JPH0311739Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to a stepping motor, and particularly to means for obtaining rotation information of its rotor.

Prior Art In a stepping motor, the rotational position of a permanent magnet rotor can be detected by a sensor such as a magnetoresistive element. Conventionally, this magnetoresistive element is
It is mounted with a holder or the like at a predetermined distance from the outer peripheral surface of the rotor. However,
According to such a mounting method, a holder is required for mounting the sensor, and the positional relationship between the holder and the stator or rotor largely depends on assembly conditions, etc., and if variations in assembly become large, the characteristics may be affected. This means that there is an element of instability on the surface.

Purpose of the invention and means for solving the problem Therefore, the purpose of the invention is to ensure the accuracy of the mounting position of the sensor, that is, the magnetic detector, in this type of stepping motor, and to make effective use of the space inside the motor. , it is possible to omit mounting tools such as holders.

Therefore, in the present invention, the magnetic sensing body is fixed inside the motor, especially between the plurality of poles of the stator, and the two sensor parts are provided at a distance equal to the distance between the magnetic flux density and density of the rotor. Only rotor rotation information is obtained without being adversely affected by the magnetic field produced by the excitation coil.

Configuration of the invention Hereinafter, the configuration of the invention will be specifically explained based on the drawings.

First, FIG. 1 shows a schematic structure of a stepping motor 1 of the present invention. The stepping motor 1 is, for example, a hybrid type, and includes four stators 3 integral with a frame 2, and a rotor 4 excited by a permanent magnet. The stator 3 generates magnetic flux by the excitation coil 5 wound around its outer periphery.

Next, FIG. 2 shows corresponding parts of the stator 3 and rotor 4 in detail. Stator 3
is formed in a T-shape in cross section, and in order to divide the step angle into small parts in the part facing the rotor 4, a plurality of poles 3a, for example four, are arranged at the same pitch and are aligned with the center line of the excitation coil 5. It is formed symmetrically around the axis. On the other hand, since the rotor 4 similarly forms poles 4a of the same pitch on its outer circumference, the magnetic flux is alternately dense and dense while drawing a sinusoidal curve on the outer circumference. of course,
These poles 3a are relative to the poles 4a of the rotor 4,
It's relatively off.

The magnetic sensing body 6 is fixed between the two central poles 3a of one stator 3, that is, in the groove portion thereof.

Next, FIG. 3 shows the structure of the magnetic sensing body 6. As shown in FIG. This magnetic sensing body 6 includes two sensor parts 7a and 7b, which are spaced apart from each other by a distance equal to 1/2 of the distance D between the poles 3a, that is, the distance between the magnetic fluxes. and is connected to electrodes 8, 9, and 10 at each end.

Next, FIG. 4 shows the connection between the magnetic sensing body 6 and the differential amplifier 11. The above sensor section 7a,
7b forms a bridge circuit together with resistors 14a and 14b between the power supply terminal 12 and the ground 13, and the electrodes 8 and 9 at the output end thereof are connected to the differential input terminal of the differential amplifier 11. ing. This output end is connected to the output terminal 15.

Function of the invention Next, the function of the stepping motor 1 will be explained.

When the excitation coil 5 is sequentially excited, the rotor 4 is sequentially rotated by stepping operation in proportion to the frequency of the excitation pulse due to the magnetic flux. At this time, the magnetic sensing body 6 is under the influence of both the magnetic flux of the stator 3 due to the excitation coil 5 and the magnetic flux due to the rotor 4 on the permanent magnet side. For position detection, it is necessary to obtain only the magnetic flux component of the rotor 4, so it is necessary to remove the magnetic flux component caused by the excitation coil 5.

Both sensor parts 7a and 7b of this magnetic sensing body 6 are
Since it is symmetrical with respect to the center line of the excitation coil 5, it is under the same conditions for the magnetic field due to the current of the excitation coil 5, and there is a phase difference of π (180 degrees) with respect to the density and density of the magnetic flux of the rotor 4. It is located with. Therefore, the sensor parts 7a and 7b form a bridge circuit, and the difference between the two signals is taken by the differential amplifier 11, so that the magnetic flux component of the exciting coil 5 is canceled, and only the magnetic field component of the rotor 4 is Detected.

Here, the resistance change rate of the magnetic sensing body 6 with respect to the magnetic field, the magnetic field by the rotor 4 in the sensor sections 7a and 7b, and the intensity of the magnetic field (bias) generated by the excitation coil 5 are set as shown in FIG. Ru. That is, the magnetic field strength at the sensor sections 7a and 7b, that is, the combined magnetic field strength by the stator 3 and rotor 4, is set within the range of linear resistance change of the magnetic resistor 6. When the above conditions are satisfied, the influence of the magnetic field generated by the excitation coil 5 can be removed.

Note that the distance between the poles 3a of the stator 3 is d
Then, the condition d>D/2 must be satisfied. This condition is not disadvantageous in terms of motor characteristics.

Modified example of the invention In the above embodiment, only one phase of the position signal of the rotor 4 is detected. By fixing it to the magnetic sensing body 6 at the portion 3, two-phase signals can be detected, and the rotational direction of the rotor 4 can be identified.

Further, in FIG. 3, the sensor sections 7a and 7b are shown as simple straight lines for convenience, but their patterns may be formed in other shapes, such as a zigzag shape. Further, the magnetic sensing body 6 can be configured with a Hall element or the like in addition to a magnetoresistive element.

Effect of invention The present invention provides the following effects.

Since the magnetic resistance body is directly incorporated inside the stepping motor, the space inside the motor can be used effectively, and the relative positional relationship between the magnetic sensing body and the stator and rotor can be ensured with high accuracy.
Furthermore, by arranging the two sensor parts of the magnetic detection body at a distance equal to the distance between the sparse and dense magnetic fluxes of the rotor, it is possible to eliminate the adverse effects of the magnetic field on the stator pole side, making it possible to obtain only rotor rotation information. can.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of a stepping motor.
Figure 2 is an enlarged cross-sectional view of the poles of the stator and rotor, Figure 3 is a plan view of the magnetic detector, Figure 4 is a connection circuit diagram of the sensor section and differential amplifier, and Figure 5 is magnetic field strength vs. resistance change. This is a graph of the rate. 1... Stepping motor, 2... Frame,
3...Stator, 3a, 4a...Pole, 4...Rotor, 5...Exciting coil, 6...Magnetic detector, 7
a, 7b...Sensor section.

Claims (1)

[Scope of utility model registration request] In a stepping motor having a stator having a plurality of poles and a rotor in which magnetic flux is alternately dense and dense, a magnetic sensing body having two sensor parts separated by a distance equal to the distance between the sparse and dense magnetic fluxes is attached to the rotor. A stepping motor characterized in that the stepping motor is fixed between the pole teeth of the stator so as to face each other.