ELLIPTICAL SPACER DESIGN FOR INCREASING CONTACT AREA IN TENSIONERS

Field Of Invention

The present invention relates to tensioner assembly for the timing belt drive system in internal combustion engines, and more particularly to an elliptical spacer design having proper mating surface with the engine cylinder head and providing an optimum tension to the timing belt drive system.

Background of the Invention

Conventional motor vehicles are provided with belts for rotatably connecting various components. For example, a timing belt is used to synchronize engine timing and rotatably connect an engine crankshaft and cam shaft sprockets. Proper vehicle operation requires the maintenance of adequate tension in such drive belts and timing belts. Tensioners are used to maintain proper tensioning of the drive and timing belts. Conventional tensioners include two types, manual tensioners and automatic tensioners. Manual accessory belt tensioners require user action to maintain proper tension throughout the life of a belt. Automatic accessory belt tensioners typically are biased into engagement with the belt for maintaining the belt under tension.

In an overhead cam shaft engine or a high cam shaft engine which utilizes a timing belt, a timing belt tensioner is provided between the crank shaft pulley and the cam shaft pulley for the purpose of eliminating any slack in the timing belt. A typical automatic belt tensioner includes a timing belt spacer which is placed to hold the ball bearing, tensioner pulley and also help to provide the optimum belt tension by adjusting the tensioner locking point. In the conventional way there is an auto tensioner for passenger vehicle and manual tensioner for trucks.

In trucks generally it is preferred to have a manual tensioner than auto tensioner, for major cost reduction. The auto tensioner consists of installation shaft, thrust washer, pulley, ball bearing, pivot bushing, arm, and spring; whereas the manual tensioner has only ball bearing and spacer for belt tension adjustment. The engine design for passenger was implicated in the truck with circular boundary condition. The tensioner pulley is adapted to be in a contact relationship with the drive belt such that the drive belt is tightened and loosened in response to movement of the spacer. When the variable load of the belt subsequently falls, the belt is momentarily slackened until the tensioner spacer respond. This slackening of the belt in the drive system often results in undesirable noise and vibrations.

In the above discussed conventional belt tensioner arrangement, the spacer design becomes a challenge for making a full contact area of the spacer. Usually the manual tensioners have a spacer with circular profile topology mating with the cylinder head.

However, the circular profiled spacer consumes more amount of space on cylinder head for better support and also limits the tensioner arm movement due to radius constrain. Moreover, the circular profiled spacer is not feasible, when there is a mismatch in the planes of cylinder head and block.
Also, in the conventional timing belt tensioners, the force applied to bearing causing that, the tensioner cannot maintain a parallel relationship with the timing belt surface thereby causing the timing belt slightly twisted and shortening in the life of the timing belt.

Further, due to the less space available in the cylinder head the conventional spacer overhangs and does not provide a good support for the tensioner, in addition it leads to the mismatch of plane for cylinder head and block the boundary condition for contact area of circular profile spacer.

Thus the circular profile of the spacer is not suited for the boundary conditions to mate completely with cylinder head, so spacers having different profile based on two boundary conditions are required.
Therefore, it is desirable to provide an improved tensioner assembly which overcomes the disadvantages of the conventional belt tension arrangement and providing optimum tension to the timing belt drive system with easier adjustment options and having enhanced mating surface with the engine cylinder head.

Objects of the Invention

The main object of the present invention is to provide an improved spacer design for the timing belt tensioner system which overcome the disadvantages and eliminating the problems associated with the prior art.

Another object of the present invention is to improve the tensioner arm movement to a maximum extent for the same space provided in the timing belt tensioner system.

Another object of the present invention is to provide a spacer having a proper mating surface with the cylinder head and to provide optimum tension for the timing belt for long period.

Further object of the present invention is to provide a spacer design with elliptical profile which allows positioning the tensioner in the interface area where the area of contact is less for the base plate.

Further object of the present invention is to design the spacer which suits for the boundary conditions and to mate completely with cylinder head of the internal combustion engine.

Summary of the Invention

The present invention which achieves the objectives relates to an improved spacer design having suitable mating surface with the engine cylinder head and providing an optimum tension to the timing belt drive system. The tensioner is designed to provide an optimum tension to the timing belt drive system. The timing belt connects the Crank shaft to the Camshaft, which in turn controls the opening and closing of the engine valves. The tensioner assembly is designed to provide an optimum tension to the timing belt drive system.

The tensioner assembly has a tensioner pulley having an elliptical spacer attached to the cylinder head through a spacer mounting bolt by mating with the elliptical profile of the spacer. The elliptical spacer mounting bolt centre line is made offset with the pulley centre line to form an eccentricity. The elliptical spacer is attached with the spacer mounting bolt to the cylinder head by mating with its elliptical profile in the full contact area.

A locking key is provided to adjust the tensioner assembly through the tensioner locking pin provided in the elliptical spacer, such that the timing belt tension is adjusted and locked through the tensioner locking pin. The tensioner pulley helps to provide an optimum tension to the timing belt, and the timing belt tension can be adjusted manually through the tensioner locking pin.

The elliptical spacer holds a ball bearing for providing free circular motion to the tensioner pulley, such that the spacers face rest with mating member of the cylinder head and give the thrust for the tensioner pulley to adjust the belt tension. The elliptical profiled spacer contacts in full surface area with the cylinder head and the eccentricity of the elliptical spacer moves the tensioner pulley for adjusting the tension for the belt drive system.

The offset of the elliptical spacer mounting bolt centre line with the pulley centre line helps to move the tensioner arm for adjusting the tension for the belt drive system. The elliptical spacer, due to its eccentricity allows maximum tensioner arm movement for the limited space provided on the cylinder head. Thus the spacer provides full support for the tensioner pulley to provide an optimum tension for long period. This improved spacer assembly can be used in the auxiliary devices either as a tensioner mounting surface or idler mounting surface.

The tensioner prevents the belt slipping from the gear tooth and also acts as a damper during engine start and stop. The spacer in the tensioner provides the effective thrust face with the help of its geometrical parameters like flatness, perpendicularity and roughness to handle the tension offered by the belt of the system. The tension for the timing belt can be set manually by adjusting the tensioner arm movement with the help of locking key adjusting the spacer locking point.

The elliptical profiled spacer according to the present invention provides full contact of surface area with the cylinder head and also maximum tensioner arm movement can be achieved for the same space provided. The spacer outer diameter acts as a bearing member and the face rest with mating member to give the thrust for tensioner pulley to adjust the tension of the belt, thus maximizing the tensioner arm movement for the same space provided.

Brief Description of the drawings

The drawings being referred herein are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same. The invention will be explained in greater detail hereinafter with reference to an illustrative embodiment shown in the accompanying drawings.

Fig. 1 shows the tensioner assembly having an improved elliptical spacer design, for timing belt drive system, in accordance to the exemplary embodiment of the present invention.

Fig. 2 shows the elliptical spacer having tensioner locking pin and a spacer mounting bolt, for the timing belt drive system of an IC engine, in accordance to the present invention.

Fig. 3 shows the cross sectional view of the elliptical spacer assembled with the tensioner assembly for the belt drive system of an engine, in accordance to the present invention.

Fig. 4 shows the eccentricity of elliptical spacer mounting bolt centre line and the pulley centre line, for the tensioner assembly, in accordance to the present invention.

Detailed Description of the Invention

The present invention relates to tensioner assembly for the timing belt drive system in internal combustion engines. The spacer design includes proper mating surface with the engine cylinder head and providing an optimum tension to the timing belt drive system. The tensioner is designed to provide an optimum tension to the timing belt drive system. The timing belt connects the Crank shaft to the Camshaft, which in turn controls the opening and closing of the engine valves. The tensioner assembly is designed to provide an optimum tension to the timing belt drive system. The present invention employs an elliptical spacer design for the tensioner assembly of cam shaft timing belt drive system having proper mating surface with the engine cylinder head and adjustable options, and thereby providing an optimum tension to the timing belt drive system.

Fig. 1 and 3 shows the tensioner assembly having an improved elliptical spacer design, for timing belt drive system, in accordance to the exemplary embodiment of the present invention. The tensioner assembly (1) has a tensioner pulley (4) having an elliptical spacer (2) attached to the cylinder head (not shown) of the engine through a spacer mounting bolt (5) by mating with the elliptical profile of the spacer. The spacer (2) generally has an elliptical or non circular profile of topology, such that the tensioner pulley provides optimum tension to the timing belt. The elliptical spacer (2) holds a ball bearing (3) for providing free circular motion to the tensioner pulley (4), such that the spacers face rest with the mating surface of the cylinder head and give the thrust for the tensioner pulley (4) to adjust the belt tension. The ball bearing (3) is placed on the outer side of the elliptical spacer (2) to have a free rotation of the spacer (2) and the tensioner pulley (4). The elliptical profiled spacer (2) contacts in full surface area with the cylinder head and the eccentricity of the elliptical spacer moves the tensioner pulley (4) for adjusting the tension for the belt drive system.

Fig. 2 shows the elliptical spacer having tensioner locking pin and a spacer mounting bolt, for the timing belt drive system of an IC engine, in accordance to the present invention. A locking pin (6) is provided through the tensioner locking pin provision in the elliptical spacer (2) to adjust the tensioner assembly (1), such that the timing belt tension is adjusted and locked through the tensioner locking pin (6). The tensioner assembly (1) helps to provide an optimum tension to the timing belt (not shown), and the timing belt tension can be adjusted manually through the tensioner locking pin (6). The topology of elliptical profiled spacer as shown in the figure provides full surface area contact with the cylinder head matting surface and also a maximum tensioner arm movement can be achieved for the same space provided.

The locking pin is moved in a circular direction to adjust the movement of the spacer in the tensioner assembly and thereby adjusting the belt tension.

Fig. 4 shows the eccentricity of elliptical spacer mounting bolt centre line and the pulley centre line, for the tensioner assembly, in accordance to the present invention. The elliptical spacer centre line (10) is made offset with the tensioner pulley centre line (9) to form an eccentricity (8). The elliptical spacer (2) is attached with the spacer mounting bolt (5) to the cylinder head by mating with its elliptical profile in a full contact area of the matting surface (7). The elliptical spacer mounting bolt (5) is enabled to mount the spacer (2) in a required eccentricity (8) with the tensioner pulley centre line (9).

In assembly, the tensioner assembly having the elliptical spacer assembly is placed in line with the timing belt drive system of the engine connecting the cam shaft and the crank shaft for required valve timings.

The tensioner assembly (1) is biased against the belt to maintain a substantially constant tension in the belt as the engine is operated. The tensioner pulley (4) is pivotally mounted to the tensioner at a mounting point which is spaced from the axis about which the pulley (4) rotates to create an eccentric (8) about which the pulley (4) can be moved to tension the belt. The difference between the pivotal mounting point (10) and the axis of rotation for the pulley (9) is typically referred to as the "arm" of the tensioner.

The spacer face rest with mating member to give the thrust for tensioner pulley (4), and the spacer is mounted with an eccentricity in the tensioner assembly, such that the tensioner arm movement is maintained at the maximum level. The tensioner assembly (1) is assembled accordingly and adjusted the movement of the elliptical spacer (2) and the pulley (4) to maintain an optimum tension in the belt drive system. The forces applied to the belt by the engine vary significantly when the engine operates, and thus operation of the belt results in significant changes in the tension in the flexible drive belt, and the biasing force which biases the pulley of the tensioner against the belt is relatively large.

In operation the elliptical spacer locking pin (6) is adjusted manually in consideration to the slackness in the belt and the force biasing against the tensioner pulley (4). The adjusted position of the elliptical spacer (2) providing required level of movement of the spacer is locked manually using the locking pin (6). A locking key (not shown) is provided to adjust the tensioner assembly through the tensioner locking pin (6) provided in the elliptical spacer (2). The timing belt tension is adjusted manually to a required level to maintain optimum belt tension through the tensioner locking pin (6) using the locking key.

The offset of the elliptical spacer mounting bolt centre line (9) with the pulley centre line (10) helps to move the tensioner arm for adjusting the tension for the belt drive system. The elliptical spacer (2), due to its eccentricity allows maximum tensioner arm movement for the limited space provided on the cylinder head. Thus enabling the elliptical spacer (2) to provide full support for the tensioner pulley (4) and providing an optimum tension for a long period. This improved spacer assembly can be used in the auxiliary devices as a tensioner mounting surface or idler mounting surface.

The tension for the timing belt can be set manually by adjusting the tensioner arm movement with the help of locking key adjusting the spacer locking point. The tensioner prevents the belt slipping from the gear tooth and also acts as a damper during engine start and stop.

The spacer in the tensioner provides the effective thrust face with the help of its geometrical parameters like flatness, perpendicularity and roughness to handle the tension offered by the belt of the system. The spacer outer diameter acts as a bearing member and the face rest with mating member to give the thrust for tensioner pulley to adjust the tension of the belt, thus maximizing the tensioner arm movement for the same space provided.

The tensioner arm movement for circular profiled spacer is limited due to radius constrain, were as the tensioner arm movement for the elliptical profiled spacer is maximum for the same space provided.

Further, the elliptical profiled spacer according to the present invention provides full contact of surface area with the cylinder head and also maximum tensioner arm movement can be achieved for the same space provided.

The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

We Claim:

1. A tensioner assembly for a belt drive system, the assembly comprises,

a tensioner pulley having an elliptical spacer attached to the cylinder head through a spacer mounting bolt by mating with the elliptical profile of the spacer, wherein the elliptical spacer mounting bolt centre line is made offset with the pulley centre line to form an eccentricity;

a locking key to adjust the tensioner assembly through the tensioner locking pin provided in the elliptical spacer, wherein the timing belt tension is adjusted and locked through the tensioner locking pin.

2. The belt tensioner assembly as claimed in claim 1, wherein the elliptical spacer holds a bearing member for providing free circular motion to the tensioner pulley.

3. The belt tensioner assembly as claimed in claim 1, wherein the elliptical spacer face rest with mating member of the cylinder head to give a thrust for the tensioner pulley and to adjust the belt tension.

4. The belt tensioner assembly as claimed in claim 1, wherein the elliptical profiled spacer contacts in full surface area with the cylinder head.

5. The belt tensioner assembly as claimed in claim 1, wherein the eccentricity of the elliptical spacer moves the tensioner pulley for adjusting the tension in the belt drive system.

6. The belt tensioner assembly as claimed in claim 1, wherein the elliptical spacer has an elliptical profile or non circular profile of topology.

7. The belt tensioner assembly as claimed in claim 2, wherein the bearing member is a ball bearing provided with the spacer.

8. The belt tensioner assembly as claimed in claim 1, wherein the tensioner pulley provides optimum tension to the timing belt in belt drive system.

9. A timing belt drive system having the belt tensioner assembly as claimed in the preceding claims.

10. An internal combustion engine having the belt tensioner assembly as claimed in the preceding claims.