JP5373006B2 - Hybrid stepping motor - Google Patents

Abstract

The invention provides a hybrid stepping motor which enables magnetic flux that penetrates through rotor iron cores to be balanced and equalized, reduces leakage magnetic flux, increases effective magnetic flux, improves motor property and becomes small. The hybrid stepping motor comprises a first rotor iron core and a second rotor iron core which are arranged in a way of taking a rotor shaft as the center, wherein the first rotor iron core is provided with a first rotor pole tooth on an outer periphery face, and the second rotor iron core is provided with a second rotor pole tooth; a third rotor iron core which is axially overlapped between the first rotor iron core and the second rotor iron core, and has a diameter smaller than that of the first rotor iron core and that of the second rotor iron core; and ring-shaped rotor magnets which are near the pole tooth of at least one rotor iron core, and is arranged in a way of taking the rotor shaft as the center in a co-core way in the first rotor iron core and the second rotor iron core, and form the following magnetic path: magnetic flux of a rotor magnet passes from one rotor pole tooth through an opposite stator pole tooth, penetrates through the pole tooth of the other rotor magnet and a third rotor magnet and then returns to the rotor magnet.

Description

  The present invention relates to a hybrid stepping motor used in, for example, a copying machine, a printer, a monitoring camera, an ATM (automatic teller machine), and the like.

  The configuration of the hybrid stepping motor is such that the rotor cores 51 and 52 (see FIG. 6) in which tooth-shaped iron cores are stacked as the rotor are shifted by a half pitch with the cylindrical rotor magnet 53 interposed therebetween, and the rotor shaft 54 It is assembled to. The rotor magnet 53 is magnetized to N / S poles in a direction parallel to the axial direction. Rotor pole teeth are formed on the outer circumferences of the rotor cores 51 and 52 so as to face the stator pole teeth 55a of the opposed stator core 55 (see FIG. 6). A coil (not shown) is wound around the stator pole teeth 55 a of the stator core 55.

  In FIG. 6, the rotor core 51 is magnetized to the N pole, and the rotor core 52 is magnetized to the S pole. At this time, the magnetic flux generated from the N pole of the rotor magnet 53 passes through the stator core 55 opposed to the rotor pole teeth 51a, enters the rotor core 52 through the rotor pole teeth 52a of the rotor core 52, and enters the rotor. A magnetic circuit returning to the S pole of the magnet 53 is formed. By energizing the coil wound around the stator pole teeth 55a of the stator core 55, torque is generated in the rotor to rotate (see Patent Document 1). FIG. 7 is an explanatory diagram of a rotor magnet used in the hybrid stepping motor of FIG.

JP-A-11-289737

The hybrid stepping motor has the following problems because the rotor has a structure in which the rotor magnet 53 is sandwiched between the rotor cores 51 and 52.
(1) When a magnetic material is used for the rotor shaft 54, a magnetic circuit that passes from the rotor magnet 53 through the rotor cores 51 and 52 through the rotor shaft 54 is formed, and the amount of magnetic flux flowing into the stator core 55 is reduced. For this reason, the motor characteristics deteriorate. Therefore, the rotor shaft 54 needs to use a non-magnetic stainless steel material. For this reason, for example, a ferromagnetic carbon-based material, which is a cheaper material, cannot be used for the rotor shaft 54.

  (2) Since the distance from the air gap between the rotor and the stator to the outer peripheral side and the inner peripheral side of the rotor magnet 53 is not equal, the magnetic flux passing through the rotor cores 51 and 52 is near the rotor magnet 53. Therefore, the magnetic flux passing through the rotor pole teeth 51a and 52a is poor due to the bias of the magnetic flux density, the vibration is large, and the leakage flux is increased, which leads to the deterioration of the motor characteristics.

  (3) In order to increase the torque, it is necessary to adjust the amount of magnetic flux according to the thickness of the rotor cores 51 and 52. Since the amount of magnetic flux is adjusted based on the cross-sectional area of the rotor magnet 53 (inner and outer diameters of the cylindrical magnet) and the thickness of the magnet, many types of magnets are required. The preparation of many types of magnets in this way requires manufacturing costs and management costs, so that in reality it is limited to only a few types of magnets and is used in many models. Therefore, many models use magnets exceeding the capacity required for motors, resulting in high manufacturing costs.

  (4) When the thickness of the rotor magnet 53 is increased, it is necessary to increase the thickness of the stator core 55, so that the motor becomes larger in the axial direction.

(5) Although the motor characteristics are determined by the amount of magnetic flux, in the structure in which the rotor magnet 53 is sandwiched between the rotor cores 51 and 52, the cross-sectional area of the rotor magnet 53 is made larger than the outer diameter of the rotor cores 51 and 52. However, there was a limit to improving the motor characteristics (torque). The torque τ of the hybrid stepping motor is expressed by the following equation.
τ = Kt · I · Sinφ
Kt: Torque constant I: Winding current Sinφ: Torque angle The torque constant Kt is expressed by the following equation.
Kt = n ・ Nr ・ Φ
n: Number of turns of winding Nr: Number of teeth of rotor Φ: Number of magnetic flux Therefore, in order to improve motor characteristics (torque), it is only necessary to increase the number of magnetic flux Φ. The magnetic flux number Φ of the magnet is expressed by the following equation.
Φ = Bd × S
Bd: Magnetic flux density at the magnet operating point S: Magnet cross-sectional area When the magnet cross-sectional area is increased, the permeance coefficient decreases and Bd decreases, but the amount of magnetic flux further increases. That is, in order to increase the amount of magnetic flux, it is preferable to increase the cross-sectional area of the magnet. In the rotor structure shown in FIG. 6, the cross-sectional area of the rotor magnet 53 cannot be increased beyond the outer diameter of the rotor cores 51 and 52, and there is a limit. For this reason, an expensive rotor magnet having a high residual magnetic flux density Br is used, or a multistage rotor is made to improve the motor characteristics.

  The present invention has been made to solve these problems, and the purpose of the present invention is to make the balance of magnetic flux passing through the rotor pole teeth uniform, reduce leakage magnetic flux, increase effective magnetic flux, and reduce motor characteristics. It is an object of the present invention to provide a hybrid type stepping motor with improved performance.

In order to solve the above problems, the present invention is characterized by having the following configuration.
A rotor in which a rotor magnet is assembled to a rotor core having a rotor pole tooth formed on the outer peripheral surface thereof, and a stator core having a coil wound around the rotor pole tooth. A stator in which a magnetic circuit is formed between the stator pole teeth and rotating by a rotational force generated between the stator pole teeth facing the rotor pole teeth by energizing the coil And a first rotor core having a first rotor pole tooth formed on an outer peripheral surface assembled around the rotor shaft, and an outer periphery assembled about the rotor shaft. A second rotor core having a second rotor pole tooth formed on a surface thereof, and at least one of the first rotor core and the second rotor core in the vicinity of the rotor pole tooth, with the rotor shaft as a center At least one of the times assembled to concentrically And the rotor magnets the thickness of the child core and the axial direction is formed in an annular shape so as to be identical, the first of the first rotor pole teeth and the second rotor pole teeth are assembled by shifting a half pitch , A third rotation formed between the first and second rotor cores so that the outer diameter is less than half of the radial thickness of the rotor magnet. comprising a child core, wherein the rotor and the third rotor core magnetic flux through the stator pole teeth opposed from one rotor pole teeth via the other rotor pole teeth and the other rotor core magnet A magnetic circuit that returns to the rotor magnet through the one rotor core is formed.

  According to the above configuration, the annular rotor magnet is concentrically assembled around the rotor shaft in the vicinity of at least one rotor pole tooth of the first rotor core and the second rotor core. The magnetic flux generated from the rotor magnet does not leak from the rotor pole teeth to the stator pole teeth, the effective magnetic flux increases, the motor characteristics are improved, and the rotor magnet from the air gap between the rotor and stator Since the magnetic distance is equal, the magnetic flux is not concentrated in the magnetic circuit, so that the magnetic balance is stabilized and vibration and noise are reduced.

In the present invention, the rotor magnet is preferably magnetized so that each of an outer peripheral surface and an inner peripheral surface is N-pole or S-pole and has the same polarity in the circumferential direction. Is preferably formed in an annular shape so as to have the same axial thickness as the rotor core .
As a result, a magnetic circuit having a large effective cross-sectional area between the rotor core and the stator core and having a sufficient magnetic flux path that circulates in the radial direction can be formed.
The rotor magnet may be a neodymium bond magnet. Thereby, a rotor magnet can be shape | molded cheaply.

In the present invention, it is desirable that an outer diameter of the third rotor core is formed to be not more than half of a radial thickness of the rotor magnet magnetized in the radial direction.
Thereby, even if the magnetic flux generated from the rotor magnet is magnetically shorted and leakage magnetic flux is generated, it can be prevented to a level that does not cause any problem.

In the present invention, an annular first rotor magnet is provided in the vicinity of the second rotor pole teeth of the second rotor core in the vicinity of the first rotor pole teeth of the first rotor core. An annular second rotor magnet may be assembled concentrically with the rotor shaft by reversing the magnetic pole in the radial direction with respect to the first rotor magnetic pole.
Thereby, the motor characteristic can be improved by increasing the amount of magnetic flux passing through the magnetic circuit formed in the first rotor core, the stator core, the third rotor core, and the second rotor core.

  In the present invention, it is preferable that a magnetic material is used for the rotor shaft. According to this, since the rotor shaft can also be used as a magnetic flux path, more magnetic flux can be passed, and furthermore, an inexpensive magnetic material can be used for the rotor shaft, thereby reducing the manufacturing cost. be able to.

  If the hybrid stepping motor described above is used, the magnetic flux balance passing through the rotor pole teeth can be made uniform, the leakage magnetic flux can be reduced, the effective magnetic flux can be increased, and the motor characteristics can be improved in a small size.

It is a section explanatory view of a hybrid type stepping motor. It is explanatory drawing of the rotor magnet used for the hybrid type stepping motor of this invention. It is sectional explanatory drawing of the hybrid type stepping motor which concerns on another example. It is a section explanatory view of a rotor. It is a section explanatory view of the rotor concerning other examples. It is sectional explanatory drawing of the conventional hybrid type stepping motor. It is explanatory drawing of the rotor magnet used for the conventional hybrid type stepping motor.

  Hereinafter, an example of a hybrid type stepping motor according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a cross-sectional explanatory view of a hybrid type stepping motor.
The hybrid type stepping motor includes a rotor 2 in which a rotor magnet is assembled to a rotor iron core that is assembled to a rotor shaft 1 and has rotor pole teeth formed on an outer peripheral surface thereof, and a coil that is disposed opposite to the rotor pole teeth. And a stator 3 in which a magnetic circuit is formed between the stator pole teeth of the wound stator iron core. When the coil is energized, a rotational force acts between the rotor pole teeth and the stator pole teeth facing the rotor pole teeth to rotate. This will be specifically described below.

In FIG. 1, the structure of the rotor 2 will be described first.
The first rotor core 4 is assembled around the rotor shaft 1 and the first rotor pole teeth 4a are formed on the outer peripheral surface at a predetermined pitch in the circumferential direction, and the rotor shaft 1 is assembled around the outer peripheral surface. The second rotor core 5 is provided with the second rotor pole teeth 5a formed at a predetermined pitch.

  Further, at least one of the first rotor core 4 and the second rotor core 5, in this embodiment, an annular rotation around the rotor shaft 1 in the vicinity of the first rotor pole teeth 4 a of the first rotor core 4. The child magnet 6 is assembled concentrically. It is preferable to arrange the rotor magnet 6 as close to the first rotor pole teeth 4a as possible. Since the effective diameter of the rotor magnet 6 can be increased, the cross-sectional area can be increased and the amount of magnetic flux can be increased.

  Further, since the rotor magnet 6 is not disposed between the first rotor core 4 and the second rotor core 5 in the axial direction, the axial thickness of the third rotor core 7 described later is made constant. be able to. Accordingly, the axial length of a conventional hybrid stepping motor using a thick rotor magnet in the axial direction can be shortened, and a small and inexpensive hybrid stepping motor can be provided. it can. Further, if the thickness is the same, the total magnetic flux can be increased, so that the motor characteristics can be improved.

Further, the rotor magnet 6 is magnetized so that the entire outer peripheral surface of the rotor has the same polarity in the circumferential direction as the N pole or the S pole. In FIG. 1, the entire outer peripheral surface of the rotor is magnetized to the N pole, and the entire inner peripheral surface is magnetized to the S pole. Of course, on the contrary, the entire outer peripheral surface of the rotor may be magnetized to the S pole and the entire inner peripheral surface may be magnetized to the N pole. In a PM (permanent magnet) stepping motor, magnets having different polarities from the N pole, S pole, N pole, S pole,... Are arranged on the outer peripheral surface of the rotor. On the other hand, in the stepping motor of the present invention, the outer peripheral surface of the rotor and the inner peripheral surface of the rotor are magnetized with the same polarity in the circumferential direction, and this is very different from the PM type stepping motor.
FIG. 2 is an explanatory view of a rotor magnet used in the hybrid stepping motor of the present invention.

  In general, a neodymium sintered magnet is used for a hybrid stepping motor. However, in the present invention, since an optimum magnetic circuit design and a magnet cross-sectional area can be increased, an inexpensive neodibonded magnet can be used. Since the neodibonded magnet can be molded, the first rotor core 4 can be easily made, and it is not necessary to prepare many types of rotor magnets 6. Note that the present invention is not limited to neodymium bond magnets, and any type of magnet may be used as long as the motor characteristics and cost are satisfied.

  A third rotor core 7 having a smaller diameter than the first and second rotor cores 4 and 5 is laminated in the axial direction between the first and second rotor cores 4 and 5, and the rotor shaft 1 is centered. It is assembled to. It is desirable that the outer diameter of the third rotor core 7 is formed to be equal to or less than half the radial thickness of the rotor magnet 6 magnetized in the N-pole and S-pole in the radial direction. Thereby, the magnetic flux generated from the rotor magnet 6 returns from the first rotor core 4 to the rotor magnet 6 through the third rotor core 7 (magnetic short-circuit), and there is no problem even if leakage magnetic flux is generated. Can be prevented. The third rotor core 7 is formed integrally with the first rotor core 4 and the second rotor core 5 or integrally with the second rotor core 5, and the first rotor core 4 and the rotor magnet 6 are formed. Alternatively, it can be assembled as an insert.

  Further, since the third rotor core 7 is filled with the total magnetic flux of the magnetic circuit formed between the rotor 2 and the stator 3, the larger outer shape is better, but the radial thickness of the rotor magnet 6 is better. If it becomes more than half of the above, the above-described magnetic short occurs, so it is preferable to set it to less than half of the radial thickness. Further, the third rotor core 7 is made of a material having a high magnetic flux density instead of an electromagnetic steel plate, such as soft iron (magnetic flux density: 2.15) or permendur (Co + Fe magnetic flux density: 2.45). It is also possible to increase the thickness of the iron core.

  In FIG. 1, a magnetic circuit is formed between a stator pole tooth 8a of a stator core 8 in which a stator 3 is opposed to a first rotor pole tooth 4a and a second rotor pole tooth 5a and wound with a coil. Is done. Specifically, when the coil is energized, the magnetic flux generated from the N pole of the rotor magnet 6 passes through the second rotor pole teeth 5a via the stator pole teeth 8a facing from the first rotor pole teeth 4a. A magnetic circuit that passes through the second rotor core 5 and returns to the S pole of the rotor magnet 6 through the third rotor core 7 and the first rotor core 4 is formed.

  According to the above configuration, the annular rotor magnet 6 is assembled concentrically around the rotor shaft 1 in the vicinity of at least one pole tooth 4a of the first rotor core 4 and the second rotor core 5. Therefore, the leakage of magnetic flux generated from the rotor magnet 6 is small, the effective magnetic flux is large, the motor characteristics are improved, and the air gap from the rotor 2 and the stator 3 to the rotor magnet 6 corresponds to the gap between the rotor 2 and the stator 3. Since the distances are equal and magnetic flux is not concentrated, magnetic balance is stabilized and vibration and noise are reduced.

  The rotor shaft 1 is made of a magnetic material. According to this, since the rotor shaft 1 can also be used as a magnetic flux path, more magnetic flux can be passed, and furthermore, an inexpensive magnetic material (carbon steel material) is used for the rotor shaft 1. Therefore, the manufacturing cost can be reduced.

Here, the motor characteristics of the hybrid stepping motor will be considered.
The torque τ of the hybrid stepping motor is expressed by the following equation.
τ = Kt · I · Sinφ
Kt: Torque constant I: Winding current Sinφ: Torque angle The torque constant Kt is expressed by the following equation.
Kt = n ・ Nr ・ Φ
n: Number of turns of winding Nr: Number of teeth of rotor Φ: Number of magnetic flux Therefore, the motor characteristics are the same if the amount of magnetic flux is the same no matter where the rotor magnet 6 is arranged.
However, there is a saturation phenomenon in the iron core, and in a motor using a normal electromagnetic steel sheet, magnetic flux leakage occurs at a magnetic flux density of 1.7 (T) or more, and sometimes the characteristics are adversely affected.

When the effective diameter of the rotor magnet is C, the iron core thickness (magnet length) is B, the tooth width is A, and the number of teeth is Nr, the total magnetic flux Φ of the magnet is Φ = Bd · πC · B (where, Bd is the magnetic flux density at the operating point of the magnet)
The total magnetic flux Φ of the core pole teeth is Φ = Bt · A · B · Nr (however, the magnetic flux density of the Bt core teeth)
When the most efficient magnetic circuit design is made such that the total magnetic flux generated by the rotor magnet is the same as the magnetic flux passing through the pole teeth, that is, no leakage magnetic flux is generated.
Bd · πC · B = Bt · A · B · Nr
Bt = (Bd · πC) / (A · Nr)
It becomes. Bd, C, A, and Nr are numbers that are determined at the design stage.

  From the above equation, if the core thickness and the magnet length are the same, the magnetic flux density of the pole teeth is determined regardless of the core thickness B. Therefore, if the magnetic circuit is designed so that the pole tooth magnetic flux density is the most efficient magnetic flux density, the most efficient motor can be designed regardless of the thickness. As described above, the motor torque is proportional to the amount of magnetic flux Φ. Therefore, in order to ensure the required characteristics, it is only necessary to determine the thickness, which not only simplifies the design but also eliminates waste and is the most efficient. A good stepping motor can be provided.

The amount of magnetic flux of the rotor magnet is expressed by the following equation, where S is the cross-sectional area of the magnet.
Φ = Bd · S
Therefore, in order to increase the amount of magnetic flux, a magnetic circuit design (increasing the permeance coefficient) that increases the magnetic flux density Bd at the magnet operating point, a high-level magnet with a high residual magnetic flux density Br, or a magnet cross-sectional area is used. Either one of
In the conventional hybrid type stepping motor, since the outer diameter of the magnet cannot be increased beyond the outer diameter of the iron core, there is a limit to increase the cross-sectional area of the magnet. For this reason, a magnet with a high residual magnetic flux density Br is used, or a multistage rotor is used. However, with this structure, if the length is increased in the stacking direction, the magnet cross-sectional area can be increased. Therefore, even if an inexpensive magnet with a small residual magnetic flux density Br is used, the motor characteristics can be secured, and a magnet of the same grade can be used. Thus, the motor characteristics can be improved. However, it is not so if the thickness can be made infinitely long. Since the generated magnetic flux passes through the iron core C, when the iron core C becomes saturated, magnetic flux leakage occurs in the inner iron core of the rotor, and there is an optimum thickness that does not improve the characteristics. Therefore, a multi-stage rotor is required when more characteristics are required.

Another example of the hybrid stepping motor is shown in FIG. The same numbers are assigned to the same members, and the description is incorporated.
In FIG. 3, a first rotor magnet 6 a assembled concentrically with the rotor shaft 1 in the vicinity of the first pole tooth 4 a of the first rotor core 4, and a second pole tooth of the second rotor core 5. A second rotor magnet 6b assembled concentrically with the rotor shaft 1 may be assembled in the vicinity of 5a. The annular first rotor magnet 6a and the second rotor magnet 6b are magnetized in the radial direction, and the first rotor magnet 6a and the second rotor magnet 6b are magnetized so that the polarities are reversed. It is magnetized.

  Further, since the third rotor core 7 is filled with the total magnetic flux of the magnetic circuit formed between the rotor 2 and the stator 3, the larger outer shape is better, but the radial thickness of the rotor magnet 6 is better. If it becomes more than half of the thickness, a magnetic short circuit occurs, so it is preferable to set it to less than half of the radial thickness.

  In FIG. 3, a magnetic circuit is formed between the stator 3 and the stator pole teeth 8a of the stator core 8 on which the coil 3 is wound so as to face the first rotor pole teeth 4a and the second rotor pole teeth 5a. Is done. Specifically, when the coil is energized, the magnetic flux generated from the N pole of the first rotor magnet 6a causes the stator pole teeth 8a and the second rotor pole teeth 5a facing the first rotor pole teeth 4a. The magnetic flux generated from the N pole of the second rotor magnet 6b passes through the second rotor core 5, the third rotor core 7, and the first rotor core 4 after returning to the S pole of the second rotor magnet 6b. A magnetic circuit that returns to the S pole of the first rotor magnet 6a is formed.

  Also with the above configuration, the amount of magnetic flux passing through the first rotor core 4, the stator core 8, the second rotor core 5, and the third rotor core 7 can be increased to improve the motor characteristics.

Moreover, although the annular magnet was used for the rotor magnet 6, it is made into a waveform annular shape (see FIGS. 4A and 4B), and the annular magnet is made into a polygonal annular shape (see FIG. 5A). Various forms such as a star shape or a tooth shape ring (see FIG. 5B) can be adopted.
As a result, the radial sectional area Sa of the rotor magnet 6 increases, and since Φ = Bd · Sa, the effective magnetic flux increases, and the motor characteristics can be improved.

DESCRIPTION OF SYMBOLS 1 Rotor shaft 2 Rotor 3 Stator 4 1st rotor core 4a 1st rotor pole tooth 5 2nd rotor core 5a 2nd rotor pole tooth 6 Rotor magnet 6a 1st rotor magnet 6b 2nd rotation Child magnet 7 Third rotor core 8 Stator core 8a Stator pole teeth

Claims (5)

A rotor in which a rotor magnet is assembled to a rotor core having a rotor pole tooth formed on the outer peripheral surface thereof, and a stator core having a coil wound around the rotor pole tooth. A stator in which a magnetic circuit is formed between the stator pole teeth and rotating by a rotational force generated between the stator pole teeth facing the rotor pole teeth by energizing the coil A hybrid stepping motor that
A first rotor core having first rotor pole teeth formed on an outer peripheral surface assembled around the rotor shaft;
A second rotor core in which second rotor pole teeth are formed on an outer peripheral surface assembled around the rotor shaft;
The first rotor core and the second rotor core are assembled concentrically around the rotor shaft in the vicinity of at least one of the rotor pole teeth, and at least one of the rotor cores and the axial thickness thereof. The rotor magnets formed in an annular shape so as to be the same ,
The first rotor pole teeth and the second rotor pole teeth are stacked between the first and second rotor cores assembled with a half-pitch shift , and the outer diameter is the radial thickness of the rotor magnet. A third rotor core formed with a diameter smaller than that of the first and second rotor cores to be less than half of
Flux one from the rotor pole teeth via the stator pole teeth opposed other rotor pole teeth and the other of the third rotor core through the rotor core of the rotor magnet, wherein one of the rotor core A hybrid stepping motor, wherein a magnetic circuit returning to the rotor magnet is formed.   2. The hybrid stepping motor according to claim 1, wherein the rotor magnet is magnetized so that each of an outer peripheral surface and an inner peripheral surface has the same polarity in the circumferential direction as an N pole or an S pole. The hybrid stepping motor according to claim 1, wherein a neodymium bond magnet is used as the rotor magnet. An annular first rotor magnet is disposed in the vicinity of the first rotor pole teeth of the first rotor core, and an annular second rotor magnet is disposed in the vicinity of the second rotor pole teeth of the second rotor core. 4. The hybrid stepping motor according to claim 1, wherein the stepping motor is assembled concentrically with the rotor shaft by reversing the magnetic pole in the radial direction with respect to the first rotor magnet . 5. The hybrid stepping motor according to claim 1, wherein a magnetic material is used for the rotor shaft .

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