JP2002315295A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance ease of assembly and reliability while flexibly changing the number of windings of an exciting coil without increasing the size of a magnetic yoke. SOLUTION: A ring-shaped stator substrate 22 is fixed on an outer periphery side of a rotor 18 supported so as to freely rotate. A pair of magnetic yokes 24, 26 is pierced through holes 40A in bobbins 40 respectively for attaching coils 34, 36 to the pair of magnetic yokes 24, 26. The pair of magnetic yokes 24, 26 is fixed at the stator substrate 22 so that respective longitudinal directions extend along the direction orthogonal to the axial direction of the rotor 18. By having parts protruding to an inner periphery side of the stator substrate 22 protrude and bent upward respectively perpendicularly to a surface of the stator substrate 22, a plurality of stator pole parts 22A to 22F are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor which can be reduced in size and can operate smoothly, and is suitable for a two-phase motor for a meter mounted on a vehicle, for example.

[0002]

2. Description of the Related Art In general, an analog type meter mounted on a vehicle and displaying an analog signal has a pointer driven by a cross coil motor. Stepping motors have been adopted.

That is, as a stepping motor for an in-vehicle meter, those described in Japanese Patent Publication No. 11-501800 and US Pat. No. 6,043,574 are known. As shown in FIGS. 5 and 6, the two support portions 114A provided on the magnetic yoke 114, which is a W-shaped stator, are radially magnetized in the direction in which the rotor 112, which is a rotor, alternates. , 114B are provided with excitation coils 116A and 116B, respectively, and have a structure in which two magnetic circuits of a W-shape are constituted by a pole piece 118 partially shared.

On the other hand, as a technique merely relating to a stepping motor, as shown in FIG. 7, a pair of W-shaped magnetic yokes 124A, 124B each having one excitation coil 126A, 126B attached thereto are separately provided on the rotor 1 respectively.
22 is located on the outer periphery of
No. 6,086,045. On the other hand, U-shaped magnetic yokes arranged separately on the outer periphery of the rotor are also disclosed in Japanese Patent Publication No. 4-74693, Japanese Patent Application Laid-Open No. 8-251902, and the like.

That is, according to these publications, a conventional general stepping motor includes a rotor composed of a permanent magnet having a plurality of magnetic poles continuously magnetized in a circumferential direction,
A structure having a pair of U-shaped or W-shaped magnetic yokes arranged around the rotor has been known.

[0006]

On the other hand, in a stepping motor, although a low current is required in recent years, the size of a bobbin around which an exciting coil is wound and a magnetic yoke to which the bobbin is mounted (for example, FIGS. FIG.
The size of the dimension L) limits the space in which the exciting coil can enter. As a result, in order to reduce the current, it is necessary to increase the number of turns of the wire or to reduce the wire diameter of the wire, but it has the following problems.

That is, even when a U-shaped or W-shaped magnetic yoke having a fixed size is used, the wire diameter can be reduced and the number of turns of the exciting coil can be increased. In this case, attention must be paid to disconnection during winding, and assemblability is reduced, and reliability is greatly affected due to the possibility of disconnection after winding. Further, when the number of turns of the exciting coil is increased while keeping the wire diameter the same, the exciting coil cannot be inserted into the U-shaped or W-shaped magnetic yoke, and as a result, the size of the magnetic yoke needs to be increased. There are drawbacks such as the necessity of increasing the size.

On the other hand, as for the meters, analog movements in which the hands smoothly move are generally required.
In the conventional stepping motor, the detent torque is large and the rotation operation is discontinuous. When the conventional stepping motor is used for a meter, the hands do not operate smoothly.

The present invention has been made in consideration of the above facts, and has as its first object to provide a stepping motor capable of improving the assemblability and reliability while freely changing the number of turns of an exciting coil without increasing the size of a magnetic yoke. A second object is to provide a stepping motor capable of performing a smooth operation by reducing the detent torque.

[0010]

According to a first aspect of the present invention, there is provided a stepping motor comprising: a rotor having a plurality of magnetic poles along a circumferential direction; a ring-shaped portion disposed at a position surrounding the rotor; A stator base having a pair of support portions each extending to the outer peripheral side of the rotor, a pair of magnetic yokes each having a base end fixed to the pair of support portions and cooperating with a magnetic pole of the rotor, and a pair of magnetic yokes. A pair of excitation coils respectively attached to and energizing the pair of magnetic yokes by drive pulses having a phase difference, respectively; and a plurality of stator magnetic poles formed integrally with the stator base and each forming a magnetic path with each magnetic yoke. And a unit.

The operation of the stepping motor according to the first aspect will be described below. In the present invention, the rotor has a plurality of magnetic poles along the circumferential direction, a ring-shaped stator base is disposed at a position surrounding the rotor, and a pair of magnetic yokes cooperated with the magnetic poles of the rotor. Are fixed to a pair of support portions respectively extending to the outer peripheral side of the ring-shaped portion of the stator base.
Further, a pair of excitation coils respectively attached to the pair of magnetic yokes excites the pair of magnetic yokes as drive pulses having respective phase differences are applied. Then, a plurality of stator magnetic pole portions formed integrally with the stator base and separate from each magnetic yoke are magnetized while forming a magnetic path with the magnetic yoke.

In other words, according to the present invention, the magnetic pole is formed separately from the magnetic yoke so that the magnetic yoke does not limit the size of the exciting coil. For example, it becomes an I shape or a T shape. As a result, unlike the U-shaped or W-shaped magnetic yoke, the restriction due to the shape of the magnetic yoke when arranging the exciting coil is reduced, and the number of turns of the exciting coil can be easily increased. Therefore, the degree of freedom of the resistance value of the exciting coil applied to the stepping motor according to the present invention is extremely high, and the degree of freedom in the shape design of the stepping motor is also improved. As described above, according to the present invention, the size of the exciting coil can be freely changed without increasing the size of the magnetic yoke, so that the assemblability and reliability can be improved while reducing the size and thickness of the stepping motor. Becomes

On the other hand, in the present invention, a pair of magnetic yokes are fixed to the stator base, and a plurality of stator magnetic pole portions are integrally formed on the stator base. Along with this, by arranging the pair of magnetic yokes and the plurality of stator magnetic pole portions in an optimal positional relationship, the magnetic force received from the magnetic poles of the rotor when the exciting coil is not energized cancels out, and the detent torque is reduced. Will operate smoothly.

Further, the present invention provides a structure in which not only the stator base and the plurality of stator magnetic pole portions are integrally formed, but also one end is opened by forming the stator base in a ring shape. Since the structure is higher in strength and easier to increase the shape accuracy, the stepping motor can be assembled while easily and accurately positioning the magnetic yoke fixed to the stator base and the stator magnetic pole portion. As a result, not only can the manufacturing cost be reduced by simply manufacturing the stator magnetic pole portion by press working or the like, but also a highly accurate magnetic circuit is formed.

In the present invention, a pair of support portions extending to the outer peripheral side of the ring-shaped stator base are formed on the stator base, and the base ends of the magnetic yokes are fixed to these support portions, respectively. Therefore, since the support portions to which the magnetic yokes are fixed are formed so as to extend to the outer peripheral side of the stator base, the stator base is formed in a ring shape, but it is necessary to make the stator base itself larger than necessary. And the size and thickness of the stepping motor can be further reduced.

The operation of the stepping motor according to claim 2 will be described below. The present invention has the same configuration as that of the first aspect and operates in the same manner. However, in the present invention, the magnetic permeability of the material forming the pair of magnetic yokes is larger than the magnetic permeability of the material forming the stator base. Have been higher. In other words, by setting the above-described relationship of the magnetic permeability, a large magnetic force can be generated with a small current, so that the stepper motor functions optimally. In addition, it is possible to use a material having a high magnetic permeability, which generally has a high material cost, only at a minimum necessary portion, so that the manufacturing cost of the stepping motor can be further reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be clarified by describing one embodiment of a stepping motor according to the present invention with reference to the drawings. As shown in FIGS. 1 to 3, an outer frame of a stepping motor 10 according to an embodiment of the present invention is constituted by a synthetic resin case body 12, and the lid of the case body 12 is also made of a synthetic resin lid. An end of a support shaft 16 is rotatably supported on the same portion of the lid member 14 and the case body 12, and the support shaft 16 is stretched between them.

A cylindrical permanent magnet 2 is mounted on the support shaft 16.
A rotor 18 having 0 disposed on the outer peripheral side is attached. The permanent magnet 20 is formed with a plurality of, for example, 10 magnetic poles at equal intervals along the circumferential direction. In other words, the N pole and the S pole are formed adjacent to each other in a form of five poles each, and have a total of ten magnetic poles.

A stator base 22 formed of a ferromagnetic material such as iron in a ring shape is fixed to an outer peripheral side of the rotor 18 and a bottom portion in the case body 12 so as to surround the rotor 18. ing. Also, a pair of T-shaped magnetic yokes 24 and 26 respectively penetrate through holes 40A of the bobbin 40 so that the pair of magnetic yokes 2
Coils 34 and 36, which are exciting coils wound around the bobbin 40, are attached to and fixed to 4, 4 respectively.

The ring-shaped stator base 22 is provided with a pair of support portions 23A and 23B extending on the outer peripheral side thereof. A pair of magnetic yokes 2 are attached to the tips of the pair of support portions 23A and 23B.
The widened base end sides 4 and 26 are respectively fixed, and the front end sides respectively face the rotor 18, and the longitudinal directions extend along the direction orthogonal to the axial direction of the rotor 18. As described above, these magnetic yokes 24 and 26 are arranged, respectively. However, FIG.
As shown in FIG. 7, the angle α between the pair of magnetic yokes 24 and 26 around the center of the rotor 18 is 90 degrees.

On the other hand, on the inner peripheral side of the stator base 22, there are provided protrusions which protrude in the direction toward the rotor 18, and the protrusions are bent upwards perpendicularly to the surface of the stator base 22. As a result, a plurality of (for example, six in this embodiment) stator magnetic pole portions 22A, 22B, 22C,
22D, 22E and 22F are provided.

That is, these six stator pole portions 22
A, 22B, 22C, 22D, 22E, and 22F are formed integrally with the stator base 22 so that the magnetic yokes 24, 2
It has a separate structure from 6. The stator magnetic pole portion 22A is disposed between the magnetic yoke 24 and the magnetic yoke 26, as shown in FIGS.
The magnetic yoke 2 around the center of the rotor 18 shown in FIG.
The angle β0 between the magnetic pole 4 and the stator magnetic pole part 22A and the angle β1 between the magnetic yoke 26 and the stator magnetic pole part 22A around the center of the rotor 18 are 45 °.

On the other hand, the angle β2 between the magnetic yoke 24 and the stator magnetic pole portion 22B around the center of the rotor 18 is set to 45 °, and the magnetic yoke 26 and the stator magnetic pole portion 22F around the center of the rotor 18 are connected to each other. Are arranged such that the angle β3 between them is 45 °. Further, the rotor 18
Between the stator magnetic pole portions 22B and 22C, between the stator magnetic pole portions 22C and 22D, between the stator magnetic pole portions 22D and 22E, and between the stator magnetic pole portions 22E and
The angle γ between the 2Fs is also 45 °.

As described above, the pair of magnetic yokes 24 and 26 and the six stator pole portions 22A to 22F are
Are arranged at equal intervals around the center of the image. Further, the pair of coils 34 and 36 are connected to a control circuit (not shown), and a current of a drive pulse having a predetermined phase difference at a predetermined frequency is sent from the control circuit.

Then, the pair of coils 34 and 36 excite the pair of magnetic yokes 24 and 26 with the drive pulse, respectively, so that a magnetic path is formed by one of the stator magnetic pole portions 22A to 22F and the magnetic yoke 24. A magnetic path is formed by any one of the stator magnetic pole portions 22A to 22F and the magnetic yoke 26. As a result, the pair of magnetic yokes 2
As the 4, 26 and six stator magnetic pole portions 22A to 22F are sequentially magnetized, the rotor 18 rotates by the number of pulses.

On the other hand, a driving gear 50 is provided above the rotor 18.
Are formed integrally with the rotor 18. The output gear 54 into which the output shaft 48 is press-fitted is rotatably supported by the case main body 12, and the intermediate gear 52 is rotatably disposed between the driving gear 50 and the output gear 54. The driving gear 50 and the intermediate gear 52 are connected to the intermediate gear 5.
The second gear 52A meshes with the output gear 54 and the intermediate gear 52 with the small gear 52B of the intermediate gear 52 to reduce the rotation of the rotor 18.

Next, the assembly of the stepping motor 10 according to the present embodiment will be described. The stator base 22 is manufactured in advance by press working or the like, and the lid member 14, the case body 1
2. The bobbin 40 and the resin material portion of the rotor 18 are respectively manufactured by injection molding or the like, and the rotor 18 is fitted to the support shaft 16 and the permanent magnet 20 is attached to the outer peripheral side of the rotor 18. Further, the permanent magnet 20 is magnetized so as to have a plurality of magnetic poles at equal intervals along the circumferential direction. When the stator base 22 is pressed or the like, each of the six stator magnetic pole portions 22A to 22F is bent.

Thereafter, the magnetic yoke 2 is attached to a pair of support portions 23A and 23B extending to the outer peripheral side of the stator base 22, respectively.
4 and 26 are fixed by welding or the like, respectively, and the through holes 40 of the bobbin 40 around which the coils 34 and 36 are wound.
A, while passing the magnetic yokes 24 and 26,
The stator base 22 is attached to the bottom of the second base. As a result, the magnetic yokes 24 and 26 respectively
The coils 34 and 36 are mounted on the stator base 22 in a state where the coils 36 penetrate the base 36.

By mounting the metal support shaft 16 to which the rotor 18 is attached from above in FIG. 1, the case body 12 supports one end of the support shaft 16 rotatably. A rotor 18 is rotatably mounted in the interior 12.

Further, after the output gear 54 into which the output shaft 48 is press-fitted is rotatably attached to the case main body 12, an intermediate gear 52 for reducing the rotation of the rotor 18 is connected to the support shaft 4.
6, the support shaft 46 is attached to the case body 12 while penetrating through a hole provided in the stator base 22. Along with this, the intermediate gear 52 is brought into mesh with the driving gear 50 and the output gear 54 formed integrally during the injection molding of the rotor 18.

Finally, the lid member 14 is attached to the upper surface of the case main body 12 while being fitted to a convex portion (not shown) formed on the case main body 12 containing the components as described above, and fixed by screws or the like. The stepping motor 10 is completed.

Next, the operation of the stepping motor 10 according to the present embodiment will be described. In the stepping motor 10 according to the present embodiment, the rotor 18 has a plurality of magnetic poles along the circumferential direction, the stator base 22 is disposed around the rotor 18, and the rotor 18 cooperates with the magnetic poles of the rotor 18. Are fixed to the stator base 22 respectively.

Further, a pair of coils 34 and 36 attached to the pair of magnetic yokes 24 and 26 are applied to the pair of magnetic yokes 24 and 26, respectively, as drive pulses having a phase difference are applied from the control circuit. Are respectively excited. Then, six stator magnetic pole portions 22A, 22B, 2 are formed integrally with the stator base 22 and are separate from the magnetic yokes 24, 26, respectively.
2C, 22D, 22E and 22F are the magnetic yokes 2
4 and 26 are magnetized while forming a magnetic path.

As a result, for example, the coils 34 and 36
When a drive pulse current having a phase difference is transmitted to the stator magnetic pole portions 22A to 22F through the magnetic yoke 24 and the stator base 22, a magnetic path is formed, and these are changed to S poles or N poles. Also, a magnetic path is formed to any one of the stator magnetic pole parts 22A to 22F through the magnetic yoke 26 and the stator base 22 with a phase difference therefrom, and these become S poles or N poles. .

As described above, these magnetic paths and the magnetic poles of the permanent magnets 20 of the rotor 18 cooperate to perform a stepping operation so that the rotor 18 rotates sequentially. The signal is transmitted to the stepping motor 10 and output to the outside of the stepping motor 10.

That is, in the present embodiment, the stator magnetic pole portions 22A to 22A, in which the magnetic path is formed by the magnetic yokes 24 and 26, are formed.
As the 2F is formed separately from the magnetic yokes 24, 26, the magnetic yokes 24, 26 have, for example, an I-shape or T-shape that does not limit the size of the coils 34, 36. . As a result, unlike the conventional U-shaped or W-shaped magnetic yoke, there are fewer restrictions when arranging the coils 34 and 36, and the desired number of turns can be obtained without reducing the wire diameter of the coils 34 and 36. , Magnetic yoke 24,
The current flowing through the coils 34 and 36 is not limited by the size of the coil 26.

Therefore, the degree of freedom of the resistance values of the coils 34 and 36 applied to the stepping motor 10 according to the present embodiment becomes extremely high, and the degree of freedom in the shape design of the stepping motor 10 is improved. As described above, in the present embodiment, the sizes of the coils 34 and 36 can be freely changed without increasing the size of the magnetic yokes 24 and 26, and the stepping motor 10 can be reduced in size and thickness.
It is possible to improve the assemblability and reliability.

On the other hand, in the present embodiment, the stator base 2
2, a pair of magnetic yokes 24 and 26 are fixed,
Six stator magnetic pole portions 22A to 22
F was formed integrally. Accordingly, the pair of magnetic yokes 24 and 26 and the six stator magnetic pole portions 22A to 22F are arranged at an optimal interval of, for example, an angle of 45 °, so that the coils 34, 26
The magnetic force received from the magnetic pole of the rotor 18 when the power is not supplied to the rotor 36 is canceled, the detent torque is reduced, and the rotor 18 operates smoothly.

As described above, since the detent torque is reduced and the rotor 18 operates smoothly, if the stepping motor 10 according to the present embodiment is adopted for meters, the hands moved by the stepping motor 10 will be smooth. It works. In the present embodiment, since the shapes of the magnetic yokes 24 and 26 are simple, the processing yield is improved. Further, since the shapes of the magnetic yokes 24 and 26 are simple and assembly can be mechanized, Manufacturing costs can be reduced.

Apart from this, in the present embodiment, the magnetic yokes 24 and 26 are formed separately,
6 and the stator base 22 and the stator magnetic pole portion 22A
It is not necessary to use the same material as the material of the 22F. For this reason, the stator base 22 and the stator magnetic pole portions 22A to 22A
The motor characteristics can be changed by changing only the magnetic yokes 24 and 26 to a material having good magnetic characteristics without changing the material of the ferromagnetic plate material constituting F or the like. Therefore, it is possible to manufacture motors having the same shape and various differences in characteristics, and diversification of types can be achieved.

Specifically, in the present embodiment, the magnetic permeability of the material forming the pair of magnetic yokes 24 and 26 is higher than the magnetic permeability of the material forming the stator base 22. In other words, not only can diversification of varieties be achieved, but by setting such a relationship of magnetic permeability, a large magnetic force can be generated with a small current, so that the stepping motor 10 functions optimally. In addition, it is possible to use a material having a high magnetic permeability, which is generally high in material cost, only at a minimum necessary portion, so that the manufacturing cost of the stepping motor 10 can be reduced.

On the other hand, in this embodiment, the stator base 2
Not only are the two and six stator magnetic pole portions 22A to 22F formed integrally, but also because the stator base 22 is formed in a ring shape, the strength is improved as compared with a structure in which one end is opened. The magnetic yokes 24, 2 fixed to the stator body 22
The stepping motor 10 can be assembled while easily and accurately positioning the stator 6 and the stator magnetic pole portions 22A to 22F. As a result, the stator magnetic pole portions 22A to 22F can be manufactured simply and with high precision by press working or the like.
An accurate magnetic circuit is formed.

Further, in this embodiment, a pair of support portions 23A, 23B
Are formed so as to extend, and these support portions 23
A, 23B has a structure in which the base ends of the magnetic yokes 24, 26 are fixed, respectively. Therefore, the magnetic yoke 2
Since the support portions 23A and 23B to which the fixing members 4 and 26 are fixed are formed so as to extend to the outer peripheral side of the stator base 22, the stator base 22 is formed in a ring shape. It is not necessary to increase the size of the stepping motor, and the size and thickness of the stepping motor 10 can be further reduced.

In the above embodiment, the number of magnetic poles of the permanent magnet is ten, but the number of poles other than ten may be used. However, it is desirable that the number of magnetic poles is 6 or more for smooth movement of the rotor, and it is more preferable that the number of magnetic poles is 8 or more for smooth movement of the rotor. On the other hand, it is conceivable to set the upper limit of the number of magnetic poles of the permanent magnet to 20 from the viewpoint of manufacturing.

Further, as a material of the magnetic yoke, for example, permalloy having a magnetic permeability of 10,000 to 15000 can be considered, and as a material of the stator base, for example, a cold-rolled steel plate having a magnetic permeability of about 1000 can be used. It is conceivable to use the metal material of the above. Further, in the above-described embodiment, six stator pole portions are formed, but a plurality other than six may be used. Accordingly, the angle between the stator magnetic pole portions at this time may be set to an angle other than 45 °.

[0046]

According to the stepping motor of the present invention,
It is possible to improve the assemblability and reliability while freely changing the number of turns of the exciting coil without increasing the size of the magnetic yoke. Further, according to the stepping motor of the present invention, it is possible to perform a smooth operation by reducing the detent torque.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a stepping motor according to one embodiment of the present invention.

FIG. 2 is a plan view of the stepping motor according to the embodiment of the present invention in a state where a cover member and gears are removed.

FIG. 3 is a sectional view of a stepping motor according to one embodiment of the present invention.

FIG. 4 is an enlarged view of a main part showing a concept of a positional relationship between a magnetic pole of a permanent magnet, a magnetic yoke, and a stator magnetic pole part of the stepping motor according to one embodiment of the present invention.

FIG. 5 is a sectional view of a stepping motor according to a first related art.

FIG. 6 is a cross-sectional plan view of a stepping motor according to a first related art.

FIG. 7 is a sectional view of a stepping motor according to a second related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Stepping motor 18 Rotor 20 Permanent magnet 22 Stator base 22A-22F Stator magnetic pole part 23A, 23B Support part 24, 26 Magnetic yoke 34, 36 Coil

Claims (2)

[Claims] 1. A rotor having a plurality of magnetic poles along a circumferential direction, and a pair of support portions formed in a ring shape and arranged at positions surrounding the rotor and each extending to the outer peripheral side of the ring portion. The base end side is fixed to each of the pair of support portions, and
A pair of magnetic yokes that cooperate with the magnetic poles of the rotor, a pair of exciting coils respectively attached to the pair of magnetic yokes, and each of which excites the pair of magnetic yokes by a driving pulse having a phase difference, And a plurality of stator magnetic pole portions each of which forms a magnetic path with each of the magnetic yokes. 2. The stepping motor according to claim 1, wherein the magnetic permeability of the material forming the pair of magnetic yokes is higher than the magnetic permeability of the material forming the stator base.