JP5029503B2 - In-cylinder / port injection internal combustion engine - Google Patents

Description

  The present invention relates to an in-cylinder / port-injection internal combustion engine provided with an in-cylinder injector and an intake manifold injector.

  In an internal combustion engine having an in-cylinder injector for injecting fuel into an engine combustion chamber and an in-cylinder injector for injecting fuel into an engine intake passage, for port injection to perform homogeneous combustion during engine high-load operation It is known that fuel injection is performed from an injector, and fuel injection is performed from an in-cylinder injector to perform stratified combustion during engine low load operation (for example, Patent Documents 1 and 2).

  In particular, in the injection control device described in Patent Document 1, in the case of performing homogeneous combustion, fuel injection is performed from only the in-cylinder injector or from both the in-cylinder injector and the port injector, and stratified combustion is performed. In this case, fuel injection is performed only from the in-cylinder injector. In any case, in an internal combustion engine having two injectors, an in-cylinder injector and an intake manifold injector, when performing stratified combustion, fuel injection is performed only from the in-cylinder injector.

JP 2007-32355 A JP 2002-364409 A Japanese Utility Model Publication No. 3-129726 JP 2005-90258 A JP 2004-353464 A

  By the way, Patent Document 3 discloses an internal combustion engine in which stratified combustion is performed by performing combustion injection from an injector for injection in an intake passage. This internal combustion engine has three intake ports, three intake valves corresponding to the respective intake ports, and an injector that injects fuel into a central one of the three intake ports. In this internal combustion engine, fuel is injected into the air flowing from the injector through the central intake port to generate a relatively rich air-fuel mixture, and this air-fuel mixture flows into the central portion of the combustion chamber, and then the ignition plug. Ignition is performed. Thereby, in the internal combustion engine described in Patent Document 3, so-called stratified combustion is realized.

  However, when stratified combustion is to be performed by injecting fuel injection from the intake manifold injector as in the internal combustion engine described in Patent Document 3, in order to perform combustion in the combustion chamber more efficiently, It is necessary to promote flame propagation in

  Accordingly, an object of the present invention is to provide an in-cylinder / port-injection internal combustion engine that promotes flame propagation in a combustion chamber in order to perform stratified combustion efficiently.

In order to solve the above problems, in a first aspect of the present invention, an in-cylinder includes an in-cylinder injector that injects fuel into an engine combustion chamber, and an in-cylinder injector that injects fuel into an engine intake passage. In a port-injection internal combustion engine, during stratified combustion operation, fuel is injected from the in-cylinder injector during the intake stroke, and after the start of fuel injection from the in-cylinder injector and before the intake valve is closed There line fuel injection from the intake manifold injector, the combustion chamber of each cylinder in fluid three intake ports communicating, the port injector is the intake port of the central of these three intake ports Injecting fuel into the passing air, and during stratified combustion operation, the flow rate of air passing through the central intake port passes through each intake port on both sides of the central intake port. The fuel injection from the port injection injector is performed when the flow rate of the excess air is higher, and during stratified combustion operation, the closing timing of the intake valve corresponding to the central intake port corresponds to the intake ports on both sides It is made later than the closing timing of the intake valve .
According to the first aspect of the present invention, by first performing fuel injection from the in-cylinder injector, the tumble flow can be strengthened and fuel can be supplied to the entire air in the combustion chamber. Can promote the propagation of flame. In addition, by performing fuel injection from the intake manifold injector immediately before closing the intake valve, the fuel injected from the intake manifold injector can be more reliably distributed near the spark plug.

In order to solve the above problems, in a second aspect of the invention, an in-cylinder includes an in-cylinder injector that injects fuel into the engine combustion chamber, and an in-cylinder injector that injects fuel into the engine intake passage. In a port-injection internal combustion engine, during stratified combustion operation, fuel is injected from the in-cylinder injector during the intake stroke, and after the start of fuel injection from the in-cylinder injector and before the intake valve is closed Fuel is injected from the injector for injection in the intake passage, and three intake ports communicate with the combustion chamber of each cylinder. The port injection injector passes through the central intake port among these three intake ports. In the stratified charge combustion operation, the flow rate of air passing through the central intake port passes through the intake ports on both sides of the central intake port. Injecting fuel from the port injector when the flow rate of excess air exceeds the intake air flow rate, and during stratified combustion operation, the intake valve lift amount corresponding to the central intake port corresponds to the intake ports corresponding to the intake ports on both sides. It is made larger than the lift amount of the valve.

In order to solve the above-described problem, in a third aspect of the invention, an in-cylinder includes an in-cylinder injector that injects fuel into the engine combustion chamber and an in-cylinder injector that injects fuel into the engine intake passage. In a port-injection internal combustion engine, during stratified combustion operation, fuel is injected from the in-cylinder injector during the intake stroke, and after the start of fuel injection from the in-cylinder injector and before the intake valve is closed Fuel is injected from the injector for injection in the intake passage, and three intake ports communicate with the combustion chamber of each cylinder. The port injection injector passes through the central intake port among these three intake ports. In the stratified charge combustion operation, the flow rate of air passing through the central intake port passes through the intake ports on both sides of the central intake port. The fuel injection from the port injector is performed when the flow rate of the excess air is larger, and during stratified combustion operation, the valve opening period of the intake valve corresponding to the central intake port corresponds to the intake ports on both sides The intake valve is made longer than the valve opening period.

In the fourth invention, in any one of the first to third inventions, in the stratified combustion operation, the fuel from the in-cylinder injector and the port injector after the time when the lift amount of the intake valve becomes maximum is reached. Perform the injection.

In the fifth invention, in any one of the first to fourth inventions, the stratified charge combustion operation and the homogeneous combustion operation can be switched. During the homogeneous combustion operation, after the fuel injection from the port injector starts, Fuel is injected from the injector for injection.

In a sixth invention, in any one of the first to fifth inventions, the valve diameter of the intake valve corresponding to the central intake port is greater than the valve diameter of the intake valve corresponding to the intake ports on both sides. Increased.

  According to the present invention, flame propagation after ignition can be promoted, and fuel injected from the injector for injection in the intake passage can be more unevenly distributed in the vicinity of the spark plug, so that stratified combustion is efficiently performed. be able to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are assigned to similar components.

  FIG. 1 is a schematic view showing the entire in-cylinder / port injection internal combustion engine of the present invention. Referring to FIG. 1, 1 is an engine body, 2 is a combustion chamber of each cylinder, 3a is an in-cylinder injector (in-cylinder injection fuel injection valve) for injecting fuel into each combustion chamber 2, and 3b. Indicates a port injection injector (port injection fuel injection valve) for injecting fuel into the intake port (intake passage), 4 indicates an ignition plug, 5 indicates an intake manifold, and 6 indicates an exhaust manifold. The intake manifold 4 is connected to an air cleaner 8 via an intake pipe 7. A throttle valve 9 driven by a step motor is disposed in the intake pipe 7. On the other hand, the exhaust manifold 6 is connected to a casing 12 containing an exhaust purification catalyst (for example, a three-way catalyst) 11 through an exhaust pipe 10.

  Referring to FIG. 2 showing details of each cylinder, 15 is a cylinder block, 16 is a cylinder head fixed on the cylinder block 15, 17 is a piston reciprocating in the cylinder block 15, 2 is a piston 17 and cylinder head 16, , 18 is a set of intake ports, 19 is a set of intake valves, 20 is a set of exhaust ports, and 21 is a set of exhaust valves. An in-cylinder injector 3 a is disposed at the center of the inner wall surface of the cylinder head 16, and a port injector 3 b is disposed in the intake branch pipe 5 a of the intake manifold 5. The intake valve 19 and the exhaust valve 21 of each cylinder are opened and closed by an intake valve drive device 22 and an exhaust valve drive device 23, respectively. The intake valve drive device 22 and the exhaust valve drive device 23 are respectively driven by the intake valve 19 and the exhaust valve 21. The intake valve 19 and the exhaust valve 21 can be opened and closed while changing the phase angle and the operating angle.

  Referring again to FIG. 1, each in-cylinder injector 3 a is connected to the fuel reservoir 25. The fuel reservoir 25 is connected to a fuel tank 27 via a fuel supply pipe 26. An electronically controlled variable discharge amount fuel pump 28 is disposed in the fuel supply pipe 26, and the fuel in the fuel tank 27 is supplied to the fuel reservoir 25 by the fuel pump 28. On the other hand, each port injector 3 b is connected to a fuel reservoir 29. The fuel reservoir 29 is connected to the fuel tank 27 via the fuel supply pipe 30. An electronically controlled variable discharge amount fuel pump 31 is disposed in the fuel supply pipe 30, and the fuel in the fuel tank 27 is supplied to the fuel reservoir 29 by the fuel pump 31.

  In the present embodiment, an electronic control unit (ECU) 40 is used as an injection control device that controls the fuel injected from both injectors 3. The ECU 40 is a digital computer, and includes a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, a CPU (Microprocessor) 44, an input port 45, and an output port 46 connected to each other by a bidirectional bus 41. . An air flow meter 49 for detecting the flow rate of air passing through the intake pipe 7 is attached to the intake pipe 7, and an air-fuel ratio sensor 50 for detecting the air-fuel ratio of the exhaust gas is attached to the exhaust pipe 10. Output signals from the air flow meter 49 and the air-fuel ratio sensor 50 are input to the input port 45 via the corresponding AD converter 47.

  A load sensor 52 that generates an output voltage proportional to the amount of depression of the accelerator pedal 51 is connected to the accelerator pedal 51, and the output voltage of the load sensor 52 is input to the input port 45 via the corresponding AD converter 47. The Further, a crank angle sensor 53 that generates an output pulse every time the crankshaft rotates, for example, 30 ° is connected to the input port 45, and the engine speed is detected by the crank angle sensor 53. On the other hand, the output port 46 is connected to the injector 3, the step motor for driving the throttle valve 9, and the fuel pumps 28 and 31 through corresponding drive circuits 48.

  FIG. 3 is a diagram schematically showing the upper surface in each cylinder. As can be seen from FIG. 3, each cylinder is provided with three intake openings 34a, 34b, 34c and two exhaust openings 35a, 35b. Each intake opening 34a, 34b, 34c communicates with the corresponding intake port 18a, 18b, 18c, and each exhaust opening 35a, 35b communicates with the corresponding exhaust port 20. The three intake ports 18 a, 18 b, 18 c communicate with one intake branch pipe 5 a of the intake manifold 5. In the following, among the three intake openings 34a, 34b, 34c, the intake opening 34b located in the center is referred to as a central intake opening, and the intake openings 34a, 34c located on both sides of the central intake opening 34b are referred to as side intake openings. explain. Further, the intake port 18b communicating with the central intake opening 34b will be described as a central intake port, and the intake ports 18a and 18c communicating with the side intake openings 34a and 34c will be described as side intake ports.

  As shown in FIG. 3, the port injector 3b is configured such that when fuel is injected, fuel is supplied only to the central intake port 18b, that is, fuel is injected into the side intake ports 18a and 18c. Arranged so as not to be supplied. Therefore, the port injector 3b is disposed downstream of the branch point from the one intake branch pipe 5a to the three intake ports 18, or is upstream of the branch point and is a port injector. The fuel injected from 3b is arranged at a position where it does not enter the side intake ports 18a, 18c. Therefore, in this embodiment, the fuel injected from the port injector 3b flows into the fuel chamber 2 of each cylinder via the central intake port 18b and the central intake opening 34b.

  The internal combustion engine of the present embodiment is operated in three operation modes according to the engine operation state. When the engine load and the engine speed are low (for example, when the engine operation state is in the region I in FIG. 4), the engine is operated in the low fuel consumption mode, and when the engine load and the engine speed are medium (for example, When the engine operating state is in the region II of FIG. 4), the operation is performed in the low / medium load mode, and the engine load and the engine speed are high (for example, when the engine operating state is in the region III of FIG. 4). Is operated in medium and high load mode.

  Here, the low fuel consumption mode is an operation mode in which stratified combustion is performed in the combustion chamber 2 in order to improve fuel consumption. On the other hand, the low-medium load mode and the medium-high load operation mode are operation modes in which homogeneous combustion is performed. The operation is performed in a relatively large state.

  Homogeneous combustion is combustion performed by making the air-fuel ratio of the air-fuel mixture substantially uniform over the entire combustion chamber and then igniting the air-fuel mixture, and the air-fuel ratio of the entire air-fuel mixture in the combustion chamber 2 is substantially reduced. While it is necessary to achieve the stoichiometric air-fuel ratio, a relatively high output can be obtained. On the other hand, stratified combustion is combustion performed by igniting an air-fuel mixture with fuel unevenly distributed only in the vicinity of the spark plug 4, and the entire air-fuel mixture in the combustion chamber 2 is very thin (lean). While combustion can be performed at a fuel ratio, only a relatively low output can be obtained.

  Hereinafter, these three operation modes will be described with reference to FIGS. First, the low fuel consumption mode will be described with reference to FIGS. 5 and 6. FIG. 5 is a diagram showing the valve lift of the intake valve 19, the crank angle transition such as the fuel injection rate from the injectors 3a and 3b, and the ignition timing. FIG. 6 is a schematic view showing the flow of intake gas and injected fuel in the intake port 18 and the combustion chamber 2.

  As shown in FIG. 5, in the low fuel consumption mode, fuel injection from the in-cylinder injector 3a (hereinafter referred to as “in-cylinder injection”) is first performed in the second half of the intake stroke, and then port injection is performed in the second half of the intake stroke. Fuel injection (hereinafter referred to as “port injection”) is performed from the injector 3b. In particular, in the present embodiment, within a period (period A in FIG. 5) from the timing when the valve lift of the intake valve 19 is maximum to the timing p between this timing and the closing timing of the intake valve 19. In-cylinder injection (DFI) is performed during this period, and port injection (PFI) is performed within the period from the timing p to the closing timing of the intake valve 19 (period B in FIG. 5). After that, immediately before the compression top dead center (engine C in FIG. 5), the ignition plug 4 ignites the air-fuel mixture in the combustion chamber 2.

  FIG. 6A shows a state in the combustion chamber 2 when the in-cylinder injection is executed in the period A of FIG. The arrows in FIG. 6 indicate the flow of intake gas. As shown in FIG. 6A, in the present embodiment, the fuel injection direction from the in-cylinder injector 3a is the same direction as the inflow direction of intake air from the intake port 18 into the combustion chamber 2, or The direction is the same as the swirling direction of the tumble flow generated in the combustion chamber 2. For this reason, the tumble flow generated in the combustion chamber 2 can be strengthened by the fuel injection from the in-cylinder injector 3a during the period A. Further, by directly injecting into the combustion chamber 2 during the intake stroke, the fuel can be diffused throughout the combustion chamber 2 while the air-fuel ratio is high. As described above, when the fuel is injected from the in-cylinder injector 3a during the period A, the tumble flow can be strengthened and the fuel can be diffused. As a result, the combustion chamber is ignited after ignition of the air-fuel mixture by the spark plug 4. Flame propagation within 2 is promoted.

  FIG. 6B shows a state in the combustion chamber 2 when the port injection is executed in the period B of FIG. As shown in FIG. 6B, fuel is injected from the port injector 3b toward the intake opening 34. For this reason, even if the port injection is performed immediately before the intake valve 19 is closed, most of the port injected fuel flows into the combustion chamber 2. Since the port injection is performed immediately before the intake valve 19 is closed, even if a relatively strong tumble flow is generated in the combustion chamber 2, most of the fuel supplied by the port injection is compression top dead center. Immediately before, as shown in FIG. 6 (C), it drifts in the vicinity of the spark plug 4, and an appropriate stratified mixture is generated in the combustion chamber 2.

  Therefore, in the low fuel consumption mode of the present embodiment, an appropriate stratified mixture can be generated by performing port injection in period B, and mixing in the combustion chamber 2 by performing in-cylinder injection in period A It is possible to promote the flame propagation during the combustion of qi. For this reason, stratified combustion is efficiently performed in the combustion chamber 2, and as a result, fuel efficiency is improved.

  In the above embodiment, the port injection is started after the in-cylinder injection is completed in the latter half of the intake stroke, but the port injection is started before the completion of the in-cylinder injection after the start of the in-cylinder injection. Also good. That is, if the port injection is started after the start of the in-cylinder injection, the in-cylinder injection and the port injection do not necessarily have to be performed in the above periods A and B, and the in-cylinder injection period and the port injection period temporarily overlap each other. Also good.

  That is, not only in the above period A, but if in-cylinder injection is performed after the opening timing of the intake valve 19, the tumble flow in the combustion chamber 2 can be enhanced. Therefore, in-cylinder injection may be performed before the period A as long as it is after the opening timing of the intake valve 19. However, a tumble flow can be made stronger by performing in-cylinder injection in the engine A. In addition to the period B, for example, if port injection is performed after the time when the lift amount of the intake valve 19 becomes maximum, most of the port injected fuel immediately before the compression top dead center is collected in the vicinity of the spark plug 4. Can do. Accordingly, the port injection may be performed before the period B after the time when the lift amount of the intake valve 19 becomes maximum. However, by performing the port injection in the period B, the fuel injected by the port can be more reliably collected in the vicinity of the spark plug 4.

  In the low fuel consumption mode, it is not always necessary to perform in-cylinder injection, and in-cylinder injection may be stopped according to the engine operating state. In particular, in-cylinder injection may be stopped during idle operation, for example, when sufficient torque corresponding to the required load can be generated without performing in-cylinder injection.

  Next, the low / medium load mode will be described with reference to FIGS. 7 and 8 are similar to FIGS. 5 and 6, respectively. As shown in FIG. 7, in the low / medium load mode, port injection is performed before the start of the intake stroke, and then in-cylinder injection is performed from the latter half of the intake stroke to the first half of the compression stroke. In particular, in this embodiment, port injection is performed within a period (period A ′ in FIG. 7) before the intake valve 19 is opened (before the lift is started), and the valve lift of the intake valve 19 is maximized. The in-cylinder injection is performed within a period (period B ′ in FIG. 7) from the present timing to a timing q later than the closing timing of the intake valve 19. Thereafter, immediately before the compression top dead center (period C in FIG. 7), the spark plug 4 ignites the air-fuel mixture in the combustion chamber 2.

  FIG. 8A shows the state of the combustion chamber 2 and the intake port 18 when the port injection is executed in the period A ′ of FIG. As shown in FIG. 8A, in this embodiment, since the fuel injection from the port injector 3b is performed before the intake valve 19 is opened, the injected fuel is separated from the air in the intake port 18 with air. Since they are mixed, it becomes easy to uniformly mix the fuel and air. Thereafter, when the intake valve 19 is opened, the air-fuel mixture sufficiently mixed in the intake port 18 is caused to flow into the combustion chamber 2.

  FIG. 8B shows a state in the combustion chamber 2 when the in-cylinder injection is executed in the period B ′ of FIG. As described above, when fuel is injected from the in-cylinder injector 3a, the tumble flow generated in the combustion chamber 2 can be strengthened. In particular, in the present embodiment, since the fuel injection from the in-cylinder injector 3a is performed from the latter half of the intake stroke to the first half of the compression process, that is, relatively late, it is reinforced by the fuel injection from the in-cylinder injector 3a. Ignition by the spark plug 4 is performed before the tumble flow is weakened. That is, a strong tumble flow continues until the ignition timing.

  Therefore, in the low / medium load mode of the present embodiment, by performing port injection within the period A ′, a homogeneous mixture in which fuel is uniformly distributed is generated, and in-cylinder injection is performed within the period B ′. Thus, a strong tumble flow can be maintained in the combustion chamber 2 until the ignition timing. For this reason, as shown in FIG. 8 (C), a homogeneous air-fuel mixture is dispersed in the combustion chamber 2 and a strong tumble flow is generated during ignition by the spark plug 4. Homogeneous combustion takes place, resulting in increased power.

  In the above-described embodiment, the in-cylinder injection is performed within the period B ′. However, the in-cylinder injection is not necessarily performed within the period B ′, for example, before the time when the valve lift of the intake valve 19 becomes maximum, In-cylinder injection may be performed after the intake valve 19 is closed. However, if the in-cylinder injection is performed within the period B ′, the flow of the intake gas into the combustion chamber 2 and the jet of the fuel injected from the in-cylinder injector 3a do not cancel each other. It is effective in that the flow can be made stronger.

  Finally, the medium / high load mode will be described with reference to FIGS. 9 and 10. 9 and 10 are similar to FIGS. 7 and 8, respectively. As shown in FIG. 9, in the medium / high load mode, port injection is performed in the first half of the intake stroke, and then in-cylinder injection is performed from the latter half of the intake stroke to the first half of the compression stroke. In particular, in this embodiment, port injection is performed within a period (period A ″ in FIG. 9) from the opening timing of the intake valve 19 to the timing when the valve lift of the intake valve 19 is maximum, In-cylinder injection is performed within a period (period B ″ in FIG. 9) from a timing when the valve lift of the valve 19 is maximum to a timing q later than the closing timing of the intake valve 19. Thereafter, immediately before the compression top dead center (period C in FIG. 9), the spark plug 4 ignites the air-fuel mixture in the combustion chamber 2.

  FIG. 10A shows the state of the combustion chamber 2 and the intake port 18 when the port injection is executed in the period A ″ in FIG. As shown in FIG. 10A, in the present embodiment, fuel injection from the port injection injector 3b is performed in the first half of the intake stroke, so that it becomes easy to uniformly mix fuel and air. Further, the volume of the air that has flowed into the combustion chamber 2 is reduced by the loss of vaporization latent heat by the port-injected fuel, and thus the flow rate of the air that flows into the cylinder is increased. For this reason, a strong tumble flow is generated in the combustion chamber 2.

  FIG. 10B shows a state in the combustion chamber 2 when the in-cylinder injection is executed in the period B ″ in FIG. Since the period B ″ is the same period as the period B ′ shown in FIG. 7, by performing the in-cylinder injection in the period B ″, the strong tumble until the ignition timing is performed as in the case shown in FIG. 8B. The flow can be sustained.

  Therefore, in the middle and high load mode of the present embodiment, by performing the port injection in the period A ″, a strong tumble flow can be generated in the combustion chamber 2 from the start of inflow of the air-fuel mixture into the combustion chamber 2. By performing the in-cylinder injection during the period B ″, a strong tumble flow can be maintained in the combustion chamber 2 until the ignition timing. For this reason, as shown in FIG. 10 (C), a very strong tumble flow is generated in the combustion chamber 2 when ignited by the spark plug 4, so that the flame easily propagates after ignition of the air-fuel mixture. , Efficient combustion.

  By the way, in an internal combustion engine having an in-cylinder injector, it is conceivable that when stratified combustion is performed, fuel is injected from the in-cylinder injector so that a stratified mixture is appropriately formed. However, in the in-cylinder injector of the present embodiment, the fuel injection is performed so that the tumble flow generated in the combustion chamber 2 becomes strong as described above, and depending on the in-cylinder injector, the stratification is appropriately performed. Inability to burn. That is, when fuel injection is performed from the in-cylinder injector in a spray form in which the tumble flow generated in the combustion chamber 2 becomes strong as in the present embodiment, when performing stratified combustion, from the in-cylinder injector Even if fuel injection is performed, it is difficult to form an appropriate stratified mixture.

  On the other hand, in the present embodiment, when performing stratified combustion, fuel injection is performed not from the in-cylinder injector but from the port injector, so that the above-described problem does not occur, and accordingly, appropriately Stratified combustion can be performed.

  In addition, in an internal combustion engine that injects fuel from the in-cylinder injector when performing stratified combustion, the fuel injected from the in-cylinder injector during stratified combustion operation is prevented from diffusing throughout the combustion chamber. A cavity is provided on the upper surface of the piston. When the cavity is provided on the upper surface of the piston in this way, this cavity becomes a resistance against the air flow swirling in the combustion chamber 2 during the engine high load operation. On the other hand, when fuel injection is performed from the port injector during stratified combustion as in this embodiment, fuel is unevenly distributed in the vicinity of the spark plug by performing fuel injection from the port injector in the latter half of the intake stroke. I try to let them. Therefore, unlike an internal combustion engine in which fuel injection is performed from an in-cylinder injector in a spray form in which a stratified mixture is appropriately formed, there is no need to provide a cavity on the upper surface of the piston, and therefore combustion during engine high load operation The resistance to the air flow swirling in the chamber 2 can be reduced, and the design / processing cost of the piston can be reduced.

  Next, an internal combustion engine according to a second embodiment of the present invention will be described with reference to FIG. The configuration of the internal combustion engine of the second embodiment is basically the same as the configuration of the internal combustion engine of the first embodiment. However, in the internal combustion engine of the second embodiment, in the low fuel consumption mode, the on-off valve characteristics (that is, the opening timing of the intake valve) of the intake valve (hereinafter referred to as “central intake valve”) 19 corresponding to the central intake opening 34b, The valve closing timing, lift amount, phase angle, working angle, etc.) are different from the on-off valve characteristics of the intake valves 19 (hereinafter referred to as “side intake valves”) corresponding to the side intake openings 34a, 34c. The

  As shown in FIG. 11, in the internal combustion engine of the second embodiment, the opening timing of the central intake valve 19 is retarded relative to the opening timing of the side intake valve 19, and the central intake valve 19 is closed. The timing is set to be retarded from the closing timing of the side intake valve 19. Furthermore, in this embodiment, the valve opening period of the central intake valve 19 is substantially the same as the valve opening period of the side intake valve 19.

  Also in this embodiment, as in the above embodiment, in-cylinder injection is performed in the latter half of the intake stroke, and then port injection is performed in the second half of the intake stroke. In particular, in the present embodiment, a period from a time when the valve lift of the central intake valve 19 is maximum to a time p between this time and the closing timing of the central intake valve 19 (period A in FIG. 11). ) In-cylinder injection is performed, and port injection is performed within the period from the timing p to the closing timing of the central intake valve 19 (period B in FIG. 11). Thereafter, immediately before the compression top dead center (period C in FIG. 11), the ignition plug 4 ignites the air-fuel mixture in the combustion chamber 2.

  As in the present embodiment, when the valve opening period of the central intake valve 19 is shifted to the retard side with respect to the valve opening period of the side intake valve 19, the lift amount of the central intake valve 19 is greater after the timing r. The lift amount of the side intake valve 19 becomes larger. For this reason, from the time r until all the intake valves are closed, the flow rate of the intake gas flowing into the combustion chamber 2 through the side intake openings 34a and 34c passes through the central intake opening 34b. The flow rate of the intake gas flowing into the combustion chamber 2 is increased. As described above, when the flow rate of the intake gas flowing into the combustion chamber 2 through the central intake opening 34b is large, the intake gas flowing into the combustion chamber 2 through the central intake opening 34b becomes the side intake opening 34a, It becomes difficult to be influenced by the intake gas flowing into the combustion chamber 2 through 34c, and flows into the central region in the combustion chamber 2 relatively stably. Thereby, it is possible to suppress the fuel injected into the intake gas flowing into the combustion chamber 2 through the central intake opening 34b from being dispersed in the combustion chamber 2, thereby generating a good stratified mixture. Will be able to.

  In the above-described embodiment, in-cylinder injection is performed within the period A from the timing when the lift amount of the central intake valve 19 is maximum to the timing p, and from the timing p to the closing timing of the central intake valve 19. Port injection is performed within period B. However, in-cylinder injection may be performed before period A (for example, period a in FIG. 11). Further, if the port injection is performed after the timing r when the lift amount of the central intake valve 19 becomes larger than the lift amount of the bilateral intake valves 19, most of the fuel injected by the port immediately before the compression top dead center is ignited. Since they can be collected in the vicinity, the port injection may be performed before the period B after the time r when the lift amount of the central intake valve 19 becomes larger than the lift amount of the side intake valves 19 (for example, , Period b) in FIG.

  Next, a modified example of the second embodiment will be described with reference to FIG. In this modified example, in the low fuel consumption mode, instead of shifting the valve opening period of the central intake valve 19 to the retard side with respect to the valve opening period of the side intake valve 19, the lift amount of the central intake valve 19 is set to the side intake air. It is larger than the lift amount of the valve 19. As shown in FIG. 12, in this modified example, the central intake valve 19 and the side intake valve 19 have the same valve opening period (that is, the valve opening timing and the valve closing timing are the same). The lift amount of the central intake valve 19 is larger than the lift amount of the side intake valve 19 over the entire period.

  If the lift amount of the central intake valve 19 is made larger than the lift amount of the side intake valve 19 over the entire valve opening period of the intake valve 19 as in this modified example, the intake valve 19 is opened over the entire valve opening period. The flow rate of the intake gas flowing into the combustion chamber 2 through the central intake opening 34b is larger than the flow rate of the intake gas flowing into the combustion chamber 2 through the side intake openings 34a, 34c. Accordingly, as in the second embodiment described above, the intake gas flowing into the combustion chamber 2 through the central intake opening 34b flows into the central region in the combustion chamber 2 relatively stably.

  Next, another modification of the second embodiment will be described with reference to FIG. In this modified example, in the low fuel consumption mode, instead of shifting the valve opening period of the central intake valve 19 to the retard side with respect to the valve opening period of the side intake valve 19, the valve opening time of the central intake valve 19 is changed to the side. The intake valve 19 is longer than the valve opening time. As shown in FIG. 13, in this modified example, the opening timing of the central intake valve 19 is substantially the same as the opening timing of the side intake valve 19, but the closing timing of the central intake valve 19 is The side intake valve 19 is set to be retarded from the closing timing.

  If the opening time of the central intake valve 19 is longer than the opening time of the side intake valve 19 as in this modified example, the lift amount of the central intake valve 19 becomes larger than the lift amount of the side intake valves 19. After the time r, the lift amount of the central intake valve 19 becomes larger than the lift amount of the side intake valve 19. Therefore, from the time r until all the intake valves 19 are closed, the flow rate of the intake gas flowing into the combustion chamber 2 through the side intake openings 34a and 34c passes through the central intake opening 34b. Thus, the flow rate of the intake gas flowing into the combustion chamber 2 is increased. As a result, the fuel that has flowed into the combustion chamber 2 is prevented from being dispersed in the combustion chamber 2 as described above, so that a good stratified mixture can be generated.

  Next, still another modification of the second embodiment will be described with reference to FIG. In this modification, the diameter of the central intake opening 34b 'is larger than the diameters of the side intake openings 34a' and 34c '. Therefore, when the intake gas flows into the combustion chamber 2, the flow rate of the intake gas flowing through the central intake opening 34b ′ is higher than the flow rate of the intake gas flowing through the side intake openings 34a ′, 34c ′. More. As a result, in the low fuel consumption mode, the fuel flowing into the combustion chamber 2 is suppressed from being dispersed in the combustion chamber 2 as described above, so that a good stratified mixture can be generated. Become.

  It should be noted that the above-described second embodiment and its modified examples or modified examples can be used in combination with each other. For example, the diameter of the central intake opening is made larger than the diameter of the side intake opening, and the valve opening period of the central intake valve 19 is shifted to the retard side of the valve opening period of the side intake valve 19 in the low fuel consumption mode. You may do it.

It is the schematic showing the whole in-cylinder and port injection type internal combustion engine. 1 is a schematic cross-sectional view of an in-cylinder / port injection internal combustion engine. It is the figure which showed the upper surface in each cylinder roughly. It is a figure which shows the operation area | region in each operation mode. It is a figure which shows transition of the fuel injection rate from both the injectors in low fuel consumption mode, etc. It is the schematic which shows the flow of the intake gas and the injection fuel in an intake port and a combustion chamber in low fuel consumption mode. It is a figure which shows transition of the fuel injection rate from both the injectors in low and medium load mode. It is the schematic which shows the flow of the intake gas and the injection fuel in an intake port and a combustion chamber in low and medium load mode. It is a figure which shows transition of the fuel injection rate from both the injectors in medium and high load mode, etc. It is the schematic which shows the flow of the intake gas and the injection fuel in an intake port and a combustion chamber in medium and high load mode. It is a figure which shows transition of the fuel injection rate from both the injectors, etc. in the low fuel consumption mode in 2nd embodiment. It is a figure which shows transition of the fuel injection rate from both the injectors, etc. in the fuel-efficient mode in the example of a change of 2nd embodiment. It is a figure which shows transition of the fuel injection rate from both the injectors, etc. in the fuel-efficient mode in another modification of 2nd embodiment. It is the figure which showed roughly the upper surface in each cylinder in another example of another change of 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 2 Combustion chamber 3a In-cylinder injector 3b Injector for port injection 4 Spark plug 5 Intake manifold 5a Intake branch pipe 18 Intake port 19 Intake valve 20 Exhaust port 21 Exhaust valve 34 Intake opening 35 Exhaust opening 40 ECU

Claims (6)

In-cylinder / port-injection type internal combustion engine comprising an in-cylinder injector for injecting fuel into an engine combustion chamber and an in-cylinder injector for injecting fuel into an engine intake passage.
During the stratified charge combustion operation, fuel is injected from the in-cylinder injector during the intake stroke, and fuel is injected from the intake manifold injector after the start of fuel injection from the in-cylinder injector and before the intake valve is closed. There line the injection,
Three intake ports communicate with the combustion chamber of each cylinder, and the port injection injector injects fuel into the air passing through the central intake port among these three intake ports,
During stratified combustion operation, fuel injection from the port injector is performed when the flow rate of air passing through the central intake port is greater than the flow rate of air passing through the intake ports on both sides of the central intake port. Done
An in- cylinder / port-injection internal combustion engine in which, during stratified combustion operation, the closing timing of the intake valve corresponding to the central intake port is delayed from the closing timing of the intake valves corresponding to the intake ports on both sides . In-cylinder / port-injection type internal combustion engine comprising an in-cylinder injector for injecting fuel into an engine combustion chamber and an in-cylinder injector for injecting fuel into an engine intake passage.
During the stratified charge combustion operation, fuel is injected from the in-cylinder injector during the intake stroke, and fuel is injected from the intake manifold injector after the start of fuel injection from the in-cylinder injector and before the intake valve is closed. There line the injection,
Three intake ports communicate with the combustion chamber of each cylinder, and the port injection injector injects fuel into the air passing through the central intake port among these three intake ports,
During stratified combustion operation, fuel injection from the port injector is performed when the flow rate of air passing through the central intake port is greater than the flow rate of air passing through the intake ports on both sides of the central intake port. Done
An in-cylinder / port-injection internal combustion engine in which the lift amount of the intake valve corresponding to the central intake port is larger than the lift amount of the intake valve corresponding to the intake ports on both sides during the stratified combustion operation . In-cylinder / port-injection type internal combustion engine comprising an in-cylinder injector for injecting fuel into an engine combustion chamber and an in-cylinder injector for injecting fuel into an engine intake passage.
During the stratified charge combustion operation, fuel is injected from the in-cylinder injector during the intake stroke, and fuel is injected from the intake manifold injector after the start of fuel injection from the in-cylinder injector and before the intake valve is closed. There line the injection,
Three intake ports communicate with the combustion chamber of each cylinder, and the port injection injector injects fuel into the air passing through the central intake port among these three intake ports,
During stratified combustion operation, fuel injection from the port injector is performed when the flow rate of air passing through the central intake port is greater than the flow rate of air passing through the intake ports on both sides of the central intake port. Done
An in- cylinder / port-injection internal combustion engine in which the opening period of the intake valve corresponding to the central intake port is longer than the opening period of the intake valves corresponding to the intake ports on both sides during the stratified combustion operation . The in-cylinder system according to any one of claims 1 to 3, wherein during stratified combustion operation, fuel is injected from an in-cylinder injector and a port injector after a time when the lift amount of the intake valve becomes maximum.・ Port injection internal combustion engine. It is possible to switch between stratified combustion operation and homogeneous combustion operation,
The in-cylinder / port-injection type internal combustion engine according to any one of claims 1 to 4, wherein during homogeneous combustion operation, fuel injection from the in-cylinder injector is performed after the start of fuel injection from the port injector. The in-cylinder engine according to any one of claims 1 to 5 , wherein a valve diameter of the intake valve corresponding to the central intake port is made larger than a valve diameter of the intake valve corresponding to the intake ports on both sides. Port injection internal combustion engine.

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