Sliding cam and sliding-cam camshaft

Abstract

The present invention relates to a sliding cam (2) for a sliding-cam camshaft, comprising a carrier tube (23), a first functional element (21) and a second functional element (22), wherein the functional elements (21, 22) are arranged immediately adjacent to one another on the carrier tube (23) and extend in an axial direction over a joining portion (24), wherein the joining portion (24) comprises a first joining region (241) in which the first functional element (21) is secured on the carrier tube (23) by means of a press-fit connection, wherein the joining portion comprises a second joining region (242) in which the second functional element (22) is secured on the carrier tube (23) by means of a press-fit connection, and wherein an undercut (243) is provided between the first joining region (241) and the second joining region (242). The present invention furthermore relates to a sliding-cam camshaft having a sliding cam (2) according to the invention.

Description

[0001] Sliding cams and sliding camshaft

[0002] The present invention relates to a sliding cam according to the preamble of claim 1, as well as a sliding camshaft according to the preamble of claim 7.

[0003] A sliding camshaft essentially comprises a base shaft and at least one sliding cam arranged axially displaceably thereon. A connecting device is arranged between the sliding cam and the base shaft, which is designed to transmit torque between the base shaft and the sliding cam. At the same time, the connecting device must ensure axial displacement of the sliding cam on the base shaft. A sliding gearing, for example, could be used as a connecting device.

[0004] The sliding cam as such comprises a support tube and at least one first functional device and one second functional device. The first functional device can be, for example, a cam assembly. The second functional device can be, for example, an adjustment gate.

[0005] The cam assembly comprises at least two cams with different cam contours. An adjusting device, such as an actuator or a push rod or adjusting element, acts on the sliding gate so that either the first cam or the second cam can be engaged with the respective gas exchange valve of an internal combustion engine, allowing the gas exchange to be adapted to the respective operating situation. Further details are well known to those skilled in the art.

[0006] The sliding cams can be built, whereby the functional elements are usually pressed onto the support tube, i.e. fixed by means of a press connection.

[0007] Here, the functional elements are arranged directly adjacent to one another on the support tube and extend in the axial direction over a joining section. The joining section comprises a first joining area in which the first functional element is secured to the support tube by means of a press connection. The joining section comprises a second joining area in which the second functional element is secured to the support tube by means of a press connection. The press connection must ensure that the intended torques can be transmitted between the support tube and the functional element, in particular between the support tube and the cam assembly.

[0008] In particular, if two functional elements are connected to the support tube directly next to each other by means of a press connection, there is a risk of mutual interference, so that the torque that can be transmitted by the functional elements can be reduced.

[0009] The object of the present invention is accordingly to propose an improved sliding cam, in particular to propose a sliding cam in which a reduction in the transmittable torque influenced by the press connections of adjacent functional elements can be excluded, or at least reduced.

[0010] According to the invention, this object is achieved by a sliding cam with the characterizing features of claim 1. By arranging an undercut between the first joining area and the second joining area, a reduction in the torque that can be transmitted by the functional elements caused by the two press connections can be avoided, or at least reduced. The press connection between the functional element(s) and the support tube is relieved. The transmittable torque of individual components on the support tube is increased because the tensile stresses on the surface of the support tube are not directly introduced into the adjacent connection. This allows the stresses to be shifted beneath the respective functional elements, and moreover, the pressure is increased due to the additional supporting effect in the respective joining area.However, the interference fit of the press joints influences each other less. An undercut between the adjacent interference fit decouples the surface tensions in both press areas. This interrupts the stress distribution on the surface of the support tube. This can, or does, increase the radial stiffness of the support tube relative to the joining areas. This can lead to an increase in the transmittable torque of individual functional elements on the support tube.

[0011] Further advantageous embodiments of the proposed invention emerge in particular from the features of the subclaims. The subject matter or features of the various claims can, in principle, be combined with one another as desired. In an advantageous embodiment of the invention, the undercut can be designed as a circumferential groove in the support tube. A circumferential groove can therefore be easily introduced.

[0012] In a further advantageous embodiment of the invention, the undercut can be arranged axially directly adjacent to the joint of the functional elements. The immediate proximity of the undercut to the joint of the two functional elements advantageously contributes to relieving the pressure on the press connection between the functional element(s) and the support tube.

[0013] In a further advantageous embodiment of the invention, the first functional element can be designed as a cam assembly and the second functional element as an adjustment gate. The preferred application of the present invention lies within the scope of such a pairing of functional elements.

[0014] In a further advantageous embodiment of the invention, the functional element can be designed as a cam, cam assembly, adjustment link, bearing ring, pump cam, sensor wheel, etc. In principle, the invention is also applicable to other functional elements or pairs of functional elements.

[0015] In a further advantageous embodiment of the invention, it can be provided that the cam package is formed in one piece, which results in easier assembly.

[0016] A further object of the present invention is to propose an improved sliding camshaft, in particular to propose a sliding camshaft with a sliding cam, in which a reduction of the transmittable torque influenced by the press connections of adjacent functional elements can be excluded, or at least reduced.

[0017] According to the invention, this object is achieved by a sliding cam having the characterizing features of claim 7. Regarding the advantages resulting from the use of a sliding cam according to the invention, reference can be made to the above statements.

[0018] Further advantageous embodiments of the proposed invention emerge in particular from the features of the subclaims. The subject matter or features of the various claims can, in principle, be combined with one another as desired. In a further advantageous embodiment of the invention, a connecting device configured to transmit torque and axially displace the sliding cam can be provided between the base shaft and the sliding cam.

[0019] In a further advantageous embodiment of the invention, it can be provided that the connecting device is designed as a sliding toothing, wherein the sliding toothing comprises in particular an internal toothing on the sliding cam side in the opening of the sliding cam and an external toothing on the base shaft.

[0020] Further features and advantages of the present invention will become clear from the following description of preferred embodiments with reference to the accompanying drawings.

[0021] Fig. 1 shows a sliding camshaft according to the invention;

[0022] Fig. 2 shows a sliding cam according to the invention for a sliding camshaft according to the invention;

[0023] Fig. 3 is an enlarged detailed view of a sliding cam according to the invention as shown in Fig. 2;

[0024] Fig. 4 is an enlarged detailed view of an embodiment of the sliding cam according to the invention;

[0025] Fig.5 is a detailed view of a sliding cam according to the prior art.

[0026] The following reference symbols are used in the figures:

[0027] 1 fundamental wave

[0028] 2 sliding cams

[0029] 3 locking device

[0030] 4 push

[0031] 11 External toothing 21 First functional element, in particular cam package

[0032] 22 second functional element, in particular adjustment link

[0033] 23 Support tube

[0034] 24 joining section

[0035] 25 Opening

[0036] 26 internal gearing

[0037] 211 first cam

[0038] 212 second cam

[0039] 241 first joining area

[0040] 242 second joining area

[0041] 243 undercut

[0042] Features and details described in connection with a method naturally also apply in connection with the device according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other. Furthermore, a method according to the invention that may be described can be carried out with the device according to the invention.

[0043] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a" and "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It will also be understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of the recited features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed elements.

[0044] First, reference is made in particular to Fig. 1.

[0045] A sliding camshaft according to the invention essentially comprises a base shaft 1 with at least one sliding cam 2. In the present embodiment, three sliding cams 2, 2a, 2b are provided. The sliding cam 2 comprises an opening 25 for receiving the base shaft 1.

[0046] A connecting device suitable for transmitting torque and axially displacing the sliding cam on the base shaft is provided between the sliding cam 2 and the base shaft 1. The connecting device can be designed, for example, as a sliding gear system comprising an external gear 11 on the base shaft side and an internal gear 26 on the sliding cam side. However, other combinations, such as those based on non-circular cross-sections, flats, etc., are also conceivable.

[0047] It may further preferably be provided that a locking device 3 is provided between the sliding cam 2 and the base shaft 1. The locking device 3 is designed to releasably fix the sliding cam selectively in a first axial position or a second axial position.

[0048] In the following, particular reference is made to Figs. 2 and 3.

[0049] The sliding cam 2 essentially comprises a support tube 23 as well as a first functional element 21 and at least one second functional element 22, wherein the functional elements 21, 22 are connected to the support tube 23 by means of a press connection. The first functional element 21 and the second functional element 22 are arranged directly adjacent to one another in the axial direction on the support tube 23 and extend in the axial direction over a joining section 24.

[0050] The joining section 24, in turn, comprises a first joining region 241, in which the first functional element 21 is secured to the support tube 23 by means of a press connection. Furthermore, the joining section 24 comprises a second joining region 242, in which the second functional element 22 is secured to the support tube 23 by means of a press connection.

[0051] The functional elements are preferably mounted on abutment 4, at least one end face of the functional element is directly opposite the end face of the other abutment element.

[0052] According to the invention, a relief cut 243 is arranged between the first joining area 241 and the second joining area 242. The circumferential relief cut 243 can also be referred to as a circumferential groove or diameter reduction.

[0053] The resulting advantage is that the press connection is relieved, in particular between the functional element 21 and the support tube 23. This tends to increase the transmittable torque of individual components, in particular the functional elements, on the support tube, since the tensile stresses on the surface of the support tube are not directly transferred into the adjacent connection. This allows the stresses to be shifted beneath the respective functional elements, and in addition, the pressure is increased due to the additional supporting effect in the respective joining area. In order to increase the pressure between the two functional elements 21, 22, the joint length of both functional elements 21, 22 should not be changed. If one functional element, for example the second functional element 23, protrudes as shown in Fig.3 and 4, via the undercut 243, the press connection of the second functional element 22 is shifted by the amount of the relief 243 and the original joining length is thus maintained. It will be clear to a person skilled in the art that the support tube 23 must be made correspondingly longer axially. If this is not desired, for example for weight reasons, the press connection can be individually designed. In relation to the joining length, the decoupling of the press connections from one another can result in a radial increase in the stiffness of the support tube 23 in the edge regions. The radial stiffness in the undercut 243 is lower, but the displacement of the second joining region 242 (the second press connection) additionally supports this spring behavior. Stresses result from displacements and stiffnesses.An increase in pressure can be achieved with the same outer diameter ratio and the same joining length, for example, by increasing the stiffness of the shaft.

[0054] Preferably, the undercut 243 is arranged in the axial direction directly next to the joint 4 of the functional elements 21, 22, so that one of the functional elements or the functional element 23 projects beyond the undercut 243. A cam or an adjustment link can be used as a functional element, for example. In the exemplary embodiment presented here, the first functional element 21 is designed as a cam package and the second functional element 22 as an adjustment link. The cam package essentially comprises a first cam 211 and a second cam 212, which differ in terms of their cam geometry. The cams 211, 212 can also have the same cam geometry, but differ in terms of their angular position relative to one another. A bearing ring, a pump cam, a sensor wheel, etc., which can be attached to the support tube in the manner outlined above, can also be used as a functional element.

[0055] The sliding camshaft, also according to the invention, comprises a sliding cam 2 according to the invention. Preferably, all sliding cams of the sliding camshaft are designed as sliding cams according to the invention. The function of such a sliding camshaft is well known to those skilled in the art. An actuator (not shown) acts on the sliding gate 22, so that either the first cam 211 or the second cam 212 of the cam assembly 21 can be brought into engagement with the respective gas exchange valve (not shown) of an internal combustion engine, so that the gas exchange can be adapted to the respective operating situation.

[0056] Below, with particular reference to Fig. 4.

[0057] In a further advantageous embodiment of the invention, the first functional element 21 can be designed as a one-piece cam assembly. The undercut 243 is projected beyond the second functional element 22.

[0058] Fig. 5 shows a detailed view of a sliding cam 2 according to the prior art, which includes the following: The sliding cam 2 comprises the first functional element 21, the second functional element 22, and the support tube 23. The joining section 24, comprising the first joining region 241 and the second joining region 242, is also visible. The sliding toothing is identified by reference numeral 26. Accordingly, there is no undercut between the first joining region 241 and the second joining region 242.

Claims

Claims sliding cam (2) for a sliding camshaft, comprising - a support tube (23), and - a first functional element (21) and a second functional element (22), wherein, - the functional elements (21, 22) are arranged directly next to one another on the support tube (23) and extend in the axial direction over a joining section (24), wherein - the joining section (24) comprises a first joining region (241) in which the first functional element (21) is fastened to the support tube (23) by means of a press connection, wherein the joining section (24) comprises a second joining region (242) in which the second functional element (22) is fastened to the support tube (23) by means of a press connection, characterized in that - an undercut (243) is arranged between the first joining region (241) and the second joining region (242). Sliding cam according to claim 1, characterized in that the undercut (243) is designed as a circumferential groove in the support tube (23). Sliding cam according to at least one of the preceding claims, characterized in that the undercut is arranged in the axial direction directly next to the joint (4) of the functional elements (21, 22). Sliding cam according to at least one of the preceding claims, characterized in that the first functional element (21) is designed as a cam package and the second functional element (22) is designed as an adjustment link. Sliding cam according to at least one of the preceding claims, characterized in that the functional element (21, 22) is designed as a cam, cam package, adjustment link, bearing ring, pump cam, sensor wheel, etc.Sliding cam according to at least one of the preceding claims, characterized in that the cam package is formed in one piece. Sliding camshaft, comprising a base shaft (1) and at least one sliding cam (2) with an opening (25) for receiving the base shaft (1), characterized in that it is a sliding cam (2) according to at least one of the preceding claims. Sliding camshaft according to claim 7, characterized in that a connecting device configured to transmit a torque and for the axial displacement of the sliding cam (2) is provided between the base shaft (1) and the sliding cam (2). Sliding camshaft according to at least one of the preceding claims, characterized in that the connecting device is designed as sliding gearing, wherein the sliding gearing in particular comprises an internal gearing (26) on the sliding cam side in the opening (25) of the sliding cam and an external gearing (11) on the base shaft (1).

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