Internal combustion engine control device

Abstract

The present invention provides a control device for an internal combustion engine, comprising: a temperature calculation unit (41) that acquires information about the temperature of a catalyst in an exhaust catalyst device (20) disposed in the exhaust passage of the internal combustion engine (1); an intake regulating unit (35) that regulates the intake air volume of the internal combustion engine (1); and a control unit (40) that controls the intake regulating unit (35) according to the load. The control unit (40) has an intake limiting unit that limits the intake air volume based on the catalyst temperature acquired by the temperature acquisition unit (41), and the greater the increase in catalyst temperature, the earlier the intake limiting unit begins to limit the intake air volume.

Description

Technical Field

[0001] This invention relates to a control device for an internal combustion engine. Background Technology

[0002] In recent years, continuous efforts have been made to mitigate climate change or reduce its impacts, and research and development related to emission improvement have been carried out to achieve this goal. As a technology related to such devices, there are previously known devices that enrich and inject fuel to protect the catalyst when operating under high loads with high exhaust temperatures. Such a device is described, for example, in Patent Document 1. In the device described in Patent Document 1, when exhaust temperature cannot be sufficiently reduced by enriching the fuel alone, the amount of air drawn into the internal combustion engine is reduced.

[0003] However, since the reduction in the amount of air drawn into the internal combustion engine is delayed, there may be a situation where the exhaust temperature overshoots and the catalyst is damaged, so it is necessary to propose countermeasures to address this.

[0004] Existing technical documents

[0005] Patent documents Patent document 1: Japanese Patent Application Publication No. 10-002216 (JPH10-002216A). Summary of the Invention

[0006] One aspect of the present invention provides a control device for an internal combustion engine, comprising: a temperature acquisition unit that acquires information about the temperature of a catalyst in an exhaust catalyst device disposed in the exhaust passage of the internal combustion engine; an intake regulating unit that regulates the intake air volume drawn into the internal combustion engine; and a control unit that controls the intake regulating unit according to the load. The control unit includes an intake limiting unit that restricts the intake air volume based on the catalyst temperature acquired by the temperature acquisition unit; the greater the rise in catalyst temperature, the earlier the intake limiting unit begins to restrict the intake air volume. Attached Figure Description

[0007] The objectives, features, and advantages of the present invention are further illustrated by the following description of embodiments in conjunction with the accompanying drawings.

[0008] Figure 1 This is a diagram that schematically illustrates the main structural components of an engine using a control device for an internal combustion engine according to an embodiment of the present invention; Figure 2 This is a block diagram showing the main structural components of the control device for an internal combustion engine according to an embodiment of the present invention; Figure 3A It is a graph showing the relationship between the load acting on the engine and the estimated value of the catalyst temperature, i.e., the estimated temperature; Figure 3B It is a graph showing the relationship between the estimated temperature and the start and end settings of the intake control; Figure 4 This is a time series diagram showing an example of how the catalyst temperature and the estimated temperature change over time; Figure 5 It is shown by Figure 2 A flowchart of an example of the processing performed by the controller; Figure 6 This is a time-series diagram illustrating an example of the change in catalyst temperature versus intake air volume; Figure 7 This is a diagram illustrating an example of calculating the catalyst temperature based on the estimated temperature. Detailed Implementation

[0009] The following is for reference Figures 1 to 7 An embodiment of the present invention will be described. The internal combustion engine control device of this embodiment is applied to vehicles equipped with a gasoline engine, which is an internal combustion engine. That is, it is applied to engine vehicles that operate solely using the engine as a drive source and hybrid vehicles that operate using both an engine and an electric motor as drive sources.

[0010] Figure 1 This is a schematic diagram showing the main structure of the internal combustion engine, i.e., engine 1, to which the control device of this embodiment is applied. Engine 1 is a spark-ignition internal combustion engine that obtains power by igniting the fuel-air mixture supplied to the combustion chamber, and is a four-stroke engine that undergoes four strokes during its working cycle: intake, compression, expansion, and exhaust. Engine 1 has multiple cylinders with the same structure. Figure 1 The structure of a single cylinder is shown.

[0011] like Figure 1 As shown, the engine 1 has a cylinder block 2 formed on the cylinder block, a piston 3 slidably disposed inside the cylinder block 2, and a combustion chamber 4 formed between the piston 3 and the cylinder head. The piston 3 is connected to the crankshaft 6 via a connecting rod 5, and the crankshaft 6 rotates as the piston 3 reciprocates along the inner wall of the cylinder block 2.

[0012] An intake port 11 and an exhaust port 12 are provided in the cylinder head. The combustion chamber 4 is connected to the intake passage 13 via the intake port 11, and to the exhaust passage 14 via the exhaust port 12. The intake port 11 is opened and closed by an intake valve 15, and the exhaust port 12 is opened and closed by an exhaust valve 16. A throttle valve 17 is provided in the intake passage 13 upstream of the intake valve 15.

[0013] Throttle valve 17, for example, is a butterfly valve, and regulates the intake air volume flowing to combustion chamber 4. Throttle valve 17 is driven by a throttle actuator such as an electric motor, depending on the operation of the accelerator pedal. Intake valve 15 and exhaust valve 16 are opened and closed by a valve mechanism (not shown) at predetermined times synchronized with the rotation of crankshaft 6. The opening and closing timing of valves 15 and 16 can be appropriately changed.

[0014] A spark plug 18 and a direct injection injector 19 are respectively installed in either the cylinder head or the cylinder block (e.g., the cylinder head) facing the combustion chamber 4 of the cylinder block 2. The spark plug 18 is positioned between the intake port 11 and the exhaust port 12, and is electrically powered to generate a spark, igniting the fuel-air mixture in the combustion chamber 4. The injector 19 is positioned next to the intake valve 15, and is electrically driven to inject fuel into the combustion chamber 4 at an angle downwards. The configuration of the injector 19 is not limited to this; it can also be positioned next to the spark plug 18. Alternatively, a port injection injector 19 can be added to the direct injection system, either as an alternative to direct injection or by adding a port injection injector that injects fuel into the intake port.

[0015] An exhaust catalyst device 20 for purifying exhaust gases is installed in the exhaust passage 14. The exhaust catalyst device 20 is a three-way catalyst that removes and purifies HC, CO, and NOx contained in the exhaust gases through oxidation-reduction reactions. Other exhaust catalyst devices, such as oxidation catalysts that oxidize CO and HC in the exhaust gases, can also be used. When the temperature of the catalyst contained in the exhaust catalyst device 20 (catalyst temperature Tc) increases, the catalyst is activated, and the purification effect of the exhaust catalyst device 20 on the exhaust gases is enhanced. However, if the catalyst temperature Tc is too high, the exhaust catalyst device 20 will be damaged. Therefore, it is necessary to suppress the catalyst temperature Tc below a specified temperature (upper limit temperature T1).

[0016] Engine 1 also includes an exhaust gas recirculation (EGR) device 25. The EGR device 25 has an EGR passage 26 and an EGR valve 27 disposed on the EGR passage 26. One end of the EGR passage 26 is connected downstream of the exhaust catalyst device 20 in the exhaust passage 14, and the other end is connected upstream of the throttle valve 17 in the intake passage 13. Exhaust gas flowing through the exhaust passage 14 can be recirculated back to the intake passage 13 via the EGR passage 21 and the EGR valve 27. The EGR valve 27 is driven by an EGR actuator such as an electric motor and is configured to adjust its opening. The exhaust gas recirculation device 25 can also be omitted.

[0017] In such an engine 1, when the accelerator pedal is depressed, the throttle valve 17 opens, increasing the intake air volume. This causes the exhaust temperature to rise, and consequently, the catalyst temperature Tc rises. Engine 1 needs to be configured such that the catalyst temperature Tc does not exceed the upper limit temperature T1. To suppress the catalyst temperature Tc, it is considered to relatively increase the fuel injection quantity from the injector 19 to enrich the air-fuel ratio. However, in this case, the increased fuel injection quantity leads to a deterioration in fuel efficiency and emissions. Therefore, in this embodiment, the control device of the internal combustion engine is configured such that the intake air volume is reduced relative to the target intake air volume corresponding to the operation of the accelerator pedal, thereby suppressing the rise in exhaust temperature and keeping the catalyst temperature Tc below the upper limit temperature T1.

[0018] However, it takes some time for the intake air to reach the exhaust catalyst device 20 after passing through the throttle valve 17. Therefore, when the accelerator pedal is depressed, the opening of the throttle valve 17 increases, thereby increasing the intake air volume, but the exhaust temperature does not rise immediately, and the rise of the catalyst temperature Tc is delayed. This is referred to as the response delay of the catalyst temperature Tc due to the intake delay. The response delay of the catalyst temperature Tc is caused by the delay in the air reaching the exhaust catalyst device 20, which is corresponding to the length of the intake or exhaust path, and the delay in heat transfer from the air to the catalyst. Therefore, when the catalyst temperature Tc is detected (or calculated), and the intake air volume is limited when the catalyst temperature Tc reaches the specified value (limit start temperature), the catalyst temperature Tc overshoots due to the response delay, and may exceed the upper limit temperature T1.

[0019] Regarding this point, when the limiting start temperature is set low, even if a response delay occurs, excessive rise in catalyst temperature Tc can be suppressed. However, in this case, with a small accelerator pedal depressor and a slow rate of exhaust temperature rise, the intake air volume may be exceeded, potentially suppressing torque generation. Therefore, in this embodiment, the control device for the internal combustion engine is configured such that the intake air volume is appropriately suppressed according to the operating conditions while the catalyst temperature T is kept below the upper limit temperature T1.

[0020] Figure 2 This is a block diagram showing the main structural components of the control device 100 for the internal combustion engine according to this embodiment, primarily showing structures related to intake air volume control. For example... Figure 2 As shown, the control device 100 is configured around the controller 40 for engine control, and includes an input unit 31 connected to the controller 40, an intake air volume sensor 32, a speed sensor 33, and an actuator 35.

[0021] The input unit 31 outputs a signal indicating the target torque of the engine 1. The input unit 31 may be, for example, an accelerator pedal opening sensor that detects the amount of accelerator pedal operation. The input unit 31 inputs a torque command value to the controller 40. The internal combustion engine control device of this embodiment can also be applied to vehicles with driver assistance functions or autonomous vehicles, in which case the vehicle control system acts as the input unit 31, inputting the torque command value to the controller 40.

[0022] The intake air volume sensor 32 is a sensor that detects the amount of air entering the engine (mass flow rate). The intake air volume sensor 32 may be, for example, an air flow meter disposed in the intake passage 13 (more specifically, upstream of the throttle valve 17). The intake air volume is a physical quantity related to the load on the engine 1. The load on the engine 1 can also be calculated using the detection values ​​of the accelerator opening sensor (input unit 31) or the pressure sensor that detects the intake pressure downstream of the throttle valve 17, and is not limited to the intake air volume sensor 32.

[0023] The speed sensor 33 is a speed sensor for detecting the engine speed 1, and may be, for example, a crankshaft angle sensor disposed next to the crankshaft 6. The crankshaft angle sensor is configured to output a pulse signal (crankshaft signal) as the crankshaft 6 rotates. That is, it outputs a crankshaft signal whenever the crankshaft rotates a predetermined angle, and the engine speed can be detected based on the crankshaft signal. The operating state, i.e., the operating point, of the engine 1 can be determined primarily based on signals from the intake air volume sensor 32 and the speed sensor 33.

[0024] Actuator 35 is a throttle actuator used to adjust the opening of throttle valve 17. Actuator 35 is driven according to a torque command value, and by driving actuator 35, the throttle opening is adjusted, thereby controlling the intake air volume. That is, the intake air volume can be controlled to a target intake air volume corresponding to the torque command value or to a limited intake air volume lower than the target intake air volume. Regarding intake air volume control, controlling it to the target intake air volume corresponding to the torque command value is called normal intake control, and controlling it to a limited intake air volume lower than the target intake air volume is called limited intake control.

[0025] It is also possible to limit the intake air volume (the amount of fresh air) by guiding EGR gas to the intake passage via the exhaust gas recirculation device 25. In this case, the actuator 35 consists of a throttle actuator and an EGR actuator.

[0026] The controller 40 is composed of an electronic control unit (ECU). More specifically, the controller 40 is configured as a computer with a CPU (central processing unit), ROM (read-only memory), RAM (random access memory), and other peripheral circuits such as I / O interfaces. The controller 40 outputs control signals to the actuator 35 based on signals from the input unit 31, the intake air volume sensor 32, and the speed sensor 33.

[0027] The controller 40 has a functional structure comprising a temperature calculation unit 41, a temperature estimation unit 42, a setting unit 43, an output unit 44, and a storage unit 45. The storage unit 45 stores various mappings, thresholds, control programs, etc. in advance. Figure 3A , Figure 3B This is a diagram showing an example of the mapping stored in the storage unit 45.

[0028] Figure 3A This is a graph showing the relationship between the load acting on engine 1 and the estimated value of catalyst temperature Tc. The estimated value of catalyst temperature Tc (estimated temperature Te) is the catalyst temperature Tc estimated for the load under the assumption that a specified load is continuously applied to engine 1, which is equivalent to the convergence value when catalyst temperature Tc converges over time. Figure 3A The characteristic f1 can be obtained in advance through experiments and analysis. For example... Figure 3AAs shown, the estimated temperature Te increases with increasing load. In the region where the load exceeds a specified value, the estimated temperature Te is above the upper limit temperature T1. As mentioned above, the load corresponds to throttle opening, intake air volume, and intake pressure. Therefore, Figure 3A The characteristic f1 can be replaced by, for example, the relationship between throttle opening (torque command value) and estimated temperature Te. The estimated temperature Te can also be obtained without mapping, by using a formula with load as a parameter.

[0029] Figure 3B Characteristic f2 is a graph showing the relationship between the estimated temperature Te and the setpoint Ta, and characteristic f3 is a graph showing the relationship between the estimated temperature Te and the setpoint Tb. The setpoint Ta is the catalyst temperature setting at which intake restriction (limited intake control) begins, i.e., the limit start setting. The setpoint Tb is the catalyst temperature setting at which limited intake control ends after the start of limited intake control, i.e., the limit end setting. Figure 3B The characteristics f2 and f3 can be obtained in advance through experiments and analysis. For example... Figure 3B As shown, both the limit start setting value Ta and the limit end setting value Tb decrease as the estimated temperature Te increases.

[0030] The limit end setpoint Tb is lower than the limit start setpoint Ta. The percentage by which the limit start setpoint Ta decreases with increasing estimated temperature Te (the slope of characteristic f2) is equal to the percentage by which the limit end setpoint Tb decreases (the slope of characteristic f3). The percentage by which the limit start setpoint Ta decreases may also differ from the percentage by which the limit end setpoint Tb decreases. The setpoints Ta and Tb can also be obtained without mapping, using a formula with the estimated temperature Te as a parameter.

[0031] The temperature calculation unit 41 calculates the catalyst temperature Tc based on the operating state of the engine 1. Specifically, the temperature calculation unit 41 calculates the current catalyst temperature Tc using a predetermined mapping or a calculation formula based on signals from the intake air volume sensor 32 and the engine speed sensor 33. The higher the intake air volume and the higher the engine speed, the higher the calculated catalyst temperature Tc. The temperature calculation unit 41 can also use the calculated catalyst temperature plus a predetermined margin as the catalyst temperature Tc. That is, it can also use a value that is higher than the actual catalyst temperature by a predetermined margin as the catalyst temperature Tc.

[0032] Alternatively, the catalyst temperature Tc can be detected by a sensor instead of calculating it based on the intake air volume and engine speed. For example, the catalyst temperature Tc can be detected directly by a temperature sensor. The temperature of other components related to the catalyst temperature Tc can also be detected, and the catalyst temperature can be calculated by the temperature calculation unit 41 based on the detected value. For example, the temperature of the combustion chamber 4 or its vicinity can be detected by a temperature sensor, and the catalyst temperature Tc can be calculated based on the temperature of the combustion chamber 4. The exhaust temperature can also be detected by a temperature sensor, and the catalyst temperature Tc can be calculated based on the exhaust temperature.

[0033] Temperature estimation unit 42 is used Figure 3A Based on the characteristic f1, the temperature estimation unit 42 calculates the estimated temperature Te of the catalyst corresponding to the load of engine 1. Specifically, the temperature estimation unit 42 takes the torque command value input by the input unit 31 as the load and calculates the estimated temperature Te corresponding to the load. Alternatively, the load of engine 1 can be detected by a pressure sensor that detects the intake pressure downstream of the throttle valve 17, and the temperature estimation unit 42 calculates the estimated temperature Te based on the detection value of the pressure sensor.

[0034] Figure 4 This is a time series diagram showing an example of how the catalyst temperature Tc and the estimated temperature Te change over time. Figure 4 The horizontal axis represents the elapsed time t from the moment the accelerator pedal is depressed (t0), i.e., the input command to increase torque. The solid lines f11–f13 in the diagram represent the changes in catalyst temperature Tc, while the dashed lines f21–f23 represent the changes in estimated temperature Te. Estimated temperature Te refers to the temperature at which the catalyst reaches its set temperature or temperature setpoint.

[0035] Characteristics f11 and f21 correspond to the first load L1, characteristics f12 and f22 correspond to the second load L2, and characteristics f13 and f23 correspond to the third load L3. The first load L1 is greater than the second load L2, and the second load L2 is greater than the third load L3 (L1>L2>L3). Alternatively, the first load L1 can be referred to as a high load, the second load L2 as a medium load, and the third load L3 as a low load for further distinction.

[0036] like Figure 4 As shown, when the accelerator pedal is depressed at time t0, the estimated temperature Te, calculated by the temperature estimation unit 42, rises. The greater the load, the greater the estimated temperature Te. Figure 3A The estimated temperatures Te corresponding to the first load L1, the second load L2, and the third load L3 are Te1, Te2, and Te3, respectively. These estimated temperatures Te1, Te2, and Te3 have a relationship of Te1 > Te2 > Te3. Figure 4In this case, as time passes, the estimated temperatures Te1, Te2, and Te3 all decrease, but this is because the intake air amount is restricted by the intake air control described later, resulting in a decrease in load ( Figure 3A ).

[0037] When the accelerator pedal is depressed at time t0, the catalyst temperature Tc calculated by the temperature calculation unit 41 also rises. The greater the load, the greater the slope of the characteristics f11 to f13, that is, the rate of increase in the catalyst temperature Tc (the amount of temperature increase per unit time). When the rates of increase in the catalyst temperatures Tc1, Tc2, and Tc3 corresponding to the first load L1, the second load L2, and the third load L3 are set as ΔTc1, ΔTc2, and ΔTc3, there is a relationship of ΔTc1 > ΔTc2 > ΔTc3 among these ΔTc1, ΔTc2, and ΔTc3. However, the rate of increase in the catalyst temperature Tc is smaller than the rate of increase in the estimated temperature Te. Therefore, immediately after the accelerator pedal is depressed, the estimated temperature Te is higher than the catalyst temperature Tc.

[0038] Figure 2 The setting unit 43 according to Figure 3B the characteristic f2 sets the set value corresponding to the estimated temperature Te, that is, the limit start set value Ta. For example, when the estimated temperature Te is Figure 4 any one of the estimated temperatures Te1, Te2, and Te3, the limit start set values Ta1, Ta2, and Ta3 corresponding to any one of the estimated temperatures Te1, Te2, and Te3 are set. The limit start set values Ta1, Ta2, and Ta3 have a relationship of Ta1 < Ta2 < Ta3, and the higher the estimated temperature Te, the lower the limit start set value Ta.

[0039] When the estimated temperature Te is constant, the setting unit 43 calculates the limit start set value Ta as a constant value. Therefore, between times t0 and t1, between times t0 and t2, and between times t0 and t3 of Figure 4 , the limit start set values Ta1, Ta2, and Ta3 are constant respectively. After time t1, after time t2, or after time t3, when the estimated temperature Te decreases, the limit start set value Ta (single dotted line) set by the setting unit 43随之 rises ( Figure 3B ).

[0040] The output unit 44 determines the magnitude relationship between the catalyst temperature Tc calculated by the temperature calculation unit 41 and the limit start set value Ta set by the setting unit 43. More specifically, the output unit 44 determines whether the catalyst temperature Tc is greater than or equal to the limit start set value Ta. Then, based on the determination result, a control signal is output to the throttle actuator 35. For example, when it is determined that Tc < Ta, the output unit 44 controls the actuator 35 according to the torque command value input by the input unit 31 (conventional intake control). Thereby, the throttle opening becomes the target throttle opening corresponding to the depression of the accelerator pedal, and the intake air volume becomes the target intake air volume corresponding to the torque command value.

[0041] On the other hand, when it is determined that Tc ≥ Ta, the output unit 44 restricts the throttle opening to be smaller than the target throttle opening (restricted intake control). Thereby, it is possible to suppress the increase and decrease of the intake air volume and suppress the rise of the catalyst temperature Tc, and the catalyst temperature Tc can be suppressed below the upper limit temperature T1. In the restricted intake control, the output unit 44 can restrict the intake air volume in various ways. For example, the output unit 44 controls the actuator 35 such that the intake air volume becomes a value obtained by multiplying the target intake air volume in the conventional intake control by a specified coefficient less than 1. Another example is that the output unit 44 can also restrict the throttle opening to a specified opening regardless of the target intake air volume during the restricted intake control.

[0042] After the start of the restricted intake control, the setting unit 43 sets the limit end set value Tb, which is the set value corresponding to the estimated temperature Te, according to Figure 3B the characteristic f3. After the start of the restricted intake control, the output unit 44 determines the magnitude relationship between the catalyst temperature Tc calculated by the temperature calculation unit 41 and the limit end set value Tb set by the setting unit 43. More specifically, the output unit 44 determines whether the catalyst temperature Tc is less than or equal to the limit end set value Tb. When it is determined that Tc > Tb, the output unit 44 continues to restrict the intake air through the restricted intake control. When it is determined that Tc ≤ Tb, the output unit 44 ends the restricted intake control and controls the actuator 35 according to the torque command value input by the input unit 31 (conventional intake control).

[0043] As described above, the controller 40 functions as an intake restriction unit that restricts the intake air volume according to the catalyst temperature Tc and a restriction release unit that releases the restriction on the intake air volume according to the catalyst temperature Tc after the start of the intake restriction unit. The intake restriction unit and the restriction release unit can be constituted by the setting unit 43 and the output unit 44.

[0044] Figure 5 It shows in Figure 2The flowchart illustrates an example of processing performed by the CPU of the controller 40, particularly an example of processing related to intake control (regular intake control, restricted intake control). The processing shown in the flowchart begins upon, for example, the activation of the engine ignition switch and is repeated at a predetermined cycle.

[0045] like Figure 5 As shown, in step S1 (S: processing step), the controller 40 first reads signals from the input unit (e.g., accelerator opening sensor) 31, the intake air volume sensor 32, and the speed sensor 33. Next, in step S2, the controller 40 (temperature calculation unit 41) calculates the current catalyst temperature Tc based on the signals from the intake air volume sensor 32 and the speed sensor 33 using a predetermined mapping or calculation formula. Then, in step S3, the controller 40 (temperature estimation unit 42) uses... Figure 3A Based on the characteristic f1, the estimated temperature Te corresponding to the load of engine 1 is calculated. For example, the temperature estimation unit 42 takes the torque command value input by the input unit 31 as the load and calculates the estimated temperature Te corresponding to the torque command value.

[0046] Next, in S4, the controller 40 (setting unit 43) determines whether the intake flag is 1. The intake flag is initially 0, and is set to 1 when intake control restriction begins. If S4 is determined to be negative (S4: No), meaning it is not under intake restriction control, the process proceeds to S5. In S5, the controller 40 (setting unit 43) determines whether the intake flag is 1. Figure 3B The characteristic f2 is set to the limit start setting value Ta corresponding to the estimated temperature Te.

[0047] Next, in S6, the controller 40 (output unit 44) determines whether the catalyst temperature Tc calculated in S2 is above the limit start setting value Ta set in S5. When S6 is negative (S6: No), proceeding to S7, the controller 40 (output unit 44) outputs a control signal to the actuator 35, controlling the throttle opening to the target throttle opening corresponding to the torque command value of the input unit 31. In this case, the intake air volume is not limited (intake air volume is unrestricted).

[0048] On the other hand, when S6 is affirmative (S6: Yes), the process proceeds to S8, where the controller 40 (output unit 44) outputs a control signal to the actuator 35 to limit the throttle opening. As a result, the throttle opening is smaller than the target throttle opening, and the intake air volume is limited (intake air volume limitation). Next, in S9, the controller 40 sets the intake flag to 1, ending the process.

[0049] In S4, when the intake flag is determined to be 1, proceed to S10. In S10, the controller 40 (setting unit 43) determines... Figure 3BThe characteristic f3 is used to set a limit end setting value Tb corresponding to the estimated temperature Te. Next, in S11, the controller 40 (output unit 44) determines whether the catalyst temperature Tc is below the limit end setting value Tb. When S11 is negative (S11: no), it enters S8, and the controller 40 (output unit 44) outputs a control signal to the actuator 35 to continue throttle limiting (intake volume limiting).

[0050] On the other hand, when S11 is affirmative (S11: Yes), the process proceeds to S12, where the controller 40 (output unit 44) outputs a control signal to the actuator 35. Similar to S7, the throttle opening is controlled to the target throttle opening (intake volume is not limited) corresponding to the torque command value of the input unit 31. Next, in S13, the controller 40 resets the intake flag to 0 and ends the process.

[0051] The main operations of the control device 100 for the internal combustion engine in this embodiment will be explained. For example, when... Figure 4 When the accelerator pedal is depressed to its maximum at time t0, the engine 1 is subjected to the first load L1. At this time, the estimated value of the catalyst temperature Tc (Tc1), i.e., the estimated temperature Te, rises sharply, and the estimated temperature Te1 corresponding to the first load L1 exceeds the upper limit temperature T1 (characteristic f21). At this time, the actual catalyst temperature Tc1 rises more gradually than the estimated temperature Te (characteristic f11).

[0052] Subsequently, at time t1, when the catalyst temperature Tc1 reaches the limit start setpoint Ta1 corresponding to the estimated temperature Te1 of the first load L1, the throttle opening is limited, thereby limiting the intake air volume (S8). As a result, the estimated temperature Te gradually decreases (characteristic f21), and the rate of increase of the catalyst temperature Tc1 ΔTc1 becomes gradual (characteristic f11). Therefore, the catalyst temperature Tc1 does not overshoot, or the overshoot is small, and it approaches the upper limit temperature T1 over time.

[0053] At time t0, when the accelerator pedal is depressed at a relatively low level, the load on engine 1 becomes a second load L2 or a third load L3, which is smaller than the first load L1. In this case, the estimated temperature Te also rises sharply, but the estimated temperature Te2 corresponding to the second load L2 and the estimated temperature Te3 corresponding to the third load L3 are lower than the estimated temperature Te1 (characteristics f22, f23). Therefore, the limit start setting values ​​Ta2 and Ta3 are higher than the limit start setting value Ta1, and the throttle opening limit (intake volume limit) begins at time t2 or t3, which is later than time t1 (S8).

[0054] Therefore, the rate of increase of catalyst temperature Tc2 corresponding to the second load L2, ΔTc2, becomes gradual after time point t2 (characteristic f12), and the rate of increase of catalyst temperature Tc3 corresponding to the third load L3, ΔTc3, becomes gradual after time point t3 (characteristic f13). Thus, when engine 1 is under the second load L2 or the third load L3, the timing of intake restriction initiation is delayed compared to when it is under the first load L1. However, the rate of increase of catalyst temperature Tc2 and Tc3 before intake restriction initiation, ΔTc2 and ΔTc3, is smaller than the rate of increase of catalyst temperature Tc1 before intake restriction initiation, ΔTc1. Therefore, catalyst temperatures Tc2 and Tc3 do not overshoot or overshoot to a small degree, and approach the upper limit temperature T1 over time.

[0055] Thus, in this embodiment, the smaller the load acting on engine 1, the later the intake restriction begins. Consequently, when the load increases due to pressing the accelerator pedal, the catalyst temperature Tc will not exceed the upper limit temperature T1, and the reduction in torque can be minimized.

[0056] Figure 6 This is a time series diagram illustrating, for example, the changes in catalyst temperature Tc and intake air flow rate G after time point t0, corresponding to the first load L1. Characteristic f14 in the diagram represents the change in catalyst temperature Tc, and characteristic f31 represents the change in intake air flow rate G. Figure 6 As shown, when the accelerator pedal is depressed at time t0, the catalyst temperature Tc (Tc1) gradually rises. At this time, the intake volume G becomes the target intake volume G1 corresponding to the torque command value.

[0057] At time t1, when the catalyst temperature Tc1 exceeds the limit start set value Ta1, the throttle opening is limited, and the intake air volume decreases (S8). At this time, the controller 40 outputs a control signal to the actuator 35, causing the throttle opening to gradually decrease (times t1 to t4). As a result, the intake air volume gradually decreases, which can suppress shock (characteristic f31). When the intake air volume is limited, the catalyst temperature Tc1 gradually decreases (characteristic f14). This prevents the catalyst temperature Tc1 from reaching the upper limit temperature T1.

[0058] Subsequently, at time t5, when the catalyst temperature Tc1 falls below the limit end temperature Tb1, the intake air restriction control ends, and the throttle opening returns to its pre-limit value (S12). The intake air volume gradually increases. Thus, when the catalyst temperature Tc falls below the limit end setting value Tb, the intake air restriction is released quickly, minimizing torque reduction. Furthermore, the limit end setting value Tb is set lower than the limit start setting value Ta, preventing frequent repetition of the intake air restriction start and end when the catalyst temperature Tc changes.

[0059] The following effects can be achieved by adopting this implementation method.

[0060] (1) The control device 100 for the internal combustion engine includes: a temperature calculation unit 41 that calculates the catalyst temperature Tc in the exhaust catalyst device 20 installed on the exhaust passage 14 of the engine 1; an actuator 35 for driving the throttle valve 17 that adjusts the intake air volume of the engine 1; and a controller 40 that controls the actuator 35 according to the load. Figure 2 The controller 40 has an intake limiting unit that limits the intake volume based on the catalyst temperature Tc calculated by the temperature calculation unit 41. Figure 4 The greater the increase in catalyst temperature Tc, the earlier the intake limiting unit begins to restrict the intake volume. Figure 4 That is, when the catalyst temperature Tc increases by a larger percentage (e.g., characteristic f11), the intake limitation begins earlier than when the increase is smaller (e.g., characteristic f13). Figure 4 Therefore, the timing of intake restriction can be varied, which can keep the catalyst temperature Tc below the upper limit temperature T1 while minimizing the torque drop.

[0061] (2) The controller 40 (intake limiting unit) calculates the estimated temperature Te, which is the temperature at which the catalyst temperature Tc reaches the operating state of the engine 1. The higher the estimated temperature Te, the earlier the intake volume is limited. Figure 4 The higher the estimated temperature Te, the greater the increase in catalyst temperature Tc. Therefore, by increasing the estimated temperature Te, the intake flow restriction can be started earlier, which can reliably prevent the catalyst temperature Tc from exceeding the upper limit temperature T1 due to the response delay of catalyst temperature Tc caused by intake delay.

[0062] (3) The higher the estimated temperature Te, the lower the intake volume limit start setting value Ta will be set by the controller 40 (intake limit unit). When the catalyst temperature Tc reaches or exceeds the limit start setting value Ta, the intake volume limit will begin to be set. Figure 5 Therefore, it can be inferred that the higher the temperature Te, the earlier the intake volume restriction can begin.

[0063] (4) The controller 40 also has a restriction release unit, which releases the restriction on the intake volume based on the catalyst temperature Tc after the intake volume restriction is started. Figure 5 The lower the estimated temperature Te, the higher the intake air volume restriction end setting Tb will be set by the restriction release unit. When the catalyst temperature Tc reaches below the restriction end setting Tb, the intake air volume restriction will be released. Figure 3B , Figure 5 Therefore, the intake restriction can be ended earlier, and the reduction in torque can be minimized.

[0064] (5) The controller 40 (restriction release unit) sets the restriction end setting value Tb to a value lower than the restriction start setting value Ta. Figure 3B This prevents the frequent repetition of the start and end of intake restriction when the catalyst temperature Tc changes.

[0065] In the above embodiment, the temperature calculation unit 41 calculates the catalyst temperature Tc based on signals from the intake air volume sensor 32 and the speed sensor 33, but the estimated temperature Te and the catalyst temperature Tc are correlated ( Figure 4 Therefore, the catalyst temperature Tc can also be calculated based on the estimated temperature Te. Figure 7 This is a graph illustrating an example of calculating the catalyst temperature Tc based on the estimated temperature Te. The horizontal axis represents time (the elapsed time from the moment the accelerator pedal is depressed, t0), and the vertical axis represents characteristics f25–f27 (dashed lines) indicating the change in estimated temperature Te and characteristics f15–f17 (solid lines) indicating the change in catalyst temperature Tc. Characteristics f25 and f15 correspond to the first load L1, characteristics f26 and f16 correspond to the second load L2, and characteristics f27 and f17 correspond to the third load L3.

[0066] like Figure 7 As shown, the temperature calculation unit 41 performs a gradual increase in the estimated temperature Te over time as the catalyst temperature Tc rises, and calculates the catalyst temperature Tc. More specifically, the higher the estimated temperature Te, the greater the rate (slope) of the increase in catalyst temperature Tc. Although the illustration is omitted, the temperature calculation unit 41 performs the same gradual increase in catalyst temperature Tc as it falls, not only when the catalyst temperature Tc rises. More specifically, the lower the estimated temperature Te, the greater the rate (slope) of the decrease in catalyst temperature Tc.

[0067] Thus, the temperature calculation unit 41 applies a moderate treatment to the estimated temperature Te, such that the higher the estimated temperature Te is when the catalyst temperature Tc rises, the more rapidly the catalyst temperature Tc rises, and the lower the estimated temperature Te is when the catalyst temperature Tc falls, the more rapidly the catalyst temperature Tc falls, and calculates the catalyst temperature Tc ( Figure 7 Therefore, the catalyst temperature Tc can be calculated with high accuracy based on the estimated temperature Te.

[0068] The above-described embodiments can be modified in various ways. Modifications will be described below. In the above-described embodiments, the temperature calculation unit 41 obtains information about the catalyst temperature Tc, but the catalyst temperature Tc information can also be obtained by detecting the catalyst temperature Tc with a sensor; the configuration of the temperature acquisition unit is not limited to those described above. In the above-described embodiments, the intake air volume is adjusted by driving the throttle actuator 35, but the intake air volume can also be adjusted by driving the EGR valve 27, or by controlling the drive of the intake valve 15. Therefore, the configuration of the intake regulating unit is not limited to those described above.

[0069] In the above embodiment, the controller 40, acting as the control unit, controls the actuator 35 according to the load. Specifically, the estimated temperature Te (reached temperature) is calculated as the temperature at which the catalyst temperature Tc reaches. The higher the estimated temperature Te, the lower the intake volume restriction start setting value Ta (limit start temperature) is set. However, as long as the estimated temperature Te is higher, the intake volume restriction starts earlier, and the processing of the intake restriction unit can take any form. As long as the catalyst temperature Tc rises to a greater extent, the intake volume restriction starts earlier, and the intake restriction unit can perform intake restriction without using the estimated temperature. For example, the degree of rise in catalyst temperature Tc (the amount of rise in catalyst temperature Tc per unit time) can be detected by a sensor or calculated by a formula, and intake restriction can be started based on this.

[0070] It is possible to combine one or more of the above-described embodiments and variations, and to combine the variations with each other.

[0071] Using this invention, the exhaust catalyst device can be well protected when the catalyst temperature rises.

[0072] The present invention has been described above in conjunction with preferred embodiments, but those skilled in the art should understand that various modifications and changes can be made without departing from the scope of the claims.

Claims

1. A control device for an internal combustion engine, characterized in that, have: Temperature acquisition unit (41) acquires information on the catalyst temperature (Tc) in the exhaust catalyst device (20) installed on the exhaust passage (14) of the internal combustion engine (1); An intake regulating unit (35) that regulates the intake air volume of the internal combustion engine (1); and The control unit (40) controls the intake regulating unit (35) according to the load. The control unit (40) has an intake limiting unit that limits the intake volume based on the catalyst temperature (Tc) obtained by the temperature acquisition unit (41). The greater the increase in catalyst temperature (Tc), the sooner the intake restriction unit begins to restrict the intake volume.

2. The control device for an internal combustion engine according to claim 1, characterized in that, The intake limiting section is estimated to correspond to the operating state of the internal combustion engine (1) as the temperature at which the catalyst temperature (Tc) reaches the catalyst temperature (Te). The higher the estimated temperature at which the catalyst temperature (Te) reaches the catalyst temperature, the earlier the intake volume is limited.

3. The control device for an internal combustion engine according to claim 2, characterized in that, The higher the catalyst temperature (Tc) reaches the temperature (Te), the lower the intake volume restriction start temperature (Ta) is set by the intake restriction unit. When the catalyst temperature (Tc) reaches or exceeds the restriction start temperature (Ta), the intake restriction unit begins to restrict the intake volume.

4. The control device for an internal combustion engine according to claim 2 or 3, characterized in that, The temperature acquisition unit (41) performs a easing process on the reached temperature (Te) such that the higher the reached temperature (Te) is when the catalyst temperature (Tc) rises, the faster the catalyst temperature (Tc) rises, and the lower the reached temperature (Te) is when the catalyst temperature (Tc) falls, the faster the catalyst temperature (Tc) falls, and calculates the catalyst temperature (Tc).

5. The control device for an internal combustion engine according to claim 2, characterized in that, It also has a torque detection unit (31) for detecting torque command values. The intake restriction unit estimates the arrival temperature (Te) based on the torque command value detected by the torque detection unit (31).

6. The control device for an internal combustion engine according to claim 3, characterized in that, The control unit (40) also has a restriction release unit, which releases the restriction on the intake volume based on the catalyst temperature (Tc) after the intake volume restriction implemented by the intake restriction unit has been initiated. The lower the catalyst temperature (Tc) reaches the temperature (Te), the higher the limit release unit sets the intake volume limit end temperature (Tb). When the catalyst temperature (Tc) reaches below the limit end temperature (Tb), the limit release unit releases the intake volume limit.

7. The control device for an internal combustion engine according to claim 6, characterized in that, The restriction release unit sets the restriction end temperature (Tb) to be lower than the restriction start temperature (Ta).

8. The control device for an internal combustion engine according to claim 1, characterized in that, It also has: An intake air volume sensor (32) detects the amount of air drawn into the internal combustion engine (1); and A speed sensor (33) detects the speed of the internal combustion engine (1). The temperature acquisition unit (41) calculates the catalyst temperature (Tc) based on the intake volume detected by the intake volume sensor (32) and the rotational speed detected by the rotational speed sensor (33).

9. A control method for an internal combustion engine, comprising an intake regulating unit (35) for regulating the intake air volume of the internal combustion engine (1), characterized in that, include: The step of obtaining information on the catalyst temperature (Tc) in the exhaust catalyst device (20) installed in the exhaust passage (14) of the internal combustion engine (1); and According to the control steps of the load control intake regulating unit (35), The control steps include limiting the intake air volume based on the catalyst temperature (Tc), and the greater the rise in the catalyst temperature (Tc), the earlier the intake air volume limitation begins.

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