JP7705288B2 - Engine Management System - Google Patents

Description

The present invention relates to an engine control system.

In engines, a filter may be installed in the exhaust pipe to remove particulate matter from the exhaust gas (see, for example, Patent Documents 1-4).

JP 2019-183658 A JP 2020-33932 A Patent No. 5096096 Patent No. 4793083

The engine may have a variable valve mechanism. The variable valve mechanism can change the operation of the intake valve and the exhaust valve regardless of the angle of the camshaft. However, even in an engine with such a variable valve mechanism, the variable operation of the valve may be restricted under certain conditions. Under such conditions, if soot accumulates on the filter of the exhaust pipe as described above, the exhaust gas pressure (back pressure) in the exhaust pipe increases. In this case, in order to suppress the increase in back pressure, it is possible to recirculate a part of the exhaust gas as intake air (this may be called EGR (Exhaust Gas Recirculation)). However, in this case, the increase in EGR may cause combustion to deteriorate, resulting in hunting of the engine speed or engine stoppage. In addition, the deterioration of combustion may cause the temperature of the filter to rise excessively.

In consideration of the above problems, the present invention aims to provide an engine control system that can suppress an increase in back pressure.

An engine control system according to one aspect of the present invention comprises:
The engine,
a variable valve mechanism configured to change the operation of an intake valve and an exhaust valve of the engine;
a particulate filter provided in an exhaust pipe connected to an exhaust port of the engine;
a sensor for detecting an amount of particulate matter deposited on the particulate filter;
a control device for controlling the engine and the variable valve mechanism;
Equipped with
The control device includes one or more processors and one or more storage media that store instructions to be executed by the one or more processors;
The one or more processors, in accordance with the instructions,
determining whether or not variable operation of the intake valve and the exhaust valve by the variable valve mechanism is restricted;
determining whether the amount of deposition of the particulate matter on the particulate filter is within a predetermined range;
limiting a torque of the engine when the variable operation of the intake valve and the exhaust valve by the variable valve mechanism is limited and the amount of deposition of the particulate matter on the particulate filter is within a predetermined range;
configured to run
Limiting the torque of the engine comprises:
Obtaining a torque guard base value, which is a maximum allowable value of the torque of the engine, capable of suppressing an increase in exhaust gas pressure in the exhaust pipe to an allowable value when the variable operation of the intake valve and the exhaust valve by the variable valve mechanism is limited and when the particulate matter accumulates in the particulate filter in an amount greater than a predetermined amount;
obtaining an actual torque guard value, which is the lowest torque guard value among all torque guard values imposed on the engine excluding the torque guard base value;
When the torque guard base value is equal to or less than the actual torque guard value, limiting the torque of the engine based on the larger of the torque guard base value and a value obtained by subtracting a predetermined adjustment amount from the actual torque guard value;
When the torque guard base value is greater than the actual torque guard value, limiting the torque of the engine based on the actual torque guard value;
Including,
The predetermined adjustment amount is determined as the maximum allowable value that produces an acceptable shock when reducing the torque .

The present invention makes it possible to suppress an increase in back pressure.

FIG. 1 is a schematic diagram showing an engine control system according to an embodiment of the present invention. FIG. 2 is a flowchart showing the processing of the ECU. FIG. 3 is a schematic diagram illustrating the relationship between the pressure loss coefficient and the table. FIG. 4 is a table showing the relationship between the engine speed and the torque guard base value. FIG. 5 is a graph showing various torque guard values when the torque guard base value is equal to or less than the actual torque guard value. FIG. 6 is a graph showing various torque guard values when the torque guard base value is larger than the actual torque guard value.

The following describes in detail an embodiment of the present invention with reference to the attached drawings. The specific dimensions, materials, values, etc. shown in the embodiment are merely examples for ease of understanding, and do not limit the present invention unless otherwise specified. In the specification and drawings, elements that have substantially the same functions and configurations are given the same reference numerals to avoid duplicated explanations. Also, elements that are not directly related to the present invention are not shown.

FIG. 1 is a schematic diagram showing an engine control system 100 according to one embodiment of the present invention. The engine control system (which may also be simply referred to as the "system" in this disclosure) 100 is applied to a vehicle 500, such as a hybrid electric vehicle (HEV), a gasoline-powered automobile, or a diesel-powered automobile. The system 100 includes an engine 10.

In this embodiment, the engine 10 is a gasoline engine. In other embodiments, the engine 10 may be a diesel engine. The engine 10 has a cylinder 11 and a piston 12. The piston 12 reciprocates within the cylinder 11. The cylinder 11 and the piston 12 define a combustion chamber 13. The piston 12 is connected to a crankshaft 18 by a rod 14.

In the engine 10 described above, a mixture of air and fuel (gasoline) is burned in the combustion chamber 13, causing the piston 12 to move back and forth within the cylinder 11. The linear motion of the piston 12 is transmitted to the crankshaft 18 by the rod 14 and converted into the rotational motion of the crankshaft 18. The rotation speed of the crankshaft 18 (the rotation speed of the engine 10) is detected by the crank angle sensor Se1. The crank angle sensor Se1 is connected to the ECU 50 (described in detail later) so as to be able to communicate with it. Note that for better understanding, only one pair of cylinders 11 and pistons 12 is shown in FIG. 1, but the engine 10 can have multiple pairs of cylinders 11 and pistons 12.

The engine 10 has an intake port 15 and an exhaust port 16. An intake valve 15a is provided in the intake port 15, and an exhaust valve 16a is provided in the exhaust port 16. The operation of each of the intake valve 15a and the exhaust valve 16a is controlled, for example, by a camshaft (not shown). The camshaft is rotated by the crankshaft 18 via, for example, a rotating belt or the like.

The system 100 includes variable valve mechanisms 15b and 16b for the intake valve 15a and the exhaust valve 16a, respectively. The variable valve mechanisms 15b and 16b can change the angle of the cam of the intake valve 15a and the exhaust valve 16a relative to the camshaft, and thereby can change the operation (position (opening) and timing) of the intake valve 15a and the exhaust valve 16a independently of the angle of the camshaft. The variable valve mechanisms 15b and 16b can be, for example, hydraulic or electric. For example, if the variable valve mechanisms 15b and 16b are hydraulic, each of the variable valve mechanisms 15b and 16b can have an oil control valve (OCV) (not shown) for controlling the hydraulic pressure. The variable valve mechanisms 15b and 16b are communicatively connected to the ECU 50. The ECU 50 controls the operation of the intake valve 15a and the exhaust valve 16a by controlling the variable valve mechanisms 15b and 16b.

In the system 100, in a specified mode, the variable operation of the intake valve 15a and the exhaust valve 16a by the variable valve mechanisms 15b and 16b is restricted.

For example, the intake valve 15a and the exhaust valve 16a have a predetermined reference position relative to the camshaft. For example, when the engine 10 is started, the ECU 50 determines whether the intake valve 15a and the exhaust valve 16a are in the reference position. When the intake valve 15a and the exhaust valve 16a are positioned in the reference position, the ECU 50 learns the current value to the OCV at that time (learning mode). Thus, in the learning mode, the intake valve 15a and the exhaust valve 16a need to be positioned in the reference position, so that variable operation is limited.

Also, for example, under certain conditions (for example, when the oil in the variable valve mechanisms 15b and 16b is at a low temperature, or when the variable valve mechanisms 15b and 16b are malfunctioning), the intake valve 15a and the exhaust valve 16a are forcibly locked in the reference position (forced lock mode). Thus, in the forced lock mode, the variable operation is restricted.

For example, while the vehicle 500 is idling, the cleaning mode may be implemented to remove impurities from the oil in the variable valve mechanisms 15b and 16b. In this case, the oil is circulated through the flow path, forcing the intake valve 15a and the exhaust valve 16a to move between the open and closed positions. Thus, variable operation is limited in the cleaning mode.

Note that the modes that limit the variable operation of the intake valve 15a and the exhaust valve 16a are not limited to the above modes, and other modes may also limit the variable operation of the intake valve 15a and the exhaust valve 16a.

The engine 10 has a fuel injection port 17. The injection port 17 is provided in the combustion chamber 13, and fuel is injected from the injection port 17 into the combustion chamber 13 (so-called direct injection). In another embodiment, the injection port 17 may be provided in the intake pipe 2 (described in detail later) (so-called premixing). An injection valve V1 for controlling the injection amount of fuel used in the engine 10 is connected to the injection port 17. The injection valve V1 is connected to the ECU 50 so as to be able to communicate with it. The ECU 50 controls the injection valve V1 to control the amount of fuel injected from the injection port 17.

The engine 10 has an ignition plug P. The ignition plug P is provided in the combustion chamber 13 and ignites a mixture of air and fuel in the combustion chamber 13. The ignition plug P is connected to the ECU 50 so as to be able to communicate with it. The ECU 50 controls the operation of the ignition plug P.

The intake pipe 2 is connected to the intake port 15. The intake pipe 2 is provided with components such as an air cleaner (not shown), and air that has passed through these components is supplied to the combustion chamber 13 via the intake port 15. The intake pipe 2 is provided with a throttle valve V2 for adjusting the flow rate of air flowing through the intake pipe 2. The throttle valve V2 is connected to the ECU 50 so as to be able to communicate with it. The ECU 50 controls the amount of intake air by controlling the throttle valve V2.

An exhaust pipe 3 is connected to the exhaust port 16. An air-fuel ratio (A/F) sensor Se2 is provided in the exhaust pipe 3. The A/F sensor Se2 measures the air-fuel ratio of the exhaust gas flowing through the exhaust pipe 3. The A/F sensor Se2 is connected to the ECU 50 so as to be able to communicate with it. For example, the ECU 50 controls the injection valve V1 and the throttle valve V2 based on the air-fuel ratio from the A/F sensor Se2 to adjust the amount of fuel injected and the flow rate of air.

A front catalyst 4 is provided downstream of the A/F sensor Se2 in the exhaust pipe 3. The front catalyst 4 removes harmful substances (e.g., at least one of hydrocarbons (HC), carbon monoxide (CO) and nitrided oxides (NO _x )) from the exhaust gas. The front catalyst 4 is, for example, a three-way catalyst.

A first temperature sensor Se3 is provided in the exhaust pipe 3 downstream of the front catalyst 4. The first temperature sensor Se3 measures the temperature of the exhaust gas after it has passed through the front catalyst 4. The first temperature sensor Se3 is communicatively connected to the ECU 50. For example, the ECU 50 determines whether the temperature of the exhaust gas is within a predetermined range based on the temperature from the first temperature sensor Se3, thereby protecting the front catalyst 4 from thermal degradation.

An _O2 sensor Se4 is provided downstream of the first temperature sensor Se3 in the exhaust pipe 3. _{The O2} sensor Se4 measures the amount of oxygen in the exhaust gas after it has passed through the front catalyst 4. The _O2 sensor Se4 is communicably connected to the ECU 50. For example, the ECU ₅₀ determines whether the front catalyst 4 has deteriorated based on the amount of oxygen in the exhaust gas from the O2 sensor Se4.

In the exhaust pipe 3, a particulate filter 5 is provided downstream of the _O2 sensor Se4. The particulate filter 5 removes particulate matter (PM) (e.g., soot) from the exhaust gas. The particulate filter 5 is, for example, a gasoline particulate filter (GPF). In another embodiment, for example, when the engine 10 is a diesel engine, the particulate filter 5 may be a die-sel particulate filter (DPF).

A differential pressure sensor Se5 is provided in the exhaust pipe 3. The differential pressure sensor Se5 detects the differential pressure ΔP between the exhaust gas pressure upstream of the particulate filter 5 and the exhaust gas pressure downstream of the particulate filter 5. When soot accumulates in the particulate filter 5, the gas permeability of the particulate filter 5 decreases and the differential pressure ΔP increases. Therefore, by monitoring the differential pressure ΔP, it is possible to determine (estimate) the amount of PM accumulated in the particulate filter 5.

A second temperature sensor Se6 is provided in the exhaust pipe 3 downstream of the particulate filter 5. The second temperature sensor Se6 measures the temperature of the exhaust gas after passing through the particulate filter 5. The second temperature sensor Se6 is connected to the ECU 50 so as to be able to communicate with it.

The PM accumulated on the particulate filter 5 is burned by high-temperature exhaust gas. The ECU 50 has multiple regeneration modes to burn the PM accumulated on the particulate filter 5. Specifically, the ECU 50 controls the engine 10 so that the temperature of the exhaust gas from the second temperature sensor Se6 is controlled to a temperature preset for each regeneration mode. For example, the ECU 50 controls at least one of the injection valve V1 or the throttle valve V2. For example, the ECU 50 selects a regeneration mode to be used from multiple regeneration modes based on the differential pressure ΔP from the differential pressure sensor Se5. When the differential pressure ΔP is larger (i.e., when the amount of PM accumulation is greater), the ECU 50 selects a regeneration mode having a higher set temperature.

For example, the multiple regeneration modes may include a normal mode M0, multiple heating modes Mi (i=1, 2, 3, ...), and a regeneration-disabled mode MF. The normal mode M0 is used when the amount of PM accumulation is small, and in the normal mode M0, the ECU 50 controls the engine 10 normally. The heating mode Mi is used when the amount of PM accumulation is large but the particulate filter 5 is regenerative, and in the heating mode Mi, the ECU 50 controls the engine 10 so that the temperature of the exhaust gas is higher than the temperature during normal operation. The regeneration-disabled mode MF is used when the amount of PM accumulation is large such that the particulate filter 5 cannot be regenerated, and in the regeneration-disabled mode MF, the ECU 50 controls the engine 10 so that the temperature of the exhaust gas is higher than the temperature during normal operation, and the particulate filter 5 needs to be replaced. For example, the multiple regeneration modes and related values are stored in a storage medium 52 (described in detail later) of the ECU 50.

The system 100 includes an ECU (control device) 50. The ECU 50 includes one or more processors 51 (e.g., a CPU, etc.), one or more storage media 52 (e.g., a ROM and a RAM, etc.), and one or more connectors 53. The ECU 50 may further include other components. The components of the ECU 50 are communicatively connected to each other via a bus. The storage medium 52 stores one or more programs executed by the processor 51. The programs include instructions for the processor 51. The operation of the ECU 50 shown in this disclosure is realized by the processor 51 executing the instructions stored in the storage medium 52. The ECU 50 is communicatively connected to the components of the system 100 via the connector 53.

Next, the operation of the system 100 will be explained.

Figure 2 is a flowchart showing the processing of the ECU 50. For example, the processing shown in Figure 2 may be repeated at a predetermined interval (e.g., tens to tens of milliseconds, a hundred to hundreds of milliseconds, one to several seconds, ten to tens of seconds, or one to several minutes) after the engine 10 is started until the engine 10 is stopped.

The processor 51 of the ECU 50 determines whether the variable operation of the intake valve 15a and the exhaust valve 16a by the variable valve mechanisms 15b and 16b is restricted (step S100). For example, the processor 51 determines whether any of the above-mentioned learning mode, forced lock mode, or cleaning mode is applied to the variable valve mechanisms 15b and 16b.

If it is determined in step S100 that the variable operation of the intake valve 15a and the exhaust valve 16a by the variable valve mechanisms 15b, 16b is not restricted (NO), the processor 51 ends the process.

In step S100, when it is determined that the variable operation of the intake valve 15a and the exhaust valve 16a by the variable valve mechanisms 15b and 16b is limited (YES), the processor 51 determines whether the amount of PM deposited on the particulate filter 5 is within a predetermined range (step S102). For example, the "predetermined range" may mean a range in which the particulate filter 5 can be regenerated, although the exhaust gas temperature needs to be higher than the temperature during normal operation in order to remove PM from the particulate filter 5. For example, the processor 51 may determine (estimate) the amount of PM deposited based on the currently used regeneration mode. Specifically, the processor 51 may determine that the amount of PM deposited is within the predetermined range when any of a plurality of heating modes Mi (or any of a selected number of heating modes Mi) is used as the regeneration mode. In another embodiment, the processor 51 may determine (estimate) the amount of PM deposited based on the differential pressure ΔP from the differential pressure sensor Se5.

If it is determined in step S102 that the amount of PM accumulation is not within the predetermined range (NO), the processor 51 ends the process.

If it is determined in step S102 that the amount of PM accumulation is within a predetermined range (YES), the processor 51 determines a torque guard base value A (step S104). In this disclosure, the "torque guard base value A" means the maximum allowable torque value of the engine 10 that can suppress the increase in exhaust gas pressure (back pressure) in the exhaust pipe 3 to an allowable value when the variable operation of the intake valve 15a and the exhaust valve 16a by the variable valve mechanisms 15b and 16b is limited and PM accumulates in the particulate filter 5 to a greater than predetermined amount. Specifically, the processor 51 determines the torque guard base value A based on the engine 10 rotation speed from the crank angle sensor Se1 and the differential pressure ΔP from the differential pressure sensor Se5.

Figure 3 is a schematic diagram explaining the relationship between the pressure loss coefficient x and tables Ta1 to Ta4, and Figure 4 is tables Ta1 to Ta4 showing the relationship between the engine 10 rotation speed and the torque guard base value A.

Referring to FIG. 3, the storage medium 52 stores multiple (four in FIG. 3) tables Ta1 to Ta4 according to the range of the differential pressure ΔP. The number of tables is not limited to this and may be more than four, or may be two or three. More specifically, in this embodiment, the storage medium 52 stores tables Ta1 to Ta4 according to the range of the pressure loss coefficient x calculated based on the differential pressure ΔP.

For this reason, the processor 51 calculates the pressure loss coefficient x based on the differential pressure ΔP (kPa) from the differential pressure sensor Se5. The pressure loss coefficient x is calculated as x = ΔP/Q. Q (L/s) indicates the volumetric flow rate of the exhaust gas passing through the particulate filter 5, and can be obtained, for example, by calculating the mass flow rate of the gas combusted in the cylinder from the intake air volume read from an air flow sensor (not shown) and the air-fuel ratio read from the A/F sensor Se2, and converting the unit to volumetric flow rate. The processor 51 selects one of the reference tables Ta1 to Ta4 stored in the storage medium 52 according to the calculated pressure loss coefficient x.

As shown in FIG. 3, table Ta2 (second table) is applied to a range of pressure loss coefficient x that is higher than the range of pressure loss coefficient x to which table Ta1 (first table) is applied. Similarly, table Ta3 (second table) is applied to a range of pressure loss coefficient x that is higher than the range of pressure loss coefficient x to which table Ta2 (first table) is applied. Similarly, table Ta4 (second table) is applied to a range of pressure loss coefficient x that is higher than the range of pressure loss coefficient x to which table Ta3 (first table) is applied.

The storage medium 52 stores multiple (six in FIG. 3) thresholds Th1 to Th6 for switching the reference table between tables Ta1 to Ta4.

For example, if the pressure loss coefficient x is x<Th1, the processor 51 selects table Ta1 as the reference table.

If the pressure loss coefficient x is Th2≦x<Th3, the processor 51 selects table Ta2 as the reference table.

If the pressure loss coefficient x is Th4≦x<Th5, the processor 51 selects table Ta3 as the reference table.

If the pressure loss coefficient x is Th6≦x, the processor 51 selects table Ta4 as the reference table.

In contrast, for example, if the pressure loss coefficient x is Th1≦x<Th2, the processor 51 selects the reference table to be used in the current routine based on the pressure loss coefficient x calculated in the current routine and the reference table selected in the previous routine.

For example, if table Ta1 was selected as the reference table in the previous routine (n-1) and the pressure loss coefficient x is Th1≦x<Th2 in the current routine (n), the processor 51 selects table Ta1, which was also selected in the previous routine (n-1), as the reference table to be used in the current routine (n).

For example, in the next routine (n+1), if the pressure loss coefficient x increases to or exceeds the threshold value Th2 (first threshold value) (x≧Th2), the processor 51 switches the reference table from table Ta1 to table Ta2.

For example, if in the next routine (n+2), the pressure loss coefficient x falls below the threshold value Th2 (x<Th2), i.e., if table Ta2 was selected as the reference table in routine (n+1) and the pressure loss coefficient x is Th1≦x<Th2 in routine (n+2), the processor 51 selects table Ta2, which was also selected in routine (n+1), as the reference table to be used in routine (n+2).

Thus, in both routine (n) and routine (n+2), the pressure loss coefficient x is Th1≦x<Th2, but in routine (n), table Ta1 is selected as the reference table, while in routine (n+2), table Ta2 is selected as the reference table.

For example, in the next routine (n+3), if the pressure loss coefficient x falls below a threshold Th1 (second threshold) that is lower than threshold Th2, the processor 51 switches the reference table from table Ta2 to table Ta1.

As described above, a predetermined difference d1 is set between the threshold value Th2 at which the reference table is switched from table Ta1 to table Ta2, and the threshold value Th1 at which the reference table is switched from table Ta2 to table Ta1. Therefore, for example, when the pressure loss coefficient x fluctuates between threshold values Th1 and Th2, frequent switching of tables (i.e., fluctuations in the torque guard base value A) can be suppressed.

Similarly, if the pressure loss coefficient x increases to or exceeds threshold value Th4 (first threshold value) while table Ta2 is selected as the reference table, processor 51 switches the reference table from table Ta2 to table Ta3. Conversely, if the pressure loss coefficient x falls below threshold value Th3 (second threshold value) that is lower than threshold value Th4 while table Ta3 is selected as the reference table, processor 51 switches the reference table from table Ta3 to table Ta2. In this way, a predetermined difference d2 is set between threshold value Th4 and threshold value Th3.

Furthermore, similarly, if the pressure loss coefficient x increases to or exceeds threshold value Th6 (first threshold value) while table Ta3 is selected as the reference table, processor 51 switches the reference table from table Ta3 to table Ta4. Conversely, if the pressure loss coefficient x falls below threshold value Th5 (second threshold value) that is lower than threshold value Th6 while table Ta4 is selected as the reference table, processor 51 switches the reference table from table Ta4 to table Ta3. In this way, a predetermined difference d3 is set between threshold value Th6 and threshold value Th5.

The differences d1 to d3 may be the same as each other or may be different from each other.

Referring to FIG. 4, each of tables Ta1 to Ta4 indicates the relationship between the rotation speed of engine 10 and torque guard base value A. Processor 51 reads out the torque guard base value A corresponding to the rotation speed of engine 10 from a reference table selected from tables Ta1 to Ta4. In this manner, torque guard base value A is determined. Note that such torque guard base value A of tables Ta1 to Ta4 can be determined in advance, for example, by experiment or analysis, according to the differential pressure ΔP (or pressure loss coefficient x) and the rotation speed of engine 10.

2, the processor 51 then determines whether the torque guard base value A is equal to or less than the actual torque guard value C (A≦C) (step S106). In the vehicle 500, various torque guard values (maximum allowable torque values) are imposed on the engine 10 based on various conditions (e.g., coolant temperature, cruise control, or component failure, etc.). In this disclosure, the "actual torque guard value C" may mean the lowest torque guard value among all torque guard values imposed on the engine 10 (excluding the torque guard base value A). The actual torque of the engine 10 is controlled to be equal to or less than the actual torque guard value C.

If it is determined in step S106 that the torque guard base value A is A≦C (YES), the processor 51 determines the larger of the torque guard base value A and the value obtained by subtracting a predetermined adjustment amount D from the actual torque guard value C as the torque guard value B by the variable valve mechanisms 15b, 16b (B=max(A,C-D)) (step S108). For example, the "adjustment amount D" may be determined as the maximum allowable value that generates an acceptable shock when reducing the torque.

Then, the processor 51 determines the actual torque guard value C as C=B (step S110), and ends the series of processes. The processor 51 controls the torque of the engine 10 based on the actual torque guard value C. For example, the processor 51 controls at least one of the injection valve V1 or the throttle valve V2.

Figure 5 is a graph showing various torque guard values when the torque guard base value A is equal to or less than the actual torque guard value C. That is, Figure 5 shows a situation where it is determined in step S106 of Figure 2 that the torque guard base value A is A <= C (YES). In Figure 5, the torque guard value B by the variable valve mechanisms 15b, 16b is shown by a dashed line, the actual torque guard value C is shown by a solid line, and the torque guard base value A is shown by a dashed line. Note that after time t1, the actual torque guard value C matches the torque guard value B, but for better understanding, these are drawn separately in Figure 5.

In FIG. 5, at time t1, it is determined that the variable operation of the intake valve 15a and the exhaust valve 16a is restricted (YES in step S100 in FIG. 2), and it is also determined that the amount of PM accumulation is within a predetermined range (YES in step S102 in FIG. 2). Therefore, the torque guard base value A appears for the first time at time t1. The torque guard base value A after time t1 is determined based on the operating conditions of the vehicle 500 (the engine 10 rotation speed and the pressure difference ΔP).

Regarding the torque guard value B by the variable valve mechanisms 15b, 16b, for example, when the intake valve 15a and the exhaust valve 16a are locked in the reference position, the torque of the engine 10 cannot output a torque higher than a predetermined torque value Tr1. Therefore, for example, when the intake valve 15a and the exhaust valve 16a are already locked in the reference position before time t1, the torque guard value B is set to the torque value Tr1 as shown in FIG. 5.

5, as described above, at time t1, the torque guard base value A is equal to or less than the actual torque guard value C (YES in step S106 in FIG. 2). Also, in FIG. 5, the value obtained by subtracting the adjustment amount D from the actual torque guard value C is greater than the torque guard base value A. Therefore, the torque guard value B is determined as B=C-D (step S108 in FIG. 2). Also, the actual torque guard value C is determined as C=B (step S110 in FIG. 2). This process makes it possible to suppress shocks when reducing the torque of the engine 10. After time t1, the actual torque guard value C is determined by the same process. As described above, if the torque guard base value A is equal to or less than the actual torque guard value C, the actual torque guard value C is changed based on the torque guard base value A (or taking into account the torque guard base value A).

2, if it is determined in step S106 that the torque guard base value A is not A≦C (YES) (i.e., if the torque guard base value A is A>C), the processor 51 sets B=A as the target and determines the torque guard value B within the range of Bn _-1 -F≦ _Bn ≦ _Bn-1 +E (step S112). _Bn indicates the torque guard value B in the current routine, and Bn _-1 indicates the torque guard value B in the previous routine. Furthermore, E indicates the limit on the increase side, and F indicates the limit on the decrease side. The processor 51 ends the series of processes.

The processor 51 continues to use the lowest torque guard value of all the torque guard values imposed on the engine 10 as the actual torque guard value C. The processor 51 controls the torque of the engine 10 based on the actual torque guard value C. For example, the processor 51 controls at least one of the injection valve V1 or the throttle valve V2.

Figure 6 is a graph showing various torque guard values when the torque guard base value A is greater than the actual torque guard value C. That is, Figure 6 shows a situation (NO) in step S106 of Figure 2 where it is determined that the torque guard base value A is not A <= C (i.e., the torque guard base value A is A > C). In Figure 6, similar to Figure 5, the torque guard value B by the variable valve mechanisms 15b, 16b is shown by a dashed line, the actual torque guard value C is shown by a solid line, and the torque guard base value A is shown by a dashed line.

In FIG. 6, as in FIG. 5, at time t1, it is determined that the variable operation of the intake valve 15a and the exhaust valve 16a is restricted (YES in step S100 in FIG. 2), and it is also determined that the amount of PM accumulation is within a predetermined range (YES in step S102 in FIG. 2). Therefore, at time t1, the torque guard base value A appears for the first time. The torque guard base value A from time t1 onwards is determined based on the operating conditions of the vehicle 500 (the engine 10 rotation speed and the pressure difference ΔP).

As shown in Fig. 6, at time t1, the torque guard base value A is greater than the actual torque guard value C (NO in step S106 in Fig. 2). Therefore, the torque guard value B is set to a target of B=A and is determined within the range of Bn _-1 -F≦ _Bn ≦Bn _-1 +E (step S112 in Fig. 2). Furthermore, the lowest torque guard value among all the torque guard values imposed on the engine 10 continues to be used as the actual torque guard value C. The processor 51 controls the torque of the engine 10 based on the actual torque guard value C. As described above, when the torque guard base value A is greater than the actual torque guard value C, the actual torque guard value C is not changed based on the torque guard base value A. However, even in this case, the processor 51 controls the torque of the engine 10 based on the actual torque guard value C as described above.

The system 100 as described above includes an engine 10, variable valve mechanisms 15b, 16b configured to change the operation of an intake valve 15a and an exhaust valve 16a of the engine 10, a particulate filter 5 provided in an exhaust pipe 3 connected to an exhaust port 16 of the engine 10, a differential pressure sensor Se5 for detecting the amount of PM accumulated in the particulate filter 5, and an ECU 50 for controlling the engine 10 and the variable valve mechanisms 15b, 16b. The ECU 50 has one or more processors 51 and one or more storage media 52 for storing instructions executed by the one or more processors 51. The processor 51 is configured to execute the following steps according to the instructions: determine whether the variable operation of the intake valve 15a and the exhaust valve 16a by the variable valve mechanisms 15b and 16b is limited (step S100); determine whether the amount of PM deposited on the particulate filter 5 is within a predetermined range (step S102); and limit the torque of the engine 10 (steps S104 to S112) if the variable operation of the intake valve 15a and the exhaust valve 16a by the variable valve mechanisms 15b and 16b is limited and the amount of PM deposited on the particulate filter 5 is within the predetermined range. Therefore, the flow rate of the exhaust gas of the engine 10 can be limited, thereby suppressing an increase in back pressure.

In addition, in the system 100, the differential pressure sensor Se5 detects the differential pressure ΔP between the exhaust gas pressure upstream of the particulate filter 5 and the exhaust gas pressure downstream of the particulate filter 5, and limiting the torque of the engine 10 includes determining the torque guard base value A based on the engine 10 rotation speed and the differential pressure ΔP detected by the differential pressure sensor Se5 (step S104). With this configuration, the torque of the engine 10 can be limited taking into account both the operating conditions of the engine 10 and the accumulation conditions of PM in the particulate filter 5.

Furthermore, in the system 100, the storage medium 52 stores a plurality of tables Ta1 to Ta4 that indicate the relationship between the rotation speed of the engine 10 and the torque guard base value A according to the range of the pressure loss coefficient x calculated based on the pressure difference ΔP, and the plurality of tables Ta1 to Ta4 include at least a first table (e.g., table Ta1) and a second table (e.g., table Ta2) that is applied to a range of the pressure loss coefficient x that is higher than the range of the pressure loss coefficient x to which the first table is applied, and the torque of the engine 10 is limited by selecting one of the plurality of tables Ta1 to Ta4 according to the pressure difference ΔP (specifically, the pressure loss coefficient x). The method includes: selecting one reference table; determining a torque guard base value A based on the selected reference table; switching the reference table to a second table (e.g., Ta2) when the pressure loss coefficient x increases to or exceeds a first threshold value (e.g., Th2) while the first table (e.g., Ta1) is selected as the reference table; and switching the reference table to the first table (e.g., Ta1) when the pressure loss coefficient x falls below a second threshold value (e.g., Th1) that is lower than the first threshold value while the second table (e.g., Ta2) is selected as the reference table. With this configuration, frequent switching of tables (i.e., fluctuations in the torque guard base value A) can be suppressed when the pressure loss coefficient x fluctuates between the first and second threshold values.

Although the embodiment has been described above with reference to the attached drawings, the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can conceive of various modified or revised examples within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. In addition, the steps of the ECU 50 in the above embodiment do not have to be performed in the above order, and may be performed in a different order as long as no technical contradiction occurs.

For example, in the above embodiment, the storage medium 52 stores tables Ta1 to Ta4 according to the range of the pressure loss coefficient x calculated based on the differential pressure ΔP. However, in other embodiments, the storage medium 52 may store tables Ta1 to Ta4 directly according to the range of the differential pressure ΔP, and the processor 51 may select one reference table from among the multiple tables Ta1 to Ta4 according to the differential pressure ΔP detected by the differential pressure sensor Se5.

3 Exhaust pipe 5 Particulate filter 10 Engine 15a Intake valve 15b Variable valve mechanism 16 Exhaust port 16a Exhaust valve 16b Variable valve mechanism 50 ECU (control device)
51 Processor 52 Storage medium 100 Engine control system A Torque guard base value (maximum allowable value of engine torque based on limitations on variable operation by the variable valve mechanism and accumulation of PM in the particulate filter)
Se5 Differential pressure sensor (sensor)
Ta1 to Ta4 Tables Th1 to Th6 Thresholds

Claims (3)

The engine,
a variable valve mechanism configured to change the operation of an intake valve and an exhaust valve of the engine;
a particulate filter provided in an exhaust pipe connected to an exhaust port of the engine;
a sensor for detecting an amount of particulate matter deposited on the particulate filter;
a control device for controlling the engine and the variable valve mechanism;
Equipped with
The control device includes one or more processors and one or more storage media that store instructions to be executed by the one or more processors;
The one or more processors, in accordance with the instructions,
determining whether or not variable operation of the intake valve and the exhaust valve by the variable valve mechanism is restricted;
determining whether the amount of deposition of the particulate matter on the particulate filter is within a predetermined range;
limiting a torque of the engine when the variable operation of the intake valve and the exhaust valve by the variable valve mechanism is limited and the amount of deposition of the particulate matter on the particulate filter is within a predetermined range;
configured to run
Limiting the torque of the engine comprises:
Obtaining a torque guard base value, which is a maximum allowable value of the torque of the engine, capable of suppressing an increase in exhaust gas pressure in the exhaust pipe to an allowable value when the variable operation of the intake valve and the exhaust valve by the variable valve mechanism is limited and when the particulate matter accumulates in the particulate filter in an amount greater than a predetermined amount;
obtaining an actual torque guard value, which is the lowest torque guard value among all torque guard values imposed on the engine excluding the torque guard base value;
When the torque guard base value is equal to or less than the actual torque guard value, limiting the torque of the engine based on the larger of the torque guard base value and a value obtained by subtracting a predetermined adjustment amount from the actual torque guard value;
When the torque guard base value is greater than the actual torque guard value, limiting the torque of the engine based on the actual torque guard value;
Including,
the predetermined adjustment amount being determined as a maximum allowable value that, when reduced, produces an acceptable shock.
Engine control system. The sensor detects a differential pressure between a pressure of the exhaust gas upstream of the particulate filter and a pressure of the exhaust gas downstream of the particulate filter,
2. The engine control system according to claim 1, wherein controlling the torque of the engine includes determining the torque guard base value based on a rotation speed of the engine and the differential pressure detected by the sensor. the storage medium stores a plurality of tables indicating a relationship between the engine speed and the torque guard base value according to the range of the differential pressure,
the plurality of tables includes at least a first table and a second table that is applied to a differential pressure range higher than a differential pressure range to which the first table is applied;
Limiting the torque of the engine comprises:
selecting one reference table from the plurality of tables in response to the differential pressure;
determining the torque guard base value based on the selected look-up table;
switching the look-up table to the second table when the differential pressure increases to or above a first threshold while the first table is selected as the look-up table;
switching the reference table to the first table when the differential pressure drops below a second threshold value lower than the first threshold value while the second table is selected as the reference table;
The engine control system of claim 2 , comprising:

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