JPH08322229A - Step motor and its controlling method - Google Patents

Abstract

PURPOSE: To increase the output torque and detent torque of a step motor by making the rotational position of the motor at which the output torque becomes the maximum different from that at which the detent torque becomes the maximum by changing the face widths of magnetic pole teeth at every phase. CONSTITUTION: Six magnetic pole teeth are provided at regular intervals of 60 deg. in each magnetic pole phase and phase differences are fixed in the order of a-, c-, b-, and d-phases by lagging the phases 15 deg. by 15 deg.. The face width of each magnetic pole tooth in a- and c-phases is set at about double of that of each magnetic pole tooth in b- and d-phases. Since both magnetic pole teeth a1 and c1 having the wider face width are excited in S-pole, the output torque of a step motor becomes the maximum and the detent torque of the motor becomes the minimum when the poles are counterposed to the N-pole of a stator. When the motor moves to the next state and teeth c1 and b1 are counterposed to the N-pole, both torques become intermediate and, when teeth b1 and d1 are counterposed to the N-pole, the output torque becomes the minimum and the detent torque becomes the maximum. Therefore, the output torque and detector torque can be increased without increasing the size of the motor when the shape of the magnetic pole teeth of the stator is contrived.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step motor which is small in size and capable of increasing both output torque and detent torque and a control method thereof.

[0002]

2. Description of the Related Art Generally, a stepping motor has a characteristic that when the output torque is increased, the stationary holding torque (detent torque) is reduced, and when the detent torque is increased, the output torque is reduced. This is well known. For this reason, for example, it is intended to use the step motor in applications such as driving and positioning the door of a vehicle air conditioner that must overcome the wind pressure to drive the door and hold the door in a required position. That was causing a big problem.

[0003]

Problem to be Solved by the Invention 1 for solving this problem
One way is to use a large motor so that both output torque and detent torque meet the requirements. However, according to this solution, there is a problem that the motor becomes large and the cost becomes high.

Therefore, an object of the present invention is to provide a stepping motor and a control method therefor capable of obtaining a large output torque and a large detent torque without increasing the size.

[0005]

The features of the present invention for solving the above-mentioned problems are that a rotor in which one magnetic pole and the other magnetic pole are alternately magnetized at equal intervals, and a magnetic pole of the rotor. In a step motor including a stator in which magnetic pole teeth of a plurality of excitation phases are formed corresponding to, and a plurality of excitation coils for exciting the magnetic pole teeth with a predetermined phase difference for each excitation phase, The width of the magnetic pole teeth is made different for each phase, so that the rotational position where the output torque becomes maximum and the rotational position where the detent torque becomes maximum occur differently.

Another feature of the present invention is that a rotor in which one magnetic pole and the other magnetic pole are alternately magnetized at equal intervals, and a plurality of excitation phases corresponding to the magnetic poles of the rotor are provided. A stator having magnetic pole teeth formed thereon, and a plurality of exciting coils for exciting the magnetic pole teeth with a predetermined phase difference for each exciting phase, and making the tooth width of the magnetic pole teeth different for each phase, As a result, in the step motor control method in which the rotational position where the output torque is maximum and the rotational position where the detent torque is maximized are generated differently, the position where the required torque can be output at each of start and stop is selected. Then, the rotor is positioned.

In this case, the rotor may be positioned at the rotational position where the output torque becomes maximum at the time of starting, and the rotor may be positioned at the rotational position where the detent torque becomes maximum at the time of stop.

[0008]

The width of the magnetic pole teeth of the stator is different for each phase, so that the combination of a plurality of magnetic pole teeth whose magnetic poles face each other is different for each stop position of the rotor. As a result, the magnitudes of the output torque and the detent torque periodically change according to the rotational position of the rotor, and the rotational position where the output torque becomes maximum and the rotational position where the detent torque becomes maximum occur differently.

This stepping motor is executed after positioning the rotor at a position where the output torque is maximized at the time of starting, and is positioned so that the detent torque is maximized at the time of stop.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of a four-phase unipolar drive step motor 1 according to the present invention. Step motor 1
In the figure, 2 is a casing, 3 is a stator, 4 is an exciting coil for the stator, and 5 is a rotor. The rotor 5 is fixed to a rotating shaft 8 which is rotatably supported by bearings 6 and 7 of the casing 2, and has 12 N poles and 12 S poles in the circumferential direction thereof as described later. They are magnetized alternately at equal intervals. The stator 3 has four poles corresponding to the magnetic poles of the rotor 5.
Magnetic pole teeth of one excitation phase are formed.

In FIG. 2, the stator 3 has a-phase, b-phase, c-phase,
Magnetic pole teeth a1 to a6, b1 to b6, c1 of each excitation phase of d phase
~ C6 and d1 to d6 are shown expanded. As shown in (a) to (d) of FIG. 2, six magnetic pole teeth of each magnetic pole phase are provided at 60 ° intervals, and the magnetic pole teeth are a phase, c
The mutual phase difference is determined so that the phase is delayed by 15 ° in the order of the phase, the b phase, and the d phase. Further, the tooth width W1 of each magnetic pole tooth of the a phase and the c phase, that is, the length of the magnetic pole tooth along the rotation direction of the rotor is about twice the tooth width W2 of each magnetic pole tooth of the b phase and the d phase. Stipulated in.

Each of the a-phase to d-phase magnetic pole phases is excited by the exciting coil 4, and when the a-phase and the c-phase are excited so as to form one magnetic pole, the b-phase and the d-phase are opposite to each other. Is excited to become the magnetic pole of. This excited state is reversed at a predetermined cycle, whereby an electromagnetic attractive force is generated between the stator and the rotor, and the rotor is given a rotational force. Since the principle of rotation itself is known, a detailed description thereof will be omitted here.

Since each magnetic pole phase of the stator 3 is configured as described above, the magnetic pole teeth of each magnetic pole phase of a phase to d phase are shown in a straight line corresponding to the magnetic pole arrangement of the rotor 5. And Fig. 3
It becomes like.

As can be seen from FIG. 3, the rotor 5 is provided with twelve magnetic poles M1 to M12 such that the N magnetic poles and the S magnetic poles alternate at equal intervals (30 ° intervals in this embodiment). ing. When the exciting coil 4 is excited by a known means, the rotor 5 is rotated stepwise so that each of the magnetic poles M1 to M12 has two 6 × 4 magnetic pole teeth as shown in the drawing. Will be done.

Next, the step motor 1 having the above-mentioned structure
The magnitude of the output torque and detent torque of the stator 3
The change in the relative positional relationship between the rotor and the rotor 5 will be described with reference to FIG.

The state shown in FIG. 4 (a) is necessary when the magnetic pole teeth a1 and c1 having a wide tooth width are both excited to become the S magnetic pole and face any of the N magnetic poles of the stator 5. Parts are shown. In this case, the output torque is maximum, but the detent torque is minimum. Next, the excited state of the stator 3 shifts to the next state, and the magnetic pole teeth c1 and b1 are set to the N level.
In the state of (b) facing the magnetic pole, both the output torque and the detent torque are medium. When the excited state of the stator 3 shifts to the next state and the magnetic pole tooth b1 and the magnetic pole d1 are in the state of (c) facing the N magnetic pole,
The output torque is minimum, but the detent torque is maximum.

Therefore, the characteristics of the output and detent torque of the step motor 1 are such that, as shown in FIG. 5, in each of the 24 steps generated in one rotation, the magnitude of the torque changes periodically, and The step position where the output torque is maximum (steps 1, 5, 9, ...
21) and the step position where the detent torque is maximum (steps 3, 7, ... 23) are different.

Therefore, according to the step motor 1 of the present invention, either the output torque or the holding torque can be made a large torque by selecting the rotating device of the rotor 5. Therefore, unlike the conventional case, the problem that it is impossible to obtain a large detent torque by increasing the output torque does not occur, and both the output torque and the detent torque are increased without increasing the size of the step motor. Then you can use this.

Next, the control method of the step motor 1 described with reference to FIGS. 1 to 5 will be described with reference to FIGS. 6 and 7.

First, a control procedure for starting the step motor 1 will be described with reference to FIG.

When the start of the start is requested, first, the load direction of the step motor 1 (direction opposite to the target position) and its magnitude are calculated (step 31). Next, it is checked whether or not the calculated load is larger than a predetermined value (step 32). When it is determined by this check that the load is larger than the predetermined value, the step motor 1 is driven by 2 pulses (two steps) in the load direction.
That is, specifically describing with reference to FIG. 5, when the start-up state of the step motor 1 is the state of step 7 (state with the largest detent torque), it is determined that the load is large, and the load direction, that is, the pull Two pulses are returned in the in direction, and the state of step 5 is set.

As described above, when the load is large, the rotor 5 is aligned with the position where the output torque is the largest at the time of starting, and then the step motor 1 is started to obtain the given target position. Then, the step motor 1 is driven (step 34). When the magnitude of the load is equal to or smaller than the predetermined value, the process of step 34 is executed without executing the process of step 33. That is, when the load is small, it is not necessary to start the step motor 1 at the position where the output torque is maximum.

According to the above-described control for starting, the step motor 1 can be started in the optimum output torque state according to the magnitude of the load, so that the step motor 1 can be started.
Can be reliably started.

Next, a control procedure for stopping the step motor 1 will be described with reference to FIG.

When the stop of the step motor 1 is requested,
It is checked whether or not the rotational position of the step motor 1 is two pulses before the target value (step 41). If the decision result in the step 41 is NO, the step motor 1 is further driven toward the target value (step 42), and it is again checked in the step 41 whether or not the target value has reached two pulses before.

When it is determined that the rotational position of the step motor 1 is two pulses before the target value in this way, the determination result of step 41 is YES, and the current rotational position of the step motor 1 is the detent torque. Is determined to be the maximum step position (step 4
3). In this embodiment, as shown in FIG. 5, the maximum detent torque is obtained in step 3, step 7, ...
.. This is the case of step 23. If the determination result of step 43 is YES, step 44 is entered to stop the step motor 1 and thereby stop the step motor 1 in the maximum detent torque state.

If the determination result in step 43 is NO, the current rotational position of the step motor 1 is at a position where the detent torque is medium, that is, step 2, step 4, step 6 in FIG. ... It is determined whether or not any of step 24 (step 45).
If the determination result in step 45 is YES, either one pulse or three pulses are further fed to set the rotating device of the step motor 1 to the maximum position of the detent torque close to the target value (step 46) and stop the step motor 1 (step 44).

If the result of the determination in step 25 is NO, the step motor 1 is in the rotational position where the detent torque is at the minimum, and therefore, in step 44, the feed of two pulses is executed again, whereby the step motor 1 is driven. Set the rotation position to the maximum detent torque position and set the step motor 1
Is stopped (step 44). In this case,
The detent torque is just maximum at the target position.

By executing the above-described control for stopping, the step motor 1 can be stopped at the step position that is closest to the target value and has the maximum detent torque. Note that, as described above, the configuration may be such that the detent torque is always stopped at the step position that maximizes the
The step motor 1 may be configured to be stopped in the optimum detent torque state according to the magnitude of the required detent torque. According to such a configuration, the stop position accuracy can be improved.

[0031]

The effects of the present invention are as follows. (1) By devising the shape of the magnetic pole teeth of the stator,
Since the maximum output torque position and the maximum detent torque position are obtained at different rotational positions, both the output torque and the detent torque can be increased without increasing the size of the step motor. (2) For this reason, the rotor of the step motor is moved to the rotation position that gives the maximum output torque at the start,
By moving the rotation of the step motor to a rotational position that gives the maximum detent torque when stopped, the step motor can be smoothly started and the step motor can be stopped with a large holding force.

[Brief description of drawings]

FIG. 1 is a sectional view showing a position embodiment of a step motor according to the present invention.

FIG. 2 is a development view showing a configuration of magnetic pole teeth of each magnetic pole phase of the stator of the step motor shown in FIG.

FIG. 3 is a diagram showing the magnetic pole teeth of each magnetic pole phase shown in FIG. 2 on a straight line corresponding to the magnetic pole arrangement of the rotor.

FIG. 4 is an explanatory diagram for explaining a relative positional relationship between a stator and a rotor, an output torque, and a relationship between detent torque.

5 is a characteristic diagram showing respective characteristics of output torque and detent torque of the step motor shown in FIG.

6 is a flowchart for explaining a control procedure for starting the step motor shown in FIG.

7 is a flowchart for explaining a control procedure for stopping the step motor shown in FIG.

[Explanation of symbols]

1 step motor 3 stator 4 exciting coil 5 rotor a1 to a6, b1 to b6, c1 to c6, d1 to d6 magnetic pole teeth

Claims (3)

[Claims] 1. A rotor in which one magnetic pole and the other magnetic pole are alternately magnetized at equal intervals, and a stator formed with a plurality of magnetic pole teeth of an excitation phase corresponding to the magnetic poles of the rotor. And a plurality of exciting coils for exciting the magnetic pole teeth with a predetermined phase difference for each exciting phase, in a step motor, the tooth width of the magnetic pole teeth is made different for each phase, and thereby the output torque The stepping motor is characterized in that the rotational position where the torque is maximum and the rotational position where the detent torque is maximized are generated differently. 2. A rotor in which one magnetic pole and the other magnetic pole are alternately magnetized at equal intervals, and a stator having a plurality of magnetic pole teeth of an excitation phase corresponding to the magnetic poles of the rotor. And a plurality of exciting coils for exciting the magnetic pole teeth with a predetermined phase difference for each excitation phase, and the width of the magnetic pole teeth is made different for each phase, thereby maximizing the output torque. In the step motor control method in which the rotational position and the rotational position at which the detent torque becomes maximum are generated differently, the rotor is positioned by selecting the position where the required torque can be generated at each of start and stop. A method of controlling a step motor, characterized in that 3. When the step motor is started, the rotor is positioned at a rotation position where the output torque is maximum, and when the step motor is stopped, the rotor is positioned at a rotation position where the detent torque is maximized. The step motor control method according to claim 2.