BACKGROUND

[0001] The present invention relates to hydraulic tensioners, and more specifically to a body integrated, variable tune, hydraulic tensioner. [0002] Hydraulic tensioners use engine oil pressure with spring force for chain motion and tension control for engine timing systems.

SUMMARY

[0003] According to one embodiment of the present invention one or more radial holes in the body of the hydraulic tensioner can be used to control the outward hydraulic flow restriction. The one or more holes can be arranged in different ways to allow the piston position to alter the outward oil flow of the tensioner.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Fig. 1 shows a hydraulic tensioner in a nose down position of a first embodiment.

[0005] Fig. 2 shows a sectional view of Figure 1 along line 2-2. [0006] Fig. 3 shows the piston of the hydraulic tensioner of Figure 1.

[0007] Fig. 4 shows a sectional view of the piston along line 4-4 of Figure 3.

[0008] Fig. 5 shows a hydraulic tensioner in a nose down position of a second embodiment.

[0009] Fig. 6 shows a sectional view of Figure 5 along line 5-5. [0010] Fig. 7 shows a sectional view of the piston of the hydraulic tensioner of Figure 5.

[0011] Fig. 8 shows a hydraulic tensioner in a nose down position of a third embodiment.

[0012] Fig. 9 shows a sectional view of Figure 8 along line 9-9.

[0013] Fig. 10 shows the piston of the hydraulic tensioner of Figure 8. [0014] Fig. 11 shows a sectional view of the piston along line 11-11 of Figure 10.

[0015] Fig. 12 shows a hydraulic tensioner in a nose down position of a fourth embodiment.

[0016] Fig. 13 shows a sectional view of Figure 12 along line 13-13.

[0017] Fig. 14 shows a sectional view of the piston of the hydraulic tensioner of Figure 13.

DETAILED DESCRIPTION

[0018] Figures 1-4 show a hydraulic tensioner 1 of a first embodiment. In this embodiment, the hydraulic tensioner 1 has a body 10 which is mounted via bolts received in bolt holes 12 to an engine in a piston nose down position. The tensioner body 10 defines a cylindrical bore 11 for slidably receiving a hollow piston 14. The cylindrical bore 11 has a first end 1 la, a second end 1 lb and a length 1 lc between the first end 11a and the second end lib. Along the length lie of the cylindrical bore 11 between the first end 11a and the second end 1 lb is a plurality of radial holes 26, 27, 28, 29, 30 which vent to atmosphere or a sump (not shown). The radial holes 26, 27, 28, 29, 30 are spaced apart a distance d.

[0019] Although the tensioner body 10 is shown having bolt holes 12 for mounting the tensioner body 10 to a stationery surface (not shown), the hydraulic tensioner 1 may alternatively be mounted in a cartridge-style mounting arrangement within the spirit of the invention, where the hydraulic tensioner 1 is mounted by a thread on the outside of the body 10. Furthermore, having the piston is nose down position is not required and the piston can be orientated in a nose up position without impacting the performance of the invention.

[0020] In one embodiment, the radial holes 26, 27, 28, 29, 30 are equidistant. In another embodiment, the distance d between each of the radial holes 26, 27, 28, 29, 30 is different. While the diameter of the radial holes 26, 27, 28, 29, 30 is shown as being the same or consistent, the diameter can vary to increase or decrease the flow rate of the fluid exiting the high pressure chamber 25. Furthermore, the diameter can vary along the length of the plurality of radial holes 26, 27, 28, 29, 30 (e.g. diameter which is larger at the cylindrical bore 11, smaller and then larger at the exit of the body 10).

[0021] The second end 1 lb of the bore 11 contains an inlet 16 in fluid communication with a reservoir 20 for pressurized source fluid. It is noted that the reservoir 20 is located within the body 10.

[0022] In another embodiment, the radial holes 26, 27, 28, 29, 30 are not equidistant.

[0023] The distance d between each of the radial holes 26, 27, 28, 29, 30 and the associated diameters can vary depending on the conditions of the chain being tensioned as well as other engine conditions and particulars.

[0024] The hollow piston 14 has a first nose end 14a and a second end 14b separated by a length with a plurality of lands 14e, 14f, 14g. Between the first nose end 14a and the second end 14b of the piston 14 is a first land 14e, a circlip groove 14d, a second land 14f, an annular vent groove 14h containing at least two cross drilled radial vents 15, 19, and a third land 14g. The two cross drilled radial vents 15, 19 result in four vent openings within the annular vent groove 14h of the piston 14. The drilled radial vents 15, 19 can have a constant diameter or a diameter which varies along the length of hole. For example, the drilled radial vents 15, 19 can have a first diameter 15a between the inner circumference 14c of the piston 14 and graduate to a larger, second diameter 15b at the outside of the piston 14 which would interact with the radial holes 26, 27, 28, 29, 30 of the body 10. An advantage of a larger, second diameter 15b is to decrease the preciseness in alignment required between the radial grooves 26, 27, 28, 29, 30 of the body 10 and the radial vents 15, 19 of the piston 14. The circlip groove 14d receives a circlip or a retaining clip (not shown). The hollow piston 14 has an inner circumference 14c. Within the inner circumference 14c of the hollow piston 14 near the first nose end 14a, a volume reducer 24 can optionally be present to vent and purge air from within the inner circumference 14c of the hollow piston 14.

[0025] A hydraulic pressure chamber 25 is defined by the inner circumference 14c of the hollow piston 14, the cylindrical bore 11, and a check valve assembly 18. Hydraulic fluid in the hydraulic pressure chamber 25 and compression spring 17 bias the piston 14 away from the body 10 of the tensioner 1. [0026] The check valve assembly 18 is located at the second end 1 lb of the cylindrical bore 11 between the inlet 16 and the hydraulic pressure chamber 25. Although any check valve assembly 18 known in the art could be used, the check valve assembly 18 in the figures includes a retainer 35, a spring 22, a ball 19, a check valve seat 21, and a seal 23 and operates to allow fluid to flow from the inlet 16 into the hydraulic pressure chamber 25 and prevents fluid from the hydraulic pressure chamber 25 from exiting through the inlet 16.

[0027] As the piston 14 slidable moves inwards and outwards within the cylindrical bore 11 of the housing 10, the radial vent holes 15, 19 of the piston 14 align with at least one of the plurality of radial holes 26, 27, 28, 29, 30 of the body 10 of the tensioner 1 to vary the fluid amount and pressure of the fluid present in the hydraulic pressure chamber 25.

[0028] When the radial vent holes 15, 19 are aligned with one of the plurality of radial holes 26, 27, 28, 29, 30 of the body 10 of the tensioner, the piston 14 additionally blocks the flow of fluid from exiting the other radial holes, thus allowing the position of the piston 14 to control the flow and damping relative to the high pressure chamber 25 at any given position of the piston 14. Furthermore, for each position of the piston 14 within the body 10, the flow of fluid, as well as the damping and hydraulic spring rate are controllable based on placement and diameter of the radial holes 26, 27, 28, 29, 30 of the body 10 of the tensioner 1 and the vent holes 15, 19 of the piston 14. Furthermore, to extend or provide additional play in allowing the vent hole 14 to align with one of the radial holes 26, 26, 28, 29, 30, the length of the annular groove 14h on the piston 14 which contains the vent holes 15, 19 can be lengthened or shortened.

[0029] The placement and diameter of the radial holes as well as the radial vent holes can vary based on whether the hydraulic tensioner is tensioning a new chain or worn chain.

[0030] In an alternate embodiment, the plurality of radial holes 26, 27, 28, 29, 30 in the body 10 is replaced by a single radial hole 28 in the body 10 of the tensioner 1 as shown in Figures 5-7 as well as a single cross drilled radial hole 15 in the piston 14. The single cross drilled radial hole 15 of the piston 14 has two openings in the annular groove 14h of the piston 14. [0031] Figures 8-11 show another embodiment of the present invention. A hydraulic tensioner 101 has a body 110 which is mounted via bolts received in bolt holes 112 to an engine in a piston nose down position. The tensioner body 110 defines a cylindrical bore 111 for slidably receiving a hollow piston 114. The cylindrical bore 111 has a first end 11 la, a second end 111b and a length 111c between the first end 111a and the second end 11 lb. Along the length 11 lc of the cylindrical bore 111 between the first end 111a and the second end 111b is a plurality of radial holes 126, 127, 128, 129, 130 which vent to a reservoir 120 defined by the body 110 of the tensioner and supplies fluid to an inlet 116 of the hydraulic tensioner 101. The radial holes 126, 127, 128, 129, 130 are spaced apart a distance d.

[0032] In one embodiment, the radial holes 126, 127, 128, 129, 130 are equidistant. In another embodiment, the distance d between each of the radial holes 126, 127, 128, 129, 130 is different. While the diameter of the radial holes 126, 127, 128, 129, 130 is shown as being the same or consistent, the diameter can vary to increase or decrease the flow rate of the fluid exiting the high pressure chamber 125. Furthermore, the diameter can vary along the length of the plurality of radial holes 126, 127, 128, 129, 130 (e.g. diameter which is larger at the cylindrical bore 111, smaller and then larger at the exit of the body 110).

[0033] In another embodiment, the radial holes 126, 127, 128, 129, 130 are not equidistant.

[0034] The distance d between each of the radial holes 126, 127, 128, 129, 130 and the associated diameters can vary depending on the conditions of the chain being tensioned as well as other engine conditions and particulars.

[0035] The second end 11 lb of the bore 111 contains an inlet 116 in fluid communication with a reservoir 120 for pressurized source fluid. It is noted that the reservoir 120 is located within the body 110.

[0036] The hollow piston 114 has a first nose end 114a and a second end 114b separated by a length with a plurality of lands 114e, 114f, 114g. Between the first nose end 114a and the second end 114b of the piston 114 is a first land 114e, a circlip groove 114d, a second land 114f, an annular vent groove 114h containing at least two cross drilled radial vents 115, 119, and a third land 114g. The two cross drilled radial vents 115, 119 result in four vent openings within the annular vent groove 114h of the piston 114.

[0037] The drilled radial vents 115, 119 can have a constant diameter or a diameter which varies along the length of hole. For example, the drilled radial vents 15, 119 can have a first diameter 115a between the inner circumference 114c of the piston 114 and graduate to a larger, second diameter 115b at the outside of the piston 114 which would interact with the radial holes 126, 127, 128, 129, 130 of the body 110. An advantage of a larger, second diameter 115b is to decrease the preciseness in alignment required between the radial grooves 126, 127, 128, 129, 130 of the body 110 and the radial vents 115, 119 of the piston 114. The circlip groove 114d receives a circlip or a retaining clip (not shown). The hollow piston 114 has an inner circumference 114c. Within the inner circumference 114c of the hollow piston 114 near the first nose end 114a, a volume reducer 124 can optionally be present to vent and purge air from within the inner circumference 114c of the hollow piston 114.

[0038] A hydraulic pressure chamber 125 is defined by the inner circumference 114c of the hollow piston 114, the cylindrical bore 111, and a check valve assembly 18. Hydraulic fluid in the hydraulic pressure chamber 125 and compression spring 117 bias the piston 114 away from the body 110 of the tensioner 101.

[0039] The check valve assembly 118 is located at the second end 11 lb of the cylindrical bore 111 between the inlet 116 and the hydraulic pressure chamber 125. Although any check valve assembly 118 known in the art could be used, the check valve assembly 118 in the figures includes a retainer 35, a spring 22, a ball 19, a check valve seat 21, and a seal 23 and operates to allow fluid to flow from the inlet 116 into the hydraulic pressure chamber 125 and prevents fluid from the hydraulic pressure chamber 125 from exiting through the inlet 116. As the piston 114 slidable moves inwards and outwards within the cylindrical bore 111 of the housing 110, the radial vent holes 115, 119 of the piston 114 aligns with at least one of the plurality of radial holes 126, 127, 128, 129, 130 of the body 110 of the tensioner 101 to vary an outward flow area defined between the piston 114 and the bore 111, thus changing the stiffness/damping characteristics of the tensioner as the flow area effectively changes by exposing and covering a different size or different number of radial holes 126, 127, 128, 129, 130 in the body that are exposed to the two cross drilled radial vents 115, 119 of the piston 114 and thus to the compressed oil in the high pressure reservoir 125.

[0040] When the radial vent holes 115, 119 are aligned with one of the plurality of radial holes 126, 127, 128, 129, 130 of the body 110 of the tensioner, the piston 114 additionally blocks the flow of fluid from exiting the other radial holes, thus allowing the position of the piston 114 to control the flow relative to the high pressure chamber 125 at any given position of the piston 114. Furthermore, each position of the piston 114 within the body 110, the flow of fluid, as well as the damping and hydraulic spring rate are controllable based on placement of the radial holes 126, 127, 128, 129, 130 of the body 110 of the tensioner 1 and the vent holes 115, 119 of the piston 114. Furthermore, to extend or provide additional play in allowing the vent hole 114 to align with one of the radial holes 126, 126, 128, 129, 130, the length of the annular groove 114h on the piston 114 which contains the vent hole 115, 119 can be lengthened or shortened.

[0041] In an alternate embodiment, the plurality of radial holes in the body is replaced by a single radial hole 128 in the body 110 of the tensioner 101 as shown in Figures 12-14 as well as a single cross drilled radial hole 115 equating to two openings in the annular groove of the piston 114.

[0042] 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.