WO2013043373A1

WO2013043373A1 - Chain drive tensioner spring force control mechanism

Info

Publication number: WO2013043373A1
Application number: PCT/US2012/053830
Authority: WO
Inventors: Kevin B. Todd
Original assignee: Borgwarner Inc.
Priority date: 2011-09-22
Filing date: 2012-09-06
Publication date: 2013-03-28
Also published as: CN103765044A; JP6609603B2; KR101939967B1; RU2014113136A; CN103765044B; JP2017215046A; DE112012003408T5; JP6189846B2; KR20140065437A; JP2014528047A

Abstract

A tensioner in which an inward force acting to push a piston into a housing creates a fluid pressure in a hydraulic chamber formed by a cylindrical bore of the housing and a moveable sleeve, causing a movable sleeve to exert an outward force on the piston through a piston spring, opposing the inward force.

Description

CHAIN DRIVE TENSIONER SPRING FORCE CONTROL MECHANISM

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The invention pertains to the field of tensioners. More particularly, the invention pertains to chain drive tensioner spring force control mechanisms.

DESCRIPTION OF RELATED ART

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

During operation, a piston of the tensioner presses against the chain to maintain tension in the chain. When tension in the chain increases during operation due to resonance of a chain span, a high load from the chain acts on the piston of the tensioner, causing the piston to retract into the housing of the tensioner.

Chain drive tensioner spring force is often too high for most operating conditions so that the spring force is sufficient to handle worst case operating conditions of the tensioner system. The effectiveness of the tensioner and the overall system behavior and efficiency could be improved if the tensioner spring force could be varied with operating conditions taking into account wear and stretching that occurs in the chain during the life of the chain.

SUMMARY OF THE INVENTION

A tensioner in which an inward force acting to push a piston into a housing creates a fluid pressure in a hydraulic chamber formed by a cylindrical bore of the housing and a moveable sleeve, causing a movable sleeve to exert an outward force on the piston through a piston spring, opposing the inward force. BRIEF DESCRIPTION OF THE DRAWING

Fig. la shows a schematic of a tensioner of a first embodiment of a passive tensioner

system tensioning a new chain. Fig. lb shows a schematic of a tensioner tensioning a worn chain without high loads. Fig. lc shows a schematic of tensioner tensioning a worn chain with high load.

Fig. 2 shows a schematic of a tensioner of a passive tensioner system of a second

embodiment tensioning a new chain.

Fig. 3 shows a schematic of a tensioner of a passive tensioner system of a third

embodiment tensioning a new chain.

Fig. 4 shows a schematic of a tensioner of a passive tensioner system of a fourth

embodiment using chambers formed between an outer circumferential flange of a moveable sleeve and a bore fiange of the housing to maintain the position of the moveable sleeve relative to the piston to tension a new chain.

Fig. 5 shows a schematic of a tensioner of a passive tensioner system of a fifth

embodiment using chambers formed between a bore flange of the housing and a cutout on the outer circumference of the moveable sleeve to maintain the position of the moveable sleeve relative to the piston to tension a new chain.

Fig. 6 shows a schematic of a tensioner of a passive tensioner system of a sixth

embodiment using chambers formed between the outer circumferential flange of a moveable sleeve and the bore of the housing to maintain the position of the moveable sleeve relative to the piston to tension a new chain.

Fig. 7 shows a schematic of a tensioner of a passive tensioner system of a seventh

embodiment using chambers formed between the an outer circumferential flange of a moveable sleeve and a bore fiange of the housing supplied by a spool valve to maintain the position of the moveable sleeve relative to the piston to tension a new chain.

Fig. 8 shows a schematic of a tensioner of a passive tensioner system of an eighth

embodiment using chambers formed between the an outer circumferential flange of a moveable sleeve and a bore of the housing supplied by a spool valve and an accumulator to maintain the position of the moveable sleeve relative to the piston to tension a new chain. Fig. 9 shows a schematic of a tensioner of an active tensioner system of a ninth

embodiment using a feedback control to move and maintain a moveable sleeve relative to a piston to tension a new chain.

Fig. 10 shows a schematic of a tensioner of an active tensioner system of a tenth

embodiment using feedback control to move a moveable sleeve relative to a piston to tension a new chain.

DETAILED DESCRIPTION OF THE INVENTION

Figures la-8 show tensioner systems using passive control to maintain the position of a moveable sleeve relative to a piston. Passive control is defined as a system in which no feedback is used to regulate the position of a movable sleeve relative to a piston of the tensioner. In contrast, Figures 9 and 10 are active control systems in which real time feedback of components of the engine and/or the moveable sleeve itself are used to regulate the position of the sleeve.

The tensioner systems of the present invention include a tensioner (described in further detail below) for a closed loop chain drive system used in an internal combustion engine. It may be utilized on a closed loop power transmission system between a driveshaft and at least one camshaft or on a balance shaft system between the driveshaft and a balance shaft. The tensioner system may also include an oil pump and be used with fuel pump drives. Additionally, the tensioner systems of the present invention may also be used with belt drives.

Figures la-lc show the tensioner of a first embodiment tensioning under various chain conditions; Figure la is tensioning a new chain; Figure lb is tensioning a worn chain without high loads; Figure lc is tensioning a worn chain under high load.

The tensioner is comprised of a housing 2 having an axially extending piston bore

2a. The piston bore 2a has an interior with first diameter portion Dl and a second diameter portion D2, with the second diameter portion D2 being larger than the first diameter portion Dl .

Received within the bore 2a of the housing 2 is a moveable sleeve 18. The moveable sleeve 18 is hollow and forms a pressure chamber 16 with a pressure PI with the bore 2a of the housing 2, the inner diameter portion 17 or the hollow interior of the hollow moveable sleeve 18, and the interior 3a of the piston 3. A sleeve spring 5 is present within the bore 2a and is received within the inner diameter portion 17 of the moveable sleeve 18, with a first end 5a of the sleeve spring 5 in contact with a bottom surface 24 of the inner flange 22 of the moveable sleeve 18 and second end 5b of the sleeve spring 5 in contact with the bottom 2c of the bore 2a. The sleeve spring 5 provides a bias force to reduce the control force required to keep the moveable sleeve 18 in the desired position relative to the piston 3.

The moveable sleeve 18 has an outer circumferential flange 20, which increases the diameter of the moveable sleeve 18 to be approximately equal to the diameter of the second diameter portion D2, but allowing the flange 20 to slide within the second diameter portion D2 of the bore 2a and to form a fluid chamber 14 between the bottom surface 27 of the outer circumferential flange 20 and the second diameter portion D2 of the bore 2a. The fluid chamber 14 is in fluid communication with an oil pressure supply 7 through a supply line 12 containing a check valve 10. The supply 7 supplies fluid to the fluid chamber 14 to make up for any leakage that may occur. The check valve 10 prevents any fluid in the fluid chamber 14 from entering back into the supply 7. It should be noted that fluid pressure is not supplied to the area between top surface 29 of the outer

circumferential flange 20 and the bore 2a.

At least a portion of the moveable sleeve 18 forward of the outer circumferential flange 20 is slidably received within the hollow piston 3. Also present within the hollow piston 3 is a piston spring 4 biasing the piston 3 outwards from the housing 2. The piston spring 4 has a first end 4a in contact with the interior 3a of the hollow piston 3 and a second end 4b in contact with a top surface 26 of the inner flange 22 of the moveable sleeve 18. A through hole 25 is present in the inner flange 22 allowing fluid from the inlet supply line 6 to interior 3a of the piston 3 and the top surface 26 of the inner flange 22 of the moveable sleeve 18.

At the bottom of the bore 2a an inlet check valve may be present (not shown) as well as an inlet supply line 6 to provide oil pressure to the pressure chamber 16. The supply 7 providing fluid to the fluid chamber 14 may be the same as the supply providing fluid to inlet supply line 6. Alternatively, the supply supplying fluid to the inlet supply line 6 may be different than the supply 7 in fluid communication with fluid chamber 14.

Furthermore, a vent or pressure relief valve (not shown) may be present within the hollow piston 3. Referring to Figure la, when the tensioner is tensioning a new chain, during operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve to pressurize the hydraulic chamber 16 and bias the piston 3 outward from the housing 2 in addition to the spring force from piston spring 4, to bias a span of the closed loop chain.

Referring to Figure lb, when the tensioner is tensioning a worn chain, without high load, during operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve (not shown) to pressurize the hydraulic chamber 16 and bias the piston 3 outward from the housing 2 in addition to the spring force from piston spring 4, to bias a span of the closed loop chain. As the chain wears, the piston 3 has to be biased further outwards from the housing 2 in order to adequately tension the chain. As a greater amount of fluid is required to add the spring force in biasing the piston 3 outwards from the housing 2, some of the fluid supplied to the hydraulic chamber 16 leaks to the fluid chamber 14 and moves the moveable sleeve 18 outwards from the housing 2. It should be noted that the movable sleeve 18 is moved outwards mostly by oil from supply 7 and not the oil from hydraulic chamber 16.

Referring to Figure lc, when the tensioner is tensioning a worn chain during high chain load, during operation, the high force pushes the piston 3 inwards towards the housing 2 from the piston position shown in Figure lb (indicated by dashed lines). The inward force and motion of the piston 3 is resisted by the fluid in fluid chamber 14, since the check valve 10 in supply line 12 blocks and fluid from exiting fluid chamber 14, essentially pressurizing the fluid chamber 14. The pressurization of the fluid chamber 14 causes the inner flange 22 of the moveable sleeve 18 to exert an outward force on the piston 3 through the piston spring 4, opposing the inward force. Once the high load is removed from the piston 3, essentially depressurizing the chamber 14, supply 7 supplies fluid through the check valve 10 and supplies fluid to the fluid chamber 14 to fill the fluid chamber 14 and compensate for the movement of the sleeve 18 relative to the piston 3 and to maintain the position of the sleeve 18 relative to the piston 3.

Movement of the moveable sleeve 18 moves the second end 4b of the piston spring 4 biasing the piston 3 outwards from the housing 2, and therefore the spring force acting on the piston 3 is variable and the piston 3 continually tensions the chain, even when the chain becomes worn and stretched. Seals (not shown) may be present between the outer circumferential flange 20 and the moveable sleeve 18 and between the second diameter portion D2 of the bore 2a and the first diameter of the bore Dl or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by pressure chamber 16 and fluid chamber 14 of the tensioner and substantially prevents inward movement of piston 3 and the moveable sleeve 18 towards the housing 2 when the chain span is under load.

Figure 2 shows a tensioner for a passive tensioner system using supply pressure to move a moveable sleeve 33 received by the hollow piston 3 of a second embodiment.

The tensioner is comprised of a housing 2 having an axially extending piston bore 2a. The piston bore 2a has an interior with a first diameter portion Dl and a second diameter portion D2, with the second diameter portion D2 being larger than the first diameter portion D 1.

A hollow moveable sleeve 33 is received within the bore 2a of the housing 2.

Received within the hollow moveable sleeve 33 is a hollow fixed sleeve 30. Within the hollow fixed sleeve 30 is sleeve spring 5. The first end 5a of the sleeve spring 5 is in contact with a bottom surface 36 of an inner flange 34 of the moveable sleeve 33 and the second end 5b of the sleeve spring 5 is in contact with a bottom surface 32 of an inner flange 31 of the hollow fixed sleeve 30 or bottom of the bore 29a, if no flange 31 is present. The sleeve spring 5 provides a bias force to reduce the control force required to keep the moveable sleeve 33 in the desired position relative to the piston 3. A pressure chamber 16 is formed between an inner diameter portion 38 of the fixed sleeve 30, the inner diameter portion 17 of the hollow interior of the hollow moveable sleeve 33, and the interior 3a of the piston 3.

The moveable sleeve 33 has a diameter which is approximately equal to the diameter of the second diameter portion D2, but still allows the moveable sleeve 33 to slide within the bore 2a. A fluid chamber 37 is formed between a bottom 2c of the bore 2a, the fixed sleeve 30 and a bottom end surface 39 of the moveable sleeve 33. The fluid chamber 37 is in fluid communication with an oil pressure supply 7 through a supply line 12 containing a check valve 10. The supply 7 supplies fluid to the fluid chamber 37 to make up for any leakage that may occur. The check valve 10 prevents any fluid in the fluid chamber 37 from entering back into the supply 7. It should be noted that fluid pressure is not supplied to the area between the piston 3, the moveable sleeve 33 and the second diameter portion D2 of the bore 2a.

At least a portion of the moveable sleeve 33 is slidably received within the hollow piston 3. Also present within the hollow piston 3 is a piston spring 4 biasing the piston 3 outwards 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 a top surface 35 of the inner flange 34 of the moveable sleeve 33. A through hole 25 is present in the inner flange 34 allowing fluid from the inlet supply line 6 to the interior 3a of the piston and the top surface 35 of the inner flange 34 of the moveable sleeve 33.

At the bottom of the bore 2a an inlet check valve may be present (not shown) as well as an inlet supply line 6 to provide oil pressure to the pressure chamber 16. The supply 7 providing fluid to the fluid chamber 37 may be the same as the supply providing fluid to inlet supply line 6. Alternatively, the supply supplying fluid to the inlet supply line 6 may be different than the supply 7 in fluid communication with fluid chamber 37.

Furthermore, a vent or pressure relief valve (not shown) may be present within the hollow piston 3.

When the tensioner is tensioning a new chain, during operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve (not shown) to pressurize the hydraulic chamber 16 and bias the piston 3 outward from the housing 2 in addition to the spring force from piston spring 4, to bias a span of the closed loop chain similar to Figure la.

When the tensioner is tensioning a worn chain, without high load, during operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve to pressurize the hydraulic chamber 16 and bias the piston 3 outward from the housing 2 in addition to the spring force from piston spring 4, to bias a span of the closed loop chain. As the chain wears, the piston 3 has to be biased further outwards from the housing 2 in order to adequately tension the chain. As a greater amount of fluid is required to add the spring force in biasing the piston 3 outwards from the housing 2, some of the fluid supplied to the hydraulic chamber 16 leaks to the fluid chamber 37 between the moveable sleeve 33, the fixed sleeve 30, and the bore 2a of the housing and moves the moveable sleeve 33 outwards from the housing 2, similar to Figure lb. It should be noted that the movable sleeve is moved outwards mostly by oil from supply 7 and not the oil from hydraulic chamber 16.

When the tensioner is tensioning a worn chain during high chain load, during operation, the high force pushes the piston 3 inwards towards the housing 2 from the piston position shown in Figure lc (indicated by dashed lines). The inward force and motion of the piston 2 is resisted by the fluid in fluid chamber 37, since the check valve 10 in supply line 12 blocks fluid from exiting fluid chamber 37, essentially pressurizing the chamber 37. The pressurization of the fluid chamber 37 causes the inner flange 34 of the moveable sleeve 33 to exert an outward force on the piston 3 through the piston spring, opposing the inward force. Once the high load is removed from the piston 3, essentially depressurizing the chamber 37, supply 7 supplies fluid through the check valve 10 and supplies fluid to the fluid chamber 37 to fill the fluid chamber 37 and compensate for the movement of the sleeve 33 relative to the piston 3 and to maintain the position of the sleeve 33 relative to the piston 3.

Movement of the moveable sleeve 33 moves the second end 4b of the piston spring

4 biasing the piston 3 outwards from the housing 2, and therefore the spring force acting on the piston 3 is variable and the piston 3 continually tensions the chain, even when the chain becomes worn and stretched.

Seals (not shown) may be present between the moveable sleeve 33 and the between the second diameter portion D2 of the bore 2a and the second diameter portion D2 and the first diameter of the bore Dl or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by pressure chamber 16 and fluid chamber 37 of the tensioner and substantially prevents inward movement of piston 3 and the moveable sleeve 33 towards the housing 2 when the chain span is under load.

Figure 3 shows a tensioner for a passive tensioner system using supply pressure to move a moveable sleeve 40 which receives a hollow piston 3 of a third embodiment.

The tensioner is comprised of a housing 2 having an axially extending piston bore 2a. Received within the bore 2a of the housing 2 is a moveable sleeve 40. The moveable sleeve 40 has a first opening 46a defined by a top inner diameter portion 46 and a top surface 43 of central inner flange 41 and a second opening 45a defined by a bottom inner diameter portion 45 and a bottom surface 42 of central inner flange 41. A through hole 47 of the central inner flange 41 connects the first opening 46a to the second opening 45a of the moveable sleeve 40. A top surface 48 of the moveable sleeve 40 is exposed to atmospheric pressure.

Received within the first opening 46a of the moveable sleeve 40, defined by the top inner diameter portion 46 and the top surface 43 of the central inner flange 41 is a hollow piston 3. Within the hollow piston 3 is a piston spring 4 biasing the piston 3 outwards 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 a top surface 43 of the central inner flange 41 of the moveable sleeve 40.

Received within the second opening 45a of the moveable sleeve 40, defined by the bottom inner diameter portion 45 and the bottom surface 42 of the central inner flange 41 is a hollow fixed sleeve 30. Within the hollow fixed sleeve 30 is sleeve spring 5. The first end 5a of the sleeve spring 5 is in contact with a bottom surface 42 of the central inner flange 41 of the moveable sleeve 40 and the second end 5b of the sleeve spring 5 is in contact with a bottom surface 32 of an inner flange 31 of the hollow fixed sleeve 30. The sleeve spring 5 provides a bias force to reduce the control force required to keep the moveable sleeve 40 in the desired position relative to the piston 3. A pressure chamber 16 is formed between an inner portion 38 of the fixed sleeve 30, or bottom of the bore if a flange 31 is not present, the inner diameter portion 17 of the second opening 45a of the moveable sleeve 40, and the interior 3a of piston 3. The through hole 47 is present in the central inner flange 41 allows fluid from the inlet supply line 6 to the interior 3a of the piston and the top surface 43 of the central inner flange 41 of the moveable sleeve 40.

A fluid chamber 37 is formed between a bottom of the bore 2a, the fixed sleeve 30 and a bottom end surface 39 of the moveable sleeve 40. The fluid chamber 37 is in fluid communication with an oil pressure supply 7 through a supply line 12 containing a check valve 10. The check valve 10 prevents any fluid in the fluid chamber 37 from entering back into the supply 7.

At the bottom of the bore 2a an inlet check valve may be present (not shown) as well as an inlet supply line 6 to provide oil pressure to the pressure chamber 16. The supply 7 providing fluid to the fluid chamber 37 may be the same as the supply providing fluid to inlet supply line 6. Alternatively, the supply supplying fluid to the inlet supply line 6 may be different than the supply 7 in fluid communication with fluid chamber 37. Furthermore, a vent or pressure relief valve (not shown) may be present within the hollow piston 3.

When the tensioner is tensioning a new chain, during operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve to pressurize the hydraulic chamber 16 and bias the piston 3 outward from the housing 2 in addition to the spring force from piston spring 4, to bias a span of the closed loop chain similar to Figure la.

When the tensioner is tensioning a worn chain, without high load, during operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve to pressurize the hydraulic chamber 16 and bias the piston 3 outward from the housing 2 in addition to the spring force from piston spring 4, to bias a span of the closed loop chain. As the chain wears, the piston 3 has to be biased further outwards from the housing 2 in order to adequately tension the chain. As a greater amount of fluid is required to add the spring force in biasing the piston 3 outwards from the housing 2, some of the fluid supplied to the hydraulic chamber 16 leaks to the fluid chamber 37 between the moveable sleeve 33 and the fixed sleeve 30 and moves the moveable sleeve 40 outwards from the housing similar to Figure lb. It should be noted that the movable sleeve is moved outwards mostly by oil from supply 7 and not the oil from hydraulic chamber 16.

When the tensioner is tensioning a worn chain during high chain load, during operation, the high force pushes the piston 3 inwards towards the housing from the piston position shown in Figure lc (indicated by dashed lines). The inward force and motion of the piston is resisted by the fluid in fluid chamber 37, since the check valve 10 in supply line 12 blocks fluid from exiting fluid chamber 37, essentially pressurizing the fluid chamber 37. The pressurization of the fluid chamber 37 causes the central inner flange 41 of the moveable sleeve 40 to exert an outward force on the piston 3 through the piston spring 4, opposing the inward force.

Once the high load is removed from the piston 3, essentially depressurizing the chamber 37, supply 7 supplies fluid through the check valve 10 and supplies fluid to the fluid chamber 37 to fill the fluid chamber 37 and compensate for the movement of the sleeve 40 relative to the piston 3 and to maintain the position of the sleeve 40 relative to the piston 3. Movement of the moveable sleeve 40 moves the second end 4b of the piston spring 4 biasing the piston 3 outwards from the housing 2, and therefore the spring force acting on the piston 3 is variable and the piston 3 continually tensions the chain, even when the chain becomes worn and stretched.

Seals (not shown) may be present between the bore 2a and the moveable sleeve 40 or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by pressure chamber 16, and fluid chamber 37 of the tensioner and substantially prevents inward movement of piston 3 and the moveable sleeve 40 towards the housing 2 when the chain span is under load.

Figure 4 shows a tensioner for a passive tensioner system using supply pressure to move a moveable sleeve received by a hollow piston 3 of a fourth embodiment.

The tensioner is comprised of a housing 2 having an axially extending piston bore 2a. The piston bore 2a has an interior with a first diameter portion Dl and a second diameter portion D2, with the second diameter portion D2 being larger than the first diameter portion Dl . A bore flange 150 separates a second diameter portion D2 of the bore 2a that receives the piston 3 and another second diameter portion D2 of the bore that receives an outer circumferential flange 141 of the moveable sleeve 140.

Received within the bore 2a of the housing 2 is a moveable sleeve 140. The moveable sleeve 140 is hollow and forms a pressure chamber 16 with the bore 2a of the housing 2, the inner diameter portion 17 of the hollow moveable sleeve 140, and the interior 3a of the piston 3. A sleeve spring 5 is present within the bore 2a and is received within the inner diameter portion 17 of the moveable sleeve 140, with a first end 5a of the spring 5 in contact with a bottom surface 147 of the inner flange 145 of the moveable sleeve 140 and second end 5b of the spring 5 in contact with the bottom 2c of the bore 2a. The sleeve spring 5 provides a bias force to reduce the control force required to keep the moveable sleeve 140 in the desired position relative to the piston 3.

The moveable sleeve 140 has an outer circumferential flange 141 with a top surface 142 with an area A2 and a bottom surface 143 with an area Al . The area A2 of the top surface 142 is less than the area Al of the bottom surface 143. A first fluid chamber 58 is formed between a top surface 142 of the outer circumferential flange 141 and the bottom surface 152 of the bore flange 150 and a second fluid chamber 57 between the bottom surface 143 of the outer circumferential flange 141 and another wall 73 of the second diameter portion D2.

The first fluid chamber 58 is connected to a supply 7 through line 55, which preferably has a check valve 53 and the second fluid chamber 57 is connected to a supply 7 through line 56, which also preferably has a check valve 54. The check valves 53, 54 prevent any fluid in the fluid chambers 58, 57 from entering back into supply 7. The supply 7 supplies fluid to the fluid chambers 58, 57 to make up for any leakage that may occur.

At least a portion of the moveable sleeve 140 forward of the outer circumferential flange 141 is slidably received within the hollow piston 3. Also present within the hollow piston 3 is a piston spring 4 biasing the piston 3 outwards 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 a top surface 146 of the inner flange 145 of the moveable sleeve 140. A through hole 144 is present in the inner flange 145 allowing fluid from the inlet supply line 6 to the interior 3a of the piston and the top surface 146 of the inner flange 145 of the moveable sleeve 140.

At the bottom of the bore 2a an inlet check valve may be present (not shown) as well as an inlet supply line 6 to provide oil pressure to the pressure chamber 16. The supply 7 providing fluid to the fluid chambers 57, 58 may be the same as the supply providing fluid to inlet supply line 6. Alternatively, the supply supplying fluid to the inlet supply line 6 may be different than the supply 7 in fluid communication with fluid chambers 57, 58. Furthermore, a vent or pressure relief valve (not shown) may be present within the hollow piston 3.

When the tensioner is tensioning a worn chain, without high load, during operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve to pressurize the hydraulic chamber 16 and bias the piston 3 outward from the housing 2 in addition to the spring force from piston spring 4, to bias a span of the closed loop chain. As the chain wears, the piston 3 has to be biased further outwards from the housing 2 in order to adequately tension the chain. As a greater amount of fluid is required to add the spring force in biasing the piston 3 outwards from the housing 2, some of the fluid supplied to the hydraulic chamber 16 leaks to the fluid chambers 57, 58 between the moveable sleeve 140 and bore 2a of the housing. It should be noted that the movable sleeve 140 is moved outwards mostly by oil from supply 7 and not the oil from hydraulic chamber 16. Since a bottom surface 143 of the outer circumferential flange 141 has a greater area Al than the area A2 of the top surface 142 of the outer circumferential flange 141, chamber 57 requires less fluid pressure to move the moveable sleeve 140 outwards from the housing similar to Figure lb, than chamber 58 to move the moveable sleeve 140 in the opposite direction.

When the tensioner is tensioning a worn chain during high chain load, during operation, the high force pushes the piston 3 inwards towards the housing 2 from the piston position shown in Figure lc (indicated by dashed lines). The inward force and motion of the piston 3 is resisted by the fluid in fluid chamber 57 since the check valve 54, in supply line 56 blocks fluid from exiting the fluid chamber 57, essentially pressurizing the fluid chamber 57. Furthermore, with the area Al of the bottom surface 143 of circumferential flange 141 being greater than the area A2 of the top surface 142 of the circumferential flange 141, the pressurization of the fluid chamber 57 causes the inner flange 145 of the moveable sleeve 33 to be "pumped" up or move the moveable sleeve 140 outward from the housing 2 and exert an outward force on the piston 3 through the piston spring 4, opposing the inward force. Once the high load is removed from the piston 3, essentially depressurizing the fluid chamber 57, supply 7 supplies fluid through the check valve 54 and supplies fluid to the fluid chamber 57 to fill the fluid chamber 57 and compensates for the movement of the sleeve 140 relative to the piston 3 and to maintain the position of the sleeve 140 relative to the piston 3.

Movement of the moveable sleeve 140 moves the second end 4b of the piston spring 4 biasing the piston 3 outwards from the housing 2, and therefore the spring force acting on the piston 3 is variable and the piston 3 continually tensions the chain, even when the chain becomes worn and stretched.

It should be noted that when fluid chamber 57 is depressurizing, fluid chamber 58 is pressurizing. The filling of fluid chamber 57 with fluid from supply 7 moves the moveable sleeve 140. The movement of the moveable sleeve 140 beyond or greater than the travel necessary to maintain the position of the piston 3 relative to the chain is resisted by the fluid in fluid chamber 58 since the check valve 53, in supply line 55 block fluid from exiting the fluid chamber 58, essentially pressurizing the chamber 58. Once the load is removed from the sleeve, the chamber 58 depressurizes and supply 7 supplies fluid through the check valve 53 and supplies fluid to the fluid chamber 58 to fill the chamber 58 and compensates for movement of the sleeve 140 relative to the piston 3 and maintains the position of the sleeve 140 relative to the piston regardless of other forces acting on sleeve.

Seals (not shown) may be present between the bore 2a and the moveable sleeve

140 or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by pressure chamber 16 and fluid chambers 57, 58 of the tensioner and substantially prevents inward movement of piston 3 and the moveable sleeve 140 towards the housing 2 when the chain span is under load.

Figure 5 shows a tensioner for a passive tensioner system using supply pressure to move a moveable sleeve received by a piston of a fifth embodiment.

2a. Received within the bore 2a of the housing 2 is a moveable sleeve 163. The moveable sleeve 163 is hollow and forms a pressure chamber 16 with the bore 2a of the housing 2, the inner diameter portion 169 of the hollow moveable sleeve 163, and the interior 3a of the piston 3.

A sleeve spring 5 is present within the bore 2a and is received within the inner diameter portion 169 of the moveable sleeve 163, with a first end 5a of the spring 5 in contact with a bottom surface 166 of the inner flange 164 of the moveable sleeve 163 and second end 5b of the spring 5 in contact with the bottom 2c of the bore 2a. The sleeve spring 5 provides a bias force to reduce the control force required to keep the moveable sleeve 163 in the desired position relative to the piston 3.

Along an outer circumferential portion of the moveable sleeve 163 is a circumferential cutout 168. The cutout 168 of the moveable sleeve 163 slidably receives a bore flange 160. The bore flange 160 has a top surface 161 with an area Al and a bottom surface 162 with an area A2. The area Al of the top surface 161 of the bore flange 160 is greater than the area A2 of the bottom surface 162 of the bore flange 160. A first fluid chamber 58 is formed between a top surface 161 of the bore flange 160 and the cutout 168 surface of the moveable sleeve 163 and a second fluid chamber 57 is formed between the bottom surface 162 of the bore flange 160 and another surface of the cutout 168 of the moveable sleeve 163. The first fluid chamber 58 is connected to a supply 7 through line 55, which preferably has a check valve 53 and the second fluid chamber 57 is connected to a supply 7 through line 56, which also preferably has a check valve 54. The check valves 53, 54 prevent any fluid in the fluid chambers 58, 57 from entering back into supply 7. Supply 7 provides fluid to the fluid chambers 57, 58 to make up for any leakage that occurs.

At least a portion of the moveable sleeve 163 forward of the cutout 168 is slidably received within the hollow piston 3. Also present within the hollow piston 3 is a piston spring 4 biasing the piston 3 outwards from the housing 2. The piston spring 4 has a first end 4a in contact with the interior 3a of the hollow piston 3 and a second end 4b in contact with a top surface 165 of the inner flange 164 of the moveable sleeve 163. A through hole 144 is present in the inner flange 164 allowing fluid from the inlet supply line 6 to the interior 3a of the piston and the top surface 165 of the inner flange 164 of the moveable sleeve 163.

When the tensioner is tensioning a worn chain, without high load, during operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve to pressurize the hydraulic chamber 16 and bias the piston 3 outward from the housing 2 in addition to the spring force from piston spring 4, to bias a span of the closed loop chain. As the chain wears, the piston 3 has to be biased further outwards from the housing 2 in order to adequately tension the chain. As a greater amount of fluid is required to add the spring force in biasing the piston 3 outwards from the housing 2, some of the fluid supplied to the hydraulic chamber 16 leaks to the fluid chambers 57, 58 between the moveable sleeve 163 and bore 2a of the housing. Since a top surface 161 of the bore flange 160 has a greater area Al than the area A2 of the bottom surface 162 of the bore flange 160, chamber 58 requires less fluid pressure to move the moveable sleeve 163 outwards from the housing similar to Figure lb than chamber 57. It should be noted that the movable sleeve 163 is moved outwards mostly by oil from supply 7 and not the oil from hydraulic chamber 16.

When the tensioner is tensioning a worn chain during high chain load, during operation, the high force pushes the piston 3 inwards towards the housing 2 from the piston position shown in Figure lc (indicated by dashed lines). The inward force and motion of the piston 3 is resisted by the fluid in fluid chamber 58 since the check valve 53 in supply line 55, blocks fluid from exiting the fluid chamber 58, essentially pressurizing the chamber 58. Furthermore, with the area Al of the top surface 161 of bore flange 160 being greater than the area A2 of the bottom surface 162 of the bore flange 160, the pressurization of the fluid chamber 58 causes the inner flange 164 of the moveable sleeve 163 to be "pumped" up or move outwards from the housing 2 and exert an outward force on the piston 3 through the piston spring 4, opposing the inward force. Once the high load is removed from the piston 3, essentially depressurizing the chamber 58, supply 7 supplies fluid through the check valve 53 and supplies fluid to the fluid chamber 58 to fill the fluid chamber 58 and compensate for the movement of the sleeve 163 relative to the piston 3 and to maintain the position of the sleeve 163 relative to the piston 3.

Movement of the moveable sleeve 163 moves the second end 4b of the piston spring 4 biasing the piston 3 outwards from the housing 2, and therefore the spring force acting on the piston 3 is variable and the piston 3 continually tensions the chain, even when the chain becomes worn and stretched.

It should be noted that when fluid chamber 58 is depressurizing, fluid chamber 57 is pressurizing. The filling of fluid chamber 58 with fluid from supply 7 moves the moveable sleeve 163. The movement of the moveable sleeve 163 beyond or greater than the travel necessary to maintain the position of the piston 3 relative to the chain is resisted by the fluid in fluid chamber 57 since the check valve 54, in supply line 56 block fluid from exiting the fluid chamber 57, essentially pressurizing the chamber 57. Once the load is removed from the sleeve, the fluid chamber 57 depressurizes and supply 7 supplies fluid through the check valve 54 and supplies fluid to the fluid chamber 57 to fill the chamber 57 and compensates for movement of the sleeve 163 relative to the piston 3 and maintains the position of the sleeve 163 relative to the piston regardless of other forces acting on sleeve.

Seals (not shown) may be present between the bore 2a and the moveable sleeve 163 or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by the chamber 16, and fluid chambers 57, 58 of the tensioner and substantially prevents inward movement of piston 3 and the moveable sleeve 163 towards the housing 2 when the chain span is under load.

Figure 6 shows a passive tensioner system using internal pressure areas and flange pressures to move a moveable sleeve received by a piston of a sixth embodiment.

The tensioner is comprised of a housing 2 having an axially extending piston bore 2a. Received within the bore 2a of the housing 2 is a moveable sleeve 80. The moveable sleeve 80 has a first opening 89a defined by a top inner diameter portion 89 and a top surface 81 of central flange 82 and a second opening 96a defined by a bottom inner diameter portion 96 and a bottom surface 83 of central inner flange 82. A through hole 97 of the central inner flange 82 connects the first opening 89a to the second opening 96a of the moveable sleeve 80. A top surface 98 of the moveable sleeve 80 is exposed to atmospheric pressure of the engine.

Received within the first opening 89a of the moveable sleeve 80, defined by the top inner diameter portion 89 and the top surface 81 of the central inner flange 82 is a hollow piston 3. Within the hollow piston 3 is a piston spring 4 biasing the piston 3 outwards 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 a top surface 81 of the central inner flange 82 of the moveable sleeve 80.

Received within the second opening 96a of the moveable sleeve 80, defined by the bottom inner diameter portion 96 and the bottom surface 83 of the central inner flange 82 is a sleeve spring 5. The first end 5a of the sleeve spring 5 is in contact with a bottom surface 83 of the central flange 82 of the moveable sleeve 80 and the second end 5b of the sleeve spring 5 is in contact with a bottom 2c of the bore 2a. The sleeve spring 5 provides a bias force to reduce the control force required to keep the moveable sleeve 80 in the desired position relative to the piston 3. A pressure chamber 16 is formed the top inner diameter portion 89 of the sleeve 80, the bottom inner diameter portion 96 of the sleeve 80, the bore 2a of the housing, and the interior 3a of the piston. The through hole 97 is present in the central inner flange 81 and allows fluid from the inlet supply line 6 to flow from the second opening 96a to the first opening 89a.

At the bottom of the bore 2a an inlet check valve may be present (not shown) as well as an inlet supply line 6 to provide oil pressure to the pressure chamber 16. The supply 7 providing fluid to the fluid chambers 94, 95 may be the same as the supply providing fluid to inlet supply line 6. Alternatively, the supply supplying fluid to the inlet supply line 6 may be different than the supply 7 in fluid communication with fluid chambers 94, 95. Furthermore, a vent or pressure relief valve (not shown) may be present within the ho How piston 3.

The moveable sleeve 80 has an outer circumferential flange 84 which is approximately equal to the width of the second diameter portion D2, but allowing the flange 84 to slide within the second diameter portion D2 of the bore 2a and to form a first fluid chamber 95 and a second fluid chamber 94. The first fluid chamber 95 is connected to a supply 7 through line 93, which preferably has a check valve 92 and the second fluid chamber 94 is connected to a supply 7 through line 91, which also preferably has a check valve 90. The check valves 92, 90 prevent any fluid in the fluid chambers 95, 94 from entering back into supply 7. Supply 7 provides fluid to the fluid chambers 94, 95 as necessary to make up for leakage. The outer diameter of the moveable sleeve 80 below the outer circumferential flange 84 is received by a first diameter portion Dl of the bore 2a, The second diameter portion D2 is greater than the first diameter portion Dl .

When the tensioner is tensioning a new chain, during operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve to pressurize the hydraulic chamber 16 and bias the piston 3 outward from the housing 2 in addition to the spring force from piston spring 4, to bias a span of the closed loop chain similar to Figure la. When the tensioner is tensioning a worn chain, without high load, during operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve to pressurize the hydraulic chamber 16 and bias the piston 3 outward from the housing 2 in addition to the spring force from piston spring 4, to bias a span of the closed loop chain. As the chain wears, the piston 3 has to be biased further outwards from the housing 2 in order to adequately tension the chain. As a greater amount of fluid is required to add the spring force in biasing the piston 3 outwards from the housing 2, some of the fluid supplied to the hydraulic chamber 16 leaks to the fluid chambers 94, 95 between the moveable sleeve 80 and bore 2a of the housing and the fluid pressure in chamber 16 on a bottom surface 99 of the sleeve 80 and on the bottom surface 83 of the central inner flange 82 moves the sleeve 80 outwards from the housing similar to Figure la. It should be noted that the movable sleeve is moved outwards mostly by oil from supply and not the oil from hydraulic chamber 16.

When the tensioner is tensioning a worn chain during high chain load, during operation, the high force pushes the piston 3 inwards towards the housing 2 from the piston position shown in Figure lc (indicated by dashed lines). The inward force and motion of the piston is resisted by the fluid in fluid chamber 94 since the check valve 90 in supply line 91 blocks fluid from exiting the fluid chamber 94, essentially pressurizing the chamber 94. The pressurization of fluid chamber 94 in addition to the pressure on the bottom surface 99 on moveable sleeve 80 causes the central inner flange 82 of the moveable sleeve 80 to exert an outward force on the piston 3 through the piston spring 4, opposing the inward force. Once the high load is removed from the piston 3, essentially depressurizing the chamber 94, supply 7 supplies fluid through the check valve 10 and supplies fluid to the fluid chamber 94 to fill the fluid chamber 94 and compensate for the movement of the sleeve 80 relative to the piston 3 and to maintain the position of the sleeve 80 relative to the piston 3.

Movement of the moveable sleeve 80 moves the second end 4b of the piston spring 4 biasing the piston 3 outwards from the housing 2, and therefore the spring force acting on the piston 3 is variable and the piston 3 continually tensions the chain, even when the chain becomes worn and stretched.

It should be noted that when fluid chamber 94 is depressurizing, fluid chamber 95 is pressurizing. The filling of fluid chamber 94 with fluid from supply 7 moves the moveable sleeve 80. The movement of the moveable sleeve beyond or greater than the travel necessary to maintain the position of the piston 3 relative to the chain is resisted by the fluid in fluid chamber 95 since the check valve 92, in supply line 93 blocks fluid from exiting the fluid chamber 95, essentially pressurizing the chamber 95. Once the load is removed from the sleeve 80, the chamber 95 depressurizes and supply 7 supplies fluid through the check valve 92 and supplies fluid to the fluid chamber 95 to fill the chamber 95 and compensates for movement of the sleeve 80 relative to the piston 3 and maintains the position of the sleeve 80 relative to the piston regardless of other forces acting on sleeve.

Seals (not shown) may be present between the bore 2a and the moveable sleeve 80 or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by the pressure chamber 16 and fluid chambers 94, 95 of the tensioner and substantially prevents inward movement of piston 3 and the moveable sleeve 80 towards the housing 2 when the chain span is under load.

Figure 7 shows a tensioner for a passive tensioner system of a seventh

embodiment.

The tensioner is comprised of a housing 2 having an axially extending piston bore 2a. The piston bore 2a has an interior with a first diameter portion Dl and a second diameter portion D2, with the second diameter portion D2 being larger than the first diameter portion Dl . A bore flange 52 separates a second diameter portion D2 of the bore 2a that receives the piston 3 and another second diameter portion D2 of the bore that receives an outer circumferential flange 20 of a moveable sleeve 18.

Received within the bore 2a of the housing is a moveable sleeve 18. The moveable sleeve 18 is hollow and forms a pressure chamber 16 with the bore 2a of the housing 2, the inner diameter portion 17 of the hollow moveable sleeve 18 and the interior of the piston 3. A sleeve spring 5 is present within the bore 2a and is received within the inner diameter portion 17 of the moveable sleeve 18, with a first end 5a of the spring 5 in contact with a bottom surface 24 of the inner flange 22 of the moveable sleeve 18 and second end 5b of the spring 5 in contact with the bottom 2c of the bore 2a. The sleeve spring 5 provides a bias force to reduce the control force required to keep the moveable sleeve 18 in the desired position relative to the piston 3. The moveable sleeve 18 has an outer circumferential flange 20 with a top surface 29 and a bottom surface 27. The outer circumferential flange 20 separates a second diameter portion D2 of the housing 2 into first and second fluid chambers 58, 57. A first fluid chamber 58 is formed between a top surface 29 of the outer circumferential flange 20 and the bottom surface 51 of the bore flange 52 and a second fluid chamber 57 between the bottom surface 27 of the outer circumferential flange 20 and another wall 73 of the second diameter portion D2.

The first fluid chamber 58 is connected to a supply 7 through line 101 and a control valve 108. The second fluid chamber 57 is connected to a supply 7 through line 100 and control valve 108. Supply 7 supplies fluid to the fluid chambers 57, 58 to make up for leakage from the chambers only. The control valve, 108, preferably a spool valve, includes a spool 109 with at least two cylindrical lands 109a, 109b slidably received within a bore 106. The bore 106 may be in the tensioner housing 2 or located remotely from the tensioner housing in the engine. One end of the spool is in contact with a spring 110 that biases the spool in a first direction.

At least a portion of the moveable sleeve 18 forward of the outer circumferential flange 20 is slidably received within the hollow piston 3. Also present within the hollow piston 3 is a piston spring 4 biasing the piston 3 outwards 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 a top surface 26 of the inner flange 22 of the moveable sleeve 18. A through hole 47 is present in the inner flange 22 allowing fluid from the inlet supply line 6 to interior 3a of the piston and the top surface 26 of the inner flange 22 of the moveable sleeve 18.

At the bottom of the bore 2a an inlet check valve may be present (not shown) as well as an inlet supply line 6 to provide oil pressure to the pressure chamber 16. The supply 7 providing fluid to the fluid chambers 57, 58 may the same as the supply providing fluid to inlet supply line 6. Alternatively, the supply supplying fluid to the inlet supply line 6 may be different than the supply 7 in fluid communication with fluid chambers 57, 58. Furthermore, a vent or pressure relief valve (not shown) may be present within the hollow piston 3.

When the tensioner is tensioning a worn chain, without high load, during operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve to pressurize the hydraulic chamber 16 and bias the piston 3 outward from the housing 2 in addition to the spring force from piston spring 4, to bias a span of the closed loop chain. As the chain wears, the piston 3 has to be biased further outwards from the housing 2 in order to adequately tension the chain. As a greater amount of fluid is required to add the spring force in biasing the piston 3 outwards from the housing 2, some of the fluid supplied to the hydraulic chamber 16 leaks to the fluid chambers 57, 58 between the moveable sleeve 18 and the bore 2a of the housing and moves the moveable sleeve 18 outwards from the housing similar to Figure lb.

When the tensioner is tensioning a worn chain during high chain load, during operation, the high force pushes the piston 3 inwards towards the housing from the piston position shown in Figure lc (indicated by dashed lines). The inward force and motion of the piston 3 is resisted by the fluid in fluid chamber 57, since the spring force from spring 110 on spool valve 108 places land 109a in a position relative to line 100 to block fluid from exiting fluid chamber 57, essentially pressurizing the chamber 57. The pressurization of the fluid chamber 57 causes the central inner flange 22 of the moveable sleeve 40 to exert an outward force on the piston 3 through the piston spring 4, opposing the inward force. Once the high load is removed from the piston 3, essentially depressurizing the chamber 57, supply 7 supplies fluid through the spool valve 108 to fluid chamber 57 and compensates for movement of the sleeve 40 relative to the piston 3 and to maintain the position of the sleeve 40 relative to the piston 3.

Movement of the moveable sleeve 18 moves the second end 4b of the piston spring 4 biasing the piston 3 outwards from the housing 2, and therefore the spring force acting on the piston 3 is variable and the piston 3 continually tensions the chain, even when the chain becomes worn and stretched.

It should be noted that when fluid chamber 57 is depressurizing, fluid chamber 58 is pressurizing. The filling of fluid chamber 57 with fluid from supply 7 moves the moveable sleeve 18. The movement of the moveable sleeve 18 beyond or greater than the travel necessary to maintain the position of the piston 3 relative to the chain is resisted by the fluid in fluid chamber 58 since the spool valve 108, blocks fluid from exiting the fluid chamber 58, essentially pressurizing the chamber 58. Once the load is removed from the sleeve, the chamber 58 depressurizes and supply 7 supplies fluid through the spool 108 and supplies fluid to the fluid chamber 58 to fill the chamber 58 and compensates for movement of the sleeve 18 relative to the piston 3 and maintains the position of the sleeve 18 relative to the piston regardless of other forces acting on sleeve.

Seals (not shown) may be present between the bore 2a and the moveable sleeve 18 or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by the chamber 16, and pressure chambers 57, 58 of the tensioner and substantially prevents inward movement of piston 3 and the moveable sleeve 40 towards the housing 2 when the chain span is under load.

Figure 8 is an alternate embodiment of Figure 7 in which the control valve 108 is in fluid communication with an accumulator 114. The accumulator 114 is also in fluid communication with the pressure chamber 16 formed by the bore 2a of the housing 2, the inner diameter portion 17 of the hollow moveable sleeve 18, and the interior 3a of the piston 3 through a check valve 125. The accumulator 114 stores or accumulates fluid from the pressure chamber 16 to supply to fluid chambers 57, 58 in case of leakage.

Received within the bore 2a of the housing is a moveable sleeve 18. The moveable sleeve 18 is hollow and forms a pressure chamber 16 with the bore 2a of the housing 2, the interior of the piston 3 and the inner diameter portion 17 of the hollow moveable sleeve 18. A sleeve spring 5 is present within the bore 2a and is received within the inner diameter portion 17 of the moveable sleeve 18, with a first end 5a of the spring 5 in contact with a bottom surface 24 of the inner flange 22 of the moveable sleeve 18 and second end 5b of the spring 5 in contact with the bottom 2c of the bore 2a. The sleeve spring 5 provides a bias force to reduce the control force required to keep the moveable sleeve 18 in the desired position relative to the piston 3.

The moveable sleeve 18 has an outer circumferential flange 20 with a top surface 29 and a bottom surface 27. The outer circumferential flange 20 separates a second diameter portion D2 of the housing 2 into first and second fluid chambers 58, 57. A first fluid chamber 58 is formed between a top surface 29 of the outer circumferential flange 20 and the bottom surface 51 of the bore flange 52 and a second fluid chamber 57 between the bottom surface 27 of the outer circumferential flange 20 and another wall 73 of the second diameter portion D2.

The first fluid chamber 58 is connected to accumulator 114 through line 101, control valve 108 and line 112. The second fluid chamber 57 is connected to accumulator 114 through line 100, control valve 108 and line 112. The accumulator 114 supplies fluid to chambers 57, 58 for make up purposes due to leakage only. The control valve, 108, preferably a spool valve, includes a spool 109 with at least two cylindrical lands 109a, 109b slidably received within a bore 106. The bore 106 may be in the tensioner housing 2 or located remotely from the tensioner housing in the engine. One end of the spool is in contact with a spring 110 that biases the spool valve in a first direction.

At least a portion of the moveable sleeve 18 forward of the outer circumferential flange 20 is slidably received within the hollow piston 3. Also present within the hollow piston 3 is a piston spring 4 biasing the piston 3 outwards 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 a top surface 26 of the inner flange 22 of the moveable sleeve 18. A through hole 47 is present in the inner flange 22 allowing fluid from the inlet supply line 6 to the interior 3a of the piston and the top surface 26 of the inner flange 22 of the moveable sleeve 18.

At the bottom of the bore 2a an inlet check valve may be present (not shown) as well as an inlet supply line 6 to provide oil pressure to the pressure chamber 16.

When the tensioner is tensioning a worn chain during high chain load, during operation, the high force pushes the piston 3 inwards towards the housing from the piston position shown in Figure lc (indicated by dashed lines). The inward force and motion of the piston is resisted by the fluid in fluid chamber 57, since the spring force from spring 110 on spool valve 108 places land 109a in a position relative to line 100 to block fluid from exiting fluid chamber 57, essentially pressurizing the chamber 57. The pressurization of the fluid chamber 57 causes the central inner flange 22 of the moveable sleeve 40 to exert an outward force on the piston 3 through the piston spring 4, opposing the inward force. Once the high load is removed from the piston 3, essentially depressurizing the chamber 57, accumulator 114 supplies fluid through the spool valve 108 to fluid chamber 57 to fill the fluid chamber 57 and compensate for the movement of the sleeve 40 relative to the piston 3.

Movement of the moveable sleeve 40 moves the second end 4b of the piston spring

It should be noted that when fluid chamber 57 is depressurizing, fluid chamber 58 is pressurizing. The filling of fluid chamber 57 with fluid from supply 7 moves the moveable sleeve 40. The movement of the moveable sleeve 40 beyond or greater than the travel necessary to maintain the position of the piston 3 relative to the chain is resisted by fluid in fluid chamber 58 since spool valve 108 blocks fluid from exiting the fluid chamber 58, essentially pressurizing the chamber 57. Once the load is removed from the piston 3, fluid chamber 58 depressurizes and fluid chamber 57 pressurizes.

Figure 9 shows an active tensioner control system of a ninth embodiment.

2a. The piston bore 2a has an interior with a first diameter portion Dl and a second diameter portion D2, with the second diameter portion D2 being larger than the first diameter portion Dl . A bore flange 52 separates a second diameter portion D2 of the bore 2a that receives the piston 3 and another second diameter portion D2 of the bore that receives an outer circumferential flange 20 of the moveable sleeve 18 through a check valve 125.

Received within the bore 2a of the housing 2 is a moveable sleeve 18. The moveable sleeve 18 is hollow and forms a pressure chamber 16 with the bore 2a of the housing 2, the interior 3 a of the piston 3 and the inner diameter portion 17 of the hollow moveable sleeve 18. A sleeve spring 5 is present within the bore 2a and is received within the inner diameter portion 17 of the moveable sleeve 18, with a first end 5a of the spring 5 in contact with a bottom surface 24 of the inner flange 22 of the moveable sleeve 18 and second end 5b of the spring 5 in contact with the bottom 2c of the bore 2a. The sleeve spring 5 provides a bias force to reduce the control force required to keep the moveable sleeve 18 in the desired position relative to the piston 3.

The moveable sleeve 18 has an outer circumferential flange 20 with a top surface 29 and a bottom surface 27. The outer circumferential flange 20 separates a second diameter portion D2 of the housing 2 into first and second fluid chambers 58, 57. A first fluid chamber 58 is formed between a top surface 29 of the outer circumferential flange 20 and the bottom surface 51 of the bore flange 50 and a second fluid chamber 57 between the bottom surface 27 of the outer circumferential flange 20 and another wall 73 of the second diameter portion D2. The first fluid chamber 58 is in fluid communication with an accumulator 114 through line 101, a control valve 108, and line 112. The second fluid chamber 57 is in fluid communication with an accumulator 114 through line 100, a control valve 108 and line 112. The accumulator 114 is also preferably in fluid communication with the pressure chamber 16 formed by the bore 2a of the housing 2 and the inner diameter portion 17 of the hollow moveable sleeve 18.

The control valve, 108, preferably a spool valve, includes a spool 109 with at least two cylindrical lands 109a, 109b slidably received within a bore 106 that can block or allow flow from the accumulator 114 to the fluid chambers 57, 58. The bore 106 may be in the tensioner housing 2 or located remotely from the tensioner housing in the engine. One end of the control valve 108 is in contact with an actuator 116. In this embodiment, the actuator 116 is a position setting actuator or linear actuator in which the actuator sets a specific position of the control valve 108. In an alternate embodiment the actuator 116 may also be a force actuator in which a force is present on one side of the control valve. It should be noted that if the actuator 116 is a force actuator a spring would be present on the opposite side of control valve influenced by the actuator 116.

The actuator is controlled by a controller 118 which receives a set point input 122 from a set point algorithm or map 124. The controller 118 also receives position feedback 120 of the moveable sleeve 18 of the tensioner via a sensor (not shown). The set point algorithm or map 124 receives input from different engine parameters 126, such as, but not limited to cam timing, engine speed, throttle, temperature, age, and tensioner position.

At least a portion of the moveable sleeve 18 forward of the outer circumferential flange 20 is slidably received within the hollow piston 3. Also present within the hollow piston 3 is a piston spring 4 biasing the piston 3 outwards 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 a top surface 26 of the inner flange 22 of the moveable sleeve 18. A through hole 47 is present in the inner flange 22 allowing fluid from the inlet supply line 6 to the inner portion 3 a of the piston 3.

Furthermore, a vent or pressure relief valve (not shown) may be present within the hollow piston 3. During operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve to pressurize the hydraulic chamber 16 and the chamber 9 formed within the inner portion 3a of the piston and bias the piston outward from the housing 2 with the spring force from piston spring 4 to bias a span of the closed loop chain.

A sensor (not shown) provides position feedback 120 of the moveable sleeve 18 to the controller 118. The controller 118 compares the position feedback of the moveable sleeve to the set point 122 from the set point algorithm or map 124 based on different engine parameters 126.

If the position of the moveable sleeve 18 is equivalent to the set point 122, then the control valve 108 is not moved or actuated and the lands 109a, 109b, blocks the flow of fluid from the accumulator 114 to the fluid chambers 57, 58. Furthermore since no fluid is being added or removed from the fluid chambers 57, 58, the position of the moveable sleeve 18 relative to the piston 3 and bore 2a of the housing is maintained.

If the position of the moveable sleeve 18 is not equivalent to the set point 122, then the control valve 108 is actuated by the actuator 116 to a position in which fluid flows from the accumulator 114 to the fluid chambers 57, 58 to move the moveable sleeve 18 relative to the piston 3 and the bore 2a of the housing. The movement of the moveable sleeve 18 moves the location of the second end 4b of the piston spring 4 which is in contact with a top surface 26 of the inner flange 22 of the moveable sleeve 18, biasing the piston 3 outwards from the housing 2 and into contact with a span of a chain or belt (not shown). With the second end 4b of the piston spring 4 biasing the piston 3 outwards from the housing 2 being moveable, the spring force acting on the piston 3 is variable and the piston 3 continually tensions the chain, even when the chain becomes worn and stretched.

Movement of the moveable sleeve 18 moves the second end 4b of the piston spring

Hydraulic stiffness of tensioner created by the chamber 16, and fluid chambers 57 and 58 of the tensioner and substantially prevents inward movement of piston 3 and the moveable sleeve 18 towards the housing 2 when the chain span is under load. Seals (not shown) may be present between the bore 2a and the moveable sleeve 40 or any other place within the tensioner as necessary.

Figure 10 an active control tensioner system of a tenth embodiment.

The tensioner is comprised of a housing 2 having an axially extending piston bore 2a. Received within the bore 2a of the housing 2 is a moveable sleeve 80. The moveable sleeve 80 has a first opening 89a defined by a top inner diameter portion 89 and a top surface 82 of central inner flange 81 and a second opening 96a defined by a bottom inner diameter portion 96 and a bottom surface 83 of central inner flange 81. A through hole 97 of the central inner flange 81 connects the first opening 89a to the second opening 96a of the moveable sleeve 80. The moveable sleeve 80 also has a top surface 98.

Received within the first opening 89a of the moveable sleeve 80, defined by the top inner diameter portion 89 and the top surface 82 of the central inner flange 81 is a hollow piston 3. Within the hollow piston 3 is a piston spring 4 biasing the piston 3 outwards 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 a top surface 82 of the central inner flange 81 of the moveable sleeve 80.

Received within the second opening of the moveable sleeve 80, defined by the bottom inner surface 96 and the bottom surface 83 of the central inner flange 81 is a sleeve spring 5. The first end 5a of the sleeve spring 5 is in contact with a bottom surface 83 of the central inner flange 81 of the moveable sleeve 80 and the second end 5b of the sleeve spring 5 is in contact with a bottom of the bore 2a. The sleeve spring 5 provides a bias force to reduce the control force required to keep the moveable sleeve 80 in the desired position relative to piston 3. A pressure chamber 16 is formed between first and second openings 89, 96 of the moveable sleeve 80, the bore 2a and the interior 3a of the piston 3. The through hole 97 is present in the central inner flange 81 allows fluid from the inlet supply line 6 to interior 3a of the piston and the top surface 82 of the central inner flange 81 of the moveable sleeve 80.

At the bottom 2c of the bore 2a an inlet check valve may be present (not shown) as well as an inlet supply line 6 to provide oil pressure to the pressure chamber 16.

Furthermore, a vent or pressure relief valve (not shown) may be present within the hollow piston 3. The moveable sleeve 80 has an outer circumferential flange 84 which is approximately equal to the width of the second diameter portion D2, but allowing the flange 84 to slide within the second diameter portion D2 of the bore 2a and to form a first fluid chamber 95 and a second fluid chamber 94. The first fluid chamber 95 is connected to an accumulator 114 through line 101, a control valve 108 and line 112. The second fluid chamber 94 is connected to the accumulator 114 through line 100, the control valve 108 and line 112. The accumulator 114 is also preferably in fluid communication with the pressure chamber 16 formed by the bore 2a of the housing 2 and the bottom inner surface 96a of the second opening 96 of the moveable sleeve 80 through a check valve 125.

The control valve, 108, preferably a spool valve, includes a spool 109 with at least two cylindrical lands 109a, 109b slidably received within a bore 106 that can block or allow flow from the accumulator 114 to the fluid chambers 94, 95. The bore 106 may be in the tensioner housing 2 or located remotely from the tensioner housing in the engine. One end of the control valve 108 is in contact with an actuator 116. In this embodiment, the actuator 116 is a position setting actuator or linear actuator in which the actuator sets a specific position of the control valve. In an alternate embodiment the actuator 116 may also be a force actuator in which a force is present on one side of the control valve. It should be noted that if the actuator 116 is a force actuator a spring would be present on the opposite side of control valve influenced by the actuator 116.

The actuator position is controlled by a controller 118 which receives a set point input 122 from a set point algorithm or map 124. The controller 118 also receives position feedback 120 of the moveable sleeve 80 of the tensioner via a sensor (not shown). The set point algorithm or map 124 receives input from different engine parameters 126, such as, but not limited to cam timing, engine speed, throttle, temperature, age, and tensioner position.

During operation, fluid is supplied to the hydraulic chamber 16 from an inlet supply line 6 and optionally through an inlet check valve to pressurize the hydraulic chamber 16 and bias the piston outward from the housing 2 with the spring force from piston spring 4 to bias a span of the closed loop chain.

A sensor (not shown) provides position feedback 120 of the moveable sleeve 80 to the controller 118. The controller 118 compares the position feedback of the moveable sleeve to the set point 122 from the set point algorithm or map 124 based on different engine parameters 126.

If the position of the moveable sleeve 80 is equivalent to the set point 122, then the control valve 108 is not moved or actuated and the lands 109a, 109b, blocks the flow of fluid from the accumulator 114 to the fluid chambers 94, 95. Furthermore since no fluid is being added or removed from the fluid chambers 94, 95, the position of the moveable sleeve 80 relative to the piston 3 and bore 2a of the housing is maintained.

If the position of the moveable sleeve 80 is not equivalent to the set point 122, then the control valve 108 is actuated by the actuator to a position in which fluid flows from the accumulator 114 to the fluid chambers 94, 95 to move the moveable sleeve 80 relative to the piston 3 and the bore 2a of the housing. The movement of the moveable sleeve 80 moves the location of the second end 4b of the piston spring 4 which is in contact with a top surface 81 of the central inner flange 81 of the moveable sleeve 80, biasing the piston 3 outwards from the housing 2 and into contact with a span of a chain or belt (not shown). With the second end 4b of the piston spring 4 biasing the piston 3 outwards from the housing 2 being moveable, the spring force acting on the piston 3 is variable and the piston

3 continually tensions the chain, even when the chain becomes worn and stretched.

Movement of the moveable sleeve 80 moves the second end 4b of the piston spring

Hydraulic stiffness of tensioner created by the chamber 16, and fluid chambers 94 and 95 of the tensioner and substantially prevents inward movement of piston 3 and the moveable sleeve 80 towards the housing 2 when the chain span is under load.

Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention.

Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.

Claims

What is claimed is:

1. A tensioner for a passive tensioner system for tensioning a chain having a chain span or a belt, comprising:

a housing having a cylindrical bore;

a hollow piston comprising a body having an open end and a closed end and a hollow interior having an inner diameter;

a hollow moveable sleeve comprising a hollow body having an interior with an inner diameter, having a first portion received by the cylindrical bore of the housing and a second portion, and an inner flange at an end of the second portion, the inner flange having a top surface and a bottom surface;

the hollow piston and the hollow moveable sleeve being coaxially arranged within the cylindrical bore of the housing, such that one of the hollow piston or the hollow moveable sleeve is received within the bore of the other of the hollow piston or hollow moveable sleeve;

a piston spring received within the hollow interior of the piston, for biasing the piston outwards from the sleeve, having a first end contacting an inner surface of the closed end of the piston and a second end contacting the top surface of a flange of the moveable sleeve;

a bias spring received within the bore of the housing and the hollow interior of the moveable sleeve, for biasing the sleeve outwards from the housing, with a first end in contact with the bottom surface of the inner flange of the sleeve and a second end;

a first hydraulic chamber formed by the hollow interior of the body of the moveable sleeve, the hollow interior of the piston, and the bore of the housing, having a first fluid input;

a second hydraulic chamber formed by the cylindrical bore of the housing and the moveable sleeve, such that an inward force acting to push the piston into the housing creates a fluid pressure in the second hydraulic chamber, causing the movable sleeve to exert an outward force on the piston through the piston spring, opposing the inward force.

2. The tensioner of claim 1, further comprising a hollow fixed sleeve received by the bore and the inner diameter of the moveable sleeve.

3. The tensioner of claim 1, wherein the cylindrical bore comprises a first portion and a second portion, the first portion having a diameter smaller than a diameter of the second portion.

4. The tensioner of claim 1, wherein the piston receives the first portion of the hollow sleeve.

5. The tensioner of claim 1, wherein the first portion of the hollow sleeve receives the piston.

6. The tensioner of claim 1, wherein the second hydraulic chamber is formed by an outer circumferential flange of the moveable sleeve and the cylindrical bore of the housing.

7. The tensioner of claim 6, wherein the second hydraulic chamber is in fluid

communication with a supply through a check valve.

8. The tensioner of claim 6, wherein the second hydraulic chamber is in fluid

communication with a supply through a control valve comprising a spool valve.

9. The tensioner of claim 8, wherein the supply is an accumulator having an input in fluid communication with the first hydraulic chamber through a check valve.

10. The tensioner of claim 6, wherein the outer circumferential flange is defined by a first surface with a first area and a second surface with a second area, the first area being greater than the second area.

11. The tensioner of claim 1, wherein the second hydraulic chamber is formed by a bore flange of the cylindrical bore and a cutout of the moveable sleeve.

12. The tensioner of claim 11, wherein the second hydraulic chamber is in fluid

communication with a supply through a check valve.

13. The tensioner of claim 11, wherein the bore flange is defined by a first surface with a first area and a second surface with a second area, the first area being greater than the second area.

14. A tensioner for a passive tensioner system for tensioning a chain having a chain span or a belt, comprising:

a housing having a cylindrical bore;

a piston comprising a body;

the piston and the hollow moveable sleeve being coaxially arranged within the

cylindrical bore of the housing, such that the piston is received within the bore of the hollow moveable sleeve;

a piston spring for biasing the piston outwards from the sleeve, having a first end contacting an end of the piston and a second end contacting the top surface of a flange of the moveable sleeve;

a first hydraulic chamber formed by the hollow interior of the body of the moveable sleeve, the end of the piston, and the bore of the housing, having a first fluid input;

a second hydraulic chamber formed by the cylindrical bore of the housing and the

moveable sleeve, such that an inward force acting to push the piston into the housing creates a fluid pressure in the second hydraulic chamber, causing the movable sleeve to exert an outward force on the piston through the piston spring, opposing the inward force.

15. A tensioner for an active tensioner system for tensioning a chain having a chain span or a belt, comprising:

a housing having a cylindrical bore with a first portion and a second portion, the first portion having a diameter smaller than a diameter of the second portion; a hollow piston comprising a body having an open end and a closed end and a hollow interior having an inner diameter;

a hollow moveable sleeve comprising a hollow body having an interior with an inner diameter, having a first portion received by the cylindrical bore of the housing and a second portion, a flange at an end of the second portion, the flange having a top surface and a bottom surface, and an outer circumferential flange between the first portion and the second portion received by the cylindrical bore the of the housing having a top surface and a bottom surface; the hollow piston and the hollow moveable sleeve being coaxially arranged within the cylindrical bore of the housing, such that one of the hollow piston or the hollow moveable sleeve is received within the bore of the other of the hollow piston or hollow moveable sleeve;

a piston spring received within the hollow interior of the piston, for biasing the piston outwards from the sleeve, having a first end contacting an inner surface of the closed end of the piston and a second end contacting the top surface of the flange of the moveable sleeve; a bias spring received within the bore of the housing and the hollow interior of the moveable sleeve, for biasing the sleeve outwards from the housing, with a first end in contact with the bottom surface of the inner flange of the sleeve and a second end;

a pressure chamber formed by the hollow interior of the piston, and the bore of the housing, having a first fluid input;

a first hydraulic chamber formed by the cylindrical bore of the housing and the top surface of the outer circumferential flange of the moveable sleeve in fluid communication with a supply;

a second hydraulic chamber formed by the cylindrical bore of the housing and the bottom surface of the outer circumferential flange of the moveable sleeve in fluid communication with a supply;

a control valve having an output coupled to the first and second hydraulic chambers and input coupled to the supply;

an actuator actuating the control valve controlled by a set point and a moveable sleeve position feedback;

wherein the actuator moves the control valve to route fluid from supply to the first hydraulic chamber or the second hydraulic chamber to move the movable sleeve to vary an outward force on the piston through the piston spring.

16. The tensioner of claim 15, wherein the actuator is a linear actuator.

17. The tensioner of claim 15, wherein the actuator is a force actuator.

18. The tensioner of claim 15, wherein the set point is determined by engine parameters and a set point algorithm.

19. The tensioner of claim 15, wherein the supply is an accumulator having an input in fluid communication with the first hydraulic chamber.

20. A tensioner for an active tensioner system for tensioning a chain having a chain span or a belt, comprising:

a housing having a cylindrical bore with a first portion and a second portion, the first portion having a diameter smaller than a diameter of the second portion;

a piston comprising a body;

a hollow moveable sleeve comprising a hollow body having an interior with an inner diameter, having a first portion received by the cylindrical bore of the housing and a second portion, a flange at an end of the second portion, the flange having a top surface and a bottom surface, and an outer circumferential flange between the first portion and the second portion received by the cylindrical bore the of the housing having a top surface and a bottom surface; the piston and the hollow moveable sleeve being coaxially arranged within the

a piston spring for biasing the piston outwards from the sleeve, having a first end contacting an end of the piston and a second end contacting the top surface of the flange of the moveable sleeve;

a pressure chamber formed by the piston, and the bore of the housing, having a first fluid input;

a control valve having an output coupled to the first and second hydraulic chambers and input coupled to the supply; an actuator actuating the control valve controlled by a set point and a moveable sleeve position feedback;

wherein the actuator moves the control valve to route fluid from supply to the first

hydraulic chamber or the second hydraulic chamber to move the movable sleeve to vary an outward force on the piston through the piston spring.