Passive tensioning system

Abstract

Passive tensioning system for tensioning a chain or belt tension, comprising: a tensioning arm (402) comprising a first sliding surface (402b) on which the chain or belt slides, and a second surface (402a) opposite the first sliding surface (402b); and a clamping device comprising: a housing (102) having a first axially extending bore (102a) with a first fluid inlet (106) and a second axially extending bore (102c) with a second fluid inlet (109); a first piston (103) slidably received by the first axially extending bore (102a), a first pressure chamber (111) in fluid communication with the first fluid inlet (106) being formed between the first piston (103) and the first axially extending bore (102a), the first piston (103) comprising a body having a first end (103a) and a second end (103c), the body of the first piston (103) further comprising an open end at the second end (103c) of the body and a closed end at the first end (103a) of the body, a lower surface at the open end, and a hollow interior (103b) having an inner diameter; a first piston spring (104) for biasing the first piston (103) outwardly from the housing (102) and received in the hollow interior (103b) of the first piston (103), the first piston spring (104) having a first end (104a) contacting the hollow interior (103b) of the first piston (103) and a second end (104b) contacting the first axially extending bore (102a); a first check valve (108) received in the first axially extending bore (102a); a second piston (260; 270) slidably received in the second axially extending bore (102c), the second piston (260; 270) comprising a body having an open end and a closed end, a lower surface (260c; 270c) at the open end, an upper surface (260a; 270a) at the closed end, and a hollow interior (260b, 270b) having an inner diameter, the second axially extending bore (102c) defining a second pressure chamber (267; 277) defined between the inner diameter of the second piston (260; 270) and the second axially extending bore (102c) in fluid communication with the second fluid inlet (109) through a second check valve (107); a second piston spring (266; 276) in the second pressure chamber (267; 277), the second piston spring (266; 276) having a first end (266a; 276a) in contact with the second piston (260; 270) and a second end (266b; 276b) in contact with a bottom (102d) of the second axially extending bore (102c); an outer piston spring (261; 271) between the second piston (260; 270) and the tensioning arm (402), the outer piston spring (261; 271) having a first end (261a; 271a) in contact with the second surface (402a) of the tensioning arm (402) and a second end (261b; 271b) in contact with the upper surface (260a; 270a) of the body of the second piston (260; 270); wherein, when a high cyclic dynamic load from the chain or belt moves the first piston (103) and the second piston (260; 270) alternately inward and outward from the housing (102), fluid is drawn from the second fluid inlet (109) through the second check valve (107) into the second pressure chamber (267; 277) as the second piston (260; 270) is moved outward from the housing (102) by the second piston spring (266; 276), a fluid pressure being created in the second pressure chamber (267; 277) as the second piston (260; 270) moves inward, causing the second piston (260; 270) to exert an outward force on the outer piston spring (261; 271) corresponding to an inward force of the high cyclic dynamic load from the tensioning boom (402) is opposite.

Description

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

[0001] The invention relates to the field of clamping devices. More specifically, the invention relates to a clamping device with a spring force control in a second bore of the housing. DESCRIPTION OF RELATED TECHNOLOGY

[0002] Generally, in timing chains for valve trains of internal combustion engines, camshaft chains used for a camshaft-to-camshaft drive and balancer chains have tensioners that are used on the slack side of a chain to take up idle in the chain and apply tension to the chain.

[0003] During operation, a tensioner piston pushes against the chain to maintain tension. As chain tension increases during operation due to resonance from chain slack, a high load from the chain acts on the tensioner piston, causing the piston to extend as the tensioner inflates to maintain chain tension.

[0004] The spring force of chain drive tensioners is often too high for most operating conditions, as the spring force must be sufficient to handle the worst-case operating conditions of the tensioner system. The effectiveness of the tensioner, as well as the overall performance and efficiency of the system, could be improved if the tensioner spring force could be varied with operating conditions that take into account the wear and elongation that occur in the chain over its service life.

[0005] JP 2005-140237 A concerns the provision of a belt tension adjustment device that contributes to low fuel consumption by reducing belt tension during low engine speed so as not to increase the rotational resistance of a crankshaft and camshaft. To this end, a tension pulley is brought into contact with a timing belt for driving the camshaft, and an automatic tensioner and a pressure device are connected to a pivoting pulley arm to press the tension pulley against the timing belt. During operating rotation of an engine, two thrust forces of the automatic tensioner and the thrust applying device are applied to the pulley arm, or the thrust of the thrust applying device is optionally applied as needed. At low speed, only the thrust of the automatic tensioner is applied to reduce the tension of the timing belt.This reduces the rotational resistance of the crankshaft and camshaft, thus resulting in lower fuel consumption.

[0006] JP 2008-267454 A also deals with the provision of a tensioner for suppressing an increase in friction and simultaneously suppressing vibration of a timing chain. The tensioner is therefore used to tension the timing chain of an engine. It comprises a hydraulic pump for generating hydraulic pressure corresponding to the rotation of a crankshaft, a first tensioner for applying greater tension to the timing chain when the hydraulic pressure supplied by the hydraulic pump is higher, and a second tensioner for applying tension to the timing chain when the hydraulic pressure from the hydraulic pump is low, while the tension on the timing chain is lower when the hydraulic pressure from the hydraulic pump is higher than when the hydraulic pressure is low.

[0007] A cam drive tensioner for use with an engine is described in US 2012 / 0192821 A1 and includes a main body mounted to a component of the engine, a shoe movably mounted on the main body for movement in a first direction, and two or more hydraulic chambers defined between the main body and the shoe, the two or more hydraulic chambers being laterally spaced from each other in a second direction generally perpendicular to the first direction.

[0008] Finally, DE 10 2007 036 920 A1 describes a hydraulic tensioning device for a traction drive, comprising a hydraulic tensioning element to which a tensioning or guiding component engaging the traction mechanism is attached or can be attached. The tensioning element comprises a cylinder, an axially movable piston guided in the cylinder, and a pressure chamber for a hydraulic fluid formed in the cylinder and, if appropriate, the piston. Furthermore, a locking element is provided that prevents the piston from being pushed back into the cylinder when the fluid pressure in the pressure chamber drops. SUMMARY OF THE INVENTION

[0009] A tensioner for tensioning the slack of a chain or belt that uses two pistons. The movement of the two pistons can be coupled together. The first piston provides damping for the slack of the chain or belt, and a second piston provides a variable and automatically adjusting spring force for the slack of the chain or belt. The tensioner automatically adjusts the average tension force to keep chain tension as low as possible without sacrificing chain or belt control, significantly improving drive efficiency under new chain or belt conditions and under dynamic load conditions. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a schematic representation of a clamping device of a first embodiment not according to the invention. Fig. Figure 2a shows a schematic representation of a tensioning device of a second embodiment not according to the invention, which tensions a chain under normal working conditions. Fig. Figure 2b shows a schematic representation of a tensioning device that tensions a chain in response to high dynamic loading. Fig. Figure 3a shows a schematic representation of a tensioning device of a third embodiment not according to the invention, which tensions a chain under normal working conditions. Fig. Figure 3b shows a schematic representation of a tensioning device that tensions a chain in response to high dynamic loading. Fig. Figure 4a shows a schematic representation of a tensioning device of a fourth embodiment not according to the invention, which tensions a chain under normal working conditions. Fig. Figure 4b shows a schematic representation of a tensioning device that tensions a chain in response to high dynamic loading. Fig. Figure 5 shows a schematic representation of a first piston in a first bore connected to a second piston in a second bore. Fig. Figure 6 shows a schematic representation of a second piston in a second bore moving a first piston in a first bore by an extension of the first piston. Fig. 7 shows an example of the tensioning device of the first embodiment which tensions a chain through a boom. Fig. Figure 8a shows a schematic representation of a tensioning device of an embodiment according to the present invention, which tensions a chain under normal working conditions. Fig. 8b shows a schematic representation of the clamping device from Fig. 8a, which tensions a chain in response to high dynamic load. Fig. Figure 9a shows a schematic representation of a tensioning device of another embodiment of the invention, which tensions a chain under normal working conditions. Fig. 9b shows a schematic representation of the clamping device from Fig. 9a, which tensions a chain in response to high dynamic load. Fig. Figure 10a shows a schematic representation of a tensioning device of another embodiment of the invention, which tensions a chain under normal working conditions. Fig. 10b shows a schematic representation of the clamping device from Fig. 10a, which tensions a chain in response to high dynamic load. Fig. 11a shows a schematic representation of a tensioning device of another embodiment of the invention, which tensions a chain under normal working conditions. Fig. 11b shows a schematic representation of the clamping device from Fig. 11a, which tensions a chain in response to high dynamic load. Fig. Figure 12a shows a schematic representation of a tensioning device of another embodiment of the invention, which tensions a chain under normal working conditions. Fig. 12b shows a schematic representation of the clamping device from Fig. 12a, which tensions a chain in response to high dynamic load. Fig. Figure 13a shows a schematic representation of a tensioning device of another embodiment of the invention, which tensions a chain under normal working conditions. Fig. 13b shows a schematic representation of the clamping device from Fig. 13a, which tensions a chain in response to high dynamic load. Fig. Figure 14a shows a schematic representation of a tensioning device of another embodiment of the invention, which tensions a chain under normal working conditions. Fig. 14b shows a schematic representation of the clamping device from Fig. 14a, which tensions a chain in response to high dynamic load. DETAILED DESCRIPTION OF THE INVENTION

[0010] The Fig. Figures 1-14 show tensioners that use a passive control system to maintain the tension of a chain or belt. Passive control is defined as a system in which no feedback is used to control the position of a first piston relative to a second piston, or between the position of a movable sleeve relative to the position of a piston. Fig. 1-7 do not show any embodiments according to the invention in this context, while the Fig. 8-14 represent embodiments of the invention.

[0011] The tensioning systems of the present invention comprise a tensioning device (described in more detail below) for a chain or belt drive control system used in an internal combustion engine. It can be used in a closed-loop power transmission system between a drive shaft and at least one camshaft, or on a balance shaft system between the drive shaft and a balance shaft. The tensioning system can also include an oil pump and be used with fuel pump drives. In addition, the tensioning systems of the present invention can also be used with belt drives.

[0012] Fig. Figure 1 shows clamping systems using passive control to maintain the position of a movable sleeve 10 relative to a piston 3. Passive control is defined as a system in which no feedback is used to control the position of a movable sleeve 10 relative to a piston 3 of the clamping device 1. The passive system contrasts with an active control system in which real-time feedback from components of the engine is used to control the position of the movable sleeve 10.

[0013] The tensioner 1 comprises a housing 2 with an axially extending piston bore 2a. A movable sleeve 10 is received in the bore 2a of the housing 2. The movable sleeve 10 has a first open end 13a and a second open end 14a separated by an inner flange 11 with a through hole 12. The first open end 13a is defined by an upper inner part diameter 13 and an upper surface 15 of the inner flange 11, and the second open end 14a is defined by a lower inner part diameter 14 and a lower surface 16 of the inner flange 11. The through hole 12 of the inner flange 11 connects the first open end 13a to the second open end 14a. An upper surface 17 of the movable sleeve 10 is exposed to atmospheric pressure of the engine.

[0014] A hollow piston 3 is received in the first open end 13a of the movable sleeve 10, which is defined by the upper inner diameter portion 13 and the upper surface 15 of the inner flange 11. A piston spring 4 is located within the hollow piston 3, which biases the piston 3 outward from the housing 2. The piston spring 4 has a first end 4a in contact with the inner portion 3a of the hollow piston 3 and a second end 4b in contact with an upper surface 15 of the inner flange 11 of the movable sleeve 10. It should be noted that, although the piston 3 is shown as hollow, the present invention may also apply to a solid piston, with the piston spring connecting the end of the piston.

[0015] A biasing sleeve spring 5 is housed in the second opening 14a of the movable sleeve 10, which is defined by the lower inner diameter 14 and the lower surface 16 of the inner flange 11. The first end 5a of the biasing sleeve spring 5 is in contact with a lower surface 16 of the inner flange 11 of the movable sleeve 10, and the second end 5b of the biasing sleeve spring 5 is in contact with a check valve 8 of the bore 2a. The biasing sleeve spring 5 provides a biasing force to maintain an outward force on the movable sleeve 10. A pressure chamber 18 is formed between the upper inner diameter 13 of the movable sleeve 10, the lower inner diameter 14 of the movable sleeve 10, the bore 2a of the housing, and the interior 3a of the piston 3. The through hole 12 is provided in the inner flange 11 and allows fluid to flow from the second opening 14a to the first opening 13a of the movable sleeve 10.

[0016] At the bottom of the bore 2a there is an inlet supply line 6 which supplies the pressure chamber 18 with fluid through an inlet check valve 8.

[0017] At least a portion of the movable sleeve 10 is coupled to a second piston 20, which is received in a second axially extending piston bore 2b of the housing 2 by a coupling 22. Although the second piston 20 is shown as being connected to the top of the movable sleeve 10, the connection may also occur on other parts of the movable sleeve 10. The coupling 22 may be a sleeve tab as in Fig. 1 or a flexible connection. The second piston 20 need not be rigidly or rigidly connected to the movable sleeve 10 and can bias the movable sleeve 10 from any contact point on the movable sleeve 10.

[0018] Although the second bore 2b of the housing 2 is shown as being parallel to the first bore 2a, the second bore 2b may also be perpendicular to the first bore 2a or be at a different angle relative to the first bore 2a.

[0019] In an alternative embodiment, the orientation of the second piston 20 may be reversed or reoriented to act on a coupling 22 which then biases the movable sleeve 10 outwardly from the housing 2.

[0020] In yet another embodiment, the second piston 20 may also have a flange around its outer diameter with a chamber on each side as shown in International Application WO 2013 / 043373 A1.

[0021] At the bottom of the second bore 2b is an input supply line 9, which supplies fluid to a pressure chamber 24 formed between the second piston 20 and the bore 2b of the housing 2 through an input check valve 7. The coupling 22 between the second piston 20 and the movable sleeve 10 is such that the movable sleeve 10 moves when the second piston 20 is moved, and vice versa. The fluid from the input supply line 9 can be controlled by a control valve (not shown).

[0022] When the tensioner 1 tensions a new chain or belt, during operation the first hydraulic chamber 18 is supplied with fluid from an input supply line 6 through an input check valve 8 to pressurize the first hydraulic chamber 18 and preload the piston 3 outward from the housing 2 in addition to the spring force from the piston spring 4 to tension a slack of the closed chain.

[0023] The supply that supplies fluid to the first bore 2a through the first input supply line 6 may be the same as the supply that supplies fluid to the second bore 2b through the input supply line 9. Alternatively, the supplies that supply fluid to the first bore 2a and the second bore 2b of the housing 2 may be different.

[0024] During operation, when the tensioner 1 is tensioning a worn chain or belt without a high load, the first hydraulic chamber 18 is supplied with fluid from an input supply line 6 through an input check valve 8 to pressurize the first hydraulic chamber 18 and preload the piston 3 outward from the housing 2. The piston 3 is also preloaded outward from the housing 2 by the spring 4 to take up any slack in the closed chain or belt. As the chain or belt wears, the piston 3 must be preloaded further outward from the housing 2 to adequately tension the chain or belt. The preload sleeve spring 5 in the second open end 14a of the movable sleeve 10 preloads the inner flange 11 outward from the housing 2, moving the end 4b of the spring 4 further outward from the housing 2 and toward the chain or belt.

[0025] When the tensioner 1 tensions a worn chain or belt under a highly dynamic load, the highly dynamic force from the chain or belt (shown by the arrow) pushes the piston 3 inward toward the housing 2 and then outward from the housing 2, with the second piston 20 also moving inward and outward, inflating the pressure or pressurizing the second pressure chamber 24 by drawing fluid through the inlet check valve 7 in the second bore 2b of the housing 2. Pressurizing the second pressure chamber 24 in the second bore 2a moves the second piston 20 and thus the movable sleeve 10 outward from the housing 2. The movement of the movable sleeve 10 causes the inner flange 11 of the movable sleeve 10 to exert an outward force on the piston 3 through the piston spring 4, counteracting the inward force of the dynamic load.

[0026] When the dynamic load of the chain or belt decreases, the pressure of the second pressure chamber 24 is released and fluid flows into the engine through the space between the second bore 2b and the second piston 20.

[0027] In the tensioning system of the present invention, the movement of the movable sleeve 10 moves the second end 4b of the piston spring 4, which biases the piston 3 outward from the housing 2, therefore the spring force acting on the piston 3 is variable and the piston 3 continuously tensions the chain or belt even when the chain or belt wears and stretches.

[0028] In addition, a venting or pressure relief valve (not shown) may be present in the hollow piston 3.

[0029] Closures (not shown) may be present between the bore 2a and the movable sleeve 10 or at any other location in the clamping device as necessary.

[0030] The pressure chambers 18 and 24 of the tensioning device create hydraulic rigidity of the tensioning device and essentially prevent the movement of the piston 3 and the movable sleeve 10 inwards towards the housing 2 when the chain or belt tensioner is loaded.

[0031] In an alternative embodiment, the movable sleeve 10 may be received within another sleeve in the first bore 2a to assist in eliminating pressure that could lead to undesired inflation.

[0032] It should be noted that this is a center position control device. It is unlikely that the frequency response would be sufficient to dynamically vary the position of the movable sleeve within an engine cycle. Pressure exerted on the lower surfaces of the movable sleeve 10 can lead to unwanted inflation. In an alternative embodiment, the movable sleeve 10 can be housed within another sleeve in the first bore 2a to help eliminate pressure that could lead to unwanted inflation. In another alternative embodiment, the piston 3 can fit over the outside of the movable sleeve 10 so that the upper and lower surfaces of the movable sleeve 10 are subjected to the same pressure.

[0033] The Fig. 2a-2b show a tensioning device of a second embodiment using passive control to tension a chain or belt under different conditions; Fig. 2a tensions a chain or belt without a high load; and Fig. 2b tensions a chain or belt with a high load.

[0034] The clamping device comprises a housing 102 having a first axially extending bore 102a parallel to a second axially extending bore 102b. Although the second bore 102c of the housing 102 is shown as parallel to the first bore 102a, the second bore 102c may be perpendicular to the first bore 102a or at a different angle relative to the first bore 102a.

[0035] A first piston 103 is slidably received in the first axially extending bore 102a. The first piston 103 has a body with a first end 103a, a second end 103c, and a hollow interior 103b. A first piston spring 104 is located in the hollow interior 103b of the first piston 103. The first piston spring 104 has a first end 104a in contact with the interior 103b of the first piston 103 or a volume reducer 105 and a second end 104b in contact with a bottom 102b of the first axially extending bore 102a of the housing 102. A first pressure chamber 111 is formed between the first piston 103 and the first axially extending bore 102a. The first pressure chamber 111 is supplied with fluid by a first supply 106 through an inlet check valve 108.The first piston 103 is biased outwardly from the housing 102 to bias a chain or belt through the first end 103a of the first piston 103 by the force of the first piston spring 104 and the oil pressure in the first pressure chamber 111.

[0036] Alternatively, the first piston 103 may not be hollow, and the first piston spring 104 would contact the body of the first piston 103 and the bottom 102b of the first axially extending bore 102a.

[0037] The second axially extending bore 102c receives a movable sleeve 112. The movable sleeve 112 has a first open end 112a and a second open end 112b separated by an inner flange 113. The first open end 112a of the movable sleeve 112 is defined by an upper inner diameter 118 and an upper surface 113a of the inner flange 113. The second open end 112b of the movable sleeve 112 is defined by a lower inner diameter 119 and a lower surface 113b of the inner flange 113. The upper surface 112d of the movable sleeve 112 and the upper surface 113a of the inner flange are exposed to atmospheric pressure of the engine.

[0038] Receiving the first open end 112a of the movable sleeve 112 is a second piston 110 having a body with a first end 110a and a second end 110b. A second piston spring 115 biases the second piston 110 outwardly from the first open end 112a of the movable sleeve 112 of the housing 102 so that the first end 110a of the second piston 110 can exert a force on the chain 400, preferably through a cantilever 401 as shown in Fig. 7. The second piston spring 115 has a first end 115a in contact with the second end 110b of the second piston 110 and a second end 115b in contact with the upper surface 113a of the inner flange 113.

[0039] Alternatively, the second piston 110 may be hollow, and the first end 110a of the second piston spring would contact a hollow interior of the second piston 110.

[0040] A bias sleeve spring 116 and an optional volume reducer 114 are received in the second open end 112b of the movable sleeve 112. The first end 116a of the bias sleeve spring 116 is in contact with a lower surface 113b of the inner flange 113 or the volume reducer 114, and a second end 116b of the bias sleeve spring 116 is in contact with a bottom 102d of the second axially extending bore 102c of the housing 102. The bias sleeve spring 116 maintains the position of the movable sleeve 112 in the second axially extending bore 102c and prevents the movable sleeve 112 from bottoming out in the second axially extending bore 102c. The biasing sleeve spring 116 biases the second piston spring 115, in other words, the second end 115b of the second piston spring 115 is moved outward from the housing 102.A second high-pressure chamber 117 is formed between the lower inner diameter 119 of the movable sleeve 112, the lower surface 113b of the inner flange 113, and the bottom 102d of the second axially extending bore 102c. The volume reducer 114 may also be present in this chamber 117. There is no fluid communication between the first open end 112a and the second open end 112b of the movable sleeve 112 except for any leakage that may occur from the second high-pressure chamber 117.

[0041] The second high-pressure chamber 117 is supplied with fluid through an input supply line 109 and preferably a check valve 107. The input supply 109 may or may not be connected to the input supply line 106.

[0042] The second piston spring 115 has a greater spring rate or spring constant than the first piston spring 104 or the preload sleeve spring 116.

[0043] Since there are two pistons 110, 103 for tensioning the chain or belt tension, the leakage of the first pressure chamber 111 can be increased (unlike a conventional hydraulic tensioner, where a medium pressure must be maintained in the pressure chamber to control the chain) to provide additional damping. The medium force required for chain control is provided by the second piston 110 in the second axially extending bore 102c.

[0044] If the tensioner requires a new chain or belt as shown in Fig. 2a, during operation the first pressure chamber 111 is supplied with fluid from the first input supply 106 and through an input check valve 108 and the first piston 103 is biased outwardly from the housing 102 in addition to the spring force of the first piston spring 104, whereby a slack of the closed chain 400 or the belt as shown in Fig. 7. At the same time, the second piston 110 is also biased outwardly by the movable sleeve 112 through the second piston spring 115 to tension any slack in the closed chain 400 or belt. Ideally, the first piston 103 and the second piston 110 are biased outwardly by approximately the same amount from the housing 102. In other words, the first ends 103a, 110a of the first and second pistons 103, 110 are as shown in Fig. 2a and Fig. 7 shown.

[0045] During operation, when the tensioner is tensioning a worn chain or belt without a high load, the first pressure chamber 111 is supplied with fluid through the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outward from the housing 102 in addition to the spring force of the first piston spring 104, thereby tightening any slack in the closed chain 400 or belt. At the same time, the second piston 110 is also biased outward from the movable sleeve 112 by the second piston spring 115 due to the movement of the movable sleeve 112 by the bias sleeve spring 116 to tighten any slack in the closed chain 400 or belt.As the chain or belt wears, there is additional free play in the chain or belt span, and the first piston 103 and the second piston 110 would need to be extended further outward from the housing 102 to adequately tension and preload the chain 400 or belt.

[0046] When the tensioner tensions a worn chain or belt under a highly dynamic chain or belt load, the highly dynamic force from the chain or belt (shown by the arrow) pushes the first piston 103 and the second piston 110 inward toward the housing 102 and then outward from the housing 102, inflating the pressure or pressurizing the second pressure chamber 117 by drawing fluid through the inlet check valve 107 in the second bore 102c of the housing 102. Pressurizing the second pressure chamber 117 in the second bore 102c moves the movable sleeve 112 outward from the housing 102. The movement of the movable sleeve 112 causes the inner flange 113 of the movable sleeve 112 to exert an outward force on the second piston 110 through the second piston spring 115, which counteracts the inward force of the dynamic load.

[0047] As the dynamic load of the chain or belt decreases, fluid within the second pressure chamber 117 leaks into the engine through the second axially extending bore 102c or through the volume reducer 114. This leakage reduces the average pressure present in the second pressure chamber 117.

[0048] It should be noted that under all operating conditions, the pressure in the second pressure chamber 117 builds up to maintain a minimum preload in the second piston spring 115. If the force or preload in the second piston spring 115 becomes too low, the movable sleeve 112 moves out of the housing due to the preload sleeve spring 116 and the pressure in the second pressure chamber 117, drawing in more oil through the input check valve 107.

[0049] Therefore, the first piston 103 in the first axially extending bore 102a provides the predominant damping of the chain tension 400 or the belt tension, and the second piston 110 in the second axially extending bore 102c provides the predominant and automatically adjusting spring force. The tensioner of the present invention automatically adjusts the average tension force to keep the chain or belt tension as low as possible without sacrificing chain or belt control, significantly improving drive efficiency under new chain and dynamic load conditions.

[0050] The Fig. 3a-3b show a tensioning device of a third embodiment using passive control to tension a chain under different conditions; Fig. 3a tensions a chain without high load; and Fig. 3b tensions a chain with a high load.

[0051] The clamping device includes a housing 102 having a first axially extending bore 102a parallel to a second axially extending bore 102c. Although the second bore 102c of the housing 102 is shown as parallel to the first bore 102a, the second bore 102c may be perpendicular to the first bore 102a or at a different angle relative to the first bore 102a.

[0052] A first piston 103 is slidably received in the first axially extending bore 102a. The first piston 103 has a body with a first end 103a, a second end 103c, and a hollow interior 103b. A first piston spring 104 is located in the hollow interior 103b of the first piston 103. The first piston spring 104 has a first end 104a in contact with the interior 103b of the first piston 103 or a volume reducer 105 and a second end 104b in contact with a bottom 102b of the first axially extending bore 102a of the housing 102. A first pressure chamber 111 is formed between the first piston 103 and the first axially extending bore 102a. The first pressure chamber is supplied with fluid by a first supply 106 through an inlet check valve 108.The first piston 103 is biased outwardly from the housing 102 to tension the chain through a first end 103a of the first piston by the force of the first piston spring 104 and the oil pressure in the first pressure chamber 111.

[0053] Alternatively, the first piston 103 may not be hollow, and the first piston spring 104 would contact the body of the first piston 103 and the bottom 102b of the first axially extending bore 102a.

[0054] The second axially extending bore 102c slidably receives a second outer piston 150 and a third piston 152. The second outer piston 150 has a body with a first end 150a, a second end 150c, and a hollow interior 150b. A second piston spring 151 is located within the hollow interior 150b to bias the second piston 150 outward from the housing 102. The second piston spring 151 has a first end 151a in contact with the interior 150b of the second outer piston 150 and a second end 151b in contact with a first end 152a of the third piston 152. Alternatively, the second outer piston 150 may not be hollow, and the first end 151a of the second piston spring 151 would contact the body of the second outer piston 150.

[0055] The third piston 152 has a body with a first end 152a, a second end 152c, and a hollow interior 152b. A third piston spring 154 is located within the hollow interior 152b to bias the third piston 152 outward from the housing and to bias the second piston spring 151; in other words, the second end 151b of the second piston spring 152 is moved outward from the housing 102. The third piston spring 154 has a first end 154a in contact with the hollow interior 152b or a volume reducer 153, and a second end 154b in contact with the bottom 102c of the second axially extending bore 102c of the housing 102.

[0056] A second high-pressure chamber 155 is formed between the hollow interior 152b, the second axially extending bore 102c, and the third piston spring 154. The second high-pressure chamber 155 is supplied with fluid through an input supply 109 and preferably a check valve 107. The input supply 109 may or may not be connected to the input supply line 106.

[0057] There is no fluid communication between the hollow interior 150b of the second piston 150 and the second high pressure chamber 155, except for any leakage that may occur.

[0058] The second piston spring 151 has a larger spring rate or spring constant than the first piston spring 104 or the third piston spring 154.

[0059] Because there are two pistons 150, 103 for tensioning the chain or belt, the leakage of the first pressure chamber 111 can be increased (unlike a conventional hydraulic tensioner, where a medium pressure must be maintained in the pressure chamber to control the chain) to provide additional damping. The medium force required for chain or belt control is provided by the second piston 150 in the second axially extending bore 102c.

[0060] If the tensioner requires a new chain or belt as shown in Fig. 3a, during operation the first pressure chamber 111 is supplied with fluid from the first input supply 106 and through an input check valve 108 and the first piston 103 is biased outwardly from the housing 102 in addition to the spring force of the first piston spring 104, whereby a slack of the closed chain 400 or the belt as shown in Fig. 7. At the same time, the second piston 150 is also biased outwardly from the second axially extending bore 102c by the second piston spring 151 to take up any slack in the closed chain 400 or belt. Ideally, the first piston 103 and the second piston 150 are biased outwardly from the housing 102 by approximately the same amount. In other words, the first ends 103a, 150a of the first and second pistons 103, 150 are as shown in Fig. 3a and Fig. 7 shown.

[0061] During operation, when the tensioner is tensioning a worn chain or belt without a high load, the first pressure chamber 111 is supplied with fluid through the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outward from the housing 102 in addition to the spring force of the first piston spring 104, thereby tensioning any slack in the closed chain 400 or belt. At the same time, the second piston 150 is also further biased outward by the second piston spring 151 due to the movement of the third piston 152 by the third piston spring 154 to tension the slack in the closed chain 400 or belt. As the chain wears, there is additional free play in the chain span, and the first piston 103 and the second piston 150 would need to be extended further outward from the housing 102 to adequately tension and preload the chain 400 or belt.

[0062] When the tensioner tensions a worn chain or belt under a highly dynamic chain or belt load, the highly dynamic force from the chain or belt (shown by the arrow) pushes the first piston 103 and the second piston 150 inward toward the housing 102 and then outward from the housing 102, inflating the pressure or pressurizing the second pressure chamber 155 by drawing fluid through the input check valve 107 into the second bore 102c of the housing 102. Pressurizing the second pressure chamber 155 in the second bore 102c moves the third piston 152 outward from the housing 102. The movement of the third piston 152 causes the first end 152a of the third piston 152 to exert an outward force on the second piston 150 through the second piston spring 151, which counteracts the inward force of the dynamic load.

[0063] As the dynamic load of the chain or belt decreases, fluid within the second pressure chamber 155 leaks into the engine through the second axially extending bore 102c or through the volume reducer 153. This leakage reduces the average pressure present in the second pressure chamber 155.

[0064] It should be noted that under all operating conditions, the pressure in the second pressure chamber 155 builds up to maintain a minimum preload in the second piston spring 151. If the force or preload in the second piston spring 151 becomes too low, the third piston 152 moves out of the housing due to the third piston spring 154 and the pressure in the second pressure chamber 155, drawing in more oil through the inlet check valve 107.

[0065] Therefore, the first piston 103 in the first axially extending bore 102a provides the predominant damping of the chain or belt tension, and the second piston 150 in the second axially extending bore 102c provides the predominant and automatically adjusting spring force. The tensioner of the present invention automatically adjusts the intermediate tension force to keep the chain or belt tension as low as possible without sacrificing chain or belt control, significantly improving drive efficiency under new chain or belt conditions and dynamic load conditions.

[0066] The Fig. 4a-4b show a tensioning device of a fourth embodiment using passive control to tension a chain under different conditions; Fig. 4a tensions a chain without high load; and Fig. 4b tensions a chain with a high load.

[0067] The clamping device comprises a housing 102 having a first axially extending bore 102a parallel to a second axially extending bore 102b. Although the second bore 102c of the housing 102 is shown as parallel to the first bore 102a, the second bore 102c may be perpendicular to the first bore 102a or at a different angle relative to the first bore 102a.

[0068] A first piston 103 is slidably received in the first axially extending bore 102a. The first piston 103 has a body with a first end 103a, a second end 103c, and a hollow interior 103b. A first piston spring 104 is located in the hollow interior 103b of the first piston 103. The first piston spring 104 has a first end 104a in contact with the interior 103b of the first piston 103 or a volume reducer 105 and a second end 104b in contact with a bottom 102b of the first axially extending bore 102a of the housing 102. A first pressure chamber 111 is formed between the first piston 103 and the first axially extending bore 102a. The first pressure chamber is supplied with fluid by a first supply 106 through an inlet check valve 108.The first piston 103 is biased outwardly from the housing 102 to tension the chain through a first end 103a of the first piston 103 by the force of the first piston spring 104 and the oil pressure in the first pressure chamber 111.

[0069] Alternatively, the first piston 103 may not be hollow, and the first piston spring 104 would contact the body of the first piston 103 and the bottom 102b of the first axially extending bore 102a.

[0070] The second axially extending bore 102b slidably receives a second piston 200. The second piston 200 includes a body with a first end 200a, a second end 200c, and a hollow interior 200b. The hollow interior 200b receives a shaft 202a of a "Y"-shaped inner piston 202. The shaft 202a of the Y-shaped inner piston 202 is connected to a body with a first end 202d, a second end 202b, and a hollow interior 202c. A second piston spring 201 is located between the second end 200c of the second piston 200 and the first end 202d of the inner piston body 202d. The second piston spring 201 has a first end 201a in contact with the second end 200c of the second piston 200 and a second end 201b in contact with the first end 202d of the inner piston 202. The second piston spring 201 biases the second piston 200 outward from the housing 102.

[0071] Alternatively, the second piston spring may be present between the shaft 202a of the Y-shaped inner piston 202 and the hollow interior 200b of the second piston 200.

[0072] An inner piston spring 204 is located within the hollow interior 202c of the inner piston 202. The inner piston spring 204 has a first end 204a in contact with a hollow interior 202c of the inner piston 202 or a volume reducer 206, and a second end 204b in contact with the bottom 102d of the second axially extending bore 102c. The inner piston spring 204 biases the inner piston 202 outward from the housing 102, biasing the second piston 200 outward from the housing by changing the preload on the second piston spring 201. In other words, moving the second end 201b of the second piston spring 201 outward from the housing 102.

[0073] A second high-pressure chamber 205 is formed between the hollow interior 202c of the inner piston 202 and the bottom 102d of the second axially extending bore 102c of the housing 102. The second high-pressure chamber 205 is supplied with fluid through an input supply 109 and preferably a check valve 107. The input supply 109 may or may not be connected to the input supply line 106.

[0074] The second piston spring 201 has a greater spring rate or spring constant than the first piston spring 104 or the inner piston spring 204.

[0075] Because there are two pistons 200, 103 for tensioning the chain or belt tension, the leakage of the first pressure chamber 111 can be increased (unlike a conventional hydraulic tensioner, where a medium pressure must be maintained in the pressure chamber to control the chain) to provide additional damping. The medium force required for chain or belt control is provided by the second piston 200 in the second axially extending bore 102c.

[0076] If the tensioner requires a new chain or belt as shown in Fig. 4a, during operation the first pressure chamber 111 is supplied with fluid from the first input supply 106 and through an input check valve 108 and the first piston 103 is biased outwardly from the housing 102 in addition to the spring force of the first piston spring 104, whereby a slack of the closed chain 400 or the belt as shown in Fig. 7. At the same time, the second piston 200 is also biased outwardly from the second axially extending bore 102c by the second piston spring 201 to take up any slack in the closed chain or belt. Ideally, the first piston 103 and the second piston 200 are biased outwardly from the housing 102 by approximately the same amount. In other words, the first ends 103a, 200a of the first and second pistons 103, 200 are as shown in Fig. 4a and Fig. 7 shown.

[0077] During operation, when the tensioner is tensioning a worn chain or belt without a high load, the first pressure chamber 111 is supplied with fluid through the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outward from the housing 102 in addition to the spring force of the first piston spring 104, thereby tensioning any slack in the closed chain 400 or belt. At the same time, the second piston 200 is also further biased outward by the second piston spring 201 due to the movement of the inner piston 202 by the inner piston spring 204 to tension the slack in the closed chain 400 or belt. As the chain wears, there is additional free play in the chain span, and the first piston 103 and the second piston 200 would need to be extended further outward from the housing 102 to adequately tension and preload the chain 400 or belt.

[0078] When the tensioner tensions a chain or belt under a highly dynamic chain or belt load, the highly dynamic force from the chain or belt (shown by the arrow) pushes the first piston 103 and the second piston 200 inward toward the housing 102 and then outward from the housing 102, inflating the pressure or pressurizing the second pressure chamber 205 by drawing fluid through the input check valve 107 into the second bore 102c of the housing 102. Pressurizing the second pressure chamber 205 in the second bore 102c moves the inner piston 202 outward from the housing 102. The movement of the inner piston 202 causes the first end 202d of the inner piston 202 to exert an outward force on the second piston 200 through the second piston spring 201, counteracting the inward force of the dynamic load.

[0079] As the dynamic load of the chain or belt decreases, fluid within the second pressure chamber 205 leaks into the engine through the second axially extending bore 102c or through the volume reducer 206. This leakage reduces the average pressure present in the second pressure chamber 205.

[0080] It should be noted that under all operating conditions, the pressure in the second pressure chamber 205 builds up to maintain a minimum preload in the second piston spring 201. If the force or preload in the second piston spring 201 becomes too low, the inner piston 202 moves out of the housing due to the inner piston spring 204 and the pressure in the second pressure chamber 205, drawing in more oil through the inlet check valve 107.

[0081] Therefore, the first piston 103 in the first axially extending bore 102a provides the predominant damping of the chain or belt tension, and the second piston 200 in the second axially extending bore 102c provides the predominant and automatically adjusting spring force. The tensioner of the present invention automatically adjusts the average tension force to keep the chain or belt tension as low as possible without sacrificing chain or belt control, significantly improving drive efficiency under new chain or belt conditions and dynamic load conditions.

[0082] The Fig. 5-6 show different possibilities for simultaneously controlling the first piston and the second piston of the embodiments of the present invention. With reference to Fig. 5, the first piston 103 and the second piston 150 are directly connected by a connection 310. Therefore, the movements of the first piston 103 and the second piston 150 are linked. When the first piston 103 and the second piston 150 are coupled, the first piston spring 104 is optional. It should be noted that, although the connection was shown with the tensioning device of the third embodiment, it is equally applicable to the tensioning devices of the Fig. 2a-2b and 4a-4b can be applied.

[0083] Fig. Figure 6 shows an alternative configuration in which the first piston has an extension 312 with an upper surface 312a and a lower surface 312b. The second piston 150 presses on the lower surface 312b of the extension 312 when the second piston 150 is biased outwardly from the housing 102. It should be noted that, although the connection was shown with the tensioner of the third embodiment, it is equally applicable to the tensioners of the Fig. 2a-2b and 4a-4b. In this embodiment, the first piston spring 104 is optional.

[0084] The volume reducers shown in any of the above embodiments may be replaced by a pressure relief valve or a vent.

[0085] It should also be noted that the clamping device of the Fig. 2a-2b in Fig. 7, but any of the tensioning devices present in the application would work with the chain tensioner.

[0086] The Fig. 8a-8b show a tensioning device of another embodiment using passive control to tension a chain or belt under different conditions; Fig. 8a shows the tensioning of a chain or belt without high loads; and Fig. Figure 8b shows the tensioning of a chain or belt with a high load.

[0087] The tensioning device tensions the chain or belt (not shown) through a tensioning arm or tensioning shoe 402. It should be noted that the tensioning device can also tension a belt through the tensioning arm or tensioning shoe 402. The tensioning arm 402 has a first sliding surface 402b in contact with the chain or belt and a second surface 402a opposite the first sliding surface 402b. The second surface 402a can be flat or nearly flat with a curvature.

[0088] The clamping device includes a housing 102 having a first axially extending bore 102a parallel to a second axially extending bore 102c. Although the second bore 102c of the housing 102 is shown as parallel to the first bore 102a, the second bore 102c may be perpendicular to the first bore 102a or at a different angle relative to the first bore 102a.

[0089] A first piston 103 is slidably received in the first axially extending bore 102a. The first piston 103 has a body with a first end 103a, a second end 103c, and a hollow interior 103b with a closed first end 103d. A first piston spring 104 is present in the hollow interior 103b of the first piston 103. The first piston spring 104 has a first end 104a in contact with the closed first end 103d of the first piston 103 or a volume reducer 105 and a second end 104b in contact with a bottom 102b of the first axially extending bore 102a of the housing 102. A first pressure chamber 111 is formed between the first piston 103 and the first axially extending bore 102a. The first pressure chamber is supplied with fluid by a first supply 106 through an inlet check valve 108.The first piston 103 is biased outwardly from the housing 102 to tension the chain through the first end 103a of the first piston, through the tensioning arm 402 by the force of the first piston spring 104 and the oil pressure in the first pressure chamber 111.

[0090] Alternatively, the first piston 103 may be a solid body, in which case the first piston spring 104 would contact a bottom of the solid body of the first piston 103 and the bottom 102b of the first axially extending bore 102a.

[0091] The second axially extending bore 102c slidably receives a second piston 260. The second piston 260 includes a body with a first end 260a, a second end 260c, and a hollow interior 260b with a closed first end 260d.

[0092] A second piston spring 266 is provided within the hollow interior 260b to bias the second piston 260 outward from the housing 102. The second piston spring 266 has a first end 266a in contact with the closed first end 260d of the interior 260b of the second piston 260 and a second end 266b in contact with the bottom 102d of the second axially extending bore 102c. Although not shown, a volume reducer may be provided within the interior 260b of the second piston 260.

[0093] An outer spring 261 is present between the first end 260a of the second piston 260 and the second planar surface 402a of the tensioning arm 402, with the first end 261a of the outer spring 260 in contact with the second surface 402a of the tensioning arm 402 and the second end 261b of the outer spring 260 in contact with the first end 260a of the second piston 260. The stiffness of the outer spring 261 is preferably greater than the stiffness of the second piston spring 266. The spring rates for both the first piston spring 104 and the second piston spring 266 are preferably low. Movement of the second piston 260 moves the second end 261b of the outer spring 261 outward from the housing 102.

[0094] A second high-pressure chamber 267 is formed through the hollow interior 260b and the second axially extending bore 102c, within which the second piston spring 266 is located. The second high-pressure chamber 267 is supplied with fluid through an input supply 109 and preferably a check valve 107. The input supply 109 may or may not be connected to the input supply line 106.

[0095] If the tensioner requires a new chain or belt as shown in Fig. 8a, during operation, the first pressure chamber 111 is supplied with fluid from the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outwardly from the housing 102 in addition to the spring force of the first piston spring 104, thereby tensioning any slack in the closed chain or belt by a tensioning arm 402. Simultaneously, the second piston 260 is also biased outwardly from the second axially extending bore 102c by the second piston spring 266, and the second pressure chamber 267 is supplied with fluid from the second input supply 109 and through the input check valve 109 to preload any slack in the closed chain or belt through the tensioning arm by the outward spring 261.

[0096] During operation, when the tensioner is tensioning a worn chain or belt without a high load, the first pressure chamber 111 is supplied with fluid through the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outward from the housing 102 in addition to the spring force of the first piston spring 104, with any slack in the closed chain or belt being tensioned by the tensioner arm 402. At the same time, the second piston 260 is also biased outward by the second piston spring 266. Tension is also maintained by the outward spring 261 on the tensioner arm 402. As the chain or belt wears, there is additional slack in the chain or belt tension, and the first piston 103 and second piston 260 would need to be extended further outward from the housing 102 to adequately tension and preload the chain or belt.

[0097] When the tensioner tensions a chain or belt under high dynamic chain load, the high cyclic dynamic force from the chain or belt (shown by the arrow in Fig. 8b), the first piston 103 and the second piston 260 alternately move inward toward the housing 102 and then outward from the housing 102. The inward movement of the second piston 260 is counteracted by fluid pressure in the second pressure chamber 267 created by the check valve 107, and the second piston 260 moves outward under the force of the spring 266. This "pumped" the piston, drawing fluid through the input check valve 107 into the second pressure chamber 267 in the second bore 102c. This causes the first end 260a of the second piston 260 to exert an outward force on the tensioning boom 402 through the outward spring 261, counteracting the inward force of the dynamic load.

[0098] As the dynamic load of the chain or belt decreases, fluid within the second pressure chamber 267 leaks into the engine through the second axially extending bore 102c or through a vent opening. This leakage reduces the average pressure present in the second pressure chamber 267.

[0099] It should be noted that under all operating conditions, the pressure in the second pressure chamber 267 builds up to maintain a minimum preload in the outer spring 261. If the force or preload in the outer spring 261 becomes too low, the second piston 260 moves out of the housing due to the second piston spring 266 and the pressure in the second pressure chamber 267, drawing in more oil through the input check valve 107.

[0100] Therefore, the first piston 103 in the first axially extending bore 102a provides the predominant damping of the chain tension or belt tension, and the second piston 260 in the second axially extending bore 102c provides the predominant and automatically adjusting spring force through the outer spring 261. The tensioner of the present invention automatically adjusts the average tension force to keep the chain or belt tension as low as possible without sacrificing chain or belt control, significantly improving drive efficiency under new chain or belt conditions and dynamic load conditions.

[0101] The Fig. 9a-9b show a tensioning device of another embodiment using passive control to tension a chain under different conditions; Fig. 9a tensions a chain without high load; and Fig. 9b tensions a chain with a high load. The tensioning device of the Fig. 9a-9b differs from the clamping device in the Fig. 8a-8b, in that the second piston 270 has a projection 270d at the first end of the outer piston 270 that extends into the outer spring 271 to guide the outer spring 271 between the tensioning arm 402 and the second piston 270, rather than having a flat surface.

[0102] The tensioning device tensions the chain or belt (not shown) through a tensioning arm or tensioning shoe 402. It should be noted that the tensioning device can also tension a belt through the tensioning arm or tensioning shoe 402. The tensioning arm 402 has a first sliding surface 402b in contact with the chain or belt and a second surface 402a opposite the first sliding surface 402b. The second surface 402a is flat or nearly flat with a curvature.

[0103] The clamping device includes a housing 102 having a first axially extending bore 102a parallel to a second axially extending bore 102c. Although the second bore 102c of the housing 102 is shown as parallel to the first bore 102a, the second bore 102c may be perpendicular to the first bore 102a or at a different angle relative to the first bore 102a.

[0104] A first piston 103 is slidably received in the first axially extending bore 102a. The first piston 103 has a body with a first end 103a, a second end 103c, and a hollow interior 103b with a closed first end 103d. A first piston spring 104 is present in the hollow interior 103b of the first piston 103. The first piston spring 104 has a first end 104a in contact with the closed first end 103d of the first piston 103 or a volume reducer 105 and a second end 104b in contact with a bottom 102b of the first axially extending bore 102a of the housing 102. A first pressure chamber 111 is formed between the first piston 103 and the first axially extending bore 102a. The first pressure chamber is supplied with fluid by a first supply 106 through an inlet check valve 108.The first piston 103 is biased outwardly from the housing 102 to tension the chain or belt through a first end 103a of the first piston, through the tensioning arm 402, by the force of the first piston spring 104 and the oil pressure in the first pressure chamber 111.

[0105] Alternatively, the first piston 103 may be a solid body, in which case the first piston spring 104 would contact the body of the first piston 103 and the bottom 102b of the first axially extending bore 102a.

[0106] The second axially extending bore 102c slidably receives a second piston 270. The second piston 270 includes a body having a first end 270a with a projection 270d extending axially outward from the body of the second piston 270, a second end 270c, and a hollow interior 270b with a closed first end 270d.

[0107] A second piston spring 266 is provided within the hollow interior 270b to bias the second piston 270 outward from the housing 102. The second piston spring 276 has a first end 276a in contact with the closed first end 270d of the interior 270b of the second piston 270 and a second end 276b in contact with the bottom 102d of the second axially extending bore 102c. Although not shown, a volume reducer may be provided within the interior 270b of the second piston 270.

[0108] An outer spring 271 is disposed between the first end 270a of the second piston 270 and the second surface 402a of the tensioning arm 402 and surrounding the projection 270d of the second piston 270. The first end 271a of the outer spring 270 is in contact with the second surface 402a of the tensioning arm 402, and the second end 271b of the outer spring 270 is in contact with the first end 270a of the second piston 270. The stiffness of the outer spring 271 is preferably greater than the stiffness of the second piston spring 276. Movement of the second piston 270 moves the second end 271b of the outer spring 271 outward from the housing 102.

[0109] A second high-pressure chamber 277 is formed between the hollow interior 270b and the second axially extending bore 102c, within which the second piston spring 276 is located. The second high-pressure chamber 277 is supplied with fluid through an input supply 109 and preferably a check valve 107. The input supply 109 may or may not be connected to the input supply line 106.

[0110] If the tensioner requires a new chain or belt as shown in Fig. 9a, during operation, the first pressure chamber 111 is supplied with fluid from the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outwardly from the housing 102 in addition to the spring force of the first piston spring 104, thereby tensioning any slack in the closed chain or belt by a tensioning arm 402. Simultaneously, the second piston 270 is also biased outwardly from the second axially extending bore 102c by the second piston spring 276, and the second pressure chamber 277 is supplied with fluid from the second input supply 109 and through the input check valve 109 to preload any slack in the closed chain or belt through the tensioning arm by the outward spring 271.

[0111] During operation, when the tensioner is tensioning a worn chain or belt without a high load, the first pressure chamber 111 is supplied with fluid through the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outward from the housing 102 in addition to the spring force of the first piston spring 104, with any slack in the closed chain or belt being tensioned by the tensioner arm 402. At the same time, the second piston 270 is also further biased outward by the second piston spring 276. Tension is also maintained by the outward spring 271 on the tensioner arm 402. As the chain or belt wears, there is additional slack in the chain or belt tension, and the first piston 103 and second piston 270 would need to be extended further outward from the housing 102 to adequately tension and preload the chain or belt.

[0112] When the tensioner tensions a chain or belt under high dynamic chain load, the high cyclic dynamic force from the chain or belt (shown by the arrow in Fig. 9b), the first piston 103 and the second piston 270 alternately move inward toward the housing 102 and then outward from the housing 102. The inward movement of the second piston 270 is counteracted by fluid pressure in the second pressure chamber 277 created by the check valve 107, and the second piston 270 moves outward under the force of the spring 276. This "inflates" the piston, drawing fluid through the input check valve 107 into the second pressure chamber 277 in the second bore 102c. This causes the first end 270a of the second piston 270, through the outer spring 271, to exert an outward force on the tensioning boom 402, counteracting the inward force of the dynamic load.

[0113] As the dynamic load of the chain or belt decreases, fluid within the second pressure chamber 277 leaks into the engine through the second axially extending bore 102c or through a vent opening. This leakage reduces the average pressure present in the second pressure chamber 277.

[0114] It should be noted that under all operating conditions, the pressure in the second pressure chamber 277 builds up to maintain a minimum preload in the outer spring 271. If the force or preload in the outer spring 271 becomes too low, the second piston 270 moves out of the housing due to the second piston spring 276 and the pressure in the second pressure chamber 277, drawing in more oil through the input check valve 107.

[0115] Therefore, the first piston 103 in the first axially extending bore 102a provides the predominant damping of the chain tension or belt tension, and the second piston 270 in the second axially extending bore 102c provides the predominant and automatically adjusting spring force through the outer spring 271. The tensioner of the present invention automatically adjusts the average tension force to keep the chain or belt tension as low as possible without sacrificing chain or belt control, significantly improving drive efficiency under new chain or belt conditions and dynamic load conditions.

[0116] The Fig. 10a-10b show a tensioning device of another embodiment using passive control to tension a chain under various conditions; Fig. 10a tensions a chain without high load; and Fig. 10b tensions a chain with a high load. The tensioning device of the Fig. 10a-10b differs from the clamping device in the Fig. 8a-8b, in that the second surface of the tensioning arm has a projection 402c extending axially into the outer spring 261, in addition to a flat surface 402a. It should be noted that the surface 402a may have a curvature.

[0117] The tensioner tensions the chain or belt (not shown) through a tensioning arm or tensioning shoe 402. It should be noted that the tensioner can also tension a belt through the tensioning arm or tensioning shoe 402. The tensioning arm 402 has a first sliding surface 402b in contact with the chain or belt and a second surface 402a opposite the first sliding surface 402b. The second surface 402a can be flat or nearly flat with a curvature, and a projection 402c projecting axially outward toward the second piston 261 can be present.

[0118] The clamping device includes a housing 102 having a first axially extending bore 102a parallel to a second axially extending bore 102c. Although the second bore 102c of the housing 102 is shown as parallel to the first bore 102a, the second bore 102c may be perpendicular to the first bore 102a or at a different angle relative to the first bore 102a.

[0119] A first piston 103 is slidably received in the first axially extending bore 102a. The first piston 103 has a body with a first end 103a, a second end 103c, and a hollow interior 103b with a closed first end 103d. A first piston spring 104 is present in the hollow interior 103b of the first piston 103. The first piston spring 104 has a first end 104a in contact with the closed first end 103d of the first piston 103 or a volume reducer 105 and a second end 104b in contact with a bottom 102b of the first axially extending bore 102a of the housing 102. A first pressure chamber 111 is formed between the first piston 103 and the first axially extending bore 102a. The first pressure chamber is supplied with fluid by a first supply 106 through an inlet check valve 108.The first piston 103 is biased outwardly from the housing 102 to preload the chain or belt through the first end 103a of the first piston, through the tensioning arm 402, by the force of the first piston spring 104 and the oil pressure in the first pressure chamber 111.

[0120] Alternatively, the first piston 103 may be a solid body, in which case the first piston spring 104 would contact the body of the first piston 103 and the bottom 102b of the first axially extending bore 102a.

[0121] The second axially extending bore 102c slidably receives a second piston 260. The second piston 260 includes a body with a first end 260a, a second end 260c, and a hollow interior 260b with a closed first end 260d.

[0122] A second piston spring 266 is provided within the hollow interior 260b to bias the second piston 260 outward from the housing 102. The second piston spring 266 has a first end 266a in contact with the closed first end 260d of the interior 260b of the second piston 260 and a second end 266b in contact with the bottom 102d of the second axially extending bore 102c. Although not shown, a volume reducer may be provided within the interior 260b of the second piston 260.

[0123] An outer spring 261 is present between the first end 260a of the second piston 260 and the second surface 402a of the tensioning arm 402, the first end 261a of the outer spring 260 being in contact with the second surface 402a of the tensioning arm 402 and surrounding a projection 402c of the tensioning arm 402. The second end 261b of the outer spring 260 is in contact with the first end 260a of the second piston 260. The stiffness of the outer spring 261 is preferably greater than that of the second piston spring 266. Movement of the second piston 260 moves the second end 261b of the outer spring 261 outward from the housing 102.

[0124] A second high-pressure chamber 267 is formed between the hollow interior 260b and the second axially extending bore 102c, within which the second piston spring 266 is located. The second high-pressure chamber 267 is supplied with fluid through an input supply 109 and preferably a check valve 107. The input supply 109 may or may not be connected to the input supply line 106.

[0125] If the tensioner requires a new chain or belt as shown in Fig. 10a, during operation, the first pressure chamber 111 is supplied with fluid from the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outwardly from the housing 102 in addition to the spring force of the first piston spring 104, thereby tensioning any slack in the closed chain or belt by a tensioning arm 402. Simultaneously, the second piston 260 is also biased outwardly from the second axially extending bore 102c by the second piston spring 266, and the second pressure chamber 267 is supplied with fluid from the second input supply 109 and through the input check valve 109 to preload any slack in the closed chain or belt through the tensioning arm by the outward spring 261.

[0126] During operation, when the tensioner is tensioning a worn chain or belt without a high load, the first pressure chamber 111 is supplied with fluid through the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outward from the housing 102 in addition to the spring force of the first piston spring 104, with any slack in the closed chain or belt being tensioned by the tensioner arm 402. At the same time, the second piston 260 is also biased outward by the second piston spring 266. Tension is also maintained by the outward spring 261 on the tensioner arm 402. As the chain or belt wears, there is additional slack in the chain or belt tension, and the first piston 103 and second piston 260 would need to be extended further outward from the housing 102 to adequately tension and preload the chain or belt.

[0127] When the tensioner tensions a chain or belt under high dynamic chain load, the high cyclic dynamic force from the chain or belt (shown by the arrow in Fig. 10b), the first piston 103 and the second piston 260 alternately move inward toward the housing 102 and then outward from the housing 102. The inward movement of the second piston 260 is counteracted by fluid pressure in the second pressure chamber 267 created by the check valve 107, and the second piston 260 moves outward under the force of the spring 266. This "inflates" the piston, drawing fluid through the input check valve 107 into the second pressure chamber 267 in the second bore 102c. This causes the first end 260a of the second piston 260 to exert an outward force on the tensioning boom 402 through the outer spring 261, counteracting the inward force of the dynamic load.

[0128] As the dynamic load of the chain or belt decreases, fluid within the second pressure chamber 267 leaks into the engine through the second axially extending bore 102c or through a vent opening. This leakage reduces the average pressure present in the second pressure chamber 267.

[0129] It should be noted that under all operating conditions, the pressure in the second pressure chamber 267 builds up to maintain a minimum preload in the outer spring 261. If the force or preload in the outer spring 261 becomes too low, the second piston 260 moves out of the housing due to the second piston spring 266 and the pressure in the second pressure chamber 267, drawing in more oil through the input check valve 107.

[0130] Therefore, the first piston 103 in the first axially extending bore 102a provides the predominant damping of the chain tension or belt tension, and the second piston 260 in the second axially extending bore 102c provides the predominant and automatically adjusting spring force through the outer spring 261. The tensioner of the present invention automatically adjusts the average tension force to keep the chain tension as low as possible without sacrificing chain or belt control, significantly improving drive efficiency under new chain or belt conditions and dynamic load conditions.

[0131] The Fig. 11a-11b show a tensioning device of another embodiment using passive control to tension a chain under different conditions; Fig. 11a tensions a chain without high loads; and Fig. 11b tensions a chain with a high load.

[0132] The tensioning device tensions the chain or belt (not shown) through a tensioning arm or tensioning shoe 402. It should be noted that the tensioning device can also tension a belt through the tensioning arm or tensioning shoe 402. The tensioning arm 402 has a first sliding surface 402b in contact with the chain and a second surface 402a opposite the first sliding surface 402b. The second surface 402a can be flat or nearly flat with a curve and can include a cutout 403. The cutout 403 is preferably large enough to accommodate a portion of an external spring 281.

[0133] The clamping device includes a housing 102 having a first axially extending bore 102a parallel to a second axially extending bore 102c. Although the second bore 102c of the housing 102 is shown as parallel to the first bore 102a, the second bore 102c may be perpendicular to the first bore 102a or at a different angle relative to the first bore 102a.

[0134] A first piston 103 is slidably received in the first axially extending bore 102a. The first piston 103 has a body with a first end 103a, a second end 103c, and a hollow interior 103b with a closed first end 103d. A first piston spring 104 is present in the hollow interior 103b of the first piston 103. The first piston spring 104 has a first end 104a in contact with the closed first end 103d of the first piston 103 or a volume reducer 105 and a second end 104b in contact with a bottom 102b of the first axially extending bore 102a of the housing 102. A first pressure chamber 111 is formed between the first piston 103 and the first axially extending bore 102a. The first pressure chamber is supplied with fluid by a first supply 106 through an inlet check valve 108.The first piston 103 is biased outwardly from the housing 102 to pretension the chain through a first end 103a of the first piston, through the tensioning arm 402, by the force of the first piston spring 104 and the oil pressure in the first pressure chamber 111.

[0135] Alternatively, the first piston 103 may be a solid body, in which case the first piston spring 104 would contact the body of the first piston 103 and the bottom 102b of the first axially extending bore 102a.

[0136] The second axially extending bore 102c slidably receives a second piston 280. The second piston 280 includes a body with a first end 280a, a second end 280c, and a hollow interior 280b with a closed first end 280d. The body of the second piston 280 does not exit the second axially extending bore 102c of the housing 102.

[0137] A second piston spring 286 for biasing the second piston 280 outwardly from the housing 102 has a first end 286a in contact with the first end 280a of the second piston 280 and a second end 286b in contact with the bottom 102d of the second axially extending bore 102c.

[0138] An outer spring 281 is located within the hollow interior 280b. The first end 281a of the outer spring 281 contacts the closed first end 280d of the interior 280b of the second piston 280, and a second end 281b of the outer spring 281 contacts the cutout 403 of the tensioning arm 402. The stiffness of the outer spring 281 is preferably greater than that of the second piston spring 286. Movement of the second piston 280 moves the second end 281b of the outer spring 281 outward from the housing 102.

[0139] A second high-pressure chamber 287 is formed between the first end 280a and the second axially extending bore 102c, within which the second piston spring 286 is located. The second high-pressure chamber 287 is supplied with fluid through an input supply 109 and preferably a check valve 107. The input supply 109 may or may not be connected to the input supply line 106. A volume reducer may be present in the second high-pressure chamber 287.

[0140] If the tensioner requires a new chain or belt as shown in Fig. 11a, during operation, the first pressure chamber 111 is supplied with fluid from the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outwardly from the housing 102 in addition to the spring force of the first piston spring 104, thereby tensioning any slack in the closed chain or belt by a tensioning arm 402. Simultaneously, the second piston 280 is also biased outwardly from the second axially extending bore 102c by the second piston spring 286, and the second pressure chamber 287 is supplied with fluid from the second input supply 109 and through the input check valve 109 to preload any slack in the closed chain or belt through the tensioning arm by the outward spring 281.

[0141] During operation, when the tensioner is tensioning a worn chain or belt without a high load, the first pressure chamber 111 is supplied with fluid through the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outward from the housing 102 in addition to the spring force of the first piston spring 104, with any slack in the closed chain or belt being tensioned by the tensioner arm 402. At the same time, the second piston 280 is also biased outward by the second piston spring 286. Tension is also maintained by the outward spring 281 on the tensioner arm 402. As the chain or belt wears, there is additional slack in the chain or belt tension, and the first piston 103 and second piston 280 would need to be extended further outward from the housing 102 to adequately tension and preload the chain or belt.

[0142] When the tensioner tensions a worn chain or belt under high dynamic chain load, the high cyclic dynamic force from the chain or belt (shown by the arrow in Fig. 11b), the first piston 103 and the second piston 280 alternately move inward toward the housing 102 and then outward from the housing 102. The inward movement of the piston 280 is counteracted by fluid pressure in the second pressure chamber 287 created by the check valve 107, and the second piston 280 moves outward under the force of the second piston spring 286. This "pumped" the piston, drawing fluid through the input check valve 107 into the second pressure chamber 287 in the second bore 102c. This causes the closed first end 280d of the second piston 280 to exert an outward force on the tensioning boom 402 through the outward spring 281, counteracting the inward force of the dynamic load.

[0143] As the dynamic load of the chain or belt decreases, fluid within the second pressure chamber 287 leaks into the engine through the second axially extending bore 102c or through a vent opening. This leakage reduces the average pressure present in the second pressure chamber 287.

[0144] It should be noted that under all operating conditions, the pressure in the second pressure chamber 287 builds up to maintain a minimum preload in the outer spring 281. If the force or preload in the outer spring 281 becomes too low, the second piston 280 moves out of the housing 102 due to the second piston spring 286 and the pressure in the second pressure chamber 287, drawing in more oil through the input check valve 107.

[0145] Therefore, the first piston 103 in the first axially extending bore 102a provides the predominant damping of the chain tension or belt tension, and the second piston 280 in the second axially extending bore 102c provides the predominant and automatically adjusting spring force through the outer spring 281. The tensioner of the present invention automatically adjusts the average tension force to keep the chain tension as low as possible without sacrificing chain control, significantly improving drive efficiency under new chain or belt conditions and dynamic load conditions.

[0146] The Fig. 12a-12b show a tensioning device of another embodiment using passive control to tension a chain under various conditions; Fig. 12a tensions a chain without high loads; and Fig. 12b tensions a chain with a high load. The difference between the tensioning device in the Fig. 11a-11b and the clamping device in the Fig. 12a-12b is that the body of the second piston is longer and extends beyond the second bore.

[0147] The tensioner tensions the chain or belt (not shown) through a tensioning arm or tensioning shoe 402. It should be noted that the tensioner can also tension a belt through the tensioning arm or tensioning shoe 402. The tensioning arm 402 has a first sliding surface 402b in contact with the chain and a second surface 402a opposite the first sliding surface 402b. The second surface 402a can be flat or nearly flat with a curve, and there can be a cutout 403. The cutout 403 is preferably large enough to accommodate part of an outer spring 291 and the second piston 290.

[0148] The clamping device includes a housing 102 having a first axially extending bore 102a parallel to a second axially extending bore 102c. Although the second bore 102c of the housing 102 is shown as parallel to the first bore 102a, the second bore 102c may be perpendicular to the first bore 102a or at a different angle relative to the first bore 102a.

[0149] A first piston 103 is slidably received in the first axially extending bore 102a. The first piston 103 has a body with a first end 103a, a second end 103c, and a hollow interior 103b with a closed first end 103d. A first piston spring 104 is present in the hollow interior 103b of the first piston 103. The first piston spring 104 has a first end 104a in contact with the closed first end 103d of the first piston 103 or a volume reducer 105 and a second end 104b in contact with a bottom 102b of the first axially extending bore 102a of the housing 102. A first pressure chamber 111 is formed between the first piston 103 and the first axially extending bore 102a. The first pressure chamber is supplied with fluid by a first supply 106 through an inlet check valve 108.The first piston 103 is biased outwardly from the housing 102 to preload the chain or belt through a first end 103a of the first piston, through the tensioning arm 402, by the force of the first piston spring 104, and the oil pressure in the first pressure chamber 111.

[0150] Alternatively, the first piston 103 may be a solid body, in which case the first piston spring 104 would contact the body of the first piston 103 and the bottom 102b of the first axially extending bore 102a.

[0151] The second axially extending bore 102c and the cutout 403 slidably receive a second piston 290. The second piston 290 includes a body with a first end 290a, a second end 290c, and a hollow interior 290b with a closed first end 290d. The body of the second piston 290 extends outwardly from the second axially extending bore 102c of the housing 102.

[0152] A second piston spring 296 for biasing the second piston 290 outwardly from the housing 102 has a first end 296a in contact with the first end 290a of the second piston 290 and a second end 296b in contact with the bottom 102d of the second axially extending bore 102c.

[0153] An outer spring 291 is located within the hollow interior 290b. The first end 291a of the outer spring 291 contacts the closed first end 290d of the interior 290b of the second piston 290, and a second end 291b of the outer spring 291 contacts the cutout 403 of the tensioning arm 402. The stiffness of the outer spring 291 is preferably greater than that of the second piston spring 296. Movement of the second piston 290 moves the second end 291b of the outer spring 291 outward from the housing 102.

[0154] A second high-pressure chamber 297 is formed between the first end 290a and the second axially extending bore 102c, within which the second piston spring 286 is located. The second high-pressure chamber 297 is supplied with fluid through an input supply 109 and preferably a check valve 107. The input supply 109 may or may not be connected to the input supply line 106. A volume reducer may be present in the second high-pressure chamber 297.

[0155] If the tensioner requires a new chain or belt as shown in Fig. 12a, during operation, the first pressure chamber 111 is supplied with fluid from the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outwardly from the housing 102 in addition to the spring force of the first piston spring 104, thereby tensioning any slack in the closed chain or belt by a tensioning arm 402. Simultaneously, the second piston 290 is also biased outwardly from the second axially extending bore 102c by the second piston spring 296, and the second pressure chamber 297 is supplied with fluid from the second input supply 109 and through the input check valve 109 to preload any slack in the closed chain or belt through the tensioning arm by the outward spring 291.

[0156] During operation, when the tensioner is tensioning a worn chain or belt without a high load, the first pressure chamber 111 is supplied with fluid through the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outward from the housing 102 in addition to the spring force of the first piston spring 104, with any slack in the closed chain or belt being tensioned by the tensioner arm 402. At the same time, the second piston 290 is also biased outward by the second piston spring 296. Tension is also maintained by the outward spring 291 on the tensioner arm 402. As the chain or belt wears, there is additional slack in the chain or belt tension, and the first piston 103 and second piston 290 would need to be extended further outward from the housing 102 to adequately tension and preload the chain or belt.

[0157] If the tensioning device detects a worn chain or belt under highly dynamic chain load as in Fig. 12b, the high cyclic dynamic force from the chain or belt (shown by the arrow) pushes the first piston 103 and the second piston 290 inward toward the housing 102 and then outward from the housing 102. The inward movement of the second piston 290 is counteracted by fluid pressure in the second pressure chamber 297 created by the check valve 107, and the second piston 290 moves outward under the force of the spring 296. This "pumped" the piston, drawing fluid through the input check valve 107 into the second pressure chamber 297 in the second bore 102c. This causes the closed first end 290d of the second piston 290 to exert an outward force on the tensioning boom 402 through the outward spring 291, counteracting the inward force of the dynamic load.

[0158] As the dynamic load of the chain or belt decreases, fluid within the second pressure chamber 297 leaks into the engine through the second axially extending bore 102c or through a vent opening. This leakage reduces the average pressure present in the second pressure chamber 297.

[0159] It should be noted that under all operating conditions, the pressure in the second pressure chamber 297 builds up to maintain a minimum preload in the outer spring 291. If the force or preload in the outer spring 291 becomes too low, the second piston 290 moves out of the housing 102 due to the second piston spring 296 and the pressure in the second pressure chamber 297, drawing in more oil through the input check valve 107.

[0160] Therefore, the first piston 103 in the first axially extending bore 102a provides the predominant damping of the chain tension or belt tension, and the second piston 290 in the second axially extending bore 102c provides the predominant and automatically adjusting spring force through the outer spring 291. The tensioner of the present invention automatically adjusts the average tension force to keep the chain tension as low as possible without sacrificing chain or belt control, significantly improving drive efficiency under new chain or belt conditions and dynamic load conditions.

[0161] The Fig. 13a-13b show a tensioning device of another embodiment using passive control to tension a chain under different conditions; Fig. 13a tensions a chain without high loads; and Fig. 13b tensions a chain with a high load.

[0162] The tensioning device tensions the chain or belt (not shown) through a tensioning arm or tensioning shoe 402. It should be noted that the tensioning device can also tension a belt through the tensioning arm or tensioning shoe 402. The tensioning arm 402 has a first sliding surface 402b in contact with the chain and a second surface 402a opposite the first sliding surface 402b. The second surface 402a can be flat or nearly flat with a curve, and can include a cutout. The cutout 403 is preferably large enough to accommodate part of a third piston spring 301 and a third piston 300.

[0163] The third piston 300 is slidably received in the cutout 403 of the tensioning arm 402 and includes a body with a first end 300a, a second end 300c, and an interior 300b with a closed first end 300d. The third piston spring 301 has a first end 301a in contact with the cutout 403 and a second end 301b in contact with the closed first end 300d of the interior 300b of the third piston 300. The third piston spring 301 biases the third piston 300 away from the tensioning arm 402 or toward the housing 102.

[0164] The clamping device includes a housing 102 having a first axially extending bore 102a parallel to a second axially extending bore 102c. Although the second bore 102c of the housing 102 is shown as parallel to the first bore 102a, the second bore 102c may be perpendicular to the first bore 102a or at a different angle relative to the first bore 102a.

[0165] A first piston 103 is slidably received in the first axially extending bore 102a. The first piston 103 has a body with a first end 103a, a second end 103c, and a hollow interior 103b with a closed first end 103d. A first piston spring 104 is present in the hollow interior 103b of the first piston 103. The first piston spring 104 has a first end 104a in contact with the closed first end 103d of the first piston 103 or a volume reducer 105 and a second end 104b in contact with a bottom 102b of the first axially extending bore 102a of the housing 102. A first pressure chamber 111 is formed between the first piston 103 and the first axially extending bore 102a. The first pressure chamber is supplied with fluid by a first supply 106 through an inlet check valve 108.The first piston 103 is biased outwardly from the housing 102 to tension the chain through a first end 103a of the first piston, through the tensioning arm 402 by the force of the first piston spring 104 and the oil pressure in the first pressure chamber 111.

[0166] Alternatively, the first piston 103 may be a solid body, in which case the first piston spring 104 would contact the body of the first piston 103 and the bottom 102b of the first axially extending bore 102a.

[0167] The second axially extending bore 102c slidably receives a second piston 260. The second piston 260 includes a body with a first end 260a, a second end 260c, and a hollow interior 260b with a closed first end 260d.

[0168] A second piston spring 266 is provided within the hollow interior 260b to bias the second piston 260 outward from the housing 102. The second piston spring 266 has a first end 266a in contact with the closed first end 260d of the interior 260b of the second piston 260 and a second end 266b in contact with the bottom 102d of the second axially extending bore 102c. Although not shown, a volume reducer may be provided within the interior 260b of the second piston 260.

[0169] The first end 260a of the second piston directly contacts and preloads the first end 300a of the third piston 300.

[0170] The stiffness of the third piston spring 301 is preferably greater than that of the second piston spring 266. The movement of the second piston 260 moves the third piston 300 and thus the second end 301b of the third piston spring 301 outward from the housing 102.

[0171] A second high-pressure chamber 267 is formed between the hollow interior 260b and the second axially extending bore 102c, within which the second piston spring 266 is located. The second high-pressure chamber 267 is supplied with fluid through an input supply 109 and preferably a check valve 107.

[0172] The input supply 109 may or may not be connected to the input supply line 106.

[0173] If the tensioner requires a new chain or belt as shown in Fig. 13a, during operation, the first pressure chamber 111 is supplied with fluid from the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outwardly from the housing 102 in addition to the spring force of the first piston spring 104, thereby tensioning any slack in the closed chain or belt by a tensioning arm 402. Simultaneously, the second piston 260 is also biased outwardly from the second axially extending bore 102c by the second piston spring 266, and the second pressure chamber 267 is supplied with fluid from the second input supply 109 and through the input check valve 109 to preload any slack in the closed chain or belt through the tensioning arm by the third piston spring 301 and the third piston 300.

[0174] During operation, when the tensioner is tensioning a worn chain or belt without a high load, the first pressure chamber 111 is supplied with fluid through the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outward from the housing 102 in addition to the spring force of the first piston spring 104, with any slack in the closed chain or belt being tensioned by the tensioner arm 402. At the same time, the second piston 260 is also biased outward by the second piston spring 266. Tension is also maintained by the third piston spring 301 and the third piston on the tensioner arm 402. As the chain or belt wears, there is additional slack in the chain tension, and the first piston 103 and second piston 260 would need to be extended further outward from the housing 102 to adequately tension and preload the chain or belt.

[0175] When the tensioner tensions a worn chain or belt under high dynamic chain load, the high cyclic dynamic force from the chain or belt (shown by the arrow in Fig. 13b) moves the first piston 103 and the second piston 260 inward toward the housing 102 and then outward from the housing 102. The inward movement of the second piston 260 is counteracted by fluid pressure in the second pressure chamber 267 created by the check valve 107, and the second piston 260 moves outward under the force of the spring 266. This "pumped" the piston, drawing fluid through the input check valve 107 into the second pressure chamber 267 in the second bore 102c. This causes the first end 260a of the second piston 260, through the third piston 300 and the third piston spring 301 of the tensioning boom 402, to exert an outward force on the tensioning boom 402, counteracting the inward force of the dynamic load.

[0176] As the dynamic load of the chain or belt decreases, fluid within the second pressure chamber 267 leaks into the engine through the second axially extending bore 102c or through a vent opening. This leakage reduces the average pressure present in the second pressure chamber 267.

[0177] It should be noted that under all operating conditions, the pressure in the second pressure chamber 267 builds up to maintain a minimum preload in the third piston spring 301 by the third piston 300. When the force or preload in the outer spring 301 becomes too low, the second piston 260, due to the second piston spring 266 and the pressure in the second pressure chamber 267, moves out of the housing under the preload of the third piston 300 toward the tensioning boom and draws more oil in through the inlet check valve 107.

[0178] Therefore, the first piston 103 in the first axially extending bore 102a provides the predominant damping of the chain tension or belt tension, and the second piston 260 in the second axially extending bore 102c provides the predominant and automatically adjusting spring force through the third piston 300 and the third piston spring 301. The tensioner of the present invention automatically adjusts the average tension force to keep the chain or belt tension as low as possible without sacrificing chain or belt control, significantly improving drive efficiency under new chain and dynamic load conditions.

[0179] The Fig. 14a-14b show a tensioning device of another embodiment using passive control to tension a chain under various conditions; Fig. 14a tensions a chain without high loads; and Fig. 14b tensions a chain with a high load. The tensioning device of the Fig. 14a-14b differs from the clamping device of the Fig. 9a-9b, in that the tensioning arm has a cutout which, if necessary, accommodates the outer spring 271 and the second piston 270.

[0180] The tensioner tensions the chain or belt (not shown) through a tensioning arm or tensioning shoe 402. The tensioning arm 402 has a first sliding surface 402b in contact with the chain and a second surface 402a opposite the first sliding surface 402b. The second surface 402a may be flat or nearly flat with a curve and may include a cutout 403. The cutout 403 is preferably large enough to accommodate a portion of the second piston 270.

[0181] The tensioning device includes a housing 102 having a first axially extending bore 102a parallel to a second axially extending bore 102c. It should be noted that the tensioning device can also tension a belt through the tensioning arm or tensioning shoe 402. Although the second bore 102c of the housing 102 is shown as parallel to the first bore 102a, the second bore 102c can be perpendicular to the first bore 102a or at a different angle relative to the first bore 102a.

[0182] A first piston 103 is slidably received in the first axially extending bore 102a. The first piston 103 has a body with a first end 103a, a second end 103c, and a hollow interior 103b with a closed first end 103d. A first piston spring 104 is present in the hollow interior 103b of the first piston 103. The first piston spring 104 has a first end 104a in contact with the closed first end 103d of the first piston 103 or a volume reducer 105 and a second end 104b in contact with a bottom 102b of the first axially extending bore 102a of the housing 102. A first pressure chamber 111 is formed between the first piston 103 and the first axially extending bore 102a. The first pressure chamber is supplied with fluid by a first supply 106 through an inlet check valve 108.The first piston 103 is biased outwardly from the housing 102 to tension the chain through a first end 103a of the first piston, through the tensioning arm 402 by the force of the first piston spring 104 and the oil pressure in the first pressure chamber 111.

[0183] Alternatively, the first piston 103 may be a solid body, in which case the first piston spring 104 would contact the body of the first piston 103 and the bottom 102b of the first axially extending bore 102a.

[0184] The second axially extending bore 102c slidably receives a second piston 270. The second piston 270 includes a body with a first end 270a having a projection 270e extending axially outward from the body of the second piston 270, a second end 270c, and a hollow interior 270b having a closed first end 270d. The projection 270e centers and guides the outer spring 271.

[0185] A second piston spring 276 is provided within the hollow interior 270b to bias the second piston 270 outward from the housing 102. The second piston spring 276 has a first end 276a in contact with the closed first end 270d of the interior 270b of the second piston 270 and a second end 276b in contact with the bottom 102d of the second axially extending bore 102c. Although not shown, a volume reducer may be provided within the interior 270b of the second piston 270.

[0186] An outer spring 271 is disposed between the first end 270a of the second piston 270 and the second flat surface 402a of the tensioning arm 402, surrounding the projection 270e of the second piston 270. The first end 271a of the outer spring 270 is in contact with the cutout 403 of the tensioning arm 402, and the second end 271b of the outer spring 270 is in contact with the first end 270a of the second piston 270. The stiffness of the outer spring 271 is preferably greater than that of the second piston spring 276. Movement of the second piston 270 moves the second end 271b of the outer spring 271 outward from the housing 102.

[0187] A second high-pressure chamber 277 is formed between the hollow interior 270b and the second axially extending bore 102c, within which the second piston spring 276 is located. The second high-pressure chamber 277 is supplied with fluid through an input supply 109 and preferably a check valve 107. The input supply 109 may or may not be connected to the input supply line 106.

[0188] If the tensioner requires a new chain or belt as shown in Fig. 14a, during operation, the first pressure chamber 111 is supplied with fluid from the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outwardly from the housing 102 in addition to the spring force of the first piston spring 104, thereby tensioning any slack in the closed chain or belt by a tensioning arm 402. Simultaneously, the second piston 270 is also biased outwardly from the second axially extending bore 102c by the second piston spring 276, and the second pressure chamber 277 is supplied with fluid from the second input supply 109 and through the input check valve 109 to preload any slack in the closed chain or belt through the tensioning arm by the outward spring 271.

[0189] During operation, when the tensioner is tensioning a worn chain or belt without a high load, the first pressure chamber 111 is supplied with fluid through the first input supply 106 and through an input check valve 108, and the first piston 103 is biased outward from the housing 102 in addition to the spring force of the first piston spring 104, with any slack in the closed chain or belt being tensioned by the tensioner arm 402. At the same time, the second piston 270 is also biased outward by the second piston spring 276. Tension is also maintained by the outward spring 271 on the tensioner arm 402. As the chain or belt wears, there is additional slack in the chain or belt tension, and the first piston 103 and second piston 270 would need to be extended further outward from the housing 102 to adequately tension and preload the chain or belt.

[0190] When the tensioner tensions a worn chain or belt under high dynamic chain or belt load, the high cyclic dynamic force from the chain or belt (shown by the arrow in Fig. 14b), the first piston 103 and the second piston 270 alternately move inward toward the housing 102 and then outward from the housing 102. The inward movement of the second piston 270 is counteracted by fluid pressure in the second pressure chamber 277 created by the check valve 107, and the second piston 270 moves outward under the force of the spring 276. This "inflates" the piston, drawing fluid through the input check valve 107 into the second pressure chamber 277 in the second bore 102c. This causes the first end 270a of the second piston 270, through the outer spring 271, to exert an outward force on the tensioning boom 402, counteracting the inward force of the dynamic load.

[0191] As the dynamic load of the chain or belt decreases, fluid within the second pressure chamber 277 leaks into the engine through the second axially extending bore 102c or through a vent opening. This leakage reduces the average pressure present in the second pressure chamber 277.

[0192] It should be noted that under all operating conditions, the pressure in the second pressure chamber 277 builds up to maintain a minimum preload in the outer spring 271. If the force or preload in the outer spring 271 becomes too low, the second piston 270 moves out of the housing due to the second piston spring 276 and the pressure in the second pressure chamber 277, drawing in more oil through the input check valve 107.

[0193] Therefore, the first piston 103 in the first axially extending bore 102a provides the predominant damping of the chain tension or belt tension, and the second piston 270 in the second axially extending bore 102c provides the predominant and automatically adjusting spring force through the outer spring 271. The tensioner of the present invention automatically adjusts the average tension force to keep the chain tension as low as possible without sacrificing chain control, significantly improving drive efficiency under new chain and dynamic load conditions.

[0194] In any of the above embodiments, the first outer pistons and the second outer pistons may include grooves on an outer circumference that engage and lock with a pawl or a locking pawl, as known in the art.

[0195] Seals can be used to minimize leakage around the pistons.

[0196] In the Fig. 8a-10b and 13a-13b the second piston can be made of one piece or a solid body.

[0197] In the above embodiments, leakage of the high pressure chamber of the first piston can be controlled by a vent or a pressure relief valve.

Claims

[1] Passive tensioning system for tensioning a chain or belt tension, comprising: a tensioning arm (402) comprising a first sliding surface (402b) on which the chain or belt slides, and a second surface (402a) opposite the first sliding surface (402b); and a clamping device comprising: a housing (102) having a first axially extending bore (102a) with a first fluid inlet (106) and a second axially extending bore (102c) with a second fluid inlet (109); a first piston (103) slidably received by the first axially extending bore (102a), a first pressure chamber (111) in fluid communication with the first fluid inlet (106) being formed between the first piston (103) and the first axially extending bore (102a), the first piston (103) comprising a body having a first end (103a) and a second end (103c), the body of the first piston (103) further comprising an open end at the second end (103c) of the body and a closed end at the first end (103a) of the body, a lower surface at the open end, and a hollow interior (103b) having an inner diameter; a first piston spring (104) for biasing the first piston (103) outwardly from the housing (102) and received in the hollow interior (103b) of the first piston (103), the first piston spring (104) having a first end (104a) contacting the hollow interior (103b) of the first piston (103) and a second end (104b) contacting the first axially extending bore (102a); a first check valve (108) received in the first axially extending bore (102a); a second piston (260; 270) slidably received in the second axially extending bore (102c), the second piston (260; 270) comprising a body having an open end and a closed end, a lower surface (260c; 270c) at the open end, an upper surface (260a; 270a) at the closed end, and a hollow interior (260b, 270b) having an inner diameter, the second axially extending bore (102c) defining a second pressure chamber (267; 277) defined between the inner diameter of the second piston (260; 270) and the second axially extending bore (102c) in fluid communication with the second fluid inlet (109) through a second check valve (107); a second piston spring (266; 276) in the second pressure chamber (267; 277), the second piston spring (266; 276) having a first end (266a; 276a) in contact with the second piston (260; 270) and a second end (266b; 276b) in contact with a bottom (102d) of the second axially extending bore (102c); an outer piston spring (261; 271) between the second piston (260; 270) and the tensioning arm (402), the outer piston spring (261; 271) having a first end (261a; 271a) in contact with the second surface (402a) of the tensioning arm (402) and a second end (261b; 271b) in contact with the upper surface (260a; 270a) of the body of the second piston (260; 270); wherein, when a high cyclic dynamic load from the chain or belt moves the first piston (103) and the second piston (260; 270) alternately inward and outward from the housing (102), fluid is drawn from the second fluid inlet (109) through the second check valve (107) into the second pressure chamber (267; 277) as the second piston (260; 270) is moved outward from the housing (102) by the second piston spring (266; 276), a fluid pressure being created in the second pressure chamber (267; 277) as the second piston (260; 270) moves inward, causing the second piston (260; 270) to exert an outward force on the outer piston spring (261; 271) corresponding to an inward force of the high cyclic dynamic load from the tensioning boom (402) is opposite. [2] The clamping system of claim 1, further comprising a projection (270e; 402c) surrounded by one end of the outer piston spring (261; 271). [3] A clamping system according to claim 2, wherein the projection (270e) extends axially from the upper surface (270a) at the closed end of the body of the second piston (270). [4] The clamping system of claim 2, wherein the projection (402c) extends from the second surface (402a) of the clamping arm (402). [5] The clamping system of claim 1, wherein the second surface (402a) of the clamping arm (402) further comprises a cutout (403) for receiving the first end (271a) of the outer piston spring (271). [6] A tensioning system according to claim 1, wherein the outer piston spring (261; 271) has a greater spring constant than the second piston spring (266; 276) and the first piston spring (104). [7] Passive tensioning system that tensions a chain or belt tension, comprising: a tensioning arm (402) comprising a first sliding surface (402b) on which the chain or belt slides, and a second surface (402a) opposite the first sliding surface (402b), the second surface (402a) comprising a cutout portion (403); and a clamping device comprising: a housing (102) having a first axially extending bore (102a) with a first fluid inlet (106) and a second axially extending bore (102c) with a second fluid inlet (109); a first piston (103) slidably received by the first axially extending bore (102a), a first pressure chamber (111) in fluid communication with the first fluid inlet (106) being formed between the first piston (103) and the first axially extending bore (102a), the first piston (103) comprising a body having a first end (103a) and a second end (103c), the body of the first piston (102) further comprising an open end at the second end (103c) of the body and a closed end at the first end (103a) of the body, a lower surface at the open end, and a hollow interior (103b) having an inner diameter; a first piston spring (104) for biasing the first piston (103) outwardly from the housing (102) and received in the hollow interior (103b) of the first piston (103), the first piston spring (104) having a first end (104a) contacting the hollow interior (103b) of the first piston (103) and a second end (104b) contacting the first axially extending bore (102a); a first check valve (108) received in the first axially extending bore (102a); a second piston (260) slidably received in the second axially extending bore (102c), the second piston (260) comprising a body having an open end and a closed end, a lower surface (260c) at the open end, an upper surface (260a) at the closed end, and a hollow interior (260b) having an inner diameter, the second axially extending bore (102c) defining a second pressure chamber (267) defined between the inner diameter of the second piston (260) and the second axially extending bore (102c) in fluid communication with the second fluid inlet (109) through a second check valve (107); a second piston spring (266) in the second pressure chamber (267), the second piston spring (266) having a first end (266a) in contact with the second piston (266) and a second end (266b) in contact with a bottom (102d) of the second axially extending bore (102c); a third piston (300) slidably received in the cutout (403) of the tensioning boom (402), the third piston (300) comprising a body having an open end and a closed end, a lower surface (300c) at the open end, an upper surface (300a) at the closed end, and a hollow interior (300b) having an inner diameter; a third piston spring (301) received by the hollow interior (300b) of the third piston (300), the third piston spring (301) having a first end (301a) in contact with the cutout (403) of the tensioning arm (402) and a second end (301b) in contact with the third piston (300); and the upper surface (300a) at the closed end of the third piston (300) is in contact with the upper surface (260a) of the second piston (260); wherein, when a high cyclic dynamic load from the chain or belt moves the first piston (103) and the second piston (260) inwardly and outwardly from the housing (102), fluid is drawn from the second fluid inlet (109) through the second check valve (107) into the second pressure chamber (267) as the second piston (260) is moved outwardly from the housing (102) by the second piston spring (266), whereby a fluid pressure is created in the second pressure chamber (267) as the second piston (260) moves inwardly, causing the second piston (260) to exert an outward force on the third piston (300) and the third piston spring (301) that opposes an inward force of the high cyclic dynamic load from the tensioning boom (402). [8] Passive tensioning system that tensions a chain or belt tension, comprising: a tensioning arm (402) comprising a first sliding surface (402b) on which the chain or belt slides, and a second surface (402a) opposite the first sliding surface (402b), the second surface (402a) comprising a cutout portion (403); and a clamping device comprising: a housing (102) having a first axially extending bore (102a) with a first fluid inlet (106) and a second axially extending bore (102c) with a second fluid inlet (109); a first piston (103) slidably received by the first axially extending bore (102a), a first pressure chamber (111) in fluid communication with the first fluid inlet (106) being formed between the first piston (103) and the first axially extending bore (102a), the first piston (103) comprising a body having a first end (103a) and a second end (103c), the body of the first piston (103) further comprising an open end at the second end (103c) of the body and a closed end at the first end (103a) of the body, a lower surface at the open end, and a hollow interior (103b) having an inner diameter; a first piston spring (104) for biasing the first piston (103) outwardly from the housing (102) and received in the hollow interior (103b) of the first piston (103), the first piston spring (104) having a first end (104a) contacting the hollow interior of the first piston (103) and a second end (104b) contacting the first axially extending bore (102b); a second piston (280; 290) slidably received in the second axially extending bore (102c), the second piston (280; 290) comprising a body having an open end and a closed end, a lower surface at the open end, an upper surface (280a, 290a) at the closed end, and a hollow interior (280b; 290b) having an inner diameter, the second axially extending bore (102c) defining a second pressure chamber (287; 297), which is defined between the upper surface (280a, 290a) at the closed end of the second piston (280; 290) and the second axially extending bore (102c), in fluid communication with the second fluid inlet (109) through a second check valve (107); a second piston spring (286; 296) in the second pressure chamber (287; 297), the second piston spring (286; 296) having a first end (286a; 296a) in contact with the second piston (280; 290) and a second end (286b; 296b) in contact with a bottom (102d) of the second axially extending bore (102c); an outer piston spring (281; 291) between the second piston (280; 290) and the tensioning arm (402), the outer piston spring (281; 291) having a first end (281a; 291a) in contact with the cutout (403) of the tensioning arm (402) and a second end (281b; 291b) in contact with the second piston (280; 290); wherein, when a high cyclic dynamic load from the chain or belt moves the first piston (103) and the second piston (280; 290) alternately inward and outward from the housing (102), fluid is drawn from the second fluid inlet (109) through the second check valve (107) into the second pressure chamber (287; 297) when the second piston (280; 290) is moved outward from the housing (102) by the second piston spring (286; 296), whereby a fluid pressure is created in the second pressure chamber (287; 297) when the second piston (280; 290) moves inward, causing the second piston (280; 290) to exert an outward force on the outer piston spring (281; 291) corresponding to an inward force of the high cyclic dynamic load from the tensioning boom (402) is opposite. [9] A tensioning system according to claim 8, wherein the outer piston spring (281; 291) has a greater spring constant than the second piston spring (286; 296) and the first piston spring (104) for biasing the first piston (103) outwardly from the housing (102).

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