JPH0718971Y2 - Magnetic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In a magnetic circuit in which magnetic fluxes having different intensities are distributed in a moving direction of a magnetic sensor, the whole structure is close to a closed magnetic circuit, and a single permanent magnet is used. Improve the practicality by making it a structure to be housed in.

[Industrial application field]

The present invention relates to a magnetic circuit for distributing magnetic fluxes having different strengths in a moving direction of a magnetic sensor.

[Conventional technology]

Since magnetic sensors such as Hall elements and magnetoresistive elements can detect not only the intensity of magnetic flux but also the polarity, conventionally, a magnetic circuit as shown in FIG. 3 was constructed to measure minute movement amount and rotation angle of the object to be measured. Are used for.

In the example shown in FIG. 3, a pair of permanent magnets 1 and 2 are arranged in opposite polarities, and a pair of magnetic bodies 3 and 4 are fixed on the top and bottom to form a magnetic circuit. In this magnetic circuit, most of the magnetic flux emitted from the N pole of the right magnet 1 reaches the S pole of the left magnet 2 through the lower magnetic plate 4, but at this time, some magnetic flux leaks and the upper magnet It tries to return to the south pole of the right magnet 1 through the body 3. This leakage magnetic flux 5 is also generated by the left permanent magnet 2 according to the same principle, but the strength of the magnets 1 and 2 is the same because the magnets 1 and 2 have opposite polarities.
The distribution characteristic is 0 in the middle part of, and increases with the opposite polarity with increasing distance. Therefore, the current position of the magnetic sensor 6 movable between the magnetic bodies 3 and 4 can be determined from the intensity and polarity of the magnetic flux detected by the sensor 6.

[Problems to be solved by the device]

 However, the structure of FIG. 3 has the following drawbacks.

(1) Since two permanent magnets are required, the cost becomes high.

(2) If the strengths of the two permanent magnets are not equal, a symmetrical distribution characteristic in which the leakage magnetic flux becomes 0 at the intermediate portion cannot be obtained.

(3) Since most of the magnetic flux passes through the magnetic substance, the amount of leakage detected by the magnetic sensor is small (only about 1%), and the amplitude of the detection signal is small.

(4) Since the structure for movably holding the magnetic sensor is provided separately from the magnetic circuit, the structure becomes complicated.

The present invention aims to improve such a point.

[Means for Solving the Problems]

According to the present invention, a first magnetic body coupled to one pole of a single permanent magnet and second and third magnetic bodies coupled to the other pole of the permanent magnet are opposed to each other with a predetermined gap. This forms a fixed magnetic path, and the magnetic sensor (C) is interposed between the fourth and fifth magnetic bodies (B ₁ , B ₂ ) and these are fixed together, and these fourth and fifth magnetic bodies (B ₁ and B ₂ ) are fixed. Of the magnetic body are arranged side by side in a direction connecting the second and third magnetic bodies, and the movable magnetic path (B) is configured by making the gap movable in the direction. is there.

[Action]

In the fixed magnetic path A, leakage magnetic flux is generated not only between the first magnetic body A ₁ and the second magnetic body A ₂ but also between the first magnetic body A ₁ and the third magnetic body A _3. . When the magnetic flux between A _{1 and} A ₂ is φ ₂ and the magnetic flux between A _{1 and} A ₃ is φ ₃ , when the magnetic flux generated from the magnet M is φ ₁ (constant value), approximately φ ₁ = φ ₂ + φ ₃ holds.

When the movable magnetic path B is interposed in the gap of the fixed magnetic path A, the magnetic resistance between A _{1 and} A ₂ is A ₁ -A ₃ if the movable magnetic path B is at the center.
Since it is equal to the interval, φ ₂ = φ ₃ .

On the other hand, when the movable magnetic path B moves to the second magnetic body A ₂ side, the magnetic resistance between A _{1 and} A ₂ decreases and the magnetic resistance between A _{1 and} A ₃ increases, so φ ₂ >. φ ₃ becomes, and φ ₂ moves sensor C in movable magnetic path B from A ₃ side to A
Pass to side ₂ .

On the other hand, when the movable magnetic path B moves to the third magnetic body A ₃ side, A ₁
Since the magnetic resistance between −A ₃ decreases and the magnetic resistance on the A ₁ −A ₂ side increases, φ ₂ <φ ₃ , and φ ₃ passes the sensor C from the A ₂ side to the A ₃ side.

Since the values of the magnetic fluxes φ ₂ and φ ₃ are determined by the position of the movable magnetic path B, the magnetic sensor C having the same movement as this produces an output having polarity as in the conventional case.

〔Example〕

FIG. 1 is a perspective view showing an embodiment of the present invention. In the fixed magnetic path A of this example, a permanent magnet M is arranged at the center, a U-shaped first magnetic body A ₁ is fixed to the upper portion thereof, and a U-shaped second magnetic member having a common base end is attached to the lower portion. The third magnetic body A ₂ and A ₃ are fixed. There is an equal gap between the magnetic bodies A ₁ and A _{2 and} between A ₁ and A ₃ , and the magnetic flux φ ₁ emitted from the magnet M branches and passes between them. φ ₂ and φ ₃ are the branched magnetic fluxes and correspond to the leakage magnetic flux 5 in FIG.

On the other hand, the movable magnetic path B is a prism-shaped magnetic body B ₁ , B ₂ having the same shape.
A gap is provided between the magnetic sensor C and the magnetic sensor C. The movable magnetic path B is interposed between the magnetic body A ₁ and the magnetic bodies A ₂ and A ₃ of the fixed magnetic path A and slidably supported in the direction of the solid arrow.

When the movable magnetic path B is located at the center as shown in FIG. 2 (a), the magnetic flux φ ₂ passes through the magnetic path of A ₁ -B ₁ -A _{2 and} the magnetic flux φ ₃ is
Passing through the magnetic path of the A ₁ -B ₂ -A _3. Since these magnetic paths have almost the same magnetic resistance value, approximately φ ₂ = φ ₃ . As a result, the φ ₂ and φ ₃ components passing through the sensor C cancel each other, so that the sensor output is close to zero.

On the other hand, when the movable magnetic path B is moved to the left as shown in FIG. 4B, φ ₂ passes through the magnetic path of A ₁ -B ₂ -B ₁ -A ₂ , whereas
phi ₃ passes through the magnetic path of the A ₁ -B ₂ -A _3. In this case, since the magnetic path through which φ ₂ passes has a lower magnetic resistance, φ ₂ > φ ₃ , and the sensor C produces an output according to the value of φ ₂ of the polarity from B ₂ to B ₁ .

On the other hand, when the movable magnetic path B is shifted to the right as shown in FIG. 7C, φ ₂ passes through the magnetic path of A ₁ -B ₁ -A ₂ , while φ ₃ is A _1-.
Passing through the magnetic path of the B ₁ -B ₂ -A _2. In this case, since the magnetic path through which φ ₃ passes has a lower magnetic resistance, φ ₂ <φ ₃ , and the sensor C produces an output according to the value of φ ₃ of the polarity from B ₁ to B ₂ .

The change characteristic of the magnetic resistance due to the movement of the movable magnetic path B is determined by the distance la between the magnetic bodies A ₂ and A ₃ and the length lb of the magnetic bodies B ₁ and B ₂ . For example, when lb> la, the magnetic resistance between B ₂ -A ₃ in (b) or between B ₁ -A ₂ in (c) becomes smaller than the magnetic resistance of B ₁ -B ₂ and passes through the sensor C. There is less magnetic flux. In such cases, it is necessary to set la> lb.
The magnetic materials B ₁ and B ₂ do not have to be completely separated,
A recess for accommodating the sensor C may be formed in the center of one magnetic body. Further, the movable magnetic path B may be in contact with the fixed magnetic path A as long as it does not hinder sliding.

[Effect of device]

 The magnetic circuit of the present invention described above has the following advantages.

(1) Since only one permanent magnet is required, it can be implemented at low cost.

(2) Since there is only one permanent magnet, it is not necessary to consider the balance of strength as in the conventional case.

(3) Since the magnetic path is close to the closed magnetic path, a large amount of magnetic flux passes through the magnetic sensor, and a large output can be obtained even with a small permanent magnet.

(4) Since the magnetic sensor can be held in the movable magnetic path, the holding mechanism is simple and the size can be easily reduced. For example, if the movable magnetic path is held by a spring, a small accelerometer with a side of about 1 cm can be realized.

(5) The measured quantity is easily transmitted to the movable magnetic path.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is an operation explanatory view of the present invention, and FIG. 3 is a configuration diagram showing an example of a conventional magnetic circuit. In the figure, A is a fixed magnetic path, A _{1 to} A ₃ are magnetic bodies, M is a permanent magnet,
B is a movable magnetic path, B ₁ and B ₂ are magnetic bodies, C is a magnetic sensor, and φ ₁
~ Φ ₃ is the magnetic flux.

Claims (1)

[Scope of utility model registration request] 1. A _first magnetic body (A ₁ ) coupled to one pole of a single permanent magnet (M) and second and third magnetic bodies coupled to the other pole of the permanent magnet (M). A fixed magnetic path (A) is formed by facing the body (A ₂ , A ₃ ) with a predetermined gap, and a magnetic field is provided between the fourth and fifth magnetic bodies (B ₁ , B ₂ ). The sensor (C) is interposed and these are fixed together, and the fourth and fifth magnetic bodies are arranged side by side in the direction connecting the second and third magnetic bodies and move in the gap in that direction. A magnetic circuit characterized by enabling a movable magnetic path (B).