Differential pressure sensor

Abstract

A differential pressure sensor can prevent a diaphragm from being damaged due to icing. The differential pressure sensor according to the present invention comprises: a housing; the metal isolation diaphragm is arranged in the shell; the metal isolation diaphragm is arranged in the shell, the silicon diaphragm is arranged in the shell, the internal space of the shell is divided into a high-pressure cavity located on one side of the metal isolation diaphragm and a low-pressure cavity located on one side of the silicon diaphragm by the metal isolation diaphragm and the silicon diaphragm, and the space between the metal isolation diaphragm and the silicon diaphragm is filled with silicone oil. The surface, close to one side of the high-pressure cavity, of the metal isolation diaphragm and the surface, close to one side of the low-pressure cavity, of the silicon diaphragm are coated with hydrophobic layers.

Description

Technical Field

[0001] The present invention relates to a differential pressure sensor, for example, used in an auxiliary power unit (APU) of an aircraft. Background Art

[0002] The auxiliary power unit is a small turbine engine that is currently widely used on civil aircraft. Its main function is to provide generator shaft power for the aircraft power system on the ground and in the air, and to provide bleed air for the air source system.

[0003] The APU bleed air system typically includes components such as the load compressor, pressure sensors, inlet guide vanes, bleed air valves, and an anti-surge control valve. Pressure sensors primarily include total pressure, static pressure, and differential pressure sensors. The differential pressure sensor measures the total static pressure differential at the load compressor outlet and sends a corresponding signal to the ECU. The ECU receives the signal and, through internal control logic, controls the opening of the anti-surge control valve (SCV). When the aircraft is not bleeding air or the bleed air flow is too low, the anti-surge control valve opens and is controlled at an appropriate position to discharge excess air and prevent surge in the load compressor.

[0004] During normal airline operations, the APU is most commonly used to supply air to the forward environmental control system during ground starts of the main engines, and to start the main engines using bleed air. After a successful main engine start, the APU is typically shut down, and unless a malfunction occurs during flight, the APU is not used. When the APU is used for bleed air, the bleed air temperature is high. After the bleed air is stopped, the water vapor in the pressure chamber of the differential pressure sensor condenses into liquid. This can freeze in the low temperatures of the air, damaging the isolation diaphragm and the silicon diaphragm, leading to a high failure rate for the differential pressure sensor.

[0005] Currently, most civil aircraft use piezoresistive solid-state differential pressure sensors welded in a sealed housing. The pressure-sensing part is made of single-crystal silicon, micro-machined into a mechanical pressure-sensitive diaphragm, with a Wheatstone bridge in the middle, which is used to convert pressure changes into changes in resistance value signals; the isolation diaphragm is made of metal, and silicone oil is used to fill the space between it and the silicon diaphragm.

[0006] The differential pressure sensor cannot be repaired. It is an LRU (Line Replaceable Unit) component and is generally replaced directly if damaged.

[0007] When the APU system operates in a high-humidity environment, water vapor in the air will enter the differential pressure sensor through the bleed air duct. Since the APU bleed air temperature is usually high, the water is in the form of water vapor at this time. After the APU stops bleed air, the water vapor in the pressure chamber of the differential pressure sensor condenses into liquid. When the aircraft operates in a high-altitude, low-temperature environment, the condensed water that enters the differential pressure sensor and adheres to the diaphragms (isolation diaphragm and silicon diaphragm) will freeze. The concentrated stress generated by freezing may damage the silicon diaphragm and cause cracks. In addition, when the APU restarts to provide bleed air, the performance of the pressure-sensing diaphragm is reduced due to surface ice, and the pressure on both sides of the diaphragm may damage the diaphragm and the chip mounted on it. Summary of the Invention

[0008] In view of the above problems, an object of the present invention is to provide a differential pressure sensor that can prevent the diaphragm from being damaged by icing.

[0009] In order to achieve the above-mentioned purpose of the present invention, the present invention provides a differential pressure sensor, comprising: a shell; a metal isolation diaphragm arranged inside the shell; and a silicon diaphragm arranged inside the shell, the internal space of the shell is separated by the metal isolation diaphragm and the silicon diaphragm into a high-pressure cavity on one side of the metal isolation diaphragm and a low-pressure cavity on one side of the silicon diaphragm, silicone oil is used to fill the space between the metal isolation diaphragm and the silicon diaphragm, and a hydrophobic layer is coated on the surface of the metal isolation diaphragm close to the high-pressure cavity and the surface of the silicon diaphragm close to the low-pressure cavity.

[0010] According to the differential pressure sensor of the present invention, by coating a hydrophobic layer on the diaphragm (metal isolation diaphragm and silicon diaphragm) of the differential pressure sensor, condensed water can be prevented from accumulating on the diaphragm surface, thereby preventing the diaphragm from freezing and causing damage in a low-temperature environment.

[0011] Preferably, a water collecting groove is provided in a portion of the shell located below the high-pressure chamber and a portion of the shell located below the low-pressure chamber.

[0012] According to the differential pressure sensor of the present invention, condensed water can be collected by using the water collecting tank.

[0013] Preferably, the water collecting tank on the lower side of the high-pressure chamber is arranged at a position laterally separated from the metal isolation diaphragm by a certain distance, and the water collecting tank on the lower side of the low-pressure chamber is arranged at a position laterally separated from the silicon diaphragm by a certain distance.

[0014] According to the differential pressure sensor of the present invention, condensed water collected by the water collecting tank can be kept away from the diaphragm of the differential pressure sensor.

[0015] Preferably, air is fed into the high-pressure chamber through a total pressure air intake pipe, and air is fed into the low-pressure chamber through a static pressure air intake pipe.

[0016] According to the differential pressure sensor of the present invention, air can be easily introduced into the high-pressure chamber and the low-pressure chamber.

[0017] Preferably, a circuit and a cable are provided on the silicon diaphragm for sensing pressure changes on both sides and converting them into resistance value signal changes.

[0018] According to the differential pressure sensor of the present invention, differential pressure detection and output can be easily performed using an electric circuit and a cable.

[0019] Preferably, the differential pressure sensor is used in an auxiliary power unit (APU) of an aircraft.

[0020] The differential pressure sensor according to the present invention can prevent damage to the differential pressure sensor caused by ice on the diaphragm surface, improve the reliability of the differential pressure sensor, and reduce the failure probability of the APU bleed air system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 FIG1 is a schematic diagram schematically showing the structure of a differential pressure sensor according to an embodiment of the present invention.

[0022] Figure 2 The structure of the differential pressure sensor according to the embodiment of the present invention is schematically shown. Figure 1 AA cross-sectional view.

[0023] (Explanation of Symbols)

[0024] 1 Housing

[0025] 2 water collection tanks

[0026] 3 Total pressure intake pipe

[0027] 4 Metal isolation diaphragm

[0028] 5 High-pressure chamber

[0029] 6 Silicone oil

[0030] 7 Static pressure intake pipe

[0031] 8 Silicon diaphragm

[0032] 9 Low-pressure chamber

[0033] 10 Circuits and cables DETAILED DESCRIPTION

[0034] Various embodiments of the present invention will now be described in detail, examples of which are shown in the accompanying drawings and described below. Although the present invention will be described in conjunction with exemplary embodiments, it should be appreciated that this description is not intended to limit the invention to those exemplary embodiments. On the contrary, the present invention is intended to cover not only those exemplary embodiments, but also various alternatives, modifications, equivalents, and other embodiments that may be included within the spirit and scope of the invention as defined by the appended claims.

[0035] Next, combine Figures 1 to 2 A differential pressure sensor according to an embodiment of the present invention will be described.

[0036] Figure 1 FIG1 is a schematic diagram schematically showing the structure of a differential pressure sensor according to an embodiment of the present invention. Figure 2 The structure of the differential pressure sensor according to the embodiment of the present invention is schematically shown. Figure 1 AA cross-sectional view.

[0037] (Structure of Differential Pressure Sensor According to Embodiment of the Present Invention)

[0038] The pressure differential sensor of the present invention is, for example, installed in an aircraft auxiliary power unit to measure the total static pressure difference at the outlet of a load compressor. However, the application scenario of the pressure differential sensor of the present invention is not limited to this and can be applied to any scenario requiring pressure differential measurement.

[0039] like Figures 1 to 2 As shown, in the differential pressure sensor of the present invention, the internal space of the shell 1 is divided into a high-pressure chamber 5 and a low-pressure chamber 9 by a metal isolation diaphragm 4 and a silicon diaphragm 8. The total pressure intake pipe 3 intakes air into the high-pressure chamber 5, and the static pressure intake pipe 7 intakes air into the low-pressure chamber 9. The silicon diaphragm 8 is provided with a circuit and a cable 10 (specifically, the circuit is provided on the silicon diaphragm 8, and the cable is led out from the circuit), which senses the pressure changes on both sides and converts them into resistance value signal changes. Silicone oil 6 is used to fill the space between the metal isolation diaphragm 4 and the silicon diaphragm 8.

[0040] The surface of the metal isolation diaphragm 4 close to the high-pressure chamber 5 and the surface of the silicon diaphragm 8 close to the low-pressure chamber 9 are coated with a hydrophobic layer to prevent condensed water from accumulating on the surfaces of the metal isolation diaphragm 4 and the silicon diaphragm 8.

[0041] In addition, the housing 1 is grooved downwards at the lower side of the high pressure chamber 5 and the low pressure chamber 9 to form a water collecting tank 2 to collect condensed water. The water collecting tank 2 is located between the metal isolation diaphragm 4 and the silicon diaphragm 8 in the horizontal direction ( Figure 1 Keep a certain distance in the left and right directions).

[0042] (Technical Effects of the Differential Pressure Sensor According to the Embodiments of the Present Invention)

[0043] When the APU is not bleed air, water vapor turns into condensed water. Due to the hydrophobic layer on the surfaces of the metal isolation diaphragm 4 and the silicon diaphragm 8, this condensed water cannot accumulate on them. Instead, gravity causes the condensed water to flow downward and eventually accumulate in the water collection tank 2, away from the metal isolation diaphragm 4 and the silicon diaphragm 8 of the differential pressure sensor. In cold conditions, even if ice forms inside the differential pressure sensor, the ice will only be contained in the water collection tank 2 and will not form on the surfaces of the metal isolation diaphragm 4 and the silicon diaphragm 8.

[0044] After the APU starts to bleed air, the differential pressure sensor can work normally. Since the APU bleed air temperature is high, the condensed water inside the differential pressure sensor will turn into water vapor and be carried away.

[0045] This prevents damage to the differential pressure sensor caused by ice on the surface of the diaphragm (collectively, the metal isolation diaphragm 4 and the silicon diaphragm 8 ), improves the reliability of the differential pressure sensor, and reduces the failure probability of the APU bleed air system.

[0046] (Features of the present invention and its technical effects)

[0047] The differential pressure sensor of the present invention includes: a housing 1; a metal isolation diaphragm 4 arranged inside the housing 1; and a silicon diaphragm 8 arranged inside the housing 1. The internal space of the housing 1 is separated by the metal isolation diaphragm 4 and the silicon diaphragm 8 into a high-pressure chamber 5 on one side of the metal isolation diaphragm 4 and a low-pressure chamber 9 on the side of the silicon diaphragm 8. Silicone oil 6 is used to fill the space between the metal isolation diaphragm 4 and the silicon diaphragm 8. A hydrophobic layer is coated on the surface of the metal isolation diaphragm 4 close to the high-pressure chamber 5 and the surface of the silicon diaphragm 8 close to the low-pressure chamber 9.

[0048] According to the differential pressure sensor of the present invention, by coating a hydrophobic layer on the diaphragm (metal isolation diaphragm 4 and silicon diaphragm 8) of the differential pressure sensor, condensed water can be prevented from accumulating on the diaphragm surface, thereby preventing the diaphragm from freezing and causing damage in a low-temperature environment.

[0049] In addition, a water collecting tank 2 is provided in the portion of the housing 1 located below the high-pressure chamber 5 and the portion of the housing 1 located below the low-pressure chamber 9 .

[0050] According to the differential pressure sensor of the present invention, the condensed water can be collected by using the water collecting tank 2 .

[0051] In addition, the water collecting tank 2 on the lower side of the high-pressure chamber 5 is set at a position separated from the metal isolation diaphragm 4 by a certain distance in the horizontal direction, and the water collecting tank 2 on the lower side of the low-pressure chamber 9 is set at a position separated from the silicon diaphragm 8 by a certain distance in the horizontal direction.

[0052] According to the differential pressure sensor of the present invention, the condensed water collected by the water collecting tank 2 can be kept away from the diaphragm of the differential pressure sensor.

[0053] In addition, air is supplied to the high-pressure chamber 5 through the total pressure intake pipe 3 , and air is supplied to the low-pressure chamber 9 through the static pressure intake pipe 7 .

[0054] The differential pressure sensor according to the present invention can conveniently allow air to enter the high-pressure chamber 5 and the low-pressure chamber 9 .

[0055] In addition, a circuit and a cable 10 are provided on the silicon diaphragm 8 for sensing pressure changes on both sides and converting them into resistance value signal changes.

[0056] According to the differential pressure sensor of the present invention, differential pressure detection and output can be easily performed using the circuit and the cable 10 .

[0057] Furthermore, differential pressure sensors are used in the auxiliary power units (APUs) of aircraft.

[0058] The differential pressure sensor according to the present invention can prevent damage to the differential pressure sensor caused by ice on the diaphragm surface, improve the reliability of the differential pressure sensor, and reduce the failure probability of the APU bleed air system.

[0059] (Variation)

[0060] The present invention is described above by way of example with reference to the accompanying drawings. It is apparent that the specific implementation of the present invention is not limited to the above-mentioned embodiments.

[0061] (1) The arrangement of the water collecting tank 2 is not particularly limited, as long as it can collect condensed water.

[0062] (2) The arrangement of the circuit and the cable 10 provided on the silicon diaphragm 8 can be appropriately selected according to needs.

[0063] (3) The material and coating method of the hydrophobic layer are not particularly limited and can be appropriately selected as needed as long as they can prevent condensed water from adhering to the membrane.

[0064] Although the structure and working principle of the present invention have been described above in conjunction with preferred embodiments, those skilled in the art will recognize that the above examples are for illustration only and are not intended to limit the present invention. Therefore, modifications and variations may be made to the present invention within the spirit of the claims, and such modifications and variations will fall within the scope of the claims.

Claims

1. A differential pressure sensor, comprising: case; a metal isolation diaphragm disposed inside the housing; as well as A silicon diaphragm is provided inside the housing, The internal space of the housing is separated by the metal isolation diaphragm and the silicon diaphragm into a high-pressure chamber on one side of the metal isolation diaphragm and a low-pressure chamber on the other side of the silicon diaphragm. Silicone oil is used to fill the space between the metal isolation diaphragm and the silicon diaphragm. It is characterized by: A hydrophobic layer is coated on the surface of the metal isolation diaphragm close to the high-pressure cavity and the surface of the silicon diaphragm close to the low-pressure cavity.

2. The differential pressure sensor according to claim 1, wherein: A water collecting tank is provided at a portion of the shell located at a lower side of the high-pressure chamber and a portion of the shell located at a lower side of the low-pressure chamber.

3. The differential pressure sensor according to claim 2, wherein: The water collecting tank on the lower side of the high pressure chamber is arranged at a position spaced a certain distance laterally from the metal isolation diaphragm. The water collecting tank located at the lower side of the low-pressure chamber is arranged at a position spaced a certain distance laterally from the silicon diaphragm.

4. The differential pressure sensor according to claim 1, wherein Air is fed into the high-pressure chamber through a total pressure air intake pipe, and air is fed into the low-pressure chamber through a static pressure air intake pipe.

5. The differential pressure sensor according to claim 1, wherein: Circuits and cables are provided on the silicon diaphragm for sensing pressure changes on both sides and converting them into resistance value signal changes.

6. The differential pressure sensor according to any one of claims 1 to 5, characterized in that The differential pressure sensor is used in an auxiliary power unit of an aircraft.

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