JPH04106705U - magnetic circuit - Google Patents

Abstract

(57) [Summary] [Purpose] To magnetically correct the magnetic flux direction of a magnetic circuit so that there is no need to electrically correct the zero point of the sensor. [Structure] In a magnetic circuit in which first and second permanent magnets are fixed facing each other and magnetic flux for detection is generated between them, the direction of the magnetic flux is set near the first and second permanent magnets. A magnetic flux direction adjustment body made of a magnet or magnetic material for correction is provided.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention relates to a magnetic circuit that can magnetically adjust the zero point of a magnetic sensor.

0002

[Conventional technology]

The magnetic sensor shown in FIG. While the permanent magnets 1 and 2 of 2 are fixed facing each other, the MR (magnetic resistance) element 13 is The center of the rotary plate 12 is approached without contact.

0003 Since the MR element 13 has its sensitivity direction in the direction of arrow A shown in FIG. In the field where the magnetic flux B going from the N pole of magnet 1 to the S pole of magnet 2 is orthogonal to the sensitivity direction A, In this case, the sensor output becomes zero, and the directions of A and B match as shown in (b) of the same figure. The maximum output is when The angle θ formed by A and B changes as the rotating plate 12 rotates. Since the magnitude of the magnetic flux applied in the A direction changes with Bsinθ, for example, the rotating plate 1 When 2 is rotated in one direction, the sensor output changes as shown in FIG. 2(c).

0004 This MR rotation sensor is manufactured so that the output is zero in the state of θ = 0 as shown in Figure 5(a). However, in reality, the assembly dimensional error of the rotating shaft 11, rotating plate 12, and magnets 1 and 2 , parallelism error between the positions of the magnets 1 and 2 and the generated magnetic flux B, and the sensitivity direction A of the MR element 13 Due to assembly angle errors, etc., even if the rotating shaft 11 is at the zero point position, the magnetic flux B and the MR element The sensitivity direction A of the sensor 13 is not at right angles as shown in Figure 6, and some output voltage error occurs. live.

[0005] For this reason, conventionally, the MR element 13 (equivalently shown in a bridge configuration) as shown in FIG. ) A buffer is installed at one input of the differential amplifier DIF that removes the common mode component from the differential output of the The zero point voltage for correction is superimposed through the BUF, and the zero point is corrected electrically. Ru.

[0006]

[Problem that the idea aims to solve]

However, in the circuit of Fig. 7, the means for generating the zero point voltage is a fixed resistor R as shown in a. 1, R2, it is inconvenient to replace the resistor during adjustment. Also, as shown in b, the volume When using VR, it is easy to adjust, but the settings may change due to vibrations, etc., making it less reliable. There are drawbacks.

[0007] This invention eliminates the need for electrical zero point correction by performing magnetic zero point correction. The purpose is to

[0008]

[Means to solve the problem]

In the present invention, first and second permanent magnets are fixed facing each other, and a detection device is used between them. in a magnetic circuit that generates a magnetic flux, near the first and second permanent magnets. A magnetic flux direction adjustment body made of a magnet or a magnetic material is provided to correct the direction of the magnetic flux. It is characterized by the following.

[0009]

[Effect]

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

0010

【Example】

FIG. 1 is a block diagram of a first embodiment of the present invention. In this example, the rotation is similar to that shown in Figure 4. While arranging and fixing the first and second permanent magnets 1 and 2 facing each other on the diameter of the plate 12, A third permanent magnet 3A is arranged and fixed in the vicinity thereof. Third permanent magnet 3 A is a magnetic flux that is different from the magnetic flux B1 that goes directly from the first permanent magnet 1 to the second permanent magnet 2. Magnetic flux B2 heading from magnet 1 to magnet 3A and magnetic flux B3 heading from magnet 3A to magnet 2 occurs.

[0011] Therefore, if magnet 3A is fixed between magnets 1 and 2 as shown in Figure 1(b), In this case, the magnetic flux between magnets 1 and 2 is horizontal as in the case without magnet 3A, but in the same figure When magnet 3A is located on the left side as shown in (a), the magnetic flux between magnets 1 and 2 consists of B1 and B3. As a whole, the direction is downward to the right depending on the minute. On the contrary, as shown in the same figure (c), magnet 3A is located on the right side, the magnetic flux between magnets 1 and 2 will be on the right side as a whole due to the B1 and B2 components. Turn upward.

0012 The magnet 3A can be fixed at any position on the rotary plate 12 with adhesive. or rotate A long groove is provided in the plate 12, and the magnet 3A is slid parallel to the line connecting magnets 1 and 2. It may also have a structure in which it is screwed in any position.

[0013] FIG. 2 is a block diagram of a second embodiment of the present invention. In this example, a magnet is used instead of the magnet 3A in Figure 1. This uses sex plate 3B. The material of this magnetic plate 3B is permalloy, electromagnetic soft Use high permeability materials such as iron, silicon steel, and steel plates. In this case as well, the same process as in Figure 1 is used. Useful, effective.

[0014] FIG. 3 is a block diagram of a third embodiment of the present invention. In this example, instead of magnet 3A in Figure 1, Use plastic magnet 3C. This plastic magnet 3C is inside the plastic It is easy to process because it is magnetized by scattering magnetic powder in the parts. Therefore, Fig. 3(b) ), fix the plastic magnet 3C between magnets 1 and 2 with adhesive, and The right end or left end is cut off as shown in (a) or (c) accordingly. This is shown in Figure 1. This is equivalent to moving magnet 3A to the left or right, and similarly moving magnet 3A between magnets 1 and 2. The direction of magnetic flux can be adjusted.

[0015] The above is an example of application to a rotation sensor, but it can also be applied to a sliding sensor as shown in Figure 8. Applicable. This sensor has first and second magnetic plates between both ends of parallel iron plates 14 and 15. A frame-shaped magnetic circuit with stones 1 and 2 sandwiched and fixed is used. This magnetic circuit consists of magnet 1, In addition to the main magnetic flux that comes out from the iron plates 14 and 15 and passes through the iron plates 14 and 15, the magnetic flux that leaks from the iron plates 14 and 15 Generate a bunch. This leakage magnetic flux has opposite magnetic properties on the left and right, and as it goes from both ends to the center. (at the center they cancel each other out and become zero). Slide this kind of magnetic circuit left and right. The MR element 13 placed in the center without contact measures the magnitude and direction of the leakage magnetic flux. To detect.

[0016] In this magnetic circuit, leakage magnetic flux must become zero at the center, but in reality, The zero point shifts slightly to the left and right. Therefore, the third permanent magnet 3A as shown in Fig. 1 is connected to the magnetic circuit. Fix it to the side and correct the zero point. Magnetic plate 3B in Figure 2, plastic magnet 3C in Figure 3, etc. But that's fine.

[0017]

[Effect of the idea]

As described above, according to the present invention, the magnetic flux direction of the magnetic circuit can be magnetically corrected. Therefore, there is no need to electrically perform zero point correction of the sensor.

[Brief explanation of 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 a diagram showing the operating principle 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.

FIG. 8 is an explanatory diagram of a sliding magnetic sensor.

[Explanation of symbols]

1 First permanent magnet 2 Second permanent magnet 3 Magnetic flux direction adjustment body

Claims (1)

[Scope of utility model registration request] 1. In a magnetic circuit in which first and second permanent magnets are fixed facing each other and a magnetic flux for detection is generated between the two, a magnetic flux is generated near the first and second permanent magnets. A magnetic circuit characterized in that a magnetic flux direction adjusting body made of a magnet or a magnetic material is provided to correct the direction.