JPH05142076A - Differential pressure sensor and its diaphragm - Google Patents

Abstract

PURPOSE:To realize highly accurate detection with excellent linearity and reduce the size by providing the film formation section for pressure detection, which can be manufactured at the same time, on the side-face sides opposed to respective pressure receiving faces of at least two protruding and distorted parts in a sensor which senses two different pressures to measure the difference between two pressures. CONSTITUTION:A differential pressure sensor 1 can be manufactured in such a way that a diaphragm 1A will be composed of one kind of metallic member and two protruding and distorted parts will form the same pressure sensing plane on the diaphragm IA under the same processing condition. For example, the processing can be performed by using an end mill that is adjusted to equalize the depths of two drills and holes 6 and 7. Further, the drilling the holes 6 and 7 to form two protruding and distorted parts 2 can be performed under the same temperature condition and at the same processing accuracy. Thus, the depths of the holes 6 and 7 will become identical, resulting in equalizing respective thicknesses of the parts 2 and the sensitivities of respective parts 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 a diaphragm thereof, and more particularly to a differential pressure sensor suitable for detecting a differential pressure of each part of a hydraulic circuit of a hydraulic system incorporated in a civil engineering machine or a construction machine and the diaphragm thereof. Regarding

[0002]

2. Description of the Related Art An example of a conventional differential pressure sensor is as follows. First, as a typical first configuration, two pressure sensors that detect a single pressure are prepared, different pressures are detected by each of these pressure sensors, and the difference between them is calculated to obtain the differential pressure. It is an example configured to. This pressure sensor includes a portion that guides pressure, a strain-generating portion that is deformed by the pressure, and a pressure-detecting film-forming portion that detects the applied pressure based on the deformed state of the strain-generating portion. The film forming unit for pressure detection is provided with a strain detection unit of a predetermined pattern made of semiconductor. As a second configuration, two different pressures are applied to both front and back surfaces of one plate-shaped diaphragm, and when the diaphragm is deformed according to the pressure difference between the two pressures, the deformed state is This is an example configured to perform detection based on the pressure detecting film forming portion formed on one surface. In the pressure detecting film forming section, a plurality of strain gauges are used to detect the pressure or the differential pressure.

[0003]

In the configuration example in which two pressure sensors are used to measure the differential pressure, since the respective pressure sensors are manufactured separately, they cannot be made completely identical to each other. The pressure detection characteristics do not become the same. Therefore, since it is not the difference between the two pressures detected based on the same detection characteristic, the accuracy of the calculated differential pressure is lowered, and the linearity of the detection signal with respect to the actual pressure difference is not good. Therefore, an adjustment circuit is required to match the detection characteristics of the pressure sensors, but this increases the cost of the product. Furthermore, since a configuration that incorporates two pressure sensors must be adopted, there is a problem in that the device cannot be downsized.

In a differential pressure sensor constructed by using both sides of a single diaphragm as pressure receiving surfaces, one pressure oil or the like is directly applied to the side of the diaphragm surface on which the pressure detecting film forming portion is formed. It is necessary to sufficiently protect the film forming portion for pressure detection. However, as a practical problem, the pressure detection film formation unit cannot be completely protected, and as a result, the reliability of the detection function of the pressure detection film formation unit decreases, and the reliability of the sensor itself decreases. May occur. Furthermore, since the signal take-out wire for taking out the detection signal connected to the film forming unit for pressure detection is to be wired in the pressure oil, it may be affected by the pressure oil and cut. There is a problem in terms of reliability.

From the above viewpoints, when manufacturing a differential pressure sensor having high practicality, when two pressure detecting parts are included,
The pressure detection characteristics of these pressure detection parts are basically the same as the structure without any special adjustment circuit after fabrication, and stable after long-term continuous use. It is desired that the differential pressure is detected with good detection characteristics, the structure is not damaged, and the operation reliability is high.

In the manufacture of a differential pressure sensor, a pressure detecting member, which is a metal body, is machined to form a thin strained portion, and a semiconductor film forming technique is applied to the film forming surface of this strained portion. Therefore, the film forming portion for pressure detection must be formed. In this manufacturing process, high alignment accuracy is required.

An object of the present invention is to provide a practical small-sized differential pressure sensor which has a good detection characteristic linearity, a high detection accuracy, and a high operational reliability.

Another object of the present invention is to provide a diaphragm having a structure which is structurally high in pressure detection accuracy and which can accurately and easily align the positions of various parts in the manufacturing process.

[0009]

A differential pressure sensor according to the present invention is a differential pressure sensor which is sensitive to two different pressures and which measures the difference between the two pressures, and which has at least two strain generating portions. A member is provided, and a pressure detection film-forming portion that is manufactured at the same time is provided on the opposite side of each pressure receiving surface of the two strain generating portions. In the above configuration, preferably, the pressure detection member is formed by one member. In the above configuration, preferably, the pressure detection member is a support member having at least two holes, and a plate-like member joined to an end surface of the support member having the two holes opened so as to close the opening of each hole. Composed of. In the above structure, preferably, the areas of the pressure receiving surfaces of the two strain-flexing portions are the same. In the above configuration, the areas of the pressure receiving surfaces of the two strain-flexing portions are preferably different. In the above configuration, preferably, the opposite side surface of the strain-flexing portion forms a single plane. In the above structure, preferably, the two strain-flexing parts are formed at positions close to each other. The diaphragm according to the present invention is formed of a single plate-shaped member and has at least two strain-generating portions by forming at least two thin-walled portions, and the film-forming surface of these strain-generating portions is a single surface. is there. In the above structure, a step is formed around the film-forming surface, and two step alignment parts having a predetermined positional relationship are provided by utilizing this step.

[0010]

In the differential pressure sensor according to the present invention, two pressure sensitive parts are formed based on the same manufacturing condition and the film formation by the same manufacturing batch under the condition that the positions are relatively close by using the same pressure detecting member. As a result, it is possible to provide two pressure sensitive portions having very similar pressure detection characteristics. Therefore, it is not necessary to provide a correction circuit for adjusting the characteristics of the two pressure sensitive parts. The diaphragm according to the present invention is a diaphragm used exclusively for the differential pressure sensor described above, and is for realizing the differential pressure sensor. Since the two strain generating portions are formed by one pressure detecting member, the deformation characteristics of the two strain generating portions can be made substantially the same. Further, since the two alignment portions having a right angle positional relationship are formed by utilizing the step formed on the upper surface of the diaphragm, the diaphragm and the differential pressure sensor can be manufactured by performing accurate alignment. ..

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 3 show a first embodiment of the present invention,
1 is a cross-sectional view showing a state in which the differential pressure sensor is assembled to the main body device, FIG. 2 is a plan view showing only the differential pressure sensor in an enlarged scale,
FIG. 3 is a vertical sectional view of the differential pressure sensor.

1 to 3, reference numeral 1 is a differential pressure sensor according to the present invention. The differential pressure sensor 1 is a diaphragm 1A.
And a film forming portion 1B for detecting a pressure formed at a predetermined position on the upper surface of the diaphragm 1A. The diaphragm 1A is a pressure detection member that is formed by machining a plate-shaped metal material having required strength and thickness, and that has at least two strain generating portions. Reference numeral 2 is a strain-flexing portion, which has a function of being deformed by receiving pressure on the lower surface in the figure.

In the differential pressure sensor 1 according to this embodiment, the diaphragm 1A is formed by one member. The differential pressure sensor 1 has a circular planar shape as shown in FIG.
As shown in FIG. 3, on the upper surface of the differential pressure sensor 1, a slight step 5 is formed between the circular central portion 3 and the annular peripheral portion 4. The surface part corresponding to the central part 3 is formed as a single face. Then, at the position corresponding to the central portion 3, two holes 6 and 7 having, for example, a circular cross section are formed from the lower surface side. In this embodiment, the holes 6 and 7 have the same diameter. Holes 6 and 7 are preferably formed in the central portion 3 at positions symmetrical with respect to a straight line 8 passing through the center point 3a.
By forming the holes 6 and 7, the strain generating section 2 having a required thickness is formed. The two strain generating portions 2 are formed under the same conditions. The holes 6 and 7 are passages that guide the pressure of the pressure oil or the like to the pressure receiving surface of the strain-flexing portion 2. When viewed from the holes 6 and 7, the surface of the hole bottom is the pressure receiving surface of the strain-flexing portion 2.

The film forming portion 1B is formed so as to correspond to the upper surface of the differential pressure sensor 1, especially the central portion 3. Film forming unit 1B
Detects the pressure applied based on the generated strain when the strain generating section 2 receives pressure and is deformed. The film forming unit 1B is manufactured as follows. First, an insulating film of SiO ₂ is formed on the upper surface of the diaphragm 1A by using, for example, plasma CVD. A plurality of semiconductor strain gauges made of polysilicon are further formed thereon in a predetermined pattern. The pattern of strain gauges is positioned by applying lithographic techniques. The plurality of strain gauges are electrically connected.
This electrical connection forms a Wheatstone bridge circuit. A Cr / Au film is used as wiring for electrical connection in the film forming unit 1B. In order to take out the signal detected by the film forming unit 1B to the outside, an intermediate substrate (not shown) is usually provided, and a wire is drawn to the outside through this intermediate substrate.

FIG. 2 shows an arrangement state of a plurality of strain gauges 9. The strain gauges 9 form a set of four strain gauges and are arranged on the upper surface of the strain-flexing portion 2 corresponding to the holes 6 and 7. This surface is the surface opposite to the pressure receiving surface of the strain generating section 2.

Reference numeral 10 denotes a member to which the differential pressure sensor 1 is attached. The attached member 10 is, for example, a wall portion of a machine including a hydraulic device. This mounted member 1
At 0, a recess 11 for forming the pressure sensor 1 is formed. The attached member 10 is formed with two pressure introduction holes 12 and 13 opened at the bottom of the recess 11. The pressure introducing hole 12 communicates with the hole 6, and the pressure introducing hole 13 communicates with the hole 7. Pressure A is applied to one of the strain-flexing parts 2 via the pressure introducing hole 12 and the hole 6. In addition, the pressure introducing hole 13
The pressure B is applied to the other strain-generating portion 2 via the hole 7 and the hole 7. In this way, different pressures A and B are applied to the two strain generating portions 2, respectively.

At the bottom of the recess 11, pressure introducing holes 12, 1 are provided.
Ring-shaped grooves are formed around the circumference of the groove 3, and O-rings 14 and 15 are arranged in these grooves, respectively. The O-rings 14 and 15 contact the lower surface of the differential pressure sensor 1 and exert a sealing action.

Reference numeral 16 is a cap-shaped pressing member, and the differential pressure sensor 1 arranged in the recess 11 of the mounted member 10 is
The peripheral portion 4 is pressed down from above and fixed with bolts 17.

The differential pressure sensor 1 mounted on the mounted member 10 receives the two pressures A and B by the respective strain generating portions 2 and deforms them to detect the two pressures.
Two pressures are transmitted as electric signals to the processing circuit, and pressure A,
Calculate the differential pressure of B.

In the differential pressure sensor 1 of the first embodiment described above, the diaphragm 1A is formed of one metal member, and the two strain-generating portions 2 are formed on this diaphragm 1A under the same processing conditions to form the same pressure-sensitive plane. Can be formed as follows. Eg 2
The machining can be performed using two drills and an end mill adjusted so that the depths of the holes 6 and 7 are equal. Further, under the same processing conditions, the holes 6 and 7 for forming the two strain-generating portions 2 can be processed under the same temperature condition, whereby the processing accuracy of the two strain-generating portions 2 can be improved. Can be the same. In this way, the depths of the holes 6 and 7 can be made the same so that the respective thicknesses of the strain-flexing portions 2 can be made equal and the sensitivities of the strain-generating portions 2 can be made equal.

Since the film-forming surface on which the film-forming portion 1B is formed on the upper surface of the diaphragm 1A is also polished by the same polishing operation, the surface accuracy of the upper surfaces of the two strain-flexing portions 2 which are pressure-sensitive portions is the same. Therefore, it becomes easy to form the same film on the upper surface of the strain generating section 2.

In addition, in forming the pressure detecting film forming portion 1B on the upper surface of each of the two strain generating portions 2, the strain generating portions are set so that the steps such as film formation and lithography are set as close to each other as possible. Since it is possible to perform the same series of film forming processes on the two locations, the pressure detection characteristics of the film forming unit 1B configured by a plurality of strain gauges can be made very similar. Since the temperature characteristics that greatly affect the detection accuracy of the strain gauges can be made the same, the pressure detection characteristics of the two strain generating sections 2 can be made substantially the same. From this,
A correction circuit for adjustment is unnecessary, and the configuration of the signal processing circuit in the subsequent stage is simplified.

In the embodiment shown in FIG. 4, the central pressing portion 16a is provided on the inner ceiling portion of the pressing member 16 in the structure of the first embodiment described above. The central pressing portion 16a has, for example, a rod shape. According to the pressing member 16 including the central pressing portion 16a, the central portion of the upper surface of the differential pressure sensor 1 attached to the main body device 10 can be pressed from above by the central pressing portion 16a, and thus the peripheral portion of the differential pressure sensor 1 can be pressed. Combined with the action of pressing 4, the entire differential pressure sensor 1 can be pressed uniformly. As a result, the pressure sensitivity of the two strain-generating parts 2 of the differential pressure sensor 1 can be further increased.

In the above embodiment, the diaphragm 1A has two
The two holes 6 and 7 for forming the one strain-flexing part 2 had the same diameter. As a result, the pressure detection characteristics of the two strain generating sections 2 can be made the same.

On the other hand, as another embodiment, as shown in FIG. 5, a diaphragm 1A constructed so that the areas of the strain-flexing portions 2a and 2b are made different by making the diameters of the holes 6a and 7a different is considered. be able to. Here, the diameters of the strain generating portions 2a and 2b having a circular planar shape are C ₁ and C, respectively.
₂ (C ₁ > C ₂ ). As a result, in the pressure / output characteristic of FIG. 6, two output characteristics are determined for each of the diameters C ₁ and C ₂ . This differential pressure sensor is used as follows. The same pressure P is applied to the strain-flexing portions 2a and 2b.
_{When 1} is applied, as is apparent from the output characteristics of FIG. 6, the output v ₁ is generated in the strain generating portion 2a and the output v ₁ ′ is generated in the strain generating portion 2b. When the output v ₁ ′ is converted on the strain-flexing portion 2a side, it corresponds to the pressure P ₁ ′. Utilizing the above relationship is effective for detecting the load of a single rod type cylinder or the like as shown in FIG. 7, for example. That is, in the single rod type cylinder, since the pressure receiving areas are different between the rod side and the bottom side, the pressure is different even if the loads on both sides are balanced. Therefore, if the above-mentioned differential pressure sensor is applied and the bottom side is connected to the strain-flexing portion 2a having the diameter C ₁ and the rod side is connected to the strain-generating portion 2b having the diameter C ₂ , the ratio of P ₁ ′ / P ₁ is By adjusting the ratio of the pressure receiving areas of the cylinders, it is possible to directly compare the two applied pressures with the output value of the differential pressure sensor. The differential pressure sensor can be applied to valve spools having different diameters.

Next, the differential pressure sensor 1 shown in FIGS. 2 and 3.
The manufacturing process of will be described. FIG. 8 is a detailed plan view of the differential pressure sensor 1 in consideration of the manufacturing process. A structural difference from the example shown in FIG. 2 is that the step 5 is used to form the two alignment portions 21 and 22. These two alignment portions 21 and 22 are preferably formed in a positional relationship orthogonal to each other. By providing such alignment portions 21 and 22, the positions of the two strain generating portions 2 and the position of the strain gauge 9 are determined with reference to these. In this way, in the diaphragm 1A of the differential pressure sensor 1, the holes 6 and 7 for introducing pressure and the plurality of strain gauges 9 for detecting the deformation of the strain-flexing portion 2 can be formed in accurate alignment. This makes it possible to make the sensitivities of the two strain-flexing parts 2 that are pressure sensitive parts substantially equal.

With reference to FIGS. 9 to 15, the alignment section 21,
A manufacturing process of the differential pressure sensor 1 using 22 will be described. First, a step 5 is formed on the upper surface of the plate member 31 which is the material of the diaphragm.
And simultaneously form the alignment portions 21 and 22. The two alignment parts are in a positional relationship orthogonal to each other (see FIGS. 9 and 1).
0). Next, holes 6 and 7 for introducing pressure are formed on the lower surface side of the plate member 31 with reference to the alignment portions 21 and 22. By forming the holes 6 and 7, it becomes 2 as thin part.
The strain generating portion 2 is formed at the location. Thus, the diaphragm 1A is formed as shown in FIG. After that, an insulating film 32 is formed on the upper surface of the diaphragm 1A, and, for example, a poly (polycrystalline) silicon film 33 is formed thereon. Further, a resist film 34 is formed on the polycrystalline silicon film 33. Reference numeral 35 in FIG. 13 is a glass mask for forming a plurality of strain gauges that are pressure detection units. Reference numerals 37 and 38 are strain gauge patterns formed on the glass mask 35. 39,
Reference numeral 40 is a registration mark. Alignment marks 39, 40 and strain gauge patterns 37, 38 on the glass mask 35
Are the alignment portions 21 and 2 of the diaphragm 1A, respectively.
2 and the holes 6 and 7 for introducing pressure formed in the diaphragm 1A. Figure 1
Alignment portions 21, 22 of diaphragm 1A as shown in FIG.
The alignment marks 39 and 40 of the glass mask 35 are aligned with each other, and exposure and development are performed to manufacture a resist pattern. Next, the polysilicon film 33 is etched to form a strain gauge 9 as shown in FIG. The pressure detecting film forming portion 1B formed by the strain gauge 9 is accurately formed on the upper surface of the strain generating portion 2. After that, electrode wiring connecting the strain gauges 9 is formed. The electrode wiring is formed by forming a film to be an electrode wiring, forming a resist film on the film, exposing it using a glass mask on which a pattern of the electrode wiring is formed, and performing etching to form a pattern of the electrode wiring. Form. Finally, a passivation film is formed on the entire upper surface of the film formation portion.

A second embodiment of the differential pressure sensor according to the present invention,
This will be described with reference to FIGS. 16 and 17. The differential pressure sensor of this embodiment is formed of two members. One member is the sensor base body 51 in which holes 52 and 53 for introducing pressure are formed, and the other member is a plate-like member 54 including a portion that serves as a strain-flexing portion. The sensor base 51 has a cylindrical shape in appearance, and the two holes 52 and 53 are parallel to the axis. The plate member 54 has a disc shape. The plate member 54 is joined to one end surface of the sensor base body 51. A portion of the plate member 54 corresponding to each opening of the two holes 52 and 53 of the sensor base body 51 serves as a strain generating portion. Thus, the differential pressure sensor according to this embodiment has two
It is formed by two members. The material is the same as that of the first embodiment.

A modified embodiment is as follows. In the above embodiment, the number of strain generating portions is two, but the number may be more. Further, the positional relationship between the two alignment portions can be set to an angle other than a right angle.

[0030]

As is apparent from the above description, the present invention has the following effects. In the differential pressure sensor, at least two strain-generating parts are formed on a single surface and close to each other under the same processing conditions, and a film-forming portion for pressure detection formed on one surface of the two strain-generating parts. Can be manufactured under the same film forming conditions, the pressure detection characteristics of the two pressure detection sensitive parts are the same, and a highly accurate differential pressure sensor with high practicality can be manufactured. The electric circuit section for adjusting the section is unnecessary. Since two pressure sensitive portions are formed on one pressure detecting base portion, the differential pressure sensor can be made compact as a whole. Since two pressure sensitive parts and pressure detecting film forming parts can be manufactured in the same manufacturing batch, the manufacturing process can be simplified and the manufacturing cost can be reduced. When manufacturing a differential pressure sensor using one member, two alignment portions having a predetermined positional relationship are formed by utilizing a step between the central portion and the peripheral portion formed on the upper surface of the diaphragm, By using these alignment parts to align the holes for introducing pressure and the film formation part for pressure detection including the strain gauge, we manufactured a differential pressure sensor with accurate alignment. can do.

[Brief description of drawings]

FIG. 1 shows a first embodiment of a differential pressure sensor according to the present invention,
It is a longitudinal cross-sectional view of a mounted state.

FIG. 2 is a plan view of a differential pressure sensor.

FIG. 3 is a vertical sectional view of only a differential pressure sensor.

FIG. 4 is a vertical sectional view showing a modification of the first embodiment of the differential pressure sensor.

FIG. 5 is a vertical cross-sectional view showing another embodiment of the diaphragm in which the diameters of pressure introducing holes are different.

FIG. 6 is a graph showing each pressure detection characteristic of a strain-flexing part having a different pressure receiving area.

FIG. 7 is an internal structure diagram showing an example of an application device of a differential pressure sensor having pressure introduction holes of different diameters.

FIG. 8 is a plan view showing in detail the shape of the differential pressure sensor.

FIG. 9 is a plan view of a diaphragm base material at an early stage of manufacturing.

FIG. 10 is a vertical cross-sectional view of a diaphragm base material.

FIG. 11 is a vertical cross-sectional view of a diaphragm having a hole for introducing pressure.

FIG. 12 is a vertical cross-sectional view of a state in which various films are formed on the upper surface of the diaphragm.

FIG. 13 is a plan view of a glass mask for producing a strain gauge.

FIG. 14 is a plan view in which a glass mask and a diaphragm are aligned with each other.

FIG. 15 is a plan view of the manufactured differential pressure sensor.

FIG. 16 is a plan view of the differential pressure sensor according to the second embodiment of the present invention.

FIG. 17 is a vertical cross-sectional view of the differential pressure sensor of the second embodiment.

[Explanation of symbols]

 1 Differential pressure sensor 1A Diaphragm 1B Film forming part 2 Straining part 3 Central part 4 Peripheral part 5 Step 6,7 hole 9 Strain gauge 10 Attached member 12, 13 Pressure introducing hole 16 Holding member 16a Central pressing part 21, 22 Position Alignment part 35 Glass mask 39, 40 Alignment mark 51 Sensor base 52 Plate-shaped member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Sakamoto 650 Kazunachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura factory

Claims (9)

[Claims] 1. A differential pressure sensor which is sensitive to two different pressures and measures the difference between the two pressures, wherein at least two.
A differential pressure sensor, comprising: a pressure detecting member having two strain-generating portions, and a pressure-detecting film-forming portion simultaneously formed on the opposite side of each pressure-receiving surface of the two strain-generating portions. 2. The differential pressure sensor according to claim 1, wherein the pressure detection member is formed of one member. 3. The differential pressure sensor according to claim 1, wherein the pressure detection member has a support member having at least two holes, and an opening of each of the holes on an end surface of the support member where the two holes are open. And a plate-like member joined so as to close the pressure difference sensor. 4. The differential pressure sensor according to claim 1, wherein the areas of the pressure receiving surfaces of the two strain-flexing portions are the same. 5. The differential pressure sensor according to claim 1, wherein the areas of the pressure receiving surfaces of the two strain-flexing portions are different from each other. 6. The differential pressure sensor according to claim 1, wherein the opposite side surface of the strain-flexing portion forms a single plane. 7. The differential pressure sensor according to claim 1, wherein the two strain-flexing portions are formed at positions close to each other. 8. A single plate-shaped member, which has at least two strain-generating portions by forming at least two thin-walled portions, and the film-forming surface of these strain-generating portions is a single surface. Diaphragm. 9. The diaphragm according to claim 8, wherein
A diaphragm, wherein a step is formed around the film-forming surface, and two alignment parts having a predetermined positional relationship are provided by utilizing the step.