JP2008045524A - Supercharger of diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a good balance between acceleration response and exhausting performance even if fuel injection is executed immediately after an acceleration request. <P>SOLUTION: A cooling air intake passage 15 and a bypass air intake passage 17 are provided at an air intake passage. An inter cooler 16 is provided in the cooling air intake passage 15 and the bypass air intake passage 17 introduces intake air to an engine main body 1 bypassing the inter cooler 16. An electric supercharger 18 is provided for this bypass air intake passage 17. During normal operation, route switch means 20, 21, 100 stop the electric supercharger 18 by switching a route in an air intake passage 10 to a cooling route PH1. On the other hand, in the case where a predetermined acceleration condition is satisfied, the electric supercharger 18 is actuated by switching a route in the air intake passage 10 to a supercharging route PH2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a turbocharger for a diesel engine, and more particularly to a turbocharger for a diesel engine employing an exhaust turbocharger.

  In order to improve the performance of an engine employing an exhaust turbocharger, as disclosed in Patent Document 1, a passage that bypasses the intercooler provided in the intake passage is provided, and in a predetermined operating state, the intercooler There is known a gasoline engine that prevents the intake air temperature from being excessively reduced by bypassing the engine.

On the other hand, recently, as disclosed in Patent Document 2, as a means for increasing the engine torque, an exhaust turbocharger and an electric supercharger are used in combination, and an operation in which turbocharging is insufficient during acceleration is performed. Engines that supplement the supercharging capability with electric superchargers in the area are known.
Japanese Patent Laid-Open No. 62-60926 JP 2004-108152 A

  By the way, when the diesel engine is accelerated again after decelerating from the high-speed operation state, or when the accelerator pedal is stepped on suddenly in a steady operation at a low load, sufficient exhaust performance is ensured. For this reason, in the configurations of Patent Documents 1 and 2, acceleration response must be reduced. Especially when an EGR that improves exhaust performance by returning a part of the exhaust gas to the intake passage is used, or when a variable capacity turbocharger that can change the supercharging capacity is used. During acceleration, since EGR remaining in the intake passage is supplied to the combustion chamber, there is a problem that smoke is generated even if the fuel injection amount is increased immediately after acceleration. Therefore, it has been extremely difficult to achieve both the acceleration response and the exhaust performance.

  This invention is made | formed in view of the said malfunction, and makes it the subject to provide the supercharging apparatus of the diesel engine which can make acceleration response and exhaust performance compatible.

  In order to solve the above-described problems, the present invention provides a turbocharger for a diesel engine having an exhaust turbocharger having a compressor wheel in an intake passage, and is disposed downstream of the compressor wheel and an intercooler is disposed. A cooling intake passage, a bypass intake passage that bypasses the intercooler, an electric supercharger that is disposed in the bypass intake passage and supercharges air in the bypass intake passage, and the electric supercharger And a path switching means for switching the intake path to at least one of a supercharging path for guiding the intake air to the engine body and a cooling path for guiding the intake air from the intercooler to the engine body, and depending on the operating state of the engine body Path switching means and control means for controlling the operation of the electric supercharger. The path in the intake passage is switched to the cooling path to stop the electric supercharger, and when a predetermined acceleration condition is satisfied, the path in the intake path is switched to the supercharge path to change the electric supercharger. A turbocharger for a diesel engine characterized by being operated. In this aspect, during normal operation, the intake passage is supplied to the engine body while being supercharged to the compressor wheel of the exhaust turbocharger via the cooling path. On the other hand, when a predetermined acceleration condition (for example, a state where the accelerator pedal is stepped on suddenly from the low load operation state) is established, the path of the intake passage is switched to the supercharging path, and the electric supercharger in the supercharging path Operates. For this reason, since the supercharged fresh air is supplied to the engine body bypassing the intercooler, the airflow resistance can be reduced and the supercharged air can be supplied quickly, so that the blowdown energy can be increased quickly and the exhaust The supercharging pressure by the turbocharger can be increased in a short time. As a result, even if the fuel injection is executed immediately after the acceleration request, it is possible to prevent the exhaust performance from being deteriorated. Therefore, it becomes possible to enhance the responsiveness as much as possible and to maintain the exhaust performance.

  In a preferred embodiment, the bypass intake passage also bypasses the compressor wheel of the exhaust turbocharger. In this aspect, it is possible to reduce the air resistance of the compressor wheel having a low supercharging pressure immediately after acceleration.

  In a preferred aspect, the control means, when the electric turbocharger is operating after the acceleration condition is satisfied, when the supercharging pressure of the exhaust turbocharger reaches a predetermined value or more, The electric supercharger is stopped by switching the path to the cooling path during normal operation. In this aspect, since the electric supercharger can be operated in a necessary and sufficient operating range, it is possible to achieve both reduction in exhaust performance and improvement in acceleration response while saving power consumption.

  In a preferred embodiment, the communication passage that connects the downstream side of the intercooler of the cooling intake passage and the upstream side of the electric supercharger of the bypass intake passage, and the communication passage is opened and closed by control of the control means. The control means includes an acceleration degree determining means for determining an acceleration degree when the acceleration condition is satisfied, and the control means determines whether the acceleration degree determined by the acceleration condition determining means is a predetermined threshold when the acceleration condition is satisfied. When the value is equal to or greater than the value, the communication on-off valve is closed, and when the acceleration degree is less than the threshold value, the communication path is opened. In this aspect, when the acceleration condition is satisfied and the acceleration degree is equal to or greater than a predetermined threshold, fresh air is quickly supplied to the engine body through a path with a small resistance, and the urgency of the fresh air supply is relatively low. Therefore, it is possible to increase the supercharging pressure while preventing the exhaust performance from being lowered by increasing the blow energy in a particularly high operating region. On the other hand, when the acceleration degree is less than the predetermined threshold value, the cooling path and the supercharging path are communicated with each other through the communication path, so that the fresh air cooled by the intercooler is supercharged by the electric supercharger. In this state, it is supplied to the engine body. As a result, in the operation region where the urgency of fresh air supply is relatively low, the cooled fresh air with a high oxygen concentration can be supercharged and supplied to the engine body, so that the charging efficiency can be improved. It is possible to increase the supercharging pressure by the exhaust turbocharger while further improving the exhaust performance.

  In a preferred aspect, an EGR passage that recirculates a part of the exhaust gas from the exhaust passage of the engine body to the downstream side of the intercooler of the intake passage, and an EGR opening / closing valve that opens and closes the EGR passage under the control of the control means And an intake air temperature sensor that detects an intake air temperature supplied to the engine main body downstream of the bypass intake passage and the EGR passage and outputs a detected value to the control means. When the acceleration condition is established, the higher the intake air temperature detected by the intake air temperature sensor, the higher the rotational speed of the electric supercharger is operated. In this aspect, when the EGR is returned to the intake passage, the higher the intake air temperature, the higher the supercharging pressure by the electric supercharger, and the effect of lowering the intake air temperature. It is possible to increase the supercharging pressure by the exhaust turbocharger while further improving the exhaust performance.

  In a preferred aspect, the control means closes the EGR opening / closing valve when the acceleration condition is satisfied when the EGR opening / closing valve is opened. In this aspect, even in the EGR region where the EGR is recirculated to the intake air, it is possible to stop the recirculation of the EGR when the acceleration is requested, and increase the supercharging pressure to improve the acceleration response.

  As described above, according to the present invention, when a predetermined acceleration condition is satisfied, the supercharged fresh air is supplied to the engine body bypassing the intercooler, so that fuel injection is executed immediately after the acceleration request. However, since the exhaust performance can be prevented from being lowered, the acceleration response and the exhaust performance can both be achieved.

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

  FIG. 1 is an overall configuration diagram of an engine including a supercharging device according to an embodiment of the present invention.

  Referring to FIG. 1, an engine body 1 of a diesel engine shown in FIG. 1 is provided with a plurality of cylinders (4 cylinders in the illustrated example) 1 a to 1 d. A combustion chamber 2 is formed in each of the cylinders 1a to 1d. Each combustion chamber 2 has an intake port and an exhaust port, and an intake valve 3 and an exhaust valve 4 are provided at these ports. Furthermore, a fuel injection valve 6 is provided for each combustion chamber 2. In the present embodiment, if the cylinders 1a to 1d are defined as the first cylinder 1a to the fourth cylinder 1d, the combustion order is that of the first cylinder 1a, the third cylinder 1c, the fourth cylinder 1d, and the second cylinder 1b. It is in order.

  Connected to the engine body 1 are an intake passage 10 for supplying fresh air to the cylinders 1a to 1d and an exhaust passage 30 for deriving exhaust gas from the cylinders 1a to 1d.

  The intake passage 10 includes an intake manifold 12 having an intake passage 11 for each cylinder connected to the intake ports of the cylinders 1a to 1d, and a common intake passage 13 upstream thereof.

  An air cleaner 14 is provided on the upstream side of the common intake passage 13.

  Between the downstream side of the air cleaner 14 of the common intake passage 13 and the intake manifold 12, a cooling intake passage 15 constituting a cooling passage PH1 used during normal operation and an intercooler 16 provided in the cooling intake passage 15 are provided. A bypass intake passage 17 is provided in parallel to bypass the. An electric supercharger 18 is provided in the bypass intake passage 17, and a supercharging path PH <b> 2 is configured in a passage after the electric supercharger 18. The electric supercharger 18 is constituted by an impeller or the like directly driven by an electric motor. The electric motor of the electric supercharger 18 is configured to be able to supply power from both an alternator and a battery (not shown).

  Further, in the illustrated embodiment, a communication passage 19 that connects the cooling intake passage 15 and the bypass intake passage 17 is provided. The communication path 19 communicates the downstream side of the intercooler 16 and the upstream side of the electric supercharger 18. In order to change the route of the intake passage 10, a bypass on-off valve 20 and a communication on-off valve 21 are provided in the bypass intake passage 17 and the communication passage 19, respectively.

  Next, the exhaust passage 30 includes an exhaust manifold 32 having exhaust passages 31a to 31d for each cylinder connected to exhaust ports of the respective cylinders 1a to 1d, a common exhaust pipe 33 downstream thereof, and a downstream of the common exhaust pipe 33. And a diesel smoke purification device 34 connected to the vehicle.

  The diesel smoke purification device 34 has a catalytic function and collects exhaust smoke fine particles of diesel smoke. Although simplified in the figure, specifically, the oxidation catalyst and the oxidation catalyst And a particulate filter unit disposed on the downstream side.

  A variable capacity supercharger (VGT) 40 as an exhaust turbocharger is provided between the intake passage 10 and the exhaust passage 30.

  The variable capacity supercharger 40 includes a turbine wheel 41 that rotates by being driven by the energy of exhaust gas, and a compressor wheel 43 that is connected to the turbine wheel 41 via a shaft 42. The intake air is supercharged by the rotation of the linked compressor wheel 43.

  FIG. 2 is a schematic enlarged cross-sectional view of the turbine chamber of the variable capacity turbocharger according to the embodiment of FIG.

  Referring to FIG. 2, the turbine wheel 41 of the variable capacity supercharger 40 according to the present embodiment has a turbine chamber 41a into which exhaust gas flows in the direction of the arrow, and at the entrance side of the turbine chamber 41a. A plurality of vane shafts 41c are equally arranged at intervals along a circumference of a circle concentric with the turbine blade 41b. Each vane shaft 41c supports a movable vane 41d. The movable vane 41d constitutes an air vane nozzle that drives the turbine blade 41b, and is configured to be rotatable within a predetermined range around the corresponding vane shaft 41c. And the opening (vane opening) of a vane nozzle changes with rotation of each movable vane 41d, and it is comprised so that a supercharging amount can be adjusted.

  More specifically, as shown by a solid line in FIG. 2, if the movable vane 41d is displaced so as to be close to each other, that is, the movable vane 41d extends in a direction close to the circumferential direction, the vane opening degree is Get smaller. On the other hand, as shown by the phantom line in FIG. 2, if the movable vane 41d is displaced so as to be separated from each other, that is, the movable vane 41d extends in a direction close to the radial direction, the vane opening degree increases.

  When the vane opening is small, the flow rate of the exhaust gas in the turbine chamber 41a is increased, and the flow of the exhaust gas is directed in the tangential direction of the turbine blade 41b, so that the supercharging efficiency is increased. However, when the vane nozzle is throttled, the exhaust pressure increases. Therefore, the vane opening is set small to increase the supercharging efficiency when the rotational speed of the engine body 1 is relatively low.

  On the other hand, when the vane opening degree is large, the exhaust pressure does not increase, but the flow rate in the turbine chamber 41a becomes slow. Therefore, if the flow rate of the exhaust gas entering the turbine chamber 41a is slow, the supercharging force decreases. Therefore, the vane opening is set to be large when the rotational speed of the engine body 1 is relatively high.

  The movable vane 41d is driven by an engine control unit 100, which will be described in detail later, by a negative pressure pushing type actuator 41e (see FIG. 1). Although not specifically shown, the turbine wheel 41 is provided with a waste gate valve, and an upper limit of the supercharging pressure is set with a predetermined supercharging pressure as an intercept point IP.

  Returning to FIG. 1, the turbine wheel 41 of the variable capacity supercharger 40 is interposed in the common exhaust pipe 33. The compressor wheel 43 is interposed at the upstream end of the cooling intake passage 15. The intercooler 16 is configured to cool the air supercharged to the compressor wheel 43.

  Next, a high pressure EGR passage 50 and a low pressure EGR passage 60 are provided between the intake passage 10 and the exhaust passage 30.

  The high-pressure EGR passage 50 communicates between the upstream side of the common exhaust pipe 33 with respect to the turbine wheel 41 and the intake manifold 12 (downstream side with respect to the intercooler 16), and drives the variable displacement supercharger 40. A part of the previous exhaust gas having a relatively high temperature and high pressure is returned to the intake passage 10.

  The low pressure EGR passage 60 communicates between the downstream side of the common exhaust pipe 33 from the turbine wheel 41 and the downstream side of the intercooler 16 of the cooling intake passage 15 to drive the variable capacity supercharger 40. A part of the later exhaust gas having a relatively low pressure is returned to the intake passage 10. The cooling intake passage 15 is provided with a one-way valve 22 that prevents the EGR from the low pressure EGR passage 60 from flowing backward to the upstream side of the intake passage 10.

  The EGR passages 50 and 60 are provided with EGR opening / closing valves 51 and 61, respectively, and are controlled to be opened and closed by an engine control unit 100 described later. In addition, EGR coolers 52 and 62 are provided on the upstream side (exhaust side) of the EGR open / close valves 51 and 61.

  In order to detect the operating state of the engine as described above, the engine body 1 is provided with a speed sensor SW1 that detects the rotational speed of a crankshaft (not shown).

  In the intake passage 10, in order to detect the air flow rate immediately after passing through the air cleaner 14, the common intake passage 13 is downstream of the air cleaner 14 and upstream of the cooling intake passage 15 and the bypass intake passage 17. An airflow sensor SW2 disposed on the side is provided. Next, the intake manifold 12 is provided with an intake air temperature sensor SW3 for detecting the intake air temperature and an intake air pressure sensor SW4 for detecting the intake air pressure in the same manner as a known configuration. Further, the cooling intake passage 15 is provided with a supercharging pressure sensor SW5 for detecting the supercharging pressure.

  Further, the engine is provided with an accelerator sensor SW6 that detects the amount of depression of the accelerator pedal 70.

  Furthermore, an engine control unit 100 is provided in the engine. The engine control unit 100 includes a CPU 101, a memory 102, an interface 103, and a bus 104 for connecting these units 101 to 103.

  Various sensors including the sensors SW1 to SW6 are connected to the interface 103 as input elements, and the operation state can be determined by receiving detection signals from the sensors SW1 to SW6 and the like. The interface 103 is connected to an unillustrated controller and driver as output elements, and the electric supercharger 18, the on-off valves 20, 21 and the EGR on-off valves 51, 61 are connected via these units. It is comprised so that it can drive.

  The memory 102 stores a program and data for controlling the entire engine, and the engine control unit 100 executes the route of the intake passage 10 by executing the program based on a flowchart described in detail later. A path switching means for switching to one of the cooling path PH1 and the supercharging path PH2, a control means for controlling the electric supercharger 18, and an acceleration judgment means for judging acceleration are functionally configured.

  First, in order to control the vane opening degree of the variable capacity supercharger 40 described above, the memory 102 has control maps M1 (see FIG. 7) and M2 (see FIG. 8) based on the graphs of FIGS. , M3 (see FIG. 7), and M4 (see FIG. 9) are stored.

  FIG. 3 is a characteristic diagram showing the relationship between the accelerator opening and the engine speed for explaining the control map M1 of the high-pressure and low-pressure EGR on-off valves 51 and 61.

  Referring to FIG. 3, the non-EGR region A for stopping the EGR reflux is set on the relatively high speed side or the high load side, and the EGR reflux is required in the other low, medium and high speed, low and medium load operation regions. Each EGR area B is set. In the low pressure region B1 on the relatively high speed and high load side in the EGR region B, the EGR from the low pressure EGR passage 60 where the pressure of EGR is low is set to return to the intake passage 10, and in the remaining region, The EGR from the high pressure EGR passage 50 is set to return to the intake passage 10.

  The operation areas A and B based on FIG. 3 are stored in the memory 102 as a control map M1 based on data obtained through experiments or the like.

  Next, FIG. 4 is a characteristic diagram of the accelerator opening and the engine speed for explaining the target oxygen concentration control map M2 for determining the EGR amount.

  Referring to FIGS. 1 and 4, in EGR region B, for example, each EGR on-off valve 51, 61 is opened so that the actual oxygen concentration of the intake air supplied to intake manifold 12 becomes a predetermined target oxygen concentration. The valve amount is feedback controlled.

  In the example of FIG. 4, the target oxygen concentration is set with the engine speed and the accelerator opening as parameters, and is set so as to decrease as the engine speed decreases and as the accelerator opening decreases. ing.

  The characteristics of the target oxygen concentration are stored in the memory 102 as a control map M2 based on data obtained through experiments or the like.

  However, the reason why the target oxygen concentration is set to be smaller as the load is lower in this way is to reduce NOx particularly at a low load, and the method for setting the target oxygen concentration is not limited to this. Is.

  In the present embodiment, a program for detecting (estimating) oxygen concentration using existing sensors SW3 and SW4 is stored in the memory 102 from the viewpoint of cost reduction. This program is executed based on the following principle.

  First, the intake air density is calculated from the intake air temperature detected by the intake air temperature sensor SW3 and the intake air pressure detected by the intake air pressure sensor SW4. Next, the filling amount is calculated from the intake air density and the volumetric efficiency determined by the engine operating state. Since the intake amount of fresh air passing through the air cleaner 14 is detected by the air flow sensor SW2, the EGR amount is calculated by subtracting the detected fresh air amount from the calculated filling amount. Since the oxygen concentration of fresh air is known, if the oxygen concentration of the EGR recirculated this time can be known, the oxygen concentration of the intake air in the intake manifold 12 can be known. Then, the oxygen concentration of the EGR refluxed this time is estimated by delaying the oxygen concentration of the EGR estimated in the past. Here, since the fuel injection amount is a value set by the engine control unit 100 itself, it can be known, and the amount of oxygen consumed (related to combustion) according to the fuel injection amount can be easily known. Therefore, when the intake air containing the exhaust gas having a certain oxygen concentration estimated in the past is exhausted as the exhaust gas from the combustion chamber after being combusted, based on the above-mentioned known information, You can know the oxygen concentration. The oxygen concentration of the exhaust gas exhausted this time takes into account the passage length (volume) of the EGR passage 50 (60) used, etc., and the intake manifold is subsequently used by a delay process until it is introduced into the intake manifold 12. 12 is used as the oxygen concentration of EGR introduced into the No. 12. At the start of EGR, an estimated initial value of the oxygen concentration in the EGR introduced into the intake manifold 12 is used. The estimated initial value is stored in advance in the memory 102 as a predetermined value determined experimentally, for example.

  FIG. 5 is a characteristic diagram for explaining a control map M3 of the variable capacity supercharger 40 according to the embodiment of FIG.

  Referring to FIG. 5, as described above, the vane opening degree is relatively high after the intercept point IP has elapsed, until the intercept point IP is reached. It is set to open with a gradient.

  The characteristics of the vane opening are stored in the memory 102 as a control map M3 based on data obtained through experiments or the like.

  FIG. 6 is a characteristic diagram showing the relationship between the intake air temperature and the electric supercharger rotational speed for explaining the control map M4 of the electric supercharger 18 according to the embodiment of FIG.

  Referring to FIG. 6, smoke is likely to be generated when the intake air temperature becomes a predetermined value (for example, 40 ° C.) or more. Therefore, when an acceleration request is made in EGR region B in this embodiment, as will be described later. The EGR on-off valves 51 and 61 are both fully closed to suppress the rise in intake air temperature. However, a considerable amount of EGR may still remain in the intake manifold 12 and the intake air temperature may increase. Therefore, in the present embodiment, in order to prevent the occurrence of smoke when the acceleration is requested, the rotational speed of the electric supercharger 18 is increased in proportion to the intake air temperature based on the value detected by the intake air temperature sensor SW3. When set to 40 ° C. or higher, the rotational speed of the electric supercharger 18 is set to MAX. In particular, in this embodiment, the high-pressure EGR passage 50 is employed, and in the EGR region B other than B1, the high-pressure EGR passage 50 is used to recirculate a large amount of EGR. In the operation region where the oxygen concentration becomes high and the oxygen concentration becomes low, the intake air cooling effect and the oxygen concentration increasing effect by the electric supercharger 18 can be enhanced.

  The relationship between the rotational speed of the electric supercharger 18 and the intake air temperature is stored in the memory 102 as a control map M4 based on data obtained through experiments or the like.

  Further, in order to appropriately control the operation state, the memory 102 includes an EGR flag indicating that the operation state is in the EGR region B when the value is L or H, and a supercharging path when the value is 1. An area for storing an electric supercharging flag indicating that the PH2 is opened and the electric supercharging operation by the electric supercharger 18 is performed is set. Here, when the value of the EGR flag is L, it indicates that the low-pressure EGR passage 60 is open, and when it is H, the high-pressure EGR passage 50 is open. It is shown that.

  Next, a control example of this embodiment by the engine control unit 100 will be described.

  FIG. 7 is a flowchart showing an example of operation control according to the embodiment of FIG.

  Referring to FIG. 7, when this operation control is executed, engine control unit 100 executes initialization of each part. Specifically, in the intake passage 10, the on-off valves 20 and 21 of the bypass intake passage 17 and the communication passage 19 are closed. Further, the EGR opening / closing valves 51 and 61 provided in the EGR passages 50 and 60 are also closed. Further, the EGR flag and the electric supercharge flag are also set to 0 indicating stop. As a result, in an initial state (so-called normal operation), fresh air that has passed through the air cleaner 14 is supplied to the engine body 1 via the cooling path PH1 and is not recirculated to the intake path 10 from the exhaust path 30. After being purified through the diesel smoke purification device 34, it is discharged outside the vehicle.

  Next, the engine control unit 100 reads various data and grasps the operating state (step S21). Next, the engine control unit 100 identifies the current operating state based on the characteristics of the control map M1 described above (step S22). Next, it is determined whether or not the current operating state is the non-EGR region A (step S23). If it is non-EGR area A (YES in step S23), an EGR stop control subroutine is executed (step S24). If it is EGR area B (YES in step S23), EGR operation is performed. A control subroutine is executed (step S25).

  After executing any subroutine, the engine control unit 100 determines whether or not a predetermined acceleration condition is satisfied (step S26). Here, the acceleration condition refers to, for example, a case where the stepping speed of the accelerator opening is a predetermined speed, or a case where the stepping amount per predetermined unit time of the accelerator opening is a predetermined amount or more.

  If the acceleration condition is satisfied, the engine control unit 100 executes an electric supercharging operation control subroutine (step S27), and then, based on the characteristics of the control map M3 described above, the vane of the variable capacity supercharger 40. The opening degree is controlled according to the operating state (step S28). On the other hand, if the acceleration condition is not satisfied in step S26, step S27 is bypassed and step S28 is executed. Thereafter, the engine control unit 100 determines whether or not the value of the electric supercharging flag is 1, that is, whether or not the electric supercharging is being performed (step S29). If the value of 0 is 0 (that is, if electric supercharging has not been executed), the flow returns to step S21 to repeat the above-described flow, and if the value of the electric supercharging flag is 1, supercharging It is determined whether or not the supercharging pressure SP detected by the pressure sensor SW5 by the variable capacity supercharger 40 is equal to or greater than a predetermined value SPs (step S30). Here, when the supercharging pressure SP is equal to or higher than the predetermined value SPs, it can be determined that the operation state is already high in the supercharging pressure of the intake passage 10, so in this case, the electric supercharging stop A control subroutine is executed (step S31), and then the process returns to step S21 to repeat the above-described flow. On the other hand, when the supercharging pressure SP by the variable capacity supercharger 40 is less than the predetermined value SPs, it can be determined that the supercharging operation by the electric supercharger 18 is still necessary. In this case, the process proceeds to step S274 (see FIG. 10) of the electric supercharging operation control subroutine, and the supercharging operation by the electric supercharger 18 is continued.

  FIG. 8 is a flowchart showing the EGR stop control subroutine (step S24) of FIG.

  Referring to FIG. 8, engine control unit 100 first determines the value of the EGR flag to determine whether any of EGR on / off valves 51 and 61 is open (step S241). If there are any open EGR on-off valves 51, 61, both EGR on-off valves 51, 61 are fully closed (step S242). Thereafter, the value of the EGR flag is updated to 0 (step S243), and the process returns to the main routine. On the other hand, if both EGR on-off valves 51 and 61 are already fully closed in step S241, the process directly returns to the main routine.

  FIG. 9 is a flowchart showing the EGR operation control subroutine (step S25) of FIG.

  Referring to FIG. 9, when the EGR operation control subroutine of step S25 is executed, engine control unit 100 first determines whether or not the current operation region is low pressure region B1 (step S251). Here, when the operation region is the low pressure operation region B1, the engine control unit 100 closes the high pressure EGR on / off valve 51, opens the low pressure EGR on / off valve 61 (step S252), and sets the value of the EGR flag. Update to L (step S253). On the other hand, if the operation region is an EGR region other than the low-pressure operation region B1 in step S251, the engine control unit 100 opens the high-pressure EGR on-off valve 51 and closes the low-pressure EGR on-off valve 61 (step S254). ), The value of the EGR flag is updated to H (step S255).

  After step S253 or step S255, the engine control unit 100 indexes the target oxygen concentration from the control map M2 described in FIG. 4 (step S256). Next, the engine control unit 100 calculates the oxygen concentration of the intake manifold 12 based on the above-described principle (step S257). Thereafter, the engine control unit 100 feedback-controls the valve opening amount of the opened EGR on-off valve 51 (61) (step S258), controls the EGR amount to an appropriate value, and returns to the main routine.

  FIG. 10 is a flowchart showing the electric supercharging operation control subroutine (step S27) of FIG.

  Referring to FIG. 10, when the electric supercharging operation control subroutine of step S27 is executed, engine control unit 100 refers to the EGR flag and determines whether or not the EGR operation is being executed (step S271). . If the EGR operation is being performed, that is, if the value of the EGR flag is set to L or H, the engine control unit 100 fully closes both the EGR on-off valves 51 and 52 and performs the EGR operation. It stops (step S272) and updates the value of the EGR flag to 0 (step S273). Thus, even in the EGR operation region, when the acceleration condition is satisfied, the supply of EGR is forcibly stopped, and the boost pressure can be increased to improve the acceleration response.

  Next, the engine control unit 100 calculates the acceleration degree Aa when the acceleration condition is satisfied (step S274). Here, the acceleration degree Aa refers to the degree of rapid increase in the required torque, for example, a degree determined by the amount of depression of the accelerator pedal 70 per unit time, the ratio of the required torque to the actual torque of the engine body 1, etc. It is. If the EGR operation is not executed in step S271, that is, if the value of the EGR flag is set to 0, the engine control unit 100 bypasses steps S272 and S273 and immediately executes step S274. .

  The engine control unit 100 determines whether or not the calculated acceleration degree is equal to or greater than a predetermined threshold value As (step S275). If the acceleration Aa is less than the threshold value As, the engine control unit 100 closes the on-off valve 20 in the bypass intake passage 17 and opens the on-off valve 21 in the communication passage 19 (step S276). Thereby, the upstream side of the supercharging path PH2 communicates with the cooling path PH1, and the cooled fresh air is supercharged by the electric supercharger 18 and then supplied to the intake manifold 12. Thereby, in the operation region where the urgency of fresh air supply is relatively low, the cooled fresh air with a high oxygen concentration can be supercharged by the electric supercharger 18 and supplied to the engine body 1. The efficiency can be improved, and the boost pressure by the variable capacity supercharger 40 can be increased while further improving the exhaust performance.

  On the other hand, if the acceleration Aa is equal to or greater than the threshold value As in step S275 (YES in step S275), the engine control unit 100 opens the on-off valve 20 in the bypass intake passage 17 and opens and closes the communication passage 19. The valve 21 is closed (step S277). As a result, the upstream side of the supercharging path PH2 is only the bypass intake passage 17 from the air cleaner 14, and the variable capacity supercharger 40 and the intercooler 16 are bypassed. As a result, fresh air is supplied to the intake manifold 12 through a path with extremely low air resistance. Therefore, even when EGR remains in the intake manifold 12, the ratio of fresh air (and thus the oxygen concentration of the intake air) can be rapidly increased. For this reason, since the intake air temperature can be lowered, the charging efficiency can be improved and the torque performance is improved. In addition, since the oxygen concentration can be increased rapidly, there is no risk of smoke being generated even if fuel injection is immediately performed when there is a request for re-acceleration from an operating state where fuel cut is being performed. . For this reason, it is possible to improve acceleration response as much as possible while suppressing a decrease in exhaust performance.

  After executing Step S276 or S277, the engine control unit 100 indexes the rotational speed of the electric supercharger 18 from the control map M4 described in FIG. 6 based on the intake air temperature detected by the intake air temperature sensor SW3 (Step S278). ). As a result, the temperature of the intake air supplied to the intake manifold 12 is appropriately controlled, and while maintaining a suitable charging efficiency and oxygen concentration, the supercharging pressure by the variable displacement supercharger 40 is increased, and the blowdown energy is increased. Can be achieved.

  Thereafter, the engine control unit 100 updates the value of the electric supercharging flag to 1 (step S279), and returns to the main routine.

  As a result, as described with reference to FIG. 7, after the value of the electric supercharging flag is set to 1, until the VGT vane opening is fully opened, the control after step S274 is executed, and the electric supercharging operation is performed. continue.

  It should be noted that the electric supercharge stop control subroutine (step S31) of FIG. 7 only returns the route of the intake passage 10 to the initial state described in step S20 and stops the electric supercharger 18; Will not be described.

  FIG. 11 is a timing chart showing an operation example in which the flowcharts of FIGS. 7 to 10 are executed.

  Referring to FIG. 11, the illustrated example shows a case where the engine body 1 is decelerated at time t <b> 1 and the known fuel cut control is performed in a state where the engine body 1 is running in the high speed and low load operation state. Yes. Along with this deceleration, the opening degree of the vane opening of the variable capacity supercharger 40 is gradually reduced based on the operation control of the control map M3 shown in FIG. Become. Therefore, in this operating state, the vane opening cannot be closed until the exhaust gas flow rate is increased, making it difficult to rapidly increase the supercharging pressure.

  Next, from time t2 to time t5, an example is shown in which the electric supercharging stop control subroutine of step S31 is executed from the electric supercharging operation control subroutine of step S27.

  First, when the accelerator pedal 70 is depressed at time t2 and the acceleration condition is satisfied, the bypass intake passage 17 is closed and the cooling path PH1 is communicated with the supercharging path PH2 by steps S275 and S276 of the electric supercharging operation control subroutine S27. As a result, fresh air cooled by the intercooler 16 can be supplied to the intake manifold 12 while being supercharged by the electric supercharger 18. As a result, fuel injection can be executed immediately from the operating state where the fuel cut has been executed. It is possible to change to a state. On the other hand, conventionally, in order to prevent the generation of smoke until the intake air reaches a sufficient oxygen concentration or until the sufficient boost pressure is reached, the fuel injection operation is performed as shown by the phantom line in the figure. Therefore, it was necessary to delay the switching. In addition, conventionally, the amount of depression of the accelerator is considerably delayed, and the high-load operation request continues for a long time.

  Next, in the illustrated example, the accelerator pedal 70 is continuously depressed even after the time t2 has elapsed, and the amount of depression corresponding to the case where the threshold value As is exceeded at the time t3 has been reached. As a result, as a result of executing step S277 in the determination of step S275, the bypass intake passage 17 is opened and the communication passage 19 is closed, so that fresh air is quickly supplied to the intake manifold 12 via a path with less resistance. Will be. As a result, the acceleration response of the engine is greatly enhanced, and after the time t4 has elapsed, the operating state has again shifted to the low-load operating region where the acceleration is less than the threshold value As. Thereafter, as the supercharging pressure increases, the vane opening degree is controlled to be fully opened, so that at time t5 when the vane opening degree is fully opened, the bypass intake passage 17 is closed, and fresh air is supplied only to the cooling path. And is fed to the intake manifold 12.

  As described above, in the present embodiment, during normal operation, the intake passage 10 is supplied to the engine body 1 while being supercharged to the compressor wheel 43 of the variable displacement supercharger 40 via the cooling path PH1. The On the other hand, when a predetermined acceleration condition is satisfied, the route of the intake passage 10 is switched to the supercharging route PH2, and the electric supercharger 18 in the supercharging route PH2 is operated. For this reason, since the supercharged fresh air bypasses the intercooler 16 and is supplied to the engine body 1, the ventilation resistance can be reduced and the supercharged air can be supplied quickly, so that the blowdown energy can be increased rapidly. The supercharging pressure by the variable capacity supercharger 40 can be increased in a short time. As a result, even if the fuel injection is executed immediately after the acceleration request, it is possible to prevent the exhaust performance from being deteriorated. Therefore, it becomes possible to enhance the responsiveness as much as possible and to maintain the exhaust performance.

  In the present embodiment, the bypass intake passage 17 also bypasses the compressor wheel 43 of the variable capacity supercharger 40. For this reason, in this embodiment, it becomes possible to reduce the air resistance of the compressor wheel 43 having a low supercharging pressure immediately after acceleration.

  Further, in the present embodiment, the variable displacement supercharger 40 having a movable vane configured to reduce the vane opening degree at the time of high load is employed as the exhaust turbocharger. For this reason, in the present embodiment, during the acceleration, the variable capacity supercharger 40 becomes in an operation state where the supercharging capacity cannot be sufficiently obtained. However, fresh air passing through the bypass intake passage 17 is By bypassing the compressor wheel 43 of the feeder 40, the blowdown energy can be quickly increased. As a result, the supercharging pressure is also quickly increased, so that the vane opening can be quickly increased. It becomes possible to contribute to an increase in torque and an improvement in fuel consumption.

  Further, in the present embodiment, when the supercharging pressure of the variable displacement supercharger 40 reaches a predetermined value or more in a state where the electric supercharger 18 is operating after the acceleration condition is satisfied (according to the present embodiment) In other words, when the vane opening is fully open), the intake air path is switched to the cooling intake passage 15 during normal operation, and the electric supercharger 18 is stopped. For this reason, in this embodiment, since the electric supercharger 18 can be operated in a necessary and sufficient operation region, it is possible to achieve both reduction in exhaust performance and improvement in acceleration response while saving power consumption. It becomes possible.

  In the present embodiment, the communication passage 19 that communicates the downstream side of the intercooler 16 of the cooling intake passage 15 and the upstream side of the electric supercharger 18 of the bypass intake passage 17, and engine control of the communication passage 19 are performed. And an on-off valve 21 that opens and closes under the control of the unit 100, and the engine control unit 100 functionally constitutes an acceleration judgment means for judging an acceleration feeling Aa when the acceleration condition is satisfied. When the acceleration degree Aa determined when the acceleration condition is satisfied is equal to or greater than a predetermined threshold value As, the engine control unit 100 closes the on-off valve 21 and the acceleration degree Aa is less than the threshold value As. In some cases, the communication passage 19 is opened. Therefore, in this embodiment, when the acceleration condition is satisfied and the acceleration degree Aa is equal to or greater than the predetermined threshold value As, fresh air is quickly supplied to the engine body 1 through a path with a small resistance, and the fresh air It is possible to increase the boost pressure while preventing the deterioration of the exhaust performance by increasing the blow energy in the operation region where the urgency of supply is relatively high. On the other hand, when the acceleration degree Aa is less than the predetermined threshold value, the cooling path PH1 and the supercharging path PH2 are communicated with each other by the communication path 19, so that fresh air cooled by the intercooler 16 is electrically driven. The engine body 1 is supplied in a state of being supercharged by the feeder 18. As a result, in the operation region where the urgency of fresh air supply is relatively low, the cooled fresh air with a high oxygen concentration can be supercharged and supplied to the engine body 1, so that the charging efficiency can be improved. It is possible to increase the supercharging pressure by the variable capacity supercharger 40 while further improving the exhaust performance.

  In the present embodiment, the high-pressure and low-pressure EGR passages 50 and 60 for returning a part of the exhaust gas from the exhaust passage 30 of the engine body 1 to the downstream side of the intercooler 16 in the intake passage 10, And EGR opening / closing valves 51 and 61 for opening and closing the low pressure EGR passages 50 and 60, and the intake air temperature supplied to the engine body 1 downstream of the bypass intake passage 17 and the high pressure and low pressure EGR passages 50 and 60 are detected. And the intake air temperature sensor SW3 that outputs the detected value to the engine control unit 100. The engine control unit 100 increases the intake air temperature detected by the intake air temperature sensor SW3 when the acceleration condition is satisfied. It is operated by increasing the number of revolutions. For this reason, in the present embodiment, when the EGR is recirculated to the intake passage 10, the higher the intake air temperature, the higher the supercharging pressure by the electric supercharger 18 and the lowering the intake air temperature. It is possible to increase the supercharging pressure by the variable capacity supercharger 40 while further improving the exhaust performance.

  In the present embodiment, the engine control unit 100 closes the EGR on / off valves 51 and 61 when the acceleration condition is satisfied when the EGR on / off valves 51 and 61 are open. For this reason, in this embodiment, even in the EGR region where the EGR is recirculated to the intake air, it is possible to stop the recirculation of the EGR when acceleration is requested and increase the boost pressure to improve the acceleration response.

  As described above, according to the present embodiment, when a predetermined acceleration condition is satisfied, the supercharged fresh air bypasses the intercooler 16 and is supplied to the engine body 1. Even if it is executed immediately after that, it is possible to prevent the exhaust performance from being lowered. As a result, it is possible to achieve both the acceleration response and the exhaust performance.

  The above-described embodiments are merely preferred specific examples of the present invention, and the present invention is not limited to the above-described embodiments.

  FIG. 12 is an overall configuration diagram of an engine provided with a supercharging device according to another embodiment of the present invention, and FIG. 13 is a flowchart showing an electric supercharging operation control subroutine according to the embodiment of FIG. FIG. 14 is a timing chart showing an operation example in which the flowchart of FIG. 13 is executed.

  Referring to FIG. 12, the communication path 19 described in FIG. 1 may be omitted. In that case, steps S274 to S276 are omitted in the electric supercharging operation control subroutine S27 as shown in FIG.

  When the configurations of FIGS. 12 and 13 are adopted, as shown in FIG. 14, the electric supercharging operation is executed only by opening and closing the bypass intake passage 17, but this also makes the conventional product In comparison, high acceleration performance and exhaust performance can be obtained.

  In addition, it goes without saying that various modifications are possible within the scope of the claims.

1 is an overall configuration diagram of an engine including a supercharging device according to an embodiment of the present invention. It is a general | schematic expanded sectional view of the turbine chamber of the variable capacity | capacitance supercharger which concerns on embodiment of FIG. It is a characteristic view showing the relationship between the accelerator opening and the engine speed for explaining the control map of the high-pressure and low-pressure EGR on-off valves. It is a characteristic view of the accelerator opening and engine speed for explaining the control map of the target oxygen concentration for determining the amount of EGR. It is a characteristic view for demonstrating the control map of the variable capacity | capacitance supercharger which concerns on embodiment of FIG. It is a characteristic view which shows the relationship between the intake air temperature and electric supercharger rotation speed for demonstrating the control map of the electric supercharger which concerns on embodiment of FIG. It is a flowchart which shows an example of the operation control which concerns on embodiment of FIG. It is a flowchart which shows the EGR stop control subroutine of FIG. It is a flowchart which shows the EGR driving | operation control subroutine of FIG. It is a flowchart which shows the electric supercharging operation control subroutine of FIG. It is a timing chart which shows the example of an operation which performed the flow chart of Drawings 7-10. It is a whole block diagram of the engine provided with the supercharging device which concerns on another embodiment of this invention. It is a flowchart which shows the electric supercharging operation control subroutine which concerns on embodiment of FIG. It is a timing chart which shows the example of an operation which performed the flow chart of Drawing 13.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 10 Intake path 12 Intake manifold 13 Common intake passage 14 Air cleaner 15 Cooling intake passage 16 Intercooler 17 Bypass intake passage 18 Electric supercharger 19 Communication passage 20 Open / close valve 21 Open / close valve 30 Exhaust passage 40 Variable displacement supercharger 41 Turbine wheel 43 Compressor wheel 50 High pressure EGR passage 51 High pressure EGR opening / closing valve 60 Low pressure EGR passage 61 Low pressure EGR opening / closing valve 70 Accelerator pedal 100 Engine control unit PH1 Cooling path PH2 Supercharging path

Claims (6)

In a turbocharger for a diesel engine equipped with an exhaust turbocharger having a compressor wheel in the intake passage,
A cooling intake passage disposed downstream of the compressor wheel and in which an intercooler is disposed;
A bypass intake passage for bypassing the intercooler;
An electric supercharger that is arranged in the bypass intake passage and supercharges the air in the bypass intake passage;
Path switching means for switching the intake path to at least one of a supercharging path for guiding intake air to the engine body via the electric supercharger and a cooling path for guiding intake air from the intercooler to the engine body;
The path switching means and a control means for controlling the operation of the electric supercharger according to the operating state of the engine body,
The control means switches the path in the intake passage to the cooling path during normal operation, stops the electric supercharger, and changes the path in the intake passage to the supercharge path when a predetermined acceleration condition is satisfied. The turbocharger for a diesel engine, wherein the electric supercharger is operated by switching to In the supercharging device of the diesel engine according to claim 1,
The turbocharger for a diesel engine, wherein the bypass intake passage also bypasses the compressor wheel of the exhaust turbocharger. The turbocharger for a diesel engine according to claim 1 or 2,
When the supercharging pressure of the exhaust turbocharger reaches a predetermined value or more when the electric supercharger is operating after the acceleration condition is satisfied, the control means performs normal operation of the intake path. A turbocharger for a diesel engine, wherein the electric supercharger is stopped by switching to a cooling path at the time. The diesel engine supercharging device according to any one of claims 1 to 3,
A communication passage communicating the downstream side of the intercooler of the cooling intake passage with the upstream side of the electric supercharger of the bypass intake passage;
A communication on-off valve that opens and closes the communication path under the control of the control means;
An acceleration determination means for determining the acceleration when the acceleration condition is satisfied,
The control means closes the communication on-off valve when the acceleration condition determined by the acceleration condition determination means is equal to or greater than a predetermined threshold value when the acceleration condition is satisfied, and the acceleration condition indicates the threshold value. The diesel engine supercharging device is characterized in that the communication passage is opened when it is less than the range. In the supercharging device of the diesel engine according to any one of claims 1 to 4,
An EGR passage that recirculates part of the exhaust gas from the exhaust passage of the engine body to the downstream side of the intercooler of the intake passage;
An EGR on-off valve that opens and closes the EGR passage under the control of the control means;
An intake air temperature sensor that detects an intake air temperature supplied to the engine main body downstream of the bypass intake passage and the EGR passage and outputs a detected value to the control means;
When the acceleration condition is satisfied, the control means increases the rotational speed of the electric supercharger and operates as the intake air temperature detected by the intake air temperature sensor is higher. Feeding device. In the supercharging device of the diesel engine according to claim 5,
The supercharger for a diesel engine, wherein the control means closes the EGR opening / closing valve when the acceleration condition is satisfied when the EGR opening / closing valve is open.

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