JPH09311008A - Magnetic sensor - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a magnetic sensor capable of reducing the size of a magnet. A base block (10), two permanent magnets (21,22) arranged so as to sandwich the base block (10) from both sides, and a front end of the base block (10) and between the two permanent magnets (21,22). And a magnetic detection element 30 that has been formed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a Hall element and an MR.
The present invention relates to a magnetic sensor that detects the approach of a magnetic body (metal or the like) by changing the magnetic field by using a magnetic detection element such as an element.

[0002]

2. Description of the Related Art For example, in an automobile, a sensor for detecting a cam position for driving the supply / exhaust valve may be installed in order to control the opening / closing timing of the engine's supply / exhaust valve according to conditions such as the engine speed. However, as this sensor, a magnetic sensor using a magnetic detecting element such as a Hall element utilizing the so-called Hall effect or an MR element (magnetoresistive element) utilizing the so-called magnetoresistive effect is used. As a conventional magnetic sensor of this type, as shown in FIG. 9, one permanent magnet 1 for generating a magnetic field and one magnetic detection element 2 for detecting a change in the magnetic field due to the approach of an object to be detected are bases. Front end 3a of block 3
There is known a structure in which a sensor head portion is configured by being attached to a sensor head portion, and the sensor head portion is covered with a cover 4 in a hermetically sealed state. In FIG. 9, reference numeral 5 indicates a circuit board on which the magnetic detection element 2 is mounted and which constitutes a detection circuit formed of the magnetic detection element 2.

[0003]

The conventional magnetic sensor described above has the following problems in terms of performance, cost, and adjustment workability. (1) In order to obtain the magnetic field necessary for detection, the size of the permanent magnet becomes large, and the cost of the permanent magnet becomes high. (2) Since the amount of change in the magnetic field due to the approach of the object to be detected is minute, the position accuracy of detection is low. (3) Since there is no method for adjusting the detection performance and characteristics other than changing the positional relationship between the magnet and the magnetic detection element, it is difficult to determine the characteristics and the workability of the characteristics adjustment work during production or assembly is poor. Further, once the positional relationship between the magnet and the magnetic detection element is fixed, readjustment is practically impossible.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic sensor capable of reducing the size of a magnet, improving the accuracy of position detection, and facilitating adjustment work.

[0005]

In order to achieve the above object, a magnetic sensor according to claim 1 comprises a base block,
It is characterized by comprising two permanent magnets arranged so as to sandwich the base block from both sides, and a magnetic detection element arranged at a front end portion of the base block and between the two permanent magnets.

A magnetic sensor according to a second aspect of the present invention is characterized in that the arrangement direction of the two permanent magnets is set to a direction perpendicular to the moving direction of the object to be detected. Further, in the magnetic sensor according to claim 3, the relative position of the permanent magnet and the magnetic detection element can be adjusted, and the adjustment yoke for adjusting the magnetic field of the permanent magnet can be adjusted behind the permanent magnet. It is characterized by being provided.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are views for explaining an example of a magnetic sensor according to the present invention. Of these, FIG. 1 is an exploded perspective view showing the overall configuration of the magnetic sensor of this example. As shown in FIG. 1, the magnetic sensor of this example includes a base block 10, two permanent magnets 21 and 22, one magnetic detection element (for example, a Hall element) 30, an adjustment yoke 40, and a cover 50. With. The base block 10 is formed with a protrusion 12 forming a sensor head portion on the front end side of a base 11, and grooves on which permanent magnets 21 and 22 are slidably mounted on both sides of the front end of the protrusion 12. 1
3 and 14 are formed, and an adjusting yoke 40 is arranged so as to be movable back and forth on the base end side of the protrusion 12 (the rear position of the permanent magnets 21 and 22).

The permanent magnets 21, 22 are screwed, bonded, and
It is fixed to the protruding portion 12 of the base block 10 by caulking or the like. The adjusting yoke 40 is slidably fitted in a groove (not shown) formed in the projecting portion 12 of the base block 10, and is pushed and pulled by a screw (not shown) to move back and forth. By rotating this screw, the position can be easily adjusted even after assembly. A connector (not shown) for inputting a power source or outputting a detection signal is formed on the back side of the base portion 11 of the base block 10.

The two permanent magnets 21 and 22 are both much smaller than conventional ones, and are arranged symmetrically so as to sandwich the projecting portion 12 of the base block 10 from both sides. The arrangement direction of the two permanent magnets 21 and 22 is set to the direction perpendicular to the direction in which the detected object A moves, as shown in FIG. The magnetic detection element 30 is, for example, a Hall element, and is mounted on the circuit board 31 attached to one side surface (the upper surface in FIG. 1) of the protrusion 12 of the base block 10. The circuit board 31 constitutes a detection circuit including the magnetic detection element 30, and is connected to the above-mentioned connector by a lead frame (not shown). In addition,
As shown in FIGS. 2 and 3, the magnetic detection element 30 is arranged at the front end of the protruding portion 12 of the base block 10 and between the two permanent magnets 21 and 22. For example, by adjusting the mounting position of the circuit board 31. After finely adjusting the front, rear, left, and right positions with respect to the permanent magnets 21, 22, the circuit board 31 is fixed by being attached to the projecting portion 12 of the base block 10 by screwing or the like.

The adjusting yoke 40 is made of a magnetic material such as iron, cobalt, nickel or the like, and is for adjusting the detection performance or characteristics by changing the magnetic field generated by the permanent magnets 21 and 22 from the back surface. . When the adjusting yoke 40 moves back and forth by the mechanism as described above, the influence state on the magnetic field generated by the permanent magnets 21 and 22 changes, and the performance as a magnetic sensor changes accordingly. . Further, the cover 50 hermetically covers and protects the sensor head portion in which the permanent magnets 21, 22 and the magnetic detection element 30 are attached to the protruding portion 12 of the base block 10 as described above. The magnetic detection element 30 is attached to the. In FIG. 1, reference numeral 51 is a hole for inserting a mounting bolt for assembling the entire sensor to an automobile engine or the like.

Next, the operation of the magnetic sensor configured as described above will be described. When the object A to be detected is not close to the sensor (non-detection), a stable magnetic field is formed around the permanent magnets 21 and 22, as shown in FIG. In the region between the formed permanent magnets 21 and 22, the lines of magnetic force generated by both magnets are overlapped, and a large and strong magnetic field can be obtained while using a small magnet.
When the detected object A approaches this sensor (at the time of detection)
As shown in FIG. 8, the magnetic flux of the magnetic field is attracted by the permanent magnets 21 and 22, and the direction of the magnetic force lines is reliably and completely reversed in the region where the magnetic detection element 30 is arranged.
The output signal from the magnetic detection element 30 changes clearly.

Although not shown in FIGS. 7 and 8,
Adjustment yoke 4 arranged on the back surface of the permanent magnets 21 and 22.
When 0 is arranged at a position close to the permanent magnets 21 and 22, the permanent magnets 21,
The magnetic field due to 22 is more strongly affected. In particular,
By attracting the magnetic flux to the adjustment yoke 40,
For example, the state of the magnetic field in which the output signal is in the non-detection state is strongly maintained, and the sensitivity can be adjusted for the purpose of preventing malfunction. On the contrary, when the adjusting yoke 40 is arranged at a position farther from the permanent magnets 21 and 22, the effect of the adjusting yoke 40 on the magnetic field is weakened, and the output signal is easily switched to the detection state. Adjustments such as increasing the sensitivity are possible.

Therefore, performances such as the detection position accuracy and the detection distance can be highly realized, and the cost of the magnet can be reduced and the work such as the sensitivity adjustment can be facilitated. That is, in the sensor of this example, the two permanent magnets 21 and 22 are provided, and the magnetic detection element 3 is located at a position where the magnetic fields of both magnets overlap.
Since 0 is arranged, the magnetic efficiency is improved, and two permanent magnets 2 are provided in the region where the magnetic detection element 30 is arranged.
By 1 and 22, a sufficiently strong magnetic field can be obtained, and the permanent magnet can be made much smaller than the conventional one, and the cost can be reduced. Since the two permanent magnets 21 and 22 can share the same parts as the same magnet, the number of magnets used is increased compared to the conventional one, but the cost is reduced due to the effect of downsizing and mass production. Is fully possible.

The arrangement direction of the permanent magnets 21 and 22 is
As described above, since it is set in the direction perpendicular to the moving direction of the detected object A, as shown in FIG. 8, when the detected object A approaches, the magnetic fields of both the permanent magnets 21 and 22 are simultaneously affected. Therefore, the amount of change in the magnetic field due to the approach of the object A to be detected is significantly increased as compared with the conventional case. Therefore, the position accuracy of detection is significantly improved. Further, after assembly (after fixing the permanent magnets 21, 22 and the magnetic detection element 30), the position of the adjustment yoke 40 allows the state of the magnetic field to be changed from the rear surface to improve the characteristics such as sensitivity and detection distance. Since the sensor can be changed, the manufacturing yield of the sensor itself can be improved, and the fine adjustment (re-adjustment) work can be facilitated when the sensor is assembled into an automobile and the productivity of the automobile can be improved.

It should be noted that the present invention is not limited to the above-mentioned form example, and may have various forms. For example, as shown in FIG. 4, a configuration (second example) may be provided in which the adjustment yoke 41 is formed so that the positions on both sides facing the back surfaces of the permanent magnets 21 and 22 project. As shown, each permanent magnet 21,
A configuration (third example) may be provided in which the adjustment yokes 42 and 43 having a small width are respectively provided at the positions facing 22. Further, as shown in FIG. 6, the permanent magnets 21, 22 may be arranged so as to be inclined with respect to the front-back direction of the sensor head (fourth example).

[0016]

According to the magnetic sensor of the first aspect of the present invention, two permanent magnets are provided, and the magnetic detecting element is arranged at a position where the magnetic fields of both magnets overlap each other. In the region where the magnetic detection element is arranged, a sufficiently strong magnetic field can be obtained by the two permanent magnets, and the permanent magnet can be remarkably downsized as compared with the conventional one, and the cost can be reduced. Since the two permanent magnets can share the same parts as the same magnet, the number of magnets used is larger than before, but the cost can be sufficiently reduced by the effect of miniaturization and mass production. Becomes

Further, according to the magnetic sensor of the second aspect, since the arrangement direction of the permanent magnets is set to the direction perpendicular to the moving direction of the object to be detected, the magnetic field generated by each permanent magnet when the object to be detected approaches. Will be affected at the same time, and the amount of change in the magnetic field due to the approach of the object to be detected will be much greater than in the past. Therefore, the detection position accuracy can be significantly improved.

According to the magnetic sensor of the third aspect, even after the positional relationship between the permanent magnet and the magnetic detecting element is adjusted and fixed, the position of the adjusting yoke is adjusted to adjust the state of the magnetic field to the back side. Since it is possible to finely adjust the characteristics such as sensitivity and detection distance by changing from the above, the manufacturing yield of this sensor itself will be improved, and the work of fine adjustment (re-adjustment) at the time of assembly to the automobile etc. It will be easier and the productivity of automobiles will be improved.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an overall configuration of a magnetic sensor that is an example of the present invention.

FIG. 2 is a diagram showing an arrangement direction of permanent magnets of the magnetic sensor.

FIG. 3 is a diagram showing a shape and an arrangement relationship of main constituent elements (permanent magnet, magnetic detection element, adjustment yoke) of the magnetic sensor.

FIG. 4 is a diagram showing a shape and an arrangement relationship of main constituent elements (a permanent magnet, a magnetic detection element, an adjusting yoke) of a magnetic sensor which is a second example of the present invention.

FIG. 5 is a diagram showing a shape and an arrangement relationship of main constituent elements (a permanent magnet, a magnetic detection element, an adjusting yoke) of a magnetic sensor which is a third example of the present invention.

FIG. 6 is a diagram showing a shape and an arrangement relation of main constituent elements (a permanent magnet, a magnetic detection element, an adjusting yoke) of a magnetic sensor which is a fourth example of the present invention.

FIG. 7 is a diagram showing an operating principle (when not detected) of the magnetic sensor of the present invention.

FIG. 8 is a diagram showing an operating principle (at the time of detection) of the magnetic sensor of the present invention.

FIG. 9 is an exploded perspective view showing a configuration of a conventional magnetic sensor.

[Explanation of symbols]

 10 Base Blocks 21 and 22 Permanent Magnet 30 Magnetic Detection Element 40 Adjustment Yoke

Claims (3)

[Claims] 1. A base block, two permanent magnets arranged so as to sandwich the base block from both sides, and a magnetic detection element arranged at a front end portion of the base block and between the two permanent magnets. A magnetic sensor comprising: 2. The magnetic sensor according to claim 1, wherein an arrangement direction of the two permanent magnets is set to a direction perpendicular to a moving direction of the object to be detected. 3. A relative position between the permanent magnet and the magnetic detection element is adjustable, and an adjustment yoke for adjusting a magnetic field of the permanent magnet is provided behind the permanent magnet so as to be positionally adjustable. The magnetic sensor according to claim 1 or 2.