JP2586429B2 - Step motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PM (permanent magnet) type step having a large detent torque and capable of holding a rotor stop position accurately, uniformly and strongly. The present invention relates to a motor, and is suitable for use as, for example, a drive device to be controlled by various control devices for automobiles. 2. Description of the Related Art A conventionally known PM step motor has a structure as shown in FIG. 1 in order to convert a rotary motion of a rotor into a linear motion of a shaft by a screw or the like. In FIG. 1, reference numeral 1 denotes a cup-shaped first housing, and reference numeral 2 denotes a disk-shaped second housing, both of which are integrally fixed by screws 3 to form an outer shell of the motor. Reference numeral 4 denotes a rotor, in which a cylindrical permanent magnet 5 is arranged in a circumferential direction of an outer peripheral portion thereof, and an internal thread 6 is formed in an inner peripheral portion thereof. Further, stopper surfaces 7a and 7 for limiting the axial movement of the shaft 8 are provided at both ends of the rotor 4. The female screw 6 has a male screw 9 provided on a shaft 8.
They are trying to interact. The shaft 8 is provided with two stopper pins 10 and 11 at intervals, and the stopper surfaces 7a and 7b at both ends of the rotor 4 are engaged with the stopper pins 10 and 11, respectively. The axially movable length of the shaft 8 is determined by the one stopper surface 7a of the rotor 4 and the stopper pin 10
From the position where the stopper pin locks to the position where the other stopper surface 7b of the rotor 4 and the stopper pin 11 of the shaft 8 lock. Bearings 12, 12 ′ are provided at both ends of the rotor 4.
The rotor 4 is rotatably held by the first housing 1 and the second housing 2 via 2 '. Axis 8
Are the sintered oil-impregnated bearings 13,1 fixed to each housing 1,2
It is rotatably held by 3 '. A starter core 1 serving as a stator pole is provided on the outer peripheral side of the rotor 4 with an air gap 14 therebetween.
5, 15 'are provided and fixed to the first housing 1. Inside the stator cores 15, 15 ', stator exciting coils 17, 17' insulated by bobbins 16 are wound. The two stator cores 15, 15 'are combined in a pair on the exciting coil 17 side and the exciting coil 17' side, respectively, and are arranged on the outer peripheral surface of the permanent magnet 5 of the rotor 4 in the first and second rows. A row of cores is formed, and magnetic pole teeth 21, 22 or 23, 24 shown in FIG. 5 to be described later are formed alternately on the inner peripheral portion of the stator cores 15, 15 '. The exciting coils 17, 17 'are provided with intermediate taps as shown in FIG. 2, are connected in four phases, and are connected to the collectors of transistors TR1 to TR4 of a driving circuit as shown in FIG. By turning on and off the energizing current of the exciting coils 17, 17 'in the order determined by TR1 to TR4, the rotor 4 rotates stepwise, and the rotor 4
The shaft 8 moves forward or backward through the engagement between the female screw 6 and the male screw 9 of the shaft 8. In the case of two-phase excitation, the excitation is performed at the timing shown in FIG.
The number of revolutions of the rotor 4 is determined by the time interval t of the timing. Also, the excitation of the excitation coils 17, 17 'and the rotor 4
In general, the rotation is always performed regardless of whether the motor is rotating or stopped. In this case, the holding torque (holding torque) of the rotor 4 at the time of stopping is strong, but the transistors TR1 to TR4 can withstand continuous energization. In addition, a transistor that is resistant to destruction due to self-heating is required, so that a large transistor needs to be used. Further, even when the motor is stopped, the exciting coils 17, 17 'are continuously energized, so that extra power is consumed. Therefore, the excitation coils 17, 17 'are excited only when the rotor 4 is rotating, and the rotor 4
The present inventor has tried to reduce the heat generation and the power consumption of the transistors TR1 to TR4 by adopting a method of stopping the excitation of all the exciting coils 17, 17 'when the operation is stopped. [0003] However, when such a stepping motor is employed in a valve driving device for controlling the amount of intake air to the engine of an automobile, for example, when the stepping motor stops, the engine is stopped. There is a problem that the rotor 4 rotates due to the vibration of the rotor. The present inventor examined the cause of this problem, and found that the excitation coil
When the excitation of 17,17 'is stopped, the stator cores 15,15'
Since the N and S poles disappear, and the stator cores 15 and 15 'simply become ferromagnetic substances, only the attractive force (dent torque) of the magnetic substance by the permanent magnet 5 of the rotor 4 is obtained. As shown in FIGS. (A) and (B), the stator core 1
The distance between the magnetic pole teeth 21 and 22 and the magnetic pole teeth 23 and 24 (the distance between the center lines of the magnetic pole teeth) is equal to 2 W, and the N pole magnetized by the permanent magnet 5 and the S pole It has been found that the width of the poles is uniform at 2 W, and as a result, the rotor holding force (detent torque) due to the attractive force of the permanent magnet 5 becomes a relatively small value. 5 (A) and 5 (B) schematically show the circumferential arrangement of the magnetic pole teeth 21, 22, 23 and 24 of the permanent magnet 5 and the stator cores 15 and 15 '. FIG. 5 (B) shows a state where the stop position of the rotor 4 has moved to the right in the figure by one step from FIG. 5 (A). Stator core
Rows (1st row) of the magnetic pole teeth 21 and 22 of 15,15 'and magnetic pole teeth 2
In each of the rows on the 3,24 side (second row), these teeth are arranged at equal intervals of 2W, and the width of the N pole and S pole of the permanent magnet 5 is also equal to 2W. In the rotor stop position shown in FIG. 7A, the magnetic pole teeth are provided on the first row side of the stator cores 15, 15 '.
Both the north and south poles are induced at 21, 21 respectively, and the magnetic flux cancels out at these teeth 21, 22. Therefore, the magnetic pole teeth 21 and 22 in the first row do not substantially contribute to the generation of the detent torque. Then, N induced in the magnetic pole teeth 23, 24 of the second row
Only the pole and the south pole contribute to the generation of detent torque. At the rotor stop position shown in FIG.
Since both the N pole and the S pole are induced in the magnetic pole teeth 23, 24 on the row side, there arises a problem that the magnetic pole teeth 23, 24 in the second row do not contribute to the generation of detent torque. in this way,
In the conventional structure, only one of the magnetic pole teeth of the first row or the second row functions effectively for generating the detent torque, so that the rotor holding force has a relatively small value. 4 rotates. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. In addition to a magnetic circuit formed between each pole tooth of a stator core by a magnetomotive force of a permanent magnet when a current is not supplied to an exciting coil, a new circuit is provided. A stepping motor capable of effectively improving a holding force (corresponding to a detent torque) with respect to a rotor having a permanent magnet by arranging an auxiliary projection for forming a magnetic circuit at a center position of the permanent magnet. The purpose is to provide. [0005] In order to achieve the above object, the present invention has a cylindrical permanent magnet (5) formed by alternately magnetizing N poles and S poles on an outer peripheral surface. Rotor (4), a housing (1, 2) rotatably holding the rotor (4) inside itself, and an inner peripheral wall of the housing (1, 2) and an outer periphery of the rotor (4). A large number of magnetic pole teeth (21, 22, 23) disposed between the rotor and the N pole or the S pole of the permanent magnet (5) on the outer peripheral surface of the rotor (4) and opposed to the N pole or the S pole via a constant gap (14). , 24) and the stator core (15, 1 ').
5 ′), and the magnetic pole teeth (21, 22, 23,
An excitation coil (17, 1 ') for driving the rotor (4) in a stepwise manner by magnetizing 24), and magnetic pole teeth (21, 22, 22) of the stator core (15, 15').
23, 24) are divided into two rows, a first row and a second row, around the permanent magnet (5) of the rotor (4), and are arranged in the circumferential direction so as to surround the rotor (4). The magnetic pole teeth (21, 22) constituting the first row of the stator cores (15, 15 ') and the magnetic pole teeth (23, 24) constituting the second row are arranged on the circumference of the rotor (4). The positions in the direction are arranged to be shifted from each other by a predetermined amount, and in the housing (1, 2), a plurality of cylindrical permanent magnets (5) are opposed only to an axial center portion thereof, A projection-like auxiliary projection (101) made of a magnetic material is provided, and receives the magnetic flux from the permanent magnet (5) when the excitation coil (17, 1 ') is not excited. In between, a magnetic circuit that generates detent torque is formed To adopt a surgical means. According to the above technical means, when the rotor is stopped, the magnetic force of the permanent magnet induces only one of the S-pole and the N-pole on each of the auxiliary projections 101, and the gap between each of the projections and the permanent magnet is generated. A magnetic circuit is formed on the substrate. At this time, each auxiliary projection 101 is arranged only at the axial center of the cylindrical permanent magnet having the highest magnetic flux density.
Therefore, a large detent torque can be exhibited even when the exciting coil is not excited. In the first row of stator cores and the second row of stator cores, if auxiliary projections are arranged near the stator cores whose surfaces are opposed to each other, the auxiliary projections can be arranged so as to face the center of the permanent magnet. . The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 6 is a longitudinal sectional view of a step motor specifically illustrating one embodiment of the present invention,
Reference numerals 5,15 'denote the exciting coil 17 side and the exciting coil 1 similarly to the conventional structure shown in FIGS. 1 and 5 (A) and (B).
The two pairs of stator cores 15 and 15 'are combined with each other at 7' to form two rows of cores on the outer periphery of the permanent magnet 5 of the rotor 4. N
A number of magnetic pole teeth 21, 22, 23, 24 arranged in a row in the circumferential direction of the rotor 4 and arranged in opposition to a pole or an S pole via a fixed gap 14.
Are formed integrally. The arrangement of the magnetic pole teeth 21 to 24 is, as shown in FIGS. 8 and 9, the magnetic pole teeth 21 and 22 on the first row (the left row in FIG. 6) and the second row (in FIG. In each of the magnetic pole teeth 23 and 24 on the right side (row), magnetic pole teeth adjacent in the circumferential direction of the rotor 4 are arranged at equal intervals (2W). Here, the interval 2W is the interval between the center lines of adjacent magnetic pole teeth. On the other hand, the width of the N pole and the S pole magnetized by the permanent magnet 5 of the rotor 4 is the same as the above-mentioned interval 2W. As shown in FIGS. 8 and 9, the magnetic pole teeth (21, 22) and (23, 24) of the first and second rows are positioned at a predetermined distance from each other in the circumferential direction of the rotor. They are offset by half the size of 2W. In this embodiment, a disk-shaped auxiliary stator core 100 made of a magnetic material is provided between the stator cores 15 and 15 '. As shown in FIG. 7, the auxiliary stator core 100 has a protrusion 101 at an inner diameter portion facing the magnetic pole of the permanent magnet 5.
Are provided at twice the number of poles magnetized on the outer periphery of the permanent magnet 5 at equal intervals. The auxiliary stator core 100 includes
A hole 102 is provided at a position on the outer peripheral side of the protrusion 101, and a protrusion (not shown) provided on the stator cores 15 and 15 'is fitted into the hole 102, so that the relative position between the stator cores 15, 15' and the auxiliary stator core 100 is increased. This is for determining the positional relationship. Even if the auxiliary stator core 100 is not provided between the stator cores 15 and 15 ', as long as the auxiliary stator core 100 is located at a position facing the magnetic poles of the permanent magnet 5, for example, the end face portion of one of the stator cores 15 which is not in contact with the other stator core 15' Can also be provided. According to the configuration of the above-described embodiment, since the auxiliary stator core 100 is not affected by the magnetization of the exciting coils 17, 17 ', the same operation as that of the conventional motor is performed when the exciting coils 17, 17' are energized. On the other hand, when the rotor is stopped and power is not supplied, the teeth 21 and 22 of the stator cores 15 and 15 ',
23 and 24 are simply iron claws, and the auxiliary stator core 100
Similarly, a magnetic circuit is established by the stator cores 15, 15 'and the auxiliary stator core 100 by the magnetomotive force of the permanent magnet 5, and a detent torque is generated in the rotor 4. Hereinafter, the generation form of the detent torque will be described with reference to FIGS.
This will be specifically described with reference to the drawings. The number of the magnetic pole teeth 21, 22, 23, 24 of the stators 15, 15 'is the same as the number of the magnetic poles of the permanent magnets 5 in the first and second rows. At this time, two north poles and two south poles are induced on the first row side pole teeth 21 and 22 at the rotor stop position shown in FIG. Therefore, since the magnetic fluxes cancel each other at the teeth 21 and 22, they do not substantially contribute to the generation of the detent torque. FIG. 9 shows a state in which the rotor 4 has moved to the right in the figure by one step from FIG. 8, and in FIG. , These teeth 23, 24 do not contribute to the generation of detent torque. However, in this embodiment, at the rotor position shown in FIG.
9 and the projections 101 of the auxiliary stator core 100, and at the rotor position shown in FIG.
The detent torque can be effectively improved by the combination of 2 and the projection 101 of the auxiliary stator core 100. That is,
Since the number of protrusions 101 of the auxiliary stator core 100 is two for each magnetic pole of the permanent magnet 5, a magnetic circuit is formed as shown in FIG. Here, in FIG.
(C), (d) and (e) attached to FIG. 1 are shown in FIG. 8 and FIG.
Corresponds to c, d, e. 8 or 9, only one of the S pole and the N pole is induced in the projection 101, and an attractive force is generated between each projection 101 and the magnetic pole of the magnet 5. First row or second row of stator cores 15, 15 '
The detent torque by the magnetic pole teeth of the row can be effectively enhanced. Here, assuming that the projection 101 is not provided on the auxiliary stator core 100, a magnetic circuit is formed between the permanent magnet 5 and the auxiliary stator core 100 regardless of the position of the rotor 4, and an attractive force is generated between the two. Will happen. On the other hand, the detent torque between the magnetic pole teeth of the first or second row of the stator cores 15 and 15 'and the permanent magnet 5 is such that the magnetic pole of the magnet 5 faces the magnetic pole teeth of the first or second row. Since the magnetic flux is generated at a predetermined position of the rotor, if the magnetic circuit is formed at any position of the rotor 4 as described above, the detent torque by the magnetic pole teeth of the first or second row at the predetermined position cannot be effectively reinforced. Therefore, it is necessary to provide the projection 101 on the auxiliary stator core 100. And the projection 101
By selecting the position and number, the rotor stop position at which the detent torque can be enhanced can be set freely. From the above, the detent torque at the time of non-energization at the time of stoppage is determined by the torque generated from the relationship between the permanent magnet 5 and the magnetic pole teeth of the first or second row of the stator cores 15 and 15 'and the protrusion 101 of the auxiliary stator core 100 and the permanent magnet. The stop position of the rotor 4 is held by a large holding force because the torque is generated from the relationship with the magnet 5. Next, another embodiment shown in FIG. 10 will be described. In the above-described embodiment, the portion of the torque generated between the magnetic pole of the permanent magnet 5 and the auxiliary stator core 100 is formed on the outer peripheral portion of the permanent magnet 5. The torque generating portion is formed on the side end surface. For this reason, the auxiliary stator core 100 is provided at a position facing the side end surface of the permanent magnet 5 as shown in FIG. In this case, if the side end surface of the permanent magnet 5 is magnetized similarly to the outer periphery, the effect is further enhanced. Further, in both of the above embodiments, the linear operation type in which the rotation of the rotor 4 is converted into the linear movement of the shaft 8 has been described.
The present invention can also be applied to a case where the rotation is stopped only at a certain angle.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing an example of a conventional step motor. FIG. 2 is a schematic connection diagram of an excitation circuit of the motor shown in FIG. 1; FIG. 3 is a schematic connection diagram of an excitation circuit of the motor shown in FIG. 1; FIG. 4 is a time chart showing an energizing mode of an exciting coil of the motor. FIGS. 5A and 5B are schematic views showing an arrangement of magnetic pole teeth of the conventional motor. FIG. 6 is a longitudinal sectional view showing a configuration of an embodiment of a step motor according to the present invention. FIG. 7 is a plan view of an auxiliary stator core in the motor of the present invention shown in FIG. 6; FIG. 8 is a schematic view showing a magnetic pole tooth and a projection arrangement of an auxiliary stator core in the motor of the present invention. FIG. 9 is a schematic diagram showing a projection arrangement of magnetic pole teeth and auxiliary stator cores in the motor of the present invention. FIG. 10 is a longitudinal sectional view showing the configuration of another embodiment of the step motor according to the present invention. DESCRIPTION OF SYMBOLS 1, 2 Housing 1, 2 Housing 4 Rotor 5 Permanent magnet 14 Magnetic coil 15, 15 'Stator core 17, 17' Exciting coil 21, 22, 23, 24 Magnetic pole teeth of stator core 100 Auxiliary stator core, 101 patent

Claims (1)

(1) A rotor (4) having a cylindrical permanent magnet (5) formed by alternately magnetizing N poles and S poles on the outer peripheral surface; ) Is rotatably held therein, and an inner peripheral wall of the housing (1, 2) and the rotor (4).
Between the N pole and the S pole of the permanent magnet (5) on the outer peripheral surface of the rotor (4).
4), a large number of magnetic pole teeth (21, 2)
2,23,24) with stator core (15,15 ')
An exciting coil (17,20) wound around the stator core (15,15 ') and magnetizing the magnetic pole teeth (21,22,23,24) to drive the rotor (4) stepwise.
1 ′), and the magnetic pole teeth (2) of the stator core (15, 15 ′).
1, 2, 23, 24) are divided into two rows, a first row and a second row, around the permanent magnet (5) of the rotor (4) so as to surround the rotor (4) in the circumferential direction. The magnetic pole teeth (21, 22) forming a first row of the stator core (15, 15 ′) and the magnetic pole teeth (23, 24) forming a second row of the stator core (15, 15 ′) are arranged in the rotor (4). ) Are arranged so as to be shifted from each other by a predetermined amount in the circumferential direction. Further, in the housing (1, 2), a plurality of the permanent magnets (5) are opposed only to the axial center portion of the cylindrical permanent magnet (5). In this manner, the projection-like auxiliary projections (10
The auxiliary projection (1) that receives a magnetic flux from the permanent magnet (5) when the excitation coil (17, 1 ′) is not excited.
A step motor wherein a magnetic circuit for generating a detent torque is formed between the step motors.