GB2521934A

GB2521934A - Valve train for an internal combustion engine, in particular of a vehicle

Info

Publication number: GB2521934A
Application number: GB1421632.9A
Authority: GB
Inventors: Adam Miller
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2014-12-05
Filing date: 2014-12-05
Publication date: 2015-07-08
Also published as: GB201421632D0

Abstract

The invention relates to a valve train 10 for an internal combustion engine, the valve train 10 comprising: a least one rocker arm 26, 28 pivotable about a pivot axis 30, 32; at least one roller 44, 46 rotatably mounted on the rocker arm 26, 28 for interaction with the cams 22, 24; and at least one cover element 48 for covering the rocker arm 26, 28 and the roller 44, 46, wherein the cover element 48 comprises at least one drip-off element 54, 56 configured to make a lubricant deposited on the cover element 48 drip off the cover element 48 onto the roller 44, 46. The drip off element including a tearing edge 64 and a wall extending towards the edge 66, the slope of the wall increases towards to edge and a portion of the wall is concave. Preferably the cover 48 and the drip off element 54, 56 are formed in a single piece.

Description

Valve Train for an Internal Combustion Engine, in particular of a Vehicle The invention relates to a valve train for an internal combustion engine, in particular of a vehicle, according to the preamble of patent claim 1.

Such valve trains for internal combustion engines are well-known from the general prior art. Such a valve train comprises at least one rocker arm which is pivotable about a pivot axis. The valve train further comprises at least one roller rotatably mounted on the rocker arm. For example, the roller is mounted on the rocker arm by a bearing. Thus, the roller is rotatable in relation to the rocker arm. Moreover, the valve train comprises at least one cover element for covering the rocker arm and the roller. With respect to a completely assembled state of a vehicle comprising the internal combustion engine and, thus, the valve train the cover element is arranged above the rocker arm and the roller with respect to the vertical direction of the vehicle.

Conventionally, the internal combustion engine comprises at least one cam shaft having at least one cam. The cam shaft and, thus, the cam which is connected to the cam shaft in a rotationally fixed manner are rotatable about a rotation axis which, for example, extends parallel to the pivot axis of the rocker arm. The cam is configured to actuate and, thus, pivot the rocker arm about the pivot axis via the roller. This means the rocker arm is configured to interact with the cam via the roller, wherein the cam can roll off the roller thereby pivoting the rocker arm about the pivot axis when the cam shaft is rotating.

Moreover, the internal combustion engine can comprise at least one charge-cycle valve which is moveable from a closed position into at least one open position by the rocker arm. By actuating, i.e. pivoting the rocker arm by means of the cam the charge-cycle valve is moved from the closed position into the open position by the rocker arm.

Since the cam rolls off the roller during the operation of the internal combustion engine an interface between the cam and the roller, i.e. respective surfaces of the roller and the cam are lubricated by a liquid lubricant which is, for example, oil. Usually, the roller is mounted on a roller axle of the rocker arm by an axle journal bearing. For example, pressurized oil is fed through the roller axle to lubricate the roller and the axle journal bearing. Some of that oil can make it to said cam and roller interface. But primarily this interface is lubricated by splash oil which is not a directed or targeted oil supply.

It is therefore an object of the present invention to provide a valve train of the aforementioned kind, in which the roller can be purposefully supplied with a lubricant in a particularly easy way.

This object is solved by a valve train having the features of patent claim 1. Advantageous embodiments with expedient developments of the invention are indicated in the other patent claims.

In order to provide a valve train of the kind indicated in the preamble of patent claim 1, in which valve train the roller can be purposefully supplied with lubricant in a particularly easy way according to the present invention the cover element comprises at least one drip-off element configured to make a lubricant deposited or condensed on the cover element drip off the cover element onto the roller. In other words, the drip-off element forms a drip-off location or a so-called drip side at which liquid lubricant such as oil is purposefully made drip off the cover element onto the roller so that a directed or targeted lubricant supply of the roller can be realized. The lubricant dripped off the cover element onto the roller can spread across a surface of the roller. Since the roller interacts with a cam of a cam shaft during the operation of the internal combustion engine not only the surface of the roller but also a surface of the cam can be purposefully supplied with the lubricant so that both the roller and the cam and, thus, an interface between the roller and the cam can be lubricated. In comparison with conventional valve trains a higher quantity of lubricant can be directed to the roller and, thus, the cam with no additional lubricant flow required and very little cost in series production. This means that additional ducts and/or pumps to convey lubricant are not necessary to purposefully supply the roller and, thus, the cam with lubricant. Moreover, in comparison with conventional valve trains in which the roller and the cam are lubricated by splash oil a particularly direct and targeted lubricant supply can be realized in the valve train according to the present invention.

Further advantages, features, and details of the invention derive from the following description of a preferred embodiment as well as from the drawings. The features and features combinations previously mentioned in the description as well as the features and feature combinations mentioned in the following description of the figures and/or shown in the figures alone can be employed not only in the respective indicated combination but also in any other combination or taken alone without leaving the scope of the invention.

The drawings show in: Fig. 1 a schematic sectional view of a valve train for an internal combustion engine, the valve train comprising at least one rocker arm, at least one roller, and at least one cover element, wherein the cover element comprises at least one drip-off element configured to make a lubricant deposited on the cover element drip off the cover element onto the roller; Fig. 2 a further schematic sectional view of the valve train; Fig. 3 a further schematic sectional view of the valve train; and Fig. 4 a further schematic sectional view of the valve train.

In the figures the same elements or elements having the same functions are indicated by the same reference signs.

Fig. 1 shows a valve train 10 for an internal combustion engine which is configured as a reciprocating piston engine. The internal combustion engine comprises a cylinder housing which is not shown in Fig. 1, and a cylinder head 12 attached to the cylinder housing. The internal combustion engine is part of a vehicle which can be driven by the internal combustion engine. Moreover, the internal combustion engine has an intake side 14 and an exhaust side 16. The cylinder housing comprises at least one combustion chamber in the form of a cylinder. On the intake side 14 air can flow into said cylinder. Moreover, the cylinder is supplied with fuel thereby creating a mixture of said air and said fuel in the cylinder. Said mixture is combusted which results in exhaust gas which can flow out of the cylinder on the exhaust side 16. In order to control the flow of the air into the cylinder and the flow of the exhaust gas out of the cylinder the internal combustion engine comprises at least one first charge-cycle valve in the form of an intake valve arranged on the intake side 14 and at least one second charge-cycle valve in the form of an exhaust valve arranged on the exhaust side 16. The charge-cycle valves are movably mounted on the cylinder head 12 wherein the charge-cycle valves are translationally movable in relation to the cylinder head 12. The valve train 10 is configured to move the charge-cycle valves from respective closed positions into respective open positions. For this purpose the valve train 10 comprises cam shafts 18 and 20 having respective cams 22 and 24. Moreover, the valve train comprises rocker arms 26 and 28 pivotably mounted on the cylinder head 12 about respective pivot axes 30 and 32. For example, the rocker arm 26 is pivotably mounted on the cylinder head 12 by a rocker shaft 34.

The cams 22 and 24 are connected to the cam shafts 18 and 20 in a rotationally fixed manner so that the cam shafts 18 and 20 and the cams 22 and 24 rotate about respective rotation axes 36 and 38. The cam shafts 18 and 20 are rotatably mounted on the cylinder head 12 about the rotation axes 36 and 38. The rocker arms 26 and 28 have respective rocker axles 40 and 42 on which respective rollers 44 and 46 are rotatably mounted.

Thus, the rollers 44 and 46 can rotate in relation to the respective rocker arms 26 and 28.

During the operation of the internal combustion engine the cams 22 and 24 rotate about the rotation axes 36 and 38. Since the cams 22 and 24 are in contact with the rollers 44 and 46 at least temporarily the rollers 44 and 46 roll off the respective cams 22 and 24 or vice versa. Thereby, friction can be kept particularly low. When the cams 22 and 24 rotate about the rotation axes 36 and 38 the rocker arms 26 and 28 are actuated and, thus, pivoted by the cams 22 and 24 via the rollers 44 and 46 thereby moving the respective charge-cycle valves from the respective closed positions into the respective open positions.

The valve train 10 further comprises a cover element 48 which is also referred to as a rocker cover configured to cover the rocker arms 26 and 28 and the rollers 44 and 46.

With respect to a completely assembled state of the vehicle and, thus, the internal combustion engine the cover element 48 is arranged above the rocker arms 26 and2s and the rollers 44 and 46 with respect to the vertical direction of the vehicle. In other words, the rocker arms 26 and 28 and the rollers 44 and 46 are overlapped by the cover element 48 in the vertical direction of the vehicle towards the top. Thereby, a receiving space 50 is bounded at least partially by the cover element 48, wherein the valve train 10 is arranged at least partially in the receiving space 50. As can be seen from Fig. 1, at least the rocker arms 26 and 28 and the rollers 44 and 46 are arranged in the receiving space 50.

For example, the valve train 10 comprises components which move during the operation of the internal combustion engine, said components being arranged in the receiving space 50. Such a component is the rocker arm 26, the rocker arm 28, the cam shaft 18 and the cam shaft 20. Said moving components swirl up lubricant in the form of oil in the receiving space 50, wherein the cover element 48 prevents the swirled up oil from leaving the internal combustion engine. Thus, at least some of the swirled up oil can deposit or condense on an inner surface 52 of the cover element 48, the inner surface 52 facing at least some of said moving components of the valve train 10.

In order to purposefully lubricate the cairns 22 and 24 and the rollers 44 and 46 in a particularly easy way the cover element 48 comprises respective drop off elements 54 and 56 which are configured to make the oil deposited on the surface 52 drip off the cover element 48 onto the rollers 44 and 46. As can be seen from Fig. 1, the drip-off elements 54 and 56 overlap the respective rollers 44 and 46 in the vertical direction of the internal combustion engine and, thus, the vehicle towards the top so that oil dripping off the drip-off elements 54 and 56 can drip directly onto respective outer circumferential surfaces 58 and 60 of the rollers 44 and 46. The oil can spread across the surfaces 58 and 60 and come between the rollers 44 and 46 and the cams 22 and 24 so that respective outer circumferential surfaces 62 and 64 of the cams 22 and 24 are lubricated by the oil as well.

Thereby, a targeted or directed oil supply of the rollers 44 and 46 and the cams 22 and 24 can be realized. This means oil can be encouraged to arrive at the rollers 44 and 46 and the cams 22 and 24 where it is needed.

The drip-off elements 54 and 56 comprise a tearing edge 64 and a wall 66 respectively, the wall 66 extending towards the tearing edge 64. As can be seen from Fig. 1, a slope of the respective wall 66 increases towards the tearing edge 64, wherein at least a portion of the wall 66 is concave, i.e. curved away from the receiving space 50. Moreover, the drip-off elements 54 and the cover element 48 are formed in one piece so that the walls 66 are walls of the cover element 48. As can be seen from Figs. 2 to 4, splash oil and oil mist condensation can run down the slope or the respective wall 66 and drip off at the lowest point of the respective drip-off element 54, the lowest point being formed by the tearing edge 64. The tearing edge 64 is arranged directly above the rollers 44 and 46 respectively so that the oil can drip off onto the rollers 44 and 46.

Fig. 2 shows droplets 68 of oil mist condensed on the surface 52. The droplets 68 can run down the slope of the wall 66, wherein the droplets 68 unite thereby forming a big drop 70 consisting of oil. The drop 70 runs further down the wall 66 until it reaches the tearing edge 64. As can be seen from Fig. 4 the drop 70 drops off the tearing edge 64 and directly onto the corresponding roller 44 or 46 due to gravity thereby lubricating the roller 44 and the cam 22 or the roller 46 and the cam 24.

List of reference signs valve train 12 cylinder head 14 intake side 16 exhaust side 18 camshaft cam shaft 22 cam 24 cam 26 rocker arm 28 rocker arm pivot axis 32 pivot axis 34 rocker shaft 36 rotation axis 38 rotation axis rocker axle 42 rocker axle 44 roller 46 roller 48 cover element receiving space 52 inner surface 54 Drip-off element 56 drip-off element 56 circumferential surface circumferential surface 62 circumferential surface 64 tearing edge 66 wall 68 droplets drop

Claims

Claims A valve train (10) for an internal combustion engine, the valve train (10) comprising: -a least one rocker arm (26, 28) pivotable about a pivot axis (30, 32); -at least one roller (44, 46) rotatably mounted on the rocker arm (26, 28); and -at least one cover element (48) for covering the rocker arm (26, 28) and the roller (44, 46); characterized in that the cover element (48) comprises at least one drip-off element (54, 56) configured to make a lubricant deposited on the cover element (48) drip off the cover element (48) onto the roller (44, 46).
2. The valve train (10) according to claim 1, characterized in that the drip-off element (54, 56) comprises a tearing edge (64) and a wall (66) extending towards the tearing edge (66).
3. The valve train (10) according to claim 2, characterized in that a slope of the wall (66) increases towards the tearing edge (64).
4. The valve train (10) according to claim 2 or 3, characterized in that at least a portion of the wall (66) is concave.
5. The valve train (10) according to any one of the preceding claims, characterized in that the drip-off element (54, 56) and the cover element (48= are formed in one piece.