Tsubakimoto Chain Company

Sumio Watanabe

Katsuya Nakakubo

Shigekazu Fukuda

A hydraulic tensioner includes a ball check valve disposed inside a tensioner body for permitting the flow of oil only in one direction from an oil passage connected to an oil source toward and a high-pressure chamber formed behind a plunger within a plunger receiving hole in the tensioner body. The ball check valve includes a valve seat on which a check ball rests when closed. The valve seat has a tapered seating surface outwardly diverging at an angle of 60&deg;-110&deg;, and the check ball has a mass of 0.1 g or less. The check ball enables following up oil pressure variations of high frequencies, and even in a region wherein the load acting on the plunger varies at high frequencies it is possible to ensure a sufficient backstop force without increasing the oil pressure supplied.

Hydraulic tensioner

A hydraulic tensioner 10 includes a piston rod 12 slidably fitted in a cylinder 14 with a small gap or clearance therebetween, and a housing 16 containing the cylinder 14. A ball seat 20 is press-fitted in an end of the cylinder 14 opposite to the piston rod 12 so as to define within the cylinder 14 a high pressure oil chamber 21. The housing 16 has a partition wall 26 at a substantially central portion thereof. The cylinder 14 is loosely fitted in the housing 16 with its longitudinal portion extending forwardly from the partition wall 26. The partition wall 26 has an oil passage 32 having an inside diameter smaller than the outside diameter of the ball seat 20, so that the cylinder 14 and the ball seat 20 are in abutment with the partition wall 26 of the housing 16. A force tending to retract the piston rod 12 generates a pressure which acts on the partition wall 26 either directly via a spring 24 and the cylinder 14 or via the high pressure oil chamber 21 and the ball seat 20.

A hydraulic tensioner 10 includes a hollow housing 14 having formed therewith an intermediate partition wall 12, a circular hollow cylinder 16 disposed concentrically in the housing 14, and a piston rod 18 slidably received in the cylinder 16 with a small gap or clearance therebetween. The cylinder 16 and the piston rod 18 jointly define therebetween a high pressure oil chamber 20. The pressure in the high pressure oil chamber 20 counteracts the force tending to retract the piston rod 18. The piston rod 18 projects from an open end of the housing 14, and a seal 24 surrounds the piston rod 18 to seal or close the end of the housing 14. The piston rod 18 has secured thereto a rod guide 28 disposed within the low pressure oil chamber 26. A spring 36 is disposed in a compressed condition between the housing 14 and the rod guide 28 to urge the piston rod 18 in the advancing direction. The rod guide 28 has radially elongated oil holes or passages 38 formed in its surface which engages the spring 36. The oil passages 38 extend radially outwardly from an inner peripheral surface of the rod guide 28 press fitted with the piston rod 18 and also extends axially through the rod guide 28, and are positioned so that they are not closed by the end of the spring.

Growing community of inventors

Saitama-ken, Japan

Sumio Watanabe