Abstract:
A control device for camshaft systems of an internal combustion engine with n banks of cylinders arranged in a V-shaped configuration. The control device has a distribution system with a first distributor gear which intermeshes with an output gear arranged on a crankshaft of the internal combustion engine. The distribution system has m&lt;n secondary distributor gears which intermesh with the first distributor gear and transmit a driving force to the n camshaft systems of the n banks of cylinders through n endless-chain drives.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a control device for camshaft systems of an internal combustion engine with n banks of cylinders arranged in a V-shaped configuration, the control device having a distribution system with a first distributor gear, which intermeshes with an output gear arranged on a crankshaft of the internal combustion engine. 
     A central output of generic type for an internal combustion engine of a motorcycle is disclosed by U.S. Pat. No. 4,671,223. In this case a straightforward gear drive is produced, a separate distribution system being assigned to each camshaft system of one bank of cylinders. The gears of each distribution system are mounted in a respective frame. The straightforward gear drive has the disadvantage that it generates very loud noise. Furthermore, having a separate output line for each camshaft system makes this arrangement mechanically expensive, and it takes up a lot of space. A central output for the control device of an internal combustion engine for a motor vehicle would not be practically feasible with this system, since all cylinder banks would have to have at least one division. This would lead, however, to considerable mechanical weakening of the engine block, which with the torques and forces occurring in motor vehicles could not be tolerated. 
     A central control output is furthermore disclosed in the article “The Porsche 4.5-liter Racing Sports Car, Type 917” by H. Metzger, which appeared in the offprint from a German periodical, Automobiltechnische Zeitschrift (ATZ), Vol. 71 No. 9/12/1969, pages 313 to 320 for an air-cooled four-stroke engine with two flat rows of cylinders, which is designed especially for racing purposes. The drive to four camshafts comes from a central output gear on the crankshaft to both rows of cylinders, in each case by way of five straight-toothed gears on needle-roller bearings. In other words, a separate control device is assigned to each row of cylinders. The five gears arranged between crankshaft and each of the camshafts are in each case arranged in a gear housing, which can be bolted to a crankcase. This, too, is a straightforward gear drive, which has the aforementioned disadvantage that it generates considerable noise levels. In the case of a racing car for a Constructors&#39; World Championship this may not be critical, but for a comfortable motor vehicle for day-to-day use in public road traffic it is unacceptable. 
     SUMMARY OF THE INVENTION 
     The object of the present invention therefore is to provide a simple control device of the above-mentioned type that takes up little overall space and overcomes the above-mentioned disadvantages. 
     To this end it is proposed, according to the invention, that the distribution system have m&lt;n secondary distributor gears, which intermesh with the first distributor gear and transmit a driving force to the n camshaft systems of the n banks of cylinders through n endless-chain drives. 
     This has the advantage that all camshaft systems of respective cylinders can be driven by a single distribution system proceeding from the middle of the internal combustion engine, for example. This advantageously simplifies the mechanical construction of the control device and reduces the overall space required and the weight. 
     A particularly space-saving central output for the control device is obtained by arranging the output gear centrally on the crankshaft. 
     It is advisable if m=n−1 or m=n−2, it being particularly preferable if n=2, 3 or 4. 
     For ease of assembly the first and the secondary distributor gears are arranged in a common carrier, which when pre-assembled can be fixed to a crankcase of the internal combustion engine. For example, with a central output for the control device, bolting the carrier onto the crankcase provides additional reinforcement for the engine block, which is actually mechanically weakened by corresponding recesses required for the central output. 
     Simple assembly of the control device, for example in a recess in a crankcase for a central output, is achieved by providing a module that carries the endless-chain drive between each secondary distributor gear and each camshaft system. The module being pre-assembled so that it carries a chain sprocket, which can be frictionally and coaxially fitted to the respective secondary distributor gear, at one end and at least one camshaft gear on an opposite end, the endless-chain drive passing around the chain sprocket and the camshaft gear. 
     A suitable transmission ratio between the crankshaft and the respective camshaft system is effectively achieved by selecting a tooth ratio of the secondary distributor gear to the chain sprocket such that a crankshaft to camshaft system transmission ratio of 2:1 is obtained. 
     Secure guiding of the chain of the endless-chain drive is achieved in that the module has a U-shaped guide plate for the endless-chain drive on the idle strand side. 
     Reliable, frictional running of the chain of the endless-chain drive with low mechanical wear and low noise is achieved in that the module has a chain-tensioning fixture on the load strand side. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features, advantages and advantageous developments of the invention follow from the following description of an example of an embodiment of the invention, with reference to the drawings attached, in which 
     FIG. 1 shows a front view of a preferred embodiment of a control device according to the invention, 
     FIG. 2 shows a perspective view thereof, 
     FIG. 3 shows a front view of a carrier for a distribution system of a control device according to the invention, 
     FIG. 4 shows a top view thereof, 
     FIG. 5 shows a sectional view along the line A—A in FIG. 3, 
     FIG. 6 shows a sectional view along the line B—B in FIG.  3  and 
     FIG. 7 shows a side view of a module of a control device according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment of a control device according to the invention represented in FIGS. 1 and 2 comprises an output gear  12  arranged on a crankshaft  10 , which gear intermeshes with a first distributor gear  14 . Two secondary distributor gears  16  and  18 , which are coaxially arranged and frictionally connected with chain sprockets  20 ,  22  and  24  of each module  26 ,  28  and  30  respectively, intermesh with a distributor gear  42 , frictionally coupled to the first distributor gear  14 , only the intermediate gears  20  and  24  being visible in FIGS. 1 and 2. The chain sprocket  22  is hidden behind the chain sprocket  20  (cf. FIG.  5 ). 
     Power is transmitted by way of respective endless-chain drives  32  to each of the camshaft gears  34 , which are frictionally connected to corresponding camshafts (not shown). In so doing, the modules  26 ,  28  and  30  carry the respective chain sprockets  20 ,  22 ,  24  at one end and the camshaft gears  34  at an opposite end, the respective endless-chain drive  32  passing around the chain sprockets  20 ,  22  and  24  and the associated camshaft gears  34 . The endless-chain drive  32  results in an essentially vibration-neutralized or vibration-damped power transmission. 
     In the embodiment represented in FIG. 1, the output gear  12  of the crankshaft  10  also intermeshes with a further distributor gear  36 , which by way of a frictionally coupled gear  33  intermeshes with a first intermediate gear  35 , which in turn intermeshes with a secondary intermediate gear  38 . The secondary intermediate gear  38  in turn intermeshes with a drive gear  40  of an oil pump (not shown), so that the crankshaft  10 , by way of its output gear  12 , simultaneously drives the oil pump. The distributor gear  35  has, for example, thirty-seven teeth, the first intermediate gear  36  eighteen teeth, the secondary intermediate gear  38  eighteen teeth and the drive gear  40  eighteen teeth. 
     For the control device, a transmission ratio from the crankshaft  10  to the camshaft gears of  2 : 1  is needed. This is achieved, for example, by thirty-eight teeth on the output gear  12 , sixty-four teeth on a smaller gear rim  42  of the intermediate gear  14 , fifty-seven teeth on the secondary distributor gears  16 ,  18 , eighteen teeth on the chain sprockets  20 ,  22 ,  24  and thirty-two teeth on the camshaft gears  34 . 
     The embodiment of a control device according to the invention represented in FIGS. 1 and 2 is designed for an internal combustion engine with three rows of cylinders arranged in a V-shaped configuration and denoted below by the letters A, B and C, each module  26 ,  28  and  30  being assigned to a row of cylinders A, B or C or to a respective camshaft system of a row of cylinders A, B or C. It will be immediately apparent that all three camshaft systems of the three rows of cylinders are actuated by just one distribution system  14 ,  16 ,  18 . 
     The arrangement represented by way of example is thereby particularly suitable for a central output for the control device, since in order to bring the control device out away from the crankshaft  10 , that is from an inner area of a crankcase (not shown), to the external camshaft gears  34 , only one of the rows of cylinders, namely the middle cylinder row B, needs to have a central recess or division. The adjacent rows of cylinders A and C may be designed without a division as continuous cylinder rows A and C. The camshaft gears  34  of the two adjacent rows of cylinders A and C are actuated by the modules  26  and  30  likewise proceeding from the middle row of cylinders B. 
     The first and the secondary distributor gears  14 ,  16  and  18  are arranged in a common carrier  44 , as can be seen from FIGS. 3 and 4. Said carrier  44  holds the first distributor gear  14  and the secondary distributor gears  16  and  18 , it being possible, for example, to insert the pre-assembled carrier into a recess or division in the middle bank of cylinders B and to bolt it to the crankcase. Respective insertion guides  46 ,  48  and  50  for each of the modules  26 ,  28  and  30  are furthermore formed on the carrier  44 . After fixing the carrier  44  on the crankcase, the modules  26 ,  28  and  30  each with pre-assembled chain sprockets  20 ,  22  and  24  together with pre-assembled camshaft gears  34  and endless-chain drive  32  can be inserted into said insertion guides  46 ,  48  and  50 . As soon as all gears are at their predetermined location, they can be rotatably fixed to the corresponding shaft and bearings. 
     This is the case for the chain sprockets  20 ,  22  together with the secondary distributor gear  16  in FIG.  5 . When fitted on a common shaft  52 , these gears  16 ,  20  and  22  are non-positively connected to one another by frictional adhesion, a central bolt  54  fixing this arrangement. The shaft  52  is mounted so that it can rotate by means of ball bearings  56  in relation to the carrier  44 . The central bolt furthermore fixes a gear  58 , which serves as drive for a water pump (not shown). 
     FIG. 6 illustrates the arrangement of the secondary distributor gear  18  with the chain sprocket  24  in the assembled state. In this case, a shaft  60  is provided, which is fixed by two central bolts  62  and  64 . The central bolt  64  furthermore fixes a gear  66 , which serves for a drive for a further water pump (not shown). The two aforementioned water pumps are, for example, arranged directly adjacent to the carrier  44  in respective V-shaped intermediate spaces between the rows of cylinders A and B or B and C in such a way that their drive gears intermesh directly with each of the gears  58  and  66  respectively. 
     FIG. 7 illustrates, by way of example, the module  26  for cylinder row A. Said module  26  comprises a frame  68  and a U-shaped guide plate  70  on the idle strand side with a running surface  72  for the chain of the endless-chain drive, not shown in FIG.  7 . When pre-assembled, the chain passes around the chain sprocket  20  and the camshaft gears  34  and holds these fast to the frame  68 , no further fixing of any kind being otherwise provided for the chain sprocket  20  and the camshaft gears  34 . Only after fitting or inserting the modules  26 ,  28  and  30  are these finally rotatably fixed by means of corresponding shafts, such as the aforementioned shafts  52  and  60  for the chain sprockets  20 ,  22  and  24 , for example. A chain tensioning fixture  72 , for example, is provided on the load strand side, as can be seen from FIG.  2 .