JP5521707B2 - Engine supercharger - Google Patents

Description

  The present invention relates to an engine supercharging device.

  Conventionally, as an engine equipped with a turbocharger, a turbocharger compressor is disposed in an intake passage, and an intake bypass passage for bypassing the compressor and an intake bypass for opening and closing the intake bypass passage Engines with valves are known. For example, an engine according to Patent Document 1 includes a first turbocharger and a second turbocharger. In the intake passage, a first compressor of the first turbocharger and a second compressor of the second turbocharger are arranged in series. Further, the intake passage is provided with an intake bypass passage for bypassing the second compressor. The intake bypass passage is provided with an intake bypass valve for opening and closing the intake bypass passage. The engine control device performs intake air recirculation by opening the intake bypass valve in order to increase the intake air temperature during cold start. Specifically, by opening the intake bypass valve, the intake air supercharged by the second compressor flows backward in the intake bypass passage and flows again into the upstream side of the second compressor, and the supercharging by the second compressor is repeated. It is. Thus, the intake air is heated to improve the ignitability.

  Further, in the engine according to Patent Document 1, the nozzle of the first turbine is a variable nozzle, and is configured such that the nozzle passage cross-sectional area is reduced when performing intake recirculation. By doing so, the boost pressure of the first turbocharger is improved, and the intake air amount taken in by the first compressor is increased. As a result, the amount of intake air sent to the engine is ensured to prevent the engine from misfiring. At this time, the exhaust bypass valve provided in the bypass passage of the first turbine is closed so that the exhaust flows into the first turbine without bypassing the first turbine.

JP 2009-264335 A

  By the way, at the time of cold start, the temperature of the catalyst is low and the catalyst is not activated. Also, the exhaust temperature is not limited to the cold start, and the idling may be prolonged, and the catalyst may become inactive. As described above, when the catalyst is in an inactive state, the emission performance is deteriorated. Therefore, it is necessary to activate the catalyst at an early stage.

  Here, as in the supercharging device according to Patent Document 1, if the configuration is such that intake air recirculation is performed to increase the intake air temperature, the exhaust gas temperature is also increased, and the catalyst can be activated early. It is done. However, from the viewpoint of early activation of the catalyst, the intake air recirculation according to Patent Document 1 is insufficient and further improvement is required.

  The technology disclosed herein has been made in view of such a point, and an object thereof is to raise the intake air temperature early and to activate the catalyst early.

The technology disclosed here is intended for an engine supercharging device. The engine supercharging device includes an engine mounted on a vehicle, a catalyst provided in an exhaust passage of the engine, and a first compressor disposed upstream of the throttle valve in the intake passage of the engine. , and the exhaust and first turbocharger that having a first turbine disposed upstream of Oite the catalyst passage, the intake of the first said a upstream of the throttle valve passage the second compressor arranged in series on the downstream side of the compressor, and the exhaust passage smell Te before Symbol second turbocharger that having a second turbine disposed in series on the upstream side of the first turbine An intake bypass passage that is connected to the intake passage and bypasses the second compressor; an intake bypass valve that is disposed in the intake bypass passage; and the first turn connected to the exhaust passage. An exhaust bypass passage for bypassing the engine, an exhaust bypass valve disposed in the exhaust bypass passage, and a supercharging control means for controlling the throttle valve, the intake bypass valve and the exhaust bypass valve, control means, when the catalyst has not been activated, said and open the intake air bypass valve the throttle valve with causing an at least partially closed intake recirculation, and controlled to open the exhaust bypass valve When the intake air temperature becomes equal to or higher than a predetermined upper limit temperature during the intake air recirculation, the intake valve is adjusted so that the throttle valve is opened, and the intake air recirculation is continued. Recirculation shall be terminated .

  According to the above configuration, when the catalyst is in an inactive state, the pressure on the downstream side of the second compressor is higher than the pressure in the intake bypass passage, so that the intake air supercharged by the second compressor passes through the intake bypass passage. It flows through and flows into the upstream side of the second compressor. In this way, intake air recirculation is performed by the second compressor. As a result, the intake air temperature rises. At this time, the exhaust bypass valve is opened in the exhaust passage. Thereby, since the back pressure of the second turbine decreases, the work of the second turbine increases. As a result, the rotational force of the second compressor increases and the intake air temperature raising capability by intake air recirculation is improved. In addition, by opening the exhaust bypass valve, the exhaust bypasses the first turbine and flows into the catalyst. As a result, it is possible to prevent the heat quantity of the exhaust from being dissipated by the first turbine, and it is possible to reduce exhaust heat dissipation until the exhaust reaches the catalyst. Thereby, the temperature of a catalyst can be raised early.

Further, various components of the engine are respectively a heat resistant temperature. Therefore, it is not preferable that the intake air temperature becomes too high. Also, from the viewpoint of intake charging efficiency, it is not preferable that the intake air temperature becomes too high. Therefore, according to the above configuration, when the intake air temperature becomes equal to or higher than the predetermined temperature, the throttle valve is adjusted to open. Thereby, the circulation amount of intake recirculation is suppressed, and the rise in intake air temperature is suppressed. That is, by appropriately setting the predetermined temperature according to the purpose, it is possible to suppress an increase in intake air temperature according to the predetermined temperature.

  According to the engine supercharging device, by opening the exhaust bypass valve, the efficiency of the second turbine can be improved and the intake air temperature can be raised early. In addition, since the heat release of the exhaust heat to the first turbine can be prevented, the catalyst can be activated early.

It is the schematic which shows the structure of the engine with a turbocharger which concerns on embodiment. It is a block diagram which shows the structure of the control system of an engine supercharging apparatus. It is an operation map of a large-sized and small turbocharger. It is a flowchart which shows the control action in intake recirculation. It is a timing chart which shows the operating state of an intake bypass valve and a throttle valve in intake recirculation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<< Embodiment of the Invention >>
FIG. 1 shows a schematic configuration of an engine 1 that employs a supercharging device according to an embodiment. The engine 1 is a diesel engine mounted on a vehicle, and includes a cylinder block 11 provided with a plurality of cylinders 11a (only one is shown), a cylinder head 12 disposed on the cylinder block 11, An oil pan 13 is disposed below the cylinder block 11 and stores lubricating oil. In each cylinder 11a of the engine 1, a piston 14 is fitted and removably fitted. A top surface of the piston 14 is formed with a cavity that defines a deep dish combustion chamber 14a. The piston 14 is connected to the crankshaft 15 via a connecting rod 14b. The cylinder block 11 is provided with a water temperature sensor SW1 that detects the temperature of engine cooling water.

  In the cylinder head 12, an intake port 16 and an exhaust port 17 are formed for each cylinder 11a, and an intake valve 21 and an exhaust valve that open and close the opening of the intake port 16 and the exhaust port 17 on the combustion chamber 14a side. 22 are arranged respectively. In the valve operating system for driving these intake and exhaust valves 21 and 22, respectively, a hydraulically operated variable mechanism (not shown; hereinafter omitted) that switches the operating state of the exhaust valve 22 between a normal mode and a special mode is provided on the exhaust valve side. VVM (Variable Valve Motion) is provided. Although the detailed illustration of the VVM is omitted, two types of cams having different cam profiles, a first cam having one cam crest and a second cam having two cam crests, It includes a lost motion mechanism that selectively transmits the operating state of one of the second cams to the exhaust valve, and when the operating state of the first cam is transmitted to the exhaust valve 22, While the operation state of the valve 22 is a normal mode in which the valve is opened only once during the exhaust stroke, when the operation state of the second cam is transmitted to the exhaust valve 22, the operation state of the exhaust valve 22 is This is a special mode in which the valve is opened during the exhaust stroke and is also opened during the intake stroke, so-called exhaust opening twice. The special mode can be used in the control related to the internal EGR. In order to enable switching between the normal mode and the special mode, an electromagnetically driven valve system in which the exhaust valve is driven by an electromagnetic actuator may be employed.

  The cylinder head 12 is provided with an injector 18 for injecting fuel and a glow plug 19 for warming intake air and improving fuel ignitability when the engine 1 is cold. The injector 18 is disposed so that its fuel injection port faces the combustion chamber 14a from the ceiling surface of the combustion chamber 14a, and is configured to directly inject and supply fuel to the combustion chamber 14a near the top dead center of the compression stroke. It has become.

  An intake passage 30 is connected to one side of the engine 1 so as to communicate with the intake port 16 of each cylinder 11a. On the other hand, an exhaust passage 40 for discharging burned gas (exhaust gas) from the combustion chamber 14a of each cylinder 11a is connected to the other side of the engine 1. The intake passage 30 and the exhaust passage 40 are provided with a large turbocharger 61 and a small turbocharger 62 that supercharge intake air.

  An air cleaner 31 that filters intake air is disposed at the upstream end of the intake passage 30. On the other hand, a surge tank 33 is disposed near the downstream end of the intake passage 30. The intake passage 30 downstream of the surge tank 33 is an independent passage branched for each cylinder 11a, and the downstream end of each independent passage is connected to the intake port 16 of each cylinder 11a. The surge tank 33 is provided with a supercharging pressure sensor SW2 that detects the pressure of air supplied to the combustion chamber 14a.

  Between the air cleaner 31 and the surge tank 33 in the intake passage 30, an intake air temperature sensor SW 3 that detects the temperature of the intake air in order from the upstream side, and compressors of large and small turbochargers 61 and 62 described later in detail. 61a, 62a, a supercharged air temperature sensor SW4 for detecting the temperature of the air compressed by the compressors 61a, 62a, an intercooler 35 for cooling the air compressed by the compressors 61a, 62a, and the cylinders 11a. And a throttle valve 36 for adjusting the amount of intake air into the combustion chamber 14a. The throttle valve 36 is basically fully opened, but is fully closed when the engine 1 is stopped so that no shock is generated.

  The upstream portion of the exhaust passage 40 is constituted by an exhaust manifold having an independent passage branched for each cylinder 11a and connected to the outer end of the exhaust port 17 and a collecting portion where the independent passages gather. Yes.

  On the downstream side of the exhaust manifold in the exhaust passage 40, turbines 62 b and 61 b of small and large turbochargers 62 and 61, and an exhaust purification device 41 that purifies harmful components in the exhaust gas, in order from the upstream side. A silencer 42 is provided.

The exhaust purification device 41 includes an oxidation catalyst 41a and a diesel particulate filter (hereinafter referred to as a filter) 41b, which are arranged in this order from the upstream side. The oxidation catalyst 41a and the filter 41b are accommodated in one case. The oxidation catalyst 41a has an oxidation catalyst carrying platinum or platinum added with palladium or the like, and promotes a reaction in which CO and HC in the exhaust gas are oxidized to produce CO ₂ and H ₂ O. Is. The oxidation catalyst 41a constitutes a catalyst. The filter 41b collects particulates such as soot contained in the exhaust gas of the engine 1. The filter 41b may be coated with an oxidation catalyst. An exhaust temperature sensor SW5 that detects the temperature of the exhaust gas that has passed through the oxidation catalyst 41a is disposed between the oxidation catalyst 41a and the filter 41b.

  Further, a portion of the intake passage 30 between the surge tank 33 and the throttle valve 36 (that is, a portion on the downstream side of the small compressor 62a of the small turbocharger 62), the exhaust manifold in the exhaust passage 40 and a small size. The portion between the turbocharger 62 and the small turbine 62b (that is, the portion upstream of the small turbine 62b of the small turbocharger 62) is exhaust for returning a part of the exhaust gas to the intake passage 30. They are connected by a gas recirculation passage 50. The exhaust gas recirculation passage 50 includes a main passage 51 in which an EGR cooler 52 is disposed, and a cooler bypass passage 53 that branches from the main passage 51 and bypasses the EGR cooler 52 and then merges with the main passage 51 again. doing. The EGR cooler 52 cools the circulating exhaust gas with engine cooling water. The main passage 51 is provided with an exhaust gas recirculation valve 51 a for adjusting the flow rate of the exhaust gas flowing through the main passage 51. On the other hand, the cooler bypass passage 53 is provided with a cooler bypass valve 53 a for adjusting the flow rate of the exhaust gas flowing through the cooler bypass passage 53.

  Further, the engine 1 is provided with two crank angle sensors SW6 and SW7 for detecting the rotation angle of the crankshaft 15. The engine speed (rotation speed) is detected based on the detection signal output from one crank angle sensor SW6, and the crank angle is detected based on the detection signal out of phase output from both crank angle sensors SW6 and SW7. The position is detected. The engine 1 includes an accelerator opening sensor SW8 that detects an accelerator opening corresponding to an operation amount of an accelerator pedal (not shown) of the vehicle, and a brake pedal sensor that detects an operation of a brake pedal (not shown) of the vehicle. SW9, a clutch pedal sensor SW10 that detects an operation of a clutch pedal (not shown) of the vehicle, a shift lever sensor SW11 that detects an operation of a shift lever (not shown) of the vehicle, and a vehicle speed sensor SW12 that detects the speed of the vehicle. And are provided.

  Here, the configuration of the large turbocharger 61 and the small turbocharger 62 will be described in detail.

  The large turbocharger 61 has a large compressor 61 a disposed in the intake passage 30 and a large turbine 61 b disposed in the exhaust passage 40. The large compressor 61a is disposed between the air cleaner 31 and the intercooler 35 in the intake passage 30 (specifically, between the intake air temperature sensor SW3 and the supercharged air temperature sensor SW4). On the other hand, the large turbine 61b is disposed between the exhaust manifold and the oxidation catalyst 41a in the exhaust passage 40. The large turbocharger 61 constitutes a first turbocharger, the large compressor 61a constitutes a first compressor, and the large turbine 61b constitutes a first turbine.

The small turbocharger 62 has a small compressor 62 a disposed in the intake passage 30 and a small turbine 62 b disposed in the exhaust passage 40. The small compressor 62 a is disposed on the downstream side of the large compressor 61 a in the intake passage 30. On the other hand, the small-sized turbine 62b is disposed on the upper stream side of the large turbine 61b in the exhaust passage 40. The small turbocharger 62 constitutes a second turbocharger, the small compressor 62a constitutes a second compressor, and the small turbine 62b constitutes a second turbine. The small turbocharger 62 is relatively small, and the large turbocharger 61 is relatively large. That is, the large turbine 61 b of the large turbocharger 61 has a larger inertia than the small turbine 62 b of the small turbocharger 62.

  That is, in the intake passage 30, a large compressor 61a and a small compressor 62a are arranged in series from the upstream side, and in the exhaust passage 40, a small turbine 62b and a large turbine 61b are arranged in series from the upstream side. Has been. The large and small turbines 61b and 62b are rotated by the exhaust gas flow, and the large and small turbines 61a and 62a connected to the large and small turbines 61b and 62b are rotated by the rotation of the large and small turbines 61b and 62b, respectively. Each operates. An intermediate pressure sensor SW13 for detecting the pressure of intake air supercharged by the large compressor 61a is provided between the large compressor 61a and the small compressor 62a in the intake passage 30.

  The intake passage 30 is connected to an intake bypass passage 63 that bypasses the small compressor 62a. The intake bypass passage 63 is provided with an intake bypass valve 63 a for adjusting the amount of air flowing to the intake bypass passage 63. The intake bypass valve 63a is configured to be in a fully closed state (normally closed) when no power is supplied. Thus, when the intake bypass valve 63a fails, it is possible to prevent the small compressor 62a from over-rotating by circulating the intake air through the intake bypass passage 63 in the same manner as the intake recirculation.

  On the other hand, the exhaust passage 40 is connected to a small exhaust bypass passage 64 that bypasses the small turbine 62b and a large exhaust bypass passage 65 that bypasses the large turbine 61b. The small exhaust bypass passage 64 is provided with a regulating valve 64a for adjusting the exhaust amount flowing to the small exhaust bypass passage 64, and the large exhaust bypass passage 65 has an exhaust amount flowing to the large exhaust bypass passage 65. A wastegate valve 65a for adjusting the pressure is provided. Both the regulating valve 64a and the waste gate valve 65a are configured to be in a fully open state (normally open) when no power is supplied. The large exhaust bypass passage 65 constitutes an exhaust bypass passage, and the waste gate valve 65a constitutes an exhaust bypass valve.

  The large turbocharger 61 and the small turbocharger 62 are integrated into a single unit including the intake passage 30 and the exhaust passage 40 in which the large turbocharger 61 and the small turbocharger 62 are arranged, thereby forming a supercharger unit 60. doing. The supercharger unit 60 is attached to the engine 1. The outlet of the intake passage 30 of the supercharger unit 60 is connected to the upstream end of the intercooler 35 via a rubber hose 30a. That is, the intercooler 35 is attached to the vehicle body, and vibration different from that of the supercharger unit 60 attached to the engine 1 occurs. Therefore, the vibrations of the supercharger unit 60 and the intercooler 35 are absorbed by the rubber hose 30a so that they do not affect each other. For the same reason, the downstream end of the intercooler 35 and the upstream portion of the throttle valve 36 of the intake passage 30 are also connected via a rubber hose 30b.

  The turbocharged engine 1 configured as described above is controlled by a powertrain control module (hereinafter referred to as PCM) 10. The PCM 10 includes a CPU, a memory, a counter timer group, an interface, and a macro processor having a path connecting these units. This PCM 10 constitutes a supercharging control means. As shown in FIG. 2, the PCM 10 receives detection signals from the sensors SW1 to SW13, performs various calculations based on these detection signals, determines the state of the engine 1 and the vehicle, and responds accordingly. Control signals are output to the injector 18, the valve-operated VVM, and the actuators of various valves. The PCM 10 outputs a control signal to the injector 18 and starter motor (not shown) when the engine 1 is started, and also outputs a control signal to the glow plug 19 as necessary. Further, the PCM 10 outputs a control signal to a regulator circuit built in an alternator (not shown) connected to the crankshaft 15 by a timing belt or the like, thereby generating power corresponding to the electric load of the vehicle and the voltage of the vehicle battery. Perform quantity control.

In the present embodiment, the PCM 10 automatically stops the engine 1 when a predetermined automatic stop condition is satisfied for the purpose of reducing fuel consumption, suppressing CO ₂ emission, and the like, and then the predetermined restart condition is satisfied. So-called idle stop control is performed so that the engine 1 is sometimes restarted.

  Specifically, the PCM 10 stops the fuel injection by the injector 18 when the automatic stop condition is satisfied. For example, the brake pedal depressing operation determined based on the detection signal of the brake pedal sensor SW9 continues for a predetermined time, and the vehicle speed determined based on the detection signal of the vehicle speed sensor SW12 is set to a preset low speed (for example, speed per hour). It can be set as an automatic stop condition that the vehicle is substantially stopped at 2-5 km or less. At the time of this automatic stop, the engine 1 is stopped at a piston position suitable for restarting the engine 1 by performing throttle valve opening / closing control and alternator control together.

  Thereafter, when the restart condition is satisfied, the PCM 10 starts fuel supply to each cylinder 11a and restarts the engine 1 in a short time by the combustion (so-called combustion start). In the present embodiment, the PCM 10 increases the pressure in the cylinder by driving the starter motor together with the PCM 10. In addition, for example, the remaining capacity of the vehicle battery is reduced and charging is required, the operation of the compressor of the air conditioner is required, or the detection signal from the accelerator opening sensor SW8 or the clutch pedal sensor SW10 is used. Based on this, it is possible to make the restart condition that the accelerator operation or the clutch operation by the occupant is detected. Among these, the fact that the remaining capacity of the vehicle battery has decreased and charging has become necessary, and that the operation of the compressor of the air conditioner has been required can be said to be a start condition without a start request, conversely, The detection of the accelerator operation or the clutch operation can be regarded as a start condition accompanied by a start request.

  The PCM 10 controls the operations of the large and small turbochargers 61 and 62 when the engine is operating. Specifically, the PCM 10 controls the openings of the intake bypass valve 63a, the regulator valve 64a, and the wastegate valve 65a to the openings set according to the operating state of the engine 1, respectively.

  Specifically, the PCM 10 has a low load and low rotation side region A (the engine load is smaller than a predetermined load (smaller as the engine speed increases)) in the map having the engine speed and the engine load as parameters shown in FIG. ), The intake bypass valve 63a and the regulating valve 64a are set to an opening other than fully opened, and the wastegate valve 65a is fully closed to operate both the large and small turbochargers 61 and 62. . On the other hand, in the high load and high rotation side region B (region where the engine load is larger than the predetermined load), the small turbocharger 62 becomes exhaust resistance, so the intake bypass valve 63a and the regulator valve 64a are fully opened. By setting the opening degree of the wastegate valve 65a close to the fully closed state, the small turbocharger 62 is bypassed and only the large turbocharger 61 is operated. The waste gate valve 65a is slightly opened to prevent over-rotation.

  Further, the PCM 10 controls the throttle valve 36, the intake bypass valve 63a, the regulating valve 64a, and the wastegate valve 65a when the oxidation catalyst 41a is in an inactive state, such as during cold start or when idling continues for a long period of time. By doing so, intake recirculation is performed. This intake recirculation is performed in the light load region C where the load and the rotational speed are very low, even in the region A in the map shown in FIG. This region C corresponds to an idle operation region, particularly a fast idle region during cold start. Specifically, the PCM 10 estimates the temperature of the oxidation catalyst 41a based on the detection signal of the exhaust temperature sensor SW5, and determines whether or not the oxidation catalyst 41a is in an inactive state. At the same time, the PCM 10 determines whether or not the engine operating state is in the light load region C based on detection signals from the accelerator opening sensor SW8 and the crank angle sensor SW6. When the oxidation catalyst 41a is inactive and the engine operating state is in the light load region C, the PCM 10 fully opens the intake bypass valve 63a and the wastegate valve 65a, and fully closes the regulating valve 64a. Further, the throttle valve 36 is throttled to a predetermined opening degree. In the exhaust passage 40, the regulating valve 64a is fully closed, so that the exhaust gas flows into the small turbine 62b and operates the small compressor 62a. In the intake passage 30, the intake air is supercharged by the operation of the small compressor 62 a, but the throttle valve 36 is throttled, whereas the intake bypass valve 63 a is fully opened. The pressure on the downstream side of the small compressor 62 a becomes higher than the pressure in the intake bypass passage 63. Therefore, the intake air supercharged by the small compressor 62a flows backward in the intake bypass passage 63 and flows into the upstream side of the small compressor 62a. This intake air is again supercharged by the small compressor 62a. In this way, the intake air recirculation is performed by the small compressor 62a, and the temperature of the intake air eventually increases. At this time, since the waste gate valve 65a is opened in the exhaust passage 40, the back pressure of the small turbine 62b decreases. Thereby, the efficiency of the small turbine 62b increases. As a result, the rotational force of the small compressor 62a is increased, and the intake air temperature raising capability by intake air recirculation is improved. In addition, since the wastegate valve 65a is opened, the exhaust gas bypasses the large turbine 61b and flows into the oxidation catalyst 41a. That is, the exhaust heat is transported to the oxidation catalyst 41a without being radiated by the large turbine 61b. As a result, the temperature of the oxidation catalyst 41a rises early.

  During the intake air recirculation, the exhaust gas recirculation valve 51a is closed so as not to recirculate the exhaust gas. As a result, it is possible to prevent the inert gas from being dry-distilled on the intake side and preventing the exhaust heat from rising.

  Hereinafter, detailed control operations of the throttle valve 36, the intake bypass valve 63a, the regulate valve 64a, and the wastegate valve 65a by the PCM 10 will be described based on the flowchart of FIG. 4 and the timing chart of FIG.

  First, in step ST1, it is determined whether or not the oxidation catalyst 41a is in an inactive state, and whether or not the operating state of the engine 1 is in the light load region C is determined. Specifically, the PCM 10 determines whether or not the temperature of the exhaust gas downstream of the oxidation catalyst 41a is equal to or lower than a predetermined value (for example, 220 ° C.) based on the detection signal from the exhaust temperature sensor SW5. This predetermined value is the temperature of the exhaust gas estimated that the oxidation catalyst 41a is in an inactive state. That is, the exhaust gas temperature immediately downstream of the oxidation catalyst 41a is correlated with the temperature of the oxidation catalyst 41a, and the temperature of the oxidation catalyst 41a can be estimated from this exhaust gas temperature. The PCM 10 determines that the oxidation catalyst 41a is in an inactive state when the temperature of the exhaust gas downstream of the oxidation catalyst 41a is equal to or lower than a predetermined value, while the temperature of the exhaust gas downstream of the oxidation catalyst 41a is greater than a predetermined value. Then, it is determined that the oxidation catalyst 41a is in an active state. In addition, the PCM 10 determines whether or not the operating state of the engine 1 is in the light load region C. The PCM 10 obtains the engine load from the detection signal of the accelerator opening sensor SW8 and obtains the engine speed from the detection signal of the crank angle sensor SW6. When the engine load is equal to or lower than the predetermined load (for example, when the accelerator pedal is not depressed) and the engine speed is equal to or lower than the predetermined speed, the PCM 10 operates in the light load region C. On the other hand, when the engine load is larger than the predetermined load or the engine speed is faster than the predetermined speed, it is determined that the operating state of the engine 1 is outside the light load region C. The predetermined load and the rotational speed for determining to be in the light load region C are set in the range of the load and the rotational speed in the idle operation state including the fast idle operation, for example.

  When it is determined that the oxidation catalyst 41a is in an inactive state and the operation state of the engine 1 is in the light load region C, the process proceeds to step ST2, while the oxidation catalyst 41a is not in an inactive state or the engine 1 When it is determined that the operating state is other than the light load region C, step ST1 is repeated.

  In step ST2, the PCM 10 turns on a bypass execution flag for executing intake recirculation (see T1 in FIG. 5A). When the bypass execution flag is changed to ON, the PCM 10 sets the intake bypass valve 63a to the ON state, that is, the fully open state. At this time, the PCM 10 fully closes the exhaust gas recirculation valve 51a in order to stop the recirculation of the exhaust gas.

  Next, in step ST3, the PCM 10 determines whether the intake air temperature after supercharging is equal to or higher than a predetermined upper limit temperature based on the output signal of the supercharging air temperature sensor SW4. In this embodiment, the upper limit temperature is set based on the heat-resistant temperatures of the components of the engine 1, the intake passage 30, and the exhaust passage 40. More specifically, it is set based on the heat resistant temperature of the rubber hose 30a. Since the rubber hose 30a is located immediately downstream of the large and small compressors 61a and 62a, the rubber hose 30a is a component that is exposed to the hottest intake air in the intake system. Therefore, the upper limit temperature is set based on the heat resistant temperature of the rubber hose 30a so that the intake air temperature does not exceed the heat resistant temperature of the rubber hose 30a. The upper limit temperature is set to a value lower than the allowable temperature limit of the rubber hose 30a. The upper limit temperature may be set based on a temperature other than the heat resistant temperature of the component. For example, an upper limit value of the intake air temperature for realizing a desired intake air charging efficiency may be set as the upper limit temperature. The PCM 10 turns on the upper limit temperature determination flag when the intake air temperature after supercharging is equal to or higher than the upper limit temperature, and turns off the upper limit temperature determination flag when the intake air temperature after supercharging is lower than the upper limit temperature. Since the intake air temperature is low immediately after the start of intake recirculation, the upper limit temperature determination flag is normally turned off as indicated by T1 in FIG.

  When the upper limit temperature determination flag is OFF, the PCM 10 throttles the throttle valve 36 to a predetermined throttle value in step ST4 (see T1 in FIG. 5C). The predetermined aperture value is a value that can maintain at least the idling operation of the engine 1. The predetermined aperture value is not a fixed value, and may be a value that is appropriately adjusted based on environmental conditions or engine operating conditions. In FIG. 5, the throttle valve 36 is throttled to a predetermined throttle value all at once, but may be gradually reduced to a predetermined throttle value. Then, the pressure on the downstream side of the small compressor 62 a in the intake passage 30 becomes higher than the pressure in the intake bypass passage 63. As a result, the supercharged intake air flows back through the intake air bypass passage 63 and is again supercharged to the small compressor 62a, and intake air recirculation is started. When the intake air recirculation is started, the intake air temperature gradually increases as indicated by T1 in FIG. Thereafter, in step ST6, the PCM 10 determines whether or not the oxidation catalyst 41a is activated. The determination of the activation of the oxidation catalyst 41a is performed in the same manner as the determination of the inactive state of the oxidation catalyst 41a in step ST1. If the oxidation catalyst 41a is not activated, the PCM 10 returns to step ST3 and repeats the flow after step ST3. That is, intake recirculation is continued.

  If the intake air recirculation is continued, the intake air temperature may rise to the upper limit temperature or more (see T2 in FIG. 5D). In this case, in step ST3, the upper limit temperature determination flag is turned on (see T2 in FIG. 5B). When the upper limit temperature determination flag is turned ON, the PCM 10 adjusts the throttle valve 36 so as to gradually open in step ST5 (see T2 in FIG. 5C). Thereafter, the PCM 10 proceeds to step ST6 and determines whether or not the oxidation catalyst 41a is activated as described above. When the oxidation catalyst 41a is not activated, the intake air recirculation is further continued.

  When the circulation amount of the intake air in the intake recirculation is reduced by adjusting the throttle valve 36 to open, the intake air temperature gradually decreases as indicated by T2 to T3 in FIG. Eventually, the intake air temperature becomes lower than the upper limit temperature (see T3 in FIG. 5D). When the intake air temperature becomes lower than the upper limit temperature, the PCM 10 turns off the upper limit temperature determination flag in step ST3 (see T3 in FIG. 5B). When the upper limit temperature determination flag is turned OFF, the PCM 10 gradually throttles the throttle valve 36 to the predetermined throttle value (see T3 in FIG. 5C). When the throttle valve 36 is throttled, the intake air temperature begins to rise again. Thereafter, the flow of steps ST3, ST4, ST6 or the flow of steps ST3, ST5, ST6 is repeated. Thus, when the intake air temperature becomes equal to or higher than the upper limit temperature, the throttle valve 36 is adjusted to open. When the intake air temperature becomes lower than the upper limit temperature, intake recirculation is continued while the throttle valve 36 is throttled to a predetermined throttle value. To go. It should be noted that the opening and closing operations of the throttle valve 36 are performed gradually rather than abruptly. This prevents the control from diverging.

  This intake air recirculation is continued until the oxidation catalyst 41a is activated. When the PCM 10 determines that the oxidation catalyst 41a is activated in step ST6, the process proceeds to step ST7, and the bypass execution flag is turned OFF (see T4 in FIG. 5A). When the bypass execution flag is turned OFF, the PCM 10 fully closes the intake bypass valve 63a and fully opens the throttle valve 36 (see T4 in FIG. 5C). In FIG. 5, the throttle valve 36 is gradually opened fully, but it may be opened all at once. In this way, intake recirculation is completed.

  According to this embodiment, the back pressure of the small turbine 62b can be reduced by opening the waste gate valve 65a in the exhaust passage 40 during intake air recirculation. Thereby, the work amount of the small turbine 62b increases, and the rotational force of the small compressor 62a can be increased. As a result, the intake air temperature raising capability by intake air recirculation can be improved.

  In addition, by opening the wastegate valve 65a, the exhaust gas can flow into the oxidation catalyst 41a by bypassing the large turbine 61b. As a result, the exhaust heat can be prevented from being dissipated by the large turbine 61b. That is, exhaust heat radiation until the exhaust reaches the oxidation catalyst 41a can be reduced. Thereby, the temperature of the oxidation catalyst 41a can be raised early.

  Also, during intake air recirculation, the intake air temperature is monitored, and when the intake air temperature exceeds a predetermined upper limit temperature, the throttle valve 36 is adjusted to open so that the amount of intake air circulated in the intake air recirculation can be reduced. It can reduce and the rise width of intake temperature can be controlled. That is, when the intake air temperature rises too much, the rise in the intake air temperature can be suppressed. By appropriately setting the upper limit temperature, it is possible to prevent the intake air temperature from excessively rising and the intake charging efficiency from being lowered, or that the intake air temperature becomes equal to or higher than the heat resistance temperature of the components of the intake system such as the rubber hose 30a. Can be prevented.

<< Other Embodiments >>
The present invention may be configured as follows with respect to the embodiment.

  For example, in the above description, a diesel engine has been described. However, the present embodiment may be applied not only to a diesel engine but also to a gasoline engine.

  In the embodiment described above, the active state of the oxidation catalyst 41a is determined based on the exhaust temperature immediately downstream of the oxidation catalyst 41a. However, the present invention is not limited to this. For example, since the temperature of the oxidation catalyst 41a is low at the time of cold start, it is determined whether or not it is during the cold start based on the cooling water temperature of the engine 1, and thus whether or not the oxidation catalyst 41a is in an active state. Good. Further, the activation state of the oxidation catalyst 41a may be determined based on the exhaust temperature immediately below the oxidation catalyst 41a immediately before the engine 1 is stopped and the elapsed time after the engine 1 is stopped. That is, any method can be adopted as long as it can roughly estimate the active state of the oxidation catalyst 41a.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or its use.

  As described above, the present invention is useful for an engine control device equipped with a turbocharger.

1 engine 10 PCM (supercharging control means)
30 Intake passage 36 Throttle valve 40 Exhaust passage 41a Oxidation catalyst (catalyst)
61 Large turbocharger (1st turbocharger)
61a Large compressor (first compressor)
61b Large turbine (first turbine)
62 Small turbocharger (second turbocharger)
62a Small compressor (second compressor)
62b Small turbine (second turbine)
63 Intake bypass passage 63a Intake bypass valve 65 Large exhaust bypass passage (exhaust bypass passage)
65a Wastegate valve (exhaust bypass valve)

Claims (1)

An engine mounted on the vehicle,
A catalyst provided in an exhaust passage of the engine;
The first compressor is disposed upstream of the throttle valve in the intake passage of the engine, and the first turbocharger that having a first turbine disposed upstream of Oite the catalyst in the exhaust passage Machine,
The second compressor is disposed in series on the downstream side of the first compressor a upstream of the throttle valve in the intake passage, and in series with the upper stream side of the first turbine before Symbol Te the exhaust passage smell a second turbocharger that having a second turbine disposed,
An intake bypass passage connected to the intake passage and bypassing the second compressor;
An intake bypass valve disposed in the intake bypass passage;
An exhaust bypass passage connected to the exhaust passage and bypassing the first turbine;
An exhaust bypass valve disposed in the exhaust bypass passage;
Supercharging control means for controlling the throttle valve, the intake bypass valve and the exhaust bypass valve,
The supercharging control means includes
When the catalyst is in an inactive state, the intake bypass valve is opened and the throttle valve is at least partially closed to perform intake recirculation, and the exhaust bypass valve is controlled to open .
When the intake air temperature becomes equal to or higher than a predetermined upper limit during the intake air recirculation, the intake valve is adjusted to open the throttle valve and the intake air recirculation is continued.
The supercharging device for an engine, wherein when the catalyst is activated, the intake air recirculation is terminated .

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