Control device of internal combustion engine, control method of internal combustion engine, computer program product, and storage medium

Abstract

This invention provides a control device for an internal combustion engine, a control method for an internal combustion engine, a computer program product, and a storage medium. When the intake air volume is calculated based on a flow rate signal, the control device (36) of the internal combustion engine (10) performs catalyst protection control to limit the intake air volume based on the exhaust temperature and a first predetermined temperature to protect the catalyst. When the intake air volume is calculated based on a pressure signal, the control device (36) of the internal combustion engine (10) performs catalyst protection control based on the exhaust temperature and a second predetermined temperature different from the first predetermined temperature. Accordingly, the timing of initiating catalyst protection control when the intake air volume is calculated based on a flow rate signal is different from the timing of initiating catalyst protection when the intake air volume is calculated based on a pressure signal.

Description

Technical Field

[0001] This invention relates to a control device for an internal combustion engine, a control method for an internal combustion engine, a computer program product, and a storage medium. Background Technology

[0002] Japanese Patent Publication No. 2020-12387 discloses an engine control device. When it is determined that the engine is not in a state of large intake pulsation, the engine control device calculates the intake volume based on the intake flow rate detected by an air flow meter. Conversely, when it is determined that the engine is in a state of large intake pulsation, the engine control device calculates the intake volume based on the intake manifold pressure. Summary of the Invention

[0003] For a long time, relevant measures have been continuously implemented to mitigate or reduce the impact of climate change. In order to achieve this goal, research and development of exhaust gas purification devices are underway.

[0004] Furthermore, in exhaust gas purification devices, there is a desire for a better internal combustion engine control device, a better internal combustion engine control method, a program for executing the better internal combustion engine control method on a computer, and a storage medium storing the program for executing the better internal combustion engine control method on a computer. To solve the above-mentioned technical problems, the present invention aims to provide a better internal combustion engine control device, a better internal combustion engine control method, a program for executing the better internal combustion engine control method on a computer, and a storage medium storing the program for executing the better internal combustion engine control method on a computer. Ultimately, this will help mitigate or reduce the impacts of climate change.

[0005] The first aspect of the present invention is a control device for an internal combustion engine, comprising a flow signal acquisition unit, a pressure signal acquisition unit, an intake air volume calculation unit, an exhaust temperature acquisition unit, and a control unit. The flow signal acquisition unit acquires a flow signal from an air flow meter that varies according to the air flow rate in the intake manifold of the internal combustion engine; the pressure signal acquisition unit acquires a pressure signal from a pressure sensor that varies according to the pressure in the intake manifold; the intake air volume calculation unit calculates the amount of air drawn into the internal combustion engine, i.e., the intake air volume, based on the flow signal or the pressure signal; the exhaust temperature acquisition unit acquires the exhaust temperature of the internal combustion engine; and the control unit... The throttle opening is adjusted to limit the amount of intake air for catalyst protection control. When the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, the control unit performs catalyst protection control based on the exhaust temperature obtained 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 catalyst protection control based on the exhaust temperature obtained by the exhaust temperature acquisition unit and a second predetermined temperature different from the first predetermined temperature.

[0006] The second aspect of the present invention is a control method for an internal combustion engine, comprising a signal acquisition step, an intake air volume calculation step, an exhaust temperature acquisition step, and a control step. In the signal acquisition step, a flow signal acquisition unit acquires a flow signal that varies according to the air flow rate in the intake manifold of the internal combustion engine from an air flow meter, or a pressure signal acquisition unit acquires a pressure signal that varies according to the pressure in the intake manifold from a pressure sensor. In the intake air volume calculation step, an intake air volume calculation unit calculates the amount of air drawn into the internal combustion engine, i.e., the intake air volume, based on the flow signal or the pressure signal. In the exhaust temperature acquisition step, an exhaust temperature acquisition unit acquires the exhaust temperature of the internal combustion engine. Temperature; In the control step, the control unit performs catalyst protection control by adjusting the throttle opening to limit the intake air volume, thereby protecting the catalyst. When the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, the control unit performs catalyst protection control based on the exhaust temperature obtained 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 catalyst protection control based on the exhaust temperature obtained by the exhaust temperature acquisition unit and a second predetermined temperature different from the first predetermined temperature.

[0007] The third aspect of the present invention is a program that causes a computer to execute the control method of the internal combustion engine of the second aspect.

[0008] The fourth aspect of the present invention is a computer-readable non-transitory storage medium storing the program of the third aspect.

[0009] According to the present invention, a better control device for an internal combustion engine, a better control method for an internal combustion engine, a program for a computer to execute the better control method for an internal combustion engine, and a storage medium storing the program for a computer to execute the better control method for an internal combustion engine can be provided.

[0010] The above-described objectives, features, and advantages should be readily understood through the description of the following embodiments with reference to the accompanying drawings. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the internal combustion engine and intake / exhaust system in the first embodiment.

[0012] Figure 2 This is a block diagram showing the structure of the control device in the first embodiment.

[0013] Figure 3 This is a mapping diagram showing the flow signal region and pressure signal region in the calculation of the intake air volume in the first embodiment.

[0014] Figure 4 This is a flowchart of throttle opening control in the first embodiment.

[0015] Figure 5 It is a graph showing the changes in accelerator pedal opening over time, exhaust temperature over time, air-fuel ratio (λ) over time, and intake air volume over time.

[0016] Figure 6 It is a graph showing the changes in accelerator pedal opening over time, exhaust temperature over time, air-fuel ratio (λ) over time, and intake air volume over time.

[0017] Figure 7 It is a graph showing the changes in accelerator pedal opening over time, exhaust temperature over time, air-fuel ratio (λ) over time, and intake air volume over time.

[0018] Figure 8 It is a graph showing the relationship between the throttle opening and the output torque of the internal combustion engine in the second embodiment.

[0019] Figure 9 This is a mapping diagram showing the target throttle opening relative to the required opening in the second embodiment.

[0020] Figure 10 This is a mapping diagram representing the flow signal region and the pressure signal region in the second embodiment.

[0021] Figure 11 This is a flowchart of throttle opening control in the second embodiment. Detailed Implementation

[0022] In many gasoline vehicles, under high load operation, a control mechanism is implemented to maintain the air-fuel mixture in a state richer than the stoichiometric air-fuel ratio (stoichiometric ratio, λ=1) (rich fuel, λ=0.8, hereinafter referred to as rich control). This is achieved by vaporizing the fuel within the cylinders of the internal combustion engine to absorb heat, thereby maintaining high output while ensuring that the exhaust gas temperature (hereinafter referred to as exhaust temperature) does not exceed the heat resistance temperature of the catalyst, etc.

[0023] However, rich-fuel control presents the problem of increased exhaust gas volume due to the large amount of fuel input. Furthermore, rich-fuel control deviates the stoichiometric ratio from the standard stoichiometric ratio, thus reducing the redox efficiency of the three-way catalytic converter. Therefore, from the perspective of exhaust gas purification, operation at the stoichiometric ratio is required even under high-load conditions.

[0024] As a control that protects catalysts and other components by suppressing exhaust temperature (hereinafter referred to as catalyst protection control), there exists a control that limits the amount of air drawn into the internal combustion engine by reducing the throttle opening (hereinafter referred to as intake air volume) (hereinafter referred to as air volume limiting control). However, while maintaining the stoichiometric ratio, as the air volume limiting control restricts the intake air volume, the fuel injection quantity is also limited, and therefore, the output of the internal combustion engine is also limited.

[0025] There is a need to shorten the period during which air volume restriction control, as a catalytic converter protection measure, is applied, and to shorten the period during which the internal combustion engine's output is restricted. Additionally, there is a need to narrow the operating range in which the internal combustion engine's output is restricted.

[0026] In this invention, it is possible to perform air volume restriction control as a means of suppressing exhaust temperature while simultaneously shortening the period during which the output of the internal combustion engine is restricted. Furthermore, it is possible to narrow the operating range in which the output of the internal combustion engine is restricted.

[0027] Hereinafter, the control device, control method, program, and storage medium of the internal combustion engine according to the first and second embodiments will be described with reference to the accompanying drawings.

[0028] The programs (computer programs, computer software) of the first and second embodiments can also be referred to as computer program products. Computer program products are not limited to computer programs stored on storage media, but also include computer programs transmitted, distributed, or downloaded via the Internet or the like.

[0029] [First Embodiment] [Internal combustion engine and intake / exhaust system] Figure 1 This is a schematic diagram of the internal combustion engine 10 and the intake and exhaust system 12 in the first embodiment.

[0030] The internal combustion engine 10 is a gasoline engine. The intake and exhaust system 12 has an intake pipe 14 for drawing in air, an exhaust pipe 16 for expelling the 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.

[0031] An air filter 20, a throttle valve 22, an air flow meter 24, and a pressure sensor 26 are installed on the intake manifold 14. The air filter 20 filters the intake air, removing impurities, dust, etc. The throttle valve 22 adjusts the amount of air (hereinafter referred to as intake air volume) drawn into the intake manifold 14 according to the driver's desired opening degree. The air flow meter 24 is located between the air filter 20 and the throttle valve 22. Furthermore, the air flow meter 24 is positioned upstream (on the air filter 20 side) of the connection point of the EGR pipe 18 relative to the intake manifold 14. The air flow meter 24 outputs a flow signal that varies according to the air flow rate within the intake manifold 14. The pressure sensor 26 is positioned downstream (on the internal combustion engine 10 side) of the connection point of the EGR pipe 18 relative to the intake manifold 14. The pressure sensor 26 outputs a pressure signal that varies according to the pressure within the intake manifold 14.

[0032] A catalyst 28 and a temperature sensor 30 are installed in the exhaust pipe 16. The catalyst 28 is, for example, a three-way catalyst. The catalyst 28 converts hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), etc., contained in the exhaust gas into water, carbon dioxide, nitrogen, oxygen, etc., by oxidizing or reducing them. The temperature sensor 30 detects the temperature of the exhaust gas (hereinafter referred to as exhaust temperature). The temperature sensor 30 is located upstream of the catalyst 28 (on the side of the internal combustion engine 10).

[0033] An EGR cooler 32 and an EGR valve 34 are provided on the EGR pipe 18. The EGR cooler 32 cools the exhaust gas returning to the intake pipe 14. The EGR valve 34 regulates the amount of exhaust gas returning to the intake pipe 14 according to its opening degree.

[0034] [Control device] Figure 2 This is a block diagram showing the structure of the control device 36 in the first embodiment.

[0035] The control device 36 includes an arithmetic unit 38 and a storage unit 40. The arithmetic unit 38 is, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The arithmetic unit 38 includes a flow signal acquisition unit 42, a pressure signal acquisition unit 44, an intake air volume calculation unit 46, an exhaust temperature acquisition unit 48, a required opening degree acquisition unit 50, and a control unit 54. The flow 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 are implemented by the arithmetic unit 38 executing a program stored in the storage unit 40. At least a portion of the flow 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 can also be implemented using integrated circuits such as ASICs (Application Specific Integrated Circuits) or FPGAs (Field-Programmable Gate Arrays). At least a portion of the flow 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 can also be implemented by electronic circuits including discrete components.

[0036] Storage unit 40 is a computer-readable, non-transitory tangible storage medium. Storage unit 40 comprises volatile memory (not shown) and non-volatile memory (not shown). Volatile memory includes, for example, RAM (Random Access Memory). Non-volatile memory includes, for example, ROM (Read Only Memory), flash memory, etc. Data is stored, for example, in volatile memory. Programs, tables, maps, etc., are stored, for example, in non-volatile memory. At least a portion of storage unit 40 may also be disposed in the aforementioned processor, integrated circuit, etc. At least a portion of storage unit 40 may also be mounted in a device connected to control device 36 via a network.

[0037] The flow signal acquisition unit 42 acquires a flow 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 signal or the pressure signal. The exhaust temperature acquisition unit 48 acquires the exhaust temperature detected by the temperature sensor 30. The exhaust temperature acquisition unit 48 can also acquire an exhaust temperature estimated based on parameters related to the exhaust temperature. Examples of parameters related to the exhaust temperature include the engine speed of the internal combustion engine 10, the intake air volume of the internal combustion engine 10, and the temperature of the cooling water in the internal combustion engine 10. The required opening acquisition unit 50 acquires the opening of the accelerator pedal 58 detected by the accelerator pedal opening sensor 56. The required opening acquisition unit 50 calculates the required value of the throttle opening, i.e., the required opening, based on the opening of the accelerator pedal 58. The control unit 54 controls the throttle valve 22 to adjust the throttle opening. Controlling the throttle valve 22 specifically refers to 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 required opening degree.

[0038] [Calculation of intake air volume] Figure 3 This is a mapping diagram showing the flow signal region and pressure signal region in the first embodiment. The flow signal region refers to the region where the intake air volume calculation unit 46 calculates the intake air volume based on the flow signal. The pressure signal region refers to the region where the intake air volume calculation unit 46 calculates the intake air volume based on the pressure signal. Figure 3 In this context, T_max[deg] represents the throttle opening when it is fully open. T_max[deg] is approximately 80[deg].

[0039] To maintain the stoichiometry, the fuel injection quantity is determined based on the intake air volume, with the air-to-fuel weight ratio in the gas mixture being 14.7:1. Therefore, the intake air volume needs to be calculated with high precision.

[0040] The air flow meter 24 has a thermistor element. The thermistor element is heated to a constant temperature by a heater. Furthermore, a constant current flows through the thermistor element. The resistance of the thermistor element changes due to exposure to the flowing air, thereby causing a change in the voltage applied to the thermistor element. The air flow meter 24 outputs a voltage signal that varies according to the amount of air drawn in as a flow signal. The air flow meter 24 can also output a frequency signal obtained by digitally converting the voltage signal as a flow signal. The greater the amount of air drawn in, the greater the voltage change; therefore, the amount of air drawn in can be calculated from the voltage applied to the thermistor element. That is, the amount of air drawn in can be directly calculated from the flow signal.

[0041] The pressure sensor 26 has a diaphragm with a strain gauge. A constant current flows through the strain gauge. The diaphragm deforms due to air pressure, causing a change in the resistance of the strain gauge, which in turn changes the voltage applied to the strain gauge. The pressure sensor 26 outputs a voltage signal that varies according to the intake air pressure as a pressure signal. The pressure sensor 26 can also output a frequency signal obtained by digitally converting the voltage signal as a pressure signal. The higher the intake air pressure, the greater the voltage change; therefore, the intake air pressure can be calculated from the voltage applied to the strain gauge. The amount of intake air is calculated based on the intake air pressure obtained from the pressure signal.

[0042] As mentioned above, the intake air volume is calculated indirectly based on the pressure signal, rather than directly based on the flow rate signal. Therefore, the intake air volume calculated based on the flow rate signal is more accurate in tracking changes in actual airflow rate compared to the intake air volume calculated based on the pressure signal.

[0043] Each cylinder of the internal combustion engine 10 experiences pulsation within the intake manifold 14 due to the opening and closing of the intake valves and positive crankcase ventilation. When the internal combustion engine 10 operates at low to medium loads, the throttle opening is relatively small, resulting in minimal pulsation. However, when the internal combustion engine 10 operates at high loads, the throttle opening is larger, leading to increased pulsation. Due to its structure, the airflow meter 24 has low sensitivity to the reverse flow component of the airflow; therefore, in operating regions with significant pulsation, the accuracy of the intake air volume calculated from the flow signal decreases.

[0044] In regions with a relatively large throttle opening, the change in intake air volume is smaller relative to changes in throttle opening. Therefore, when the internal combustion engine 10 is operating under high load, the accuracy of the intake air volume calculated based on the pressure signal is higher than the accuracy of the intake air volume calculated based on the flow signal.

[0045] In the first embodiment, when the throttle opening is less than a predetermined opening and the internal combustion engine 10 is operating at low to medium load, the intake air volume calculation unit 46 calculates the intake air volume based on a flow rate signal. On the other hand, when the throttle opening is greater than a predetermined opening and the internal combustion engine 10 is operating at high load, the intake air volume calculation unit 46 calculates the intake air volume based on a pressure signal. Figure 3 As shown, the specified opening degree is set according to the speed of the internal combustion engine 10.

[0046] [Regarding catalyst protection control] In the first embodiment, air volume restriction control is performed as a catalyst protection control. By performing air volume restriction control, the exhaust temperature is prevented from exceeding the heat resistance temperature of the catalyst, etc.

[0047] In air volume restriction control, the intake air volume is restricted to keep the exhaust temperature below a first specified temperature or a second specified temperature. The control unit 54 controls the throttle valve 22 based on the intake air volume calculated by the intake air volume calculation unit 46.

[0048] Because the intake air volume calculated by the intake air volume calculation unit 46 contains errors, the first and second specified temperatures are set to be lower than the heat resistance temperature. As described above, when the internal combustion engine 10 is operating under high load, the accuracy of the intake air volume calculated based on the pressure signal is higher than the accuracy of the intake air volume calculated based on the flow rate signal. Therefore, the second specified temperature is set to be higher than the first specified temperature. Accordingly, the difference between the heat resistance temperature and the second specified temperature is smaller than the difference between the heat resistance temperature and the first specified temperature.

[0049] In the flow signal region, catalyst protection control is performed based on the exhaust temperature reaching a first predetermined temperature. 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 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 the second predetermined temperature higher than the first predetermined temperature. Since the internal combustion engine 10 is in the pressure signal region when operating under high load, it is possible to suppress the reduction in output of the internal combustion engine 10 under conditions of high output demand during driving.

[0050] In the flow signal region, catalyst protection control can also be implemented before the exhaust temperature reaches a first specified temperature to prevent the exhaust temperature from reaching the first specified temperature. Similarly, in the pressure signal region, catalyst protection control can also be implemented before the exhaust temperature reaches a second specified temperature to prevent the exhaust temperature from reaching the second specified temperature.

[0051] [Throttle opening control] Figure 4 This is a flowchart of throttle opening control in the first embodiment. In the control device 36, throttle opening control is performed at predetermined cycles during the driving of the internal combustion engine 10.

[0052] In step S1, the intake air volume calculation unit 46 determines whether the throttle opening is less than the specified opening. If it is determined that the throttle opening is less than the specified opening (step S1: yes), the process proceeds to step S2.

[0053] In step S2, the flow signal acquisition unit 42 acquires a flow signal from the air flow meter 24. After this, the process proceeds to step S3.

[0054] In step S3, the intake air volume calculation unit 46 calculates the intake air volume based on the flow signal. After this, the process proceeds to step S4.

[0055] In step S4, the exhaust temperature acquisition unit 48 acquires the exhaust temperature. After that, the process proceeds to step S5.

[0056] In step S5, the control unit 54 determines whether the exhaust temperature is higher than the first specified temperature.

[0057] If it is determined in step S1 that the throttle opening is above the specified opening (step S1: No), proceed to step S6.

[0058] In step S6, the pressure signal acquisition unit 44 acquires a pressure signal from the pressure sensor 26. After this, the process proceeds to step S7.

[0059] In step S7, the intake air volume calculation unit 46 calculates the intake air volume based on the pressure signal. After this, the process proceeds to step S8.

[0060] In step S8, the exhaust temperature acquisition unit 48 acquires the exhaust temperature from the temperature sensor 30. After this, the process proceeds to step S9.

[0061] In step S9, the control unit 54 determines whether the exhaust temperature is higher than the second specified temperature.

[0062] If it is determined in step S5 that the exhaust temperature is higher than the first specified temperature (step S5: Yes), or if it is determined in step S9 that the exhaust temperature is higher than the second specified temperature (step S9: Yes), proceed to step S10.

[0063] In step S10, the control unit 54 performs catalyst protection control. Catalyst protection control refers to the aforementioned air quantity limitation control.

[0064] If in step S5 it is determined that the exhaust temperature is below the first specified temperature (step S5: No), or in step S9 it is determined that the exhaust temperature is below the second specified temperature (step S9: No), proceed to step S11.

[0065] In step S11, the opening calculation unit 52 is required to obtain the required opening. After this, the process proceeds to step S12.

[0066] In step S12, the control unit 54 controls the throttle valve 22 according to the required opening degree.

[0067] [Effects] Figures 5-7This is a graph showing the changes in accelerator pedal opening over time, exhaust temperature over time, air-fuel ratio (λ) over time, and intake air volume over time. Figures 5-7 Within the time range shown on the horizontal axis, the rotational speed of the internal combustion engine 10 remains constant. Figures 5-7 The graph schematically represents the changes in exhaust temperature, air-fuel ratio (λ), and intake air volume.

[0068] Within the time range from time point t0 to time point t1, the accelerator pedal opening is less than A1 [%], and at this time, the throttle opening is less than the specified opening. Within the time range from time point t0 to time point t1, the intake air volume calculation unit 46 calculates the intake air volume (flow signal area) based on the flow signal. Furthermore, within the time range after time point t1, the accelerator pedal opening reaches or exceeds A1 [%], and at this time, the throttle opening reaches or exceeds the specified opening. Within the time range after time point t1, the intake air volume calculation unit 46 calculates the intake air volume (pressure signal area) based on the pressure signal.

[0069] Figure 5 The graphs represent the changes in throttle pedal opening, exhaust temperature, air-fuel ratio (λ), and intake air volume under the catalyst protection control of the first comparative example.

[0070] In the catalyst protection control of the first comparative example, rich fuel control and air quantity limitation control are performed. In the catalyst protection control of the first comparative example, rich fuel control is initiated based on the exhaust temperature reaching a first predetermined temperature, regardless of whether the flow signal region or pressure signal region is in effect. Figure 5 In the example shown, in the pressure signal region, rich fuel control begins at time point t2 [s] when the exhaust temperature reaches the first specified temperature. In rich fuel control, the air-fuel ratio is adjusted within a range from λ=1, for example, to λ=0.8, so that the exhaust temperature does not exceed the first specified temperature. Air volume restriction control begins at time point t3 when the air-fuel ratio reaches λ=0.8.

[0071] Figure 6 The graphs represent the changes in throttle pedal opening, exhaust temperature, air-fuel ratio (λ), and intake air volume under the catalyst protection control conditions of the second comparative example.

[0072] In the catalyst protection control of the second comparative example, only airflow limitation control is performed. In the catalyst protection control of the first comparative example, airflow limitation control begins when the exhaust temperature reaches a first predetermined temperature, regardless of whether the flow signal region or the pressure signal region is in effect. Figure 6In the example shown, in the pressure signal region, air volume restriction control begins at the time point t2 [s] when the exhaust temperature reaches the first specified temperature.

[0073] In the first comparative example, air volume restriction control begins at time point t3. On the other hand, in the second comparative example, air volume restriction control begins at time point t2, which is earlier than time point t3. Therefore, compared with the first comparative example, the period of air volume restriction control in the second comparative example is longer, and the period during which the output of the internal combustion engine 10 is restricted is also longer.

[0074] Figure 7 The graphs represent the changes in throttle pedal opening, exhaust temperature, air-fuel ratio (λ), and intake air volume under the catalyst protection control of the first embodiment.

[0075] In the catalyst protection control of the first embodiment, only air volume restriction control is performed. In the catalyst protection control of the first embodiment, when in the flow signal region, air volume restriction control begins when the exhaust temperature reaches a first predetermined temperature; when in the pressure signal region, air volume restriction control begins when the exhaust temperature reaches a second predetermined temperature. Figure 7 In the example shown, in the pressure signal region, air volume restriction control begins at the time point t4 [s] when the exhaust temperature reaches the second specified temperature.

[0076] In the second comparative example, air volume restriction control begins at time point t2. On the other hand, in the first embodiment, air volume restriction control begins at time point t4, which is later than time point t2. Therefore, compared to the second comparative example, the period for performing air volume restriction control can be shortened in the first embodiment, thereby shortening the period during which the output of the internal combustion engine 10 is restricted. Furthermore, the operating range where the output of the internal combustion engine 10 is restricted can be narrowed.

[0077] [Second Implementation] Figure 8 This is a graph showing the relationship between the throttle opening and the output torque of the internal combustion engine 10 in the second embodiment. For example... Figure 8 As shown, the larger the throttle opening, the smaller the change in output torque. Within the range where the throttle opening is above opening T1 [deg], the output torque remains roughly unchanged relative to the change in throttle opening.

[0078] Figure 9This is a mapping diagram of the target throttle opening relative to the required opening in the second embodiment. When the throttle opening is above opening T1 [deg], the output torque response to the throttle opening is small, making it difficult to control the output torque through the throttle opening. In the second embodiment, when the required opening, calculated based on the accelerator pedal opening, is above opening T1 [deg] but less than opening T_max [deg], the target throttle opening is set to opening T1 [deg]. Furthermore, when the required opening is opening T_max [deg], the target throttle opening is set to opening T_max [deg]. Opening T_max [deg] indicates that the throttle opening is fully open.

[0079] Furthermore, in hybrid vehicles, even when both the output torque of the internal combustion engine and the output torque of the drive motor are used as driving forces, the relationship between throttle opening and the output torque of the internal combustion engine is still related to... Figure 8 The relationships shown are the same.

[0080] Figure 10 This is a mapping diagram representing the flow signal region and the pressure signal region in the second embodiment. Figure 10 Mapping diagram and Figure 3 The mapping is the same, but... Figure 10 The mapping diagram shows the opening degree T1 [deg]. For example... Figure 10 As shown, the opening degree T1 [deg] is set according to the speed of the internal combustion engine 10.

[0081] like Figure 10 As shown, the opening degree T1 [deg] is set to a value smaller than the specified opening degree. Therefore, in the second embodiment, the pressure signal region is only in effect when the throttle opening degree is fully open, i.e., opening degree T_max [deg].

[0082] [Throttle opening control] Figure 11 This is a flowchart of throttle opening control in the second embodiment. In the control device 36, throttle opening control is performed at predetermined cycles during the driving of the internal combustion engine 10.

[0083] In step S21, the intake air volume calculation unit 46 determines whether the throttle opening is less than the specified opening. If it is determined that the throttle opening is less than the specified opening (step S21: yes), the process proceeds to step S22.

[0084] In step S22, the opening calculation unit 52 is required to determine whether the required opening is fully open. If it is determined that the required opening is not fully open (step S22: No), the process proceeds to step S23.

[0085] In step S23, the flow signal acquisition unit 42 acquires a flow signal from the air flow meter 24. After this, the process proceeds to step S24.

[0086] In step S24, the intake air volume calculation unit 46 calculates the intake air volume based on the flow signal. After this, the process proceeds to step S25.

[0087] In step S25, the opening calculation unit 52 is required to obtain the required opening. After this, the process proceeds to step S26.

[0088] In step S26, the exhaust temperature acquisition unit 48 acquires the exhaust temperature. After this, the process proceeds to step S27.

[0089] In step S27, the control unit 54 determines whether the exhaust temperature is higher than the first specified temperature.

[0090] If in step S21 it is determined that the throttle opening is above the specified opening (step S21: No), or in step S22 it is determined that the opening is required to be fully open (step S22: Yes), proceed to step S28.

[0091] In step S28, the pressure signal acquisition unit 44 acquires a pressure signal from the pressure sensor 26. After this, the process proceeds to step S29.

[0092] In step S29, the intake air volume calculation unit 46 calculates the intake air volume based on the pressure signal. After this, the process proceeds to step S30.

[0093] In step S30, the exhaust temperature acquisition unit 48 acquires the exhaust temperature. After this, the process proceeds to step S31.

[0094] In step S31, the control unit 54 determines whether the exhaust temperature is higher than the second specified temperature.

[0095] If it is determined in step S27 that the exhaust temperature is higher than the first specified temperature (step S27: Yes), or if it is determined in step S31 that the exhaust temperature is higher than the second specified temperature (step S31: Yes), proceed to step S32.

[0096] In step S32, the control unit 54 performs catalyst protection control. Catalyst protection control refers to the aforementioned air quantity limitation control.

[0097] If in step S27 it is determined that the exhaust temperature is below the first specified temperature (step S27: No), or in step S31 it is determined that the exhaust temperature is below the second specified temperature (step S31: No), proceed to step S33.

[0098] In step S33, the opening calculation unit 52 is required to obtain the required opening. After this, the process proceeds to step S34.

[0099] In step S34, the control unit 54 controls the throttle valve 22 according to the required opening degree.

[0100] In the second embodiment, even when the throttle opening is less than a predetermined opening and within the flow signal region, the exhaust temperature at which catalyst protection control begins is set to a second predetermined temperature when the required opening is fully open. The change in throttle opening is slightly delayed relative to the change in the required opening. However, when the required opening is fully open, the throttle opening reaches the predetermined opening or higher within a short time, reaching the pressure signal region. Therefore, even when within the flow signal region, when the required opening is fully open, the intake air flow is calculated based on the pressure signal, and the exhaust temperature at which catalyst protection control begins is set to the second predetermined temperature. Accordingly, the period for performing air volume restriction control can be shortened, thereby shortening the period during which the output of the internal combustion engine 10 is restricted. Furthermore, the operating range where the output of the internal combustion engine 10 is restricted can be narrowed.

[0101] In the flow signal region, catalyst protection control can be implemented before the exhaust temperature reaches a first predetermined temperature to prevent it from reaching that temperature. Similarly, in the pressure signal region, catalyst protection control can be implemented before the exhaust temperature reaches a second predetermined temperature to prevent it from reaching that temperature. Furthermore, even in the flow signal region, when the required opening is fully open, the intake air flow rate can be calculated based on the pressure signal, and catalyst protection control can be implemented before the exhaust temperature reaches the second predetermined temperature to prevent it from reaching that temperature.

[0102] The following notes are also disclosed regarding the above-described embodiments.

[0103] (Note 1) The control device (36) of the internal combustion engine (10) of the present invention includes a flow signal acquisition unit (42), a pressure signal acquisition unit (44), an intake air volume calculation unit (46), an exhaust temperature acquisition unit (48), and a control unit (54). The flow signal acquisition unit (42) acquires a flow signal from an air flow meter (24) that varies according to the air flow rate in the intake manifold (14) of the internal combustion engine; the pressure signal acquisition unit (44) acquires a pressure signal from a pressure sensor (26) that varies according to the pressure in the intake manifold; the intake air volume calculation unit (46) calculates the amount of air drawn into the internal combustion engine, i.e., the intake air volume, based on the flow signal or the pressure signal; the exhaust temperature acquisition unit (48)... The control unit (54) acquires the exhaust temperature of the internal combustion engine; the control unit (54) performs catalyst protection control to limit the intake air volume by adjusting the throttle opening to protect the catalyst (28). When the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, the control unit performs 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 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. Accordingly, the timing of starting catalyst protection control when the intake air volume is calculated based on the flow signal is different from the timing of starting catalyst protection when the intake air volume is calculated based on the pressure signal.

[0104] (Note 2) In the control device for the internal combustion engine described in Appendix 1, when the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, the control unit performs catalyst protection control when the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the first predetermined temperature; and 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 when the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the second predetermined temperature.

[0105] (Note 3) In the control device for the internal combustion engine described in Appendix 1, when the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, the control unit performs catalyst protection control to keep the exhaust temperature below 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 catalyst protection control to keep the exhaust temperature below a second predetermined temperature.

[0106] (Note 4) In the control device of the internal combustion engine described in Appendix 1 or 2, the intake air volume calculation unit may calculate the intake air volume based on the flow signal when the throttle opening is less than a specified opening, and the intake air volume calculation unit may calculate the intake air volume based on the pressure signal when the throttle opening is greater than the specified opening.

[0107] (Note 5) In the control device for the internal combustion engine described in Appendix 1 or 2, the second specified temperature may be a temperature higher than the first specified temperature.

[0108] (Note 6) In the control device of the internal combustion engine described in Appendix 1 or 2, it may also include a required opening degree acquisition unit (50), which acquires the required value of the throttle opening degree, i.e., the required opening degree. When the required opening degree is fully open, the intake air volume calculation unit calculates the intake air volume based on the pressure signal. Even when the air volume is calculated based on the flow signal, the control unit performs the catalyst protection control based on the exhaust temperature and the second specified temperature.

[0109] (Note 7) The control method for an internal combustion engine of the present invention includes a signal acquisition step, an intake air volume calculation step, an exhaust temperature acquisition step, and a control step. In the signal acquisition step, a flow signal acquisition unit acquires a flow signal that varies according to the air flow rate in the intake manifold of the internal combustion engine from an air flow meter, or a pressure signal acquisition unit acquires a pressure signal that varies according to the pressure in the intake manifold from a pressure sensor. In the intake air volume calculation step, an intake air volume calculation unit calculates the amount of air drawn into the internal combustion engine, i.e., the intake air volume, based on the flow signal or the pressure signal. In the exhaust temperature acquisition step, an exhaust temperature acquisition unit acquires the exhaust temperature of the internal combustion engine. In the control steps, the control unit performs catalyst protection control by adjusting the throttle opening to limit the intake air volume, thereby protecting the catalyst. When the intake air volume calculation unit calculates the intake air volume based on the flow signal, the control unit performs catalyst protection control based on the exhaust temperature obtained by the exhaust temperature acquisition unit and a first predetermined temperature. When the intake air volume calculation unit calculates the intake air volume based on the pressure signal, the control unit performs catalyst protection control based on the exhaust temperature obtained by the exhaust temperature acquisition unit and a second predetermined temperature different from the first predetermined temperature.

[0110] (Postscript 8) In the control method of the internal combustion engine described in Appendix 7, when the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, the control unit performs the catalyst protection control when the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the first predetermined temperature; and 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 when the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the second predetermined temperature.

[0111] (Note 9) In the control method of the internal combustion engine described in Appendix 7, when the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, the control unit performs catalyst protection control to keep the exhaust temperature 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 keep the exhaust temperature below the second predetermined temperature.

[0112] (Postscript 10) In the control method of the internal combustion engine described in Appendix 7, the intake air volume calculation unit may calculate the intake air volume based on the flow signal when the throttle opening is less than a predetermined opening, and the intake air volume calculation unit may calculate the intake air volume based on the pressure signal when the throttle opening is greater than the predetermined opening.

[0113] (Postscript 11) In the control method of the internal combustion engine described in Appendix 7, the second specified temperature may be a temperature higher than the first specified temperature.

[0114] (Postscript 12) In the control method of the internal combustion engine described in Appendix 7, there may be an additional step of obtaining the required opening degree. In this step, the required opening degree obtaining unit obtains the required value of the throttle opening degree, i.e., the required opening degree. When the required opening degree is fully open, the intake air volume calculation unit calculates the intake air volume based on the pressure signal. Even when the air volume is calculated based on the flow signal, the control unit performs catalyst protection control based on the exhaust temperature and the second predetermined temperature.

[0115] (Postscript 13) The program of the present invention enables a computer to execute the control method of the internal combustion engine described in any one of Appendices 7 to 12.

[0116] (Postscript 14) The computer-readable non-transitory storage medium of the present invention stores the program described in Appendix 13.

[0117] The present invention has been described in detail, but it is not limited to the various embodiments described above. Various additions, substitutions, modifications, and partial deletions can be made to these embodiments without departing from the spirit of the invention or the spirit of the invention derived from the content described in the technical solutions and their equivalents. Furthermore, these embodiments can also be implemented in combination. For example, in the embodiments described above, the order of each action and the order of each process are shown as an example, but are not limited thereto. The same applies to the use of numerical values ​​or mathematical formulas in the description of the embodiments described above.

[0118] The computer program (computer software) in this embodiment can also be referred to as a computer program product. A computer program product is not limited to a computer program stored on a storage medium, but also includes computer programs transmitted, distributed, or downloaded via the Internet or the like.

Claims

1. A control device for an internal combustion engine, characterized in that, It has a flow signal acquisition unit, a pressure signal acquisition unit, an intake air volume calculation unit, an exhaust temperature acquisition unit, and a control unit, wherein, The flow signal acquisition unit acquires a flow signal from the air flow meter that varies according to the air flow rate in the intake manifold of the internal combustion engine; The pressure signal acquisition unit acquires a pressure signal that varies according to the pressure inside the intake pipe from the pressure sensor; The intake air volume calculation unit calculates the amount of air drawn into the internal combustion engine, i.e., the intake air volume, based on the flow signal or the pressure signal. The exhaust temperature acquisition unit acquires the exhaust temperature of the internal combustion engine; The control unit limits the amount of air intake for catalyst protection by adjusting the throttle opening. When the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, the control unit performs catalyst protection control based on the exhaust temperature obtained 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 catalyst protection control based on the exhaust temperature obtained by the exhaust temperature acquisition unit and a second predetermined temperature different from the first predetermined temperature.

2. The control device for an internal combustion engine according to claim 1, characterized in that, When the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, and the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the first predetermined temperature, the control unit performs the catalyst protection control. When the intake air volume is calculated by the intake air volume calculation unit based on the pressure signal, and the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the second predetermined temperature, the control unit performs the catalyst protection control.

3. The control device for an internal combustion engine according to claim 1, characterized in that, When the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, the control unit performs catalyst protection control to keep the exhaust temperature 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 keep the exhaust temperature below the second specified temperature.

4. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, When the throttle opening is less than a specified opening, the intake air volume calculation unit calculates the intake air volume based on the flow signal. When the throttle opening is above the specified opening, the intake air volume calculation unit calculates the intake air volume based on the pressure signal.

5. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, The second specified temperature is a temperature higher than the first specified temperature.

6. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, It also includes a throttle opening requirement acquisition unit, which acquires the required value of the throttle opening, i.e., the required opening. When the required opening is fully open, the intake air volume calculation unit calculates the intake air volume based on the pressure signal. Even when the air volume is calculated based on the flow signal, the control unit performs catalyst protection control based on the exhaust temperature and the second specified temperature.

7. A control method for an internal combustion engine, characterized in that, It includes a signal acquisition step, an intake air volume calculation step, an exhaust temperature acquisition step, and a control step, among which, In the signal acquisition step, the flow signal acquisition unit acquires a flow signal that varies according to the air flow in the intake manifold of the internal combustion engine from the air flow meter, or the pressure signal acquisition unit acquires a pressure signal that varies according to the pressure in the intake manifold from the pressure sensor. In the intake air volume calculation step, the intake air volume calculation unit calculates the amount of air drawn into the internal combustion engine, i.e., the intake air volume, based on the flow signal or the pressure signal. In the exhaust temperature acquisition step, the exhaust temperature acquisition unit acquires the exhaust temperature of the internal combustion engine; In the control step, the control unit limits the amount of intake air by adjusting the throttle opening to protect the catalyst. When the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, the control unit performs catalyst protection control based on the exhaust temperature obtained 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 catalyst protection control based on the exhaust temperature obtained by the exhaust temperature acquisition unit and a second predetermined temperature different from the first predetermined temperature.

8. The control method for an internal combustion engine according to claim 7, characterized in that, When the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, and the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the first predetermined temperature, the control unit performs the catalyst protection control. When the intake air volume is calculated by the intake air volume calculation unit based on the pressure signal, and the exhaust temperature obtained by the exhaust temperature acquisition unit is higher than the second predetermined temperature, the control unit performs the catalyst protection control.

9. The control method for an internal combustion engine according to claim 7, characterized in that, When the intake air volume is calculated by the intake air volume calculation unit based on the flow signal, the control unit performs catalyst protection control to keep the exhaust temperature 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 keep the exhaust temperature below the second specified temperature.

10. The control method for an internal combustion engine according to claim 7, characterized in that, When the throttle opening is less than a specified opening, the intake air volume calculation unit calculates the intake air volume based on the flow signal. When the throttle opening is above the specified opening, the intake air volume calculation unit calculates the intake air volume based on the pressure signal.

11. The control method for an internal combustion engine according to claim 7, characterized in that, The second specified temperature is a temperature higher than the first specified temperature.

12. The control method for an internal combustion engine according to claim 7, characterized in that, It also includes a required opening degree acquisition step, in which the required opening degree acquisition unit acquires the required value of the throttle opening degree, i.e., the required opening degree. When the required opening is fully open, the intake air volume calculation unit calculates the intake air volume based on the pressure signal. Even when the air volume is calculated based on the flow signal, the control unit performs catalyst protection control based on the exhaust temperature and the second specified temperature.

13. A computer program product, characterized in that, The computer is made to execute the control method of the internal combustion engine according to any one of claims 7 to 12.

14. A computer-readable non-transitory storage medium, characterized in that, The program as described in claim 13 is stored therein.

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