JP4345439B2 - Control device for internal combustion engine and control method for internal combustion engine - Google Patents

Description

  The present invention relates to control of an internal combustion engine including a port injection valve and an in-cylinder injection valve. More specifically, the present invention relates to a control device for an internal combustion engine and a control method for the internal combustion engine capable of improving torque in a homogeneous combustion region. About.

A so-called direct injection internal combustion engine that injects fuel directly into a cylinder and ignites it directly injects fuel during the compression stroke to form a mixture that is easily ignited by stopping the fuel spray near the spark plug. Separate from the surrounding air layer, that is, stratify. In this state, an ultra lean combustion operation can be realized by igniting and burning the air-fuel mixture in the vicinity of the spark plug and operating under so-called stratified combustion. As a result, the fuel consumption of the internal combustion engine can be improved and the amount of CO ₂ emission can be reduced.

  A direct-injection internal combustion engine is operated under a so-called homogeneous combustion in which fuel is directly injected into the cylinder during the intake stroke to diffuse the fuel into the cylinder to form and burn a homogeneous mixture. Can do. In the homogeneous combustion region, the intake air can be further cooled by the heat of vaporization of the fuel directly injected into the cylinder during the intake stroke, so that the charging efficiency can be increased. Thereby, a high output can be obtained in the operation in the homogeneous combustion region of the direct injection internal combustion engine. Due to such advantages, in recent years, direct-injection spark ignition internal combustion engines have attracted attention and have been put into practical use.

  When a direct-injection internal combustion engine is operated with homogeneous combustion, the amount of fuel to be supplied is particularly large at high output or high load, so fuel vaporization is not in time, resulting in poor homogeneous combustion, Torque may be reduced. In order to solve such a problem, Patent Document 1 includes a main fuel injection valve that directly injects fuel into a cylinder, and a sub fuel injection valve that injects fuel into an intake port. An engine fuel injection control technique for variably setting the rate based on the operating state of the engine is disclosed.

JP 2001-20837 A

  By the way, the above-mentioned patent document 1 discloses the sharing ratio between the fuel injection amount of the main fuel injection valve and the fuel injection amount of the sub fuel injection valve. However, it is not possible to maintain good homogeneous combustion simply by making the share ratio variable, and there is room for improvement in order to improve the torque of the internal combustion engine. Therefore, the present invention has been made in view of the above, and a control device for an internal combustion engine and an internal combustion engine capable of improving the torque of the internal combustion engine when in-cylinder injection and port injection are used in combination in a homogeneous combustion region. It aims at providing the control method of an engine.

  As a result of diligent research to achieve the above-mentioned object, the present inventors paid attention to the fuel injection timing by in-cylinder injection, and the engine speed and in-cylinder injection timing of the internal combustion engine are the internal combustion engine in the homogeneous combustion region. The present invention has been completed.

A control device for an internal combustion engine according to the present invention controls an internal combustion engine including a port injection valve and a cylinder injection valve, and determines whether or not the internal combustion engine is operated in a homogeneous combustion region. And when the internal combustion engine is operated in a homogeneous combustion region and the engine rotational speed of the internal combustion engine is within a predetermined rotational speed range, the port injection valve and the in-cylinder injection valve An injection determination unit that determines that the fuel injection condition is to inject fuel from both, and fuel injection by an in-cylinder injection valve when the engine speed in the predetermined rotation speed range is low when the injection condition is determined A cylinder that injects fuel from the in-cylinder injection valve with the timing set to the intake bottom dead center side and the fuel injection timing by the in-cylinder injection valve to the intake top dead center side in the range where the engine speed in the predetermined range is high. An internal injection timing determination unit; It comprise characterized in that it is configured.

  When the fuel injection is performed using both the port injection valve and the in-cylinder injection valve in the homogeneous combustion region, the control device for the internal combustion engine lowers the fuel injection timing of the in-cylinder injection valve in the range where the engine speed is low. The dead center side is controlled so that it is on the intake top dead center side in the high engine speed range. Thereby, torque can be improved by using air cooling in a range where the engine speed is low and by promoting mixing of fuel and air in a range where the engine speed is high. As a result, it is possible to improve the torque of the internal combustion engine when in-cylinder injection and port injection are used together in the homogeneous combustion region.

  Further, the internal combustion engine control apparatus according to the present invention is characterized in that in the internal combustion engine control apparatus, a torque peak of the internal combustion engine due to fuel injection of the in-cylinder injection valve on the intake top dead center side is an intake bottom dead center. Fuel is injected from both the port injection valve and the in-cylinder injection valve when the engine speed exceeds the torque peak of the internal combustion engine due to fuel injection of the in-cylinder injection valve on the side. It is determined that the injection condition is satisfied.

  This internal combustion engine control apparatus is configured to provide a cylinder speed at which the torque peak when the in-cylinder injection on the intake top dead center side continues is higher than the torque peak when the in-cylinder injection on the intake bottom dead center side continues. Control to add port injection in addition to internal injection. Thereby, the air cooling effect by in-cylinder injection and the mixing promotion effect of the fuel and air by port injection can be made compatible, and the torque in a homogeneous combustion area | region can be improved.

Further, an internal combustion engine control apparatus according to the present invention is the internal combustion engine control apparatus,
The in-cylinder injection timing determination unit advances the fuel injection timing by the in-cylinder injection valve to the intake top dead center side of the internal combustion engine as the engine speed increases in the predetermined rotation speed range. It is characterized by.

  Thus, by controlling the fuel injection timing of the in-cylinder injection valve to shift to the intake top dead center side as the engine speed increases, the fuel and air can be mixed even in the high engine speed range. Can be further promoted. As a result, the torque of the internal combustion engine can be improved when in-cylinder injection and port injection are used in the homogeneous combustion region.

  Further, the internal combustion engine control apparatus according to the present invention is characterized in that in the internal combustion engine control apparatus, the in-cylinder injection timing determination unit includes the low rotation range and the high rotation range in the predetermined rotation speed range. In the case of an intermediate rotational speed range, fuel is injected into the in-cylinder injection valve on the intake top dead center side and the intake bottom dead center side of the internal combustion engine.

  By controlling in this way, it is possible to improve the torque of the internal combustion engine within the range of the intermediate rotation speed within the range of the engine speed that uses both the in-cylinder injection and the port injection, and the fuel injection of the in-cylinder injection valve. Torque fluctuations that occur when the timing is switched can be smoothed.

  Further, the internal combustion engine control apparatus according to the present invention is characterized in that, in the internal combustion engine control apparatus, the fuel injection ratio by the in-cylinder injection valve at the intake top dead center side and the intake bottom dead center side of the internal combustion engine. Is further provided with an injection ratio determining unit that changes the fuel injection ratio of the in-cylinder injection valve in accordance with the engine speed.

  By controlling in this way, as the engine speed increases, the fuel injection amount of the in-cylinder injection valve on the intake bottom dead center side is decreased, and the fuel injection amount of the in-cylinder injection valve on the intake top dead center side is increased. Fuel can be injected into the cylinder. As a result, the torque fluctuation of the internal combustion engine due to the switching of the in-cylinder injection timing can be made smoother. In addition, within the range of engine speed when in-cylinder injection is performed on the intake top dead center side and the intake bottom dead center side, fuel is supplied into the cylinder while maintaining an optimal balance between air cooling and fuel / air mixing. Can be injected, so that torque can be improved.

  In the internal combustion engine control apparatus according to the present invention, in the internal combustion engine control apparatus, the injection ratio determination unit further determines an injection ratio between the port injection valve and the in-cylinder injection valve. The number is changed according to the number or the load of the internal combustion engine.

  With such a configuration, it is possible to control to increase the fuel injection ratio by the port injection valve as the engine speed increases or the load on the internal combustion engine increases. As a result, the engine speed can be increased and the mixing of fuel and air by the port injection valve can be further promoted. Therefore, when the in-cylinder injection and the port injection are used in combination, the torque of the internal combustion engine is increased. Can do.

  Further, the following control method for an internal combustion engine according to the present invention determines whether or not the internal combustion engine is operated in a homogeneous combustion region when controlling the internal combustion engine including the port injection valve and the in-cylinder injection valve. And when the internal combustion engine is operated in a homogeneous combustion region and the engine speed of the internal combustion engine is within a predetermined speed range, fuel is supplied from both the port injection valve and the in-cylinder injection valve. The procedure for determining that the injection condition is to be injected, and the fuel injection timing by the in-cylinder injection valve is determined to be the intake bottom dead center side in the range where the engine speed in the predetermined speed range is low, and the predetermined range And a procedure for determining the fuel injection timing by the in-cylinder injection valve to the intake top dead center side in a range where the engine speed is high.

  In this internal combustion engine control method, when fuel is injected using both the port injection valve and the in-cylinder injection valve in the homogeneous combustion region, the fuel injection timing of the in-cylinder injection valve is reduced to the intake air in the range where the engine speed is low. The dead center side, and the intake top dead center side in the high engine speed range. Thereby, torque can be improved by using air cooling in a range where the engine speed is low and by promoting mixing of fuel and air in a range where the engine speed is high. As a result, it is possible to improve the torque of the internal combustion engine when in-cylinder injection and port injection are used together in the homogeneous combustion region.

  In the internal combustion engine control method according to the present invention, in the internal combustion engine control method, in the predetermined rotational speed range, an intermediate rotational speed range between the low rotational speed range and the high rotational speed range. In some cases, fuel is injected into the in-cylinder injection valve at an intake top dead center side and an intake bottom dead center side of the internal combustion engine.

  With such a configuration, it is possible to improve the torque of the internal combustion engine within the range of the intermediate rotation speed within the range of the engine speed that uses both the in-cylinder injection and the port injection, and the fuel injection timing of the in-cylinder injection valve. Torque fluctuations that occur when switching can be smoothed.

Further, the control device for an internal combustion engine according to the present invention described below is the control method for an internal combustion engine,
Further, the injection ratio between the port injection valve and the in-cylinder injection valve is changed according to the engine speed or the load of the internal combustion engine.

In this way, it is possible to increase the fuel injection ratio by the port injection valve as the engine speed increases or the load on the internal combustion engine increases. As a result, the mixing of the fuel and the air can be further promoted along with the increase in the engine speed, etc., so that the torque of the internal combustion engine can be increased when the in-cylinder injection and the port injection are used together.

  According to the internal combustion engine control apparatus and internal combustion engine control method according to the present invention, it is possible to improve the torque of the internal combustion engine when in-cylinder injection and port injection are used together in a homogeneous combustion region.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements of the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same. The present invention can be preferably applied to a reciprocating internal combustion engine, and is particularly preferable for an internal combustion engine mounted on a vehicle such as a passenger car, a bus, or a truck.

  The control apparatus for an internal combustion engine according to the present invention is used to control an internal combustion engine that includes a fuel injection valve that injects fuel into a cylinder and a fuel injection valve that injects fuel into an intake port. The control device and control method for an internal combustion engine according to the present invention of this embodiment are characterized by the following points. That is, when operating in the homogeneous combustion region, it is determined according to the engine speed whether or not fuel is injected from both the port injection valve and the in-cylinder injection valve. In the range of the engine speed at which fuel is injected from both the port injection valve and the in-cylinder injection valve, when the engine speed is low, the in-cylinder injection timing is set to the intake bottom dead center side, and the engine speed When the engine speed is high, the in-cylinder injection timing is set to the intake top dead center side.

  FIG. 1 is a conceptual diagram showing an example in which an internal combustion engine is controlled by a control device for an internal combustion engine according to an embodiment of the present invention. An internal combustion engine 1 that is a control target of the control device 10 of the internal combustion engine is a reciprocating internal combustion engine using gasoline as fuel, a port injection valve 2 for injecting fuel F into an intake passage 4, and a fuel in a cylinder 1s. And an in-cylinder injection valve 3 for injecting F. Then, the fuel F is supplied to the internal combustion engine 1 by the port injection valve 2 and the in-cylinder injection valve 3.

  The air introduced into the cylinder 1s from the intake passage 4 forms an air-fuel mixture with the fuel F injected from the port injection valve 2 or the in-cylinder injection valve 3, and this air-fuel mixture is ignited by the spark plug 7 and burns. . The combustion pressure of the air-fuel mixture is transmitted to the piston 5 and causes the piston 5 to reciprocate. The reciprocating motion of the piston 5 is converted into rotational motion by the crankshaft 6 and is taken out as the output of the internal combustion engine 1. A crank angle sensor 41 is attached to the crankshaft 6. An ECU (Engine Control Unit) 30 acquires the output of the crank angle sensor 41, and the port injection valve 2 and the in-cylinder injection valve 3 inject fuel F. Used to control timing.

  The ECU 30 acquires the outputs from the crank angle sensor 41, the accelerator sensor 42, the air flow sensor 43, and other various sensors, and controls the operation of the internal combustion engine 1. In this embodiment, the control device 10 for an internal combustion engine according to the present invention is connected to the ECU 30, and the control function of the internal combustion engine 1 provided in the ECU 30 is used in realizing the control method for the internal combustion engine according to the present invention. It is configured to be able to.

  The in-cylinder injection valve 3 can directly inject the fuel F into the cylinder 1 s of the internal combustion engine 1. That is, the internal combustion engine 1 is a so-called direct injection internal combustion engine, and can be operated in both the stratified combustion region and the homogeneous combustion region. Here, in order to improve the performance of the internal combustion engine 1 in the homogeneous combustion region, it is necessary to make the mixing of air and fuel homogeneous and to introduce more air (oxygen) into the cylinder 1s. Become.

  When fuel is directly injected into the cylinder 1 s by the in-cylinder injection valve 3, the mixing of the fuel and air is inferior, but the air in the cylinder 1 s can be efficiently cooled, and the intake air amount of the internal combustion engine 1 is increased to increase the volume. Efficiency can be improved. For this reason, in the low-rotation region where the mixing time of fuel and air has a margin, the performance of in-cylinder injection is excellent due to the effects of homogeneous mixing and air cooling. On the other hand, when the fuel F is directly injected into the cylinder 1s by the in-cylinder injection valve 3 in a high rotation region where there is no time for mixing the fuel and air, the mixing of the fuel and air tends to be insufficient. . As a result, the torque of the internal combustion engine 1 is reduced.

  FIG. 2 is an explanatory diagram showing the relationship between fuel injection timing and torque when fuel is directly injected into a cylinder. The fuel injection timing into the cylinder 1s is represented by a piston position when the ignition top dead center is 0 degree (CA), and the piston position is represented by a crank angle CA. Here, (CA) means displaying with a crank angle (the same applies hereinafter). The fuel injection timing into the cylinder 1s is represented by BTDC (Before Top Death Center). The “top dead center” in BTDC is an ignition top dead center. FIG. 3A is an explanatory diagram illustrating a state in which fuel is injected into the cylinder in the vicinity of the intake top dead center. FIG. 3-2 is an explanatory view showing a state in which fuel is injected into the cylinder in the vicinity of the intake bottom dead center.

  In FIG. 2, torque values when fuel is injected into the cylinder 1 s of the internal combustion engine 1 near the intake top dead center (near BTDC 300 degrees (CA)) and near the bottom intake dead center (near BTDC 200 degrees (CA)). Is expressed using the engine speed NE as a parameter. In the vicinity of the intake top dead center, the torque generated by the internal combustion engine 1 increases as the engine speed NE increases. This is because when the engine speed NE is large, as shown in FIG. 3A, fuel and air can be sufficiently mixed by starting injection of the fuel F from the vicinity of the intake top dead center. This is because the torque can be increased. That is, in the case of in-cylinder injection, in the region where the engine speed NE is large, the mixture of fuel and air becomes dominant with respect to the improvement in the torque of the internal combustion engine 1. Therefore, in the case of in-cylinder injection, in order to improve the torque of the internal combustion engine 1 when the engine speed NE is large, it is effective to inject fuel into the cylinder 1s in the vicinity of the intake top dead center.

  On the other hand, in the vicinity of the intake bottom dead center, the engine speed NE decreases and the torque generated by the internal combustion engine 1 increases. This is because when the engine speed NE is low, a sufficient time can be secured for mixing the fuel and air. That is, as shown in FIG. 3-2, the air in the cylinder 1s can be cooled by injecting fuel in the vicinity of the intake bottom dead center, and more air can be introduced into the cylinder 1s. This is because the torque generated by the internal combustion engine 1 can be increased by the effect of this air cooling. That is, in the case of in-cylinder injection, air cooling is dominant for torque improvement in a region where the engine speed NE is small. Therefore, in the case of in-cylinder injection, in order to improve the torque when the engine speed NE is small, it is effective to inject the fuel F into the cylinder 1s in the vicinity of the intake bottom dead center.

  As shown in FIG. 2, in the case of in-cylinder injection, when the engine speed NE increases, it is more effective for improving the torque to promote the mixing of fuel and air than to promote air cooling. It can be seen that it is. That is, in such a case, in-cylinder injection near the intake top dead center is effective in improving torque. Here, the port injection in which the fuel is injected into the intake passage 4 by the port injection valve 2 is excellent in the performance in the high rotation region where the mixing time of the fuel and the air has no margin because the mixing of the air and the fuel F is good. Therefore, as the mixture of fuel and air shifts to a region where the increase in torque is dominant, the port injection is gradually added, so that the cooling effect by in-cylinder injection and the mixing of fuel and air are promoted. It is possible to effectively balance the effect. Thereby, the torque of the internal combustion engine 1 can be improved.

  Here, the region where the mixture of fuel and air is dominant is that the torque peak when the fuel injection from the in-cylinder injection valve 3 is continued in the vicinity of the intake top dead center (around BTDC 300 degrees (CA)). It means the range of engine speed NE1 or more that exceeds the torque peak when fuel injection by the in-cylinder injection valve 3 is continued near the bottom dead center (around BTDC 200 degrees (CA)). In FIG. 2, the engine speed approximately in the middle between NEb and NEc generally corresponds to this engine speed NE1. In the present invention, when the engine speed NE becomes equal to or higher than the engine speed NE1, port injection is added and the ratio of port injection is increased as the engine speed NE increases. As a result, the cooling effect by in-cylinder injection and the effect of promoting the mixing of fuel and air can be effectively made compatible to improve the torque. Next, the relationship between the engine speed NE and the injection valve used for fuel injection will be described.

  FIG. 4 is an explanatory diagram showing the relationship between the injection valve used for fuel injection and the engine speed. As described above, in the range of the engine speed where air cooling is dominant, fuel is directly injected into the cylinder 1s using only the in-cylinder injection valve 3. That is, as shown in FIG. 4, an engine in which the torque peak due to fuel injection at the in-cylinder injection valve 3 near the intake top dead center exceeds the torque peak due to fuel injection at the in-cylinder injection valve 3 near the intake bottom dead center. Until the rotational speed NE1, only the in-cylinder injection valve 3 is used.

  When the engine speed NE of the internal combustion engine 1 becomes equal to or higher than the engine speed NE1, the fuel F is supplied to the internal combustion engine 1 using both the in-cylinder injection valve 3 and the port injection valve 2. At this time, as shown in FIG. 4, the ratio of port injection by the port injection valve 2 is increased as the engine speed NE increases, and the ratio of in-cylinder injection by the in-cylinder injection valve 3 is decreased. When the engine speed NE is further increased and reaches NE2, the influence of the promotion of mixing of fuel and air becomes extremely large in order to improve the torque. Therefore, the fuel is supplied to the internal combustion engine 1 only by the port injection valve 2.

  5-1 is explanatory drawing which shows the injection timing of the cylinder injection valve in the area | region which uses both a cylinder injection valve and a port injection valve. In the homogeneous combustion region where the in-cylinder injection valve 3 and the port injection valve 2 are used, that is, in the range where the engine speed NE is from NE1 to NE2, the in-cylinder The injection timing of the injection valve 3 is changed. A region where air cooling is dominant, that is, a region where the in-cylinder injection valve 3 and the port injection valve 2 are used, and a range where the engine speed NE is low (NE1 ≦ NE ≦ NE3, NE3 is the third engine speed). Now, let the fuel injection timing of the in-cylinder injection valve 3 be the intake bottom dead center side. As a result, the effect of air cooling can be exhibited, so that the torque generated by the internal combustion engine 1 can be improved when the engine speed NE is in the range of NE1 ≦ NE ≦ NE3.

  The region where the mixing of fuel and air is dominant, that is, the region where the in-cylinder injection valve 3 and the port injection valve 2 are used and the engine speed NE is high (NE4 ≦ NE ≦ NE2: NE4 is the fourth In the engine speed), the fuel injection timing of the in-cylinder injection valve 3 is set to the intake top dead center side. Conventionally, in such a region where the mixture of fuel and air is dominant, the fuel is supplied to the internal combustion engine 1 only by the port injection. In the present invention, in addition to the port injection, the intake top dead center side is provided. Fuel is injected from the in-cylinder injection valve 3 into the cylinder 1s. As a result, in addition to the effect of mixing fuel and air, the effect of air cooling by in-cylinder injection can also be exhibited, so that the torque generated by the internal combustion engine 1 when the engine speed NE is in the range of NE4 ≦ NE ≦ NE2. Can be improved. Here, the engine speeds NE1, NE2, NE3 and NE4 are values determined according to the shape of the fuel spray formed by the in-cylinder injection valve 3 and the specifications of the in-cylinder injection valve 3. NE1, NE2, NE3, and NE4 can be obtained in advance by experiment, numerical simulation, or the like.

In a region where the effect of air cooling and the effect of mixing of fuel and air are substantially equal, that is, in the range where engine speed NE is NE3 <NE <NE4, the fuel injection timing of in-cylinder injection valve 3 is set as follows: To do. That is, as shown in FIG. 5A, fuel is injected from the in-cylinder injection valve 3 into the cylinder 1s in two steps, that is, the intake bottom dead center side and the intake top dead center side. As a result, the torque of the internal combustion engine 1 within the range of the engine speed can be improved, and torque fluctuations that occur when the fuel injection timing of the in-cylinder injection valve 3 is switched can be smoothed.

  FIG. 5B is a conceptual diagram illustrating the intake top dead center side and the intake bottom dead center side. Whether it is the intake top dead center side or the intake bottom dead center side is determined based on BTDC 270 degrees (CA) when the ignition top dead center is 0 degrees (CA). That is, as shown in FIG. 5-2, the intake top dead center side is closer to the intake top dead center (BTDC 360 degrees (CA)) than BTDC 270 degrees (CA), and is lower than the BTDC 270 degrees (CA). The one near the dead point (BTDC 180 degrees (CA)) is the intake bottom dead center side. In addition, BTDC270 degree | times (CA) shall be included in the intake bottom dead center side. Further, the crankshaft 6 (see FIG. 1) rotates in the direction of arrow R in FIG.

  FIG. 6 is an explanatory diagram showing the configuration of the control device for the internal combustion engine according to the embodiment of the present invention. The configuration of the control device 10 for an internal combustion engine according to the embodiment of the present invention will be described with reference to FIG. The control device 10 for an internal combustion engine includes a processing unit 10p and a storage unit 10m. The processing unit 10p further includes a combustion determination unit 21, an injection determination unit 22, an in-cylinder injection timing determination unit 23, and an injection ratio determination unit 24. Here, the combustion determination unit 21, the injection determination unit 22, the in-cylinder injection timing determination unit 23, and the injection ratio determination unit 24 are portions that execute the control method for the internal combustion engine according to the present invention.

  The storage unit 10m, the combustion determination unit 21, the injection determination unit 22, the in-cylinder injection timing determination unit 23, and the injection ratio determination unit 24 are an input / output port (I / O) 29 of the control device 10 for the internal combustion engine. Connected through. Thereby, the memory | storage part 10m, the combustion determination part 21, the injection determination part 22, the in-cylinder injection timing determination part 23, and the injection ratio determination part 24 are comprised so that each can exchange data bidirectionally. . Note that data may be transmitted and received in one direction as required in the device configuration.

  The control device 10 of the internal combustion engine and the ECU 30 are connected via an input / output port (I / P) 29 of the control device 10 of the internal combustion engine and can exchange data with each other. Thereby, the control device 10 of the internal combustion engine acquires the internal combustion engine control data that the ECU 30 has, acquires information from various sensors of the internal combustion engine 1 via the ECU, or controls the control device 10 of the internal combustion engine. The engine control routine of the ECU 30 can be interrupted. Further, the control device 10 for the internal combustion engine according to the present invention may be incorporated in the ECU 30, and the function of the control device 10 for the internal combustion engine according to the present invention may be realized by using a part of the function of the ECU 30. .

  The storage unit 10m stores a computer program including a processing procedure of the control method for the internal combustion engine according to the present invention, a fuel injection timing, a fuel injection ratio between the cylinder and the intake port, and other data maps. Here, the storage unit 10m can be configured by a volatile memory such as a RAM (Random Access Memory), a nonvolatile memory such as a flash memory, or a combination thereof. The processing unit 10p can be configured by a memory and a CPU.

  The computer program may be capable of realizing the processing procedure of the control method for an internal combustion engine according to the present invention by a combination with a computer program already recorded in the processing unit 10p or the ECU 30. The processing unit 10p implements the functions of the combustion determination unit 21, the injection determination unit 22, the in-cylinder injection timing determination unit 23, and the injection ratio determination unit 24 using dedicated hardware instead of the computer program. There may be. Next, a procedure for realizing the control method of the internal combustion engine according to the embodiment of the present invention by using the control device 10 for the internal combustion engine will be described. In this description, please refer to FIGS.

  FIG. 7 is a flowchart showing a control procedure of the control method of the internal combustion engine according to the embodiment of the present invention. In realizing the control method of the internal combustion engine according to the embodiment of the present invention, first, the ECU 30 requires the internal combustion engine 1 under the operating conditions from the air flow rate and load of the internal combustion engine 1 or the engine speed NE. A total fuel injection amount TAU is calculated (step S101). Next, the combustion determination unit 21 of the control device 10 for the internal combustion engine determines whether or not it is a homogeneous combustion region (step S102). Whether or not it is a homogeneous combustion region is determined from the accelerator opening of the internal combustion engine 1, the intake pressure of the intake passage 4, and the like. The homogeneous combustion region is generally a high-load operation region, which is a so-called WOT (Wide Open Throttle) region. Therefore, it can be determined as a homogeneous combustion region in a high load region (WOT region). For example, when the accelerator opening is approximately 80% or more, it is determined as the homogeneous combustion region (high load operation region).

  When the combustion determination part 21 determines that it is a homogeneous combustion region (step S102; Yes), the injection determination part 22 determines whether or not the fuel F is injected from both the port injection valve 2 and the in-cylinder injection valve 3. To do. In this determination, the injection determination unit 22 acquires the engine speed NE of the internal combustion engine 1, and when the engine speed NE is equal to or higher than NE1 (step S103; Yes) and is equal to or lower than NE2 (step S104; Yes), the port. It is determined that the fuel F is injected from both the injection valve 2 and the in-cylinder injection valve 3. The engine speed NE1 is greater than the torque peak when the in-cylinder injection on the intake top dead center side is continued in the internal combustion engine 1 when the in-cylinder injection on the intake bottom dead center side is continued. Is the engine speed.

  If the engine speed NE is smaller than NE1 (step S103; No), the injection determination unit 22 determines that fuel is injected only by the in-cylinder injection valve 3 (step S109), and the engine speed NE is greater than NE2. Is larger (step S104; No), the injection determination unit 22 determines that fuel is injected only by the port injection valve 2 (step S110). When the combustion determination unit 21 determines that it is not the homogeneous combustion region (step S102; No), the internal combustion engine 1 is operated in the stratified combustion region by injection only from the in-cylinder injection valve 3 (step S108). Here, NE1 is the first engine speed for switching from fuel injection by in-cylinder injection only to fuel injection by in-cylinder and port injection, and NE2 is fuel injection by in-cylinder and port injection only by port injection. To the second engine speed.

  The first engine speed NE1 is around 2000 rpm (Revolution Per Minute), and the second engine speed NE2 is around 5000 rpm. These values may be changed depending on the spray form of the in-cylinder injection valve 3. For example, when the spray form of the in-cylinder injection valve 3 is designed in a form that emphasizes engine output, NE2 becomes larger, and the spray form of the in-cylinder injection valve 3 is designed in a form that places importance on intake efficiency. In this case, NE2 becomes smaller.

  When fuel F is injected from both the port injection valve 2 and the in-cylinder injection valve 3 (step S103; Yes, step S104; Yes), the in-cylinder injection timing determination unit 23 performs the fuel injection of the in-cylinder injection valve 3. The time is determined (step S105). Next, the fuel injection timing of the in-cylinder injection valve 3 will be described. FIG. 8 is a flowchart showing a procedure for determining the injection timing by the in-cylinder injection valve in the control method of the internal combustion engine according to the embodiment of the present invention. FIGS. 9A and 9B are explanatory diagrams illustrating a fuel injection timing map of the in-cylinder injection valve. The in-cylinder injection timing determination unit 23 of the control device 10 for the internal combustion engine first determines whether or not the engine speed NE is equal to or less than NE3 (step S201).

If NE is equal to or less than NE3 (step S201; Yes), the in-cylinder injection timing determination unit 23 sets the engine speed NE to the low rotation side injection timing map 50 (FIG. 9-1) stored in the storage unit 10m. Then, the fuel injection timing (hereinafter referred to as in-cylinder injection timing) Θdi of the in-cylinder injection valve 3 corresponding to the engine speed NE is determined (step S205). In step S205, the in-cylinder injection timing Θdi is determined so that the in-cylinder injection valve 3 injects fuel on the intake bottom dead center side.

  If NE> NE3 (step S201; No), the in-cylinder injection timing determination unit 23 of the control device 10 for the internal combustion engine determines whether the engine speed NE is equal to or greater than NE4 (step S202). If the engine speed NE is greater than or equal to NE4 (step S202; Yes), the in-cylinder injection timing determination unit 23 displays the engine rotation in the high rotation side injection timing map 51 (FIG. 9-2) stored in the storage unit 10m. A number NE is given, and the in-cylinder injection timing Θdi corresponding to the engine speed NE is determined (step 206). In step S206, the in-cylinder injection timing Θdi is determined so that the in-cylinder injection valve 3 injects fuel on the intake top dead center side.

  The low rotation side injection timing map 50 and the high rotation side injection timing map 51 are set as shown in FIGS. 9-1 and 9-2, for example. When NE1 ≦ NE ≦ NE3, as shown in the low-rotation side injection timing map 50, the in-cylinder injection timing Θdi is in the range of BTDC 180 degrees (CA) to 270 degrees (CA), and the engine speed NE increases. At the same time, it is preferable to set so as to shift to the intake top dead center side. When NE4 ≦ NE ≦ NE2, the in-cylinder injection timing Θdi increases in the engine speed NE within a range of BTDC 290 degrees (CA) to 360 degrees (CA) as shown in the high-rotation side injection timing map 51. At the same time, it is preferable to set so as to shift to the intake top dead center side. This is due to the following reason. As the engine speed NE increases, a sufficient time for fuel vaporization cannot be ensured. Therefore, by shifting the in-cylinder injection timing Θdi to the intake top dead center side as the engine speed NE rises, the fuel F and air can be sufficiently mixed and the torque of the internal combustion engine 1 can be improved. It is. The in-cylinder injection timing Θdi on the intake bottom dead center side is in the range of BTDC 180 degrees (CA) to 270 degrees (CA), and the in-cylinder injection timing Θdi on the intake top dead center side is BTDC 290 degrees (CA) to 360 degrees. Within a range of degrees (CA) or less, one value may be determined within each of the above ranges regardless of the engine speed NE.

  The low rotation side injection timing map 50 and the high rotation side injection timing map 51 may be controlled so that the in-cylinder injection timing Θdi shifts to the intake top dead center side as the engine speed NE increases. Therefore, as shown by the solid lines of the low rotation side injection timing map 50 and the high rotation side injection timing map 51, the relationship between the in-cylinder injection timing Θdi and the engine speed NE may be linear, It may be non-linear as indicated by a two-dot chain line. The low rotation side injection timing map 50 and the high rotation side injection timing map 51 can be created by experiments or numerical simulations.

When the engine speed NE satisfies the relationship NE3 <NE <NE4 (step S201; No: step S202; No), the in-cylinder injection timing determination unit 23 determines whether the intake top dead center side and the intake bottom dead center side are The in-cylinder injection timing Θdi is determined so as to inject fuel into the cylinder 1s in steps (step S203). Specifically, the in-cylinder injection timing Θdi on the intake bottom dead center side is BTDC 270 degrees (CA), and the in-cylinder injection timing Θdi on the intake top dead center side is BTDC 290 degrees (CA). This is because when the in-cylinder injection timing Θdi is switched from the intake bottom dead center side to the intake top dead center side with the third and fourth engine speeds NE3 and NE4 as a boundary, the torque of the internal combustion engine 1 changes abruptly. Because it deteriorates the ability. Therefore, by determining the in-cylinder injection timing Θdi as described above, the in-cylinder injection timing Θdi is smoothly switched while suppressing rapid torque fluctuations. At this time, the injection ratio determination unit 24 included in the control device 10 for the internal combustion engine determines the intake top dead center side fuel injection amount _FTDC and the intake bottom dead center side fuel injection amount _FBDC (step S204). This determination procedure will be described.

FIG. 10 is an explanatory diagram showing a fuel injection ratio determination map describing the relationship of the fuel injection ratio determination coefficient with respect to the engine speed. As shown by the solid line of the fuel injection ratio determination map 52, the fuel injection ratio determination coefficient K _BDC of the intake bottom dead center side fuel injection amount F _BDC is determined so as to decrease as the engine speed NE increases. At this time, the fuel injection rate determination coefficient K _TDC of the intake top dead center side fuel injection amount F _TDC is represented by (1-K _BDC). The intake bottom dead center side fuel injection amount F _BDC is determined by K _BDC × TAU _di , and the intake top dead center side fuel injection amount F _TDC is determined by K _TDC × TAU _di = (1−K _BDC ) × TAU _di . Is done.

By doing so, the intake bottom dead center side fuel injection amount _FBDC is decreased as the engine speed NE rises, and the intake top dead center side fuel injection amount _FTDC is increased to inject fuel into the cylinder 1s. it can. As a result, the torque fluctuation of the internal combustion engine 1 due to the switching of the in-cylinder injection timing Θdi can be made smoother. In addition, when the engine speed NE is in the range of NE3 <NE <NE4, fuel can be injected into the cylinder 1s while maintaining an optimal balance between air cooling and mixing of fuel and air. Improvement can also be achieved. Note that the fuel injection ratio determination coefficient K _BDC of the intake bottom dead center side fuel injection amount F _BDC may be determined so as to decrease as the engine speed NE increases. It may be non-linear as shown by the dotted line. Here, the fuel injection ratio determination map 52 can be created by experiment or numerical simulation. The injection ratio between the intake bottom dead center side fuel injection amount _FBDC and the intake top dead center side fuel injection amount _FTDC may be 1: 1 irrespective of the engine speed NE. In this way, the algorithm for controlling the fuel injection amount can be simplified. When the above procedure by determining an intake top dead center side fuel injection amount F _TDC and the intake bottom dead center the fuel injection amount F _BDC, determination procedure Θdi injection timing cylinder is completed.

  When the fuel injection timing of the in-cylinder injection valve 3 is determined (step S105), the injection ratio determination unit 24 provided in the control device 10 for the internal combustion engine determines the in-cylinder injection ratio and the port injection ratio (step S106). This injection ratio determination procedure will be described. FIG. 11 is a flowchart illustrating a procedure for determining the in-cylinder injection ratio and the port injection ratio. FIG. 12 is an explanatory diagram showing an in-cylinder injection ratio map describing the in-cylinder injection ratio.

  When fuel is injected from both the port injection valve 2 and the in-cylinder injection valve 3, the fuel injection ratio from the port injection valve 2 and the fuel injection ratio from the in-cylinder injection valve 3 are changed according to the engine speed NE. Let In order to increase the torque of the internal combustion engine 1, it is effective to promote the mixing of fuel and air as the engine speed NE increases. For this reason, as the engine speed NE increases, the fuel injection ratio by the port injection valve 2 is increased to further promote the mixing of fuel and air.

The injection ratio determination unit 24 gives the engine speed NE to the in-cylinder injection ratio map 55 stored in the storage unit 10m, determines the in-cylinder injection ratio K _di at the engine speed NE, and obtains this. (Step S301). Then, the fuel injection amounts from the port injection valve 2 and the in-cylinder injection valve 3 are determined as follows (step S302).
Fuel injection amount TAUp = (1-K _di ) × TAU by the port injection valve 2
Fuel injection amount by cylinder injection valve 3 TAU _di = K _di × TAU
Here, TAU is the total fuel injection amount determined by the load of the internal combustion engine 1, the engine speed NE, and the like.

As shown in FIG. 12, the in-cylinder injection ratio map 55 according to this embodiment changes the in-cylinder injection ratio K _di from 80% to 20% as the engine speed NE increases. Thus, when fuel F is injected from both the port injection valve 2 and the in-cylinder injection valve 3, the fuel injection amount by the in-cylinder injection valve 3 is 80% of the total fuel injection amount TAU as the engine speed NE increases. To 20%. Further, the fuel injection amount by the port injection valve 2 changes from 20% to 80% of the total fuel injection amount as the engine speed NE increases. The in-cylinder injection ratio map 55 is an example, and the amount of change in the in-cylinder injection ratio K _di is not limited to this. Further, the in-cylinder injection ratio K _di may be changed not by the engine speed NE but by the engine load (charging efficiency) KE.

Further, the in-cylinder injection ratio K _di may be determined so as to decrease as the engine speed NE increases. Therefore, the relationship between the in-cylinder injection ratio K _di and the engine speed NE may be not only linear as shown by the solid line in FIG. 12 but also non-linear as shown by the dotted line in the in-cylinder injection ratio map 55. The in-cylinder injection ratio map 55 can be created by experiment or numerical simulation.

  When the fuel injection amounts from the port injection valve 2 and the in-cylinder injection valve 3 are determined as described above, the injection ratio determination procedure ends. The port injection valve 2 and the in-cylinder injection valve 3 inject fuel into the intake passage 4 and the cylinder 1s, respectively, at the determined fuel injection ratio and fuel injection timing (step S107). Note that the injection timing of the port injection valve 2 may be the intake stroke of the internal combustion engine 1. Here, when there is an overlap between the timing at which the intake valve 58 is opened and the timing at which the exhaust valve 59 is closed, the exhaust valve 59 is closed to prevent the fuel injected by the port injection valve 2 from blowing into the exhaust passage 9. It is preferable to inject the fuel by the port injection valve 2.

Here, in step S109, when the injection determination unit 22 determines that the fuel F is injected only by the in-cylinder injection valve 3, the injection ratio determination unit 24 sets the in-cylinder injection ratio K _di to 1.0 and sets the total fuel. Is injected from the in-cylinder injection valve 3 into the cylinder 1s. In step S110, when the injection determination unit 22 determines that the fuel F is to be injected only by the port injection valve 2, the injection ratio determination unit 24 sets the in-cylinder injection ratio K _di to 0 and all the fuel is port injection valves. 2 is controlled to be injected into the intake passage 4.

Next, the control result when the control of the internal combustion engine is executed by the control device and control method for the internal combustion engine according to the embodiment of the present invention will be described. FIG. 13 is an explanatory diagram showing the relationship between the engine speed and torque of the internal combustion engine. When the internal combustion engine control method according to the present invention is executed by the control apparatus for an internal combustion engine according to the present invention, both the port injection valve 2 and the in-cylinder injection valve 3 are in the region where the engine speed NE is NE1 or higher. Fuel was injected. Further, as the engine speed NE increases from NE1 to NE2, the in-cylinder injection ratio K _di is changed from 80% to 20%, whereby the fuel injection amounts of the port injection valve 2 and the in-cylinder injection valve 3 are changed. Controlled. The control result is expressed as a change in the torque of the internal combustion engine 1 with respect to the engine speed NE. As a comparison object, the case of only the in-cylinder injection valve 3 (shown by a dotted line in FIG. 13) and the case of only the port injection valve 2 (shown by an alternate long and short dash line in FIG. 13) are shown. Note that both are homogeneous combustion regions.

  As shown in FIG. 13, when the operation of the internal combustion engine is controlled according to the present invention, fuel is injected only by the port injection valve 2 or the in-cylinder injection valve 3 when the engine speed NE is in the range of NE1 to NE2. It can be seen that the torque of the internal combustion engine 1 is improved substantially over the entire range as compared with the case. Thus, according to the present invention, in the homogeneous combustion region, the fuel is injected by the port injection and the in-cylinder injection, and the timing of the port injection is changed according to the engine speed NE. Compared with the case of injection only, the torque can be improved.

  As described above, in the present invention, in the homogeneous combustion region where both the in-cylinder injection valve and the port injection valve are used, in-cylinder injection is performed on the intake bottom dead center side when the engine speed is low. When the rotational speed is high, in-cylinder injection is performed on the intake top dead center side. As a result, air cooling is effectively used to improve the charging efficiency in the range where the engine speed is low, and in the range where the engine speed is high, the mixing of fuel and air is promoted efficiently, so that the fuel and air Can be effectively homogenized. As a result, it is possible to improve the torque in the homogeneous combustion region where both the in-cylinder injection valve and the port injection valve are used.

  In addition, in addition to in-cylinder injection, the engine speed is such that the torque peak when in-cylinder injection on the intake top dead center side continues to be greater than the torque peak when in-cylinder injection on the intake bottom dead center side continues. Add port injection. Thereby, the air cooling effect by in-cylinder injection and the mixing promotion effect of fuel and air by port injection can both be made effective effectively. As a result, the torque of the internal combustion engine in the homogeneous combustion region can be improved as compared with the case of in-cylinder injection or port injection alone.

  Further, in the homogeneous combustion region where both the in-cylinder injection port and the port injection valve are used and the engine speed is other than low and high, the vicinity of the intake bottom dead center and the intake top dead center In-cylinder injection is performed from the in-cylinder injection valve in two steps with the vicinity. Thereby, torque can be improved, and torque fluctuations that occur when the fuel injection timing from the in-cylinder injection valve is switched can be smoothed.

  Further, in the homogeneous combustion region where both the in-cylinder injection valve and the port injection valve are used, the fuel injection ratio by the in-cylinder injection valve is reduced as the engine speed increases. Thus, in order to increase the torque, in a region where it is more effective to promote the mixing of fuel and air, that is, in a region where the engine speed is high, the fuel injection rate by the port injection valve is increased to increase the fuel. The torque of the internal combustion engine can be improved by promoting the mixing with air.

  As described above, the control device and control method for an internal combustion engine according to the present invention are suitable for an internal combustion engine including a port injection valve and a cylinder injection valve, and are suitable for improving the torque of the internal combustion engine in a homogeneous combustion region. Yes.

It is a conceptual diagram which shows an example in the case of controlling an internal combustion engine with the control apparatus of the internal combustion engine which concerns on the Example of this invention. It is explanatory drawing which shows the relationship between the fuel injection timing in the case of injecting a fuel directly in a cylinder, and a torque. It is explanatory drawing which shows the state which injected the fuel in the cylinder in the vicinity of an intake top dead center. It is explanatory drawing which shows the state which injected the fuel in the cylinder in the vicinity of an intake bottom dead center. It is explanatory drawing which shows the relationship between the injection valve used for fuel injection, and an engine speed. It is explanatory drawing which shows the injection timing of the cylinder injection valve in the area | region which uses both a cylinder injection valve and a port injection valve. It is a conceptual diagram explaining the intake top dead center side and the intake bottom dead center side. It is explanatory drawing which shows the structure of the control apparatus of the internal combustion engine which concerns on the Example of this invention. It is a flowchart which shows the control procedure of the control method of the internal combustion engine which concerns on the Example of this invention. It is a flowchart which shows the procedure which determines the injection timing by the cylinder injection valve in the control method of the internal combustion engine which concerns on the Example of this invention. It is explanatory drawing which shows the fuel injection timing map of a cylinder injection valve. It is explanatory drawing which shows the fuel injection timing map of a cylinder injection valve. It is explanatory drawing which shows the fuel injection ratio determination map which described the relationship of the fuel injection ratio determination coefficient with respect to engine speed. It is a flowchart explaining the determination procedure of a cylinder injection ratio and a port injection ratio. It is explanatory drawing which shows the cylinder injection ratio map which described the cylinder injection ratio. It is explanatory drawing which showed the relationship between the engine speed of an internal combustion engine, and a torque.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 1s Cylinder 2 Port injection valve 3 In-cylinder injection valve 4 Intake passage 5 Piston 9 Exhaust passage 10 Control apparatus of an internal combustion engine 10m Memory | storage part 10p Processing part 21 Combustion determination part 22 Injection determination part 23 Injection ratio determination part 23 In-cylinder Injection timing determination unit 24 Injection ratio determination unit 58 Intake valve 59 Exhaust valve

Claims (8)

Control an internal combustion engine having a port injection valve and a cylinder injection valve,
A combustion determination unit that determines whether or not the internal combustion engine is operated in a homogeneous combustion region;
The internal combustion engine is operated in a homogeneous combustion region, and the engine speed of the internal combustion engine is such that the torque peak of the internal combustion engine due to fuel injection of the in-cylinder injection valve on the intake top dead center side When the engine speed exceeds a torque peak of the internal combustion engine due to fuel injection of the cylinder injection valve on the dead center side, both the port injection valve and the cylinder injection valve An injection determination unit that determines that the injection condition for injecting fuel from
When it is determined that the injection condition is satisfied, the fuel injection timing by the in-cylinder injection valve is set to the intake bottom dead center side in the range where the engine speed in the predetermined speed range is low, and the engine speed in the predetermined range. In-cylinder injection timing determination unit for injecting fuel from the in-cylinder injection valve, with the fuel injection timing by the in-cylinder injection valve as the intake top dead center side in the range of high rotation,
A control apparatus for an internal combustion engine, comprising: The in-cylinder injection timing determination unit
2. The fuel injection timing by the in-cylinder injection valve is advanced to the intake top dead center side of the internal combustion engine as the engine speed increases in the predetermined speed range. Control device for internal combustion engine. The in-cylinder injection timing determination unit
In the predetermined rotational speed range, when the rotational speed range is intermediate between the low rotational speed range and the high rotational speed range, the cylinder is formed between the intake top dead center side and the intake bottom dead center side of the internal combustion engine. 3. The control device for an internal combustion engine according to claim 1, wherein fuel is injected into the internal injection valve. The fuel injection system according to claim 1, further comprising: an injection ratio determining unit that changes a fuel injection ratio by the in-cylinder injection valve on an intake top dead center side and an intake bottom dead center side of the internal combustion engine according to an engine speed. Item 4. The control device for an internal combustion engine according to Item 3 . The injection ratio determination unit
5. The control apparatus for an internal combustion engine according to claim 4, wherein an injection ratio between the port injection valve and the in-cylinder injection valve is changed according to the engine speed or a load of the internal combustion engine. In controlling an internal combustion engine provided with a port injection valve and a cylinder injection valve,
Determining whether the internal combustion engine is operated in a homogeneous combustion region;
The internal combustion engine is operated in a homogeneous combustion region, and the engine rotation speed of the internal combustion engine is such that the torque peak of the internal combustion engine due to fuel injection of the in-cylinder injection valve on the intake top dead center side is on the intake bottom dead center side. When the engine speed exceeds a torque peak of the internal combustion engine due to fuel injection from the in-cylinder injection valve, fuel is injected from both the port injection valve and the in-cylinder injection valve. A procedure for determining that the injection condition is
When the engine speed in the predetermined speed range is low, the fuel injection timing by the in-cylinder injection valve is determined to the intake bottom dead center side, and in the range where the engine speed in the predetermined range is high, the fuel injection timing is determined. A procedure for determining the fuel injection timing by the in-cylinder injection valve to the intake top dead center side;
A control method for an internal combustion engine comprising: In controlling an internal combustion engine provided with a port injection valve and a cylinder injection valve,
Determining whether the internal combustion engine is operated in a homogeneous combustion region;
Injection in which fuel is injected from both the port injection valve and the in-cylinder injection valve when the internal combustion engine is operated in a homogeneous combustion region and the engine rotation speed of the internal combustion engine is within a predetermined rotation speed range. A procedure for determining that the condition is satisfied;
When the engine speed in the predetermined speed range is low, the fuel injection timing by the in-cylinder injection valve is determined to the intake bottom dead center side, and in the range where the engine speed in the predetermined range is high, the fuel injection timing is determined. A procedure for determining the fuel injection timing by the in-cylinder injection valve to the intake top dead center side;
And the intake top dead center side and the intake bottom dead center side of the internal combustion engine when the predetermined rotational speed range is an intermediate rotational speed range between the low rotational speed range and the high rotational speed range A method for controlling an internal combustion engine, wherein fuel is injected into the in-cylinder injection valve.   8. The control method for an internal combustion engine according to claim 7, wherein an injection ratio between the port injection valve and the in-cylinder injection valve is changed in accordance with the engine speed or a load on the internal combustion engine.

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