DE102017205721B4 - Transmission unit for a motor vehicle - Google Patents

Abstract

The invention relates to a transmission unit (1) for a power steering system of a motor vehicle, comprising an output shaft (2) running along an X direction, two worm wheels (3, 14) coupled thereto, the first worm wheel (3) and the second worm wheel (14 ) are coupled to the output shaft (2), and a first worm shaft (4) which extends along a direction perpendicular to the X direction Y-direction, with the first worm wheel (3) cooperates and torque transmitting to a first motor unit (6) is coupled .
in which
a second worm shaft (9) cooperating with the second worm wheel (14) and torque transmittingly coupled to a second motor unit (11), the first worm shaft (4) cooperating with a first portion (17) of the first worm wheel (3); second worm shaft (9) cooperates with a second section (18) of the second worm gear (14) arranged offset in the X direction, and wherein the first section (17) on the first worm wheel (3) and the second section (18) on the second Worm wheel (14) is formed and the slope of the first portion (17) opposite to the slope of the second portion (18).

Description

The invention relates to a transmission unit for a motor vehicle having an output shaft extending along an X direction, two worm wheels coupled thereto, the first worm wheel and the second worm wheel being coupled to the output shaft, and a first worm shaft extending along a direction perpendicular to the X direction Y-direction, cooperates with the first worm wheel and torque-transmitting coupled to a first motor unit.

The DE 25 26 208 deals with a reduction worm gear. A wheel with a horizontal axis of rotation has a sprocket. In the ring gear, a double toothing is cut, which interact simultaneously with two screw shafts.

The DE 10 2010 017 540 A1 deals with a steering control system. This has a transmission ratio steering (VGRS), a steering torque detection device and an electric power steering (EPS). The EPS device supports a steering force based on the steering torque. The VGRS device controls a steering ratio. Both the VGRS device and the EPS device each have an electric motor which rotates the respective screws. The EPS device, which can be considered as a transmission unit for a power steering system of a motor vehicle, but has only a worm wheel, which cooperates with a single worm shaft.

The FR 1 177 305 discloses a transmission for a high power transmission in locomotives. Here, two tangential wheels are arranged on a driven shaft, which mesh with screws. The worm shafts are driven by two auxiliary motor shafts, the drive of which is ensured in opposite directions from the individual main drive shaft by means of a suitable gear set. The auxiliary motor shafts are driven by the shaft of the motor.

Modern motor vehicles are usually equipped with a power steering, in which the steering movements of the driver are supported on the vehicle side or possibly even on the vehicle side a certain steering torque can be generated, which indicates the driver to a recommended steering movement. In addition to hydraulic power steering motor-driven power steering systems are used above all. In the latter, usually an electric servomotor with a drive shaft acts on a worm shaft, which in turn interacts with a worm wheel. The worm wheel sits on the actual steering shaft, which acts, for example. Via a pinion and a rack on a tie rod. Similar systems with servomotor, worm shaft and worm wheel are also used in motor vehicles in other areas, e.g. for window regulators, for use.

In practice, engagement between the worm shaft and worm wheel may be affected by manufacturing or assembly inaccuracies, wear effects, contamination, and environmental factors such as humidity and temperature. At times, the engagement may be too tight, resulting in increased wear, or too loose, which may result in undesirable clashing and associated noise. Normally, attempts are made to limit this problem by biasing the worm shaft against the worm wheel at least on one side via a spring-loaded rotary bearing.

Various factors limit the torque provided by the power steering. On the one hand, the worm gear or at least its outer part, which forms the toothing, is usually made of plastic, for example polyamide. Although this reduces weight and manufacturing costs compared to a metal worm wheel, the overall strength and the mechanical strength are also reduced. Due to the limited space available, the worm wheel can not simply be dimensioned larger in order to increase its stability. The flexibility of the individual teeth and the lateral stiffness of the worm wheel have a significant influence on its ability to transmit torque. The latter plays a role because due to the helical gearing of the worm wheel together with the tangentially acting force always an axially (ie perpendicular to the plane of extension of the worm wheel) acting force component is generated. On the drive side, the available torque is usually limited by the size of the motor and the available electrical power.

The CN 103448789 A discloses a motor-gear unit for power steering. Here, two drive-side worm shafts act on a driven-side worm wheel. According to one embodiment, the worm shafts are arranged at an angle to each other and in turn coupled via bevel gears to each other, wherein only one of the worm shafts is driven directly by a motor unit. According to a further embodiment, the worm shafts are arranged parallel to one another on opposite sides of the worm wheel and are driven by two separate motor units. The two motor units can do this be arranged either side by side or on opposite sides of the worm wheel.

The FR 2 938 493 A1 shows a further motor-gear unit for power steering, in turn, two worm shafts cooperate with a worm wheel. The worm shafts, which are driven by two separate motor units, are arranged parallel to each other on opposite sides of the worm wheel.

Engine-gearbox units with appropriate arrangement are in the JP 2006-076353 A and the JP 2005-119578 A described.

The JP 2006-232183 A shows a steering gear, in which two separate motor units act on a worm wheel via two worm shafts. The motor units are arranged side by side and the worm shafts are at an acute angle to each other on opposite sides of the worm wheel. In the JP 2007-069848 A a similar arrangement is shown, where there are the worm shafts at an obtuse angle to each other.

The JP 2009-078792 A shows a power steering with two motor units that drive parallel aligned worm shafts. Each of the worm shafts acts on one of two separate worm wheels, which are arranged one behind the other on a driven-side shaft. The worm shafts are arranged on the same side of the output-side shaft. A similar system is in the JP H08-258728 A discloses, where there the two worm shafts are arranged on opposite sides of the driven-side shaft.

The US 7,517,262 B2 shows a power steering for an outboard motor of a boat in which two separate servomotors drive two parallel worm shafts, which act on a common worm wheel. The worm wheel is designed here as a bevel gear.

The US 6,318,496 B1 a motor-gear unit for a power steering, in which 2 worm shafts act on a worm wheel. The worm shafts may be parallel or at an angle to each other and are coupled to each other via ordinary gears or bevel gears, one of the worm shafts being directly driven by a motor unit.

In view of the cited prior art, the provision of a compact and powerful gear unit with a worm gear offers room for improvement. This relates in particular to the provision of the highest possible torque. It would also be desirable to minimize wear and to ensure optimum engagement between the worm shaft and the worm wheel.

The invention has for its object to provide a compact and powerful transmission unit with a worm gear available.

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. The object is therefore achieved with a transmission unit for a power steering system of a motor vehicle, with an output shaft extending along an X direction, two worm wheels coupled thereto, wherein the first worm wheel and the second worm wheel are coupled to the output shaft, and a first worm shaft along a Y-direction perpendicular to the X-direction, cooperating with the first worm wheel and torque-transmitting coupled to a first motor unit. A second worm shaft cooperates with the second worm gear and is torque-transmittingly coupled to a second motor unit, wherein the first worm shaft cooperates with a first section of the first worm wheel and the second worm shaft cooperates with a second section of the second worm gear arranged staggered in the X direction, and wherein the first portion is formed on the first worm wheel and the second portion is formed on the second worm wheel and the pitch of the first portion is opposite to the pitch of the second portion.

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 transmission unit for a motor vehicle. As motor vehicles are especially cars and trucks in question. In particular, it may be a transmission unit for a power steering, although other applications, for example. For windows, electric seat adjustments or other eligible.

The gear unit has an output shaft extending along an X direction and at least one worm wheel coupled thereto, that is to say two worm wheels coupled thereto. The at least one worm wheel is normally non-rotatably connected to the output shaft, and also a one-piece training is conceivable. As the term "output shaft" indicates, this belongs to the output-side part of the transmission unit. The course of the output shaft is of course identical with its axis of rotation. In this context, the term "X-direction" is generally not to be equated with the longitudinal axis of the motor vehicle, although in some cases these may be identical in the installed state of the case. This is merely a term by means of which a reference system or coordinate system is described in the steering system. The X-direction could also simply be referred to as the "first direction" and the Y and Z directions mentioned below as the "second" and "third directions".

Furthermore, the gear unit has a first worm shaft which runs along a Y direction perpendicular to the X direction, with which at least one worm wheel cooperates and is coupled to transmit torque to a first motor unit. The motor unit may, for example, be a servomotor. The first worm shaft is normally coupled to a drive shaft of the first motor unit, and a clutch or clutch assembly is capable of transmitting torque from the drive shaft to the first worm shaft. Optionally, a mechanical transmission or reduction between the first motor unit and the first worm shaft may be provided. Furthermore, the clutch may be at least partially elastic, for example. To reduce negative effects of variations in speed or torque on the transmission. It is also possible that a mechanical translation or reduction between the motor unit and the first worm shaft is interposed or integrated into the motor unit. The first worm shaft in turn cooperates in the operating state with the at least one worm wheel, whereby a reduction is normally achieved.

The gear unit has a second worm shaft, which cooperates with the at least one worm wheel and is coupled to transmit torque to a second motor unit. The above statements regarding the first motor unit and the coupling of the first worm shaft to the first motor unit apply mutatis mutandis to the second worm shaft and the second motor unit. The two motor units can be identical. In this case, the driving force of the two motor units can be transmitted to the output shaft via the two worm shafts and the at least one worm wheel. This has a number of advantages.

First, to achieve a certain torque on the output shaft, the torques generated by the two worm shafts can be added. That the individual torque and thus also the force acting between the respective worm shaft and the at least one worm wheel are smaller. This ensures, on the one hand, that the mechanical wear of the respective worm shaft and possibly also the wear of the at least one worm wheel are reduced. The mechanical stability of the worm shaft and / or the worm wheel must meet even lower requirements, which is why the respective component can be dimensioned weaker or smaller or less deformation occurs with the same dimensions.

Since the respective motor unit also has to generate only a smaller torque, it can be made smaller and / or it is less electrically and mechanically loaded, thereby increasing its service life. It is also possible depending on the configuration that certain forces or torques, which act on the part of the two worm shafts on the at least one worm and the output shaft and do not support the actual drive, partially compensate. This is especially true for acting perpendicular to the plane of extension of the worm wheel axial forces. Apart from this, it is possible that the smoothness of the gear unit improves, for example. Due to the fact that certain production-related deviations from the ideal shape of one of the worm shafts or at least one worm wheel statistically rarely equal effect on both worm shafts, so to speak "additive" noticeable. It is more likely that the effects of such deviations will at least partially level out.

The first worm shaft, the second worm shaft and the output shaft can be mounted on a common housing (or frame) via suitable pivot bearings. At least one rotary bearing can hereby also be designed to be pivotable. Such a housing forms a reference frame normally stationary with respect to the vehicle, by means of which the relative positions of the movable gear parts are at least partially defined. The housing may be formed one or more parts. It can be more or less open. It is also possible that the transmission components mentioned here, possibly together with other transmission components, are largely enclosed by the housing. In the gear unit according to the invention, it is possible to exert oppositely acting torques on the output shaft, since the two worm shafts are operated by separate motor units. As a result, the respective worm shaft and the at least one worm wheel against each other biased, so that there are no unwanted relative movements, which can lead to rattling noises. Thus, under certain circumstances can be dispensed with an additional bias of the worm shaft against the worm wheel on one of their bearings.

In addition, the first worm shaft cooperates with a first portion of the at least one worm wheel and the second worm shaft cooperates with a second section of the at least one worm wheel arranged offset in the X direction. This implies that the first and the second worm shaft are arranged offset to one another in the X direction. The two sections can optionally also be offset from one another in the Y direction and / or Z direction. The fact that the worm shafts interact with different sections, the mechanical stress of the individual section is further reduced. It is also conceivable that in the case of a mechanical failure in the region of a section, the function of the gear unit can continue to be ensured via the other section. If, for example, a tooth breaks off in one section while the other section is still completely intact, the missing tooth can in a sense be "bridged".

In an embodiment according to the invention, a first worm wheel and a second worm wheel are coupled to the output shaft, wherein the first section is formed on the first worm wheel and the second section is formed on the second worm wheel. In other words, the first worm shaft cooperates with the first worm wheel and the second worm shaft merges with the second worm wheel. A possible advantage with such an arrangement is that the two worm gears can be arranged in a (within certain limits) arbitrary distance along the X direction on the output shaft, whereby the distance of the two worm shafts and the associated motor units are varied in this direction can. It is also conceivable that the two worm wheels have different radii, whereby, for example, a different translation can be realized. In this case, adjust the speed and torque control of the motors.

Alternatively, the first portion and the second portion may be formed on a single worm wheel, which is not included in the scope of the invention. This may, for example, have the advantage that production and / or assembly of the transmission unit are simpler than with two worm wheels. Also, with the same total weight or volume, such a single worm wheel is stiffer and mechanically more stable overall than two individual worm wheels.

According to the invention, the pitch of the first section is opposite to the pitch of the second section. In other words, if there is a right-increasing toothing in the first section, there is a left-hand toothing in the second section and vice versa. This embodiment has the advantage that the forces resulting in the engagement of worm shaft and worm wheel in the X direction at least partially compensate each other. These axial forces with respect to the output shaft are produced as it were by the helical toothing of the worm wheel as a by-product of the tangential forces. Of course, in the embodiment described here, the pitch of the first worm shaft must also be opposite to the pitch of the second worm shaft. The amount of helix angle and / or the pitch (ie the distance between two teeth) may be the same or different in the two sections. This in turn affects the slope of the respective associated worm shaft. It may also be necessary to match the speeds and torques of the two worm shafts on the part of the motor units so that an equal speed for the first and the second section results.

As already indicated above, it is possible that a different ratio exists between the first worm shaft and the output shaft than between the second worm shaft and the output shaft. This can be achieved in different ways. For example. the two worm shafts (in terms of amount) may have different pitches, the worm angle and the pitch being different in the first and second sections. However, in the case of two worm wheels, it is also possible for the worm wheels to have different radii, which results in different ratios even with identical worm shafts.

According to one embodiment, the second worm shaft extends in the Y direction, ie parallel to the first worm shaft. According to an alternative embodiment, it runs at an angle to the y-direction. In principle, the angle can have any desired values (apart from 0 ° or 180 °). For example, it may be an acute angle between 0 and 90 °. Even a right angle is conceivable, as well as an obtuse angle between 90 and 180 °. The choice of the angle can i.a. depend on the available space, inasmuch as the angle on the positions of the two screw shafts and also affects the positions of the first and second motor unit coupled thereto.

Both in an embodiment in which the second worm shaft extends at an angle to the Y direction, as well as in an embodiment in which they In the Y-direction, you can in principle distinguish two ways in which the two worm shafts can be arranged with respect to the output shaft. According to a first alternative, the second worm shaft is arranged along a Z-direction, which is perpendicular to the X-direction and the Y-direction, on the same side of the output shaft as the first worm shaft. If both worm shafts engage with one and the same worm wheel and the angle between the two worm shafts, for example, is significantly less than 90 °, such a configuration is normally only possible if the two worm shafts are offset from each other in the X direction. According to an alternative embodiment, the second worm shaft is arranged along the Z direction on an opposite side of the first worm shaft. This embodiment is particularly advantageous when both screw shafts at a small angle to each other (in particular parallel) and have no or only a small offset in the X direction.

Apart from the arrangement of the screw shafts to each other can also be varied, the arrangement of the two motor units. According to one embodiment, the first motor unit and the second motor unit face each other with respect to the output shaft in the Y direction and in the Z direction. That is, both when looking at the Y direction and when looking at the Z direction, the two motor units are arranged on opposite sides of the output shaft. This normally allows the maximum distance between the motor units to each other, which may be advantageous especially in confined space.

According to an alternative embodiment, the first motor unit and the second motor unit are arranged in the Y direction on the same side of the output shaft. It may be possible to operate both motor units with a single control unit. This can often be combined with a configuration in which the two worm shafts are arranged in the Z direction on opposite sides of the output shaft. Depending on the dimensioning of the motor units and if the two screw shafts are offset sufficiently in the X direction to each other, but the two screw shafts can also be arranged along the Z direction on the same side of the output shaft, and they can be arranged side by side, in particular in the X direction ,

• 1 eine schematisierte Darstellung einer Getriebeeinheit gemäß einer nicht von dem Schutzbereich der Erfindung umfassten Ausführungsform;
• 2 eine schematisierte Darstellung einer Getriebeeinheit gemäß einer weiteren nicht von dem Schutzbereich der Erfindung umfassten Ausführungsform;
• 3 eine schematisierte Darstellung einer Getriebeeinheit gemäß einer nur bezüglich nicht entgegengesetzter Steigungen nicht von dem Schutzbereich der Erfindung umfassten Ausführungsform;
• 4 eine schematisierte Darstellung einer Getriebeeinheit gemäß einer erfindungsgemäßen Ausführungsform;
• 5 eine schematisierte Darstellung einer Getriebeeinheit gemäß einer zweiten erfindungsgemäßen Ausführungsform;
• 6 eine schematisierte Darstellung einer Getriebeeinheit gemäß einer dritten erfindungsgemäßen Ausführungsform;
• 7 eine schematisierte Darstellung einer Getriebeeinheit gemäß einer weiteren nicht von dem Schutzbereich der Erfindung umfassten Ausführungsform; sowie
• 8 eine schematisierte Darstellung einer Getriebeeinheit gemäß einer weiteren nicht von dem Schutzbereich der Erfindung umfassten Ausführungsform.

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 transmission unit according to an embodiment not included in the scope of the invention;
• 2 a schematic representation of a transmission unit according to another embodiment not included in the scope of the invention embodiment;
• 3 a schematic representation of a transmission unit according to an embodiment only with respect to non-opposite slopes not included in the scope of the invention embodiment;
• 4 a schematic representation of a transmission unit according to an embodiment of the invention;
• 5 a schematic representation of a transmission unit according to a second embodiment of the invention;
• 6 a schematic representation of a transmission unit according to a third embodiment of the invention;
• 7 a schematic representation of a transmission unit according to another embodiment not included in the scope of the invention embodiment; such as
• 8th a schematic representation of a transmission unit according to another embodiment not included in the scope of the invention.

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 gear unit not included in the scope of the invention 1 which can be used, for example, as part of a power steering system of a motor vehicle. On an output shaft 2 sits a worm wheel 3 rotatable on. The output shaft 2 extends in an in 2 perpendicular to the plane extending X-direction. Along a Y-direction perpendicular to this runs a first worm shaft 4 that have a clutch 5 torque transmitting to a first motor unit 6 is coupled. Two pivot bearings 7 . 8th serve to support the first worm shaft 4 opposite a housing, not shown here. A second worm shaft 9 is along a Z-direction of the output shaft perpendicular to the X-direction and to the Y-direction 2 arranged opposite. The second worm shaft 9 is about a clutch 10 torque transmitting with a second motor unit 11 connected. Two pivot bearings 12 . 13 serve for the rotatable mounting of the second worm shaft 9 opposite the housing. At this the embodiment shown, the two worm shafts run 4 . 9 parallel to each other along the Y direction. The first worm shaft acts 4 with a first section 17 of the worm wheel 3 together, which is arranged in the X-direction and in the Y-direction in the same position as a second section 18 of the worm wheel 3 with which the second worm shaft 9 interacts. The two sections 17 . 18 However, each other along the Z-direction with respect to the output shaft 2 across from.

The two motor units 6 . 11 can be controlled via a common control unit, not shown here. As long as no rotation of the output shaft 2 is desired, the motor units 6 . 11 be driven so that they the worm wheel 3 apply opposite torques, causing the two worm shafts 4 . 9 against the worm wheel 3 be biased. As a result, the risk of undesirable relative movement and a rattle associated therewith between one of the screw shafts 4 . 9 and the worm wheel 3 essentially prevented. Such opposite torques within the worm wheel 3 are rectified torques within the two worm shafts 4 . 9 generated. Should a rotation of the worm wheel 3 and the output shaft 2 take place, so this is an opposite rotation of the two screw shafts 4 . 9 necessary. At the in 1 in an embodiment shown in solid line, in which the motor units 6 . 11 in the Y direction on the same side with respect to the output shaft 2 are arranged, these motor units must 6 . 11 so be operated in opposite directions.

In dashed lines, an alternative arrangement is shown in which the second worm shaft 9 via a clutch 10a with a second motor unit 11a is connected, with respect to the output shaft 2 both in the Z direction and in the Y direction of the first motor unit 6 opposite. Here, the two motor units 6 . 11a for generating a rotation of the output shaft 2 be operated in the same direction (ie both clockwise or counterclockwise).

2 shows a further embodiment of a gear unit not covered by the scope of the invention 1 that largely coincides with the in 1 illustrated embodiment is identical and therefore not described again. However, the second worm shaft runs 9 not in the Y direction, but at an angle of 30 °. This may, for example, in view of a limited space in the transmission unit 1 advantageous over the embodiment in FIG 1 be. The first and the second section 17 . 18 with which the first and second worm shaft 4 . 9 interact, are still in the X direction at the same height, but are now shifted in both the Y direction and in the Z direction against each other.

While 1 and 2 Embodiments show where two worm shafts 4 . 9 with a single worm wheel 3 interact is in 3 an embodiment shown in which two worm wheels 3 . 14 with the output shaft 2 are connected. In 3 (as in 4 - 8th ), the X-direction and the Z-direction are respectively in the plane of the drawing and the Y-direction is perpendicular thereto. In this illustration, it can be seen that the output shaft 2 over two pivot bearings 15 . 16 is rotatably mounted on the housing. The first and second worm shaft 4 . 9 both extend in the Y direction and are on the same side of the output shaft with respect to the Z direction 2 arranged. The first and second motor unit 6 . 11 are here along the Y direction on opposite sides of the output shaft 2 arranged and with respect to the Z direction on the same side. Here is the first section 17 with which the first worm shaft 4 cooperates, on a first worm wheel 3 formed during the second section 18 with which the second worm shaft 9 cooperates, on a second worm wheel 14 is trained. The two sections 17 . 18 are offset from each other in the X direction.

The distance between the two worm wheels 3 . 14 in the X direction is chosen so that the two worm shafts 4 . 9 can be spaced apart so that they can not collide with each other. Also the first worm shaft 4 is at a distance to the second motor unit 11 arranged and the second worm shaft 9 at a distance to the first motor unit 6 , In contrast to the embodiments with a worm wheel 3 is in this embodiment of the invention, the wear of the individual worm wheel 3 . 14 lower. In addition, if, for example, one of the teeth of a first worm wheel 3 should break, the function of the gear unit still through the second worm wheel 14 ensured (and vice versa). However, in the embodiment in FIG 3 Forces in the X direction on the worm wheels 3 . 14 one on the output shaft 2 be transferred and add up.

This problem is, for example, in the in 4 illustrated embodiment of the invention, otherwise with those in 3 is identical, solved in that the slope of the second worm wheel 14 opposite to that of the first worm wheel 3 is. As a result, the lift in the X direction to the output shaft 2 acting forces on each other. Of course, the slopes of the two worm shafts must also be 4 . 9 be opposite.

5 shows a modification of the embodiment 4 wherein the second motor unit 11 with the second worm shaft 9 on one of the first worm shaft 4 along the Z-direction opposite side of the output shaft 2 is arranged. In this design, it would, for example, possible., The two worm wheels 3 . 14 and the associated worm shafts 4 . 9 in the X direction closer together, so as to save space, if necessary.

6 shows a further modification of the embodiment 4 in contrast to 5 the second motor unit 11 in the Y direction on the same side of the output shaft 2 is arranged like the first motor unit 6 , In such an arrangement, it is due to the relatively small distance between the two motor units 6 . 11 again easier to operate them through a common control unit.

7 shows a further embodiment of a gear unit not covered by the scope of the invention 1 , in turn, only a single worm wheel 3 with the output shaft 2 connected is. The latter, however, is contrary to 1 and 2 in the X-direction so broad that the first worm shaft 4 in a first section 17 worm 3 can interact, leading to a second section 18 is offset, in which the second worm shaft 9 with the worm wheel 3 interacts. The arrangement of the worm shafts 4 . 9 as well as the motor units 6 . 11 corresponds to this 6 , although the distance between the two worm shafts 4 . 9 is lower in the X direction. Again, to eliminate unwanted forces in the X direction, there are two opposite slopes in the sections 17 . 18 provided by an arrow toothing of the worm wheel 3 are realized. An advantage over the embodiment in 6 here is that the worm wheel 3 thicker in the X direction and thus more rigid overall.

Another embodiment not covered by the scope of the invention is disclosed in U.S. Pat 8th represented essentially those in 7 is similar, with the single worm wheel 3 However, no arrow teeth, but has a simple helical teeth. The slopes of the two worm shafts 4 . 9 are accordingly not opposite, but the same.

In the 3 . 7 and 8th is only one possible configuration of the worm shafts 4 . 9 and motor units 6 . 11 shown. It should be noted that in the worm wheels shown in these figures 3 . 14 all in 4 - 6 illustrated configurations for both the worm shafts 4 . 9 as well as for the motor units 6 . 11 possible are. It would also be possible to have the two motor units 6 . 11 both in the Y direction and in the Z direction on the same side of the output shaft 2 to arrange, so to speak, side by side. For this would have compared to the embodiments in 3 to 6 the distance between the worm wheels 3 . 14 be enlarged in the X direction or compared to the in 7 and 8th shown embodiments, the width of the worm wheel 3 be enlarged in the X direction. Finally, it is also possible to use all embodiments in 3 - 8th in that the second worm shaft 14 at an angle to the Y-direction, as well as in 2 shown.

LIST OF REFERENCE NUMBERS

1

gear unit

2

output shaft

3.14

worm

4, 9

worm shaft

5, 10, 10a

clutch

6, 11, 11a

motor unit

7, 8, 12, 13, 15, 16

pivot bearing

17

first section

18

second part

X

X-direction

Y

Y-direction

Z

Z-direction

Claims (6)

Transmission unit (1) for a power steering system of a motor vehicle, with an output shaft (2) running along an X direction, two worm wheels (3, 14) coupled thereto, wherein the first worm wheel (3) and the second worm wheel (14) are connected to the output shaft (2) coupled to a first worm shaft (4) extending along a direction perpendicular to the X direction Y, cooperating with the first worm wheel (3) and torque transmitting coupled to a first motor unit (6), wherein a second Worm shaft (9), with the second worm wheel (14) cooperates and torque transmitting to a second motor unit (11) is coupled, wherein the first worm shaft (4) with a first portion (17) of the first worm wheel (3) cooperates and the second worm shaft (9) cooperates with a second section (18) of the second worm wheel (14) arranged offset in the X direction, and wherein the first section (17) cooperates on the first Worm wheel (3) and the second portion (18) on the second worm wheel (14) is formed and the slope of the first portion (17) opposite to the slope of the second portion (18). Gear unit after Claim 1 , characterized in that between the first worm shaft (4) and the output shaft (2) is a different translation than between the second worm shaft (9) and the output shaft (2). Gear unit after Claim 1 or 2 , characterized in that the second worm shaft (9) extends in the Y direction or at an angle to the Y direction. Transmission unit according to one of the preceding claims, characterized in that the second worm shaft (9) along a Z-direction which is perpendicular to the X-direction and the Y-direction, on the same side of the output shaft (2) is arranged as the first Worm shaft (4) or on an opposite side. Transmission unit according to one of the preceding claims, characterized in that the first motor unit (6) and the second motor unit (11) opposite each other with respect to the output shaft (2) in the Y direction and in the Z direction. Transmission unit according to one of Claims 1 to 4 , characterized in that the first motor unit (6) and the second motor unit (11) are arranged in the Y direction on the same side of the output shaft (2).

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