JPH0495817A - Revolution detection apparatus - Google Patents

Abstract

PURPOSE:To simply form an apparatus to have high accuracy and to obtain a detecting signal with high accuracy and constant amplitude by processing a magnetic material of a rotary body into the shape of a gear. CONSTITUTION:A magnetic resistance body 16 of a detector 14 is formed into a thin strip to extend in a direction perpendicular to the moving direction of a gear 131 of a rotary body, for example, when the gear 131 comes close to the magnetic resistance body 16, and moreover, the magnetic resistance body 16 is set so that a magnetic filed generated by a permanent magnet 17 crosses the resistance body 16. In consequence, a magnetic path penetrating the resistance body 16 to the gear 131 is formed. When the gear 131 is moved away from the resistance body 16, a magnetic path crossing only the resistance body 16 is formed. In accordance with the rotation of the rotary body 12, the value of the resistance body 16 is clearly changed, so that a clear detecting signal with high accuracy is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] [Prior Art] It has been widely known to construct a rotation detecting device using a magnetoresistive body made of a ferromagnetic thin film. For example, a rotating body made of permanent magnets with N and S magnetic poles formed at equal intervals on the circumferential surface is used, and a magnetic resistance element is fixedly placed in a position close to the circumferential surface of this rotating body. . In other words, as the rotating body rotates, its magnetic poles move closer to and away from the magnetoresistive member, changing the strength of the magnetic field acting on the magnetoresistive member, and detecting electrical signals with varying amplitudes. I try to let them do it.

However, in the rotation detection device configured in this way,
When the polarization and magnetic strength of each magnetic pole formed on the rotating body changes,
The amplitude of the detection signal changes, and if the magnetization accuracy and strength of each magnetic pole are not constant, the detection output waveform will be uneven. This detection output may be shaped into a rectangular waveform output signal, for example. If you try to obtain this signal, the duty ratio of this signal waveform will vary.

[Problems to be Solved by the Invention] This invention has been made in view of the above points, and allows for simple and low-cost construction without requiring high magnetization accuracy, and It is an object of the present invention to provide a rotation detection device using a magnetoresistive element that can obtain an output signal with a constant duty ratio even when a detection signal is output after waveform shaping.

[Means for Solving the Problems] The rotation detecting device according to the present invention includes a rotating body constituted by a gear made of a magnetic material having a plurality of protruding teeth around the circumference, and a rotation detecting device configured by a gear wheel made of a magnetic material having a plurality of protruding teeth formed around the rotating body. A magnetoresistive element made of a strip-shaped ferromagnetic thin film formed on an insulating substrate is installed on the rotor, and the magnetoresistive element is set to extend in a direction that coincides with the direction of the rotation axis of the rotating body. A magnetic field generating means for generating a magnetic field in a direction perpendicular to the extending direction of the magnetic resistor is disposed on the back surface of the insulating substrate.

[Operations] According to the rotation detecting device configured in this way, the rotating body can be easily shaped into a highly accurate shape by machining the magnetic material into a gear shape, and the magnetic resistor has a fixed magnetic field. Since it is made to act, a highly accurate detection signal with a constant amplitude can be obtained. Here, the magnetic field generating means acts on a magnetic field in a direction perpendicular to the direction in which the strip-shaped magnetic resistance body extends, and the teeth of the rotating body penetrate this magnetic resistance body while being close to the magnetic resistance body. As a result, a magnetic path is formed that reaches the teeth of the rotating body, and a detection signal with stable intensity can be obtained with high precision.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows its configuration, in which a rotating body 1 made of magnetic material is attached to a rotating shaft 11 that rotates together with the object to be measured.
2 is installed. That is, this rotating body 12 is rotationally driven together with the object to be measured. Here, this rotating body■
2 is configured in the shape of a gear with a plurality of teeth 131, 132, . . . protruding from the outer periphery.

A detector 14 is fixedly set to such a rotating body 12 at a position close to its outer peripheral surface. This detector 14
is equipped with an insulating substrate 15 whose surface is parallel to the tangential direction of the outer peripheral surface of the rotating body 12, and a ferromagnetic substrate 15 is provided on the side of the substrate 15 facing the rotating body 12. A thin film magnetoresistive element 16 is formed by vapor deposition, printing, or the like.

Here, the magnetic resistance body 16 is configured in a strip shape so as to extend in a direction perpendicular to the rotating direction of the rotating body I2, that is, in a direction coinciding with the direction of the rotating shaft 11.

Then, the substrate 15 on which the magnetoresistive element 16 is formed in this way
A magnetic field generating means by a permanent magnet 17 is set on the back side of the magnetic field generator, and the direction in which the magnetic field is generated by the permanent magnet 17 is set to cross the direction in which the five strip-like magnetic resistors 1B extend. has been done.

In the rotation detecting device configured in this way, when the rotating body 12 is rotated together with the object to be measured (not shown), the teeth 131, 132, . . .
By approaching and moving away from the magnetoresistive element 16
The magnetic resistance changes as shown in FIG.

Therefore, by causing a constant DC current to flow through the magnetoresistive element I6, a detection signal corresponding to this resistance change can be extracted.

Here, for example, when the teeth 131 of the rotating body I2 come close to the magnetic resistance body 16 of the detector 14 as shown in FIG. The permanent magnet 17 is configured in an elongated strip shape.
Since the magnetic field is set in a direction that crosses this strip-shaped magnetic resistor 16, a magnetic path is formed that passes through the magnetic resistor 18 and reaches the tooth 131, as shown by the arrow in this figure. . When the teeth 131 move away from the magnetic resistor 16, a magnetic path is formed that crosses only the magnetic resistor 16, and as the rotating body 12 rotates, the resistance of the magnetic resistor 16 increases. The value is clearly changed,
A highly accurate and clear detection signal can now be obtained.

In such a device, the strength of the magnetic field acting on the magnetoresistive element 16 is reliably kept constant, and the detection output can be stably obtained. Therefore, even when the electrical detection signal corresponding to the change in the resistance value of the magnetoresistive element 16 is waveform-shaped into a rectangular wave, the duty ratio thereof can be made very stable.

In this embodiment, a permanent magnet 1 is used as the magnetic field generating means.
7 was used, but this does not need to be constructed using a permanent magnet, and an electromagnet may be used.

In the embodiment shown in FIG. 5, a coil 20 is set on the back surface of an insulating substrate 15 on which a magnetic resistor 16 is set,
By passing a DC current from a DC power supply 21 through this coil 20, a magnetic field is generated in a direction perpendicular to the direction in which the magnetic resistance body 1B extends.

Here, although the coil 20 is schematically shown in the figure, the coil 20 is actually
may be formed. Alternatively, the coils 20 formed of windings may be set in contact with each other.

Alternatively, the same effect can be obtained by forming a magnet by depositing a Co--Pt thin film on the back surface of the substrate 15 by sputtering and magnetizing it.

[Effects of the Invention] As described above, according to the rotation detection device of the present invention, the rotating body is composed of gears that can be easily machined with high precision, and a stable magnetic field acts on the magnetic resistance body. You will be able to do it. In particular, when the teeth of the rotating body are close to the magnetic resistance element, a magnetic path leading to the teeth of the rotating body is clearly formed.
Since the structure allows the gap between the tooth and the magnetic resistor to be easily set close to each other, the detection characteristics can be made highly accurate and stable.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram illustrating a rotation detection device according to an embodiment of the present invention, FIG. 2 is a diagram showing the state of resistance value change of a magnetoresistive element obtained by this detection device, and FIG. Diagram 4 showing the state of the magnetic path when the tooth approaches the magnetoresistive element.
The figure is a configuration diagram illustrating another embodiment of the present invention. 11... Rotating shaft, 12... Rotating body, 131.132
,...teeth, 14...detector, 15...substrate (insulating), 16...magnetic resistance, 17...permanent magnet,
20...Coil. Figure 1 Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (1)

[Claims] (1) A rotating body made of a magnetic material and having a plurality of protruding teeth at equal intervals on its outer periphery, and a rotating body formed on an insulating substrate and extending in a direction coinciding with the rotation axis of the rotating body. a magnetoresistive body made of a strip-like ferromagnetic thin film, which is formed by a magnetoresistive member formed by a thin strip of ferromagnetic film, and which is set close to and facing a rotating peripheral surface of the rotating body; A rotation detecting device comprising: a magnetic field generating means set in contact with a back surface, the magnetic field generating means generating a magnetic field in a direction perpendicular to the direction in which the magnetic resistance body extends.