Linear motor

Abstract

To provide a linear motor capable of suppressing generation of thrust force in a vertical direction that causes vibration, noise and the like, and at the same time, largely enhancing thrust force.SOLUTION: A three-phase driven linear motor comprises three-phase coils and magnets arranged along a driving direction at positions facing the three-phase coils. A winding width of a coil in a portion facing a magnet is in a range of 120±7.7° in an electric angle. An average width of the coils in the portion facing the magnets is in a range of 144±4.6°in the electric angle. A pitch between the three-phase coils is 90±180°×n (n is an integer of 0 or more) in the electric angle. (where, the winding width of the coil means a width dimension in the driving direction of a substantially linear portion that faces a magnet of a coil in which a winding is wound. The average width of the coil means a distance between centers in the driving direction of the substantially linear portion that faces the magnet of the coil in which the winding is wound.)SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to linear motors. [Background technology]

[0002] Conventionally, a linear motor capable of high-speed response has been used to move a lens frame of a lens barrel in the optical axis direction (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-248290 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned conventional linear motor has the following problems. That is, in recent years, the size of image sensors used in image pickup devices has been increasing in order to increase the number of pixels, improve the dynamic range, and so on. As the image pickup device becomes larger, the lens used in the lens barrel also inevitably becomes larger, and the amount of movement of the lens also increases.

[0005] In order to drive such a large lens, the actuator that drives the lens is required to have a larger thrust and a longer stroke than conventional actuators. The technology described in the above Patent Document 1 discloses a configuration in which a plurality of field magnet portions are provided for one coil, thereby improving thrust. However, there is a limit to how much thrust can be increased with the technology described in Patent Document 1. In addition, when the stroke is increased, magnetic saturation in the yoke cannot be ignored, making it difficult to increase the stroke.

[0006] An object of the present disclosure is to provide a linear motor that can suppress the generation of vertical thrust that causes vibration, noise, etc., while at the same time significantly increasing thrust. [Means for solving the problem]

[0007] The linear motor according to the present disclosure is a three-phase driven linear motor, and includes three-phase coils and magnets arranged along the drive direction at positions facing the three-phase coils. The winding width of the coils at the portions facing the magnets is in the range of 120°±7.7° electrical angle. The average width of the coils at the portions facing the magnets is in the range of 144°±4.6° electrical angle. The pitch between the three-phase coils is 90°±180°×n electrical angle (n is an integer equal to or greater than 0). (Note that the winding width of the coils refers to the width dimension in the drive direction of the approximately straight portion of the coils around which the windings are wound that faces the magnets. The average coil width refers to the distance between the centers in the drive direction of the approximately straight portion of the coils around which the windings are wound that faces the magnets.) [Effects of the Invention]

[0008] According to the linear motor of the present disclosure, by placing magnets on both sides of the coil, it is possible to suppress the generation of vertical thrust that causes vibration, noise, etc., while at the same time significantly increasing thrust. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a perspective view showing a focus unit according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the focus unit according to the first embodiment. [Figure 3] FIG. 2 is an exploded perspective view of the focus unit according to the first embodiment. [Figure 4] FIG. 2 is an explanatory diagram showing the relationship between a coil and a magnet according to the first embodiment. [Figure 5] FIG. 4 is an explanatory diagram showing the relationship between a coil and a magnet. [Figure 6A]This is a diagram showing a simulation of the change in thrust force when the coil winding width Wc is changed while keeping the average coil width Wa constant at 180°. [Figure 6B] This is a diagram showing a simulation of the change in thrust force when the coil winding width Wc is changed while keeping the average coil width Wa constant at 180°. [Figure 7A] This is a diagram showing a simulation of the change in thrust force when the coil winding width Wc is changed while keeping the average coil width Wa constant at 180°. [Figure 7B] This is a diagram showing a simulation of the change in thrust force when the coil winding width Wc is changed while keeping the average coil width Wa constant at 180°. [Figure 8A] This is a diagram showing a simulation of the change in thrust when the coil winding width Wc is kept constant at 90° and the average coil width Wa is changed. [Figure 8B] This is a diagram showing a simulation of the change in thrust when the coil winding width Wc is kept constant at 90° and the average coil width Wa is changed. [Figure 9A] This is a diagram showing a simulation of the change in thrust when the coil winding width Wc is kept constant at 90° and the average coil width Wa is changed. [Figure 9B] This is a diagram showing a simulation of the change in thrust when the coil winding width Wc is kept constant at 90° and the average coil width Wa is changed. [Figure 10A] FIG. 10 is an explanatory diagram showing the relationship between a coil and a magnet in a comparative example. [Figure 10B] FIG. 10 is an explanatory diagram showing the relationship between the coil and the magnet in an example different from the first embodiment. [Figure 11] 10B is a diagram comparing the comparative example shown in FIG. 10A, the configuration of the present embodiment shown in FIG. 4, and the configuration of another embodiment shown in FIG. 10B. [Figure 12A] FIG. 10 is a front view of a field magnet portion according to a second embodiment. [Figure 12B] FIG. 10 is a side view of a field portion according to a second embodiment. [Figure 13] FIG. 10 is an exploded perspective view of a field magnet portion according to a second embodiment. [Figure 14] FIG. 10 is an explanatory diagram showing the principle of harmonics reduction in the field magnet portion according to the second embodiment. [Figure 15A] FIG. 11 is a side view showing the configuration of a field portion according to a third embodiment. [Figure 15B] FIG. 11 is a perspective view showing the configuration of a field part according to a third embodiment. [Figure 16A] FIG. 11 is a diagram showing magnetic field lines in a field magnet portion according to the third embodiment. [Figure 16B] FIG. 10 is a diagram showing magnetic field lines in a field magnet portion of a comparative example. [Figure 17] FIG. 2 is a diagram showing a drive circuit for a two-phase linear motor. [Figure 18A] 10 is a graph showing the relationship between thrust constant and phase. [Figure 18B] 10 is a graph showing the relationship between a current waveform and a phase. [Figure 18C] 18C is a graph showing the relationship between thrust and phase, obtained by superimposing the graph of FIG. 18A and the graph of FIG. 18B. [Figure 19] FIG. 2 is an external perspective view showing the configuration of a lens barrel equipped with the focus unit of FIG. [Figure 20] FIG. 20 is an external perspective view showing the configuration of a camera to which the lens barrel of FIG. 19 is attached. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art. The inventors provide the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and do not intend for them to limit the subject matter described in the claims.

[0011] Furthermore, the expression "approximately **" is intended to include not only exactly the same, but also those that are recognized as substantially the same, taking "almost the same" as an example. The same applies to the expressions "near **" and "about **." It should be noted that the drawings are not necessarily strict illustrations, and in the drawings, the same reference numerals are used to designate substantially the same components, and redundant explanations will be omitted or simplified.

[0012] (Embodiment 1) Next, the configuration of the focus unit (linear motor) 1 according to the first embodiment will be described with reference to FIGS. 1 to 11 and 17 to 20. FIG. The focus unit 1 includes a lens that mainly performs focusing and a linear motor that drives the lens, in an interchangeable lens barrel 40 (see FIG. 19).

[0013] Fig. 1 is a perspective view showing a focus unit 1 according to embodiment 1. Fig. 2 is a cross-sectional view of the focus unit 1 according to embodiment 1. Fig. 3 is an exploded perspective view of the focus unit 1 according to embodiment 1. Fig. 4 is an explanatory diagram showing the relationship between the coil and magnet according to embodiment 1. In FIG. 1, the direction parallel to the optical axis J of a camera (imaging device) 50 (see FIG. 20) equipped with a lens barrel 40 and a camera body (body) 51 to which the lens barrel 40 is attached is defined as the Y-axis direction, the horizontal direction is defined as the X-axis direction, and the vertically upward direction is defined as the Z-axis direction. The subject side is defined as the positive Y-axis direction, and the imaging element side is defined as the negative Y-axis direction. Note that in FIG. 1, the Y-axis direction and the Z-axis direction change depending on the mode of use, and are not limited to these. The same applies to the figures subsequent to FIG. 1.

[0014] As shown in FIGS. 1 to 3, the focus unit 1 includes a holding frame 2, a focus lens L1, a lens frame 3, a main guide pole 4, a sub-guide pole 5, and a guide cover 6. The holding frame 2 is made of a resin material and is open on the positive Y-axis direction side. As shown in Figures 2 and 3, a field magnet part having a main yoke 7, a sub yoke 8, and a drive magnet (magnet) 9 is fixed to the holding frame 2, and a storage space is formed to store the lens frame 3 so that it can move in the optical axis direction.

[0015] The main yoke 7 has a substantially U-shaped cross section and is disposed along the outer peripheral surface of the holding frame 2 . The sub-yoke 8 has a flat plate shape and is in contact with an end face of the main yoke 7 . The drive magnet 9 is provided along the inner circumferential surface of the main yoke 7. The drive magnet 9 is multi-pole magnetized so that the inner circumferential side along the optical axis direction has alternating north and south poles. The coils 10a and 10b are fixed to the lens frame 3. Power is supplied to the coils 10a and 10b from a power supply unit. The power is supplied via a flexible substrate 11.

[0016] Here, by passing a current through the coils 10a and 10b according to the position of the lens frame 3, the coils 10a and 10b are subjected to a Lorentz force, which acts in the Y-axis direction, causing the lens frame 3 to move along the Y-axis direction. Here, when the magnet is configured with a unipolar magnet, as in the technology described in Patent Document 1, increasing the stroke in the optical axis direction increases the magnetic flux density of the yoke in accordance with the length of the magnet, causing magnetic saturation of the yoke, which often results in a decrease in thrust.

[0017] On the other hand, in the configuration of this embodiment, by lengthening the drive magnet 9 in the optical axis direction and increasing the number of magnetic poles, it is possible to easily extend only the stroke while maintaining the same thrust. As shown in FIGS. 2 and 3, the lens frame 3 is movable along the Y-axis direction. The lens frame 3 has a focus lens L1 and an MR (Magneto-Resistive) element 12 (an example of a position detection sensor). The holding frame 2 has an MR magnet 13 (an example of a position detection member). The lens frame 3 is formed in a substantially cylindrical shape and holds the focus lens L1 in its inner diameter portion. The lens frame 3 is formed with a pole insertion hole 31 through which the main guide pole 4 is inserted. A sub-guide pole 5 is fixed to the holding frame 2 so that the lens frame 3 can move linearly in the Y-axis direction.

[0018] In the present embodiment, the MR element 12 is used as an example of a position detection sensor, but instead of the MR element 12, a photocoupler may be used as an example of a position detection sensor. In this embodiment, the MR magnet 13 is used as an example of the position detection member, but the position detection member may be, for example, a reflecting mirror. 3, the MR magnet 13 is provided on the holding frame 2 near the MR element 12. When the lens frame 3 on which the MR element 12 is provided moves, the MR element 12 detects a change in the magnetic field generated in the MR magnet 13.

[0019] The MR element 12 is provided in the lens frame 3. For example, when the lens frame 3 is moved during shooting, the position of the MR magnet 13 relative to the MR element 12 changes. At this time, the magnetic flux at the position of the MR element 12 changes, and the output of the MR element 12 changes. In this way, by detecting the output of the MR element 12, the shift position of the lens frame 3 can be detected.

[0020] As shown in Fig. 3, the main guide pole 4 and the sub guide pole 5 are cylindrical metal members that extend substantially parallel to the Y-axis direction. The main guide pole 4 supports the lens frame 3 so that it can move in the Y-axis direction. In other words, the main guide pole 4 guides the lens frame 3 so that it moves along the optical axis J. One end of the main guide pole 4 (the negative Y-axis side) is held by the holding frame 2, and the other end of the main guide pole 4 (the positive Y-axis side) is held by the guide cover 6.

[0021] The guide cover 6 is a resin cover member provided at the end on the positive side of the Y axis. Specifically, the guide cover 6 is fixed (held) with screws to the end of the holding frame 2 on the positive side of the Y axis (the subject side). FIG. 4 is an explanatory diagram showing the positional relationship between the coils 10a and 10b and the drive magnet 9 according to the first embodiment.

[0022] In FIG. 4, all angle dimensions are in electrical angle. 4, coil 10a and coil 10b have exactly the same configuration and are fixed at positions offset from each other by an electrical angle of 270° in the Y direction. Coil 10a and coil 10b are driven by passing a sinusoidal current through them according to the position of magnet 9 (shown by the broken line in the drawing).

[0023] Coil 10a and coil 10b are out of phase with each other by 270° (-90°), and can therefore be driven by passing two-phase currents with a phase difference of 90° therebetween. The shape of the coils 10a and 10b is designed so that the winding width of the coil is 120° in electrical angle and the average width of the coil is 144° in electrical angle. Here, the reason why the coils 10a and 10b are shaped as described above will be explained with reference to FIG.

[0024] FIG. 5 is an explanatory diagram showing the positional relationship between the coil 10a and the drive magnet 9. As shown in FIG. In FIG. 5, the shape of the coil 10a is such that the winding width of the coil 10a is Wc and the average width of the coil is Wa. If the magnetic flux density of the magnetic flux generated by the drive magnet 9 varies sinusoidally in the Y direction, the thrust generated in the coils 10a and 10b becomes completely constant when the thrust of the two phases is summed up.

[0025] However, the magnetic flux density of the magnetic flux generated by the drive magnet 9 usually contains harmonic components such as third, fifth, seventh, and so on. When the magnetic flux density contains harmonic components, the thrust force generated by the coil 10a generally also contains harmonic components. If the thrust contains harmonic components, the thrust will fluctuate depending on the position, causing vibrations and noise and reducing the positional accuracy during position control, so it is desirable to have as few harmonic components as possible.

[0026] 6A to 7B are diagrams showing a simulation of changes in thrust force when the winding width Wc of coil 10a is changed while keeping the average width Wa of coil 10a constant at 180° in the magnetic circuit shown in FIG. The above is a calculation of the thrust force when the coil conductor diameter and number of turns are changed so that the coil resistance and the coil conductor space factor are constant.

[0027] As shown in Figure 6A, the fundamental wave component of the thrust peaked at 150° when the coil winding width Wc was wide or narrow, and then decreased. Furthermore, as shown in FIG. 6B, the third harmonic component becomes zero near 120°. Furthermore, as shown in FIG. 7A, the fifth harmonic component becomes zero near 72° and 144°.

[0028] Furthermore, as shown in FIG. 7B, the seventh harmonic component becomes zero near 103° and 154°. The reason for this will be explained in detail below using the diagram. In FIG. 5, consider the thrust generated at part I of the coil. In Figure 5, f1 indicates one turn at the left end of the coil part I, and fk indicates one turn at the right end of the coil. The total thrust is the sum of the thrusts f1...fk, in other words, the integrated value.

[0029] Here, if the coil winding width Wc is set to an electrical angle of 120° (equivalent to 360° for the third harmonic), the third harmonic will be integrated for exactly one period, and the value will become zero. Furthermore, if the winding width Wc is set to an electrical angle of 72° or 144° (corresponding to 360° or 720° for the fifth harmonic), the fifth harmonic will be integrated for exactly one or two periods, and the value will become zero.

[0030] Similarly, For the 7th harmonic, 51.4°, 102.9°, and 154.3° For the 9th harmonic, 40°, 80°, 120°, and 160° becomes zero. Although the above shows the electrical angle at which the angle becomes exactly zero, if the winding width Wc is set to a value close to the above, it is possible to reduce specific harmonic components of the thrust force.

[0031] For example, for the third harmonic, the coil winding width Wc is 112.3° <Wc<127.7° If the relationship is satisfied, the third harmonic component can be reduced to one-fifth or less, and sufficient effect can be obtained. Generally, for the nth harmonic component, if the coil winding width is Wc and m is an integer greater than or equal to 1, then (m×360-23.07) / n <Wc<(m×360+23.07) / n×23.07=asin(0.2)×2 If the design is made to satisfy the relationship, the n-th harmonic component can be reduced to one-fifth or less, and sufficient effect can be obtained. (m×360-11.48) / n <Wc<(m×360+11.48) / n×11.48=asin(0.1)×2 If the design satisfies the above relationship, the n-th harmonic component can be reduced to one-tenth or less, resulting in even greater effectiveness.

[0032] 8A to 9B are diagrams showing a simulation of changes in thrust force when the winding width Wc of the coil is kept constant at 90° and the average width Wa of the coil is changed. As shown in Figure 8A, the fundamental component of the thrust peaked at 170° and decreased regardless of whether the average coil width was wide or narrow. Furthermore, as shown in FIG. 8B, the third harmonic component becomes zero near 120°.

[0033] Furthermore, as shown in FIG. 9A, the fifth harmonic component becomes zero near 72° and 144°. Furthermore, as shown in FIG. 9B, the seventh harmonic component becomes zero near 103° and 154°. The reason for this will be explained in detail below using the diagram.

[0034] In FIG. 5, the thrust generated at part I of the coil and the thrust generated at part II are considered. Since parts I and II are connected, the direction of the current flowing when the coil is energized is opposite between parts I and II. If the average coil width Wa is set to 180°, the magnetic flux densities in parts I and II will have opposite signs and equal magnitudes. Because the current flows in opposite directions, the thrust generated in parts I and II will be the same.

[0035] On the other hand, when the average width Wa of the coil is shifted from 180°, the thrust generated at parts I and II will be shifted in phase by the amount of the shift from 180°. Here, if the average coil width Wa is set to an electrical angle of 120° (a deviation of 60° from 180°, equivalent to a deviation of 180° in the third harmonic), the third harmonic will generate thrust forces of opposite phases in parts I and II, and will be cancelled out overall to become zero.

[0036] Furthermore, if the winding width is set to an electrical angle of 72° or 144° (a deviation of 108° or 36° from 180°, equivalent to a deviation of 540° or 180° in the fifth harmonic), the fifth harmonic will generate thrust forces in opposite phases in parts I and II, and will be cancelled out overall to become zero. Similarly, For the 7th harmonic, 51.4°, 102.9°, and 154.3° For the 9th harmonic, 40°, 80°, 120°, and 160° becomes zero.

[0037] In the above, the electrical angle at which it becomes exactly zero is shown, but if the average width Wa is set to a value close to the above, it is possible to reduce specific harmonic components of the thrust force. For example, for the fifth harmonic, the average coil width Wa is 139.4° <Wa<148.6° If the relationship is satisfied, the fifth harmonic component can be reduced to one-fifth or less, and sufficient effect can be obtained.

[0038] Generally, for the nth harmonic component, if the coil winding width is Wa and m is an integer greater than or equal to 1, then (m×360-23.07) / n <Wa<(m×360+23.07) / n×23.07=asin(0.2)×2 If the design is made to satisfy the relationship, the n-th harmonic component can be reduced to one-fifth or less, and sufficient effect can be obtained. (m×360-11.48) / n <Wa<(m×360+11.48) / n×11.48=asin(0.1)×2 If the design satisfies the above relationship, the n-th harmonic component can be reduced to one-tenth or less, resulting in even greater effectiveness.

[0039] Therefore, in the configuration shown in Figure 4, the coil winding width Wc is set to 120° to reduce the third harmonic component, and the coil average width Wa is set to 144° to reduce the fifth harmonic component. Another possible combination of the coil winding width Wc and the coil average width that simultaneously reduces both the third and fifth harmonics is the combination shown in Figure 10B, where the coil winding width Wc is 72° and the coil average width Wa is 120°.

[0040] FIG. 11 is a table comparing the comparative example shown in FIG. 10A, the configuration shown in FIG. 4, and another configuration shown in FIG. 10B. In the configuration of the comparative example in FIG. 10A, the average coil width Wa is set to 180°, and the winding width Wc is designed to be 90°, which is the maximum value within the range where the coils do not overlap with adjacent coils. In the table, the numerical values ​​in the upper row indicate absolute values, and the numerical values ​​in the lower row indicate percentages when the fundamental wave component of the comparative example is set to 100%.

[0041] As shown in FIG. 11, the third and fifth harmonics almost completely disappeared in the configuration shown in FIG. 4 and the alternative configuration shown in FIG. 10B. 4 showed the highest value of 106.46% for the fundamental wave component. This indicates that the configuration of the present embodiment 1 does not generate harmful harmonic components of the thrust, despite the high thrust.

[0042] This is thought to be because the coil shape of the comparative example shown in Figure 5 has a large hollow portion in the middle of the coil, whereas the coil shape of this embodiment 1 shown in Figure 4 has almost no wasted hollow portion and there is a large space in which the coil can be wound, resulting in a larger cross-sectional area of ​​the coil and a larger number of turns in the coil. As described above, in this first embodiment, the thrust density of the linear motor can be improved, and the linear motor can be made smaller. Furthermore, by reducing the harmonic components of the thrust, a linear motor with less thrust fluctuation and less vibration and noise can be provided.

[0043] Furthermore, by devising the configuration of the coil and field magnet section, it is possible to reduce the harmonic components of the thrust, which are an issue when driving in multiple phases, and provide a linear motor and imaging device that can be positioned with high precision. The linear motor of this embodiment can also be represented by a drive circuit shown in FIG.

[0044] Specifically, as shown in FIG. 17, the linear motor has a two-phase drive circuit including a circuit 20a for driving the coil 10a on the A-phase side, a circuit 20b for driving the coil 10b on the B-phase side, and a drive magnet 9 arranged in close proximity to the coils 10a and 10b. The A-phase circuit 20a has positive-side transistors 21a and 21b and negative-side transistors 22a and 22b.

[0045] The B-phase circuit 20b has positive-side transistors 23a and 23b and negative-side transistors 24a and 24b. As a result, by alternately turning on / off the positive and negative sides of the A-phase circuit 20a and the B-phase circuit 20b, the lens frame 3 can be driven back and forth in the optical axis direction relative to the drive magnet 9.

[0046] Furthermore, in the A-phase circuit 20a and the B-phase circuit 20b, the thrust constant with respect to the phase is plotted as a sine wave as shown in FIG. 18(a). The current waveform relative to the phase is as shown in FIG. 18(b). Therefore, by summing the graphs of FIG. 18(a) and FIG. 18(b), the linear motor can obtain a substantially constant thrust force, as shown by the dotted line in FIG. 18(c).

[0047] In the first embodiment, a two-phase drive system using two coils has been shown, but a three-phase drive system using three coils is also possible. However, when using three-phase drive, it is necessary to use three coils lined up in the optical axis direction, and the actuator tends to be longer in the optical axis direction than when using two-phase drive, so two-phase drive is more suitable for lens drive.

[0048] (Embodiment 2) The above-mentioned first embodiment has explained a method for improving performance by devising the shape of the coil, but the second embodiment will show an example of further improving performance by devising the configuration of the field part including the magnet. The configuration of the field part according to the second embodiment will be described with reference to FIGS.

[0049] In the first embodiment, a single magnet 9 is configured by magnetizing it into multiple poles, but in the second embodiment, the magnet 9 is configured by dividing it into magnetic poles. FIG. 12 is a front view and a side view of a field portion according to the second embodiment. In FIG. 12, the field magnet section is made up of a main yoke 7, six large magnets 9a, and two small magnets 9b each half the width of the large magnets.

[0050] The large magnets 9a are arranged on the main yoke 7 so that their magnetic poles are oriented alternately in the north and south directions. The magnetic pole pitch in the multi-pole direction is set to Wp, but the width of the large magnets 9a is made narrower than the magnetic pole pitch by Wg. Small magnets 9b are also arranged on both ends of the large magnets 9a, with a gap of Wg between them. Generally, when magnetizing a single magnet with multiple poles, it is difficult to fully magnetize the area where the magnetic poles change, but by arranging magnets that have already been fully magnetized with a single pole, it becomes easier to bring out the full potential of the magnet, and in many cases it is possible to extract more magnetic flux than when using a single magnet.

[0051] FIG. 13 is an exploded perspective view of the field portion according to the second embodiment. In FIG. 13, a plurality of protrusions 7a are formed on the main yoke 7 by press working. During assembly, the large magnets 9a can be arranged regularly by inserting them between the protrusions a. FIG. 14 is an explanatory diagram showing the principle of harmonics reduction in the field magnet portion according to the second embodiment.

[0052] It is known that the magnetic circuit configuration can be calculated by superposition in the region where magnetic saturation does not occur. It can be understood that the configuration of the field magnet portion of the present embodiment 2 is equivalent to a combination of field magnet portion A, which is magnetized in multiple poles at magnetic pole pitch Wp in FIG. 14, and field magnet portion B, which is magnetized in multiple poles at the same magnetic pole pitch Wp and is shifted in phase by Wg.

[0053] The magnetic flux density generated by field magnet section A and the magnetic flux density generated by field magnet section B have the same waveform and amplitude, but are out of phase by Wg. Here, for example, if Wg is set to an electrical angle of 36°, the phase of the magnetic flux densities of field magnet section A and field magnet section B will be out of phase by 36° (equivalent to 180° for the fifth harmonic), resulting in an overall state in which the fifth harmonic is cancelled out. Similarly, in general, if the gap between adjacent magnets is Wg, the harmonic component to be reduced is the kth order, and j is an arbitrary integer, then: Wg=180×(1+2j) / k If the design is made to satisfy the relationship, the k-th harmonic component can be completely canceled.

[0054] Although the above shows the electrical angle at which it becomes exactly zero, if Wg is set to a value close to the above, it is possible to reduce certain harmonic components of the thrust. In general, if the gap between adjacent magnets is Wg, the harmonic component to be reduced is the kth order, and j is an arbitrary integer, then: {180×(1+2j)-23.07} / k <Wg<{180×(1+2j)+23.07} / k×23.07=asin(0.2)×2 If the design satisfies the above relationship, the k-th harmonic component can be reduced to one-fifth or less, which is a sufficient effect. Furthermore, if the gap between adjacent magnets is Wg, the harmonic component to be reduced is k-th, and j is an arbitrary integer, then: {180×(1+2j)-11.48} / k <Wg<{180×(1+2j)+11.48} / k×11.48=asin(0.1)×2 If the design satisfies the above relationship, the k-th harmonic component can be reduced to one-tenth or less, and an even greater effect can be obtained.

[0055] It goes without saying that reducing the harmonic components of the magnetic flux also reduces the harmonic components of the thrust force. Although the second embodiment described above has shown a method for reducing the harmonic components of the thrust force by configuring the field magnet section, performance can be further improved by combining it with the coil shape shown in the first embodiment described above.

[0056] For example, as explained in the first embodiment, the seventh harmonic component of the magnetic flux can be canceled by reducing the third and fifth harmonic components by changing the coil shape and then setting Wg=25.7°. Therefore, it is possible to reduce the seventh harmonic of the thrust, which could not be reduced by the coil shape alone. Alternatively, while it is theoretically possible to completely cancel the third harmonic by adjusting the coil shape or the configuration of the field magnet, this is impossible in actual manufacturing due to variations in coil dimensions and magnet dimensions. Therefore, by reducing the third and fifth harmonic components through the coil shape and then setting Wg = 60°, the third harmonic component of the magnetic flux can be canceled. Therefore, by doubly reducing the third harmonic of the thrust force through the coil shape and the configuration of the field magnet, the third harmonic component, which is already large, can be effectively reduced, making it possible to stably reduce the harmonic component of the thrust force even when there are dimensional variations.

[0057] (Embodiment 3) The above-mentioned first and second embodiments have described methods for reducing the harmonic components of the thrust force by devising the shape of the coil and the configuration of the field magnet section, but this third embodiment will show an example of further improving performance. 15A and 15B are a side view and a perspective view showing the configuration of the field part according to the third embodiment.

[0058] In the above-mentioned embodiment 1, a configuration was shown in which magnets 9 were arranged only on the outer periphery side of coils 10a and 10b, but in this embodiment 3, a configuration is shown in which magnets 9 are arranged on both the inner and outer periphery sides of the coils. The advantages of placing magnets 9 on both sides of the coil will be explained below. FIG. 16A is a magnetic field line diagram of the field magnet portion of the third embodiment, and FIG. 16B is a magnetic field line diagram of the field magnet portion of the comparative example.

[0059] FIG. 16B shows a magnetic field line diagram in a state where a magnet 9 is placed only on one side of the coil, as in the first embodiment. As shown in FIG. 16B, it can be seen that the magnetic flux of the coil section is directed obliquely. This shows that the coil generates not only the thrust in the optical axis direction necessary to drive the lens, but also a thrust in the vertical direction. As a result of conducting a magnetic field analysis of this comparative example, the thrust in the vertical direction was found to be a maximum of approximately 35% of the thrust in the optical axis direction.

[0060] Vertical thrust causes vibration of the lens frame, noise, etc., so it is desirable that it be as small as possible. FIG. 16A shows a magnetic field line diagram in a state where magnets 9 are placed on both sides of the coil. As shown in Figure 16A, the magnetic flux density of the coil section is significantly straightened compared to Figure 16B. As a result of performing a magnetic field analysis of this example, it was found that no thrust force was generated in the vertical direction.

[0061] Therefore, by placing the magnets 9 on both sides of the coil, vibrations, noise, etc. of the lens frame are less likely to occur. 16A and 16B, it can be seen that the density of the magnetic lines of force in the coil section is higher. A higher density of the magnetic lines of force (= magnetic flux density) means a higher thrust. As a result of performing a magnetic field analysis of this example, it was confirmed that the thrust is improved by approximately 1.5 times by placing magnets 9 on both sides of the coil.

[0062] By arranging magnets 9 on both sides of the coil as in this embodiment, it is possible to suppress the generation of vertical thrust that causes vibration, noise, etc., while at the same time significantly increasing the thrust. In the third embodiment, only the arrangement of magnets 9 on both sides of the coil has been described, but it goes without saying that the techniques of the first and second embodiments can be used in combination.

[0063] As described above, the first to third embodiments have been described as examples of the technology in the present disclosure, and the accompanying drawings and detailed descriptions have been provided for this purpose. Therefore, the components shown in the accompanying drawings and detailed description may include not only essential components for solving the problem, but also components that are not essential for solving the problem in order to illustrate the above technology. Therefore, the fact that these non-essential components are shown in the accompanying drawings or detailed description should not be interpreted as immediately indicating that these non-essential components are essential.

[0064] Furthermore, since the above-described embodiments are intended to illustrate the technology of the present disclosure, various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents. [Industrial Applicability]

[0065] The linear motor of the present disclosure has the effect of increasing thrust and lengthening stroke, and therefore can be widely applied to various devices such as imaging devices that move a lens frame in the optical axis direction to capture an image of a subject. [Explanation of symbols]

[0066] 1 Focus unit (linear motor) 2 Retaining frame 3 Lens frame 4 Main guide pole 5 Sub-guide pole 6 Guide cover 7. Lord Yoke 8 Sub-yoke 9 Drive magnet (magnet) 9a Large Magnet 9b Small magnet 10a, 10b Coil 11 Flexible PCB 12 MR element (position detection sensor) 13 MR magnet (position detection component) 20a, 20b circuits 21a, 21b Transistor 22a, 22b transistors 23a, 23b transistors 24a, 24b Transistors 31 Pole insertion hole 40 Lens barrel 50 Camera (imaging device) 51 Camera body (main body)

Claims

1. A three-phase driven linear motor, A three-phase coil, a magnet disposed along a driving direction at a position facing the three-phase coil; Equipped with The winding width of the coil at the portion facing the magnet is in the range of 120°±7.7° in electrical angle, The average width of the coil at the portion facing the magnet is in the range of 144°±4.6° in electrical angle, The pitch between the three phase coils is 90°±180°×n electrical angles (n is an integer equal to or greater than 0). Linear motor. (Note that the winding width of the coil refers to the width dimension in the driving direction of the substantially straight portion of the coil around which the winding wire is wound that faces the magnet. The average width of the coil refers to the distance between the centers in the driving direction of the substantially straight portion of the coil around which the winding wire is wound that faces the magnet.)

2. The magnet further includes a field magnet portion in which a plurality of the unipolar magnetized magnets are arranged with N poles and S poles alternately arranged, When the gap between adjacent magnets is Wg, the harmonic order to be reduced is k-th order, and j is an arbitrary integer, {180°×(1+2j)-23.07°} / k<Wg<{180°×(1+2j)+23.07°} / k Satisfy the relationship of 2. The linear motor according to claim 1.

3. The magnetic field portion further includes the magnets disposed on both sides of the coil so as to sandwich the coil.

2. The linear motor according to claim 1.

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