JP2010101729A - Electrostatic type encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic type encoder which can detect position information by an electrostatic action and enables elongation of stators as much as possible as the need arises. <P>SOLUTION: This electrostatic type encoder includes the stators 31 each of which has an induction electrode and a potential detecting electrode, a mover 32 which has an interdigital electrode and is so provided as to move on the stators, and a signal processing device 50 which forms an output signal relating to relative displacement of the mover to the stators, based on signals output from the potential detecting electrodes of the stators. The potential detecting electrode of the stator includes an electrode 31c of four phases, and the stators in a plurality are disposed so that the electrodes (A, B, C and D) of four phases are arranged at positions at regular distances to each other. A connection circuit part 112 which connects the electrodes of four phases is provided between the individual stators. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrostatic encoder, and in particular, has a function of detecting position information by electrostatic action, and has a connected structure and is suitable for elongating a stator in a linear shape or a cylindrical shape. The present invention relates to an electrostatic encoder.

  An example of a conventional electrostatic encoder is disclosed in Patent Document 1. In the electrostatic encoder disclosed in Patent Document 1, a moving element is provided so as to move with respect to the stator, and the position of the moving element can be measured. According to this electrostatic encoder, the stator is formed as a plate body having an induction electrode and a potential detection electrode, and the mover is formed as a plate body having an electrode. With respect to the plate-shaped stator, the plate-shaped mover is disposed on the plate-shaped stator and is provided so as to move, thereby forming a sensor unit of the electrostatic encoder. The sensor unit of the electrostatic encoder of Patent Document 1 can be made thin and small.

  As a related prior art, Patent Document 2 discloses a capacitive displacement encoder. The capacitive displacement encoder is a mechanism for sensing the position of the moving body relative to the stationary body, and includes at least one stationary element coupled to the stationary body, and a moving element coupled to the moving body in the vicinity of the stationary element. Consists of The electric field transmission device generates an electrostatic field, and this electrostatic field is modulated by a capacitance change that appears between the two elements as the two elements move relative to each other. The processing circuit senses the modulated electrostatic field and determines the position measurement of the mobile body in response.

Furthermore, Patent Document 3 discloses a linear motor incorporating an optical encoder as a related prior art. Conventional encoders for linear motors generally use optical encoders. The optical encoder is roughly composed of an encoder head and a linear scale. The space between the encoder head and the linear scale is set to be about 0.5 to 1.0 mm. This gap is kept constant without changing depending on the location of the encoder head.
JP 2005-221472 A JP-T-2002-542476 Japanese Patent No. 40688848

  The optical encoder used in the linear motor disclosed in Patent Document 3 has the following problems from the viewpoint of practicality.

(1) On the structure, the moving encoder head is attached to the guide rail, and is required to move completely parallel to the linear scale. The demand for parallelism between the encoder head and the linear scale is high, and alignment adjustment after installation is not easy. As for the mounting relationship of the encoder head, it is necessary to take out the circuit output of the optical encoder and mechanically adjust the mounting angle while observing the Lissajous waveform with an oscilloscope or the like. As described above, the optical encoder requires a high-strength attachment mechanism, and further requires adjustment of the head portion after attachment, resulting in an increase in cost.
(2) The optical encoder head portion requires optical components such as a light emitting element, a light receiving element, and a lens, and there are limits to miniaturization and weight reduction. Further, a signal line is necessary on the moving head portion side, and a large signal transmission mechanism portion is necessary. For example, the linear motor disclosed in Patent Document 3 uses a flexible signal cable and a caterpillar cable bear.
(3) Further, in the optical encoder, since the head unit moving with respect to the linear scale takes out position information at a point, a plurality of linear scales are prepared, and when these are combined to be elongated, There arises a problem that it becomes difficult to realize a long length as a discontinuous point. Also, there has been no idea of lengthening the stator even in the conventional electrostatic encoder.

  The problem (3) will be generalized and described in more detail. According to the conventional optical encoder, there are many dozens of scales, such as 100 mm, 150 mm, 200 mm, 250 mm, ..., 500 mm, 600 mm, 700 mm, ..., 2000 mm, etc. according to the measurement length. It was necessary to keep. In an optical encoder, light from a light emitting element provided in a head is collected by an optical element such as a lens and applied to a scale made of glass or the like, and received by using the transmitted light or reflected light. A numerical value and a position are detected. For this reason, for example, it was impossible to prepare a standard scale of 300 mm in length and connect them together. This is because the light projected from the lens is scattered at the joining points of the scales, resulting in discontinuous points in the measurement. For this reason, there has been a need to prepare many scales having different lengths and select them according to user specifications.

  Further, the linear scale is formed of glass or the like because fine slits are cut at intervals of 40 μm, for example, and it is necessary to increase accuracy. For this reason, it is difficult to bend the linear scale. When the linear scale has a length of 1000 mm or more, there is a drawback that it is not easy to store or transport the linear scale and takes time.

  The measurement accuracy of the encoder is directly affected by the accuracy of the linear scale, and has a characteristic that the influence of expansion and contraction is particularly large on temperature and humidity. For this reason, it is made of glass or the like that is not easily affected by temperature and humidity. In addition, the expansion / contraction of the scale becomes obvious as the scale length increases.

  On the other hand, in order to measure the rotation angle of a cylindrical member with high accuracy, a circumference measurement type encoder that arranges a scale around the cylindrical member and reads the angle is used in part. This circumference measurement type encoder has a drawback that it is difficult to manufacture and process a cylindrical scale, and the price is high. In addition, there is a problem that various cylindrical scales must be prepared in order to cope with the diameter of the cylindrical member used by the user.

  In view of the above-described problems, the object of the present invention is to detect position information by electrostatic action, to easily mount a mover, to align the mover and the stator, to stabilize the measurement signal level, and to measure reliability. In addition, it has a simple connection structure, and the stator can be made as long as possible in a linear shape or a cylindrical shape, making it easy to connect and divide, and store it. The object is to provide an electrostatic encoder that can be easily handled such as transportation.

  Another object of the present invention is to reduce the types of linear or cylindrical scale members to easily correspond to the measurement length desired by the user, and it is sufficient to prepare a standard scale. A low-cost, high-accuracy scale that is not affected by temperature and humidity can be realized, and when applied to machine tools, the temperature coefficient of the workpiece is approximately the same as the temperature coefficient of the machine tool and there is little error. An object of the present invention is to provide an electrostatic encoder capable of performing work.

  The electrostatic encoder according to the present invention is configured as follows to achieve the above object.

  A first electrostatic encoder (corresponding to claim 1) includes a stator having an induction electrode and a potential detection electrode, a comb-like electrode, and a mover provided to move on the stator And signal processing means for generating an output signal related to the relative displacement of the movable element with respect to the stator based on a signal output from the potential detection electrode of the stator, and the potential detection electrode of the stator is a four-phase electrode The plurality of stators are arranged such that the four-phase electrodes are arranged at regular distance positions, and each of the plurality of stators includes a connection circuit unit that connects the four-phase electrodes to each other. Configured.

  According to the electrostatic encoder described above, a standard stator is made in a ruled form with a length of about 30 cm by using, for example, a flexible substrate, and a plurality of the stators are prepared, and two fixed It becomes possible to make a linear long stator by connecting a plurality of stators in a tandem shape by connecting the elements through a connection circuit section. At this time, the arrangement of the four-phase potential detection electrodes formed on each stator with respect to the mover is created so that the same position detection condition is satisfied even at the boundary between the stators. The mover has a certain area as a part facing the stator, and detects the signal with the entire area of the mover. Therefore, the mover passes through the boundary where the stator is connected. Even when moving, the measurement error is less likely to occur.

  In the above configuration, the second electrostatic encoder (corresponding to claim 2) is preferably arranged such that each of the four-phase electrodes is arranged such that the electrode pitch is p and n is 1, 2, 3,. , The first electrode is 4 np, the second electrode is (4n + 1) p, the third electrode is (4n + 2) p, and the fourth electrode is (4n + 3) p. With this configuration, the four-phase electrodes are arranged at regular distance positions by the potential detection electrodes of the stator.

  A third electrostatic encoder (corresponding to claim 3) has an induction electrode and a potential detection electrode, a stator formed of resin around these electrodes, and a base having an arbitrary temperature coefficient, An adhesive layer that attaches the stator to the base, two comb-like electrodes that are not connected to the outside, a movable element that is arranged to move on the stator, and a potential detection electrode of the stator Measuring means for measuring relative displacement of the movable element with respect to the stator based on the output signal.

  According to the electrostatic encoder described above, the stator is bonded to a base made of glass, marble, or the like with an adhesive, and the thermal expansion is basically defined by the base, and has an excellent thermal expansion coefficient. It has the characteristics.

  A fourth electrostatic encoder (corresponding to claim 4) includes a plurality of stators each having an induction electrode and a potential detection electrode, each of which is formed of a resin, and a base having an arbitrary temperature coefficient. A base, an adhesive layer for affixing a plurality of stators to the base, two comb-like electrodes not connected to the outside, a movable element provided to move on the stator, and a stator Signal processing means for generating an output signal related to the relative displacement of the moving element with respect to the stator based on a signal output from the potential detecting electrode, the potential detecting electrode of the stator including four-phase electrodes, The stator is configured so that four-phase electrodes are arranged at regular distance positions, and a connection circuit unit that connects the four-phase electrodes is provided between each of the plurality of stators. The With this configuration, it is possible to have a connection structure, easily achieve a long length, and have excellent characteristics in thermal expansion coefficient.

  The fifth electrostatic encoder (corresponding to claim 5) includes a cylindrical member, an induction electrode, and a four-phase potential detection electrode, and the entire circumferential surface of the cylindrical member has one or one circumferential direction. A stator having a comb-like electrode and an arcuate opposing surface provided to move on the stator, and a signal output from the potential detection electrode of the stator And a signal processing means for generating an output signal related to the relative angle of the rotor with respect to the stator. In this configuration, a cylindrical electrostatic encoder capable of detecting rotation less than 360 degrees can be realized by using a cylindrical member attached to a stator in the circumferential direction.

  In the above configuration, the sixth electrostatic encoder (corresponding to claim 6) is preferably an annular stator attached in the entire circumferential direction of the circumferential surface of the cylindrical member, The four-phase electrodes are arranged at regular distance positions between one end and the other end of the annular stator and between one end and the other end of the annular stator. A connection circuit unit that connects four-phase electrodes on which the stator is arranged is provided.

  A seventh electrostatic encoder (corresponding to claim 7) has a cylindrical member, an induction electrode, and a four-phase potential detection electrode, and is attached to the circumferential surface of the cylindrical member in the entire circumferential direction. From two or more arc-shaped stators, a rotor having comb-like electrodes and having arc-shaped opposing surfaces provided to move on the two or more stators, and a potential detection electrode of the stator Signal processing means for generating an output signal related to the relative angle of the rotor with respect to the stator based on the output signal, and each potential detection electrode of the two or more stators includes a four-phase electrode, The two or more stators are arranged so that the four-phase electrodes are arranged at regular distance positions, and each of the two or more stators includes a connection circuit unit that connects the four-phase electrodes to each other. Configured as follows.

  The eighth electrostatic encoder (corresponding to claim 8) is preferably characterized in that, in the above configuration, the stator is attached to the outer peripheral surface of the cylindrical member.

  In a ninth electrostatic encoder (corresponding to claim 9), preferably, the stator is attached to the inner peripheral surface of the cylindrical member in the above configuration.

The electrostatic encoder according to the present invention has the following effects.
First, it is possible to realize an electrostatic encoder having a long stator of, for example, 3 m or the like only by producing a plurality of standard length stators and preparing a connection circuit portion for connecting these stators. be able to. The length can be increased simply by connecting and connecting a standard stator at the connection circuit portion, and the effect that it is not necessary to manufacture one long electrostatic encoder by a special method is exhibited.
Second, since the stator is connected on the user side, the effect is that the packaging can be made small even though a long electrostatic encoder can be made. Therefore, the transportation cost can be reduced.
Third, the side that manufactures and provides the electrostatic encoder does not need to prepare a large number of stators according to the user's request.
Fourthly, it has a simple connection structure and can be made as long as possible in a linear or cylindrical shape, and it is easy to connect and divide. Handling such as transportation can be easily performed.
Fifth, even if the stator is elongated, the moving element that moves on the stator is coupled to the movable part of the driving device by an elastic member and is brought into press contact with the stator with an appropriate pressing force. As a result, the mounting structure of the moving element is simplified, troublesome alignment is not required, the measurement signal level can be stabilized, and the measurement reliability can be further improved.
Sixth, when connecting a plurality of stators to make them elongated, the four-phase electrodes of the potential detection electrodes provided on each stator are arranged at regular distance positions. The position can be detected and measured smoothly and with high accuracy without generating a missing scale portion.
Seventh, since the base portion and the stator are attached with an adhesive and glass or the like is used as the base material, a scale having an excellent thermal expansion coefficient can be made.
Eighth, because the circumferential surface of the cylindrical member is used to attach at least one stator to all or a part thereof, and a rotor that moves on the stator is disposed with respect to the stator. A cylindrical rotation sensor having high accuracy can be realized.
Ninth, in a linear or cylindrical scale member, it is possible to realize a high-accuracy scale that is relatively low-cost and not affected by temperature and humidity. By making the temperature coefficient and the temperature coefficient of the machine tool substantially the same, it is possible to perform a machine with little error.

  DESCRIPTION OF EMBODIMENTS Preferred embodiments (examples) of the present invention will be described below with reference to the accompanying drawings.

  First, a linear motor configured using an electrostatic encoder including one standard stator will be described, and the configuration of the standard electrostatic encoder will be described.

  In FIG. 1, 10 is a linear motor, and 30 is an electrostatic encoder. This linear motor is, for example, a moving magnet type device. The linear motor 10 includes a base 11 on which an electrostatic encoder 30 is mounted and a vertical wall portion 13 to which a guide rail 12 is attached. The base 11 and the vertical wall portion 13 have a long shape in the horizontal direction in FIG. 1, and the vertical wall portion 13 is fixed along one long side of the base 11. The guide rail 12 is provided in the longitudinal direction on the inner surface of the vertical wall portion 13. The guide rail 12 is disposed in a direction substantially parallel to the base 11. As shown in FIG. 2, for example, a shaft motor magnet 14 having a substantially rectangular parallelepiped shape is attached to the guide rail 12 so as to be guided by the guide rail 12 and to slide along the guide rail 12. A shaft motor coil 15 is disposed at a position parallel to the guide rail 12 and above the base 11. The shaft motor coil 15 has a substantially cylindrical bar shape. Both end portions of the shaft motor coil 15 are fixed to end wall portions not shown in FIG. The end surface wall portion is fixed in common to the end portions of the base 11 and the vertical wall portion 13. The shaft motor magnet 14 has a shaft motor coil 15 inserted through a hole 14a in the center thereof. The shaft motor magnet 14 is moved while sliding in the left-right direction (forward or backward) in FIG. 1 in the axial direction in a state of insertion mounting with the shaft motor coil 15. The shaft motor magnet 14 is composed of, for example, three magnets arranged in the moving direction. The shaft motor coil 15 is wound with U-phase, V-phase, and W-phase windings, and U-phase current, V-phase current, and W-phase current flow through each of the three windings. A moving magnetic field is generated based on the three-phase current. The shaft motor magnet 14 moves forward or backward in the axial direction of the shaft motor coil 15 in accordance with the moving magnetic field generated by the shaft motor coil 15. In FIG. 1, a three-phase power source for supplying a three-phase current to the shaft motor coil 15 is not shown.

  As shown in FIG. 2, the sliding engagement portion 16 of the shaft motor magnet 14 is engaged with the guide rail 12 fixed to the inner surface of the vertical wall portion 13. Based on the engagement relationship between the guide rail 12 and the sliding engagement portion 16, the shaft motor magnet 14 moves smoothly along the guide rail 12. The shaft motor magnet 14 is formed by, for example, arranging three magnets M1, M2, and M3 in parallel and connecting their end portions with fixing plates 17 and 18. The arrangement of the magnetic poles (S or N) of the magnets M1, M2, M3 is, for example, (S, N), (N, S), (S, N) from left to right in the axial direction in FIG. is there.

  Next, the electrostatic encoder 30 will be described in detail. The electrostatic encoder 30 includes a stator 31 and a mover 32. The stator 31 and the mover 32 constitute a sensor unit of the electrostatic encoder 30. The electrostatic encoder 30 is roughly divided into a sensor unit and a signal processing device that processes a signal output from the sensor unit. The configuration of the signal processing apparatus is shown in FIG. The stator 31 is mounted on and fixed to the base 11 described above. The planar shape of the stator 31 is shown in FIG. The stator 31 corresponds to the scale of the electrostatic encoder 30. The planar shape of the mover 32 is shown in FIG.

  In particular, as shown in FIGS. 3 and 4, the mover 32 is placed on the stator 31 and arranged so as to be movable in the longitudinal direction of the stator 31 as indicated by an arrow 33. The planar shape of the plate-like moving element 32 is rectangular (rectangular or square), and is in a state of facing the stator 31 with a facing surface having an appropriate area. The stator 31 shown in FIG. 3 has a rectangular plate shape having a length of about 30 cm, for example. The width of the stator 31 and the width of the mover 32 are approximately equal. The stator 31 and the mover 32 have predetermined electrode structures, as will be described later, and the relative displacement of the mover 32 based on the electrostatic action between the stator 31 and the mover 32 when the mover 32 moves. Can be measured.

  As a structural feature, the moving element 32 has a rectangular planar shape, a film 34 on which a predetermined electrode is formed on the lower side, and an upper reinforcing plate made of, for example, an acrylic material that reinforces the film 34. 35. The film 34 is fixed to the lower surface of the reinforcing plate 35 by adhesion or the like. The moving element 32 formed integrally with the film 34 and the reinforcing plate 35 has a sliding member 36 attached to, for example, four corners on the lower surface of the rectangle. The sliding member 36 has a plate shape, and the thickness is preferably 25 to 50 μm. As the sliding material 36, for example, a Teflon (registered trademark) film is used. The sliding member 36 is brought into contact with the surface of the stator 31. The sliding member 36 allows the moving element 32 to move smoothly on the upper surface of the stator 31. At this time, the film 34 on which the predetermined electrode in the moving element 32 is formed is held at a desired minute constant distance from the upper surface of the stator 31. The pressing force by the leaf spring member 37 is appropriately adjusted, and the surface of the stator 31 is not scratched even when the mover 32 moves in contact with the stator 31.

  On the upper side of the moving element 32, for example, a leaf spring member 37 having an elastic characteristic is attached. The plate spring member 37 bends a plate material such as a metal having elasticity to further exhibit its elastic characteristics. The lower end of the leaf spring member 37 is joined to the upper surface of the moving element 32, and the upper end thereof is joined to the lower surface of the shaft motor magnet 14. The mover 32 is coupled to the shaft motor magnet 14 by a leaf spring member 37. Therefore, the mover 32 moves in conjunction with the movement of the shaft motor magnet 14. The leaf spring member 37 has high rigidity in the moving direction of the moving element 32.

  According to the above structure, the leaf spring member 37 always presses the movable element 32 against the stator 31 to contact it. Accordingly, the gap between the moving element 32 and the stator 31 is determined by the thickness of the sliding member 36 described above. Even if the distance between the stator 31 and the shaft motor magnet 14 fluctuates, the mover 32 is pressed against the stator 31 based on the elastic action of the leaf spring member 37, and the distance between the mover 32 and the stator 31 is increased. Always kept at a certain distance.

  In general, the base 11 and the guide rail 12 are preferably assembled in a parallel positional relationship. However, it is impossible to make the base 11 and the guide rail 12 completely parallel to each other. For example, when the dimension in the longitudinal direction is 30 cm, a deviation of about 0.5 mm with respect to the parallelism easily occurs. In this respect, the guide rail 12 is disposed in a direction substantially parallel to the base 11. However, according to the configuration of the present embodiment, the deviation can be absorbed by the elastic action of the leaf spring member 37. As a result, the gap distance between the mover 32 and the stator 31 is always kept constant, and the reliability and stability of the encoder signal is greatly increased.

  In the above embodiment, the leaf spring member 37 is used as an elastic member for coupling the mover 32 to the shaft motor magnet 14, but the elastic member (elastic means) having a coupling function is not limited to the leaf spring member. One or a plurality of small spring members, or an elastic plate such as rubber or sponge can also be used.

  Next, the structure and operational relationship of the stator 31 and the mover 32 will be described in detail. As shown in FIG. 5, the stator 31 includes a first induction electrode 31a, a second induction electrode 31b, and a four-phase potential detection electrode 31c, and is incorporated in an insulator. A terminal P for inputting a carrier wave is connected to the first induction electrode 31a, and the other terminal Q is connected to the second induction electrode 31b. The stator 31 is manufactured by a printed circuit board or a flexible printed circuit board (FPC) generally used for electronic equipment.

  A mover 32 is positioned on the stator 31. As shown in FIG. 6, the movable element 32 has comb-like electrodes 32 a and 32 b arranged relative to each other in a crossed manner in an insulator, and the bases of the comb-like electrodes 32 a and 32 b are guided by the stator 31. It arrange | positions so that it may overlap on electrode 31a, 31b. The moving element 32 is supplied with electric energy via the induction electrodes 31a and 31b of the stator 31 by the principle of electrostatic induction even if there is no electrical connection with an external cable or the like. The mover 32 can freely move in conjunction with the shaft motor magnet 14 without restrictions such as signal line routing.

  Next, the signal processing device 50 will be described with reference to FIGS. 5 and 7.

  Inside the signal processing device 50, a resolver / digital converter 51, differential amplifiers 52 and 53, an amplifier 54, and a phase adjustment circuit 55 are provided. For the resolver / digital converter 51, a resolver / digital conversion IC is used. An AC transmitter (not shown) is built in the resolver / digital converter 51. The AC transmission output of the AC transmitter is amplified to an appropriate magnitude via an amplifier 54 and output as an AC signal TX as shown in FIG. The AC signal TX is applied between the terminal P and the terminal Q of the stator 31 as a differential output of a carrier wave. Then, a signal (“SIN”: (B) in FIG. 7) obtained at the terminals A and C of the stator 31 is received between the two input terminals of the differential amplifier 52, and is also sent to the terminals B and D. The obtained signal (“COS”: FIG. 7C) is received between the two input terminals of the differential amplifier 53. The output signals of the operational amplifiers 52 and 53 are input to the resolver / digital converter 51 as reception signals “SIN” and “COS”, respectively. For these two received signals “SIN” and “COS”, the following processing is performed in the resolver / digital converter 51.

  First, each of the “SIN” and “COS” signals is subjected to a difference calculation by an arithmetic unit together with an internal feedback signal, and then rectified by a synchronous detection circuit. Based on this rectified signal, it is counted by a digital counter, and this count value is input as a parameter to the arithmetic unit, and automatic feedback is applied so that the magnitude of rectification of the synchronous detection circuit becomes zero. The value of the digital count at this time indicates the phase relationship between the two signals “SIN” and “COS”. From the digital count value, an A-phase pulse and a B-phase pulse as shown in FIG. The signals related to the A-phase pulse and the B-phase pulse are supplied to the up / down counter 56. The relative displacement amount of the moving element 32 is displayed by the numerical value displayed on the up / down counter 56.

  As shown in FIGS. 7B and 7C, the received signal SIN and the received signal COS are respectively transmitted to the stator 31 and the mover 32 with respect to the AC signal TX that is a transmitted signal from the signal processing device 50. Since the signal is a capacitor component composed of electrodes, a phase shift θe occurs. When such a phase shift occurs, an error in the displacement measurement result increases. In particular, when the length of the stator 31 is increased, the capacitor component changes, so that the influence of the phase shift θe becomes significant. Therefore, by providing the phase adjustment circuit 55 as shown in FIG. 5, the phase of the AC signal TX is delayed and supplied to the resolver / digital converter 51 as the reference signal REF ((D) of FIG. 7). In the reference signal REF, the phase is shifted by the phase θt by the transmission signal TX so that the phase shift θe is eliminated. The most desirable state is θe = θt.

  There are two modes for the phase adjustment operation by the phase adjustment circuit 55. The first operation mode is phase adjustment by the adjustment operator 55a. This phase adjustment is performed before the start of the operation of the apparatus, and the operator operates the adjustment operator 55a so that the phase shift presented by a measuring instrument such as an oscilloscope is visually recognized and becomes zero. The second operation mode is phase adjustment based on an automatic adjustment operation during operation of the apparatus. This is because the received signal “SIN”, “COS” and the transmitted signal TX are compared with the phase shift that may occur during operation of the apparatus, and the phase shift is obtained. Then, a signal (reference signal REF) for adjusting the phase of the transmission signal TX so that the phase shift becomes 0 is output. Due to this configuration, the phase adjustment circuit 55 is provided with comparison means for obtaining a phase shift and, for example, a conversion table for outputting a reference signal REF for adjustment corresponding to the obtained amount of phase shift. It has been.

  The linear motor 10 described with reference to FIG. 1 and FIG. 2 is a moving magnet type linear motor in which a shaft motor magnet magnet 14 moves, but the side of the magnet (permanent magnet) is fixed to the base 11 and fixed. However, it may be a moving coil type linear motor that moves the coil side. At this time, the moving element 32 of the electrostatic encoder 30 is coupled and fixed to the moving coil portion via the leaf spring member (elastic member) 37.

  In the stator 31 shown in FIG. 5, when the electrode pitch of the four-phase potential detection electrode 31c is 0.2 mm, one period of the potential distribution is 0.8 mm. In the resolver / digital converter 51, the resolution of the electrostatic encoder is determined by performing an interpolation process on the basis of one period of 0.8 mm of the potential distribution. If the output is 10 bits, an interpolation process of 1024 times is possible, and as a result, the resolution is 0.8 (mm) /1024=0.78 μm.

  Next, a structure that allows the stator 31 to be elongated will be described with reference to FIGS. There is no change in the other configuration of the electrostatic encoder 30.

  FIG. 8 shows the electrostatic encoder 30 including the elongated stator 101, the signal processing device 50, and the up / down counter 56. For the convenience of explanation, for example, three stators 31 are connected in cascade with the stator 101. The boundary portions of the three stators 31 are connected by the connection circuit unit 102. The structure of each of the two stators 31 is as described above. The mover 32 moves on the long stator 101 to which the ends are connected. The mover 32 moves smoothly at the connecting portion between the stators 31. Reference numeral 103 denotes a connection cable. Six signal lines are bundled in the connection cable 103. The signal processing device 50 has a box shape and is connected to a power supply line 104. The stator 31 is a standard stator, and has a maximum length of about 30 cm, for example. The length of the long stator 101 is arbitrarily set as necessary, and as many standard stators 31 as necessary for the length are prepared and connected.

  FIG. 9 shows an enlarged connection portion between two adjacent stators 31. The structure of the electrodes and the like formed on the surfaces of the left and right stators 31 in FIG. 9 is as described in FIG. That is, two induction electrodes 31 a and 31 b and a four-phase potential detection electrode 31 c are formed on the surface of each stator 31. In the potential detection electrode 31c, the four-phase (A, B, C, D) potential detection electrodes are repeatedly formed at regular intervals (a constant electrode pitch). When the electrode pitch is p and n is 1, 2, 3,..., The position (DA) of the A potential detection electrode is given by DA = 4 np, and the position (DB) of the B potential detection electrode is DB = The position (DC) of the C potential detection electrode is given by DC = (4n + 2) p, and the position (DD) of the D potential detection electrode is given by DD = (4n + 3) p.

  Terminals A, C, and Q (lower side in FIG. 9) and terminals B, D, and P (upper side in FIG. 9) are formed on the same side at the locations of the opposite end portions of the two stators 31. The same terminals on the same side are connected by corresponding connection lines 111. A plurality of connection lines 111 constitute the connection circuit unit 102 described above. Further, as shown by a broken line 112, for example, two potential detection electrodes are removed from the surface portion of the opposite end portion of each stator 31 to form a blank region portion. The blank region is a region where a total of four potential detection electrodes are to be formed as indicated by the broken line 112. These four potential detection electrodes correspond to A, B, C, and D described above. Therefore, the two adjacent stators 31 are set so that the order of the positional relationship of the four-phase potential detection electrodes does not deviate even when passing through the boundary portion.

  A portion between the two adjacent stators 31 where the potential detection electrode 31c at the end of the stator is partially missing, that is, the length of the blank region is E as shown in the figure. On the other hand, the entire electrode length of the mover 32 is HL as shown in FIG. At this time, the signal decrease is simply calculated by “signal decrease rate = E / HL”.

  For example, when HL is 30 mm and E is 0.8 mm for one cycle, the signal decrease rate is 2.67%. Therefore, there is almost no trouble. Furthermore, when used as a linear scale, since the distance to be measured is calculated by the “phase” of the signal, there is almost no measurement error. In other words, since the moving element 32 is rectangular and has a certain area and the entire electrode length has a certain large dimension, the problem of the gap between the connecting portions of the two stators 31 is measured. From the point of view, it has the characteristic that it can be eliminated.

  FIG. 10 is a perspective view showing a mounting structure of a plurality of stators 31 when the length is increased. The plurality of stators 31 are fixed on a base 121 having a required thickness, for example, with an adhesive or a double-sided tape 122. When the stator 31 is made of a flexible printed circuit board (FPC) as described above, the material is a polyimide resin, so that it expands and contracts due to temperature and humidity. Therefore, a plurality of stators 31 are attached to a base 121 made of glass or marble or the like that does not expand and contract at a temperature and humidity with an adhesive 122 or the like, thereby making a long stator 101. A longitudinal sectional view of the stator 31 fixed to the stator 101 with an adhesive 122 or the like is shown in FIG. Accordingly, the expansion and contraction of the stator 31 can be suppressed as much as possible, and the entire expansion and contraction of the elongated stator 101 can be reduced, thereby improving the measurement accuracy.

  If a metal such as iron is used for the base 121 and it is applied to a machine tool, the linear scale using the electrostatic encoder and the workpiece have the same temperature coefficient, which is caused by the difference in expansion between the two. The measurement error that occurs can be eliminated.

  Next, an embodiment of a cylindrical electrostatic encoder in which the stator has an annular shape (ring shape) will be described with reference to FIG.

  In the electrostatic encoder 201, a portion corresponding to the base (11 or 121) described in the above embodiment is formed as a cylindrical member 202 having a cylindrical shape. The cylindrical member 202 has a structure in which a long base (11 or 121) is curved to form an annular shape. A support portion 203 that supports the cylindrical member 202 is provided below the cylindrical member 202.

  One stator 204 is attached to the entire circumference of the outer circumferential surface (outer circumferential surface) 202a of the cylindrical member 202 with an adhesive or the like. In the example shown in FIG. 12, for example, one long stator 204 is curved and fixed to the entire circumference of the outer peripheral surface 202 a of the cylindrical member 202. The structure and the like of various electrodes formed on the surface of the stator 204 are the same as those of the stator 31 described above, and two induction electrodes and a four-phase potential detection electrode are provided. One end and the other end of the elongated stator 204 are arranged at opposite positions, and a gap between them is located at a position where one end and the other end of each of the four-phase elongated stators 204 on the one end side and the other end side face each other. The gaps between them are formed such that the four-phase potential detection electrodes on one end side and the other end side are aligned so that they do not shift and are continuous. The four-phase potential detection electrodes are arranged at regular distance positions, and this relationship is the same at the gaps. In this case, it is not necessary to provide a connection circuit portion between one end and the other end of the stator 204. In order to adjust the position, the stator 204 may be stretched and pulled. Further, the diameter of the stator 204 can be adjusted by inserting a thin tape-like material between the cylindrical member 202 and the stator 204. The surface of the stator 204 is curved corresponding to the degree of curvature of the surface of the cylindrical member 202. A rotor 205 is disposed on the surface of the stator 204 on which the four-phase potential detection electrodes are formed. The rotor 205 is a member corresponding to the moving element 32 described above, and has the same function based on the electrostatic induction action between the stator 204 and the electrodes. The mover 32 is a mover that moves linearly on a linear stator, whereas the rotor 205 moves on an annular stator 204, and from one end to the other end. Will result in rotation around the cylindrical member 202. In this case, at least the facing surface of the rotor 205 is curved so as to be parallel to the curved surface of the stator 204. In FIG. 12, illustration of a structure portion that supports the rotor 205 that enables the rotor 205 to rotate is omitted. Note that the stator 205 is formed in an annular shape as a whole shape, and the rotor 205 can be freely rotated many times in any direction of arrows 206 and 207 across the gap. . A signal line 208 from a terminal associated with each electrode is drawn out from the end of the stator 205, and the plurality of signal lines 208 are bundled and accommodated in the connection cable 209. The connection cable 209 is led to a signal processing circuit.

According to the cylindrical electrostatic encoder 201 as described above, the circumferential length (rotation angle) of the cylindrical object can be measured as the rotation sensor. A rotation angle of completely 360 degrees (or less than 360 degrees) can be detected continuously.
The diameter (2R) of the annular stator 204 is 100 mm, the electrode pitch (p) of the stator is 0.2 mm,
Further, assuming that the interpolation coefficient (k) is 1024, the resolution (η) is about 0.0009 degrees (3.2 seconds) from the following equation.
η = 360 (degrees) / [(2πR / 4p) · k]

The cylindrical electrostatic encoder 201 can be modified as follows. In the above embodiment, one annular stator 204 is used, but two or more stators are connected to be elongated as a whole, and the entire outer circumferential surface (outer circumferential surface) 202a of the cylindrical member 202 is made. An annular stator having a larger diameter can be formed around the circumference. In the case of this configuration, a connection circuit unit that connects four-phase electrodes is provided between adjacent stators of two or more stators.
Further, at least one stator can be curved and pasted to a part of the arcuate region of the outer circumferential surface (outer circumferential surface) 202a of the cylindrical member 202. In this case, the position of the rotor 205 can be measured in an angle range smaller than 360 degrees.
Further, at least one stator 204 may be attached to the inner peripheral surface of the cylindrical member 202 as in the case of the outer peripheral surface, and the rotor 205 may be disposed.

  The configurations, shapes, sizes, and arrangement relationships described in the above embodiments are merely schematically shown to the extent that the present invention can be understood and implemented, and the numerical values and the compositions (materials) of the respective components Is just an example. Therefore, the present invention is not limited to the described embodiments, and can be variously modified without departing from the scope of the technical idea shown in the claims.

  The electrostatic encoder according to the present invention is used as an encoder for a drive device such as a linear motor, and is particularly suitable for use as an encoder having a lengthened stator.

1 is a perspective view showing a basic configuration of an electrostatic encoder according to the present invention. 1 is an end view of an electrostatic encoder according to the present invention. It is the principal part perspective view which took out and showed only the structure part regarding the stator and the moving element in an electrostatic encoder. It is a side view of the structure part regarding the arrangement | positioning relationship of a stator and a moving element. It is the top view and circuit block diagram which show the structure of a stator, and the structure of a signal processing apparatus. It is a top view which shows the structure of a needle | mover. It is a timing chart about the waveform of each part of a circuit for explaining phase adjustment. It is a block diagram which shows the system configuration | structure of the electrostatic encoder which consists of an elongate stator, a signal processing apparatus, and an up / down counter. It is a top view which expands and shows the connection part of two stators adjacent by the elongate stator. It is a perspective view which shows the attachment structure of the several stator when lengthening. It is a longitudinal cross-sectional view of the base with which the stator was affixed with the adhesive agent. It is an external appearance perspective view which shows the basic composition of the cylindrical electrostatic encoder which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Linear motor 11 Base 12 Guide rail 13 Vertical wall part 14 Shaft motor magnet 15 Shaft motor coil 16 Sliding engagement part 30 Electrostatic encoder 31 Stator 32 Mover 34 Film 35 Reinforcement plate 36 Sliding material 37 Plate spring Member 50 Signal processor 51 Resolver / digital converter 55 Phase adjustment circuit 56 Up / down counter 101 Lengthened stator 102 Connection circuit unit 111 Connection line 121 Base 122 Adhesive 201 Electrostatic encoder 202 Cylindrical member 204 Stator 205 Rotor

Claims (9)

A stator having an induction electrode and a potential detection electrode;
A mover having a comb-like electrode and provided to move on the stator;
An electrostatic encoder comprising: a signal processing unit that generates an output signal related to a relative displacement of the moving element with respect to the stator based on a signal output from the potential detection electrode of the stator.
The potential detection electrode of the stator includes a four-phase electrode;
The plurality of stators are arranged such that the four-phase electrodes are arranged at regular distance positions,
A connection circuit unit that connects the four-phase electrodes between each of the plurality of stators,
An electrostatic encoder characterized by that.   The arrangement positions of the four-phase electrodes are 4 np for the first electrode and (4n + 1) p for the second electrode when the electrode pitch is p and n is 1, 2, 3,. 2. The electrostatic encoder according to claim 1, wherein the third electrode is (4n + 2) p and the fourth electrode is (4n + 3) p. A stator having an induction electrode and a potential detection electrode, and a periphery of these electrodes formed of resin;
A base having an arbitrary temperature coefficient;
An adhesive layer for attaching the stator to the base;
A movable element having two comb-like electrodes not connected to the outside and provided to move on the stator;
Measuring means for measuring relative displacement of the movable element with respect to the stator based on a signal output from the potential detection electrode of the stator;
An electrostatic encoder comprising: A plurality of stators having induction electrodes and potential detection electrodes, and the periphery of these electrodes formed of resin;
A base having an arbitrary temperature coefficient;
An adhesive layer for attaching the plurality of stators to the base;
A movable element having two comb-like electrodes not connected to the outside and provided to move on the stator;
Signal processing means for generating an output signal related to the relative displacement of the mover with respect to the stator based on a signal output from the potential detection electrode of the stator;
With
The potential detection electrode of the stator includes a four-phase electrode;
The plurality of stators are arranged such that the four-phase electrodes are arranged at regular distance positions,
A connection circuit unit that connects the four-phase electrodes between each of the plurality of stators,
An electrostatic encoder characterized by that. A cylindrical member;
A stator having an induction electrode and a four-phase potential detection electrode, and attached to the circumferential surface of the cylindrical member in whole or in part in the circumferential direction;
A rotor having a comb-like electrode and having an arcuate facing surface provided to move on the stator;
Signal processing means for generating an output signal related to a relative angle of the rotor with respect to the stator based on a signal output from the potential detection electrode of the stator;
An electrostatic encoder comprising:   The stator is an annular stator attached in the entire circumferential direction of the circumferential surface of the cylindrical member, and between the one end and the other end of the annular stator, 6. The electrostatic encoder according to claim 5, wherein the stator is arranged so that the electrodes are arranged at regular distance positions. A cylindrical member;
Two or more arc-shaped stators having induction electrodes and four-phase potential detection electrodes and attached to the circumferential surface of the cylindrical member in all circumferential directions;
A rotor having a comb-like electrode and having an arcuate facing surface provided to move on two or more of the stators;
Signal processing means for generating an output signal related to a relative angle of the rotor with respect to the stator based on a signal output from the potential detection electrode of the stator;
With
The potential detection electrode of each of the two or more stators includes a four-phase electrode;
The two or more stators are arranged such that the four-phase electrodes are arranged at regular distance positions,
Between each of the two or more of the plurality of stators, comprising a connection circuit portion for connecting the four-phase electrodes.
An electrostatic encoder characterized by that.   The electrostatic encoder according to claim 5, wherein the stator is attached to an outer peripheral surface of the cylindrical member.   The electrostatic encoder according to claim 5, wherein the stator is attached to an inner peripheral surface of the cylindrical member.

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