Control method for exhaust gas purification device of internal combustion engine, and control device for exhaust gas purification device of internal combustion engine

Abstract

The present invention provides a control method for an exhaust gas purification device for an internal combustion engine that can reduce harmful substances such as hydrocarbons and particulate matter contained in the exhaust gas during engine startup, and a control device for an exhaust gas purification device for an internal combustion engine. [Solution] The control method and control device for an exhaust gas purification device for an internal combustion engine according to the present invention initiate fuel injection and start the engine when the engine cylinder wall temperature CWT reaches a first threshold ST1 or higher (CWT≧ST1). This promotes atomization of the in-cylinder spray and reduces the amount of fuel adhering to the cylinder wall. As a result, harmful substances such as hydrocarbons and particulate matter contained in the exhaust gas can be reduced when the engine is started.

Description

Technical Field

[0001] The present invention relates to a control method for an exhaust gas purification device of an internal combustion engine and a control device for an exhaust gas purification device of an internal combustion engine.

Background Art

[0002] As a control device for a conventional exhaust gas purification device of an internal combustion engine, for example, the one described in Patent Document 1 below is known.

[0003] In a conventional exhaust gas purification device for an internal combustion engine, a heating heater was provided upstream of the catalytic converter in the exhaust pipe. Then, by energizing the heating heater during cranking and closing the valve (exhaust throttle valve) on the downstream side of the catalyst, the high-temperature gas on the downstream side of the catalyst preheated by the heater was introduced into the cylinder of the engine through the EGR passage.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the conventional exhaust gas purification device for an internal combustion engine performs the reflux of the high-temperature gas on the downstream side of the preheated catalyst in a short time of cranking at the start of the engine. Therefore, there is still room for improvement in that the temperature of the inner wall surface of the cylinder cannot be sufficiently increased.

[0006] Further, the conventional exhaust gas purification device for an internal combustion engine guides the high-temperature gas on the downstream side of the preheated catalyst to the EGR passage by closing the exhaust throttle valve during cranking. Therefore, there is still room for improvement in that the pump loss during cranking becomes large.

[0007] Therefore, the present invention was devised in view of the technical problems of the conventional exhaust gas purification devices for internal combustion engines, and aims to provide a control method for an exhaust gas purification device for an internal combustion engine that can reduce harmful substances such as hydrocarbons and particulate matter contained in the exhaust gas during engine startup, and a control device for an exhaust gas purification device for an internal combustion engine. [Means for solving the problem]

[0008] In one aspect, the present invention provides a control method for an exhaust gas purification device of an internal combustion engine used in a hybrid system equipped with an electrically heated catalyst, comprising: a first preheating means for raising the temperature of the catalyst; and a second preheating means for raising the cylinder wall surface temperature, wherein fuel injection is started to start the engine when the cylinder wall surface temperature reaches or exceeds a first threshold. [Effects of the Invention]

[0009] According to the present invention, since fuel injection is started and the engine is started when the cylinder wall temperature reaches a first threshold, atomization of the cylinder spray is promoted, and the amount of fuel adhering to the cylinder wall is reduced. As a result, harmful substances such as hydrocarbons and particulate matter contained in the exhaust gas during engine startup can be reduced. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram illustrating the configuration of a hybrid system to which the present invention is applied. [Figure 2] Figure 1 is a schematic diagram showing the configuration of the intake and exhaust passages of an internal combustion engine. [Figure 3] This flowchart shows a control method for an exhaust gas purification device for an internal combustion engine according to the present invention. [Figure 4] This is a time chart illustrating the control method for the exhaust gas purification device of an internal combustion engine according to the present invention. [Modes for carrying out the invention]

[0011] The following describes in detail, with reference to the drawings, an embodiment of the control method for an exhaust gas purification device for an internal combustion engine and an embodiment of the control device for an exhaust gas purification device for an internal combustion engine according to the present invention.

[0012] (Hybrid system configuration) Figure 1 shows a diagram illustrating the configuration of a hybrid system to which the present invention is applied.

[0013] For example, as shown in Figure 1, a vehicle V to which the present invention is applied has a drive unit DU that drives the drive wheels WR and WL, and a power generation unit GU that generates electricity to drive the drive wheels WR and WL.

[0014] The drive unit DU includes a drive motor DM, which acts as a second electric motor to rotate the drive wheels WR and WL, and a first gear train GT1 and differential gear DF, which transmit the driving force of the drive motor DM to the drive wheels WR and WL. Power is supplied to the drive motor DM from a battery VT, which is charged with electricity generated by the power generation unit GU.

[0015] The power generation unit GU includes a generator GE, which is a first electric motor that generates electricity to be supplied to the drive motor DM; an engine 1, which is an internal combustion engine that drives the generator GE; and a second gear train GT2 that transmits the rotation of the engine 1 to the generator GE.

[0016] Based on the above configuration, vehicle V is a so-called series hybrid vehicle that does not use engine 1 as its primary power source, and engine 1 is mounted on the vehicle for power generation. Therefore, when, for example, the battery VT's charge level becomes low, vehicle V drives engine 1 to charge battery VT and generates electricity with generator GE.

[0017] (Engine configuration) Figure 2 shows a schematic diagram illustrating the configuration of the intake and exhaust passages of the engine 1 according to this embodiment.

[0018] For example, as shown in FIG. 2, the engine 1 according to the present embodiment is, for example, a three-cylinder four-stroke spark ignition engine equipped with a turbocharger 2 which is a supercharger. In the intake passage 3 of the engine 1, an air cleaner 30 is arranged at the inlet portion which is the upstream end, and a compressor 21 of the turbocharger 2 is arranged in the middle of the intake passage 3.

[0019] Also, on the upstream side of the compressor 21 in the intake passage 3, a negative pressure generation valve 31 for generating a negative pressure in the region between the compressor 21 is provided. The negative pressure generation valve 31 has a so-called butterfly valve type configuration, and the opening degree is controlled by an engine controller 5 as a control device (control unit) via an electric actuator so as to generate a necessary negative pressure according to the operating conditions of the engine 1. That is, by providing this negative pressure generation valve 31, it becomes possible to generate a necessary negative pressure according to the operating conditions of the engine 1, which contributes to the appropriate recirculation of blow-by gas and EGR gas. <9000090> Also, on the downstream side of the compressor 21 in the intake passage 3, a throttle valve 32 for controlling the intake air amount of the engine 1 is provided. The throttle valve 32 is a so-called electronically controlled throttle valve equipped with an electric actuator such as a motor, and the opening degree is controlled by the engine controller 5 which is a control device.

[0021] Furthermore, on the downstream side of the compressor 21 in the intake passage 3, a water-cooled intercooler 33 is provided between the compressor 21 and the throttle valve 32. The intercooler 33 cools the intake air compressed by the compressor 21 by heat exchange with the cooling water flowing through the inside.

[0022] Meanwhile, the exhaust passage 4 of engine 1 is equipped with a turbine 22 of turbocharger 2. Downstream of the turbine 22 in the exhaust passage 4, there is a well-known three-way catalytic converter 41, an electrically heated catalytic converter 42 located downstream of the three-way catalytic converter 41 which is heated and activated by the application of electricity, an exhaust particulate filter (GPF) 43 located downstream of the electrically heated catalytic converter 42 which is coated with the three-way catalytic converter, and a main catalytic converter 44 located downstream of the exhaust particulate filter 43. In addition, an air-fuel ratio sensor (A / F sensor) 73 for detecting the air-fuel ratio is located between the turbine 22 and the three-way catalytic converter 41 in the exhaust passage 4.

[0023] Furthermore, the engine 1 is provided with a well-known EGR passage 6 for recirculating a portion of the exhaust gas from the exhaust passage 4 to the intake passage 3. One end of this EGR passage 6 is connected, for example, between the electrically heated catalyst 42 and the exhaust particulate filter 43 in the exhaust passage 4, and the other end of the EGR passage 6 is connected upstream of the compressor 21 in the intake passage 3. In addition, the EGR passage 6 is provided with, for example, a water-cooled EGR cooler 61 for cooling the EGR gas, and an EGR valve 62 for controlling the recirculation flow rate of the EGR gas. The opening degree of the EGR valve 62 is controlled by the engine controller 5.

[0024] The engine controller 5 is a control device that manages engine control and receives detection signals from various sensors, including a throttle position sensor 71 that detects throttle opening, a crank angle sensor 72 that detects the rotational speed of the engine 1, an air-fuel ratio sensor (A / F sensor) 73 that detects the exhaust air-fuel ratio in the exhaust passage 4, a water temperature sensor 74 that detects coolant temperature, and an intake air temperature sensor 75 that detects intake air temperature. The engine controller 5 then performs various controls on the engine 1, such as controlling the fuel injection amount and injection timing by a fuel injector (not shown), controlling the ignition timing by a spark plug (not shown), controlling the opening amount of the negative pressure generating valve 31 and the throttle valve 32, and controlling the boost pressure of the turbocharger 2.

[0025] Furthermore, the engine controller 5 according to this embodiment includes a first preheating control unit 51 that raises the catalyst temperature CAT of the electric heating catalyst 42 by heating the electric heating catalyst 42 by applying an electric current, and a second preheating control unit 52 that raises the cylinder wall temperature CWT, which is the wall temperature of the cylinder 10 of the engine 1, by recirculating the gas behind the catalyst that has become hot after being heated by the energized electric heating catalyst 42.

[0026] (Control method for hybrid systems) Figure 3 shows a flowchart illustrating the control details of the hybrid system according to this embodiment.

[0027] For example, as shown in Figure 3, first, when the ignition is turned on (step S1), with engine 1 stopped (step 10), the energy management system request for vehicle V is calculated (step S11), and it is determined whether or not there is a request to start engine 1 (step S12). If there is no request to start engine 1, the process returns to step S11 and the energy management system request is calculated again. On the other hand, if there is a request to start engine 1 in step S12, the process proceeds to step S13, which will be described later.

[0028] Also, simultaneously, after turning on the ignition (step S1), with the energization of the electric heating catalyst 42 being off (step S20), in parallel with the calculation of the energy management system requirement in step S11, it is determined whether the catalyst downstream gas temperature CGT, which is the downstream gas temperature of the electric heating catalyst 42, is equal to or higher than a third threshold value ST3 (e.g., "200°C") as the target set temperature, that is, whether "CGT ≥ T3" (step S21). Here, if step S21 is "Yes", the process proceeds to step S13 described later. On the other hand, if step S21 is "No", the energization of the electric heating catalyst 42 is turned on to start the warm-up (preheat) of the electric heating catalyst 42 (step S22). Then, it is determined whether the catalyst downstream gas temperature CGT of the downstream gas of the electric heating catalyst 42 warmed up by the energization has risen to be equal to or higher than the third threshold value ST3 (step S23). In this step S23, if it is "No", the warm-up of the electric heating catalyst 42 is continued. If it is "Yes", the process proceeds to step S13 described later.

[0029] And, in step S12, when there is a start request for the engine 1 and in step S23 the catalyst downstream gas temperature CGT is equal to or higher than the third threshold value ST3, the EGR valve 62 is opened (step S13) and motoring is started (step S14). When motoring is started, first, the cylinder inner wall surface temperature CWT is calculated (step S15), and it is determined whether the cylinder inner wall surface temperature CWT is equal to or higher than a first threshold value ST1 (e.g., "40°C") as the allowable set temperature, that is, whether "CWT ≥ ST1" (step S16). Here, if the cylinder inner wall surface temperature CT is less than the first threshold value ST1, that is, "CWT < ST1", while continuing motoring, the process returns to step S15 to calculate the cylinder inner wall surface temperature CWT again. On the other hand, if in step S16 the cylinder inner wall surface temperature CWT is equal to or higher than the first threshold value ST1, that is, "CWT ≥ ST1", the process proceeds to step S17 described later.

[0030] In the step S16, when it is determined that the temperature CWT of the inner wall surface of the cylinder is equal to or higher than the first threshold ST1, that is, "CWT ≥ ST1", subsequently, it is determined whether the catalyst temperature CAT of the electric heating catalyst 42 is equal to or higher than the second threshold ST2 (for example, "450°C") which is the allowable set temperature, that is, "CAT ≥ ST2" (step S17). Here, when the catalyst temperature CAT is lower than the second threshold ST2, that is, "CAT < ST2", while continuing the motoring, the process returns to the step S15 to calculate the temperature CWT of the inner wall surface of the cylinder again. On the other hand, in the step S16, when the catalyst temperature CAT is equal to or higher than the second threshold ST2, that is, "CAT ≥ ST2", the process proceeds to the step S18 described later to start the engine 1 (step S18). Then, after the engine 1 is started, by closing the EGR valve 62, a series of controls in the flowchart shown in FIG. 3 are completed.

[0031] FIG. 4 is a time chart showing the control contents of the hybrid system according to the present embodiment. Column (a) is the catalyst energization state which is the energization state of the electric heating catalyst 42, column (b) is the catalyst temperature CAT, column (c) is the gas temperature CGT behind the catalyst, column (d) is the engine speed, column (e) is the engine torque, column (f) is the opening degree of the EGR valve 62, column (g) is the temperature CWT of the inner wall surface of the cylinder, and column (h) is the exhaust gas temperature EGT at the outlet (exhaust port) of the engine 1, respectively.

[0032] For example, as shown in FIG. 4, when the ignition is turned on at time t1, the electric heating catalyst 42 is energized and the warm-up (preheat) of the electric heating catalyst 42 is started. Then, with the warm-up of the electric heating catalyst 42, the gas temperature CGT behind the catalyst gradually rises.

[0033] Eventually, at time T2, when the catalytic converter back gas temperature CGT reaches the target set temperature, which is the third threshold ST3, the EGR valve 62 is opened and motoring is started while the electric heating catalyst 42 continues to warm up. As a result, the engine 1 is driven by negative torque due to motoring, and the catalytic converter back gas, which has been heated to a high temperature by the electric heating catalyst 42, is recirculated to the intake side as EGR, and this high-temperature catalytic converter back gas flows into the cylinder of the engine 1. This causes the cylinder wall temperature CWT to rise and the engine outlet gas temperature EGT to rise. On the other hand, due to motoring, heat is removed from the electric heating catalyst 42 by the exhaust gas from the engine 1 (engine outlet gas), causing the temperature of the electric heating catalyst 42 to decrease and the catalytic converter back gas temperature CGT to decrease.

[0034] Subsequently, at time T3, when the cylinder wall temperature CWT of engine 1 reaches the first threshold ST1, which is the permitted set temperature, and the catalyst temperature CAT of the electric heating catalyst 42 reaches the second threshold ST2, which is the permitted set temperature, the power to the electric heating catalyst 42 is de-energized to end the warm-up (preheating) of the electric heating catalyst 42, and fuel injection is started to ignite and start engine 1.

[0035] (Effects of this embodiment) With the above configuration, in this embodiment, when the cylinder wall temperature CWT of the engine 1 reaches a first threshold ST1 or higher (CWT ≥ ST1), fuel injection is started and the engine 1 is ignited. This promotes atomization of the in-cylinder spray and reduces the amount of fuel adhering to the cylinder wall. As a result, harmful substances such as hydrocarbons and particulate matter contained in the exhaust gas can be reduced when the engine 1 is started.

[0036] Furthermore, in this embodiment, when the cylinder wall temperature CWT is equal to or greater than the first threshold ST1 and the catalyst temperature CAT is equal to or greater than the second threshold ST2, fuel injection is started to start the engine 1. As a result, in addition to good combustion in the cylinder due to the rise in the cylinder wall temperature CWT, the electric heating catalyst 42 is warmed up (preheated) and reaches an optimal temperature, thereby improving the purification performance of the electric heating catalyst 42.

[0037] Furthermore, in this embodiment, the first preheating control unit 51 of the engine controller 5 raises the catalyst temperature CAT by warming up (heating) the electric heating catalyst 42 by applying an electric current, as the first preheating means. Therefore, it is possible to manage and control the catalyst temperature CAT of the electric heating catalyst 42 by the amount of electric current supplied to the electric heating catalyst 42, without using a temperature sensor that directly detects the catalyst temperature CAT. This simplifies the temperature control of the electric heating catalyst 42.

[0038] Furthermore, in this embodiment, the second preheating control unit 52 of the engine controller 5, as a second preheating means, warms up (preheats) the electric heating catalyst 42, and then, after motoring, introduces the high-temperature gas heated by the electric heating catalyst 42 into the cylinder via the EGR passage 6, thereby increasing the cylinder wall temperature CWT. As a result, it is possible to raise the cylinder wall temperature CWT efficiently in a short time, and to raise the cylinder wall temperature CWT more effectively.

[0039] (First variation) If the engine 1 is equipped with a well-known valve timing control device capable of changing the opening and closing timing of an intake valve (not shown), it is desirable to retard the closing timing of the intake valve via the valve timing control device during motoring, compared to the bottom dead center of the intake stroke (intake bottom dead center).

[0040] In this way, by delaying the closing timing of the intake valve using a valve timing control device, it becomes possible to introduce a large amount of fresh air into the cylinder through motoring. As a result, a large amount of fresh air is compressed inside the cylinder, and this compression action can raise the cylinder wall temperature (CWT).

[0041] Furthermore, by delaying the closing timing of the intake valve after the catalyst has warmed up, it becomes possible to introduce more of the high-temperature gas downstream of the electrically heated catalyst 42, which is recirculated through the EGR passage 6 during motoring, into the cylinder. In this way, by introducing more of the high-temperature gas downstream of the electrically heated catalyst 42 into the cylinder, the cylinder wall temperature CWT can be increased more effectively.

[0042] (Second variation) If the engine 1 is equipped with a well-known valve timing control device capable of changing the opening and closing timing of an exhaust valve (not shown), it is desirable to retard the closing timing of the exhaust valve via the valve timing control device during motoring, compared to the top dead center of the exhaust stroke (exhaust top dead center).

[0043] In this way, by delaying the closing timing of the exhaust valve after the catalyst has warmed up, it becomes possible to introduce the high-temperature gas heated by the catalyst into the cylinder through the exhaust port, which opens and closes with the motoring, via the exhaust valve. This makes it possible to more effectively improve the cylinder wall temperature (CWT).

[0044] The present invention is not limited to the configurations exemplified in the embodiments described above, and can be freely modified according to the specifications of the hybrid system to which the present invention is applied. [Explanation of Symbols]

[0045] 1…Engine 2… Turbocharger (supercharger) 3…Intake passage 4… Exhaust passage 42…Electric heating catalyst (catalyst) 5…Engine controller (control device) 51...First preheating means 52...Second preheating means 6…EGR passage CWT…Cylinder wall temperature CAT…Catalyst temperature ST1...First threshold ST2...Second threshold

Claims

1. A control method for an exhaust gas purification device of an internal combustion engine used in a hybrid system equipped with an electrically heated catalyst, A first preheating means for raising the temperature of the catalyst, A second preheating means for raising the temperature of the inner wall surface of the cylinder, It has, When the cylinder wall temperature reaches or exceeds a first threshold, fuel injection is started to start the engine. A control method for the exhaust gas purification system of an internal combustion engine.

2. A control method for an exhaust gas purification device for an internal combustion engine according to claim 1, When the cylinder wall temperature is above a first threshold and the catalyst temperature is above a second threshold, fuel injection is started to start the engine. A control method for the exhaust gas purification system of an internal combustion engine.

3. A control method for an exhaust gas purification device for an internal combustion engine according to claim 2, The first preheating means heats the catalyst by applying an electric current to raise the temperature of the catalyst. A control method for the exhaust gas purification system of an internal combustion engine.

4. A control method for an exhaust gas purification device for an internal combustion engine according to claim 3, The second preheating means, after heating the catalyst, increases the temperature of the inner wall surface of the cylinder by introducing the high-temperature gas heated by the catalyst into the cylinder via the EGR passage in conjunction with motoring. A control method for the exhaust gas purification system of an internal combustion engine.

5. A control method for an exhaust gas purification device for an internal combustion engine according to claim 4, The aforementioned internal combustion engine is equipped with a valve timing control device that variably controls the opening and closing timing of the intake valves. In the second preheating means, the valve timing control device retards the closing timing of the intake valve from bottom dead center. A control method for the exhaust gas purification system of an internal combustion engine.

6. A control method for an exhaust gas purification device for an internal combustion engine according to claim 3, The aforementioned internal combustion engine is equipped with a valve timing control device that variably controls the opening and closing timing of the exhaust valve. The second preheating means, after heating the catalyst, delays the closing timing of the exhaust valve beyond top dead center using the valve timing control device, and, in conjunction with motoring, introduces the high-temperature gas heated by the catalyst into the cylinder via the exhaust port of the internal combustion engine, thereby increasing the cylinder wall temperature. A control method for the exhaust gas purification system of an internal combustion engine.

7. A control device for an exhaust gas purification system of an internal combustion engine used in a hybrid system equipped with an electrically heated catalyst, A first preheating control unit that raises the temperature of the catalyst, A second preheating control unit that raises the temperature of the inner wall surface of the cylinder, It has, When the cylinder wall temperature reaches or exceeds a first threshold, fuel injection is started to start the engine. A control device for exhaust gas purification systems in internal combustion engines.

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