Housing for an actuator for receiving an electric motor and an assembly

A housing for an actuator for receiving an electric motor and further functional units of the actuator, wherein a can is integrally molded to an inner face of the housing that is designed to receive the electric motor and wherein means of fastening are integrally molded to the can that are designed to position and fix the electric motor accommodated in the can.

FIELD OF THE INVENTION

The invention relates to a housing for an actuator for receiving an electric motor as well as an assembly having a housing and an electric motor.

BACKGROUND

One field of application of the invention is in actuators having small motors that require a compact construction and light weight, particularly small-scale brushless DC motors which are used in the automotive industry, such as a small motor actuator, a fan and cooler motor, a drive for flap actuators used, for example, in air conditioning units and for cooling the motor etc., the invention not being limited to these applications. Other electric motors could also be used.

Common electric motors generally have a motor housing by means of which they are connected to the housing of the actuator. Electric motors for flap actuators that do not have their own motor housing are also known, their shape being made to conform to a recess in the housing of the actuator in such a manner that allows them to be fixedly supported in the recess. For example, small motors having a partially out-of-round stator are thus supported in a positive fit in an appropriate recess in a wall of the housing.

For known actuators there is the problem that an additional motor housing or specially formed components of the electric motor have to be provided so as to fixedly position the electric motor in the housing of the actuator, further means having to be provided for the purpose of fixing the electric motor to the housing. This accordingly results in an increase in the amount of material needed and requires a more complex assembly of the electric motor in the housing of the actuator.

It is thus an object of the invention to provide a means of support and attachment for an electric motor in a housing of an actuator that avoids the disadvantages described above and at the same time allows the simplest possible and most compact construction for the housing.

SUMMARY

The invention provides a housing for an actuator for receiving an electric motor and further functional units of the actuator, where a can that is designed to receive the electric motor is integrally molded to an inner face of the housing. Means of fastening are in turn integrally molded to the can which are designed to position and fix the electric motor accommodated in the can.

In the housing according to the invention, the electric motor can be easily disposed, positioned and fixed. Here, there is no need for either an extra motor housing or for further components of the electric motor. Moreover, it is not necessary for the electric motor to be given a shape that conforms to the housing whose only function is to allow its non-rotatable support in the housing through a positive fit with the housing. Instead, according to the invention, a can for receiving the electric motor is integrally molded to an inner face of the housing, the can being equipped through the use of integrally molded fastening means to position and fix the electric motor.

The can makes it possible to precisely position and center the electric motor and safeguards the motor against radial displacement. Moreover, the distance of the means of fastening with respect to one another and to the can may be used to ensure that the centered electric motor can only be inserted into the can with a desired orientation. Since no further production steps for adjusting the electric motor need be carried out, assembly is made more simple and speedier. In addition, the means of fastening may engage in the electric motor so as to fix the electric motor. The electric motor is accordingly effectively safeguarded by the can and the means of fastening not only from turning but also from any radial and axial displacement in the housing.

In one embodiment, the means of fastening takes the form of pins integrally molded to the can that interact with corresponding fastening elements, such as mounting ears, on the electric motor. It is also possible to provide mounting ears on the can and corresponding pins on the electric motor or any other kind of interacting fastening elements, such as locking or snap connectors. In one embodiment, mounting ears are integrally molded to the outside circumference of the electric motor, into which pins on the outside circumference of the can engage. Moreover, fastening bars may be integrally molded to the outside circumference of the can that form supporting surfaces from which at least one pin projects in an axial direction and on which the corresponding fastening element of the electric motor rests, so that the pin engages, for example, in a mounting ear. One pin can be provided for each fastening bar, the pin engaging in a mounting ear of a fastening element. Two or more pins per fastening bar may also be provided, each of which can engage in separate fastening elements or in the same fastening element. The pins (means of fastening) engaging in the mounting ears (fastening elements) safeguard the electric motor against turning as well as against any radial displacement. To effectively prevent an axial displacement, the pins may be connected to the mounting ears using a positive fit or a force fit.

The can may be dimensioned such that it tightly encloses the outside circumference of the electric motor and forms a motor housing. In this way, the electric motor can be particularly effectively safeguarded against radial displacement. In addition, noise and vibrations caused by the electric motor can be dampened through the shape given to the can.

The housing may be designed to receive a gear unit having at least two gear stages and to position and support the gear stages with respect to one another and with respect to the electric motor. For this purpose, either bearing supports may be provided in the housing that can receive a shaft of a gear wheel of one of the gear stages, or bearing supports for axles which can receive a shaft of a gear wheel may be provided. Here, the bearing supports may be injection molded to an inner wall of the housing and take the form of hollow cylinders or cylindrical projections in which the corresponding axles of the gear stages can be inserted. This kind of bearing support may also be formed in or on the side wall of the can so as to make positioning of the electric motor even more simple.

According to a further embodiment of the invention, pins or other means of fastening are integrally molded to the housing, such as snap-in hooks, bars etc., for positioning and fixing further functional units, such as circuit boards. The pins may be formed on bars in the housing that act as a supporting surface for the respective functional unit, where the pins can engage in corresponding fastening elements of the functional units, for example, in corresponding openings in the circuit board. This goes to produce a particularly stable support for the functional units. Through a circuit board or other functional unit disposed above the electric motor, the electric motor may additionally be safeguarded against displacement in an axial direction. The means of fastening engaging in the fastening elements of the functional units, such as pins led through the openings in the circuit board, may be hot caulked. As an alternative, the pins may take the form, for example, of snap-in connectors or press-fit pins that interact with the functional units.

In one embodiment, the housing is designed as a single piece injection-molded part. Here in particular, the can and the pins may be injection molded to the housing. This one-piece construction makes the manufacture of the housing more simple since no further production steps are needed to affix additional components for positioning and fixing the electric motor.

The housing according to the invention may be used in an assembly having an electric motor whose stator has slot insulation, where the slot insulation has fastening elements that interact with the means of fastening integrally molded to the can. The stator of the electric motor can thus be inserted into the can such that mounting ears integrally molded to the slot insulation, for example, rest on the rim of the can and project laterally beyond the rim of the can, so that they interact with pins integrally molded to the can.

Since the fastening elements are directly formed on the slot insulation, the manufacture of the stator is made considerably more simple. In particular, no further production steps whatsoever are needed to affix additional means of fastening to the stator or the electric motor. It is advantageous if the slot insulation is manufactured as a two-piece injection-molded plastic part and slid onto each side of the stator of the electric motor in an axial direction.

In one embodiment of the invention, a flange is formed on an end face of the slot insulation to which the fastening elements are integrally molded, the fastening elements protruding radially from the flange. The flange may form a supporting surface that is adapted to conform to the rim of the can in the housing. The flange can then lie flush on the rim of the can and the fastening elements integrally molded to the flange can jut out from the rim of the can, which goes to facilitate the support and positioning of the stator for its attachment in the housing.

In a further embodiment of the invention, at least one projection for aligning the electric motor is formed on the inner face of the can. Thus a projection extending in an axial direction may be formed on the inner face, the projection interacting with a corresponding groove on the electric motor such that the electric motor is safeguarded against turning. For example, longitudinal axial grooves may be formed on the outer face of the stator back yoke, one of the longitudinal grooves being slid over the projection in the can as the electric motor is inserted.

In an embodiment, the bottom of the can and the opposing bottom end face of the slot insulation interact with each other so as to position the stator of the electric motor. Thus the slot insulation on the bottom end face may have, for example, a depression, so that the stator can be fixedly supported on the correspondingly shaped can bottom. The stator can be additionally safeguarded against turning by the depressions, and with the appropriate design and number of depressions also against radial displacement. Thus, in the bottom of the can at least one radially aligned strut may be formed that engages in a corresponding depression. The design of the inner face of the can and the bottom of the can may thus allow the stator of the electric motor to be more effectively safeguarded against turning within the can.

In a further embodiment of the invention, one or more bearing supports are formed on an inner wall of the housing that are used to support a hollow shaft of the rotor of the electric motor and/or axles of one or more gear stages.

In an embodiment, at least one bearing support, which is used to support an axle of a gear wheel, is formed in the side wall of the can. A corresponding recess may be provided in the slot insulation that at least partly engages around the bearing support in the side wall when the electric motor is set in the can. This makes it possible for the stator to be even more effectively safeguarded against turning, and positioning the stator in the can is made more simple.

In an embodiment, projections are formed on the end face of the slot insulation facing away from the can bottom, the projections projecting in an axial direction and forming a wire guide. The projections may be formed near an inside circumference of the slot insulation and have at their exposed ends an angled rim, so as to produce an L-shaped cross-section. The rim ensures that the wires led through the wire guide cannot be displaced in an axial direction over the ends of the projections. The wire guide thus allows the wires to be accurately led to individual coils of the electric motor. Since the projections can be integrally formed with the other components of the slot insulation as one piece, this results in increased material savings and an optimization of the manufacturing process.

In a further embodiment, a connector pin is embedded in at least one of the axial projections. The connector pin may extend in an axial direction from the end face. The connector pins may be pressed into the respective projection and establish electrical contact to one of the respective coils via a wire fed into the wire guide, thus allowing the individual coils to be controlled simply and effectively without the need for any other structural elements to be provided on the stator.

According to one embodiment, a circuit board is disposed on the end face of the electric motor facing away from the bottom of the can and connected to the housing such that the electric motor is safeguarded against displacement in an axial direction. Here, the circuit board may cover the electric motor, the shaft of the rotor of the electric motor being led through a corresponding opening in the circuit board. The circuit board is in contact with connector pins of the stator, so that the coils of the electric motor are electrically connected to the circuit board via the connector pins. In addition, the circuit board can be supported and fixed to the housing by pins, using, for example, a positive-fit or force-fit attachment. Thus through the circuit board, the coils of the electric motor may be controlled via the connector pins, and at the same time, in addition to its attachment using the fastening elements, the electric motor can also be safeguarded against axial displacement using the circuit board.

As mentioned above, in one embodiment of the present invention the motor housing is formed only by the can.

In one possible application, the assembly according to the invention is an actuating drive for a flap actuator in a motor vehicle and has a brushless DC motor whose outside circumference is less than or equal to 60 mm, or less than or equal to 30 mm. The stator of the electric motor may have a diameter between 12 and 50 mm, such as about 24 mm. The rotor of the electric motor may accordingly have a diameter between 8 and 30 mm, such as about 12 mm.

DESCRIPTION OF EMBODIMENTS

FIG. 1shows an assembly according to an embodiment of the present invention in an exploded view. The assembly1has an electric motor, particularly a brushless DC motor having a stator3and a rotor5, a circuit board7for controlling the DC motor and a gear unit9that is driven by the DC motor. The DC motor, the circuit board7and the gear unit9are disposed in a housing11that can be closed by a cover11′. The cover11′ may additionally have a seal so as to protect the interior of the assembly1from soiling and any other outside influences.

The DC motor is accommodated in the housing11in a can13that is integrally molded to an inner face of the housing11. The can13has an inside diameter that largely corresponds to the outside diameter of the stator3, so that the can13tightly encloses the stator3. According to the invention, pins15are integrally molded to the can13for the purpose of positioning and fixing the DC motor. The stator3is provided with slot insulation17that has a flange19on an end face to which mounting ears21are integrally molded that project in a radial direction from the outside circumference of the slot insulation17. The pins15are led through the mounting ears21so as to position the stator3in the can13with respect to the housing11and to fix it to the housing11. For this purpose, the pins15are formed on the rim of the can13such that the rim of the can forms a supporting surface for the flange19and the mounting ears21of the slot insulation17, and the pins15are led through the mounting ears21. This goes to safeguard the stator3against any radial displacement and turning. The pins15led through the mounting ears21may, for example, be hot caulked so that the stator3can also be safeguarded against any axial displacement.

Thus, to attach the DC motor to the housing11, it is not necessary to have an extra motor housing nor do parts of the DC motor need to be given a special form so as to allow the stator3to be supported in the housing11in a positive fit. According to the invention, the stator3is rather directly positioned with respect to the housing11and fixed to the housing11using the can13and the integrally molded pins15. This makes mounting the DC motor in the housing11considerably more simple.

The support for the stator3may be further optimized in that a longitudinal groove27is provided in a back yoke ring25of the stator3into which a corresponding projection (not illustrated) in the inner wall of the can13can be guided. What is more, evenly spaced depressions29are formed on a bottom end face of the slot insulation17opposing the bottom of the can in the region of the stator slots, into which appropriately formed projections (not illustrated) in the bottom of the can13may engage. The depressions29as well as the longitudinal groove27safeguard the stator3against turning in the can13in addition to the mounting ears21of the slot insulation17.

In order to simplify mounting and adjusting the stator3and thus the DC motor in the can13, a bearing support31for a shaft or an axle of the gear unit9is furthermore formed on the side wall of the can13. The flange19of the slot insulation17accordingly has a recess33which at least partially encloses the bearing support31when the stator3is set in the can13. This goes to ensure that the stator3inserted in the can13always assumes a predetermined orientation. Moreover, through the slot insulation17, the bearing support31additionally safeguards the stator3against turning.

The DC motor is additionally attached with the aid of the circuit board7that rests on the end face of the slot insulation17and thus secures the stator3in an axial direction. The circuit board7is attached to the housing11using bars37that form a supporting surface for the circuit board7, pins of the bars37engaging in corresponding openings39in the circuit board. The ends of the pins may be hot caulked so as to permanently fix the circuit board7. However, the invention is not limited in this respect. So that instead of hot-caulked pins, other positive-fit and/or force-fit connections, such as snap-in connectors and press-fit pins may be used. On its end face facing the circuit board7, the slot insulation17has a series of L-shaped projections35that act as wire guides for the coil wires.

The electrical contact between the circuit board7and the stator3is effected using connector pins41that are pressed into the projections35of the slot insulation17and extend in an axial direction from the end face of the slot insulation17. The connector pins41are led through corresponding openings in the circuit board7and soldered on there. The connector pins41are in turn connected to the respective coils of the stator3so as to establish electrical contact between the circuit board7and the coils of the stator3.

Alongside a processing unit, the circuit board7may include a plurality of sensors that determine the rotational position of the rotor5. For example, at least one Hall sensor may be disposed on the circuit board7to directly measure the axial leakage field of the rotor5. The circuit board7may furthermore have an interface for communication and/or power supply, such as a connection to any data bus or a specialized field bus like the LIN bus.

The rotor5comprises a magnet carrier43on which an annular permanent magnet45is disposed. The magnet carrier43is integrally formed with a shaft47which is led through an opening49in the circuit board7. The shaft47has a gear wheel47′ that drives the downstream gear unit9. Both the shaft47as well as the gear wheels53,53′,53″ are supported on axles55aor55b,55cand55d, where the axle55ais disposed in the can13and the axle55bis disposed in the bearing support31in the side wall of the can13. Moreover, the shaft of the gear wheel53′″ is directly supported in a bearing support in the housing11.

Thanks to the integral construction of the housing11as one piece, the illustrated embodiment of the assembly1according to the invention facilitates material-saving in the manufacturing process and thanks to the can13and the integrally molded pins15, it enables rapid mounting of the DC motor in the housing11.

The illustrated assembly1can be used as an actuator where the rotational speed of the rotor5may, for example, be up to 4,000 rpm, for example, in the range of 500 to 2,500 rpm in order to generate a rotational speed at the drive side of, for example, 3 to 10 rpm and a torque of, for example, 1 to 2 Nm. One field of application of the invention is in the automotive industry for controlling flap actuators, for example, in air conditioning units or for the motor control, the present invention not being restricted to these applications.

The housing11and the stator3of the assembly1according to the embodiment of the invention illustrated inFIG. 1are further illustrated in a view from below and in a perspective view inFIGS. 2aor2brespectively. As can be seen inFIGS. 2aand2b, the stator3is set in the can13of the housing11with the flange19resting on the rim of the can13and the pins15engaging through the mounting ears21. In the bottom of the can13, a number of radially aligned struts57are formed that engage in the depressions29in the bottom of the slot insulation17so as to safeguard the stator3against turning in the can13. Furthermore, alongside the bearing support31, the bearing support for the axle55aof the shaft47in the bottom of the can13is shown. Moreover, in the bottom of the housing11further bearing supports59for axles55c,55dof the downstream gear unit9are formed, the bottom of the housing11being reinforced by struts61extending radially to the respective axle55c,55d.

FIGS. 3aand3bshow a section through and an exploded view of a rotor as can be used in an assembly according to an embodiment of the present invention. Corresponding components are accordingly indicated by the same reference numbers as inFIG. 1. The rotor5has a magnet carrier43taking the form of a hollow shaft and a circular cylindrical permanent magnet45in which a recess63is provided through which the magnet carrier43can be guided so as to connect the shaft47to the permanent magnet45. Such a two-piece embodiment for the rotor5is particularly more cost-effective for medium-sized manufacture with a production rate of less than 1 million pieces a year than, for example, one-piece manufacture.

In the illustrated embodiment of the rotor5, the recess63through the permanent magnet45is designed as a hexagonal recess. However, the recess63could also take the form of any other polygonal recess or it may have an oval contour or any other non-circular contour. For its connection to the permanent magnet45, the magnet carrier43has at least one first connecting element65that establishes a positive fit with the recess63in the permanent magnet45, as well as at least one second connecting element67that establishes a force fit between the magnet carrier43and the permanent magnet45.

The positive fit involving the first connecting element65is established in particular using line contact that is produced through a projecting rib69which is formed in the first connecting element65parallel to the axis of the shaft and which engages in an edge71of the recess63. The projecting rib69may be high enough to allow a gap to be formed between the adjacent surfaces of the first connecting element65and the surfaces of the recess63adjacent to the edge71, so that the adjacent surfaces do not rest against each other at all or only to a very small extent. In addition, the edge71of the recess63may itself be chamfered so as to create a space between the surfaces of the first connecting element65and the recess63. This particularly advantageous embodiment of the first connecting element65reduces the risk of jamming when the two components of the rotor5are assembled, thanks to the small overlap.

The first connecting element65is bounded at one end by a projection73that extends in a radial direction from the shaft47and forms a supporting surface for the permanent magnet45mounted onto the magnet carrier43. The first connecting element65is longer than the recess63, so that the first connecting element65fully inserted into the recess63projects slightly out of the permanent magnet45in an axial direction and may be hot caulked, for example, at the end face of the permanent magnet45in order to fix the magnet carrier43to the permanent magnet45. For this purpose, the permanent magnet45has a chamfer75at the rim of the recess63that can receive the material of the first connecting element65displaced by the hot-caulking process. As an alternative or in addition, the magnet carrier43may have clips or other means of fastening to fix the magnet carrier43axially to the permanent magnet45. Irrespective of the way in which the magnet carrier43is axially fixed to the permanent magnet45, the first and second connecting elements65,67as provided can effectively solve the problem of distortion during assembly of the rotor.

The second connecting element67that establishes a force fit with the permanent magnet45may be designed as a bending or locking element. As shown inFIG. 3b, the second connecting element67comprises two adjacent wings77aand77band a bar extending parallel to the axis of the shaft and projecting radially that connects the wings77aand77bin the manner of a Y profile. When the magnet carrier43is thus inserted into the permanent magnet45, the wings77aand77bexert pressure at their exposed longitudinal ends on the adjacent surfaces of the recess63, the pressure being high enough to hold the magnet carrier43in the permanent magnet45but low enough to allow the magnet carrier43to be inserted manually into the permanent magnet45. Alternatively, the wings77aand77bmay be dimensioned such that the exposed longitudinal ends engage in the edges71of the recess63or in corresponding chamfers of the edges71and thus exert pressure on the permanent magnet45.

The second connecting element67thus allows a force fit to be established, alongside the positive fit, in a particularly advantageous way, the force fit compensating for the radial play that occurs due to manufacturing tolerances. Particularly with regard to the connections known in the prior art using a press fit and injecting the magnet carrier43, the illustrated positive-fit and force-fit connection allows simpler mounting and increased resilience in operation.

In the illustrated embodiment, the magnet carrier43may comprise two opposing first connecting elements65and added to this two opposing second connecting elements67offset by 90°, so that in the illustrated hexagonal recess63, the ribs69are inserted into the opposing edges71of the recess63and the bars of the second connecting elements67are positioned in the middle and perpendicular to a surface of the recess63. If the wings77a,77bare made wide enough, each edge71of the recess63is then connected to the magnet carrier43in either a positive fit or a force fit, as shown inFIG. 3c.

The permanent magnet45may be manufactured as an injection-molded magnet or as a pressed sintered magnet. The polarization of the permanent magnet45may be adapted to the recess63such that if the recess63has a polygonal contour, the pole transitions of the permanent magnet45are formed at the edges71or narrow areas between the recess63and the outer wall of the permanent magnet45, as shown inFIG. 3c. For example, for a hexagonal recess, a six-pole permanent magnet is then provided. The magnet carrier43may be manufactured in one piece in an injection-molding process using a thermoplastic material.

FIGS. 4 and 5illustrate a gear unit as can be used in an assembly according to an embodiment of the present invention. Here,FIG. 4shows an exploded view of the gear unit andFIG. 5a view from below of the assembled gear unit ofFIG. 4. Corresponding components inFIGS. 4 and 5are indicated by the same reference numbers as inFIG. 1. The gear unit9of the assembly1comprises a plurality of double gear wheels that are indicated inFIGS. 4 and 5by79a,79band79c. Each of the double gear wheels takes part in two gear stages, where a first gear stage is formed between the gear wheel47′ on the shaft of the electric motor and the first double gear wheel79a, a second gear stage is formed between the first and the second double gear wheel79a,79b, a third gear stage is formed between the second double gear wheel and the third double gear wheel79band79cand a fourth gear stage is formed between the third double gear wheel79cand the drive wheel81. In the illustrated embodiment, the third double gear wheel79ccomprises two identical double gear wheels83,83′ connected in parallel which mesh with the second double gear wheel79bto form the third gear stage, and with the drive wheel81to form the fourth gear stage. The torque transmitted by the second double gear wheel79bis thus evenly distributed to the two third double gear wheels83,83′ and from there concentrated again to the drive wheel81.

As mentioned at the outset, increased torque occurs at the drive wheel81for any specific load due to gear reduction in the respective gear stages, which necessitates designing the geometry and the material of the gear wheels at the drive side to be correspondingly more robust so as to withstand the greater load. In practice, for example, in the last gear stage, i.e. from the third double gear wheel79cto the drive wheel81, a torque can be transmitted which is ten times greater than the torque transmitted by the first stage. If we assume that due to cost considerations and in order to limit space requirements, each gear wheel is only designed to be as large and as stable as is required by the expected load in its gear stage, then for gear chains having only one gear wheel per stage, the gear wheels have to be designed with materials of varying resilience and/or with varying geometries; in particular, the gear wheel in the last stage has to be made of a particularly resilient material and/or with a reinforced gear geometry and a thicker shaft, so as to be able to transmit maximum torque in all possible applications. This results in increased manufacturing costs for the assembly1. If the assembly1is to be of use in different applications in which different nominal torques are to be transmitted, it always has to be designed to take the largest potential load. In contrast, the assembly1according to the invention allows high torque to be transmitted to the drive wheel81and at the same time the load on the individual gear wheels83,83′ of the last stage to be alleviated. When the two double gear wheels83,83′ are used, they are driven in parallel by the previous double gear wheel79band they themselves in turn drive the drive wheel81in parallel. This goes to halve the torque acting on the two double gear wheels83,83′ and despite the lower load on the individual double gear wheels83,83′, increased torque can accordingly be transmitted to the drive wheel81. This in turn makes it possible to use a comparably less robust and thus more cost-effective material as well as a smaller gear geometry, shaft diameter etc.

The invention also makes it possible for one of the double gear wheels83,83′, for example the double gear wheel83′, to be subsequently removed from the gear unit9when there is no need for increased torque on the drive side81. The function of the assembly1remains the same with the only difference being that with one double gear wheel83the maximum torque at the drive side81is less. The gear unit9is thus particularly versatile in its application.

In an embodiment having a gear ratio of approximately 4 to 5 per gear stage and a rotational speed at the drive side81of between 3 and 10 rpm, having, for example, one double gear wheel83in the last stage on the drive side81, a nominal torque of approximately 1.2 Nm is transmitted and with two double gear wheels83and83′, a nominal torque of approximately 1.75 Nm is transmitted. This data is simply meant to provide an idea of the scale of magnitude of the gear unit according to the invention.

Plastics having a filler may be used as the materials, such as polyoxymethylene and various types of polyamide. For the filling material, fiber glass, glass beads or mineral fillers are used, the stiffness of the double gear wheels83,83′ varying according to the plastics or plastic mix used. In addition, polytetrafluorethylene can be used for lubrication.

Although the gear unit9inFIG. 4andFIG. 5is described on the basis of gear wheels and double gear wheels, the gear unit9that can find application in the assembly1according to the invention is not limited to gear wheels and double gear wheels. Rather, any kinds of gear units and gear wheels can be used, such as in a planetary gear, spiral gear, worm gear, chain gear or in a gear unit having a synchronous belt drive and in other gear units, gear wheels, frictional wheels, worm wheels and others supported on different shafts.

Due to the constant reduction of the gear stages and the thereby increasing torque, it is advantageous to use two gear wheels83,83′ connected in parallel before the drive side so as to reduce the load placed on the gear wheels in the last gear stage.

The characteristics revealed in the above description, the claims and the figures can be important for the realization of the invention in its various embodiments both individually and in any combination whatsoever.

IDENTIFICATION REFERENCE LIST