JP2004204745A - System and method for controlling engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent undesired premature ignition and knocking due to high temperature of gas in a cylinder immediately after switching to two cycle operation from four cycle operation. <P>SOLUTION: When switching to premix compression self ignition two cycle operation from premix spark ignition four cycle operation is carried out, an exhaust valve 134 is opened for a long time or twice in a transition period to suck exhaust gas discharged to an exhaust port 16 once in a cylinder 142 again. Since temperature of exhaust gas discharged once and sucked in again via the exhaust valve 134 drops due to heat exchange, gas temperature in the cylinder during premix compression self ignition two cycle operation drops and undesired premature ignition and knocking do not occur. <P>COPYRIGHT: (C)2004,JPO&NCIPI

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).
[Patent Document 1]
Patent No. 2742825
[Patent Document 2]
JP-A-2002-256911
[0003]
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. .
[0004]
[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 ignition combustion is performed in the two cycles under the predetermined operation conditions, a problem is likely to occur when switching between the two combustion methods. Was found. In particular, in the four-cycle operation, the gas temperature in the cylinder is higher than that in the two-cycle operation. Therefore, if the operation shifts to the two-cycle self-ignition operation as it is, the gas temperature in the cylinder is too high, and early ignition and knocking are likely to occur. Would. Along with this, problems have been pointed out, such as generation of a tapping sound and reduction in durability of an engine cylinder.
[0005]
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.
[0006]
[Means for Solving the Problems and Their Functions and Effects]
An 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 and two cycles,
When switching from the four-cycle operation in which spark ignition combustion is performed to the two-cycle operation in which compression ignition combustion is performed, the gist of the present invention is to provide a gas temperature lowering means for lowering the in-cylinder gas temperature at the time of switching transition.
[0007]
In addition, the invention of an engine control method corresponding to this engine control device,
A method for controlling a variable cycle engine capable of switching a combustion cycle between four cycles and two cycles,
When switching from the four-cycle operation in which spark ignition combustion is performed to the two-cycle operation in which compression ignition combustion is performed, a measure is taken to lower the in-cylinder gas temperature for a predetermined period during the switching transition.
The gist is.
[0008]
According to such an engine control device and its method, when switching from the four-cycle operation in which spark ignition combustion is performed to the two-cycle operation in which compression self-ignition combustion is performed, the in-cylinder gas temperature during the switching transition is reduced. It does not occur as early as desired or knock. 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 and method, various methods for lowering the temperature of the in-cylinder gas are conceivable. For example, an intake valve and / or an exhaust valve provided in the engine is opened at least in a part of the exhaust and intake strokes. It can be realized by making the state adjustable and setting the intake valve and / or the exhaust valve to the open state when the operation cycle is switched. When at least one of the intake valve and the exhaust valve is opened in a part of the exhaust stroke and the intake stroke, the high-temperature gas in the cylinder temporarily goes outside via the intake or exhaust valve, and thereafter, one of the high-temperature gas flows out of the cylinder. The part returns inside the cylinder. When the gas enters and exits through the intake valve and / or the exhaust valve, a part of the heat amount is taken by the passing valve and the intake and exhaust pipes, so that the temperature of the in-cylinder gas decreases.
[0010]
In addition, for example, by providing a mechanism for adjusting the scavenging amount when the engine is operated in two cycles, and controlling the scavenging amount, the scavenging amount of the two-cycle operation can be controlled in the initial stage of the two-cycle operation when the operation cycle is switched. Is increased from the scavenging amount after the elapse of the switching transition, the temperature of the in-cylinder gas can be reduced. This is because the higher the scavenging amount, the higher the temperature of the in-cylinder gas is replaced.
[0011]
Such an increase in the scavenging amount can be realized by adjusting the valve opening timing of the intake valve and / or the exhaust valve provided in the engine and controlling the valve opening timing of these valves. This is because the scavenging amount can be increased by opening the valve early. Of course, if the magnitude of the preload can be adjusted in the preload means for scavenging, the scavenging amount can be increased by increasing the preload.
[0012]
In the configuration in which the temperature of the in-cylinder gas is decreased by increasing the scavenging amount, the scavenging amount of the two-cycle operation that has been increased is gradually reduced over a predetermined period after the transition of the operation cycle. Alternatively, the scavenging amount may be returned to the steady scavenging amount of the two-cycle operation. Since the increase in the scavenging amount is performed in accordance with the switching of the operation cycle, it is desirable that the scavenging amount be increased quickly. However, it is preferable that the scavenging amount be reduced gradually without causing a sudden change in the output torque of the engine. It is.
[0013]
The control for lowering the temperature of the in-cylinder gas during the transition of the operation cycle is provided with a mechanism for adjusting the opening of the exhaust valve provided in the engine, and the exhaust valve is operated in the last cycle of the four-cycle operation during the transition of the operation. It can also be realized by once opening and performing exhaust, and then performing scavenging by opening the intake valve in the first cycle of the two-cycle operation at the time of switching transition. In this case, the temperature of the in-cylinder gas can be rapidly reduced by replacing the gas, and one cycle time is emptied at the time of switching transition, so that the temperature of the in-cylinder gas can be further reduced. Therefore, early ignition in the first cycle of the two-cycle operation can be suppressed. Further, if the exhaust valve is opened as much as possible, pumping loss accompanying gas exchange can be reduced, which is preferable from the viewpoint of thermal efficiency. Further, in the two-cycle operation after the switching, the valve can be opened and closed as a normal two-cycle operation from the first cycle, so that there is an advantage that control of valve opening and closing can be simplified. As a result, the valve control can be speeded up and the control stability can be improved.
[0014]
As another configuration for lowering the in-cylinder gas temperature, a mechanism is provided that recirculates a part of the exhaust gas into the intake air of the engine via an EGR passage communicating the exhaust system and the intake system of the engine, It is possible to consider a configuration in which the amount of exhaust gas that is recirculated and mixed into the intake air is increased during the transition of the operation cycle. Since the temperature of the exhaust gas that is recirculated and mixed into the intake air has decreased, the temperature of the in-cylinder gas can be quickly decreased. For this reason, even when switching the opening / closing valve timing of the intake / exhaust valves using a variable cam type valve system with low responsiveness, it is possible to quickly control the temperature of the in-cylinder gas and suppress the occurrence of early ignition. can do. Of course, such an EGR amount adjustment mechanism may be combined with a highly responsive electromagnetically driven valve system.
[0015]
It is desirable that the amount of exhaust gas increased at the time of the switching transition is gradually reduced over a predetermined period after the lapse of the switching transition to return to the steady amount of the two-cycle operation. By gradually returning the torque, a large change in torque does not occur, and the effect of preventing early ignition by lowering the in-cylinder gas temperature for a predetermined period can be enjoyed.
[0016]
In accordance with the increase in the amount of exhaust gas mixed into the intake air through the EGR passage, the mechanism for adjusting the scavenging amount when the engine is operated for two cycles is controlled to switch the scavenging amount for two-cycle operation. The scavenging amount after the passage of time may be increased. In this way, in addition to the decrease in the in-cylinder gas temperature due to an increase in the amount of exhaust gas to be recirculated, the effect of a decrease in the in-cylinder gas temperature due to an increase in the scavenging amount can be obtained. Of course, such a scavenging amount can be gradually reduced over a predetermined period after the elapse of the switching transition time. Also in this case, the effect of preventing early ignition by lowering the in-cylinder gas temperature for a predetermined period without the occurrence of torque fluctuation due to a sudden change in the scavenging amount can be enjoyed.
[0017]
As another method for preventing an increase in the in-cylinder gas temperature, it is possible to employ a reduction in the effective compression ratio in the cylinder. The effective compression ratio can be adjusted by, for example, changing the stroke of the piston or changing the cylinder length.However, simply, the closing timing of at least one of the intake valve or the exhaust valve provided in the engine is determined. It can also be realized by making the adjustment possible and delaying the closing timing of at least one of the intake valve and the exhaust valve at the time of transition of the operation cycle. If the effective compression ratio is controlled to be low, it is possible to suppress an increase in the in-cylinder gas temperature during the compression stroke, and to lower the in-cylinder gas temperature. Moreover, such a method has an extremely high responsiveness, and thus has an advantage of being excellent in transient controllability.
[0018]
When such control of the effective compression ratio is performed during the transition of the operating cycle, the delayed valve closing timing is gradually changed over a predetermined period after the transition of the switching, and the steady-state amount of the two-cycle operation is changed. It is desirable to return to the same as in other controls.
[0019]
As a switching method of the operation cycle, in the transition transition, the two-cycle operation can be started by performing the scavenging / exhaust stroke of the two-cycle operation following the expansion stroke of the four-cycle operation. In this way, no extra period is required to switch the operation cycle. That is, the torque can be smoothly taken over from the beginning of the switching period without causing a decrease in torque due to the switching. Further, in the two-cycle operation after the switching, the valve can be opened and closed as a normal two-cycle operation from the first cycle, so that there is an advantage that control of valve opening and closing can be simplified. As a result, the valve control can be speeded up and the control stability can be improved.
[0020]
In addition to this control, a mechanism for adjusting the opening and closing timing of the intake valve and / or the exhaust valve provided in the engine is provided, and by controlling this, the end timing of the expansion stroke of the four-cycle operation can be determined by the BDC of the engine. It can be near. If such a configuration is employed, the thermal efficiency can be improved by utilizing the work by expansion. Further, as a result of the expansion stroke being lengthened, the temperature of the burned in-cylinder gas is reduced, and the adverse effect of early ignition can be suppressed.
[0021]
Alternatively, a mechanism for adjusting at least the closing timing of the intake valve and / or the exhaust valve provided in the engine is provided, and by controlling the mechanism, the intake air in the first cycle of the two-cycle operation during the transition of the operation cycle is switched. The effective compression ratio may be reduced by delaying the closing timing of the valve and / or the exhaust valve. As described above, the reduction in the effective compression ratio is effective in reducing the in-cylinder gas temperature.
[0022]
Further, a mechanism for adjusting the opening / closing timing of the intake valve and / or the exhaust valve provided in the engine is provided, and the expansion stroke of the four-cycle operation is set to the same period as the expansion stroke of the two-cycle operation, and the next opening of the exhaust valve is performed. The control may be shifted from the valve timing to the operation as the valve opening / closing timing during the steady operation of the two-cycle operation. In this way, the torque can be smoothly taken over from the beginning of the switching period without causing a decrease in torque due to the switching. Further, in the two-cycle operation after the switching, the valve can be opened and closed as a normal two-cycle operation from the first cycle, so that there is an advantage that control of valve opening and closing can be simplified. As a result, the valve control can be speeded up and the control stability can be improved.
[0023]
In addition to the above control, it is also preferable to perform control to delay the closing timing of the intake valve and / or the exhaust valve to lower the effective compression ratio at the beginning of the two-cycle operation in the steady operation, as described above. .
[0024]
Alternatively, a mechanism for adjusting the amount of fuel supplied to the engine, for example, the amount of fuel injection, may be provided, and the amount of fuel supplied to the engine may be increased in at least the last cycle of the four-cycle operation at the time of transition of the operation cycle. In the last cycle of the four cycles, the work extracted by the expansion is lower than that of the previous cycle, but the increase in the amount of fuel can suppress the reduction in torque accompanying the switching. As a result, smooth switching becomes possible.
[0025]
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.
[0026]
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 a mixture in a 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.
[0027]
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.
[0028]
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.
[0029]
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 adjusting 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. 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.
[0030]
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.
[0031]
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, the exhaust passage 16 is provided with an excess air ratio sensor 28 for detecting an excess air ratio λ of the air-fuel mixture formed in the combustion chamber, an exhaust temperature sensor 29 for detecting the exhaust gas temperature TB, and the like. The excess ratio sensor 28 (also referred to as an air-fuel ratio sensor) can detect the excess air ratio of the air-fuel mixture formed in the combustion chamber by detecting the concentration of oxygen contained in the exhaust gas.
[0032]
The operation of the gasoline engine 10 is controlled by the ECU 30. 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.
[0033]
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 this 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 premixed compression ignition combustion is performed. I also do. 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.
[0034]
(2) Operation cycle
The gasoline engine 10 of this embodiment switches between two-cycle operation and four-cycle operation according to the engine speed. That is, two-cycle operation with high thermal efficiency is performed in a range where the engine rotation speed is relatively low, and four-cycle operation in which high-speed rotation is easy is performed in a range where the engine rotation speed is high. 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.
[0035]
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. The area of the two-cycle operation is further divided into four areas according to the load, and the formation of the air-fuel mixture is adjusted. Two-cycle operation by self-ignition combustion will be described. The detailed description of the known four-cycle operation and other operation conditions in two cycles is omitted.
[0036]
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.
[0037]
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).
[0038]
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.
[0039]
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.
[0040]
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 1.2 to 3.
[0041]
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.
[0042]
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.
[0043]
(3) Control during operation cycle switching transition-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. FIGS. 5 and 6 are flowcharts showing the control performed by the ECU 30 in the first embodiment. FIG. 7 is an explanatory diagram showing a stroke and switching valve timings of the intake valve 132 and the exhaust valve 134 when switching from the four-cycle operation to the two-cycle operation. Hereinafter, the transient control will be described with reference to these drawings.
[0044]
The switching transient control processing routine shown in FIG. 5 is repeatedly executed at predetermined intervals. When this routine is started, first, it is determined whether or not there is a request for switching the operation cycle (step S100). If there is no request, the routine ends without performing any operation. When the load condition on the engine 10 changes and the operating condition changes from the high rotation condition (the hatched area shown in FIG. 2) to the low rotation condition (the area without the hatching shown) shown in FIG. It is determined that a request for switching to cycle operation has occurred.
[0045]
In this case, it is next determined whether or not it is time to switch the cycle (step S110). The timing at which the switching can be performed means after the time when one combustion cycle of the four-cycle operation is completed. This is because the operation cycle cannot be switched before the exhaust stroke of the four-cycle operation in which control has already been started is completed for one cylinder whose operation cycle is to be switched. Since the operation of the engine can be considered as a combustion cycle from the intake to the exhaust, in the case of the four-cycle operation, it is determined that the operation of the four cycles is completed at the top dead center (TDC) after the exhaust stroke is completed. I have. Note that the intake valve 132 and the exhaust valve 134 of each cylinder of this embodiment do not use a cam driven by a common camshaft, but are individually driven using electric actuators 162 and 164. The operation timing can be freely switched every time. Therefore, in this embodiment, the switching from the 4-cycle to the 2-cycle operation is performed for each cylinder. Of course, it is possible to wait until the four-cycle operation for all cylinders is completed, and then switch to the two-cycle operation.
[0046]
If it is determined that the timing cannot be switched, the processing routine ends without performing any operation. If the cylinder of interest has completely completed one combustion cycle of the four-cycle operation, then it is determined whether or not the switching period has ended (step S120). This is because, after completely shifting to the two-cycle operation, the control at the time of switching transition is not necessary. Even when the switching period has been completed, this routine ends without performing any operation. On the other hand, if there is a request for switching from the four-cycle operation to the two-cycle operation, and the cylinder of interest can be switched after the four-cycle combustion cycle is completed, and the switching period has not ended, Control of valve timing for each cycle is performed (step S130).
[0047]
FIG. 6 shows the details of the control of the valve timing for each cycle. That is, in the switching control to the operation in two cycles, and in the transition period before the start of the two-cycle operation (this is also referred to as a 0th cycle), the first cycle, the second cycle,. Then, processing is performed to control the timing of opening and closing the intake valve 132 and the exhaust valve 134, respectively. The control of the valve timing will be described below based on FIG. 6 which is a flowchart showing the process and FIG. 7 which is an explanatory diagram showing the valve opening / closing timing. In addition, for convenience of illustration, in FIG. 7, the intake valve and the exhaust valve are respectively described as “intake valve” and “exhaust valve”.
[0048]
When the valve timing control routine is started, it is first determined whether or not the current cycle number n is 0 (step S200). As shown in FIG. 7, the four-cycle operation is completed with the top dead center at which the exhaust stroke is completed, but the two-cycle operation starts with the scavenging stroke in which the intake and exhaust simultaneously proceed, so that one cycle of the two-cycle operation is performed. Is from the bottom dead center (BDC) to the next bottom dead center. Therefore, in the transition period (0th cycle) from the last top dead center (TDC) of the four-cycle operation to the first top dead center (BDC) of the two-cycle operation, control that does not belong to any of the two- and four-cycle operations Is performed, a process of selecting the valve timing of the transition period is performed (step S210). In the first embodiment, as shown in FIG. 7, the valve timing is maintained while the exhaust valve 134 is kept open, and the intake valve 132 is opened shortly before entering the first cycle (first cycle) of the two-cycle operation. The valve will open. The valve timing is selected, and thereafter, in synchronization with the rotation of the crankshaft 148, the electric actuators 162 and 164 are controlled to perform opening / closing valve control for driving the intake valve 132 and the exhaust valve 134 (step S220).
[0049]
As shown in FIG. 7, when the exhaust valve 134 is kept open during this transition period (0th cycle), more exhaust gas is exhausted through the exhaust valve 134 than in a normal combustion cycle. It is discharged to the passage 16 side. In a normal combustion cycle, not all of the combustion gas after combustion is exhausted, and part of the combustion gas remains in the cylinder and is used to keep the temperature of the air-fuel mixture high in the next combustion cycle. I have. On the other hand, by keeping the exhaust valve 134 open during the transition period, more combustion gas than usual flows through the exhaust valve 134 and exits to the exhaust passage 16 side. In this process, the combustion gas comes into contact with members such as the exhaust valve 134 and the exhaust passage 16 and lowers its temperature. In the second half of the transition period, the piston 144 descends, so that the combustion gas that once goes out and has a lowered temperature returns from the exhaust passage 16 side to the combustion chamber via the exhaust valve 134. Therefore, the temperature of the residual gas in the cylinder at the time when the two-cycle operation is started is lower than that in the case where the combustion cycle is continuous.
[0050]
In the transition period (n = 0), after performing the above control to lower the temperature of the in-cylinder gas, the two-cycle operation is started. At this time, the ECU 30 shifts the control to step S230, and determines the current cycle number n (step S230). Subsequently, a process of selecting the valve timing of the n-th cycle based on the determined number of cycles n is performed (step S240). Subsequently, by driving the intake and exhaust valves 132 and 134 at a valve timing selected according to the cycle number n (step S220), in this embodiment, in the first cycle immediately after the start of the two-cycle operation, the exhaust is performed. Control is performed in which the valve opening time of the valve 134 is made longer than the normal cycle, and gradually approaches the normal valve opening time in the second cycle, the third cycle, and so on. That is, when the operation is switched from the four-cycle operation to the two-cycle operation, the first five cycles of the two-cycle operation following the transition period are regarded as a switching transition period, and the valve opening period of the exhaust valve 134 is gradually shortened. The amount of exhaust gas discharged / re-sucked via the valve 134 is gradually changed. This situation is shown in FIG. In the figure, the vertical axis indicates the amount of exhaust gas that is once exhausted through the exhaust valve 134 and then re-sucked. However, in other embodiments described later, the scavenging amount is similarly gradually changed. In order to make the figures common, the vertical axis also shows the “scavenging amount”.
[0051]
According to the engine 10 and the control device of the first embodiment described above, the air-fuel mixture is compressed from the four-cycle operation in which the air-fuel mixture is ignited by the spark formed in the ignition plug 136 to perform explosive combustion. When switching to the two-cycle operation in which explosive combustion by self-ignition is performed, the exhaust valve 134 is opened longer than normal control, combustion gas is taken in and out through the exhaust valve 134, and the temperature of gas remaining in the cylinder is reduced. be able to. This is because the exhaust gas heated to a high temperature by the combustion enters and exits through the exhaust valve 134 and the exhaust port, so that the exhaust valve and the exhaust port deprive the heat amount and lower the temperature. As a result, the temperature of the in-cylinder gas maintained at a high temperature in the four-cycle operation is lowered by the start of the two-cycle operation, and in the two-cycle operation, undesired early ignition and knocking can be prevented. it can. Therefore, it is possible to obtain a desirable result in terms of drivability and durability without causing a problem such as generation of vibration and abnormal noise at the time of switching transition. If the valve opening time of the intake valve 132 is increased in the exhaust stroke and the intake stroke, a part of the exhaust gas once goes out to the intake port side via the intake valve 132 and is sucked again. Drops. Therefore, the same control can be performed on the intake valve to achieve the same effect.
[0052]
Moreover, in this embodiment, since a large amount of combustion gas is discharged and re-sucked using the transition period, the temperature of the residual gas in the cylinder can be rapidly reduced in a short period of time. Furthermore, after that, when the two-cycle operation is started, the valve opening timing of the exhaust valve 134 is not immediately returned to the original one, but gradually over the gradual change period (the first cycle to the fifth cycle in this embodiment). Since the operation is returned to the normal timing, the operation and effect of reducing the in-cylinder gas temperature due to the extension of the valve opening time can be secured for a predetermined period, and the sudden closing timing of the exhaust valve 134 is changed. There is no occurrence of torque shock or the like of the engine 10. In the present embodiment, the gradual change period is set to about 5 cycles, but the length may be appropriately determined according to the characteristics of the engine. Also, instead of gradually changing the valve timing, some timings may be determined in advance and switched according to the number of cycles n.
[0053]
(4) Modification:
Next, a modification of the first embodiment will be described. In the modification, as shown in FIG. 9, the switching itself from the four-cycle operation to the two-cycle operation is performed in the same manner as in the first embodiment, and the mechanism for lowering the temperature of the gas remaining in the cylinder is also the first mechanism. This is the same as the embodiment. In the modified example, the timing of opening and closing the exhaust valve 134 in the last cycle and the transition period of the four-cycle operation is different. As shown in FIG. 9, the exhaust valve 134 is temporarily closed at a timing t1 during the exhaust stroke of the final cycle of the four-cycle operation. As in the first embodiment, the combustion gas is discharged to the exhaust passage 16 side by blowdown. After that, in the transition period, the exhaust valve 134 is opened again (timing t2 in the figure), and subsequently, the intake valve 132 is opened. The valve opening timing of the intake valve 132 is a valve opening timing corresponding to the scavenging stroke of the normal two-cycle operation. When the exhaust valve 134 is opened for the second time, the intake valve 132 is also opened immediately and scavenging is started. As a result, scavenging is sufficiently performed before the start of the two-cycle operation, and fresh air not involved in combustion enters the cylinder from the intake passage 12 side, so that the gas temperature in the cylinder is sufficiently reduced.
[0054]
By performing such control, the occurrence of undesired early ignition or knocking can be prevented as in the first embodiment, and the exhaust valve 134 is not fully opened for a long period of time. No pump loss occurs. As a result, the thermal efficiency can be increased as a whole without excessively lowering the thermal efficiency and, consequently, lowering the fuel efficiency. In addition, since the control can be performed at the normal valve opening / closing timing from the first cycle of the two-cycle operation, the stability of the valve control can be improved. It is also preferable that the control for sufficiently performing scavenging to lower the in-cylinder gas temperature be continued for a while after the two-cycle operation is started. As described with reference to FIG. 8, the scavenging amount control can also gradually approach the scavenging amount of the normal two-cycle operation by providing a gradual change period. In this embodiment and the modification, the electric actuator is used to drive the intake and exhaust valves 132 and 134, so that the intermittent valve opening and closing shown in FIG. 9 can be easily realized. Of course, a camshaft and a driving cam for a four-cycle operation and a camshaft and a driving cam for a two-cycle operation are prepared. Can be easily realized.
[0055]
(5) Control during switching transition in the second embodiment:
Next, a second embodiment of the present invention will be described. FIG. 10 is a schematic configuration diagram of a gasoline engine 100 according to the second embodiment. This engine 100 has substantially the same configuration as the first embodiment, but differs from the first embodiment in that an external EGR mechanism for recirculating exhaust gas from the exhaust passage 16 to the intake passage 12 is further provided. The exhaust gas recirculation mechanism includes a recirculation passage 170 extending from the exhaust passage 16 to the intake passage 12, and an EGR amount adjusting valve 172 for adjusting the amount of recirculated gas. For convenience of explanation, in FIG. 10, members other than the recirculation mechanism are denoted by the same reference numerals as those in FIG. The EGR amount adjusting valve 172 is connected to the ECU 30, and by adjusting the opening thereof, the amount of exhaust gas circulating from the exhaust passage 16 to the intake passage 12 can be controlled. Since it is considered that the combustion gas described in the first embodiment is once discharged into the exhaust passage 16 and then returned to the cylinder via the exhaust valve 134 again, it is considered as a kind of EGR. When it is necessary to distinguish the exhaust gas from the configuration in which the exhaust gas is returned from the exhaust passage 16 to the intake passage 12, the latter is referred to as an external EGR.
[0056]
In the second embodiment, the ECU 30 performs substantially the same control as the first embodiment, but executes a valve timing control routine shown in FIG. 11 instead of the process shown in FIG. Note that, among the processing shown in FIG. 11, those having the same last two digits as the processing of FIG. 5 have the same processing content. That is, the second embodiment is different from the control of the first embodiment in that steps S315 and S345 are added.
[0057]
In the valve timing control routine of the second embodiment, when the switching from the four-cycle operation to the two-cycle operation is started, in the transition period (n = 0), the exhaust valve 134 is opened at a unique valve timing during the transition period. Then, the intake valve 132 is opened (step S300 → S310). After selecting the valve switching timing, in the second embodiment, the EGR amount during the transition period is adjusted (step S315). Similarly, in the first cycle, the second cycle,... After the start of the two-cycle operation, the number n of cycles is determined, the valve timing of the n-th cycle is selected (step S330 → S340), and then the n-th cycle is performed. The cycle EGR amount is set (step S345). An example of the control of the valve timing and the EGR amount is shown in FIG. As shown, in this embodiment, the EGR amount is maximized during the transition period, and thereafter, is gradually reduced as the cycle proceeds. As a result, the external EGR amount is adjusted during the transition from the four-cycle operation to the two-cycle operation. The valve opening / closing timing may be the same as the timing shown in FIG. 9, or the exhaust valve 134 may be set to the normal opening / closing valve timing, and the combustion gas remaining in the cylinder may be returned via the exhaust valve 134. May not be performed.
[0058]
The external EGR amount in the second embodiment is increased at the time of switching transition as compared with the four-cycle operation. Since the temperature of the exhaust gas circulated through the recirculation passage 170 to the intake system and drawn into the cylinder has dropped considerably, according to the second embodiment, during the transition of the operation cycle, the internal The gas temperature can drop rapidly. As a result, undesired early ignition or knocking does not occur immediately after switching to the two-cycle operation. For this reason, problems such as occurrence of a tapping sound and deterioration of durability are not caused.
[0059]
In the second embodiment as well, the external EGR can be performed over several cycles at the time of the switching transition, but this period in which the external EGR is added may be appropriately determined according to the characteristics of the engine 10 and the like. Further, similarly to the first embodiment, it is preferable that the external EGR amount is gradually changed or switched over several steps. In the present embodiment, the switching of the valve timing is also performed (steps S310 and S340), but the valve temperature may not be controlled, and the gas temperature in the cylinder may be reduced only by the external EGR amount. In this case, there is an advantage that the control of the valve timing accompanying the switching of the operation cycle becomes unnecessary. In addition, even when the valve timing is switched using a valve train system with not so high responsiveness instead of the electric actuators 162 and 164, there is also an advantage that the gas temperature in the cylinder can be quickly reduced by the external EGR. can get.
[0060]
Next, a modification of the above embodiment will be described. In this modification, the same hardware configuration and control as in the first embodiment or the second embodiment are performed, and further, in the first few cycles in which the operation is switched to the two-cycle operation, the intake valve 132 and the exhaust valve 134 are changed. At least one of the valve closing timings is delayed, and control is performed to lower the effective compression ratio by lowering the degree of compression of the air-fuel mixture by the piston 144. That is, as shown in FIG. 13, the valve closing timing INC2 of the intake valve 132 is delayed to the angle θi or the valve closing timing EXC2 of the exhaust valve 134 is changed from the normal two-cycle opening / closing valve timing shown in FIG. Control is performed to delay the angle θo.
[0061]
As a result, the effective compression ratio of the air-fuel mixture in the cylinder is reduced to the extent that self-ignition is possible, and its temperature rise is suppressed. As a result, undesired early ignition or knocking due to an excessive rise in the cylinder gas temperature. There is no problem such as the occurrence of the problem. The control of the effective compression ratio by delaying the closing timing of the intake and exhaust valves 132 and 134 may be gradually changed to the normal valve timing after the two-cycle operation is started, similarly to other controls. . By performing such a gradual change control, the operation state of the engine 10 can be switched to the normal control of the two-cycle operation without causing a torque shock or the like, which is preferable. This control may be performed alone, but if the control is performed in conjunction with the control of the discharge and re-intake of the combustion gas via the exhaust valve 134 during the switching transition or the control of the external EGR amount during the switching transition, the in-cylinder control can be further performed. Needless to say, this contributes to a reduction in gas temperature. In this modification, the control for lowering the effective compression ratio was realized by adjusting the closing timing of the intake and exhaust valves. However, if the engine has a mechanical compression ratio variable mechanism, the control is realized by controlling the mechanism. You may. As such a mechanical compression ratio variable mechanism, a connecting rod 146 connecting the piston 144 and the crankshaft 148 is divided into a plurality of members, and a bending rod type having a mechanism for varying the net length in the middle, Various configurations are known, such as a type in which a stroke is varied by eccentricity of a crank pin, and a mechanism in which a cylinder swings or moves to vary a compression ratio.
[0062]
(6) Control of the third embodiment:
Next, a third embodiment of the present invention will be described. In the third embodiment, the hardware configuration is the same as that of the first or second embodiment, but is different from the first or second embodiment at the time of transition from the four-cycle operation to the two-cycle operation, and is different from the first or second embodiment in the transition period. Switching is performed without providing a corresponding period. That is, in the switching transition processing routine shown in FIG. 5, in the determination of "is it possible to switch?" (Step S110), in the first and second embodiments, the process waits until the last TDC of the four-cycle operation, and thereafter In contrast to the transition to the two-cycle operation after the transition period (n = 0), in this embodiment, the last BDC of the four-cycle operation determines that “switching to the two-cycle operation is possible” and the transition is made. The two-cycle operation has started without passing the period. This is shown in FIG.
[0063]
Therefore, in the third embodiment, in the valve timing control routine (FIGS. 6 and 11), it is determined whether or not the number of cycles n is 0, or the process when n = 0 (steps S210, S310, S315) does not exist. It is considered that the first cycle of the two-cycle operation has started from the last BDC of the last cycle of the four-cycle operation, and thereafter, depending on whether the n-th cycle of the two-cycle operation (n = 1, 2,...) Change the timing. In the final cycle of the four-cycle operation (that is, the first cycle of the two-cycle operation), the timing for opening the exhaust valve 134 is particularly delayed to near BDC. As a result, in the final cycle of the four-cycle operation, the engine 10 completes the work due to the expansion, the energy is worked out and taken out, and the temperature of the in-cylinder gas is sufficiently reduced. As a result, it is possible to prevent an excessive rise in the gas temperature in the cylinder at the time when the two-cycle operation is started, and to suppress occurrence of undesired early ignition and knocking. Since the expansion stroke is sufficiently taken in the last cycle of the four-cycle operation, the thermal efficiency of the engine 10 can be increased. Further, according to the present embodiment, it is not necessary to provide a transition period that is not involved in the combustion cycle from the final cycle of the four-cycle operation to the first cycle of the two-cycle operation, so that the engine torque is temporarily dropped. There is no problem. Further, since the control of the two-cycle operation is immediately started without providing a transition period, the control of the valve timing of the intake and exhaust valves 132 and 134 can be simplified, and the valve opening / closing valve control can be simplified. Valve control can be performed stably. Further, the cycle of valve control can be shortened.
[0064]
Furthermore, in the first cycle of the two-cycle operation, if the effective compression ratio is lowered by delaying the closing timing of the intake and exhaust valves 132 and 134, the temperature of the in-cylinder gas can be reduced more efficiently. Further, control such as a decrease in the in-cylinder gas temperature due to an increase in the scavenging amount described as a modification of the first embodiment, a decrease in the in-cylinder gas temperature due to an increase in the external EGR amount described in the second embodiment, or a second embodiment It is also easy to combine the process of lowering the effective compression ratio described as a modification of the example with the control of the third embodiment. In this case, the temperature of the in-cylinder gas can be further reduced.
[0065]
(7) Modification of the third embodiment:
Next, a modification of the third embodiment will be described. This modification is the same as the third embodiment in that the first cycle of the two-cycle operation is started from the BDC of the last cycle of the four-cycle operation as shown in FIG. In this modification, the closing timing of the exhaust valve 134 in the final cycle of the four-cycle operation is earlier than in the third embodiment, and the expansion stroke is set to be substantially the same as that in the two-cycle operation. That is, the exhaust valve 134 opens much before BDC. On the other hand, the next valve opening timing of the exhaust valve 134 is the timing of normal two-cycle operation.
[0066]
In this modification, the opening and closing timing of the valve is further simplified, the control is simple, and the stability can be improved. The control for lowering the in-cylinder gas temperature may be performed by combining the methods of some of the above-described embodiments. For example, the in-cylinder gas temperature may be lowered by delaying the closing timing of the intake / exhaust valves 132 and 134 in the scavenging / compression stroke to lower the effective compression ratio. Alternatively, the external EGR amount may be increased (see FIG. 11). Further, by making the work of the expansion stroke in the final cycle of the four-cycle operation smaller than that in the third embodiment, the output torque from the engine 10 apparently decreases. Increasing and correcting the fuel injection amount is also useful for suppressing the torque fluctuation of the engine 10. FIG. 16 illustrates an example of a process when the fuel is increased and corrected in the final cycle. When there is a request to switch the operation cycle (step S400), ECU 30 determines whether or not fuel injection has already been performed (step S401). If fuel injection has not been performed, ECU 30 calculates the fuel injection amount Tm of cycle m by a coefficient. A process of increasing the amount by Kv (Kv> 1) is performed (step S402). On the other hand, if the fuel injection of the cycle has already been performed, the fuel injection amount is not corrected. Thereafter, it is determined whether or not the operation cycle can be switched (step S410). Since the subsequent processing is basically the same as that of the first embodiment shown in FIG. 5, the description is omitted.
[0067]
In each of the above embodiments, the intake / exhaust valve is driven by the electric actuator. However, the intake / exhaust valve can be opened / closed by using a cam and rotating the crankshaft. In this case, since the opening and closing timings of the valves are greatly different between the four-cycle operation and the two-cycle operation, a mechanism that can freely adjust the opening and closing timing of the intake and exhaust valves is required. Since various mechanisms are known for such a valve train, a detailed description thereof will be omitted. However, the valve movement for one rotation of the crankshaft 148 is greatly different between the two-cycle operation and the four-cycle operation. Alternatively, a dedicated camshaft may be prepared, and the camshaft may be switched with the switching of the operation cycle. Such a switching mechanism of the valve train is known. Further, in the operating camshaft, a mechanism for freely controlling the valve opening timing and the valve closing timing of the intake and exhaust valves includes a mechanism for controlling a valve opening period by varying a valve lift amount by a valve driving cam, A mechanism that changes the phase by changing the phase of the driving cam with respect to the rotation of the crankshaft 148 can be configured in combination. By adjusting the lift amounts of the intake valve 132 and the exhaust valve 134 and the phase with respect to the crankshaft, as a result, both the valve opening timing and the valve closing timing of each valve can be freely controlled. The adjustment of the valve lift amount can be easily realized by providing a mechanism for varying the length of a member that connects the cam profile tracing member and the intake / exhaust valve.
[0068]
As described above, the embodiments of the present invention have been described. However, the present invention is not limited to these embodiments at all, and may be embodied in various forms without departing from the gist of the present invention. Of course. For example, in the present embodiment, a three-cylinder engine is taken as an example. However, the present invention can be applied to engines other than three cylinders, for example, engines having different numbers of cylinders such as four cylinders, five cylinders, six cylinders, eight cylinders, and twelve cylinders. . Further, as another configuration for lowering the in-cylinder gas temperature at the time when the operation cycle is switched to the two-cycle operation, for example, a temporary decrease in the intake air temperature by an intercooler, a cooling of a cylinder block using a semiconductor element, and the like. Of course, a method can be adopted. As a method of reducing the in-cylinder gas temperature, there are a method of introducing a gas having a low temperature (or a lowered temperature) (external EGR, fresh air, etc.), a method of lowering the temperature of the exhaust gas itself, and a method of rapidly lowering the temperature of the cylinder block. As a result, various methods such as a method of lowering the in-cylinder gas temperature can be adopted.
[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 illustrating a switching transient processing routine.
FIG. 6 is a flowchart showing a valve timing control routine at the time of switching transition.
FIG. 7 is an explanatory diagram showing valve timing at the time of switching operation cycles in the first embodiment.
FIG. 8 is an explanatory diagram showing a state of a gradual change in a re-suction exhaust gas amount and a scavenging amount.
FIG. 9 is an explanatory diagram showing valve timing at the time of switching operation cycles in a modification of the first embodiment.
FIG. 10 is a schematic configuration diagram of an engine 100 and a control device thereof according to a second embodiment.
FIG. 11 is a flowchart illustrating a valve timing control routine according to a second embodiment.
FIG. 12 is an explanatory diagram showing valve timing at the time of switching operation cycles in the second embodiment.
FIG. 13 is an explanatory diagram showing opening and closing valve timings of intake and exhaust valves in a modification of the second embodiment.
FIG. 14 is an explanatory diagram showing valve timing at the time of switching operation cycles in the third embodiment.
FIG. 15 is an explanatory diagram showing valve timing at the time of switching operation cycles in a modification of the third embodiment.
FIG. 16 is a flowchart illustrating a switching transient processing routine in a modification of the third 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
24 ... Electric actuator
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 ... Compressor
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
148 ... Crankshaft
162, 164: Electric actuator
170: Recirculation passage
172: EGR amount adjustment valve

Claims (19)

An apparatus for controlling a variable cycle engine capable of switching a combustion cycle between four cycles and two cycles,
An engine control device provided with a gas temperature lowering means for lowering in-cylinder gas temperature at the time of switching transition when switching from four-cycle operation in which spark ignition combustion is performed to two-cycle operation in which compression ignition combustion is performed. The engine control device according to claim 1,
A valve opening adjusting means for adjusting an intake valve and / or an exhaust valve provided in the engine to an open state at least in a part of an exhaust and intake strokes;
The gas temperature lowering unit is configured to reduce the in-cylinder gas temperature by controlling the valve opening adjusting unit during the switching transition to open the intake valve and / or the exhaust valve. Engine control device. The engine control device according to claim 1,
A scavenging amount adjusting means for adjusting a scavenging amount when the engine is operated for two cycles;
The gas temperature lowering means controls the scavenging amount adjustment means to control the scavenging amount adjustment means to control the scavenging amount of the two-cycle operation during the switching transition at the initial stage of the two-cycle operation. An engine control device that is realized by increasing the scavenging amount after the passage of time. The engine control device according to claim 3, wherein
The scavenging amount adjustment unit is a valve opening adjustment unit that adjusts a valve opening timing of an intake valve and / or an exhaust valve provided in the engine.
The engine control device, wherein the gas temperature lowering unit is a unit that increases the scavenging amount by controlling the valve opening adjusting unit. The engine control device according to claim 3 or 4, wherein:
The gas temperature lowering means gradually reduces the increased scavenging amount of the two-cycle operation over a predetermined period after the elapse of the switching transition, so as to gradually return the scavenging amount to the steady scavenging amount of the two-cycle operation. An engine control device comprising means. The engine control device according to claim 1,
With valve-opening adjusting means for adjusting the opening of the exhaust valve provided in the engine,
The gas temperature lowering means controls the valve opening adjustment means to reduce the in-cylinder gas temperature, and once in the last cycle of the four-cycle operation at the time of the switching transition, opens the exhaust valve once and executes exhaust. An engine control device which is realized by opening the exhaust valve and performing scavenging in the first cycle of the two-cycle operation during the switching transition. The engine control device according to claim 1,
An external EGR means for recirculating a part of the exhaust gas into the intake air of the engine via an EGR passage communicating the exhaust system and the intake system of the engine,
The engine temperature control means is a means for realizing the reduction of the in-cylinder temperature by controlling the external EGR means to increase the amount of exhaust gas mixed into the intake air during the switching transition. apparatus. The engine control device according to claim 7, wherein
The gas temperature lowering means controls the external EGR means and gradually reduces the increased amount of exhaust mixed during the switching transition over a predetermined period after the switching transition, thereby achieving the two-cycle operation. An engine control device provided with a gradual decrease means for returning to a steady amount. The engine control device according to claim 7 or 8, wherein:
A scavenging amount adjusting means for adjusting a scavenging amount when the engine is operated for two cycles;
The gas temperature lowering means controls the scavenging amount adjusting means in accordance with increasing the amount of exhaust gas mixed into the intake air by controlling the external EGR means, thereby switching the scavenging amount in the two-cycle operation. An engine control device provided with a means for increasing a scavenging amount after a transition has elapsed. The engine control device according to claim 9, wherein
The gas temperature lowering means gradually reduces the scavenging amount increased by controlling the scavenging amount adjusting means over a predetermined period after the switching transition time to a steady amount of the two-cycle operation. An engine control device including a return taper. The engine control device according to claim 1,
With a valve-closing adjusting means for adjusting the valve-closing timing of at least one of the intake valve or the exhaust valve provided in the engine,
The gas temperature lowering means realizes the lowering of the in-cylinder gas temperature by controlling the valve closing adjusting means at the time of the switching transition to delay the closing timing of at least one of the intake valve and the exhaust valve. The engine control device that is the means. The engine control device according to claim 11, wherein
The gas temperature lowering means gradually changes the valve closing timing controlled by controlling the valve closing adjusting means over a predetermined period after the switching transition time, so that the two-cycle operation can be continuously performed. An engine control device including a gradual change means for returning to an amount. The engine control device according to claim 1, further comprising:
An engine control device comprising an operation switching means for starting the two-cycle operation by performing a scavenging / exhaust stroke of the two-cycle operation following the expansion stroke of the four-cycle operation during the switching transition. The engine control device according to claim 13,
An opening / closing valve adjusting means for adjusting opening / closing valve timing of an intake valve and / or an exhaust valve provided in the engine;
The engine control device, wherein the operation switching unit sets the end time of the expansion stroke of the four-cycle operation to be close to the BDC of the engine by controlling the on-off valve adjusting unit. 14. The engine control device according to claim 13, further comprising: a valve closing adjusting unit that adjusts at least a valve closing timing of an intake valve and / or an exhaust valve provided in the engine.
In the first cycle of the two-cycle operation at the time of the switching transition, by controlling the valve closing adjusting means, the closing timing of the intake valve and / or the exhaust valve is delayed to reduce the effective compression ratio. An engine control device comprising: The engine control device according to claim 13,
An opening / closing valve adjusting means for adjusting opening / closing valve timing of an intake valve and / or an exhaust valve provided in the engine;
The operation switching means sets the expansion stroke of the four-cycle operation to the same period as the expansion stroke of the two-cycle operation, and determines the valve opening / closing timing during the steady operation of the two-cycle operation from the next valve opening timing of the exhaust valve. An engine control device that transfers control to the operation of the vehicle. The engine control device according to claim 16, wherein
An engine control apparatus comprising: a compression ratio adjusting unit that delays a closing timing of the intake valve and / or the exhaust valve to lower an effective compression ratio at an early stage of a two-cycle operation during the steady operation. The engine control device according to claim 13,
Fuel supply amount adjusting means for adjusting the amount of fuel supplied to the engine;
An engine control device comprising: fuel increasing means for increasing an amount of fuel supplied to the engine in at least a final cycle of the four-cycle operation at the time of the switching transition. A method for controlling a variable cycle engine capable of switching a combustion cycle between four cycles and two cycles,
An engine control method for performing a measure to reduce the in-cylinder gas temperature for a predetermined period of time when the switching is performed, when switching from four-cycle operation in which spark ignition combustion is performed to two-cycle operation in which compression ignition combustion is performed.

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