DE102017202418B4 - gear unit - Google Patents

Abstract

The invention relates to a gear unit (1), comprising a first shaft (2) with a first gear (3) attached thereto and a second shaft (5) with a shaft wheel (6) attached thereto, which cooperates with the first gear (3) , In order to achieve a structurally simple way to minimize the noise during operation of a balance shaft, the invention provides that the shaft wheel (6) on the shaft side an inelastic base body (7) and on the outside with the base body (7) torque transmitting connected sprocket assembly (10), the elastically deformable outer teeth (12) for engagement with the first gear (3), wherein the sprocket assembly (10) is positively connected to the base body (7).

Description

The invention relates to a gear unit having the features of the preamble of claim 1, comprising a first shaft with a first gear attached thereto and a second shaft with a shaft wheel attached thereto cooperating with the first gear, the shaft wheel on the shaft side formed as a second gear inelastic base body and on the outside a torque transmitting connected to the base body, integrally formed sprocket assembly having elastically deformable outer teeth for engagement with the first gear, and inner teeth disposed between the base body teeth of the base body, whereby the sprocket assembly is positively connected to the base body , And the sprocket assembly is placed under elastic expansion on the base body and thus biased radially inwardly against the base body.

In reciprocating engines, for example, internal combustion engines of motor vehicles such as trucks or cars, there is generally the problem that the engine is subjected to time-varying acceleration forces in the course of the piston movement, which leads to vibrations that represent a mechanical load and also amplify the engine noise. As a countermeasure for this purpose, it is known to couple the crankshaft with a balance shaft (possibly also two balance shafts). In this case, eccentric weights are attached to the balancer shaft, whose movement is used, the o.g. At least partially compensate for acceleration forces. Usually, the balance shaft rotates with a simple, possibly double crankshaft speed. The coupling of the balancer shaft to the crankshaft can be done by gears, chains or timing belt.

Regardless of the type of mechanical coupling, however, there is a risk that the mechanical components used due to an almost always given game as well as manufacturing inaccuracies, for example, affect the concentricity, clash or rub against each other, which in turn leads to undesirable noise. This problem can be controlled to a certain extent, if particularly low manufacturing tolerances are met, which, however, leads to increased costs. In addition, it is known to use a shared gear with mutually braced gear halves instead of simple, one-piece gears. Due to the tension of the gears any play is avoided, which reduces the noise. However, the comparatively complicated structure of such a two-part gear again leads to increased costs.

The DE 42 39 963 A1 discloses a flexible drive mechanism for a belt drive. This is formed as a wave-shaped belt or belt of a plastic strip, which can be guided over a toothed drive wheel, wherein the belt is made of a plastically deformed by embossing plastic. At least on one side of the corrugation, preferably on both sides, the belt has a laterally projecting edge strip for receiving a longitudinal traction. In one embodiment, the belt is guided over the drive wheel and a driven wheel, wherein another gear on the opposite side of the belt loosely meshes with the drive wheel.

From the DE 10 2014 220 551 A1 is a method for the production of drive belts with profiled on both sides known. In this case, a belt forming roller, which is provided on the outside with a negative mold for the inner profiling of the drive belt, provided with a drive belt blank. To build the drive belt blank, tensile cords are wound on a fabric stocking, a rubber layer is applied and in turn a fabric layer. The blank is passed between the belt forming roller and a mold forming the negative mold for the external profiling. The rotational movement of the belt forming roller and the forming belt are synchronized with each other so that there is no shift between inner and outer profiling. The belt forming roll is heated on the inside so that a vulcanization of the blank takes place.

The EP 0 214 742 B1 discloses a double-sided power transmission belt having an elastomeric body portion having first and second peripheral surfaces and a tension band embedded in the body portion. First teeth are formed on a first side of the body region and second teeth on a second side of the body region. Both the first and second teeth have an elastomeric interior and a coating. In this case, a first coating of the first teeth has a substantially non-stretchable tissue, and a second coating of the second teeth comprises a stretchable tissue. It is thereby achieved that the teeth covered with the stretchable fabric cover have a higher spring rate than the flexible teeth covered with the substantially non-stretchable fabric cover.

The DE 39 31 480 A1 discloses a toothed belt of elastomeric material for a toothed belt and gear belt drive. It is provided that in the head surface of each belt tooth, a head piece is embedded, which consists of a material with a relation to the belt material greater elasticity. This Headpiece is bulged in such a way from the head surface of the belt tooth, that it hits the gear initially with a highest elevation of its bulged outer side at the bottom of the Zahnradnuten when running the belt and then by the operational radial belt tension to a flat contact its outside at the bottom of the gear grooves is compressed.

The DE 11 2014 000 744 shows a device with a sprocket having a plurality of teeth, which are formed along the circumference of a sprocket body and which are separated by tooth roots along the circumference of the chain body. The sprocket body has a bore formed at its center and at least one radially extending slot in which an elastomeric material is embedded. In this case, the slot may, for example, be arranged in a tooth or in a tooth base.

In the DE 603 05 682 T2 there is disclosed a sprocket that includes a hub and a plurality of teeth projecting radially outward from the hub and separated by tooth spaces. Furthermore, the sprocket includes first and second elastomeric damping rings connected to the hub on opposite first and second axial sides of the teeth. Each of the first and second damper rings defines a plurality of pressure pads circumferentially separated from one another by axially extending grooves, each aligned with the tooth spaces and disposed radially inwardly therefrom.

The US 5 908 364 A discloses a noise suppressing chain drive. This comprises a drive chain whose chain links each have rollers which are flanked by plate-shaped tabs. A toothed surface of a pinion engages the drive chain. In this case, a circumferential groove is formed along the toothed surface, in which an elastic element is arranged. The respective roller has a circumferential bead which engages in the groove, whereby the roller at least partially rests on the elastic element.

The JP 2007-211836 A shows a split gear with two tangentially braced halves. One half is used primarily for power transmission and the other half primarily for the absorption of shocks. In order to minimize the noise, a plurality of elastic elements are arranged axially between the two halves.

The KR 10 2004 0026966 A discloses a gear for a balance shaft, which is intended to cooperate with a roller chain. The gear consists of a central part, on which the teeth are formed, and two axially attached thereto cheek parts. On both sides adjacent to the teeth, an O-ring made of rubber-elastic material is inserted between the middle part and in each case a cheek part in order to minimize the noise between the chain and the gearwheel.

The US 3,068,710 A discloses a toothed belt made of flexible plastic material, in which a tensile material is incorporated. In particular, the tensile material can be formed by a wire rope, which is performed like a coil several times along the entire toothed belt. In this case, the wire on the side of the teeth is completely covered by plastic material, while protruding on an opposite side of individual sections of the wire from the plastic material.

The GB 744,907 A shows a method for producing a drive belt, for example a toothed belt, wherein reinforcing inserts are placed in a mold and then a thermoplastic material is poured into the mold. The reinforcements may be layered or formed by longitudinal or transverse wires. It can also be applied an abrasion-resistant cover layer.

The DE 10 2011 053 287 A1 discloses a toothed belt having an elongated rubber back in which a plurality of twisted wires are embedded and a toothed rubber having a plurality of belt teeth formed on the plurality of twisted wires. In operation, the belt teeth mesh with pulley teeth of a pulley, the pulley teeth are straight teeth, while the belt teeth are helically toothed.

The US 3,183,734 A discloses a gear having a central member having an edge with a plurality of outwardly directed ribs. On the ribs is a metallic cable, which is guided around the middle element several times. A plurality of teeth are each formed between two ribs on the inner member, each tooth enclosing the turns of the cable.

The DE 196 53 967 A1 relates to a method for producing toothed components by bringing at least one toothed belt or toothed belt section into operative connection with at least one carrier element. Shown is, inter alia, a cylindrical support member on which a toothed belt section is vulcanized.

The DE 38 33 989 A1 discloses a sprocket member having a base body and a gear carrier surrounding it, both Preformed parts are and of which at least one is elastic. The toothing carrier may be a toothed belt, which may in particular be toothed on both sides, wherein the base body is provided with a toothed belt facing toothed mounting surface. The toothed belt can be held by clamping on the base body.

The US 1,222,625 A shows a gear with a disc-shaped center part, which consists of two discs made of sheet steel. From the outer edge of the middle section go out slits, each opening into circular openings. On the edge of teeth formed of sheet steel are provided, each one opening serves as an anchoring point for two teeth.

In view of the prior art that has been pointed out, the minimization of the noise during the operation of a balancing shaft still offers room for improvement. In particular, a structurally simple and cost-effective solution would be desirable.

The invention has for its object to achieve a structurally simple way minimizing the noise during operation of a balance shaft.

According to the invention the object is achieved by a gear unit with the features of claim 1, wherein the dependent claims relate to advantageous embodiments of the invention.

It should be noted that the features listed in the following description as well as measures in any technically meaningful way can be combined with each other and show other embodiments of the invention. The description additionally characterizes and specifies the invention, in particular in connection with the figures.

The invention provides a gear unit having a first shaft with a first gear attached thereto and a second shaft with a shaft gear attached thereto cooperating with the first gear. Of course, the first and the second shaft are rotatably mounted on a common, possibly multi-part, housing or frame, whereby the relative positions of the two waves is fixed to each other. In particular, the first shaft may be loaded in the operating state by imbalances and the second shaft may be formed as a balance shaft, are arranged on the operating state weights, by means of which acceleration forces caused by the imbalance, at least partially compensated. Namely, the first shaft may rotate the crankshaft of an internal combustion engine, e.g. a motor vehicle engine, be. Conversely, it is also possible that the first shaft is designed as a balance shaft and the second shaft is loaded with imbalances, in particular, the second shaft may be formed as a crankshaft. The gear arrangement can be used not only in an internal combustion engine, but, for example, for example. In a drive of an oil pump. The first gear is preferably formed in one piece and at least predominantly, usually completely inelastic or rigid. It may consist in particular of metal, for example of sintered metal, gray cast iron, steel or aluminum. It sits at least rotatably on the first wave. A one-piece production with the first wave or with a part of the same is possible. Normally, the first gear has a straight toothing, but in principle would also be a helical toothing, Pfeilzahnung or the like conceivable. The first gear is like the other subsequently mentioned gears normally designed as a spur gear.

On the second shaft, a wave wheel is mounted, which in turn is at least rotationally fixed on the second shaft. The wave wheel cooperates with the first gear, i. it engages with the first gear, wherein a torque between the first gear and the shaft wheel and thus between the first shaft and the second shaft is transmitted in a known manner by positive locking. In cases where the second shaft acts as a balance shaft, a gear ratio of 1 or 2 is normally provided between the first gear and the shaft gear.

On the shaft side, the shaft wheel has an inelastic base body formed as a second gearwheel and, on the outside, a integrally formed sprocket arrangement connected in a torque-transmitting manner to the base body, which has elastically deformable outer teeth for engagement with the first gearwheel. That is, the wave wheel consists of at least two parts, which can be differentiated in terms of their material properties. The one part, the base body, is arranged on the shaft side, ie towards the shaft or radially inside. The other part, the sprocket arrangement, is arranged on the outside, that is to say remote from the shaft or radially outside. Preferably, the base body extends radially from the shaft to the sprocket assembly. Further preferably, the base body is integrally formed. It can be made of the same or a similar material as the first gear, so typically metal. The sprocket assembly may surround the base body radially outside partially or completely. It is arranged in its entirety on the outside adjacent to the base body and can in particular at least partially in contact with this. In In any case, it is torque-transmitting connected to the base body, ie there is a connection between the sprocket assembly and the base body, by which a force acting on the sprocket assembly torque is transmitted to the base body and vice versa. This implies that rotation of the sprocket assembly with respect to the base body (tangential with respect to the axis of the second shaft) is prevented or at least restricted by said connection. However, this alone does not rule out the fact that at least parts of the sprocket assembly to a limited extent compared to the base body tangentially move because of the elastic property of the outer teeth.

The sprocket assembly is integrally formed. In the simplest case, it can be formed by a single molding step of an elastic material. In any case, the manufacturing process is simplified by a one-piece production. The same applies to the assembly of the gear unit, since only a single part must be added to the shaft body for the production of the wave wheel. A one-piece sprocket assembly can be described as a whole ring.

The sprocket assembly is positively connected to the base body. This means in particular a positive connection in the tangential direction, ie in the direction of rotation with respect to the second shaft. By this positive locking a rotation of the sprocket assembly relative to the base body (tangential to the axis of the second shaft) is prevented or at least limited to a negligible extent. In the broadest sense, this means that an inner contour of the sprocket assembly and an outer contour of the base body engaged therewith are not formed concentrically circular with respect to the second shaft. Rather, the base body has radially outwardly projecting structures which engage with radially outwardly receding structures of the sprocket assembly and / or the sprocket assembly has radially inwardly projecting structures which engage with radially inwardly receding structures of the base body.

It is envisaged that a slight elastic expansion is necessary for placing the sprocket assembly on the base body, so that the sprocket assembly is then biased radially inwardly against the base body, thereby providing e.g. the positive connection improved and / or can be supplemented by a traction. In other words, the sprocket assembly is placed under elastic expansion on the base body and thus biased radially inwardly against the base body.

As mentioned, the sprocket assembly has outer teeth that are elastically deformable while the base body is inelastic. These properties are first of all to be understood in relation to one another, i. the elasticity of the outer teeth is significantly greater than that of the base body, so that the latter can be neglected during normal operation of the gear unit. One could also call the base body rigid or rigid. For example. For example, the base body may be made of a material whose modulus of elasticity is at least 10 times greater than that of a material from which the teeth are made (at least in part). The modulus of elasticity of a material of the teeth may in particular be less than 10. As will be explained later, in addition to elastic materials, the outer teeth may also have inelastic materials. The outer teeth engage with the first gear, or with teeth thereof. In its entirety, the wave wheel thus acts like a gear. The term "outer teeth" means that they lie radially outward with respect to the second shaft. The pitch (that is, the distance from the center of the tooth to the center of the tooth) of the sprocket assembly is normally identical to that of the first sprocket, although slight deviations from this would be conceivable. Preferably, the outer teeth are arranged concentrically with respect to the second shaft or at the same distance from it.

The outer teeth do not behave rigidly with respect to the base body, but may experience elastic deformation upon engagement with the first gear. This makes it possible that even if the shape of the sprocket assembly is not exactly matched to the first gear, nevertheless a play-free engagement takes place, since any inaccuracies are compensated by an elastic deformation of the outer teeth. It would even be conceivable that this could compensate for a systematic inequality of the pitch of the sprocket assembly and the first gear, if this inequality is not too large. The same applies to any lack of concentricity of the first gear or the shaft wheel. Since therefore no particularly low manufacturing tolerances must be met, the manufacturing process is cheaper. In addition, by the elastic material of the outer teeth, a noise by the collision with the teeth of the first gear is largely suppressed. In addition, the transmission of vibrations between the first and second shaft is damped. In this case, the gear unit according to the invention can be realized inexpensively, since the base body can be made in one piece, which stands in contrast to strained two-piece gears in the prior art. The sprocket assembly can be made relatively inexpensive. As a result of that the first gear is in engagement with the elastic outer teeth, it is mechanically less loaded, so that can be dispensed with, if necessary, a costly curing.

The base body is formed as a second gear, wherein the sprocket assembly has inner teeth which are arranged between base body teeth of the base body. The positive connection is thus produced by the inner teeth and the base body teeth. The inner teeth are preferably elastically deformable. In principle, the pitch of the second gear can be selected independently of that of the first gear, since these two gears do not mesh directly with each other. If a gear ratio of 1 between the first gear and the shaft wheel is provided, the first gear normally has a larger outer radius than the second gear, since the gear ring arrangement is still arranged on this outside. To ensure the safest possible engagement, the number of inner teeth preferably corresponds to the number of base body teeth, so that in each case an inner tooth is arranged between two base body teeth and vice versa. If the inner teeth or at least adjacent parts of the sprocket assembly are elastically deformable, the shape or arrangement of the inner teeth must not be adapted with particular accuracy to the shape or arrangement of the base body teeth, since any deviations can be compensated by elastic deformation. The embodiment described here can be advantageous insofar as it may not be necessary to provide a specially designed component for the base body, but rather a somewhat conventional gear wheel can be used.

According to the invention, in each case an inner tooth is arranged opposite an outer tooth. By this is meant that said teeth face each other radially. This may in some circumstances have advantages in terms of stability, since the inner tooth between two base body teeth is normally arranged relatively stable and an adjacent arrangement of the outer tooth can stabilize the latter with.

At least some of the inner teeth and / or the outer teeth have, according to the invention, an inelastic core, which is at least partially surrounded by elastic material and is formed continuously from an outer tooth to an inner tooth. Normally, all outer teeth have an inelastic core. Such a core may, for example, consist of metal, ceramic or hard plastic. Its function is to give the respective tooth a better stability. By making the inelastic core continuous from an outer tooth to an inner tooth, the above-mentioned stabilization of the outer tooth by the inner tooth is maximized. The elastic material forms a cover layer over the inelastic core. It may, for example, be rubber-elastic material in which optional fibers are incorporated for reinforcement.

Preferably, the inner and outer teeth extend from an intermediate, annular band portion. In this case, the annular band section effectively produces the cohesion of the sprocket arrangement. It can be optimized in terms of shape and composition with respect to this function, for example. Such that it optimally absorbs tangential forces acting between adjacent teeth. As such, the band portion may be in the shape of a cylinder barrel from which the respective teeth extend radially inward and outward, respectively. In this embodiment, the sprocket assembly may be formed by a double or double toothed toothed belt. However, its dimension is selected so that it surrounds the base body circumferentially, with at most regions, a slight distance between the timing belt and the base body is given. The base body is in turn designed as a gear, so that the gear unit can be realized with conventional per se components, which are used here, however, in a non-conventional manner.

The advantages of the gear unit according to the invention can be realized particularly well when the sprocket assembly is at least partially made of rubber-elastic material. One could also speak of an elastomer. Conceivable materials here would be, for example, rubber, certain types of rubber or polyurethane. In particular, at least one near-surface region of the inner and / or outer teeth can consist of rubber-elastic material.

Advantageously, the sprocket assembly is at least partially made of composite material. Here, a layered structure is conceivable in which, for example, the above-mentioned band section can be constructed of several layers. Furthermore, it is conceivable that the sprocket assembly has a layer on a surface, for example, has a particular abrasion resistance. If, as described above, a near-surface region of the teeth consists of rubber-elastic material, then a (thin) cover layer can be applied to this, which only slightly affects the overall rubber-elastic behavior. It is also possible that in the band portion, the inner teeth and / or the outer teeth individual fibers or fabrics or scrim of fibers are embedded, for example, to increase the tensile strength or rigidity. It could also be incorporated hard material particles that increase the abrasion resistance. The fibers or particles would be each embedded in a matrix of elastic material, such as rubber-elastic material, which includes the possibility that they partially protrude from this material. In addition to the positive connection in order to further improve the structural integrity of the wave wheel, it is possible that the sprocket assembly is integrally connected to the base body. That is, the sprocket assembly can be made separately in advance and then adhered to the base body.

According to one embodiment, which can be advantageously used, for example, in an internal combustion engine with two balance shafts, the transmission unit has a third shaft with a third gear attached thereto, wherein the shaft wheel engages in the third gear. The above-described positive effects of the coupling of the first gear on the elastic outer teeth arise here, of course, also in the coupling of the third gear to the shaft wheel. The third gear may be similar to the first gear inelastic, for example. Made of metal, be formed. Also, a one-piece and thus cost-effective production of the third gear is possible, in contrast to the prior art, with comparable arrangements, an additional two-piece gear is necessary to prevent unwanted play. In this case, the first shaft may be the crankshaft of the engine, while the second and third shaft are two mutually coupled balancing shafts. Alternatively, however, it would also be conceivable, for example, for the first and third shafts to be designed as balancing shafts, while the second shaft is the crankshaft.

• 1 eine schematische Darstellung einer ersten Ausführungsform einer erfindungsgemäßen Getriebeeinheit;
• 2 eine schematische Darstellung einer zweiten Ausführungsform einer erfindungsgemäßen Getriebeeinheit; sowie
• 3 eine vergrößerte teilweise Schnittdarstellung eines Teils der Getriebeeinheit aus 1.

Further advantageous details and effects of the invention are explained in more detail below with reference to exemplary embodiments illustrated in the figures. Show it:

• 1 a schematic representation of a first embodiment of a transmission unit according to the invention;
• 2 a schematic representation of a second embodiment of a transmission unit according to the invention; such as
• 3 an enlarged partial sectional view of a part of the transmission unit 1 ,

In the different figures, the same parts are always provided with the same reference numerals, which is why these are usually described only once.

1 shows a first embodiment of a transmission unit according to the invention 1 , which in the present case is part of an internal combustion engine of a motor vehicle. Here is a first gear 3 rotationally fixed to a crankshaft 1 coupled, which is rotatably mounted on a (not shown) motor housing. The first gear 3 consists of metal, for example sintered metal, steel, gray cast iron or aluminum, and is essentially inelastic or stiff. This means that the first gear 3 and in particular a plurality of first teeth 4 which are formed on the outside, experience no appreciable deformation during operation of the transmission unit.

The first gear 3 works with a wave wheel 6 together, the rotation with a balance shaft 5 connected is. While the first gear 3 is made in one piece, has the Wellenrads 6 inside a second gear 7 on, that is a base body of the wave wheel 6 forms, and on the outside a double-toothed timing belt 10 , which is a sprocket assembly of the wave wheel 6 forms. The dimensions of the toothed belt 10 are chosen so that it under slight radial bias outside on the second gear 7 seated. This internal teeth attack 11 of the toothed belt 10 in second teeth 8th of the second gear 7 one or are arranged intermittently between them. This is in the tangential direction a positive connection between the second gear 7 and the timing belt 10 manufactured, whereby these are torque-coupled to each other. Outer teeth 12 of the toothed belt 10 , each inner teeth 11 are arranged opposite each other, grab in the first teeth 4 and thus enable a torque transmission from the first gear 3 on the wave wheel 6 , To the structure of the second teeth 8th To make it more visible is part of the timing belt 10 omitted and shown with a dashed line whose contour.

As in the partial sectional view in 3 It can be seen that a part of the wave wheel 6 shows, points the timing belt 10 a matrix of rubber 13 on, in the area of the internal teeth 11 as well as external teeth 12 reinforcing body 14 are embedded in metal. Instead of rubber, another elastomer could be used. Here is each reinforcing body 14 from an inner tooth 11 into an outer tooth 12 formed throughout. This results in a total stabilization of the outer teeth 12 and an improved coupling to the second gear 7 , The reinforcing body 14 forms an inelastic core of the respective tooth 11 . 12 However, it is made of an elastic rubber coat 13 is surrounded. This is the particular tooth 11 . 12 still elastically deformable. As an alternative to the embodiment shown here, the reinforcing body could 14 also be completely omitted, it could be separate reinforcing body for the inner teeth 11 and outer teeth 12 be provided or the respective reinforcing body could be on the inner tooth 11 or the outer tooth 12 be limited. Like both in 1 as well as in 3 recognizable, go the inner and outer teeth 11 . 12 on both sides of a band section 15 out, which is circular along the toothed belt 10 extends. To this band section 15 To stabilize against tangentially acting tensile forces, this can, for example, by fibers 16 (For example, carbon fibers or glass fibers) are reinforced. In 3 end the fibers 16 each before a reinforcing body 14 but you can also be around it. Both the reinforcing body 14 as well as the fibers 16 become during the original forming of the toothed belt 10 in the matrix of rubber 13 stored. The positive connection between the toothed belt 10 and the second gear 7 can optionally be supplemented by a material connection in which the timing belt 10 is glued.

Because of that, the first teeth 4 in the elastically deformable outer teeth 12 intervene, the noise of the gear unit 1 significantly reduced. In addition, any vibrations are only slightly between the crankshaft 2 and the balance shaft 5 be transferred because of this by the rubber 13 of the toothed belt 10 be steamed. In addition, for a backlash-free intervention neither the first teeth 4 even the outer teeth 12 be made with special precision, since any deviations due to the elastic deformation of the outer teeth 12 can be compensated. In addition, the mechanical load of the first teeth is reduced 4 , which is why they do not need to be hardened consuming. The same applies, of course, for the second teeth 8th of the second gear 7 ,

As an alternative to the embodiment shown here, a shaft wheel, which has a shaft-side toothed wheel and a toothed belt seated thereon, could be attached to the crankshaft 2 be attached while on the balancer shaft 5 a one-piece gear is attached. This would essentially involve the same advantages.

1 shows a gear unit 1 with a single balance shaft 5 , There is a gear ratio of 1 given. 2 shows an alternative embodiment with two balance shafts 5 . 17 , This engages the wave wheel 6 a first balance shaft 5 with the first gear 3 the crankshaft 2 one. The first gear 3 can be used for the embodiment in 1 be formed identical. In contrast to 1 Here is a ratio of 2 between the first gear 3 and the wave wheel 6 selected. Accordingly, both the second gear 7 as well as the on this seated timing belt 10 smaller dimensions than in 1 and have a smaller number of second teeth 8th , internal teeth 11 as well as external teeth 12 on. The wave wheel 6 acts with a third gear 18 together, the rotation with a second balance shaft 17 connected is. In this case, the third gear 18 also be made in one piece from metal. Outside third teeth 19 of the third gear 18 grab it in the outer teeth 12 a, which is characterized by the elastic deformability of the outer teeth 12 here too the above with respect to the first gear 3 and the wave wheel 6 described advantage.

Both at 1 as well as at 2 is the wave wheel 6 mechanically comparatively simple and can be manufactured inexpensively. It consists of a substantially conventional, integrally manufactured second gear 7 as well as a toothed belt 10 , which is also made in one piece. A mechanically complicated multi-part manufacturing is eliminated and there are no particularly low manufacturing tolerances to comply. Because of this, the transmission unit 1 especially inexpensive to produce.

LIST OF REFERENCE NUMBERS

1

gear unit

2,5,17

wave

3, 7, 18

gear

4, 8, 19

tooth

6

shaft wheel

10

toothed belt

11

inner tooth

12

outer tooth

13

rubber

14

reinforcing body

15

band section

16

fiber

Claims (5)

A gear unit (1) comprising a first shaft (2) having a first gear (3) attached thereto and a second shaft (5) having a shaft gear (6) attached thereto and cooperating with the first gear (3), the shaft gear (6) on the shaft side has an inelastic base body (7) designed as a second gearwheel and on the outside a integrally formed sprocket assembly (10) connected in a torque transmitting manner to the base body (7), the elastically deformable outer teeth (12) for engagement with the first gearwheel (3 ) and inner teeth (11) which are arranged between base body teeth (8) of the base body (7), whereby the sprocket assembly (10) is positively connected to the base body (7), and the sprocket assembly (10) under elastic Expansion on the base body (7) placed and thus biased radially inwardly against the base body (7), characterized in that in each case an inner tooth (11) an outer tooth (12) is arranged opposite and at least some of the inner teeth (11 ) and the outer teeth (12) comprise an inelastic core (14) at least partially surrounded by an elastic material (13) and formed continuously from an outer tooth (12) to an inner tooth (11). Gear unit after Claim 1 , characterized in that the inner (11) and outer teeth (12) emanate from an intermediate, annular band portion (15). Transmission unit according to one of the preceding claims, characterized in that the sprocket assembly (10) at least partially made of rubber-elastic material (13). Transmission unit according to one of the preceding claims, characterized in that the sprocket assembly (10) is integrally connected to the base body (7). Transmission unit according to one of the preceding claims, characterized by a third shaft (17) with a third toothed wheel (18) attached thereto, the shaft wheel (6) engaging with the third toothed wheel (18).

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