EP2906803A1

EP2906803A1 - Method and device for operating an internal combustion engine

Info

Publication number: EP2906803A1
Application number: EP13785826.2A
Authority: EP
Inventors: Michael Wirkowski; Christian MEY; Christoph Klesse
Original assignee: Continental Automotive GmbH
Current assignee: Continental Automotive GmbH
Priority date: 2012-10-11
Filing date: 2013-10-04
Publication date: 2015-08-19
Anticipated expiration: 2033-10-04
Also published as: JP2015534625A; CN104704223A; EP2906803B1; US9518545B2; CN104704223B; US20150247480A1; KR102122622B1; KR20150065747A; DE102012218525B4; DE102012218525A1; WO2014056798A1

Abstract

An internal combustion engine (1) has a pressure accumulator (20), a high-pressure pump (22), a controllable actuator, and a rotatably mounted camshaft (27) with a longitudinal axis. The high-pressure pump (22) comprises a cylinder chamber and a pump piston (31) which is movably arranged in the cylinder chamber. The pump piston (31) is supported at least indirectly on the camshaft (27) and thus influences an open volume of the cylinder chamber depending on a rotation of the camshaft (27). The cylinder chamber of the high-pressure pump (22) is hydraulically coupled at least indirectly to the pressure accumulator (20) in order to pump the fluid into the pressure accumulator (20). The actuator is designed and arranged to drive the camshaft (27) such that the camshaft (27) rotates about the camshaft longitudinal axis in a specified angular range into a first direction or into an opposite second direction. The method has the following steps: the high-pressure pump (22) is controlled during a specified time period prior to an expected motor start such that the high-pressure pump is in a self-priming operating state and the actuator is controlled such that the camshaft (27) rotates about the camshaft longitudinal axis in the specified angular range at least once into the first direction and at least once into the second direction.

Description

description

Method and device for operating an internal combustion engine The invention relates to a method and a device for operating an internal combustion engine.

Modern motor vehicles have direct fuel injection internal combustion engines in which the fuel is injected under high pressure directly into or into multi-cylinder internal combustion engines into the combustion chambers. Such a fuel direct injection requires a fuel supply device, which provides pressurized fuel in any operating situation. Elements of this fuel supply device are the high-pressure pump, which conveys the fuel to the required pressure level, and a pressure accumulator (rail), in which the fuel is stored under high pressure and from which the fuel injectors are supplied with fuel.

In an effort by automobile manufacturers to further reduce fuel consumption and emissions of automobiles, new vehicle functions have been developed, such as the automatic start-stop function whereby the engine is automatically shut down and ignored without the intervention of a motor vehicle driver to actuate the start button can be automatically started again, for example by tapping the gas ^¬ or clutch pedal. The shutdown of the internal combustion engine is done in particular in longer idling periods in which the driving force of the internal combustion engine is not needed. In this way, especially in city traffic with many traffic-light stops, considerable fuel consumption savings can be achieved. ^

When starting the engine of an internal combustion engine with fuel ^¬ injection systems, the fuel must be under a sufficiently high pressure. In general, the sufficiently high pressure at engine start, both after a longer and after a short shutdown phase, must first be generated by the high pressure pump mechanically coupled to the engine. The engine of a motor vehicle is driven during a starting phase by a starter of the motor vehicle without combustion until reaching a target injection release pressure. It is to be ^expected that the setpoint injection release pressure will be further increased in the future due to stricter limit values with regard to a particle emission.

The object underlying the invention is to provide a method and a device for operating an internal combustion engine, which contributes to improving a starting capability of an engine of the internal combustion engine.

The object is solved by the features of the independent claims. Advantageous developments of the invention are characterized in the subclaims. The invention is characterized by a method and a corresponding device for operating an internal combustion engine. The internal combustion engine has a Druckspei ^¬ cher, a high pressure pump, a controllable actuator and a rotatably mounted camshaft with a longitudinal axis. The high-pressure pump comprises a cylinder chamber and a pump piston movably arranged in the cylinder chamber. The pump piston is supported at least indirectly on the camshaft and thus influences a free volume of the cylinder chamber depending on a rotation of the camshaft. The cylinder chamber of High-pressure pump is hydraulically coupled at least indirectly with the pressure accumulator for conveying the fluid into the pressure accumulator. The actuator is configured and arranged to drive the camshaft such that the camshaft rotates in a predetermined angular range about its longitudinal axis in a first direction or in an opposite second direction. The method comprises the following steps: During a predetermined period of time before an expected engine start, the high pressure pump is driven so that it has a self-priming operating state and the actuator is so ^¬ controls that the camshaft at least once in the first direction and at least once in the second direction rotates in the predetermined angular range about its longitudinal axis.

Advantageously, this makes it possible to rotate the camshaft and thus at least one drive cam of the camshaft already before the expected engine start by means of the actuator, so that the high-pressure pump is driven. In this case, the at least one drive cam of the camshaft, on which the pump piston is at least indirectly supported, is rotated back and forth. The Pum ^¬ penkolben thereby results in the cylinder chamber suction and

Pumphubbewegungen off. The suction and Pumphubbewegungen the pump piston allow fluid delivery of the high-pressure pump, in particular a fuel delivery, and thus a pressure build-up in the accumulator before the engine is started. The high pressure pump is preferably designed such that it can have a self-priming operating state with a suitable control. This allows the

A high pressure pump in very fast working and effective ^¬ settable. Furthermore, this allows full delivery of the high-pressure pump without synchronization of the cam and a crankshaft. The high-pressure pump can be designed as a normally closed pump or as a normally open pump. In the event that the high-pressure pump is designed as a normally closed pump is formed, the high-pressure pump is operated without current. In the case that the high-pressure pump is designed as a normally open pump, the high-pressure pump is operated with a continuous current, analogous to a normal operation of the high-pressure pump in an active operating state of the engine. The expected Mo ^¬ gate start can be detected depending on an opening of a driver door and / or a seat occupancy. For a start-stop automatic function, the expected engine start can be determined as a function of a medium short-time shut-off time. Depending on the anticipated engine start, camshaft rotation may begin to build up pressure in the accumulator. The pressure in the pressure accumulator can thus already have a desired value at an actual engine start. This has the advantage, in particular in the case of a motor vehicle, that a period of time can be shortened by an engine start desired by a vehicle driver and / or vehicle-controlled engine start, in which an activation signal for the engine is generated, for example, up to an actual start of combustion in the combustion chamber. Even with an increase of the desired injection release pressure, a size of the pressure accumulator can be maintained by the build-up of pressure before the expected engine start, without the start ^¬ ability of the engine is delayed. A reduction in the size of the pressure accumulator and the associated extended quality requirements for other components, for example pressure relief valves and injectors, may be dispensable.

In an advantageous embodiment, the predetermined period of time is immediately before the expected engine start. This has the advantage that an already established pressure does not have to be kept for a longer time and / or a particle emission can be reduced and / or a possible leakage in the fuel system can be tolerated. _n

5

In a further advantageous embodiment, the actuator is controlled during the predetermined period of time such that the camshaft rotates several times each first in the first and then in the second direction in the predetermined angle kelbereich about its longitudinal axis until a predetermined injection release pressure prevails in the pressure accumulator.

This allows already present at an engine start of the injection ^¬ release pressure and can be started already at a first top dead center of the engine with a fuel injection.

In a further advantageous embodiment, the

Internal combustion engine to a variable valve train and the camshaft is coupled to a gas inlet valve and / or a gas outlet valve of a combustion chamber of the internal combustion engine and the actuator is arranged and formed by driving and / or adjusting the camshaft an opening and / or closing time of the gas inlet valve or gas ^¬ outlet valve to control. Advantageously, the actuator can thus be used for the variable valve train and as a high-pressure pump drive. An operability of the variable valve train is maintained because the actuator is used only when the engine is started for the variable valve train. In a further advantageous embodiment, the variable valve train comprises an electric variable valve train. The variable valve train may include an electric actuator. Advantageously, this makes it very easy to rotate and / or drive the camshaft when the engine is at a standstill.

In a further advantageous embodiment, the high-pressure pump comprises a digitally switching high-pressure pump. Before ^¬ geous enough, this allows a rapid pressure build-up. It Both directions of movement can be used for the pressure build-up, since the pressure build-up is independent of a respective direction of rotation.

Advantageous embodiments of the invention are explained below with reference to the schematic drawings. Show it:

Figure 1 is an exemplary schematic representation of a

Internal combustion engine,

Figure 2 is a schematic partial view of a high-pressure pump in a longitudinal section and

Figure 3 shows a time course of a rail pressure in one

Accumulator and a crankshaft signal.

Elements of the same construction or function are identified across the figures with the same reference numerals.

The internal combustion engine 1 comprises at least one cylinder 2 and a piston 3 movable up and down in the cylinder 2. The internal combustion engine 1 further comprises an intake tract 40, downstream of an intake opening 4 for drawing in fresh air, an air mass sensor 5, a throttle valve 6, a suction pipe 7 and a controllable intercooler 60 are arranged. The charge air cooler 60 can have water cooling or air cooling. The intake tract 40 opens into a combustion chamber 30 bounded by the cylinder 2 and the piston 3. The fresh air required for combustion is introduced into the combustion chamber 30 via the intake tract 40, the fresh air supply being controlled by opening and closing a gas inlet valve 8. In the internal combustion engine 1 shown here is an internal combustion engine 1 with direct fuel injection, in which the fuel required for the combustion via an input injection valve 9 is injected directly into the combustion chamber 30. A likewise protruding into the combustion chamber 30 ignition plug is used to trigger the combustion 10. The combustion exhaust gases are discharged through a gas outlet 11 into an exhaust pipe 16 of the internal combustion engine 1 and purified by means of an in the Ab ^¬ gas line 16 catalyst 12th

The power transmission to the drive train (not shown) via a coupled to the piston 3 crankshaft 13 whose speed detects a speed sensor 15.

The internal combustion engine 1 has a variable Ven ^¬ tiltrieb 50, by means of which the control times (opening and closing time) of the gas inlet valves 8 and the gas outlet valves 11 can be adjusted individually. A No ^¬ ckenwelle 27 (not shown in Figure 1) is coupled to the gas outlet valve and the crankshaft 13 respectively with the gas inlet valve 8 and / or. The internal combustion engine 1 may have ckenwelle game as an intake camshaft and / or a Auslassno- at ^¬. The variable valve train 50 is coupled to the camshaft 27 and the crankshaft 13 and allows at least one phase of the camshaft 27 to be adjusted to the crankshaft 13. The variable valve train 50 may be realized, for example, by a hydraulically adjustable camshaft (not shown in FIG. 1). in which the different timing of the valves 8, 11 result by switching between cam 28 with different survey curves. However, an electric variable valve train is possible in which the valves 8, 11 are driven individually, electrically.

For example, the variable valve train 50 may include an actuator that is configured and arranged the camshaft 27 to drive. The actuator is configured to drive the camshaft 27 such that the camshaft 27 rotates in a predetermined angular range about its longitudinal axis in a first direction or in an opposite second direction. For example, the actuator may be configured to drive the camshaft 27 depending on a predetermined electrical pulse.

The internal combustion engine 1 further has a fuel supply system which has a fuel tank 17 and a fuel pump 18 arranged therein. The fuel is supplied by means of the fuel pump 18 via a supply ^¬ lines 19, 19 a pressure accumulator 20. This is a common pressure accumulator, from which the injection valves 9 for several cylinders 2 with

supplied pressurized fuel. In the supply line 19, a fuel filter 21 and a high-pressure pump 22 are further arranged. The high-pressure pump 22 serves to supply the fuel delivered by the fuel pump 18 at relatively low pressure (approximately 3 bar) to the pressure accumulator 20 at high pressure (typically up to 150 bar).

The internal combustion engine 1 is a control device 23 assigns supplied ^¬ which tuatoren on signal and data lines with all AK and connected sensors of the internal combustion engine. 1

Figure 2 shows at least partially the high pressure pump 22 with a pump housing 25 and a pump unit 25. The high pressure pump 22 includes, for example, a digital high pressure switching pump.

The pump unit 25 shown is preferably a plurality of pump units 25 of the high-pressure pump 22, which are operated by a ge ^¬ jointly used with the drive shaft. Is preferred the drive shaft, the cam shaft 27 which is coupled to the gas inlet ^¬ outlet valve 8 and / or the gas outlet valve. 11

The camshaft 27 is rotatably supported, for example, with a rotation axis D in the pump housing 25. In the example shown exporting approximately ^¬ example, the camshaft 27 includes at least one cam 28, the cam 28 may be formed as multiple cams. In the exemplary embodiment shown in FIG. 2, the camshaft 27 has two cams 28. The number of conveying and compression strokes can be specified via the number of cams 28. The number of conveying or compression strokes corresponds to the number of cams 28.

The pump unit 25 basically includes the cylinder housing 26, which is arranged in the cylinder housing 26 cylinder chamber 311, a pump plunger 31, a plunger 29 and a return spring 33. The cylinder housing 26, the cylinder chamber 311, the Pum ^¬ penkolben 31, the plunger 29 and the Return spring 33 are preferably arranged coaxially with one another along a longitudinal axis L of the pump piston 31.

The pump piston 31 is axially movably mounted in the cylinder chamber 311 of the cylinder housing 26 in a cylindrical recess of a pump piston guide portion 32 of the cylinder housing 26 and is in operative connection with the camshaft 27. The pump piston 31 is driven in particular by the cam 28 of the camshaft 27 in a lifting movement in at least approximately radial direction to the axis of rotation D of the camshaft 27. The pump piston 31 is axially movably guided in the pump piston guide section 32 to deliver fuel from the supply line 19 via pump inlet valve 3112 into the cylinder chamber 311 with the pump discharge valve 3117 closed during a suction stroke, downwardly in FIG Pumphubs, in Figure 2 directed upward, in the To compress fuel located in the cylinder chamber 311 and possibly via the pump outlet valve 3117 under high pressure to the supply line 19 a to the accumulator 20 with closed pump inlet valve 3112.

FIG. 2 shows a possible embodiment of a pump inlet valve 3112 as a digitally switchable valve. It is a so-called. Normally open valve. Via a current coil 3114 of the valve, a valve plunger 3116 with a valve closing element against the force of a spring 3115 can be actively brought into a closed position of the valve 3112, in which no fuel can get from the supply line 19 into the cylinder chamber 311 of the pump 22 and not the other way around. If the coil 3114 is not energized, the valve 3112 is in its open position and the suction of fuel from the supply line 19 in a suction phase of the pump 22 is made possible. In a self-priming operation, the coil is not energized in this type of intake valve. Alternatively, another valve principle could be used, the

Self-sucking operation would be different accordingly.

In the illustrated embodiment, the pump outlet valve 3117 of the pump 22 is a check valve 3118, which, with a correspondingly high pressure in the cylinder chamber 311 of the pump, allows fluid to be conveyed into the supply line 19a towards the high-pressure accumulator 20.

FIG. 3 shows a time profile of a rail pressure P_rail in the pressure accumulator 20.

To build up a desired rail pressure P_rail in the pressure ^¬ memory 20, the high-pressure pump 22 is driven so even before an expected engine start during a predetermined period of time, that it a self-priming operating state and the actuator is controlled such that the camshaft 27 rotates at least once in the first direction and at least once in the second direction in the predetermined angular range about its longitudinal axis.

In the example shown in Figure 3, the actuator is controlled so during the predetermined period of time that the No ^¬ ckenwelle 27 several times in each case first angle range is rotating in the first and ^¬ closing in the second direction in the predetermined angular about its longitudinal axis. This can be done until a predetermined injection release pressure is reached in the pressure accumulator 20.

Before the engine, for example of the motor vehicle, is started, the camshaft 27 is moved back and forth, for example by means of the at least one actuator of the variable valve drive 50. The rail pressure P_rail increases due to the reciprocating movements at least approximately stepped. The time course of the rail pressure P_rail represents a test stand measurement. The rail pressure P_rail, for example, increases by about 7 to 10 bar at a camshaft rotation of 45 ° in total (22.5 ° in the first direction and 22.5 ° back in the second direction). The camshaft 27 was rotated in the example shown at an angular velocity of 75 ° / s. An injection release pressure of more than 60 bar can thus be achieved within a period of less than two seconds. The duration is also dependent on an embodiment of the

High-pressure pump 22. Furthermore, Figure 3 shows the time course of a Kurbelwel ^¬ lensignals CRK, which is detected for example by means of Kurbelwel ^¬ lensensors (respective maximum point 6 ° crankshaft 13, 3 ° camshaft 27). In Figure 3, the respective phases of the rotational movement in different directions are also to detect. During a respective first phase Phl the rotation is in the first Reichung and during a respective second phase Ph2 is performed, the rotation in the second, entge ^¬ gengesetzte direction.

Claims

claims

A method of operating an internal combustion engine (1) comprising a pressure accumulator (20), a high-pressure pump (22), a controllable actuator and a rotatably mounted camshaft (27) having a longitudinal axis, wherein

- The high-pressure pump (22) has a cylinder chamber (311) and a in the cylinder chamber (311) movably arranged pump piston (31) which is at least indirectly on the camshaft (27) supported and so depending on a rotation of the camshaft (27) free volume of the cylinder chamber (311) influenced,

- The cylinder chamber (311) of the high-pressure pump (22) hydraulically coupled ^¬ at least indirectly with an accumulator (20) for conveying the fluid in the

Pressure accumulator (20),

- The actuator is designed and arranged to drive the No ^¬ ckenwelle (27) such that the camshaft (27) rotates in a predetermined angular range about its longitudinal axis in a first direction or in an opposite second direction, and wherein the method the following steps includes:

- During a predetermined period of time before an expected engine start, the high pressure pump (22) is driven so that it has a self-priming operating state and the actuator is controlled such that the camshaft (27) at least once in the first direction and at least once in the second Direction in the predetermined angular range rotates about its longitudinal axis.

2. The method according to claim 1,

wherein the predetermined time period is immediately before the expected engine start.

3. The method according to claim 1 or 2,

in which during the predetermined period of time the actuator is controlled in such a way that the camshaft (27) rotates several times in the first and then in the second direction in the predetermined angular range about its longitudinal axis until a predetermined injection release pressure prevails in the pressure accumulator (20) ,

4. The method according to any one of the preceding claims,

in which the internal combustion engine (1) has a variable Ven ^¬ tiltrieb (50) and the camshaft (27) is coupled to a gas inlet valve (8) and / or a gas ^¬ outlet valve (11) of a combustion chamber of the internal combustion engine (1) and the actuator is arranged and formed by driving and / or adjusting the camshaft (27) to control an opening and / or closing time of the gas inlet valve (8) or gas outlet valve.

5. The method according to claim 4,

wherein the variable valve train (50) comprises an electric variable valve train.

6. The method according to any one of the preceding claims,

in which the high-pressure pump (22) comprises a digitally switching high-pressure pump.

7. An apparatus for operating an internal combustion engine (1), which is designed to carry out the method according to one of claims 1 to 6.