Control device for an internal combustion engine

Abstract

An object of the present application is to suppress and reduce the generation or accumulation of deposits in an intake port during low-speed operation such as idling. A control device of an internal combustion engine that is provided with an injector that injects fuel into an intake port, wherein the controller is provided with: an intake port injection determination section that determines whether or not an operation condition for intake port injection is satisfied (step S1); a deposit accumulation determination section that determines whether or not there is deposit accumulation in the intake port (step S2); an idling determination section that determines whether or not a condition for idling operation is satisfied (step S3); and an idling condition change section that changes the operation condition during idling operation in the case where it is determined that the operation condition for intake port injection is satisfied, it is determined that there is deposit accumulation, and it is determined that the condition for idling operation is satisfied (step S4).

Description

Technical Field

[0001] This invention relates to a device for controlling the operating state of an internal combustion engine, such as its speed, and more particularly to a device for controlling an internal combustion engine equipped with an injector that injects fuel into the air intake. Background Technology

[0002] An internal combustion engine (hereinafter referred to as an engine) is known to inject fuel into the intake port or the interior of the cylinder. A technical challenge in the case of fuel injection into the intake port is the problem of deposit accumulation. Substances contained in the fuel, remaining as droplets on the inner wall of the intake port or at the intake valve, solidify due to temperature drops or chemical reactions, gradually accumulating to form deposits. These deposits in the intake port not only narrow the intake manifold but, in the event of detachment, can also become lodged between the intake valve and its seat, preventing the intake valve from closing completely and potentially causing misfires.

[0003] Patent Document 1 describes a device configured to suppress deposits. The control device described in Patent Document 1 is for an engine configured to inject fuel into the intake port (hereinafter, sometimes referred to as intake port injection) and into the cylinder (hereinafter, sometimes referred to as cylinder injection). It is configured to control the suppression of deposits adhering to the back of the valve head (the side facing the intake port) in the intake valve. According to Patent Document 1, during cylinder injection operation, and in a specific operating state such as high load and high speed operation, which easily leads to deposits adhering to the back of the valve head of the intake valve, a portion of the fuel injection amount supplied to the cylinder each time is injected as an intake port injection amount by an intake port injection injector, while the remaining fuel injection amount is injected as a cylinder injection amount by a cylinder injection injector. In this way, the valve head of the intake valve is cooled and cleaned by the fuel injected from the intake port injection injector, thus suppressing deposits.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2015-117661 Summary of the Invention

[0005] Deposits formed by the condensation of so-called solid components contained in the fuel are produced when the fuel remains in droplet form, its temperature drops, or it reacts with NOx or the like. Therefore, they are generated not only on the back of the intake valve head due to in-cylinder injection, but also within the intake port through intake manifold injection. For example, in operation where the intake port is closed with a delay compared to compression within the cylinder, the intake air that once entered the cylinder may sometimes flow back to the intake port side, causing a backflow phenomenon. Fuel in this backflowing intake air may temporarily remain within the intake port, forming droplets, which can sometimes contribute to increased deposits. The device described in Patent Document 1, because it controls the process by increasing intake manifold injection, may potentially increase deposits within the intake port.

[0006] The control device described in Patent Document 1 converts a portion of the in-cylinder fuel injection to port injection. However, for example, during idling, to avoid noise from the pump that pressurizes the fuel for in-cylinder injection, in-cylinder injection may sometimes be omitted. In this case, all the fuel will be injected through the port, which may exacerbate deposit buildup. Moreover, deposits are more likely to form during low-speed, low-load operation, such as idling, due to factors such as the slow flow rate in the intake port. There are currently no known technologies to suppress such intake port deposits, therefore, it is necessary to develop new technologies.

[0007] The present invention was made against the background described above, and its purpose is 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.

[0008] To achieve the above-mentioned objective, the present invention provides a control device for an internal combustion engine, the internal combustion engine comprising: an intake port for allowing intake air to flow into the interior of a cylinder; and a fuel injector for injecting fuel into the intake port, wherein the control device includes a controller for controlling the internal combustion engine, the controller comprising: an intake port injection determination unit for determining whether operating conditions for injecting fuel from the fuel injector into the intake port are met; a deposit accumulation determination unit for determining whether deposit accumulation exists in the intake port; an idle speed determination unit for determining whether conditions for idling are met; and an idle speed condition changing unit for changing the operating conditions for idling when the intake port injection determination unit determines that operating conditions for injecting fuel into the intake port are met, the deposit accumulation determination unit determines that deposit accumulation exists in the intake port, and the idle speed determination unit determines that the conditions for idling are met.

[0009] In this invention, the idle condition changing unit may be configured to increase the load or speed, which is the operating condition during idle operation, based on the value determined when there is no deposit accumulation in the air intake.

[0010] In this invention, the controller may further include a deposit accumulation elimination determination unit, which determines whether the accumulation of deposits in the air intake has been eliminated, and is configured to cancel the change of operating conditions during idling operation when it is determined that the accumulation of deposits in the air intake has been eliminated.

[0011] Invention Effects

[0012] In this invention, when the conditions of fuel injection into the intake port, deposit accumulation within the intake port, and idling are met, idling is not always performed under operating conditions set for a steady state, but rather the operating conditions are modified. This modification can involve increasing the load or speed during idling. Therefore, the intake volume or velocity along the inner wall of the intake port increases, thereby suppressing deposit accumulation or removing existing deposits. This suppresses the adhesion and accumulation of deposits within the intake port, or reduces the amount of existing deposits. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating the principle of an engine as an object in an embodiment of the present invention.

[0014] Figure 2 It is a block diagram used to illustrate the functional structure of the controller.

[0015] Figure 3 This is a flowchart illustrating an example of control implemented in an embodiment of the present invention. Detailed Implementation

[0016] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the embodiments described below are merely examples of how to implement the present invention and are not intended to limit the invention.

[0017] In this invention, the internal combustion engine (hereinafter referred to as the engine) controlled is an engine that injects and supplies fuel, and can be an engine with a conventionally known structure as described in Patent Document 1, etc., mentioned above. Figure 1 The schematic diagram illustrates the principle structure of the engine 1 in an embodiment of the present invention. A piston 3 is provided that reciprocates inside a cylinder 2. Between the piston 3 and the cylinder head 4 is a combustion chamber 5. Conversely, within the cylinder 2... Figure 1The lower part of the cylinder head 4 is equipped with a crankcase 6, which houses a crankshaft 7 connected to a piston 3. An intake port 8 and an exhaust port 9 are provided on the cylinder head 4. The intake port 8 communicates with an intake passage 10, and the exhaust port 9 communicates with an exhaust passage 11. An intake valve 12 is provided to open and close the intake port 8 according to the rotation angle of the crankshaft 7, and similarly, an exhaust valve 13 is provided to open and close the exhaust port 9 according to the rotation angle of the crankshaft 7. Furthermore, the intake port 8 and exhaust port 9 refer not only to the openings opened and closed by valves 12 and 13, but also to the defined ranges on each passage 10 and 11 side.

[0018] Figure 1 The engine 1 shown is a gasoline-powered engine, with a spark plug 14 positioned near the top of the combustion chamber 5. A throttle valve 16 is installed in the intake passage 10 to adjust the amount of air drawn in via the air filter 15. The throttle valve 16 is an electronically controlled throttle valve whose opening is electrically controlled according to the engine 1's load (or output request). Furthermore, an intake 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.

[0019] Engine 1 serves as the driving force source for the vehicle equipped with it, and a transmission 20 equipped with a torque converter 19 is connected to its output side. This transmission 20 can be an automatic transmission of a conventional structure, configured to output driving torque to drive wheels (not shown). Alternatively, a clutch 21 can be provided that selectively connects and disconnects the torque converter 19 from the engine 1. Furthermore, auxiliary equipment type 22, which operates with the power output from engine 1, is connected to the output side of engine 1. Examples of auxiliary equipment type 22 include an air conditioning system or an alternator. These torque converters 19 and auxiliary equipment type 22 consume the power output from engine 1 through operation, thus becoming devices that load engine 1. When these loads are applied, engine 1 increases the opening of the throttle valve 16 to output power corresponding to the load, thereby increasing the fuel supply accordingly. Therefore, the load is manifested in the opening of the throttle valve 16.

[0020] In the aforementioned engine 1, deposits sometimes adhere to and accumulate inside the air intake 8. A controller 23 is provided to control the suppression of these deposits. The controller 23 is mainly composed of a microcomputer consisting of a processing unit (CPU), storage units (RAM, ROM), and an interface. It performs calculations using input data or pre-stored data and outputs the results as command signals. Examples of input data include vehicle speed V, throttle opening ACC (not shown), engine speed Ne, engine coolant temperature T, and signals indicating potential misfires during cold starts. Furthermore, an example of pre-stored data is a map with vehicle speed V and throttle opening ACC as parameters. This map defines the operating area for intake manifold injection (fuel injection into the air intake 8) and the operating area for in-cylinder injection (fuel injection into the combustion chamber 5). Furthermore, the output control command signals include signals that control the opening degree of the throttle valve 16, signals that control the amount of fuel injection, signals that select the fuel injector, signals that engage or disengage the aforementioned clutch 21, and signals that control auxiliary equipment 22, etc.

[0021] The controller 23 is configured to perform control to suppress or reduce deposits during idling operation, where operating conditions can be set relatively freely. The functional structure for performing this control is shown below. Figure 2 The controller 23 includes an intake manifold injection determination unit 23a, which determines whether the operating 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 throttle opening ACC, and the aforementioned mapping stored in the controller 23.

[0022] Furthermore, a sediment accumulation determination unit 23b is provided in the controller 23. When sediment accumulates to a certain extent in the air intake 8, misfires may occur when the engine 1 is started in a cold state. Therefore, the sediment accumulation determination unit 23b can be configured to determine that sediment accumulation exists when misfires occur continuously or when the number of misfires within a specified time reaches a specified number.

[0023] Furthermore, the idle speed determination unit 23c is provided in the controller 23. When the ignition switch (not shown) of the vehicle equipped with engine 1 is turned on, and the throttle opening ACC is actually "0", the engine 1 is made to idle. Therefore, the idle speed determination unit 23c determines whether the conditions for idling are met based on the state of these ignition switches and the throttle opening ACC.

[0024] The controller 23 includes an idle condition changing unit 23d. When the engine 1 is idling, it controls the opening of the throttle valve 16 or the amount of fuel injection based on factors such as the coolant temperature, the operating status of auxiliary equipment 22, and the shift position selected by the transmission 20, and selects the injector to maintain a preset target speed. Therefore, these idling operating conditions are determined based on the state of the engine 1 or the vehicle at that point in time. The idle condition changing unit 23d is configured to change these determined operating conditions (load or speed, etc.). Load changes include, for example, starting the air conditioning system, generating electricity by the alternator, or engaging the clutch 21 to connect the torque converter 19 to the engine 1.

[0025] Furthermore, a sediment accumulation elimination determination unit 23e is provided in the controller 23. The sediment accumulation elimination determination unit 23e is a functional unit that determines whether the sediment accumulation determined by the sediment accumulation determination unit 23b has been eliminated; therefore, it can be said to be a functional unit that performs a determination opposite to that of the sediment accumulation determination unit 23b. This determination can be made, for example, by the absence of detected engine misfire, the absence of continuous misfire, or a misfire frequency below a predetermined frequency.

[0026] If the control is described as being performed by the aforementioned controller 23, then Figure 3 This is a flowchart illustrating an example of the control. The routine shown here is repeatedly executed at predetermined short cycles when the ignition switch or ready switch of the vehicle equipped with engine 1 is turned on and engine 1 is started. In step S1, it is determined whether the intake manifold injection conditions are met. This determination is performed by the aforementioned intake manifold injection determination unit 23a. That is, the determination in step S1 can be based on vehicle speed V, throttle opening ACC, and a pre-stored mapping diagram.

[0027] If the result of the determination in step S1 is "no", the process returns without any special control. Conversely, if the result of the determination in step S1 is "yes", step S2 determines whether there is deposit accumulation in the air inlet 8. This determination is performed by the aforementioned deposit accumulation determination unit 23b. That is, the determination in step S2 can be based, for example, on the state of fire, which is determined based on the detection signal from the knock sensor or the like.

[0028] If the result of the judgment in step S2 is "no", no special control is performed and the process returns. If the result of the judgment in step S2 is "yes", then proceed to step S3 to perform idle speed determination. Idle speed determination refers to determining whether the conditions for causing engine 1 to idle are met. Figure 3 In the control example shown, since engine 1 is already running, it is possible to determine that the throttle opening ACC is actually "0".

[0029] If the throttle opening increases due to actions such as pressing the accelerator pedal (not shown), the result of the judgment in step S3 is "No". In this case, no special control is performed, and the process returns to normal. Conversely, if the result of the judgment in step S3 is "Yes", the process proceeds to step S4, where the operating conditions during idling are changed. This control is performed by the aforementioned idling condition changing unit 23d. That is, as mentioned above, the operating conditions during idling are determined based on the state of the engine 1 or the vehicle equipped with the engine 1 at that point in time. More specifically, the target idling speed is set based on conditions such as the coolant temperature T or the load caused by auxiliary equipment type 22. In step S4, the target idling speed or the load based on it is changed. More specifically, the value of the target idling speed or the load is increased. Regarding the target idling speed, the target value is the speed obtained by adding a preset speed. Furthermore, the load can be increased by driving the auxiliary equipment type 22, increasing its speed, or connecting the torque converter 19 to the engine 1.

[0030] By changing the operating conditions (speed or load) during idling as described above, the intake volume or flow rate in the intake port 8 increases compared to the so-called normal operating conditions before the change. Therefore, it avoids or suppresses the formation of deposits due to fuel droplets adhering to the inner wall of the intake port 8 caused by backflushing, and the solidification of solid components. Furthermore, the amount of already accumulated deposits is reduced by peeling or flushing. Thus, in step S5, it is determined whether the deposits have decreased and their accumulation has been eliminated. This determination is performed by the aforementioned deposit accumulation elimination determination unit 23e; in other words, it is the opposite of the determination of deposit accumulation in step S2. Therefore, the determination of deposit accumulation elimination can be made, for example, by the absence of detected misfires or a reduction 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 continues under the changed operating conditions. Conversely, if the result of the determination in step S5 is "yes," the process returns. That is, the operating conditions during the changed idling operation are restored to their original state, and the control measures used to suppress or reduce deposits are terminated.

[0031] According to the control described in the embodiments of the present invention, the amount of deposits generated or accumulated in the intake port 8 can be reduced, thus reducing the likelihood of misfire in the engine 1 and improving so-called misfire resistance. Furthermore, in this case, only port injection is required; high-pressure in-cylinder injection is not necessary. Therefore, the high-pressure pump used for in-cylinder injection is not driven, nor is the accompanying noise generated, thus preventing deterioration of the vehicle's vibration and noise characteristics (NV characteristics).

[0032] Furthermore, the present invention is not limited to the embodiments described above. The controller may be a controller separately from the engine control device, or it may be part of the engine control device. Moreover, the determination of whether deposits have accumulated is not limited to engine misfire; it can be performed using various methods known in the past. Furthermore, in the present invention, the idle conditions before being changed by the idle condition changing unit are only those determined during normal operation. Therefore, the present invention can be configured to change the operating conditions during idle operation based on intake manifold injection, deposit accumulation, and the determination of idle operation as conditions.

[0033] Symbol Explanation

[0034] 1-Engine, 2-Cylinder, 3-Piston, 4-Cylinder head, 5-Combustion chamber, 6-Crankcase, 7-Crankshaft, 8-Intake port, 9-Exhaust port, 10-Intake passage, 11-Exhaust passage, 12-Intake valve, 13-Exhaust valve, 14-Spark plug, 15-Air filter, 16-Throttle valve, 17-Intake port injector, 18-In-cylinder injector, 19-Torque converter, 20-Transmission, 21-Clutch, 22-Auxiliary equipment, 23-Controller, 23a-Intake port injection determination unit, 23b-Deposit accumulation determination unit, 23c-Idle speed determination unit, 23d-Idle speed condition modification unit, 23d-Idle operation condition modification unit, 23e-Deposit accumulation removal determination unit.

Claims

1. A control device for an internal combustion engine, the internal combustion engine comprising: an intake port for directing intake air into the interior of a cylinder; and a fuel injector for injecting fuel into the intake port, the control device for the internal combustion engine being characterized in that... The control device has a controller for controlling the internal combustion engine. The controller has: The intake manifold injection determination unit determines whether the operating conditions for injecting fuel from the injector into the intake port are met. A sediment accumulation determination unit determines whether sediment accumulation exists within the air inlet. The idle speed determination unit determines whether the conditions for idling are met. and The idle condition changing unit changes the operating conditions during idle operation when the intake manifold injection determination unit determines that the operating condition of injecting fuel into the intake port is met, the deposit accumulation determination unit determines that there is deposit accumulation in the intake port, and the idle condition determination unit determines that the condition of idling operation is met.

2. The control device for an internal combustion engine according to claim 1, characterized in that, The idle condition modification unit is configured to increase the load or speed used as the operating condition during idle operation from the value determined when there is no deposit accumulation in the air intake.

3. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, The controller further includes a sediment accumulation elimination determination unit, which determines whether the sediment accumulation in the air inlet has been eliminated. Furthermore, it is configured to cancel the change of operating conditions during idling operation when it is determined that the accumulation of deposits in the air intake has been eliminated.

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