JP3077123B2 - Position detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detector used for position measurement in a machine tool, and more particularly to a mounting mechanism for the position detector.

[0002]

2. Description of the Related Art In a position detector for detecting a position and a displacement of a machine tool, a main scale serving as a reference scale is attached in parallel to a moving direction of a machine main body without distortion, so that accurate positioning is achieved. Important above. Hereinafter, a simple configuration and a mounting portion of a main scale will be described by taking an optical encoder as an example. FIG. 8 is a configuration diagram showing an example of a general optical encoder. The optical encoder 100 is provided with a graduated track in which a light transmitting portion and a light transmitting portion are repeated at a constant pitch, and includes a main scale 1 that moves in a longitudinal direction, a light source 4, a light receiving element 5, and the like. And a reading unit 3 for optically detecting a scale on the main scale 1. The reading unit 3 detects the position of the main scale 1 which moves in the longitudinal direction with the movement of the machine, and sends the position to the control device. It has become. Usually, the main scale 1 is attached to the machine body via some attachment member 2.
Conventionally, as a method of fixing the main scale 1 to the mounting member 2, for example, there is a method of firmly bonding the main scale 1 to the reference surfaces PH and PV of the mounting member 2 with an adhesive.

[0003]

In the above-described position transducer, the main scale is often made of a glass material, and has a coefficient of thermal expansion different from that of the machine body or the mounting member. Therefore, in the fixing method using an adhesive, when there is a large temperature change, the adhesive layer is subjected to stress and peels off, or the main scale is distorted.
Other methods have been proposed, such as floating the main scale from the mounting member with a resilient material or pressing the mounting member against the mounting member with a spring mechanism. There have been problems such as difficulty in maintaining the parallelism of the mounting member and the main scale being displaced by a small external force and not being restored.

Here, several conditions required for the mounting member of the position detector are listed. If the longitudinal direction of the main scale is not exactly parallel to the axis of movement of the machine, or if the main scale is distorted for any reason, the position may not be accurately detected. Needs to be kept accurate. When the material of the main scale has a different coefficient of thermal expansion from the machine or the mounting member, stress may be applied to the main scale due to the thermal expansion when there is a temperature change. Therefore, it is necessary to release the expansion and contraction in the longitudinal direction. Even if a certain force is applied to the main scale and the positional relationship with the mounting member changes, it is necessary to have the ability to restore the original positional relationship. Without restoring power, it can be left out or out of place.
However, it has been difficult to satisfy all of these conditions with the conventional main scale mounting method. The present invention has been made under the circumstances described above, and an object of the present invention is to
It is an object of the present invention to provide a position detector provided with a mounting member on which a main scale is accurately mounted on a machine and which does not change with time.

[0005]

SUMMARY OF THE INVENTION The present invention comprises a main scale which is scaled and moves in a longitudinal direction, and a reading unit which reads the scale and detects the position of the main scale. The present invention relates to a position detector to be attached to a machine via an attachment member, and the above object of the invention is achieved by incorporating a shrinkage element which attracts the main scale to a reference surface of the attachment member by shrinkage. Is done. Further, the contraction element is achieved by being an elastic material filled in a groove provided in the mounting member. Alternatively, the contraction element is achieved by being a spring installed in the mounting member. The elastic material is achieved by having a property that the volume shrinkage rate at the time of curing is larger than the temperature shrinkage in the use temperature range of the position detector. Further, the groove portion provided on the reference surface of the mounting member is achieved by being discontinuous in the longitudinal direction of the main scale.

[0006]

In the position detector of the present invention, since the main scale is fixed to the reference surface of the mounting member with a material having a contracting force, such as an elastic resin, an elastic adhesive or a spring mechanism, The main scale can be attached to the machine so that the main scale and the reference plane are kept parallel and are not easily affected by temperature changes and external forces.

[0007]

FIG. 1 shows a first example of a position detector according to the present invention.
FIG. The same components as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted. In this example, the reference surfaces PH and P in contact with the main scale 1
V is provided with long grooves GH and GV, respectively, in the longitudinal direction. These grooves GH and GV are filled with an elastic material FM while having a contracting force. The main scale 1 attached in this manner is made of an elastic material FM.
The reference plane P in both the horizontal and vertical directions
Attracted to H and PV.

Here, the characteristics of the main scale attached by the above method will be described. Usually, the reference plane P of the mounting member
H and PV are precisely machined so as to be parallel to the machine movement direction. Therefore, the straightness of the main scale and the parallelism with the moving direction of the machine are accurately maintained by the main scale being attracted to the reference plane. In addition, even if temperature changes occur in the environment in which the main scale is used, and a different amount of expansion or contraction occurs in the longitudinal direction due to the difference in the coefficient of thermal expansion between the main scale and the machine or the mounting member, the main scale will remain Is relatively free of stress. Further, even if an external force F which is likely to be generated in the structure as shown in FIG. 1 and presses the main scale right and left is applied, the elasticity of the material in the groove prevents the main scale from being broken, and the external force F is eliminated. Sometimes it can be restored to the original correct state again.

Here, as an example, a method of attaching the main scale to the attachment member will be introduced. Main scale 1 in Fig. 1
When the main member 1 is attached to the attachment member 2, the elastic material FM which does not lose its elasticity even after being cured, such as an elastic resin or an elastic adhesive, is formed in the groove G while the main scale 1 is in contact with the reference surfaces PH and PV.
Fill H and GV. Alternatively, the elastic material FM is put in the grooves GH and GV before being cured, and then the main scale 1 is placed so as to be in contact with the reference surfaces PH and PV, and then cured. However, the elastic material FM has a property of contracting in volume upon curing. The main scale 1 attached in this manner is attracted to the reference planes PH and PV both horizontally and vertically by the contraction force of the elastic material FM during curing.

FIG. 2 is a partial sectional view showing a second example of the position detector according to the present invention. In this example, the elastic material FM is formed in the groove.
Is not filled, and the wall surface of the groove and the elastic material F
The elastic material FM has a contraction force, and one of the left and right end faces is attached to the main scale 1 and the other is attached to the mounting member 2. As described above, when the main scale is attached, the characteristics of the first embodiment are not lost, and the tolerance of the displacement due to the external force is increased by the amount of the gap. FIG. 3 is a partial cross-sectional view of the portion of the mounting member 2 in FIG. 1 as viewed from the direction of arrow R, and shows one of variations using the above-described mounting method. This figure shows that the grooves are separated in the longitudinal direction and each groove is filled with an elastic material.

According to this structure, the influence of the longitudinal expansion and contraction of the elastic material caused by a temperature change or the like is separated at each portion and is not accumulated in the longitudinal direction. Also, if the elastic material is divided into five in the longitudinal direction, for example, as indicated by FMa to FMe in the figure, and the left end FMa portion is made of a hard material and the other portion is made of a relatively soft material, the temperature change may occur. , The main scale expands and contracts rightward with respect to the mounting member with respect to the left end. If the center FMc is made of a hard material, both ends of the main scale expand and contract with respect to the center. As described above, by appropriately changing the properties of the material of each portion, it is possible to set a reference for expansion and contraction due to a temperature change to a desired portion.

In the above-described embodiments, the example of mounting the main scale in the horizontal direction and the vertical direction by the same method has been described. However, the same method is not required. For example, FIGS. 4 and 5
Compensates for the disadvantages of the existing method by combining the existing method with the method according to the invention. The main scale 1 is pressed against the reference plane PV by the spring mechanism 6 in FIG. 4 and by the rubber 7 in FIG. However, if the main scale 1 shifts in the vertical direction due to an external force or an impact, the conventional method has no restoring force, so that the main scale 1 is left shifted. Therefore, the mounting mechanism according to the present invention is mounted on the reference plane P
By providing the main scale at the H portion, even if the main scale is displaced in the vertical direction due to external force or impact, it can be restored to the correct position.

The next embodiment is shown in FIG. In this example, the main scale 1 is deformed as shown in FIG. 2B by applying a force Fa as shown by an arrow to an elastic material FM which has a shape as shown in FIG. Glue to At this time, the main scale 1 is attracted to the reference plane PV by the contraction force Fb of the elastic material FM. To deform as shown in FIG. 3B, the elastic material FM may be deformed by mechanically pressing it with something, or may be deformed by applying pressure from outside with air or the like into the groove. It is possible. Further, a similar effect can be obtained by incorporating a spring 8 into the mounting member 2 instead of these elastic materials as shown in FIG. 7 and utilizing the contraction force of the spring 8.

[0014]

As described above, according to the position detector of the present invention, it is possible to realize a compact mounting that is not easily affected by expansion and contraction due to temperature and external force while maintaining good mounting accuracy of the main scale. Therefore, it is possible to achieve higher precision and lower cost of the optical encoder and the like.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first example of a position detector of the present invention.

FIG. 2 is a partial cross-sectional view showing a second example of the position detector of the present invention.

FIG. 3 is a view of a part of the mounting member of FIG.
It is a partial sectional view showing a third example.

FIG. 4 is a partial sectional view showing a fourth example of the position detector of the present invention.

FIG. 5 is a partial sectional view showing a fifth example of the position detector of the present invention.

FIG. 6 is a partial sectional view showing a sixth example of the position detector of the present invention.

FIG. 7 is a partial sectional view showing a seventh example of the position detector of the present invention.

FIG. 8 is a configuration diagram illustrating an example of a general optical encoder.

[Explanation of symbols]

GH, GV Groove FM, FMa, FMb, FMc, FMd, FMe Elastic material 8 Spring

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01D 5/00-5/62 B23Q 17/22 G01P 1/00-3/80 G01B 21/00-21 / 32

Claims (5)

(57) [Claims] 1. A main scale provided with a scale and moving in a longitudinal direction, and a reading unit for reading the scale and detecting a position of the main scale, and mounting the main scale to a machine via a mounting member. In the position detector, a shrinkage element that attracts the main scale to a reference surface of the attachment member by shrinkage is incorporated in the attachment member. 2. The position detector according to claim 1, wherein the contraction element is an elastic material filled in a groove provided in the mounting member. 3. The position detector according to claim 2, wherein the elastic material has such a property that a volumetric shrinkage ratio at the time of curing is larger than a temperature shrinkage in a use temperature range of the position detector. 4. The position detector according to claim 2, wherein a groove provided on a reference surface of the mounting member is discontinuous in a longitudinal direction of the main scale. 5. The position detector according to claim 1, wherein the contraction element is a spring installed in the mounting member.