A combined piston hydraulic automatic tensioner and engine system

Abstract

The automatic tensioner comprises a housing, a piston and a plunger, the piston is built in the housing, the plunger is partially built in the piston, one end of the plunger is in the piston, the other end of the plunger extends out of the piston to abut against a chain, the housing, the piston and the plunger jointly enclose an oil cavity, the piston and the plunger can move along the axial direction of the housing, a control oil path is formed between the overlapping parts of the piston and the plunger, the control oil path can be switched between an adjusting station and a closing station, when the distance that the plunger moves relative to the piston towards the direction of pressing into the oil cavity is less than a set threshold, the control oil path is in the adjusting station to communicate the oil cavity with the outside, in the adjusting station, the length of the control oil path increases with the increase of the moving distance of the plunger into the oil cavity, when the distance that the plunger moves relative to the piston towards the direction of pressing into the oil cavity meets the set threshold, the control oil path is switched to the closing station, the length of the control oil path increases to the maximum, and the control oil path is disconnected with the outside.

Description

Technical Field

[0001] This invention relates to the field of engine system technology, and more specifically, to a combined piston-type hydraulic automatic tensioner and an engine system. Background Technology

[0002] As a core component of the engine chain system, the hydraulic automatic tensioner is responsible for functions such as tensioning the chain, compensating for chain wear and tear, suppressing chain vibration, and reducing dynamic impact on the system. Because the working conditions and load levels of the chain system vary significantly across different engine speeds and operating conditions, traditional hydraulic automatic tensioners have a fixed hydraulic stiffness. Therefore, their hydraulic stiffness must be sufficiently high to ensure effective chain tensioning under high engine speeds, heavy loads, and certain extreme operating conditions.

[0003] However, since the working conditions and load levels of the chain system vary greatly depending on the engine speed range and operating conditions, this tensioner design is not optimal for the medium and low speed load conditions that users use more often. In the medium and low speed range that users use more often, the excessive stiffness of the tensioner will increase the friction loss of the chain system and cause excessive noise.

[0004] In view of this, there is an urgent need to provide a technical solution that can effectively tighten the chain when the engine is running at high speed and heavy load, while also allowing the chain to run under lower tension when the engine is operating at medium and low speed, thereby reducing friction loss and noise of the chain system. Summary of the Invention

[0005] One objective of this invention is to provide a new technical solution for a combined piston-type hydraulic automatic tensioner and an engine system. By improving the structure of the automatic tensioner, it is possible to ensure that the tensioner is sufficiently stiff when the engine is operating at high speed and heavy load, so as to effectively tighten the chain. At the same time, when the engine is operating at medium and low speed, the tensioner can exhibit softer tension characteristics, allowing the chain to operate at the minimum tension required to maintain stable operation, thereby reducing frictional losses and noise of the chain system.

[0006] In one aspect of this application, a combined piston-type hydraulic automatic tensioner is provided, the automatic tensioner including a housing, a piston, and a plunger, the piston being built into the housing, the plunger being partially built into the piston, one end of the plunger extending from the piston to abut against a chain, the housing, the piston, and the plunger together forming an oil chamber filled with engine oil to provide hydraulic pressure, and both the piston and the plunger being axially movable along the housing;

[0007] Because the plunger has a smaller diameter and a smaller cross-sectional area than the piston, when moving the same distance, the change in the volume of the oil chamber by the plunger is smaller than that by the piston. Therefore, the hydraulic damping effect on the plunger is also smaller, resulting in a softer working characteristic compared to the piston.

[0008] In addition, the tensioner also includes a control oil passage, and the overlapping portion between the piston and the plunger forms the control oil passage, which has an adjustment position and a closing position.

[0009] When the distance the plunger moves relative to the piston toward the direction of pressing into the oil chamber is less than a set threshold, the control oil circuit is in the adjustment position to connect the oil chamber with the outside. In the adjustment position, the length of the control oil circuit increases as the distance the plunger moves into the oil chamber increases.

[0010] When the distance the plunger moves relative to the piston in the direction of pressing into the oil chamber meets the set threshold, the control oil circuit switches to the off position, the length of the control oil circuit increases to the maximum value, and the control oil circuit is disconnected from the outside.

[0011] By employing the method described in this embodiment, the plunger moves under the force of the chain. When the distance traveled is less than a set threshold, the control oil circuit is in a connected state and in an adjustment position. In this position, the oil output speed of the control oil circuit can be adjusted. The length of the control oil circuit can increase as the distance the plunger is pressed into the oil chamber increases; as the length of the control oil circuit increases, the oil output speed of the oil chamber decreases accordingly. Thus, the oil output speed of the control oil circuit is adjusted by regulating the length of the control oil circuit.

[0012] In other words, the greater the distance the plunger travels into the oil chamber, the longer the control oil circuit becomes, resulting in a slower oil output speed within the chamber. Consequently, the stiffness of the tensioner also increases. This means the damping effect of the tensioner on the chain also increases.

[0013] Conversely, the shorter the distance the plunger travels into the oil chamber, the shorter the length of the control oil circuit, and thus the faster the oil output speed from the chamber. At this time, the stiffness of the tensioner also decreases. Therefore, the tensioner's damping effect on the chain can be changed according to the magnitude of the reaction force applied by the chain to the plunger, thereby better balancing the dynamic tension and vibration of the chain and optimizing the performance of the engine chain system.

[0014] When the plunger moves a distance relative to the piston in the direction of pressing into the oil chamber, meeting a set threshold, the control oil circuit switches to the closed position. In the closed position, the control oil circuit is disconnected from the outside.

[0015] When the control oil circuit is disconnected from the external system, it stops leaking oil. At this time, the tensioner operates in a high-tension, high-damping mode, thus more effectively tightening the rail. This prevents chain vibration, excessive phase deviation between the drive and driven pulleys connected to the chain rotation, and other dynamic problems in the chain system such as abnormal noise and tooth skipping.

[0016] Optionally, the plunger includes a rod portion, the outer peripheral wall of the rod portion being in clearance fit with the inner peripheral wall of the piston;

[0017] The rod has a first oil groove and a second oil groove that are connected to each other. The first oil groove is closer to and connected to the oil cavity. The cross-sectional area of ​​the first oil groove is larger than that of the second oil groove.

[0018] The portion of the piston's inner wall that covers the first and second oil grooves constitutes the control oil circuit.

[0019] Optionally, the second oil groove extends in a spiral shape.

[0020] Optionally, the first oil groove extends in a straight line.

[0021] Optionally, a filling part is also provided in the oil cavity, and the filling part is connected to the plunger.

[0022] Optionally, the piston includes a first port and a second port arranged axially opposite to each other, the piston has a stepped diameter structure, the inner diameter of the first port is larger than the inner diameter of the second port, and the second port is sleeved on the outside of the plunger.

[0023] Optionally, the tensioner includes a first elastic element and a second elastic element, wherein the first elastic element is disposed in the oil chamber, one end of which contacts the bottom end of the housing, and the other end of which contacts the inner stepped surface of the piston;

[0024] The second elastic element is sleeved outside the piston, with one end contacting the outer stepped surface of the piston and the other end contacting the end of the plunger that extends out of the piston.

[0025] Optionally, an oil drain channel is also provided between the piston and the housing, and the oil drain channel always connects the oil chamber to the outside.

[0026] Optionally, the housing is configured with an oil inlet, and the tensioner further includes a one-way valve disposed at the oil inlet. The valve port of the one-way valve is connected to the oil inlet, and an oil return channel is provided on the outer wall and bottom surface of the one-way valve. The oil return channel will always form a bypass between the oil chamber and the oil inlet.

[0027] Both the drain channel and the return channel supplement the control oil circuit. The difference is that the return channel allows a portion of the oil to flow directly back to the inlet, thereby reducing the oil consumption of the hydraulic tensioner.

[0028] In another aspect of this application, an engine system is also provided, comprising a chain and the aforementioned combined piston-type hydraulic automatic tensioner, wherein the plunger is directly or indirectly abutted against the chain.

[0029] Other features and advantages of this specification will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0030] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of this specification and, together with their description, serve to explain the principles of this specification.

[0031] Figure 1 This is a schematic diagram illustrating the working principle of the tensioner and chain in an embodiment of the present invention;

[0032] Figure 2 This is a simplified diagram illustrating the basic structure and working principle of the tensioner in this embodiment of the invention;

[0033] Figure 3 This is a schematic diagram of the tensioner structure when the engine is in the first operating condition in an embodiment of the present invention;

[0034] Figure 4 yes Figure 3 A magnified schematic diagram of a local structure;

[0035] Figure 5 This is a schematic diagram of the tensioner structure when the engine is in the second operating condition in an embodiment of the present invention;

[0036] Figure 6 yes Figure 5 A magnified schematic diagram of a local structure;

[0037] Figure 7 This is a schematic diagram of the tensioner structure when the engine is in the third operating condition in an embodiment of the present invention;

[0038] Figure 8 yes Figure 7 A magnified schematic diagram of a local structure.

[0039] Explanation of reference numerals in the attached figures:

[0040] 1. Housing; 11. Oil inlet; 12. Check valve; 13. Open end; 14. Bottom end;

[0041] 2. Piston; 21. First port; 22. Second port; 23a. Inner stepped surface; 23b. Outer stepped surface; 24. Oil cavity;

[0042] 3. Plunger;

[0043] 4. Chain;

[0044] 5. Tensioning rail;

[0045] 61. Control oil circuit; 62. Oil drain channel; 63. Oil return channel;

[0046] 71. First oil tank; 72. Second oil tank;

[0047] 81. Filling section;

[0048] 91. First elastic element; 92. Second elastic element;

[0049] 10. Combined piston type hydraulic automatic tensioner. Detailed Implementation

[0050] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] In some embodiments of this application, such as Figure 1 and Figure 2 As shown, a combined piston-type hydraulic automatic tensioner 10 is provided. The combined piston-type automatic tensioner 10 includes a housing 1, a piston 2, and a plunger 3.

[0052] like Figure 1 and Figure 3 As shown, piston 2 is housed within housing 1, and plunger 3 is housed within piston 2. One end of plunger 3 extends from inside piston 2 to press against chain 4. Housing 1, piston 2, and plunger 3 together form oil chamber 24. Both piston 2 and plunger 3 can move axially to change the volume of oil chamber 24.

[0053] The housing 1 has an open end 13 and a bottom end 14 opposite to the open end 13. An oil inlet 11 is provided at the bottom end 14 of the housing 1, and a one-way valve 12 is installed thereon. The inlet of the one-way valve 12 is connected to the oil inlet 11 of the housing 1. Engine oil is filled into the oil chamber 24 through the oil inlet 11 of the housing 1 and the one-way valve 12. At the same time, when the piston 2 and the plunger 3 move toward the bottom end 14 of the housing 1, the one-way valve 12 can prevent the engine oil in the oil chamber 24 from flowing back to the oil inlet 11 of the housing 1, thereby creating high pressure in the oil chamber 24.

[0054] The piston 2 is tubular, having a first opening 21 and a second opening 22, with the first opening 21 closer to the oil inlet 11. The second opening 22 is fitted onto the outside of the plunger 3. The outer diameter of the piston 2 matches the inner bore of the housing 1, and one end of the plunger 3 is located inside the piston 2, forming an oil cavity 24 together with the inner wall of the piston 2 and the housing 1. Optionally, a filling part 81 is also integrated or connected to the end of the plunger 3 located in the oil cavity 24 to adjust the volume of the oil cavity 24.

[0055] Although both piston 2 and plunger 3 can change the volume of oil chamber 24 by moving axially, thus causing changes in oil pressure within oil chamber 24, since the diameter and cross-sectional area of ​​plunger 3 are much smaller than those of piston 2, when piston 2 and plunger 3 move the same distance, the change in volume of oil chamber 24 and the change in oil pressure within the high-pressure chamber caused by plunger 3 will be smaller than those caused by piston 2. Therefore, plunger 3 experiences less hydraulic resistance and thus exhibits softer working characteristics compared to piston 2.

[0056] See also Figure 1 and Figure 3 The other end of the plunger 3 extends from the second port 22 to directly or indirectly abut against the chain 4. When the plunger 3 abuts against the chain 4 indirectly, a tension rail 5 is also connected between the plunger 3 and the chain 4, and the plunger 3 abuts against the chain 4 through the tension rail 5.

[0057] The combined piston-type hydraulic automatic tensioner 10 also includes a first elastic element 91 and a second elastic element 92. To provide support for the first and second elastic elements 91 and 92, the piston 2 has a stepped diameter structure, with the inner diameter of the first opening 21 being larger than that of the second opening 22. The first elastic element 91 is located within the oil chamber 24, with one end contacting the bottom end 14 of the housing 1 and the other end contacting the inner stepped surface 23a of the piston 2. Therefore, the piston 2 is subjected to the combined action of the oil pressure within the oil chamber 24 and the axial thrust of the first elastic element 91.

[0058] The second elastic element 92 is disposed outside the oil chamber 24. The second elastic element 92 is sleeved on the outside of the piston 2, with one end abutting against the outer stepped surface 23b of the piston 2, and the other end abutting against the end of the plunger 3 extending out of the piston 2. That is, in addition to being subjected to the thrust of the oil pressure within the oil chamber 24, all the axial forces acting on the piston 2 mentioned earlier are also transmitted to the end of the plunger 3 via the second elastic element 92 to jointly press against the chain 4. The deformation of the second elastic element 92 directly determines the displacement of the plunger 3 relative to the piston 2. Therefore, to avoid excessive displacement of the plunger 3 or impact with the piston 2, the second elastic element 92 must have sufficient structural strength and compressive stiffness. Conversely, when the plunger 3 is subjected to the force of the chain 4, the second elastic element 92 acts as a force transmitter, transferring a portion of the force applied to the plunger 3 by the chain 4 to the piston 2, ultimately balancing the thrust of the first elastic element 91 and the hydraulic pressure of the oil chamber 24.

[0059] like Figure 3 and Figure 4 As shown, the combined piston-type hydraulic automatic tensioner 10 also includes a control oil circuit 61, which is formed between the overlapping portions of the piston 2 and the plunger 3. The control oil circuit 61 can be switched between an adjustment position and a disconnect position. The overlapping portion of the piston 2 and the plunger 3 during movement refers to the radial overlap between the inner wall of the piston 2 and the outer wall of the plunger 3 when the plunger 3 moves axially relative to the piston 2.

[0060] The control oil circuit 61 has an adjustment position and a closing position. When the distance that the plunger 3 moves relative to the piston 2 toward the oil chamber 24 is less than a set threshold, the control oil circuit 61 is in the adjustment position, and the oil chamber 24 is connected to the outside. The length of the control oil circuit 61 increases as the distance that the plunger 3 is pressed into the oil chamber 24 increases.

[0061] Specifically, the plunger 3 moves under the force of the chain 4. When the distance moved is less than a set threshold, the control oil circuit 61 is in a connected state and in an adjustment position. In this position, the oil output speed of the control oil circuit 61 can be adjusted. The length of the control oil circuit 61 can increase as the plunger 3 is pressed into the oil chamber 24. When the length of the control oil circuit 61 increases, the oil output speed of the oil chamber 24 decreases accordingly. Thus, the oil output speed of the control oil circuit 61 is adjusted by regulating its length.

[0062] In other words, the greater the distance the plunger 3 is pressed into the oil chamber 24, the longer the control oil circuit 61 becomes, and thus the slower the oil output speed in the oil chamber 24. At this time, the hardness of the combined piston hydraulic automatic tensioner 10 also increases. That is to say, the damping of the chain 4 by the combined piston hydraulic automatic tensioner 10 also increases.

[0063] Conversely, the shorter the distance the plunger 3 is pressed into the oil chamber 24, the shorter the length of the control oil circuit 61, and thus the faster the oil output speed of the oil chamber 24. At this time, the hardness of the combined piston-type hydraulic automatic tensioner 10 will also decrease. As a result, the damping of the tensioner 10 on the chain 4 can be changed according to the magnitude of the reaction force applied by the chain 4 to the plunger 3, thereby better balancing the dynamic tension and vibration of the chain 4 and optimizing the performance of the engine chain system.

[0064] When the distance that the plunger 3 moves relative to the piston 2 in the direction of pressing into the oil chamber 24 meets the set threshold, the control oil circuit 61 switches to the closed position. In the closed position, the control oil circuit 61 is disconnected from the outside.

[0065] When the control oil circuit 61 is disconnected from the outside, the control oil circuit 61 no longer leaks oil. At this time, the tensioner 10 operates in a high-tension, high-damping mode, which can more effectively tension the rail 5. This avoids excessive vibration of the chain 4, as well as excessive phase deviation between the driving and driven pulleys connected to the chain 4, and other dynamic problems of the chain system such as abnormal noise and tooth skipping.

[0066] In one specific embodiment, the plunger 3 includes a rod portion, the outer peripheral wall of which slides in engagement with the inner wall of the piston 2. The rod portion is constructed with a first oil groove 71 and a second oil groove 72. The first oil groove 71 and the second oil groove 72 are recessed from the outer peripheral surface of the rod portion to form a groove-like structure. The inner wall of the piston 2 can cover the openings of the first oil groove 71 and the second oil groove 72 to form a control oil passage 61 for the oil in the oil chamber 24 to flow out of the oil chamber 24 through the control oil passage 61.

[0067] The first oil tank 71 and the second oil tank 72 are connected to form a control oil circuit 61, with the first oil tank 71 being closer to the oil chamber 24. The cross-sectional area of ​​the first oil tank 71 is larger than that of the second oil tank 72. Due to the different cross-sectional sizes of the first oil tank 71 and the second oil tank 72, the oil output speed of the control oil circuit 61 is different when it is in the adjustment position. Furthermore, since the first oil tank 71 is closer to the oil inlet 11 and the second oil tank 72 is farther from the oil inlet 11, the first oil tank 71 and the second oil tank 72 can cooperate to function similarly to a throttle valve.

[0068] Specifically, the first oil groove 71, the second oil groove 72 and the inner wall of the piston 2 together form the control oil passage 61, which is located within the range where the inner wall of the piston 2 and the plunger 3 can overlap during movement.

[0069] The portion of the inner wall of piston 2 covering the first oil groove 71 and the second oil groove 72 constitutes the control oil passage 61. The portion of the first oil groove 71 and the second oil groove 72 not covered by the inner wall of piston 2 does not belong to the control oil passage 61. Since the inner wall of piston 2 does not cover the groove openings, oil cannot flow in this portion, therefore this portion does not belong to the control oil passage 61. In other words, when the portion of piston 2 covering the first oil groove 71 and the second oil groove 72 increases, the length of the control oil passage 61 increases, and the oil outlet speed of oil chamber 24 decreases. Conversely, when the length of the control oil passage 61 decreases, the oil outlet speed of oil chamber 24 increases.

[0070] When the control oil circuit 61 is in the disconnected position, the inner wall of the piston 2 covers the oil outlet of the second oil groove 72, thereby disconnecting the second oil groove 72 from the outside. At this time, the first oil groove 71 can still be in communication with the oil chamber 24. Of course, the effect of disconnecting the control oil circuit 61 from the outside can also be achieved by blocking the first oil groove 71.

[0071] Optionally, the second oil groove 72 extends in a spiral shape. The spiral extension of the second oil groove 72 increases its length within each unit dimension of axial movement. Of course, the second oil groove 72 can also be a straight groove. However, the spiral extension of the second oil groove 72 increases the range of oil speed regulation in the oil passage 61 controlled by the plunger 3 within each unit distance of axial movement.

[0072] Optionally, the first oil groove 71 extends in a straight line. Since the cross-section of the first oil groove 71 is larger than that of the second oil groove 72 and the first oil groove 71 is closer to the oil cavity 24, the straight-extending first oil groove 71 can play a better guiding role. At the same time, it can improve the response speed of the control oil circuit 61 when it is in the adjustment position.

[0073] It is understood that, in this embodiment, the preferred option is that the first oil groove 71 extends in a straight line and the second oil groove 72 extends in a spiral shape. However, it is also possible that both the first oil groove 71 and the second oil groove 72 extend in a straight line or both extend in a spiral shape, as long as the oil outlet speed adjustment requirement of the control oil passage can be met. Those skilled in the art can make their own settings as needed.

[0074] In this embodiment, the combined piston-type hydraulic automatic tensioner 10 also includes an oil drain channel 62, located between the piston 2 and the housing 1, which always connects the oil chamber 24 to the outside. The oil drain channel 62 also serves to drain the oil from the oil chamber 24. However, the difference between the oil drain channel 62 and the control oil passage is that the control oil passage can switch between an adjustment position and a closed position as the plunger 3 moves relative to the piston 2. Simultaneously, when the control oil passage is in the adjustment position, the oil outlet speed of the control oil circuit 61 is adjustable. However, the oil drain channel 62 always connects the oil chamber 24 to the outside, and its length and oil drain speed are constant, thus providing a fixed oil drain speed and throttling effect for the oil chamber 24. Based on this, the overall oil outlet speed of the tensioner 10 is adjusted by regulating the oil outlet speed of the control oil passage through the moving distance of the plunger 3 relative to the piston 2, thereby adjusting the stiffness and damping value of the combined piston-type hydraulic tensioner 10.

[0075] In a specific embodiment, such as Figure 3 As shown, the combined piston-type hydraulic automatic tensioner 10 also includes a return oil passage 63 located between the bottom end 14 of the housing 1 and the oil chamber 24 and capable of bypassing the one-way valve 12. The return oil passage 63 serves as a bypass path with a fixed cross-section and length between the oil chamber 24 and the oil inlet 11 of the housing 1, and always connects the oil chamber 24 and the oil inlet 117 of the housing 1. Similar to the function of the drain channel 62, the return channel 63 also supplements the control oil circuit 61. When the plunger 3 and piston 2 move towards the bottom end 14 of the housing 1, the control oil circuit 61, drain channel 62, and return channel 63 can all allow the high-pressure oil in the oil chamber 24 to flow out of the oil chamber 24 at a certain drain speed. However, the biggest difference between the return channel 63 and the control oil circuit 61 and drain channel 62 is that the oil flowing out of the oil chamber 24 through the return channel 63 will not be directly discharged to the outside of the combined piston hydraulic automatic tensioner 10, but will return to the oil inlet 11 of the housing 1. This realizes the internal circulation of this part of the oil in the combined piston hydraulic automatic tensioner 10, reducing the oil consumption of the combined piston hydraulic automatic tensioner 10.

[0076] Optionally, the return oil channel 63 is a labyrinthine slot formed by indentation on the outer wall and bottom surface of the one-way valve 12. The slot is located in the contact area and sealing surface between the one-way valve 12 and the bottom end 14 of the housing 1. The two ends of the slot are connected to the oil inlet 11 and the oil chamber 24 of the housing 1, respectively.

[0077] The combined piston-type hydraulic automatic tensioner 10 of this application can adapt its damping characteristics to different engine operating conditions during actual use. The specific ways in which the damping characteristics of the combined piston-type hydraulic automatic tensioner 10 change under different engine operating conditions are described below. For ease of explanation, in the following embodiments, the specific engine operating conditions are divided into a first operating condition, a second operating condition, and a third operating condition. The first operating condition refers to the engine operating at low to medium speeds. The third operating condition refers to extreme operating conditions such as high speed and high load. The second operating condition refers to the engine speed being between the first and third operating conditions.

[0078] <First Operating Condition>

[0079] like Figure 3 and Figure 4 As shown, when the engine operates under partial load at low to medium speeds, the chain system runs smoothly, with minimal vibration of the chain 4 and small sway of the tension rail 5. Therefore, the force exerted by the tension rail 5 on the plunger 3 is relatively small. The compression of the second elastic element 92 is also relatively small. The displacement of the plunger 3 relative to the piston 2 is also relatively small (less than the set threshold range).

[0080] The additional thrust on piston 2 due to the increased oil pressure in oil chamber 24 is roughly equivalent to the spring force generated by the compression of the second elastic element 92, at which point piston 2 remains essentially stationary. The main function is achieved by the plunger 3 of the combined piston-type hydraulic automatic tensioner 10; that is, the axial displacement of the plunger 3 primarily provides a reaction force to the tensioning rail 5.

[0081] At this time, because the diameter and cross-sectional area of ​​the plunger 3 are relatively small, the movement of the plunger 3 has a small impact on the volume change of the oil chamber 24, thus the oil pressure resistance experienced by the plunger 3 during small movements is lower. Furthermore, the axial movement distance of the plunger 3 is small, therefore the length of the control oil circuit 61 is short. The oil in the oil chamber 24 can flow out quickly through the control oil circuit 61, resulting in a faster oil output speed from the oil chamber 24. Therefore, the combined piston-type hydraulic automatic tensioner 10 operates in a low-tension, low-damping mode, exhibiting a very soft characteristic. This helps reduce the dynamic tension of the chain 4, thereby achieving better noise performance and lower friction loss in the chain system.

[0082] <Second Working Condition>

[0083] like Figure 5 and Figure 6As shown, with the increase of the chain system's rotational speed and load, the tension of chain 4 increases, and the vibration of chain 4 and the swing amplitude of tension rail 5 increase. Since piston 2 and plunger 3 are connected by a second elastic element 92, as the second elastic element 92 is compressed, plunger 3 will have a corresponding displacement relative to piston 2 along the axial direction. At this time, the output force of the combined piston hydraulic automatic tensioner 10 becomes two parts. Plunger 3 itself will be subjected to the thrust generated by the oil pressure in oil chamber 24, while the thrust of piston 2 subjected to the combined action of oil pressure in oil chamber 24 and first elastic element 91 will also be superimposed on plunger 3 through second elastic element 92, ultimately pushing tension rail 5 to press chain 4.

[0084] At this time, the displacement of plunger 3 increases, but because the diameter and cross-sectional area of ​​plunger 3 are small, the increase in oil pressure in oil chamber 24 caused by its displacement is not enough to generate an elastic force on piston 2 that can balance the large compression of the second elastic element 92. Therefore, piston 2 will also undergo a certain degree of axial movement, further compressing oil chamber 24. Thus, in the second working condition, piston 2 and plunger 3 work together, and the higher the tension of chain 4, the greater the role of piston 2.

[0085] As the compression of the second elastic element 92 increases further, the length of the control oil circuit 61 also increases accordingly, and the oil outlet speed of the oil chamber 24 decreases accordingly. The combined piston-type hydraulic automatic tensioner 10 exhibits stiffer characteristics. At this time, the combined piston-type hydraulic automatic tensioner 10 can also better balance the dynamic tension and vibration of the chain 4 according to the engine's operating conditions, thus optimizing the chain system performance.

[0086] <Third Working Condition>

[0087] like Figure 7 and Figure 8 As shown, when the engine operates under high speed and high load conditions, or encounters other extreme conditions such as rapid engine acceleration that cause sudden changes in the tension of chain 4, the vibration of chain 4 increases significantly. The plunger 3 of the combined piston-type hydraulic automatic tensioner 10 works together with the piston 2, and the second elastic element 92 is greatly compressed. The distance the plunger 3 moves meets the set threshold (the set threshold for the movement of the plunger 3 can also be the limit value of the axial movement of the plunger 3, or other thresholds, which can be set by those skilled in the art as needed). At this time, the inner wall of the piston 2 completely covers the oil outlet position of the second oil groove 72, thereby controlling the length of the oil passage 61 to its maximum and disconnecting the oil passage 61 from the outside. At this time, the oil in the oil chamber 24 can only be discharged through the drain channel 62 and the return channel 63, and the oil outlet speed of the oil chamber 24 will be greatly reduced.

[0088] At this time, the combined piston hydraulic automatic tensioner 10 operates in a high-tension, high-damping mode, which can more effectively tighten the rail 5, avoid excessive vibration of the chain 4, avoid excessive phase deviation between the driving wheel and the driven wheel of the chain system, and avoid other dynamic problems of the chain system such as abnormal noise and tooth skipping of the chain 4.

[0089] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A combined piston-type hydraulic automatic tensioner, characterized in that, The device includes a housing, a piston, and a plunger. The piston is housed within the housing, and the plunger is partially housed within the piston. One end of the plunger is located within the piston, and the other end extends out of the piston to press against the chain. The housing, piston, and plunger together form an oil chamber. Both the piston and the plunger are axially movable along the housing. The tensioner also includes a control oil circuit, which is formed between the overlapping portions of the piston and the plunger. The control oil circuit can switch between an adjustment position and a shutdown position. When the distance the plunger moves relative to the piston toward the direction of pressing into the oil chamber is less than a set threshold, the control oil circuit is in the adjustment position to connect the oil chamber with the outside. In the adjustment position, the length of the control oil circuit increases as the distance the plunger moves into the oil chamber increases. When the distance the plunger moves relative to the piston in the direction of pressing into the oil chamber meets the set threshold, the control oil circuit switches to the closed position, the length of the control oil circuit increases to the maximum value, and the control oil circuit is disconnected from the outside.

2. The combined piston-type hydraulic automatic tensioner according to claim 1, characterized in that, The plunger includes a rod portion, and the outer peripheral wall of the rod portion is in clearance fit with the inner peripheral wall of the piston; The rod has a first oil groove and a second oil groove that are connected to each other. The first oil groove is closer to and connected to the oil cavity. The cross-sectional area of ​​the first oil groove is larger than that of the second oil groove. The portion of the piston's inner wall that covers the first and second oil grooves constitutes the control oil circuit.

3. The combined piston-type hydraulic automatic tensioner according to claim 2, characterized in that, The second oil groove extends in a spiral shape.

4. The combined piston-type hydraulic automatic tensioner according to claim 2, characterized in that, The first oil tank extends in a straight line.

5. The combined piston-type hydraulic automatic tensioner according to claim 2, characterized in that, A filling part is also provided in the oil cavity, and the filling part is connected to the plunger.

6. The combined piston-type hydraulic automatic tensioner according to any one of claims 1-5, characterized in that, The piston includes a first port and a second port arranged axially opposite to each other. The piston has a stepped diameter structure. The inner diameter of the first port is larger than the inner diameter of the second port. The second port is sleeved outside the plunger.

7. The combined piston-type hydraulic automatic tensioner according to claim 6, characterized in that, The tensioner includes a first elastic element and a second elastic element. The first elastic element is disposed in the oil chamber, with one end contacting the bottom end of the housing and the other end contacting the inner stepped surface of the piston. The second elastic element is sleeved outside the piston, with one end contacting the outer stepped surface of the piston and the other end contacting the end of the plunger that extends out of the piston.

8. The combined piston-type hydraulic automatic tensioner according to any one of claims 1-5, characterized in that, An oil drain channel is also provided between the piston and the housing, and the oil drain channel always connects the oil chamber to the outside.

9. The combined piston-type hydraulic automatic tensioner according to any one of claims 1-5, characterized in that, The housing has an oil inlet, and the tensioner also includes a one-way valve disposed at the oil inlet. The valve port of the one-way valve is connected to the oil inlet. An oil return channel is provided on the outer wall and bottom surface of the one-way valve. The oil return channel will always form a bypass between the oil chamber and the oil inlet.

10. An engine system, characterized in that, Includes a chain and a combined piston-type hydraulic automatic tensioner as described in any one of claims 1-9, wherein the plunger is directly or indirectly pressed against the chain.

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