DE102019209168B4 - PISTON ARRANGEMENT, INTERNAL COMBUSTION ENGINE AND METHOD OF VARYING A COMPRESSION RATIO OF AN INTERNAL ENGINE - Google Patents

Abstract

Piston arrangement (1) for an internal combustion engine, with:
a crankshaft (10);
a piston (20);
a connecting rod (30) having a first end portion (31) rotatably mounted on the crankshaft (10) and a second end portion (32) rotatably mounted on the piston (20); and
an oil supply system (40) having a spray nozzle (41) for spraying oil onto the connecting rod (30), the spray nozzle (41) facing the connecting rod (30) and connected to an oil supply line (42), and having a temperature adjusting device (43 ) for varying the temperature of oil which is conveyed via the supply line (42) to the spray nozzle (41), the temperature adjusting device (43) of the oil supply system (40) being a heating device or a combined heating-cooling device.

Description

Technical field of the invention

The present invention relates to a piston arrangement, an internal combustion engine and a method for varying a compression ratio of an internal combustion engine. The invention also relates to a vehicle with an internal combustion engine.

background

It is desirable to reduce the fuel consumption of internal combustion engines, particularly in the automotive sector, for various reasons. However, customers also expect a certain level of performance. Attempts have therefore been made to improve the efficiency of internal combustion engines.

One way to improve the efficiency of piston-type internal combustion engines is to increase the compression ratio of the engine at high load conditions. The compression ratio is commonly defined as the ratio between the volume of a combustion chamber before compression and the volume of the combustion chamber after compression. Here, the volume of the combustion chamber is determined by a position of a piston within a cylinder, the piston being connected to a crankshaft by a connecting rod. Increasing the compression ratio actually leads to an increase in engine efficiency. However, the engine is also prone to knocking during high load operation.

To reduce the impact of these conflicting compression ratio requirements, variable compression ratio engines have been proposed. For example, describes the EP 1 496 219 A1 a motor having a connecting rod divided into two sections coupled to each other by means of a pivot, the pivot being axially displaceable by means of a control rod to flexibly adjust an effective length of the connecting rod. Lubrication is typically provided to the connecting rod of an internal combustion engine. For example, describes the JP 2010 - 209 844 A cooling and lubricating bearings at both ends of the connecting rod to reduce wear.

The DE 10 2012 214 659 A1 describes a connecting rod for an internal combustion engine, which is made up of two mutually displaceable parts. A temperature-reactive wax element is arranged between the parts, the change in volume of which as a result of a change in temperature leads to a change in the length of the connecting rod and thus the compression ratio of the engine.

GB 2 498 591 A describes an internal combustion engine with a piston which is linearly guided in a cylinder and to which a connecting rod is coupled. In order to reduce a compression ratio when the engine is warmed up, the piston can be sprayed with oil from the inside to reduce the thermal expansion of the piston.

Disclosure of Invention

One of the ideas of the invention is to provide a mechanically simple solution for adapting a compression ratio of an internal combustion engine in a flexible manner.

The present invention relates to a piston arrangement according to claim 1, an internal combustion engine according to claim 8, a vehicle according to claim 10 and a method according to claim 11.

Further embodiments of the present invention result from the further dependent claims and the following description with reference to the figures.

According to a first aspect of the invention, there is provided a piston assembly for an internal combustion engine. The piston assembly includes a crankshaft, a piston, a connecting rod having a first end portion pivoted to the crankshaft and a second end portion pivoted to the piston, and an oil supply system. The oil supply system includes a spray nozzle for spraying oil onto the connecting rod, the spray nozzle facing the connecting rod and connected to an oil supply line, and a temperature adjusting device for varying a temperature of oil supplied to the spray nozzle via the supply line.

According to a second aspect of the invention, an internal combustion engine is provided. The internal combustion engine includes a cylinder having a cylinder housing defining a stroke axis and a piston assembly according to the first aspect of the invention. The crankshaft is rotatably mounted. The piston is guided in the cylinder housing along the stroke axis between a top dead center, TDC, and a bottom dead center, BDC.

According to a third aspect of the invention, there is provided a vehicle having an internal combustion engine according to the second aspect of the invention hen. The vehicle can be a car, truck, bus, or motorcycle.

According to a fourth aspect of the invention, a method of varying a compression ratio of an internal combustion engine is provided. The method according to this aspect of the invention can be used for example for controlling or varying the compression ratio of the internal combustion engine according to the second aspect of the invention. The method includes varying a temperature of a connecting rod of the internal combustion engine by spraying oil of a predetermined temperature onto the connecting rod to increase or decrease a length of the connecting rod, the connecting rod having a first end portion rotatably supported on a crankshaft of the internal combustion engine and having a second end portion is rotatably mounted on a piston of the internal combustion engine.

One of the ideas underlying the invention is to increase or decrease a length of a connecting rod coupling a piston to a crankshaft by varying the temperature of the connecting rod. According to the invention, the temperature of the connecting rod is varied by spraying oil of a predetermined temperature onto the connecting rod. Due to thermal expansion or thermal shrinkage of the connecting rod material, the length of the rod can be varied by spraying oil onto the rod, the oil being at a different temperature than the connecting rod. By varying the length of the connecting rod, a position of the piston relative to a cylinder, in particular relative to a cylinder head of the internal combustion engine, can be varied. Thereby, the compression ratio of the internal combustion engine can be increased or decreased by applying oil of a predetermined temperature to the connecting rod.

One of the advantages of the present invention is that the compression ratio of an internal combustion engine can be varied in an efficient manner. In particular, complicated kinematics for varying the compression ratio can be dispensed with. The simple construction improves reliability over the life of the piston assembly. The flexible adjustment of the compression ratio increases thermal efficiency, which reduces the fuel consumption of an internal combustion engine. Furthermore, the knock sensitivity can be reduced.

Another advantage of the invention is that by spraying oil on the connecting rod, the piston system can easily be implemented in internal combustion engines, since internal combustion engines usually have an oil reservoir for lubrication purposes or the like. For example, the oil supply line of the oil supply system can be connected to an oil reservoir of the engine. Furthermore, the temperature adjusting device allows a flexible variation of the temperature of the mob that is sprayed onto the connecting rod. In particular, high heat transfer rates can be achieved by directing a jet of oil at the connecting rod.

According to one embodiment of the piston assembly, the spray nozzle faces a middle portion of the connecting rod to spray oil onto the middle portion, the middle portion being located between the first end portion of the connecting rod and the second end portion of the connecting rod. The connecting rod may extend in a longitudinal direction, with the end portions being spaced apart from one another with respect to the longitudinal direction by a central portion. For example, the midsection may define at least 50 percent of a length of the connecting rod. By arranging the spray nozzle opposite to the center portion, the oil can be sprayed directly onto it. Thus, the temperature of the central portion, which forms a substantial part of the length of the connecting rod, is increased or decreased. This allows the length of the connecting rod to be varied very efficiently. That is, temperature changes of the center portion quickly cause large amounts of change in the length of the connecting rod.

According to a further embodiment of the piston arrangement, the oil supply system additionally has a valve arranged in the supply line for varying a flow rate of the oil. The valve is an example of a hydraulic control component for controlling a flow rate of oil supplied to the spray nozzle via the supply line. An advantage of using a valve as the control component is that it can easily block the supply line when compression ratio variation is not required. As a result, the control valve increases the flexibility of the piston assembly to vary the compression ratio.

The valve can be implemented as a solenoid valve, for example. This further facilitates the operation of the oil supply system. For example, the solenoid valve can be electronically controlled.

As an alternative or in addition to a valve, the oil supply system can have a pump arranged in the supply line for varying have a flow rate of the oil. The pump can be an electric oil pump, for example. This further increases flexibility in varying the compression ratio. For example, the oil pump can increase the flow rate of oil to more quickly vary the connecting rod temperature. In particular, the pump allows for high flow rates, which further increases heat transfer between the oil and the connecting rod.

In the case of the piston arrangement according to the invention, the temperature setting device of the oil supply system is a heating device or a combined heating/cooling device. In general, the temperature of the oil that is supplied to the spray nozzle and sprayed onto the connecting rod can be varied by the temperature adjusting device, that is, the temperature can be decreased or increased. Typically, when oil is taken from a reservoir of the engine, the oil has already been used for cooling or lubricating purposes of parts of the engine and is therefore at high temperatures, for example in the range between 80 degrees Celsius and 90 degrees Celsius. The connecting rod typically has temperatures in the range of about 180 degrees Celsius at the second end portion and in the range of about 80 degrees Celsius at the first end portion during operation. In this situation, a cooling device such as a heat exchanger may preferably be provided to reduce the temperature of the oil in the oil supply line. For example, the heat exchanger may be an air-cooled heat exchanger, using cool or ambient air to cool the oil. However, it is also possible to provide a heater such as an electric heater or a combined heating-cooling device having heating and cooling sections, for example a heat exchanger as a cooling section and an electric heater as a heating section.

According to a further embodiment, the piston arrangement can have a control device which is connected to the oil supply system and is set up to control the oil supply system. The control device can have, for example, an electronic control unit with a processor such as a CPU and a data memory, in particular a non-volatile data memory such as a hard disk or a flash memory. For example, the controller may be in data communication with the temperature adjustment device, the optional valve, and/or the optional pump. The control device is set up to generate control commands for actuating one or more of the above-mentioned components of the oil supply system.

According to a further embodiment, the connecting rod is formed at least partially from a metal material. An advantage of metal materials is that they usually have high thermal expansion coefficients. In particular, a metal material with a thermal expansion coefficient such as aluminum or aluminum alloys. This offers the advantage that large changes in length can be achieved with relatively small changes in temperature. For example, at least the central portion of the connecting rod is formed of metal material. Optionally, the connecting rod may be formed entirely of a metal material. Regardless of the material, the end portions and the middle portion of the connecting rod are preferably formed integrally as one piece.

According to one embodiment of the internal combustion engine, the piston arrangement has a control device functionally connected to the oil supply system, as described above, and a pressure sensor for detecting pressure in the cylinder, in particular in a combustion chamber, the pressure sensor being connected to the control device, and the control device configured to control the oil supply system based on the sensed pressure. The combustion chamber is defined by the piston and the cylinder, specifically a cylinder head that defines an axial end of the cylinder with respect to the stroke axis. By varying the pressure ratio, the volume of the combustion chamber at TDC is varied. The pressure, for example a maximum pressure, which is detected by the pressure sensor in the pressure chamber is therefore an indicator of the compression ratio. Based on this information, the control device can generate control commands such that the oil supply system sprays oil of a specific temperature onto the connecting rod in order to vary the compression ratio, for example such that the current compression ratio is regulated to a desired compression ratio. A desired compression ratio may be determined, for example, from a current load condition of the engine, such as a load torque applied to the crankshaft, and an engine operating map correlating a compression ratio of the engine to a load condition of the engine.

In the method according to the invention, a load condition, in particular a current load condition of the internal combustion engine, is detected. For example, as described above in connection with the internal combustion engine, a load torque applied to the crankshaft can be used as a representation of the load condition of the engine ing physical quantity can be recorded. Furthermore, a pressure in a combustion chamber of the internal combustion engine is detected, the combustion chamber being defined by the piston and a cylinder of the internal combustion engine as described above. As a result, a physical variable that represents a current compression ratio of the internal combustion engine is detected by the pressure sensor. The method additionally includes controlling at least one of temperature of the oil and flow rate of the oil based on the load condition and the sensed pressure. That is, the compression ratio can be controlled such that the current compression ratio corresponds to a desired compression ratio for the current load condition of the engine. The desired compression ratio can be determined, for example, from an engine map as described above.

According to a further embodiment of the method, the predetermined temperature of the oil is in a range between 15 degrees Celsius and 80 degrees Celsius. In general, varying the temperature of the connecting rod can include cooling the connecting rod, in particular by means of oil which is approximately at ambient temperature. This allows the length of the connecting rod and thus the sealing ratio to be reduced very efficiently.

Optionally, the predetermined temperature of the oil is in a range between 20 degrees Celsius and 30 degrees Celsius. In this area, a particularly good balance between cooling the oil and varying the length of the connecting rod is achieved.

Those skilled in the art will clearly and unequivocally understand that the features and advantages described in connection with one aspect of the invention are also disclosed for the other aspects of the invention and vice versa.

character list

• 1 zeigt eine schematische Ansicht eines Verbrennungsmotors gemäß einem Ausführungsbeispiel der Erfindung;
• 2 zeigt eine beispielhafte Seitenansicht eines Verbindungsstabs des Verbrennungsmotors aus 1;
• 3 zeigt ein Flussdiagramm eines Verfahrens gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;
• 4 zeigt schematisch ein Fahrzeug gemäß einem Ausführungsbeispiel der vorliegenden Erfindung, wobei ein Verbrennungsmotor des Fahrzeugs in einem Hochlastbetriebszustand betrieben wird;
• 5 zeigt schematisch das Fahrzeug aus 4, wobei der Verbrennungsmotor des Fahrzeugs in einem Niederlastbetriebszustand betrieben wird;
• 6 zeigt schematisch das Fahrzeug aus 4, wobei der Verbrennungsmotor des Fahrzeugs in einem Hochlastbetriebszustand betrieben wird; und
• 7 zeigt schematisch das Fahrzeug aus 4, wobei der Verbrennungsmotor des Fahrzeugs in einem Niederlastbetriebszustand betrieben wird.

For a more complete understanding of the present invention and the advantages thereof, reference is made to the following description in conjunction with the accompanying figures. The invention will be explained in more detail with reference to embodiments shown in the schematic figures, of which:

• 1 12 shows a schematic view of an internal combustion engine according to an embodiment of the invention;
• 2 FIG. 12 shows an exemplary side view of a connecting rod of the internal combustion engine of FIG 1 ;
• 3 shows a flowchart of a method according to an embodiment of the present invention;
• 4 12 schematically shows a vehicle according to an embodiment of the present invention, wherein an internal combustion engine of the vehicle is operated in a high-load operating state;
• 5 shows the vehicle schematically 4 wherein the engine of the vehicle is operated in a low load operating condition;
• 6 shows the vehicle schematically 4 wherein the engine of the vehicle is operated in a high load operating condition; and
• 7 shows the vehicle schematically 4 wherein the engine of the vehicle is operated in a low load operating condition.

In the figures, the same reference symbols denote the same elements unless otherwise stated.

Detailed description of exemplary embodiments

1 12 shows an internal combustion engine 100 with a piston assembly 1 and a cylinder 120. The piston assembly 1 has a crankshaft 10, a piston 20, a connecting rod 30, an oil supply system 40 and an optional control device 50. FIG.

As schematic in 1 1, the cylinder 120 includes a cylinder body 121 defining a stroke axis A121 and a cylinder head 122 fixed to an upper end portion 121B of the cylinder body 121. As shown in FIG. As in 1 As further shown, the piston 20 is guided in the cylinder housing 121 along the stroke axis A121. The piston 20 has an outer peripheral surface in contact with an inner peripheral surface of the cylinder housing 121 . As schematic in 1 As shown, the piston 20 and cylinder 120, specifically the piston 20, cylinder body 121, and cylinder head 122, together define a combustion chamber 140, that is, a volume bounded by the piston 20, cylinder body 121, and cylinder head 122.

In 1 By way of example, the piston 20 is shown in a position in the vicinity of a lower end portion 121A of the cylinder housing 121, the lower end portion 121A being opposite to the upper end ab section 121B of the cylinder housing 121 is located. In general, the piston is guided in the cylinder housing 121 along the stroke axis A121 between a top dead center, TDC, and a bottom dead center, BDC. At TDC, piston 20 is spaced a first distance from cylinder head 122 . In the BDC, the piston 20 is disposed a second distance from the cylinder head 122, the second distance being greater than the first distance. Piston 20 and cylinder one hundred and twenty strokes 120 define a first volume at TDC of piston 20 and a second volume at BDC that is greater than the first volume. A compression ratio may be defined by the ratio between the first volume and the second volume. In particular, the compression ratio can be defined by dividing the second volume by the first volume.

The crankshaft 10 is rotatably supported, for example on an engine block (not shown). In particular, the crankshaft 10 is rotatably mounted about a first axis of rotation A1. The first axis of rotation A1 can be defined by a base section 11 of the crankshaft 10, as shown in FIG 1 is shown. The crankshaft 10 also has a crank section 11 which defines a second axis of rotation A2. The crank portion 12 is offset relative to the base portion 11 such that the crank portion 12 is rotatable about the base portion 11 when the base portion 11 is rotatably supported about the first pivot axis A1. Both the base section 11 and the crank section 12 can both have a circular cross-section, as is exemplified in FIG 1 is shown. As in 1 As shown, the base portion 11 and the crank portion 12 can be connected to each other by a coupling portion 13, which extends transversely to the base portion 11, in particular transversely to the first axis of rotation A1. Furthermore, the first and the second axis of rotation A1, A2 can extend parallel to one another.

The connecting rod 30 is shown as an example in 2 shown. The connecting rod 30 is implemented as an elongate structure having a first end portion 31, a second end portion 32 spaced from the first end portion, and a lever portion or middle portion 33 connecting the first end portion 31 and the second end portion 32. As this schematic in 2 As shown, the first and second end portions 31, 32 of the connecting rod may each at least partially form a through hole or sleeve. As exemplified in 2 shown, the first end portion 31 forms a half-shell. In order to define a closed, circular structure, a bracket 34 can be attached to the first end portion 31, for example by means of screws 35. The central portion 33 can be formed by an elongate, profiled structure, for example the central portion 33 can have an I- have shaped cross-section.

An overall length I30 of the connecting rod 30 can be defined as a distance between a central axis of the sleeve defined by the first end portion 31 and a central axis of the sleeve defined by the second end portion 32, as shown in FIG 2 shown. A length I33 of the middle section 33 can be at least 50 percent of the overall length I30 of the connecting rod 30 .

The connecting rod 30 is preferably formed of a metal material, such as aluminum or an aluminum alloy. For example, at least the center portion 33 may be formed of a metal material.

As schematic in 1 shown, the first end portion 31 of the connecting rod 30 is rotatably mounted on the crankshaft 10, in particular on the crank portion 12 of the crankshaft 10. The second end portion 32 of the connecting rod 30 is rotatably mounted on the piston 20, for example by means of a piston pin 21.

Expansion of gas in the combustion chamber 140 moves the piston 20 toward the lower end portion 121A of the cylinder body 121 along the stroke axis A121. Thereby, the connecting rod 30 rotates the crank portion 12 of the crankshaft 10 about the first rotation axis A1, and the base portion 11 is thus rotated about the first rotation axis A1. As a result, the axial movement of the piston 20 is converted into a rotary movement of the crankshaft 10 .

The oil supply system 40 of the piston arrangement 1 comprises a spray nozzle 41 for spraying oil onto the connecting rod 30, an oil supply line 42 for supplying oil to the spray nozzle 41, a temperature adjusting device 43 for varying a temperature of oil which is supplied to the spray nozzle 41 via the supply line 42 is supplied, an optional valve 44 and an optional pump 45.

The oil supply line or umbilical 42 may have one end hydraulically connected to an oil reservoir (not shown) of the engine 100 . For example, the oil reservoir may be a pressurized reservoir. Alternatively, the oil supply line 42 may be coupled to another oil source. The spray nozzle 41 is connected to the other end of the supply line 42, as shown schematically in FIG 1 is shown. The supply line 42 thus supplies oil to the spray nozzle 41 .

The spray nozzle 41 may generally be configured to emit a jet of fluid. Optionally, the spray nozzle 41 can be set up to eject a controlled jet of fluid J, as is shown schematically in FIG 1 is shown. As in 1 As further shown, the spray nozzle 41 faces the connecting rod 30 . Specifically, an outlet port (not shown) of the nozzle 41 through which the fluid jet J is ejected is oriented to face the connecting rod 30 . Optionally, the spray nozzle 41 faces a central portion 33 of the connecting rod 30 so that the jet of fluid J is directed toward the central portion 33 of the connecting rod.

The temperature adjusting device 43 is arranged in the supply line 42 . In particular, the temperature setting device may have an inlet 43A through which oil is conveyed into the temperature setting device 43, an outlet 43B through which oil is conveyed out of the temperature setting device 43, and a heat transfer section 43C for cooling and/or heating the oil. The temperature adjusting device 43 can be realized, for example, as a heat exchanger, in particular as an oil cooler. The temperature adjusting device 43, particularly the heat transfer section 43C, is a heating device or a combined heating-cooling device. Thus, the temperature adjusting device 43 is generally set up to vary the temperature of the oil which is supplied to the nozzle 41 via the supply line 42 .

The optional valve 44 is located in the supply line 42 upstream of the heat actuator 43 and is operative to vary a flow rate of the oil in the supply line 42 . For example, the valve 44 can be implemented as a solenoid valve. Generally, the valve 44 is switchable between an open and a closed state, in the closed state a flow area of the supply line 42 is blocked and in the open state fluid flow through the valve 44 is permitted.

The optional pump 45 can be provided in addition to or as an alternative to the valve 44 and serves to vary a flow rate of the oil. The pump 45 can be an electrically driven pump, the throughput of which is preferably continuously variable. The pump 45 is arranged in the supply line 42 upstream of the temperature adjusting device 43 . As exemplified in 1 shown, the pump 45 can be arranged in the supply line 42 between the temperature setting device 43 and the valve 44 .

The optional control device 50 is connected to the oil supply system 40 . "Connected" in this context is to be understood as a connection that is set up for wired or wireless data communication. For example, the control device 50 can have an interface set up for wired data communication, such as a BUS interface, e.g. a CAN BUS interface. Additionally or alternatively, the control device 50 can have an interface that is set up for wireless data communication, such as a WIFI interface, a Bluetooth interface or the like.

As in 1 shown by way of example, the control device 50 can be connected to the temperature setting device 43 , the optional valve 44 and the optional pump 45 . As further in 1 is shown, the control device 50 can also be connected to an optional pressure sensor 101 of the internal combustion engine 100 . As shown, the pressure sensor 101 is disposed proximate to the combustion chamber 140 and configured to sense a pressure within the combustion chamber 140 . A physical variable representing a current compression ratio can thus be detected by means of pressure sensor 101 and made available to control device 50 .

Control device 50 is also set up to generate control commands for operating or actuating oil supply system 40, in particular for operating or actuating temperature setting device 43 in order to vary the temperature of the oil, and for operating or actuating valve 44 and/or pump 45 to vary the flow rate of the oil.

In order to change the compression ratio of the internal combustion engine 100, oil is sprayed onto the connecting rod 30 via the nozzle 41, the temperature of the oil being adjusted by the temperature adjusting device 43 so that the connecting rod 30 is either cooled or heated. This changes the length I30 of the connecting rod 30 due to thermal expansion or contraction of the connecting rod 30. Consequently, at TDC of the piston, the volume of the combustion chamber 140 is either increased or decreased and thus the compression ratio is either decreased or increased.

3 FIG. 12 shows an exemplary flow chart of a method M for varying the compression ratio of an internal combustion engine 100. The method M is described by way of example with reference to the engine 100 and the piston assembly 1 described above.

The method generally includes varying a temperature of the connecting rod 30 of the internal combustion engine 100 by spraying oil of a predetermined temperature onto the connecting rod 30 to increase or decrease a length I30 of the connecting rod 30 . This step of method M is in 3 shown as block M4. An advantage of spraying oil on the connecting rod 30 is that high heat transfer rates between the oil and the connecting rod 30 can be achieved. This allows the compression ratio to be dynamically adjusted. In particular, no kinematic mechanisms are required, which improves the reliability of the motor 100.

In addition, the method M includes a detection M1 of a current load state of the internal combustion engine 100 and a detection M2 of a pressure in the combustion chamber 140 of the internal combustion engine 100. For example, the pressure in the combustion chamber 140 can be detected by the pressure sensor 101 and the control device 50 can be provided. The current load condition of engine 100 may be represented by a torque requested at crankshaft 10, for example.

The 4 until 7 12 show exemplary situations in which high or low engine load conditions occur when the engine 100 is installed in a vehicle 200. FIG. The 4 until 7 show an example of a vehicle designed as a truck. In general, vehicle 200 may be a land vehicle such as a truck, a car, a bus, a tank or motorcycle, a watercraft such as a ship, or any other type of vehicle. In 4 the vehicle 200 travels at a speed V on a road 2, the road 2 being substantially horizontal with respect to the direction of gravity G, and the vehicle 200 transporting a large amount of payload P. Due to the payload P, a high torque is required at the crankshaft 10, which corresponds to a high-load or full-load operating state of the engine 100.

In the 5 The situation shown corresponds to that in 4 situation shown, however, the vehicle 200 does not carry a payload P. That is, compared to FIG 4 a smaller torque is requested at the crankshaft 10, which corresponds to a low-load or part-load operating state of the engine 100.

6 12 shows an example of a situation in which the vehicle 200 is traveling uphill on a road 2 that is inclined with respect to the direction of gravity G. Due to the uphill grade of the road 2, a high torque is requested at the crankshaft 10, which corresponds to a high load operating condition of the engine 100.

In 7 the vehicle 200 travels downhill on a road 2 that is inclined with respect to the direction of gravity G. Due to the downward gradient of road 2 compared to 6 a smaller torque on the crankshaft 10 is requested. Thus shows 7 a situation that corresponds to a low load operating condition of the engine 100 .

The current load condition of the engine 100 can be detected, for example, by a torque sensor (not shown) on the crankshaft 10 and made available to the control device 50 .

During high load or full load conditions of the engine 100, it may be desirable to decrease the compression ratio. During low load or part load conditions of the engine 100, it may be desirable to increase the compression ratio, particularly to a higher compression ratio compared to full load conditions.

The method M further includes a step M3 of controlling at least one of the temperature of the oil and the flow rate of the oil based on the load condition and the detected pressure. In general, the control device 50 can be set up to control the oil supply system 40 based on the detected pressure in the combustion chamber 140 and optionally also based on the detected load state of the engine 100 .

As in 3 1, it is detected in step M3 whether there is a need to vary the compression ratio of the engine 100. For example, the controller 50 may obtain appropriate information from an engine control unit, ECU (not shown), or may determine such a need itself. In general, an engine operating map that correlates a load condition of the vehicle to a required compression ratio can be used to determine the required compression ratio. For example, the controller 50 can communicate the current load condition of the engine, eg, a torque demanded at the crankshaft 10, to the ECU, or the ECU can receive a signal indicative of the current load condition directly from a sensor. The ECU then determines a required compression ratio for the current load condition and makes this available to the control device 50 . The controller 50 may determine the current compression ratio based on the sensed pressure and determine a difference between the required compression ratio and the actual compression ratio. Alternatively, the controller 50 the sensed pressure to the ECU, which then determines a difference between the required compression ratio and the current compression ratio and, conversely, sends a corresponding signal indicating this difference to the control device 50.

If in block M3 no difference is determined between the required compression ratio and the current compression ratio or if it is determined that the difference is less than a predetermined threshold value, as is the case in 3 is indicated by the symbol "-", no further step is taken, that is, the present state of the oil supply system 40 is maintained (block M5). If it is determined in block M3 that the current compression ratio deviates from the required compression ratio by more than a predetermined amount, the method continues with block M4, as indicated in 3 shown by the symbol "+".

The step of varying the temperature of the connecting rod 30, as represented by block M4, may, for example, involve generating command signals by the control device 50 to open the valve 44 and/or to actuate the pump 45 and/or to control the temperature setting device 43 in order to to cool or to heat the oil supplied to the nozzle 41. For example, the temperature of the oil can be set in a range between 15 degrees Celsius and 80 degrees Celsius, in particular in a range between 20 degrees Celsius and 30 degrees Celsius. In particular, the valve 44 can be opened to increase or decrease the flow rate of oil. Additionally or alternatively, the pump 45 can be actuated to increase or decrease the flow rate of oil. Increasing or decreasing the flow rate will quickly change the temperature of the connecting rod 30 and is therefore an efficient way of varying the compression ratio.

To further illustrate the efficiency of the method and arrangement described above, an example of an internal combustion engine will be evaluated approximately.

The example relates to a petrol engine with a stroke s=40 mm, a bore diameter b=98 mm, a length I30 of the connecting rod 30 of 102 mm (I _conrod ). Stroke s is the length that piston 20 is displaced between TDC and BDC along stroke axis A121. The bore diameter b is the diameter defined by the inner surface of the cylinder body. In the example it is assumed that the engine is operated with a compression ratio ∈ ₀ = 14.

The compression ratio ε can be defined as $$e=\frac{V_H+V_C}{V_C}$$

In this formula, V _H is the volume defined by the displacement of piston 20 between BDC and TDC. Vc corresponds to the volume of the combustion chamber at TDC of piston 20. In the present example, _VH is 0.3 liters and Vc is 0.023 liters.

A change in length Δl _conrod of the connecting rod 30 can be calculated as: $$\Delta l_{cOn\mathrm{right}O\mathrm{i.e}}=a\cdot l_{cOn\mathrm{right}O\mathrm{i.e}}\cdot \Delta T$$

In this formula, α corresponds to the coefficient of thermal expansion of the material of the connecting rod 30. In this example, the connecting rod 30 is made entirely of aluminum. Thus, α can be approximately taken as 23 · 10 ^-6 [1/°C]. ΔT is the temperature change of the connecting rod. If a temperature change of ΔT = 60°C is achieved, for example by spraying chilled oil onto the connecting rod 30, then from the above formula Δl _conrod = 0.14mm. In the present example it is assumed that the connecting rod is cooled by about 60 °C. Δl _conrod is therefore negative, ie the connecting rod shrinks.

berechnet werden, wobei b der oben genannte Bohrungsdurchmesser ist. Mit den verwendeten Werten für b und Δl_conrod berechnet sich ΔV_c zu 0,001 Liter. Da der Verbindungsstab geschrumpft ist, wurde Vc um etwa 0,001 Liter vergrößert.From Δl _conrod, a change in volume ΔV _c of the combustion chamber at TDC of piston 20 can be calculated as $$\Delta V_c=\Delta l_{cOn\mathrm{right}O\mathrm{i.e}}\cdot \pi \cdot {\left(\frac{b}{2}\right)}^2$$

be calculated, where b is the bore diameter mentioned above. With the values used for b and Δl _conrod, ΔV _c is calculated as 0.001 liters. As the connecting rod shrunk, Vc increased by about 0.001 liters.

Using the compression ratio formula above, a new, revised compression ratio ∈ _Δl , can be calculated to be 13.5. Thus, a reduction in the temperature of the tie rod results in a reduction in the length of the rod and consequently a reduced compression ratio.

Although the internal combustion engine and the method mentioned above have been described in the context of vehicles, it is clearly and unequivocally understood by the person skilled in the art that the aspects described here can be used in different Objects that have an internal combustion engine can be applied.

The invention has been described in detail with reference to specific embodiments. However, it will be apparent to those skilled in the art that these embodiments can be modified without departing from the principles and central ideas of the invention, the scope of the invention as defined in the claims, and their equivalents.

Reference List

1

piston assembly

2

Street

10

crankshaft

11

base section

12

crank section

13

coupling section

20

Pistons

21

plunger pin

30

connecting rod

31

first end portion of the connecting rod

32

second end portion of the connecting rod

33

Center section of the connecting rod

34

hanger

35

screws

40

oil supply system

41

spray nozzle

42

oil feed line

43

temperature setting device

43A

inlet

43B

outlet

43C

heat transfer section

44

Valve

45

pump

50

control device

100

combustion engine

101

pressure sensor

120

cylinder

121

cylinder body

121A

lower end portion of the cylinder body

121B

upper end portion of the cylinder body

122

cylinder head

200

vehicle

A1

first axis of rotation

A2

second axis of rotation

G

direction of gravity

J

fluid jet

I30

Connecting rod length

I33

Length of the middle section of the connecting rod

M

Proceedings

M1-M5

process steps

P

payload

Claims (13)

Piston arrangement (1) for an internal combustion engine, with: a crankshaft (10); a piston (20); a connecting rod (30) having a first end portion (31) rotatably mounted on the crankshaft (10) and a second end portion (32) rotatably mounted on the piston (20); and an oil supply system (40) having a spray nozzle (41) for spraying oil onto the connecting rod (30), the spray nozzle (41) facing the connecting rod (30) and connected to an oil supply line (42), and having a temperature adjusting device (43 ) for varying the temperature of oil which is conveyed via the supply line (42) to the spray nozzle (41), the temperature adjusting device (43) of the oil supply system (40) being a heating device or a combined heating-cooling device. Piston assembly (1) after claim 1 , wherein the spray nozzle (41) faces a middle portion (33) of the connecting rod (30) to spray oil onto the middle portion (33), the middle portion (33) being between the first end portion (31) of the connecting rod (30) and the second end portion (32) of the connecting rod (30). Piston assembly (1) after claim 1 or 2 , wherein the oil supply system (40) additionally has a valve (44) arranged in the supply line (42) for varying a flow rate of the oil. Piston assembly (1) after claim 3 , wherein the valve (44) is a solenoid valve. Piston arrangement (1) according to one of the preceding claims, in which the oil supply system (40) additionally has a pump (45) arranged in the supply line (42) for varying a flow rate of the oil. Piston assembly (1) according to any one of the preceding claims, additionally comprising: a control device (50) connected to the oil supply system (40), which is set up to control the oil supply system (40). Piston assembly (1) according to any one of the preceding claims, wherein the connecting rod (30) is at least partially formed of a metal material. Internal combustion engine (100), with: a cylinder (120) having a cylinder housing (121) defining a stroke axis (A121); and a piston arrangement (1) according to any one of the preceding claims; wherein the crankshaft (10) is rotatably mounted; and wherein the piston (20) is guided in the cylinder housing (121) along the stroke axis (A121) between a top dead center, TDC, and a bottom dead center, BDC. Internal combustion engine (100) after claim 8 with the piston assembly (1). claim 6 and a pressure sensor (101) for detecting a pressure within the cylinder (120), the pressure sensor (101) being connected to the control device (50), and the control device (50) being set up to control the oil supply system (40) based on to control the sensed pressure. Vehicle (200) with an internal combustion engine (100) according to one of Claims 8 or 9 . Method (M) for varying a compression ratio of an internal combustion engine, the method comprising: detecting (M1) a load condition of the internal combustion engine (100); detecting a pressure in a combustion chamber (140) of the internal combustion engine (100) defined by the piston (20) and a cylinder (120) of the internal combustion engine; controlling (M3) at least one of temperature of the oil and flow rate of the oil based on the load condition and the detected pressure; and varying (M4) a temperature of a connecting rod (30) of the internal combustion engine (100) by spraying oil of a predetermined temperature onto the connecting rod (30) to increase a length (130) of the connecting rod (30), or to reduce, wherein the connecting rod (30) is rotatably mounted with a first end section (31) on a crankshaft (10) of the internal combustion engine (100) and with a second end section (32) rotatable on a piston (20) of the internal combustion engine (100) is stored. Procedure (M) according to claim 11 , wherein the predetermined temperature of the oil is in a range between 15 degrees Celsius and 80 degrees Celsius. Procedure (M) according to claim 12 , wherein the predetermined temperature of the oil is in a range between 20 degrees Celsius and 30 degrees Celsius.

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