JP2012242313A - Encoder and actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an encoder capable of improving an optical system to obtain larger optical signal contrast and thereby achieving stability and high reliability of signal processing in a subsequent process, and an actuator including the encoder.SOLUTION: A light shielding plate is disposed between an optical detector and a light source. The light shielding plate is located closer to the optical detector. Thus, stray light is reduced to improve signal contrast, and stability and high reliability of signal processing are achieved in a subsequent process.

Description

The present invention relates to, for example, an encoder used in a precision positioning system and an actuator using the encoder, and in particular, is configured to obtain a larger optical signal contrast by improving the optical system, thereby enabling subsequent steps. The present invention relates to a device devised so that signal processing can be stabilized and reliability can be improved.

In the precision positioning apparatus, for example, a linear encoder is used as a sensor for positioning feedback. This is due to the high accuracy and low cost of the linear encoder. However, the linear encoder that is widely used at present is an incremental type that requires an origin return operation. In the case of this type of incremental type linear encoder, it is necessary to perform an origin return operation when the apparatus is started up or when a trouble occurs, which causes a problem that the operating rate of the apparatus decreases.

Therefore, it has been proposed to use an absolute linear encoder instead of the incremental linear encoder. This is because in the case of this type of absolute type linear encoder, the above origin return operation is not required.

The patent applicant has also filed an application relating to a simple absolute linear encoder that can know the absolute position by moving a short distance when the apparatus is started, as shown in Patent Document 1. The absolute type linear encoder disclosed therein is configured to move the movable part of the device on which the sensor for reading the data of the required number of bits of the PN code sequence is mounted, so that one sensor is provided. The absolute position can be known with a simple configuration.

However, depending on the device, there is a device that damages the workpiece, jigs, etc. even if it moves even a little when the device is started up. In such a case, there is a problem that the simple absolute linear encoder cannot be applied.

On the other hand, there have been many proposals of absolute linear encoders that do not need to move at all. For example, Patent Literature 2 and Patent Literature 3 disclose such absolute type linear encoders.

JP 2009-68978 A Japanese Patent Laid-Open No. 03-274414 JP 2005-121593 A

The conventional configuration has the following problems.
That is, in the case of the absolute type linear encoder disclosed in Patent Document 2 and Patent Document 3, the reliability is insufficient and the cost is high, and it is difficult to make the detection head compact. There was a problem. Specifically, first, in the case of the absolute linear encoder described in Patent Document 2, it is possible to detect a 1-bit error or an odd-numbered term error, but a 2-bit error or an even number. There was a problem that this error could not be detected for the term error. In addition, in order to perform error detection of all bits, it is necessary to inspect a bit length that is about twice the required number of bits, which necessitates a large number of sensors (light receiving elements). There was also a problem that the cost became difficult.
In the case of the invention described in Patent Document 3, a compact sensor unit is disclosed. However, in that case, only light receiving elements corresponding to the number of bits necessary for a predetermined detection are mounted. Limited error detection was possible.
Further, in the case of the invention described in Patent Document 2, when an error is detected by the error detection method disclosed therein, there is also a problem that the apparatus remains stopped.
Incidentally, as shown in Patent Document 4, the present patent applicant has filed another patent application to solve this type of problem.

JP 2010-217160 A

However, in order to ensure more stable reliability, it is desirable to obtain a greater contrast of the optical signal by improving the optical system. That is, the larger contrast of the optical signal is converted into a larger signal output by the optical detector, which leads to stabilization of signal processing and improvement of reliability in the subsequent steps.

The present invention has been made based on these points, and the object of the present invention is to improve the optical system so that a larger optical signal contrast can be obtained. An object of the present invention is to provide an encoder capable of stabilizing and improving reliability and an actuator equipped with the encoder.

In order to achieve the above object, an encoder according to claim 1 of the present invention is characterized in that a light shielding plate is provided between an optical detector and a light source, and the light shielding plate is disposed at a position close to the optical detector. To do.
An encoder according to a second aspect is the encoder according to the first aspect, wherein the light shielding plate is in contact with the optical detector.
According to a third aspect of the present invention, in the encoder according to the second aspect of the present invention, the light shielding plate has a spring property and is attached to the optical detector.
According to a fourth aspect of the present invention, in the encoder of the third aspect, the light shielding plate shields both sides of the optical detector.
According to a fifth aspect of the present invention, in the encoder according to the fourth aspect, the single optical detector can read two kinds of scales.
According to a sixth aspect of the present invention, in the encoder of the fifth aspect, the light shielding plate is crowned and fixed to one optical detector.
An actuator according to claim 7 uses the absolute linear encoder according to any one of claims 1 to 6.

As described above, according to the encoder of the first aspect of the present invention, the light shielding plate is provided between the optical detector and the light source, and the light shielding plate is installed at a position close to the optical detector. Therefore, first, stray light can be reduced, thereby improving signal contrast and stabilizing signal processing and increasing reliability in subsequent processes. Further, since the light shielding plate is disposed closer to the optical detector, the above effect can be further ensured.
According to an encoder according to claim 2, in the encoder according to claim 1, the light shielding plate is in contact with the optical detector. Positioning etc. becomes easy.
According to an encoder according to claim 3, in the encoder according to claim 2, the light shielding plate has a spring property and is configured to be attached to the optical detector. Positioning and holding of the light shielding plate is ensured.
According to an encoder according to claim 4, in the encoder according to claim 3, since the light shielding plate is configured to shield both sides of the optical detector, a small number of light shielding plates is sufficient.
According to an encoder according to claim 5, in the encoder according to claim 4, since the optical detector is configured to be able to read two kinds of scales, the configuration is simplified in combination with the configuration described above. Can be achieved.
In the encoder according to claim 6, in the encoder according to claim 5, the light shielding plate is configured to be crowned and fixed to one optical detector, so that the light shielding plate can be easily positioned and attached. It becomes.
Further, according to the actuator according to claim 7, since the absolute linear encoder according to any one of claims 1 to 6 is used, it is possible to provide a low-cost and highly reliable actuator. it can.

It is a figure which shows the 1st Embodiment of this invention and is a top view which shows the structure of an actuator. It is a figure which shows the 1st Embodiment of this invention, and is a block diagram which shows the structure of an absolute linear encoder. It is a figure which shows the 1st Embodiment of this invention, and is a block diagram which shows the structure of LSFR. 4A and 4B are diagrams illustrating a first embodiment of the present invention, in which FIG. 4A is a side view illustrating the configuration of an optical detector and a light source, and FIG. 4B is a view taken along the line bb in FIG. FIG. 4C is a cross-sectional view taken along the line cc of FIG. 5A and 5B are diagrams showing a second embodiment of the present invention, in which FIG. 5A is a side view showing a configuration of an optical detector and a light source, and FIG. 5B is a view taken along the line bb in FIG. FIG.5 (c) is cc sectional drawing of Fig.5 (a). FIGS. 6A and 6B are diagrams showing a third embodiment of the present invention, FIG. 6A is a side view showing the configuration of an optical detector and a light source, and FIG. 6B is a view taken along the line bb in FIG. 6 (c) is a cross-sectional view taken along the line cc of FIG. 6 (a), and FIG. 6 (d) is an enlarged plan view of the light shielding plate. FIGS. 7A and 7B are views showing a fourth embodiment of the present invention, FIG. 7A is a side view showing the configuration of an optical detector and a light source, and FIG. 7B is a view taken along the line bb in FIG. FIG. 7C is a cross-sectional view taken along the line cc of FIG. FIGS. 8A and 8B are views showing a fourth embodiment of the present invention, in which FIG. 8A is a plan view of a light shielding plate, FIG. 8B is a view taken along the line bb in FIG. 8A, and FIG. FIG. 8A is a perspective view of the light shielding plate, and FIG. 8D is a perspective view of the light shielding plate.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. This embodiment shows an example in which the present invention is applied to a uniaxial actuator. FIG. 1 is a plan view showing the entire configuration of the actuator according to the present embodiment. First, there is a housing 1. A slider 3 is attached to the housing 1 so as to be movable in the left-right direction (arrow a direction) in FIG. A ball screw 5 is housed in the housing 1 and a drive motor 7 is installed. The ball screw 5 is connected to the output shaft of the drive motor 7 and is configured to be rotated and driven by the drive motor 7.
In the illustrated actuator, the ball screw 5 and the output shaft of the drive motor 7 are integrated. However, the actuator is not limited to such an actuator.

  A ball nut (not shown) is screwed and arranged on the ball screw 5 in a state where its rotation is restricted. The slider 3 already described is fixed to this ball nut. Guides 9 and 11 are installed in the housing 1, and the guides 9 and 11 guide the movement of the slider 3 in the left-right direction (arrow a direction) in FIG. Then, by rotating the drive motor 7 in an appropriate direction, the ball screw 5 rotates in the same direction, whereby the slider 3 is guided by the guides 9 and 11 via the ball nuts in the left and right direction in FIG. Move in the direction of arrow a).

A linear scale portion 21 is installed on the guide 11 side, while a detection head portion 23 is attached to the slider 3. A controller unit 25 is installed at a location separated from the actuator.

Next, the configuration of the linear scale unit 21, the detection head unit 23, and the controller unit 25 will be described in detail. FIG. 2 shows the linear scale unit 21, the detection head unit 23, and the controller unit 25 extracted from FIG. First, the linear scale unit 21 includes a phase detection linear scale 31 and a PN code sequence absolute linear scale 33. The PN code sequence absolute linear scale 33 alone can provide the necessary functions, but the resolution of the PN code sequence absolute linear scale 33 is equal to one bit of the absolute signal. It is difficult to achieve both a long stroke and high resolution in terms of response speed and cost.
Therefore, in the case of the present embodiment, the PN code sequence absolute linear scale 33 having a slightly rough width is used to moderately reduce the number of necessary PN code sequence bits with respect to the stroke and further increase the absolute 1 bit. A phase detection linear scale 31 that can be divided into resolutions is provided separately.
Incidentally, in order to achieve a resolution of 0.1 μm with a stroke of 2.6 m, a phase detection linear scale 31 is required that is capable of 800 divisions (phase 0.45 °) with a 15-bit PN code sequence with an absolute 1 bit width of 80 μm It becomes.

The linear scale 31 for phase detection has a striped shape, and is configured as an optical reflection type having a pitch of 80 μm, for example. That is, the linear scale 31 for phase detection has a configuration in which high-reflectance regions 31a of 40 μm and low-reflection regions 31b of 40 μm are alternately arranged.

On the other hand, the PN code sequence absolute linear scale 33 is configured such that one bit is 80 μm, and the high reflectance region 33a and the low reflection region 33b are arranged based on the PN code sequence.
In FIG. 2, the pattern of the absolute linear scale 33 has a high reflectivity region (black) 33a and a low reflectivity region (white) so as to correspond to 1: 1 for the PN code series for ease of explanation. The absolute linear scale 33 in the present embodiment modulates the PN code sequence to narrow the band.
The PN code sequence is a pseudo-random sequence (Pseudo Random Noise, part of which is also called an M sequence). This pseudo-random sequence is widely used for spread spectrum communication, white noise generation, encryption, error correction, and the like.

A shift register called LFSR (Linear Feedback Shift Register) is used for generating the PN code sequence. This shift register is configured as shown in FIG. 3, and is configured to provide feedback by an XOR gate (or XNOR gate) 50.
The LFSR will be described in detail later.

Returning to FIG. 2, the configuration on the detection head unit 23 side will be described. First, a phase detection linear scale optical detector (using a CMOS linear array) 35 corresponding to the phase detection linear scale 31; A PN code sequence absolute linear scale optical detector (using a CMOS linear array) 37 corresponding to the PN code sequence absolute linear scale 33 is installed. The phase detection linear scale 31 and the phase detection linear scale optical detector 35 constitute a phase detection linear scale section. The PN code series absolute linear scale 33 and the PN code series absolute linear scale optical detector 37 constitute an absolute linear scale section.

The phase detection linear scale optical detector 35 and the PN code series absolute linear scale optical detector 37 are installed as shown in FIG. Reference numeral 39 in FIG. 4 denotes an LED light source. In the configuration shown in FIG. 4, two LED light sources 39 and 39 are installed. LED light is projected from the LED light source 39 to the linear scale 31 for phase detection. The light reflected by the phase detection linear scale 31 is received by the phase detection linear scale optical detector 35. The same applies to the optical detector 37 for the PN code series absolute linear scale. That is, LED light is projected from the LED light source 39 to the PN code series absolute linear scale 33. The light reflected by the PN code series absolute linear scale 33 is received by the optical detector 37 for the PN code series absolute linear scale. Depending on the reflectivity of the phase detection linear scale 31 and the PN code sequence absolute linear scale 33, the intensity of light incident on the phase detection linear scale optical detector 35 and the PN code sequence absolute linear scale optical detector 37 is increased. Unlike this, the signal patterns of the phase detection linear scale 31 and the PN code series absolute linear scale 33 can be read.
Incidentally, the light intensity reflected by the low reflectance region 33b of the PN code series absolute linear scale 33 is low, and the optical detector 37 for the PN code series absolute linear scale detects that the intensity is low, and the signal “0” can be detected. In addition, the light intensity reflected by the high reflectance region 33a is high, and the optical detector 37 for the PN code series absolute linear scale detects high intensity, and the signal “1” can be detected.

In the optical system of FIG. 4, the signal pitch on the phase detection linear scale optical detector 35 and the PN code series absolute linear scale optical detector 37 is the phase detection linear scale 31 or PN code series absolute linear scale. In order to make it easier to understand in the schematic diagram of FIG. 2, the phase detection linear scale 31, the PN code series absolute linear scale 33, and the phase detection linear scale optical detector 35 are enlarged. The signal of the optical detector 37 for the PN code series absolute linear scale is described so as to correspond up and down at the same magnification.

In the present embodiment, the optical detector for phase detection linear scale (using a CMOS linear array) 35 and the optical detector for PN code series absolute linear scale (using a CMOS linear array) 37 are used. A general-purpose packaged CMOS linear array and a general-purpose packaged chip LED are surface-mounted on a printed circuit board. By using such a general-purpose product, it can be manufactured at a low cost. In FIG. 4, two LED light sources 39 are mounted. The phase detecting linear scale optical detector (using a CMOS linear array) 35, the PN code series absolute linear scale optical detector. This is to enable switching to the other LED light source 39 when the LED light source 39 whose lifetime is shorter than that of 37 (using a CMOS linear array) deteriorates. Moreover, the irradiation area of the LED light source 39 can be expanded by switching the two LED light sources 39.

Further, the phase detection linear scale 31 and the PN code series absolute linear scale 33 in this embodiment perform thermal transfer printing on the PET film by thermal transfer printing of the aluminum vapor deposition layer, and further thermal transfer printing of black ink thereon. By doing so, a repetitive pattern of the phase detection linear scale 31 and a PN signal sequence (modulation) pattern of the PN code sequence absolute linear scale 33 are formed by the high reflection region by the aluminum vapor deposition layer and the low reflection region by the black ink. .

As shown in FIG. 2, the detection head unit 23 is provided with a phase calculator 41, an absolute position data calculator 43, an absolute position data composer 45, and a transceiver 47. The controller unit 25 is provided with a transceiver 49 and a controller 51. The absolute position data calculator 43 detects the matching absolute position via the LFSR. However, it may be obtained from a correspondence table of signal data and absolute position prepared in advance.

The signal output from the optical detector 37 for the PN code series absolute linear scale is input to the absolute position data calculator 43, and the absolute position in absolute bits is obtained by the absolute position data calculator 43. On the other hand, the signal output from the optical detector 35 for phase detection linear scale is input to the phase calculator 41, where the phase calculator 41 calculates the phase with the absolute 1 bit set to 360 degrees, and the information with higher resolution. Is obtained. The absolute position data construction unit 45 combines the results obtained from the absolute position data calculator 43 and the phase calculator 41 to calculate and output absolute position data with a long stroke and high resolution. The high-resolution absolute position data is input to the controller 51 via the transceiver 47 and the transceiver 49. The controller 51 controls the drive motor 7 based on the input high-resolution absolute position data to position the slider 3.

Note that the absolute linear encoder in the present embodiment has two encoder functions, ie, a phase detection linear scale portion and an absolute linear scale portion, as already described. As described above, the necessary functions can be obtained even with only the absolute linear scale part, but the response speed is increased and the cost is reduced by increasing the stroke and the resolution of the absolute linear scale part. Was difficult. Therefore, in the case of the present embodiment, by providing a phase detection linear scale section and further dividing the absolute 1 bit into a higher resolution, a slightly rough absolute bit can be used. This realizes an absolute linear encoder with high response speed and low cost.
The above is the schematic configuration of the actuator according to the present embodiment and the absolute linear encoder used therein. Hereinafter, the configuration of each part will be described with its actions and effects.

First, the above-described LFSR will be described in detail. As shown in FIG. 3, the LFSR is configured by 15 (15 bits from 0 to 14) shift registers. In the LFSR having such a configuration, the period length of the PN code sequence that can be generated (PN code sequence length, L) is as shown in the following equation (I).
L = 2 ^m -1 --- (I)
However,
L: PN code sequence length m: Number of bits (number of detected continuous signals)
It is.
The PN code sequence is one of binary “0/1 (in this case, black and white)” pseudo-random sequence, and is a signal that can obtain a long signal period (L) with relatively short consecutive m signals. It is a series. For example, if m = 15, the PN code sequence length (L) is as shown in the following formula (II) according to the formula (I) already described.
L = 2 ¹⁵ -1 = 32767-(II)
In the case of the LFSR in this embodiment, as described above, the 0-bit and 1-bit signals are fed back to 14 bits via the XOR gate 50.

The phase detection linear scale 31 shown in FIG. 2 has a pitch of 80 μm as already described. Also, the PN code sequence absolute linear scale 33 has one bit of 80 μm. Therefore, the stroke (S) of the PN code sequence absolute scale 33 at m = 15 is as shown in the following equation (III).
S = 80 μm × 32767 = about 2.6 m --- (III)
As is clear from the equations (I) and (II), a long stroke can be realized by increasing the number m of detected continuous signals of the PN code sequence on the absolute linear scale side.

As described above, the PN code sequence absolute linear scale optical detector 37 is used to detect the signal from the PN code sequence absolute linear scale 33. The PN code sequence absolute linear scale optical detector 37 is used. 37 is required to have a detection element having more than the number of PN code sequence bits required for the stroke. For example, in the above example, a 15-bit PN code sequence is required for a stroke of 2.6 m, and 15 or more detection elements are required. As described above, the absolute detector 37 requires a large number of detection elements, and a dedicated semiconductor IC is developed and used in order to make the detector compact. However, the dedicated semiconductor IC has a drawback that it is very expensive. On the other hand, since the output of the CMOS linear array can be increased by a charge amplifier, the output can be easily secured even if the light receiving area is reduced, and the reliability is high, and the size is small and the cost is low. Therefore, in the case of the present embodiment, a general-purpose CMOS linear array is used to achieve compactness and cost reduction.

The CMOS linear array is, for example, a detector in which 512 detection elements are arranged at a pitch of 12.5 μm and incorporates many detection elements. Further, since the signal output cannot be performed at the same time, the signal output becomes one by one. For example, if it is attempted to obtain the signal output of 512 detection elements, it takes about 500 times as much time. The high-speed signal output is difficult. Therefore, in the case of the present embodiment, not a method of outputting position data continuously (or with an extremely short time response) but a method of outputting position data at a certain time interval (or a response time). By using it, a method is adopted in which the output of the detection element of the CMOS linear array is obtained within a certain sampling time and error check, calculation of absolute position data, and the like are performed.

For example, if the output time per detection element of a CMOS linear array is 170 nsec (6 MHz), it takes about 100 μsec (10 KHz) to obtain the output of all 512 detection elements. Therefore, if other loss times are ignored, this approximately 10 KHz is the maximum response frequency. This response frequency is sufficiently high compared with the response frequency of the actuator of about 100 Hz at most, which is practically sufficient.

Further, as shown in FIG. 2, the phase detection linear scale 31 further divides one bit of the PN code sequence absolute linear scale 33 to obtain a high resolution. As described above, the PN code sequence absolute scale 31 is used. The high reflectivity portion 31a of approximately 1/2 bits and the low reflectivity portion 31b of approximately 1/2 bits correspond to 1 bit of the linear scale 33. When one bit of the PN code series absolute linear scale 33 is set to 360 degrees, phase detection is performed so that the light reflection intensity from the high reflectivity portion 31a and the low reflectivity portion 31b is approximately one sine wave period (360 degrees). Detection is performed by the linear scale optical detector 35.

The optical detector 35 for phase detection linear scale requires at least two detection elements and has a phase difference of approximately 90 degrees (corresponding to an absolute 1/4 bit). When two signal intensities having a phase difference of 90 degrees are obtained, the phase is calculated by the phase calculator 41 based on the following equations (IV) and (V).
tan θ = sin θ / cos θ
= {Α · sinθ} / {α · sin (θ−90 °)} ――― (IV)
θ = arctan ⁻¹ θ ――― (V)

Then, the position in the absolute 1 bit is obtained by the phase. Since one absolute bit corresponds to 360 degrees, for example, when a phase of 45 degrees is calculated, the position is as shown in the following equation (VI).
80μm × 45 ° / 360 ° = 10μm --- (VI)
That is, the position is 10 μm inside the absolute 1 bit. In this way, the resolution of the somewhat rough absolute scale portion can be improved by using the phase detection linear scale portion.

Incidentally, in the phase detection linear scale detector 35, as already described, at least two detection elements having a phase difference of approximately 90 degrees are required. It is common to develop and use ICs. However, the dedicated semiconductor IC has a drawback that it is very expensive. Therefore, in the present embodiment, as in the case of the optical detector 37 for the PN code series absolute linear scale described above, a general-purpose CMOS linear array is used to achieve compactness and cost reduction. A CMOS linear array is, for example, a detector in which 512 detection elements are arranged at a pitch of 12.5 μm and incorporates many detection elements, and not only two detection elements having a phase difference of about 90 degrees. A large number of detection elements having a phase difference of approximately 90 degrees can be used. The detection elements of each set have the same phase difference (an integer multiple of 360 degrees), and the signal output can be stabilized by averaging using a large number of detection elements in one set. For example, even if the signal output deteriorates due to dust adhesion or the like at a position where the phase detection linear scale 31 is present, the influence of the dust can be minimized if it is averaged over a wider range. Further, by providing a detection element having a phase difference of 180 ° with each set, it is possible to obtain a differential with each signal output, thereby increasing the signal output and increasing the disturbance stability.

In addition, since a large number of narrow-pitch detection elements are built in, it is easy to associate with the PN code series absolute linear scale optical detector 37. If the fixed position of the optical detector 37 for the PN code series absolute linear scale and the fixed position of the optical detector 35 for the phase detection linear scale are shifted due to mounting variations of the detector, the phase detection linear scale is used. Adjustment can be made by selecting the detection element to be selected in the optical detector 35 by shifting it by the shift amount. For example, it is only necessary to rewrite the FPGA (Field Programmable Gate Array) software to determine the output number of the detection element to be selected.

As described above, in the present embodiment, by using the two scale parts, that is, the absolute scale part and the phase detection scale part, the absolute number of bits of the PN code sequence can be set to an appropriate number using absolute bits with a slightly rough width. In addition to realizing a long stroke, the phase detection scale unit further phase-divides the absolute 1 bit to achieve high resolution. In order to realize these in a low-cost and compact manner, a CMOS linear array is used as each detector, that is, a phase detection linear scale optical detector 35 and a PN code series absolute linear scale optical detector 37. As described above, the CMOS linear array incorporates a large number of detection elements, and it is difficult to output signals at high speed. Therefore, by using a method of obtaining the output of the detection element within a certain sampling time and performing absolute position data calculation or the like, an appropriate response frequency is ensured while being low-cost and compact.

Therefore, the output from the absolute position data composer 45 shown in FIG. 2 is not continuous but is intermittently updated at a certain sampling time. Therefore, the transceiver 47 for transmitting the data received from the absolute position data composer 45 to the controller 51 side is preferably an appropriate transmission bit rate, and is preferably a serial communication transceiver that can save wiring.

Also, as shown in FIG. 4, there is a U-shape between the phase detection linear scale optical detector 35 and the LED light source 39, and between the PN code series absolute linear scale optical detector 37 and the light source 39. Thus, light shielding plates 51 and 53 made of thin plates are provided. By installing these light-shielding plates 51 and 53, the incidence of stray light on the optical detector 35 for phase detection linear scale and the optical detector 37 for PN code series absolute linear scale is reduced, so that the contrast of the optical signal is reduced. Is devised so that signal processing can be stabilized and reliability can be improved in subsequent processes.

The light shielding plates 51 and 53 will be described in detail. As described above, the light shielding plates 51 and 53 are U-shaped and made of a thin plate. Between the optical detector 35 for phase detection linear scale and one LED light source 39, a PN code series absolute linear is used. It is installed between the optical detector 37 for scale and the other LED light source 39. The reason why the light shielding plates 51 and 53 are formed in a U-shape is based on the fact that they are made of thin plates and are difficult to stand on their own, so that they can be made independent by bending both ends of the thin plates. . Further, the light shielding plates 51 and 53 are bonded and fixed on the detection head unit 23 by, for example, an adhesive.

The light shielding plates 51 and 53 are made of a metal such as stainless steel or a resin such as polyacetal resin. Further, the surfaces of the light shielding plates 51 and 53 are preferably not a mirror surface but a matte state so that light is not easily reflected, and the color is preferably black or gray. The LED light source 39 used in the present embodiment is a pseudo-point light source that emits light radially from a minute light emitting portion (for example, a diameter of several tens of micrometers) in all directions. Therefore, as shown in FIG. 4, the light emitted from the LED light source 39 is reflected by the phase detection linear scale 31 and the PN code series absolute linear scale 33, and the reflected light is detected by the phase detection linear scale optical detector. 35 and the PN code series absolute linear scale optical detector 37, not only the light passing through an ideal path, but also reflected at various points to be used as a phase detecting linear scale optical detector 35 or PN. It enters the optical detector 37 for the code series absolute linear scale (this is “stray light”). In this way, both the signal light reflected by the ideal path and the stray light are incident on the optical detector 35 for the linear scale for phase detection and the optical detector 37 for the PN code series absolute linear scale. When there is a lot of stray light, the contrast of the signal light is lowered, and the detected signal quality is deteriorated.

Therefore, in the present embodiment, the light shielding plates 51 and 53 are provided. That is, by installing the light shielding plates 51 and 53, it is intended to reduce the stray light and improve the contrast of the signal light. In this embodiment, since the LED light source 39 which is a pseudo point light source is used, for example, even if the LED light source 39 is attached in a slightly inclined state, light is emitted in all directions. The performance as a light source is sufficiently secured. Therefore, the mounting posture of the LED light source 39, the optical detector 35 for the phase detection linear scale, and the optical detector 39 for the PN code series absolute linear scale to the detection head 23, the mounting posture of the detection head 23 to the actuator, and phase detection The linear scale 31 and the PN code series absolute linear scale 33 can have a relatively large permissible area for the mounting posture (rolling, pitching, yawing) to the actuator.

Further, if the light shielding plates 51 and 53 are too close to the LED light source 39 side, many parts of the LED light source 39 that is a pseudo point light source are blocked, and the allowable mounting posture is limited. Become. In addition, since the light shielding plates 51 and 53 installed near the LED light source 39 shield stronger light, even the light shielding plates 51 and 53 with reduced reflectance reflect a considerable amount of light. And they will lead to stray light. Therefore, the light-shielding plates 51 and 53 are between the phase detection linear scale optical detector 35 and the LED light source 39, and between the N code series absolute linear scale optical detector 37 and the LED light source 39, and are used for phase detection. It is desirable that the optical detector 35 for the linear scale and the optical detector 37 for the PN code series absolute linear scale be installed at a position close to the optical detector 37 for the linear scale.

As described above, according to the present embodiment, the following effects can be obtained.
First, the light shielding plates 51 and 53 are installed between the phase detection linear scale optical detector 35 and the LED light source 39, and between the PN code series absolute linear scale optical detector 37 and the LED light source 39. In other words, so-called stray light can be reduced, whereby the contrast of the signal light can be improved, and signal processing can be stabilized and highly reliable in the subsequent steps.
The light shielding plates 51 and 53 are disposed between the phase detection linear scale optical detector 35 and one LED light source 39, and between the N code series absolute linear scale optical detector 37 and the other LED light source 39. In addition, since the optical detector 35 for the phase detecting linear scale and the optical detector 37 for the PN code series absolute linear scale are installed, the above effect can be further ensured.
Further, since the light shielding plates 51 and 53 are U-shaped and have high self-supporting properties, positioning and bonding / fixing operations using an adhesive are easy.
In this embodiment, the LED light source 39, which is a pseudo-point light source, is used as the light source. Therefore, the mounting posture of the detection head 23 can be achieved by arranging the light shielding plates 51 and 53 closer to the optical detectors 35 and 37. In addition, the phase detection linear scale 31 and the PN code series absolute linear scale 33 can have a relatively large allowable region with respect to the mounting posture (rolling, pitching, yawing).

Next, a second embodiment of the present invention will be described with reference to FIG.
The same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
In the case of the second embodiment, as shown in FIG. 5, the light shielding plates 61 and 63 are formed by bending one side of the thin plate and having an L shape, and the side surface of the phase detection linear scale optical detector 35 and the PN. The code series absolute linear scale optical detector 37 is installed in a state of being affixed to each side surface.
Since the other configuration is the same as that of the first embodiment, description thereof is omitted.

The reason why the L-shaped light-shielding plates 61 and 63 are attached to the phase detection linear scale optical detector 35 and the PN code series absolute linear scale optical detector 37 is as follows. That is, a light-shielding plate is installed with high positional accuracy between the phase detection linear scale optical detector 35 and one LED light source 39, and between the PN code series absolute linear scale optical detector 37 and the other LED light source 39. In order to do so, it is considered that some mechanical positioning protrusions are indispensable. However, if such positioning protrusions are to be provided, an installation space for the positioning protrusions is required and costs are increased. .

Therefore, in the case of the present embodiment, L-shaped light shielding plates 61 and 63 are attached to the side surfaces of the phase detection linear scale optical detector 35 and the PN code series absolute linear scale optical detector 37. It is. As a result, high-precision positioning is possible without providing additional positioning protrusions. Further, since it is L-shaped, there is an advantage that it is easy to install the light shielding plates 61 and 63 at right angles to the head mounting portion 23.

Next, a third embodiment of the present invention will be described with reference to FIG.
The same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
In the case of the third embodiment, as shown in FIG. 6 (particularly, FIG. 6 (d)), a light shielding plate having a spring property by bending both sides of the thin plate and making the mouth narrower than the U-shaped The light shielding plates 71 and 73 are fitted and fixed to the phase detection linear scale optical detector 35 and the PN code series absolute linear scale optical detector 37, respectively.
Since the other configuration is the same as that of the first embodiment, description thereof is omitted.

In the case of the second embodiment, it is necessary to hold the light shielding plates 61 and 63 until the adhesive is cured. On the other hand, in the case of the present embodiment, since the light shielding plates 71 and 73 themselves have spring properties, the light shielding plates 71 and 73 are simply connected to the phase detection linear scale optical detector 35 and the PN code. It can be fixed simply by being fitted to the optical detector 37 for a series absolute linear scale. Further, even when the adhesive is used for bonding and fixing, the spring state is fitted to the phase detection linear scale optical detector 35 and the PN code series absolute linear scale optical detector 37. Has the advantage that it is not necessary to wait for the adhesive to cure.

Next, a fourth embodiment of the present invention will be described with reference to FIGS.
The same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
In the case of the fourth embodiment, a U-shaped light-shielding plate 81 having a spring property as shown in FIG. 8 is crowned and fixed from above the single optical detector 91. ing. In addition, LED light sources 93, 95, 97, and 99 are installed so as to sandwich the optical detector 91. Then, as shown in FIG. 7, the light is shielded on both sides of the optical detector 91 simultaneously by a single light shielding plate 81.

Details will be described below. As shown in FIG. 8 (particularly, FIGS. 8C and 8D), the light shielding plate 81 has a U-shaped narrow cross section on the opening side. The light shielding plate 81 is elastically held by the optical detector 91 with its own spring property. In addition, a child that increases the holding reliability by using an adhesive can also be considered. Further, as shown in FIG. 8A, the light shielding plate 81 is formed with a large opening 81a so that light can enter through the opening 81a. Further, the side surfaces 81b and 81c on both sides are portions that exhibit a light shielding function.
Incidentally, the light shielding plate 81 shown in FIG. 8 is manufactured by punching a stainless steel thin plate (SUS304) having a thickness of 0.1 mm and bending it, and the surface treatment is matte black chrome plating.
However, this is only an example, and the material and surface treatment are not limited to this. For example, the material may be a steel plate, phosphor bronze plate, or resin plate, and the surface treatment may be black nickel plating or black matte coating. good.
Since the other configuration is the same as that of the first embodiment, description thereof is omitted.

In the case of the fourth embodiment, light incident from both the left and right sides of the light shielding plate 81 can be shielded by the side surfaces 81b and 81c. Therefore, as shown in FIG. Optical signals from both sides can be switched and detected, and the number of expensive photodetectors used can be halved. For example, when reading the signal of the PN code series absolute linear scale 33, the signal is read by turning on only the LED light source 97 (or LED light source 99). Further, when the signal of the phase detection linear scale 31 is read, it can be read by turning on only the LED light source 93 (or the LED light source 95).

The present invention is not limited to the first to fourth embodiments.
For example, in the case of the first to fourth embodiments, the detection continuous signal number m is mainly 15 here, but the optimum value of m varies depending on the resolution and stroke required for the absolute linear encoder. Come. For example, m = 16-18 may be suitable for longer strokes.
In the case of the first to fourth embodiments, since the cost is low, an example using a CMOS linear array has been described. However, for example, even if a CCD linear array is used, the cost is high. However, the same effect can be expected.
In the present embodiment, an example in which the present invention is applied to an absolute linear encoder has been described.

The present invention relates to an encoder and an actuator using the encoder, and in particular, is configured to obtain a larger optical signal contrast by improving the optical system, thereby stabilizing and reliability of signal processing in subsequent processes. For example, it is suitable for a precision positioning system.

DESCRIPTION OF SYMBOLS 1 Housing 3 Slider 5 Ball screw 7 Drive motor 9 Guide 11 Guide 21 Linear scale part 23 Detection head part 25 Controller part 31 Phase detection linear scale 33 Absolute linear scale 35 Phase detection linear scale optical detector 37 Absolute linear scale optical Detector 41 Phase calculator 43 Absolute position data calculator 45 Absolute position data composer 47 Transceiver 49 Transceiver 51 Controller

Claims (7)

An encoder characterized in that a light shielding plate is provided between the optical detector and the light source, and the light shielding plate is disposed at a position close to the optical detector. The encoder according to claim 1, wherein
An encoder, wherein the light shielding plate is in contact with the optical detector. The encoder according to claim 2,
The encoder, wherein the light shielding plate has a spring property and is attached to the optical detector. The encoder according to claim 3, wherein
The encoder characterized in that the light shielding plate shields both sides of the optical detector. The encoder according to claim 4,
An encoder characterized in that one optical detector can read two kinds of scales. The encoder according to claim 5, wherein
An encoder characterized in that the light shielding plate is crowned and fixed to one optical detector. An actuator using the encoder according to any one of claims 1 to 6.

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