JPH0640734B2 - Step Motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a PM having a large detent torque, which is designed to hold a rotor stop position accurately and uniformly and strongly.
The present invention relates to a (permanent magnet) type step motor, and is suitable for use as a drive device to be controlled by various vehicle control devices, for example.

[Conventional technology]

The PM type step motor known in the related art is designed to convert the rotary motion of the rotor into a linear motion of the shaft by means of a screw or the like.
It has a structure as shown in the figure.

In FIG. 1, 1 is a cup-shaped first housing, 2 is a disk-shaped second housing, and both are integrally fixed to each other by screws 3 to form an outer shell of a 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 a female screw 6 is formed on an inner peripheral portion thereof. Further, stopper surfaces 7a and 7b that limit the axial movement of the shaft 8 are provided at both ends of the rotor 4. A male screw 9 provided on a shaft 8 is engaged with the female screw 6.

In addition, two stopper pins 10, which are spaced apart from each other on the shaft 8,
11 are provided and stopper surfaces 7 at both ends of the rotor 4 are provided.
Since a and 7b are engaged with the stopper pins 10 and 11, the axially movable length of the shaft 8 is fixed to the rotor 4 from the position where the stopper surface 7a of the rotor 4 and the stopper pin 10 are engaged. It is up to the position where the provided stopper surface 7b and the stopper pin 11 of the shaft 8 are locked.

Bearings 12 and 12 'are provided at both ends of the rotor 4, and the rotor 4 is connected to the first housing 1 through the bearings 12 and 12'.
And rotatably held in the second housing 2. The shaft 8 is rotatably held by sintered oil-impregnated bearings 13 and 13 'fixed to the housings 1 and 2. On the outer peripheral side of the rotor 4, stator cores 15 and 15 ′ that serve as stator poles are formed by leaving a gap 14 and are fixed to the first housing 1. This stator core 15,1
Inside the 5 ′, stator exciting coils 17 and 17 ′ insulated by a bobbin 16 are wound.

The two stator cores 15 and 15 'are the exciting coil 1
A pair of cores are formed around the outer circumference of the permanent magnet 5 of the rotor 4 in a first row and a second row by being paired with each other on the 7 side and the exciting coil 17 'side. Further, magnetic pole teeth 21, 22 or 23, 24 shown in FIG. 5 which will be described later are alternately bent and formed on the inner peripheral portions of the stator cores 15, 15 '.

The exciting coils 17 and 17 'are provided with intermediate taps as shown in FIG. 2 and are connected in four phases.
Transistors TR1 to TR4 of the drive circuit as shown in the figure
Connected to the collector of the transistors TR1 to TR
Exciting coils 17, 17 'in the order defined by 4
The rotor 4 is rotated stepwise by turning ON / OFF the energizing current of the shaft 4, and the shaft 8 performs forward or backward linear motion through the meshing between the female screw 6 of the rotor 4 and the male screw 9 of the shaft 8. .

In the excitation method, in the case of two-phase excitation, the excitation is performed at the timing shown in FIG. 4, and the rotation speed of the rotor 4 is determined by the timing time interval t. Also, the exciting coil 1
Excitation of 7 and 17 'is generally performed at all times when the rotor 4 is rotating and when it is stopped. In this case, the holding torque (holding torque) of the rotor 4 when the rotor 4 is stopped.
Is strong, but instead, transistors TR1 to TR4
Requires a transistor that can withstand continuous energization and can be destroyed by self-heating, so that a large transistor must be used. In addition, the excitation coil 1 is used even when stopped.
Since 7, 17 'continue to be energized, it means that extra power is consumed.

Therefore, only when the rotor 4 rotates, the exciting coils 17, 1
The inventor of the present invention intends to reduce the heat generation and the power consumption of the transistors TR1 to TR4 by adopting a method in which the excitation of 7'is performed and the excitation of the excitation coils 17 and 17 'is also stopped when the rotor 4 is stopped. I tried.

[Problems to be Solved by the Invention]

However, for example, when such a step motor is used as a valve drive device that controls the amount of intake air to the engine of an automobile, the rotor 4 rotates due to engine vibration when the step motor is stopped. Occurred. The present inventor has studied the cause of this problem. When the excitation of the exciting coils 17 and 17 'is stopped, the N and S poles of the stator cores 15 and 15' disappear, and the rotor becomes a mere ferromagnetic body. Although only the attraction force (detent torque) of the magnetic body by the permanent magnet 5 of No. 4 is used, in the conventional motor, as shown in FIG.
The distance between the 5 ′ magnetic pole teeth 21 and 22 and the magnetic pole teeth 23 and 24 (the distance between the magnetic pole tooth center lines) is equal to 2W,
The widths of the N pole and the S pole magnetized in the permanent magnet 5 are equal to 2 W, respectively, and as a result, the rotor holding force (detent torque) due to the attraction force of the permanent magnet 5 becomes a relatively small value. I found out that

This will be described in more detail. FIG. 5 shows the permanent magnet 5 and the magnetic pole teeth 21, 22, 2 of the theta cores 15, 15 '.
3A and 3B schematically show the circumferential arrangement of the stator cores 15 and 15 '(first row) and the pole teeth 23 and 24 side rows (second row). In any of the rows, these teeth are arranged at equal intervals of 2 W, and the widths of the N pole and the S pole of the permanent magnet 5 are also equal to 2 W, so on the first row side of the stator cores 15 and 15 '. Both N and S poles are respectively induced in the magnetic pole teeth 21 and 22, and the magnetic fluxes cancel each other out in these teeth 21 and 22. Therefore, the magnetic pole teeth 21 and 22 of the first row do not substantially contribute to the generation of detent torque. And the second row of pole teeth 2
Only the N and S poles induced in 3 and 24 contribute to the generation of detent torque.

Thus, in the conventional structure, the magnetic pole teeth 21, 2 on the first row side are arranged.
Since 2 does not function effectively in generating detent torque,
The rotor holding force becomes a relatively small value, and as a result, the rotor 4 rotates due to external vibration or the like.

The present invention has been made in view of the above problems, and by intentionally shifting the widths of the N pole and the S pole magnetized by the permanent magnet, the holding force (detent) between the rotor and the stator core when the exciting coil is deenergized. It is an object of the present invention to provide a step motor capable of improving torque).

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention has a rotor having a cylindrical permanent magnet formed by alternately magnetizing N poles and S poles on the outer peripheral surface, and rotatably holding the rotor inside itself. And a plurality of magnetic poles provided between the inner peripheral wall of the housing and the outer periphery of the rotor, and arranged to face the N pole or the S pole of the permanent magnet on the outer peripheral surface of the rotor with a constant gap therebetween. A stator core having teeth; and an exciting coil wound inside the stator core and magnetizing the magnetic pole teeth to drive the rotor in a stepwise manner. The rotor is divided into two rows, a first row and a second row, around the outer periphery and arranged in the circumferential direction so as to surround the rotor, and the magnetic pole teeth forming each row of the stator core have a circumference of the rotor. In the direction Adjacent magnetic pole teeth are arranged at equal intervals to each other, and the total width of the N pole and the S pole of the permanent magnet is set to twice (4 W) the distance (2 W) between the center lines of the adjacent magnetic pole teeth. The width of the N pole of the permanent magnet is set in the range of 2W <N pole width <4W or 0 <N pole width <2W.

〔Example〕

 An embodiment of the present invention will be described below.

What is shown in FIG. 1 is, for example, a 24 step / rotation motor shown for specifically explaining the embodiment of the present invention, and the stator cores 15 and 15 'are, as described above, the excitation coil 17 side and the excitation coil. The coils 17 'are combined in pairs to form two rows of cores on the outer circumference of the permanent magnet 5 of the rotor 4, and the two rows of stator cores 15,
A large number of magnetic pole teeth 21, 22, 23, 15 arranged in the circumferential direction of the rotor 4 are arranged on the inner peripheral portion of 15 ′ so as to be opposed to the N pole or the S pole of the permanent magnet 5 with a constant gap 14. 24 is integrally formed by bending.

The arrangement of the magnetic pole teeth 21 to 24 is as shown in FIG.
The magnetic pole teeth 21, 22 of the first row (the left row in FIG. 1) and the magnetic pole teeth 23, 2 of the second row (the right row in FIG. 1) side
In each case, the magnetic pole teeth adjacent to each other in the circumferential direction of the rotor 4 are arranged at equal intervals (2 W). Here, the space 2W is the space between the center lines of the adjacent magnetic pole teeth.

On the other hand, the total width of the N and S poles magnetized by the permanent magnet 5 of the rotor 4 is, as shown in FIG. 6, the distance between the center lines of the adjacent magnetic pole teeth (21, 22 or 23, 24). 2W
Is set to twice (4W).

The widths of the N pole and the S pole of the permanent magnet 5 are not equal and are intentionally shifted within the range of 4 W. In the example of FIG. 6, the width of the N pole is S. It is larger than the pole.

That is, in the example of FIG. 6, the width of the N pole of the permanent magnet 5 is 2
It is set in the range of W <N pole width <4W.

The present invention is characterized in that the widths of the north pole and the south pole of the permanent magnet 5 are intentionally shifted, and the width of the south pole may be larger than the width of the north pole.

In this case, the width of the N pole of the permanent magnet 5 is 0 <the width of the N pole <2.
It is set to the range of W.

The method of changing the widths of the N pole and the S pole of the permanent magnet 5 can be carried out by setting the width of the magnetic pole of the magnetized core to the width desired to be magnetized in the permanent magnet 5 in advance. If there is a magnetizing step in the manufacturing step, the width of the magnetic pole of the magnetized core in the magnetizing step is set in advance in the same manner as described above.
This can be done by setting the width to be magnetized to 1, and magnetizing the permanent magnet 5 with this magnetizing core. Also, by changing the gap between the magnetizing core and the permanent magnet 5, or by changing the magnetomotive force generated by the magnetizing coil by changing the number of turns of the coil, changing the coil resistance, or changing the voltage applied to the coil. The widths of the N pole and the S pole can be changed by controlling them.

With this configuration, the magnetizing width (magnetizing angle) of the permanent magnet 5 is different between the N pole and the S pole, but the distance between the center lines of the N pole and the S pole of the magnet 5 is 2 W, so When operated, it operates the same as a conventional motor.

On the other hand, when the electric power is not supplied when stopped, the stator core 1
The magnetic pole teeth 5 and 15 'are simply iron claws, and the magnetomotive force of the permanent magnet 5 establishes a magnetic circuit including the stator core (15, 15') to generate detent torque in the rotor 4. In that case, Since the magnetic pole teeth are arranged in two rows with respect to the NS pole, the stator core 1
The number of magnetic pole teeth of 5, 15 'is doubled, so that two magnetic pole teeth of the stator cores 15, 15' are attracted to one pole of the permanent magnet 5.

At this time, due to the magnetomotive force of the permanent magnet 5, the stator core 1
Magnetic poles 21, 22, 23, 24 of 5, 15 'are induced by magnetic poles as shown in FIG. 6 (exciting coils 17, 17').
Is deenergized at this time) One pole (N pole in this case) of the magnet 5 and magnetic pole teeth 2 on the first row side that substantially linearly overlap
The magnetic pole teeth 24 on the second and second rows are both magnetized to the S pole, and the two teeth 22 and 24 and the N pole of the magnet 5 strongly attract each other to generate a strong attracting state. This allows
As compared with the conventional structure shown in FIG. 5, that is, in which only one magnetic pole tooth 24 has a stable attraction relationship with the N pole of the magnet 5, the structure of the present invention significantly increases the detent torque. is there.

Therefore, the final excitation phase before the non-energization is set to the permanent magnet 5
If the exciting phase is set at a position as shown in FIG. 6 where the poles of # 1 and the teeth of the stator core are strongly balanced with each other, or at a position adjacent to that position, the rotor 4 can be reliably stopped at the position where the detent torque is large. it can.

In the above-described embodiment, the linear motion type in which the rotation of the rotor 4 is converted into the linear motion of the shaft 8 has been described, but the present invention is also applicable to the case where the rotary type motor is rotated by a certain angle and stopped. The invention can be applied.

Further, it goes without saying that the number of steps can be arbitrarily set.

[Advantages of the Invention] As described above, in the present invention, strengthening of the holding force (detent torque) of the rotor when the exciting coil is deenergized can be achieved by changing the width of the magnetic poles of the permanent magnets. There is an excellent effect that the stationary state of the exciting coil when not energized can be maintained more strongly with a simple structure.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an example of a conventional motor and a step motor used for explaining the motor of the present invention, FIGS. 2 and 3 are schematic wiring diagrams of an excitation circuit of the motor of FIG. 1, and FIG. FIG. 1 is a time chart showing a biasing mode of an exciting coil of a motor, FIG. 5 is a schematic view showing an arrangement of magnetic pole teeth of a conventional motor, and FIG. 6 is an arrangement of magnetic pole teeth in an embodiment of a motor of the present invention. It is a schematic diagram. 1, 2 ... Housing, 4 ... Rotor, 5 ... Permanent magnet, 8 ... Shaft, 14 ... Air gap, 15, 15 '... Stator core, 17, 17' ... Excitation coil, 21, 22, 2
3, 24 ... Magnetic pole teeth of the stator core.

Claims (1)

[Claims] 1. A rotor (4) having a cylindrical permanent magnet (5) formed by alternately magnetizing N-poles and S-poles on the outer peripheral surface, and rotating the rotor (4) inside itself. A housing (1, 2) held freely, and a permanent magnet (5) provided on the outer peripheral surface of the rotor (4) provided between the inner peripheral wall of the housing (1, 2) and the outer periphery of the rotor (4). ), A large number of magnetic pole teeth (21, 22, 23, 2) which are arranged to face the N pole or the S pole via a constant air gap (14).
4) having a stator core (15, 15 ') and wound inside the stator core (15, 15') to magnetize the magnetic pole teeth (21, 22, 23, 24) to step the rotor (4). Excitation coil (17,1)
7 '), and the magnetic pole teeth (2) of the stator core (15, 15').
1, 22, 23, 24) are permanent magnets of the rotor (4)
It is divided into two rows, a first row and a second row, around the outer periphery of (5) and arranged circumferentially so as to surround the rotor (4), and each row of the stator core (15, 15 ') The magnetic pole teeth (21, 22, 23, 24) constituting the
In the circumferential direction of (4), adjacent magnetic pole teeth are arranged at equal intervals, and the total width of the N pole and the S pole of the permanent magnet (5) is between the center lines of the adjacent magnetic pole teeth. The width of the N pole of the permanent magnet (5) is set to be in the range of 2W <N pole width <4W or 0 <N pole width <2W while being set to twice (4W) the interval (2W). A step motor characterized by being set.