Control device for internal combustion engine, method for controlling internal combustion engine, program and storage medium

Abstract

The exhaust gas purification device provides a better control device for an internal combustion engine, a better control method for an internal combustion engine, a program that causes a computer to execute the better control method for an internal combustion engine, and a storage medium that stores the program that causes a computer to execute the better control method for an internal combustion engine. [Solution] When the intake air volume is calculated based on a flow rate signal, the control device 36 of the internal combustion engine performs catalyst protection control to limit the intake air volume in order to protect the catalyst based on the exhaust temperature and a first predetermined temperature. When the intake air volume is calculated based on a pressure signal, the control device 36 performs catalyst protection control based on the exhaust temperature and a second predetermined temperature different from the first predetermined temperature.

Description

Technical Field

[0001] The present disclosure relates to a control device for an internal combustion engine, a control method for an internal combustion engine, a program, and a storage medium.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2020-12387 discloses an engine control device. When it is determined that the intake pulsation is not in a large state, the engine control device calculates the intake air amount based on the intake air flow rate detected by the air flow meter. Further, when it is determined that the intake pulsation is in a large state, the engine control device calculates the intake air amount based on the intake pipe pressure.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, efforts aimed at mitigating or reducing the impact of climate change have been continued, and research and development on exhaust gas purification devices have been carried out towards this realization.

[0005] Incidentally, in exhaust gas purification systems, there is a strong demand for a better internal combustion engine control device, a better internal combustion engine control method, a program that causes a computer to execute the better internal combustion engine control method, and a storage medium that stores the program that causes the computer to execute the better internal combustion engine control method. This disclosure aims to solve the above problems by providing a better internal combustion engine control device, a better internal combustion engine control method, a program that causes a computer to execute the better internal combustion engine control method, and a storage medium that stores the program that causes a computer to execute the better internal combustion engine control method. This will ultimately contribute to mitigating or reducing the impact of climate change. [Means for solving the problem]

[0006] A first aspect of the present disclosure is a control device for an internal combustion engine, comprising: a flow rate signal acquisition unit that acquires a flow rate signal from an air flow meter that changes according to the air flow rate in the intake pipe of an internal combustion engine; a pressure signal acquisition unit that acquires a pressure signal from a pressure sensor that changes according to the pressure in the intake pipe; an intake air amount calculation unit that calculates an intake air amount, which is the amount of air the internal combustion engine takes in, based on the flow rate signal or the pressure signal; an exhaust temperature acquisition unit that acquires the exhaust temperature of the internal combustion engine; and a control unit that performs catalyst protection control to limit the intake air amount in order to protect the catalyst by adjusting the throttle valve opening, wherein when the intake air amount is calculated by the intake air amount calculation unit based on the flow rate signal, the control unit performs the catalyst protection control based on the exhaust temperature acquired by the exhaust temperature acquisition unit and a first predetermined temperature, and when the intake air amount is calculated by the intake air amount calculation unit based on the pressure signal, the control unit performs the catalyst protection control based on the exhaust temperature acquired by the exhaust temperature acquisition unit and a second predetermined temperature different from the first predetermined temperature.

[0007] A second aspect of the present disclosure includes a signal acquisition step in which a flow rate signal acquisition unit acquires a flow rate signal that changes according to the airflow rate in the intake piping of an internal combustion engine from an airflow meter, or a pressure signal acquisition unit acquires a pressure signal that changes according to the pressure in the intake piping from a pressure sensor, an intake air amount calculation step in which an intake air amount calculation unit calculates the amount of air that the internal combustion engine inhales based on the flow rate signal or the pressure signal, an exhaust temperature acquisition step in which an exhaust temperature acquisition unit acquires the exhaust temperature of the internal combustion engine, and a catalyst protection control that limits the intake air amount to protect the catalyst, with a throttle bar A control method for an internal combustion engine, comprising: a control step performed by the control unit by adjusting the lubricant opening; wherein when the intake air amount is calculated by the intake air amount calculation unit based on the flow rate signal, the control unit performs the catalyst protection control based on the exhaust temperature acquired by the exhaust temperature acquisition unit and a first predetermined temperature; and when the intake air amount is calculated by the intake air amount calculation unit based on the pressure signal, the control unit performs the catalyst protection control based on the exhaust temperature acquired by the exhaust temperature acquisition unit and a second predetermined temperature different from the first predetermined temperature.

[0008] A third aspect of this disclosure is a program that causes a computer to execute the control method for an internal combustion engine according to the second aspect.

[0009] A fourth aspect of this disclosure is a computer-readable, non-transient storage medium storing the program of the third aspect. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a better control device for an internal combustion engine, a better control method for an internal combustion engine, a program for causing a computer to execute the better control method for an internal combustion engine, and a storage medium storing the program for causing a computer to execute the better control method for an internal combustion engine. [Brief explanation of the drawing]

[0011] [Figure 1]Figure 1 is a schematic diagram of the internal combustion engine and intake / exhaust system in the first embodiment. [Figure 2] Figure 2 is a block diagram showing the configuration of the control device in the first embodiment. [Figure 3] Figure 3 is a map showing the flow rate signal region and the pressure signal region in the calculation of the intake air volume in the first embodiment. [Figure 4] Figure 4 is a flowchart of throttle valve opening control in the first embodiment. [Figure 5] Figure 5 is a graph showing the changes in accelerator pedal opening, exhaust temperature, air-fuel ratio (λ), and intake air volume over time. [Figure 6] Figure 6 is a graph showing the changes in accelerator pedal opening, exhaust temperature, air-fuel ratio (λ), and intake air volume over time. [Figure 7] Figure 7 is a graph showing the changes in accelerator pedal opening, exhaust temperature, air-fuel ratio (λ), and intake air volume over time. [Figure 8] Figure 8 is a graph showing the relationship between the throttle valve opening and the output torque of the internal combustion engine in the second embodiment. [Figure 9] Figure 9 is a map of the target throttle valve opening relative to the required opening in the second embodiment. [Figure 10] Figure 10 is a map showing the flow rate signal region and the pressure signal region in the second embodiment. [Figure 11] Figure 11 is a flowchart of throttle valve opening control in the second embodiment. [Modes for carrying out the invention]

[0012] In many gasoline vehicles, control is performed to make the air-fuel mixture richer than the stoichiometric ratio (λ = 1) (hereinafter referred to as rich control) during high-load operation. By vaporizing fuel in the cylinder of the internal combustion engine, heat is taken away, and while maintaining high output, the exhaust gas temperature (hereinafter referred to as exhaust temperature) is prevented from exceeding the heat-resistant temperature of the catalyst or the like.

[0013] However, in rich control, a problem is that the amount of exhaust gas increases due to the large amount of fuel input. Also, in rich control, since the air-fuel ratio deviates from the stoichiometric ratio, a problem is that the oxidation-reduction efficiency of the three-way catalyst decreases. Therefore, from the perspective of cleaning exhaust gas, operation at the stoichiometric ratio is required even during high-load operation.

[0014] As control for suppressing the exhaust temperature and protecting the catalyst or the like (hereinafter referred to as catalyst protection control), there is control for restricting the amount of air inhaled into the internal combustion engine (hereinafter referred to as intake air amount) by throttling the throttle valve opening (hereinafter referred to as air amount restriction control). However, when the stoichiometric ratio is maintained, the fuel injection amount is also restricted along with the restriction of the intake air amount by the air amount restriction control, so the output of the internal combustion engine is restricted.

[0015] It is required to shorten the period during which air amount restriction control is performed as catalyst protection control and shorten the period during which the output of the internal combustion engine is restricted. Also, it is required to reduce the operating range in which the output of the internal combustion engine is restricted.

[0016] In the present disclosure, while performing air amount restriction control as exhaust temperature suppression control, the period during which the output of the internal combustion engine is restricted can be shortened. Also, the operating range in which the output of the internal combustion engine is restricted can be reduced.

[0017] The control device for an internal combustion engine, the control method for an internal combustion engine, the program, and the storage medium according to the first embodiment and the second embodiment will be described below with reference to the drawings.

[0018] The programs (computer programs, computer software) according to the first and second embodiments may also be referred to as computer program products. Computer program products are not limited to computer programs recorded on recording media, but also include computer programs that are transmitted, distributed, or downloaded via the Internet or the like.

[0019] [First Embodiment] [Internal combustion engines and intake / exhaust systems] Figure 1 is a schematic diagram of the internal combustion engine 10 and the intake and exhaust system 12 in the first embodiment.

[0020] The internal combustion engine 10 is a gasoline engine. The intake and exhaust system 12 includes an intake pipe 14 for drawing in air, an exhaust pipe 16 for discharging exhaust gas from the internal combustion engine 10, and an exhaust gas recirculation (EGR) pipe 18 for returning the exhaust gas to the intake pipe 14.

[0021] The intake pipe 14 is equipped with an air filter 20, a throttle valve 22, an airflow meter 24, and a pressure sensor 26. The air filter 20 filters the inhaled air to remove dirt, dust, and other particles contained in the air. The throttle valve 22 adjusts the amount of air drawn into the intake pipe 14 (hereinafter referred to as the intake air amount) by opening it according to the driver's request. The airflow meter 24 is installed between the air filter 20 and the throttle valve 22. The airflow meter 24 is also installed upstream (on the air filter 20 side) of the connection point of the EGR pipe 18 to the intake pipe 14. The airflow meter 24 outputs a flow rate signal that changes according to the airflow rate in the intake pipe 14. The pressure sensor 26 is installed downstream (on the internal combustion engine 10 side) of the connection point of the EGR pipe 18 to the intake pipe 14. The pressure sensor 26 outputs a pressure signal that changes according to the pressure in the intake pipe 14.

[0022] The exhaust pipe 16 is equipped with a catalyst 28 and a temperature sensor 30. The catalyst 28 is, for example, a three-way catalyst. The catalyst 28 oxidizes or reduces hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), etc., contained in the exhaust gas, converting them into water, carbon dioxide, nitrogen, oxygen, etc. The temperature sensor 30 detects the temperature of the exhaust gas (hereinafter referred to as exhaust temperature). The temperature sensor 30 is installed upstream of the catalyst 28 (on the internal combustion engine 10 side).

[0023] The EGR piping 18 is equipped with an EGR cooler 32 and an EGR valve 34. The EGR cooler 32 cools the exhaust gas returned to the intake piping 14. The EGR valve 34 adjusts the amount of exhaust gas returned to the intake piping 14 depending on how much it is open.

[0024] [Control device] Figure 2 is a block diagram showing the configuration of the control device 36 in the first embodiment.

[0025] The control device 36 has a calculation unit 38 and a storage unit 40. The calculation unit 38 is a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The calculation unit 38 has a flow rate signal acquisition unit 42, a pressure signal acquisition unit 44, an intake air volume calculation unit 46, an exhaust temperature acquisition unit 48, a requested opening degree acquisition unit 50, and a control unit 54. The flow rate signal acquisition unit 42, the pressure signal acquisition unit 44, the intake air volume calculation unit 46, the exhaust temperature acquisition unit 48, the requested opening degree acquisition unit 50, and the control unit 54 are realized by the execution of a program stored in the storage unit 40 in the calculation unit 38. At least a part of the flow rate signal acquisition unit 42, the pressure signal acquisition unit 44, the intake air volume calculation unit 46, the exhaust temperature acquisition unit 48, the requested opening degree acquisition unit 50, and the control unit 54 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). At least a portion of the flow rate signal acquisition unit 42, pressure signal acquisition unit 44, intake air volume calculation unit 46, exhaust temperature acquisition unit 48, required opening degree acquisition unit 50, and control unit 54 may be implemented by electronic circuits including discrete devices.

[0026] The storage unit 40 is a computer-readable, non-transient, tangible storage medium. The storage unit 40 is composed of volatile memory (not shown) and non-volatile memory (not shown). The volatile memory is, for example, RAM (Random Access Memory). The non-volatile memory is, for example, ROM (Read Only Memory), flash memory, etc. Data is stored in the volatile memory, for example. Programs, tables, maps, etc. are stored in the non-volatile memory, for example. At least a portion of the storage unit 40 may be provided in the processor, integrated circuit, etc., as described above. At least a portion of the storage unit 40 may be mounted on equipment connected to the control device 36 by a network.

[0027] The flow rate signal acquisition unit 42 acquires a flow rate signal from the air flow meter 24. The pressure signal acquisition unit 44 acquires a pressure signal from the pressure sensor 26. The intake air volume calculation unit 46 calculates the intake air volume based on the flow rate signal or pressure signal. The exhaust temperature acquisition unit 48 acquires the exhaust temperature detected by the temperature sensor 30. The exhaust temperature acquisition unit 48 may also acquire the exhaust temperature estimated from parameters related to exhaust temperature. Parameters related to exhaust temperature include the rotational speed of the internal combustion engine 10, the intake air volume of the internal combustion engine 10, and the temperature of the coolant of the internal combustion engine 10. The requested opening degree acquisition unit 50 acquires the opening degree of the accelerator pedal 58 detected by the accelerator pedal opening degree sensor 56. The requested opening degree acquisition unit 50 determines the requested opening degree, which is the requested value for the throttle valve opening degree, based on the opening degree of the accelerator pedal 58. The control unit 54 controls the throttle valve 22 to adjust the throttle valve opening degree. Specifically, controlling the throttle valve 22 means controlling the drive motor (not shown) that opens and closes the throttle valve 22. The control unit 54 controls the throttle valve 22 based on the intake air volume and the desired opening degree.

[0028] [Regarding the calculation of intake air volume] Figure 3 is a map showing the flow rate signal region and the pressure signal region in the first embodiment. The flow rate signal region is the region in which the intake air volume calculation unit 46 calculates the intake air volume based on the flow rate signal. The pressure signal region is the region in which the intake air volume calculation unit 46 calculates the intake air volume based on the pressure signal. In Figure 3, T_max[deg] represents the opening degree when the throttle valve is fully open. T_max[deg] is approximately 80[deg].

[0029] To maintain the stoichiometry ratio, the fuel injection amount is determined according to the intake air volume so that the weight ratio of air to fuel in the fuel-air mixture is 14.7:1. Therefore, it is necessary to determine the intake air volume with high precision.

[0030] The airflow meter 24 is equipped with a thermosensitive resistance element. The thermosensitive resistance element is heated to a constant temperature by a heater. A constant current is also flowing through the thermosensitive resistance element. When the thermosensitive resistance element is exposed to the flowing air, its resistance changes, and the voltage applied to the thermosensitive resistance element changes. The airflow meter 24 outputs a voltage signal that changes according to the intake air volume as a flow rate signal. The airflow meter 24 may also output a frequency signal obtained by digitally converting the voltage signal as a flow rate signal. Since the voltage change becomes larger as the intake air volume increases, the intake air volume can be converted from the voltage applied to the thermosensitive resistance element. In other words, the intake air volume can be calculated directly from the flow rate signal.

[0031] The pressure sensor 26 includes a diaphragm with strain gauges. A constant current flows through the strain gauges. As the diaphragm deforms due to air pressure, the resistance of the strain gauges changes, and the voltage applied to the strain gauges changes. The pressure sensor 26 outputs a voltage signal that changes according to the intake air pressure as a pressure signal. The pressure sensor 26 may also output a frequency signal obtained by digitally converting the voltage signal as a pressure signal. As the intake air pressure increases, the voltage change becomes larger, so the voltage applied to the strain gauges can be converted to intake air pressure. The intake air volume is calculated from the intake air pressure obtained from the pressure signal.

[0032] As mentioned above, the intake air volume is calculated directly from the flow rate signal, while it is calculated indirectly from the pressure signal. Therefore, the intake air volume calculated based on the flow rate signal is more responsive to changes in actual airflow than the intake air volume calculated based on the pressure signal.

[0033] In each cylinder of the internal combustion engine 10, pulsation occurs within the intake piping 14 due to the opening and closing of the intake valve, blow-by gas recirculation, etc. During low to medium load operation of the internal combustion engine 10, the throttle valve opening is relatively small, and the pulsation is relatively small. However, during high load operation of the internal combustion engine 10, the throttle valve opening is relatively large, and the pulsation increases. Due to its structure, the airflow meter 24 has low sensitivity to the reverse flow component of the airflow rate, and in operating ranges where pulsation is relatively large, the accuracy of the intake air volume calculated based on the flow rate signal decreases.

[0034] In the range where the throttle valve opening is relatively large, the change in intake air volume is small in response to the change in throttle valve opening. Therefore, during high-load operation of the internal combustion engine 10, the accuracy of the intake air volume calculated based on the pressure signal is relatively higher than the accuracy of the intake air volume calculated based on the flow rate signal.

[0035] In the first embodiment, when the throttle valve opening is less than a predetermined opening and the internal combustion engine 10 is operating at a medium to low load, the intake air volume calculation unit 46 calculates the intake air volume based on the flow rate signal. On the other hand, when the throttle valve opening is greater than or equal to a predetermined opening and the internal combustion engine 10 is operating at a high load, the intake air volume calculation unit 46 calculates the intake air volume based on the pressure signal. The predetermined opening is set according to the rotational speed of the internal combustion engine 10, as shown in Figure 3.

[0036] [Regarding catalyst protection control] In the first embodiment, air volume limiting control is performed as catalyst protection control. By performing air volume limiting control, the exhaust temperature is prevented from exceeding the heat resistance temperature of the catalyst and other components.

[0037] In air volume limiting control, the intake air volume is limited so that the exhaust temperature falls below a first predetermined temperature or a second predetermined temperature. The control unit 54 controls the throttle valve 22 according to the intake air volume calculated by the intake air volume calculation unit 46.

[0038] Because the intake air volume calculated by the intake air volume calculation unit 46 contains errors, the first predetermined temperature and the second predetermined temperature are set to temperatures lower than the heat resistance temperature. As mentioned above, during high-load operation of the internal combustion engine 10, the accuracy of the intake air volume calculated based on the pressure signal is relatively higher than the accuracy of the intake air volume calculated based on the flow rate signal. Therefore, the second predetermined temperature is set to a temperature higher than the first predetermined temperature. As a result, the difference between the heat resistance temperature and the second predetermined temperature becomes smaller than the difference between the heat resistance temperature and the first predetermined temperature.

[0039] In the flow rate signal region, catalyst protection control is performed based on the exhaust temperature reaching a first predetermined temperature, and in the pressure signal region, catalyst protection control is performed based on the exhaust temperature reaching a second predetermined temperature higher than the first predetermined temperature. In other words, in the flow rate signal region, catalyst protection control is not performed until the exhaust temperature reaches the first predetermined temperature, and in the pressure signal region, catalyst protection is not performed until the exhaust temperature reaches a second predetermined temperature higher than the first predetermined temperature. During high-load operation of the internal combustion engine 10, the system enters the pressure signal region, which helps to suppress the output reduction of the internal combustion engine 10 when the driver demands high output.

[0040] In the flow rate signal region, catalyst protection control may be performed before the exhaust temperature reaches a first predetermined temperature to prevent the exhaust temperature from reaching the first predetermined temperature. Similarly, in the pressure signal region, catalyst protection control may be performed before the exhaust temperature reaches a second predetermined temperature to prevent the exhaust temperature from reaching the second predetermined temperature.

[0041] [Throttle valve opening control] Figure 4 is a flowchart of throttle valve opening control in the first embodiment. Throttle valve opening control is performed by the control device 36 at predetermined intervals while the internal combustion engine 10 is running.

[0042] In step S1, the intake air volume calculation unit 46 determines whether the throttle valve opening is less than a predetermined opening. If it is determined that the throttle valve opening is less than a predetermined opening (step S1: YES), the process proceeds to step S2.

[0043] In step S2, the flow rate signal acquisition unit 42 acquires a flow rate signal from the air flow meter 24. Then, the process proceeds to step S3.

[0044] In step S3, the intake air volume calculation unit 46 calculates the intake air volume based on the flow rate signal. Then, the process proceeds to step S4.

[0045] In step S4, the exhaust temperature acquisition unit 48 acquires the exhaust temperature. Then, the process proceeds to step S5.

[0046] In step S5, the control unit 54 determines whether the exhaust temperature is higher than the first predetermined temperature.

[0047] If it is determined in step S1 that the throttle valve opening is greater than or equal to a predetermined opening (step S1: NO), the process proceeds to step S6.

[0048] In step S6, the pressure signal acquisition unit 44 acquires a pressure signal from the pressure sensor 26. Then, the process proceeds to step S7.

[0049] In step S7, the intake air volume calculation unit 46 calculates the intake air volume based on the pressure signal. Then, the process proceeds to step S8.

[0050] In step S8, the exhaust temperature acquisition unit 48 acquires the exhaust temperature from the temperature sensor 30. Then, the process proceeds to step S9.

[0051] In step S9, the control unit 54 determines whether the exhaust temperature is higher than the second predetermined temperature.

[0052] If it is determined in step S5 that the exhaust temperature is higher than the first predetermined temperature (step S5: YES), or if it is determined in step S9 that the exhaust temperature is higher than the second predetermined temperature (step S9: YES), the process proceeds to step S10.

[0053] In step S10, the control unit 54 performs catalyst protection control. Catalyst protection control refers to the air volume limiting control described above.

[0054] If it is determined in step S5 that the exhaust temperature is below the first predetermined temperature (step S5: NO), or if it is determined in step S9 that the exhaust temperature is below the second predetermined temperature (step S9: NO), the process proceeds to step S11.

[0055] In step S11, the requested opening degree calculation unit 52 obtains the requested opening degree. Then, the process proceeds to step S12.

[0056] In step S12, the control unit 54 controls the throttle valve 22 based on the requested opening.

[0057] [Effects and Effects] Figures 5 to 7 are graphs showing the changes in accelerator pedal opening, exhaust temperature, air-fuel ratio (λ), and intake air volume over time. The rotational speed of the internal combustion engine 10 remains constant over the time range shown on the horizontal axis of Figures 5 to 7. The graphs in Figures 5 to 7 schematically illustrate the changes in exhaust temperature, air-fuel ratio (λ), and intake air volume.

[0058] In the range from time t0 to time t1, the accelerator pedal opening is less than A1[%], and at this time the throttle valve opening is less than a predetermined opening. In the range from time t0 to time t1, the intake air volume calculation unit 46 calculates the intake air volume based on the flow rate signal (flow rate signal region). In the range from time t1 onward, the accelerator pedal opening is A1[%] or greater, and at this time the throttle valve opening is greater than or equal to a predetermined opening. In the range from time t1 onward, the intake air volume calculation unit 46 calculates the intake air volume based on the pressure signal (pressure signal region).

[0059] The graph in Figure 5 shows the changes in accelerator pedal opening, exhaust temperature, air-fuel ratio (λ), and intake air volume when catalyst protection control is performed in the first comparative example.

[0060] In the catalyst protection control of the first comparative example, rich control and air volume limiting control are performed. In the catalyst protection control of the first comparative example, rich control is initiated based on the exhaust temperature reaching a first predetermined temperature, regardless of whether it is in the flow signal region or the pressure signal region. In the example shown in Figure 5, rich control is initiated at time t2 [s] when the exhaust temperature reaches the first predetermined temperature in the pressure signal region. In rich control, the air-fuel ratio is adjusted from λ=1 to, for example, λ=0.8 so that the exhaust temperature does not exceed the first predetermined temperature. Air volume limiting control is initiated at time t3 when the air-fuel ratio reaches λ=0.8.

[0061] The graph in Figure 6 shows the changes in accelerator pedal opening, exhaust temperature, air-fuel ratio (λ), and intake air volume when catalyst protection control is performed in the second comparative example.

[0062] In the catalyst protection control of the second comparative example, only air volume limiting control is performed. In the catalyst protection control of the first comparative example, regardless of whether it is in the flow rate signal region or the pressure signal region, air volume limiting control is started based on the exhaust temperature reaching a first predetermined temperature. In the example shown in Figure 6, in the pressure signal region, air volume limiting control is started at time t2 [s] when the exhaust temperature reaches the first predetermined temperature.

[0063] In the first comparative example, air volume limiting control is initiated at time t3. On the other hand, in the second comparative example, air volume limiting control is initiated at time t2, which is earlier than time t3. Therefore, in the second comparative example, the period during which air volume limiting control is performed is longer compared to the first comparative example, and the period during which the output of the internal combustion engine 10 is limited is prolonged.

[0064] The graph in Figure 7 shows the changes in accelerator pedal opening, exhaust temperature, air-fuel ratio (λ), and intake air volume when the catalyst protection control of the first embodiment is performed.

[0065] In the catalyst protection control of the first embodiment, only air volume limiting control is performed. In the catalyst protection control of the first embodiment, if it is in the flow rate signal region, air volume limiting control is started based on the exhaust temperature reaching a first predetermined temperature, and if it is in the pressure signal region, air volume limiting control is started based on the exhaust temperature reaching a second predetermined temperature. In the example shown in Figure 7, in the pressure signal region, air volume limiting control is started at time t4 [s] when the exhaust temperature reaches the second predetermined temperature.

[0066] In the second comparative example, air volume limiting control is initiated at time t2. On the other hand, in the first embodiment, air volume limiting control is initiated at time t4, which is later than time t2. Therefore, in the first embodiment, the period during which air volume limiting control is performed can be shortened compared to the second comparative example, and the period during which the output of the internal combustion engine 10 is limited can be shortened. In addition, the operating range in which the output of the internal combustion engine 10 is limited can be reduced.

[0067] [Second Embodiment] Figure 8 is a graph showing the relationship between the throttle valve opening and the output torque of the internal combustion engine 10 in the second embodiment. As shown in Figure 8, the amount of change in output torque decreases as the throttle valve opening increases. In the range where the throttle valve opening is T1 [deg] or greater, the output torque does not change significantly with respect to changes in the throttle valve opening.

[0068] Figure 9 is a map of the target throttle valve opening relative to the requested opening in the second embodiment. In the range where the throttle valve opening is greater than or equal to opening T1[deg], the response of output torque to the throttle valve opening is small, making it difficult to control the output torque by the throttle valve opening. In the second embodiment, if the requested opening determined based on the accelerator pedal opening is greater than or equal to opening T1[deg] and less than opening T_max[deg], the target throttle valve opening is set to opening T1[deg]. Also, if the requested opening is opening T_max[deg], the target throttle valve opening is set to opening T_max[deg]. Opening T_max[deg] indicates that the throttle valve opening is fully open.

[0069] Furthermore, even in hybrid vehicles where both the output torque of the internal combustion engine and the output torque of the drive motor are used as driving force, the relationship between the throttle valve opening and the output torque of the internal combustion engine is equivalent to the relationship shown in Figure 8.

[0070] Figure 10 is a map showing the flow rate signal region and the pressure signal region in the second embodiment. The map in Figure 10 is the same as the map in Figure 3, but the map in Figure 10 shows the opening degree T1 [deg]. The opening degree T1 [deg] is set according to the rotational speed of the internal combustion engine 10, as shown in Figure 10.

[0071] As shown in Figure 10, the opening degree T1[deg] is set to a value smaller than a predetermined opening degree. Therefore, in the second embodiment, the pressure signal region is reached only when the throttle valve opening degree is fully open, which is the opening degree T_max[deg].

[0072] [Throttle valve opening control] Figure 11 is a flowchart of throttle valve opening control in the second embodiment. Throttle valve opening control is performed by the control device 36 at predetermined intervals while the internal combustion engine 10 is running.

[0073] In step S21, the intake air volume calculation unit 46 determines whether the throttle valve opening is less than a predetermined opening. If it is determined that the throttle valve opening is less than a predetermined opening (step S21: YES), the process proceeds to step S22.

[0074] In step S22, the requested opening degree calculation unit 52 determines whether the requested opening degree is fully open or not. If it is determined that the requested opening degree is not fully open (step S22: NO), the process proceeds to step S23.

[0075] In step S23, the flow rate signal acquisition unit 42 acquires a flow rate signal from the air flow meter 24. Then, the process proceeds to step S24.

[0076] In step S24, the intake air volume calculation unit 46 calculates the intake air volume based on the flow rate signal. Then, the process proceeds to step S25.

[0077] In step S25, the requested opening degree calculation unit 52 obtains the requested opening degree. Then, the process proceeds to step S26.

[0078] In step S26, the exhaust temperature acquisition unit 48 acquires the exhaust temperature. Then, the process proceeds to step S27.

[0079] In step S27, the control unit 54 determines whether the exhaust temperature is greater than the first predetermined temperature.

[0080] If, in step S21, it is determined that the throttle valve opening is greater than or equal to a predetermined opening (step S21: NO), or if, in step S22, it is determined that the requested opening is fully open (step S22: YES), the process proceeds to step S28.

[0081] In step S28, the pressure signal acquisition unit 44 acquires a pressure signal from the pressure sensor 26. Then, the process proceeds to step S29.

[0082] In step S29, the intake air volume calculation unit 46 calculates the intake air volume based on the pressure signal. Then, the process proceeds to step S30.

[0083] In step S30, the exhaust temperature acquisition unit 48 acquires the exhaust temperature. Then, the process proceeds to step S31.

[0084] In step S31, the control unit 54 determines whether the exhaust temperature is greater than the second predetermined temperature.

[0085] If it is determined in step S27 that the exhaust temperature is greater than the first predetermined temperature (step S27: YES), or if it is determined in step S31 that the exhaust temperature is greater than the second predetermined temperature (step S31: YES), the process proceeds to step S32.

[0086] In step S32, the control unit 54 performs catalyst protection control. Catalyst protection control refers to the air volume limiting control described above.

[0087] If it is determined in step S27 that the exhaust temperature is below the first predetermined temperature (step S27: NO), or if it is determined in step S31 that the exhaust temperature is below the second predetermined temperature (step S31: NO), the process proceeds to step S33.

[0088] In step S33, the requested opening degree calculation unit 52 obtains the requested opening degree. Then, the process proceeds to step S34.

[0089] In step S34, the control unit 54 controls the throttle valve 22 based on the requested opening degree.

[0090] In the second embodiment, even if the throttle valve opening is less than a predetermined opening and is in the flow signal region, if the requested opening is fully open, the exhaust temperature at which catalyst protection control is initiated is set to a second predetermined temperature. The change in throttle valve opening is slightly delayed in response to the change in the requested opening. However, if the requested opening is fully open, the throttle valve opening quickly becomes greater than or equal to the predetermined opening and enters the pressure signal region. Therefore, even if it is in the flow signal region, if the requested opening is fully open, the intake air flow rate is calculated based on the pressure signal, and the exhaust temperature at which catalyst protection control is initiated is set to a second predetermined temperature. This shortens the period during which air volume limiting control is performed, and shortens the period during which the output of the internal combustion engine 10 is limited. It also reduces the operating range in which the output of the internal combustion engine 10 is limited.

[0091] In the flow rate signal region, catalyst protection control may be performed before the exhaust temperature reaches a first predetermined temperature to prevent the exhaust temperature from reaching the first predetermined temperature. Similarly, in the pressure signal region, catalyst protection control may be performed before the exhaust temperature reaches a second predetermined temperature to prevent the exhaust temperature from reaching the second predetermined temperature. Furthermore, even in the flow rate signal region, if the required opening is fully open, the intake air flow rate may be calculated based on the pressure signal, and catalyst protection control may be performed before the exhaust temperature reaches a second predetermined temperature to prevent the exhaust temperature from reaching the second predetermined temperature.

[0092] The following additional information is disclosed regarding the above embodiment.

[0093] (Note 1) The control device (36) for the internal combustion engine (10) of this disclosure includes: a flow rate signal acquisition unit (42) that acquires a flow rate signal from an air flow meter (24) that changes according to the air flow rate in the intake pipe (14) of the internal combustion engine; a pressure signal acquisition unit (44) that acquires a pressure signal from a pressure sensor (26) that changes according to the pressure in the intake pipe; an intake air amount calculation unit (46) that calculates the intake air amount, which is the amount of air the internal combustion engine inhales, based on the flow rate signal or the pressure signal; an exhaust temperature acquisition unit (48) that acquires the exhaust temperature of the internal combustion engine; and a catalyst that limits the intake air amount to protect the catalyst (28). The system includes a control unit (54) that performs protective control by adjusting the throttle valve opening. When the intake air volume is calculated by the intake air volume calculation unit based on the flow rate signal, the control unit performs the catalyst protection control based on the exhaust temperature acquired by the exhaust temperature acquisition unit and a first predetermined temperature. When the intake air volume is calculated by the intake air volume calculation unit based on the pressure signal, the control unit performs the catalyst protection control based on the exhaust temperature acquired by the exhaust temperature acquisition unit and a second predetermined temperature different from the first predetermined temperature. This makes it possible to differentiate the timing at which catalyst protection control is started when the intake air volume is calculated based on the flow rate signal and the timing at which catalyst protection is started when the intake air volume is calculated based on the pressure signal.

[0094] (Note 2) In the control device for an internal combustion engine described in Appendix 1, if the intake air amount is calculated by the intake air amount calculation unit based on the flow rate signal, the control unit may perform the catalyst protection control if the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the first predetermined temperature. If the intake air amount is calculated by the intake air amount calculation unit based on the pressure signal, the control unit may perform the catalyst protection control if the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the second predetermined temperature.

[0095] (Note 3) In the control device for an internal combustion engine described in Appendix 1, if the intake air amount is calculated by the intake air amount calculation unit based on the flow rate signal, the control unit may reduce the exhaust temperature to the first predetermined temperature or lower by performing the catalyst protection control. If the intake air amount is calculated by the intake air amount calculation unit based on the pressure signal, the control unit may reduce the exhaust temperature to the second predetermined temperature or lower by performing the catalyst protection control.

[0096] (Note 4) In the control device for an internal combustion engine described in Appendix 1 or 2, if the throttle valve opening is less than a predetermined opening, the intake air amount calculation unit may calculate the intake air amount based on the flow rate signal, and if the throttle valve opening is equal to or greater than the predetermined opening, the intake air amount calculation unit may calculate the intake air amount based on the pressure signal.

[0097] (Note 5) In the control device for an internal combustion engine described in Appendix 1 or 2, the second predetermined temperature may be higher than the first predetermined temperature.

[0098] (Note 6) In the control device for an internal combustion engine described in Appendix 1 or 2, the control device further includes a requested opening degree acquisition unit (50) that acquires a requested opening degree, which is a requested value for the throttle valve opening degree. When the requested opening degree is fully open, the intake air amount calculation unit calculates the intake air amount based on the pressure signal. The control unit may perform the catalyst protection control based on the exhaust temperature and the second predetermined temperature, even if the air amount is calculated based on the flow rate signal.

[0099] (Note 7) The control method for an internal combustion engine according to this disclosure includes: a signal acquisition step in which a flow rate signal acquisition unit acquires a flow rate signal that changes according to the airflow rate in the intake pipe of the internal combustion engine from an airflow meter, or a pressure signal acquisition unit acquires a pressure signal that changes according to the pressure in the intake pipe from a pressure sensor; an intake air amount calculation step in which an intake air amount calculation unit calculates the amount of air that the internal combustion engine inhales based on the flow rate signal or the pressure signal; an exhaust temperature acquisition step in which an exhaust temperature acquisition unit acquires the exhaust temperature of the internal combustion engine; and a catalyst protection control that limits the intake air amount in order to protect the catalyst. The control includes a control step performed by the control unit by adjusting the throttle valve opening, wherein when the intake air amount is calculated by the intake air amount calculation unit based on the flow rate signal, the control unit performs the catalyst protection control based on the exhaust temperature acquired by the exhaust temperature acquisition unit and a first predetermined temperature, and when the intake air amount is calculated by the intake air amount calculation unit based on the pressure signal, the control unit performs the catalyst protection control based on the exhaust temperature acquired by the exhaust temperature acquisition unit and a second predetermined temperature different from the first predetermined temperature.

[0100] (Note 8) In the control method for an internal combustion engine described in Appendix 7, if the intake air amount is calculated by the intake air amount calculation unit based on the flow rate signal, the control unit may perform the catalyst protection control if the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the first predetermined temperature. If the intake air amount is calculated by the intake air amount calculation unit based on the pressure signal, the control unit may perform the catalyst protection control if the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the second predetermined temperature.

[0101] (Note 9) In the control method for an internal combustion engine described in Appendix 7, if the intake air amount is calculated by the intake air amount calculation unit based on the flow rate signal, the control unit may reduce the exhaust temperature to the first predetermined temperature or lower by performing the catalyst protection control. If the intake air amount is calculated by the intake air amount calculation unit based on the pressure signal, the control unit may reduce the exhaust temperature to the second predetermined temperature or lower by performing the catalyst protection control.

[0102] (Note 10) In the control method for an internal combustion engine described in Appendix 7, if the throttle valve opening is less than a predetermined opening, the intake air amount calculation unit may calculate the intake air amount based on the flow rate signal, and if the throttle valve opening is equal to or greater than the predetermined opening, the intake air amount calculation unit may calculate the intake air amount based on the pressure signal.

[0103] (Note 11) In the control method for an internal combustion engine described in Appendix 7, the second predetermined temperature may be higher than the first predetermined temperature.

[0104] (Note 12) In the control method for an internal combustion engine described in Appendix 7, the method further includes a requested opening step in which a requested opening unit acquires a requested opening, which is a required value for the throttle valve opening. If the requested opening is fully open, the intake air volume calculation unit calculates the intake air volume based on the pressure signal. The control unit may perform catalyst protection control based on the exhaust temperature and the second predetermined temperature, even if the air volume is calculated based on the flow rate signal.

[0105] (Note 13) The program of this disclosure causes a computer to execute the control method for an internal combustion engine described in any one of the appendices 7 to 12.

[0106] (Note 14) The computer-readable, non-transient storage medium of this disclosure stores the program described in Appendix 13.

[0107] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the intent of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of Symbols]

[0108] 10...Internal combustion engine 14...Intake piping 24…Airflow meter 26…Pressure sensor 28...Catalyst 36...Control device 42...Flow rate signal acquisition unit 44...Pressure signal acquisition unit 46...Intake air volume calculation unit 48...Exhaust temperature acquisition unit 50...Requested opening degree acquisition unit 54...Control unit

Claims

1. A flow signal acquisition unit that acquires a flow signal from an airflow meter that changes according to the airflow rate in the intake piping of an internal combustion engine, A pressure signal acquisition unit that acquires a pressure signal from a pressure sensor that changes according to the pressure in the intake pipe, An intake air amount calculation unit calculates the intake air amount, which is the amount of air that the internal combustion engine inhales, based on the flow rate signal or the pressure signal. An exhaust temperature acquisition unit for acquiring the exhaust temperature of the internal combustion engine, A control unit that performs catalyst protection control by adjusting the throttle valve opening to limit the amount of intake air in order to protect the catalyst, Equipped with, When the intake air volume is calculated by the intake air volume calculation unit based on the flow rate signal, the control unit performs catalyst protection control based on the exhaust temperature obtained by the exhaust temperature acquisition unit and the first predetermined temperature. When the intake air volume is calculated by the intake air volume calculation unit based on the pressure signal, the control unit performs catalyst protection control based on the exhaust temperature acquired by the exhaust temperature acquisition unit and a second predetermined temperature different from the first predetermined temperature, in a control device for an internal combustion engine.

2. In the control device for an internal combustion engine according to claim 1, When the intake air volume is calculated by the intake air volume calculation unit based on the flow rate signal, the control unit performs the catalyst protection control if the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the first predetermined temperature. A control device for an internal combustion engine, wherein, when the intake air amount is calculated by the intake air amount calculation unit based on the pressure signal, the control unit performs catalyst protection control if the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the second predetermined temperature.

3. In the control device for an internal combustion engine according to claim 1, When the intake air volume is calculated by the intake air volume calculation unit based on the flow rate signal, the control unit performs catalyst protection control to reduce the exhaust temperature to below the first predetermined temperature. When the intake air volume is calculated by the intake air volume calculation unit based on the pressure signal, the control unit performs catalyst protection control to reduce the exhaust temperature to the second predetermined temperature or lower, thereby controlling the exhaust temperature of an internal combustion engine.

4. In the control device for an internal combustion engine according to claim 1 or 2, If the throttle valve opening is less than a predetermined opening, the intake air volume calculation unit calculates the intake air volume based on the flow rate signal. A control device for an internal combustion engine, wherein when the throttle valve opening is greater than or equal to the predetermined opening, the intake air volume calculation unit calculates the intake air volume based on the pressure signal.

5. In the control device for an internal combustion engine according to claim 1 or 2, A control device for an internal combustion engine, wherein the second predetermined temperature is higher than the first predetermined temperature.

6. In the control device for an internal combustion engine according to claim 1 or 2, The system further includes a requested opening degree acquisition unit that acquires a requested opening degree, which is a requested value for the throttle valve opening degree. A control device for an internal combustion engine, wherein when the requested opening is fully open, the intake air volume calculation unit calculates the intake air volume based on the pressure signal, and the control unit performs catalyst protection control based on the exhaust temperature and the second predetermined temperature, even when the air volume is calculated based on the flow rate signal.

7. A signal acquisition step in which a flow rate signal acquisition unit acquires a flow rate signal that changes according to the airflow rate in the intake piping of an internal combustion engine from an airflow meter, or a pressure signal acquisition unit acquires a pressure signal that changes according to the pressure in the intake piping from a pressure sensor, An intake air amount calculation step in which the intake air amount calculation unit calculates the intake air amount, which is the amount of air that the internal combustion engine inhales, based on the flow rate signal or the pressure signal, An exhaust temperature acquisition step in which the exhaust temperature acquisition unit acquires the exhaust temperature of the internal combustion engine, A control step in which the control unit performs catalyst protection control by adjusting the throttle valve opening to limit the amount of intake air in order to protect the catalyst, It has, When the intake air volume is calculated by the intake air volume calculation unit based on the flow rate signal, the control unit performs catalyst protection control based on the exhaust temperature obtained by the exhaust temperature acquisition unit and the first predetermined temperature. A control method for an internal combustion engine, wherein, when the intake air amount is calculated by the intake air amount calculation unit based on the pressure signal, the control unit performs catalyst protection control based on the exhaust temperature acquired by the exhaust temperature acquisition unit and a second predetermined temperature different from the first predetermined temperature.

8. In the control method for an internal combustion engine according to claim 7, When the intake air volume is calculated by the intake air volume calculation unit based on the flow rate signal, the control unit performs the catalyst protection control if the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the first predetermined temperature. A control method for an internal combustion engine, wherein, when the intake air amount is calculated by the intake air amount calculation unit based on the pressure signal, the control unit performs the catalyst protection control if the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the second predetermined temperature.

9. In the control method for an internal combustion engine according to claim 7, When the intake air volume is calculated by the intake air volume calculation unit based on the flow rate signal, the control unit performs catalyst protection control to reduce the exhaust temperature to below the first predetermined temperature. A control method for an internal combustion engine, wherein, when the intake air volume is calculated by the intake air volume calculation unit based on the pressure signal, the control unit performs catalyst protection control to reduce the exhaust temperature to the second predetermined temperature or lower.

10. In the control method for an internal combustion engine according to claim 7, If the throttle valve opening is less than a predetermined opening, the intake air volume calculation unit calculates the intake air volume based on the flow rate signal. A control method for an internal combustion engine, wherein, when the throttle valve opening is greater than or equal to a predetermined opening, the intake air volume calculation unit calculates the intake air volume based on the pressure signal.

11. In the control method for an internal combustion engine according to claim 7, A control method for an internal combustion engine, wherein the second predetermined temperature is higher than the first predetermined temperature.

12. In the control method for an internal combustion engine according to claim 7, The system further includes a requested opening degree acquisition step in which a requested opening degree acquisition unit acquires a requested opening degree, which is a requested value for the throttle valve opening degree. A control method for an internal combustion engine, wherein when the requested opening is fully open, the intake air volume calculation unit calculates the intake air volume based on the pressure signal, and the control unit performs catalyst protection control based on the exhaust temperature and the second predetermined temperature, even when the air volume is calculated based on the flow rate signal.

13. A program that causes a computer to execute the control method for an internal combustion engine described in any one of claims 7 to 12.

14. A computer-readable, non-transient storage medium storing the program described in claim 13.

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