BACKGROUND OF THE INVENTION

Field of the Invention

The invention pertains to the field of hydraulic tensioners. More particularly, the invention pertains to a hydraulic tensioner with a piston containing an internal check valve.

Description of Related Art

In conventional hydraulic tensioners, check valves are placed on the bottom of an open-ended bore of the tensioner housing, which receives a plunger, close to an inlet supply and in a high pressure chamber formed between the plunger of the tensioner and a bore of the tensioner housing.

SUMMARY OF THE INVENTION

A hydraulic tensioner for an internal combustion engine for tensioning a span of a chain or a belt has a piston with an internal reservoir connected to a high pressure chamber through a check valve assembly. The check valve assembly has: a disk seat formed by an internal bulge within the piston; a check valve retainer within the piston, and a moveable disk received between the disk seat formed by the internal bulge and the check valve retainer and moveable between a first position and a second position, and a check valve spring received between the moveable disk and the check valve retainer.

In a first disk position, the moveable disk is biased against the disk seat by the check valve spring, preventing fluid from passing from the internal reservoir to the hydraulic high pressure chamber within the piston. In a second disk position, the moveable disk is biased against the check valve spring, such that fluid can flow from the internal reservoir to the high pressure chamber adjacent to the disk seat and within the piston. When the disk is fully open in the second position, the disk is biased against the retainer by the force of the oil flowing between the disk seat and the internal bulge.

When dynamic load from the chain or belt moves the piston inwards and outwards from the housing, fluid from the internal reservoir is drawn into the high pressure chamber between the internal bulge and the moveable disk of the check valve assembly, increasing the fluid pressure within the high pressure chamber, exerting an outward force on the piston, opposing an inward force of the dynamic load from the chain or belt.

Unlike conventional tensioners, the check valve assembly of the present invention is placed within a transition diameter of the bore of the piston. The transition diameter is formed by the internal bulge or a pinched portion of the piston. The transition diameter is between a first diameter which has an internal reservoir and a second diameter which has a high pressure chamber and a tensioner spring. By placing the check valve assembly within the transition diameter between the internal reservoir and the high pressure chamber, the response time of the piston reaction force is improved, as the oil reservoir is moved closer to the high pressure chamber as compared to a conventional ball inlet check valve that is placed in the outlet of an external reservoir.

