Encoder device

Abstract

A slit 130 of a rotary disk 120 comprises: annular first slits 130a having an N1 count per rotation, and annular second slits 130b having an N2 count per rotation at different radial positions on a concentric circle. A single encoder detection unit 140 comprises a first light receiving part 142a that receives light transmitted through the first slit 130a, and a second light receiving part 142b that receives light transmitted through the second slit 130b. An encoder processing unit 150 converts a light reception signal of the first light receiving part 142a into a first electric angle signal θe1 and then calculates first mechanical angle data P1, converts a light reception signal of the second light receiving part 142b into a second electric angle signal θe2, and then calculates second mechanical angle data P2, and subtracts a first absolute value accuracy error ∆1 included in the first mechanical angle data P1 by using optical arrangement information to calculate a rotation angle θ.

Description

Encoder Device

[0001] The present invention relates to an encoder device, and more particularly to an encoder device that takes into consideration errors when detecting a rotation angle.

[0002] There is an optical encoder device that includes a rotating disk with slits, an encoder detector with a light-receiving and light-emitting element, and an encoder processor that calculates the rotation angle of the rotating disk from the detection result of the encoder detector. In this encoder device, it is known that if the rotation center of the rotating disk and the center of the slit pattern are not precisely aligned, an error of one period per rotation (hereinafter referred to as absolute value accuracy error) will occur.

[0003] In order to eliminate the above-mentioned absolute value accuracy error, Patent Document 1 proposes a method in which encoder detection units are placed at two positions facing each other across the center of rotation of the rotating disk, thereby generating two sets of angle data that are 180 degrees out of phase with each other, and then averaging these two sets of angle data.

[0004] Japanese Unexamined Patent Publication No. 60-146113

[0005] The technique of Patent Document 1 generates two pieces of angle data that are 180° out of phase with each other, so it is necessary to accurately position the two encoder detectors at positions that face each other across the center of rotation of the rotating disk.

[0006] Providing encoder detection units in two locations in this way has caused problems such as an increase in the size of the encoder device, increased costs due to an increased number of parts, and poor installation workability due to the need to adjust the two encoder detection units.

[0007] Therefore, there is a need for an encoder device that can be easily installed without increasing the size and cost of the device and requiring no complicated adjustments when optically detecting the rotation of the slits in a rotating disk and calculating the rotation angle, and that can accurately eliminate the absolute value accuracy error of one period per rotation contained in the angle data.

[0008] The present invention aims to provide a small, easy-to-install encoder device that eliminates absolute value accuracy errors contained in the detected angle when the rotation of a slit in a rotating disk is optically detected to calculate the rotation angle.

[0009] The encoder device according to the present invention detects the rotation of a rotating disk provided with slits using a single encoder detection unit, and calculates the rotation angle θ of the rotating disk using an encoder processing unit, the slits being concentric and comprising first slits arranged in an annular pattern with N1 counts per revolution at different radial positions, and second slits arranged in an annular pattern with N2 counts per revolution different from the N1 count, the single encoder detection unit comprising a light emitting unit and a light receiving unit, the light receiving unit including a first light receiving unit that receives transmitted light emitted from the light emitting unit and transmitted through the first slits, and a second light receiving unit that receives transmitted light emitted from the light emitting unit and transmitted through the second slits. and a second light receiving unit that receives transmitted light emitted from the first light receiving unit, and the encoder processing unit converts the first light receiving signal obtained by the first light receiving unit into a first electrical angle signal θe1, converts the second light receiving signal obtained by the second light receiving unit into a second electrical angle signal θe2, calculates first mechanical angle data P1 from the first electrical angle signal θe1, calculates second mechanical angle data P2 from the second electrical angle signal θe2, and calculates the rotation angle θ by subtracting a first absolute value accuracy error Δ1 included in the first mechanical angle data P1 using the first mechanical angle data P1, the second mechanical angle data P2, a first optical radius r1 from a rotation center C1 of the rotating disk to the first light receiving unit, and a second optical radius r2 from the rotation center C1 to the second light receiving unit.

[0010] In the encoder device according to the present invention, the encoder processing unit includes an electrical angle data conversion unit that converts the first light receiving signal into a first electrical angle signal θe1 and converts the second light receiving signal into a second electrical angle signal θe2; a mechanical angle data calculation unit that calculates first mechanical angle data P1 from the first electrical angle signal θe1 and second mechanical angle data P2 from the second electrical angle signal θe2; an error calculation unit that calculates the first absolute value accuracy error Δ1 as Δ1 = (r2 / (r2 - r1)) · (P1 - P2) using the first absolute value accuracy error Δ1, the second absolute value accuracy error Δ2 included in the second mechanical angle data P2, the first optical radius r1, and the second optical radius r2; and a correction unit that subtracts the first absolute value accuracy error Δ1 from the first mechanical angle data P1 to calculate the rotation angle θ.

[0011] In the encoder device according to the present invention, when first slits of N1 count are provided on the outer periphery of the rotary disk and second slits of N2 count are provided on the outer periphery of the rotary disk, it is determined that N1>N2.

[0012] According to this invention, when the rotation of the slits in a rotating disk is optically detected to calculate the rotation angle, it is possible to provide an encoder device that is small and easy to install, eliminating the absolute value accuracy error contained in the detected angle.

[0013] Fig. 1 is a configuration diagram showing a circuit configuration of an encoder device according to a first embodiment of the present invention. Fig. 2 is a schematic diagram showing the configuration of a main part of an encoder device according to a first embodiment of the present invention. Fig. 3 is a schematic diagram showing a detailed configuration of a light receiving part according to a first embodiment of the present invention. Fig. 4 is an explanatory diagram showing an optical radius from the center of rotation of a rotating disk to a light receiving part according to a first embodiment of the present invention. Fig. 5 is a schematic diagram showing the configuration of a main part of a conventional encoder device.

[0014] Hereinafter, embodiments of an encoder device of the present invention will be described with reference to the drawings. In each drawing, the same parts are given the same reference numerals. Embodiment 1. First, the basic configuration of an encoder device 100 according to embodiment 1 of the present invention will be described with reference to Figs. 1 and 2. Fig. 1 is a configuration diagram showing the circuit configuration of the encoder device 100 according to embodiment 1 of the present invention. Fig. 2 is a schematic diagram showing the configuration of the main parts of the encoder device 100 according to embodiment 1 of the present invention.

[0015] 1, the encoder device 100 calculates the rotation angle of the rotating body 1, and mainly includes a rotating shaft 110, a rotating disk 120, an encoder detection unit 140, and an encoder processing unit 150. This encoder device 100 is characterized in that, when calculating the rotation angle of the rotating body 1, it corrects absolute value accuracy errors included in the angle data.

[0016] The rotating disk 120 has slits 130 formed in a circular ring shape as a whole, with each light transmitting portion being radial. The rotating disk 120 is connected to the rotating body 1 by a rotating shaft 110. Therefore, the rotating disk 120 with the slits 130 formed therein rotates at the same rotational speed as the rotating body 1.

[0017] The slit 130 is a concentric circle having a first slit 130a in which N1 counts of transparent portions are arranged in a circular ring shape at different radial positions, and a second slit 130b in which N2 counts of transparent portions different from the N1 count are arranged in a circular ring shape per revolution.

[0018] The rotating disk 120 has the first slits 130a on the outer periphery and the second slits 130b on the inner periphery. The spacing between adjacent slits tends to increase toward the outer periphery of the rotating disk 120, while the spacing between adjacent slits tends to decrease toward the inner periphery of the rotating disk 120. Therefore, it is preferable to set the relationship N1 > N2 between the first slits 130a on the outer periphery (N1 count) and the second slits 130b on the inner periphery (N2 count). By reducing the number of the second slits 130b on the inner periphery (N2 count) compared to the first slits 130a on the outer periphery (N1 count), deterioration in the readability of the second slits 130b on the inner periphery can be prevented. Furthermore, by increasing the number of slits in the first slits 130a on the outer periphery (N1 count) compared to the second slits 130b, highly accurate rotation angle calculation is possible using the first slits 130a on the outer periphery, without being affected by the readability of the second slits 130b on the inner periphery.

[0019] The encoder detection unit 140 has a light-emitting unit 141 and a light-receiving unit 142 including a first light-receiving unit 142a and a second light-receiving unit 142b, which are arranged to sandwich the first slit 130a and the second slit 130b of the rotating disk 120. Here, a single encoder detection unit 140 is provided for the rotating disk 120. Therefore, the single encoder detection unit 140 is a transmission-type sensor in which the light-emitting unit 141 irradiates the first slit 130a and the second slit 130b of the rotating disk 120 with light, and the first light-receiving unit 142a and the second light-receiving unit 142b receive the transmitted light that has passed through the transmission units of the first slit 130a and the second slit 130b, respectively, and optically detects the rotation of the rotating disk 120. Note that if a reflective pattern is formed on the rotating disk 120 instead of the slit 130, a reflective sensor can be used for the encoder detection unit 140. As described above, since the encoder device 100 has the first slit 130a and the second slit 130b with two different count numbers and the first light receiving portion 142a and the second light receiving portion 142b, the encoder device 100 calculates the rotation angle using the Nonius method.

[0020] FIG. 3 shows a detailed configuration of the light receiving unit 142 in a single encoder detection unit 140. FIG. 3 is a schematic diagram showing a detailed configuration of the light receiving unit 142 in embodiment 1 of the present invention. In the encoder detection unit 140, the light receiving unit 142 has a first light receiving unit 142a and a second light receiving unit 142b arranged at the same position in the circumferential direction of the rotating disk 120 but at different positions in the radial direction of the rotating disk 120. The first light receiving unit 142a receives transmitted light emitted from the light emitting unit 141 and transmitted through the first slit 130a. The second light receiving unit 142b receives transmitted light emitted from the light emitting unit 141 and transmitted through the second slit 130b.

[0021] The first light receiving unit 142a and the second light receiving unit 142b each comprise a light receiving element set consisting of a set of four light receiving elements. That is, the light receiving unit 142 has a plurality of light receiving element sets necessary for generating angle data arranged in a predetermined arrangement. The four light receiving elements that make up the light receiving element set are assigned a+, a-, b+, and b-. By adding and subtracting the signals from the a+, a-, b+, and b- light receiving elements, two-phase light receiving signals with different phases can be obtained for calculating angle data.

[0022] The encoder processing unit 150 mainly includes an electrical angle data conversion unit 151, a mechanical angle data calculation unit 152, an error calculation unit 153, a correction unit 154, and an output unit 155. The electrical angle data conversion unit 151 includes a first electrical angle data conversion unit 151a and a second electrical angle data conversion unit 151b. The mechanical angle data calculation unit 152 includes a first mechanical angle data calculation unit 152a and a second mechanical angle data calculation unit 152b.

[0023] The first electrical angle data converter 151a processes a two-phase first light-receiving signal obtained by the first light-receiving unit 142a and converts it into a first electrical angle signal θe1. The first electrical angle signal θe1 is an electrical angle signal corresponding to the number of detected slits. The first light-receiving unit 142a reads the first light-receiving signal, which is obtained by reading the first light-receiving unit 142a's transmitted light that has passed through the first slits 130a for N1 counts per revolution. The second electrical angle data converter 151b processes a two-phase second light-receiving signal obtained by the second light-receiving unit 142b and converts it into a second electrical angle signal θe2. The second electrical angle signal θe2 is an electrical angle signal corresponding to the number of detected slits. The second electrical angle data converter 151b processes a second light-receiving signal, which is obtained by reading the second light-receiving unit 142b's transmitted light that has passed through the second slits 130b for N2 counts per revolution.

[0024] The first mechanical angle data calculation unit 152a calculates first mechanical angle data P1 from the first electrical angle signal θe1. The first mechanical angle data P1 includes a first absolute value accuracy error Δ1 with one cycle per rotation. The second mechanical angle data calculation unit 152b calculates second mechanical angle data P2 from the second electrical angle signal θe2. The second mechanical angle data P2 includes a second absolute value accuracy error Δ2 with one cycle per rotation.

[0025] The error calculation unit 153 calculates the first absolute value precision error Δ1 for one period per rotation contained in the first mechanical angle data P1 by referring to the first mechanical angle data P1, the second mechanical angle data P2, and the optical arrangement information described later.

[0026] The optical layout information will now be described with reference to Fig. 4. Fig. 4 is an explanatory diagram showing the optical radii from the rotation center C1 of the rotating disk 120 to the light receiving units in the first embodiment of the present invention. The optical layout information includes a first optical radius r1 from the rotation center C1 of the rotating disk 120 to the center of the first light receiving unit 142a, and a second optical radius r2 from the rotation center C1 to the center of the second light receiving unit 142b.

[0027] The correction unit 154 subtracts the first absolute value accuracy error Δ1 from the first mechanical angle data P1 to correct the absolute accuracy of the angle data for one rotation, and calculates the rotation angle θ of the rotating disk 120. The output unit 155 outputs the rotation angle θ of the rotating disk 120 to an external device. The output unit 155 may have a communication function that enables communication with the external device in order to output the rotation angle θ to the external device.

[0028] [Processing of Encoder Device 100] Next, a description will be given of the processing performed by the encoder device 100 to optically detect the rotation of the slit 130 of the rotating disk 120, correct the absolute value accuracy error, and calculate the rotation angle θ. Here, the terms, parameters, and data used in calculating the rotation angle θ are as follows:

[0029] In the encoder device 100, if the rotation center C1 of the rotating disk 120 and the pattern center C2 of the slit 130 do not coincide, the rotation of the slit 130 will be detected by the encoder detection unit 140 as being different from a perfect circle in one rotation period. For this reason, the angle data calculated by the encoder processing unit 150 contains an error of one period per rotation with respect to the true rotation angle θ. This error of one period per rotation is called an absolute value accuracy error.

[0030] The parameters in the first embodiment are defined as follows: N1: the number of counts (slit number) per circumference arranged in an annular shape in the first slits 130a, N2: the number of counts (slit number) per circumference arranged in an annular shape in the second slits 130b that is different from N1, θ (rad): the rotation angle of the rotary disk 120 in an error-free state, θe1: a first electrical angle signal obtained by converting a first light-receiving signal from the first slits 130a in the first light-receiving unit 142a using the first electrical angle data converter 151a, θe2: a second electrical angle signal obtained by converting a second light-receiving signal from the second slits 130b in the second light-receiving unit 142b using the second electrical angle data converter 151b, P1 (rad): first mechanical angle data calculated by the first mechanical angle data calculator 152a based on the first electrical angle signal θe1. P2 (rad): second mechanical angle data calculated by the second mechanical angle data calculation unit 152b based on the second electrical angle signal θe2; Δ1 (rad): first absolute value precision error included in the first mechanical angle data P1; and Δ2 (rad): second absolute value precision error included in the second mechanical angle data P2.

[0031] A state in which the rotation center of the rotating disk 120 and the pattern center of the slit 130 do not coincide will be described with reference to FIG. 4 . FIG. 4 is an explanatory diagram showing the optical radius from the rotation center C1 of the rotating disk 120 to the light receiving unit 142 as optical layout information in the first embodiment of the present invention. The optical layout information in the first embodiment is defined as follows: C1: rotation center of the rotating disk 120; C2: pattern center of the slit 130; r1: optical radius of the first light receiving unit 142a determined by the distance from the rotation center C1 to the center of the first light receiving unit 142a; r2: optical radius of the second light receiving unit 142b determined by the distance from the rotation center C1 to the center of the second light receiving unit 142b; and δ: deviation between the rotation center C1 of the rotating disk 120 and the pattern center C2 of the slit 130. Note that the optical layout information may also include information such as the distance and angle between multiple sets of light receiving elements.

[0032] The error calculation unit 153 calculates the first absolute value precision error Δ1 included in the first mechanical angle data P1 as follows. Here, the first absolute value precision error Δ1 can be expressed as Δ1 = (δ / r1) · sin θ. Furthermore, the absolute value precision error Δ2 can be expressed as Δ2 = (δ / r2) · sin θ. Rearranging the above two equations for the first absolute value precision errors Δ1 and Δ2 and excluding sin θ, we obtain Δ1 = (r2 / (r2 - r1)) · (Δ1 - Δ2).

[0033] Then, by using P1 = θ + Δ1 and P2 = θ + Δ2 and eliminating Δ2 from the above equation for Δ1, the following expression can be obtained: Δ1 = (r2 / (r2 - r1)) · (P1 - P2). That is, the error calculation unit 153 can calculate the first absolute value precision error Δ1 using the first optical radius r1 and second optical radius r2, which are optical layout information, the first mechanical angle data P1, and the second mechanical angle data P2. Here, (r2 / (r2 - r1)) in the equation for calculating Δ1 is a constant determined for each device. Therefore, the error calculation unit 153 can quickly calculate the first absolute value precision error Δ1 using the difference between the first mechanical angle data P1 and the second mechanical angle data P2 and the constant.

[0034] Correction unit 154 calculates rotation angle θ as follows: θ=P1−Δ1 using first absolute value precision error Δ1 calculated by error calculation unit 153. Here, correction unit 154 can quickly calculate rotation angle θ by simply subtracting Δ1 calculated by error calculation unit 153 from first mechanical angle data P1 calculated by first mechanical angle data calculation unit 152a.

[0035] That is, the encoder processing unit 150 receives a count number (number of slits) N1 per revolution arranged in an annular shape in the first slit 130a, a count number (number of slits) N2 per revolution arranged in an annular shape in the second slit 130b that is different from N1, a first electrical angle signal θe1 obtained by converting a first light-receiving signal of the first slit 130a in the first light-receiving unit 142a by the first electrical angle data conversion unit 151a, and a second light-receiving signal of the second slit 130b in the second light-receiving unit 142b. Using the second electrical angle signal θe2 obtained by converting the first electrical angle signal θe1 by the second electrical angle data converter 151b, the first mechanical angle data P1 calculated by the first mechanical angle data calculator 152a based on the first electrical angle signal θe1, the second mechanical angle data P2 calculated by the second mechanical angle data calculator 152b based on the second electrical angle signal θe2, the first optical radius r1 of the first light receiving unit 142a, and the second optical radius r2 of the second light receiving unit 142b, the rotation angle θ of the rotating disk 120 without including any error can be calculated as follows: θ=P1-Δ1=P1-(r2 / (r2-r1))(P1-P2) Here, because (r2 / (r2-r1)) is a constant, it is possible to calculate the rotation angle θ quickly and accurately from the first mechanical angle data P1 and P2 and the constant.

[0036] It should be noted that the rotation angle θ can be calculated in the same way by swapping θe1, θe2, P1, P2, Δ1, and Δ2 in the above explanation and setting θ = P2 - Δ2. However, the spacing between adjacent slits tends to increase as one approaches the outer periphery of the rotary disk 120. For this reason, by setting N1 > N2 and setting θ = P1 - Δ1, θ can be calculated with higher accuracy than when θ = P2 - Δ2.

[0037] [Configuration and Operation of Comparative Example (Encoder Device 100A)] Here, the configuration of a conventional encoder device 100A will be described as a comparative example to the encoder device 100 of embodiment 1. FIG. 5 is a schematic diagram showing the configuration of the main parts of the conventional encoder device 100A. In FIG. 5, a rotating disk 120 provided with a single slit 131 is connected to a rotating body 1, which is the detection target, via a rotation shaft 110 and rotates at the same speed as the rotating body 1. Two encoder detection units 140A and 140B each include a light-emitting unit and a light-receiving unit, and are located opposite each other across the center of rotation of the rotating disk 120. They detect the passage and blocking of light by the single slit 131 in the rotating rotating disk 120. That is, the multiple light-emitting units and multiple light-receiving units detect the passage and blocking of light by the single slit 131 in the rotating rotating disk 120.

[0038] When the rotation center of the rotating disk 120 does not coincide with the pattern center of the single slit 131, the absolute value precision error contained in the first mechanical angle data calculated from the light receiving signal of the encoder detection unit 140A and the second mechanical angle data calculated from the light receiving signal of the encoder detection unit 140B theoretically has a phase difference of 180°. Therefore, by averaging the first mechanical angle data and the second mechanical angle data, the absolute value precision error for one period per rotation is canceled out and eliminated.

[0039] As described above, the conventional encoder device 100A requires the encoder detectors 140A and 140B to be accurately positioned opposite each other across the center of rotation of the rotating disk 120, which increases the size of the encoder device 100. Furthermore, the need to provide the encoder detectors 140A and 140B increases the number of components, resulting in higher costs. Furthermore, to offset the absolute value accuracy error by averaging, the positions of the two encoder detectors 140A and 140B must be finely adjusted so that the phase difference between the absolute value accuracy error included in the first mechanical angle data and the absolute value accuracy error included in the second mechanical angle data is exactly 180°, which reduces installation workability.

[0040] [Comparison between encoder device 100 and encoder device 100A] As described above, the encoder device 100 of embodiment 1 can use a single encoder detection unit 140 compared to the conventional encoder device 100A, which does not result in an increase in the size and cost of the device, can be easily installed without requiring complicated adjustments, and can eliminate absolute value accuracy errors contained in the detected angles.

[0041] Effects of the Embodiment The encoder device 100 according to the first embodiment is an encoder device 100 that uses a single encoder detection unit 140 to detect the rotation of a rotating disk 120 having slits 130, and calculates the rotation angle θ of the rotating disk 120 using an encoder processing unit 150. The slits 130 are concentric and include first slits 130a arranged in an annular pattern with N1 counts per revolution, and second slits 130b arranged in an annular pattern with N2 counts per revolution, which is different from the N1 count, at different radial positions. The single encoder detection unit 140 includes a light-emitting unit 141 and a light-receiving unit 142. The light-receiving unit 142 includes a first light-receiving unit 142a that receives transmitted light emitted from the light-emitting unit 141 and transmitted through the first slits 130a, and a second light-receiving unit 142b that receives transmitted light emitted from the light-emitting unit 141 and transmitted through the second slits 130b. The encoder processing unit 150 converts the first light receiving signal obtained by the first light receiving unit 142a into a first electrical angle signal θe1, converts the second light receiving signal obtained by the second light receiving unit 142b into a second electrical angle signal θe2, calculates first mechanical angle data P1 from the first electrical angle signal θe1, calculates second mechanical angle data P2 from the second electrical angle signal θe2, and calculates the rotation angle θ by subtracting the first absolute value accuracy error Δ1 included in the first mechanical angle data P1 using the first mechanical angle data P1, the second mechanical angle data P2, a first optical radius r1 from the slit center C2 of the rotating disk 120 to the first light receiving unit 142a, and a second optical radius r2 from the slit center C2 to the second light receiving unit 142b.

[0042] Here, the single encoder detection unit 140 optically detects the rotation of the rotating disk 120 using the first slits 130a and the second slits 130b, which are concentric circles with different counts at different radial positions, and detects the rotation angle θ that does not include absolute value precision errors, thereby eliminating absolute value precision errors included in the detected angle and providing a compact, easy-to-install encoder device 100. Furthermore, because the encoder device 100 optically detects the rotation of the slits 130 of the rotating disk 120 using the single encoder detection unit 140 and detects the rotation angle θ that does not include absolute value precision errors, it does not require the cumbersome adjustment required in conventional encoder devices that use two encoder detection units, and can be easily installed.

[0043] In the encoder device 100 of the first embodiment, the encoder processing unit 150 includes an electrical angle data conversion unit 151 that converts the first light-receiving signal into a first electrical angle signal θe1 and converts the second light-receiving signal into a second electrical angle signal θe2, a mechanical angle data calculation unit 152 that calculates first mechanical angle data P1 from the first electrical angle signal θe1 and second mechanical angle data P2 from the second electrical angle signal θe2, an error calculation unit 153 that calculates a first absolute value accuracy error Δ1, and a correction unit 154 that subtracts the first absolute value accuracy error Δ1 from the first mechanical angle data P1 to calculate the rotation angle θ. Here, the error calculation unit 153 calculates the first absolute value accuracy error Δ1 as Δ1 = (r2 / (r2 - r1)) · (P1 - P2) using the first absolute value accuracy error Δ1, the second absolute value accuracy error Δ2 included in the second mechanical angle data P2, the first optical radius r1, and the second optical radius r2. The error calculation unit 153 can quickly calculate the first absolute value precision error Δ1 using the difference between the first mechanical angle data P1 and the second mechanical angle data P2 and the constant (r2 / (r2-r1)). The correction unit 154 simply subtracts the first absolute value precision error Δ1 calculated by the error calculation unit 153 from the first mechanical angle data P1, and can therefore quickly and accurately calculate the rotation angle θ.

[0044] In the encoder device 100 of the first embodiment, when the first slits 130a with N1 counts are provided on the outer periphery of the rotating disk 120 and the second slits 130b with N2 counts are provided on the outer periphery of the rotating disk 120, it is determined that N1 > N2. As a result, by reducing the number of second slits 130b with N2 counts on the inner periphery compared to the first slits 130a with N1 count on the outer periphery, it is possible to prevent deterioration in the readability of the second slits 130b on the inner periphery. Furthermore, by increasing the number of first slits 130a with N1 counts on the outer periphery compared to the second slits 130b without being affected by the readability of the second slits 130b on the inner periphery, it is possible to calculate the rotation angle with high accuracy using the first slits 130a on the outer periphery.

[0045] [Other Embodiments] In the encoder detection unit 140, a specific example has been shown in which the first light receiving unit 142 a and the second light receiving unit 142 b are arranged at different positions in the radial direction of the rotating disk 120, but the arrangement is not limited to this and various other arrangements are possible. When the arrangement of the first light receiving unit 142 a and the second light receiving unit 142 b is changed, the first absolute value accuracy error Δ1 can be calculated by performing a calculation according to the new arrangement, and the rotation angle θ can be calculated with high accuracy.

[0046] In the encoder processing unit 150, a specific example in which data is output from the output unit 155 has been shown, but this can be replaced with a communication unit that communicates with an external device.

[0047] In the configuration of the encoder device 100 shown in FIG. 1, the error calculation unit 153 in the encoder processing unit 150 may be divided into a subtraction unit that calculates (P1-P2) and a multiplication unit that calculates (r2 / (r2-r1))*(P1-P2).

[0048] Furthermore, in the configuration of the encoder device 100 shown in FIG. 1, the error calculation unit 153 and the correction unit 154 in the encoder processing unit 150 may be integrated, and the rotation angle θ may be calculated as θ=P1-(r2 / (r2-r1))·(P1-P2) by the integrated error calculation correction unit.

[0049] 1 Rotating body, 100 Encoder device, 110 Rotating shaft, 120 Rotating disk, 130 Slit, 130a First slit, 130b Second slit, 131 Single slit, 140 Encoder detection unit, 141 Light emitting unit, 142 Light receiving unit, 142a First light receiving unit, 142b Second light receiving unit, 150 Encoder processing unit, 151 Electrical angle data conversion unit, 151a First electrical angle data conversion unit, 151b Second electrical angle data conversion unit, 152 Mechanical angle data calculation unit, 153 Error calculation unit, 154 Correction unit, 155 Output unit, C1 Rotation center, C2 Pattern center, P1 First mechanical angle data, P2 Second mechanical angle data, r1 First optical radius, r2 Second optical radius, δ Distance (deviation) between rotation center and pattern center, Δ1 First absolute value accuracy error, Δ2 Second absolute value accuracy error, θ Rotation angle.

Claims

1. An encoder device that uses a single encoder detection unit to detect the rotation of a rotating disk having slits, and calculates the rotation angle θ of the rotating disk using an encoder processing unit, wherein the slits are concentric and comprise first slits arranged in an annular pattern with N1 counts per revolution at different radial positions, and second slits arranged in an annular pattern with N2 counts per revolution different from the N1 count, wherein the single encoder detection unit comprises a light emitting unit and a light receiving unit, wherein the light receiving unit comprises a first light receiving unit that receives transmitted light emitted from the light emitting unit and transmitted through the first slits, and a second light receiving unit that receives transmitted light emitted from the light emitting unit and transmitted through the second slits, wherein the encoder processing unit converts a first received light signal obtained by the first light receiving unit into a first electrical angle signal θe1, converts a second received light signal obtained by the second light receiving unit into a second electrical angle signal θe2, and calculates first mechanical angle data P1 from the first electrical angle signal θe1, an encoder device that calculates second mechanical angle data P2 from the second electrical angle signal θe2; and subtracts a first absolute value accuracy error Δ1 included in the first mechanical angle data P1 using the first mechanical angle data P1, the second mechanical angle data P2, a first optical radius r1 from a rotation center C1 of the rotating disk to the first light receiving unit, and a second optical radius r2 from the rotation center C1 to the second light receiving unit to calculate the rotation angle θ.

2. The encoder device according to claim 1, wherein the encoder processing unit comprises: an electrical angle data conversion unit that converts the first light reception signal into the first electrical angle signal θe1 and converts the second light reception signal into the second electrical angle signal θe2; a mechanical angle data calculation unit (152) that calculates the first mechanical angle data P1 from the first electrical angle signal θe1 and the second mechanical angle data P2 from the second electrical angle signal θe2; an error calculation unit (153) that calculates the first absolute value accuracy error Δ1 as Δ1 = (r2 / (r2 - r1)) (P1 - P2) using the first absolute value accuracy error Δ1, the second absolute value accuracy error Δ2 included in the second mechanical angle data P2, the first optical radius r1, and the second optical radius r2; and a correction unit that subtracts the first absolute value accuracy error Δ1 from the first mechanical angle data P1 to calculate the rotation angle θ.

3. An encoder device according to claim 1 or 2, wherein when the first slits of the N1 count are provided on the outer periphery of the rotating disk and the second slits of the N2 count are provided on the outer periphery of the rotating disk, N1>N2 is set.

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