Engine control system

Abstract

To provide an engine control system capable of suppressing an increase in back pressure.SOLUTION: A system includes an engine, a variable valve mechanism, a particulate filter, a sensor for detecting accumulation amount of particulate matters in the particulate filter and a control device. One or a plurality of processors are configured to execute: determining whether or not variable operations of an intake valve and an exhaust valve are restricted in accordance with an order; determining whether or not the accumulation amount of particulate matters in the particulate filter is within a predetermined range; and restricting engine toque when the variable operations of the intake valve and the exhaust valve are restricted and the accumulation amount of particulate matters in the particulate filter is within the predetermined range.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an engine control system.

Background Art

[0002] In an engine, a filter may be provided in an exhaust pipe in order to remove particulate matter from exhaust gas (see, for example, Patent Documents 1 to 4).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] An engine may have a variable valve mechanism. The variable valve mechanism can change the operations of the intake valve and the exhaust valve regardless of the angle of the camshaft. However, even in an engine having such a variable valve mechanism, under certain conditions, the variable operation of the valve may be restricted. When soot accumulates on the filter in the exhaust pipe under such conditions, the pressure (back pressure) of the exhaust gas in the exhaust pipe increases. In this case, in order to suppress the increase in the back pressure, it may be considered to recirculate a part of the exhaust gas as intake air (which may be referred to as EGR (Exhaust Gas Recirculation)). However, in this case, combustion may deteriorate due to an increase in EGR, and engine speed hunting or engine stop may occur. Further, due to the deterioration of combustion, the temperature of the filter may rise excessively.

[0005] In view of the above problems, an object of the present invention is to provide an engine control system capable of suppressing an increase in back pressure.

Means for Solving the Problems

[0006] An engine control system according to an aspect of the present invention includes: an engine; a variable valve mechanism configured to be able to change the operations of the intake valve and the 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 the amount of particulate matter deposited on the particulate filter; a control device for controlling the engine and the variable valve mechanism; and the control device includes one or more processors and one or more storage media storing instructions executed by the one or more processors, the one or more processors, according to the instructions, determine whether the variable operations of the intake valve and the exhaust valve by the variable valve mechanism are restricted; determine whether the amount of the particulate matter deposited on the particulate filter is within a predetermined range; when the variable operations of the intake valve and the exhaust valve by the variable valve mechanism are restricted and the amount of the particulate matter deposited on the particulate filter is within a predetermined range, limit the torque of the engine; and is configured to execute 、 Restricting the torque of the engine means that when the variable operation of the intake valve and the exhaust valve by the variable valve mechanism is restricted and the particulate matter accumulates in the particulate filter in an amount greater than a predetermined amount, a torque guard base value, which is the maximum allowable value of the torque of the engine, can be obtained by suppressing the increase in the pressure of the exhaust gas in the exhaust pipe to an allowable value; obtaining an actual torque guard value, which is the lowest torque guard value among all the torque guard values imposed on the engine excluding the torque guard base value; when the torque guard base value is less than or equal to the actual torque guard value, restricting the torque of the engine based on the larger value among the torque guard base value and the 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, restricting the torque of the engine based on the actual torque guard value; including the predetermined adjustment amount is determined as the maximum allowable value for generating an acceptable shock when reducing the torque 。

Advantages of the Invention

[0007] According to the present invention, an increase in back pressure can be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Specific dimensions, materials, numerical values, etc. shown in such embodiments are merely examples for facilitating understanding and do not limit the present invention unless otherwise specified. In the specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to omit duplicate description. Further, elements not directly related to the present invention are not shown.

[0010] FIG. 1 is a schematic diagram showing an engine control system 100 according to an embodiment of the present invention. The engine control system (which may also be simply referred to as the "system" in the present disclosure) 100 is applied to a vehicle 500 such as a HEV (Hybrid Electric Vehicle), a gasoline vehicle, or a diesel vehicle, for example. The system 100 includes an engine 10.

[0011] In the present 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 the crankshaft 18 by a rod 14.

[0012] In the engine 10 as described above, in the combustion chamber 13, a mixture of air and fuel (gasoline) burns, whereby the piston 12 reciprocates 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 rotational speed of the crankshaft 18 (the rotational speed of the engine 10) is detected by a crank angle sensor Se1. The crank angle sensor Se1 is communicably connected to an ECU 50 (to be described in detail later). For better understanding, only one set of the cylinder 11 and the piston 12 is shown in FIG. 1, but the engine 10 can have a plurality of sets of the cylinder 11 and the piston 12.

[0013] The engine 10 has an intake port 15 and an exhaust port 16. An intake valve 15a is provided at the intake port 15, and an exhaust valve 16a is provided at the exhaust port 16. The operation of each of the intake valve 15a and the exhaust valve 16a is controlled by, for example, a camshaft (not shown). The camshaft is rotated by the crankshaft 18 via, for example, a rotating belt or the like.

[0014] System 100 includes variable valve mechanisms 15b and 16b for intake valve 15a and exhaust valve 16a, respectively. The variable valve mechanisms 15b and 16b can each change the cam angles of the intake valve 15a and the exhaust valve 16a with respect to the camshaft, thereby changing 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, when 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 communicably 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.

[0015] In system 100, in a predetermined mode, the variable operation of the intake valve 15a and the exhaust valve 16a by the variable valve mechanisms 15b and 16b is restricted.

[0016] For example, the intake valve 15a and the exhaust valve 16a have a predetermined reference position with respect 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, since the intake valve 15a and the exhaust valve 16a need to be positioned in the reference position, the variable operation is restricted.

[0017] Further, for example, under predetermined conditions (e.g., when the oil of the variable valve mechanisms 15b and 16b is at a low temperature and when the variable valve mechanisms 15b and 16b are malfunctioning, etc.), the intake valve 15a and the exhaust valve 16a are forcibly locked at the reference position (forced lock mode). Thus, in the forced lock mode, the variable operation is restricted.

[0018] Also, for example, when the vehicle 500 is idling, a cleaning mode may be implemented to remove impurities from the oil of the variable valve mechanisms 15b and 16b. In this case, since the oil is circulated in the flow path, the intake valve 15a and the exhaust valve 16a are forcibly moved between the open position and the closed position. Thus, in the cleaning mode, the variable operation is restricted.

[0019] Note that the modes for restricting 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 restrict the variable operation of the intake valve 15a and the exhaust valve 16a.

[0020] The engine 10 has a fuel injection port 17. The injection port 17 is provided in the combustion chamber 13, and fuel is injected into the combustion chamber 13 from the injection port 17 (so-called direct injection). In other embodiments, the injection port 17 may be provided in the intake pipe 2 (specifically described later) (so-called premixing). An injection valve V1 for controlling the injection amount of the fuel used in the engine 10 is connected to the injection port 17. The injection valve V1 is communicably connected to the ECU 50. The ECU 50 controls the injection amount of the fuel from the injection port 17 by controlling the injection valve V1.

[0021] The engine 10 has a spark plug P. The spark plug P is provided in the combustion chamber 13 and ignites the air-fuel mixture in the combustion chamber 13. The spark plug P is communicably connected to the ECU 50. The ECU 50 controls the operation of the spark plug P.

[0022] An 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 the air that has passed through these components is supplied to the combustion chamber 13 through the intake port 15. The intake pipe 2 is provided with a throttle valve V2 for adjusting the flow rate of the air flowing through the intake pipe 2. The throttle valve V2 is communicably connected to the ECU 50. The ECU 50 controls the intake air amount by controlling the throttle valve V2.

[0023] An exhaust pipe 3 is connected to the exhaust port 16. The exhaust pipe 3 is provided with an air-fuel ratio (A / F) sensor Se2. 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 communicably connected to the ECU 50. 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, and adjusts the fuel injection amount and the air flow rate.

[0024] In the exhaust pipe 3, a front catalyst 4 is provided downstream of the A / F sensor Se2. The front catalyst 4 removes harmful substances (for example, at least one of hydrocarbons (HC), carbon monoxide (CO), or nitrogen oxides (NO x x)) from the exhaust gas. The front catalyst 4 is, for example, a three-way catalyst.

[0025] In the exhaust pipe 3, a first temperature sensor Se3 is provided downstream of the front catalyst 4. The first temperature sensor Se3 measures the temperature of the exhaust gas after passing through the front catalyst 4. The first temperature sensor Se3 is communicably 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, and thereby can protect the front catalyst 4 from thermal degradation.

[0026] In the exhaust pipe 3, an O2 sensor Se4 is provided downstream of the first temperature sensor Se3. The O2 sensor Se4 measures the amount of oxygen in the exhaust gas after passing 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 is deteriorated based on the amount of oxygen in the exhaust gas from the O2 sensor Se4.

[0027] 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 GPF (Gasoline particulate filter). In other embodiments, for example, when the engine 10 is a diesel engine, the particulate filter 5 may be a DPF (Diesel Particulate Filter).

[0028] In the exhaust pipe 3, a differential pressure sensor Se5 is provided. The differential pressure sensor Se5 detects the differential pressure ΔP between the pressure of the exhaust gas upstream of the particulate filter 5 and the pressure of the exhaust gas 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, the amount of PM deposition in the particulate filter 5 can be determined (estimated).

[0029] In the exhaust pipe 3, a second temperature sensor Se6 is provided 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 communicably connected to the ECU 50.

[0030] The PM deposited on the particulate filter 5 is burned by the high-temperature exhaust gas. The ECU 50 has a plurality of regeneration modes to burn the PM deposited 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 preset temperature 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 among a plurality of 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 deposition amount of PM is larger), the ECU 50 selects a regeneration mode having a higher set temperature.

[0031] For example, the plurality of regeneration modes may include a normal mode M0, a plurality of heating modes Mi (i = 1, 2, 3, ···), and a non-regenerable mode MF. The normal mode M0 is used when the deposition amount of PM is small. In the normal mode M0, the ECU 50 controls the engine 10 as usual. The heating mode Mi is used when the deposition amount of PM is large but the particulate filter 5 is regenerable. In the heating mode Mi, the ECU 50 controls the engine 10 so that the temperature of the exhaust gas becomes higher than the temperature during normal operation. The non-regenerable mode MF is used when the deposition amount of PM is large so that the particulate filter 5 is non-regenerable. In the non-regenerable mode MF, the ECU 50 controls the engine 10 so that the temperature of the exhaust gas becomes higher than the temperature during normal operation, and the particulate filter 5 needs to be replaced. For example, the plurality of regeneration modes and related values are stored in the storage medium 52 of the ECU 50 (to be described in detail later).

[0032] System 100 includes an ECU (control device) 50. The ECU 50 has one or more processors 51 (such as a CPU, etc.), one or more storage media 52 (such as ROM and RAM, etc.), and one or more connectors 53. The ECU 50 may further have other components. The components of the ECU 50 are communicably connected to each other by a bus. The storage media 52 stores one or more programs executed by the processor 51. The program includes instructions for the processor 51. The operations of the ECU 50 shown in the present disclosure are realized by executing the instructions stored in the storage media 52 by the processor 51. The ECU 50 is communicably connected to the components of the system 100 via the connector 53.

[0033] Subsequently, the operation of the system 100 will be described.

[0034] FIG. 2 is a flowchart showing the processing of the ECU 50. For example, the processing shown in FIG. 2 may be repeated at a predetermined interval (such as ten to several tens of milliseconds, one hundred to several hundreds of milliseconds, one to several seconds, ten to several tens of seconds, or one to several minutes) after the engine 10 is started until the engine 10 is stopped.

[0035] 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, 16b is restricted (step S100). For example, the processor 51 determines whether any one of the above learning mode, forced lock mode, or cleaning mode is applied to the variable valve mechanisms 15b, 16b.

[0036] In step S100, if it is determined 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 processing.

[0037] 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, 16b is restricted (YES), the processor 51 determines whether the deposition amount of PM on the particulate filter 5 is within a predetermined range (step S102). For example, the "predetermined range" may mean a range in which the temperature of the exhaust gas needs to be higher than the temperature during normal operation to remove PM from the particulate filter 5, but the particulate filter 5 can be regenerated. For example, the processor 51 may determine (estimate) the deposition amount of PM based on the currently used regeneration mode. Specifically, when any one of the plurality of heating modes Mi (or any one of the selected several heating modes Mi) is used as the regeneration mode, the processor 51 may determine that the deposition amount of PM is within a predetermined range. In other embodiments, the processor 51 may determine (estimate) the deposition amount of PM based on the differential pressure ΔP from the differential pressure sensor Se5.

[0038] In step S102, when it is determined that the deposition amount of PM is not within the predetermined range (NO), the processor 51 ends the process.

[0039] In step S102, when it is determined that the deposition amount of PM is within the predetermined range (YES), the processor 51 determines the torque guard base value A (step S104). In the present disclosure, the "torque guard base value A" means the maximum allowable value of the torque of the engine 10 that can suppress the increase in the pressure (back pressure) of the exhaust gas 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, 16b is restricted and PM accumulates on the particulate filter 5 in an amount greater than a predetermined amount. Specifically, the processor 51 determines the torque guard base value A based on the rotational speed of the engine 10 from the crank angle sensor Se1 and the differential pressure ΔP from the differential pressure sensor Se5.

[0040] FIG. 3 is a schematic diagram for explaining the relationship between the pressure loss coefficient x and the tables Ta1 to Ta4, and FIG. 4 is the tables Ta1 to Ta4 showing the relationship between the rotational speed of the engine 10 and the torque guard base value A.

[0041] Referring to FIG. 3, the storage medium 52 stores a plurality (four in FIG. 3) of 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 the present embodiment, the storage medium 52 stores the tables Ta1 to Ta4 according to the range of the pressure loss coefficient x calculated based on the differential pressure ΔP.

[0042] Therefore, 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) represents the volume 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 burned in the cylinder from the intake air amount read from an air flow sensor (not shown) and the air-fuel ratio read from the A / F sensor Se2, and performing unit conversion on the volume flow rate. The processor 51 selects one reference table from the tables Ta1 to Ta4 stored in the storage medium 52 according to the calculated pressure loss coefficient x.

[0043] As shown in FIG. 3, the table Ta2 (second table) is applied to a range of the pressure loss coefficient x higher than the range of the pressure loss coefficient x to which the table Ta1 (first table) is applied. Similarly, the table Ta3 (second table) is applied to a range of the pressure loss coefficient x higher than the range of the pressure loss coefficient x to which the table Ta2 (first table) is applied. Further similarly, the table Ta4 (second table) is applied to a range of the pressure loss coefficient x higher than the range of the pressure loss coefficient x to which the table Ta3 (first table) is applied.

[0044] The storage medium 52 stores a plurality (six in FIG. 3) of threshold values Th1 to Th6 for switching the reference table among the tables Ta1 to Ta4.

[0045] For example, when the pressure loss coefficient x is x < Th1, the processor 51 selects table Ta1 as the reference table.

[0046] When the pressure loss coefficient x is Th2 ≤ x < Th3, the processor 51 selects table Ta2 as the reference table.

[0047] When the pressure loss coefficient x is Th4 ≤ x < Th5, the processor 51 selects table Ta3 as the reference table.

[0048] When the pressure loss coefficient x is Th6 ≤ x, the processor 51 selects table Ta4 as the reference table.

[0049] In contrast, for example, when 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.

[0050] For example, when 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).

[0051] For example, in the next routine (n + 1), when the pressure loss coefficient x increases to be equal to or greater than the threshold Th2 (the first threshold) (x ≥ Th2), the processor 51 switches the reference table from table Ta1 to table Ta2.

[0052] For example, in the next routine (n + 2), when the pressure loss coefficient x drops below the threshold Th2 (x < Th2), that is, when table Ta2 is selected as the reference table in routine (n + 1) and the pressure loss coefficient x is such that 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).

[0053] Therefore, in both routine (n) and routine (n + 2), the pressure loss coefficient x satisfies Th1 ≤ x < Th2. However, in routine (n), table Ta1 is selected as the reference table, while in routine (n + 2), table Ta2 is selected as the reference table.

[0054] For example, in the next routine (n + 3), when the pressure loss coefficient x drops below the threshold Th1 (the second threshold), which is lower than the threshold Th2, the processor 51 switches the reference table from table Ta2 to table Ta1.

[0055] As described above, a predetermined difference d1 is set between the threshold Th2 for switching the reference table from table Ta1 to table Ta2 and the threshold Th1 for switching the reference table from table Ta2 to table Ta1. Therefore, for example, when the pressure loss coefficient x fluctuates between the threshold Th1 and the threshold Th2, frequent switching of the table (i.e., fluctuation of the torque guard base value A) can be suppressed.

[0056] Similarly, while table Ta2 is selected as the reference table, when the pressure loss coefficient x increases to be equal to or higher than the threshold Th4 (the first threshold), the processor 51 switches the reference table from table Ta2 to table Ta3. Conversely, while table Ta3 is selected as the reference table, when the pressure loss coefficient x drops below the threshold Th3 (the second threshold), which is lower than the threshold Th4, the processor 51 switches the reference table from table Ta3 to table Ta2. In this way, a predetermined difference d2 is set between the threshold Th4 and the threshold Th3.

[0057] Furthermore, similarly, while the table Ta3 is selected as the reference table, if the pressure loss coefficient x increases to be equal to or higher than a threshold Th6 (first threshold), the processor 51 switches the reference table from the table Ta3 to the table Ta4. Conversely, while the table Ta4 is selected as the reference table, if the pressure loss coefficient x decreases to be lower than a threshold Th5 (second threshold) that is lower than the threshold Th6, the processor 51 switches the reference table from the table Ta4 to the table Ta3. In this way, a predetermined difference d3 is set between the threshold Th6 and the threshold Th5.

[0058] The differences d1 to d3 may be the same as each other or may be different from each other.

[0059] Referring to FIG. 4, each of the tables Ta1 to Ta4 shows the relationship between the rotational speed of the engine 10 and the torque guard base value A. The processor 51 reads out the torque guard base value A corresponding to the rotational speed of the engine 10 from the reference table selected from the tables Ta1 to Ta4. In this way, the torque guard base value A is determined. Note that the torque guard base values A of such tables Ta1 to Ta4 can be determined in advance by, for example, experiments or analyses according to the differential pressure ΔP (or the pressure loss coefficient x) and the rotational speed of the engine 10.

[0060] Referring to FIG. 2, subsequently, the processor 51 determines whether the torque guard base value A is less than or equal to 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 (for example, the temperature of the cooling water, cruise control, or failure of components). In the present disclosure, the "actual torque guard value C" may mean the lowest torque guard value among all the torque guard values imposed on the engine 10 (however, excluding the torque guard base value A). The actual torque of the engine 10 is controlled to be less than or equal to the actual torque guard value C.

[0061] In step S106, when it is determined that the torque guard base value A satisfies A ≤ C (YES), the processor 51 determines the larger value between 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 and 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 impact when reducing the torque.

[0062] Subsequently, 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.

[0063] FIG. 5 is a graph showing various torque guard values when the torque guard base value A is less than or equal to the actual torque guard value C. That is, FIG. 5 shows the situation (YES) where in step S106 of FIG. 2, it is determined that the torque guard base value A satisfies A ≤ C. In FIG. 5, the torque guard value B by the variable valve mechanisms 15b and 16b is indicated by a broken line, the actual torque guard value C is indicated by a solid line, and the torque guard base value A is indicated by a one-dot chain line. After time t1, the actual torque guard value C coincides with the torque guard value B, but for better understanding, they are drawn separately in FIG. 5.

[0064] In FIG. 5, at time t1, it is determined that the variable operations of the intake valve 15a and the exhaust valve 16a are restricted (YES in step S100 of FIG. 2), and it is determined that the PM deposition amount is within a predetermined range (YES in step S102 of FIG. 2). Therefore, at time t1, the torque guard base value A appears for the first time. The torque guard base value A after time t1 is determined based on the driving situation of the vehicle 500 (the engine speed and the differential pressure ΔP).

[0065] Regarding the torque guard value B by the variable valve mechanisms 15b and 16b, for example, when the intake valve 15a and the exhaust valve 16a are locked at the reference positions, the torque of the engine 10 cannot output a torque higher than a predetermined torque value Tr1. Therefore, for example, if the intake valve 15a and the exhaust valve 16a have already been locked at the reference positions before the time t1, the torque guard value B is set to the torque value Tr1 as shown in FIG. 5.

[0066] In FIG. 5, as described above, at the time t1, the torque guard base value A is less than or equal to the actual torque guard value C (YES in step S106 of 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). According to such processing, when reducing the torque of the engine 10, an impact can be suppressed. After the time t1, the actual torque guard value C is determined by the same processing. As described above, when the torque guard base value A is less than or equal to the actual torque guard value C, the actual torque guard value C is changed based on (or in consideration of) the torque guard base value A.

[0067] Referring to FIG. 2, in step S106, when it is determined that the torque guard base value A is not A ≤ C (YES) (that is, when the torque guard base value A is A > C), the processor 51 sets B = A as the target, and B n-1 - F ≤ B n ≤ B n-1 + E in the range to determine the torque guard value B (step S112). B n represents the torque guard value B in this routine, and B n-1 represents the torque guard value B in the previous routine. Also, E represents the upper limit on the increasing side, and F represents the lower limit on the decreasing side. The processor 51 ends a series of processing.

[0068] The processor 51 continues to use, as the actual torque guard value C, the lowest torque guard value among all the torque guard values imposed on the engine 10. 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.

[0069] FIG. 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, FIG. 6 shows a situation (NO) in which it is determined in step S106 of FIG. 2 that the torque guard base value A is not A≦C (that is, the torque guard base value A is A>C). In FIG. 6, similar to FIG. 5, the torque guard value B by the variable valve mechanisms 15b, 16b is indicated by a broken line, the actual torque guard value C is indicated by a solid line, and the torque guard base value A is indicated by a one-dot chain line.

[0070] In FIG. 6, similar to FIG. 5, at time t1, it is determined that the variable operations of the intake valve 15a and the exhaust valve 16a are restricted (YES in step S100 of FIG. 2), and it is determined that the deposition amount of PM is within a predetermined range (YES in step S102 of FIG. 2). Therefore, at time t1, the torque guard base value A appears for the first time. The torque guard base value A after time t1 is determined based on the driving situation of the vehicle 500 (the rotational speed of the engine 10 and the differential pressure ΔP).

[0071] 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 of FIG. 2). Therefore, the torque guard value B is set with the target of B = A, and B n-1 -F≦B n ≦B n-1It is determined within the range of +E (step S112 in FIG. 2). Also, as the actual torque guard value C, the lowest torque guard value among all the torque guard values imposed on the engine 10 is continuously used. 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.

[0072] The system 100 as described above includes an engine 10, variable valve mechanisms 15b and 16b configured to be able to change the operations of the intake valve 15a and the 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 deposited on the particulate filter 5, and an ECU 50 for controlling the engine 10 and the variable valve mechanisms 15b and 16b. The ECU 50 has one or more processors 51 and one or more storage media 52 that store instructions executed by the one or more processors 51. The processor 51 determines whether the variable operations of the intake valve 15a and the exhaust valve 16a by the variable valve mechanisms 15b and 16b are restricted (step S100), determines whether the amount of PM deposited on the particulate filter 5 is within a predetermined range (step S102), and when the variable operations of the intake valve 15a and the exhaust valve 16a by the variable valve mechanisms 15b and 16b are restricted and the amount of PM deposited on the particulate filter 5 is within a predetermined range, restricts the torque of the engine 10 (steps S104 to S112). Therefore, the flow rate of the exhaust gas of the engine 10 can be restricted, thereby suppressing an increase in back pressure.

[0073] In the system 100, the differential pressure sensor Se5 detects the differential pressure ΔP between the pressure of the exhaust gas upstream of the particulate filter 5 and the pressure of the exhaust gas downstream of the particulate filter 5. Limiting the torque of the engine 10 includes determining a torque guard base value A based on the rotational speed of the engine 10 and the differential pressure ΔP detected by the differential pressure sensor Se5 (step S104). According to such a configuration, the torque of the engine 10 can be limited in consideration of both the operating condition of the engine 10 and the deposition condition of PM on the particulate filter 5.

[0074] In the system 100, the storage medium 52 stores a plurality of tables Ta1 to Ta4 indicating the relationship between the rotational 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 differential pressure ΔP. The plurality of tables Ta1 to Ta4 include at least a first table (for example, table Ta1) and a second table (for example, table Ta2) applied to a range of the pressure loss coefficient x higher than the range of the pressure loss coefficient x to which the first table is applied. Limiting the torque of the engine 10 includes selecting one reference table according to the differential pressure ΔP (specifically, the pressure loss coefficient x) from among the plurality of tables Ta1 to Ta4, determining the torque guard base value A based on the selected reference table, switching the reference table to the second table (for example, Ta2) when the pressure loss coefficient x increases to be equal to or higher than a first threshold value (for example, Th2) while the first table (for example, Ta1) is selected as the reference table, and switching the reference table to the first table (for example, Ta1) when the pressure loss coefficient x decreases to be lower than a second threshold value (for example, Th1) lower than the first threshold value while the second table (for example, Ta2) is selected as the reference table. According to such a configuration, when the pressure loss coefficient x fluctuates between the first threshold value and the second threshold value, frequent switching of the table (that is, fluctuation of the torque guard base value A) can be suppressed.

[0075] The embodiments have been described above with reference to the accompanying drawings, but the present invention is not limited to such embodiments. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and it is naturally understood that they also belong to the technical scope of the present invention. In addition, the steps of the ECU 50 in the above embodiments do not have to be performed in the above order, and can be performed in a different order as long as there is no technical contradiction.

[0076] For example, in the above embodiment, the storage medium 52 stores the 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 directly store the tables Ta1 to Ta4 according to the range of the differential pressure ΔP, and the processor 51 may select one reference table according to the differential pressure ΔP detected by the differential pressure sensor Se5 from among the plurality of tables Ta1 to Ta4.

Explanation of Signs

[0077] 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 (the maximum allowable value of the engine torque based on the limitation of the variable operation by the variable valve mechanism and the deposition of PM on the particulate filter) Se5 Differential pressure sensor (sensor) Ta1~Ta4 Tables Th1~Th6 Threshold values

Claims

1. An engine, a variable valve mechanism configured to be able to change the operations of the intake valve and the 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 the amount of particulate matter deposited on the particulate filter, a control device for controlling the engine and the variable valve mechanism, comprising: the control device has one or more processors and one or more storage media storing instructions executed by the one or more processors, the one or more processors, according to the instructions, determine whether the variable operations of the intake valve and the exhaust valve by the variable valve mechanism are restricted, determine whether the amount of the particulate matter deposited on the particulate filter is within a predetermined range, when the variable operations of the intake valve and the exhaust valve by the variable valve mechanism are restricted and the amount of the particulate matter deposited on the particulate filter is within a predetermined range, limit the torque of the engine, is configured to execute, limiting the torque of the engine includes: when the variable operations of the intake valve and the exhaust valve by the variable valve mechanism are restricted and the particulate matter deposits on the particulate filter more than a predetermined amount, obtain a torque guard base value which is the maximum allowable value of the torque of the engine and can suppress the increase in the pressure of the exhaust gas in the exhaust pipe to an allowable value, obtain an actual torque guard value which is the lowest torque guard value among all torque guard values applied to the engine except the torque guard base value, when the torque guard base value is less than or equal to the actual torque guard value, limit the torque of the engine based on the larger value of the torque guard base value and the 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, limit the torque of the engine based on the actual torque guard value, including, the predetermined adjustment amount is determined as the maximum allowable value for generating an acceptable shock when reducing the torque, an engine control system.

2. The sensor detects a differential pressure between the pressure of the exhaust gas upstream of the particulate filter and the pressure of the exhaust gas downstream of the particulate filter. The controlling of the torque of the engine includes determining the torque guard base value based on the rotational speed of the engine and the differential pressure detected by the sensor, according to the engine control system of claim 1.

3. The storage medium stores a plurality of tables indicating the relationship between the rotational speed of the engine 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 applied to a differential pressure range higher than the differential pressure range to which the first table is applied. The limiting of the torque of the engine is selecting one reference table according to the differential pressure from among the plurality of tables; determining the torque guard base value based on the selected reference table; when the differential pressure increases to be equal to or higher than a first threshold while the first table is selected as the reference table, switching the reference table to the second table; when the differential pressure decreases to be lower than a second threshold lower than the first threshold while the second table is selected as the reference table, switching the reference table to the first table; including the engine control system of claim 2.

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