Sprocket with damper and compensator

A sprocket unit comprising: a damper mounted on the first shaft with a first face defining a recess and a second face defining chambers for receiving spring loaded weights; a sprocket mounted to the first shaft with a hub defining an aperture and a slot; a front end plate mounted on the shaft with a hub defining an aperture aligned with the aperture of the sprocket; and a spring received within the aperture of the sprocket, the aperture of the front end plate, and the recess of the damper. When the first shaft rotates and firing frequency of the engine coincides with a resonant frequency of the first shaft, the spring loaded weights slide in the chambers of the damper, dampening out the resonant frequency in the first shaft and when the sprocket rotates the spring compresses and extends, reducing torsional load of the first shaft on the second shaft.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to the field of sprockets. More particularly, the invention pertains to a sprocket with a damper and a compensator.

2. Description of Related Art

As modern vehicles and engine compartments become smaller, the requirement to have more compact engines becomes greater. One way to achieve this is to put the crankshaft damper inside the timing drive cover. Since this is an environment that is subjected to oil conditions, a damper must be able to tolerate these extreme conditions. Current dampers with rubber will not withstand the hot oil environment for the life of the vehicle. Also, as the electrification of accessories becomes common place, the need for the crankshaft to extend out of the engine is minimized.

SUMMARY OF THE INVENTION

A sprocket unit mounted to a shaft comprising a damper with recesses and chambers for receiving spring loaded weights; a sprocket mounted adjacent to the damper having a hub defining at least one aperture and at least one slot having a length; a front end plate mounted on the first shaft adjacent to the sprocket with a hub defining an apertures aligned with the apertures of the sprocket; and springs received within the apertures of the sprocket, the apertures of the front end plate, and the recesses of the damper. When the shaft rotates and the firing frequency of the engine is in tune with the resonant frequency of the first shaft, the spring loaded weights slide in the chambers of the damper to dampen out resonant frequency in the first shaft. The torsional load of the first shaft on the second shaft is decreased by the sprocket rotating an amount no greater than the length of the slot and the spring received within the damper, sprocket, and end plate extends and compresses, reducing the torsional load to the second shaft from the first shaft.

DETAILED DESCRIPTION OF THE INVENTION

The sprocket unit50of the present invention includes a compensator and a damper mounted together as a single unit on a first shaft. The compensator reduces torsional load of the first shaft relative to the second shaft and the damper dampens the vibrations and twisting motion of the first shaft when the resonance of the firing frequency of the engine coincides with the resonance of the first shaft. The damper of the sprocket unit50of the present invention is able to run in a hot oil environment for the life of the vehicle. The sprocket unit50may be mounted to a drive shaft or a driven shaft. The chain drive or belt in which the sprocket of the sprocket unit50engages may be used to drive many devices in the engine, including but not limited to a camshaft, electric motor, or balance shaft system.

FIGS. 1-5show the sprocket unit50of the present invention. It should be noted that inFIG. 1the chain lid has been removed from the figure for clarity. The sprocket unit50is mounted to the reduced diameter portion2bof shaft2and is held in position by a bolt4received within a bore2aof the first shaft2and a washer40.

The sprocket10is mounted to a first shaft2at a reduced diameter portion2b. The sprocket10has a toothed outer periphery10athat meshes with and engages an endless chain (not shown) to transfer rotary motion and torque. Alternatively, the sprocket10may be designed to engage a belt. The endless chain (not shown) is also wrapped around a second sprocket8on a second shaft6which is spaced a distance away from the sprocket10. The sprocket10has at least one semi-circular aperture10b, but preferably at least two apertures are present as shown on the hub10dor the sprocket face that receives compensator springs12. The sprocket face or hub10das used in this description refers to the portion of the sprocket that does not contain sprocket teeth10a. Also on the hub10dof the sprocket is a slot10cextending a length. The slot10creceives a bolt5. The length of the slot10cprovides a clearance for the bolts5to slide back and forth as the sprocket10rotates to reduce the torsional load from the first shaft2to the second shaft6.

On a first side of the sprocket10, a front end plate17is mounted to the first shaft2at the reduced diameter portion2b.The front plate17is bolted and fixed to the sprocket10by bolts5. The bolts5are received by holes17bpresent along the hub of the front end plate17. Also located on the face of the front end plate17are at least one semi-circular aperture17a,however, preferably two apertures are present as shown, that correspond to and align with the semi-circular aperture10bin the sprocket10and receive a portion of the compensator springs12. On the other side of the front end plate17, opposite the side adjacent to the sprocket10, a washer40is present.

On the second side of the sprocket10, opposite the first side, is a damper20with a first face adjacent to the sprocket10and a second face adjacent to a back plate32. On the first face of the damper20is at least one semicircular recess20a,although preferably two recesses are present as shown, that correspond to and align with the semi-circular aperture10bin the sprocket10, and the semi-circular aperture17aof the front end plate17and receive a portion of the compensator springs12. The damper20is held in place on the first shaft2by the washer40. Bolts5hold front end plate17relative to the sprocket10and the damper20. The bolts5are received by holes20bpresent along the hub of the damper20. The damper20is defined by an inner annular wall21, an outer annular wall22, and an end wall23. The inner wall21extends radially from the first face of the damper20along the reduced diameter portion2bof the first shaft2. A bearing surface42is created between the sprocket10and a portion of the inner wall21that extends radially along the reduced diameter portion of the first shaft2. The outer annular wall22extends and defines the outer periphery of the damper20and forms a portion defining chambers25. The end wall23of the damper20extends transversely between the inner and outer walls21,22, with partitions24extending diametrically between the inner and outer walls21,22to divide part of the second face of the damper20into chambers25. Inertia weights28and springs30are received within the chambers25. Springs30on either side of the inertia weights28allow the inertia weights28to move or slide along the inside22aof the outer wall22to dampen out resonance or a resonant frequency in the first shaft2. A back plate32prevents the inertia weights28from moving radially out of the chambers25.

As the first shaft2rotates, the sprocket unit50rotates with the first shaft2. When the firing frequency of the engine coincides with or is equivalent to the resonant frequency of the first shaft2, the inertia weights in chambers25on the second face of the damper20slide along the inside22aof the outer wall22to dampen out the resonance excitation in the first shaft2. Additionally, the sprocket10may rotate an amount no greater than the length of the slot10cto reduce the torsional load of the first shaft2on the second shaft6by compressing and extending the compensator springs12.

While two semi-circular apertures 1% on the sprocket10are shown, four or six semi-circular apertures equally spaced along the face or hub of the sprocket10may also be used. It should be noted that if the number of apertures were to increase or decrease, a corresponding number of apertures would have to be present on the front plate17and the front face of the damper20.

The damper20of the sprocket unit50is preferably a friction or tuned absorber, although a coulomb damper may also be used. Other methods of compensation may be used without deviating from the scope of the invention.

Friction material may be added to the inertia weights to change the damping characteristics as necessary.

The sprocket unit50may be used with any shaft that rotates and has torsional oscillation and drives another shaft either by means of a chain, belt or gear.

The sprocket unit50can run in hot or cold oil.

The sprocket unit50may also perform in a non-lubricated environment if the components were plated to prevent rust and the friction material is such that it will perform in the non-lubricated environment.