JP2005110373A - Linear stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear stepping motor which gets a relatively large starting torque without decreasing a detent torque and besides without increasing a power consumption at start. <P>SOLUTION: The linear stepping motor 10 includes a vehicle 12, and the vehicle 12 is composed of a permanent magnet 20, a soft magnetic body 22, and a coupling retaining member 24. The permanent magnet 20 and the soft magnetic body 22 are coupled to each other by the coupling retaining member 24. Two stator cores 14 are arranged around the vehicle 12, and a plurality of stator coils 18 are caught at equal intervals by these two stator cores 14. When three stator coils 18, for example, No.(10), No.(11) and No.(12) are switched on, a travelling magnetic field is generated, and the driving force by it works, and the permanent magnet 20 is shifted into a position opposed to a stator coil 18 No.(11). At this time, stator coils 18 No.(2), No.(3) and No.(4) connected in series to each of the three stator coils 18 are switched on, too, consequently the same driving force works on the soft magnetic body 22, too. A drag torque is increased without increasing the quantity of a current. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a linear stepping motor, and more particularly to, for example, a linear stepping motor that linearly moves a moving element formed in a rod shape in the axial direction of the moving element.

An example of a conventional linear stepping motor of this type is disclosed in Patent Document 1. As shown in FIG. 7, the cylindrical linear pulse motor 1 disclosed in Patent Document 1 includes an output side shaft case 2 and a counter output side case 3. A bearing 2 a provided in the case 2 and a bearing 3 a provided in the case 3 constitute a moving element 4 and support a shaft 5 that is moved in the axial direction. The mover 4 includes a shaft 5, magnetic pole cores 4a and 4b, and a ring-shaped permanent magnet 4c sandwiched between the magnetic pole cores 4a and 4b and magnetized in the axial direction. In addition, five (two in the drawing) stators 6 are provided around the shaft 5 so as to be sandwiched between the case 2 and the case 3. The stator 6 includes a stator core 6a and a stator winding 6b. In the cylindrical linear pulse motor 1 having such a configuration, when a current is passed through the stator winding 6b wound around the stator core 6a, the mover 4 is moved in the axial direction (vertical direction in the figure). It was.
JP-A-7-177723 [G02K 41/03]

  In such a conventional technique, since the moving element 4 is stopped at a desired position, the moving element 4 has a holding torque (detent torque) based on an attractive force acting between the permanent magnet 4c and the stator core 6a. Yes. Therefore, when the detent torque is large, the attractive force acting between the permanent magnet 4c and the stator core 6a is increased, so that it is also necessary to increase the starting torque. As a method for increasing the starting torque, it is conceivable to increase the amount of current flowing through the stator winding 6b when the moving element 4 is moved. However, when the amount of current is increased, the amount of heat generated in the stator winding 6b is increased, leading to a problem that power consumption is wasted. For this reason, when the detent torque is reduced to reduce the power consumption, there is a problem that the movable element 4 may not be held at a desired position.

  Therefore, a main object of the present invention is to provide a linear stepping motor that can obtain a relatively large starting torque without reducing detent torque and without increasing power consumption during driving.

  A first aspect of the present invention is a rod-shaped mover, a stator core provided around the mover, and a plurality of stator coils wound around the mover inside the stator core. Each of which includes a permanent magnet, a soft magnetic material, and a non-magnetic material, each of which is connected so that the non-magnetic material is sandwiched between the permanent magnet and the soft magnetic material, This is a linear stepping motor that applies a driving force to a soft magnetic material.

  In the invention of claim 1, the linear stepping motor includes a moving element formed in a rod shape. A stator core is provided around the mover, and a plurality of stator coils wound around the mover are arranged inside the stator core. The mover is composed of a permanent magnet, a soft magnetic material, and a non-magnetic material, and is connected to each other so that the non-magnetic material is sandwiched between the permanent magnet and the soft magnetic material. In the linear stepping motor having such a configuration, in a stationary state, the moving element is held in a stationary state by an attractive force acting between the permanent magnet and the stator core. This holding torque is called detent torque. Further, when the moving element is moved (driven), a driving force is applied to the permanent magnet and the soft magnetic body.

  According to the first aspect, since the driving force is simultaneously applied to the permanent magnet and the soft magnetic material, a larger driving force can be obtained as compared with the case where the driving force is applied only to the permanent magnet. For this reason, the amount of current during driving can be suppressed without reducing the detent torque.

  The invention of claim 2 is dependent on claim 1, and when the arrangement pitch of adjacent stator coils is L and the number of consecutive stator coils that are simultaneously turned on is n (n is an integer of 3 or more), it is permanent. The length of the magnet was determined to be (n−2) L, and the length of the soft magnetic material was determined to be nL.

  In the invention of claim 2, when the arrangement pitch of adjacent stator coils is L and the number of consecutive stator coils that are simultaneously turned on is n (n is an integer of 3 or more), the length of the permanent magnet Is preferably determined to be (n−2) L, and the length of the soft magnetic material is preferably determined to be nL. This is because the permanent magnet is inside the electromagnet generated by turning on the stator coil and takes a stable point at the center (becomes a stationary state), so that it does not protrude from the electromagnet region. It is to do. On the other hand, the soft magnetic material is intended to reduce the loss because the magnetic flux generated by the electromagnet is stabilized at the position where the magnetic flux flows most efficiently and the magnetic flux passes through the air with low permeability. Therefore, for example, when n = 3, the length of the permanent magnet is determined to be L, and the length of the soft magnetic material is set to 3L.

  According to the second aspect, since the permanent magnet and the soft magnetic material can be set to appropriate lengths, the movable element can be moved efficiently and can be kept stationary in a stable state.

  The invention of claim 3 is dependent on claim 1 or 2, and a plurality of stator coils are connected in series every number corresponding to the arrangement distance between the permanent magnet and the soft magnetic material.

  In the invention of claim 3, a plurality of stator coils are connected in series every number corresponding to the arrangement distance between the permanent magnet and the soft magnetic material. Therefore, when the stator coil is turned on so as to apply a driving force toward the traveling direction to the permanent magnet, the fixed coil connected in series to the permanent coil is also turned on, whereby the same driving force is also applied to the soft magnetic material.

  According to the third aspect, since the stator coils to be driven simultaneously are connected in series, the number of wirings can be reduced as compared with the case where the on / off of the plurality of stator coils is individually controlled. Therefore, the linear stepping motor itself can be reduced in size.

  According to this invention, a non-magnetic material is sandwiched between a permanent magnet and a soft magnetic material to form a moving element, and a driving force is applied to the permanent magnet and the soft magnetic material when the moving element is driven. As a result, an increase in the amount of current during driving can be prevented without reducing the detent torque. Thereby, useless power consumption can be reduced.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

  Referring to FIG. 1, a linear stepping motor (hereinafter simply referred to as “linear motor”) 10 according to an embodiment of the present invention includes a moving element 12 and two stator cores 14 provided around the moving element 12. including. The two stator cores 14 are arranged so as to face each other, and bearings 16 that support the mover 12 and hold (fix) the stator core 14 are provided at both ends thereof. A plurality of (in this embodiment, 40) stator coils 18 are provided so as to be sandwiched between the two stator cores 14.

  In FIG. 1, the number of stator coils 18 is 26 in order to show the overall configuration of the linear motor 10 in an easily understandable manner.

  The moving element 12 is formed in a rod (cylindrical) shape, and is a cross-sectional view taken along the line IIA-IIA in FIG. 1 and an enlarged view of a part of FIG. As can be seen from FIG. 2 (B), a permanent magnet 20 having a first predetermined length (L in this embodiment) in its axial direction is included. The permanent magnet 20 is provided at a predetermined position on the axis of the moving element 12. Thus, when the permanent magnet 20 is continuously provided on the axis of the moving element 12, the linear motor 10 can be reduced in size.

  In FIG. 2A, the stator coil 18 is omitted for easy understanding of a groove 14a and a protrusion 14b described later. Further, the length L of the permanent magnet 20 does not include the length of the portion (convex portions at both ends) connected to the connection holding member 24 as described later.

  Further, as shown in FIG. 2A, the moving element 12 includes a plurality (three in this embodiment) of soft magnetic bodies 22, and the soft magnetic bodies 22 are formed in a cylindrical shape. A second predetermined length (3 L in this embodiment) is provided in the axial direction. The permanent magnet 20 and the soft magnetic body 22 are connected (joined) by the connection holding member 24, and the soft magnetic bodies 22 are also connected by the connection holding member 24. Specifically, in this embodiment, the moving element 12 includes a connection holding member 24, a soft magnetic body 22, a permanent magnet 20, a connection holding member 24, and a soft magnetic body from the top to the bottom of FIG. 22, the connection holding member 24 and the soft magnetic body 22 are joined in this order. In this embodiment, in the connection holding member 24 that connects between the permanent magnet 20 and the soft magnetic body 22 and between the soft magnetic bodies 22, the center of the permanent magnet 20 and the center of the three soft magnetic bodies 22 are respectively set. The length is selected to be equally spaced. That is, the adjacent permanent magnets 20 and the three soft magnetic bodies 22 are arranged at a predetermined pitch P. Further, the connection holding members 24 provided at both ends of the moving element 12 are selected to have an appropriate length in which the moving element 12 is pivotally supported by the bearing 16 in the state shown in FIGS. 1 and 2A. .

  The permanent magnet 20 is magnetized in the axial direction of the moving element 12, and for example, a neodymium magnet formed in a substantially cylindrical shape can be used. The soft magnetic body 22 is formed of, for example, iron or silicon steel, and is formed in a substantially cylindrical shape like the permanent magnet 20. The connection holding member 24 is formed of aluminum or the like which is a nonmagnetic material, and a cylindrical aluminum pipe or the like is used as an example. Since the connection holding member 24 is formed in a cylindrical shape (tubular shape) in this way, as shown in FIG. 2B, the both end surfaces (both end portions) of the permanent magnet 20 and the soft magnetic body 22 The fitting convex part is formed, and the permanent magnet 20 and the soft magnetic body 22 are fitted and bonded to the connection holding part 24.

  FIG. 3A is an illustrative view (perspective view) showing a part of the stator core 14. As shown in FIG. 3A, the stator core 14 includes a core 140 and a support member 142 that supports the core 140. As shown in the front view of FIG. 3B, the core 140 has a substantially rectangular shape, and has an uneven surface on one main surface. That is, the groove 14a and the protrusion 14b are formed. Although details are omitted in FIG. 3 (A), as can be seen from the top view of FIG. 3 (B), the core 140 is formed by laminating soft magnetic silicon steel plates into a thick plate shape, for example. is there. As will be described later, this is in a direction orthogonal to the current flowing through the stator coil 18 so that the driving force applied to the moving element 12 generated when a current flows through the stator coil 18 is made stronger (larger). This is to reduce the flowing current. Therefore, each silicon steel plate forming the core 140 is shielded although it cannot be expressed in the drawing.

  Further, the support member 142 is formed of a non-magnetic material (for example, aluminum) in a substantially quadrangular prism shape, and a groove 142a for supporting (fitting) the above-described core 140 is formed on one main surface thereof. That is, the support member 142 is formed in a U shape.

  In this embodiment, the stator core 14 is configured by the core 140 and the support member 142. However, the stator core 14 can also be configured by using only a silicon steel plate as a soft magnetic material. is there. However, silicon steel is inferior in workability and thermal conductivity as compared with aluminum, and is expensive.

  Therefore, as shown in FIGS. 2A and 2B, the linear motor 10 has a longitudinal direction (an axial direction corresponding to the axis of the moving element 12) on one side of the stator core 14 as shown in FIGS. A plurality of (in this embodiment, 40) grooves 14a are formed at a predetermined pitch L, whereby a plurality (39 in this embodiment) of protrusions 14b are alternately formed with the grooves 14a at a predetermined pitch L. The axial widths of the grooves 14a and the protrusions 14b are set as appropriate, but in this embodiment, the width of the protrusions 14b is set smaller than that of the grooves 14a. Thus, in this embodiment, the length L of the permanent magnet 20 described above is set to be the same as the formation pitch L of the grooves 14a and the protrusions 14b.

  The two stator cores 14 are arranged such that the plurality of grooves 14a and the protrusions 14b face each other. Each of the stator coils 18 is sandwiched between two stator cores 14 so that a part of the stator coils 18 is accommodated in the two opposing grooves 14a (see FIG. 4A). Further, the stator coil 18 is partly provided on the stator core 14 and is sandwiched between the protrusions 14b adjacent to each other. Therefore, the stator coils 18 are also provided at a predetermined pitch L. For example, the stator coil 18 is composed of a conductive wire such as copper (nonmagnetic material).

  As shown in FIG. 4A, which is a cross-sectional view taken along the line IVA-IVA of FIG. 1, the stator coil 18 is wound so that a hole 18a is provided at the center thereof, that is, formed in a donut shape. The diameter is slightly larger than the outer diameter of the moving element 12. In addition, an attractive force acts between the permanent magnet 20 provided on the moving element 12 and each of the two stator cores 14 disposed so as to face each other. Thereby, a gap of a predetermined interval (for example, about 0.5 mm) is provided between the outer peripheral surface of the mover 12 and the inner peripheral surface (hole 18a) of the stator coil 18.

  Further, in a portion where the stator coil 18 does not exist, the mover 12 is disposed so as to pass between the protrusions 14b of the two stator cores 14 (cores 140) as shown in FIG. 4B. The gap between the outer peripheral surface of the moving element 12 and the protruding surface of the protrusion 14b of the stator core 14 is the same as or substantially the same as the predetermined interval. Note that FIG. 4B is a cross-sectional view in the same direction as that in FIG.

  The soft magnetic body 22 (excluding the convex portion) and the connection holding member 24 have the same diameter as the permanent magnet 20 (excluding the convex portion), and the moving element 12 (the permanent magnet 20, the soft magnetic body 22 and the The outer surface (outer peripheral surface) of the connection holding member 24) is smoothed. This is because the attractive force acting between the permanent magnet 20 and the stator core 14 may be different between one stator core 14 and the other stator core 14, and at this time, the mover 12 is fixed. This is to reduce the frictional resistance due to the contact even if the inner surface of the child coil 18 is contacted.

  The manner of operation of the linear motor 10 having such a configuration is shown in FIGS. 5 and 6. In FIGS. 5 and 6, for simplicity, the number of stator coils 18 is set to 16, and a part of the mover 12 is omitted. Each stator coil 18 is distinguished by a parenthesis number. 5 and 6, the cross section of the stator core 14 (core 140) in a state where the longitudinal direction of the linear motor 10 is horizontal (horizontal) (hatching is omitted in the drawings for simplicity). Is shown.

  Although not shown in FIGS. 1 and 2, the stator coils 18 are connected in series every predetermined number (eight in this embodiment) as shown in FIG. However, one end is grounded and the other end is connected to a driver (driving device). Therefore, the stator coils 18 connected in series are simultaneously driven (on) / stopped (off) by the driver. Thus, when connected in series, the number of wires can be reduced as compared with the case where each of the stator coils 18 is individually controlled. In this embodiment, when a voltage is applied to the stator coil 18 (current is supplied), that is, when the stator coil 18 is turned on, a magnetic pole (magnetic field) as shown in FIG. 5B is generated. .

  Here, the interval between the stator coils 18 connected in series is determined by the interval P between the adjacent permanent magnets 20 and the soft magnetic bodies 22 and the interval P between the adjacent soft magnetic bodies 22 in the formed mover 12. The Conversely, a stator (stator core 14 and stator coil 18) in which stator coils 18 are connected in series every predetermined number is prepared, and the permanent magnet 20 and three soft magnets are spaced at an interval corresponding to the predetermined number. The moving element 12 may be formed by determining the arrangement pitch of the magnetic bodies 22.

  For example, in the initial state, when none of the stator coils 18 is turned on, the positional relationship as shown in FIG. 5A is obtained by the attractive force between the stator core 14 and the permanent magnet 20 of the mover 12. Thus, the moving element 12 is stationary. Here, since the length L of the permanent magnet 20 is set to be the same as the formation pitch L of the grooves 14a and the protrusions 14b of the stator core 14 in this embodiment, both ends of the permanent magnet 20 are in the width direction of the protrusions 14b. Located in the approximate center. The holding torque (non-excitation holding torque) of the moving element 12 in such a state (stationary state) is called “detent torque”.

  As shown in FIG. 6A, the (10) -th stator coil 18 facing the permanent magnet 20 and the (11) and (12) -th positions arranged in the moving direction of the mover 12 (permanent magnet 20). The stator coil 18 is turned on and the state is maintained. Then, by the magnetic field (traveling magnetic field) generated in the (10), (11), and (12) stator coils 18, the direction indicated by the arrow in FIG. 6 (A) (the right direction in FIG. 6 (A)). A driving force is obtained, and the permanent magnet 20 moves one step and stops at a position facing the next ((11)) stator coil 18 as shown in FIG. 6 (B). In this case, the moving distance is equal to L.

  Note that in FIG. 6A and FIG. 6B, connection (connection line) is omitted for simplicity.

  At this time, the (2), (3) and (4) stator coils 18 connected in series to the (10), (11) and (12) stator coils 18 are also turned on. That state is maintained. Therefore, the soft magnetic body 22 obtains a driving force in the same direction as the traveling direction of the permanent magnet 20 by the traveling magnetic field generated in the (2), (3), and (4) stator coils 18. Here, in FIGS. 5 (A), 6 (A) and 6 (B), since only a part of the movable element 12 is shown, it is difficult to understand, but as shown in FIG. And the three soft magnetic bodies 22 are arranged at a predetermined pitch P, and the two omitted soft magnetic bodies 22 are also the stator coils 18 (No. (10), (11), (12)) (or ( The same driving force is obtained by turning on the stator coils 18 connected in series to the stator coils 18) of Nos. 2), (3), and (4).

  Thus, since the moving element 12 can obtain a driving force not only in the portion where the permanent magnet 20 is provided but also in the portion where the soft magnetic body 22 is provided, without reducing the pull-in (starting) torque, An increase in the amount of current can be prevented. That is, wasteful power consumption during driving can be reduced without reducing the detent torque.

  In other words, in order to obtain a driving force for both the permanent magnet 20 and the soft magnetic body 22, the arrangement pitch of the permanent magnet 20 and the three soft magnetic bodies 22 is set at an equal interval, and the interval therebetween. Thus, the interval between the stator coils 18 connected in series is determined.

  In this embodiment, in order to move the permanent magnet 20, the number of stator coils 18 that are driven at a time is set to three (here, the stator coil 18 that drives the soft magnetic body 22 is excluded). It is. This is because when the permanent magnet 20 is located inside the electromagnet formed by turning on the stator coil 18, a stable point is taken at the center (becomes a stationary state), and the arrangement pitch is set. When n stator coils 18 of L are turned on once (simultaneously), the length of the electromagnet is nL, and if the permanent magnet 20 is moved by the arrangement pitch L of the stator coil 18, This is because the length of the magnet 20 is (n−2) L. Therefore, in this embodiment, since n = 3, the length of the permanent magnet 20 is set to L as described above. For example, when five stator coils 18 are simultaneously turned on, the length of the permanent magnet 20 is set to 3L.

  Further, the soft magnetic body 22 is stabilized at a position where the magnetic flux generated by the electromagnet flows most efficiently. Further, since a loss occurs when the magnetic flux passes through the air having a low magnetic permeability, in order to reduce the loss as much as possible, the length is set to the same length nL as the electromagnet. Therefore, in this embodiment, since n = 3, the length of the soft magnetic body 22 is set to 3L as described above. For example, as described above, when the five stator coils 18 are simultaneously turned on, the length of the soft magnetic body 22 is set to 5L.

  When the stator coils 18 of (2), (3), (4), (10), (11) and (12) are turned off in the state shown in FIG. Is held stationary by the suction force with the stator core 14.

  Although illustration is omitted, when the stator coils 18 of (11), (12), and (13) are turned on in the state shown in FIG. 6 (B), further driving force is obtained and permanent magnets are obtained. 20 further moves one step and stops at a position facing the (12) -th stator coil 18. At this time, since the stator coils 18 of Nos. (3), (4), and (5) are also turned on, a driving force acts on the soft magnetic body 22 in the traveling direction as described above.

  Furthermore, although illustration is omitted, in the state shown in FIG. 5A, when the stator coils 18 of (8), (9), and (10) are turned on, the permanent magnet 20 is turned into FIG. A driving force is obtained in the direction opposite to the direction shown in A) (the left direction in FIG. 6A). The same applies to the soft magnetic body 22. Therefore, the movable element 12, that is, the permanent magnet 20 is moved by one step in the left direction in FIG. That is, the mover 12 is linearly moved in the axial direction by the stator coil 18 that is turned on.

  Thus, by controlling the voltage application to the stator coil 18, the movement of the permanent magnet 20, that is, the moving element 12 can be controlled. The applied voltage is, for example, a PWM pulse train, and the application time, pulse width, level (pulse height), and the like are appropriately set according to the driving conditions of the motors to be configured.

  According to this embodiment, a non-magnetic material is connected between a permanent magnet and a soft magnetic material so as to form a moving element. When the moving element is driven, both the permanent magnet and the soft magnetic material are used. Since the driving force is applied, the amount of current can be suppressed without reducing the detent torque. In other words, the amount of current can be suppressed without reducing the starting torque. For this reason, generation | occurrence | production of heat can be suppressed as much as possible, and useless power consumption can be reduced.

  Further, since it is not necessary to reduce the detent torque, the moving element can be reliably held in a stationary state.

  In addition, the linear motor shown in the above-mentioned Example is an example, and does not need to be limited to this. If the moving element is configured as shown in the above-described embodiment, other configurations are possible. For example, the cylindrical linear pulse motor disclosed in Japanese Patent Application Laid-Open No. 7-177723 exemplified in the background art or the linear motor disclosed in Japanese Patent Application No. 2003-49834 filed earlier by the present applicant is used. Can do.

It is an illustration figure which shows an example of the linear stepping motor of this invention. It is IIA-IIA sectional drawing of the linear stepping motor shown in FIG. 1 Example, and the enlarged view to which a part was expanded. It is an illustration figure which shows an example of the stator core which comprises the linear stepping motor shown in FIG. 1 Example. FIG. 2 is a cross-sectional view of the linear stepping motor shown in the embodiment in FIG. 1, and a cross-sectional view of a portion where the stator coil is not arranged in the same cross section as the cross-sectional view. It is an illustration figure for demonstrating operation | movement of the linear stepping motor shown in FIG. 1 Example. It is an illustration figure for demonstrating operation | movement of the linear stepping motor shown in FIG. 1 Example. It is an illustration figure which shows the cylindrical linear pulse motor of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Linear stepping motor 12 ... Mover 14 ... Stator core 16 ... Bearing 18 ... Stator coil 20 ... Permanent magnet 22 ... Soft-magnetic body 24 ... Connection holding member 140 ... Core 142 ... Support member

Claims (3)

A mover formed in a rod shape;
A stator core provided around the mover;
A plurality of stator coils that are inside the stator core and wound around the mover;
The mover includes a permanent magnet, a soft magnetic material, and a non-magnetic material,
The movable element is formed by connecting the permanent magnet and the soft magnetic material so as to sandwich the non-magnetic material,
A linear stepping motor in which a driving force is applied to the permanent magnet and the soft magnetic body.   When the arrangement pitch of the adjacent stator coils is L and the number of consecutive stator coils that are simultaneously turned on is n (n is an integer of 3 or more), the length of the permanent magnet is (n−2). The linear stepping motor according to claim 1, wherein the length is determined to be L and the length of the soft magnetic material is determined to be nL.   3. The linear stepping motor according to claim 1, wherein the plurality of stator coils are connected in series every number corresponding to an arrangement distance between the permanent magnet and the soft magnetic body.

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