Method and device for controlling the ignition of an internal combustion engine

Abstract

To suppress waste of electric power by making energizing time to an ignition coil appropriate.SOLUTION: A reference energization time is determined based on a voltage of a power supply and a rotation speed. On the basis of a condition related to the combustion state of the internal combustion engine, it is determined whether the combustion state of the internal combustion engine is in a relatively stable first operation state or in a relatively unstable second operation state. To judge whether an actual combustion state is good or bad by detecting the actual combustion state of an internal combustion engine. When it is determined that the combustion state is good in the first operation state (time t1), the energization time is largely reduced and corrected from the reference energization time to a predetermined level, and thereafter, when it is determined that the actual combustion state is bad, the energization time is gradually corrected to be longer by a minute amount (time t2, t3). In the second operation state, when it is determined that the combustion state is good, the energization time is corrected to be gradually shortened by a minute amount from the reference energization time.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an ignition control technique for optimizing the time for which current is applied to an ignition coil of an internal combustion engine. [Background technology]

[0002] Generally, an ignition device for an internal combustion engine is configured so that a discharge occurs between the electrodes of the spark plug connected to the secondary coil by passing and interrupting a primary current through the primary coil of the ignition coil. Basically, the longer the time that current is passed through the primary coil, the greater the ignition energy that is provided.

[0003] In general, the time for which current is applied to the primary coil is set to be long when the battery voltage is low and short when the rotation speed is high.

[0004] Patent Document 1 discloses that the combustion state of an internal combustion engine is detected, and when a poor combustion state continues for a predetermined period of time, the current supply time is increased. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-275876 Summary of the Invention [Problem to be solved by the invention]

[0006] If the current supply time is determined uniformly based on the battery voltage and rotation speed, the current supply time must be set with a margin to ensure reliable ignition and combustion even when the engine is cold, resulting in wasted power and worsening fuel efficiency.

[0007] In Patent Document 1, a long current application time is given when poor combustion conditions continue, but under other conditions, the current application time is not necessarily controlled to the minimum required time, and there is room for improvement. [Means for solving the problem]

[0008] The present invention provides an ignition control method for an internal combustion engine, which determines a reference current-carrying time based on a voltage of a power source and a rotation speed as a current-carrying time for an ignition coil of the internal combustion engine, and corrects the reference current-carrying time based on a condition related to a combustion state of the internal combustion engine, Based on the above conditions, determining whether the combustion state of the internal combustion engine is in a first operating state in which it is relatively stable or in a second operating state in which it is relatively unstable; Detecting the actual combustion state of an internal combustion engine and determining whether this actual combustion state is good or bad, If the combustion state is determined to be good when in the first operating state, the current conduction time is greatly reduced to a predetermined level at which the combustion state may deteriorate, and thereafter, if the actual combustion state is determined to be poor, the current conduction time is gradually increased by small amounts, If the combustion state is determined to be good in the second operating state, the current application time is gradually shortened by a small amount.

[0009] That is, when the internal combustion engine is in a first operating state in which the combustion state is considered relatively stable, if the combustion state is determined to be good, the current supply time is initially corrected by significantly decreasing it to a predetermined level at which the combustion state may deteriorate. After that, if the actual combustion state is determined to be poor, the current supply time is corrected by gradually increasing it by small amounts. Therefore, the current supply time is shortened within a range that does not deteriorate the combustion state.

[0010] On the other hand, when the internal combustion engine is in a second operating state where the combustion state is relatively unstable, if the combustion state is determined to be good, the current supply time is gradually shortened by small increments from the reference current supply time, thereby avoiding misfires caused by an excessively short current supply time and ensuring that the current supply time corresponds to the actual combustion state. [Effects of the Invention]

[0011] According to this invention, the time for which current is applied to the ignition coil can be set appropriately depending on various conditions and the actual combustion state, thereby making it possible to avoid misfires and suppress unnecessary power consumption. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is an explanatory diagram of the configuration of a series hybrid vehicle. [Figure 2] 1 is a diagram illustrating the configuration of an internal combustion engine equipped with an ignition device according to an embodiment of the present invention; [Figure 3] 6 is a time chart showing an example of changes in current application time in a first operating state. [Figure 4] 6 is a time chart showing an example of changes in current application time in a second operating state. [Figure 5] 6 is a time chart showing the change in power supply time when battery power consumption is required; DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a schematic configuration of a series hybrid vehicle as an example of a vehicle to which the present invention can be applied. The series hybrid vehicle includes a power-generating motor-generator 1 that operates primarily as a generator, an internal combustion engine 2 used as a power-generating internal combustion engine that drives the power-generating motor-generator 1 in response to a power demand, a traction motor-generator 4 that operates primarily as a motor to drive drive wheels 3, and a battery 5 that stores the generated power. The power obtained by the internal combustion engine 2 driving the power-generating motor-generator 1 is stored in the battery 5 via an inverter device (not shown). The traction motor-generator 4 is driven and controlled using the power from the battery 5. The power generated by the traction motor-generator 4 during regeneration is stored in the battery 5 via an inverter device (not shown).

[0014] The operation of the motor generators 1 and 4, the charging and discharging of the battery 5, and the operation of the internal combustion engine 2 are controlled by a controller 6. The controller 6 is composed of multiple controllers connected to each other so that they can communicate with each other, such as a motor controller 7 that controls the motor generators 1 and 4, an engine controller 8 that controls the internal combustion engine 2, and a battery controller 9 that manages the battery 5. Information such as the accelerator pedal position and vehicle speed (not shown) is input to the controller 6. The battery controller 9 also calculates the SOC of the battery 5 based on the voltage and current of the battery 5. When the SOC drops to a predetermined lower limit, the internal combustion engine 2 is started via the engine controller 8 to generate electricity. Such a series hybrid vehicle has two driving modes: an EV mode in which the vehicle runs on power from the battery 5 without combustion operation of the internal combustion engine 2, and an HEV mode in which the vehicle runs while generating electricity through combustion operation of the internal combustion engine 2. Even if the SOC is above the lower limit, the internal combustion engine 2 is driven and the vehicle runs in the HEV mode when the required driving force of the vehicle is relatively large.

[0015] The internal combustion engine 2 is a four-stroke spark-ignition internal combustion engine, commonly known as a gasoline engine. FIG. 2 shows the system configuration of the internal combustion engine 2 equipped with an ignition device. Each of the multiple cylinders 12 of the internal combustion engine 2 is equipped with a piston 13 and is connected to an intake port 15 opened and closed by an intake valve 14 and an exhaust port 17 opened and closed by an exhaust valve 16. A fuel injection valve 18 is also provided to inject fuel into the cylinder. The fuel injection timing and fuel injection amount of the fuel injection valve 18 are controlled by an engine controller 8. An ignition plug 19 is provided, for example, in the center of the ceiling surface to ignite the air-fuel mixture generated in the cylinder by the fuel injection valve 18. Note that the illustrated example is configured as a direct-injection internal combustion engine, but a port injection type configuration in which a fuel injection valve is provided in the intake port 15 may also be used. The engine controller 8 receives detection signals from a number of sensors, such as an air flow meter 31 that detects the amount of intake air, a crank angle sensor 32 that detects the engine rotation speed, a temperature sensor 33 that detects the coolant temperature, an atmospheric pressure sensor 34 that detects the atmospheric pressure, and a battery voltage sensor 35.

[0016] An ignition unit 21 is connected to each cylinder of the spark plug 19, outputting a discharge voltage to the spark plug 19 in response to an ignition signal from the engine controller 8. The ignition unit 21 is well known and is not shown in detail, but it includes an ignition coil including a primary coil and a secondary coil, and an igniter that controls the flow of primary current to the primary coil of the ignition coil. A power source 22 is connected to the ignition unit 21. The voltage of the power source 22 is detected by a battery voltage sensor 35. In one embodiment, the battery 5 of the traveling system is also used as the power source 22 for the ignition device. If the voltage of the battery 5 of the traveling system is high, it can be converted to an appropriate voltage before use. Alternatively, an auxiliary battery of approximately 12 to 48 V for vehicle electrical equipment, separate from the battery 5 of the traveling system, may be used as the power source 22.

[0017] As is well known, in an ignition system, a primary current is applied to a primary coil via an igniter in response to an ignition signal from the engine controller 8, and then the current is cut off at the target ignition timing. This cutoff of the primary current generates a high discharge voltage in the secondary coil, causing a discharge between the electrodes of the spark plug 19. The discharge energy at this time is basically correlated with the duration of the primary current. Furthermore, a relatively long current duration is required to obtain the same discharge energy when the battery voltage is low. Therefore, the engine controller 8 has a reference current duration map, which uses the voltage and rotational speed of the power source 22 as parameters. The reference current duration is determined according to this reference current duration map. The final current duration is then set by correcting this reference current duration based on conditions related to the combustion state of the internal combustion engine 2. The reference current duration map has the characteristic that the lower the voltage, the longer the current duration, and the higher the rotational speed, the shorter the current duration. The reference current duration is set to a sufficient length to ensure reliable ignition and combustion even under adverse conditions. Since an excessively long current application time can cause deterioration or damage to the spark plug 19, the reference current application time is set to a relatively long time within a range that does not cause such deterioration or damage.

[0018] Next, a current supply time control according to one embodiment will be described with reference to the time charts of Figures 3 and 4. In one embodiment, it is determined whether the current state of the internal combustion engine 2 falls into a first operating state in which the combustion state of the internal combustion engine 2 is relatively stable, or a second operating state in which the combustion state of the internal combustion engine 2 is relatively unstable, based on conditions related to the combustion state of the internal combustion engine 2 (including operating conditions such as the coolant temperature of the internal combustion engine 2 and environmental conditions such as atmospheric pressure).

[0019] For example, the first operating state in which the combustion state is stable is determined to be when the engine is in stoichiometric combustion after warm-up is complete, when the engine is idling after warm-up is complete, and when the vehicle is coasting. In other words, these are states in which stable ignition and combustion are possible with a relatively small amount of ignition energy.

[0020] Additionally, cold operation, high-volume exhaust gas recirculation operation, and lean combustion are identified as second operating states in which combustion is likely to become unstable. In other words, these correspond to states in which misfires are likely to occur if ignition energy is insufficient.

[0021] Furthermore, the actual combustion state of the internal combustion engine 2 during operation is detected and the combustion state is judged to be good or bad. The combustion state may be detected by any method. For example, the combustion state of the internal combustion engine 2 may be detected from minute changes in the crankshaft rotation speed, variations in combustion pressure, etc.

[0022] FIG. 3 shows the final change in the energization time when the internal combustion engine 2 is in the first operating state. For example, when the rotational speed of the internal combustion engine 2 changes to a certain rotational speed, ignition is initiated in the initial cycle with a reference energization time. If the combustion state is determined to be good at time t1, the energization time is significantly reduced to a predetermined level. This is achieved, for example, by multiplying by a correction coefficient or subtracting a correction amount. The energization time may be at a level that could potentially deteriorate the combustion state. To shorten the average energization time, the energization time is corrected to as short a level as possible without causing misfires. If the actual combustion state is determined to be poor at time t2 due to the short energization time, the energization time is extended by a predetermined small amount (i.e., brought closer to the reference energization time). Furthermore, in the illustrated example, the actual combustion state is determined to be poor at time t3, and the energization time is again extended by a small amount. It is desirable to determine whether the combustion state is good or poor after a predetermined time or a predetermined number of cycles have been detected as good or poor. Alternatively, it may be determined that the combustion state is poor when misfire is detected even in one cycle.

[0023] In this way, in the first operating state, the current conduction time is initially significantly reduced and then gradually increased according to the actual combustion state, thereby shortening the average current conduction time and reducing power consumption. Note that, because the first operating state is relatively stable, misfires are unlikely to occur even if the current conduction time is significantly reduced at time t1.

[0024] FIG. 4 shows the final change in the current conduction time when the state of the internal combustion engine 2 is the second operating state. In this case, too, for example, when the rotational speed of the internal combustion engine 2 changes to a certain rotational speed, ignition is initiated in the initial cycle with the reference current conduction time. Thereafter, at time t11, if it is determined that the combustion state is good, the current conduction time is corrected and decreased by a predetermined small amount. Thereafter, if it is determined that the actual combustion state is good at time t12, it is considered that there is sufficient current conduction time, so the current conduction time is corrected and decreased again by a predetermined small amount. In the illustrated example, it is further determined that the combustion state is good at time t13, and the current conduction time is reduced by a predetermined small amount.

[0025] In this way, in the second operating state, the current flow time is gradually reduced and corrected from the standard current flow time within a range that does not deteriorate the combustion state, thereby avoiding misfires that may occur due to shortened current flow time, and making it possible to maintain the current flow time at an appropriate length while avoiding misfires.

[0026] In this embodiment, when the state of the internal combustion engine 2 is basically stable, the mode is as shown in Figure 3, and when it is basically unstable, the mode is as shown in Figure 4.The current supply time is adjusted to a length that corresponds to the actual combustion state, so that misfires can be avoided while power waste is minimized to the maximum extent possible.

[0027] Next, FIG. 5 is a time chart showing an example of current supply time control when the battery 5 of the driving system is also used as the power source 22 of the ignition device in a series hybrid vehicle as described above. In hybrid vehicles, including series hybrid vehicles, the charge level of the battery 5 may become saturated due to regeneration while driving down a long slope. In such a case, if power consumption from the battery 5 is required at time t21, for example, the current supply time is extended as much as possible. For example, even if the combustion state is good, the current supply time is set to the reference current supply time. Alternatively, the current supply time may be set longer than the reference current supply time as long as it does not cause deterioration or damage to the ignition plug 19.

[0028] This allows for consumption of power from the battery 5. Note that the total energization time may be extended by increasing the number of ignitions.

[0029] While one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible. In the above embodiment, an example in which the present invention is applied to an internal combustion engine for generating electricity in a series hybrid vehicle has been described, but the present invention can also be applied to an ignition device for an internal combustion engine that serves as a driving source for the vehicle. [Explanation of symbols]

[0030] 1...Power generating motor generator 2...Internal combustion engine 4...Traction motor generator 5. Battery 8...Engine controller 19...Spark plug 21...Ignition unit 22…Power supply 35...Voltage sensor

Claims

1. An ignition control method for an internal combustion engine, comprising: determining a reference current conduction time based on a voltage of a power source and a rotation speed as a current conduction time for an ignition coil of the internal combustion engine; and correcting the reference current conduction time based on a condition related to a combustion state of the internal combustion engine, Based on the above conditions, it is determined whether the combustion state of the internal combustion engine is in a first operating state in which it is relatively stable or in a second operating state in which it is relatively unstable; Detecting the actual combustion state of the internal combustion engine and determining whether this actual combustion state is good or bad; If the combustion state is determined to be good when in the first operating state, the current conduction time is greatly reduced to a predetermined level at which the combustion state may deteriorate, and thereafter, if the actual combustion state is determined to be poor, the current conduction time is gradually increased by a small amount. If it is determined that the combustion state is good in the second operating state, the current application time is gradually shortened by a small amount. A method for controlling ignition in an internal combustion engine.

2. As the conditions, the first operating state is determined to be when the engine is in stoichiometric combustion after warm-up is complete, when the engine is idling after warm-up is complete, and when the vehicle is coasting.

2. The ignition control method for an internal combustion engine according to claim 1.

3. As the above conditions, the second operating state is determined to be during cold operation, during large-volume exhaust gas recirculation operation, and during lean combustion.

2. The ignition control method for an internal combustion engine according to claim 1.

4. The internal combustion engine is a power generating internal combustion engine that drives a generator in a series hybrid vehicle.

2. The ignition control method for an internal combustion engine according to claim 1.

5. When power consumption of the battery is required, the power supply time is set to the reference power supply time or a predetermined power supply time longer than the reference power supply time, regardless of the combustion state.

5. The ignition control method for an internal combustion engine according to claim 4.

6. An ignition control device for an internal combustion engine, which determines a reference current-carrying time based on a voltage of a power source and a rotation speed as a current-carrying time to an ignition coil of the internal combustion engine, and corrects the reference current-carrying time based on a condition related to a combustion state of the internal combustion engine, Based on the above conditions, it is determined whether the combustion state of the internal combustion engine is in a first operating state in which it is relatively stable or in a second operating state in which it is relatively unstable; Detecting the actual combustion state of the internal combustion engine and determining whether this actual combustion state is good or bad; If the combustion state is determined to be good when in the first operating state, the current conduction time is greatly reduced to a predetermined level at which the combustion state may deteriorate, and thereafter, if the actual combustion state is determined to be poor, the current conduction time is gradually increased by a small amount. If it is determined that the combustion state is good in the second operating state, the current application time is gradually shortened by a small amount. Ignition control device for internal combustion engines.

Images