Exhaust emission control performance control system and exhaust emission control performance control method

Abstract

To provide a technique capable of purifying exhaust gas during cold operation.SOLUTION: An exhaust emission control performance control system comprises: a catalyst state control section that causes an exhaust emission control catalyst to become an active state by controlling a temperature regulation section that regulates a temperature of the exhaust emission control catalyst disposed in an exhaust passage of an internal combustion engine provided in a vehicle; an internal combustion engine control section that starts the internal combustion engine; and a perturbation control section that controls an air-fuel ratio regulation section that regulates an air-fuel ratio of the internal combustion engine when the exhaust emission control catalyst is in the active state and the internal combustion engine is in cold operation and executes perturbation in which control for making the air-fuel ratio richer than a predetermined value and control for making the air-fuel ratio leaner than the predetermined value are repeated.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an exhaust gas purification performance control system and an exhaust gas purification performance control method. [Background technology]

[0002] Conventionally, an electrically heated catalyst is known that activates an exhaust purification catalyst by heating the exhaust purification catalyst. For example, Patent Document 1 discloses a technology that controls a power supply device to supply power to an electrically heated catalyst prior to starting an internal combustion engine, thereby executing a preheat process to warm up the exhaust purification catalyst. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-165778 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the prior art, it is disclosed that a recovery process is performed to recover from a state in which a conductive path is formed due to the adhesion of carbon contained in the exhaust gas or condensed water formed by condensing moisture in the exhaust gas to the inside of the case 24 that is coated with an insulating coating (Patent Document 1, 0068). The recovery process is a process for recovering insulation resistance that has decreased in an electrically heated catalyst, and it is disclosed that the air-fuel ratio of some cylinders is made lean and the air-fuel ratio of the remaining cylinders is made rich, and control is performed to switch the air-fuel ratio for each cylinder for each cycle (Patent Document 1, 0073). Since the recovery process is a process for evaporating condensed water (Patent Document 1, 0069), it is necessary that the warm-up of the internal combustion engine 20 has been completed to a certain extent and the temperature of the exhaust gas is high in order to execute the recovery process (Patent Document 1, 0071). Therefore, in Patent Document 1, the recovery process is executed when the water temperature Tw, which is the temperature of the cooling water of the internal combustion engine 20, is higher than a predetermined temperature T0 (Patent Document 1, 0071). In this conventional technology, recovery processing cannot be performed unless the internal combustion engine has finished warming up, and therefore the performance of the electrically heated catalyst cannot be fully demonstrated during cold operation when the internal combustion engine has not finished warming up. The present invention has been made in consideration of the above problems, and has an object to provide a technique capable of purifying exhaust gas during cold operation. [Means for solving the problem]

[0005] In order to achieve the above-mentioned object, the exhaust purification performance control system comprises a catalyst state control unit that controls a temperature adjustment unit that adjusts the temperature of an exhaust purification catalyst arranged in an exhaust passage of an internal combustion engine equipped in a vehicle, thereby bringing the exhaust purification catalyst into an active state, an internal combustion engine control unit that starts the internal combustion engine, and a perturbation control unit that controls an air-fuel ratio adjustment unit that adjusts the air-fuel ratio of the internal combustion engine when the exhaust purification catalyst is in the active state and the internal combustion engine is operating in a cold state, and executes perturbation that repeats control to make the air-fuel ratio richer than a predetermined value and control to make the air-fuel ratio leaner than the predetermined value.

[0006] Perturbation is realized by repeating control to make the air-fuel ratio richer than a predetermined value and control to make the air-fuel ratio leaner than a predetermined value, and by repeating the storage and release of oxygen in the exhaust purification catalyst, the purification performance of the exhaust purification catalyst can be improved. If the temperature of the exhaust purification catalyst is adjusted to be in an active state, purification by the exhaust purification catalyst is realized, so that the performance of the exhaust purification catalyst can be maximized by using the activation of the exhaust purification catalyst and perturbation in combination. Therefore, if the configuration is such that perturbation is executed when the exhaust purification catalyst is in an active state and the internal combustion engine is operating in a cold state, the performance of the exhaust purification catalyst can be effectively utilized even in a cold state when there is a lot of exhaust, and it is possible to purify the exhaust gas during cold operation. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing a configuration of a vehicle. [Diagram 2] 1 is a cross-sectional view of an internal combustion engine provided in a vehicle, and a diagram showing the relationship between various sensors provided in the internal combustion engine and an ECU. [Diagram 3] FIG. 13 is a diagram showing an example of perturbation control in a configuration in which the fuel injection amount is increased or decreased in a stepwise manner. [Figure 4] 4 is a flowchart of an exhaust purification performance control process. [Diagram 5] FIG. 5A is a diagram showing a torque obtained by a moving average, FIG. 5B is a diagram showing torque fluctuation due to perturbation, and FIG. 5C is a diagram showing torque in the opposite phase. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Here, the embodiments of the present invention will be described in the following order. (1) Configuration of exhaust purification performance control system: (2) Exhaust purification performance control treatment: (3) Other embodiments:

[0009] (1) Configuration of exhaust purification performance control system: The exhaust purification performance control system is mounted on a vehicle for use. Fig. 1 is a diagram showing the configuration of a vehicle 10 mounted with an ECU (Electronic Control Unit) 100 that functions as the exhaust purification performance control system. Fig. 2 is a diagram showing a cross-sectional view of an internal combustion engine 20 provided in the vehicle 10, and a relationship between the ECU 100 and various sensors provided in the internal combustion engine 20.

[0010] The vehicle 10 includes an internal combustion engine 20 and a second motor generator 32 as power sources. In other words, the vehicle 10 is a hybrid vehicle. Among hybrid vehicles, the vehicle 10 is a plug-in hybrid vehicle that can be connected to an external power source 60 to charge the battery 50. For this reason, 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.

[0011] A catalytic converter 29 is installed in the exhaust passage 21 of the internal combustion engine 20. The catalytic converter 29 is equipped with an exhaust purification catalyst 210. In this embodiment, the exhaust purification catalyst 210 is a three-way catalyst having an oxygen storage function. This three-way catalyst is made of ceria (CeO 2 ) and has the property of absorbing and releasing oxygen in the exhaust gas. That is, the exhaust purification catalyst 210 adsorbs and holds the excess oxygen present in the exhaust gas when the air-fuel ratio in the exhaust gas becomes lean, and releases the adsorbed and held oxygen when the air-fuel ratio becomes rich. In this embodiment, the exhaust purification catalyst 210 is an electrically heated catalyst whose temperature is adjusted by a heating portion that generates heat in response to the passage of current. The exhaust purification catalyst 210 is connected to the battery 50 via the power supply device 70.

[0012] The second motor generator 32 is connected to a battery 50 via a power control unit (PCU) 35. The second motor generator 32 is linked to driving wheels 40 via a reduction mechanism .

[0013] The internal combustion engine 20 is also 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 20 between the first motor generator 31 and the drive wheels 40.

[0014] The first motor generator 31 generates electricity by receiving driving force from the internal combustion engine 20 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 20 when starting the internal combustion engine 20. 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] The ECU 100 includes a CPU for performing calculations, a RAM for storing various information such as calculation results, a backup RAM in which the stored contents are held by a battery, and a ROM for storing various control programs. The ECU 100 can control various devices mounted on the vehicle 10. In this embodiment, the ECU 100 functions as an exhaust purification performance control system. The ECU 100 also functions as a control device for a normal vehicle. For example, the ECU 100 controls the internal combustion engine 20, the first motor generator 31, and the second motor generator 32. That is, the ECU 100 functions as a control device for controlling the power train of the vehicle 10, which is a plug-in hybrid vehicle.

[0019] As shown in Fig. 2, the internal combustion engine 20 includes an ignition plug 220, a cylinder 230, injectors 240a, 240b, and a throttle 250. The ECU 100 can start the internal combustion engine 20 and continue the operation after starting. Starting may be performed by various methods, for example, the ECU 100 may control the first motor generator 31 via the PCU 35 to function as a starter that rotates the crankshaft of the internal combustion engine 20. When the internal combustion engine 20 is started, the ECU 100 controls the ignition plug 220 to ignite the air-fuel mixture in each cylinder 230, thereby causing the internal combustion engine 20 to generate driving force.

[0020] Furthermore, when combustion occurs in the cylinder 230, the ECU 100 controls at least one of the injectors 240a and 240b to inject fuel into the intake passage 22 or the cylinder 230. The injector 240a is an injector for the intake passage 22, and air sucked in from the outside through the intake passage 22 is mixed with fuel injected from the injector 240a, and the mixture is sucked into the cylinder 230. The injector 240b is an injector for the cylinder 230, and air sucked in from the outside through the intake passage 22 and reaching the cylinder 230 is mixed with fuel injected from the injector 240b, and the mixture is sucked in. When the sucked mixture is combusted inside the cylinder 230, the burned gas is exhausted to the exhaust passage 21. Various methods can be used as a control method for generating the air-fuel mixture by the injectors 240a and 240b, and the air-fuel mixture may be generated by only the injector 240a, only the injector 240b, or both the injectors 240a and 240b. Furthermore, the internal combustion engine 20 may be equipped with only one of the injectors 240a and 240b.

[0021] A throttle 250 that adjusts the amount of intake air drawn into the cylinder 230 is disposed in the intake passage 22. An airflow sensor 260a is provided upstream (on the intake port side) of the throttle 250. The airflow sensor 260a is a sensor that detects the amount of air passing through the intake passage 22. The ECU 100 obtains the amount of air passing through the intake passage 22 based on an output signal of the airflow sensor 260a.

[0022] A crank angle sensor 260b that detects the rotation angle of the crankshaft is attached near the crankshaft of the internal combustion engine 20. The ECU 100 obtains the crank angle based on an output signal from the crank angle sensor 260b, and obtains the angular acceleration of the crank from the crank angle.

[0023] A passage Pw through which the cooling water of the internal combustion engine 20 flows is provided around the cylinder 230, and a water temperature sensor 260c for detecting the temperature of the cooling water is attached to an outlet 260c1 of the passage Pw. The ECU 100 can acquire the temperature of the cooling water of the internal combustion engine 20 based on an output signal of the water temperature sensor 260c. The ECU 100 can determine that the warm-up of the internal combustion engine 20 is completed when the temperature of the cooling water indicated by the water temperature sensor 260c is equal to or higher than a predetermined warm-up determination threshold value (for example, any temperature between 80°C and 90°C). Therefore, for example, when it is determined that the warm-up of the internal combustion engine 20 is completed, it is possible to perform the recovery process described in Patent Document 1.

[0024] Air-fuel ratio sensors 260d1 and 260d2 are provided in the exhaust passage 21. In this embodiment, the air-fuel ratio sensors are provided at a total of two locations on either side of the exhaust purification catalyst 210. That is, the air-fuel ratio sensor 260d1 is provided upstream of the exhaust purification catalyst 210 (on the cylinder 230 side), and the air-fuel ratio sensor 260d2 is provided downstream of the exhaust purification catalyst 210 (on the opposite side of the cylinder 230).

[0025] In this embodiment, the air-fuel ratio sensors 260d1 and 260d2 are linear air-fuel ratio sensors that linearly detect the exhaust air-fuel ratio from the oxygen concentration in the exhaust at the mounting position. Note that these air-fuel ratio sensors 260d1 and 260d2 cannot perform accurate detection unless the temperature reaches a predetermined temperature (e.g., 350°C) or higher. Therefore, the ECU 100 controls a power supply unit (not shown) to supply power to the air-fuel ratio sensors 260d1 and 260d2, so that the air-fuel ratio sensors 260d1 and 260d2 reach a predetermined temperature or higher.

[0026] The ECU 100 can execute various control programs stored in the ROM. In this embodiment, the various control programs include an exhaust purification performance control program. When the ECU 100 executes the exhaust purification performance control program, the ECU 100 functions as a catalyst state control unit 100a, an internal combustion engine control unit 100b, a perturbation control unit 100c, and a torque control unit 100d.

[0027] The catalyst state control unit 100a has a function of controlling a temperature adjustment unit that adjusts the temperature of the exhaust purification catalyst 210 arranged in the exhaust passage 21 of the internal combustion engine 20 equipped in the vehicle 10, thereby putting the exhaust purification catalyst 210 into an active state. In this embodiment, the temperature adjustment unit is the power supply device 70 and a heat generating unit (not shown). That is, the ECU 100, by using the function of the catalyst state control unit 100a, issues a control instruction to the power supply device 70 to supply electric power to the heat generating unit equipped in the exhaust purification catalyst 210. As a result, when the temperature of the exhaust purification catalyst 210 becomes equal to or higher than a threshold value (e.g., 350°C), the exhaust purification catalyst 210 enters an active state.

[0028] The internal combustion engine control unit 100b has a function of starting the internal combustion engine 20. In this embodiment, the ECU 100 controls the first motor generator 31 to drive the rotating shaft of the internal combustion engine 20, thereby starting the internal combustion engine 20. After the internal combustion engine 20 is started, if a condition for stopping the internal combustion engine 20 does not occur, the ECU 100 controls at least one of the ignition plug 220 and the injectors 240a, 240b to continue the operation of the internal combustion engine 20 while controlling the air-fuel ratio.

[0029] The perturbation control unit 100c has a function of controlling the air-fuel ratio adjustment unit to execute perturbation. In this embodiment, the air-fuel ratio adjustment unit includes the injectors 240a, 240b, the air flow sensor 260a, and the air-fuel ratio sensor 260d1. That is, the ECU 100 can perform feedback control to increase or decrease the amount of fuel injected by the injectors 240a, 240b based on the output results of the air flow sensor 260a and the air-fuel ratio sensors 260d1, 260d2 (the air-fuel ratio sensor 260d2 does not necessarily have to be used).

[0030] Perturbation is a control that repeats a control for making the air-fuel ratio of the internal combustion engine 20 richer than a predetermined value and a control for making the air-fuel ratio leaner than the predetermined value. In this embodiment, the predetermined value is the stoichiometric air-fuel ratio.

[0031] Specifically, while the internal combustion engine 20 is running, the ECU 100 estimates the current air-fuel ratio based on the output value of the air-fuel ratio sensor 260d1. If the current air-fuel ratio is estimated to be leaner than the stoichiometric air-fuel ratio, the ECU 100 controls the injectors 240a, 240b to increase the fuel injection amount. If the current air-fuel ratio is estimated to be richer than the stoichiometric air-fuel ratio, the ECU 100 controls the injectors 240a, 240b to decrease the fuel injection amount.

[0032] The increase and decrease of the fuel injection amount may be specified by various methods. For example, the ECU 100 may increase or decrease the fuel injection amount stepwise, or may determine the increase and decrease of the fuel injection amount according to the value of the air-fuel ratio or the oxygen storage amount of the exhaust purification catalyst 210. Fig. 3 is a diagram showing a control example in a configuration in which the fuel injection amount is increased or decreased stepwise. In Fig. 3, two graphs are shown, one above the other, and the upper graph shows the time change of the current air-fuel ratio estimated from the output of the air-fuel ratio sensor, and the lower graph shows the correction value of the fuel injection amount.

[0033] The upper graph showing the current air-fuel ratio illustrates the change over time of the current air-fuel ratio, based on a state in which the air-fuel ratio estimated based on the output value of the air-fuel ratio sensor is the stoichiometric air-fuel ratio. In this graph, the air-fuel ratio alternates between lean and rich states on either side of the stoichiometric air-fuel ratio.

[0034] The graph below the fuel injection amount correction value shows the relative fuel injection amount when the fuel injection amount for achieving the stoichiometric air-fuel ratio is set to 1.0, and if it is greater than 1.0, the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio, and if it is less than 1.0, the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio. As shown in Fig. 3, when the current air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio, the ECU 100 increases the fuel injection amount beyond the fuel injection amount that achieves the stoichiometric air-fuel ratio. Also, the ECU 100 increases the fuel injection amount in stages until the current air-fuel ratio becomes richer than the stoichiometric air-fuel ratio.

[0035] On the other hand, as shown in FIG. 3, when the current air-fuel ratio becomes richer than the stoichiometric air-fuel ratio, the ECU 100 reduces the fuel injection amount to less than the fuel injection amount that realizes the stoichiometric air-fuel ratio. Also, the ECU 100 increases the fuel injection amount stepwise until the current air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio. The stepwise increase and decrease amounts of the fuel injection amount may be predetermined amounts. Also, the increase and decrease amounts of the fuel injection amount may be adjusted so that the fluctuation width of the air-fuel ratio is within a predetermined range. For example, the increase and decrease amounts of the fuel injection amount may be determined so that the air-fuel ratio changes within a range of about ±4% of the stoichiometric air-fuel ratio. Furthermore, the increase and decrease amounts of the fuel injection amount may be adjusted so that the fluctuation frequency of the air-fuel ratio is within a predetermined range. For example, the increase and decrease amounts of the fuel injection amount may be determined so that the fluctuation frequency is about 1 Hz.

[0036] Although not limited to the above-mentioned stepwise control, the ECU 100 can execute perturbation in which the air-fuel ratio is repeatedly made richer and leaner than the stoichiometric air-fuel ratio. In this embodiment, the ECU 100 executes perturbation when the exhaust purification catalyst 210 is in an active state and the internal combustion engine 20 is in cold operation.

[0037] The condition that the exhaust purification catalyst 210 is in an active state is a condition for the exhaust purification catalyst 210 to exhibit the desired purification performance. That is, the exhaust purification catalyst 210 according to this embodiment exhibits the desired purification performance when the temperature is equal to or higher than the threshold value, so the ECU 100 does not execute perturbation when the temperature of the exhaust purification catalyst 210 is lower than the threshold value.

[0038] The condition that the internal combustion engine 20 is cold-operated is a condition for operating the exhaust purification catalyst 210 in a state where the need for exhaust purification is high. That is, when the internal combustion engine 20 is cold-operated, conventionally, exhaust purification by the exhaust purification catalyst 210 is not performed, and exhaust purification including perturbation is not performed. For this reason, when the internal combustion engine 20 is cold-operated, such as immediately after a cold start, exhaust purification is not performed.

[0039] Therefore, in this embodiment, when the internal combustion engine 20 is in cold operation, the function of the exhaust purification catalyst 210 is not stopped, but the exhaust purification catalyst 210 is activated and perturbation is also performed. According to the above configuration, since the exhaust purification catalyst 210 functions when the internal combustion engine 20 is in cold operation, it is possible to purify the exhaust gas when the internal combustion engine 20 is in cold operation, such as immediately after the internal combustion engine 20 is started in cold operation.

[0040] In this embodiment, cold operation refers to the internal combustion engine 20 being operated in a state where the temperature of the internal combustion engine 20 is equal to or lower than a predetermined value. In this embodiment, the temperature of the internal combustion engine 20 is the detection value of the water temperature sensor 260c. The predetermined value is a value determined in advance, and is 40° C. in this embodiment. Therefore, the ECU 100 executes the above-mentioned perturbation in a state where the exhaust purification catalyst 210 is in an active state and the detection value of the water temperature sensor 260c is lower than the predetermined value.

[0041] The torque control unit 100d is a function that causes the motor of the vehicle 10 to generate a torque of an opposite phase to the torque fluctuation caused by perturbation in the internal combustion engine 20. In this embodiment, the object to be controlled by the torque control unit 100d is the second motor generator 32. The ECU 100 identifies the torque fluctuation caused by perturbation in the internal combustion engine 20. Then, the ECU 100 issues a control instruction to the PCU 35 by the function of the torque control unit 100d, and controls the second motor generator 32 to generate a torque of an opposite phase. In this embodiment, superimposing a torque of an opposite phase on the torque (torque for driving the vehicle 10) generated in the second motor generator 32 is regarded as generating a torque of an opposite phase. According to the above configuration, it is possible to reduce the torque fluctuation caused by perturbation, and to improve the comfort felt by the occupants of the vehicle 10.

[0042] (2) Exhaust purification performance control treatment: Next, the exhaust purification performance control process using the above configuration will be described in detail. FIG. 4 is a flowchart showing the exhaust purification performance control process. When the power supply of the vehicle 10 is on (ignition is on), the ECU 100 executes a main routine (not shown) at a predetermined calculation cycle. When a predetermined condition is satisfied while the main routine is being executed, the exhaust purification performance control process shown in FIG. 4 is started. The predetermined condition may be various conditions, and for example, when the internal combustion engine 20 is not started and the vehicle 10 is running using the second motor generator 32 as a power source (i.e., EV running), the operation prohibition state of the internal combustion engine 20 is released and a transition to a hybrid running mode is permitted. In addition, the exhaust purification performance control process may be started when a start condition for preheating the exhaust purification catalyst 210 before the start of the internal combustion engine 20 is satisfied.

[0043] When the exhaust purification performance control process is started, the ECU 100 warms up the air-fuel ratio sensors 260d1 and 260d2 by the function of the perturbation control unit 100c (step S100). That is, the ECU 100 controls a power supply unit (not shown) to supply power to the air-fuel ratio sensors 260d1 and 260d2. As a result, the temperatures of the air-fuel ratio sensors 260d1 and 260d2 rise.

[0044] Next, the ECU 100 acquires a target amount of electric power, which is an amount of electric power required to make the temperature of the exhaust purification catalyst 210 equal to or higher than a threshold value, by the function of the catalyst state control unit 100a (step S105). Specifically, the ECU 100 acquires a difference between an estimated value of the current temperature of the exhaust purification catalyst 210 and the threshold value. The ECU 100 also acquires the target amount of electric power by multiplying the amount of electric power required for a predetermined unit temperature increase by the difference. Note that, in the process in which the exhaust purification performance control process shown in FIG. 4 is repeated, if the target amount of electric power has already been acquired, step S105 may be omitted, or step S105 may be executed each time the process is repeated. Also, the estimated value of the current temperature of the exhaust purification catalyst 210 may be acquired by various methods, and for example, the estimated value may be acquired based on the detection value of the water temperature sensor 260c.

[0045] Next, the ECU 100 warms up the exhaust purification catalyst 210 using the function of the catalyst state control unit 100a (step S110). That is, the ECU 100 uses the function of the catalyst state control unit 100a to issue a control instruction to the power supply device 70 to supply electric power to a heat generating unit included in the exhaust purification catalyst 210. As a result, the temperature of the exhaust purification catalyst 210 rises. In this embodiment, the ECU 100 warms up the exhaust purification catalyst 210 by continuing to supply electric power to the exhaust purification catalyst 210 until the amount of electric power, which is an integrated value of the electric power supplied to the exhaust purification catalyst 210, reaches a target amount of electric power.

[0046] Next, the ECU 100 determines whether or not the warm-up of the air-fuel ratio sensors 260d1, 260d2 is completed by using the function of the perturbation control unit 100c (step S115). In this embodiment, the ECU 100 can detect the impedance values ​​of the air-fuel ratio sensors 260d1, 260d2 and can specify the temperatures of the air-fuel ratio sensors 260d1, 260d2 based on the impedance values. Therefore, the ECU 100 specifies the temperatures of the air-fuel ratio sensors 260d1, 260d2, and when the temperatures are equal to or higher than a predetermined temperature, determines that the warm-up of the air-fuel ratio sensors 260d1, 260d2 is completed. In addition, if it is determined in step S115 that the warm-up of the air-fuel ratio sensors 260d1, 260d2 has been completed, step S100 may be skipped until it is no longer determined that the warm-up of the air-fuel ratio sensors 260d1, 260d2 has been completed during the process of repeating the exhaust purification performance control process.

[0047] In step S115, if it is not determined that the warm-up of the air-fuel ratio sensors 260d1, 260d2 is completed, the ECU 100 ends the exhaust purification performance control process and returns to the main routine. In other words, if the air-fuel ratio sensors 260d1, 260d2 are in a state in which accurate detection cannot be performed, the ECU 100 does not perform perturbation and ends the exhaust purification performance control process.

[0048] On the other hand, when it is determined in step S115 that the warm-up of the air-fuel ratio sensors 260d1, 260d2 has been completed, the ECU 100 determines whether or not the warm-up of the exhaust purification catalyst 210 has been completed by the function of the catalyst state control unit 100a (step S120). That is, when the integrated value of the electric power supplied to the exhaust purification catalyst 210 reaches the target electric power amount acquired in step S105, the ECU 100 determines that the warm-up of the exhaust purification catalyst 210 has been completed. Note that, when it is determined in step S120 that the warm-up of the exhaust purification catalyst 210 has been completed, steps S105 and S110 may be skipped. Also, when a sensor that directly or indirectly detects the temperature of the exhaust purification catalyst 210 is used, or when the temperature of the exhaust purification catalyst 210 can be estimated, it may be detected that the warm-up of the exhaust purification catalyst 210 has not been completed again after the warm-up of the exhaust purification catalyst 210 has been completed. In this case, steps S105 and S110 may be executed again.

[0049] In step S120, if it is not determined that the warm-up of the exhaust purification catalyst 210 is completed, the ECU 100 ends the exhaust purification performance control process and returns to the main routine. In other words, if the temperature of the exhaust purification catalyst 210 has not risen sufficiently, the ECU 100 does not perform perturbation and ends the exhaust purification performance control process.

[0050] On the other hand, when it is determined in step S120 that the warm-up of the exhaust purification catalyst 210 has been completed, the ECU 100 determines whether or not the internal combustion engine 20 is in operation by the function of the internal combustion engine control unit 100b (step S125). That is, the ECU 100 determines whether or not the internal combustion engine 20 has been started and is continuing to operate by controlling the ignition plug 220, the injectors 240a, 240b, etc.

[0051] If it is not determined in step S125 that the internal combustion engine 20 is in operation, the ECU 100 starts the internal combustion engine 20 by the function of the internal combustion engine control unit 100b (step S130). That is, the ECU 100 controls the first motor generator 31 via the PCU 35 to drive the rotating shaft of the internal combustion engine 20 and start the internal combustion engine 20. After the engine is started, the ECU 100 controls the spark plug 220, the injectors 240a, 240b, etc. to continue the operation of the internal combustion engine 20. Therefore, after the internal combustion engine 20 is started, if step S125 is executed again in the process of repeating the exhaust purification performance control process, it is determined that the internal combustion engine 20 is in operation. If it is determined in step S125 that the internal combustion engine 20 is in operation, step S130 is skipped.

[0052] When step S130 is performed, or when it is determined in step S125 that the internal combustion engine 20 is operating, the ECU 100 determines whether the internal combustion engine 20 is operating in a cold state by the function of the perturbation control unit 100c (step S135). That is, the ECU 100 acquires a detection value of the water temperature sensor 260c, and determines that the internal combustion engine 20 is operating in a cold state when the temperature of the internal combustion engine 20 indicated by the detection value is lower than a predetermined value.

[0053] If it is not determined in step S135 that the engine is in cold operation, the ECU 100 ends the exhaust purification performance control process and returns to the main routine. That is, if the internal combustion engine 20 is in cold operation and the need for exhaust purification is not high, the ECU 100 does not perform perturbation and ends the exhaust purification performance control process. Note that, if the exhaust purification performance control process is ended without executing step S140 after the determinations of steps S115, S120, and S135 and the process returns to the main routine, perturbation may be performed by satisfying a condition different from that of the exhaust purification performance control process. For example, perturbation may be performed on the condition that the warm-up of the air-fuel ratio sensors 260d1 and 260d2, the warm-up of the exhaust purification catalyst 210, and the warm-up of the internal combustion engine 20 are completed in the main routine.

[0054] On the other hand, when it is determined in step S135 that the engine is in cold operation, the ECU 100 executes perturbation by the function of the perturbation control unit 100c (step S140). Specifically, the ECU 100 estimates the current air-fuel ratio based on the output value of the air-fuel ratio sensor 260d1, and controls the injectors 240a, 240b to change the fuel injection amount so that the current air-fuel ratio alternates between lean and rich sides of the theoretical air-fuel ratio. As a result, perturbation can be executed in a state in which the exhaust purification catalyst is activated during the cold operation of the internal combustion engine 20. Therefore, the performance of the exhaust purification catalyst can be maximized during the cold operation of the internal combustion engine 20, and the performance of the exhaust purification catalyst can be effectively utilized even in the cold state where there is a lot of exhaust, making it possible to purify the exhaust gas during the cold operation.

[0055] Next, the ECU 100 executes torque control of the second motor generator 32 by the function of the torque control unit 100d (step S145). In this embodiment, the torque generated by the second motor generator 32 is a torque for offsetting the fluctuation in the torque of the internal combustion engine 20 caused by perturbation.

[0056] Specifically, the ECU 100 obtains the crank angle of the internal combustion engine 20 based on the output signal of the crank angle sensor 260b, and obtains the angular acceleration of the crankshaft from the crank angle. Furthermore, the ECU 100 obtains the torque of the internal combustion engine 20 from the angular acceleration. The torque can be obtained by various methods, and for example, the torque T (N m) = moment of inertia J (kg m 2 )×angular acceleration α(rad / sec 2 ) In this case, the moment of inertia is specified in advance.

[0057] The ECU 100 smoothes the obtained change in torque over time. The smoothing may be performed so as to clarify the change in torque over time due to perturbation while suppressing abrupt changes in torque in a short period of time. The smoothing may be performed by various methods, and for example, the smoothing can be performed by calculating a moving average.

[0058] Specifically, the period of the explosion peak torque of the internal combustion engine 20 coincides with the rotation period of the crankshaft of the internal combustion engine 20, and is, for example, about 30 ms when the four-cylinder internal combustion engine 20 is operated at 1000 rpm. On the other hand, the frequency of perturbation is about 1 Hz, and the period is about 1 s. Therefore, the ECU 100 smoothes the torque fluctuation caused by the rotation of the crankshaft, sets a period during which the torque fluctuation caused by the perturbation remains, and calculates a moving average for each period.

[0059] Fig. 5A is a diagram showing a model of the torque obtained by the moving average. In Fig. 5A, the torque after the moving average is shown by a solid line, and a straight line obtained by linearly approximating the torque is shown by a dashed line. That is, the dashed line shows the time change of the torque excluding the influence of perturbation. The linear approximation shown by the dashed line may be performed by various methods, and a moving average using a longer period than the period used to obtain the torque shown by the solid line may be obtained, or the least square method or the like may be used.

[0060] As shown by the solid line in Fig. 5A, the torque changes in a state where the change in each perturbation period Tp is superimposed on the base torque shown by the dashed line. Therefore, the ECU 100 obtains the torque fluctuation caused by the perturbation by subtracting the base torque from the torque. Fig. 5B is a diagram showing the torque fluctuation caused by the perturbation obtained as described above. As shown in Fig. 5B, the torque caused by the perturbation changes so that positive torque and negative torque appear periodically in the period Tp.

[0061] When the torque fluctuation caused by the perturbation is acquired, the ECU 100 acquires a torque of an opposite phase obtained by inverting the torque fluctuation with respect to a torque of 0 (see FIG. 5C). Then, the ECU 100 issues a control instruction to the PCU 35 to control the second motor generator 32 to generate a torque of an opposite phase. Various control methods for generating a torque of an opposite phase may be used. For example, since the second motor generator 32 is used to drive the vehicle 10, at the stage where steps S140 and S145 are executed, the second motor generator 32 is rotating to drive the vehicle 10 and generates a torque.

[0062] Therefore, the ECU 100 obtains a value obtained by superimposing a torque of an opposite phase on the torque generated by the second motor generator 32 for the drive, and sets the value as a control target of the torque in the second motor generator 32. The relationship between the rotation speed and the torque in the second motor generator 32 is specified in advance, and the ECU 100 can specify the rotation speed of the second motor generator 32 required to generate a desired torque based on the relationship. The ECU 100 controls the second motor generator 32 via the PCU 35 to generate the control target torque. As a result, the torque fluctuation caused by the perturbation can be reduced, and the comfort felt by the occupants of the vehicle 10 can be improved.

[0063] When the torque control is executed in step S145, the ECU 100 returns to the main routine. Note that, when the perturbation is executed in step S140 and the torque control is executed in step S145, these perturbation and torque control are continuously executed. However, when steps S115, S120, and S135 are executed again in the process of repeating the exhaust purification performance control process, and the condition for skipping steps S140 and S145 is satisfied, the perturbation and torque control may be stopped.

[0064] (3) Other embodiments: The above embodiment is an example for carrying out the present invention, and various other embodiments can be adopted. For example, the vehicle in which the exhaust purification performance control system is used is not limited to a plug-in hybrid vehicle, and may be a hybrid vehicle that is not charged by an external power source. In addition, the vehicle 10 according to the above embodiment is a series-parallel type vehicle equipped with two motor generators, but the exhaust purification performance control system may be used in a parallel type vehicle equipped with one motor generator.

[0065] Furthermore, the above-mentioned exhaust purification catalyst 210 is a directly heated catalyst, but the exhaust purification performance control system may be used in an indirectly heated catalyst. Of course, the fuel for the internal combustion engine 20 is not limited to gasoline, and may be diesel or CN fuel. Furthermore, the air-fuel ratio sensors 260d1, d2 may be oxygen sensors that detect whether the exhaust air-fuel ratio is a predetermined value or not based on the oxygen concentration in the exhaust at the mounting position.

[0066] Furthermore, the order of the processes shown in Fig. 4 may be changed, and optional processes may be omitted. For example, the order of steps S115, S120, S125, and S135 shown in Fig. 4 may be interchanged. However, steps S125 and S130 are interchanged as a set. When the order is interchanged, it may become post-heat, unlike pre-heat, in which the exhaust purification catalyst 210 is heated before the internal combustion engine 20 is started.

[0067] For example, if steps S125 and S130 are performed before step S115, the internal combustion engine 20 is started before warming up the exhaust purification catalyst 210, and steps S140 and after are executed when warming up of the air-fuel ratio sensors 260d1 and 260d2 and the exhaust purification catalyst 210 is completed during cold operation after the engine is started. The order of steps S115, S120, and S135 can also be arbitrarily changed.

[0068] Also, a configuration may be adopted in which the determination in step S115 is omitted. For example, if the main routine has already confirmed that the air-fuel ratio sensor has been warmed up, or if warming up of the air-fuel ratio sensor is not necessary, step S115 may be omitted. Furthermore, in a configuration in which the internal combustion engine 20 is started in the main routine, the embodiment of post-heat can be realized by performing the exhaust purification performance control process shown in FIG. 4. In this case, steps S120 and S130 may be omitted.

[0069] Furthermore, the perturbation and torque control in steps S140 and S145 may be stopped by various interruptions. For example, when the load of the internal combustion engine 20 exceeds a predetermined standard, the perturbation and torque control may not be performed. Also, if the torque fluctuation width due to the perturbation is less than the standard width and does not affect the drivability, the torque control in step S145 may be omitted. The load of the internal combustion engine 20 may be identified by various methods. For example, the ECU 100 can determine that the load exceeds the standard when the amount of air detected by the air flow sensor 260a reaches a predetermined ratio or more of the upper limit amount estimated from the exhaust amount. Then, the ECU 100 stops the perturbation and torque control when the load of the internal combustion engine 20 exceeds the predetermined standard. According to this configuration, it is possible to protect the exhaust system components without applying an excessive load to the exhaust system components.

[0070] Furthermore, in perturbation, the fluctuation range and the fluctuation frequency of the air-fuel ratio may depend on various factors. For example, the ECU 100 may change at least one of the fluctuation range and the fluctuation frequency of the air-fuel ratio in perturbation according to at least one of the type, temperature, and deterioration degree of the exhaust purification catalyst 210.

[0071] For example, since appropriate fluctuation width and fluctuation frequency may differ depending on the type of exhaust purification catalyst 210, a configuration may be adopted in which the ECU 100 determines the fluctuation width and fluctuation frequency according to the type of exhaust purification catalyst 210. According to this configuration, even if the type of exhaust purification catalyst 210 changes, it becomes easier to bring out the perturbation effect in each exhaust purification catalyst 210.

[0072] In addition, since the appropriate fluctuation width and fluctuation frequency may differ if the temperature of the exhaust purification catalyst 210 differs, a configuration in which the ECU 100 determines the fluctuation width and fluctuation frequency according to the temperature of the exhaust purification catalyst 210. With this configuration, it is possible to suppress a decrease in the perturbation effect caused by fluctuations in the temperature of the exhaust purification catalyst 210.

[0073] An example of a configuration in which the fluctuation range is determined according to the temperature of the exhaust purification catalyst 210 is, for example, a configuration in which the ECU 100 increases the fluctuation range of the air-fuel ratio as the difference between the temperature of the exhaust purification catalyst 210 and the reference temperature increases. That is, the reference temperature is a temperature value or temperature range in which the performance of the exhaust purification catalyst 210 is maximized, and the performance of the exhaust purification catalyst 210 is less likely to be exhibited as the temperature of the exhaust purification catalyst 210 deviates from the reference temperature. In this case, if the fluctuation range is increased as the temperature deviation increases, the storage and release of oxygen in the exhaust purification catalyst 210 can be more actively promoted. As a result, it becomes possible to suppress a decrease in the perturbation effect caused by the deviation between the temperature of the exhaust purification catalyst 210 and the reference temperature.

[0074] Furthermore, since appropriate fluctuation width and fluctuation frequency may differ depending on the deterioration degree of the exhaust purification catalyst 210, a configuration may be adopted in which the ECU 100 determines the fluctuation width and fluctuation frequency according to the deterioration degree of the exhaust purification catalyst 210. With this configuration, it is possible to suppress the reduction in the perturbation effect caused by the progress of deterioration of the exhaust purification catalyst 210. Note that the deterioration degree can be determined, for example, according to the period of use.

[0075] An example of a configuration for determining the fluctuation range according to the deterioration degree of the exhaust purification catalyst 210 is, for example, a configuration in which the greater the deterioration degree, the smaller the fluctuation range of the air-fuel ratio. This configuration is adopted when the effect of promoting oxygen storage and release due to the fluctuation of the air-fuel ratio decreases with the progress of deterioration. In other words, when the effect of promoting oxygen storage and release due to the fluctuation of the air-fuel ratio decreases due to the progress of deterioration, it becomes difficult to promote oxygen storage and release even if the air-fuel ratio is changed. This state can be said to be a state in which torque fluctuation occurs even though the desired effect regarding storage and release cannot be obtained due to the fluctuation of the air-fuel ratio. Therefore, if the fluctuation of the air-fuel ratio is reduced, it is possible to suppress the torque fluctuation while accepting that the promotion of oxygen storage and release is insufficient.

[0076] Also, a configuration may be adopted in which the greater the degree of deterioration, the greater the fluctuation range of the air-fuel ratio. This configuration is adopted when the speed at which oxygen storage and release is promoted decreases as deterioration progresses. That is, as deterioration progresses, the effect of promoting oxygen storage and release by the fluctuation of the air-fuel ratio is reduced compared to before deterioration, but if the air-fuel ratio is fluctuated more greatly, it may be possible to promote oxygen storage and release. In this case, if the fluctuation of the air-fuel ratio is increased, it is possible to suppress the decrease in the perturbation effect caused by the deterioration of the exhaust purification catalyst 210.

[0077] The catalyst state control unit only needs to control a temperature adjustment unit that adjusts the temperature of an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine equipped in a vehicle to activate the exhaust purification catalyst. In other words, it is only needed that the exhaust purification catalyst can purify the exhaust gas passing through the exhaust passage. In the above-mentioned embodiment, the catalyst supported on the catalyst carrier is a three-way catalyst, but the type of the exhaust purification catalyst is not limited, and may be, for example, an oxidation catalyst, an occlusion reduction type NOx catalyst, a selective reduction type NOx catalyst, or the like.

[0078] The temperature adjustment may be any adjustment for making the exhaust purification catalyst active after adjustment. Generally, the active state is realized when the exhaust purification catalyst reaches a temperature equal to or higher than a predetermined value, so the adjustment for making the temperature equal to or higher than the predetermined value may be a temperature adjustment, but other configurations may also be used. For example, the adjustment may be for making the temperature of the exhaust purification catalyst within a predetermined range. The temperature may be indirectly evaluated by input power or the like as in the above-mentioned embodiment, or may be evaluated by a temperature sensor or the like, and various configurations can be adopted.

[0079] The active state may be a state in which the exhaust purification catalyst exerts a predetermined performance, may be a state in which the exhaust purification catalyst is at a temperature equal to or higher than a predetermined temperature, or may include other conditions, such as recovery from a state in which carbon contained in the exhaust gas adheres to the catalyst or water condensed from the exhaust gas adheres to the catalyst.

[0080] The perturbation control unit only needs to be able to control the air-fuel ratio adjustment unit that adjusts the air-fuel ratio of the internal combustion engine when the exhaust purification catalyst is in the activated state and the internal combustion engine is operating in a cold state, and to execute perturbation that repeats control to make the air-fuel ratio richer than a predetermined value and control to make the air-fuel ratio leaner than the predetermined value. In other words, the perturbation control unit only needs to be able to control the air-fuel ratio of the internal combustion engine to vary across a predetermined value. In the above embodiment, the predetermined value is the value of the stoichiometric air-fuel ratio, but is not limited to this value and may be a value obtained by adding a predetermined margin to the stoichiometric air-fuel ratio.

[0081] The state in which the internal combustion engine is cold-operated is a state in which the internal combustion engine is operated with the temperature of the internal combustion engine below a predetermined value, and the temperature of the internal combustion engine may be measured directly or indirectly. For example, the indirect measurement may be a measurement of the temperature of the cooling water as in the above-mentioned embodiment. The predetermined value may be any value that is previously determined, and may be a value smaller than the value at which the warm-up of the internal combustion engine is considered to be complete. For example, the value may be 40°C, but is not limited to 40°C. In addition, whether or not the internal combustion engine is cold-operated may be identified without measuring the temperature of the internal combustion engine. For example, when a cold start is performed in which the internal combustion engine is started at a temperature equal to or lower than the outside air temperature, the internal combustion engine may be considered to be cold-operated within a predetermined period after the cold start. [Explanation of symbols]

[0082] 10...vehicle, 20...internal combustion engine, 21...exhaust passage, 22...intake passage, 24...case, 29...catalytic converter, 30...power split mechanism, 31...first motor generator, 32...second motor generator, 34...reduction mechanism, 35...power control unit, 40...drive wheel, 50...battery, 51...charger, 60...external power source, 70...power supply device, 100...ECU, 100a...catalyst state control unit, 100b...internal combustion engine control unit, 100c...perturbation control unit, 100d...torque control unit, 210...exhaust purification catalyst, 220...ignition plug, 230...cylinder, 240...injector, 250...throttle, 260a...air flow sensor, 260b...crank angle sensor, 260c...water temperature sensor, 260d1, 260d2...air-fuel ratio sensor

Claims

1. a catalyst state control unit that controls a temperature adjustment unit that adjusts the temperature of an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine of a vehicle to activate the exhaust purification catalyst; an internal combustion engine control unit that starts the internal combustion engine; a perturbation control unit that controls an air-fuel ratio adjusting unit that adjusts an air-fuel ratio of the internal combustion engine when the exhaust purification catalyst is in the activated state and the internal combustion engine is in cold operation, and executes perturbation that repeats a control to make the air-fuel ratio richer than a predetermined value and a control to make the air-fuel ratio leaner than the predetermined value; An exhaust purification performance control system comprising:

2. A torque control unit is further provided that generates, in a motor provided in the vehicle, a torque having an opposite phase to a torque fluctuation generated in the internal combustion engine by the perturbation. The exhaust gas purification performance control system according to claim 1 .

3. a step of controlling a temperature adjustment unit that adjusts the temperature of an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine of a vehicle to activate the exhaust purification catalyst; starting the internal combustion engine; a step of controlling an air-fuel ratio adjusting unit that adjusts an air-fuel ratio of the internal combustion engine when the exhaust purification catalyst is in the activated state and the internal combustion engine is in cold operation, and executing perturbation that repeats a control to make the air-fuel ratio richer than a predetermined value and a control to make the air-fuel ratio leaner than the predetermined value; The exhaust purification performance control method includes the following:

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