JP4165210B2 - Engine control apparatus and method thereof - Google Patents

Description

[0001]
BACKGROUND 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]
Conventionally, a variable cycle engine that is operated by switching an operation cycle between four cycles and two cycles is known. Such variable cycle engines seek to fully exploit the advantages of both cycles in engines operating over a wide dynamic range. Such an engine is described in Patent Document 1 below, for example. In recent years, a technique has been proposed in which the engine performance is maximized by combining a combustion method with an operation cycle (see Patent Document 2 below).
[Patent Document 1]
Japanese Patent No. 2742825
[Patent Document 2]
JP2002-256911
[0003]
This technique combines a premixed combustion method in which a preformed air-fuel mixture is sucked into a cylinder of an engine and then spark-ignited and burned, and 2-cycle and 4-cycle operation, while fuel is injected into the cylinder in the first half of the intake stroke. By combining the method of compressing the air-fuel mixture formed by performing self-ignition combustion and four-cycle operation, the engine is operated efficiently while avoiding knocking in a wide operating range. .
[0004]
[Problems to be solved by the invention]
However, if premixed spark ignition combustion is actually performed in four-cycle operation and premixed compression auto-ignition combustion is performed in two cycles under predetermined operating conditions, a problem is likely to occur when switching between both combustion methods. Was found. In particular, in the 4-cycle operation, the in-cylinder gas temperature is higher than that in the 2-cycle operation. Therefore, when shifting to the 2-cycle self-ignition operation as it is, the in-cylinder gas temperature is too high and early ignition and knocking are likely to occur. End up. Along with this, it has been pointed out that there are hitting sounds and the durability of the cylinder of the engine is lowered.
[0005]
The apparatus of the present invention has been made for the purpose of solving such problems and smoothly switching the combustion system 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 problems is as follows.
  An apparatus for controlling a variable cycle engine capable of switching a combustion cycle between 4 cycles and 2 cycles,
  Switching from 4-cycle operation with spark ignition combustion to 2-cycle operation with compression ignition combustionAt the time of switching transition, following the expansion stroke of the 4-cycle operation, the scavenging / exhaust stroke of the 2-cycle operation is performed to start the 2-cycle operation,The gist is that a gas temperature lowering means for lowering the in-cylinder gas temperature at the time of switching transition is provided.
[0007]
  The invention of the engine control method corresponding to this engine control device
  A method of controlling a variable cycle engine capable of switching a combustion cycle between 4 cycles and 2 cycles,
  Switching from 4-cycle operation with spark ignition combustion to 2-cycle operation with compression ignition combustionAt the time of switching transition, following the expansion stroke of the 4-cycle operation, the scavenging / exhaust stroke of the 2-cycle operation is performed to start the 2-cycle operation,Take measures to lower the in-cylinder gas temperature during switching transitions
  Is the gist.
[0008]
  According to the engine control device and the method thereof, when switching from the 4-cycle operation in which the spark ignition combustion is performed to the 2-cycle operation in which the compression auto-ignition combustion is performed, the in-cylinder gas temperature at the switching transition time is lowered, It does not occur as early as desired or knocks.In addition, the thermal efficiency can be increased by taking advantage of work due to expansion. Further, as a result of the expansion stroke becoming longer, the temperature of the burned in-cylinder gas is lowered, and the adverse effects of early ignition can be suppressed. No extra time is required for switching operation cycles. That is, the torque can be taken over smoothly from the beginning of the switching period without incurring a decrease in torque associated with the switching. Further, in the two-cycle operation after switching, the valve can be opened and closed as a normal two-cycle operation from the first cycle, so that the advantage that the control of valve opening and closing can be simplified is also obtained. As a result, the speed of valve control and the stability of control can be improved.In addition, the compression self-ignition combustion in this specification means the combustion system which compresses the preformed air-fuel mixture (pre-air mixture) and self-ignites. Such an air-fuel mixture may be formed by injecting fuel into the cylinder in the intake stroke, or may be formed by supplying fuel to an intake port or the like.
[0009]
In such an engine control apparatus and method, various methods for reducing 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 adjusted to the state, and can be realized by opening the intake valve and / or the exhaust valve at the transition transition of the operation cycle. If 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 once goes outside through the intake or exhaust valve, and thereafter, The part returns to the cylinder. As the gas flows in and out through the intake valve and / or the exhaust valve, a part of the heat is taken away by the passing valve and the intake / exhaust pipe, so that the temperature of the in-cylinder gas decreases.
[0010]
In addition, for example, a mechanism for adjusting the scavenging amount when the engine is operated for two cycles is provided, and by controlling this, the scavenging amount for the two-cycle operation at the initial stage of the two-cycle operation at the transition transition of the operating cycle. Also, the temperature of the in-cylinder gas can be lowered by increasing the amount of scavenging after the passage of switching transition. This is because if the scavenging amount increases, the hot in-cylinder gas is replaced accordingly.
[0011]
Such an increase in the scavenging amount can be realized by making it possible to adjust the opening timings of the intake valves and / or the exhaust valves provided in the engine and controlling the opening timings 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 is adjustable 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 once increased is gradually decreased over a predetermined period after the transition time of the operation cycle switching. It is good also as what returns to the steady scavenging amount of 2 cycle operation. Since the increase in the scavenging amount is performed in accordance with the switching of the operation cycle, it is desirable to perform it quickly. However, it is preferable to gradually reduce the scavenging amount because it does not cause a sudden change in the engine output torque. It is.
[0013]
The control for lowering the temperature of the in-cylinder gas during the switching 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 controlled in the last cycle of the four-cycle operation during the switching transition. It can also be realized by once opening and executing exhaust, and opening the intake valve and executing scavenging in the first cycle of the two-cycle operation at the time of switching transition. In this way, the temperature of the in-cylinder gas can be rapidly reduced by replacing the gas, and moreover, one cycle time is freed 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. Also, if the exhaust valve is fully opened as much as possible, the pumping loss associated with gas exchange can be reduced, which is also preferable from the viewpoint of thermal efficiency. Further, in the two-cycle operation after switching, the valve can be opened and closed as a normal two-cycle operation from the first cycle, so that the advantage that the control of valve opening and closing can be simplified is also obtained. As a result, the speed of valve control and the stability of control can be improved.
[0014]
As another configuration for reducing the in-cylinder gas temperature, there is provided a mechanism for recirculating and mixing a part of the exhaust into the intake air of the engine via the EGR passage communicating the exhaust system of the engine and the intake system. A configuration in which the amount of exhaust gas that is recirculated and mixed into the intake air can be considered at the time of switching transition of the operation cycle. Since the temperature of the exhaust gas recirculated and mixed into the intake air has decreased, the temperature of the in-cylinder gas can be quickly decreased. This makes it possible to quickly control the temperature of the in-cylinder gas and suppress the occurrence of premature ignition even when switching the valve timing of the intake and exhaust valves using a variable cam type valve system with low responsiveness. can do. Of course, such an EGR amount adjusting mechanism may be combined with a highly responsive electromagnetically driven valve system.
[0015]
Note that it is desirable that the amount of exhaust gas increased at the time of the switching transition be gradually reduced over a predetermined period after the switching transition has elapsed to return to a steady amount of two-cycle operation. This is because the effect of preventing early ignition by reducing the in-cylinder gas temperature over a predetermined period can be enjoyed without gradually changing torque by gradually returning.
[0016]
In accordance with the increase in the amount of exhaust gas mixed into the intake air via the EGR passage, a 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. It may be greater than the scavenging amount after the passage of time. In this way, in addition to the decrease in the in-cylinder gas temperature due to the increase in the amount of exhaust gas recirculated, the effect of the decrease in the in-cylinder gas temperature due to the increase in the scavenging amount can be obtained. Naturally, such a scavenging amount can be gradually decreased over a predetermined period after the switching transition has elapsed. Also in this case, torque fluctuation due to a sudden change in the scavenging amount does not occur, and the effect of preventing early ignition by reducing the in-cylinder gas temperature over a predetermined period 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, for example, by changing the stroke of the piston or by changing the cylinder length, but for simplicity, the closing timing of at least one of the intake valve and the exhaust valve provided in the engine is set. It can also be realized by delaying the closing timing of at least one of the intake valve and the exhaust valve when the operation cycle is switched. If the effective compression ratio is controlled to be low, an increase in the in-cylinder gas temperature in the compression stroke can be suppressed, and thus the in-cylinder gas temperature can be lowered. In addition, since such a method has extremely high responsiveness, an advantage of excellent transient controllability can be obtained.
[0018]
In addition, when such control of the effective compression ratio is performed at the time of switching transition of the operation cycle, the delayed valve closing timing is gradually changed over a predetermined period after the time of switching transition, and the steady amount of the two-cycle operation. It is desirable to return to the same as other controls.
[0020]
  Of the present inventionIn addition to the control, a mechanism for adjusting the opening / closing valve 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 is determined in the vicinity of the engine BDC. It can be. If such a configuration is adopted, the thermal efficiency can be increased by making use of the work by expansion. Further, as a result of the expansion stroke becoming longer, the temperature of the burned in-cylinder gas is lowered, and the adverse effects 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 is taken into the intake cycle in the first cycle of the two-cycle operation during the transition cycle of the operation cycle. The effective compression ratio may be lowered by delaying the valve 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]
In addition, 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. The control may be shifted from the valve timing to the operation as the valve opening / closing timing in the steady operation of the two-cycle operation. In this way, torque can be taken over smoothly from the beginning of the switching period without incurring a decrease in torque associated with the switching. Further, in the two-cycle operation after switching, the valve can be opened and closed as a normal two-cycle operation from the first cycle, so that the advantage that the control of valve opening and closing can be simplified is also obtained. As a result, the speed of valve control and the stability of control can be improved.
[0023]
In addition to such control, it is also preferable to perform control to lower the effective compression ratio by delaying the closing timing of the intake valve and / or the exhaust valve at the initial stage of the two-cycle operation at the time of steady operation. .
[0024]
Alternatively, a mechanism for adjusting the amount of fuel supplied to the engine, for example, a fuel injection amount, may be provided, and the amount of fuel supplied to the engine may be increased in at least the final cycle of the four-cycle operation during the transition transition of the operation cycle. In the last cycle of four cycles, the work taken out by expansion is lower than the previous cycle, but by increasing the fuel amount, it is possible to suppress a decrease in torque associated with switching. As a result, smooth switching is 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 automobiles, but can be applied to engines such as ships and airplanes. Further, the present invention can be grasped not only as the engine control device described above but also as a mobile device (such as a vehicle) equipped with such a control device.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described based on examples.Although the third embodiment directly corresponds to the present invention, the control described as the first and second embodiments can be implemented in combination with the control of the third embodiment. The overall configuration, the first embodiment, the second embodiment, and the third embodiment will be described in this order.
(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 ECU) 30 which is a control device thereof. As will be described later, the engine 10 is a type that can be operated by switching between 4-cycle operation and 2-cycle operation. The gasoline engine 10 includes 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 the four strokes of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke, and the combustion heat generated at that time is machined. It is converted into work and output as power. On the other hand, in the case of two-cycle operation, the 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 the cylinder block 140, a piston 144 that slides up and down in the cylinder 142, a cylinder head 130 provided in the upper part of the cylinder block, and the like. Has been. The piston 144 is connected to the crankshaft 148 via a connecting rod 146. The piston 144 slides up and down in the cylinder 142 in accordance with the rotation of the crankshaft 148.
[0028]
In the combustion chamber, a fuel injection valve 14 for injecting fuel into the combustion chamber and a spark plug 136 for igniting the injected fuel are provided. 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 configuration of the intake system and the exhaust system will be described.
[0029]
From the upstream side, an air cleaner 20 that removes dust, an air flow meter 13 that detects an intake air amount Q, a compressor 54 of a supercharger 50, an intercooler 62 that lowers the intake air temperature that has risen due to 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 the intake air temperature TA. Under the control of the ECU 30, the electric actuator 24 controls the throttle valve 22 to an appropriate opening, so that 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. The fuel injection valve 14 provided in each combustion chamber is supplied with fuel pressurized to a high pressure by a fuel pump (not shown). The intake valve 132 and the exhaust valve 134 are provided with electric actuators 162 and 164, respectively, and both the valves 132 and 134 are driven by the 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 disc-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 (period from the valve opening timing to the valve closing timing) of each cylinder in the present embodiment can be freely controlled. For example, it is possible to open the exhaust valve 134 in the exhaust stroke, then close it once, and then reopen it for a short time in the intake stroke. The opening / closing valve timings of the valves 132 and 134 will be described in detail later.
[0031]
A 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 the exhaust gas. In addition, the exhaust passage 16 is provided with an air excess ratio sensor 28 for detecting the excess air ratio λ of the air-fuel mixture formed in the combustion chamber, an exhaust temperature sensor 29 for detecting the exhaust temperature TB, and the like. The excess ratio sensor 28 (also referred to as an air-fuel ratio sensor) can detect the excess ratio of the air-fuel mixture formed in the combustion chamber by detecting the oxygen concentration 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 connecting a CPU, a RAM, a ROM, an A / D conversion element, a D / A conversion element, and the like with a bus. The ECU 30 detects the engine speed Ne and the accelerator opening θac, and drives the electric actuator 24 based on these to control the throttle valve 22 to an appropriate opening. The engine speed Ne can be detected by a crank angle sensor 32 provided at the tip of the crankshaft 148. The accelerator opening degree θac can be detected by an accelerator opening degree sensor 34 incorporated in the accelerator pedal. Further, the ECU 30 supplies an appropriate amount of fuel to the combustion chamber at an appropriate timing by driving the fuel injection valve 14 at an appropriate timing based on the intake air amount Q detected using the air flow meter 13. . Further, since the excess air ratio sensor 28 is provided in the exhaust passage 16, the drive time of the fuel injection valve 14 or the opening of the throttle valve 22 is controlled based on the output from the excess air ratio sensor 28. It is also possible to control so that the excess air ratio of the air-fuel mixture formed in the combustion chamber becomes an appropriate value.
[0033]
The ECU 30 also performs ignition timing control for controlling the timing at which a spark is formed in the spark plug 136 and control of opening / closing valve timings of the intake valve 132 and the exhaust valve 134. In this embodiment, since the engine 10 is operated by switching between a 4-cycle operation in which premixed spark ignition combustion is performed and a 2-cycle operation in which premixed compression self-ignition combustion is performed, the ECU 30 controls ignition timing in the 4-cycle operation. I also do it. The control of the opening / closing valve timings of the intake / exhaust valves 132 and 134 varies greatly depending on the operation cycle. Hereinafter, the control of the combustion cycle and the opening / closing valve timings of the intake / exhaust valves 132 and 134, particularly the control at the transition transition of the operation cycle will be described in detail.
[0034]
(2) Operation cycle
The gasoline engine 10 of this embodiment switches between 2-cycle operation and 4-cycle operation according to the engine speed. That is, two-cycle operation with high thermal efficiency is performed in a range where the engine speed is relatively low, and four-cycle operation where high-speed rotation is easy is performed in a range where the engine speed is high. In the gasoline engine 10, the intake valve 132 and the exhaust valve 134 are operated by the electric actuators 162 and 164. 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 in accordance with the engine speed and load in this embodiment. In the figure, the hatched region is a region where the 4-cycle operation is performed, and the non-hatched region is a region where the 2-cycle operation is performed. In addition, the two-cycle operation area is further divided into four areas depending on the load, and the formation of the air-fuel mixture is adjusted. Two-cycle operation by self-ignition combustion will be described. Detailed explanations of the known four-cycle operation and other operation conditions in two cycles are omitted.
[0036]
FIG. 3 is an explanatory diagram conceptually showing the operation of the gasoline engine 10 under a low load condition. Unlike a 4-cycle gasoline engine, a 2-cycle gasoline engine has a stroke called a scavenging stroke. Further, the two-cycle engine is different from the four-cycle engine in that the entire cycle is completed while the crankshaft 148 makes one rotation. 3A to 3F conceptually show the respective strokes of an expansion stroke, an exhaust stroke, a scavenging stroke (above and later), an intake stroke, and a compression stroke of the two-cycle engine. In the two-cycle engine, these strokes are switched one after another by opening and closing the two valves of the intake valve 132 and the exhaust valve 134 at appropriate timing while moving the piston 144 up and down in the cylinder 142. The open / close states of the intake valve 132 and the exhaust valve 134 accompanying the movement of the piston are also schematically shown in FIG.
[0037]
For convenience of explanation, the description will be made from the state in which the air-fuel mixture in the combustion chamber is combusted. When the air-fuel mixture is burned, high-pressure combustion gas is generated in the combustion chamber and tries to push down the piston 144. As shown in FIG. 3A, in the expansion stroke, while the piston 144 is lowered, the pressure generated in the combustion chamber is converted into torque and output to the crankshaft 148 as power. When the piston 144 is lowered to some extent, the exhaust valve 134 is opened at an appropriate timing. Since the combustion gas is still confined at a high pressure in the combustion chamber, 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 pushes out the combustion gas remaining in the combustion chamber from the exhaust valve 134. It is made to discharge (refer FIG.3 (c)). In the figure, the hatched portion indicates the region where the combustion gas remains, and the non-hatched portion indicates the region where the intake air flows. Thus, the operation of discharging the combustion gas from the combustion chamber by pushing it out with the intake air is called “scavenging”. Further, the process of performing scavenging is called a scavenging process. In the two-cycle engine, since the inside of the intake passage is pressurized, the combustion gas in the combustion chamber can still be scavenged even when the piston 144 goes up after passing through the bottom dead center (hereinafter also referred to as BDC). . FIG. 3D conceptually shows how the combustion chamber is scavenged while raising the piston 144 in the latter half of the scavenging stroke. In the two-cycle operation, the fuel injection valve 14 is opened at this timing, and a predetermined amount of fuel is injected. As a result, an air-fuel mixture is formed in the cylinder.
[0039]
As the scavenging progresses and the mixture is formed, the exhaust valve 134 is closed as shown in FIG. 3E. However, until the pressure in the combustion chamber reaches the pressure in the intake passage, the exhaust valve 134 is passed through the intake valve 132. Inhalation air still flows in. The intake valve 132 is closed at the timing when the pressure in the combustion chamber reaches the pressure in the intake passage. Then, as the piston 144 rises, the air-fuel mixture in the combustion chamber is compressed (see FIG. 3F). The compressed air-fuel mixture is ignited and explodes. Thus, the operation cycle returns to FIG. 3A, and the operation is repeated again from the expansion / exhaust stroke. 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 just before the exhaust valve 134 is closed, specifically, the bottom dead center from 20 degrees before the bottom dead center of the scavenging stroke. It is set to an appropriate period set within a range of 60 degrees after the point.
[0040]
After the fuel is injected, after the exhaust valve 134 is closed at a predetermined timing, as shown in FIG. 3E, the pressurized air flows from the intake valve 132 into the combustion chamber. 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 second half of the scavenging stroke is dispersed in the combustion chamber by the flow of the intake air and mixed 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 a low load condition has a value of about 1.2 to 3.
[0041]
When the intake valve 132 is closed at a predetermined timing, the air-fuel mixture in the combustion chamber is compressed as the piston rises 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 at which the intake valve 132 is closed can be set as appropriate, typically in the range of about 50 ° to about 70 °. By setting at such timing, the substantial compression ratio of the air-fuel mixture can be set to a desired value in the range of 10-14. In the engine 10 of the embodiment, the substantial compression ratio is set to 12.
[0042]
When the piston 144 is raised after the intake valve 132 is closed at an appropriate timing, as shown in FIG. 3 (f), the air-fuel mixture is compressed in the combustion chamber, and the top dead center of the piston (hereinafter also referred to as TDC). Say) Self-ignite nearby. As a result, the air-fuel mixture formed in the combustion chamber explodes and burns quickly.
[0043]
(3) Control during transition of operation cycle-First Example-
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 when the operating conditions change is described in detail below. 5 and 6 are flowcharts showing the control performed by the ECU 30 in the first embodiment. FIG. 7 is an explanatory diagram showing the stroke and switching timing of the intake valve 132 and the exhaust valve 134 when switching from the 4-cycle operation to the 2-cycle operation. Hereinafter, the transient control will be described with reference to these drawings.
[0044]
The switching transient time control processing routine shown in FIG. 5 is repeatedly executed at predetermined intervals. When this routine is started, it is first determined whether or not there is a request for switching the operation cycle (step S100). If there is no request, this routine is terminated without performing anything. When the load condition for the engine 10 is changed and the operation condition is changed from the high rotation condition (shown hatched area) shown in FIG. It is determined that there is a request for switching to cycle operation.
[0045]
In this case, it is next determined whether or not it is the timing at which the cycle can be switched (step S110). The timing at which switching can be performed means after the time point when one combustion cycle of four-cycle operation is completed. This is because the operation cycle cannot be switched before the exhaust stroke of the four-cycle operation for which control has already started is completed for one cylinder to be switched. The engine operation can be considered as a combustion cycle from intake to exhaust, so in the 4-cycle operation, it is determined that the 4-cycle operation is completed at the top dead center (TDC) after the exhaust stroke is completed. Yes. 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, and are individually driven using the electric actuators 162 and 164. The operation timing can be freely switched every time. Therefore, in this embodiment, switching from 4 cycle to 2 cycle operation is performed for each cylinder. Of course, it is possible to wait for the completion of the four-cycle operation for all the cylinders, and then switch to the two-cycle operation.
[0046]
If it is determined that it is not possible to switch, this processing routine is terminated without performing anything. If the target cylinder has completely completed one combustion cycle of the four-cycle operation, it is next determined whether or not the switching period has ended (step S120). This is because the control at the time of switching transition is not necessary after completely shifting to the two-cycle operation. Even when the switching period has been completed, this routine is terminated without performing anything. On the other hand, when there is a request for switching from the 4-cycle operation to the 2-cycle operation, and the cylinder of interest is capable of switching after the combustion cycle in the 4th cycle is completed, and the switching period has not ended, The valve timing for each cycle is controlled (step S130).
[0047]
Details of the control of the valve timing for each cycle are shown in FIG. That is, the transition control to the operation in the 2-cycle and the transition period until the start of the 2-cycle operation (this is also referred to as the 0th cycle), the first cycle, the second cycle, ..., the nth cycle Then, a process for controlling the timing of the open / close valves of the intake valve 132 and the exhaust valve 134 is performed. Based on FIG. 6 which is a flowchart showing the process and FIG. 7 which is an explanatory diagram showing valve opening / closing timing, the control of the valve timing will be described below. For convenience of illustration, in FIG. 7, the intake valve and the exhaust valve are referred to as “intake valve” and “exhaust valve”, respectively.
[0048]
When the valve timing control routine is activated, it is first determined whether or not the current cycle number n is 0 (step S200). As shown in FIG. 7, the 4-cycle operation is completed at the top dead center where the exhaust stroke is completed, but the 2-cycle operation starts with a scavenging stroke in which intake and exhaust simultaneously proceed. 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 4-cycle operation to the first top dead center (BDC) of the 2-cycle operation, the control does not belong to any of the 2 or 4 cycle operations. Is performed, the 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 opened, and the intake valve 132 is turned on slightly before entering the first cycle (first cycle) of the two-cycle operation. The valve opens. The valve timing is selected, and then the electric actuators 162 and 164 are controlled in synchronization with the rotation of the crankshaft 148 to perform the on-off valve control for driving the intake valve 132 and the exhaust valve 134 (step S220).
[0049]
As shown in FIG. 7, if 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 the 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 some of it remains in the cylinder and is used to keep the temperature of the mixture in the next combustion cycle high. Yes. On the other hand, by keeping the exhaust valve 134 open during the transition period, more combustion gas than usual passes 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 decreases its temperature. In the latter half of the transition period, the piston 144 descends, so that the combustion gas that has once gone out and the temperature has decreased returns from the exhaust passage 16 side to the combustion chamber via the exhaust valve 134. For this reason, 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), the above control is performed to lower the temperature of the in-cylinder gas, and then the two-cycle operation is started. At this time, the ECU 30 shifts to the control of step S230 and determines the current cycle number n (step S230). Subsequently, a process of selecting the valve timing of the nth cycle is performed based on the determined cycle number n (step S240). Subsequently, by driving the intake / exhaust valves 132 and 134 at a valve timing selected according to the number of cycles 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 as the second cycle, the third cycle,... That is, when switching from the 4-cycle operation to the 2-cycle operation, the first five cycles of the 2-cycle operation following the transition period are regarded as the switching transition period, and the valve opening period of the exhaust valve 134 is gradually shortened. The amount of exhaust gas discharged and re-sucked through the valve 134 is gradually changed. This situation is shown in FIG. In the figure, the vertical axis indicates the amount of exhaust gas once exhausted through the exhaust valve 134 and then re-inhaled, but in other embodiments described later, the scavenging amount is gradually changed in the same manner. In order to make the figures common, the vertical axis also shows “scavenging amount”.
[0051]
According to the engine 10 and the control device thereof according to the first embodiment described above, the mixture is compressed from the four-cycle operation in which the mixture is ignited by the spark formed on the spark plug 136 to perform the explosion combustion. When switching to two-cycle operation in which explosion combustion is performed by self-ignition, the exhaust valve 134 is opened longer than normal control, and combustion gas is taken in and out through the exhaust valve 134 to lower the temperature of the gas remaining in the cylinder. be able to. This is because the exhaust gas heated to high temperature by combustion passes through the exhaust valve 134 and the exhaust port, so that the heat quantity is taken away by the exhaust valve and the exhaust port, and the temperature decreases. 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 undesired early ignition and occurrence of knocking can be prevented in the two-cycle operation. it can. Therefore, it is possible to obtain a desirable result from the viewpoint of drivability and durability without incurring problems such as vibration and abnormal noise during switching transition. As for the intake valve 132, if the valve opening time is increased in the exhaust stroke and the intake stroke, a part of the exhaust once goes out to the intake port side through the intake valve 132 and is sucked again. Will decline. Therefore, the same control can be performed for the intake valve to achieve the same effect.
[0052]
In addition, in this embodiment, since a large amount of combustion gas is discharged and re-suctioned using the transition period, the temperature of the residual gas in the cylinder can be rapidly lowered within a short period. Further, when the two-cycle operation starts thereafter, the valve opening timing of the exhaust valve 134 is not restored immediately, but gradually over a gradual change period (the first cycle to the fifth cycle in this embodiment). Since the normal timing is restored, the action and effect of lowering the in-cylinder gas temperature by extending the valve opening time can be secured over a predetermined period, and the valve closing timing of the exhaust valve 134 is suddenly changed. Torque shock or the like of the engine 10 does not occur. In the present embodiment, the gradual change period is about 5 cycles, but the length may be appropriately determined according to engine characteristics and the like. Further, 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, switching from the 4-cycle operation to the 2-cycle operation itself 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. It is the same as that of an Example. In the modified example, the timing of the open / close valve of the exhaust valve 134 in the final cycle of the four-cycle operation and the transition period are different. As shown in FIG. 9, the exhaust valve 134 is once closed at timing t1 during the exhaust stroke of the final cycle of the four-cycle operation. The combustion gas is discharged to the exhaust passage 16 side by blowdown, as in the first embodiment. Thereafter, in the transition period, the exhaust valve 134 is opened again (illustration, timing t2), and subsequently, the intake valve 132 is opened. The valve opening timing of the intake valve 132 is the valve opening timing corresponding to the scavenging stroke of the normal two-cycle operation. As soon as the exhaust valve 134 is opened for the second time, the intake valve 132 is also opened 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 lowered.
[0054]
When such control is performed, it is possible to prevent the occurrence of undesired early ignition or knocking as in the first embodiment, and the exhaust valve 134 is not fully opened over a long period of time. There is no pump loss. As a result, the thermal efficiency can be increased as a whole without causing an excessive decrease in the thermal efficiency and hence no deterioration in fuel consumption. Further, 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 scavenging to lower the in-cylinder gas temperature is continued for a while after the two-cycle operation is started. As described with reference to FIG. 8, the control of the scavenging amount can also be gradually brought closer to the scavenging amount of the normal two-cycle operation by providing a gradual change period. In the present embodiment and the modified example, since the electric actuator is used to drive the intake / exhaust valves 132 and 134, the intermittent valve opening and closing shown in FIG. 9 can be easily realized. Of course, if a camshaft and a driving cam for four-cycle operation, a camshaft and a driving cam for two-cycle operation are prepared, and the configuration for switching them is used, the control shown in FIG. 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 the gasoline engine 100 of the second embodiment. The engine 100 has substantially the same configuration as that of the first embodiment, but is different from the first embodiment in that it further includes an external EGR mechanism that recirculates exhaust gas from the exhaust passage 16 to the intake passage 12. 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 gas to be recirculated. For convenience of explanation, members other than the recirculation mechanism in FIG. 10 have the same reference numerals as those in FIG. The EGR amount adjusting valve 172 is connected to the ECU 30, and the exhaust amount circulating from the exhaust passage 16 to the intake passage 12 can be controlled by adjusting the opening degree thereof. Since the combustion gas described in the first embodiment is once discharged into the exhaust passage 16 and then returned to the cylinder again through the exhaust valve 134, it can be considered as a kind of EGR. Therefore, the EGR amount adjusting valve 172 is used. Thus, when it is necessary to distinguish 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 external EGR.
[0056]
In the second embodiment, the ECU 30 performs substantially the same control as in the first embodiment, but the valve timing control routine executes the process shown in FIG. 11 instead of the process shown in FIG. Of the processes shown in FIG. 11, the last two digits that are the same as those in FIG. 5 have the same processing contents. That is, the second embodiment is different from the control of the first embodiment in that step S315 and step S345 are added.
[0057]
In the valve timing control routine of the second embodiment, when switching from the 4-cycle operation to the 2-cycle operation is started, the exhaust valve 134 is opened at the unique valve timing during the transition period (n = 0). Then, the intake valve 132 is opened (steps S300 → S310). After selecting the valve switching timing, in the second embodiment, the EGR amount in the transition period is adjusted (step S315). Similarly, in the first cycle, the second cycle,... After the two-cycle operation is started, after determining the cycle number n and selecting the valve timing of the n-th cycle (steps S330 → S340), the n-th cycle A 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 the figure, in this embodiment, the EGR amount is maximized in the transition period, and then gradually reduced as the cycle is followed. As a result, the external EGR amount is adjusted at the time of transition from the 4-cycle operation to the 2-cycle operation. The valve opening / closing timing may be the same as the timing shown in FIG. 9, or the exhaust valve 134 is set to a normal opening / closing valve timing, and the combustion gas remaining in the cylinder is returned via the exhaust valve 134. It is good also as what does not perform.
[0058]
The amount of external EGR in the second embodiment is increased at the time of switching transition compared to that at the time of four-cycle operation. Since the temperature of the exhaust gas that circulates to the intake system via the recirculation passage 170 and is sucked into the cylinder is considerably lowered, according to the second embodiment, the cylinder in the cylinder during the switching transition of the operation cycle The gas temperature can be rapidly reduced. 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 generation of hitting sound and deterioration of durability are not invited.
[0059]
In the second embodiment, the external EGR can be performed over several cycles at the time of switching transition, but this period during which the external EGR is applied may be appropriately determined according to the characteristics of the engine 10 and the like. As in the first embodiment, it is also preferable to gradually change the external EGR amount or switch over several stages. In this embodiment, the valve timing is also switched (steps S310 and S340). However, the valve timing is not controlled, and the gas temperature in the cylinder may be lowered only by the external EGR amount. In this case, there is an advantage that the valve timing control associated with the switching of the operation cycle becomes unnecessary. Further, in place of the electric actuators 162 and 164, even when the valve timing is switched using a valve system that is not so responsive, there is an advantage that the gas temperature in the cylinder can be lowered early 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 then the intake valve 132 and the exhaust valve 134 are switched in the first few cycles switched to the two-cycle operation. At least one of the valve closing timings is delayed, and the piston 144 is controlled to lower the degree of compression of the air-fuel mixture to lower the effective compression rate. That is, as shown in FIG. 13, the closing timing INC2 of the intake valve 132 is delayed to the angle θi or the closing timing EXC2 of the exhaust valve 134 is set to the normal two-cycle opening / closing valve timing shown in FIG. Control to delay to the angle θo is performed.
[0061]
As a result, the effective compression rate of the air-fuel mixture in the cylinder is reduced within a range where self-ignition is possible, and the temperature rise is suppressed, resulting in undesired early ignition and knocking due to excessive rise in the cylinder gas temperature. The problem of the occurrence of The control of the effective compression ratio by delaying the closing timing of the intake / exhaust valves 132 and 134 may be gradually changed to the normal valve timing after the two-cycle operation is started, as in other controls. . If such gradual change control is performed, 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 independently. However, if the control is performed in combination with the exhaust of the combustion gas through the exhaust valve 134 at the switching transition and the re-intake or the control of the external EGR amount at the switching transition, etc. Of course, it contributes to the reduction of the gas temperature. In this modification, the control for reducing the effective compression ratio is 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. You may do it. As such a mechanical compression ratio variable mechanism, a connecting rod 146 that connects the piston 144 and the crankshaft 148 is divided into a plurality of members, and a bent rod system having a mechanism for changing the net length in the middle, Various configurations are known, such as a type in which the crankpin is eccentric and the stroke is variable, and a mechanism in which the cylinder swings or moves to vary the 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. However, unlike the first or second embodiment at the time of transition from the 4-cycle operation to the 2-cycle operation, the hardware configuration is changed. Switching is performed without providing a corresponding period. That is, in the switching transition time processing routine shown in FIG. 5, in the determination (step S110) of “Is it possible to switch?”, In the first and second embodiments, the process waits until the last TDC of the four-cycle operation. 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 is determined as “switchable to the two-cycle operation” and the transition is made. Two-cycle operation is started without passing through the period. This situation 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, and the processing 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 final 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), in particular, the timing for opening the exhaust valve 134 is 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 the temperature of the in-cylinder gas is sufficiently lowered. As a result, it is possible to prevent an excessive increase in the gas temperature in the cylinder at the time when the two-cycle operation is started, and to suppress the occurrence of undesired early ignition and knocking. Since the expansion stroke is sufficiently taken in the final cycle of the 4-cycle operation, the thermal efficiency of the engine 10 can be increased. Furthermore, according to the present embodiment, it is not necessary to provide a transition period not related to the combustion cycle from the final cycle of the four-cycle operation to the first cycle of the two-cycle operation. There is no problem. In addition, since the control of the two-cycle operation is started immediately without providing a transition period, the valve timing control 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. In addition, the valve control cycle can be shortened.
[0064]
Furthermore, in the first cycle of the two-cycle operation, the temperature of the in-cylinder gas can be lowered more efficiently by delaying the closing timing of the intake and exhaust valves 132 and 134 to lower the effective compression rate. Also, a 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 control such as a decrease in the in-cylinder gas temperature due to an increase in the external EGR amount described in the second embodiment, or the second embodiment. It is also easy to combine the process of reducing the effective compression rate described as a modification of the example with the control of the third embodiment. In this way, 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. As shown in FIG. 15, 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 final cycle of the four-cycle operation. In this modification, the closing timing of the exhaust valve 134 in the final cycle of the four-cycle operation is earlier than that in the third embodiment, and the expansion stroke is substantially the same as that in the case of the two-cycle operation. That is, the exhaust valve 134 is opened long before BDC. On the other hand, the opening timing of the next exhaust valve 134 is the timing of normal two-cycle operation.
[0066]
In this modification, the valve timing of the valve becomes simpler, the control is simple, and the stability can be improved. In addition, what is necessary is just to combine the method of the several Example mentioned above for the control which reduces in-cylinder gas temperature. For example, the in-cylinder gas temperature may be lowered by delaying the closing timing of the intake and exhaust valves 132 and 134 in the scavenging / compression stroke to lower the effective compression rate. Alternatively, the external EGR amount may be increased (see FIG. 11). Further, since the work of the expansion stroke in the final cycle of the four-cycle operation is made smaller than that in the third embodiment, the output torque from the engine 10 apparently decreases. Correcting the fuel injection amount to be increased is also useful for suppressing the torque fluctuation of the engine 10. FIG. 16 shows an example of processing when the fuel is corrected to be increased in the final cycle. When there is a request for switching the operation cycle (step S400), the ECU 30 determines whether or not fuel injection has already been performed (step S401). If not, the ECU 30 calculates the fuel injection amount Tm of the cycle m as a coefficient. A process of correcting the increase 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), but the subsequent processing is basically the same as that of the first embodiment shown in FIG.
[0067]
In each of the above-described embodiments, the intake / exhaust valve is driven by an electric actuator, but can be opened and closed using a rotation of a crankshaft using a cam. In this case, since the valve opening / closing timing differs greatly between the 4-cycle operation and the 2-cycle operation, a mechanism capable of freely adjusting the opening / closing valve timing of the intake / exhaust valve is required. Since various mechanisms are known for such a valve operating system, detailed description thereof is omitted. However, the valve movement with respect to one rotation of the crankshaft 148 is greatly different between the 2-cycle operation and the 4-cycle operation. Alternatively, a dedicated camshaft may be prepared, and the camshaft may be switched in accordance with the switching of the operation cycle. Such a switching mechanism for the valve operating system is known. Further, in the camshaft in operation, the mechanism for freely controlling the opening and closing timings of the intake and exhaust valves is a mechanism for controlling the valve opening period by varying the valve lift amount by the valve driving cam; This mechanism can be configured by a mechanism that is changed by combining with a mechanism that varies the phase of the drive cam relative to the rotation of the crankshaft 148. By adjusting the lift amount of the intake valve 132 and the exhaust valve 134 and the phase with respect to the crankshaft, both the valve opening timing and the valve closing timing of each valve can be freely controlled as a result. The adjustment of the valve lift amount can be easily realized by providing a mechanism for changing the length of the member that connects the intake and exhaust valves to the member that traces the cam profile.
[0068]
As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, and in the range which does not deviate from the summary of this invention, it can implement with a various form. Of course. For example, in this embodiment, a three-cylinder engine is taken as an example, but the present invention can be applied to engines other than three cylinders, such as engines having different numbers of cylinders, such as four cylinders, five cylinders, six cylinders, eight cylinders, and 12 cylinders. . Other configurations for reducing the in-cylinder gas temperature at the time when the operation cycle is switched to the two-cycle operation include, for example, a temporary lowering of the intake air temperature by an intercooler, cooling of a cylinder block using a semiconductor element, and the like. Of course, the method can be adopted. As a method for reducing the in-cylinder gas temperature, a method of introducing a low temperature (or reduced) gas (external EGR, fresh air, etc.), a method of reducing the exhaust gas temperature itself, and a temperature of the cylinder block are rapidly reduced. As a result, various methods such as a method of reducing the in-cylinder gas temperature can be employed.
[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 the relationship between the engine speed and load and the operation cycle.
FIG. 3 is an explanatory diagram for explaining a stroke of a two-cycle operation.
FIG. 4 is an explanatory diagram showing opening / closing valve timings of intake and exhaust valves in a two-cycle operation.
FIG. 5 is a flowchart showing a switching transition 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 timings when switching operation cycles in the first embodiment.
FIG. 8 is an explanatory diagram showing a state of gradual change in the amount of re-suction exhaust gas and scavenging amount.
FIG. 9 is an explanatory diagram showing valve timings when 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 showing a valve timing control routine in the second embodiment.
FIG. 12 is an explanatory diagram showing valve timing at the time of switching of operation cycles in the second embodiment.
FIG. 13 is an explanatory diagram showing on / off valve timings of intake and exhaust valves in a modification of the second embodiment.
FIG. 14 is an explanatory diagram showing valve timings at the time of switching operation cycles in the third embodiment.
FIG. 15 is an explanatory diagram showing valve timings when switching operation cycles in a modification of the third embodiment.
FIG. 16 is a flowchart showing a switching transition 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 ... Excess air ratio sensor
29 ... Exhaust 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 (18)

An apparatus for controlling a variable cycle engine capable of switching a combustion cycle between 4 cycles and 2 cycles,
At the time of switching switching from the 4-cycle operation in which spark ignition combustion is performed to the 2-cycle operation in which compression ignition combustion is performed, the scavenging / exhaust stroke in the 2-cycle operation is performed following the expansion stroke in the 4-cycle operation, and the 2-cycle operation is performed. An engine control device comprising gas temperature lowering means for lowering in-cylinder gas temperature at the time of switching transition by starting operation . 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 a valve open state at least in a part of the exhaust and intake stroke;
The gas temperature lowering means realizes a decrease in the in-cylinder gas temperature by controlling the valve opening adjusting means and opening the intake valve and / or the exhaust valve during the switching transition. Ru an 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 reduction means controls the scavenging amount of the two-cycle operation at the initial stage of the two-cycle operation at the time of the switching transient by controlling the scavenging amount adjustment means to reduce the in-cylinder gas temperature. engine control apparatus comprising means for implementing by increasing from scavenging amount after the lapse of time. The engine control device according to claim 3,
The scavenging amount adjusting means is a valve opening adjusting means for adjusting a valve opening timing of an intake valve and / or an exhaust valve provided in the engine,
The increase in pre-Symbol scavenging ratio, the engine control unit you realized by controlling the the open valve adjustment means. The engine control apparatus 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 switching transition time to return to the steady scavenging amount of the two-cycle operation. An engine control device comprising means. The engine control device according to claim 1,
A valve opening adjusting means for adjusting the opening of an exhaust valve provided in the engine;
The gas temperature lowering means controls the valve opening adjusting means to decrease the in-cylinder gas temperature, and temporarily opens the exhaust valve in the last cycle of the four-cycle operation at the time of the switching transition to execute exhaust. , first performing a scavenging opening the exhaust valve in the cycle, the engine controller Ru comprising means for implementing a two cycle operation when said switching transients. The engine control device according to claim 1,
An external EGR means for recirculating and mixing 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 gas temperature reduction means, engine deterioration of the in-cylinder temperature at the time of the switching transient, the external EGR means by controlling the increasing the amount of exhaust gas that is mixed into the intake, Ru comprises means for implementing the Control device. The engine control device according to claim 7, wherein
The gas temperature lowering means gradually reduces the exhaust amount mixed during the switching transient, which is increased by controlling the external EGR means, over a predetermined period after the switching transient elapses, so that the two-cycle operation is performed. An engine control device comprising gradual reduction means for returning to a steady amount. The engine control device according to claim 7 or 8,
A scavenging amount adjusting means for adjusting a scavenging amount when the engine is operated for two cycles;
The gas temperature lowering unit controls the scavenging amount in the two-cycle operation by controlling the scavenging amount adjusting unit as the exhaust amount mixed into the intake air is increased by controlling the external EGR unit. An engine control device comprising means for increasing the amount of scavenging after the passage of a transient. 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 transient has elapsed, thereby obtaining a steady amount for the two-cycle operation. An engine control device comprising a gradually decreasing means for returning. The engine control device according to claim 1,
A valve closing adjusting means for adjusting a closing timing of at least one of an intake valve and an exhaust valve provided in the engine;
The gas temperature lowering means realizes the reduction 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 or the exhaust valve. the engine control unit Ru provided with means. The engine control device according to claim 11,
The gas temperature lowering means gradually changes the valve closing timing delayed by controlling the valve closing adjusting means over a predetermined period after the switching transition has elapsed, so that the steady state of the two-cycle operation is increased. An engine control device comprising gradual change means for returning the amount. An engine control apparatus according to claim 1 Symbol placement,
An on-off valve adjusting means for adjusting on-off valve timing of an intake valve and / or an exhaust valve provided in the engine;
The operation switching means sets the end timing of the expansion stroke of the four-cycle operation to the vicinity of the BDC of the engine by controlling the on-off valve adjusting means. An engine control apparatus according to claim 1 Symbol placement, a closed adjusting means for further adjusting at least closing timing of the intake valve and / or exhaust valve provided in the engine,
In the first cycle of the two-cycle operation during the switching transition, by controlling the valve closing adjustment 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: An engine control apparatus according to claim 1 Symbol placement,
An on-off valve adjusting means for adjusting on-off 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 the valve opening / closing timing at the time of steady operation of the two-cycle operation from the next valve opening timing of the exhaust valve. The engine control device that shifts control to driving. The engine control device according to claim 15 ,
The engine control device is provided with a compression ratio adjusting means for delaying the closing timing of the intake valve and / or the exhaust valve and lowering the effective compression ratio in the initial stage of the two-cycle operation during the steady operation. An engine control apparatus according to claim 1 Symbol placement,
Fuel supply amount adjusting means for adjusting the amount of fuel supplied to the engine;
An engine control device comprising: a fuel increase means for increasing the amount of fuel supplied to the engine in at least the final cycle of the four-cycle operation during the switching transition. A method of controlling a variable cycle engine capable of switching a combustion cycle between 4 cycles and 2 cycles,
At the time of switching switching from the 4-cycle operation in which spark ignition combustion is performed to the 2-cycle operation in which compression ignition combustion is performed, the scavenging / exhaust stroke in the 2-cycle operation is performed following the expansion stroke in the 4-cycle operation, and the 2-cycle operation is performed. An engine control method for taking measures to lower the in-cylinder gas temperature at the time of switching transition by starting operation .

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