JP5412043B2 - Linear motor - Google Patents

Description

  The present invention relates to a linear motor, and particularly relates to an improvement of a linear motor that performs linear translation useful as a high-speed repetitive positioning means.

  Conventionally, linear motors have been used as driving sources for constant-speed feeding or high-speed positioning feed in the field of conveying devices and the like. By the way, regarding a linear motor comprising a stator in which a plurality of magnets are arranged in series in a cylindrical member and a moveable mover that is arranged opposite to the outer peripheral surface of the stator, the total number of magnets to be used is A technique for reducing the cost and weight of the linear motor and improving the speed ripple of the linear motor has been proposed (see, for example, Patent Document 1).

In addition, by selecting a material having a relative permeability greater than 2.0 for the cylindrical member (sleeve material) that houses the plurality of magnets arranged in series, the motor thrust is increased and the resistance to resistance is increased. Linear motor technology with improved wear characteristics has been proposed (see, for example, Patent Document 2).
JP 2005-237165 A JP 2005-525773 A

  However, when a linear motor is used as a power source for a transport apparatus, particularly a high-speed transport apparatus, there is a demand to increase the motor thrust as much as possible because it is desired to shorten the travel time.

  Therefore, considering the magnet spacing K proposed in Patent Document 1, with respect to speed and thrust, the spacing K that is inferior in performance to the case where adjacent magnets are brought into close contact with each other is generally the length in the axial direction of the magnet. A thickness of 10% or less of the length L is considered suitable. Furthermore, although it is slightly inferior in speed performance, the interval K, which is considered not to cause a big problem in the thrust performance of the linear motor, is generally described as 30% or less of the axial length L of the magnet.

  However, even if the distance K between the magnets is controlled, it is the speed ripple that has not been proposed for increasing the thrust.

  In general, a material having a higher relative magnetic permeability tends to rust more easily. Therefore, when the linear motor proposed in Patent Document 2 is used in an environment where it easily comes into contact with moisture and is used outdoors, the material having a higher relative magnetic permeability has a longer life of the conveying device including the linear motor. There is a problem that the time is significantly shortened and the reliability of the apparatus is remarkably impaired.

  The present invention has been made in view of the circumstances as described above, and the object of the present invention is to adapt to a wide range of usage environments, increase the effective magnetic flux density linked to the armature coil, and improve the motor thrust. Another object of the present invention is to provide a linear motor.

According to one aspect of the present invention , there is provided a magnet body formed by adhering two permanent magnets having the same magnetization direction to a hollow portion of a cylindrical member so that the magnetic poles are opposed to each other through a spacer having a predetermined thickness. A field yoke composed of a magnet array arranged in series, in close contact with each other so as to be alternately different magnetic poles,
An armature having an armature coil disposed opposite to the magnet body row via a magnetic gap;
A magnetic property sudden change portion that is disposed at an end portion or in the middle of the magnet body row and changes a magnetic property of the magnet body row;
The magnet body row is configured as a magnetic scale portion, the length between the two magnet bodies is set as the scale pitch of the magnetic scale portion, and provided in the longitudinal direction of the armature, Among the plurality of first magnetic detectors arranged with the phase shifted by 90 ° (corresponding to a quarter wavelength of the scale pitch), the phase is changed in electrical angle from the first magnetic detector on the end side of the scale head. A magnetic linear encoder for position detection having a second magnetic detector arranged by being shifted by 180 ° (corresponding to 1/2 wavelength of the scale pitch),
The magnetic characteristic sudden change unit changes the magnetic characteristic of the magnet array so that a signal synthesized from the first magnetic detector and the second magnetic detector exceeds a predetermined threshold,
One of the field yoke and the armature is used as a stator, and the other is used as a mover. The scale head of the magnetic linear encoder is provided on the armature side, and the field yoke and the armature are relative to each other. A linear motor characterized in that the vehicle travels linearly is provided.

  According to the present invention, it is possible to obtain a linear motor with high motor thrust that is adapted to a wide range of use environments, increases the effective magnetic flux density linked to the armature coil.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same portions are denoted by the same reference numerals, and redundant description is omitted. In the linear motor according to the present invention, either the field yoke or the armature is used as a stator and the other is used as a mover, and the field yoke and the armature are relatively linearly run. In the embodiments described below, for convenience of explanation, the field yoke is a stator and the armature is a mover. However, the present invention is not construed as being limited to these embodiments.

<First Embodiment>
FIG. 1 is a front view showing a schematic configuration of a linear motor employing a magnetic linear encoder embodying the present invention. 2 is a cross-sectional view taken along line AA in FIG.

  As shown in FIGS. 1 and 2, the linear motor 1 includes a base portion 2 serving as a base and a linear guide 3 for guiding the linear motor 1 to move in a linear direction. The linear guide 3 includes a guide rail 3A attached to the base portion 2 and a slider 3B that slides on the guide rail 3A. On the upper surface of the slider 3B, for example, a table 3C for mounting a machine or device to which the linear motor 1 is applied is placed.

  The base portion 2 is provided with a field yoke 4 that constitutes a stator (fixed portion) of the linear motor 1 and generates a field. The field yoke 4 is composed of a magnet row in which a cylindrical member (sleeve) 6 and a columnar permanent magnet 8 inserted into the hollow interior of the cylindrical member 6 are in close contact. The plurality of permanent magnets 8 are members each having the same shape and dimensions. Each permanent magnet 8 is magnetized in the longitudinal direction of the cylindrical member 6. The magnet row is configured by arranging a plurality of adjacent permanent magnets 8 with the same magnetic poles (N pole-N pole or S pole-S pole) facing each other and in close contact with each other. The length of the linear motor 1 in the moving direction, that is, the maximum moving distance is obtained by subtracting the length of the mover from the length of the magnet rows of the permanent magnets 8 arranged.

  A neodymium type is suitable as the type of magnet. The permanent magnet 8 is not limited to a columnar shape, that is, a solid one, and may be a cylindrical shape, for example. Thus, since the same magnetic pole of the permanent magnet 8 is arranged in close contact with each other, a very strong repulsive force is generated. FIG. 8 shows the magnetic characteristics of the permanent magnet 8 obtained by simulation. FIG. 8 shows the spatial distribution characteristics of the combined magnetic field, where the horizontal axis direction represents the axial distance of the cylindrical member 6 and the vertical axis direction represents the combined magnetic field when the same-polar magnets are brought into close contact with each other. A magnetic flux component that is formed in the radial direction of the cylindrical member 6 and perpendicularly enters and exits the surface of the cylindrical member 6 becomes an effective magnetic flux with respect to the armature coil 12 that is disposed so as to face the gap. However, in the linear motor 1 according to the embodiment of the present invention, since the magnetic fluxes of the same pole collide with each other on the contact surface, the magnetic flux close to the center of the magnet is compared with the opposite magnet from all directions compared to the magnetic flux on the outer periphery of the magnet. Is affected by the magnetic field generated. For this reason, the magnetic flux near the magnet center is bent by repulsion in the opposite direction to the counterpart magnet. As a result, the bent component is shifted from the radial direction of the cylindrical member 6 and enters and exits the cylindrical surface, and it can be inferred that the effective magnetic flux for the armature coil 12 is reduced.

  The cylindrical member 6 is made of a nonmagnetic material, and its relative permeability is preferably 2.0 or less. When the cylindrical member 6 is made of a magnetic material, most of the magnetic flux flows through a magnetic circuit composed of 8 rows of permanent magnets → cylindrical member 6 → 8 rows of permanent magnets, and the effective magnetic flux reaching the armature coil 12 is reduced. It is.

  An insertion hole through which the cylindrical member 6 is inserted is formed in the movable element (movable part) 10 of the linear motor 1 and is configured to be movable in the longitudinal direction of the cylindrical member 6. The mover 10 includes an armature, a housing that houses the armature, and a magnetic linear encoder (linear sensor) attached to the housing. A three-phase armature coil 12 is attached to the armature.

  FIG. 3 is a schematic view seen from the side of the linear motor 1, and FIG. 6 is an enlarged view of a part of FIG. The magnetic linear encoder includes a magnetic scale portion for forming a magnetic pole pattern for detecting the position of the mover, and a scale head for detecting the magnetic pole pattern of the magnetic scale portion. As shown in FIG. 3, in this embodiment, the permanent array 8 used in the field yoke 4 of the linear motor 1 without separately arranging the magnetic scale portion and the scale head in the base portion 2 or the like. However, the magnetic scale unit 19 is also used as a detected body of the magnetic linear encoder 16. Further, as shown in FIGS. 3 and 6, the length Lp when the two permanent magnets 8 are in close contact with each other is configured to be the scale pitch Lp of the magnetic scale unit 19. In addition, when the variation in dimension exists in each permanent magnet 8, in order to eliminate the influence by variation, desired correction | amendment can be performed. Since this correction method is not the gist of the present invention, it will not be described in detail here.

  A scale head 18 of a magnetic linear encoder 16 is mounted on the mover 10 side, that is, at one end of the armature coil 12, on the origin side of the linear motor 1. Here, the origin side means that when the linear motor 1 moves from the current position, the direction in which the amount of information representing the position increases away from the origin and the direction in which the information amount decreases decreases toward the origin. The mounting position of the scale head 18 is not limited to the above, and may be mounted at the center position of the mover 10, for example.

  The magnetic linear encoder 16 includes two first magnetic detectors 14 for detecting the magnetic flux of the eight rows of permanent magnets of the stator. The first magnetic detectors 14 are arranged so as to have a phase difference of 90 ° in electrical angle (corresponding to a quarter wavelength of the scale pitch Lp), and their output signals have two phases. Thereby, the electrical angle of the linear motor 1 and the traveling direction of the linear motor 1 can be detected.

  From these first magnetic detection units 14, analog signals da and db of two-phase sine waves that are the basis of the current position information of the scale head 18 are output. These first magnetic detectors 14 are preferably Hall elements capable of linearly converting magnetism into electrical signals. Further, in the magnetic linear encoder 16, a magnetic characteristic sudden change position detection unit 22 is provided in the scale head 18 in the longitudinal direction of the armature in order to detect a magnetic characteristic sudden change position of a magnetic characteristic sudden change part 32 (described later). It has been. The magnetic property sudden change position detection unit 22 processes and determines a signal from the first magnetic detection unit 14 and a signal from the second magnetic detection unit 20.

  The second magnetic detection unit 20 moves in the moving direction of the linear motor 1 so that the phase is 180 ° (corresponding to 1/2 wavelength of the scale pitch Lp) in electrical angle with respect to the first magnetic detection unit 14. Has been placed. The second magnetic detector 20 outputs a sine wave analog signal dc. The second magnetic detection unit 20 is preferably a Hall element that can convert magnetism linearly into an electrical signal.

  The magnetic characteristic sudden change position detection unit 22 is, for example, the output signal dc of the second magnetic detection unit 20 and the first magnetic detection unit 14 (see FIG. 6) whose position is shifted by Lp / 2 wavelengths. An addition circuit (not shown) for adding the output signal da and a comparator (not shown) for determining the magnetic characteristic sudden change position from the addition result can be configured.

  When the waveforms of the analog signals da and db output from the two first magnetic detectors 14 and the analog signal dc output from the second magnetic detector 20 are shown along the field yoke 4, FIG. become that way. In FIG. 4, the vertical axis direction represents the magnetic flux density Br, the horizontal axis direction represents the position of the scale head 18, and the vertical axis direction represents the magnetic flux density Br of the effective magnetic flux from the eight rows of permanent magnets at that position. become. Further, when the waveforms of the analog signals da and db output from the first magnetic detector 14 around the origin are partially enlarged, the result is as shown in FIG.

  Next, the drive system 50 of the linear motor 1 according to the embodiment of the present invention will be described. FIG. 10 is a block diagram showing a configuration example of the drive system. As shown in FIG. 10, the drive system 50 includes a motor drive control device (servo driver) 30, a magnetic characteristic sudden change position detection unit 22, a position information converter 28, and a fixed storage unit 31 that is a writable memory. Has been. A position information converter 28 that receives analog signals da and db of a two-phase sine wave output from the first magnetic detection unit 14 and converts them into position data, and a position command instructed to the linear motor 1 from the outside. (Not shown) and a motor drive control device 30 for calculating a current command for the armature coil 12 are connected by a signal pos of the current position of the scale head 18 obtained by the position information converter 28.

  The motor drive control device (servo driver) 30 includes, for example, a central processing unit (or a microprocessor), a ROM, a RAM, an input / output circuit, a power amplifier, and the like.

  Based on the magnetic signal from the first magnetic detection unit 14, the linear motor 1 is driven and controlled while controlling the current flowing through the coil.

  The position information converter 28 is an analog signal indicating the current position of the mover 10 read from the scale head 18 attached to the end of the armature coil 12, that is, a two-phase sine output from the first magnetic detection unit 14. Wave analog signals da and db are input and converted into position data. The position information converter 28 is not only a position converter but also a position counter representing the current position of the scale head 18. The position information converter 28 receives the reset signal rst signal output from the motor drive control device 30 when the origin return is completed, and sets the value as the position counter to zero.

  The motor drive control device 30 calculates a current command based on the current position information pos of the scale head 18, sends a control current to the mover via a power supply line (not shown), and determines the target position and moving speed of the mover. Control.

  In the above description, the position information converter 28 is independent as one component of the drive system 50. However, the position information converter 28 is not limited to this and may be disposed inside the magnetic linear encoder 16. . The magnetic linear encoder 16 may be disposed inside the motor drive control device 30 as one component. Conversely, the motor drive control device 30 may be disposed inside the magnetic linear encoder 16 as one component.

  The magnetic characteristic sudden change position detection unit 22 receives the analog signal da output from the first magnetic detection unit 14 and the analog signal dc output from the second magnetic detection unit 20, and adds both signals.

  Since the analog signal da and the analog signal dc are 180 degrees out of phase, there is a relationship of da≈−dc. Therefore, when both are added, they cancel each other, and the magnitude of the addition signal ac is close to zero at the place where the permanent magnets 8 rows are in close contact. The reason why it does not become zero is that there are variations in the magnetic characteristics and shapes of the individual permanent magnets 8, the first magnetic detector 14, and the second magnetic detector 20.

  And the magnitude | size of this addition signal ac is processed (for example, threshold value process), and a magnetic characteristic sudden change position is detected. Then, at the position where the magnetic characteristics are suddenly changed, the relationship da≈−dc is broken, and da + dc becomes a large output signal. FIG. 5 shows how the addition signal ac, that is, the combined sensor output changes over the entire field yoke 4. Further, an enlarged waveform of the addition signal ac around the origin is as shown in FIG. In accordance with the threshold processing described above, the magnetic property sudden change position detection unit 22 outputs the magnetic property sudden change position detection signal dth and the overrun signal dov to the motor drive control device 30. Further, the threshold processing described above can be set as appropriate according to the accuracy required for the transport apparatus to which the linear motor is applied.

  Note that the magnetic property sudden change position detector 22 may be disposed inside the magnetic linear encoder 16 as one component. Furthermore, since the magnetic linear encoder 16 can be disposed as one component of the motor drive control device 30, the magnetic characteristic sudden change position detector 22 is provided inside the motor drive control device 30. It is also possible to arrange.

<Abrupt change in magnetic properties>
In the linear motor according to the embodiment of the present invention, as shown in FIG. 3, a magnetic characteristic sudden change portion 32 is provided as a part of the field yoke 4 at both ends where a plurality of permanent magnets 8 are closely arranged. ing. In FIG. 3, the magnetic characteristic sudden change part 32 provided at the left end is used for detecting the origin position of the linear motor, and the magnetic characteristic sudden change part 32 provided at the right end is used for overrun position detection.

  The magnetic characteristic sudden change portion 32 may be made of a non-magnetic material or a magnetic material. A material having a relative permeability r of 50 or more is preferable, a material having a relative permeability r of 100 or more is more preferable, and a material having a relative permeability r of 10,000 or more is most preferable.

  Moreover, as a material of the magnetic characteristic sudden change part 32, nonmagnetic materials, such as an aluminum alloy, a copper alloy, nonmagnetic stainless steel (for example, SUS304), can be utilized, for example. Furthermore, it is more preferable to use magnetic stainless steel, mild steel, silicon iron BFM, carbon steel, low carbon steel or the like as a magnetic material having a high relative permeability.

  Although the thickness (length) of the linear motor 1 in the moving direction of the magnetic characteristic sudden change portion 32 can be shorter than the length of the magnetization direction of one permanent magnet 8, the length of the magnetization direction of the permanent magnet 8 can be used. Longer than this is preferable. This is because the magnetic characteristic sudden change position detector 22 stably detects the magnetic characteristic sudden change position. The suddenly changing magnetic characteristic portion 32 has an outer diameter that is substantially the same as the inner diameter of the cylindrical member 6, and after applying an adhesive to the outer peripheral portion, press-fit from one end of the cylindrical member 6 or by caulking The cylindrical member 6 is preferably fixed or fixed to the cylindrical member 6.

  If the magnetic characteristic suddenly changing portion 32 is not disposed at the end of the permanent magnet 8 row and the air gap is formed, the magnetic flux exiting the end immediately returns to the different polarity of the permanent magnet 8 itself located at the end. I will try. On the other hand, when the magnetic characteristic sudden change portion 32 is arranged at the end of the row of permanent magnets 8, the magnetic flux exiting the end passes through the magnetic characteristic sudden change portion 32 and the permanent magnet 8 itself located at the end. Trying to return to the opposite. In addition, if the material of the magnetic property sudden change portion 32 is made of a high relative permeability, the loop drawn by the magnetic flux exiting the end portion becomes more prominent.

Moreover, the magnetic detector reacts greatly to magnetic fluxes orthogonal to it.

  That is, as is apparent from the array of the permanent magnets 8 and the sudden change in magnetic characteristics 32 shown in FIG. 3 and the waveform of the combined sensor output ac shown in FIG. By monitoring both output signals of the combined sensor output ac, it is possible to detect the occurrence of an overrun of the mover 10. It can be seen that when the overrun of the mover 10 occurs at the left end or the right end of the eight rows of permanent magnets shown in FIG. 3, the output of the combined sensor output ac suddenly increases as shown in FIG. Therefore, it is possible to detect the overrun state of the mover 10 by performing threshold processing on a state in which the output of the combined sensor output ac has changed more than a predetermined magnitude by the change magnetic characteristic sudden change position detection unit 22. The threshold processing here can be appropriately set according to, for example, the accuracy required for the transport apparatus to which the linear motor is applied.

  In this way, during normal operation control, when the mover 10 is moving rightward at the right end of FIG. 3, the magnetic characteristic sudden change position detector 22 detects the right end position x4 shown in FIG. This position x4 can be used for detecting the right end overrun state of the mover 10. If the origin setting reference position x1 (described later) is detected by threshold processing during normal operation control and the mover 10 is moving leftward at the left end of FIG. It can be used to detect an overrun condition at the left end of the. In a linear motor, it is desired that the origin position is easily established. For reference, an example of an operation command for the mover during the origin setting process is shown in FIG. Here, the establishment of the origin position is not described in detail because it deviates from the gist of the present invention.

  As shown in FIG. 3 and FIG. 6, as the magnetic property sudden change portion 32, solid nonmagnetic stainless steel SUS304 (relative magnetic permeability 1) having a diameter substantially the same as that of the permanent magnet 8 inside the cylindrical member 6. .0008) is shown by a curve ga in FIG. In FIG. 11, the horizontal axis represents the position of the scale head, and the vertical axis represents the magnitude of the combined sensor output signal.

  Here, a modified example of the magnetic characteristic sudden change portion will be described. 13 is a high-permeability magnetic body 33 having a relative permeability r = 10000 and a diameter half that of the permanent magnet 8 is used for the axial center portion, and the outside thereof. In addition, nonmagnetic stainless steel (SUS304) 34 is used. The addition signal ac of the analog signal when the magnetic characteristic sudden change portion 32b is configured in this way is shown by a curve gb in FIG.

  14 is a high relative permeability magnetic body having a relative permeability r = 10000 and having a diameter that is the same as that of the permanent magnet 8. An addition signal ac of the analog signal of this modification is shown by a curve gc in FIG. From the magnetic characteristic curve groups ga to gc shown in FIG. 11, it can be understood that any material of a non-magnetic material or a magnetic material can be used as the material of the magnetic property sudden change portion.

  Based on the above, FIG. 12 shows a simulation result performed by the inventors for the magnetic characteristics when the material of the magnetic characteristic sudden change portion is changed. From the simulation results shown in FIG. 12, it is preferable to use at least a material containing a magnetic body having a relative permeability r of 50 or more, more preferably using a material containing a magnetic body having a relative permeability r of 100 or more, It can be understood that it is more preferable to use a material containing a magnetic material having a relative permeability r of 10,000 or more.

  Further, the position of the magnetic characteristic sudden change portion is not limited to the above-described embodiment, and it goes without saying that several variations are possible. For example, the magnetic characteristic sudden change portion can be disposed not in the end portion side of the magnet row but in the middle of the field yoke. Furthermore, the magnetic characteristic sudden change portions can be disposed at a plurality of locations, such as at the end of the magnet row and in the middle of the field yoke.

  According to the present embodiment, since a plurality of permanent magnets are placed in close contact with each other in the hollow portion of a cylindrical member having a small relative permeability and arranged in series, a linear motor with strong motor thrust Is obtained. In addition, the permanent magnet array that is part of the linear motor is also used as the linear scale part of the linear encoder, so there is no reduction in detection sensitivity due to dust and dirt adhering to the optical encoder. An excellent linear motor can be realized.

<Second Embodiment>
Next, a second embodiment will be described. The configuration of the linear motor 1a shown in FIG. 15 is different from the configuration of the linear motor 1 in the first embodiment in the following points.

  In this embodiment, the effective magnetic flux linked to the armature coil is improved while improving the assembling work of the permanent magnets in which the same magnetic poles (N pole-N pole, or S pole-S poles) are opposed to and in close contact with each other. However, the linear motor is arranged so as to be larger than the linear motor 1 in the first embodiment, and the thrust is further improved.

  In general, when a rare earth magnet is used as the field permanent magnet 8 of the linear motor, a very strong magnetic field can be generated. As shown in FIG. 8, when assembling the same magnetic pole of a columnar neodymium magnet 8 in the hollow portion of a non-magnetic cylindrical member 6 so as to face each other and in close contact with each other, Since they face each other, a very strong repulsive force is generated. Therefore, the assembling work for bringing the objects that are going to be separated with a strong repulsive force into close contact with each other is extremely difficult.

  Further, the effective magnetic field component of the permanent magnet, which is the thrust of the linear motor, permeates more into the inside of the cylindrical member 6 with a low magnetic resistance than through the air gap portion with a large magnetic resistance to reach the armature coil. . As shown in FIG. 9, when a cylindrical member 6 having a high relative permeability is used and a magnet row is accommodated in the hollow portion, the thrust of the linear motor is such that the cylindrical member 6 having a large relative permeability m is When used, it can be understood that it is lower than that of the cylindrical member 6 having a small relative permeability m. Therefore, the cylindrical member 6 is made of a non-magnetic material, and its relative permeability is preferably 2.0 or less.

  As shown in FIG. 15, two permanent magnets 8 having the same shape and dimensions and magnetized in the longitudinal direction of the cylindrical member 6 are opposed to the same magnetic pole, and a spacer 36 having a predetermined thickness is provided. A pair of magnet bodies 38 is formed by interposing between the permanent magnets 8 and closely contacting them. The spacer 36 is composed of a member having a relative magnetic permeability n (where n is 1.5 or more), and may be a magnetic body.

  In the cylindrical member 6 having a hollow portion, a plurality of the magnet bodies 38 are arranged side by side and arranged in series. In the plurality of magnet bodies 38 arranged in the cylindrical member 6, the permanent magnets 8 at the ends of the magnet bodies 38 adjacent to each other are in close contact with each other with different magnetic poles to form the field yoke 4. .

  The spacer 36 is preferably thicker than the plate thickness of the cylindrical member 6. The relative permeability n of the spacer 36 is preferably 0.5 or more larger than the relative permeability m of the cylindrical member 6. The relative permeability n of the spacer 36 is more preferably 10 or more than the relative permeability m of the cylindrical member 6, and the relative permeability n is more preferably 50 or more than the relative permeability m of the cylindrical member 6. The relative permeability n is more preferably 100 or more than the relative permeability m of the cylindrical member 6. That is, as the relative permeability n of the spacer 36 is larger than the relative permeability m of the cylindrical member 6, the member from the end of each permanent magnet 8 constituting the magnet body 38 toward the armature coil 12 is more Effective magnetic flux can be supplied to the air, and the effect of enhancing the thrust of the linear motor 1a can be expected.

  In the linear motor 1a having such a configuration, the magnet body 38 is configured to serve as both the field of the linear motor 1a and the magnetic scale portion 19a that is the detected body of the magnetic linear encoder 16a. As shown in FIG. 15, the magnet body 38 in which the N pole permanent magnets 8 are disposed in close contact with both surfaces of the spacer 36 and the magnet body 38 in which the S pole permanent magnets 8 are disposed in close contact with both surfaces of the spacer 36 are paired. A length Lq when the magnetic pole faces are opposed to each other and are in close contact with each other is a basic unit of the magnetic scale portion 19a. Therefore, the scale pitch of the magnetic scale portion 19a is Lq.

  Further, as shown in FIG. 15, magnetic characteristic sudden change portions 32 c that abruptly change the magnetic characteristics of the magnet body 38 are disposed at the left and right ends where the plurality of magnet bodies 38 are disposed in series. The magnetic property sudden change portion 32c is preferably a magnetic material having a relative permeability r of 100 or more, more preferably 10,000 or more. The magnetic characteristic sudden change portion 32c is provided for detecting the origin or overrun point, as in the first embodiment.

  An insertion hole through which the cylindrical member 6 is inserted is formed in the mover (movable part) 10 of the linear motor 1 a and is configured to be movable in the longitudinal direction of the cylindrical member 6. The mover 10 includes an armature, a housing that houses the armature, and a magnetic linear encoder 16a (linear sensor) attached to the housing. Further, the magnetic scale portion 19a of the magnetic linear encoder 16a is also used as the field yoke 4 as in the first embodiment. A three-phase armature coil 12 is attached to the armature.

  The scale head 18a of the magnetic linear encoder 16a is provided adjacent to the armature coil 12 along the longitudinal direction of the armature (X direction in FIG. 15), and has an electrical angle of 90 ° (scale pitch Lq). The first magnetic detectors 14 are arranged so as to be shifted from each other (corresponding to a quarter wavelength). Thereby, it is possible to detect the electrical angle of the linear motor and the traveling direction of the linear motor. Further, a second magnetic detection unit 20 is arranged on the movable element side so that the phase is shifted by 180 ° (corresponding to a half wavelength of the scale pitch Lq) from the first magnetic detection unit 14. .

  In the magnetic linear encoder 16a, the two-phase sine wave analog signals da and db output from the first magnetic detection unit 14 are processed to generate a current position signal. Further, the analog signal da output from the first magnetic detection unit 14 and the analog signal dc output from the second magnetic detection unit 20 are added and calculated, for example, threshold processing is performed to detect a magnetic property sudden change position. A characteristic sudden change position detector 22 is provided in the scale head 18a.

  Thus, when comparing the magnetic linear encoder 16 and the magnetic linear encoder 16a, only the scale pitch of the linear scale of the linear encoder is changed from Lp to Lq, and the operation is the same as in the case of the first embodiment. Exactly the same.

  In the linear motor 1a according to the present embodiment, the arrangement of the permanent magnets is more complicated than the arrangement of the permanent magnets in the first embodiment. Therefore, the magnetic field distribution (magnetic profile) in the space where the armature coil 12 moves also changes in a complicated manner. Therefore, in order to control the linear motor 1a more precisely and to perform acceleration / deceleration control at a high speed in a state where vibration is further reduced, the magnetic body 38 of the linear motor 1a is scanned in advance from the left end to the right end of the magnetic scale portion 19a. Is preferably stored and stored in a battery-backed RAM, a rewritable fixed storage unit 31, or the like provided in the motor control device 30.

  Creation of the magnetic profile of the magnet body 38 will be described. FIG. 16 is a schematic diagram showing the configuration of a system used for creating a magnetic profile. When the assembly of the linear motor 1a is completed, an absolute position measuring device 44-46 such as a laser range finder or a precise magnetic linear scale is installed in parallel with the linear motor 1a in advance. Are connected by a connector 42. A control device 48 such as a personal computer measures the magnetic flux density and the like together with the absolute position at predetermined intervals from the left end to the right end of the linear motor 1a. Such magnetic profile data is compressed using a suitable compression technique. As the compression method, for example, a method of Fourier-transforming magnetic profile data and storing only the coefficients is suitable. The compressed data is transferred from the controller 48 to the motor drive controller 30 and stored in a rewritable ROM or the like. As shown in FIG. 16, the field yoke can be fixed by a clamp fitting 40.

  Next, a modified example will be described for the left and right end portions of the magnet body 38 in which two types of magnet bodies 38 are alternately in close contact. In the case of the configuration shown at the left end of FIG. 15, the magnetic linear encoder 16a and the magnetic characteristic sudden change position detection unit 32c use, for example, the zero-cross position hpA of the A-phase analog signal as the origin, as in FIG. 7A. I can do it. In the configuration in which the south pole of the permanent magnet 8 is further in close contact with the left end of the magnet body 38 shown in the left end portion of FIG. 17, the magnetic linear encoder 16a and the magnetic property sudden change position detecting portion 32c are used as shown in FIG. For example, the zero-cross position hpB of the B-phase analog signal can be set as the origin. Further, in the case where the left end of the magnet body 38 shown in the left end portion of FIG. 19 has the south pole configuration of the permanent magnet 8, as shown in FIG. 20, by the magnetic linear encoder 16a and the magnetic property sudden change position detection unit 32c, For example, the zero-cross position hpC of the A-phase analog signal can be set as the origin. Further, in the case of the configuration in which the N pole of the permanent magnet 8 is further in close contact with the left end of the magnet body 38 shown in the left end portion of FIG. 21, the magnetic linear encoder 16a and the magnetic property sudden change position detection unit 32c can be used as shown in FIG. As shown, for example, the zero-cross position hpD of the B-phase analog signal can be set as the origin. In any case, the advantage of using the zero cross point is that the threshold value can be fixed regardless of the magnet and can be easily set because it is in the same position regardless of the magnitude of the magnetic flux generated by the magnet. Further, the reason why hpA to hpD are used among the many zero cross points is that the magnetic flux is stabilized and the thrust can be stably generated from the vicinity of the positions of hpA to hpD.

  The inventors examined how the shape and dimensional relationship of the permanent magnets 8 and the spacers 36 constituting the magnet body 38 affect the magnetic field distribution in the permanent magnet outer circumferential space. First, as shown in FIG. 23, the combined length L1 of the permanent magnet 8 and the axial length t of the spacer 36 is L = L1 + t, and the outer diameter of the permanent magnet 8 is D. .

  When the change in the magnetic field distribution in the outer peripheral space of the permanent magnet was examined, a characteristic diagram as shown in FIG. 24 was obtained. In FIG. 24, the ratio between the length t of the spacer 36 and the combined length L is calculated, and the horizontal axis is normalized. When the value of the ratio D / L between the outer diameter D and the combined length L of the permanent magnet 8 is variously changed, for example, assuming that the relative relative permeability of the spacer 36 is 100, the vertical axis in FIG. The increase rate of magnetic flux density was measured. That is, it can be seen that the magnetic field outside the periphery of the permanent magnet 8 can be effectively increased by inserting the spacer 36 between the permanent magnet 8 and selecting the shape appropriately.

  According to FIG. 24, when the relative relative permeability of the spacer 36 is around 100, the magnetic field outside the periphery of the permanent magnet 8 is obtained when the ratio D / L of the outer diameter D and the combined length L is 0.1. An increase in magnetic flux density cannot be observed. If the value of the ratio D / L between the outer diameter D and the combined length L is 0.3 or more, when the shape of the permanent magnet 8 and the length t of the spacer 36 are appropriately selected, It is possible to increase the magnetic flux density in the magnetic field. In particular, if the value of the ratio D / L between the outer diameter D and the combined length L is 1 or more, it is possible to effectively increase the magnetic flux density in the magnetic field outside the periphery of the permanent magnet 8. . When a member having a larger relative permeability of the spacer 36 is used, the magnetic flux outside the periphery of the permanent magnet 8 is affected by the magnetic field outside the permanent magnet 8 even for the smaller value D / L of the outer diameter D and the combined length L. It is possible to bring about an increase in density.

  Regarding the length (thickness) t of the spacer 36, the ratio t / L to the composite length L is generally in the range of 0.005 to 0.3 from the horizontal axis in FIG. It can be seen that it is possible to increase the magnetic flux density in the external magnetic field, and a range of 0.01 to 0.2 is more preferable.

  The shape parameter is the ratio D / L = 1 between the outer diameter D and the combined length L = 1, the ratio t / L = 0.05 between the length t of the spacer 36 and the combined length L of the permanent magnet 8 and the spacer 36. Further, the relative permeability of the cylindrical member 6 is set to 1.1, the relative permeability of the spacer 36 is changed in the range of 1.0 to 10,000, and the radius is increased outside the cylindrical member 6. The magnitude of the magnetic flux density at a position 3 mm from the outer peripheral surface of the permanent magnet 8 in the direction (center position of the armature coil 12) was simulated. According to this, as shown in FIG. 25, a characteristic curve was obtained in which the magnetic flux density monotonously increases as the relative permeability increases. FIG. 26 shows a partially enlarged view for observing in detail the change in relative permeability near 1.0. According to FIG. 26, when the relative permeability of the spacer 36 is around 1.4 and the magnetic flux density increase rate is 1, from FIG. 25, if the relative permeability of the spacer 36 is 1.5 or more, It can be observed that the size of the effective magnetic flux interlinking with the armature coil 12 can be increased by 1.0 or more, that is, substantially.

  According to the present embodiment, a spacer having a relatively large relative magnetic permeability is interposed between the extreme parts of the permanent magnet so that the two types of magnet bodies 38 are brought into close contact in series to form a field yoke. Therefore, the assembling work is very easy. Moreover, since the spacer is interposed, the usage amount of the permanent magnet can be reduced. Even if the amount of the permanent magnet used is reduced, the effective magnetic flux can be efficiently supplied to the armature coil via the spacer, so that a linear motor capable of improving motor thrust and moving at high speed can be obtained.

  Furthermore, since the outer peripheral portion of the magnet body is encapsulated and sealed with a cylindrical member having a relative permeability of 1.0 to 2.0 or less, the permanent magnet and the spacer having a high relative permeability can come into contact with moisture or be oxidized. Thus, a linear motor having excellent durability can be obtained.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

It is a front view showing a schematic structure of a linear motor concerning a 1st embodiment. It is sectional drawing in AA in FIG. 1 is a schematic side view of a linear motor according to a first embodiment. It is an output waveform of the 1st magnetic detection part of 1st Embodiment. It is the waveform which added the output of the 2nd magnetism detection part of a 1st embodiment. It is the elements on larger scale around the origin of the linear motor concerning a 1st embodiment. 6A is a partial enlarged view of the output waveform of the first magnetic detection unit in FIG. 6, FIG. 6B is a partial enlarged view of the waveform obtained by adding the output of the second magnetic detection unit in FIG. 6, and FIG. It is a reference figure which shows the driving | operation command with respect to the needle | mover in the case of a setting. It is a figure which shows the simulation result of the synthetic | combination magnetic field at the time of making a homopolar magnet oppose and contact | adhere. It is a figure which shows the simulation result of the synthetic | combination magnetic field at the time of using the cylindrical member of a high relative permeability while making the same-pole magnet oppose and contact | adhere. It is a block diagram which shows the structural example of the drive system of the linear motor which concerns on embodiment of this invention. It is a figure which shows the synthetic | combination sensor output which changes according to a relative magnetic permeability. It is a figure which shows the simulation result performed about the synthetic | combination sensor output which changes according to a relative magnetic permeability. It is a figure which shows another structural example of the magnetic characteristic sudden change part of this invention. It is a figure which shows another structural example of the magnetic characteristic sudden change part of this invention. It is a figure which shows the structure of the linear motor concerning 2nd Embodiment. It is a figure which shows the structural example of a magnetic profile measurement system. It is a figure which shows another example of edge part structure of a permanent magnet arrangement | sequence. It is a figure which shows the output waveform of the magnetic detection part shown in FIG. It is a figure which shows another example of edge part structure of a permanent magnet arrangement | sequence. It is a figure which shows the output waveform of the magnetic detection part shown in FIG. It is a figure which shows another example of edge part structure of a permanent magnet arrangement | sequence. It is a figure which shows the output waveform of the magnetic detection part shown in FIG. It is a figure for demonstrating the shape and dimensional relationship of a permanent magnet and a spacer. It is a figure which shows the change of the magnetic flux density at the time of changing D / L in FIG. It is a figure which shows the relationship between a relative magnetic permeability and a magnetic flux density increase rate. It is a figure which shows the relationship between a relative magnetic permeability and a magnetic flux density increase rate.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 1a ... Linear motor, 4 ... Field yoke, 6 ... Cylindrical member, 8 ... Permanent magnet, 10 ... Mover, 12 ... Armature coil, 14, 20 ... Magnetic detection section, 16, 16a ... Magnetic linear encoder, 18, 18a ... Scale head, 19, 19a ... Magnetic scale section, 22 ... Magnetic property sudden change position detection section, 28. ..Position information converter, 30... Motor drive control device, 32, 32b, 32c... Sudden change of magnetic characteristics, 36... Spacer, 38.

Claims (7)

A plurality of magnet bodies in which two permanent magnets having the same magnetization direction are brought into close contact with each other through a spacer having a predetermined thickness in a hollow portion of a cylindrical member so as to be alternately different magnetic poles. A field yoke composed of magnet body rows arranged in series in close contact with each other;
An armature having an armature coil disposed opposite to the magnet body row via a magnetic gap;
A magnetic property sudden change portion that is disposed at an end portion or in the middle of the magnet body row and changes a magnetic property of the magnet body row;
The magnet body row is configured as a magnetic scale portion, the length between the two magnet bodies is set as the scale pitch of the magnetic scale portion, and provided in the longitudinal direction of the armature, Among the plurality of first magnetic detectors arranged with the phase shifted by 90 ° (corresponding to a quarter wavelength of the scale pitch), the phase is changed in electrical angle from the first magnetic detector on the end side of the scale head. A magnetic linear encoder for position detection having a second magnetic detector arranged by being shifted by 180 ° (corresponding to 1/2 wavelength of the scale pitch),
The magnetic characteristic sudden change unit changes the magnetic characteristic of the magnet array so that a signal synthesized from the first magnetic detector and the second magnetic detector exceeds a predetermined threshold,
One of the field yoke and the armature is used as a stator, and the other is used as a mover. The scale head of the magnetic linear encoder is provided on the armature side, and the field yoke and the armature are relative to each other. A linear motor characterized in that it travels in a straight line. The ratio D / L between the outer diameter D of the permanent magnet and the combined length L of the magnetization direction length and the spacer thickness of the permanent magnet is 0.3 or more. The linear motor according to 1 . A ratio t / L between the thickness t of the spacer and the length L in the magnetization direction of the permanent magnet and the combined length L of the thickness of the spacer is in the range of 0.005 to 0.5. The linear motor according to claim 1 or 2 . The cylindrical member is, m (where, m is greater than 1.0, 2.0 or less) according to any one of claims 1 to 3, characterized in that a material having a relative permeability of Linear motor. Linear motor according to any one of claims 1 to 4 the thickness of the spacer, being larger than the thickness of said cylindrical member. The spacer, relative permeability n (where, n is 0.5 larger value than than m) linearly according to any one of claims 1 to 5, characterized in that a member or the magnetic body having motor. The linear motor according to claim 6 , wherein a relative permeability n of the spacer is 1.5 or more.

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