JP2535170Y2 - Magnetic circuit of magnetic sensor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic circuit capable of magnetically adjusting a zero point of a magnetic sensor.

[0002]

2. Description of the Related Art A magnetic sensor shown in FIG. 4 has first and second permanent magnets 1 and 2 on a rotating plate 12 supported on a rotating shaft 11.
2 and the MR (magnetic resistance) element 1
3 is brought closer to the center of the rotating plate 12 in a non-contact manner.

Since the MR element 13 has a sensitivity direction in the direction of an arrow A shown in FIG. 5, a magnetic flux B traveling from the N pole of the magnet 1 to the S pole of the magnet 2 as shown in FIG. When they are orthogonal, the sensor output becomes zero, and when the directions of A and B match as shown in FIG.
The angle θ between A and B changes with the rotation of the rotating plate 12.
Since the magnitude of the magnetic flux applied in the direction A changes with Bsinθ, for example, when the rotating plate 12 is rotated in one direction, the sensor output changes as shown in FIG.

[0004] This MR rotation sensor has a θ shown in FIG.
Although it is manufactured so that the output becomes zero in the state of = 0, actually, the assembly dimensional error of the rotating shaft 11, the rotating plate 12, the magnets 1 and 2, the parallelism between the positions of the magnets 1 and 2 and the generated magnetic flux B. The error, the assembly angle error of the sensitivity direction A of the MR element 13 and the like overlap, and even if the rotating shaft 11 is at the zero point, the magnetic flux B and the MR
The sensitivity direction A of the element 13 is not perpendicular as shown in FIG. 6, and some output voltage errors occur.

For this reason, conventionally, as shown in FIG.
A zero-point voltage for correction is superimposed through a buffer BUF on one input of a differential amplifier DIF for removing a common-mode component from a differential output (equivalently represented by a bridge configuration) so as to electrically correct the zero point. I have.

[0006]

However, means for generating a zero point voltage in the circuit of FIG.
If the value is 1, R2, it is inconvenient to replace the resistor during adjustment.
Further, when the volume VR is used as shown in b, the adjustment is easy, but there is a disadvantage that the set value changes due to vibration or the like, so that the reliability is lacking.

An object of the present invention is to eliminate the need for electrical zero correction by performing magnetic zero correction.

[0008]

According to the present invention, there is provided a magnetic circuit in which first and second permanent magnets are fixed to face each other and a magnetic flux for detection is generated therebetween. A magnetic flux direction adjuster made of a magnet or a magnetic material for correcting the direction of the magnetic flux is provided near the permanent magnet.

[0009]

The magnetic flux direction adjuster can correct the direction of the magnetic flux generated between the first permanent magnet and the second permanent magnet. Therefore, the output error at the zero point can be magnetically corrected, and the electrical correction on the sensor signal processing circuit side can be omitted.

[0010]

1 is a block diagram of a first embodiment of the present invention.
In this example, the first and second permanent magnets 1 and 2 are arranged and fixed facing each other on the diameter of the rotating plate 12 as shown in FIG. 4, while the third permanent magnet 3A is arranged in the vicinity thereof. It is fixed. The third permanent magnet 3A is different from the magnetic flux B1 directly from the first permanent magnet 1 to the second permanent magnet 2 and is a magnetic flux B2 from the magnet 1 to the magnet 3A and a magnetic flux from the magnet 3A to the magnet 2 Generate B3.

Therefore, when the magnet 3A is fixed in the middle of the magnets 1 and 2 as shown in FIG. 1 (b), the magnetic flux between the magnets 1 and 2 is horizontal like the case without the magnet 3A. ,
When the magnet 3A is located on the left side as shown in FIG. 3A, the magnetic flux between the magnets 1 and 2 is directed downward as a whole by the B1 and B3 components. On the contrary, as shown in FIG.
Is located on the right side, the magnetic flux between the magnets 1 and 2 is B1, B2
As a whole, the component is directed to the upper right.

The magnet 3A can be fixed at any position on the rotating plate 12 by an adhesive. Alternatively, a structure may be adopted in which a long groove is provided in the rotating plate 12, and the magnet 3A is slid in parallel with the line connecting the magnets 1 and 2 and screwed to an arbitrary position.

FIG. 2 is a block diagram of a second embodiment of the present invention. In this example, a magnetic plate 3B is used instead of the magnet 3A of FIG. The material of this magnetic plate 3B is permalloy,
Use high magnetic permeability materials such as electromagnetic soft iron, silicon steel, and steel plate. In this case, the same operation and effect as those in FIG. 1 are obtained.

FIG. 3 is a block diagram of a third embodiment of the present invention. In this example, a plastic magnet 3C is used instead of the magnet 3A of FIG. Since the plastic magnet 3C is magnetized by dispersing magnetic powder inside the plastic, it is easy to process. Therefore, as shown in FIG. 3B, the plastic magnet 3C is fixed between the magnets 1 and 2 with an adhesive, and the right end or the left end is cut off as shown in FIGS. This is equivalent to moving the magnet 3A left or right in FIG. 1, and the direction of the magnetic flux between the magnets 1 and 2 can be similarly adjusted.

[0015]

[0016]

[0017]

[Effect of the Invention] As described above, according to the present invention, the magnetic flux
Since the magnetic flux direction can be magnetically corrected by the direction adjuster ,
There is no need to electrically correct the zero point of the sensor. Furthermore, magnetic
Since the position of the bundle direction adjuster can be adjusted, individual sensors
Adjust the magnetic flux direction by simply changing the position of the magnetic flux direction adjuster with
can do.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a third embodiment of the present invention.

FIG. 4 is a structural diagram of an MR rotation sensor.

FIG. 5 is an operation principle diagram of the MR rotation sensor.

FIG. 6 is an explanatory diagram of an output error at a zero point.

FIG. 7 is a configuration diagram of a signal processing circuit of an MR element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st permanent magnet 2 2nd permanent magnet 3 Magnetic flux direction adjustment body

Claims (1)

(57) [Scope of request for utility model registration] 1. A first and a second permanent magnet are fixed to face each other , and a first permanent magnet and a second permanent magnet are fixed to each other.
A magnetoresistive element is interposed between the first permanent magnet and the second permanent magnet.
Of the magnetic flux generated between the permanent magnet and the magnetoresistive element
The output becomes zero when the sensitivity direction of the
The output is maximum when the direction of the bundle and the sensitivity direction match.
The magnetic sensor according to claim 1 , wherein the magnetic field is generated between the first permanent magnet and the second permanent magnet.
The direction of the magnetic flux is perpendicular to the sensitivity direction of the magnetoresistive element.
Such that the output is zero, magnetic, characterized in that a magnetic flux direction adjusting member consisting of positions adjustable magnet or magnetic material for correcting the direction of the magnetic flux in the vicinity of the first and second permanent magnets The magnetic circuit of the sensor .