with high accuracy. Can be.

In the position detecting device according to the present invention,
The detection head held by the head holder is held so as to be tiltable with respect to the longitudinal direction of the recording medium and is urged and clamped by a pair of clamping members provided coaxially with the central axis of the recording medium, The position of the two members that relatively linearly move is detected. As a result, in this position detection device, the recording medium and the holding mechanism of the detection head have a coaxial structure, and a deviation from the center axis of the recording medium is allowed. The bending moment applied to the medium can be reduced.

Further, in this position detecting device, the center axis of the head holder holding the detecting head is held by the pair of holding members and the self-aligning means fixed to the head holder with a predetermined elastic force. It coincides with the central axis of the member. As a result, this position detection device can reduce both the detection error due to the difference in the position of the detection head on the recording medium and the error due to the difference in the moving direction of the detection head, and perform position detection with high accuracy. Can be.

[Brief description of the drawings]

FIG. 1 is a perspective view of a position detecting device according to a first embodiment of the present invention.

FIG. 2 is a side view of the position detection device according to the first embodiment.

FIG. 3 is a cross-sectional view illustrating an internal structure of the position detection device according to the first embodiment.

FIG. 4 is an exploded perspective view of a main part of a head holding unit of the position detecting device according to the first embodiment.

FIG. 5 is a perspective view of a main part for describing a guide mechanism of the position detection device according to the first embodiment.

FIG. 6 is a view for explaining a biasing direction of a head holder by the guide mechanism.

FIG. 7 is a view for explaining a modified example of the guide mechanism.

FIG. 8 is a sectional view illustrating an internal structure of a position detecting device according to a second embodiment of the present invention.

FIG. 9 is a perspective view of a main part for describing a self-aligning spring of the position detecting device according to the second embodiment.

FIG. 10 is a perspective view of a conventional position detecting device.

FIG. 11 is a side view of the conventional position detecting device.

FIG. 12 is a cross-sectional view illustrating an internal structure of the conventional position detecting device.

FIG. 13 is an exploded perspective view of a main part of a head holding unit of the conventional position detecting device.

FIG. 14 is a diagram for explaining a change in attitude of a detection head of the conventional position detection device.

FIG. 15 is a diagram for explaining a posture change state when the detection head moves on a scale having flexure.

FIG. 16 is a diagram for explaining an error amount when the detection head moves on a scale having flexure.

[Explanation of symbols]

1, 71 position detecting device, 2 main body, 3 head slider, 4 reference portion, 5 movable portion, 11 housing, 12 scale, 34, 72 head holder, 35 signal detection head, 36, 38 sliding support member, 39 , 40 first spacer, 41, 42 second spacer, 43, 44 head holder holding member, 45 spring, 50 guide mechanism,
73 self-aligning spring

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F063 AA02 BA21 CA21 CB10 CC08 DB04 EA02 GA06 KA04 ZA01 2F069 AA02 AA06 AA34 BB01 DD12 DD21 EE04 EE26 GG06 GG12 GG62 HH14 HH21 MM04 MM09 MM13 MM21MM26

Claims (2)

[Claims] A first member and a second member which move relatively linearly;
A position detection device for detecting a relative movement position with respect to a member, a long recording medium in which a position signal is recorded along a longitudinal direction, a housing fixed to the first member, and the housing And a main body having a fixing member for fixing the recording medium, a head holder slidably attached to the recording medium in a longitudinal direction of the recording medium, and recording on the recording medium held by the head holder. A detection head that detects the position signal, and a pair of holding members that are attached to the recording medium so as to be movable in the longitudinal direction of the recording medium and bias the head holder in the longitudinal direction of the recording medium, and A head holder supporting member fixed to the head holder and supporting the head holder by sliding with the housing; and an urging device for urging the head holder in a direction orthogonal to a longitudinal direction of the recording medium. A head slider having a step and a head carrier connected to the pair of holding members and fixed to the second member, wherein the pair of holding members have a center axis coaxial with the recording medium in a moving direction thereof. The head holder has a center axis with respect to the moving direction,
The pair of holding members can be tilted with respect to a center axis with respect to the moving direction, and are held between the pair of holding members. The urging means is adapted to slide between the head holder support member and the housing. A position detecting device for urging the head holder in a direction toward the head. 2. A first member and a second member which relatively move linearly.
A position detection device for detecting a relative movement position with respect to a member, a long recording medium in which a position signal is recorded along a longitudinal direction, a housing fixed to the first member, and the housing And a main body having a fixing member for fixing the recording medium, a head holder slidably attached to the recording medium in a longitudinal direction of the recording medium, and recording on the recording medium held by the head holder. A detection head that detects the position signal, and a pair of holding members that are attached to the recording medium so as to be movable in the longitudinal direction of the recording medium and bias the head holder in the longitudinal direction of the recording medium, and A self-aligning means fixed to the pair of holding members and the head holder; and a head slider having a head carrier connected to the pair of holding members and fixed to the second member. For example, the pair of clamping members, the central axis is provided on the recording medium coaxially with respect to the movement direction, the head holder, the center axis with respect to the moving direction thereof,
The pair of holding members can be tilted with respect to the center axis with respect to the moving direction, and are held between the pair of holding members. The self-aligning means has a predetermined elastic force and has a predetermined elastic force. A position detecting device, wherein a center axis of the head holder is made to coincide with the center axis.