A sealing structure of an oil-filled cavity of an oil-filled pressure sensor

Abstract

The utility model relates to pressure sensor technical field discloses a kind of sealing structure of oil-filled pressure sensor oil-filled cavity, including metal base, diaphragm, compression ring, solid filler, composite structure dowel, the compression ring, diaphragm, metal base welding fixed connection, the diaphragm is located in the middle of compression ring and metal base, the metal base is opened and oil hole, the metal base and diaphragm are surrounded and are composed of oil-filled cavity, the solid filler is located in oil-filled cavity, the oil-filled cavity is communicated with outside by oil hole, the oil-filled cavity and oil hole are filled with silicone oil, the composite structure dowel is welded in the end of oil hole far from oil-filled cavity, form sealing structure. The utility model changes the structure of dowel, realizes lower silicone oil filling amount, can reduce the temperature drift problem caused by silicone oil.

Description

Technical Field

[0001] This utility model relates to the field of pressure sensors, and in particular to a sealing structure for the oil filling cavity of an oil-filled pressure sensor. Background Technology

[0002] Oil-filled pressure sensors are pressure sensors that isolate the measured medium from the core sensing element (MEMS chip) by filling it with silicone oil. They typically consist of a metal base, MEMS chip, oil-filled cavity, isolation diaphragm, pins, and a sealing ball. This design protects the delicate MEMS chip from external damage and transmits the sensed pressure to the MEMS chip losslessly and without distortion through the incompressible silicone oil. However, the coefficient of thermal expansion of silicone oil is much greater than that of the metal casing. When the ambient temperature rises, the expansion volume of the silicone oil exceeds the additional space provided by the expansion of the metal cavity. This causes an increase in pressure within the cavity even without external pressure, leading to an output shift in the MEMS pressure chip, i.e., thermal zero-point drift. Therefore, the amount of silicone oil filled must be strictly controlled within a certain range. To achieve a smaller zero-point drift, the amount of silicone oil should be minimized while ensuring complete immersion of the chip and sufficient clearance between the diaphragm and the chip. Utility Model Content

[0003] This invention provides a novel oil-filled cavity sealing structure that ensures the normal output of the MEMS oil-filled pressure sensor at room temperature and solves the problem of large thermal zero-point drift in existing MEMS oil-filled pressure sensors.

[0004] To address the aforementioned problems, this utility model provides a sealing structure for the oil-filled cavity of an oil-filled pressure sensor, comprising a metal base, a diaphragm, a pressure ring, a solid filler, and a composite structure pin. The pressure ring, diaphragm, and metal base are welded and fixedly connected. The diaphragm is located between the pressure ring and the metal base. The metal base has an oil injection hole. The metal base and diaphragm surround and form an oil-filled cavity. The solid filler is located within the oil-filled cavity. The oil-filled cavity is connected to the outside through the oil injection hole. The oil-filled cavity and the oil injection hole are filled with silicone oil. The composite structure pin is welded to the end of the oil injection hole away from the oil-filled cavity, forming a sealing structure.

[0005] Preferably, the pressure ring presses the diaphragm onto the base, and the pressure ring and the base are fixed together by welding.

[0006] Preferably, the solid filler is located in the oil-filled cavity and fixed in the groove of the metal base, and the coefficient of thermal expansion of the solid filler is close to the coefficient of thermal expansion of the metal base.

[0007] Preferably, the solid filler is a ceramic sintered body composed of alumina.

[0008] Preferably, the silicone oil is phenyl silicone oil with a coefficient of thermal expansion of 8.9 × 10⁻⁶. -5 / ℃, the dynamic viscosity at 25℃ is 50cst.

[0009] Preferably, the filling silicone oil is injected into the oil-filling cavity through the oil injection hole under a high vacuum environment (10⁻²~10⁻³ Pa).

[0010] Preferably, the composite structure pin is connected to the base by a pressure resistance welding process.

[0011] Preferably, the composite structure pin has the following structural features: the whole is composed of two cylinders of different diameters connected together by a frustum, the total length of which is greater than the length of the oil injection hole, wherein the diameter of one section of the smaller diameter cylinder is smaller than the diameter of the oil injection hole and the length of the smaller diameter cylinder is less than the length of the oil injection hole, the diameter of one section of the larger diameter cylinder is greater than the diameter of the oil injection hole, and the other section of the larger diameter cylinder is a spherical structure.

[0012] The beneficial effects of this utility model are: This solution reduces the volume of the oil-filled cavity by fixing a solid filler in the groove of the metal base that holds the MEMS chip, thereby reducing the amount of silicone oil required. At the same time, the structure of the pin is changed so that most of the volume of the oil injection hole is occupied by the pin, and the volume of the internal oil-filled cavity is further reduced after welding and fixing.

[0013] This solution reduces the volume of the oil-filled cavity and the amount of silicone oil used by fixing the solid filler and changing the pin structure, thus mitigating pressure output drift caused by changes in silicone oil volume. Furthermore, this solution does not affect the original design of the oil-filled pressure sensor, nor does it alter the structure and dimensions of the metal base. Attached Figure Description

[0014] Appendix Figure 1 This is a cross-sectional structural schematic diagram of the present invention; Icons: 1-Metal base; 2-Diaphragm; 3-Pressure ring; 4-Silicone oil; 5-Solid filler; 6-Composite structure pin. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0016] See attached document Figure 1The sealing structure of the oil-filled pressure sensor's oil-filled cavity includes a metal base 1, a diaphragm 2, a pressure ring 3, a solid filler 5, and a composite structure pin 6. The metal base 1 has a groove and an oil filling hole. The groove is used to fix the MEMS chip and the solid filler 5. The pressure ring 3 presses the diaphragm 2 tightly against the side of the metal base 1 with the groove. The diaphragm 2 and the metal base 1 surround each other to form an oil-filled cavity, which is filled with silicone oil 4. The composite structure pin 6 is piezoresistive welded to the end of the oil filling hole away from the oil-filled cavity.

[0017] The solid filler 5 is located in the oil-filled cavity and fixed in the groove of the metal base 1. The coefficient of thermal expansion of the solid filler 5 is close to that of the metal base 1. It is preferably a sintered ceramic body with alumina as its composition. The solid filler 5 occupies more than half of the volume of the oil-filled cavity.

[0018] Silicone oil 4 is made of phenyl silicone oil, with a coefficient of thermal expansion of 8.9 × 10⁻⁶. -5 / ℃, the dynamic viscosity at 25℃ is 50 cst. When injecting silicone oil 4 into the oil-filled cavity, in a high vacuum environment (10 -2 ~10 -3 The oil is injected into the oil-filled cavity through the oil injection hole (pa).

[0019] The operation process is as follows: The MEMS chip is fixed to the bottom of the pressure sensor groove, and then the solid filler 5 is fixed to the bottom of the pressure sensor groove. The diaphragm 2 is pressed tightly onto the metal base 1 using a pressure ring 3, and the pressure ring 3 and the metal base 1 are fixed together by laser welding. Under high vacuum, silicone oil 4 is filled into the oil-filled cavity formed by the diaphragm and the metal base through the oil injection hole on the metal base. After filling, the composite structure pin 6 is fixed to the end of the oil injection hole away from the oil-filled cavity, and then fixed by piezoresistive welding to form a sealed structure.

[0020] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be covered within the protection scope of the present utility model.

Claims

1. A sealing structure for the oil-filled cavity of an oil-filled pressure sensor, characterized in that: The pressure sensor has a metal base and a diaphragm surrounding it to form an oil-filled cavity. The base is provided with an oil injection hole. The oil-filled cavity and the oil injection hole are connected. The oil-filled cavity is filled with a solid filler and silicone oil. The end of the oil injection hole away from the oil-filled cavity is welded with the composite structure pin.

2. The sealing structure of the oil-filled cavity of the oil-filled pressure sensor according to claim 1, characterized in that, The pressure ring presses the diaphragm onto the base, and the pressure ring and the base are fixed together by welding.

3. The sealing structure of the oil-filled cavity of the oil-filled pressure sensor according to claim 1, characterized in that, The solid filler is located in the oil-filled cavity and fixed in the groove of the metal base. The coefficient of thermal expansion of the solid filler is close to that of the metal base.

4. The sealing structure of the oil-filled cavity of the oil-filled pressure sensor according to claim 1, characterized in that, The composite structure pin is connected to the base through a pressure resistance welding process.

5. The sealing structure of the oil-filling cavity of the oil-filling pressure sensor according to claim 4, characterized in that, The composite structure pin consists of two cylinders of different diameters connected together by a frustum. The total length is greater than the length of the oil injection hole. The diameter of one section of the smaller diameter cylinder is smaller than the diameter of the oil injection hole, and its length is also less than the length of the oil injection hole. The diameter of one section of the larger diameter cylinder is greater than the diameter of the oil injection hole, and the other section of the larger diameter cylinder is a spherical structure.

6. The sealing structure of the oil-filled cavity of the oil-filled pressure sensor according to any one of claims 1 to 5, characterized in that, The solid filler is a ceramic sintered body composed of alumina.

7. The sealing structure of the oil-filled cavity of the oil-filled pressure sensor according to any one of claims 1 to 5, characterized in that, The silicone oil is phenyl silicone oil with a coefficient of thermal expansion of 8.9 × 10⁻⁶. -5 / ℃, the silicone oil at 10 -2 Up to 10 -3 Under the high vacuum environment of pa, the oil is injected into the oil-filled cavity through the oil injection hole.

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