EP2766582A1

EP2766582A1 - Valve train for an internal combustion engine

Info

Publication number: EP2766582A1
Application number: EP12766882.0A
Authority: EP
Inventors: Axel Groenendijk; Martijn VAN DER HEIJDEN
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2011-10-15
Filing date: 2012-09-13
Publication date: 2014-08-20
Also published as: DE102011116130A1; WO2013053421A1; CN103857882A; CN103857882B

Abstract

The invention relates to a valve train for an internal combustion engine with at least two cam shafts and a phase regulator (20), wherein the phase regulator (20) comprises a drive wheel (26), a first actuator which is connected to a first of the cam shafts, and a second actuator which is connected to a second of the cam shafts. By adjusting the first and/or the second actuator, a phase angle of the respective cam shaft can be adjusted relative to the drive wheel (26). Said valve train is characterized in that the adjustment of the second actuator is implemented based upon the adjustment of the first actuator.

Description

description

Valve train for an internal combustion engine

The invention relates to a valve train for an internal combustion engine having at least two camshafts and a phaser, wherein the phaser a drive wheel, a first actuator which is rotatably connected to a first of the camshaft, and a second actuator which is rotatably connected to a second of the camshaft , wherein by adjusting the first and / or the second actuator, a phase angle with respect to the drive wheel can be adjusted.

The valve train for a piston internal combustion engine comprises at least one, regularly two intake and exhaust valves for each cylinder of the internal combustion engine. These intake and exhaust valves are controlled by camshafts, with two engines per cylinder usually operating at more than two valves

Camshafts are used. In many cases, the arrangement of these camshafts is such that one of them all inlet valves and the other all

Exhaust valves controls.

To improve the operating behavior of an internal combustion engine, it is known to change the valve timing of the individual intake and / or exhaust valves in that the phase angles of the camshafts controlling them are adjusted. For this purpose, the respective camshaft by means of a phaser relative to a drive wheel, via which it is driven in rotation, by a defined angle, the

Phase angle, twisted, whereby the valve timing of the thus controlled valves in the direction of "early" or "late" can be adjusted.

Also known are internal combustion engines in which the camshafts each control both intake and exhaust valves. These are often referred to as "mixed camshafts." In principle, a phase adjustment leads to such

(simple) mixed camshaft to a change in the valve timing of both the controlled intake and exhaust valves in the same

Direction and with the same phase angle. However, this is not desirable in many cases. Rather, the valve timing of the intake and exhaust valves should be independently controllable. This is achieved for mixed camshafts by that these are in the form of double camshafts, so-called cam-in-cam camshafts, are formed. These consist of an outer shaft and an inner shaft mounted inside the outer shaft, wherein both the inner and the outer shaft are provided with cams for the control of the intake and exhaust valves. The cams of the inner shaft protrude through openings in the outer shaft. By means of a phaser, which can rotate the inner and the outer shaft independently, then there is the possibility of the timing of the intake and

To adjust exhaust valves independently.

Such a phase divider is known, for example, from US Pat. No. 7,841,31,2 B2. This includes a drive wheel, which is driven by any drive means (gear, timing belt, timing chain) rotating from a crankshaft of an internal combustion engine. The rotation of the drive wheel is transmitted via two impellers to a double camshaft, wherein one of the impellers acts on the inner shaft and the other impeller on the outer shaft of the camshaft. The impellers are within limits rotatable within a likewise driven by the drive wheel housing, whereby a phase adjustment of the associated with the impellers inner shaft and

Outer shaft opposite the drive wheel can be achieved. The adjustment of the two impellers within the housing is hydraulic and independent of each other, i. the phase position of a wave has no effect on the

Adjustability of the other shaft. With the known from US 7,841, 31 1 B2

Phase divider, it is thus possible to control the phase adjustment of inner and outer shaft of a double camshaft completely independently.

A disadvantage of this phase divider is the high design complexity and the high control engineering effort for the independent phase adjustment of the two waves.

Based on this prior art, the invention was the object of an improved generic valve train for an internal combustion engine

specify. In particular, this should be a structurally simple

distinguished trained phaser.

This object is achieved by a valve train according to independent claim 1. Advantageous embodiments are the subject of the dependent

Claims and will become apparent from the following description of the invention. According to the invention, a generic valve train for a

Internal combustion engine having at least two camshafts and a phaser, wherein the phase divider comprises a drive wheel, a first actuator which is non-rotatably connected to a first of the camshaft, and a second actuator which is non-rotatably connected to a second of the camshaft, wherein an adjustment of the first and / or the second actuator, a phase angle with respect to the drive wheel can be adjusted by the fact that the adjustment of the second actuator takes place in dependence on the adjustment of the first actuator. In other words, the first and second actuators are coupled or connected to one another directly or indirectly via a coupling element, in particular mechanically or electrically.

Unlike the phase adjuster according to US Pat. No. 7,841,31,2 B2, it is therefore not intended to be able to adjust or displace the two camshafts controlled by the actuators completely independently of one another, but rather an adjustment of one of the camshafts from a defined position of the other

To make camshaft dependent. This approach is based on the idea that it is not regularly necessary for an operation of an engine provided with such a valvetrain to be able to control the valves completely independently of each other and that by dispensing with this possibility of independent control not only the design effort for Phase controller can be reduced, but also the control effort is significantly lower, whereby the computational effort for the intended purpose for this purpose control device can be kept low.

It is preferably provided that the phase adjuster is hydraulically actuated. A rotation of the individual camshaft can then take place, for example, by one or two pressure chambers which (each) from one side of a

pivotable, associated with the respective camshaft actuator are limited to be filled or emptied with the hydraulic fluid: In two, separate from the actuator pressure chambers, can by an alternativerdes

Filling / emptying the pressure chambers a purely hydraulic twisting of the respective camshaft can be realized in both directions. If only one pressure chamber used, it can be provided that a filling of this pressure chamber to a

Pivoting the control element takes place against a spring force, which - then

Emptying the pressure chamber - ensures a safe return. Of course, it is alternatively possible to confirm the phaser with substantially the same construction pneumatically and not hydraulically. The main advantage of the hydraulic actuation, however, lies in the incompressibility of the

Hydraulic fluid, whereby the required accuracy for the adjustment can be achieved in a relatively simple manner.

In addition to a hydraulic or pneumatic actuation of the Phasensteliers of course, there is also the alternative, this mechanically and / or electrically operated. In addition, there is still the possibility to operate the two actuators in different ways, for example, one of the actuators hydraulically and the other mechanically or electrically.

A structurally simple and preferred way to realize a

Dependence of the adjustment of the second actuator on an adjustment of the first actuator can be achieved in the case of a hydraulic (or pneumatic) phase divider in that it comprises at least one valve which is closed or opened as a function of a position of the first actuator and thereby the

corresponding adjustment of the second actuator causes. The valve can be designed in particular as a simple opening, which is connected in dependence on the position of a movable (in particular pivotable) actuating element of the first actuator with a hydraulic fluid (or compressed air) filled pressure chamber or separated from it.

To further simplify the construction of the phaser and the

Control effort may be further provided that the adjustment of the second actuator only digital, i. between two adjustment positions, takes place.

In this case, provision may in particular be made for a small phase angle of the second actuator to be set at a small and / or large phase angle of the first actuator (adjustable in a defined phase angle range) and / or for a large phase angle of the second actuator to be set for a mean phase angle of the first actuator becomes. In this case, the phase angle direction is preferably such that a small phase angle early control times and a large phase angle late control times of the valves controlled by the corresponding camshaft

Internal combustion engine corresponds. In a preferred embodiment of the valve drive according to the invention it is provided that the first and the second camshaft in the form of an outer shaft and an inner shaft disposed within the outer shaft is formed. The two camshaft thus form a double camshaft, wherein the phaser causes a dependent, but not necessarily rectified and equal adjustment of the inner and outer shaft of the double camshaft. The phase divider of the valve train according to the invention is thus also advantageous for so-called mixed (double) camshaft suitable in which the inner shaft controls one type of valves (intake or exhaust valves) and the outer shaft, the other type of valves. Preferably, it is accordingly provided that at least one inlet valve is associated with the first camshaft and at least one outlet valve is associated with the second camshaft.

A preferred concrete control of the intake and exhaust valves of such a valve train according to the invention with a mixed (double) camshaft can provide that the first actuator has a Gesamtverstellbereich for the phase angle of 0 ° to about 50 °, wherein a position of the first actuator in a small phase angle, in particular in a range between 0 ° and 10 °, leads to a position of the second actuator with a large phase angle. Thus, preferably, "early" timing for the intake valves is combined with "late" timing for the exhaust valves of the engine. These control times may be provided in particular at an operation of the internal combustion engine (near) at full load and low speeds in order to exploit a maximum expansion work in the cylinders. This allows the specific fuel consumption of the

Internal combustion engine to be kept low.

With a position of the first actuator in a middle phase angle, in particular in a range between approximately 10 ° and approximately 25 °, it may then be preferable to arrange for the second actuator to be adjusted towards a small phase angle. This can be provided in particular during operation of the internal combustion engine (near) at full load and at high rotational speeds. The "early" control times for the exhaust valves controlled by the second camshaft then ensure a sufficient change of charge in the combustion chambers of the internal combustion engine.

At a position of the first actuator in a large phase angle, in particular in a range of about 25 ° to about 50 °, it may then further be provided that the second actuator is (again) adjusted to a large phase angle. This can be provided in particular during operation of the internal combustion engine in partial load, in order to achieve a so-called "Miller cycle" for a better utilization of the expansion work.

As a possibility for structurally simple storage of the waves of a double camshaft may preferably be provided that the inner shaft, the

is preferably provided for controlling the intake valves of the internal combustion engine, is connected to the first actuator, while for the control of the

Exhaust valves provided external shaft is connected to the second actuator.

In an alternative embodiment of the valve train according to the invention is provided to combine the phase divider of the valve train according to the invention with two double camshafts, i. both the first and the second camshaft are in the form of an outer shaft and an inner shaft disposed within the outer shaft, wherein the first actuator is connected to the inner or outer shaft of a camshaft and the second actuator to the inner or outer shaft of the second camshaft , Such a configuration can be provided, in particular, if the two camshafts are not "mixed", ie only control either only inlet or outlet valves Phase angle of the first actuator, which is preferably connected to the camshaft, which are associated with the intake valves (ie at "late" timing for the intake valves), a small phase angle of the second actuator is realized (ie, "early" timing for the exhaust valves).

Of course, there is also the possibility of the two actuators of the

According to the invention valve train with two camshafts, which are not double and / or not mixed form.

The invention is described below with reference to an illustrated in the drawings

Embodiment explained in more detail. In the drawing shows:

1 shows a schematic representation of an embodiment of a

Valve gear according to the invention.

Fig. 1 shows a schematic representation of the essential components of an embodiment of a valve train according to the invention. This includes one Camshaft 10, which is in the form of a double, mixed camshaft. For this purpose, the camshaft comprises an outer shaft 12 with a plurality of distributed over the length arranged cam 14, which is used to control the exhaust valves of a

Internal combustion engine are provided. Within the outer shaft 12, an inner shaft 16 is rotatably mounted. Also on the outside of the inner shaft 16 a plurality of distributed over the length of the cam 18 are arranged, which serve to control intake valves of the internal combustion engine.

With its one end, the camshaft 10 is connected to a phase splitter 20. The phase adjuster comprises two actuators, of which a first with the inner shaft 16 and a second with the outer shaft 12 of the camshaft 10 is rotatably connected. The actuators have rotors 22 with adjusting wings (four in the present case in each case), which form pressure chambers with walls of a housing 24 of the phaser. The size of the pressure chambers is variable by a rotation of the respective rotor 22. This rotation is realized by all or individual, the respective rotors 22 associated pressure chambers with a hydraulic fluid (under a defined pressure) to be filled. With regard to the structural details, in particular the rotors 22 and the housing 24 formed with the

Pressure chambers, the phase divider can be formed according to the known from US 7,841, 31 1 B2 phase divider.

By rotating the two rotors 22, a phase angle is adjusted with respect to a housing connected to the drive wheel 26, which is driven in rotation by a crankshaft, not shown, of the internal combustion engine. This phase angle is transmitted through the non-rotatable connection of the rotors 22 with the respective inner 16 and outer shaft 12 to the respective cams, whereby the timing of the controlled by the cam inlet and outlet valves is changed.

According to the invention, it is provided that the adjustment of the second actuator in

Dependent on the position of the first actuator takes place. For this purpose, valve openings and overflow lines 28 (shown schematically by an arrow) are provided. Depending on the position of the rotor 22 of the first actuator, individual ones of the valve openings are released and thereby individual ones of the pressure chambers formed by the first rotor 22 and the housing 24 are connected to individual ones of the overflow lines. As a result, hydraulic fluid, which is present in the pressure chambers of the first actuator, can flow into the released pressure chambers of the second actuator and adjust it accordingly. In the exemplary embodiment described, it is provided that the first actuator has an adjustment range from 0 ° to approximately 50 °. In this case, the phase angle increases in the direction of rotation of the first actuator, so that an increasing

If the rotor of the first actuator is in a range between 0 ° and 10 °, which can be regarded as "early" timing of the controlled by the cams of the inner shaft intake valves , the pressure chambers of the second actuator are filled via correspondingly enabled overflow lines 28, which rotate the rotor of the second actuator (up to a defined stop) in the direction of the general direction of rotation and consequently towards a phase angle defined as large. Accordingly, the timing of the exhaust valves controlled by the cams 14 of the outer shaft 12 are changed to "late." These phase angles of the two actuators are designed to operate the engine (near) at full load and low speeds to take advantage of maximum expansion work in the cylinders. This allows the specific fuel consumption of the

Internal combustion engine to be kept low.

At a position of the rotor of the first actuator in a range between about 10 ° and about 25 ° is provided that the rotor 22 of the second actuator by a corresponding filling of the pressure chambers of the second actuator (up to a defined stop) against the general Direction of rotation is adjusted. This results in "early" timing for the exhaust valves, which may be provided at full load and high rpm operation of the engine (near) .The "early" timing of the exhaust valves then ensures sufficient charge exchange in the combustion chambers of the engine.

At a position of the rotor 22 of the first actuator in a range of about 25 ° to about 50 ° is provided that the rotor 22 of the second actuator (again) is adjusted to a large phase angle. This is provided during operation of the internal combustion engine with partial load. LIST OF REFERENCE NUMBERS

camshaft

outer shaft

cam

inner shaft

cam

phaser

rotor

casing

drive wheel

overflow

Claims

claims

1. Valve drive for an internal combustion engine having at least two camshafts and a phase divider (20), wherein the phase divider (20) has a drive wheel (26), a first actuator which is connected to a first of the camshafts, and a second actuator which is connected to a second of the camshafts is connected, wherein an adjustment of the first and / or the second actuator, a phase angle of the respective camshaft with respect to the drive wheel (26) is adjustable, characterized in that the adjustment of the second

Actuator in response to the adjustment of the first actuator takes place.

2. Valve drive according to claim 1, characterized in that the phase adjuster (20) is hydraulically actuated.

3. Valve drive according to claim 2, characterized in that the phase divider (20) comprises at least one valve which is closed or opened in dependence on a position of the first actuator.

4. Valve drive according to one of the preceding claims, characterized in that the adjustment of the second actuator is digital.

5. Valve drive according to one of the preceding claims, characterized in that

a small and / or large phase angle of the first actuator causes a small phase angle of the second actuator; and or

- A mean phase angle of the first actuator causes a large phase angle of the second actuator.

6. Valve drive according to one of the preceding claims, characterized in that the first and the second camshaft in the form of an outer shaft (12) and within the outer shaft (12) arranged inner shaft (16) are formed.

7. Valve gear according to claim 6, characterized in that the first

Camshaft at least one inlet valve and the second camshaft is associated with at least one exhaust valve.

8. Valve drive according to claim 6 or 7, characterized in that the first actuator has an adjustment range of 0 ° to about 50 °, wherein

- Is set at an adjustment of the first actuator in a range of 0 ° to about 10 ° or in a range of about 25 ° to about 50 °, a small phase angle of the second actuator; and

- When adjusting the first actuator in a range of about 10 ° to about

25 °, a large phase angle of the second actuator is set

9. Valve drive according to one of claims 6 to 8, characterized in that the first actuator with the inner shaft (16) and the second actuator with the outer shaft (12) is connected.

10. Valve gear according to one of claims 1 to 5, characterized in that the first camshaft in the form of an outer shaft (12) and arranged within the outer shaft inner shaft (16) is formed and the second

Camshaft in the form of an outer shaft (12) and arranged within the outer shaft inner shaft (16) is formed, wherein the first actuator with the inner (16) or outer shaft (12) of the first camshaft and the second actuator with the inner (12 ) or outer shaft (16) of the second camshaft is connected.