JP3101289B2 - Optical encoder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical encoder, in particular, a main scale and an index scale are arranged to face each other,
The present invention relates to an optical encoder that photoelectrically measures a relative displacement between a main scale and an index scale.

(Prior art)

This type of optical encoder is provided with a grid portion in which light-transmitting portions and light-shielding portions are alternately arranged on a main scale, and a grid portion in which light-transmitting portions and light-shielding portions are alternately arranged on an index scale. Is provided, the grating portions of both scales are opposed to each other, and both scales are arranged between the light source and the light receiving element. Of the light from the light source, the light passing through each grating portion of both scales is received by the light receiving element, The relative displacement of both scales is measured by photoelectric conversion.

In the encoder having such a configuration, if the interval between the grating portions of both scales fluctuates, it becomes difficult to output a signal having a stable amplitude and waveform from the light receiving element, and the measurement accuracy is deteriorated. Therefore, conventionally, an effort has been made to maintain a constant interval between both lattice portions of the main scale and the index scale.

[Problems to be solved by the invention]

A conventional optical encoder which is a premise of the present invention will be described in detail with reference to FIGS. The encoder of this example is a rotary type encoder, which is used to measure the amount of movement of the main scale 1 by rotating the main scale 1 in conjunction with the movement of the taking lens of the camera.

5 and 6, 1 and 2 each represent 1 on a scale.
Is a main scale that rotates around the optical axis o, and 2 is a fixed index scale. The main scale 1 has protrusions 1d and 1e protruding from the lattice portion 1c, and the index scale 2 also has protrusions 2d and 2 protruding from the lattice portion 2c.
e, and these projections 1d, 1e, 2d, 2e have a flat surface as a sliding surface on their upper part. Then, the protrusion 1d of the main scale 1 and the protrusion 2d of the index scale 2 contact each other's sliding surfaces, and the protrusion 1e of the main scale 1 and the protrusion 2e of the index scale 2 contact each other's sliding surfaces. Is in contact. Therefore, the main scale 1 and the index scale 2 relatively displace while sliding on each other via these sliding surfaces. Also,
The heights of the sliding surfaces of the respective projections 1d, 1e, 2d, 2e from the corresponding grids 1c, 2c are all equal.

Each of the grid portion 1c and the protrusions 1d and 1e of the main scale 1 is integrally formed by plastic molding using acrylic as a material, and the grid portion of the index scale 2 is formed.
Both 2c and the projections 2d and 2e are integrally formed by the plastic molding method using the above-mentioned acrylic as a material.

Reference numeral 4 denotes a light source unit, 3 denotes a light receiving element, 5 denotes a main scale 1, and a ring-shaped scale holder that rotates in conjunction with the movement of an object to be measured (for example, first camming-less) (not shown). Hold index scale 2,
A leaf spring for urging the scale 2 so that the scale 2 comes into contact with the rotating main scale 1, a light source unit 4, a collimator lens 4a, a condenser lens 3a, and an interrupter holding the light receiving element 3; An interrupter holder 9 that holds the leaf spring 6 and the interrupter 7 via screws, and a fixed housing 9 that rotatably holds the scale holder 5 and holds the interrupter holder 8. Reference numeral 10 denotes a ring-shaped holding ring fixed to the housing 9 so that the rotating scale holder 5 is prevented from coming off by the flange portion 10a.

When the device under test rotates, the scale holder 5 rotates along the inner periphery of the housing 9 in conjunction with the rotation of the device under test. Therefore, the main scale 1 integrally held by the scale holder 5 also rotates. At this time, since the fixed index scale 2 is urged by the leaf spring 6 so as to be in contact with the main scale 1, each of the projections 1 d, 2
The sliding surfaces of d, 1e, and 2e contact each other, and the grids 1c and 2 of the scales 1 and 2
A predetermined gap is kept between c.

In the present embodiment described above, the leaf spring 6 is used as an elastic member for pressing the index scale 2 fixed to the rotating main scale 1, and the leaf spring 6 is used as an elastic member.
Are fixed with an adhesive while maintaining a surface contact state with the index scale 2.

However, as shown in FIG. 8, the index scale 2 is tilted with respect to the main scale 1 due to the non-uniformity of the shape of the leaf spring 6 and the non-uniformity of the spring coefficient, and furthermore, a slight bonding error during manufacture. It turned out that it was pressed with. In other words, where the interval between the scale portions 1c and 2c should be kept constant, for the above-mentioned reason, this interval cannot be reliably maintained, and as a result, the light receiving element cannot detect a good light / dark light intensity change. In some cases, an error signal was generated.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical encoder, which has a relatively simple configuration and stably maintains a constant scale interval, and in particular, to provide a holder for the optical encoder.

[Summary of the Invention]

For this purpose, the optical encoder according to the first aspect of the present invention includes a first encoder provided with a grating section in which light-transmitting sections and light-blocking sections are alternately arranged along a predetermined direction. And the second scale, and the first and second scales are opposed to each other so as to keep the gap between the grid portions of the first and second scales. An elastic member for elastically pressing the light, a light irradiation unit, and a photoelectric conversion unit, wherein the first and second scales are disposed between the light irradiation unit and the photoelectric conversion unit. The first and second scales are illuminated with light from the light irradiating means, and the light passes through the respective grid portions of the first and second scales by the photoelectric conversion means. Receiving the light and converting it into an electric signal, An optical encoder for measuring a relative displacement of a scale, wherein said first and second scales are respectively opposed to each other with a predetermined relationship between said grating portions and mutually slidably arranged on said grating portion. A movable sliding surface, wherein the elastic member or the first scale is provided with a spherical projection on one of the first scales so that the projection is disposed in a direction perpendicular to the surface of the sliding surface. And wherein the elastic member is configured to press the first scale against the second scale.

Further, the optical encoder according to the fourth aspect of the present invention includes a first and a second scale each having a grid portion in which light transmitting portions and light shielding portions are alternately arranged along a predetermined direction. While the first and second scales are opposed to each other so as to keep the gap between the grid portions of the first and second scales,
An elastic member for elastically pressing the first scale against the second scale, a light irradiation unit, and a photoelectric conversion unit, and between the light irradiation unit and the photoelectric conversion unit The first and second scales are relatively moved in the direction, the first and second scales are illuminated with light from the light irradiating means, and the first and second scales are illuminated by the photoelectric conversion means. An optical encoder for measuring the relative displacement of the first and second scales by receiving light that has passed through each grid portion of the second scale and converting the light into an electric signal, wherein the first and second scales are measured. Each of the two scales has a sliding surface in which the lattice portions face each other with a predetermined relationship therebetween and slides side by side with the lattice portion, and is provided on one of the elastic member or the first scale. The spherical projection is attached to the other side of the spherical projection. Parts are provided so that the spherical projections are arranged in a direction perpendicular to the surface of the sliding surface, and a pin is provided on the first scale and the pin is provided on the elastic member. A pin fitting portion for fitting to the first scale and the elastic member;
The pin portion and the pin fitting portion, and the spherical protrusion and the spherical protrusion receiving portion are connected at at least two places, and the connecting portion between the spherical protrusion and the spherical protrusion receiving portion is connected to the second scale. The first scale is pressed and adhered by the elastic member, and the pin portion and the pin fitting portion are prevented from falling out by allowing relative displacement, and the spherical projection is received from the spherical projection receiving portion. Stroke A from which the part is disengaged, and the thrust movable amount B between the pin part and the pin fitting part are set so that A> B, and the elastic member and the first scale are unitized. Features.

〔Example〕

Before specifically describing the embodiment of the present invention, the measurement principle of the encoder will be described with reference to FIGS. 4 (A) and 4 (B). FIGS. 4A and 4B are cross-sectional views of a system including a main scale, an index scale, light irradiation means, and photoelectric conversion means. 1 is a main scale movable in the vertical direction on the paper, 2 is a fixed index scale, 4
Is a light source unit, 4a is a collimator lens, 3 is a light receiving element, and 3a is a condenser lens. The light irradiating means fixed by the light source unit 4 and the collimator lens 4a is changed to a condenser lens 3a.
And the light receiving element 3 constitute a photoelectric conversion means, and the optical axis of the light irradiation means (4, 4a) is orthogonal to the surface of the scales 1, 2. 4 (A) and 4 (B) show cross sections of only the lattice portions of the scales 1 and 2, however, as will be described later, each of the scales 1 and 2 has its own lattice portion. It has a pair of protrusions that protrude more than
The two 2 are brought into contact with each other and slide with each other. And by adopting such a configuration,
The interval between the lattice portions 1c and 2c of the scales 1 and 2 is kept at a predetermined distance.

The scales 1 and 2 are made of a material such as acrylic, and this material is transparent to light emitted by the light source unit 4. The light source unit 4 has an LED as a light source. The grating portions 1c and 2c of the scales 1 and 2 have the same shape as each other, and each of the grating portions 1c and 2c has a translucent portion 1a, 2a formed of a plane substantially parallel to the moving direction of the scale 1, and is inclined with respect to this plane. Shielding portions 1b, 2b composed of V-shaped grooves having a pair of slopes
A grid is formed by alternately and regularly arranging the light-transmitting portions 1a and 2a and the light-shielding portions 1b and 2b along the moving direction of the scale 1. The V-shaped groove extends in a direction orthogonal to the direction in which the scale 1 moves.

The main scale 1 is disposed on the light receiving element 3 side, the index scale 2 is disposed on the light source unit 4 side, and the grating section of the main scale 1 is arranged so that the light incident through the inside of the scale is modulated. The unit is set to modulate light that has passed through the air layer in the gap between the scales 1 and 2.

The light emitted from the light source unit 4 is converted into parallel light by the collimator lens 4a,
Turned to Light illuminating the surface of the index scale 2 opposite to the grating portion passes through the scale and enters the grating portion. The light that has entered the light-transmitting portion 2a (plane) of the grating portion travels straight therethrough and travels toward the main scale 1, and the light that has entered the light-shielding portion 2b (V-shaped groove) of the grating portion has a pair. The light is sequentially totally reflected on the inclined surface and returns to the light source unit 4 side. Of the light traveling from the scale 2 to the scale 1, the light incident on the light-transmitting portion 1a (flat surface) of the scale 1 travels straight therethrough, and also travels straight inside the scale 1 via the condenser lens 3a. And is condensed on the light receiving element 3,
The light that has entered the light-shielding portion 2b (V-shaped groove) of the scale 2 is refracted and deflected by the pair of slopes, passes through the inside of the scale 1, and moves from the scale 1 so as not to enter the condenser lens 3a. The light is emitted and does not enter the light receiving element 3.

Therefore, as shown in FIG. 4A, when the phases of the grating portions of the scales 1 and 2 match each other, the intensity of light received by the light receiving element 3 becomes maximum. On the other hand, as shown in FIG. 4 (B), when the phases of the grating portions of the scales 1 and 2 are relatively shifted by 180 °, the intensity of light received by the light receiving element 3 becomes minimum. When the main scale 1 moves and the lattice portions of the scales 1 and 2 are relatively displaced, the intensity of light incident on the light receiving element 3 via both the lattice portions of the scales 1 and 2 changes periodically. I do. Therefore, from the light receiving element 3,
A periodic signal corresponding to the amount of movement of the main scale 1 is output. This signal is input to an amplification circuit (not shown), amplified and processed, and becomes a pulse signal train according to the movement amount. By counting the number of pulses, the movement amount of the main scale 1 is measured.

In this embodiment, acrylic is used as a material.
Other synthetic resin materials and glass materials may be used. Whatever material is used, according to the optical encoder of the present embodiment, both the main scale 1 and the index scale 2 can be simultaneously and integrally molded with the lattice portion and the projection portion, so that it is easy in a short time. Encoders can be manufactured.

Hereinafter, an embodiment of the present invention that can obtain a stable received light output while having a simple configuration in consideration of the above-described problems of the conventional example will be described.

FIG. 1 is a perspective view showing a holding device of the optical encoder of the present invention, FIG. 2 is a cross-sectional view showing a holding device of the optical encoder of the present invention, and FIG. It is a fragmentary sectional view of a holding device. The same parts as those in FIGS. 4 to 7 are denoted by the same reference numerals, and description thereof will be omitted. Since there are two parts that differ from the above-described premise, a spring member and a fixed index scale, the structure will be mainly described with reference to FIGS. 1 to 3.

Reference numeral 101 denotes a leaf spring (elastic member), which has an embossed portion (spherical protrusion) protruding toward the fixed index scale.
1f and 101g are provided in two places, and a pin portion 102b described later is provided.
There is provided a hole 101f that fits into the hole. Reference numeral 102 denotes a fixed index scale having two concave conical groove portions 102f and 102g and a pin portion 102h. The fixed index scale 102 has two conical groove portions 102f,
Embossed portions 101f, 10f of the leaf spring (elastic member) 101 are added to 102g.
The fixed index scale 102 is provided with a hole 101h corresponding to a pin portion 102h of the fixed index scale 102 so as to correspond to a loose fit.
Further, as described above, the fixed index scale 102 is provided with the grid portions 102c corresponding to 2c and 2d in the above-described embodiment and the flat sliding surface 2d.

Next, a method of unit assembly in this structure is shown in FIG.
This will be described with reference to FIG. The leaf spring (elastic member) 101 and the fixed index scale 102 are assembled so as to correspond to the pair of embossed portions 101f and 101g, the pair of conical grooves 102f and 102g, the hole 101h and the pin 102h, respectively.
Note that the pin portion 102h before being unitized has no bulge portion in the form of a two-dot chain line as shown in FIG. After being assembled, the tip of the pin portion 102h is crushed by heat caulking or the like to form a shape like a solid line (bulge portion) and the fixed index scale 102 of the leaf spring (elastic member) 101 so as to have some backlash. To keep from falling off. At that time, the stroke A where the embossed portions 101f and 101g are disengaged from the conical groove portions 102f and 102g and the thrust play amount B between the pin portion 102h and the hole portion 101h have a play such that A> B to prevent looseness, The leaf spring 101 and the fixed scale 102 are flexibly unitized. Then, as shown in FIG. 2, a leaf spring (elastic member) 101 is fixed to the interrupter holder 8 in the same manner as in the prior art, so that the fixed index scale 102 is attached to the movable main scale 1 by its spring property. Press. In this case, the pressing force of the leaf spring (elastic member) 101 is
f, 101g is a structure for transmitting to the fixed index scale 1. The pressing locations of the embossed portions 101f and 101g are as follows:
In order to secure a constant gap between the fixed index scale 102 and each of the lattice portions 1c, 102c of the main scale 1, the sliding surfaces 102d, 2d of the fixed index scale 102 and the movable main scale 1 must be secured. The sliding surfaces 102d and 1d are provided on a line perpendicular to the sliding surfaces 102d and 1d so as to make planar contact with the sliding surfaces 102d and 1d.

In this embodiment, the leaf spring (elastic member) 101 has embossed portions 101f and 101g, and the fixed scale 102 has a conical groove 102.
Although f and 102g are provided, conversely, it is also possible to provide a concave conical groove or a hole in the leaf spring (elastic member) 101 and provide a protruding emboss on the index scale 102.

〔The invention's effect〕

As described above, according to the first invention, each of the first and second scales is provided with a sliding surface in which the lattice portions face each other at a predetermined relationship and slide in parallel with each other. The first scale and the elastic member are brought into contact with each other by the spherical projections, and the first scale is pressed and adhered to the second scale. There is an effect that the sliding surface can surely be brought into close contact with the sliding surface. Also, by configuring the spherical projections so as to be arranged not perpendicular to the lattice portion but to the surface of the sliding surface, the sliding surfaces are brought into planar contact with each other without deforming the lattice portion. There is also an effect that can be done.

According to the fourth aspect of the present invention, in addition to the above-described effects, the spherical portion is connected, and furthermore, the pin portion and the pin fitting portion are prevented from falling out while allowing relative displacement by the pin portion and the pin fitting portion. Is made so as not to come off from the spherical projection receiving portion, so that the elastic member and the first scale are unitized to prevent separation of the two and the spherical projection from coming off from the receiving portion. The flexible pressing for surely bringing the scales into flat contact with each other on the sliding surfaces can be maintained by the allowance of the pin portion and the pin fitting portion, and furthermore, the second scale of the first scale due to the dimensional accuracy of the elastic member and the like. There is no effect on the pressure contact with the surface, and the effect is enormous including performance and incorporation.

[Brief description of the drawings]

1 is a perspective view of a holding device of an optical encoder embodying the present invention, FIG. 2 is a cross-sectional view of FIG. 1, and FIG. 3 is a partial cross-sectional view of a holding device of an optical encoder embodying the present invention. 4 is an optical principle diagram of the optical encoder, FIG. 5 is a perspective view of a general optical encoder holding device, FIG. 6 is a mechanical configuration diagram of the optical encoder, and FIG. 7 is FIG. FIG. 8 is a view showing a problem of a general optical encoder holding device. 1 is a movable scale (main scale), 1c is a grid, 1b
Is a sliding surface, 5 is a scale holder, 6 is a leaf spring, 8 is an interrupter holder, 9 is a housing, 101 is a leaf spring (elastic member), 101f and 101g are embossed portions (spherical projections), and 101h is a hole portion. , 102 is a fixed scale (index scale), 102
f and 102g are concave conical groove portions, 102h is a pin portion, 102c is a lattice portion, and 102d is a sliding surface.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-20803 (JP, A) JP-A-57-194310 (JP, A) Japanese Utility Model Sho 62-187805 (JP, U) Japanese Utility Model Utility Model Sho 55- 51739 (JP, U) JP-A 57-129114 (JP, U) JP-B 57-17241 (JP, B1) JP-B 59-16642 (JP, B1) JP-B 63-10485 (JP, Y1) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01D 5/36 G01P 3/486

Claims (4)

(57) [Claims] 1. A first and a second, each having a grating portion in which light transmitting portions and light blocking portions are alternately arranged along a predetermined direction.
And the first scale is elastically attached to the second scale while the first and second scales are opposed to each other so as to keep a space between the first scale and the grid portion of the second scale. An elastic member for pressing, a light irradiation unit, and a photoelectric conversion unit, wherein the first and second scales are relatively positioned in the direction between the light irradiation unit and the photoelectric conversion unit. The first and second scales are illuminated with light from the light irradiating means, and light transmitted through the respective grating portions of the first and second scales is received by the photoelectric conversion means. An optical encoder for measuring a relative displacement of the first and second scales by converting the first and second scales into electric signals, wherein the first and second scales have a predetermined relationship And are parallel to the lattice part The elastic member or the first scale is provided with a spherical projection on one of the first scales, and the projection is arranged in a direction perpendicular to the surface of the sliding surface. An optical encoder, wherein the elastic member presses the first scale to the second scale via the protrusion. 2. The optical encoder according to claim 1, wherein said projection is an embossed portion of said elastic member. 3. The elastic member or the first scale is provided with a spherical projection on one side and a concave part is provided on the other side in contact with the projection.
Optical encoder according to the item. 4. A first and a second, each having a grating portion in which light transmitting portions and light shielding portions are alternately arranged along a predetermined direction.
And the first scale is elastically attached to the second scale while the first and second scales are opposed to each other so as to keep the gap between the first scale and the second scale. An elastic member for pressing, a light irradiation unit, and a photoelectric conversion unit, wherein the first and second scales relatively move in the direction between the light irradiation unit and the photoelectric conversion unit; And irradiating the first and second scales with light from the light irradiating means, and receiving light having passed through the respective lattice portions of the first and second scales by the photoelectric conversion means. An optical encoder for measuring a relative displacement of the first and second scales by converting the first and second scales into electrical signals, wherein the first and second scales each have a predetermined relationship between the grating portions. Opposed at a distance and juxtaposed to the lattice The elastic member or the first scale is provided with a spherical projection on one side and a receiving portion for the spherical projection on the other. The first scale is provided so as to be arranged perpendicular to the sliding surface, and the first scale is provided with a pin portion, and the elastic member is provided with a pin fitting portion for fitting to the pin portion; 1 and the elastic member, at least two of the pin portion and the pin fitting portion, the spherical protrusion portion and the spherical protrusion receiving portion.
The first scale is pressed against and adhered to the second scale by the elastic member at a connecting portion between the spherical protrusion and the spherical protrusion receiving portion, and the pin portion and the pin are connected to each other. The fitting portion is configured to allow relative displacement and is prevented from falling out, the stroke A at which the spherical projection is disengaged from the spherical projection receiving portion, and the thrust movable amount between the pin portion and the pin fitting portion. An optical encoder, wherein B is such that A> B, and the elastic member and the first scale are unitized.