EP3004668A1

EP3004668A1 - Telescopic drive shaft

Info

Publication number: EP3004668A1
Application number: EP14727163.9A
Authority: EP
Inventors: Frank Buschbeck
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2013-06-05
Filing date: 2014-05-23
Publication date: 2016-04-13
Also published as: US20160123376A1; WO2014194989A1; CN105308335A; DE102013009497A1; JP2016520184A

Abstract

The present invention discloses a drive shaft (1) which has at least one outer shaft section (11) with a hollow end section of cylindrical internal cross section and at least one inner shaft section (12) which penetrates at least along a first penetrating depth (L₁) into the hollow end section of the outer shaft section (11). The shaft sections (11, 12) are connected in an integrally joined manner on a contact surface between an outer wall of the inner shaft section (12) and an inner wall of the outer shaft section (11) along the first penetrating depth (L₁). The integrally joined connection (12') has a longitudinally axial load-bearing capability, which is lower than a predefined buckling force, for buckling the shaft sections (11, 12) when the drive shaft (1) is loaded in a longitudinally axial manner. The inner shaft section (12) can penetrate more deeply than the first penetrating depth (L₁) into the hollow end of the outer shaft section (11) when an axial force is applied which is greater than the buckling force.

Description

Telescopic drive shaft

The present invention relates to a drive shaft for a motor vehicle.

In motor vehicles whose engine is not directly coupled to the driven axle, drive shafts are used with one or more joints connecting the engine and the axle drive for transmitting torque along the shaft

Couple vehicle longitudinal axis. For torque transmission, the waves are usually made very solid, such as a hollow shaft made of steel, but due to this massive and rigid design in the event of a crash, a significant risk of injury to the occupants of the vehicle and for the crash opponent dar. Increasingly stringent requirements for the crash behavior, both Occupant protection as well as the protection of the crash opponents, make it therefore necessary, including the drive shaft in the crash concept

included.

There are known telescopic steering columns, which can be pushed together in the event of a crash, so that they do not penetrate into the interior in an impact. But it also drive shafts have been developed that can transmit both the required torque as well as fail when exceeding a defined Axialkraftbelastung and can be pushed together telescopically, such as drive shafts with a

Puncture joint.

Moreover, from DE 10 2009 009 682 A1 a fiber-reinforced propeller shaft is known, which has two shaft sections, which are connected by a transition section, which is a predetermined breaking section which, when exceeding a

Boundary pressure load breaks. The predetermined breaking section has a curved cross section. The one shaft section has a smaller diameter than the other shaft section, so that it can penetrate in case of failure of the predetermined breaking section in the other shaft part.

The DE 101 04 547 A1 relates to an axially collapsible drive shaft, which consists of a single piece of material, but which has a plurality of sections; a first shaft portion and a second shaft portion, which by a Predetermined breaking section are connected. The predetermined breaking section has a circumferential

Bulge on, in towards the other shaft section

Receiving section connects, whose diameter is larger than that of the first

Shaft section. At a defined Axialkraftbelastung the bulge begins to deform due to the bending moment occurring in the edge of the bulge fiber until it fails and the material cohesion is resolved. The first shaft section can now move into the receiving section, whereby the

Total length of the shaft is shortened.

Finally, from DE 37 25 959 A, a compound of a hollow shaft made of a fiber-reinforced material which is coupled at the end with a pin known. The diameter of the pin is larger than the inner diameter of the hollow shaft, which is why the hollow shaft is expanded to connect and the pin can be held non-positively. When a limit torque is exceeded, the non-positive connection slips through.

However, the release force can not be adjusted in the known telescopic drive shafts, without re-dimensioning the shaft body, since the release force significantly from the geometry and the material properties just this

Shaft body is determined. Because of the comparatively complex geometry in the predetermined breaking sections, any adaptation of the triggering force can thus be realized only at an increased cost, since a change in the geometry of the

Sollbruchabschnitts always new forms for manufacturing, such as through

Drop forging or hydroforming, must be made.

Starting from this prior art, it is an object of the present invention to provide an improved drive shaft which is collapsible and can be formed from less complex semi-finished products. It is also desirable that it makes it possible to dimension the release force without replacing the essential shaft components and that it is cheaper to produce than known telescopic drive shafts.

This object is achieved by a drive shaft with the features of claim 1. Further developments of the device are set forth in the subclaims.

The drive shaft according to the invention comprises, in a first embodiment, at least one outer shaft portion having a hollow end portion which is a cylindrical one Inner cross section has, and at least one inner shaft portion, which is immersed along a first insertion depth in the hollow end of the outer shaft portion. The shaft portions are integrally bonded to a contact surface between the outer wall of the inner shaft portion and the inner wall of the outer shaft portion along the first insertion depth. The cohesive connection has a longitudinal axial load capacity, which is less than a predetermined buckling force, which leads to buckling of the shaft sections with longitudinal axial load of the drive shaft. The inner shaft portion may be larger upon application of an axial force

Buckling force, deeper than the first immersion depth in the hollow end of the outer

Dip shaft section.

"Resilience" as used herein means total bond strength of the adhesive bond which results in failure thereof In order to obtain a sufficiently strong bonded bond, the inner cross section of the hollow cylindrical end portion of the outer shaft portion along the first insertion depth should correspond to the outer cross section of the inner shaft portion while the gap width on the used

Additive of the cohesive connection is adaptable. The operating torque is ultimately transmitted via the additive in the annular gap between the inner shaft portion and the outer shaft portion.

By the solution according to the invention, it is possible to build from comparatively simple semi-finished products, such as cylindrical tubes, a telescopic drive shaft, the release force is very simple and without changes to the geometry of

Shaft sections can be adjusted. The force that leads to the failure of

cohesive connection can be determined simply by changing the immersion depth, the strength of the additive and the gap width between the inner and the outer shaft portion.

Suitably, the torque to be transmitted is also included in the dimensioning of the integral connection. However, the force that causes failure should only be as high as the force that would cause buckling of the slimmer shaft section. Through suitable design of the connection, an almost constant (or predefined, for example path-dependent) force level is set over the entire sliding path, which provides the optimum characteristic curve in the entire vehicle for the relevant crash load cases. , The force for pushing the shaft together is preferably set in a range of 40 to 80 kN

drive shaft according to the invention therefore does not buckle in a crash, but leaves Collapse under the axial thrust load occurring during the crash, whereby the risk of injury to vehicle occupants and crash opponents can be reduced.

In this case, the drive shaft can be produced more cheaply than known

telescopic drive shafts, as to achieve different triggering forces always the same shaft sections can be used and only changes to the cohesive connection are necessary. As a result, both construction and storage costs can be reduced.

The cross section of the shaft sections may advantageously be circular, since this results in a homogeneous stress distribution and a good torsional load

Material utilization result.

In a further embodiment, one or both shaft sections can consist of a fiber-reinforced material at least along a longitudinal axis section, wherein a fiber-reinforced plastic, in particular CFK or GFK, are advantageous.

If the drive shaft is made of the fiber-reinforced material, known advantages in terms of increased torsional rigidity with reduced weight and in the vehicle overall system of increased driving dynamics can be achieved because a smaller mass must be accelerated.

The fiber types mentioned are not intended to be limiting; rather, if it makes sense, other fiber types can be used, such as aramid fibers. It can also be provided that the shaft sections only along one

Longitudinal axis section made of fiber reinforced material, such as in the section in which they are connected to the other shaft portion.

In yet another embodiment, the integral connection may be a fiber-free connection, wherein an adhesive connection or a connection formed by a matrix material of the at least one shaft section of the fiber-reinforced material is advantageous.

The fiber-free connection is advantageous because the mechanical properties of pure materials are more predictable than those of fiber-reinforced materials, since in these often aging effects change the mechanical properties over time. Thus, the release force of the drive shaft can be dimensioned sufficiently accurate and it can be assumed that the dimensioned "release force" does not change significantly even after a long period of use

Failure mechanism of a fiber-free connection another; For example, after the failure, there are no sharp break edges and open fiber ends, which can also reduce the risk of injury, especially when recycling.

According to a further embodiment, the shaft portion of the

fiber-reinforced material to show a fiber orientation, in which the fibers come to lie at an angle in the range of 25 ° to 70 ° with respect to the longitudinal axis; An angle in a range of 35 ° to 55 ° is also considered to be advantageous, and a range of 40 ° to 50 ° is considered to be particularly advantageous.

The fiber alignment described is advantageous in a torsionally loaded drive shaft, since the longitudinal axes of the fibers are aligned in accordance with power flow. In order to better withstand changing torsional loads, the fibers can also be arranged crossed. The production of such a fiber material tube is possible for example by pultrusion and easy to automate. Likewise, prepregs or preforms can also be used.

If a constant outer diameter is to be implemented, or more

Adjustment parameters must be used in terms of setting load level and running behavior, the predetermined breaking surface and stepped between the individual fiber layers can be realized. This means that within a tubular shaft section, a plurality of fiber layers are separated from one another by fiber-free adhesive surfaces or fiber-free matrix regions arranged in each case between them. In the event of a crash then defined areas fail without fiber composite, i. made of adhesive or matrix, and the two tube halves first slide over each other and - with appropriate run length - into each other. Preferably, a controlled increase in the load level takes place at the end. It is important that the PTO shaft yields to a constant and well-defined force level. The level of this force is preferably at a value in the range of 40 to 80 kN, particularly preferably 50 or 80 kN.

Furthermore, coaxially over the inner shaft portion, a second inner

Shaft section to be guided along a longitudinal axis portion with the inner Shaft section is connected. Between the hollow end portion of the outer

Shaft portion and the opposite end of the second inner

Shaft section is a first circumferential gap predetermined längsaxialer

Expansion ago, which serves as a stop for the outer shaft section.

As used herein, the term "end" is to be understood in relation to the longitudinal axial extent of the shaft portions such that the circumferential gap is between opposing end surfaces of the two shaft portions, thereby providing a drive shaft having a constant outer cross section over almost the entire length At the position of the circumferential gap, the drive shaft has a smaller cross section

Zusammenschiebeweg the drive shaft are limited by the longitudinal axial extent of the circumferential gap, since it serves as a stop when moving.

Moreover, also coaxially over the outer shaft portion a second outer shaft portion may be guided, which is connected at least along a longitudinal axis portion with the outer shaft portion. The second outer shaft portion is materially bonded to the second inner along a second insertion depth

Connected shaft section. The cohesive connection has a longitudinal axial

Load capacity which is less than the predetermined buckling force, which leads to buckling of the second shaft sections in longitudinal axial load of the drive shaft. The second inner shaft portion may be immersed deeper than the second insertion depth in the second outer shaft portion upon application of an axial force greater than the buckling force.

In this embodiment, an arrangement as formulated according to claim 1, made again and pushed radially outward on the drive shaft. As a result, a higher torque can be transmitted and also the axial force at which the

cohesive connection fails, can be selected higher, since this axial force is now divided into two cohesive connections. If it is shaft sections of fiber reinforced plastic, the drive shaft after this

Embodiment simply by "stacking" and then laminating individual shaft blanks are made.

According to yet another embodiment, over the second inner

Shaft portion and the second outer shaft portion a predetermined number be guided further inner shaft sections and / or outer shaft sections.

Between opposite ends of an n-th inner shaft portion and a (n-1) -th outer shaft portion, there is respectively an n-th circumferential gap having a predetermined longitudinal axial extent.

By radially further outward shaft sections are "stacked" on the second shaft sections, almost after the atroschka principle, the maximum transmissible torque and the damping characteristics of the wave can be targeted dimensioned, the damping properties significantly by the

Properties of the additive are determined in the annular gaps. However, the axial force which leads to the "triggering" of the integral connections can also be dimensioned by including the insertion depths of the n-th inner into the n-th outer shaft sections as well as the strength of the integral connections into the design be provided that the shaft portion of highest "order" is an inner shaft portion which is not performed in an outer shaft portion of the same order, that is, virtually forms a compensation sleeve. The outer cross section of this compensating sleeve can particularly advantageously correspond to the outer cross section of the longitudinal axial outer shaft section arranged opposite, since such a

Drive shaft with constant except for the circumferential gap between them

External cross section can be obtained.

These and other advantages are set forth by the following description with reference to the accompanying figures. The reference to the figures in the description is to aid in the description and understanding of the

Object. Articles or parts of objects which are substantially the same or similar may be given the same reference numerals. The figures are merely a schematic representation of an embodiment of the invention.

Showing:

1 is a longitudinal section of the collapsible drive shaft,

Fig. 2 is a longitudinal section of another collapsible drive shaft.

A simple design of a drive shaft 1 according to the invention is shown in FIG. The inner shaft portion 12 is along the insertion depth in the outer

Shaft section 11 introduced. It can be seen that the outer diameter D ₂ of inner shaft portion 12 is smaller than the inner diameter Ό of the outer shaft portion 11, which is why there is an annular gap 12 'between them. The two shaft sections 11, 12 are cylindrical at least at their ends guided into one another, it being possible for the shaft sections 11, 12 to have a different shape outside the end sections, they may of course also be cylindrical over the entire length. In particular, the cross section may be circular, since with a circular cross section the best material utilization results in torsional loading. Along the annular gap 12 ', the two shaft sections 11, 12 are materially connected, so that an operating torque can be transmitted via this connection. The size of the transmittable operating torque can be adjusted while maintaining the dimensions of the two shaft sections 1 1, 12 solely by changing the immersion depth L-, and by the strength of the cohesive connection in the annular gap 12 '. The cohesive connection can be realized using an additive, such as an adhesive. If the shaft sections 11, 12 are FRP pipes, then the additive may also be the matrix plastic of the FRP pipes, since it is known from this that it bonds well with the shaft sections 11, 12.

If the drive shaft 1 is loaded by an axial force, such as during a crash, the cohesive connection in the annular gap 12 'will fail if a limit force is exceeded. The limit force can be dimensioned via the possibilities described above and should only be chosen so large that it is ensured that none of the shaft sections 11, 12 fails by buckling, as this represents an increased risk of injury. After the failure of the cohesive connection, the inner

Shaft portion 12 penetrate into the outer shaft portion 11; When it comes to pipes, the penetration path is basically unlimited. However, it is also conceivable that only the end portion of the outer shaft portion 11, the inner

Shaft portion 12 receives, is hollow and the rest of a full wave; then that is

Penetration limited, but this is not shown in the figure. In such a case, it may even be advantageously possible that after reaching this stop, further energy is dissipated by crushing the FRP shaft sections. Advantageously, the shaft sections made of FRP can be produced by pultrusion, wherein the fibers can be arranged, for example, at a load flow rate approximately at a ± 45 ° angle, which, however, can not be deduced from FIG.

However, the drive shaft 1 according to the invention not only has the advantage that it can be pushed together in the event of a crash, but it is also possible over the Dimensioning the cohesive connection in the annular gap 12 'to limit the maximum transmittable torque, which is advantageous if the drive train while driving suddenly, as effectively a dangerous blocking of the driven axle can be prevented because the drive shaft 1 quasi as

Slip clutch acts.

In Fig. 2, another embodiment of the drive shaft 1 is shown in longitudinal section. The basic structure with inner shaft portion 12 and outer shaft portion 11 corresponds to the drive shaft 1, which is shown in Fig. 1.

In order to transmit a larger torque, or to obtain a greater release force of the cohesive connection in the annular gap, are on the known from Fig. 1 inner and outer shaft portions 11, 12 which form the first shaft sections, outwardly more inner and outer shaft sections 14,15,16 arranged. Over the inner shaft portion 12, a second inner shaft portion 14 is guided, whose inner cross section corresponds to the outer cross section of the first inner shaft portion 12, while the two shaft portions 12,14 are interconnected. Between opposite end surfaces of the second inner shaft portion 14 and the first outer shaft portion 11, there is a circumferential gap 18 which extends in the longitudinal direction of the shaft 1. This gap 17 defined by the

Failure of the integral connection 12 ', the maximum displacement of the first inner shaft portion 12 and the first outer shaft portion 11. Still further outside, a second outer shaft portion 15 is connected to the first outer shaft portion 11, along the predetermined insertion depth L ₂ on the inner

Shaft section second order 14 is pushed, with which it is materially connected on the length L ₂ . This cohesive connection in the annular gap 14 'contributes in addition to the cohesive connection in the annular gap 12' to the force and

Torque transmission of the drive shaft 1 at. Before pushing the

Drive shaft 1 must in this embodiment of the shaft both cohesive connections in the annular gaps 12 ', 14' have failed, while the maximum collapsible path in addition to the circumferential gap 17 is also limited by the second circumferential gap 18. The circumferential gap 18 extends with the length L ₄ along the longitudinal axis and is located between opposite end faces of the second outer shaft portion 15 and a sleeve 16 as the second inner shaft portion 14 striped third inner shaft portion 16. By the sleeve 16 is achieved that the drive shaft 1 over its entire length, so to speak same outer diameter, which is only "interrupted" by the circumferential gap 18.

Claims

claims

1. drive shaft (1) having at least one outer shaft portion (11) with a

hollow end portion having a cylindrical inner cross-section and at least one inner shaft portion (12), at least along a first

Immersion depth (L ^ immersed in the hollow end portion of the outer shaft portion (11),

characterized in that

the shaft sections (11, 12) are materially connected at a contact surface between an outer wall of the inner shaft section (12) and an inner wall of the outer shaft section (11) along the first insertion depth (L,), the cohesive connection (12 ') being longitudinally axial Provides load that is less than a predetermined buckling force, which leads to buckling of the shaft sections (11, 12) in longitudinal axial load of the drive shaft (1), and wherein the inner shaft portion (12) upon application of an axial force which is greater than the buckling force Lower than the first immersion depth (L in the hollow end of the outer shaft portion (11) is immersed.

2. Drive shaft according to claim 1,

characterized in that

at least one of the shaft sections (1 1, 12) at least along one

Longitudinal axis section consists of a fiber-reinforced material, preferably made of FRP, particularly preferably CFK or GRP.

3. Drive shaft according to claim 1 or 2,

characterized in that

the integral connection (12 ') is a fiber-free connection (12') which is preferred

- an adhesive bond is or

- Is formed by a matrix material of the at least one shaft portion of the fiber-reinforced material.

4. Drive shaft according to claim 2 or 3,

characterized in that

the shaft section (11,12) made of the fiber-reinforced material with respect to the longitudinal axis has a fiber orientation in a range of 25 ° to 70 °, preferably in a range of 35 ° to 55 °, particularly preferably in a range of 40 ° to 50 ° ,

5. Drive shaft according to at least one of claims 1 to 4,

characterized in that

coaxially over the inner shaft portion (12) a second inner shaft portion (14) is guided, which is connected at least along a longitudinal axis portion with the inner shaft portion (12), wherein between the hollow

End portion of the outer shaft portion (1) and the opposite end of the second inner shaft portion (14) is a first circumferential gap (17) of predetermined longitudinal axial extent (L ₃ ), which is designed as a stop for the outer shaft portion (11).

6. drive shaft according to claim 5,

characterized in that

coaxially over the outer shaft portion (11) a second outer

Shaft portion (15) is guided, at least along a

Longitudinal axis portion is connected to the outer shaft portion (11) and along a second insertion depth (L ₂ ) is integrally connected to the second inner shaft portion (14), wherein the cohesive connection (14 ') provides a longitudinal axial load capacity, which is less than one predetermined

Buckling force, which leads to buckling of the second shaft sections (14, 15) when the drive shaft (1) is subjected to longitudinal axial loading, and wherein the second inner shaft section (14) is lower than the second insertion depth when an axial force greater than the buckling force is applied ( L ₂ ) in the second outer shaft portion (11) is submersed.

7. Drive shaft according to claim 5 or 6,

characterized in that

over the second inner shaft portion (14) and the second outer

Shaft section (15) a predetermined number of other inner shaft sections and outer shaft portions, wherein there is an n-th circumferential gap (18) of predetermined longitudinal axial extent between opposite ends of an n-th inner shaft portion and a (n-1) -th outer shaft portion, respectively.

8. drive shaft (1) having at least one outer shaft portion (11) with a hollow end portion with a cylindrical inner cross section and at least one inner shaft portion (12) at least along a first insertion depth () in the hollow end portion of the outer shaft portion (11) is immersed,

characterized in that

the outer shaft portion (11) is connected to the inner shaft portion (12) via an adhesive connection and the adhesion is adjusted so that the two shaft portions are pushed into each other at an axial load above 40 kN.