JP2013255331A - Linear encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate size reduction of the whole device as well as shortening of a response time.SOLUTION: A linear encoder is fitted to a linear motor which includes a magnet part 21 having a plurality of magnets 24N, 24S having different magnetic poles arrayed alternately at equal intervals, and an armature 25 having a plurality of coils 29U, 29V, and 29W, and moves one of the magnet part 21 and armature 25 as a movable element 25 in a direction in which the magnets 24N, 24S are arrayed by producing a magnetic field by supplying currents to the coils 29U, 29V, and 29W. The linear encoder includes a plurality of wireless tags 40 which are fitted to the magnet part 21 opposite the armature 25, and stores reference position information indicating the positions where they are fitted respectively, and a wireless tag readout part 28 fitted to the armature 25 and reading out the information stored in the wireless tags 40.

Description

  The present invention relates to a linear encoder.

  In controlling the linear motor, position information obtained by a linear encoder or the like is used. In general, linear encoders measure the distance from a predetermined origin position (reference position) on a scale and output position information, and acquire position information from information recorded on the scale. There is an absolute type that outputs.

  Although the incremental type linear encoder is less expensive than the absolute type, it is necessary to detect the origin on the scale before obtaining the position information, and therefore it is necessary to drive the linear motor. If the movement distance for acquiring the origin position becomes long, the time until the position information can be acquired (response time) becomes long. Therefore, it is considered to shorten the distance (Patent Document 1). ).

JP 2009-128262 A

  However, since the technique described in Patent Document 1 uses a magnetic sensor to acquire the origin position, it is not affected by magnetism emitted from a linear motor, for example, magnetism emitted from a driving magnet or a coil. There is a need. For this reason, there is a restriction on the position where the linear encoder is attached, and there is a problem that it is difficult to downsize the entire apparatus including the linear motor and the linear encoder.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a linear encoder that shortens the response time and facilitates the miniaturization of the entire apparatus.

  In order to solve the above-described problem, the present invention includes a magnet unit including a plurality of magnets in which different magnetic poles are alternately arranged at equal intervals, and an armature including a plurality of coils. A linear encoder attached to a linear motor that moves one of the magnet portion and the armature as a mover in a direction in which the magnets are arranged by generating a magnetic field, and is opposed to the armature A plurality of wireless tags that are attached to the magnet unit and store reference position information indicating the positions where each is attached, and a wireless that is attached to the armature and reads information stored in the wireless tag A linear encoder including a tag reading unit.

  According to the present invention, the linear encoder grasps the position of the mover based on the reference position information read when the mover is moved. In addition, since a plurality of wireless tags are arranged in the magnet portion, the distance to move the mover can be shortened, and the response time can be shortened. Furthermore, since the reference position information stored in the wireless tag is read out by wireless communication between the wireless tag reading unit and the wireless tag, it is not affected by the magnetic field generated by the linear motor. That is, since it is not necessary to consider the influence of the magnetic field when attaching the wireless tag and the wireless tag reading unit to the linear motor, the selection range of the position for attaching the wireless tag and the wireless tag reading unit can be expanded, and the linear motor is included. The entire apparatus can be easily reduced in size.

It is the schematic which shows the motor system 1 which comprises the linear encoder in embodiment which concerns on this invention. FIG. 3 is a first schematic diagram illustrating a relative positional relationship between an MR sensor 27, a coil 29, and a driving magnet 24 and a relative positional relationship between a wireless tag reader and a wireless tag 31 in the present embodiment. FIG. 6 is a second schematic diagram illustrating a relative positional relationship between the MR sensor 27, the coil 29, and the driving magnet 24 and a relative positional relationship between the wireless tag reader and the wireless tag 31 in the present embodiment. FIG. 2 is a schematic block diagram illustrating configurations of a motor control device 10, a stator 21, and a mover 25 in the present embodiment. It is a flowchart which shows the reset process which the motor system 1 in this embodiment performs after starting.

Hereinafter, a linear encoder according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a motor system 1 including a linear encoder according to an embodiment of the present invention. The motor system 1 includes a motor control device 10 and a linear motor 20 as shown in FIG. The motor control device 10 controls to drive the linear motor 20 based on the position command value input from the host control device. The linear motor 20 includes a long stator 21, a mover 25 that moves on the stator 21, and a pair of guide devices 22 and 22 that assemble the stator 21 and the mover 25.

  The guide device 22 includes, for example, a track rail 23 and slide blocks 26 and 26 assembled via a ball. The track rail 23 of the guide device 22 is fixed to the base 54 of the stator 21, and the slide block 26 of the guide device 22 is fixed to the mover 25. Thereby, the mover 25 is freely guided along the track rail 23 on the stator 21.

  The stator 21 includes a plurality of driving magnets 24 arranged between the pair of track rails 23 and 23. The plurality of drive magnets 24 are arranged so that the N-pole and S-pole magnetic poles alternate in the direction in which the mover 25 moves. Further, the drive magnets 24 have the same length in the arranged direction, and a constant thrust can be obtained regardless of where the mover 25 is located on the stator 21. ing.

The mover 25 has three coils corresponding to the U phase, the V phase, and the W phase. Electric power is supplied from the motor control device 10 to the U-phase, V-phase, and W-phase coils via the power line 31. The mover 25 moves along the guide of the guide device 22 by the force generated by the interaction between the current flowing through each coil and the magnetic field generated by each drive magnet 24.
The movable element 25 is attached with a table 53 for placing a conveyed product, and an MR sensor 27 and a wireless tag reader 28 for detecting the position of the movable element 25 on the stator 21. The MR sensor 27 and the wireless tag reader 28 output the detected signal to the motor control device 10 via the transmission line 32.

The MR sensor 27 outputs two sine wave signals (A phase signal and B phase signal) having a phase difference of 90 degrees to the motor control device 10 in accordance with the direction of the magnetic flux lines generated by the drive magnet 24. The MR sensor 27 is, for example, an AMR (Anitorpic Magneto Resistance) sensor, and includes two full-bridge AMR sensor circuits therein, each of which outputs a sine wave signal one by one. .
The wireless tag reader 28 reads reference position information indicating a reference position stored in a wireless tag attached on the driving magnet 24, and outputs the read reference position information to the motor control device 10.

2 and 3 are schematic diagrams showing the relative positional relationship between the MR sensor 27, the coil 29, and the driving magnet 24 and the relative positional relationship between the wireless tag reader 28 and the wireless tag 40 in the present embodiment. is there.
In the stator 21, as described above, the driving magnet 24N disposed with the N pole facing the mover 25, and the driving magnet 24S disposed with the S pole facing the mover 25 are arranged. Are alternately arranged in the moving direction in which the mover 25 moves. On the driving magnet 24 (24N, 24S), a plurality of wireless tags 40 are arranged in the moving direction. The wireless tag 40 includes a power generation unit 41 and a transmission unit 42.

The mover 25 has three coils 29u, 29v, 29w corresponding to the above-described U phase, V phase, and W phase, and an MR sensor 27 and a wireless tag reader 28 are attached to one end in the moving direction. The MR sensor 27 is attached to a position passing through a straight line connecting the centers of the drive magnets 24 and parallel to the moving direction. Thereby, the position where the magnetic field generated by the drive magnet 24 is the strongest can be passed through the MR sensor 27.
The wireless tag reader 28 is attached at a position facing the wireless tag 40 arranged on the driving magnet 24.

  As shown in FIG. 3, the power generation unit 41 of the wireless tag 40 generates power according to the magnetic flux change of the magnetic field generated by the coils 29 u, 29 v, and 29 w when the mover 25 of the linear motor 20 moves. The transmitted power is supplied to the transmitter 42. The transmission unit 42 transmits the reference position information stored in advance as a radio signal using the power supplied from the power generation unit 41. The reference position information transmitted by the transmission unit 42 is different for each wireless tag 40 and is information indicating a location where the wireless tag 40 is located on the stator 21. The motor control device 10 can grasp where the movable element 25 is located on the stator 21 by acquiring the reference position information from the wireless tag 40 via the wireless tag reader 28. As shown in FIG. 3, the wireless tags 40 are arranged one by one between the adjacent drive magnets 24.

  FIG. 4 is a schematic block diagram illustrating the configuration of the motor control device 10, the stator 21, and the mover 25 in the present embodiment. As shown in FIG. 1, the motor control device 10 includes a control unit 11, a drive unit 12, an electrical angle calculation unit 13, and a position calculation unit 14. As described above, the mover 25 includes the MR sensor 27, the wireless tag reader 28, and the three coils 29u, 29v, and 29w. The stator 21 includes a plurality of driving magnets 24 arranged in the moving direction as described above. On the driving magnet 24, a plurality of wireless tags 40 are arranged at equal intervals. Note that the interval at which the wireless tags 40 are arranged is determined based on the response time required in the motor system 1, the cost of the wireless tag 40, and the like.

The control unit 11 calculates a current command value for moving the mover 25 to the position indicated by the position command value based on the position command value input from the outside and the position information calculated by the position calculation unit 14. . This current command value includes a current value that flows through each of the coils 29u, 29v, and 29w, and is calculated by control using a deviation between the position command value and the position of the mover 25 indicated by the position information, for example, PID control. .
Based on the current command value calculated by the control unit 11, the drive unit 12 drives the linear motor 20 by causing current to flow through the coils 29 u, 29 v, and 29 w.

  The electrical angle calculation unit 13 calculates the electrical angles of the coils 29u, 29v, and 29w with respect to the drive magnet 24 based on the two sine wave signals output from the MR sensor 27. The position calculation unit 14 calculates the position of the mover 25 on the stator 21 based on the electrical angle calculated by the electrical angle calculation unit 13 and the position information read from the wireless tag 40 by the wireless tag reader 28. The position calculation unit 14 outputs position information indicating the calculated position to the control unit 11.

  In the present embodiment, the electrical angle calculation unit 13 and the position calculation unit 14 included in the motor control device 10, the MR sensor 27 and the wireless tag reader 28 attached to the mover 25, and the drive included in the stator 21. The magnet 24 and the plurality of wireless tags 40 constitute the linear encoder 2 that detects the position of the mover 25.

FIG. 5 is a flowchart showing a return process performed after the motor system 1 according to this embodiment is started. The return process is a process for grasping where on the stator 21 the mover 25 is located after the power is turned on.
In the motor control device 10, when the return process is started, the control unit 11 outputs a current command value for moving the mover 25 in any direction to the drive unit 12 to move the mover 25 (step S101). ). At this time, the current command value output by the control unit 11 is a command value for causing the mover 25 to move a predetermined distance. The predetermined distance is longer than the interval between the wireless tags 40 arranged on the drive magnet 24.

  Of the wireless tags 40 arranged on the stator 21, the wireless tag 40 facing the mover 25 generates power by the power generation unit 41 according to the magnetic flux change of the magnetic field generated by the coils 29 u, 29 v, 29 w. The transmission unit 42 transmits the reference position information with the received power. The wireless tag reader 28 receives the reference position information transmitted from the wireless tag 40 and outputs the received reference position information to the motor control device 10 (step S102).

  The electrical angle calculation unit 13 calculates the electrical angle based on the two sine wave signals output by the MR sensor 27 according to the magnetic field of the driving magnet 24 (step S103). The position calculation unit 14 calculates where on the stator 21 the mover 25 is located from the reference position information input from the wireless tag reader 28 and the electrical angle calculated by the electrical angle calculation unit 13 (step S104), the return process is terminated.

  Thereafter, the position calculation unit 14 calculates the position of the mover 25 from the variation amount of the electrical angle calculated by the electrical angle calculation unit 13 with the position calculated in the return process as a reference. That is, the position calculation unit 14 operates as an increment type linear encoder that calculates the position of the mover 25 based on the variation amount of the electrical angle after the return process. Moreover, the control part 11 controls the drive of the linear motor 20 based on the position calculated in the return process.

  In the motor system 1 in the present embodiment, the position of the mover 25 is detected using the reference position information stored in the wireless tag 40 in the return process. Thereby, the process in which the wireless tag reader 28 reads the reference position information from the wireless tag 40 is hardly affected by the magnetic field generated by the linear motor 20. Therefore, restrictions on the position where the wireless tag reader 28 and the wireless tag 40 are attached to the linear motor 20 can be reduced, and the linear motor 20 can be easily reduced in size. Also, as shown in FIG. 3, since the wireless tags 40 are arranged between adjacent drive magnets 24, that is, for each drive magnet 24, the distance for moving the mover 25 in the return process is driven at most. The width of the working magnet 24 can be made, and the response time can be shortened.

  In addition, the wireless tag 40 according to the present embodiment includes a power generation unit 41 that generates power in accordance with a change in the speed of the magnetic field generated by the coil 29u, and operates the transmission unit 42 using the power generated by the power generation unit 41. This eliminates the need for the wireless tag reader 28 to supply power for operating the wireless tag 40, simplifying the wireless tag reader 28, and further facilitating downsizing and cost reduction of the wireless tag reader 28. Can do.

  In the motor system 1 according to the present embodiment, the position calculator 14 calculates the amount of movement of the mover 25 based on changes in two sine wave signals output from the MR sensor 27 attached to the mover 25. . For this reason, it is not necessary to prepare a scale for detecting the amount of movement of the mover 25 and to secure a position where the scale is arranged, so that the linear motor 20 can be further reduced in size.

  In the above-described embodiment, the configuration in which the wireless tag 40 is attached to the stator 21 for each driving magnet 24 is shown. However, the present invention is not limited to this, and for each two driving magnets 24 or more. The wireless tag 40 may be attached to every number of drive magnets 24. In this case, the distance to move the mover 25 in step S101 of the return process is changed according to the interval at which the wireless tag 40 is arranged.

  In the above-described embodiment, the linear motor 20 has an example in which the mover 25 (armature) including the coils 29u, 29v, and 29w moves on the stator 21 (magnet unit) including the drive magnet 24. Explained. However, an armature including a plurality of coils may be used as a stator, and a magnet unit including a plurality of drive magnets may be used as a mover. In this case, the wireless tag 40 is attached to the magnet unit that is a mover, and the wireless tag reader 28 is attached to the armature that is a stator.

  DESCRIPTION OF SYMBOLS 2 ... Linear encoder, 14 ... Position calculation part, 20 ... Linear motor, 21 ... Stator (magnet part), 24, 24N, 24S ... Drive magnet (magnet), 25 ... Movable element (armature), 27 ... MR Sensor (magnetic sensor), 28 ... wireless tag reader (wireless tag reading unit), 29, 29u, 29v, 29w ... coil, 40 ... wireless tag, 41 ... power generation unit

Claims (4)

A magnet unit including a plurality of magnets in which different magnetic poles are alternately arranged at equal intervals; and an armature including a plurality of coils; and by causing a current to flow through the coils to generate a magnetic field, the magnet unit and the A linear encoder attached to a linear motor that moves one of the armatures as a mover in the direction in which the magnets are arranged,
A plurality of wireless tags that are attached to the magnet unit so as to face the armature, and that store reference position information indicating positions where the magnets are attached,
A linear encoder comprising: a wireless tag reading unit that is attached to the armature and reads information stored in the wireless tag. The linear encoder according to claim 1,
The wireless tag includes a power generation unit that generates electric power by changing a magnetic field when the mover moves. A linear encoder according to claim 1 or claim 2,
A magnetic sensor attached to the armature so as to face the magnet provided in the magnet unit, and outputting a signal corresponding to the direction of the magnetic flux lines generated by the magnet;
A linear encoder, further comprising: a position calculation unit that calculates a position of the mover based on reference position information read by the wireless tag reading unit and a signal output by the magnetic sensor. A linear encoder according to any one of claims 1 to 3,
The wireless tag is attached to each of the magnets provided in the magnet unit.

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