JP3705397B2 - Stepping motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stepping motor including a magnet rotor, an excitation coil, and a stator core that transmits a magnetic field generated by the excitation coil to the magnet rotor.
[0002]
[Prior art]
A stator core, which is one of the components constituting the stepping motor, includes a base portion having an insertion hole through which the magnet rotor is inserted, and a plurality of excitation pole teeth formed so as to protrude from the base portion. In recent years, with this type of stepping motor, it is considered to be as large as possible to secure a maximum tooth area. That is, as the area of the pole teeth increases, the area that receives the magnetic field of the rotor increases. As a result, the magnetic field of the rotor can be used more effectively, and the output torque of the motor increases.
[0003]
By the way, when securing a large pole tooth area, there are two ways of thinking, namely, the idea of increasing the pole tooth height and the idea of widening the pole tooth width. However, when the width of the pole teeth becomes wider than the magnetization width per pole of the rotor, the magnetic fluxes cancel each other, and the torque is reduced. Therefore, in order to ensure a large pole tooth area, the pole tooth height must be increased.
[0004]
Here, some conventional methods for manufacturing a stator core will be described below.
The first prior art method is as follows. As shown in FIG. 9, first, a metal disc 31 is prepared as a stator core plate material, and a predetermined portion of the disc 31 is punched out by a press. As a result, a circular punching hole 32 is formed at the center of the disc 31. In the periphery of the punching hole 32, portions other than the portion to be the excitation pole teeth later are removed by being punched out in a substantially fan shape. Next, as shown in FIG. 10, a portion that will later become an excitation pole tooth is caused to move from the inner peripheral side to the outer peripheral side of the disc 31, and the portion is bent at a right angle at the base. As a result, a plurality of exciting pole teeth 34 protrude from one side surface of the base 33, and the stator core 35 is completed.
[0005]
The second prior art method is as follows. First, a metal disk 36 is prepared. As shown in FIG. 11, a punching hole 32 is also formed at the center of the disk 36. Around the punched hole 32, a plurality of cut-and-raised holes 37 having a portion to be an excitation pole tooth later are formed by punching. Next, a portion that is to become an excitation pole tooth later is caused from the outer peripheral side to the inner peripheral side of the disk 36, and the portion is bent at a right angle at the base. As a result, a plurality of exciting pole teeth 34 protrude from one side surface of the base 33, and the stator core 38 as shown in FIG. 12 is completed. Examples of similar techniques include those disclosed in Japanese Utility Model Publication Nos. 1-35588, Japanese Utility Model Publication No. 5-5821, and Japanese Utility Model Application Publication No. 64-6779.
[0006]
[Problems to be solved by the invention]
However, the first prior art has a problem that the pole tooth height is restricted by the diameter of the central punching hole 32 determined by the plate thickness of the stator core 35 and the pole tooth portion inner diameter after being bent. Therefore, this point is an obstacle to torque up the motor.
[0007]
Further, in the second prior art, since it is necessary to provide the non-punched portion 39 in the outer peripheral side region of the cut and raised hole 37, there is a problem that the pole tooth height is restricted due to the existence thereof. For this reason, it is difficult to set a torque that meets the needs.
[0008]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a stepping motor that can easily increase the torque because the height of the pole teeth can be increased.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, in the invention according to claim 1, in the stepping motor comprising a magnet rotor, an excitation coil, and a stator core that transmits a magnetic field generated by the excitation coil to the magnet rotor, the stator core Is arranged radially with the insertion hole as a center so as to oppose the outer peripheral surface of the magnet rotor, and protrudes from one side surface of the base. As described above, a plurality of exciting pole teeth formed by bending from the root portion in the rotation axis direction of the magnet rotor, and a peripheral portion of the insertion hole are formed by burring, and on the side opposite to the one side surface of the base portion and a burring part formed so as to protrude from the surface, the excitation in the previous state folded The length from the core center of the tooth, the radius of the above size der is, the insertion hole of said base, and wherein Rukoto formed is enlarged by the burring small-diameter hole from the insertion hole The gist of the stepping motor is as follows.
[0010]
According to a second aspect of the present invention, in the first aspect, when the base portion is formed by being bent in the direction of the rotation axis of the magnet rotor so as to be substantially cup-shaped, the excitation in a state before the bending is performed. The length of the pole teeth from the core center is assumed to be equal to or greater than the radius of the base before bending.
[0011]
According to a third aspect of the present invention, in the first or second aspect, the width of the base portion of the exciting pole teeth is equal to or less than the width of the base portion of the plurality of base portion forming pieces constituting the base portion.
[0012]
According to a fourth aspect of the present invention, in the third aspect, the width of the punched portion existing between the exciting pole teeth and the base forming piece is 1.0 to 1.5 times the plate thickness of the stator core. It was decided that it was the size.
[0013]
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the excitation pole teeth are formed to become wider toward the tip .
[0014]
Hereinafter, the “action” of the present invention will be described.
According to the inventions of claims 1 to 5 , the pole tooth height is higher than the conventional technique in which the length from the core center of the excitation pole tooth in the state before bending is less than the size of the radius of the base, As a result, a large pole tooth area is secured.
[0015]
According to the invention described in claim 3, by setting the width of the root portion of the excitation pole teeth to be equal to or less than the width of the root portion of the plurality of base forming pieces, magnetic saturation due to cancellation of magnetic flux can be prevented in advance. .
[0016]
According to the invention described in claim 4, by setting the width of the punched portion existing between the exciting pole tooth and the base forming piece within such a suitable range, a large pole tooth can be obtained without hindering punching by a press. An area can be secured.
[0017]
According to the fifth aspect of the present invention, since the exciting pole teeth are formed so as to be wider toward the tip portion, a larger pole tooth area can be secured even if the pole teeth height is the same. Can do.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a stepping motor M1 embodying the present invention will be described in detail with reference to FIGS.
[0020]
FIG. 1 shows a PM (Permanent Magnet) type stepping motor M1 in this embodiment. FIG. 2 shows a stator core plate 2 used in manufacturing the stator core 1 of the PM type stepping motor M1. FIG. 3 shows the stator core plate 2 that has undergone bending. FIG. 4 shows the stator core 1 completed through the burring process.
[0021]
As shown in FIG. 4, the base 3 constituting the stator core 1 of the present embodiment is formed in a substantially cup shape by being bent at a right angle in the direction of one side surface (upper surface in FIG. 4). The base 3 has an insertion hole 4 through which the magnet rotor 17 is inserted. The insertion hole 4 has a circular shape and is expanded in diameter through burring.
[0022]
The stator core 1 includes a plurality of exciting pole teeth 5. These excitation pole teeth 5 are formed so as to protrude from the upper surface side of the base portion 3 by being bent at right angles to the rotation axis direction of the magnet rotor 17 (that is, the core central axis direction). Thereby, the excitation pole teeth 5 are arranged radially so as to face the outer peripheral surface of the magnet rotor 17. Note that the burring portion 6 formed on the peripheral edge of the insertion hole 4 is formed so as to protrude to the lower surface side of the base 3.
[0023]
In this embodiment, the length L1 from the core center of the exciting pole teeth 5 in the state before bending is set in advance so as to be equal to or larger than the radius R1 of the base 3 before bending.
[0024]
Here, the mechanical configuration of the stepping motor M1 of this embodiment will be briefly described with reference to FIG.
A pair of stator cores 1 are disposed inside a motor case 11 constituting the stepping motor M1. A first exciting coil 12a is accommodated on the outer peripheral surface side of one of the two stator cores 1 (the right one in FIG. 1). On the outer peripheral surface side of the other (left side in FIG. 1) stator core 1, a second exciting coil 12b is accommodated. The connector portion 15 in the motor case 11 includes a plurality of terminals 16. A direct current is supplied to both excitation coils 12a and 12b through these terminals 16. A substantially cylindrical magnet rotor 17 is disposed in the insertion hole 4 of both stator cores 1. The magnet rotor 17 has a hole at its center. A rotor shaft 18 as a rotating shaft is inserted and fixed in the center hole. The rotor shaft 18 is rotatably supported by a metal bearing (ball bearing) 19 and a slide bearing 13. The magnet rotor 17 includes a multi-pole magnetized magnet 14 on its outer periphery.
[0025]
In the stepping motor M1 configured as described above, the magnetic field generated by the exciting coils 12a and 12b is transmitted to the magnet rotor 17 by the stator core 1.
[0026]
Next, a procedure for manufacturing such a stator core 1 will be described. The stator core plate member 2 shown in FIG. 2 is made of a substantially circular metal material having protruding portions at four locations, and is obtained by stamping with a press. The stator core plate 2 of the present embodiment includes a circular insertion hole 4 at the center thereof. The stator core plate 2 includes four exciting pole teeth 5 and four base forming pieces 7. These excitation pole teeth 5 are arranged radially with the insertion hole 4 as the center in an angle of 90 ° with each other. Similarly, the base forming pieces 7 are arranged radially.
[0027]
As shown in FIG. 2, each excitation pole tooth 5 in the stator core plate 2 is formed to become thinner toward the tip. The length L1 of the exciting pole teeth 5 from the core center is larger than the size of the radius R1 of the base 3 (in other words, the length of the base forming piece 7 constituting the base 3 from the core center). Therefore, in this embodiment, the tip of each excitation pole tooth 5 is in a state extending from the circumference of the plate material. In FIG. 2, the length L1 is about 1.3 times the radius R1.
[0028]
Further, the width W1 of the base portion of the excitation pole teeth 5 is preferably formed to be equal to or less than the width W2 of the base portion of the base forming piece 7 constituting the base 3. The reason is that if the width W1 is larger than the width W2, the magnetic fluxes cancel each other due to the magnetic circuit, and there is a possibility that the magnetic saturation may occur. Therefore, in the present embodiment, the width W1 is set to a size of about 0.8 to 0.9 times the width W2 in order to avoid torque reduction due to magnetic saturation.
[0029]
As shown in FIG. 2, a punched portion 8 exists between the base forming piece 7 having a substantially fan shape and the exciting pole teeth 5 in the stator core plate 2. The width W3 of the punched portion 8 is preferably 1.0 to 1.5 times the plate thickness T1 of the stator core plate 2. If the width W3 is less than 1.0 times the plate thickness T1 of the stator core plate 2, the punching process by the press may be hindered. On the other hand, if the width W3 exceeds 1.5 times the plate thickness T1 of the stator core plate 2, the problem of obstructing the punching process is solved, but the excitation pole teeth 5 become narrow. This makes it impossible to secure a large pole tooth area. Therefore, the torque cannot be increased.
[0030]
Then, after the stator core plate 2 as described above is manufactured in advance, bending is then performed by a press. By this processing, first, the root portion of each excitation pole tooth 5 is bent at right angles to the core central axis direction, and each excitation pole tooth 5 is caused on the upper surface side of the base portion 3. Subsequently, each base forming piece 7 constituting the base 3 is similarly bent at right angles to the core center direction, thereby causing each base forming surface 7 in the upper surface direction of the base 3. Thereby, the substantially cup-shaped base 3 is formed. In the present embodiment, the height of the excitation pole teeth 5 is slightly more than twice the depth of the cup. The stator core plate 2 may be bent in two stages, or may be performed in one stage using the same forming jig. In the case of performing in two stages, the base forming piece 7 may be bent before the exciting pole teeth 5 are bent.
[0031]
After such a bending step, burring is performed on the peripheral edge of the insertion hole 4 at the base 3. By performing the burring process, the insertion hole 4 is expanded to a diameter of more than twice, and the burring process part 6 is rolled up on the lower surface side of the base part 3. As a result, the insertion hole 4 can allow the magnet rotor 17 to be inserted, and the stator core 1 shown in FIG. 4 is completed.
[0032]
Now, the characteristic effects of the present embodiment will be listed below.
(A) Since the base 3 is substantially cup-shaped in the stator core 1 of the present embodiment, the length L1 from the core center of the excitation pole tooth 5 in the state before bending is set to the radius R1 of the base 3 before bending. More than that. On the other hand, in each said prior art (refer FIGS. 9-12), the length from the core center of the exciting pole tooth 5 in the state before bending is less than the magnitude | size of the radius of the base part 3. FIG. Therefore, according to the stator core 1, the pole tooth height is higher than that of the prior art, and as a result, a large pole tooth area can be secured. For this reason, as a result of the area receiving the magnetic field of the magnet rotor 17 being increased, the magnetic field of the magnet rotor 17 can be used more effectively. Therefore, the torque increase of the motor M1 can be achieved relatively easily. In the present embodiment, since the non-punched portion 39 as shown in FIGS. 11 and 12 does not exist, there is no situation in which the pole tooth height is restricted thereby. This means that the pole tooth height can be arbitrarily set, and the pole tooth area can be significantly improved as compared with the prior art.
[0033]
(B) In the stator core 1 of the present embodiment, the width W1 of the root portion of the excitation pole teeth 5 is set to be equal to or less than the width W2 of the root portion of the base forming piece 7. Therefore, magnetic saturation due to cancellation of magnetic flux can be prevented in advance, and torque reduction caused by it can be surely avoided.
[0034]
(C) In the stator core 1 of the present embodiment, the width W3 of the punched portion 8 existing between the exciting pole teeth 5 and the base forming piece 7 is set to 1.0 to 1.5 times the plate thickness T1 of the stator core 1. Is set to a suitable range of size. Therefore, a large pole tooth area can be secured without hindering punching by pressing. Therefore, there is no difficulty in manufacturing even when the torque is increased.
[0035]
(D) In the stator core 1 of the present embodiment, burring is applied to the peripheral portion of the insertion hole 4 in the base 3. Therefore, when the stator core plate 2 is manufactured by punching, it is sufficient to form the small-diameter insertion hole 4. This also has a positive effect on increasing the height of the pole teeth.
[0036]
In addition, this invention is not limited to the said embodiment, For example, it can be changed into the following forms.
A different example of the stator core 21 shown in FIGS. 5 and 6A and 6B may be used. In the stator core 21, after the burring process is performed on the peripheral edge portion of the insertion hole 4, the burring process part 6 is further bent in the core outer peripheral direction. Since the bent burring portion 6 is in a state of being substantially in contact with the lower surface side of the base portion 3, the thickness of the peripheral edge portion of the insertion hole 4 is substantially twice that of the above embodiment. With such a configuration, since the burring portion 6 forms a magnetic circuit, even the configuration in which the magnetic path is reduced can be compensated for. Therefore, it is advantageous when the configuration of the above embodiment in which the width W1 is equal to or smaller than the width W2 is adopted, and torque increase can be achieved more easily and reliably.
[0037]
As in the stator core 26 of another example shown in FIG. 7B, the excitation pole teeth 27 are preferably formed to become wider toward the tip. With such a configuration, even if the height of the same pole teeth is the same, a larger pole tooth area can be ensured as much as the width becomes wider. Therefore, torque increase can be achieved more easily and reliably. FIG. 7A shows a stator core plate 28 for manufacturing another example of the stator core 26. Of course, in the stator core 26 of this other example, the burring portion 6 may be bent in the core outer peripheral direction.
[0038]
The width W1 of the root portion of the excitation pole teeth 5 and 27 can be the same as the width W2 of the root portion of the base forming piece 7.
The number of exciting pole teeth 5 and 27 is not limited to four and can be increased or decreased.
[0039]
The excitation pole teeth 5 and 27 may be provided with excitation pole teeth having a uniform width instead of the configuration of the embodiment described above where the widths of the excitation pole teeth 5 and 27 are not uniform.
◎ The present invention is not limited to the stator cores 1, 2, 26 having the substantially cup-shaped base 3, but is specifically described as the stator core 29 having the flat base 3 </ b> A, in other words, the stator core 29 in which the base-forming piece is not bent. Of course, it may be realized. In this case, the length L1 from the core center of the exciting pole teeth 5 in the state before bending is required to be not less than the radius R1 of the base 3A. FIG. 8 shows a specific example thereof.
[0040]
Here, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiments are listed below together with their effects.
(1) A metal plate provided with an insertion hole formed by punching, and a plurality of excitation pole teeth and a plurality of base forming pieces that are formed by punching and are arranged radially about the insertion hole. A plate material for a stator core of a stepping motor, wherein the length of the excitation pole tooth from the core center is formed to be greater than the length of the base forming piece from the core center. With this configuration, it is possible to reliably manufacture the stator core according to the first aspect.
[0041]
The technical terms used in this specification are defined as follows.
“Burling: A type of plastic working method that refers to a forming method that widens holes formed in a plate.”
[0042]
【The invention's effect】
As described above in detail, according to the first to fifth aspects of the invention, the height of the pole teeth can be increased, so that a stepping motor with a simple torque increase can be provided.
[0043]
According to the third aspect of the present invention, torque reduction due to magnetic saturation can be reliably avoided.
According to the fourth aspect of the present invention, there is no difficulty in manufacturing even when the torque is increased.
[0044]
According to the fifth aspect of the present invention, it is possible to achieve torque increase more easily and reliably.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a stepping motor according to an embodiment of the present invention.
FIG. 2 is a plan view showing a stator core plate material before bending.
FIG. 3 is a cross-sectional view showing a stator core plate that has been similarly bent.
FIG. 4 is a cross-sectional view of a stator core completed through burring.
FIG. 5 is a sectional view showing another example of a stepping motor.
6A is a bottom view showing another example of the stator core, and FIG. 6B is a cross-sectional view thereof.
7A is a plan view showing a stator core plate of another example stator core, and FIG. 7B is a cross-sectional view showing another completed stator core.
FIG. 8 is a cross-sectional view showing another example of a stator core.
FIG. 9 is a plan view of a stator core plate member of the first conventional stator core.
FIG. 10 is a sectional view of a first prior art stator core.
FIG. 11 is a plan view of a stator core plate member of a second prior art stator core.
FIG. 12 is a cross-sectional view of a second prior art stator core.
[Explanation of symbols]
1, 2, 26, 29 ... stator core, 2, 28 ... plate material for stator core, 3, 3A ... base, 4 ... insertion hole, 5, 27 ... exciting pole teeth, 6 ... burring portion, 7 ... base forming piece, 8 DESCRIPTION OF SYMBOLS ... Punching part, 17 ... Magnet rotor, 18 ... Rotor shaft as a rotating shaft of a magnet rotor, L1 ... Length from the core center of the excitation pole tooth in the state before bending, R1 ... Base part (in the state before bending) Radius, W1... Width of base portion of exciting pole teeth, W2... Width of base portion of base forming piece, W3...

Claims (5)

In a stepping motor comprising a magnet rotor, an excitation coil, and a stator core that transmits a magnetic field generated by the excitation coil to the magnet rotor,
The stator core is disposed radially with a base portion having an insertion hole through which the magnet rotor is inserted at the center thereof and the insertion hole so as to face the outer peripheral surface of the magnet rotor, and from one side surface of the base portion. A plurality of exciting pole teeth formed by bending from the root portion in the rotation axis direction of the magnet rotor so as to protrude, and formed by burring on the peripheral edge portion of the insertion hole and opposite to one side surface of the base portion and a burring part formed to protrude from the surface on the side, the length of the core center of the exciting pole teeth in the state before folding, Ri the radius of magnitude or more der of the base, the insertion stepping motor holes, which from the insertion hole is a small diameter hole was characterized by Rukoto formed is enlarged by the burring.   When the base is formed to be bent in the direction of the rotation axis of the magnet rotor so as to be substantially cup-shaped, the length from the core center of the excitation pole tooth in the state before bending is The stepping motor according to claim 1, wherein the stepping motor is equal to or larger than a radius of the base portion.   3. The stepping motor according to claim 1, wherein a width of a root portion of the excitation pole teeth is equal to or less than a width of a root portion of a plurality of base portion forming pieces constituting the base portion.   The width of the punched portion existing between the exciting pole teeth and the base forming piece is 1.0 to 1.5 times the plate thickness of the stator core. The stepping motor described.   5. The stepping motor according to claim 1, wherein the exciting pole teeth are formed so as to become wider toward a tip portion. 6.

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