JPH07243869A - Encoder - Google Patents

Abstract

PURPOSE:To provide an encoder with less mechanical vibration. CONSTITUTION:A gas scale 10 is provided with a slit of a small pitch. A sensor head 12 consists of a light reception part 14, a substrate 16, and a bearing 18. The light reception part 14 receives light from a light source through the slit of the glass scale 10 and outputs a signal corresponding to the intensity. A bearing 18 is mounted to the substrate 16 so that the bearing is parallel to the glass scale 10 and rotates around an axis crossing the longitudinal direction. The sensor head 12 is supported so that the bearing 18 is always in contact with the glass scale 10 by a leaf spring 22 whose both edges are fixed to the substrate 16 and a support structure 20. The leaf spring 22 is created by bending a metal plate such as stainless copper plate and bronze steel plate. An attenuation member 24 partially consisting of butyl rubber and gellike substance is mounted to the surface of the leaf spring 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an encoder used in a microscope, a measuring instrument, peripheral equipment thereof and the like.

[0002]

2. Description of the Related Art An optical linear encoder, which is a type of encoder, generally includes a glass plate, that is, a glass scale provided with slits having a fine pitch, a light source for irradiating the glass scale with a certain amount of light, and a glass scale. It is composed of a sensor head that optically reads the slit. In a linear encoder with such a structure,
In order to obtain stable operation without malfunction, it is desirable to keep the gap between the glass scale and the sensor head constant.

[0003]

Therefore, in a linear encoder, the glass scale support structure and the sensor head support structure have high rigidity, processing accuracy, and assembly accuracy in order to prevent the gap from varying. I'm using one. However, a support structure having high rigidity, processing accuracy, and assembly accuracy is so expensive that it causes an increase in cost.

In another linear encoder, as shown in FIG. 3, for example, a substrate 16 of the sensor head 12 is provided with a supporting member such as a bearing 18 having a low friction coefficient so that the supporting member is always in contact with the glass scale 10. The head 12 is supported by a leaf spring 22 made of a stainless steel plate or a phosphor bronze steel plate. In this structure, if the distance and the levelness between the light receiving surface of the sensor head 12 and the glass scale 10 are maintained by the three bearings 18, the support structure 20 is provided.
Even if there is a slight misalignment between the glass scale 10 and the glass scale 10, it can be absorbed by the leaf spring 22 and the glass scale 1 can be absorbed by the elastic force of the leaf spring 22.
Since the sensor head 12 can be pressed against 0, the glass scale 10 can be satisfactorily scanned by the sensor head 12 without increasing the rigidity, processing accuracy, and assembly accuracy of the support structure, and the cost is low. There is an advantage that it can be realized.

However, since the glass scale 10 and a part of the sensor head 12 are constantly in contact with each other, the surface of the glass scale 10 is scratched, dusty, or undulated, and the surface of the bearing 18 of the sensor head 12 is undulated or the central axis thereof. The sensor head 12 microscopically changes in the vertical direction with respect to the glass scale 10 due to such blurring.

The sensor head 12 includes a pair of support structures 2
Since the pair of leaf springs 22 holds the both ends in a doubly supported beam shape during 0, when internal vibration occurs at the contact portion between the glass scale 10 and the sensor head 12, external vibration from the drive source or the like also occurs. When transmitted to the glass scale 10 or the sensor head 12, the sensor head 12 vibrates due to the natural vibration determined by the spring coefficient. This mechanical vibration causes a change in the amount of light that enters the light receiving unit 14, and noise is added to the electric signal. Since the natural frequency of this mechanical vibration is usually within the frequency range of the required electrical signal, the electrical noise caused by this mechanical vibration is removed by electrical processing using a low-pass filter, high-pass filter, band-pass filter, or the like. It is virtually impossible.

An object of the present invention is to provide an encoder of a type in which a sensor head is brought into contact with and supported by a glass scale, and which has less mechanical vibration between the glass scale and the sensor head.

[0008]

The encoder of the present invention comprises:
A digital scale having a periodic structure, a sensor head for scanning the digital scale and converting a periodic change of the periodic structure into a digital signal, and a leaf spring for supporting the sensor head in contact with the digital scale. A vibration damping member provided on the leaf spring and having a characteristic of controlling vibration is provided.

Alternatively, a digital scale having a periodic structure, a sensor head for scanning the digital scale and converting a periodic change of the periodic structure into a digital signal, and supporting the sensor head in contact with the digital scale However, a leaf spring having a characteristic of suppressing vibration is provided.

[0010]

The digital scale is constructed by arranging opaque patterns periodically on a transparent scale substrate, for example.
An example of the transparent scale substrate is a transparent glass substrate.

Etched slits can be used as the opaque pattern. When the digital scale in which the slit patterns are periodically arranged on the transparent glass substrate is used, the sensor head is composed of a light source and a light receiving element which are arranged with the digital scale interposed therebetween. The slit pattern, which is a periodic structure, is converted into a digital signal by receiving the transmitted light that has passed through the digital scale by the light receiving element and extracting it as an electric signal.

A reflection pattern can also be used as the opaque pattern. When a digital scale in which mirror-like slit-like reflection patterns are periodically arranged on a transparent glass substrate is used, the sensor head has a light source arranged on one side of the digital scale at a predetermined angle, The light receiving element is arranged on the reflection optical axis of the light source. The reflection pattern having a periodic structure is converted into a digital signal by receiving the reflected light from the reflection pattern with a light receiving element and extracting the light as an electric signal.

The digital scale may be formed by periodically arranging slit-shaped holes as a transmission pattern on an opaque scale substrate. In this case, the sensor head is composed of a light source and a light receiving element which are arranged with the digital scale interposed therebetween. The transmission pattern having a periodic structure is converted into a digital signal by receiving the transmitted light that has passed through the digital scale by the light receiving element and extracting it as an electric signal.

The digital scale may be constructed by periodically arranging two-color patterns of different lightness and darkness on the scale substrate. In this case, the sensor head is composed of a light receiving element that detects a light amount change due to the light and shade of the pattern, and a digital signal is obtained by converting the light amount change due to the light and shade of the pattern into an electric signal.

The digital scale may be constructed by periodically recording at least one polarity on the magnetic scale substrate. In this case, the sensor head is composed of a magnetic head, and a magnetic signal is converted by the magnetic head into an electric signal to obtain a digital signal.

The digital scale may be constructed by periodically arranging a pattern of irregularities on the scale substrate. In this case, the sensor head is composed of a displacement sensor that detects the displacement of the unevenness, and a digital signal is obtained by converting the displacement of the unevenness of the pattern into an electric signal by the displacement sensor.

As the damping member, for example, a high molecular substance can be cited. By laminating this on a leaf spring made of a stainless steel plate or a phosphor bronze steel plate, vibration generated in the leaf spring itself is damped without impairing the strength of the leaf spring. Can be made.

For example, a three-layer structure in which a vibration damping member having a vibration suppressing property is sandwiched between two leaf springs has excellent damping characteristics, but one plate spring has a vibration damping member on one side. Attenuating effect can be obtained even by attaching a two-layer structure.

When a two-layer structure is used, these damping members are formed on a sheet and thermocompression-bonded to a steel plate which is a material of a leaf spring, and the steel plate is punched into a desired shape by a press to obtain a plate. Form a spring. In addition, in a state where a polymer substance is dissolved in a solvent, it is applied to one or both sides of a steel plate which is a material of a leaf spring by using a roll coater or the like, and after drying to remove the solvent, a desired shape is obtained by this steel plate press. Form a leaf spring by punching.

When a leaf spring having a three-layer structure is used, a thin film of a polymer substance restrains both steel plates, and the viscoelastic shear deformation of the polymer substance exerts a vibration damping property. That is, the resin layer undergoes shear deformation along with bending due to vibration, and at that time, energy is absorbed by the viscoelastic behavior of the resin, and even small deformation such as vibration causes large shear deformation, and the vibration is absorbed by the resin layer. It

When a leaf spring having a two-layer structure is used, the resin layer expands and contracts due to bending of the steel sheet to absorb energy, and the elastic deformation of the polymer material provides vibration damping.
However, in the case of a leaf spring having a two-layer structure, the size of the deformation is proportional to the thickness of the resin layer because the polymer substance is elastically deformed.
The resin layer must be thicker than that of the three-layer structure.

Rubber or resin is used as the high molecular substance which is the vibration damping member. Natural rubber and synthetic rubber are known as rubber. Known resins include vinyl acetate-based resins, acrylic ester-based resins, polyester-based resins, polyisobutylene-based resins, and the like.

Other materials for the vibration damping member include vibration absorbing paints and gel substances. As a vibration absorbing paint,
Urethane, acrylic, and silicone resin paints are known. As the gel-like substance, there is a gel-like substance in which the product becomes insoluble during polymer synthesis, and organogel, gel rubber, polymer gel, silicone gel, fluorine ion exchange resin and the like are known.

Further, instead of providing the plate spring with a vibration damping member, the plate spring itself may be made of a member having a high damping property. Such leaf springs can be made of fiber reinforced plastic, for example. Examples of the fiber reinforced plastic include carbon fiber. Also,
It may be made of a vibration-damping alloy material in which at least one plate surface is subjected to corrosion treatment. For example, a stainless steel plate can be made of intergranular corrosion stainless whose surface layer has been corroded with an aqueous solution of sulfuric acid and copper sulfate.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the structure of the optical linear encoder of the present embodiment, especially around the sensor head. The glass scale 10 is provided with slits having a fine pitch. The sensor head 12 includes a light receiving portion 14, a substrate 16, and a bearing 1.
It is composed of 8. The light receiving section 14 is composed of a photoelectric conversion element such as a photodiode which receives light from a light source (not shown) passing through the slit of the glass scale 10 and outputs a signal corresponding to the intensity of the light. The bearing 18 is attached to the substrate 16 so as to be rotatable about an axis parallel to the glass scale 10 and orthogonal to its longitudinal direction. In the sensor head 12, the bearings 18 are always provided on the glass scale 1 by the leaf springs 22 whose both ends are fixed to the substrate 16 and the support structure 20, respectively.
It is supported as if it touches 0. The leaf spring 22 is made by bending a metal plate such as a stainless steel plate or a phosphor bronze steel plate. A damping member 24 made of butyl rubber or a gel-like substance is attached to a part of the surface of the leaf spring 22.

The damping member 24 attached to the leaf spring 22 is
The damping of mechanical vibration generated in the sensor head 12 is accelerated. To clarify this, FIG. 2 shows the damping characteristics when the leaf spring 22 with the damping member 24 attached is used, and with the leaf spring 22 without the damping member 24 (that is, the conventional example of FIG. 3). 4) shows the attenuation characteristics of FIG.

If the sensor head 12 vibrates during sampling in a digital servo, from the viewpoint of the servo system, it cannot be determined whether the signal from the linear encoder detects the position or whether the sensor head vibrates. . Therefore, it is desirable that the generated mechanical vibrations converge reliably within the sampling period.

2 and 4, the sampling period is 0.0.
Shown as 3 seconds. In the linear encoder (FIG. 1) of the present embodiment, the generated vibration is almost contained within the sampling cycle, as shown in FIG. 2, so that its output is hardly affected by the vibration. On the other hand, in the conventional linear encoder (FIG. 3), the vibration generated as shown in FIG. 4 does not settle within the sampling period, so that its output is affected by the vibration. This tendency becomes more remarkable as the resolution of the linear encoder is higher.

As described above, in the linear encoder of this embodiment, since the damping member 24 is attached to the leaf spring 22, the mechanical vibration is quickly damped, and the output thereof is less affected by the vibration.

In the above-mentioned embodiment, the damping member is attached to the leaf spring in order to accelerate the damping of mechanical vibration, but the same effect can be obtained even if the leaf spring itself is made of a material having a high damping ability. Such materials include fiber reinforced plastics such as carbon fibers.

From the above description, the present invention can be summarized as follows. 1. A digital scale having a periodic structure, a sensor head for scanning the digital scale and converting a periodic change of the periodic structure into a digital signal, and a leaf spring for supporting the sensor head in contact with the digital scale. An encoder provided with the above-mentioned leaf spring, and a damping member having a characteristic of controlling vibration.

2. In Claim 1, the leaf spring is made of a metal member, and the vibration damping member is laminated on at least one plate surface of the leaf spring. 3. In the first aspect, the leaf spring is characterized in that a damping member is sandwiched between a plurality of metal plates.

4. In the first item, the vibration damping member is made of a flexible material. 5. In the first item, the vibration damping member is made of a polymer material.

6. In the first item, the vibration damping member is made of a gel-like substance. 7. In Claim 1, the damping member is made of a vibration absorbing paint and is applied to a leaf spring.

8. A digital scale having a periodic structure, a sensor head for scanning the digital scale and converting periodical changes of the periodic structure into a digital signal, and supporting the sensor head in contact with the digital scale to suppress vibration. An encoder comprising: a leaf spring having a characteristic of

9. In Claim 8, the leaf spring is made of fiber reinforced plastic, and the encoder is characterized. 10. In Claim 8, the leaf spring is made of a vibration damping alloy material in which at least one of the leaf surfaces is subjected to a corrosion treatment, and the encoder is characterized in that.

[0037]

According to the present invention, since mechanical vibration is quickly attenuated, an encoder having less vibration influence, that is, noise, on its output can be provided.

[Brief description of drawings]

FIG. 1 is a side view (A) and a top view (B) of a linear encoder according to an embodiment of the present invention.

FIG. 2 is a diagram showing a damping characteristic of mechanical vibration in the linear encoder of FIG.

FIG. 3 is a side view (A) and a top view (B) of a conventional linear encoder.

FIG. 4 is a diagram showing a damping characteristic of mechanical vibration in the linear encoder of FIG.

[Explanation of symbols]

10 ... Glass scale, 12 ... Sensor head, 22 ... Leaf spring, 24 ... Damping member.

Claims (4)

[Claims] 1. A digital scale having a periodic structure, a sensor head for scanning the digital scale and converting a periodic change of the periodic structure into a digital signal, and supporting the sensor head in contact with the digital scale. An encoder, comprising: a leaf spring for controlling the vibration, and a damping member provided on the leaf spring and having a characteristic of controlling vibration. 2. The encoder according to claim 1, wherein the plate spring is made of a metal member, and the vibration damping member is laminated on at least one plate surface of the plate spring. 3. The encoder according to claim 1, wherein the plate spring has a vibration damping member sandwiched between a plurality of metal plates. 4. A digital scale having a periodic structure, a sensor head for scanning the digital scale and converting periodical changes of the periodic structure into a digital signal, and supporting the sensor head in contact with the digital scale. An encoder comprising: a leaf spring having a characteristic of suppressing vibration.