Embedded mounting structure and method for two-stroke aero-piston engine wall temperature sensor

Abstract

This invention belongs to the field of aero-piston engine technology. It discloses a pre-embedded installation structure and method for a two-stroke aero-piston engine wall temperature sensor, including a temperature sensor, a sensor sleeve, a hollow clamping nut, and a stepped hole on the outer wall of the cylinder head combustion chamber. The structure adopts a flat-bottomed hole and a transition fit design with the sensor sleeve. The hollow clamping nut is connected to the pre-embedded hole via a fine-pitch thread. The depth of the countersunk hole is less than the effective length of the sensor sleeve, and the material of the clamping nut is preferably selected. Torque control is used to improve the fit. The method includes preparation, insertion, and clamping stages. During assembly, strict control is exercised over oil contamination inside the countersunk hole and on the sleeve surface, as well as thread impurities. Pipe thread connection is used, and thread glue is strictly prohibited. This invention, through optimization of the combustion chamber cylinder block temperature sensor installation interface structure and assembly process, effectively controls the problems of high-temperature oxidation and increased contact thermal resistance, ensuring the accuracy of cylinder block temperature measurement and the long-term safety of the sensor, thereby improving the overall reliability of the engine.

Description

Technical Field

[0001] This invention belongs to the field of aviation piston engine technology, specifically relating to a pre-embedded installation structure and method for a wall temperature sensor in a two-stroke aviation piston engine. Background Technology

[0002] With the widespread application of multi-purpose, long-range unmanned aerial vehicles (UAVs), the technology of two-stroke aero-piston engines, which have a higher power-to-weight ratio, has been widely adopted. Combustion chamber temperature is one of the key indicators collected by the engine safety operation and control system. However, compared with four-stroke engines of the same displacement, two-stroke piston engines have a higher power density. When the temperature sensor is not working properly, the combustion chamber wall temperature of the two-stroke engine is higher under the same speed conditions, and the cylinder temperature rise rate is greater under the same load increase rate. Inappropriate design of the temperature sensor's embedded hole, assembly process, and maintenance methods of components can all lead to abnormal temperature data.

[0003] Two-stroke aero-piston engines frequently experience abnormal cylinder temperature signals during operation, leading to misjudgments of operating conditions and seriously affecting safe use and flight control. The primary cause is that the thermal resistance between the sensor and the measured object increases with engine operation. Under the periodic impact of piston engine operating conditions, temperature signals become abnormal, and excessive local heat load can even damage the sensor. Heat in the combustion chamber is transferred through the cylinder head to the sleeve, and further to the temperature sensor. The sensor feeds back the temperature signal to the control system. The accuracy of the signal is closely related to the contact conditions between components. The standard for measuring the impact on heat transfer efficiency is contact thermal resistance, and the morphological characteristics of the contact area directly affect the thermal resistance between the temperature sensor and the measured object. Summary of the Invention

[0004] In view of this, the purpose of this invention is to solve the problem of increased thermal resistance between the wall temperature sensor and the measured object during engine operation, and to provide a pre-embedded installation structure and method for a wall temperature sensor of a two-stroke aero-piston engine.

[0005] To achieve the above objectives, the present invention provides the following technical solution: An embedded mounting structure for a wall temperature sensor of a two-stroke aero-piston engine includes a temperature sensor, a sensor sleeve, and a hollow clamping nut. A stepped hole is provided on the outer wall of the cylinder head combustion chamber. The bottom of the stepped hole is a pre-embedded mounting hole, which is a flat-bottomed hole. The temperature sensor is located inside the sensor sleeve, and its tail cable is led out through the inner hole of the hollow clamping nut. The sensor sleeve is inserted into the pre-embedded mounting hole and forms axial contact with the bottom surface of the pre-embedded mounting hole and radial contact with the hole wall. The hollow clamping nut is threaded to the opening side of the stepped hole and presses the sensor sleeve into the pre-embedded mounting hole, realizing the heat transfer path of the combustion chamber heat to the temperature sensor through the cylinder head and the sensor sleeve.

[0006] Furthermore, the sensor sleeve and the pre-embedded mounting hole adopt a transition fit, and the depth of the pre-embedded mounting hole is less than the effective length of the sensor sleeve, so as to enhance heat transfer in the connection area and reduce contact thermal resistance.

[0007] Furthermore, the radial contact between the sensor sleeve and the pre-embedded mounting hole adopts a K6 / h7 transition fit based on the shaft to ensure the quality of radial contact; the effective length of the sensor sleeve is at least 1 mm greater than the depth of the pre-embedded mounting hole.

[0008] Furthermore, the hollow clamping nut and the cylinder head thread are made of fine thread with a tolerance of 5H / 4g, which enhances the heat transfer process of the threaded pair and improves the sealing performance of the threaded connection, thus preventing the sensor housing and the surface of the combustion chamber cylinder block countersunk hole from oxidizing more rapidly during the high-temperature operation of the engine.

[0009] Furthermore, the hollow compression nut is made of a material with a thermal conductivity greater than 240 W / (m·K).

[0010] As a preferred embodiment, the hollow clamping nut is made of brass, and the outer wall of the cylinder head combustion chamber is made of a lightweight material with excellent heat dissipation efficiency, namely ZL107 aluminum alloy.

[0011] A method for pre-embedding a wall temperature sensor for a two-stroke aero-piston engine, employing the pre-embedded mounting structure described above, includes the following steps in the installation process: a) Preparation stage: Remove oil stains, control humidity and treat oxide layer on the inside of the pre-embedded mounting hole of the stepped hole, the outer surface of the sensor sleeve and the threaded surface of the hollow clamping nut; b) Insertion stage: Insert the sensor sleeve into the pre-embedded mounting hole, so that its bottom surface is axially fitted with the flat bottom of the pre-embedded mounting hole and radially contacts the hole wall, and at the same time, lead out the temperature sensor tail cable through the inner hole of the hollow clamping nut; c) Tightening stage: Screw the hollow clamping nut into the threaded part of the stepped hole, and apply a specified torque to tighten and fix the sensor sleeve in the pre-embedded mounting hole.

[0012] Furthermore, in the preparation stage, a carburetor is used to clean the inside of the pre-embedded mounting hole and the surface of the sensor sleeve, and a white lint-free cloth is used to wipe it until no visible particles are visible on the surface of the lint-free cloth; after cleaning, the sensor sleeve and the hollow clamping nut are placed in a 30°C oven for 20 minutes to remove surface moisture; the oxide layer on the inner surface of the ZL107 aluminum alloy of the pre-embedded mounting hole in the cylinder head is polished to remove it; compressed air is used to clean the threaded surface of the hollow clamping nut and the corresponding threaded surface of the stepped hole.

[0013] Furthermore, the threaded connection used in the tightening stage is a fine thread, and it is forbidden to apply any thread sealant to the thread surface during the assembly process. Loosening is prevented through a precise tight fit of the threads.

[0014] Furthermore, to ensure smooth assembly and prevent wear on the threaded parts, the hollow clamping nut and the outer wall of the cylinder head combustion chamber are heated to 80°C before being screwed into the thread. After the thread is screwed in, the assembly is cooled to room temperature, and a torque of 8 N·m is applied to the hollow clamping nut to axially press and fix the sensor sleeve into the pre-embedded mounting hole.

[0015] The beneficial effects of this invention are as follows: This invention optimizes the mounting interface structure and assembly process of the combustion chamber cylinder block temperature sensor. By controlling foreign objects, installation methods, and sealing performance, the thermal resistance of the heat transfer process is effectively controlled. This not only ensures the accuracy of the temperature sensor measurement but also ensures the safety of the temperature sensor during long-term engine operation.

[0016] Specifically, the mounting structure employs a stepped hole with a flat-bottomed pre-embedded mounting hole at the bottom, a transition fit between the sensor sleeve and the pre-embedded mounting hole (radial base shaft system K6 / h7), an effective length of the sensor sleeve that is at least 1 mm greater than the depth of the pre-embedded mounting hole, a hollow clamping nut with a fine thread for a precise tight fit, and brass material with a thermal conductivity greater than 240 W / (m·K). This fundamentally strengthens the radial contact, axial fit, and heat transfer path of the threaded pair, effectively suppressing the trend of increasing contact thermal resistance over time during engine operation and avoiding thermal resistance fluctuations and abnormal temperature signals caused by periodic operating condition impacts. At the same time, the high thermal conductivity material and precise fit structure disperse the local heat load of the cylinder head, preventing the sensor from being damaged due to excessive local heat load. The assembly process strictly follows the specific implementation of the preparation stage (oil removal, wiping with a lint-free cloth until no visible particles are visible, baking at 30℃ for 20 minutes to remove humidity, grinding of oxide layer, and cleaning of threads with compressed air), the insertion stage (axial fitting and radial contact of the sleeve + orderly cable lead-out), and the clamping stage (precise tight fit of fine thread, prohibition of thread adhesive, and application of 8 N·m torque). This further eliminates the influence of foreign matter, humidity, and oxidation on the contact interface, ensuring minimal initial contact thermal resistance and stability during long-term operation.

[0017] Compared with existing technologies, this invention directly solves the core problems of increased thermal resistance between the sensor and the measured object during operation, abnormal signals under periodic impacts, and sensor damage caused by excessive local heat loads, under the high power density characteristics of two-stroke aero-piston engines. It avoids brief overheating during high-speed load increases, providing the control system with a true and reliable cylinder temperature signal, completely preventing misjudgments of engine operating conditions, and significantly improving the product's safe operation and flight control reliability. Through these optimizations, not only is the signal stability of the temperature sensor significantly improved under periodic operating conditions, but the sensor's lifespan is also extended, adapting to stable measurement requirements under varying loads, reducing the disruption of the temperature field during measurement, and overall improving the engine's safety, reliability, and flight mission success rate. In practical applications, this invention achieves accurate temperature monitoring under long-term stable operation by continuously suppressing the increase in contact thermal resistance and enhancing heat load dispersion, effectively eliminating safety hazards caused by abnormally increased thermal resistance, and providing more reliable power support for multi-purpose, long-range UAVs.

[0018] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the pre-embedded installation structure of the wall temperature sensor for a two-stroke aero-piston engine in this invention.

[0020] Figure 2 The flowchart of temperature acquisition and heat transfer on the outer wall of the combustion chamber in this invention.

[0021] Figure 3 The process flow diagram of the temperature sensor assembly process in this invention.

[0022] Reference numerals: 1-Cylinder head; 2-Sensor sleeve; 3-Hollow clamping nut. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0024] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0025] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0026] Example 1 like Figure 1 The diagram shows a pre-embedded mounting structure for a wall temperature sensor in a two-stroke aero-piston engine, comprising a cylinder head 1, a sensor sleeve 2, and a hollow clamping nut 3. A stepped hole is provided on the outer wall of the combustion chamber of the cylinder head 1, with the bottom of the stepped hole serving as a pre-embedded mounting hole. This pre-embedded mounting hole is flat-bottomed and countersunk to ensure good contact between the bottom of the hole and the axial end face of the sensor sleeve 2. The temperature sensor is located inside the sensor sleeve 2, and its tail cable is led out through the inner hole of the hollow clamping nut 3. The sensor sleeve 2 is inserted into the pre-embedded mounting hole, forming axial contact with the bottom surface of the hole and radial contact with the hole wall. The hollow clamping nut 3 is threaded to the opening side of the stepped hole, pressing the sensor sleeve 2 tightly within the pre-embedded mounting hole, thus achieving a heat transfer path from the combustion chamber through the cylinder head 1 and sensor sleeve 2 to the temperature sensor.

[0027] The sensor sleeve 2 and the pre-embedded mounting hole adopt a transition fit, and the radial contact adopts a K6 / h7 transition fit based on the shaft. The effective length of the sensor sleeve 2 is at least 1 mm greater than the depth of the pre-embedded mounting hole. The hollow clamping nut 3 and the cylinder head 1 are threaded with M10×1 fine threads, and the fit tolerance is 5H / 4g, which improves the sealing performance of the threaded connection and avoids accelerated oxidation of the sensor housing and the surface of the countersunk hole of the combustion chamber cylinder block during high-temperature engine operation. The hollow clamping nut 3 is made of brass with a thermal conductivity greater than 240W / (m·K), and the outer wall of the combustion chamber of the cylinder head 1 is made of ZL107 aluminum alloy, which enhances the heat transfer process of the threaded pair and reduces the damage to the temperature field of the outer wall of the combustion chamber caused by the installation of the cylinder temperature sensor.

[0028] Example 2 like Figure 3 The image shows a pre-embedded mounting structure for a wall temperature sensor in a two-stroke aero-piston engine. The installation process is carried out in the following sequence: a) Preparation stage: Oil stain removal, humidity control, and oxide layer treatment are performed on the interior of the pre-embedded mounting hole of the stepped hole, the outer surface of the sensor sleeve 2, and the threaded surface of the hollow clamping nut 3. Specifically, a carburetor is used to clean the interior of the pre-embedded mounting hole and the surface of the sensor sleeve 2, and then wiped with a white lint-free cloth until no visible particles are visible on the cloth. After cleaning, the sensor sleeve 2 and the hollow clamping nut 3 are placed in a 30℃ oven for 20 minutes to remove surface moisture. The oxide layer on the ZL107 aluminum alloy inner surface of the pre-embedded mounting hole of the cylinder head 1 is removed by grinding. Compressed air is used to clean the threaded surface of the hollow clamping nut 3 and the corresponding threaded surface of the stepped hole.

[0029] b) Insertion stage: Insert the sensor sleeve 2 into the pre-embedded mounting hole, so that its bottom surface is axially fitted with the flat bottom of the pre-embedded mounting hole and the hole wall is radially contacted. At the same time, lead out the temperature sensor tail cable through the inner hole of the hollow clamping nut 3.

[0030] c) Tightening stage: To ensure smooth assembly and prevent wear on the threaded parts, heat the hollow clamping nut and the outer wall of the cylinder head combustion chamber to 80°C before screwing in the threads; screw the hollow clamping nut 3 into the threaded part of the stepped hole. Do not apply any thread adhesive to the threaded surface during the assembly process. After the threads are screwed in, cool to room temperature and apply a torque of 8 N·m to the hollow clamping nut 3 to axially press and fix the sensor sleeve 2 in the pre-embedded mounting hole.

[0031] like Figure 2As shown, during the operation of a two-stroke aero-piston engine, heat from the combustion chamber is transferred through the cylinder head 1 to the sensor sleeve 2, and then to the temperature sensor. The sensor feeds back the temperature signal to the control system. The contact thermal resistance between the sensor and the measured object is strictly controlled to a minimum level through the above-mentioned structural fit and assembly process: flat-bottomed holes, K6 / h7 transition fit, and a length difference of at least 1mm ensure radial and axial contact quality; the high thermal conductivity of the brass hollow clamping nut 3 and the precision tight fit of the fine thread enhance the heat transfer path of the thread pair; thorough cleaning during the preparation stage, baking at 30℃ for 20 minutes to dehumidify, grinding of the oxide layer, cleaning with compressed air, and a clamping torque of 8N·m and prohibition of the use of thread sealant during the clamping stage completely eliminate the influence of oil, humidity, oxides and impurities on the contact interface, ensuring that the initial contact thermal resistance is minimized and remains stable during long-term engine operation.

[0032] When the engine is under high speed and load, periodic operating condition shocks occur. Since the contact thermal resistance does not increase with the running time, the temperature signal always accurately reflects the actual temperature change trend of the combustion chamber, avoiding misjudgment of the operating condition by the control system. At the same time, the precise fit and high thermal conductivity material effectively disperse the local heat load of the cylinder head, preventing the sensor from being damaged due to excessive local heat load.

[0033] After the above installation is completed before engine start, during normal engine operation, the heat from the combustion chamber is continuously and efficiently transferred to the temperature sensor through cylinder head 1 and sensor sleeve 2. When the load increases and the cylinder temperature rises at a faster rate, the contact thermal resistance remains stable, the temperature data is accurate, and there is no brief overheating phenomenon. Even under long-term periodic impact, the sensor will not show abnormal signals or be damaged, thus ensuring the safe operation of the engine and the reliability of flight control.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A pre-embedded mounting structure for a wall temperature sensor in a two-stroke aero-piston engine, characterized in that, Includes temperature sensor, sensor sleeve, and hollow clamping nut; A stepped hole is provided on the outer wall of the cylinder head combustion chamber. The bottom of the stepped hole is a pre-embedded mounting hole, which is a flat-bottomed hole. The temperature sensor is located inside the sensor sleeve, and its tail cable is led out through the inner hole of the hollow clamping nut. The sensor sleeve is inserted into the pre-embedded mounting hole and forms axial contact with the bottom surface of the pre-embedded mounting hole and radial contact with the hole wall. The hollow clamping nut is threaded to the opening side of the stepped hole and presses the sensor sleeve into the pre-embedded mounting hole, realizing the heat transfer path of the combustion chamber heat to the temperature sensor through the cylinder head and the sensor sleeve.

2. The pre-embedded installation structure according to claim 1, characterized in that, The sensor sleeve and the pre-embedded mounting hole adopt a transition fit, and the depth of the pre-embedded mounting hole is less than the effective length of the sensor sleeve, so as to enhance heat transfer in the connection area and reduce contact thermal resistance.

3. The pre-embedded installation structure according to claim 2, characterized in that, The radial contact between the sensor sleeve and the pre-embedded mounting hole adopts a K6 / h7 transition fit based on the shaft system to ensure the quality of radial contact; the effective length of the sensor sleeve is at least 1 mm greater than the depth of the pre-embedded mounting hole.

4. The pre-embedded installation structure according to claim 1, characterized in that, The hollow clamping nut and the cylinder head thread are made of fine thread with a tolerance of 5H / 4g to improve the sealing performance of the threaded connection and enhance the heat transfer process of the threaded pair.

5. The pre-embedded installation structure according to claim 1, characterized in that, The hollow compression nut is made of a material with a thermal conductivity greater than 240 W / (m·K).

6. The pre-embedded installation structure according to claim 5, characterized in that, The hollow clamping nut is made of brass, and the outer wall of the cylinder head combustion chamber is made of ZL107 aluminum alloy.

7. A method for pre-embedding a wall temperature sensor for a two-stroke aero-piston engine, characterized in that, The installation process using the pre-embedded installation structure as described in any one of claims 1 to 6 includes the following steps: a) Preparation stage: Remove oil stains, control humidity and treat oxide layer on the inside of the pre-embedded mounting hole of the stepped hole, the outer surface of the sensor sleeve and the threaded surface of the hollow clamping nut; b) Insertion stage: Insert the sensor sleeve into the pre-embedded mounting hole, so that its bottom surface is axially fitted with the flat bottom of the pre-embedded mounting hole and radially contacts the hole wall, and at the same time, lead out the temperature sensor tail cable through the inner hole of the hollow clamping nut; c) Tightening stage: Screw the hollow clamping nut into the threaded part of the stepped hole, and apply a specified torque to tighten and fix the sensor sleeve in the pre-embedded mounting hole.

8. The pre-embedded installation method according to claim 7, characterized in that, During the preparation stage, a carburetor is used to clean the inside of the pre-embedded mounting hole and the surface of the sensor sleeve, and a white lint-free cloth is used to wipe it until no visible particles are visible on the surface of the lint-free cloth. After cleaning, the sensor sleeve and the hollow clamping nut are placed in a 30°C oven for 20 minutes to remove surface moisture. The oxide layer on the inner surface of the ZL107 aluminum alloy of the pre-embedded mounting hole in the cylinder head is polished to remove it. Compressed air is used to clean the threaded surface of the hollow clamping nut and the corresponding threaded surface of the stepped hole.

9. The pre-embedded installation method according to claim 7, characterized in that, The threaded connection used in the tightening stage is a fine thread, and no thread-locking adhesive is allowed to be applied to the thread surface during assembly. Loosening is prevented through a precise tight fit of the threads.

10. The pre-embedded installation method according to claim 9, characterized in that, The hollow clamping nut and the outer wall of the cylinder head combustion chamber are heated to 80°C and then screwed in with threads. After the threads are screwed in, they are cooled to room temperature. A torque of 8 N·m is applied to the hollow clamping nut to axially press and fix the sensor sleeve into the pre-embedded mounting hole.

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