Method for warming up catalyst in internal combustion engine system and internal combustion engine system

Abstract

To suppress an increase in fuel consumption until a temperature of a catalyst device reaches an activation temperature while performing early warm-up of the catalyst device by retarding ignition timing.SOLUTION: A controller (120) of an internal combustion engine system (1) is configured to: set an operation mode to catalyst warm-up operation to operate an internal combustion engine (10) when a temperature of a catalyst device (51) when the internal combustion engine is started from a stopped state is lower than an activation temperature of the catalyst device; continue the catalyst warm-up operation until the temperature of the catalyst device becomes equal to or higher than a first threshold value set to be lower than the activation temperature; stop the internal combustion engine when the temperature of the catalyst device is equal to or higher than the first threshold; and set the operation mode to normal operation to operate the internal combustion engine when the temperature of the catalyst device is equal to or higher than the activation temperature after the internal combustion engine is stopped due to the fact that the temperature of the catalyst device is equal to or higher than the first threshold.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for warming up a catalyst of an internal combustion engine system and an internal combustion engine system, and more particularly to a method for warming up a catalyst of an internal combustion engine system and an internal combustion engine system including a spark-ignition internal combustion engine, a catalyst device provided in an exhaust passage of the internal combustion engine, and a controller for controlling the internal combustion engine.

Background Art

[0002] Conventionally, a catalyst device such as a three-way catalyst has been used to purify harmful components such as unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in exhaust gas discharged from an internal combustion engine of a vehicle. Since the catalyst device cannot exhibit the desired purification performance in an un-warmed state below the activation temperature, it is necessary to warm up the catalyst device to the activation temperature at an early stage during cold start when the catalyst temperature is low.

[0003] Therefore, for example, when the catalyst device is in an un-warmed state below the activation temperature during cold start, the ignition timing of the spark-ignition internal combustion engine is significantly retarded until after top dead center, thereby increasing the exhaust heat loss and raising the temperature of the exhaust gas, and a method for quickly raising the temperature of the catalyst device has been proposed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the conventional technology as described above, the control of retarding the ignition timing of the internal combustion engine is continued to quickly warm up the catalyst device until the catalyst device reaches the activation temperature from the cold start. When the ignition timing is retarded in this way, the exhaust heat loss is large, and the combustion efficiency and output torque of the internal combustion engine are reduced compared to the normal operation after warm-up. As a result, until the temperature of the catalyst device reaches the activation temperature, the fuel consumption increases compared to the normal operation.

[0006] The present invention has been made to solve such problems, and while performing early warm-up of the catalyst device by retarding the ignition timing, it is possible to suppress an increase in fuel consumption until the temperature of the catalyst device reaches the activation temperature. An object of the present invention is to provide a catalyst warm-up method for an internal combustion engine system and an internal combustion engine system.

Means for Solving the Problems

[0007] To achieve the above object, a method for warming up a catalyst of an internal combustion engine system according to the present invention is a method for warming up a catalyst of an internal combustion engine system including a spark-ignition internal combustion engine mounted on a vehicle, a catalyst device provided in an exhaust passage of the internal combustion engine, and a controller for controlling the internal combustion engine. The controller includes steps of: acquiring the temperature of the catalyst device; when the temperature of the catalyst device when starting from a stopped state of the internal combustion engine is equal to or higher than the activation temperature of the catalyst device, setting the operation mode of the internal combustion engine to normal operation and operating the internal combustion engine; when the temperature of the catalyst device when starting from a stopped state of the internal combustion engine is lower than the activation temperature of the catalyst device, setting the operation mode to a catalyst warming-up operation in which the ignition timing is retarded compared to normal operation and operating the internal combustion engine; after starting the operation of the internal combustion engine with the operation mode set to the catalyst warming-up operation, continuing the catalyst warming-up operation until the temperature of the catalyst device becomes equal to or higher than a first threshold value set lower than the activation temperature; when the temperature of the catalyst device is equal to or higher than the first threshold value after starting the operation of the internal combustion engine with the operation mode set to the catalyst warming-up operation, stopping the internal combustion engine; and when the temperature of the catalyst device is equal to or higher than the activation temperature after stopping the internal combustion engine due to the temperature of the catalyst device being equal to or higher than the first threshold value, setting the operation mode to normal operation and operating the internal combustion engine.

[0008] According to the present invention configured as described above, when the temperature of the catalyst device when starting from a state where the internal combustion engine is stopped is lower than the activation temperature of the catalyst device, the operation mode is set to the catalyst warm-up operation until the temperature of the catalyst device becomes equal to or higher than a first threshold value set lower than the activation temperature, and the internal combustion engine is operated. When the temperature of the catalyst device is equal to or higher than the first threshold value, the internal combustion engine is stopped. Therefore, after the temperature of the catalyst device becomes equal to or higher than the first threshold value, unburned fuel adhering to the catalyst device during the catalyst warm-up operation reacts with ambient oxygen as an oxidant to generate reaction heat, so that the internal combustion engine can be stopped while the temperature of the catalyst device rises from the first threshold value to the activation temperature, and fuel consumption can be stopped. Thereby, while performing early warm-up of the catalyst device by retarding the ignition timing, an increase in fuel consumption until the temperature of the catalyst device reaches the activation temperature can be suppressed.

[0009] Also, preferably in the present invention, after stopping the internal combustion engine because the temperature of the catalyst device is equal to or higher than the first threshold value, when the temperature of the catalyst device is lower than the activation temperature and the temperature increase rate of the catalyst device is lower than a predetermined threshold value, the controller includes a step of setting the operation mode to the catalyst warm-up operation and operating the internal combustion engine.

[0010] According to the present invention configured as described above, even when the temperature of the catalyst device is equal to or higher than the first threshold value, if the temperature of the catalyst device cannot be raised to the activation temperature only by the reaction heat of the unburned fuel adhering to the catalyst device during the catalyst warm-up operation, the catalyst device can be warmed up early by setting the operation mode to the catalyst warm-up operation and operating the internal combustion engine.

[0011] Also, preferably in the present invention, the internal combustion engine system is mounted on a hybrid vehicle including a motor that is a driving power source of the vehicle, a battery that supplies power to the motor, and a generator that generates power for supplying to the motor and the battery and is driven by the internal combustion engine, and the controller includes a step of starting or stopping the internal combustion engine based on the SOC of the battery.

[0012] According to the present invention configured as described above, in a hybrid vehicle in which the temperature of the catalytic converter tends to decrease due to the stop of the internal combustion engine based on the SOC of the battery, while performing early warm-up of the catalytic converter by retarding the ignition timing, it is possible to suppress an increase in fuel consumption until the temperature of the catalytic converter reaches the activation temperature.

[0013] In another aspect, the internal combustion engine system according to the present invention includes a spark ignition type internal combustion engine, a catalytic converter provided in the exhaust passage of the internal combustion engine, and a controller that controls the internal combustion engine. The controller acquires the temperature of the catalytic converter. When the temperature of the catalytic converter when starting from a stopped state of the internal combustion engine is equal to or higher than the activation temperature of the catalytic converter, the controller sets the operation mode of the internal combustion engine to normal operation and operates the internal combustion engine. When the temperature of the catalytic converter when starting from a stopped state of the internal combustion engine is lower than the activation temperature of the catalytic converter, the controller sets the operation mode to a catalyst warm-up operation in which the ignition timing is retarded more than in normal operation and operates the internal combustion engine. After starting the operation of the internal combustion engine with the operation mode set to the catalyst warm-up operation, the controller continues the catalyst warm-up operation until the temperature of the catalytic converter becomes equal to or higher than a first threshold value set lower than the activation temperature. After starting the operation of the internal combustion engine with the operation mode set to the catalyst warm-up operation, when the temperature of the catalytic converter is equal to or higher than the first threshold value, the controller stops the internal combustion engine. After stopping the internal combustion engine because the temperature of the catalytic converter is equal to or higher than the first threshold value, when the temperature of the catalytic converter is equal to or higher than the activation temperature, the controller sets the operation mode to normal operation and operates the internal combustion engine.

[0014] Also according to the present invention configured as described above, when the temperature of the catalyst device is lower than the activation temperature when the internal combustion engine starts from a stopped state, the controller sets the operation mode to the catalyst warm-up operation and operates the internal combustion engine until the temperature of the catalyst device becomes equal to or higher than a first threshold value set lower than the activation temperature. When the temperature of the catalyst device is equal to or higher than the first threshold value, the internal combustion engine is stopped. Therefore, after the temperature of the catalyst device becomes equal to or higher than the first threshold value, unburned fuel adhering to the catalyst device during the catalyst warm-up operation reacts with ambient oxygen as an oxidant to generate reaction heat, and the internal combustion engine can be stopped while the temperature of the catalyst device rises from the first threshold value to the activation temperature, thereby stopping fuel consumption. As a result, it is possible to perform early warm-up of the catalyst device by retarding the ignition timing and suppress an increase in fuel consumption until the temperature of the catalyst device reaches the activation temperature.

[0015] Further, preferably in the present invention, after the controller stops the internal combustion engine because the temperature of the catalyst device is equal to or higher than the first threshold value, when the temperature of the catalyst device is lower than the activation temperature and the temperature increase rate of the catalyst device is lower than a predetermined threshold value, the controller is configured to set the operation mode to the catalyst warm-up operation and operate the internal combustion engine.

[0016] According to the present invention configured as described above, even when the temperature of the catalyst device is equal to or higher than the first threshold value, if the reaction heat of the unburned fuel adhering to the catalyst device during the catalyst warm-up operation alone cannot raise the temperature of the catalyst device to the activation temperature, the catalyst device can be warmed up early by setting the operation mode to the catalyst warm-up operation and operating the internal combustion engine.

[0017] Further, preferably in the present invention, the internal combustion engine system is mounted on a hybrid vehicle including a motor that is a driving power source of the vehicle, a battery that supplies power to the motor, and a generator that generates power for supplying to the motor and the battery and is driven by the internal combustion engine, and the controller is configured to start or stop the internal combustion engine based on the SOC of the battery.

[0018] According to the present invention configured as described above, in a hybrid vehicle in which the temperature of the catalytic converter tends to decrease due to the stop of the internal combustion engine based on the SOC of the battery, while performing early warm-up of the catalytic converter by retarding the ignition timing, it is possible to suppress an increase in fuel consumption until the temperature of the catalytic converter reaches the activation temperature.

Advantages of the Invention

[0019] According to the catalytic converter warm-up method and the internal combustion engine system of the present invention, while performing early warm-up of the catalytic converter by retarding the ignition timing, it is possible to suppress an increase in fuel consumption until the temperature of the catalytic converter reaches the activation temperature.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0022] <System Configuration> First, referring to FIGS. 1 and 2, the configuration of the vehicle and the internal combustion engine system according to this embodiment will be described. FIG. 1 is a configuration diagram of the vehicle, and FIG. 2 is a configuration diagram of the internal combustion engine system.

[0023] As shown in FIG. 1, the vehicle 100 is a so-called series hybrid vehicle. The vehicle 100 includes an internal combustion engine system 1 for power generation, an electric drive unit 110 for driving the drive wheels 101 of the vehicle 100 using electric power, a battery B capable of supplying power to the electric drive unit 110, and a controller 120 for controlling the internal combustion engine system 1 and the electric drive unit 110.

[0024] The electric drive unit 110 has a motor 111 that is a driving force source for driving the drive wheels 101, a speed reducer 112, and a generator 113. The motor 111 operates by receiving power supply from the battery B and the generator 113. The speed reducer 112 reduces the output of the motor 111 and transmits it to the drive wheels 101. The generator 113 is driven by the internal combustion engine 10 to generate electricity to supply to the motor 111 and the battery B. Also, the generator 113 functions as a starting device for starting the internal combustion engine 10 by receiving power supply from the battery B.

[0025] The battery B is charged by the electric power generated by the generator 113. Also, the battery B supplies the stored electric power to the motor 111. The battery B is provided with a voltage sensor SN6 for detecting the output voltage of the battery B and a current sensor SN7 for detecting the output current of the battery B. These voltage sensor SN6 and current sensor SN7 output electrical signals corresponding to their respective detected values to the controller 120.

[0026] As shown in FIG. 2, the internal combustion engine system 1 includes a spark ignition internal combustion engine 10. In the present embodiment, the internal combustion engine 10 is a rotary engine, but it may also be a reciprocating engine. The internal combustion engine 10 includes a rotor 11 accommodated in a rotor accommodation chamber R, a fuel injection device 12 for injecting fuel into the rotor accommodation chamber R, and a spark plug 13 provided so that an electrode is exposed toward the rotor accommodation chamber R.

[0027] An intake passage 3 and an exhaust passage 5 are connected to the internal combustion engine 10, and air is guided into the rotor accommodation chamber R through the intake passage 3, and exhaust gas in the rotor accommodation chamber R is discharged through the exhaust passage 5.

[0028] An air cleaner 31 is provided on the most upstream side of the intake passage 3, a throttle valve 32 is provided on the downstream side thereof, and an intake manifold 33 is connected between the throttle valve 32 and the internal combustion engine 10. An air flow sensor SN1 is provided near the outlet of the air cleaner 31, and an intake pressure sensor SN2 for detecting the intake air pressure in the intake passage 3 is provided in the intake manifold 33.

[0029] Further, the exhaust passage 5 is provided with an exhaust manifold 52 connected to the internal combustion engine 10 and a downstream exhaust passage 53 connected to the downstream side of the exhaust passage 5. An EGR device 4 for recirculating a part of the exhaust gas in the exhaust passage 5 to the downstream side of the throttle valve 32 in the intake passage 3 is connected to the exhaust manifold 52. Further, a catalytic device 51 having a three-way catalyst for purifying harmful components such as unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas is provided in the downstream exhaust passage 53. Further, a linear A / F sensor SN5 for detecting the oxygen concentration in the exhaust gas is provided in the exhaust manifold 52.

[0030] The EGR device 4 has an EGR passage 40 connecting the exhaust passage 5 and the intake passage 3, an EGR cooler 41 for cooling the recirculating exhaust gas in the EGR passage 40 to increase the density, and an EGR valve 42 for controlling the EGR rate.

[0031] Furthermore, the internal combustion engine 10 is provided with a rotational speed sensor SN3 for detecting the rotational speed of the internal combustion engine 10 and a coolant temperature sensor SN4 for detecting the temperature of the coolant water (engine coolant temperature) of the internal combustion engine 10.

[0032] The internal combustion engine system 1 includes a controller 120 as an arithmetic unit and a control unit for controlling the internal combustion engine 10. The controller 120 is a controller 120 based on a well-known microcomputer. The controller 120 is composed of a computer including one or more processors 121 (typically a CPU), a storage unit 122 (such as ROM, RAM, etc.) for storing various programs, and the like.

[0033] Based on the signals input from the various sensors SN1 to SN7 described above, the controller 120 estimates the temperature of the catalyst device 51 and the SOC (State of Charge) of the battery B, calculates the control amounts of the respective devices of the internal combustion engine 10 such as the fuel injection device 12, the ignition plug 13, the throttle valve 32, the EGR valve 42, etc., and the control amount of the motor 111, and outputs an electric signal corresponding to the calculated control amount to those devices.

[0034] <Engine control process> As a result of earnestly studying measures to suppress the fuel consumption until the temperature of the catalyst device reaches the activation temperature during the warm-up operation of the catalyst device, the inventors of the present application have found that when the temperature of the catalyst device is lower than the activation temperature, the temperature of the catalyst device may continue to rise even if the operation of the internal combustion engine is stopped.

[0035] When performing control to retard the ignition timing of an internal combustion engine in order to quickly warm up a catalyst device, a part of the fuel injected by a fuel injection device flows into an exhaust passage without being burned and adheres to the catalyst device. When the temperature of the catalyst device is equal to or higher than a predetermined temperature lower than the activation temperature, the unburned fuel adhering to this catalyst device reacts with the surrounding oxygen as an oxidizing agent by the action of the catalyst device to generate reaction heat, so that it is considered that the temperature of the catalyst device has risen even though the internal combustion engine has stopped. Thus, in the following description, the temperature that becomes the threshold value at which the temperature of the catalyst device begins to rise due to the reaction heat of the unburned fuel adhering to the catalyst device is referred to as the "partial activation temperature".

[0036] Therefore, when the inventors of the present application are operating the internal combustion engine by retarding the ignition timing for warming up the catalyst device, when the temperature of the catalyst device becomes equal to or higher than a predetermined partial activation temperature, the operation of the internal combustion engine is stopped, and then, when the temperature of the catalyst device becomes equal to or higher than the activation temperature, the inventors have come up with the idea of controlling the internal combustion engine to start normal operation. By performing control in this way, when warming up the catalyst device, the fuel consumption can be suppressed by stopping the internal combustion engine while the temperature of the catalyst device rises from the partial activation temperature to the activation temperature.

[0037] Hereinafter, with reference to FIGS. 4 to 6, the flow of the engine control process according to the present embodiment will be described. FIG. 4 is a flowchart of the engine control process according to the present embodiment, FIG. 5 is a flowchart of the catalyst warm-up operation control process according to the present embodiment, and FIG. 6 is a time chart showing changes in the operation mode, catalyst temperature, and SOC of the battery B in the engine control according to the present embodiment.

[0038] The engine control process shown in FIG. 4 is repeatedly executed by the controller 120 at a predetermined cycle when the power supply of the internal combustion engine system 1 is ON.

[0039] When the engine control process starts, the controller 120 acquires signals from each of the sensors SN1 to SN7 (step S1). Acquisition of signals from each of the sensors SN1 to SN7 is constantly executed in the background also in the processes after step S1.

[0040] Next, the controller 120 determines which of the normal operation, stop, or catalyst warm-up operation the current operation mode of the internal combustion engine 10 corresponds to (step S2). Here, "normal operation" is an operation mode selected when the temperature of the catalyst device 51 is equal to or higher than the activation temperature (for example, 450°C). For example, the ignition timing is set so that the combustion efficiency of the internal combustion engine 10 is optimal under various conditions. Also, "stop" is a mode in which the operation of the internal combustion engine 10 is stopped. Further, "catalyst warm-up operation" is a mode selected when the temperature of the catalyst device 51 is lower than the activation temperature. The ignition timing is retarded compared to when the operation mode is "normal operation", and the temperature of the exhaust gas is raised compared to that during "normal operation". The controller 120 can determine the operation mode of the internal combustion engine 10 based on, for example, the rotational speed of the internal combustion engine 10 acquired from the rotational speed sensor SN3, or the control signals output from the controller 120 to the fuel injection device 12 and the ignition plug 13. Also, information specifying which operation mode the internal combustion engine 10 is operating in may be stored in the storage unit 122 and updated by the controller 120 as needed.

[0041] As a result of the determination in step S2, when the operation mode is "normal operation" (step S2: normal operation), the controller 120 determines whether or not the stop condition for stopping the internal combustion engine 10 is satisfied (step S3). The stop condition for stopping the internal combustion engine 10 includes that the SOC of the battery B estimated based on the signals acquired from the voltage sensor SN6 and the current sensor SN7 of the battery B is higher than a predetermined stop threshold value (for example, 80%). Other conditions may also be included, such as that the required driving force of the vehicle 100 is less than a predetermined value.

[0042] If, as a result of the determination in step S3, the stop condition for stopping the internal combustion engine 10 is not satisfied (step S3: NO), the controller 120 repeats the determination in step S3 until the stop condition for stopping the internal combustion engine 10 is satisfied. That is, the normal operation of the internal combustion engine 10 continues.

[0043] On the other hand, if the stop condition for stopping the internal combustion engine 10 is satisfied (step S3: YES), for example, when the SOC of the battery B estimated based on the signals acquired from the voltage sensor SN6 and the current sensor SN7 of the battery B exceeds a predetermined stop threshold value, the controller 120 stops the operation of the internal combustion engine 10 (step S4). Thereby, the operation mode of the internal combustion engine 10 becomes "stopped". After that, the controller 120 ends the engine control process.

[0044] Also, if, as a result of the determination in step S2, the operation mode is "stopped" (step S2: stopped), the controller 120 determines whether or not the start condition for starting the internal combustion engine 10 is satisfied (step S5). The start condition for starting the internal combustion engine 10 includes that the SOC of the battery B estimated based on the signals acquired from the voltage sensor SN6 and the current sensor SN7 of the battery B is lower than a predetermined start threshold value (for example, 20%). Other conditions may also be included, such as that the required driving force of the vehicle 100 is greater than a predetermined value.

[0045] If, as a result of the determination in step S5, the start condition for starting the internal combustion engine 10 is not satisfied (step S5: NO), the controller 120 repeats the determination in step S5 until the start condition for starting the internal combustion engine 10 is satisfied. That is, the stop of the internal combustion engine 10 continues.

[0046] When the starting conditions for starting the internal combustion engine 10 are satisfied on one hand (step S5: YES), for example, when the SOC of the battery B estimated based on the signals acquired from the voltage sensor SN6 and the current sensor SN7 of the battery B is below a predetermined starting threshold, the controller 120 starts the internal combustion engine 10 (step S6).

[0047] Also, the controller 120 determines whether the temperature of the catalyst device 51 is equal to or higher than the second threshold value Tth2 (step S7). Here, the second threshold value Tth2 is a threshold value set to be equal to or higher than the activation temperature of the catalyst device 51, and in this embodiment, it is equal to the activation temperature (for example, 450°C). The controller 120 inputs parameters including the amount of air inhaled into the internal combustion engine 10 based on the signal acquired from the air flow sensor SN1, the intake air pressure based on the signal acquired from the intake air pressure sensor SN2, the engine speed based on the signal acquired from the rotational speed sensor SN3, the cooling water temperature based on the signal acquired from the water temperature sensor SN4, the oxygen concentration in the exhaust gas based on the signal acquired from the linear A / F sensor SN5, etc. into the catalyst temperature estimation model pre-stored in the storage unit 122 and performs calculations to estimate the temperature of the catalyst device 51. The catalyst temperature estimation model can be experimentally obtained, for example, by measuring the temperature of the catalyst device 51 when the internal combustion engine 10 is operated under various operating conditions and performing regression analysis using parameters such as the amount of air inhaled, the intake air pressure, the engine speed, the cooling water temperature, and the oxygen concentration in the exhaust gas.

[0048] As a result of the determination in step S7, when the temperature of the catalyst device 51 is equal to or higher than the second threshold value Tth2 (step S7: YES), that is, when the temperature of the catalyst device 51 is equal to or higher than the activation temperature, the warm-up of the catalyst device 51 is completed, so the controller 120 sets the operation mode of the internal combustion engine 10 to normal operation and starts the operation of the internal combustion engine 10 (step S8). That is, the operation mode of the internal combustion engine 10 becomes "normal operation". Thereafter, the controller 120 ends the engine control process.

[0049] On the other hand, when the temperature of the catalyst device 51 is not equal to or higher than the second threshold value Tth2 (step S7: NO), that is, when the temperature of the catalyst device 51 is lower than the activation temperature, it is necessary to warm up the catalyst device 51. Therefore, the controller 120 sets the operation mode of the internal combustion engine 10 to the catalyst warm-up operation and starts the operation of the internal combustion engine 10 (step S9). That is, the operation mode of the internal combustion engine 10 becomes the "catalyst warm-up operation". After that, the controller 120 ends the engine control process.

[0050] Also, as a result of the determination in step S2, when the operation mode is the "catalyst warm-up operation" (step S2: catalyst warm-up operation), the controller 120 executes the catalyst warm-up operation control (step S10). After that, the controller 120 ends the engine control process. Hereinafter, the details of the catalyst warm-up operation control will be described.

[0051] When the catalyst warm-up operation control process shown in FIG. 5 is started, the controller 120 determines whether the temperature of the catalyst device 51 is equal to or higher than the first threshold value Tth1 (step S11). Here, the first threshold value Tth1 is a threshold value set lower than the activation temperature of the catalyst device 51 and is set to be equal to or higher than the above-described "partial activation temperature". For example, by causing the internal combustion engine to perform the catalyst warm-up operation under various initial conditions, stopping the internal combustion engine when the temperature of the catalyst device is lower than the activation temperature and measuring the subsequent temperature change of the catalyst device, the first threshold value Tth1 suitable for suppressing the fuel consumption while performing the early warm-up of the catalyst device can be set. In the present embodiment, the first threshold value Tth1 is, for example, 250°C.

[0052] As a result of the determination in step S11, when the temperature of the catalyst device 51 is not equal to or higher than the first threshold value Tth1 (step S11: NO), the controller 120 repeats the determination in step S11 until the temperature of the catalyst device 51 becomes equal to or higher than the first threshold value Tth1. That is, when the operation of the internal combustion engine 10 is stopped, the temperature of the catalyst device 51 also decreases, so the catalyst warm-up operation of the internal combustion engine 10 is continued.

[0053] On the one hand, when the temperature of the catalyst device 51 is equal to or higher than the first threshold value Tth1 (step S11: YES), the controller 120 stops the operation of the internal combustion engine 10 (step S12). Since the temperature of the catalyst device 51 is equal to or higher than the first threshold value Tth1 set to be equal to or higher than the partial activation temperature, the unburned fuel adhering to the catalyst device 51 in the previous catalyst warm-up operation reacts with the surrounding oxygen as an oxidant under the action of the catalyst device 51 to generate reaction heat. Therefore, the temperature of the catalyst device 51 continues to rise even after the internal combustion engine 10 stops.

[0054] Next, the controller 120 determines whether the temperature of the catalyst device 51 is equal to or higher than the second threshold value Tth2 (step S13). When the temperature of the catalyst device 51 is equal to or higher than the second threshold value Tth2 (step S13: YES), that is, when the temperature of the catalyst device 51 is equal to or higher than the activation temperature, the warm-up of the catalyst device 51 is completed. Therefore, the controller 120 starts the internal combustion engine 10 (step S14), sets the operation mode to normal operation, and starts the operation of the internal combustion engine 10 (step S15). That is, the operation mode of the internal combustion engine 10 becomes "normal operation". Thereafter, the controller 120 ends the catalyst warm-up operation control process.

[0055] On the other hand, when the temperature of the catalyst device 51 is not equal to or higher than the second threshold value Tth2 (step S13: NO), that is, when the temperature of the catalyst device 51 is lower than the activation temperature, the controller 120 determines whether the temperature increase rate (temperature increase width per unit time) of the catalyst device 51 is smaller than a predetermined threshold value TIth (step S16). The threshold value TIth of the temperature increase rate is a reference value for determining whether the reaction heat generated by the oxidation reaction of the unburned fuel adhering to the catalyst device 51 is sufficient to raise the temperature of the catalyst device 51 to the activation temperature, and is, for example, 0 °C / sec.

[0056] As a result, when the temperature increase rate of the catalyst device 51 is not less than the threshold value TIth (step S16: NO), since the temperature of the catalyst device 51 is rising at a sufficient speed, the controller 120 re-determines whether the temperature of the catalyst device 51 is equal to or higher than the second threshold value Tth2 (step S13). Thereafter, the processes of steps S13 and S16 are repeated until the temperature of the catalyst device 51 becomes equal to or higher than the second threshold value Tth2, or the temperature increase rate of the catalyst device 51 becomes less than the threshold value TIth.

[0057] In step S16, when the temperature increase rate of the catalyst device 51 is less than the threshold value TIth (step S16: YES), it is considered that the temperature of the catalyst device 51 cannot be raised to the activation temperature even if the internal combustion engine 10 is stopped as it is. Therefore, the controller 120 starts the internal combustion engine 10 (step S17) and resumes the operation of the internal combustion engine 10 with the operation mode set to the catalyst warm-up operation (step S18).

[0058] Next, the controller 120 determines whether the temperature of the catalyst device 51 is equal to or higher than the second threshold value Tth2 (step S19). As a result, when the temperature of the catalyst device 51 is not equal to or higher than the second threshold value Tth2 (step S19: NO), that is, when the temperature of the catalyst device 51 is lower than the activation temperature, the controller 120 repeats the determination in step S19 until the temperature of the catalyst device 51 becomes equal to or higher than the second threshold value Tth2.

[0059] On the other hand, when the temperature of the catalyst device 51 is equal to or higher than the second threshold value Tth2 (step S19: YES), that is, when the temperature of the catalyst device 51 is equal to or higher than the activation temperature, the warm-up of the catalyst device 51 is completed. Therefore, the controller 120 changes the operation mode from the catalyst warm-up operation to the normal operation and operates the internal combustion engine 10 (step S15). That is, the operation mode of the internal combustion engine 10 becomes "normal operation". Thereafter, the controller 120 ends the catalyst warm-up operation control process.

[0060] The time chart in FIG. 6 shows an example of changes in the operation mode, the temperature of the catalyst device 51, and the SOC of the battery B when the above-described engine control process is executed. Specifically, the left end in the time chart represents a state where the operation mode of the internal combustion engine 10 is stopped, and the vehicle 100 is traveling using the power of the battery B, so the SOC is gradually decreasing.

[0061] After that, when the SOC falls below the start threshold value at time T1, the internal combustion engine 10 starts. At this time, since the temperature of the catalyst device 51 is lower than the second threshold value Tth2, the operation mode of the internal combustion engine 10 is set to the catalyst warm-up operation. That is, the ignition timing of the internal combustion engine 10 is retarded more than during normal operation. Thereby, the temperature of the exhaust gas rises, and the temperature of the catalyst device 51 begins to rise.

[0062] At time T2, when the temperature of the catalyst device 51 becomes equal to or higher than the first threshold value Tth1, the internal combustion engine 10 stops. In this case, since the temperature of the catalyst device 51 is equal to or higher than the first threshold value Tth1, unburned fuel adhering to the catalyst device 51 in the previous catalyst warm-up operation reacts with ambient oxygen as an oxidant by the action of the catalyst device 51 to generate reaction heat. Therefore, the temperature of the catalyst device 51 continues to rise even after the internal combustion engine 10 stops.

[0063] After that, as shown by the solid line in FIG. 6, when the temperature of the catalyst device 51 continues to rise and becomes equal to or higher than the second threshold value Tth2 at time T3, the internal combustion engine 10 restarts and starts operating with the operation mode set to normal operation. Thereby, the SOC of the battery B begins to rise as the generator 113 driven by the internal combustion engine 10 generates electricity. When the SOC exceeds the stop threshold value at time T4, the internal combustion engine 10 stops.

[0064] On the other hand, as shown by the dashed-dotted line in FIG. 6, when the temperature rise of the catalyst device 51 stops and the temperature rise rate becomes smaller than the threshold value TIth at time T3´, the internal combustion engine 10 restarts and resumes operation in the catalyst warm-up operation mode. As a result, the temperature of the catalyst device 51 rises again. Thereafter, when the temperature of the catalyst device 51 becomes equal to or higher than the second threshold value Tth2 at time T4´, the internal combustion engine 10 restarts and starts operating in the normal operation mode. As a result, the SOC of the battery B starts to increase as the generator 113 driven by the internal combustion engine 10 generates electricity. When the SOC exceeds the stop threshold value at time T5´, the internal combustion engine 10 stops.

[0065] <Modification example> As described above, the embodiments of the present invention have been described. However, the specific configurations and means of the present invention can be arbitrarily modified and improved within the scope of the technical idea of each invention described in the claims. Hereinafter, such modification examples will be described.

[0066] First, the problems to be solved by the invention and the effects of the invention are not limited to the above-described contents. According to the present invention, it is also possible to solve problems not described or achieve effects not described, and it is also possible to solve only some of the described problems or achieve only some of the described effects.

[0067] In the above-described embodiment, the case where the internal combustion engine system 1 is mounted on the vehicle 100 of a series hybrid vehicle has been described as an example. However, the internal combustion engine system 1 and the engine control of the present embodiment can also be applied to an internal combustion engine system mounted on a parallel hybrid vehicle, a split hybrid vehicle, or a non-hybrid vehicle.

[0068] <Operation and effect> Next, the catalyst warm-up method of the internal combustion engine system of the present embodiment and the operation and effect of the internal combustion engine system will be described.

[0069] According to the present embodiment, when the temperature of the catalyst device 51 when the internal combustion engine 10 starts from a stopped state is lower than the activation temperature (second threshold value Tth2) of the catalyst device 51, the controller 120 sets the operation mode to the catalyst warm-up operation and operates the internal combustion engine 10 until the temperature of the catalyst device 51 becomes equal to or higher than the first threshold value Tth1 set lower than the activation temperature. When the temperature of the catalyst device 51 is equal to or higher than the first threshold value Tth1, the internal combustion engine 10 is stopped. Therefore, after the temperature of the catalyst device 51 becomes equal to or higher than the first threshold value Tth1, unburned fuel adhering to the catalyst device 51 during the catalyst warm-up operation reacts with ambient oxygen as an oxidant to generate reaction heat. While the temperature of the catalyst device 51 rises from the first threshold value Tth1 to the activation temperature, the internal combustion engine 10 can be stopped and fuel consumption can be stopped. Thereby, while performing early warm-up of the catalyst device 51 by retarding the ignition timing, an increase in fuel consumption until the temperature of the catalyst device 51 reaches the activation temperature can be suppressed.

[0070] Further, after the controller 120 stops the internal combustion engine 10 because the temperature of the catalyst device 51 is equal to or higher than the first threshold value Tth1, when the temperature of the catalyst device 51 is lower than the activation temperature and the temperature rise rate of the catalyst device 51 is lower than a predetermined threshold value TIth, the controller 120 sets the operation mode to the catalyst warm-up operation and operates the internal combustion engine 10. Therefore, even when the temperature of the catalyst device 51 is equal to or higher than the first threshold value Tth1, when the temperature of the catalyst device 51 cannot be raised to the activation temperature only by the reaction heat of the unburned fuel adhering to the catalyst device 51 during the catalyst warm-up operation, the catalyst device 51 can be warmed up early by setting the operation mode to the catalyst warm-up operation and operating the internal combustion engine 10.

[0071] Further, the internal combustion engine system 1 is mounted on the hybrid vehicle 100, and the controller 120 starts or stops the internal combustion engine 10 based on the SOC of the battery B. Therefore, in the hybrid vehicle 100 where the temperature of the catalytic converter 51 tends to decrease due to the stop of the internal combustion engine 10 based on the SOC of the battery B, the ignition timing is retarded to warm up the catalytic converter 51 early, and the increase in fuel consumption until the temperature of the catalytic converter 51 reaches the activation temperature can be suppressed.

Description of Symbols

[0072] 1 Internal combustion engine system 10 Internal combustion engine 11 Rotor 12 Fuel injection device 13 Spark plug R Rotor housing chamber 3 Intake passage 31 Air cleaner 32 Throttle valve 33 Intake manifold 4 EGR device 40 EGR passage 41 EGR cooler 42 EGR valve 5 Exhaust passage 51 Catalytic converter 52 Exhaust manifold 53 Downstream exhaust passage 100 Vehicle 101 Driving wheel 110 Electric drive unit 111 Motor 112 Reducer 113 Generator B Battery 120 Controller 121 Processor 122 Memory unit SN1 Airflow sensor SN2 Intake pressure sensor SN3 Rotation speed sensor SN4 Water temperature sensor SN5 Linear A / F sensor SN6 Voltage Sensor SN7 Current Sensor

Claims

Claim 1 A method for warming up a catalyst of an internal combustion engine system, comprising a spark ignition type internal combustion engine mounted on a vehicle, a catalyst device provided in an exhaust passage of the internal combustion engine, and a controller for controlling the internal combustion engine, wherein the controller obtains the temperature of the catalyst device; when the temperature of the catalyst device when the internal combustion engine starts from a stopped state is equal to or higher than the activation temperature of the catalyst device, the controller sets the operation mode of the internal combustion engine to normal operation and operates the internal combustion engine; when the temperature of the catalyst device when the internal combustion engine starts from a stopped state is lower than the activation temperature of the catalyst device, the controller sets the operation mode to a catalyst warming-up operation in which the ignition timing is retarded more than in the normal operation and operates the internal combustion engine; after the controller sets the operation mode to the catalyst warming-up operation and starts the operation of the internal combustion engine, the controller continues the catalyst warming-up operation until the temperature of the catalyst device becomes equal to or higher than a first threshold value set lower than the activation temperature; after the controller sets the operation mode to the catalyst warming-up operation and starts the operation of the internal combustion engine, when the temperature of the catalyst device is equal to or higher than the first threshold value, the controller stops the internal combustion engine; after the internal combustion engine is stopped because the temperature of the catalyst device is equal to or higher than the first threshold value, when the temperature of the catalyst device is equal to or higher than the activation temperature, the controller sets the operation mode to the normal operation and operates the internal combustion engine; A method for warming up a catalyst of an internal combustion engine system, comprising the above steps. Claim 2 after the internal combustion engine is stopped because the temperature of the catalyst device is equal to or higher than the first threshold value, when the temperature of the catalyst device is lower than the activation temperature and the temperature rising rate of the catalyst device is lower than a predetermined threshold value, the method includes the step of the controller setting the operation mode to the catalyst warming-up operation and operating the internal combustion engine, The method for warming up a catalyst of an internal combustion engine system according to Claim 1. Claim 3 The internal combustion engine system is mounted on a hybrid vehicle, and includes a motor that is a driving force source of the vehicle, a battery that supplies power to the motor, and a generator that generates power for supplying to the motor and the battery and is driven by the internal combustion engine. The controller includes a step of starting or stopping the internal combustion engine based on the SOC of the battery. A method for warming up a catalyst of the internal combustion engine system according to claim 1 or 2.

4. A spark-ignition internal combustion engine, a catalyst device provided in an exhaust passage of the internal combustion engine, and a controller that controls the internal combustion engine. The controller, acquires the temperature of the catalyst device, when the temperature of the catalyst device when the internal combustion engine starts from a stopped state is equal to or higher than the activation temperature of the catalyst device, sets the operation mode of the internal combustion engine to normal operation and operates the internal combustion engine, when the temperature of the catalyst device when the internal combustion engine starts from a stopped state is lower than the activation temperature of the catalyst device, sets the operation mode to a catalyst warming-up operation in which the ignition timing is retarded compared to the normal operation and operates the internal combustion engine, after starting the operation of the internal combustion engine by setting the operation mode to the catalyst warming-up operation, continues the catalyst warming-up operation until the temperature of the catalyst device becomes equal to or higher than a first threshold value set lower than the activation temperature, after starting the operation of the internal combustion engine by setting the operation mode to the catalyst warming-up operation, if the temperature of the catalyst device is equal to or higher than the first threshold value, stops the internal combustion engine, after stopping the internal combustion engine due to the temperature of the catalyst device being equal to or higher than the first threshold value, if the temperature of the catalyst device is equal to or higher than the activation temperature, sets the operation mode to normal operation and operates the internal combustion engine. It is configured as follows. Internal combustion engine system.

5. The controller is configured to, after stopping the internal combustion engine due to the temperature of the catalyst device being equal to or higher than the first threshold value, set the operation mode to the catalyst warming-up operation and operate the internal combustion engine when the temperature of the catalyst device is lower than the activation temperature and the temperature increase rate of the catalyst device is lower than a predetermined threshold value. The internal combustion engine system according to claim 4.

6. The internal combustion engine system is mounted on a hybrid vehicle, and includes a motor that is a driving force source of the vehicle, a battery that supplies power to the motor, and a generator that generates power for supplying to the motor and the battery and is driven by the internal combustion engine. The controller is configured to start or stop the internal combustion engine based on the SOC of the battery. The internal combustion engine system according to claim 4 or 5.

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