Control device for internal combustion engine

Abstract

The present invention addresses the problem of providing a control device for an internal combustion engine capable of stably controlling an injection mode. A control device for an internal combustion engine that controls an internal combustion engine having a first fuel injection valve that injects fuel into a cylinder of the internal combustion engine and a second fuel injection valve that injects fuel into an intake pipe, the control device being provided with: a first setting unit that determines a first fuel injection amount; a second setting unit that determines a threshold value of the fuel injection amount and a hysteresis width; and an injection control unit that switches the injection mode of the fuel between a first mode in which the fuel is injected from the first fuel injection valve and a second mode in which the fuel is injected from the second fuel injection valve.

Description

Technical Field

[0001] This invention relates to a control device for an internal combustion engine. Background Technology

[0002] Fuel is injected into the internal combustion engine from the fuel injection valve. Techniques are known to control the lift of the fuel injection valve and to perform full-lift injection and partial-lift injection (Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2016-008569 Summary of the Invention

[0004] Injecting the required injection quantity in a single injection within one injection cycle is called single injection. Injecting the required injection quantity in multiple injections within one injection cycle is called multi-injection. Multi-injection, which includes partial-lift injection, is called partial-lift multi-injection. Sometimes, the injection mode is switched between single intake port injection and partial-lift multi-injection. However, if the switching is frequent, the air-fuel ratio (A / F) becomes unstable. Therefore, the object of the present invention is to provide a control device for an internal combustion engine that can stably control the injection mode.

[0005] The aforementioned objective can be achieved by a control device for an internal combustion engine, which controls an internal combustion engine having a first fuel injection valve for injecting fuel into the cylinders of the internal combustion engine and a second fuel injection valve for injecting fuel into the intake manifold. The control device comprises: a first setting unit that determines a first fuel injection quantity; a second setting unit that determines a threshold value and a hysteresis width for the fuel injection quantity; and an injection control unit that switches the fuel injection mode between a first mode of injecting fuel from the first fuel injection valve and a second mode of injecting fuel from the second fuel injection valve. The second setting unit sets the hysteresis width to a constant multiple of the first fuel injection quantity. If the first fuel injection quantity is less than the threshold value, the injection control unit selects the second mode. If the first fuel injection quantity is greater than or equal to the sum of the threshold value and the hysteresis width, the injection control unit selects the first mode. If the first fuel injection quantity is greater than or equal to the threshold value but less than the sum of the threshold value and the hysteresis width, the injection control unit maintains the previous injection mode.

[0006] The injection control unit can enable the first fuel injection valve to perform multiple injections in the first mode.

[0007] The second setting unit can set the hysteresis width to less than 0.5 times the first fuel injection amount.

[0008] The first fuel injection quantity can be the amount of fuel injected when the air-fuel ratio of the internal combustion engine is set to the stoichiometric air-fuel ratio.

[0009] The threshold can be the minimum injection amount injected by the second fuel injection valve.

[0010] Invention Effects

[0011] This invention provides a control device for an internal combustion engine that can stably control the injection mode. Attached Figure Description

[0012] Figure 1 This is a schematic diagram illustrating an internal combustion engine.

[0013] Figure 2 This is a flowchart illustrating the process in an illustrative implementation.

[0014] Figure 3 This is a schematic diagram illustrating the injection mode. Detailed Implementation

[0015] Hereinafter, the control device for the internal combustion engine of this embodiment will be described with reference to the accompanying drawings. Figure 1 This is a schematic diagram illustrating an internal combustion engine 10, showing one cylinder. The internal combustion engine 10 burns fuel to output power. The fuel may be, 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 the cylinder block 32. A piston 33 is housed within the cylinder block 32. In each cylinder, a combustion chamber 34 is divided by the piston 33, the cylinder block 32, and the cylinder head 30.

[0016] A fuel injection valve 22 (first fuel injection valve), an intake valve 25, an exhaust valve 26, and a spark plug 27 are provided on the cylinder head 30. The fuel injection valve 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.

[0017] An air filter 15, an air flow meter 16, a throttle valve 18, and a fuel injection valve 24 (second fuel injection valve) are sequentially installed on the intake manifold 12 from the upstream side. The fuel injection valve 24 is an intake manifold injector that injects fuel into the intake manifold 12.

[0018] Air filter 15 removes dust and other particles from the air. Air flow meter 16 detects the airflow. Throttle valve 18 regulates the airflow. The larger the opening of throttle valve 18, the greater the airflow. The smaller the opening, the smaller the airflow.

[0019] Air flows into the combustion chamber 34 from the intake manifold 12 as the intake valve 25 opens. Fuel injected from the fuel injection valves 22 or 24 is also introduced into the combustion chamber 34. The air and fuel mix to form an air-fuel mixture. The spark plug 27 ignites the mixture. The mixture generates driving force through combustion.

[0020] The exhaust gas produced by combustion is discharged into the exhaust pipe 14 when the exhaust valve 26 is opened. The catalyst 20 installed in the exhaust pipe 14 purifies PM, carbon monoxide (CO), unburned fuel (HC), nitrogen oxides (NOx), etc. in the exhaust gas.

[0021] An air-fuel ratio sensor 29 is disposed upstream of the catalyst 20 in the exhaust pipe 14. The air-fuel ratio sensor 29 detects the air-fuel ratio. A temperature sensor 52 detects the temperature of the cooling water in the internal combustion engine 10 or the temperature of the outside air. A speed sensor 54 detects the speed of the internal combustion engine 10.

[0022] Fuel is stored in fuel tank 40. Fuel system 48 includes fuel passage 42 and fuel piping 46. Fuel system 47 includes fuel passage 43, high-pressure pump 44, and fuel piping 45.

[0023] A fuel supply pump 41 is installed in the fuel tank 40. The fuel supply pump 41 draws fuel from the fuel tank 40 and supplies it to fuel passages 42 and 43. Fuel passage 42 is connected to fuel piping 46. Fuel piping 46 is connected to the fuel injection valve 24 of each cylinder. Fuel is supplied to the fuel injection valve 24 through fuel passage 42 and fuel piping 46.

[0024] Fuel passage 43 branches off from fuel passage 42 and connects to fuel line 45. Fuel line 45 connects to the fuel injection valve 22 of each cylinder. A high-pressure pump 44 is installed in fuel passage 43. Fuel is pressurized by the high-pressure pump 44, flows through fuel passage 43 and fuel line 45, and is supplied to the fuel injection valve 22.

[0025] The Electronic Control Unit (ECU) 50 is the control device for the internal combustion engine 10, and has a computing device such as a Central Processing Unit (CPU), a Read Only Memory (ROM), and a Random Access Memory (RAM).

[0026] ECU 50 controls the opening of throttle valve 18 and the valve timing of intake valve 25 and exhaust valve 26. ECU 50 acquires the air flow rate detected by air flow meter 16. ECU 50 acquires the air-fuel ratio detected by air-fuel ratio sensor 29. ECU 50 acquires the temperature detected by temperature sensor 52. ECU 50 acquires the engine speed detected by speed sensor 54. ECU 50 controls supply pump 41 and high-pressure pump 44 and adjusts the amount of fuel dispensed from these pumps.

[0027] ECU50 controls fuel injection valves 22 and 24, controlling injection timing, injection frequency, and injection quantity. ECU50 can perform both direct injection using fuel injection valve 22 and intake manifold injection using fuel injection valve 24, or perform only one of these.

[0028] A needle valve is installed in the housing of the fuel injection valve. The ECU50 energizes the fuel injection valve and controls the lift of the needle valve. If the lift of the needle valve is zero, the fuel injection valve is closed. The fuel injection valve opens as the needle valve lifts. At its maximum lift (100%), the fuel injection valve is fully open. Fuel injection performed when the valve is fully open is recorded as full-lift injection. Injection performed with a lift greater than zero but less than the maximum lift is recorded as partial-lift injection.

[0029] In a single injection cycle, injecting the required fuel quantity all at once is called a single injection. In a single injection cycle, injecting the required fuel quantity in segments is called a multi-injection.

[0030] A multi-injection system that includes partial-lift injection is defined as a partial-lift multi-injection system. 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 system. Multiple injections can all be partial-lift injections. If all multiple injections are full-lift injections, the multi-injection is not a partial-lift multi-injection system. Fuel injection valve 22 sometimes performs single injection and multiple injections, and sometimes performs full-lift injection, partial-lift injection, and partial-lift multi-injection. Fuel injection valve 24 performs full-lift injection.

[0031] ECU 50 functions as an injection control unit that switches injection modes between Mode 1 and Mode 2. In Mode 1, fuel injection valve 22 sometimes performs direct injection, and fuel injection valve 24 injects fuel together with fuel injection valve 22. That is, fuel injection can be performed using both fuel injection valves 22 and 24. In Mode 1, fuel injection valve 22 sometimes performs multi-injection and partial-lift multi-injection. By performing multi-injection using fuel injection valve 22, combustion can be improved and particulate matter (PM) in the exhaust can be reduced. In Mode 2, intake manifold injection is performed using fuel injection valve 24. Fuel injection valve 22 does not inject fuel.

[0032] ECU 50 functions as the first setting unit, setting the basic injection quantity Qb (first fuel injection quantity), the required injection quantity in the cylinder Qd, and the required injection quantity in the intake manifold Qp. ECU 50 also functions as the second setting unit, determining the fuel injection quantity threshold Qmip and the hysteresis width H.

[0033] The basic injection quantity Qb is the theoretical injection quantity used to set the air-fuel ratio of the internal combustion engine 10 to the stoichiometric air-fuel ratio. The required injection quantity in the cylinder Qd is the injection quantity required by the fuel injection valve 22. The required injection quantity in the intake manifold Qp is the injection quantity required by the fuel injection valve 24.

[0034] The required injection quantity Qp for the intake manifold is calculated, for example, by the following formula (1). k is the feedback rate, determined based on the air-fuel ratio, etc. Qm is the amount of fuel that does not contribute to combustion.

[0035] Qp=(Qb×(1+k / 100))+Qm (1)

[0036] Uncontributed fuel includes, for example, unburned fuel adhering to the intake manifold or other parts of the fuel injected from the fuel injection valve 24. If fuel that does not contribute to combustion is generated, the injection quantity is increased to compensate for the uncontributed portion. That is, Qm becomes a positive value. On the other hand, sometimes uncontributed fuel generated in the previous injection cycle is detached from the adhering portion and introduced into the combustion chamber 34. In this case, Qm becomes a negative value.

[0037] ECU50 switches the injection mode between mode 1 and mode 2 based on the threshold Qmip and the hysteresis width H. The threshold Qmip is the minimum injection quantity in the intake manifold injection. The hysteresis width H is a constant multiple of the basic injection quantity Qb, as shown in the following formula (3).

[0038] H = c × Qb (3)

[0039] c is a constant, for example, less than 0.5, or less than 0.4, 0.3, or 0.2. c can be, for example, 0.1 or 0.2.

[0040] Figure 2 This is a flowchart illustrating the process in an illustrative embodiment. ECU 50 determines whether the required injection quantity Qp of the intake manifold is greater than or equal to the sum of the threshold Qmip and the hysteresis width H (Qmip+H) (step S10). If the determination is affirmative (yes), ECU 50 sets the injection mode to mode 1 (step S12).

[0041] In step S10, if the determination is negative (No), ECU 50 determines whether the required injection quantity Qp of the intake manifold is less than the threshold Qmip (step S14). If the determination is positive, ECU 50 sets the injection mode to mode 2 (step S16). If the determination is negative, ECU 50 maintains the injection mode of the previous injection cycle (step S18). The process ends thereafter.

[0042] Figure 3This is a schematic diagram illustrating the injection pattern. The horizontal axis represents the fuel injection quantity, which increases from left to right. The sum of these quantities, Qmip+H, is set at a position corresponding to the hysteresis width H to the right of the threshold Qmip.

[0043] like Figure 3 As shown, in the portion of the intake manifold where the required injection quantity Qp is lower than the threshold Qmip, the injection mode is mode 2. Figure 2 Step S16). For the portion of the intake manifold where the required injection quantity Qp is greater than or equal to Qmip+H, the injection mode is mode 1 (…). Figure 2 (Step S12). For the portion of the intake manifold where the required injection quantity Qp is above the threshold Qmip and less than Qmip+H, the previous injection mode is maintained (Step S18).

[0044] For example, if the injection mode is switched between mode 1 and mode 2 with the threshold Qmip as the boundary, the injection mode changes frequently and the air-fuel ratio becomes unstable.

[0045] According to the implementation method, the ECU 50 determines the hysteresis width H as a constant multiple of the basic injection quantity Qb (H = c × Qb). The ECU 50 switches the injection mode based on the threshold Qmip and the hysteresis width H. This suppresses frequent switching of the injection mode and performs stable control.

[0046] like Figure 2 and Figure 3 As shown, when the required injection quantity Qp is less than the threshold Qmip, the injection mode is mode 2. When the required injection quantity Qp is greater than or equal to Qmip+H, the injection mode is mode 1. When the required injection quantity Qp is greater than or equal to the threshold Qmip but less than or equal to Qmip+H, the previous injection mode is maintained. For example, once the injection mode becomes mode 1, mode 1 will be maintained even if the required injection quantity Qp is within the range of Qmip to Qmip+H. The frequency of switching to mode 2 decreases. In other words, it is easier to maintain mode 1. The air-fuel ratio remains stable.

[0047] The basic injection quantity Qb changes depending on factors such as the load rate of the internal combustion engine 10. If the hysteresis width H is set to a constant value, then even if the basic injection quantity Qb changes, the hysteresis width H will not change. The hysteresis width H does not follow the changes in the basic injection quantity Qb, making it difficult to control the injection mode. If the hysteresis width H is relatively large relative to the basic injection quantity Qb, it is difficult for the injection mode to switch. It is difficult to change from mode 2 to mode 1, and the PM in the exhaust may deteriorate. When the hysteresis width H is relatively small relative to the basic injection quantity Qb, the injection mode switches frequently, and the air-fuel ratio becomes unstable.

[0048] According to the implementation method, the hysteresis width H is a constant multiple of the basic injection quantity Qb, but less than Qb. The hysteresis width H changes in accordance with the basic injection quantity Qb. In other words, the hysteresis width H maintains a constant ratio relative to the basic injection quantity Qb. The switching frequency of the injection mode is controlled to an appropriate number of times. The coefficient c is less than 1, for example, less than 0.7, less than 0.5, less than 0.3, less than 0.2, less than 0.1, etc. When the coefficient c is 0.1, the hysteresis width H is 0.1 times the basic injection quantity Qb (10% of Qb).

[0049] In Mode 1, ECU 50 causes fuel injection valve 22 to perform multiple injections. Multiple injections facilitate fuel vaporization, thereby improving combustion. PM in the exhaust is reduced. According to the implementation, Mode 1 is easily maintained by setting the hysteresis width H to c×Qb. Combustion is effectively improved. The maximum number of injections included in the multiple injections within one cycle is set to be less than or equal to the total injection amount Q of one cycle. Combustion is further improved.

[0050] The basic injection quantity Qb is the injection quantity that makes the air-fuel ratio equal to the stoichiometric air-fuel ratio. The hysteresis width H is a constant multiple of Qb. The basic injection quantity Qb changes according to the operating conditions of the internal combustion engine 10. The hysteresis width H changes in accordance with Qb. To maintain the hysteresis width H at an appropriate size, the injection mode can be stably controlled.

[0051] The minimum injection quantity Qmip for intake manifold injection is a threshold used for injection mode switching. In this implementation, injection mode switching is based on the threshold Qmip and the sum of Qmip and the hysteresis width H, Qmip+H. Figure 3 It can stably control the injection mode.

[0052] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to this specific embodiment. Various modifications and alterations can be made within the scope of the spirit of the present invention as set forth in the claims.

[0053] Symbol Explanation

[0054] 10-Internal combustion engine, 12-Intake manifold, 14-Exhaust manifold, 15-Air filter, 16-Air flow meter, 18-Throttle valve, 20-Catalyst, 22, 24-Fuel injection valves, 25-Intake valve, 26-Exhaust valve, 27-Spark plug, 29-Air-fuel ratio sensor, 30-Cylinder head, 32-Cylinder block, 33-Piston, 34-Combustion chamber, 40-Fuel tank, 41-Fuel supply pump, 42, 43-Fuel passage, 44-High pressure pump, 45, 46-Fuel piping, 47, 48-Fuel system, 50-ECU, 52-Temperature sensor, 54-Speed ​​sensor.

Claims

1. A control device for an internal combustion engine, comprising controlling an internal combustion engine having a first fuel injection valve for injecting fuel into the cylinders of the internal combustion engine and a second fuel injection valve for injecting fuel into the intake manifold, the control device for the internal combustion engine being characterized in that it includes: The first setting unit determines the first fuel injection quantity; The second setting unit determines the threshold value of the fuel injection quantity and the hysteresis width; and The injection control unit switches the fuel injection mode between a first mode in which fuel is injected from the first fuel injection valve and a second mode in which fuel is injected from the second fuel injection valve. The second setting unit sets the hysteresis width to a constant multiple of the first fuel injection quantity. If the first fuel injection quantity is less than the threshold, the injection control unit selects the second mode. When the first fuel injection quantity is greater than or equal to the sum of the threshold and the hysteresis width, the injection control unit selects the first mode. If the first fuel injection quantity is above the threshold and less than the sum of the threshold and the hysteresis width, the injection control unit maintains the previous injection mode.

2. The control device for an internal combustion engine according to claim 1, characterized in that, In the first mode, the injection control unit causes the first fuel injection valve to perform multiple injections.

3. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, The second setting unit sets the hysteresis width to less than 0.5 times the first fuel injection amount.

4. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, The first fuel injection quantity is the amount of fuel injected when the air-fuel ratio of the internal combustion engine is set to the stoichiometric air-fuel ratio.

5. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, The threshold is the minimum injection amount injected by the second fuel injection valve.

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