WO2020181310A1

WO2020181310A1 - System and method for adjusting an effective length of a connecting rod with an adjustable length

Info

Publication number: WO2020181310A1
Application number: PCT/AT2020/060066
Authority: WO
Inventors: Siegfried Lösch; Helmut Melde-Tuczai; Martin Rath; Mirko NATHER
Original assignee: Avl List Gmbh
Priority date: 2019-03-08
Filing date: 2020-03-06
Publication date: 2020-09-17
Also published as: AT522071B1; AT522071A4

Abstract

The invention relates to a system (1) for adjusting an effective length of a connecting rod (2) with an adjustable length for a reciprocating piston machine. In this case, the connecting rod (2) has at least a first connecting rod part (3) and a second connecting rod part (4), which connecting rod parts can be shifted in the direction of a longitudinal axis (2a) of the connecting rod parts (3, 4) and/or one inside the other by means of a length adjustment device (5). The reciprocating piston machine has at least one reciprocating piston (6) which oscillates along a reciprocating piston longitudinal axis (6a). A crank drive (7) converts the oscillating movement of the reciprocating piston (6) into a rotational movement of a drive shaft (8) by means of the connecting rod (2). The system (1) has an angle adjustment device (9) which is configured to set a defined angle β, 0° < β ≤ 45°, preferably 4° ≤ β ≤ 45°, between the connecting rod part longitudinal axis (2a) and the reciprocating piston longitudinal axis (6a) as long as the reciprocating piston machine is in an idle mode or is adjusted to an idle mode. The invention also relates to a method (100, 200) for setting an effective length of a connecting rod (2) with an adjustable length for a reciprocating piston machine. The reciprocating piston machine has an angle adjustment device (9) which carries out at least the following method steps: determining an operating mode of the reciprocating piston machine (101, 201); and if the reciprocating piston machine is in an idle mode, acting (102, 202) on the reciprocating piston machine so that an angle β between the connecting rod part longitudinal axis (2a) and the reciprocating piston longitudinal axis (6a) is set to 0° < β ≤ 45°, preferably 4° ≤ β ≤ 45°

Description

System and method for setting an effective length of a

length adjustable connecting rod

The invention relates to a system for setting an effective length of a length-adjustable connecting rod for a reciprocating piston engine, in particular an internal combustion engine. The invention also relates to a method for setting an effective length of a length-adjustable connecting rod.

Reciprocating piston engines, in particular internal combustion engines, generally have at least one reciprocating piston which oscillates along a reciprocating piston longitudinal axis in an operating mode. A crank drive converts the oscillating movement of the reciprocating piston by means of a connecting rod into a rotational movement of a drive shaft.

In order to increase the efficiency of reciprocating piston engines, it is known to equip them with variable compression ratios. To achieve this, length-adjustable connecting rods can be used. These preferably have a first connecting rod part and a second connecting rod part, which are moved towards and / or into each other by means of a length adjustment device, preferably by means of a hydraulic cylinder, in the direction of a connecting rod part longitudinal axis of the connecting rod parts, in particular telescopically.

If such two-part connecting rods do not have an anti-rotation device, the connecting rod part of the connecting rod that is connected to the reciprocating piston - together with the reciprocating piston - can rotate against the other connecting rod part when the reciprocating piston engine is in a sleep mode. If the reciprocating piston machine is put back into operation in such a twisted state, this can damage the components. For example, the connecting rod can bend or break, or the reciprocating piston can jam in a cylinder.

It is the object of the invention to provide an improved system and an improved method for setting an effective length of a length-adjustable connecting rod for a reciprocating piston engine. In particular, it is an object of the invention to minimize the risk of damage to the components, in particular the connecting rod parts, the reciprocating pistons or cylinders. This object is achieved by a system according to claim 1 and a method according to claim 14. Advantageous embodiments are claimed in the dependent claims. The teaching of the claims is hereby made part of the description.

A first aspect of the invention relates to a system for setting an effective length of a length-adjustable connecting rod for a reciprocating piston engine, in particular an internal combustion engine, having an angle setting device which is designed to set a defined angle ß, 0 ° <ß <45 °, preferably 4 ° < ß <45 °, to be set between the longitudinal axis of the connecting rod and the longitudinal axis of the reciprocating piston, as long as the reciprocating piston engine is in an idle mode or is being brought.

A second aspect of the invention relates to a method which is preferably carried out by means of a system according to the first aspect of the invention, comprising the following work steps:

Determining an operating mode of a reciprocating piston machine; and, when the reciprocating piston machine is in a sleep mode, acting on the reciprocating piston machine so that an angle β between the longitudinal axis of the connecting rod and the longitudinal axis of the reciprocating piston is set to 0 ° <β <45 °, preferably 4 ° <β <45 °.

A rest mode within the meaning of the invention is preferably present when a reciprocating piston engine, in particular an internal combustion engine, is not in drive mode, in particular combustion mode, and in particular does not convert any chemical energy from a fuel into kinetic energy.

A connecting rod longitudinal axis within the meaning of the invention is preferably one

Axis of symmetry of at least two connecting rod parts of a length-adjustable connecting rod, around which the connecting rod parts can preferably rotate relative to one another if rotation is not prevented by an anti-rotation device.

A reciprocating piston longitudinal axis within the meaning of the invention is preferably one

Axis of symmetry of a cylinder or a reciprocating piston around which the reciprocating piston can rotate in the cylinder, especially if this is not done by a

Anti-twist protection is prevented. A length adjustment device within the meaning of the invention is preferably a device which makes it possible to change an effective length of a connecting rod. This can be done hydraulically, for example, by means of a hydraulic cylinder. A mechanical adjustment of the length, for example by means of an eccentric, is also possible. The length adjustment can also be implemented using electrical components, for example using a linear motor. A length adjustment takes place in particular in the direction of the longitudinal axis of the connecting rod.

An angle adjustment device in the sense of the invention preferably enables the reciprocating piston engines to act in the idle mode or when switching to idle mode such that a defined angle β is set between a longitudinal axis of the connecting rod and a longitudinal axis of the reciprocating piston. This can in particular be done hydraulically or pneumatically by means of a hydraulic / pneumatic cylinder. In particular, the angle setting can also be implemented by means of electrical components, for example by means of an electric motor. The angle adjustment device can preferably be designed as a hardware and / or software component or components. The angle adjustment device preferably uses components that are already present in a reciprocating piston engine or a drive train.

The invention is based in particular on the knowledge that twisting of the connecting rod parts relative to one another can be prevented by a suitable position of the connecting rod. The degrees of freedom of the connecting rod are specifically restricted by the bearings on the large and small connecting rod eyes and defined positions of the connecting rod. If, in the idle mode of the reciprocating piston engine, an angle ß, 0 ° <ß <45 °, preferably 4 ° <ß <45 °, is set between the longitudinal axis of the connecting rod and the longitudinal axis of the piston, this prevents - due to the degrees of freedom of the mechanical components - the first connecting rod part can rotate relative to the second connecting rod part. In the drive mode of the reciprocating piston machines, connecting rod parts do not twist - even without a rotation lock - due to the permanent movement of the reciprocating piston machines.

In other words, it was recognized that due to the locking effect of the bearings in the large and small connecting rod eyes, when the reciprocating piston machines are in rest mode, an angle ß, 0 ° <ß <45 °, preferably 4 ° <ß <45 °, between the longitudinal axis of the connecting rod and adjust the reciprocating piston longitudinal axis in order to prevent the connecting rod parts from twisting relative to one another.

A mechanical anti-rotation device, for example in the form of a groove between the reciprocating piston and the cylinder or between the first and second connecting rod part, is not required with the invention. This has the advantage that no additional components - such as anti-rotation devices, guides or the like - have to be attached to the reciprocating piston and connecting rod. This reduces the weight of the moving parts and lowers the manufacturing costs. In addition, the susceptibility to wear caused by such additional components is prevented.

The angle setting device can preferably determine the operating mode of the reciprocating piston machine by accessing a control of the reciprocating piston machine, in particular an engine control, and / or by means of a sensor. By setting the angle β between the longitudinal axis of the connecting rod and the longitudinal axis of the reciprocating piston in the rest mode, it is prevented that the connecting rod parts can rotate relative to one another.

In an advantageous embodiment of the system, the angle setting device has a drive and a control unit and is in particular set up in such a way that the angle β is set via the drive shaft. If the angle β is set via the drive shaft, this has the advantage that the drive can, for example, be fixedly attached to a housing wall of the reciprocating piston engine. This makes it easier to control and supply the drive with energy.

In a further advantageous embodiment of the system, the

Winkeleinstelleinrichtung at least one sensor to adjust the angle ß. An angle sensor is advantageously used. A sensor offers the advantage that the angle can be adjusted as precisely as possible according to the actual position of the reciprocating piston machine.

In a further advantageous embodiment of the system, the

Angle setting device a starter or starter generator of the reciprocating piston machine as a drive and / or a motor controller of the reciprocating piston machine as a control unit and / or at least one sensor of the reciprocating piston machine to set the angle β. This can reduce the costs of the system, since as many existing standard components as possible can be used. In a further advantageous embodiment of the system, the angle setting device has a control unit and a pressure generating unit which are set up in such a way that the angle β is set via a reciprocating piston by means of a defined pressure in a combustion chamber. According to this embodiment, the angle β is thus not set via the drive shaft, but - from the other side - via the reciprocating piston. This has the advantage that existing components of the reciprocating piston engine, such as the reciprocating piston and an associated combustion chamber, can be used to build up a force for setting the angle a.

In a further advantageous embodiment of the system, the pressure generating unit has a compressor and in particular a pressure reservoir. In particular, a compressor of smaller dimensions can be selected through the pressure reservoir, since the pressure of a required amount of fluid can be built up over a longer period of time and can then be used quickly by means of the pressure reservoir.

In a further advantageous embodiment of the system, the control unit is part of an engine control of the reciprocating piston engine. This can reduce the costs of the system, since no additional control unit is necessary.

In a further advantageous embodiment of the system, the angle adjustment device has at least one sensor, in particular a pressure sensor. This makes it easier to set the angle β, since, for example, the actual position of the reciprocating piston in a cylinder can be deduced from the measured pressure.

In a further advantageous embodiment of the system, the reciprocating piston machine has at least two reciprocating pistons, and the angle adjustment device is set up in such a way that the same pressure is applied to at least two reciprocating pistons in order to set the angle β. Reciprocating piston machines generally have several reciprocating pistons above a certain power. So that the angle adjustment device can apply the force required to bring the reciprocating pistons into the desired position, the application of pressure to several or all of the reciprocating pistons is advantageous in this case. In the case of several reciprocating pistons, the angle β of a reciprocating piston is selected such that none of the reciprocating pistons is in a dead center position when the reciprocating piston machine is in a rest mode.

A dead center position within the meaning of the invention is preferably a position in which a reciprocating piston assumes a position in which rotation of a reciprocating piston and an associated first connecting rod part with respect to the corresponding second connecting rod part is possible due to the degree of freedom of guidance and storage. In particular, this is in each case a reversal point of a reciprocating piston, at which it changes its direction of movement.

In a further advantageous embodiment of the system, different pressure ratios are applied to different reciprocating pistons in order to set the angle β. Depending on the construction of the reciprocating piston machine and the number of reciprocating pistons, a more precise setting of the angle β can be achieved.

In a further advantageous embodiment of the system, the angle adjustment device is set up in such a way that the angle β is determined indirectly via an angle a, in particular by means of an angle sensor, with a being spanned by a longitudinal axis of the reciprocating piston and an axis of cranking of an associated reciprocating piston on an associated crank star. In other words, the angle α indicates the position of the drive shaft - including the crank drive - with respect to a reciprocating piston longitudinal axis. The angle α can be measured more easily than the angle β. In order to measure the angle α, an angle sensor can preferably be attached between the drive shaft and a corresponding housing. Possible cabling of the sensor is then preferably carried out via the fixed component of the sensor attached to the housing. In contrast, generally no cost-effective standard angle sensor can be used to measure the angle β, since the connecting rod is moved both translationally and rotationally.

The control unit can determine the angle β by means of the angle α, by means of a connecting rod length L and by means of a stroke radius r of the crank, preferably using the following equation: sin (β) = sin (a) x (r / L). In a further advantageous embodiment of the system, the reciprocating piston engine is a 3-cylinder in-line engine, and the angle α is set to approximately 15 °.

In a further advantageous embodiment of the system, the reciprocating piston engine is a 4-cylinder in-line engine, and the angle α is set to approximately 90 °.

In a further advantageous embodiment of the system, the reciprocating piston engine is a 5-cylinder in-line engine, and the angle α is set to approximately 18 °.

In a further advantageous embodiment of the system, the reciprocating piston engine is a 6-cylinder V-engine, and the angle α is set to approximately 15 °.

In a further advantageous embodiment of the system, the reciprocating piston engine is an 8-cylinder V-engine, and the angle α is set to approximately 45 °.

All of the configurations mentioned in relation to 3- to 8-cylinder engines offer the advantage that no reciprocating piston is in a dead center position in the specified angular position. Rotation of the connecting rod parts relative to one another - in the idle mode of the reciprocating piston engine - is thus prevented and the risk of damage to the components - during operation - is minimized.

In a further advantageous embodiment of the system, the reciprocating engine is a boxer engine, an H engine or a swash plate motor, and the angle β is set such that no reciprocating piston is in a dead center position when the reciprocating engine is at rest. This also prevents the connecting rod parts from twisting with respect to one another and thus damaging components.

In a further advantageous embodiment, the system has an anti-twist device which can fix the system at the required angle α in the idle mode. The anti-rotation device is used in particular for the purpose of transporting the reciprocating piston engine. If the reciprocating piston motor is being transported and neither a drive nor a pressure generating unit are connected, the anti-rotation device can prevent a reciprocating piston from moving into a dead center position. The anti-twist device can in particular be implemented by a bolt. Such a bolt can, for example, connect a flywheel to a housing or a vibration damper or a belt pulley to the housing. The features and advantages described above in relation to the first aspect of the invention also apply correspondingly to the second aspect of the invention and vice versa.

According to a preferred embodiment of the method, the angle adjustment device acts on the combustion chambers of at least two reciprocating pistons each with a defined pressure in order to set the angle β. All combustion chambers are preferably subjected to the same pressure in order to set the angle β. This is technically particularly easy to implement, since, for example, all combustion chambers are connected to a pressure reservoir. The pressure in the combustion chambers creates an equilibrium situation in which no reciprocating piston is in a dead center position.

According to a further preferred embodiment of the method, the

Angle adjustment device set the angle ß using the following steps:

When the reciprocating piston engine is in a rest mode, measuring an angle β between the longitudinal axis of the connecting rod and the longitudinal axis of the reciprocating piston; and

Control in particular a starter or start generator in order to set the angle β via the drive shaft.

In this case, the angle β is not set by applying pressure to the reciprocating piston, but by mechanically setting the drive shaft. This is particularly advantageous when the starter or start generator of the reciprocating piston engine is used as a drive. This means that additional components can be saved.

According to a further preferred embodiment of the method, the

Angle adjustment device also perform the following steps:

Measuring an angle α, where α lies between a longitudinal axis of the reciprocating piston and an axis of cranking of an associated reciprocating piston on an associated crank star; and

Determining the angle ß as a function of angle a, a connecting rod length L and a stroke radius r. This is advantageous because the angle α is technically easier to measure than the angle β. The angle a can, for example, be read off directly between the drive shaft and the motor housing using inexpensive angle sensors. To measure the angle β, more complex sensors are necessary, since the connecting rod moves both in a translatory and in a rotary manner. The control unit then determines the angle β by means of the measured angle α, by means of a determined connecting rod length L and by means of a stroke radius r of the crank: sin (β) = sin (a) x (r / L).

The invention is explained in more detail below with the aid of non-limiting exemplary embodiments which are at least partially shown in the figures. Further features and advantages emerge from these exemplary embodiments in connection with the corresponding figures. It shows at least partially schematically:

1 shows a first embodiment of a system for setting an effective length of a length-adjustable connecting rod for a reciprocating piston engine;

2 shows a crankshaft of a 3-cylinder in-line engine;

3 shows a plan view of a crank star of a 3-cylinder in-line engine according to FIG. 2 after activation of an angle adjustment device;

4 shows a crankshaft of a 4-cylinder in-line engine;

FIG. 5 shows a plan view of a crank star of a 4-cylinder in-line engine according to FIG. 4 after activation of an angle adjustment device; FIG.

6 shows a crankshaft of a 5-cylinder in-line engine;

FIG. 7 shows a plan view of a crank star of a 5-cylinder in-line engine according to FIG. 6 after activation of an angle adjustment device; FIG.

8 shows a crankshaft of a 6-cylinder V-engine; 9 is a plan view of a crank star of a 6-cylinder V-engine according to FIG

8 after activation of an angle adjustment device;

10 shows a crankshaft of an 8-cylinder V-engine;

Fig. 11 is a plan view of a crank star of an 8-cylinder V-engine according to

10 after activation of an angle adjusting device;

12 shows a second exemplary embodiment of a system for setting an effective length of a length-adjustable connecting rod for a

Reciprocating engine; and

13 shows a first exemplary embodiment of a method for setting an effective length of a length-adjustable connecting rod for a

Reciprocating engine, and

14 shows a second exemplary embodiment of a method for setting an effective length of a length-adjustable connecting rod for a

Reciprocating engine.

1 shows a first exemplary embodiment of a system 1 for setting an effective length of a length-adjustable connecting rod 2 for a reciprocating piston engine. The reciprocating piston engine is described below in a non-restrictive and purely exemplary manner as an internal combustion engine.

The internal combustion engine has at least one reciprocating piston 6. In a drive mode of the internal combustion engine, a fuel is burned in a combustion chamber 14 and the reciprocating piston 6 is set in an oscillating movement along a reciprocating piston longitudinal axis 6a in this way. A crank drive 7 converts the oscillating movement of the reciprocating piston 6 into a rotation of a drive shaft 8 (runs normal to the plane of the sheet of FIG. 1). The crank drive 7 in turn has a connecting rod 2 which can be adjusted in length via a length adjustment device 5. The connecting rod 2 has a first connecting rod part 3 and a second connecting rod part 4. The connecting rod parts 3 and 4 are preferably hydraulically displaceable towards one another / into one another along a longitudinal axis 2a of the connecting rod part, in order to set the desired length of the connecting rod 2. When the internal combustion engine is in a sleep mode or is brought into a sleep mode, no more fuel is burned in the combustion chamber 14. Due to the design, the first connecting rod part 3 - together with the reciprocating piston 6 - can rotate against the second connecting rod part 4 when a reciprocating piston longitudinal axis 6a and a connecting rod longitudinal axis 2a are aligned. For example, such a rotation can occur when an internal combustion engine with the structure described is transported in the parked state, for example by train or with a truck.

Rotation of the connecting rod parts 3, 4 could be prevented by a guide or a groove in the length adjustment device 2. In the illustrated embodiment, a solution was chosen which does not necessarily require such a guide to prevent rotation.

Here, a control unit 11 activates a pressure generating unit 13 in the idle mode of the internal combustion engine. The control unit 11 is preferably part of an existing engine control of the internal combustion engine. The pressure generating unit 13 is preferably a compressor. The pressure generating unit 13 applies a defined pressure to the combustion chamber 14 in order to set an angle β between the reciprocating piston longitudinal axis 6a and the connecting rod longitudinal axis 2a through the movement of the reciprocating piston 6 caused thereby. For example, 30 bar with a correspondingly adapted flow rate can be selected as a defined pressure.

It has been found that an angle ß, 4 ° <ß <45 ° is optimal to prevent mutual rotation of the connecting rod parts 3, 4.

In addition to the angle β, an angle α also indicates the position of the reciprocating piston 6 or the position of the crankshaft 8. The angle a lies between a reciprocating piston longitudinal axis 6a and an associated offset axis 15 of an associated reciprocating piston 6. In other words, the angle a indicates the position of the drive shaft 8 - including the crank drive 7 - with respect to a reciprocating piston longitudinal axis 6a. The angles a and ß are dependent on each other, depending on the size of a connecting rod length L and depending on the size of a stroke radius of the offset r: sin (ß) = sin (a) x (r / L). A calculation using sin (ß) = sin (180 ° - a) x (r / L) is also possible.

The internal combustion engine can be a 3-cylinder in-line engine, for example. This has three reciprocating pistons 6 according to FIG. 1, which, as shown in FIG. 2 and FIG of a crank drive 7 are connected to a drive shaft 8. The crankshaft 8 of the crankshaft drive 7 has three crankings - evenly distributed over the circumference - with their respective cranking axes 15.

Preferably, all three reciprocating pistons 6 of the 3-cylinder in-line engine - when this is in a rest mode - are each acted upon by at least essentially the same pressure by means of the pressure generating unit 13. The pressure generates a torque on the crankshaft 8, the magnitude and sign of which depends on the position of the respective offset axis 15 of the individual reciprocating pistons in relation to the connecting rod 2. The reciprocating pistons 6 and thus also the crankshaft 8 then automatically assume that position in which an equilibrium is established between the torques of the three reciprocating pistons. The crankshaft 8 can rotate the respective offset axis 15 through a dead center or turn back through the dead center. This can be either the top or bottom dead center.

A dead center is the position of the reciprocating piston 6 in the respective cylinder, in which an oscillating movement of the reciprocating piston 6 changes the direction of movement. The top dead center is arranged in the direction of the injection valves and the bottom dead center in the direction of the drive shaft.

The pressure generating unit 13 consists for example of a compressor and a pressure reservoir. The pressure reservoir preferably has reservoir inlet valves and reservoir outlet valves. If the pressure reservoir is filled by means of the compressor, the reservoir inlet valves are open, the reservoir outlet valves are closed, and the compressor preferably conveys ambient air into the pressure reservoir. When the required pressure is reached, the reservoir inlet valves are closed and the compressor is switched off.

In order to be able to apply a suitable pressure to the reciprocating pistons 6, in particular cylinder inlet valves and cylinder outlet valves of the respective reciprocating pistons 6 are appropriately controlled. The cylinder inlet valves are used in particular for fuel injection, and the cylinder outlet valves in particular to expel exhaust gases after the combustion process has taken place. The pressurization is preferably carried out by means of the pressure generating unit 13 via at least one partially open cylinder inlet valve, while the cylinder outlet valve or the cylinder outlet valves are at least partially closed. To do this, the Reservoir outlet valves and the cylinder inlet valves open and so do the reciprocating pistons

6 pressurized. Due to the pressurization of the reciprocating pistons 6, an equilibrium position is established between all the reciprocating pistons 6 that are pressurized.

In the case of the 3-cylinder in-line engine, the angle α to be set for the energy minimum is around 15 °. A crank axis 15 of a reciprocating piston 6 of the crank star 16 must assume the aforementioned angle to the reciprocating piston longitudinal axis 6a. This ensures that none of the three reciprocating pistons 6 is in a dead center position or comes to a standstill. Mutual rotation of the connecting rods 3, 4 is thus prevented and damage to the components of the internal combustion engine is avoided when it starts up again.

Alternatively, the reservoir outlet valves can also open directly into the cylinder. In this case, both the cylinder inlet valves and the cylinder outlet valves are closed and then the reservoir outlet valves are opened in order to apply pressure to the reciprocating piston.

The angle setting described above by means of a pressure generating unit 13 can also be used analogously for internal combustion engines with two or even more than three reciprocating pistons. The same pressure is applied to all of the reciprocating pistons 6, and the reciprocating pistons 6 and the crankshaft 7 then independently assume that position in which the pressure energy present in the combustion chambers 14 reaches a minimum.

In a 4-cylinder in-line engine with a crankshaft 8 according to FIG. 4 - as shown in FIG. 5 - the crank star 16 is set in the position of the energy minimum at an angle α of approximately 90 °.

In a 5-cylinder in-line engine with a crankshaft according to FIG. 6, as in FIG.

7 - the crank star 16 is set in the position of the energy minimum at an angle α of approximately 18 °. The five cranks 15 of the reciprocating piston 6 are evenly distributed over the circumference of the crankshaft, which corresponds to a division of 72 ° in each case.

Fig. 8 shows the crankshaft of a 6-cylinder V-engine. Two reciprocating pistons 6 each hang on a common offset axis 15 of a crankshaft 8 The reciprocating piston longitudinal axes 6a of these reciprocating pistons 6 which belong together have a V shape with respect to one another, which intersect the center point of the drive axis 8. The three crank axes 15 are evenly distributed over the circumference of the crankshaft 8, as shown in FIG. 9 on the basis of the crank spider 16. In this case, the angle a lies between a reciprocating piston longitudinal axis 6a and an offset axis 15. The angle is set to an angle a of approximately 15 °.

10 and 11 show an 8-cylinder V-engine crankshaft 8. As in the 6-cylinder V-engine, two reciprocating pistons 6 each hang on a crank axis 15, their reciprocating piston longitudinal axes 6a adopting a V shape with respect to one another. The four cranks 15 of the eight reciprocating pistons 6 are evenly distributed over the circumference of the crankshaft 8. In this case, the angle is set to an angle α of approximately 45 °.

FIG. 12 shows an alternative exemplary embodiment of a system 1 for setting an effective length of a length-adjustable connecting rod. Here, the angle adjustment device 9 is not implemented by means of a pressure generating unit 13, but by means of a drive 10. A starter or start generator of the internal combustion engine is preferably used as the drive 10. An angle sensor 12 preferably measures the position of the crankshaft 8 or the drive shaft 8. A control unit 11 processes the sensor signal and controls the drive 10 in order to set the required angle α or β. In the case of a 4-cylinder in-line engine, the starter rotates the crankshaft to an angle of about 15 °. For a 5-cylinder in-line engine, the value of the angle a should be between about 15 ° and about 18 °. In the case of an 8-cylinder V-engine, turning to a value of the angle α of about 15 ° to about 45 ° would be sufficient.

The aim in all of the cases described is to prevent a reciprocating piston from coming to rest in a dead center position.

The required angle a depends on the number of cylinders and their arrangement. The angle α can thus vary from approximately 15 ° to approximately 90 ° and the corresponding angle β from approximately 4 ° to approximately 45 °.

An exemplary embodiment of a method 100 for setting an effective length of a length-adjustable connecting rod for a 3-cylinder in-line engine is described below with reference to FIG. An angle adjustment device 9 carries out the following work steps: Determining 101 an operating mode of the 3-cylinder in-line engine. This is preferably done by reading out a motor controller.

If it is determined that the 3-cylinder in-line engine is in a sleep mode, the 3-cylinder in-line engine is acted on 102, so that an angle β between the longitudinal axis 2a of the connecting rod and the longitudinal axis 6a of the piston is 0 ° <β <45 °, preferably 4 ° <ß <45 °, is set. For this purpose, all three combustion chambers are subjected to the same pressure 102a, preferably by connecting all three combustion chambers to a pressure reservoir. The pressure in the combustion chambers creates an equilibrium situation in which no reciprocating piston is in a dead center position.

At least one inlet valve per reciprocating piston of the internal combustion engine is preferably kept open or open, 102b, in particular during the application of pressure. More preferably, an outlet valve or outlet valves of the reciprocating piston is or are kept closed or kept closed, 102c, in particular during the application of pressure. Furthermore, all inlet valves and outlet valves of the associated reciprocating piston are preferably closed or kept closed, 102d, when the application of pressure has been completed. The pressure built up cannot escape from the associated combustion chamber 14 and the set angle β between connecting rod longitudinal axis 2a and reciprocating piston longitudinal axis 6a remains set to 0 ° <β <45 °, preferably 4 ° <β <45 °.

A further exemplary embodiment of a method 200 for setting an effective length of a length-adjustable connecting rod for a 3-cylinder in-line engine is described below with reference to FIG. An angle adjustment device 9 carries out the following work steps:

Determination 201 of an operating mode of the 3-cylinder in-line engine. This is preferably done by reading out a motor controller.

If it is determined that the 3-cylinder in-line engine is in a sleep mode, an angle a is measured, in particular by means of an angle sensor a indicates the position of a reciprocating piston 6 or the position of a crankshaft 8. The angle a lies between a reciprocating piston longitudinal axis 6a and an associated offset axis 15 of an associated reciprocating piston 6. In other words, the angle a gives the position of Drive shaft 8 - together with the crank drive 7 - with respect to a reciprocating piston longitudinal axis 6a. After determining 201 a of the angle a, the angle β is determined 201 b based on the measured angle a: sin (β) = sin (a) x (r / L).

This is followed by an action 202 on the 3-cylinder in-line engine, so that an angle β between the longitudinal axis 2a of the connecting rod and the longitudinal axis 6a of the reciprocating piston is set to 0 ° <β <45 °, preferably 4 ° <β <45 °. For this purpose, a starter or starter generator is preferably activated 202a in order to set the angle β via the drive shaft.

The exemplary embodiments explained by way of example are merely examples that are not intended to restrict the scope of protection, the applications and the structure of the invention in any way. Rather, the preceding description provides a person skilled in the art with a guide for the implementation of at least one exemplary embodiment, changes, in particular combinations of individual features of different embodiments, can be made with regard to the function and arrangement of the described components without the disclosed scope of protection leave.

List of reference symbols

1 system

2 connecting rods

2a connecting rod part longitudinal axis

3 first connecting rod part

4 second connecting rod part

5 length adjustment device

6 reciprocating pistons

6a reciprocating piston longitudinal axis

7 crank mechanism

8 drive shaft

9 Angle adjustment device

10 drive

1 1 control unit

12 sensor

13 Pressure generation unit

14 combustion chamber

15 crank axis

16 crank star

Claims

1. System (1) for setting an effective length of a length-adjustable connecting rod (2) for a reciprocating piston engine, in particular an internal combustion engine, the connecting rod (2) having at least a first connecting rod part (3) and a second connecting rod part (4) and the two connecting rod parts (3, 4) by means of a length adjustment device (5) in the direction of a connecting rod part longitudinal axis (2a) of the connecting rod parts (3, 4), in particular telescopically, can be moved towards and / or into one another,

wherein the reciprocating piston machine has at least one reciprocating piston (6) which can oscillate along a reciprocating piston longitudinal axis (6a),

wherein a crank drive (7) converts the oscillating movement of the reciprocating piston (6) by means of the connecting rod (2) into a rotational movement of a drive shaft (8),

wherein the system (1) has an angle adjustment device (9) which is set up to set a defined angle ß, 0 ° <ß <45 °, preferably 4 ° <ß <45 °, between the longitudinal axis of the connecting rod (2a) and the longitudinal axis of the piston (6a) set as long as the reciprocating piston machine is in a sleep mode or is brought into a sleep mode.

2. System (1) according to claim 1, wherein the angle adjustment device (9) sets the angle β via the drive shaft (8) by means of a drive (10) and a control unit (1 1).

3. System (1) according to claim 1 or 2, wherein the angle adjustment device (9) has at least one sensor (12), in particular an angle sensor.

4. System (1) according to any one of the preceding claims, wherein the angle adjustment device (9) has a drive (10), in particular a starter or starter generator of the reciprocating piston engine, and / or a motor controller of the reciprocating piston engine as a control unit (1 1), and / or at least has a sensor (12) of the reciprocating piston engine for setting the angle β.

5. System (1) according to claim 1, wherein the angle adjustment device (9) has a control unit (11) and a pressure generating unit (13), set up to adjust the angle β via a reciprocating piston (6) by means of a defined pressure in a combustion chamber (14 ).

6. System (1) according to claim 5, wherein the pressure generating unit (13) comprises a compressor and a pressure reservoir.

7. System (1) according to one of claims 1 to 6, wherein the control unit (1 1) is part of an engine control of the reciprocating piston engine.

8. System (1) according to one of claims 5 to 7, wherein the angle adjustment device (9) has at least one sensor (12), in particular a pressure sensor.

9. System (1) according to one of claims 5 to 8, wherein the reciprocating piston machine has at least two reciprocating pistons (6) and the angle adjustment device (9) is set up in such a way that the same pressure, or different pressures, is applied to at least two reciprocating pistons (6) be applied to set the angle ß.

10. System (1) according to one of the preceding claims 1 to 9, wherein the angle adjustment device (9) is set up such that the angle β is determined indirectly via an angle a by means of an angle sensor, a between a reciprocating piston longitudinal axis (6) and a Crank axis (15) of an associated reciprocating piston (6) lies on an associated crank star (16).

1 1. System (1) according to claim 10, wherein the reciprocating engine

- is a 3-cylinder in-line engine and the angle α is set to approx. 15 °; or

- is a 4-cylinder in-line engine and the angle α is set to approx. 90 °; or

- is a 5-cylinder in-line engine and the angle α is set to approx. 18 °; or

- is a 6-cylinder V-engine and the angle α is set to approx. 15 °; or - it is an 8-cylinder V-engine and the angle a is set to approx. 45 °.

12. System (1) according to one of claims 1 to 10, wherein the reciprocating engine is a boxer engine, an H engine or a swash plate motor and the angle ß is set such that there is no reciprocating piston (6) in a rest position of the reciprocating engine is in a dead center position.

13. System (1) according to one of the preceding claims 1 to 12, having a rotation lock, which can fix the system (1) in the rest mode in a position, in particular with the required angle α.

14. The method (100, 200) for setting an effective length of a length-adjustable connecting rod (2) for a reciprocating piston engine, in particular an internal combustion engine, the connecting rod (2) having at least a first connecting rod part (3) and a second connecting rod part (4) and the two connecting rod parts (3, 4) by means of a length adjustment device (5) in the direction of a

Connecting rod part longitudinal axis (2a) of the connecting rod parts (3, 4), in particular telescopically, can be moved towards and / or into one another, the reciprocating piston machine having at least one reciprocating piston (6) which extends along a

The reciprocating piston longitudinal axis (6a) can oscillate, a crank mechanism (7) converting the oscillating movement of the reciprocating piston (6) into a rotational movement of a drive shaft (8) by means of the connecting rod (2), having the following working steps:

Determining (101, 201) an operating mode of the reciprocating piston machine; and

Acting (102, 202) on the reciprocating piston engine when the reciprocating piston engine is in a sleep mode, so that an angle β between the longitudinal axis of the connecting rod (2a) and the longitudinal axis of the reciprocating piston (6a) is 0 ° <β <45 °, preferably 4 ° <β <45 °, is set.

15. The method according to claim 14, wherein the acting comprises the following substep:

Applying (102a) the combustion chambers (14) to at least two reciprocating pistons (6) each with a defined pressure in order to set the angle β.

16. The method of claim 15, further comprising the following step:

Opening or keeping open (102b) at least one intake valve per cylinder of the reciprocating piston engine; and

Closing or keeping closed (102c) an exhaust valve or exhaust valves of the cylinders of the reciprocating piston engine.

17. The method according to claim 15 or 16, further comprising the following working step:

Pressurize (102a) all combustion chambers with the same pressure in order to set the angle β.

18. The method according to claim 14, further comprising the following working step:

when the reciprocating engine is in a sleep mode, measuring (201) one

Angle ß between a connecting rod longitudinal axis (2a) and a

Reciprocating piston longitudinal axis (6a); and

Activation (202) of a drive, in particular a starter or starter generator, in order to set the angle β via the drive shaft (8).

19. The method according to one of the preceding method claims 14 to 18, in which the angle adjustment device (9) also carries out the following work steps:

Measuring (201a) an angle a, where a lies between a longitudinal axis (6) of a reciprocating piston and an axis of cranking (15) of an associated reciprocating piston (6) on an associated crank star (16); and

Determination (201 b) of the angle β as a function of angle α, a connecting rod length (L) and a stroke radius (r).