JPH06100515B2 - Pressure sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor, and more particularly to a pressure sensor based on a change in magnetic permeability of an amorphous magnetic metal foil fixed to a diaphragm serving as a pressure receiving portion of a fluid to be detected. The present invention relates to a pressure sensor adapted to detect the pressure of a fluid to be detected.

(Prior Art) As a sensor for detecting pressure in automobile equipment and various industrial machines, detection is performed based on a change in magnetic permeability of an amorphous magnetic metal foil (hereinafter, referred to as an amorphous foil) attached to a diaphragm serving as a pressure receiving portion. A pressure sensor designed to detect the pressure of a fluid has been considered. An example of this pressure sensor will be described with reference to the drawings.

FIG. 6 is a sectional view showing an example of a conventional pressure sensor.

In the figure, a casing 9 molded of a non-magnetic material has an introduction hole 7 for introducing a fluid from a fluid circuit (not shown) such as a hydraulic circuit, a pressure chamber 8 connected to the introduction hole 7, and A diaphragm 2 forming one wall surface of the pressure chamber 8 is formed.

A circular amorphous foil 1 is entirely fixed to the diaphragm 2 by a method such as adhesion.

The bobbin 4 around which the cylindrical core 10 and the rod-shaped core 13 and the sensing coil 5 are wound is inserted into the recess 12 of the casing 9 so as to face the amorphous foil 1, and the cap 6 is screwed onto the casing 9. Fixed by that.

The pressure sensor has a threaded portion 14 through a sealing O-ring 11.
Is attached to the detected part.

In the pressure sensor configured as described above, when the sensing coil 5 is energized, a magnetic flux is generated, and the magnetic flux passes through the core 10, the core 13 and the amorphous foil 1.
When the pressure of the fluid introduced into the pressure chamber 8 changes in this state, the strain amount of the diaphragm 2 and the amorphous foil 1 fixed to this changes. As a result, the magnetic permeability of the amorphous foil 1 changes and the inductance of the sensing coil 5 changes.

The pressure is detected by releasing the change in the inductance as a change in the voltage, for example.

By the way, since the pressure sensor cannot accurately detect the pressure when air is mixed in the fluid to be detected, an appropriate air venting means is provided. In FIG. 6, an air venting means is composed of the screw holder 15 and the screw 16 screwed into the screw holder 15. The screw 16 is fed into the screw 16
The pressure chamber 8 is closed when the tip tapered portion 18 contacts the end portion of the communication hole 17, and the air in the pressure chamber 8 can be discharged by retracting the screw 16.

(Problems to be Solved by the Invention) The above-described conventional pressure sensor has the following problems.

As shown in FIG. 6, in the conventional pressure sensor, the bobbin 4, the sensing coil 5 wound around the bobbin 4, and the stress detecting portion including the tubular core 10 and the rod-shaped core are included in the entire pressure sensor. Is very large in volume.

Furthermore, the output characteristics of the sensing coil 5 may change depending on the temperature of the fluid to be detected and the ambient temperature.
Although not shown in FIG. 6, a temperature compensation coil is generally provided in addition to the sensing coil 5 in order to reduce the influence of this temperature change.

As described above, since the volume of the stress detecting portion occupied by the components is large, if the pressure sensor becomes large in size, it becomes difficult to secure a space for mounting the pressure sensor, and the pressure sensor cannot be installed at a desired position.

An object of the present invention is to solve the above-mentioned problems of the prior art and to downsize the pressure sensor by reducing the volume of the stress detecting portion.

(Means and Actions for Solving the Problems) In order to solve the above-mentioned problems and achieve the object, the present invention provides a surface close to an amorphous foil attached to a diaphragm and parallel to the amorphous foil. A point including an arranged insulating substrate, a spiral sensing coil and a temperature compensating coil which are planarly developed and printed on the substrate, and a yoke arranged in proximity to the sensing coil and the temperature compensating coil. Is characterized by.

In the present invention having the above characteristics, since the sensing coil and the temperature compensation coil (hereinafter, referred to as compensation coil) are arranged in a plane, it is possible to reduce the volume of the stress detection portion occupied in the pressure sensor.

(Example) With reference to drawings, the Example of this invention is described below. FIG. 1 is a sectional view of a pressure sensor showing an embodiment of the present invention, and the same symbols as in FIG. 6 indicate the same or equivalent portions.

In the figure, the stress detector is configured as follows. A substrate 19 is provided in the recess 12 of the casing 9 so as to face the amorphous foil 1. The substrate 19 is a flexible printed board (FPC) or a glass epoxy resin board, and a sensing coil 20 and a compensating coil 21 described later are printed on it. A yoke member 22 made of a high magnetic permeability material is arranged above the substrate 19 in order to increase the inductance of the sensing coil 20 and the compensation coil 21.
Leads 20a, 2 of the sensing coil 20 and the compensation coil 21
1a penetrates a hole (described later) of the yoke material 22 and is drawn out upward.

The substrate 19 and the yoke material 22 are pressed by the collar 23 by screwing the cap 6 into the casing 9 and fixed to the bottom of the recess 12.

Next, the stress detector will be described in more detail. FIG. 2 is an exploded perspective view of the stress detector.

In the figure, the amorphous foil 1, the substrate 19, and the yoke material 22 are inserted into the casing 9 in the direction indicated by the arrow and assembled.

On the substrate 19, a sensing coil 20 and a compensation coil 21 arranged on the outer periphery of the sensing coil 20 are spirally printed.

At the time of assembly, first, the amorphous foil 1 is fixed to the diaphragm 2 of the casing 9 by a method such as adhesion. Next, the substrate 19 is placed on the amorphous foil 1, and the yoke material 22 is further stacked thereon. York material
When stacking 22 on the substrate 19, the lead portions 20a and 21a of the sensing coil 20 and the compensation coil 21 are connected to the holes 20b and 20 of the yoke member 22, respectively.
It is pulled out upward through c, 21b, 21c.

The yoke material 22 is not limited to an integral plate common to the coils 20 and 21, and may be formed of a divided plate corresponding to each of the coils 20 and 21.

FIG. 3 is a perspective view showing an example of a divided yoke material.
The yoke material is formed of an inner yoke material 22a corresponding to the sensing coil 20 and an outer yoke material 22b corresponding to the compensation coil 21.

Further, the printed patterns of the sensing coil 20 and the compensation coil 21 are not limited to the shapes shown in FIG. FIG. 4 shows another example of the printed patterns of the sensing coil 20 and the compensation coil 21. In this embodiment, the sensing coil 20 is printed in the center of the substrate 19, a large number of coils 24 having a small diameter are printed around it, and the coils 24 are connected to form the compensation coil 21.

Next, the operation of this embodiment will be described.

FIG. 7 is a sensing coil based on the strain amount of the amorphous foil 1 and the magnetic permeability of the amorphous foil 1 corresponding to the strain amount.
FIG. 10 is a characteristic diagram showing a relationship with the output voltage of 20 and the compensation coil 21. As shown in the figure, the output voltage increases as the tensile strain due to the tensile stress increases, and the output voltage decreases as the compressive strain due to the compressive stress increases. When the amorphous foil 1 is not distorted, the voltage E0 is output.

Since the output voltage of the sensing coil 20 and the compensation coil 21 exhibits the characteristics as described above, the coil 20 of the present embodiment,
In the arrangement of 21, the following output voltage is detected.

FIG. 5 is a cross-sectional view of an essential part of the stress detecting portion, and the drawing schematically shows the distortion and the like of the diaphragm 2 for ease of explanation.

In FIG. 4A, magnetic circuits F1 and F2 passing through the amorphous foil 1 and the yoke materials 22a and 22b are formed by the lines of magnetic force generated in the sensing coil 20 and the compensation coil 21.
When no detection pressure is applied to the diaphragm 2, that is, when there is no load, an external circuit (not shown) is adjusted in advance so that the output voltage of the sensing coil 20 and the output of the compensation coil 21 both become the voltage value E0. . That is, the difference between the output voltage of the sensing coil 20 and the output voltage of the compensation coil 21 (differential output signal) is adjusted to zero.

When the pressure of the fluid to be detected is applied to the diaphragm 2 as shown in FIG. 6 (b) in the state where the output is adjusted in this way, tensile stress acts on the central portion of the amorphous foil 1 to cause tensile strain, The magnetic flux of the magnetic circuit F1 increases. on the other hand,
Compressive stress acts on the outer peripheral portion of the amorphous foil 1 to cause compressive strain, and the magnetic flux of the magnetic circuit F2 is reduced. As a result, the output voltage of the sensing coil 20 increases and the output voltage of the compensation coil 21 decreases according to the output characteristic. If the differential output signals of the sensing coil 20 and the compensation coil 21 at this time are detected as the pressure of the fluid to be detected, the change in strain amount due to a slight change in pressure can be extracted as a large change in output voltage.

Further, since the differential output signal is detected as the pressure of the fluid to be detected, the influence of the temperature change is canceled and an accurate output with little temperature dependence can be obtained.

In the present embodiment, an example in which the coils 20 and 21 are printed on one side of the substrate 19 is shown, but a similar coil is printed on both sides of the substrate 19 to make a through-hole connection, so that the magnetic field can be increased. The detection sensitivity can be improved. When the coils are printed on both sides of the substrate 1, the sensing coil 20 may be printed on one side and the compensation coil may be printed on the other side.

Further, if a plurality of such substrates 1 are provided and these substrates are laminated, the number of turns of the coil can be increased and the magnetic field can be further strengthened.

The sensing coil 20 and the compensation coil 21 are not necessarily printed on the substrate as in the present embodiment, but for example, an insulating layer may be formed on the yoke material 22 and the coil may be printed on this layer. In short, it suffices to form a layered structure in which a coil is planarly formed by printing between the amorphous foil 1 and the yoke material 22.

Further, instead of the amorphous foil 1, a metal material whose magnetic permeability changes depending on the magnitude of strain is deposited on the diaphragm 2,
Alternatively, it may be applied to form a layer having a predetermined thickness.

By the way, when the amorphous foil 1 or a layer of the metal material equivalent thereto is fixed on the diaphragm 2, the pressure measurement range is expanded by pre-pressing the diaphragm 2 from the pressure chamber 8 side. , The measurement sensitivity is also improved.

That is, when the amorphous foil 1 or the layer of the metal material is fixed under the preload, a compressive strain S may be generated in the amorphous foil 1 or the layer of the metal material without the preload, that is, in the unloaded state. Yes (see Figure 7). As a result, as shown in Fig. 7, the output voltage at no load changes from E0 to EC, the pressure measurement range moves from the tensile strain side to the compression strain side, the pressure measurement range expands, and the measurement sensitivity increases. improves.

(Effects of the Invention) As is clear from the above description, according to the present invention, the volume ratio of the sensing coil and the compensating coil to the pressure sensor can be reduced, so that the pressure sensor can be miniaturized. As a result, the place where the pressure sensor is installed is less limited, and the desired fluid pressure can be detected at any place.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a pressure sensor showing an embodiment of the present invention, FIG. 2 is an exploded perspective view of the pressure sensor, FIG. 3 is a perspective view of a yoke member, FIG. 4 is a perspective view of a substrate, FIG. 5 is a sectional view of the stress detecting portion, FIG. 6 is a sectional view of a conventional pressure sensor, and FIG.
The figure is a characteristic diagram showing the relationship between distortion and output voltage. 1 ... Amorphous foil, 2 ... Diaphragm, 8 ... Pressure chamber,
19 ... Substrate, 20 ... Sensing coil, 21 ... Compensation coil, 22
... York material

Claims (7)

[Claims] 1. A diaphragm that forms one wall surface of a pressure chamber and is elastically deformed by receiving the pressure of a fluid to be detected, an amorphous foil fixed to the diaphragm, and an electrical output signal based on the magnetic permeability of the amorphous foil. In a pressure sensor with a sensing coil for taking out, bring it close to the amorphous foil fixed to the diaphragm,
In addition, an insulating substrate arranged in parallel with the amorphous foil, a spiral sensing coil and a temperature compensating coil which are planarly developed and printed on the substrate, and are placed close to the sensing coil and the temperature compensating coil. A pressure sensor, comprising: a yoke member arranged in a line. 2. The pressure sensor according to claim 1, wherein a sensing coil is arranged in a central portion of the substrate and a temperature compensation coil is arranged in a peripheral portion thereof. 3. The pressure sensor according to claim 1, wherein the compensation coil comprises a plurality of coils. 4. The pressure sensor according to claim 1, wherein the yoke material is formed of one sheet of high magnetic permeability material common to the sensing coil and the temperature compensation coil. 5. The pressure sensor according to claim 1, wherein the yoke material is divided corresponding to the sensing coil and the temperature compensation coil, respectively. 6. The pressure sensor according to claim 1, wherein the sensing coil and the temperature compensation coil are printed on both surfaces of the substrate. 7. The pressure sensor according to claim 1, wherein a plurality of the substrates are laminated.