A solenoid pressure sensor sensing element and its preparation method

Abstract

The present invention discloses a sensitive element of a solenoid pressure sensor and a preparation method thereof. The preparation method includes: establishing a digital model of a pressure-sensitive diaphragm, setting a bottom surface annular extension part and a bottom surface outflow hole at the bottom of the pressure-sensitive diaphragm, and setting a top surface annular extension part and a top surface outflow hole at the upper part of the pressure-sensitive diaphragm; printing by a selective laser melting method to obtain a pressure-sensitive diaphragm precursor; polishing with abrasive fluid abrasive to remove the bottom surface annular extension part and the top surface annular extension part on the pressure-sensitive diaphragm precursor to prepare a pressure-sensitive diaphragm; printing a central rod precursor, preparing an inner hole on the central rod precursor by a drilling method and polishing to prepare a central rod, and welding the central rod with the pressure-sensitive diaphragm to prepare a sensitive element of a solenoid pressure sensor. The above preparation method can effectively solve the problems of low surface roughness consistency and inability to meet the requirements of mass production existing in the existing sensitive elements, and provides a preparation method of a sensitive element with high preparation efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of pressure sensors, and particularly relates to a sensitive element of a solenoid pressure sensor and a preparation method thereof. Background Art

[0002] The structure of the sensitive element for a solenoid pressure sensor to sense the change of the measured external pressure is as Figure 1 shown. The sensitive element includes a pressure-sensitive diaphragm and a central rod. When the pressure-sensitive diaphragm is subjected to an external pressure, it will drive the central rod to move axially. When the central rod is used as a movable armature and placed in the coil winding, it will cause a change in the output voltage of the sensor. Therefore, as the core element for the solenoid pressure sensor to sense the measured pressure, the manufacturing method and accuracy of the pressure-sensitive diaphragm have an important impact on the output accuracy of this type of sensor. The existing manufacturing method of the pressure-sensitive diaphragm is traditional die stamping. Due to the continuous wear of the die during use, there will be certain differences in the shape, position, accuracy, and surface roughness of products in different batches, resulting in the need to repeatedly debug and test during the general assembly process of the solenoid pressure sensor to determine process parameters such as the number of washers and the screwing depth of fastening screws, causing extremely unstable problems in the product production cycle and the finished product rate.

[0003] As the method with the highest forming accuracy for additive manufacturing of metal parts at present, selective laser melting (SLM) technology integrates multiple fields of technology such as CAD, numerical control, materials, electronics, and lasers. Using fine pre-placed metal powder with a particle size of 300 - 500 meshes and directly driven by a CAD model, it can quickly fabricate a three-dimensional model of a product into a functional part with any shape and complete metallurgical bonding. The dimensional accuracy of the part can reach 20 - 50 μm and has good density, surface finish, and mechanical properties. Therefore, it has been widely used in the research and production of various products. This technology can meet the dimensional accuracy requirements of ±50 μm for the sensitive element of the sensor. Therefore, selective laser melting technology provides a new technical approach for the manufacturing of the sensitive element of the solenoid pressure sensor.

[0004] However, the pressure-sensitive diaphragm in the sensor sensitive element has a high-precision requirement for surface roughness of 0.8 Ra / μm, while the surface roughness of the parts fabricated by the existing selective laser melting technology is as high as 5 - 40 Ra / μm, which cannot meet the requirements of the pressure-sensitive diaphragm for surface roughness. Moreover, due to the flat and special structure of the pressure-sensitive diaphragm, the conventional polishing methods in the existing grinding technology are not applicable to the preparation of this pressure-sensitive diaphragm. Summary of the Invention

[0005] In view of the above deficiencies in the prior art, the present invention provides a sensitive element for a solenoid pressure sensor and a preparation method thereof. The sensitive element can effectively solve the problems of low surface roughness consistency and inability to meet the requirements of mass production existing in the existing sensitive elements, and provides a preparation method for the sensitive element with high preparation efficiency.

[0006] To achieve the above object, the technical solution adopted by the present invention to solve its technical problems is as follows:

[0007] A preparation method for a sensitive element of a solenoid pressure sensor includes the following steps:

[0008] (1) Establish a digital model of the pressure-sensitive diaphragm. In the digital model, a bottom surface annular extension is provided at the bottom of the pressure-sensitive diaphragm, and a bottom surface outflow hole is provided on the bottom surface annular extension. A top surface annular extension is provided at the upper part of the pressure-sensitive diaphragm, and a top surface outflow hole is provided on the top surface annular extension;

[0009] (2) Print according to the data of the digital model of the pressure-sensitive diaphragm by means of selective laser melting to obtain a pressure-sensitive diaphragm precursor;

[0010] (3) Use an abrasive flow polishing device to introduce abrasive flow abrasive into the bottom surface annular extension and the top surface annular extension respectively to polish the pressure-sensitive diaphragm precursor. The polished abrasive flows out through the bottom surface outflow hole and the top surface outflow hole respectively;

[0011] (4) After the polishing is completed, remove the bottom surface annular extension and the top surface annular extension on the pressure-sensitive diaphragm precursor by milling to obtain a pressure-sensitive diaphragm;

[0012] (5) Use selective laser melting to print a center rod precursor, then use a drilling method to prepare an inner hole on the center rod precursor, polish the inner and outer walls of the center rod precursor with abrasive flow, obtain a center rod, and connect the center rod and the pressure-sensitive diaphragm by laser welding to obtain a sensitive element for a solenoid pressure sensor.

[0013] Further, in step (1), the heights of the bottom surface annular extension and the top surface annular extension are both 9 - 12 mm.

[0014] Further, in step (1), the bottom surface outflow hole is arranged at the top of the bottom surface annular extension, and the top surface outflow hole is arranged at the bottom of the top surface annular extension.

[0015] Further, in step (2), the material for selective laser melting printing is stainless steel powder of model 17 - 4PH or 316L.

[0016] Further, the particle size of the stainless steel powder is 15 - 50 μm.

[0017] Further, in step (3), abrasive water jet polishing is stopped when the surface roughness of the pressure-sensitive diaphragm precursor ≤ 0.8 Ra / μm.

[0018] Further, the abrasive material in step (3) is diamond powder, silicon carbide or boron carbide.

[0019] Further, the abrasive grain size is 1800 - 2200#, the abrasive concentration is 18 - 22%, and the processing pressure is 5 - 7 Mpa.

[0020] Further, it also includes setting support blocks in the data model. After numerical control printing, a pressure-sensitive diaphragm with support blocks is obtained, then the support blocks are removed by milling, and finally abrasive water jet is used to polish the pressure-sensitive diaphragm precursor.

[0021] A solenoid pressure sensor sensitive element is prepared by the above method.

[0022] The beneficial effects produced by the present invention are as follows:

[0023] 1. In this application, the selective laser melting technology is used to prepare the solenoid pressure sensor sensitive element. Compared with the existing preparation methods, this method has the advantages of high preparation efficiency, high yield, short preparation cycle and low production cost.

[0024] 2. When printing the pressure-sensitive diaphragm precursor by the selective laser melting technology in this application, a bottom annular extension part and a top annular extension part are additionally printed, and a bottom outflow hole and a top outflow hole are respectively printed on the bottom annular extension part and the top annular extension part. The annular extension part and the outflow hole are used to form a pipeline structure on the pressure-sensitive diaphragm, which is convenient for the abrasive to flow in the pipeline when using abrasive water jet for polishing. During the flow of the abrasive, the pressure-sensitive diaphragm is polished to achieve the purpose of reducing the surface roughness of the pressure-sensitive diaphragm. Since the pressure-sensitive diaphragm is a flat bottle cap type structure, and the conventional printing idea is to directly print the required components, therefore, when directly using the SLM method to print the pressure-sensitive diaphragm, the surface roughness requirement cannot be met. In this application, the conventional printing idea is overcome, and the annular extension part and the outflow hole structure are additionally printed to facilitate subsequent polishing by the abrasive water jet polishing method. After polishing, the redundant annular extension part can be directly removed.

[0025] 3. In this application, the pressure-sensitive diaphragm and the central rod structure are printed separately, and the pressure-sensitive diaphragm and the central rod are polished separately, which can improve the subsequent polishing effect of the pressure-sensitive diaphragm and the central rod.

[0026] 4. In the present application, a support block is printed at the center of the top of the pressure-sensitive diaphragm during the printing process. The support block can increase the structural strength of the pressure-sensitive diaphragm, avoiding collapse and bulging of the pressure-sensitive diaphragm during processing and removal. After printing is completed, the support block is removed, facilitating subsequent polishing operations and not affecting the overall structure of the pressure-sensitive diaphragm. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic structural diagram of the sensitive element;

[0028] Figure 2 is the digital model structure of the pressure-sensitive diaphragm in Embodiment 1;

[0029] Figure 3 is the digital model structure of the pressure-sensitive diaphragm in Embodiment 2;

[0030] Figure 4 is a schematic diagram of the flow of abrasive during polishing of the pressure-sensitive diaphragm;

[0031] Figure 5 is a schematic structural diagram of the central rod;

[0032] Reference numerals: 1, pressure-sensitive diaphragm; 2, central rod; 3, bottom annular extension; 4, bottom outflow hole; 5, top annular extension; 6, top outflow hole; 7, inner hole; 8, support block. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0034] Therefore, the following detailed description of the provided embodiments of the present invention is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0035] It should be noted that relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.

[0036] The features and performance of the present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings.

[0037] Example 1

[0038] A sensitive element of a solenoid pressure sensor, and a preparation method thereof includes the following steps:

[0039] (1) Establish a digital model of the pressure-sensitive diaphragm 1. In the digital model, a bottom surface annular extension 3 is provided at the bottom of the pressure-sensitive diaphragm 1, and a bottom surface outflow hole 4 is provided on the bottom surface annular extension 3. A top surface annular extension 5 is provided on the upper part of the pressure-sensitive diaphragm 1, and a top surface outflow hole 6 is provided on the top surface annular extension 5. The heights of both the bottom surface annular extension 3 and the top surface annular extension 5 are 10 mm. The bottom surface outflow hole 4 is provided at the top of the bottom surface annular extension 3, and the top surface outflow hole 6 is provided at the bottom of the top surface annular extension 5, so that pipeline structures are respectively formed at the bottom and top of the pressure-sensitive diaphragm 1, facilitating the subsequent flow of abrasive fluid abrasive, and realizing polishing of the pressure-sensitive diaphragm 1 during the flow process;

[0040] (2) Use software to call the data packet of the digital model of the pressure-sensitive diaphragm 1, slice the digital model to generate a two-dimensional printing numerical control program, then clean the equipment and put the printing material into the powder feeder for selective laser melting printing. The printing material is stainless steel powder of 17-4PH with a particle size of 15-50 μm to obtain a pressure-sensitive diaphragm precursor;

[0041] (3) Use an abrasive fluid polishing device to respectively introduce silicon carbide abrasive fluid abrasive into the bottom surface annular extension 3 and the top surface annular extension 5 to polish the pressure-sensitive diaphragm precursor. The abrasive particle size is 2000#, the abrasive concentration is 20%, and the processing pressure is 6 Mpa. The polished abrasives flow out through the bottom surface outflow hole 4 and the top surface outflow hole 5 respectively, and stop polishing when the surface roughness of the pressure-sensitive diaphragm precursor ≤ 0.8 Ra / μm;

[0042] (4) After the polishing is completed, the bottom annular epitaxial part 3 and the top annular epitaxial part 5 on the pressure-sensitive diaphragm precursor are removed by milling to obtain the pressure-sensitive diaphragm 1;

[0043] (5) The center rod precursor is printed by selective laser melting, and then an inner hole 7 is prepared on the center rod precursor by drilling. Abrasive flow polishing is used to polish the inner and outer walls of the center rod precursor. When the surface roughness ≤ 3.2 Ra / μm, the processing is stopped to obtain the center rod 2. The center rod 2 and the pressure-sensitive diaphragm 1 are connected by laser welding. The laser power is 500 W and the welding rate is 180° / s to obtain the sensitive element of the solenoid pressure sensor.

[0044] Example 2

[0045] A sensitive element of a solenoid pressure sensor, and its preparation method includes the following steps:

[0046] (1) Establish a digital model of the pressure-sensitive diaphragm. In the digital model, a bottom annular epitaxial part 3 is arranged at the bottom of the pressure-sensitive diaphragm 1, and a bottom outflow hole 4 is arranged on the bottom annular epitaxial part 3. A top annular epitaxial part 5 is arranged at the upper part of the pressure-sensitive diaphragm 1, and a top outflow hole 6 is arranged on the top annular epitaxial part 5. A support block 8 is arranged in the middle of the pressure-sensitive diaphragm 1 to improve the structural strength of the pressure-sensitive diaphragm 1 and prevent the pressure-sensitive diaphragm 1 from collapsing and bulging during processing and removal. The heights of the bottom annular epitaxial part 3 and the top annular epitaxial part 5 are both 10 mm; the bottom outflow hole 4 is arranged at the top of the bottom annular epitaxial part 3, and the top outflow hole 6 is arranged at the bottom of the top annular epitaxial part 5, so that a pipeline structure is formed at the bottom and top of the pressure-sensitive diaphragm 1, facilitating the flow of abrasive flow abrasive in the follow-up process, and realizing the polishing of the pressure-sensitive diaphragm 1 during the flow process;

[0047] (2) Use software to call the data packet of the digital model of the pressure-sensitive diaphragm, slice the digital model to generate a two-dimensional printing numerical control program, then clean the equipment and put the printing material into the powder feeder for selective laser melting printing. The printing material is stainless steel powder with 17-4PH and a particle size of 15-50 μm to obtain the pressure-sensitive diaphragm precursor, and the support block in the middle of the pressure-sensitive diaphragm precursor is removed by milling;

[0048] (3) Use an abrasive flow polishing device to introduce silicon carbide abrasive flow abrasive into the bottom annular epitaxial part 3 and the top annular epitaxial part 5 respectively to polish the pressure-sensitive diaphragm precursor. The abrasive particle size is 2000#, the abrasive concentration is 20%, and the processing pressure is 6 Mpa. The polished abrasives flow out through the bottom outflow hole and the top outflow hole respectively, and stop polishing when the surface roughness of the pressure-sensitive diaphragm precursor ≤ 0.8 Ra / μm;

[0049] (4) After the polishing is completed, the bottom annular epitaxial portion 3 and the top annular epitaxial portion 5 on the precursor of the pressure-sensitive diaphragm are removed by milling to obtain the pressure-sensitive diaphragm 1;

[0050] (5) The center rod precursor is printed by selective laser melting, and then an inner hole 7 is prepared on the center rod precursor by drilling. The inner and outer walls of the center rod precursor are polished by abrasive flow polishing, and the processing is stopped when the surface roughness ≤ 3.2 Ra / μm to obtain the center rod 2. The center rod 2 and the pressure-sensitive diaphragm 1 are connected by laser welding with a laser power of 500 W and a welding rate of 180° / s to obtain the sensitive element of the solenoid pressure sensor.

[0051] When the sensitive element of the sensor is prepared by the above method, it has the advantages of high preparation efficiency, high yield, short preparation cycle and low production cost. When the pressure-sensitive diaphragm of the existing sensitive element of the solenoid pressure sensor is made, first, the stainless steel strip needs to be repeatedly rolled to obtain a non-standard strip with a specified thickness, then cut into sheets by a blanking machine, and then the sheets are ground many times to obtain sheets with a surface roughness meeting the requirements. Finally, it is stamped and formed by a stamping and forming device with a special mold. The entire production cycle often takes more than a week. The method for making the pressure-sensitive diaphragm based on additive manufacturing and precision grinding technology proposed by the present invention can obtain the pressure-sensitive diaphragm finished product within 8 hours due to its short process flow and programmed process. Compared with the existing manufacturing method, the production cycle is greatly shortened. When the existing sensitive element of the solenoid pressure sensor is made, due to the long and complex process path, the yield from raw materials to qualified products is less than 30%, resulting in waste of raw materials and man-hours and pushing up the production cost. The method for making the sensitive element based on additive manufacturing and precision grinding technology proposed by the present invention has a short process flow and is completed by an automatic processing method with programmed control, so that the processing yield of the sensitive element is stabilized above 70%, effectively reducing the production cost; at the same time, the manufacturing method proposed by the present invention does not require the use of high-precision stamping dies compared with the existing manufacturing method, which also promotes the further reduction of the production cost.

[0052] For the method for making the sensitive element based on additive manufacturing and precision grinding technology proposed by the present invention, when the size of the sensitive element changes, there is no need to re-make special grinding jigs and stamping dies. Therefore, compared with the existing manufacturing method, it is more suitable for customizing sensitive elements of various non-standard sizes and can better meet the design requirements and customer needs; by replacing the SLM printing powder material, the manufacturing method proposed by the present invention can make various sensitive elements made of stainless steel, copper alloy and titanium alloy, and has a wider material adaptability compared with the existing manufacturing method.

[0053] The sensitive element in Example 2 is assembled with components such as the base, stopper, iron core coil, spring piece, and housing to form a solenoid pressure sensor. After assembly, a pressure gauge and gas circuit are connected for output testing.

[0054] The test results show that in the temperature range of -55°C to 80°C and the pressure range of 0 to 10 Mpa, the output error of the sensor is 0.18 V, and the output difference between the forward and reverse strokes is 0.076 V, meeting the index requirements of the sensor's output error ≤ 0.2 V and the output difference between the forward and reverse strokes ≤ 0.08 V. This proves that the method for fabricating the sensor sensitive element based on additive manufacturing and precision grinding technology proposed in the present invention can be successfully applied in pressure sensor products.

Claims

1. A preparation method of a sensitive element of a solenoid pressure sensor, characterized in that, It includes the following steps: (1) Establish a digital model of the pressure-sensitive diaphragm. In the digital model, a bottom annular extension is provided at the bottom of the pressure-sensitive diaphragm, and a bottom outflow hole is provided on the bottom annular extension. A top annular extension is provided at the upper part of the pressure-sensitive diaphragm, and a top outflow hole is provided on the top annular extension; (2) Use the selective laser melting method to print according to the data of the digital model of the pressure-sensitive diaphragm to obtain a pressure-sensitive diaphragm precursor; (3) Use an abrasive flow polishing device to introduce abrasive flow abrasive into the bottom annular extension and the top annular extension respectively to polish the pressure-sensitive diaphragm precursor, and the polished abrasive flows out through the bottom outflow hole and the top outflow hole respectively; (4) After polishing, use milling to remove the bottom annular extension and the top annular extension on the pressure-sensitive diaphragm precursor to obtain a pressure-sensitive diaphragm; (5) Use selective laser melting to print the center rod precursor, then use drilling to prepare an inner hole on the center rod precursor, use abrasive flow to polish the inner and outer walls of the center rod precursor to obtain a center rod, and connect the center rod and the pressure-sensitive diaphragm by laser welding to obtain a solenoid pressure sensor sensitive element.

2. The preparation method of the solenoid type pressure sensor sensing element according to claim 1, characterized in that, In step (1), the heights of the bottom annular extension and the top annular extension are both 9-12 mm.

3. The preparation method of the solenoid pressure sensor sensing element according to claim 1, characterized in that, In step (1), the bottom outflow hole is arranged at the top of the bottom annular extension, and the top outflow hole is arranged at the bottom of the top annular extension.

4. The preparation method of the solenoid pressure sensor sensitive element according to claim 1, characterized in that In step (2), the material for selective laser melting printing is stainless steel powder with the model number 17-4PH or 316L.

5. The preparation method of the solenoid pressure sensor sensing element according to claim 4, characterized in that, The particle size of the stainless steel powder is 15-50μm.

6. The preparation method of the solenoid pressure sensor sensing element according to claim 1, characterized in that, In step (3), stop abrasive flow polishing when the surface roughness of the pressure-sensitive diaphragm precursor is ≤0.8Ra / μm.

7. The preparation method of the solenoid type pressure sensor sensing element according to claim 1, characterized in that, The abrasive material in step (3) is diamond powder, silicon carbide or boron carbide.

8. The preparation method of the solenoid type pressure sensor sensing element according to claim 1, characterized in that, The abrasive particle size is 1800-2200#, the abrasive concentration is 18-22%, and the processing pressure is 5-7 Mpa.

9. The preparation method of the solenoid type pressure sensor sensing element according to claim 1, characterized in that, It also includes setting a support block in the data model, obtaining a pressure-sensitive diaphragm with a support block after numerical control printing, then using milling to remove the support block, and finally using abrasive flow to polish the pressure-sensitive diaphragm precursor.

10. A sensitive element of a solenoid pressure sensor, characterized in that, It is obtained by using the method described in any one of claims 1-9.

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