JP5334768B2 - Optical encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical encoder capable of detecting main signals and subsignals and enlarging the range of operating temperatures. <P>SOLUTION: A first light-receiving element 3 is fixed to a casing 4 via a substrate 5. The substrate 5 is supported by the casing 4 movably in a prescribed direction, so that the amount of movement of the first light-receiving element 3 in the prescribed direction to changes in operating temperatures is based on a linear expansion coefficient of the substrate 5. A second light-receiving element 2 is directly fixed to the casing 4, so that its amount of movement in a prescribed direction to changes in operating temperatures is based on a linear expansion coefficient of the casing 4. By making a ratio of the distance A between a fixed part 53 of the substrate 5 fixed to the casing 4 and the first light-receiving element 3 along the prescribed direction to the distance B between the fixed part 53 and the second light-receiving element 2 along the prescribed direction equal to a ratio of the linear expansion coefficient of the casing 4 to the linear expansion coefficient of the substrate 5, it is therefore possible to reduce changes in the positional relation between the first and second light-receiving elements 3 and 2 due to changes in operating temperatures and improve measurement accuracy. Thereby, it becomes possible to enlarge the range of operating temperatures. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an optical encoder.

Conventionally, a detection head provided with a light receiving element for detecting a main signal such as a relative displacement signal and a light receiving element for detecting a sub signal such as an origin signal is provided with a reflecting portion or a transmitting portion arranged at regular intervals, for example. The optical grating for the main signal and the optical grating for the sub signal (for the origin signal) in which the reflection part or the transmission part is arranged at a predetermined position, for example, are moved relative to the scale, and each optical grating is moved. An optical encoder that detects the main signal and the sub signal by receiving light reflected by the light or light transmitted through each optical grating by each light receiving element is used (for example, Patent Document 1).
In such an optical encoder, the following configuration is conceivable as a configuration of the detection head provided with the light receiving element for detecting the main signal and the light receiving element for detecting the sub signal.

FIG. 5 is a cross-sectional view showing an example of the configuration of a detection head 1B provided with a light receiving element 2 for detecting a main signal and a light receiving element 3 for detecting a sub signal.
That is, as the configuration of the detection head 1B, the light receiving element 2 for detecting the main signal is fixed to the casing 4, more specifically, the light receiving element 2 is fixed to the transparent glass substrate 42 fixed to the casing body 41 made of aluminum. A configuration in which the light receiving element 3 for detecting the sub signal is fixed to the glass epoxy substrate 5 fixed to the housing 4 is conceivable.

JP 2008-122320 A

  However, in such a configuration, the linear expansion coefficient of the casing 4 (the linear expansion coefficient of the casing main body 41 because the linear expansion coefficient of the glass substrate 42 is very low) and the linear expansion coefficient of the substrate 5 are used. Depending on the temperature, there may be a difference between the amount of expansion / contraction of the housing 4 and the amount of expansion / contraction of the substrate 5, and the positional relationship between the light receiving elements 2 and 3 may change. When the positional relationship between the light receiving elements 2 and 3 changes, there is a problem that the measurement accuracy is lowered, and the use temperature range in which the accuracy can be guaranteed is limited.

  An object of the present invention is to provide an optical encoder that can detect a main signal and a sub-signal and can expand an operating temperature range.

  The optical encoder of the present invention moves a detection head provided with first and second light receiving elements relative to a scale, detects one of a main signal and a sub signal by the first light receiving element, and An optical encoder for detecting the other of the main signal and the sub-signal by two light receiving elements, wherein the detection head includes a substrate on which the first light receiving element is mounted, and the second light receiving element to which the substrate is attached. And a fixing portion fixed to the casing is provided on one end side of the substrate in a predetermined direction, and the other end side of the substrate in the predetermined direction moves in the predetermined direction. A ratio of a distance along the predetermined direction from the fixed portion to the first light receiving element, supported by the casing, and a distance along the predetermined direction from the fixed portion to the second light receiving element. Is the linear expansion of the housing And coefficients, characterized in that equal to the ratio of the linear expansion coefficient of the substrate.

  According to the present invention, the main signal and the sub signal can be detected by the first and second light receiving elements. Of the first and second light receiving elements, the first light receiving element is fixed to the housing via the substrate. Since the substrate is supported by the housing so as to be movable in the predetermined direction, the amount of movement of the first light receiving element in the predetermined direction with respect to the change in operating temperature is based on the linear expansion coefficient of the substrate. On the other hand, since the second light receiving element is directly fixed to the housing, the amount of movement of the second light receiving element in a predetermined direction with respect to a change in operating temperature is based on the linear expansion coefficient of the housing.

Here, the distance along the predetermined direction from the fixed portion of the substrate fixed to the housing to the first light receiving element is A (FIG. 5), the distance along the predetermined direction from the fixed portion to the second light receiving element is B, Assuming that the distance along the predetermined direction between the first and second light receiving elements is X, the linear expansion coefficient of the substrate is E _A , the linear expansion coefficient of the housing is E _B , and the change in operating temperature is T, the first and second The variation ΔX of the distance X between the light receiving elements is
ΔX = ΔB−ΔA
= B x E _B x TA x E _A x T
= (B x E _B -A x E _A ) x T
It is expressed. Therefore, when the _{(B × E B -A × E} A) = 0, i.e. A: _{B =} E _B: when _{E A,} first irrespective of the use temperature change T, the distance X between the second light-receiving element It can be seen that the fluctuation amount ΔX becomes zero.

Therefore, in the present invention, the first and second light receiving elements are arranged at positions where A: B = E _B : E _A and the variation ΔX is set to zero. Thereby, in this invention, the change of the positional relationship between the 1st, 2nd light receiving elements by use temperature change can be suppressed, and a measurement precision can be improved. Therefore, the operating temperature range can be expanded.

In the optical encoder according to the aspect of the invention, a lubricating layer may be laminated on any one of a contact surface with the other end side of the housing and a contact surface with the housing on the other end side. preferable.
According to the present invention, since the lubricating layer is laminated on one of the contact surfaces of the housing and the substrate, the friction between them can be reduced, and the substrate can be reliably expanded and contracted according to a change in operating temperature. Therefore, in the present invention, the first and second light receiving elements are disposed at predetermined positions on the premise that the substrate and the housing expand and contract in accordance with a change in use temperature. A change in the positional relationship between the second light receiving elements can be reliably suppressed.

In the optical encoder according to the aspect of the invention, a through hole extending along the predetermined direction is formed on the other end side, and the housing includes a screw that penetrates the through hole, It is preferable that the other end side is held between the contact surface and the screw so as to be movable in the predetermined direction.
According to the present invention, since the through hole extends along a predetermined direction, the housing can be clamped so that the other end side of the substrate can be moved in the predetermined direction by a screw inserted through the through hole. Therefore, since the housing sandwiches the other end side of the substrate, the other end side of the substrate can be stably supported. Moreover, since the structure which clamps the other end side of a board | substrate so that a movement to a predetermined direction is implement | achieved using a screw | thread, this structure is realizable with a simple structure.

  In the optical encoder according to the aspect of the invention, the housing includes first and second fixing portions fixed at positions separated from each other in the predetermined direction, the substrate is attached, and the second light receiving element is fixed. Is formed so as to be elastically deformable along the predetermined direction, and the other end of the main body portion and the other of the first and second fixing portions are connected to one of the first and second fixing portions. It is preferable to provide an elastic part to be connected.

  According to the present invention, the substrate is attached to the main body of the housing, and the second light receiving element is fixed. One end of the main body is connected to one of the first and second fixing parts fixed at a predetermined position, and the other end is connected to the other first and second fixing parts via an elastic part. When the main body part expands and contracts due to a change in use temperature, a restoring force is applied to the main body part by the elastic part. Therefore, the restoring force can assist the main body part in restoring to a stretched state before the use temperature change. Therefore, reproducibility with respect to temperature can be improved.

1 is a cross-sectional view showing a detection head according to a first embodiment of the present invention. The top view which shows the detection head of 1st Embodiment. Sectional drawing which shows the detection head which concerns on 2nd Embodiment of this invention. The top view which shows the detection head of 2nd Embodiment. Sectional drawing which shows an example of a structure of a detection head.

[First Embodiment]
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings.
The optical encoder according to the present embodiment includes a detection head provided with a light receiving element for detecting a main signal such as a relative displacement signal and a sub signal such as an origin signal, and a proximity to the detection head. And a scale on which an optical grating for main signals and an optical grating for sub signals are formed, and a light source that emits light to each optical grating. When the detection head moves relative to the scale, the light emitted from the light source and reflected by each optical grating or transmitted through each optical grating is received by each light receiving element. Based on the main signal and the sub signal detected by each light receiving element, the relative movement amount of the scale is calculated by a user side device connected to the optical encoder.

  The optical grating for the main signal is exemplified by an incremental pattern in which reflection portions or transmission portions are arranged at regular intervals. As an optical grating for sub-signals, a reflection part or a transmission part is arranged at a predetermined position to generate a signal indicating the origin, or a reflection part or a transmission part is arranged at random intervals to indicate an absolute distance from the origin. An absolute pattern that generates a signal is exemplified.

When an incremental pattern is used as the optical grating, the optical encoder is provided with a signal processing unit, and a signal from the light receiving element is processed by the signal processing unit and then output to a user side device. When an absolute pattern is used as the optical grating, the optical encoder is provided with an arithmetic unit. Based on a signal from the light receiving element, position information is calculated by an arithmetic device, and the position information is output to a user side device. Based on these signals, the relative movement amount of the scale is calculated by the device on the user side.
Since the entire configuration of an optical encoder that detects a main signal and a sub signal using two light receiving elements is known as described in Patent Document 1, description of a scale and the like is omitted below, and the present invention is omitted. The configuration of the characteristic detection head will be mainly described.

FIG. 1 is a cross-sectional view showing the detection head 1, and FIG. 2 is a plan view showing the detection head 1. Hereinafter, the vertical and horizontal directions in FIG. 1 are the vertical and horizontal directions.
The detection head 1 includes a light receiving element 2 as a second light receiving element, a light receiving element 3 as a first light receiving element, a substrate 5, and a housing 4. A scale is disposed below the detection head 1 in FIG. As will be described later, a glass substrate 42 is provided on the lower surface of the housing 4 facing the scale.
The light receiving element 2 is mounted on the upper surface of the glass substrate 42 with the light receiving surface facing downward. The light receiving element 2 receives the light reflected by the optical grating for main signals formed on the scale or the light transmitted through the optical grating through the glass substrate 42, and detects the main signal such as a relative displacement signal.

As will be described later, the substrate 5 is provided above the glass substrate 42 in the housing 4.
The light receiving element 3 is mounted on the lower surface of the substrate 5 with the light receiving surface facing downward. The light receiving element 3 receives the light reflected by the optical grating for sub signals formed on the scale or the light transmitted through the optical grating through the glass substrate 42, and detects the sub signals such as the origin signal.
The substrate 5 is made of glass epoxy, and through holes 51 and 52 are formed at both left and right ends.

The housing 4 includes a housing body 41, a glass substrate 42, and screws 43.
The housing main body 41 is made of aluminum and includes a main body portion 6 and protruding end portions 71 and 72.
The main body portion 6 is formed in a rectangular shape, and projecting end portions 71 and 72 are connected to both left and right ends. The protruding end portions 71 and 72 protrude upward. The projecting end portions 71 and 72 are not fixed at predetermined positions in the present embodiment, and the housing 4 can be expanded and contracted in the left-right direction due to a change in use temperature.

  A recess 611 is formed on the upper end surface 61 of the main body 6, and a recess 621 smaller than the recess 611 is formed on the lower end surface 62 at a position overlapping the recess 611 in plan view. The bottom 63 of both the recesses 611 and 621 is common. A hole 631 is formed in the bottom 63, and both the recesses 611 and 621 communicate with each other through the hole 631. A glass substrate 42 is attached to the lower surface 632 of the bottom 63, and the glass substrate 42 is accommodated in the recess 621. The light receiving element 2 is mounted on the upper surface exposed from the hole 631 of the glass substrate 42.

  The substrate 5 is screwed to the upper end surface 61 of the main body 6. Specifically, a fixing portion 53 fixed to the main body portion 6 with a screw 43 is provided on the left end side of the substrate 5. On the other hand, the through hole 51 formed on the right end side of the substrate 5 is a fool hole whose diameter is slightly larger than the shaft diameter of the screw 43, and there is play in the left and right direction, that is, the through hole 51 extends in the left and right direction. For this reason, the right end side of the substrate 5 is attached to the main body 6 by the screw 43 so as to be movable in the left-right direction. On the upper end surface 61 of the main body 6, a lubricating layer 64 having a lower coefficient of friction than the upper end surface 61 is laminated on the right side portion to which the right end side of the substrate 5 is attached. As the lubricating layer 64, a fluororesin layer such as a polytetrafluoroethylene layer or a DLC layer (Diamond like Carbon layer) is employed. Since the substrate 5 has a fixed portion 53 on the left end side and is movable in the left and right direction on the right end side, the substrate 5 expands and contracts in the left and right directions with the fixed portion 53 as a base point when the operating temperature changes. At this time, the friction between the right end side of the substrate 5 and the housing 4 is reduced by the lubricating layer 64.

In this embodiment, the light receiving element 2 is attached to the main body 6 via the glass substrate 42 having a very low linear expansion coefficient, so that the casing 4 (main body 6) is moved in the left-right direction due to a change in operating temperature. When it expands and contracts, the light receiving element 2 moves in the left-right direction along with the expansion and contraction. Therefore, the amount of movement of the light receiving element 2 in the left-right direction with respect to the change in operating temperature is based on the linear expansion coefficient of the housing 4.
On the other hand, since the light receiving element 3 is fixed to the substrate 5 that can be expanded and contracted in the left and right direction, when the substrate 5 expands and contracts in the left and right direction due to a change in operating temperature, the light receiving element 3 also moves in the left and right direction. Therefore, the amount of movement of the light receiving element 3 in the left-right direction with respect to the change in operating temperature is based on the linear expansion coefficient of the substrate 5.

Here, the distance along the left-right direction from the fixed portion 53 to the light receiving element 3 at the left end of the substrate 5 is A, the distance along the left-right direction from the fixed portion 53 to the light receiving element 2 is B, and between the light receiving elements 2 and 3 The distance along the horizontal direction is X, the linear expansion coefficient of the glass epoxy substrate 5 is E _A (= 60 × 10 ⁻⁶ ° C.), and the linear expansion coefficient of the aluminum housing 4 is E _B (= 21 × 10). ⁻⁶ ° C.), and ^{assuming that the} change in operating temperature is T, the fluctuation amount ΔX of the distance X between the light receiving elements 2 and 3 is
ΔX = ΔB−ΔA
= B x E _B x TA x E _A x T
= (B x E _B -A x E _A ) x T
It is expressed. Therefore, when the _{(B × E B -A × E} A) = 0, i.e. A: _{B =} E _B: when _{E A,} the fluctuation amount of the distance X between the light receiving elements 2 and 3 regardless of the use temperature change T It can be seen that ΔX becomes zero.

Therefore, in the present embodiment, the light receiving elements 2 and 3 are arranged at positions where A: B = E _B (= 21 × 10 ⁻⁶ ° C.): E _A (= 60 × 10 ⁻⁶ ° C.) = 1: 3. The Thereby, since the variation ΔX is set to 0, in this embodiment, the change in the positional relationship between the light receiving elements 2 and 3 due to the change in operating temperature T can be suppressed, and the measurement accuracy can be improved. Therefore, the operating temperature range can be expanded.

In the above embodiment, the following effects can be obtained.
The main signal and the sub signal can be detected by the light receiving elements 2 and 3.
The ratio of the distance A along the left-right direction from the fixing portion 53 of the substrate 5 fixed to the housing 4 to the light-receiving element 3 and the distance B along the left-right direction from the fixing portion 53 to the light-receiving element 2 is The light receiving element 2 at a position equal to the ratio 1: 3 of the linear expansion coefficient E _B (= 21 × 10 ⁻⁶ ° C.) of the body 4 and the linear expansion coefficient E _A (= 60 × 10 ⁻⁶ ° C.) of the substrate 5; 3 is arranged, it is possible to suppress a change in the positional relationship between the light receiving elements 2 and 3 due to a change in operating temperature, and to improve measurement accuracy. Therefore, the operating temperature range can be expanded. And it can respond to the request | requirement of a user's use temperature diversification by expansion of a use temperature range.

Since the lubricating layer 64 is laminated on the upper end surface 61 of the housing 4 in contact with the substrate 5, friction between the upper end surface 61 and the substrate 5 can be reduced, and the substrate 5 is reliably expanded and contracted according to a change in use temperature. be able to. Therefore, when the light receiving elements 2 and 3 are arranged at predetermined positions on the premise that the substrate 5 and the housing 4 expand and contract in accordance with a change in operating temperature, the precondition is maintained. Changes in the positional relationship can be reliably suppressed.
Since the housing 4 sandwiches the right end side of the substrate 5, the right end side of the substrate 5 can be stably supported. In addition, since the configuration for holding the right end side of the substrate 5 so as to be movable in the left-right direction is realized using the screw 43, the configuration can be realized with a simple configuration.

[Second Embodiment]
FIG. 3 is a sectional view of the detection head 1A according to the present embodiment, and FIG. 4 is a plan view showing the detection head 1A.
In the present embodiment, the protruding end portions 71 and 72 (first and second fixing portions) are fixed at positions separated from each other in the left-right direction, and the right protruding end portion 72 (second fixing portion) and the main body portion 6 Are connected by the elastic portion 8. The elastic portion 8 is a parallel leaf spring, has a crank shape in plan view, and can be elastically deformed in the left-right direction. Other configurations of the present embodiment are the same as those of the first embodiment.

  In the present embodiment, the same effects as in the first embodiment can be obtained, and when the main body portion 6 expands and contracts due to a change in use temperature, a restoring force is applied to the main body portion 6 by the elastic portion 8. Thereby, it can assist that the main-body part 6 restore | restores in the expansion-contraction state before use temperature change. Therefore, reproducibility with respect to temperature can be improved.

[Modification of Embodiment]
Note that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope in which the object of the present invention can be achieved are included in the present invention.
In each of the above embodiments, the right end side of the substrate 5 is sandwiched between the screw 43 and the casing 4, but the right end side of the substrate 5 is simply placed on the casing 4 and supported by the casing 4. Also good.
In each of the above embodiments, the fixing portion 53 provided on the left end side of the substrate 5 is fixed to the housing 4 by the screw 43, but the fixing portion 53 may be fixed to the housing 4 by adhesion.

In each of the above embodiments, the lubricating layer 64 is laminated on the housing 4 side, but the lubricating layer 64 may be laminated on the substrate 5 side.
In each said embodiment, although the through-hole 51 was made into a fool hole, the through-hole 51 may be formed in the slit shape extended in the left-right direction.

In each of the above embodiments, the casing 4 is made of aluminum and the substrate 5 is made of glass epoxy. However, the materials of the members 4 and 5 can be appropriately selected.
In each of the above embodiments, the transparent glass substrate 42 and the glass epoxy substrate 5 are stacked and disposed along the normal direction of the scale. However, the glass substrate 42 and the substrate 5 are along the plane direction of the scale. May be arranged side by side.
The optical encoder of the present invention can be applied to a linear encoder, a rotary encoder, a linear gauge, an arc encoder, and the like.

1,1A Detection head 2 Light receiving element (second light receiving element)
3 Light receiving element (first light receiving element)
4 Housing 5 Substrate 6 Main body 8 Elastic portion 43 Screw 51 Through hole 53 Fixing portion 61 Upper end surface (contact surface with other end side of housing)
64 Lubrication layer 71 Protruding end (first fixed part)
72 Protruding end (second fixed part)

Claims (4)

The detection head provided with the first and second light receiving elements is moved relative to the scale, one of the main signal and the sub signal is detected by the first light receiving element, and the main signal and the sub signal are detected by the second light receiving element. An optical encoder that detects the other of the signals,
The detection head includes a substrate on which the first light receiving element is mounted, and a housing to which the substrate is attached and the second light receiving element is fixed.
A fixing portion fixed to the housing is provided at one end side of the substrate in a predetermined direction, and the other end side of the substrate in the predetermined direction is supported by the housing so as to be movable in the predetermined direction,
The ratio of the distance along the predetermined direction from the fixed part to the first light receiving element and the distance along the predetermined direction from the fixed part to the second light receiving element is the linear expansion coefficient of the casing. And the ratio of the linear expansion coefficient of the substrate to the optical encoder. The optical encoder according to claim 1,
An optical encoder, wherein a lubricating layer is laminated on one of a contact surface with the other end side of the housing and a contact surface with the housing on the other end side. The optical encoder according to claim 2, wherein
A through hole extending along the predetermined direction is formed on the other end side,
The housing includes a screw penetrating the through hole, and the other end side is movably clamped in the predetermined direction by the contact surface with the other end side and the screw. . The optical encoder according to any one of claims 1 to 3,
The housing is
First and second fixing portions fixed at positions separated from each other in the predetermined direction;
A main body portion to which the substrate is attached and the second light receiving element is fixed, and one end is connected to one of the first and second fixing portions,
An optical encoder, comprising: an elastic portion formed so as to be elastically deformable along the predetermined direction and connecting the other end of the main body portion and the other of the first and second fixing portions.

Images