JP2004211618A - Engine control apparatus and method - Google Patents

Abstract

An object of the present invention is to prevent the supercharging pressure from being inappropriate immediately after switching from four-cycle operation to two-cycle operation and causing a sudden change in torque.
When the operating state of an engine changes between a region in which a premixed spark ignition four-cycle operation is performed and a region in which a premixed compression self-ignition two-cycle operation is performed, an actual operation is performed prior to switching of the operation cycle. The supercharging pressure Pr is appropriately controlled so that the operation of the engine 10 after switching the operation cycle is performed properly. Further, if the valve timing of the intake / exhaust valves 132 and 134 is adjusted in accordance with the change of the supercharging pressure Pr so that the amount of air sucked into the cylinder 142 is kept substantially constant, the fluctuation of the torque is further reduced. Is done.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for controlling a variable cycle engine capable of switching a combustion cycle between four cycles and two cycles.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been known a variable cycle engine that is operated by switching the operation cycle between four cycles and two cycles. Such variable cycle engines seek to fully exploit the benefits of both cycles in engines that operate over a wide dynamic range. Such an engine is described, for example, in Patent Document 1 below. In recent years, there has been proposed a technique for maximizing engine performance by combining a combustion method with an operation cycle (see Patent Document 2 below).
[0003]
[Patent Document 1]
Patent No. 2742825
[Patent Document 2]
JP-A-2002-256911
[0004]
This technique combines a two-cycle and four-cycle operation with a premixed combustion system in which a pre-formed air-fuel mixture is drawn into a cylinder of an engine and then ignited by spark ignition, while fuel is injected into a cylinder in the first half of an intake stroke. The present invention is intended to efficiently operate the engine while avoiding the occurrence of knocking in a wide operating range by combining the method of compressing the air-fuel mixture formed by performing the combustion and performing the self-ignition combustion with the four-cycle operation. .
[0005]
[Problems to be solved by the invention]
However, if the premixed spark ignition combustion is actually performed in the four-cycle operation and the premixed compression auto-ignition combustion is performed in the two-cycle operation under predetermined operating conditions, a problem is likely to occur when switching between the two combustion systems. A problem was found. In particular, in an engine provided with a supercharger such as a turbocharger or a supercharger in the intake system, supercharging is normally performed only during two-cycle operation, so that the supercharging pressure immediately after switching of the operation cycle may not be properly controlled. Problem was found.
[0006]
The device of the present invention has been made to solve these problems and to smoothly switch the combustion method in a variable cycle engine.
[0007]
[Means for Solving the Problems and Their Functions and Effects]
A first engine control device of the present invention that solves at least a part of the above-described problems,
An apparatus for controlling a variable cycle engine capable of switching a combustion cycle between four cycles for performing spark ignition combustion and two cycles for performing compression ignition combustion,
Supercharging means for supercharging the intake air of the engine,
A switching-time supercharging pressure increasing means for controlling the supercharging means to increase the supercharging pressure prior to the switching of the operation cycle when a request for switching from the four-cycle operation to the two-cycle operation is generated;
The gist is that it is provided.
[0008]
According to this engine control device, when a request for switching from four-cycle operation to two-cycle operation is issued, the supercharging pressure is increased prior to the switching of the operation cycle. Is increased toward the pressure required for two-cycle operation. Therefore, the supercharging pressure immediately after the switching of the operation cycle is increased, and the two-cycle operation can be started smoothly. It should be noted that the compression ignition combustion in the present specification means a combustion method in which a mixture (a premix) formed in advance is compressed and self-ignited. Such an air-fuel mixture may be formed by injecting fuel into a cylinder during an intake stroke, or may be formed by supplying fuel to an intake port or the like.
[0009]
In such an engine control device, when increasing the supercharging pressure, the amount of intake air of the engine can be controlled to suppress an increase in the output torque of the engine. In this way, there is no accidental increase in torque due to supercharging when the operation cycle is switched. As means for suppressing such fluctuations in the engine torque, a means for shortening the opening period of the intake valve over a predetermined period as the boost pressure increases can be adopted. This is because if the opening period of the intake valve is shortened, the phenomenon of an increase in the amount of air drawn into the cylinder due to an increase in the supercharging pressure can be reduced. The shortening of the opening period of the intake valve can be realized by delaying the opening timing of the intake valve, by increasing the closing timing of the intake valve, or by both. Further, in order to suppress the increase in the engine torque, a configuration in which the air-fuel ratio is controlled lean over a predetermined period, or a configuration in which the ignition timing is controlled to the retard side can be considered.
[0010]
The second engine control device of the present invention includes:
An apparatus for controlling a variable cycle engine capable of switching a combustion cycle between four cycles for performing spark ignition combustion and two cycles for performing compression ignition combustion,
Supercharging means for supercharging the intake air of the engine,
When a request for switching from the two-cycle operation to the four-cycle operation occurs, prior to the switching of the operation cycle, a switching-time supercharging pressure reducing unit that controls the supercharging unit to reduce the supercharging pressure.
The gist is that it is provided.
[0011]
According to this engine control device, when a request for switching from two-cycle operation to four-cycle operation is made, the supercharging pressure is reduced prior to the switching of the operation cycle. Is reduced toward the pressure required for four-cycle operation. Therefore, the supercharging pressure immediately after the switching of the operation cycle is reduced, and the four-cycle operation can be started smoothly.
[0012]
In such an engine control device, when reducing the supercharging pressure, it is possible to control the intake air amount of the engine to suppress a decrease in the engine output torque. This prevents the torque from being reduced unexpectedly due to supercharging when the operation cycle is switched. As means for suppressing such a decrease in engine torque, a means for increasing the valve opening period of the intake valve over a predetermined period as the supercharging pressure is reduced can be adopted. This is because, if the valve opening period of the intake valve is extended, the phenomenon that the amount of air taken into the cylinder decreases due to the reduction of the supercharging pressure can be reduced. The extension of the opening period of the intake valve can be realized by making the opening timing of the intake valve earlier, delaying the closing timing of the intake valve, or both. Further, in order to suppress the decrease in the engine torque, a configuration in which the air-fuel ratio is controlled to be rich over a predetermined period, or a configuration in which the ignition timing is controlled to the advanced side can be considered. The engine control device may implement both the first invention and the second invention.
[0013]
The above invention can be understood as an engine control method. That is, the first engine control method of the present invention includes:
A method for controlling a variable cycle engine capable of switching a combustion cycle between four cycles for performing spark ignition combustion and two cycles for performing compression ignition combustion,
When a request for switching from the four-cycle operation to the two-cycle operation occurs, the supercharging pressure of the intake air of the engine is increased,
Then, performing the requested operation cycle switching
The gist is.
[0014]
Further, the second engine control method includes:
A method for controlling a variable cycle engine capable of switching a combustion cycle between four cycles for performing spark ignition combustion and two cycles for performing compression ignition combustion,
When a request for switching from the two-cycle operation to the four-cycle operation occurs, the supercharging pressure of the intake air of the engine is reduced,
Then, the operation cycle of the container is switched.
The gist is.
[0015]
According to these methods, the supercharging pressure is controlled first, and then the operation cycle is switched, so that the engine after the switching of the operation cycle can be operated at an appropriate supercharging pressure. Is the same as the above-described invention of the engine control device.
[0016]
Other aspects of the invention
The present invention can be applied to engines having various numbers of cylinders. Further, the engine is not limited to an automobile, and can be applied to an engine for a ship, an aircraft, or the like. Further, the present invention can be understood as not only the above-described engine control device but also a mobile device (vehicle or the like) equipped with such a control device.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
(1) Overall configuration of the embodiment:
First, the configuration of the embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram showing an engine 10 according to a first embodiment and an engine control unit (hereinafter, referred to as an ECU) 30 as a control device thereof. The engine 10 is of a type that can be operated by switching between four-cycle operation and two-cycle operation, as described later. This gasoline engine 10 has three cylinders # 1 to # 3. In the case of four-cycle operation, these cylinders burn the air-fuel mixture in the combustion chamber while repeating four strokes of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. It converts it into a work and outputs it as power. On the other hand, when the two-cycle operation is performed, the air-fuel mixture is burned while repeating the two strokes of the suction / compression stroke and the explosion / scavenging stroke to obtain power.
[0018]
The combustion chamber of the gasoline engine 10 is formed by a cylindrical cylinder 142 provided in a cylinder block 140, a piston 144 sliding up and down in the cylinder 142, a cylinder head 130 provided on an upper portion of the cylinder block, and the like. Have been. Piston 144 is connected to crankshaft 148 via connecting rod 146. The piston 144 slides up and down in the cylinder 142 in accordance with the rotation of the crankshaft 148.
[0019]
A fuel injection valve 14 for injecting fuel into the combustion chamber and an ignition plug 136 for igniting the injected fuel are provided in the combustion chamber. Further, each combustion chamber is connected to an intake passage 12 for taking in intake air, an exhaust passage 16 for discharging combustion gas generated in the combustion chamber, and the like. Hereinafter, the configurations of the intake system and the exhaust system will be described.
[0020]
In the intake passage 12, an air cleaner 20 for removing dust, an air flow meter 13 for detecting an intake air amount Q, a compressor 54 of a supercharger 50, an intercooler 62 for reducing intake air temperature increased by supercharging, A throttle valve 22 for controlling the amount of intake air and a surge tank 60 for reducing pulsation of intake air are provided. The intake passage 12 is provided with an intake air temperature sensor 15 for detecting an intake air temperature TA and a pressure sensor 23 for detecting an intake pipe pressure. The electric actuator 24 controls the throttle valve 22 to an appropriate opening degree under the control of the ECU 30, whereby the amount of air taken into the combustion chamber is adjusted.
[0021]
The cylinder head to which the intake passage 12 is connected is provided with an intake valve 132, an exhaust valve 134, a spark plug 136, and the like, in addition to the fuel injection valve 14 described above. Fuel pressurized to a high pressure by a fuel pump (not shown) is supplied to a fuel injection valve 14 provided in each combustion chamber. The intake valve 132 and the exhaust valve 134 are provided with electric actuators 162 and 164, respectively. The valves 132 and 134 are driven by electric actuators 162 and 164 instead of a normal cam mechanism. These electric actuators 162 and 164 have a structure in which a plurality of disk-shaped electrostrictive elements are stacked. By outputting a signal from the ECU 30 and changing the voltage applied to the electrostrictive element, the electric actuators 162 and 164 can open and close the respective intake valves 132 and exhaust valves 134 at an arbitrary timing. For this reason, the valve opening period (the period from the valve opening timing to the valve closing timing) of the valve of each cylinder in this embodiment can be freely controlled. For example, it is possible to open the exhaust valve 134 in the exhaust stroke, close it once, and then reopen it for a short time in the intake stroke. The on-off valve timing of each of the valves 132 and 134 will be described later in detail.
[0022]
The catalyst 26 is provided downstream of the exhaust passage 16 via an exhaust-side turbine 52 of the supercharger 50. The catalyst 26 is a known catalyst for purifying air pollutants contained in exhaust gas. In addition, a waste gate valve 25 for controlling the supercharging pressure, an excess air ratio sensor 28 for detecting an excess air ratio λ of the air-fuel mixture in the combustion chamber from the state of exhaust gas, or an exhaust gas temperature TB is provided in the exhaust passage 16. An exhaust temperature sensor 29 and the like for detection are provided. The waste gate valve 25 regulates the exhaust gas supplied to the exhaust-side turbine 52 of the supercharger 50 by adjusting the opening thereof, and consequently the supercharged state by the intake-side turbine 54, that is, the supercharged state. The pressure can be controlled. The opening of the wastegate valve 25 is controlled by the ECU 30.
[0023]
The ECU 30 controls not only the supercharging pressure but also the entire operation of the gasoline engine 10. The ECU 30 is a well-known microcomputer configured by mutually connecting a CPU, a RAM, a ROM, an A / D conversion element, a D / A conversion element, and the like by a bus. The ECU 30 detects the engine rotation speed Ne and the accelerator opening θac, drives the electric actuator 24 based on these, and controls the throttle valve 22 to an appropriate opening. The engine rotation speed Ne can be detected by the crank angle sensor 32 provided at the tip of the crankshaft 148. The accelerator opening θac can be detected by an accelerator opening sensor 34 built in the accelerator pedal. Further, the ECU 30 drives the fuel injection valve 14 at an appropriate timing based on the intake air amount Q detected by using the air flow meter 13, thereby supplying an appropriate amount of fuel to the combustion chamber at an appropriate timing. . Further, since the excess air ratio sensor 28 is provided in the exhaust passage 16, the driving time of the fuel injection valve 14 or the opening degree of the throttle valve 22 is controlled based on the output from the excess air ratio sensor 28. It is also possible to control the excess air ratio of the air-fuel mixture formed in the combustion chamber to be an appropriate value.
[0024]
The ECU 30 also performs ignition timing control for controlling the timing at which sparks are formed in the ignition plug 136, and controls the opening and closing timing of the intake valve 132 and the exhaust valve 134. In the present embodiment, the engine 10 is operated by switching between the four-cycle operation in which the premixed spark ignition combustion is performed and the two-cycle operation in which the compression ignition combustion is performed, so that the ECU 30 also controls the ignition timing in the four-cycle operation. Te The control of the opening / closing valve timing of the intake / exhaust valves 132 and 134 greatly differs depending on the operation cycle. Hereinafter, control of the combustion cycle and the timing of opening and closing the intake and exhaust valves 132 and 134, particularly control during transition of the operation cycle, will be described in detail.
[0025]
(2) Operation cycle:
The gasoline engine 10 of the present embodiment switches between two-cycle operation and four-cycle operation in accordance with the operating range of the engine. That is, in a region where the engine load is relatively low, a two-cycle operation with high thermal efficiency is performed, and in a region where the engine load is high, a four-cycle operation in which high-speed rotation is easy is performed. The valve opening / closing timing for the movement of the piston differs between when performing the two-cycle operation and when performing the four-cycle operation. In the gasoline engine 10, the electric actuators 162 and 164 operate the intake valve 132 and the exhaust valve 134. As described above, the opening / closing timing of these valves can be easily switched.
[0026]
FIG. 2 is an explanatory diagram conceptually showing how the ECU 30 switches operating conditions according to the engine speed and the load in the present embodiment. In the drawing, a hatched area is an area where the four-cycle operation is performed, and an unhatched area is an area where the two-cycle operation is performed. Hereinafter, the two-cycle operation by the compression ignition combustion will be described. Detailed description of known four-cycle operating conditions is omitted.
[0027]
FIG. 3 is an explanatory diagram conceptually showing an operation of the gasoline engine 10 under a low load condition. Unlike a four-cycle gasoline engine, a two-cycle gasoline engine has a stroke called a scavenging stroke. Further, the two-stroke engine differs from the four-stroke engine in that the entire cycle is performed during one revolution of the crankshaft 148. FIGS. 3A to 3F conceptually show the expansion stroke, the exhaust stroke, the scavenging stroke (the above and the latter stages), the intake stroke, and the compression stroke of the two-stroke engine. In a two-stroke engine, these strokes are switched one after another by opening and closing two valves, an intake valve 132 and an exhaust valve 134, at appropriate timing while moving a piston 144 up and down within a cylinder 142. FIG. 3 also schematically shows the opening / closing state of the intake valve 132 and the exhaust valve 134 due to the movement of the piston.
[0028]
For convenience of explanation, the state in which the air-fuel mixture in the combustion chamber is burned will be described. When the air-fuel mixture is burned, high-pressure combustion gas is generated in the combustion chamber, and tends to push down the piston 144. As shown in FIG. 3A, in the expansion stroke, the pressure generated in the combustion chamber is converted into torque and output to the crankshaft 148 as power while the piston 144 is lowered. When the piston 144 has descended to some extent, the exhaust valve 134 is opened at an appropriate timing. Since the combustion gas is still trapped in the combustion chamber at a high pressure, the combustion gas can be discharged by opening the exhaust valve 134 even when the piston 144 is lowered (see FIG. 3B).
[0029]
Subsequently, when the intake valve 132 is opened at an appropriate timing, the air in the intake passage 12 pressurized by the supercharger 50 flows in, and the combustion gas remaining in the combustion chamber is pushed out from the exhaust valve 134. It is discharged (see FIG. 3C). In the figure, the hatched portion indicates a region where the combustion gas remains, and the non-hatched portion indicates a region where the intake air flows. The operation of discharging the combustion gas from the combustion chamber by pushing it out with the intake air is called "scavenging". The scavenging process is called a scavenging process. In the two-stroke engine, the intake passage is pressurized, so that even if the piston 144 starts rising after passing through the bottom dead center (hereinafter also referred to as BDC), the combustion gas in the combustion chamber can still be scavenged. . FIG. 3D conceptually shows a state in which the piston 144 is raised in the latter half of the scavenging stroke while scavenging the inside of the combustion chamber. In the two-cycle operation, the fuel injection valve 14 is opened at this timing to inject a predetermined amount of fuel. As a result, an air-fuel mixture is formed in the cylinder.
[0030]
With the progress of scavenging and the formation of the air-fuel mixture, the exhaust valve 134 is closed as shown in FIG. 3 (e). However, the exhaust valve 134 is closed via the intake valve 132 until the pressure in the combustion chamber reaches the pressure in the intake passage. The intake air still flows in. At a timing when the pressure in the combustion chamber reaches the pressure in the intake passage, the intake valve 132 is closed. Then, as the piston 144 rises, the air-fuel mixture in the combustion chamber is compressed (see FIG. 3F). The compressed air-fuel mixture ignites and explodes. Thus, the operation cycle returns to FIG. 3A, and the operation is repeated from the expansion and exhaust stroke again. In the gasoline engine 10 of this embodiment, in the two-cycle operation, the intake valve 132 is opened at a timing of about 30 ° before the bottom dead center (BDC) of the piston as shown in FIG. Further, in this embodiment, the fuel spray injection period is a period from the vicinity of the bottom dead center (BDC) of the piston to immediately before the exhaust valve 134 closes, specifically, from 20 degrees before the bottom dead center of the scavenging stroke to the bottom dead center. An appropriate period is set within a range of 60 degrees after the point.
[0031]
After the fuel is injected and the exhaust valve 134 is closed at a predetermined timing, the air pressurized from the intake valve 132 flows into the combustion chamber as shown in FIG. The timing EXC1 for closing the exhaust valve 134 can be suitably set within a range of about 20 ° to about 50 ° after the bottom dead center (BDC) of the piston (see FIG. 4). The fuel spray injected in the latter half of the scavenging stroke is dispersed in the combustion chamber by the flow of intake air and mixes with the intake air. In the engine 10 of the present embodiment, the fuel injection amount is set so that the excess air ratio of the air-fuel mixture thus formed under low load conditions has a value of about 0.2 to 0.6.
[0032]
Then, when the intake valve 132 is closed at a predetermined timing, the air-fuel mixture in the combustion chamber is compressed with the rise of the piston thereafter. In the engine 10 of the embodiment, the timing INC1 for closing the intake valve 132 is set to about 60 ° after the bottom dead center (BDC) of the piston as shown in FIG. The timing for closing the intake valve 132 can be appropriately set typically in the range of about 50 ° to about 70 °. By setting such timing, the substantial compression ratio of the air-fuel mixture can be set to a desired value in the range of 10 to 14. In the engine 10 of the embodiment, the substantial compression ratio is set to 12.
[0033]
When the piston 144 is moved up after closing the intake valve 132 at an appropriate timing, the air-fuel mixture is compressed in the combustion chamber as shown in FIG. Self-ignite in the vicinity. As a result, the air-fuel mixture formed in the combustion chamber explodes and burns quickly.
[0034]
(3) Operation cycle switching processing in the first embodiment:
The control in the case where the engine 10 that has been operated for four cycles under the high rotation condition shown in FIG. 2 is switched to the two-cycle operation by changing the operating conditions will be described in detail below. 5 to 7 are flowcharts showing the control performed by the ECU 30 in the first embodiment. FIG. 8 is a timing chart showing the state of each part when switching is performed between the four-cycle operation and the two-cycle operation. Hereinafter, the transient control will be described with reference to these drawings. In the following description, the four-cycle operation means a four-cycle operation in which the pre-mixed air-fuel mixture is spark-ignited to perform combustion, and the two-cycle operation means that the pre-mixed air-fuel mixture is compressed. This means two-cycle operation in which combustion is performed by self-ignition.
[0035]
The operation cycle switching processing routine shown in FIG. 5 is repeatedly executed at predetermined intervals, and when this processing routine is started, first, the operation state of the engine 10 is read and processing is performed (step S100). In the present embodiment, as the operating state of the engine 10, the rotational speed Ne and the intake air amount Q are read. The rotation speed Ne can be read directly from the rotation speed sensor. The intake air amount Q may be predicted based on the accelerator opening θac, the opening of the throttle valve 22, or the valve timing of the intake or exhaust valve.
[0036]
Next, based on the engine speed Ne and the intake air amount Q, a process for determining the operation cycle of the engine 10 is performed with reference to the map shown in FIG. 2 (step S110). As shown in FIG. 2, the four-cycle operation is generally selected in a high-load and high-speed range. Specifically, the operation cycle is determined by setting the value of the flag F1 to 1 when it is determined that the vehicle is in the operation region in which the two-cycle operation is to be performed, and by setting the flag F1 in the operation region where the four-cycle operation is to be performed. It is set to the value 0, respectively. Therefore, a process of calculating the target supercharging pressure P0 is performed according to the determined operation cycle (step S120). The target supercharging pressure P0 is a supercharging pressure finally required in each operation cycle. Although the target supercharging pressure P0 is higher in the two-cycle operation, the supercharging is not performed in the four-cycle operation in the present embodiment. Therefore, the target supercharging pressure P0 in the four-cycle operation is set to the value 0. . Next, according to the value of the flag F1, a process of determining the operation cycle determined based on the operation region of the engine 10 is performed (step S130).
[0037]
Here, when it is determined that the two-cycle operation is set, the process proceeds to step S140 and thereafter, and first, a process of calculating the target switching supercharging pressure P02 is performed. The target switching supercharging pressure P02 is a pressure that is lower than the final target supercharging pressure P0 of the two-cycle operation, but is set as a pressure at which it can be determined that the switching to the two-cycle operation is possible. Thereafter, it is determined whether or not the flag F2 is 0 (step S150). As will be described later, the flag F2 is set to a value of 1 after the operation cycle of the engine 10 is switched to the two-cycle operation, and is set to a value of 0 after the operation cycle is switched to the four-cycle operation. Therefore, if four cycles are currently being operated (step S130), the determination in step S150 is "YES", and the process of setting the value 1 to the flag F4 is performed (step S160). This flag F4 indicates that the switching control of the operation cycle involving the adjustment of the supercharging pressure P is being performed.
[0038]
Thereafter, the supercharging pressure increase switching control (step S170) is performed to perform a process of increasing the actual supercharging pressure Pr toward the target switching supercharging pressure P02. Although this process will be described in detail later, as shown in FIG. 8, when the operation cycle is changed from four to two, the boost pressure Pr is increased. In the process of increasing the supercharging pressure Pr, the operation cycle is switched, which will also be described later. Thereafter, assuming that the operation cycle has been switched, flag F4 is set to a value of 0 (step S190), and this processing routine ends.
[0039]
The above-described boost pressure increase switching control will be described with reference to FIG. When the supercharging pressure switching control is executed, first, a process of increasing the supercharging pressure is performed (step S171). The boost pressure can be increased by gradually closing the waste gate valve 25 and increasing the amount of exhaust gas from the engine 10 that passes through the exhaust turbine 52. Therefore, when the waste gate valve 25 is controlled in the closing direction, supercharging is started, and as a result, the intake pressure of the engine 10 starts to increase toward the target supercharging pressure P0. Therefore, a process of detecting the actual supercharging pressure Pr is performed next (step S172). The actual supercharging pressure Pr is detected by a pressure sensor 23 provided in the intake pipe 12. It is determined whether or not the detected actual boost pressure Pr is higher than the target switching boost pressure P02 set in step S140 (step S173). If the detected actual boost pressure Pr is equal to or lower than the target switching boost pressure P02, the process returns to step S172. While the actual boost pressure Pr is being detected, the process waits until the actual boost pressure Pr exceeds the target switching boost pressure P02.
[0040]
If the wastegate valve 25 is gradually closed to send more exhaust gas to the exhaust-side turbine 52, the actual supercharging pressure Pr increases by the action of the compressor 54 (see FIG. 8). When the actual supercharging pressure Pr exceeds the target switching supercharging pressure P02, the ECU 30 performs a process of switching the operation cycle of the engine 10 from the 4-cycle operation to the 2-cycle operation (step S174). Subsequently, since the operation cycle has been switched to two cycles, a process of setting the flag F2 indicating the current operation cycle to the value 1 and simultaneously initializing the variable M to the value 0 is performed (step S175). As a result, as shown in FIG. 8, the value of the flag F2 changes in synchronization with the switching of the operation cycle.
[0041]
The variable M is a variable for a timer used to continue operation according to the operation cycle for a certain period after switching the operation cycle. The operation state of the engine 10 changes in a short time due to the driver's intention and the like. Therefore, when the engine 10 is operated near the boundary between the four-cycle operation region and the two-cycle operation region shown in FIG. 2, a process of changing the operation cycle in a short time may occur. In such a case, the variable M is used as a timer and counted (step S176) until the variable M reaches a preset value M0 (step S180) so that the operation cycle is not changed in a very short time. Continue driving. In the meantime, while detecting the actual supercharging pressure Pr (step S177), it is determined whether or not the actual supercharging pressure Pr is equal to or higher than the final target supercharging pressure P0 in the two-cycle operation (step S178). If the supercharging pressure Pr is equal to or higher than the target supercharging pressure P0, the waste gate valve 25 is maintained at the opening (step S179). If the actual supercharging pressure Pr has not yet reached the target supercharging pressure P0, the control is continued as it is, and the actual supercharging pressure Pr is gradually increased to the target supercharging pressure P0. If it is determined that the predetermined period determined by the variable M has elapsed while continuing such processing (step S180), the process exits from "END" and ends this routine. This predetermined period may be appropriately determined according to the characteristics of the engine 10 and the like. In order to prevent frequent switching of the operation cycle within a short time, the switching map of the operation cycle is provided with hysteresis, and when switching to one operation cycle occurs, switching to the other operation cycle is performed. It is also conceivable to make it less likely.
[0042]
In the operation switching process routine shown in FIG. 5, when the request for the engine 10 changes from the region in which the four-cycle operation is performed to the region in which the two-cycle operation is to be performed, first, as shown in FIG. The flag F1 indicating the operation cycle to be operated is set to the value 1, the flag F4 indicating that the operation cycle is being switched is set to the value 1, and the supercharging pressure increase switching control routine shown in FIG. Execute When this control routine is executed, the waste gate valve 25 is controlled, the supercharger 50 starts supercharging, and the actual supercharging pressure Pr gradually increases. When the actual supercharging pressure Pr exceeds the target switching supercharging pressure P02, the operation cycle of the engine 10 is switched to the two-cycle operation, the flag F2 indicating the actual operation cycle is set to a value of 1, and the two-cycle operation is performed for at least a predetermined period. Is performed.
[0043]
As a result of the above processing, the engine 10 is operated for two cycles. If the engine operation region remains in the region where two-cycle operation is to be performed (F1 = 1), the supercharging pressure Pr is held at the high target supercharging pressure P0 for two-cycle operation, indicating an actual operation cycle. The flag F2 is also kept at the value 1. Therefore, the determination in step S150 is "NO", the operation cycle switching process is not performed, and the process exits to "END" and ends this routine.
[0044]
Eventually, when the request for the engine 10 changes and the operating state enters the operating range of the rotational speed Ne and the intake air amount Q at which the four-cycle operation is to be performed, the determination in step S110 is that the four-cycle operation should be performed. (F1 ← 0), the determination in step S130 is reversed, and the processes in and after step S240 are executed. Steps S240 to S290 correspond to steps S140 to S190 described above, and only the contents of the determination (F2 = 1?) In step S250 and the contents of the supercharging pressure control in step S270 correspond to steps S150 and S170. The opposite is true. That is, in step S240, the target switching supercharging pressure P04 for switching to the four-cycle operation is calculated, and thereafter, in step S250, it is determined whether or not the flag F2 has a value of 1. If the engine 10 has been operated for two cycles up to that time, the flag F2 is set to the value 1 (FIG. 6, step S175), so the determination in step S250 is "YES", and the switching control is performed. The flag F4 is set to the value 1 (step S260). Thereafter, the boost pressure reduction switching control (step S270) is performed, and when the switching control is completed, the flag F4 is returned to the value 0, and this routine ends.
[0045]
The supercharging pressure drop switching control (step S270) is control corresponding to the supercharging pressure increase switching control (step S170), and details thereof are shown in FIG. In this process, the supercharging pressure is reduced, and first, control for reducing the supercharging is started (step S271). The supercharging is reduced by gradually opening the waste gate valve 25. As a result, the exhaust gas from the engine 10 bypasses the exhaust-side turbine 52 and gradually does not flow into the exhaust-side turbine 52, the rotation of the compressor 54 decreases, and the intake pressure of the engine 10 starts to gradually decrease. Next, a process of detecting the actual supercharging pressure Pr is performed (step S272), and it is determined whether the actual supercharging pressure Pr is lower than a preset target switching supercharging pressure P04 (step S240) (step S240). S273) If it is equal to or higher than the target switching supercharging pressure P04, the process returns to step S272 to wait for the actual supercharging pressure Pr to fall below the target switching supercharging pressure P04 while detecting the actual supercharging pressure Pr.
[0046]
If the waste gate valve 25 is gradually opened to bypass the exhaust gas, the actual boost pressure Pr decreases (see FIG. 8). When the actual supercharging pressure Pr is lower than the target switching supercharging pressure P04, the ECU 30 performs a process of switching the operation cycle of the engine 10 from the two-cycle operation to the four-cycle operation (step S274). Subsequently, since the operation cycle has been switched to four cycles, the flag F2 indicating the current operation cycle is set to the value 0, and at the same time, the process of initializing the variable M to the value 0 is performed (step S275). As a result, the value of the flag F2 changes (1 → 0) in synchronization with the switching of the operation cycle, as shown in FIG. The variable M is used as a timer, which is counted (step S276), and the four-cycle operation is continued until the variable M reaches at least a preset value M0 (step S280). In the meantime, while detecting the actual supercharging pressure Pr (step S277), it is determined whether the actual supercharging pressure Pr is equal to or lower than the final target supercharging pressure P0 in the four-cycle operation (step S278). When the supercharging pressure Pr becomes equal to or lower than the target supercharging pressure P0, the control of keeping the waste gate valve 25 at the opening thereof (step S279) is the same as the corresponding supercharging pressure increase switching control routine. If it is determined that the predetermined period determined by the variable M has elapsed while continuing such processing (step S280), the process exits from “END” and ends this routine.
[0047]
Thereafter, if the engine 10 remains in the operating region where four-cycle operation is to be performed, the flag F1 is set to the value 0 and the flag F2 is also set to the value 0. "NO", and the operation cycle switching processing routine ends without performing any switching control.
[0048]
According to the present embodiment described above, when the operating state of the engine 10 changes from the rotation speed Ne and the intake air amount Q to an operation region in which four-cycle operation is to be performed for two cycles, prior to the two-cycle operation. Then, the supercharging pressure is increased, and after the supercharging pressure is sufficiently increased (Pr ≧ P02), the operation cycle is switched to the two-cycle operation. Therefore, a sufficient boost pressure can be obtained from the beginning of the two-cycle operation, and scavenging can be performed stably. As a result, torque shock does not occur at the time of switching operation cycles, and emission and thermal efficiency do not decrease.
[0049]
In the present embodiment, when the operating state of the engine 10 changes from the two-cycle operation to the operation region in which the four-cycle operation is to be performed, the supercharging pressure is reduced prior to the four-cycle operation, and the supercharging pressure is sufficiently reduced. After decreasing (Pr ≦ P04), the operation cycle is switched to four-cycle operation. Therefore, an appropriate intake pressure can be obtained from the beginning of the four-cycle operation. As a result, abnormal combustion or the like is not caused when the operation cycle is switched, and there is no possibility that a torque shock is generated or emission or thermal efficiency is reduced.
[0050]
(4) Operation cycle switching processing in the second embodiment:
Next, a second embodiment of the present invention will be described. The engine control device of the second embodiment has basically the same hardware configuration as that of the first embodiment, and the basic control regarding the operation of the engine 10 is also the same. For example, the operation cycle switching routine shown in FIG. 5 accompanying the switching of the operation cycle is similarly executed. In the second embodiment, the supercharging pressure increase switching control (step S170) and the supercharging pressure decrease switching control (step S270) in the operation cycle switching routine are different from the first embodiment. Details of these switching controls are shown in FIG. 9 and FIG.
[0051]
FIG. 9 is a flowchart illustrating a supercharging pressure increase switching control routine according to the second embodiment. The same processes as those in the supercharging pressure increase switching control routine (FIG. 6) of the first embodiment are denoted by the same step numbers. When the switching control routine is started, similarly to the first embodiment, supercharging increase control is started (step S171), and the actual supercharging pressure Pr is detected (step S172). Thereafter, in the second embodiment, a process of determining the valve operation timing VT4 in the four-cycle operation based on the detected actual boost pressure Pr is performed (step S310). In the embodiment, since the operation of the intake and exhaust valves 132 and 134 is performed by the electric actuators 162 and 164, the operation timing can be easily adjusted by electric control. The ECU 30 controls the electric actuator 164 based on the valve timing VT4 set in step S310 to finely control the opening / closing timing of the intake and exhaust valves 132 and 134. Actually, the actual supercharging pressure Pr increases along with the switching from the four-cycle operation to the two-cycle operation, and the effective intake air amount sucked into the cylinder 142 is also increasing. The opening period of the intake valve 132 is gradually shortened. That is, the valve opening period of the intake valve 132 is gradually changed so that the actual air amount involved in combustion is kept constant. FIG. 11 schematically shows how the valve timing VT is switched in the second embodiment, together with changes in other flags.
[0052]
Thereafter, as in the first embodiment, until the actual supercharging pressure Pr becomes larger than the target switching supercharging pressure P02 (step S173), the actual supercharging pressure Pr is detected (step S172), and the valve timing VT4 is set. When the actual supercharging pressure Pr exceeds the target switching supercharging pressure P02 (step S310), the operation of the engine 10 is switched to the two-cycle operation (step S174), the flag F2 is set to a value of 1, and the timer Is initialized to a value 0 (step S175). Thereafter, the actual supercharging pressure Pr is detected again (step S320), and a process for setting the valve timing VT2 of the intake and exhaust valves 132, 134 in the two-cycle operation is performed (step S330). The valve timing VT2 in this case is also set so as to mainly shorten the valve opening period of the intake valve 132 gradually. Since the supercharging pressure Pr increases and the output from the engine 10 changes in two-cycle operation, the intake air is gradually changed so that torque shock does not occur. Since the basic valve timing is different between the valve timing VT4 for the four-cycle operation and the valve timing VT2 for the two-cycle operation, the valve timing VT is discontinuous as shown in FIG. The valve timing in the same operation cycle during supercharging, that is, the valve opening periods of the intake and exhaust valves 132 and 134 are continuously controlled.
[0053]
Thereafter, similarly to the first embodiment, the timer variable M is incremented (step S176), and it is determined whether the actual supercharging pressure Pr is equal to or higher than the target supercharging pressure P0 (step S178). Pr is held (step S179), the timer variable M value is determined (step S180), and the processing after the detection of the actual supercharging pressure Pr (step S320) is continued until the timer variable M exceeds the value M0. repeat. As a result, the process of setting the valve timing VT2 of the intake / exhaust valves 132, 134 for the two-cycle operation based on the actual supercharging pressure Pr is repeated until the timer variable M exceeds the predetermined value M0. . The switching of the valve timing VT2 is also schematically shown in FIG. Further, control for maintaining the actual supercharging pressure Pr at the target supercharging pressure P0 is also performed.
[0054]
On the other hand, when the operating state of the engine 10 changes from the two-cycle operation to the four-cycle operation region, the supercharging pressure reduction switching control routine shown in FIG. 10 is executed. The processing shown in FIG. 10 is basically symmetric with the processing shown in FIG. The same processes as those shown in FIG. 7 are denoted by the same step numbers. Therefore, the supercharging pressure drop switching control will be briefly described focusing on processing different from the processing in FIG. This switching control routine is started, a process for reducing the supercharging is started (step S271), and the actual supercharging pressure Pr is detected (step S272). Thereafter, based on the detected actual supercharging pressure Pr, A process for determining the valve operation timing VT2 in the two-cycle operation is performed (step S410). As the switching from the two-cycle operation to the four-cycle operation is performed, the actual supercharging pressure Pr decreases, and the effective intake air amount drawn into the cylinder 142 is also decreasing. The opening period is gradually extended. The switching of the valve timing VT in the second embodiment is shown in the latter half of FIG.
[0055]
Thereafter, when the actual supercharging pressure Pr becomes smaller than the target switching supercharging pressure P04 (step S273), the operation of the engine 10 is switched to the four-cycle operation (step S274), the flag F2 is set to the value 0, and the timer is used. The variable M is initialized (step S275). Thereafter, the actual supercharging pressure Pr is detected again (step S420), and a process for setting the valve timing VT4 of the intake and exhaust valves 132 and 134 in the four-cycle operation is performed (step S430). The valve timing VT4 in this case is also set so that the opening period of the intake valve 132 is gradually increased. Since the supercharging pressure Pr decreases and the output from the engine 10 changes in four-cycle operation, the intake air is gradually changed so that torque shock does not occur.
[0056]
Thereafter, the timer variable M is incremented (step S276), and it is determined whether the actual supercharging pressure Pr is equal to or less than the target supercharging pressure P0 (step S278). If Pr ≦ P0, the actual supercharging pressure Pr is held (step S279). Is performed, and the value of the timer variable M is determined (step S280), and the processing following the detection of the actual supercharging pressure Pr (step S420) is repeated until the timer variable M exceeds the value M0. As a result, the process of setting the valve timing VT4 of the intake / exhaust valves 132, 134 for the four-cycle operation based on the actual supercharging pressure Pr is repeated until the variable M for the timer exceeds the predetermined value M0. . This switching of the valve timing VT2 is also schematically shown in the latter half of FIG. Further, control for maintaining the actual supercharging pressure Pr at the target supercharging pressure P0 is also performed.
[0057]
According to the second embodiment described above, similarly to the first embodiment, the supercharging pressure is appropriately controlled prior to the switching of the operation cycle, so that abnormal combustion occurs, emission / thermal efficiency decreases, and further, a sudden change in torque occurs. There is no possibility of occurrence of the accompanying torque shock. In addition, in the second embodiment, the valve timing of the intake and exhaust valves 132 and 134 is set based on the supercharging pressure Pr and gradually switched in accordance with the switching of the operation cycle. Therefore, even if the supercharging pressure changes, the amount of air sucked into the cylinder 142 can be controlled to be substantially constant, and a sudden change in torque can be prevented more reliably.
[0058]
(5) Modification:
Although some embodiments of the present invention have been described above, the present invention is not limited to these embodiments of the present invention, and may be implemented in various modes without departing from the gist of the present invention. Wear. For example, in the above embodiment, the intake and exhaust valves 132 and 134 are driven by the electric actuators 162 and 164, and the valve timing is adjusted by the electric drive timing of the electric actuators 162 and 164. The camshaft that rotates in conjunction with the crankshaft is provided with a mechanism that can adjust the phase of the cam with respect to the rotation of the shaft, and a mechanism that varies the lift amount of the valve shaft by the cam. The timing may be controlled. In this case, the movement of the cam for one revolution of the crankshaft is essentially different between the four-cycle operation and the two-cycle operation. Is also good.
[0059]
Alternatively, in the above-described embodiment, a so-called turbocharger in which the turbine is rotated by the exhaust gas to supercharge the intake air is used. It is. Alternatively, a supercharging mechanism such as a motor-assisted turbo for supercharging by driving a pump with an electric motor can also be adopted. It is also possible to adopt a supercharging method such as a roots type or a resholm type. Further, in the second embodiment, the intake air amount is controlled mainly by adjusting the opening period of the intake valve 132 so that the torque does not suddenly change with the switching of the operation cycle. By controlling the fuel injection amount, the torque of the engine 10 may be controlled so as not to cause a sudden change in the torque. In the embodiment, fuel is supplied by in-cylinder injection. However, a mechanism for injecting fuel into the intake port may be provided.
[0060]
In this embodiment, a three-cylinder engine is used as an example. However, the present invention is applied to engines other than three cylinders, for example, engines having different numbers of cylinders, such as two cylinders, four cylinders, five cylinders, six cylinders, eight cylinders, and twelve cylinders. can do. If the in-cylinder gas temperature at the time when the operation cycle is switched to the two-cycle operation is maintained at the high gas temperature obtained by the four-cycle operation, abnormal combustion is likely to occur. It is also desirable to use control for lowering the temperature of the in-cylinder gas by using a method such as introducing EGR or fresh air. Such a decrease in the in-cylinder gas temperature may be achieved by a method of lowering the temperature of the exhaust gas itself, a method of rapidly lowering the temperature of the cylinder block to thereby lower the in-cylinder gas temperature, or a method of temporarily lowering the intake air temperature by an intercooler. Various methods are known.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an engine 10 and a control device thereof according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a relationship between an engine speed and a load and an operation cycle.
FIG. 3 is an explanatory diagram illustrating a stroke of a two-cycle operation.
FIG. 4 is an explanatory diagram showing opening and closing valve timings of intake and exhaust valves in a two-cycle operation.
FIG. 5 is a flowchart showing an operation cycle switching processing routine in the embodiment.
FIG. 6 is a flowchart illustrating a supercharging pressure increase switching control routine according to the first embodiment.
FIG. 7 is a flowchart illustrating a supercharging pressure reduction switching control routine according to the first embodiment.
FIG. 8 is a timing chart showing various switching timings in the first embodiment.
FIG. 9 is a flowchart illustrating a supercharging pressure increase switching control routine according to a second embodiment.
FIG. 10 is a flowchart illustrating a supercharging pressure reduction switching control routine according to a second embodiment.
FIG. 11 is a timing chart showing various switching timings in the second embodiment.
[Explanation of symbols]
10. Gasoline engine
12 ... intake passage
13 ... Air flow meter
14 ... Fuel injection valve
15. Intake air temperature sensor
16 Exhaust passage
20 ... Air cleaner
22 ... Throttle valve
23 ... Pressure sensor
24 ... Electric actuator
25 ... Waste gate valve
26 ... catalyst
28 ... Air excess rate sensor
29… Exhaust gas temperature sensor
30 ... ECU
32 ... Crank angle sensor
34 Accelerator opening sensor
50 ... Supercharger
52 ... exhaust side turbine
54 ... Inlet side turbine
60 ... Surge tank
62 ... Intercooler
100 ... gasoline engine
130 ... Cylinder head
132 ... intake valve
134 ... exhaust valve
136 ... Spark plug
140 ... cylinder block
142 ... cylinder
144 ... piston
146… Connecting rod
148 ... Crankshaft
162, 164: Electric actuator

Claims (10)

An apparatus for controlling a variable cycle engine capable of switching a combustion cycle between four cycles for performing spark ignition combustion and two cycles for performing compression ignition combustion,
Supercharging means for supercharging the intake air of the engine,
A switching-time supercharging pressure increasing means for controlling the supercharging means to increase the supercharging pressure prior to the switching of the operation cycle when a request for switching from the four-cycle operation to the two-cycle operation is provided. Engine control device. The engine control device according to claim 1,
An engine control device comprising: a torque fluctuation suppressing unit that controls an intake air amount of the engine when increasing the supercharging pressure to suppress an increase in output torque of the engine. The engine control device according to claim 2,
The engine control device, wherein the torque fluctuation suppressing unit is a unit that shortens a valve opening period of the intake valve over a predetermined period as the supercharging pressure increases. An apparatus for controlling a variable cycle engine capable of switching a combustion cycle between four cycles for performing spark ignition combustion and two cycles for performing compression ignition combustion,
Supercharging means for supercharging the intake air of the engine,
A switching-time supercharging pressure reducing unit configured to control the supercharging unit to reduce a supercharging pressure prior to the switching of the operation cycle when a request to switch from the two-cycle operation to the four-cycle operation is provided. Engine control device. The engine control device according to claim 4, wherein
An engine control device comprising: a torque fluctuation suppressing unit that controls an intake air amount of the engine when reducing the supercharging pressure, thereby suppressing a decrease in an output torque of the engine. The engine control device according to claim 5, wherein
The engine control device, wherein the torque fluctuation suppressing unit is a unit that extends a valve opening period of the intake valve over a predetermined period as the supercharging pressure decreases.
Engine control device equipped with The engine control device according to claim 4, wherein
When a request for switching from the four-cycle operation to the two-cycle operation is issued, prior to the switching of the operation cycle, switching-time supercharging pressure increasing means for controlling the supercharging means to increase the supercharging pressure is provided. Engine control device. The engine control device according to any one of claims 1 to 6, wherein
The supercharging means is any one of an exhaust type supercharger that performs supercharging by using energy of exhaust gas, a mechanical supercharger that pressurizes intake air by driving a prime mover, and an electric supercharger that pressurizes intake air by an electric motor. Engine control device. A method for controlling a variable cycle engine capable of switching a combustion cycle between four cycles for performing spark ignition combustion and two cycles for performing compression self-ignition combustion,
When a request for switching from the four-cycle operation to the two-cycle operation occurs, the supercharging pressure of the intake air of the engine is increased,
Then, an engine control method for switching the requested operation cycle. A method for controlling a variable cycle engine capable of switching a combustion cycle between four cycles for performing spark ignition combustion and two cycles for performing compression ignition combustion,
When a request for switching from the two-cycle operation to the four-cycle operation occurs, the supercharging pressure of the intake air of the engine is reduced,
Then, an engine control method for switching the operation cycle of the container.

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