Control device for internal combustion engine

Abstract

To suppress deterioration of emission right after start of an engine.SOLUTION: A controller 100 is applied to an internal combustion engine comprising an electric heating type first catalyst 26 housed in a case 24 and heated by energization, and a second catalyst 27 provided on an exhaust downstream side with respect to the first catalyst 26. The controller 100 executes a preheating process of warming up the first catalyst 26 by energizing the first catalyst 26 prior to starting the internal combustion engine, and a process of starting the internal combustion engine when the preheating process is completed. Then, the controller 100 executes a post-heating process of energizing the first catalyst 26 while the internal combustion engine is running after the pre-heating process is completed, and a limitation processing of limiting the output of the internal combustion engine to a lower output when the post-heating process is being performed than when the post-heating process is not performed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] A catalyst that purifies exhaust gas from an internal combustion engine exhibits sufficient performance at an activation temperature after the engine has been warmed up. Therefore, if the catalyst temperature is below the activation temperature, the catalyst may not be able to purify exhaust gas sufficiently.

[0003] In view of this, an electrically heated catalyst is known that is housed in a case provided in the exhaust passage of the internal combustion engine and heated by passing electricity through it (for example, Patent Document 1, etc.). The electrically heated catalyst can be warmed up prior to engine start-up by executing a preheat process in which electricity is passed through it before starting the internal combustion engine. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-072665 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, immediately after the engine start-up, the temperature of the exhaust gas flowing into the electrically heated catalyst is low. Therefore, the temperature of the electrically heated catalyst, which has been warmed up by the execution of the preheating process, drops. If the temperature of the electrically heated catalyst drops in this way, there is a risk that emissions will deteriorate. [Means for solving the problem]

[0006] The means for solving the above problems and their effects will be described below. A control device for an internal combustion engine for solving the above problems is applied to an internal combustion engine including an electrically heated first catalyst that is housed in a case provided in an exhaust passage and heated by passing current through it, and a second catalyst that is provided downstream of the first catalyst in the exhaust gas. This control device executes a preheat process for warming up the first catalyst by passing current through the first catalyst prior to starting the internal combustion engine, a process for starting the internal combustion engine when the preheat process is completed, a postheat process for passing current through the first catalyst while the internal combustion engine is operating after the preheat process is completed, and a limiting process for limiting the output of the internal combustion engine to a lower output when the postheat process is being performed, compared to when the postheat process is not being performed.

[0007] According to the above control device, even after the preheat process is completed and engine start is started, the first catalyst is energized by the postheat process. By executing such postheat process, the temperature drop of the first catalyst that has completed warming up is suppressed. Therefore, the control device can suppress the deterioration of emissions immediately after engine start. However, when engine start is started, exhaust gas containing moisture flows into the case. Therefore, there is a risk that moisture in the exhaust gas will condense on the inner wall of the case. If such condensation occurs, there is a risk that the insulation of the first catalyst will decrease. It is not preferable to continue energizing in a state where the insulation has decreased. Therefore, the above control device limits the output of the internal combustion engine while executing the postheat process. As a result, the control device suppresses the inflow of moisture into the case. That is, the above control device can suppress the interruption of the postheat process due to the decrease in insulation. In addition, the control device can continue the postheat process to reduce emissions.

[0008] In one aspect of the control device for an internal combustion engine, the limiting process is a process for steadily operating the internal combustion engine at a constant output and a constant engine rotation speed. As described above, engine operation with the output of the internal combustion engine limited can be achieved by steadily operating the internal combustion engine at a constant output and a constant engine speed.

[0009] In one embodiment of the control device for an internal combustion engine, the limiting process is a process for limiting the output of the internal combustion engine to a lower output as the insulation resistance value of the first catalyst becomes lower. The first catalyst should be energized only after a certain level of insulation has been ensured. If the insulation resistance of the first catalyst is low to begin with, there is little margin of insulation for continuing the post-heat process. The control device sets the degree of limiting the output of the internal combustion engine according to the degree of this margin of insulation. Therefore, the control device can prevent the output of the internal combustion engine from being restricted more than necessary.

[0010] In one aspect of the control device for an internal combustion engine, the limitation process is a process for limiting the output of the internal combustion engine to a lower output as the outside air temperature becomes lower. The lower the outside temperature, the more likely it is that moisture in the exhaust will condense. Therefore, the lower the outside temperature, the more likely it is that insulation will deteriorate. The above-mentioned control device can set the degree of limiting the output of the internal combustion engine according to the degree to which insulation will deteriorate. Therefore, the control device can appropriately suppress the deterioration of emissions even when the outside temperature is low.

[0011] In one embodiment of the control device for an internal combustion engine, the restriction process is a process for operating the internal combustion engine with an ignition timing retarded when the outside air temperature is low compared to when the outside air temperature is high. When the outside air temperature is low, moisture in the exhaust gas is likely to condense, and insulation is likely to deteriorate. Retarding the ignition timing increases the exhaust gas temperature. When the outside air temperature is low, the above control device retards the ignition timing to increase the exhaust gas temperature. This makes it difficult for condensation to occur even when the outside air temperature is low. In other words, the above control device can suppress deterioration of insulation even when the outside air temperature is low.

[0012] In one embodiment of a control device for an internal combustion engine, current is applied to the first catalyst by the post-heat processing until the temperature of the second catalyst reaches the activation temperature of the second catalyst, and the restriction processing is terminated when the post-heat processing is terminated.

[0013] If the temperature of the second catalyst reaches the activation temperature, the second catalyst purifies the exhaust gas. Therefore, even if the power supply to the first catalyst is stopped, the exhaust gas is purified. Therefore, the above-mentioned control device continues power supply to the first catalyst by the post-heat process until the second catalyst reaches the activation temperature. Then, the control device ends the restriction process when the post-heat process ends. Therefore, the control device can prevent the output of the internal combustion engine from being restricted more than necessary. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a configuration of a vehicle equipped with a control device for an internal combustion engine; [Diagram 2] FIG. 2 is a schematic diagram showing the system configuration of an electrically heated catalyst mounted on the vehicle. [Diagram 3] 4 is a flowchart showing a procedure of a process executed by the control device of the embodiment. [Figure 4] 4 is a graph showing the relationship between the maximum oxygen storage amount and the activation temperature of the catalyst. [Diagram 5] 4 is a graph showing a relationship between a first catalyst temperature and a maximum oxygen storage amount, and a target electric power amount. [Figure 6] 1 is a graph showing the relationship between the insulation resistance value and a correction coefficient a1. [Figure 7] 1 is a graph showing the relationship between the maximum oxygen storage amount and a judgment value. [Figure 8] 8 is a time chart showing the transition of various states when the vehicle system is started up, in which Fig. 8(a) shows the transition of the engine output, Fig. 8(b) shows the electrification state of the electrically heated catalyst, and Fig. 8(c) shows the transition of the first catalyst temperature and the second catalyst temperature. [Figure 9] 10 is a flowchart showing a part of a procedure of a process executed by a control device in a modified example of the embodiment. [Figure 10] 11 is a graph showing the relationship between the outside air temperature and a correction coefficient a2. [Figure 11] 1 is a graph showing the relationship between the outside air temperature and the ignition timing retard amount b. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, one embodiment of a control device for an internal combustion engine will be described with reference to FIGS. <Vehicle 10 Configuration> The configuration of a vehicle 10 equipped with a control device 100 for controlling an internal combustion engine 11 will be described with reference to FIG.

[0016] The vehicle 10 includes an internal combustion engine 11 and a second motor generator 32 as power sources. In other words, the vehicle 10 is a hybrid vehicle. The vehicle 10 is a plug-in hybrid vehicle that can be connected to an external power source 60 to charge the battery 50. Therefore, a charger 51 for external charging is connected to the battery 50. The battery 50 is, for example, a 400V high-voltage battery. The second motor generator 32 is, for example, a three-phase AC motor generator.

[0017] The internal combustion engine 11 includes an intake passage 12 and an exhaust passage 21. In the example shown in FIG. 1, the internal combustion engine 11 includes four cylinders. The intake passage 12 includes a throttle valve 13 for adjusting the flow rate of intake air flowing through the intake passage 12. The internal combustion engine 11 includes a plurality of fuel injection valves 14 for injecting fuel during intake, one for each cylinder. The plurality of fuel injection valves 14 may be provided for each cylinder, or the number of the fuel injection valves 14 provided for each cylinder may differ. The internal combustion engine 11 includes a spark plug 15 for igniting a mixture of fuel and intake air by spark discharge, one for each cylinder. The plurality of spark plugs 15 may be provided for each cylinder, or the number of the spark plugs provided for each cylinder may differ.

[0018] A catalytic converter 29 is installed in the exhaust passage 21 of the internal combustion engine 11. The catalytic converter 29 is equipped with an electrically heated catalyst 210 that generates heat in response to the passage of current. The electrically heated catalyst 210 is connected to a battery 50 via a power supply device 220. A detailed configuration of an electrically heated catalyst system 200 including the electrically heated catalyst 210 will be described later with reference to FIG. 2.

[0019] In addition, a filter 36 is provided downstream of the catalytic converter 29 in the exhaust passage 21. The filter 36 collects particulate matter contained in the exhaust gas. The particulate matter is fine particulate matter produced by combustion and composed mainly of carbon.

[0020] The second motor generator 32 is connected to a battery 50 via a power control unit 35. In addition, the second motor generator 32 is linked to driving wheels 40 via a reduction mechanism .

[0021] The internal combustion engine 11 is connected to drive wheels 40 via a power split mechanism 30 and a reduction mechanism 34. A first motor generator 31 is also connected to the power split mechanism 30. The first motor generator 31 is, for example, a three-phase AC motor generator. The power split mechanism 30 is a planetary gear mechanism, and can split the driving force of the internal combustion engine 11 between the first motor generator 31 and the drive wheels 40.

[0022] The first motor generator 31 generates electricity by receiving driving force from the internal combustion engine 11 and driving force from the drive wheels 40. The first motor generator 31 also serves as a starter that drives the rotating shaft of the internal combustion engine 11 when starting the internal combustion engine 11. At that time, the first motor generator 31 functions as a motor that generates driving force in response to the supply of electric power from the battery 50.

[0023] The first motor generator 31 and the second motor generator 32 are connected to a battery 50 via a power control unit 35. AC power generated by the first motor generator 31 is converted to DC power by the power control unit 35 and charged into the battery 50. In other words, the power control unit 35 functions as an inverter.

[0024] Moreover, the DC power of the battery 50 is converted to AC by the power control unit 35 and supplied to the second motor generator 32. When the vehicle 10 is decelerated, the second motor generator 32 generates power by utilizing the driving force from the drive wheels 40. The generated power is then charged to the battery 50. That is, the vehicle 10 performs regenerative charging. At this time, the second motor generator 32 functions as a generator. At this time, the AC power generated by the second motor generator 32 is converted to DC by the power control unit 35 and charged to the battery 50.

[0025] When the first motor generator 31 is caused to function as a starter, the power control unit 35 converts the DC power of the battery 50 into AC power and supplies it to the first motor generator 31.

[0026] <Control device 100> The control device 100 controls the internal combustion engine 11, the first motor generator 31, and the second motor generator 32. In other words, the control device 100 is a control device that controls the powertrain of the vehicle 10, which is a plug-in hybrid vehicle. Therefore, the control device 100 controls the internal combustion engine 11 including the electrically heated catalyst system 200. The control device 100 also controls the electrically heated catalyst system 200.

[0027] The control device 100 receives detection signals from sensors provided in various parts of the vehicle 10. The detection signals input to the control device 100 include the vehicle speed SP, the accelerator pedal opening degree ACCP, and the state of charge SOC according to the remaining capacity of the battery 50. The control device 100 is connected to a water temperature sensor 101 that detects a water temperature Tw, which is the temperature of the cooling water of the internal combustion engine 11. The control device 100 is also connected to a power switch 102 that allows the driver of the vehicle 10 to start and stop the system of the vehicle 10. Therefore, the control device 100 grasps the start-up state of the system of the vehicle 10 based on an input signal from the power switch 102. The control device 100 is connected to an upstream air-fuel ratio sensor 103 that detects an upstream air-fuel ratio AFu, which is the air-fuel ratio of the exhaust gas flowing into the catalytic converter 29. The upstream air-fuel ratio sensor 103 is disposed in the exhaust passage 21 upstream of the catalytic converter 29. The control device 100 is connected to a downstream air-fuel ratio sensor 104 that detects a downstream air-fuel ratio AFd, which is the air-fuel ratio of the exhaust gas that has passed through the catalytic converter 29. The downstream air-fuel ratio sensor 104 is disposed in the exhaust passage 21 downstream of the catalytic converter 29 and upstream of the filter 36. The control device 100 is connected to an air flow meter 105 that detects the intake air temperature Tin, which is the temperature of the air taken into the internal combustion engine 11, and the intake air amount GA, which is the mass, and a crank angle sensor 106 that detects the rotation angle of the crankshaft of the internal combustion engine 11. The control device 100 calculates the engine speed NE based on the output signal Scr of the crank angle sensor 106. The control device 100 also calculates an engine load factor KL based on the engine speed NE and the intake air amount GA. The engine load factor KL is a parameter that determines the amount of air filled in the combustion chamber of the internal combustion engine 11, and is the ratio of the amount of inflow air per combustion cycle of one cylinder to a reference amount of inflow air. The reference inflow air amount is variably set according to the engine speed NE.

[0028] The vehicle 10 configured as described above can perform EV running in which the drive wheels 40 are driven using only the second motor generator 32 by using the power stored in the battery 50 to drive the second motor generator 32. In addition, the vehicle 10 can also perform hybrid running in which the drive wheels 40 are driven using the internal combustion engine 11 and the second motor generator 32.

[0029] <Configuration of Electrically Heated Catalyst System 200> Next, the configuration of the electrically heated catalyst system 200 will be described with reference to FIG. As shown in Fig. 2, the catalytic converter 29 is equipped with a second catalyst 27 for exhaust gas purification in addition to a first catalyst 26 for exhaust gas purification constituting an electrically heated catalyst 210. Both the first catalyst 26 and the second catalyst 27 are three-way catalysts supported on a honeycomb-structured catalyst carrier in which multiple passages extending in the exhaust gas flow direction are defined. The second catalyst 27 is provided downstream of the first catalyst 26 in the exhaust gas flow direction.

[0030] The first catalyst 26 and the second catalyst 27 are housed in a case 24. The case 24 is a cylinder made of metal, for example, stainless steel. The case 24 constitutes a part of the exhaust passage 21. Inside the case 24, a mat 28 is interposed between the case 24 and the first catalyst 26 and second catalyst 27. The mat 28 is an insulator, and is made of, for example, inorganic fibers containing alumina as a main component.

[0031] The mat 28 is interposed in a compressed state between the first catalyst 26 and the second catalyst 27 and the case 24. Therefore, the first catalyst 26 and the second catalyst 27 are held in the case 24 by the restoring force of the compressed mat 28.

[0032] An upstream connecting pipe 23, the diameter of which decreases toward the upstream side, is fixed to the upstream side of the case 24. A downstream connecting pipe 25, the diameter of which decreases toward the downstream side, is fixed to the downstream side of the case 24.

[0033] 2, the upstream connecting pipe 23 connects the upstream exhaust pipe 22, which has a smaller diameter than the case 24, to the case 24. Similarly, the downstream connecting pipe 25 connects the downstream exhaust pipe, which has a smaller diameter than the case 24, to the case 24. In this manner, the case 24, which contains the first catalyst 26 and the second catalyst 27, the upstream connecting pipe 23, and the downstream connecting pipe 25 constitute a catalytic converter 29 that constitutes a part of the exhaust passage 21.

[0034] The diameter of the upstream end of case 24 becomes smaller as it approaches upstream exhaust pipe 22, and the diameter of the part closest to upstream exhaust pipe 22 is approximately equal to the diameter of upstream exhaust pipe 22.

[0035] The second catalyst 27 is located downstream of the first catalyst 26 in the exhaust gas flow. The catalyst carrier of the first catalyst 26 is made of a material that becomes electrically resistant and generates heat when electricity is applied. For example, silicon carbide can be used as such a material. The catalyst carrier has the property that its electrical resistance is smaller when the temperature is high than when the temperature is low.

[0036] A first electrode 211 and a second electrode 212 are attached to the first catalyst 26. The first electrode 211 is a positive electrode, and the second electrode 212 is a negative electrode. A current flows through the first catalyst 26 by applying a voltage between the first electrode 211 and the second electrode 212. When a current flows through the first catalyst 26, the catalyst support generates heat due to the electrical resistance of the catalyst support.

[0037] In order to pass current uniformly through the entire catalyst carrier, the first electrode 211 and the second electrode 212 extend in the circumferential and axial directions along the outer circumferential surface of the catalyst carrier. Two openings 24K are formed in the case 24, and an insulator 213 made of an insulating material such as alumina is fitted into each opening 24K. The first electrode 211 and the second electrode 212 each pass through the insulator 213 fitted into the opening 24K.

[0038] The opening 24K is closed by a metallic electrode chamber 80. A terminal 85 provided at the end of a power line that supplies power to the first electrode 211 and the second electrode 212 is inserted into this electrode chamber 80. The terminal 85 is connected to the first electrode 211 and the second electrode 212.

[0039] An insulating coating is applied to the inner peripheral surface of the case 24. For example, a glass coating can be used as the insulating coating. As a result, the first catalyst 26 is electrically insulated from the case 24.

[0040] As described above, the first catalyst 26 is equipped with the first electrode 211 and the second electrode 212. This makes the first catalyst 26 an electrically heated catalyst 210 that generates heat when supplied with electric power. Hereinafter, the electrically heated catalyst 210 is referred to as EHC 210. The catalyst support generates heat when electricity is applied, thereby heating the first catalyst 26 and promoting activation.

[0041] Furthermore, when the internal combustion engine 11 starts operating and exhaust gas begins to flow, the exhaust gas is warmed as it passes through the EHC 210, and the heat is transferred to the second catalyst 27 as well. This also facilitates the warming up of the second catalyst 27.

[0042] The first electrode 211 and the second electrode 212 are connected to the battery 50 via a power circuit 221 of the power supply device 220. The power supply device 220 includes a power circuit 221 including an isolation transistor and a power switching element, and a power supply microcomputer 222 that controls the power supply circuit 221. The power supply circuit 221 is provided with a current sensor 224 and a voltage sensor 225. The current sensor 224 and the voltage sensor 225 are connected to the power supply microcomputer 222. The power supply microcomputer 222 detects the current supplied to the EHC 210 based on a signal output by the current sensor 224. In addition, the power supply microcomputer 222 detects the voltage applied to the EHC 210 based on a signal output by the voltage sensor 225. An auxiliary battery 55 is connected to the power supply device 220.

[0043] In addition, the power supply device 220 is provided with a leakage detection circuit 223 that is connected to the power supply circuit 221 and detects the insulation resistance of the EHC 210 to detect leakage. For example, the leakage detection circuit 223 includes a reference resistor. The auxiliary battery 55 supplies power to the power supply circuit 221 including the leakage detection circuit 223. The power supply microcomputer 222 calculates the insulation resistance value Rt of the EHC 210 based on the current value and voltage value detected by the current sensor 224 and voltage sensor 225 at this time.

[0044] The power supply device 220 is connected to the control device 100 so as to be mutually communicable, and the insulation resistance value Rt calculated by the power supply microcomputer 222 is output to the control device 100. In addition, the control device 100 outputs a command to the power supply device 220 and controls the energization of the EHC 210 via the power supply device 220.

[0045] <Regarding the energization of the EHC 210> In the vehicle 10 which is a plug-in hybrid vehicle, when there is sufficient margin in the state of charge SOC of the battery 50, it travels in the EV running mode using only the second motor generator 32 as a driving power source for running. The control device 100 at this time maintains the internal combustion engine 11 in a stopped state. Then, the control device 100 controls the power control unit 35 so that the second motor generator 32 generates torque that can obtain the driving force corresponding to the required driving force.

[0046] In addition, when the state of charge SOC of the battery 50 falls below a certain value during running in the EV running mode, the control device 100 switches the running mode of the vehicle 10 from the EV running mode to the hybrid running mode. The hybrid running mode is a running mode that uses both the internal combustion engine 11 and the second motor generator 32 as driving power sources for running.

[0047] In order to be able to exhibit sufficient exhaust purification ability immediately after switching to the hybrid running mode, it is desirable to energize the EHC 210 and warm up the first catalyst 26 before starting the internal combustion engine 11 after shifting to the hybrid running mode.

[0048] Therefore, before starting the internal combustion engine 11, the control device 100 performs a preheat process of warming up the first catalyst 26 by energizing the EHC 210. Further, the control device 100 performs a post-heat process of continuously energizing the EHC 210 even after the start of the internal combustion engine 11. Note that warming up the catalyst means raising the temperature of the catalyst to the activation temperature.

[0049] <Processing related to energization of EHC210> Referring to FIG. 3, the processing procedure for energization of the EHC 210 including the preheat process and the post-heat process will be described. The process shown in this FIG. 3 is repeatedly executed by the control device 100 when the power switch 102 is ON and the system of the vehicle 10 is operating. In the following, step numbers are represented by numbers preceded by "S".

[0050] As shown in FIG. 3, when starting this process, the control device 100 first determines whether or not the EHC energization request is ON in the process of S100. The EHC energization request refers to a request for energizing the EHC 210. Specifically, the control device 100 determines that the EHC energization request is ON when both of the following two conditions are satisfied.

[0051] · There is a start request for the internal combustion engine 11. Note that the start request for the internal combustion engine 11 includes, for example, the case where the state of charge SOC is lower than the switching threshold value to the hybrid driving mode, or the case where the vehicle driving torque required by the vehicle driver cannot be obtained in the EV driving.

[0052] · The first catalyst temperature Tcat1, which is the temperature of the first catalyst 26, is equal to or lower than a predetermined temperature lower than the activation temperature. The control device 100 estimates the first catalyst temperature Tcat1. For example, when the operation of the internal combustion engine 11 is stopped, the control device 100 stores the first catalyst temperature Tcat1 at that time as the first temperature at stop Toff1 and starts the soak timer. Then, the control device 100 continues the time measurement by the soak timer while the internal combustion engine 11 is stopped. When the internal combustion engine 11 is started, the control device 100 calculates a product obtained by multiplying the difference obtained by subtracting the first temperature at stop Toff1 from the outside air temperature TA by a convergence rate. Then, the control device 100 calculates a sum by adding the product to the first temperature at stop Toff1. The sum calculated in this way is set as the first catalyst temperature Tcat1 at the time of engine start. The convergence rate is calculated based on the soak time. The convergence rate is a value between 0 and 1. The convergence rate approaches 1 as the soak time becomes longer. For example, when the convergence rate is 1, the catalyst temperature T becomes equal to the outside air temperature TA. This indicates that when the convergence rate is 1, the first catalyst temperature Tcat1 converges to the outside air temperature TA. The control device 100 regards the intake air temperature Tin detected by the air flow meter 105 as the outside air temperature TA and uses it to calculate the first catalyst temperature Tcat1.

[0053] During engine operation, the control device 100 calculates a first temperature change amount dT1, which is a temperature change amount of the first catalyst temperature Tcat1. The first temperature change amount dT1 is added to the first catalyst temperature Tcat1 calculated immediately before to calculate the latest first catalyst temperature Tcat1. The first temperature change amount dT1 changes due to the influence of exhaust heat and the amount of heat generated by the EHC 210. Therefore, the control device 100 calculates the first temperature change amount dT1 using parameters that affect the amount of thermal energy of the exhaust gas and parameters that affect the amount of heat generated by the EHC 210. Examples of parameters that affect the amount of thermal energy of the exhaust gas include the engine speed NE, the engine load factor KL, the water temperature Tw, the intake air amount GA, the vehicle speed SP, and the intake air temperature Tin. Examples of parameters that affect the amount of heat generated by the EHC 210 include the amount of electric power input to the EHC 210.

[0054] The control device 100 also estimates the second catalyst temperature Tcat2, which is the temperature of the second catalyst 27. For example, when the internal combustion engine 11 is stopped, the control device 100 stores the second catalyst temperature Tcat2 at that time as the second temperature at stop Toff2 and starts the soak timer. The control device 100 continues to measure time using the soak timer while the internal combustion engine 11 is stopped. When the internal combustion engine 11 is started, the control device 100 calculates a product obtained by multiplying the difference obtained by subtracting the second temperature at stop Toff2 from the outside air temperature TA by a convergence rate. Then, the control device 100 calculates a sum by adding the product to the second temperature at stop Toff2. The sum thus calculated is set as the second catalyst temperature Tcat2 at the time of engine start. The convergence rate is calculated based on the soak time. The convergence rate is a value between 0 and 1. The convergence rate approaches 1 as the soak time becomes longer. For example, when the convergence rate is 1, the catalyst temperature T becomes equal to the outside air temperature TA. This indicates that when the convergence rate is 1, the second catalyst temperature Tcat2 converges to the outside air temperature TA.

[0055] During engine operation, the control device 100 calculates a second temperature change amount dT2, which is the amount of temperature change in the second catalyst temperature Tcat2. The second temperature change amount dT2 is then added to the previously calculated second catalyst temperature Tcat2 to calculate the latest second catalyst temperature Tcat2. The second temperature change amount dT2 changes due to the influence of exhaust heat. Therefore, the control device 100 calculates the second temperature change amount dT2 using parameters that affect the amount of thermal energy of the exhaust gas. Examples of parameters that affect the amount of thermal energy of the exhaust gas flowing into the second catalyst 27 include the first catalyst temperature Tcat1, the intake air amount GA, and the intake air temperature Tin.

[0056] In the process of S100, when it is determined that the EHC energization request is not ON (S100: NO), the control device 100 ends this process once. That is, in this case, the control device 100 does not execute the pre-heat process and the post-heat process.

[0057] On the other hand, when it is determined in the process of S100 that the EHC energization request is ON (S100: YES), the control device 100 advances the process to S110. In the process of S110, the control device 100 prohibits the internal combustion engine 11 from starting.

[0058] Next, in the process of S112, the control device 100 obtains the insulation resistance value Rt at this time point. Then, in the process of S114, the control device 100 determines whether the insulation resistance value Rt is greater than a threshold value A1. The threshold value A1 is a threshold value for determining whether the insulation resistance, which is the electrical resistance of the EHC 210, is large enough to suppress leakage current.

[0059] When it is determined in the process of S114 that the insulation resistance value Rt is equal to or less than the threshold value A1 (S114: NO), the control device 100 advances the process to S116. Then, in the process of S116, the control device 100 releases the inhibition of starting the internal combustion engine 11 and starts the starting of the internal combustion engine 11. Then, this process is temporarily ended.

[0060] On the other hand, when it is determined in the process of S114 that the insulation resistance value Rt is greater than the threshold value A1 (S140: YES), the control device 100 advances the process to S120. In the process of S120, the control device 100 calculates a target electric power amount Q0. Specifically, the control device 100 calculates the target electric power amount Q0 according to the first catalyst temperature Tcat1 estimated when the process of S100 was executed and the maximum oxygen storage amount Cmax calculated during the previous operation of the internal combustion engine 11.

[0061] The maximum oxygen storage amount Cmax is the maximum amount of oxygen that can be stored by the two catalysts provided in the catalytic converter 29, i.e., the first catalyst 26 and the second catalyst 27, when the two catalysts are regarded as one catalyst. The control device 100 estimates the maximum oxygen storage amount Cmax based on, for example, the values ​​of the upstream air-fuel ratio AFu and the downstream air-fuel ratio AFd during engine operation. Here, as the deterioration of the first catalyst 26 and the second catalyst 27 progresses and their degree of deterioration increases, the maximum oxygen storage amount Cmax decreases. Therefore, the maximum oxygen storage amount Cmax is deterioration information that is information related to the degree of deterioration of the first catalyst 26 and the second catalyst 27.

[0062] As shown in FIG. 4, when the maximum oxygen storage amount Cmax decreases due to an increase in the degree of deterioration of the first catalyst 26 or the second catalyst 27, the activation temperatures of the first catalyst 26 or the second catalyst 27 tend to increase.

[0063] In the preheat process, the first catalyst 26 is heated to or above its activation temperature by continuing to supply electricity to the EHC 210 until the amount of electricity Q, which is the integrated value of the input power, reaches a target amount of electricity Q0, thereby warming up the first catalyst 26. In other words, the target amount of electricity Q0 is the amount of electricity required to heat the first catalyst 26 from the temperature before the start of electricity supply until the warm-up is completed.

[0064] Therefore, as shown in Fig. 5, in the process of S120, the control device 100 calculates a larger value as the target electric power amount Q0 as the first catalyst temperature Tcat1 is lower. Note that the electric power amount Q is an integrated value of the electric power actually supplied to the EHC 210. Also, as shown in Fig. 5, in the process of S120, the control device 100 calculates a larger value as the target electric power amount Q0 as the maximum oxygen storage amount Cmax is smaller and the activation temperature is higher.

[0065] Next, in the process of S130, the control device 100 sets the power supplied to the EHC 210 to the first power W1. In this embodiment, the power supplied to the EHC 210 in the pre-heat process and the post-heat process is both the first power W1. However, the power supplied to the EHC 210 in the pre-heat process and the post-heat process may be different.

[0066] Next, the control device 100 advances the process to S140. In the process of S140, the control device 100 starts energizing the EHC 210. In the preheat process, the control device 100 controls the power supply circuit 221 so that the input power becomes a set value, converts the voltage of the battery 50, and supplies power to the EHC 210. When the temperature of the first catalyst 26 rises due to the preheat process, the insulation resistance value Rt gradually decreases. Therefore, the control device 100 lowers the voltage in accordance with the decrease in the insulation resistance value Rt to maintain the input power at the first power W1. In addition, the control device 100 controls the voltage within a range equal to or less than the upper limit voltage so that the voltage does not exceed a preset upper limit voltage value. That is, the upper limit voltage is the upper limit value of the voltage when controlling the voltage in the preheat process. In addition, when energization is started, the control device 100 reads the current value detected by the current sensor 224 and the voltage value detected by the voltage sensor 225, and starts integrating the input power. While power is being applied to the EHC 210, the control device 100 continues to calculate the amount of power Q input to the EHC 210 by integrating the input power.

[0067] In the next process of S150, the control device 100 determines whether the amount of power Q is equal to or greater than the target amount of power Q0. If the amount of power Q is determined to be less than the target amount of power Q0 in the process of S150 (S150: NO), the control device 100 repeats the process of S150.

[0068] On the other hand, when it is determined in the process of S150 that the electric power amount Q is equal to or greater than the target electric power amount Q0 (S150: YES), the control device 100 proceeds to the process of S160. Then, in the process of S160, the control device 100 cancels the start inhibition of the internal combustion engine 11 and starts the start of the internal combustion engine 11. By starting the internal combustion engine 11 in this manner, the process of warming up the first catalyst 26 by energizing the EHC 210 transitions from a pre-heat process to a post-heat process.

[0069] Next, the control device 100 calculates the correction coefficient a1 in the process of S170. Specifically, the control device 100 calculates the correction coefficient a1 based on the insulation resistance value Rt acquired in the process of S112.

[0070] As shown in FIG. 6, the correction coefficient a1 is a positive value equal to or less than 1. In the process of S170, the control device 100 calculates a smaller value as the correction coefficient a1 as the insulation resistance value Rt is smaller. Specifically, as shown in FIG. 6, when the insulation resistance value Rt is equal to or less than the first threshold value Rt1, the control device 100 calculates, for example, 0.3 as the correction coefficient a1. When the insulation resistance value Rt is equal to or greater than the second threshold value Rt2 that is larger than the first threshold value Rt1, the control device 100 calculates 1.0 as the correction coefficient a1. When the insulation resistance value Rt is larger than the first threshold value Rt1 and smaller than the second threshold value Rt2, the control device 100 calculates a value larger than 0.3 and smaller than 1.0 according to the magnitude of the insulation resistance value Rt. In this case, as shown in FIG. 6, the control device 100 calculates the correction coefficient a1 so that the correction coefficient a1 becomes larger as the insulation resistance value Rt becomes larger.

[0071] Next, the control device 100 executes engine output limitation in the process of S172. Specifically, the control device 100 sets the product of multiplying the default output P1 by the correction coefficient a1 as the upper limit value Pec of the engine output Pe. The default output P1 is, for example, the output when the internal combustion engine 11 is operated at idle in a state where the warm-up of the second catalyst 27 is completed. That is, the default output P1 is multiplied by the correction coefficient a1 smaller than 1.0, so that the upper limit value Pec of the engine output Pe is set to a value lower than the default output P1. As a result, the engine output Pe is limited.

[0072] Next, in the process of S174, the control device 100 starts steady operation so as to keep the engine output Pe at the upper limit value Pec and the engine speed NE at a default value Ne. The default value Ne is set to a value slightly lower than the engine speed NE at which the amount of exhaust gas discharged from the internal combustion engine 11 is appropriate for suppressing the occurrence of condensation in the case 24.

[0073] By performing such steady operation, the engine is operated in a state where the output of the internal combustion engine 11 is limited. That is, the processes of S170, S172, and S174 are limiting processes that limit the output of the internal combustion engine 11 to a lower output when the post-heat process is being performed compared to when the post-heat process is not being performed. By performing such limiting processes, the deterioration of emissions is suppressed even if the engine is operated in a state where the warm-up of the second catalyst 27 is incomplete.

[0074] Next, the control device 100 calculates the reference value Tref in the process of S180. The reference value Tref is the activation temperature of the second catalyst 27. As described above, the activation temperature of the second catalyst 27 changes depending on the deterioration level of the second catalyst 27. The deterioration level of the second catalyst 27 is correlated with the maximum oxygen storage amount Cmax. Therefore, in the process of S180, the control device 100 acquires the maximum oxygen storage amount Cmax, which is the deterioration information of the second catalyst 27. Then, the control device 100 calculates the reference value Tref based on the acquired maximum oxygen storage amount Cmax.

[0075] As shown in FIG. 7, the control device 100 calculates the reference value Tref so that the smaller the maximum oxygen storage amount Cmax is, the higher the reference value Tref becomes. Next, the control device 100 acquires the second catalyst temperature Tcat2 in the process of S190. Then, the control device 100 judges whether the second catalyst temperature Tcat2 is equal to or higher than the judgment value Tref. Then, in the process of S190, when it is judged that the second catalyst temperature Tcat2 is less than the judgment value Tref (S190: NO), the control device 100 repeats the process of S190.

[0076] On the other hand, in the process of S190, when it is determined that the second catalyst temperature Tcat2 is equal to or higher than the reference value Tref (S190: YES), the control device 100 advances the process to S200. In the process of S200, the control device 100 ends the engine output limitation and steady operation described above.

[0077] Next, in the process of S210, the control device 100 stops the supply of electricity to the EHC 210. That is, the control device 100 ends the post-heat process. Then, the control device 100 temporarily ends this process.

[0078] <effect> The operation of this embodiment will now be described. Fig. 8 is a time chart showing the transition of various states when the vehicle system is started up. Fig. 8(a) shows the transition of the output of the internal combustion engine 11, Fig. 8(b) shows the energization state of the EHC 210, and Fig. 8(c) shows the transition of the first catalyst temperature Tcat1 and the second catalyst temperature Tcat2.

[0079] As shown in FIG. 8, when it is determined at time t1 that the EHC power supply request is ON, power supply to the EHC 210 begins, causing the first catalyst temperature Tcat1 to rise. Then, at time t2, when the amount of electric power Q supplied to the EHC 210 becomes equal to or greater than the target amount of electric power Q0 and the warm-up of the first catalyst 26 is completed, engine start is started. When engine start is started, the above-mentioned limitation process is performed, so that the engine output Pe is maintained at the upper limit value Pec and the engine speed NE is maintained at the default value Ne. The supply of electricity to the EHC 210 from time t1 to time t2 is a preheat process for warming up the first catalyst 26 by supplying electricity to the first catalyst 26 prior to the start of the internal combustion engine 11.

[0080] In this embodiment, the supply of electricity to the EHC 210 continues even after the engine start is initiated. Then, at time t3, when the second catalyst temperature Tcat2 becomes equal to or higher than the determination value Tref and the warm-up of the second catalyst 27 is completed, the above-described restriction process is ended and the supply of electricity to the EHC 210 is stopped. The supply of electricity to the EHC 210 from time t2 to time t3 is a post-heat process in which electricity is supplied to the first catalyst 26 after the internal combustion engine 11 has begun to start.

[0081] In the example shown in FIG. 8, at time t3, the limiting process ends, and the engine output Pe increases to the default output P1. <About the effects> The effects of this embodiment will be described.

[0082] (1) Even after the pre-heat process is completed and engine startup is initiated, the post-heat process continues to energize the first catalyst 26. By executing the post-heat process, a decrease in temperature of the first catalyst 26 that has completed warming up is suppressed. Therefore, the control device 100 can suppress a deterioration in emissions immediately after engine startup.

[0083] (2) When the engine start is started, exhaust gas containing moisture flows into the case 24. Therefore, moisture in the exhaust gas may condense on the inner wall of the case 24 or the inner wall of the electrode chamber 80. If such condensation occurs, the insulation of the EHC 210 may be deteriorated. In addition, when the temperature of the first catalyst 26 rises due to the preheat process, the moisture absorbed in the mat 28 evaporates. This evaporated moisture may condense again on the inner wall of the case 24 or the inner wall of the electrode chamber 80, which may deteriorate the insulation of the EHC 210. It is not preferable to continue to energize the first catalyst 26 in a state in which the insulation has deteriorated. Therefore, the control device 100 limits the output of the internal combustion engine 11 while the postheat process is being performed. As a result, the control device 100 reduces the flow rate of the exhaust gas and suppresses the inflow of moisture into the case 24. That is, the control device 100 can suppress the interruption of the postheat process due to the deterioration of the insulation. In addition, the control device 100 can continue the postheat process to reduce emissions.

[0084] (3) Electricity should be passed through the first catalyst 26 only after a certain level of insulation has been ensured. If the insulation resistance value Rt of the EHC 210 is low to begin with, there is little margin of insulation for continuing the post-heat process. The control device 100 sets the degree of limitation of the output of the internal combustion engine 11 according to the degree of this margin of insulation. Therefore, the control device 100 can prevent the output of the internal combustion engine 11 from being restricted more than necessary.

[0085] (4) When electricity is applied to the first catalyst 26 by the post-heat process, the temperature drop of the exhaust gas passing through the first catalyst 26 is suppressed, and the warming up of the second catalyst 27 by the exhaust gas is promoted. The control device 100 applies electricity to the first catalyst 26 by the post-heat process until the second catalyst 27 reaches its activation temperature. Therefore, the time required to complete the warming up of the second catalyst 27 is shortened, which also suppresses the deterioration of emissions immediately after the engine start.

[0086] (5) The first catalyst 26 is energized by the post-heat process until the second catalyst temperature Tcat2 reaches a reference value Tref, which is set as the activation temperature. As the deterioration of the second catalyst 27 progresses, the activation temperature of the second catalyst 27 tends to become higher. In this regard, the control device 100 sets the reference value Tref to a higher temperature as the degree of deterioration of the second catalyst 27 indicated in the deterioration information of the second catalyst 27 becomes higher. More specifically, the control device 100 sets the reference value Tref to a higher temperature as the maximum oxygen storage amount Cmax becomes smaller. Therefore, the control device 100 can appropriately energize the first catalyst 26 by the post-heat process according to the degree of deterioration of the second catalyst 27.

[0087] (6) The control device 100 terminates the limitation process when the post-heat process is terminated. Therefore, the control device 100 can prevent the output of the internal combustion engine 11 from being restricted more than necessary.

[0088] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0089] In the process of S120, the control device 100 calculates the target electric power amount Q0 according to the first catalyst temperature Tcat1 and the maximum oxygen storage amount Cmax. Alternatively, the target electric power amount Q0 may be calculated according to either the first catalyst temperature Tcat1 or the maximum oxygen storage amount Cmax. The target electric power amount Q0 may also be calculated according to other parameters.

[0090] The engine output limit in the limiting process is a steady operation in which the engine output Pe and the engine speed NE are controlled to be constant values. Alternatively, the engine output limit may be a control of the engine output Pe within a range equal to or less than the upper limit value Pec so that the engine output Pe does not exceed the upper limit value Pec.

[0091] The limiting process is an example in which the processes of S170, S172, and S174 are executed. In the above example, the upper limit value Pec is calculated using the correction coefficient a1 that is set based on the insulation resistance value Rt. The limiting process is not limited to this. The limiting process may be any process that limits the output of the internal combustion engine 11 to an output that is lower than when the post-heat process is not executed.

[0092] A processing procedure in one of such modified examples is shown in Fig. 9. Fig. 9 also shows differences from the processing shown in Fig. 3. As shown in Fig. 9, after completing the above-mentioned processing of S160, the control device 100 next calculates the correction coefficient a2 as processing of S300. Specifically, the control device 100 calculates the correction coefficient a2 based on the outside air temperature TA.

[0093] As shown in FIG. 10, the correction coefficient a2 is a positive value equal to or less than 1. In the process of S300, the control device 100 calculates a smaller value as the correction coefficient a2 as the lower the outside air temperature TA. Specifically, as shown in FIG. 10, when the outside air temperature TA is equal to or less than the first temperature TA1, the control device 100 calculates, for example, 0.3 as the correction coefficient a2. When the outside air temperature TA is equal to or greater than a third temperature TA3 higher than the first temperature TA1, the control device 100 calculates 1.0 as the correction coefficient a2. When the outside air temperature TA is higher than the first temperature TA1 and lower than the third temperature TA3, the control device 100 calculates a value greater than 0.3 and smaller than 1.0 according to the magnitude of the value of the outside air temperature TA. In this case, as shown in FIG. 10, the control device 100 calculates the correction coefficient a2 so that the lower the outside air temperature TA, the smaller the correction coefficient a2.

[0094] Next, in the process of S320, the control device 100 calculates the ignition timing retard amount b. Specifically, the control device 100 calculates the ignition timing retard amount b based on the outside air temperature TA. As shown in FIG. 11, the lower the outside air temperature TA, the larger the ignition timing retard amount b is set by the control device 100. Specifically, as shown in FIG. 11, when the outside air temperature TA is equal to or higher than a fourth temperature TA4, the control device 100 calculates 0 as the ignition timing retard amount b. When the outside air temperature TA is lower than the fourth temperature TA4 and equal to or higher than a second temperature TA2 lower than the fourth temperature TA4, the control device 100 calculates a value larger than 0 according to the value of the outside air temperature TA. In this case, as shown in FIG. 11, the control device 100 calculates the ignition timing retard amount b so that the ignition timing retard amount b is larger as the outside air temperature TA is lower. When the outside air temperature TA is lower than the second temperature TA2, the control device 100 calculates the ignition timing retard amount b to a value equal to that when the outside air temperature TA is the second temperature TA2.

[0095] Next, the control device 100 executes engine output limitation in the process of S330. Specifically, the control device 100 sets the product of multiplying the default output P1 by the correction coefficient a2 to the upper limit value Pec of the engine output Pe. That is, by multiplying the default output P1 by the correction coefficient a2 that is smaller than 1.0, the upper limit value Pec of the engine output Pe is set to a value lower than the default output P1. This limits the engine output Pe.

[0096] Next, in the process of S340, similar to the process of S174, the control device 100 starts steady operation so as to maintain the engine output Pe at the upper limit value Pec and to maintain the engine rotation speed NE at the preset value Ne.

[0097] Next, the control device 100 executes ignition retard to retard the ignition timing in the process of S350. Specifically, the control device 100 retards the ignition timing by the ignition timing retard amount b. As a result, the internal combustion engine 11 starts steady operation with the ignition timing retarded. When the control device 100 starts steady operation with the ignition timing retarded in this way, the control device 100 advances the process to S180 described above.

[0098] In this modification, the restriction process includes steps S300, S320, S330, S340, and S350. Therefore, the restriction process in this modification is such that the output of the internal combustion engine 11 is restricted to a lower output as the outside air temperature TA becomes lower.

[0099] The lower the outside air temperature TA, the more likely it is that moisture in the exhaust gas will condense. Therefore, the lower the outside air temperature TA, the more likely it is that the insulating properties of the first catalyst 26 will deteriorate. The control device 100 of this modified example can set the degree of limitation on the output of the internal combustion engine 11 in accordance with how easily the insulating properties deteriorate. Therefore, the control device 100 can appropriately suppress the deterioration of emissions even when the outside air temperature TA is low.

[0100] Moreover, the restriction process in this modified example is a process for operating the internal combustion engine 11 with the ignition timing retarded when the outside air temperature TA is low compared to when the outside air temperature TA is high. When the outside air temperature TA is low, moisture in the exhaust gas is likely to condense, and the insulating properties of the first catalyst 26 are likely to deteriorate. When the ignition timing is retarded, the exhaust gas temperature increases. When the outside air temperature TA is low, the control device 100 of this modified example retards the ignition timing to increase the exhaust gas temperature. This makes it difficult for condensation to occur even when the outside air temperature TA is low. In other words, the control device 100 can suppress deterioration of insulating properties even when the outside air temperature TA is low.

[0101] A process for calculating the correction coefficient a1 based on the insulation resistance value Rt and a process for calculating the ignition timing retard amount b based on the outside air temperature TA may be executed, and a configuration for retarding the ignition timing in the above embodiment may be adopted.

[0102] When the outside air temperature TA is below a certain level, the ignition timing may be switched to a specific ignition timing that is more retarded than the ignition timing when the outside air temperature TA is above the certain level. In the above modified example, the engine output is limited and the ignition timing is retarded. Alternatively, either one of the engine output limit and the ignition timing retard may be implemented.

[0103] The reference value Tref is changed according to the maximum oxygen storage amount Cmax, but may be a predetermined constant value, for example, the activation temperature when it is assumed that the deterioration level of the second catalyst 27 has reached an allowable limit.

[0104] Although the maximum oxygen storage amount Cmax is used as catalyst deterioration information, other values ​​may be used. For example, the longer the total operating time of the internal combustion engine 11, the higher the degree of catalyst deterioration tends to be. Therefore, the total operating time may be used as catalyst deterioration information.

[0105] In the process of S190, the second catalyst temperature Tcat2 is compared with the reference value Tref to determine the time to end the energization of the EHC 210. However, the time to end the energization may be determined by comparing with another value.

[0106] For example, the timing to end the energization may be determined based on the amount of electric power supplied to the first catalyst 26 reaching the amount of electric power required from the start of the internal combustion engine 11 until the second catalyst 27 reaches its activation temperature.

[0107] The limiting process does not necessarily have to end when the post-heat process ends. The limiting process may end after the post-heat process ends. Also, the post-heat process may end after the limiting process ends.

[0108] The catalyst supported on the catalyst carrier is not limited to a three-way catalyst, but may be, for example, an oxidation catalyst, a NOx storage reduction catalyst, or a NOx selective reduction catalyst. The vehicle 10 on which the electrically heated catalyst system 200 and the control device 100 are mounted is not limited to a plug-in hybrid vehicle, but may also be a hybrid vehicle without a plug-in function, or a vehicle powered only by an internal combustion engine 11.

[0109] The control device 100 may be configured as one or more dedicated hardware circuits, such as one or more processors that execute various processes according to a computer program (software) or an application specific integrated circuit (ASIC) that executes at least some of the various processes. The control device 100 may also be configured as a circuit including a combination of these. The processor includes a CPU and memory, such as RAM and ROM, which stores program code or instructions configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or special-purpose computer. [Explanation of symbols]

[0110] 10. Vehicle 11...Internal combustion engine 21...Exhaust passage 24…Case 24K…Aperture 26…First catalyst 27…Second catalyst 28…Matt 29…Catalytic converter 36…Filter 50…Battery 55…Auxiliary battery 80...Electrode chamber 100...Control device 101...Water temperature sensor 102…Power switch 103...Upstream air-fuel ratio sensor 104...Downstream air-fuel ratio sensor 105...Air flow meter 106...Crank angle sensor 200…Electrically heated catalyst system 210...Electrically heated catalyst (EHC) 220…Power supply device 221…Power circuit 222…Power supply microcomputer 224...Current sensor 225…Voltage sensor

Claims

1. A control device applied to an internal combustion engine including an electrically heated first catalyst that is housed in a case provided in an exhaust passage and heated by passing electricity through it, and a second catalyst that is provided downstream of the first catalyst in the exhaust gas, a preheat process of warming up the first catalyst by energizing the first catalyst prior to starting the internal combustion engine; a process of starting the internal combustion engine when the preheat process is completed; a post-heat process in which, after the pre-heat process is completed, current is applied to the first catalyst while the internal combustion engine is in operation; a limiting process for limiting the output of the internal combustion engine to a lower output when the post-heat process is being executed, compared to when the post-heat process is not being executed; The limiting process is a process for limiting the output of the internal combustion engine to a lower output as the insulation resistance value of the first catalyst decreases. A control device for an internal combustion engine.

2. A control device applied to an internal combustion engine including an electrically heated first catalyst that is housed in a case provided in an exhaust passage and heated by passing electricity through it, and a second catalyst that is provided downstream of the first catalyst in the exhaust gas, a preheat process of warming up the first catalyst by energizing the first catalyst prior to starting the internal combustion engine; a process of starting the internal combustion engine when the preheat process is completed; a post-heat process in which, after the pre-heat process is completed, current is applied to the first catalyst while the internal combustion engine is in operation; a limiting process for limiting the output of the internal combustion engine to a lower output when the post-heat process is being executed, compared to when the post-heat process is not being executed; The limitation process is a process for limiting the output of the internal combustion engine to a lower output as the outside air temperature decreases. A control device for an internal combustion engine.

3. A control device applied to an internal combustion engine including an electrically heated first catalyst that is housed in a case provided in an exhaust passage and heated by passing electricity through it, and a second catalyst that is provided downstream of the first catalyst in the exhaust gas, a preheat process of warming up the first catalyst by energizing the first catalyst prior to starting the internal combustion engine; a process of starting the internal combustion engine when the preheat process is completed; a post-heat process in which, after the pre-heat process is completed, current is applied to the first catalyst while the internal combustion engine is in operation; a limiting process for limiting the output of the internal combustion engine to a lower output when the post-heat process is being executed, compared to when the post-heat process is not being executed; The restriction process is a process for operating the internal combustion engine with the ignition timing retarded when the outside air temperature is low compared to when the outside air temperature is high. A control device for an internal combustion engine.

4. The limiting process is a process for steadily operating the internal combustion engine at a constant output and a constant engine rotation speed. The control device for an internal combustion engine according to any one of claims 1 to 3.

5. The post-heat treatment is performed by passing current through the first catalyst until the temperature of the second catalyst reaches an activation temperature of the second catalyst; When the post-heat process is terminated, the limiting process is terminated. The control device for an internal combustion engine according to any one of claims 1 to 4.

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