Control device for internal combustion engine

Abstract

To accurately raise a temperature through motoring without causing deterioration of energy efficiency, vibration or deterioration of abnormal noise, etc.SOLUTION: In a control device for an internal combustion engine that uses alcohol-containing fuel, a controller that controls motoring and starting includes: detection means for detecting at least either one of a temperature of the internal combustion engine or an alcohol concentration during the motoring (Step S2); air amount calculation means for calculating an air amount to be sucked into a cylinder during the motoring on the basis of at least either one of the temperature of the internal combustion engine or the alcohol concentration (Step S3); and motoring time calculation means for calculating a duration of the motoring on the basis of at least either one of the temperature of the internal combustion engine or the alcohol concentration detected by the detection means and the air amount calculated by the air amount calculation means (Step S4). The motoring is executed for the duration while the calculated air amount is maintained.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a device for controlling an internal combustion engine, and more particularly to a device for controlling the starting of an internal combustion engine that burns fuel containing alcohol. [Background technology]

[0002] An internal combustion engine using a fuel containing alcohol is known, but this type of fuel may be more difficult to ignite or light than gasoline. Therefore, for example, in the invention described in Patent Document 1, instead of heating, a motoring request time is calculated based on the alcohol concentration and temperature, motoring is performed for the motoring request time, and then the internal combustion engine is started. That is, the higher the temperature of the fuel containing alcohol, the more the alcohol vaporizes and the better the engine startability is, so in order to raise the temperature at the start, motoring is performed by rotating the engine by the motor with the fuel supply stopped. In this case, the target temperature varies depending on the alcohol concentration, and the amount of heat required to reach the target temperature varies depending on the fuel temperature, so the motoring request time is calculated based on the alcohol concentration and the temperature of the engine water, etc. Patent Document 1 also describes that in order to speed up the temperature rise by motoring, the opening and closing timing of the intake valve and exhaust valve may be controlled by a variable valve mechanism to increase the amount of air trapped and compressed inside the cylinder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-63411 Summary of the Invention [Problem to be solved by the invention]

[0004] When motoring is performed by stopping the supply of fuel and rotating the engine with a motor, the engine can be heated and increased in temperature by frictional heat generated between the piston and the cylinder and heat generated by compressing the air. In the invention described in Patent Document 1, the required time for motoring is set based on the engine water temperature and the alcohol concentration. Specifically, the lower the engine water temperature and the higher the alcohol concentration, the longer the required time for motoring is. In this way, if the required time for motoring is set based on the engine water temperature and the alcohol concentration, the engine and fuel can be heated without using a heating means such as a heater, and the engine can be started smoothly. In addition, if the amount of compressed air is increased, the amount of heat generated increases, and the required time for motoring can be shortened. However, if the amount of compressed air is always increased as much as possible in order to speed up the start of the engine, the motoring time will be shortened, but not only will the amount of energy consumed in motoring increase, deteriorating energy efficiency (fuel consumption and electricity consumption), but the pressure inside the cylinder will repeatedly increase, resulting in increased vibration and noise during motoring, which may cause discomfort to passengers in the vehicle.

[0005] The present invention has been made with attention to the above-mentioned technical problems, and aims to provide a control device that can accurately raise the temperature by motoring without causing a decrease in energy efficiency or an increase in vibration or abnormal noise, in order to improve the starting performance of an internal combustion engine that uses a fuel containing alcohol. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a control device for an internal combustion engine which draws in an air-fuel mixture containing alcohol and fuel into a cylinder, compresses it with a piston, and ignites or light the mixture to burn the mixture, and which, when a start request is received, performs motoring, which draws in air not supplied with fuel into the cylinder and rotates it prior to starting to burn the mixture, the control device having a controller which controls the motoring and the starting, the controller having a detection means for detecting at least one of a temperature of the internal combustion engine and a concentration of the alcohol during the motoring, and The present invention is characterized in that it comprises an air amount calculation means for calculating the amount of air to be taken into the cylinder during motoring based on at least one of the temperature of the internal combustion engine and the alcohol concentration, and a motoring time calculation means for calculating the duration of the motoring based on at least one of the temperature of the internal combustion engine and the alcohol concentration detected by the detection means and the air amount calculated by the air amount calculation means, and the controller performs motoring for the duration calculated by the motoring time calculation means while controlling the amount of air to be taken into the cylinder to the air amount calculated by the air amount calculation means.

[0007] In the present invention, the air amount calculation means may be configured to make the air amount larger when the temperature of the internal combustion engine or the alcohol concentration is lower than a predetermined value than the air amount when the temperature or the alcohol concentration is the predetermined value.

[0008] In the present invention, the internal combustion engine may have a throttle valve that controls the amount of air taken into the cylinder, an intake valve that opens and closes the intake port of the cylinder, and a variable valve mechanism that controls the opening or opening and closing timing of the intake valve, and the air amount calculation means may further calculate at least one of the opening of the throttle valve and the opening of the intake valve by the variable valve mechanism so that the amount of air to be taken into the cylinder is determined based on at least one of the temperature of the internal combustion engine and the alcohol concentration, and the controller may be configured to output a control command signal to control at least one of the opening of the throttle valve and the opening of the intake valve by the variable valve mechanism calculated by the air amount calculation means. Effect of the Invention

[0009] According to the present invention, the amount of intake air during motoring performed prior to engine start is calculated based on the temperature of the internal combustion engine or the alcohol concentration of the fuel, and the motoring time is set according to the amount of intake air, so that when the temperature is high or the alcohol concentration is low, the amount of air can be reduced, and therefore vibrations and abnormal noise during motoring can be suppressed or prevented, and the amount of energy consumed during motoring can be reduced. Conversely, when the temperature is low or the alcohol concentration is high, the amount of intake air can be increased, so that the motoring time can be shortened and a delay in engine start can be avoided or suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram for explaining an example of an engine, and is a schematic cross-sectional view of one of the cylinders. [Diagram 2] FIG. 2 is a functional block diagram for explaining an example of a controller. [Diagram 3] FIG. 4 is a conceptual diagram for explaining an example of a map that determines a target temperature according to an alcohol concentration. [Figure 4]4 is a conceptual diagram for explaining an example of a map that determines the intake air amount depending on the alcohol concentration and the temperature. FIG. [Diagram 5] 10 is a conceptual diagram for explaining the difference in motoring time between when the intake air amount is increased and when it is not increased during motoring. FIG. [Figure 6] 4 is a flowchart illustrating an example of control executed in the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Next, the present invention will be described with reference to the embodiments shown in the accompanying drawings. Note that the embodiment described below is merely one example of a case in which the present invention is implemented, and is not intended to limit the present invention.

[0012] 1 shows an example of an internal combustion engine (hereinafter referred to as engine) 1 that is the subject of this invention, and this engine 1 is an engine that can burn a mixture of air and fuel that is a mixture of gasoline and alcohol, and is an engine that is installed in a so-called FFV (Flexible Fuel Vehicle).The engine 1 may also be an engine in a vehicle that uses only an internal combustion engine motored by a starter as a driving force source, or in a so-called hybrid vehicle that uses an electric motor as a driving force source and is equipped with an internal combustion engine motored by the electric motor.

[0013] The engine 1 is a so-called multi-cylinder engine, and FIG. 1 shows a schematic cross-sectional view of one of its cylinders 2. A piston 3 that moves up and down in the vertical direction of FIG. 1 is housed inside the cylinder 2, and the portion between the piston 3 and a cylinder head 4 forms a combustion chamber. An intake pipe 5 and an exhaust pipe 6 are connected to the cylinder head 4. An intake valve 7 is provided to open and close an intake port, which is an opening end of the intake pipe 5, and an exhaust valve 8 is provided to open and close an exhaust port, which is an opening end of the exhaust pipe 6. Variable valve mechanisms (IN-VVT, EX-VVT) 7A, 8A are provided to control the opening and timing of these valves 7, 8. These variable valve mechanisms 7A, 8A are of a conventionally known configuration, and are electrically controlled to change the lift (opening) of each of the valves 7, 8 and the opening and closing timing relative to the crank angle of the engine 1. In FIG. 1, the reference numeral "9" denotes a spark plug.

[0014] An injector 10 that injects fuel into an intake port is provided at a predetermined position in the intake pipe 5. The fuel 11 injected from this injector 10 is a fuel containing alcohol, and the fuel is supplied to the injector 10 from a fuel tank 12. An alcohol concentration sensor 13 that detects the concentration of alcohol (e.g., ethanol) in the fuel 11 and outputs a detection signal is provided midway through a fuel supply pipe 14. A throttle valve 15 is provided in the intake pipe 5 upstream of the injector 10. This throttle valve 15 is a so-called electronically controlled valve, and is configured to be electrically controlled based on a drive demand represented by an accelerator opening or the like, to control the amount of air taken into the cylinder 2.

[0015] Meanwhile, a water jacket 16 is provided on the outer periphery of the cylinder 2. Also, a water temperature sensor 17 is provided for detecting the temperature of the engine 1 (specifically, the temperature of the engine coolant) and outputting a detection signal. Note that in this embodiment of the invention, it is sufficient to detect the engine temperature that affects the atomization or evaporation of alcohol in the fuel, so the sensor for detecting such a temperature may be a sensor other than the water temperature sensor 17.

[0016] The example shown in FIG. 1 is an example of an engine mounted on a hybrid vehicle, and an electric motor 18 is provided to control the rotation speed of the engine 1. The electric motor 18 is a motor with a generating function, i.e., a motor generator, and is connected to an electric storage device such as a battery via an inverter (not shown). The electric motor 18 is connected to the output shaft (crankshaft) of the engine 1 directly, or via a clutch (not shown), or via a power split mechanism (not shown) consisting of a planetary gear mechanism or the like. Therefore, the electric motor 18 is configured to apply a so-called negative torque to the engine 1 by functioning as a generator to suppress an increase in the engine rotation speed, and conversely, to apply a so-called positive torque to the engine 1 by functioning as a motor to maintain or increase the engine rotation speed. The electric motor 18 can also function as a starter, and is configured to rotate the engine 1 by the electric motor 18 when there is a request to start the engine 1, and prior to that, to perform motoring by the electric motor 18 to rotate the engine 1 without supplying (injecting) fuel.

[0017] Although not specifically shown, other sensors such as an engine rotation speed sensor, a vehicle speed sensor, a throttle opening sensor, and an electric motor rotation speed sensor are further provided.

[0018] An electronic control unit (ECU) 19 is provided to control the starting of the engine 1 and the motoring prior to the starting. Note that "motoring" in the embodiment described here refers to control in which the engine 1 is rotated by external power for a predetermined time in order to heat and increase the temperature of the engine 1, fuel, etc. Therefore, fuel is not supplied during motoring.

[0019] The ECU 19 is mainly composed of a microcomputer including a calculation element, a storage element, an interface, etc., and is configured to perform calculations using input data and pre-stored data, and to output the results of the calculations as a control command signal. The main function of the ECU 19 is to control motoring for warming up the engine 1 prior to starting the engine 1, and various data required for this control are input to the ECU 19. Specifically, the alcohol concentration detected by the alcohol concentration sensor 13, the temperature detected by the water temperature sensor 17 which is the temperature of the engine 1, the engine 1 rotation speed, vehicle speed, the opening of the throttle valve 15, the motor 18 rotation speed, etc. are input to the ECU 19.

[0020] Motoring is a control in which the engine 1 is rotated by the electric motor 18 for a predetermined time to raise the temperature while the supply of fuel is stopped, and therefore the ECU 19 outputs a control command signal to the injector 10 and a control command signal to control the rotation speed of the electric motor 18. In addition to these, the ECU 19 outputs a control command signal to control the opening of the throttle valve 15 and a control command signal to control the opening (lift amount) and opening / closing timing of the intake valve 7 (these may be collectively referred to as the VVT ​​opening) in order to control the amount of intake air during motoring or the amount of air trapped and compressed inside the cylinder 2. The ECU 19 holds data for determining the control command values ​​to be output by these control signals, and holds and stores, for example, a map that defines the motoring time according to the alcohol concentration or engine water temperature, or a program that calculates the motoring time.

[0021] The ECU 19 is configured to determine various control amounts using these input data and pre-stored data and programs, and its functional configuration is shown in Figure 2. Figure 2 is a block diagram for explaining the functional configuration of the ECU 19, which corresponds to the controller in the embodiment of the present invention, and the ECU 19 has concentration detection means 19a that detects the alcohol concentration in the fuel 11 based on a signal input from the alcohol concentration sensor 13 described above, and temperature detection means 19b that detects the engine water temperature or engine temperature based on a signal input from the water temperature sensor 17.

[0022] The ECU 19 is further provided with an air amount calculation means 19c for calculating the amount of air to be drawn into the cylinder 2 based on the alcohol concentration in the fuel 11 detected by the concentration detection means 19a and the temperatures of the engine 1 and engine coolant detected by the temperature detection means 19b, or based on at least one of them. If the amount of air in the cylinder 2 during motoring is increased, the amount of heat generated by the compression of the air increases, and it is possible to promote the temperature rise of the engine 1 and the like. On the other hand, the torque for rotating the engine 1 by the electric motor 18 increases, which in turn increases the vibration and abnormal noise due to gear meshing, and further increases the power consumed by the electric motor 18. Therefore, the amount of air is increased only when the amount of heat required for temperature rise is large.

[0023] FIG. 3 is a diagram conceptually showing the relationship between the alcohol concentration in the fuel 11 and the target temperature by motoring, and the higher the alcohol concentration, the higher the target temperature. This is because the amount of alcohol to be atomized or evaporated at the start of the engine 1 is greater. Therefore, the amount of air is increased so that the temperature can be raised to the target temperature in a short time. FIG. 4 conceptually shows the relationship between the alcohol concentration and the amount of air, and when the alcohol concentration is high, the amount of heat required to raise the temperature to the target temperature is greater, so the amount of air is increased. For example, as shown by the solid line in FIG. 4, the relationship between the two is determined so that the higher the alcohol concentration, the greater the amount of air. Note that, as shown by the dashed line in FIG. 4, when the alcohol concentration is high and exceeds the threshold value Th, the amount of air may be set to a constant amount corresponding to the alcohol concentration, and when the alcohol concentration is equal to or less than the threshold value Th, the amount of air may be set to a constant amount less than the amount when the alcohol concentration exceeds the threshold value Th. FIG. 4 also shows the relationship between the detected temperature, such as the engine water temperature, and the amount of air, and the higher the detected temperature, the smaller the amount of air. This is because the higher the detected temperature, the smaller the amount of heat required to raise the temperature to the target temperature.

[0024] The air amount calculation means 19c stores in advance a map that defines the relationship between the air amount, the alcohol concentration, and the temperature, for example, as shown in FIG. 4, and calculates the air amount based on the map and the detected alcohol concentration and temperature. Since air is taken into the cylinder 2 through the intake pipe 5, the intake air amount can be controlled by the throttle valve 15 provided in the intake pipe 5. In addition, the amount of air trapped inside the cylinder 2 can be changed according to the opening degree (lift amount) of the intake valve 7 and the timing of opening and closing the intake valve 7. Therefore, the air amount calculation means 19c may obtain, in addition to the above-mentioned air amount, the opening degree of the throttle valve 15 and the opening degree of the intake valve 7 by the intake side variable valve mechanism (IN-VVT) 7A to achieve the air amount. When the closing timing of the intake valve 7 is set to the retard side from the intake bottom dead center, the intake air amount into the cylinder 2 is increased by advancing the opening and closing timing of the intake valve 7.

[0025] The ECU 19 is provided with a motoring time calculation means 19d that calculates the duration of motoring (motoring time) based on the alcohol concentration, temperature, and air volume obtained by the concentration detection means 19a, temperature detection means 19b, and air volume calculation means 19c. The amount of heat generated by motoring varies depending on the structure of the engine 1, the amount of air compressed inside the cylinder 2, or the rotation speed of the engine 1 during motoring, but the gradient of the temperature rise and the time required to reach the target temperature can be roughly known in advance by experiments and simulations using an actual machine. Therefore, the motoring time calculation means 19d prepares a map that defines in advance the relationship between the alcohol concentration, temperature, and air volume and the time required to reach the target temperature (i.e., the motoring time), and calculates the motoring time based on the map.

[0026] In order to avoid shocks when starting the engine, motoring is performed at an engine speed that corresponds to the vehicle speed at the end of motoring, i.e., when the engine is started. The amount of heat generated by motoring, i.e., the motoring time until the target temperature is reached, also varies depending on the engine speed. Therefore, it is preferable to take the engine speed into consideration when calculating the motoring time, and specifically, the higher the engine speed during motoring, the shorter the motoring time is made.

[0027] As described above, the amount of air compressed inside the cylinder 2 during motoring is increased, so the amount of heat generated by motoring increases, and the motoring time required to raise the temperature to the target temperature is shortened. This relationship is conceptually shown in FIG. 5, and when the amount of air is increased, the rising gradient of the motoring time relative to the target temperature is smaller than when the amount of air is not increased, as shown by the dashed line in FIG. 5. Also, in the embodiment of the present invention, as described with reference to FIG. 4, when the detected temperature is high or the alcohol concentration is low, that is, when the amount of heat required to raise the temperature to the target temperature is small and the temperature is easily raised, the amount of air taken into the cylinder 2 during motoring, that is, the amount of air compressed during motoring, is reduced, or the amount of air is not increased. Therefore, since it is not necessary to constantly increase the torque required for motoring, vibrations and abnormal noise during motoring can be avoided or reduced, the amount of power consumed can be reduced, and further, the motoring time is shortened to improve the startability of the engine 1.

[0028] An example of the motoring control prior to the above-mentioned start will be described with reference to the flowchart shown in FIG. 6. The routine shown in FIG. 6 is executed when a vehicle equipped with an engine 1 using fuel containing alcohol starts moving, or when the engine 1 is stopped temporarily due to hybrid driving, and then the engine 1 is started due to an acceleration request, a decrease in the remaining charge, or the like. First, it is determined whether or not there is a request to start the engine (ENG) (step S1). The start request is generated when an ignition switch (not shown) is turned on, when the engine 1 that has been stopped due to a temporary stop at a stop light, etc. is restarted by turning the accelerator on, or when there is a request to accelerate while the hybrid vehicle is running on the motor, or when it becomes necessary to generate electricity due to a decrease in the remaining charge. If there is no start request and the determination result in step S1 is "no," the routine shown in FIG. 6 is temporarily terminated without performing any particular control.

[0029] If the determination result in step S1 is "Yes", the vehicle speed, engine water temperature, and alcohol concentration are obtained (step S2). Note that data such as the vehicle speed, engine water temperature, and alcohol concentration may be obtained all the time. Next, a target amount of air to be taken in during motoring is calculated based on the vehicle speed, engine water temperature, and alcohol concentration, and the throttle opening, intake valve 7 opening, and timing (opening of the intake side variable valve mechanism (IN-VVT)) required to achieve that amount of air are also calculated (step S3). This calculation is as explained above as the function of the air amount calculation means 19c.

[0030] Furthermore, as the air volume is calculated, the motoring time (duration) is calculated based on the air volume, the temperature, and the alcohol concentration, and the rotation speed (required rotation speed) for executing motoring is calculated based on the vehicle speed (step S4). The motoring time is calculated as explained above as the function of the motoring time calculation means 19d. Furthermore, the target rotation speed is controlled not for the purpose of generating heat for temperature increase, but for the purpose of minimizing the difference between the rotation speed by the electric motor 18 and the rotation speed at start-up as much as possible when the supply of fuel to the engine 1 is started to start the engine 1, thereby avoiding or suppressing shock, and therefore the target rotation speed is calculated based on the vehicle speed.

[0031] In the above manner, the throttle opening, IN-VVT opening, motoring time, and target rotation speed are determined, and a control command signal based on them is output to execute motoring (step S5). In this case, if the temperature is low or the alcohol concentration is high, the amount of intake air increases and the amount of heat generated by motoring increases, so the temperature rises quickly. In other words, the motoring time is shorter than when control to increase the amount of air is not performed. Conversely, when the temperature is high or the alcohol concentration is low, the amount of air is reduced or control to increase the amount of air is not performed, so vibrations and abnormal noise during motoring can be reduced or prevented.

[0032] Then, after motoring for the calculated time, the engine 1 is started (step S6). That is, fuel is supplied to the engine 1 to rotate autonomously. The present invention is not limited to the above-described embodiment, and can be modified and implemented as appropriate within the scope of the object of the present invention. [Explanation of symbols]

[0033] 1. Internal combustion engine 2 Cylinder 3 Piston 4. Cylinder head 5. Intake pipe 6 Exhaust pipe 7 Intake valve 8 Exhaust valve 7A, 8A variable valve mechanism 9 Spark plug 10 Injector 11 Fuel 12 Fuel tank 13 Alcohol concentration sensor 14 Fuel supply pipe 15 Throttle valve 16 Water Jacket 17 Water temperature sensor 18 Electric motor 19 Electronic Control Unit (ECU) 19a Concentration detection means 19b Temperature detection means 19c Air volume calculation method 19d Motoring time calculation means

Claims

1. A control device for an internal combustion engine that draws an air-fuel mixture containing alcohol and air into a cylinder, compresses it with a piston, and ignites or light the mixture to burn the mixture, and that, when a start request is received, performs motoring by drawing air to which no fuel has been supplied into the cylinder and rotating the cylinder prior to starting to burn the mixture, a controller for controlling the motoring and the starting; The controller: a detection means for detecting at least one of a temperature of the internal combustion engine and a concentration of the alcohol during motoring; an air amount calculation means for calculating an amount of air to be taken into the cylinder during motoring based on at least one of a temperature of the internal combustion engine and the alcohol concentration; a motoring time calculation means for calculating a duration of the motoring based on at least one of the temperature of the internal combustion engine and the alcohol concentration detected by the detection means and the air amount calculated by the air amount calculation means; Equipped with The controller performs motoring for the duration calculated by the motoring time calculation means while controlling the amount of air taken into the cylinder to the amount of air calculated by the air amount calculation means. A control device for an internal combustion engine.

2. 2. The control device for an internal combustion engine according to claim 1, The control device for an internal combustion engine, wherein the air amount calculation means is configured to make the air amount larger when the temperature of the internal combustion engine or the alcohol concentration is lower than a predetermined value than the air amount when the temperature of the internal combustion engine or the alcohol concentration is the predetermined value.

3. The control device for an internal combustion engine according to claim 1 or 2, the internal combustion engine has a throttle valve that controls the amount of air taken into the cylinder, an intake valve that opens and closes an intake port of the cylinder, and a variable valve mechanism that controls an opening degree or an opening / closing timing of the intake valve, the air amount calculation means further calculates at least one of an opening degree of the throttle valve and an opening degree of the intake valve controlled by the variable valve mechanism so as to obtain an amount of air to be drawn into the cylinder, the amount being determined based on at least one of a temperature of the internal combustion engine and the alcohol concentration; The controller is configured to output a control command signal for controlling at least one of the opening of the throttle valve calculated by the air amount calculation means and the opening of the intake valve by the variable valve mechanism. A control device for an internal combustion engine.

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