EP3129614B1 - Adjustable camshaft - Google Patents

Description

The present invention relates to an adjustable camshaft for the valve train of an internal combustion engine with an outer shaft and with an extending through the outer shaft inner shaft, wherein on the outer shaft at least one cam member and rotatably connected to the inner shaft, wherein the cam member rotatable to form a bearing is absorbed on the outside of the outer shaft.

STATE OF THE ART

The DE 10 2005 014 680 A1 shows an example of an adjustable camshaft for the valve train of an internal combustion engine with an outer shaft and with an extending through the outer shaft inner shaft, wherein arranged on the outer shaft cam elements and are rotationally fixedly connected to the inner shaft via a bolt. If the phase position of the inner shaft is changed relative to the phase position of the outer shaft, the cam elements on the outer shaft execute a rotational movement independently of a rotation of the camshaft, for example in a cylinder head or in a cylinder head cover. As a result, the adjustable cam elements are rotated against firmly arranged on the outer shaft further cam elements, so that the timing of, for example, intake valves and exhaust valves to each other can be changed.

The cam elements have cam tracks in contact with tapping elements. If the camshaft rotates about its longitudinal axis, a periodic application of force to the cam elements is effected by the tapping elements. The dynamic application of force to the cam members results in a periodic cycling of the bearing formed by the rotatable engagement of the cam members on the outside of the outer shaft.

Wear tests have shown that although this alternating load, although an improved oil exchange in the sliding gap between the cam member and the outer side of the outer shaft causes, as a kind of pumping effect sets, however, a periodic, minimal tilting movement of the cam elements on the outside of the outer shaft to increased wear.

Basically, cam elements are rotatably received on the outside of outer shafts via slide bearings. If the sliding bearings are designed with very low bearing air, the lubricant exchange in the bearing gap deteriorates. A poor supply of lubricant also leads to increased wear during prolonged use of the camshaft. If the bearing air is increased so that a slightly larger gap between the bore in the cam member and the outside of the outer shaft is formed, although the lubricant exchange is improved, but it can lead to edge bearing effects, which are also to be avoided.

Another disadvantage of a very low internal clearance, which is formed for example when the cam elements are slightly biased on the outside of the outer shaft, affect higher necessary adjustment forces, especially since a plurality of cam elements rotatably received on the outside of the outer shaft are provided on a camshaft. So if the inner shaft to be rotated in the outer shaft, for example by a hydraulically acting phaser, so this must be adapted to the increased Verstellmomenten, which disadvantageously an increased oil supply is necessary.

DISCLOSURE OF THE INVENTION

The object of the invention is the development of an adjustable camshaft with an improved recording of the cam elements on the outside of the outer shaft. In particular, the wear of the camshaft should be minimized.

This object is achieved on the basis of an adjustable camshaft according to the preamble of claim 1 in conjunction with the characterizing features. Advantageous developments of the invention are specified in the dependent claims.

The invention includes the technical teaching that the bearing between the cam member and the outside of the outer shaft arranged rolling elements.

Between the cam member and the outer side of the outer shaft arranged rolling bearings allow a rotatable mounting of the cam member on the outer shaft, with which the above-mentioned disadvantages of the prior art can be overcome.

By the rolling elements, a rolling bearing assembly can be created, which allows a torque minimum rotation of the cam member on the outer shaft, since a rolling bearing has a lower loss friction compared to a plain bearing. Furthermore, the wear of the bearing can be reduced, since with a sliding contact of a cam member on the outer shaft full lubrication due to the very small, and only short-term rotational movements can not be fully built. A particular advantage is further characterized in that a rolling bearing can be biased despite maintaining low torque, so that the periodic introduction of force by a tapping element on the cam member does not lead to a recurrent tilting of the cam member on the outer shaft. As a result, no edge support effects, so that a total of a roller bearing arranged between the cam member and the outer side of the outer shaft rolling elements allows a slightly biased recording of the cam member on the outer shaft, without larger torsional torques are required.

For the design of a rolling bearing with arranged between the cam member and the outer side of the outer shaft rolling elements several variants can be provided. For example, the cam member may have a receiving bore for receiving the rolling elements, wherein the rolling elements may abut against the inner surface of the receiving bore. Thus, the rolling elements can roll directly in the bore in the cam element, so that the cam element at the same time assumes the function of a bearing outer ring.

Furthermore, it can be provided that the rolling elements bear against the outside of the outer shaft in direct contact, so that the outer side of the outer shaft forms a bearing inner ring on which the rolling elements can roll off.

As an alternative embodiment for directly receiving the rolling elements in the receiving bore of the cam member and on the outside of the outer shaft is the further possibility to provide a bearing with a bearing outer ring and / or with a bearing inner ring. For example, the bearing may comprise a bearing outer ring, which is seated in the receiving bore of the cam member and against which the rolling elements. Regardless of the arrangement of a bearing outer ring and a bearing inner ring can be provided, which rests on the outside of the outer shaft and abut against the rolling elements and roll.

The rolling elements can form, for example, needles or rollers, wherein balls can also be provided, which are arranged between the outer side of the outer shaft and the cam member. For example, two ball bearing sets can be provided, which are located in the outer areas of the receiving bore.

With further advantage, a circumferential bearing groove can be introduced in the outer side of the outer shaft, in which the rolling elements are at least a part of their diameter. The bearing groove has a smaller diameter than the diameter of the outside of the outer shaft. As a result, the advantage is achieved that the rolling elements can be provided with a larger diameter, without the basic geometric dimensions of an adjustable camshaft must be changed. However, the bearing groove should not be inserted too deeply into the outer shaft, so that the outer shaft is not permanently weakened.

The cam member may be rotatably connected to the inner shaft with a bolt, and this may be passed through an opening in the outer shaft, wherein the bearing axially adjacent to the bolt or to the opening can be arranged. As a result, the arrangement of the bolt does not interfere with the inclusion of rolling elements between the cam member and the outside of the outer shaft. In particular, the cam element may have a cam collar, which is integrally formed on a base body of the cam element. The rolling elements may be limited in length to the width of the base body. Thus, the rolling elements can be located in the receiving bore within or below the base body and laterally the cam collar connects, which serves to receive the bolt.

With further advantage may be formed between the cam collar and the outer side of the outer shaft, a sliding contact, in particular to form a sliding bearing. Thus, a further stabilization of the cam element on the outer shaft against tilting can be developed, so that a bearing combination between a rolling bearing and a plain bearing for receiving a cam element is provided on the outer shaft. In particular, such a combination of sliding bearing and rolling bearing provides particular advantages in terms of minimal wear, easy adjustment and minimal tilting of the cam member on the outer shaft.

According to a further advantageous embodiment of the bearing for receiving the cam member on the outer shaft, a bearing cage may be provided in which the Rolling, in particular self-holding, are added. It is also possible to attach locking washers to the cam element in order to fix the bearing cage with the rolling elements in the axial position.

PREFERRED EMBODIMENT OF THE INVENTION

Figur 1

eine Querschnittsansicht einer verstellbaren Nockenwelle mit einem Nockenelement, das erfindungsgemäß über Wälzkörper auf der Außenseite einer Außenwelle aufgenommen ist,

Figur 2

eine quergeschnittene Ansicht einer Außenwelle für eine verstellbare Nockenwelle zur Aufnahme von Wälzkörpern auf der Außenseite der Außenwelle,

Figur 3

ein weiteres Ausführungsbeispiel einer verstellbaren Nockenwelle mit einer Lagerung, die durch ein Wälzlager mit Wälzkörpern ausgebildet ist,

Figur 4

eine perspektivische Ansicht einer verstellbaren Nockenwelle mit einem Nockenelement, das über Wälzkörper auf der Außenwelle aufgenommen ist, und

Figur 5

eine Querschnittsansicht einer weiteren verstellbaren Nockenwelle mit einem Nockenelement, das erfindungsgemäß über Wälzkörper auf der Außenseite einer Außenwelle aufgenommen ist,

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

FIG. 1

a cross-sectional view of an adjustable camshaft with a cam member which is received according to the invention via rolling elements on the outside of an outer shaft,

FIG. 2

a cross-sectional view of an outer shaft for an adjustable camshaft for receiving rolling elements on the outside of the outer shaft,

FIG. 3

Another embodiment of an adjustable camshaft with a bearing, which is formed by a rolling bearing with rolling elements,

FIG. 4

a perspective view of an adjustable camshaft with a cam member which is received on the outer shaft via rolling elements, and

FIG. 5

a cross-sectional view of another adjustable camshaft with a cam member which is received according to the invention via rolling elements on the outside of an outer shaft,

FIG. 1 shows a cross-section of an adjustable camshaft 1, which can serve for the valve train of an internal combustion engine. The camshaft 1 has an outer shaft 10 and an inner shaft 11 extending through the outer shaft 10, wherein the inner shaft 11 is rotatable in the outer shaft 10. On the outside of the outer shaft 10, a cam member 12 is arranged, which is rotatably connected via a pin 19 with the inner shaft 11. The cam member 12 is rotatably received on the outer side 14 of the outer shaft 10 to form a bearing 13.

The bearing 13 has rolling bodies 15, which are located in the receiving bore in the cam member 12 and via which the cam member 12 is mounted on the outer side 14 of the outer shaft 10. In this case, by way of example, an upper rolling element 15 is cut and a lower rolling element 15 is shown uncut. The rolling elements 15 are formed as needles and distributed over the circumference at the same distance a plurality of needles between the cam member 12 and the outer side 14 of the outer shaft 10 are arranged.

The cam element 12 has a base body 22 and a cam collar 21. The base body 22 has on the outside a cam track 24, via which a tapping element taps a control movement for a valve of the internal combustion engine. Laterally to the base body 22, the cam collar 21 connects, and the rolling elements 15 have a length which is limited to the width of the base body 22. Thus, there are no rolling elements under the cam collar 21, and the bolt 19 can be arranged in the cam collar 21.

The forces acting on the base body 22 periodically via the cam track 24 are absorbed by the rolling elements 15, so that the rolling elements 15 are arranged on the cam element 12 under the force introduction region of the forces. As a result, during operation of the camshaft 1, the cam element 12 is seated substantially tilt-free on the outer side 14 of the outer shaft 10, whereby a sliding contact can additionally be provided between the cam collar 21 and the outer side 14 of the outer shaft 10.

FIG. 2 shows a cross-sectional view of the outer shaft 10 with inserted therein openings 20 for passing the bolt 19. In the outer side 14 of the outer shaft 10 for receiving the rolling elements 15, a bearing groove 18 is introduced, which has a width which corresponds substantially to the length of the rolling elements 15 , A substantial advantage of the bearing groove 18 is the possibility that can be carried out without structural changes of the camshaft 1, the rolling elements 15 can be performed with a customized diameter, and for example, the bearing groove 18 is a radial Have depth that corresponds approximately to half the diameter of the rolling elements 15.

FIG. 3 shows a further embodiment of an adjustable camshaft 1 with an outer shaft 10 and an inner shaft 11 and on the outer side 14 of the outer shaft 10, a cam member 12 is received via a bearing 13. The storage 13 is as complete rolling bearing with a bearing outer ring 16 and running with a bearing inner ring 17, and between the bearing outer ring 16 and the bearing inner ring 17, the rolling elements 15 are rolling the rolling elements 15 against the bearing outer ring 16 and the bearing inner ring 17 from, and the bearing outer ring 16 is in the Receiving bore inserted in the cam member 12, and the bearing inner ring 17 is applied to the outer side 14 of the outer shaft 10.

The rolling bearing with the rolling elements 15, the bearing outer ring 16 and the bearing inner ring 17 is located below the base body 22, and thus laterally to the cam collar 21 with the pin 19th

If the inner shaft 11 is rotated about the shaft axis 23 relative to the outer shaft 10, then the bolt 19 connected to the inner shaft 11 pivots in the elongated openings 20 in the outer shaft 10. As a result, the rolling elements 15 roll against the rings 16 and 17, and that Cam element 12 can pivot relative to the outer shaft 10 together with the inner shaft 11.

FIG. 4 finally shows a perspective view of the adjustable camshaft 1 with the outer shaft 10 which extends in the shaft axis 23 and on the outer shaft 10, the cam member 12 is received via the bearing 13. The perspective view shows a plurality of rolling elements 15 for forming the bearing 13, which are located below the main body 22 of the cam member 12. The side of the body 22 subsequent cam collar 21 serves to receive the bolt 19th

FIG. 5 shows a cross-sectional view of another embodiment of an adjustable camshaft 1 according to the invention, which can serve for the valve train of an internal combustion engine. The in the FIG. 5 shown camshaft 1 substantially corresponds to that in the FIG. 1 shown camshaft 1 and thus also has an outer shaft 10 and extending through the outer shaft 10 extending inner shaft 11, wherein the inner shaft 11 in the outer shaft 10 is rotatable. On the outside of the outer shaft 10, a cam member 12 is arranged, which is rotatably connected via a pin 19 with the inner shaft 11. The cam member 12 is rotatably received on the outer side 14 of the outer shaft 10 to form a bearing 13.

The bearing 13 has rolling elements 15 which are located in the receiving bore in the cam member 12 and via which the cam member 12 on the outside 14 of the Outer shaft 10 is mounted. In this case, by way of example, an upper rolling element 15 is cut and a lower rolling element 15 is shown uncut. The rolling elements 15 are formed as needles and distributed over the circumference at the same distance a plurality of needles between the cam member 12 and the outer side 14 of the outer shaft 10 are arranged. The in the FIG. 5 shown camshaft 1 differs from that in the FIG. 1 shown camshaft 1 substantially in that the outer shaft 10 is no bearing groove 18 for the axial guidance of the rolling elements 15, in particular in the FIG. 2 shown. Rather, the rolling elements 15 bear against the outside of the outer shaft 10 in direct contact, so that the outer side of the outer shaft 10 advantageously forms a bearing inner ring on which the rolling elements can roll off. A prior processing of the outer shaft 10 to create bearing grooves 18 is therefore advantageously not required.

As further in the FIG. 5 shown, the cam member 12 has a base body 22 and a cam collar 21. The base body 22 has on the outside a cam track 24, via which a tapping element taps a control movement for a valve of the internal combustion engine. Laterally to the base body 22, the cam collar 21 connects, and the rolling elements 15 have a length which is limited to the width of the base body 22. Thus, there are no rolling elements under the cam collar 21, and the bolt 19 can be arranged in the cam collar 21.

The forces acting on the base body 22 periodically via the cam track 24 are absorbed by the rolling elements 15, so that the rolling elements 15 are arranged on the cam element 12 under the force introduction region of the forces. As a result, during operation of the camshaft 1, the cam element 12 is seated substantially tilt-free on the outer side 14 of the outer shaft 10, whereby a sliding contact can additionally be provided between the cam collar 21 and the outer side 14 of the outer shaft 10.

Claims (10)

1. Adjustable camshaft (1) for the valve drive of an internal combustion engine, with an outer shaft (10) and with an inner shaft (11) extending through the outer shaft (10), wherein at least one cam element (12) is arranged on the outer shaft (10) and is connected to the inner shaft (11) for rotation therewith, wherein the cam element (12) is accommodated rotatably on the outer side (14) of the outer shaft (10), thereby forming a bearing (13), characterized in that the bearing (13) comprises rolling bodies (15) arranged between the cam element (12) and the outer side (14) of the outer shaft (10).
2. Adjustable camshaft (1) according to Claim 1, characterized in that the cam element (12) comprises a receiving bore for receiving the rolling bodies (15), wherein the rolling bodies (15) lie against the inner surface of the receiving bore.
3. Adjustable camshaft (1) according to Claim 1 or 2, characterized in that the rolling bodies (15) lie against the outer side (14) of the outer shaft (10).
4. Adjustable camshaft (1) according to either of Claims 1 and 3, characterized in that the bearing (13) comprises a bearing outer ring (16) which sits in the receiving bore of the cam element (12) and against which the rolling bodies (15) lie.
5. Adjustable camshaft (1) according to one of Claims 1, 2 or 4, characterized in that the bearing (13) comprises a bearing inner ring (17) which sits on the outer side (14) of the outer shaft (10) and against which the rolling bodies (15) lie.
6. Adjustable camshaft (1) according to one of Claims 1 to 4, characterized in that an encircling bearing groove (18), in which the rolling bodies (15) at least partially sit, is introduced into the outer side (14) of the outer shaft (10).
7. Adjustable camshaft (1) according to one of the preceding claims, characterized in that the cam element (12) is connected with a bolt (19) to the inner shaft (11) for rotation therewith, wherein the bolt (19) is guided through an opening (20) in the outer shaft (10), and wherein the bearing (13) is arranged axially adjacent to the bolt (19) or to the opening (20).
8. Adjustable camshaft (1) according to one of the preceding claims, characterized in that the cam element (12) has a cam collar (21) which is integrally formed laterally on a basic body (22) of the cam element (12), wherein the rolling bodies (15) are limited in length to the width of the basic body (22).
9. Adjustable camshaft (1) according to Claim 8, characterized in that a sliding contact is formed between the cam collar (21) and the outer side (14) of the outer shaft (10), in particular so as to form a sliding bearing.
10. Adjustable camshaft (1) according to one of the preceding claims, characterized in that a bearing cage is provided in which the rolling bodies (15) are accommodated in particular in a self-retaining manner.

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