Fuel injection control device for internal combustion engine

Abstract

To avoid or suppress shortage of a fuel injection amount at so-called start at high temperature.SOLUTION: A fuel injection control device for an internal combustion engine having an injector for injecting fuel and a radiator fan for performing cooling in dead soak includes: start temperature determination means (step S1) for determining that a temperature is in a high temperature state that is a prescribed temperature or higher at start; fan drive time detection means (steps S2-4) for detecting a drive time of the radiator fan in dead soak before starting; internal combustion engine temperature detection means for detecting at least either one of a cooling water temperature of the internal combustion engine or an intake air temperature of the internal combustion engine; and fuel injection amount calculation means (step S6) for determining a fuel injection amount when the internal combustion engine is started in the high temperature state on the basis of either one of the detected cooling water temperature or the intake air temperature and the drive time of the radiator fan.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an internal combustion engine configured to inject and supply fuel, and more particularly to a device for controlling fuel injection during start-up at high temperatures. [Background technology]

[0002] It is known that when an engine is started at a high temperature, fuel evaporates, generating vapor, which inhibits fuel injection. Conventionally, Patent Documents 1 to 3 propose devices for avoiding or suppressing the effects of vapor to prevent fuel shortages. The device described in Patent Document 1 is configured to prevent or suppress a decrease in engine startability when the engine temperature and intake air temperature are so-called high, in which fuel vapor inhibits fuel injection, causing a lean engine. It is configured to increase the amount of fuel injected when starting at a so-called high temperature. Patent Document 1 does not disclose means for detecting engine temperature, but engine temperature is generally determined from the coolant temperature.

[0003] Patent Document 2 describes a device that, when the engine is stopped, drives a radiator fan or a fuel pump to cool the injector to a temperature that does not generate vapor. When the engine is stopped, the circulation of the cooling water also stops, so by driving the radiator fan, the entire engine is forcibly air-cooled from the outside.

[0004] Patent Document 3 describes a device configured to increase the fuel injection amount of an in-cylinder injector when it is predicted that a predetermined amount or more of vapor will be generated in the fuel in the port injector during engine start-up. The injection pressure of an in-cylinder injector is set higher than that of a port injector, so vapor is less likely to be generated in an in-cylinder injector than in a port injector. Therefore, the device described in Patent Document 3 is said to be able to appropriately increase the fuel injection amount using the in-cylinder injector when it is predicted that a predetermined amount or more of vapor will be generated in the fuel in the port injector. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-085240 [Patent Document 2] Japanese Patent Application Publication No. 07-103022 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-012964 Summary of the Invention [Problem to be solved by the invention]

[0006] In an internal combustion engine (hereinafter referred to as an engine) equipped with a fuel injection system, fuel evaporation occurs more actively at higher temperatures when the engine is stopped. Therefore, the amount of fuel injected is increased according to the temperature. In the system described in Patent Document 1, the temperature that determines the amount of fuel injection is determined by the engine temperature and intake air temperature. However, because the injector that injects fuel is not directly cooled by the engine coolant or intake air, there may be a large difference between the engine temperature and intake air temperature and the injector temperature. In such cases, the amount of fuel injected may be increased to correspond to a low temperature even when the temperature is actually high, resulting in an insufficient amount of fuel injection. In particular, during a dead soak when the engine is stopped and heat is being dissipated, the temperature difference becomes large. If the engine is restarted under these conditions, the amount of fuel injected may be insufficient, resulting in unstable idling or even engine stall.

[0007] The same situation applies to the device described in Patent Document 2. That is, when the radiator fan is driven during dead soak to forcibly cool the engine from the outside, the temperature of the intake air drops earlier than, or even before, the temperature of the engine components such as the injectors. As a result, even if the temperature that is the basis for increasing the fuel injection amount is actually high, there is a possibility that the increase will be based on a lower temperature.

[0008] Furthermore, the device described in Patent Document 3 increases the fuel injection amount based on a prediction of vapor generation, but this prediction is based on the engine coolant temperature. As mentioned above, the temperature of the engine coolant and the temperature of components such as the injectors are not necessarily related, and there is a large discrepancy between the two temperatures, especially during dead soak. Therefore, even with the device described in Patent Document 3, there is a possibility that problems such as unstable idling due to insufficient fuel injection may occur during so-called high-temperature starting.

[0009] The present invention has been made with an eye on the above-mentioned technical problems, and aims to provide a fuel injection control device that can avoid or suppress a shortage of fuel injection amount during startup under so-called high temperature conditions. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object, the present invention provides a fuel injection control device for an internal combustion engine equipped with an injector that injects fuel and a radiator fan that performs cooling during dead soak, and is characterized by comprising: a start-up temperature determination means that determines whether the temperature is at a high temperature above a predetermined temperature at start-up; a fan drive time detection means that detects the drive time of the radiator fan during the dead soak before start-up; an internal combustion engine temperature detection means that detects at least one of the coolant temperature of the internal combustion engine and the intake air temperature of the internal combustion engine; and a fuel injection amount calculation means that calculates the fuel injection amount when starting the internal combustion engine in the high temperature state based on the detected coolant temperature or intake air temperature and the drive time of the radiator fan. [Effects of the Invention]

[0011] In the fuel injection control device of the present invention, when it is determined that the engine is starting in a so-called high-temperature state, the radiator fan drive time during dead soak and at least one of the coolant temperature and intake air temperature are detected, and the fuel injection amount is calculated based on the radiator fan drive time and either the coolant temperature or the intake air temperature. That is, the fuel injection amount (or its increase) is not calculated based on the coolant temperature (temperature of the internal combustion engine) or the intake air temperature, but is calculated taking into account the radiator fan drive time in addition to the coolant temperature (temperature of the internal combustion engine) or the intake air temperature. If the radiator fan is driven during dead soak, the coolant temperature or intake air temperature drops earlier than the temperatures of components such as the injectors. Therefore, the radiator fan drive time affects the difference (temperature difference) between the coolant temperature or intake air temperature and the temperatures of components such as the injectors. In the present invention, the fuel injection amount (or its increase) calculated based on the cooling water temperature or intake air temperature is corrected (increased correction) based on the driving time of the radiator fan, thereby calculating the fuel injection amount or its increase, thereby making it possible to avoid or suppress (optimize) a shortage of fuel injection amount during high-temperature startup. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic diagram illustrating a control system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram illustrating the functional configuration of a controller. [Figure 3] FIG. 4 is a diagram schematically illustrating an example of a map for calculating an increase in the fuel injection amount. [Figure 4] 4 is a flowchart illustrating an example of control executed by a controller. [Figure 5] 5 is a time chart showing changes in the fan drive time, engine water temperature, engine intake air temperature, etc. when the control shown in FIG. 4 is executed. DETAILED DESCRIPTION OF THE INVENTION

[0013] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is merely an example of how the present invention can be implemented, and is not intended to limit the present invention.

[0014] An internal combustion engine (hereinafter referred to as the engine) in an embodiment of the present invention is an engine configured to supply fuel by injection using injectors, and examples thereof include a gasoline engine and a diesel engine. FIG. 1 schematically shows an engine 1, with an injector 2 provided for each cylinder. These injectors 2 are configured to operate, for example, in accordance with the crank angle, to inject fuel supplied from a common rail (not shown) into intake ports 3 of the engine 1 or into the cylinders. Reference numeral 4 in FIG. 1 denotes an intake manifold, which distributes and supplies air taken in via a throttle valve 5 to each intake port 3. An intake temperature sensor 6 is provided to detect the temperature of the intake air and output a signal.

[0015] The engine 1 is a water-cooled engine, and a circulation water channel is provided between an internal water jacket (not shown) and a radiator 7, so that heat from the engine 1 is carried by the coolant to the radiator 7, where it is dissipated. A radiator fan 8 is provided to promote heat dissipation from the radiator 7, in other words, to air-cool the radiator 7. The radiator fan 8 is a fan driven by a motor 9, and is controlled to turn on and off according to the temperature of the engine 1 (the temperature of the coolant). A coolant temperature sensor 10 is provided to detect the engine temperature (the temperature of the coolant) and output a signal.

[0016] The amount of fuel supplied by the injector 2 is controlled to an amount determined according to the required drive amount, such as the throttle opening, plus or minus a correction amount according to the coolant temperature, lean or rich requirements, etc. An increase correction is also performed to suppress the effects of vapor caused by fuel evaporation. A controller 11 is provided to calculate the increase in the fuel injection amount, or the fuel injection amount including the increase, particularly the fuel injection amount when starting the engine 1 at high temperatures.

[0017] The controller 11 is an electronic control device primarily composed of a computer including a processing element (CPU), memory elements (RAM, ROM), or various interfaces. The controller 11 may also function as a part of an engine controller (not shown) that controls the throttle opening, ignition timing, intake / exhaust valve timing, and the like of the engine 1. The controller 11 is configured to perform calculations according to a pre-stored program using data input as detection signals and pre-stored data, and to output the results of the calculations as control signals. Examples of input data include the intake air temperature detected by the intake air temperature sensor 6, the engine temperature (coolant temperature) detected by the coolant temperature sensor 10, the operating time of the radiator fan 8, and the outside air temperature. The pre-stored data includes threshold values ​​for determining whether the input temperature is high or low.

[0018] The configuration of the controller 11 is shown in Fig. 2 by functional means. The controller 11 includes a start-up temperature determination means 11A to determine whether the engine 1 is started at a high temperature. Here, the high temperature state may be a state determined by design, and therefore the start-up temperature determination means 11A may be configured to determine whether an appropriate temperature related to the engine 1 is equal to or higher than a predetermined threshold value. This will be described in detail later.

[0019] When engine 1 is stopped, a dead soak occurs in which the temperature rises due to heat retained inside, so radiator fan 8 may be driven to lower the temperature of engine 1 or to prevent the temperature of engine 1 from rising. If radiator fan 8 is driven while engine 1 is stopped, the temperature difference between various parts of engine 1 becomes transiently large, and this temperature difference affects fuel injection, so fan drive time detection means 11B for detecting the drive time of radiator fan 8 is provided in controller 11.

[0020] Furthermore, the controller 11 is provided with an internal combustion engine temperature detection means 11C for detecting the temperature of the engine 1. The temperature of the engine 1 is the temperature detected by the intake air temperature sensor 6 or the coolant temperature detected by the coolant temperature sensor 10.

[0021] The controller 11 further includes a fuel injection amount calculation means 11D. This fuel injection amount calculation means 11D may be configured to calculate an increment to be added to a so-called basic fuel injection amount, or may be configured to calculate a total fuel injection amount including the increment, and is configured to calculate an increment in the fuel injection amount, particularly when starting at a high temperature. If the temperature of the engine 1 is high enough to cause fuel evaporation and vaporization or to increase the amount of vaporization, the vapor may inhibit fuel injection, resulting in a fuel shortage. To avoid or suppress such a fuel shortage, the fuel injection amount is increased. Fuel evaporation and fuel injection are affected by the intake air temperature and the coolant temperature, but they are also affected by the temperature of components that come into contact with the fuel, such as the injector 2. The fuel injection amount calculation means 11D is configured to calculate the fuel injection amount taking these temperatures into account. One example of this calculation is a method in which a three-dimensional map as shown in FIG. 3 is obtained by experiment or simulation, in which the increase value of the fuel injection amount is determined using the engine temperature, which is the cooling water temperature or the intake air temperature, and the driving time of the radiator fan 8 as parameters, and the increase value is calculated from the three-dimensional map.

[0022] An example of control by the controller 11 will be described with reference to the flowchart shown in Fig. 4. The routine shown in Fig. 4 is executed when the operation (ignition) of the engine 1 is stopped (ignition off (IG-OFF)). First, it is determined whether or not the engine is in a high temperature state (step S1). This determination may be made based on the coolant temperature of the engine 1 and the outside air temperature, and it is determined, for example, whether or not the coolant temperature when the engine 1 is stopped (water temperature at stop) is equal to or higher than a predetermined water temperature for determining fan drive, and whether or not the outside air temperature when the engine is stopped (outside air temperature at stop) is equal to or higher than a predetermined outside air temperature for determining fan drive. The function of making the determination in step S1 is an example of the function of the start-up temperature determination means 11A described above.

[0023] If the result of the determination in step S1 is "NO", no particular control is performed and the routine of FIG. 4 is temporarily terminated. Conversely, if the result of the determination in step S1 is "YES", the engine is in dead soak mode. In this case, the time for driving the radiator fan 8 is determined based on the water temperature and the outside air temperature (step S2). This driving time is the time required for the temperature of the engine 1 to drop below a predetermined temperature, and can be determined in advance by experiment, simulation, or the like. The radiator fan 8 is driven for that driving time (step S3). During this process, the time for which the radiator fan 8 is operating (driving time) is counted and stored as a memory value of the driving time (step S4).

[0024] When the ignition is turned on after these processes have been performed, that is, when control to start the engine 1 is initiated (step S5), the increase in the fuel injection amount when starting the engine 1 at a high temperature is calculated (step S6). This calculation may be performed using the three-dimensional map described above. Alternatively, the increase in the fuel injection amount is calculated based on the stored fan drive time value and the water temperature, and the increase in the fuel injection amount is also calculated based on the stored fan drive time value and the intake air temperature. Next, the larger of these two increases in the fuel injection amount is adopted (step S7). Then, the adopted increase is added to the fuel injection amount in a state other than a high temperature (low temperature or normal temperature), that is, the increase is reflected in the total fuel injection amount (step S8). The injector 2 is controlled to inject fuel in the total fuel injection amount thus obtained.

[0025] At an appropriate time after the processing based on the stored fan drive time value, such as step S6, is performed, the stored fan drive time value is initialized (cleared).

[0026] FIG. 5 is a time chart showing the changes in the ignition switch (IG-SW), engine start request, fan drive request, fan drive time, their stored values, engine speed, engine water temperature, engine intake air temperature, fuel injection amount increase (multiplication factor), fuel injection amount, and air-fuel ratio (A / F) when the above control is performed. When the ignition is turned off at time t1 while engine 1 is running, dead soak begins. With the ignition turned off, the engine start request disappears (for example, it becomes OFF), and the fan drive request is activated (for example, it becomes ON) to suppress the temperature rise due to dead soak. Therefore, the fan drive time is successively integrated and gradually increases.

[0027] After the engine 1 is stopped, the engine water temperature and engine intake air temperature gradually increase due to the heat retained inside, but these temperatures stabilize after a certain time due to the operation of the radiator fan 8. As a result, the fan drive request is turned off, and the fan drive time (integrated value) at time t2 is stored as a memory value.

[0028] If an engine start request occurs during the dead soak period, i.e., during high-temperature operation, the ignition is turned on and engine 1 is started (at time t3). In this case, an increase in the fuel injection amount is calculated based on the stored value of the fan drive time and the engine water temperature or engine intake air temperature, and a corresponding amount of fuel is injected. Therefore, the air-fuel ratio (A / F) temporarily decreases (toward the rich side or toward the stoichiometric side). As engine 1 begins to rotate, the engine water temperature and engine intake air temperature decrease due to the circulation of coolant and the introduction of outside air. Once engine 1 startup is complete, the fuel injection amount is set to an amount corresponding to the engine water temperature or engine intake air temperature, and the increase in the injection amount is reduced. Furthermore, although the air-fuel ratio temporarily shifts to the lean side based on the change in fuel injection amount, it immediately stabilizes at the normal air-fuel ratio. Furthermore, the stored value of the fan drive time is cleared.

[0029] Although the embodiments of the present invention have been described above, the present invention can be modified and implemented as appropriate. For example, the high temperature state when starting the engine may be determined based on other factors, such as the coolant temperature when the engine is stopped and the elapsed time since the engine was stopped, rather than the water temperature and outside air temperature when the engine was stopped. Furthermore, the increase in the fuel injection amount may be calculated without relying on a pre-prepared map. Furthermore, while the above-described embodiments use both the water temperature and the intake air temperature to calculate the increase in the fuel injection amount, the present invention may use either the water temperature or the intake air temperature and calculate the increase in the fuel injection amount taking this and the fan drive time into consideration. [Explanation of symbols]

[0030] 1 engine 2 injectors 3 intake ports 4 intake manifold 5 Throttle valve 6 Intake air temperature sensor 7 Radiator 8 Radiator Fan 9 Motor 10 Coolant temperature sensor 11 Controller 11A Starting temperature determination means 11B Fan driving time detection means 11C Internal combustion engine temperature detection means 11D Fuel injection amount calculation means

Claims

[Claim 1] A fuel injection control device for an internal combustion engine equipped with an injector that injects fuel and a radiator fan that performs cooling during dead soak, a start-up temperature determination means for determining whether the temperature is a high temperature state equal to or higher than a predetermined temperature at the time of start-up; a fan operation time detection means for detecting an operation time of the radiator fan during a dead soak period before the start of the engine; an internal combustion engine temperature detection means for detecting at least one of a coolant temperature of the internal combustion engine and an intake air temperature of the internal combustion engine; a fuel injection amount calculation means for calculating a fuel injection amount when starting the internal combustion engine in the high temperature state, based on the detected coolant temperature or the detected intake air temperature and the driving time of the radiator fan; Equipped with A fuel injection control device for an internal combustion engine.

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