WO2021014471A1

WO2021014471A1 - A hydraulic tensioner for uniform load distribution

Info

Publication number: WO2021014471A1
Application number: PCT/IN2020/050641
Authority: WO
Inventors: Prashant Vishwanath PATIL; Mahesh Suresh Bokil; Pratik Gajanan Paratwar; Prafull Krupadan Holkar; Deepak Singh; Shyam Balaram GAWADE; Pinaki JENA
Original assignee: Advik Hi-Tech Pvt. Ltd.
Priority date: 2019-07-25
Filing date: 2020-07-24
Publication date: 2021-01-28

Abstract

A hydraulic tensioner (1) according to present invention comprises a hollow cylindrical housing (2) having an open top (2a) and a closed bottom wall (2b); a plunger (3), having a tip portion (3a) and a closed bottom wall (3b), longitudinally slidably fitted into the hollow cylindrical housing (2) and configured to define a pressurized oil chamber (4); a barrel spring (5), facing closed bottom wall (2b) of the hollow cylindrical housing (2), compressibly coaxially disposed into the hollow cylindrical housing (2) to define a spring-loaded pressure chamber (6); and a check valve assembly (7) removably mounted between the barrel spring (5) and the bottom wall (3b) of the plunger (3), and fixed with the plunger (3). Further, the barrel spring (5) has least buckling and high stiffness, and provides uniform load distribution for having a parabolic spring rate.

Description

A HYDRAULIC TENSIONER FOR UNIFORM LOAD DISTRIBUTION

Field of Invention

The present invention relates with the field of tensioner and more particularly, it relates to a hydraulic tensioner for uniform load distribution which induces a smooth and silent drive system (transmission mechanism) in internal combustion engine of automotive vehicles.

Background of Invention

A tensioner is a mechanical device that applies a force to create or generate a tension. The force is generated by a spring, in both mechanical tensioners and hydraulic tensioners. In hydraulic tensioners, oil is additionally used to avoid retraction of plunger during operation. A tensioner plays an important role in maintaining a certain degree of tension in a timing chain in engine of vehicles, to prevent noise. Further, application of proper tension on a chain guide allows proper functioning of a cam shaft.

Hydraulic tensioner is a key focus to maintain an accurately correct tension of the timing chain in high capacity internal combustion (IC) of automotive vehicles. Since last few decades, a gradual evolution is being carrying out in an automobile industry to develop an improved hydraulic tensioner than that of the existing one to achieve a smooth and silent mechanical transmission in vehicles’ engines.

In internal combustion engines, a timing chain is a key element for transmitting rotary motion of the crankshaft to the camshaft and auxiliaries to synchronize the motion of engine pistons with the cams that govern an air intake and exhaust emission. However, the length of the timing chain is caused to be elongated due to thermal expansion and vibrations in IC engines. Therefore, the timing chain will inevitably be slacked which causes wear and tear thereof.

Conventionally, hydraulic tensioners are widely used to suppress backlash and vibration due to changes in tension in timing belts and timing chains which transmit rotation from the crankshaft to one or more camshafts in a vehicle engine. A typical hydraulic tensioner comprises a plunger slidable in and protruding from, a housing. The plunger and housing cooperate to provide a pressurized oil chamber into which oil is introduced through a ball-type check valve for blocking backflow of oil from the pressurized oil chamber. Although the check valve unit, in conventional hydraulic tensioner, can block backflow of oil from the pressurized oil chamber, air can become mixed with the oil in the pressurized oil chamber. The compressibility of the air allows backlash and vibration of the traveling transmission medium, especially upon engine start-up.

One such conventional hydraulic tensioner has been disclosed in US patent no. US 5833220, which includes a plunger being slidably fitted in cylinder and a spring urging the plunger upwardly. However, the problem associated with said conventional hydraulic tensioner is having non-uniform load distribution due to conventional spring effect, which cannot uniformly apply an accurately correct tension to the timing belt or timing chain of vehicle’s engine, which results in increased level of noise and reduced lifespan of the mechanical transmission system of vehicles’ engines.

One more such hydraulic tensioner is disclosed in US patent no.6383103 which includes a relief valve mechanism assembled in a plunger which is slidably inserted in a housing; the relief valve mechanism is having an orifice formed in an outer circumferential surface thereof, and a spring urging the sleeve toward the high-pressure chamber. Said hydraulic tensioner of US6383103 encounters with the problem of increased noise of engine due to non-uniform load (tension) onto the timing chain. Further, said hydraulic tensioner of US6383103 is not able to effectually reduce the noise of mechanical transmission system of the vehicles’ IC engines.

Therefore, a need yet exists to provide a smooth drive system of internal combustion (IC) engine for improved lifespan of timing chain and better performance of IC engines by achieving uniform load or tension distribution of the hydraulic tensioner. Although, the conventional hydraulic tensioners are proved to be suitable for certain applications, there is still scope to provide an improved hydraulic tensioners having an effectually improved functionality; which can almost eliminate the noise of camshaft drive and auxiliaries drive systems of internal combustion engines to increase the lifecycle of the timing chain and improve the performance of internal combustion (IC) engines. Hence, it is desperately required to provide and develop a hydraulic tensioner which can overcome the aforesaid drawbacks and shortcomings of the conventional hydraulic tensioners.

Object of Invention

The main object of the present invention is to provide a hydraulic tensioner.

Another object of the present invention is to provide a hydraulic tensioner which eliminates the slippage and unmeshing of the toothed timing chain.

Still another object of the present invention is to provide a hydraulic tensioner which induces uniform load or tension onto the timing chain of the drive system in IC engine.

Yet another object of the present invention is to provide a hydraulic tensioner which substantially ameliorate the lifecycle and functionality of the drive system in IC engine.

Yet another object of the present invention is to provide a hydraulic tensioner which is configured to induce a smooth and silent drive system in IC engine.

Yet another object of the present invention is to provide a hydraulic tensioner which enables an easy installation while assembling.

Yet another object of the present invention is to provide a hydraulic tensioner which is having a spring of maximum stiffness and least buckling.

Yet another object of the present invention is to provide a hydraulic tensioner which overcomes drawbacks and shortcomings of prior art hydraulic tensioners.

Summary of Invention

This summary is provided to introduce aspects related to a hydraulic tensioner, and the aspects are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter. A hydraulic tensioner according to present invention comprises a hollow cylindrical housing having an open top and a closed bottom wall; a plunger, having a tip portion and a closed bottom wall, longitudinally slidably fitted into the hollow cylindrical housing and configured to define a pressurized oil chamber; a barrel spring, facing closed bottom wall of the hollow cylindrical housing, compressibly coaxially disposed into the hollow cylindrical housing to define a spring-loaded pressure chamber; and a check valve assembly removably mounted between the barrel spring and the bottom wall of the plunger, and fixed with the plunger. Further, barrel spring has least buckling and high stiffness, and provides uniform load distribution for having a parabolic spring rate. Therefore, with usage of the barrel spring, a smooth and silent drive system is provided. Such smooth and silent operation substantially ameliorates lifecycle and functionality of the drive system in IC engine.

In one embodiment, a hydraulic tensioner comprises a hollow cylindrical housing having an open top and a closed bottom wall. Further, a plunger having a tip portion and a closed bottom wall may be longitudinally slidably fitted into the hollow cylindrical housing. A barrel spring facing the closed bottom wall of the hollow cylindrical housing may be used in the hydraulic tensioner. The barrel spring has least buckling and high stiffness. The barrel spring provides uniform load distribution for having a parabolic spring rate. The barrel spring may be compressibly coaxially disposed into the hollow cylindrical housing to define a spring- loaded pressure chamber. A check valve assembly may be removably mounted between the barrel spring and the bottom wall of the plunger, and fixed with the plunger. The hydraulic tensioner maintains tension onto a timing chain by extending the hollow cylindrical housing towards the timing chain, using resilience energy of the barrel spring, when the timing chain tends to slack. The cylindrical housing may be extendible, around the plunger, upto a released length of the barrel spring, to compensate slackness of the timing chain.

In one embodiment, the bottom wall may comprise an aperture to define a pressurized oil chamber. The check valve assembly may comprise a valve cap mountably facing the barrel spring. The valve cap may comprise openings to allow flow of the oil from the pressurized oil chamber to the spring-loaded pressure chamber. A valve ball may be movably fixed into the valve cap. Further, a valve spring may be compressibly disposed between the valve ball and the valve cap. In one embodiment, the check valve assembly may be a press-fit check valve assembly or an integrated check valve assembly, which is rigidly fixed to the bottom wall of the plunger, in such manner that the valve cap is supportably sited onto the barrel spring. Alternatively, the check valve assembly may be a floating type assembly, which is removably fixed through a valve seat to the bottom wall of the plunger, in such manner that the valve cap is supportably sited onto the barrel spring.

Upon elongation of the plunger towards the exterior of the hollow cylindrical housing, a volume may be created into the spring-loaded pressure chamber which leads to decrease in pressure therein, to cause oil to flow from the pressurized oil chamber into the spring-loaded pressure chamber, through the aperture present on the bottom wall of the plunger. Furthermore, upon elongation of the plunger to compensate slackness of the chain, the plunger is prevented from moving towards the bottom wall of the cylindrical housing, due to incompressible property of the oil.

Brief description of drawings

Various other objects, features and many of the attendant advantages of the present invention will be understood by reference to the following detailed description of the preferred embodiment of the present invention when considered in connection with the accompanying drawings, in which:

Fig.l illustrates a cross sectional view of the hydraulic tensioner, according to an embodiment of present invention;

Fig. 2 illustrates a cross-sectional view of hydraulic tensioner, according to another embodiment of the present invention;

Fig. 3 illustrates a perspective view of a convex/ barrel spring, being utilized in hydraulic tensioner, according to an embodiment of the present invention;

Fig. 4a illustrates spring load distribution characteristics of the barrel spring, according to an embodiment of the present invention; and Fig. 4b illustrates a performance curve of the barrel spring, according to an embodiment of the present invention.

Detailed description of Invention

The nature of the invention and the manner in which it works is clearly described in the provisional specification. The invention has various embodiments and they are clearly described in the following pages of the provisional specification. Before explaining the present invention, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.

Before explaining the present invention, it is to be understood that a hydraulic tensioner is normally installed in a compressed state (condition) of a spring which gradually elongates and extends, as a timing chain tends to slack or loose due to thermal expansion and vibration in an IC engine, to maintain a required tension onto the timing chain.

Now referring to Figs. 1-2 collectively, a hydraulic tensioner (1) according to the present invention comprises a hollow cylindrical housing (2) having an open top (2a) and a closed bottom wall (2b); a plunger (3) having a tip portion (3a) and a closed bottom wall (3b), longitudinally slidably fitted into the hollow cylindrical housing (2); a barrel spring (5) facing the closed bottom wall (2b) of the hollow cylindrical housing (2), compressibly coaxially disposed into the hollow cylindrical housing (2) to define a spring-loaded pressure chamber (6); and a check valve assembly (7) removably mounted between the barrel spring (5) and the bottom wall (3b) of the plunger (3). Further, the check valve assembly (7) may be fixed with the plunger (3).

The term“plunger”, herein described, refers to a hollow cylindrical body, having a bore open at the tip portion (3a) and closed with the bottom wall (3b) having an aperture (not shown in figure) to define a pressurized oil chamber (4). Further referring to Figs. 1-2 collectively, said plunger (3) is configured to be slidably guided within the hollow cylindrical housing (2), and being urged by the barrel spring (5) that causes hollow cylindrical housing (2) to be projected and extended towards the chain due to a resilience energy of the barrel spring (5), when the timing chain tends to slack or loose. Before explaining the detailed invention, it is to be noted that the hydraulic tensioner (1) works on principal of incompressible property of oil, in which the check valve assembly (7) permits an oil to flow into the spring-loaded pressure chamber (6) through an aperture (not shown in figure) of the plunger (3) [at predefined pressure of the hydraulic tensioner] from the pressurized oil chamber (4) while preventing the oil from flowing out of the spring-loaded pressure chamber (6). Said plunger (3) is configured to be prevented to move in reverse direction [towards the bottom wall (2b) of the cylindrical housing (2)] due to incompressible property of oil.

Further referring to Figs.1-2 collectively, the check valve assembly (7) includes a valve cap (8) of cup-shaped mountably facing the barrel spring (5) and having openings to allow the oil to flow from the pressurized oil chamber (4) to the spring-loaded pressure chamber (6); a valve ball (9) movably fixed into the cup-shaped valve cap (8); and a valve spring (10) compressibly disposed between the valve ball (9) and the valve cap (8).

The term“released length”, hereinafter described, refers to a length of the barrel spring (5) at which the plunger (3) is effectually and operatively fully extended through the open top

(2a) of the cylindrical housing (2) in working condition of the hydraulic tensioner (1).

According to first embodiment of the present invention, the check valve assembly (7), as depicted in Fig.l, is rigidly fixed to the bottom wall (3b) of the plunger (3), in such manner that the cup-shaped valve cap (8) is supportably sited onto the barrel spring (5). Said check valve assembly (7), as depicted in Fig. 1, is referred to as a press-fit or integrated check valve assembly.

According to another embodiment of the present invention, the check valve assembly (7), as depicted in Fig. 2, is removably fixed through a valve seat (11) to the bottom wall (3b) of the plunger (3), in such manner that the valve cap (8) is supportably sited onto the barrel spring (5). Said check valve assembly (7), as depicted in Fig. 2, is referred to as a floating type assembly.

Now referring to Fig. 3 of the present invention, shape and properties of the barrel spring (5) are explained. The barrel spring (5) has a highest diameter at middle section, and the diameter keeps decreasing towards both ends of the barrel spring (5). Because the diameter of the barrel spring (5) is highest at the middle section, compared to diameter at ends, chances of buckling are very low. Therefore, the barrel spring (5) has least buckling and high stiffness (spring-rate).

Fig. 4a illustrates spring load distribution characteristics of the barrel spring (5), according to an embodiment of the present invention. As illustrated in Fig. 4a, the barrel spring (5) provides a parabolic spring rate i.e. spring load increases as the barrel spring (5) goes into a relaxed condition. Such property of the barrel spring (5) is very different from regular compression springs, because in regular compression springs, spring load decreases when the regular compression spring goes into a relaxed condition. Therefore, because of its parabolic spring rate, the barrel spring (5) provides uniform load distribution with respect to stroke.

Fig. 4b illustrates a performance curve of the barrel spring, according to an embodiment of the present invention. As illustrated in Fig. 4b, performance curve of the barrel spring (5) is almost linear. Thus, the barrel spring (5) could suitably bear variable loads, resulting in a silent operation of drive systems in IC engines.

The term“installed length”, hereinafter disclosed, refers to a length of the barrel spring (5) at which the hydraulic tensioner (1) is initially installed as per predefined load of the timing chain.

In operational characteristics of the present invention, initially the hydraulic tensioner (1) is installed in wound condition, having an installed length of the barrel spring (5) to sustain the tension of timing chain according to predefined load of the timing chain. Now, when the timing chain tends to slack/loose due to thermal expansion and vibration, the plunger (3) of the hydraulic tensioner (1) is configured to be elongated and extended towards an exterior of the hollow cylindrical housing (2) through the open top (2a) due to resilience of the barrel spring (5) to maintain the required tension onto the timing chain. After elongation or extension of the plunger (3) towards an exterior of the hollow cylindrical housing (2), a volume is created into the spring-loaded pressure chamber (6) which leads to decrease in pressure therein to cause the oil flow from the pressurized oil chamber (4) into the spring-loaded pressure chamber (6).

Now, when the plunger (3) is extended to a specific distance to compensate slackness of the timing chain, the plunger (3) is now prevented to move in a reverse direction [i.e. towards the bottom wall (2b) of the cylindrical housing (2)] due to an incompressible property of oil. Further, the cylindrical housing (2) is allowed to be extended, around the plunger (3), upto a released length of the barrel spring (5), to compensate slackness of the timing chain.

The hydraulic tensioner of the present invention induces a smooth and silent drive system by reducing the rattling noise and substantially ameliorates the lifecycle and functionality of the drive system in IC engine. Further, said hydraulic tensioner also eliminates the unmeshing of the timing chain and induces uniform load or tension onto the timing chain of the drive system in IC engine. Said hydraulic tensioner enables an easy installation while assembling in assembly unit. The present invention has been described with reference to the specific embodiment, which is merely illustrative and not intended to limit the scope of the present invention as defined in the specification.

Claims

CLAIMS:

1. A hydraulic tensioner (1) comprising: a hollow cylindrical housing (2) having an open top (2a) and a closed bottom wall (2b); a plunger (3) having a tip portion (3a) and a closed bottom wall (3b), longitudinally slidably fitted into the hollow cylindrical housing (2); a barrel spring (5) facing the closed bottom wall (2b) of the hollow cylindrical housing (2), wherein the barrel spring (5) is compressibly coaxially disposed into the hollow cylindrical housing (2) to define a spring-loaded pressure chamber (6); and a check valve assembly (7) removably mounted between the barrel spring (5) and the bottom wall (3b) of the plunger (3), and fixed with the plunger (3), wherein the hydraulic tensioner (1) maintains tension onto a timing chain by extending the hollow cylindrical housing (2) towards the timing chain, using resilience energy of the barrel spring (5), when the timing chain tends to slack.

2. The hydraulic tensioner (1) as claimed in claim 1, wherein the barrel spring (5) has least buckling and high stiffness.

3. The hydraulic tensioner ( 1 ) as claimed in claim 1 , wherein the barrel spring (5) provides uniform load distribution for having a parabolic spring rate.

4. The hydraulic tensioner (1) as claimed in claim 1, wherein the bottom wall (3b) comprises an aperture to define a pressurized oil chamber (4).

5. The hydraulic tensioner (1) as claimed in claim 4, wherein the check valve assembly

(7) comprises: a valve cap (8) mountably facing the barrel spring (5), wherein the valve cap (8) comprises openings to allow flow of the oil from the pressurized oil chamber (4) to the spring-loaded pressure chamber (6); a valve ball (9) movably fixed into the valve cap (8); and a valve spring (10) compressibly disposed between the valve ball (9) and the valve cap (8).

6. The hydraulic tensioner (1) as claimed in claim 5, wherein the check valve assembly (7) is a press-fit check valve assembly or an integrated check valve assembly, which is rigidly fixed to the bottom wall (3b) of the plunger (3), in such manner that the valve cap (8) is supportably sited onto the barrel spring (5).

7. The hydraulic tensioner (1) as claimed in claim 5, wherein the check valve assembly (7) is a floating type assembly, which is removably fixed through a valve seat (11) to the bottom wall (3b) of the plunger (3), in such manner that the valve cap (8) is supportably sited onto the barrel spring (5).

8. The hydraulic tensioner (1) as claimed in claim 4, wherein upon elongation of the plunger (3) towards the exterior of the hollow cylindrical housing (2), a volume is created into the spring-loaded pressure chamber (6) which leads to decrease in pressure therein, to cause oil to flow from the pressurized oil chamber (4) into the spring-loaded pressure chamber (6), through the aperture present on the bottom wall (3b) of the plunger (3).

9. The hydraulic tensioner (1) as claimed in claim 8, wherein upon elongation of the plunger (3) to compensate slackness of the chain, the plunger (3) is prevented from moving towards the bottom wall (2b) of the cylindrical housing (2), due to incompressible property of the oil.

10. The hydraulic tensioner (1) as claimed in claim 1, wherein the cylindrical housing (2) is extendible, around the plunger (3), upto a released length of the barrel spring (5), to compensate slackness of the chain.