Patent Application
20060035738
The invention relates to a belt drive, especially a timing-belt drive for an internal-combustion engine.
In the class-forming DE 195 20 508 A1, a belt drive for an internal-combustion engine is described, with a driving gear of a driveshaft, at least one driven gear of a driven shaft, and a belt drive means, wherein, due to its noncircular shape and its phase position, the driving gear or the driven gear imparts additional irregularity to the belt drive, which leads to stable running of the belt means.
The effectiveness of the noncircular gear depends on the exact setting of the phase position and its constancy. However, the above document lacks any indication on how the phase position of the noncircular gear is to be set and maintained.
The invention is based on the objective of providing a belt drive, in particular a timing-belt drive for an internal-combustion engine, whose noncircular gear necessary for stable running of the belt means can be mounted easily and in phase, as well as with a stable position.
The objective is addressed according to the invention in that the driving gear or the driven gear which imparts additional irregularity to the belt drive due to its noncircular shape and its phase position and leads to stable running of the belt means, has in its in-phase rotational position a rotationally fixed connection to its driving or driven shaft
Because the noncircular gear in its in-phase rotational position has a rotationally fixed connection with its shaft, the in-phase rotational position is achieved and also held permanently easily and reliably.
It is advantageous that the rotationally fixed connection between the noncircular gear and its shaft is realized by a positive fit. This is especially suitable if precision in the setting and long service life are required.
It is also advantageous that the positive fit is achieved through corresponding, matching rotationally non-symmetric contact surfaces of the noncircular gear and the associated shaft. Since now there is only one possible way for assembly, the rotationally non-symmetric contact surfaces exclude incorrect assembly and therefore simplify the assembly of the timing-belt drive.
The object of the invention is also addressed by a further feature of the invention. After the driveshaft and the driven shaft have been positioned relative to each other, the in-phase rotational position of the noncircular gear is set with a setting device. This has the advantage that a conventional timing-belt drive can be retrofitted with a noncircular gear without high expense.
An advantageous setting device, which adapts to the geometry of the noncircular gear, is mounted or aligned on the engine and disassembled after the setting. An axial pin, for example, mounted eccentrically on the noncircular gear, or a corresponding bore can be used as a geometrical feature, which comes into contact with a complementary part of the setting device and thus fixes the in-phase rotational position of the noncircular gear.
The object of the invention is also addressed by further features of the invention, that is, by means of a visual setting aid. This is realized in that, after the driveshaft and the driven shaft are positioned relative to each other, a marking on the noncircular gear is brought into alignment with a counter marking. Then the noncircular gear is located in the in-phase rotational position relative to its shaft and is connected to this shaft.
It is advantageous if the counter marking is fixed relative to the engine and located on the crankcase or on a cover fixed to the crankcase.
An alternative visual setting aid is provided in that the counter marking is arranged on a shaft, that is, the shaft holding the marked noncircular gear. The counter marking can be arranged on the periphery of the shaft and in the axial direction or on the front side of the shaft and radially.
Additional features of the invention follow from the description below and the drawings, in which embodiments of the invention are shown schematically.
Shown are:
a a longitudinal section through the noncircular toothed belt gear of
a a longitudinal section through the noncircular toothed belt gear of
a a longitudinal section through the noncircular toothed belt gear of
a a longitudinal section through the noncircular toothed belt gear of
a a longitudinal section through the noncircular toothed belt gear of
a a longitudinal section through the noncircular toothed belt gear of
a a longitudinal section through the noncircular toothed belt gear of
In today's conventional timing-belt drives, the assembly of the toothed belt gears is often realized through a friction fit by means of a press fit. This enables the equalization of tolerances, which is necessary, above all, in timing-belt drives.
At first, the driving crankshaft and the driven camshaft are positioned relative to each other. Then the driving and driven gears are placed on the crankshaft and camshaft and the belt means are set. Then the crankshaft and the camshaft are connected to the driving gear and driven gear after successful tolerance compensation through a friction fit. Here, there is no positional allocation between the shafts and the gears. This results in no disadvantages, because the gears are round. However, the situation changes for noncircular gears, which must be mounted at a specific relative rotational position relative to their shaft.
In FIGS. 1 to 7a, toothed belt gears 1 to 7 are shown. They are used as driving gears of a not-shown timing-belt drive of an internal-combustion engine. Their teeth 8 are arranged on an ellipse 9 with a major axis 10 and a minor axis 11. In this way, the required noncircular shape is achieved.
The gears 1 to 7 have differently shaped central openings. They are pushed onto a matching free end of a not-shown crankshaft and tightened to the crankshaft.
In order to achieve an in-phase rotational position relative to the crankshaft, there is a positive fit between the toothed belt gears 1 to 5 and the crankshaft. This is realized in various ways. The toothed belt gears 1 to 5 represent examples from an unlimited number of conceivable variants, which all satisfy the condition of rotationally non-symmetric contact surfaces.
The noncircular toothed belt gear 1 of
In the noncircular toothed belt gear 2 of
In the noncircular toothed belt gear 3 of
In the noncircular toothed belt gear 4 of
In the noncircular toothed belt gear 5 of
The noncircular toothed belt gear 6 of
The in-phase rotational position of the noncircular toothed belt gear 7 of
The counter marking can also be mounted on the shaft holding the marked noncircular gear, that is, on the periphery of the shaft in the axial direction of this shaft or on its front side in the radial direction.
The assembly of a timing-belt drive with a noncircular gear differs from the assembly of a conventional timing-belt drive merely through the noncircular gear, which is aligned in a defined way relative to a driveshaft or driven shaft. All of the other gears can be assembled without being aligned and fixed with a friction fit after successful tolerance compensation.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 039 070.3 | Aug 2004 | DE | national |
| Number | Date | Country | |
|---|---|---|---|
| 60604110 | Aug 2004 | US |
