Encoder

Abstract

Provided is an encoder that can measure displacement with high accuracy by cancelling the influence of external noise. The encoder includes a rotor, a stator, and a computing unit. The stator has an even number of detectors that read scales and output signals. The calculation unit has a phase calculation unit that calculates a phase on the basis of the signal output by the detector, and an averaging unit that averages the phase calculated by the phase calculation unit. The even number of detectors are each located at a position that is an integer multiple of a period shifted by a scale from the other adjacent detector in the measurement direction. The first signal output by one half of the detector and the second signal output by the other half of the detector have opposite polarities at the input of the phase calculation unit.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This nonprovisional application claims priority under 35 USC §119(a) to Japanese Patent Application No. 2023-133983 filed on August 21, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to encoders. Background Art

[0004] It is known that a conventional encoder is equipped with a scale having a scale, and a head that is opposite to the scale and moves relative to the scale along a measuring direction. For example, the electromagnetic induction rotary encoder disclosed in JP 2006-322927A has a stator and a rotor, the stator has a transmitting winding and a receiving winding corresponding to the head, and the rotor has a magnetic flux coupling body corresponding to the scale. In this electromagnetic induction rotary encoder, a transmitting current that periodically changes the current direction is applied to the transmitting winding. The magnetic flux coupling body generates an induced current based on a magnetic field generated by the transmitting current flowing through the transmitting winding. The receiving winding detects the magnetic field generated by the induced current flowing through the magnetic flux coupling body, and detects a signal corresponding to the magnetic field strength.

[0005] With such encoders, noise may adversely affect detection performance.

[0006] In JP2020-193887A, the rotary encoder is arranged close to the motor or other devices with high current flow. Since the wiring for the motor and the wiring for the rotary encoder are usually routed through the same conduit, the high-frequency noise generated when the motor is driven is induced in the power line of the rotary encoder. In position detection, if external noise is introduced into the power supply or high-frequency noise is introduced into the signal, the noise is superimposed on the detected signal and may cause errors in position calculation. In order to solve these problems, the rotary encoder of JP2020-193887A is equipped with a noise suppression component that prevents noise from being superimposed on the detected signal. However, when the drive output of the motor is large, or when the feedback frequency is high to improve the response characteristics of the drive output, the high-frequency noise from the drive current is also large, so the number of noise suppression components to be equipped must be increased.

[0007] In addition, high-frequency noise is introduced into the analog circuit of the electrical components of the rotary encoder via the motor housing, drive shaft, rotary encoder housing, etc. The rotary encoder in JP2020-134505A uses a low-pass filter to attenuate the high-frequency noise induced in the analog circuit. However, in this case, the detected signal is also attenuated along with the noise, which may deteriorate the accuracy and increase the jitter of the angle detection data.

[0008] As a method for suppressing noise superimposed on a detection signal without using a noise suppression component and without causing the detection signal to attenuate along with the noise, JP2019-109093A discloses a method for eliminating noise in a rotary encoder by the following operation: two detection sensors are arranged so that the phase difference of the output signals is 180°, and the position calculation results are averaged, which are the signals output from the two detection sensors. Summary of the invention

[0009] Technical issues

[0010] However, in the rotary encoder of JP2019-109093A, the physical distance between the two detection sensors must be (integer + 1 / 2) times the scale pitch, which makes it difficult to achieve the effect of noise cancellation when the sensors are arranged at an integer multiple of the pitch. Therefore, the rotary encoder has the following problem: due to physical limitations, noise cancellation using two detection sensors to cancel noise may not be effective.

[0011] An object of the present invention is to provide an encoder that can measure displacement with high accuracy by eliminating the influence of external noise.

[0012] Technical Solution

[0013] The encoder according to the present invention includes: a scale having scales arranged at a predetermined period along a measuring direction; a head arranged to be opposite to the scale and to move relative to the scale along the measuring direction; and a calculation unit calculating the relative displacement of the scale and the head. The head has an even number of detectors, which read the scales and output a signal corresponding to the relative displacement of the scale and the head. The calculation unit has a phase calculation unit and an averaging unit, the phase calculation unit calculates the phase based on the signals output by each detector, and the averaging unit averages the phase calculated by the phase calculation unit based on the signals output by each detector. The even number of detectors are each located at a position shifted from other adjacent detectors along the measuring direction by an integer multiple of the scale period. The first signal output by half of the even number of detectors and the second signal output by the other half of the detectors have opposite polarities at the input of the phase calculation unit.

[0014] According to the present invention, by configuring the first signal output by half of the detectors among the even number of detectors and the second signal output by the other half of the detectors to have opposite polarities at the input of the phase calculation unit, and by averaging the calculated phases, the influence of external noise superimposed on the signal can be eliminated. Therefore, even in an environment where external noise may occur, high-precision displacement detection can be performed without the need for a noise suppression component.

[0015] In this case, the encoder is preferably an electromagnetic induction encoder, the scale has a scale coil as a scale, and the head is preferably equipped with a transmitting coil and a receiving coil, the transmitting coil generates magnetic flux to the scale coil, and the receiving coil receives changes in magnetic flux from the scale coil as a detector.

[0016] According to this configuration, even if the encoder is an electromagnetic induction encoder, the influence of external noise can be eliminated without requiring any noise suppression component, thereby enabling high-precision displacement detection even in an environment where external noise may occur.

[0017] In the electromagnetic induction encoder as described above, the transmitting current may be applied in opposite directions to the transmitting coils of half of the even-numbered detectors 43 and the transmitting coils of the remaining half of the detectors.

[0018] According to this configuration, the detector can output signals so that the first signal output by half of the even-numbered detectors and the second signal output by the other half of the detectors have opposite polarities at the input of the phase calculation unit, and by averaging the calculated phases, the influence of external noise is canceled. Therefore, even in an environment where external noise may occur, the encoder can perform high-precision displacement detection without the need for a noise suppression component.

[0019] In the present invention, it is preferred that half of the detector and the other half of the detector output signals of the same polarity according to the relative displacement of the scale and the head, and in the propagation path from the detector to the input of the phase calculation unit in the calculation unit, the polarity of the second signal is opposite to that of the first signal (i.e., the positive and negative of the signals are swapped).

[0020] According to this configuration, by configuring the first signal output by half of the detectors among the even number of detectors and the second signal output by the other half of the detectors to have opposite polarities at the input of the phase calculation unit, and by averaging the calculated phases, the calculation unit can cancel the influence of external noise superimposed on the signal. Therefore, even in an environment where external noise may occur, high-precision displacement detection can be performed without the need for a noise suppression component. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a front view of the digital micrometer according to the first embodiment.

[0022] Figure 2 is a schematic plan view of a rotor according to a first embodiment.

[0023] Figure 3 is a schematic plan view of a stator according to the first embodiment.

[0024] Figure 4is a circuit block diagram showing the configuration of a calculation unit of the first embodiment.

[0025] Figure 5A and Figure 5B The principle of errors in calculation results caused by external noise is shown. Specifically, Figure 5A An example of the waveform of the 2-phase signal at the input of the phase calculation unit 55 is shown. Figure 5B Shown by Figure 5A The Lissajous waveforms of the two-phase signals shown in FIG.

[0026] FIG. 6A to FIG. 6D The principle of eliminating external noise is shown. Specifically, Fig. 6A An example of the waveform of a 2-phase signal obtained from the first signal S1 detected by the first group of detectors is shown. Figure 6B An example of the waveform of a 2-phase signal obtained from the second signal S2 detected by the second group of detectors is shown. Figure 6C and Fig.6D They are shown according to Fig. 6A and Figure 6B The Lissajous waveforms of the 2-phase signals shown are plotted.

[0027] Figure 7 is a schematic plan view of a stator and a rotor according to a second embodiment.

[0028] Figure 8 is a schematic diagram showing a calculation unit according to the second embodiment.

[0029] Fig. 9 is a schematic diagram showing a calculation unit according to a modification of the second embodiment. DETAILED DESCRIPTION

[0030] First embodiment

[0031] The first embodiment of the present invention will be described below with reference to some drawings. In the following description, the same reference numerals are given to the same components, and components that have been described will not be described again as appropriate.

[0032] Figure 1 A front view of a digital micrometer 1 incorporating an encoder 4 according to an embodiment of the present invention is shown. The encoder 4 is disposed inside the digital micrometer 1 and detects the amount of displacement of the measuring element 2.

[0033] like Figure 1 As shown, the digital micrometer 1 comprises a measuring element 2 and an encoder 4. The measuring element 2 has a cylindrical spindle 21 having a contact surface 22 at one end. The contact surface 22 is a surface at the end of the spindle 21 for contacting a surface of an object to be measured.

[0034] The digital micrometer 1 includes a sleeve 31 and a ratchet knob 32 as a mechanism for moving the measuring element 2. The digital micrometer 1 advances or retracts the spindle 21 against the object to be measured by rotating the sleeve 31 or the ratchet knob 32 in the direction of the arrow in the figure with the spindle 21 as the axis.

[0035] The digital micrometer 1 is also provided with a jig 11 for fixing the spindle 21 , operation units 12 a to 12 c for receiving operations from a user and performing various settings on the digital micrometer 1 , an anvil 13 , and an arm 14 .

[0036] The anvil 13 is a reference position in the digital micrometer 1, and is disposed opposite to the contact surface 22 of the measuring element 2. The arm 14 is formed roughly in a U-shape. A sleeve 31, a ratchet knob 32, and other components of the measuring element 2 are located at one end of the arm 14. The anvil 13 is located at the other end of the arm 14. The digital micrometer 1 clamps the object to be measured between the contact surface 22 of the measuring element 2 and the anvil 13, and measures the length from the contact surface 22 to the anvil 13.

[0037] The measurement results (such as the measured values) of the digital micrometer 1 are displayed on the display unit 10. The display unit 10 is composed of an LCD panel and displays at least the measured values. The display unit 10 mainly displays the measured values ​​and other information on a 7-segment digital display.

[0038] Figure 2 : is a schematic plan view showing the configuration of the encoder 4 according to the present embodiment.

[0039] The encoder 4 is an electromagnetic induction type rotary encoder, and includes a rotor 41, a stator 42, and a calculation unit 45. The encoder 4 detects a movement displacement amount of the measuring element 2 from a reference position (eg, a position where the contact surface 22 contacts the anvil 13).

[0040] like Figure 2 As shown, the rotor 41 has a scale coil 40 as a scale arranged along the measuring direction (circumferential direction) at a predetermined pattern period P. The rotor 41 is disposed opposite to the stator 42 so as to be rotatable about the rotation axis O.

[0041] The stator 42 corresponds to the head and is disposed opposite to the rotor 41. Figure 3 As shown, the stator 42 includes an even number of detectors 43, which detect the displacement amount (i.e., the rotational displacement amount) of the rotor 41 relative to the stator 42 and output a signal corresponding to the displacement amount. Each detector 43 is located at a position shifted from the adjacent detector 43 along the measuring direction by n times (n is a natural number greater than or equal to 1) of the pattern period P of the scale coil 40. Due to this arrangement, each detector 43 detects a common phase in the periodic pattern of the scale coil 40.

[0042] Each detector 43 includes a transmitting coil 6 and a receiving coil 7. An AC transmitting current is applied to the transmitting coil 6 by a transmitter circuit 44. The transmitting current causes the transmitting coil 6 to generate an alternating magnetic field. In the rotor 41, the scale coil 40 opposite to the transmitting coil 6 generates a magnetic flux to cancel the alternating magnetic field generated by the transmitting coil 6.

[0043] In this embodiment, the transmitting current is applied in opposite directions to the transmitting coils 6 of half of the detectors (hereinafter referred to as the first group) and the transmitting coils 6 of the remaining half of the detectors 43 (hereinafter referred to as the second group) among the plurality of detectors 43. In other words, when the transmitting current flows clockwise to the transmitting coils 6 of the first group, the transmitting current flows counterclockwise to the transmitting coils 6 of the second group. With this transmitting current, in the rotor 41, the scale coils 40 facing the transmitting coils 6 of the first group and the scale coils 40 facing the transmitting coils 6 of the second group generate magnetic fluxes in opposite directions. In this embodiment, since two detectors 43 are provided, the first group and the second group each have one detector 43.

[0044] The receiving coil 7 receives the change of the magnetic flux generated by the scale coil 40 as a signal corresponding to the position (displacement amount). The receiving coil 7 includes three receiving coil wires 70 to receive a 3-phase signal from the magnetic flux generated by the transmitter coil wire 60. That is, the receiving coil wire 70 includes a first receiving coil wire 701 that receives a 0° phase signal SC1, a second receiving coil wire 702 that receives a 120° phase signal SC2, and a third receiving coil wire 703 that receives a 240° phase signal SC3. In the following description, the signals SC1, SC2, and SC3 detected by the first group of receiving coils 7 may be referred to as the first signal S1, and the signals SC1, SC2, and SC3 detected by the second group of receiving coils 7 may be referred to as the second signal S2.

[0045] As described above, in the rotor 41, the scale coil 40 facing the first group of transmitting coils 6 and the scale coil 40 facing the second group of transmitting coils 6 generate magnetic flux in opposite directions. Therefore, the first signal S1 detected by the first group of receiving coils 7 and the second signal S2 detected by the second group of receiving coils 7 have opposite polarities. The first signal S1 and the second signal S2 are input to the calculation unit 45 and propagate in the calculation unit 45, so that the first signal S1 and the second signal S2 have opposite polarities at the input of the phase calculation unit 55.

[0046] Figure 4 4 is a circuit block diagram showing the configuration of the calculation unit 45 provided by the encoder 4 in this embodiment. Figure 4As shown, the calculation unit 45 includes a first amplifier 51, a 3-phase to 2-phase conversion circuit 52, a second amplifier 53, an A / D converter 54, a phase calculation unit 55, an averaging unit 56, and an output unit 57. Among them, for each independent detector 43, the first amplifier 51, the 3-phase to 2-phase conversion circuit 52, the second amplifier 53, the A / D converter 54, and the phase calculation unit 55 are independently provided. On the other hand, only one averaging unit 56 and one output unit 57 are provided in the calculation unit 45. The calculation unit 45 calculates the movement displacement of the measuring element 2 based on the signal via the rotor 41 and the stator 42. The rotor 41 can move relative to the stator 42 along the measuring direction.

[0047] The first amplifier 51 receives the signals S1 and S2 detected by the detector 43, and amplifies and outputs these signals. The first amplifier 51 is implemented using, for example, an operational amplifier. The 3-phase to 2-phase conversion circuit 52 converts the signals S1 and S2, which are 3-phase signals via the first amplifier 51, into analog 2-phase signals. The second amplifier 53 is an amplifier that inputs the signal converted into an analog 2-phase signal by the 3-phase to 2-phase conversion circuit 52. The A / D converter 54 converts the analog 2-phase signal into a digital 2-phase signal through the second amplifier 53. The phase calculation unit 55 calculates the phase based on the digital 2-phase signal output by the A / D converter 54. As described above, the first amplifier 51, the 3-phase to 2-phase conversion circuit 52, the second amplifier 53, the A / D converter 54, and the phase calculation unit 55 are set for each individual detector 43 (that is, the signals S1 and S2, respectively), so that the phase calculated based on the signal S1 and the phase calculated based on the signal S2 are obtained.

[0048] The averaging unit 56 calculates an average value for the phases calculated by each phase calculation unit 55, and further calculates the displacement amount with respect to the phase. The output unit 57 outputs the displacement amount calculated by the averaging unit 56 to, for example, a monitor (see Figure 1 ) or a data storage device such as a PC.

[0049] Figure 5A and Figure 5B is a graph showing the principle that an error occurs in a phase calculation result due to external noise. Specifically, Figure 5A An example of the waveform of a 2-phase signal at the input of the phase calculation unit 55 for the signal detected by the receiving coil 7 is shown. Figure 5A , the vertical axis is the amplitude of the signal (digital signal value), and the horizontal axis is time. Figure 5B Shown by Figure 5A The Lissajous waveforms of the 2-phase signals shown in FIG. Figure 5A The numbers 0-3 on the time axis of the graph correspond to Figure 5BThe numbers 0-3 in the Lissajous waveform in . Figure 5A The illustrated signals DA1 and DB1 are superimposed with external noise N at time X. Although this is not the case with the micrometer 1 in the present embodiment, in an assembly configuration in which a motor carrying a large current is installed near the encoder 4, wiring for the motor and wiring for the encoder are generally passed through the same conduit, and external noise N is easily superimposed on the signal detected by the receiving coil 7. This external noise N causes Figure 5B The sudden fluctuation in the waveform is shown as NR in the illustrated Lissajous waveform, and causes an error NG in the phase calculated in the phase calculation unit 55 .

[0050] In the encoder 4 of the present embodiment, the error caused by the external noise N is canceled by averaging the phases calculated based on the signals detected by each detector 43 . FIG. 6A to FIG. 6D The principle of eliminating the error caused by external noise N by averaging is shown.

[0051] Fig. 6A An example of the waveform of a 2-phase signal obtained from the first signal S1 detected by the first group detector 43 is shown. Figure 6B FIG. 4 shows an example of a waveform of a 2-phase signal obtained from the second signal S2 detected by the second group detector 43. Fig. 6A and Figure 6B , the vertical axis is the amplitude of the 2-phase signal, and the horizontal axis is time. Figure 6C and Fig.6D They are shown according to Fig. 6A and Figure 6B The Lissajous waveforms of the 2-phase signals shown are plotted. Fig. 6A and Figure 6B The numbers 0-3 on the time axis of the graph correspond to Figure 6C and Fig.6D The numbers 0-3 in the Lissajous waveform in . Figure 6C and Fig.6D The Lissajous waveform sources in the diagram have signals S1 and S2 that are opposite in polarity. Therefore, note that Figure 6C and Fig.6D In the Lissajous waveform, the phases corresponding to the same time are shifted by 180° from each other.

[0052] like Fig. 6A and Figure 6B As shown in FIG. 1 , each 2-phase signal is superimposed with external noise N at time X. When a Lissajous waveform is drawn based on the 2-phase signal superimposed with these noises N, as shown in FIG. Figure 6C and Fig.6D As shown in the figure, the external noise N causes a change in the Lissajous waveform NR and an error in the calculated phase NG. Fig. 6A and Figure 6BAs shown, the external noise N superimposed on the 2-phase signal at time X has a positively changing amplitude, so the Lissajous waveform fluctuates to the upper right with the external noise N, as shown in FIG. Figure 6C and Fig.6D As shown in NR. Based on the Lissajous waveform of signal S1 ( Figure 6C ), this change of the Lissajous waveform caused by the external noise N becomes the error NG of the delayed phase. On the other hand, in the Lissajous waveform ( Fig.6D ), the change becomes an error NG of the advanced phase. Since the phase calculated based on the signal S1 and the phase calculated based on the signal S2 have opposite effects on the phase, the error NG can be offset and removed by averaging the phase calculated based on the signal S1 and the phase calculated based on the signal S2. This allows the encoder 4 to calculate the displacement amount with high accuracy by eliminating the influence of external noise.

[0053] According to this first embodiment, the following advantageous effects can be achieved:

[0054] (1) By configuring the first signal S1 output by half of the even-numbered detectors 43 and the second signal S2 output by the other half of the detectors 43 to have opposite polarities at the input of the phase calculation unit 55, and by averaging the calculated phases, the influence of external noise superimposed on the signals S1 and S2 can be eliminated. Therefore, even in an environment where external noise may occur, the encoder 4 can perform highly accurate displacement detection without the need for a noise suppression component.

[0055] (2) By configuring only the current flowing to the transmitting coil 6 in the first group of detectors 43 and the current flowing to the transmitting coil 6 in the second group of detectors 43 to be in opposite directions, and averaging the phases calculated based on the signals detected by the plurality of detectors 43, the influence of external noise can be eliminated without making any other significant changes to the configuration of the conventional encoder.

[0056] Second embodiment

[0057] A second embodiment of the present invention will be described below with reference to some drawings. In the following description, previously described components are denoted by the same reference numerals, and description thereof will be omitted.

[0058] Figure 7 1 is a schematic plan view of a stator and a rotor in an encoder 4A according to the second embodiment. In the first embodiment, the encoder 4 is an electromagnetic induction rotary encoder, but in the second embodiment, the encoder 4A is different from the first embodiment in that it is an optical rotary encoder. Figure 7As shown, the rotor 41A and the stator 42A in the encoder 4A have a structure similar to that of a conventional optical rotary encoder. That is, the rotor 41A constitutes a scale having a scale 40A, which is circularly engraved on its surface with a predetermined period P. The stator 42A includes an even number of detectors 43A. Each detector 43A is located at a position where the period P of the scale 40A is n times (n is a natural number greater than or equal to 1) shifted from the adjacent detector 43A in the measuring direction. Due to this arrangement, each detector 43A detects a common phase with a periodic pattern of the scale 40A. Half of the detector 43A and the other half (i.e., all detectors 43A) output signals of the same polarity according to the relative displacement of the scale and the head.

[0059] Each detector 43A includes a light source 6A that irradiates light onto the scale 40A, and a light receiving unit 7A that receives light that has passed through the scale 40A and outputs a signal corresponding to the position (displacement). The signal output by the light receiving unit 7A is input to the calculation unit 45A.

[0060] Figure 8 4 is a schematic diagram showing a calculation unit 45A according to the second embodiment. Figure 8 As shown, the computing unit 45A has Figure 4 The calculation unit 45 of the first embodiment shown in FIG. Figure 8 As shown, in the calculation unit 45A, the signal S1 from half of the detectors in the even-numbered detectors 43A is input to the first amplifier 51 without any special processing. On the other hand, for the signal S2 from the other half of the detectors in the even-numbered detectors 43A, as shown in FIG. Figure 8 As shown in K1 in FIG. 5 , the signal polarity is reversed (positive and negative are exchanged) and input to the first amplifier 51. In this way, the signal S1 from the first group detector 43A and the signal S2 from the second group detector 43A propagate in the calculation unit 45A so that they have opposite polarities at the input of the phase calculation unit 55. As a result, as in the first embodiment, even if external noise is superimposed on the signal, the influence of the external noise can be removed by averaging the phase calculated by the phase calculation unit 55. Therefore, even in an environment where external noise may occur, the encoder 4A can calculate the displacement amount with high accuracy.

[0061] Fig. 9 45B according to a modification of the second embodiment. The computing unit 45B may be replaced by the computing unit 45A of the second embodiment. Figure 8 ), the polarity of the signal S2 from the second group of detectors 43A is inverted at the input of the first amplifier 51 compared to the signal from the first group, as shown in FIG. Figure 8However, the location where the signal polarity is reversed may not be at the input of the first amplifier 51, but between the 3-phase to 2-phase conversion circuit 52 and the second amplifier 53, as shown in FIG. Fig. 9 As shown in K2 in. In this case, at the 3-phase to 2-phase conversion circuit 52, the calculation unit 45B converts the signal S2 from the second group of detectors 43A into a 2-phase signal of the same polarity as the signal S1 from the first group of detectors 43A, and inputs the signal to the second amplifier 53. As the positive and negative are exchanged, the converted 2-phase signal is input to the second amplifier 53 with the polarity reversed. In this way, the signal S1 from the first group of detectors 43A and the signal S2 from the second group of detectors 43A propagate in the calculation unit 45B so that they have opposite polarities at the input of the phase calculation unit 55. As a result, even in this modification, even if external noise is superimposed on the signal, the influence of the external noise can be removed by averaging the phase calculated by the phase calculation unit 55. Therefore, even in an environment where external noise may occur, the encoder 4A can calculate the displacement amount with high accuracy. The position of the signal polarity exchange may be different from the position shown in the above-mentioned second embodiment and its variations, as long as it is configured to make the polarity of the second signal opposite to the first signal (i.e., the positive and negative of the signals are exchanged) in the propagation path from the detector to the input of the phase calculation unit in the calculation unit.

[0062] In this present embodiment, the same advantageous effects as (1) in the above-mentioned first embodiment can be achieved.

[0063] Variations of the Embodiments

[0064] It should be noted that the present invention is not limited to the above-mentioned embodiments, and any changes, improvements, etc. are included in the present invention to the extent that the purpose of the present invention can be achieved. For example, in each of the above-mentioned embodiments, the instrument using the encoder 4, 4A is the digital micrometer 1, but it can be any other measuring instrument such as an indicator, a caliper, etc., or any other instrument other than a measuring instrument. In the above-mentioned embodiments, the optical encoder 4, 4A is a rotary encoder, but it can be a linear encoder. In the second embodiment, the encoder 4A is of an optical type, but any type such as an electromagnetic induction, magnetic or capacitive type can be adopted.

[0065] In the above-mentioned embodiments, the receiving coil 7 and the light receiving unit 7A detect 3-phase signals, but the detected signals may be 2-phase or 4-phase signals instead of 3-phase signals. The calculation units 45, 45A in the above-mentioned embodiments have the 3-phase to 2-phase conversion circuit 52, but the 4-phase to 2-phase conversion circuit 52 may be provided when a 4-phase signal is processed, or the conversion circuit may not be provided when a 2-phase signal is processed.

[0066] In the above-mentioned various embodiments, the rotor corresponding to the scale moves relative to the stator corresponding to the fixed head, but the head can move relative to the fixed scale. In other words, one of the scale and the head can move relative to the other along the measuring direction. In the case of a linear encoder or the like, a configuration in which the head moves relative to the fixed scale is common.

[0067] Any addition, deletion and design modification of the constituent elements in the embodiment and any combination of the features of the embodiment that can be conceived by those skilled in the art may also fall within the scope of the present invention as long as they include the spirit of the present invention.

[0068] Industrial Applicability

[0069] As described above, the present invention can be applied to an encoder used in a noisy environment.

Claims

1. An encoder, comprising: a ruler having scales arranged at a predetermined period along a measuring direction; a head, arranged to be opposite to the scale and to move relative to the scale along the measuring direction; as well as a calculation unit, for calculating the relative displacement between the ruler and the head, wherein the head includes an even number of detectors, the even number of detectors reading the scale and outputting a signal corresponding to the relative displacement between the scale and the head, The computing unit comprises: a phase calculation unit that calculates a phase based on the signals output by the respective detectors; and an averaging unit that averages the phases calculated by the phase calculation unit based on the signals output by the respective detectors, and wherein each of the even number of detectors is located at a position shifted from other adjacent detectors by an integer multiple of the scale period along the measurement direction, and The first signal output by half of the even-numbered detectors and the second signal output by the remaining half of the detectors have opposite polarities at the input of the phase calculation unit.

2. The encoder according to claim 1, wherein The encoder is an electromagnetic induction encoder, The scale includes a scale coil as the scale, and The head includes a transmitting coil that generates a magnetic flux to the scale coil and a receiving coil that receives a change in the magnetic flux from the scale coil as a detector.

3. The encoder according to claim 2, wherein: The transmission current is applied to the transmission coils of the half of the detectors and the transmission coils of the remaining half of the detectors among the even-numbered detectors in opposite directions.

4. The encoder according to claim 1, wherein The half detector and the remaining half detector output signals of the same polarity according to the relative displacement between the scale and the head, and In a propagation path from the detector to an input of the phase calculation unit in the calculation unit, the polarity of the second signal is opposite to that of the first signal.

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