JPH10318785A - Magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small, high sensitivity magnetic sensor. SOLUTION: The magnetic sensor 1 comprises a magnetoelectric conversion element, i.e., a Hall IC 2, and two magnets 3A, 3B arranged on the opposite sides thereof. The magnets 3A, 3B direct same pole toward the Hall IC 2 and they are set to cancel the field in the vicinity of the detecting point of the Hall IC 2. Consequently, the axial flux density of the magnetic sensor 1 is 0 in the vicinity of the intermediate point and maximized on the surface of both magnets while reversing the direction. When the interval between both magnets is shortened, the distance between the magnetic sensor and the magnet can be shortened as compared with a case employing one magnet and thereby the size of the sensor can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor particularly suitable for use as a rotation sensor, and more particularly to a small-sized magnetic sensor capable of obtaining a sufficient output.

[0002]

2. Description of the Related Art Conventional magnetic sensors of this type include:
For example, an electromagnetic power generation type as shown in FIG. 3 is known. In the magnetic sensor 101, a coil 104 is wound around a magnetic pole 102 made of a magnetic material such as iron via a bobbin 103 made of resin or the like. A magnet 105 is mounted on one end of the magnetic pole 102 to create a magnetic field around the coil 104. These are integrated by being housed in a non-magnetic case 106, and the end face 106
A is a detection surface.

The magnetic sensor 101 has a detection surface 106A.
When the magnetic substance to be detected is moved closer and further apart, the magnetic flux passing through the magnetic pole 102 changes to generate an AC voltage at both ends of the coil 104.

[0004]

In order to obtain a sufficient output from such a magnetic sensor of the electromagnetic power generation type, it is necessary to increase the number of turns of the coil or make the magnet strong. However, increasing the number of turns of the coil causes a problem that the sensor becomes large. In order to make the magnet strong, the size of the iron core is increased accordingly, which increases the material cost and increases the size. Further, the electromagnetic power generation type has a problem that the output fluctuates depending on the moving speed of the magnetic substance to be detected, and there is a possibility that a sufficient output cannot be obtained particularly in a low speed region.

Therefore, in addition to the electromagnetic power generation type, a semiconductor type using a Hall element, which is a magnetoelectric conversion element, or a Hall IC in which a Hall element and an amplifier circuit are combined, is known. The Hall element performs an analog output according to the magnetic flux density, and the Hall IC internally processes the output of the Hall element and outputs an ON-OFF signal. However, also in these cases, in order to increase the fluctuation of the magnetic flux, it is necessary to increase the moving distance of the magnetic substance to be detected or to use a strong magnet. When the object to be detected is a rotating body, a permanent magnet is attached, and N-
Although there is a method of applying magnetic flux alternately with S, there is a problem that the manufacturing process becomes complicated and that it is difficult to apply the method to anything other than the rotating body.

Further, in the combination of the Hall IC and one magnet, the output is turned on and off when the magnetic flux density at the detection point of the Hall IC becomes near 0 or a predetermined magnetic flux density with a slight offset. To have been
Unless the Hall IC is moved away from the magnet to some extent, the magnetic flux density of the detection section of the Hall element does not decrease to a value at which the output of the element is switched. Therefore, in the case of a sensor having a magnet and a Hall IC, it is difficult to reduce the size. Magnet and Hall I
In order to shorten the distance from C, it is conceivable to use a relatively weak magnet as a magnet for generating a magnetic field, but if the magnet is weakened, the sensitivity is reduced. Further, if the magnet is strengthened to increase the sensitivity, there is a problem that the sensor becomes large for the above-mentioned reason.

[0007]

Therefore, a magnetic sensor according to the present invention has a magnet for generating a magnetic field and a magnetoelectric conversion element, and detects a change in a magnetic field due to proximity and separation of a magnetic body. The magnet is constituted by at least two magnets, and the magnetism conversion element is arranged so as to be sandwiched in the detection direction, and is arranged such that the same poles face each other.

Another feature resides in that the detection points of the magneto-electric conversion element are arranged at a portion where the magnetic flux density is set to substantially zero by a plurality of magnets.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a magnetic sensor according to an embodiment of the present invention. A magnetic sensor 1 shown in a sectional view in FIG. 1 has a Hall IC 2 which is a magnetoelectric conversion element and two magnets 3A and 3B arranged so as to sandwich the Hall IC. The distance between the magnet and the Hall IC is defined by spacers 4A and 4B made of a non-magnetic material such as resin. Magnet 3
A and 3B have the same polarity, for example, the S poles are Hall IC2.
, And are set so as to cancel out the magnetic field near the detection point of the Hall IC 2. Therefore, the magnetic flux density in the axial direction of the magnetic sensor 1 becomes maximum on the surface of the magnet 3A,
In the vicinity of the intermediate point (however, when the magnets 3A and 3B are magnets having substantially the same magnetic flux density), the value becomes 0, and the direction of the magnetic flux reverses in the forward and reverse directions at this equilibrium point. Become.

These components are integrally housed in a non-magnetic case 5 and sealed and fixed by a filler 6 such as a synthetic resin. A plurality of lead terminals 7 for inputting / outputting a control signal and a detection signal are led out of the Hall IC 2. In this embodiment, an example is described in which the internal components are put into a case and sealed with a filler, but for example, the internal components are securely fixed in the case and sealed to the extent that there is no problem in use. In this case, the filler is not always necessary. On the contrary, it is needless to say that the case may be omitted by molding the whole with resin or the like.

The magnetic sensor 1 is attached to, for example, a compressor for a car air conditioner. The detection surface 5A faces a rotating portion, which is a portion to be detected, or an Oldham ring in a scroll type compressor. Is detected. Here, in both cases, the detected part is made of a magnetic material such as iron,
The amount of movement is such that the magnetic field inside the magnetic sensor 1 can be sufficiently changed, and the mounting position of the magnetic sensor 1 is set such that the output fluctuates between the proximity position and the separation position of the detection target. Have been.

Next, the operation of the magnetic sensor 1 will be described with reference to the characteristic diagram of FIG. The horizontal axis of this characteristic diagram represents the magnetic flux density and the direction, and the direction of the magnetic flux is reversed NS with respect to the magnetic flux density 0 point. The vertical axis indicates the output voltage of the Hall IC 2. In the present embodiment, an example in which the operating point of the Hall IC is slightly shifted will be described. However, the operation is the same in a Hall IC in which the operating points are set substantially symmetrically with respect to the magnetic flux density 0 point. . First, when a magnetic body such as an Oldham ring is not approaching the detection surface 5A of the magnetic sensor 1, the hole I of the magnetic sensor 1 is
The magnetic flux density near the detection point of C2 is about 0 due to the fact that the magnets 3A and 3B whose S poles face each other cancel each other out.
The state is lower than a second threshold (Brp) described later. At this time, the output (Vout) of the Hall IC 2 is high (H).

When a magnetic substance approaches the detection surface 5A, the magnet 3
The point at which the magnetic flux distribution between A and 3B changes and the magnetic flux is balanced 0 moves in the axial direction of the magnetic sensor 1. As the balance point moves, the magnetic flux density near the detection point of the Hall IC 2 increases, and when the magnetic flux density exceeds the first threshold (Bop), the output changes from a high output to a low output (L).

Further, when the magnetic material moves away from the magnetic sensor 1 again after passing the proximity position, the balance point of the magnetic flux moves in a direction opposite to that in the proximity of the magnetic material, so that the magnetic flux density near the detection point of the magnetic sensor decreases. The output of the Hall IC 2 switches from the low output (L) to the high output (H) again when the output becomes lower than the second threshold (Brp). Here, the first threshold (Bop) and the second threshold (Brp) have a predetermined hysteresis width, and do not cause so-called chattering.

The above-mentioned magnetic sensor 1 changes its output in accordance with the proximity and separation of a magnetic body which is a portion to be detected. In the above description, the case where the magnetic body is used as a rotation sensor is described. However, it goes without saying that the magnetic body can be used as a stroke sensor or the like since the movement of the magnetic body is smaller than that of the conventional one.

In the embodiment, a Hall IC in which a control circuit such as a Hall element and an amplifier circuit is integrated as a magnetoelectric conversion element.
Although an example using a magnetic element is described, as the magnetoelectric element, not only an element having a Hall element and a control circuit separately, but also a circuit having a magnetoresistive element or the like in addition to the Hall element may be used. .

Further, since the magnetic field is canceled by a plurality of magnets, the size of the ferrite magnet or the rare earth magnet can be similarly reduced regardless of the strength of the single magnet.

[0018]

According to the magnetic sensor of the present invention, a plurality of magnets are provided, and the magnetic field is canceled by each other to provide a balance point at which the magnetic flux density becomes zero at the intermediate point.
The detection point of the magneto-electric conversion element is located near this balance point. As a result, the distance between the strong magnet and the magnetoelectric conversion element can be reduced as compared to a conventional magnet using only one magnet, so that the entire magnetic sensor can be downsized, and the amount of operation of the magnetic material is small. Since the change in the magnetic flux density at the detection point can be further increased, the degree of freedom of the detection target increases.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a magnetic sensor according to the present invention.

FIG. 2 is a characteristic diagram of a magnetoelectric conversion element used in the present invention.

FIG. 3 shows an example of a conventional magnetic sensor.

[Explanation of symbols]

 1: Magnetic sensor 2: Magnetoelectric conversion element (Hall element) 3A, 3B: Magnet 4A, 4B: Spacer 5: Case 6: Filler

Claims (2)

[Claims] 1. A magnetic sensor having a magnet for generating a magnetic field and a magneto-electric conversion element for detecting a change in a magnetic field due to proximity and separation of a magnetic body, wherein the magnet comprises at least two magnets and the magneto-electric conversion A magnetic sensor, wherein the elements are arranged so as to be sandwiched in the detection direction and are arranged so that the same poles face each other. 2. The magnetic sensor according to claim 1, wherein the detection points of the magnetoelectric conversion element are arranged at a portion where the magnetic flux density is set to approximately 0 by a plurality of magnets.