JP7635735B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to a control device for an internal combustion engine.

It is well known to provide an exhaust passage of an internal combustion engine with a filter for trapping particulate matter.
The following Patent Document 1 describes a control device that executes a process to stop combustion control of all cylinders of a multi-cylinder internal combustion engine as a filter regeneration process. This control device stops stopping combustion control when the cumulative air amount during the regeneration process is equal to or greater than a predetermined value. Here, the predetermined value is determined by the temperature of the filter and the amount of particulate matter trapped by the filter at the start of the process to stop combustion control.

In addition, the following Patent Document 2 describes a device that performs a process to stop combustion control only for some of the cylinders of a multi-cylinder internal combustion engine as a filter regeneration process.

JP 2019-190358 A JP 2021-60027 A

However, when combustion control is stopped only for some of the cylinders, the combustion reaction in the cylinders for which combustion control is not stopped and the oxidation reaction in the exhaust system of the unburned fuel discharged from those cylinders can cause the temperature of the filter to rise. Therefore, when determining the above-mentioned predetermined value for stopping the process of stopping combustion control only for some of the cylinders based on the filter temperature and the amount of particulate matter captured by the filter when combustion control is stopped, there is a risk that the predetermined value will not be appropriate.

Means for solving the above problems and their effects will be described below.
A control device for an internal combustion engine is applied to a multi-cylinder internal combustion engine having a filter in an exhaust passage that captures particulate matter in the exhaust, and is configured to execute a stop process, a temperature acquisition process, a deposition amount acquisition process, a tolerance calculation process, and a cancellation process, wherein the stop process is a process of stopping combustion control in some of the multiple cylinders of the multi-cylinder internal combustion engine and making the air-fuel ratio of the mixture in cylinders other than the some of the multiple cylinders less than the stoichiometric air-fuel ratio, the temperature acquisition process is a process of acquiring the temperature of the filter, the deposition amount acquisition process is a process of acquiring the deposition amount, which is the amount of particulate matter captured on the filter, the tolerance calculation process is a process of repeatedly calculating a tolerance based on the temperature of the filter at each time and the deposition amount at each time, and the cancellation process is a process of canceling the stop process if the amount of air flowing into the exhaust passage in a predetermined period of time becomes equal to or greater than the tolerance value.

In the above configuration, the tolerance is calculated based on the filter temperature and the amount of deposition each time. Here, the filter temperature used to calculate the tolerance is a value that reflects the combustion reaction in the cylinder where combustion control is not stopped and the oxidation reaction in the exhaust system of the unburned fuel discharged from the cylinder. In addition, the amount of deposition used to calculate the tolerance determines the amount of temperature rise in the filter caused by air flowing into the filter. Therefore, by using the tolerance calculated based on the filter temperature and the amount of deposition each time, it is possible to accurately predict that the filter temperature will become excessively high if the amount of air flowing in during a specified period is equal to or greater than the tolerance. Therefore, the stop process can be appropriately stopped.

1 is a diagram showing a configuration of a drive system of a vehicle according to an embodiment; FIG. 2 is a block diagram showing a part of a process executed by a control device according to the embodiment. 4 is a flowchart showing a procedure of a process executed by a control device according to the embodiment. 4A and 4B are time charts showing the regeneration process in the above embodiment.

Hereinafter, an embodiment will be described with reference to the drawings.
"Prerequisite configuration"
An intake passage 12 of an internal combustion engine 10 shown in FIG. 1 is provided with a throttle valve 14. Air drawn in from the intake passage 12 flows into a combustion chamber 16. Fuel is injected into the combustion chamber 16 by a fuel injection valve 18. In the combustion chamber 16, a mixture of fuel and air is burned by spark discharge from an ignition device 20. The combustion energy generated at this time is converted into the rotational energy of a crankshaft 22. The mixture burned is discharged to an exhaust passage 30 as exhaust. A three-way catalyst 32 having an oxygen storage capacity and a gasoline particulate filter (GPF 34) are provided in the exhaust passage 30. The GPF 34 is a filter that collects PM and supports a three-way catalyst.

The control device 40 operates the operating parts of the internal combustion engine 10, such as the throttle valve 14, the fuel injection valve 18, and the ignition device 20, in order to control the control variables of the internal combustion engine 10 as the control target, such as torque and exhaust gas component ratio. FIG. 1 shows the operation signals MS1 to MS3 of the throttle valve 14, the fuel injection valve 18, and the ignition device 20. In order to control the control variables of the internal combustion engine 10, the control device 40 refers to the intake air amount Ga detected by the air flow meter 50 and the output signal Scr of the crank angle sensor 52. The control device 40 also refers to the water temperature THW detected by the water temperature sensor 54 and the air-fuel ratio Af detected by the air-fuel ratio sensor 56. The control device 40 also refers to the outside air temperature TO detected by the outside air temperature sensor 58 and the vehicle speed SPD detected by the vehicle speed sensor 60.

The control device 40 includes a PU 42, a storage device 44, and peripheral circuits 46. The PU 42 is a software processing device such as a CPU, a GPU, and a TPU. Here, the peripheral circuits 46 include a circuit that generates a clock signal that regulates internal operations, a power supply circuit, a reset circuit, and the like. The control device 40 controls the control amount by the PU 42 executing a program stored in the storage device 44.

"control"
2 shows a part of the process executed by the control device 40. The process shown in FIG. 2 is realized by the PU 42 executing a program stored in the storage device 44.

The output gas temperature calculation process M10 is a process for calculating the output gas temperature Tout, which is the temperature of the exhaust gas discharged into the exhaust passage 30, based on the rotation speed NE, the charging efficiency η, and the ignition timing aig. This can be achieved, for example, by calculating an output gas temperature base value from the rotation speed NE and the charging efficiency η, and then correcting the output gas temperature base value according to the ignition timing. Specifically, the PU 42 first calculates the output gas temperature base value by performing a map calculation using map data previously stored in the storage device 44. Here, the map data is data in which the rotation speed NE and the charging efficiency η are input variables and the output gas temperature base value is an output variable. The PU 42 then reduces the output gas temperature Tout relative to the output gas temperature base value as the ignition timing aig moves away from the MBT ignition timing.

Map data is a set of discrete values of input variables and values of output variables corresponding to each of the input variable values. The map calculation may be a process in which, when the value of an input variable matches any of the values of the input variables in the map data, the value of the corresponding output variable in the map data is used as the calculation result. The map calculation may be a process in which, when the value of an input variable does not match any of the values of the input variables in the map data, the value obtained by interpolating the values of multiple output variables included in the map data is used as the calculation result. Alternatively, the map calculation may be a process in which, when the value of an input variable does not match any of the values of the input variables in the map data, the value of the output variable in the map data that corresponds to the closest value among the values of multiple output variables included in the map data is used as the calculation result.

The rotation speed NE is calculated by the PU 42 based on the output signal Scr. The charging efficiency η is calculated by the PU 42 based on the rotation speed NE and the intake air amount Ga.
The exhaust manifold temperature calculation process M12 is a process for calculating the exhaust manifold temperature Texm, which is the temperature of the exhaust manifold, based on the exit gas temperature Tout, the vehicle speed SPD, and the outside air temperature TO. Here, the PU 52 calculates the exhaust manifold temperature Texm to a higher value when the exit gas temperature Tout is high than when it is low. Also, the PU 42 calculates the exhaust manifold temperature Texm to a lower value when the vehicle speed SPD is high than when it is low. Also, the PU 42 calculates the exhaust manifold temperature Texm to a lower value when the outside air temperature TO is low than when it is high.

The inlet gas temperature calculation process M14 is a process for calculating the inlet gas temperature Tin, which is the temperature of the exhaust gas flowing into the three-way catalyst 32, based on the outlet gas temperature Tout and the exhaust manifold temperature Texm. Here, PU42 calculates the inlet gas temperature Tin to a higher value when the outlet gas temperature Tout is high than when it is low. Also, PU42 calculates the inlet gas temperature Tin to a lower value when the exhaust manifold temperature Texm is low than when it is high.

The catalyst temperature calculation process M16 is a process for calculating the catalyst temperature Tcat, which is the temperature of the three-way catalyst 32, based on the exhaust manifold temperature Texm, the inlet gas temperature Tin, the air-fuel ratio Af, and the intake air amount Ga. When the inlet gas temperature Tin is high, the PU 42 calculates the catalyst temperature Tcat to a higher value than when the inlet gas temperature Tin is low. When the exhaust manifold temperature Texm is low, the PU 42 calculates the catalyst temperature Tcat to a lower value than when the exhaust manifold temperature Texm is high. In addition, the PU 42 increases the catalyst temperature Tcat according to the amount of heat generated according to the amount of unburned fuel or oxygen flowing into the three-way catalyst 32, based on the air-fuel ratio Af and the intake air amount Ga. When the regeneration process M22 described below is executed, the PU 42 may determine the amount of oxygen flowing into the three-way catalyst 32 based on that information.

The filter temperature calculation process M18 is a process for calculating the filter temperature Tgpf, which is the temperature of the GPF 34, based on the catalyst temperature Tcat, the vehicle speed SPD, the outside air temperature TO, and the PM accumulation amount DPM. When the catalyst temperature Tcat is high, the PU 42 calculates the filter temperature Tgpf to a higher value than when the catalyst temperature Tcat is low. When the vehicle speed SPD is high, the PU 42 calculates the filter temperature Tgpf to a lower value than when the vehicle speed SPD is low. When the outside air temperature TO is low, the PU 42 calculates the filter temperature Tgpf to a lower value than when the outside air temperature TO is high. When the PM accumulation amount DPM is high, the PU 42 calculates the filter temperature Tgpf to a higher value than when the PM accumulation amount DPM is low.

The accumulation amount calculation process M20 is a process for calculating the PM accumulation amount DPM, which is the amount of PM trapped in the GPF 34, based on the rotation speed NE, the filling efficiency η, the water temperature THW, and the filter temperature Tgpf. Here, PU42 calculates the amount of PM in the exhaust gas based on the rotation speed NE, the filling efficiency η, and the water temperature THW. Then, PU42 increases the update amount of the PM accumulation amount DPM when the amount of PM in the exhaust gas is large compared to when it is small. Also, when the regeneration process M22 is performed, PU42 calculates the update amount of the PM accumulation amount DPM to a smaller value when the filter temperature Tgpf is large compared to when it is small. Note that a negative update amount means that the PM accumulation amount DPM is decreased.

The regeneration process M22 is a process for oxidizing and removing the PM trapped in the GPF 34. The PU 42 stops the injection of fuel from the fuel injection valve 18 of any one of the cylinders #1 to #4. The PU 42 also makes the air-fuel ratio of the mixture in the combustion chamber 16 of the remaining cylinders richer than the theoretical air-fuel ratio. This process is a process for burning and removing the PM trapped by the GPF 34 by discharging oxygen and unburned fuel into the exhaust passage 30 and raising the temperature of the GPF 34. That is, by discharging oxygen and unburned fuel into the exhaust passage 30, the unburned fuel is burned in the three-way catalyst 32 or the like, thereby raising the temperature of the exhaust. This makes it possible to raise the temperature of the GPF. Also, by supplying oxygen to the GPF 34, the PM trapped by the GPF 34 can be burned and removed.

Figure 3 shows the procedure for processing when a request for regeneration of GPF 34 by regeneration process M22 occurs. The processing shown in Figure 3 is realized by PU 42 repeatedly executing a program stored in storage device 44, for example, at a predetermined interval. Note that below, the step number of each process is represented by a number preceded by "S."

In the series of processes shown in FIG. 3, the PU 42 first acquires the intake air amount Ga, the filter temperature Tgpf, and the PM accumulation amount DPM (S10). Next, the PU 42 determines whether the stop flag F is "1" or not (S12). When the stop flag F is "1", it indicates that the regeneration process M22 is stopped. When the stop flag F is "0", it indicates that the regeneration process M22 is being executed.

When the PU 42 determines that the stop flag F is "0" (S12: NO), it calculates the allowable value Inth based on the filter temperature Tgpf and the PM accumulation amount DPM acquired in the process of S10 (S14). Here, the PU 42 calculates the allowable value Inth when the filter temperature Tgpf is large to be equal to or less than the allowable value Inth when the filter temperature Tgpf is small. The PU 42 also calculates the allowable value Inth when the PM accumulation amount DPM is large to be equal to or less than the allowable value Inth when the PM accumulation amount DPM is small. This process can be realized, for example, by having the PU 42 perform map calculations to calculate the allowable value Inth with map data stored in the storage device 44. Here, the map data is data in which the filter temperature Tgpf and the PM accumulation amount DPM are input variables and the allowable value Inth is an output variable.

The PU 42 also calculates the amount of air In flowing into the GPF 34 during a predetermined period based on the intake air amount Ga (S16). Here, the PU 42 substitutes the value obtained by multiplying the intake air amount Ga by a coefficient K for the air amount In. The coefficient K may be a value obtained by multiplying the proportion of the number of cylinders for which combustion control is stopped in the regeneration process M22 by the length of the predetermined period. Note that the predetermined period may be a time longer than the update cycle of the filter temperature Tgpf in the process of FIG. 2.

Next, PU42 determines whether the amount of air In is greater than the allowable value Inth (S18). This process is to determine whether there is a risk that the temperature of GPF34 will rise rapidly and deviate from the allowable temperature if the regeneration process M22 is continued. If PU42 determines that the amount of air In is greater than the allowable value Inth (S18: YES), it assigns "1" to the stop flag F and stops the regeneration process M22 (S20).

On the other hand, when PU42 determines that the stop flag F is "1" (S12: YES), it determines whether the filter temperature Tgpf is equal to or lower than the permitted temperature Tth (S22). This process is to determine whether it is OK to restart the regeneration process M22. The permitted temperature Tth is set to a temperature at which the regeneration process M22 is not expected to be stopped again within a short period of time even if it is restarted. When PU42 determines that the filter temperature is equal to or lower than the permitted temperature Tth (S22: YES), it assigns "0" to the stop flag F and permits the regeneration process M22 (S24).

When the PU 42 completes the processes of S20 and S24, or when a negative determination is made in the processes of S18 and S22, the PU 42 temporarily ends the series of processes shown in FIG.
Here, the operation and effects of this embodiment will be described.

FIG. 4A illustrates a process for determining whether to stop the regeneration process M22 according to the present embodiment.
As shown in Fig. 4A, the PU 42 calculates the permissible value Inth each time the regeneration process M22 is performed according to the filter temperature Tgpf and the PM accumulation amount DPM. If the amount of air flowing into the GPF 34 during a predetermined period of time exceeds the permissible value Inth, the regeneration process M22 is stopped. This makes it possible to prevent the temperature of the GPF 34 from becoming excessively high.

Figure 4 (b) shows a case where the allowable value Inth of the cumulative air amount InGa from the start of the regeneration process M22 is set based on the PM accumulation amount DPM and the filter temperature Tgpf at the start of the regeneration process M22. In this case, it is not possible to take into account the amount of heat generated in the rich-burn cylinder, which is richer than the theoretical air-fuel ratio when the regeneration process M22 is executed, and the effect of the oxidation heat of the unburned fuel discharged from the rich-burn cylinder. Therefore, there is a risk that the timing to stop the regeneration process M22 will be delayed.

When the regeneration process M22 is stopped because the filter temperature Tgpf exceeds the upper limit of the allowable temperature, the regeneration process M22 is stopped later than in this embodiment. In other words, the filter temperature Tgpf is an estimate of the current temperature of the GPF 34. In contrast, the process of S18 predicts whether or not there is a risk that the temperature of the GPF 34 will exceed the upper limit of the allowable temperature if the current state continues for a predetermined period of time.

<Correspondence>
The correspondence between the matters in the above embodiment and the matters described in the "Means for solving the problem" section is as follows: The filter corresponds to the GPF 34. The stop process corresponds to the regeneration process M22. The temperature acquisition process corresponds to the process of S10. The accumulation amount acquisition process corresponds to the process of S10. The allowable value calculation process corresponds to the process of S14. The stop process corresponds to the processes of S18 and S20.

<Other embodiments>
This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

The filter temperature Tgpf does not have to be an estimated value. For example, by providing a temperature sensor such as a thermistor in the GPF 34, the detected value may be used.
In the stop process, the number of cylinders for which combustion control is to be stopped is not limited to one.

-It is not essential that the GPF 34 be placed downstream of the three-way catalyst 32.

Reference Signs List 10 internal combustion engine 12 intake passage 14 throttle valve 16 combustion chamber 18 fuel injection valve 20 ignition device 22 crankshaft 30 exhaust passage 32 three-way catalyst 34 GPF
40...Control device

Claims (1)

The present invention is applied to a multi-cylinder internal combustion engine equipped with a filter in an exhaust passage for collecting particulate matter in the exhaust,
The apparatus is configured to execute a stop process, a temperature acquisition process, a deposition amount acquisition process, a tolerance calculation process, and an interruption process;
the stop processing is processing for stopping combustion control in some cylinders among a plurality of cylinders of the multi-cylinder internal combustion engine and making an air-fuel ratio of an air-fuel mixture in a cylinder other than the some cylinders among the plurality of cylinders less than a stoichiometric air-fuel ratio,
the temperature acquisition process is a process of acquiring a temperature of the filter,
the deposition amount acquisition process is a process for acquiring a deposition amount, which is the amount of particulate matter trapped in the filter,
the tolerance calculation process is a process of repeatedly calculating a tolerance based on each temperature of the filter and each amount of the deposition,
A control device for an internal combustion engine, wherein the interruption process is a process for interrupting the stop process when an amount of air flowing out into the exhaust passage during a predetermined period of time becomes equal to or greater than the permissible value.

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