JP7639741B2 - Internal combustion engine control system - Google Patents

Description

This disclosure relates to a control system for an internal combustion engine.

Conventionally, PM sensors that detect particulate matter accumulated on a filter attached to an exhaust purification device are known (see, for example, Patent Document 1). Patent Document 1 discloses a control system for an internal combustion engine that uses a PM sensor to determine fuel properties.

JP 2016-109512 A

In recent years, biofuels have been developed to reduce carbon dioxide emissions. Biofuels are often used in combination with petroleum-derived fuels. Therefore, it is preferable that the control system of an internal combustion engine be able to determine the mixing ratio of these two types of fuels based on the accumulation state of particulate matter.

The objective of the present disclosure is to provide an internal combustion engine control system that can determine the mixture ratio of a fuel mixture based on the accumulation state of particulate matter.

A control system for an internal combustion engine according to the present disclosure is a control system for an internal combustion engine capable of using a mixture of a first fuel and a second fuel, the control system for an internal combustion engine including a filter for collecting particulate matter, a detection unit disposed upstream of the filter for detecting an accumulation state of the particulate matter, and a control device for executing a determination control for determining a mixing ratio of the first fuel and the second fuel based on a first accumulation amount that is a preset amount of accumulation of the particulate matter accumulated and increased by the first fuel, a second accumulation amount that is a preset amount of accumulation of the particulate matter accumulated and increased by the second fuel, and a third accumulation amount of the particulate matter detected by the detection unit.

This internal combustion engine control system can determine the mixture ratio of the first fuel and the second fuel based on the first accumulation amount, the second accumulation amount, and the third accumulation amount detected by the detection unit.

The present disclosure provides an internal combustion engine control system that can determine the mixture ratio of a fuel mixture based on the accumulation state of particulate matter.

1 is a system diagram of an internal combustion engine control system according to an embodiment of the present disclosure. FIG. 4 is a diagram showing a mixture ratio determined by a control device according to an embodiment of the present disclosure. 4 is a flowchart showing a control procedure of a control device according to an embodiment of the present disclosure.

Embodiments of the present disclosure will be described below with reference to the drawings. Note that in the following specification, the upstream side in the flow direction of intake or exhaust air will be referred to as "upstream" and the downstream side will be referred to as "downstream."

As shown in FIG. 1, the control system 1 of the internal combustion engine 2 includes a filter 4, a PM sensor (an example of a detection unit) 6, an exhaust gas recirculation device 8, a fuel tank 10, a fuel filler lid 12, a turbocharger 14, an intercooler 16, a throttle valve 18, and a control device 20. The internal combustion engine 2 of this embodiment is a diesel engine that can use a fuel mixture of biofuel (an example of a first fuel) and diesel (an example of a second fuel) stored in the fuel tank 10. The internal combustion engine 2 sends intake air from an intake passage 2a to a cylinder 2b, and mixes the intake air with fuel injected from a fuel injection valve 2c. The internal combustion engine 2 compresses the mixture with a piston 2d and self-ignites it. The internal combustion engine 2 of this embodiment is mounted on a vehicle (e.g., an automobile).

In this embodiment, in the internal combustion engine 2, the exhaust gas discharged from the cylinder 2b rotates the turbine 14a of the turbocharger 14. The turbine 14a rotates the compressor 14b arranged on the same shaft, and supercharges the intake air. The supercharged intake air is cooled by the intercooler 16. However, the turbocharger 14 is not necessarily required.

The filter 4 is disposed in the exhaust purification device 3 that purifies the exhaust. The filter 4 captures particulate matter contained in the exhaust. In this embodiment, the filter 4 is a diesel particulate filter that captures particulate matter (PM) from a diesel engine. An oxidation catalyst 4a is disposed upstream of the filter 4. The oxidation catalyst 4a causes a combustion reaction of the fuel injected from the fuel injection valve 2c, raising the exhaust temperature. This causes the exhaust gas flowing into the filter 4 to become hot. The hot exhaust gas burns the particulate matter captured in the filter 4, regenerating the filter 4. The exhaust purification device 3 may also have a NOx trap or a urea selective reduction catalyst (not shown) disposed downstream of the filter 4.

The PM sensor 6 is disposed upstream of the filter 4 and detects the accumulation state of particulate matter. The PM sensor 6 is a sensor whose current value changes when particulate matter accumulates. Specifically, when particulate matter accumulates, the current flows more easily and the current value increases. The PM sensor 6 has a heater 6a. The heater 6a burns and removes particulate matter accumulated in the PM sensor 6. The other configurations of the PM sensor 6 may be the same as those of existing PM sensors, and a detailed description will be omitted. In this embodiment, the PM sensor 6 is disposed between the oxidation catalyst 4a and the filter 4. This can prevent the adhesion of fuel residues and the like to the PM sensor 6. However, the PM sensor 6 may be disposed upstream of the oxidation catalyst 4a. The PM sensor 6 is electrically connected to the control device 20 and transmits a current value to the control device 20. The operation of the heater 6a is controlled by the control device 20.

The exhaust recirculation device 8 is a device that introduces exhaust recirculation gas into the internal combustion engine 2. More specifically, the exhaust recirculation device 8 is a device that recirculates the exhaust discharged from the cylinder 2b to the intake passage 2a. The exhaust recirculation device 8 has an exhaust recirculation passage 8a and an exhaust recirculation valve 8b. The exhaust recirculation passage 8a connects the exhaust passage 4b and the intake passage 2a. The exhaust recirculation valve 8b is provided on the exhaust recirculation passage 8a, and introduces the exhaust recirculation gas recirculated from the exhaust into the intake passage 2a by opening and closing the exhaust recirculation passage 8a. The exhaust recirculation valve 8b is electrically connected to the control device 20 and is controlled by the control device 20. The control device 20 controls the exhaust recirculation valve 8b to control the amount of exhaust recirculation gas introduced into the intake. In this embodiment, the control device 20 controls the throttle valve 18 and closes the throttle valve 18 to generate negative pressure in the intake passage 2a. The control device 20 can also control the amount of exhaust recirculation gas introduced by this.

The fuel tank 10 is a device for storing biofuel and diesel and supplying them to the fuel injection valve 2c. In this embodiment, the fuel tank 10 has a fuel filler lid 12 that opens and closes the fuel filler port 10a, and a fuel level sensor 10b. The fuel filler lid 12 is electrically connected to the control device 20 and transmits the open/closed state of the fuel filler lid 12 to the control device 20. The fuel level sensor 10b is electrically connected to the control device 20 and transmits the remaining amount of fuel (fuel level) in the fuel tank 10 to the control device 20.

The control device 20 executes a determination control to determine the mixing ratio (mixing rate) of the biofuel and diesel based on a first accumulation amount, which is a preset amount of particulate matter accumulated by the biofuel, a second accumulation amount, which is a preset amount of particulate matter accumulated by the diesel, and a third accumulation amount of particulate matter detected by the PM sensor 6.

2, the control device 20 stores the change in the first deposition amount (see dashed line in FIG. 2), which is the deposition amount of particulate matter during a predetermined time, when only biofuel is used in the internal combustion engine 2. The control device 20 also stores the change in the second deposition amount (see dashed line in FIG. 2), which is the deposition amount of particulate matter during a predetermined time, when only diesel is used in the internal combustion engine 2. The predetermined time may be the time during which the change in the first deposition amount and the change in the second deposition amount are measured by experiment. The control device 20 compares the first deposition amount, the second deposition amount, and the third deposition amount obtained from the PM sensor 6 (see solid line in FIG. 2), to determine the mixing ratio of biofuel and diesel.

In this embodiment, the control device 20 calculates an estimated deposition amount (see the two-dot chain line in FIG. 2) according to the mixture ratio of biofuel and diesel based on the first deposition amount and the second deposition amount. The control device 20 acquires a third deposition amount corresponding to the deposition amount of particulate matter actually flowing in the exhaust gas from the current value of the PM sensor 6. The control device 20 judges whether the actual mixture ratio is higher or lower than the estimated mixture ratio by comparing the acquired third deposition amount with the estimated deposition amount. When the third deposition amount is higher than the estimated mixture ratio, the control device 20 corrects the ratio of diesel to be higher than the estimated ratio. On the other hand, when the third deposition amount is lower than the estimated mixture ratio, the control device 20 corrects the ratio of biofuel to be higher than the estimated ratio. This allows the control device 20 to determine the mixture ratio. The PM sensor 6 has a dead zone for a certain period until particulate matter is deposited in the sensor element of the PM sensor 6. The control device 20 calculates the estimated deposition amount during this period as well.

The control device 20 determines the introduction ratio of the exhaust recirculation gas, and controls the opening of the exhaust recirculation valve 8b so that the amount of exhaust recirculation gas introduced is the introduction ratio determined for the intake air volume detected by the air flow sensor 22 attached to the air cleaner 32. The control device 20 may determine the introduction ratio of the exhaust recirculation gas based on a map that defines the introduction ratio of the exhaust recirculation gas for each operating range of the internal combustion engine 2.

In addition, the control device 20 may control each device, such as the fuel injection valve 2c, the exhaust recirculation valve 8b, and the boost pressure of the turbocharger 14, so that the internal combustion engine 2 is in a desired operating state, based on values obtained from sensors such as the airflow sensor 22 and the accelerator position sensor 30a. The control device 20 is actually an ECU (Electronic Control Unit) composed of a microcomputer including a calculation device, memory, input/output buffers, etc. The control device 20 controls each device so that the internal combustion engine 2 is in a desired operating state, based on maps and programs stored in the memory. Note that the various controls are not limited to processing by software, and can also be processed by dedicated hardware (electronic circuits).

Next, the control procedure executed by the control device 20 will be described with reference to the flowchart in FIG. 3. The control device 20 starts the control operation when an ignition switch (not shown) is turned on.

In step S1, the control device 20 determines whether refueling has been performed. In this embodiment, the control device 20 detects the open/closed state of the fuel filler lid 12, and determines that refueling has started when the fuel filler lid 12 is open. Alternatively, the control device 20 may determine that refueling has been performed when it determines that the fuel level has risen. When the control device 20 determines that refueling has been performed, the process proceeds to step S2.

In step S2, the control device 20 activates the heater 6a to remove particulate matter accumulated in the PM sensor 6 and executes a sensor reset to reset the third accumulation amount. This allows the mixing ratio of biofuel and diesel to be determined more accurately. However, the control device 20 does not necessarily have to execute a sensor reset. Specifically, the control device 20 may execute a sensor reset after determining whether or not a sensor reset is necessary based on the current value of the third accumulation amount of the PM sensor 6. For example, the control device 20 may execute a sensor reset when the third accumulation amount is greater than a predetermined amount. After executing the sensor reset, the control device 20 proceeds to step S3.

In step S3, the control device 20 determines whether a predetermined period of time has elapsed since it was determined that refueling had been performed. The predetermined period of time may be set, for example, according to the time it takes for the refueled fuel to reach the fuel injection valve 2c. In other words, the predetermined period of time is set based on the time it takes for the fuel remaining in the piping from the fuel tank 10 to the fuel injection valve 2c to be replaced. The predetermined period of time may be calculated, for example, from the capacity from the fuel tank 10 to the fuel injection valve 2c, the amount of fuel transported per unit time, or the amount of fuel injected per unit time. Furthermore, the control device 20 may include a period that takes into account the dead zone of the PM sensor 6 in the predetermined period of time. This allows the control device 20 to more accurately determine the mixture ratio. If the control device 20 determines that the predetermined period of time has elapsed (step S3 YES), the process proceeds to step S4.

In step S4, the control device 20 executes exhaust recirculation control to control the exhaust recirculation device 8 so that the exhaust recirculation gas is at a predetermined ratio or more in the intake air of the internal combustion engine 2. Since biofuel contains oxygen atoms, even if the amount of exhaust recirculation gas is increased, particulate matter tends to increase less than with diesel. For this reason, increasing the amount of exhaust recirculation gas increases the difference between the amount of particulate matter deposited by diesel and the amount of particulate matter deposited by biofuel in the third deposition amount.

For example, when the amount of exhaust recirculation gas introduced in the normal state in the same operating range is a first introduction ratio (e.g., 30%) relative to the intake air volume, the predetermined ratio may be a second introduction ratio (e.g., 40%) that is greater than the first introduction ratio. Also, when the introduction ratio is equal to or greater than the predetermined ratio at another operating point, the control device 20 may maintain the introduction ratio. In this way, the control device 20 increases the amount of exhaust recirculation gas to control the difference between the amount of particulate matter deposited due to diesel and the amount of particulate matter deposited due to biofuel in the third accumulation amount to be greater. After executing exhaust recirculation control, the control device 20 proceeds to step S5.

In step S5, the control device 20 determines whether the engine is idling. In this embodiment, the control device 20 determines that the engine is idling when the accelerator pedal 30 is not depressed, the output of the accelerator position sensor 30a is zero, and the fuel injection valve 2c is injecting fuel to maintain the rotation of the internal combustion engine 2. However, the determination of whether the engine is idling may be made by other methods.

When the control device 20 determines in step S5 that the vehicle is not idling (step S5 NO), the process proceeds to step S6. In step S6, the control device 20 determines whether the vehicle is in steady running or not. Steady running is an example of a state in which the output change of the internal combustion engine 2 is within a predetermined range. The predetermined range may be, for example, a range that indicates a state in which the internal combustion engine 2 is operated at a constant output, such as an output change within ±5 kW or a torque change within ±5 Nm. The control device 20 may determine whether the vehicle is in steady running or not based on the rate of change in the output of the accelerator position sensor 30a. Specifically, the control device 20 may determine that the vehicle is in steady running when the rate of change in the output of the accelerator position sensor 30a is within a predetermined range. The control device 20 may also obtain the output change of the internal combustion engine 2 and determine that the vehicle is in steady running when the output change is constant.

If the control device 20 determines that the vehicle is in steady-state driving (YES in step S6), the process proceeds to step S7 and executes judgment control. After executing judgment control in step S7, the control device 20 proceeds to step S1.

If the control device 20 determines in step S1 that fuel has not been refueled (step S1 NO), the process proceeds to step S4 and executes the exhaust gas recirculation control described above.

If the control device 20 determines in step S3 that the predetermined period has not elapsed (step S3 NO), it waits until the predetermined period has elapsed. This allows the control device 20 to suppress erroneous detection of the mixture ratio.

When the control device 20 determines in step S5 that the engine is idling (step S6 NO), the control device 20 proceeds to step S8 and prohibits judgment control. When the engine is idling, particulate matter is less likely to be emitted. Therefore, by prohibiting judgment control during idling, the control device 20 can more accurately determine the mixture ratio. After prohibiting judgment control, the control device 20 proceeds to step S5.

If the control device 20 determines in step S6 that the vehicle is not in steady-state driving (step S6 NO), the process proceeds to step S8 and prohibits judgment control. Excessive particulate matter is likely to be emitted when the vehicle is not in steady-state driving. For this reason, the control device 20 can more accurately determine the mixture ratio by prohibiting judgment control when the vehicle is not in steady-state driving. If the control device 20 determines in step S6 that the vehicle is in steady-state driving (step S6 YES), the control device 20 proceeds to step S7 and performs judgment control, and returns to step S1. The control device 20 repeatedly executes the processes from step S1 to step S8 at predetermined time intervals.

As described above, according to the control system 1 of the internal combustion engine 2 disclosed herein, the control device 20 can determine the mixing ratio of biofuel and diesel based on the first and second accumulation amounts and the third accumulation amount detected by the PM sensor 6.

Furthermore, when a vehicle is actually traveling, it repeatedly accelerates and decelerates. This causes the amount of particulate matter that accumulates to easily change at any time. Therefore, it is preferable that the mixture ratio can be determined in as short a period as possible. For example, it is preferable that the mixture ratio can be determined during steady driving over a short period of time.

By executing exhaust gas circulation control, the control device 20 controls the difference between the amount of particulate matter deposited in the third deposition amount due to diesel and the amount of particulate matter deposited in the third deposition amount due to biofuel to be larger. This allows the mixture ratio to be determined in a short period of time, and makes it easier to determine the mixture ratio of biofuel and diesel more accurately.

<Other embodiments>
Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention. In particular, the multiple modifications described in this specification can be arbitrarily combined as necessary.

(a) In the above embodiment, a diesel engine using the filter 4 has been described as an example, but the present disclosure is not limited thereto. The internal combustion engine 2 may be a gasoline engine. In this case, the internal combustion engine 2 may be an internal combustion engine 2 that can use bioethanol fuel (an example of a first fuel) and gasoline (an example of a second fuel). In addition, in this case, the filter 4 may be a gasoline particulate filter.

(b) In the above embodiment, an example was described in which the control system 1 for the internal combustion engine 2 was applied to a vehicle equipped with a diesel engine, but the present disclosure is not limited to this. For example, the control system 1 for the internal combustion engine 2 may be applied to a plug-in hybrid electric vehicle (PHEV) that is capable of external charging or external power supply.

1: Control system 2: Internal combustion engine 4: Filter 6: PM sensor 6a: Heater 8: Exhaust gas recirculation device 10: Fuel tank 20: Control device

Claims (7)

A control system for an internal combustion engine capable of using a mixture of a first fuel and a second fuel,
A filter for collecting particulate matter;
A detection unit disposed upstream of the filter and configured to detect a deposition state of the particulate matter;
a control device that executes a determination control to determine a mixing ratio of the first fuel and the second fuel based on a first accumulation amount, which is a preset accumulation amount of the particulate matter that is accumulated and increased by the first fuel, a second accumulation amount, which is a preset accumulation amount of the particulate matter that is accumulated and increased by the second fuel, and a third accumulation amount of the particulate matter detected by the detection unit; and
A control system for an internal combustion engine comprising: The fuel supply system further includes a fuel tank for storing fuel to be supplied to the internal combustion engine.
the control device determines whether or not fuel has been supplied to the fuel tank, and executes the determination control when a predetermined period of time has elapsed since it was determined that fuel has been supplied to the fuel tank.
2. The control system for an internal combustion engine according to claim 1. An exhaust gas recirculation device for introducing exhaust gas into the internal combustion engine is further provided,
the control device executes exhaust gas recirculation control for controlling the exhaust gas recirculation device so that the exhaust gas recirculation gas becomes a predetermined ratio or more to an intake air amount of the internal combustion engine after the predetermined period has elapsed.
3. The control system for an internal combustion engine according to claim 2. The control device executes the determination control while executing the exhaust gas recirculation control.
4. The control system for an internal combustion engine according to claim 3. The detection unit has a heater,
the control device activates the heater and resets the third accumulation amount when it determines that fuel has been supplied to the fuel tank.
5. A control system for an internal combustion engine according to claim 2. When the change in output of the internal combustion engine is within a predetermined range for a predetermined period of time, the determination control is executed.
A control system for an internal combustion engine according to any one of claims 1 to 5. The determination control is prohibited while the internal combustion engine is idling.
7. A control system for an internal combustion engine according to any one of claims 1 to 6.