A method for fixing and protecting a sensor wire harness of a wind-cooled aviation piston engine

Abstract

The present application belongs to the technical field of aviation piston engine. In order to solve the problem of short service life and unstable signal transmission of sensor wire harness under high temperature and high vibration conditions, a kind of fixing and protecting method for air-cooled aviation piston engine sensor wire harness is disclosed. Pre-tightening force is applied to the wire harness at the wire harness fixing part of the engine structure, the gap between the insulation layer and the wire core is eliminated, and the insulation layer and the wire core form a closely combined composite load-bearing structure, and the insulation layer is used to improve the vibration resistance. Metal sleeve with high thermal conductivity is arranged between different fixing parts of the wire harness, which can quickly spread and conduct the local heat along the axial direction of the sleeve, balance the temperature distribution of each part of the wire harness, and at the same time, the heat capacity can buffer the periodic temperature fluctuation. The present application blocks the coupling degradation cycle of high temperature and vibration, and improves the service life and signal transmission stability of the wire harness.

Description

Technical Field

[0001] This invention belongs to the field of aviation piston engine technology, specifically relating to a method for fixing and protecting sensor wiring harnesses in air-cooled aviation piston engines. Background Technology

[0002] With the vigorous development of the low-altitude economy and the continuous expansion of the unmanned industry, the market demand for small, air-cooled two-stroke aircraft piston engine technology is showing a year-on-year upward trend. As the core power unit of aircraft, the reliability and stability of aircraft piston engines are directly related to flight safety. As a complex system, the engine includes actuators and control units as structural components. Among them, the sensor harness, as an important channel for engine signal feedback and command transmission, is responsible for transmitting key parameters such as cylinder temperature, cylinder pressure, and speed to the electronic control unit in real time, and is a key component affecting the safe and stable operation of the engine.

[0003] In aerospace equipment, limited space dictates a compact system layout, making a coupled layout design between the wiring harness and the engine block essential. The wiring harness is fixed using structural components as fulcrums or embedded within these components for routing. The operating environment for cylinder temperature sensor wiring harnesses near the cylinder block is particularly harsh. The cylinder surface temperature of a two-stroke air-cooled engine is higher and vibrates more strongly than that of a water-cooled engine. Combined with greater heat dissipation at high altitudes and low temperatures, the wiring harnesses laid around the engine block are constantly exposed to high temperatures. Simultaneously, the cyclical operating characteristics of piston engines cause periodic fluctuations in cylinder temperature. Heat transferred from the high-temperature fluctuating gases within the cylinder via thermal conduction, as well as the intense vibrations generated by the piston's reciprocating motion, are directly transmitted to the wiring harness through fixed contact points.

[0004] Existing technologies for wire harness fixing and protection design have the following shortcomings: First, vibration and impact significantly affect the fixing area. Insufficient clamping force is detrimental to the insulation layer's reinforcement of the wire core, leading to relative separation between the insulation layer and the metal wire core under vibration. Multiple wire cores may become loose or even fatigue-fractured due to lack of insulation protection. Second, direct contact between the wire harness and high-temperature structural components causes localized heat load concentration. Under periodic high-temperature conditions, gaps gradually form between the wire core and the insulation layer, reducing the structural rigidity of the wire harness and shortening its service life. Third, the uneven temperature distribution around the engine block results in significant differences in heating at different parts of the wire harness. This uneven heat load can interfere with sensor signal transmission, affecting the stability of measurement results and the accuracy of the control system. Furthermore, air-cooled engine block components have numerous heat sinks. Cables passing through the heat dissipation zone will come into contact with these spaced-apart heat sinks, easily leading to localized stress and overheating, further exacerbating the risk of wire harness damage. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to solve the above problems and provide a method for fixing and protecting the sensor wiring harness of an air-cooled aero-piston engine.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for fixing and protecting sensor wiring harnesses in an air-cooled aero-piston engine includes the following steps: At the fixing point of the wiring harness on the engine structural component, a pre-tightening force is applied to the wiring harness to eliminate the gap between the wiring harness insulation layer and the wire core, so that the insulation layer and the wire core form a tightly fitting composite load-bearing structure. The insulation layer participates in the load bearing to improve the vibration resistance of the wiring harness fixing point. A metal sleeve with a high thermal conductivity is installed between different fixed parts of the wire harness. The high thermal conductivity of the metal sleeve is used to conduct the local heat from the fixed contact point to the wire harness rapidly along the axial direction of the sleeve, so as to balance the temperature distribution of each part of the wire harness. At the same time, the heat capacity of the metal sleeve is used to buffer the periodic temperature fluctuations, so as to avoid interference to signal transmission caused by uneven local heating and periodic temperature changes.

[0007] Furthermore, the method to eliminate the gap between the wire harness insulation layer and the wire core is as follows: heat shrink tubing is fitted onto the wire harness fixing part, and the radial compression force is applied to the insulation layer by utilizing the heat shrinkage characteristics of the heat shrink tubing to eliminate the gap.

[0008] Furthermore, the material of the heat shrink tubing is PTFE or high-temperature resistant polyolefin.

[0009] Furthermore, the method for applying pre-tightening force to the wire harness is as follows: clamps are used to clamp and fix the wire harness fixing parts, forming a rigid hard contact between the clamps and the wire harness.

[0010] Furthermore, before applying a tightening torque to the clamp, the wire harness fixing part is first heated to a temperature of 120°C.

[0011] Furthermore, the metal sleeve is made of a material with better heat insulation properties than the engine block material, enabling the cable to operate in a near-constant temperature environment.

[0012] Furthermore, the metal sleeve is a stainless steel sleeve.

[0013] Furthermore, the wire core of the wire harness is a multi-strand twisted pair structure, and the outer layer of the wire harness is PVC insulating rubber.

[0014] The beneficial effects of this invention are as follows: The method for fixing and protecting the sensor harness of an air-cooled aero-piston engine provided by this invention achieves the following beneficial effects through the synergistic design of structural reinforcement and thermal equilibrium: I. Improved vibration resistance at wiring harness fixing points. At the wiring harness fixing points on engine structural components, a pre-tightening force is applied to the wiring harness to eliminate gaps between the insulation layer and the wire core, creating a tightly fitted composite load-bearing structure. The methods for eliminating gaps include using heat-shrink tubing at the wiring harness fixing points. The heat-shrink tubing's shrinkage properties apply radial pressure to the insulation layer, ensuring a tight fit between the three components. Simultaneously, clamps are used to secure the wiring harness fixing points, creating a rigid contact between the clamps and the wiring harness, further ensuring the adhesion between the insulation layer and the wire core. When vibration and impact reach the fixed part, the force is transmitted and dispersed and absorbed layer by layer through the clamp, heat shrink tubing, insulation layer, and wire core. The wire core is no longer an isolated component that bears the vibration and impact alone, but together with the insulation layer and heat shrink tubing, it forms a composite load-bearing structure. The insulation layer truly participates in the load-bearing, which greatly reduces the equivalent stress level of the wire core and avoids the problem of mutual wear and fatigue fracture of multiple wire cores due to loose insulation layer. This significantly improves the service life of the wiring harness in the high vibration environment of the engine.

[0015] Second, it effectively reduces the interference of uneven heat load on sensor signals. Metal sleeves are installed between different fixed points of the wiring harness. These sleeves are made of a material with superior insulation properties compared to engine block materials. Utilizing their high thermal conductivity, the localized heat transferred from the fixed contact points to the wiring harness is rapidly diffused along the sleeve's axis, preventing heat concentration at the contact points and ensuring a more uniform temperature across the wiring harness. This avoids physical damage caused by localized overheating. Simultaneously, the heat capacity of the metal sleeves buffers periodic temperature fluctuations, keeping the wiring harness in a near-constant temperature operating environment. This effectively reduces the interference of temperature changes on sensor signal transmission, improving the stability of measurement results and the accuracy of the control system.

[0016] Third, the synergistic effect of the two technologies breaks the coupled degradation cycle of high temperature and vibration. In existing technologies, high temperature causes the insulation layer to expand and separate from the wire core, and vibration accelerates the fatigue fracture of the separated wire core, with the harmful effects of the two loads superimposed. This invention eliminates gaps through structural reinforcement, allows the insulation layer to participate in load bearing, and reduces the temperature load level through thermal equalization, fundamentally breaking the thermal-vibration coupled degradation cycle. This effectively solves the problems of short cable life and frequent failures in high-temperature and high-vibration areas of the engine, further improving the engine's adaptability to complex flight conditions and its ability to resist external interference, and enhancing the safety of the aircraft.

[0017] 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

[0018] 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 metal sleeve and cylinder structure in this invention.

[0019] Figure 2 This is a schematic diagram of the wire harness and clamp in this invention.

[0020] Reference numerals: 1-Cylinder body; 2-Wire harness; 3-Metal sleeve; 21-Twisted pair wire core; 22-Insulating rubber; 23-Heat shrink tubing. Detailed Implementation

[0021] 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.

[0022] 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.

[0023] 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.

[0024] Example 1 like Figures 1-2The image shows a method for fixing and protecting sensor wiring harnesses in air-cooled aero-piston engines. This method is applied to the installation of sensor wiring harnesses in air-cooled aero-piston engines and includes two technical measures: structural reinforcement and thermal equalization. The wiring harness 2 includes a twisted pair core 21 and a PVC insulating sheath 22 covering the outside of the twisted pair core 21. The twisted pair core 21 is a multi-strand twisted pair structure used to transmit electrical signals from the sensor. The multi-strand twisted pair design improves the wiring harness 2's resistance to electromagnetic interference. The PVC insulating sheath 22 serves as an insulating layer, ensuring good insulation performance between the wiring harness 2 and the engine mounting parts and adjacent external locations.

[0025] The structural reinforcement measures include heat shrink tubing 23 and clamps. Heat shrink tubing 23 is fitted onto the fixed part of the wire harness 2 where it is fixed to engine structural components such as the cylinder block 1. It is made of PTFE material. The heat shrink tubing 23 applies radial pressure to the outer surface of the PVC insulation rubber 22 by utilizing its heat shrinkage characteristics, eliminating the gap between the PVC insulation rubber 22 and the twisted pair core 21, so that the heat shrink tubing 23, the PVC insulation rubber 22 and the twisted pair core 21 form a tightly fitted composite load-bearing structure. The clamp is used between the fixing bracket and the wire harness 2 to clamp and fix the fixed part of the wire harness 2 with the heat shrink tubing 23. The clamp and the wire harness 2 form a rigid hard contact.

[0026] The heat balance measure is to use a metal sleeve 3, which is made of stainless steel. Stainless steel has a better heat insulation effect than the engine body material. The metal sleeve 3 is sleeved between different fixing parts of the wire harness 2. The inner diameter of the metal sleeve 3 is larger than the outer diameter of the wire harness 2. The wire harness 2 passes through the inside of the metal sleeve 3. The two ends of the metal sleeve 3 are close to the fixing parts of the wire harness 2 on the engine structural components.

[0027] When installing sensor wiring harnesses on air-cooled aero piston engines, heat shrink tubing 23 is first pre-installed at the fixed locations where the wiring harness 2 needs to be fixed to engine structural components such as the cylinder block 1. The heat shrink tubing 23 is heated to shrink it. After shrinking, the heat shrink tubing 23 applies a continuous radial pressure to the outer surface of the PVC insulation 22, eliminating the initial gap between the PVC insulation 22 and the twisted pair core 21, so that the heat shrink tubing 23, the PVC insulation 22, and the twisted pair core 21 form a tightly fitted whole.

[0028] Then, the fixing part of the wire harness 2 is heated and the heating temperature is controlled at 120℃. This makes the thickness of the PVC insulation 22 stabilize after it expands due to heat during installation, reducing the installation deviation caused by the thickness of the PVC insulation 22 changing with temperature. This ensures that the PVC insulation 22 and the twisted pair core 21 are fully in contact before subsequent clamping operations.

[0029] Subsequently, clamps are used to clamp and fix the wire harness 2 after it has been treated with heat shrink tubing 23, so that the fixing bracket and the wire harness 2 form a rigid hard contact through the clamps. By applying an appropriate tightening torque to the clamps, the clamps squeeze the heat shrink tubing 23 and the PVC insulation rubber 22 to further eliminate the residual gaps at the fixing part of the wire harness 2, and ensure that the PVC insulation rubber 22 and the twisted pair core 21 maintain a reliable fit in the high vibration environment of the engine.

[0030] Finally, stainless steel metal sleeves 3 are installed between different fixing parts of the wire harness 2, such as... Figure 1 As shown, the metal sleeve 3 is fitted onto the wire harness 2 and is located in the area between the heat sinks of the cylinder 1, and is used to provide thermal equalization protection for the wire harness 2.

[0031] When an air-cooled aero-piston engine is running, the surface temperature of cylinder block 1 is relatively high. Cylinder block 1 is designed with numerous heat sinks. Wiring harness 2 passes through the heat dissipation zone and contacts the spaced-apart heat sinks, resulting in localized heat load concentration at the fixed contact points (e.g., ...). Figure 1 The temperatures at each contact point (t1, t2, t3, t4, t5, t6, t7, t8, t9) are measured. Heat from the high-temperature flue gas inside cylinder 1, conducted through thermal conduction, is transferred to the wiring harness 2 via the fixed contact points. The stainless steel metal sleeve 3 has a high thermal conductivity coefficient, allowing the localized heat conducted from the fixed contact points to the wiring harness 2 to be rapidly conducted and diffused along the axial direction of the metal sleeve 3. This prevents localized heat concentration at the contact points, resulting in a more uniform temperature across the wiring harness 2. Simultaneously, the heat capacity of the stainless steel metal sleeve 3 buffers the temperature fluctuations caused by the periodic operation of the piston engine, smoothing out temperature peaks and troughs, thus placing the wiring harness 2 in a near-constant temperature working environment and ensuring the cable operates in a near-constant temperature environment.

[0032] When the vibration generated by the piston engine is transmitted to the fixing part of the wiring harness 2 through the cylinder 1, the vibration impact force is transmitted and dispersed and absorbed layer by layer through the clamp → heat shrink tubing 23 → PVC insulation 22 → twisted pair core 21 due to the rigid hard contact between the clamp and the wiring harness 2. The twisted pair core 21 is no longer an isolated component that bears the vibration impact alone, but together with the PVC insulation 22 and the heat shrink tubing 23, it forms a composite load-bearing structure. The PVC insulation 22 truly participates in the load bearing, which greatly reduces the equivalent stress level of the twisted pair core 21 and avoids the problem of mutual wear and fatigue fracture of multiple cores due to the loosening of the PVC insulation 22.

[0033] When the piston engine is in a periodic high-temperature operating state, the PVC insulation 22 tends to separate from the twisted pair core 21 due to thermal expansion. However, because the heat shrink tubing 23 applies a continuous radial clamping force to the PVC insulation 22 and the clamp provides rigid constraint, the adhesion between the PVC insulation 22 and the twisted pair core 21 is maintained, and the load-bearing function of the insulation layer will not be lost due to the temperature rise. At the same time, the stainless steel metal sleeve 3 quickly equalizes the heat of local hot spots, reduces the temperature peak of each fixed part of the wire harness 2, and further ensures the continuity of the structural reinforcement effect.

[0034] The two technologies work synergistically to fundamentally prevent the coupling degradation cycle of high temperature and vibration on harness 2. Structural reinforcement measures eliminate the gap between the PVC insulation sheath 22 and the twisted-pair core 21, allowing the insulation layer to truly participate in load-bearing and improving the vibration resistance of harness 2. Thermal equalization measures utilize the high thermal conductivity and heat capacity of the stainless steel sheath 3 to quickly equalize local hot spots and buffer periodic temperature fluctuations, reducing the interference of temperature unevenness on signal transmission. The organic combination of these two technologies effectively solves the problems of short cable life and frequent failures in high-temperature and high-vibration areas of the engine, further improving the engine's adaptability to complex flight conditions and its resistance to external interference, thus enhancing the safety of the aircraft.

[0035] 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 method for fixing and protecting the sensor wiring harness of an air-cooled aero-piston engine, characterized in that, Includes the following steps: At the fixing point of the wiring harness on the engine structural component, a pre-tightening force is applied to the wiring harness to eliminate the gap between the wiring harness insulation layer and the wire core, so that the insulation layer and the wire core form a tightly fitting composite load-bearing structure. The insulation layer participates in the load bearing to improve the vibration resistance of the wiring harness fixing point. A metal sleeve with a high thermal conductivity is installed between different fixed parts of the wire harness. The high thermal conductivity of the metal sleeve is used to conduct the local heat from the fixed contact point to the wire harness rapidly along the axial direction of the sleeve, so as to balance the temperature distribution of each part of the wire harness. At the same time, the heat capacity of the metal sleeve is used to buffer the periodic temperature fluctuations, so as to avoid interference to signal transmission caused by uneven local heating and periodic temperature changes.

2. The method according to claim 1, characterized in that, The method to eliminate the gap between the wire harness insulation layer and the wire core is as follows: heat shrink tubing is fitted onto the wire harness fixing part, and the radial compression force is applied to the insulation layer by utilizing the heat shrink characteristics of the heat shrink tubing to eliminate the gap.

3. The method according to claim 2, characterized in that, The heat shrink tubing is made of PTFE or high-temperature resistant polyolefin.

4. The method according to claim 1 or 2, characterized in that, The method for applying pre-tightening force to the wire harness is to use clamps to clamp and fix the wire harness fixing parts, forming a rigid hard contact between the clamps and the wire harness.

5. The method according to claim 4, characterized in that, Before applying a tightening torque to the clamp, the wire harness fixing part is first heated to a temperature of 120℃.

6. The method according to claim 1, characterized in that, The metal sleeve is made of a material with better insulation performance than the engine block material, allowing the cable to operate in a near-constant temperature environment.

7. The method according to claim 1, characterized in that, The metal sleeve is a stainless steel sleeve.

8. The method according to claim 1, characterized in that, The wire core of the wire harness is a multi-strand twisted pair structure, and the outer layer of the wire harness is PVC insulating rubber.

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