JPH06180263A - Pressure introducing mechanism of differential pressure sensors - Google Patents

Abstract

PURPOSE:To provide a pressure introducing mechanism for differential pressure sensor using a both-surface pressure receiving type diaphragm where a partitioning structure between a protective fluid and a pressurizing fluid is made to be simple, small-sized and compact and have high degree of design freedom by filling the periphery of differential pressure detecting film forming part with a protective fluid. CONSTITUTION:In a pressure introducing mechanism for differential pressure sensor where a differential pressure signal between two pressures applied on both surfaces of a diaphragm is picked up in a differential pressure detecting film forming section 8 formed on one surface of a both-surface pressure receiving type diaphragm 6a, a protective fluid 10 is filled in the periphery of the section 8 and a magnetic fluid 16 is arranged in the boundary part between the fluid 10 and a pressurizing fluid for partitioning the both. Then a magnet 17 is prepared to hold the fluid 16, which is arranged in a pressurizing fluid introducing route.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure introducing mechanism for a differential pressure sensor, and more particularly, it is suitable for detecting a pressure difference of hydraulic oil in a hydraulic drive system of civil engineering and construction machinery, and various pressures. The present invention relates to a pressure introduction mechanism of a differential pressure sensor suitable for detecting a differential pressure of a fluid.

[0002]

2. Description of the Related Art Conventionally, for example, a hydraulic fluid, which is a pressure medium, is brought into contact with both surfaces of a diaphragm made of metal, and the pressure difference between two hydraulic oils applied to both sides of the diaphragm is formed on one surface. There is a detector configured to detect. The differential pressure detector is formed based on a semiconductor film forming technique and includes a Wheatstone bridge circuit including, for example, four strain gauges. Hereinafter, the Wheatstone bridge circuit is referred to as a bridge circuit, and the differential pressure detection unit is referred to as a differential pressure detection film formation unit. In the film forming unit for detecting the differential pressure, when two strains are applied to the strain-causing portion of the diaphragm, the resistance values of the four strain gauges change in response to the strain, and the output ends of the bridge circuit are changed. A voltage corresponding to the pressure difference is output. In this differential pressure detection film formation unit, a predetermined current is flowing through each strain gauge that is a resistance element in the bridge circuit, and the voltage generated due to the resistance value change of each strain gauge is output from the output end of the bridge circuit. To be done. This output voltage corresponds to the pressure difference between the two hydraulic oils. The voltage signal is taken out by the signal lead wire.

[0003]

A type in which a difference between two pressures is obtained by bringing hydraulic oil into contact with both surfaces of the diaphragm to generate a strain in the diaphragm straining portion generated based on the pressures of the two hydraulic oils. The differential pressure sensor using the double-sided pressure receiving type diaphragm has the following problems.

The first problem is that the hydraulic oil that is in direct contact with the film forming section for differential pressure detection has a chemical attack on the film forming section. The second problem is that the hydraulic oil may contain air. A third problem is that when the pressure fluid to be measured is hydraulic fluid of a hydraulic drive system applied to a construction machine or the like, the hydraulic fluid passing through the hydraulic equipment is a sliding part existing in the hydraulic equipment. Is to contain various metal ions and sometimes water.

The problems associated with the above-mentioned chemical aggression in the pressure fluid, the contained air, metal ions, water content, etc. are caused by the film forming section for differential pressure detection and the signal detected by this film forming section to the outside. We raise the problem of affecting the signal line for taking out. Therefore, conventionally, in order to protect the film forming unit, a protective film is provided to cover the film forming unit. However, the protection film has a limited service life and cannot be completely protected. In addition, no special protection was provided for the signal line for extracting the detection signal.

Therefore, in order to protect the film forming unit for detecting the differential pressure and the signal line for extracting the detection signal, the space around the film forming unit for detecting the differential pressure and the signal line is adversely affected in the film forming unit and the like. And a silicone oil or the like for stably holding those states is filled, and the partition structure between the silicone oil and the hydraulic oil in the hydraulic oil introducing mechanism is simplified.
It is desired that the pressure sensor be formed small and compact so that the pressure of the hydraulic oil is applied to the diaphragm with good responsiveness.

From another point of view, it is desired that the partition structure can be easily assembled and the degree of freedom of design is high.

In view of the aforementioned demands, an object of the present invention is to provide a differential pressure sensor using a double-sided pressure receiving type diaphragm, in which silicon oil is provided around a differential pressure detecting film forming portion formed on one surface of the diaphragm. Adopting a structure that fills with protective fluid such as, the partition structure between this protective fluid and hydraulic oil is simple, small, and compact, and the pressure introduction mechanism of the differential pressure sensor is provided with a high degree of design freedom. To do.

[0009]

A pressure introducing mechanism of a differential pressure sensor according to the present invention forms a differential pressure detecting film forming portion on one surface of a double-sided pressure receiving type diaphragm, and forms the differential pressure detecting film. Section is applied to a differential pressure sensor that takes out a signal relating to the differential pressure between two pressures introduced so as to be applied to both sides of the diaphragm. The protective fluid is filled, the magnetic fluid is arranged at the boundary between the protective fluid and the pressure fluid, and the magnetic fluid is partitioned. In the above configuration, preferably, a magnet for holding the magnetic fluid is provided, and the magnetic fluid is arranged in the introduction passage of the pressure fluid. Further, preferably, two magnets are provided, and the magnetic fluid is arranged in the pressure fluid introduction passage located between these two magnets. The magnetic fluid is formed by coating magnetite fine particles having an average particle diameter of about 10 nm with a surfactant and dispersing them in a floating state.

[0010]

In the present invention, the protective fluid such as silicone oil is filled in the space around the differential pressure detecting film forming portion formed on one surface of the diaphragm to keep the pressure fluid away from the differential pressure detecting film forming portion. The partition structure is formed by not directly contacting the film forming portion and the like, and by interposing a magnetic fluid between the protective fluid and the pressure fluid. According to this partition structure, since the magnetic fluid is used as the partition means, the introduction path of the pressure fluid can be used, and the structure for disposing the magnetic fluid can be made simple, small, and compact.
Further, since the magnet is used to hold the magnetic fluid, the mounting is relatively easy and the mounting position can be easily designed, and the degree of freedom in design is high. Since the partition means is a magnetic fluid, it is possible to maintain good transmissivity when transmitting the measured pressure to the diaphragm and maintain high responsiveness.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 1 is a signal extraction member having a plurality of hermetically sealed portions (not shown). Two
Is a signal lead line fixed to each hermetic seal portion, and a plurality of signal lead lines are provided. The signal lead-out member 1 has a substantially flat columnar shape, and is arranged at an upper position in an accommodating recess 4 having a circular cross section formed in the center of the main body 3. An O-ring 5 is provided between the signal lead-out member 1 and the accommodation recess 4 of the main body 3. The main body 3
Is a wall portion in the vicinity of the main oil passage in the hydraulic equipment.

Reference numeral 6 is a diaphragm member. The diaphragm member 6 has a substantially flat cylindrical shape, and is arranged at the bottom of the housing recess 4 of the main body 3. An O-ring 7 is provided between the diaphragm member 6 and the accommodation recess 4. A thin diaphragm portion 6 a is formed on the diaphragm member 6. The diaphragm portion 6a receives different pressures on its both surfaces and acts as a strain-generating portion that internally distorts based on the difference between the two pressures. A film forming portion 8 for detecting a differential pressure is formed on one surface of the diaphragm portion 6a. This film forming unit 8
Is produced by applying a semiconductor film forming technique. The film forming unit 8 includes, for example, four strain gauges, and these strain gauges are electrically connected so as to form a Wheatstone bridge circuit. Each strain gauge acts as a resistance element in this bridge circuit. Pressure is applied to both sides of the diaphragm portion 6a to cause strain therein, the resistance value of each strain gauge changes correspondingly, and a voltage corresponding to the differential pressure is output to the output end of the bridge circuit. ..

A cylindrical spacer 9 is arranged between the signal lead-out member 1 and the diaphragm member 6. With this spacer 9, the signal lead-out member 1 and the diaphragm member 6
The required space is maintained between and. The structure of the spacer 9 is arbitrary. This space is filled with a protective fluid 10 such as silicon oil or fluorine oil. In addition, for example, an FPC (flexible printed circuit) 11 that electrically connects the output end of the film forming unit 8 and the end of the signal lead-out line 2 is arranged in this space. Therefore, the FPC 11 is placed in the protective fluid 10. According to this structure, the diaphragm member 6 having the film forming portion 8 and the signal lead-out member 1 having the hermetic seal portion are formed in separate steps, and then the output end of the film forming portion 8 and the signal lead-out wire 2 are formed. These are connected by a flexible FPC 11, and the diaphragm member 6 and the signal lead-out member 1 are housed in the housing recess 4 while the spacer 9 is interposed and assembled. Body 3
After assembling each part to, attach the cover member 12,
Secure with a plurality of bolts (not shown).

As described above, according to the above-mentioned structure, the assemblability is improved, the disassembly is facilitated, and the disassemblability is improved. Further, since the protective fluid 10 is filled in the space around the film forming section 8 and the FPC 11, the protection of the portion for detecting the differential pressure signal and the extraction portion can be enhanced, the stability can be enhanced, and the reliability can be enhanced.

The body portion 3 has two pressure introducing holes 13, 14
Are formed. The pressure introducing hole 13 communicates with the pressure introducing portion 15 of the diaphragm member 6, and the pressure introducing hole 14 is
It communicates with the space filled with the protective fluid 10. Different hydraulic oils are introduced into the pressure introducing holes 13 and 14, respectively. One hydraulic oil introduced through the pressure introducing hole 13 is directly applied to one surface of the diaphragm portion 6a of the diaphragm member 6. The other hydraulic oil introduced through the pressure introducing hole 14 applies pressure to the protective fluid 10 via the magnetic fluid 16, and this pressure is then applied to the other surface of the diaphragm 6a.

The magnetic fluid 16 is placed in a portion formed as a passage for introducing hydraulic oil. Reference numeral 17 denotes a ring-shaped permanent magnet, which is preferably attached along the inner wall of the introduction path and embedded in the inner wall. In this example, in particular, the permanent magnet 17 is fixed to the bottom portion of the screw portion 18 using a nipple or the like of a hydraulic component. The magnetic fluid 16 is retained in the space formed as an internal space thereof based on the magnetic action of the permanent magnet 14. The magnetic fluid 16 has a function as a partitioning means between the protective fluid 10 and the hydraulic oil. In this way, it is possible to prevent the operating oil from directly contacting the film forming unit 8 and the FPC 11 and having a bad influence. As the order of assembling, the protective fluid 10 is first filled in a predetermined space, and then the magnetic fluid 16 is put in the vicinity of the permanent magnet 17.

The magnetic fluid 16 has, for example, an average particle size of about 1
It is formed by coating fine particles of magnetite of 0 nm with a surfactant and dispersing them in a floating state in oil. It is desirable that the base oil of the magnetic fluid be the same as the hydraulic fluid that is a pressure fluid. More preferably, it is preferable to use the same base oil as the liquid on both sides of the magnetic fluid. This can eliminate chemical changes between fluids.

According to the above structure, the pressure introduced to the film forming portion forming surface of the diaphragm portion 6a is given through the magnetic fluid 16 and the protective fluid 10. Since the protective fluid 10 does not adversely affect the film forming unit 8 and the FPC 11, it is possible to extend the service life and enhance the reliability of the differential pressure sensor.

Further, in FIG. 1, 19 is a signal lead wire 2
It is a circuit component such as an amplifier circuit for processing the detection signal sent by the above, and these are attached by the tubular member 20.

In the embodiment shown in FIG. 2, the arrangement positions of the permanent magnet 21 and the magnetic fluid 22 are designed as a part of the spacer 9. The other structure is the same as that of the above-mentioned embodiment.

FIG. 3 shows another embodiment relating to the mounting locations of the magnetic fluid and the permanent magnet. In this embodiment, a permanent magnet 32 is arranged in a hydraulic oil introduction passage 31a formed inside the housing 31 corresponding to the main body 3 described above.
The permanent magnet 32 allows the magnetic fluid 33 to flow through a part of the introduction path.
Are placed. 34 shows a part of the wall of the hydraulic device,
Reference numeral 35 is an oil passage for the first hydraulic oil, and 36 is an oil passage for the second hydraulic oil. The oil passage 35 communicates with a pressure introducing portion on the lower surface of the diaphragm portion 6a in the figure, and the pressure of the first hydraulic oil is applied to the lower surface of the diaphragm portion 6a. The oil passage 36 communicates with the introduction passage 31 a, and the pressure of the second hydraulic oil is the diaphragm portion 6 a via the magnetic fluid 33 and the protective fluid 10.
Applied to the upper surface of. The lower end portion of the housing 31 is fixed to a hole 34a formed in the wall portion 34 with O-rings 37 provided at a plurality of required portions. Other configurations are the same as those of the embodiment described above, and in the drawings, substantially the same elements are denoted by the same reference numerals.

The embodiment shown in FIG. 4 is a modification of the embodiment shown in FIG. In this embodiment, in the configuration shown in FIG. 3, a permanent magnet 41 is further added to the permanent magnet 32 in the introduction passage 31a, and the magnetic fluid 42 is added to the place of the introduction passage 31a between the two permanent magnets 32, 41. It is configured to fill. According to this structure, a part of the magnetic fluid is replaced by the pulsation of the hydraulic fluid, or a part of the magnetic fluid is extruded in the direction of the hydraulic fluid. Even if it occurs, it is possible to secure a sufficient amount of magnetic fluid, and the two permanent magnets 3
High reliability can be maintained by providing the holding portions at two places by 2, 41.

[0024]

As is apparent from the above description, according to the present invention, in the pressure introducing mechanism of the differential pressure sensor using the double-sided pressure receiving type diaphragm, the differential pressure detecting component formed on one surface of the diaphragm. Since a structure that seals a protective fluid such as silicon oil around the membrane part is used and a magnetic fluid is used as a partitioning means between the protective fluid and the pressure fluid, the reliability of signal detection and signal extraction can be improved. At the same time, since it can be arranged by using the pressure introducing passage, it can be manufactured in a simple, small and compact manner. Further, since the mounting position of the partition means can be determined only by selecting the mounting position of the permanent magnet, the mounting position of the partition means can be freely selected, and the degree of freedom in design can be increased. Further, since a fluid called a magnetic fluid is used as a partitioning means between the protective fluid and the pressure fluid, the responsiveness can be enhanced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is a vertical sectional view showing a modification of the first embodiment.

FIG. 3 is a vertical sectional view showing a second embodiment of the present invention.

FIG. 4 is a vertical sectional view showing a modification of the second embodiment.

[Explanation of symbols]

1 ... Signal take-out member 2 ... Signal lead-out wire 3 ... Main body part 4 ... Accommodating recess 5,7,37 ... O-ring 6 ... Diaphragm member 6a ... Diaphragm part 8 ... Differential pressure detection film forming part 9 ... Spacer 10 ... Protective fluid 11 ... FPC (flexible printed circuit) 12 ... cover member 13, 14 ... pressure introduction hole 16, 22, 33, 42 ... magnetic fluid 17, 21, 32, 41 ... permanent magnet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoshi Tanaka 650 Jinrachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura factory (72) Inventor Fujio Fujio 650 Kintate-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Ceremony Company Tsuchiura Factory

Claims (4)

[Claims] 1. A differential pressure detecting film forming portion is formed on one surface of a double-sided pressure receiving type diaphragm, and a differential pressure between two pressures introduced so as to be applied to the diaphragm is formed in the differential pressure detecting film forming portion. In the differential pressure sensor for taking out the signal according to the above, a protective fluid is filled around the film forming portion for detecting the differential pressure, and a magnetic fluid is arranged at the boundary between the protective fluid and the pressure fluid to partition the two. A pressure introduction mechanism for a differential pressure sensor, which is characterized in that 2. The pressure introducing mechanism of a differential pressure sensor according to claim 1, wherein a magnet for holding the magnetic fluid is provided, and the magnetic fluid is arranged in an introducing passage of the pressure fluid. The pressure introduction mechanism of the differential pressure sensor. 3. The pressure introducing mechanism for a differential pressure sensor according to claim 2, wherein two of said magnets are provided, and said magnetic fluid is arranged in said introducing passage between these two magnets. Pressure introduction mechanism of differential pressure sensor. 4. The pressure introducing mechanism of the differential pressure sensor according to claim 1, wherein the magnetic fluid is made by coating magnetite fine particles having an average particle diameter of about 10 nm with a surfactant and floating. A pressure introducing mechanism for a differential pressure sensor, which is characterized in that the pressure introducing mechanism has a structure in which the pressure introducing mechanism is dispersed.