Variable tune hydraulic tensioner

One or more radial holes in the body of the hydraulic tensioner are used to control outward hydraulic flow restriction from the hydraulic pressure chamber within the piston. 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.

BACKGROUND

The present invention relates to hydraulic tensioners, and more specifically to a body integrated, variable tune, hydraulic tensioner.

Hydraulic tensioners use engine oil pressure with spring force for chain motion and tension control for engine timing systems.

SUMMARY

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.

DETAILED DESCRIPTION

FIGS.1-4show a hydraulic tensioner1of a first embodiment. In this embodiment, the hydraulic tensioner1has a body10which is mounted via bolts received in bolt holes12to an engine in a piston nose down position. The tensioner body10defines a cylindrical bore11for slidably receiving a hollow piston14. The cylindrical bore11has a first end11a, a second end11band a length11cbetween the first end11aand the second end11b. Along the length11cof the cylindrical bore11between the first end11aand the second end11bis a plurality of radial holes26,27,28,29,30which vent to atmosphere or a sump (not shown). The radial holes26,27,28,29,30are spaced apart a distance d.

Although the tensioner body10is shown having bolt holes12for mounting the tensioner body10to a stationery surface (not shown), the hydraulic tensioner1may alternatively be mounted in a cartridge-style mounting arrangement within the spirit of the invention, where the hydraulic tensioner1is mounted by a thread on the outside of the body10. 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.

In one embodiment, the radial holes26,27,28,29,30are equidistant. In another embodiment, the distance d between each of the radial holes26,27,28,29,30is different. While the diameter of the radial holes26,27,28,29,30is 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 chamber25. Furthermore, the diameter can vary along the length of the plurality of radial holes26,27,28,29,30(e.g. diameter which is larger at the cylindrical bore11, smaller and then larger at the exit of the body10).

The second end11bof the bore11contains an inlet16in fluid communication with a reservoir20for pressurized source fluid. It is noted that the reservoir20is located within the body10.

In another embodiment, the radial holes26,27,28,29,30are not equidistant.

The distance d between each of the radial holes26,27,28,29,30and the associated diameters can vary depending on the conditions of the chain being tensioned as well as other engine conditions and particulars.

The hollow piston14has a first nose end14aand a second end14bseparated by a length with a plurality of lands14e,14f,14g. Between the first nose end14aand the second end14bof the piston14is a first land14e, a circlip groove14d, a second land14f, an annular vent groove14hcontaining at least two cross drilled radial vents15,19, and a third land14g. The two cross drilled radial vents15,19result in four vent openings within the annular vent groove14hof the piston14. The drilled radial vents15,19can have a constant diameter or a diameter which varies along the length of hole. For example, the drilled radial vents15,19can have a first diameter15abetween the inner circumference14cof the piston14and graduate to a larger, second diameter15bat the outside of the piston14which would interact with the radial holes26,27,28,29,30of the body10. An advantage of a larger, second diameter15bis to decrease the preciseness in alignment required between the radial grooves26,27,28,29,30of the body10and the radial vents15,19of the piston14. The circlip groove14dreceives a circlip or a retaining clip (not shown). The hollow piston14has an inner circumference14c. Within the inner circumference14cof the hollow piston14near the first nose end14a, a volume reducer24can optionally be present to vent and purge air from within the inner circumference14cof the hollow piston14.

A hydraulic pressure chamber25is defined by the inner circumference14cof the hollow piston14, the cylindrical bore11, and a check valve assembly18. Hydraulic fluid in the hydraulic pressure chamber25and compression spring17bias the piston14away from the body10of the tensioner1.

The check valve assembly18is located at the second end11bof the cylindrical bore11between the inlet16and the hydraulic pressure chamber25. Although any check valve assembly18known in the art could be used, the check valve assembly18in the figures includes a retainer35, a spring22, a ball19, a check valve seat21, and a seal23and operates to allow fluid to flow from the inlet16into the hydraulic pressure chamber25and prevents fluid from the hydraulic pressure chamber25from exiting through the inlet16.

As the piston14slidable moves inwards and outwards within the cylindrical bore11of the housing10, the radial vent holes15,19of the piston14align with at least one of the plurality of radial holes26,27,28,29,30of the body10of the tensioner1to vary the fluid amount and pressure of the fluid present in the hydraulic pressure chamber25.

When the radial vent holes15,19are aligned with one of the plurality of radial holes26,27,28,29,30of the body10of the tensioner, the piston14additionally blocks the flow of fluid from exiting the other radial holes, thus allowing the position of the piston14to control the flow and damping relative to the high pressure chamber25at any given position of the piston14. Furthermore, for each position of the piston14within the body10, the flow of fluid, as well as the damping and hydraulic spring rate are controllable based on placement and diameter of the radial holes26,27,28,29,30of the body10of the tensioner1and the vent holes15,19of the piston14. Furthermore, to extend or provide additional play in allowing the vent hole14to align with one of the radial holes26,26,28,29,30, the length of the annular groove14hon the piston14which contains the vent holes15,19can be lengthened or shortened.

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.

In an alternate embodiment, the plurality of radial holes26,27,28,29,30in the body10is replaced by a single radial hole28in the body10of the tensioner1as shown inFIGS.5-7as well as a single cross drilled radial hole15in the piston14. The single cross drilled radial hole15of the piston14has two openings in the annular groove14hof the piston14.

FIGS.8-11show another embodiment of the present invention. A hydraulic tensioner101has a body110which is mounted via bolts received in bolt holes112to an engine in a piston nose down position. The tensioner body110defines a cylindrical bore111for slidably receiving a hollow piston114. The cylindrical bore111has a first end111a, a second end111band a length111cbetween the first end111aand the second end111b. Along the length111cof the cylindrical bore111between the first end111aand the second end111bis a plurality of radial holes126,127,128,129,130which vent to a reservoir120defined by the body110of the tensioner and supplies fluid to an inlet116of the hydraulic tensioner101. The radial holes126,127,128,129,130are spaced apart a distance d.

In one embodiment, the radial holes126,127,128,129,130are equidistant. In another embodiment, the distance d between each of the radial holes126,127,128,129,130is different. While the diameter of the radial holes126,127,128,129,130is 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 chamber125. Furthermore, the diameter can vary along the length of the plurality of radial holes126,127,128,129,130(e.g. diameter which is larger at the cylindrical bore111, smaller and then larger at the exit of the body110).

In another embodiment, the radial holes126,127,128,129,130are not equidistant.

The distance d between each of the radial holes126,127,128,129,130and the associated diameters can vary depending on the conditions of the chain being tensioned as well as other engine conditions and particulars.

The second end111bof the bore111contains an inlet116in fluid communication with a reservoir120for pressurized source fluid. It is noted that the reservoir120is located within the body110.

The hollow piston114has a first nose end114aand a second end114bseparated by a length with a plurality of lands114e,114f,114g. Between the first nose end114aand the second end114bof the piston114is a first land114e, a circlip groove114d, a second land114f, an annular vent groove114hcontaining at least two cross drilled radial vents115,119, and a third land114g. The two cross drilled radial vents115,119result in four vent openings within the annular vent groove114hof the piston114.

The drilled radial vents115,119can have a constant diameter or a diameter which varies along the length of hole. For example, the drilled radial vents15,119can have a first diameter115abetween the inner circumference114cof the piston114and graduate to a larger, second diameter115bat the outside of the piston114which would interact with the radial holes126,127,128,129,130of the body110. An advantage of a larger, second diameter115bis to decrease the preciseness in alignment required between the radial grooves126,127,128,129,130of the body110and the radial vents115,119of the piston114. The circlip groove114dreceives a circlip or a retaining clip (not shown). The hollow piston114has an inner circumference114c. Within the inner circumference114cof the hollow piston114near the first nose end114a, a volume reducer124can optionally be present to vent and purge air from within the inner circumference114cof the hollow piston114.

A hydraulic pressure chamber125is defined by the inner circumference114cof the hollow piston114, the cylindrical bore111, and a check valve assembly18. Hydraulic fluid in the hydraulic pressure chamber125and compression spring117bias the piston114away from the body110of the tensioner101.

The check valve assembly118is located at the second end111bof the cylindrical bore111between the inlet116and the hydraulic pressure chamber125. Although any check valve assembly118known in the art could be used, the check valve assembly118in the figures includes a retainer35, a spring22, a ball19, a check valve seat21, and a seal23and operates to allow fluid to flow from the inlet116into the hydraulic pressure chamber125and prevents fluid from the hydraulic pressure chamber125from exiting through the inlet116. As the piston114slidable moves inwards and outwards within the cylindrical bore111of the housing110, the radial vent holes115,119of the piston114aligns with at least one of the plurality of radial holes126,127,128,129,130of the body110of the tensioner101to vary an outward flow area defined between the piston114and the bore111, 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 holes126,127,128,129,130in the body that are exposed to the two cross drilled radial vents115,119of the piston114and thus to the compressed oil in the high pressure reservoir125.

When the radial vent holes115,119are aligned with one of the plurality of radial holes126,127,128,129,130of the body110of the tensioner, the piston114additionally blocks the flow of fluid from exiting the other radial holes, thus allowing the position of the piston114to control the flow relative to the high pressure chamber125at any given position of the piston114. Furthermore, each position of the piston114within the body110, the flow of fluid, as well as the damping and hydraulic spring rate are controllable based on placement of the radial holes126,127,128,129,130of the body110of the tensioner1and the vent holes115,119of the piston114. Furthermore, to extend or provide additional play in allowing the vent hole114to align with one of the radial holes126,126,128,129,130, the length of the annular groove114hon the piston114which contains the vent hole115,119can be lengthened or shortened.

In an alternate embodiment, the plurality of radial holes in the body is replaced by a single radial hole128in the body110of the tensioner101as shown inFIGS.12-14as well as a single cross drilled radial hole115equating to two openings in the annular groove of the piston114.