JPH0560639A - Differential pressure sensor - Google Patents

Abstract

PURPOSE:To prevent peeling of a diaphragm by always applying a high pressure to a higher side of the diaphragm which is more resistive to pressures by means of a high pressure selecting valve and preventing the pressure of a lower side from becoming higher than that of the higher side. CONSTITUTION:A pressure oil C from an input port 4 is introduced to the lower side of a diaphragm 1, and also guided to a valve member 12 of a high pressure selecting valve through a branching path. A pressure oil D from an input port 9 is sent to the upper side of the diaphragm 1 through the position where the member 12 is arranged. The pressures of the pressure oils C, D are applied to the member 12. The position of the member 12 is determined by the relationship, large or small of the pressure oils C, D. When the pressure of the pressure oil D is larger than that of the pressure oil C, the member 12 is positioned at the lower position, thereby applying the pressure oil D to the upper surface of the diaphragm 1 and the pressure oil C to the lower surface of the diaphragm 1. The state is maintained as the normal state. Meanwhile, when the relationship of the pressures is inverse, the member 12 is located at the upper position, so that the high pressure of the oil C impressed to the upper surface of the diaphragm 1. Accordingly, even if a high pressure is applied to the lower resistant side, the diaphragm 1 can be prevented from being separated from a main body 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential pressure sensor, and more particularly to a differential pressure sensor suitable for measuring a difference in pressure oil inside a hydraulic system used as a drive device for civil engineering machines and construction machines. Is.

[0002]

2. Description of the Related Art In principle, there are a strain gauge method and a reactance method as detection methods of conventional differential pressure sensors. Figure 3
Shows a structure of a typical differential pressure sensor configured by a strain gauge method. In FIG. 3, reference numeral 31 is a diaphragm, and the peripheral portion of the lower surface of the diaphragm 31 is joined to the lower body member 32 with an adhesive 33 or the like. Alternatively, diffusion bonding can be used as the bonding means. Reference numeral 34 is a main body upper member. The lower body member 32 and the upper body member 34 include an O-ring 35.
It is in the state of being fitted by interposing. Each of the main body lower member 32 and the main body upper member 34 has input ports 35 and 36 in the central axis portion thereof, and by these input ports,
Different pressure oils are introduced into the cavities 37 and 38, and are applied to the upper surface (or front surface) and the lower surface (or back surface) of the diaphragm 31. When pressure is applied to the pressure receiving portion of the diaphragm 31, the pressure receiving portion is deformed according to the pressure, and strain is generated inside the diaphragm.

FIG. 4 is an enlarged sectional view of the essential part of the diaphragm 31. An insulating film 40 is formed on the upper surface of the diaphragm 31, and on the insulating film 40,
Further, four polycrystalline silicon films 41 having a strain gauge function are formed. Reference numeral 42 is an electrode wiring functioning as an electric wiring. The strain gauge 41 and the electrode wiring 42 form a Wheatstone bridge circuit. Reference numeral 43 is a passivation film for protecting the strain gauge and the like.

According to the structure of the differential pressure sensor described above, when different pressures are applied to the upper surface and the lower surface of the diaphragm 31 and the diaphragm 31 is distorted, the strain gauge 41 can measure the difference between the two pressures. .. A signal processing circuit is additionally required for measuring the differential pressure, but it is omitted in the illustrated example.

[0005]

In the conventional differential pressure sensor composed of one diaphragm, the diaphragm 31 is fixed to one part of the main body with an adhesive 33 or the like on one side thereof. According to this fixing structure, in the diaphragm 31, the pressure resistance of the surface side A on which the adhesive 33 is provided is weak,
The opposite surface side B has a characteristic that the pressure resistance is strong. That is, when the pressure on the surface side A is higher than the pressure on the surface side B by a predetermined amount, the diaphragm 31 may be peeled off from the main body. On the surface side B, even if the pressure becomes high, the structure has a high pressure resistance, so that no problem occurs.

An object of the present invention is to provide a differential pressure sensor having a structure in which a single diaphragm is used and pressure is applied to both surfaces of the diaphragm to measure the differential pressure. It is to provide a differential pressure sensor that prevents the above.

[0007]

DISCLOSURE OF THE INVENTION A differential pressure sensor according to the present invention comprises a diaphragm which receives pressure from both front and back surfaces and one side of which is joined to a main body, and a strain gauge which is formed on one surface of the diaphragm. A thin film portion including, a signal related to the pressure output from the thin film portion is input through an electric wiring portion, and an electric circuit portion for signal processing, and a protective film for protecting the thin film portion are provided, and both surfaces of the diaphragm are provided. Assuming that the sensor is a differential pressure sensor that measures the difference in applied pressure, a high pressure selection valve is provided so that high pressure is always applied to the side with high pressure resistance of both sides of the diaphragm. In the above configuration, the high pressure selection valve is preferably a shuttle valve. Further, as another aspect, the differential pressure sensor according to the present invention is premised to be the differential pressure sensor described above, and both sides of the diaphragm are distinguished into a high pressure resistant side and a low pressure resistant side based on the mounting structure thereof. When the pressure applied to the low pressure side becomes higher than the pressure applied to the high pressure side, it has an introduction mechanism for introducing the high-pressure fluid to the high pressure side, It is configured to mutually cancel the pressure applied to both sides of the diaphragm.

[0008]

The differential pressure sensor according to the present invention has a structure in which a passage through which different pressures are introduced is provided on each of the front surface and the back surface of the diaphragm, and a high pressure selection valve is provided between the two passages. Here, it is assumed that the front surface side has high pressure resistance and the back surface side has low pressure resistance. When the pressure applied to the front surface is high and the pressure applied to the back surface is low, the normal state is maintained. When the pressure relationship is reversed and the applied pressure on the back surface side becomes higher than the applied pressure on the front surface side, the high pressure selection valve operates and the high pressure on the back surface side is applied to the front surface side. Thus, even if a high pressure is applied to the side of the diaphragm having low pressure resistance, the diaphragm can be prevented from peeling off from the main body.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a vertical cross-sectional view of an essential part of a differential pressure sensor according to the present invention, and FIG. 2 is a diagram in which the differential pressure sensor shown in FIG. 1 is represented by a hydraulic circuit symbol. In this embodiment, the pressure oil will be described as an example, but other pressure fluid may be used instead of the pressure oil. In FIG. 1, 1 is a diaphragm, and 2 is a main body to which a differential pressure sensor is assembled. The diaphragm 1 has, for example, a disc shape, and is fixed to the protruding mounting portion 2 a of the main body 2. The diaphragm 1 has an adhesive 3 on the pedestal of a recess 2b formed inside the upper side of the mounting portion 2a.
(Or diffusion bonding). An input port 4 and a passage 5 are formed in the body 2. The pressure oil A is introduced through the input port 4 and the passage 5 to the fixed position of the diaphragm and applied to the lower surface of the diaphragm 1 in the figure.

According to the above-described mounting structure of the diaphragm 1, in the drawing, the upper surface side has high pressure resistance and the lower surface side has low pressure resistance.

Reference numeral 6 denotes a pressing member, which is the above-mentioned mounting portion 2a.
And has a space 7 that keeps the upper part of the diaphragm 1 open. The pressing member 6 is attached to the attachment portion 2a of the main body 2 via the O-ring 8A in a fitted state. Also in the pressing member 6, the input port 9 and the passages 10a and 10b are formed. The passage 10a is
It communicates with the branch passage 5 a of the main body 2. An O-ring 8B is arranged around the communicating portion between the passage 10a and the passage 5a.

Reference numeral 11 is a shuttle valve, and 12 is a valve member. The valve member 12 is disposed in the void 13 and the void 13
It is arranged so that it can be moved. Input port 9 and passage 10a,
10b leads to the vacant space 13, respectively. Valve member 12
The void 7 located above the diaphragm 1 is configured to communicate with either the input port 9 or the input port 4 depending on the position. The shuttle valve 11 is attached to a required position of the pressing member 6. Shuttle valve 11
The O-rings 14, 15, 16 are respectively provided at the joints between the pressing member 6 and the pressing member 6 where sealing is required.
Is provided. In the space 13, the valve member 12 moves up and down in the figure. In this space 13, valve seats 17 and 18 for receiving and supporting the valve member 12 are arranged.

In the above-mentioned structure, the pressure oil C supplied from the input port 4 is introduced into the void formed under the diaphragm 1 and is introduced into the valve member 12 via the branch passage. be introduced. Further, the pressure oil D supplied from the input port 9 is introduced into the void on the upper surface side of the diaphragm 1 in principle via the location of the valve member 12. In the valve member 12 of the shuttle valve 11, the pressure by the pressure oil C and the pressure by the pressure oil D are applied, and the position of the valve member 12 in the space 13 is determined by the magnitude relation between the two pressures.
Normally, it is assumed that the pressure of the pressure oil C is lower than the pressure of the pressure oil D. In this case, since the pressure of the pressure oil D is higher than the pressure of the pressure oil C, the valve member 12 is located on the lower side. In this pressure relationship, the pressure of the pressure oil C is applied to the lower surface of the diaphragm 1, and the pressure of the pressure oil D is applied to the upper surface thereof. As a result, the diaphragm 1 measures the difference between the pressure applied to the upper surface side and the pressure applied to the lower surface side by the differential pressure detection unit formed on the upper surface thereof. It can be said that the diaphragm 1 is in a normal state in which a relatively low pressure is applied to the lower side of the diaphragm 1 having a low pressure resistance and a relatively high pressure is applied to the upper side of the diaphragm 1 having a high pressure resistance.

Next, when the pressure of the pressure oil C becomes larger than the pressure of the pressure oil D for some reason, the pressure of the pressure oil D is applied to the lower surface of the diaphragm 1 in a swaying manner as in the above case. At the same time, the valve member 12 is pushed up and set to the upper position, and the pressure of the pressure oil C is also applied to the upper surface of the diaphragm 1. Thus, when the pressure of the pressure oil C becomes higher than the pressure of the pressure oil D, the action of the shuttle valve 11 prevents the high pressure from being applied to the lower surface side of the diaphragm 1 having low pressure resistance. A high pressure is applied to the upper surface of the diaphragm 1 to cancel the pressure from the lower surface side. By producing such an action, the diaphragm 1 is configured to be prevented from peeling off from the main body 2 when a high pressure is applied to the low pressure resistance side of the diaphragm 1.

As described above, the shuttle valve 11 operates as a high-pressure selection valve that functions so as not to become the high-pressure side on the surface having low pressure resistance of the diaphragm 1 in relation to the pressure applied to both the front and back surfaces of the diaphragm 1. To do. The high pressure selection valve having a similar function is not limited to the shuttle valve.

FIG. 2 is a circuit diagram showing a hydraulic circuit that produces the above-mentioned action. The same reference numerals are given to the elements described in FIG. Reference numeral 20 represents a differential pressure sensor body.

Although not described in detail, the structure of the differential pressure detecting portion including the strain gauge formed on the upper surface of the diaphragm 1 is the same as that of the conventional differential pressure sensor described above.

The measured output of the differential pressure sensor is as follows. When the pressure of the pressure oil D is higher than the pressure of the pressure oil C,
When the pressure oil D is applied to the upper surface of the diaphragm 1 and the pressure oil C is applied to the lower surface of the diaphragm 1, the differential pressure detection unit detects and outputs the difference between the two pressures. When the pressure of the pressure oil C is higher than the pressure of the pressure oil D, the diaphragm 1
Since the same pressure of the pressure oil C is applied to the upper surface and the lower surface, no differential pressure is produced and the differential pressure detected is zero.

[0019]

As is apparent from the above description, according to the present invention, different pressures are applied to the front and back surfaces of a single diaphragm, and two pressures are applied by the pressure detecting portion provided on one surface. A differential pressure sensor configured to measure a difference, comprising:
In a differential pressure sensor that has a high pressure side and a low pressure resistance side that is fixed to the main body using one surface, the pressure applied to both the front and back sides of the diaphragm is compared to determine the applied pressure on the low pressure resistance side of the diaphragm. Since the high pressure selection valve is provided so as not to be higher than the other, it is possible to prevent the diaphragm from being damaged or peeled off from the main body.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a structure of a differential pressure sensor according to the present invention.

FIG. 2 is a circuit diagram showing a hydraulic circuit of a differential pressure sensor.

FIG. 3 is a vertical cross-sectional view showing a typical structure of a conventional differential pressure sensor.

FIG. 4 is a cross-sectional view showing a main structure of a diaphragm.

[Explanation of symbols]

 1 Diaphragm 2 Main body 3 Adhesive 4 Input port 6 Holding member 9 Input port 11 Shuttle valve 12 Valve member

Front page continuation (72) Inventor Hisagi Hashimoto, 650 Kintatecho, Tsuchiura, Ibaraki Prefecture Tsuchiura Plant, Hitachi Construction Machinery Co., Ltd. Tsuchiura factory

Claims (3)

[Claims] 1. A plate member which receives pressure from both sides of the front and back surfaces and one side of which is joined to a main body, a thin film portion including a strain gauge formed on one surface of the plate member, and a pressure output from the thin film portion. A differential pressure sensor for inputting a signal relating to the signal through an electric wiring section, having an electric circuit section for signal processing, and a protective film for protecting the thin film section, and measuring a difference in pressure applied to both surfaces of the plate material. A differential pressure sensor, characterized in that a high pressure selection valve is provided so that a high pressure is always applied to a side having high pressure resistance of the both sides of the plate material. 2. The differential pressure sensor according to claim 1, wherein the high pressure selection valve is a shuttle valve. 3. A plate member which receives pressure from both sides of the front and back surfaces and one side of which is joined to the main body, a thin film portion including a strain gauge formed on one surface of the plate member, and a pressure output from the thin film portion. A differential pressure sensor for inputting a signal relating to the signal through an electric wiring section, having an electric circuit section for signal processing, and a protective film for protecting the thin film section, and measuring a difference in pressure applied to both surfaces of the plate material. , Both sides of the plate are distinguished into a high pressure resistant side and a low pressure resistant side based on the mounting structure,
When the pressure applied to the low pressure resistance side becomes higher than the pressure applied to the high pressure resistance side, the plate material has an introduction mechanism for introducing the high pressure to the high pressure resistance side. A differential pressure sensor characterized by mutually canceling the pressure applied to both sides.