Voice coil motor

Abstract

A voice coil motor according to the present disclosure comprises: a cylindrical or columnar inner yoke; a cylindrical outer yoke surrounding the inner yoke so as to form a cylindrical gap between the inner yoke and itself; a cylindrical coil disposed in the gap; a magnet disposed inside the coil in a state of being in contact with the inner yoke, or disposed outside the coil in a state of being in contact with the outer yoke; a first connection yoke connecting one end in the axial direction of the inner yoke and one end in the axial direction of the outer yoke; and a second connection yoke connecting the other end in the axial direction of the inner yoke and the other end in the axial direction of the outer yoke. At least one of the first connection yoke and the second connection yoke has a plurality of yoke pieces arranged in a cylindrical shape so as to connect the inner yoke and the outer yoke. The plurality of yoke pieces are composed of separate members from the inner yoke and the outer yoke so as to be attached to the inner yoke and the outer yoke. A gap for taking out the output of the voice coil motor is provided between the adjacent yoke pieces.

Description

Voice Coil Motor

[0001] The present disclosure relates to voice coil motors.

[0002] A conventional voice coil motor has a configuration in which one axial end of a cylindrical inner yoke is connected to one axial end of a cylindrical outer yoke arranged to form a cylindrical gap between the inner yoke and the outer yoke by a one-end connecting yoke. The one-end connecting yoke is integrally molded with the outer yoke and closes an opening on one axial end of the gap. The opening on the other axial end of the gap is open so that the output of a coil arranged in the gap can be extracted while being movable axially of the gap.

[0003] In the case of a voice coil motor configured as described above, in order to improve the axial thrust of the voice coil motor, the other axial end of the inner yoke and the other axial end of the outer yoke are connected by an other-end connecting yoke. The other-end connecting yoke is integrally molded with the outer yoke and closes the opening on the other axial end side of the gap. However, as mentioned above, the other axial end side of the gap needs to be open, so the other-end connecting yoke has a through-hole for extracting the output of the coil. Typically, a connecting member that connects the coil to a drive unit driven by the output of the voice coil motor passes through the through-hole of the other-end connecting yoke.

[0004] In a voice coil motor having the above-described through hole, a connecting member needs to be passed through the through hole during assembly. Therefore, the connecting member must be configured to be able to pass through the through hole, and this point must be taken into consideration when designing. In other words, in the case of conventional voice coil motors, the connecting member has limited design freedom.

[0005] Japanese Patent Application Laid-Open No. 2000-23442

[0006] In order to solve the above-mentioned problems, a voice coil motor that can improve the degree of freedom in design while improving the thrust force is desired.

[0007] The voice coil motor of the present disclosure includes a cylindrical or columnar inner yoke, a cylindrical outer yoke surrounding the inner yoke to form a cylindrical gap between the inner yoke and the outer yoke, a cylindrical coil disposed in the gap, a magnet disposed inside the coil while in contact with the inner yoke or outside the coil while in contact with the outer yoke, a first connecting yoke connecting one axial end of the inner yoke to one axial end of the outer yoke, and a second connecting yoke connecting the other axial end of the inner yoke to the other axial end of the outer yoke. At least one of the first connecting yoke and the second connecting yoke has a plurality of yoke pieces arranged in a cylindrical shape to connect the inner yoke to the outer yoke, the plurality of yoke pieces being formed from separate members from the inner yoke and the outer yoke so as to be attached to the inner yoke and the outer yoke, and a gap is provided between adjacent yoke pieces to extract output from the voice coil motor.

[0008] FIG. 1 is a schematic perspective view showing a voice coil motor according to an embodiment of the present invention. FIG. 2 is a sectional view taken along line AA' in FIG. 1. FIG. 3 is a sectional view taken along line BB' in FIG. 4. FIG. 4 is a sectional view taken along line CC' in FIG. 5. FIG. 5 is a schematic perspective view showing a voice coil motor according to an embodiment of the present invention, showing a state before yoke pieces are attached to the inner yoke and the outer yoke. FIG. 6 is a schematic perspective view showing a voice coil motor according to an embodiment of the present invention, showing a state in which yoke pieces are in the process of being attached to the inner yoke and the outer yoke. FIG. 7 is a schematic longitudinal sectional view showing a first modified example of the voice coil motor of the present invention. FIG. 8 is a schematic longitudinal sectional view showing a second modified example of the voice coil motor of the present invention.

[0009] A voice coil motor according to one aspect of the present disclosure will be described below with reference to the drawings. A voice coil motor 1 according to this embodiment will be described with reference to FIGS. 1 to 6. The voice coil motor 1 includes an inner yoke 2, an outer yoke 3, a coil 4, a magnet 5, a first connecting yoke 6, a second connecting yoke 7, and a coupling member 8. Note that, hereinafter, the axial direction J1 is defined as the up-down direction. In this regard, one end side of the axial direction J1 is defined as the lower side J11, and the other end side of the axial direction J1 is defined as the upper side J12.

[0010] The inner yoke 2 is cylindrical or columnar. In the illustrated example, the inner yoke 2 is columnar, and the axial direction J1 is aligned in the up-down direction. The inner yoke 2 may also be cylindrical. In this case, the inner yoke 2 is typically cylindrical.

[0011] The outer yoke 3 is cylindrical. In the illustrated example, the outer yoke 3 is cylindrical, and the axial direction J1 runs along the vertical direction. The inner diameter of the outer yoke 3 is larger than the diameter of the cylindrical inner yoke 2. As shown in FIGS. 2 and 4 , the outer yoke 3 is arranged coaxially with the inner yoke 2 so as to surround the inner yoke 2. When the outer yoke 3 surrounds the inner yoke 2, a cylindrical gap 9 is formed between the outer yoke 3 and the inner yoke 2. This gap 9 is cylindrical and is a space between an inner circumferential surface 10 of the outer yoke 3 and an outer circumferential surface 11 of the inner yoke 2. An upper opening J12 of the cylindrical gap 9 opens upward, and a lower opening J11 of the cylindrical gap 9 opens downward.

[0012] The coil 4 is cylindrical. In the illustrated example, the coil 4 is cylindrical, and the axial direction J1 is aligned in the vertical direction. The inner diameter of the coil 4 is larger than the diameter of the inner yoke 2, and the outer diameter of the coil 4 is smaller than the inner diameter of the outer yoke 3. As shown in FIGS. 2 and 4 , the coil 4 is disposed in the gap 9 between the inner yoke 2 and the outer yoke 3, on the same axis as the inner yoke 2 and the outer yoke 3.

[0013] The magnet 5 is cylindrical. In the illustrated example, the magnet 5 is cylindrical, with the axial direction J1 aligned vertically. The outer diameter of the magnet 5 is smaller than the inner diameter of the coil 4. As shown in FIGS. 2 and 4 , the magnet 5 is fixed to the inner yoke 2 with the inner peripheral surface 12 of the magnet 5 in contact with the outer peripheral surface 11 of the inner yoke 2. When fixed to the inner yoke 2, the magnet 5 is arranged coaxially with the inner yoke 2 and the outer yoke 3. When fixed to the inner yoke 2, the magnet 5 is surrounded by the coil 4 located in the gap 9. In this way, the magnet 5 is arranged inside the coil 4 in contact with the inner yoke 2. Note that the magnet 5 in this embodiment is a permanent magnet.

[0014] The first connecting yoke 6 is disk-shaped and connects the inner yoke 2 and the outer yoke 3 at a position J11 below the magnet 5 provided on the inner yoke 2. Specifically, the inner yoke 2 and the outer yoke 3 are fixed to the first connecting yoke 6 with a surface 13 on the lower side J11 of the inner yoke 2 and a surface 14 on the lower side J11 of the outer yoke 3 contacting a plate surface 15 on the upper side J12 of the first connecting yoke 6. For example, the inner yoke 2 and the outer yoke 3 are fixed to the first connecting yoke 6 with screws. When the inner yoke 2 and the outer yoke 3 are fixed to the first connecting yoke 6, the gap 9 is formed between the inner yoke 2 and the outer yoke 3. In this way, the first connecting yoke 6 connects one end of the inner yoke 2 in the axial direction J1 to one end of the outer yoke 3 in the axial direction J1.

[0015] 3 , the second connecting yoke 7 has a plurality of yoke pieces 16 arranged in a cylindrical shape to connect the inner yoke 2 and the outer yoke 3. The plurality of yoke pieces 16 are formed as separate members from the inner yoke 2 and the outer yoke 3 so as to be attached to the inner yoke 2 and the outer yoke 3. In the illustrated example, each of the plurality of yoke pieces 16 is a plate-like member that is approximately fan-shaped in a plan view. Specifically, the yoke piece 16 has a plate surface 17 located on the upper side J12, a plate surface 18 located on the lower side J11, and four end surfaces 19, 20, 21, and 22 that connect the plate surface 17 located on the upper side J12 and the plate surface 18 located on the lower side J11.

[0016] The end face 19 connects one circumferential end of the plate surface 17 to one circumferential end of the plate surface 18, and the end face 20 connects the other circumferential end of the plate surface 17 to the other circumferential end of the plate surface 18. The end faces 19 and 20 are inclined so as to move away from each other as they extend outward in the radial direction K1. That is, the circumferential length between the end faces 19 and 20 increases as they extend outward in the radial direction K1. The end face 21 connects the inner end of the plate surface 17 in the radial direction K1 to the inner end of the plate surface 18 in the radial direction K1, and the end face 22 connects the outer end of the plate surface 17 in the radial direction K1 to the outer end of the plate surface 18 in the radial direction K1. The end face 21 is a curved surface that is recessed in an arc-like shape outward in the radial direction K1 in a plan view, and the end face 22 is a curved surface that bulges outward in an arc-like shape in a plan view.

[0017] Each of the multiple yoke pieces 16 is provided between the inner yoke 2 and the outer yoke 3 at a position J12 above the magnets 5 provided on the inner yoke 2. Specifically, the yoke pieces 16 are fixed to the inner yoke 2 and the outer yoke 3 with the end faces 21 of the yoke pieces 16 in contact with the outer peripheral surface 11 of the inner yoke 2 and the end faces 22 of the yoke pieces 16 in contact with the inner peripheral surface 10 of the outer yoke 3. For example, the yoke pieces 16 are press-fitted between the inner yoke 2 and the outer yoke 3 and attached to the inner yoke 2 and the outer yoke 3 with an adhesive. In this way, the second connecting yoke 7 connects the other end of the inner yoke 2 in the axial direction J1 to the other end of the outer yoke 3 in the axial direction J1.

[0018] When the second connecting yoke 7 is attached to the inner yoke 2 and the outer yoke 3, the end faces 22 of the yoke pieces 16 are located on the outer yoke 3 side, and the end faces 21 of the yoke pieces 16 are located on the inner yoke 2 side. Therefore, the circumferential length of the ends of the yoke pieces 16 located on the outer yoke 3 side is greater than the circumferential length of the ends of the yoke pieces 16 located on the inner yoke 2 side. As described above, the yoke pieces 16 are provided between the inner yoke 2 and the outer yoke 3. Therefore, when the yoke pieces 16 are fixed, the end faces 22 of the yoke pieces 16 located on the outer yoke 3 side are in contact with the inner peripheral surface 10 of the outer yoke 3, and the end faces 21 of the yoke pieces 16 located on the inner yoke 2 side are in contact with the outer peripheral surface 11 of the inner yoke 2.

[0019] When the second connecting yoke 7 is attached to the inner yoke 2 and the outer yoke 3, adjacent yoke pieces 16, 16 do not contact each other. That is, there is a gap between the end faces 19, 20 of adjacent yoke pieces 16, 16. Therefore, a gap 23 that penetrates vertically is provided between adjacent yoke pieces 16, 16. This gap 23 is for extracting the output of the voice coil motor 1. In the illustrated example, a connecting member 8 that connects the coil 4 to a drive unit (not shown) that is driven by the output of the voice coil motor 1 is passed through the gap 23 between adjacent yoke pieces 16, 16.

[0020] The connecting member 8 has a drive unit-side connection piece 24 located on the upper side J12, a motor side connection piece 25 located on the lower side J11, and multiple connection pieces 26 connecting the drive unit-side connection piece 24 and the motor side connection piece 25. The drive unit-side connection piece 24 is disk-shaped and is arranged with its plate surface facing up and down. A drive unit is connected to the drive unit-side connection piece 24. The motor side connection piece 25 is short cylindrical and opens to the lower side J11. An upper wall 27 of the motor side connection piece 25 has a circular through-hole 28 that penetrates in the up and down direction. The coil 4 is supported on the end of the lower side J11 of the motor side connection piece 25. When the coil 4 is supported by the motor side connection piece 25, the axial direction J1 of the coil 4 is aligned with the up and down direction. Each of the multiple connection pieces 26 is plate-shaped. The upper end J12 of the connection piece 26 is connected to the drive unit side connection piece 24, and the lower end J11 of the connection piece 26 is connected to the upper wall 27 of the motor side connection piece 25.

[0021] When the drive-side connection piece 24 and the motor-side connection piece 25 are connected by the connection piece 26, the drive-side connection piece 24 and the motor-side connection piece 25 are spaced apart in the vertical direction. When the multiple connection pieces 26 are connected to the drive-side connection piece 24 and the motor-side connection piece 25, they are spaced apart in the circumferential direction of the drive-side connection piece 24 and the circumferential direction of the motor-side connection piece 25. That is, there is a gap between adjacent connection pieces 26, 26. With this configuration, the connecting member 8 has a yoke gap 29 surrounded by the upper walls 27 of the drive-side connection piece 24 and the motor-side connection piece 25 and the adjacent connection pieces 26, 26. The yoke gap 29 opens outward in the radial direction K1 of the drive-side connection piece 24 and the motor-side connection piece 25. A yoke piece 16 is disposed in the yoke gap 29. In this embodiment, the connecting member 8 is integrally molded from an appropriate material.

[0022] 2 and 4 , the connecting member 8 connects the drive unit and the coil 4 while passing through the gap 23. In this case, with the connecting piece 26 of the connecting member 8 passing through the gap 23, the drive unit side connecting piece 24 is located on the upper side J12 of the second connecting yoke 7, and the motor side connecting piece 25 is located within the gap 9 on the lower side J11 of the second connecting yoke 7. The coil 4 is provided at the end of the lower side J11 of the motor side connecting piece 25 so as to extend to the lower side J11. When supported by the motor side connecting piece 25, the coil 4 is disposed between the outer yoke 3 and the magnet 5 provided on the inner yoke 2.

[0023] In the voice coil motor 1 configured as described above, the coil 4 can be moved in the axial direction J1 by applying current to the coil 4. The movement of the coil 4 in the axial direction J1 causes the connecting member 8, which supports the coil 4, to move in the axial direction J1. Therefore, the voice coil motor 1 can drive the drive unit connected to the connecting member 8.

[0024] Next, the manufacture of the voice coil motor 1 of this embodiment will be described with reference to FIGS. 5 and 6 . To manufacture the voice coil motor 1, first, the outer yoke 3 and the inner yoke 2 are fixed to the first connecting yoke 6, and the magnet 5 is fixed to the inner yoke 2. In the illustrated example, the outer side of the magnet 5 in the radial direction K1 is the north pole, and the inner side of the magnet 5 in the radial direction K1 is the south pole. Next, the yoke pieces 16 are inserted from the outer side in the radial direction K1 into the yoke gaps 29 of the connecting member 8, in which the coil 4 is supported. The yoke pieces 16 are temporarily fixed to the connecting member 8 while inserted into the yoke gaps 29. With the yoke pieces 16 inserted into the yoke gaps 29, the coil 4 supported by the connecting member 8 is inserted into the gap 9 through the opening of the upper side J12 of the gap 9. After the coil 4 is inserted into the gap 9, the yoke pieces 16 are fixed to the inner yoke 2 and the outer yoke 3. When the yoke pieces 16 are fixed to the inner yoke 2 and outer yoke 3, the inner yoke 2 passes through the through-holes 28 of the connecting member 8. When the yoke pieces 16 are temporarily fixed to the connecting member 8, the positional relationship between the yoke pieces 16 and the outer yoke 3 is preferably such that when the connecting member 8 is moved downward J11, the end faces 22 of the yoke pieces 16 come into contact with the inner peripheral surface 10 of the outer yoke 3. In this manner, the voice coil motor 1 of this embodiment is manufactured.

[0025] The voice coil motor 1 of this embodiment has a first connecting yoke 6 and a second connecting yoke 7. Therefore, as shown in FIG. 4 , in the voice coil motor 1, a magnetic circuit 30 is formed by the inner yoke 2, the outer yoke 3, and the first connecting yoke 6, and a magnetic circuit 31 is formed by the inner yoke 2, the outer yoke 3, and the second connecting yoke 7. Therefore, the voice coil motor 1 of this embodiment can improve the thrust of the coil 4. Furthermore, in the voice coil motor 1 of this embodiment, the second connecting yoke 7 is attached to the inner yoke 2 and the outer yoke 3. Therefore, with the voice coil motor 1 of this embodiment, it is not necessary to pass the connecting member 8 through the second connecting yoke 7 when it is attached to the inner yoke 2 and the outer yoke 3, and therefore the degree of freedom in designing the connecting member 8 can be improved.

[0026] In the voice coil motor 1 of this embodiment, the yoke pieces 16 are generally fan-shaped in plan view, and therefore the circumferential length of the ends of the yoke pieces 16 located on the outer yoke 3 side is greater than the circumferential length of the ends of the yoke pieces 16 located on the inner yoke 2 side. Therefore, with the voice coil motor 1 of this embodiment, the greatest circumferential length of the voids 23 is smaller than the radial length of the voids 23, making it possible to ensure the cross-sectional area of ​​the voids 23 while suppressing interference with the flow of magnetic flux by the voids 23. By ensuring the cross-sectional area of ​​the voids 23, the connecting pieces 26 of the coupling member 8 can be made thicker, thereby increasing the strength of the coupling member 8.

[0027] In the voice coil motor 1 of this embodiment, the connecting member 8 is integrally molded. Therefore, with the voice coil motor 1 of this embodiment, the rigidity of the connecting member 8, which is the moving member, can be improved. This makes it possible to suppress vibration of the connecting member 8 during movement, thereby improving the performance of the voice coil motor 1. Furthermore, with the voice coil motor 1 of this embodiment, the connecting member 8 has yoke gaps 29 into which the yoke pieces 16 are inserted. This allows the yoke pieces 16 to be attached to the inner yoke 2 and outer yoke 3 with the yoke pieces 16 inserted into the yoke gaps 29 during manufacture of the voice coil motor 1. Therefore, with the voice coil motor 1 of this embodiment, the assembly of the voice coil motor 1 can be ensured.

[0028] According to the present embodiment described above, the voice coil motor 1 includes the first connecting yoke 6 and the second connecting yoke 7 having a plurality of yoke pieces 16 that are separate members from the inner yoke 2 and the outer yoke 3, and a gap 23 is provided between adjacent yoke pieces 16, 16. Therefore, it is possible to provide a voice coil motor 1 that can improve thrust and increase design freedom.

[0029] Although the present disclosure has been described in detail, the present disclosure is not limited to the above-described embodiments. Various additions, substitutions, modifications, partial deletions, etc. are possible within the scope of the gist of the present disclosure, or within the scope of the gist of the present disclosure derived from the content of the claims and their equivalents. In the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0030] For example, as in Modification 1 shown in Fig. 7, the magnet 5 may be provided on the outer yoke 3. Note that components having the same reference numerals as those in the above embodiment have the same functions, and therefore, the description thereof may be omitted below.

[0031] In the voice coil motor 1a of the first modified example, the inner diameter of the cylindrical magnet 5 is larger than the outer diameter of the coil 4. As shown in FIG. 7 , the magnet 5 is fixed to the outer yoke 3 with the outer peripheral surface 32 of the magnet 5 in contact with the inner peripheral surface 10 of the outer yoke 3. In the illustrated example, the outer side of the magnet 5 in the radial direction K1 is the north pole, and the inner side of the magnet 5 in the radial direction K1 is the south pole. With the magnet 5 fixed to the outer yoke 3, the coil 4 located in the gap 9 is surrounded by the magnet 5. In other words, the coil 4 is disposed between the magnet 5 fixed to the outer yoke 3 and the inner yoke 2. In this way, the magnet 5 is disposed outside the coil 4 while in contact with the outer yoke 3.

[0032] The magnet 5 and the inner yoke 2 may also have the configuration of Modification 2 shown in Fig. 8. Note that components having the same reference numerals as those in the above embodiment have the same functions, and therefore, the description thereof may be omitted below.

[0033] In the voice coil motor 1b of the second modified example, the magnet 5 is columnar. In the illustrated example, the magnet 5 is cylindrical, with the axial direction J1 aligned vertically. The magnet 5 is fixed to the first connecting yoke 6. Specifically, the magnet 5 is fixed to the first connecting yoke 6 with the surface 33 of the lower side J11 of the magnet 5 in contact with the plate surface 15 of the upper side J12 of the first connecting yoke 6. When fixed to the first connecting yoke 6, the magnet 5 extends from the first connecting yoke 6 to the upper side J12. When fixed to the first connecting yoke 6, the magnet 5 is arranged coaxially with the outer yoke 3. The upper side J12 portion of the magnet 5 is a north pole, and the lower side J11 portion of the magnet 5 is a south pole.

[0034] In the voice coil motor 1b of the second modified example, the inner yoke 2 is columnar. In the illustrated example, the inner yoke 2 is cylindrical, with the axial direction J1 extending in the vertical direction. The inner yoke 2 is fixed to the first connecting yoke 6 via the magnet 5. Specifically, the inner yoke 2 is fixed to the magnet 5 with the surface 13 of the lower side J11 of the inner yoke 2 in contact with the surface 34 of the upper side J12 of the magnet 5. When fixed to the first connecting yoke 6, the inner yoke 2 is arranged on the same axis as the magnet 5 and the outer yoke 3.

[0035] The diameter of the inner yoke 2 and the diameter of the magnet 5 are smaller than the inner diameter of the outer yoke 3. Therefore, a continuous cylindrical gap 9 is formed between the inner yoke 2 and the outer yoke 3, and between the magnet 5 and the outer yoke 3, in the vertical direction. The coil 4 supported by the connecting member 8 is disposed in this gap 9. The coil 4 is disposed on the same axis as the inner yoke 2 and the outer yoke 3.

[0036] Furthermore, in the above embodiment, of the first connecting yoke 6 and the second connecting yoke 7, the second connecting yoke 7 has a plurality of yoke pieces 16, but of the first connecting yoke 6 and the second connecting yoke 7, the first connecting yoke 6 may have a plurality of yoke pieces 16, or both the first connecting yoke 6 and the second connecting yoke 7 may have a plurality of yoke pieces 16. In other words, it is sufficient that at least one of the first connecting yoke 6 and the second connecting yoke 7 has a plurality of yoke pieces 16 arranged in a cylindrical shape so as to connect the inner yoke 2 and the outer yoke 3.

[0037] In the above embodiment, the gap 23 is generally fan-shaped in plan view, but is not limited thereto and may be, for example, rectangular or circular in plan view. In this case, the inner yoke 2, the outer yoke 3, and the yoke pieces 16 have appropriate shapes.

[0038] The following supplementary note is further disclosed regarding the above embodiment: (Supplementary Note 1) A voice coil motor (1) includes a cylindrical or columnar inner yoke (2), a cylindrical outer yoke (3) surrounding the inner yoke (2) to form a cylindrical gap (9) between the inner yoke (2) and the outer yoke (3), a cylindrical coil (4) disposed in the gap (9), a magnet (5) disposed inside the coil (4) while in contact with the inner yoke (2) or outside the coil (4) while in contact with the outer yoke (3), a first connecting yoke (6) connecting one end of the inner yoke (2) in the axial direction (J1) to one end of the outer yoke (3) in the axial direction (J1), and a second connecting yoke (7) connecting the other end of the inner yoke (2) in the axial direction (J1) to the other end of the outer yoke (3) in the axial direction (J1). At least one of the first connecting yoke (6) and the second connecting yoke (7) has a plurality of yoke pieces (16) arranged in a cylindrical shape to connect the inner yoke (2) and the outer yoke (3), the plurality of yoke pieces (16) being formed as separate members from the inner yoke (2) and the outer yoke (3) so as to be attached to the inner yoke (2) and the outer yoke (3), and a gap (23) is provided between adjacent yoke pieces (16, 16) for extracting output from the voice coil motor (1). (Supplementary Note 2) In the voice coil motor (1) of Supplementary Note 1, it is preferable that the circumferential length of the end of the yoke piece (16) located on the outer yoke (3) side is greater than the circumferential length of the end of the yoke piece (16) located on the inner yoke (2) side. (Supplementary Note 3) In the voice coil motor (1) of Supplementary Note 1 or 2, it is preferable that an end face (22) of the yoke piece (16) located on the outer yoke (3) side is in contact with the inner peripheral surface (10) of the outer yoke (3), and an end face (21) of the yoke located on the inner yoke (2) side is in contact with the outer peripheral surface (11) of the inner yoke (2).(Supplementary Note 4) In any of Supplementary Notes 1 to 3, the voice coil motor (1) is provided with a connecting member (8) that penetrates the gap (23) and connects the coil (4) to a drive unit that is driven by the output of the voice coil motor (1), and the connecting member (8) preferably has a yoke gap (29) in which the yoke piece (16) is disposed and is integrally molded.

[0039] REFERENCE SIGNS LIST 1 Voice coil motor 2 Inner yoke 3 Outer yoke 4 Coil 5 Magnet 6 First connecting yoke 7 Second connecting yoke 8 Connecting member 9 Gap 10 Inner peripheral surface of outer yoke 11 Outer peripheral surface of inner yoke 16 Yoke piece 21 End surface of yoke piece 22 End surface of yoke piece 23 Air gap 29 Air gap for yoke

Claims

1. A voice coil motor comprising: a cylindrical or columnar inner yoke; an outer yoke that is cylindrical and surrounds the inner yoke to form a cylindrical gap between the inner yoke; a cylindrical coil arranged in the gap; a magnet that is arranged inside the coil while in contact with the inner yoke, or outside the coil while in contact with the outer yoke; a first connecting yoke connecting one axial end of the inner yoke to one axial end of the outer yoke; and a second connecting yoke connecting the other axial end of the inner yoke to the other axial end of the outer yoke, wherein at least one of the first connecting yoke and the second connecting yoke has a plurality of yoke pieces arranged in a cylindrical shape to connect the inner yoke to the outer yoke, the plurality of yoke pieces are made of separate members from the inner yoke and the outer yoke so as to be attached to the inner yoke and the outer yoke, and a gap is provided between adjacent yoke pieces for extracting output of the voice coil motor.

2. The voice coil motor according to claim 1, wherein the circumferential length of the end of said yoke piece located on said outer yoke side is greater than the circumferential length of the end of said yoke piece located on said inner yoke side.

3. A voice coil motor as described in claim 1 or 2, wherein an end face of the yoke piece located on the outer yoke side is in contact with the inner peripheral surface of the outer yoke, and an end face of the yoke piece located on the inner yoke side is in contact with the outer peripheral surface of the inner yoke.

4. A voice coil motor as claimed in any one of claims 1 to 3, further comprising a connecting member which passes through the gap and connects the coil to a drive section which is driven by the output of the voice coil motor, the connecting member having a yoke gap in which the yoke piece is disposed and which is integrally molded.

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