Controller of internal combustion engine

Abstract

To suppress deterioration of drivability caused by use of fuel with a high octane number, in an internal combustion engine in which fuel cut is implemented.SOLUTION: In a controller of an internal combustion engine, fuel cut is implemented according to generated torque. The controller performs control to reduce an amount of air supplied to the internal combustion engine according to an octane number of fuel used in the internal combustion engine so that the internal combustion engine generates torque that avoids the implementation of the fuel cut.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Conventionally, an internal combustion engine in which control is performed to change the ignition timing according to the octane number of fuel is known (see, 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 the way, an internal combustion engine may be mounted on a hybrid vehicle in a state combined with a motor generator (MG1). In a hybrid vehicle, fuel cut (F / C) may be performed so that the torque of the internal combustion engine does not exceed the allowable torque of MG1. Also, it is known that the torque output by the internal combustion engine increases as the octane number of the fuel increases. For this reason, it is considered that the opportunity to perform F / C increases as the octane number of the fuel increases.

[0005] However, when F / C is performed, the drivability of the vehicle deteriorates. Deterioration of drivability is desirably avoided. Patent Document 1 above does not propose suppressing deterioration of vehicle drivability.

[0006] Therefore, an object of the invention disclosed in this specification is to suppress deterioration of drivability associated with the use of high-octane fuel in an internal combustion engine in which fuel cut is performed.

Means for Solving the Problems

[0007] The above problem is solved by a control device for an internal combustion engine in which a Fel cut is carried out according to the torque to be generated, and control is carried out to reduce the amount of air supplied to the internal combustion engine according to the octane number of the fuel used in the internal combustion engine so that the internal combustion engine generates torque to avoid the implementation of the Fel cut.

Effect of the Invention

[0008] The invention disclosed in this specification can suppress the deterioration of drivability associated with the use of high-octane fuel in an internal combustion engine in which a Fel cut is carried out.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, etc. of each part may not be shown to be exactly the same as the actual ones. Also, depending on the drawings, details may be omitted.

[0011] (Embodiment) First, referring to FIG. 1, the schematic configuration of a hybrid vehicle (hereinafter simply referred to as "vehicle") 20 according to an embodiment will be described. The vehicle 20 according to the embodiment includes a planetary gear 30, a motor MG1 as a first electric motor, an MG2 as a second electric motor, an intermediate shaft 32 as a transmission member, and a counter drive gear 61 in a power transmission path between an internal combustion engine 100 and drive wheels DW. The vehicle 20 also includes inverters 41 and 42. The vehicle 20 further includes a battery 50 and an ECU (Electronic Control Unit) 70 that functions as a control device.

[0012] The internal combustion engine 100 is configured to be capable of operating using a fuel containing alcohol such as ethanol. The alcohol concentration in the fuel is not constant, and it is assumed that fuels with various alcohol concentrations are used for the internal combustion engine 100. As the alcohol concentration increases, the octane number of the fuel increases. The internal combustion engine 100 is operationally controlled by the ECU 70. Here, referring to FIG. 2, the schematic configuration of the internal combustion engine 100 will be described.

[0013] The internal combustion engine 100 includes a plurality of cylinders 2 in a cylinder block 1a (only one cylinder 2 is shown in FIG. 1). A piston 3 is slidably accommodated in each cylinder 2, and the piston 3 forms a combustion chamber 2a between itself and a cylinder head 1b disposed above the cylinder block 1a. The piston 3 is connected to a crankshaft 5 via a connecting rod 4. An injector 6 for injecting fuel into the cylinder and a spark plug 7 are provided in the combustion chamber 2a. The fuel injected from the injector 6 is made into an air-fuel mixture in the combustion chamber 2a and is ignited by the spark plug 7. The ignited air-fuel mixture burns and explodes, pushing down the piston 3. The pushed-down piston 3 transmits the explosive force to the crankshaft 5 via the connecting rod 4, rotating the crankshaft 5. The injector 6 may be provided in the intake pipe 10 near the combustion chamber 2a.

[0014] The internal combustion engine 100 is provided with an intake port 8 and an exhaust port 9 so as to face the combustion chamber 2a. An intake pipe 10 forming an intake passage is connected to the intake port 8, and an exhaust pipe 11 forming an exhaust passage is connected to the exhaust port 9.

[0015] The intake pipe 10 is provided with an air cleaner 12, an air flow meter 13, a throttle valve 17, and an intake manifold 18 in order from the upstream side of the intake flow. A throttle opening sensor 17a is provided on the throttle valve 17. The air flow meter 13 detects the amount of air flowing in the intake pipe 10. The throttle valve 17 adjusts the amount of air sent into the combustion chamber 2a. The throttle opening sensor 17a detects the opening of the throttle valve 17.

[0016] The intake pipe 10 branches at the intake manifold 18 and is connected to the intake port 8 of each cylinder. The exhaust pipe 11 is provided with an exhaust manifold 19 and a catalyst 21 in order from the upstream side of the exhaust flow. The catalyst 21 purifies the exhaust.

[0017] The internal combustion engine 100 includes an intake valve 23 that opens and closes the intake port 8 and an exhaust valve 24 that opens and closes the exhaust port 9. The intake valve 23 and the exhaust valve 24 open and close in accordance with the rotation of an intake camshaft and an exhaust camshaft (not shown) that are drivingly connected to the crankshaft 5. Thereby, the intake valve 23 and the exhaust valve 24 are synchronized with the rotation of the crankshaft 5 and are driven to open and close at a predetermined timing corresponding to the reciprocating movement of each piston 3.

[0018] The planetary gear 30 is configured as a single pinion type planetary gear mechanism. The planetary gear 30 distributes the output of the internal combustion engine 100 to the MG1 and the counter drive gear 61.

[0019] The torque output to the intermediate shaft 32 is transmitted to the left and right drive wheels DW via the gear mechanism 60, differential gear DF, and drive shaft DS. The gear mechanism 60 includes a counter drive gear 61 fixed to the intermediate shaft 32, and a counter driven gear 63 fixed to a counter shaft 62 extending parallel to the intermediate shaft 32 and meshing with the counter drive gear 61. The gear mechanism 60 also includes a drive pinion gear 64 fixed to the counter shaft 62, and a differential ring gear 65 meshing therewith and connected to the differential gear DF.

[0020] The rotor of the motor MG1 is connected to the sun gear 30s of the planetary gear 30. The rotor of the motor MG2 is connected to the rotary shaft 67. A rotary gear 68 is attached to the rotary shaft 67, and the rotary gear 68 meshes with the counter driven gear 63. The inverters 41 and 42 are used to drive the motors MG1 and MG2 and are connected to the battery 50.

[0021] The ECU 70 includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a storage device, etc. The ECU 70 controls the internal combustion engine 100 by executing programs stored in the ROM and storage device. The ECU 70 in this embodiment functions as an F / C control unit 70a. The ECU 70 also functions as a required torque calculation unit 70b, a required engine (ENG) torque calculation unit 70c, a KCS (Knock Control System) learning value determination unit 70d, a subtraction coefficient calculation unit 70e, and a required air amount calculation unit 70f. An accelerator opening sensor 101 and a knock sensor 102 are connected to the ECU 70. In addition to these, various sensors for controlling the vehicle 20 are electrically connected to the ECU 70, but detailed descriptions thereof are omitted here.

[0022] When the torque generated by the internal combustion engine 100 exceeds the allowable torque of MG1, the F / C control unit 70a performs control to cut off the fuel supply to protect MG1.

[0023] The required torque calculation unit 70b calculates the value of the torque for rotating the drive shaft DS of the vehicle 20 based on the detected value of the accelerator opening sensor 101. The accelerator opening sensor 101 detects the operation amount of the accelerator pedal operated by the driver.

[0024] The required ENG torque calculation unit 70c calculates the value of the torque generated by the internal combustion engine 100 in order to obtain the required torque. The required ENG torque is calculated in consideration of the pumping loss in the internal combustion engine 100 and the friction loss in the power transmission path from the internal combustion engine 100 to the drive shaft DS, based on the required torque in the drive shaft DS.

[0025] The KCS learning value determination unit 70d determines whether or not the ignition timing (advance angle amount) set based on the detected value of the knock sensor 102 is smaller than a preset threshold value. The knock sensor 102 detects the change in the combustion state accompanying the change in the octane number of the fuel used. The KCS learning value is set to the advance angle side of the ignition timing as the detected value of the knock sensor 102 indicates a higher octane number. The threshold value in the present embodiment is set to the KCS learning value when alcohol fuel is used.

[0026] The subtraction coefficient calculation unit 70e is a coefficient for correcting the value of the required ENG torque according to the octane number of the fuel. When the octane number of the fuel increases, the value of the torque actually output increases accordingly. For example, when comparing the octane number of gasoline and the octane number of alcohol fuel, the octane number of alcohol fuel is high and the torque generated by the internal combustion engine 100 increases. Therefore, the subtraction coefficient calculation unit 70e calculates a subtraction coefficient for reducing the required ENG torque so that the fuel cut by the F / C control unit 70a is not executed. The subtraction coefficient is less than 1, and the value becomes smaller as the octane number is higher. In the present embodiment, control based on the KCS learning value having a correlation with the octane number is performed. Therefore, the larger the advance angle amount of the ignition timing, the smaller the subtraction coefficient (see Fig. 3(B)).

[0027] The required air quantity calculation unit 70f calculates a required air quantity corresponding to the calculated required ENG torque.

[0028] Next, with reference to FIGS. 3(A) and 3(B), the control of the intake air quantity will be described. The internal combustion engine 100 controls the intake air quantity supplied into the cylinder by adjusting the opening degree of the throttle valve 17 based on the calculated required air quantity.

[0029] First, in step S11, the required torque calculation unit 70b calculates a required torque based on the detection value of the accelerator opening sensor 101. In step S12, which is executed subsequent to step S11, the KCS learning value determination unit 70d determines whether the KCS learning value is smaller than a preset threshold value. The KCS learning value is calculated at a predetermined cycle based on the detection value of the knock sensor 102, and the latest detection value at that time is compared with the threshold value. When the ECU 70 makes an affirmative (Yes) determination in step S12, it proceeds to step S13, and when it makes a negative (No) determination in step S12, it proceeds to step S16.

[0030] In step S13, the required ENG torque calculation unit 70c calculates a normal required ENG torque. The normal required ENG torque is the ENG torque required when gasoline is used as fuel and the octane number is low compared to alcohol fuel.

[0031] In step S14, the required air quantity calculation unit 70f calculates a normal required air quantity corresponding to the normal required ENG torque. After the processing in step S14 is completed, the ECU 70 proceeds to step S15. In step S15, the ECU 70 adjusts the opening degree of the throttle valve 17 so that it becomes the normal required air quantity, and a series of controls ends.

[0032] In step S16, the subtraction coefficient calculation unit 70e calculates a subtraction coefficient. The subtraction coefficient is calculated based on, for example, the map illustrated in FIG. 3(B). The subtraction coefficient is set such that the larger the difference between the KCS learning value and the threshold value, that is, the larger the ignition timing advance amount, the smaller the value. The fact that the ignition timing advance amount is large indicates that the octane number is high and torque is easily generated. Therefore, the subtraction coefficient is set such that the higher the octane number, the larger the decrease in the ENG torque.

[0033] In step S17, the required ENG torque calculation unit 70c calculates a subtraction required ENG torque. The subtraction required ENG torque is calculated by multiplying the normal required ENG torque calculated in the same manner as in step S13 by the subtraction coefficient.

[0034] In step S18, the required air amount calculation unit 70f calculates a subtraction required air amount corresponding to the subtraction required ENG torque. After the process of step S18 is completed, the ECU 70 proceeds to step S15. In step S15, the ECU 70 adjusts the opening degree of the throttle valve 17 so that the subtraction required air amount, that is, the air amount reduced from the normal required air amount, and a series of controls are terminated.

[0035] According to the present embodiment, in the internal combustion engine 100 in which the F / C control is performed, when a fuel with a high octane number is used, an operation of subtracting the required air amount is performed to reduce the torque generated by the internal combustion engine 100. Thereby, it is avoided that the torque generated by the internal combustion engine 100 exceeds the allowable torque of the MG1. As a result, since the fuel cut by the F / C control is avoided, the deterioration of the drivability in the vehicle 20 is suppressed.

[0036] In this embodiment, a subtraction required ENG torque is calculated using a subtraction coefficient, and a subtraction required air amount corresponding thereto is calculated. On the other hand, the subtraction required air amount may be calculated by multiplying the normal required air amount by the subtraction coefficient. In this embodiment, the subtraction coefficient is calculated based on the KCS learning value. On the contrary, the octane number of the fuel may be evaluated by a conventionally known method, and the subtraction coefficient may be set according to the level of the octane number (see Fig. 3(B)). For example, the alcohol concentration of the fuel may be detected by an alcohol concentration sensor, and the octane number may be evaluated based on the detected value to calculate the subtraction coefficient.

[0037] The above embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Modifying these embodiments variously is within the scope of the present invention. Further, it is obvious from the above description that various other embodiments are possible within the scope of the present invention.

Explanation of Signs

[0038] 20…Hybrid vehicle, 70…ECU (control device), 70a…F / C control unit, 70b…Required torque calculation unit 70b, 70c…Required ENG torque calculation unit, 70d…KCS learning value determination unit, 70e…Subtraction coefficient calculation unit, 70f…Required air amount calculation unit, 100…Internal combustion engine

Claims

【Claim 1】 A control device for an internal combustion engine in which a fuel cut is performed according to the generated torque, performing control to reduce the amount of air supplied to the internal combustion engine according to the octane number of the fuel used in the internal combustion engine so that the internal combustion engine generates a torque that avoids performing the fuel cut. A control device for an internal combustion engine.

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