Hydro Tensioner

Abstract

summary This hydraulic tensioner has a piston that slides around the outer surface of a pin or rod, with the area between the piston's inner diameter and the rod's outer diameter creating a high-pressure chamber for chain control. A spring around the outside of the piston rod presses against the bottom of the piston, urging the piston outward under low oil pressure. Preferably, the piston is steel and the rod is aluminum, which is the opposite of prior art designs, meaning the clearance between the piston and the bore decreases as the temperature increases. This offsets the decrease in oil viscosity and maintains the same performance at operating temperatures.

Description

[Technical field]

[0001] The present invention is in the field of chain or belt tensioners, and more particularly, the present invention relates to hydrotensioners. [Background technology]

[0002] Most modern automotive hydro tensioners use a piston mounted in a bore in the tensioner body. High pressure oil in the bore urges the piston outward against an arm, providing the tension to control a chain or belt driven timing rod. The piston is usually aluminum and the body is steel.

[0003] Many prior art tensioners are designed with piston-to-bore clearances that increase as the oil temperature in the engine increases due to the difference in the thermal expansion coefficients of steel and aluminum. This, combined with the decrease in oil viscosity with temperature, means that the performance of the tensioner changes with temperature, which is undesirable. Summary of the Invention

[0004] A hydro tensioner has a piston that slides around the outside of a pin or rod, and the area between the piston inner diameter and the rod outer diameter creates a high pressure chamber for chain control. A spring around the outside of the piston rod presses against the bottom of the piston, urging the piston outward under conditions of low or zero oil pressure. Preferably, the piston is steel and the rod is aluminum, which is the opposite of prior art designs, meaning that the piston-to-bore clearance decreases as the temperature increases. This allows the oil viscosity to be offset and maintains the same performance at operating temperatures. [Brief description of the drawings]

[0005] [Figure 1] FIG. 2 is a top view of a tensioner according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic diagram of a tensioner according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a view of the tensioner in the direction of arrow AA in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] 1-3, the improved hydro tensioner has a body 1 preferably fabricated from aluminum, although other materials are possible. Body 1 allows the tensioner to be bolted to the engine as is currently the case, such as by passing a bolt through holes 6 in mounting ears 7. Body 1 may be extruded, die cast, machined from a billet, or manufactured by other methods known to those skilled in the art.

[0007] A hollow pin, tube or rod 4 is secured to the body 1, for example by inserting a first end 18 of the rod 4 into the body 1 using a press fit or a screw. The rod 4 has an inner bore 5 which is in fluid communication with an oil supply 25 from the engine, which will be described below. The rod 4 may be made from die cast aluminium, or from other materials and methods as required. Suitably, the tensioner may be of a design in which the body 1 and the rod 4 are one piece. An outer surface 17 of the rod 4 forms the sliding surface for the piston 2.

[0008] The piston 2 is slidably received in a rod 4. The piston 2 is made of steel, although aluminum or other materials are possible. An outer end 12 of the piston 2 is preferably positioned to press against an arm in a timing system to tension a timing chain or belt (not shown).

[0009] By forming the rod 4 from aluminum and the piston 2 from steel, the gap becomes smaller as the temperature increases.

[0010] A low pressure chamber (LPC) 19 is formed within the inner bore 5 of the rod 4 .

[0011] A high pressure chamber (HPC) 3 is formed between the outer surface 17 and second end 16 of the rod 4 and the bore 2a of the piston 2. A first check valve 15 resides in the HPC 3 between the rod 4 and the bore 2a of the piston 2 to allow oil to flow into the HPC 3 but prevent oil from flowing out. The first check valve 15 can be of various designs such as a spherical check valve or a disk valve. In the design shown in FIG. 1, the first check valve 15 has a body 9 and a check element 11 biased by an internal spring 10 as known to those skilled in the art. The first check valve 15 can be formed of different materials such as steel or plastic, as required. The first check valve 15 can be optionally attached to the tip of the rod 4 via a clip and seal 14. The seal 14 can also be used to seal the piston 2 around the rod 4 to prevent oil from flowing between the aluminum rod 4 and the steel piston 2. If required, the first check valve 15 and the seal 14 can be used as a spray prevention mechanism.

[0012] Check valve 15 (not shown) may be provided with small holes to allow for "tuning" of oil flow and subsequent tensioner stiffness. Tuning may also be accomplished by a torturous path in a plastic seal (not shown).

[0013] The external spring 8 creates a bias to extend the piston 2 and to keep it extended when no hydraulic pressure is present. By having the spring 8 outside the piston 2 there are fewer load / speed design constraints. Also, by mounting the spring 8 on the outside of the rod 4 it is possible to use a larger diameter spring which reduces stresses, lowers spring stiffness and reduces spring load variation between new and worn chains.

[0014] An optional second check valve 13 may be provided at the first end 18 of the rod 4 to control the flow of oil from the engine oil supply behind the tensioner through the inlet hole 25 and oil supply 27 into the LPC 19 to capture oil in the LPC 19 in applications where the oil can drain after the piston 2 is "nose up" and the engine is turned off. A subsequent sump of oil can be recalled in the LPC 19 the next time the engine is started, preventing start-up noise and improving chain control during cranking and the first revolutions of the engine.

[0015] Oil from an oil supply 25 flows to the LPC 19 via an oil feed line 27. In one embodiment, the fluid enters the LPC 19 through the oil feed line 27, the second check valve 13, which helps capture the oil when the tensioner and piston are installed on the engine with the "nose up." Alternatively, oil may flow directly from the oil supply to the LPC 19.

[0016] If the fluid force is greater than the fluid force present in the HPC 3, the fluid can enter the HPC 3 from the LPC 19 through the first check valve 15. When the outer end 12 of the piston 2 receives pressure from the belt or chain through the tensioner arm, the piston 2 compresses the spring 8 and the first check valve 15 prevents the fluid from exiting the HPC 3.

[0017] The first check valve 15 separates the LPC 19 and the HPC 3. In one embodiment, the second check valve 13 helps retain oil in the LPC 19 when the oil is drained from the internal engine oil supply 25 when the engine is shut down, thus ensuring an instantaneous oil volume when the engine is restarted.

[0018] Accordingly, it is to be understood that the embodiments of the invention described herein are merely illustrative of the application of the principles of the invention. References to details of the embodiments shown herein are not intended to limit the scope of the claims, but rather to recite those features which are themselves regarded as essential to the invention.

Claims

1. A hydrotensioner, a) a main body; b) a rod secured to the body, the rod having a first end, a second end, an inner bore and an outer surface defining a low pressure chamber; c) a piston having an inner end, an outer end, and a bore slidably fitted around an outer surface of the rod, the bore of the piston and the second end of the rod forming a high pressure chamber; d) a first check valve attached to the second end of the rod and configured to control the flow of fluid between the high pressure chamber and the low pressure chamber; e) a high pressure chamber seal at the second end of the rod, sealed in the bore of the piston between the first check valve and the second end of the rod, and clipped to the second end of the rod; f) an external spring mounted around the outer surface of the rod and around the outer surface of the piston between the inner end of the piston and the body, providing a force between the body and the inner end of the piston biasing the piston outwardly relative to the body.

2. A hydrotensioner as described in claim 1, characterized in that the first end of the rod is formed integrally with the main body.

3. A hydrotensioner, a) a main body; b) a rod secured to the body, the rod having a first end, a second end, an inner bore and an outer surface defining a low pressure chamber; c) a piston having an inner end, an outer end, and a bore slidably fitted around an outer surface of the rod, the bore of the piston and the second end of the rod forming a high pressure chamber; d) a first check valve attached to the second end of the rod and configured to control the flow of fluid between the high pressure chamber and the low pressure chamber; e) an external spring mounted about the outer surface of the rod and about the outer surface of the piston between the inner end of the piston and the body, providing a force between the body and the inner end of the piston biasing the piston outwardly relative to the body; A hydrotensioner, wherein the first end of the rod is integrally formed with the body.

4. A hydrotensioner as claimed in any one of claims 1 to 3, wherein the first end of the rod is press fit into the body.

5. 4. The hydrotensioner according to claim 1, wherein the rod is made of aluminum.

6. The hydrotension device according to any one of claims 1 to 3, characterized in that the piston is made of steel. Shona.

7. 4. A hydrotensioner as claimed in any one of claims 1 to 3, further comprising a second check valve at the first end of the rod for controlling the flow rate from the low pressure chamber.

8. 4. The hydrotensioner according to claim 1, wherein the first check valve is made of plastic.

9. 4. A hydrotensioner as claimed in claim 1, wherein the first check valve is made of steel.

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