EP3068983B1 - Adjustable camshaft - Google Patents

Description

The present invention relates to an adjustable camshaft for an internal combustion engine with a extending in the direction of a rotation axis carrier shaft, wherein on the carrier shaft at least one cam package having at least one cam member is slidably received in the direction of the axis of rotation, wherein the cam package on the carrier shaft in at least two axial locking positions can be latched, and wherein for forming the detent positions at least one biased with a spring element locking element and at least one locking element receiving are provided so that the locking element can engage in the locking positions in the locking element recording.

STATE OF THE ART

Adjustable camshafts for internal combustion engines are known having a support shaft extending in a rotation axis, and at least one cam package is movably received on the support shaft in the direction of the rotation axis. The cam package rotates with rotation of the carrier shaft, for which a wedge structure can serve between the carrier shaft and the cam package, and the wedge structure prevents the cam assembly from rotating on the carrier shaft. In order to lock in discrete axial positions the cam package on the carrier shaft in reproducible axial positions, locking elements are known which can be biased by spring elements, and the locking elements can engage in locking element receptacles, whereby the axial position of the cam stack is defined on the carrier shaft. The different axial positions of the cam pack on the carrier shaft serve to connect various cam elements, which may comprise the cam pack, with valves or tap elements for driving valves. The different cam elements may determine different timing for opening and closing the valves of the internal combustion engine, or the valve lift may be changed by various cam elements operatively connected to a tapping element or directly with a valve. The change takes place by taking various, discrete axial positions of the cam pack on the Carrier shaft, and the displacement of the cam package is effected for example by a resting in the cylinder head received manipulation means which can cooperate with an adjusting element, which can also be covered by the cam package.

For example, the shows DE 10 2010 011 897 A1 an adjustable camshaft for an internal combustion engine having a support shaft extending in a rotation axis, and on the support shaft, a cam package is received axially movable. For latching the cam package in discrete axial positions is a locking element in the form of a ball which is acted upon by a spring force of a spring element. The ball can engage in various profile grooves by the spring force, and the profile grooves are arranged with respect to their axial position so that each profile groove corresponds to the contact of an associated cam track of a cam member against a tap member.

The latching element and the spring element for applying force to the latching element are arranged in a receiving bore of the camshaft, wherein the latching element receptacles are introduced in the form of the profile grooves on the inside in the cam package. If the camshaft must be mounted, the spring element must first be inserted in the receiving bore in the camshaft, then the locking element must be inserted against the spring force even before the arrangement of the cam package on the support shaft in the receiving bore. The subsequent postponement of the cam package thereby creates the difficulty that the locking element must be pressed into the receiving bore against the spring force of the spring element to prevent blocking of the cam pack when pushed onto the support shaft by the spherical locking element.

Furthermore, there is the disadvantage that when the spring element or the locking element is not correctly mounted when mounting the cam package on the support shaft or if the locking element or the spring element lost, so this error is found only at a final check of the camshaft. A rework is disadvantageously not possible without complete disassembly of the camshaft.

In the preparation of the holes in the support shaft is also important to ensure that the adjacent wedge structure sufficient exemption is present so that in an optional subsequent hardening of the carrier shaft or a surface finishing there is no delay of the receiving bore for receiving the spring element and the locking element. This would affect the lack of freedom of movement of the locking element and the spring element detent.

Another example of an adjustable camshaft with a locking element in the form of a ball describes JP 2013 060858 A ,

DISCLOSURE OF THE INVENTION

The object of the invention is the development of an adjustable camshaft for an internal combustion engine with a carrier shaft and an axially slidably received on the carrier shaft cam package, means for locking the cam package to be formed in discrete axial positions on the carrier shaft, which are simple, the light Allow mounting of the cam package on the carrier shaft and in particular are readjustable.
This object is achieved on the basis of an adjustable camshaft for an internal combustion engine according to the preamble of claim 1 and starting from a method for assembling a camshaft according to the known features of claim 10. Advantageous developments of the invention are specified in the dependent claims.
The invention includes the technical teaching that the spring element and the biased with this locking element are accommodated in the cam package and that the at least one locking element receptacle is arranged on the carrier shaft.
Due to the inventive arrangement of the locking means comprising at least one locking element and at least one spring element for biasing the locking element in the cam package, the above-described disadvantages are overcome in an advantageous manner. In particular, the cam package can be pushed onto the carrier shaft without the prior arrangement of the latching element and the spring element, and there is no blocking of the cam packet by the particular spherical latching element. Farther There is the advantage that the latching element and the spring element can be arranged on the cam shaft after the arrangement of the cam package on the cam and that the bias of the locking element by the spring element can be applied only subsequently. As a result, a particularly good control of the proper bias of the locking element by the spring element and the engagement of the cam package in the discrete detent positions on the carrier shaft is possible, and any required reworking on the elements without a renewed disassembly of the camshaft, in particular without a removal of the cam package from the carrier shaft.

With further advantage can be dispensed by arranging the locking element and the spring element in the cam package on the arrangement of a receiving bore in the carrier shaft. A positive locking geometry can be provided between the carrier shaft and the cam packet, which comprises, for example, a groove structure or a wedge structure on the inside of the cam pack and on the outside of the carrier shaft and wherein the structures engage in such a way that the cam pack can slide on the carrier shaft in a rotationally and axially movable manner , The form fit geometry can preferably be formed as a wedge structure and fed to a subsequent hardening process. This does not create the disadvantage that the receiving bore for receiving the spring element and the locking element by, for example, a heat input experiences a delay. Furthermore, it is not necessary to ensure that the adjacent wedge structure is sufficiently free from the receiving bore.

According to an advantageous further developed embodiment for forming the locking element receiving a circumferential groove can be introduced in the carrier shaft for each of the locking element receptacles, can engage in the arranged on the cam package locking elements by the spring force of the spring element. If, for example, two latching positions for the cam pack have to be provided, then two adjacent circumferential grooves can be introduced in the carrier shaft. In the case of three axial latching positions of the cam pack on the carrier shaft, for example if three cam elements with different contours or winding position are arranged on the cam pack, can be correspondingly introduced three circumferential grooves in the carrier shaft, etc ..
According to an alternative embodiment, the latching element receptacle can be designed as a groove bounded on a circumferential region or as a depression in the outer circumference of the carrier shaft. The recess can be designed, for example, funnel-shaped, in particular in the form of a counterbore. The limited to a peripheral region groove, for example, have a tangential course and are produced by a milling operation. On the other hand, the circumferential groove can be introduced by a rotation operation in the carrier shaft.
According to yet another embodiment, the locking element receptacle can be formed by an insert element, wherein a receiving groove can be introduced in the outer circumference of the carrier shaft for receiving the insert element. The insert element can be inserted into the receiving groove. Receptacles for receiving insert elements are particularly suitable for hollow support shafts having a smaller wall thickness if the introduction of a peripheral groove or a groove bounded on a peripheral region is technically impossible or not meaningfully possible due to the small wall thickness. In the case of several grooves, the latching element receptacle can have a waveform pointing in the direction of the latching element, and the latching element can travel along the axis of rotation in the case of a movement of the cam stack via the waveform. In particular, the wave troughs correspond to the waveform of the number of locking element receptacles and thus the number of grooves.
According to a further feature of the present inventive design of the cam package, this has at least one receiving bore in which the spring element and the biased with this locking element are received. The receiving bore is designed as a threaded bore, and wherein a screw is provided which is screwed into the threaded bore. As a result, the advantage is achieved that the spring element between the locking element and the screw can be clamped so that the spring preload against the locking element is adjustable by a change in the depth of engagement of the screw in the receiving bore. Preferably, the receiving bore extends in a bore axis which is perpendicular to the axis of rotation of the carrier shaft, the latter forming the axial displacement direction of the cam stack. Thus, the receiving bore also extends perpendicular to the direction of displacement of the cam package.
Finally, in addition to the at least one cam element, the cam packet may comprise an adjusting element, wherein the receiving bore for receiving the locking element and the spring element may be at least partially incorporated in the adjusting element. In the context of the present invention, it is also possible to provide a plurality of receiving bores in the cam pack, and in each of the receiving bores is an associated latching element and a spring element. Thus, for example, spaced detent element receptacles can be provided in the support shaft, which thus need not be adjacent to each other.
The object of the present invention is further achieved by a method for assembling a camshaft for an internal combustion engine having a support shaft extending in a rotation axis, wherein on the carrier shaft at least one cam package having at least one cam member is slidably disposed in the direction of the axis of rotation, wherein the formation of At least two locking positions of the cam stack in the direction of the axis of rotation on the carrier shaft at least one biased with a spring element locking element is provided, and the method provides first providing a support shaft with at least one arranged on this locking element receptacle, then the step of pushing the cam stack on the Carrier shaft provided and then the locking element and the spring element are arranged on the cam package.

According to the invention, the latching element and the spring element are introduced into a receiving bore introduced into the cam pack, wherein furthermore a screw element is provided, which is screwed into the receiving bore according to a further step of the method. Subsequently, the step of setting the Spring preload of the spring element against the locking element by changing the screwing of the screw in the receiving bore follow.

PREFERRED EMBODIMENTS OF THE INVENTION

Figur 1

eine Ansicht eines ersten Ausführungsbeispiels einer Nockenwelle in einem Querschnitt, und die Nockenwelle weist eine Trägerwelle auf, die massiv ausgeführt ist, und auf der Trägerwelle ist axial beweglich ein Nockenpaket angeordnet,

Figur 2

die vergrößerte Ansicht eines Details X gemäß Figur 1,

Figur 3

eine Ansicht einer Trägerwelle mit in dieser eingebrachten Rastelementaufnahmen in Form von umlaufenden Nuten,

Figur 4a

ein weiteres Ausführungsbeispiel einer Trägerwelle mit einer Rastelementaufnahme in Form einer lokal begrenzten Nut, wobei die Nut seitlich dargestellt ist,

Figur 4b

das Ausführungsbeispiel der Trägerwelle gemäß Figur 4a in einer Ansicht, in der die Nut in einer Draufsicht dargestellt ist,

Figur 5

eine Querschnittsansicht eines Ausführungsbeispiels der Nockenwelle mit einer Trägerwelle, die hohl ausgeführt ist und auf der ein axial verschieblich ausgebildetes Nockenpaket angeordnet ist,

Figur 6

die vergrößerte Ansicht eines Details Y gemäß Figur 5,

Figur 7a

ein weiteres Ausführungsbeispiel einer Trägerwelle mit einer Aufnahmenut in einer Seitenansicht,

Figur 7b

das Ausführungsbeispiel der Trägerwelle gemäß Figur 7a, wobei die Aufnahmenut in einer Draufsicht dargestellt ist.

Further, measures improving the invention will be described in more detail below together with the description of preferred embodiments of the invention with reference to FIGS. It shows:

FIG. 1

a view of a first embodiment of a camshaft in a cross section, and the camshaft has a carrier shaft, which is made solid, and on the carrier shaft axially movably a cam packet is arranged,

FIG. 2

the enlarged view of a detail X according to FIG. 1 .

FIG. 3

a view of a carrier shaft with this introduced locking element receptacles in the form of circumferential grooves,

FIG. 4a

a further embodiment of a carrier shaft with a locking element receptacle in the form of a locally limited groove, wherein the groove is shown laterally,

FIG. 4b

the embodiment of the carrier shaft according to FIG. 4a in a view in which the groove is shown in a plan view,

FIG. 5

a cross-sectional view of an embodiment of the camshaft with a support shaft, which is hollow and on which an axially displaceable cam assembly is arranged,

FIG. 6

the enlarged view of a detail Y according to FIG. 5 .

Figure 7a

a further embodiment of a carrier shaft with a receiving groove in a side view,

FIG. 7b

the embodiment of the carrier shaft according to Figure 7a , wherein the receiving groove is shown in a plan view.

In the FIG. 1 an embodiment of a camshaft 1 with the features of the present invention is shown in a cross-sectional view. The camshaft 1 is intended for an internal combustion engine and may, for example, be rotatably received about an axis of rotation 10 in the cylinder head of the internal combustion engine. The camshaft 1 has a support shaft 11, which is designed as a solid rod. On the carrier shaft 11, a cam package 12 is received, and the cam package 12 has a passage through which the carrier shaft 11 extends therethrough. The cam package 12 is longitudinally movable in the direction of the axis of rotation 10 and can be reciprocated in both directions of the axis of rotation 10 according to the double arrow shown. In order to initiate the displacement movement in the cam package 12, the cam package 12 has an adjusting element 23 into which an external manipulation means, not shown, can engage, and which axially displaces the cam assembly 12.

The cam package 12 has, for example, two cam elements 13 with mutually different different cam contours, and depending on the axial position of the cam package 12 on the support shaft 11, the various cam elements 13 can be brought into connection with a tap element for valve actuation. In order to fix the cam package 12 in two discrete axial positions on the carrier shaft 11, locking means are provided, which are described in more detail below.

To form the axial detent positions of the cam package 12 on the support shaft 11, a detent element 15 in the form of a ball is shown by way of example, and the detent element 15 can engage in a detent element receptacle 16. For latching the locking element 15 in the locking element receptacle 16, a spring element 14 is provided, which biases the locking element 15 into the locking element receptacle 16.

The latching element receptacle 16 comprises, corresponding to the number of the cam elements 13, two axially spaced circumferential grooves 17, which in the Carrier shaft 11 are introduced. The locking element 15 and the spring element 14 are arranged in the cam package 12th

The illustration shows the cam package 12 in a latching position, which is determined by the right circumferential groove 17, see FIG. 2 , If the cam package 12 is displaced to the left by the external manipulation means in engagement with an adjusting element 23, then the catch element 15 can be brought out of the right-hand circumferential groove 17 against the force of the spring element 14 until the latching element 15 snaps into the left-hand circumferential groove 17. Consequently, with the illustrated cam package 12, two axial positions can be taken.

In order to fix the spring element 14 and the latching element 15 in a receiving bore 21 provided for receiving in the cam pack 12, a screw 22 is shown, and the screw 22 is used to adjust the spring bias of the spring element 14 against the latching element 15, as in connection with FIG. 2 described in more detail.

FIG. 2 shows in an enlarged view the detail X according to FIG. 1 , The detail shows a part of the massively executed support shaft 11, which extends along the axis of rotation 10. In the outer periphery of the support shaft 11, the two circumferential grooves 17 are shown in more detail for forming the locking element receptacles 16, and the illustration shows the locking of the locking element 15 in one of the locking element receptacles 16, formed by the right side circumferential groove 17 formed in the support shaft eleventh

For receiving the spring element 14 and the locking element 15 in the cam package 12, a receiving bore 21 is introduced into the cam package 12. The receiving bore 21 extends perpendicular to the axis of rotation 10 of the support shaft 11 and guides the spherical detent element 15 so that the detent element 15 in the receiving bore 21 against the spring force of the spring element 14 can perform a lifting movement. By the axial displacement of the cam package 12 so that the locking element 15 can engage either in the right (as shown) circumferential groove 17 or in the left circumferential groove 17 of the locking element receptacle 16.

The receiving bore 21 is designed at least in sections as a threaded bore, so that the screw 22 can be screwed into the receiving bore 21 finally. By the depth of engagement of the screw 22 in the receiving bore 21, the biasing force of the spring element 14 can be changed so that the locking means can be adjusted with a variable locking force. The receiving bore 21 is introduced in sections in the adjusting element 23, wherein the cam pack 12 comprises a base body 25, through which the receiving bore 21 extends further.

FIG. 3 shows in a side view the support shaft 11 extending along the axis of rotation 10, and on the outer periphery of the support shaft 11, a wedge structure 24 is shown to prevent rotation of the cam stack 12 on the support shaft 11. A corresponding inside wedge structure is located in the passage of the cam package 12, so that the wedge structure 24 can engage positively in the wedge structure in the cam package 12. On the outer circumference of the support shaft 11, the locking element receptacles 16 are shown in the form of two circumferential grooves 17 which are arranged adjacent to each other. This creates a wave contour through the locking element receptacle 16, along which the latching element 15 can run along in the receiving bore 21 by performing a lifting movement.

The FIGS. 4a and 4b show a further embodiment of a support shaft 11 which extends along an axis of rotation 10, and the locking element receptacle 16 is introduced in the form of two grooves 18 in the support shaft 11, which are not formed circumferentially, but are limited only to a peripheral region of the support shaft 11. Dabei shows FIG. 4a the carrier shaft 11 in a rotational position, which laterally illustrates the grooves 18, so that the wave structure is recognizable by the grooves 18, and FIG. 4b shows the carrier shaft 11 in a rotational position, which represents the grooves 18 in a plan view. According to this embodiment, it is necessary to tune the position of the locking element 15 in the cam package 12 to the circumferential position of the groove 18 in the carrier shaft 11, the advantage is that the carrier shaft 11 is weakened by the only locally limited grooves 18 less.

FIG. 5 shows a further embodiment of a camshaft 1 with a along a rotation axis 10 extending support shaft 11, wherein the support shaft 11 is hollow and thus formed by a tube. On the outside of the carrier shaft 11 is a wedge structure 24 for engagement in a wedge structure, which is introduced on the inside in the cam package 12. The cam package 12 has cam elements 13 and an adjusting element 23, wherein the embodiment of the cam package 12 has three axially juxtaposed cam elements 13. Corresponding to the number of cam elements 13, the locking element receptacle 16 on the support shaft 11 has three notches 26, as in connection with FIG. 6 described in more detail below.
The locking means according to this embodiment of the camshaft 1 comprise an insert element 19, in which the locking element receptacle 16 is introduced with three recesses. The insert element 19 is located in a receiving groove 20, which is introduced on the outer circumference of the tubular carrier shaft 11. This results in the advantage that in the support shaft 11 with a small wall thickness no deeper grooves must be introduced, as in connection with FIG. 1 described.
In the adjusting element 23 of the cam package 12, the receiving bore 21 for receiving the spherical detent element 15, the spring element 14 and the screw 22 is formed, and via the screw 22 can, as in connection with FIG. 1 already described, the biasing force of the spring element 14 are changed against the locking element 15.
The FIGS. 7a and 7b show the carrier shaft 11 according to the embodiment in Figures 5 and 6, and Figure 7a shows the carrier shaft 11 in a rotational position about the axis of rotation 10, in which the receiving groove 20 is shown from the side, and FIG. 7b shows the carrier shaft 11 in a rotational position about the rotation axis 10, in which the receiving groove 20 in a plan view shows.

LIST OF REFERENCE NUMBERS

1

adjustable camshaft

10

axis of rotation

11

carrier wave

12

cam package

13

cam member

14

spring element

15

locking element

16

Rest element receptacle

17

circumferential groove

18

groove

19

insertion element

20

receiving groove

21

location hole

22

screw

23

adjustment

24

wedge structure

25

body

26

notch

Claims (9)

1. Adjustable camshaft (1) for an internal combustion engine having a support shaft (11) which extends in the direction of a rotational axis (10), at least one cam pack (12) having at least one cam element (13) being received on the support shaft (11) such that it can be displaced in the direction of the rotational axis (10), it being possible for the cam pack (12) to be latched on the support shaft (11) in at least two axial latching positions, and at least one latching element (15) which is prestressed by way of a spring element (14) and at least one latching element receptacle (16) arranged on the support shaft (11) being provided in order to form the latching positions, with the result that the latching element (15) can latch into the latching element receptacle (16) in the latching positions, characterized in that the spring element (14) and the latching element (15) which is prestressed by way of the former are received in a receiving bore (21) configured in the cam pack (12), the receiving bore (21) being configured as a threaded bore, and a screw element (22) being provided which is screwed into the threaded bore and the spring element (14) being braced between the latching element (15) and the screw element (22), with the result that the spring prestress against the latching element (15) can be set by way of a change in the screw-in depth of the screw element (22) in the receiving bore (21).
2. Adjustable camshaft (1) according to Claim 1, characterized in that the latching element receptacle (16) is configured as a circumferential groove (17) in the outer circumference of the support shaft (11).
3. Adjustable camshaft (1) according to Claim 1, characterized in that the latching element receptacle (16) is configured as a groove (18) which is limited to one circumferential region or depression in the outer circumference of the support shaft (11).
4. Adjustable camshaft (1) according to Claim 1, characterized in that the latching element receptacle (16) is formed by an insert element (19), a receiving groove (20) being made in the outer circumference of the support shaft (11), into which receiving groove (20) the insert element (19) is introduced.
5. Adjustable camshaft (1) according to one of the preceding claims, characterized in that the latching element receptacle (16) has an undulating shape which points in the direction of the latching element (15) and over which the latching element (15) can slide along during a movement of the cam pack (12) in the direction of the rotational axis (10) .
6. Adjustable camshaft (1) according to one of the preceding claims, characterized in that the cam pack (12) comprises an adjusting element (23), the receiving bore (21) being made at least partially in the adjusting element (23).
7. Method for assembling an adjustable camshaft (1) according to one of the preceding Claims 1 to 6 for an internal combustion engine having a support shaft (11) which extends in the direction of a rotational axis (10), at least one cam pack (12) having at least one cam element (13) being arranged on the support shaft (11) such that it can be displaced in the direction of the rotational axis (10), at least one latching element (15) which is prestressed by way of a spring element (14) being provided in the direction of the rotational axis (10) on the support shaft (11) in order to form at least two latching positions of the cam pack (12), the method comprising at least the following steps:

   - provision of a support shaft (11) with at least one latching element receptacle (16) which is arranged on it,

   - pushing of the cam pack (12) onto the support shaft (11),

   - arranging of the latching element (15) and the spring element (14) on the cam pack (12).
8. Method according to Claim 7, characterized in that the latching element (15) and the spring element (14) are introduced into a receiving bore (21) which is made in the cam pack (12), a screw element (22) being provided, furthermore, which is screwed into the receiving bore (21) in accordance with a further step of the method.
9. Method according to Claim 8, characterized by the further step of setting of the spring prestress of the spring element (14) against the latching element (15) by way of changing the screw-in depth of the screw element (22) in the receiving bore (21) .

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