DE102015113954B4 - Combustion control device - Google Patents

Abstract

A combustion control device that controls combustion in a direct injection internal combustion engine, the combustion control device comprising: an injection rate waveform acquisition section (5: S110) that acquires an injection rate waveform representing a timing of a fuel injection rate; a heat release rate calculating section (5 : S160) that calculates a heat release rate based on a cylinder pressure detected upon fuel injection performed according to the injection rate waveform; a difference calculating section (5; S 170 - S180) that calculates a difference between an inclination of a waveform that represents a time course of an integrated value of the fuel injection rate, and calculates a slope of a waveform representing a time course of an integrated value of the heat release rate; anda combustion control section (5: S210) that controls combustion such that the difference calculated by the difference calculation section is in a predetermined allowable range.

Description

Technical area

The present disclosure relates to a combustion control device that controls combustion in a direct injection internal combustion engine.

background

In a diesel engine, there is a need to appropriately control a combustion state (a heat release rate) according to a running state so that fuel consumption, combustion noise, and exhaust emission can be reduced.

The JP-2008-169717A ( DE 10 2008 000 012A1 ) shows an engine control system in which an ideal heat release amount expected from a fuel supply amount and an actual heat release amount is calculated. Based on the ideal heat release amount and the actual heat release amount, a combustion rate is calculated so that an ignition timing and the like are controlled.

When the combustion state of a diesel engine is appropriate, the combustion is terminated with an ignition lag after the fuel injection timing. In this case, an injection rate waveform representing a fuel injection ratio and a heat release rate waveform representing a heat release rate approach each other. On the other hand, if the combustion state of the diesel engine is inadequate, the combustion continues even after the ignition delay. In this case, rising and falling of the injection ratio waveform moderates rather than that of the heat release rate waveform.

In the conventional system, however, only the burning rate is controlled. A combustion process (time course of the heat release rate) is not controlled. Thus, the state of combustion is not always properly controlled.

short version

It is an object of the present disclosure to provide a combustion control device that controls combustion in a cylinder to an appropriate combustion state.

The combustion control device is provided with an injection rate waveform acquisition section, a heat release rate calculation section, a difference calculation section, and a combustion control section. The injection rate waveform acquiring section acquires an injection rate waveform representing a time history of a fuel injection rate. The heat release rate calculating section calculates a heat release rate based on a cylinder pressure detected upon fuel injection performed according to the injection rate waveform. The difference calculating section calculates a difference between an inclination of a waveform representing a time history of an integrated value of the fuel injection rate and an inclination of a waveform showing a time history of an integrated value of the heat release modes. The combustion control section controls the combustion so that the difference calculated by the difference calculation section is in a predetermined allowable range.

According to the present disclosure, the heat release rate waveform can be close to the injection rate waveform, whereby an adequate combustion state can be achieved. In addition, since the heat release rate waveform varies according to the injection rate waveform, the injection rate waveform can be appropriately varied so that the appropriate combustion state is maintained.

Advantageous further developments are the subject of the further dependent claims.

Figure list

• 1 ein Blockdiagramm, das eine Konfiguration eines Maschinensteuerungssystems zeigt;
• 2 ein Flussdiagramm, das eine Verbrennungszustandssteuerung zeigt;
• 3 einen Graphen, der eine Einspritzraten-Wellenform, eine Wärmefreisetzungsraten-Wellenform und eine Integralwellenform in Bezug auf einen angemessenen Verbrennungszustand und einen unangemessenen Verbrennungszustand zeigt;
• 4 einen Graphen, der eine Variation eines Verhältnisses (F/H) zwischen einer Einspritzrate „F“ und der Wärmefreisetzungsrate „H“ zeigt; und
• 5 einen Graphen, der eine jeweilige Wellenform in einem Fall zeigt, in dem ein Einspritzungssignal geteilt wird.

The above and further aspects, features and advantages of the present disclosure are explained in more detail on the basis of the following detailed description with reference to the accompanying drawings. Show it:

• 1 Fig. 4 is a block diagram showing a configuration of an engine control system;
• 2 a flowchart showing combustion state control;
• 3 Fig. 13 is a graph showing an injection rate waveform, a heat release rate waveform, and an integral waveform with respect to an appropriate combustion state and an inappropriate combustion state;
• 4th is a graph showing a variation of a ratio (F / H) between a Shows injection rate "F" and heat release rate "H"; and
• 5 Fig. 13 is a graph showing respective waveforms in a case where an injection signal is divided.

Detailed description

Embodiments of a combustion control device will be explained below with reference to the drawings.

[Configuration]

According to a present embodiment, a combustion control device is based on an engine control system 1 applied to a four-cylinder diesel engine with a common rail.

As in 1 shown is the machine control system 1 with a diesel engine 2 , a fuel delivery system 3 , an air intake and exhaust system 4 and an electronic control unit (ECU 5 ) Mistake.

[Machine]

The machine 2 is provided with four cylinders. A piston moves back and forth in each cylinder. Each piston is with a crankshaft 21st connected. A reciprocating motion of the piston is applied to the crankshaft 21st transfer.

A NE pulsar 22nd is on the crankshaft 21st appropriate. There is also a crank angle sensor 23 arranged in such a way that it matches the NE pulsar 22nd opposite. The crank angle sensor 23 gives crank angle signals that indicate a rotation angle of the crankshaft 21st represent to the ECU 5 out. In addition, at least one of the cylinders has a cylinder pressure sensor 24 on. The cylinder pressure sensor 24 outputs cylinder pressure signals representing pressure in a combustion chamber to the ECU 5 out.

[Fuel supply system]

The fuel delivery system 3 is with a feed pump 31 , a common rail 32 and a fuel injector 33 Mistake. The feed pump 31 pumps up fuel from a fuel tank (not shown). The pressurized fuel becomes the common rail 32 fed. The common rail 32 collects the high pressure fuel and supplies the high pressure fuel to each fuel injector 33 to. The fuel injector 33 injects the fuel into the combustion chamber according to the control signals from the ECU 5 one. The feed pump 31 adjusts the pressure in the common rail 32 and the injection pressure of the fuel injector 33 according to the control signals from the ECU 5 on.

[Air inlet and outlet system]

The air intake and exhaust system 4 has an intake manifold 41 , an exhaust manifold 42 , an air filter 43 , a turbocharger 44 , a charge air cooler 45 , a throttle valve 46 and an EGR (exhaust gas recirculation) 47 Mistake.

The intake manifold 41 is connected to an intake port of a respective cylinder. An intake pipe defining an intake conduit is associated with the intake manifold 41 connected. The exhaust manifold 42 is connected to an exhaust port of each cylinder. An exhaust pipe defining an exhaust conduit is associated with the exhaust manifold 42 connected. The air filter 43 removes particles contained in the atmosphere. The turbocharger 44 rotates a turbine by using an exhaust gas and drives a compressor so that the intake air is compressed. The turbocharger also fits 44 the inlet pressure according to the command signals from the ECU 5 on. The intercooler 45 is a heat exchanger that cools the intake air, its temperature through the turbocharger 44 is increased. The throttle valve 46 adjusts the intake air flow rate passing through the machine's intake duct 2 flows. The AGR 47 consists of an EGR pipe 471 and an EGR valve 472 . The EGR pipe 471 connects the intake manifold 41 and the exhaust manifold 42 . The valve 472 fits a fluid line portion of the EGR pipe 471 on. Part of the exhaust gas is returned to an intake pipe so that an amount of NOx emission is reduced.

The intake air coming through the air filter 43 , is compressed by the turbocharger and by the intercooler 45 chilled. Its flow rate is adjusted by the throttle valve. Then the intake air goes to each cylinder through the intake manifold 41 fed. In addition, the exhaust gas flows out of each cylinder of the engine 2 is discharged into the exhaust manifold 42 . Then the exhaust gas goes through the turbocharger 44 discharged. Part of the exhaust gas flows through the EGR 47 back into the intake manifold 41 .

[ECU]

The ECU is composed of a microcomputer including a CPU, RAM, ROM and the like. The ECU 5 controls the feed pump 31 , the fuel injector 33 and the turbocharger 44 so that the machine 2 is controlled to an optimal state.

The machine control system 1 is equipped with an inlet pressure sensor, a common rail A pressure sensor, an accelerator pedal position sensor, an O2 sensor and a coolant temperature sensor are provided, which are not shown in the drawing.

The ECU 5 executes injection control and combustion state control. In the injection control, the ECU generates 5 an injection signal for controlling the injection timing and the injection amount of the fuel injector 33 based on the machine drive state estimated from the detection values of the various sensors. The ROM of the ECU 5 stores programs and various data for executing the above control operations. An injection quantity map is stored in the ROM. The injection amount map indicates a relationship between a waveform of the injection signal (timing of injection rate) and the fuel injection amount with respect to each fuel injection pressure (common rail pressure). In addition, the values recorded by the various sensors are stored in the RAM. The saved values are updated periodically.

[Injection control]

In the injection control, a target injection amount, a target injection pressure, and a target injection timing are set according to the engine driving state. The ECU 5 controls the feed pump so that the target injection pressure is obtained. With regard to the injection quantity map, the ECU defines 5 a waveform of an injection signal based on the target injection amount and the target fuel injection pressure. The waveform of the injection signal is referred to as an injection rate waveform. The ECU 5 outputs the injection signal according to the target injection timing. It should be noted that the injection control is a well known control.

[Combustion state control]

Referring to an in 2 In the flowchart shown, a procedure of the combustion state control is described below.

The ECU 5 executes the combustion state control over and over again for each combustion cycle.

In step S110 gets the ECU 5 the injection rate waveform determined in the injection control. In step S120 determines the ECU 5 whether the target fuel injection timing is set. That means the ECU 5 determines whether it is fuel injection start timing. If the answer is in step S120 If YES, the procedure goes to step S130 where the cylinder pressure continued by the cylinder pressure sensor 24 is obtained.

In step S140 determines the ECU 5 whether an increase in cylinder pressure due to fuel combustion has been detected. If the answer is in step S140 If NO, the procedure returns to step S130 . When the answer is YES in S140, the procedure in step S150 continued where the ecu 5 stores a delay time from a fuel injection start to an increase in cylinder pressure.

wenn „V“ ein Zylinderinnenvolumen darstellt, „P“ einen Zylinderdruck darstellt und „κ“ einen Isotropenexponenten darstellt.In step S160 calculates the ECU 5 a heat release rate “H” based on the cylinder pressure generated in step S130 or S200 is obtained according to the following formula (1). $$\text{H}=\left(\text{V}\cdot \text{dP}+\mathrm{\kappa }\cdot \text{P}\cdot \text{dV}\right)/\left(\mathrm{\kappa }-1\right)$$

if “V” represents an internal cylinder volume, “P” represents a cylinder pressure and “κ” represents an isotropic exponent.

In step S170 calculates the ECU 5 an injection rate “F” prior to the delay time based on the injection rate waveform obtained in step S 110 and the delay time obtained in step S 110 S150 has been saved.

In step S180 determines the ECU 5 whether a ratio (F / H) between the heat release rate “H” and the injection rate “F” is greater than a predetermined threshold “α” (α> 1). As the ratio (F / H) approaches “1”, a waveform showing a time history of an integrated value of the heat release rate becomes more similar to a waveform showing a time history of an integrated value of the injection rate.

If the answer is in step S180 NO is determined by the ECU 5 that the state of combustion is appropriate. The procedure is at step S190 continued where the ecu 5 determines whether the fuel injection executed by the injection process has been completed. If the answer is in step S190 If YES, the process ends. If the answer is in step S190 If NO, the process in step S200 continued where the cylinder pressure is obtained. Then the procedure returns to step S160 back.

If the answer is in step S180 YES is determined by the ECU 5 that the state of combustion is inappropriate. The process is then at step S210 continued where the common rail pressure has increased by a specific value, e.g. B. by 5 MPa is increased. Then the process is ended.

By increasing the common rail pressure, the fuel injection pressure through the fuel injector is increased 33 elevated. Thus, the amount of intake air is increased so that the air-fuel ratio in the combustion chamber becomes high (lean), which is suitable for fuel combustion.

[Business]

3 Fig. 13 shows an injection rate waveform, a heat release rate waveform, and integral waveforms of the injection rate and the heat release rate with respect to a drive state “A” and a drive state “B”. In drive state "A", the combustion state is appropriate. In drive state "B", the combustion state is inappropriate. Each waveform is displayed by adjusting the crank angle (time axis) so that the fuel injection timing and the pressure increase timing coincide with each other. 4th Fig. 13 is a graph showing a variation in the ratio (F / H) between the injection rate “F” and the heat release rate “H” with respect to the drive state “A” and the drive state “B”.

As in 3 as shown, a difference in inclination of the integrated waveforms between the injection rate and the heat release rate is small when the combustion state is appropriate. When the combustion state is inadequate, the difference in inclination of the integrated waveforms is large. That is, the slopes of the integrated waveforms indicate the injection rate and the heat release rate. By comparing the inclinations with each other, it can be determined whether the combustion condition is appropriate or inappropriate. As in 4th shown, the ratio (F / H) is maintained close to “1” in drive status “A” without exceeding the threshold value “α”. In the driving state “A”, the ratio (F / H) is gradually increased along with an elapsed time and exceeds the threshold value “α” at a specified control timing. In this case, the combustion state is improved by increasing the fuel injection pressure so that the ratio (F / H) is less than or equal to the threshold value “α”.

[Benefits]

As described above, according to the present embodiment, the heat release rate can be close to the injection rate waveform, whereby an adequate combustion state can be achieved. In addition, since the heat release rate waveform varies according to the injection rate waveform, the injection rate waveform can be appropriately varied so that the appropriate combustion state is maintained.

(Different embodiment)

The preferred embodiment has been described above. The present disclosure is not limited to the above embodiments.

(1) In the above embodiment, when it is determined that the combustion state is not appropriate (F / H> α), the common rail pressure (fuel injection pressure) is increased. However, it is not limited to this. The turbocharger 44 is z. B. controlled so that the inlet pressure increases.

As in 5 is shown, a pulse waveform of the injection signal can also be divided into multiple pulses. That is, the fuel injection is temporarily stopped before the deviation of the heat release rate waveform relative to the injection rate waveform increases. The deviation of the waveform is reset, whereby the deviation can be suppressed. It is preferable that the interval of the divided pulse is a minimum interval that depends on the characteristics of the fuel injector and the like.

(2) In the above embodiment, the combustion state is determined based on the ratio (F / H). However, the combustion state can be determined based on a difference between the injection rate “F” and the heat release rate “H”.

(3) In the above embodiment, a function of one element can be divided into plural elements.

(4) The present disclosure may be composed of a system including a combustion control device, computer programs, and storage media.

Claims (4)

A combustion control device that controls combustion in an in-cylinder injection type internal combustion engine, the combustion control device comprising: an injection rate waveform obtaining section (5: S110) that obtains an injection rate waveform representing a time history of a fuel injection rate; a heat release rate calculating section (5: S160) that calculates a heat release rate based on a cylinder pressure obtained at detecting fuel injection performed according to the injection rate waveform; a difference calculating section (5; S 170 - S180) that calculates a difference between an inclination of a waveform representing a time history of an integrated value of the fuel injection rate and an inclination of a waveform showing a time history of an integrated value of the heat release rate; and a combustion control section (5: S210) that controls the combustion so that the difference calculated by the difference calculation section is in a predetermined allowable range. Combustion control device according to Claim 1 wherein the combustion control section increases a fuel injection pressure when the difference exceeds the predetermined allowable range. Combustion control device according to Claim 1 wherein the combustion control section increases an intake pressure when the difference exceeds the predetermined allowable range. Combustion control device according to Claim 1 wherein the combustion control section executes the fuel injection a plurality of times when the difference exceeds the predetermined allowable range.

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