Control device for internal combustion engines

Abstract

This device suppresses and reduces the formation or accumulation of deposits in the intake port during low-speed operation, such as idling. [Solution] A control device for an internal combustion engine equipped with an injector that injects fuel toward an intake port, the controller comprising: a port injection determination unit (step S1) that determines whether the operating conditions for port injection are met; a deposit accumulation determination unit (step S2) that determines whether deposits have accumulated in the intake port; an idling determination unit (step S3) that determines whether the conditions for idling operation are met; and an idling condition change unit (step S4) that changes the operating conditions during idling operation when it is determined that the operating conditions for port injection are met, deposits have accumulated, and the conditions for idling operation are met.

Description

Technical Field

[0001] The present invention relates to a device for controlling an operating state such as the rotational speed of an internal combustion engine, and particularly to a device for controlling an internal combustion engine provided with an injector that injects fuel into an intake port.

Background Art

[0002] An internal combustion engine (hereinafter referred to as an engine) configured to inject fuel into an intake port or the inside of a cylinder is known. As a technical problem in the case of injecting fuel into an intake port, there is a problem of deposit accumulation. Substances contained in the fuel remaining as droplets on the inner wall surface of the intake port, the intake valve, etc. coagulate due to a temperature drop, chemical reaction, etc., and deposits are gradually formed as this accumulates. Deposits in the intake port not only narrow the intake passage, but also, when peeled off, get caught between the intake valve and the seat, causing the intake valve not to close completely and resulting in misfires.

[0003] A device configured to suppress deposits is described in Patent Document 1. The control device described in Patent Document 1 is a control device for an engine configured to perform fuel injection into an intake port (hereinafter sometimes referred to as port injection) and fuel injection into a cylinder (hereinafter sometimes referred to as in-cylinder injection), and is configured to perform control to suppress deposits from adhering to the back surface of the umbrella portion (the surface on the intake port side) of the intake valve. According to the description of Patent Document 1, in an operating state where in-cylinder injection is performed, when a predetermined operating state such as high load and high rotational speed operation occurs where deposits are likely to adhere to the back surface of the umbrella portion of the umbrella portion of the intake valve, a part of the fuel injection amount supplied to the cylinder each time is injected by the port injection injector as the port injection amount, and the remaining part of the fuel injection amount is injected by the in-cylinder injection injector as the in-cylinder injection amount. By doing so, the umbrella portion of the intake valve is cooled and washed by the fuel injected from the port injection injector, so it is said that deposits can be suppressed.

Prior Art Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-117661 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Deposits caused by the condensation of so-called solid components in fuel occur when fuel remains as liquid droplets, their temperature drops, or they react with NOx, etc. Therefore, deposits occur not only on the underside of the intake valve umbrella due to in-cylinder injection, but also in the intake port due to port injection. For example, if the intake port closes with a delay after compression in the cylinder, blowback may occur where intake air that has entered the cylinder flows back to the intake port. The fuel in this blowback intake air remains in the intake port and forms liquid droplets, which can increase deposits. The device described in Patent Document 1 controls the system to increase port injection, which may increase deposits in the intake port.

[0006] The control device described in Patent Document 1 uses port injection for a portion of the fuel that is injected into the cylinder. However, for example, during idling, in order to avoid noise from the pump that pressurizes the fuel for in-cylinder injection, in-cylinder injection may not be performed. In such cases, the entire amount of fuel is injected into the port, which increases the likelihood of deposit buildup. Moreover, during low-speed, low-load operation such as idling, deposits are more likely to form due to factors such as slow airflow velocity in the intake port. Conventionally, no technology has been known to suppress deposits in the intake port, and it was necessary to develop a new technology.

[0007] The present invention has been made against the background described above, and aims to provide a control device for an internal combustion engine that can suppress or reduce the generation or accumulation of deposits in the intake port during low-speed operation such as idling. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides a control device for an internal combustion engine comprising an intake port through which intake air flows into the inside of a cylinder, and an injector that injects fuel into the intake port, wherein the device has a controller for controlling the internal combustion engine, and the controller is characterized by comprising: a port injection determination unit that determines whether the operating conditions for injecting fuel from the injector into the intake port are met; a deposit accumulation determination unit that determines whether deposits have accumulated in the intake port; an idling determination unit that determines whether the conditions for performing idling operation are met; and an idling condition change unit that changes the operating conditions during idling operation when the port injection determination unit determines that the operating conditions for injecting fuel into the intake port are met, the deposit accumulation determination unit determines that deposits have accumulated in the intake port, and the idling determination unit determines that the conditions for performing idling operation are met.

[0009] In the present invention, the idling condition changing unit may be configured to increase the load or rotational speed, which are the operating conditions during idling operation, from the value during idling operation when the determination that deposits have accumulated in the intake port has not been made.

[0010] In the present invention, the controller may further include a deposit accumulation elimination determination unit that determines whether the accumulation of deposits in the intake port has been eliminated, and may be configured to eliminate the change in operating conditions during idling operation when the determination that the accumulation of deposits in the intake port has been eliminated is successful. [Effects of the Invention]

[0011] In this invention, when fuel is injected into the intake port, deposits have accumulated in the intake port, and conditions for idling operation are met, the idling operation is not performed uniformly under the operating conditions defined for steady state, for example, but rather the operating conditions are changed. The change in operating conditions may be an increase in the load or rotational speed during idling operation. Therefore, by increasing the amount or velocity of intake air along the inner wall surface of the intake port, the accumulation of deposits is suppressed or accumulated deposits are removed, thereby suppressing the adhesion and accumulation of deposits in the intake port or reducing the amount of deposited deposits. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram illustrating the principle of the engine targeted in the embodiment of the present invention. [Figure 2] This is a block diagram illustrating the functional configuration of the controller. [Figure 3] This is a flowchart illustrating an example of the control implemented in an embodiment of the present invention. [Modes for carrying out the invention]

[0013] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the embodiments described below are merely examples of how the present invention can be implemented and do not limit the invention.

[0014] The internal combustion engine (hereinafter referred to as "engine") to be controlled in the present invention is an engine that supplies fuel by injection, and may be an engine with a conventionally known configuration as described in the aforementioned Patent Document 1, etc. Figure 1 shows a schematic diagram of the principle configuration of the engine 1 in an embodiment of the present invention. A piston 3 that reciprocates inside the cylinder 2 is provided, and the space between the piston 3 and the cylinder head 4 is the combustion chamber 5. Conversely, a crankcase 6 is provided in the lower part of the cylinder 2 in Figure 1, and a crankshaft 7 housed inside it is connected to the piston 3. The cylinder head 4 is provided with an intake port 8 and an exhaust port 9, with an intake passage 10 communicating with the intake port 8 and an exhaust passage 11 communicating with the exhaust port 9. In addition, an intake valve 12 is provided that opens and closes the intake port 8 according to the rotation angle of the crankshaft 7, and similarly, an exhaust valve 13 is provided that opens and closes the exhaust port 9 according to the rotation angle of the crankshaft 7. Note that the intake port 8 and exhaust port 9 refer not only to the open ends that are opened and closed by valves 12 and 13, but also to predetermined areas on the sides of each passage 10 and 11.

[0015] The engine 1 shown in Figure 1 is a gasoline-fueled engine, with a spark plug 14 located near the top of the combustion chamber 5. The intake passage 10 is equipped with a throttle valve 16 that adjusts the amount of air drawn in via an air filter 15. The throttle valve 16 is an electronic throttle valve whose opening is electrically controlled according to the load (or power demand) of the engine 1. Furthermore, a port injector 17 is provided to inject fuel into the intake port 8. Additionally, an in-cylinder injector 18 is provided to directly inject fuel into the combustion chamber 5.

[0016] Engine 1 is the power source for the vehicle in which it is installed, and a transmission 20 equipped with a torque converter 19 is connected to its output side. This transmission 20 may be an automatic transmission of a conventional configuration, and is configured to output drive torque to drive wheels (not shown). A clutch 21 may be provided to selectively connect and disconnect the torque converter 19 from the engine 1. In addition, auxiliary equipment 22 that operates using the power output by the engine 1 is connected to the output side of the engine 1. Examples of auxiliary equipment 22 include an air conditioning system and an alternator. These torque converter 19 and auxiliary equipment 22 consume the power output by the engine 1 when they operate, and therefore are devices that load the engine 1. When these loads are applied, the engine 1 increases the opening of the throttle valve 16 to output power corresponding to the load, and increases the fuel supply amount accordingly. Therefore, the load manifests as the opening of the throttle valve 16.

[0017] In the engine 1 described above, deposits may adhere to and accumulate in the intake port 8, and a controller 23 is provided to control the system to suppress these deposits. The controller 23 is mainly composed of a microcomputer consisting of a processing element (CPU), memory elements (RAM, ROM), and interfaces, and performs calculations using input data and pre-stored data, outputting the results of the calculations as command signals. Examples of input data include vehicle speed V, accelerator pedal depression ACC (not shown), engine speed Ne, engine coolant temperature (water temperature) T, and signals for misfires that are likely to occur during cold starts. An example of pre-stored data is a map that defines the operating range for port injection, where fuel is injected into the intake port 8, and the operating range for in-cylinder injection, where fuel is injected into the combustion chamber 5, using vehicle speed V and accelerator pedal depression ACC as parameters. Furthermore, the output control command signals include signals to control the opening degree of the throttle valve 16, signals to control the fuel injection amount, signals to select the injector to inject fuel, signals to engage or disengage the aforementioned clutch 21, and signals to control the auxiliary equipment 22.

[0018] The controller 23 is configured to perform control to suppress or reduce deposits during idling operation, where driving conditions can be set relatively freely, and the functional configuration for this control is shown in Figure 2. The controller 23 includes a port injection determination unit 23a that determines whether the driving conditions for injecting fuel into the intake port 8 are met. This determination can be made, for example, based on the vehicle speed V, the accelerator opening ACC, and the aforementioned map stored in the controller 23.

[0019] In addition, a deposit accumulation determination unit 23b is provided in the controller 23. When deposits have accumulated to a certain extent in the intake port 8, misfires may occur when the engine 1 is started in a cold state. Therefore, the deposit accumulation determination unit 23b can be configured to determine that deposits are accumulated when misfires occur continuously or when the number of misfires within a predetermined time reaches a predetermined number.

[0020] Furthermore, an idling determination unit 23c is provided in the controller 23. Since the engine 1 is idling when the ignition switch (not shown) of the vehicle on which the engine 1 is mounted is on and the accelerator opening ACC is substantially "0", the idling determination unit 23c determines that the conditions for performing idling operation are satisfied based on the state of the ignition switch and the accelerator opening ACC.

[0021] The controller 23 includes an idling condition changing unit 23d. During the idling operation of the engine 1, the opening of the throttle valve 16, the fuel injection amount, and the injector are controlled so as to maintain a predetermined target rotational speed according to the water temperature, the operating state of the accessories 22, the shift position selected by the transmission 20, etc. Therefore, these operating conditions during idling operation are determined based on the state of the engine 1 or the vehicle at that time. The idling condition changing unit 23d is configured to change the thus determined operating state (load, rotational speed, etc.). The change of load is, for example, control such as starting the air conditioning system, generating electricity by the alternator, engaging the clutch 21 to connect the torque converter 19 to the engine 1.

[0022] And a deposit accumulation cancellation determination unit 23e is provided in the controller 23. The deposit accumulation cancellation determination unit 23e is a functional means for determining that the accumulation of the deposit determined by the above-described deposit accumulation determination unit 23b has been canceled, and thus can be said to be a functional means for making a determination opposite to that of the above-described deposit accumulation determination unit 23b. The determination can be made, for example, by the fact that the result of the engine 1 is not detected, or that continuous misfires are not detected, or that the frequency of misfires is below a predetermined frequency.

[0023] To explain the control executed by the above-described controller 23, FIG. 3 is a flowchart for explaining an example of the control. The routine shown here is repeatedly executed in a predetermined short cycle in a state where an ignition switch or a ready switch of a vehicle equipped with the engine 1 is turned on and the engine 1 is started. In step S1, it is determined whether or not the port injection condition is satisfied. This determination is executed as its function by the above-described port injection determination unit 23a. That is, the determination in step S1 can be made based on the vehicle speed V, the accelerator opening ACC, and a map stored in advance.

[0024] If the result of the determination in step S1 is "No", the process returns without performing any particular control. Conversely, if the result of the determination in step S1 is "Yes", in step S2, it is determined whether or not there is deposit accumulation in the intake port 8. This determination is executed as its function by the above-described deposit accumulation determination unit 23b. That is, the determination in step S2 can be made based on the misfire state determined based on a detection signal from, for example, a knock sensor.

[0025] If the result of the judgment in step S2 is "no", the system returns without any further control. If the result of the judgment in step S2 is "yes", the system proceeds to step S3 to perform an idle determination. The idle determination determines whether the conditions for idling engine 1 are met. In the control example shown in Figure 3, since engine 1 is already running, this determination can be made by determining that the accelerator opening ACC is effectively "0".

[0026] If the accelerator pedal is pressed down (not shown) or the accelerator opening is increased, the result of the judgment in step S3 will be "No". In that case, the system returns without any further control. On the other hand, if the result of the judgment in step S3 is "Yes", the system proceeds to step S4 to change the driving conditions during idling. This control is performed by the idling driving condition changing unit 23d as described above. That is, as described above, the driving conditions during idling are determined based on the state of the engine 1 or the vehicle in which it is installed at that time, and more specifically, the target idle speed is set based on the load from the water temperature T and auxiliary equipment 22. In step S4, the target idle speed and the load on which it is based are changed. More specifically, the target idle speed and the load values ​​are increased. The target idle speed is set to a value obtained by adding a predetermined number of rotational speeds. The load can be increased by driving the auxiliary equipment 21, increasing their rotational speed, or connecting the torque converter 19 to the engine 1.

[0027] By changing the operating conditions (engine speed and load) during idling as described above, the amount and flow velocity of intake air in the intake port 8 increases compared to so-called normal operation before changing the operating conditions. As a result, so-called blowback fuel droplets adhering to the inner wall surface of the intake port 8, and solid particles solidifying to form deposits are avoided or suppressed, and already accumulated deposits are peeled off or washed away, reducing their amount. Thus, in step S5, it is determined whether the deposits have decreased and their accumulation has been eliminated. This determination is a function of the deposit accumulation elimination determination unit 23e described above, and in other words, it is the opposite of the determination in step S2 that deposit accumulation is present. Therefore, the determination that deposit accumulation has been eliminated can be made, for example, by the absence of misfire detection, or by the decrease in the number or frequency of misfires to below a predetermined value. If the result of the determination in step S5 is "no", the process returns to step S4, and idling operation continues with the changed operating conditions. If the result of the judgment in step S5 is "yes," the system returns. That is, the modified idling conditions are restored to their original state, and the control for suppressing or reducing deposits is terminated.

[0028] According to the control described above in the embodiment of the present invention, the amount of deposits generated or accumulated in the intake port 8 can be reduced, making misfires of the engine 1 less likely and improving so-called misfire resistance. Furthermore, in this case, so-called port injection is sufficient, and there is no need to perform high-pressure in-cylinder injection, so there is no need to drive a high-pressure pump for in-cylinder injection or generate the associated noise, thus not worsening the vehicle's vibration noise characteristics (NV characteristics).

[0029] It should be noted that the present invention is not limited to the embodiments described above, and the controller may be a controller provided separately from the control device that controls the engine, or it may be configured as part of the control device that controls the engine. Furthermore, the determination of whether deposits have accumulated is not limited to determination based on engine misfires, but may be performed by various conventionally known means. Moreover, the idling conditions before being changed by the idling condition change unit in the present invention may be any conditions determined in so-called normal operation, and therefore, the present invention is essentially configured to change the operating conditions during idling operation on the condition that port injection, deposit accumulation, and idling operation are determined to be successful. [Explanation of Symbols]

[0030] 1 Engine 2 liters 3 pistons 4 Cylinder head 5 Combustion chamber 6 Crankcase 7 Crankshaft 8 intake ports 9 Exhaust Ports 10 Intake passage 11 Exhaust passage 12 Intake valves 13 Exhaust valve 14 Spark plugs 15 Air filter 16 Throttle valve 17 Port Injector 18 In-cylinder injectors 19 Torque converter 20-speed transmission 21 Clutch 22 Auxiliary equipment 23 Controllers 23a Port injection determination unit 23b Deposit deposition determination section 23c Idling detection unit 23d Idling Condition Change Section 23d Idling operation condition change section 23e Deposit accumulation removal determination section

Claims

1. A control device for an internal combustion engine, comprising an intake port through which intake air flows into the inside of a cylinder, and an injector that injects fuel into the intake port, It has a controller that controls the internal combustion engine, The aforementioned controller, A port injection determination unit that determines whether the operating conditions for injecting fuel from the injector into the intake port are met, A deposit accumulation determination unit that determines whether deposits have accumulated in the intake port, An idling determination unit that determines whether the conditions for idling operation are met, When the port injection determination unit determines that the operating conditions for injecting fuel into the intake port are met, the deposit accumulation determination unit determines that deposits have accumulated in the intake port, and the idling determination unit determines that the conditions for performing idling operation are met, the idling condition change unit changes the operating conditions during idling operation. It is equipped with A control device for an internal combustion engine, characterized by the following features.

2. A control device for an internal combustion engine according to claim 1, The idling condition changing unit is configured to increase the load or rotational speed, which are the operating conditions during idling operation, from the value during idling operation when the determination that deposits have accumulated in the intake port has not been made. A control device for an internal combustion engine, characterized by the following features.

3. A control device for an internal combustion engine according to claim 1 or 2, The controller further includes a deposit accumulation elimination determination unit that determines whether the deposit accumulation in the intake port has been eliminated. The system is configured to eliminate changes to the operating conditions during idling operation when it is determined that the deposit buildup in the intake port has been eliminated. A control device for an internal combustion engine, characterized by the following features.

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