Abstract:
A device for electrically adjusting the relative rotation of two shafts, particularly a camshaft ( 15 ) in relation to a crankshaft of an internal combustion engine is provided. The adjusting device includes an adjusting gear system which is embodied as a triple-shaft gear mechanism and is provided with a crankshaft-fixed input part, a camshaft-fixed output part, and an adjusting shaft ( 13 ) that is connected in a torsion-proof manner to an electric adjusting motor shaft ( 32 ) of an electric adjusting motor ( 3 ). The adjusting motor ( 3 ) is configured as a brushless DC motor having a housing-fixed stator ( 35 ) and a permanent magnet rotor ( 34 ). A high degree of adjustment accuracy and adjustment speed are provided with minimal space requirements and low power consumption. This is achieved through the use of a double eccentric gear mechanism ( 2 ) and a double planetary gear mechanism, which are provided with a speed reduction of up to about 1:250 and low friction, as an adjusting gear system while using a highly inductive permanent magnet rotor for the adjusting motor ( 3 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of PCT/EP2003/011286, filed Oct. 11, 2003, which is incorporated herein by reference as if fully set forth. 

   FIELD OF THE INVENTION 
   The invention relates to a camshaft adjuster for electrically adjusting the position of the angle of rotation of the camshaft in relation to the crankshaft of an internal-combustion engine, and in particular to an adjusting gear mechanism, which is formed as a triple-shaft gear mechanism and which has a crankshaft-fixed driving part, a camshaft-fixed driven part, and an adjusting shaft connected in a torsion-proof manner to an adjusting motor shaft of an electric adjusting motor, wherein the adjusting motor is formed as a brushless DC motor with a housing-fixed stator and a permanent magnet rotor. 
   BACKGROUND 
   For hydraulic camshaft adjusting systems, in which the adjustment is realized through the motor oil pressure, the function of the camshaft adjuster is greatly dependent on the temperature of the motor oil. At low temperatures and thus viscous oil, no regulation or adjustment is possible, because the oil can flow not at all or only very slowly through the oil lines to the adjuster or away from the adjuster. A high oil pressure is achieved but no or only minimal volume flow. At high temperatures, the opposite occurs. The oil is very thin, which causes a large amount of leakage. Therefore, high pressure is not established and only slow adjustment can be realized or the set position can be maintained only poorly. In addition, the oil pressure and thus the function of the camshaft adjuster depends on the engine speed of the internal-combustion engine. In contrast, electric camshaft adjusters function independent of oil pressure. Therefore, the previously discussed problems do not occur, so that the operating range and the operating reliability of the adjuster are increased. 
   In DE 41 10 195 A1, an adjusting device for electrical adjustment of the relative position of the angle of rotation of two shafts, especially a camshaft in relation to a crankshaft of an internal-combustion engine, with an adjusting gear mechanism formed as a triple-shaft gear mechanism is disclosed, which comprises a crankshaft-fixed driving part, a camshaft-fixed driven part, and an adjusting shaft connected in a torsion-proof manner to an adjusting-motor shaft of an electric adjusting motor, wherein the adjusting motor is formed as a brushless DC motor with a housing-fixed stator and a permanent magnet rotor. The adjusting gear mechanism is formed as a planetary gear mechanism, whose self-locking is mentioned multiple times and is emphasized as an advantage. 
   However, such self-locking produces disadvantages in terms of the adjusting speed and the necessary adjusting energy. In addition, the unbalanced eccentric drive leads to non-quiet running when the adjusting motor is working. 
   SUMMARY 
   Therefore, the invention is based on the objective of providing an adjusting device for electric adjustment of the position of the angle of rotation of a camshaft in relation to a crankshaft of an internal-combustion engine, which features high adjustment accuracy and adjustment speed with low space and energy requirements. 
   According to the invention, the problem is solved by providing the adjusting gear mechanism preferably formed as a double eccentric gear mechanism or the adjusting gear mechanism is preferably formed as a double planetary gear mechanism. Both adjusting gear mechanisms are distinguished by high speed reduction of preferably ≦250 and low friction. The high speed reduction enables precise angle setting and permits the use of small, fast-running adjusting motors. These save structural space and costs. The low friction has a positive effect on the power consumption and the stator heating in adjusting operation. In addition to the double eccentric and double planetary gear mechanisms, among other types, other high speed-reducing adjusting gear mechanisms, for example, single eccentric and single planetary gear mechanisms, shaft gear mechanisms, such as, for example, the harmonic-drive gear mechanism, twin-spin gear mechanisms, as well as wobble and reduction-servo gear mechanisms, can also be considered. 
   The adjusting motor can be configured with or without brushes. The brushless version offers the advantage of lower friction and the lack of wear, which more than compensates for the additional expense for electronic commutation. 
   The housing-fixed stator enables a simple, reliable, and wear-free power supply to the stator windings. The highly inductive permanent magnet rotor containing rare-earth metals has a high torque and self-holding moment, which brings and fixes the camshaft quickly into the set position in connection with the high speed reduction of the adjusting gear mechanism and despite its low friction and lack of self-locking. The motor can also be formed as a disk armature. 
   In addition to the typical aligned arrangement of the adjusting motor and adjusting gear mechanism, there is also the possibility of a radial allocation of the same with, for example, a connection through a bevel gear pair or a worm gear pair. In addition, it is conceivable to arrange the adjusting motor parallel to the adjusting gear mechanism if there is a lack of axial installation space. A connection between the two can be realized through a toothed-belt or chain drive or by means of toothed wheels or a cardan shaft. In this way, a large degree of flexibility is given in terms of shape and volume of the adjusting device. 
   A contribution to minimizing the friction of the adjusting gear mechanism and adjusting motors is realized by forming their bearings preferably as roller bearings. However, sliding bearings can also be used, if cost and installation-space reasons are dominant. This applies, for example, for the bearing of the driving wheel. 
   In one advantageous configuration of the invention, central tension screws or a circular spline connection is provided, which has cylindrical screw heads or a cylindrical circular spline bore hub, which are used as a bearing surface for roller bearings, for torsion-proof connection of the camshaft and adjusting gear mechanism. Therefore, separate space for the bearing is eliminated, which saves structural length. The circular spline connection also offers the advantage that no additional components, such as feather keys or screws, are required. Therefore, installation space is also saved, which can be used for other purposes. 
   The advantage of reduced installation space also offers a direct screw connection. In this connection, the adjusting gear mechanism is screwed directly onto the camshaft. For this purpose, on the drive-side end of the camshaft, a camshaft journal with external threading is required and on a camshaft-fixed component of the adjusting gear mechanism, internal threading is required. In this way, the adjusting gear mechanism can be screwed directly onto the camshaft and tightened by means of a tool like for the circular spline connection. Both in the circular spline connection and also in the direct screw connection, an exact position-ing of the adjusting gear mechanism is not possible and also not necessary in the controlled case. 
   An advantageous improvement of the invention can be seen in that for torsion-proof connection of the adjusting shafts and the adjusting-motor shafts, a one-piece configuration of the two shafts is provided in the shape of a single hollow shaft (integrated adjusting motor) and between both shafts, a rotational backlash-free, disengaging coupling is provided for connecting the separate shafts (separate adjusting motor). The solution with integrated adjusting motor is simpler in production, because it can get by with only two instead of three bearings for both shafts. In addition, the otherwise necessary coupling can be eliminated. However, the integrated adjusting motor cannot be completed in advance. It must be completed with the help of an assembly tool on the adjusting gear mechanism itself. 
   In contrast, in the solution with separate adjusting motor, at least two, but preferably three, bearings are needed for the two separate shafts. In addition, a rotational backlash-free, disengaging coupling between both shafts is required, which, however, permits advance completion of the adjusting motor and simple assembly of the same on the adjusting gear mechanism. 
   The assembly of the integrated adjusting motor and the centering of its stator on its permanent magnet rotor is simplified such that an assembly tool is provided, whose preferably three equal vanes arranged at equal spacing can be inserted through three corresponding assembly slots in the outer adjusting motor housing into the air gap between the permanent magnet rotor and the stator with slight radial play and the assembly slots can be closed by a fitting closing cover. 
   As rotational backlash-free, disengaging couplings, preferably two-edge couplings, feather key couplings, or splined shaft couplings are considered. Profiled shaft couplings, such as polygonal, toothed, and four-edge or six-edge shaft couplings are also conceivable. 
   The assembly of the adjusting motor is realized through simple insertion of the coupling part located on the free end of the adjusting motor shaft into the complementary coupling part of the adjusting shaft. Because both coupling parts fit together with practically no backlash and are self-centering, absolutely no additional measures are required for the assembly and disassembly. The axial movement of the shaft connections permits unimpaired heat expansion of the camshaft, adjusting shaft, and adjusting motor shaft. 
   For the bearing of the hollow shaft, it is advantageous that this has an outer grooved ball bearing in front of the permanent magnet rotor and the other hollow shaft has another internal rotor bearing on another cylindrical screw head of an elongated, central tension screw in the region of the permanent magnet rotor. 
   If the hollow shafts have at least one outlet bore hole and an adjusting motor-side closing stopper, then the oil can be removed and thus the rotary mass moment of inertia of the hollow shafts can be minimized. At the same time, supply of oil from the hollow shafts into the interior of the adjusting motor is prevented. 
   Corresponding to its different function, it is advantageous that the adjusting gear mechanisms have oil-lubricated roller bearings and the adjusting motors have oil-lubricated and grease-lubricated roller bearings. The roller bearings of the adjusting motor must partially also take over sealing functions for its interior. 
   A simple and effective lubrication of the adjusting gear mechanism and the oil-lubricated bearing of the adjusting motors is achieved, such that the lubricating oil is fed from the oil supply of the end bearing of the camshaft near the gear mechanism through lubricating-oil bore holes into the region of the adjusting gear mechanism near the axle and from there through centrifugal force to the bearings and into the peripheral region, as well as farther into the space of the cylinder head, where it is used for centrifugal oiling or as spray oil for lubricating the oil-lubricated roller bearing of the adjusting motors. 
   It is advantageous that the grease-lubricated roller bearing of the adjusting motors have one seal on both bearing sides and the oil-lubricated roller bearings of the adjuster motors have one seal on the adjusting motor side. In grease-lubricated roller bearings, the two-sided seals are used for protection against loss of lubricant. In oil-lubricated roller bearings, the seal on the adjusting motor side permits the entrance of the lubricating oil to the bearing and simultaneously prevents the loss of oil in the adjusting motor interior. 
   In an alternative solution of lubricating the roller bearings of the adjusting motors, their roller bearings are formed without seals, but a screen or filter for protection against metal particles is arranged at least on the adjusting gear mechanism side and in this case, the stator, together with a PC board or Hall sensor, has an injection-molded part or a cover film made from heat-resistant and oil-resistant plastic. In this way, destruction due to motor oil of the insulating lacquer of the stator winding of the adjusting motors and their PC boards or Hall sensors is prevented. In this case, motor oil is permitted in the interior of the adjusting motor, at the same time the screen or filter prevents the penetration of iron residue in the motor oil, which would become fixed to the permanent magnet rotor. An advantage of this type of seal in comparison with radial shaft seals is their lack of frictional resistant and their small structural length. 
   The structural length of the adjusting motor is also reduced, in that the grease-lubricated roller bearings of an adjusting motor are arranged on a preferably solid adjusting motor shaft directly next to the permanent magnet rotor and at least partially within the winding heads of the stator. The solid adjusting motor shaft has a relatively small diameter, which offers sufficient space for housing the roller bearings within the winding heads. 
   The centrifugal disk mounted on the gear mechanism-side outer side of the grease-lubricated roller bearing acts like a labyrinth seal as an additional seal against motor oil. Therefore, in connection with the two-side sealed, grease-lubricated roller bearings, a lubricating oil-free interior of the adjusting motor is achieved, whereby special lubricating-oil protection of the stator becomes unnecessary. 
   Because the length of the permanent magnet rotor is increased relative to the stator by its maximum difference in length due to expansion, the active length of the stator remains constant even at different component temperatures. The same effect is achieved with a correspondingly lengthened stator, but with the acceptance of increased structural length. 
   The housing-fixed stator can also be cooled advantageously by air or coolant. Therefore, its load can be increased and thus its structural volume can be decreased without reducing its service life. 
   It has been shown to be advantageous that the adjusting shaft of the double eccentric gear mechanism is formed as a double eccentric shaft with equal eccentrics, which are offset by 180° and which drive equal spur pinions that mesh with equal internal gearing of a crankshaft-fixed ring gear, whose drive moment can be transferred by means of driving pins to a camshaft-fixed closing wall. The equal eccentrics offset by 180° have the effect, together with the equal spur pinions, of total mass balancing and therefore vibration-free running of the double eccentric gear mechanism in the adjusting operation. The crankshaft-fixed ring gear can also have a divided configuration, wherein the tooth backlash can be overcome by mutual tensioning of the two parts. 
   It is also advantageous that the driving pins are pressed into axis parallel pin bore holes of the closing wall and engage with a positive fit in axis parallel spur pinion bore holes of the spur pinions. 
   For the assembly of the double eccentric gear mechanism, it is advantageous that the diameter of the spur pinion bore holes corresponds at least to the diameter of the driving pins increased by twice the eccentricity of the eccentrics and that the spur pinion bore holes and the pin bore holes have equal pitch diameters and equal spacing. 
   One advantageous improvement of the invention is provided in that the adjusting shaft of the double planetary gear mechanism is formed as a sun wheel, which is supported on a central tension screw in a sun wheel bearing and which is connected in a torsion-proof manner to a not-shown adjusting motor by means of a splined shaft coupling. In addition, the sun wheel meshes with first planetary gears, which are each connected in a torsion-proof manner to coaxial second planetary gears of smaller or larger diameter according to the design. The desired large speed reduction of this adjusting gear mechanism follows from the slightly different number of teeth of the planetary gears and the ring gears. 
   Advantageous structural configurations of the double planetary gear mechanism are provided in that the first planetary gears mesh with internal gearing of a crankshaft-fixed ring gear and the second planetary gears mesh with internal gearing of smaller or larger diameter of a camshaft-fixed ring gear and that the planetary gears are formed in one piece and supported by means of planetary bearings on axis parallel connecting pins, which are connected to a planetary carrier that is supported by rollers by means of a planetary carrier bearing on another cylindrical screw head. 
   An alternative shaping of the planetary gears is characterized in that separately manufactured planetary gears are connected in a torsion-proof manner by a splined shaft and other separately manufactured planetary gears are connected in a torsion-proof manner by a feather-key connection and are supported by rollers directly in the planetary carrier and its closing plate. 
   Advantageously, the drive and driven shafts of the adjusting gear mechanism can be connected by a biased spring, preferably a spiral spring, which moves the camshaft into a starting or emergency-running position against the friction moment of the camshaft if the power or the adjusting motor fails. The spiral spring has a fail safe function, because if the internal-combustion engine dies, also in the case of loss of power, the camshaft moves into a position, from which restarting and thus at least emergency operation is possible. The spiral spring also overcomes the friction moment of the valve drive and possible seizing in the adjusting gear mechanism. Instead of the spiral spring, other springs can also be used. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional features of the invention emerge from the following description and the drawings, in which several preferred embodiments of the invention are shown schematically. 
     In the drawings: 
       FIG. 1  is a longitudinal section through the adjusting device according to the invention with an eccentric gear mechanism and an adjusting motor, whose adjusting motor shaft is connected in a disengaging way by a two-edge shaft coupling to a double eccentric shaft of a double eccentric gear mechanism, which is supported on the cylindrical head of a central tension screw by means of a needle bushing; 
       FIG. 2  is a cross section X—X through the enlarged two-edge shaft coupling from  FIG. 3 ; 
       FIG. 3  is an enlarged longitudinal section through the two-edge shaft coupling from  FIG. 2 ; 
       FIG. 4  is a view of the double eccentric gear mechanism from  FIG. 1 , but with a standard tension screw and a bearing bushing, as well as a feather key shaft coupling between double eccentric and adjusting motor shaft; 
       FIG. 5  is a view of the double eccentric gear mechanism from  FIG. 1 , but with a circular spline connection between the double eccentric gear mechanism and the camshaft; 
       FIG. 6   a  is a cross section through a circular spline connection fitted one in the other with backlash; 
       FIG. 6   b  is a view of the circular spline connection from  FIG. 6   a  in slightly rotated, backlash-free state; 
       FIG. 6   c  is a view of the circular spline connection from  FIG. 6   b  in positive and non-positive connection through further rotation; 
       FIG. 7  is a longitudinal section through the adjusting device according to the invention from  FIG. 1 , but with double eccentric and adjusting motor shaft, which is formed as a hollow shaft in one piece and which has an outer grooved ball bearing in addition to the eccentric shaft bearing; 
       FIG. 8  is a cross section through an assembly tool for assembling the stator from  FIG. 7 ; 
       FIG. 9  is a plan view of the assembly tool from  FIG. 8 ; 
       FIG. 10  is a longitudinal section through the adjusting motor from  FIG. 7  in the assembled state with an arrow in the assembly direction of the stator; 
       FIG. 11  is a partial section of the electric motor housing from  FIG. 10  with assembly slots for the assembly tool; 
       FIG. 12  is a longitudinal section through a closing cover for the assembly slots from  FIG. 11 ; 
       FIG. 13  is a longitudinal section through a variant of the adjusting device from  FIG. 7 , in which the one-piece hollow shaft is supported with the eccentric shaft bearing and with an internal rotor bearing on an extended tension screw; 
       FIG. 14  is a longitudinal section through an adjusting gear mechanism formed as a double planetary gear mechanism, with one-piece planetary gears supported on planetary bearings; 
       FIG. 15  is a longitudinal section through the planetary gears for the double planetary gear mechanism from  FIG. 14 , but formed separately and connected in a torsion-proof manner to an externally supported splined shaft; 
       FIG. 15   a  is a cross section through a planetary gear from  FIG. 15 ; 
       FIG. 16  is a longitudinal section through separately formed planetary gears, of which one has a shaft butt end, on which the other is fixed with a feather key connection; 
       FIG. 17  is a longitudinal section through an adjusting motor similar to that from  FIG. 1 , but whose stator has an injection-molded part made from plastic; 
       FIG. 18  is a longitudinal section through the adjusting motor similar to that from  FIG. 1 , but with a stator covered by a cover film; 
       FIG. 19  is a longitudinal section through an adjusting motor as in  FIG. 1 , but with a solid adjusting motor shaft, which is supported in two grooved ball bearings, which are arranged next to a permanent magnet rotor, which are lubricated with grease, and which are sealed on two side; 
       FIG. 20  is a cross section X—X through a spiral spring from  FIG. 21 , which connects a chain wheel formed as a drive shaft to a closing cover of a double eccentric gear mechanism formed as a driven shaft; 
       FIG. 21  is a partial longitudinal section Y—Y through the double eccentric gear mechanism from  FIG. 20  with its spiral spring. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows an embodiment of an adjusting device  1  formed according to the invention comprising a high speed-reducing adjusting gear mechanism (speed reduction up to 1:250), which is formed as a double eccentric gear mechanism  2 , and an adjusting motor  3 , which is a brushless DC motor. The double eccentric gear mechanism  2  and the adjusting motor  3  are separate units. 
   The adjusting gear mechanism is formed as a triple shaft gear mechanism comprising a drive shaft, a driven shaft, and an adjusting shaft. The drive shaft is formed as a ring gear  4 , on whose periphery a chain wheel  5  is arranged. On its inner periphery, there is internal gearing  6 . The chain wheel  5  is connected in a torsion-proof manner by means of a chain to the crankshaft, both of which are not shown. The internal gearing  6  meshes with two spur pinions  7 ,  8 , which are driven by means of spur pinion bearings  9 ,  10  by 180° offset eccentrics  11 ,  12  of an adjusting shaft, which is formed as double eccentric shaft  13 . The ring gear  4  is supported on a chain wheel bearing  51  formed as a sliding bearing of a closing wall  14 , wherein the closing wall  14  is centered on a camshaft  15  or on a guide  16  of a central tension screw  17 . The guide  16  is centered in the camshaft  15 . 
   With the central tension screw  17 , the closing wall  14  is tensioned in a torsion-proof manner against the camshaft  15  and thus has the function of a driven shaft. Driving pins  21  are connected rigidly to the closing wall  14 . They are used for transferring the torque of the spur pinions  7 ,  8  to the camshaft  15  by means of the closing wall  14 . The driving pins  21  project through bore holes  22 ,  23  of the spur pinions  7 ,  8 , wherein the diameter of the bore holes  22 ,  23  corresponds to that of the driving pins  21  plus twice the eccentricity of the eccentrics  11 ,  12 . The number of driving pins  21  depends on the magnitude of the torque to be transferred. In the present case, there are eight. 
   At the free end of the driving pins  21 , there is a closing cover  29 , which forms the seal of the adjusting gear mechanism and which has the effect of fixing the adjusting shaft  13  in the axial direction and also guiding the lubricating oil within the adjusting gear mechanism. The closing cover  29  is fixed in the axial direction by a retaining ring  24  on its periphery or by retaining rings  25  on the free end of each driving pin  21  (see  FIG. 4 ). 
   The adjusting shaft formed as hollow double eccentric shaft  13  is supported in the region of the eccentrics  11 ,  12  by means of a double eccentric shaft bearing  30 , which is formed as a needle bushing, on a cylindrical screw head  31  of the central tension screw  17 . The double eccentric shaft bearing  30  can also be formed alternatively with two needle bushings lying one next to the other or with roller bearings. The double eccentric shaft  13  is connected to an adjusting motor shaft  32  of the adjusting motor  3  by means of a two-edge shaft coupling  33  (see also  FIGS. 2 and 3 ) in a rotational backlash-free but movable in the longitudinal direction manner. A permanent magnet rotor  34  is mounted on the adjusting motor shaft  32 . This is surrounded by a stator  35  and windings with winding heads  36  and separated from this stator by an air gap  37 . 
   The adjusting motor  3  has a housing, which comprises an outer adjusting motor housing  38  and an inner adjusting motor housing  39 . Both housings  38 ,  39  are connected to each other by a not-shown transport lock before installation of the adjusting motor  3 . The housings  38 ,  39  are sealed from each other and from a cylinder head  40  by O-rings  41 ,  42 . The seal between attachment screws  43  and the cylinder head  40  is realized by means of a sealing mass applied to the screw threading. It is also conceivable to provide pocket hole threaded bore holes in the cylinder head  40  instead of the through hole threaded bore holes, which would make sealing of the attachment screws  43  unnecessary. In order to be able to compensate for alignment errors between the axes of the adjusting motor  3  and the camshaft  15  during assembly, the through holes for the attachment screws  43  have a greater diameter. 
   The adjusting motor shaft  32  is supported in two grooved ball bearings  44 ,  45 . The grooved ball bearing  44  is located in the interior of the adjusting motor shaft  32  on a journal  46  of the outer adjusting motor housing  38 . It is lubricated with grease and sealed on two sides. The grooved ball bearing  45  is arranged on the outer periphery of the adjusting motor shaft  32  and in the inner adjusting motor housing  39 . It has a seal  47  on the adjusting motor side. Therefore, the interior of the adjusting motor remains oil-free, while the grooved ball bearing  45  is lubricated by centrifugal oiling. Because the hollow adjusting motor shaft  32  is closed on its coupling end, its interior also remains oil-free. 
   The double eccentric gear mechanism  2  is lubricated by motor oil. This is led through lubricating oil bore holes  48 ,  49  in the end bearing  50  of the camshaft  15  near the gear mechanism and in the closing wall  14  to the double eccentric shaft bearing  30 . From there, it flows outwards due to the effect of centrifugal force towards the spur pinion bearings  9 ,  10 , the driving pins  21 , the spur pinions  7 ,  8 , and the internal gearing  6  of the ring gear  4 , until it flows out through the chain wheel bearing  51  and through outlet openings  52  in the closing cover  29  into the space of the cylinder head  40 . There it is used for centrifugal oiling or as spray oil for lubricating the oil-lubricated roller bearings  45 ;  30   a ,  44 ′,  45 ′ of the adjusting motors  3 ,  3 ′″,  3 ″″. 
     FIG. 2  shows a cross section X—X through an enlarged longitudinal section of the two-edge shaft coupling  33  of  FIG. 1  shown in  FIG. 3 . It is used for transferring the torque of the adjusting motor shaft  32  to the double eccentric shaft  13 . Due to the drive moments changing according to direction and magnitude, it is guaranteed that the two-edge shaft coupling  33  has practically no rotational backlash. In the axial direction, relative movement of the two-edge shaft coupling  33  is possible and necessary due to the expansion of the camshaft and adjusting shaft  15 ,  13  due to heat. 
     FIG. 4  shows a double eccentric gear mechanism  2 ′, which differs from that of  FIG. 1  by a central standard tension screw  18  with standard screw head  31 ′ and an additional bearing bushing  53  for the double eccentric bearing  30 , as well as by a feather key shaft coupling  54  between a double eccentric shaft  13 ′ and the not-shown adjusting motor shaft. The advantage of this variant is that two easy-to-produce standard parts instead of the relatively complicated central tension screw  17  are used for tightening with the camshaft  15 . A disadvantage is the greater necessary axial installation space. 
   In the double eccentric shaft  13 ′, at the height of the standard screw head  31 ′ there are radial bore holes  55 . These bore holes prevent motor oil from collecting in the hollow double eccentric shaft  13 ′ and leading to an increase of the mass moment of inertia of the same. A closing cover  29 ′ is mounted axially in a different way than in  FIG. 1  by retaining rings  25  on the free ends of the driving pins  21 ′. 
     FIG. 5  shows a double eccentric gear mechanism  2 ″, which is connected to the camshaft  15 ′ in a different way than in  FIG. 1  by means of a circular spline connection  56 . The principle of the circular spline connection  56  is explained with reference to  FIGS. 6   a ,  6   b ,  6   c . It concerns a positive and non-positive shaft-hub connection. This connection comprises a round inner part  57 , whose periphery has at least two circular splines  58 , and an outer part  59  with a bore hole, whose inner surface has the same number of complementary circular splines as the inner part  57 . After the parts  57 ,  59  have been joined with play (see  FIG. 6   a ), these are turned relative to each other so far until there is no play between them (see  FIG. 6   b ). Through further turning, the circular spline surfaces are pressed against each other, so that a positive and non-positive connection is produced (see  FIG. 6   c ). Here, the connection in the closing direction is a non-positive and positive fit. In the opening direction, it is only a non-positive connection. Therefore, backlash-free moment and force transfer in the rotational and axial direction is achieved, without additional components and their installation space being necessary. For this reason, the circular spline connection  56  is especially well suited for an electrical adjusting device with aligned axes of the adjusting gear mechanism and adjusting motor, because their axial installation space can be strongly reduced due to the lack of screw heads. In electrical camshaft adjusting devices with lateral adjusting motor, the circular spline connection provides smaller installation space advantages. Obviously, instead of the circular spline connection, polygonal or hyperbolic connections, for example, can also be used. 
   In  FIG. 5 , a camshaft end  60  carries the outer contours of the circular spline connection  56  and a circular spline bore hub  61  connected rigidly to the closing wall  14  carries the inner contours of the same. The circular spline bore hub  61  is also used as a bearing surface for the double eccentric shaft bearing  30 . The double eccentric gear mechanism  2 ″ is pushed onto the camshaft end  60  and turned by a certain angle. For this reason, on the free end of the driving pins  21 ″, there are profiles  62 , on which a tool for turning can be placed. Alternatively, for example, bore holes, in which a tool engages with journals or hook wrenches, which engage the chain wheel, are conceivable. A double eccentric shaft  13 ″ with double eccentric shaft bearing  30 , feather key shaft coupling  54 , and radial bore holes  55  shows the gain in installation length relative to the double eccentric shaft  13 ′ of  FIG. 4 . 
   In order to also bias the circular spline connection  56 , the double eccentric gear mechanism  2 ″ can be loaded by means of a press and turned in this state during assembly and before tightening in the axial direction. The circular spline connection  56  with three circular splines  58  offers the advantage of self-centering. However, two, four, and more circular splines  58  are also conceivable according to the application and the torque to be transferred. In order to increase the moment that can be transferred, the hub  61  can also be lengthened and/or increased in diameter. 
     FIG. 7  shows a longitudinal section through an adjusting device  1 ′with the double eccentric gear mechanism  2  and an adjusting motor  3 ′, which represents a variation of the adjusting device  1  from  FIG. 1 . It has a one-piece hollow shaft  64  formed from the double eccentric shaft  13  and the adjusting motor shaft  32 ′. Therefore, the otherwise necessary coupling between the shafts  13 ,  32 ′ is eliminated. 
   The hollow shaft  64  is supported on its camshaft-side end by the double eccentric shaft bearing  30  on the cylindrical screw head  31  of the central tension screw  17 . In addition, the hollow shaft  64  is supported in the cylinder head  40  by means of the grooved ball bearing  45  sealed on one side. Here, the seal  47  is also mounted on the adjusting motor side in order to guarantee the lubrication of the grooved ball bearing  45  by means of motor oil and to protect the adjusting motor  3 ′ against the penetration of oil. The hollow shaft  64  is screwed onto the camshaft  15  together with a permanent magnet rotor  34 ′, the grooved ball bearing  45 , and the double eccentric gear mechanism  2 . The hollow shaft  64  enables the central tension screw  17  to be reached with a screwdriver. 
   To prevent the motor oil from being led through the hollow shaft  64  into the adjusting motor  3 ′, its end away from the camshaft is closed with a closing stopper  65 . In  FIG. 7 , a threaded closing stopper  65  with an O-ring is selected. Alternatively, plastic stoppers can also be considered, which only have to be pressed in. The motor oil collecting in the hollow shaft  64  is discharged through an outlet opening  26 . 
   Because the adjusting motor  3 ′ in the variant of  FIG. 7  cannot be mounted as a unit, the outer adjusting motor housing  38  together with the stator  35  must be mounted separately. For this purpose, an assembly tool  66  from  FIGS. 8 and 9  is helpful. This is used for centering the stator  35  on the permanent magnet rotor  34 ′. It consists of a base plate  70 , on which three vanes  67  are arranged rigidly at the same spacing on the diameter of the air gap  37  (see  FIG. 7 ), as well as with its thickness. 
     FIG. 10  shows the assembly tool  66  during the assembly of the adjusting motor  3 ′. The assembly direction is indicated by the arrow  28 . The vanes  67  have been guided through assembly slots  69  of the outer adjusting motor housing  38  and along the stator  35 . The vanes  67  extend into the air gap  37 , so that the outer adjusting motor housing  38  is aligned with the stator  35  on the permanent magnet rotor  34 ′ and slides in its end position in the cylinder head  40  in order to be screwed in there. In principle, the positioning and aligning of the stator  35  can also be realized in a different way than by means of the air gap  37 . The assembly slots  69  in the outer adjusting motor housing  38  (see also  FIG. 11 ) are closed after their assembly and after removing the assembly tool  66  with a closing cover  68  (see  FIG. 12 ) in order to prevent penetration of dirt and water into the outer adjusting motor housing  38 . Similar to the assembly tool  66 , the closing cover  68  has a cover plate  71  with double-walled cover vanes  72 . These engage in the assembly slot  69  in a spring-like way and thus fix the closing cover  68 . This state is shown in  FIGS. 7 and 13 . The outer adjusting motor housing  38  is sealed relative to the cylinder head  40  by an O-ring, whose groove can be located in the outer adjusting motor housing  38  or in the cylinder head  40 . The threading of the attachment screws  43 ′ are sealed as in  FIG. 1  with sealing mass or by a pocket hole threaded bore hole. 
   The solution variant from  FIG. 7  can also be formed with an outer and inner adjusting motor housing  38 ,  39  from  FIG. 1 . Then the grooved ball bearing  45  is not located in the cylinder head  40  but instead in the inner adjusting motor housing  39 . Here, it must be guaranteed that the outer diameter of the grooved ball bearing  45  is greater than the outer diameter of the permanent magnet rotor  34 ′, so that the inner adjusting motor housing  39  can be pushed over the permanent magnet rotor  34 ′ during assembly. 
     FIG. 13  shows a longitudinal section through an adjusting device  1 ″, with the double eccentric gear mechanism  2  and an adjusting motor  3 ″, which represents a variant of the adjusting device  1 ′ of  FIG. 7 . Here, the double eccentric shaft  13  and an adjusting motor shaft  32 ″ together also form a one-piece hollow shaft  64 ′. However, in addition to the double eccentric shaft bearing  30 , this also has an inner rotor bearing  30   a , which is likewise formed as a needle bushing and which is supported on another cylindrical screw head  31 ″ of an extended central tension screw  19 . The adjusting motor  3 ″ is sealed relative to the double eccentric gear mechanism  2  by a radial shaft seal ring  73  and a closing stopper  65 ′ sealing the hollow shaft  64 ′. For reducing the friction moment, instead of the radial shaft sealing ring  73 , contact force-reducing sealing means, such as PTFE sealing rings, can also be used. Oil is removed from the hollow shaft  64 ′ through a radial outlet opening  27  into the space of the cylinder head  40 . 
   Due to the expansion of the camshaft  15  due to heat (see  FIGS. 7 and 13 ) together with the resulting tightly connected hollow shafts  64 ,  64 ′, the axial position of the permanent magnet rotor  34 ′,  34 ″ changes relative to the stator  35 . To always keep the usable rotor length equal to the length of the stator armature stampings, the length of the permanent magnet rotor  34 ′,  34 ″ must exceed that of the stator  35  by the extent of axial expansion due to heat. Alternatively, the armature stampings of the stator  35  can be longer than the permanent magnet rotor  34 ,  34 ″ by at least the axial displacement. Therefore, however, the total length of the adjusting motor  3 ′,  3 ″ is increased by the extent of the maximum expansion due to heat. 
     FIG. 14  shows another high speed reducing adjusting gear mechanism in the configuration of a double planetary gear mechanism  74 . As an adjusting shaft, a sun wheel  75 , which can be driven by a not-shown adjusting motor shaft, is used. The sun wheel  75  is supported in a grooved ball bearing  77  and a planetary carrier  76  is supported in a planetary carrier bearing  78  directly on a central tension screw  20 . In this case, it is also possible to replace the grooved ball bearing  77  and the planetary carrier bearing  78  by sliding bearings and the tension screw  20  by a standard screw with matching bearing bushing. The sun wheel  75  meshes with planetary gears  79 ,  79 ′, which have a different diameter, which are formed in one piece, and which are supported by means of planetary bearings  78   a ,  78 ′ on connecting pins  80 . The connecting pins  80  are connected rigidly to the planetary carrier  76  and in a sliding manner to a closing plate  81 . The closing plate  81  is connected in a disengaging manner to the planetary carrier  76  by screws  82 . It is used for assembling the planetary gears  79 ,  79 ′. The planetary gear  79  meshes with the internal gearing  98  of a crankshaft-fixed ring gear  83  and the planetary gear  79 ′ meshes with the internal gearing  99  of a camshaft-fixed ring gear  84 , which is tensioned by the central tension screw  20  with the camshaft  15 . Through the slightly different number of teeth of the planetary gears  79 ,  79 ′ and the ring gears  83 ,  84 , the desired large speed reduction is achieved. The crankshaft-fixed ring gear  83  is supported on the camshaft-fixed ring gear  84  in a sliding bearing  63 . However, it can also be supported on roller bearings. 
   In  FIGS. 15 ,  15   a , and  16 , separately formed planetary gears  79   a ,  79   a ′, and  79   b ,  79   b ′ are shown, which are connected in a torsion-proof manner by a splined shaft  85  or a feather key connection  86 . The splined shaft  85  with the planetary gears  79   a  and  79   a ′, as well as the planetary gears  79   b  and  79   b ′, are supported by rollers in the planetary carrier  76  and in the closing plate  81 . 
   In  FIGS. 17 and 18 , brushless adjusting motors  3 ′″,  3 ″″ with a stator  35  and a permanent magnet rotor  34 ′″ are shown in longitudinal section, which are similar to the adjusting motor  3  from  FIG. 1 . However, they have unsealed, oil-lubricated, and especially low-friction grooved ball bearings  44 ′,  45 ′. Due to the lack of sealing, motor oil penetrates into the interior of the adjusting motors  3 ′″,  3 ″″. Therefore, there is the risk that the insulating coating on the winding wire of the stator  35  will be attacked and a winding short circuit will be triggered. In addition, the PC board or the Hall sensors necessary for the electronic commutation could be destroyed. Therefore, all components vulnerable to motor oil are protected against motor oil in  FIG. 17  by an injection-molded part  87  made from heat-resistant and oil-resistant plastic and in  FIG. 18  by covers with a covering film  88  made from comparable plastic, wherein the covering film  88  can also be configured differently than shown. 
   To prevent metal filings from the motor oil from settling on the permanent magnet rotor  34 ′″, which itself does not have to be protected from penetrating oil, a filter or screen can be arranged in front of the grooved ball bearings  44 ′ and  45 ′. Because this configuration concerns non-contacting seals, a sealing-specific friction moment is also not produced. 
   In  FIG. 19 , an enlarged longitudinal section of a brushless adjusting motor  3 ′″″is shown, which is formed as a separate unit. This has a solid adjusting motor shaft  89 , which is connected rigidly to a permanent magnet rotor  34 ″″ and which is supported on grooved ball bearings  44 ″,  45 ″. The relatively small diameter of the solid adjusting motor shaft  89  enables the housing of the grooved ball bearings  44 ″,  45 ″ within the winding heads  36  of the stator  35 . Therefore, a small structural length is achieved. The grooved ball bearing  45 ″ is arranged in an adjusting motor housing  90  and the grooved ball bearing  44 ″ is arranged in its housing cover  91 . Both grooved ball bearings  44 ″,  45 ″ are lubricated with grease and sealed on two sides with seals  47 . 
   A centrifugal disk  92 , which is covered by the adjusting motor housing  90  and which acts as an additional labyrinth seal, is arranged in front of the grooved ball bearing  45 ″ on the gear mechanism-side of the adjusting motor shaft  89 . Naturally, other labyrinth seals are also possible. On the gear mechanism-side end of the adjusting motor shaft  89 , there is a coupling head  93  with a splined shaft profile  96 , which can be inserted into the corresponding part of the adjusting shaft of an adjusting gear mechanism. 
     FIG. 20  shows a view of a double eccentric gear mechanism  2  similar to that in  FIG. 1 , comprising a spiral spring  94  shown in a cross section X—X. This connects a chain wheel  5 ′ (equal to the drive shaft) modified by retaining pin  95  via a modified closing cover  29 ″ (equal to the driven shaft), the cylinder pins  21 , and the closing wall  14  under the interaction of a central tension screw  17  with the camshaft  15 . 
     FIG. 21  shows a partial longitudinal section through the double eccentric gear mechanism  2  and the spiral spring  94  with one of the retaining pins  95  for the spiral spring  94  and with a part of the closing cover  29 ″, on which the spiral spring  94  is likewise anchored. The biased spiral spring  94  guides the camshaft  15  back into a starting or emergency running position if there is a failure of the electric angle of rotation adjustment, in order to guarantee reliable restarting of the internal-combustion engine. It thus fulfills a fail safe function. 
   In the adjusting device according to the invention, the adjusting motor is operated so that when it is adjusted in the early direction, the camshaft overtakes the crankshaft and when it is adjusted in the late direction, the crankshaft overtakes the camshaft, while in the set position, all three shafts of the adjusting gear mechanism rotate at the speed of the camshaft. The direction of rotation of the adjusting motor during the adjustment depends on whether the adjusting gear mechanism is a positive or negative gear mechanism. 
   All of the previously described variants can be combined with each other in terms of gear mechanism, adjusting motor, bearing, sealing, and lubrication. 
   
     
       
             
           
             
             
             
           
         
             
                 
             
             
               List of reference symbols 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                 
               1, 1′, 1″ 
               Adjusting device 
             
             
                 
               2, 2′, 2″ 
               Double eccentric gear mechanism 
             
             
                 
               3, 3′, 3″, 3″′, 3″″, 3″″′ 
               Adjusting motor 
             
             
                 
               4 
               Ring gear 
             
             
                 
               5, 5′ 
               Chain wheel 
             
             
                 
               6 
               Internal gearing 
             
             
                 
               7 
               Spur pinion 
             
             
                 
               8 
               Spur pinion 
             
             
                 
               9 
               Spur pinion bearing 
             
             
                 
               10 
               Spur pinion bearing 
             
             
                 
               11 
               Eccentric 
             
             
                 
               12 
               Eccentric 
             
             
                 
               13, 13′, 13″ 
               Double eccentric shaft 
             
             
                 
               14 
               Closing wall 
             
             
                 
               15, 15′ 
               Camshaft 
             
             
                 
               16 
               Guide 
             
             
                 
               17 
               Central tension screw 
             
             
                 
               18 
               Central standard tension screw 
             
             
                 
               19 
               Extended central tension screw 
             
             
                 
               20 
               Central tension screw 
             
             
                 
               21, 21′, 21″ 
               Driving pin 
             
             
                 
               22 
               Spur pinion bore hole 
             
             
                 
               23 
               Spur pinion bore hole 
             
             
                 
               24 
               Retaining ring 
             
             
                 
               25 
               Retaining ring 
             
             
                 
               26 
               Outlet opening 
             
             
                 
               27 
               Outlet opening 
             
             
                 
               28 
               Arrow 
             
             
                 
               29, 29′, 29″ 
               Closing cover 
             
             
                 
               30 
               Double eccentric shaft bearing 
             
             
                 
               30a 
               Inner rotor bearing 
             
             
                 
               31, 31″, 31″′ 
               Cylindrical screw head 
             
             
                 
               31′ 
               Standard screw head 
             
             
                 
               32, 32′, 32″ 
               Adjusting motor shaft 
             
             
                 
               33 
               Two-edge shaft coupling 
             
             
                 
               34, 34′, 34″, 34″′, 34″″ 
               Permanent magnet rotor 
             
             
                 
               35 
               Stator 
             
             
                 
               36 
               Winding head 
             
             
                 
               37 
               Air gap 
             
             
                 
               38 
               Outer adjusting motor housing 
             
             
                 
               39 
               Inner adjusting motor housing 
             
             
                 
               40 
               Cylinder head 
             
             
                 
               41 
               O-ring 
             
             
                 
               42 
               O-ring 
             
             
                 
               43, 43′ 
               Attachment screw 
             
             
                 
               44, 44′, 44″ 
               Grooved ball bearing 
             
             
                 
               45, 45′, 45″ 
               Grooved ball bearing 
             
             
                 
               46 
               Journal 
             
             
                 
               47 
               Seal 
             
             
                 
               48 
               Lubricating oil bore hole 
             
             
                 
               49 
               Lubricating oil bore hole 
             
             
                 
               50 
               End bearing 
             
             
                 
               51 
               Chain wheel bearing 
             
             
                 
               52 
               Outlet opening 
             
             
                 
               53 
               Bearing bushing 
             
             
                 
               54 
               Feather key shaft coupling 
             
             
                 
               55 
               Radial bore hole 
             
             
                 
               56 
               Circular spline connection 
             
             
                 
               57 
               Inner part 
             
             
                 
               58 
               Circular spline 
             
             
                 
               59 
               Outer part 
             
             
                 
               60 
               Camshaft end 
             
             
                 
               61 
               Circular spline bore hub 
             
             
                 
               62 
               Profile 
             
             
                 
               63 
               Sliding bearing 
             
             
                 
               64, 64′ 
               Hollow shaft 
             
             
                 
               65, 65′ 
               Closing stopper 
             
             
                 
               66 
               Assembly tool 
             
             
                 
               67 
               Vane 
             
             
                 
               68 
               Closing cover 
             
             
                 
               69 
               Assembly slot 
             
             
                 
               70 
               Base plate 
             
             
                 
               71 
               Cover plate 
             
             
                 
               72 
               Cover vane 
             
             
                 
               73 
               Radial shaft sealing ring 
             
             
                 
               74 
               Double planetary gear mechanism 
             
             
                 
               75 
               Sun wheel 
             
             
                 
               76 
               Planetary carrier 
             
             
                 
               77 
               Sun wheel bearing 
             
             
                 
               78 
               Planetary carrier bearing 
             
             
                 
               78a, 78a′ 
               Planetary bearing 
             
             
                 
               79, 79′ 
               Planetary gear 
             
             
                 
               79a, 79a′ 
               Planetary gear 
             
             
                 
               79b, 79b′ 
               Planetary gear 
             
             
                 
               80 
               Connecting pin 
             
             
                 
               81 
               Closing plate 
             
             
                 
               82 
               Screw 
             
             
                 
               83 
               Crankshaft-fixed ring gear 
             
             
                 
               84 
               Camshaft-fixed ring gear 
             
             
                 
               85 
               Splined shaft 
             
             
                 
               86 
               Feather key connection 
             
             
                 
               87 
               Injection-molded part 
             
             
                 
               88 
               Cover film 
             
             
                 
               89 
               Solid adjusting motor shaft 
             
             
                 
               90 
               Adjusting motor housing 
             
             
                 
               91 
               Housing cover 
             
             
                 
               92 
               Centrifugal disk 
             
             
                 
               93 
               Coupling head 
             
             
                 
               94 
               Spiral spring 
             
             
                 
               95 
               Holding pin 
             
             
                 
               96 
               Splined shaft coupling 
             
             
                 
               97 
               Pin bore hole 
             
             
                 
               98 
               Internal gearing 
             
             
                 
               99 
               Internal gearing