JP2008051017A - Premixed compression self-igniting internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a premixed compression self-igniting internal combustion engine, highly accurately adjusting a fuel mixture temperature by using back flow gas, while performing self-ignition combustion not generating misfire by using residual gas. <P>SOLUTION: An exhaust valve solenoid drive mechanism and an intake valve solenoid device mechanism leave over part of burnt gas as residual gas in a combustion chamber by negative overlap of a first exhaust valve opening period EX1 with an intake valve opening period IN. The exhaust valve solenoid drive mechanism makes the other part of the burnt gas flow back as back flow gas from the exhaust port into the combustion chamber. The back flow gas is slightly lower in temperature than the residual gas. An accelerator opening sensor detects an accelerator operation amount, which indicates engine load. In high load side operation, a CPU retards timing finishing the first exhaust valve opening period EX1 and second exhaust valve opening period EX2 so that a ratio of a residual gas amount with respect to a back flow gas amount in the high load side operation is smaller than that in low load side operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a premixed compression self-ignition internal combustion engine (hereinafter simply referred to as a self-ignition (self-ignition) by compressing a mixed gas in a combustion chamber in a compression stroke and burning the self-ignited mixed gas in an expansion stroke. Sometimes referred to as “institution”).

  One conventionally known engine of this type controls self-ignition combustion by burning gas including air, fuel, and burned gas (exhaust gas). More specifically, this institution uses an external EGR system or an internal EGR system.

  The external EGR system is a well-known system including an exhaust gas recirculation conduit, an EGR valve, a heat exchanger, and the like. This external EGR system uses a heat exchanger to cool the burned gas discharged from the combustion chamber, and returns the cooled burned gas to the engine intake system through the exhaust gas recirculation pipe (recirculation). Let burned gas flow into the chamber. Hereinafter, the gas introduced into the combustion chamber by the external EGR system is referred to as “reflux gas”. The amount of the reflux gas flowing into the combustion chamber is adjusted by changing the opening of the EGR valve.

  One of the internal EGR systems is configured to cause the burnt gas to flow backward from the exhaust port to the combustion chamber by opening the exhaust valve during a predetermined valve opening period during the intake operation. This burned burned gas is called “backflow gas”. The amount of the backflow gas is adjusted by changing the valve opening period during the intake operation. Another one of the internal EGR systems is to close the exhaust valve in order to end the exhaust operation and then open the intake valve to start the intake operation. This so-called “negative overlap of the exhaust valve and the intake valve” is performed. Used to leave burnt gas in the combustion chamber. Here, the burnt gas remaining in the combustion chamber is referred to as “residual gas”. The amount of residual gas is adjusted by changing the negative overlap period.

  For example, the engine disclosed in Patent Document 1 is an engine that uses both the cooled recirculation gas and the higher-temperature backflow gas, and changes the ratio of the recirculation gas amount and the backflow gas amount according to the engine load. It is supposed to let you. That is, this conventional engine increases the temperature of the mixed gas in the combustion chamber (compression end temperature at which the mixed gas begins to burn) at the timing of self-ignition by increasing the amount of backflow gas during low-load operation, thereby causing misfire. Prevents self-ignition and stabilizes combustion. On the other hand, by increasing the amount of recirculated gas during high load operation, this engine suppresses an excessive temperature rise in the combustion chamber before and after the self-ignition timing, thereby preventing abnormal combustion (such as premature ignition or knocking). Moreover, this patent document 1 discloses that the backflow gas and the residual gas can be handled as internal EGR gas that can be replaced with each other. In other words, the disclosed engine changes the ratio of the amount of recirculated gas and the amount of residual gas in accordance with the load of the engine instead of the ratio of the amount of recirculated gas and the amount of backflow gas.

However, in the conventional engine, the recirculated gas that flows more into the combustion chamber during high-load operation is cooled, so the temperature of the mixed gas in the combustion chamber increases only when the amount of the recirculated gas that flows in increases slightly. It will decline. In other words, in spite of the importance of accurately adjusting the temperature of the mixed gas in order to control the timing of self-ignition, it is difficult to fine-tune the temperature of the mixed gas in conventional engines, and as a result It is difficult to control the timing at which the gas reaches the compression end temperature and self-ignites sufficiently accurately.
Japanese Patent Laid-Open No. 2005-16407

  Accordingly, one of the objects of the present invention is to make it possible to finely adjust the temperature of the mixed gas using the backflow gas while performing stable self-ignition combustion that does not cause misfire or the like using the residual gas. It is to provide a premixed compression self-ignition internal combustion engine.

  The premixed compression self-ignition internal combustion engine according to the present invention sequentially executes a combustion cycle including each operation of intake, compression, expansion and exhaust in a predetermined number of cylinders. In the combustion chamber formed in each cylinder, the engine is configured to self-ignite and burn by compressing a mixed gas containing air and fuel, and a residual gas generating means, a backflow gas generating means, And an output state detecting means and a ratio control means.

  Residual gas generation means is a part of the burned gas generated in the combustion chamber due to the combustion of the mixed gas in the previous combustion cycle as residual gas, in the mixed gas combusted in the current combustion cycle that follows the previous time. A portion of this burned gas is left in the combustion chamber to be included.

  The backflow gas generation means is configured such that the other part of the burned gas that is part of the gas once exhausted from the combustion chamber to the exhaust port by the exhaust operation after the occurrence in the previous combustion cycle is the backflow gas. The other part of the burned gas is caused to flow back into the combustion chamber so as to be included in the mixed gas burned in the combustion cycle. Since the temperature in the exhaust port and the valve seat is lower than that in the combustion chamber, the backflow gas is deprived of heat by the exhaust port and the valve seat, and the temperature is slightly lower than the residual gas. On the other hand, the temperature of the backflow gas is higher than the temperature of the reflux gas described above.

  The output state detection means detects an output state value that changes according to the output of the engine. Specifically, as described later, the engine load or the rotational speed is used as the output state value. Furthermore, the engine torque, the temperature of the gas or exhaust gas in the combustion chamber, the compression top dead center, or the pressure of the gas in the combustion chamber before and after combustion may be used as the output state value. The ratio control means is configured to reduce the ratio of the amount of residual gas remaining to the amount of counterflow gas to be backflowed as the engine output corresponding to the detected output state value increases. At least one of the gas generating means and the backflow gas generating means is controlled.

  According to this engine, as the output of the engine increases, the ratio of the amount of residual gas to be left to the amount of counterflow gas to be backflowed is adjusted to be smaller. As a result, since the ratio of the residual gas amount is larger during low-power operation, combustion by self-ignition can be more stabilized without causing misfire. Further, during high power operation, the engine does not increase the ratio of the recirculated gas cooled in order to prevent abnormal combustion, but increases the ratio of the backflow gas that is slightly lower in temperature than the residual gas. Therefore, the temperature of the mixed gas can be adjusted more finely and with high accuracy. As a result, the self-ignition timing can be appropriately controlled regardless of whether the operation is a low output operation or a high output operation.

  In the premixed compression self-ignition internal combustion engine of the present invention, the output state detection means may detect the engine load as the output state value. Since the engine load can be expressed by, for example, the intake air amount, the throttle valve opening, the accelerator pedal operation amount, the fuel injection amount, or the like, the output state detection means detects any of these. Here, the ratio control means controls at least one of the residual gas generation means and the backflow gas generation means so that the ratio of the residual gas amount to the backflow gas amount becomes smaller as the detected engine load increases.

  Normally, during high load operation, the intake air amount and the fuel injection amount increase, and the combustion chamber becomes hotter, so abnormal combustion tends to occur. On the other hand, in this engine, the ratio of the residual gas amount is adjusted to be smaller during high-load operation, which causes the compression end temperature of the mixed gas to rise excessively during high-load operation, resulting in premature ignition, etc. It is possible to prevent abnormal combustion.

  In the premixed compression self-ignition internal combustion engine of the present invention, the output state detection means may detect the engine speed as the output state value. Here, the ratio control means controls at least one of the residual gas generation means and the backflow gas generation means so that the ratio of the residual gas amount to the backflow gas amount becomes smaller as the detected rotational speed of the engine increases. .

  Normally, during high-speed operation, the time for opening the exhaust valve is shortened due to the exhaust operation, so the burnt gas itself is less likely to be discharged to the exhaust port due to the inertia of the burnt gas itself remaining in the combustion chamber. As a result, the amount of residual gas increases during high-speed operation. At the same time, during high-speed operation, the heat transfer time from the burned gas to the side wall of the combustion chamber is shortened. As a result, the temperature of the mixed gas becomes higher during high-speed operation. On the other hand, in this engine, the ratio of the residual gas amount is adjusted to be smaller during high-speed operation, thereby preventing abnormal combustion during high-speed operation.

  This engine preferably further includes a gas amount adjusting means for increasing the amount of air taken into the combustion chamber as the detected rotational speed of the engine increases. For example, the increase in intake gas during high-speed operation can be achieved by correcting the throttle valve opening relative to the accelerator opening so that it is larger than normal, and increasing the boost pressure raised by the turbocharger more than normal. This is done by correcting to a large value. According to this, air at a lower temperature than the residual gas or the backflow gas is sucked in a large amount into the combustion chamber during high-speed operation, so that the compression end temperature of the mixed gas can be more effectively lowered to prevent abnormal combustion. .

  In this engine, the residual gas generating means is a period in which the exhaust valve is opened during the first exhaust valve opening period during which the exhaust operation is performed during the previous combustion cycle and the intake operation is performed during the current combustion cycle. It is desirable that a part of the burned gas generated in the combustion chamber by the combustion of the mixed gas is left as the residual gas in the combustion chamber by opening the intake valve during the intake valve opening period. Then, the backflow gas generating means opens the exhaust valve during the second exhaust valve opening period having the start timing within the intake valve opening period during the current combustion cycle, so that the gas once discharged from the combustion chamber It is desirable that the other part of the burned gas, which is a part, is caused to flow back into the combustion chamber as the backflow gas. According to this, an effect such as fine adjustment of the temperature of the mixed gas can be achieved by a simple configuration for changing the opening and closing timings of the exhaust valve and the intake valve, and a complicated structure is not required. Therefore, the manufacturing cost of the engine can be kept low.

  In the engine described above, the cylinders may be arranged as follows: (1) 3 cylinders in series or 3 cylinders in each row in V type. Hereinafter, in the above-described engine, an engine having such a cylinder arrangement is simply referred to as an “in-line three-cylinder engine”. In the inline three-cylinder engine or the like, the ratio control unit controls the backflow gas generation unit, so that the output state value (that is, the load or the rotational speed) detected by the output state detection unit increases. It is preferable to delay the end timing of the two exhaust valve opening period (see FIG. 5A).

  Incidentally, the second exhaust valve opening period in one cylinder is generally set to a period from the middle stage to the latter stage of the intake stroke. Therefore, in an engine such as an inline three cylinder, the initial period of the second exhaust valve opening period overlaps with the timing at which blowdown occurs immediately after the exhaust valves of other cylinders are opened, and the exhaust pressure (exhaust pressure) The pressure in the vicinity of the port, exhaust manifold and exhaust pipe) fluctuates rapidly and is not stable. On the other hand, the exhaust pressure in the second half of the second exhaust valve opening period is relatively stable.

  The second exhaust valve opening period will be described more specifically. This engine is an in-line three-cylinder engine, and each cylinder is identified as a first cylinder, a second cylinder, and a third cylinder in order from a position away from the engine output side. The initial period of the second exhaust valve opening period (second exhaust valve opening period EX2 of cylinder # 1 in FIG. 4) in the first cylinder is the first exhaust valve opening period (cylinder # in FIG. 4) of the third cylinder. 3 and the initial timing of the exhaust valve opening period EX1), the timing immediately after the blowdown by the third cylinder occurs (see the solid line of BD # 3 in FIG. 4). The exhaust pressure (exhaust pressure PE in FIG. 4) rapidly increases by blowdown, and then decreases rapidly. Even if an attempt is made to adjust the amount of backflow gas sucked into the combustion chamber at the timing before and after the blowdown, the amount of backflow gas may fluctuate greatly every time the exhaust valve is opened. The backflow gas amount greatly fluctuates with a slight change in the opening timing. That is, it is difficult to finely adjust the backflow gas amount in the second exhaust valve opening period by changing the start timing of the second exhaust valve opening period. On the other hand, since the exhaust pressure is relatively little changed and stable in the later stage of the second exhaust valve opening period, the amount of the backflow gas is stable when the backflow gas is sucked before and after this timing. That is, it is possible to finely adjust the backflow gas amount during the second exhaust valve opening period by changing the end timing of the second exhaust valve opening period.

  Accordingly, the larger the detected output state value (for example, the load) in an in-line three-cylinder engine, etc., the more the backflow gas is increased by delaying the end timing of the second exhaust valve opening period, thereby increasing the flow of other cylinders. The temperature of the mixed gas is finely adjusted while the influence of the down is prevented.

  Further, a start timing control means may be further provided in an engine such as an inline three cylinder. The start timing control means adjusts the start timing so as to delay the start timing of the first exhaust valve opening period as the detected output state value increases by controlling the residual gas generation means (see FIG. (See 5 (B).) In this case, the ratio control means controls the backflow gas generation means so that the start timing of the second exhaust valve opening period is relative to the start timing of the first exhaust valve opening period adjusted by the start timing control means. Delay until the pre-adjusted timing.

  The above-described adjustment of the start timing of the first exhaust valve opening period by the start timing control means is performed for the purpose of changing the expansion ratio of the engine, for example. That is, here, the start timing (and end timing) of the first exhaust valve opening period during the high load operation is retarded from that during the low load side self-ignition operation, thereby increasing the expansion ratio. The thermal efficiency is increased by increasing the expansion ratio in this way. On the other hand, the start timing (and end timing) of the first exhaust valve opening period is advanced during the low load side self-ignition operation, compared with the high load operation, thereby reducing the expansion ratio. If the burnt gas is sufficiently adiabatically expanded, the temperature is lowered, but the temperature drop is suppressed by the advance angle of the first exhaust valve opening period. The start timing of the first exhaust valve opening period may be adjusted for the purpose of adjusting the residual gas amount.

  Further, as described above, in an engine such as an in-line 3 cylinder or a V type 6 cylinder, the initial period of the second exhaust valve opening period in one cylinder overlaps with the initial stage of the exhaust stroke in the other cylinder, and the amount of backflow gas (first 2) It is difficult to stabilize the amount of burned gas from the exhaust port during the exhaust valve opening period. On the other hand, as in this engine, the start timing of the second exhaust valve opening period can be delayed to a previously adjusted timing in accordance with the change of the start timing of the first exhaust valve opening period by the start timing control means. For example, it is possible to prevent the backflow gas amount from fluctuating due to blowdown of other cylinders. (Of course, the plurality of cylinders of the engine are premised on that the start timing of the exhaust valve opening period is similarly adjusted and the second exhaust valve opening period is similarly changed.)

  In addition, in the engine described above, the cylinders may be (2) eight cylinders arranged in series, four cylinders or four V cylinders in each row. Hereinafter, in the above-described engine, an engine having such a cylinder arrangement is simply referred to as an “in-line four-cylinder engine”. In an engine such as an inline 4-cylinder engine, the ratio control unit controls the backflow gas generation unit so that the start timing of the second exhaust valve opening period increases as the output state value detected by the output state detection unit increases. It is desirable to further advance (see FIG. 5C).

  The second exhaust valve opening period will be described more specifically. As this engine is an in-line four-cylinder engine, each cylinder is identified as a first cylinder, a second cylinder, a third cylinder, and a fourth cylinder in order from a position away from the output side in the same manner as described above. At this time, the second exhaust valve opening period (second exhaust valve opening period EX2 of cylinder # 1 in FIG. 8) in the first cylinder is the first exhaust valve opening period (FIG. 8) in the fourth cylinder. This overlaps with the initial period of the first exhaust valve opening period EX1) of cylinder # 4. That is, the latter period of the second exhaust valve opening period of the first cylinder is the timing at which blowdown by the fourth cylinder occurs. Before and after this blowdown, the exhaust pressure rises and falls violently (see the solid line for BD # 4 in FIG. 8). On the other hand, the exhaust pressure in the initial stage of the second exhaust valve opening period is relatively stable.

  Accordingly, in an in-line four-cylinder engine or the like, the larger the detected output state value is, the more the backflow gas is increased by advancing the start timing of the second exhaust valve opening period, so that the second exhaust valve opening period becomes another It overlaps with the blow-down of the cylinder, and it is possible to prevent the backflow gas amount during the opening period of the second exhaust valve from fluctuating rapidly under the influence of the blow-down.

  Further, another start timing control means may be further provided in an inline 4-cylinder engine. The start timing control means adjusts the start timing so as to delay the start timing of the first exhaust valve opening period as the detected output state value increases by controlling the residual gas generation means (see FIG. (See (D) of 5). At this time, the ratio control means controls the backflow gas generation means so that the end timing of the second exhaust valve opening period is relative to the start timing of the first exhaust valve opening period adjusted by the start timing control means. Delay until the pre-adjusted timing. As a result, adverse effects caused by blowdown of other cylinders can be avoided.

  Hereinafter, embodiments of a premixed compression self-ignition internal combustion engine according to the present invention will be described with reference to the drawings.

a. First Embodiment FIG. 1 shows a schematic configuration of an internal combustion engine according to a first embodiment. The internal combustion engine 10 is a four-stroke in-line three-cylinder engine. That is, the three cylinders of the engine 10 are arranged in a line (in a direction perpendicular to the paper surface), and one combustion cycle sequentially executed in each cylinder is in order an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. Is included. The engine 10 is operated by switching between the self-ignition operation method and the spark ignition operation method. Although FIG. 1 shows only a longitudinal section of one cylinder, the other cylinders have the same configuration.

  The engine 10 includes a cylinder block 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head 30 fixed on the cylinder block 20, and air (fresh air) to the cylinder block 20. An intake system 40 for supplying and an exhaust system 50 for releasing the exhaust gas from the cylinder block unit 20 to the outside are included.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and this reciprocation is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 rotates. The side wall surface of the cylinder 21 and the top surface of the piston 22 together with the lower surface of the cylinder head portion 30 form a pent roof type combustion chamber 25.

  The cylinder head portion 30 includes an intake port 31 communicating with the combustion chamber 25 for sucking mixed gas (including at least air and fuel) into the combustion chamber 25, and an intake valve 32 for opening and closing the intake port 31. The intake valve electromagnetic drive mechanism 32 a is connected to the drive circuit 33 and electromagnetically opens and closes the intake valve 32 in response to a drive signal from the drive circuit 33. The intake valve electromagnetic drive mechanism 32a opens the intake valve 32 at a preset opening / closing timing (crank angle) prior to opening / closing of the intake valve 32 and by a preset lift amount VL. The CPU 71 can variably set the opening / closing timing and the lift amount VL according to the load of the engine 10. The same applies to an exhaust valve electromagnetic drive mechanism 38a described later.

  Further, the cylinder head portion 30 directly injects fuel for forming a mixed gas into the combustion chamber 25 toward the upper portion in the combustion chamber 25 at a predetermined timing during the intake stroke. In addition, a spark plug 35 that sparks and ignites the mixed gas from the spark discharge at the electrode portion exposed in the upper part of the combustion chamber 25 is provided. An accumulator chamber, a fuel pump, and a fuel tank (not shown) are connected to the direct injection valve 34 in this order. These pressure accumulating chambers, fuel pumps, and fuel tanks are provided one by one in the engine 10 and are shared among the direct injection valves provided in the three cylinders. The fuel pump raises the fuel in the fuel tank to high pressure and supplies it to the pressure accumulation chamber. The pressure accumulation chamber stores high pressure fuel. The direct injection valve 34 is configured to inject high-pressure fuel from the pressure accumulation chamber into the combustion chamber 25 when opened in response to a drive signal (fuel injection signal). An igniter 36 including an ignition coil that generates a high voltage to be applied to the spark plug 35 is connected to the spark plug 35. The spark plug 35 is controlled so as to ignite the mixed gas during the spark ignition operation and to stop the spark ignition during the self-ignition operation.

  Further, the cylinder head portion 30 includes an exhaust port 37 communicating with the combustion chamber 25 for discharging burned gas (gas generated by the combustion of the mixed gas) from the combustion chamber 25, and an exhaust valve for opening and closing the exhaust port 37. 38, and an exhaust valve electromagnetic drive mechanism 38a that is connected to the drive circuit 33 and electromagnetically opens and closes the exhaust valve 38 in response to a drive signal from the drive circuit 33.

  The intake system 40 includes an intake manifold 41 that branches and communicates with an intake port 31 of each cylinder on the downstream side, a surge tank 42 that is a gathering portion on the upstream side of the intake manifold 41, and one end of the surge tank 42. The connected intake duct 43, the air filter 44 disposed in the intake duct 43 in order from the other end of the intake duct 43 toward the downstream side, the compressor 81a of the turbocharger 81, and the bypass flow rate adjustment valve 45. , An intercooler 46 and a throttle valve 47 are provided.

  In addition, the intake system 40 includes a bypass passage 48 for bypassing the intercooler 46. One end of the bypass passage 48 is connected to the bypass flow rate adjusting valve 45, and the other end is connected to the intake duct 43 at a position between the intercooler 46 and the throttle valve 47. The bypass flow rate adjusting valve 45 changes the valve opening degree in response to the drive signal, so that the amount of air flowing into the intercooler 46 and the amount of air flowing into the bypass passage 48 (air bypassing the intercooler 46). Amount) and can be adjusted. The intercooler 46 is water-cooled in this example, and cools the air passing through the intake duct 43.

  The throttle valve 47 is rotatably supported by the intake duct 43 in the intake duct 43, and is connected to a throttle motor 47a. The throttle motor 47a rotationally drives the throttle valve 47, thereby changing the opening cross-sectional area of the intake duct 43.

  The exhaust system 50 includes an exhaust manifold 51 and a collection of exhaust manifolds 51 each including a passage that branches and communicates with the exhaust port 37 of each cylinder on the upstream side, and a collecting portion that joins the passages on the downstream side. The exhaust pipe 52 communicated from the collecting section downstream of the turbine section, the turbine 81b of the turbocharger 81 disposed in the exhaust pipe 52, and both ends upstream and downstream of the turbine 81b so that the exhaust gas bypasses the turbine 81b. A waste gate passage 53 communicating with the exhaust pipe 52, a supercharging pressure adjusting valve 53a disposed in the waste gate passage 53, and a three-way catalyst 54 disposed in the exhaust pipe 52 downstream of the turbine 81b. Yes.

  By arranging the portions of the intake system 40 and the exhaust system 50 as described above, the turbine 81b of the turbocharger 81 is rotated by the energy of the exhaust gas, and the rotation of the turbine 81b is transferred to the compressor 81a coaxial with the turbine 81b. The air in the compressor 81a is compressed by the transmitted rotation. The turbocharger 81 supercharges air to the engine 10 in this way. Further, the supercharging pressure adjustment valve 53a adjusts the amount of exhaust gas flowing into the turbine 81b in response to the drive signal, thereby adjusting the pressure (supercharging pressure) in the intake manifold 41. Yes.

  The engine 10 includes an air flow meter 61, a crank position sensor 62, and an accelerator opening sensor 63. The air flow meter 61 outputs a signal representing the amount of air Ga that is being inhaled. The crank position sensor 62 outputs a signal having a narrow pulse every time the crankshaft 24 rotates 10 ° and a signal having a wide pulse every time the crankshaft 24 rotates 360 °. This wide pulse signal represents the rotational speed NE of the engine 10. The accelerator opening sensor 63 outputs a signal representing the operation amount Accp of the accelerator pedal 82 operated by the driver.

  The electric control device 70 includes a CPU 71 connected to each other by a bus, a routine (program) executed by the CPU 71, a table (look-up table, map), a ROM 72 in which constants are stored in advance, and the CPU 71 temporarily stores data as necessary. The microcomputer includes a RAM 73 to be stored, a backup RAM 74 that stores data while the power is turned on, and retains the stored data while the power is shut off, and an interface 75 including an AD converter. The interface 75 is connected to the sensors 61 to 63, and supplies signals from the sensors 61 to 63 to the CPU 71. The interface 75 is connected to the drive circuit 33, the direct injection valve 34, the igniter 36, the bypass flow rate adjustment valve 45, the throttle motor 47a, and the supercharging pressure adjustment valve 53a. It is supposed to be sent out.

  In addition, the electric control device 70 performs switching control between the self-ignition operation method and the spark ignition operation method according to the load L and the rotational speed NE of the engine 10, and further, the intake valve 32 and the exhaust gas according to each operation method. The opening / closing timing and lift amount VL of the valve 38, the fuel injection timing and injection amount by the direct injection valve 34, the presence / absence of spark ignition by the ignition plaque 35, and the like are set. In this example, the load L of the engine 10 is represented by the operation amount Accp of the accelerator pedal 82.

  This operation mode switching will be described more specifically. First, the operation region map shown in FIG. 2 is stored in the ROM 72 of the electric control device 70. This operation region map includes a low load side self-ignition operation method, a high load side (medium / high load side) self-ignition operation method, a spark ignition operation method, a load L of the engine 10 (operation amount Accp of the accelerator pedal 82), and a rotational speed NE. Defines the relationship. In the low load side self-ignition region R1 and the high load side autoignition region R2 shown in the operation region map, operation by the self-ignition operation method and operation by the spark ignition operation method are possible. The low load side self-ignition region R1 is a low load and low to medium rotation speed region in the entire operation region, and the high load side self ignition region R2 is higher than the low load side self ignition region R1. This is the area on the load side. The ranges of the low-load side self-ignition region R1 and the high-load side self-ignition region R2 are set in advance based on the fact that no large combustion noise or misfire occurs during operation. As will be described later, the timing for opening and closing the intake valve 32 and the exhaust valve 38 is different between the low load side autoignition region R1 and the high load side autoignition region R2.

  In the spark ignition region R3 in the operation region map, only the operation by the spark ignition operation method is possible. The spark ignition region R3 is a region obtained by excluding the self-ignition regions R1 and R2 from the entire operation region, and among the entire operation regions, “extremely low load or high load and a region from a low rotation speed to a medium rotation speed” and “A region of extremely low load to high load and high rotational speed”.

(Adjustment of ratio of residual gas amount and backflow gas amount)
One of the features of the engine 10 is that during the self-ignition operation, operation on the low load side (operation in the low load side self-ignition region R1) and operation on the high load side (operation in the high load side self-ignition region R2) The opening / closing timing of the intake valve 32 and the exhaust valve 38 is made different between the two. As a result, the ratio between the amount of residual gas and the amount of backflow gas in the combustion chamber 25 is adjusted. Here, the residual gas refers to burned gas remaining in the combustion chamber 25 at the timing when exhaust is completed in the exhaust stroke. The backflow gas refers to burnt gas that flows back from the exhaust port 37 into the combustion chamber 25 by opening the exhaust valve 38 during a predetermined period having a start timing in the intake stroke.

  FIG. 3 schematically shows a change in the lift amount VL according to the crank angle CA of the intake valve 32 and the exhaust valve 38 of each cylinder during the self-ignition operation. A curve C1 represents a change in the lift amount VL of the exhaust valve 38 that is opened and closed for the exhaust operation during the low load side self-ignition operation, and a curve C2 is for the exhaust operation during the high load side auto ignition operation. This represents a change in the lift amount VL of the exhaust valve 38 to be opened and closed. A curve C3 represents a change in the lift amount VL of the intake valve 32 that is opened and closed for the intake operation during the low load side self-ignition operation and the high load side self ignition operation. A curve C4 represents a change in the lift amount VL of the exhaust valve 38 that is opened and closed for intake of the backflow gas during the low load side self-ignition operation, and a curve C5 represents the backflow gas during the high load side autoignition operation. This represents a change in the lift amount VL of the exhaust valve 38 that is opened and closed for inhalation.

  As described above, one combustion cycle includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke in order. Each of these four strokes is a stroke every 180 ° as a crank angle, and is a stroke from TDC (top dead center) to BDC (bottom dead center) or from BDC to TDC as a piston position. Here, the operation of the intake valve 32 and the exhaust valve 38 and the like in one cylinder will be described, but the intake valve and the exhaust valve and the like operate similarly in other cylinders. The three cylinders of the engine 10 are referred to as a first cylinder, a second cylinder, and a third cylinder in order from the cylinder located at a position away from the side from which the output of the engine 10 is extracted. The combustion order in the engine 10 is first cylinder → third cylinder → second cylinder. The phase difference between two cylinders that continuously undergo combustion is all equal to 240 ° in crank angle. First, for the convenience of the low load side self-ignition operation, for the sake of convenience, the description starts from the expansion stroke and the exhaust stroke in the second half of the previous combustion cycle, and continues to the intake stroke and the compression stroke in the first half of the current combustion cycle.

  The expansion stroke is a stroke from the compression TDC to the expansion BDC as shown in FIG. In this expansion stroke, the gas mixture self-ignited in the combustion chamber 25 from the beginning burns and becomes burned gas, and the pressure of the gas generated during this combustion pushes down the piston 22. When the crank angle becomes a predetermined crank angle CAeo1 in the latter stage of the expansion stroke, the CPU 71 sends a drive signal to the drive circuit 33 to drive the exhaust valve electromagnetic drive mechanism 38a, thereby closing the exhaust valve 38 that has been closed. open. When the exhaust valve 38 is opened, the burned gas having a high temperature and high pressure is discharged from the combustion chamber 25 to the exhaust port 37. Blowdown occurs immediately after opening the exhaust valve 38. That is, the burnt gas is ejected at once to the exhaust system 50 through the exhaust port 37, and the exhaust pressure PE (pressure from the exhaust port 37 to the exhaust pipe 52) temporarily rises rapidly. By the time immediately after the timing CAeo1 when the exhaust valve 38 is opened, the work of burning and expanding the gas to push down the piston 22 is completed. That is, the expansion ratio is determined by this timing CAeo1.

  The exhaust stroke is a stroke from the expansion BDC to the exhaust TDC. In this exhaust stroke, burned gas has been discharged to the exhaust port 37 from the beginning. Then, when the crank angle becomes the predetermined crank angle CAec1 at the later stage of the exhaust stroke, the CPU 71 drives the exhaust valve electromagnetic drive mechanism 38a to close the opened exhaust valve 38. By closing the exhaust valve 38, the discharge of the burned gas in the combustion chamber 25 is completed. The opening period of the exhaust valve 38 in the exhaust stroke, that is, the period from the timing CAeo1 when the exhaust valve 38 is opened to the timing CAec1 when it is closed is referred to as a first exhaust valve opening period EX1. Next, when the crank angle reaches a predetermined crank angle CAio at the end of the exhaust stroke, the CPU 71 sends a drive signal to the drive circuit 33 to drive the intake valve electromagnetic drive mechanism 32a, thereby closing the intake valve 32 that has been closed. open. By opening the intake valve 32, air starts to be sucked from the intake port 32 into the combustion chamber 25.

  Here, a timing CAec1 at which the exhaust valve 38 is closed at the later stage of the exhaust stroke and a timing CAio at which the intake valve 32 is opened at the end of the exhaust stroke, a predetermined amount of residual gas is generated in the combustion chamber 25. It is adjusted in advance so that That is, a part of the burned gas generated in the previous expansion stroke remains as residual gas until the start timing CAio of the intake valve opening period IN without being discharged from the combustion chamber 25 in the subsequent exhaust stroke, This residual gas is used for the subsequent steps. The intake valve opening period IN is the opening period of the intake valve 32 in the intake stroke, in other words, the period from the timing CAio at which the intake valve 32 is opened to the predetermined timing CAic at which the intake valve 32 is closed. Then, by adjusting the end timing CAec1 of the first exhaust valve opening period EX1 and the start timing CAio of the intake valve opening period IN with respect to the exhaust TDC, that is, before and after the exhaust TDC, the first exhaust valve opening period EX1. It is possible to increase or decrease the amount of residual gas remaining in the combustion chamber 25 by adjusting the negative or positive overlap between the intake valve opening period IN and the intake valve opening period IN.

  The intake stroke is a stroke from the exhaust TDC to the intake BDC. From the beginning of the intake stroke, air has been sucked into the combustion chamber 25 from the intake port 31. Thereafter, when the crank angle reaches a predetermined crank angle CAd just before the middle of the intake stroke, the CPU 71 opens the direct injection valve 34 to inject fuel into the combustion chamber 25. A mixed gas is formed by the injected fuel and the air in the combustion chamber 25. Thereafter, when the crank angle reaches a predetermined crank angle CAeo2 in the middle of the intake stroke, the CPU 71 drives the exhaust valve electromagnetic drive mechanism 38a to reopen the closed exhaust valve 38. Due to the restart valve of the exhaust valve 38, the burned gas starts to be sucked into the combustion chamber 25 from the exhaust port 37 as a backflow gas. On the other hand, air continues to be sucked from the intake port 31 into the combustion chamber 25 during this time. The backflow gas, the air, and the mixed gas are mixed to become a substantially homogeneous gas. Next, when the crank angle becomes a predetermined crank angle CAec2 in the latter stage of the intake stroke, the CPU 71 closes the opened exhaust valve 38 in the same manner as described above. By closing the exhaust valve 38, the suction of the backflow gas into the combustion chamber 25 is completed. The opening period of the exhaust valve 38 in the intake stroke, that is, the period from the timing CAeo2 when the exhaust valve 38 is opened to CAec2 when it is closed is referred to as a second exhaust valve opening period EX2. By adjusting the second exhaust valve opening period EX2, it is possible to increase or decrease the amount of the backflow gas sucked into the combustion chamber 25.

  The compression stroke is a stroke from the intake BDC to the compression TDC. The piston 22 rises from the beginning of the compression stroke, and the mixed gas is compressed in the combustion chamber 25 along with this. When the crank angle becomes the crank angle CAic, the CPU 71 drives the intake valve electromagnetic drive mechanism 32a to close the opened intake valve 32. The inflow of air into the combustion chamber 25 continues for a short time after passing through the intake BDC due to the inertia of the air, but this inflow also ends when the intake valve 32 is closed. In this example, the second exhaust valve opening period EX2 is included as a part of the intake valve opening period IN. Thereafter, the mixed gas in the combustion chamber 25 is compressed to a high temperature and a high pressure through the latter half of the compression stroke. This mixed gas self-ignites immediately before the compression TDC and burns violently in the expansion stroke. Combustion due to the self-ignition of the mixed gas pushes down the piston 22 and generates power for the engine 10.

  Thus, the combustion cycle for one cycle is completed. As described above, from the latter stage of the expansion stroke, the combustion gas generated by this combustion starts to be discharged, and this combustion cycle is repeatedly executed.

  In contrast to the operation of the intake valve 32 and the exhaust valve 38 in the cylinder during the low load side self-ignition operation described above, the first operation as shown by the curves C1 and C2 in FIG. The end timing of the exhaust valve opening period EX1 (timing when the exhaust valve 38 is closed) CAec1 is retarded (delayed) than the end timing CAec1 during the low load side self-ignition operation. Due to the retardation of the end timing CAec1, the amount of residual gas in the combustion chamber 25 becomes smaller than that in the low load side self-ignition operation. In addition, during the high load side self-ignition operation, as shown by the curves C4 and C5 in FIG. 3, the end timing CAec2 of the second exhaust valve opening period EX2 is also retarded from the low load side self-ignition operation. . Due to the retardation of the end timing CAec2, the amount of the backflow gas sucked into the combustion chamber 25 becomes larger.

  That is, in the engine 10, during the low load side operation, the end timing CAec1 of the first exhaust valve opening period EX1 and the second exhaust valve are set such that the ratio of the residual gas amount to the backflow gas amount becomes the first predetermined value. The end timing CAec2 of the valve opening period EX2 is set in advance. During the high load side operation, the end timing CAec1 of the first exhaust valve opening period EX1 and the second exhaust valve are set so that the ratio of the residual gas amount becomes a second predetermined value smaller than the first predetermined value. The end timing CAec2 of the valve opening period EX2 is set in advance. Here, the values of the timings CAec1 and CAec2 during the low load side operation and during the high load side operation are determined by experiments or simulations. When the CPU 71 detects the shift from the low load side to the high load side, for example, by the operation amount Accp of the accelerator pedal 82, the low load is set so that the ratio of the residual gas amount is changed from the first predetermined value to the second predetermined value. The end timing CAec1 of the first exhaust valve opening period EX1 during the side operation and the end timing CAec2 of the second exhaust valve opening period EX2 are respectively set to the end timing of the first exhaust valve opening period EX1 during the high load side operation. The timing is delayed to CAec1 and the end timing CAec2 of the second exhaust valve opening period EX2.

  More specifically, the retardation of the end timing CAec2 of the second exhaust valve opening period EX2 during the high load side operation will be described with reference to FIG. FIG. 4 shows the change of the exhaust pressure PE according to the crank angle CA. Here, cylinder # 1, cylinder # 2 and cylinder # 3 represent the first cylinder, the second cylinder and the third cylinder, respectively. For example, before and after the start of the second exhaust valve opening period EX2 of the first cylinder, it overlaps immediately after the timing at which blowdown occurs by the third cylinder. Therefore, the exhaust pressure PE (pressure from the exhaust manifold 51 to the exhaust pipe 52) fluctuates rapidly and is not stable (see the solid line BD # 3 in FIG. 4). Even if an attempt is made to adjust the amount of backflow gas sucked into the combustion chamber at the timing before and after the blowdown, the amount of backflow gas may fluctuate greatly each time the exhaust valve 38 is opened. The amount of backflow gas greatly fluctuates with a slight change in the timing of opening 38. On the other hand, in the latter period of the second exhaust valve opening period EX2 of the first cylinder, the sudden fluctuation of the exhaust pressure PE due to the blowdown of the third cylinder is stopped, and the exhaust pressure PE is relatively stable. Therefore, it is possible to finely adjust the backflow gas amount in the second exhaust valve opening period EX2 by changing the end timing CAec2 of the second exhaust valve opening period EX2.

  In this example, the end timing CAec2 of the second exhaust valve opening period EX2 is retarded in order to increase the amount of backflow gas during high-load operation, so that the backflow gas amount is not increased due to blowdown of other cylinders. It is prevented from becoming stable. That is, for example, the backflow gas amount can be adjusted more precisely than changing the start timing CAeo2.

  As described above, according to the engine 10 according to the first embodiment of the present invention, the ratio of the residual gas amount to the backflow gas amount is adjusted according to the load L of the engine 10. Specifically, as shown in FIG. 5A, this adjustment is performed when the end timing CAec1 of the first exhaust valve opening period EX1 and the end timing CAec2 of the second exhaust valve opening period EX2 at the time of high load side operation. This is done by being delayed more than during low-load operation.

  In this way, the engine increases the compression end temperature by allowing the residual gas to remain in the combustion chamber 25. Therefore, in the low load side self-ignition operation, the combustion by self-ignition is further stabilized without causing misfire. be able to. Further, during the high load side self-ignition operation, the engine 10 is recirculated by a conventionally cooled recirculated gas (known external EGR system) to prevent abnormal combustion or combustion noise due to abnormal combustion. Gas) is used, and a backflow gas having a temperature slightly lower than the residual gas is used. Therefore, the temperature of the mixed gas can be adjusted more finely and with high accuracy. In addition, the residual gas amount and the mixed gas amount are appropriately adjusted according to whether the load L is on the low load side or the high load side, and the self-ignition timing is appropriately controlled regardless of the size of the load L. be able to. As a result, the high load limit can be expanded as compared with the conventional case. Further, these effects can be achieved by a simple structure such as an intake valve electromagnetic drive mechanism 32a, an exhaust valve electromagnetic drive mechanism 38a, a CPU 71, etc. for changing the opening / closing timing of the intake valve 32 and the exhaust valve 38. I don't need it. Therefore, the manufacturing cost of the engine can be kept low.

  Note that the engine 10 according to the embodiment described above is described as follows: “A combustion cycle including each operation of intake, compression, expansion, and exhaust is sequentially performed in a predetermined number of cylinders, and air and combustion are formed in combustion chambers formed in the respective cylinders. It is a “premixed compression self-ignition internal combustion engine” that self-ignites and burns by compressing a mixed gas containing fuel. The intake valve 32, the intake valve electromagnetic drive mechanism 32a, the exhaust valve 38, the exhaust valve electromagnetic drive mechanism 38a, the CPU 71, and the like indicate that “a part of the burned gas generated in the combustion chamber by the combustion of the mixed gas in the previous combustion cycle”. Corresponds to “residual gas generating means for causing a part of burned gas to remain in the combustion chamber” so as to be included in the mixed gas combusted in the present combustion cycle next to the previous time as residual gas. Further, the exhaust valve 38, the exhaust valve electromagnetic drive mechanism 38a, the CPU 71, and the like indicate that the burned gas that becomes part of the gas once exhausted from the combustion chamber to the exhaust port by the exhaust operation after being generated in the previous combustion cycle. It corresponds to “backflow gas generating means for backflowing the other part of the burned gas into the combustion chamber so that the other part of the burned gas is included in the mixed gas combusted in the current combustion cycle as the backflow gas.

  The accelerator opening sensor 63 corresponds to “output state detecting means for detecting an output state value that changes according to the output of the engine”, and the CPU 71 or the like “reversely flows as the engine output corresponding to the detected output state value increases. It corresponds to a “ratio control means for controlling at least one of the residual gas generation means and the backflow gas generation means” so that the ratio of the amount of residual gas remaining to the amount of backflow gas to be reduced becomes smaller.

b. Second Embodiment Next, an internal combustion engine according to a second embodiment of the present invention will be described. This engine is also a four-stroke in-line three-cylinder internal combustion engine as in the first embodiment, and is based on the same operation region map as in FIG. 2, the low load side self-ignition operation method, the high load side self-ignition operation method, and the spark ignition operation method. It is possible to drive by switching between In the engine of the second embodiment, the operation of the intake valve 32 and the exhaust valve 38 in each cylinder during the low load side self-ignition operation is the same as that of the engine of the first embodiment. As shown in FIG. 5B, the engine of the second embodiment reduces the first exhaust valve opening period EX1 (both its start timing CAeo1 and end timing CAec1) during the high load side self-ignition operation. The second embodiment is different from the first embodiment shown in FIG. 5A in that the second exhaust valve opening period EX2 is retarded by delaying from the load-side self-ignition operation. Hereinafter, this difference will be mainly described.

  FIG. 6 schematically shows a change in the lift amount VL according to the crank angle CA of the intake valve 32 and the exhaust valve 38 of each cylinder during the self-ignition operation. In FIG. 6, as in FIG. 3, curves C1, C3, and C4 represent changes in the lift amount VL of the exhaust valve 38 and the intake valve 32 during the low load side self-ignition operation, and the curve C2 A curve C5 represents a change in the lift amount VL of the exhaust valve 38 during the high load side self-ignition operation.

  The CPU 71 retards the first exhaust valve opening period EX1 during the high load side operation as shown by the curves C1 and C2 in FIG. Thereby, the residual gas amount becomes smaller than that during low-load operation, and the ratio of the residual gas amount to the backflow gas amount becomes smaller. That is, the start timing CAeo1 and end timing CAec1 of the first exhaust valve opening period EX1 during the low load side operation so that the ratio of the residual gas amount to the backflow gas amount becomes the first predetermined value during the low load side operation. Is preset. On the other hand, at the time of high load side operation, the start timing CAeo1 and the end timing CAec1 of the first exhaust valve opening period EX1 so that the ratio of the residual gas amount becomes a second predetermined value smaller than the first predetermined value. Is preset. When the CPU 71 detects the shift from the low load side to the high load side, for example, by the operation amount Accp of the accelerator pedal 82, the low load is set so that the ratio of the residual gas amount is changed from the first predetermined value to the second predetermined value. The start timing CAeo1 and end timing CAec1 during the side operation are retarded.

  Then, during the high load side operation, the CPU 71 adjusts to the retardation of the first exhaust valve opening period EX1 described above, as shown by the curves C4 and C5 in FIG. (Both the start timing CAeo2 and the end timing CAec2) are retarded than during low-load operation. As a result, as will be described in detail later, the backflow gas amount in the second exhaust valve opening period EX2 can be maintained substantially constant during the low load side operation and during the high load side operation. Here, it is assumed that the first exhaust valve opening period EX1 and the second exhaust valve opening period EX2 are similarly retarded in each of the first cylinder, the second cylinder, and the third cylinder.

  Specifically, how the backflow gas amount is maintained substantially constant by the retardation of the second exhaust valve opening period EX2 will be described with reference to FIG. When the start timing CAeo1 of the first exhaust valve opening period EX1 is set to 45 ° before expansion BDC, the exhaust pressure PE changes as shown by the solid line in FIG. In this case, for example, the timing at which the blowdown of the third cylinder occurs immediately before the exhaust valve 38 of the first cylinder is opened in the second exhaust valve opening period EX2, and during the second exhaust valve opening period EX2, the exhaust pressure PE Does not change so rapidly and is almost stable. On the other hand, when the start timing CAeo1 of the first exhaust valve opening period EX1 is retarded by 15 ° before the expansion BDC, the exhaust pressure PE changes as indicated by the dotted line in FIG. In this case, the timing of blowdown by the third cylinder is immediately after the exhaust valve 38 of the first cylinder is opened in the second exhaust valve opening period EX2, and during the second exhaust valve opening period EX2, the exhaust pressure PE is It goes up and down suddenly and is not stable. According to this, when the start timing CAeo1 of the first exhaust valve opening period EX1 is 45 ° before expansion BDC during high load side operation, the amount of the backflow gas sucked into the combustion chamber 25 is low load side. During operation, the start timing CAeo1 of the first exhaust valve opening period EX1 is significantly greater than when it is set to 15 ° before expansion BDC.

  Therefore, during the high load side operation, this engine is operated according to the transition of the exhaust pressure PE due to the blowdown that is delayed according to the delay of the start timing CAeo1 of the first exhaust valve opening period EX1. 2 The second exhaust valve opening period EX2 is retarded from the time of low load side operation so as not to overlap the exhaust valve opening period EX2. Due to the delay of the second exhaust valve opening period EX2, the backflow gas amount is maintained substantially constant during both the high load side operation and the low load side operation, while the delay of the first exhaust valve opening period EX1 described above. The ratio of the residual gas amount and the backflow gas amount can be accurately adjusted by the angle.

c. Third Embodiment Subsequently, an internal combustion engine according to a third embodiment of the present invention will be described. Unlike the first and second embodiments, this engine is a four-stroke in-line four-cylinder internal combustion engine. Further, similarly to the first embodiment and the second embodiment, the engine can be operated by switching the low load side self-ignition operation method, the high load side self ignition operation method, and the spark ignition operation method based on the operation region map. Is possible. Further, in the engine of the third embodiment, the operation of the intake valve 32, the exhaust valve 38, etc. in each cylinder during the low load side self-ignition operation is the same as that of the first embodiment. As shown in FIG. 5C, the engine of the third embodiment, which is an in-line four-cylinder engine, with respect to the retardation of the end timing CAec1 of the first exhaust valve opening period EX1 during the high load side operation, The second exhaust valve opening period EX2 is different from the first embodiment shown in FIG. 5A in that the start timing CAeo2 is advanced (advanced) from the low load side operation. This difference will be mainly described.

  FIG. 7 schematically shows the change in the lift amount VL according to the crank angle CA of the intake valve 32 and the exhaust valve 38 of each cylinder during the self-ignition operation, as in FIGS. 3 and 6. Similar to FIGS. 3 and 6, curves C1, C3, and C4 represent changes in the lift amount VL of the exhaust valve 38 and the intake valve 32 during the low load side self-ignition operation, and the curves C2 and C5 Represents a change in the lift amount VL of the exhaust valve 38 during the high load side self-ignition operation.

  The CPU 71 delays the end timing CAec1 of the first exhaust valve opening period EX1 during the high load side operation as shown by the curves C1 and C2 in FIG. 7, thereby reducing the residual gas amount during the low load side operation. Less. In addition, the CPU 71 advances the start timing CAeo2 of the second exhaust valve opening period EX2 as shown by the curves C4 and C5 in FIG. Make more. That is, in this engine, during the low load side operation, the end timing CAec1 of the first exhaust valve opening period EX1 and the opening of the second exhaust valve so that the ratio of the residual gas amount to the backflow gas amount becomes the first predetermined value. The start timing CAeo2 of the valve period EX2 is set in advance. Then, during the high load side operation, the end timing of the first exhaust valve opening period EX1 during the high load side operation so that the ratio of the residual gas amount becomes a second predetermined value smaller than the first predetermined value. The start timing CAeo2 of CAec1 and the second exhaust valve opening period EX2 is set in advance. When the CPU 71 detects the shift from the low load side to the high load side, for example, by the operation amount Accp of the accelerator pedal 82, the low load is set so that the ratio of the residual gas amount is changed from the first predetermined value to the second predetermined value. The end timing CAec1 of the first exhaust valve opening period EX1 during the side operation is retarded and the start timing CAeo2 of the second exhaust valve opening period EX2 is advanced.

  Specifically, the advance angle of the start timing CAeo2 of the second exhaust valve opening period EX2 during the high load side operation will be described with reference to FIG. For example, before and after the end of the second exhaust valve opening period EX2 of the first cylinder, it overlaps before and after the timing at which blowdown occurs by the fourth cylinder, and the exhaust pressure PE fluctuates rapidly and is not stable (FIG. 8). (See BD # 4.) Therefore, even if an attempt is made to adjust the amount of backflow gas sucked into the combustion chamber at the timing before and after the blowdown, the amount of backflow gas may fluctuate greatly each time the exhaust valve 38 is opened. The backflow gas amount greatly fluctuates with a slight change in the timing of opening the exhaust valve 38. That is, it is difficult to finely adjust the backflow gas amount at the timing before and after the blowdown. On the other hand, the exhaust pressure PE is relatively stable at the initial stage of the second exhaust valve opening period EX2 of the first cylinder. Therefore, in this example, during the high load side operation, the start timing CAeo2 of the second exhaust valve opening period EX2 is adjusted so as to advance more than the low load side operation so that the backflow gas amount is increased. This prevents the amount of backflow gas from becoming unstable due to the blowdown of other cylinders.

d. Fourth Embodiment An internal combustion engine according to a fourth embodiment of the present invention will be described. This engine is also a four-stroke in-line four-cylinder internal combustion engine as in the third embodiment. Similarly, based on the operation region map, the low-load side self-ignition operation method, the high-load side self-ignition operation method, and the spark ignition operation method are used. It is possible to switch and drive. Further, in the engine of the fourth embodiment, the operation of the intake valve 32, the exhaust valve 38, etc. in each cylinder during the low load side self-ignition operation is the same as that of the third embodiment. As shown in FIG. 5 (D), the engine of the fourth embodiment retards the first exhaust valve opening period EX1 during the high load side self-ignition operation, and interlocks with this. This is different from the third embodiment shown in FIG. 5C in that the end timing CAec2 of the second exhaust valve opening period EX2 is retarded.

  FIG. 9 schematically shows the change in the lift amount VL according to the crank angle CA of the intake valve 32 and the exhaust valve 38 of each cylinder during the self-ignition operation, as in FIG. Similar to FIG. 3 and the like, the curves C1, C3, and C4 represent changes in the lift amount VL of the exhaust valve 38 and the intake valve 32 during the low load side self-ignition operation, and the curves C2 and C5 are The change in the lift amount VL of the exhaust valve 38 during the high load side self-ignition operation is shown.

  The CPU 71 retards the first exhaust valve opening period EX1 during the high load side operation as shown by the curves C1 and C2 in FIG. Thereby, the residual gas amount becomes smaller than that during low-load operation, and the ratio of the residual gas amount to the backflow gas amount becomes smaller. Further, the CPU 71 sets the end timing CAec2 of the second exhaust valve opening period EX2 to a low load as shown by the curves C4 and C5 in FIG. 9 in accordance with the retardation of the first exhaust valve opening period EX1. The angle is retarded compared to the side driving. Thereby, as described below, the backflow gas amount in the second exhaust valve opening period EX2 can be stably flowed into the combustion chamber 25 during the low load side operation and during the high load side operation.

  Specifically, how the backflow gas amount is stabilized by the delay of the end timing CAec2 of the second exhaust valve opening period EX2 will be described with reference to FIG. For example, when the start timing CAeo1 of the first exhaust valve opening period EX1 during low load side operation is set to 30 ° before the expansion BDC, the exhaust pressure PE changes as shown in FIG. In this case, for example, the timing at which blowdown of the fourth cylinder occurs is immediately before the exhaust valve 38 of the first cylinder is closed in the second exhaust valve opening period EX2, and part of the period during which blowdown occurs is the second. It overlaps part of the exhaust valve opening period EX2. On the other hand, when the first exhaust valve opening period EX1 is retarded from 30 ° before the expansion BDC during the high load side operation, the blowdown period of the fourth cylinder is also retarded and the second cylinder 2 It will not overlap with the exhaust valve opening period EX2. Therefore, the second exhaust valve opening period is set so that a part of this blow-down period is included in the second exhaust valve opening period EX2 during the high load side operation as well as during the low load side operation. Delay the EX2 end timing CAec2. This makes it possible to prevent the backflow gas amount from changing suddenly between the high load side operation and the low load side operation.

  As described above, the engine of each embodiment can finely adjust the temperature of the mixed gas using the backflow gas while performing stable self-ignition combustion using the residual gas without causing misfire or the like. . That is, in the engine of each embodiment, abnormal combustion of the residual gas during high load operation is prevented by using the backflow gas having a temperature slightly lower than that of the residual gas without using the cooled recirculated gas as in the prior art. Therefore, it is possible to adjust the temperature of the mixed gas more finely and accurately.

  In addition, this invention is not limited to the said embodiment (1st-4th embodiment), A various modification is employable within the range of the invention. For example, in the above embodiment, the electric control device 70 adjusts the residual gas amount or the backflow gas amount by changing the opening / closing timing of the exhaust valve 38. In addition to these opening / closing timings, the lift amount VL of the exhaust valve may be changed as appropriate. Naturally, the exhaust pressure PE is taken into consideration when changing the lift amount VL of the exhaust valve in the second exhaust valve opening period EX2.

  In the above embodiment, the start timing CAio of the intake valve opening period IN is fixedly set within the exhaust stroke. The start timing CAio may be set within the intake stroke. Further, the start timing CAio may be variably set for the purpose of adjusting the residual gas amount.

  In the embodiment described above, the electric control device 70 sets the start timing and end timing of the first exhaust valve opening period EX1 and the second exhaust valve opening period EX2 according to the load L of the engine 10 at the low load side self-ignition operation. The angle is advanced or retarded in two stages, that is, during the high load side self-ignition operation. The number of stages of the engine load L may be set to three or more stages, and the start timing or end timing of the exhaust valve opening periods EX1 and EX2 may be adjusted according to the set stage. The threshold for the engine load L may be changed according to the engine speed NE.

  Also, unlike the adjustment of the start timing and end timing of the exhaust valve opening periods EX1, EX2 according to the load L, in addition to this, the start timing and end timing of these exhaust valve opening periods EX1, EX2 are The angle may be advanced or retarded according to the rotational speed NE of 10. In this case, it is preferable that the intake air amount into the combustion chamber is increased as the rotational speed NE increases. Specifically, the intake air amount can be increased by the electric control device correcting the throttle valve opening or the supercharging pressure to a value larger than usual. According to this, air at a lower temperature than the residual gas or the backflow gas is sucked in a large amount into the combustion chamber during high-speed operation, so that the compression end temperature of the mixed gas can be more effectively lowered to prevent abnormal combustion. .

  Furthermore, unlike the adjustment of the start timing and end timing of the exhaust valve opening periods EX1 and EX2 according to the rotational speed NE, for example, the temperature of the exhaust gas is detected by a temperature sensor (output state detection means), and the detected temperature is Further, the advance or retard of the start timing or end timing of the exhaust valve opening periods EX1 and EX2 may be performed. In this case, if the detected temperature is lower than the preset target temperature, the start timing or end timing of the exhaust valve opening periods EX1, EX2 is set so that the ratio of the residual gas amount to the backflow gas amount becomes larger than the current value. adjust. On the other hand, if the detected temperature is higher than the target temperature, the start timing or end timing of the exhaust valve opening periods EX1 and EX2 is adjusted so that the ratio of the residual gas amount becomes smaller than the current value. Instead of the temperature of the exhaust gas, the temperature of the gas in the combustion chamber, the torque of the engine, the pressure of the gas in the combustion chamber before and after combustion (compression BDC), and the like may be used.

  In the above embodiment, the intake valve electromagnetic drive mechanism 32a and the exhaust valve electromagnetic drive mechanism 38a electromagnetically open and close the intake valve 32 and the exhaust valve 38. Instead, a known variable valve timing lift mechanism can be used. For example, the intake valve and the exhaust valve may be opened and closed by mechanical control or by control using hydraulic pressure. In the case of mechanical control, the intake valve drive mechanism includes a cam and a cam shaft, and opens and closes the intake valve at a predetermined timing and by a predetermined lift amount VL. Furthermore, in the case of control using hydraulic pressure, the intake valve drive mechanism includes a mechanism that rotates the camshaft in the advance angle or retard angle direction using hydraulic pressure according to the operating state of the engine. The same applies to the exhaust valve drive mechanism. In order to variably set the opening / closing timing or the lift amount VL, the position of the fulcrum of the rocker arm may be changed. In addition, for example, a cam having a cam profile used when the engine is at a low rotation speed and a cam having a cam profile used when the engine is at a high rotation speed may be switched. Further, the shape of the intake valve and the exhaust valve may be a rotary type or the like instead of a poppet shape.

  In the above embodiment, the electric control device 70 controls the igniter 36 so as to stop the spark ignition during the self-ignition operation. Unlike this, spark ignition may be performed at a predetermined timing so as to assist the self-ignition of the mixed gas.

  In the above embodiment, the fuel injection by the direct injection valve 34 is performed only once during the intake stroke. The fuel injection may be performed once during the compression stroke, or may be performed a plurality of times during the intake stroke and during the compression stroke. It is also possible to switch such that the injection is performed during the intake stroke during high load operation, and the injection is performed during the compression stroke during low load operation. Further, a port injection valve may be used instead of the direct injection valve, and both the direct injection valve and the port injection valve may be used.

  In the present invention, the start timing of the second exhaust valve opening period EX2 only needs to be within the intake stroke, and the end timing may be, for example, late in the intake stroke or early in the compression stroke.

  The first embodiment and the second embodiment are in-line three-cylinder engines. The engine of these embodiments may be a V-type 6-cylinder engine or the like in which the opening / closing timing of the intake valve and the exhaust valve is the same. The third embodiment and the fourth embodiment are in-line four-cylinder engines. The engine of these embodiments may be a V-type 8-cylinder engine having the same opening / closing timing of the intake valve and the exhaust valve.

  In the second and fourth embodiments, the electric control device 70 operates the operating angle (working angle) of the exhaust valve 38 during the first exhaust valve opening period EX1 between the low load side operation and the high load side operation. ) Is not changed. Unlike this, the magnitude of the operating angle may be variably adjusted, and the end timing CAec1 may be kept constant without being changed. Similarly, in the second embodiment, the operating angle of the exhaust valve 38 related to the second exhaust valve opening period EX2 may be changed.

  In the second embodiment, in order to reduce the ratio of the residual gas amount to the backflow gas amount in the high load side self-ignition operation, the first exhaust valve opening period EX1 is set to be longer than that in the low load side self ignition operation. It is retarded. On the other hand, for the purpose of increasing the expansion ratio, the first exhaust valve opening period EX1 may be retarded. That is, this engine retards the first exhaust valve opening period EX1 during the high load side self-ignition operation compared to during the low load side self ignition operation, thereby increasing the expansion ratio. The thermal efficiency is increased by increasing the expansion ratio in this way. On the other hand, at the time of low load side self-ignition operation, this engine advances the first exhaust valve opening period EX1 more, thereby reducing the expansion ratio. If the burned gas is sufficiently adiabatically expanded, the temperature is lowered, but this temperature drop is suppressed by the advance angle of the first exhaust valve opening period EX1.

1 is a schematic configuration diagram of an internal combustion engine according to a first embodiment of the present invention. It is the driving | operation area | region map which CPU of an electric control apparatus refers. It is explanatory drawing which showed typically the opening / closing timing of the intake valve and exhaust valve in each cylinder at the time of self-ignition operation. It is the graph which showed the change of the exhaust pressure according to the crank angle in an inline 3 cylinder engine. It is the figure which showed the difference in the 1st and 2nd exhaust valve opening period in each engine of 1st-4th embodiment. It is explanatory drawing which showed typically the opening / closing timing of the intake valve and exhaust valve of each cylinder at the time of the self-ignition operation of the engine which concerns on 2nd Embodiment. It is explanatory drawing which showed typically the opening / closing timing of the intake valve and exhaust valve of each cylinder at the time of the self ignition operation of the engine which concerns on 3rd Embodiment. It is the graph which showed the change of the exhaust pressure according to the crank angle in an inline 4 cylinder engine. It is explanatory drawing which showed typically the opening / closing timing of the intake valve and exhaust valve of each cylinder at the time of the self ignition operation of the engine which concerns on 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 32a ... Intake valve electromagnetic drive mechanism, 34 ... Direct injection valve, 37 ... Exhaust port, 38 ... Exhaust valve, 38a ... Exhaust valve electromagnetic drive Mechanism, 70 ... electric control device, 71 ... CPU.

Claims (9)

A combustion cycle including intake, compression, expansion, and exhaust operations is sequentially executed by a predetermined number of cylinders, and the mixture gas containing air and fuel is compressed by a combustion chamber formed in each cylinder. A premixed compression self-ignition internal combustion engine that ignites and burns,
A part of the burned gas generated in the combustion chamber due to the combustion of the mixed gas in the previous combustion cycle is included as a residual gas in the mixed gas burned in the current combustion cycle next to the previous one. A residual gas generating means for leaving a part of the burned gas in the combustion chamber;
Another part of the burned gas that becomes a part of the gas once exhausted from the combustion chamber to the exhaust port by the exhaust operation after being generated in the previous combustion cycle is used as the backflow gas, and the current combustion cycle. Backflow gas generating means for backflowing another part of the burnt gas into the combustion chamber so as to be included in the mixed gas burned in
Output state detecting means for detecting an output state value that changes in accordance with the output of the engine;
The residual gas generating means and the back flow are set such that the ratio of the amount of the residual gas to be left to the amount of the back flow gas to be back flowed becomes smaller as the engine output corresponding to the detected output state value increases. A ratio control means for controlling at least one of the gas generation means;
A premixed compression self-ignition internal combustion engine. The premixed compression self-ignition internal combustion engine according to claim 1,
The output state detection means includes
The engine load is detected as the output state value,
The ratio control means includes
The premixed compression self-control is performed so that at least one of the residual gas generation means and the backflow gas generation means is controlled such that the ratio of the residual gas amount to the backflow gas amount decreases as the detected engine load increases. Ignition internal combustion engine. The premixed compression self-ignition internal combustion engine according to claim 1,
The output state detection means includes
The engine speed is detected as the output state value,
The ratio control means includes
Premix compression in which control of at least one of the residual gas generation means and the backflow gas generation means is performed such that the ratio of the residual gas amount to the backflow gas amount becomes smaller as the detected rotational speed of the engine increases. Self-igniting internal combustion engine. A premixed compression self-ignition internal combustion engine according to claim 3,
A premixed compression self-ignition internal combustion engine further comprising gas amount adjusting means for increasing the amount of air taken into the combustion chamber as the detected rotational speed of the engine increases. The premixed compression self-ignition internal combustion engine according to any one of claims 2 to 4,
The residual gas generating means includes
The exhaust valve is opened during the first exhaust valve opening period during which the exhaust operation is performed during the previous combustion cycle and the intake valve is opened during the intake valve opening period during which the intake operation is performed during the current combustion cycle. By opening the valve, a part of the burned gas generated in the combustion chamber by the combustion of the mixed gas is left in the combustion chamber as the residual gas,
The backflow gas generating means includes
The exhaust valve is opened during a second exhaust valve opening period having a start timing within the intake valve opening period during the current combustion cycle, thereby becoming a part of the gas once exhausted from the combustion chamber. A premixed compression self-ignition internal combustion engine configured to cause another part of burned gas to flow back into the combustion chamber as the backflow gas. In the premixed compression self-ignition internal combustion engine according to claim 5,
The cylinder is
In the engine, 3 cylinders are arranged in series or 6 cylinders are arranged in each row and 3 cylinders in V type,
The ratio control means includes
A premixed compression self-ignition internal combustion engine configured to delay the end timing of the second exhaust valve opening period as the detected output state value increases by controlling the backflow gas generating means. A premixed compression self-ignition internal combustion engine according to claim 5,
The control apparatus further includes a start timing control means for adjusting the start timing so as to delay the start timing of the first exhaust valve opening period as the detected output state value increases by controlling the residual gas generation means. ,
The cylinder is
In the engine, 3 cylinders are arranged in series or 6 cylinders are arranged in each row and 3 cylinders in V type,
The ratio control means includes
By controlling the backflow gas generating means, the start timing of the second exhaust valve opening period is delayed to a timing that is adjusted in advance with respect to the adjusted start timing of the first exhaust valve opening period. A premixed compression self-ignition internal combustion engine configured. In the premixed compression self-ignition internal combustion engine according to claim 5,
The cylinder is
In the engine, 4 cylinders are arranged in series, or 8 cylinders are arranged in each row, 4 cylinders in V type,
The ratio control means includes
A premixed compression self-ignition internal combustion engine configured to advance the start timing of the second exhaust valve opening period as the detected output state value increases by controlling the backflow gas generating means. A premixed compression self-ignition internal combustion engine according to claim 5,
The control apparatus further includes a start timing control means for adjusting the start timing so as to delay the start timing of the first exhaust valve opening period as the detected output state value increases by controlling the residual gas generation means. ,
The cylinder is
In the engine, four cylinders are arranged in series or eight cylinders are arranged in each row and four cylinders in V type,
The ratio control means includes
By controlling the backflow gas generating means, the end timing of the second exhaust valve opening period is delayed to a timing that is adjusted in advance with respect to the adjusted start timing of the first exhaust valve opening period. A premixed compression self-ignition internal combustion engine configured.

Images