JPS6031313Y2 - Non-contact displacement switch - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a non-contact displacement switch using a magnetoresistive element.

A non-contact displacement switch outputs a switch signal (for example, a TTL signal) that takes two states (on and off) depending on the displacement, and since it has no mechanical contacts, there is no contact wear or chattering, making it extremely reliable. It has the characteristic of high durability and is beginning to be used as a switch element such as keyboard switches and proximity switches.

Furthermore, in addition to simply detecting distance displacement, pressure,
It is also considered to have a wide range of applications as a sensor that detects changes in physical quantities such as flow rate, temperature, and strain by first converting them into displacement.

As one such non-contact displacement switch, one using a ferromagnetic magnetoresistive element (hereinafter abbreviated as MR element) is known.

The MR element is a ferromagnetic magnetoresistive film (hereinafter abbreviated as MR film)
This is a magnetic sensing element that takes advantage of the fact that the electrical resistance of the magnetic field changes depending on the strength and direction of the magnetic field.

A conventional non-contact displacement switch using an MR element is configured to detect changes in magnetic field strength due to linear displacement between the MR element and a permanent magnet.

However, when changing the strength of the magnetic field, so-called Barkhausen noise and hysteresis tend to occur in the MR film, and when the magnetic field is weak, even a relatively small noise magnetic field from the outside can cause chattering and change the operating point. In other words, there is a drawback that the displacement when the switch signal is turned on and off tends to fluctuate.

The inventors of this invention have filed Utility Application No. 54-54277.
No. 154408) discloses a non-contact displacement detector including a non-contact displacement switch as a type thereof, and solves the above-mentioned drawbacks.

This consists of permanent magnets and M
The structure includes an R element and a drive detection circuit that outputs relative displacement as an electric signal, and the strength of the magnetic field acting on the MR film is determined by the strength required for magnetization rotation due to the relative displacement between the permanent magnet and the MR element. While maintaining the above, the magnetic poles of the permanent magnet are configured such that the direction of the magnetic field rotates within a plane parallel to the surface of the permanent magnet facing the MR element (hereinafter referred to as the opposing surface).

As a result, unlike non-contact displacement detectors that use conventional MR elements, the resistance change of the MR film is continuous and smooth, making it possible to create a highly reliable non-contact displacement detector without chattering or malfunction. There is.

This non-contact displacement detector can obtain an analog output according to displacement, but by configuring the drive detection circuit to obtain a switch signal that simply takes two states, it can be operated without chattering as it is. This is a highly reliable non-contact displacement switch with stable points.

However, the non-contact displacement switch obtained in this way also has the disadvantage that the possible displacement range, that is, the operating range, is limited, and when used with a larger displacement, it is necessary to avoid complicating the magnetic field configuration and drive detection circuit. I can't do it.

An object of the present invention is to provide a non-contact displacement switch that is highly reliable, has a simple configuration, and can provide an arbitrary operating range.

That is, the non-contact switch of the present invention includes a permanent magnet and an MR element that are linearly displaced relative to each other, and a drive detection circuit that outputs an on or off switch signal in accordance with this relative displacement. However, the MR film of the element and the opposing surface of the permanent magnet are almost parallel, and the MR element has an MR
In order to ensure that the direction of the magnetic field acting on the membrane rotates on the inner surface of the membrane, if there is a boundary between opposite magnetic poles on the opposing surfaces, the area other than the boundary, and if there is a single magnetic pole, the area near the edge is relatively , and the strength of the permanent magnet is at least strong enough to magnetize and rotate the can film at the position where this and the gripping element intersect,
Further, the drive detection circuit includes an MR element output detection circuit having a hysteresis characteristic having a value smaller than the peak value of the can element output.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 schematically shows the configuration of the non-contact displacement switch of the present invention.

This basically consists of a can element 1, a permanent magnet 2, and a drive detection circuit 3, and when the permanent magnet 2 and the MR element 1 are linearly displaced relative to each other, the It outputs an on or off switch signal.

Since the displacement of either the MR element 1 or the permanent magnet 2 is completely equivalent, the following description will be made assuming that the MR element 1 is displaced in the X direction.

The MR element 1 in this example has a bridge configuration of four striped MR films formed on a substrate.

An enlarged view is shown in Fig. 2. Four striped films 22 and electrode terminals 2 with current directions perpendicular to each other are formed on the substrate 21.
3, 24, 25°26 are formed.

Supply voltage ■ between electrode terminals 23 and 24.

When M is applied, the potential difference between electrode terminals 25 and 26 becomes M
R element output VMR is obtained.

As is well known, the saturation magnetic field, that is, the can element output V
When the magnetic field H8 that saturates the MR is applied in the direction of the angle θ, the MR element output VMR is V28=Onichij.

It is expressed as 2°.

Furthermore, when no magnetic field is applied, it becomes almost zero.

Here, α is the so-called resistance change rate of the MR film 22,
The angle θ is an angle whose reference direction is a direction 27 that is 45° with the direction of the stripes of each film 22.

In this way, as the magnetic field H rotates in the direction, the element output V smoothly changes V0α (peak value).
In reality, even a magnetic field that causes a change of about 70% of Voα can cause a sufficiently smooth change, and this is defined as the strength sufficient to rotate the magnetization.

In FIG. 1, the MR element is displaced on a displacement line 5 along the reference direction (X direction).

In this example, the permanent magnet 2 is a plate-like base magnetized in the thickness direction, and the entire opposing surface is one magnetic pole (N pole or S pole), and the displacement line 5 is at the right angle vertex. It is arranged near the edge of the magnetic pole.

Thereby, the magnetic field 4 rotates along the X-axis on the displacement line in a plane parallel to the opposing surface.

The drive detection circuit 3 supplies the MR element 1 with a voltage V. supply,
This is a circuit that detects the can element output VMR and outputs an on/off electrical signal.
V) (has a so-called hysteresis characteristic, and is also provided with an initial setting circuit 7 that sets the state (on or off) when the power is turned on.

Next, the operation of this non-contact switch will be explained.

(2) The MR element output VMR when the element 1 is displaced between points XA and Xc on the displacement line 5 is shown in FIG.

between XA and X8, and between Xp and X.

The region between xB and X5 is a region where the distance from the permanent magnet 2 is large and the magnetic field strength is weak, while the region from xB to X5 is a region where a rotating magnetic field stronger than the strength required for magnetization rotation is applied.

The drive detection circuit 3 detects this can element output VMR with the MR element output detection circuit 6, and outputs a switch signal that is turned off if the MR element output VMR is equal to or higher than VH, and turned on if it is equal to or lower than -VH.

Therefore, when the MR element 1 is displaced from point X^ toward X(l+), the switch signal is switched from OFF to ON at the point Xo+δ where the MR element output VMR becomes less than -VH for the first time, and after that the seed element output VMR becomes One ■.

It remains on even after the above point, and conversely, when moving from point Xc toward XA, point X becomes equal to or higher than vH for the first time when the MR element output VMR becomes higher than vH.

At −δ, the switch signal switches from on to off, and VMR
It is maintained as it is even if it becomes below VH.

In this way, the switch signal can be turned on and off only at points X±δ within a given distance of displacement.

The non-contact displacement detector of Utility Model Application No. 54-54277 cited above had a configuration similar to that shown in FIG. 1, and used the region between point Xc and point XE where a rotating magnetic field could be obtained.

That is XA and X8% XF and X. In the region between, the magnetic field strength is weak, so unstable hysteresis output and Barkhausen noise are likely to occur in the MR element output VMR itself, and
This is because the non-contact displacement detector is easily influenced by external noise magnetic fields, reducing the reliability of the non-contact displacement detector.

Therefore, the displacement range of non-contact displacement switches using this switch is limited, and in order to obtain a wider operating range, it is necessary to arrange multiple permanent magnets 2 in series and perform complicated processing with a drive detection circuit. was necessary.

In contrast, in the non-contact displacement switch of the present invention, switching occurs only in the region where the rotating magnetic field is obtained between Xc and xo, while the region between XA and XB and Xp and Xc is the area where the can element outputs. Due to the hysteresis characteristic of the detection circuit 6, there will be no effect unless there is a noise output higher than IVHI, and therefore reliability will not be impaired.

In this way, a non-contact displacement switch has the same reliability as the non-contact displacement detector of Utility Application No. 54-277 cited above, and can set displacement in any range with a simpler permanent magnet configuration. ing.

The magnitude of hysteresis ■8 is MR element output vMR
The MR at points Xo and x5 is larger than its own hysteresis, Barkhausen noise, external noise, etc.
It may be set within a range smaller than the element output VMR peak value.

In addition, if the mechanical vibration is large, the switch may fluctuate between on and off near point Xo, but in that case, the hysteresis V)l is set so that 2δ is larger than the amplitude of this mechanical vibration. By setting this, you can eliminate this flapping.

As a means to realize this hysteresis, for example, the sixth
The circuit shown in figure a is suitable.

This uses a comparator 61 and resistors 64, 65, and 66, and the MR element output VM is connected between input terminals 62 and 63.
R is added, and the potential of the terminal 67 becomes bi-level ■ accordingly.

H and low level V.

It turns on and off between L. Hysteresis VH due to this
As is well known, the size of 2vH= ” (V OL, I V OL ) r
1+r2, and can be set to any value by changing the value r2 of the resistor 66.

However, the approximation is made assuming that the resistance value of the MR element is negligible with respect to rl.

For example, ■ in Figure 3. When setting the peak value of the can element output VMR to the warning color, use r1+r! It is only necessary to set r2 so that it becomes 2.

However, here, the value of (■0) (VOL) is almost the power supply voltage■
0, and the supply voltage of the element.

is equal to . As I have used so far, once it is in operation, it operates as a non-contact displacement switch without any problems, but when the power is turned on, the MR element output VMR is V8.
and -VH, that is, if the MR element 1 is displaced to point XA, Xc, or Xo, it is completely unclear whether the switch signal will be turned on or off.

At that time, you can turn it on or off externally, or
Alternatively, by once displacing the MR element and passing around point Xc or XE, the normal operating state can be achieved.

However, when actually using a non-contact displacement switch, the displacement state is always the same (for example, point XA or XC) when the power is turned on.
In many cases, when the power is turned on, an initial setting circuit 7 is provided that sets the switch state according to the displacement (for example, off for point XA and on for point Xc). be able to solve problems.

To configure such an initial setting circuit, for example, use the circuit shown in FIG.
You only need to connect to either one.

In other words, when the power is turned on, the input terminals 62 and 63 reach almost the full potential, but the potential of the contact 69 rises slowly after that time. In the other case, the potential will drop through the diode 70.

If the terminal 68 is connected to the input terminal 62 in this way, the terminal 67
becomes bi-level V when the power is turned on.

It can be initialized to H, and if connected to the input terminal 63, it can be initialized to low level VOL.

Furthermore, after a certain period of time has elapsed since the power was turned on, the potential of contact 69 becomes ■
.

, the potentials of the input terminals 62 and 63 are reversed, so the initial setting circuit shown in FIG. 6 is separated from the MR element output detection circuit shown in FIG. do not have.

The permanent magnet 2 shown in FIG. 1 is just an example, and the magnetic poles are configured so that the direction of the magnetic field rotates as the permanent magnet is displaced relative to the translation element. All you have to do is have it.

For example, as shown in the specification and drawings of Utility Application No. 54-54277 cited above, the opposing surfaces are rectangular S poles 31 and N poles 32 as shown in FIG. Even if the opposing surfaces are rectangular and have a single magnetic pole, such as the N pole 35, as shown in FIG. displacement line 3
3, 36, 39, that is, the direction of the magnetic field 34, 37, 40 can be rotated in a region that is not on the boundary line between opposite magnetic poles or on the displacement line near the edge of the magnetic pole, and the non-contact displacement switch of the present invention can be rotated. Can be configured.

Furthermore, the MR element 1 shown in FIG. 2 is just an example, and a bridge configuration of four striped MR films is preferable because the offset of the MR element output VMR changes less with temperature. A non-contact displacement switch can be constructed in the same manner by replacing two or three of the four striped MR films with ordinary resistors.

Next, FIG. 5 shows an example in which the non-contact displacement switch of the present invention is applied to a flow rate switch.

This outputs a switch signal that turns on and off depending on the flow rate, and includes a cylinder 41 through which the fluid flows, an inlet 42,
Outlet 43, float 44 enclosed in a cylinder, permanent magnet 45 fixed thereto, oxygen element 46, drive detection circuit 4
7. It is composed of a slide mechanism 48 and a frame 49 that holds the whole.

The float 44 has two protrusions 50 that fit into the groove 51 on the inner surface of the cylinder 41 and connect the float 44 and the permanent magnet 45.
is made so that it does not rotate.

The MR element 46 is similar to that shown in FIG. 2, and the reference direction 27 in FIG. 2 is indicated by an arrow.

This oxygen element 46 is moved up and down by a slide mechanism 48 together with a drive detection circuit 47, and can be fixed at any position.

The permanent magnet 45 is similar to that shown in FIG. 4a,
Opposing surfaces are fixedly magnetized to N and S poles.

The fluid flows from the bottom to the top in the cylinder 41, and the float 44 and the permanent magnet 45 are displaced up and down depending on the flow rate.

When the range of displacement within the cylinder 41 corresponds to that shown in FIG. 3, the times when the permanent magnet 45 is at the lower end and the upper end of the cylinder 41 correspond to X to g Xc in FIG. 53 and the lower side 54 reach the position of the oxygen element 46, respectively, are Xc and XE, and when the center of the permanent magnet 45 and the center of the MR element 46 coincide, is X.

corresponds to When the flow rate is zero, the permanent magnet 45 is the cylinder 41
The oxygen output (MR) is at the lower end of xA in FIG. 3, and the output of the flow rate switch is off.

As the flow rate increases, the permanent magnet 45 is displaced upward, and when it reaches the position of the oxygen element 46 (corresponding to x + δ in Figure 3)
The switch output turns on.

Then, even when the flow rate increases further and reaches the position corresponding to Xp and Xc in FIG. Since the detection circuit has a hysteresis characteristic of VH, the switch output remains on.

In this way, in the case of Utility Application No. 54-54277 cited above, in which only the displacement region in which the magnetic field of the permanent magnet 45 rotates is used, the size of the permanent magnet 45 is approximately the distance between the upper side 53 and the lower side 54 of the permanent magnet 45. However, by providing a hysteresis characteristic to the MR element output detection circuit in the present invention, the flow rate switch can be used in a much wider range (from the upper end to the lower end of the cylinder 41).

The slide mechanism 48 is used to move the MR element 46 up and down to set the critical flow rate for turning it on and off to an arbitrary value.

Furthermore, when such a flow rate switch is used, the flow rate is generally zero when the power is turned on, so the drive detection circuit 47 is provided with an initial setting circuit that turns off the switch output when the power is turned on.

This completely eliminates uncertainty in the switch output when the power is turned on.

This flow rate switch is just one application example of the non-contact displacement switch of the present invention, and if the permanent magnet is made to displace according to temperature and pressure instead of according to the flow rate as in this embodiment, it can be easily sensed. It can be used as a temperature switch or a pressure-sensitive switch, and if it can be pressed by hand to displace it, it can be used as a so-called key switch.

Furthermore, if a permanent magnet is made to make one reciprocation for each unit flow rate of gas such as propane gas or city gas or liquid such as water, by counting the number of switches, it is possible to create a model different from this application example. It can also be used as a flow meter.

Ferrite, rare earth magnets, etc. can be used as the material for the permanent magnet, and they can be magnetized into a predetermined shape or used in combination with already magnetized materials to form magnetic poles suitable for carrying out the present invention. be able to.

MR elements are made of silicon or glass with an insulating film formed on the surface.
MR films of single elements such as iron, nickel, and cobalt or alloys containing these as main components are formed on sufficiently smooth insulating substrates such as ceramics using well-known thin film formation techniques such as vapor deposition, sputtering, and plating, as well as resist processing and etching techniques. It is formed and produced by et al.

Typical shapes of can membranes include membrane thicknesses of 200 to 1000A.
A stripe with a width of several μrn or ~100 μm, or a stripe folded multiple times, or a plurality of such stripes arranged so that their directions form an angle between 06 and 900 degrees. concrete numbers,
The length, etc. are determined according to the size of the permanent magnet used, the required resistance value, etc.

For example, 81% NiFe with a film thickness of 500 A and a width of 20μ9.
For the alloy, the strength required for the aforementioned magnetization rotation is about 25 oersted, and the sheet resistance is about 40 oersted.

Note that in the case of an MR element in which the drive detection circuit is formed on the same substrate as the MR film by IC manufacturing technology, silicon is used as the substrate.

The drive detection circuit includes, in addition to the element output detection circuit and the initial setting circuit, a circuit that supplies current to the can element and a circuit that outputs a switch signal to the outside.

Furthermore, the output form of the switch signal can be a normal TTL signal or an open collector output.

Furthermore, in the case of a flowmeter configured to perform one reciprocating relative displacement for each unit flow rate of gas or liquid, the drive detection circuit includes a counting circuit that counts the number of times these switches are made.

As explained above, the non-contact displacement switch of the present invention arranges the magnetic poles of the permanent magnet so that the magnetic field acting on the MR film rotates with the relative displacement between the permanent magnet and the element. In addition, the MR element output detection circuit is provided with hysteresis characteristics.

As a result, the switch is turned on and off in a region where the direction of the magnetic field is rotating, that is, in a region where hysteresis or Barkhausen noise of the can membrane itself does not occur and is not easily affected by external noise magnetic fields, so no chattering occurs. In addition, the operating point does not change, and even in other regions it is not affected by MR membrane hysteresis, Barkhausen noise, or external noise magnetic fields, so it can have a displacement range of any size and is free from malfunctions. It is a highly reliable non-contact displacement switch.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the configuration of the present invention, Figure 2 is a plan view showing an enlarged element, Figure 3 is a waveform diagram of the output VMR of the element, Figure 4 a, b, and c are permanent magnets. Figure 5 is a partially cutaway front view showing an example in which the non-contact displacement switch of the present invention is applied to a flow rate switch, and Figure 6a is a diagram showing another example of M.
FIG. 6 is a circuit diagram showing an example of an R element output detection circuit, and FIG. 6 is a circuit diagram showing an example of an initial setting circuit. In the figure, 1.46 is an MR element, 2.45°72 is a permanent magnet, 3.47 is a drive detection circuit, 4°34, 37, 4
0 is the magnetic field due to permanent magnet, 5, 33.36.39 is MR
6 is the element output detection circuit, 7 is the initial setting circuit, 8, 9, 10, 11 are electrode terminals, 21 is the substrate of the can element, 22 is the MR film, 27.52 is the reference signal of the can element, XA9 XB? Xcg XD?
XE? Xpt xc is a point on the displacement line, 31.32 is the magnetic pole area of the opposing surface of the permanent magnet, 35 is the opposing surface of the permanent magnet, 41 is the cylinder, 42 is the inlet, 43 is the outlet, 44 is the piece inside the cylinder, 48 is a slide mechanism, 49 is a frame, 50 is a convex portion of the piece, 51 is a groove on the inner surface of the cylinder, 53.54 is the upper and lower sides of the opposing surface of the permanent magnet, 61 is a comparator, and 62.63 is an input terminal. , 64, 65.66 is resistance,
67 and 68 represent terminals, 69 a contact, and 70 a diode.

Claims (1)

[Claims for Utility Model Registration] 1. A permanent magnet and a ferromagnetic magnetoresistive element that are linearly displaced relative to each other, and a drive detection circuit that outputs a switch signal that takes on two types of states depending on the relative displacement. The ferromagnetic magnetoresistive film of the ferromagnetic magnetoresistive element is substantially parallel to the opposing surface of the permanent magnet facing the ferromagnetic magnetoresistive film, and the ferromagnetic magnetoresistive element is configured to include the When a boundary between opposite magnetic poles exists on the opposing surface so that the direction of the magnetic field acting on the ferromagnetic magnetoresistive film rotates within the film plane of the ferromagnetic magnetoresistive film, a region other than on the boundary; In the case of a single magnetic pole, the vicinity of its edge is relatively displaced, and the strength of the permanent magnet magnetizes the ferromagnetic magnetoresistive film at the position where the permanent magnet and the ferromagnetic magnetoresistive element intersect. A non-contact displacement switch having a strength sufficient to rotate the switch, wherein the drive detection circuit has a hysteresis value smaller than a peak value of the output of the ferromagnetic magnetoresistive element. 2. When the power is turned on, the permanent magnet and the ferromagnetic magnetoresistive element always have a mechanism to perform a predetermined relative displacement, and the drive detection circuit outputs a switch signal corresponding to the predetermined relative displacement when the power is turned on. The non-contact displacement switch according to claim 1, wherein the drive detection circuit includes an initial setting circuit for setting the same.