JP2013042640A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology which efficiently radiates heat generated from a rotor core and suppresses vibrations which becomes a problem of a stepping motor.SOLUTION: A metal shaft 108 is fixed in the rotation center of a rotor 110 including rotor cores 111, 112, and a metal disc like plate 116 is fixed to a portion of a bracket 105 of the shaft which protrudes to the exterior. The rotor cores 111, 112 generates heat due to iron loss during driving, however, the heat is transmitted from the shaft 108 to the disc like plate 116 and is radiated from the disc like plate 116. The disc like plate 116 functions as an inertial load and has a function that suppresses vibrations in addition to the contribution to the heat radiation.

Description

  The present invention relates to a stepping motor characterized by a structure for preventing vibration and radiating heat.

  The stepping motor rotates by rotating by the step angle and moves to the next stable point. However, at the time of stopping, the stepping motor stops while the vibration converges while performing the damped vibration by the inertia force of the rotor (rotor). For this reason, it is conventionally known to use a damper as a vibration countermeasure. As a technique for dealing with this problem, for example, Patent Document 1 describes a technique in which a disk-shaped damper using rubber (natural rubber or synthetic rubber) is attached to a rotor shaft. In this technique, it is said that the vibration of the rotor of the stepping motor can be suppressed by a damper formed from a rubber material.

  On the other hand, when the stepping motor is continuously driven, heat is generated and the temperature of the stepping motor rises. This heat generation is mainly caused by the core iron loss. Here, the iron loss is divided into hysteresis loss and eddy current loss. In Patent Document 2, in an inner rotor type stepping motor, in order to promote heat dissipation of heat generated from a stator iron core, black alumite treatment is applied to the front and rear bracket surfaces sandwiching the stator iron core. A configuration that produces a heat and heat dissipation effect is described.

JP-A-7-236263 JP-A-4-372546

  By the way, in the inner rotor type HB (hybrid) type stepping motor, in addition to the heat generation from the stator-side core, the rotor also has the core (rotor core), so the heat generation from the rotor core is also a problem. Since the rotor is generally disposed inside a stator that is hardly air permeable, the temperature increase promotes the temperature increase of the entire motor. Further, when the rotor magnet is composed of a neodymium magnet having a low heat-resistant temperature, the rise in the temperature of the rotor becomes a factor in reducing the magnetic force of the rotor magnet. However, the techniques of Patent Documents 1 and 2 cannot cope with heat generated from the rotor core.

  In such a background, an object of the present invention is to provide a technique capable of efficiently dissipating heat generated from a rotor core and further suppressing generation of vibration that causes a problem in a stepping motor.

  The invention according to claim 1 includes a stator core, a pair of brackets that sandwich the stator core, and a rotor core that is held in a rotatable state inside the stator core and is made of a soft magnetic material. A rotor provided with the shaft, a shaft fixed to the rotation center of the rotor, and a metal member attached to a portion of the shaft that protrudes to the outside of the bracket and extending in a direction away from the rotation center; And the metal member functions as a heat radiating portion that radiates heat generated in the rotor core to the outside and an inertia load that adds an inertia moment to the rotor. According to the first aspect of the present invention, the heat generated in the rotor core is transmitted to the metal member, and is further radiated from there to the air. By this heat dissipation, the temperature rise of the rotor is suppressed. Further, since the metal member becomes an inertia load and the rotational moment of the rotor increases, a vibration suppressing effect can also be obtained.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the metal member is a disk-shaped plate having a disk shape, and irregularities are formed on the disk-shaped plate. To do. According to invention of Claim 2, the surface area of a disk shaped plate increases and the thermal radiation efficiency from the disk shaped plate at the time of rotation becomes high.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the metal member is a disk-shaped plate having a disk shape, and a plurality of through holes are formed in the disk-shaped plate. It is characterized by being. According to the third aspect of the present invention, heat radiation from the inner peripheral surface of the through hole is also added, so that the heat radiation effect from the disk-shaped plate is enhanced as compared with the case where no through hole is provided.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the pair of brackets are made of metal. According to invention of Claim 4, the heat | fever which generate | occur | produced in the stator core conducts to the bracket comprised with the metal, and is thermally radiated from there. The heat radiation efficiency can be increased by configuring the pair of brackets with metal.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the metal member has a shape that generates an airflow by rotating. According to the fifth aspect of the present invention, an air flow is generated from the metal member during rotation, thereby improving the efficiency of heat dissipation from the metal member itself. The efficiency of heat dissipation from the core is also improved.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which can thermally radiate the heat which generate | occur | produces from a rotor core, and can suppress generation | occurrence | production of the vibration which becomes a problem with a stepping motor is provided.

It is sectional drawing of the HB type stepping motor in embodiment of this invention. It is a graph which shows the change of motor surface temperature.

(Constitution)
FIG. 1 shows an HB (hybrid) type stepping motor 100 according to an embodiment of the present invention. The HB type stepping motor 100 includes a stator core (stator core) 101. The stator core 101 has the same structure as the stator core of a normal HB type stepping motor. The stator core 101 is made of a soft magnetic material. In this example, the stator core 101 is configured by stacking SECCs (electromagnetic steel plates) that are soft magnetic materials. Although not apparent from FIG. 1, the stator core 101 is a protrusion extending in the direction of the center of a plurality of shafts arranged along the circumferential direction, as in the case of a stator core in a general HB type stepping motor. It has a pole. A resin bobbin 102 is attached to the salient pole, and a field coil 103 is wound around the bobbin 102.

  The stator core 101 is held in a state of being sandwiched by a pair of brackets 104 and 105 made of aluminum die casting from the front and rear in the axial direction. The brackets 104 and 105 and the stator core 101 are coupled by a coupling member such as a screw or a bolt (not shown). The bracket 104 holds a shaft 108 serving as a rotation shaft through a bearing 106 in a rotatable state. In addition, a shaft 108 is rotatably held by the bracket 105 via a bearing 107. A rotor 110 is fixed to the shaft 108. With this structure, the rotor 110 is held in a rotatable state inside the stator core 101. The shaft 108 is made of a metal material (for example, stainless steel) in order to efficiently conduct heat generated in the rotor 110.

  The rotor 110 includes a pair of rotor cores 111 and 112 and a substantially disc-shaped (or substantially cylindrical) rotor magnet 113. The rotor magnet 113 is magnetized so as to have different polarities in the axial direction, and magnetizes the rotor cores 111 and 112 to different polarities. The rotor magnet 113 is sandwiched and held between the rotor cores 111 and 112 in the axial direction. The structure of the rotor 110 is the same as that of a normal HB type stepping motor. The rotor cores 111 and 112 are made of a soft magnetic material. In this example, the rotor cores 111 and 112 are configured by laminating electromagnetic steel plates. The reason why the stator core 101 and the rotor cores 111 and 112 have a structure in which electromagnetic steel sheets are laminated is to suppress the generation of eddy current and iron loss. In addition, the rotor cores 111 and 112 are configured to be in direct contact with the shaft 108, and heat generated in the rotor cores 111 and 112 is easily transmitted to the shaft 108.

  A gear 115 is attached to one end of the shaft 108, and a disk-like plate 116 is attached to the other end of the shaft 108. The gear 115 meshes with another gear (not shown) and transmits the rotation of the rotor 110 to the outside. The disk-shaped plate 116 is an example of a metal member having a shape extending in a direction away from the rotation center. In this example, the disk-shaped plate 116 is configured by laminating the same electromagnetic steel plates as the rotor cores 111 and 112. The disc-like plate 116 is provided with a press-fitting hole in the center, and the shaft 108 is press-fitted into the press-fitting hole, thereby being fixed to the shaft 108. By adopting a structure in which the disk-shaped plate 116 and the shaft 108 are in direct contact with each other, a structure in which the heat of the rotor 110 is conducted to the disk-shaped plate 116 through the shaft 108 and is efficiently radiated from the disk-shaped plate 116 is obtained. ing. Here, in order to reduce the cost, the example in which the disk-shaped plate 116 is made of an electromagnetic steel plate has been described. However, the material of the disk-shaped plate 116 is a material that can gain mass and has good heat conduction. Any other metal material may be used.

  The disk-shaped plate 116 also functions as an inertia load that increases the rotational moment of the rotor 110. The presence of the disk-shaped plate 116 increases the moment of inertia of the rotor 110 and provides a vibration suppressing effect. The value of inertia generated by attaching the disk-shaped plate 116 can be adjusted by selecting the thickness and diameter of the disk-shaped plate 116.

(Heat dissipation function)
When the HB type stepping motor 100 is continuously driven, iron loss occurs in the stator core 101 and the rotor cores 111 and 112, and the stator core 101 and the rotor cores 111 and 112 generate heat. The heat generated in the stator core 101 is radiated from the outer periphery of the stator core 101, is transmitted to the brackets 104 and 105 made of aluminum die casting, and is radiated from there. Heat generated in the rotor cores 111 and 112 is transmitted to the disk-shaped plate 116 via the shaft 108 and is radiated from the disk-shaped plate 116. The disc-shaped plate 116 is made of a metal material having high thermal conductivity, has a relatively large area with respect to other members, and further rotates and air-cools, so that it functions as a radiator with high heat dissipation efficiency. . For this reason, the heat generated from the rotor cores 111 and 112 in a sealed (or near-sealed) environment does not concentrate on the rotor 110, but is effectively dissipated from the disk-shaped plate 116, and the temperature rise of the rotor 110 is suppressed. .

(Demonstration experiment)
Separately from the HB type stepping motor 100 shown in FIG. 1, a comparative sample having a structure in which the disk-like plate 116 is removed from the structure of the HB type stepping motor 100 was produced. Then, the HB type stepping motor 100 and the comparative sample were driven so as to have the same rotational speed (number of revolutions / minute), and the temperature around the stator core 101 was measured with a thermocouple.

  FIG. 2 shows the results of the above experiment. FIG. 2 shows how the temperature of the motor rises as the drive time elapses. In FIG. 2, the data of the above comparative sample (without the disc-shaped plate) is shown by the plot points of (a), and the data of the HB stepping motor 100 of the embodiment is shown by the plot points of (b). As shown in FIG. 2, the HB type stepping motor 100 of the present embodiment in which the disk-shaped plate 116 is mounted on the shaft 108 is compared with the HB type stepping motor (comparative sample) in which the disk-shaped plate 116 is not mounted. The result was that the surface temperature of the motor was about 20 ° C. lower. As a result, heat generated due to iron loss in the rotor cores 111 and 112 is conducted from the shaft 108 to the disk-shaped plate 116 and is radiated from the disk-shaped plate 116, so that the heat is generated inside the stator core 101. This is thought to be due to a decrease in the amount of heat that is accumulated.

(Superiority)
As described above, in the HB type stepping motor 100 according to the embodiment, the metal shaft 108 is fixed to the rotation center of the rotor 110 including the rotor cores 111 and 112, and the portion of the shaft 108 that protrudes outside the bracket 105 is used. A metal disk-like plate 116 is fixed. The rotor cores 111 and 112 generate heat due to iron loss during driving, but this heat is conducted from the shaft 108 to the disk-shaped plate 116 and is radiated from the disk-shaped plate 116 to the surrounding space. In addition to contributing to heat dissipation, the disk-shaped plate 116 also functions as an inertial load and exhibits a function of suppressing vibration.

  When the stepping motor is used in a sealed space where air permeability is poor, the efficiency of heat dissipation is low, and the stepping motor is likely to be heated. Even in such a situation, the HB type stepping motor 100 using the present invention efficiently dissipates heat and suppresses a decrease in motor characteristics.

  When a neodymium magnet having a low heat-resistant temperature is used as the rotor magnet 113, the motor characteristics may deteriorate due to thermal demagnetization (a phenomenon in which the magnetic force is weakened due to a temperature rise). On the other hand, in the HB type stepping motor 100 of this embodiment, since the temperature rise of the rotor 110 can be suppressed, even if a magnet that is weak against heat is used as the rotor magnet 113, the motor characteristics due to the above-mentioned thermal demagnetization are obtained. It can be difficult to cause a decrease.

  The disk-shaped plate 116 also functions as an inertia load, and increases the inertia mass of the rotor 110. By increasing the inertial mass of the rotor 110, an effect of suppressing the vibration that causes a problem in the stepping motor is obtained.

  In addition, since the discoid plate 116 made of inexpensive SECC (electromagnetic steel plate) is used as an inertial body, it can be made cheaper than an elastic damper.

(Other)
FIG. 1 shows an example in which the surface of the disk-shaped plate 116 is not processed at all, but protrusions and grooves are formed on the surface of the disk portion of the disk-shaped plate 116 so as to have an uneven shape. The surface area may be increased. By forming protrusions and grooves on the surface of the disk-shaped plate 116, the amount of heat dissipated is increased, and the heat dissipation effect can be enhanced. Further, a plurality of through holes may be formed in the disk-shaped plate 116. By providing the through hole, the inner peripheral surface of the through hole also contributes to heat dissipation, and the heat dissipation effect can be enhanced.

  The shape of the disc-shaped plate 116 viewed from the axial direction is not limited to a circle, and other shapes can be selected as long as the balance with respect to the rotation center is ensured. For example, a disk-shaped structure having a polygonal shape such as a regular hexagon or a regular octagon when viewed from the axial direction can be used instead of the disk-shaped plate 116. Further, the disk-shaped plate 116 can be shaped to generate a flow of airflow by rotation, and function as a heat radiating means, an inertial load, and a cooling fan (or a heat radiating fan). In this case, since the amount of air hitting the disk-shaped plate 116 is increased, the cooling effect by air cooling of the disk-shaped plate itself is further improved, and in addition, the air cooling effect of the bracket 105 and other parts by the air flow generated by the disk-shaped plate 116 is improved. Can also be obtained. As a shape that generates an airflow by this rotation, a shape that generates an airflow on the same principle as that of a fan or a propeller can be used.

  As a structure for generating an air flow in the disk-shaped plate 116 at the time of rotation, a plurality of cuts extending in a direction away from the shaft are made in the disk-shaped plate 116 and bent so that an axial flow is generated at the time of rotation. The example etc. which form are mentioned.

  In addition to the structure in which the disk-shaped plate 116 is disposed on the right side of the bracket 105 in FIG. 1, a structure in which the disk-like plate 116 is disposed on the left side of the bracket 104 is also possible. According to this structure, the heat dissipation path through the shaft 108 is increased as compared with the case of FIG. 1, and heat generated in the rotor 110 can be dissipated more efficiently.

  The aspect of the present invention is not limited to the individual embodiments described above, and includes various modifications that can be conceived by those skilled in the art, and the effects of the present invention are not limited to the contents described above. That is, various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

  The present invention can be used for a stepping motor.

  DESCRIPTION OF SYMBOLS 100 ... HB type stepping motor, 101 ... Stator iron core, 102 ... Bobbin, 103 ... Field coil, 104 ... Bracket, 105 ... Bracket, 106 ... Bearing, 107 ... Bearing, 108 ... Shaft, 110 ... Rotor, 111 ... Rotor core , 112 ... rotor core, 113 ... rotor magnet, 115 ... gear, 116 ... disk-shaped plate.

Claims (5)

A stator core,
A pair of brackets sandwiching the stator core;
A rotor having a rotor core that is held in a rotatable state inside the stator core and is made of a soft magnetic material;
A shaft fixed to the rotation center of the rotor;
A metal member attached to a portion of the shaft that protrudes outside the bracket, and having a shape extending in a direction away from the rotation center;
The stepping motor, wherein the metal member functions as a heat radiating portion that radiates heat generated in the rotor core to the outside and an inertia load that applies an inertia moment to the rotor. The metal member is a disk-shaped plate having a disk shape,
The stepping motor according to claim 1, wherein unevenness is formed on the disk-shaped plate. The metal member is a disk-shaped plate having a disk shape,
The stepping motor according to claim 1, wherein a plurality of through holes are formed in the disk-shaped plate.   The stepping motor according to any one of claims 1 to 3, wherein the pair of brackets are made of metal.   The stepping motor according to any one of claims 1 to 4, wherein the metal member has a shape that generates an airflow by rotating.

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