Patent Application
20090133653
The invention relates to a spur gear drive for an internal combustion engine including a crankshaft gear and at least one camshaft gear with intermediate spur gears for transferring power from the crankshaft gear to the camshaft gear or gears.
Spur gear drives of this type are known in practice for driving camshafts and engine auxiliary units. Such spur gear drives are used in particular in internal combustion engines with a large displacement volume as they are used for example in utility motor vehicles.
A spur gear drive for an internal combustion engine is also known from DE 25 02 033 A1, wherein, a camshaft gear is driven by a crankshaft gear via intermediate spur gears.
The gears of the spur gear drive transmit power and adapt the rotational speed to the requirements of the auxiliary units and of a first and, if applicable, a second camshaft. The transmission ratio between the crankshaft and camshafts of 1:0.5 required for a four-stroke internal combustion engine is generally realized by means of a double gear.
Double gears are however relatively complex to produce, and additionally require a relatively large installation space.
It is the object of the present invention to provide an improved spur gear drive for an internal combustion engine.
In a spur gear drive for driving the camshaft of an overhead valve internal combustion engine wherein the drive power is transmitted from the crankshaft to the camshaft via spur gears mounted on the crankshaft and the camshaft which is rotatably supported on the cylinder head, a third, intermediate, gear is adjustably supported in the power train between engine block-mounted gears and cylinder head-mounted gears so that changes in the distance between the crankshaft and the camshaft can be accommodated and, with the use of smaller gears, the spur gear drive becomes smaller and lighter overall.
According to a preferred embodiment of the invention, an oil pump for supplying the internal combustion engine with lubricant is arranged below the crankshaft axis as viewed in the direction of the latter, and therefore situated opposite the camshaft or camshafts with respect to the crankshaft axis. Accordingly, the spur gear according to this preferred embodiment is characterized in that an oil pump gear is arranged, with respect to the crankshaft axis, opposite the crankshaft gear. It is thereby possible for the spur gear drive to be of narrow design.
It is fundamentally possible for the oil pump gear to be driven directly by the crankshaft gear. According to one preferred embodiment of the invention, however, the oil pump gear is driven by the crankshaft gear via an oil pump intermediate gear since, with such a design, the desired transmission ratio can be realized with particularly small and light gears.
According to a further preferred embodiment of the invention, a fuel pump gear is provided in order that also the fuel supply to the internal combustion engine can be provided by means of the spur gear drive. The fuel pump gear is preferably driven by means of a first and a second intermediate gear, so that the position of the fuel pump can be selected such that as compact a design of the internal combustion engine as possible is obtained. A corresponding situation applies for the drive of a turbocompound for which, according to one preferred embodiment of the invention, a turbo-compound gear and—more preferably—a turbocompound intermediate gear are provided.
According to further preferred embodiments of the invention, it is intended to provide a compressor gear for a compressor, in order to also be able to drive a compressor with the spur gear drive. It is particularly advantageous if the compressor gear is driven by the first intermediate gear.
According to a particularly preferred embodiment of the invention, the first intermediate gear is embodied as a single gear with only one toothing. This reduces not only the required installation space and weight but also the production expenditure.
According to a further preferred embodiment of the invention, the turbocompound intermediate gear is embodied as a single gear with only one toothing. The required installation space, the weight and the production expenditure are also reduced in this way.
According to another further embodiment of the invention, the second intermediate gear is a double gear with two toothings. By means of this embodiment, it is possible to realize the desired transmission ratio between the crankshaft on the one hand and the camshaft(s) on the other hand of 1:0.5 with low weight and little required installation space. Here, the first intermediate gear which is a single gear can be designed with a relatively small diameter.
According to an alternative preferred embodiment of the invention, the first and the third intermediate gears are embodied as double gears with two toothings. Such an embodiment makes it possible to realize the desired transmission ratio between the crank shaft on the one hand and the camshafts on the other hand of 1:0.5 and at the same time to work with a particularly small diameter for the compressor gear, the second intermediate gear and the fuel pump gear.
If—as is provided according to a further preferred embodiment of the invention—the turbocompound intermediate gear is a double gear with two toothings, it is possible to situate the axis of the turbocompound gear closer to the crankshaft axis, as a result of which the spur gear drive is very compact. In addition, it is then also possible for the turbocompound gear to have a very small diameter.
According to a further particularly preferred embodiment of the invention, a second camshaft gear is provided in addition to the first camshaft gear, with the first camshaft gear actuating at least one first inlet valve and the second camshaft gear actuating at least one first outlet valve. With such an embodiment, it is possible to combine the advantages known from multi-valve technology with those of the invention.
If two camshaft gears are provided for two camshafts, as is provided according to a particularly preferred embodiment of the invention, it is advantageous to provide a distributor gear as a fourth intermediate gear, via which distributor gear the first and the second camshaft gears are driven by the third intermediate gear. The first and the second camshaft gears and the fourth intermediate gear are then preferably arranged on a cylinder head, so that when the cylinder head is assembled on a cylinder block, only the fourth intermediate gear must be placed in engagement with the third intermediate gear, which facilitates assembly.
According to a further aspect of the invention, it is provided that the third intermediate gear is arranged in a moveable fashion in order to compensate a variation in the axis spacing of the first camshaft gear and if appropriate the second camshaft gear with respect to the second intermediate gear. Such a variation of the axis spacing occurs in particular when the planar surfaces of the cylinder head and/or of the cylinder block are remachined, which is often the case in the course of an overhaul of an internal combustion engine. According to said aspect of the invention, a possibility is created for allowing for said variation, so that it is possible overall to work with smaller tolerances, which contributes to a reduction in the installation space.
For said adjustment of the axis spacing, the third intermediate gear is preferably mounted on an eccentric disc which can be adjusted by means of a spindle drive. Such an arrangement is particularly simple and space-saving.
The invention will become more readily apparent from the following description of particular embodiment thereof with reference to the accompanying drawings.
The preferred first embodiment of a spur gear drive 100 according to the invention as shown in
The camshaft gears 112, 114 are arranged for driving a first and a second camshaft. The spur gear drive 100 extends below the crankshaft gear 102, and at the end opposite the camshaft gears 112, 114, is provided with an oil pump gear 116 which is driven by the crankshaft gear 102 via an oil pump intermediate gear 118.
A compressor gear 120 is driven by the first intermediate gear 104. A fuel pump gear 122 is driven by the second intermediate gear 106. A turbocompound gear 124 is driven by means of a turbocompound intermediate gear 126.
While the first camshaft gear 112, the second camshaft gear 114 and the fourth intermediate gear 110, which serves as a distributor gear, are mounted on a cylinder head (not shown), the remaining gears are mounted on a gear housing 128 which is preferably part of the engine block.
With regard to the individual gears, the following gear data have been proven to be particularly advantageous, so that these data are considered as relating to a particularly preferred embodiment of the invention:
In the above table, the variable t represents the number of teeth of the relevant gear, with a further embodiment being indicated in parenthesis.
According to the invention, and in particular according to the preferred embodiment of the invention described above, there is a resulting advantage of a relatively small first intermediate gear 104. In addition, the first intermediate gear 104 is arranged within the contour of the engine block. One gear fewer is required than in comparable spur gear drives. All the gears can and do preferably have straight toothings, which facilitates assembly. In addition, the flywheel housing flange on the housing block can be reduced in size. The oil pump rotational direction is reversed. The above-described embodiment can also be used for relatively large internal combustion engines, for example for a 12.8 l diesel unit.
The second embodiment shown in
As in the first embodiment, an oil pump gear 216 is provided which is situated, with respect to the camshaft axis (not shown), opposite the camshaft gears 212, 214. However, the oil pump gear 216 is driven directly by the crankshaft gear 202.
A compressor gear 220 is driven by the first intermediate gear 204. A fuel pump gear 222 is driven by the second intermediate gear 206. A turbocompound gear 224 is driven by a turbocompound intermediate gear 226.
In contrast to the first embodiment, in the spur gear drive 200, the first intermediate gear 204 is a double gear, with the larger toothing being in engagement with the crankshaft gear 202, and with the smaller toothing driving the second intermediate gear 206 and the compressor gear 220. The second intermediate gear 206 is a single gear which is in engagement with the fuel pump gear 222 and the third intermediate gear 208. The third intermediate gear 208 is again a double gear whose larger toothing meshes with the second intermediate gear 206, with the smaller toothing of the third intermediate gear 208 driving the fourth intermediate gear 210.
In addition, the turbocompound intermediate gear 226 is embodied as a double gear, with the larger toothing being in engagement with the crankshaft gear 202 and the smaller toothing meshing with the toothing of the turbocompound gear 224.
While the first camshaft gear 212, the second camshaft gear 214 and the fourth intermediate gear 210 are mounted on a cylinder head (not shown), the remaining gears are mounted on a gear transmission housing 228, with said gear transmission housing 228 preferably being formed in one piece with the engine block.
In connection with
The third intermediate gear 208 is rotatably supported by a bearing journal 232 which is mounted to the cylinder block (not shown—
