JP5594047B2 - Absolute encoder - Google Patents

Description

  The present invention relates to an absolute encoder that detects an absolute position or angle.

  The encoder is used in various mechanical devices to detect the position and angle of the movable element. In general, there are encoders that detect relative positions or angles and encoders that detect absolute positions or angles. An encoder that detects an absolute position or angle is called an absolute encoder (Patent Document 1). In recent years, absolute encoders are required to be both compact and have high resolution in order to cope with miniaturization and high accuracy of various machines to be applied.

  In another absolute encoder (Patent Document 2), an optically detectable optical pattern consisting of a curve approximating a circle whose radius varies according to the rotation angle of the rotating disk is formed on the rotating disk. This is detected by the first and second optical sensors arranged at an angle of 90 degrees toward the rotation direction of the rotating disk, thereby generating signals that are 90 degrees out of phase. Based on the two signals, the resolver / digital converter generates and outputs an absolute signal group having a required number of bits.

  In a magnetic absolute encoder (Patent Document 3), an annular magnetic encoder that is concentrically attached to an inner ring that is a rotating side race ring and an outer ring that is a stationary side race ring are attached to detect the magnetism of the magnetic encoder. It is known to include a magnetic sensor and detect the absolute angle of the rotating raceway. In the magnetic encoder, for example, the thickness of the magnet continuously changes over one round. As a result, the strength of the magnetic field detected by the magnetic sensor changes continuously over one turn of the magnetic encoder.

Japanese Patent Laid-Open No. 11-344359 Japanese Patent Laid-Open No. 9-96544 JP 2006-322474 A

  However, in order to increase the resolution of the absolute encoder, it is necessary to increase the number of tracks. Increasing the number of tracks increases the size of the rotating disk. Absolute encoders cannot be miniaturized and the cost increases if the resolution is increased. Moreover, since the absolute encoders of Patent Document 2 and Patent Document 3 use only one sensor corresponding to the signal pattern, it is necessary to consider individual differences between the sensors.

  The present invention has been made in view of the above, and an object of the present invention is to provide an absolute encoder that has a high resolution without increasing the number of tracks and can reduce the influence of individual differences in sensors.

  An absolute encoder according to the present invention includes a plurality of sensors capable of reading a signal pattern, an encoder unit including a sensor assembly arranged so that positions of the plurality of sensors are different and a base including the signal pattern, An arithmetic unit that calculates an absolute position between the sensor assembly and the base body from an output of the sensor assembly, and detecting the plurality of sensors when the sensor assembly and the base body move relative to each other. The signal pattern moves in a range.

  In the absolute encoder according to the present invention, the signal pattern moves within the detection range of the plurality of sensors, so that it is not necessary to increase the number of tracks and the resolution of the absolute encoder can be increased. As a result, the base of the absolute encoder becomes smaller, and the absolute encoder can be made smaller. Moreover, since it has a some sensor, the influence of the individual difference of one sensor can be reduced.

  As a desirable mode of the present invention, it is preferable that the signal pattern can be detected by both of a pair of adjacent sensors among the plurality of sensors. As a result, even if the signal pattern moves through the detection ranges of the plurality of sensors, the detection range cannot be blinded.

  As a desirable mode of the present invention, the sensor assembly includes a first voltage detection terminal and a second voltage detection terminal connected to the first voltage detection terminal via a predetermined resistor, and a power supply voltage. Is applied to the plurality of sensors, and each of the plurality of sensors can output between the first voltage detection terminal and the second voltage detection terminal, and adjacent sensors are connected to each other from the respective sensors. And the arithmetic unit is connected to the first voltage output of the first voltage detection terminal and the second voltage detection terminal of the second voltage detection terminal. Preferably, a voltage value obtained by dividing a subtraction value obtained by subtracting the voltage output by an addition value obtained by adding the first voltage output and the second voltage output is output as a sensor output.

  In the absolute encoder according to the present invention, the center position of the current distribution of the plurality of sensors is ((first voltage output V1−second voltage output V2) / (first voltage output V1 + second voltage output V2)). It is proportional to The center position of the current distribution of the plurality of sensors is output by averaging the variations of the plurality of sensors as compared with the case where detection is performed by a single sensor, so that the influence of individual differences among the sensors can be reduced. In addition, since (first voltage output V1−second voltage output V2) is confirmed, a stable sensor output is output regardless of disturbance of light quantity, magnetic field, and environmental conditions. As a result, the absolute encoder can reduce the possibility of causing an error.

  As a desirable mode of the present invention, the sensor assembly includes a first voltage detection terminal and a second voltage detection terminal connected to the first voltage detection terminal via a predetermined resistor, and a power supply voltage. Is applied to the plurality of sensors, and each of the plurality of sensors can output between the first voltage detection terminal and the second voltage detection terminal, and adjacent sensors are connected to each other from the respective sensors. And the arithmetic unit is connected to the first voltage output of the first voltage detection terminal and the second voltage detection terminal of the second voltage detection terminal. A subtracted value obtained by subtracting the voltage output is output as a sensor output.

  In the absolute encoder according to the present invention, the center positions of the current distributions of the plurality of sensors are proportional to ((first voltage output V1−second voltage output V2). Compared with the case where detection is performed by a single sensor, the variation of a plurality of sensors is averaged and output, so that it is possible to reduce the influence of individual differences between the sensors. Since the voltage output V2) is confirmed, a stable sensor output is output regardless of the disturbance of the light quantity, magnetic field, and environmental conditions, and as a result, the absolute encoder can reduce the possibility of causing an error. Therefore, the configuration of the arithmetic device can be simplified.

  As a desirable mode of the present invention, in the absolute encoder, it is preferable that the plurality of sensors are light receiving elements, and the signal pattern is a pattern having a light reflectance different from that of the substrate. Since the absolute encoder of the present invention can be configured with a simple pattern, the manufacturing cost can be reduced.

  As a desirable aspect of the present invention, in the absolute encoder, the plurality of sensors are preferably magnetic sensors, and the signal pattern is a pattern that forms a magnetic field. Since the absolute encoder of the present invention can be configured with a simple pattern, the manufacturing cost can be reduced. Further, even if foreign matter is mixed between the sensor assembly and the signal pattern, the absolute encoder can operate.

  According to the absolute encoder of the present invention, it is possible to achieve high resolution without increasing the number of tracks, and to reduce the influence due to individual differences of sensors.

FIG. 1 is a configuration diagram of an absolute encoder according to this embodiment. FIG. 2 is a configuration diagram of the encoder unit according to the present embodiment. FIG. 3 is a cross-sectional view of the encoder unit shown in FIG. FIG. 4 is a partial configuration diagram illustrating another modification of the encoder unit. FIG. 5 is a schematic diagram for explaining the relationship between the sensor and the signal pattern according to the present embodiment. FIG. 6 is an explanatory diagram for explaining the sensor connection circuit according to the present embodiment. FIG. 7 is a configuration diagram of an arithmetic processing unit according to the present embodiment. FIG. 8 is an explanatory diagram for explaining the relationship between the sensor output and the rotation angle according to the present embodiment. FIG. 9 is a configuration diagram of an encoder unit according to the present embodiment. FIG. 10 is a schematic diagram for explaining the relationship between the sensor and the signal pattern according to the present embodiment. FIG. 11 is an explanatory diagram for explaining the sensor connection circuit according to the present embodiment.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the constituent elements described below can be appropriately combined.

(Embodiment 1)
FIG. 1 is a configuration diagram of an absolute encoder according to the first embodiment. FIG. 2 is a configuration diagram of the encoder unit according to the present embodiment. FIG. 3 is a cross-sectional view of the encoder unit shown in FIG. First, the outline of the absolute encoder according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 1, the absolute encoder 100 includes an encoder unit 1 and a calculation device 40. The arithmetic device 40 of the absolute encoder 100 is connected to a control unit 65 of a rotary machine such as a motor. The encoder unit 1 will be described later in detail with reference to FIGS. 2 and 3. The arithmetic device 40 includes a sensor signal processing circuit 41 and an arithmetic processing unit 42. The calculation processing unit 42 includes AD conversion units 51 and 52, angle calculation units 61 and 62, and an angle synthesis unit 63. The absolute encoder 100 according to this embodiment outputs absolute angle data, which is angle information, as the absolute position data D to the control unit 65. Note that the absolute encoder 100 may output the absolute position data D in coordinates or the like.

  As shown in FIGS. 2 and 3, the encoder unit 1 includes a rotor 30 as a base, a plurality of sensor assemblies (reading units) 10 and 20, and a shaft 38. The rotor 30 is a disk-shaped member. The rotor 30 is made of silicon, glass, polymer material or the like. The rotor 30 has a signal pattern 31 on a substrate surface 32 which is one plate surface. Further, the shaft 30 is attached to the rotor 30 so that the rotation center O of the plate surface coincides with the central axis of the shaft 38.

  The shaft 38 shown in FIGS. 2 and 3 is attached to the rotor 30 and is connected to a rotary machine such as a motor. When the shaft 38 is rotated by rotation from the motor, the rotor 30 rotates around the rotation center O in conjunction with the shaft 38.

  The signal pattern 31 is a curved belt-like pattern formed with a constant width in the radial direction of the rotor 30. The signal pattern 31 is made of a pattern having a light reflectance different from that of the substrate surface 32. In the present embodiment, for example, the signal pattern 31 is formed by depositing gold (Au) on the surface of the rotor 30. As another modified example, paper having the same shape as the disk of the rotor 30 is prepared, the base pattern is printed in black, the signal pattern 31 is printed in white, and the signal pattern 31 is formed by pasting on the substrate surface 32. .

From the position m which represents the position of the inner circumference of the signal patterns 31 shown in FIG. 2 for the distance X _P to the center of rotation O is described. In FIG. 2, straight lines passing through the rotation center and orthogonal to each other are lines L1 and L2. Points where the line L1 intersects the inner periphery of the signal pattern 31 are defined as a position m ₀ and a position m ₁₈₀ . The points where the line L2 intersects the inner periphery of the signal pattern 31 are defined as a position m ₉₀ and a position m ₂₇₀ . The signal pattern 31 has the shortest distance to the rolling center O in the position m ₀ within the inner periphery of the signal pattern 31. When the position m representing the position on the inner periphery of the signal pattern 31 is at the position m ₀ , the distance _XP is the distance X ₀ , and the distance X ₀ represents the shortest distance from the position m to the rotation center O. With reference to the position m representing the position on the inner periphery of the signal pattern 31 at the position m ₀ , the central angle θ _P is centered on the rotation center O and the central angle θ is 0 ° (position m ₀ ) to the central angle 180 ° ( distance _{X P} position m when position to _{m 180)} moves through the position _{m 90} changes as shown in equation 1. K in Equation 1 is a non-zero constant.

Distance X _P is a always different distances depending on the central angle θ _P. Thereby, the radial distance of the rotor 30 differs in the position m according to the central angle of the rotor 30 from 0 ° to 180 °. Next, with reference to the position m representing the position on the inner circumference of the signal pattern 31 at the position m ₀ , the center angle θ _P is centered on the rotation center O from the center angle 180 ° (position m ₁₈₀ ). 360 ° (0 °, position _{m 0)} distance _{X P} position m when moving through to the position m ₂₇₀ changes as shown in equation 2. K in Equation 2 is a non-zero constant.

The signal pattern 31 has a line symmetrical shape with respect to the line L1. The signal pattern 31 is asymmetric with respect to the line L2. Distance X _P is a always different distances depending on the central angle θ _P. Thereby, the position m differs in the radial position of the rotor 30 according to the central angle of 180 ° to 360 ° (0 °) of the rotor 30.

Signal pattern 31, if necessarily different distances X _P position m according to the rotation angle theta _P, not limited to the pattern of FIG. For example, as another modification, there is a signal pattern 33 shown in FIG. In FIG. 4, straight lines passing through the rotation center and orthogonal to each other are lines L1 and L2. Points where the line L1 intersects the inner periphery of the signal pattern 33 are defined as a position n ₀ and a position n ₁₈₀ . The points where the line L2 intersects the inner periphery of the signal pattern 31 are defined as a position n ₉₀ and a position n ₂₇₀ . The signal pattern 33 has the shortest distance to the rotation center O at the position n _{0 in} the inner periphery of the signal pattern 33. When the position n representing the position on the inner periphery of the signal pattern 33 is at the position n ₀ , the distance _XP is the distance X ₀ , and the distance X ₀ represents the shortest distance from the position n to the rotation center O. Position when the central angle θ _P moves from the central angle 0 ° to the central angle 360 ° around the rotation center O with reference to the position m representing the position on the inner periphery of the signal pattern 33 at the position n _0. distance X _P of n varies as shown in equation 3. K in Equation 3 is a non-zero constant.

Distance X _P is a always different distances depending on the central angle θ _P. When the central angle 360 ° is moved around the rotation center O, n ₀ and n ₃₆₀ are in positions that do not overlap on the line L1. Further, the signal pattern end portion 33a and the signal pattern end portion 33b are discontinuous. Thus, the position n of the rotor 30 varies in the radial direction according to the rotation angle 0 ° to 360 ° (0 °) of the rotor 30. Since the signal pattern 31 of the first embodiment has no discontinuous points at the end of the signal pattern as compared with the signal pattern 33 of the modification, the output of the sensor assembly can be continuously changed. Therefore, the signal pattern 31 of the first embodiment is easier to process the sensor output when the rotor 30 is continuously rotated than the signal pattern 33 of the modification.

  The sensor assemblies 10 and 20 are fixed to a stator independent of the shaft 38 and the rotor 30. When the rotor 30 rotates, the relative positions of the sensor assemblies 10 and 20 and the rotor 30 change. The sensor assemblies (reading units) 10 and 20 are sensor assemblies having the same structure arranged so that the phase of the relative position with respect to the rotor 30 is shifted. The phase shift of the sensor assemblies (reading units) 10 and 20 shown in FIG. 2 is 90 °. The phase shift of the sensor assemblies (reading units) 10 and 20 may be other than 180 °. Hereinafter, the sensor assembly 10 will be described as a representative.

  FIG. 5 is a schematic diagram for explaining the relationship between the sensor and the signal pattern according to the present embodiment. FIG. 6 is an explanatory diagram for explaining the sensor connection circuit according to the present embodiment. As shown in FIG. 5, the sensor assembly 10 includes optical sensors 11, 12, 13, 14, 15 and a sensor substrate 16. The optical sensors 11, 12, 13, 14, 15 are arranged on the sensor substrate 16 on the side facing the rotor 30 at every sensor interval p. As shown in FIG. 5, when the sensor assembly 10 faces the rotor 30, the sensor substrate 16 and the substrate surface 32 of the rotor 30 are parallel to each other, and the optical sensors 11, 12, 13, 14, 15 and the substrate surface 32 are aligned. The distance d is constant. The positions of the optical sensors 11, 12, 13, 14, and 15 are different with respect to the radial direction of the rotor 30. The sensor assemblies 10 and 20 are not limited to five as long as the number of optical sensors is plural. As the number of sensors increases, the resolution of the absolute encoder 100 improves.

  In the present embodiment, the optical sensors 11, 12, 13, 14, and 15 are reflection type photo interrupters that can read the signal pattern 31. The optical sensors 11, 12, 13, 14, 15 shown in FIG. 6 have light emitting elements 111, 121, 131, 141, 151 and light receiving elements 112, 122, 132, 142, 152, respectively. The light emitting elements 111, 121, 131, 141, 151 are the same light emitting diode (LED). The light receiving elements 112, 122, 132, 142, and 152 are the same phototransistor. The light emitting elements 111, 121, 131, 141, 151 emit light to the base surface 32, and the light receiving elements 112, 122, 132, 142, 152 receive the reflected light from the base surface 32. As compared with the substrate surface 32 and the signal pattern 31, the reflection intensity at which the light emitted to the substrate surface 32 is reflected is higher in the signal pattern 31. When the light receiving elements 112, 122, 132, 142, 152 receive the reflected light of the signal pattern 31, the amount of current increases. The light receiving elements 112, 122, 132, 142, and 152 can also use photodiodes.

  The optical sensors 11, 12, 13, 14, and 15 shown in FIG. 5 have detection ranges D11, D12, D13, D14, and D15 that are limited by the sensitivity range unique to the sensor. The detection ranges D11, D12, D13, D14, and D15 have regions U1, U2, U3, and U4 where at least adjacent detection ranges overlap. In the areas U1, U2, U3, and U4, the sensors that are adjacent detection ranges can detect the signal pattern 31. If there is a detection range in which the signal pattern 31 can be detected by both of a pair of adjacent sensors among a plurality of sensors, a blind spot in the detection range cannot be made. For this purpose, it is desirable to adjust the detection ranges D11, D12, D13, D14, D15, the sensor interval p, the distance d to the substrate surface 32, and the signal pattern width W. For example, the sensor interval p is determined based on the constraints of the size of the sensor and the substrate itself, and the distance d from the substrate surface 32 is determined in consideration of the output characteristics and detection ranges of the optical sensors 11, 12, 13, 14, 15. Then, the signal pattern width W is adjusted.

A sensor connection circuit 17 shown in FIG. 6 is formed on the sensor substrate 16. The sensor connection circuit 17 includes power supply voltages VDD1, VDD2, resistors r11, r12, r13, r14, r15, r16, R1, R2, R _LED , voltage detection terminals T1, T2, and optical sensors 11, 12, 13, 14 and 15 are connected to each other.

The light emitting elements 111, 121, 131, 141, 151 are connected in series. The light emitting element 111 which is one end of the light emitting elements connected in series is connected to the power supply voltage VDD2 via the resistor R _LED , and the light emitting element 151 which is the other end is connected to the reference potential (GND). The light emitting elements 111, 121, 131, 141, 151 are driven with a constant current and emit light.

  The collector terminals of the light receiving elements 112, 122, 132, 142, 152 are all connected to the power supply voltage VDD1. The resistors r11, r12, r13, r14, r15, r16 are a group of resistors connected in series. The resistors r11, r12, r13, r14, r15, r16 all have the same resistance value. The resistor r11 at one end of the resistor group is connected to the voltage detection terminal T2, and the resistor r16 at the other end is connected to the voltage detection terminal T1. The voltage detection terminal T2 is connected to the resistor r11 and to the reference potential (GND) through the resistor R2. The voltage detection terminal T1 is connected to the resistor r16 and to the reference potential (GND) via the resistor R1.

  The emitter terminal of the light receiving element 112 is connected between the resistor r11 and the resistor r12. Similarly, the emitter terminal of the light receiving element 122 is connected between the resistor r12 and the resistor r13. The emitter terminal of the light receiving element 132 is connected between the resistor r13 and the resistor r14. The emitter terminal of the light receiving element 142 is connected between the resistor r14 and the resistor r15. The emitter terminal of the light receiving element 152 is connected between the resistor r15 and the resistor r16. That is, a power supply voltage is applied to a plurality of sensors, and each of the plurality of sensors can output between the voltage detection terminal T1 and the voltage detection terminal T2, and adjacent sensors are connected to each other from each sensor by the first voltage detection terminal. The resistors r11, r12, r13, r14, r15, and r16, which are predetermined resistors, are connected in a ladder shape so that the resistance values thereof are different.

  The voltage detection terminal T1 outputs a voltage V1. The voltage detection terminal T2 outputs a voltage V2. The voltage detection terminals T1 and T2 are connected to the sensor signal processing circuit 41 shown in FIG. The sensor signal processing circuit 41 receives the voltage signals S1 and S2 of the voltages V1 and V2 output from the voltage detection terminals T1 and T2 of the sensor assemblies 10 and 20, and sends the sensor outputs G1 and G2 to the arithmetic processing unit 42. It is an analog circuit that outputs. For example, the sensor signal processing circuit 41 is an analog circuit that processes the voltage signal S1 of the sensor assembly 10 as G1 = ((V1−V2) / (V1 + V2)). The sensor signal processing circuit 41 is an analog circuit that processes the voltage signal S2 of the sensor assembly 20 as G2 = ((V1−V2) / (V1 + V2)). As a result, the sensor signal processing circuit 41 obtains a subtraction value obtained by subtracting the first voltage output V1 of the first voltage detection terminal T1 and the second voltage output V2 of the second voltage detection terminal T2 as the first voltage detection. Voltage values obtained by dividing the first voltage output V1 of the terminal T1 and the second voltage output V2 of the second voltage detection terminal T2 by the added value are output as sensor outputs G1 and G2.

  The sensor outputs G1 and G2 indicate that the center position of the current distribution flowing through each of the light receiving elements 112, 122, 132, 142, and 152 is proportional to ((V1−V2) / (V1 + V2)). . The center position of the current distribution is a value representing a position where the reflected light is high among the phototransistors of the respective light receiving elements 112, 122, 132, 142, and 152. Compared to the case of detection by a single sensor, the sensor outputs G1 and G2 of this embodiment can output the average of the variations of the light receiving elements 112, 122, 132, 142, and 152, so that individual differences among sensors Can reduce the effects of

  In the present embodiment, it has been found that (V1 + V2) is proportional to the total amount of light received by all the light receiving elements. For example, if the distance d between the optical sensors 11, 12, 13, 14, 15 and the substrate surface 32 is constant and the signal pattern width W is constant, the light receiving elements 112, 122, 132, 142, 152 receive light. The total amount of light emitted is always considered constant. As a result, (V1 + V2) is considered to be constant, and therefore the sensor signal processing circuit 41 described above may process the voltage signal S1 of the sensor assembly 10 as G1 = (V1-V2). Similarly, the sensor signal processing circuit 41 processes the voltage signal S2 of the sensor assembly 20 as G2 = (V1-V2). In the sensor signal processing circuit 41, the addition process of (V1 + V2) and the division process of dividing (V1-V2) by (V1 + V2) can be omitted. Thereby, a sensor signal processing circuit can be simplified. The sensor signal processing circuit 41 outputs subtracted values obtained by subtracting the first voltage output V1 of the first voltage detection terminal T1 and the second voltage output V2 of the second voltage detection terminal T2 as sensor outputs G1 and G2. To do. In the sensor outputs G1 and G2, the center position of the current distribution flowing in each light receiving element 112, 122, 132, 142, 152 is proportional to (V1-V2). Thus, the center position of the current distribution is a value representing a position where the reflected light is high among the phototransistors of the light receiving elements 112, 122, 132, 142, and 152. Compared to the case of detection by a single sensor, the sensor outputs G1 and G2 of this embodiment can output the average of the variations of the light receiving elements 112, 122, 132, 142, and 152, so that individual differences among sensors Can reduce the effects of

  FIG. 7 is a configuration diagram of an arithmetic processing unit according to the present embodiment. The arithmetic processing unit 42 is a computer such as a microcomputer, and includes an input interface 42a, an output interface 42b, a CPU 42c, a ROM 42d, a RAM 42e, and an internal storage device 42f. The input interface 42a, the output interface 42b, the CPU 42c, the ROM 42d, the RAM 42e, and the internal storage device 42f are connected to an internal bus.

  The input interface 42a receives the sensor outputs G1 and G2 from the sensor signal processing circuit 41 and outputs them to the CPU 42c. The output interface 42 b receives the absolute position data D from the CPU 42 c and outputs it to the control unit 65.

  The ROM 42d stores a program such as BIOS. The internal storage device 42f is, for example, an HDD or a flash memory, and stores an operating system program and application programs. The CPU 42c implements various functions by executing programs stored in the ROM 42d and the internal storage device 42f while using the RAM 42e as a work area.

  The internal storage device 42f stores an absolute position (absolute angle) database in which absolute positions (absolute angles) are associated with sensor outputs G1 and G2. The calculation processing unit 42 includes the AD conversion units 51 and 52, the angle calculation units 61 and 62, and the angle synthesis unit 63 shown in FIG. The AD converters 51 and 52 perform digital conversion of analog data using the input interface 42a. While the CPU 42c uses the RAM 42e as a temporary storage work area, the angle calculation units 61 and 62 provide the sensor outputs G1 and G2 to the absolute position (absolute angle) database stored in the internal storage device 42f, and the absolute position ( An arithmetic process for deriving an absolute angle is performed. The angle synthesis unit 63 determines the final absolute angle from the calculation results of the angle calculation unit 61 and the angle calculation unit 62, and outputs absolute position data (absolute angle data) D to the control unit 65 via the output interface 42b. To do.

  Next, an absolute angle detection procedure of the absolute encoder 100 having the encoder unit 1 will be described with reference to FIGS. 1, 2, and 5 to 8. FIG. 8 is an explanatory diagram for explaining the relationship between the sensor output and the rotation angle according to the present embodiment. In the encoder unit 1, when the shaft 38 is rotated by rotation from the motor, the rotor 30 rotates around the rotation center O in conjunction with the shaft 38. The relative positions of the sensor assemblies 10 and 20 and the rotor 30 change, and the sensor assemblies 10 and 20 detect the reflected light of the signal pattern 31 on the rotor 30.

For example, when the opposing position of the sensor assembly 10 is m ₀ , the signal pattern 31 exists in the detection ranges D11 and D12 of the optical sensor 11 and the optical sensor 12 illustrated in FIG. When the opposing position of the sensor assembly 10 is m ₉₀ , the signal pattern 31 exists in the detection ranges D12 and D13 of the optical sensor 12 and the optical sensor 13 shown in FIG. When a position opposite to the sensor assembly 10 is _{m 180,} signal pattern 31 is present in the detection area D14, D15 of the optical sensor 14 and optical sensor 15 shown in FIG. When the sensor assembly 10 and the rotor 30 move relatively, the signal pattern 31 moves from the detection range D11 to the detection range D15.

  When the signal pattern 31 moves from the detection range D11 to the detection range D15, the voltage V1 at the voltage detection terminal T1 shown in FIG. 6 increases and the voltage V2 at the voltage detection terminal T2 decreases. The sensor signal processing circuit 41 processes the voltage signal S1 of the sensor assembly 10 as sensor output G1 = ((V1−V2) / (V1 + V2)), and the sensor signal processing circuit 41 outputs the voltage signal S2 of the sensor assembly 20 to the sensor output G2 = ((( When processing as (V1-V2) / (V1 + V2)), the sensor outputs G1, G2 are increased or decreased as shown in FIG.

  The arithmetic device 40 stores the relationship between the sensor output and the rotation angle shown in FIG. 8 in the internal storage device 42f as an absolute position (absolute angle) database in which the absolute angle and the sensor output are associated with each other. The sensor outputs G1 and G2, which are analog data, are digitally converted by the AD converters 51 and 52 and sent to the angle calculators 61 and 62. The angle calculators 61 and 62 give the digitally converted sensor outputs G1 and G2 to the absolute position (absolute angle) database, and obtain data of the rotation angle θ. The angle calculation units 61 and 62 may obtain data of the rotation angle θ by calculation using the digitally converted sensor outputs G1 and G2. In this case, the angle synthesizer 63 obtains and outputs absolute position data (absolute angle data) D that minimizes the absolute value of the angle difference from the plurality of rotation angle θ data obtained by the angle calculators 61 and 62. To do.

  Further, the angle synthesis unit 63 may obtain and output absolute position data (absolute angle data) D using the magnitude relationship between the sensor outputs G1 and G2, for example. Alternatively, the angle synthesis unit 63 combines the data of the plurality of rotation angles θ obtained by the angle calculation units 61 and 62, calculates the absolute value of the difference, and uses the absolute value of the difference to obtain absolute position data (absolute angle Data) D may be obtained and output.

  In the present embodiment, the arithmetic device 40 includes a sensor signal processing circuit 41 and an arithmetic processing unit 42. As another modification, the arithmetic unit 40 can omit the sensor signal processing circuit 41. When the sensor signal processing circuit 41 is omitted, the arithmetic processing unit 42 receives the voltage signals S1 and S2 of the voltages V1 and V2 output from the voltage detection terminals T1 and T2 of the sensor assemblies 10 and 20 directly. The AD converters 51 and 52 digitally convert the voltage signals S1 and S2 of the voltages V1 and V2 using the input interface 42a. The CPU 42c processes the voltage signal S1 of the sensor assembly 10 as G1 = ((V1−V2) / (V1 + V2)) while using the RAM 42e as a temporary storage work area. Further, the CPU 42c processes the voltage signal S2 of the sensor assembly 20 as G2 = ((V1−V2) / (V1 + V2)) while using the RAM 42e as a work area for temporary storage.

  In the present embodiment, since the signal pattern 31 and the sensor assemblies 10 and 20 that are line symmetric with respect to the line L1 are included, the AD conversion units 51 and 52, the angle calculation units 61 and 62, and the angle synthesis Part 63 is required. Further, even if the signal pattern 31 is applied to a product having a rotation angle that is an angle smaller than 180 °, only one sensor assembly, AD conversion unit, and angle calculation unit may be used. In addition, the angle synthesis unit may be unnecessary. In addition, when applied to a product whose movement range is an angle smaller than 360 °, such as a robot joint, a signal pattern asymmetric with respect to the line L1 such as the signal pattern 33 shown in FIG. 4 may be used. it can. At this time, since the position of the signal pattern 33 in the radial direction is uniquely determined with respect to the rotation angle of the rotor 30, only one sensor assembly, AD conversion unit, and angle calculation unit are required, and no angle synthesis unit is required. You can also

  The absolute encoder 100 described above includes a plurality of optical sensors 11, 12, 13, 14, 15 that can read the signal pattern 31, and is arranged so that the positions of the plurality of optical sensors 11, 12, 13, 14, 15 are different. From the sensor units 10 and 20, the encoder unit 1 including the rotor 30 that is a base including the signal pattern 31, and the sensor outputs G1 and G2 of the sensor assemblies 10 and 20, the sensor assemblies 10 and 20 And an arithmetic device 40 that calculates an absolute position with respect to the rotor 30. When the sensor assemblies 10 and 20 and the rotor 30 move relatively, the signal pattern 31 moves through the detection ranges D11, D12, D13, D14, and D15 of the plurality of light receiving elements 112, 122, 132, 142, and 152.

  In the absolute encoder of this embodiment, the signal pattern moves through the detection ranges of a plurality of sensors, so that it is not necessary to increase the number of tracks and the resolution of the absolute encoder can be increased. As a result, the rotor of the absolute encoder becomes smaller, and the absolute encoder can be made smaller.

  Moreover, it is preferable that the signal pattern 31 can be detected by both of a pair of adjacent sensors among the plurality of light receiving elements 112, 122, 132, 142, 152. As a result, even if the signal pattern moves through the detection ranges of the plurality of sensors, the detection range cannot be blinded.

  The sensor assemblies 10 and 20 are connected in series by a first voltage detection terminal T1, and the first voltage detection terminal T1 and resistors r11, r12, r13, r14, r15, r16 which are predetermined resistances. The power supply voltage VDD1 is applied to the plurality of light receiving elements 112, 122, 132, 142, and 152, and the plurality of light receiving elements 112, 122, 132, 142, and 152 are respectively the first voltage. A resistor r11, which is a predetermined resistor, can output between the detection terminal T1 and the second voltage detection terminal T2, and the adjacent sensors have different resistance values from each sensor to the first voltage detection terminal. , R12, r13, r14, r15, r16, and the arithmetic unit 40 includes the first voltage output V1 of the first voltage detection terminal T1 and the first voltage output of the second voltage detection terminal T2. A voltage value obtained by dividing a subtraction value obtained by subtracting the voltage output V2 by an addition value obtained by adding the first voltage output V1 of the first voltage detection terminal T1 and the second voltage output V2 of the second voltage detection terminal T2 is obtained. It is preferable to output as sensor outputs G1 and G2.

  In the absolute encoder of the present embodiment, the center position of the current distribution of the plurality of sensors is proportional to ((first voltage output V1−second voltage output V2). The center position of the current distribution of the plurality of sensors is Compared with the case where detection is performed by a single sensor, the variation of a plurality of sensors is averaged and output, so that it is possible to reduce the influence of individual differences between the sensors. Since the voltage output V2) is confirmed, a stable sensor output is output regardless of disturbance of light quantity and environmental conditions.

  For example, since the absolute encoder (Patent Document 2) of the prior art document uses only one sensor, it is necessary to consider individual differences between the sensors. In order to take into account individual differences, it is necessary to adjust a coefficient for converting sensor output to rotation angle data and a conversion map for each individual. In the absolute encoder (Patent Document 2) of the prior art document, the current output of the position detection element is proportional to the current value corresponding to a predetermined distance from the other terminal on which the light is incident. When the amount of light changes due to disturbance or environmental conditions, the absolute encoder (Patent Document 2) of the prior art document cannot output the correct absolute position because the current value changes. On the other hand, in the absolute encoder of this embodiment, the center position of the current distribution of the plurality of sensors is proportional to ((first voltage output V1−second voltage output V2)). Even if the amount of light changes, the center position of the current distribution of the plurality of sensors does not change, and as a result, the absolute encoder can reduce the possibility of errors.

  In the absolute encoder of the present embodiment, it is preferable that the plurality of sensors are light receiving elements and the signal pattern is a pattern having a light reflectance different from that of the substrate surface. In the absolute encoder of the present invention, since reflected light is used, it is not necessary to provide a transmission hole such as a slit in the rotor, or it is not necessary to limit the material of the rotor to transmissive glass. As a result, since the signal pattern can be configured with a simple pattern, the manufacturing cost can be reduced.

(Embodiment 2)
FIG. 9 is a configuration diagram of an encoder unit according to the second embodiment. The absolute encoder according to this embodiment is characterized in that the sensor assembly of the encoder unit is a magnetic sensor that senses magnetism. In addition, the same code | symbol is attached | subjected to the same member as what was demonstrated in embodiment mentioned above, and the overlapping description is abbreviate | omitted. FIG. 10 is a schematic diagram for explaining the relationship between the sensor and the signal pattern according to the present embodiment. FIG. 11 is an explanatory diagram for explaining the sensor connection circuit according to the present embodiment.

  In the absolute encoder according to the present embodiment, the encoder unit 1 shown in FIG. 1 is replaced with the encoder unit 2 shown in FIG. 9, and other configurations are the same. Further, the sensor assembly 10 in FIG. 1 corresponds to the sensor assembly 70, and the sensor assembly 20 corresponds to the sensor assembly 80. As shown in FIG. 9, the encoder unit 2 includes a rotor 30 that is a base, sensor assemblies (reading units) 70 and 80, and a shaft 38.

  The rotor 30 is made of silicon, glass, polymer material or the like. The rotor 30 has a signal pattern 34 on a substrate surface 35 which is one plate surface. The substrate surface 35 is nonmagnetic.

Signal pattern 34 is a locus of the distance X _P having the same equations 1 and 2 and the signal pattern 31 shown in FIG. 2 described above. As a result, the position m of the signal pattern 34 becomes a position where the radial direction of the rotor 30 varies depending on the rotation angle 0 ° to 180 ° of the rotor 30, and the rotation angle 180 ° to 360 ° (0 °) of the rotor 30. The radial direction of the rotor 30 varies depending on (°). The signal pattern 34 is a curved belt-like pattern formed with a constant width in the radial direction of the rotor 30. The signal pattern 34 is formed by cutting a magnet sheet on the substrate surface 35. For example, a rubber magnet sheet containing a neodymium rare earth magnet is used as the magnet sheet. The signal pattern 34 is magnetized so that the sensor aggregate 70, 80 side is a single pole of S pole or N pole. The signal pattern 34 forms a magnetic field. As a modification of the signal pattern 34, a ferromagnetic material such as ferrite may be attached to the substrate surface 35 and magnetized. Further, the rotor 30 itself is formed of a ferromagnetic material such as iron, and a permanent magnet is disposed on the opposite side of the base mirror surface 35 on which the signal pattern 34 is formed. In addition, if the signal pattern 34 is convex, the signal pattern 34 may be a pattern having different magnetic field strengths due to the difference in height between the substrate surface 35 and the signal pattern 34.

  The sensor assemblies 70 and 80 are fixed to a stator independent of the shaft 38 and the rotor 30. When the rotor 30 rotates, the relative positions of the sensor assemblies 70 and 80 and the rotor 30 change. The sensor assemblies 70 and 80 are sensor assemblies having the same structure arranged so that the phase of the relative position to the rotor 30 is shifted. The phase shift of the sensor assemblies 70 and 80 shown in FIG. 9 is 90 °. The phase shift of the sensor assemblies 70 and 80 may be other than 180 °. Hereinafter, the sensor assembly 70 will be described as a representative.

  As shown in FIG. 10, the sensor assembly 70 includes magnetic sensors 71, 72, 73, 74, 75 and a sensor substrate 76. The magnetic sensors 71, 72, 73, 74, and 75 are arranged at every sensor interval p on the sensor substrate 76 on the side facing the rotor 30. As shown in FIG. 10, when the sensor assembly 70 faces the rotor 30, the sensor substrate 76 is parallel to the base surface 35 of the rotor 30, and the magnetic sensors 71, 72, 73, 74, 75 and the base surface 35 The distance d is constant. The positions of the magnetic sensors 71, 72, 73, 74, and 75 are different with respect to the radial direction of the rotor 30. The sensor assemblies 70 and 80 are not limited to five as long as the number of sensors is plural. As the number of sensors increases, the resolution of the absolute encoder 100 improves.

In the present embodiment, the magnetic sensors 71, 72, 73, 74, and 75 are magnetic sensors that can read the signal pattern 34. Magnetic sensors 71, 72, 73, 74, and 75 shown in FIG. 10 are the same magnetoresistance effect element. A magnetoresistive effect element is an element whose electric resistance value changes depending on the magnetic field intensity in the vicinity of the element. The magnetoresistive element is formed, for example, by forming a Ni ₈₁ Fe ₁₉ alloy film on the sensor substrate 76. Since the magnetoresistive effect element is desired to be used in a region where the resistance change is linear, a bias magnet such as CoCrPt alloy is formed on the Ni ₈₁ Fe ₁₉ alloy film via an insulating layer such as Al ₂ O _3. Is desirable. Alternatively, the element can be used in a region where the change in resistance value is linear even when a bias magnet is arranged around the magnetoresistive effect element. When the magnetic sensors 71, 72, 73, 74, and 75 detect the magnetic field of the signal pattern 34, the resistance increases or decreases due to the magnetic polarity of the signal pattern 34. The magnetic sensors 71, 72, 73, 74, and 75 can be giant magnetoresistive elements or Hall elements.

  The magnetic sensors 71, 72, 73, 74, and 75 shown in FIG. 10 include detection ranges D71, D72, D73, D74, and D75 that are not as clear as the optical sensors but are limited by the sensitivity range unique to the sensor. The detection ranges D71, D72, D73, D74, D75 have regions U71, U72, U73, U74 where at least adjacent detection ranges overlap. In the regions U71, U72, U73, and U74, the sensors that are adjacent detection ranges can detect the signal pattern 34. If there is a detection range in which the signal pattern 34 can be detected by both of a pair of adjacent sensors among a plurality of sensors, a blind spot in the detection range cannot be made. For this purpose, it is desirable to adjust the detection ranges D71, D72, D73, D74, D75, the sensor interval p, the distance d to the substrate surface 35, and the signal pattern width W. The sensor interval p is determined from the constraints of the size of the sensor and the substrate itself, the distance d from the substrate surface 35 is determined in consideration of the output characteristics and detection range of the magnetic sensors 71, 72, 73, 74, 75, The signal pattern width W is adjusted.

  A sensor connection circuit 77 shown in FIG. 11 is formed on the substrate 76. The sensor connection circuit 77 uses the same circuit except for the sensor connection circuit 17 described above and connection circuits related to the light emitting elements 111, 121, 131, 141, and 151. The sensor connection circuit 77 includes a power supply voltage VDD, resistors r11, r12, r13, r14, r15, r16, R1, R2, voltage detection terminals T1, T2, and magnetic sensors 71, 72, 73, 74, 75. It is a circuit to be connected.

  One ends of the magnetic sensors 71, 72, 73, 74, and 75 are all connected to the power supply voltage VDD. The resistors r11, r12, r13, r14, r15, r16 are a group of resistors connected in series. The resistors r11, r12, r13, r14, r15, r16 all have the same resistance value. The resistor r11 at one end of the resistor group is connected to the voltage detection terminal T2, and the resistor r16 at the other end is connected to the voltage detection terminal T1. The voltage detection terminal T2 is connected to the resistor r11 and to the reference potential (GND) via the resistor R1. The voltage detection terminal T1 is connected to the resistor r16 and to the reference potential (GND) via the resistor R2.

  The other end of the magnetic sensor 71 is connected between the resistor r11 and the resistor r12. Similarly, the other end of the magnetic sensor 72 is connected between the resistor r12 and the resistor r13. The other end of the magnetic sensor 73 is connected between the resistor r13 and the resistor r14. The other end of the magnetic sensor 74 is connected between the resistor r14 and the resistor r15. The other end of the magnetic sensor 75 is connected between the resistor r15 and the resistor r16. That is, a power supply voltage is applied to a plurality of sensors, and each of the plurality of sensors can output between the voltage detection terminal T1 and the voltage detection terminal T2, and adjacent sensors are connected to each other from each sensor by the first voltage detection terminal. The resistors r11, r12, r13, r14, r15, and r16, which are predetermined resistors, are connected in a ladder shape so that the resistance values thereof are different.

  The voltage detection terminal T1 outputs a voltage V1. The voltage detection terminal T2 outputs a voltage V2. The voltage detection terminals T1 and T2 are connected to the sensor signal processing circuit 41 shown in FIG. The sensor signal processing circuit 41 receives the voltage signals S1 and S2 of the voltages V1 and V2 output from the voltage detection terminals T1 and T2 of the sensor assemblies 70 and 80, and sends the sensor outputs G1 and G2 to the arithmetic processing unit 42. It is an analog circuit that outputs. For example, the sensor signal processing circuit 41 is an analog circuit that processes the voltage signal S1 of the sensor assembly 70 as G1 = ((V1−V2) / (V1 + V2)). The sensor signal processing circuit 41 is an analog circuit that processes the voltage signal S2 of the sensor assembly 80 as G2 = ((V1−V2) / (V1 + V2)). As a result, the sensor signal processing circuit 41 obtains a subtraction value obtained by subtracting the first voltage output V1 of the first voltage detection terminal T1 and the second voltage output V2 of the second voltage detection terminal T2 as the first voltage detection. Voltage values obtained by dividing the first voltage output V1 of the terminal T1 and the second voltage output V2 of the second voltage detection terminal T2 by the added value are output as sensor outputs G1 and G2.

  The sensor outputs G1 and G2 indicate that the center position of the current distribution flowing through the magnetic sensors 71, 72, 73, 74, and 75 is proportional to ((V1−V2) / (V1 + V2)). The center position of the current distribution is a value representing a position where the resistance is changed by detecting the magnetic field of the signal pattern 34 among the magnetoresistive elements of the magnetic sensors 71, 72, 73, 74, and 75. Compared to the case of detection by a single sensor, the sensor outputs G1 and G2 of the present embodiment can average and output the variations of the magnetic sensors 71, 72, 73, 74, and 75. Can reduce the effects of

  Next, a procedure for detecting an absolute angle of the absolute encoder 100 having the encoder unit 2 will be described with reference to FIGS. 1 and 7 to 11. In the encoder unit 2, when the shaft 38 is rotated by rotation from the motor, the rotor 30 rotates around the rotation center O in conjunction with the shaft 38. The relative positions of the sensor assemblies 70 and 80 and the rotor 30 change, and the sensor assemblies 70 and 80 detect the magnetic field of the signal pattern 34 on the rotor 30.

For example, when the opposing position of the sensor assembly 70 is m ₀ , the signal pattern 34 exists in the detection ranges D71 and D72 of the magnetic sensor 71 and the magnetic sensor 72 shown in FIG. When the opposing position of the sensor assembly 70 is m ₉₀ , the signal pattern 34 exists in the detection ranges D72 and D73 of the magnetic sensor 72 and the magnetic sensor 73 shown in FIG. When a position opposite to the sensor assembly 70 is _{m 180,} signal pattern 34 is present in the detection area D74, D75 of the magnetic sensor 74 and the magnetic sensor 75 shown in FIG. 10. When the sensor assembly 70 and the rotor 30 move relatively, the signal pattern 34 moves from the detection range D71 to the detection range D75.

  When the signal pattern 34 moves from the detection range D71 to the detection range D75, the voltage V1 at the voltage detection terminal T1 shown in FIG. 11 increases and the voltage V2 at the terminal T2 decreases. The sensor signal processing circuit 41 processes the voltage signal S1 of the sensor assembly 10 as sensor output G1 = ((V1−V2) / (V1 + V2)), and the sensor signal processing circuit 41 outputs the voltage signal S2 of the sensor assembly 20 to the sensor output G2 = ((( When processing as (V1-V2) / (V1 + V2)), the sensor outputs G1, G2 are increased or decreased as shown in FIG.

  The arithmetic device 40 stores the relationship between the sensor output and the rotation angle shown in FIG. 8 in the internal storage device 42f as an absolute position (absolute angle) database in which the absolute angle and the sensor output are associated with each other. The sensor outputs G1 and G2, which are analog data, are digitally converted by the AD converters 51 and 52 and sent to the angle calculators 61 and 62. The angle calculators 61 and 62 give the digitally converted sensor outputs G1 and G2 to the absolute position (absolute angle) database, and obtain data of the rotation angle θ. The angle calculation units 61 and 62 may obtain data of the rotation angle θ by calculation using the digitally converted sensor outputs G1 and G2. In this case, the angle synthesizer 63 obtains and outputs absolute position data (absolute angle data) D that minimizes the absolute value of the angle difference from the plurality of rotation angle θ data obtained by the angle calculators 61 and 62. To do.

  Further, the angle synthesis unit 63 may obtain and output absolute position data (absolute angle data) D using the magnitude relationship between the sensor outputs G1 and G2, for example. Alternatively, the angle synthesis unit 63 combines the data of the plurality of rotation angles θ obtained by the angle calculation units 61 and 62, calculates the absolute value of the difference, and uses the absolute value of the difference to obtain absolute position data (absolute angle Data) D may be obtained and output.

  The absolute encoder 100 described above includes a plurality of magnetic sensors 71, 72, 73, 74, 75 that can read the signal pattern 34, and is arranged so that the positions of the plurality of magnetic sensors 71, 72, 73, 74, 75 are different. Sensor assemblies 70 and 80, the rotor 30 that is a base including the signal pattern 34, and the sensor assemblies 70 and 80 from the sensor outputs G 1 and G 2 of the sensor assemblies 70 and 80. And an arithmetic device 40 that calculates an absolute position with respect to the rotor 30. When the sensor assemblies 70 and 80 and the rotor 30 move relatively, the signal pattern 34 moves in the detection ranges D71, D72, D73, D74, and D75 of the plurality of magnetic sensors 71, 72, 73, 74, and 75.

  In the absolute encoder of this embodiment, the signal pattern moves through the detection ranges of a plurality of sensors, so that it is not necessary to increase the number of tracks and the resolution of the absolute encoder can be increased. As a result, the rotor of the absolute encoder becomes smaller, and the absolute encoder can be made smaller.

  Moreover, it is preferable that the signal pattern 34 can be detected by both of a pair of adjacent sensors among the plurality of magnetic sensors 71, 72, 73, 74, 75. As a result, even if the signal pattern moves through the detection ranges of the plurality of sensors, the detection range cannot be blinded.

  The sensor assemblies 70 and 80 are connected in series by the first voltage detection terminal T1, and the first voltage detection terminal T1 and resistors r11, r12, r13, r14, r15, r16 which are predetermined resistances. The power supply voltage VDD is applied to the plurality of magnetic sensors 71, 72, 73, 74, 75, and each of the plurality of magnetic sensors 71, 72, 73, 74, 75 is a first voltage. A resistor r11, which is a predetermined resistor, can output between the detection terminal T1 and the second voltage detection terminal T2, and the adjacent sensors have different resistance values from each sensor to the first voltage detection terminal. , R12, r13, r14, r15, r16 are connected in a ladder shape, and the arithmetic unit 40 includes a first voltage output V1 of the first voltage detection terminal T1 and a second voltage output V2 of the second voltage detection terminal T2. The A voltage value obtained by dividing the calculated subtraction value by an addition value obtained by adding the first voltage output V1 of the first voltage detection terminal T1 and the second voltage output V2 of the second voltage detection terminal T2 is output from the sensor outputs G1 and G2. It is preferable to output as

  In the absolute encoder of this embodiment, the center position of the current distribution of the plurality of sensors is ((first voltage output V1−second voltage output V2) / (first voltage output V1 + second voltage output V2)). It is proportional to The center position of the current distribution of the plurality of sensors is output by averaging the variations of the plurality of sensors as compared with the case where detection is performed by a single sensor, so that the influence of individual differences among the sensors can be reduced. Further, since the voltage value is confirmed, a stable sensor output is output regardless of the disturbance of the magnetic field and the environmental conditions.

  For example, since the absolute encoder (Patent Document 3) of the prior art document uses only one sensor, it is necessary to consider individual differences between the sensors. Further, in the absolute encoder (Patent Document 3) of the prior art document, the thickness of the magnet is assumed to continuously change over one round. As a result, the strength of the magnetic field detected by the magnetic sensor changes continuously over one turn of the magnetic encoder. In addition, the absolute encoder (Patent Document 3) of the prior art document has a rotor in which the thickness of the magnet continuously changes over one round, so that the position of the center of gravity of the rotor is decentered. For this reason, in the absolute encoder (Patent Document 3) of the prior art document, there is a possibility that the rotor vibrates due to the rotation of the rotor. On the other hand, in the absolute encoder of this embodiment, since the center position of the current distribution of the plurality of sensors is proportional to (first voltage output V1−second voltage output V2), the magnetic field depends on disturbances and environmental conditions. Even if changes, the center position of the current distribution of the plurality of sensors does not change. The absolute encoder of the present embodiment can provide an absolute encoder at a low cost with a magnet sheet having a constant magnet thickness, without using a magnet with a manufacturing cost in which the magnet thickness continuously changes over one round. . Further, in the absolute encoder of this embodiment, the position of the center of gravity of the rotor is not decentered, and no vibration is generated.

  In the absolute encoder of this embodiment, it is preferable that the plurality of sensors are magnetic sensors and the signal pattern is a pattern that forms a magnetic field. Since the absolute encoder of the present invention can be configured with a simple pattern, the manufacturing cost can be reduced. Further, even if foreign matter is mixed between the sensor assembly and the signal pattern, the absolute encoder can operate.

  The absolute encoders of the first and second embodiments described above can be applied to a servo motor system that does not need to return to the origin after a power failure because the absolute position can be grasped even after the power failure has been recovered. Examples of the servo motor system include various mechanical devices, robots, and automobile component parts, and products that use these servo motor systems can be reduced in size.

  As described above, the absolute encoder according to the present invention has high resolution without increasing the number of tracks, and is useful for reducing the influence of individual differences among sensors.

1, 2, Encoder unit 10, 20, 70, 80 Sensor assembly 11, 12, 13, 14, 15 Optical sensor 17, 77 Sensor connection circuit 16, 76 Sensor substrate 30 Rotor 31, 33, 34 Signal pattern 32, 35 Base Surface 33a, 33b Signal pattern end 38 Shaft 40 Arithmetic device 41 Sensor signal processing circuit 42 Arithmetic processing unit 51, 52 AD conversion unit 61, 62 Angle calculation unit 63 Angle composition unit 65 Control unit 71, 72, 73, 74, 75 Magnetic sensor 100 Absolute position detection device 111, 121, 131, 141, 151 Light emitting element 112, 122, 132, 142, 152 Light receiving element

Claims (5)

An encoder unit including a plurality of sensors capable of reading a signal pattern, the sensor assembly being arranged so that the positions of the plurality of sensors are different, and a substrate including the signal pattern; and an output of the sensor assembly, An arithmetic unit that calculates the absolute position of the sensor assembly and the base body,
When the sensor assembly and the base body move relative to each other, an absolute encoder in which the signal pattern moves through a detection range of the plurality of sensors ,
The sensor assembly includes a first voltage detection terminal, and a second voltage detection terminal connected to the first voltage detection terminal via a predetermined resistor,
A power supply voltage is applied to the plurality of sensors, and the plurality of sensors can output between the first voltage detection terminal and the second voltage detection terminal, respectively, and adjacent sensors are connected to each other from each sensor. It is connected to the predetermined resistor so that the resistance value is different up to the first voltage detection terminal,
The arithmetic unit calculates a subtracted value obtained by subtracting the first voltage output of the first voltage detection terminal and the second voltage output of the second voltage detection terminal, as the first voltage output and the second voltage output. An absolute encoder that outputs a voltage value divided by an added value obtained by adding as a sensor output . An encoder unit including a plurality of sensors capable of reading a signal pattern, the sensor assembly being arranged so that the positions of the plurality of sensors are different, and a substrate including the signal pattern; and an output of the sensor assembly, An arithmetic unit that calculates the absolute position of the sensor assembly and the base body,
When the sensor assembly and the base body move relative to each other, an absolute encoder in which the signal pattern moves through a detection range of the plurality of sensors,
The sensor assembly includes a first voltage detection terminal, and a second voltage detection terminal connected to the first voltage detection terminal via a predetermined resistor,
A power supply voltage is applied to the plurality of sensors, and the plurality of sensors can output between the first voltage detection terminal and the second voltage detection terminal, respectively, and adjacent sensors are connected to each other from each sensor. It is connected to the predetermined resistor so that the resistance value is different up to the first voltage detection terminal,
The absolute encoder outputs a subtraction value obtained by subtracting the first voltage output of the first voltage detection terminal and the second voltage output of the second voltage detection terminal as a sensor output . Absolute encoder according to claim 1 or 2, wherein the signal pattern can be detected by both the pair of sensors adjacent of the plurality of sensors. Wherein the plurality of sensors is a light receiving element, the absolute encoder according to any one of claims 1 3 signal pattern are different patterns of light reflectivity from the substrate. Wherein the plurality of sensors is a magnetic sensor, absolute encoder according to any one of claims 1 to 3 wherein the signal pattern is a pattern for forming a magnetic field.

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