JP2009228448A - Supercharging device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for enabling the appropriate adjustment of an engine braking force in accordance with required deceleration while effectively preventing a temperature of an exhaust gas cleaning catalyst of an engine from becoming lower than an activation temperature at deceleration. <P>SOLUTION: In the engine DE, an electric supercharger 21 is driven to prevent a delay of supercharge caused by a delay of the operation of an exhaust gas turbocharger 19 at acceleration. Moreover, when the temperature of the exhaust gas cleaning catalyst 30 is not lower than a reference temperature at deceleration, the electric supercharger 21 is driven while fuel injection is stopped and an engine braking force is controlled according to required deceleration. When the temperature of the catalyst 30 is lower than a reference temperature, the supercharger 21 is stopped while fuel injection is performed by the reduced and corrected amount of injection and the temperature of the catalyst 30 is raised. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a supercharging device for an engine provided with an electric supercharger.

  In general, in a vehicle driven by an engine, wheels are driven by the engine during normal driving. When the accelerator pedal is released from this state, or when the accelerator pedal is depressed, the engine is driven. When the force becomes smaller than the rotational resistance of the engine, a braking force is generated by the engine brake, and the wheel is braked by the rotational resistance of the engine. Therefore, when the driver of the vehicle needs to decelerate, the vehicle can be effectively braked if the engine brake is appropriately used together with the foot brake or instead of the foot brake.

Here, if the engine braking force can be adjusted according to the driver's deceleration request or the state of the vehicle or the engine, the vehicle can be braked more appropriately according to the driving state or the traveling environment. Therefore, a vehicle or engine is proposed in which the engine braking force is adjusted by changing the supercharging pressure of the turbocharger in accordance with the required mode of braking force during deceleration (see, for example, Patent Document 1). ). In the engine described in Patent Document 1, the rotation of the turbine of the turbocharger is assisted by an electric motor.
JP 2007-132293 A (paragraph [0061], FIG. 3)

  On the other hand, since the engine exhaust gas contains air pollutants such as NOx (nitrogen oxide) and HC (hydrocarbon), the engine exhaust passage is usually used to purify the exhaust gas. An exhaust gas purification device including an exhaust gas purification catalyst is provided. In general, the exhaust gas purification catalyst cannot effectively purify the exhaust gas unless its temperature is equal to or higher than the activation temperature.

  In a conventional vehicle or engine in which the engine braking force during deceleration is adjusted by changing the supercharging pressure of the turbocharger, the energy of exhaust gas is consumed as the turbine is driven. The temperature of the exhaust gas decreases. For this reason, the temperature of the exhaust gas purification catalyst may not be maintained above its activation temperature during deceleration, and in this case, the amount of air pollutant emissions increases and emissions become worse.

  The present invention has been made to solve the above-mentioned conventional problems, and effectively prevents the exhaust gas purification catalyst of the engine from lowering below the activation temperature when the vehicle is decelerated, while the driver or the vehicle. It is an object of the present invention to provide a means capable of appropriately adjusting the engine braking force in accordance with the required deceleration.

  An engine supercharging device according to the present invention made to solve the above-described problems is provided with an electric supercharger having a compressor disposed in an intake passage and a motor for driving the compressor, and an exhaust passage. An exhaust gas purifying device, and a deceleration control means for stopping the fuel supply to the engine and operating the electric supercharger when the engine or a vehicle equipped with the engine is decelerated. Is.

  In the supercharging device for an engine according to the present invention, when the engine is provided with temperature detecting means for detecting the temperature of the exhaust gas purifying device or a temperature related to or corresponding to the temperature (for example, exhaust gas temperature), the deceleration control means When the temperature detected by the temperature detecting means (hereinafter referred to as “sensor detected temperature”) is equal to or lower than a preset reference temperature, the operation of the electric supercharger is stopped (prohibited) and the engine It is preferable that the fuel supply to the vehicle is performed by correcting the decrease.

  In the engine supercharging device according to the present invention, when the engine includes an exhaust turbocharger and an intercooler disposed in the intake passage downstream from the blower (compressor) of the exhaust turbocharger, The electric supercharger is preferably disposed in the intake passage downstream of the intercooler.

  In the engine supercharging device according to the present invention, the deceleration control means is configured to set the operating rotational speed of the electric supercharger according to the required deceleration of the engine or a vehicle equipped with the engine. Is preferred. In this case, the deceleration control means is more preferably configured to calculate or set the required deceleration based on at least one parameter among the vehicle speed, the accelerator return speed, and the gear ratio of the transmission.

  According to the supercharger for an engine according to the present invention, supercharging is performed by the electric supercharger disposed in the intake passage during deceleration, but this supercharging does not consume the energy of the exhaust gas from the engine. The temperature of the exhaust gas does not decrease. For this reason, it is possible to appropriately adjust the engine braking force by increasing the compression resistance by the operation of the electric supercharger while suppressing a decrease in the temperature of the exhaust gas purification device or the exhaust gas purification catalyst during deceleration. That is, the engine braking force can be generated while enabling fuel cut during deceleration from a high vehicle speed state. Therefore, it is possible to appropriately adjust the engine braking force according to the driver or the required deceleration of the vehicle while effectively preventing the engine exhaust gas purification catalyst from lowering its activation temperature when the vehicle decelerates. it can.

  In the engine supercharging device according to the present invention, when the sensor detected temperature is equal to or lower than the reference temperature, the operation of the electric supercharger is stopped, and the fuel supply to the engine is corrected by reducing the amount. The temperature of the exhaust gas is increased by the combustion of the fuel. For this reason, the fall of the temperature of an exhaust-gas purification apparatus or an exhaust-gas purification catalyst can be prevented or suppressed more effectively.

  In the engine supercharging device according to the present invention, when the electric supercharger is disposed in the intake passage downstream from the intercooler, the air that is adiabatically compressed by the electric supercharger and the temperature thereof is increased is the intercooler. Since it is supplied to the combustion chamber of the engine without being cooled, it is possible to more effectively prevent or suppress a decrease in the temperature of the exhaust gas, and thus a decrease in the temperature of the exhaust gas purification device or the exhaust gas purification catalyst.

  In the engine supercharging device according to the present invention, at the time of deceleration, the operating rotational speed of the electric supercharger is set according to the required deceleration calculated based on, for example, the vehicle speed, the accelerator return speed, the gear ratio of the transmission, and the like. In such a case, it is possible to apply an engine braking force according to the driving state or driving environment of the engine or the vehicle or the deceleration request of the driver of the vehicle, and to brake the vehicle appropriately.

  Embodiments 1 and 2 of the present invention will be specifically described below with reference to the accompanying drawings. The first embodiment relates to a supercharger for a diesel engine, and the second embodiment relates to a supercharger for a gasoline engine. Note that, in the drawings according to the first and second embodiments, the same reference numerals are assigned to the components having the same or corresponding structures or functions.

(Embodiment 1)
FIG. 1 shows a system configuration of a direct injection diesel engine DE (hereinafter referred to as “engine DE” for short) according to the present invention. The engine DE is a multi-cylinder (for example, four cylinders, six cylinders, etc.) engine, but only one cylinder is shown in FIG. 1, and the other cylinders are not shown. As shown in FIG. 1, in the engine DE, when the intake valve 1 is opened, fuel combustion air is sucked into the combustion chamber 3 from the intake port 2 (hereinafter, this air is referred to as “intake air”). That said.) The intake air in the combustion chamber 3 is compressed by the piston 4 to be in a high temperature / high pressure state. In the vicinity of the top dead center of the compression stroke, fuel (light oil or the like) is injected from the fuel injection valve 5 into the combustion chamber 3, and this fuel self-ignites and burns. Gas generated by combustion, that is, exhaust gas, is discharged to the exhaust port 7 when the exhaust valve 6 is opened. Although not shown, the fuel is supplied from the fuel tank to the fuel injection valve 5 through the common rail at a high pressure.

  A series of these operations is repeated, and the piston 4 repeats reciprocating motion in the cylinder axial direction within the cylinder 8. The reciprocating motion of the piston 4 is converted into a rotational motion (torque) of the crankshaft 10 by a link mechanism including a connecting rod 9, a crank arm (not shown), a crankpin (not shown), and the like. The rotational movement of the crankshaft 10 is taken out as engine output and drives a vehicle equipped with the engine DE, and drives auxiliary equipment such as an alternator and an air conditioner (not shown). The engine DE is driven (cranked) by the engine starter 11 at the time of starting. Although not shown, the driving force of the crankshaft 10 is transmitted to driving wheels via a transmission, a final gear, and the like.

  In the engine DE, the intake valve 1 is opened and closed by the intake valve opening / closing cam mechanism 12 at a predetermined timing. An electromagnetic intake valve cam control device 13 (VVT: variable valve timing control device) is provided for the intake valve opening / closing cam mechanism 12. The intake valve cam control device 13 can advance or retard the opening / closing timing of the intake valve 1 via the intake valve opening / closing cam mechanism 12 in accordance with a control signal from the control unit C.

  On the other hand, the exhaust valve 6 is opened and closed by the exhaust valve opening / closing cam mechanism 14 at a predetermined timing. An electromagnetic exhaust valve cam control device 15 (VVT) is provided for the exhaust valve opening / closing cam mechanism 14. The exhaust valve cam control device 15 can advance or retard the opening / closing timing of the exhaust valve 6 via the exhaust valve opening / closing cam mechanism 14 in accordance with a control signal from the control unit C.

  An intake system (intake system) that supplies intake air to the combustion chamber 3 of each cylinder of the engine DE is provided with a single common intake passage 16 that is common to all cylinders. The front end (upstream end) of the common intake passage 16 is opened to the atmosphere, and an air cleaner (not shown) that removes dust and the like in the intake air sequentially from the upstream side in the flow direction of the intake air near the front end. And an air flow sensor 17 (see FIG. 3) for detecting the flow rate of the intake air.

  Further, in the common intake passage 16, electromagnetic intake control in which the valve opening degree (that is, the cross-sectional area of the common intake passage 16) is controlled by the control unit C in order from the upstream side in the intake air flow direction. A valve 18, a blower 19 a (compressor) of the exhaust turbocharger 19, and an air-cooled intercooler 20 are provided. Here, the blower 19a (exhaust turbocharger 19) supercharges the engine DE by pressurizing and compressing the intake air. In addition, the intercooler 20 cools the intake air whose temperature has increased due to pressurization and compression (substantially adiabatic compression) of the blower 19a.

  The common intake passage 16 branches into a first branch intake passage 16a and a second branch intake passage 16b on the downstream side of the intercooler 20, and both the branch intake passages 16a and 16b are gathered slightly downstream from the branch portion to be simply separated. One common intake passage 16 is formed. An electric supercharger 21 is provided in the first branch intake passage 16a. The electric supercharger 21 includes a compressor 21a disposed in the first branch intake passage 16a, and a motor 21b that rotates the compressor 21a when electric power is supplied from a battery (not shown) or an alternator (not shown). (Electric motor). On the other hand, the second branch intake passage 16b is provided with a check valve 22 for opening and closing the second branch intake passage 16b. Here, the check valve 22 closes the second branch intake passage 16b when the electric supercharger 21 (compressor 21a) is driven, and opens the second branch passage 16b when the electric supercharger 21 is stopped. open.

  The downstream end of the common intake passage 16 is connected to a surge tank 23 that attenuates the pulsation of the intake air and stabilizes the flow at the downstream side of the gathering portion of the first branch intake passage 16a and the second branch intake passage 16b. ing. A plurality of independent intake passages 24 for supplying intake air individually to the combustion chambers 3 of the respective cylinders are connected to the surge tank 23, and the downstream ends of these independent intake passages 24 are respectively connected to the intake ports 2 of the corresponding cylinders. It is connected. The surge tank 23 is provided with an intake pressure sensor 25 that detects the pressure of intake air.

  Further, the engine DE is provided with an exhaust system (exhaust system) that exhausts exhaust gas discharged from each combustion chamber 3 into the atmosphere, and this exhaust system has a single common exhaust passage common to each cylinder. 26 is provided. However, in the exhaust gas flow direction, in the vicinity of the upstream end (exhaust manifold), the exhaust system is branched for each cylinder and connected to the exhaust port 7 of the corresponding cylinder. The common exhaust passage 26 is provided with a turbine 19b of an exhaust turbocharger 19 driven by exhaust gas.

  The exhaust turbocharger 19 is a variable capacity supercharger (VGT) provided with a variable capacity mechanism capable of changing the passage cross-sectional area of the exhaust gas to the turbine 19b by a large number of movable vanes 27. The angle or direction of the movable vanes 27 is controlled by the movable vane actuator 28. Then, the control unit C changes the passage cross-sectional area of the exhaust gas via the movable vane actuator 28 and the movable vane 27, and the rotational speed of the turbine 19b (exhaust turbocharger 19), that is, the rotational speed of the blower 19a, As a result, supercharging pressure is controlled. The specific structure and function of the variable capacity mechanism of the exhaust turbocharger 19 will be described later (see FIG. 2).

  Further, in the common exhaust passage 26, an exhaust gas purification catalyst 30 for purifying exhaust gas and a particulate filter 31 (DPF) for collecting soot (particulates) downstream of the turbine 19b in the exhaust flow direction. An exhaust gas purification device 32 is provided.

  Although not shown, the exhaust gas purification catalyst 30 includes an oxidation catalyst (for example, a catalyst made of platinum, rhodium, palladium, etc.) that oxidizes and purifies HC and CO, and a reduction catalyst (platinum) that reduces and purifies NOx. , A catalyst made of barium, etc.) is supported on a support material made of, for example, zeolite, and the catalytic action or exhaust gas when the temperature is higher than the activation temperature (for example, 200 to 250 ° C.) It is a catalyst that effectively exhibits a purifying action. The soot collected by the particulate filter 31 is appropriately set to an operation state in which the exhaust gas purification catalyst 31 is heated to a high temperature when, for example, the differential pressure before and after the particulate filter 31 exceeds a set value. For example, by performing fuel injection in an expansion stroke, the fuel is burned and removed.

  A first temperature sensor 33 and a second temperature sensor 34 are respectively provided at a portion immediately downstream of the exhaust gas purification catalyst 30 and a portion downstream of the particulate filter 31 in the flow direction of the exhaust gas. It has been. Here, the first temperature sensor 33 detects the temperature of the exhaust gas exiting the exhaust gas purification catalyst 30. The temperature of the exhaust gas at this portion is related to or corresponds to the temperature of the exhaust gas purification catalyst 30, and is substantially the same as the temperature of the exhaust gas purification catalyst 30. Therefore, it can be said that the first temperature sensor 33 substantially detects the temperature of the exhaust gas purification catalyst 30. A temperature sensor that directly measures the temperature of the exhaust gas purification catalyst 30 may be provided.

  Further, the common exhaust passage 26 is provided with an exhaust on-off valve 35 for opening and closing the common exhaust passage 26 on the downstream side of the particulate filter 31 or the second temperature sensor 34. The valve opening degree of the exhaust opening / closing valve 35 (that is, the passage sectional area of the common exhaust passage 26) is controlled by the control unit C.

  Further, the engine DE mainly takes a part of the relatively high-pressure exhaust gas upstream of the turbine in the common exhaust passage 26 as EGR gas for the main purpose of reducing the amount of NOx generated due to fuel combustion. A high pressure EGR device 36 is provided for refluxing the system. The high pressure EGR device 36 is provided with a high pressure EGR passage 37 serving as an EGR gas flow path. Here, the upstream end of the high-pressure EGR passage 37 as viewed in the flow direction of the EGR gas is connected to the common exhaust passage 26 at a portion upstream of the turbine 19b as viewed in the flow direction of the exhaust gas. On the other hand, the downstream end of the high-pressure EGR passage 37 is connected to the surge tank 23 in the EGR gas flow direction. In the high-pressure EGR passage 37, a water-cooled high-pressure EGR cooler 38 that cools high-temperature (for example, 600 to 800 ° C.) EGR gas in order from the upstream side in the flow direction of the EGR gas, and the supply amount of EGR gas And a high-pressure EGR control valve 39 for controlling the.

  Further, the engine DE mainly has a purpose of reducing the amount of NOx generated due to fuel combustion, and a part of the relatively low pressure exhaust gas downstream of the particulate filter (downstream of the turbine) of the common exhaust passage 26. Is provided as a low-pressure EGR device 41 that recirculates gas to the intake system as EGR gas. The low pressure EGR device 41 is provided with a low pressure EGR passage 42 that serves as a flow path for EGR gas. Here, the upstream end of the low pressure EGR passage 42 as viewed in the flow direction of the EGR gas is connected to the common exhaust passage 26 at a portion between the particulate filter 31 and the exhaust opening / closing valve 35. On the other hand, the downstream end of the low pressure EGR passage 42 as viewed in the EGR gas flow direction is connected to the common intake passage 16 at a portion between the intake control valve 18 and the blower 19a. The low-pressure EGR passage 42 includes an air-cooled low-pressure EGR cooler 43 that cools the EGR gas and a low-pressure EGR control valve 44 that controls the supply amount of the EGR gas in order from the upstream side in the flow direction of the EGR gas. Is provided.

  Next, a specific structure and function of the variable capacity mechanism of the exhaust turbocharger 19 which is a variable capacity supercharger (VGT) will be described with reference to FIG. FIG. 2 is a cross-sectional view of the turbine 19 b of the exhaust turbocharger 19. As shown in FIG. 2, the turbine 19 b has a turbine chamber 52, and exhaust gas flows into the turbine chamber 52 in the direction indicated by the arrow D. In the turbine chamber 52, a plurality of movable vanes 27 are arranged so as to surround the turbine blades 53 on the exhaust gas inflow side, that is, the exhaust inlet side. Each of these movable vanes 27 can be rotated around a shaft 55, and the angle or direction of these movable vanes 27 is changed by the rotation.

  Here, as shown by a solid line in FIG. 2, if the movable vanes 27 are arranged close to each other, that is, if the movable vanes 27 extend in a direction closer to the circumferential direction of the turbine blade 53, each movable vane 27 is provided. The opening of the nozzles 54 formed therebetween (hereinafter referred to as “vane nozzle opening”) becomes small. In particular, if the vane nozzle opening is reduced when the engine speed is low, the exhaust gas flow rate increases, and the exhaust gas flow is directed in the tangential direction (circumferential direction) of the turbine 19b, so that the supercharging efficiency increases. . However, in this case, the exhaust pressure (exhaust gas pressure) of the engine DE increases.

  Further, as shown by a virtual line (two-dot chain line) in FIG. 2, if the movable vanes 27 are separated from each other, that is, the movable vanes 27 extend in a direction closer to the radial direction of the turbine blade 53, Vane nozzle opening increases. In particular, when the opening degree is increased when the engine speed is high, the flow rate of the exhaust gas can be increased, so that the supercharging efficiency is increased. The control unit C controls the angle or direction of the movable vanes 27, that is, the vane nozzle opening degree, from the fully closed position to the fully opened position via the movable vane actuator 28.

Hereinafter, the control system of the engine DE will be described.
As shown in FIG. 3, the engine DE is provided with various sensors for collecting various types of information regarding the operating state. That is, in addition to the air flow sensor 17, the intake pressure sensor 25, the first temperature sensor 33, and the second temperature sensor 34, an engine speed sensor 56 that detects the speed of the crankshaft 10 (engine speed), A crank angle sensor 57 that detects the crank angle, an engine water temperature sensor 58 that detects the coolant temperature of the engine DE (engine water temperature), an accelerator opening sensor 59 that detects the opening of the accelerator pedal (accelerator opening), An intake air temperature sensor 60 for detecting the temperature and a vehicle speed sensor 61 for detecting the vehicle speed are provided. Detection signals from these sensors are input to the control unit C as control information such as the engine DE.

  The control unit C is an overall control means for the engine DE or its accessory devices including the “deceleration control means” described in the section for solving the problems. Although not shown in detail, the control unit C includes an input / output unit (interface) that inputs and outputs control signals, a storage unit (ROM, RAM, and the like) that stores data and control information, and a central unit that performs various arithmetic processes. A computer including a processing unit (CPU), a timer, a counter, and the like.

  And the control unit C is based on the various data detected by each said sensor, the fuel injection valve 5, the intake valve cam control apparatus 13, the exhaust valve cam control apparatus 15, the intake control valve 18, the electric supercharger 21, By controlling or driving the check valve 22, movable vane actuator 28, exhaust opening / closing valve 35, high pressure EGR control valve 39, low pressure EGR control valve 44, etc., fuel injection control, EGR control, supercharging pressure control, particulate filter Of the electric supercharger 21 and the fuel injection valve 5 for performing normal engine control such as regeneration control of the engine 31 and generating an appropriate engine braking force when the engine DE or a vehicle equipped with the engine DE is decelerated. Control (hereinafter referred to as “engine brake control”) is performed. However, the control method for ordinary engine control is well known to those skilled in the art, and since such ordinary engine control is not the gist of the present invention, the description thereof is omitted.

  Hereinafter, according to the flowchart shown in FIG. 4, the control procedure of the engine brake control according to the present invention, which is executed by the control unit C, will be specifically described. As shown in FIG. 4, in this engine brake control, when the control is started (start), first, in step S1, the physical property values or detections detected by the sensors 17, 25, 33, 34, 56 to 61 are detected. Various signals corresponding to the values are read.

  Next, in step S2, it is determined whether or not the engine DE (or vehicle) is in a decelerating state based on the accelerator opening or the decreasing speed. Here, when it is determined that the engine DE is in a deceleration state (YES), in steps S3 to S7, the engine DE or the driving state or driving environment of the vehicle, or the engine braking force corresponding to the driver's deceleration request is applied. Control is performed to produce it. As will be described later, when it is determined that the engine DE is not in a deceleration state (NO), normal electric supercharger control or fuel injection control in which engine braking force is not controlled in steps S8 to S11. Is done.

  When it is determined in step S2 that the engine DE is in a decelerating state, first, in step S3, the temperature of the exhaust gas purification catalyst 30 or a temperature related thereto (hereinafter referred to as “catalyst temperature”) is set in advance. It is determined whether or not the temperature α is exceeded. Here, the reference temperature α is set to the activation temperature of the exhaust gas purification catalyst 30 or a temperature slightly higher (for example, 10 ° C.).

  If it is determined in step S3 that the catalyst temperature exceeds the reference temperature α (YES), in step S4, the electric supercharger 21 is operated at the number of revolutions corresponding to the vehicle speed, deceleration, etc. The valve 22 is closed. Subsequently, in step S5, fuel injection from the fuel injection valve 5 is stopped (fuel cut), and thereafter, the process returns to step S1 (return). That is, in steps S4 to S5, the engine supercharging force is controlled so as to obtain the required deceleration by operating the electric supercharger 21 during deceleration to control the amount of intake air flowing into the combustion chamber 3. By cutting the fuel, the engine braking force is increased and the fuel efficiency is improved.

  FIG. 5 shows the relationship between the accelerator return speed and the required deceleration. The accelerator return speed is the rate of change in the decreasing direction of the accelerator pedal depression amount, that is, the accelerator opening decreasing speed. The requested deceleration is the engine DE or the deceleration of the vehicle, that is, the rate of change in the speed decreasing direction, which is requested according to the intention of the driver of the vehicle or the traveling state of the vehicle. As is apparent from FIG. 5, the required deceleration is larger as the accelerator return speed is larger. Such control of the engine braking force is optimal when the required deceleration is not obtained by simply returning the accelerator pedal, although the deceleration enough to use the foot brake is not required. .

  FIG. 6 shows the relationship between the vehicle speed and the requested deceleration. As is apparent from FIG. 6, the required deceleration increases as the vehicle speed increases in the low speed range, but conversely in the high speed range, the required deceleration decreases as the vehicle speed increases. This is because, when the vehicle speed reaches a certain level, the engine braking force acts as a strong brake on the drive wheels to reduce the running stability of the vehicle, so that it is necessary to moderately control the deceleration in the high speed range.

  Thus, in this engine brake control, basically, the engine braking force is based on the accelerator return speed, the vehicle speed, the gear ratio of the transmission, etc. so as to satisfy the request for the accelerator return speed and the request for the vehicle speed. To control. The engine braking force is generated by the compression work of the intake air entering the combustion chamber 3, but this compression work is generally considered to be a wasteful work. In this type of conventional engine or vehicle, when fuel is decelerated, fuel efficiency is improved by cutting the fuel or opening the movable vane 27 of the variable displacement turbocharger (VGT). Not done.

  In the engine brake control according to the present invention, by using the electric supercharger 21, even when the exhaust turbocharger 19 (VGT) is in operation or in a fuel cut state, the engine brake is effectively used to drive the vehicle. The deceleration required by the person can be realized. As described above, in this engine brake control, the required deceleration is calculated or set based on the accelerator return speed according to the request of the driver of the vehicle and the vehicle speed that is the driving state of the vehicle. In order to adjust or control the required deceleration as described above, it is necessary to know in advance the relationship between the driving force of the vehicle and the running resistance of the vehicle at that time.

  FIG. 7 shows the change characteristics of the driving force of the vehicle and the normal running resistance of the vehicle with respect to the vehicle speed. As is apparent from FIG. 7, the driving force of the vehicle becomes smaller as the transmission gear ratio is higher (high speed stage). Further, in a normal traveling state, the traveling resistance of the vehicle increases as the vehicle speed increases.

  FIG. 8 is a basic map for engine brake control, for example, which takes the relationship between the driving force of the vehicle and the running resistance of the vehicle shown in FIG. 7 and shows the required deceleration as the vehicle speed and the accelerator return speed as parameters. It is. This basic map is stored in advance in the memory of the control unit C. In step S4, the required deceleration at that time is calculated or set based on the gear ratio of the transmission being used, the vehicle speed, the accelerator return speed, and the like using this basic map. As shown in FIG. 8, in this basic map, the required deceleration is basically set so as to decrease as the vehicle speed increases and to increase as the accelerator return speed increases. For example, when the vehicle speed is low and the access return speed is high, the set required deceleration becomes large.

  Then, the electric turbocharger 21 is driven to perform supercharging so that the amount of intake air that can be generated by the engine DE at a torque corresponding to the required deceleration calculated based on the basic map, and the required deceleration is achieved. Appropriate engine braking force is obtained. When the electric supercharger 21 is stopped, the electric supercharger 21 is gently stopped for a certain period of time in order to prevent a sudden change in the engine braking force or deceleration generated in this way. It is necessary.

  On the other hand, when it is determined in step S3 that the catalyst temperature is equal to or lower than the reference temperature α (NO), in step S6, the electric supercharger 1 is stopped and the check valve 22 is opened. Subsequently, in step S7, fuel is injected from the fuel injection valve 5 with the injection amount corrected to decrease. As described above, in spite of the deceleration, the electric supercharger 21 is stopped and the fuel is injected with the injection amount corrected for reduction. The exhaust gas is caused by lowering the catalyst temperature by raising the temperature of the exhaust gas. This is to prevent a decrease in the activity of the purification catalyst 30. Thereafter, the process returns to step S1 (return).

  By the way, when it is determined in step S2 that the engine DE is not in a decelerating state (NO), normal control without engine brake force control is performed as described above. In this case, first, in step S8, It is determined whether or not the engine DE (or the vehicle) is in an acceleration state based on the accelerator opening or the increasing speed. In general, when the accelerator pedal is depressed and the engine DE starts accelerating, a supercharging delay (turbo lag) due to the operation delay of the turbine 19b and the blower 19a of the exhaust turbocharger 19 with respect to the depressing operation of the accelerator pedal. Occurs. For this reason, the intake air becomes insufficient due to a delay in the rise (supercharging) of the intake air pressure, and the engine DE cannot be accelerated quickly. Therefore, in this engine DE, when the engine DE is in an acceleration state, the electric supercharger 21 is driven to assist the increase (supercharging) of the intake air pressure, thereby preventing or suppressing the occurrence of the supercharging delay. I am doing so.

  If it is determined in step S8 that the engine DE is in an accelerated state (YES), in step S3, the electric supercharger 21 is operated at a predetermined operating rotational speed (for example, 50,000 to 70000 rpm), but a check is not performed. The valve 22 is closed. In this case, the intake air is quickly pressurized by the electric supercharger 21 to prevent or suppress the occurrence of a supercharging delay. Next, after normal fuel injection control is performed in step S11, the process returns to step S1 (return).

  On the other hand, if it is determined in step S8 that the engine DE is not in an accelerated state (NO), there is no need to drive the electric supercharger 21, so that the electric supercharger 21 is stopped in step S10 and a check is made. The valve 22 is opened. In this case, the intake air bypasses the electric supercharger 21 and flows via the second branch intake passage 16b. Thereafter, the process returns to step S1 (return).

  As described above, the engine DE or engine brake control according to the first embodiment effectively prevents the exhaust gas purification catalyst 30 from lowering below the activation temperature when the engine DE or the vehicle is decelerated, while the driver. Or, the engine braking force can be appropriately adjusted according to the required deceleration of the vehicle.

(Embodiment 2)
The second embodiment of the present invention will be described below with reference to FIGS. However, the second embodiment is substantially the same as the first embodiment except that the engine is an ignition spark type gasoline engine instead of a diesel engine, and the differences that accompany this. Therefore, in the following, in order to avoid duplication of explanation, differences from the first embodiment will be mainly described. Although the reciprocating type gasoline engine is described in the second embodiment, the present invention is applied to other spark ignition type engines, for example, reciprocating type or rotary type spark ignition engines using hydrogen or propane as fuel. Of course it can also be applied.

  As shown in FIGS. 9 and 10, in the gasoline engine CE (hereinafter referred to as “engine CE” for short), when the intake valve 1 is opened, an air-fuel mixture is introduced into the combustion chamber 3 from the intake port 2. Inhaled. Then, the air-fuel mixture in the combustion chamber 3 is compressed by the piston 4, and is ignited and burned by the spark plug 63 at a predetermined timing. Gas generated by combustion, that is, exhaust gas, is discharged to the exhaust port 7 when the exhaust valve 6 is opened. These series of operations are repeated, and the piston 4 repeats reciprocating motion in the cylinder 8. The mechanism for converting the reciprocating motion of the piston 4 into the rotational motion of the crankshaft 10 and the mechanism for starting the engine CE are the same as those of the engine DE according to the first embodiment.

  In the intake system of the engine CE, the intake control valve 18 is not provided in the common intake passage 16. A throttle valve 64 is provided in the common intake passage 16 on the downstream side of the electric supercharger 21. Further, each independent intake passage 24 is provided with a fuel injection valve 65 for injecting fuel. The fuel injection valve 65 may inject fuel directly into the combustion chamber 3. In addition, since the engine CE is a gasoline engine, it does not include a common rail for a diesel engine. Other configurations of the intake system of the engine CE are the same as those of the engine DE according to the first embodiment.

  In the exhaust system of the engine CE, in order to purify the exhaust gas in the common exhaust passage 26 on the downstream side of the turbine 19b of the exhaust turbocharger 19, an exhaust gas provided with an exhaust gas purification catalyst 66 made of, for example, a three-way catalyst. A purification device 32 is interposed. Since the engine CE is a gasoline engine and soot is not generated, no particulate filter is provided in the exhaust gas purification device 32. Further, no exhaust opening / closing valve is provided in the common exhaust passage 26. Other configurations of the exhaust system of the engine CE are the same as those of the engine DE according to the first embodiment.

  In the engine CE, as in the engine DE, a high-pressure EGR device 36 that recirculates a part of the relatively high-pressure exhaust gas upstream of the turbine in the common exhaust passage 26 to the intake system as EGR gas is provided. The high-pressure EGR device 36 includes a high-pressure EGR passage 37, a high-pressure EGR cooler 38, and a high-pressure EGR control valve 39, like the engine DE. However, the engine CE is not provided with a low pressure EGR device.

  The control unit C controls the ignition plug 63, the throttle valve 64, and the fuel injection valve 65, and performs engine throttle control, fuel injection control, and ignition timing control in a gasoline engine, except that the engine performs normal throttle valve opening control, fuel injection control, and ignition timing control. The same engine control as in the case of DE is performed. Further, the control unit C basically performs engine brake control similar to that in the case of the engine DE according to the flowchart shown in FIG. In the engine CE, the temperature of the exhaust gas purification catalyst 66 or the temperature (catalyst temperature) related thereto is detected by the second temperature sensor 34.

  Other configurations and functions of the engine CE are the same as those of the engine DE. Thus, in the second embodiment, as in the first embodiment, the exhaust gas purification catalyst 66 (for example, a three-way catalyst) of the engine CE is effectively prevented from lowering its activation temperature when the vehicle is decelerated. However, the engine braking force can be appropriately adjusted according to the driver's or vehicle's required deceleration.

It is a schematic diagram which shows the system configuration | structure of the diesel engine which concerns on Embodiment 1 of this invention. It is side surface sectional drawing of the turbine of the exhaust gas turbocharger of the engine shown in FIG. It is a block diagram which shows the structure of the control system of the engine shown in FIG. It is a flowchart which shows the control procedure of the engine brake control of the engine shown in FIG. It is a graph which shows the relationship between an accelerator return speed and a request | requirement deceleration. It is a graph which shows the relationship between a vehicle speed and a request | requirement deceleration. It is a graph which shows the change characteristic with respect to the vehicle speed of the driving force and running resistance of a vehicle. It is a basic map for calculating the required deceleration using the vehicle speed and the accelerator return speed as parameters. It is a schematic diagram which shows the system configuration | structure of the gasoline engine which concerns on Embodiment 2 of this invention. It is a block diagram which shows the structure of the control system of the engine shown in FIG.

Explanation of symbols

  DE diesel engine, CE gasoline engine, C control unit, 1 intake valve, 2 intake port, 3 combustion chamber, 4 piston, 5 fuel injection valve, 6 exhaust valve, 7 exhaust port, 8 cylinder (cylinder), 9 connecting rod, 10 crankshaft, 11 engine starter, 12 intake valve opening / closing cam mechanism, 13 intake valve cam control device, 14 exhaust valve opening / closing cam mechanism, 15 exhaust valve cam control device, 16 common intake passage, 16a first branch intake passage, 16b first 2-branch intake passage, 17 air flow sensor, 18 intake control valve, 19 exhaust turbocharger, 19a blower, 19b turbine, 20 intercooler, 21 electric supercharger, 21a compressor, 21b motor, 22 check valve, 23 surge Tank, 24 independent intake passages, 25 intake pressure Sensor, 26 common exhaust passage, 27 movable vane, 28 movable vane actuator, 30 exhaust gas purification catalyst, 31 particulate filter, 32 exhaust gas purification device, 33 first temperature sensor, 34 second temperature sensor, 35 exhaust opening / closing valve, 36 High pressure EGR device, 37 High pressure EGR passage, 38 High pressure EGR cooler, 39 High pressure EGR control valve, 41 Low pressure EGR device, 42 Low pressure EGR passage, 43 Low pressure EGR cooler, 44 Low pressure EGR control valve, 52 Turbine chamber, 53 Turbine blade, 54 nozzle, 55 movable vane shaft, 56 engine speed sensor, 57 crank angle sensor, 58 engine water temperature sensor, 59 accelerator opening sensor, 60 intake air temperature sensor, 61 vehicle speed sensor, 63 spark plug, 64 throttle valve, 65 fuel Injection valve, 66 exhaust gas Catalyst.

Claims (5)

An electric supercharger having a compressor disposed in the intake passage and a motor for driving the compressor;
An exhaust gas purification device disposed in the exhaust passage;
An engine supercharger comprising: deceleration control means for stopping the fuel supply to the engine and operating the electric supercharger when the engine or a vehicle equipped with the engine is decelerated apparatus. The engine includes temperature detecting means for detecting the temperature of the exhaust gas purifying device or a temperature related to the temperature;
The deceleration control means stops the operation of the electric supercharger and corrects the fuel supply to the engine to be reduced when the temperature detected by the temperature detection means is equal to or lower than a preset reference temperature. The supercharging device for an engine according to claim 1, wherein the supercharging device for the engine is configured to be performed as described above. An exhaust turbocharger, and an intercooler disposed in the intake passage downstream from the blower of the exhaust turbocharger,
The supercharger for an engine according to claim 1, wherein the electric supercharger is disposed in the intake passage downstream from the intercooler.   The said deceleration control means is comprised so that the operating rotation speed of the said electric supercharger may be set according to the request | requirement deceleration of this engine or the vehicle carrying the engine. The engine supercharger described in 1.   The said deceleration control means is comprised so that the said required deceleration may be calculated based on at least 1 parameter among a vehicle speed, an accelerator return speed, and the gear ratio of a transmission. Engine supercharger.

Images