Hydraulic tensioner

Abstract

A hydraulic tensioner has a piston that slides around the outer surface of a pin or rod, such that a high-pressure chamber for chain control is formed by the region between the inner diameter of the piston and the outer diameter of the rod. A spring surrounding the outer side of the rod presses against the bottom of the piston, thereby biasing the piston outward during low oil pressure conditions. Preferably, the piston is steel and the rod is aluminum, which, contrary to prior art designs, means that the clearance between the piston and the orifice decreases as temperature increases. This counteracts the decrease in oil viscosity and maintains the same performance during operating temperatures.

Description

Technical Field

[0001] This invention relates to the field of tensioners for chains or belts. More specifically, this invention relates to hydraulic tensioners. Background Technology

[0002] Most current automotive hydraulic tensioners use a piston fitted into an inner bore within the tensioner body. High-pressure oil in the bore biases the piston outward against an arm, providing tension to control the timing of chain or belt drives. Typically, the piston is made of aluminum, and the body is made of steel.

[0003] Many existing tensioner designs have a piston-orifice gap that increases as the oil temperature in the engine rises due to the difference in thermal expansion coefficients between steel and aluminum. This, combined with the fact that oil viscosity decreases with temperature, means that the tensioner's performance changes with temperature, which is undesirable. Summary of the Invention

[0004] A hydraulic tensioner has a piston that slides around the outer surface of a pin or rod, such that a high-pressure chamber for chain control is formed by the region between the inner diameter of the piston and the outer diameter of the rod. A spring around the outer side of the rod presses against the bottom of the piston, biasing the piston outward during low or zero oil pressure conditions. Preferably, the piston is steel and the rod is aluminum, which, contrary to prior art designs, means that the clearance between the piston and the orifice decreases as temperature increases. This counteracts the decrease in oil viscosity and maintains the same performance during operating temperatures. Attached Figure Description

[0005] Figure 1 A top view of a tensioner according to an embodiment of the present invention is shown.

[0006] Figure 2 A schematic diagram of a tensioner according to an embodiment of the present invention is shown.

[0007] Figure 3 It shows along Figure 1 A cross-sectional view of the tensioner of line AA. Detailed Implementation

[0008] See Figures 1 to 3 An improved hydraulic tensioner has a body 1, which is preferably made of aluminum, although other materials are also possible. Body 1 allows the tensioner to be bolted to the engine in the same manner as currently used, for example, using bolts passing through holes 6 in mounting lugs 7. Body 1 can be extruded, die-cast, machined from a blank, or manufactured by other methods known in the art.

[0009] For example, the hollow pin, tube, or rod 4 can be secured to the body 1 by press-fitting the first end 18 of the rod 4 into the body 1 or by using threads. The rod 4 has an inner bore 5 that is in fluid communication with the oil supply 25 from the engine, which will be discussed in more detail below. The rod 4 is made of die-cast aluminum, or of other materials and manufactured by other methods as needed. Optionally, the tensioner can be configured as a one-piece design with the body 1 and the rod 4. The outer surface 17 of the rod 4 forms the sliding surface of the piston 2.

[0010] Piston 2 is slidably housed on rod 4. Piston 2 is made of steel, although aluminum or other materials are also possible. The outer end 12 of piston 2 is preferably positioned to press against an arm in the timing system to tension the timing chain or belt (not shown).

[0011] The aluminum rod 4 and the steel piston 2 are formed so that the gap decreases as the temperature increases.

[0012] The low-pressure chamber (LPC) 19 is formed in the inner hole 5 of the rod 4.

[0013] A high-pressure chamber (HPC) 3 is formed between the outer surface 17 and the second end 16 of the rod 4 and the inner bore 2a of the piston 2. A first check valve 15 is present within the HPC 3 between the rod 4 and the inner bore 2a of the piston 2. The first check valve 15 allows oil to flow into the HPC 3 but not out. The first check valve 15 can have various designs, such as a ball check valve or a disc valve. Figure 1 In the illustrated design, the first check valve 15 has a body 9 and a check element 11 biased by an inner spring 10, as known in the art. The first check valve 15 can be made of different materials, such as steel or plastic, as needed. The first check valve 15 can optionally be attached to the top of the rod 4 via a clip and a seal 14. The seal 14 can also be used to seal the piston 2 around the rod 4, thereby preventing oil from flowing between the aluminum rod 4 and the steel piston 2. If desired, the first check valve 15 and the seal 14 can serve as anti-jet features.

[0014] An orifice (not shown) can be provided in check valve 15 to allow oil flow and “regulation” of subsequent tensioner stiffness. Regulation can also be achieved through a tortuous path in a plastic seal (not shown).

[0015] When there is no oil pressure, the outer spring 8 generates a bias to allow the piston 2 to extend and remain extended. By having the spring 8 outside the piston 2, there are fewer design constraints on load / stiffness. Furthermore, mounting the spring 8 on the outside of the rod 4 allows for the use of a larger diameter spring, which reduces stress and spring stiffness, resulting in less variation in spring load between the new and worn chains.

[0016] An optional second check valve 13 may be disposed in the first end 18 of the rod 4. The second check valve 13 controls the flow of engine oil from the rear of the tensioner into the LPC 19 through the inlet port 25 and oil supply 27, thereby trapping the oil in the LPC 19 for the application of piston 2 "protrusion" and draining it once the engine is shut off. The subsequent oil reservoir in the LPC 19 can be called up during the next engine start to prevent starting noise and increase chain control during engine start and first rotation.

[0017] Oil from oil supply 25 flows to LPC 19 via inlet line 27. In one embodiment, fluid flows through inlet line 27, through a second check valve 13, and into LPC 19. The second check valve 13 helps to trap oil when the tensioner and piston are "protruding" in the engine. Alternatively, oil flows directly from oil supply to LPC 19.

[0018] When the force of the fluid is greater than the force of the fluid present in HPC 3, the fluid can flow from LPC 19 through the first check valve 15 and into HPC 3. Once the outer end 12 of piston 2 receives pressure from the belt or chain via the tensioner arm, piston 2 compresses spring 8 and prevents fluid from leaving HPC 3 through the first check valve 15.

[0019] The first check valve 15 separates the LPC 19 from the HPC 3. In one embodiment, the second check valve 13 helps retain oil in the LPC 19 once the engine is off, and the oil is discharged from the oil supply 25 in the engine once the engine is restarted, thus achieving instantaneous oil volume.

[0020] Therefore, it should be understood that the embodiments of the invention described herein are merely illustrative of the application of the principles of the invention. The references to details of the illustrated embodiments herein are not intended to limit the scope of the claims, which themselves enumerate those features considered essential to the invention.

Claims

1. A hydraulic tensioner, comprising: a) The main body; b) A rod having a first end fixed to the body, a second end, an inner hole forming a low-pressure chamber, and an outer surface; c) A piston having an inner end, an outer end, and an inner bore slidably fitted around the outer surface of the rod, the inner bore of the piston and the second end of the rod forming a high-pressure chamber; d) A first check valve, which is installed at the second end of the rod to control the flow between the high-pressure chamber and the low-pressure chamber; as well as e) An outer spring, which is mounted around the outer surface of the piston and provides a force between the body and the inner end of the piston, biasing the piston outward relative to the body.

2. The hydraulic tensioner according to claim 1, wherein the first end of the rod is press-fitted into the body.

3. The hydraulic tensioner according to claim 1, wherein the first end of the rod is integrally formed with the body.

4. The hydraulic tensioner according to claim 1, wherein the rod is formed of aluminum.

5. The hydraulic tensioner according to claim 1, wherein the piston is formed of steel.

6. The hydraulic tensioner of claim 1, further comprising a seal for the high-pressure chamber at the second end of the rod, the seal sealing the inner bore of the piston.

7. The hydraulic tensioner according to claim 1, further comprising a second check valve located at the first end of the rod, the second check valve controlling the flow from the low-pressure chamber.

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

9. The hydraulic tensioner according to claim 1, wherein the first check valve is made of steel.

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