Hydraulic tensioner with internal hollow rod and ratchet mechanism
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- BORGWARNER INC
- Filing Date
- 2023-11-14
- Publication Date
- 2026-07-23
AI Technical Summary
Current automotive hydraulic tensioners face challenges with ratchet mechanisms due to thermal expansion and viscosity changes, leading to performance variability with temperature fluctuations, and require complex control systems to compensate.
A hydraulic tensioner design featuring an aluminum body, floating sleeve, and steel piston with an external spring and check valve configuration, which maintains stable clearance fits across temperature variations, allowing for a ratchet mechanism without compromising performance.
Stabilizes tensioner performance across varying temperatures, reducing reliance on high-performance controllers and enhancing throughput efficiency.
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Abstract
Description
BACKGROUND
[0001] The present invention relates to hydraulic tensioners and, more particularly, to a hydraulic tensioner sliding on an external bolt with a ratchet mechanism.
[0002] Most current automotive hydraulic tensioners use a piston that fits into an internal bore in the tensioner body. High-pressure oil in the bore biases the piston outward against an arm, providing tension to control a chain- or belt-driven timing drive.
[0003] Most timing applications require a ratchet mechanism to prevent chain jump on either the camshaft or crankshaft sprocket. However, this hydraulic tensioner configuration complicates the use of many conventional ratchet mechanisms.
[0004] Many prior art tensioner designs exhibit piston-to-bore clearances that increase with rising engine oil temperatures due to the difference in the thermal expansion coefficients of steel and aluminum. This, combined with a temperature-induced reduction in oil viscosity, means that tensioner performance changes with temperature, which is undesirable. SUMMARY
[0005] According to one embodiment of the present invention, a hydraulic tensioner is disclosed. The hydraulic tensioner comprises: a body, a rod, a hollow piston, a movable sleeve, an external spring, a ratchet clamp, and a check valve.
[0006] The rod has a first end, a second end, an outer surface, and an inner bore. The second end of the rod is attached to the body. The inner bore of the rod defines a low pressure chamber of the tensioner. The hollow piston is slidably received about the outer surface of the rod such that the piston slides relative to the outer surface of the rod. The hollow piston has a body defining an outer periphery and an inner bore, a first end, and a second end. Between the first end and the second end on the outer periphery of the body is a top portion, a collar extending radially outward to form a shoulder, a smooth portion, and a plurality of ratchet teeth, the inner bore of the hollow piston and the first end of the rod defining a high pressure chamber. The movable sleeve surrounds the outer periphery of the body of the hollow piston and is aligned with the plurality of ratchet teeth.The movable sleeve has a first end, a second end, and a bore defining a ratchet clip groove. The external spring is located between the first end of the movable sleeve and the shoulder of the collar of the hollow piston and provides a force between the movable sleeve and the shoulder of the collar of the hollow piston, thereby biasing the hollow piston outwardly with respect to the body. The ratchet clip is received between the plurality of ratchet teeth and the movable sleeve for engagement with the plurality of ratchet teeth, and the check valve is received in the bore of the hollow piston and in the first end of the rod for controlling fluid flow between the low-pressure chamber and the high-pressure chamber.
[0007] In one embodiment, the tensioner body, floating sleeve, and rod are preferably made of aluminum, and the piston is preferably made of steel. By forming the tensioner body, floating sleeve, and rod from aluminum and the piston from steel, clearances are reduced as temperatures rise. In other words, tight clearance fits occur at high temperatures and loose clearance fits occur at cold temperatures. The tensioner materials and construction allow for more stable tensioner performance across engine operating temperatures and allow for less reliance on high-performance control devices to compensate for flow variability. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a perspective view of the hydraulic tensioner of an embodiment of the present invention. Fig. 2 shows the hydraulic tensioner with the floating ratchet sleeve removed. Fig. 3 shows a sectional view of the hydraulic tensioner of Fig. 1. Fig. Figure 4 shows a graph of flow rate as a function of pressure of a conventional hydraulic tensioner with an aluminum body at 120 °C. Fig. Figure 5 shows a graph of flow rate as a function of pressure of the hydraulic tensioner of an embodiment of the present invention at 120°C. Detailed description
[0008] Fig. 1-3 show a hydraulic tensioner of one embodiment of the present invention. The hydraulic tensioner 50 may be used in a timing drive or in a vehicle track drive, such as a transfer case or electric vehicle drive module. The hydraulic tensioner 50 includes a body 1 that allows the tensioner 50 to be bolted to an engine, for example, using mounting holes 6. The body 1 may be extruded, die-cast, machined from a blank, or manufactured in any other manner known in the art. In one embodiment, the body is L-shaped, with the horizontal portion 1b of the L-shaped body 1 providing a surface for anchoring the tensioner 50 and the vertical portion 1a of the L-shaped body 1 being perpendicular to the hydraulic tensioner 50.
[0009] A hollow bolt, tube, or rod 4 is attached to the horizontal portion 1b of the body 1. In some embodiments, the hollow rod 4 is formed as part of the body, press-fitted into the horizontal portion 1b of the body, or secured using a screw thread in the horizontal portion 1b of the body 1. The hollow rod 4 has a first end 4a, a second end 4b, and an internal bore 5 in fluid communication with an oil supply (not shown). The hollow rod 4 is preferably made of die-cast aluminum or other materials and by other methods as required. Optionally, the hollow rod 4 is formed integrally with the body 1 and cast as a single piece.
[0010] A hollow piston 2 is slidably received around the outer surface 17 of the hollow rod 4 and within a bore 18 of the piston 2. The piston 2 includes a body 2c having a first end 2a and a second end 2b. Between the first end 2a and the second end 2b of the piston body 2c are an upper portion 30, a collar 31, a smooth portion 32 along the outer periphery 2d of the body 2c, a series of ratchet teeth 33, and a transport clamp stop groove 34 along the outer periphery 2d of the body 2c. The collar 31 extends radially outward from the piston body 2c and forms a shoulder 35 adjacent the smooth portion 32 of the piston body 2c. An external spring groove 36 is provided along the smooth portion 32. The external spring groove 36 helps to hold the external spring 36 to the smooth portion 32 of the outer circumference 2d of the piston 2.
[0011] A floating sleeve 40 is provided around the outer periphery 2d of the piston body 2c and is aligned with the row of ratchet teeth 33. The floating sleeve 40 has a first end 40a and a second end 40b and defines a bore 40c. A ratchet clamp groove 41 and a through hole 43 for receiving a transport clamp 60 are located in the bore 40c from the first end 40a to the second end 40b.
[0012] A ratchet clamp 80 is received between the ratchet teeth 33 and the bore 40c of the floating sleeve. The ratchet clamp 80 engages with the ratchet teeth 33 of the outer periphery 2d of the piston body 2c and engages and disengages with the ratchet teeth 33 in the ratchet clamp groove 41 of the floating sleeve 40.
[0013] An external spring 37 is located between the shoulder 35 of the collar 31 and the ratchet grooves 33 on the outer circumference 2c of the piston body 2c of the hollow piston 2 and the first end 40a of the floating sleeve 40.
[0014] During transportation of the hydraulic tensioner 50 and during installation of the hydraulic tensioner 50 in the engine, a transportation clamp 60 having a first leg 60a connected to the second leg 60b is used to secure the piston 2 to the floating sleeve 40 and to place the spring load from the external spring 37 between the piston 2 and the floating sleeve 40. Specifically, the second leg 60b is received in the through hole 43 of the floating sleeve 40 and engages the transportation clamp stop groove 34 on the outer periphery 2d of the piston 2. The first leg 60a, connected to the second leg 60b, is received in a groove 1c of the horizontal portion 1b of the body 1.
[0015] A low pressure chamber (LPC) 19 is created in the inner bore 5 of the hollow rod 4. A high pressure chamber (HPC) 3 is formed between the first end 4a of the hollow rod 4, a check valve 70, and the piston inner bore 18 at the first end 2a of the piston 2 in the upper portion 30, the collar 31, and the piston body 2c.
[0016] The check valve 70 includes an L-shaped valve seat 74 that is press-fitted into the first end 4a of the inner pin 4, such that the valve seat 74 seals the inner bore 5 of the inner pin 4 and only allows fluid to flow through an opening 74a of the valve seat 74 when a check element 75 is not seated on the valve seat 74. The check element 75 may be a ball or other shape that closes and exposes the opening 74a of the valve seat 74. A U-shaped retainer 71 surrounds the valve seat 74, with the ends of the "U" of the retainer 71 adjacent to the horizontal portion of the L-shaped valve seat 74. The retainer 71 includes one or more holes 72. The check element 75 and a spring 73 are located within the retainer 71.The check element 75 is biased into engagement with the valve seat 74 by the spring 73, which is held between a retainer 71 and the check element 75. Fluid can flow from the LPC 19 in the hollow rod 4 through the valve seat 74, and when the pressure of the fluid in the LPC 19 is high enough, the check element 75 moves away from the opening 74a of the valve seat 74 against the bias of the spring 73, so that fluid flows through the opening 74a of the valve seat 74 and through the holes 72 of the retainer 71 into the HPC 3. The check valve 70 separates the HPC 3 from the LPC 19.
[0017] The check valve 70 can be made of various materials, such as steel or plastic, as required. For steel, the retaining device 71 can be formed by rolling. A small hole in the check valve 71 (not shown) could be provided to allow oil flow and later adjustment of the tensioner stiffness. Adjustment can be achieved through a serrated path in a plastic seal (not shown).
[0018] The external spring 37 creates a preload to allow the piston 2 to extend and remain extended when no oil pressure is present. Because the spring 71 is located outside the piston 2, there are fewer design restrictions regarding load / rate. Furthermore, the attachment of the spring 7 to the outside of the hollow rod 4 allows the use of a larger diameter spring, which can reduce tension, and a reduction in the spring rate, resulting in less spring load variation between a new and a worn chain.
[0019] Oil from the oil supply (not shown) flows into the LPC 19. Fluid flows from the LPC 19 through the check valve 70 and into the HPC 3 when the force of the fluid is greater than the force of the fluid present in the HPC 3. Once the first end 2a of the piston 2 receives pressure from the belt or chain via a tensioner arm, the piston 2 compresses the external spring 37, and the leakage of fluid from the HPC 3 is prevented by the check valve 70.
[0020] In another embodiment, a second check valve may be placed between the engine oil supply and the LPC 19. The second check valve may help retain oil in the LPC 19 once the engine is shut down and oil drains from the oil supply into the engine, thereby allowing immediate oil volume upon engine restart.
[0021] The floating sleeve 40 outside the piston 2 allows the use of a ratchet mechanism consisting of the ratchet clamp 80, the associated ratchet grooves 33, and the floating sleeve 40 without compromising the functional advantage offered by the tensioner configuration. The floating sleeve 40 also provides a degree of freedom to allow the addition of the ratchet function without overstressing the piston 2.
[0022] The body 1 of the tensioner 50, the floating sleeve 40, and the rod 4 are preferably made of aluminum, and the piston 2 is preferably made of steel. By forming the body 1 of the tensioner 50, the floating sleeve 40, and the rod 4 from aluminum and the piston 2 from steel, clearance is reduced as the temperature rises. In other words, tight clearance fits occur at high temperatures and loose clearance fits occur at cold temperatures. The materials of the tensioner 50 and the construction allow for more stable tensioner performance across engine operating temperatures and allow for less reliance on high-performance control devices to compensate for flow variability.
[0023] For example, in Fig. As shown in Figure 4, a conventional tensioner with an aluminum body has a maximum throughput of 44 cm 3 / s at 120 degrees Celsius, as shown in the graph of total flow rate as a function of pressure. Fig. Figure 5 shows the total flow rate as a function of pressure at 120 degrees Celsius for the tensioner of the present invention. The maximum flow rate is 16 cm 3 / s, increasing the maximum throughput by 28 cm 3 / s is reduced.
[0024] Accordingly, it is to be understood that the embodiments of the invention described herein are merely exemplary of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which, in turn, recite those features believed essential to the invention.
Claims
[1] Hydraulic tensioner comprising: a body; a rod having a first end, a second end, an outer surface and an inner bore, the second end of the rod being attached to the body, wherein the inner bore of the rod defines a low pressure chamber; a hollow piston slidably received around the outer surface of the rod so that the piston slides relative to the outer surface of the rod, the hollow piston having a body defining an outer periphery and an inner bore, the body having a first end and a second end, wherein between the first end and the second end on the outer periphery of the body there is an upper portion, a collar, which extends radially outward to form a shoulder, a smooth portion and a plurality of ratchet teeth, wherein the inner bore of the hollow piston and the first end of the rod define a high pressure chamber; a movable sleeve surrounding the outer periphery of the body of the hollow piston and aligned with the plurality of ratchet teeth, the movable sleeve having a first end, a second end and a bore defining a ratchet clamp groove; an external spring between the first end of the movable sleeve and the shoulder of the collar of the hollow piston, providing a force between the movable sleeve and the shoulder of the collar of the hollow piston, thereby biasing the hollow piston outwardly with respect to the body; a ratchet clamp received between the plurality of ratchet teeth and the movable sleeve for engagement with the plurality of ratchet teeth; and a check valve received in the bore of the hollow piston and in the first end of the rod for controlling the flow of fluid between the low pressure chamber and the high pressure chamber. [2] A hydraulic tensioner according to claim 1, wherein the body is L-shaped such that the piston is mounted perpendicular to a vertical portion of the body and to a horizontal portion of the body. [3] A hydraulic tensioner according to claim 1 or claim 2, wherein a transport clamp stop groove is located between the row of ratchet teeth and the second end of the body of the piston. [4] A hydraulic tensioner according to claim 3, further comprising a transport clamp, wherein a first leg of the transport clamp is received by the body and the second leg is received in a through hole of the movable sleeve and engages the transport clamp stop groove of the body of the piston, thereby securing the movable sleeve and the piston in a fixed position. [5] A hydraulic tensioner according to any preceding claim, wherein the smooth portion of the outer periphery of the body of the piston further comprises an external spring groove for engaging the external spring and holding it in position on the piston. [6] A hydraulic tensioner according to any one of the preceding claims, wherein the check valve further comprises: a valve seat in the first end of the rod defining a hole and a seat; a check member movable between closing and exposing the hole of the valve seat; a retainer defining a plurality of holes and enclosing the check member; and a spring between the retainer and the check member biasing the check member to close the hole of the valve seat. [7] A hydraulic tensioner according to any one of the preceding claims, wherein the second end of the rod is press-fitted into the body. [8] A hydraulic tensioner according to any one of claims 1 to 6, wherein the second end of the rod is formed integrally with the body. [9] A hydraulic tensioner according to any one of the preceding claims, wherein the rod is formed of aluminum. [10] A hydraulic tensioner according to any one of the preceding claims, wherein the movable sleeve is formed of aluminum. [11] A hydraulic tensioner according to any one of the preceding claims, wherein the piston is formed of steel. [12] A hydraulic tensioner according to any one of claims 6 to 11, wherein the holding device comprises steel and is formed by rolling.