JPS62238413A - Magnetic drum for built-in type magnetic encoder - Google Patents

Abstract

PURPOSE:To stabilize output while reducing the outer periphery fluctuation of a magnetic drum, by a simple constitution wherein the base of the magnetic drum is integrally coupled with a motor shaft. CONSTITUTION:The magnetization of the magnetic strap on the surface of a magnetic drum is detected by a magnetic resistor element to operate the sensor of a motor. The shaft 11 of the motor is inserted in the drum base of the magnetic drum under pressure to integrally couple the base 13 with the shaft 11 and the outer periphery fluctuation of the magnetic drum is reduced by a simple constitution and detection output is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic drum of a magnetic encoder used as a sensor for a motor.

2. Description of the Related Art In recent years, magnetic encoders have become popular as various sensors including motor sensors due to their simple structure and good performance.

An example of the above-mentioned conventional magnetic encoder will be described below with reference to the drawings.

3 and 4 show the structure of a conventional built-in magnetic encoder. In FIG. 3, 1 is a magnetoresistive element. 2 is a magnetic drum subjected to strug magnetization, which is made of a magnetic material 3 with a small thermal expansion coefficient and small specific gravity, and is inserted into a magnetic drum base 4 or
They are integrated by heat-fitting and are configured as a magnetic drum.

The magnetoresistive element 1 is attached to a magnetoresistive element mounting base 5 while facing the magnetic drum 2 with a certain gap therebetween, and obtains an output by rotation of the magnetic drum 2. This output goes to the amplifier circuit 6 through a terminal directly connected to the magnetoresistive element 1, and is made usable as a sensor signal. These basic magnetic encoder configurations are housed in an encoder cover 7 and attached to a motor 10.
The encoder is attached to the base 8 with screws 9, etc.

At this time, the rotation of the motor 10 is caused by the output shaft 11 of the motor,
The signal is transmitted via the coupling 12.

FIG. 4 shows a magnetic drum 2 of a conventional magnetic encoder, which is composed of a magnetic material 3 and a magnetic drum base 4. As shown in FIG.

The magnetic drum 2 in this state is press-fitted into the coupling 12 or fixed by adhesive.

The operation of the built-in magnetic encoder configured as described above will be described below.

The output of the magnetic encoder is obtained by converting the leakage magnetic field of the magnetic drum 2 into voltage using the magnetoresistive element 1, and the change in this output is not significantly affected by the size of the outer circumferential vibration of the magnetic drum 2. , is a well-known fact.

Problems to be Solved by the Invention Particularly, conventional built-in magnetic encoders have the disadvantage that the use of the coupling 12 causes variations in accuracy during adhesion and press-fitting, which further worsens output changes. , it is said that the method of use is extremely difficult, and the challenge to improve output accuracy is to reduce the outer circumference runout of the magnetic drum with a built-in type.

In view of the above problems, the present invention uses a built-in type to reduce the outer circumferential runout of the magnetic drum and stabilize the output.
The purpose is to simplify the method of use as a magnetic encoder and offer it to the market as a cheaper sensor.

Means for Solving the Problems In order to solve the above-mentioned problems, the built-in magnetic encoder of the present invention is of the type that also uses a coupling that directly attaches the inner diameter of the magnetic drum to the motor shaft.

Effect of the Invention With the above-described configuration, the present invention can reduce the outer circumferential runout of the magnetic drum and reduce the output change of the magnetoresistive element.

In conventional built-in magnetic encoders, the cumulative measurement of the four elements of coupling, magnetic drum deviation, bearing runout, press fitting, and adhesive variation deviation results in magnetic drum outer circumference runout, but with the encoder of the present invention, the magnetic drum outer circumference Since there are only two factors, runout and bearing wear, the accumulation is small and the outer circumference runout of the magnetic drum can also be reduced. Furthermore, since the inner diameter of the magnetic drum base is attached as the medium compared to the conventional built-in encoder type magnetic encoder, the thermal and humid expansion of the magnetic drum can be easily calculated, and the accuracy of structural design can also be improved.

EXAMPLE Hereinafter, a built-in magnetic encoder according to an example of the present invention will be described with reference to the drawings.

In addition, the same reference numerals are given to the same components as those in the conventional structure in the description.

In Fig. 1, 1 is a magnetic resistance element, 13 is a magnetic drum base, and 3 is a magnetic material composed of a resin magnet with multipole strap magnetization on the outer circumferential surface. It constitutes a magnetic drum 14.

Reference numeral 5 designates a base to which the magnetic resistance element 1 is attached, and is configured to be adjustable so that the magnetic resistance element 1 can detect leakage magnetic flux generated by the outer peripheral surface of the magnetic drum at an appropriate position.

Reference numeral 6 denotes an output amplifier circuit, which is directly connected to the terminal of the magnetoresistive element 1 and takes out an output for use as a sensor.

These configurations are incorporated into the encoder cover 7,
It is connected and mounted to the motor 10 with screws 15.

Next, the magnetic drum section shown in FIG. 2 will be explained. The magnetic drum base 13 has a cylindrical shape, and has a magnet mounting portion 13a in the middle thereof.

In this configuration, a bearing 16 is disposed on the outer periphery of the cylindrical tip of the magnetic drum base 13, and the motor shaft 11 is fixed to the inner diameter of the magnetic drum base 13 by press-fitting or adhesive. The rotation is transmitted to the magnetic drum 14. Normally, magnetic drums have their outer diameter cut based on their inner diameter in order to ensure accuracy. If the magnetic drum is processed with high precision at this single item stage, the outer circumferential runout of the magnetic drum will be the same as the accuracy of the magnetic drum itself even after it is mounted on the motor, and high accuracy can be ensured.

As described above, by attaching the inner diameter of the magnetic drum base 13 directly to the motor shaft 11 and making the coupling part common to the magnetic drum base 13, the manufacturing cost of the magnetic drum is the same as that of the conventional magnetic drum, and the magnetic The fifth
The output waveform can be stabilized as shown in FIG. 6.

FIG. 5 shows the ripple output performance of the conventional built-in magnetic encoder, and FIG. 6 shows the improved ripple performance in the embodiment of the present invention.

As shown in Figure 6, the ripple in the output waveform per revolution of the shaft is thicker (improved).Furthermore, the degree to which the ripple output is affected by the outer periphery of the magnetic drum is clearly shown. There is.

In addition, from a structural standpoint, it is possible to eliminate the man-hours required to connect conventional couplings and magnetic drums, making it cheaper.
A high-performance built-in magnetic encoder is obtained.

Effects of the Invention As is clear from the above description, according to the present invention, a magnetic encoder with a stable output and a small outer circumferential runout of the magnetic drum can be obtained at low cost with an extremely simple configuration.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a built-in magnetic encoder according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of the same magnetic drum, Fig. 3 is a cross-sectional view of a conventional magnetic encoder, and Fig. 4 is the same. FIG. 5 is a sectional view of the magnetic drum, FIG. 5 is an output waveform diagram of a conventional built-in magnetic encoder, and FIG. 6 is an output waveform diagram of the built-in magnetic encoder of the present invention. 1...Magnetic resistance element, 11...Motor shaft, 13...Magnetic drum base, 14...
...Magnetic drum. Name of agent: Patent attorney Toshio Nakao and one other person Figure 3 Figure 4

Claims (1)

[Claims] In a built-in magnetic encoder equipped with a magnetic resistance element and a cylindrical magnetic drum with strap magnetization on the surface of the magnetic material, the coupling that connects the encoder and motor shaft is integrated with the magnetic drum base. Magnetic drum with built-in magnetic encoder.