JP2009264138A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine control device improving the heat efficiency of a Miller-cycle engine provided with an engine output assist means such as a mechanical supercharger. <P>SOLUTION: This engine includes a variable valve control means variably controlling valve timing for an intake valve and an exhaust valve, an alcohol concentration detection means detecting an alcohol concentration contained in alcohol-mixed fuel; and the engine output assist means assisting the output of the engine. The valve timing is changed according to the alcohol concentration, and also the driving condition of the engine output assist means is changed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control apparatus for a mirror cycle engine compatible with FFV (Flexible Fuel Vehicle).

  2. Description of the Related Art Conventionally, an Otto cycle gasoline engine having four strokes (strokes) of intake, compression, expansion, and exhaust has been widely used as a drive source for vehicles such as automobiles. In such a gasoline engine, thermal efficiency is improved by various improvements and devices, but further improvement in thermal efficiency is desired.

  In order to improve the thermal efficiency, it is known that the expansion ratio can be increased by lengthening the stroke when the engine is expanded. In the case of an Otto cycle gasoline engine, the piston stroke in each stroke is the same, and the expansion ratio and compression ratio are the same. For this reason, when the expansion ratio is increased, the compression ratio is also increased, and the air-fuel mixture is ignited early in the combustion chamber and knocking is likely to occur. As a technique for solving this problem, a mirror cycle engine is known.

  In the Miller cycle engine, the expansion ratio is set high and the intake valve timing is adjusted (the intake valve is closed early or late) to reduce the charging efficiency and reduce the substantial compression ratio, thereby improving thermal efficiency and knocking. Prevents both. However, since the charging efficiency is lowered, there is a problem that the output is lower than that of the engine with the same displacement. In order to cope with this problem, there is an engine that can obtain the same output as an engine with the same displacement even though it is a mirror cycle engine by increasing the charging efficiency using a mechanical supercharger (for example, Patent Documents) 1).

  On the other hand, in recent years, FFV-compatible engines that can be operated with a mixed fuel of gasoline and alcohol have been developed. Alcohol fuel has characteristics such as calorific value and octane number that are very different from gasoline fuel, and in order to obtain the same output as gasoline engine, it is necessary to control engine peripherals appropriately according to fuel properties .

Japanese Patent Laid-Open No. 2-119620

  However, in a mirror cycle engine having an engine output auxiliary means such as a conventional mechanical supercharger, the countermeasure when using an alcohol mixed fuel has not been sufficiently considered from the viewpoint of thermal efficiency. For example, control for improving thermal efficiency has not been made according to the properties of the alcohol-mixed fuel.

  An object of the present invention is to provide an engine control device that improves the thermal efficiency of a Miller cycle engine provided with engine output auxiliary means such as a mechanical supercharger in order to solve the above-mentioned problems.

  In order to achieve the above object, an engine control apparatus according to the present invention includes variable valve control means for variably controlling valve timings of an intake valve and an exhaust valve, and alcohol concentration detection means for detecting the alcohol concentration contained in the alcohol mixed fuel. And an engine output assisting means for assisting engine output, the valve timing is changed according to the detection result of the alcohol concentration detecting means, and the driving state of the engine output assisting means is changed. is there.

  According to the present invention, the actual compression ratio of the engine can be increased, and the thermal efficiency is reduced by reducing the load ratio of the engine output auxiliary means such as a supercharger in consideration of the increase in the engine output due to the improvement of the actual compression ratio. Can be improved.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.
(First embodiment)
FIG. 1 is a schematic diagram illustrating a configuration of an engine control system including an engine control device according to the first embodiment. As shown in FIG. 1, the engine control system includes an FFV (Flexible Fuel Vehicle) compatible engine body, an intake system and an exhaust system attached to the engine body, an engine output auxiliary means provided in the intake system, And a control device. In the present embodiment, the engine output auxiliary means is an FFV-compatible supercharger.

  The configuration of the engine control system will be described along the flow of air discharged from the intake pipe inlet (intake system) through the combustion chamber (engine body) through the exhaust pipe (exhaust system) to the outside of the vehicle.

  As shown in FIG. 1, in the intake system, impurities are removed from air sucked from the intake pipe inlet 2 a by an air cleaner 5 provided in the intake pipe 2. The air amount of the air from which impurities are removed is measured by the air flow sensor 6. A throttle valve 8 and a throttle opening sensor 9 are provided downstream of the air flow sensor 6, and the throttle valve 8 and the throttle opening sensor 9 are engine control units (hereinafter referred to as “ECUs”) that are engine control devices. 7 is connected. The ECU 7 determines the opening degree of the throttle valve 8 based on the requested engine torque, and controls the opening degree of the throttle valve 8 based on the signal from the throttle opening degree sensor 9, so that the intake pipe inlet 2a actually Adjust the amount of air taken into the engine. The intake pipe 2 downstream of the throttle valve 8 is branched into two pipes, a pipe 11 where the supercharger 10 is installed and a bypass pipe 12 which bypasses the supercharger 10. The bypass pipe 12 is provided with a bypass control valve 13. In a state where the supercharger 10 is not driven, the bypass control valve 13 is fully opened, and the sucked air is sent into the combustion chamber 4 through the bypass pipe 12 and the surge tank 14. On the other hand, since the bypass control valve 13 is closed in a state where the supercharger 10 is driven, the absorbed air passes through the supercharger 10, and further, an intercooler 15 installed downstream of the supercharger 10, It passes through the surge tank 14 and is sent into the combustion chamber 4 of the engine body 1. Here, the supercharger 10 is a mechanical supercharger that is driven by a transmission means such as a belt 17 by an engine output shaft 16, and the driving of the supercharger 10 is controlled by a supercharger drive clutch 18. Is done. The engine output shaft 16 is provided with a crank angle sensor 19 for measuring the engine speed. An injector 20 that injects fuel into the combustion chamber 4 is installed downstream of the surge tank 14, that is, on the intake port 1 a side of the engine body 1.

  In this engine control system, a mixed fuel of gasoline and alcohol (hereinafter simply referred to as “mixed fuel”) is assumed as a fuel to be used. A fuel tank 21 for supplying mixed fuel is connected to the injector 20 via a fuel supply pipe 21a. The fuel supply pipe 21a is provided with an alcohol concentration sensor 22 that measures the concentration of alcohol contained in the mixed fuel. The alcohol concentration detection means for acquiring the alcohol concentration of the mixed fuel is not limited to the alcohol concentration sensor 22. Further, the installation position of the alcohol concentration sensor 22 is not limited to the fuel supply pipe 21a between the injector 20 and the fuel tank 21, and may be disposed in the fuel storage tank or a portion through which the mixed fuel passes.

  The fuel injected from the injector 20 and the air flowing through the intake pipe 2 are mixed with each other to become an air-fuel mixture, which is introduced into the combustion chamber 4 by opening the intake valve 23. The intake valve 23 is provided with a variable valve mechanism (not shown) capable of adjusting the opening / closing timing of the valve by hydraulic pressure. The variable valve mechanism may be at least a variable valve mechanism that can change the closing timing of the intake valve 23, and may be a valve mechanism that opens and closes the intake valve 23 with an electric motor.

The air-fuel mixture in the combustion chamber 4 is compressed as the piston 1b rises, and is ignited by the ignition plug 24 at an appropriate ignition timing. The air-fuel mixture pushes down the piston 1 by its combustion pressure, generates a desired engine torque, and then, when the exhaust valve 25 is opened as the piston 1b rises, it becomes exhaust gas and is pushed out to the exhaust port 1c side. An oxygen concentration sensor 26 and a three-way catalyst 27 are installed in the exhaust pipe 3 connected to the exhaust port 1 c of the engine body 1. NO _x , CO ₂ , and HC contained in the exhaust gas are purified by the three-way catalyst 27 and then discharged outside the vehicle. Since the three-way catalyst 27 can purify the exhaust gas most efficiently when burned at the stoichiometric air-fuel ratio, air-fuel ratio feedback control that adjusts the fuel injection amount according to the output of the oxygen concentration sensor 26 so as to maintain the stoichiometric air-fuel ratio. I do. The ECU 7 receives signals from the air flow sensor 6, the throttle opening sensor 9, the crank angle sensor 19, the alcohol concentration sensor 22, the oxygen concentration sensor 26, and the like, and the fuel of the injector 20 according to the intake air amount and alcohol concentration. The injection amount and the ignition timing of the spark plug 24 are controlled, and the variable valve mechanisms 23, 24, the bypass control valve 13 of the supercharger 10, the drive determination of the supercharger 10, and the supercharging pressure are controlled.

  FIG. 2 is a block diagram showing a functional configuration of the ECU 7. As shown in FIG. 2, the ECU 7 includes a target torque calculation unit 101 and a target torque realization unit 102. The target torque calculation unit 101 includes driver request torque calculation means 103 and request torque selection means 104. The driver request torque calculation means 103 is a means for calculating the engine torque required by the driver, and calculates the basic request torque based on the accelerator operation (accelerator opening) of the driver. The required torque selecting means 104 selects the optimum engine torque from the external required torque such as traction control and cruise control and the driver required engine torque in consideration of safety and comfort. The torque selected by the requested torque selection means 104 is transmitted to the target torque realization unit 102 as the target torque.

  In the target torque realizing unit 102, first, the torque distribution calculating unit 105 distributes the torque operation amount to the ignition system, the fuel system, and the intake system in order to realize the target torque, and the ignition timing correction calculating unit 106, the fuel injection Torque operation amount command values are transmitted to the amount calculation means 107 and the torque distribution calculation means 108, respectively. The ignition timing correction calculation means 106 calculates the ignition retard amount based on the torque manipulated variable command value (for example, the reference ignition retard amount), and transmits it to the spark plug 24. The fuel injection amount calculation means 107 calculates the fuel injection amount based on the torque operation amount command value (for example, the reference fuel injection amount) and transmits it to the injector 20. The intake system torque distribution calculating unit 108 calculates the alcohol concentration of the mixed fuel, which is the calculation result of the alcohol concentration calculating unit 109, and the torque operation amount command value (for example, the reference target throttle opening, the reference target supercharging pressure, and the reference valve timing). Based on the above, the target throttle opening, the supercharging pressure of the supercharger, and the valve timing are calculated. The target throttle opening is transmitted to the throttle valve opening sensor 9, the supercharging pressure is transmitted to the supercharger 10, and the valve timing is transmitted to the variable valve mechanism. The spark plug 24, the injector 20, the throttle valve 8, the supercharger 10, and the intake valve 23 are driven according to the transmitted signals, respectively, and a desired engine torque is obtained.

  FIG. 3 is a block diagram showing a detailed configuration of the intake system torque distribution calculating means 108. As shown in FIG. 3, the valve timing calculation unit 201 calculates the closing timing θM of the intake valve 23 according to the alcohol concentration of the mixed fuel calculated by the alcohol concentration calculation unit 109, and calculates the result as the engine output calculation. Transmit to means 202. Here, the closing timing θM of the intake valve 23 will be described with reference to FIG.

  FIG. 4 is a graph showing the relationship between the crank angle and the valve lift amount of the intake valve 23. A graph IV1 in FIG. 4 shows the valve lift characteristic of the intake valve 23, and a graph EV1 shows the lift characteristic of the exhaust valve 25. In general, the exhaust valve 25 opens near the bottom dead center BDC (BDC (1) in FIG. 4) at the end of the expansion stroke, and closes after the top dead center TDC. On the other hand, the intake valve 23 is set to open before the top dead center TDC and close after the bottom dead center BDC (BDC (2) in FIG. 4) at the end of the intake stroke. Therefore, there is an overlap period (O / L) in which both the intake valve 23 and the exhaust valve 25 are open near the top dead center TDC. As described above, in the Miller cycle engine, knocking is prevented by opening the intake valve 23 until the middle of the compression stroke as in IV1 and returning a part of the intake air to the intake port 2a to reduce the substantial compression ratio. It is out.

  On the other hand, it is known that alcohol mixed fuel has a higher octane number than gasoline fuel and is difficult to knock. Therefore, in the present embodiment using the alcohol mixed fuel, the intake valve 23 is closed earlier than IV1 as shown in the valve lift characteristic IV2 (the valve closing timing of the intake valve 23 is advanced). Thereby, since a substantial compression ratio can be increased as compared with pure gasoline fuel, it becomes possible to improve the output of the engine. In particular, knocking occurs when the closing timing of the intake valve 23 is too early, but the engine output is maximized by advancing the closing timing θM of the intake valve 23 to the knocking limit. Can do.

  The alcohol-mixed fuel has a lower combustion temperature in the combustion chamber 4 than gasoline fuel, has a cooling loss reduction effect, and can obtain a larger output than gasoline fuel having the same compression ratio. FIG. 5 is a graph showing the relationship between the engine output of a gasoline engine and alcohol fuel of the same displacement. A curve T1 in FIG. 5 represents an engine performance curve of a gasoline engine having a compression ratio C1, a curve T2 represents an alcohol fuel engine having a compression ratio C1, and a curve T3 represents an alcohol performance engine of an alcohol fuel engine having a compression ratio C2 (> C1). As shown in FIG. 5, it is understood that the engine output of alcohol fuel is improved as compared with gasoline fuel.

Returning to FIG. 3, the engine output calculation means 202 outputs the engine output based on the mixed fuel alcohol concentration transmitted from the alcohol concentration detection means 109 and the intake valve closing timing θM transmitted from the valve timing calculation means 201. The improvement rate P _M / P ₀ is calculated. The reference value P ₀ of the engine output improvement rate is the engine output at the intake valve maximum advance valve closing timing when the alcohol concentration M = 0% (when gasoline fuel is used). The intake valve maximum advance valve closing timing means a value when the valve closing timing is advanced to the knocking occurrence limit. P _M is the estimated engine output value when the valve timing .theta.M. The calculation result of the engine output calculation means 202 is transmitted to the target boost pressure calculation means 203, and the target boost pressure calculation means 203 calculates the target boost pressure of the supercharger 10 based on the result of the engine output calculation means 202. calculate.

  The mechanical supercharger 10 is switched ON / OFF by a supercharger drive clutch 18, and the maximum supercharging pressure of the mechanical supercharger 10 is adjusted by a bypass control valve 13. The switching of ON / OFF of the supercharger 10 is determined based on the map showing the drive region of the supercharger shown in FIG.

As shown in FIGS. 6A to 6C, the maps indicating the drive region of the supercharger are set according to the alcohol concentration of the mixed fuel. As shown in FIG. 6A, for example, when the alcohol concentration M = 0 (pure gasoline), the improvement rate of the engine output due to the use of alcohol fuel is small (P _M / P ₀ = 1), and mechanical supercharging is performed. Large area to drive the machine. On the other hand, as shown in FIG. 6C, for example, when the alcohol concentration M = 100% (pure alcohol), the improvement rate of the engine output due to the use of alcohol fuel is large, and the mechanical supercharger is driven. Is small. In other words, when the alcohol concentration of the mixed fuel is high, the engine supercharger OFF region has a higher rotation speed and higher load than pure gasoline fuel, taking into account the increase in engine output resulting from the use of alcohol mixed fuel. The use of mechanical superchargers can be avoided. Thereby, improvement in thermal efficiency can be realized. At the same time, even in the mechanical supercharger ON area, it is possible to reduce the drive loss of the mechanical supercharger by allocating the improved engine output to the reduction of the supercharging pressure of the mechanical supercharger, This leads to further improvement in thermal efficiency.

  As described above, according to the engine control apparatus of the present embodiment, the alcohol concentration is calculated by the alcohol concentration detection means (sensor) 22, and the closing timing of the intake valve 23 is limited to the level at which knocking occurs according to the alcohol concentration. The actual compression ratio can be increased by advancing. Furthermore, in consideration of the increase in the engine output due to the improvement in the actual compression ratio, the thermal efficiency can be improved by reducing the supercharging load ratio of the mechanical supercharger 10.

In this embodiment, in accordance with the improvement in engine output due to the use of alcohol fuel, the supercharging pressure of the mechanical supercharger is lowered and the load is reduced to improve the thermal efficiency. The turbocharger is not limited to a mechanical supercharger, and may be another supercharger such as a turbocharger.
(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS.

  The basic components of the engine control device of the present embodiment are substantially the same as those of the engine control device of FIG. 1 described above, but a motor is used instead of the supercharger 10 as engine output auxiliary means, and an internal combustion engine. This is different from the previous embodiment in that it is a hybrid engine system having two prime movers, that is, an engine and a motor.

  Therefore, as shown in FIG. 7, in the engine control apparatus according to the present embodiment, the target torque realization unit 102 of the ECU 7 has a motor / internal combustion engine torque distribution calculation unit 301 instead of the torque distribution calculation unit 105. A motor has been added to the target. The motor load calculation means 302 changes the torque distribution ratio according to the alcohol concentration calculation means 109.

  FIG. 8 is a block diagram showing the configuration of the motor load calculation means 302. As shown in FIG. 8, in the motor load calculation means 302, first, as in the previous embodiment, the intake valve 23 is based on the torque operation amount command value and the alcohol concentration transmitted from the motor / internal combustion engine torque distribution calculation means 301. The valve closing timing is set, and the engine output improvement value is calculated. The calculation result from the engine output calculation means 202 is transmitted to the motor current value calculation means 401. The motor current value calculation unit 401 determines the load on the motor based on the engine output improvement value, the torque operation amount distributed by the motor / internal combustion engine torque distribution calculation unit 301, and the calculation result of the motor / internal combustion engine drive determination unit 402. To do.

  In the hybrid engine system, the load ratio of the motor and the internal combustion engine is changed according to the driving situation. In general, the driving pattern of the hybrid engine includes (1) driving only by the motor, (2) driving by the motor and the engine, (3) It is classified into three patterns in which only the engine is driven. When the result of the motor / internal combustion engine drive determination unit 402 is driven by the motor and the internal combustion engine, the drive range of only the engine can be expanded by reducing the torque distribution ratio to the motor for the engine output improvement.

  The drive pattern of the motor and engine is determined based on the map shown in FIG. 9 showing the drive areas of the motor and engine. FIG. 9A shows the driving range of the motor and the engine when pure gasoline fuel is used (M = 0), and FIG. 9B shows the driving range of the motor and the engine when the alcohol concentration is 100% (M = 100). A region R1 indicates a region where only the motor is driven, R2 indicates a region where only the engine is driven, and R3 indicates a region where both the motor and the engine are driven. As shown in FIGS. 9 (a) and 9 (b), as the alcohol concentration increases, the engine-only drive region R2 is enlarged, and the engine and motor drive region R3 are reduced. That is, since the use of the motor can be refrained, the fuel consumption can be improved.

  As described above, the present invention is not limited to the above-described embodiment, and various other ones are assumed.

It is the schematic which shows the hardware constitutions of the control apparatus of the engine of the 1st Embodiment of this invention. It is a block diagram which shows a part of structure of a control means (ECU). It is a block diagram which shows the structure of the intake system torque distribution calculating means of FIG. It is a graph which shows the relationship between the advance amount of the valve closing timing of an intake valve, and an engine output. It is a graph which shows the relationship between the engine speed of a gasoline engine and an alcohol fuel engine, and a torque. It is a graph which shows the drive region of the mechanical supercharger set up for every alcohol concentration, (a) is when alcohol concentration M is 0, (b) is when alcohol concentration M is arbitrary, (c) is alcohol It is a graph when density M is 100. It is a block diagram which shows the structure of the control means of the control apparatus of the engine of the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the intake system torque distribution calculating means of FIG. 5 is a graph showing the relationship between the motor and the internal combustion engine drive region in a hybrid engine system using a motor and an internal combustion engine, where (a) is when the alcohol concentration M is 0 and (b) is when the alcohol concentration M is 100. It is a graph of.

Explanation of symbols

1 Engine 7 ECU
DESCRIPTION OF SYMBOLS 10 Supercharger 22 Alcohol concentration sensor 23 Intake valve 25 Exhaust valve 201 Valve timing calculating means 202 Engine output calculating means 203 Target supercharging pressure calculating means

Claims (11)

Variable valve control means for variably controlling the valve timing of the intake valve or the exhaust valve;
Alcohol concentration detection means for detecting the alcohol concentration contained in the alcohol mixed fuel;
In an engine having engine output assisting means for assisting engine output,
An engine control apparatus characterized by changing the valve timing in accordance with the alcohol concentration and changing the driving state of the engine output auxiliary means.   2. The engine control apparatus according to claim 1, wherein the closing timing of the intake valve is changed in accordance with the alcohol concentration.   3. The engine control device according to claim 2, wherein the closing timing of the intake valve is advanced so as to improve the charging efficiency as the alcohol concentration is higher.   The engine control apparatus according to claim 1, wherein an engine output change accompanying a change in the alcohol concentration is calculated, and the driving state of the engine output auxiliary means is changed using the output change as an index.   5. The engine control apparatus according to claim 1, wherein the engine output auxiliary means is a supercharger.   6. The engine control apparatus according to claim 5, wherein the supercharger is a mechanical supercharger or a turbocharger.   The engine control device according to claim 5 or 6, wherein a target supercharger pressure of the supercharger is changed in accordance with the alcohol concentration.   8. The engine control apparatus according to claim 7, wherein a valve timing calculation means for calculating a closing timing of the intake valve based on the alcohol concentration, and an output change of the engine based on the alcohol concentration and the valve closing timing. An engine control device comprising: engine output calculating means for calculating the engine output; and target supercharging pressure calculating means for calculating a target supercharging pressure of the supercharger from the engine output change and the target torque.   5. The engine control apparatus according to claim 1, wherein the engine output auxiliary means is a motor.   The engine control apparatus according to claim 9, wherein the current value of the motor is changed in accordance with the alcohol concentration.   11. The engine control apparatus according to claim 10, wherein a motor / internal combustion engine drive determining means for determining a motor and an engine drive pattern, and a valve timing calculating means for calculating the closing timing of the intake valve based on the alcohol concentration. Engine output calculating means for calculating an engine output change based on the alcohol concentration and the valve closing timing, an output change of the engine, a calculation result of the motor / internal combustion engine drive determining means, and a target torque. An engine control device comprising motor current value calculation means for calculating a current value of the motor.

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