JP5579128B2 - Core linear motor - Google Patents

Description

  The present invention relates to a linear motor with a core.

  Linear motors are used to convert electrical energy into linear motion. FIG. 1 is a cross-sectional view illustrating a configuration example of a linear motor. The linear motor 2 includes a stator (stator) 10 and a mover (mover) 20 that are arranged to face each other with a predetermined gap. The stator 10 includes a secondary yoke 12 extending in the moving direction of the mover 20 indicated by an arrow in the figure, and permanent magnets 14 (N having different polarities arranged alternately on the secondary yoke 12. , S).

  The mover 20 is wound around a primary iron core (core) 22 having a repetitive concave-convex shape, in other words, a comb-teeth shape, and a plurality of convex portions (teeth 24) of the primary iron core 22 in the movable direction. Coil 26. When both ends of the primary iron core 22 are open, the magnetic resistance viewed from the magnet 14 periodically changes as the mover 20 moves, and this causes periodic thrust fluctuation (cogging). In order to prevent this cogging, members called auxiliary teeth 28 are attached to both ends of the primary iron core 22.

JP-A-5-103457 JP-A-6-38500

  In the linear motor 2 of FIG. 1, a thrust ripple in which the thrust varies depending on the position of the mover 20 is generated. FIG. 2 is a diagram illustrating thrust fluctuation. The presence of thrust ripple is not preferable because a deviation occurs between the control command of the linear motor 2 and the actual position of the mover.

  The present invention has been made in view of such problems, and one of the exemplary purposes of the certain aspect is to reduce the thrust ripple of the linear motor.

  One embodiment of the present invention relates to a linear motor. This linear motor has a plurality of teeth arranged at intervals in the movable direction, a core whose cross section in the movable direction has a comb-teeth shape, a coil wound around each of the core teeth, A mover having auxiliary teeth provided at both ends, and a stator having a plurality of magnets arranged in the moving direction of the mover and arranged to face the mover with a gap therebetween. The tooth on which the coil at the rearmost end is wound with respect to the moving direction of the mover is configured such that its magnetic state is different from the magnetic state of the other teeth.

  The tooth around which the last coil is wound may be configured so that magnetic saturation is less likely to occur.

  The last tooth (core) with respect to the traveling direction has a local magnetic saturation, which tends to generate magnetomotive harmonics. According to this aspect, by designing the core so that magnetic saturation does not occur at the rearmost end portion of the core, it is possible to suppress magnetomotive force harmonics and to reduce thrust ripple.

In one aspect, the length of the gap between the tooth and the magnet around which the last coil is wound may be longer than the length of the gap between the other teeth and the magnet.
Thereby, the magnetic saturation in the last end part of a core can be suppressed, and a thrust ripple can be reduced.

The tooth material around which the last coil is wound may be different from the other tooth materials. The tooth around which the last coil is wound may be made of a material having a higher saturation magnetic flux density than other tooth materials.
Thereby, the magnetic saturation in the last end part of a core can be suppressed, and a thrust ripple can be reduced.

  Another aspect of the present invention is also a linear motor. This linear motor has a plurality of teeth arranged at intervals in the movable direction, a core formed so that the cross section has a comb-teeth shape, a coil wound around each of the teeth of the core, A mover having auxiliary teeth provided at both ends of the core, and a stator having a plurality of magnets arranged in the moving direction of the mover and arranged to face the mover with a gap therebetween. The length of the gap between the tooth and the magnet around which the last coil is wound with respect to the moving direction of the mover is configured to be longer than the length of the gap between the other teeth and the magnet.

  Yet another embodiment of the present invention is also a linear motor. This linear motor has a plurality of teeth arranged at intervals in the movable direction, a core formed so that the cross section has a comb-teeth shape, a coil wound around each of the teeth of the core, A mover having auxiliary teeth provided at both ends of the core, and a stator having a plurality of magnets arranged in the moving direction of the mover and arranged to face the mover with a gap therebetween. The tooth around which the last coil is wound with respect to the moving direction of the mover is made of a material having a higher saturation magnetic flux density than other tooth materials.

  According to the present invention, thrust ripple of the linear motor can be reduced.

It is sectional drawing which shows the structural example of a linear motor. It is a figure which shows a thrust fluctuation | variation. It is a figure which shows the cross section of the linear motor which concerns on 1st Embodiment. The first to third poles of the linear motor in FIG. 1 are generated in the U phase, the fourth to sixth poles are driven in the V phase, and the seventh to ninth poles are driven in the W phase. It is a wave form diagram which shows magnetic flux density. FIG. 5A is a diagram showing the thrust generated with respect to the electrical angle when the steel plate grade of the last tooth is changed, and FIG. 5B is a diagram showing the frequency characteristics of the thrust. It is a figure which shows the cross section of the linear motor which concerns on 2nd Embodiment. FIG. 7A is a diagram showing the thrust generated with respect to the electrical angle when the length of the last tooth is changed, and FIG. 7B is a diagram showing the frequency characteristics of the thrust.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

(First embodiment)
FIG. 3 is a diagram showing a cross section of the linear motor 2a according to the first embodiment. The linear motor 2a includes a stator (stator) 10 and a mover (mover) 20a that are opposed to each other with a predetermined gap. The stator 10 includes secondary side yokes 12 extending in the movable direction of the mover 20a indicated by arrows in the drawing, and magnets 14 (N, N, N) alternately arranged on the secondary side yoke 12. S).

  The mover 20a is wound around a primary iron core (core) 22a having a repetitive uneven shape, in other words, a comb-teeth shape, and a plurality of convex portions (teeth 24_1 to 24_9) of the primary iron core 22a. Coils 26_1 to 26_9 to be mounted. Auxiliary teeth 28 for suppressing cogging are attached to both ends of the primary iron core 22a.

  The tooth 24_1 around which the coil 26_1 at the rearmost end is wound with respect to the moving direction of the mover 20a (the arrow direction in the figure) is configured such that its magnetic state is different from the magnetic state of the other teeth 24_2 to 24_9. Is done. More specifically, the last tooth 24_1 is configured not to be magnetically saturated by the magnetic flux generated by the magnet and the coil 26_1 while the mover 20a is moving.

  In the first embodiment, attention is paid to the material of the teeth 24 as an approach for making the magnetic state at the rearmost end different from the magnetic state at other positions.

  Specifically, the teeth 24_2 to 24_9 except for the rearmost end are made of the same material, and the rearmost tooth 24_1 is made of a different material. More specifically, the steel material of the rearmost tooth 24_1 is made of a material having a higher saturation magnetic flux density than other steel materials.

  The above is the configuration of the linear motor 2a.

  Before explaining the operation of the linear motor 2a, the reason why attention is paid to the magnetic state at the end in the present invention will be explained. In the linear motor 2 of FIG. 1, electromagnets composed of pairs of teeth 24 and coils 26 in order from the rearmost end to the forefront are referred to as first pole P1 to ninth pole P9. 4 shows the first pole P1 to the third pole P3 of the linear motor 2 of FIG. 1 in the U phase, the fourth pole P4 to the sixth pole P6 in the V phase, and the seventh pole P7 to the ninth pole P9 in the W phase. It is a wave form diagram which shows the magnetic flux density of each pole when driven by a phase. In the first pole P1 at the rearmost end with respect to the traveling direction, local magnetic saturation occurs due to the armature reaction and the influence of the auxiliary teeth 28.

  If magnetic saturation does not exist, when a sinusoidal drive current is supplied to the coil, the resulting magnetic flux density waveform also becomes a sine wave. However, when magnetic saturation exists, the peak of the sine wave is crushed, thereby generating harmonics. When the peak of the sine wave is crushed, the waveform approaches a rectangular wave, so that odd-order harmonic components are mainly generated.

where θ is the electrical angle,
The drive current I _U · sin θ is applied to the U-phase coils 26_1 to 26_3,
A drive current I _V · sin (θ−120) is applied to the V-phase coils 26_4 to 26_6.
A drive current I _W · sin (θ-240) is applied to the W-phase coils 26_7 to 26_9.
Let us consider the situation in which magnetic saturation occurs only in the U phase. Assuming that the generation of harmonics due to magnetic saturation is dominated by the third harmonic, the amount of magnetic flux with respect to the electrical angle θ in the U phase, V phase, and W phase is
U phase: φ _U · sin (θ) + φ _U3rd sin (3θ)
Phase V: φ _V · sin (θ-120)
W phase: φ _W · sin (θ-240)
Given in. At this time, the magnetomotive force F of the linear motor 2 is given by Equation (1) using the number of turns n of each coil.
F = n · φ _U · I _U · sin ² θ + n · φ _V · I _V · sin ² (θ−120 °) + n · φ _W · I _W · sin ² (θ−240 °) + n · φ _U3rd · I _U・ sinθ ・ sin (3θ)
... (1)

For simplification, assuming that I _U = I _V = I _W = I and φ _U = φ _V = φ _W = φ, the magnetomotive force F is expressed by Equation (2).
F = 3 * n * (phi) * I / 2 + n * (phi) _U3rd * I (cos2 (theta) -cos4 (theta)) / 2 ... (2)

  In other words, when magnetic saturation occurs only in the U phase, the harmonic components cannot be canceled by the magnetomotive forces of the V and W phases, and thrust ripples having frequencies twice and four times that of the fundamental wave are generated.

  Returning to FIG. In the linear motor 2a of FIG. 3, magnetic saturation is suppressed by using a material having a high saturation magnetic flux density as the material of the tooth 24_1 at the end of the end where magnetic saturation is likely to occur. FIG. 5A is a diagram showing the thrust generated with respect to the electrical angle when the steel plate grade of the tooth 24_1 is changed to 50A230, 50A600, and 50A1300, and FIG. 5B is a diagram showing the frequency characteristics of the thrust. . A steel material 50A600 is used as a portion excluding the rearmost end of the primary iron core 22a.

  The saturation magnetic flux density increases in the order of 50A230, 50A600, and 50A1300. As can be seen from FIG. 5B, the thrust ripple of the second-order harmonic component decreases as the saturation magnetic flux density of the rearmost tooth 24 increases.

  Thus, according to the linear motor 2a which concerns on 1st Embodiment, the magnetic saturation which arises in it can be suppressed by optimizing the steel material of the tooth | gear 24_1 of the last end. As a result, the change in the amount of magnetic flux caused by the magnet and the coil 26_1 in the tooth 24_1 approaches a sinusoidal waveform, and thrust ripple can be reduced.

(Second Embodiment)
In the first embodiment, the approach of suppressing magnetic saturation by optimizing the material of the rearmost tooth 24_1 has been described. In the second embodiment, as another approach, an approach for suppressing magnetic saturation by reducing the magnitude of the magnetic flux generated in the rearmost tooth 24_1 will be described.

  FIG. 6 is a diagram showing a cross section of the linear motor 2b according to the second embodiment. In the linear motor 2b, the teeth 24_2 to 24_9 excluding the rear end and the gap lengths d2 to d9 of the magnet 14 on the stator 10 side are made uniform. And the gap length d1 of the magnet 14 with the tooth | gear 24_1 of the last end is comprised long compared with the other gap lengths d2-d9. In other words, the last tooth 24_1 is shorter than the other teeth 24_2 to 24_9.

The above is the configuration of the linear motor 2b.
FIG. 7A is a diagram showing the generated thrust with respect to the electrical angle when the length of the tooth 24_1 is changed, and FIG. 7B is a diagram showing the frequency characteristic of the thrust. “Default” indicates that the length of the tooth 24_1 is equal to the lengths of the other teeth 24_2 to 24_9, and “Cut0.2mm” indicates that the length of the tooth 24_1 is 0.2 mm shorter than the other teeth 24_2 to 24_9. “Cut 0.4 mm” indicates a case where the length of the tooth 24_1 is 0.4 mm shorter than the other teeth 24_2 to 24_9.

As shown below, the three-phase magnetomotive force F _{U to} F _W includes a fundamental wave component F _{1 that} is a second harmonic of the driving frequency of the coil current, and a harmonic component F ₂ that is an integral multiple of the fundamental wave component, F ₃ ,...
F _U = F ₁ cos 2θ + F ₂ cos 4θ + F ₃ cos 6θ +.
F _V = F ₁ cos2 (θ−120) + F ₂ cos4 (θ−120) + F ₃ cos6 (θ−120) +.
F _W = F ₁ cos2 (θ−240) + F ₂ cos4 (θ−240) + F ₃ cos6 (θ−240) +.
Here, the second harmonic is canceled by the phase difference of 120 ° equidistant of the three-phase alternating current, but the third harmonic is not canceled. This causes a thrust ripple with a frequency six times the driving frequency.

  By increasing the gap length of the rearmost tooth 24, the magnetic resistance in the gap is increased, so that the amount of magnetic flux in the U phase is reduced, thereby relaxing the magnetic saturation. As is clear from FIG. 7B, the above-described 6th harmonic thrust ripple can be reduced mainly by optimizing the gap length.

  The amplitude of the thrust ripple is 39.9 Np-p, 35.2 Np-p, 56.5 Np-p for each of “Default”, “0.2 mm”, and “0.4 mm”, and the gap length is too long. Since the magnetomotive force of the U phase is smaller than that of the V phase and the W phase, magnetomotive force imbalance occurs, and the ripple amplitude increases.

  In other words, by optimizing the length of the gap length of the last tooth 24_1 and optimizing the gap length of the other teeth 24_2 to 24_9, the thrust ripple of the sixth harmonic can be mainly reduced. The amplitude of the thrust ripple itself can also be reduced.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. is there. Hereinafter, such modifications will be described.

  In the embodiment, the linear motor 2 is described as moving only in one direction, but the present invention is not limited to this. In many applications, the linear motor 2 is movable in both directions and reciprocates. In this case, it is desirable that the thrust ripple is reduced when moving in any direction.

  In the linear motor 2 that performs the reciprocating motion, the tooth 24_9, which is the most advanced when the mover 20 moves in the first direction, becomes the last end when it moves in the second direction. Therefore, in the linear motor 2 that reciprocates, the magnetic state of the teeth 24_1 and 24_9 at both ends may be configured to be different from the teeth 24_2 to 24_8 other than both ends.

  Specifically, in the first embodiment, the material of the teeth 24_1 and 24_9 at both ends may be configured using a material different from the material of the teeth 24_2 to 24_8 other than both ends, more specifically. The material of the teeth 24_1 and 24_9 at both ends may be made of a material having a higher saturation magnetic flux density than the material of the teeth 24_2 to 24_8 other than both ends. In the second embodiment, the gap length of the teeth 24_1 and 24_9 at both ends may be configured to be shorter than the gap length of the teeth 24_2 to 24_8 other than both ends. Such modifications are naturally included in the scope of the present invention defined by the claims.

  In the embodiment, the case where each phase includes three poles has been described. However, the present invention is not limited to this, and the number of poles for each phase is not particularly limited.

  In the second embodiment, the case where the magnetoresistance is changed by changing the gap length has been described, but in addition to the gap length, the thickness, shape, density, etc., or any combination thereof can be changed, The magnetoresistance can be changed, and such an embodiment is also included in the scope of the present invention.

  In the above, this invention was demonstrated based on the Example. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, various modifications are possible, and such modifications are within the scope of the present invention. By the way.

DESCRIPTION OF SYMBOLS 2 ... Linear motor, 10 ... Stator, 12 ... Secondary side yoke, 14 ... Magnet, 20 ... Movable element, 22 ... Primary iron core, 24 ... Teeth, 26 ... Coil, 28 ... Auxiliary teeth

Claims (7)

A core having a plurality of teeth arranged at intervals in the movable direction, the cross section of the movable direction having a comb shape, a coil wound around each of the teeth of the core, and provided at both ends of the core A mover having an auxiliary tooth,
A plurality of magnets arranged in a moving direction of the mover, and a stator arranged to be opposed to the mover at an interval;
With
Of the teeth around which the coil is wound, the tooth positioned adjacent to the auxiliary tooth at the rearmost end with respect to the moving direction of the mover has a magnetic state greater than that of the tooth around which the other coil is wound. A linear motor characterized in that magnetic saturation is less likely to occur . The length of the gap between the tooth located adjacent to the auxiliary tooth at the rearmost end and the magnet is longer than the length of the gap between the tooth around which the other coil is wound and the magnet. The linear motor according to claim 1 . Linear motor according to claim 1, wherein the last tooth located adjacent to the auxiliary tooth edge material, characterized in that is different from the other teeth material. The linear motor according to claim 3 , wherein a tooth located adjacent to the auxiliary tooth at the rearmost end is made of a material having a saturation magnetic flux density higher than that of other tooth materials. A core having a plurality of teeth arranged at intervals in the movable direction, the cross-section of which has a comb-teeth shape, a coil wound around each of the teeth of the core, and auxiliary teeth provided at both ends of the core A mover having, and
A plurality of magnets arranged in a moving direction of the mover, and a stator arranged to be opposed to the mover at an interval;
With
Of the teeth around which the coil is wound , the length of the gap between the tooth located adjacent to the auxiliary tooth at the rearmost end with respect to the moving direction of the mover and the magnet, and the tooth around which the other coil is wound And a linear motor characterized by being configured to be longer than the length of the gap between the magnets. A core having a plurality of teeth arranged at intervals in the movable direction, the cross-section of which has a comb-teeth shape, a coil wound around each of the teeth of the core, and auxiliary teeth provided at both ends of the core A mover having, and
A plurality of magnets arranged in a moving direction of the mover, and a stator arranged to be opposed to the mover at an interval;
With
Of the teeth around which the coil is wound , the tooth located adjacent to the auxiliary tooth at the rearmost end with respect to the moving direction of the mover has a saturation magnetic flux density higher than that of the tooth material around which the other coils are wound. A linear motor that is made of high materials. A core having a plurality of teeth arranged at intervals in the movable direction, the cross section of the movable direction having a comb shape, a coil wound around each of the teeth of the core, and provided at both ends of the core A mover having an auxiliary tooth,
A plurality of magnets arranged in a moving direction of the mover, and a stator arranged to be opposed to the mover at an interval;
With
Of the teeth around which the coil is wound, is the tooth located adjacent to the auxiliary tooth at the rearmost end with respect to the moving direction of the mover higher in saturation magnetic flux density than the teeth around which other coils are wound ? or by increasing the reluctance linear motor, characterized in that the magnetic flux density at the last end is configured to suppress be saturated.

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