Balance shaft gear carrier drive

An engine drive assembly includes a camshaft gear, and a first idler gear engaged with the camshaft gear. The engine drive assembly further includes a crankshaft gear engaged with the first idler gear and a second idler gear assembly engaged with the crankshaft gear. Additionally, the engine drive assembly includes a balance shaft gear engaged with the second idler gear. The crankshaft gear drives the camshaft gear via the first idler gear and the crankshaft gear drives the balance shaft gear via the second idler gear assembly.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to internal combustion engines, and relates more specifically to driving a camshaft with a crankshaft in a system that includes a balance shaft.

BACKGROUND OF THE INVENTION

Internal combustion engines balance shaking forces resulting from crankshaft and connecting rod assembly rotation. The balance shaft is operable to offset rotational energy created by the rotation of the crankshaft. Both the camshaft and balance shaft are typically driven by gears, or sprockets. A crankshaft gear drives both the camshaft gear and the balance shaft gear, often using belts or chains. Unfortunately, belts or chains may break and often require tensioners. Tensioners add to the complexity, and cost, of building or repairing engines. In addition, tensioners may be remotely located and tensioner placement can result in parasitic energy losses.

Each gear rotates at a speed inversely proportional to its relative radius compared to the crankshaft gear. For example, if camshaft gear radius is twice the radius of the crankshaft gear, the camshaft will rotate at half the speed of the crankshaft gear. Similarly, balance shaft gear rotates at twice the speed of the crankshaft gear, if the radius of the balance shaft gear is half the radius of the crankshaft gear.

SUMMARY OF THE INVENTION

One aspect of the invention provides an engine drive assembly including a camshaft gear engaged with a first idler gear. The first idler gear is engaged with a crankshaft gear. The crankshaft gear is engaged with a second idler gear assembly. The second idler gear assembly is engaged with a balance shaft gear. The crankshaft gear drives the camshaft gear via the first idler gear and the crankshaft gear drives the balance shaft gear via the second idler gear assembly.

Another aspect of the invention provides an auxiliary shaft (such as a balance shaft) gear carrier drive including an auxiliary shaft housing and a camshaft gear supported by the balance shaft housing. The auxiliary shaft gear carrier drive further includes a first idler gear engaged with the camshaft gear and a crankshaft gear engaged with the first idler gear, the crankshaft gear supported by the auxiliary shaft housing. The second idler gear assembly is engaged with the crankshaft gear. The balance shaft gear carrier drive further includes a auxiliary shaft gear engaged with the second idler gear, the auxiliary shaft gear supported by the auxiliary shaft housing. The crankshaft gear drives the camshaft gear via the first idler gear and the crankshaft gear drives the auxiliary shaft gear via the second idler gear assembly.

Yet another aspect of the invention provides an auxiliary shaft gear carrier system. The system includes means for rotating a camshaft in a camshaft direction using idler gear means; and means to rotate a auxiliary shaft in a direction opposite the camshaft direction using idler gear means. The means for rotating the camshaft and auxiliary shaft includes a crankshaft.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1shows one embodiment of an engine drive assembly100according to the present invention. The engine drive assembly100includes balance shaft housing4supporting camshaft gear1, crankshaft gear7, and balance shaft gear11. Crankshaft gear7rotates about a crankshaft gear centerline9. Crankshaft26(FIG. 4) drives crankshaft gear7. Camshaft gear1rotates about camshaft centerline8and is operable to rotate camshaft25(FIG. 4) in a camshaft direction. Balance shaft gear11rotates about balance shaft gear centerline42and is operable to rotate balance shaft12(which also forms an auxiliary shaft in accordance with the present invention) in a balance shaft direction opposite to the camshaft direction. For example, if camshaft25rotates clockwise, balance shaft12rotates counter-clockwise.

Engine drive assembly100includes axial shaft3pressed and roll formed into balance shaft housing4. Axial shaft3supports first idler gear2. Axial shaft5supports needle bearing compliment6. First idler gear2is engaged with crankshaft gear7. In one embodiment, first idler gear2is in direct physical engagement with crankshaft gear7, such that the gear teeth of first idler gear2intermesh with the gear teeth of crankshaft gear7. Distance A, between crankshaft gear centerline9and camshaft gear centerline8accommodates first idler gear2. In one embodiment, the radius of first idler gear2is substantially the same as the radius of crankshaft gear7. In one embodiment, the radius of first idler gear2is substantially one half the radius of camshaft gear1.

In the embodiment, illustrated inFIGS. 1–4, engine drive assembly100further includes second idler gear10. Second idler gear10is engaged with crankshaft gear7. In one embodiment, second idler gear10is in direct physical engagement with crankshaft gear7, such that the gear teeth of second idler gear10intermesh with the gear teeth of crankshaft gear7. Distance E, between crankshaft gear centerline9and balance shaft gear centerline42accommodates second idler gear10. In one embodiment, the radius of second idler gear10is substantially the same as the radius of crankshaft gear7. In one embodiment, the radius of second idler gear10is substantially twice the radius of balance shaft gear11.

First and second idler gears2,10are loaded into carrier segment13of balance shaft housing4in direction of arrow B and arrow C, respectively. Axial shaft5is loaded into carrier segment13in direction of arrow D to retain first and second idler gears2,10. Balance shaft housing4is mounted to an engine (not shown) in direction of arrow D.

Balance shaft housing4includes balance shaft housing centerline28. In one embodiment, camshaft gear centerline8intersects balance shaft housing centerline28. In one embodiment, crankshaft gear centerline9intersects balance shaft housing centerline28. In one embodiment, balance shaft gear centerline42intersects balance shaft housing centerline28. In one embodiment, balance shaft housing centerline28is co-linear with the radius of first and second idler gears2,10such that the center of first and second idler gears2,10is disposed upon balance shaft housing centerline28. In the embodiment illustrated inFIGS. 5–8, only the radius of first idler gear52is co-linear upon balance shaft housing centerline28.

FIG. 3illustrates balance shaft housing4mounted to bearing caps18and22behind oil pump cover plate23.FIG. 4further illustrates crankshaft counterweights27. Those of ordinary skill in the art will readily recognize that dynamic masses are not illustrated on balance shaft12, but dynamic masses may be used in accordance with the invention.

As shown inFIGS. 1–4, camshaft gear1rotates one half speed of the first idler gear2. As further shown inFIGS. 1–4, second idler gear10includes a single gear. Those of ordinary skill in the art will readily recognize that the second idler gear10will require additional means to rotate the balance shaft gear in the opposite direction as the camshaft direction. It should also be noted that the means to rotate the balance shaft gear in the opposite direction include, in one embodiment, providing an even number of first idler gears between the camshaft gear and the crankshaft gear.

The size and pitch of first idler gear2and second idler gear is a design and manufacturing choice. The size and pitch of first and second idler gear2,10are further constrained by the distance between camshaft gear1and crankshaft gear7and the distance between crankshaft gear7and balance shaft gear11.

FIGS. 5–8illustrate another embodiment of an engine drive assembly150in accordance with the present invention. Engine drive assembly150includes camshaft gear51, crankshaft gear57, and balance shaft gear60. Engine drive assembly150further includes first idler gear52and second idler gear assembly53. Second idler gear assembly53includes crankshaft idler gear54and balance shaft idler gear55. Crankshaft gear57rotates in the direction indicated by arrow K. Second idler gear assembly53engages with crankshaft gear57and balance shaft gear60to rotate balance shaft gear60in the direction indicated by arrow L.

As in the embodiment illustrated inFIGS. 1–4, the gear teeth of first idler gear52engage with the gear teeth of camshaft gear51and crankshaft gear57such that the gear teeth intermesh and enable crankshaft gear57to drive camshaft gear51via first idler gear52. Similarly, the gear teeth of crankshaft gear57engage with the gear teeth of crankshaft idler gear54and the gear teeth of crankshaft idler gear54engage with balance shaft idler gear55. The gear teeth of balance shaft idler gear55engage the gear teeth of balance shaft60such that crankshaft gear57drives balance shaft60via second idler gear assembly53.

FIG. 6is a perspective view of the engine drive assembly150. Block59is shown. Furthermore,FIG. 6illustrates that the centerlines of camshaft gear51, crankshaft gear57and balance shaft60are parallel to each other and disposed along a block centerline61. As illustrated inFIG. 6, the centerlines of crankshaft idler gear54and balance shaft idler gear55lie parallel to the centerline of camshaft gear51. However, the centerlines of crankshaft idler gear54and balance shaft idler gear55could be disposed along block centerline61if the radiuses of crankshaft idler gear54and balance shaft idler gear55were set such that second idler gear assembly53could fit between crankshaft gear57and balance shaft gear60.

FIG. 7is a side view of the engine drive assembly150. Balance shaft71is shown connected to balance shaft gear60. Similarly, camshaft72is shown extending through block59and connected to camshaft gear51. Crankshaft73extends through block59and connects to crankshaft gear57. Bearing cap78supports balance shaft71.

FIG. 8illustrates cover90over engine drive assembly150. In one embodiment cover90assists in maintaining the position of second idler gear assembly53and first idler gear52. Similar covers may be used to maintain position of the first and second idler gears2,10depicted inFIGS. 1–4. In one embodiment, the cover is implemented as a carrier segment of a balance shaft housing.

The embodiments of the invention illustrated inFIGS. 1–8may also be implemented as a balance shaft gear carrier drive. In such embodiments, the balance shaft gear carrier drive includes a balance shaft housing and a camshaft gear supported by the balance shaft housing. The camshaft gear is engaged with a first idler gear that is further engaged with a crankshaft gear that is supported by the balance shaft housing. The crankshaft gear is further engaged with a second idler gear assembly that is engaged with a balance shaft gear. The balance shaft gear is supported by the balance shaft housing. As inFIGS. 1–8, the crankshaft gear drives the camshaft gear via the first idler gear and the crankshaft gear drives the balance shaft gear via the second idler gear assembly.

The size and pitch of first idler gear52, crankshaft idler gear54and balance shaft idler gear55is a design and manufacturing choice. The size and pitch of first idler gear52, crankshaft idler gear54and balance shaft idler gear55are further constrained by the distance between camshaft gear51and crankshaft gear57and the distance between crankshaft gear57and balance shaft gear60.

Use of a first and second idler gear assembly as described herein, in one embodiment, reduces parasitic energy loss within a balance shaft system by providing a compact system. As used herein, the term “gear” includes rotors or hubs connected to a shaft to rotate the shaft in a desired direction.

The disclosure herein encompasses a design wherein an idler gear assembly is included between the crankshaft gear and camshaft gear and a single gear is included between the crankshaft gear and balance shaft gear. While the embodiment of the invention disclosed herein is presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.