JPH041449B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic proximity switch device using a ferromagnetic magnetoresistive element. The object of the present invention is to provide a proximity switch that can be used at a low cost.

[Conventional technology]

Proximity switch devices 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.

The reed switch type has the advantage of having a simple structure and low cost, while the high frequency oscillation type can detect all metal objects with extremely high accuracy and has stable detection operation. The capacitive type has the advantage of being able to detect all kinds of objects, not just metals, and the optical switch type has the advantage of being able to detect relatively large objects. This method has the advantage of being able to obtain a range of distances and accurately detecting the distance to the object to be detected.

[Problem that the invention seeks to solve]

However, each of the above-mentioned conventional proximity switch devices has disadvantages in terms of basic operation, function of use, and practical use.

In other words, since the reed switch type is a contact structure, it is susceptible to external vibrations and shocks, and may sometimes cause chattering, ensuring stable and accurate detection operation at all times. There was the inconvenience that it was not always possible to do so.

Furthermore, the high-frequency oscillation type is currently in most use due to its stability and accuracy of detection operation, but there are complaints that it is expensive and there is a limit to miniaturization.

Furthermore, the capacitive type requires a large number of components to construct the switch device, and therefore has the disadvantage of being considerably larger and more expensive than a proximity switch device. be.

The optical switch type has a fatal drawback in terms of its operational function, in that detection cannot be performed due to adhesion of dust and other contaminants, and it also has the disadvantages that the entire device is large and expensive. There is.

In order to eliminate the drawbacks of these reed switch type, high frequency oscillation type, capacitance type, and optical switch type proximity switch devices,
There is a magnetic proximity switch device using a magnetoresistive element disclosed in Japanese Unexamined Patent Publication No. 90745 and Japanese Utility Model Application Publication No. 120239/1983.

The magnetic proximity switch device disclosed in Japanese Utility Model Application Publication No. 60-90745 arranges a pair of permanent magnets in a posture in which the imaginary lines connecting both magnetic poles of each permanent magnet are almost parallel, and the same magnetic poles are oriented in the same direction. one end of both permanent magnets is connected with a ferromagnetic material, and a magnetically sensitive material such as a Hall element is connected between the other end of the permanent magnet on the side that is not connected with this ferromagnetic material. The structure is such that the

The magnetic proximity switch device disclosed in Japanese Utility Model Application Publication No. 60-90745 has the advantage that the detection operation of approaching and separating magnetic bodies is stable and reliable, and the detection response is quick. It has the advantage of being able to manufacture the entire device at low cost and in a small size.

Furthermore, the magnetic proximity switch device disclosed in Japanese Utility Model Application Publication No. 62-120239 includes a circuit board on which electronic components are attached, a magnetoelectric transducer attached to the circuit board, and a magnetoelectric transducer attached to the circuit board. The sensor is configured to include a permanent magnet that causes a magnetic flux that changes depending on the approach of a detection object to act on the magnetoelectric conversion element.

The magnetic proximity switch device disclosed in Japanese Utility Model Application No. 62-120239 has the magnetoelectric transducer and permanent magnet constituting the magnetic proximity switch device mounted on a single circuit board, and electrical connections are also made on this circuit board. Since this is achieved through the process, it has the advantage of improving manufacturing workability and reducing costs.

[Problem to be solved by the invention]

In this way, the conventional magnetic proximity switch device using the above-mentioned magnetoresistive element can exhibit the excellent effects of being inexpensive, small, and manufactured at a lower cost. The magnetic force that acts between multiple permanent magnets acts in a direction that changes their mutual positional relationship, making it difficult to accurately position and fix multiple permanent magnets. In addition to requiring sufficient attention to fixation, achieving immovable and strong fixation of the permanent magnets requires a long working time and a special fixing jig, which poses a problem in that the workability of assembling the device is poor.

Furthermore, since the surface area on the detection surface side is large, the space conditions in which it can be installed and used are greatly limited, and there is a problem in that it cannot be inserted and used in a narrow place.

As mentioned above, since the surface area on the detection surface side is large, it is natural that the permanent magnet used must have a large surface Gaussian amount, which limits the miniaturization of the entire device. There was a problem.

Furthermore, since the entire surface of the magnetoelectric conversion element is exposed to the detection surface, it is easily susceptible to external magnetic influences, and is therefore strongly influenced by the surrounding environmental conditions of the installation location. There was a problem in that the position needed to be reset, which required troublesome and difficult adjustment work at the installation site.

Therefore, the present invention was devised to solve the problems in the prior art described above, and the mutual positional relationship of a plurality of permanent magnets constituting a magnetic proximity switch device is regulated to be constant by the magnetic force of the permanent magnets themselves. The technical challenge is to reduce the surface area on the detection surface side, thereby facilitating assembly work by achieving accurate positioning between the permanent magnets, and achieving sufficient miniaturization. The purpose is to achieve the following.

[Means for solving problems]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to drawings showing one embodiment of the present invention.

The means of the present invention includes a first ring-shaped ring with magnetic poles located on the end surface.
and a magnet body 1 in which second permanent magnets 2 and 3 are arranged coaxially with different magnetic poles facing each other via a spacer 4 made of a non-magnetic material; A ferromagnetic magnetoresistive element (hereinafter simply referred to as MR for simplicity) is assembled so as to be relatively displaceable along straight line K, which is the central axis of
This MR element body 6 has a bias magnet 5 integrally assembled with the straight line connecting both magnetic poles perpendicular to the straight line K; The output of the MR element body 6 Comparator 7 to which the terminal is connected
and a detection body 9 made of a magnetic material that is movable toward and away from the combination of the magnet body 1, MR element body 6, and bias magnet 5.

The reason why the MR element body 6 is displaceable with respect to the magnet body 1 is that by displacing the MR element body 6 with respect to the magnet body 1, the mode of action of the magnetic flux acting from the magnet body 1 to the MR element body 6 can be changed. , since the output of the MR element 6, that is, the resistance value, is to be changed in accordance with the change in the mode of action of this magnetic flux, the assembly posture of the MR element 6 with respect to the magnet 1 is such that both surfaces thereof are aligned with a straight line K. It will be in line with that.

[Effect]

A first permanent magnet 2 and a second permanent magnet arranged on a coaxial core.
Since the permanent magnets 3 have different magnetic poles facing each other via the spacer 4, a magnetic attraction force acts between both the permanent magnets 2 and 3. Therefore, the permanent magnets 2 and 3 Due to their own magnetic force, they maintain their mutual positional relationship and are combined.

The MR element body 6 is located on the straight line K with respect to the magnet body 1, and the first and second permanent magnets 2
and 3 have a ring shape arranged coaxially and have different magnetic poles facing each other, so that the MR element body 6 can be located on a specified line K as shown in FIG. When the permanent magnets 2 and 3 are placed at the same position, the magnetic forces from both permanent magnets 2 and 3 along the straight line K become equal in positive and negative (see Fig. 3b), and the MR is substantially
Magnetic force from both permanent magnets 2 and 3 is not acting on the element body 6 along the straight line K.

From this state, that is, the state in which the magnetic force from the magnet body 1 is not substantially acting on the MR element body 6, as shown in FIG.
When the detection body 9, which is a magnetic material, is located near the combination with the magnetic body, a part of the magnetic flux from the magnet body 1 is drawn toward the detection body 9, and acts from the magnet body 1 on the MR element body 6. The action distribution of the magnetic flux changes, and the amount of action of the magnetic force in either the positive or negative direction along the straight line K increases, and this increase in the amount of action of the magnetic force causes the MR element body 6 to
The output voltage of is increased or decreased (see FIG. 4b).
That is, as the detection object 9 approaches the combination of the magnet 1 and the MR element 6 from a distance, the output of the MR element 6 decreases, and the output of the MR element 6 decreases.
When the distance L between the object 9 and the detection object 9 becomes zero, MR
An operating characteristic is drawn as shown by a characteristic curve S in FIG. 5, in which the output of the element body 6 is minimum. By detecting increases and decreases in the output voltage of the MR element body 6, it is possible to detect that the detection object 9 has approached.

In this way, since one end surface side of the first permanent magnet 2 is used as the detection surface, the area of the detection surface of the device is sufficiently small. Furthermore, since the MR element body 6 is arranged within the cylindrical magnet body 1, the magnetic force from the first permanent magnet 2 and the second permanent magnet 3 acts extremely effectively on the MR element body 6. As a result, permanent magnets 2 and 3 with low magnetic force are sufficient. Furthermore, since the MR element body 6 is disposed within the cylindrical magnet body 1 in this way, the magnet body 1 exerts a magnetic shielding effect against magnetic force from the outside. be less affected.

In addition, apart from this detection operation, the output characteristics of the MR element body 6 due to the relative displacement of the magnet body 1 with respect to the MR element body 6 are determined along the y-axis (MR element Among the magnetic forces acting on the body 6, when the magnetic force in the direction along the y-axis increases, the output value of the MR element body 6 decreases) along a straight line K.
When the magnet body 1 and the MR element body 6 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 6 is applied so that the output decreases as the magnetic force in the y-axis direction increases, and the output increases as the magnetic force increases in the x-axis direction, both permanent The maximum output value is reached at a position where the center O' of the magnet body 1 and the center O of the MR element body 6 are displaced by a distance Δl, where the magnetic forces acting along the y-axis from the magnets 2 and 3 are equal in the positive and negative directions. An output characteristic is drawn in which the output voltage value of the MR element body 6 decreases as the displacement from this position along the y-axis, that is, along the straight line K, increases.

The change in the output value of the MR element body 6 due to the change in the amount of displacement l and the change in the distance L due to the approach and separation of the detection body 9 from the combination of the magnet body 1 and the MR element body 6 described above. Since the change in the output value is exactly the same (the polarity of the output voltage is reversed in Figures 5 and 6b), the displacement l is set in advance to keep the output value of the MR element 6 at a constant value. , and by knowing from this state that the output of the MR element 6 decreases due to the approach of the detecting object 9, detection of the detecting object 9 can be achieved.

However, the magnet body 1 shown in FIG.
Only in combination with the MR element body 6, the MR element body 6
Since it is not possible to apply a magnetic force in the x-axis direction to the MR element body 6, and therefore the maximum output value of the MR element body 6 cannot be greater than zero [V], the increase or decrease in the output voltage value of the MR element body 6 is compared. Although it cannot be detected by the MR device 7, a bias magnet 5 is integrally attached to the MR element 6 in advance, and this bias magnet 5 causes a certain amount of force in the x-axis direction to be applied to the MR element 6. Since the magnetic force is always acting on the MR element body 6, when the magnetic force acting along the y-axis is substantially zero, the MR element body 6 is moved away from the bias magnet 5 as shown by the T curve in FIG. 6b. The output value VB will be output due to the acting magnetic force of .

Therefore, by fixing the displacement l,
By setting the output value V6 of the MR element body 6 in advance and setting the threshold value V7 of the comparator 7 connected to this MR element body 6 to a value smaller than this output value V6, this can be achieved. From the state, the detection object 9 is
As explained above, when the MR element 6 approaches the MR element 6, the amount of magnetic flux acting on the MR element 6 along the y-axis direction from the magnet 1 increases, causing the output value of the MR element 6 to change from the output value V6. begins to decline. When the detection object 9 approaches to a certain distance, the output value of the MR element body 6 becomes smaller than the threshold value V7 of the comparator 7, and therefore the comparator 7 changes the level of its output. The approach of the detection object 9 is detected by a change in the output level of the comparator 7.

In this way, the detection operation of the detection object 9 by the device of the present invention is performed using the threshold value V of the comparator 7 set to a constant value.
This is achieved by changing the output value of the MR element body 6 due to the detection body 9 relative to the detection body 9.
The change in the output value of the MR element body 6 due to the detection body 9
The position of the detection object 9 to be detected can be determined by appropriately changing the difference between the preset threshold value V7 and the output value V6. In other words, the detection distance L can be changed freely.

In addition, since it is composed of an extremely small MR element body 6 and a comparator 7, a magnet body 1 that can be sufficiently miniaturized, and a bias magnet 5, the whole can be made extremely compact, and the components Since the number of parts is small, it is easy to assemble and manufacture, and since each component is inexpensive, the entire device can be manufactured at low cost.

〔Example〕

In the case of the embodiment shown in FIGS. 1 and 2, the magnet body 1 has a second permanent magnet 3 having a larger magnetic force than the first permanent magnet 2, so that the MR element body 6
The position along the straight line K where the amount of action of the magnetic force in the positive and negative directions along the y-axis acting on the magnetic force is equal is made to be largely biased toward the first permanent magnet 2. In addition, the connection of the MR element body 6 to the power supply 8 is such that the output value when no external magnetic force is acting on the MR element body 6,
That is, the unbalanced voltage is set to be 0 [V]. In this manner, by setting the unbalanced voltage of the MR element body 6 to 0 [V], the output voltage value VB by the bias magnet 5 can be set easily and accurately. In the embodiment shown in FIG. 6, the threshold value V7 of the comparator 7 is set to 0 [V], so the position of the MR element body 6 along the straight line K with respect to the magnet body 1 is set at this position. The output value V6 of the MR element body 6 is set to be smaller than the output value VB, but larger than the threshold value V7.

When setting the output value V6 of the MR element body 6, if the displacement position of the MR element body 6 with respect to the magnet body 1 is set near point a in FIG.
The output value of the MR element body 6 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 detecting object 9 is not large.
Since the output value of the MR element body 6 cannot be lower than the threshold value V7, unless the detection object 9 approaches the MR element body 6 sufficiently, that is, the distance L
Since the detection object 9 cannot be detected unless it becomes small, the detection range can be made small.

For example, the magnet body 2 is a ring-shaped body with an inner diameter of 4 mm, an outer diameter of 7 mm, and a thickness of 1 mm, and the surface magnetic force is 100 Gauss, and the magnet body 3 has an inner diameter of 4 mm, an outer diameter of 7 mm, and a thickness of 3.5 mm.
A ring-shaped body with a surface magnetic force of 400 Gauss,
The bias magnet 5 has a rectangular parallelepiped shape with a width and depth of 2.5 mm in the direction along the straight line connecting both magnetic poles, a thickness of 1 mm, and a surface magnetic force of 100 Gauss, and the comparator 7
With the threshold value V7 set to 0mV, the relationship between displacement l and detection distance is as follows: when displacement l is 1.5 mm, the detection distance is 3 mm, and when displacement l is 1.7 mm, the detection distance is
3.5 mm, the displacement l was 1.8 mm, and the detection distance was 4 mm, achieving highly accurate detection capability.

〔Effect of the invention〕

As is clear from the above description, the present invention can fully exhibit the accurate and reliable detection function of an approaching detection object, can make the entire device extremely compact, and can be manufactured at an extremely low cost. Furthermore, the distance at which the object is to be detected can be set easily, over a wide range, and accurately.
In addition, since assembly can be achieved easily and accurately, manufacturing costs can be sufficiently reduced, and since the surface area of the detection surface is extremely small and is less susceptible to external magnetic influences, it can be used in narrow spaces. It can be installed without being influenced by the surroundings, and has excellent effects such as not requiring troublesome adjustment operations at the installation site. It exhibits many excellent effects.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of the device of the present invention and also showing the electrical connection procedure. Figure 2 shows a basic example of the configuration of a combination of a magnet body, an MR element body, and a bias magnet. Figure 2a is a front view, Figure 2b is a side view, and Figure 2c is a side view. FIG. FIG. 3a is an explanatory diagram showing how the magnetic force of the magnet body acts 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. Figure 4a is an explanatory diagram for explaining the influence of the detection object on the magnetic force of the magnet body on the MR element body, and Figure 4b is an explanatory diagram showing the direction and magnitude relationship of the magnetic force acting on the MR element body. It is. Fifth
The figure is a characteristic line diagram showing the changing characteristics of the form of action of the magnetic force on the MR element body by the detecting body shown in FIG. 4. Fig. 6 is for explaining the operating characteristics of the embodiment shown in Fig. 1, Fig. 6a is an explanatory diagram showing the displacement form of the MR element body with respect to the magnet body, and Fig. 6b is an explanatory diagram showing the detection operation. FIG. 3 is an explanatory diagram showing characteristics. Explanation of the symbols: 1; magnet body; 2; first permanent magnet; 3; second permanent magnet; 4; spacer; 5; bias magnet; 6; ferromagnetic magnetoresistive element (MR
element body), 7; comparator, 8; power supply, K; straight line,
l: Displacement amount, L: Distance, V6: Output value, VB: Output value, V7: Threshold value, O, O': Center.

Claims (1)

[Claims] 1 The first ring is shaped like a ring and has magnetic poles located on the end surface.
and a magnet body 1 in which second permanent magnets 2 and 3 are arranged coaxially with different magnetic poles facing each other via a spacer 4 made of a non-magnetic material; A ferromagnetic magnetoresistive element body 6 is assembled so as to be relatively displaceable along a straight line K, which is a central axis, and a straight line connecting both magnetic poles of the ferromagnetic magnetoresistive element body 6 is perpendicular to the straight line K. A comparator 7 to which the bias magnet 5 integrally assembled with the output terminal of the ferromagnetic magnetoresistive element body 6 is connected.
and a detection body 9 made of a magnetic material and provided movably toward and away from the combination of the magnet body 1, the ferromagnetic magnetoresistive element body 6, and the bias magnet 5.