Control device for internal combustion engine

Abstract

To provide a control device for an internal combustion engine, which can control the flow rate of EGR gas.SOLUTION: A control device for an internal combustion engine comprises an acquisition unit for acquiring a requested amount of a load factor of the internal combustion engine, and a control unit for controlling the flow rate of EGR gas on the basis of the requested amount of the load factor and a load factor at the time when a throttle valve is fully opened.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] There is known an internal combustion engine having an EGR (Exhaust Gas Recirculation) device that recirculates a part of the exhaust gas to the intake passage, and a device that purges the vaporized fuel (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By introducing EGR gas, the temperature of the combustion gas is lowered, and the occurrence of knocking is suppressed. As a result, combustion can be performed at a more efficient timing. By reducing the negative pressure in the intake passage, pumping loss is also reduced. Therefore, fuel efficiency can be improved. However, by increasing the amount of EGR gas, the negative pressure in the intake passage decreases. It becomes difficult to purge the evaporated fuel and introduce blow-by gas that utilize the negative pressure. Therefore, an object is to provide a control device for an internal combustion engine capable of controlling the flow rate of EGR gas.

Means for Solving the Problems

[0005] The above object can be achieved by A control device for an internal combustion engine having a purge passage for introducing vaporized fuel, a PCV passage for introducing blow-by gas, and an EGR passage for introducing EGR gas into the intake passage of the internal combustion engine, the control device including a negative pressure acquisition unit that acquires a negative pressure in the intake passage, a first load factor acquisition unit that acquires a first load factor that is a load factor of the internal combustion engine, a second load factor acquisition unit that acquires a second load factor that is a load factor of the internal combustion engine, a third load factor acquisition unit that acquires a third load factor that is a load factor of the internal combustion engine, and a fourth load factor acquisition unit that acquires a fourth load factor that is a load factor of the internal combustion engine based on the rotational speed and load of the internal combustion engine, and by controlling an EGR valve provided in the EGR passage, the a control unit that controls the flow rate of EGR gas, The negative pressure acquisition unit acquires a first negative pressure determined based on the fuel consumption of the internal combustion engine, a second negative pressure required to introduce the vaporized fuel into the intake passage, and a third negative pressure required to introduce the blow-by gas into the intake passage. The first load factor acquisition unit acquires the first load factor corresponding to the minimum of the first negative pressure, the second negative pressure, and the third negative pressure. The second load factor acquisition unit acquires the second load factor by dividing the amount of fresh air introduced from the intake passage by the amount of air when a throttle valve provided in the intake passage is fully opened. The third load factor acquisition unit acquires the third load factor by subtracting the first load factor and the second load factor from the load factor when the throttle valve is fully opened. The control unit controls the opening degree of the EGR valve to an opening degree corresponding to the smaller of the third load factor and the fourth load factor to control the flow rate of the EGR gas and a control device for an internal combustion engine.

Effects of the Invention

[0006] It is possible to provide a control device for an internal combustion engine capable of controlling the flow rate of EGR gas.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0008] FIG. 1 is a schematic diagram illustrating an engine system 100 according to an embodiment. The engine system 100 includes an internal combustion engine 10, a purge system 20, an EGR device 30, a PCV (Positive crankcase ventilation) system 40, and an ECU (Electronic Control Unit) 50.

[0009] An intake passage 12 and an exhaust passage 14 are connected to the internal combustion engine 10. A throttle valve 16 is provided in the intake passage 12. A catalyst 18 is provided in the exhaust passage 14. Air passes through the intake passage 12 and is introduced into the internal combustion engine 10. When the opening degree of the throttle valve 16 increases, the flow rate of air in the intake passage 12 increases. The internal combustion engine 10 is, for example, a gasoline engine, and burns a mixture of air and fuel. The exhaust generated in the internal combustion engine 10 is discharged into the exhaust passage 14. The catalyst 18 purifies the exhaust.

[0010] The purge system 20 has a canister 22, a purge passage 24, and a purge valve 26. The canister 22 is connected to the fuel tank 19 and adsorbs the evaporated fuel (vapor). The purge passage 24 is connected to the canister 22 and the intake passage 12. The purge valve 26 is provided in the purge passage 24. When the purge valve 26 opens, the fuel collected in the canister 22 is introduced into the intake passage 12 through the purge passage 24.

[0011] The EGR device 30 has an EGR passage 32, an EGR cooler 34, and an EGR valve 36. The EGR passage 32 is connected to the exhaust passage 14 and the intake passage 12. The EGR cooler 34 and the EGR valve 36 are provided in the EGR passage 32 and are arranged in this order from the closer to the exhaust passage 14. When the EGR valve 36 opens, a part of the exhaust gas (EGR gas) is introduced into the intake passage 12 through the EGR passage 32. The EGR cooler 34 cools the EGR gas.

[0012] The PCV system 40 has a PCV passage 42 and a PCV valve 44. The PCV passage 42 is connected to, for example, the internal combustion engine 10 and the intake passage 12. The PCV valve 44 is provided in the PCV passage 42. Blow-by gas is generated in the internal combustion engine 10. When the PCV valve 44 opens, the blow-by gas is introduced into the intake passage 12 through the PCV passage 42.

[0013] The vapor, the EGR gas, and the blow-by gas are supplied to the internal combustion engine 10 together with air and burned.

[0014] By supplying the EGR gas to the internal combustion engine 10, the combustion temperature can be lowered, and the fuel efficiency can be improved, etc. However, by introducing the EGR gas into the intake passage 12, the negative pressure in the intake passage 12 decreases compared to the case where the EGR gas is not introduced. That is, the pressure increases. Due to the decrease in the negative pressure, it becomes difficult to purge the vapor and introduce the blow-by gas. By controlling the flow rate of the EGR gas to an appropriate magnitude, it becomes possible to introduce the purge and the blow-by gas.

[0015] The ECU 50 is a control device for the internal combustion engine 10. The ECU 50 includes an arithmetic unit such as a CPU (Central Processing Unit), and storage devices such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The ECU 50 controls the opening degrees of the throttle valve 16, the purge valve 26, the EGR valve 36, and the PCV valve 44. The ECU 50 performs various controls by executing programs stored in the ROM and the storage device. The ECU 50 functions as an acquisition unit that acquires the required amount of the load factor of the internal combustion engine 10, and a control unit that controls the flow rate of the EGR gas.

[0016] Figures 2 to 3(b) are flowcharts illustrating the processes executed by the ECU 50. As shown in Figure 2, the ECU 50 acquires a fuel consumption required negative pressure, for example, based on the fuel consumption (step S10).

[0017] The ECU 50 acquires a purge required negative pressure (step S12). At this time, the ECU 50 performs the process of Figure 3(a). The ECU 50 acquires a correction coefficient reflecting the concentration of the vaporized fuel (vapor) (step S30). The ECU 50 acquires the negative pressure of the intake passage 12 at the time when the vapor concentration is maximum based on the operating conditions (load, rotational speed, etc.) of the internal combustion engine 10 (step S32). The ECU 50 acquires the basic negative pressure of the intake passage 12 based on the operating conditions (load, rotational speed, etc.) of the internal combustion engine 10 (step S34). The ECU 50 may store a map of the correction coefficient, a map associating the operating conditions with the negative pressure at the time of maximum concentration, and a map associating the operating conditions with the basic negative pressure. The ECU 50 acquires the purge required negative pressure using, for example, the following formula (1) (step S36). Purge required negative pressure = Basic negative pressure - (Basic negative pressure - Negative pressure at the time of maximum vapor concentration) × Correction coefficient (1)

[0018] As shown in FIG. 2, the ECU 50 acquires the PCV required negative pressure (step S14). At this time, the ECU 50 performs the process of FIG. 3(b). The ECU 50 acquires the correction amount of the negative pressure reflecting the pressure in the PCV passage 42 (step S40). The ECU 50 acquires the basic negative pressure of the intake passage 12 based on the operating conditions (load, rotational speed, etc.) of the internal combustion engine 10 (step S42). The ECU 50 may store a map of the correction amount and a map associating the operating conditions with the basic EGR opening degree. The ECU 50 acquires the PCV required negative pressure using, for example, the following formula (2) (step S44). PCV required negative pressure = basic negative pressure - correction amount (2)

[0019] The ECU 50 selects the minimum negative pressure among the fuel consumption required negative pressure, the purge required negative pressure, and the PCV required negative pressure, and sets it as the required amount of negative pressure (step S16). That is, the negative pressure farthest from the atmospheric pressure among the three is selected. The ECU 50 acquires the load factor (required amount of load factor) of the internal combustion engine 10 corresponding to the selected negative pressure (step S17). The higher the negative pressure, the higher the load factor. The ECU 50 acquires the fresh air load factor based on the torque required for the internal combustion engine 10, etc. (step S18). The fresh air load factor is calculated by the following formula (3). Fresh air load factor = amount of fresh air / amount of air when the throttle valve 16 is fully open (3)

[0020] The ECU 50 acquires the limit EGR load factor by the following formula (4) (step S19). The limit EGR load factor is the EGR load factor corresponding to the combustion limit of the internal combustion engine 10. The throttle fully open load factor is the load factor when the throttle valve 16 is fully open. Limit EGR load factor = throttle fully open load factor - fresh air load factor - required amount of load factor - pressure loss (4)

[0021] The ECU 50 also acquires the basic EGR load rate based on the operating conditions of the internal combustion engine 10. The basic EGR load rate is the load rate corresponding to the basic opening degree (basic EGR opening degree) of the EGR valve 36. The ECU 50 may store a map associating the operating conditions with the basic EGR opening degree. The ECU 50 selects the smaller of the limit EGR negative pressure rate and the basic EGR load rate as the EGR load rate (step S20). The ECU 50 controls the EGR valve 36 based on the EGR load rate (step S22). The opening degree of the EGR valve 36 becomes a size corresponding to the EGR load rate. The flow rate of the EGR gas is adjusted to an amount corresponding to the opening degree of the EGR valve 36.

[0022] According to the present embodiment, the ECU 50 acquires the required amount of the load rate (step S17), and acquires the EGR load rate based on the required amount and the throttle full - open load rate (steps S20, equation (4)). The ECU 50 controls the EGR valve 36 according to the EGR load rate, thereby controlling the flow rate of the EGR gas. By controlling the flow rate of the EGR gas, it is possible to introduce the purge of the evaporated fuel and the blow - by gas together with the introduction of the EGR gas. The deterioration of emissions due to the evaporated fuel is suppressed. The deterioration of the engine oil due to the blow - by gas is suppressed.

[0023] The ECU 50 sets the smaller of the limit EGR load rate and the basic EGR load rate as the EGR load rate (step S20). By reducing the EGR load rate, the decrease in the negative pressure in the intake passage 12 is suppressed. By obtaining the negative pressure in the intake passage 12, the purge of the vapor and the introduction of the blow - by gas are effectively performed.

[0024] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0025] 10 Internal combustion engine 12 Intake passage 14 Exhaust passage 16 Throttle valve 18 Catalyst 19 Fuel tank 20 Purge system 22 Canister 24 Purge passage 26 Purge valve 30 EGR device 32 EGR passage 34 EGR cooler 36 EGR valve 40 PCV system 42 PCV passage 44 PCV valve 50 ECU 100 Engine system

Claims

A control device for an internal combustion engine having a purge passage for introducing vaporized fuel, a PCV passage for introducing blow-by gas, and an EGR passage for introducing EGR gas into the intake passage of the internal combustion engine, wherein: a negative pressure acquisition unit that acquires the negative pressure in the intake passage; a first load factor acquisition unit that acquires a first load factor that is the load factor of the internal combustion engine; a second load factor acquisition unit that acquires a second load factor that is the load factor of the internal combustion engine; a third load factor acquisition unit that acquires a third load factor that is the load factor of the internal combustion engine; a fourth load factor acquisition unit that acquires a fourth load factor that is the load factor of the internal combustion engine based on the rotational speed and load of the internal combustion engine; a control unit that controls the flow rate of the EGR gas by controlling an EGR valve provided in the EGR passage; the negative pressure acquisition unit acquires a first negative pressure determined based on the fuel consumption of the internal combustion engine, a second negative pressure required to introduce the vaporized fuel into the intake passage, and a third negative pressure required to introduce the blow-by gas into the intake passage; the first load factor acquisition unit acquires the first load factor corresponding to the minimum of the first negative pressure, the second negative pressure, and the third negative pressure; the second load factor acquisition unit acquires the second load factor by dividing the amount of fresh air introduced from the intake passage by the amount of air when a throttle valve provided in the intake passage is fully opened; the third load factor acquisition unit acquires the third load factor by subtracting the first load factor and the second load factor from the load factor when the throttle valve is fully opened; the control unit controls the opening degree of the EGR valve to an opening degree corresponding to the smaller of the third load factor and the fourth load factor to control the flow rate of the EGR gas.

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