EP1608849B1 - Valve drive of an internal combustion engine comprising a cylinder head - Google Patents

Abstract

The invention relates to a valve drive of an internal combustion engine, comprising at least one camshaft whereon at least one cam carrier is arranged in a rotationally fixed and axially displaceable manner. Means for applying axial tension are formed between the at least one camshaft and the at least one cam support, thereby enabling the at least one cam support to be fixed in an axial manner.

Description

The invention relates to a valve train of a cylinder head having an internal combustion engine according to the preamble of claim 1.

To improve the thermodynamic properties of internal combustion engines mechanical devices are known which influence the working cycle of the valve train and, for example, allow a speed-dependent change in the opening times or the stroke of the gas exchange valve.

From the documents DE 42 30 877 and DE 199 08286 such a device is known in which a cam carrier rotatably and axially displaceably arranged on a base camshaft. The cam carrier consists of a tubular material, on which at least one cam is arranged, in which emerge from a common base circle axially offset several different cam tracks. By the axial displacement of the cam piece on the base camshaft, a gas exchange valve can be actuated by the differently shaped cam tracks, wherein the cam tracks differ in the Hubkontur and / or in the phase position.

An advantageous device for the axial displacement of a cam carrier is known from the document EP 0 798 451, according to which a worm drive is formed on both sides of the cam carrier, which has a curved path as a recess into which an actuator can engage for the axial displacement of the cam carrier.

For a cam support to remain on the base camshaft in the position in which it has been displaced by the engagement of the actuator in the worm drive, a locking device is provided which consists of a arranged in the base camshaft locking means which engages in locking grooves, which worked out in the cam carrier are. According to the three cam tracks, the are formed on a cam, three locking grooves are worked out in the cam carrier.
The main disadvantage of this camshaft-centered arrangement of the locking device is that the basic camshaft and the cylinder head of the internal combustion engine are often made of different materials with different thermal expansion coefficients. As a result, the camshaft-centered latching device will not rest precisely either when the engine is cold or when the internal combustion engine is not operating. This effect can be amplified by inaccuracies in production, assembly or operational type so far that reliable operation of the internal combustion engine is not possible.

A cylinder-centered locking device for a basic camshaft with axially displaceable cam carriers is known from DE 101 48 243, the bearing of the basic camshaft in the cylinder head of the internal combustion engine being effected by at least one cam carrier bearing comprising the cam carrier.
The locking device consists of a arranged in the camshaft bearing locking means which engages in locking grooves, which are worked out in the cam carrier. In a cam carrier with two cams, each having two cam tracks, two axially adjacent locking grooves are required in the cam carrier, in which engages the locking means.
The main disadvantage of this cylinder-head centered locking device is the high wear that occurs in the camshaft bearing, as a substantial part of the bearing sliding surfaces is spent on the locking grooves. In addition, the base camshaft and the cam carrier are moved by the locking means to one side of the camshaft bearing. This locking device require a good supply of lubricant, which can not be guaranteed on the custom-fit and often polished Lagergleitflächen.

The invention has for its object to provide a valve gear according to the features of the preamble of claim 1, wherein the cam carrier are reliably held in position after moving independently of thermal influences.

This object is achieved by the features in the characterizing part of patent claim 1, according to which a first axial position of the cam carrier is defined by the fact that a first cam-holder-mounted stop surface abuts against a first cylinder head fixed stop surface.
Accordingly, a second axial position of the cam carrier is defined by the fact that a second cam carrier fixed abutment surface bears against a second stopper surface fixed to the cylinder head.
It is provided that means for applying an axial clamping force are formed between the base camshaft and the at least one cam carrier. This clamping force is directed so that the cam carrier is also displaced in the direction of this first axial position in the first axial position. Likewise, the cam carrier is also displaced in the direction of this second axial position in the second axial position. This clamping force is effective regardless of thermally induced expansion effects of the valve train.
It is provided that the first cam carrier fixed axial abutment surface and the second cam carrier fixed abutment surface side surfaces of the at least one cam of the cam carrier.

The first cylinder-stop-fixed abutment surface and the second cylinder-head-fixed abutment surface are side surfaces of the at least one cam carrier bearing comprising the cam carrier.

In an advantageous development of the invention it is provided that the means for applying an axial clamping force is formed by the base camshaft on the cam carrier as a locking device.

The locking device far a arranged in the camshaft, movably mounted in the radial direction locking means, wherein the locking means is pressed by a force in the radial direction outwardly preferably against the inner surface of the cam carrier. Correspondingly, at least two encircling and axially spaced latching grooves are formed on the inside of the cam carrier, wherein the latching grooves are approximately V-shaped in the cam carrier, and whereby both sides of the latching groove form a ramp for the latching means. The locking grooves could basically also be formed in the basic camshaft, wherein the locking device would be arranged in the cam carrier.

In a further advantageous embodiment of the invention it is provided that the radially directed force is the restoring force of a spring element.

In a next advantageous embodiment of the invention it is provided that the locking means is a locking bolt, wherein the locking grooves facing side of the locking bolt is rounded.

In an alternative advantageous development of the invention it is provided that the locking means is a locking ball.

In a last advantageous development of the invention, it is provided that a cam carrier is arranged on the at least one base camshaft for each cylinder of the internal combustion engine.

Fig.1

Seitenansicht eines erfindungsgemäßen vierzylindrigen Verbrennungsmotors;

Fig. 2

Darstellung des Verbrennungsmotors von Fig. 1 in Ansicht II-II von Fig.1;

Fig. 3

Perspektivische Darstellung der im Verbrennungsmotor der Fig.1 und Fig. 2 eingebauten Nockenwellen mit abgenommener Zylinderkopfhaube

Fig. 4

Darstellung einer der beiden Nockenwellen im ausgebauten Zustand;

Fig. 5

Abschnitt der in Fig. 3 dargestellten Nockenwelle mit einem von einem Nockenwellenlagerbock umfassten Nockenträger;

Fig. 6

Schnittdarstellung des in Fig. 5 dargestellten Nockenträgers in der ersten Ventilhubsteuerposition;

Fig. 7

Schnittdarstellung des in Fig. 5 dargestellten Nockenträgers in der zweiten Ventilhubsteuerposition.

In the following, an inventive valve train of an internal combustion engine is illustrated and explained with reference to an embodiment in connection with seven figures.

Fig.1

Side view of a four-cylinder internal combustion engine according to the invention;

Fig. 2

Representation of the internal combustion engine of Figure 1 in view II-II of Figure 1;

Fig. 3

Perspective representation of the internal combustion engine of Figure 1 and Figure 2 installed camshafts with removed cylinder head cover

Fig. 4

Representation of one of the two camshafts in the removed state;

Fig. 5

Section of the camshaft shown in Figure 3 with a cam carrier comprised of a cam carrier;

Fig. 6

Sectional view of the cam carrier shown in Figure 5 in the first valve lift control position.

Fig. 7

Sectional view of the cam carrier shown in Fig. 5 in the second valve lift control position.

In FIGS. 1 to 3, by way of example, there is shown a spark-ignited four-cylinder in-line engine having a cylinder crankcase 30 with a cylinder head 31 mounted thereon and with a cylinder head cover 33 formed in a known conventional manner. Two intake and two exhaust valves are formed per cylinder in a known manner, not shown, wherein the intake valves of an intake camshaft and the exhaust valves are controlled by an exhaust camshaft 16 controlled in a known manner. For this purpose, the intake camshafts and the exhaust camshaft 16 are aligned parallel to the engine longitudinal axis and rotatably mounted in the cylinder head 31 on both sides of the row of cylinders.

The exhaust camshaft 16 and the intake camshaft, which consists of a base camshaft 1 and four cam carriers 2 are driven in a known, not shown manner.

FIG. 4 shows the inlet camshaft, on whose base camshaft 1 the four cam carriers 2 designed as hollow shafts are arranged axially spaced apart. The cam pieces 2 are axially slidably mounted on the base camshaft 1 but rotatably mounted. As shown in Figures 3, 4, 5, 6 and 7 is at both ends of each cam carrier 2, a worm gear with a recess formed as an axial curve 10 and 11, respectively, which winds helically around the cam carrier axis.
On each cam carrier 2, two cams are arranged, with each cam from the same base circle axially offset two different cam tracks 6, 7 and 8, 9 emerge. The cylindrical region of the lateral surface of each cam piece 2 located between the two cams is designed as a bearing surface for a camshaft bearing 3.
As shown in Figures 3, 5, 6 and 7, each cam carrier 2 is rotatably and axially displaceably mounted with this cylindrical bearing surface in a camshaft bearing block 3 of the cylinder head 31.
The two camshaft bearing block 3 facing end faces of the cams are formed as abutment surfaces 18 and 19. Accordingly, the cam facing end faces of the camshaft bearing block 3 are formed as a contact surface 17 and 20 respectively. The distance between the two contact surfaces 17 and 18 of the cam is greater than the distance of the contact surfaces 19 and 20 of the camshaft bearing block third

The maximum distance, the contact surfaces 17 and 19, and the contact surfaces 18 and 20 may have from each other, the width of the cam tracks 6, 7, 8, 9, and the distance that a cam carrier by the axial curves 10 and 11 of the Worm gears can be moved.
The gas exchange valves 27, 28 of the internal combustion engine are actuated by the cam via cam follower 21, which are designed to reduce friction with a roller 23.
Associated with the follower levers 21, 22 is in a conventional manner a trained in the cylinder head clearance compensation element 25 and 26 respectively.

As shown in Figures 6 and 7, the inside of the cam carrier 2 has two mutually parallel, axially spaced, the entire inner circumference of the cam carrier circumferential locking grooves 34, 35. The locking grooves are approximately V-shaped, wherein the known of the V-shaped locking groove are rounded.
The two locking grooves 34, 35 are formed with radially outwardly to radially inwardly inclined groove walls forming the conical surfaces 36 and 37, wherein the conical surface 36 of the groove 34 has a pitch angle α to the axis of rotation of the camshaft 1 and the surface 37 of the groove 35 has a pitch angle β to the axis of rotation of the camshaft 1.

In the camshaft - as shown in Figures 5, 6, 7 is shown - in a trained in the radial direction blind bore 38 a locking ball 40 of known type slidably mounted. The locking ball 40 is biased by a coil spring 39, which is supported at one end in the bottom of the blind bore 38 formed as an abutment and which is supported at the other end of the ball 40, biased so that the locking ball 40 radially outwardly against the radially biased inner surface of the cam carrier 2 is applied to this.
The distance between the conical surfaces 36 and 37 of the two grooves 34 and 35 to each other and the axial position of the blind bore 38 are coordinated so that when abutment of the contact surface 18 of the cam 8 on the contact surface 20 of the bearing block 3, the locking ball 40 at the conical surface 37 rests - as shown in Figure 7 - and that upon contact of the contact surface 19 of the cam 7 on the contact surface 17 of the cam bearing block 3, the locking ball 40 abuts against the conical surface 36 of the groove 34 - as shown in Figure 5 and Figure 6 is shown.
In this way, in the position of the cam carrier 2 shown in Figures 5 and 6, in which the abutment surface 19 of the cam 7 rests against the abutment surface 17 of the bearing block 3, via the Arretierkugel 40 and the conical surface 36 of the circumferential groove 34, an axial force of the camshaft 1 is introduced into the cam carrier 2, which is directed in the opposite direction to the force acting from the bearing block 3 via the contact surface 17 on the contact surface 19 of the cam 9 axial force. In this way, the cam carrier 2 is fixed for both axial directions.
In the position of the cam carrier 2 shown in Figure 7, in which the contact surface 18 of the cam 8 is in touching contact with the contact surface 20 of the bearing block 3, the Arretierkugel 40 is in touching contact with the conical surface 37 of the second circumferential groove 35, whereby of the camshaft 1 in the cam carrier 2, an axial force is introduced, which is directed from the contact surface 20 of the bearing block 3 via the force acting on the contact surface 18 of the cam 8 axial force. Also in this operating position, the cam carrier 2 is fixed axially in both directions.
A different extent of the base camshaft relative to the cylinder head causes only a slight displacement of the contact point between the ball 40 and the conical surface 36 (first position as shown in Figure 6) or the conical surface 37 (second position as shown in Figure 7). In this case, the required axial force in the cam carrier 2 is further introduced via the ball 40 according to the inclination α or β of the conical surfaces 36, 37.
The adjustment of the Hubventilsteuerung of the operating state shown in Figures 5 and 6 in the operating state shown in Figure 7 is effected in that - as shown in Figure 6 - the driving pin 14 of an arranged in the cylinder head 31 electric actuator, which is associated with the axial curve 10 , engages in the formed as a recess axial cam 10. Due to the rotation of the camshaft 1 and the cam carrier 2, the cam carrier 2 is displaced axially as far to the left by contact contact between the driver pin 14 and the groove walls of the axial cam 10 until the ball 40 prestressed by the spring 39 overflows into the groove 35 of the cam carrier 2.
While the ball 40 rolls on the axial movement of the cam carrier 2 along the conical surface 37, the contact surface 18 of the moves Cam 8 on the contact surface 20 of the bearing block 3 and device with this in axial contact. The ball 40 is still in axial contact with the contact surface 37. The cam carrier 2 is axially fixed. The driving pin 14 is pulled out by means of the electric actuator 12 in a known manner again from the formed as a circumferential groove 10 axial curve.

For adjusting the Hubventilsteuerung of the operating state shown in Figure 7 for the Hubventilsteuerung in the operating condition shown in Figure 5 and Figure 6, the driving pin 15 of the axial cam 11 associated and arranged in the cylinder head 31 electric actuator 13 from the actuator in the recess formed as Axial curve 11 introduced.
Due to the rotation of the camshaft 1, the cam carrier 2 in FIG. 7 is displaced axially to the right via the contact contact between the groove walls of the axial cam 11 and the driver pin 15, so that the arresting ball 40 moves along the contour of the conical surface 37 counter to the spring force of the spring 39 from the groove 35 rolls out until the locking ball 40 along the contour of the conical surface 36 into the groove 34 penetrates by the restoring force of the spring 39 and the contact surface 17 of the cam 7 comes into contact with the abutment surface 19 of the bearing block 3. The contact between the driving ball 40 and conical surface 36 is maintained. The cam carrier 2 is fixed by the system between the contact surface 17 of the cam 7 and the contact surface 19 of the bearing block 3 on the one hand and by the system between cone 36 and locking ball 40 on the other hand axially in both directions. The driving pin 15 is pulled out by means of the electric actuator 13 in a known manner from the circumferential groove of the axial cam 11.

The operation of the electric actuators we controlled in a known, not shown manner by the engine control unit, not shown.

The angles .alpha. And .beta. Are dimensioned in this way-depending on the individual requirement-that ensures the required axial fixing force in the operating positions for the Hubventilsteuerung and releasing the locking connection after engagement of the driving pins 14 and 15 in the circumferential grooves 10 and 11 during rotation the camshaft 1 is ensured in the operating direction. For example, the angles α and β are the same size between 15 ° and 45 °, for example, selected at 30 °.

Although in the illustrated embodiments, the conical surfaces 36 and 37 along their axial extent each have a constant pitch angle α and β, it is also conceivable - as far as a dynamic Axialkraftverlauf is useful - the slope of one or both conical surfaces 36 and 37 with Form axial direction continuously variable pitch angle α or β.

The four cam carrier 2 of the camshaft 1 shown in Figures 3 and 4, can be adjusted in this way individually by the associated actuators 12 and 13 between their two operating positions for Hubventlisteuerung.

Such a configuration of the adjustment of the lift valve control is possible both for an intake camshaft 1 controlling only intake valves and also for an exhaust camshaft 16 controlling only exhaust valves. It is also possible to provide such a design also on a camshaft which controls both intake valves and exhaust valves.

In an internal combustion engine, which - as shown in Figures 1 to 3 - has two camshafts 1 and 16, one of which is designed only for controlling the intake valves and the other only for controlling the exhaust valves, it is possible in the above Embodiments shown adjustment of the Hubventilsteuerung form only on one of the two camshafts or on both camshafts.

Such a design of a controlled adjustment of the Hubventilsteuerung is also possible on internal combustion engines with more or fewer cylinders than the four cylinders shown in the embodiment. Such a design of the controlled adjustment of the Hubventilsteuerung is also possible on different cylinder arrangements of engines, such as in-line engines, V-engines or VR or W motors. The illustrated Hubventilsteuerungsverstellung is possible both spark-ignition and self-ignited internal combustion engines.

Claims (9)

1. Valve train of an internal combustion engine having a cylinder head, with at least one camshaft (1) on which at least one cam support (2)¹ is arranged so as to be non-rotatable and axially displaceable,

   - wherein the at least one cam support (2)² has at least one cam (5, 6) on which at least two different cam paths (5.1, 5.2, 6.1, 6.2) are formed,

   - whereby, for supporting the at least one camshaft (1, 16), the at least one cam support (2) is surrounded by at least one camshaft bearing (3) fixed to the cylinder head,

   - whereby means for axial displacement of the at least one cam support (2) relative to the at least one camshaft (1) is provided between a first axial position and at least one second axial position,

   characterised in that

   - in the first axial position of the cam support, a first stop surface (17) fixed to the cam support lies against a first stop surface fixed to the cylinder head,

   - in the second axial position of the cam support, a second stop surface (18) fixed to the cam support lies against a second stop surface fixed to the cylinder head, and

   - between the camshaft (1) and the cam support (2), means are formed for applying an axial clamping force, whereby the axial clamping force displaces the cam support in the region of the first axial position in the direction of the first axial position, and in the region of the second axial position in the direction of the second axial position.

   ¹ Translator's note: There appears to be an error in the German original at this point. The reference number (3) has been used in association with a word that is otherwise associated with the reference number (2). This has been amended accordingly in the translation.
   ² See footnote 1.
2. Valve train according to claim 1, characterised in that the first axial stop surface (17) fixed to the cam support and the second stop surface (18)³ fixed to the cam support are side surfaces of the at least one cam.
   ³ The reference number (17) has been used in association with a term that is otherwise associated with the reference number (18). This has been amended accordingly in the translation.
3. Valve train according to claim 1 or 2, characterised in that the first stop surface fixed to the cylinder head and the second stop surface fixed to the cylinder head are side surfaces of the at least one camshaft bearing.
4. Valve train according to one of the claims 1 to 3, characterised in that means for applying an axial clamping force from the basic camshaft (1) onto the cam support (2) is designed as a snap-in locking device.
5. Valve train according to claim 4, characterised in that the snap-in locking device has detent means (40) arranged in the camshaft (1) and mounted movable in the radial direction, wherein the detent means (40) is pressed outwardly by a force in the radial direction against the inner surface of the cam support (2), and that at least two peripheral, axially spaced detent grooves (36, 37) are formed on the inside of the cam support (2), and that the detent grooves (36, 37) are formed V-shaped in the cam support, whereby both sides of the detent groove comprise a ramp for the detent means (40).
6. Valve train according to claim 5, characterised in that the radially directed force is the restoring force of a spring element.
7. Valve train according to claim 5 or 6, characterised in that the detent means (40) is a catch bolt, and that the side of the catch bolt facing towards the detent grooves is rounded.
8. Valve train according to claim 5 or 6, characterised in that the detent means is a detent ball (40).
9. Valve train according to one of the claims 1 to 8, characterised in that a cam support (2) is arranged on the at least one basic camshaft (1) for each cylinder of the internal combustion engine.

Images