JP5126464B2 - Stepping motor and camera focus adjustment actuator - Google Patents

Description

  The present invention relates to a stepping motor, and more particularly to a small and small stepping motor used for driving a lens of an optical disk device or a camera.

  Conventionally, along with the demand for downsizing of devices such as optical disk devices, video cameras, and digital cameras, lens driving stepping motors housed in the devices are also required to be downsized in accordance with the accommodation space. It is coming. In response to such demands, a rotor having a multipolar magnetized magnet on the outer peripheral surface, an outer yoke having pole teeth close to the outer peripheral surface, an inner yoke, a coil bobbin wound with an exciting coil for exciting the same, etc. A stepping motor that includes a stator and has a coil bobbin disposed at both ends in the axial direction of the magnet, thereby reducing the outer diameter of the motor to a value approximately equal to the outer diameter of the magnet plus the thickness of the pole teeth. Has been proposed (see, for example, Patent Document 1).

  Specifically, as shown in the cross-sectional view of FIG. 7 and the exploded perspective view of FIG. 8, the stepping motor 100 includes a rotor 110 having a rotor magnet 111 magnetized on the outer peripheral surface and a rotor 110 as an axis. This is a claw pole type stepping motor having two sets of stators 120 facing each other in the direction of the direction and having the exciting coils 125 of the stator 120 disposed on both ends of the rotor magnet 111 in the axial direction. The stator 120 is disposed on each end in the axial direction of the rotor magnet 111, and the stator 120 includes an outer yoke 123 having pole teeth 123b that are close to and opposed to the outer periphery of the rotor magnet 111 magnetized in multiple poles, and pole teeth. The inner yoke 121 includes 121b, and the outer yoke 123 and a coil bobbin 122 around which a coil 125 for exciting the inner yoke 121 is wound.

The inner yoke 121 is made of a magnetic material, and is disposed on one end surface side of the coil bobbin 122 facing the disc-shaped side surface of the rotor magnet 111, and extends from the flat plate portion 121a to face the outer peripheral end surface of the rotor magnet 111. And a plurality of pole tooth portions 121b. Similarly, the outer yoke 123 is formed of a magnetic material, and extends from the flat plate portion 123a disposed on the side surface of the coil bobbin 122 opposite to the surface on which the flat plate portion 121a of the inner yoke 121 is disposed, and the flat plate portion 123a. And a plurality of pole teeth 123b facing the outer peripheral surface of the rotor magnet 111. The pole teeth 121b of the inner yoke 121 and the pole teeth 123b of the outer yoke 123 are alternately meshed on the same circumference to form a cylindrical space. Moreover, the pole teeth 123b of the outer yoke 123 and the pole teeth 121b of the inner yoke 121 are arranged with a phase difference of 180 degrees in electrical angle. A terminal block 122 b in which terminal pins 126 are planted is formed at the outer peripheral end of the coil bobbin 122. The inner yoke 121 and the outer yoke 123 are on the inner diameter side of the coil bobbin 122, and are formed of a magnetic material into an opening formed in the flat plate portion 121a of the inner yoke 121 and an opening formed in the flat plate portion 123a of the outer yoke 123. The inner boss 121 and the outer yoke 123 are magnetically and mechanically coupled to each other by fitting the cylindrical bosses 124 respectively. The generation of unnecessary magnetic loops between the two sets of stators 120 is prevented by spacers 134 made of a non-magnetic material sandwiched between the stators 120.
Furthermore, each stator 120 is covered from the outside by a case 131 made of a non-magnetic material, and the two ends of the stator 120 are fixed to each other by the open end of the case 131 being blocked by the bracket 132. Reference numeral 113 denotes a resin washer, and reference numeral 133 denotes a bearing. The shaft 112 of the rotor 110 is pivotally supported by the case 131 and the bracket 132 via the bearing 133.

JP 2003-9497 A

  The conventional stepping motor 100 has a small size and a small diameter, and is therefore used as a lens driving motor in zooming and focusing operations of video cameras and digital cameras. However, for the following reasons, it is difficult to satisfy the demands of recent focusing operations such as moving to a desired position and positioning (access) at high speed and with high accuracy. By the way, in order to access a desired position at high speed and with high accuracy, it is necessary that the high speed response is excellent. However, the high speed response of the stepping motor is greatly influenced by the moment of inertia of the rotor 110. It is well known that a low moment of inertia is indispensable for realizing high-speed response. For this reason, the weight reduction of the rotor magnet 111 is effective in reducing the moment of inertia of the rotor 110.

  Here, in view of the fact that the moment of inertia of the cylindrical rotating body is proportional to the fourth power, the length, and the density of the diameter of the cylindrical rotating body, Forming a sleeve made of a non-magnetic material at the inner peripheral end of the rotor, (ii) reducing the axial length (thickness) of the rotor magnet, and (iii) reducing the outer diameter of the rotor magnet. However, in the conventional stepping motor 100 shown in FIG. 7, in the type used for a video camera, a digital camera, or the like, the outer diameter of the stepping motor 100 is reduced to 6 mm in order to reduce the size and diameter. For this reason, it is very difficult to realize the method (i) of forming the sleeve made of the nonmagnetic material at the inner peripheral end of the rotor magnet 111 in terms of securing the installation space. Further, the method (ii) for reducing the axial length (thickness) of the rotor magnet 111 has a drawback that the motor torque is greatly reduced and a predetermined motor torque cannot be obtained.

  On the other hand, the method (iii) of reducing the outer diameter dimension of the rotor magnet 111 is the most effective as a method of reducing the moment of inertia of the rotor 110, but the gap (distance) between the rotor magnet 111 and the pole teeth 121b and 123b. ) Is expanded more than necessary, and as a result, the motor torque is greatly reduced, resulting in a problem that a predetermined motor torque cannot be obtained. In the method (iii), in order to prevent an increase in the gap (distance) between the rotor magnet 111 and the pole teeth 121b and 123b, the pole teeth 121b and 123b are bent toward the inner diameter side to narrow the gap to a necessary level. Even if the method is adopted, the diameter dimension of the inner space formed by the pole tooth portions 121b and 123b becomes smaller than the outer diameter dimension of the coil bobbin 122, which causes a problem that the coil bobbin 122 cannot be disposed. On the other hand, when the outer diameter dimension of the coil bobbin 122 is further reduced in accordance with the diameter dimension of the inner space narrowed by the pole tooth portions 121b and 123b, the magnetomotive force decreases as the number of turns of the coil 125 decreases. It becomes difficult to obtain a predetermined motor torque. As described above, as long as the structure of the conventional stepping motor 100 is followed, it has been difficult to take measures to reduce the moment of inertia of the rotor while ensuring the necessary motor torque.

The present invention has been made in view of the above problems, and the object of the present invention is to reduce the outer diameter of the rotor magnet in order to obtain desired motor characteristics in a small and thin stepping motor. It is possible to increase the degree of freedom in selecting the internal layout. Then, in a small stepping motor having a small diameter, it is to reduce the moment of inertia of the rotor without lowering the motor torque, and to secure the necessary high-speed response.

In order to solve the above problems, the stepping motor of the present invention is a stepping motor in which the outer peripheral surface of the rotor magnet is surrounded by pole teeth protruding in the axial direction from the stators arranged on both sides of the rotor magnet in the axial direction. Thus, by making the pole tooth part of the stator yoke constituting the stator a separate structure, it is possible to facilitate measures for increasing the degree of freedom of selection of the stator structure, such as reducing the outer diameter of the rotor, and the inertia of the rotor The moment is reduced and the necessary high-speed response is ensured.
In addition, the camera focus adjustment actuator of the present invention includes the stepping motor according to the present invention, so that it is possible to perform focus adjustment quickly and accurately while being small.
(Aspect of the Invention)
The following aspects of the present invention exemplify the configuration of the present invention, and will be described separately for easy understanding of various configurations of the present invention. Each item does not limit the technical scope of the present invention. Therefore, the technical aspects of the present invention also apply to those in which some of the constituent elements in each section are replaced, deleted, or other constituent elements are added while referring to the best mode for carrying out the invention. It can be included in the range.

(1) A stepping motor in which an outer peripheral surface of a rotor magnet is surrounded by pole teeth protruding in an axial direction from a stator disposed on both axial sides of the rotor magnet,
The stator includes a coil bobbin, a bottomed cylindrical housing having a bottom wall at one end, the other end being opened, and storing the coil bobbin, and first and second stator yokes,
The coil bobbin includes a core part and flange parts at both ends of the core part, and a terminal block is integrally formed on one of the flange parts,
A notch for projecting the terminal block to the outside of the housing is formed in the cylindrical wall of the housing. A central portion of the bottom wall of the housing has a through hole, and the through hole extends from the through hole toward the inside of the housing. And a cylindrical core penetrating the central hole of the coil bobbin is provided,
The first stator yoke is provided with an annular portion and a plurality of pole teeth portions that are arranged at equal intervals along the inner peripheral end of the annular portion and project in the axial direction.
The second stator yoke is provided with an annular portion and a plurality of pole teeth portions that are arranged at equal intervals along the outer peripheral end of the annular portion and project in the axial direction.
An annular portion of the first stator yoke is fixed to an inner wall near the open end of the housing, and an annular portion of the second stator yoke is fixed to the core, so that the first stator yoke and The second stator yoke is mechanically and magnetically coupled via the housing, and the pole teeth of the first stator yoke and the pole teeth of the second stator yoke have the same circumference. A meshing cylindrical space is formed alternately on top,
The rotor magnet is disposed in the cylindrical space, the rotating shaft of the rotor magnet is inserted into the core, and the terminal blocks of the coil bobbin protruding from the notch of the housing are disposed so that the axial side surfaces are close to each other. Further, a pair of stators are arranged opposite to each other on both sides in the axial direction of the rotor magnet, and the open ends of the housing are closely fixed to each other (Claim 1).

In the stepping motor described in this section, a cylindrical core protrudes from the through hole formed in the center of the bottom wall of the bottomed cylindrical housing toward the inside of the housing, and the core passes through the center hole of the coil bobbin. In this way, the second stator yoke is fixed to the core that is housed in the housing and penetrates the coil bobbin, so that the coil bobbin is in a state where the terminal block protrudes from the notch of the housing and the bottom wall of the housing and The periphery is covered by the inner wall of the cylindrical surface and the second stator yoke fixed to the core. Furthermore, by fixing the first stator yoke to the inner wall near the open end of the housing, the first stator yoke and the second stator yoke are mechanically and magnetically coupled via the housing, and The pole teeth of the first stator yoke and the pole teeth of the second stator yoke are alternately meshed on the same circumference to form a cylindrical space.
That is, the outer yoke which is a basic element of the claw pole type stepping motor is constituted by the housing and the first stator yoke, and the inner part which is the basic element of the stator of the claw pole type stepping motor is constituted by the second stator yoke. A yoke is constructed. The rotor magnet is disposed in the cylindrical space, the rotation shaft of the rotor magnet is inserted into the hollow hole of the core, and the terminal block protruding from the notch of the housing is disposed so that the axial side surfaces are close to each other. in so that, disposed opposite the pair of stators in the axial direction on both sides of the rotor magnet, in Rukoto to open ends to each other tightly fixed in the housing, the outer peripheral end face and the distance and the minimum required for each pole teeth of the rotor magnet It is possible to generate a predetermined motor torque even though it is a small and thin stepping motor that is opposed to each other.

In addition, as a fixing method of a housing and a core, it is possible to use the method of press-fitting a cylindrical core with respect to the through-hole formed in the bottom wall center part, for example. As a method for fixing the annular portion of the first stator yoke to the inner wall near the open end of the housing, for example, a method of press-fitting the outer peripheral end of the annular portion into the inner wall of the housing can be used. Furthermore, as a method of fixing the annular portion of the second stator yoke to the core, for example, a method of press-fitting the inner peripheral end of the annular portion into the outer peripheral wall of the core can be used.
In the stator of the present invention, the first stator yoke, the second stator yoke, the coil bobbin, and the core are all housed inside the housing, and the open end of the housing is closed by the first stator yoke. It has a structure that can be removed. Therefore, when performing each of the above fixing operations, by fixing the annular portion of the first stator yoke to the inner wall near the open end of the housing at the end, the operation of fixing the core to the center of the bottom wall of the housing, The operation of storing the coil bobbin in the housing and the operation of fixing the second stator yoke to the core can be performed smoothly by passing the central hole of the coil bobbin through the core.

(2) A plurality of pole teeth portions arranged at equal intervals along the inner peripheral end of the annular portion of the first stator yoke protrude toward the bottom wall of the housing, and the annular portion of the second stator yoke A stepping motor characterized in that the plurality of pole teeth portions arranged at equal intervals along the outer peripheral end protrude in the direction of the open end of the housing (claim 2).
In the stepping motor described in this section, the pole teeth of the first stator yoke and the pole teeth of the second stator yoke are alternately meshed with each other not only on the same circumference but also in the axial direction. By forming a cylindrical space, the space in the axial direction of the stator is effectively used, and an increase in the axial dimension is prevented.

(3) The rotor magnet is formed with a smaller diameter than the outer diameter of the coil bobbin,
The inner diameter of the cylindrical space formed by alternately engaging the pole teeth of the first stator yoke and the pole teeth of the second stator yoke is matched to the outer diameter of the rotor magnet, A stepping motor formed to have a smaller diameter than the outer diameter of the coil bobbin.
In the stepping motor described in this section, the rotor magnet is formed with a diameter smaller than the outer diameter of the coil bobbin, so that the inertia moment of the rotor is reduced and the required high-speed response is ensured. Further, the inner diameter of the cylindrical space formed by alternately engaging the pole teeth of the first stator yoke and the pole teeth of the second stator yoke on the same circumference is the outer diameter of the rotor magnet. In addition, the outer diameter of the coil bobbin is smaller than the outer diameter of the coil bobbin so that the outer peripheral edge of the rotor magnet and each pole tooth face each other with a minimum necessary distance to generate the necessary motor torque. To be.
The present invention has a structure in which the annular portion of the first stator yoke is fixed to the inner wall near the open end of the housing, that is, the pole tooth portion of the outer yoke which is a basic element of the stator of the claw pole type stepping motor. Is formed separately from the housing, the rotor magnet is formed to have a smaller diameter than the outer diameter of the coil bobbin, and the inner diameter of the cylindrical space formed by the pole teeth according to the outer diameter of the rotor magnet However, even if it employs a structure in which the pole tooth portion overlaps the coil bobbin when viewed in the axial direction by being formed with a diameter smaller than the outer diameter of the coil bobbin, it does not hinder the assembly of each part.

(4) The coil bobbin includes a small diameter portion disposed adjacent to the radially outer side of the core and a large diameter portion disposed adjacent to the radially outer side of the pole tooth portion of the second stator yoke. A stepping motor comprising a stepped cylindrical winding core portion and a coil wound around both the small diameter portion and the large diameter portion.
In the stepping motor described in this section, the coil bobbin has a large diameter that is disposed adjacent to the radially outer side of the pole tooth portion of the second stator yoke and a small diameter portion that is disposed adjacent to the radially outer side of the core. A stepped cylindrical core portion comprising a portion, and by increasing the number of turns of the coil by winding the coil around both the small diameter portion and the large diameter portion, the magnetomotive force of the coil increases, The motor torque is increased.

(5) The coil bobbin includes a flange portion that extends radially outward from both ends of a cylindrical core, a terminal block is formed on one of the flange portions, and the cylindrical wall of the housing has an external portion from the inside of the housing. A stepping motor having a notch for exposing the terminal block.
In the stepping motor described in this section, the winding end position of the coil is determined by the flange portion of the coil bobbin. Further, a terminal block is formed on one of the flange portions, so that terminals connected to both ends of the coil are fixed to the coil bobbin by the terminal block. In addition, a notch for exposing the terminal block from the inside of the housing to the outside is formed in the cylindrical wall of the housing, and the position of the coil bobbin relative to the housing is reliably determined by the terminal block and the notch.

(6) A stator disposed on both axial sides of the rotor magnet is a stepping motor in which housings are directly fixed.
In the stepping motor described in this section, when the housings are directly fixed, the outer diameter dimension of the stator becomes the outer diameter dimension of the stepping motor as it is.

(7) A focus adjusting actuator for a camera comprising the stepping motor according to any one of (1) to (4).
Since the focus adjusting actuator of the camera described in this section has the characteristics of the stepping motor described in any one of (1) to (4) above, it is small and fast and accurate. Focus adjustment can be performed.

  Since the present invention is configured as described above, in a small and thin stepping motor, in order to obtain desired motor characteristics, it is possible to increase the degree of freedom in selecting the internal layout, such as reducing the outer diameter of the rotor magnet. It becomes possible. In a small and thin stepping motor, it is possible to reduce the moment of inertia of the rotor without lowering the motor torque and to secure the necessary high-speed response.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Here, parts that are the same as or correspond to those in the prior art are denoted by the same reference numerals, and detailed description thereof is omitted.
As shown in FIGS. 1 and 2, the stepping motor 1 according to the first embodiment of the present invention includes a pair of rotor magnets 3 constituting the rotor 2 (FIG. 2) arranged on both sides in the axial direction. This is a PM type (claw pole type) stepping motor in which the outer peripheral surface of the rotor magnet 3 is surrounded by pole teeth 7b and 8b protruding in the axial direction from the stator 5. The outer peripheral surface of the rotor magnet 3 is multipolarly magnetized, and the rotating shaft 4 passes through the center. In the present embodiment, the rotor magnet 3 is an Nd—Fe—B based bonded magnet, and is fixed to the rotating shaft 4 with an adhesive.
For convenience of explanation, one stator is referred to as an A-phase stator 5A, and the other stator is referred to as a B-phase stator 5B. The A-phase stator 5A and the B-phase stator 5B are positioned so as to have a phase difference of 90 degrees in electrical angle. Since the A-phase stator 5A and the B-phase stator 5B have the same structure, only the A-phase stator 5A will be described in detail below.

  As shown in FIGS. 3 and 4, the A-phase stator 5A includes a coil bobbin 9, a bottomed cylindrical housing 6 in which the coil bobbin is housed, a first stator yoke 7, and a second stator yoke 8. Including. Here, the coil bobbin 9 is made of a nonmagnetic material, and the housing 6, the first stator yoke 7, and the second stator yoke 8 are made of a magnetic material. In the present embodiment, the coil bobbin 9 is injection-molded using a synthetic resin (for example, liquid crystal polymer), and includes a flange portion 9a that extends radially outward from both ends of a cylindrical core portion having a constant radius. ing. A terminal block 9b is integrally formed on one side of the flange portion 9a. A terminal pin 9c is formed integrally with the terminal block 9b, and a lead portion of the coil 10 wound around the coil bobbin 9 is connected to the terminal pin 9c.

  On the other hand, the housing 6 is formed by drawing using a soft magnetic plate material (for example, an electromagnetic steel plate, a silicon steel plate, a pure iron plate, or the like). The cylindrical wall of the housing 6 is formed with a notch 6 a for exposing the terminal block 9 b of the coil bobbin 9 from the inside of the housing 6 to the outside. A through hole 6b (FIG. 2) is formed in the center of the bottom wall of the housing 6. A cylindrical core 11 that protrudes from the through hole 6 b toward the inside of the housing 6 and penetrates the center hole 9 d of the coil bobbin 9 is provided. The cylindrical core 11 is made of a magnetic material (for example, iron-based sintered alloy, pure iron, etc.). In the illustrated example, the cylindrical core 11 is press-fitted into the through-hole 6b of the housing 6 to thereby form the housing 6 and the core. The through-hole 6b of the housing 6 and the outer diameter 11b of the core 11 are set so that 11 is mechanically and magnetically coupled. Further, an oil-impregnated sintered bearing 12 is press-fitted into the hollow hole 11 a of the core 11, and the rotating shaft 4 (FIGS. 1 and 2) of the rotor 2 is pivotally supported by the oil-impregnated sintered bearing 12.

The first stator yoke 7 includes a relatively large-diameter annular portion 7a and a plurality of (five in the illustrated example) pole teeth that are arranged at equal intervals along the inner peripheral end of the annular portion 7a. Part 7b. The outer diameter of the annular portion 7a is a diameter that can be press-fitted into the cylindrical inner wall of the housing 6, and the inner diameter of the annular portion 7a is set so as to ensure the strength required for the annular portion 7a. In the illustrated example, the pole tooth portion 7 b is bent so as to protrude toward the bottom wall of the housing 6 while being fixed to the housing 6. The inner diameter of the cylindrical space surrounded by the pole tooth portion 7b (the diameter of the center hole 7c in FIG. 4) is the inner diameter of the cylindrical space surrounded by the pole tooth portion 8b of the second stator yoke 8 described later. And the same diameter.
The second stator yoke 8 includes a relatively small-diameter annular portion 8a and a plurality of (five in the illustrated example) pole tooth portions 8b that are arranged at equal intervals along the outer peripheral end of the annular portion 8a. And are provided. The inner diameter of the annular portion 8a (the diameter of the center hole 8c in FIG. 4) is a diameter that can be press-fitted into the cylindrical outer wall of the core 11, and the outer diameter of the annular portion 8a can ensure the strength required for the annular portion 8a. Is set as follows. In the illustrated example, the pole tooth portion 8 b is bent so as to protrude toward the open end of the housing 6 while being fixed to the core 11. The inner diameter of the cylindrical space surrounded by the pole tooth portion 8b is the same as the inner diameter of the cylindrical space surrounded by the pole tooth portion 7b of the first stator yoke 7 described above.

The annular portion 7 a of the first stator yoke 7 is fixed to the inner wall near the open end of the housing 6, and the annular portion 8 a of the second stator yoke 8 is fixed to the core 11, thereby The stator yoke 7 and the second stator yoke 8 are mechanically and magnetically coupled via the housing 6, and the pole teeth 7 b of the first stator yoke 7 and the pole teeth of the second stator yoke 8 are combined. 8b and is, meshes alternately on the same circumference, the cylindrical space S, shown in Figure 3 with a diameter D _S is formed. Then, as shown in FIG. 1, the rotor magnet 3 (FIG. 1) is disposed in the cylindrical space S, and the rotating shaft 4 of the rotor 2 is inserted into the hollow hole 11 a of the core 11.
In the present embodiment, as shown in FIG. 1, the outer diameter D _M of the rotor magnet 3 is formed smaller in diameter than the outer diameter D _B of the coil bobbin 9 of the stator 5. Even the inside diameter D _S of the cylindrical space S pole teeth portion 7b of the first stator yoke 7 on the same circumference and the pole teeth portion 8b of the second stator yoke 8 is formed meshed alternately, in accordance with the outer diameter D _M of the rotor magnet 3 is formed to have a diameter smaller than the outer diameter D _B of the coil bobbin 9.

An example of the assembly procedure of the stepping motor 1 according to the first embodiment of the present invention is as follows. First, an assembly procedure of the A-phase stator 5A will be described with reference to FIG. First, the coil bobbin 9 is inserted into the housing 6 by aligning the terminal block 9 b of the coil bobbin 9 with the notch 6 a provided in the housing 6. On the other hand, one end of the core 11 in which the oil-impregnated sintered bearing 12 is press-fitted in advance into the hollow hole 11 a is press-fitted into the center hole 8 c of the second stator yoke 8, and the annular portion of the second stator yoke 8 is inserted into the outer periphery of the core 11. 8a is fixed. Then, the other end of the core 11 is inserted into the center hole 9 d of the coil bobbin 9 and press-fitted into the through hole 6 b of the housing 6 for positioning. Finally, the pole teeth 7b of the first stator yoke 7 and the pole teeth 7b of the first stator yoke 7 are alternately engaged with the pole teeth 7b of the first stator yoke 7 and the pole teeth 8b of the second stator yoke 8. After adjusting the position of the second stator yoke 8 so that it has an electrical phase difference of 180 degrees, the annular portion 7a of the first stator yoke 7 is press-fitted into the inner wall near the open end of the housing 6. And fix.
The procedure is such that the pole teeth 7b of the first stator yoke 7 and the pole teeth 8b of the second stator yoke 8 can be accurately positioned so as to have an electrical phase difference of 180 degrees. Well, it is not limited to the above assembly procedure. Further, the assembly procedure of the B-phase stator 5B is exactly the same as this, and therefore detailed description thereof is omitted.

Subsequently, the A-phase stator 5A and the B-phase stator 5B are arranged to face both sides of the rotor magnet 3 in the axial direction, and a resin washer 13 such as a polyslider (see FIGS. 1 and 2) is disposed on the rotating shaft 4. The rotor magnet 3 is slidable with respect to the A-phase stator 5A and the B-phase stator 5B. The rotating shaft 4 is inserted into the hollow holes 11a of the cores 11 of the A-phase stator 5A and the B-phase stator 5B, and the rotating shaft 4 is supported by the oil-impregnated sintered bearing 12. After the A-phase stator 5A and the B-phase stator 5B are adjusted to a position where the electrical angle is 90 degrees, the open ends of the housings 6 of the A-phase stator 5A and the B-phase stator 5B are opened. Adhere to each other. At this time, the terminal bases 9b of the coil bobbins 9 of the A-phase stator 5A and the B-phase stator 5B are close to each other in the axial direction, and are opposed to each other in the axial direction (see FIG. 1). Furthermore, the stepping motor 1 is completed by fixing the housings 6 of the A-phase stator 5A and the B-phase stator 5B by welding.
In addition, by forming a complementary uneven shape at the open ends of the housing 6 of the A-phase stator 5A and the B-phase stator core 5B, the phase difference between the A-phase stator 5A and the B-phase stator core 5B can be reduced. Adjustment can be easily performed.

According to the first embodiment of the present invention configured as described above, the following operational effects can be obtained.
First, the cylindrical core 11 protrudes toward the inside of the housing 6 from the through hole 6a formed in the center of the bottom wall of the bottomed cylindrical housing 6, and the coil bobbin 9 passes through the center hole 9d. The second stator yoke 8 is fixed to the core 11 that is housed in the housing 6 and penetrates the coil bobbin 9, so that the coil bobbin 9 has the terminal block 9 b protruding from the notch 6 a of the housing 6. The outer wall is covered with the bottom wall of the housing 6 and the inner wall of the cylindrical surface, and the second stator yoke 8 fixed to the core 11. Further, the first stator yoke 7 is fixed to the inner wall near the open end of the housing 6, so that the first stator yoke 7 and the second stator yoke 8 are mechanically and magnetically interposed via the housing 6. The pole teeth 7b of the first stator yoke 7 and the pole teeth 8b of the second stator yoke 8 are alternately engaged with each other on the same circumference to form a cylindrical space S. .
That is, the housing 6 and the first stator yoke 7 constitute an outer yoke which is a basic element of the claw pole type stepping motor, and the second stator yoke 8 is a basic element of the claw pole type stepping motor stator. An inner yoke is configured. The rotor magnet 3 is disposed in the cylindrical space S, the rotating shaft 4 of the rotor magnet 3 is inserted into the core 11, and the terminal block 9b protruding from the notch 6a of the housing 6 is provided between the axial side surfaces. as There are close opposed, oppositely disposed pair of stator 5A, and 5B in the axial direction on both sides of the rotor magnet 3, in Rukoto to open ends to each other tightly fixed in the housing 6, the outer peripheral surface of the rotor magnet 3 and the The pole tooth portions 7b and 8b face each other with a necessary minimum distance, and a predetermined motor torque can be generated even though the stepping motor has a small size and a small diameter.

  The stator 5 is a housing in which the first stator yoke 7, the second stator yoke 8, the coil bobbin 9 and the core 11 are all housed inside the housing 6, and the open end of the housing 6 is the first end. The stator yoke 7 is closed. Therefore, when performing the fixing operation of each of the above components, the operation of fixing the annular portion 7a of the first stator yoke 7 to the inner wall near the open end of the housing 6 is finally performed, so that the center of the bottom wall of the housing 6 is performed. The operation of fixing the core 11, the operation of storing the coil bobbin 9 in the housing 6 so that the center hole 9 d of the coil bobbin 9 penetrates the core 11, and the operation of fixing the second stator yoke 8 to the core 11 are all smooth. Can be done.

A plurality of pole teeth 7b project from the inner peripheral end of the annular portion 7a of the first stator yoke 7 toward the bottom wall of the housing 6, and a plurality of pole teeth 7b protrude from the outer peripheral end of the annular portion 8a of the second stator yoke 8. The pole teeth 8b of the first stator yoke 7 and the pole teeth 8b of the second stator yoke 8 are alternately arranged in the circumferential direction. Since the cylindrical space S is formed by alternately meshing with each other in the axial direction, the space in the axial direction of the stator 5 is effectively used, and an increase in the dimension in the axial direction is prevented.
Unlike the illustrated example, even when the plurality of pole tooth portions 7b protrude from the inner peripheral end of the annular portion 7a of the first stator yoke 7 toward the open end of the housing 6 (FIG. 7). As in FIG. 8), the pole teeth 7 b of the first stator yoke 7 and the pole teeth 8 b of the second stator yoke 8 are alternately meshed to form a cylindrical space S. Therefore, it is also possible to change the protruding direction of the pole tooth portion 7b of the first stator yoke 7 as necessary. For example, the first stator yoke 7 is press-fitted into the housing 6 slightly deeper in the opposite direction with respect to the example of FIGS. 1 and 2 (for example, the annular portion 7a of the first stator yoke 7 and the first stator yoke 7 The stator 5 can also be configured by setting the annular portion 8a of the second stator yoke 8 to the same position in the axial direction.

Further, by the outer diameter D _M of the rotor magnet 3 is formed smaller than the outer diameter D _B of the coil bobbin 9, the moment of inertia of the rotor 2 is reduced, it is possible to ensure high-speed response required . Further, the inner diameter D _S of the cylindrical space S pole teeth portion 7b of the first stator yoke 7 on the same circumference and the pole teeth portion 8b of the second stator yoke 8 is formed meshed alternately, in accordance with the outer diameter D _M of the rotor magnet 3, that is formed to have a smaller diameter than the outer diameter D _B of the coil bobbin 9, the outer peripheral surface and the respective pole teeth portion 7b of the rotor magnet 3, and the 8b They face each other with a necessary minimum distance and generate necessary motor torque.
In the present embodiment, the annular portion 7a of the first stator yoke 7 is fixed to the inner wall near the open end of the housing 6, that is, the outer yoke which is a basic element of the stator of the claw pole type stepping motor. Since the pole tooth portion 7b is formed separately from the housing 6, the rotor magnet 3 and each pole tooth portion 7b, 8b are configured in the above dimensional relationship, so that the outer yoke with respect to the coil bobbin 9 is formed. Even if the pole tooth portion 7b adopts a structure that overlaps when viewed in the axial direction as described above, it does not hinder the assembly of each portion.

  FIG. 5 compares the starting characteristic (pull-in torque characteristic) of the stepping motor 1 according to the first embodiment of the present invention with the starting characteristic of the conventional stepping motor 100 shown in FIGS. An example is shown. In the illustrated example, the outer diameters of the stepping motors 1 and 100 are both 6 mm, but the outer diameter of the rotor magnet 3 of the stepping motor 1 is 3 mm, and the outer diameter of the rotor magnet 111 of the stepping motor 100 (FIGS. 7 and 8). The diameter is 5 mm. In addition, both the step angle and the coil resistance value are the same, and the measurement conditions are also the same (3 V, two-phase excitation).

  As apparent from FIG. 5, the starting characteristic (reference PII) of the stepping motor 1 according to the embodiment of the present invention has a smaller maximum torque value than the starting characteristic (reference PIA) of the conventional stepping motor 100. However, it extends to the drive frequency region where the pull-in torque is high, and is excellent in high-speed response. Therefore, the stepping motor 1 according to the embodiment of the present invention does not require a particularly large torque, but an application in which high-speed response is important, for example, an actuator for driving a lens (focus adjustment) of an optical disk device or a camera. It will be understood that it has suitable characteristics as a power source.

  Further, if the camera focus adjustment actuator including the stepping motor 1 according to the embodiment of the present invention is configured, the power source of the actuator has the characteristics of the stepping motor 1 as it is, so that the actuator is small. However, it becomes possible to adjust the focus accurately at high speed.

Subsequently, a stepping motor 30 according to a second embodiment of the present invention will be described with reference to FIG. Note that the same or corresponding portions as those in the first embodiment of the present invention are denoted by the same reference numerals, and detailed description thereof is omitted.
Now, as a difference between the stepping motor 30 according to the second embodiment of the present invention and the stepping motor 1 according to the first embodiment, there is a difference in the shape of the coil bobbin 9. Specifically, the coil bobbin 9 of the stepping motor 30 according to the second embodiment of the present invention includes a small diameter portion 9e disposed adjacent to the outer side in the radial direction of the core 11 and the pole of the second stator yoke 8. A stepped cylindrical winding core portion is provided, which includes a large-diameter portion 9f disposed adjacent to the radially outer side of the tooth portion 8b. The coil 10 is wound around both the small diameter portion 9e and the large diameter portion 9f of the coil bobbin 9.

According to the second embodiment of the present invention, the following operational effects can be obtained. That is, the coil bobbin 9 has a small diameter portion 9e disposed adjacent to the outer side in the radial direction of the core 11 and a large diameter portion 9f disposed adjacent to the outer side in the radial direction of the pole tooth portion 8b of the second stator yoke 8. And the number of turns of the coil 10 is increased by winding the coil 10 around both the small diameter portion 9e and the large diameter portion 9f. Therefore, the magnetomotive force of the coil 10 is increased, and the motor torque can be further increased.
In addition, detailed description of the same or corresponding parts as those of the first embodiment of the present invention is omitted.

1 is a cross-sectional perspective view of a stepping motor according to a first embodiment of the present invention. FIG. 2 is an exploded perspective view of the stepping motor shown in FIG. 1. It is a cross-sectional perspective view of a stator of the stepping motor shown in FIG. FIG. 4 is an exploded perspective view of the stator shown in FIG. 3. It is the graph which compared the starting characteristic of the stepping motor shown by FIG. 1 with the starting characteristic of the conventional stepping motor. It is a cross-sectional perspective view of the stepping motor which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the conventional stepping motor. FIG. 8 is an exploded perspective view of the conventional stepping motor shown in FIG. 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 30: Stepping motor, 2: Rotor, 3: Rotor magnet, 4: Rotating shaft, 5: Stator, 6: Housing, 6b: Through-hole, 7: 1st stator yoke, 7a: Annular part, 7b: Pole Tooth part, 8: Second stator yoke, 8a: Annular part, 8b: Polar tooth part, 9: Coil bobbin, 9d: Center hole, 9e: Small diameter part, 9f: Large diameter part, 10: Coil, 11: Core, 11a: hollow hole, D _B : outer diameter of coil bobbin, D _M : outer diameter of rotor magnet

Claims (5)

A stepping motor in which the outer peripheral surface of the rotor magnet is surrounded by pole teeth protruding in the axial direction from a stator disposed on both axial sides of the rotor magnet,
The stator includes a coil bobbin, a bottomed cylindrical housing having a bottom wall at one end, the other end being opened, and storing the coil bobbin, and first and second stator yokes,
The coil bobbin includes a core part and flange parts at both ends of the core part, and a terminal block is integrally formed on one of the flange parts,
A notch for projecting the terminal block to the outside of the housing is formed in the cylindrical wall of the housing. A central portion of the bottom wall of the housing has a through hole, and the through hole extends from the through hole toward the inside of the housing. And a cylindrical core penetrating the central hole of the coil bobbin is provided,
The first stator yoke is provided with an annular portion and a plurality of pole teeth portions that are arranged at equal intervals along the inner peripheral end of the annular portion and project in the axial direction.
The second stator yoke is provided with an annular portion and a plurality of pole teeth portions that are arranged at equal intervals along the outer peripheral end of the annular portion and project in the axial direction.
An annular portion of the first stator yoke is fixed to an inner wall near the open end of the housing, and an annular portion of the second stator yoke is fixed to the core, so that the first stator yoke and The second stator yoke is mechanically and magnetically coupled via the housing, and the pole teeth of the first stator yoke and the pole teeth of the second stator yoke have the same circumference. A meshing cylindrical space is formed alternately on top,
The rotor magnet is disposed in the cylindrical space, the rotating shaft of the rotor magnet is inserted into the core, and the terminal blocks of the coil bobbin protruding from the notch of the housing are disposed so that the axial side surfaces are close to each other. And a pair of stators arranged opposite to each other on both sides of the rotor magnet in the axial direction, and the open ends of the housing are fixed in close contact with each other . A plurality of pole teeth portions arranged at equal intervals along the inner peripheral end of the annular portion of the first stator yoke protrude toward the bottom wall of the housing,
2. The stepping motor according to claim 1, wherein the plurality of pole teeth portions arranged at equal intervals along the outer peripheral end of the annular portion of the second stator yoke protrude in the open end direction of the housing. The rotor magnet is formed with a smaller diameter than the outer diameter of the coil bobbin,
The inner diameter of the cylindrical space formed by alternately engaging the pole teeth of the first stator yoke and the pole teeth of the second stator yoke is matched to the outer diameter of the rotor magnet, The stepping motor according to claim 1, wherein the stepping motor is formed to have a smaller diameter than an outer diameter of the coil bobbin. The coil bobbin is stepped comprising a small-diameter portion disposed adjacent to the radially outer side of the core and a large-diameter portion disposed adjacent to the radially outer side of the pole tooth portion of the second stator yoke. 4. The stepping motor according to claim 1, further comprising a cylindrical winding core portion, wherein a coil is wound around both the small diameter portion and the large diameter portion. An actuator for adjusting a focus of a camera, comprising the stepping motor according to claim 1.

Images