An aeroengine compressor based on a shock absorption control mechanism

Abstract

The present invention relates to the technical field of mechanical parts, and particularly to an aeroengine compressor based on a shock absorption and regulation mechanism, which includes an engine casing, a fan assembly, a fan casing, a high-pressure compressor casing, a combustion chamber, a high-pressure turbine casing, etc.; a fan casing is connected inside the casing, a fan assembly is connected inside the fan casing, a high-pressure compressor casing is connected to one side of the fan casing, a combustion chamber is connected to one side of the high-pressure compressor casing, and a high-pressure turbine casing is connected to one side of the combustion chamber. The present invention is provided with multiple groups of first hydraulic dampers and first shock absorption springs, which can reduce the longitudinal vibration amplitude of the connecting plate. It is also provided with multiple groups of second hydraulic dampers, second shock absorption springs, third hydraulic dampers and third shock absorption springs, which can reduce the transverse vibration amplitude of the connecting plate, thereby helping to maintain the stability and uniformity of the internal air flow of the present invention, improving the quality of air flow, contributing to enhancing the energy conversion efficiency of the present invention, and achieving an energy-saving effect.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical parts, and particularly to a compressor of an aeroengine based on a shock absorption control mechanism. Background Art

[0002] The development of aerospace, although originating from the needs of military applications, has far-reaching impacts on the national economy and social life. It is not only a symbol of a country's scientific and technological strength but also an important force driving global progress. Through applications such as satellite communication, weather forecasting, and earth observation, aerospace technology has profoundly changed the way of human life. As one of the most intuitive applications in the civilian field, the aviation industry has greatly promoted the development of international trade and tourism.

[0003] In aerospace aircraft, the engine is one of the most core and crucial components. Existing aircraft engines mainly rely on fuel combustion to drive the rotor to rotate at high speed, thereby generating thrust or lift to provide flight power for the aircraft. However, in this process, the high-speed movement of the internal airflow and the extremely high air pressure difference in the engine create extreme working conditions. Such extreme working conditions will cause severe vibrations of the internal mechanism, and the excessive vibration level will accelerate the wear between mechanical components, cause structural fatigue, and may even lead to component damage, seriously affecting the performance and lifespan of the engine. Summary of the Invention

[0004] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a compressor of an aeroengine based on a shock absorption control mechanism.

[0005] A compressor of an aeroengine based on a shock absorption control mechanism includes an engine housing, a fan assembly, a fan casing, a high-pressure compressor housing, a combustion chamber, a high-pressure turbine housing, a low-pressure turbine housing, a connecting plate, a first connecting block, a first hydraulic damper, and a first shock-absorbing spring. The fan casing is connected inside the housing, the fan assembly is connected inside the fan casing, the high-pressure compressor housing is connected to one side of the fan casing, the combustion chamber is connected to one side of the high-pressure compressor housing, the high-pressure turbine housing is connected to one side of the combustion chamber, the low-pressure turbine housing is connected to one side of the high-pressure turbine housing. At least two connecting plates are connected between the high-pressure compressor housing and the high-pressure turbine housing, and the connecting plates are evenly distributed circumferentially along the high-pressure compressor housing and the high-pressure turbine housing. At least two first connecting blocks are connected to the inner wall of the engine housing at circumferential intervals, and a first hydraulic damper is connected between each first connecting block and the connecting plate. The piston rod of the first hydraulic damper is fixedly connected to the connecting plate, and a first shock-absorbing spring is connected between the first hydraulic damper and the connecting plate.

[0006] As a further preferred solution, it further includes a second hydraulic damper, a first rotating rod and a second shock-absorbing spring. Second hydraulic dampers are connected to the mutually remote sides of the connecting plates. The second hydraulic dampers are all located on the side of the connecting plates close to the high-pressure turbine housing. Second shock-absorbing springs are connected between the housing and the piston rod of each second hydraulic damper. First rotating rods are rotatably connected to the piston rods of the second hydraulic dampers, and the first rotating rods are all rotatably connected to the first hydraulic damper.

[0007] As a further preferred solution, it further includes a third hydraulic damper, a second rotating rod and a third shock-absorbing spring. Third hydraulic dampers are connected to the mutually remote sides of the connecting plates. The third hydraulic dampers are all located on the side of the connecting plates close to the high-pressure compressor housing. Third shock-absorbing springs are connected between the housing and the piston rod of each third hydraulic damper. Second rotating rods are rotatably connected to the piston rods of the third hydraulic dampers, and the second rotating rods are all rotatably connected to the first hydraulic damper.

[0008] As a further preferred solution, it further includes a first connecting frame and a second connecting frame. First connecting frames are connected between the piston rods of adjacent second hydraulic dampers, and second connecting frames are connected between the piston rods of adjacent third hydraulic dampers.

[0009] As a further preferred solution, it further includes a temperature detector and a pressurizing component. Pressurizing components are connected to the first hydraulic damper, the second hydraulic damper and the third hydraulic damper. Temperature detectors are connected to the connecting plates. The temperature detectors are electrically connected to the engine system, and the pressurizing components are all electrically connected to the engine system.

[0010] As a further preferred solution, the pressurizing component includes a cylinder, a liquid storage tank and a connecting pipe. Cylinders and connecting pipes are connected to the housing of the first hydraulic damper, the second hydraulic damper and the third hydraulic damper. Liquid storage tanks are connected between the connecting pipes and the cylinders. The first hydraulic damper, the second hydraulic damper and the third hydraulic damper are all communicated with the connecting pipe. The liquid storage tanks are all communicated with the connecting pipe. The piston rods of the cylinders all extend into the liquid storage tanks, and the cylinders are all electrically connected to the engine system.

[0011] As a further preferred solution, it further includes a connecting frame and an air-sealing shock-absorbing ring. A connecting frame is connected inside the engine housing, and an air-sealing shock-absorbing ring is connected between the fan casing and the connecting frame.

[0012] As a further preferred solution, it further includes a second connecting block, a third connecting block, a fourth hydraulic damper and a fourth shock-absorbing spring. At least two second connecting blocks are circumferentially and spacedly connected to the outer wall of the low-pressure turbine housing, and at least two third connecting blocks are circumferentially and spacedly connected to the inner wall of the engine housing. A fourth hydraulic damper is connected between the second connecting block and the third connecting block. The piston rods of the fourth hydraulic dampers are fixedly connected to the second connecting blocks, and a fourth shock-absorbing spring is connected between the housing of the fourth hydraulic damper and its piston rod.

[0013] The present invention has the following advantages: 1. The present invention is provided with multiple groups of first hydraulic dampers and first shock-absorbing springs, which can reduce the longitudinal vibration amplitude of the connecting plate. It is also provided with multiple groups of second hydraulic dampers, second shock-absorbing springs, third hydraulic dampers and third shock-absorbing springs, which can reduce the transverse vibration amplitude of the connecting plate, thereby helping to maintain the stability and uniformity of the internal air flow of the present invention, improving the quality of air flow, contributing to enhancing the energy conversion efficiency of the present invention, and achieving an energy-saving effect.

[0014] 2. The present invention is also provided with a connecting frame and an air seal shock-absorbing ring, which can reduce the vibration amplitude of the fan casing and improve the stability and uniformity of air intake. It is also provided with a fourth hydraulic damper and a fourth shock-absorbing spring, which can reduce the vibration amplitude of the low-pressure turbine housing, further extend the service life of the present invention, and reduce potential safety hazards.

[0015] 3. The present invention is also provided with a temperature detector and a pressurizing component to improve the pressure-bearing capacity of the first hydraulic damper, the second hydraulic damper and the third hydraulic damper to adapt to different output powers of the present invention and ensure the shock-absorbing effect of the compressor of the present engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a three-dimensional structural schematic diagram of the present invention.

[0017] Figure 2 is a cross-sectional schematic diagram of the engine housing of the present invention.

[0018] Figure 3 is a structural schematic diagram of the combustion chamber, the high-pressure turbine housing and the low-pressure turbine housing, etc. of the present invention.

[0019] Figure 4 is a structural schematic diagram of the first connecting block and the first hydraulic damper, etc. of the present invention.

[0020] Figure 5 is a structural schematic diagram of the connecting plate, the first connecting block and the first hydraulic damper, etc. of the present invention.

[0021] Figure 6 is a structural schematic diagram of the fan assembly, the fan casing and the high-pressure compressor housing, etc. of the present invention.

[0022] Figure 7 These are schematic diagrams of the structures such as the fan casing, connection frame, and air seal shock absorber ring of the present invention.

[0023] Figure 8 These are schematic diagrams of the structures such as the second connection block and the third connection block of the present invention.

[0024] Wherein: 1 - engine casing, 2 - fan assembly, 201 - fan casing, 3 - high-pressure compressor casing, 4 - combustion chamber, 5 - high-pressure turbine outer casing, 6 - low-pressure turbine outer casing, 7 - connecting plate, 8 - first connection block, 9 - first hydraulic damper, 10 - first shock-absorbing spring, 11 - second hydraulic damper, 111 - first connection frame, 12 - first rotating rod, 13 - second shock-absorbing spring, 14 - third hydraulic damper, 141 - second connection frame, 15 - second rotating rod, 16 - third shock-absorbing spring, 17 - cylinder, 18 - liquid storage tank, 19 - connecting pipe, 20 - connection frame, 21 - air seal shock absorber ring, 22 - second connection block, 23 - third connection block, 24 - fourth hydraulic damper, 25 - fourth shock-absorbing spring, 26 - temperature detector. Detailed implementation manners

[0025] The following describes the implementation manners of the present invention with reference to the accompanying drawings.

[0026] An aeroengine compressor based on a shock-absorbing control mechanism, as Figures 1 - 8 shown, includes an engine casing 1, a fan assembly 2, a fan casing 201, a high-pressure compressor casing 3, a combustion chamber 4, a high-pressure turbine outer casing 5, a low-pressure turbine outer casing 6, a connecting plate 7, a first connection block 8, a first hydraulic damper 9, and a first shock-absorbing spring 10. The fan casing 201 is fixedly connected inside the casing. The fan assembly 2 is connected inside the fan casing 201. The high-pressure compressor casing 3 is fixedly connected to the right side of the fan casing 201. The combustion chamber 4 is fixedly connected to the right side of the high-pressure compressor casing 3. The high-pressure turbine outer casing 5 is fixedly connected to the right side of the combustion chamber 4. The low-pressure turbine outer casing 6 is fixedly connected to the right side of the high-pressure turbine outer casing 5. Three connecting plates 7 are fixedly connected between the outer walls of the high-pressure compressor casing 3 and the high-pressure turbine outer casing 5. The connecting plates 7 are evenly distributed circumferentially along the high-pressure compressor casing 3 and the high-pressure turbine outer casing 5. Three first connection blocks 8 are fixedly connected to the inner wall of the engine casing 1 at equal intervals circumferentially. A first hydraulic damper 9 is fixedly connected between each first connection block 8 and the connecting plate 7. The piston rod of the first hydraulic damper 9 is fixedly connected to the connecting plate 7. A first shock-absorbing spring 10 is fixedly connected between the first hydraulic damper 9 and the connecting plate 7.

[0027] As Figures 2 - 5As shown in the figure, it further includes a second hydraulic damper 11, a first rotating rod 12, a second shock-absorbing spring 13, a third hydraulic damper 14, a second rotating rod 15 and a third shock-absorbing spring 16. Second hydraulic dampers 11 are fixedly connected to the mutually remote sides of the connecting plate 7. The second hydraulic dampers 11 are all located on the side of the connecting plate 7 close to the high-pressure turbine housing 5. Second shock-absorbing springs 13 are fixedly connected between the housing and the piston rod of each second hydraulic damper 11. First rotating rods 12 are rotatably connected to the piston rods of the second hydraulic dampers 11. The first rotating rods 12 are all rotatably connected to the first hydraulic damper 9. Third hydraulic dampers 14 are fixedly connected to the mutually remote sides of the connecting plate 7. The third hydraulic dampers 14 are all located on the side of the connecting plate 7 close to the high-pressure compressor housing 3. Third shock-absorbing springs 16 are fixedly connected between the housing and the piston rod of each third hydraulic damper 14. Second rotating rods 15 are rotatably connected to the piston rods of the third hydraulic dampers 14. The second rotating rods 15 are all rotatably connected to the first hydraulic damper 9.

[0028] When the compressor of this engine is operating, the air flow pressure in the high-pressure compressor casing 3 and the high-pressure turbine outer casing 5 increases. Under the action of the high-speed movement of the air flow inside the high-pressure compressor casing 3 and the high-pressure turbine outer casing 5 and the extremely high air pressure difference, the high-pressure compressor casing 3 and the high-pressure turbine outer casing 5 will cause the connecting plate 7 to vibrate. Due to the elastic characteristics of the first shock-absorbing spring 10, the first shock-absorbing spring 10 can quickly compress or stretch to absorb and store part of the energy. As the first shock-absorbing spring 10 deforms, the piston rod of the first hydraulic damper 9 moves towards its casing. The liquid in the first hydraulic damper 9 will generate resistance to the movement of the piston rod. The first hydraulic damper 9 can suppress the secondary vibration that may be caused when the first shock-absorbing spring 10 rebounds, thereby reducing the longitudinal vibration amplitude of the connecting plate 7, and further achieving the shock-absorbing effect on the high-pressure compressor casing 3 and the high-pressure turbine outer casing 5. When the vibration amplitude weakens, the first shock-absorbing spring 10 can make the piston rod of the first hydraulic damper 9 rebound and reset. The first hydraulic damper 9 can prevent the excessive oscillation of the first shock-absorbing spring 10. When the connecting plate 7 vibrates horizontally, the piston rod of the second hydraulic damper 11 extends, the first connecting block 8 rotates, the piston rod of the third hydraulic damper 14 retracts, and the second connecting block 22 rotates in the reverse direction. Under the elastic action of the second shock-absorbing spring 13 and the third shock-absorbing spring 16, the piston rod of the second hydraulic damper 11 retracts, the first connecting block 8 rotates in the reverse direction, the piston rod of the third hydraulic damper 14 extends, and the second connecting block 22 rotates. According to the shock-absorbing principle of the first hydraulic damper 9 and the first shock-absorbing spring 10 above, the second hydraulic damper 11, the second shock-absorbing spring 13, the third hydraulic damper 14 and the third shock-absorbing spring 16 can reduce the horizontal vibration amplitude of the high-pressure compressor casing 3 and the high-pressure turbine outer casing 5, and further can help maintain the stability and uniformity of the air flow inside the compressor of this engine, thereby improving the quality of air flow, helping to improve the energy conversion efficiency of the entire engine, achieving the energy-saving effect, and also being able to extend the service life of the compressor of this engine, reduce the replacement frequency of parts, and reduce the maintenance cost.

[0029] As Figures 2 - 4 shown, it also includes a first connecting frame 111 and a second connecting frame 141. A first connecting frame 111 is fixedly connected between the piston rods of adjacent second hydraulic dampers 11, and a second connecting frame 141 is fixedly connected between the piston rods of adjacent third hydraulic dampers 14. The first connecting frame 111 can improve the stability between adjacent second hydraulic dampers 11, and the second connecting frame 141 can improve the stability between adjacent third hydraulic dampers 14, thereby improving the shock-absorbing effect of the compressor of this engine.

[0030] As Figure 2 , Figure 3 , Figure 6 , Figure 7 and Figure 8As shown in the figure, it further includes a connection frame 20, an air seal shock absorber ring 21, a second connection block 22, a third connection block 23, a fourth hydraulic damper 24 and a fourth shock spring 25. A connection frame 20 is fixedly connected inside the engine housing 1. An air seal shock absorber ring 21 is fixedly connected between the fan casing 201 and the connection frame 20. Three second connection blocks 22 are fixedly connected to the outer wall of the low-pressure turbine housing 6 at equal intervals along the circumferential direction. Three third connection blocks 23 are connected to the inner wall of the engine housing 1 at intervals along the circumferential direction. Fourth hydraulic dampers 24 are fixedly connected between the second connection blocks 22 and the third connection blocks 23. The piston rods of the fourth hydraulic dampers 24 are fixedly connected to the second connection blocks 22. Fourth shock springs 25 are fixedly connected between the housings and the piston rods of the fourth hydraulic dampers 24. The second connection blocks 22 are made of high-temperature resistant materials, which can isolate the high temperature of the low-pressure turbine housing 6, thereby protecting the fourth hydraulic dampers 24.

[0031] When the compressor of this engine is working, the fan assembly 2 quickly sucks in the outside air. The high-speed flowing air will cause the fan casing 201 to vibrate. The air seal shock absorber ring 21 can reduce the vibration generated by the fan casing 201 and improve the stability and uniformity of air intake. When the high-temperature gas jets out from the low-pressure turbine housing 6, the high-temperature gas will affect the air stability near the low-pressure turbine housing 6, thereby causing vibration of the low-pressure turbine housing 6. According to the shock absorption principle of the first hydraulic damper 9 and the first shock spring 10 mentioned above, the fourth hydraulic damper 24 and the fourth shock spring 25 can reduce the vibration amplitude of the low-pressure turbine housing 6, further extend the service life of the compressor of this engine, and reduce potential safety hazards.

[0032] As Figures 2 - 5 shown in the figure, it further includes a temperature detector 26 and a pressurizing assembly. Pressurizing assemblies are connected to the first hydraulic damper 9, the second hydraulic damper 11 and the third hydraulic damper 14. Temperature detectors 26 are fixedly connected to the mutually remote sides of the connecting plate 7. The temperature detectors 26 are electrically connected to the engine system. The pressurizing assemblies are electrically connected to the engine system.

[0033] As Figures 2 - 5 shown in the figure, the pressurizing assembly includes a cylinder 17, a liquid storage tank 18 and a connecting pipe 19. Cylinders 17 and connecting pipes 19 are fixedly connected to the housings of the first hydraulic damper 9, the second hydraulic damper 11 and the third hydraulic damper 14. Liquid storage tanks 18 are fixedly connected between the connecting pipes 19 and the cylinders 17. The liquid storage tanks 18 store the same liquid as that inside the first hydraulic damper 9, the second hydraulic damper 11 and the third hydraulic damper 14. The first hydraulic damper 9, the second hydraulic damper 11 and the third hydraulic damper 14 are respectively communicated with the connecting pipes 19 thereon. The liquid storage tanks 18 are communicated with the connecting pipes 19 thereon. The piston rods of the cylinders 17 extend into the liquid storage tanks 18. The cylinders 17 are electrically connected to the engine system.

[0034] When increasing the output power of the compressor of this engine, the temperature inside the engine housing 1 rises, and the vibration amplitude will increase. At this time, the temperature detector 26 detects the temperature inside the engine housing 1. When the temperature inside the engine housing 1 rises, the temperature detector 26 transmits a signal to the engine system, and the engine system controls the piston rod of the cylinder 17 to extend, so that the liquid in the liquid storage tank 18 is injected into the first hydraulic damper 9, the second hydraulic damper 11, and the third hydraulic damper 14, thereby being able to adjust the damping characteristics of the first hydraulic damper 9, the second hydraulic damper 11, and the third hydraulic damper 14, and improving the pressure-bearing capacity of the first hydraulic damper 9, the second hydraulic damper 11, and the third hydraulic damper 14 to adapt to different output powers of the compressor of this engine and ensure the shock-absorbing effect of the compressor of this engine.

[0035] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claimed rights.

Claims

1. An aero-engine compressor based on a shock-absorbing control mechanism, comprising an engine housing (1), a fan assembly (2), a fan casing (201), a high-pressure compressor housing (3), a combustion chamber (4), a high-pressure turbine outer casing (5) and a low-pressure turbine outer casing (6). The fan casing (201) is connected inside the housing, the fan assembly (2) is connected inside the fan casing (201), the high-pressure compressor housing (3) is connected to one side of the fan casing (201), the combustion chamber (4) is connected to one side of the high-pressure compressor housing (3), and the high-pressure turbine outer casing (5) is connected to one side of the combustion chamber (4). The high-pressure turbine housing (5) is connected to the low-pressure turbine housing (6) on one side, characterized in that, It further comprises a connecting plate (7), a first connecting block (8), a first hydraulic damper (9) and a first shock-absorbing spring (10). At least two connecting plates (7) are connected between the high-pressure compressor housing (3) and the high-pressure turbine outer casing (5). The connecting plates (7) are evenly distributed circumferentially along the high-pressure compressor housing (3) and the high-pressure turbine outer casing (5). At least two first connecting blocks (8) are connected to the inner wall of the engine housing (1) at circumferential intervals. A first hydraulic damper (9) is connected between each first connecting block (8) and the connecting plate (7). The piston rod of the first hydraulic damper (9) is fixedly connected to the connecting plate (7). A first shock-absorbing spring (10) is connected between each first hydraulic damper (9) and the connecting plate (7). It further comprises a second hydraulic damper (11), a first rotating rod (12) and a second shock-absorbing spring (13). A second hydraulic damper (11) is connected to each side of the connecting plate (7) away from each other. The second hydraulic dampers (11) are all located on the side of the connecting plate (7) close to the high-pressure turbine outer casing (5). A second shock-absorbing spring (13) is connected between the housing and the piston rod of each second hydraulic damper (11). A first rotating rod (12) is rotatably connected to the piston rod of each second hydraulic damper (11). The first rotating rods (12) are all rotatably connected to the first hydraulic damper (9). It further comprises a third hydraulic damper (14), a second rotating rod (15) and a third shock-absorbing spring (16). A third hydraulic damper (14) is connected to each side of the connecting plate (7) away from each other. The third hydraulic dampers (14) are all located on the side of the connecting plate (7) close to the high-pressure compressor housing (3). A third shock-absorbing spring (16) is connected between the housing and the piston rod of each third hydraulic damper (14). A second rotating rod (15) is rotatably connected to the piston rod of each third hydraulic damper (14). The second rotating rods (15) are all rotatably connected to the first hydraulic damper (9). It is characterized in that it further comprises a first connecting frame (111) and a second connecting frame (141). A first connecting frame (111) is connected between the piston rods of adjacent second hydraulic dampers (11), and a second connecting frame (141) is connected between the piston rods of adjacent third hydraulic dampers (14).

2. The aeroengine compressor based on a shock absorption regulation mechanism according to claim 1, characterized in that, It further includes a temperature detector (26) and a pressurizing assembly. Pressurizing assemblies are connected to the first hydraulic damper (9), the second hydraulic damper (11), and the third hydraulic damper (14). Temperature detectors (26) are connected to the connecting plate (7). The temperature detector (26) is electrically connected to the engine system, and the pressurizing assemblies are electrically connected to the engine system.

3. The aero-engine compressor based on a shock absorption control mechanism according to claim 2, characterized in that, The pressurizing assembly includes a cylinder (17), a liquid storage tank (18), and a connecting pipe (19). The cylinders (17) and the connecting pipes (19) are connected to the shells of the first hydraulic damper (9), the second hydraulic damper (11), and the third hydraulic damper (14). The liquid storage tanks (18) are connected between the connecting pipes (19) and the cylinders (17). The first hydraulic damper (9), the second hydraulic damper (11), and the third hydraulic damper (14) are all in communication with the connecting pipe (19), and the liquid storage tanks (18) are all in communication with the connecting pipe (19). The piston rods of the cylinders (17) extend into the liquid storage tanks (18), and the cylinders (17) are all electrically connected to the engine system.

4. The aero-engine compressor based on a shock absorption control mechanism according to claim 3, characterized in that, This engine compressor further includes a connecting frame (20) and an air seal shock-absorbing ring (21). The connecting frame (20) is connected inside the engine housing (1), and an air seal shock-absorbing ring (21) is connected between the fan casing (201) and the connecting frame (20).

5. A compressor of an aeroengine based on a shock absorption control mechanism according to claim 4, characterized in that, This engine compressor further includes a second connecting block (22), a third connecting block (23), a fourth hydraulic damper (24), and a fourth shock-absorbing spring (25). At least two second connecting blocks (22) are circumferentially and spacedly connected to the outer wall of the low-pressure turbine housing (6), and at least two third connecting blocks (23) are circumferentially and spacedly connected to the inner wall of the engine housing (1). The fourth hydraulic dampers (24) are connected between the second connecting blocks (22) and the third connecting blocks (23). The piston rods of the fourth hydraulic dampers (24) are fixedly connected to the second connecting blocks (22), and the fourth shock-absorbing springs (25) are connected between the shells of the fourth hydraulic dampers (24) and their piston rods.

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