JPS61184419A - Magnetic rotary sensor - Google Patents

Abstract

PURPOSE:To reduce the change quantity of the gap between a rotor and a magnetic resistor element due to thermal expansion, by constituting a rotor from an austenite ductile cast iron material. CONSTITUTION:A drum 3 comprising an austenite ductile cast iron material (Ni-Resist material) is connected to a shaft 2 driven by a motor 1 as a rotor. A glass substrate 6 is fixed to the support table 5 fixed to the housing of the motor 1 and a magnetic resistor element 7 having patterns formed thereto is formed to the surface of the substrate 6 and opposed to the magnetic recording medium 4 arranged on the peripheral surface of the drum 3 so as to provide a gap 8 therebetween. By employing the Ni-Resist material as the material of the rotor, the change quantity of the gap 8 by thermal expansion can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the configuration of a magnetic rotation sensor,
In particular, the present invention relates to a magnetic rotation sensor that can perform high-precision measurements and is suitable for applications such as NG machine tools and robot motors.

[Prior Art] Conventionally, for example, in order to position a servo motor at a rotational speed of one revolution, magnetic signals obtained from magnetic patterns magnetized at equal intervals on a magnetic recording medium arranged around the entire circumference of a rotating body are used in close proximity. A magnetic rotation sensor is used that can detect the rotation angle of a rotating body by reading it as an electrical signal using a magnetoresistive element arranged in the same direction. However, in recent years, demands from industry have led to a desire for higher degree precision measurements. In general, in this type of magnetic rotation sensor, the higher the number of output signals per rotation of the rotating body, the more accurate measurement can be performed. All you have to do is make it smaller. However, when the pitch of the magnetic pattern is reduced in this way,
Since the magnetic signal obtained therefrom also becomes smaller, it becomes necessary to further reduce the distance from the magnetoresistive element that detects the magnetic signal.

On the other hand, aluminum is usually used for drums, disks, etc. as rotating bodies because it is non-magnetic and easy to machine.

[Problems to be Solved by the Invention] However, the coefficient of thermal expansion of aluminum material is 23X 10/
℃, so depending on the temperature change during use, the distance between the magnetoresistive element and the magnetoresistive element may change due to eccentricity with the iron-based material shaft to which the rotating body is attached, or an increase in the radial direction of the rotating body itself. becomes large and a predetermined interval width cannot be maintained, resulting in the drawback that highly accurate and stable measurement cannot be performed. In order to eliminate such drawbacks, it has been proposed that the rotating body is made of a ceramic material (Japanese Patent Application Laid-Open No. 192915/1982), but since ceramic is not necessarily easy to machine, it is difficult to machine it. There is a desire for a magnetic rotation sensor using a rotating body that has good performance and can maintain a predetermined interval width with high precision.

The present invention has been made in view of the above circumstances, and its purpose is to provide a magnetic rotation sensor that can maintain the interval between a rotating body and a magnetic resistance element at a predetermined width with high precision. There is a particular thing.

[Means for Solving the Problems] In order to achieve the above object, the present invention is characterized in that the rotating body itself is made of an iron-based material similar to the shaft material. In the present invention, the most suitable iron-based material is an austenitic ductile cast iron material (commonly known as Niresist material), which has a coefficient of thermal expansion of 8 to 13 x 10/°C, is non-magnetic, and has excellent workability.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional configuration diagram of essential parts showing an example of a magnetic rotation sensor according to the present invention. In the figure, a drum 3 made of Niresist material and having a diameter of 50 mm and a length of 15 mm is coupled as a rotating body to a shaft 2 driven by a motor 1. A magnetic recording medium 4 having a magnetic pattern magnetized at a constant pitch over the entire circumference of the drum 3 is disposed on the outer peripheral surface of the drum 3 by a coating method. Further, a glass substrate 6 is fixed on the support stand 5 fixed to the housing of the motor 1, and a magnetoresistive element 7 patterned from a permalloy thin film obtained by vapor deposition is formed on the surface of this substrate 6. , and are opposed to the magnetic recording medium 4 disposed on the circumferential surface of the drum 3 with an interval 8 of about 100 μm therebetween. This magnetic rotation sensor is 40 to 100
When used in a temperature range of .degree. C., the maximum change in distance 8 due to thermal expansion was 45 .mu.m. For comparison, a drum of the same size and shape was made from aluminum and an experiment was conducted under the same conditions, and the amount of change was about 80 μm. In addition, in terms of workability, precision processing could be easily performed without any difference from conventional aluminum materials.

[Effects of the Invention] As explained above, by using Niresist material for the rotating body, it is possible to reduce the amount of change in the interval 8 due to thermal expansion to approximately half that of the conventional one, and at the same time, the workability is also lower than that of the conventional aluminum material. By being able to process with the same efficiency and precision as the conventional ceramic materials, the change in spacing 8 (m) can be improved due to the small coefficient of thermal expansion of known ceramic materials, but there was a problem in terms of processability, but this aspect has also been improved. It is judged as a thing. It goes without saying that the present invention is not limited to the drum 3, but can also be applied to a disk to obtain exactly the same effect.

As described above, by using the Niresist material for the rotating body, there is an extremely excellent effect that a magnetic sensor excellent in terms of reliability and quality can be obtained at low cost.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional configuration diagram of essential parts showing an example of a magnetic rotation sensor according to the present invention. 1: Motor, 2: Shaft, 3 Drum, 4: Magnetic recording medium, 5: Support stand, 6: Glass substrate, 7: Magnetoresistive element.

Claims (1)

[Claims] A rotating body having a magnetic recording medium formed of a plurality of magnetic patterns magnetized at a constant pitch around the entire circumference, and a magnetoresistive element disposed near the rotating body so as to face the magnetic recording medium. . A magnetic rotation sensor that detects periodic electrical resistance changes due to the magnetic pattern, wherein the rotating body is made of an austenitic ductile cast iron material.