Coding device or encoder and method for measuring a movement distance

Abstract

Encoders (1; 1A-1D), comprising: a scale (5; 5A-5D) provided on a measuring target part (W1), wherein markings (C; C2; C3) are arranged on the scale (5; 5A-5D); and a detector (3) which is provided on another measurement target part (W2) and is configured to detect an amount of relative motion with the scale (5; 5A-5D), wherein the detector (3) includes at least one rolling element (8) which is configured to roll in contact with the scale (5; 5A-5D) when the position is normal; and wherein the scale (5; 5A-5D) includes a detection unit (9; 9A; 9B) configured to detect a deviation of the position of the detector (3) relative to the scale (5; 5A-5D), wherein the detection unit (9; 9A; 9B) is configured to detect a deviation of the position of the detector (3) relative to the scale (5; 5A-5D) by detecting whether the rolling link (8) is in contact with the scale (5; 5A-5D).

Description

field of technology

[0001] This invention relates to an encoder and a method for measuring a moving distance, which detects a deviation of a position of a detector relative to a scale. Technical background

[0002] An encoder is known in the relevant art that detects the amount of relative movement between a pair of measurement targets that move relative to each other. The encoder includes a scale with markings and a detector with a reading unit that moves along the scale. The detector detects the amount of relative movement between the scale and the detector based on a signal read by the reading unit from the markings on the scale.

[0003] There is a problem with this encoder in that in a case where the detector is rotated relative to the scale or the like and the position of the detector with respect to the scale changes, the signal read by the reading unit also changes and, as a result, the accuracy with which the amount of relative movement is detected decreases.

[0004] In response to this problem, for example, a photoelectric encoder disclosed in JP 4 838 117 B2 includes a main scale (a scale) and a light-receiving unit (a detector), with a light-receiving element (a reading unit) that receives light (a signal) via the main scale, which detects an amount of relative movement of the main scale from the light received by the light-receiving element. The photoelectric encoder has a first lens and a second lens between the main scale and the light-receiving unit. The first lens and the second lens are identical, and the first lens and the second lens are oppositely arranged. The photoelectric encoder has an aperture between the first lens and the second lens.The opening is arranged at the position of the focal points of the first lens and the second lens and has a slit extending in a direction along which the light-receiving unit moves relative to the main scale and in a direction orthogonal to a vertical line on a surface of the scale on which the markings are arranged.

[0005] In the photoelectric encoder according to JP 4 838 117 B2, the fact that the second lens and the first lens are arranged opposite each other makes it possible to inversely correct aberrations that occur in the first lens due to the light-receiving unit being rotated relative to the main scale, or the like. Furthermore, since the aperture is located at the focal point of the second lens, the light emitted from the second lens to the light-receiving element can be made into parallel light.Therefore, the photoelectric encoder inversely corrects aberrations using the second lens and parallelizes the light using the aperture. Therefore, even in a case where the light-receiving unit is away from the main scale, for example, the same amount of light can be emitted to the light-receiving element as when the light-receiving unit is placed in the normal position (not away from the main scale). Therefore, the photoelectric encoder can stabilize the accuracy of detecting the amount of relative movement detected by the light-receiving unit and improve reliability.

[0006] DE 43 01 971 A1 discloses a position measuring device with at least one graduation track on a measuring standard, which is read by a scanning device movable in the measuring direction relative to the measuring standard, wherein means are integrated in the measuring device which determine angular changes between the scanning device and the measuring standard during the relative movement, and a correction value for the measured value can be formed from the determined angular change. Summary of the inventionTechnical problem

[0007] In the state of the art, a deviation of the position of the detector relative to the scale is detected based on a signal that is read by the reading unit of the detector.

[0008] In such a detector, the signal read by the reading unit does not change easily due to the lenses, the aperture, and the like, and therefore there is a problem that even in a case where there is a deviation in the position of the detector from the scale, this deviation cannot be detected.

[0009] An object of the invention is to provide an encoding device which can detect a deviation of the position of a detector relative to a scale. Solution to the task

[0010] This object is achieved according to the invention by the features of the independent claims. Preferred embodiments of the invention are the subject of the dependent claims.

[0011] According to one aspect, an encoder is provided that includes a scale and a detector. The scale is provided with markings arranged on the scale on one measurement target part, and the detector is provided on another measurement target part and configured to detect an amount of relative movement with the scale. The scale includes a detection unit configured to detect a deviation of a position (i.e., orientation or position) of the detector relative to the scale.

[0012] According to this aspect, the scale includes the detection unit that detects the attitude or orientation or position of the detector with respect to the scale, and therefore, even in a case where a deviation of the attitude or orientation of the detector with respect to the scale cannot be detected from a signal read by a reading unit, the deviation can still be detected.

[0013] The detector includes at least one rolling element or member configured to roll in contact with the scale when the attitude or orientation or position is normal, and the detection unit is configured to detect a deviation of the attitude or orientation or position of the detector relative to the scale by detecting whether the rolling element or member is in contact with the scale.

[0014] According to this configuration, the attitude or orientation or position of the detector relative to the scale is the normal attitude or orientation or position when the rolling element is in contact with a surface of the scale. However, the rolling element is lifted from the surface of the scale when the detector is arranged tilted relative to the scale in, for example, the roll direction, the pitch direction, or the yaw direction. It should be noted that the roll direction is specifically a rotation direction, with the arrangement direction of the marks on the scale being taken as an axis, the pitch direction is specifically a rotation direction, with the width direction of the scale being taken as an axis, and the yaw direction is specifically a rotation direction, with a direction orthogonal to the roll direction and the pitch direction being taken as an axis.

[0015] In particular, if the detector includes three rolling elements arranged, for example, in a substantially triangular shape, at least one of the three rolling elements is lifted from the surface of the scale when the detector is tilted relative to the scale in the roll direction, the pitch direction, or the yaw direction. Furthermore, all three rolling elements are lifted from the surface of the scale when the detector is tilted in a direction away from the scale (a gap direction).

[0016] In particular, the detection unit may detect the attitude or orientation or position of the detector relative to the scale as normal when the rolling element is in contact with the scale, and may detect the attitude or orientation or position of the detector relative to the scale as deviated when the rolling element is not in contact with the scale.

[0017] Consequently, the detection unit can detect a deviation in the attitude or orientation or position of the detector relative to the scale based on whether the rolling element is in contact with the scale, even if a deviation in the attitude or orientation or position of the detector relative to the scale cannot be detected based on a signal read by a reading unit.

[0018] It is preferable that the detector includes the rolling element(s), wherein the rolling element(s) is conductive; that the detection unit has a detection portion, wherein the detection portion is preferably in the form of a film and a voltage is applied; that the detection unit is configured to detect the rolling element as being in contact with the scale when the voltage applied to the detection portion changes; and that the detection unit is configured to detect the rolling element as not being in contact with the scale when the voltage applied to the detection portion does not change.

[0019] Here, the voltage applied to the sensing section changes when the conductive rolling element comes into contact with the sensing section.

[0020] In particular, the detection unit can detect the rolling element as being in contact with the scale and the attitude or orientation or position of the detector as normal when the voltage applied to the detection section changes, and can detect the rolling element as not being in contact with the scale and the attitude or orientation or position of the detector as deviated when the voltage applied to the detection section does not change. Consequently, due to the fact that the detector includes the conductive rolling element, the detection unit can detect a deviation of the attitude or orientation or position of the detector relative to the scale based on changes in the voltage at the detection section.In addition, the detection unit includes the detection section which is in the form of a film, and thus the encoder can achieve greater space saving than when a sensor or the like is provided for detecting the attitude or orientation or position of the detector with respect to the scale.

[0021] It is preferable that the scale includes at least one measuring range and at least one detection range, wherein the measuring range is a range in which an amount of relative movement is detected by the detector based on the markings, and the detection range is a range which includes the detection unit and is arranged outside the measuring range.

[0022] The detection portion of the detection unit, which is particularly in the form of a film, is formed of a metal such as chromium (Cr) and is subject to wear when it comes into contact with the rolling element. The encoder may experience detection malfunctions due to wear deposits generated by wear on the detection portion, which is in the form of a film.

[0023] In particular, the scale includes the measuring range and the detection range, and therefore the measurement of the amount of relative movement between the scale and the detector can be carried out in the measuring range, while the detection of a deviation of the attitude or orientation or position of the detector with respect to the scale can be carried out in the detection range.

[0024] In other words, the detector moves within the measuring range during measurement and does not cause the rolling element to come into contact with the detecting section, and thus the generation of wear deposits on the detecting section due to wear can be prevented.

[0025] In addition, the detection area is arranged in particular outside the measuring area, and thus the encoder can detect a deviation of the position or orientation or position of the detector with respect to the scale by moving the detector to the detection area when detecting the state of the detector.

[0026] It is preferable that the detector includes a plurality of rolling elements; that the scale includes a detection position for the detection unit for detecting a deviation of the attitude or orientation or position of the detector; and that the detection unit includes a plurality of detection sections arranged in the detection position at positions substantially coincident with or corresponding to the plurality of rolling elements.

[0027] According to this configuration, the detection unit includes the plurality of detection sections arranged in the detection position at positions corresponding to the positions of the plurality of rolling elements. Thus, the plurality of detection sections provided in the detection position correspond one-to-one to the plurality of rolling elements. The detection unit can simultaneously detect the states of each of the rolling elements by moving the detector to the detection position so that the plurality of rolling elements come into contact with the plurality of detection sections.

[0028] Furthermore, when the attitude or orientation or position of the detector relative to the scale deviates, the encoder can detect which of the plurality of rolling elements is not in contact with the scale by using the plurality of detection sections provided in the detection position. The encoder can detect how the attitude or orientation or position of the detector relative to the scale is tilted relative to the scale by identifying the rolling elements that are not in contact with the scale.

[0029] It is preferable that the detector includes a first rolling element or member and a second rolling element or member; that the scale includes a first detection position and a second detection position for detecting, by the detection unit, a deviation in the location or orientation or position of the detector; that the detection unit includes a first detection section provided at a position substantially coinciding with or corresponding to the first rolling element only when the detector is positioned at the first detection position, and a second detection section provided at a position substantially coinciding with or corresponding to the second rolling element only when the detector is positioned at the second detection position.

[0030] Furthermore, a common voltage is preferably applied to the first detection section and the second detection section.

[0031] If the configuration is such that all of the multiple rolling elements are in contact with the multiple detection sections at once, individual voltages are applied to each of the multiple detection sections. Even if a rolling element is not in contact with the scale, the voltage changes because one of the other rolling elements is in contact with one of the multiple detection sections. Therefore, the detection unit cannot detect the contact of the rolling element.

[0032] Specifically, the first detection section, which is arranged in a position that coincides only with the first rolling element when the detector is arranged at the first detection position, and the second detection section, which is arranged in a position that coincides only with the second rolling element when the detector is arranged at the second detection position, are arranged in the detection unit. Since only the first detection section and the first rolling element are in contact in the first detection position and only the second detection section and the second rolling element are in contact in the second detection position, the detection unit can detect which of the rolling elements is not in contact with the scale, even in a case where individual voltages are not applied to each of the plurality of detection sections.

[0033] The encoder can detect the manner in which the attitude or orientation or position of the detector relative to the scale is tilted by identifying the rolling elements that are not in contact with the scale. Furthermore, the first sensing section and the second sensing section can detect the attitude or orientation or position of the detector relative to the scale using a common applied voltage. Consequently, it is not necessary to apply individual voltages to each of the multiple sensing sections, and thus the encoder can achieve cost reduction.

[0034] Here, it is preferable that the rolling element is grounded via the detector, that the detection unit includes a conductive layer having conductivity and formed on the scale along the arrangement direction of the marks; and that the detection portion is formed to extend from the conductive layer in a direction intersecting with the arrangement direction of the marks on the scale.

[0035] The scale, which is or may be made of glass or the like, can be charged while the rolling elements roll in contact with the surface of the scale. Discharge of the charge in the scale can cause disturbances in the detector's electrical system (voltages, frequencies, and the like) and cause noise. Furthermore, when the scale is charged, dust can easily adhere to the scale, the detector, or the like, which can cause detection errors and the like.

[0036] However, according to this configuration, the rolling elements are grounded via the detector, and thus a charge can be easily discharged in the scale by bringing the rolling elements and the detecting sections into contact with each other.

[0037] According to another aspect, there is provided a method for measuring a distance of movement between at least a pair of measurement target parts, comprising: providing a scale on one measurement target part, wherein markings are arranged on the scale; providing a detector on another measurement target part and configured to detect an amount of relative movement with the scale; and detecting a deviation of an attitude (ie, orientation or position) of the detector with respect to the scale.

[0038] According to the invention, if it is detected that at least one rolling element of the detector is in contact with the scale, it is determined that the attitude of the detector is normal; and a deviation of the attitude or orientation or position of the detector with respect to the scale is determined by detecting whether the rolling element is in contact with the scale. Brief description of the drawings

[0039] These and other objects, features, and advantages of this invention will become more apparent upon reading the following detailed description of preferred embodiments and the accompanying drawings. It should be noted that while embodiments are described separately, individual features thereof may be combined to form further embodiments. Fig. 1A and Fig. 1B are a front view and a cross-sectional view of an encoder according to a first embodiment. Fig. 2 is a front view of a scale and a detection unit of the encoder. Fig. 3 is a diagram showing a relationship between a detector and a detection position in the encoder. Fig. Figure 4 is a block diagram showing the coding device. Fig. 5 is a flowchart illustrating a control method of the encoder. Fig. 6 is a front view of a scale and a detection unit of an encoder according to a second embodiment. Fig. 7 is a diagram showing a relationship between a detector and a first detection position in the encoder. Fig. 8 is a diagram showing a relationship between a detector and a second detection position in the encoder. Fig. 9 is a diagram showing a relationship between a detector and a third detection position in the encoder. Fig. 10 is a diagram showing changes in the voltage applied to detecting sections of the encoder. Fig. 11 is a block diagram illustrating the encoder. Fig. 12 is a flowchart illustrating a control method of the encoder. Fig. 13 is a diagram showing a detection unit of a scale according to a first modified example. Fig. 14 is a diagram showing a detection unit of a scale according to a second modified example. Fig. 15 is a diagram showing a detection unit of a scale according to a third modified example. Description of embodiments

[0040] A first specific embodiment of the invention is described below with reference to the drawings.

[0041] The Fig. 1A and Fig. 1B are a front view and a cross-sectional view of an encoder according to the first specific embodiment. In particular, Fig. 1A is a front view of a coding device 1, and Fig. Figure 1B is a cross-sectional view of the encoder taken along section AA in Fig. 1A viewed from.

[0042] As in the Fig. 1A and Fig. 1B, the encoder 1 is, in particular, a measuring device that measures a moving distance between a pair of measurement target parts W1 and W2 that move relative to each other or are displaced relative to each other. The encoder 1 is, for example, a linear encoder with electromagnetic induction.

[0043] The encoding device 1 includes an encoder main unit 2 and a detector 3, which is movably arranged in the encoder main unit 2. In the encoding device 1, the two measurement target parts W1 and W2 are mounted by attaching one measurement target part W1 to the encoder main unit 2 and the other measurement target part W2 to the detector 3.

[0044] The encoder main unit 2 consists of or includes a (particularly long or elongated) scale frame 4 and a scale 5 arranged in, on, or on the scale frame. The scale frame 4 is formed, in particular, from an extrusion molded part made of an aluminum alloy or the like and / or is, in particular, formed to have an overall substantially hollow rectangular shape.

[0045] In the following descriptions and in the drawings, a direction corresponding to a longitudinal direction of the scale frame 4 and / or a moving direction of the detector (particularly both) may be referred to as an X direction; a width direction of the scale frame 4 (a depth direction) orthogonal to the X direction may be referred to as a Y direction; and a vertical direction orthogonal to both the X and Y directions may be referred to as a Z direction.

[0046] The detector 3 includes a detector main unit 6, which is arranged (in particular outside) on the scale frame 4 and / or is attached to the other measurement target part W2, and a detection unit 7, which is arranged in particular such that it extends from the detector main unit 6 into the scale frame 4.

[0047] The detection unit 7 includes a reading unit 7a, which reads or detects an amount of relative movement between the detector 3 and the scale 5, and one or more bearings 8 connected to the detection unit 7, which bearings 8 are in particular rolling elements that come into contact with a surface(s) of the scale 5 and roll when the detector 3 is in a normal attitude or orientation or position relative to the scale 5.

[0048] The reading unit 7a specifically includes an excitation coil and a detection coil. When the encoder 1 applies current to the excitation coil, the excitation coil generates a magnetic flux and causes a magnetic flux to arise in markings C that are substantially opposite or facing the excitation coil. The magnetic flux generated in the markings C also causes a magnetic flux to arise in the detection coil of the reading unit 7a substantially opposite the markings C. The detection coil reads an amount of displacement in the magnetic flux generated in the markings C and detects the amount of relative displacement between the detector 3 and the scale 5.

[0049] Fig. Figure 2 is a front view showing the scale and a detecting unit of the encoder. In particular, Fig. 2 a diagram showing scale 5 from one side of the -Y direction.

[0050] As in Fig. As shown in Figure 2, the scale 5 includes a (particularly long or elongated) scale base element 5a, which is particularly made of glass or the like, a detection unit 9, which detects a deviation in the position or orientation or position of the detector 3 relative to the scale 5, and the markings C (which are particularly made of coils or comprise coils) arranged at a constant spacing in the longitudinal direction (the X direction) of the scale base element 5a. The markings C are particularly formed from a conductor, such as copper (Cu).

[0051] The detection unit 9 has one or more detection sections 10 to which a voltage is applied. Specifically, the detection sections 10 include detection sections 11, 12, and 13, which are formed from a conductor such as chromium (Cr) in the form of a film. The detection sections 10 are described in detail below.

[0052] The scale 5 further includes a measuring area 20, at which the amount of relative displacement is detected by the detector 3 from the markings C, and a detection area 30, which includes the detection unit 9 and is arranged outside the measuring area 20 (or independently of it).

[0053] In particular, the measuring area 20 is formed continuously along the longitudinal direction (the X-direction) of the scale base element 5a. As such, the detector 3 performs the measurement within the measuring area 20 without passing through the detection area 30.

[0054] The detection area 30 includes a detection position 40 for detecting a deviation of the attitude or orientation or position of the detector 3 using the detection unit 9 and / or is formed in particular at an end portion on one end side (the +X direction side) of the scale base member 5a in the longitudinal direction.

[0055] It should be noted that the detection area 30 may be formed only at an end portion on one end side (the +X direction side) of the scale base member 5a in the longitudinal direction, or only at or near an end portion on the other end side (the -X direction side) of the scale base member 5a in the longitudinal direction, or at or near both ends of the scale base member 5a.

[0056] Fig. 3 is a diagram showing a relationship between the detector and the detection position in the encoder.

[0057] As in Fig. 3, the bearings 8 comprise in particular one or more conductive bearings 8a, 8b, 8c, 8d and 8e. The bearings are connected via the detector 3 and / or the other measuring target part W2 (see Fig. 1B) earthed.

[0058] Specifically, the bearing 8a is disposed at a position where the bearing 8a rolls along the marks C. The bearing 8b is disposed at a position where the bearing 8b rolls along the marks C and rolls substantially along the same path as the bearing 8a. The bearing 8c is disposed in a position where it pinches the marks C and substantially opposite the bearings 8a and 8b and rolls along a path parallel to the paths of the bearings 8a and 8b. The bearing 8d is disposed at a position where the bearing 8e rolls in contact with a side surface (on the -Z direction side) of the scale base member 5a. The bearing 8e is disposed at a position where the bearing 8d rolls in contact with the side surface (on the -Z direction side) of the scale base member 5a and rolls substantially along the same path as the bearing 8d.

[0059] Specifically, the detecting portion 11 is arranged at a position that coincides with or corresponds to the position of the bearing 8a when the detecting unit 7 (the detector 3) stops at the detecting position 40.

[0060] The detection section 12 is arranged at a position which coincides with or corresponds to the position of the bearing 8b when the detection unit 7 stops at the detection position 40.

[0061] The detection section 13 is arranged at a position which coincides with or corresponds to the position of the bearing 8c when the detection unit 7 stops at the detection position 40.

[0062] The engagement portions 11, 12, and 13 are formed at positions and / or with sizes that allow reliable contact with the bearings 8a, 8b, and 8c within the engagement position 40. Specifically, the engagement portions 11, 12, and 13 are formed with lengths that allow the bearings 8a, 8b, and 8c to roll a certain distance in the X direction.

[0063] The detection unit 9 detects a deviation in the attitude or orientation or position of the detector 3 relative to the scale 5 by moving the detection unit 7 to the detection position 40 of the detection area 30 and / or detecting whether the bearings 8 are in contact with the scale 5. Specifically, the detection unit 9 detects the bearings 8 as being in contact with the scale 5 when a voltage applied to the detection sections 10 changes, and detects the bearings 8 as not being in contact with the scale 5 when the voltage applied to the detection sections 10 does not change. In this embodiment, the bearings 8 are grounded via the detector 3 and / or the other measurement target part W2, and thus the voltage changes to 0 when the bearings 8 and the detection sections 10 are in contact.

[0064] Voltages are applied to the sensing section(s) 11, 12, and / or 13. For example, if only the bearing 8a is not in contact with the scale 5, the voltages applied to the sensing sections 12 and 13 change to 0, while the voltage applied to the sensing section 11 remains unchanged. Consequently, the sensing unit 9 can detect which of the bearings 8 are not in contact with the scale 5 and, by extension, can detect or determine how the position of the detector 3 is tilted relative to the scale 5 based on changes in the voltage applied to the sensing sections 10.

[0065] Fig. Figure 4 is a block diagram showing the coding device.

[0066] As in Fig. As shown in Figure 4, the coding device 1 includes a position determining means 50 which determines the position of the detector 3 relative to the coding device 1, and a display unit 60 which displays information.

[0067] The two measuring target parts W1 and W2, to which the coding device 1 is attached (see Fig. 1B), contain a control unit or regulating unit 100, which controls or regulates the two measurement target parts W1 and W2, and a drive unit 70, which is controlled or regulated by the control unit 100.

[0068] The drive unit 70 is specifically a motor or includes a motor or the like which moves the scale 5 and the detector 3, which are fixed to the pair of measurement target parts W1 and W2, relative to each other.

[0069] The control unit 100 controls the drive unit 70 based on detection results and the like from the position detecting means 50 of the encoder 1. The control unit 100 controls the drive unit 70 to drive the other measurement target part W2 to which the detector 3 is attached and to move the detector 3 (the detection unit 7).

[0070] The position determination means 50 includes a storage unit 51 which stores detection results from the detection unit 9 of the scale 5, a position determination unit 52 which determines whether the detection unit 7 has moved to the detection position 40, and / or a position determination unit 53 which determines the position or orientation or position of the detector 3 relative to the scale 5 based on the detection results from the detection unit 9.

[0071] Specifically, the position determination unit 52 determines whether the detection unit 7 has moved to the detection position 40 by reading the marks C. Specifically, the position determination unit 52 compares a measurement value read by the reading unit 7a with detection position information corresponding to the detection position 40, which has been previously stored in the storage unit 51 or the like, and determines whether the detection unit 7 has moved to the detection position 40. Note that the position determination unit 52 can determine or confirm whether the detection unit 7 has moved to the detection position 40 by reading an alignment mark or the like provided on the scale 5.

[0072] The position determination unit 53 determines from the state of the contact between the bearings 8 and the detection sections 10 detected by the detection unit 9 whether the position or orientation or position of the detector 3 is normal or deviated with respect to the scale 5.

[0073] The display unit 60 displays a result of the determination made by the position detection unit 53, specifically using a light-emitting diode (LED), a display device, or the like. In this embodiment, the display unit 60 is comprised of a blue LED and a red LED (not shown). The blue LED lights up when the position of the detector 3 relative to the scale 5 is normal, and the red LED lights up when the position of the detector 3 relative to the scale 5 is abnormal.

[0074] Fig. 5 is a flowchart illustrating a control method of the encoder.

[0075] Operations by which the encoder 1 detects a deviation in the position of the detector 3 are carried out on the basis of Fig. 5 described.

[0076] As in Fig. 5, the control unit 100 first performs a start step in which the other measurement target part W2 is driven using the drive unit 70 and the detection unit 7 of the encoder 1 is moved to the detection position 40 in the detection area 30 (step ST01).

[0077] Then, the position determination unit 52 determines whether the detection unit 7 has substantially moved to the detection position 40 (step ST02). If the position determination unit 52 determines that the detection unit 7 has not moved to the detection position 40 (NO in step ST02), the control unit 100 drives the drive unit 70 and moves the detection unit 7 until it determines that the detection unit 7 has moved to the detection position 40. If the position determination unit 52 determines that the detection unit 7 has moved to the detection position 40 (YES in step ST02), the control unit 100 performs a stop step of stopping the drive unit 70 so that the detection unit 7 stops at the detection position 40 (step ST03).

[0078] Then, the detection unit 9 performs a position determination step in which the position of the detector 3 relative to the scale 5 is determined, specifically, by detecting whether the bearings 8a, 8b, and 8c included in the stopped detection unit 7 are in contact with the detection sections 11, 12, and 13 provided at the detection position 40, respectively (step ST04). The detection result from the detection unit 9 is stored in the storage unit 51.

[0079] The position determination unit 53 determines, in particular based on the detection result stored in the storage unit 51, whether the bearings 8a, 8b and 8c are in contact with the detection sections 11, 12 and 13, respectively.

[0080] When the position detecting unit 53 detects that the bearings 8a, 8b and 8c are in contact with the detecting sections 11, 12 and 13, respectively, the display unit 60 lights the blue LED to indicate that the position of the detector 3 relative to the scale 5 is normal (step ST05).

[0081] However, when the position detecting unit 53 detects that one of the bearings 8a, 8b, and 8c is not in contact with the detecting portions 11, 12, and 13, respectively, the display unit 60 lights up the red LED to indicate that the position of the detector 3 deviates from the scale 5 (step ST05).

[0082] It should be noted that, as a position detection step, the position detection unit 53 can detect the manner in which the attitude or orientation or position of the detector 3 is deviated from the scale 5 based on the bearings 8a, 8b and 8c and detection sections 11, 12 and 13 which are not in contact with each other as detected by the detection unit (step ST04).

[0083] Specifically, for example, when the detection unit 9 detects that the bearings 8a and 8b are in contact with the detection sections 11 and 12, but the bearing 8c is not in contact with the detection section 13, the attitude determination unit 53 determines that the detector 3 is in a position where the detector 3 is tilted relative to the scale 5 in the rolling direction. Similarly, when the detection unit 9 detects that the bearings 8b and 8c are in contact with the detection sections 12 and 13, but the bearing 8a is not in contact with the detection section 11, the attitude determination unit 53 determines that the detector 3 is in a position where the detector 3 is tilted relative to the scale 5 in the tilting direction.

[0084] The result of the determination made by the position detection unit 53 is displayed by the display unit 60 such as a liquid crystal display (LCD) (step ST05).

[0085] Accordingly, an encoder is provided that can detect a deviation in the position of a detector relative to a scale. The encoder 1 includes a scale 5 and a detector 3, wherein the scale 5 is arranged at one measurement target part and marks C are arranged on the scale 5, and the detector 3 is arranged at another measurement target part and is configured to detect an amount of relative movement with the scale 5. The scale 5 includes a detection unit 9 that detects the position of the detector 3 relative to the scale 5, and thus, even in a case where a deviation in the position of the detector 3 relative to the scale 5 cannot be detected based on a change in a signal read by a reading unit 7a, the deviation can still be detected.

[0086] According to this specific embodiment, the following effects can be achieved. (1) The scale 5 includes the detection unit 9 which detects the position of the detector 3 with respect to the scale 5, and thus even in a case where a deviation of the position of the detector 3 with respect to the scale 5 cannot be detected from a change in a signal read by the reading unit 7a, the deviation can still be detected. (2) The detection unit 9 can detect a deviation of the position of the detector 3 with respect to the scale 5 based on whether the bearings 8 are in contact with the scale 5, even if a deviation of the position of the detector 3 with respect to the scale 5 cannot be detected based on a change in a signal read by the reading unit 7a. (3) Since the detector 3 includes the bearing(s) 8, which are in particular conductive rolling elements, the detection unit 9 can detect a deviation of the position of the detector 3 with respect to the scale 5 based on changes in the voltage at the detection section(s) 10. (4) The detection unit 9 particularly includes the detection section(s) in the form of a film, and thus the encoder 1 can achieve greater space saving than in a case where a sensor or the like is provided for detecting the position of the detector with respect to the scale. (5) The detector 3 moves within the measuring range 20 during the measurement and does not cause the bearing(s) 8 to come into contact with the detecting section(s) 10, and thus the generation of wear deposits due to wear on the detecting sections 10 can be avoided. (6) The detection area 30 is arranged in particular outside the measuring area 20, and thus the coding device 1 can detect a deviation of the position of the detector 3 with respect to the scale 5 by moving the detector 3 in the detection area 30 when the state of the detector 3 is detected. (7) Specifically, the detection unit 9 includes the plurality of detection sections 11 to 13 provided at positions that coincide or correspond to the positions of the plurality of bearings 8a to 8c, respectively, in the detection position 40, and thus the plurality of detection sections 11 to 13 provided in the detection position 40 correspond one-to-one to the plurality of bearings 8a to 8c. The detection unit 9 can detect the states of the bearings 8a to 8c simultaneously by moving the detector 3 to the detection position 40 so that the plurality of bearings 8a and 8c come into contact with the plurality of detection sections 11 to 13. (8) When the attitude or orientation or position of the detector 3 with respect to the scale 5 is deviated, the encoder 1 can detect which of the plurality of bearings 8a to 8c is not in contact with the scale 5 using the plurality of detecting sections 11 to 13 provided in the detecting position 40. By identifying the bearings 8a to 8c that are not in contact with the scale 5, the encoder 1 can detect how the attitude of the detector 3 with respect to the scale 5 is tilted with respect to the scale 5. Second embodiment

[0087] A second specific embodiment of the invention will be described below based on the drawings. Note that in the following descriptions, the same reference numerals are assigned to parts already described, and descriptions thereof are omitted.

[0088] In this particular embodiment, the bearing 8a corresponds to a first rolling element; the bearing 8c corresponds to a second rolling element; and the bearing 8b corresponds to a third rolling element.

[0089] Fig. 6 is a front view of a scale and a detection unit of an encoder according to the second embodiment.

[0090] The detection unit 9 of the encoder 1 according to the first specific embodiment includes the detection sections 10, which are arranged at positions that correspond one-to-one with the bearings 8 in the detection position 40.

[0091] As in Fig. 6, a detection unit 9A of an encoder 1A according to this specific embodiment differs from the detection unit 9 according to the first embodiment in that the detection unit 9A further includes a conductive layer D having electrical conductivity and marks C2 formed on the conductive layer D and consisting of coils or comprising coils arranged at a constant pitch, and / or in that detection sections 10A are formed extending from the conductive layer D.

[0092] Specifically, the conductive layer D is a conductor or comprises a conductor such as chromium (Cr), and / or is formed in a substantially linear shape on a surface on the -Y direction side of a scale 5A along the longitudinal direction (the X direction).

[0093] The markings C2 are formed from a conductor made of another conductive material, such as copper (Cu), which has a higher conductivity than the conductive layer D. It should be noted that any conductor can be used for the conductive layer D and the markings C2, as long as the markings C2 have a higher conductivity than the conductive layer D.

[0094] The detection sections 10A are formed to extend from the conductive layer D in a direction (the Z direction) which intersects with an arrangement direction (the X direction) of the marks C2 of the scale 5A.

[0095] The measuring area 20 of the scale 5 according to the first embodiment includes the marks C, and the detection area 30 includes the detection position 40 at which the plurality of detection sections 11, 12 and 13 are arranged.

[0096] A measuring region 20A of the scale 5A according to this embodiment differs from that of the first embodiment in that the measuring region 20A includes marks C2 formed on the conductive layer D. Another difference from the first embodiment is specifically that a detection region 30A includes a first detection position 41 corresponding to the bearing 8a corresponding to the first rolling element, a second detection position 42 corresponding to the bearing 8c corresponding to the second rolling element, and a third detection position 43 corresponding to the bearing 8b corresponding to the third rolling element.

[0097] In the first embodiment, a voltage is applied to each of the plurality of sensing sections 11, 12, and 13. The plurality of sensing sections 14, 15, and 16 according to this embodiment differ from the first embodiment in that a voltage is applied to them collectively through the conductive layer D. In other words, in this embodiment, a voltage is applied to the conductive layer D.

[0098] Specifically, the first detection position 41 includes a first detection portion 14 provided at a position corresponding only to the bearing 8a corresponding to or coinciding with the first rolling element. The second detection position 42 includes a second detection portion 15 provided at a position corresponding only to the bearing 8c corresponding to or coinciding with the second rolling element. The third detection position 43 includes a third detection portion 16 provided at a position corresponding only to the bearing 8b corresponding to or coinciding with the third rolling element.

[0099] The Fig. 7 to 9 are diagrams showing relationships between the detector and the detection position in the encoder, and Fig. 10 is a diagram illustrating changes in the voltage applied to the detecting sections of the encoder.

[0100] In particular, Fig. 7 is a diagram illustrating the contact between the bearing 8a corresponding to the first rolling element and the first detecting portion 14 at the first detecting position 41; Fig. Fig. 8 is a diagram illustrating the contact between the bearing 8c corresponding to the second rolling element and the second detecting portion 15 at the second detecting position 42; and Fig. Fig. 9 is a diagram illustrating the contact between the bearing 8b corresponding to the third rolling element and the third detecting portion 16 at the third detecting position 43. As for (A), (B) and (C) in Fig. 10, (A) corresponds to the Fig. 7, (B) corresponds to the Fig. 8, and (C) corresponds to the Fig. 9. Changes in the voltage applied to the conductive layer D when the bearings 8 and the detecting sections 10A come into contact are calculated based on the Fig. 7 to 10 described.

[0101] As in Fig. 7, the detection unit 7 is first moved or shifted in the +X direction along the scale 5A. When the bearing 8a, which corresponds to the first rolling element, and the first detecting section 14 come into contact, the voltage applied to the conductive layer D changes to 0 when the position of the detector 3 with respect to the scale 5A is normal, as shown by (A) in Fig. 10 is displayed.

[0102] Since the bearings 8 are grounded via the detector 3 and the other measurement target part W2, the conductive layer D is grounded when the bearings 8 and the conductive layer D are in contact. The voltage applied to the conductive layer D changes to 0 due to the grounding while the bearings 8 and the conductive layer D (the detection sections 10A) are in contact. The charge in the scale 5A is thus discharged via the conductive layer D.

[0103] As in Fig. 8, the detection unit 7 is then moved to the second detection position 42. When the bearing 8b, which corresponds to the second rolling element, and the second detection section 15 come into contact, the voltage applied to the conductive layer D changes to 0 when the position of the detector 3 is normal to the scale 5A, as shown by (B) in Fig. 10 is displayed.

[0104] As in Fig. 9, the detection unit 7 is then moved or shifted to the third detection position 43. When the bearing 8c, which corresponds to the third rolling element, and the third detection section 16 come into contact, the voltage applied to the conductive layer D changes to 0 when the position of the detector 3 is normal to the scale 5A, as shown by (C) in Fig. 10 is displayed.

[0105] Fig. 11 is a block diagram showing the encoder.

[0106] As in Fig. As shown in Fig. 11, the encoder 1A according to this embodiment has substantially the same configuration as that of the first embodiment, except for the scale and a position detecting means 50A.

[0107] The detection unit 9A included in the scale 5A further includes the first detection section 14, the second detection section 15 and / or the third detection section 16.

[0108] A position detection unit 52A of the position detection means 50A determines whether the detection unit 7 has moved to each of the first detection position 41, the second detection position 42, and the third detection position 43. A position detection unit 53A determines whether the attitude or orientation or position of the detector 3 relative to the scale 5A is normal or abnormal, specifically based on the state of contact between the bearings 8 and the detection sections 10A, which is detected by the detection unit 9A at the first detection position 41, the second detection position 42, and the third detection position 43.

[0109] Fig. 12 is a flowchart illustrating a control method of the encoder.

[0110] Operations by which the encoder 1A detects a deviation in the position or orientation or position of the detector 3 are determined by Fig. 12 described.

[0111] As in Fig. 12, the control unit 100 first performs a start step in which the other measurement target part W2 is driven using the drive unit 70 and the detection unit 7 of the encoder 1A is moved to the detection positions 41 to 43 within the detection range 30A (step ST11).

[0112] Then, the position determination unit 52A determines whether the detection unit 7 has moved to the first detection position 41 (step ST12). If the position determination unit 52A determines that the detection unit 7 has not moved to the first detection position 41 (NO in step ST12), the control unit 100 drives the drive unit 70 and moves or displaces the detection unit 7 until it determines that the detection unit 7 has moved to the first detection position 41. In the case where the position determination unit 52A determines that the detection unit 7 has moved to the first detection position 41 (YES in step ST12), the control unit 100 drives the drive unit 70 and moves or displaces the detection unit 7 past the first detection position 41 and to the second detection position 42.At this time, a detection result indicating whether the first detection portion 14 arranged in the first detection position 41 has come into contact with the bearing 8a corresponding to the first rolling element is stored in the storage unit 51.

[0113] Then, the position determination unit 52A determines whether the detection unit 7 has moved to the second detection position 42 (step ST13). If the position determination unit 52A determines that the detection unit 7 has not moved to the second detection position 42 (NO in step ST13), the control unit 100 drives the drive unit 70 and moves or displaces the detection unit 7 until it determines that the detection unit 7 has moved to the second detection position 42. If the position determination unit 52A determines that the detection unit 7 has moved to the second detection position 42 (YES in step ST13), the control unit 100 drives the drive unit 70 and moves or displaces the detection unit 7 past the second detection position 42 and to the third detection position 43.At this time, a detection result indicating whether the second detection portion 15 arranged in the second detection position 42 has come into contact with the bearing 8c corresponding to the second rolling element is stored in the storage unit 51.

[0114] Then, the position determination unit 52A determines whether the detection unit 7 has moved to the third detection position 43 (step ST14). If the position determination unit 52A determines that the detection unit 7 has not moved to the third detection position 43 (NO in step ST14), the drive unit 70 is driven, and the detection unit 7 is moved or shifted until it is determined that the detection unit 7 has moved to the third detection position 43. If the position determination unit 52A determines that the detection unit 7 has moved to the third detection position 43 (YES in step ST15), the control unit 100 performs a stop step in which the drive unit 70 is stopped so that the detection unit 7 stops at the third detection position 43 (step ST15).

[0115] At this time, a detection result indicating whether the third detection portion 16 arranged in the third detection position 43 has come into contact with the bearing 8b is stored in the storage unit 51.

[0116] Then, the attitude detection unit 53A performs an attitude or orientation or position detection step of determining whether the bearings 8a, 8b and 8c are in contact with the detection portions 14, 15 and 16 at the first detection position 41, the second detection position 42 and the third detection position 43, respectively, based on the detection results stored in the storage unit (step ST16).

[0117] When the attitude detecting unit 53A detects that the bearings 8a, 8b, and 8c are in contact with the detecting portions 14, 15, and 16, respectively, the display unit 60 lights the blue LED to indicate that the attitude or orientation or position of the detector 3 relative to the scale 5A is normal (step ST17).

[0118] However, if the position detecting unit 53A detects that one of the bearings 8a, 8b, and 8c is not in contact with the detecting portions 14, 15, and 16, respectively, the display unit 60 lights the red LED to indicate that the attitude or orientation or position of the detector 3 is deviated from the scale 5A (step ST17).

[0119] It should be noted that, as a position detection step, the position detection unit 53A can detect the manner in which the position or orientation or position of the detector 3 is deviated from the scale 5, starting from the bearings 8a, 8b and 8c and detection sections 14, 15 and 16 which are not in contact as detected by the detection unit 9A (step ST16), as described in the first embodiment,

[0120] According to this embodiment, in addition to the same effects as those described in (1) to (6) in the first embodiment, the following effects can be achieved. (9) Even in a case where no individual voltages are applied to each of the plurality of detection sections 10A, in a case where only the first detection section 14 and the bearing 8a corresponding to the first rolling element are in contact at the first detection position 41, and only the second detection section 15 and the bearing 8c corresponding to the second rolling element are in contact at the second detection section 42, the detection unit 9A can identify which of the bearings 8 is not in contact with the scale 5A. (10) By identifying the bearings 8 that are not in contact with the scale 5A, the encoder 1A can detect how the attitude or orientation or position of the detector 3 is tilted relative to the scale 5A. (11) The first detecting section 14 and the second detecting section 15 can detect the attitude or orientation or position of the detector 3 relative to the scale from a common voltage applied. Therefore, it is not necessary to apply individual voltages to each of the plurality of detecting sections 10A, and thus the encoder 1A can achieve a cost reduction. (12) The bearings 8 are grounded to the other measurement target part W2 via the detector 3, and thus the charge of the scale 5A can be discharged simply by bringing the bearings 8 and the detecting section 10A (the conductive layer D) into contact with each other. Modified examples of embodiments

[0121] It should be noted that the invention is not limited to the above embodiments, and variations, improvements and the like which are within the scope within which the object of the invention can be achieved are also included in the invention.

[0122] For example, while the above embodiments describe cases where the invention is applied to encoders 1 and 1A, which are electromagnetic induction linear encoders, the encoders may also be photoelectric linear encoders. In other words, it is sufficient for encoders 1 and 1A to include a detector movably disposed in the encoder main unit 2, and the type, detection system, and the like of the detector are not specifically limited.

[0123] The encoders 1 and / or 1A may be rotary encoders instead of linear encoders. In this case, the detector moves along a circumferential direction of a scale base member, and a detection area is provided in a portion of a measuring area formed along the circumferential direction of the scale base member.

[0124] In the above embodiments, the detection unit 9 or 9A detects the attitude or orientation or position of the detector 3 relative to the scale 5 or 5A by bringing the bearings 8 into contact with the detection sections 10 or 10A. However, the detection unit may be any unit capable of detecting the attitude or orientation or position of the detector relative to the scale and may, for example, be a sensor such as a distance sensor.

[0125] In addition, although the bearings 8 are used as the rolling member in the above embodiments, any configuration may be used as long as the detection unit 9 or 9A is brought into contact with the detection sections 10 or 10A by moving the detection unit 7.

[0126] In the above embodiments, the detection unit includes the detection sections 10 or 10A for detecting whether contact is made with the bearings 8; however, the detection sections may be sensors such as pressure sensors, contactors, or strain gauges. In other words, the detection unit can have any configuration as long as a deviation in the attitude or orientation or position of the detector relative to the scale can be detected by detecting whether a bearing, which is a rolling element, is in contact with the scale.

[0127] In the above embodiments, the voltage applied to the detection sections 10 or 10A changes to 0 by bringing the bearings 8 into contact with the detection sections 10 or 10A, and the detection unit 9 or 9A detects the attitude or orientation or position of the detector 3 with respect to the scale 5 or 5A from this. However, the detection unit can detect the attitude or orientation or position of the detector 3 from any value as long as the voltage applied to the detection sections changes by bringing the rolling element into contact with the detection sections. In other words, the detection sections 10 or 10A do not need to be grounded via the detector 3 and the other measurement target part W2.

[0128] In the above embodiments, the detection area 30 or 30A is formed at an end portion on one end side (the +X direction side) of the scale 5 or 5A in the longitudinal direction thereof; however, the detection area 30 or 30A may be formed in a central portion of the measuring area 20. Furthermore, the detection area 30 or 30A may be formed over a wider area than the measuring area 20, or the detection area 30 or 30A and the measuring area 20 may be alternately arranged.

[0129] Fig. 13 is a diagram showing a detection unit of a scale according to a specific first modified example.

[0130] In the second specific embodiment, the conductive layer D of the encoder 1A is formed over both the measuring area 20A and the detection area 30A.

[0131] As in Fig. However, as shown in Fig. 13, a conductive layer D2 of an encoder 1B according to the first modified example may be formed in a detection area 30B of scale 5B so as to connect the detection sections 10A while omitting the part corresponding to the marks C2. In other words, when the voltage is applied to the detection sections 10A together, the conductive layer can be formed in any manner as long as the conductive layer is not segmented.

[0132] Fig. 14 is a diagram showing a detection unit of a scale according to a specific second modified example.

[0133] In the second specific embodiment, the markings C2 of a scale 5A are formed in both the measuring area 20A and the detecting area 30A.

[0134] As in Fig. However, as shown in Fig. 14, marks C3 of an encoder 1C according to the second modified example may be arranged in a detection area 30C. Furthermore, when the encoder is a photoelectric linear encoder, the marks C3 arranged in the detection area 30C may be embedded or the like, so that they do not function.

[0135] Fig. 15 is a diagram showing a detection unit of a scale according to a specific third modified example.

[0136] In the previous embodiments, the detection area 30 or 30A in the scale 5 or 5A includes the detection positions 40 or 41 to 43, but the detection area does not need to include a detection position.

[0137] As in Fig.15, the detection unit 9B of an encoder 1D according to the third modified example includes detection sections 10B formed to extend from a conductive layer D3 in a direction (the Z direction) intersecting with the arrangement direction (the X direction) of the marks C2 of a scale 5D.

[0138] The detection sections 10B include a first detection section 17 formed from the conductive layer D3 in the +Z direction and a second detection section 18 formed from the conductive layer D3 in the -Z direction.

[0139] According to this modified example, in the case where the attitude or orientation or position of the detector 3 is normal with respect to the scale 5D, when the detection unit 7 is moved in the +X direction along the scale 5D, the bearing 8a corresponding to the first rolling element first contacts the first detection section 17 in a detection area 30D. As the detection unit 7 moves further in the +X direction along the scale 5D, the bearing 8c corresponding to the second rolling element first contacts the second detection section 18. As the detection unit 7 moves further in the +X direction along the scale 5D, the bearing 8b corresponding to the third rolling element first contacts the first detection section 17.

[0140] Thus, according to this configuration, the rolling elements 8 contact the detection sections 10B one by one as the detection unit 7 is moved in the X direction along the scale 5D. Even in a case where a common voltage is applied to the conductive layer 3D and the detection area 30D has no detection position, a deviation of a position or orientation of the detector 3 relative to the scale 5D can be detected.

[0141] In addition, when the attitude or orientation or position of the detector 3 is deviated from the scale 5D, the bearings that are not in contact with the scale 5D can be identified by comparing a measured value read by the reading unit 7a with position information or the like previously stored in the storage unit 51 or the like.

[0142] In the above embodiments, the detecting portions 10 and / or 10A are formed on the surface where the marks C or C2 are formed; however, the detecting portions 10 or 10A may be provided on a side surface of the scale base member 5a so as to correspond to the bearings 8d and 8c. In other words, it is sufficient that the detecting portions 10 or 10A are capable of detecting whether the attitude or orientation or position of the detector 3 is deviated from the scale 5 or 5A by making contact with the bearings 8.

[0143] In the second specific embodiment, the first rolling element corresponds to the bearing 8a, and the second rolling element corresponds to the bearing 8c; however, the first rolling element may correspond to the bearing 8c, and the second rolling element may correspond to the bearing 8b. Accordingly, the first detecting portion may be disposed in the first detecting position, and the second detecting portion may be disposed in the second detecting position.

[0144] Although the above embodiments describe the plurality of detection sections 10 or 10A as three units, the detection unit 9 or 9A may include three or more detection sections. Industrial applicability

[0145] As described so far, the invention can be advantageously applied to control systems for encoders, encoders and methods for control systems for encoders. List of reference symbols 1, 1A to 1D coding device or encoder 3 Detector 5, 5A to 5D scale 7 Detection unit 8 camps 9, 9A, 9B Recording unit 10, 10, 10B Recording section 20, 20A measuring range 30, 30A to 30D detection range 40 detection position 41 first recording position 42 second detection position C, C2, C3 marking D, D2, D3 conductive layer W1, W2 pair of target parts

Claims

[1] Encoder (1; 1A-1D), comprising: a scale (5; 5A-5D) provided on a measurement target part (W1), wherein markings (C; C2; C3) are arranged on the scale (5; 5A-5D); and a detector (3) provided on another measurement target part (W2) and configured to detect an amount of relative movement with the scale (5; 5A-5D), wherein the detector (3) includes at least one rolling member (8) configured to roll in contact with the scale (5; 5A-5D) when the posture is normal; and wherein the scale (5; 5A-5D) includes a detection unit (9; 9A; 9B) configured to detect a deviation of a position of the detector (3) relative to the scale (5; 5A-5D), wherein the detection unit (9; 9A; 9B) is configured to detect a deviation of the position of the detector (3) relative to the scale (5; 5A-5D) by detecting whether the rolling member (8) is in contact with the scale (5; 5A-5D). [2] Encoder according to claim 1, wherein the rolling member (8) is conductive; the detection unit (9; 9A, 9B) includes a detection section (10; 10A; 10B), wherein the detection section (10; 10A; 10B) preferably has the form of a film and a voltage is applied to the detection section (10; 10A, 10B); the detection unit (9; 9A, 9B) is configured to detect the rolling member (8) as being in contact with the scale (5; 5A-5D) when the voltage applied to the detection section (10; 10A; 10B) changes; and the detection unit (9; 9A; 9B) is configured to detect the rolling member as not being in contact with the scale (5; 5A-5D) when the voltage applied to the detection section (10; 10A; 10B) does not change. [3] An encoder according to any one of the preceding claims, wherein the scale (5; 5A-5D) includes: at least one measuring area (20; 20A), which is an area in which the amount of relative movement is detected by the detector (3) based on the markings (C; C2; C3); and at least one detection area (30; 30A-30D), which is an area containing the detection unit (9; 9A; 9B) and is provided outside the measuring area (20; 20A). [4] Encoder according to claim 2 or 3, wherein the detector (3) includes a plurality of rolling members (8); the scale (5; 5A-5D) includes a detection position for the detection unit (9; 9A; 9B) for detecting a deviation in the position of the detector (3); and the detection unit (9; 9A; 9B) includes a plurality of detection sections (10; 10A; 10B) which are provided in the detection position at positions corresponding respectively to the plurality of rolling members (8). [5] Encoder according to one of the preceding claims, wherein the detector (3) includes a first rolling member (8a) and a second rolling member (8b); the scale (5A) includes a first detection position (41) and a second detection position (42) at which the detection unit (9A) detects a deviation in the position of the detector (3); and the detection unit (9A) includes a first detection section provided at a position corresponding only to the first rolling member (8a) when the detector (3) is positioned at the first detection position (41), and a second detection section provided at a position corresponding only to the second rolling member (8b) when the detector (3) is positioned at the second detection position (42). [6] An encoder according to claim 5, wherein a common voltage is applied to the first detecting section and the second detecting section. [7] Encoder according to one of the preceding claims, wherein the rolling member (8) is earthed via the detector (3); the detection unit (9; 9A; 9B) includes a conductive layer (D; D2; D3) having conductivity, which is formed on the scale (5; 5A-5D) along the arrangement direction of the markings (C); and the detection section (10; 10A; 10B) is formed extending from the conductive layer (D; D2; D3) in a direction which intersects with the arrangement direction of the marks (C) on the scale (5; 5A-5D). [8] A method for measuring a moving distance between at least one pair of measurement target parts (W1, W2), comprising: Providing a scale (5; 5A-5D) on a measurement target part (W1), wherein markings (C; C2; C3) are arranged on the scale (5; 5A-5D); Providing a detector (3) at another measurement target part (W2) and which is configured to detect an amount of relative movement with the scale (5; 5A-5D), wherein, when it is detected that at least one rolling member (8) of the detector (3) rolls in contact with the scale (5; 5A-5D), it is determined that the posture of the detector (3) is normal; and Detecting a deviation of a position of the detector (3) relative to the scale (5; 5A-5D) by detecting whether the rolling member (8) is in contact with the scale (5; 5A-5D).

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