JP2001317967A - Linear encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a damper member which restrains the resonance of a linear scale. SOLUTION: The damper member 10 is constituted of a damper material 11, which is constituted of a synthetic resin, such as Duracon resin(R) (polyacetal resin) or a synthetic rubber. The damper member 10 is constituted of a damper pin 12, which passes through the damper material 11 and which comes into contact with the second pivot bearing 34 of a pivot bearing 32. The damper member 10 is constituted of support plates 13a, 13b, composed of elastic bodies such as leaf springs which pass through the square shape part 28 of a fixed link 31 so as to be sandwiched. The damper member 10 is constituted of a mounting part 14 to the fixed link 31. The pivot bearing 34 of the pivot bearing 32, which connects a slider to the fixed link 31, is brought into point contact with the damper pin 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical linear scale suitable for measuring a relative movement amount during machining of a machine tool or the like. The present invention relates to an optical linear scale provided with a mechanism for preventing resonance.

[0002]

2. Description of the Related Art In a machine tool or the like, it is extremely important to accurately measure a relative movement amount of a tool with respect to a workpiece in performing precision machining, and various measuring devices have been commercialized. .

[0003] As one of them, an optical scale utilizing moiré fringes obtained by superposing two optical gratings has been conventionally known. This optical scale is
As shown in FIG. 7, a main scale 40 in which a grid (notched line) is provided on one surface of a reflective glass scale 22 so that light transmitting portions and non-light transmitting portions are arranged at a predetermined pitch,
7 has an index scale 41 on one surface of a transparent glass provided with a grid (line) so that light transmitting portions and non-light transmitting portions are arranged at a predetermined pitch, as shown in FIG. The main scale 40 and the index scale 4
1 are arranged at a small interval, and a grid of an index scale 41 is arranged so as to be inclined at a small angle with respect to a grid of a main scale 40, as shown in FIG.

The grids provided on the main scale 40 and the index scale 41 are glass scales 22,
Chromium is vacuum-deposited on glass provided on the surface of the sensor unit 27, and is formed by a lattice having the same pitch formed by etching.

With this arrangement, moire fringes are generated at regular intervals. The moire fringes have dark or bright portions at regular intervals (not shown). The dark or bright portions correspond to the direction in which the index scale 41 moves left and right relative to the main scale 40. Move from top to bottom or bottom to top. In this case, the pitch of the grid of the main scale 40 and the index scale 41 is P, and the mutual inclination angle is θ.
[Rad], assuming the interval W between moiré fringes, the interval W between moiré stripes is expressed as W = P / θ, and the interval W between moiré stripes is an optically enlarged lattice interval P 1 / θ times. It will be. When the grating moves by one pitch P, the moire fringes are displaced by the interval W between the fringes, and by reading the change in transmitted light or reflected light of the slit within the interval W, the amount of movement within one pitch P is reduced. It will be possible to measure accurately.

The configuration of a conventional linear encoder is shown in FIGS.
As shown in FIG. 4 is a perspective view of a conventional linear encoder 100, FIG. 5 is a front view thereof, and FIG. 6 is a side view thereof. The linear encoder 100 includes a slider 26 for sliding the glass scale 22 and a fixed link 31 for attachment to a movable portion 51 of a machine tool or the like (not shown). The slider 26 includes a sensor unit 27 for reading the displacement, left and right side guide rollers 23 provided with a leaf spring for sliding the glass scale 22 with less deflection, a lower guide roller 24, and a lower guide roller receiver 25. In use, as shown in FIG. 6, the slider 26 is covered with a case 21, and the opening thereof is sealed by a shielding member 39.

The fixed link 31 is connected to a movable portion 51 of the machine tool.
, The square shape part 28, the arm 29, the shaft 30
The square portion 28 has a degree of freedom in connection with the slider 26 due to the shaft 30.

The connecting pivot 32 includes a first pivot bearing 33 provided on the slider 26, a second pivot bearing 34 provided on the fixed link 31, a connecting pivot 35, a tension coil spring, and a first pivot bearing. Pivot screw 37, pivot screw 3 of second pivot bearing
8. The tension coil spring 36
The bearings 33 and 34 are pulled in the directions opposite to the arrows A and B, and a load is applied to the connection pivot 35 via the pivot screws 37 and 38.

With the above-described configuration, the slider 26 having the sensor portion 27 is connected from the square portion 28 of the fixed link 31 via the connection pivot 35, and the encoder 100 follows the vibration from the machine tool. It can have sex.

The scale body 22 and the encoder 100 are attached to the fixed part 50 and the movable part 51 of the machine tool, respectively, and the moving amount (displacement) of the movable part 51 of the machine tool is measured by the scale body (glass scale) 22 and the encoder 100.
(Slider sensor unit 27) is detected as a relative movement amount.

A mechanical system originally has a natural frequency due to its constituent parts, and when a vibration corresponding to the natural frequency is applied from the outside, a resonance phenomenon occurs, and acceleration and amplitude are amplified. Even a conventional encoder has a natural frequency, and when this natural frequency matches the vibration from the machine tool, resonance occurs, and the followability to the behavior of the machine tool is lost, and only the encoder resonates.

An encoder 10 as shown in FIGS.
Even in the case of 0, when the glass scale 22 is mounted on the machine tool and used as a linear length measuring sensor, cutting vibrations and the like generated during heavy cutting of the machine tool are transmitted to the glass scale 22 and a problem occurs in reading the scale. There are cases.

In particular, since heavy cutting has recently been performed, high-frequency vibrations, which hardly occur in the past, have occurred. For this reason, the main scale 22 is vibrated by the vibration during the heavy cutting, and the resonance phenomenon of the main scale 22 causes an abnormal run-out of the sensor unit 27, which causes a scale alarm (excessive response speed) and poor behavior following (abnormal). Due to the occurrence of displacement output, etc., the number of cases where the machine tool stops and the workpiece machining accuracy is poor has increased.

FIG. 8A is a diagram showing the relationship between the Lissajous rotation speed on an oscilloscope for each frequency when vibration is applied to a conventional linear encoder. As clearly shown in the figure, the vibration frequency exceeds 600 Hz,
It can be seen that considerable resonance occurs in the frequency range up to about 0 Hz, and especially the peak Lissajous rotation is 3.0.
It reaches five times.

On the other hand, since the vibration frequency range generated from the machine tool varies depending on the cutting conditions and the like and cannot be specified, even if the spring constant of the spring which is a component of the encoder is changed, only the natural frequency range slightly changes. Fundamentally, such a resonance phenomenon cannot be avoided.

The following problems occur due to the resonance phenomenon of the encoder. 1. Due to resonance, only the encoder causes amplification of the acceleration and amplitude, and shakes at high speed, so that the encoder exceeds the displacement reading allowable speed and a reading error occurs. 2. Since only the encoder resonates, the ability to follow the vibration of the machine tool is lost, the behavior of the machine tool cannot be accurately measured, and the processing accuracy of the final product is inferior. 3. Excitation acceleration is amplified by the occurrence of resonance,
Encoder may be damaged.

[0017]

SUMMARY OF THE INVENTION An object of the present invention is to provide a damper member for suppressing the resonance of a linear scale in order to avoid the above-mentioned problems.

[0018]

According to the present invention, in order to solve the above-mentioned problems, a damper member for suppressing resonance is provided with a vibration transmitting pivot, a damper member, and a pressing member for attaching to a fixed link on a resonance generating portion of an encoder. It is constituted by a support plate made of a spring, and the damper material is made of a material having good vibration absorption.

According to a first aspect of the present invention, there is provided a first support attached to a position to be measured, and a scale which is swingably supported by the first support and abuts on a relatively movable scale. A linear encoder provided with a second support for detecting a movement length, wherein the first support and the second
A self-resonance of the second support member is suppressed by providing a damper member abutting between the support members.

According to a second aspect of the present invention, the movement length is detected by detecting a scale of a long glass scale by light. In a third aspect of the invention, the damper member is made of rubber or synthetic rubber. It is characterized by using resin as a material.

[0021]

1 to 3 show an embodiment of a linear encoder according to the present invention. FIG. 1 is a sectional view of a main part of an example of an embodiment in which a damper member is attached to a pivot bearing of a linear encoder of the present invention, FIG. 2 is a front view thereof, and FIG. 3 is attached to a machine tool or the like. The side view of the case is shown.

Hereinafter, embodiments of the present invention will be described in detail. However, except for the damper member and the mounting thereof, it is the same as the above-described conventional encoder, and therefore, detailed description thereof will be omitted. The damper member 10 according to the present invention includes a damper member 11 made of a synthetic resin such as a Duracon resin or a synthetic rubber, and a second part of the pivot bearing 32 that penetrates the damper member 11.
Damper pin 12 in point contact with a pivot bearing 34 of
The support plate 1 made of an elastic body such as a leaf spring that presses the rectangular portion 28 of the fixed link 31 so as to sandwich it.
3a, 13b, and a fixing link 31 and an attachment portion 14 are provided. The support plate 13 is formed of an elastic body such as a leaf spring, and the support plate 13a on the side shown in FIGS. 1 and 2 is fixed by the fixed link 31 and the mounting portion 14, and the support on the right side shown in FIG. The plate 13b is slightly thicker than the support plate 13a, and is pressed so as to sandwich the rectangular portion 28, and its end is free.

As shown in FIGS. 2 and 3, the damper member 10
Is attached to the fixed link 31 of the encoder 20 attached to the movable portion 51 side of the machine tool or the like by the attaching portion 14. The damper pin 12 is connected to a second pivot bearing 34.
Point contact with the rear part of the pivot screw 38.

As described above, since the damper material of the present invention is attached to the encoder 20, the vibration at the time of processing transmitted from the movable portion 51 to the fixed plate 51 is transmitted directly from the pivot bearing 32 to the slider 26. Even if a vibration having a frequency at which resonance is generated is transmitted to the damper member 10, the vibration is absorbed by the damper member 10, so that the resonance is suppressed without being transmitted to the slider.

As shown in FIG. 8 (b), the encoder equipped with the damper member of the present invention has a peak vibration frequency of 100% compared to an unsupported encoder shown in FIG. 8 (a).
It changes as hertz and the peak Lissajous rotation speed drops to less than half.

As described above, the structure of the present invention has a simple structure in which a damper member including a damper pin, a damper material, and a support plate is attached to a conventional encoder to attenuate resonance. In particular, in the conventional encoder, since the rectangular portion of the fixed link is a source of resonance,
In this embodiment, in order to transmit the vibration from the rectangular portion to the damper member, the vibration is transmitted to the damper material by the damper pin. Further, the damper pin and the damper material are pressed against a local portion of the fixed link by a support plate formed of a leaf spring, thereby enabling reliable transmission and attenuation of vibration. As the material of the damper material, a material having a natural frequency far apart from the natural frequency of the encoder and having excellent damping properties is good, and a synthetic resin material such as Duracon resin and a rubber material such as NBR are effective. .

In the embodiment of the present invention described above, the fixed link side is the moving section, but the fixed link side may be the fixed section. Also, regarding the mounting of the damper member, in the embodiment of the present invention, because of the structure of the case and the like,
Although the embodiment in the state where the mounting place is restricted has been described,
The present embodiment is not limited to the mounting position as long as the mounting position can attenuate the vibration transmitted to the fixed link.

[0028]

According to the present invention, the following improvement effects can be obtained by providing a damper member at the main cause of the resonance of the encoder, thereby suppressing the resonance phenomenon of the encoder and improving the vibration resistance. 1. By suppressing the resonance of the encoder (slider), abnormal high-speed vibration of the sensor unit of the slider is suppressed, and occurrence of an error due to exceeding the permissible displacement reading speed can be prevented. 2. Amplitude amplification and high-speed fluctuation of only the encoder due to resonance can be suppressed, the behavior followability of the machine tool can be improved, precise displacement measurement can be performed, and the processing accuracy of the processed product is improved. 3. The increase in acceleration caused by resonance can be suppressed,
Encoder breakage can be prevented. 4. By providing such a simple damper member with respect to the encoder having the conventional structure, the vibration resistance of the encoder can be improved. 5. INDUSTRIAL APPLICABILITY The damping structure of the present invention is applicable not only to linear scale encoders but also to encoders for measuring linear displacement and angular displacement.

[Brief description of the drawings]

FIG. 1 is a front view of a damper member according to the present invention.

FIG. 2 is a front view showing a state where the damper member of the present invention is attached to an encoder.

FIG. 3 is a side view showing a state where the damper member of the present invention is attached to an encoder.

FIG. 4 is a perspective view showing a configuration of a connection portion between a fixed plate and a slider of a conventional encoder.

FIG. 5 is a front view showing a configuration of a connection portion between a fixed plate and a slider of a conventional encoder.

FIG. 6 is a side view showing a configuration of a connection portion between a fixed plate and a slider of a conventional encoder.

FIGS. 7A and 7B are a side view and a plan view showing the principle of an optical linear scale for measuring a relative movement amount during machining of a machine tool or the like.

8A and 8B are diagrams illustrating a relationship between a vibration frequency and a Lissajous rotation speed when an encoder is vibrated. FIG. 8A illustrates a case of a conventional encoder, and FIG. 8B illustrates a case of attaching a damper member of the present invention. Show.

[Explanation of symbols]

10: Damper, 11: Damper member, 12: Damper pin, 13a, 13b: Support plate, 14: Mounting part,

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Claims (3)

[Claims] A first support attached to a position to be measured; a first support which is swingably supported with respect to the first support; In a linear encoder provided with a second support for detection, a self-resonance of the second support is suppressed by providing a damper member abutting between the first support and the second support. A linear encoder characterized by: 2. The linear encoder according to claim 1, wherein the movement length is detected by detecting a scale of a long glass scale by light. 3. The linear encoder according to claim 1, wherein the damper member is made of rubber or synthetic resin.