Internal combustion engine

Abstract

This technology provides a way to suppress the excessive accumulation of fuel-derived deposits in the intake ports of internal combustion engines. [Solution] The internal combustion engine includes a first injection valve that injects fuel into the intake port, a second injection valve that injects fuel into the cylinder of the internal combustion engine, and a control unit that controls the in-cylinder injection ratio, which is the ratio of the in-cylinder injection amount to the total amount of the port injection amount (fuel injection amount from the first injection valve) and the in-cylinder injection amount (fuel injection amount from the second injection valve). The control unit of the internal combustion engine sets the in-cylinder injection ratio to 100% in a predetermined operating range in response to the detection of deposit accumulation in the intake port.

Description

Technical Field

[0006] , , , , , ,

[0001] The present disclosure relates to an internal combustion engine.

Background Art

[0002] An internal combustion engine including a port injection valve that injects fuel into an intake port and an in-cylinder injection valve that directly injects fuel into a cylinder is known. In such an internal combustion engine, in a predetermined operating state where deposits are likely to adhere to the back of the intake valve umbrella, a part of the fuel injection amount to be supplied to the cylinder per cycle is injected from the port injection valve, and the rest is injected from the in-cylinder injection valve (see, for example, Patent Document 1).

[0003] Also, a technique is known in which when deposits adhering to the back of the intake valve umbrella are to be cleaned, the fuel injection from the in-cylinder injection valve is stopped and the fuel injection from the port injection valve is performed (see, for example, Patent Document 2).

[0004] Also, when fuel injection is being performed from the port injection valve in an idle operating state, if the estimated amount of deposit accumulation in the in-cylinder injection valve becomes larger than a predetermined amount, a technique is known in which the fuel injection from the port injection valve is stopped and the fuel injection from the in-cylinder injection valve is performed (see, for example, Patent Document 3).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0007] The aspect of this disclosure is an internal combustion engine. In that case, the internal combustion engine is, for example, A first injection valve that injects fuel into the intake port of an internal combustion engine, A second injection valve that injects fuel into the cylinder of the internal combustion engine, A control unit controls the in-cylinder injection ratio, which is the ratio of the in-cylinder injection amount to the total amount of the port injection amount, which is the fuel injection amount of the first injection valve, and the in-cylinder injection amount, which is the fuel injection amount of the second injection valve. Equipped with, The control unit, To detect the accumulation of deposits in the intake port, In response to the detection of deposit accumulation in the intake port, the in-cylinder injection ratio in a predetermined operating range is set to 100%. It may be configured to perform the following: [Effects of the Invention]

[0008] This disclosure provides an effective technique for suppressing the excessive accumulation of fuel-derived deposits in the intake ports of internal combustion engines. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram schematically shows an example of the general configuration of a vehicle in an embodiment. [Figure 2] This figure schematically shows an example of a fuel injection map in an embodiment. [Figure 3] This flowchart shows an example of a processing routine executed by the ECU in the deposit detection process of the embodiment. [Figure 4] This flowchart shows an example of a processing routine executed by the ECU in the deposit accumulation suppression process of the embodiment. [Modes for carrying out the invention]

[0010] In an internal combustion engine equipped with a first injection valve that injects fuel into the intake port and a second injection valve that injects fuel into the cylinder, if the engine is operated in a low-load, low-speed operating range (for example, the idle operating range) where the in-cylinder injection ratio (the ratio (percentage) of the in-cylinder injection amount to the total amount of fuel injected into the port (the fuel injection amount from the first injection valve) and the in-cylinder injection amount (the fuel injection amount from the second injection valve) is 0%, some of the fuel injected from the first injection valve may blow back from the cylinder into the intake port and adhere to the intake port wall. As a result of repeated diligent experiments and verifications by the inventors of this invention, it has been found that if the internal combustion engine is operated for a long time in an operating state where the in-cylinder injection ratio is 0%, deposits derived from the fuel adhering to that part (hereinafter sometimes referred to as "adhered fuel") may be generated and accumulate on the intake port wall, and that the accumulation of deposits may peel off from the intake port wall, causing a malfunction of the intake valve. Therefore, measures are needed to prevent excessive deposit buildup on the intake port wall.

[0011] The internal combustion engine described herein was developed to solve the above-mentioned problems and includes a control unit configured to set the in-cylinder injection ratio to 100% in a predetermined operating range in response to the detection of deposit accumulation in the intake port. The "predetermined operating range" in this disclosure may, in one example, be an operating range where the in-cylinder injection ratio is set to 0% under normal conditions (when no deposit accumulation in the intake port is detected), such as a low-load, low-speed operating range. In another example, the "predetermined operating range" may be an operating range where the in-cylinder injection ratio is set to less than 100% under normal conditions (an operating range where the port injection ratio (the ratio of the port injection amount to the total amount of port injection amount and in-cylinder injection amount (percentage)) is set to a percentage greater than 0%). In this case, the in-cylinder injection ratio is set to 100% (port injection ratio is 0%) in all operating ranges of the internal combustion engine.

[0012] According to the internal combustion engine according to the present disclosure, it is possible to suppress an excessive amount of deposits derived from the fuel injected from the first injection valve from accumulating on the back surface of the umbrella portion of the intake port and the intake valve.

[0013] Here, in the internal combustion engine according to the present disclosure, detecting the accumulation of deposits in the intake port may include determining that deposits have accumulated in the intake port in response to detecting consecutive misfires at the start of the internal combustion engine, detecting compression loss at the start of the internal combustion engine, or the time length until a rich deviation in the air-fuel ratio occurs from the fuel injection timing of the first injection valve becoming equal to or greater than a predetermined threshold value. Further, in the internal combustion engine according to the present disclosure, the predetermined operating region may at least include a low load and low rotation operating region.

[0014] Hereinafter, specific embodiments of the present disclosure will be described based on the drawings. The hardware configuration, module configuration, functional configuration, etc. described in the following embodiments are not intended to limit the technical scope of the disclosure only to those without specific description.

[0015] <Embodiment> FIG. 1 is a diagram showing an example of a schematic configuration of a vehicle 1 to which the present disclosure is applied. The vehicle 1 illustrated in FIG. 1 is an automobile equipped with an internal combustion engine 10. Such a vehicle 1 may be an internal combustion engine vehicle having the internal combustion engine 10 as a prime mover, may be a HEV (Hybrid Electric Vehicle) or a PHEV (Plug-in Hybrid Electric Vehicle) having a hybrid system of the internal combustion engine 10 and an electric motor as a prime mover, or may be a BEV (Battery Electric Vehicle) having an electric motor that operates using the electric power generated by the internal combustion engine 10 as a prime mover.

[0016] The internal combustion engine 10 has one or more cylinders 101 and is a spark ignition four-cycle engine (gasoline engine) that uses gasoline as fuel. The internal combustion engine 10 in the present embodiment includes an intake port 102, an exhaust port 103, a port injection valve 104, an in-cylinder injection valve 105, a spark plug 106, an intake valve 107, and an exhaust valve 108. The intake port 102 is a passage through which air inhaled into the cylinder 101 flows. The exhaust port 103 is a passage through which the burned gas discharged from the inside of the cylinder 101 flows. The port injection valve 104 is a fuel injection valve (injector) that injects fuel into the intake port 102. The in-cylinder injection valve 105 is a fuel injection valve (injector) that injects fuel into the cylinder 101. The spark plug 106 is a component for igniting the air-fuel mixture generated inside the cylinder 101. The intake valve 107 is a poppet valve that opens and closes the open end on the downstream side of the intake port 102. The exhaust valve 108 is a poppet valve that opens and closes the open end on the upstream side of the exhaust port 103. In the present embodiment, the port injection valve 104 corresponds to the "first injection valve" according to the present disclosure, and the in-cylinder injection valve 105 corresponds to the "second injection valve" according to the present disclosure.

[0017] In addition, the vehicle 1 in the present embodiment is equipped with a fuel tank 20, a feed pump 21 ("FP" in FIG. 1), and a supply pump 22 ("SP" in FIG. 1). The fuel tank 20 is a tank that stores gasoline, which is the fuel for the internal combustion engine 10. The feed pump 21 is a pump that pumps up the fuel stored inside the fuel tank 20 and sends the pumped-up fuel to each of the port injection valve 104 and the supply pump 22. The supply pump 22 is a pump that pressurizes the fuel sent from the feed pump 21 and sends the pressurized fuel to the in-cylinder injection valve 105.

[0018] In addition, the vehicle 1 in the present embodiment is equipped with an ECU (Electronic Control Unit) 30 for electrically controlling the internal combustion engine 10 and its peripheral devices. The ECU 30 is CP This is a computer having a U, ROM, RAM, and auxiliary storage device. In this embodiment, in addition to the fuel level sensor 301 described above, the ECU 30 is connected to various sensors such as a crank position sensor 302, an accelerator position sensor 303, an air flow meter 304, a water temperature sensor 305, an A / F sensor 306, and an outside air temperature sensor 307, and the signals from these sensors are input to the ECU 30. The crank position sensor 302 is a sensor that detects the rotational position of the output shaft (crankshaft) of the internal combustion engine 10. The accelerator position sensor 303 is a sensor that detects the amount of operation of the accelerator pedal. The air flow meter 304 is a sensor that detects the amount of intake air of the internal combustion engine 10. The water temperature sensor 305 is a sensor that detects the temperature of the coolant circulating in the internal combustion engine 10. The A / F sensor 306 is a sensor that detects the air-fuel ratio (A / F) of the mixture used for combustion in the cylinder 101 according to the oxygen concentration in the exhaust of the internal combustion engine 10. The outside temperature sensor 307 is a sensor that detects the temperature outside the vehicle.

[0019] Furthermore, the ECU 30 is electrically connected to the aforementioned devices such as the port injection valve 104, in-cylinder injection valve 105, spark plug 106, feed pump 21, and supply pump 22. The ECU 30 is configured to control the port injection valve 104, in-cylinder injection valve 105, spark plug 106, feed pump 21, and supply pump 22 in response to signals input from the aforementioned sensors.

[0020] In one example, the ECU 30 determines the fuel injection amount per cycle for each of the port injection valve 104 and the in-cylinder injection valve 105, according to the operating state of the internal combustion engine 10. More specifically, the ECU 30 first calculates the engine rotational speed Ne and the engine load ratio KL for each cycle of the internal combustion engine 10. Here, the engine rotational speed Ne is the rotational speed of the crankshaft per unit time and is calculated according to the signal from the crank position sensor 302. The engine load ratio KL is the ratio of the current intake air amount to the maximum intake air amount corresponding to each engine rotational speed Ne (intake air amount at full load) and is calculated according to the signal from the airflow meter 304 (intake air amount) and the engine rotational speed Ne.

[0021] The ECU 30 calculates the in-cylinder injection ratio (percentage) according to the calculated engine rotation speed Ne and engine load ratio KL. The in-cylinder injection ratio here refers to the total fuel injection amount per cycle for each cylinder 101 (the sum of the amount of fuel injected from the port injection valve 104 (port injection amount) and the amount of fuel injected from the in-cylinder injection valve 105 (in-cylinder injection amount)). In one example, the ECU 30 calculates the in-cylinder injection ratio using an injection distribution map with engine rotation speed Ne and engine load ratio KL as arguments. The injection distribution map is pre-stored in the ROM or auxiliary storage device of the ECU 30. At that time, the ROM or auxiliary storage device of the ECU 30 stores multiple injection distribution maps according to the coolant temperature and ambient temperature, etc.

[0022] Here, an example of an injection distribution map is shown in Figure 2. The injection distribution map shown in Figure 2 is a map that sets the in-cylinder injection ratio after the internal combustion engine 10 has finished warming up. In the example shown in Figure 2, in the low-load, low-speed operating region (region M1 in Figure 2) where the engine speed Ne and engine load ratio KL are relatively low, the in-cylinder injection ratio is set to 0%. In the high-speed operating region where the engine speed Ne is relatively high and / or the high-load operating region where the engine load ratio KL is relatively high (region M3 in Figure 2), the in-cylinder injection ratio is set to 100%. Furthermore, in the medium-load, medium-speed operating region other than regions M1 and M3 (region M2 in Figure 2), the in-cylinder injection ratio is set within the range of 1% to 99% according to the engine speed Ne and engine load ratio KL.

[0023] The ECU 30 calculates the in-cylinder injection amount and the port injection amount according to the in-cylinder injection ratio and the total fuel injection amount. Specifically, the ECU 30 calculates the in-cylinder injection amount by multiplying the total fuel injection amount by the in-cylinder injection ratio. The total fuel injection amount per cycle for each cylinder 101 may, for example, be calculated according to the signal from the airflow meter 304 (intake air amount) and the target air-fuel ratio (e.g., stoichiometric air-fuel ratio). The ECU 30 also calculates the port injection amount by subtracting the in-cylinder injection ratio from the total fuel injection amount. Alternatively, the port injection amount may be calculated by first calculating the port injection ratio from the in-cylinder injection ratio (100% - in-cylinder injection ratio) and then multiplying the calculated port injection ratio by the total fuel injection amount.

[0024] The ECU 30 controls the supply pump 22 and the in-cylinder injection valve 105 according to the calculated in-cylinder injection amount, and also controls the port injection valve 104 according to the calculated port injection amount. This allows fuel to be injected from both the port injection valve 104 and the in-cylinder injection valve 105 at an in-cylinder injection ratio suitable for the operating state of the internal combustion engine 10.

[0025] Furthermore, the ECU 30 in this embodiment also has a function to perform a deposit accumulation detection process. The deposit accumulation detection process is a process for detecting the accumulation of deposits in the intake port 102. In addition, the ECU 30 in this embodiment also has a function to perform a deposit accumulation suppression process in response to the detection of deposit accumulation in the intake port 102. The deposit accumulation suppression process is a process for suppressing the increase in the amount of deposit accumulation in the intake port 102. The ECU 30 having these functions corresponds to the "control unit" in this disclosure.

[0026] (Deposit detection process) Here, the deposit accumulation detection process in this embodiment will be described. When the internal combustion engine 10 is operated with a certain amount or more of deposits accumulated on the wall surface of the intake port 102, some of the deposits may peel off from the wall surface of the intake port 102 during the cranking of the internal combustion engine 10, causing a malfunction in the closing of the intake valve 107. This results in a loss of compression, where the compression pressure of cylinder 101 decreases, and consequently, a series of misfires (a phenomenon in which misfires occur continuously for two or more cycles) occurs in that cylinder 101. Such loss of compression and series of misfires are likely to occur during cranking when the engine is cold-started. Therefore, in the deposit accumulation detection process in this embodiment, the ECU 30 is configured to determine whether a series of misfires has occurred in each cylinder 101 during the cranking of the internal combustion engine 10.

[0027] Figure 3 is a flowchart showing an example of a processing routine executed by the ECU 30 in the deposit accumulation detection process of this embodiment. The processing routine shown in Figure 3 is executed when the cranking of the internal combustion engine 10 is started.

[0028] In Figure 3, the ECU 30 determines whether a misfire has occurred in any of the cylinders 101 of the internal combustion engine 10 (step S101). The method for determining a misfire is not particularly limited, and any well-known method may be used. For example, the ECU 30 may determine whether a misfire has occurred in each cylinder 101 based on the angular velocity of the crankshaft during cranking of the internal combustion engine 10. For example, if a misfire occurs in the first cylinder 101, the angular velocity of the first cylinder 101 immediately after ignition (e.g., during the expansion stroke) will be significantly lower than the angular velocity of the second cylinder 101 immediately after ignition, which was ignited immediately before the first cylinder 101. Therefore, the ECU 30 may determine that a misfire has occurred in the first cylinder 101 if the angular velocity of the first cylinder 101 immediately after ignition is less than a certain value from the angular velocity of the second cylinder 101 immediately after ignition. If it is determined that a misfire has occurred in any of the cylinders 101 of the internal combustion engine 10 (affirmative determination in step S101), the ECU 30 executes the process in step S102.

[0029] In step S102, the ECU 30 determines whether a misfire occurred in the immediately preceding cycle of cylinder 101 (hereinafter sometimes referred to as "target cylinder 101"), which was determined to have misfired in step S101. That is, the ECU 30 determines whether a series of misfires occurred in target cylinder 101. In making such a determination, the ECU 30 may store the identification information (e.g., cylinder ID) of cylinder 101, which was determined to have misfired in the immediately preceding cycle, in an auxiliary storage device. The ECU 30 then compares the cylinder ID of target cylinder 101 with the cylinder ID stored in the auxiliary storage device, and determines that a series of misfires occurred in target cylinder 101 if the comparison is successful. If it is determined that a series of misfires has occurred in the target cylinder 101 (affirmative determination in step S102), the ECU 30 determines that a certain amount or more of deposit has accumulated on the wall surface of the intake port 102 of the target cylinder 101, and executes the process in step S103.

[0030] In step S103, the ECU 30 sets the value of the deposit flag to "1". The deposit flag is a memory area allocated to the auxiliary memory of the ECU 30, and "1" is stored when it is determined that a certain amount or more of deposit has accumulated on the wall surface of the intake port 102 of any cylinder 101 of the internal combustion engine 10. The initial value of the deposit flag is "0". After completing the process in step S103, the ECU 30 executes the process in step S104.

[0031] In step S104, the ECU 30 stores the flag expiration date, which is the expiration date of the deposit flag set in step S103, in the auxiliary storage device. The flag expiration date is the end of the period required for a certain amount or more of deposit accumulated on the wall surface of the intake port 102 to be removed by chance (or reduced to a sufficiently small amount). In one example, the flag expiration date is several years (for example, about 1 to 2 years) after the deposit flag was set to "1". Furthermore, the time required for a certain amount or more of deposit accumulated on the wall surface of the intake port 102 to be removed by chance (or reduced to a sufficiently small amount) may be determined in advance by experiment and / or simulation, and the flag expiration date may be determined according to the determined time. The flag expiration date determined as described above may be stored in the auxiliary storage device in association with the deposit flag. In addition, it is possible that continuous misfires may occur even when a flag expiration date has already been set. In that case, the flag expiration date stored in the auxiliary storage device may remain as the already set flag expiration date, or it may be updated (overwritten) with a new flag expiration date. When the ECU 30 has finished executing the process in step S104, it terminates the execution of the processing routine in Figure 3.

[0032] Furthermore, if it is determined in step S101 that no misfires have occurred in any of the cylinders 101 of the internal combustion engine 10 (negative determination in step S101), and if it is determined in step S102 that no continuous misfires have occurred in the target cylinder 101 (negative determination in step S102), the ECU 30 executes the process in step S105.

[0033] In step S105, the ECU 30 determines whether the internal combustion engine 10 has finished starting. Various well-known methods can be used to determine whether the internal combustion engine 10 has finished starting. For example, the ECU 30 may determine that the internal combustion engine 10 has finished starting when the engine rotational speed Ne rises to or above a predetermined threshold. If it is determined that the internal combustion engine 10 has not finished starting (negative determination in step S105), the ECU 30 repeats the process in step S101. On the other hand, if it is determined that the internal combustion engine 10 has finished starting (positive determination in step S105), the ECU 30 executes the process in step S106.

[0034] In step S106, the ECU 30 determines whether the value of the deposition flag stored in the auxiliary storage device is "1". If the value of the deposition flag is "1" (positive determination in step S106), the ECU 30 executes the process in step S107.

[0035] In step S107, the ECU 30 determines whether the flag stored in the auxiliary storage device has expired. If the flag has expired (positive determination in step S107), the ECU 30 executes the process in step S108.

[0036] In step S108, the ECU 30 resets the value of the accumulation flag and the flag expiration date stored in the auxiliary storage device. Specifically, the ECU 30 resets the value of the accumulation flag from "1" to "0" and clears (deletes) the flag expiration date. Thus, in this embodiment, if no continuous misfires occur during the period from when the value of the accumulation flag is set to "1" until the flag expiration date arrives, the accumulation flag and flag expiration date are reset. After completing the process in step S108, the ECU 30 terminates the execution of the processing routine shown in Figure 3.

[0037] Furthermore, if it is determined in step S106 that the value of the deposition flag is not "1" (deposition flag = "0") (negative determination in step S106), and if it is determined in step S107 that the flag expiration date has not yet arrived (negative determination in step S107), the ECU 30 terminates the execution of the processing routine shown in Figure 3.

[0038] (Deposit accumulation suppression treatment) Next, the deposit accumulation suppression treatment in this embodiment will be described. The deposit accumulation suppression treatment in this embodiment suppresses the generation and accumulation of deposits on the wall surface of the intake port 102 of the target cylinder 101 until a certain amount or more of deposits accumulated on the wall surface of the intake port 102 of the target cylinder 101 are removed (or reduced to an amount significantly less than a certain amount). This is a process for that purpose. In one example, the deposit accumulation suppression process may be a process that sets the in-cylinder injection ratio in a predetermined operating area to 100% during the period when the accumulation flag is set to "1" (the period until the flag expires). The predetermined operating area is an operating area in which the in-cylinder injection ratio is less than 100% (the port injection ratio is greater than 0%), and in which deposits originating from the fuel injected from the port injection valve 104 are likely to accumulate on the wall surface of the intake port 102. In one example, the predetermined operating area may be an operating area in which the engine load ratio KL and engine rotational speed Ne are low, as shown in the M1 area in Figure 2, and in which the in-cylinder injection ratio is set to 0%. In another example, the predetermined operating area may include the M2 area in addition to the M1 area in Figure 2. That is, the predetermined operating area may also be an operating area in which the in-cylinder injection ratio is less than 100% (the port injection ratio is greater than 0%).

[0039] Figure 4 is a flowchart showing an example of a processing routine executed by the ECU 30 in the deposit accumulation suppression process of this embodiment. The processing routine shown in Figure 4 is repeatedly executed at a predetermined period (for example, every cycle) while the internal combustion engine 10 is running.

[0040] In Figure 4, the ECU 30 determines whether the current operating state of the internal combustion engine 10 belongs to a predetermined operating region (step S201). The predetermined operating region is, as described above, the M1 region in Figure 2 (or the combined operating region of the M1 and M2 regions). In this determination, the ECU 30 first calculates the engine rotational speed Ne and engine load ratio KL in accordance with the signals from the crank position sensor 302 and the airflow meter 304. Next, the ECU 30 accesses the injection distribution map in Figure 2 with the calculated engine rotational speed Ne and engine load ratio KL as arguments to determine whether the operating state specified by the engine rotational speed Ne and engine load ratio KL belongs to the M1 region (or the combined operating region of the M1 and M2 regions). If it is determined that the operating state of the internal combustion engine 10 belongs to the predetermined operating region (affirmative determination in step S201), the ECU 30 executes the process in step S202.

[0041] In step S202, the ECU 30 determines whether the value of the deposition flag stored in the auxiliary storage device is "1". If the value of the deposition flag stored in the auxiliary storage device is "1" (positive determination in step S202), the ECU 30 executes the process in step S203.

[0042] In step S203, the ECU 30 sets the in-cylinder injection ratio to 100% (port injection ratio to 0%). In this case, in a predetermined operating range, the entire amount of fuel is injected from the in-cylinder injection valve 105. That is, in a predetermined operating range, no fuel is injected from the port injection valve 104. As a result, deposits originating from the fuel injected from the port injection valve 104 are not generated in the intake port 102, and the increase in the amount of deposit accumulation on the wall surface of the intake port 102 is suppressed.

[0043] Furthermore, if it is determined in step S201 that the operating state of the internal combustion engine 10 does not belong to a predetermined operating range (negative determination in step S201), the ECU 30 executes the process in step S204. In step S204, the ECU 30 sets the in-cylinder injection ratio according to the injection distribution map in Figure 2 and calculates the in-cylinder injection amount and port injection amount according to the set in-cylinder injection ratio. After completing the process in step S204, the ECU 30 terminates the execution of the processing routine in Figure 4.

[0044] (Effects and Effects of the Embodiment) In this embodiment, if it is determined (estimated) that a certain amount or more of deposit has accumulated on the wall surface of the intake port 102 of the internal combustion engine 10, the in-cylinder injection ratio in a predetermined operating range is set to 100% until the period required for the deposits accumulated on the wall surface of the intake port 102 to be removed (or reduced to a sufficiently small amount) has elapsed. The port injection ratio is set to 0%. This prevents the formation of deposits in the intake port 102 that originate from the fuel injected from the port injection valve 104. As a result, it is possible to suppress the accumulation of deposits on the wall surface of the intake port 102.

[0045] <Example 1> In the deposit accumulation detection process, the ECU 30 may determine that a certain amount or more of deposit has accumulated on the wall surface of the intake port 102 in response to detecting a loss of compression during the cranking of the internal combustion engine 10. Various well-known methods can be used to detect a loss of compression. For example, the ECU 30 may determine whether a loss of compression has occurred based on the angular velocity of the crankshaft when the piston of each cylinder 101 passes the top dead center of compression.

[0046] <Modification 2> In the deposit accumulation detection process, the ECU 30 may determine that a certain amount or more of deposit has accumulated on the wall surface of the intake port 102, depending on whether the time from the fuel injection timing of the port injection valve 104 during the operation of the internal combustion engine 10 until a rich shift in the air-fuel ratio occurs is longer than a predetermined time.

[0047] Here, during the operation of the internal combustion engine 10, some of the fuel injected from the port injection valve 104 adheres to the wall surface of the intake port 102. The fuel that adheres to the wall surface of the intake port 102 in this way (adhered fuel) flows into the cylinder 101 in the intake stroke of the next cycle and beyond. In other words, there is a time delay before the adhered fuel flows into the cylinder 101. This time delay in the flow of the adhered fuel into the cylinder 101 causes a shift in the air-fuel ratio towards the rich side.

[0048] The time delay described above can vary depending on the amount of deposits accumulated on the wall surface of the intake port 102. Specifically, if a certain amount or more of deposits are accumulated on the wall surface of the intake port 102, the time delay tends to be longer than when no deposits are accumulated on the wall surface of the intake port 102 or when the amount of deposits accumulated on the wall surface of the intake port 102 is less than a certain amount. Consequently, if a certain amount or more of deposits are accumulated on the wall surface of the intake port 102, the time from the injection timing of the port injection valve 104 to the occurrence of the richness shift tends to be longer than when no deposits are accumulated on the wall surface of the intake port 102 or when the amount of deposits accumulated on the wall surface of the intake port 102 is less than a certain amount.

[0049] Therefore, if the time elapsed from the fuel injection timing of the port injection valve 104 to the occurrence of a rich air-fuel ratio deviation during the operation of the internal combustion engine 10 is longer than a predetermined time elapsed, it can be determined (estimated) that a certain amount or more of deposit has accumulated on the wall surface of the intake port 102.

[0050] <Variation 3> In the deposit accumulation detection process, the ECU 30 may determine that a certain amount or more of deposit has accumulated on the wall surface of the intake port 102, depending on whether the correction amount of the port injection amount during operation of the internal combustion engine 10 is equal to or greater than a predetermined amount.

[0051] Here, as deposits accumulate on the wall surface of the intake port 102, deposits may also accumulate around the injection holes of the port injection valve 104. In particular, when a fuel with properties that easily generate deposits is used, deposits are likely to accumulate not only on the wall surface of the intake port 102 but also around the injection holes of the port injection valve 104. If the amount of deposits accumulated around the injection holes of the port injection valve 104 becomes large, the injection holes may be narrowed. In that case, the air-fuel ratio feedback control based on the signal from the A / F sensor 306 will control the amount of port injection. The amount is corrected to increase the injection volume. The amount of correction is increased as the amount of deposit accumulation around the injection holes of the port injection valve 104 increases. Therefore, if the amount of correction for the port injection volume is greater than or equal to a predetermined amount, it can be estimated that a certain amount or more of deposit has accumulated on the wall surface of the intake port 102.

[0052] <Other> The embodiments and modifications described above are merely examples, and this disclosure may be modified as appropriate without departing from its essence. For example, the embodiments and modifications described above can be freely combined and implemented, as long as no technical inconsistencies arise. [Explanation of Symbols]

[0053] 1...Vehicle, 10...Internal combustion engine, 102...Intake port, 104...Port injection valve, 30...ECU, 302...Crank position sensor, 304...Airflow meter, 306...A / F sensor

Claims

1. A first injection valve that injects fuel into the intake port of an internal combustion engine, A second injection valve that injects fuel into the cylinder of the internal combustion engine, A control unit controls the in-cylinder injection ratio, which is the ratio of the in-cylinder injection amount to the total amount of the port injection amount, which is the fuel injection amount of the first injection valve, and the in-cylinder injection amount, which is the fuel injection amount of the second injection valve. Equipped with, The control unit, To detect the accumulation of deposits in the intake port, In response to detecting the accumulation of deposits in the intake port, the in-cylinder injection ratio in a predetermined operating range is set to 100%. Configured to perform, Internal combustion engine.

2. Detecting the accumulation of deposits in the intake port includes determining that deposits have accumulated in the intake port in response to detecting a series of misfires during the startup of the internal combustion engine. The internal combustion engine according to claim 1.

3. Detecting the accumulation of deposits in the intake port includes determining that deposits have accumulated in the intake port in response to detecting a loss of compression during the startup of the internal combustion engine. The internal combustion engine according to claim 1.

4. Detecting deposit accumulation in the intake port includes determining that deposits have accumulated in the intake port when the time elapsed from the fuel injection timing of the first injection valve to the occurrence of a rich air-fuel ratio shift exceeds a predetermined threshold. The internal combustion engine according to claim 1.

5. The predetermined operating range includes at least a low-load, low-speed operating range. The internal combustion engine according to claim 1.

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