AT521559B1 - VARIABLE VALVE GEAR DEVICE - Google Patents

Abstract

The invention relates to a variable valve drive device (1) for actuating at least one gas exchange valve of an internal combustion engine, with a camshaft (2) mounted so as to be rotatable about an axis of rotation (2a) and with at least one cam element (3) adjustable via an adjusting device (20), the cam element ( 3) between at least a folded-in first position (A) and a folded-out second position (B) about a pivot axis (3a) which runs parallel to the axis of rotation (2a) and at a first distance (a) from it on the camshaft (2) and wherein the adjustable cam element (3) is arranged adjacent in the direction of the axis of rotation (2a) of the camshaft (2) to at least one base cam (4a, 4b) rigidly connected to the camshaft (2), the adjusting device (20) at least one within the camshaft (2) displaceable between at least a first thrust position (A1) and a second thrust position (B1). designated push rod (6), wherein the push rod (6) has at least one stop surface (7) for the cam element (3) and at least one ramp surface (8) that is at least partially inclined to the axis of rotation (2a) of the camshaft (2). The cam element (3) has a counter-ramp surface (13) which interacts with the ramp surface (8) of the connecting rod (6) and is designed at least partially inclined to the axis of rotation (2a) of the camshaft (2).

Description

The invention relates to a variable valve drive device for actuating at least one gas exchange valve of an internal combustion engine, with a camshaft that is mounted such that it can rotate about an axis of rotation and has at least one cam element that can be adjusted via an adjusting device, the cam element being mounted pivotably about a pivot axis between at least a folded-in first position and a folded-out second position which runs parallel to the axis of rotation and is arranged on the camshaft at a first distance from it, and wherein the adjustable cam element is arranged adjacent in the direction of the axis of rotation of the camshaft to at least one base cam rigidly connected to the camshaft, the adjusting device having at least one inside the camshaft between at least a first thrust position and a second thrust position displaceably arranged push rod, wherein the push rod at least one preferably parallel to the axis of rotation se of the camshaft has a stop surface for the cam element and at least one inclined to the axis of rotation of the camshaft ramp surface.

Different requirements are placed on the valve train devices of internal combustion engines, depending on the operating state. At low loads, it is advantageous if the valve lift is less than at high loads, so as not to adversely affect the combustion processes in the individual cylinders. At the same time, there is a need to be able to vary the valve lift curve to affect the opening and closing of the intake and exhaust valves. Various solutions for variable valve trains are therefore known in the prior art in order to

to provide appropriate opportunities for influence.

WO 95/16852 A1 describes a solution for using a push rod that can be displaced axially in a hollow camshaft in order to extend a cam element from a first position into a second position in order to vary the valve lift curve. The push rod has a ramp on its lateral surface which acts on a ball which is arranged in a radial bore of the camshaft and which contacts an inner surface of the rotatably mounted cam element. During an axial displacement process of the connecting rod, the ball is moved in the radial bore and the cam element is thus pivoted from a first position into a second position. Through this solution are only small

Deflections between the first and second position possible and can only

realize minor changes to the valve lift curve. Furthermore, there is a risk of increased wear due to the multiple contact surfaces between the connecting rod, ball and cam element.

EP 3 045 690 A2 describes a variable valve actuation device with a camshaft on which cam elements pivotable between two positions are arranged. Each pivotable cam element is actuated via a piston element which is mounted within the camshaft so that it can be displaced in the direction of the axis of rotation of the camshaft and which can be deflected hydraulically against a return spring in a guide sleeve arranged within the camshaft. The piston element has a ramp on the lateral surface, which interacts with a retaining pin that can be displaced transversely to the piston element in a radial bore of the camshaft. If the piston element is deflected by hydraulic pressure, the ramp pushes the retaining pin outwards in the radial bore of the camshaft, the retaining pin pressing the cam element into its pivoted-out second position and holding it in this position. In the depressurized state, the piston element is pushed into the rest position by the restoring spring, in which the retaining pin is released and the cam element can thus be pivoted into its first position. In the extended, second position, the cam element can be fixed via a fixing device. The fixing device has at least one locking pin that can be actuated hydraulically against a return spring, which is displaceably mounted in a guide cylinder arranged eccentrically in the camshaft and, in a locking position, engages in a pin hole of the cam element. A disadvantage is the large number of components and contact surfaces, especially in the power flow between the piston part and the cam part, which

have an unfavorable effect on the overall tolerance and the actuation play.

It is known from FR 322 489 A to actuate a cam element, which is mounted pivotably in the camshaft, by means of a push rod which is arranged in a displaceable manner in the camshaft. The push rod has a relatively flat ramp surface, which is formed by the casing of a frustoconical section of the push rod. The cam element is rotatably mounted in an area of the cam which area has the highest cam elevation. As a result, only one flank of the elevation curve, but not the entire elevation curve, can be changed by extending the cam element. In particular, the

maximum stroke are not affected. Another disadvantage is that the ramp is formed by a frusto-conical portion of the push rod. With the embodiment shown in FR 322 489 A, the cam element can at most only be displaced by half the diameter of the connecting rod, the ramp surface acting on a lateral edge of the cam element. A counter-ramp surface on the cam element is not provided - this can lead to incorrect actuation and jamming, which has a negative effect on operational safety. In addition, this known valve drive device is relatively susceptible to wear. This also applies to the similar cam control device known from FR 569 928 A, but without a base cam

is executed.

DE 102 42 235 A1 describes a valve control with a camshaft with a main cam and an additional cam, which can be adjusted in the radial direction relative to an axis of rotation of the camshaft. For this purpose, an adjusting element mounted within the camshaft is provided, which has an adjusting part running obliquely to the axis of rotation. By adjusting the actuating element in the axial direction of the camshaft

the additional cam can be brought into different positions steplessly.

In EP 3 045 690 A-2, a valve train device is described in which a base cam with a cam element movable in the radial direction is supplemented on a camshaft. The cam element is held in different positions by a stop element, which can be adjusted by a support element that can be moved in the axial direction of the camshaft and has a concave part and a hump part.

DE 10 2016 103 233 A1 discloses a variable valve actuation device in which at least one cam member is pivotally mounted on the camshaft between a first position and a second position, with a resilient member acting on the cam member towards the extended second position. In the extended position, the cam element can be fixed via a fixing device. Here, too, the fixing device has at least one locking pin that can be actuated hydraulically against a return spring, which is displaceably mounted in a guide cylinder arranged eccentrically in the camshaft and, in a locking position, in a pin hole of the

Cam element engages. The cam element is connected to a drive element

connected, which cooperates with a pressing part. The cam element can be moved back into the first position by the pressing part via the drive element. JP 2016 200053 A shows a similar one

valve actuator.

A disadvantage of the known solutions is that existing valve lifting curves can only be influenced but not changed by the pivotable cam elements. In addition, the mechanisms for twisting

of the cam elements is consistently complex and prone to wear and tear.

It is therefore an object of the invention to provide a simple, operationally reliable

Provide valve train device with great variability in the valve lift.

Based on a valve drive device of the type mentioned at the outset, the object is achieved according to the invention in that the cam element has a counter-ramp surface which interacts with the ramp surface of the connecting rod and is designed at least partially inclined to the axis of rotation of the camshaft,

wherein the ramp surface is arranged on an end face of the push rod.

When the push rod is moved, the ramp surface and counter-ramp surface slide onto one another. As a result, wear and tear can be reduced and, on the other hand, jamming of the mechanism can be largely ruled out.

Favorably, the cam element can be contacted directly with the push rod in at least one push position, so that the push rod acts directly on the cam element. There are therefore no transmission elements between the push rod and cam element necessary. This has the advantage that the overall tolerance and the actuation play can be kept small. Thus, a much more precise adjustment of the valve lift is possible. In addition, the wear of the device is reduced due to the lower number of point or surface contacts

reduced.

In one embodiment variant of the invention, it is provided that the ramp surface extends over the entire front surface of the front side. As a result, a relatively large adjustment range of the valve lift between the first and the second position of the cam element is possible.

A variant embodiment of the invention provides that the ramp surface has at least two areas with different angles of inclination in relation to the axis of rotation of the camshaft. The ramp surface is preferably spatially curved at least in sections and is preferably formed by a surface of revolution. In one variant, the ramp surface is formed by a conical surface. The ramp surface is thus preferably formed by a surface which, by rotating a line, for example a straight line, about a

axis is generated.

The counter-ramp surface of the cam element is advantageously spatially curved, at least in sections. In variants, the counter-ramp surface is formed by a surface of revolution, in particular a conical surface. Preferably, the counter-ramp surface of the cam element has at least two sections with different angles of inclination with respect to the axis of rotation of the camshaft.

In one embodiment variant of the invention, it is provided that the ramp surface and/or the counter-ramp surface is/are inclined at least in sections at an angle of inclination of between approximately 30° and 60° to the axis of rotation of the camshaft. This makes it possible that, if the adjustment is incomplete, the cam element pushes the push rod back into the rest position and the cam element resumes the pivoted-in first position. A self-locking between the ramp surface and the counter ramp surface can

are largely avoided.

In a further embodiment variant of the invention, the cam element has a counter-stop surface which interacts with the stop surface of the push rod and is preferably of cylindrical design. The counter-stop surface is preferably arranged axially adjacent to the counter-ramp surface--in relation to the axis of rotation of the camshaft. It is advantageous if the counter-ramp surface in the cam element is a chamfer around the counter-stop surface

is trained.

In the first position of the cam element, the counter-ramp surface of the cam element abuts the ramp surface of the push rod. In the second position of the cam element lies the counter-stop surface of the cam element

on the stop surface of the connecting rod.

It is particularly advantageous if the cam element is prestressed in the direction of the first position by a restoring element, which is preferably formed by a torsion spring. The cam element is thus pressed into its folded-in first position by the restoring element. By axial displacement of the push rod, the cam element is pressed against the restoring force of the restoring element by means of the ramp surface of the push rod into the unfolded second position.

According to one embodiment variant of the invention, it is provided that at least one limiting element is provided which is fixedly connected to the camshaft, the cam element having a limiting surface which corresponds to the limiting element, the limiting surface of the cam element bearing against the limiting element when the cam element is in a maximum swiveling-out position. The delimiting element is designed, for example, as a delimiting pin. The limiting element limits the outward deflection movement of the cam element. This can lead to early signs of wear

and damage avoided.

In order to allow the lift curve of the gas exchange valve to be adjusted as far as possible, it is particularly advantageous if the cam element in the second position completely covers the contour of at least one base cam, preferably two base cams axially adjoining the cam element on both sides, viewed in the direction of the axis of rotation of the camshaft . This makes it possible to realize completely different lift curves with a simple structure, while the solutions from the prior art mostly only partially

Allow changing of existing lifting curves.

The invention is illustrated below with reference to the figures, not

limiting embodiment explained in more detail.

Show in it:

Fig. 1 shows a variable valve train device according to the invention in one

axonometric representation,

2 shows the valve train device in an exploded view,

Fig. 3 shows a cam element of the valve train device in an axonometric view

Depiction,

Fig. 4 shows the valve drive device in a first position of the cam element

a cut representation and

Fig. 5 shows the valve train device in a second position of the cam element

a cut representation.

1 shows a variable valve drive device 1 for actuating at least one gas exchange valve of an internal combustion engine, not shown in any more detail. The valve-actuating device 1 has a camshaft 2 that is rotatably mounted about an axis of rotation 2a and has at least one cam element 3 that can be adjusted via an adjusting device 20 . The cam element 3 is mounted pivotably about a pivot axis 3a between a folded-in first position A (FIG. 4) and an unfolded second position B (FIG. 5). This pivot axis 3a is aligned parallel to the axis of rotation 2a of the camshaft 2 and is arranged on the camshaft 2 at a first distance a therefrom. In other words, the cam element 3 is mounted pivotably in the camshaft 2 , the pivot axis 3a of the cam element 3 running parallel to and at a first distance a from the axis of rotation 2a of the camshaft 2 .

The adjustable cam element 3 is arranged adjacent to two base cams 4a, 4b of a cam body 4 in the direction of the axis of rotation 2a of the camshaft 2 . The cam body 4 has a receptacle 5 in which the cam element 3 is predominantly accommodated and in which the cam element

3 can be pivoted.

Reference numeral 21 designates a cam follower element, for example a rocker arm, which rests against base cam 4a, 4b or cam element 3 via a roller 22 and is deflected according to the cam contour of base cam 4a, 4b or cam element 3. The cam follower element 21 acts on at least one gas exchange valve (not shown) of the internal combustion engine

and controls its hub.

Adjusting device 20 has at least one inside camshaft 2

slidably arranged push rod 6 with a substantially cylindrical shape

on, with the push rod 6 between a first push position A1 and a second push position B1 axially - i.e. parallel to the axis of rotation 2a of the camshaft 2

- can be moved. The first thrust position A1 corresponds to the first position A of the cam element 3. The second thrust position B1 corresponds to the second position B of the cam element 3. The push rod 6 is cylindrical in the exemplary embodiment, but a prismatic or other shape is also possible. The push rod 6 is arranged on the same axis as the camshaft 2 - the longitudinal axis 6a of the push rod 6 therefore coincides with the axis of rotation 2a of the camshaft 2.

The push rod 6 has a stop surface 7 for the cam element 3 which is parallel to the axis of rotation 2a of the camshaft 2 . The stop surface 7 is formed by the cylindrical outer surface of the push rod 6 and serves as a stop for the cam element 3 in the unfolded second position. By the stop surface 7 so a pivoting back of the pivoted

Cam element 3 from the second position B to the first position A prevented

Furthermore, the push rod 6 has a ramp surface 8 that is inclined to the axis of rotation 2a of the camshaft 2 . The ramp surface 8 serves to transfer the axial movement of the push rod 6 into a radial pivoting movement of the cam element 3 and the cam element 3 from the first

Position A to move to the second position B.

The ramp surface 8 is arranged on a first end face 9 of the push rod 6 . The displacement of the push rod 6 takes place via an actuator indicated with reference numeral 11 in Fig. 1, 4 and 5 - e.g. hydraulically, pneumatically, electrically, electromagnetically or otherwise actuatable - which acts, for example, on a second end face 10 of the push rod facing away from the first end face 9 .

In the exemplary embodiment, the ramp surface 8 extends over the entire face of the first face 9 of the connecting rod 6.

In the exemplary embodiment, the ramp surface 8 is spatially curved and is formed, for example, by a surface of revolution—such as a conical surface. The ramp surface 8 can have at least two areas 8a, 8b with different inclinations in relation to the longitudinal axis 6a of the push rod 6 or the axis of rotation 2a of the

Camshaft 2 have. Preferably, between the two areas 8a,

8b different inclination executed a smooth transition. The angle of inclination ß between the ramp surface 8 (or at least one of the two areas 8a, 8b) and the axis of rotation 2a of the camshaft 2 (shown in Fig. 5 as an angle between the axis of rotation 2a and a dash-dotted line following the ramp surface 8) is between about 30° and 60°. The ramp surface 8 is advantageously designed symmetrically to a longitudinal plane 6b of the push rod 6 containing the longitudinal axis 6a of the push rod 6 .

As can be seen in particular from FIG. 3, the cam element 3 has a counter-stop surface 12 which rests on the stop surface 7 of the push rod 6 in the second position B of the cam element 3 . The counter-abutment surface 12 is, for example—analogous to the abutment surface 7 of the connecting rod 6—cylindrically shaped.

The cam element 3 has a counter-ramp surface 13, on which the ramp surface 8 of the connecting rod 6 acts during the adjustment from the first position A to the second position B. The counter-ramp surface 13 is inclined in accordance with the ramp surface 8 , the shape of the counter-ramp surface 13 corresponding to the shape of the ramp surface 8 . Like the ramp surface 8, the counter-ramp surface 13 can have at least two sections 13a, 13b with different inclinations, between which a continuous transition is preferably implemented. The angle of inclination v of the counter-ramp surface 13 to the axis of rotation 2a of the camshaft 2 (shown in FIG. 5 as the angle between the axis of rotation 2a and a dot-dash line following the counter-ramp surface 13) is also between 30° and 60°. In the exemplary embodiment, the counter-ramp surface 13 is arranged axially adjacent to the counter-stop surface 12 and concentrically to the counter-stop surface 12 . In the exemplary embodiment, the counter-ramp surface 13 is designed as an approximately conical chamfer in the axial connection to the cylindrical counter-stop surface 12 . The conical surface of the counter-ramp surface 13 and the cylindrical surface of the counter-stop surface 12 therefore have the same axis 12a. The spatial contours of the ramp surface 8 and the counter-ramp surface 13 have the advantage that the contact between the ramp surface 8 and the counter-ramp surface 13 when the cam element 3 is deflected via a contact surface and not just - as in the case of a flat ramp surface - via two contact points or contact lines - or even only one point of contact occurs.

The inclinations of the ramp surface 8 and the corresponding counter-ramp surface 13 have the effect that when the push rod 6 is moved from the first push position A1 to the second push position B1, they slide on one another without jerks and without getting caught. Therefore, preferably at least those areas of the ramp surface 8 and the counter-ramp surface 13, which interact when the valve device 1 is used as intended, with

corresponding inclinations executed.

Jamming or tensioning of the touching parts is thus avoided. Together with the above-mentioned angles of inclination βB, γ of the ramp surface 8 and the counter-ramp surface 13, this also has the effect that faulty switching and undesired intermediate positions of the cam element 3 between the first position A and the second position B are avoided. If the movement of the push rod 6 from the first push position A1 to the second push position B1 is incomplete or interrupted in between, the push rod 6 can be moved back to the first push position A1 via the ramp surface 8 and the counter-ramp surface 13 by the cam element 3. The prerequisite is that the angles of inclination ß, v of the ramp surface 8 and the counter-ramp surface 13 are made large enough in relation to the axis of rotation 2a of the camshaft 2 to a

to avoid self-locking.

The cam element 3 has a lifting surface 14 which, in the exemplary embodiment, is approximately symmetrical to a longitudinal plane 3b of the cam element, which runs through the axis 12a of the cylinder surface of the counter-stop surface 12 or the conical surface of the counter-ramp surface 13 . The pivot axis 3a of the cam element 3 is located on one side of the cam element longitudinal plane 3b in the area of the lifting surface 14, in particular in an area between the lifting surface 14 and the

Counter ramp surface 13.

At a second distance b from the pivot axis 3a, the cam element 3 has a groove-like recess 15 with a boundary surface 16 on at least one side flank 3c, 3d—preferably on both side flanks. The width d of the groove-like recess 15 is at least as large as the diameter D of a limiting element 17 formed by a limiting pin, which is firmly connected to the camshaft 2 . The limit pin is in a hole

18 of the camshaft 2 parallel to the axis of rotation 2a of the camshaft 2 used.

The pivoting movement of the cam element 3 is limited by the limiting element 17 so that damage and undesired noise development are avoided. A reversed embodiment, in which the groove-like recess is formed in the camshaft 2 and the limiting element is formed in the cam element 3, is also possible.

The cam element 3 is biased towards the first position A by a restoring element 19 formed by a torsion spring (see FIG. 2). Fig. 4 shows the cam element 3 in the effected by the return element 19 pivoted first position A, wherein the push rod 6 in the first

Push position A1 is, which corresponds to the rest position.

If the push rod 6 is moved by the actuator 11 from the first push position A1 into the second push position B1, the cam element 3 is pivoted out into the second position B shown in FIG. In the second position B--viewed in the direction of the axis of rotation 2a of the camshaft 2--the contour of the base cams 4a, 4b is completely covered by the contour of the cam element 3.

As soon as the push rod 3 is pulled back from the second push position B1 shown in Fig. 5 to the first push position A1 shown in Fig. 4, the cam element 3 is returned to the first position A by the return element 19

swung back.

The solution according to the invention thus allows the realization of different

Valve lift curves in a simple and low-wear and low-error way.

Claims (1)

(New) CLAIMS Variable valve drive device (1) for actuating at least one gas exchange valve of an internal combustion engine, with a camshaft (2) which is mounted such that it can rotate about an axis of rotation (2a) and has at least one cam element (3) which can be adjusted via an adjusting device (20), the cam element (3) between at least a folded-in first position (A) and a folded-out second position (B) about a pivot axis (3a) which runs parallel to the axis of rotation (2a) and is arranged on the camshaft (2) at a first distance (a) from it and wherein the adjustable cam element (3) is arranged adjacent in the direction of the axis of rotation (2a) of the camshaft (2) adjacent to at least one base cam (4a, 4b) rigidly connected to the camshaft (2), the adjusting device (20) at least one push rod arranged displaceably within the camshaft (2) between at least a first push position (A1) and a second push position (B1). (6), wherein the push rod (6) has at least one stop surface (7) for the cam element (3) which is preferably parallel to the axis of rotation (2a) of the camshaft (2) and at least one at least partially inclined to the axis of rotation (2a) of the camshaft ( 2) has a ramp surface (8), characterized in that the cam element (3) has a counter-ramp surface (13) which interacts with the ramp surface (8) of the connecting rod (6) and which is at least partially inclined to the axis of rotation (2a) of the camshaft (2nd ) is formed, wherein the ramp surface (8) is arranged on an end face (9) of the push rod (6). Valve train device (1) according to Claim 1, characterized in that the cam element (3) can be contacted directly with the push rod (6) in at least one push position (A1, B1), so that the push rod (6) acts directly on the cam element (3). Valve train device (1) according to Claim 1 or 2, characterized in that the ramp surface (8) extends over the entire end face of the end face (9). 11. 2 Valve drive device (1) according to one of Claims 1 to 3, characterized in that the ramp surface (8) has at least two areas (8a, 8b) with different angles of inclination (ß) in relation to the axis of rotation (2a) of the camshaft (2). Valve train device (1) according to one of Claims 1 to 4, characterized in that the ramp surface (8) is spatially curved at least in sections and is preferably formed by a surface of revolution is. Valve train device (1) according to claim 5, characterized in that the ramp surface (8) is formed by a conical surface. Valve train device (1) according to one of Claims 1 to 6, characterized in that the counter-ramp surface (13) of the cam element (3) is spatially curved at least in sections. Valve train device (1) according to one of Claims 1 to 7, characterized in that the counter-ramp surface (13) of the cam element (3) has at least two sections (13a, 13b) with different inclination angles (y) with respect to the axis of rotation (2a) of the camshaft (2). Valve drive device (1) according to one of Claims 1 to 8, characterized in that the ramp surface (8) and/or the counter-ramp surface (13) are at least partially inclined at an angle (ß, v) of between approximately 30° and 60° to the axis of rotation (2a ) the Camshaft (2) is/are inclined. Valve drive device (1) according to one of Claims 1 to 9, characterized in that the cam element (3) has a counter-stop surface (12) which interacts with the stop surface (7) of the push rod (6). has, which is preferably cylindrical. Valve drive device (1) according to Claim 10, characterized in that the counter-stop surface (12) - in relation to the axis of rotation (2a) of the camshaft (2) - is arranged axially adjacent to the counter-ramp surface (13). 12. Valve drive device (1) according to claim 10 or 11, characterized in that the counter-ramp surface (13) is designed as a chamfer around the counter-stop surface (12). 13. Valve train device (1) according to one of claims 1 to 12, characterized in that the cam element (3) by a restoring element (19), which is preferably formed by a torsion spring, in the direction of the first position (A) is biased. 14. Valve train device (!) according to one of Claims 1 to 13, characterized in that at least one limiting element (17) fixedly connected to the camshaft (2) is provided, the cam element (3) having a limiting surface which corresponds to the limiting element (17). (16), wherein the boundary surface (16) of the cam element (3) bears against the boundary element (17) when the cam element (3) is in a maximum pivoted-out position. 15. Valve drive device (1) according to claim 14, characterized in that the limiting element (17) is designed as a limiting pin. 16. Valve drive device (1) according to one of claims 1 to 15, characterized in that the cam element (3) in the second position (B) has the contour of at least one base cam (4a, 4b), preferably two, axially on the cam element (3) base cam (4a, 4b) adjoining on both sides - viewed in the direction of the axis of rotation (2a) of the camshaft (2) - completely covered. 02.03.2020 FU