WO2019233642A1

WO2019233642A1 - Gearwheel made of plastic, and steering gear

Info

Publication number: WO2019233642A1
Application number: PCT/EP2019/056226
Authority: WO
Inventors: Jens-Uwe Hafermalz; Dennis Fuechsel
Original assignee: Robert Bosch Gmbh
Priority date: 2018-06-07
Filing date: 2019-03-13
Publication date: 2019-12-12
Also published as: DE102018209050A1

Abstract

A highly durable gearwheel made of plastic comprises an annular outer part (13) which is configured at least partially from plastic and which configures the teeth of the gearwheel on its outer side. Furthermore, the gearwheel comprises an inner part which is likewise configured at least partially from plastic and which comprises a bearing part which is provided for mounting the gearwheel rotatably about a rotational axis. The outer part (13) and the inner part are connected to one another, wherein in each case one engagement section of the inner part extends as far as into the teeth of the outer part (13), with the result that the outer part (13) has a meandering wall course. It is provided that the wall thickness (a₁) of the meandering wall course is greater in each case in the tooth root than in the sections which adjoin it on both sides, and/or the engagement sections configure, in each case on at least one side which lies in the circumferential direction with regard to the rotational axis, a projection or a depression which interact in each case in an engaging manner with a depression (27) or a projection of the outer part (13).

Description

Plastic gear and steering gear

The invention relates to an existing at least partially made of plastic gear and a method for producing such a gear. The invention further relates to a steering gear for a steering system of a motor vehicle with such a gear.

In most motor vehicles, power steering systems are installed, which generate a supportive torque during steering and thereby reduce the steering torque to be applied by the driver to the steering column.

The known power steering systems are based on a steering gear that translates the drive power of a hydraulic or electric steering motor and transmits, for example, the steering column. Such steering gear can be in the form of a Schraubwälzgetriebes and in particular as Schraubradgetriebe or as

Worm gear be formed. These then comprise a gear wheel, which may be directly or indirectly connected to the steering column, as well as an intermeshing, driven by a shaft of the steering motor pinion.

The gear of such a steering gear may be at least partially formed of plastic, whereby a relatively low component weight and a favorable acoustic behavior during operation of the steering gear, in particular in combination with a pinion of metal, can be achieved.

Such a gear, which is partially formed of plastic and intended for use in a steering gear is described in DE 10 2014 104 284 A1.

The invention had the object of improving a gear for a steering gear, which is at least partially made of plastic, in terms of load capacity.

This object is achieved by means of a gear according to the patent claim 1. A method for producing such a gear and a steering gear for a steering system with such a gear are subject matter of claims 9 and 10. Advantageous embodiments of the gear according to the invention and the steering gear according to the invention and preferred embodiments of the method according to the invention are objects of the further claims and / or arise from the following description of the invention. According to the invention, a gear is provided with a closed ring-shaped outer part, at least partially, preferably completely

Plastic, in particular of a single plastic, is formed and which forms on its outer side which is provided for a meshing engagement with another gear, in particular a pinion of a steering gear according to the invention teeth of the gear.

The gear further has an inner part, which is also at least partially made of plastic and which comprises a bearing part which is provided for rotatably supporting the gear around a rotation axis. A connecting part of the inner part may be at least partially, preferably made entirely of plastic, in particular of a single plastic. In this case, the connecting part may further preferably made of a different material than the

Storage part of the inner part to be formed. Since the bearing part of the rotatable mounting of the gear is used, this can preferably be made of metal, for example a steel. The storage part can be provided for example in the form of a (sleeve-shaped) hub or a shaft.

The outer part and the inner part of a gear according to the invention are interconnected, wherein in each case an engagement portion of the inner part extends into the teeth of the outer part such that the outer part in at least a portion of the width (ie the extension along the axis of rotation) of its teeth a meandering wall course having.

According to the invention, such a gear is characterized in that the

Wall thickness of the meandering wall course in the tooth root is greater than in the sides adjacent thereto sections, these adjacent sections preferably each extend at least over half of the tooth flank length and / or up to the pitch circle diameter of the gear. Particularly preferably, it can be provided that the wall thickness of the meandering

Wandverlaufs in the tooth roots is greatest.

Additionally or alternatively, a gear according to the invention is characterized

in that the engagement sections each form at least one, preferably at the two circumferentially located with respect to the rotation axis side (s) at least one projection or a recess which cooperate with a recess or a projection of the outer part engaging, whereby a positive connection between the outer part and the inner part, which acts at least with respect to the respective radial direction of the individual engagement portions, can be realized.

The two features according to the invention, each in isolation, but especially in combination with each other, a particularly high load capacity of the gear, whereby gear damage during operation of such a gear comprehensive, steering gear according to the invention can be avoided.

Such a steering gear according to the invention for a steering system of a motor vehicle comprises at least one housing, a gear according to the invention with a

Gear meshing pinion and a (screw) pinion shaft that includes the pinion.

According to a preferred embodiment of a gear according to the invention can be provided that the radially inner wall surface of the

Meander-shaped course of the wall in the tooth root and on both sides

adjacent sections has a teilelliptischen course. This also has an advantageous effect on the load capacity of the gear wheel, in particular of the outer part thereof.

A relatively high load capacity of the gear, in particular in terms of

Connection between the outer member and the inner member may also be achieved by the engaging projections and recesses of the outer member and the engaging portions of the inner member each extending the entire width (i.e., the extension along the rotation axis) of the engagement portions.

Preferably, it may be provided that the plastic used for the formation of the inner part is different from the plastic used for the formation of the outer part. In particular, it can be provided that the plastic of the inner part is fiber-reinforced, i. by means of fibers or other particles, for example made of glass or carbon, which are embedded in a matrix of the plastic (for example a thermoplastic) is reinforced. The plastic of the outer part,

For example, also a thermoplastic, however, can be unreinforced, ie not reinforced by such fibers. The unreinforced plastic of the outer part may be particularly advantageous in terms of wear behavior of a cooperating with the gear pinion of a steering gear according to the invention. This is especially true if, as is preferably provided, the pinion of a Steering gear according to the invention of an uncured metal, in particular an unhardened steel is formed.

An inventive method for producing a gear according to the invention provides that the outer part is produced in a first injection molding and then in a second injection molding, in which the inner part is formed, partially encapsulated with the provided for forming the inner part of plastic. This represents an advantageous and, in particular, cost-effective manner that can be implemented in mass production for producing a gear according to the invention. If, as is preferably provided, the inner part comprises a bearing part made of, in particular, a metal, it can continue to be part of a

be provided according to the method that the previously separately prepared storage part is also molded in the second injection molding process with the provided for forming the inner part of plastic.

The pinion shaft of a steering gear according to the invention may be mounted on one side of the pinion in a fixed bearing, which comprises a pivot bearing, in which the pinion shaft is received. For this purpose, the rotary bearing comprises at least one inner bearing ring and an outer bearing ring and optionally, in a preferred embodiment as a rolling and in particular as a ball bearing, a plurality of arranged between the bearing rings rolling elements, in particular balls. The pinion shaft is then received within the inner race of the pivot bearing. The pivot bearing and in particular an outer bearing ring of the pivot bearing of the fixed bearing can continue to be accommodated in a bearing sleeve. In addition, the bearing may comprise a pivot ring which has an outer ring and an inner ring which are pivotally connected to one another via a plurality of (in particular two) torsion bars, wherein the inner ring is received in the bearing sleeve and the outer ring is mounted inside the housing of the steering gear and in particular ( with respect to at least one, preferably with respect to all directions, ie fixed immovably) is arranged.

The pinion shaft of a steering system according to the invention may preferably be mounted on the other side of the pinion in a floating bearing comprising a pivot bearing in which the pinion shaft is received, wherein for the pivot bearing (and thus also for the end of the pinion shaft received therein) a radial mobility within the housing. Preferably, it can be provided that the pivot bearing and in particular an outer bearing ring thereof in a bearing bush is received, which is received within the housing so that a radial mobility of the pivot bearing and thus the end of the pinion shaft received therein within the housing is granted. Such a floating bearing can for example have an embodiment according to DE 10 2005 035 020 A1.

The invention also relates to a steering system comprising at least one steering gear according to the invention as well as a steering motor connected in rotation with the pinion shaft. The gear of the steering gear can also be rotatably or rotationally drivingly connected to a steering shaft, in particular a steering column, the steering system. The steering system according to the invention can be designed in particular as a power steering system, in which by means of the steering motor, a supporting torque can be generated so that one of a driver of a power steering system comprehensive motor vehicle for steering the motor vehicle to be applied to the steering column steering torque reduced (possibly temporarily up to to zero). Alternatively, there is also the possibility of the steering system in such a way that is always generated by the steering motor, the entire steering torque required for steering, in particular to realize a so-called steer-by-wire functionality of the steering system or the motor vehicle, in the no mechanical connection between a steering handle (if provided) and the steerable wheels is present.

The invention further relates to a motor vehicle with a steering system according to the invention.

The indefinite articles ("a", "an", "an" and "an"), in particular in the patent claims and in the claims generally explaining

Description, are to be understood as such and not as number words. Corresponding to this concretized components are thus to be understood that they are present at least once and may be present more than once.

The invention will be described below with reference to the drawings

Embodiment examples explained in more detail. In the drawings shows:

1 shows a longitudinal section through an inventive steering gear.

Fig. 2: an inventive gear for a steering gear in a

perspective view;

3 shows a cross section through the gear; 4 shows a longitudinal section through the gear;

Fig. 5: an outer part of the gear in a side view;

FIG. 6 shows the detail marked VI in FIG. 5 in an enlarged view

Presentation; and

Fig. 7: a portion of a longitudinal section through the outer part.

Fig. 1 shows the essential components of an inventive

Steering gear. This comprises a housing 1, within which a

Gear 2 according to the invention and a pinion 3 meshing with the gear 2 are rotatably arranged in the form of a Schraubritzels. The pinion 3 and the pinion 3 comprehensive (screw) pinion shaft 4 are integrally formed in the form of a worm.

The gear 2 is fixedly mounted on an output shaft 5 of the steering gear. This output shaft 5 may, for example, mesh with a handlebar formed at least in a portion as a rack, whereby the rack performs a translational movement in a known manner via Radlenkhebel (not shown) in a pivoting movement steerable wheels (not shown) of the

Motor vehicle can be translated. In the output shaft 5 but it may also be a steering column of a power steering system, which is connected to a steering wheel and which acts via a steering pinion on the handlebar.

The pinion shaft 4 has a drive-side end over which this with the

Output shaft of a steering motor (not shown, for example, an electric motor) is connectable. In the region of this drive-side end, the pinion shaft 4 is mounted in the housing 1 by means of a first bearing. This bearing is designed as a fixed bearing 6, which allows a pivoting of the pinion shaft 4 about a pivot axis. This

Pivot axis extends in Fig. 1 approximately perpendicular to the plane of the drawing. Such pivoting causes a deflection of the drive end

opposite end of the pinion shaft 4, which is mounted there by means of a movable bearing 7 within the housing 1. This movable bearing 7 is designed so that it allows the resulting from the pivoting of the pinion shaft 4 deflection of this end.

Both the fixed bearing 6 and the floating bearing 7 each comprise a rotary bearing in the form of a ball bearing 8. In inner bearing rings 9 of these ball bearings 8, the corresponding portions of the pinion shaft 4 are supported, while outer bearing rings 10 the ball bearing 8 are each mounted in a bearing device 1 1, 12, which in turn are accommodated in the housing 1. The bearing devices 1 1, 12 are structurally designed so that they allow in the case of the fixed bearing 6, the pivoting of the pinion shaft 4 about the pivot axis and in the case of the movable bearing 7, the deflection of the free end of the pinion shaft 4.

2 to 7 show an embodiment of a gear 2 according to the invention for example, a steering gear, as shown in FIG. 1.

The toothed wheel 2 comprises an annular outer part 13 (cf., in particular, also FIGS. 5 to 7), on whose outer side teeth are formed, with which the toothed wheel 2 is in engagement with the teeth of a pinion 3 of the steering gear. Furthermore, the gear 2 has an inner part which comprises a sleeve-shaped bearing part 14, which is provided for a rotationally fixed connection to an output shaft 5 of the steering gear, and a connecting part 15 which surrounds the outer part 13 with the bearing part

14 firmly connects, so that acting as a result of the interaction with the rotationally driven pinion gear teeth 3 for generating a

Torque can be transmitted to the output shaft 5 of the steering gear.

To realize a permanently secure connection to the output shaft 5, the support member 14 is formed of metal and in particular steel. The connecting part

15 and the outer part 13, however, are completely formed of plastic, whereby a relatively low weight of the gear 2 and an advantageous acoustic operating behavior in cooperation with the pinion 3 is achieved. For a high load capacity with the least possible deformation of the connecting part 15 is formed of a fiber-reinforced plastic, while the outer part 13 consists of an unreinforced plastic. Due to the lack of fiber reinforcement of the plastic of the outer part 13 is an increased wear effect that could have such reinforcing fibers on the preferably formed of an uncured steel pinion 3 of the steering gear avoided.

The teeth of the outer part 13 are formed by an annular outer portion 16 which extends over the entire width of the outer part 13 and the axially centrally, ie halfway, in an inner, annular disc-shaped reinforcing portion 17 passes (see Fig .. 5 and 7) , The outer portion 16 forms on both axially (with respect to the axis of rotation 18 of the gear 2) located sides of the reinforcing portion 18 each one of the tooth contour following, Meander-shaped wall course, so that within each tooth, a free space 19 is formed.

In each of these free spaces 19 engages an engaging portion 28 of the connecting part 15 of the inner part, which is formed between the outer part 13 and the connecting part 15 a circumferentially effective, positive connection.

Furthermore, each tooth of the formed from unreinforced plastic outer part 13 by two "cores" made of fiber-reinforced plastic, which for the

Production of the connecting part 15 is provided, reinforced, whereby a relatively high load capacity is realized at the same time relatively low deformation of the teeth.

The circumferentially effective, positive connection between the outer part 13 and the connecting part 15 is additionally provided by a plurality of approximately rectangular projections 20 which are provided on both sides of the reinforcing portion 17 of the outer part 13 in an annular arrangement and in

engage complementary recesses of the connecting part 15 causes.

An effective in the axial direction, positive connection between the

Outer part 13 and the connecting part 15 is realized in that the

Reinforcement portion 17 of the outer part 13 is embedded in the connecting part 15.

As is apparent from FIGS. 2 and 4, the connecting part 15 is formed such that it covers the two axially located end faces of the outer portion 16 of the outer part 13 substantially completely, so that for these two annular disc-shaped portions 21 of the connecting part 15th a substantially the toothing contour of the outer part 13 corresponding tooth contour results.

In this case, only a relatively small shoulder between the toothing contour of the outer part 13 and the toothing contours of the connecting part 15 is provided, which results from a correspondingly smaller dimensioning of the toothing contours of the connecting part 15. A contact of the connecting part 15 with the pinion 3 of the steering gear is thereby avoided.

In addition to the two annular disk-shaped and toothing contour forming portions 21, the connecting part 15 also includes a central portion 22 having a plurality of axially and radially extending spokes 23, wherein each two adjacent spokes 23 axially centrally or halfway through a circumferentially extending, flat connecting portion 24 are connected. In these connecting portions 24 and in the adjacent portions of the spokes 25, the reinforcing portion 17 of the outer part 13 is embedded.

Radially inward, the central portion 22 merges into a hub portion 25, which serves to connect to the support member 14, wherein an effective in both the axial and circumferential direction, positive connection by means of projections 26 which are formed on the outside of the support member 14 and the engage in complementary recesses on the inside of the hub portion 25 of the connecting part 15 (see Fig. 4) is realized.

As can be seen in particular from FIG. 6, the meandering

Wall curves wall thicknesses that are cyclical over the length of those

Sections that each form a tooth, change. In each case, the largest wall thickness ai is present in the tooth root. Furthermore, it is provided that the radially inner wall surfaces of the meander-shaped wall profiles are each partially elliptical in the tooth roots and the sections adjacent thereto on both sides, which extend approximately up to half of the tooth flank length IF.

In addition, it is provided that on both sides of the inner surfaces of the meandering wall progressions formed by these within the teeth peaks, i. at the two circumferentially located sides, two recesses 27 are formed, each over the entire width of the meandering

Wall courses and thus from the respectively associated end face of the outer part 13 extend to the reinforcing portion 17 and which have approximately a rectangular cross-section. In these recesses 27 project complementarily formed projections 29 of the engaging portions 28 of the connecting part 15, which in turn form-fitting connections between the outer part 13 and the connecting part 15 are formed by the particular local relative movements between those portions of the outer part 13, which form the individual teeth, and the engaging portions 28 received therein of the connecting part 15 are avoided. These positive connections support a positive connection between the outer part 13 and the connecting part 15, which is realized thereby, and that on the two end faces of the outer portion 16 of

Außenenteils13 each a closed meandering circumferential projection 30 is formed, which engages in a complementary recess of the connecting part 15. A production of the gear 2 is carried out by injection molding of the outer part 13 in a first injection molding using a first injection mold (not shown). Furthermore, the storage part 14 is produced in a separate manufacturing process, for example by casting and subsequent mechanical post-processing. Subsequently, the sufficiently cured outer part 13 and the bearing part 14 within a second injection mold (not shown) is arranged and provided for forming the reinforcing member 15 plastic introduced as part of a second injection molding in the cavity of this second injection mold. In this case, the outer part 13 and the bearing part 14 are partially encapsulated, resulting in the described connections between the

Components of the gear 2 result.

LIST OF REFERENCES

1 housing

2 gear

3 (screw) pinion

4 (screw) pinion shaft

5 output shaft of the steering gear

6 fixed storage

7 floating bearings

8 ball bearings

9 inner bearing ring of a ball bearing

10 outer bearing ring of a ball bearing

1 1 Storage facility of the fixed storage

12 bearing device of the floating bearing

13 External part of the gear

14 bearing part of the gear

15 connecting part of the gear

16 outer section of the outer part

17 reinforcement section of the outer part

18 axis of rotation of the gear

19 free space within a tooth

20 projection of the reinforcing section

21 annular disc-shaped portion of the connecting part

22 middle section of the connecting part

23 spoke of the middle section

24 connecting portion of the middle section

25 hub portion of the connecting part

26 projection of the bearing part

27 deepening of the outer section

28 engaging portion of the connecting part

29 projection of the engaging portion

30 projection on a front side of the outer portion ai wall thickness in the tooth root

I _F tooth flank length

Claims

claims:

1. gear (2) having an annular outer part (13) which is at least partially made of plastic and on its outside the teeth of the

Gearwheel (2) is formed, and with an inner part which is at least partially formed of plastic and which comprises a bearing part (14) which is provided for rotatably supporting the gear (2) about a rotation axis (18), wherein the outer part (13 ) and the inner part are connected to each other and wherein in each case an engagement portion (28) of the inner part extends into the teeth of the outer part (13), so that the outer part has a meandering wall course, characterized in that

- The wall thickness (a-i) of the meandering wall course in the tooth root is greater than in the sides adjacent thereto sections and / or

- The engaging portions (28) each form on at least one circumferentially located side a projection (29) or a recess, each cooperating with a recess (27) or a projection of the outer part (13).

2. gear (2) according to claim 1, characterized in that the radially inner wall surface of the meandering wall course in each case in the tooth root and in the adjacent thereto on both sides a part elliptical course.

3. Gear (2) according to claim 1 or 2, characterized in that the engagement portions (28) respectively at the two circumferentially located sides form a projection (29) or a recess, each with a recess (27) or a projection the outer part (13) engaging interaction.

4. gear (2) according to one of the preceding claims, characterized

characterized in that the engagingly cooperating projections (29) and recesses (27) extend respectively over the entire width of the

Engage engagement portions (28).

5. gear (2) according to one of the preceding claims, characterized

in that the plastic of the outer part (13) is unreinforced and the plastic of the inner part is fiber-reinforced.

6. Gear (2) according to one of the preceding claims, characterized in that the inner part comprises a connecting part (15), wherein the connecting part (15) and the bearing part (14) are formed of different materials.

7. gear (2) according to claim 6, characterized in that the

Storage part (14) is formed of metal.

8. gear (2) according to claim 6 or 7, characterized in that the outer part (13) is formed entirely of a first plastic and the connecting part (14) completely made of a second plastic.

9. A method for producing a gear (2) according to one of

preceding claims, characterized in that the outer part (13) produced in a first injection molding and then in a second injection molding, in which the inner part is formed, partially encapsulated with the plastic used to form the inner part.

10. Steering gear for a steering system of a motor vehicle having a housing (1), a gear (2) according to one of the preceding claims, one with the gear (2) meshing pinion (3) and a pinion (3) comprising the pinion shaft (4) ,