JPH0353731B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a ferromagnetic magnetoresistive element (MR element).
The present invention relates to a magnetic proximity switch device using a magnetic proximity switch.

[Conventional technology]

Proximity switch devices conventionally used as a main part of positioning devices and detection devices include reed switch types, high frequency oscillation types, capacitance types, and optical switch types.

These devices have the following advantages and disadvantages. The reed switch type has a simple structure and is inexpensive, but because it has a contact structure, it is vulnerable to external vibrations and shocks, sometimes chattering, and lacks stability.

The high-frequency oscillation type is currently most commonly used because it can detect any metal object with extremely high precision and its detection operation is stable, but it is expensive and there are limits to miniaturization.

The capacitive type can detect all kinds of objects, not just metals, but it requires a large number of components to configure the switch device, making it large and expensive.

The optical switch type can obtain a relatively large detection distance range and can accurately detect the distance to the object to be detected, but on the other hand, the detection operation may become impossible due to the adhesion of dirt such as dust. In addition to having a fatal drawback in terms of operation and functionality, the entire device is large and expensive.

In view of the conventional devices having these many drawbacks, the present applicant previously filed an application for a magnetic proximity switch device shown in FIG. This consists of a cylindrical first permanent magnet 6 and a second permanent magnet 7 with different poles facing each other and a spacer 8 between them to form a magnet body 1, and a bias magnet 3 inside the magnet body 1. This is an integrated body with a magnetoresistive element body (MR element body 2), which is assembled with the same central axis.

This device solves many of the drawbacks of conventional devices, exhibits stable performance comparable to high-frequency oscillation types, and has the excellent effect of being compact and inexpensive to manufacture.

[Problem that the invention seeks to solve]

However, this device also has problems that need to be resolved. As shown in Fig. 11, the magnetic flux distribution is disturbed due to the presence of magnetic substances other than the detection object 5 in the surroundings, and the preset detection distance, which is the distance from the detection object 5, is distorted. That's true. Therefore, as shown in FIG. 12, if there is a magnetic substance in the surrounding area, it is necessary to newly set the detection distance during or after assembly. This detection distance is set by moving the integral body of the bias magnet 3 and the MR element body 2 forward or backward in the axial direction with respect to the magnet body 1, and accordingly, moving the magnet body 1 forward or backward from the assembly part. It is a troublesome thing to have to retreat.

In order to solve these problems, the magnet body 1 and
A method of magnetically shielding the bias magnet 3 and the MR element body 2 by covering the integrated body (hereinafter referred to as the magnetic circuit body 10) with an inexpensive iron shielding material is also considered. However, iron shielding material has a large coercive force, so when a strong magnetic field is applied from the outside, the shielding material becomes magnetized, which changes the magnetic circuit and distorts the detection distance. Since the detection distance must be adjusted while considering the above, problems such as troublesome adjustment occur.

The present invention was devised to solve these problems, and the present invention aims to eliminate the above problems in a magnetic proximity switch device having excellent features such as high performance, small size, and low cost. Take it as a challenge.

[Means for solving problems]

As a means for this purpose, it is composed of a magnet body 1, a ferromagnetic magnetoresistive element body (MR element body) 2, a bias magnet 3, a shield body 4, and a detection body 5.

The magnet body 1 has a ring shape, and includes a first permanent magnet 6 and a second permanent magnet 7, each having a magnetic pole located on its end face.
Different magnetic poles are arranged coaxially and facing each other via a spacer 8 made of a non-magnetic material.

The MR element body 2 is assembled to the magnet body 1 so as to be movable relative to the magnet body 1 along a straight line that is the central axis of the magnet body 1, and has an output terminal connected to a comparator 9.

The bias magnet 3 is integrally assembled to the MR element body 2 in such a manner that a straight line connecting both magnetic poles is perpendicular to the straight line.

The shield body 4 is a magnetic circuit body 1 that is a combination of a magnet body 1, an MR element body 2, and a bias magnet 3.
0, and is cylindrical in shape and made of a material with low coercive force.

The detection body 5 is made of a magnetic material and is movable toward and away from the assembly of the magnetic circuit body 10 and the shield body 4.

Then, the magnetic circuit body 10 and the shield body 4 are housed and assembled in a positional relationship in which their central axes are eccentric.

[Effect]

The basic operation of the device of the present invention is as follows.
The MR element body 2 is located on the central axis (straight line K) of the magnet body 1, and the first permanent magnet 6 and the second permanent magnet 7 are arranged coaxially in a ring shape and have different magnetic poles. By locating the MR element body 2 at a specified location on the coaxial line, as shown in FIG. (see Figure 3b), and the MR element body 2 is essentially
, there is no magnetic force acting along the straight line K from both permanent magnets.

From this state, as shown in FIG.
When the detection body 5, which is a magnetic material, is located near the combination with the MR element body 2, a part of the magnetic flux from the magnet body 1 is drawn toward the detection body 5, and is transferred from the magnet body 1.
The distribution of the magnetic flux acting on the MR element body 2 changes, and the amount of magnetic force acting in either the positive or negative direction along the straight line K increases, and this increase in the amount of magnetic force acting on the MR element body 2 The output voltage increases or decreases (4th
(see figure b). That is, the magnet body 1 and the MR element body 2
The output of the MR element body 2 decreases as the detection body 5 approaches the combination of
The output of the MR element body 2 becomes minimum. This operating characteristic is shown by the characteristic curve in FIG. Therefore, by detecting increases and decreases in the output voltage of the MR element body 2,
This means that the approach of the detection object 5 can be detected.

In addition to this detection operation, the MR element body 2 due to the relative displacement of the magnet body 1 with respect to the MR element body 2
The output characteristic of (output value decreases) is a straight line K
When the magnet body 1 and the MR element body 2 are moved relative to each other along the y-axis, that is, the straight line K, the result is a T' curve shown in FIG. 6b. In other words, if the voltage applied to the MR element body 2 is applied in such a way that the output decreases as the magnetic force increases in the y-axis direction, and increases as the magnetic force increases in the x-axis direction, both permanent The center of the magnet body 1 where the magnetic force acting along the y-axis from the magnet is equal in the positive and negative directions
The maximum output value is reached at a position where O' and the center O of the MR element body 2 are displaced by a distance Δl, and y from this position
An output characteristic is drawn in which the output voltage value of the MR element body 2 decreases as the displacement along the axis, that is, the straight line K increases.

The change in the output value of the MR element body 2 due to this change in displacement and the change in the distance L due to the approach and separation of the detection body 5 from the combination of the magnet body 1 and the MR element body 2 described above. Since the change in the output value is almost the same, the displacement amount l is set in advance to set the output value of the MR element body 2 to a constant value, and from this state, the decrease in the output of the MR element body 2 due to the approach of the detection object 5 can be detected. By knowing this, detection of the detection object 5 can be achieved.

However, the magnet body 1 shown in Fig. 3 and the MR
Only in combination with the element body 2, it is not possible to cause magnetic force to act on the MR element body 2 in the x-axis direction, and therefore the maximum output value of the MR element body 2 cannot be made greater than zero [V]. Therefore, the comparator 9 cannot detect an increase or decrease in the output voltage value of the MR element body 2. Therefore, the bias magnet 3 is integrally assembled to the MR element body 2 in advance. This bias magnet 3 always acts on the MR element body 2 with a constant magnetic force in the x-axis direction, so the MR element body 2
When the magnetic force acting along the y-axis is substantially zero, the output value VB due to the magnetic force acting from the bias magnet 3 is as shown by the T curve in FIG. 6b.
will be output.

Therefore, by fixing the displacement l,
This state can be avoided by setting the output value of the MR element body 2 in advance and setting the threshold value V7 of the comparator 9 connected to this MR element body 2 to a value smaller than this output value V6. Therefore, when the detector 5 approaches the combination of the magnet 1 and the MR element 2, the magnetic flux from the magnet 1 along the y-axis direction acts on the MR element 2 as described above. As the amount increases, the output value of the MR element body 2 begins to decrease from the output value V6. When the detection object 5 approaches a certain distance, the output value of the MR element body 2 becomes smaller than the threshold value of the comparator 9.
Therefore, the comparator 9 changes its output level, and the approach of the detection object 5 is detected by this change in the output level of the comparator 9.

As described above, the basic function of the detection operation by the device of the present invention is that the threshold value V of the comparator 9 is set to a constant value.
7, and changes in the output value of the MR element body 2 due to the approaching and separating of the detecting body 5. The change in the output value of the MR element body 2 due to the approach and separation of the detection object 5 is as follows.
Since it changes along a certain linear line according to the displacement of the detection object 5, the detection object to be detected can be changed by appropriately changing the difference between the preset threshold value V7 and the output value V6. 5, that is, the detection distance L can be freely set and changed.

The device of the present invention has an extremely small MR element body 2.
Since it is composed of a comparator 9, a magnet body 1 which can be sufficiently miniaturized, and a bias magnet 3, the whole can be made extremely compact, and the number of component parts is small, making assembly and manufacturing easy. Moreover, since each component is inexpensive, the entire device can be manufactured at low cost.

A major feature of the device of the present invention is that, as shown in FIG. 7, by shielding the magnetic circuit body 10 with a shield body 4 made of a material with a small coercive force, the magnetic flux is reduced as shown in the figure. Therefore, even if a magnetic substance is present in a portion other than the detection surface, the magnetic flux distribution is not disturbed by the magnetic shielding by the shield body 4, and the detection distance does not change. Therefore, even if it is assembled into a machine made of magnetic material, the detection distance will not change due to its magnetism. or,
As described above, since this shield body 4 has a small coercive force, it does not become magnetized and disturb the magnetic flux unlike the conventional shield body, and thus does not affect the detection distance.

Further, in the present invention, the magnetic circuit body 10 and the shield body 4 are housed and assembled in a positional relationship in which their central axes are eccentric, so that adjustment for setting the detection distance can be easily performed. . 8 and 9 show the MR element body 2 in a state where the magnetic circuit body 10 and the shield body 4 are assembled in an eccentric posture.
The bias of the magnetic flux distribution from the magnet body 1 acting on the magnet body 1 is shown by the slope of the magnetic force vector.
Since the magnetic flux applied to the MR element body 2 is tilted in the direction of the shield body 4 with which the magnet body 1 is in contact, it is biased counterclockwise in FIG. 8 and clockwise in FIG. The magnetic force vector in the axial direction becomes larger.

The detection distance is set using these properties. That is, when the shield body 4, which is a magnetic material, is attached to the magnetic circuit body 10 having a fixed detection distance, the aforementioned detection distance will be distorted, but this discrepancy will cause the magnetic circuit body 10 to It can be adjusted by moving it along the circumferential direction. For example, if the magnetic force vector is tilted in the y-axis direction and the output from the MR element body 2 is reduced, if the magnetic circuit body 10 and the shield body 4 are assembled in the posture shown in FIG. 9, the magnetic force vector will be tilted in the x-axis direction. , the output value from the MR element body 2 increases, and the detection distance is thereby adjusted. On the other hand, if the output value of the MR element body 2 increases, assemble both of them in the posture shown in Figure 8 and tilt the magnetic force vector in the y-axis direction.
The output from the MR element body 2 is reduced, thereby adjusting the detection distance.

In this way, the detection distance can be adjusted using the magnetic circuit body 10.
This can be done by simply moving the shield body 4 along the circumferential direction of the inner circumferential surface of the shield body 4, so the reference plane for measuring the detection distance does not change. This makes it necessary to move the integral body of the bias magnet 3 and the MR element body 2 in the axial direction in order to adjust the detection distance as in the conventional case.
The problem of changing the reference plane and making adjustment extremely difficult and troublesome has been solved.

〔Example〕

An embodiment of the present invention is shown in FIGS. 1 and 2. FIG.
In this embodiment, the magnetic force of the second permanent magnet 7 is made larger than that of the first permanent magnet 6, and the MR
The position along the straight line K where the amount of magnetic force acting on the element body 2 in the positive and negative directions along the y-axis is equal is largely biased toward the first permanent magnet 6.

Moreover, the connection of the MR element body 2 to the power supply 13 is as follows.
The output value when no external magnetic force is acting on the MR element body 2, that is, the unbalanced voltage is set to be 0 [V]. In this manner, by setting the unbalanced voltage of the MR element body 2 to 0 [V], the output voltage value VB by the bias magnet 3 can be easily and accurately set. In FIG. 6, the threshold value V7 of the comparator 9 is 0 [V]
Therefore, the position setting of the MR element body 2 along the straight line K with respect to the magnet body 1 is such that the output value V6 of the MR element body 2 due to this position setting is the output value VB.
is smaller than V7, but larger than threshold V7.

When setting the output value V6 of the MR element body 2, if the displacement position of the MR element body 2 with respect to the magnet body 1 is set near point a in FIG.
Because the output value of the MR element body 2 becomes a value lower than the threshold value V7 due to the slight influence of When set near the corresponding point b, the magnetic influence of the detection object 5 is not large.
Since it is not possible to make the output value of the MR element body 2 lower than the threshold value, the detection object 5 does not come close enough to the MR element body 2, that is, unless the distance L becomes small. cannot be detected, so the detection range can be made smaller.

Various methods can be considered for assembling the magnetic circuit body 10 to the shield body 4, but an elastic material (for example, sponge, etc.) may be inserted between the magnetic circuit body 10 and the inner surface of the shield body 4 as the assembly material 11. When the magnetic circuit body 10 is elastically assembled to the shield body 4, the magnetic circuit body 1 for setting the detection distance is assembled.
A slight movement of 0 can be easily performed. Once the detection distance is set, it is preferable to fix the position with adhesive or the like.

In this embodiment, a case body 12 made of a non-magnetic material and having a capped cylinder shape is fitted onto the outer surface of the shield body 4, but by doing so, the mounting location of the device of the present invention is made of a magnetic material. In this case, since a gap equal to at least the thickness of the case body 12 is formed between the magnetic body and the device of the present invention, the influence of the magnetic body can be further reduced.

〔Effect of the invention〕

As described above, the present invention adds a shield body with a small coercive force to the central axis of the magnetic circuit body in the magnetic proximity switch device previously applied for by the present applicant, which has excellent features such as high performance, small size, and low cost. Since they are assembled in a staggered manner, the effects of external magnetism are eliminated, further improving performance.

In addition, since the detection distance can be set by moving the magnetic circuit body circumferentially around the inner surface of the shield, unlike conventional devices, it is necessary to move the magnetic circuit body in the axial direction. It has many excellent effects, such as solving the problem of difficult and troublesome adjustment of the detection distance.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention;
FIG. 2 is a front sectional view of the same. Figure 3a shows the MR of the magnet.
FIG. 3B is an explanatory diagram showing the mode of action of magnetic force on the MR element body, and FIG. 3B is an explanatory diagram showing the direction and magnitude relationship of the magnetic force acting on the MR element body. FIG. 4a is an explanatory diagram for explaining the influence of the detecting body on the action of the magnetic force of the magnet body on the MR element body, and FIG. 4b is an explanatory diagram showing the direction and magnitude relationship of the magnetic force acting on the MR element body. Fifth
The figure is a characteristic diagram showing the changing characteristics of the form of magnetic force exerted on the MR element body by the detecting body shown in FIG. 4.
FIG. 6 explains the operating characteristics of the present invention, a
is an explanatory diagram showing the displacement form of the MR element body with respect to the magnet body, and b is an explanatory diagram showing the detection operation characteristics. FIG. 7 is an explanatory diagram showing the flow of magnetic flux in one embodiment of the present invention. FIG. 8 and FIG. 9 are explanatory diagrams showing the relationship between the assembly position of the magnetic circuit body and the shield body and the direction of the magnetic vector. FIG. 10 is a sectional view showing a device previously filed by the applicant. FIG. 11 is an explanatory diagram showing the flow of magnetic flux with respect to the external magnetic body in the device. FIG. 12 is a sectional view showing the device assembled to a magnetic body. Explanation of symbols, 1: Magnet body, 2: MR element body,
3: bias magnet, 4: shield body, 5: detection body, 6: first permanent magnet, 7: second permanent magnet, 8:
Spacer, 9: Comparator, 10: Magnetic circuit body, 1
1: Assembly material, 12: Case body, 13: Power supply,
m: central axis of magnetic circuit body, n: central axis of shield body,
K: Straight line, l: Displacement, L: Distance, V6: Output value, V7: Threshold, O, O': Center.

Claims (1)

[Claims] 1. A first permanent magnet 6 and a second permanent magnet 7, which are ring-shaped and have magnetic poles located on their end faces, are coaxially connected via a spacer 8 made of a non-magnetic material and have different magnetic poles. A magnet body 1 is arranged to face each other, and a power source is attached to the magnet body 1 so as to be relatively displaceable along a straight line that is the central axis of the magnet body 1, and whose output terminal is connected to a comparator 9. a magnetic magnetoresistive element body (MR element body) 2; a bias magnet 3 integrally assembled to the ferromagnetic magnetoresistive element body 2 in a posture in which a straight line connecting both magnetic poles is orthogonal to the straight line; A magnetic circuit body 10 is a combination of a magnet body 1, a ferromagnetic magnetoresistive element 2, and a bias magnet 3.
a cylindrical shield body 4 made of a material with a small coercive force to accommodate and assemble the magnetic circuit body 10 and the shield body 4; and a detection body made of a magnetic material that is movable toward and away from the assembly of the magnetic circuit body 10 and the shield body 4. 5, a magnetic proximity switch device in which the central axis m of the magnetic circuit body 10 and the central axis n of the shield body 4 are offset. 2. A magnet in which a ring-shaped first permanent magnet 6 and a second permanent magnet 7 with magnetic poles located on the end faces are arranged coaxially with different magnetic poles facing each other with a spacer 8 made of a non-magnetic material interposed therebetween. a ferromagnetic magnetoresistive element body which is assembled to the magnet body 1 so as to be relatively displaceable along the straight line that is the central axis of the magnet body 1, and whose output terminal is connected to the comparator 9; (MR element body) 2; a bias magnet 3 integrally assembled with the ferromagnetic magnetoresistive element body 2 in a posture in which a straight line connecting both magnetic poles is perpendicular to the straight line; and the magnet body 1 and the ferromagnetic A magnetic circuit body 10 which is a combination of a magnetic resistance element 2 and a bias magnet 3
a cylindrical shield body 4 made of a material with a small coercive force to accommodate and assemble the magnetic circuit body 10 and the shield body 4; and a detection body made of a magnetic material that is movable toward and away from the assembly of the magnetic circuit body 10 and the shield body 4. 5, and a case body 12 made of a non-magnetic material for storing and assembling an assembly of the magnetic circuit body 10 and the shield body 4, and a case body 12 made of a non-magnetic material, and a central axis m of the magnetic circuit body 10 and the shield body 4 A magnetic proximity switch device in which the center axis n of the switch is eccentric. 3. A patent claim in which the magnetic circuit body 10 and the shield body 4 are housed and assembled by inserting an assembly material 11 made of an elastic material between the magnetic circuit body 10 and the shield body 4 A magnetic proximity switch device according to item 1 or 2.