JP2023091572A - Controller of internal combustion engine - Google Patents

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

The present invention relates to a control system for an internal combustion engine.

A catalyst that purifies exhaust gas from an internal combustion engine exhibits sufficient performance at the activation temperature after warm-up is completed. Therefore, when the temperature of the catalyst is lower than the activation temperature, the exhaust gas may not be sufficiently purified.

Therefore, an electrically heated catalyst that is housed in a case provided in an exhaust passage of an internal combustion engine and heated by energization is known (for example, Patent Document 1, etc.). The electrically heated catalyst can be warmed up prior to starting the engine by performing a preheating process of energizing the internal combustion engine before starting the engine.

JP 2012-072665 A

By the way, immediately after the engine starts, 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. When the temperature of the electrically heated catalyst drops in this way, emissions may deteriorate.

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-mentioned problems includes an electrically heated first catalyst that is housed in a case provided in an exhaust passage and is heated by energization; and a second catalyst. The control device includes a preheating process for warming up the first catalyst by energizing the first catalyst prior to starting the internal combustion engine, and starting the internal combustion engine when the preheating process is completed. a post-heating process of energizing the first catalyst while the internal combustion engine is running after the pre-heating process is completed; and an output of the internal combustion engine during the post-heating process. to a lower output than when the post-heating process is not performed.

According to the control device described above, even after the preheating process is completed and the engine is started, the postheating process energizes the first catalyst. By executing such a post-heating process, a decrease in the temperature of the first catalyst that has been warmed up is suppressed. Therefore, the control device can suppress deterioration of emissions immediately after the engine is started. However, when the engine starts, exhaust containing moisture flows into the case. Therefore, moisture in the exhaust gas may condense on the inner wall of the case. If such condensation occurs, the insulating properties of the first catalyst may deteriorate. It is not preferable to continue the energization in a state where the insulation has deteriorated. Therefore, the control device described above limits the output of the internal combustion engine during the post-heating process. Thereby, the control device suppresses the inflow of water into the case. That is, the control device described above can suppress the interruption of the post-heating process due to the deterioration of the insulation. As a result, the control device can continue the post-heating process to reduce emissions.

In one aspect of the control device for an internal combustion engine, the limiting process is a process of steady-state operation of the internal combustion engine at a constant output and a constant engine speed.
As described above, the engine operation with the output of the internal combustion engine limited can be realized by steady operation of the internal combustion engine at a constant output and a constant engine speed.

In one aspect of the control device for an internal combustion engine, the limiting process is a process of limiting the output of the internal combustion engine to a lower output as the insulation resistance value of the first catalyst is lower.
Energization of the first catalyst should be carried out after ensuring insulation at a certain level or higher. In the first place, when the insulation resistance value of the first catalyst is low, there is little insulation margin for continuing the post-heat treatment. The control device described above sets the degree of limitation of the output of the internal combustion engine in accordance with the degree of insulation margin. Therefore, the control device can prevent excessive restriction of the output of the internal combustion engine more than necessary.

In one aspect of the control device for an internal combustion engine, the limiting process is a process of limiting the output of the internal combustion engine to a lower output as the outside air temperature is lower.
The lower the outside temperature, the easier it is for moisture in the exhaust to condense. Therefore, the lower the outside air temperature is, the more likely the insulation is to deteriorate. The control device described above can set the degree of restriction of the output of the internal combustion engine according to the ease with which the insulation deteriorates. Therefore, the control device can appropriately suppress deterioration of emissions even when the outside air temperature is low.

In one aspect of the control device for an internal combustion engine, the limiting process is a process of 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.
When the outside temperature is low, the moisture in the exhaust gas tends to condense, and the insulation tends to deteriorate. Retarding the ignition timing increases the temperature of the exhaust. The control device described above raises the temperature of the exhaust gas by retarding the ignition timing when the outside air temperature is low. As a result, dew condensation is less likely to occur even when the outside air temperature is low. That is, the control device described above can suppress deterioration in insulation even when the outside air temperature is low.

In one aspect of the control device for an internal combustion engine, the energization of the first catalyst by the post heat treatment is performed until the temperature of the second catalyst reaches an activation temperature of the second catalyst, and the post heat treatment is terminated. When the limit is set, the limit processing is terminated.

If the temperature of the second catalyst reaches the activation temperature, the exhaust gas is purified by the second catalyst. Therefore, exhaust gas is purified even when the power supply to the first catalyst is stopped. Therefore, the control device described above continues to energize the first catalyst by the post-heating process until the second catalyst reaches the activation temperature. Then, the control device ends the restriction process together with the end of the post-heating process. Therefore, the control device can suppress continuing to limit the output of the internal combustion engine more than necessary.

1 is a schematic diagram showing a configuration of a vehicle provided with a control device for an internal combustion engine; FIG. FIG. 2 is a schematic diagram showing a system configuration of an electrically heated catalyst mounted on the vehicle; It is a flowchart which shows the procedure of the process which the control apparatus of the same embodiment performs. 4 is a graph showing the relationship between the maximum oxygen storage amount and the catalyst activation temperature. 4 is a graph showing the relationship between the first catalyst temperature, the maximum oxygen storage amount, and the target power amount; It is a graph which shows the relationship between an insulation resistance value and the correction coefficient a1. 4 is a graph showing the relationship between the maximum oxygen storage amount and the judgment value; 4 is a time chart showing transitions of various states when a vehicle system is activated; FIG. 8(a) shows changes in the engine output, FIG. 8(b) shows changes in the energized state of the electrically heated catalyst, and FIG. 8(c) shows changes in the first catalyst temperature and the second catalyst temperature. It is a flowchart which shows the part about the procedure of the process which a control apparatus performs in the modification of the same embodiment. It is a graph which shows the relationship between outside temperature and the correction coefficient a2. 4 is a graph showing the relationship between outside air temperature and ignition timing retard amount b.

An embodiment of a control device for an internal combustion engine will be described below with reference to FIGS. 1 to 8. FIG.
<Configuration of vehicle 10>
A 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.

The vehicle 10 includes an internal combustion engine 11 and a second motor generator 32 as power sources. That is, vehicle 10 is a hybrid vehicle. Vehicle 10 is a plug-in hybrid vehicle in which battery 50 can be charged by connecting to external power supply 60 . Therefore, the battery 50 is connected to a charger 51 for external charging. The battery 50 is, for example, a high voltage battery of 400V. The second motor generator 32 is, for example, a three-phase AC motor generator.

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

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 when energized. The electrically heated catalyst 210 is connected to the battery 50 via the power supply device 220 . A detailed configuration of the electrically heated catalyst system 200 including the electrically heated catalyst 210 will be described later with reference to FIG.

A filter 36 is provided downstream of the catalytic converter 29 in the exhaust passage 21 . Filter 36 collects particulate matter contained in the exhaust. Particulate matter is a fine particulate matter mainly composed of carbon generated by combustion.

The second motor generator 32 is connected to the battery 50 via the power control unit 35 . Also, the second motor generator 32 is connected to the drive wheels 40 via a speed reduction mechanism 34 .

The internal combustion engine 11 is connected to drive wheels 40 via a power split device 30 and a speed reduction mechanism 34 . A first motor generator 31 is also connected to the power split device 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 .

The first motor generator 31 receives the driving force of the internal combustion engine 11 and the driving force from the driving wheels 40 and generates electric power. The first motor generator 31 also serves as a starter that drives the rotation 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 according to the supply of electric power from the battery 50 .

The first motor generator 31 and the second motor generator 32 are connected to the battery 50 via the power control unit 35 . The AC power generated by the first motor generator 31 is converted into DC power by the power control unit 35 and charged in the battery 50 . That is, the power control unit 35 functions as an inverter.

Also, the DC power of the battery 50 is converted into AC power by the power control unit 35 and supplied to the second motor generator 32 . When decelerating the vehicle 10 , the driving force from the drive wheels 40 is used to generate power in the second motor generator 32 . Then, the generated power is charged in 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 into DC power by the power control unit 35 and charged to the battery 50 .

When the first motor generator 31 functions 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 .

<Control device 100>
The control device 100 controls the internal combustion engine 11 , the first motor generator 31 and the second motor generator 32 . That is, control device 100 is a control device that controls the power train of 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 controller 100 also controls the electrically heated catalyst system 200 .

A detection signal from a sensor provided in each part of the vehicle 10 is input to the control device 100 . The detection signal input to control device 100 includes vehicle speed SP, accelerator pedal opening ACCP, and state of charge SOC corresponding to the remaining capacity of battery 50 . A water temperature sensor 101 is connected to the control device 100 to detect a water temperature Tw, which is the temperature of the cooling water of the internal combustion engine 11 . A power switch 102 is also connected to the control device 100 for the driver of the vehicle 10 to start and stop the system of the vehicle 10 . Therefore, control device 100 grasps the activation state of the system of vehicle 10 based on the input signal from 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 . Note that the upstream air-fuel ratio sensor 103 is arranged in the exhaust passage 21 upstream of the catalytic converter 29 . A downstream side air-fuel ratio sensor 104 that detects a downstream side air-fuel ratio AFd, which is the air-fuel ratio of exhaust that has passed through the catalytic converter 29 , is connected to the control device 100 . The downstream air-fuel ratio sensor 104 is arranged in the exhaust passage 21 downstream of the catalytic converter 29 and upstream of the filter 36 . The control device 100 includes an air flow meter 105 that detects an intake air temperature Tin that is the temperature of the air taken into the internal combustion engine 11 and an intake air amount GA that is the mass, and a crankshaft that detects the rotation angle of the crankshaft of the internal combustion engine 11. An angle sensor 106 is connected. Control device 100 calculates engine speed NE based on output signal Scr of crank angle sensor 106 . The control device 100 also calculates the 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 charged into 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 the reference amount of inflow air. Note that the reference inflow air amount is variably set according to the engine speed NE.

The vehicle 10 configured as described above drives the second motor generator 32 using the electric power stored in the battery 50, thereby driving the drive wheels 40 using only the second motor generator 32. EV driving can be performed. In addition, it is possible to perform hybrid running in which the drive wheels 40 are driven using the internal combustion engine 11 and the second motor generator 32 .

<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 purifying exhaust gas in addition to the first catalyst 26 for purifying exhaust gas that constitutes an electrically heated catalyst 210 . Each of the first catalyst 26 and the second catalyst 27 has a three-way catalyst carried on a honeycomb-structured catalyst carrier in which a plurality of passages extending in the exhaust flow direction are defined. The second catalyst 27 is provided on the exhaust downstream side of the first catalyst 26 .

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

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

The upstream side portion of the case 24 is covered with and fixed from the outside by an upstream connecting pipe 23 whose diameter decreases toward the upstream side. A downstream connecting pipe 25 whose diameter decreases toward the downstream side is covered and fixed to the downstream portion of the case 24 from the outside.

As shown in FIG. 2 , the upstream connecting pipe 23 connects the upstream exhaust pipe 22 having a smaller diameter than the case 24 and the case 24 . Similarly, the downstream connecting pipe 25 connects the downstream exhaust pipe having a smaller diameter than the case 24 and the case 24 . Thus, the case 24 housing the first catalyst 26 and the second catalyst 27, the upstream connection pipe 23, and the downstream connection pipe 25 constitute a catalytic converter 29 that constitutes a part of the exhaust passage 21. .

The upstream end of the case 24 has a smaller diameter as it approaches the upstream exhaust pipe 22 , and the diameter of the portion closest to the upstream exhaust pipe 22 is substantially equal to the diameter of the upstream exhaust pipe 22 . It's becoming

The second catalyst 27 is located on the exhaust downstream side of the first catalyst 26 . The catalyst carrier of the first catalyst 26 is made of a material that becomes electrical resistance and generates heat when energized. For example, silicon carbide can be used as such material. It should be noted that the catalyst carrier has the characteristic that when the temperature is high, the electrical resistance is smaller than when the temperature is low.

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 an electric current flows through the first catalyst 26, the catalyst carrier generates heat due to the electrical resistance of the catalyst carrier.

The first electrode 211 and the second electrode 212 extend in the circumferential direction and the axial direction along the outer peripheral surface of the catalyst carrier in order to uniformly pass the current through the entire 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 in each of the openings 24K. The first electrode 211 and the second electrode 212 penetrate an insulator 213 fitted in the opening 24K.

The opening 24K is closed with an electrode chamber 80 made of metal. 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 the electrode chamber 80 . The terminal 85 is connected to the first electrode 211 and the second electrode 212 .

In addition, the inner peripheral surface of the case 24 is coated with an insulating material to form an insulating coat. As the insulating coat, for example, a glass coat can be used. Thereby, the first catalyst 26 is electrically insulated from the case 24 .

As described above, the first electrode 211 and the second electrode 212 are attached to the first catalyst 26 . Thus, the first catalyst 26 is an electrically heated catalyst 210 that generates heat when electric power is supplied. The electrically heated catalyst 210 is hereinafter referred to as EHC 210 . The first catalyst 26 is heated by the heat generated by the catalyst carrier due to the energization, and its activation is promoted.

Further, when the internal combustion engine 11 is operated and the exhaust gas starts to flow, heat is also transferred to the second catalyst 27 by the exhaust gas that has passed through the EHC 210 and is warmed. This also promotes warm-up of the second catalyst 27 .

The first electrode 211 and the second electrode 212 are connected to the battery 50 via the power supply circuit 221 of the power supply device 220 . The power supply device 220 includes a power supply 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 voltage sensor 225 are connected to the power microcomputer 222 . The power supply microcomputer 222 detects the current supplied to the EHC 210 based on the signal output by the current sensor 224 . The power supply microcomputer 222 also detects the voltage applied to the EHC 210 based on the signal output by the voltage sensor 225 . An auxiliary battery 55 is connected to the power supply device 220 .

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 has a reference resistor. Power is supplied from auxiliary battery 55 to power supply circuit 221 including 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.

The power supply device 220 is connected to the control device 100 so as to be able to communicate with each other, and the insulation resistance value Rt calculated by the power supply microcomputer 222 is output to the control device 100 . Further, control device 100 outputs a command to power supply device 220 to control energization of EHC 210 via power supply device 220 .

<Electricity of EHC210>
Vehicle 10, which is a plug-in hybrid vehicle, travels in the EV travel mode in which only second motor generator 32 is used as a power source for travel when the state of charge SOC of battery 50 has a sufficient margin. At this time, the control device 100 keeps the internal combustion engine 11 stopped. Then, the control device 100 controls the power control unit 35 so that the second motor generator 32 generates torque with which the required driving force can be obtained.

Further, when the state of charge SOC of battery 50 falls below a certain value while traveling in the EV traveling mode, control device 100 switches the traveling mode of vehicle 10 from the EV traveling mode to the hybrid traveling mode. The hybrid driving mode is a driving mode in which both the internal combustion engine 11 and the second motor generator 32 are used as power sources for driving.

In order to exhibit a sufficient exhaust purification capability immediately after switching to the hybrid driving mode, the EHC 210 is energized to warm the first catalyst 26 before the internal combustion engine 11 is started after shifting to the hybrid driving mode. It is desirable to keep it.

Therefore, the control device 100 performs a preheating process for warming up the first catalyst 26 by energizing the EHC 210 prior to starting the internal combustion engine 11 . Further, the control device 100 executes a post-heating process in which the EHC 210 is continuously energized even after the start of the internal combustion engine 11 is started. Warming up the catalyst means raising the temperature of the catalyst to the activation temperature.

<Process for Energizing EHC 210>
Referring to FIG. 3, a procedure for energizing the EHC 210 including preheating and postheating will be described. The processing shown in FIG. 3 is repeatedly executed by control device 100 when power switch 102 is ON and the system of vehicle 10 is in operation. In the following description, step numbers are represented by numerals prefixed with "S".

As shown in FIG. 3, when this process is started, the control device 100 first determines in the process of S100 whether or not the EHC energization request is ON. An EHC energization request is a request to energize the EHC 210 . Specifically, control device 100 determines that the EHC energization request is ON when both of the following two conditions are satisfied.

- There is a request to start the internal combustion engine 11 . Note that the request to start the internal combustion engine 11 may be made, for example, when the state of charge SOC is below a threshold for switching to the hybrid driving mode, or when the vehicle driving torque requested by the vehicle driver cannot be obtained in EV driving. .

- A first catalyst temperature Tcat1, which is the temperature of the first catalyst 26, is equal to or lower than a predetermined temperature that is 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 stop first temperature 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 the product of the difference obtained by subtracting the first temperature Toff1 at stop from the outside air temperature TA and multiplying the difference by the convergence rate. Then, the sum is calculated by adding the product to the first stop temperature Toff1. The sum calculated in this way is taken as the first catalyst temperature Tcat1 at engine start. Note that 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 increases. For example, when the convergence rate is 1, the catalyst temperature T is 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.

Further, during engine operation, the control device 100 calculates a first temperature change amount dT1, which is the temperature change amount of the first catalyst temperature Tcat1. Then, the latest first catalyst temperature Tcat1 is calculated by adding the first temperature change amount dT1 to the immediately preceding first catalyst temperature Tcat1. Note that the first temperature change amount dT1 changes under 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 a parameter that affects the heat energy amount of the exhaust gas, a parameter that affects the heat generation amount of the EHC 210, and the like. Parameters that affect the heat energy amount of the exhaust include the engine speed NE, the engine load factor KL, the water temperature Tw, the intake air amount GA, the vehicle speed SP, the intake air temperature Tin, and the like. Also, parameters that affect the amount of heat generated by the EHC 210 include the amount of electric power supplied to the EHC 210 .

Also, the control device 100 estimates a second catalyst temperature Tcat2, which is the temperature of the second catalyst 27 . For example, when the operation of the internal combustion engine 11 is stopped, the control device 100 stores the second catalyst temperature Tcat2 at that time as the stop second temperature 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 Toff2 at stop from the outside air temperature TA and multiplying the difference by the convergence rate. Then, the product is added to the stop second temperature Toff2 to calculate the sum. The sum calculated in this way is taken as the second catalyst temperature Tcat2 at engine start. Note that 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 increases. For example, when the convergence rate is 1, the catalyst temperature T is 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.

Further, during engine operation, the control device 100 calculates a second temperature change amount dT2, which is the temperature change amount of the second catalyst temperature Tcat2. Then, the latest second catalyst temperature Tcat2 is calculated by adding the second temperature change amount dT2 to the immediately preceding second catalyst temperature Tcat2. Note that the second temperature change amount dT2 changes under the influence of exhaust heat. Therefore, the control device 100 calculates the second temperature change amount dT2 using a parameter that affects the heat energy amount of the exhaust gas. Parameters that affect the amount of heat energy of the exhaust gas flowing into the second catalyst 27 include the first catalyst temperature Tcat1, the intake air amount GA, the intake air temperature Tin, and the like.

In the processing of S100, if it is determined that the EHC energization request is not ON (S100: NO), the control device 100 temporarily terminates this processing. That is, in this case, the control device 100 does not perform the preheating process and the postheating process.

On the other hand, when it is determined in the process of S100 that the EHC energization request is ON (S100: YES), 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.

Next, the control device 100 acquires the insulation resistance value Rt at this point in the process of S112. Then, in the process of S114, the control device 100 determines whether or not the insulation resistance value Rt is greater than the threshold value A1. The threshold A1 is a threshold for determining whether the insulation resistance, which is the electric resistance of the EHC 210, is large enough to suppress electric leakage.

In the process of S114, when it is determined that the insulation resistance value Rt is equal to or less than the threshold A1 (S114: NO), the control device 100 advances the process to S116. Then, in the process of S116, the control device 100 cancels the prohibition of starting the internal combustion engine 11 and starts starting the internal combustion engine 11 . Then, this process is terminated once.

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 the target power consumption Q0. Specifically, the control device 100 sets the target 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. Calculate

The maximum oxygen storage amount Cmax is the maximum amount of oxygen that the catalyst can store when the two catalysts provided in the catalytic converter 29, that is, the first catalyst 26 and the second catalyst 27 are regarded as one catalyst. The control device 100 estimates the maximum oxygen storage amount Cmax, for example, based on each value of the upstream side air-fuel ratio AFu and the downstream side air-fuel ratio AFd during engine operation. Here, as the deterioration of the first catalyst 26 and the second catalyst 27 progresses and the degree of deterioration thereof increases, the maximum oxygen storage amount Cmax decreases. Therefore, the maximum oxygen storage amount Cmax is deterioration information that is information about the degree of deterioration of the first catalyst 26 and the second catalyst 27 .

As shown in FIG. 4, when the degree of deterioration of the first catalyst 26 and the second catalyst 27 increases and the maximum oxygen storage amount Cmax decreases, the activation temperature of the first catalyst 26 and the second catalyst 27 increases. Tend.

In the preheating process, the EHC 210 continues to be energized until the power Q, which is the integrated value of the input power, reaches the target power Q0, thereby heating the first catalyst 26 to the activation temperature or higher for warming up. That is, the target power amount Q0 is the amount of power required to heat the first catalyst 26 from the temperature before the start of energization until the warm-up is completed.

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

Next, control device 100 sets the input power to EHC 210 to first power W1 in the process of S130. In this embodiment, the power supplied to the EHC 210 in both the preheating process and the postheating process is the first power W1. However, the power supplied to the EHC 210 may differ between the preheating process and the postheating process.

Next, control device 100 advances the process to S140. Then, control device 100 starts energizing EHC 210 in the process of S140. In the preheating process, control device 100 controls power supply circuit 221 to convert the voltage of battery 50 and supply power to EHC 210 by controlling power supply circuit 221 so that the input power reaches a set value. As the temperature of the first catalyst 26 increases due to the preheating process, the insulation resistance value Rt gradually decreases. Therefore, the control device 100 maintains the input power at the first power W1 by lowering the voltage in accordance with the decrease in the insulation resistance value Rt. In addition, the control device 100 controls the voltage within a range equal to or lower than the upper limit voltage so that the voltage does not exceed the 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 preheating process. Note that when the 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 the EHC 210 is being energized, the control device 100 continues to calculate the amount of electric power Q input to the EHC 210 by integrating the input power.

In the next process of S150, the control device 100 determines whether or not the power amount Q is equal to or greater than the target power amount Q0. Then, when it is determined in the process of S150 that the power amount Q is less than the target power amount Q0 (S150: NO), the control device 100 repeats the process of S150.

On the other hand, in the process of S150, when it is determined that the power amount Q is equal to or greater than the target power amount Q0 (S150: YES), the control device 100 advances the process to S160. Then, in the process of S160, the control device 100 cancels the prohibition of starting the internal combustion engine 11 and starts starting 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 shifts from preheating to postheating.

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

As shown in FIG. 6, the correction coefficient a1 is a positive value of 1 or less. 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, the control device 100 calculates, for example, 0.3 as the correction coefficient a1 when the insulation resistance value Rt is equal to or less than the first threshold value Rt1. Then, the control device 100 calculates 1.0 as the correction coefficient a1 when the insulation resistance value Rt is equal to or greater than the second threshold value Rt2, which is larger than the first threshold value Rt1. Then, when the insulation resistance value Rt is greater than the first threshold value Rt1 and less than the second threshold value Rt2, the control device 100 determines that the insulation resistance value Rt is greater than 0.3 and less than 1.0 depending on the magnitude of the insulation resistance value Rt. is also small. At this time, as shown in FIG. 6, control device 100 calculates correction coefficient a1 such that correction coefficient a1 increases as insulation resistance value Rt increases.

Next, control device 100 executes engine output limitation in the process of S172. Specifically, control device 100 sets upper limit value Pec of engine output Pe to the product of predetermined output P1 multiplied by correction coefficient a1. The predetermined output P1 is, for example, an output when the internal combustion engine 11 is idling with the second catalyst 27 being completely warmed up. That is, by multiplying the predetermined output P1 by a correction coefficient a1 smaller than 1.0, the upper limit value Pec of the engine output Pe is set to a value lower than the predetermined output P1. This restricts the engine output Pe.

Next, in the process of S174, the control device 100 starts steady operation so that the engine output Pe is maintained at the upper limit value Pec and the engine rotation speed NE is maintained at the default value Ne. Note that the predetermined value Ne is set to a value slightly lower than the engine rotation speed NE at which the amount of exhaust gas discharged from the internal combustion engine 11 is an appropriate amount for suppressing the occurrence of dew condensation in the case 24 .

By executing such a steady operation, the engine can be operated while the output of the internal combustion engine 11 is limited. That is, the processes of S170, S172 and S174 are limiting processes for limiting the output of the internal combustion engine 11 to a lower output when the post-heating process is being performed than when the post-heating process is not being performed. be. By performing such restriction processing, even if the engine is operated in a state in which the second catalyst 27 is incompletely warmed up, deterioration of emissions can be suppressed.

Next, control device 100 calculates determination 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 according to the degree of deterioration of the second catalyst 27 . The degree of deterioration of the second catalyst 27 is correlated with the maximum oxygen storage amount Cmax. Therefore, the control device 100 acquires the maximum oxygen storage amount Cmax, which is the deterioration information of the second catalyst 27, in the process of S180. Then, the determination value Tref is calculated based on the acquired maximum oxygen storage amount Cmax.

As shown in FIG. 7, the control device 100 calculates the reference value Tref such that the lower the maximum oxygen storage amount Cmax, the higher the temperature of the reference value Tref.
Next, the control device 100 acquires the second catalyst temperature Tcat2 in the process of S190. Then, the control device 100 determines whether or not the second catalyst temperature Tcat2 is equal to or higher than the determination value Tref. Then, in the process of S190, when it is determined that the second catalyst temperature Tcat2 is less than the determination value Tref (S190: NO), the control device 100 repeats the process of S190.

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

Next, control device 100 terminates the energization of EHC 210 in the process of S210. That is, control device 100 terminates the post-heating process. Then, the control device 100 once terminates this process.

<Action>
The operation of this embodiment will be described.
FIG. 8 is a time chart showing the transition of various states when the system of the vehicle is activated. 8(a) shows the output of the internal combustion engine 11, FIG. 8(b) shows the energized state of the EHC 210, and FIG. 8(c) shows changes in the first catalyst temperature Tcat1 and the second catalyst temperature Tcat2.

As shown in FIG. 8, at time t1, when it is determined that the EHC energization request is ON, energization of EHC 210 is started, thereby increasing first catalyst temperature Tcat1.
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 when the warm-up of the first catalyst 26 is completed, the engine starts. When the engine starts, the engine output Pe is maintained at the upper limit value Pec and the engine rotation speed NE is maintained at the default value Ne by performing the above-described limiting process. The energization of the EHC 210 from time t1 to time t2 is a preheating process for warming up the first catalyst 26 by energizing the first catalyst 26 prior to starting the internal combustion engine 11 .

In this embodiment, the EHC 210 continues to be energized even after the engine is started. Then, at time t3, when the second catalyst temperature Tcat2 becomes equal to or higher than the reference value Tref and the warm-up of the second catalyst 27 is completed, the above limiting process is ended and the power supply to the EHC 210 is stopped. The energization of the EHC 210 from the time t2 to the time t3 is a post-heat process in which the first catalyst 26 is energized after the internal combustion engine 11 has started.

In the example shown in FIG. 8, at time t3, the engine output Pe is increased to the predetermined output P1 by completing the restriction process.
<About effect>
Effects of the present embodiment will be described.

(1) Even after the preheating process is completed and the engine is started, the postheating process continues to energize the first catalyst 26 . By executing such a post-heating process, the temperature drop of the first catalyst 26 that has been warmed up is suppressed. Therefore, control device 100 can suppress deterioration of emissions immediately after the engine is started.

(2) When the engine 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 and the inner wall of the electrode chamber 80 . If such condensation occurs, the insulating properties of the EHC 210 may deteriorate. Further, when the temperature of the first catalyst 26 rises due to the preheating process, the water absorbed in the mat 28 evaporates. The evaporated water may condense again on the inner wall of the case 24 and the inner wall of the electrode chamber 80, which may reduce the insulating properties of the EHC 210. FIG. It is not preferable to continue the energization of the first catalyst 26 in a state where the insulation has deteriorated. Therefore, the control device 100 limits the output of the internal combustion engine 11 while performing the post-heating process. 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 post-heating process due to the deterioration of the insulation. As a result, the control device 100 can continue the post-heating process to reduce emissions.

(3) Energizing the first catalyst 26 should be carried out after ensuring a certain level of insulation. In the first place, when the insulation resistance value Rt of the EHC 210 is low, there is little insulation margin for continuing the post-heating process. The control device 100 sets the degree of limitation of the output of the internal combustion engine 11 according to the degree of insulation margin. Therefore, the control device 100 can prevent excessive restriction of the output of the internal combustion engine 11 more than necessary.

(4) When the first catalyst 26 is energized by the post-heating process, the temperature drop of the exhaust gas passing through the first catalyst 26 is suppressed, so that the warming-up of the second catalyst 27 by the exhaust gas is promoted. The control device 100 energizes the first catalyst 26 by post-heating until the second catalyst 27 reaches the activation temperature. Therefore, the time required for the warm-up of the second catalyst 27 to be completed is shortened, which also suppresses the deterioration of the emissions immediately after the engine is started.

(5) The energization of the first catalyst 26 by the post-heating process is performed until the second catalyst temperature Tcat2 reaches the set determination value Tref of the activation temperature. As the deterioration of the second catalyst 27 progresses, the activation temperature of the second catalyst 27 tends to increase. 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 by the deterioration information of the second catalyst 27 is higher. More specifically, control device 100 sets judgment value Tref to a higher temperature as maximum oxygen storage amount Cmax decreases. Therefore, the control device 100 can appropriately energize the first catalyst 26 by the post-heating process according to the degree of deterioration of the second catalyst 27 .

(6) The control device 100 ends the restriction process when the post-heating process ends. Therefore, the control device 100 can suppress continuing to limit the output of the internal combustion engine 11 more than necessary.

<Change example>
It should be noted that the above embodiment can be implemented with the following modifications. The above embodiments and the following modifications can be combined with each other within a technically consistent range.

- In the process of S120, the control device 100 calculated the target power amount Q0 according to the first catalyst temperature Tcat1 and the maximum oxygen storage amount Cmax. Alternatively, the target power amount Q0 may be calculated according to either one of the first catalyst temperature Tcat1 and the maximum oxygen storage amount Cmax. Also, the target power consumption Q0 may be calculated according to other parameters.

- The engine output restriction in the restriction process is to perform steady operation by controlling the engine output Pe and the engine rotation speed NE to constant values. Alternatively, the engine output limit may control the engine output Pe within a range equal to or lower than the upper limit value Pec so that the engine output Pe does not exceed the value of the upper limit value Pec.

- An example of executing the processing of S170, S172 and S174 as the restriction processing is shown. In the above example, the upper limit value Pec is calculated using the correction coefficient a1 set based on the insulation resistance value Rt. Restriction processing is not limited to such a mode. The limiting process may be any process as long as it limits the output of the internal combustion engine 11 to a lower output than when the post-heating process is not performed.

FIG. 9 shows the processing procedure in one such modification. Note that FIG. 9 shows differences from the processing shown in FIG. As shown in FIG. 9, after completing the processing of S160 described above, the control device 100 next calculates a correction coefficient a2 as the processing of S300. Specifically, control device 100 calculates correction coefficient a2 based on outside air temperature TA.

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

Next, the control device 100 calculates the ignition timing retardation amount b in the process of S320. 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 controller 100 sets the ignition timing retard amount b to a larger value as the outside air temperature TA is lower. Specifically, as shown in FIG. 11, the control device 100 calculates 0 as the ignition timing retard amount b when the outside air temperature TA is equal to or higher than the fourth temperature TA4. Then, 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 sets a value greater than 0 according to the value of the outside air temperature TA. calculate. At this time, as shown in FIG. 11, the control device 100 calculates the ignition timing retardation amount b so that the ignition timing retardation amount b increases as the outside air temperature TA decreases. Note that when the outside air temperature TA is lower than the second temperature TA2, the control device 100 calculates the same value as the ignition timing retardation amount b when the outside air temperature TA is the second temperature TA2.

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

Next, in the process of S340, 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 the default value Ne, similarly to the process at S174.

Next, the control device 100 executes ignition retardation for retarding 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 performs steady operation with the ignition timing retarded. When steady operation is started with the ignition timing retarded in this manner, control device 100 advances the process to S180 described above.

In this modified example, the processes of S300, S320, S330, S340 and S350 are executed as the restriction process. Therefore, the restriction processing in this modification is processing for restricting the output of the internal combustion engine 11 to a lower output as the outside air temperature TA is lower.

The lower the outside air temperature TA, the easier it is for moisture in the exhaust to condense. Therefore, the lower the outside air temperature TA, the easier it is for the insulation of the first catalyst 26 to deteriorate. The control device 100 of this modified example can set the degree of limitation of the output of the internal combustion engine 11 according to the ease of deterioration of the insulation. Therefore, the control device 100 can appropriately suppress deterioration of emissions even when the outside air temperature TA is low.

Further, the restriction process in this modification is a process of operating the internal combustion engine 11 with the ignition timing retarded more than when the outside air temperature TA is high when the outside air temperature TA is low.
When the outside air temperature TA is low, moisture in the exhaust gas tends to condense, so the insulation of the first catalyst 26 tends to deteriorate. Retarding the ignition timing increases the temperature of the exhaust. The control device 100 of this modification raises the temperature of the exhaust gas by retarding the ignition timing when the outside air temperature TA is low. As a result, dew condensation is less likely to occur even when the outside air temperature TA is low. That is, the control device 100 can suppress deterioration of insulation even when the outside air temperature TA is low.

A configuration for retarding the ignition in the above embodiment by executing a process of calculating the correction coefficient a1 based on the insulation resistance value Rt and a process of calculating the ignition timing retard amount b based on the outside air temperature TA. can also be adopted.

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 a certain level.
・In the above modified example, the engine output is restricted and the ignition timing is retarded. Alternatively, either one of engine output limitation and ignition timing retardation may be implemented.

- Although the determination value Tref is changed according to the maximum oxygen storage amount Cmax, it may be a predetermined constant value. This constant value can be, for example, the activation temperature when it is assumed that the degree of deterioration of the second catalyst 27 has reached the allowable limit.

- Although the maximum oxygen storage amount Cmax was 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 deterioration of the catalyst. Therefore, such total operating time may be used as catalyst deterioration information.

In the process of S190, the second catalyst temperature Tcat2 and the reference value Tref are compared to determine the end time of energization of the EHC 210, but the end time of energization to the EHC 210 may be determined by comparing other values. .

For example, the energization end timing is determined based on the amount of electric power supplied to the first catalyst 26, which is required for the second catalyst 27 to reach the activation temperature after starting the internal combustion engine 11. You can judge.

- It is not always necessary to end the restriction process when the post-heating process ends. The restriction process may be terminated after the post-heating process is terminated. Alternatively, the post-heating process may be terminated after the restriction process is terminated.

- The catalyst supported on the catalyst carrier is not limited to a three-way catalyst, and may be, for example, an oxidation catalyst, a storage reduction NOx catalyst, or a selective reduction NOx catalyst.
The vehicle 10 equipped with the electrically heated catalyst system 200 and the control device 100 is not only a plug-in hybrid vehicle, but also a hybrid vehicle that does not have a plug-in function, or a vehicle that uses only the internal combustion engine 11 as a power source. good too.

The control device 100 includes one or more processors that execute various processes according to a computer program (software), and one or more dedicated processors such as an application specific integrated circuit (ASIC) that executes at least part of the various processes. can be configured as a hardware circuit of Also, the control device 100 can be configured as a circuit including a combination of these. A processor includes a CPU and memory, such as RAM and ROM, which stores program code or instructions configured to cause the CPU to perform processes. Memory or computer-readable media includes any available media that can be accessed by a general purpose or special purpose computer.

DESCRIPTION OF SYMBOLS 10... Vehicle 11... Internal combustion engine 21... Exhaust passage 24... Case 24K... Opening 26... First catalyst 27... Second catalyst 28... Mat 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... Electric heating catalyst system 210... Electric heating catalyst (EHC )
220 power supply device 221 power supply circuit 222 power supply microcomputer 224 current sensor 225 voltage sensor

Claims (6)

Applied to an internal combustion engine comprising an electrically heated first catalyst that is housed in a case 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 control device that
a preheating 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 preheating process ends;
a post-heating process of energizing the first catalyst while the internal combustion engine is running after the pre-heating process is completed;
a limiting process for 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 being performed. Control device for an internal combustion engine . 2. The control device for an internal combustion engine according to claim 1, wherein the limiting process is a process for causing the internal combustion engine to operate steadily at a constant output and a constant engine speed. 3. The control device for an internal combustion engine according to claim 1, wherein the limiting process is a process of limiting the output of the internal combustion engine to a lower output as the insulation resistance value of the first catalyst is lower. 3. The control device for an internal combustion engine according to claim 1, wherein the restriction process is a process of restricting the output of the internal combustion engine to a lower output as the outside air temperature is lower. 5. The process according to any one of claims 1 to 4, wherein the restriction process is a process of operating the internal combustion engine with 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. energizing the first catalyst by the post heat treatment until the temperature of the second catalyst reaches an activation temperature of the second catalyst;
The control device for an internal combustion engine according to any one of claims 1 to 5, wherein the limiting process is terminated when the post-heating process is terminated.

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