JP2019090378A - Engine with supercharger - Google Patents

Abstract

To attain both of fuel economy performance and acceleration performance in acceleration of a vehicle.SOLUTION: An engine with a supercharger comprises: an engine body 10; a first injector 38 configured to supply fuel into a cylinder 30a; an electric supercharger 18; a high-pressure EGR passage 80; a second injector 81 configured to supply fuel to the high-pressure EGR passage 80; a reforming catalyst 82 configured to reform fuel supplied from the second injector 81; and a control unit (PCM 100) configured to supply, into the cylinder 30a, fuel reformed by the reforming catalyst 82 in acceleration of a vehicle, and adjust a suction amount supplied into the cylinder 30a by the electric supercharger 18 so that an air-fuel ratio A/F of mixture is larger than 15.SELECTED DRAWING: Figure 8

Description

  The technology disclosed herein relates to a supercharged engine.

  Patent Document 1 discloses an example of a supercharged engine. Specifically, the engine disclosed in Patent Document 1 includes a turbo charger (exhaust turbo charger) for supercharging using exhaust energy and an electric overcharging for supercharging without using exhaust energy. It is comprised as a diesel engine provided with the feeder (electric supercharger).

JP, 2009-222007, A

  By the way, a so-called lean burn engine has been proposed as a measure for improving the fuel consumption performance of the engine. In the lean burn engine, pump loss can be reduced by keeping the throttle valve open near full opening.

  However, general lean-burn engines have room for improvement in terms of the ignitability of the air-fuel mixture, and it is necessary to realize stable lean combustion when the engine load rises sharply as during vehicle acceleration. It was difficult. Therefore, until now, the ability to stabilize lean combustion has been limited to steady operation after acceleration.

  In addition, at the time of acceleration of the vehicle, the amount of supplied fuel also rapidly increases as the load on the engine increases. Then, in order to realize the air-fuel ratio set to the lean side, it is necessary to rapidly increase the introduction amount of air so as to follow the supply amount of fuel. A turbocharger using exhaust energy like a turbocharger has a problem in the responsiveness of air due to circumstances such as a turbo lag.

  Under these circumstances, even if lean combustion can be realized with the above configuration, it is limited to the low load area where the amount of air introduced is small, and there is room for improvement in securing the acceleration performance of the engine. was there.

  As a result of intensive studies, the inventors of the present invention have a configuration that improves the ignitability of the air-fuel mixture, and supercharging that does not utilize exhaust energy as in the electric turbocharger described in Patent Document 1 above. Focusing on the aircraft, we came to the completion of the technology disclosed here.

  The technology disclosed herein has been made in view of the above point, and its purpose is to achieve both fuel efficiency and acceleration performance at the time of acceleration of the vehicle.

  The technology disclosed herein is, in a supercharged engine, introducing fuel reformed by a reforming catalyst into a cylinder during acceleration of a vehicle and supercharging without using exhaust energy. It is characterized in that lean combustion is realized by adjusting the intake air amount by the machine.

  Specifically, the supercharged engine disclosed herein includes an engine body mounted on a vehicle, an intake passage and an exhaust passage connected to the engine body, gasoline, naphtha, and the like into cylinders of the engine body. A first fuel supply portion for supplying fuel containing at least one of ethanol, a supercharger provided in the intake passage and supercharging without utilizing exhaust energy, the exhaust passage, and the intake passage And an EGR passage for recirculating a portion of the exhaust gas to the intake passage, a second fuel supply unit for supplying fuel to the EGR passage, and the EGR passage provided in the EGR passage, the second fuel supply unit A reforming catalyst for reforming the fuel supplied from the first fuel supply section, and the first and second fuel supply sections and the second fuel supply section at the time of acceleration of the vehicle in response to an acceleration request signal to increase the fuel supply amount by the first fuel supply section. To the supercharger By outputting the control signal, the fuel reformed by the reforming catalyst is supplied into the cylinder, and the air-fuel ratio A / F of the air-fuel mixture formed in the cylinder, or in the cylinder Adjusting the amount of intake air supplied into the cylinder by the supercharger such that the relationship G / F between the total gas weight G and the weight F of the fuel supplied into the cylinder is greater than 15; And a controller configured to adjust the A / F or G / F.

  Here, the supercharger includes a so-called electric supercharger and a mechanical supercharger.

  The reforming catalyst may generate hydrogen by reforming the fuel supplied from the second fuel supply unit.

  According to the above configuration, at the time of acceleration of the vehicle, the control unit supplies the fuel reformed by the reforming catalyst into the cylinder. As a result, since the ignitability of the mixture can be enhanced, stable lean combustion can be realized.

  Further, in the above configuration, the control unit adjusts the amount of intake air supplied into the cylinder by the supercharger in addition to the supply of the reformed fuel. As a result, it is possible to increase the intake amount (introduction amount of air) with good response, and it is possible to maintain the intake amount in the required lean state even during acceleration. This makes it possible to maintain lean combustion and accelerate.

  As described above, by combining the reforming of the fuel by the reforming catalyst and the adjustment of the intake air amount by the turbocharger, it is possible to realize stable and responsive lean combustion, and also lean combustion. The operating range that can be implemented can be expanded to the high load side.

  Thus, at the time of acceleration of the vehicle, the fuel consumption performance can be improved while maintaining the acceleration performance, and in particular, the fuel consumption performance at the time of acceleration in a predetermined load region can be improved.

  The supercharger may be an electric supercharger that performs supercharging by rotationally driving a compressor provided in the intake passage with an electric motor.

  According to this configuration, supercharging with excellent responsiveness can be realized.

  In addition, the control unit is configured to cause the electric motor to have a torque lower than the maximum torque during acceleration of the vehicle and / or to cause the compressor to have a rotational speed lower than a limit rotational speed. It is also possible to operate the supercharger.

  When the electric supercharger is operated in the partial state as described above, it is possible to operate the electric supercharger for a long time or always operate from the viewpoint of reliability. In this case, generation of electromotive force (electromotive force at each startup) of the electric motor is suppressed, and therefore, power consumption can be suppressed low. At the same time, the pressure ratio indicating the ratio of the intake pressure before and after the compressor can be kept within a predetermined range, so that the compressor can continue to use the area where it works with high efficiency. In particular, in a supercharged engine equipped with both a turbocharger and an electric supercharger, power consumption can be reduced by operating the electric supercharger auxiliary.

  The supercharger may be a mechanical supercharger that operates by receiving power transmitted from a crankshaft of the engine body.

  According to this configuration, supercharging with excellent responsiveness can be realized.

  The EGR passage may communicate the exhaust passage upstream of the exhaust gas purification catalyst with the intake passage downstream of the supercharger.

  According to this configuration, the EGR passage (here, tentatively referred to as “high-pressure EGR passage”) is connected upstream of the exhaust gas purification catalyst in the exhaust gas passage, and for example, is connected downstream of the exhaust gas purification catalyst The reformed fuel (for example, hydrogen) can be quickly supplied into the cylinder when compared to another EGR passage (herein referred to as a “low pressure EGR passage”).

  Further, an EGR cooler having a gas cooling function may be provided downstream of the reforming catalyst in the EGR passage.

  According to this configuration, it is possible to prevent the in-cylinder temperature from becoming too high.

  The control unit may also supply the fuel reformed by the reforming catalyst into the cylinder when the vehicle accelerates and the engine body is in the warm state. Good.

  According to the above configuration, when the engine body is in the warm state, the temperature of the exhaust gas generally increases, so that the fuel reforming by the reforming catalyst also proceeds. It is effective even when lean combustion is performed, that is, when the combustion temperature is low.

  Further, the control unit controls the air-fuel ratio A / F of the air-fuel mixture formed in the cylinder or the total gas weight G in the cylinder and the weight of fuel supplied into the cylinder when the vehicle accelerates. The amount of intake air supplied into the cylinder by the supercharger may be adjusted so that the relationship G / F with F is 25 or more.

  In order to make A / F and G / F 25 or more, it is required to supply a large amount of air into the cylinder. The above configuration is particularly effective under such circumstances.

  Further, the supercharger-equipped engine communicates the exhaust passage downstream of the exhaust gas purification catalyst with the intake passage upstream of the supercharger, and recirculates part of exhaust gas to the intake passage. A second EGR passage, a third fuel supply unit for supplying fuel to the second EGR passage, and a second reforming catalyst provided in the second EGR passage for reforming the fuel supplied from the third fuel supply unit And, when the vehicle accelerates, if the exhaust gas temperature upstream of the exhaust gas purification catalyst is less than a predetermined temperature, the control unit further includes the fuel reformed by the reforming catalyst in the cylinder. Alternatively, the fuel reformed by the second reforming catalyst may be supplied into the cylinder when the exhaust temperature is equal to or higher than a predetermined temperature.

  According to this configuration, since the second EGR passage (low pressure EGR passage) is connected downstream of the exhaust gas purification catalyst in the exhaust passage, for example, the second EGR passage (low pressure) is compared with the EGR passage (high pressure EGR passage). The EGR gas recirculated through the EGR passage) has a relatively low temperature.

  When the exhaust temperature is relatively low, the reforming catalyst provided in the high pressure EGR passage is more active than the second reforming catalyst provided in the low pressure EGR passage. Make the quality function more effective. Therefore, at this time, the fuel reformed by the reforming catalyst is supplied into the cylinder through the high pressure EGR passage. Thus, the reformed fuel can be supplied into the cylinder in a responsive manner as compared with the case where the second reforming catalyst provided in the low pressure EGR passage is used.

  On the other hand, when the exhaust gas temperature is relatively high, the reforming catalyst may be excessively hot, and its reforming function may not be sufficiently exhibited (that is, it may leave the so-called reforming zone). On the other hand, the EGR gas recirculated through the low pressure EGR passage is at a relatively low temperature, and the second reforming catalyst is also at a lower temperature than the reforming catalyst. Therefore, at this time, the fuel reformed by the second reforming catalyst is supplied into the cylinder via the low pressure EGR passage. In this way, the reformed fuel can be supplied into the cylinder even when the exhaust temperature is relatively high. This is effective in expanding the operating range where lean combustion can be performed.

  Further, a particulate filter is provided downstream of the exhaust purification catalyst in the exhaust passage, and a communication portion between the second EGR passage and the exhaust passage is a portion downstream of the particulate filter, and the control is performed. When the vehicle accelerates, if the exhaust temperature upstream of the exhaust purification catalyst and the exhaust temperature downstream of the particulate filter are both lower than a predetermined temperature, the reforming catalyst When the exhaust temperature upstream of the exhaust purification catalyst is higher than a predetermined temperature and the exhaust temperature downstream of the particulate filter is lower than a predetermined temperature while the fuel is supplied into the cylinder, The fuel reformed by the second reforming catalyst may be supplied into the cylinder.

  According to this configuration, when there is a possibility that the temperature of the reforming catalyst in the EGR passage (high pressure EGR passage) becomes excessively high and the reforming function thereof is not sufficiently exhibited, the second EGR passage (low pressure EGR passage) When it is assumed that the reforming catalyst sufficiently exhibits the reforming function (However, when the particulate filter is in the active state, the exhaust temperature downstream of the particulate filter is excessively raised, and the second reforming catalyst is excessive. Supply the fuel reformed by the second reforming catalyst into the cylinder only when the high temperature case is removed), and it is possible to expand the operating range where lean combustion can be performed. Become.

  As described above, the technology disclosed herein can achieve both fuel efficiency and acceleration performance at the time of acceleration of a vehicle.

FIG. 1 is a schematic view showing a supercharged engine according to a first embodiment. FIG. 2 is a cross-sectional view showing the inside of the cylinder of the supercharged engine. FIG. 3 is a block diagram showing a control system of the supercharged engine. FIG. 4 is a map showing the operating state of the electric supercharger. The upper drawing of FIG. 5 is a performance curve graph showing the characteristics of the compressor of the electric supercharger, and the lower drawing of FIG. 5 is a graph showing the characteristics of the electric motor of the electric supercharger. FIG. 6 is a map showing the operating range of the supercharged engine. FIG. 7 compares the transition of the air-fuel ratio when lean combustion is performed in each of the comparative example without the reforming catalyst and the electric supercharger and the embodiment including the reforming catalyst and the electric supercharger. FIG. FIG. 8 is a flow chart showing the processing performed by the PCM. FIG. 9 is a schematic view showing a supercharged engine according to a second embodiment. FIG. 10 is a view corresponding to FIG. 6 showing an operating range of the supercharged engine. FIG. 11 is a flow chart showing processing executed by the PCM. FIG. 12 is a schematic view showing a supercharged engine according to a third embodiment.

First Embodiment
Hereinafter, a first embodiment for carrying out the present invention (hereinafter simply referred to as "embodiment" or "first embodiment") will be described in detail with reference to the drawings. The following description is an example.

  FIG. 1 is a schematic view showing a supercharged engine (hereinafter simply referred to as “engine”) 1 according to the first embodiment. FIG. 2 is a cross-sectional view showing the inside of a cylinder 30 a of the engine 1, and FIG. 3 is a block diagram showing a control system of the engine 1.

(Whole engine configuration)
The engine 1 is a four-stroke internal combustion engine mounted on a vehicle and powered by fuel containing at least one of gasoline, naphtha and ethanol, and as shown in FIG. It is considered to be a supercharged engine equipped with eighteen.

  A crankshaft, which is an output shaft of the engine 1, is connected to drive wheels via a transmission (not shown). As the engine 1 operates, the output is transmitted to the drive wheels to propel the vehicle.

  The engine 1 mainly includes an engine body 10 having a cylinder 30a, an intake passage 50 and an exhaust passage 60 connected to the engine body 10, and an electric supercharger 18 provided in the intake passage 50. It is done.

  Specifically, the engine body 10 has a cylinder block 30 provided with a plurality of cylinders 30a (only one is shown in FIG. 2), and a cylinder head 31 provided on the cylinder block 30. An oil pan 39 disposed under the cylinder block 30 and having lubricating oil stored therein. The engine body 10 is mounted on the above-described vehicle.

  A piston 32 (see FIG. 2) is inserted in each cylinder 30a of the cylinder block 30 so as to be reciprocatively slidable, and the combustion chamber 33 (the cylinder 32, the cylinder block 30, and the cylinder head 31) See Figure 2).

  The top surface of the piston 32 is formed with a cavity 32a as shown in an enlarged manner in FIG. The cavity 32 a faces the first injector 38 described later when the piston 32 is located near the compression top dead center.

  The piston 32 is also connected to the crankshaft via a connecting rod. The shape of the combustion chamber 33 is not limited to the illustrated shape. For example, the shape of the cavity 32a, the top surface shape of the piston 32, the shape of the ceiling of the combustion chamber 33, and the like can be changed as appropriate.

  As shown in FIG. 2, an intake port 34 and an exhaust port 35 are formed in each cylinder 30 a in the cylinder head 31, and the intake port 34 and the exhaust port 35 have openings at the combustion chamber 33 side. The intake valve 36 and the exhaust valve 37 which open and close are each arrange | positioned.

  Each intake valve 36 is opened and closed by an intake side cam 40, and each exhaust valve 37 is opened and closed by an exhaust side cam 41. The intake side cam 40 and the exhaust side cam 41 are rotationally driven in conjunction with the rotation of the crankshaft. Although not shown, in order to adjust the open / close timing and open / close period of the intake valve 36 and the exhaust valve 37, for example, a hydraulically operated valve variable mechanism is provided.

  The cylinder head 31 is provided with a first injector 38 for directly injecting fuel into the cylinder 30 a and an ignition plug 42 for igniting the mixture formed in the combustion chamber 33 for each cylinder 30 a. There is.

  As shown in FIG. 2, the first injector 38 is disposed such that the injection port thereof faces the inside of the combustion chamber 33 from the central portion of the ceiling surface of the combustion chamber 33. The first injector 38 directly injects, into the combustion chamber 33, fuel of an amount according to the operating condition of the engine 1 at an injection timing set according to the operating condition of the engine 1. The first injector 38 is an example of the “first fuel supply unit”.

  Also, as described above, the fuel supplied from the first injector 38 includes at least one of gasoline, naphtha and ethanol. That is, only gasoline may be used, only naphtha may be used, or only ethanol may be used, mixed fuel of gasoline and naphtha, mixed fuel of ethanol and other fuels You may use

  The naphtha usable for the engine 1 includes light naphtha, heavy naphtha and whole range naphtha. In addition, modified naphtha in which a small amount of crude oil or heavy oil is mixed in naphtha may be used.

  Further, the spark plug 42 is disposed such that its tip end faces the inside of the combustion chamber 33 from the ceiling surface of the combustion chamber 33. The spark plug 42 burns the mixture by igniting the mixture formed in the combustion chamber 33. That is, the engine 1 is configured as a spark ignition engine.

  As shown in FIG. 1, an intake passage 50 is connected to one side surface of the engine body 10. The intake passage 50 is in communication with the intake port 34 of each cylinder 30 a and supplies intake air to each cylinder 30 a via the intake port 34. The above-described electric supercharger 18 is provided in the intake passage 50.

  On the other hand, an exhaust passage 60 is connected to the other side surface of the engine body 10. The exhaust passage 60 is in communication with the exhaust port 35 of each cylinder 30a, and exhausts burned gas (that is, exhaust gas) from each cylinder 30a via the exhaust port 35.

  An air cleaner 54 for filtering intake air is disposed at the upstream end of the intake passage 50. On the other hand, a surge tank 51 is disposed in the vicinity of the downstream end of the intake passage 50. The intake passage 50 downstream of the surge tank 51 is an independent intake passage branched for each cylinder 30a, and the downstream end of each independent intake passage is connected to the intake port 34 of each cylinder 30a.

  Between the air cleaner 54 and the surge tank 51 in the intake passage 50, the electric supercharger 18, the throttle valve 55, and a water-cooled intercooler 57 as a heat exchanger are sequentially arranged from the upstream side to the downstream side. And are arranged. The intercooler 57 is provided, for example, in an intake manifold.

  The intake passage 50 is provided with an intake side bypass passage 53 that bypasses the electric supercharger 18. The upstream end of the intake side bypass passage 53 is connected to the upstream of the electric supercharger 18 in the intake passage 50. On the other hand, the downstream end of the intake side bypass passage 53 is connected to the downstream of the electric supercharger 18 in the intake passage 50.

  In the intake side bypass passage 53, an intake side bypass valve 58 for adjusting the amount of air flowing through the intake side bypass passage 53 is disposed. By adjusting the opening degree of the intake side bypass valve 58, the ratio between the intake amount supercharged by the electric supercharger 18 and the intake amount passing through the intake side bypass passage 53 is changed stepwise or continuously. You will be able to

  The electric supercharger 18 includes a compressor wheel 18a provided in the intake passage 50, and an electric motor 18b that rotationally drives the compressor wheel 18a. By driving the electric motor 18b, the compressor wheel 18a is rotationally driven to perform intake supercharging. That is, the electric supercharger 18 is a supercharger that does not use exhaust energy. The electric supercharger 18 is an example of a "supercharger" that performs supercharging without utilizing exhaust energy, and the compressor wheel 18a is an example of a "compressor".

  The supercharging pressure capacity of the electric supercharger 18 (that is, the supercharging pressure by the electric supercharger 18) is changed by changing the driving force of the electric motor 18b. Although the details will be described later, the electric supercharger 18 is operated in a partial state while the engine 1 is in operation.

  The electric motor 18b is driven by the power stored in the battery 19 mounted on the vehicle. The magnitude of the driving force of the electric motor 18b is changed according to the magnitude of the power supplied to the electric motor 18b. In the battery 19, for example, power generated by an alternator (not shown) mounted on a vehicle is accumulated. The battery 19 may be, for example, a 48V battery. The electric motor 18 b may be driven by being supplied with a 48 V current.

  The intercooler 57 is water-cooled, and is connected to the radiator 90 via a supply path 91 and a return path 92. A water pump 93 is connected to the supply path 91. Cooling water as a refrigerant discharged to the supply passage 91 by the water pump 93 passes through the supply passage 91, the intercooler 57, the return passage 92, and the radiator 90, and is returned to the water pump 93 again to the supply passage 91 again. It is discharged and supplied to the intercooler 57. Then, when the cooling water passes through the intercooler 57, heat is exchanged between the cooling water and the intake air to cool the intake air. The cooling water whose temperature has been increased by the amount by which the intake air is cooled is subjected to heat exchange in the radiator 90 and cooled. In addition, the intercooler 57 is not essential in this structural example (especially 1st Embodiment).

  An upstream portion of the exhaust passage 60 is constituted by an exhaust manifold. The exhaust manifold has a plurality of independent exhaust passages branched for each cylinder 30a and connected to the outer end of the exhaust port 35, and a collecting portion in which the independent exhaust passages gather.

  On the downstream side of the exhaust manifold 60 in the exhaust passage 60, a three-way catalyst 61 and a gasoline particulate filter (hereinafter referred to as GPF) 62 are disposed sequentially from the upstream side. The GPF 62 is an example of the “particulate filter”.

  The three-way catalyst 61 is activated at a predetermined temperature or higher to promote the redox reaction of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) contained in the exhaust gas. It has become. Also, the GPF 62 is for collecting particulates such as soot contained in the exhaust gas. The three-way catalyst 61 is an example of the “exhaust purification catalyst”.

  A high pressure EGR passage 80 is provided between the intake passage 50 and the exhaust passage 60. The high pressure EGR passage 80 communicates the exhaust passage 60 with the intake passage 50 so that a part of the exhaust gas can be recirculated to the intake passage 50. The high pressure EGR passage 80 is an example of the “EGR passage”.

  Specifically, the upstream end of the high pressure EGR passage 80 is connected to the portion of the exhaust passage 60 between the exhaust manifold and the three-way catalyst 61 (that is, the portion on the upstream side of the three-way catalyst 61). On the other hand, the downstream end of the high pressure EGR passage 80 is connected to the portion of the intake passage 50 between the intercooler 57 and the surge tank 51 (that is, the portion on the downstream side of the electric supercharger 18).

  Further, the high pressure EGR passage 80 is supplied with a second injector 81 for supplying fuel into the high pressure EGR passage 80 in order from the upstream side (one end side connected to the exhaust passage 60), and the second injector 81 Of a reforming catalyst 82 for reforming fuel, a high pressure EGR cooler 83 having a gas cooling function, and exhaust gas (hereinafter referred to as high pressure EGR gas) recirculated to the intake passage 50 through the high pressure EGR passage 80 A high pressure EGR valve 84 for adjusting the flow rate is provided. Hereinafter, a system configured of the second injector 81, the reforming catalyst 82, the high pressure EGR cooler 83, and the high pressure EGR valve 84 will be referred to as a high pressure EGR system 8.

  The second injector 81 is disposed such that its injection port faces the high pressure EGR passage 80. The second injector 81 injects fuel of an amount according to the operating state of the engine 1 at the injection timing set according to the operating state of the engine 1 when the lean combustion described later is performed, in the high pressure EGR passage 80. Direct injection to The second injector 81 is an example of the “second fuel supply unit”.

  The reforming catalyst 82 is activated at a predetermined temperature or higher, and promotes chemical reaction of the fuel. The chemical reaction promoted by the reforming catalyst 82 generates hydrogen from the fuel.

  The high pressure EGR cooler 83 is configured to cool the gas passing through the high pressure EGR cooler 83 in order to adjust the high pressure EGR gas to an appropriate temperature.

  The high pressure EGR valve 84 is a butterfly type electromagnetic valve, and is configured to adjust the flow rate of the high pressure EGR gas through the opening adjustment.

  Therefore, the fuel injected from the second injector 81 is led to the reforming catalyst 82 according to the flow of the high pressure EGR gas. The fuel led to the reforming catalyst 82 generates hydrogen through a chemical reaction. The hydrogen thus generated passes through the high pressure EGR cooler 83 and the high pressure EGR valve 84 in order according to the flow of the high pressure EGR gas and is recirculated to the intake passage 50. The hydrogen returned to the intake passage 50 is led to the combustion chamber 33 together with the high pressure EGR gas and the fresh air. Thus, hydrogen can be added to the mixture. An air-fuel mixture to which hydrogen is added is superior in ignitability as compared with an air-fuel mixture to which hydrogen is not added.

  The engine 1 has a geometrical compression ratio of 14 or more, and is configured to have a relatively high compression ratio so that the mixture can be sufficiently burned. In this engine 1, lean combustion at the time of vehicle acceleration is realized by adjusting the amount of fresh air by the electric supercharger 18, adding hydrogen to the mixture, and increasing the geometric compression ratio to a high compression ratio. There is.

(Configuration of engine control system)
The engine 1 configured as described above is controlled by a powertrain control module (hereinafter referred to as "PCM") 100 shown in FIG. The PCM 100 is composed of a microprocessor having a CPU 101, a memory 102, a counter timer group 103, an interface 104, and a bus 105 connecting these units. The PCM 100 is an example of the “control unit”.

  Detection signals of various sensors are input to the PCM 100. For example, the PCM 100 includes a water temperature sensor SW1 that detects the temperature of engine cooling water, a boost pressure sensor SW2 that detects a boost pressure, an intake temperature sensor SW3 that detects an intake air temperature, and an exhaust temperature sensor SW4 that detects an exhaust temperature. A crank angle sensor SW5 for detecting the rotation angle of the crankshaft, an accelerator opening sensor SW6 for detecting an accelerator opening corresponding to an operation amount of an accelerator pedal (not shown) of the vehicle, and a vehicle speed sensor for detecting the vehicle speed of the vehicle SW7 is input.

  The PCM 100 performs various calculations based on the detection signals of the sensors SW1 to SW7 to determine the state of the engine 1 or the vehicle, and receives the determination to operate the engine 1 by the control signal generated. Control.

  For example, the PCM 100 estimates the engine speed from the detection result of the crank angle sensor SW5, and calculates the engine load from the detection result of the accelerator opening sensor SW6.

  Further, when the temperature detected by the water temperature sensor SW1 is lower than the predetermined temperature Tc, the PCM 100 determines that the temperature in the cylinder 30a is low and the engine 1 is in a cold state.

  The PCM 100 generates a control signal based on the determination result, and sends control signals to the actuators of the first injector 38, the electric motor 18b, the spark plug 42, the second injector 81, the various valves 55, 58, 84, and the spark plug 42. Output The PCM 100 also outputs a control signal to the variable valve mechanism of the intake valve 36 and the exhaust valve 37.

(Outline of Control of Electric Turbocharger)
Next, control of the electric supercharger 18 by the PCM 100 will be described. FIG. 4 shows an aspect of control of the electric supercharger 18. The PCM 100 basically keeps the electric supercharger 18 constantly rotating during operation of the engine body 10, but the temperature of the engine coolant detected by the water temperature sensor SW1 and the crank angle sensor SW5 Based on the detected rotational speed of the engine 1, the number of revolutions of the electric supercharger 18 (that is, the supercharging pressure) is controlled. Specifically, control is performed so as to decrease the rotational speed as the high water temperature or the engine speed becomes higher from the region of low water temperature to low engine speed where the rotation speed is the highest.

  Further, in the present embodiment, in a region where the water temperature is 80 ° C. or more, the electric supercharger 18 is put into an idle rotation state, and the intake side bypass valve 58 is fully opened, thereby the electric supercharger The supercharging by 18 is substantially prevented. In this way, supercharging can be substantially stopped without stopping the rotation of the electric supercharger 18.

  As described above, the electric supercharger 18 is constantly rotated to adjust the amount of intake air supplied into the cylinder 30 a by the electric supercharger 18 as described later. The electric supercharger 18 (strictly, for operating the electric supercharger 18, rather than performing the on-off control so as to temporarily stop the machine 18 and drive it when necessary, The electric motor 18b) can be operated efficiently.

  FIG. 5 shows a performance curve that represents the characteristics of the electric supercharger 18. The upper part of FIG. 5 is a performance curve graph showing the characteristics of the compressor wheel 18a of the electric supercharger 18, the vertical axis is the pressure ratio of the electric supercharger 18 (ie, the upstream pressure with respect to the downstream pressure) Ratio), the horizontal axis is the discharge flow rate. In the upper diagram of FIG. 5, a curve LL represents a rotation limit line, a straight line SL represents a surge line, and a straight line CL represents a choke line. The area surrounded by these lines is the operable area of the electric turbocharger 18. The operating efficiency of the electric supercharger 18 becomes higher as it is located on the center side of this region.

  Since the electric supercharger 18 is used for the purpose of adjusting the amount of fresh air introduced into the cylinder 30a, the engine cooling is performed in a region away from the rotation limit line as shown by the mesh in the upper drawing of FIG. Depending on the temperature of the water and the engine speed, it is operated at an appropriate speed. In other words, the electric supercharger 18 is operated in a partial state largely separated from the limit rotational speed.

  The lower part of FIG. 5 exemplifies the characteristics of the electric motor 18b of the electric turbocharger 18. The vertical axis represents the torque of the electric motor 18b, and the horizontal axis represents the number of rotations of the electric motor 18b. The one-dot chain line in the lower part of FIG. 5 indicates a line for equal power consumption, the higher the power consumption at the upper right of the figure and the lower the power consumption at the lower left. The electric supercharger 18 is operated in the area shown by the mesh in the upper view of FIG. 5, while the electric motor 18b is operated in the area shown by the mesh in the lower view of FIG. The power consumption of the electric motor 18b is relatively low, and the efficiency of the electric motor 18b is relatively high. A state in which the electric motor 18 b is operating at a torque lower than the maximum torque may be referred to as operating in a partial state of the electric supercharger 18. As described above, although the electric supercharger 18 is always rotating during operation of the engine body 10, the power consumption can be reduced by operating the electric supercharger 18 in the partial state. It is.

  In the idle rotation region shown in FIG. 4, the electric supercharger 18 may be stopped.

(Engine combustion control)
The basic control of the engine 1 by the PCM 100 mainly determines the required driving force based on the accelerator opening degree, and the amount of fresh air and high pressure introduced into the cylinder 30a so that the corresponding combustion state is realized. The EGR gas amount is adjusted, and the injection amount of fuel, the injection timing, and the like are realized by controlling the operation of the first injector 38.

  In particular, the amount of fresh air introduced into the cylinder 30a and the amount of fuel injection are determined based on the stoichiometric air fuel ratio. That is, the air-fuel mixture basically burns stoichiometrically.

(Engine control during vehicle acceleration)
By the way, as a measure for improving the fuel consumption performance of the engine 1, so-called lean combustion is proposed instead of the above-described stoichiometric combustion. When lean combustion is performed, the relationship G between the air-fuel ratio A / F of the mixture formed in the cylinder 30a or the total gas weight G in the cylinder 30a and the weight F of the fuel supplied in the cylinder 30a / F is adjusted to be larger than 15. That is, since a relatively large amount of gas is introduced as compared with the stoichiometric combustion, the opening degree of the throttle valve 55 is maintained near the full opening. Thereby, the pump loss of the engine 1 can be reduced.

  However, in general, lean combustion has room for improvement in terms of the ignitability of the air-fuel mixture, and it is difficult to realize stable lean combustion when the engine load rises sharply as during vehicle acceleration. there were. Therefore, conventionally, lean combustion can be stabilized only in steady-state operation after acceleration.

  In addition, at the time of acceleration of the vehicle, the amount of supplied fuel also rapidly increases as the load on the engine increases. Then, in order to realize the air-fuel ratio set to the lean side, it is necessary to rapidly increase the introduction amount of air so as to follow the supply amount of fuel. A turbocharger using exhaust energy like a turbocharger has a problem in the responsiveness of air due to circumstances such as a turbo lag.

  In addition, at the time of acceleration of the vehicle, the amount of supplied fuel also rapidly increases as the load on the engine increases. Then, in order to realize the A / F or G / F set on the lean side, it is necessary to rapidly increase the gas introduction amount so as to follow the fuel supply amount. A turbocharger using exhaust energy like a turbocharger has a problem in air responsiveness in consideration of a turbo lag and the like.

  Therefore, even if lean combustion can be realized, it is limited to a low load area where the amount of air introduced is small as in the lean area A shown in the upper diagram of FIG. 6, and the engine acceleration performance is secured. There was room for improvement on the

  On the other hand, the engine 1 is configured to include the reforming catalyst 82 capable of enhancing the ignitability of the air-fuel mixture and the electric supercharger 18 not utilizing exhaust energy. By performing control in combination with the supercharger 18, it is possible to realize lean combustion with excellent stability even at the time of acceleration of the vehicle.

  That is, the PCM 100 outputs a control signal to the first and second injectors 38 and 81 and the electric supercharger 18 when the vehicle accelerates in response to the acceleration request signal and increasing the fuel supply amount by the first injector 38. Thus, the fuel (hydrogen in this configuration example) reformed by the reforming catalyst 82 is supplied into the cylinder 30a, and the A / F or G / of the mixture formed in the cylinder 30a is also supplied. The amount of intake air supplied into the cylinder 30a by the electric supercharger 18 is adjusted such that F is greater than 15. In this configuration example, the A / F or G / F of the mixture is adjusted to be 25 or more.

  As described above, by supplying the fuel reformed by the reforming catalyst 82 into the cylinder 30a at the time of acceleration of the vehicle, it is possible to improve the ignitability of the air-fuel mixture. As a result, stable lean combustion can be realized.

  Further, the PCM 100 adjusts the amount of intake air supplied into the cylinder 30 a by the electric supercharger 18 together with the supply of the reformed fuel. The amount of intake air (the amount of air introduced) can be increased with good response, and the amount of intake air can be maintained in the required lean state even during acceleration. This enables acceleration with maintaining lean combustion.

  As described above, the combination of the reforming of the fuel by the reforming catalyst 82 and the adjustment of the intake air amount by the electric supercharger 18 can realize stable and responsive lean combustion. At the same time, as in the lean area A 'shown in the lower part of FIG. 6, the operation area in which lean combustion can be performed can be expanded to the high load side.

  Thus, at the time of acceleration of the vehicle, the fuel consumption performance can be improved while maintaining the fuel consumption performance, and in particular, the fuel consumption performance at the time of acceleration in a predetermined load region can be improved.

  In addition, when the exhaust gas temperature is high and the reforming catalyst 82 becomes excessively high temperature, there is a possibility that the reforming function of the reforming catalyst 82 is not sufficiently exhibited.

  Therefore, when it is determined that the exhaust gas temperature is equal to or higher than the predetermined temperature T1, the PCM 100 stops the supply of fuel by the second injector 81 even during acceleration of the vehicle. The exhaust temperature T1 is set, for example, in accordance with the activation temperature of the reforming catalyst 82. As a result, fuel can be supplied from the second injector 81 more than necessary, and fuel consumption performance can be improved.

  Further, as described above, the exhaust temperature of the PCM 100 is set to the predetermined temperature T1 as described above even when the operating state of the engine body 10 is outside the range of the lean region A 'or within the range of the lean region A'. In the above case, the fuel supply by the second injector 81 is stopped even during acceleration of the vehicle. In this case, the PCM 100 stoichiometrically burns the mixture. Even when the fuel supply by the second injector 81 is stopped, it is possible to supply only the EGR gas through the high pressure EGR passage 80. In this case, the target EGR rate may be determined as appropriate according to the operating state of the engine body 10.

  For example, FIG. 7 shows the air when lean combustion is performed in each of the comparative example without the reforming catalyst 82 and the electric supercharger 18 and the embodiment including the reforming catalyst 82 and the electric supercharger 18. It is a figure which shows transition of a fuel ratio.

  Specifically, the upper diagram of FIG. 7 shows the transition of the engine load. On the other hand, the lower diagram of FIG. 7 shows the transition of the air-fuel ratio corresponding to the engine load shown in the upper diagram. The transition of the engine load is the same between the comparative example and the embodiment. Specifically, the engine shown in FIG. 7 performs transient acceleration from time t0 to time t1, and then operates with load P1 from time t1 to time t2. Then, after passing through the deceleration region from time t2 to t3, operation is performed with a predetermined load P2 lower than the load P1 from time t3 to t4.

  As shown in the lower part of FIG. 7, in the configuration according to the comparative example, rich air-fuel mixture is burned to generate stable torque during transient acceleration from time t0 to time t1. After that, operation is performed with a constant load from time t1 to t2. At this time, although the air-fuel ratio of the air-fuel mixture shifts to the lean side compared to that at the time of acceleration, it is stoichiometric combustion. Then, the lean combustion is performed after the load decreases from P2 to P1. That is, in the comparative example, while rich or stoichiometric combustion is performed from time t0 to time t3, it is possible to finally execute lean combustion at a low load after time t4.

  On the other hand, in the embodiment, as described above, at the time of acceleration, the reforming of the fuel by the reforming catalyst 82 and the increase of the supercharging pressure by the electric turbocharger 18 are performed. Specifically, the PCM 100 causes the spark plug 42 to ignite the mixture to which hydrogen is added while introducing a large amount of air into the cylinder 30 a by the electric turbocharger 18.

  Thus, lean combustion can be realized during transient acceleration in which the load rises sharply. In addition, even with a steady load on the medium load side, lean combustion can be stabilized. Therefore, in the embodiment, it is possible to realize lean combustion in the entire region from time t0 to time t4 even in the transient acceleration or in the middle load region.

  In addition, as a combustion form of the mixture, as described above, the entire mixture is burned (spark ignition combustion) by igniting the mixture to which hydrogen is added by the spark plug 42. ing.

  Next, processing operation of engine control by the PCM 100 will be described based on the flowchart of FIG. The flowchart shown in FIG. 10 is a flowchart when the engine body 10 is in the warm state.

  In the first step S101, the PCM 100 reads signals from various sensors and determines the operating state of the engine 1. In the next step S102, the PCM 100 determines, according to the map illustrated in FIG. 4, whether or not the electric supercharger 18 is in an idle rotation state. When the determination in step S102 is NO, the control process proceeds to step S103. In step S103, the PCM 100 drives the electric supercharger 18. The PCM 100 sets the rotation number of the electric supercharger 18 to a high rotation number, a middle rotation number, or a low rotation number according to the water temperature of the engine 1 and the engine rotation number.

  When the determination in step S102 is YES, the control process skips step S103 and proceeds to step S104. In this case, the electric supercharger 18 is in an idle rotation state.

  In step S104, the PCM 100 determines whether the driver's acceleration request has been made. The PCM 100 determines the presence or absence of the driver's acceleration request based on the detection value of the accelerator opening sensor SW6. When an acceleration request is made, the control process proceeds to step S105, and when there is no acceleration request, the control process proceeds to step S112.

  In step S105, the PCM 100 calculates a required driving force of the engine 1 (a driving force based on an accelerator opening degree or the like). Then, in step S106, the PCM 100 calculates the target intake air amount, the target EGR rate, the target boost pressure, and the fuel injection amount from the first injector 38 (target value to realize the required driving force calculated in the above step S105). And control timings such as the timing (target timing) at which fuel is injected from the first injector 38. These control amounts are determined such that a mixture of stoichiometric (λ = 1) is formed in the cylinder 30a.

  In step S107 following step S106, the PCM 100 determines whether the operating state of the engine body 10 is within the range of the lean region A 'shown in FIG. If it is in the range of the lean area A ', the process proceeds to step S108, while if it is in the range of the lean area A', the process proceeds to step S115 to execute the stoichiometric combustion.

  In step S108, the PCM 100 determines whether the exhaust gas temperature is less than the predetermined temperature T1. The exhaust temperature may be obtained by the exhaust temperature sensor SW4 or may be estimated by model calculation. When the exhaust gas temperature is less than the predetermined temperature T1, the process proceeds to step S109. When the exhaust gas temperature is equal to or more than the predetermined temperature T1, it is determined that the fuel injected from the second injector 81 is not sufficiently reformed. The process proceeds to step S115 to execute stoichiometric combustion.

  In step S109, the PCM 100 determines a control amount such that a lean mixture is formed in the cylinder 30a, based on the control amount determined in step S106. At this time, the target air-fuel ratio is determined based on the limit value of the excess air ratio λ (in particular, the upper limit value on the lean side). The limit value is determined based on the operating state of the engine body 10. For example, when the load of the engine 1 is high, the limit value may be set to the rich side. Although the detailed flow is omitted, depending on the limit value of the excess air ratio λ, the process may proceed to step S115 to perform stoichiometric combustion.

  Further, in step S109, the fuel injection amount (target value) from the second injector 81 is also determined. The fuel injection amount is determined based on the target boost pressure of the electric supercharger 18, the target air-fuel ratio, and the like. For example, when the target boost pressure is large, more air will be introduced into the cylinder 30a, so in order to keep the target air-fuel ratio constant, the second injector 81 is more than when the target boost pressure is small. It is sufficient to increase the fuel injection amount from Similarly, when the target air-fuel ratio is large, the fuel injection amount from the second injector 81 may be smaller than when the target air-fuel ratio is small. Further, the target EGR rate and the fuel injection amount from the second injector 81 may be correlated with each other.

  Then, in step S110 following step S109, the PCM 100 injects fuel from the second injector 81 and supplies the reformed fuel into the cylinder 30a. Then, in step S111, the PCM 100 adjusts the amount of intake air supplied into the cylinder 30a via the electric supercharger 18. Then, in step S112, the PCM 100 executes fuel injection from the first injector 38 and the like. Thus, the aforementioned lean combustion is realized.

  The control process then returns to step S101. Even when the boost pressure of the electric supercharger 18 is increased in the early stage of acceleration of the vehicle, if the drive of the electric supercharger 18 becomes unnecessary in the late stage of acceleration, the boost pressure by the electric supercharger 18 is descend.

  On the other hand, in step S113 where there is no acceleration request, the PCM 100 calculates the required driving force of the engine 1 as in step S105, and in the subsequent step S114, the PCM 100 performs step S113 in the same manner as step S106. In order to realize the required driving force calculated in the above, the control amount for burning the stoichiometric mixture is determined.

  In step S115, the PCM 100 executes, for example, fuel injection from the first injector 38 based on the control amount determined in step S114. Then, stoichiometric combustion is realized.

  As described above, with the configuration according to the present embodiment, it is possible to improve the fuel consumption performance while maintaining the acceleration performance at the time of acceleration of the vehicle, and in particular, to improve the fuel consumption performance at the time of acceleration in a predetermined load region. It is possible to improve.

  In addition, since the electric supercharger 18 operates in the partial state as shown in FIG. 5, it is possible to prevent the rush electric power from being supplied to the electric motor 18 b of the electric supercharger 18 at each acceleration. Can. As a result, it is possible to suppress power consumption when operating the electric supercharger 18, and it is also advantageous to improve the reliability of the electric supercharger 18.

  Further, as shown in FIG. 1, since the high pressure EGR passage 80 is connected upstream of the three-way catalyst 61 in the exhaust passage 60, for example, another passage connected downstream of the three-way catalyst 61 When compared, the reformed fuel can be quickly supplied into the cylinder 30a.

  Also, in order to make A / F and G / F 25 or more, it is required to supply a large amount of air into the cylinder 30a. The engine 1 using the electric supercharger 18 is particularly effective in that air can be supplied as quickly as possible even under such circumstances.

Second Embodiment
Subsequently, a second embodiment for carrying out the present invention (hereinafter simply referred to as “the second embodiment”) will be described with reference to the drawings. As in the first embodiment, the following description is merely exemplary. Further, in the following description, the same reference numerals are used for the same or corresponding components as those in the first embodiment.

  FIG. 9 is a schematic view showing an engine 1 according to the second embodiment.

  The engine 1 according to the second embodiment has a configuration provided with a turbocharger 56 in addition to the electric supercharger 18, when it is described focusing on the difference from the first embodiment. It is done.

  The turbocharger 56 is rotationally driven by receiving energy of exhaust gas (ie, exhaust energy). Specifically, when the turbine 56b of the turbocharger 56 receives exhaust energy and is rotationally driven, the compressor 56a is rotationally driven via the connection shaft 56c to perform intake supercharging.

  Specifically, the turbine 56 b of the turbocharger 56 is disposed between the upstream end of the high pressure EGR passage 80 in the exhaust passage 60 and the three-way catalyst 61. On the other hand, the compressor 56 a of the turbocharger 56 is disposed between the air cleaner 54 in the intake passage 50 and the electric turbocharger 18. And turbine 56b and compressor 56a are connected via connection shaft 56c.

  Further, an exhaust side bypass passage 63 for bypassing the turbocharger 56 is provided in the exhaust passage 60. The exhaust side bypass passage 63 is provided with a waste gate valve 65 for adjusting the flow rate of the exhaust gas flowing to the exhaust side bypass passage 63. The turbocharger 56 is housed in a turbine case (not shown).

  The turbocharger 56 may be a variable displacement turbocharger in which movable vanes are disposed in a turbine case. If it is possible to flow the exhaust gas substantially bypassing the turbine 56b by adjusting the opening degree of the movable vane, the exhaust side bypass passage 63 and the waste gate valve 65 can be omitted.

  A low pressure EGR passage 70 is provided between the intake passage 50 and the exhaust passage 60. The low pressure EGR passage 70 is disposed downstream of the three-way catalyst 61 (in this example, downstream of the three-way catalyst 61 and the GPF 62), and upstream of the electric turbocharger 18 (in this example, the electric supercharger). The supply passage 18 and the intake passage 50 upstream of the compressor 56 a communicate with each other, and a portion of the exhaust gas can be returned to the intake passage 50. The low pressure EGR passage 70 is an example of the “second EGR passage”.

  Further, the low pressure EGR passage 70 is supplied with a third injector 71 for supplying fuel into the low pressure EGR passage 70 in order from the upstream side (one end side connected to the exhaust passage 60), and the third injector 71 A second reforming catalyst 72 for reforming the fuel, a low pressure EGR cooler 73 having a gas cooling function, and an exhaust gas recirculated to the intake passage 50 through the low pressure EGR passage 70 (hereinafter referred to as low pressure EGR gas And a low pressure EGR valve 74 for adjusting the flow rate of The third injector 71, the second reforming catalyst 72, the low pressure EGR cooler 73, and the low pressure EGR valve 74 constitute a low pressure EGR system 7.

  The configuration of the third injector 71 is substantially the same as that of the second injector 81 except for the mounting point thereof. The third injector 71 is an example of the “third fuel supply unit”. Similarly, the configuration of the second reforming catalyst 72 is substantially the same as the configuration of the reforming catalyst 82.

  Further, the low pressure EGR cooler 73 is configured to cool the gas passing through the low pressure EGR cooler 73 in order to adjust the low pressure EGR gas to an appropriate temperature. The low pressure EGR valve 74 is an electromagnetic butterfly valve, and is configured to adjust the flow rate of the low pressure EGR gas through the opening adjustment.

  An exhaust shutter valve 64 is provided downstream of the upstream end of the low pressure EGR passage 70 in the exhaust passage 60. The exhaust shutter valve 64 is a valve capable of adjusting the exhaust pressure in the exhaust passage 60 by adjusting the opening degree thereof. The exhaust shutter valve 64 may be used, for example, to increase the exhaust pressure in the exhaust passage 60 when the low pressure EGR passage 70 causes part of the exhaust gas flowing through the exhaust passage 60 to be recirculated to the intake passage 50. is there.

  As described above, by using the turbocharger 56 and the electric supercharger 18 in combination, the electric supercharger 18 can be auxiliary operated, particularly when the engine 1 is in steady state. As a result, power consumption can be reduced.

  Further, by using the turbocharger 56 and the electric turbocharger 18 in combination, a larger amount of air can be supplied to the cylinder 30a. This is particularly effective in setting the target air-fuel ratio higher. Also, by supplying a larger amount of air into the cylinder 30a, it is possible to expand the operation area where lean combustion can be performed to a higher load side as in the lean area A ′ ′ shown in FIG. It becomes.

  By the way, when the exhaust gas temperature is relatively low, the reforming catalyst 82 provided in the high pressure EGR passage 80 is more active than the second reforming catalyst 72 provided in the low pressure EGR passage 70. The quality catalyst 82 exerts its reforming function more effectively. Therefore, at this time, the fuel reformed by the reforming catalyst 82 is supplied into the cylinder 30 a via the high pressure EGR passage 80. As a result, compared to when using the second reforming catalyst 72 provided in the low pressure EGR passage 70, the reformed fuel can be supplied into the cylinder 30a in a responsive manner.

  However, when the exhaust gas temperature is relatively high (in particular, when the temperature is higher than the above-mentioned predetermined temperature T1), the reforming catalyst 82 may not generate sufficient hydrogen (it may leave the so-called reforming zone) . On the other hand, since the EGR gas recirculated through the low pressure EGR passage 70 is the exhaust gas after passing through the turbine 56 b or the waste gate valve 65, the three-way catalyst 61 and the GPF 62, it flows through the high pressure EGR passage 80 The temperature is relatively low compared to the exhaust gas. Therefore, the second reforming catalyst 72 also has a temperature lower than that of the reforming catalyst 82.

  Therefore, as shown in FIG. 11, when the exhaust gas temperature upstream of the three-way catalyst 61 is less than the predetermined temperature T1 during acceleration of the vehicle, the PCM 100 performs high-pressure fuel reforming with the reforming catalyst 82 as shown in FIG. The gas is supplied into the cylinder 30 a through the EGR passage 80. On the other hand, the PCM 100 supplies the fuel reformed by the second reforming catalyst 72 into the cylinder 30a via the low pressure EGR passage 70 when the exhaust temperature is equal to or higher than the predetermined temperature T1 when the vehicle accelerates. (Refer step S116-step S117 of FIG. 11).

  This makes it possible to supply the reformed fuel into the cylinder 30a even when the exhaust temperature is relatively high. This is effective in expanding the operating range where lean combustion can be performed.

  In addition, control is performed focusing on the fact that the GPF 62 is provided downstream of the three-way catalyst 61 and that the communication portion between the low pressure EGR passage 70 and the exhaust passage 60 is downstream from the GPF 62. You can also.

  That is, at the time of acceleration of the vehicle, in the PCM 100, both the exhaust temperature upstream of the three-way catalyst 61 and the exhaust temperature downstream of the GPF 62 may be the same as or different from the predetermined temperature T2. In the case of less than), the fuel reformed by the reforming catalyst 82 is supplied into the cylinder 30a, while the exhaust temperature upstream of the three-way catalyst 61 is at a predetermined temperature T2 or more and downstream of the GPF 62 If the exhaust temperature is lower than the predetermined temperature T2, the fuel reformed by the second reforming catalyst 72 may be supplied into the cylinder 30a. Then, when the exhaust temperature upstream of the three-way catalyst 61 and the exhaust temperature downstream of the GPF 62 are both equal to or higher than the predetermined temperature T2, the PCM 100 does not perform reforming of the fuel.

  That is, the second reforming catalyst 72 of the low pressure EGR passage 70 is sufficiently reformed when the reforming catalyst 82 of the high pressure EGR passage 80 has an excessively high temperature and there is a possibility that its reforming function is not sufficiently exhibited. In the case where it is assumed that the function is exhibited (however, except in the case where the exhaust gas temperature downstream of the GPF 62 is excessively raised and the second reforming catalyst 72 becomes excessively high when the GPF 62 is in the active state) Only by supplying the fuel reformed by the second reforming catalyst 72 into the cylinder 30a, it is possible to expand the operation range in which lean combustion can be performed.

  Further, when the exhaust temperature upstream of the three-way catalyst 61 and the exhaust temperature downstream of the GPF 62 are both equal to or higher than the predetermined temperature T2, both the reforming catalyst 82 and the second reforming catalyst 72 have excessively high temperatures. It is assumed that In this case, although the fuel reforming is not performed as described above, such an operating state is mainly considered to be in the high load area, and therefore unlike the acceleration from the low to medium load area, And the need for fuel reforming is low.

Third Embodiment
Although the said embodiment demonstrated the structure provided with the electrically driven supercharger 18 as an example of a supercharger, it is not restricted to this structure. For example, the supercharger may be a mechanical supercharger (so-called super charger) that operates by receiving the power transmitted from the crankshaft of the engine body 10.

  The engine 1 provided with the mechanical supercharger 218 is shown in FIG. The mechanical supercharger 218 is connected to the crankshaft 43 via a drive belt 219 and operates by receiving the power transmitted from the crankshaft 43. The mechanical supercharger 218 is turned on / off via a clutch (not shown). An air bypass valve 258 is provided in the air bypass passage 253 bypassing the mechanical supercharger 218. Adjusting the ratio of the amount of intake air supercharged by the mechanical supercharger 218 and the amount of intake air passing through the air bypass passage 253 stepwise or continuously by adjusting the opening degree of the air bypass valve 258 Will be able to

  The engine 1 equipped with the mechanical supercharger 218 can realize supercharging with excellent responsiveness as in the case equipped with the electric supercharger 18 through the control of the air bypass valve 258 and the clutch. .

Other Embodiments
Also, the processing performed by the PCM 100 can be appropriately changed, for example, by changing the order of the steps. Furthermore, the PCM 100 may perform processing via the target value of G / F instead of processing via the target air-fuel ratio.

1 Engine 10 Engine Body 18 Electric Turbocharger (Supercharger)
18a Compressor hole (compressor)
18b electric motor 30a cylinder 38 first injector (first fuel supply unit)
Reference Signs List 50 intake passage 56 turbocharger 56a compressor 56b turbine 60 exhaust passage 61 three-way catalyst (exhaust purification catalyst)
62 GPF (particulate filter)
70 Low pressure EGR passage (second EGR passage)
71 Third injector (third fuel supply unit)
72 second reforming catalyst 80 high pressure EGR passage (EGR passage)
81 Second injector (second fuel supply unit)
82 Reforming catalyst 83 High pressure EGR cooler (EGR cooler)
100 PCM (control unit)
218 Mechanical Turbocharger (Supercharger)

Claims (10)

An engine body mounted on a vehicle,
An intake passage and an exhaust passage connected to the engine body;
A first fuel supply unit for supplying fuel containing at least one of gasoline, naphtha and ethanol into the cylinder of the engine body;
A supercharger provided in the intake passage and supercharging without utilizing exhaust energy;
An EGR passage communicating the exhaust passage with the intake passage and returning a part of the exhaust gas to the intake passage;
A second fuel supply unit for supplying fuel to the EGR passage;
A reforming catalyst provided in the EGR passage and reforming the fuel supplied from the second fuel supply unit;
The control signal is outputted to the first and second fuel supply units and the supercharger at the time of acceleration of the vehicle upon increasing the fuel supply amount by the first fuel supply unit in response to the acceleration request signal. The fuel reformed by the reforming catalyst is supplied into the cylinder, and the air-fuel ratio A / F of the mixture formed in the cylinder, or the total gas weight G in the cylinder and the cylinder The A / F or G / F is adjusted by adjusting the amount of intake air supplied into the cylinder by the supercharger so that the relationship G / F with the weight F of the supplied fuel is greater than 15. And a control unit to adjust the supercharged engine. In the supercharged engine according to claim 1,
An engine with a supercharger, wherein the supercharger is an electric supercharger that performs supercharging by rotationally driving a compressor provided in the intake passage with an electric motor. In the supercharged engine according to claim 2,
The control unit is configured to cause the electric motor to generate a torque lower than the maximum torque during acceleration of the vehicle and / or to set the rotational speed lower than the limit rotational speed to the compressor. A supercharged engine that operates a feeder. In the supercharged engine according to claim 1,
The supercharger-equipped engine according to claim 1, wherein said supercharger is a mechanical supercharger that operates by receiving power transmitted from a crankshaft of said engine body. In the supercharged engine according to any one of claims 1 to 4,
The supercharger-equipped engine, wherein the EGR passage communicates the exhaust passage upstream of the exhaust gas purification catalyst with the intake passage downstream of the supercharger. In the supercharged engine according to claim 5,
An engine with a supercharger, wherein an EGR cooler having a gas cooling function is provided downstream of the reforming catalyst in the EGR passage. The supercharged engine according to any one of claims 1 to 6,
The control unit is configured to supply the fuel reformed by the reforming catalyst into the cylinder when the vehicle accelerates and the engine body is in a warm state. . In the supercharged engine according to any one of claims 1 to 7,
The control unit controls the air-fuel ratio A / F of the air-fuel mixture formed in the cylinder or the total gas weight G in the cylinder and the weight F of the fuel supplied in the cylinder when the vehicle accelerates, and An engine with a supercharger, which adjusts the amount of intake air supplied into the cylinder by the supercharger so that the relationship G / F of the above becomes 25 or more. The supercharged engine according to any one of claims 1 to 8, wherein
A second EGR passage communicating the exhaust passage downstream of the exhaust gas purification catalyst with the intake passage upstream of the turbocharger and recirculating part of the exhaust gas to the intake passage;
A third fuel supply unit for supplying fuel to the second EGR passage;
And a second reforming catalyst provided in the second EGR passage to reform the fuel supplied from the third fuel supply unit.
The control unit supplies the fuel reformed by the reforming catalyst into the cylinder when the exhaust temperature upstream of the exhaust purification catalyst is lower than a predetermined value at the time of acceleration of the vehicle. The engine with a supercharger which supplies the fuel reformed by the second reforming catalyst into the cylinder when the exhaust temperature is higher than a predetermined value. In the supercharged engine according to claim 9,
A particulate filter is provided downstream of the exhaust gas purification catalyst in the exhaust gas passage,
A communicating portion between the second EGR passage and the exhaust passage is a portion downstream of the particulate filter,
The control unit is configured to accelerate the vehicle.
If the exhaust temperature upstream of the exhaust purification catalyst and the exhaust temperature downstream of the particulate filter are both lower than a predetermined temperature, the fuel reformed by the reforming catalyst is introduced into the cylinder. While supplying
If the exhaust gas temperature upstream of the exhaust gas purification catalyst is equal to or higher than the predetermined temperature and the exhaust gas temperature downstream of the particulate filter is lower than the predetermined temperature, the fuel reformed by the second reforming catalyst is A supercharged engine that feeds into the cylinder.

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