Control device for internal combustion engines

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

[0004] , , , , ,

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

Background Art

[0002] Internal combustion engines that use fuels containing alcohol are known, but such fuels may be more difficult to ignite or catch fire compared to gasoline. Therefore, for example, in the invention described in Patent Document 1, instead of heating, the motoring required time is calculated based on the alcohol concentration and temperature, and motoring is executed during that motoring required time, and then the internal combustion engine is started. That is, since the higher the temperature of the fuel containing alcohol, the greater the vaporization of alcohol and the better the starting performance of the engine, in order to raise the temperature at startup, motoring is performed to rotate the engine by a motor with the fuel supply stopped. In that case, the target temperature varies depending on the alcohol concentration, and the amount of heat required to reach the target temperature also varies depending on the fuel temperature, so the motoring required time is determined based on the alcohol concentration and temperatures such as the engine coolant temperature. Further, Patent Document 1 describes that in order to speed up the temperature rise by motoring, the opening and closing timings 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

Summary of the Invention

Problems to be Solved by the Invention

[0004] By stopping the fuel supply and rotating the engine with a motor (motoring), the engine can be heated and its temperature raised by the frictional heat generated between the piston and cylinder, and the heat generated by compressing the air. In the invention described in Patent Document 1, the required motoring time is set based on the engine water temperature and alcohol concentration. Specifically, the lower the engine water temperature and the higher the alcohol concentration, the longer the required motoring time. By setting the required motoring time based on the engine water temperature and alcohol concentration in this way, the engine and fuel can be heated up without using heating means such as heaters, and the engine can be started smoothly. In addition, increasing the amount of compressed air increases the amount of heat generated, so the required motoring time can be shortened. However, if the amount of compressed air is kept as high as possible at all times in order to speed up engine starting, the motoring time will be shortened, but the amount of energy consumed during motoring will increase, worsening energy efficiency (fuel consumption and electricity consumption). Furthermore, the pressure inside the cylinder will repeatedly increase, so the vibration and noise during motoring will increase, which may cause discomfort to the occupants of the vehicle.

[0005] This invention has been made in view of the above 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 worsening of vibration or abnormal noise, in order to improve the starting performance of an internal combustion engine that uses alcohol-containing fuel. [Means for solving the problem]

[0006] To achieve the above objective, the present invention provides a control device for an internal combustion engine that draws a mixture of alcohol-containing fuel and air into a cylinder, compresses it with a piston, and ignites or ignites the mixture to burn it, and which, upon a starting request, performs motoring by drawing in air without fuel into the cylinder to rotate it prior to starting and burning the mixture, wherein the device has a controller that controls the motoring and the starting, and the controller has a detection means for detecting at least one of the temperature of the internal combustion engine and the concentration of the alcohol during the motoring, and controls the amount of air drawn into the cylinder during the motoring based on the temperature of the internal combustion engine and the concentration of the alcohol and Noi An air volume calculation means that determines the amount of air based on the difference, and the temperature of the internal combustion engine and the alcohol concentration detected by the detection means Noi The controller comprises a motoring time calculation means that determines the duration of the motoring based on one of the deviations and the amount of air determined by the air amount calculation means, and the controller controls the amount of air drawn into the cylinder to the amount of air determined by the air amount calculation means, and performs motoring for the duration determined by the motoring time calculation means.

[0007] In the present invention, the air quantity calculation means is the temperature of the internal combustion engine. Even if the temperature is lower than the specified temperature or the concentration of the aforementioned alcohol If the concentration is higher than the predetermined concentration The total amount of air is as described above. Constant temperature or predetermined concentration It may be configured to have a larger volume of air than the amount of air in the case.

[0008] In the present invention, the internal combustion engine includes a throttle valve that controls the amount of air drawn 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 degree or opening and closing timing of the intake valve, and the air amount calculation means further includes the temperature of the internal combustion engine and the concentration of the alcohol and NoiThe controller calculates at least one of the following: the opening of the throttle valve and the opening of the intake valve by the variable valve mechanism, so that the amount of air drawn into the cylinder is determined based on the difference between the two. The controller then calculates the opening of the throttle valve calculated by the air volume calculation means and the opening of the intake valve by the variable valve mechanism. Noi The system may be configured to output a control command signal that controls one of the two offsets. [Effects of the Invention]

[0009] According to the present invention, the amount of intake air during motoring, which is performed prior to engine starting, is determined 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. Therefore, when the temperature is high or the alcohol concentration is low, the amount of air can be reduced, which in turn can suppress or prevent vibrations and abnormal noises during motoring, and reduce the amount of energy consumed during motoring. Conversely, when the temperature is low or the alcohol concentration is high, the amount of intake air can be increased, which in turn can shorten the motoring time and avoid or suppress delays in engine starting. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram illustrating an example of an engine, and is a schematic cross-sectional view of one of the cylinders. [Figure 2] This is a functional block diagram illustrating an example of a controller. [Figure 3] This is a conceptual diagram illustrating an example of a map that defines target temperatures according to alcohol concentration. [Figure 4] This is a conceptual diagram illustrating an example of a map that determines the amount of inhaled air according to alcohol concentration and temperature. [Figure 5] This is a conceptual diagram to explain the difference in motoring time between increasing and not increasing the intake air volume during motoring. [Figure 6] This is a flowchart illustrating an example of control performed in an embodiment of the present invention. [Modes for carrying out the invention]

[0011] Next, the present invention will be described with reference to embodiments shown in the accompanying drawings. Note that the embodiments described below are merely examples of how the present invention may be implemented and do not limit the invention.

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

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

[0014] An injector 10 for injecting fuel into an intake port is provided at a predetermined position of an intake pipe 5. The fuel 11 injected from this injector 10 is fuel containing alcohol, and the fuel is supplied from a fuel tank 12 to the injector 10. An alcohol concentration sensor 13 for detecting the concentration of alcohol (for example, ethanol) in the fuel 11 and outputting a detection signal is provided in the middle of a fuel supply pipe 14. Further, a throttle valve 15 is provided upstream of the injector 10 in the intake pipe 5. This throttle valve 15 is a so-called electronically controlled valve, and is configured to be electrically controlled based on a drive demand amount represented by an accelerator opening degree or the like to control the amount of air inhaled into a cylinder 2.

[0015] On the other hand, a water jacket 16 is provided on the outer peripheral side of the cylinder 2. Further, a water temperature sensor 17 for detecting the temperature of the engine 1 (specifically, the temperature of engine cooling water) and outputting a detection signal is provided. In the embodiment of the present invention, since it is sufficient to detect the engine temperature that affects the atomization or evaporation of alcohol in the fuel, 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 in a hybrid vehicle, and an electric motor 18 for controlling the rotational speed of the engine 1 is provided. This electric motor 18 is a motor with a power generation function, that is, a motor-generator, and is connected to a power storage device such as a battery via an inverter not shown in the figure. This electric motor 18 is directly connected to the output shaft (crankshaft) of the engine 1, or is connected via a clutch not shown in the figure, or is connected to the engine 1 via a power split mechanism (not shown) composed of a planetary gear mechanism or the like. Therefore, it is configured to apply a so-called negative torque to the engine 1 by making the electric motor 18 function as a generator to suppress an increase in the engine rotational speed, and conversely, to apply a so-called positive torque to the engine 1 by making the electric motor 18 function as a motor to maintain or increase the engine rotational speed. Also, the electric motor 18 can function as a starter, and when there is a start request for the engine 1, the engine 1 is rotated by the electric motor 18, and prior to that, a motoring for rotating the engine 1 in a state where fuel is not supplied (injected) is performed by the electric motor 18.

[0017] Although not particularly shown in the figure, other sensors such as an engine rotational speed sensor, a vehicle speed sensor, a throttle opening sensor, and an electric motor rotational speed sensor are further provided.

[0018] An electronic control unit (ECU) 19 for controlling the start of the engine 1 and the motoring prior to the start is provided. Here, the "motoring" in the embodiment described here is control for rotating the engine 1 with external power for a predetermined time in order to heat up the engine 1, fuel, etc. Therefore, fuel is not supplied during motoring.

[0019] The ECU19 is primarily composed of a microcomputer consisting of arithmetic elements, memory elements, and interfaces. It is configured to perform calculations using input data and pre-stored data, and to output the results of these calculations as control command signals. The main function of the ECU19 is to control the motoring required to raise the temperature of the engine 1 prior to starting the engine 1, and various data necessary for this control are input to the ECU19. Specifically, the alcohol concentration detected by the alcohol concentration sensor 13, the temperature detected by the water temperature sensor 17 (which represents the temperature of the engine 1), the rotational speed of the engine 1, the vehicle speed, the opening degree of the throttle valve 15, and the rotational speed of the electric motor 18 are input to the ECU19.

[0020] Motoring is a control method in which the engine 1 is rotated by an electric motor 18 for a predetermined period of time with the fuel supply stopped to raise its temperature. Therefore, the ECU 19 outputs control command signals to the injector 10 and control command signals to control the rotational speed of the electric motor 18. In addition to these, the ECU 19 outputs control command signals to control the opening degree of the throttle valve 15 and the opening degree (lift amount) and opening / closing timing (these are sometimes collectively referred to as the VVT ​​opening degree) of the intake valve 7 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 also holds data for determining the control command values ​​to be output by these control signals, and for example, it holds and stores a map that defines the motoring time according to the alcohol concentration and engine water temperature, or a program that calculates the motoring time.

[0021] The ECU19 is configured to determine various control quantities using the input data and pre-stored data and programs, and its functional configuration is shown in Figure 2. Figure 2 is a block diagram illustrating the functional configuration of the ECU19, which corresponds to the controller in this embodiment of the invention, and the ECU19 has a concentration detection means 19a that detects the alcohol concentration in the fuel 11 based on a signal input from the aforementioned alcohol concentration sensor 13, and a 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] An air volume calculation means 19c is further provided in the ECU 19, which calculates 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 temperature of the engine 1 and engine coolant detected by the temperature detection means 19b, or based on at least one of them. Increasing the amount of air in the cylinder 2 during motoring increases the amount of heat generated by the compression of air, which can promote the heating of the engine 1, etc. However, on the other hand, the torque required to rotate the engine 1 by the electric motor 18 increases, which in turn increases vibrations and abnormal noises due to gear meshing, and also increases the power consumed by the electric motor 18. Therefore, the amount of air is increased only when a large amount of heat is required for heating.

[0023] Figure 3 is a conceptual diagram showing the relationship between the alcohol concentration in fuel 11 and the target temperature during motoring. The higher the alcohol concentration, the higher the target temperature. This is because a larger amount of alcohol needs to be atomized or evaporated at the start of engine 1. Therefore, the amount of air should be increased to raise the temperature to the target temperature in a short time. Figure 4 conceptually shows the relationship between alcohol concentration and the amount of air. 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 should be increased. For example, as shown by the solid line in Figure 4, the relationship between the two can be set so that the amount of air increases as the alcohol concentration increases. Alternatively, as shown by the dashed line in Figure 4, when the alcohol concentration is high and exceeds the threshold Th, the amount of air may be set to a corresponding fixed amount, and when it is below the threshold Th, it may be set to a fixed amount that is less than the fixed amount when it exceeds the threshold Th. Figure 4 also shows the relationship between detected temperature, such as engine water temperature, and the amount of air. The higher the detected temperature, the less air should be used. This is because the higher the detected temperature, the less heat is required to raise the temperature to the target temperature.

[0024] The air volume calculation means 19c pre-stores a map that defines the relationship between air volume, alcohol concentration, and temperature, for example, as shown in Figure 4, and calculates the air volume based on that map and the detected alcohol concentration and temperature. Since air is drawn into the cylinder 2 via the intake pipe 5, the intake air volume can be controlled by the throttle valve 15 located in the middle of the intake pipe 5. Furthermore, the amount of air confined inside the cylinder 2 can be changed according to the opening degree (lift amount) of the intake valve 7 and the timing of its opening and closing. Therefore, the air volume calculation means 19c may also determine the opening degree of the throttle valve 15 and the opening degree of the intake valve 7 by the intake-side variable valve timing mechanism (IN-VVT) 7A in addition to the air volume described above. Note that if the closing timing of the intake valve 7 is set to be retarded compared to the intake bottom dead center, the amount of intake air into the cylinder 2 can be 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 described above. 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, and the rotational speed of the engine 1 during motoring, but the gradient of temperature rise and the time to reach the target temperature can be roughly known in advance through experiments using actual equipment or simulations. Therefore, the motoring time calculation means 19d prepares a map that defines the relationship between the alcohol concentration, temperature, air volume and the time to reach the target temperature (i.e., motoring time), and calculates the motoring time based on that map.

[0026] Motoring is performed at an engine speed corresponding to the vehicle speed at the end of the motoring process, i.e., at the time of engine startup, in order to avoid shocks during engine startup. The amount of heat generated by motoring, i.e., the motoring time required to reach the target temperature, also varies depending on the engine speed. Therefore, it is preferable to take the engine speed into account when calculating the motoring time, and specifically, the higher the engine speed during motoring, the shorter the motoring time should be.

[0027] As mentioned above, increasing the amount of air compressed inside cylinder 2 during motoring increases the amount of heat generated by motoring, shortening the motoring time required to raise the temperature to the target temperature. This relationship is conceptually shown in Figure 5, and when the amount of air is increased, the gradient of the motoring time relative to the target temperature becomes smaller compared to when the amount of air is not increased, as shown by the dashed line in Figure 5. Furthermore, in the embodiment of the present invention, as explained with reference to Figure 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 rises easily, the amount of air drawn into cylinder 2 during motoring, i.e., the amount of air compressed during motoring, is reduced or not increased. Therefore, it is not necessary to constantly increase the torque required for motoring, so vibrations and abnormal noises during motoring can be avoided or reduced, the amount of power consumed can be reduced, and the motoring time can be shortened, improving the starting performance of engine 1.

[0028] An example of motor control preceding the aforementioned start-up will be explained with reference to the flowchart shown in Figure 6. The routine shown in Figure 6 is executed when a vehicle equipped with an engine 1 that uses alcohol-containing fuel starts moving, or when the engine 1 is temporarily stopped due to hybrid driving, and then the engine 1 is started again due to an acceleration request or a decrease in the remaining battery charge. First, it is determined whether or not there is a request to start the engine (ENG) (step S1). This start request occurs when the ignition switch (not shown) is turned ON, when the engine 1 that has stopped due to a stop signal is restarted by pressing the accelerator, when there is an acceleration request while the hybrid vehicle is running on the motor, or when it becomes necessary to generate power due to a decrease in the remaining battery charge. If the result of the determination in step S1 is "no" because there is no start request, the routine shown in Figure 6 is terminated without any particular control.

[0029] If the result of the judgment in step S1 is "yes", the vehicle speed, engine water temperature (temperature), and alcohol concentration are acquired (step S2). Note that this data, such as vehicle speed, engine water temperature (temperature), and alcohol concentration, may be acquired continuously. Next, based on this vehicle speed, engine water temperature (temperature), and alcohol concentration, the target amount of air to be inhaled during motoring is calculated, and at the same time, 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 calculated (step S3). This calculation is as described above as a function of the air amount calculation means 19c.

[0030] Furthermore, once the amount of air is calculated, the motoring time (duration) is calculated based on that amount of air, the temperature, and the alcohol concentration, and the rotational speed (required rotational speed) for motoring is calculated based on the vehicle speed (step S4). The calculation of the motoring time is as described above as a function of the motoring time calculation means 19d. In addition, the control of the target rotational speed is performed not so much to generate the amount of heat required for heating, but rather to minimize the difference between the rotational speed of the electric motor 18 and the rotational speed at startup when fuel is supplied to the engine 1 and the engine 1 is started, thereby avoiding or suppressing shock. Therefore, the target rotational speed is determined based on the vehicle speed.

[0031] As described above, the throttle opening, IN-VVT opening, motoring time, and target rotational speed are determined, and a control command signal based on these is output to perform motoring (step S5). In this case, if the temperature is low or the alcohol concentration is high, the intake air volume increases, and the amount of heat generated by motoring increases, so the temperature rises rapidly. In other words, the motoring time is shortened compared to when control to increase the air volume is not performed. Conversely, if the temperature is high or the alcohol concentration is low, the air volume is reduced or the control to increase the air volume is not performed, so vibrations and abnormal noises during motoring can be reduced or prevented.

[0032] Then, after motoring for the calculated time, engine 1 is started (step S6). That is, fuel is supplied to allow engine 1 to rotate on its own. It should be noted that the present invention is not limited to the embodiments described above, and can be implemented with appropriate modifications within the scope of the objectives of the present invention. [Explanation of symbols]

[0033] 1. Internal combustion engine 2 liters 3 pistons 4 Cylinder head 5. Intake pipe 6 Exhaust pipes 7 Intake valve 8 Exhaust valves 7A, 8A Variable Valve Mechanism 9. Fire hydrant 10 Injectors 11 Fuel 12 fuel tanks 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 means 19d Motoring time calculation means

Claims

1. A control device for an internal combustion engine that draws a mixture of alcohol-containing fuel and air into a cylinder, compresses it with a piston, and ignites or ignites the mixture to burn it, and which, when a starting request is made, performs motoring by drawing air, which is not supplied with fuel, into the cylinder and rotating it prior to starting by burning the mixture, It has a controller that controls the motoring and the starting, The aforementioned controller, A detection means for detecting at least one of the temperature of the internal combustion engine and the concentration of the alcohol during the motoring, An air volume calculation means that determines the amount of air drawn into the cylinder during motoring based on either the temperature of the internal combustion engine or the concentration of the alcohol, A motoring time calculation means that determines the duration of the motoring based on either the temperature of the internal combustion engine detected by the detection means or the alcohol concentration, and the amount of air determined by the air amount calculation means. Equipped with, The controller controls the amount of air drawn into the cylinder to the amount of air determined by the air amount calculation means, and performs motoring for the duration determined by the motoring time calculation means. 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 control device for an internal combustion engine is characterized in that the air quantity calculation means is configured to be greater than the air quantity when the temperature of the internal combustion engine is lower than a predetermined temperature or when the alcohol concentration is higher than a predetermined concentration.

3. A control device for an internal combustion engine according to claim 1 or 2, The internal combustion engine includes a throttle valve that controls the amount of air drawn 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 degree or opening and closing timing of the intake valve. The air volume calculation means further calculates at least one of the throttle valve opening and the intake valve opening by the variable valve mechanism so that the amount of air drawn into the cylinder is determined based on either the temperature of the internal combustion engine or the concentration of the alcohol. The controller is configured to output a control command signal that controls either the opening degree of the throttle valve calculated by the air volume calculation means or the opening degree of the intake valve by the variable valve mechanism. A control device for an internal combustion engine, characterized by the following features.

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