JPH0515041Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic linear scale that magnetically detects a position on a straight line in various fields such as printers, robots, and numerically controlled machines.

[Prior art] Conventional magnetic linear scales are a combination of a linear tooth-shaped scale made of iron and a magnetic sensor such as a Hall element or a ferromagnetic resistance element, or a magnetic sensor coated on a non-magnetic linear plate. A combination of a medium and a magnetic sensor is used. Conventionally,
As shown in the example of FIG. 2, a predetermined writing dimension P1 is written on the outer peripheral surface of the high coercivity cylindrical magnetic shaft 1 in the axial direction of the magnetic shaft 1 so that the direction of the magnetic poles is alternately opposite. A magnetic track 3 is set by continuously performing magnetic writing. Further, a magnetic sensor 2 is provided close to the magnetic track 3 and movable along the magnetic track 3. When this magnetic sensor 2 moves on the magnetic shaft 1 along the magnetic track 3,
A voltage corresponding to the writing dimension P1 is output.

The magnetic sensor 2 mainly uses a ferromagnetic magnetoresistive element (MR element) that is highly sensitive to in-plane magnetic fields, and is superior to other magnetic sensors such as Hall elements in terms of sensitivity. Written dimension P in Figure 2
1 influences the output level of the magnetic sensor 2. As shown in FIG. 3, as the writing dimension P1 decreases, the output voltage tends to decrease monotonically.

[Problem to be solved by the invention] In the conventional configuration as shown in Fig. 2, in order to increase the resolution as a scale, the writing dimension P
It is necessary to make 1 small. However, the output voltage of the magnetic sensor also decreases accordingly, and there is a drawback that achieving high resolution is electrically and mechanically difficult.

Therefore, an object of the present invention is to provide a magnetic linear scale with high resolution as a scale.

[Means for Solving the Problems] According to the present invention, there is provided a cylindrical magnetic shaft made of a magnetic metal with high coercive force, and a magnetic pole whose direction is alternately reversed at a constant length around the outer periphery of the magnetic shaft. a magnetic track formed on the outer circumferential surface of the magnetic shaft by magnetizing it so that In the magnetic linear scale, the magnetic track is spirally formed on the outer peripheral surface of the magnetic shaft so as to form a certain angle with the axial direction of the magnetic shaft, and the magnetic sensor is spirally formed along the magnetic track. A magnetic linear scale is obtained, which is characterized in that it is provided so as to move.

[Operation] In the case of a conventional magnetic linear scale, when the object to be detected moves by a distance D, the magnetic sensor also moves by D. On the other hand, in the case of the magnetic linear scale of the present invention, if the angle between the axial direction of the magnetic shaft and the longitudinal direction of the magnetic track is θ, the magnetic sensor moves in a spiral along the magnetic track. , when the object to be detected moves by a distance D, the magnetic sensor moves by D·1/cosθ. That is, the length of the magnetic track used to detect the distance D is normally D in the conventional case, but in the present invention it is D·1/cos θ. Therefore, if the writing dimensions of the magnetic tracks are the same between the conventional magnetic linear scale and the magnetic linear scale of the present invention, the number of writes can be increased by 1/cosθ times with the magnetic linear scale of the present invention. This improves resolution.

[Embodiment] FIG. 1 is a schematic diagram of the configuration of a magnetic sensing portion of a magnetic linear scale according to an embodiment of the present invention.

Referring to FIG. 1, the magnetic linear scale of this embodiment includes a magnetic shaft 1, a magnetic sensor 2,
It has a magnetic track 3.

The magnetic shaft 1 is made of a magnetic metal with high coercive force and has a cylindrical shape. One magnetic track 3 is formed on the outer peripheral surface of the magnetic track 1. The magnetic track 3 is spirally formed on the outer peripheral surface of the magnetic shaft 1 in a direction forming a constant angle θ with the axial direction of the magnetic shaft 1. As in the conventional case, a large number of magnetic writings constituting the magnetic track 3 are recorded on the outer periphery of the magnetic shaft 1 at a fixed number with a writing dimension P1, and the direction of the magnetic poles of the magnetic writings is alternately arranged.
Recorded 180° in reverse. Furthermore, the angle θ
As the angle is increased, the pitch of the magnetic tracks 3 becomes smaller in the axial direction of the magnetic shaft 1, and leakage magnetic flux between adjacent magnetic writes in the axial direction will interfere with each other. θ is set so that magnetic writing adjacent to each other in the axial direction is separated from each other so that interference of leakage magnetic flux does not occur between them.

The magnetic sensor 2 is provided close to and opposite the magnetic track 3 and so as to move helically along the magnetic track 3. In this manner, the magnetic sensor 2 moves spirally along the magnetic track 3 and detects changes in the magnetic flux in the form of an approximately sinusoidal wave. As a mechanism for moving the magnetic sensor 2 in a spiral manner, there is a mechanism such as a ball feed screw.

Now, if the angle between the axial direction of the magnetic shaft 1 and the reference line of the magnetic track 3 is θ, the same writing dimension will be obtained compared to the case where the magnetic track 3 is formed in the axial direction of the magnetic shaft 1. , a resolution of 1/cos θ can be obtained in the axial direction of the magnetic shaft 1. That is, if the diameter d of the magnetic shaft 1 is sufficiently large compared to the writing dimension P1, it is possible to increase the resolution without reducing the output level of the magnetic sensor 2.

[Advantages of the Invention] As described above, according to the present invention, it is possible to improve the resolution without reducing the output level of the magnetic sensor, as compared with the conventional magnetic linear scale.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the structure of the magnetic detection part of a magnetic linear scale according to an embodiment of the present invention, Fig. 2 is a schematic diagram of the structure of the magnetic detection part of an example of a conventional magnetic linear scale, and Fig. 3 is the writing dimension of the magnetic track. FIG. 3 is a characteristic curve diagram showing the relationship between the maximum output voltage of the magnetic sensor and the maximum output voltage of the magnetic sensor. 1... Magnetic shaft, 2... Magnetic sensor, 3
...magnetic track.

Claims (1)

[Scope of utility model registration request] A cylindrical magnetic shaft made of a magnetic metal with a high coercive force, and a magnetized outer periphery of the magnetic shaft for a certain length so that the direction of the magnetic poles are alternately reversed. A magnetic linear scale including a magnetic track formed therein, and a magnetic sensor that is movably provided along the magnetic track and detects magnetic flux leaking from the magnetic track, wherein the magnetic track is aligned with the axis of the magnetic shaft. The magnetism is formed in a spiral shape on the outer peripheral surface of the magnetic material shaft so as to form a certain angle with the direction, and the magnetic sensor is provided so as to move in a spiral shape along the magnetic track. linear scale.