Control device for internal combustion engines

Abstract

The objective is to provide a control device for an internal combustion engine that can suppress the deterioration of combustion. [Solution] A control device for an internal combustion engine comprising: a first control unit that controls a first fuel injector that injects fuel into a cylinder of an internal combustion engine; and a second control unit that controls a second fuel injector that injects fuel into an intake manifold, wherein the first control unit determines the required injection amount when performing multi-injection including partial lift injection from the first fuel injector, and if the required injection amount is greater than a predetermined amount, at least one of the following is performed: the first control unit performs a control to cause the first fuel injector to perform fuel injection, and the second control unit performs a control to cause the second fuel injector to perform fuel injection; and if the required injection amount is less than or equal to the predetermined amount, the first control unit causes the first fuel injector to perform multi-injection including partial lift injection.

Description

Technical Field

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[0001] The present invention relates to a control device for an internal combustion engine.

Background Art

[0002] Fuel is injected into an internal combustion engine from a fuel injection valve. Techniques for controlling the lift amount of the fuel injection valve and performing full-lift injection and partial-lift injection are known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the required injection amount of fuel is greater than the supply amount of fuel from the fuel system, it is difficult to inject a sufficient amount of fuel. The rotational speed of the internal combustion engine decreases. In addition, due to the deterioration of combustion, a large amount of particulate matter (PM) is generated in the exhaust. Therefore, an object is to provide a control device for an internal combustion engine that can suppress the deterioration of combustion.

Means for Solving the Problems

[0005] The above objective can be achieved by a control device for an internal combustion engine comprising a first control unit that controls a first fuel injector that injects fuel into a cylinder of an internal combustion engine, and a second control unit that controls a second fuel injector that injects fuel into an intake manifold, wherein the first control unit determines the required injection amount when performing multi-injection including partial lift injection from the first fuel injector, and at least one of the following is performed: if the required injection amount is greater than a predetermined amount, the first control unit causes the first fuel injector to perform fuel injection, and the second control unit causes the second fuel injector to perform fuel injection; and if the required injection amount is less than or equal to the predetermined amount, the first control unit causes the first fuel injector to perform multi-injection including partial lift injection.

[0006] The first fuel injector is supplied with fuel from the first fuel system, and the second fuel injector is supplied with fuel from the second fuel system. The fuel pressure in the first fuel system may be higher than the fuel pressure in the second fuel system.

[0007] The first fuel system includes a pump, and if the requested injection amount is greater than the discharge amount of the pump, the second control unit may cause injection from the second fuel injection valve.

[0008] The first control unit may determine the required injection amount based on the temperature of the cooling water of the internal combustion engine, the intake air volume of the internal combustion engine, or the alcohol concentration of the fuel of the internal combustion engine. [Effects of the Invention]

[0009] This invention provides a control device for an internal combustion engine that can suppress the deterioration of combustion. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram illustrating an internal combustion engine. [Figure 2] Figure 2 is a flowchart illustrating the process in the embodiment. [Modes for carrying out the invention]

[0011] The control device for the internal combustion engine of this embodiment will be described below with reference to the drawings. Figure 1 is a schematic diagram illustrating an internal combustion engine 10, showing one cylinder. The internal combustion engine 10 burns fuel to produce power. The fuel is, for example, gasoline or alcohol. The internal combustion engine 10 has a cylinder head 30 and a cylinder block 32. The cylinder head 30 is mounted on top of the cylinder block 32. A piston 33 is housed in the cylinder block 32. In each cylinder, the combustion chamber 34 is partitioned by the piston 33, the cylinder block 32 and the cylinder head 30.

[0012] The cylinder head 30 is equipped with a fuel injector 22 (first fuel injector), an intake valve 25, an exhaust valve 26, and a spark plug 27. The fuel injector 22 is a direct injection injector that injects fuel directly into the cylinder. An intake pipe 12 and an exhaust pipe 14 are connected to the cylinder head 30.

[0013] The intake manifold 12 is equipped with, in order from upstream, an air cleaner 15, an airflow meter 16, a throttle valve 18, and a fuel injector 24 (second fuel injector). The fuel injector 24 is a port injection injector that injects fuel into the intake manifold 12.

[0014] The air cleaner 15 removes dust and debris from the air. The airflow meter 16 detects the airflow rate. The throttle valve 18 regulates the airflow rate. The larger the opening of the throttle valve 18, the greater the airflow rate. The smaller the opening, the greater the airflow rate.

[0015] When the intake valve 25 opens, air flows from the intake manifold 12 into the combustion chamber 34. Fuel injected from the fuel injector 22 or 24 is also introduced into the combustion chamber 34. The air and fuel form a mixture. The spark plug 27 ignites the mixture. The combustion of the mixture generates driving force.

[0016] The exhaust gas generated by combustion is discharged into the exhaust pipe 14 when the exhaust valve 26 opens. The catalyst 20 provided in the exhaust pipe 14 purifies PM, carbon monoxide (CO), unburned fuel (HC), nitrogen oxides (NOx), etc. in the exhaust gas.

[0017] The temperature sensor 52 detects the temperature of the cooling water or the outside air of the internal combustion engine 10. The rotation speed sensor 54 detects the rotation speed of the internal combustion engine 10.

[0018] A fuel tank 40, a fuel system 47 (first fuel system) and a fuel system 48 (second fuel system) are provided. The fuel is stored in the fuel tank 40. The fuel system 48 includes a fuel passage 42 and a fuel pipe 46. The fuel system 47 includes a fuel passage 43, a high-pressure pump 44 and a fuel pipe 45.

[0019] A feed pump 41 is provided in the fuel tank 40. The feed pump 41 pumps up fuel from the fuel tank 40 and supplies it to the fuel passages 42 and 43. The fuel passage 42 is connected to the fuel pipe 46. The fuel pipe 46 is connected to the fuel injection valve 24 of each cylinder. The fuel passes through the fuel passage 42 and the fuel pipe 46 and is supplied to the fuel injection valve 24.

[0020] The fuel passage 43 branches from the fuel passage 42 and is connected to the fuel pipe 45. The fuel pipe 45 is connected to the fuel injection valve 22 of each cylinder. A high-pressure pump 44 is provided in the fuel passage 43. The fuel is pressurized by the high-pressure pump 44, flows through the fuel passage 43 and the fuel pipe 45, and is supplied to the fuel injection valve 2,

[0021] The ECU (Electronic Control Unit) 50 is a control device for the internal combustion engine 10, and includes an arithmetic device such as a CPU (Central Processing Unit), and a storage device such as a ROM (Read Only Memory) and a RAM (Random Access Memory).

[0022] The ECU 50 controls the opening degree of the throttle valve 18 and controls the valve timing of the intake valve 25 and the exhaust valve 26. The ECU 50 acquires the air flow rate detected by the air flow meter 16. The ECU 50 acquires the temperature detected by the temperature sensor 52. The ECU 50 acquires the rotational speed detected by the rotational speed sensor 54. The ECU 50 controls the feed pump 41 and the high-pressure pump 44 and adjusts the fuel discharge amount in these pumps.

[0023] The ECU 50 functions as a first control unit that controls the fuel injection valve 22 and functions as a second control unit that controls the fuel injection valve 24. The ECU 50 controls the injection timing, the number of injections, and the injection amount of the fuel injection valves 22 and 24. The ECU 50 can execute both direct injection using the fuel injection valve 22 and port injection using the fuel injection valve 24, and can also perform only one of these.

[0024] A needle is provided in the housing of the fuel injection valve. The ECU 50 energizes the fuel injection valve and controls the lift amount of the needle. If the lift amount of the needle is zero, the fuel injection valve is closed. When the needle lifts, the fuel injection valve opens. When the lift amount is maximum (100%), the fuel injection valve is fully open. The fuel injection performed at full open is described as full-lift injection. The injection performed in a state where the lift amount is greater than zero and less than the maximum lift amount is described as partial-lift injection.

[0025] In one injection cycle, injecting the required fuel injection amount at once is called single injection. In one injection cycle, dividing and injecting the required fuel injection amount is called multi-injection.

[0026] A multi-injection that includes a partial-lift injection is called a partial-lift multi-injection. A multi-injection includes multiple injections. If at least one of the multiple injections is a partial-lift injection, the multi-injection is a partial-lift multi-injection. All of the multiple injections may be partial-lift injections. If all of the multiple injections are full-lift injections, the multi-injection is not a partial-lift multi-injection. The fuel injector 22 may perform single injections and multi-injections, and may also perform full-lift injections, partial injections, and partial-lift multi-injections. The fuel injector 24 performs full-lift injections.

[0027] The ECU 50 determines the required fuel injection amount based on temperature, rotational speed, and airflow rate. For example, during cold starts or when the load on the internal combustion engine 10 increases, it wants to increase the fuel injection amount and raise the rotational speed of the internal combustion engine 10. When cold, fuel is difficult to vaporize. The ECU 50 performs partial lift injection from the fuel injector 22. Fuel injected by partial lift injection vaporizes easily. Therefore, it burns easily and leaves little unburned residue.

[0028] The amount of fuel injected from the fuel injector 22 is limited by the amount of fuel supplied to the fuel injector 22. If the target injection amount is greater than the discharge amount of the high-pressure pump 44, the fuel pressure cannot keep up with the target fuel pressure, resulting in poor combustion. In this embodiment, direct injection and port injection are used to suppress the deterioration of combustion.

[0029] Figure 2 is a flowchart illustrating the process in the embodiment. The ECU 50 determines whether the execution conditions for partial lift multi-injection are met (step S10). The execution conditions include, for example, the water temperature being lower than a predetermined temperature, the airflow rate being drawn in being greater than a predetermined amount, the alcohol concentration of the fuel being higher than a predetermined value, or two or more of these being met. If the determination is negative (No), the process ends.

[0030] If the result in step S10 is affirmative (Yes), the ECU 50 determines the required injection amount Fd for partial lift multi-injection and determines whether the required injection amount Fd exceeds the discharge amount Ph of the high-pressure pump 44 (step S12). If the result is affirmative, the ECU 50 prohibits partial lift multi-injection and performs basic injection control (step S14). Basic injection control may consist of direct injection only, port injection only, or both direct injection and port injection. Direct injection in basic injection control may consist of single injection or multi-injection, and may include either full-lift injection or partial lift injection. Port injection is, for example, a full-lift single injection. If the result in step S12 is negative, the ECU 50 performs partial lift multi-injection and does not perform port injection (step S16). After step S14 or S16, the process ends.

[0031] According to this embodiment, the ECU 50 controls the fuel injector 22 for direct injection and the fuel injector 24 for port injection. The ECU 50 can perform partial lift multi-injection from the fuel injector 22. If the required injection amount Fd for partial lift multi-injection is greater than a predetermined amount Ph, the ECU 50 performs basic injection control (step S14). The basic injection control includes at least one of the control to perform direct injection and the control to perform port injection. That is, only direct injection may be performed, only port injection may be performed, or both direct injection and port injection may be performed. Deterioration of combustion can be suppressed. PM generation is less likely, and the rotational speed of the internal combustion engine 10 is less likely to decrease.

[0032] In basic injection control, direct injection may be either single injection or multi-injection, and may include either full-lift injection or partial-lift injection. The injection volume of direct injection is less than or equal to the discharge volume Ph of the high-pressure pump 44. Port injection can also be performed. Combustion is less likely to deteriorate because fuel is supplied according to conditions such as water temperature and intake air volume.

[0033] If the required injection amount Fd for partial lift multi-injection is less than or equal to a predetermined amount Ph, partial lift multi-injection is performed (step S16). The fuel vaporizes more easily, and combustion is improved. PM generation is suppressed, and the rotational speed of the internal combustion engine 10 does not decrease easily.

[0034] Fuel system 47 is a higher-pressure fuel system than fuel system 48 and supplies fuel to fuel injector 22. Fuel system 48 is a lower-pressure system than fuel system 47 and supplies fuel to fuel injector 24. Fuel system 47 for direct injection and fuel system 48 for port injection are separate systems. Therefore, the fuel supply to fuel injector 22 and the fuel supply to fuel injector 24 can be controlled independently. ECU 50 may perform partial lift multi-injection using fuel injector 22 and not use fuel injector 24 (step S16). ECU 50 can also use both fuel injector 22 and fuel injector 24 in basic injection control (step S14).

[0035] The fuel system 47 includes a high-pressure pump 44. Fuel discharged from the high-pressure pump 44 is supplied to the fuel injector 22 through the fuel system 47. If the required injection amount Fd for partial-lift multi-injection is greater than the discharge amount Ph of the high-pressure pump 44, the fuel pressure cannot keep up with the target, and combustion deteriorates. According to this embodiment, the ECU 50 performs basic injection control (step S14). Not only direct injection but also port injection is possible. Since both fuel injectors 22 and 24 are used, the system is less subject to the limitation of the discharge amount Ph of the high-pressure pump 44. Combustion deterioration can be suppressed.

[0036] The ECU 50 determines whether to perform partial lift multi-injection based on water temperature, intake air volume, and fuel alcohol concentration (step S10), and sets the required injection amount Fd. The lower the water temperature, the higher the intake air volume, and the higher the alcohol concentration, the more the ECU 50 increases the required injection amount Fd. If the required injection amount Fd exceeds the discharge amount Ph of the high-pressure pump 44, partial lift multi-injection becomes difficult. The ECU 50 supplies fuel according to the conditions by performing basic injection control.

[0037] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0038] 10 Internal combustion engine, 12 Intake pipe, 14 Exhaust pipe, 15 Air cleaner, 16 Airflow meter, 18 Throttle valve, 20 Catalytic converter, 22, 24 Fuel injectors, 25 Intake valve, 26 Exhaust valve, 27 Spark plug, 30 Cylinder head, 32 Cylinder block, 33 Piston, 34 Combustion chamber, 40 Fuel tank, 41 Feed pump, 42, 43 Fuel passages, 44 High-pressure pump, 45, 46 Fuel piping, 47, 48 Fuel system, 50 ECU, 52 Temperature sensor, 54 Rotation speed sensor

Claims

1. A first control unit that controls a first fuel injection valve that injects fuel into the cylinders of an internal combustion engine, It comprises a second control unit that controls a second fuel injection valve that injects fuel into the intake manifold, The first control unit determines the required injection amount when performing multi-injection including partial lift injection from the first fuel injection valve. If the requested injection amount is greater than a predetermined amount, at least one of the following is performed: the first control unit performs a control to inject fuel from the first fuel injector, and the second control unit performs a control to inject fuel from the second fuel injector. When the requested injection amount is less than or equal to the predetermined amount, the first control unit causes the first fuel injector to perform multi-injection including the partial lift injection. This is a control device for an internal combustion engine.

2. Fuel is supplied to the first fuel injector from the first fuel system. The second fuel injector is supplied with fuel from the second fuel system. The control device for an internal combustion engine according to claim 1, wherein the fuel pressure in the first fuel system is higher than the fuel pressure in the second fuel system.

3. The first fuel system has a pump, The control device for an internal combustion engine according to claim 2, wherein if the requested injection amount is greater than the discharge amount of the pump, the second control unit causes the second fuel injection valve to perform injection.

4. The control device for an internal combustion engine according to claim 1 or 2, wherein the first control unit determines the required injection amount based on the temperature of the cooling water of the internal combustion engine, the intake amount of the internal combustion engine, or the alcohol concentration of the fuel of the internal combustion engine.

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