EP1650411A1 - Camshaft phaser and method to change cam phase by use of a artificial muscle - Google Patents

Abstract

The camshaft adjuster (1) comprises an outer disposed housing element (2) and an inner disposed adjusting shaft element (3). The camshaft adjuster comprises at least one artificial muscle (11a) which by activation changes its geometric shape in a way which a rotation of the adjusting shaft element in relation to the housing element, and therefore a change of the camshaft position in relation to a crankshaft can be realized. A drive wheel (4) in the form of a belt or chain wheel is provided on the housing element, and the housing element is connected to the crankshaft by a belt or chain. An independent claim is included for a method for the changing of the position of the camshaft in relation to the crankshaft of an internal combustion engine by means of the proposed camshaft adjuster.

Description

The invention relates to a camshaft adjuster for rotating a camshaft d. H. to change the position of the camshaft relative to the crankshaft for the purpose of adjusting the timing of an internal combustion engine with an outer housing element and with an inner, at least partially disposed in the housing element adjuster shaft element, said housing member by means of a drive with the crankshaft of the internal combustion engine and the Verstellwellenelement with the camshaft of Internal combustion engine is connected and the housing element and the adjuster shaft element are rotated against each other.

Furthermore, the invention relates to a method for changing the position of the camshaft relative to the crankshaft in order to adjust the timing of the valves of an internal combustion engine using such a camshaft adjuster.

Camshaft adjuster of the above type are required to make a camshaft adjustment, with the control times of the control elements of a valve train of an internal combustion engine can be influenced. The position of the camshaft relative to the crankshaft is changed by turning the camshaft. The variation of the timing is a solution to reduce fuel consumption.

Due to the limited resources of fossil fuels, in particular due to the limited mineral oil reserves as a raw material for the production of fuels for the operation of internal combustion engines, the development of internal combustion engines is constantly striving to minimize fuel consumption.

The problem is the fuel consumption and thus the efficiency, especially in gasoline engines. The reason for this lies in the basic working method of the gasoline engine. The gasoline engine works with a homogeneous fuel-air mixture, which - if there is no direct injection - is prepared by external mixture formation by fuel is introduced into the intake air in the intake system. The desired power is adjusted by changing the filling of the combustion chamber, so that the operating method of the gasoline engine - unlike the diesel engine - is based on a quantity control.

This load control is usually carried out by means of a throttle valve provided in the intake tract. By adjusting the throttle, the pressure of the intake air behind the throttle valve can be reduced more or less. With a constant combustion chamber volume, the air mass, i. E. the quantity will be set. The quantity control by means of throttle valve has thermodynamic disadvantages due to the pressure reduction and the associated throttle losses.

One approach to prior art de-throttling is to use a variable valvetrain. In contrast to conventional valve trains, where both the stroke of the valves and the timing, d. H. the opening and closing times of the intake and exhaust valves, due to the non-flexible, since non-adjustable mechanism of the valve train are given as immutable variables, these parameters can be varied more or less by means of variable valve trains influencing the combustion process and thus the fuel consumption. The ideal solution would be a fully variable valve control, which allows for specially tuned values for the stroke and the timing for any operating point of the gasoline engine.

Noticeable fuel savings can also be achieved with only partially variable valve trains, in which, for example, the closing time of the intake valve is adjustable. A variation of the closing time of the intake valve can be achieved by means of a camshaft adjuster of the type mentioned above, due to the unchangeable cam contour a shift in the control time "inlet closes" (ES) always at the same time an equal size Shift of the control time "inlet opens" (EO) entails and vice versa. Furthermore, it must be taken into account that, in principle, all cams of a camshaft are always rotated.

The use of a camshaft adjuster for realizing variable timing is advantageous not only with regard to the above-described Entdrosselung the internal combustion engine and associated consumption optimization of the internal combustion engine, but also in view of the problem resulting from a rigid control time on the one hand and a variable speed because there is always a compromise to be found, which takes into account the entire speed range.

Thus, the control time, to which the intake valve closes, affects the filling of the combustion chamber and thus the torque characteristic of the internal combustion engine. At low speeds, it is advantageous to close the intake valve early, but at high speeds, especially at the rated speed, resulting in unwanted filling losses. Therefore, at high speeds, it is preferable to close the intake valve late to ensure good filling of the combustion chamber in this speed range. However, a late closing of the intake valve results in partial loss of filling at low speeds due to partial expulsion of the freshly aspirated cylinder charge. A fixed control time is therefore always a compromise between the two colliding scenarios described above. It is ideal if the control time to which the intake valve closes, is variably controllable, which can be realized by means of a camshaft adjuster. At low speeds then the inlet valve could be closed early, at high speeds late, including the camshaft needs to be rotated by means of camshaft adjuster only relative to the crankshaft in a suitable manner.

Another application for a camshaft adjuster for realizing a variable valve timing is the variation of the so-called valve overlap, ie the reduction or enlargement of the crank angle window in which the exhaust valve is not yet closed when the inlet valve is open. In the area of this valve overlap, flushing losses can occur, with part of the aspirated mixture flowing through the combustion chamber without combustion participate. This leads on the one hand to poorer efficiencies, but on the other hand to a larger cylinder filling and thus to a higher performance. At low speeds, a smaller and at higher speeds a larger valve overlap is sought. A camshaft adjuster allows a variation of the valve overlap as a function of the rotational speed.

The use of a camshaft adjuster, with which the camshaft is rotated relative to the crankshaft by a certain angle, thus offers numerous possibilities to influence the timing of the valves and thus influence the combustion process, with the timing shifted to early or late.

Such camshaft adjusters or adjusting devices are actuated or controlled hydraulically, mechanically or electrically. In a hydraulic control one or more pressure chambers are selectively applied or relieved with hydraulic oil.

Such an adjusting device 100 is described in the German patent application DE 198 50 947 A1 and is shown in FIG.

As can be seen from FIG. 1, a belt pulley 110 is connected in a rotationally fixed manner to a housing cover 112 and a first intermediate element 114. The intermediate element 114 has radially inwardly a toothing 116, which meshes with a counter-toothing 120 arranged on an axially displaceably mounted piston device 118. The piston device 118 has a second toothing 122, which engages in a second counter toothing 126 arranged on a second intermediate element 124. At least one pair of gears 116, 120 and 122, 126 is helically toothed. The second intermediate element 124 is non-rotatably connected to the camshaft 128, so that upon axial displacement of the piston device 118, the camshaft 128 is rotated relative to the belt wheel 110 and thus relative to the crankshaft.

Thus, DE 198 50 947 A1 discloses a camshaft adjuster of the generic type, i. a camshaft adjuster according to the preamble of claim 1.

To displace the piston device 118, two adjustment chambers 132, 134 are provided, wherein the piston device 118 separates the two adjustment chambers 132, 134 from one another. These chambers 132,134 are acted upon for axial displacement with pressurized oil via the lines 136, 138 d. H. controlled.

Such a camshaft adjuster is not only very complex and expensive, but also has a relatively high space requirement. However, a high space requirement is the fundamental goal of the designers, in the engine compartment of the motor vehicle as effective as possible d. H. To realize dense packaging of the entire drive unit, contrary. In addition, the adjuster has a high weight.

A disadvantage of the adjusting device described in DE 198 50 947 A1, moreover, is the hydraulic control or actuation in which pressure chambers are subjected to targeted pressure chambers, for which purpose a pressurized oil supply must be provided.

Basically, an adjustment of the camshaft under all operating conditions must be able to be realized with a sufficient accuracy and a high adjustment speed. However, this can not always be guaranteed under operating conditions which are distinguished by high oil temperatures or low engine loads, because in these operating points the pressure in the oil circuit of the internal combustion engine and thus in the pressure oil supply of the adjusting device drops and may be too low to reach high adjustment speeds and sufficient To achieve adjustment accuracies.

This is justified in particular by the fact that the camshaft is a dynamically loaded component by the interaction of their cams with the valve trains of the internal combustion engine. Thus, the camshaft is loaded via their cams with an additional torque when these cams on a ram Accumulate valve gear and compress provided in the valve train return springs. This torque counteracts the actual camshaft rotation.

On the other hand, after the maximum valve lift has been reached, the energy stored in the return springs is returned to the cams during the expansion phase of the springs. The cams are loaded with a torque that supports the actual camshaft rotation, d. H. the camshaft and the torque exerted on it by the valvetrain are rectified in the closing phase of the valve.

The equipped with a hydraulic adjusting camshaft is supported indirectly via the oil in the adjusting device, which is why the force exerted by the valve train on the camshaft, dynamic torque leads to pressure fluctuations of the hydraulic oil in the adjustment and the leads.

These pressure fluctuations, in turn, affect the adjustment speed and the adjustment accuracy, especially under low engine load or high oil temperature operating conditions, where the oil pressure in the system is inherently low, increasing sensitivity to pressure fluctuations. Thus, in the case of a camming cam, the oil pressure in the system is increased by the torque exerted by the valve drive on the cams, and the oil is even pushed back into the pressurized oil supply in the worst possible scenario. To prevent this, it is proposed in the prior art to provide a valve in the pressure oil supply.

The statements made on the example of a hydraulic camshaft adjuster to show that a camshaft adjuster and to be provided for its operation control are basically very complex and costly components. The mentioned technical requirements also apply to other - mechanically or electrically operated - adjusting devices. In particular, a large adjustment speed and a high adjustment accuracy is desired, wherein the camshaft adjuster should be as inexpensive, small and light as possible.

Against this background, it is the object of the present invention to provide a camshaft adjuster of the generic type, with which the disadvantages known in the prior art are overcome and which in particular is less expensive, has a smaller space requirement and a lower dead weight than conventional adjusting devices.

Another object of the present invention is to provide a method of changing the position of the camshaft relative to the crankshaft using such a phaser.

This problem is solved by a camshaft adjuster for rotating a camshaft d. H. to change the position of the camshaft relative to the crankshaft for the purpose of adjusting the timing of an internal combustion engine with an outer housing element and with an inner, at least partially disposed in the housing element adjuster shaft element, said housing member by means of a drive with the crankshaft of the internal combustion engine and the Verstellwellenelement with the camshaft of Combustion engine is connected and the housing element and the adjuster shaft element are rotated against each other, and which is characterized in that the camshaft adjuster comprises at least one artificial muscle which changes its geometric shape by activation in such a way that a rotation of the Verstellwellenelements relative to the housing element and thus a change in the Camshaft position relative to the crankshaft is realized.

Artificial muscles are actuators whose properties are similar or similar to those of the natural musculature. Characteristic of artificial muscles is in particular a volume occurring force generation due to atomic or molecular interactions. Often, artificial muscles - like natural muscles - are made of a soft, shape-changing material.

The power generation in known artificial muscles can be, for. On electrostatic attractive forces, on the piezoelectric effect, on an ultrasonic generation, on a shape memory of materials, on one Ion exchange, based on an extension of carbon nanotubes and / or on the incorporation of hydrogen into metal hydrides.

Depending on the mode of action, artificial muscles can be made of polymers, in particular polymer gels, of ferroelectric substances, of silicon, of alloys with a shape memory or the like. A detailed description of various types of artificial muscles is known, for example, from: In EP 0 924 033 A2, US 2002/0026794 A1, US Pat. No. 6,109,852 and similar patent literature. In addition, examples of artificial muscles are described in publications of the relevant research institutes (eg Max Planck Institute for Solid State Research in Stuttgart, Department of Artificial Intelligence of MIT, Massachusetts, USA).

By using at least one artificial muscle, a complex mechanical or hydraulic adjusting device or actuator, as is known from the prior art, by the camshaft adjuster according to the invention, which is much lighter, smaller and simpler in construction and in the operation, replaced become. An artificial muscle that has the ability to change its geometric shape as a result of activation already forms an adjusting device on its own. An artificial muscle is inherently intrinsic to an adjustment device. To change the position of the camshaft, the artificial muscle only has to be activated, wherein an activation is already possible by means of an electrical signal, as will be explained in more detail below.

According to the invention, the proposed camshaft adjuster has at least one artificial muscle. In this case, the housing element and the adjuster shaft element are coupled by means of this at least one artificial muscle in such a way that upon activation of the artificial muscle not only the muscle changes its geometric shape, but a rotation of the Verstellwellenelements is realized with respect to the housing element.

The change in the position of the camshaft relative to the crankshaft is caused by the change in the geometric shape of the artificial muscle.

The known from the prior art disadvantages omitted when using the camshaft adjuster according to the invention. The material of which the artificial muscles are formed is of a lower specific gravity than conventional materials for the production of camshaft adjusters, so that the inventive camshaft adjuster formed using an artificial muscle is lighter than a conventional adjusting device. This reduces the masses of the camshaft or valve train and the dynamic mass forces caused by the rotation of the adjusting elements.

The number of components can also be reduced by using artificial muscles. Thus, the adjuster according to the invention compared to the adjusting device described in DE 198 50 947 A1 has significantly fewer components, which not only reduces the production costs, but further reduces the dead weight and leads to a relatively small component volume, whereby the most effective packaging is supported ,

By the use of an artificial muscle for the formation of the camshaft adjuster, the first object underlying the invention is thus achieved, namely to provide a camshaft adjuster, with which the known disadvantages of the prior art are overcome, and is in particular less expensive, a smaller space requirement and a lower dead weight than conventional adjusting devices.

Further advantageous embodiments are discussed in connection with the subclaims.

Embodiments of the camshaft adjuster in which a drive wheel is provided on the housing element are advantageous. The housing member is rotated by the crankshaft by means of this drive wheel and a drive means engaged with the drive wheel. The In turn, the adjuster shaft element is entrained by the housing element, with which it is coupled via the artificial muscle, and thereby sets the camshaft in rotation.

Embodiments of the camshaft adjuster in which the drive wheel is a belt pulley and the housing element is connected to the crankshaft by means of a belt are advantageous.

Embodiments of the camshaft adjuster in which the drive wheel is a sprocket and the housing element is connected to the crankshaft by means of a chain are also advantageous.

To drive the camshaft belt drives or chain drives are preferably used, which in addition to a plurality of gears also have a belt or a chain as a drive means. These drives make it possible to combine the drive of several ancillary units in a belt or chain drive. The belt drive or chain drive is to transmit a large torque from the crankshaft to the camshaft with minimum energy loss and with the least possible maintenance by retightening.

Embodiments of the camshaft adjuster in which the adjuster shaft element is connected to the housing element by means of the at least one artificial muscle are advantageous in that a rotation of the adjuster shaft element relative to the housing element can be realized by activation of the artificial muscle. In this embodiment, the artificial muscle forms an independent component, which connects the Verstellwellenelement with the housing element and rotated against each other when it changes due to its activation - in the context of a transformation process - the outer shape.

Embodiments of the camshaft adjuster in which the adjuster shaft element has a cantilever projecting radially outwards, to which the at least one artificial muscle is articulated by one end, are advantageous is, wherein the other end of the at least one artificial muscle is articulated on the housing element.

The outwardly projecting boom is a lever that brings several advantages with it. On the one hand, the lever ratio ensures that already relatively small forces generated in the artificial muscle are sufficient to produce the torque required for the rotation of the camshaft. On the other hand, it is achieved with the cantilever that the artificial muscle can be arranged further apart from the axis of rotation, which is advantageous since the point of articulation during the activation or deactivation of the artificial muscle describes a circular path around the axis of rotation and with increasing radius the movement of the artificial muscle Anlenkpunktes increasingly resembles a translational movement or comes closer. The boom also supports the use of artificial muscles that expand or contract upon activation or deactivation, or otherwise change their outer shape substantially along a straight line. Finally, the boom also ensures a favorable force into the muscle and the interconnected by the muscle components. This preferred embodiment
will be explained in more detail below in connection with the description of the figures.

In this context, embodiments of the camshaft adjuster in which the housing element has an inwardly open recess in which the at least one artificial muscle is articulated to the other end are advantageous.

The recess allows one hand, relatively large lever ratios and long boom with a comparatively small component volume, since the length of the boom can be increased without the diameter of the housing element needs to be increased. On the other hand, it allows an advantageous attachment or articulation of the other end of the at least one artificial muscle, which can be clamped or arranged between the arm and the side wall of the recess.

Advantageous embodiments of the camshaft adjuster, in which two artificial muscles are provided, which are articulated on opposite sides of the cantilever with one end and are articulated in each case with the other end in the recess. This embodiment uses two artificial muscles, which reinforce each other and with which consequently greater Verstellkräfte or moments can be generated. The muscle pair can then be a muscle that expands when activated, and a muscle that contracts when activated so that upon activation of both muscles, one muscle pulls on the cantilever while the other muscle pushes the cantilever away.

Embodiments of the camshaft adjuster in which the at least one artificial muscle expands upon activation and in this way brings about a rotation of the adjuster shaft element relative to the housing element are advantageous.

Embodiments of the camshaft adjuster in which the at least one artificial muscle contracts when activated and in this way brings about a rotation of the adjuster shaft element relative to the housing element are also advantageous.

Embodiments of the camshaft adjuster in which the at least one artificial muscle changes its external shape when activated and in this way brings about a rotation of the adjuster shaft element relative to the housing element are also advantageous.

The three last-mentioned embodiments will be explained in more detail in connection with the description of the figures.

The formation of a camshaft adjuster according to the invention can be carried out using shape memory materials that change when activated, for example, from a straight-line shape into a curved or kinked shape or vice versa and thereby lead to a rotation of the camshaft relative to the crankshaft. Some shape memory materials also offer the advantage that they are multi-level changeable ie not just between two outer shapes can be transformed but assume more than two different configurations.

Embodiments of the camshaft adjuster in which the at least one artificial muscle comprises carbon nanotubes are advantageous. Such artificial muscle elements are characterized by their high heat resistance up to 1000 ° C, which is why they are extremely suitable for use in an internal combustion engine which is exposed to high thermal loads. Furthermore, such muscle elements can be controlled by electrical energy (see Science of 21.05.1999), which can be done in a simple manner by the on-board battery. Upon activation, carbon nanotubes expand.

Carbon nanotubes can be bundled in paper-like multi-layer structures and allow significant curvature of the entire muscle structure. They are also characterized by a low ratio of expansion to contraction, which is considered to be advantageous.

However, embodiments of the camshaft adjuster in which the at least one artificial muscle comprises at least one polymer gel are also advantageous. Artificial muscles based on polymer hydrogels can be controlled by electrical signals and contract upon activation (see Low, LW; Madou, MJ "Microactuators Towards Microvalves for Controlled Drug Delivery", Sensors and Actuators B: Chemical, 67 (1). 2) (2000) pp. 149-160).

In principle, however, artificial muscles can be used, which are both an active - d. H. allow for activation - contraction as well as active expansion.

Embodiments of the camshaft adjuster in which the at least one artificial muscle comprises at least one shape memory material are also advantageous.

Shape memory materials per se - so-called shape memory materials or shape memory alloys - have been known for more than fifty years. You own the Ability to change their external shape depending on the temperature, the magnetic field strength or the hydraulic pressure to which they are subjected or the like. Within the scope of the present invention, the shape memory materials include all materials which have a shape memory, in particular the shape memory alloys such as NiTi (nitinol), Fe-Pt, Cu-Al-Ni, Fe-Pd, Fe-Ni, Cu-Zn. Al, CuAlMn, but also ceramics with shape memory, such as Ce-TZP ceramic.

For example, a paper clip formed from an elongate wire may change shape such that the paperclip, placed in a pot of hot water, returns to its original shape with increasing temperature and upon reaching a so-called transition temperature T '. H. takes the form of an elongated wire. It changes its external shape or, in other words, its structural configuration.

If this transformation process is reversible, the shape memory material is a so-called two-way shape memory material, otherwise a one-way shape memory material. In addition, there are materials that have more than two structures that they can accept upon activation and are therefore multi-stage switchable.

Consequently, the above-described transition of the paper clip into an elongated wire could be reversed, with proper selection of a two-way shape memory material. For this purpose, the temperature is lowered, whereby the wire transforms into a paperclip when the temperature drops below a transition temperature T. The activation by temperature change is to be understood only as an example In the present case - a camshaft adjuster made using shape memory materials - electrical activation is more likely suitable as a thermal activation.

The formation of a camshaft adjuster according to the invention requires at least a two-way shape memory material, so that the transformation process can be reversed and the camshaft adjuster is switchable at least between two positions; the Camshaft can thus be rotated relative to the crankshaft and this rotation is reversed again in the reverse direction.

Embodiments of the camshaft adjuster in which the at least one artificial muscle is electrically controllable are advantageous. In particular, the mechanical energy generated by the muscle element can originate from the electrical energy of the signal. Electrically controlled artificial muscle elements have the advantage that they are compatible with the usual control technology of an internal combustion engine.

Embodiments of the camshaft adjuster in which the at least one artificial muscle is stepwise controllable, in particular two-stage, are advantageous. Such a configuration of the camshaft adjuster facilitates the control, especially when the artificial muscle is functioning according to an on-off circuit d. H. only from a deactivated state - rest position - to an activated state - working position - changes and vice versa. Complex maps need not be generated and provided in this embodiment, as is required for example in continuously controllable artificial muscle elements or camshaft adjusters.

However, embodiments of the camshaft adjuster in which the at least one artificial muscle can be steplessly controlled are also advantageous under other aspects. This allows an optimized adjustment of the timing at the respective operating point of the internal combustion engine, whereby the potential of the camshaft adjuster can be fully utilized, which is only partially possible with a stepwise adjustment.

The second sub-task on which the invention is based is achieved by a method for changing the position of the camshaft relative to the crankshaft of an internal combustion engine, wherein the valve timing is adjusted by using a camshaft adjuster with an outer housing element and an inner adjuster shaft element arranged at least partially in the housing element the internal combustion engine are adjusted, wherein the housing element by means of a drive with the Crankshaft of the internal combustion engine and the Verstellwellenelement is connected to the camshaft of the internal combustion engine and housing element and Verstellwellenelement are rotated against each other, and which is characterized in that the camshaft adjuster is provided with at least one artificial muscle and twisted by an activation of the artificial muscle, the Verstellwellenelements against the housing element is and thus a change in the camshaft position relative to the crankshaft is realized.

What has already been said for the camshaft adjuster according to the invention also applies to the method according to the invention.

Embodiments of the method are advantageous in which the control times of the intake valves of the internal combustion engine are retarded by activation of the at least one artificial muscle.

Thus, for example, the valve overlap can be reduced at low speeds. Because a shift in the timing of the intake valves in the proposed manner leads to a later opening of the intake valves and thus to a reduction of the crank angle window in which the exhaust valve is not closed when the inlet valve is open.

As already stated in the introduction to the description, the filling time of the combustion chamber and thus the torque characteristic of the internal combustion engine can be influenced with the control time at which the inlet valve is closed. In particular, at high speeds, it is advantageous to shift the closing time of the intake valves late and thereby ensure good cylinder filling.

Also advantageous are embodiments of the method in which the timing of the intake valves of the internal combustion engine are increasingly adjusted with increasing speed to late.

Too early closing of the intake valves leads at high speeds, in particular at the rated speed, to unwanted filling losses. In order to ensure a good filling of the combustion chamber in this speed range, the intake valves are therefore preferably closed late at high speeds. Preferably, this process is continuous.

Also advantageous are embodiments of the method in which the timing of the intake valves of the internal combustion engine are increasingly adjusted with increasing load to late.

About the control time "inlet closes" can - as mentioned - control the cylinder filling and thus the load. The change in the closing time of the intake valves is a possibility to realize a thermodynamically advantageous manner, a quantity control and at the same time to provide a Entdrosselung the internal combustion engine.

Also advantageous for the above reasons, embodiments of the method in which the activation of the at least one artificial muscle, the timing of the intake valves of the internal combustion engine are adjusted to early.

Thus, the valve overlap can be increased at high speeds. Moving the timing of the intake valves early leads to earlier opening of the intake valves and thus to an increase in the crank angle window in which the exhaust valve is not yet closed when the intake valve is open. Although this leads to poorer efficiencies at high speeds as a result of flushing losses, but also to a better filling of the combustion chamber with fresh mixture and thus to a higher performance.

Advantageous embodiments of the method in which the timing of the intake valves of the internal combustion engine are increasingly adjusted with decreasing speed to early.

At low speeds, it is advantageous to close the intake valve early to prevent expulsion of the freshly aspirated cylinder charge and to avoid charge losses at low speeds.

Also advantageous are embodiments of the method in which the timing of the intake valves of the internal combustion engine are increasingly adjusted with decreasing load to early.

In this process variant, the closing time of the intake valves is used for load control. At low load, less fresh mixture is needed, which is why the inlet valves are preferably closed earlier with decreasing load. This also contributes to a Entdrosslung the internal combustion engine.

Fig. 1

einen Nockenwellenversteller nach dem Stand der Technik im Querschnitt,

Fig. 2a

eine erste Momentaufnahme einer ersten Ausführungsform des Nockenwellenverstellers im Querschnitt,

Fig. 2b

eine zweite Momentaufnahme der in Figur 2a dargestellten ersten Ausführungsform des Nockenwellenverstellers,

Fig. 2c

eine dritte Momentaufnahme der in Figur 2a dargestellten ersten Ausführungsform des Nockenwellenverstellers,

Fig. 3a

eine erste Momentaufnahme einer zweiten Ausführungsform des Nockenwellenverstellers im Querschnitt,

Fig. 3b

eine zweite Momentaufnahme der in Figur 3a dargestellten zweiten Ausführungsform des Nockenwellenverstellers,

Fig. 3c

eine dritte Momentaufnahme der in Figur 3a dargestellten zweiten Ausführungsform des Nockenwellenverstellers,

Fig. 4a

eine erste Momentaufnahme einer dritten Ausführungsform des Nockenwellenverstellers im Querschnitt,

Fig. 4b

eine zweite Momentaufnahme der in Figur 4a dargestellten dritten Ausführungsform des Nockenwellenverstellers, und

Fig. 4c

eine dritte Momentaufnahme der in Figur 4a dargestellten dritten Ausführungsform des Nockenwellenverstellers.

In the following the invention will be described in more detail with reference to three embodiments according to Figures 1 to 4c. Hereby shows:

Fig. 1

a phaser according to the prior art in cross-section,

Fig. 2a

a first snapshot of a first embodiment of the camshaft adjuster in cross section,

Fig. 2b

2 is a second snapshot of the first embodiment of the camshaft adjuster shown in FIG. 2a,

Fig. 2c

3 shows a third snapshot of the first embodiment of the camshaft adjuster shown in FIG. 2a,

Fig. 3a

a first snapshot of a second embodiment of the camshaft adjuster in cross section,

Fig. 3b

2 shows a second snapshot of the second embodiment of the camshaft adjuster shown in FIG. 3a,

Fig. 3c

3 shows a third snapshot of the second embodiment of the camshaft adjuster shown in FIG. 3a,

Fig. 4a

a first snapshot of a third embodiment of the camshaft adjuster in cross section,

Fig. 4b

a second snapshot of the third embodiment of the camshaft adjuster shown in Figure 4a, and

Fig. 4c

a third snapshot of the third embodiment of the camshaft adjuster shown in Figure 4a.

FIG. 1 has already been explained in connection with the description of the prior art.

Figures 2a, 2b and 2c show a first embodiment of the camshaft adjuster 1 in cross section.

Figure 2a shows schematically in cross section a first embodiment of the camshaft adjuster 1 in the deactivated state. The camshaft adjuster 1 has an outer housing element 2 and an inner adjuster shaft element 3, which is arranged at least partially in the housing element 2. On the housing element 2, a drive wheel 4 in the form of a pulley 4 is provided, with which the housing element 2 is connected by means of a belt to the crankshaft of the internal combustion engine and with which the housing element 2 is rotated. The adjuster shaft member 3 is rotatably connected to the camshaft of the internal combustion engine (not shown).

The housing element 2 and the adjuster shaft element 3 are rotatable relative to one another, wherein these two components 2, 3 are coupled by means of an artificial muscle 11a. In the embodiment illustrated in FIG. 2a, the artificial muscle 11a forms an independent component, which connects the adjuster shaft element 3 to the housing element 2 and is rotated relative to one another as a result its activation - in the context of a transformation process - changes the outer shape, as seen in Figures 2b and 2c.

The adjuster shaft element 3 has a radially outwardly projecting arm 6, to which the artificial muscle 11a is articulated with one end 9a, wherein the other end 10 of the artificial muscle 11a is hinged to the side wall 8 of an inwardly open recess 7 of the housing element 2 ,

The outwardly protruding boom 6 is a lever with which due to the leverage already small, generated in the artificial muscle 11a forces sufficient to produce the required torque for the rotation of the adjuster shaft 3 and the camshaft. In addition, the boom 6 allows the artificial muscle 11a to be positioned farther apart from the rotation axis 5, which is advantageous since the articulation point 9a describes a circular path about the rotation axis 5 when the artificial muscle 11a is activated or deactivated, and becomes larger in radius the movement of the articulation point 9a increasingly resembles or comes closer to a translatory movement.

The boom 6 also supports the use of artificial muscles 11a, which upon activation or deactivation expand or contract or otherwise change their outer shape substantially along an imaginary line. Finally, the boom 6 also ensures a favorable introduction of force into the artificial muscle 11a.

The recess 7 allows relatively large leverage or long boom 6 at a comparatively small component volume, since the length of the boom 6 is increased without the diameter of the housing element 2 must be increased. In addition, the recess 7 allows an advantageous attachment or articulation of the other end 10a of the artificial muscle 11a, which is arranged between the arm 6 and the side wall 8 of the recess 7.

According to the invention, the camshaft adjuster 1 is equipped with an artificial muscle 11a, which changes its geometric shape by activation. In the embodiment shown in Figure 2a, the camshaft adjuster 1 is under Use of carbon nanotubes has been formed. Carbon nanotubes expand upon activation, as shown in FIGS. 2b and 2c, and can be controlled electrically, which makes them suitable for use in engine construction since they can be easily supplied with electrical energy via the on-board battery.

FIGS. 2 b and 2 c show the camshaft adjuster 1 schematically in cross section and in an activated state, wherein the artificial muscle 11 a is expanded in comparison to the snapshot illustrated in FIG. 2 a. The carbon nanotubes are activated and expanded along an imaginary line, whereby the housing element 2 and the Verstellwellenelement 3 are rotated against each other. Thereby, the timing of the valves of the internal combustion engine can be changed, i. be moved to early or late because with the adjuster shaft 3 and the camshaft is rotated relative to the crankshaft.

Similar effects are obtained with artificial muscles 11a, which contract upon activation, for example with polymer gel. FIG. 2c would then represent the deactivated state, while FIGS. 2a and 2b show an activated and contracted state of the artificial muscle 11a, ie exactly the reverse of the embodiment of an expanding on activation artificial muscle 11a.

Figures 3a, 3b and 3c show a second embodiment of the camshaft adjuster 1 in cross section. Only the differences from the first embodiment will be discussed, for which reason reference is otherwise made to FIGS. 2a, 2b and 2c. The same reference numerals have been used for the same components.

In contrast to the first embodiment, in the camshaft adjuster 1 shown in FIGS. 3 a, 3 b and 3 c, a second artificial muscle 11 b is provided which is articulated with one end 9 b with respect to the first artificial muscle 11 a on the opposite side of the arm 6 and hinged to the other end 10b in the recess 7.

By a suitable selection of two artificial muscles 11a, 11b or by a purposeful coordinated control of the two muscles 11a, 11b it can be achieved that the muscles reinforce each other and larger adjusting forces or moments can be generated.

As a pair of muscles, a muscle 11a may then be used which comprises, for example, carbon nanotubes and expands upon activation, and a muscle 11b, for example having a polymer gel and contracting on activation, so that upon activation of both muscles 11a, 11b, a muscle 11b is attached the boom 6 pulls while the other muscle 11a pushes the boom 6, as shown in Figures 3b and 3c. FIG. 3a then shows the camshaft adjuster 1 with deactivated muscles 11a, 11b.

Alternatively, two similar artificial muscles 11a, 11b may be used, which are controlled separately. The first muscle 11a is activated while the second muscle 11b remains deactivated and vice versa, which leads to the positions of the camshaft adjuster 1 shown in FIGS. 3a and 3c. The central position shown in Figure 3b could then be achieved by half activating both muscles 11a, 11b, which can be achieved with multi-stage or continuously variable artificial muscles 11a, 11b.

Figures 4a, 4b and 4c show a third embodiment of the camshaft adjuster 1 in cross section. Only the differences from the first embodiment will be discussed, for which reason reference is otherwise made to FIGS. 2a, 2b and 2c. The same reference numerals have been used for the same components.

In contrast to the first embodiment, in the camshaft adjuster 1 illustrated in FIGS. 4 a, 4 b and 4 c, an artificial muscle 11 a is provided that has been formed using shape memory materials.

In the deactivated state, the artificial muscle 11a has an angled shape and thus a small length (FIG. 4a), ie the distance between the two articulation points 9a, 10a is low. On the other hand, the artificial muscle 11a stretches upon activation, so that the artificial muscle 11a assumes an increasingly oblong shape in the activated state, as shown in FIGS. 4b and 4c.

A two-way shape memory material was used so that the transformation process of the muscle 11a is reversible and valve timing can be retarded early and retarded. The artificial muscle 11a can be shortened and lengthened, ie, it can be changed as desired between the different structural configurations.

reference numeral

1

Phaser

2

housing element

3

Verstellerwellenelement

4

Drive wheel, pulley

5

axis of rotation

6

boom

7

recess

8th

sidewall

9a

an end of the artificial muscle, articulation point

9b

an end of the artificial muscle, articulation point

10a

other end of the artificial muscle, articulation point

10b

other end of the artificial muscle, articulation point

11a

artificial muscle

11b

artificial muscle

State of the art:

100

adjustment

110

pulley

112

housing cover

114

first intermediate element

116

gearing

118

piston device

120

first counter toothing

122

second gearing

124

second intermediate element

126

second counter-toothing

128

camshaft

132

adjusting chamber

134

adjusting chamber

136

management

138

management

Claims (25)

Camshaft adjuster (1) - for rotating a camshaft ie for changing the position of the camshaft relative to the crankshaft for the purpose of adjusting the timing of an internal combustion engine - with an outer housing element (2) and with an inner, at least partially in the housing element (2) arranged Verstellwellenelement (3 ), wherein the housing element (2) by means of a drive with the crankshaft of the internal combustion engine and the Verstellwellenelement (3) is connected to the camshaft of the internal combustion engine and the housing element (2) and Verstellwellenelement (3) are rotated against each other,
characterized in that
the camshaft adjuster (1) comprises at least one artificial muscle (11a) which by activation changes its geometric shape in such a way that a rotation of the adjuster shaft element (3) relative to the housing element (2) and thus a change of the camshaft position relative to the crankshaft can be realized , Camshaft adjuster (1) according to claim 1,
characterized in that
on the housing element (2) a drive wheel (4) is provided. Camshaft adjuster (1) according to claim 2,
characterized in that
the drive wheel (4) is a belt pulley (4) and the housing element (2) is connected to the crankshaft by means of a belt. Camshaft adjuster (1) according to claim 2,
characterized in that
the drive wheel (4) is a sprocket and the housing element (2) is connected to the crankshaft by means of a chain. Camshaft adjuster (1) according to one of the preceding claims,
characterized in that
the adjuster shaft element (3) is connected to the housing element (2) by means of the at least one artificial muscle (11a, 11b) in such a way that a rotation of the adjuster shaft element (3) relative to the housing element (11a, 11b) is activated by activation of the artificial muscle (11a, 11b). 2) is feasible. Camshaft adjuster (1) according to claim 5,
characterized in that
the adjuster shaft element (3) has a radially outwardly projecting arm (6) to which the at least one artificial muscle (11a, 11b) is articulated with one end (9a, 9b), the other end (10a, 10b) of the at least an artificial muscle (11a, 11b) is articulated on the housing element (2). Camshaft adjuster (1) according to claim 6,
characterized in that
the housing element (2) has an inwardly open recess (7) into which the at least one artificial muscle (11a, 11b) is articulated to the other end (10a, 10b). Camshaft adjuster (1) according to claim 7,
characterized in that
two artificial muscles (11a, 11b) are provided, which are articulated on opposite sides of the arm (6) with one end (9a, 9b) and in each case with the other end (10a, 10b) articulated in the recess (7). Camshaft adjuster (1) according to one of the preceding claims,
characterized in that
the at least one artificial muscle (11a, 11b) expands upon activation and in this way brings about a rotation of the adjuster shaft element (3) relative to the housing element (2). Camshaft adjuster (1) according to one of claims 1 to 8,
characterized in that
the at least one artificial muscle (11 a, 11 b) contracts on activation and in this way causes a rotation of the adjuster shaft element (3) relative to the housing element (2). Camshaft adjuster (1) according to one of claims 1 to 8,
characterized in that
the at least one artificial muscle (11a, 11b) changes its outer shape when activated and in this way brings about a rotation of the adjuster shaft element (3) relative to the housing element (2). Camshaft adjuster (1) according to one of claims 1 to 9,
characterized in that
the at least one artificial muscle (11a, 11b) comprises carbon nanotubes. Camshaft adjuster (1) according to one of claims 1 to 8 or 10,
characterized in that
the at least one artificial muscle (11a, 11b) comprises at least one polymer gel. Camshaft adjuster (1) according to one of claims 1 to 8 or 11,
characterized in that
the at least one artificial muscle (11a, 11b) comprises at least one shape memory material. Camshaft adjuster (1) according to one of the preceding claims,
characterized in that
the at least one artificial muscle (11a, 11b) is electrically controllable. Camshaft adjuster (1) according to one of the preceding claims,
characterized in that
the at least one artificial muscle (11a, 11b) is stepwise controllable. Camshaft adjuster (1) according to claim 16,
characterized in that
the at least one artificial muscle (11a, 11b) is switchable in two stages. Camshaft adjuster (1) according to one of claims 1 to 15,
characterized in that
the at least one artificial muscle (11a, 11b) is infinitely controllable. Method for changing the position of the camshaft relative to the crankshaft of an internal combustion engine, in which using a camshaft adjuster (1) with an outer housing element (2) and with an internal, at least partially in the housing element (2) arranged adjuster shaft element (3), the timing of the Valves of the internal combustion engine to be adjusted, wherein the housing element (2) by means of a drive with the crankshaft of the internal combustion engine and the Verstellwellenelement (3) is connected to the camshaft of the internal combustion engine and housing element (2) and Verstellwellenelement (3) are rotated against each other,
characterized in that
the camshaft adjuster (1) is provided with at least one artificial muscle (11a, 11b) and, by activation of the artificial muscle (11a, 11b), the adjuster shaft element (3) is rotated relative to the housing element (2) and thus a change in the camshaft position relative to the camshaft position Crankshaft is realized. Method according to claim 19,
characterized in that
by an activation of the at least one artificial muscle (11a, 11b), the timing of the intake valves of the internal combustion engine are retarded. Method according to claim 20,
characterized in that
the timing of the intake valves of the internal combustion engine are increasingly retarded with increasing speed. Method according to claim 20 or 21,
characterized in that
the timing of the intake valves of the internal combustion engine are increasingly retarded with increasing load. Method according to claim 19,
characterized in that
by an activation of the at least one artificial muscle (11a, 11b), the timing of the intake valves of the internal combustion engine are adjusted to early. Method according to claim 23,
characterized in that
the timing of the intake valves of the internal combustion engine are increasingly adjusted with decreasing speed to early. Method according to claim 23 or 24,
characterized in that
the timing of the intake valves of the internal combustion engine are increasingly adjusted with decreasing load to early.

Images