Control device for internal combustion engine

Abstract

To suppress deterioration of emission right after start of an engine.SOLUTION: An internal combustion engine comprises an electric heating type first catalyst 26 provided in an exhaust passage and heated by energization, and a second catalyst 27 provided on an exhaust downstream side with respect to the first catalyst 26. A controller 100 executes: a preheating process of warming up the first catalyst 26 by energizing the first catalyst 26 prior to starting an internal combustion engine; a process of starting the internal combustion engine after execution of the preheating process is completed; and a post-heating process of energizing the first catalyst 26 after the start of the internal combustion engine. Then, the controller 100 energizes the first catalyst 26 by the post-heating process until the second catalyst 27 reaches an activation temperature.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 provided in the exhaust passage of an internal combustion engine and heated by passing current through it (for example, Patent Document 1, etc.). The electrically heated catalyst can warm up the catalyst prior to engine start by executing a preheat process in which current is passed through it before the internal combustion engine is started. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-96209 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, immediately after 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 immediately after engine start-up. [Means for solving the problem]

[0006] A control device for an internal combustion engine that solves the above problems is applied to an internal combustion engine that includes an electrically heated first catalyst that is provided in an exhaust passage and heated by current flow, and a second catalyst that is provided downstream of the first catalyst in the exhaust gas. This control device executes a preheat process that warms up the first catalyst by current flowing through the first catalyst prior to starting the internal combustion engine, a process that starts starting the internal combustion engine after the execution of the preheat process is completed, and a postheat process that currents the first catalyst after the start of the internal combustion engine. The control device then continues current flow through the first catalyst by the postheat process until the temperature of the second catalyst reaches an activation temperature of the second catalyst.

[0007] According to this configuration, even after the preheat process is completed and the engine start is started, the first catalyst is energized by the postheat process. By executing the postheat process, the temperature drop of the first catalyst that has completed warming up is suppressed, and therefore the deterioration of emissions immediately after the engine start is suppressed.

[0008] In addition, if the temperature of the second catalyst reaches the activation temperature, the second catalyst purifies the exhaust gas, so the exhaust gas can be purified even if the power supply to the first catalyst is stopped. Therefore, in this configuration, the power supply to the first catalyst by the post-heat process is continued until the second catalyst reaches the activation temperature. Therefore, the deterioration of the emissions is suppressed even if the power supply to the first catalyst is stopped.

[0009] In the control device, a process for acquiring the temperature of the second catalyst is executed, and the post-heat process may be a process for supplying current to the first catalyst until the acquired temperature of the second catalyst reaches a predetermined judgment value to which the activation temperature is set.

[0010] In addition, when performing such post-heat processing, a process may be executed to acquire deterioration information, which is information regarding the degree of deterioration of the second catalyst, and a process to set the judgment value to a higher temperature when the degree of deterioration indicated in the acquired deterioration information is higher.

[0011] As the deterioration of the second catalyst progresses, the activation temperature of the second catalyst tends to become higher. In this regard, according to this configuration, the higher the degree of deterioration of the second catalyst indicated in the acquired deterioration information, the higher the judgment value is set to. Therefore, it becomes possible to appropriately apply electricity to the first catalyst by the post-heat process according to the degree of deterioration of the second catalyst.

[0012] In addition, in the control device, when the amount of power supplied to the first catalyst required from the start of the internal combustion engine until the second catalyst reaches an activation temperature is defined as an activation power amount, the post-heat processing may be a process of supplying electricity to the first catalyst until the amount of power supplied to the first catalyst from the start of the internal combustion engine reaches the activation power amount.

[0013] In addition, when performing such post-heat processing, a process of acquiring deterioration information, which is information regarding the deterioration level of the second catalyst, and a process of setting the activation power amount to a larger value when the deterioration level indicated in the acquired deterioration information is higher may be performed.

[0014] As described above, as the deterioration of the second catalyst progresses, the activation temperature of the second catalyst tends to become higher. Therefore, as the deterioration of the second catalyst progresses, the activation power amount becomes a larger value. In this regard, according to this configuration, the higher the degree of deterioration of the second catalyst indicated in the acquired deterioration information, the larger the activation power amount is set to. Therefore, even with this configuration, it becomes possible to appropriately apply electricity to the first catalyst by the post-heat process according to the degree of deterioration of the second catalyst. [Brief description of the drawings]

[0015] [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 maximum oxygen storage amount and a judgment value. [Figure 7] 7 is a time chart showing the transition of various states when the vehicle system is started up, in which Fig. 7(a) shows the engine output, Fig. 7(b) shows the electrification state of the electrically heated catalyst, and Fig. 7(c) shows the transition of the first catalyst temperature and the second catalyst temperature. [Figure 8] 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 9] 1 is a graph showing the relationship between the maximum oxygen storage amount and the amount of activation power. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, one embodiment of a control device for an internal combustion engine will be described with reference to Figs. <Vehicle configuration> The configuration of a vehicle 10 equipped with an internal combustion engine control device 100 will be described with reference to FIG.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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 .

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] <Control device> 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.

[0028] 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.

[0029] 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.

[0030] <Configuration of Electrically Heated Catalyst System> 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] In order to pass a current uniformly throughout the 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. In addition, the first electrode 211 and the second electrode 212 each penetrate the case 24.

[0039] Insulators 213 made of an insulating material such as alumina are fitted between the case 24 and each of the first electrode 211 and the second electrode 212. An insulating coating is applied to the inner peripheral surface of the case 24 by applying an insulating material. 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] Further, 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 the 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. Further, the control device 100 outputs a command to the power supply device 220 and controls the energization to the EHC 210 via the power supply device 220.

[0045] <Regarding the energization of the EHC> 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 the 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 capable of obtaining the driving force corresponding to the required driving force.

[0046] Further, 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 the driving power source 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, the control device 100 executes a preheat process for warming up the first catalyst 26 by energizing the EHC 210 prior to the start of the internal combustion engine 11. Further, the control device 100 executes a post-heat process for continuously energizing the EHC 210 even after the start of the internal combustion engine 11 has been started. Note that warming up the catalyst means raising the temperature of the catalyst to the activation temperature.

[0049] <Processing related to energization of EHC> With reference to FIG. 3, the processing procedure for energization of the EHC including the preheat process and the post-heat process will be described. The processing 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, the step numbers are represented by numbers with "S" added at the beginning.

[0050] As shown in FIG. 3, when starting this main 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 the energization request to 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 by 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 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 thus calculated 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. This indicates that when the convergence rate is 1, the first catalyst temperature Tcat1 converges to the outside air temperature. The control device 100 regards the intake air temperature Tin detected by the air flow meter 105 as the outside air temperature 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 control device 100 stops the operation of the internal combustion engine 11, it stores the second catalyst temperature Tcat2 at that time as the second temperature at stop Toff2 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 the product of the difference obtained by subtracting the second temperature at stop Toff2 from the outside air temperature and multiplying it by the convergence rate. Then, it calculates the sum by adding the product to the second temperature at stop Toff2. The sum calculated in this way 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. This indicates that when the convergence rate is 1, the second catalyst temperature Tcat2 converges to the outside air temperature.

[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. Then, in the process of S110, the control device 100 prohibits the starting of the internal combustion engine 11. Next, the control device 100 advances the process to S120.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 advances the process to S160. Then, in the process of S160, the control device 100 releases the inhibition of starting the internal combustion engine 11 and starts the starting of the internal combustion engine 11.

[0067] Next, in the process of S170, the control device 100 implements engine output limitation and ignition timing retardation. The engine output limitation is to control the engine output Pe of the internal combustion engine 11 so that the engine output Pe is constant at a preset default output Pec. Note that the default output Pec is set to a value slightly less than the engine output Pe when the amount of exhaust gas discharged from the internal combustion engine 11 reaches the upper limit amount of exhaust gas that can be purified by the first catalyst 26. By implementing such engine output limitation, 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 not completed.

[0068] In addition, the ignition timing is retarded compared to when the engine is started without energizing the EHC 210. By retarding the ignition timing, the temperature of the exhaust gas discharged from the internal combustion engine 11 increases. This makes it possible to suppress a decrease in temperature of the first catalyst 26 due to the exhaust gas and to promote the warming up of the second catalyst 27.

[0069] 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.

[0070] As shown in FIG. 6, 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.

[0071] 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 the ignition timing retardation described above.

[0072] Next, in the process of S210, the control device 100 stops the supply of electricity to the EHC 210. Then, this process ends for the time being. <effect> The operation of this embodiment will now be described.

[0073] Fig. 7 is a time chart showing the transition of various states when the vehicle system is started up. Fig. 7(a) shows the transition of the output of the internal combustion engine 11, Fig. 7(b) shows the energization state of the EHC 210, and Fig. 7(c) shows the transition of the first catalyst temperature Tcat1 and the second catalyst temperature Tcat2.

[0074] As shown in FIG. 7, 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, 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, and engine start is started. When engine start is started, the engine output Pe is maintained at the default output Pec by the above-mentioned engine output limitation, and the ignition timing is retarded. 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.

[0075] In this embodiment, the supply of electricity to the EHC 210 continues even after engine start-up has commenced. 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 engine output limitation and ignition timing retard are terminated 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.

[0076] <About the effects> The effects of this embodiment will be described. (1) Even after the preheat process is completed and engine startup is initiated, the post-heat process continues to supply current to 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, thereby suppressing a deterioration in emissions immediately after engine startup.

[0077] Furthermore, if the temperature of the second catalyst 27 reaches the activation temperature, the exhaust gas is purified by the second catalyst 27, so that the exhaust gas can be purified even if the supply of electricity to the first catalyst 26 is stopped. Therefore, in this embodiment, the supply of electricity to the first catalyst 26 by the post-heat process is continued until the second catalyst 27 reaches the activation temperature. Therefore, even if the supply of electricity to the first catalyst 26 is stopped, the deterioration of emissions is suppressed.

[0078] (2) 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 thus the warming-up of the second catalyst 27 by the exhaust gas is promoted. Here, in this embodiment, electricity is applied 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.

[0079] (3) 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, in the present embodiment, the higher the degree of deterioration of the second catalyst 27 indicated in the deterioration information of the second catalyst 27, more specifically, the smaller the maximum oxygen storage amount Cmax, the higher the temperature that the reference value Tref is set to. Therefore, it becomes possible to appropriately energize the first catalyst 26 by the post-heat process according to the degree of deterioration of the second catalyst 27.

[0080] <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.

[0081] 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.

[0082] The engine output limit is to control the engine output Pe so that the engine output Pe is constant at a preset default output Pec. Alternatively, the engine output limit may be to control the engine output Pe within a range equal to or less than the preset upper limit output Pem so that the engine output Pe does not exceed the preset upper limit output Pem. Note that the value of the upper limit output Pem may be the default output Pec described above.

[0083] In the process of S170, the engine output limit and the ignition timing retard are implemented. Alternatively, either the engine output limit or the ignition timing retard may be implemented. Also, by omitting the processes of S170 and S200, it is possible to avoid implementing both the engine output limit and the ignition timing retard.

[0084] 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.

[0085] 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.

[0086] In the process of S190, the second catalyst temperature Tcat2 is compared with the reference value Tref, but another value may be compared with it. FIG. 8 shows the processing procedure of such a modified example. Note that FIG. 8 shows differences from the processing shown in FIG. 3. As shown in FIG. 8, after completing the processing of S170 described above, the control device 100 next calculates the activation power amount Qk as the processing of S300. The activation power amount Qk is the amount of power supplied to the first catalyst 26 required from the start of the internal combustion engine 11 until the second catalyst 27 reaches the activation temperature. As described above, the activation temperature of the second catalyst 27 changes depending on the deterioration degree of the second catalyst 27. And the deterioration degree of the second catalyst 27 is correlated with the maximum oxygen storage amount Cmax. Therefore, the control device 100 acquires the above-mentioned maximum oxygen storage amount Cmax, which is the deterioration information of the second catalyst 27, in the processing of S300. And, the activation power amount Qk is calculated based on the acquired maximum oxygen storage amount Cmax.

[0087] As shown in FIG. 9, the control device 100 calculates the value of the activation electric energy Qk so that the value of the activation electric energy Qk increases as the maximum oxygen storage amount Cmax decreases. Next, the control device 100 acquires the post electric power amount Qp in the process of S310. The post electric power amount Qp is the amount of electric power supplied to the first catalyst 26 after the start of the internal combustion engine 11 is started through the process of S160 shown in Fig. 3. Then, the control device 100 judges whether the post electric power amount Qp is equal to or greater than the activation electric power amount Qk. Then, when it is judged in the process of S310 that the post electric power amount Qp is less than the activation electric power amount Qk (S310: NO), the control device 100 repeats the process of S310.

[0088] On the other hand, when it is determined in the process of S310 that the post electric energy Qp is equal to or greater than the activation electric energy Qk (S310: YES), the control device 100 advances the process to S200 described above.

[0089] In this modified example, the first catalyst 26 is energized by the post heat process until the post electric power amount Qp reaches the activation electric power amount Qk. Here, as the deterioration of the second catalyst 27 progresses, the activation temperature of the second catalyst 27 tends to become higher. In this regard, in this modified example, the higher the degree of deterioration of the second catalyst 27 indicated in the deterioration information of the second catalyst 27, more specifically, the smaller the maximum oxygen storage amount Cmax, the larger the activation electric power amount Qk is set to. Therefore, even in this modified example, it becomes possible to appropriately energize the first catalyst 26 by the post heat process in accordance with the degree of deterioration of the second catalyst 27.

[0090] More simply, the activation power Qk may be set to a predetermined constant value. For example, this constant value may be the above-mentioned power amount when it is assumed that the deterioration degree of the second catalyst 27 has reached an allowable limit.

[0091] 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 that uses only an internal combustion engine 11 as a power source.

[0092] 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. 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]

[0093] 10. Vehicle 11...Internal combustion engine 21...Exhaust passage 24…Case 26…First catalyst 27…Second catalyst 28…Matt 29…Catalytic converter 36…Filter 50…Battery 55…Auxiliary battery 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 that is applied to an internal combustion engine including an electrically heated first catalyst that is provided in an exhaust passage and heated by energization, 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 after the execution of the preheat process is completed; a post-heat process of energizing the first catalyst after the internal combustion engine has started to start; A process of acquiring a temperature of the second catalyst; A process of acquiring deterioration information which is information regarding a deterioration level of the second catalyst; A process of setting a determination value which is an activation temperature of the second catalyst to a higher value as the degree of deterioration indicated by the acquired deterioration information becomes higher; In addition to carrying out the above, The post-heat processing is a processing for supplying current to the first catalyst until the acquired temperature of the second catalyst reaches the determination value. A control device for an internal combustion engine.

2. A control device that is applied to an internal combustion engine including an electrically heated first catalyst that is provided in an exhaust passage and heated by energization, 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 after the execution of the preheat process is completed; a post-heat process of energizing the first catalyst after the internal combustion engine has started to start; A process of acquiring deterioration information which is information regarding a deterioration level of the second catalyst; a process of setting the activation power amount to a larger value as the degree of deterioration indicated by the acquired deterioration information becomes higher, when the activation power amount is an amount of power supplied to the first catalyst required from the start of the internal combustion engine until the second catalyst reaches an activation temperature; In addition to carrying out the above, The post-heat processing is a processing for supplying electricity to the first catalyst from the start of the internal combustion engine until the amount of electric power supplied to the first catalyst reaches the activation amount of electric power. A control device for an internal combustion engine.

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