EP3215721B1 - Camshaft with axially displacable sleeve - Google Patents

Description

The present invention relates to a camshaft according to the preamble of claim 1.

STATE OF THE ART

From the DE 10 2011 086 161 A1 a camshaft with a basic shaft is known, and a sliding element is axially displaceably received on the basic shaft along the shaft axis of the camshaft. The basic shaft has an external longitudinal toothing, and the external longitudinal toothing engages in an internal toothing which is introduced in a passage in the sliding element. As a result, the sliding element on the basic shaft is axially displaceable in the shaft axis direction, but the sliding element on the basic shaft cannot be rotated, so that torques can be transmitted from the basic shaft to the sliding element.

When receiving sliding elements on a basic shaft provided with external longitudinal toothing, there is basically the problem of guiding the sliding element as free of play as possible. In order to enable trouble-free, permanent tapping of stroke information from a cam track of the sliding element onto a tapping element, the sliding element must be guided on the basic shaft without radial play, if possible. A minimal play of the sliding element on the basic shaft leads to a minimization of the dislocation of the sliding element on the basic shaft, so that it is desirable to make the dislocation as small as possible.

In order to guide the sliding element on the basic shaft from the toothing of the outer longitudinal toothing of the basic shaft with the inner toothing in Decoupling the sliding element beats the DE 10 2011 086 161 A1 continue to provide on the sliding element guide sections through which the sliding element is guided to minimize the decaching on the fundamental. The guide sections on the sliding element run against the tooth heads of the external longitudinal teeth of the basic shaft, but this can cause premature wear of the guide sections. If cylindrical guide sections were provided on the basic shaft, the sliding element with the internal toothing could no longer be installed, since the internal toothing in the passage of the sliding element has a smallest diameter that would be smaller than the cylinder section for guiding the sliding element on the basic shaft. If the guide sections on the sliding element had a smaller diameter and were seated on a cylinder section on the basic shaft, which also has a smaller diameter, the sliding element could also no longer be fitted, since the external longitudinal toothing on the basic shaft pushed the sliding element with guide sections of smaller diameter into place makes impossible.

From the DE 10 2011 001 711 A1 A camshaft with a basic shaft has become known, on which at least one sliding element is axially displaceably received along a shaft axis, the basic shaft having an external longitudinal toothing which engages in an internal toothing introduced in a passage in the sliding element, so that the sliding element is arranged on the basic shaft in a rotationally fixed manner , and wherein the sliding element has on its axial end sides guide sections through which the sliding element is guided to minimize a decaching of the sliding element on the basic shaft, wherein guide sleeves are received on the basic shaft, against which the guide sections of the sliding element are supported.

According to the camshaft DE 10 2011 001 711 A1 it is also provided that the centering of the sliding cam on the camshaft is provided by means of bearing sleeves axially immovably fastened on the camshaft.

Although this enables the sliding cam to be centered, there is a need for further improvement, in particular with regard to a more precise alignment of the guide sleeves.

DISCLOSURE OF THE INVENTION

The object of the invention is the development of a camshaft with a minimized decaching of an axially displaceable sliding element on a basic shaft, wherein the sliding element is to be guided radially against the basic shaft via guide sections.

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

To achieve the above object, the invention includes the technical teaching that guide sleeves are received on the basic shaft, against which the guide sections of the sliding element are supported.

The invention is based on the general idea of being able to carry out the geometrical configuration of the external longitudinal toothing on the basic shaft and the internal toothing in the passage of the sliding element in a manner known per se, but the guide sleeves according to the invention can enable the sliding element to be guided without the guide sections being one must have a smaller diameter than the largest diameter of the external longitudinal toothing. The sliding element can thus be guided against a cylindrical outer peripheral surface via the guide sections. The camshaft is assembled in a simple manner since first the sliding element can be applied to the basic shaft, and only then can the guide sleeves or at least one final guide sleeve be applied laterally to the sliding element on the basic shaft.

The guide sleeves can have an inner diameter, for example, which corresponds to the tip circle diameter of the external longitudinal toothing. In this way, the guide sleeves can be attached to the tooth heads of the external longitudinal toothing. Particularly advantageously, the guide sleeves can have internal teeth, and the internal teeth in the guide sleeves can be designed so that they can rest on the external longitudinal teeth of the basic shaft, so that teeth of the internal teeth sit in the spaces between the teeth of the teeth of the external longitudinal teeth. The dimensions of the internal toothing of the guide sleeves can be designed so that the guide sleeves can be firmly attached to the external longitudinal toothing.

The guide sleeves can be shrunk or pressed onto the basic shaft with particular advantage. For example, the guide sleeves can be heated and / or the basic shaft can be cooled, so that the guide sleeves can be applied to the basic shaft in the manner of a transverse press fit. It is also conceivable that the guide sleeves are pressed onto the basic shaft in the direction of the shaft axis in order to create a longitudinal press fit.

Two guide sleeves can be provided for guiding a sliding element, and the guide sleeves can be arranged laterally, viewed in the direction of the shaft axis, at the region of the engagement of the outer longitudinal toothing in the inner toothing on the basic shaft. The guide sleeves can be at a distance from one another, which allows the sliding element to be moved axially on the basic shaft in order to bring various cam tracks into operative connection with a tap element for valve actuation. In particular, the guide sections of the sliding element with the guide sleeves can be designed with such an axial overlap that an axial displacement of the sliding element is possible while maintaining the guidance of the guide sections on the guide sleeves.

According to the invention, it is provided that the external longitudinal toothing has cylindrical receiving sections, so that the fundamental shaft alternately has cylindrical sections with the external longitudinal teeth. The internal toothing of the guide sleeves rests on the cylindrical receiving section with tooth heads formed thereon. However, the internal toothing in the guide sleeves remains necessary, since otherwise the guide sleeves could not be guided on the basic shaft via the adjacent external longitudinal toothing. For example, the cylindrical receiving section on the basic shaft can have a diameter that is, for example, slightly larger than the diameter of the root diameter of the external longitudinal toothing.

Furthermore, the basic shaft and thus the camshaft can be arranged in bearing bridges for rotatable mounting. The bearing bridges can be part of the cylinder head of an internal combustion engine or part of a hood module in which one or more camshafts are accommodated. The guide sleeves can have a length section that forms an inner bearing ring for storage in the bearing bridge. According to the invention, the guide sleeves can thus not only be used for the radial guidance of the axial movement of the sliding elements, and the guide sleeves can also form bearing rings which, together with the bearing bridges, form slide bearing arrangements for mounting the camshaft.

For example, the guide sleeves can have a cylindrical outer peripheral surface against which the guide sections of the sliding element and at the same time the bearing bridge are supported or received. In particular, the external longitudinal toothing of the basic shaft can have interruption sections under the longitudinal sections of the guide sleeves which form the slide bearing arrangement with the bearing bridges. The interruption sections consequently do not produce a press fit of the internal toothing of the guide sleeves with the external longitudinal toothing of the basic shaft, so that the concentricity of the outer peripheral surface is not impaired by the pressing of the internal toothing with the external longitudinal toothing of the basic shaft. Otherwise, the multiple support of the guide sleeves below the slide bearing arrangement with the bearing bridges over the Tooth tips of the internal toothing press a polygon structure into the guide sleeve, which has a negative impact on the concentricity.

Sliding elements can be designed with a support tube on which a plurality of functional elements are applied. The functional elements can, for example, form cam elements or an adjusting element, and the adjusting element serves for the axial adjustment of the sliding element on the basic shaft, and can cooperate with an adjusting manipulator which is arranged at rest in the installation environment of the camshaft. For example, the carrier tube can be made so long that the functional elements protrude laterally beyond the carrier tube, and the guide sections can be formed on the inside on at least one functional element. For example, the functional elements, in particular the cam elements, can be applied to the outside of the carrier tube by means of a cylinder press fit and project laterally beyond the carrier tube. The protruding part of the functional element releases an inner cylindrical section, which forms the guide section and, together with the outer peripheral surface of the guide sleeve, forms the radial guide thereof.

PREFERRED EMBODIMENT OF THE INVENTION

Fig. 1

eine quergeschnittene Ansicht einer Nockenwelle mit Führungshülsen, die auf Aufnahmeabschnitten zwischen einer Außenlängsverzahnung auf der Grundwelle aufgebracht sind,

Fig. 2

ein nicht zur Erfindung gehörendes Ausführungsbeispiel einer Nockenwelle mit Führungshülsen, die auf einer durchgehenden Außenlängsverzahnung der Grundwelle aufsitzen,

Fig. 3

ein weiteres Ausführungsbeispiel einer Nockenwelle mit Führungshülsen, die auf der Außenlängsverzahnung der Grundwelle aufsitzen, wobei die Außenlängsverzahnung einen Unterbrechungsabschnitt aufweist.

Further measures improving the invention are shown below together with the description of a preferred embodiment of the invention with reference to the figures. It shows:

Fig. 1

2 shows a cross-sectional view of a camshaft with guide sleeves, which are applied to receiving sections between an external longitudinal toothing on the basic shaft,

Fig. 2

1 shows an embodiment of a camshaft with guide sleeves which are not part of the invention and are seated on a continuous external longitudinal toothing of the basic shaft,

Fig. 3

a further embodiment of a camshaft with guide sleeves on the external longitudinal teeth of the basic shaft sit on, the outer longitudinal toothing having an interruption section.

In Figure 1 a camshaft 1 according to a first exemplary embodiment of the invention is shown in sections. The camshaft 1 has a basic shaft 10 which extends along a shaft axis 12. On the basic shaft 10, a sliding element 11 is received, which is axially displaceable along the shaft axis 12. The camshaft 1 basically has a plurality of sliding elements 11, each of which can preferably be accommodated on the basic shaft 10 in the same way. In order to mount the camshaft 1, for example in a cylinder head or in a module hood, bearing bridges 19 are provided, and the camshaft 1 is rotatably received, for example, in two bearing bridges 19 about the shaft axis 12 with reference to the length section shown.

The basic shaft 10 has an external longitudinal toothing 13, the external longitudinal toothing 13 being shown interrupted several times along the shaft axis 12.

The sliding element 11 has a carrier tube 21, and an internal toothing 14 is formed in the inner passage of the carrier tube 21. The internal toothing 14 engages in the external longitudinal toothing 13 of the basic shaft 10, so that the sliding element 11 is received on the basic shaft 10 so that it cannot rotate and can be displaced along the shaft axis 12. The tolerance or dimensioning of the external longitudinal toothing 13 in relation to the internal toothing 14 is provided in such a way that only the torque transmission is ensured; radial guidance with a minimal decaching of the sliding element 11 on the basic shaft 10 takes place via the toothing between the external longitudinal toothing 13 and the internal toothing 14 Not.

For the radial guidance of the sliding element 11, guide sections 15 are formed thereon, and the guide sections 15 run against guide sleeves 16 which are received on the basic shaft 10. The guide sleeves 16 thus support the sliding element 11 via the guide sections 15. The guide sections 15 are formed on functional elements 22 which are received on the carrier tube 21. The exemplary embodiment shows a sliding element 11 with two functional elements 22, which are designed as cam elements 23 with different cam raceways. Between the two cam elements 23 shown there is an adjusting member 24, by means of which the sliding element 11 can be displaced on the fundamental shaft 10 in the shaft axis direction with a manipulator (not shown). The sliding element 11 is shown in a left position with respect to the image plane, so that the guide section 15 with the left guide sleeve 16 shown on the left has a greater overlap than the guide section 15 with the right guide sleeve 16 on the right. The two guide sleeves 16 are adjacent for interlocking the outer longitudinal toothing 13 with the inner toothing 14 in the support tube 21, the distance between the two guide sleeves 16 being designed such that the axial mobility of the sliding element 11 is maintained.

The guide sleeves 16 have an internal toothing 17, the internal toothing 17 being designed such that it can be guided over the external longitudinal toothing 13 of the basic shaft 10 in the direction of the shaft axis. The exemplary embodiment shows the fundamental shaft 10 with interruptions in the external longitudinal toothing 13, so that setting points generated by the latter for receiving the guide sleeves 16 are formed by cylindrical receiving sections 25. The guide sleeves 16 sit on the cylindrical receiving sections 25 with their tooth heads 17a of the internal toothing 17, and the guide sleeves 16 can be shrunk or pressed onto the receiving sections 25. For example, the diameter of the receiving sections 25 can be dimensioned such that it is slightly larger than the root diameter of the external longitudinal toothing 13 of the basic shaft 10. The guide sleeves 16 can thus be guided via the external longitudinal toothing 13 to the setting points which are formed by the receiving sections 25. When the guide sleeves 16 reach the receiving sections 25, the pressing with the basic shaft 10 takes place in the longitudinal press dressing or in the transverse press dressing.

The guide sleeves 16 have a length which is determined in such a way that the guide sleeves 16 extend with a length section 16a to below or into the bearing bridges 19. As a result, the guide sleeves 16 with their outer circumferential surface 20 form a slide bearing arrangement with the bearing bridges 19, so that the camshaft 1 can be rotatably supported about the shaft axis 12 via the guide sleeves 16. Thus, the guide sleeves 16 fulfill both a guiding function of the sliding element 11 via the guide sections 15 formed on the sliding element 11 and a bearing function for mounting the camshaft 1 in the bearing bridges 19. The outer circumferential surface 20 of the guide sleeves 16 can be dimensioned and surface-treated so that the guide sleeves 16 can serve as inner bearing rings for the plain bearing in the bearing bridges 19.

Figure 2 shows a non-inventive embodiment of the camshaft 1 with a hollow shaft 10 designed to reduce weight, which extends along a shaft axis 12. A sliding element 11 is received on the basic shaft 10, and the sliding element 11 has a carrier tube 21 which receives two cam elements 23 and an adjusting member 24. On the inside, the carrier tube 21 has an internal toothing 14 which engages in an external longitudinal toothing 13 of the basic shaft 10. As a result, the sliding element 11 is, as already in connection with Figure 1 described, axially movable and rotatably added to the base shaft 10.

The basic shaft 10 is formed with an external longitudinal toothing 13 along the shaft axis 12 so that it is uninterrupted and all elements are received on the external longitudinal toothing 13 itself. To the side of the arrangement of the sliding element 11, guide sleeves 16 are accommodated on the external longitudinal toothing 13 of the basic shaft 10, which have an internal toothing 17 on the inside. This engages in the external longitudinal toothing 13 of the basic shaft 10, and the internal toothing 17 is dimensioned such that it is pressed onto the external longitudinal toothing 13 of the basic shaft 10 in the transverse press fit or in the longitudinal press fit. In particular, tooth heads 17a of the internal toothing 17 are shown, via which the guide sleeve 16 can be pressed onto the outer longitudinal toothing 13, for example by making the tooth tip dimension of the inner toothing 17 larger (ie with a smaller tip circle diameter) than the tooth root dimension of the outer longitudinal toothing 13.

The exemplary embodiment shows guide sleeves 16 with a length section 16a, which extends into the bearing bridges 19, so that the guide sleeves 16 form a slide bearing arrangement of the camshaft 1 with the bearing bridges 19.

Guide sections 15 are formed on the inside in the cam elements 23 and are guided on the outer peripheral surface 20 of the guide sleeves 16, as a result of which the radial guidance of the sliding element 11 is achieved. The guide dimension between the guide sections 15 and the outer circumferential surface 20 of the guide sleeves 16 can be determined in such a way that the roof element 10 is minimally offset from the sliding element 11.

Finally shows Figure 3 another modified embodiment of the camshaft 1 with a basic shaft 10 which has interruption sections 18. The guide sleeves 16 are arranged along the shaft axis 12 at positions on the basic shaft 10 at which the interruption sections 18 are located. The interruption sections 18 correspond to the bearing bridges 19 for rotatably receiving the camshaft 1 via the guide sleeves 16, and the guide sleeves 16 serve, via their outer peripheral surface 20, to mount the camshaft 1 in the bearing bridges 19.

The guide sleeves 16 are longer than the width of the interruption sections 18 in the direction of the shaft axis, so that the guide sleeves 16 are attached to their outer sides on the external longitudinal toothing 13 of the basic shaft 10, in particular are pressed on. The section over which the bearing bridges 19 form a sliding bearing with the outer circumferential surface 20 of the guide sleeves 16 thus has no interference fit between the inner toothing 17 of the guide sleeves 16 and the outer longitudinal toothing 13 of the basic shaft 10, so that the concentricity of the outer circumferential surface 20 by the pressing the internal toothing 17 with the external longitudinal toothing 13 of the fundamental shaft 10 is not deteriorated.

The sliding element 11 is guided on the guide sleeves 16 in the manner described above via the guide sections 15 which are formed on cam elements 23 which are received on a carrier tube 21 of the sliding element 11. Between the two cam elements 23, an adjusting member 24 is formed for axially adjusting the sliding element along the shaft axis 12 on the basic shaft 10. An internal toothing 14, which is introduced on the inside in the carrier tube 21 and which interacts with the external longitudinal toothing 13, is used for torque transmission between the basic shaft 10 and the sliding element 11.

Reference list

1

camshaft

10th

Fundamental wave

11

Sliding element

12th

Shaft axis

13

External longitudinal teeth

14

Internal teeth

15

Guide section

16

Guide sleeve

16a

Length segment

17th

Internal teeth

17a

Tooth head

18th

Interruption section

19th

Warehouse bridge

20

Outer peripheral surface

21

Carrier tube

22

Functional element

23

Cam element

24th

Actuator

25th

Receiving section

Claims (8)

1. Camshaft (1) with a main shaft (10) on which at least one sliding element (11) is received in such a way as to be axially displaceable along a shaft axis (12), wherein the main shaft (10) comprises an outer longitudinal tooth structure (13) that meshes with an inner tooth structure (14) introduced into a passage in the sliding element (11), such that the sliding element (11) is arranged in a rotationally fixed manner on the main shaft (10), and wherein the sliding element (11), on its axial end faces, comprises guiding portions (15) by means of which the sliding element (11) is guided on the main shaft (10) in order to minimize an axial offset of the sliding element (11), wherein guiding sleeves (16) are received on the main shaft (10), and the guiding portions (15) of the sliding element (11) are supported against these, characterized in that the guiding sleeves (16) comprise an inner tooth structure (17), which is dimensioned in such a way that the guiding sleeves (16) are mounted, in a manner fixed in terms of rotation and displacement, on cylindrical receiving portions (25) of the main shaft (10).
2. Camshaft (1) according to Claim 1, characterized in that the guiding sleeves (16) are shrink-fitted or pressed onto the main shaft (10).
3. Camshaft (1) according to either of Claims 1 and 2, characterized in that the guiding sleeves (16), seen in the direction of the shaft axis, are arranged on the main shaft (10) laterally with respect to the region of engagement of the outer longitudinal tooth structure (13) in the inner tooth structure (14).
4. Camshaft (1) according to one of Claims 1 to 3, characterized in that the outer longitudinal tooth structure (13) comprises cylindrical receiving portions (25), wherein the inner tooth structure (17) of the guiding sleeves (16) sits on the cylindrical receiving portions (25) via tooth tips (17a) formed on the inner tooth structure (17).
5. Camshaft (1) according to one of the preceding claims, characterized in that the main shaft (10) can be arranged rotationally movably in bearing brackets (19), wherein the guiding sleeves (16) comprise a longitudinal portion (16a) that forms a bearing inner ring for mounting in the bearing bracket (19).
6. Camshaft (1) according to one of the preceding claims, characterized in that the guiding sleeves (16) comprise a cylindrical outer circumferential surface (20), against which the guiding portions (15) of the sliding element (11) and preferably the bearing bracket (19) are supported, and/or wherein the outer longitudinal tooth structure (13) of the main shaft (10) comprises interruption sections (18) among the longitudinal portions (16a) of the guiding sleeves (16) which, with the bearing brackets (19), form the plain bearing arrangement.
7. Camshaft (1) according to one of the preceding claims, characterized in that the guiding portions (15) of the sliding element (11) are designed to axially overlap the guiding sleeves (16) such that an axial displacement of the sliding element (11) is permitted while maintaining the guiding of the guiding portions (15) on the guiding sleeves (16).
8. Camshaft (1) according to one of the preceding claims, characterized in that the sliding element (11) comprises a carrier tube (21) on which the functional elements (22) of the sliding element (11) are received, wherein the guiding portions (15) are formed on at least one functional element (22).

Images