Start control device for internal combustion engine

Abstract

To provide a start control device for an internal combustion engine in which a combustion state is stabilized when fuel is injected by an in-cylinder injection valve on starting.SOLUTION: A start control device for an internal combustion engine having an in-cylinder injection valve capable of performing compression stroke injection that is fuel injection at a compression stroke and intake stroke injection that is fuel injection at an intake stroke includes a first control unit for performing the compression stroke injection when a request is made for starting up the internal combustion engine, and a second control unit for performing the intake stroke injection by increasing a fuel injection amount to be larger than a fuel injection amount at the compression stroke injection after performing the compression stroke injection.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] When fuel is injected from a port injection valve at the start of an internal combustion engine, some of the injected fuel may adhere to the port wall surface, resulting in a shortage of fuel that contributes to combustion and an unstable combustion state. For this reason, a technique for increasing the amount of fuel injected from the port injection valve is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-188992 A Summary of the Invention [Problem to be solved by the invention]

[0004] When fuel is injected by an in-cylinder injection valve at the start of an internal combustion engine, the amount of fuel adhering to the inner wall surface of the cylinder varies depending on the injection timing, which may result in an unstable combustion state.

[0005] SUMMARY OF THE PRESENT DISCLOSURE ... An object of the present invention is to provide a start control device for an internal combustion engine in which the combustion state is stable when fuel is injected by a direct injection valve at the time of starting. [Means for solving the problem]

[0006] The above object is to provide a start control device for an internal combustion engine having an in-cylinder injection valve capable of executing a compression stroke injection, which is a fuel injection in a compression stroke, and an intake stroke injection, which is a fuel injection in an intake stroke, comprising: a first control unit that executes the compression stroke injection when there is a request to start the internal combustion engine; and a second control unit that, after execution of the compression stroke injection, increases the fuel injection amount to be greater than the fuel injection amount in the compression stroke injection and executes the intake stroke injection. a target injection amount for the compression stroke injection is calculated as a basic injection amount plus a non-contributing fuel increase amount, the non-contributing fuel increase amount being calculated to be larger as the temperature of the cooling water of the internal combustion engine is lower; a target injection amount for the intake stroke injection is calculated by adding the non-contributing fuel increase amount to the basic injection amount and further adding an intake stroke injection increase amount, the intake stroke injection increase amount being specified to be larger as the intake air amount of the internal combustion engine is larger, the intake stroke injection increase amount is specified to be larger when the cooling water of the internal combustion engine is low temperature than when the cooling water is high temperature, and the intake stroke injection increase amount is specified to be smaller as the number of intake stroke injections increases.This can be achieved by a starting control device for an internal combustion engine. Effect of the Invention

[0007] According to the present invention, it is possible to provide a start control device for an internal combustion engine in which the combustion state is stable when fuel is injected by a direct injection valve at the time of starting. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle. [Diagram 2] FIG. 2 is a schematic diagram of the engine. [Diagram 3] FIG. 3 is a flowchart showing an example of fuel injection control executed by the ECU at the start of the engine. [Figure 4] 4A, 4B, and 4C are examples of maps that define the intake stroke injection increase amount. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [General configuration of hybrid vehicle] FIG. 1 is a schematic diagram of a hybrid vehicle 1. In the hybrid vehicle 1, a K0 clutch 14, a motor 15, a torque converter 18, and a transmission 19 are provided in this order in a power transmission path from an engine 10 to drive wheels 13. The engine 10 and the motor 15 are mounted as a drive source for running the hybrid vehicle 1. The engine 10 is an example of an internal combustion engine, and is, for example, a V-type 6-cylinder gasoline engine, but the number of cylinders is not limited thereto, and may be an in-line gasoline engine. The K0 clutch 14, the motor 15, the torque converter 18, and the transmission 19 are provided in a transmission unit 11. The transmission unit 11 and the left and right drive wheels 13 are drivingly connected via a differential 12.

[0010] The K0 clutch 14 is provided between the engine 10 and the motor 15 on the power transmission path. The K0 clutch 14 is switched from a released state to an engaged state when hydraulic pressure is supplied, connecting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 is switched to a released state when the hydraulic pressure supply is stopped, cutting off the power transmission between the engine 10 and the motor 15. The engaged state is a state in which both engagement elements of the K0 clutch 14 are connected and the engine 10 and the motor 15 have the same rotation speed. The released state is a state in which both engagement elements of the K0 clutch 14 are separated.

[0011] The motor 15 is connected to the battery 16 via an inverter 17. The motor 15 functions as a motor that generates driving force for the vehicle in response to power supplied from the battery 16, and also functions as a generator that generates electric power to charge the battery 16 in response to power transmission from the engine 10 and the drive wheels 13. The electric power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

[0012] The inverter 17 is controlled by the ECU 100 described later, and converts the DC voltage from the battery 16 into an AC voltage, or converts the AC voltage from the motor 15 into a DC voltage. In the case of powering operation in which the motor 15 outputs torque, the inverter 17 converts the DC voltage of the battery 16 into an AC voltage and adjusts the power supplied to the motor 15. In the case of regenerative operation in which the motor 15 generates power, the inverter 17 converts the AC voltage from the motor 15 into a DC voltage and adjusts the power supplied to the battery 16.

[0013] The torque converter 18 is a fluid coupling having a torque amplifying function. The transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple stages by switching the gear stage, but is not limited thereto and may be a continuously variable automatic transmission. The transmission 19 is provided between the motor 15 and the driving wheels 13 on the power transmission path. The motor 15 and the transmission 19 are connected via the torque converter 18. The torque converter 18 is provided with a lock-up clutch 20 that is supplied with hydraulic pressure and is in an engaged state to directly connect the motor 15 and the transmission 19. The torque converter 18 is not necessarily required, and may not be provided.

[0014] The transmission unit 11 is further provided with an oil pump 21 and a hydraulic control mechanism 22. The hydraulic pressure generated by the oil pump 21 is supplied to the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20 via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with hydraulic circuits for each of the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20, and various hydraulic control valves for controlling the operating hydraulic pressures thereof.

[0015] The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 100 as a control device for the vehicle. The ECU 100 is an electronic control unit including a calculation processing circuit that performs various calculation processes related to vehicle driving control, and a memory that stores control programs and data. The ECU 100 is an example of a start control device for an internal combustion engine, and functionally realizes a first control unit and a second control unit, which will be described in detail later.

[0016] The ECU 100 controls the operation of the engine 10 and the motor 15. Specifically, the ECU 100 controls the torque and rotation speed of the engine 10 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 10. The ECU 100 controls the torque and rotation speed of the motor 15 by controlling the inverter 17 to adjust the amount of power exchanged between the motor 15 and the battery 16. The ECU 100 also controls the operation of the K0 clutch 14, the lock-up clutch 20, and the transmission 19 through the control of the hydraulic control mechanism 22.

[0017] The ECU 100 receives signals from an ignition switch 71, a crank angle sensor 72, a motor revolution speed sensor 73, an accelerator opening sensor 74, an air flow meter 75, an air-fuel ratio sensor 76, and a water temperature sensor 77. The crank angle sensor 72 detects the rotation speed of the crankshaft of the engine 10. The motor revolution speed sensor 73 detects the rotation speed of the output shaft of the motor 15. The accelerator opening sensor 74 detects the accelerator pedal opening, which is the amount of depression of the accelerator pedal by the driver. The air flow meter 75 detects the amount of intake air of the engine 10. The air-fuel ratio sensor 76 detects the air-fuel ratio of the exhaust gas discharged from the catalyst 43. The water temperature sensor 77 detects the temperature of the cooling water for the engine 10.

[0018] The ECU 100 runs the hybrid vehicle in either a motor mode or a hybrid mode. In the motor mode, the ECU 100 releases the K0 clutch 14 and runs the vehicle using the power of the motor 15. In the hybrid mode, the ECU 100 switches the K0 clutch 14 to an engaged state and runs the vehicle using at least the power of the engine 10. The switching of the running mode is performed based on the required driving force of the vehicle calculated from the vehicle speed and accelerator opening, the state of charge of the battery 16, and the like.

[0019] [Engine outline] FIG. 2 is a schematic diagram of the engine 10. The engine 10 has cylinders 30, pistons 31, connecting rods 32, a crankshaft 33, an intake passage 35, an intake valve 36, an exhaust passage 37, and an exhaust valve 38. FIG. 2 shows only one of the multiple cylinders 30 of the engine 10. An air-fuel mixture is burned in the cylinder 30. A piston 31 is accommodated in each cylinder 30 so as to be capable of reciprocating, and is connected to a crankshaft 33, which is an output shaft of the engine 10, via a connecting rod 32. The connecting rod 32 converts the reciprocating motion of the piston 31 into the rotational motion of the crankshaft 33.

[0020] The intake passage 35 is connected to the intake port of each cylinder 30 via an intake valve 36. The exhaust passage 37 is connected to the exhaust port of each cylinder 30 via an exhaust valve 38. An air flow meter 75 and a throttle valve 40 that adjusts the amount of intake air are provided in the intake passage 35. An air-fuel ratio sensor 76 and a catalyst 43 for purifying exhaust gas are provided in the exhaust passage 37.

[0021] Each cylinder 30 is provided with an in-cylinder injection valve 41d. The in-cylinder injection valve 41d injects fuel directly into the cylinder 30. The intake passage 35 is provided with a port injection valve 41p that injects fuel toward the intake port. Note that if the in-cylinder injection valve 41d is provided, the port injection valve 41p does not have to be provided. Each cylinder 30 is provided with an ignition plug 42 that ignites, by spark discharge, a mixture of the intake air introduced through the intake passage 35 and the fuel injected by the in-cylinder injection valve 41d and the port injection valve 41p.

[0022] [Starting the engine] When the ignition switch 71 is switched from off to on or when an automatic restart condition is satisfied during intermittent operation, a start request is made to the engine 10 configured as above. When a start request is made to the engine 10, the ECU 100 controls the K0 clutch 14 to a slip state to start cranking the engine 10 by the motor 15 and starts combustion in the engine 10.

[0023] Specifically, the ECU 100 executes compression stroke injection by the in-cylinder injection valve 41d a predetermined target number of times, and then switches to intake stroke injection by the in-cylinder injection valve 41d and executes it a predetermined target number of times. The compression stroke injection is fuel injection performed during the compression stroke for the cylinder 30 that is to enter the compression stroke in sequence with the start of cranking. By executing the compression stroke injection, the torque of the engine 10 can be increased early. The intake stroke injection is fuel injection performed during the intake stroke for the cylinder 30 that is to enter the intake stroke in sequence. By executing the intake stroke injection, the torque of the engine 10 can be stabilized. When the compression stroke injection and the intake stroke injection have each been executed a target number of times, the operating state of the engine 10 is deemed to be stable, and the start of the engine 10 is completed.

[0024] When the starting of the engine 10 is completed, the ECU 100 engages the K0 clutch 14 and controls the operation so that the torque of the engine 10 becomes the required torque. If the engine 10 is provided with a starter motor, the engine 10 may be cranked by the starter motor instead of the motor 15.

[0025] [Fuel injection control at start-up] 3 is a flowchart showing an example of fuel injection control executed by the ECU 100 when starting the engine 10. This control is executed repeatedly at a predetermined cycle while the ignition is on. The ECU 100 determines whether or not there is a request to start the engine 10 (step S1). If the answer is No in step S1, this control ends.

[0026] If the answer is Yes in step S1, the ECU 100 calculates a target injection amount for compression stroke injection (step S2). The target injection amount for compression stroke injection is calculated as an amount obtained by adding a non-contributing fuel increase amount to the basic injection amount. The basic injection amount is calculated to be larger as the intake air amount detected by the air flow meter 75 is larger. The basic injection amount is calculated to be smaller when the air-fuel ratio detected by the air-fuel ratio sensor 77 is richer than the target air-fuel ratio, and is calculated to be larger when the air-fuel ratio is leaner. The non-contributing fuel increase amount is an increase amount that compensates for the fuel that adheres to the top surface of the piston 31 and the inner wall surface of the cylinder and does not contribute to combustion. The non-contributing fuel increase amount is calculated to be larger as the temperature of the cooling water of the engine 10 detected by the water temperature sensor 77 is lower, and is an appropriate value that is experimentally obtained in advance based on various data.

[0027] The ECU 100 performs compression stroke injection by controlling the in-cylinder injection valve 41d to open and close so that the actual fuel injection amount becomes the target injection amount calculated as described above (step S3). Steps S1 to S3 are an example of processing executed by the first control unit.

[0028] Next, the ECU 100 determines whether the number of compression stroke injections has reached the target number (step S4). The target number of compression stroke injections is set to be smaller as the torque required for the engine 10 at the time of the start request is larger. If the result in step S4 is No, the target injection amount is calculated again and the compression stroke injection is performed.

[0029] If the answer is Yes in step S4, the ECU 100 calculates the target injection amount for intake stroke injection (step S5). The target injection amount for intake stroke injection is calculated by adding the non-contributing fuel increase amount to the basic injection amount, as described above, and further adding the intake stroke injection increase amount. The intake stroke injection increase amount is an increase in the fuel injection amount to compensate for the amount of fuel adhering to the cylinder inner wall surface due to the intake stroke injection. The intake stroke injection increase amount is an appropriate value experimentally obtained in advance based on various data.

[0030] The increased amount of intake stroke injection is used to calculate the target injection amount for intake stroke injection, but is not used to calculate the target injection amount for compression stroke injection. Since compression stroke injection is performed while the piston 31 is rising and the area of ​​the cylinder inner wall surface exposed by the piston 31 is decreasing, the amount of fuel adhering to the cylinder inner wall surface is relatively small. In contrast, intake stroke injection is performed while the piston 31 is descending and the area of ​​the cylinder inner wall surface exposed by the piston 31 is increasing, so the amount of fuel adhering to the cylinder inner wall surface is relatively large. Therefore, the fuel injection amount for intake stroke injection is greater than the fuel injection amount for compression stroke injection.

[0031] Specifically, the ECU 100 calculates the intake stroke injection increase amount by referring to the maps shown in Figs. 4A to 4C. Figs. 4A to 4C are examples of maps that define the intake stroke injection increase amount. Fig. 4A is an example of a map that defines the intake stroke injection increase amount according to the intake air amount. The vertical axis indicates the intake air amount [g / sec], and the horizontal axis indicates the intake stroke injection increase amount [mg]. The map in Fig. 4A defines the intake stroke injection increase amount to be larger as the intake air amount increases. This is because if the intake air amount is large, the amount of fuel adhering to the cylinder inner wall surface will also increase due to the air introduced into the cylinder.

[0032] Fig. 4A also shows the cases where the coolant temperature is low and high. The map in Fig. 4A specifies that the intake stroke injection increase amount is greater when the coolant temperature is low than when the coolant temperature is high. This is because when the coolant temperature is low, the temperature of the cylinder inner wall surface is also low, and the amount of fuel adhering to the cylinder inner wall surface increases. Note that the temperature of the lubricating oil may be used instead of the temperature of the coolant.

[0033] FIG. 4B is an example of a map that specifies the intake stroke injection increase amount according to the number of intake stroke injections. The vertical axis indicates the number of intake stroke injections [-], and the horizontal axis indicates the intake stroke injection increase amount [mg]. In the map of FIG. 4B, the intake stroke injection increase amount is specified to decrease as the number of intake stroke injections increases. This is because the amount of new fuel adhering to the cylinder inner wall surface gradually decreases as the number of intake stroke injections increases. This makes it possible to suppress unnecessary increases in the fuel injection amount and suppress deterioration of fuel economy.

[0034] FIG. 4C is an example of a map that specifies the intake stroke injection increase amount according to the total number of compression stroke injections. The vertical axis indicates the total number of compression stroke injections [-], and the horizontal axis indicates the intake stroke injection increase amount [mg]. The total number of compression stroke injections is the total number of compression stroke injections performed after the start request of the engine 10 is made and before the intake stroke injection is performed, and is also the target number of compression stroke injections. In the map of FIG. 4C, the intake stroke injection increase amount is specified to increase as the total number of compression stroke injections decreases. This is because the compression stroke injection is switched to the intake stroke injection before the combustion state of the engine 10 becomes stable as the total number of compression stroke injections decreases. This increases the fuel injection amount in the intake stroke injection, thereby stabilizing the combustion state. The calculation of the intake stroke injection increase amount is not limited to the maps shown in FIG. 4A to FIG. 4C, and may be calculated by an arithmetic expression using the intake air amount, the coolant temperature, the intake stroke injection number, the total number of compression stroke injections, etc. as arguments.

[0035] The ECU 100 performs intake stroke injection by controlling the in-cylinder injection valve 41d to open and close so that the actual fuel injection amount becomes the target injection amount calculated as described above (step S6). Steps S5 and S6 are an example of processing executed by the second control unit.

[0036] Next, the ECU 100 determines whether the number of times the intake stroke injection has been performed has reached the target number (step S7). The target number of intake stroke injections is set to be smaller as the torque required of the engine 10 at the time of the start request is larger. If the result in step S7 is No, the target injection amount is calculated again and the intake stroke injection is performed. If the result in step S7 is Yes, this control is terminated. In this way, when the compression stroke injection and the intake stroke injection have been performed the respective target number of times, the start of the engine 10 is completed.

[0037] As described above, when fuel is injected by the in-cylinder injection valve 41d at the start of the engine 10, the fuel injection amount in the intake stroke injection is greater than the fuel injection amount in the compression stroke injection. This makes it possible to prevent the amount of fuel that actually contributes to combustion in the intake stroke injection from being insufficient, resulting in an unstable combustion state.

[0038] In the above embodiment, the hybrid vehicle is controlled by a single ECU 100. However, the present invention is not limited to this. For example, the above-described control may be performed by a plurality of ECUs, such as an engine ECU for controlling the engine 10, a motor ECU for controlling the motor 15, and a clutch ECU for controlling the K0 clutch 14.

[0039] In the above embodiment, the hybrid vehicle 1 is illustrated as having the K0 clutch 14 provided between the engine 10 and the motor 15, but is not limited thereto. For example, the hybrid vehicle may have an engine and a first motor connected to a drive shaft connected to the drive wheels via a planetary gear, and a second motor connected to the drive shaft. In addition, the hybrid vehicle is not limited to the hybrid vehicle 1, and may be an engine vehicle.

[0040] Although the 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 variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0041] 10 Engine 14 K0 clutch 15 Motor 41d In-cylinder injection valve 100 ECU (first control unit, second control unit)

Claims

[Claim 1] A start control device for an internal combustion engine having an in-cylinder injection valve capable of performing a compression stroke injection, which is a fuel injection in the compression stroke, and an intake stroke injection, which is a fuel injection in the intake stroke, comprising: a first control unit that executes the compression stroke injection when there is a request to start the internal combustion engine; a second control unit that, after the compression stroke injection, increases a fuel injection amount to be larger than the fuel injection amount in the compression stroke injection and executes the intake stroke injection, The target injection amount in the compression stroke injection is calculated as a basic injection amount plus a non-contributing fuel increase amount, The non-contributing fuel increase amount is calculated to be larger as the temperature of the cooling water of the internal combustion engine is lower, the target injection amount for the intake stroke injection is calculated by adding the non-contributing fuel increase amount to the basic injection amount, and further adding an intake stroke injection increase amount to the non-contributing fuel increase amount, the intake stroke injection increase amount is set so as to increase as the intake air amount of the internal combustion engine increases, The intake stroke injection increase amount is set to be larger when the temperature of the cooling water of the internal combustion engine is low than when the temperature of the cooling water is high, A start control device for an internal combustion engine, wherein the intake stroke injection increase amount is specified to decrease as the number of intake stroke injections increases.

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