JP2010059796A - Control unit of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology capable of optimizing valve open timing of an exhaust valve without using a sensor for measuring in-cylinder pressure in a control device of an internal combustion engine. <P>SOLUTION: The control device includes a variable valve train varying the valve open timing of the exhaust valve of the internal combustion engine, a turbocharger, a supercharged pressure measurement means measuring supercharged pressure of the internal combustion engine, an exhaust pressure estimation means estimating exhaust pressure and a determination means determining the valve open timing of the exhaust valve according to the supercharged pressure and the exhaust pressure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine.

  In an internal combustion engine equipped with a turbocharger, the supercharging pressure decreases when the atmospheric pressure is lower than when traveling on a flat ground during high altitude travel (for example, 30 kPa decreases at 3000 m). Thereby, the pressure in a cylinder becomes low. In particular, in the case of a diesel engine, the turbo work is also reduced when the gas flow rate is reduced, so that the degree of reduction of the supercharging pressure is large.

  Further, when the atmospheric pressure is lowered, the amount of fresh air is reduced, so that the exhaust state may be deteriorated. In order to suppress this, in a diesel engine equipped with a variable displacement turbocharger, the nozzle vane is closed to increase the work of the turbocharger. However, closing the nozzle vane increases the pressure of the exhaust upstream of the turbocharger.

  Here, work in the expansion stroke by the internal combustion engine and work in the exhaust stroke (in this case, negative work) vary depending on the opening timing of the exhaust valve. Therefore, the efficiency of the internal combustion engine changes according to the opening timing of the exhaust valve. For an internal combustion engine that does not have a turbocharge, when the air pressure drops from the flat ground to the high altitude, the intake pressure and the exhaust pressure drop to the same extent. It becomes almost equal on flat ground and high ground. However, when the turbocharger is provided, the degree of decrease in the supercharging pressure is greater than the degree of decrease in the exhaust pressure, and therefore the optimum valve opening timing of the exhaust valve changes.

On the other hand, a technique is known in which a sensor for measuring the pressure in each cylinder is attached to each cylinder of the internal combustion engine, and the valve timing is changed according to the pressure in each cylinder (for example, see Patent Document 1). . However, if a sensor is attached to each cylinder, the number of components of the internal combustion engine increases, resulting in an increase in manufacturing cost. In addition, the sensor mounting position may not be secured. Furthermore, since the optimum opening timing of the exhaust valve is also affected by the exhaust pressure, it is not sufficient to measure the pressure in the cylinder.
Japanese Patent Laid-Open No. 10-110638 JP 2006-161666 A JP 2000-45804 A

  The present invention has been made in view of the above-described problems, and in an internal combustion engine control apparatus, it is possible to optimize the opening timing of the exhaust valve without using a sensor for measuring the pressure in the cylinder. The purpose is to provide technology that can be used.

In order to achieve the above object, an internal combustion engine control apparatus according to the present invention employs the following means. That is, the control device for an internal combustion engine according to the present invention provides:
A variable valve mechanism for changing the opening timing of the exhaust valve of the internal combustion engine;
Turbocharger,
Supercharging pressure measuring means for measuring the supercharging pressure of the internal combustion engine;
Exhaust pressure estimating means for estimating the pressure of the exhaust;
Determining means for determining a valve opening timing of the exhaust valve according to a supercharging pressure and an exhaust pressure;
It is characterized by providing.

  Here, the variable valve mechanism only needs to change at least the opening timing of the exhaust valve. The timing for opening the exhaust valve is positive work when the piston is pushed down in the expansion stroke (hereinafter referred to as expansion work), negative work when the exhaust is pushed out during the exhaust stroke (hereinafter referred to as extrusion loss), and To affect. For example, although the expansion work increases as the opening timing of the exhaust valve is delayed toward the bottom dead center, the extrusion loss also increases, so the efficiency as a whole does not necessarily increase. That is, if the opening timing of the exhaust valve is determined in consideration of the expansion work and the extrusion loss, the exhaust valve can be opened at the time when the efficiency becomes highest.

  By the way, when the internal combustion engine is operated in a place with a low atmospheric pressure such as a high altitude, the supercharging pressure also decreases as the atmospheric pressure decreases. To compensate for this, for example, even if the nozzle vane is closed, the degree of decrease in the supercharging pressure becomes larger than the degree of decrease in the exhaust pressure. That is, an increase in extrusion loss due to an increase in exhaust pressure is greater than an increase in expansion work due to an increase in supercharging pressure. Therefore, the optimal valve opening timing of the exhaust valve changes.

  In other words, the optimum opening timing of the exhaust valve changes according to the supercharging pressure and the exhaust pressure, so if the opening timing of the exhaust valve is determined according to the supercharging pressure and the exhaust pressure, it will be an appropriate time. The exhaust valve can be opened. At this time, the opening timing of the exhaust valve may be determined so that the efficiency of the internal combustion engine becomes the highest. Thereby, the efficiency of the internal combustion engine can be increased. The relationship among the supercharging pressure, the exhaust pressure, and the opening timing of the exhaust valve may be stored in advance.

In the present invention, atmospheric pressure measuring means for measuring atmospheric pressure,
Turbo work calculating means for calculating work performed by the turbocharger based on the supercharging pressure measured by the supercharging pressure measuring means and the atmospheric pressure measured by the atmospheric pressure measuring means;
Gas amount calculating means for calculating the amount of gas sucked into the cylinder of the internal combustion engine;
With
The exhaust pressure estimating means can calculate the exhaust pressure based on the work calculated by the turbo work calculating means and the gas amount calculated by the gas amount calculating means.

  The work of the turbocharger can be calculated based on, for example, the difference in enthalpy between the gas on the downstream side and the gas on the upstream side of the turbocharger. That is, it can be calculated based on how much the enthalpy has been raised by the turbocharger.

  The amount of gas sucked into the cylinder includes the amount of fresh air and the amount of EGR gas sucked into the cylinder of the internal combustion engine.

  Then, it is possible to calculate how much energy remains in the gas exhausted from the cylinder, and to calculate the exhaust pressure based on this energy. That is, since there is a correlation between the energy remaining in the gas discharged from the cylinder and the exhaust pressure, the exhaust pressure is calculated based on the energy. Further, the energy discharged from the cylinder together with the gas (may be the energy remaining in the gas) and the energy sucked together with the gas into the cylinder (may be the energy of the gas sucked into the cylinder) and There is a correlation with the amount of gas sucked into the cylinder. Here, the energy entering the cylinder can be obtained from work performed by the turbocharger. That is, the exhaust pressure can be calculated based on the work performed by the turbocharger and the amount of gas sucked into the cylinder. The relationship between the work performed by the turbocharger, the amount of gas sucked into the cylinder, and the exhaust pressure may be stored in advance.

According to the control apparatus for an internal combustion engine according to the present invention, the opening timing of the exhaust valve can be optimized without using a sensor for measuring the pressure in the cylinder.

  Hereinafter, specific embodiments of a control device for an internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine 1 according to the present embodiment. In the present embodiment, in order to display the internal combustion engine 1 simply, some components are not shown. Further, the internal combustion engine 1 in this embodiment is a diesel engine having four cylinders 2. A fuel injection valve 82 for injecting fuel into the cylinder 2 is attached to each cylinder 2 of the internal combustion engine 1. In the internal combustion engine 1, a piston 15 connected to the crankshaft 13 via a connecting rod 14 reciprocates in the cylinder 2.

  An intake pipe 4 is connected to each cylinder 2 via an intake port 3 provided in the cylinder head 10. An intake valve 5 is provided at a location where the intake port 3 is connected to the cylinder 2. The intake air flow into the cylinder 2 is controlled by the intake valve 5. Opening and closing of the intake valve 5 is controlled by rotational driving of the intake side cam 6. On the other hand, an exhaust pipe 8 is connected to each cylinder 2 via an exhaust port 7 provided in the cylinder head 10. An exhaust valve 9 is provided at a location where the exhaust port 7 is connected to the cylinder 2. The exhaust of gas to the outside of the cylinder 2 is controlled by the exhaust valve 9. Opening and closing of the exhaust valve 9 is controlled by rotational driving of the exhaust side cam 11.

  The exhaust valve 9 is opened and closed by an opening / closing mechanism. Here, the exhaust side cam 11 is attached to the exhaust side camshaft 25, and an exhaust side pulley 27 is provided at the end of the exhaust side camshaft 25. Furthermore, a variable rotational phase mechanism (hereinafter referred to as “exhaust side VVT”) 26 that can change the relative rotational phase between the exhaust side camshaft 25 and the exhaust side pulley 27 is provided. The exhaust side VVT 26 controls the relative rotational phase between the exhaust side camshaft 25 and the exhaust side pulley 27 in accordance with a command from the ECU 90 described later. The rotation of the exhaust camshaft 25 is driven by the driving force of the crankshaft 13. And according to the exhaust side VVT26, the valve opening timing and valve closing timing of the exhaust valve 9 can be changed. In this embodiment, the exhaust side VVT 26 corresponds to the variable valve mechanism in the present invention. The variable valve mechanism may be an electromagnetically driven valve. Further, the valve closing timing of the exhaust valve 9 may be changed by changing the lift amount of the exhaust valve 9 to change the valve opening period of the exhaust valve 9.

  In the middle of the intake pipe 4, a compressor housing 50a of a turbocharger 50 that operates using exhaust energy as a drive source is provided. The intake pipe 4 upstream of the compressor housing 50a is provided with an air flow meter 95 that outputs a signal corresponding to the flow rate of the intake air flowing through the intake pipe 4. The air flow meter 95 measures the intake fresh air amount of the internal combustion engine 1.

  A turbine housing 50 b of the turbocharger 50 is provided in the middle of the exhaust pipe 8.

  The turbocharger 50 of the present embodiment employs a variable displacement turbocharger that changes the flow rate of the exhaust gas blown to the turbine by changing the opening of the nozzle vane so that the supercharging pressure becomes a desired pressure. Yes. FIG. 2 is a cross-sectional view showing the configuration of the variable capacity turbocharger. 2A shows the case where the nozzle vane 51 is open, and FIG. 2B shows the case where the nozzle vane 51 is closed.

  As shown in the figure, the variable displacement turbocharger is configured to include a plurality of nozzle vanes 51 around a turbine impeller 50c provided in a turbine housing 50b. The nozzle vane 51 is opened and closed by an actuator 52. When the nozzle vane 51 is rotated to the closing side, the gap between the adjacent nozzle vanes 51 is narrowed, and the flow path between the nozzle vanes 51 is closed. On the other hand, when the nozzle vane 51 is rotated to the opening side, the gap between the adjacent nozzle vanes 51 is widened, and the flow path between the nozzle vanes 51 is opened.

  In the variable displacement turbocharger configured as described above, the direction of the flow path between the nozzle vanes 51 and the gap between the nozzle vanes 51 are changed by adjusting the rotation direction and the rotation amount of the nozzle vanes 51 by the actuator 52. It becomes possible. That is, by controlling the rotation direction and the rotation amount of the nozzle vane 51, the direction, flow velocity, and amount of exhaust blown to the turbine impeller 50c are adjusted. Thereby, a supercharging pressure can be adjusted. At this time, the exhaust pressure changes.

  Further, the internal combustion engine 1 is provided with an EGR device 30 that recirculates a part of the exhaust gas (hereinafter referred to as EGR gas) flowing through the exhaust pipe 8 to the intake pipe 4. The EGR device 30 includes an EGR passage 31 and an EGR valve 32.

  The EGR passage 31 connects the exhaust pipe 8 upstream of the turbine housing 50b and the intake pipe 4 downstream of the compressor housing 50a. The EGR gas is recirculated through the EGR passage 31. The EGR valve 32 adjusts the amount of EGR gas flowing through the EGR passage 31 by adjusting the passage cross-sectional area of the EGR passage 31.

  Further, in the middle of the intake pipe 4 on the downstream side of the compressor housing 50 a, a supercharging pressure sensor 96 that outputs a signal corresponding to the pressure of the gas flowing in the intake pipe 4, and the gas flowing in the intake pipe 4 And an intake air temperature sensor 97 that outputs a signal according to the temperature of the intake air. In this embodiment, the supercharging pressure sensor 96 corresponds to the supercharging pressure measuring means in the present invention.

  The internal combustion engine 1 is also provided with an ECU 90 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 90 includes a CPU, a ROM, a RAM, and the like for storing various programs and maps, and a unit that controls the operating condition of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's request. It is.

  Here, in addition to the above sensors, an accelerator opening sensor 91, a crank position sensor 92, and an atmospheric pressure sensor 94 are electrically connected to the ECU 90. The ECU 90 receives a signal corresponding to the accelerator opening from the accelerator opening sensor 91 and calculates an engine load required for the internal combustion engine 1 in accordance with this signal. The ECU 90 receives a signal corresponding to the rotation angle of the output shaft of the internal combustion engine 1 from the crank position sensor 92 and calculates the engine rotational speed of the internal combustion engine 1. Further, the ECU 90 receives a signal corresponding to the atmospheric pressure from the atmospheric pressure sensor 94 and calculates the atmospheric pressure. In this embodiment, the atmospheric pressure sensor 94 corresponds to the atmospheric pressure measuring means in the present invention.

  On the other hand, the exhaust side VVT 26, the EGR valve 32, the actuator 52, and the fuel injection valve 82 are connected to the ECU 90 via electric wiring, and these devices are controlled by the ECU 90.

Here, when traveling at a high altitude with a diesel engine equipped with the turbocharger 50, the flow rate of the intake air is reduced due to a decrease in the atmospheric pressure, so the work performed by the turbocharger 50 is also reduced. For this reason, since the supercharging pressure is lower than when traveling on flat ground, the pressure in the cylinder 2 is also lower, so the optimum valve opening timing of the exhaust valve 9 changes.

  Further, in the diesel engine equipped with the variable displacement turbocharger 50 as in the present embodiment, when the atmospheric pressure drops due to traveling at a high altitude or the like, the nozzle vane 51 is closed to adjust the intake air amount to the required value. The That is, the intake air amount is increased by increasing the supercharging pressure with the nozzle vane 51 closed. As a result, the intake air amount corresponding to the decrease in atmospheric pressure can be compensated. However, when the nozzle vane 51 is closed, the pressure of the exhaust gas upstream of the nozzle vane 51 increases. At this time, since the degree of increase in the exhaust pressure becomes larger than the degree of increase in the supercharging pressure, the optimal valve opening timing of the exhaust valve 9 changes. This can be said that the optimum valve opening timing of the exhaust valve 9 changes because the degree of decrease in the exhaust pressure is smaller than the degree of decrease in the supercharging pressure.

  FIG. 3 is a graph showing the relationship between the cylinder pressure and the cylinder volume from the expansion stroke to the exhaust stroke. A broken line indicates a case where the exhaust valve 9 is opened at an optimal time on a flat ground (when the cylinder internal volume is V1). Shows a case where the exhaust valve 9 is opened at an optimum time on a flat ground in a highland area (when the cylinder volume is V1).

  When the exhaust valve 9 is opened at the optimum time on a flat ground in a high altitude area (one-dot chain line), the pressure in the cylinder 2 decreases from an early stage to decrease the positive work, while the negative work in the exhaust stroke increases. . At this time, since the decrease in expansion work (positive work) exceeds the increase in extrusion loss (negative work), compared with the case where the exhaust valve 9 is opened at the optimum time in a high altitude (solid line), Efficiency is reduced.

  At high altitudes, the increase in exhaust pressure due to the closing of the nozzle vane 51 is significant. Therefore, lowering the opening timing of the exhaust valve 9 later than the flat ground can suppress a decrease in overall efficiency.

  Here, FIG. 4 is a diagram showing the relationship between the engine speed, the optimal valve opening timing of the exhaust valve, and the travel location. In the whole engine speed range, the optimum valve opening timing of the exhaust valve 9 becomes later as the altitude becomes higher than the flat ground. This can be said that the optimum valve opening timing of the exhaust valve 9 approaches the bottom dead center.

  That is, the valve opening timing of the exhaust valve 9 is changed so that the positive work in the expansion stroke is made larger and the negative work in the exhaust stroke is made smaller. By doing in this way, since the efficiency of the internal combustion engine 1 can be improved, the deterioration of fuel consumption can be suppressed.

  That is, since the positive work in the expansion stroke is reduced as the supercharging pressure is lowered, the positive work is made larger. Further, since the negative work in the exhaust stroke increases as the exhaust pressure increases, the negative work is made smaller. Considering this positive work and negative work, the optimal valve opening timing of the exhaust valve 9 is determined so that the efficiency of the internal combustion engine 1 becomes the highest.

  The optimum valve opening timing of the exhaust valve 9 can be determined using the supercharging pressure and the exhaust pressure. FIG. 5 is a flowchart showing a flow for determining the optimum valve opening timing of the exhaust valve in the present embodiment. This routine is repeatedly executed by the ECU 13 every predetermined time.

  In step S101, the atmospheric pressure is acquired. That is, the output value of the atmospheric pressure sensor 94 is read.

  In step S102, the supercharging pressure is acquired. That is, the output value of the supercharging pressure sensor 96 is read.

  In step S103, the work (turbo work) performed by the turbocharger 50 is calculated. Here, it is calculated how much work the gas has given when passing through the compressor housing 50a. At this time, work is calculated based on the supercharging pressure and the atmospheric pressure. That is, turbo work is calculated based on the difference between the enthalpy of the gas downstream of the compressor housing 50a and the enthalpy of the upstream gas. In this embodiment, the ECU 90 that processes step S103 corresponds to the turbo work calculation means in the present invention.

  In step S104, the amount of gas sucked into the cylinder 2 is calculated. This is an amount obtained by adding the amount of fresh air and the amount of EGR gas. For example, since the amount of gas sucked into the cylinder 2 changes according to the intake air temperature and the supercharging pressure, these relationships may be obtained in advance through experiments or the like. That is, if the intake air temperature and the supercharging pressure are known, it can be understood how much gas is sucked into the cylinder 2. Further, the amount of fresh air can be obtained by the air flow meter 95. Similarly, the EGR gas amount may be obtained. In this embodiment, the ECU 90 that processes step S104 corresponds to the gas amount calculation means in the present invention.

  In step S105, the exhaust pressure upstream of the turbine housing 50b is calculated. This is calculated based on the energy remaining in the gas discharged from the cylinder 2. That is, the amount of energy remaining in the exhaust gas is calculated based on the amount of gas sucked into the cylinder 2 and the energy entering the cylinder 2. At this time, the fuel injection amount is taken into consideration. Further, the amount of gas sucked into the cylinder 2 is the value obtained in step S104. The energy that enters the cylinder 2 is obtained based on the turbo work calculated in step S103. As the fuel injection amount, a value (command value) calculated by the ECU 13 is used. These relationships may be obtained in advance by experiments or the like. In this embodiment, the ECU 90 that processes step S105 corresponds to the exhaust pressure estimating means in the present invention.

  In step S106, the optimal valve opening timing of the exhaust valve 9 is calculated. Here, the optimum valve opening timing of the exhaust valve 9 is calculated based on the supercharging pressure and the exhaust pressure. That is, the lower the atmospheric pressure, the greater the increase in the exhaust gas pressure than the increase in the supercharging pressure. Therefore, the valve opening timing of the exhaust valve 9 is brought closer to the bottom dead center according to these values. These relationships may be obtained in advance by experiments or the like. In this embodiment, the ECU 90 that processes step S106 corresponds to the determining means in the present invention.

  In step S107, the opening timing of the exhaust valve 9 is changed. That is, the ECU 13 controls the exhaust side VVT 26 so that the valve opening timing of the exhaust valve 9 becomes the optimum valve opening timing obtained in step S106. In this way, the opening timing of the exhaust valve 9 can be optimized.

  The pressure in the cylinder 2 during the expansion stroke can also be calculated based on the exhaust pressure calculated in step S105. Here, it is assumed that the adiabatic change is made in the expansion stroke. Then, if the back pressure is calculated from the exhaust pressure when the exhaust valve 9 is opened, the crank angle, and the volume in the cylinder 2 with respect to the crank angle, the pressure in the cylinder 2 for each crank angle during the expansion stroke is calculated. Can be calculated.

  Further, the optimum valve opening timing of the exhaust valve 9 can be obtained in advance through experiments or the like in association with the atmospheric pressure and mapped. That is, the optimum valve opening timing can be obtained by measuring the atmospheric pressure and substituting it into this map. Further, when a sensor for measuring the pressure in the cylinder 2 is provided, the optimum valve opening timing of the exhaust valve 9 can be obtained according to the pressure in the cylinder 2 and the atmospheric pressure.

It is a figure which shows schematic structure of the internal combustion engine which concerns on an Example, and its intake / exhaust system. It is sectional drawing which shows the structure of a variable capacity type | mold turbocharger. FIG. 2A shows the case where the nozzle vane is open, and FIG. 2B shows the case where the nozzle vane is closed. It is the figure which showed the relationship between the cylinder internal pressure and cylinder internal volume from an expansion stroke to an exhaust stroke. It is the figure which showed the relationship between an engine speed, the valve opening time of an exhaust valve, and a travel location. It is the flowchart which showed the flow which determines the optimal valve opening time of an exhaust valve in an Example.

Explanation of symbols

Reference Signs List 1 internal combustion engine 2 cylinder 3 intake port 4 intake pipe 5 intake valve 6 intake side cam 7 exhaust port 8 exhaust pipe 9 exhaust valve 10 cylinder head 11 exhaust side cam 13 crankshaft 14 connecting rod 15 piston 25 exhaust side camshaft 27 exhaust side pulley 26 Exhaust side VVT
30 EGR device 31 EGR passage 32 EGR valve 50 Turbocharger 50a Compressor housing 50b Turbine housing 50c Turbine impeller 51 Nozzle vane 52 Actuator 82 Fuel injection valve 90 ECU
91 Accelerator opening sensor 92 Crank position sensor 94 Atmospheric pressure sensor 95 Air flow meter 96 Supercharging pressure sensor 97 Intake air temperature sensor

Claims (2)

A variable valve mechanism for changing the opening timing of the exhaust valve of the internal combustion engine;
Turbocharger,
Supercharging pressure measuring means for measuring the supercharging pressure of the internal combustion engine;
Exhaust pressure estimating means for estimating the pressure of the exhaust;
Determining means for determining a valve opening timing of the exhaust valve according to a supercharging pressure and an exhaust pressure;
A control device for an internal combustion engine, comprising: Atmospheric pressure measuring means for measuring atmospheric pressure;
Turbo work calculating means for calculating work performed by the turbocharger based on the supercharging pressure measured by the supercharging pressure measuring means and the atmospheric pressure measured by the atmospheric pressure measuring means;
Gas amount calculating means for calculating the amount of gas sucked into the cylinder of the internal combustion engine;
With
The exhaust gas pressure estimating means calculates the pressure of the exhaust gas based on the work calculated by the turbo work calculating means and the gas amount calculated by the gas amount calculating means. Control device for internal combustion engine.

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