Camshaft consisting of two nested hollow shaft sections

Abstract

Camshaft (1) consisting of at least one hollow shaft section (2, 3) with at least one joined cam (N1, N2, N3, N4, N5, N6, N7) and at least two bearing points (L1, L2, L3, L4, L5) on a housing, wherein in which at least one hollow shaft section (2, 3) and at least two openings (11, 12) are provided, the two openings (11, 12) within the at least one hollow shaft section (2, 3) are connected to each other by means of a connecting element (6), the connecting element (6) is formed by a pin (7, 7a) which is inserted into the at least one hollow shaft section (2, 3) and with which the at least one hollow shaft section (2, 3) forms a cavity (10) connecting the two openings (11, 12), and a collar (15) of the pin (7) has a longitudinal groove (16), such that the cavity (10) is formed by two annular spaces (17, 18) separated from each other by the collar (15) and connected to each other by the longitudinal groove (16), characterized in that two nested hollow shaft sections (2, 3) are provided, at each of which at least one bearing point (L1, L2) with an opening (11, 12) in the hollow shaft section (2, 3) is provided.

Description

[0001] The invention relates to a camshaft, in particular for an internal combustion engine, with at least one cam and at least two bearing points for mounting on a housing.

[0002] Camshafts, for example, used to control the gas exchange between cylinders of internal combustion engines in motor vehicles, have been known for a long time. The camshafts are supported by multiple bearings relative to the housing. To lubricate the bearing points, or the bearings mounted on them, lubricant such as oil is pumped into the valve chamber, for example, in the case of overhead camshafts. Corresponding bores, channels, or similar features are provided in the housing for this purpose, leading into the valve chamber and through which the lubricant is then discharged. Due to design and constructional reasons, an insufficient supply of lubricant to a bearing point may occur.

[0003] Adjustable camshafts are known in the prior art, which have channels in the shaft for guiding a hydraulic medium to an actuating device, cf. DE 10 2006 024 794 A1, US 2008 / 0 257 104 A1 or DE 10 2006 028 611 A1. DE 10 2006 038 680 A1 describes a lubrication device for a valve train of an internal combustion engine.

[0004] The present invention therefore aims to propose a camshaft in which all bearing points are adequately supplied with lubricant. A cost-effective solution is to be sought.

[0005] The problem is solved by a camshaft with the features of the first claim. In this way, a poorly lubricated bearing point can be adequately supplied with lubricant by transporting the lubricant from the better-lubricated opening, for example, an opening arranged at a bearing point. At least one opening can be arranged below an inner bearing ring of a bearing such as a rolling or sliding bearing. For example, the inner bearing ring can be split so that the lubricant exiting the opening can reach the rolling elements directly.

[0006] It is understood that the inventive concept encompasses a connection of several bearing points in the same manner, wherein at least one opening, for example an opening arranged at a bearing point or a central supply opening which can also introduce pressurized lubricant into the interior or a channel of the at least one hollow shaft section, is supplied with lubricant, and the other openings serve as outlet openings at the bearing points. Furthermore, openings can be provided at the bearing points which, together with the connecting pipe system inside the at least one hollow shaft section, serve as a leveling element for the lubricant over at least one axial section of the camshaft.It has proven advantageous to provide the connection between the at least two openings in such a way that material is removed from the surface of an inserted connecting element between the at least two openings, so that after the insertion of the connecting element, a connecting channel or an annular space is formed with the inner circumference of the at least one hollow shaft section, which connects the at least two openings to each other.

[0007] An embodiment of a built camshaft according to the invention is constructed from several, or according to the invention two, nested hollow shaft sections, wherein at least two hollow shaft sections each have at least one bearing point with an opening in the hollow shaft section. According to the invention, the hollow shaft sections are nested together by, for example, one hollow shaft section receiving an axial projection of another hollow shaft section. The nested hollow shaft sections can be pressed together, thus providing a joining method and preventing further contamination during the camshaft manufacturing process. Alternatively, other joining methods can be used.

[0008] It has proven advantageous to seal the connecting element axially outside the openings in relation to at least one hollow shaft section, so that the lubricant flow transported between the openings is isolated from the ends of the camshaft that can exit the housing.

[0009] Particularly when using a solid shaft journal, it can be non-rotatably connected to the at least one hollow shaft section. For this purpose, the journal is preferably connected to the at least one hollow shaft section by means of an interference fit that provides sufficient sealing and transmits sufficient torque so that the journal can be driven and transmit the drive torque to the at least one hollow shaft section with the cams for controlling the internal combustion engine. For this purpose, the journal can be designed as the shaft end of the camshaft, which has a suitable engagement profile for its drive, for example, a toothed section for a camshaft chain or a profile for a timing belt.

[0010] The end of the pin opposite the drive end can have a collar that bears against the inner circumference of at least one hollow shaft section, with a ring seal arranged between the inner circumference and the collar, for example in an annular groove of the collar. Similarly, a correspondingly sealed collar can be provided on both ends of a non-driven connecting element.

[0011] The proposed method of supplying a bearing point through corresponding openings and a connecting element within at least one hollow shaft section allows for the placement of a bearing point in a poorly supplied area of ​​the camshaft. Components can therefore be positioned between two openings that, for example, impede lubricant flow to a bearing point. Such components could be, for instance, radially extending gears for driving the camshaft, or gears that transmit torque from the camshaft (which is itself also driven) to another component, such as a pump, air conditioning unit, or the like, or that function as a signal transmitter. Furthermore, one or more supply bores can be provided in the housing that do not adequately supply all bearing points with lubricant.In this way, for example, it is not necessary to provide lubricant inlets in housing areas that are critical from a design perspective, because, for example, other openings run in the housing in these areas or the wall thickness of the housing is too small or is intended to be too small.

[0012] In a further advantageous embodiment, the connecting element can be formed from a pipe section, the wall thickness being selected to be sufficient to allow radial material removal for the formation of the connecting channel or annular space. The connecting element is made of steel, particularly when subjected to high static stress, for example, when used as a drive for the camshaft. For less demanding applications, the connecting element can be made of light metals and their alloys or of plastic. Manufacturing processes suitable for mass production, such as die casting or injection molding, are preferably used.

[0013] The invention is described in relation to the invention described in the Fig. The embodiments shown in 1 to 3 are explained in more detail below. The following are shown: Fig. 1 a cutaway view of a camshaft according to the invention, Fig. 2 a cross-section through the in Fig. 1 camshaft shown and Fig. 3 a slightly modified, non-inventive embodiment of one of the camshafts of the Fig. 1 similar camshaft in detail in cutaway view.

[0014] The Fig. Figure 1 shows the camshaft 1, which is formed as a built-up camshaft from two hollow shaft sections 2, 3 that are axially joined one another. The cams N1, N2, N3, N4, N5, N6, and N7 necessary for actuating the valves of an internal combustion engine are mounted on the two hollow shafts. Bearing points L1, L2, L3, L4, and L5 are distributed along the camshaft 1 to support it in a housing or housing component (not shown), such as a cylinder head. These bearing points are equipped with, for example, rolling bearings. Furthermore, additional functional groups can be arranged on the camshaft, such as—as shown—a gear 4, which can be used to drive the camshaft 1 or to drive an auxiliary unit, such as a pump, via the camshaft.In the illustrated embodiment, the gear 4 is arranged, for example joined, on the hollow shaft section 2, which is also provided as a shaft end piece 5 and can have corresponding engagement profiles for driving the camshaft 1 by means of a toothed belt or a toothed chain.

[0015] Bearings L2 to L5, or the bearings located at these positions, are lubricated by supplying lubricant via channels provided in the housing. This lubricant is collected in a basin within a housing component, such as the cylinder head, and then returned. Bearing L1 is poorly connected to this lubrication circuit because, firstly, it is decoupled from the lubrication circuit by, for example, gear 4 and the necessary connection of the auxiliary unit, for example, via a chain tunnel. Secondly, a separate supply of lubricant via the housing would be costly or structurally unfavorable.

[0016] Due to the advantageous design of the camshaft 1 as a built-up camshaft, and in particular the design of the internally hollow shaft sections 2, 3, an axial hollow bore in the camshaft 1 can be dispensed with. A connecting element 6, which in the illustrated embodiment is designed as a journal 7, can be inserted into the two hollow shaft sections 2, 3. This journal, axially spaced from the bearing points L1, L2, defines a cavity 10 to the outside by means of the ring seals 8, 9 between the hollow shaft sections 2, 3 and the journal 7. This cavity 10 forms a connection between the two openings 11, 12 provided in the camshaft 1 at the bearing points L1, L2 in the hollow shaft sections 2, 3, so that lubricant can be received through the opening 12 of bearing point L2 and reach bearing point L1 via the cavity 10 and the opening 11.The tenon 7 is supported at its ends by the frets 13, 14 and by an intermediate fret 15.

[0017] As can be seen from a cross-section along the cutting line AA of the Fig. As can be seen from Figure 2, the collar 15 of the pin 7 has a longitudinal groove 16, so that in the illustrated embodiment the cavity 10 ( Fig. 1) by two annular spaces 17, 18 separated by the collar 15 and connected by the longitudinal groove 16 ( Fig. 1) is formed. From the Fig. 2 further shows the joined construction of the two hollow shaft sections 2, 3, wherein the sleeve 19 of the hollow shaft section 2 is joined to the end piece 20 of the hollow shaft section 3, for example by means of a press fit.

[0018] Fig. Figure 3 shows a slightly modified, non-inventive version of the camshaft 1 of the Fig. 1 in the form of camshaft 1a, which is shown in detail in a sectional view with the joined cams N1, N2, the gear 4 and the bearing points L1, L2. In contrast to camshaft 1 of the Fig. 1 The journal 7a is formed in multiple parts. The shaft end piece 5a is joined to a receiving surface 21 of the journal, for example by means of an interference fit. The cavity 10 is formed from a single annular space 22 between a radial recess of the journal 7a and the inner circumferences of the hollow shaft sections 2, 3, since the collar 15 of the camshaft 1, arranged between the flanges 13, 14, is Fig. 1 is omitted. The annular space 22 connects the two openings 11, 12 provided in the hollow shaft sections 2, 3. The ring seal 8 seals the annular space 22 to the outside. At the other end of the journal 7a, an interference fit 23 between journal 7a and hollow shaft section 2 provides sufficient sealing of the annular space 22 to the outside.

Claims

[1] Camshaft (1) consisting of at least one hollow shaft section (2, 3) with at least one joined cam (N1, N2, N3, N4, N5, N6, N7) and at least two bearing points (L1, L2, L3, L4, L5) on a housing, wherein in which at least one hollow shaft section (2, 3) and at least two openings (11, 12) are provided, the two openings (11, 12) within the at least one hollow shaft section (2, 3) are connected to each other by means of a connecting element (6), the connecting element (6) is formed by a pin (7, 7a) which is inserted into the at least one hollow shaft section (2, 3) and with which the at least one hollow shaft section (2, 3) forms a cavity (10) connecting the two openings (11, 12), and a collar (15) of the pin (7) has a longitudinal groove (16), such that the cavity (10) is formed by two annular spaces (17, 18) separated from each other by the collar (15) and connected to each other by the longitudinal groove (16), characterized by , that two nested hollow shaft sections (2, 3) are provided, at each of which at least one bearing point (L1, L2) with an opening (11, 12) in the hollow shaft section (2, 3) is provided. [2] Camshaft (1) according to claim 1, wherein the journal (7) is connected to the at least one hollow shaft section (2) in a rotationally fixed manner, and wherein the camshaft (1, 1a) is driven by means of the journal (7, 7a). [3] Camshaft (1, 1a) according to claim 1 or 2, wherein a radially extending component restricting lubricant flow is provided axially between the two openings (11, 12) on the at least one hollow shaft section (2).

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