JP7161828B2 - Control device for internal combustion engine - Google Patents

Description

The present invention is an internal combustion engine mounted on a vehicle, which is capable of switching between homogeneous charge compression ignition (hereinafter sometimes referred to as HCCI) combustion and spark ignition (hereinafter sometimes referred to as SI) combustion. The present invention relates to a control device for controlling an internal combustion engine.

In an engine vehicle equipped with an internal combustion engine as a drive source for running, SI combustion in which a mixture of fuel such as gasoline and air is ignited by a spark plug and burned, and by compressing the mixture without using a spark plug. Switching between HCCI combustion, which is ignited and burned, according to the running state of the automobile, particularly the number of revolutions and the load, has been studied (eg, Patent Documents 1 and 2).

However, the operating range in which HCCI combustion is possible (hereinafter sometimes referred to as the HCCI operating range) is limited to a low engine speed/low load to a medium engine speed/medium load, as shown in FIG. Therefore, in operating regions of extremely low engine speed, extremely low load, high engine speed and high load, the combustion is switched to SI combustion.

Patent document 1 adjusts the opening and closing timings of the intake valve and the exhaust valve by a variable valve timing mechanism, and when switching from SI combustion to HCCI combustion, provides a negative overlap period in which both valves are closed at or near top dead center. (extended) and disclose shortening the negative overlap when switching from HCCI combustion to SI combustion.

Conventionally, in engine-powered automobiles, the fuel supply to the internal combustion engine is interrupted for the purpose of improving fuel efficiency during idling stop or deceleration, and fuel supply is started by the driver depressing the accelerator pedal. is done. Patent Literature 2 discloses determining whether or not HCCI combustion is possible when canceling a fuel cut, and if the result of the determination is affirmative, performing HCCI combustion from the time of canceling a fuel cut.

JP 2010-216326 A Japanese Unexamined Patent Application Publication No. 2011-185170

During the fuel cut described above, the internal combustion engine is normally stopped. As a result, the temperature inside the cylinders of the internal combustion engine decreases. Due to the temperature drop in the cylinder, the temperature of the compressed air-fuel mixture does not easily rise to the temperature at which spontaneous ignition is possible even in a running state corresponding to the HCCI operating range immediately after returning from the fuel cut state to the fuel supply state. , HCCI combustion may not be possible. Therefore, it is desired that HCCI combustion can be stably performed after recovery from the fuel cut.

In addition, since the valve timing is significantly different before and after switching between HCCI combustion and SI combustion as described above, it tends to take a long time to change the opening/closing timing of the valve system in accordance with the combustion conditions. For example, in a state in which the driver depresses the accelerator pedal and demands a high engine speed or high load, it is desirable to switch from HCCI combustion to SI combustion. However, due to the effects of the above-described response delay of the valve system, etc., heavy knock occurs during the above-described switching, resulting in deterioration of noise and vibration (NV). Furthermore, the internal combustion engine may be damaged.

SUMMARY OF THE INVENTION Accordingly, one object of the present invention is to provide a control apparatus for an internal combustion engine that can stably perform HCCI after recovery from a fuel cut.

A control device for an internal combustion engine according to one aspect of the present invention includes:
A control device for an internal combustion engine capable of switching between homogeneous charge compression ignition combustion and spark ignition combustion,
The internal combustion engine is mounted on a series hybrid vehicle,
The control device is
an HCCI determination unit that determines whether or not homogeneous charge compression ignition combustion is possible when returning from a fuel cut state to a fuel supply state;
a continuous combustion command unit that causes the internal combustion engine to perform spark ignition combustion once and then continuously perform homogeneous charge compression ignition combustion when the HCCI determination unit determines that homogeneous charge compression ignition combustion is possible. .

In the control apparatus for the internal combustion engine described above, SI combustion is performed first even if it is determined that HCCI combustion is possible at the time of resuming fuel supply from fuel cut. Therefore, even if the temperature inside the cylinder is lowered due to the fuel cut, the temperature inside the cylinder can be reliably raised by the exhaust gas generated by the SI combustion. In addition, since the control apparatus for an internal combustion engine described above performs HCCI combustion continuously after performing SI combustion, the temperature in the cylinder does not substantially decrease, and a high temperature state can be easily maintained. Therefore, according to the above control device for an internal combustion engine, after returning from a fuel cut, it is easy to set the temperature in the cylinder to a temperature at which spontaneous ignition is possible by compressing the air-fuel mixture, and HCCI combustion can be stably performed.

In particular, the internal combustion engine control device described above is installed in a series hybrid vehicle (hereinafter sometimes referred to as an S-HV vehicle) that uses the internal combustion engine only for power generation, not as a drive source for running the vehicle. Therefore, it is easy to greatly reduce the influence of the operating state of the internal combustion engine on the running state of the vehicle. For example, when switching between HCCI combustion and SI combustion, it is difficult for the driver to feel uncomfortable about the driving state. It can be said that it is also excellent in drivability.

For example, the operating conditions of SI combustion at the time of returning to fuel supply from the above-described fuel cut are changed stepwise from low rotation speed and low load conditions that do not satisfy the HCCI operating range to high rotation speed and high load conditions. (details will be described later), knocking can be prevented. Therefore, it is difficult for the driver to feel uncomfortable due to knocking. Also, damage to the internal combustion engine due to knocking can be prevented. Furthermore, even if the internal combustion engine is operating at a relatively low rpm and low load, the running condition of the vehicle will remain in line with the driver's wishes, i. It corresponds to the state where high load is desired. Also from these points, it is excellent in drivability.

Furthermore, for example, if a fuel cut is performed when switching from HCCI combustion to SI combustion according to the operating state (details will be described later), heavy knock can be avoided, and even if there is a decrease in torque due to fuel cut, S -Because it is an HV vehicle, it does not substantially give the driver a sense of discomfort such as a feeling of stalling. Also from this point, it is excellent in drivability.

1 is a functional block diagram of a control device for an internal combustion engine according to Embodiment 1; FIG. 4 is a flowchart showing an example of a control procedure by the control device for an internal combustion engine of Embodiment 1; 4 is a graph schematically showing an operating range in which HCCI combustion is possible and an operating range in which SI combustion is possible with respect to engine speed (horizontal axis) and torque (vertical axis).

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the figure, the same reference numerals denote the same name.

[Embodiment 1]
(Overview of control device)
An internal combustion engine control device 1 of Embodiment 1 controls an internal combustion engine 2 mounted on a vehicle 10 . The internal combustion engine 2 is capable of switching between homogeneous charge compression ignition (HCCI) combustion and spark ignition (SI) combustion.

Although not shown in detail, the internal combustion engine 2 includes one or more cylinders 20, an intake valve and an exhaust valve for opening and closing a combustion chamber provided at one end of the cylinder 20, an intake passage and an exhaust passage. system and exhaust system, a spark plug that ignites the mixture of fuel such as gasoline and air in the combustion chamber, and a variable valve timing mechanism that independently adjusts the opening/closing timing and lift amount of the intake valve and exhaust valve. , and a fuel injection device for injecting fuel into the combustion chamber or the intake passage.

The control device 1 for the internal combustion engine selects an operating range in which HCCI combustion is possible (HCCI operating range) or an operating range in which SI combustion is possible (hereinafter referred to as SI operating range) based on information from various sensors 100 provided in the vehicle 10. ) is detected, and switching between HCCI combustion and SI combustion is possible based on the detection result. The operating range is basically set in advance according to the engine speed (eg, information from a speed sensor) and the load (eg, pressure information in the intake pipe from an intake pressure sensor). In addition, the HCCI operating range and the SI operating range are set as shown in FIG. , ignition timing by a spark plug, fuel injection timing by a fuel injection device, and other combustion operation conditions are set. For example, in the HCCI operating region, there is a negative overlap period (a period in which the exhaust valve and the intake valve are closed at and near the top dead center) at and near the top dead center. The opening and closing timings of both valves are set so that the intake valves are opened after the top dead center when the intake valves are closed. By setting the negative overlap period, it is easy to reduce the temperature drop in the cylinder and perform the HCCI combustion satisfactorily. In the SI operating region, on the contrary, the opening/closing timings of both valves are set so that the exhaust valve closes late and the intake valve opens early with the exhaust valve open.

Based on the above-described setting information, the control device 1 for the internal combustion engine causes the variable valve timing mechanism to adjust the opening/closing timing and lift amount of the intake valve and the exhaust valve, causes the spark plug to adjust the ignition timing, and controls the fuel injection. It is configured to adjust the fuel injection timing of the device. The control device 1 of this example includes an operating range detection unit 11 that detects an operating range based on engine speed information and load information from sensors 100, and whether or not the detected operating range is an operating range in which HCCI combustion is possible. HCCI determination unit 12 that determines the , and based on the determination result of the determination unit 12, a predetermined combustion operating condition that is preset according to each operating region is selected, and each component of the internal combustion engine 2 (for example, variable (valve timing mechanism, spark plug, fuel injection device, etc.) to execute the selected condition. The control device 1 includes a central processing unit, a storage device 18 for storing preset various information (including the above-described combustion operation conditions), an arithmetic device for performing appropriate calculations, an input interface, an output interface, etc. (any (also not shown) can be used. For the basic configuration of the control device 1, reference can be made to a known configuration for controlling an internal combustion engine capable of switching between HCCI combustion and SI combustion (eg, Patent Document 1).

(vehicle)
In particular, the vehicle 10 provided with the internal combustion engine 2 and its control device 1 is a series hybrid vehicle (S-HV vehicle 10). The S-HV vehicle 10 does not use the internal combustion engine 2 as a drive source for running the vehicle, but only for power generation, and includes an electric motor 3 as a drive source for running. Specifically, the S-HV vehicle 10 includes an internal combustion engine 2 that generates power for power generation by burning fuel such as gasoline, a generator 4 that generates power using the power generated by the internal combustion engine 2, and It includes a storage battery 5 that charges generated power and discharges it to the electric motor 3 , an electric motor 3 that is driven by the power from the storage battery 5 or the like, and wheels 6 that are rotated by the electric motor 3 . An inverter device 7 is provided between the generator 4 and the storage battery 5 to appropriately convert DC power and AC power according to the specifications of the electric motor 3 and the storage battery 5 . The output of electric motor 3 is transmitted to wheels 6 via transmission 8 and differential 9 . Only front wheels or rear wheels are illustrated as the wheels 6 in FIG.

(Details of control device)
The control device 1 for an internal combustion engine of this embodiment basically performs so-called accelerator-linked control. In the accelerator-linked control, fuel is normally supplied to the internal combustion engine 2 when the driver of the S-HV vehicle 10 depresses the accelerator pedal, that is, when power (engine speed or torque) is required. When the accelerator pedal is released, that is, when the S-HV vehicle 10 is required to decelerate or stop, the fuel supply to the internal combustion engine 2 is stopped (fuel cut). In the S-HV vehicle 10 in which accelerator-linked control is performed, basically, the operating state of the accelerator pedal and the starting/stopping state of the internal combustion engine 2 are linked. Therefore, the driver can drive the S-HV vehicle 10 with a feeling similar to that of a conventional engine vehicle, which is excellent in drivability.

The control device 1 for an internal combustion engine of Embodiment 1 performs accelerator-linked control and switches between HCCI combustion and SI combustion. For example, when the driver depresses the accelerator pedal and then releases the accelerator pedal, the control device 1 cuts the fuel, and when the driver again depresses the accelerator pedal, the fuel cut returns to the fuel supply state. The internal combustion engine 2 is controlled so as to The control device 1 also includes a fuel cut determination unit 14 that determines whether or not a fuel cut state exists, and stops the internal combustion engine 2 in a fuel cut state, and performs HCCI combustion or SI combustion in a fuel supply state. to control the internal combustion engine 2.

The fuel cut determination unit 14 of this example determines whether or not the fuel cut state is in effect, based on information such as the amount of depression of the accelerator pedal, and determines whether or not it is time to return from the fuel cut state to the fuel supply state. This is the configuration for making the determination. For example, the fuel cut determination unit 14 may be configured to determine the fuel cut state if the depression amount is not (zero) or is equal to or less than a predetermined amount. Further, for example, by comparing the current value and the immediately preceding value of the depression amount, when the depression amount changes from zero or a predetermined value or less to a state exceeding a predetermined value, the fuel supply state is determined. For example, the fuel cut determination unit 14 may be configured to determine that it is time to return.

The control device 1 for an internal combustion engine according to the first embodiment determines whether or not HCCI combustion is possible by the HCCI determination unit 12 when returning from the state of fuel cut described above to the state of fuel supply. A continuous combustion command unit 15 is provided for causing the internal combustion engine 2 to perform HCCI combustion continuously after first performing SI combustion when it is determined that HCCI combustion is possible. Such a control device 1 can appropriately create an environment in which the internal combustion engine 2 easily performs HCCI combustion even immediately after returning from a fuel cut.

The control device 1 for an internal combustion engine of the present embodiment selects at least one of a low rotation speed and a low load that do not satisfy the HCCI operating range as the operating condition for SI combustion when returning from the above-described fuel cut. The condition is to increase the value of the item that was selected step by step. For example, the control device 1 controls the internal combustion engine 2 so as to stepwise increase the rotation speed or stepwise increase the pressure in the intake pipe. The values to be changed stepwise (rotational speed and pressure) can be set in advance and stored in the storage device 18 so as to be selected, for example, from the area hatched with two-dot chain lines in the graph shown in FIG. mentioned. Such a control device 1 can easily prevent knocking even when there is a difference in variable valve timing or the like between the SI combustion operating condition and the HCCI operating region operating condition corresponding to the determination result of the HCCI determining unit 12 .

Furthermore, the control device 1 for an internal combustion engine of this example includes a fuel stop command unit 16 that temporarily stops fuel supply when switching from HCCI combustion to SI combustion based on the determination result of the HCCI determination unit 12, an intake valve and A condition adjustment command section 13 for changing the combustion operation condition of the exhaust valve to a condition corresponding to the determination result, and a supply start command section 17 for starting fuel supply after completion of changing the combustion operation condition. Such a control device 1 can avoid heavy knocking at the time of switching from HCCI combustion to SI combustion. is practically non-existent. The switching process that accompanies this fuel cut can be performed by temporarily canceling the accelerator-linked control.

(Control procedure)
A specific control procedure by the control device 1 for an internal combustion engine according to the embodiment will be described below with reference to FIG. 2 .

<Basic control>
In the control device 1 for the internal combustion engine, first, the operating range detection unit 11 presets and stores in the storage device 18 based on information from various sensors 100 (especially engine speed information and load information here). The operating area is detected by referring to the map in which the vehicle is located (step S1). Based on the detection result from the operating range detector 11, the HCCI determination section 12 determines whether or not the detected operating range is the HCCI operating range (step S2). If the determination result of the HCCI determination unit 12 is affirmative (Y determination) and HCCI combustion is possible, the condition adjustment command unit 13 calls the combustion operating conditions (HCCI conditions) corresponding to the detected operating range from the storage means. , issues a command to each component of the internal combustion engine 2 so as to operate according to the called conditions (step S3). If the determination result of the HCCI determination unit 12 is negative (N determination) and HCCI combustion is not possible, SI combustion is performed. Therefore, the condition adjustment command unit 13 calls up the combustion operating conditions (SI conditions) corresponding to the detected operating range from the storage means, and commands each component of the internal combustion engine 2 to operate according to the called up conditions. out (step S4). Typically, the control device 1 is configured such that the basic control and the following control are repeatedly performed at predetermined intervals. Further, the control device 1 is configured to cause the internal combustion engine 2 to switch between HCCI combustion and SI combustion according to the determination result of the HCCI determination section 12 .

<Control during fuel cut>
When the driver of the S-HV vehicle 10 returns to the state of fuel cut by releasing the accelerator pedal, and when the state of fuel supply is restored from the fuel cut by depressing the accelerator pedal again, in addition to the basic control described above, the internal combustion engine The control device 1 of performs the following control.

In the control device 1 for the internal combustion engine, the fuel cut determination unit 14 determines whether or not it is time to return from the fuel cut state to the fuel supply state based on information such as the depression amount of the accelerator pedal (step S21, first judgment). If the first determination result is negative (N determination), the fuel cut determination unit 14 determines whether or not the fuel is cut based on the above-described information such as the depression amount (step S22, second determination ). If the second determination result is affirmative (Y determination), the control device 1 issues a stop command to the internal combustion engine 2 because fuel is not being supplied. If the second determination result is negative (N determination), fuel is being supplied, and the control device 1 performs the processes after step S1 described above to cause the internal combustion engine 2 to perform HCCI combustion or SI combustion. .

On the other hand, if the above-mentioned first determination result is affirmative (Y determination), fuel is being supplied. Let it burn. However, in this case, it is considered that the fuel supply is immediately after the fuel supply is resumed, and there is a concern that the temperature inside the cylinder 20 will drop. Therefore, when returning from the state of fuel cut to the state of fuel supply, the HCCI determination unit 12 determines that the operating region detected in step S1 is the HCCI operating region (Y determination in step S2), continuous combustion The command unit 15 causes the internal combustion engine 2 to perform SI combustion once and then continuously perform HCCI combustion from SI combustion.

In this example, the operating conditions for SI combustion at the time of resumption of fuel supply are set to values that do not satisfy the HCCI operating range as described above and are lower than the engine speed and load in the HCCI operating range. The continuous combustion command unit 15 issues a command to the internal combustion engine 2 so as to change to . Further, after causing the internal combustion engine 2 to perform SI combustion based on the operating conditions for SI combustion read from the storage device 18, HCCI combustion is performed under the combustion operating conditions corresponding to the operating region detected by the operating region detecting unit 11. For example, the control device 1 (continuous combustion command unit 15) is configured to cause the engine 2 to perform.

<Switching control from HCCI to SI>
In the control device 1 for the internal combustion engine of the present example, HCCI combustion cannot be continued from the determination result as to whether or not it is in the HCCI operating range (step S2), and when switching from HCCI combustion to SI combustion, the fuel stop command unit 16 A command is issued to the injection device to stop the fuel supply (step S41). In other words, the fuel is temporarily cut off. During this fuel cut, the condition adjustment command unit 13 commands the variable valve timing mechanism to change the combustion operation conditions such as the opening/closing timings of the intake and exhaust valves and the amount of lift to conditions corresponding to the detected operating region. put out. When the ignition timing is also changed to the condition corresponding to the detected operating region, the condition adjustment command unit 13 issues a command to the spark plug to change the ignition timing to the condition corresponding to the detected operating region. After the completion of changing the combustion operation condition, the supply start command unit 17 issues a command to start fuel supply to the fuel injection device (step S42). Thereafter, the control device 1 controls the internal combustion engine 2 so as to execute SI combustion until the SI combustion is next switched to HCCI combustion.

Since the time until the change of the combustion operation condition is completed can be predicted to some extent, the above-mentioned fuel cut time is set in advance, and when the set time elapses, it is assumed that the change of the combustion operation condition is completed, and fuel supply is started. The control device 1 can be configured as follows. For example, the fuel cut time may be about 3 cycles or less. In this case, a relatively simple configuration can be achieved. Alternatively, the control device 1 may be configured to include an operation completion determination unit (not shown) that determines whether or not the fuel operation condition has been changed, and to start fuel supply based on the determination result. can.

(main actions and effects)
In the control device 1 for an internal combustion engine of Embodiment 1, even if HCCI combustion is possible when returning to fuel supply from a fuel cut, the internal combustion engine 2 first performs SI combustion and then performs HCCI combustion. to control. Therefore, even if the temperature in the cylinder 20 is lowered due to the fuel cut, the temperature of the cylinder 20 can be reliably raised by the exhaust gas by performing the SI combustion. In addition, since continuous combustion is performed without fuel cut between SI combustion and HCCI combustion, temperature drop in cylinder 20 is reduced and a high temperature state can be easily maintained. According to such a control device 1 for an internal combustion engine, after returning from a fuel cut, the temperature in the cylinder 20 is easily brought to a temperature at which spontaneous ignition is possible by compressing the air-fuel mixture, and HCCI combustion can be stably performed.

In particular, since the control device 1 for the internal combustion engine of Embodiment 1 is provided in the S-HV vehicle 10 , the influence of the operating state of the internal combustion engine 2 on the running state of the S-HV vehicle 10 can be greatly reduced. For example, when switching between HCCI combustion and SI combustion, it is difficult for the driver to feel uncomfortable about the running state, and drivability is also excellent.

Since the control device 1 for an internal combustion engine of this example is configured to change stepwise the operating condition of SI combustion from a condition lower than the HCCI operating range to a condition higher than the HCCI operating range when returning to the fuel supply from the above-described fuel cut. , knocking can be prevented. Therefore, it is difficult for the driver to feel uncomfortable due to knocking. Also, damage to the internal combustion engine 2 due to knocking can be prevented. Furthermore, even if the internal combustion engine 2 is operating at a relatively low speed and a low load, the electric motor 3 allows the S-HV vehicle 10 to operate in accordance with the driver's wishes, typically the accelerator pedal. Depressing the pedal restores the fuel cut and corresponds to the state where high rpm and high load are desired. Also from these points, it is excellent in drivability.

In addition, since the control device 1 for an internal combustion engine of this example is configured to cut fuel when switching from HCCI combustion to SI combustion, heavy knock can be avoided, and the feeling of stall caused by a decrease in torque due to fuel cut can be eliminated. It is difficult for the driver of the S-HV vehicle 10, and the drivability is also excellent.

The present invention is not limited to the configuration of the first embodiment described above, and appropriate modifications are possible.
For example, the configuration related to <control of switching from HCCI to SI> described above may be omitted.

1 Control Device for Internal Combustion Engine 11 Operating Range Detector 12 HCCI Determination Unit 13 Condition Adjustment Command Unit
14 fuel cut determination unit 15 continuous combustion command unit 16 fuel stop command unit 17 supply start command unit 18 storage device 2 internal combustion engine 3 electric motor 4 generator 5 storage battery 6 wheels
7 inverter device, 8 transmission, 9 differential device, 10 S-HV vehicle 20 cylinder, 100 sensors

Claims (1)

A control device for an internal combustion engine capable of switching between homogeneous charge compression ignition combustion and spark ignition combustion,
The internal combustion engine is mounted in a series hybrid vehicle that performs accelerator-linked control,
The control device is
an HCCI determination unit that determines whether or not the homogeneous charge compression ignition combustion is possible when returning from a fuel cut state to a fuel supply state;
When the HCCI determination unit determines that the homogeneous charge compression ignition combustion is possible, the continuous combustion command unit causes the internal combustion engine to perform the spark ignition combustion once and then the homogeneous charge compression ignition combustion continuously. and
The continuous combustion command unit,
The spark ignition combustion is performed under combustion operating conditions such that values lower than the engine speed and load in the HCCI operating region in which the homogeneous charge compression ignition combustion is possible are selected and changed stepwise to higher values,
performing the homogeneous charge compression ignition combustion under combustion operating conditions corresponding to the HCCI operating region;
Furthermore, when the HCCI determination unit determines that the homogeneous charge compression ignition combustion is not possible, the fuel supply to the fuel injection device is temporarily stopped when switching from the homogeneous charge compression ignition combustion to the spark ignition combustion. a fuel stop command unit that causes
a condition adjustment command unit that changes combustion operating conditions suitable for the spark ignition combustion while the fuel supply is stopped by the fuel stop command unit;
a supply start command unit for starting fuel supply to the fuel injection device after completion of changing the combustion operating condition;
A control device for an internal combustion engine.

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