JP2008255950A - Cylinder-injection type spark-ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder-injection type spark-ignition internal combustion engine in which a spray pattern is suitably changed according to the change of the rotational speed of the engine. <P>SOLUTION: This cylinder-injection type spark-ignition internal combustion engine 1 in which a fuel is jetted directly into a cylinder 4 comprises: a first fuel injection valve 21 for so spraying the fuel that the penetration force is high and the degree of atomization is high; and a second fuel injection valve 23 for so spraying the fuel that the penetration force is low and the degree of atomization is high. The first fuel injection valve and the second injection valve are so arranged that their fuel sprays are close and generally parallel to each other. The internal combustion engine further comprises a control means 10 for controlling the fuel injection. After the first fuel injection valve 21 performs the fuel injection when the internal combustion engine is in the low speed operating range, the second second fuel injection valve 23 performs the fuel injection for increasing the performance of the internal combustion engine. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a spark ignition internal combustion engine of a type in which fuel is directly injected into a cylinder, and more particularly, to a cylinder injection type spark ignition internal combustion engine capable of changing the fuel spray to a suitable one according to the operating state of the internal combustion engine. About.

  2. Description of the Related Art An in-cylinder injection type (direct injection type) spark ignition internal combustion engine that obtains an output by directly injecting and igniting fuel into a cylinder is widely known. With regard to this type of internal combustion engine, various techniques have been proposed for improving combustion and exhaust emission by forming a vortex flow such as a tumble flow in a cylinder. When an appropriate tumble flow is formed in the cylinder, the homogeneity of the air-fuel mixture can be improved at the ignition timing, and the combustion speed is improved, so that good combustion can be realized. In addition, since the exhaust emission can be improved, the performance of the internal combustion engine can be improved.

  Therefore, for example, as in the internal combustion engine disclosed in Patent Document 1, an intake control valve is provided in the intake passage, and the tumble flow formed in the cylinder is reinforced by adjusting the intake flow by opening and closing the control valve. and so on. Conventionally, many techniques for providing an intake control valve in this way have been studied.

JP 2005-180247 A

  However, the configuration of the internal combustion engine of Patent Document 1 is complicated because it is necessary to provide an intake control valve for reinforcing the tumble flow in the intake passage to control opening and closing. In this regard, in the case of a direct injection type internal combustion engine that directly injects fuel into the cylinder, an air flow is formed in the cylinder with the fuel injected from the fuel injection valve, or the tumble flow formed in the cylinder is reinforced. can do. By adopting such a method, a tumble flow can be formed or strengthened more easily. Here, in order to obtain a strong tumble flow with the fuel to be injected, the fuel injection injection form from the fuel injection valve is preferably a fuel spray with a strong penetration force (Penetration).

  However, since the rotational speed of the internal combustion engine changes depending on the load, the state of the airflow formed in the cylinder also changes. When the internal combustion engine is in a low-rotation operation region and fuel spray having a strong penetration force and a large particle size is executed, the homogeneity of the air-fuel mixture may deteriorate and the performance of the internal combustion engine may deteriorate. Although the tumble flow that is the vertical vortex is described above, the same applies to the case of the swirl that is the horizontal vortex in the cylinder.

  Accordingly, an object of the present invention is to provide a direct injection spark ignition internal combustion engine that can change the spray form to a suitable one in response to a change in the rotational speed of the internal combustion engine.

  The above object is an in-cylinder spark-ignition internal combustion engine that directly injects fuel into a cylinder, and includes a first fuel injection valve that performs fuel spray with a high penetration force and a low atomization degree, A second fuel injection valve that performs weak and high atomization fuel spraying, and the first fuel injection valve and the second fuel injection valve are arranged so that the fuel sprays are close to each other and substantially parallel to each other. This can be achieved by a direct injection spark ignition internal combustion engine characterized in that it is arranged.

  According to the present invention, the first fuel injection valve and the second fuel injection valve having different fuel spray modes are provided, and the fuel sprays are arranged so as to be close to each other and substantially in parallel. An optimal fuel spray can be formed by selecting a suitable fuel injection valve according to the state. Therefore, it is possible to improve the performance of the internal combustion engine by responding to a change in the rotational speed of the internal combustion engine and forming a spray form suitable at that time.

  In addition, the first fuel injection valve and the second fuel injection valve are configured such that the direction of fuel injection is set in a direction along the vortex airflow formed in the cylinder when the intake valve is opened. It may be. Thereby, the performance improvement of an internal combustion engine can be aimed at by strengthening the eddy current formed when an intake valve is opened. The vortex airflow can include a tumble flow and a swirl flow. And control means for controlling fuel injection of the first fuel injection valve and the second fuel injection valve, the control means being in the vicinity of the bottom dead center when the intake valve is open or in the intake stroke. The fuel injection of the first fuel injection valve may be executed.

  In addition, a control unit that controls fuel injection of the first fuel injection valve and the second fuel injection valve is provided, and the control unit is configured to control the first fuel when the internal combustion engine is in a low-rotation operation region. After the fuel injection of the injection valve is executed, the fuel injection of the second fuel injection valve may be executed. In this case, it is possible to improve the performance of the internal combustion engine by forming an optimal fuel spray when the internal combustion engine is operating at a low speed.

  In addition, a control unit that controls fuel injection of the first fuel injection valve and the second fuel injection valve is provided, and the control unit is configured to control the second fuel when the internal combustion engine is in a high speed operation region. You may make it perform only the fuel injection of an injection valve. In this case, when the internal combustion engine is operating at a high speed, an optimal fuel spray can be formed to improve performance.

  In addition, a control unit that controls fuel injection of the first fuel injection valve and the second fuel injection valve is provided, and the control unit is configured to delay the ignition timing in order to raise the catalyst temperature. Only the fuel injection of the fuel injection valve may be executed. In this case, it is possible to provide a better internal combustion engine that can quickly warm up the exhaust purification catalyst device when the internal combustion engine is started.

  According to the present invention, it is possible to provide an in-cylinder injection spark ignition internal combustion engine that can change the spray form to a suitable one in response to a change in the rotational speed of the internal combustion engine.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an in-cylinder spark ignition internal combustion engine (hereinafter simply referred to as an engine) according to an embodiment. The engine 1 is entirely controlled by an ECU (Electronic Control Unit) 10. And this ECU10 functions also as a control means which confirms the rotation speed of the engine 1 and changes it into a preferable fuel spray. The ECU 10 will be described in detail later.

  The engine 1 is arranged so that a piston 3 moves up and down in a cylinder 2 in the same manner as a general internal combustion engine. A space surrounded by the upper surface of the piston 3 and the inner wall of the cylinder 2 is an in-cylinder (combustion chamber) 4. An intake passage 5 for allowing the intake AR to flow into the cylinder 4 and an exhaust passage 6 for discharging the exhaust gas EG generated in the cylinder 4 are provided. An exhaust purification catalyst device 30 that purifies the exhaust gas EG is disposed in the middle of the exhaust passage 6.

  An intake valve 7 for adjusting the intake air AR flowing into the cylinder 4 is provided in the intake passage 5. A camshaft 8 for setting the lift amount of the intake valve 7 is disposed on the upper portion of the intake valve 7. A cam angle sensor 9 that detects the rotation of the camshaft 8 is provided. The output of the cam angle sensor 9 is supplied to the ECU 10. Similarly, an exhaust valve 12 for adjusting the discharge timing of the exhaust gas EG generated in the cylinder 4 is provided in the exhaust passage 6. The exhaust valve 12 is also provided with the same structure as the intake valve 7. That is, a camshaft 13 that sets the lift amount of the exhaust valve 12 is provided. A cam angle sensor 14 that detects the rotation of the camshaft 13 is provided. The output of the cam angle sensor 14 is also supplied to the ECU 10.

  Furthermore, a crank sensor 16 is provided for detecting the position of the crankshaft 15 that rotates as the piston 3 moves up and down. The output of the crank sensor 16 is also supplied to the ECU 10. Therefore, the ECU 10 can confirm whether the engine 1 is in a low-rotation or high-rotation operation region.

  The engine 1 has a plurality (two in FIG. 1) of fuel injection valves (injectors) 21 and 23 arranged in parallel on the side of the cylinder. These fuel injection valves 21 and 23 are installed such that an injection hole formed at the tip faces the inside 4 of the cylinder. The first fuel injection valve 21 disposed on the lower side is designed to form a fuel spray having a strong penetration force and a low atomization degree. On the contrary, the second fuel injection valve 23 arranged on the upper side is designed to form a fuel spray having a low penetration force and a high atomization degree.

  The first fuel injection valve 21 and the second fuel injection valve 23 are formed while the respective fuel injection directions SP1 and SP2 are set in directions along the tumble flow formed in the cylinder. Fuel sprays are set close to each other and substantially in parallel. Here, the fuel injection directions SP1, SP2 are axial directions of the spray center of the fuel injected from the injection holes of the fuel injection valves 21, 23.

  Since the fuel injected from the first fuel injection valve 21 has a strong penetration force, a tumble flow TS can be formed in the cylinder 4 by its own fuel injection. Here, as described above, the fuel injection direction SP1 of the first fuel injection valve 21 is set along the direction of the tumble flow formed when the intake valve 7 is opened. You can also. However, the fuel injected from the first fuel injection valve 21 is a fuel spray with a low atomization degree. In this case, since the particle size of the sprayed fuel becomes relatively large, there is a demerit that the evaporation rate is slow. Therefore, the first fuel injection valve 21 is an unsuitable fuel injection valve when the engine 1 is operated at a high speed.

  On the other hand, the fuel injected from the second fuel injection valve 23 has a low penetrating force, and the injected fuel is in the form of a mist having a small particle size. In the fuel injection by the second fuel injection valve 23, an air flow cannot be formed in the cylinder 4, and it is difficult to strengthen the tumble flow formed in the cylinder. Therefore, the second fuel injection valve 23 is an unsuitable fuel injection valve when the engine 1 is operated at a low speed and the airflow is weak. However, the fuel injected from the second fuel injection valve 23 has a merit that the atomization rate is high and the particle size of the fuel is relatively small, so that the evaporation rate is fast. When the engine 1 is operated at a high rotation speed, a strong tumble flow is formed in the cylinder 4 by the intake air flow, so that the second fuel injection valve 23 is a fuel injection valve suitable for use in the high rotation operation region. .

  As described above, the engine 1 is provided with the fuel injection valves 21 and 23 that form different fuel sprays. In this embodiment, the fuel injection valves 21 and 23 are selectively driven in accordance with the operating state of the engine 1, more specifically, the rotational speed of the engine 1, and a suitable fuel spray is formed in the cylinder at that time. . Control for this is executed by the ECU 10.

  Each part demonstrated above is controlled by ECU10. The ECU 10 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output circuit, and the like (not shown). The ROM stores a program in which various processes executed by the CPU are described, a series of data used in the program, and the like. In this embodiment, in addition to the control program for the engine 1, a program for checking the operation region of the engine 1 from the output of the crank sensor 16 and selectively driving the fuel injection valve for fuel injection based on this is stored. It is.

  FIG. 2 is a diagram showing a state of fuel injection control executed by the ECU 10. 2A shows a case where fuel is injected from the first fuel injection valve 21 to form the fuel spray FE-1, and FIG. 2B shows a case where fuel is injected from the second fuel injection valve 23 and fuel is sprayed. The case where FE-2 is formed is shown.

  The ECU 10 executes fuel injection control as follows. The ECU 10 confirms the rotational speed of the engine 1 from the output of the crank sensor 16. For example, the ECU 10 determines that the engine 1 is in the high-speed operation region when the output of the crank sensor 16 is a predetermined value greater than a predetermined number of revolutions (threshold value), and conversely, the crank sensor 16 Is determined in advance to be a value smaller than the predetermined rotation speed, it is determined that the engine 1 is in the low rotation operating region.

  When the ECU 10 determines that the engine 1 is in the low rotation operation region, the ECU 10 performs fuel injection in the order shown in FIGS. 2 (A) and 2 (B). When the engine 1 is in the low speed operation region, the air flow formed in the cylinder 4 is weak, but the tumble flow TS is formed by performing fuel injection from the first fuel injection valve 21 having a strong penetration force.

  In this embodiment, as a preferred structure, the fuel injection direction of the fuel injection valve 21 is set to a direction along the tumble flow TS formed by the intake flow AS that flows into the cylinder 4 when the intake valve 7 is opened. It is. Therefore, when the tumble flow TS is formed by the intake flow AS, the tumble flow TS can be strengthened by the fuel injection of the first fuel injection valve 21. Alternatively, the ECU 10 may be set to execute fuel injection from the first fuel injection valve 21 in the vicinity of the bottom dead center of the intake stroke so that the tumble flow TS is surely strengthened.

  As described above, when the engine 1 is in the low rotation operation region, the ECU 10 first drives the first fuel injection valve 21 to form the tumble flow TS in the cylinder 4. Thereafter, the ECU 10 performs fuel injection from the second fuel injection valve 23 having a low penetration force. The fuel spray of the second fuel injection valve 23 is mist-like and weak in penetrating force. However, since the fuel spray rides on the already formed tumble flow TS, the fuel diffuses smoothly in the cylinder 4. Executed. And since a fuel spray particle size is small, it can evaporate quickly and can form a homogeneous air-fuel mixture. Therefore, if the ignition plug 25 is ignited, the air-fuel mixture can be burned efficiently, so that the performance of the engine 1 can be improved.

  FIG. 3 is an example of a data table for switching the fuel injection valve based on the lift amount of the intake valve 7. The ECU 10 uses this data table when executing the fuel spray shown in FIG. In this data, the first fuel injection valve 21 and the second fuel injection valve 23 are switched before and after the maximum lift amount of the intake valve 7. The ECU 10 stores this data in the ROM, reads it appropriately, selects a fuel injection valve suitable at that time, and executes fuel injection.

  As described above, the engine 1 of the present embodiment has the first fuel injection valve 21 that performs fuel spray with a strong penetration force and a low atomization degree, and the first fuel injection valve 21 that performs a fuel atomization with a low penetration force and a high atomization degree. 2 fuel injection valves 23. Therefore, by selectively adopting the fuel injection valve according to the state of the engine 1, it is possible to form a fuel spray that is suitable at that time. Further, the first fuel injection valve 21 and the second fuel injection valve 23 are set such that the direction of fuel injection is along the tumble flow formed in the cylinder, and the fuel spray to be formed is They are set close to each other and substantially in parallel. Therefore, when the engine 1 is in the low speed operation region, a tumble flow is formed in the cylinder by the fuel injection of the first fuel injection valve 21, and then the fuel is injected from the second fuel injection valve 23 to be homogeneous in the cylinder. A mixture can be formed and ignited. By preceding the first spray from the first fuel injection valve 21 in this way, the time until ignition is secured and the homogenization of the air-fuel mixture is also improved. Therefore, the homogeneity of the air-fuel mixture can be ensured at the time of low rotation where it is difficult to form a tumble flow in the cylinder, and the performance of the engine 1 can be improved.

  The fuel injection control by the ECU 10 is not limited to when the engine 1 is in the low rotation operation region. The ECU 10 executes different fuel injection control when the engine 1 is in the high speed operation region. FIG. 4 is a diagram illustrating fuel injection performed by the ECU 10 when the engine 1 is in a high-speed operation region.

  When the ECU 10 confirms from the output of the crank sensor 16 that the engine 1 is in the high speed operation region, the fuel injection is performed only from the second fuel injection valve 23 as shown in FIG. Forms a weak and highly atomized fuel spray.

  When the engine 1 is in the high speed operation region, a tumble flow TS is continuously formed in the cylinder 4 by the intake flow that flows when the intake valve 7 is opened. Therefore, when the engine 1 is in the high-rotation operation region, it is not necessary to execute fuel injection by the first fuel injection valve 21 and form an auxiliary airflow unlike the low-speed operation described above. Therefore, the ECU 10 performs fuel injection only from the second fuel injection valve 23. When the engine 1 is in the high speed operation region, if fuel is injected only from the second fuel injection valve 23, the formed fuel spray has a high atomization degree, so that the fuel evaporates early and a homogeneous mixture can be formed. . Therefore, the engine 1 can be improved.

  FIG. 5 is a diagram showing an example of fuel injection control executed by the ECU 10 when the ignition timing of the engine 1 is significantly retarded. When the fuel is injected from the second fuel injection valve 23 that forms a fuel spray having a low penetration force and a high atomization degree when the ignition timing is greatly retarded, the fuel atomization having a high atomization degree is caused by the upward flow by the piston 3. A state of staying in the vicinity of the spark plug 25 can be formed. Therefore, when the engine is started, etc., this operation is executed to ignite the air-fuel mixture, so that the exhaust gas EG having a high temperature can flow and the downstream exhaust purification catalyst device 30 can be warmed up. Thus, the engine 1 of the embodiment can be provided as an improved engine that can not only strengthen the tumble flow but also warm up the purification catalyst device 30 as necessary.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed. For example, in the above-described embodiment, a case where two fuel injection valves are arranged in parallel in the vertical direction to form a tumble flow (vertical vortex flow) in the cylinder has been described, but the present invention is not limited to this. The fuel injection valves may be arranged in parallel in the cylinder circumferential direction to form a swirl flow (lateral vortex flow) in the cylinder.

It is a figure which shows the structure of the cylinder injection type engine which concerns on an Example. It is the figure which showed the mode of the fuel-injection control which ECU of an engine performs, (A) is a fuel injection from a 1st fuel-injection valve, (B) is a 2nd fuel-injection It is a figure showing the case where fuel injection is performed from a valve and fuel spray is formed. It is a figure which shows an example of the data table used when ECU performs the fuel spray shown in FIG. It is a figure which shows the case where ECU confirms that an engine is a driving | running | working area | region of high rotation, and fuel injection is formed by ECU. It is a figure which shows the example of the fuel-injection control which ECU performs when retarding the ignition timing of an engine significantly.

Explanation of symbols

1. Engine (in-cylinder injection spark ignition internal combustion engine)
4 In-cylinder 5 Intake passage 7 Intake valve 10 ECU (control means)
DESCRIPTION OF SYMBOLS 15 Crankshaft 16 Crank sensor 21 1st fuel injection valve 23 2nd fuel injection valve 30 Exhaust purification catalyst apparatus FE-1, FE-2 Fuel spray AR Intake TS Tumble flow (vortex air flow)
SP1, SP2 Fuel injection direction

Claims (6)

An in-cylinder spark ignition internal combustion engine that directly injects fuel into a cylinder,
A first fuel injection valve that performs fuel spray with a strong penetration force and a low atomization degree, and a second fuel injection valve that performs a fuel spray with a low penetration force and a high atomization degree,
The in-cylinder spark-ignition internal combustion engine, wherein the first fuel injection valve and the second fuel injection valve are arranged so that fuel sprays are close to each other and substantially in parallel. The first fuel injection valve and the second fuel injection valve are configured such that the direction of fuel injection is set in a direction along the vortex airflow formed in the cylinder when the intake valve is opened. The in-cylinder injection spark ignition internal combustion engine according to claim 1, Control means for controlling fuel injection of the first fuel injection valve and the second fuel injection valve;
3. The in-cylinder engine according to claim 2, wherein the control unit executes fuel injection of the first fuel injection valve when the intake valve is open or in the vicinity of a bottom dead center of an intake stroke. 4. Injection spark ignition internal combustion engine. Control means for controlling fuel injection of the first fuel injection valve and the second fuel injection valve;
The control means performs fuel injection of the second fuel injection valve after performing fuel injection of the first fuel injection valve when the internal combustion engine is in a low-rotation operation region. The in-cylinder injection spark ignition internal combustion engine according to claim 1 or 2. Control means for controlling fuel injection of the first fuel injection valve and the second fuel injection valve;
3. The in-cylinder injection spark according to claim 1, wherein the control means executes only fuel injection of the second fuel injection valve when the internal combustion engine is in a high speed operation region. 4. Ignition internal combustion engine. Control means for controlling fuel injection of the first fuel injection valve and the second fuel injection valve;
3. The in-cylinder injection according to claim 1, wherein the control unit executes only fuel injection of the second fuel injection valve when retarding the ignition timing to raise the catalyst temperature. 4. Type spark ignition internal combustion engine.

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