JP2008303743A - Energy recovery device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recover energy by increasing a pressure in exhaust passage upstream of an exhaust throttling valve while preventing deceleration shock. <P>SOLUTION: This energy recovery device is equipped with an exhaust throttling valve 56 provided in the exhaust passage 28 of an internal combustion engine 10, and a pressure accumulating vessel 64 communicable with the exhaust passage P upstream of the exhaust throttling valve 56 through a valve. When recovering energy from the exhaust passage P upstream of the exhaust throttling valve 56 to the pressure accumulating vessel 64, the exhaust throttling valve 56 is closed. When the exhaust throttling valve 56 is closed to recover energy, the pressure of the exhaust passage P on the upstream side of the exhaust throttling valve 56 is changed to a pressure causing no deceleration shock, by controlling the aperture of an EGR valve provided in an EGR passage 46 in communication with the exhaust gas passage P on the upstream side of the exhaust throttling valve 56. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an energy recovery apparatus that closes an exhaust throttle valve provided in an exhaust passage of an internal combustion engine and recovers energy from an exhaust passage upstream of the exhaust throttle valve to a pressure accumulating vessel.

  Patent Document 1 discloses an apparatus in which an exhaust throttle valve is disposed in an exhaust passage of an internal combustion engine, and a high-pressure gas tank is installed so as to communicate with an exhaust passage upstream of the exhaust throttle valve via a check valve. ing. This device increases the pressure of the exhaust gas upstream of the exhaust throttle valve by reducing the opening of the exhaust throttle valve, collects the exhaust gas having the increased pressure into the high-pressure gas tank via the check valve, and accumulates the pressure Configured to hold.

JP 2002-147217 A

  In the apparatus described in Patent Document 1, the pressure of the exhaust passage upstream of the exhaust throttle valve is increased by reducing the opening of the exhaust throttle valve, and the increased pressure (pressure energy) is recovered. However, if the pressure of the exhaust passage suddenly increases by reducing the opening of the exhaust throttle valve, a deceleration shock that may cause the driver to feel uncomfortable may occur in the vehicle.

  Therefore, the present invention has been made in view of such a point, and an object of the present invention is to perform energy recovery by increasing the pressure of the exhaust passage upstream of the exhaust throttle valve while preventing a deceleration shock. is there.

  In order to achieve the above object, an energy recovery device of the present invention includes an exhaust throttle valve provided in an exhaust passage of an internal combustion engine, and a pressure accumulating vessel capable of communicating with the exhaust passage upstream of the exhaust throttle valve via the valve. And an exhaust throttle valve control means for closing the exhaust throttle valve to perform energy recovery from the exhaust passage upstream of the exhaust throttle valve to the pressure accumulating vessel. When the exhaust throttle valve is controlled to be closed by the exhaust throttle valve control means, the communication passage communicating with the exhaust passage, the pressure control valve provided in the communication passage, and the exhaust throttle valve upstream of the exhaust throttle valve Pressure regulating valve control means for controlling the opening of the pressure regulating valve so that the pressure does not cause a deceleration shock.

  According to the above configuration, when the exhaust throttle valve is controlled to be closed by the exhaust throttle valve control means by the pressure control valve control means, the pressure in the exhaust passage upstream of the exhaust throttle valve does not cause a deceleration shock. Since the opening degree of the pressure control valve is controlled so as to obtain a pressure, the pressure in the exhaust passage on the upstream side of the exhaust throttle valve can be increased without causing a deceleration shock. Accordingly, energy recovery can be performed by increasing the pressure in the exhaust passage upstream of the exhaust throttle valve while preventing a deceleration shock.

  Specifically, the communication passage may be an EGR passage that connects an exhaust passage upstream of the exhaust throttle valve and an intake passage, and the pressure control valve may be an EGR valve. When an internal combustion engine is provided with an EGR passage and an EGR valve, the pressure in the exhaust passage upstream of the exhaust throttle valve can be adjusted using existing equipment.

  In the above invention, the pressure control valve control means sets the opening of the pressure control valve to an initial opening determined based on at least one of the engine speed and the vehicle speed in synchronization with the closing of the exhaust throttle valve. The opening of the pressure control valve may be controlled so as to change the opening of the pressure control valve based on at least one of the engine speed and the vehicle speed. By doing so, the opening of the pressure control valve is set to the initial opening determined based on at least one of the engine speed and the vehicle speed in synchronization with the closing of the exhaust throttle valve. From time to time, the pressure in the exhaust passage upstream of the exhaust throttle valve can be adjusted appropriately. Since the opening of the pressure control valve can be changed from the initial opening based on at least one of the engine speed and the vehicle speed, the pressure in the exhaust passage upstream of the exhaust throttle valve is appropriately increased so as not to cause a deceleration shock. Can do.

  Specifically, in the various inventions described above, the pressure control valve control means may control the opening of the pressure control valve so that the opening of the pressure control valve decreases as the engine speed decreases. By doing so, the pressure in the exhaust passage upstream of the exhaust throttle valve can be further increased as the engine speed decreases. In addition to or in place of this, the pressure control valve control means may control the opening of the pressure control valve so that the opening of the pressure control valve decreases as the vehicle speed decreases. By doing so, the pressure of the exhaust passage upstream of the exhaust throttle valve can be further increased as the vehicle speed becomes slower.

  A preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  A concept of an internal combustion engine system for a vehicle to which the energy recovery device of the embodiment is applied is shown in FIG. The internal combustion engine 10 in the present embodiment is a type of internal combustion engine that is spontaneously ignited by directly injecting light oil, which is fuel, from a fuel injection valve 12 into a combustion chamber in a compressed state, that is, a diesel engine.

  An intake port that faces the combustion chamber of the cylinder 14 and defines a part of the intake passage 16 is formed in the cylinder head and is opened and closed by an intake valve. An intake manifold 18 that defines a portion of the intake passage 16 is connected to the cylinder head, and an intake pipe 20 that also defines a portion of the intake passage 16 is connected to the upstream side of the cylinder head. An air cleaner 22 is provided on the upstream end side of the intake pipe 20 in order to remove dust and the like in the air guided to the intake passage 16. A throttle valve 26 whose opening degree is adjusted by the throttle actuator 24 is provided in the middle of the intake pipe 20.

  On the other hand, an exhaust port that faces the combustion chamber of the cylinder 14 and defines a part of the exhaust passage 28 is formed in the cylinder head and is opened and closed by an exhaust valve. An exhaust manifold 30 that defines a part of the exhaust passage 28 is connected to the cylinder head, and an exhaust pipe 32 that also defines a part of the exhaust passage 28 is connected to the downstream side of the cylinder head. A catalytic converter 34 filled with an exhaust gas purification catalyst is provided in the middle of the exhaust pipe 32.

  Further, a turbine 36 including a turbine wheel that is rotationally driven by exhaust gas is provided in the middle of the exhaust pipe 32. However, the turbine 36 is disposed upstream of the catalytic converter 34. Correspondingly, a compressor 38 including a compressor wheel that is coaxially connected to the turbine wheel and rotated by the rotational force of the turbine wheel is provided in the intake pipe 20. That is, the internal combustion engine 10 is provided with a supercharger 40 that includes a turbine 36 that extracts exhaust energy and a compressor 38 that supercharges the internal combustion engine 10 with the exhaust energy extracted by the turbine 36. An intercooler 42 is provided on the downstream side of the compressor 38 in order to cool the air compressed by the compressor 38.

  The internal combustion engine 10 is provided with an exhaust gas recirculation (EGR) system 44 that guides a part of the exhaust gas flowing through the exhaust passage 28 to the intake passage 16. The EGR system 44 includes an EGR pipe 48 that defines an EGR passage 46 that connects the exhaust passage 28 and the intake passage 16, an EGR valve 50 that adjusts the communication state of the EGR passage 46, and exhaust gas that is recirculated (EGR gas). And an EGR cooler 52 for cooling. Here, one end on the upstream side of the EGR pipe 48 is connected to the exhaust manifold 30, and the other end on the downstream side thereof is connected to the intake manifold 18. The EGR valve 50 is provided on the downstream side of the EGR cooler 52, and its opening degree is adjusted by an actuator 54. However, here, the EGR valve 50 is a poppet valve.

  Further, an exhaust throttle valve 56 is provided in the middle of the exhaust passage 28. In the present embodiment, the exhaust throttle valve 56 is a butterfly valve. When the exhaust throttle valve 56 is closed, the exhaust gas flowing through the exhaust passage 28, that is, the fluid such as combustion gas or air, is effectively blocked, and the flow of such fluid downstream from the exhaust throttle valve 56 is substantially blocked. Functions as a shutoff valve. The exhaust throttle valve 56 is driven to open and close by an actuator 58. The exhaust throttle valve 56 may be a valve having a configuration that reduces the cross-sectional area of the exhaust passage by about 50% when the valve is closed, or may completely block the exhaust passage 28 when the valve is closed. The valve may have a different configuration.

  As is clear from FIG. 1, the communication location between the exhaust passage 28 and the EGR passage 46 is upstream of the exhaust throttle valve 56. Accordingly, the EGR passage 46 communicates with an exhaust passage upstream of the exhaust throttle valve 56, that is, an exhaust passage (interval passage) P between the exhaust throttle valve 56 and the exhaust valve. As will be described later, when the exhaust throttle valve 56 is controlled to close during energy recovery, the pressure in the inter-valve passage P is adjusted by controlling the opening degree of the EGR valve 50 used as a pressure regulating valve. Is done.

  The inter-valve passage P further communicates with a pipe line 62 defined by a pipe member 60, and the pipe line 62 communicates with the exhaust passage 28 and the inside of the pressure accumulating tank 64 which is a pressure accumulating container. The accumulator tank 64 may be connected to any location, for example, the exhaust manifold 30, as long as the valve passage P, but the accumulator tank 64 of the present embodiment is located upstream of the exhaust throttle valve 56 in the exhaust passage 28. Therefore, it is connected to a location upstream of the turbine 36. The diameter of the pipeline 62 is smaller than the diameter of the exhaust passage 28. A flow rate control valve 66 is provided in the pipeline 62 for adjusting the communication state between the pressure accumulation tank 64 and the exhaust passage 28. It should be noted that when the flow control valve 66 is opened, the pressure accumulation tank 64 and the exhaust passage 28 communicate with each other, and when the flow control valve 66 is closed, the pressure accumulation tank 64 and the exhaust passage 28 communicate with each other. Is shut off, and the pressure accumulating tank 64 is substantially sealed. However, the flow control valve 66 is driven to open and close by an actuator 68. Here, the flow control valve 66 is a poppet valve.

  As will be described later, the pressure energy in the exhaust passage 28 is recovered from the exhaust passage 28 into the pressure accumulating tank 64 through the pipe line 62 with the movement of the fluid. On the other hand, the fluid having the pressure energy stored in the pressure accumulating tank 64 is discharged from the pressure accumulating tank 64 to the exhaust passage 28 via the pipe line 62 and used. That is, in the present embodiment, the energy recovery into the pressure accumulating tank 64 and the use and release of energy from the pressure accumulation tank 64 are performed through the same pipe line 62.

  In the present embodiment, the fluid recovered in the pressure accumulating tank 64, that is, the pressure energy of the fluid is released to the exhaust passage 28 via the conduit 62 particularly when the acceleration request is required. Is done. The released fluid or pressure energy is used to drive the turbine 36 of the supercharger 40. Thereby, the responsiveness improvement of the supercharger 40 is achieved.

  The internal combustion engine 10 includes various sensors that electrically output signals for detecting (derivation or estimation) of various values in an electronic control unit (ECU) 70. Here, some of them will be specifically described. An air flow meter 72 for detecting the amount of intake air is provided in the intake pipe 20. An intake air temperature sensor 74 for detecting the temperature of the intake air is provided near the air flow meter 72, and an intake air temperature sensor 76 for detecting the temperature is also provided on the downstream side of the intercooler 42. A pressure sensor 78 for detecting the supercharging pressure is provided in the intake pipe 20. Further, an accelerator opening sensor 82 for detecting a position corresponding to the depression amount of the accelerator pedal 80 operated by the driver, that is, an accelerator opening is provided. A throttle position sensor 84 for detecting the opening of the throttle valve 26 is also provided. Furthermore, a valve lift sensor 86 for detecting the opening amount of the EGR valve 50, here for detecting the lift amount thereof, is also provided. A crank position sensor 88 for detecting a crank rotation signal of a crankshaft connected to the piston via a connecting rod is attached to the cylinder block in which the piston reciprocates. Here, the crank position sensor 88 is also used as an engine speed sensor for detecting the engine speed (engine speed). Furthermore, a pressure sensor 90 is provided for detecting the pressure of a fluid such as exhaust gas, that is, combustion gas or air, in the inter-valve passage P. A pressure sensor 92 for detecting the pressure in the pressure accumulation tank 64 is also provided. Furthermore, a temperature sensor 94 for detecting the coolant temperature of the internal combustion engine 10 is provided. Furthermore, a vehicle speed sensor 96 for detecting the vehicle speed is also provided.

  The ECU 70 is composed of a microcomputer including a CPU, ROM, RAM, A / D converter, input interface, output interface, and the like. The various sensors are electrically connected to the input interface. Based on the output signals (detection signals) from these various sensors, the ECU 70 electrically outputs an operation signal (drive signal) from the output interface so that the internal combustion engine 10 can be smoothly operated according to a preset program. Output. In this way, the operation of the fuel injection valve 12, the opening degree of the throttle valve 26, the EGR valve 50, the exhaust throttle valve 56 and the flow control valve 66 are controlled. However, the ECU 70 outputs operation signals to the actuators 24, 54, 58, and 68 in order to control the opening degrees of the throttle valve 26, the EGR valve 50, the exhaust throttle valve 56, and the flow rate control valve 66.

  In the internal combustion engine 10, the intake air amount derived based on the output signal from the air flow meter 72, the engine speed derived based on the output signal from the crank position sensor 88, that is, the engine load and the engine speed. The fuel injection amount (fuel amount) and the fuel injection timing are set based on the operating state. Based on the fuel injection amount and the fuel injection timing, fuel is injected from the fuel injection valve 12.

  In the internal combustion engine 10, the engine speed derived based on the output signal from the crank position sensor 88 is equal to or higher than a predetermined speed (fuel cut speed), and based on the output signal from the accelerator opening sensor 82. When the accelerator opening degree derived in this way is 0%, that is, when the accelerator pedal 80 is not depressed, the fuel injection from the fuel injection valve 12 is set to be stopped (fuel cut). However, when such a fuel cut state continues and the engine speed decreases and reaches another predetermined speed (fuel cut return speed), fuel injection is resumed. In addition, fuel injection is resumed also when the accelerator pedal 80 is depressed and the accelerator opening exceeds 0% while the fuel cut is being performed. In addition, when the fuel cut is performed, it corresponds in general at the time of deceleration.

  The program is set in advance so that the throttle valve 26 is held in the closed state when the fuel is cut. However, at the time of energy recovery described later, the throttle valve 26 is forcibly controlled to be fully opened. The throttle valve 26 is controlled to be fully open when the internal combustion engine 10 is started, and is controlled to be fully closed when the internal combustion engine 10 is stopped. During normal traveling, the opening degree of the throttle valve 26 is controlled to an appropriate opening degree according to the engine state, the coolant temperature, and the like.

  Further, the opening degree of the EGR valve 50 is controlled based on the operation state of the internal combustion engine 10 determined based on output signals from the various sensors. Here, the high load region (including the full load region) is defined as a region where the EGR valve 50 is fully closed (outside EGR region), and the other low / medium load regions are the EGR valve 50. It is defined as an area to be opened (EGR area). In the present embodiment, the opening degree of the EGR valve 50 is set so as to be fully closed in the operation state in which the fuel cut is performed, but at this time, the EGR valve 50 may be opened to a predetermined opening degree. .

  However, at the time of energy recovery described later, the EGR valve 50 is also forcibly controlled to an opening described later regardless of the operating state. In the present specification, the opening degree of the EGR valve 50 controlled based on the operating state as described above is hereinafter referred to as a “normal opening degree”, and is forcibly controlled in preference to the normal opening degree when recovering energy. Hereinafter, the opening degree of the EGR valve 50 is referred to as “recovery opening degree”.

  By the way, during normal travel, the exhaust throttle valve 56 is controlled to be fully open, so that the exhaust gas, that is, the fluid flowing through the exhaust passage 28 passes through the catalytic converter 34 and is released to the outside air. On the other hand, when a predetermined condition for energy recovery is satisfied, the exhaust throttle valve 56 is controlled so as to be fully closed, and the fluid flowing through the exhaust passage 28 is generally blocked. Then, energy recovery is performed by effectively utilizing the fluid thus dammed up.

  Here, when the accumulator tank 64 has a margin for further energy recovery and is in an operation state in which the fuel is cut, the energy recovery is performed when the exhaust throttle valve 56 and the EGR valve 50 are closed from the beginning. An example of experimental results is shown in FIG. In FIG. 2, changes in the vehicle speed, the pressure in the inter-valve passage P, and the engine speed are shown on the same time axis. From FIG. 2, when the exhaust throttle valve 56 and the EGR valve 50 are closed in the operation state in which the fuel is cut when “accelerator is OFF” in the drawing, the pressure in the valve passage P rapidly increases to about 450 kPa. It can be seen that it increases to (curve PP in FIG. 2). The pressure rise takes only about 1 second.

  When the exhaust throttle valve 56 and the EGR valve 50 are closed in this manner, when the pressure in the inter-valve passage P increases rapidly, the deceleration of the vehicle increases abruptly, giving the driver an uncomfortable feeling. There is a risk that a deceleration shock will occur. Therefore, when the exhaust throttle valve 56 and the EGR valve 50 are closed at the same time, there is a possibility that the pressure in the inter-valve passage P may increase rapidly, the opening degree of the EGR valve 50 is controlled as follows, As indicated by the curve NP, the pressure in the intervalve passage P is gradually increased.

  Hereinafter, the energy recovery control will be described in detail according to the flowchart of FIG. However, the flowchart of FIG. 3 is repeated approximately every 20 ms.

  When the internal combustion engine 10 is activated, the ECU 70 first determines in step S301 whether or not the recovery flag is “1”, that is, whether it is ON. Here, that the recovery flag is “1” indicates that a predetermined condition for energy recovery is satisfied. On the other hand, when it is “0”, it indicates that the predetermined condition for energy recovery is not satisfied. Since the recovery flag is reset in the initial state, a negative determination is made here. In the present embodiment, the fact that the predetermined condition for energy recovery is satisfied means that the fuel is being cut and the pressure in the pressure accumulation tank 64 is equal to or lower than the predetermined pressure, as is apparent from the following description. And three things that an engine speed is below a predetermined speed are satisfied.

  If negative in step S301, it is determined in next step S303 whether or not a fuel cut is in progress. Specifically, whether or not the fuel is being cut is determined by whether or not the fuel injection amount is “0”. Note that during normal travel, in general, a fuel injection amount greater than “0” is introduced and fuel injection is performed in order to produce a predetermined output by the internal combustion engine 10. Therefore, in such a case, a negative determination is made in step S303, and the routine ends.

  If an affirmative determination is made in step S303 that the fuel is being cut, then in step S305, the pressure in the pressure accumulating tank 64 ("tank internal pressure" in FIG. 3) is a pressure allowed for the pressure accumulating tank 64, and is predetermined. It is determined whether the pressure is equal to or lower than a predetermined upper limit pressure stored in the ROM. This is to prevent further energy recovery when a sufficient amount of pressure energy, that is, fluid is stored in the pressure accumulation tank 64. The pressure in the pressure accumulation tank 64 is derived based on an output signal from the pressure sensor 92. If a negative determination is made in step S305, the routine ends.

  If an affirmative determination is made in step S305, it is then determined in step S307 whether or not the engine speed is equal to or less than a predetermined speed stored in advance in the ROM. The engine speed is derived based on the output signal from the crank position sensor 88 as described above. Here, the predetermined rotational speed is set to 2000 rpm. This determination is made because if the pressure in the inter-valve passage P rises at a predetermined speed or higher when the engine speed is high, there is a high possibility that a deceleration shock of a level felt by the driver or the like will occur in the vehicle. This is because energy recovery is performed only when the engine speed is on the low speed side. If a negative determination is made in step S307, the routine ends.

  In the present embodiment, the determination in step S307 is performed so that energy is recovered when the engine speed is on the low speed side, but not only when the engine speed is on the low speed side but when the engine speed is on the high speed side. In addition, energy recovery may be performed. That is, this step S307 can be omitted. In this case, when an affirmative determination is made in steps S303 and S305, it is determined that the predetermined condition for energy recovery is satisfied, and the process proceeds to the next step S309.

  If an affirmative determination is made in step S307, the recovery flag is set to “1” in step S309, assuming that a predetermined condition for energy recovery is satisfied. Thereby, the control for energy recovery is performed with priority over the normal control of the internal combustion engine 10. In step S311, the actuators 54, 68, and 24 are opened so that the opening degree of the EGR valve 50 is set to the recovery opening degree, the flow control valve 66 is closed, and the throttle valve 26 is opened. An operation signal is output at

  The EGR valve 50 is normally controlled on the basis of the operating state as described above. However, when the energy is recovered after reaching step S311, the EGR valve 50 is based on the mapped data stored in the ROM previously obtained by experiment. It is set as the collection opening degree which is a predetermined opening degree. This data indicates that when the exhaust throttle valve 56 is controlled to close (when the exhaust throttle valve 56 is closed and closed), the pressure in the inter-valve passage P is set to a pressure at which a deceleration shock does not occur. This shows the relationship between the opening degree of the EGR valve 50 required for the engine, the engine speed and the vehicle speed (see FIG. 4). The recovery opening degree of the EGR valve 50 will be described later. Since the flow control valve 66 is basically closed, the flow control valve 66 is kept closed. Further, the throttle valve 26 is fully opened to send air to the exhaust passage 28.

  In the next step S313, an operation signal is output to the actuator 58 so that the exhaust throttle valve 56 is closed. Thus, the routine ends.

  In step S301 of the next routine, an affirmative determination is made because the collection flag is “1”. If an affirmative determination is made in step S301, it is next determined in step S315 whether or not a fuel cut is in progress as in step S303. If an affirmative determination is made here, then in step S317, it is determined whether or not the pressure in the pressure accumulation tank 64 is equal to or lower than the upper limit pressure in the same manner as in step S305. It should be noted that the determination in step S315 and step S317 is performed in such a manner that after the recovery flag is set to “1” in step S309, the energy recovery is terminated when the predetermined energy recovery condition is not satisfied. It is to do.

  If the determination in step S317 is affirmative, then in step S319, it is determined whether or not the pressure in the pressure accumulation tank 64 is equal to or lower than the pressure in the inter-valve passage P ("passage pressure" in FIG. 3). At this time, since the exhaust throttle valve 56 has already been closed, the pressure (pressure energy) of the fluid blocked by the exhaust throttle valve 56 increases with time. And in order to investigate whether the pressure has increased so that it can collect | recover, determination by step S319 is performed. If a negative determination is made in step S319, an operation signal is output to the actuator 68 so that the flow control valve 66 is closed in the next step S321. This means that if the flow control valve 66 is already closed, the flow control valve 66 is kept closed. On the other hand, if an affirmative determination is made in step S319, an operation signal is output to the actuator 68 so that the flow control valve 66 is opened in the next step S323. As a result, the increased pressure energy in the inter-valve passage P is recovered in the pressure accumulation tank 64 via the pipe line 62.

  The pressure in the pressure accumulating tank 64 increases by recovering the fluid having high pressure energy, in other words, the fluid having high pressure energy (here, mainly air). Such energy recovery is generally continued unless a negative determination is made in step S315 or step S317.

  If a negative determination is made in step S315 or step S317 during energy recovery, control for terminating energy recovery is performed. If a negative determination is made in any of them, an operation signal is output to the actuator 54 so that the EGR valve 50 reaches the normal opening in the next step S325. Further, an operation signal is output to the actuator 68 so that the flow control valve 66 is closed. When the forced opening of the throttle valve 26 is released, an operation signal is output to the actuator 24 so that the opening degree of the throttle valve 26 becomes an opening degree based on the operating state. Further, an operation signal is output to the actuator 58 so that the exhaust throttle valve 56 is opened. In step S327, the collection flag is set to “0”. As a result, the internal combustion engine 10 is returned to a normal control state in which energy recovery is not performed.

  Here, the control of the opening degree of the EGR valve 50 during energy recovery (when a predetermined condition for energy recovery is satisfied) will be described with reference to FIGS. During the energy recovery, the opening degree of the EGR valve 50 is set to the recovery opening degree, which is a variable opening degree. When the recovery opening is set as the opening of the EGR valve 50 in step S311, first, the ECU 70 searches for the mapped data as shown in FIG. 4 based on the engine speed and the vehicle speed at that time. Thus, the opening degree of the EGR valve 50 is derived. Then, an actuation signal is output to the actuator 54 (at time T1 in FIG. 5) so that the opening degree of the EGR valve 50 becomes the derived opening degree. For example, when the derived opening degree of the EGR valve 50 is a fully opened opening degree, as shown in FIG. 5, the EGR valve 50 that has been closed fully because it is in an operating state in which the fuel is cut is fully opened. Open up to. The opening of the EGR valve 50 is performed so as to be substantially synchronized with the closing of the exhaust throttle valve 56 (see FIG. 5). That is, the opening degree control is performed so that the opening of the EGR valve 50 and the closing of the exhaust throttle valve 56 are performed in substantially the same period (T1-T2 period). Thus, the target opening degree of the EGR valve 50 that is moved in association with the closing of the exhaust throttle valve 56 at the start of energy recovery is referred to as “initial opening degree”.

  Once the opening degree of the EGR valve 50 is set to the initial opening degree, the opening degree adjustment of the EGR valve 50 is performed regardless of the opening degree control of the exhaust throttle valve 50 thereafter. Specifically, the opening degree of the EGR valve 50 is set so that the opening degree is derived by searching the mapped data as shown in FIG. 4 based on the engine speed and the vehicle speed that change from moment to moment. Be controlled. By controlling the opening degree of the EGR valve 50 in this way, as shown schematically in FIG. 5, to the fully closed opening degree that is the final opening degree (final opening degree), The opening degree of the EGR valve 50 changes gradually. The opening degree of the EGR valve 50 that is changed in this way is an opening degree that makes the pressure in the inter-valve passage P a pressure that does not cause a deceleration shock at any given time and can quickly recover energy. . That is, the mapped data as shown in FIG. 4 satisfies the pressure in the inter-valve passage P, both the reduction of the deceleration shock and the appropriate energy recovery when the exhaust throttle valve 56 is controlled to be closed. The data is pressure. In FIG. 4, it is determined that the opening degree of the EGR valve 50 in the lower left region is derived as the engine speed is lower and the vehicle speed is slower. According to FIG. 4, the opening degree of the EGR valve 50 decreases as the engine speed decreases, and the opening degree of the EGR valve 50 decreases as the vehicle speed decreases. Therefore, the lower the engine speed and the slower the vehicle speed, the higher energy can be recovered.

  FIG. 6 shows the relationship between the engine speed and the deceleration torque. FIG. 6 shows an example of experimental data in an operating state in which fuel cut is performed. The uppermost curve β1 in FIG. 6 is a torque curve in a state where the exhaust throttle valve 56 is fully opened and the EGR valve 50 is fully closed. A curve β2 located below the curve β1 is a torque curve in a state where the exhaust throttle valve 56 is fully closed and the EGR valve 50 is fully opened. When the opening degree of the EGR valve is further shifted to the closed side while the exhaust throttle valve 56 is in the fully closed state, the torque curve sequentially shifts from the curve β2 to the curve β8. A curve β8 is a torque curve in a state where the exhaust throttle valve 56 is fully closed and the EGR valve 50 is fully closed.

  A curve γ extending so as to cross the curves β1 to β8 in FIG. 6 represents a transition example of the deceleration torque accompanying the energy recovery control. Here, the change in the deceleration torque will be described according to the curve γ. However, in the following description, only the engine speed is used for deriving the opening degree of the EGR valve 50. However, the following description also applies when both the engine speed and the vehicle speed are used for the derivation.

  When the predetermined condition for energy recovery is satisfied and the recovery flag is set to “1”, deceleration torque at point C1 is generated. At this time, based on the engine speed, the fully open degree of the α1 region in FIG. 4 is derived as the initial degree of opening. As a result, when the EGR valve 50 is opened to the fully opened opening degree as the initial opening degree in synchronism with the closing of the exhaust throttle valve 56, the deceleration torque becomes the deceleration torque at the point C2. Next, when the engine speed decreases, the opening degree of 90% in the α2 region in FIG. 4 is derived, and the opening degree of the EGR valve 50 is 90 with the exhaust throttle valve 56 closed. % Opening. As a result, the deceleration torque becomes the deceleration torque at the point C3. Further, when the engine speed is lowered, an opening degree of 80% in the α3 region of FIG. 4 is derived, and the opening degree of the EGR valve 50 is 80% in a state where the exhaust throttle valve 56 is closed. Opened. As a result, deceleration torque is generated at point C4. When the engine speed is thus lowered and the opening degree of 65%, 45% and 25% in the α4, α5 and α6 regions of FIG. 4 is derived, the exhaust throttle valve 56 is closed. In such a state, the opening degrees of the EGR valve 50 are set to those opening degrees. Thus, the deceleration torque gradually increases from the deceleration torque at point C5 in FIG. 6 to the deceleration torque at point C7. Finally, when the engine speed decreases and the fully closed opening degree in the α7 region of FIG. 4 is derived, the opening degree of the EGR valve 50 is fully opened while the exhaust throttle valve 56 is closed. The opening is closed. Thus, the deceleration torque at the point C8 in FIG. 6 is generated. Further, when the engine speed decreases, the generated deceleration torque changes along the curve β8 in FIG.

  As described above, since the opening degree of the EGR valve 50 is changed from the initial opening degree to the final opening degree as the engine speed and the vehicle speed are reduced, the deceleration torque is gradually increased from the start of closing the exhaust throttle valve 50. Will be. The deceleration torque gradually increased in this way does not cause an obvious deceleration shock in the vehicle. In this process, when the pressure in the valve passage P increases and the pressure in the valve passage P exceeds the pressure in the pressure accumulation tank 64, the flow control valve 66 is opened and energy recovery is performed. (Steps S319 and S323). Therefore, energy recovery can be performed while preventing a deceleration shock.

  In addition, as described above, the amount of change in the opening degree of the EGR valve 50 is increased as the engine speed is lower or the vehicle speed is lower. This is because the lower the engine speed or the slower the vehicle speed, the greater the deceleration that causes a deceleration shock that can be felt by the driver. Therefore, the lower the engine speed or the slower the vehicle speed, the smaller the opening of the EGR valve 50 and the higher the pressure rise rate of the inter-valve passage P. Therefore, the lower the engine speed or the slower the vehicle speed, the higher energy can be recovered without causing a deceleration shock.

  Further, in the present embodiment, when the opening degree of the EGR valve 50 reaches the final opening degree, the EGR passage 46 and the exhaust passage 28 are disconnected so that the pressure of the intervalve passage P becomes substantially constant at a target pressure (for example, 500 kPa). Area, length, etc. are defined. Therefore, in the T3-T4 period of FIG. 5, the energy (pressure energy) of the target pressure can be recovered more appropriately in the pressure accumulation tank 64.

  FIG. 7 schematically shows changes in the pressure in the intervalve passage P. Curve I in FIG. 7 is a pressure curve when the EGR valve 50 is fully closed at the start of energy recovery, and curve II is a pressure curve when the above control for energy recovery is started when the engine speed is low. A curve III represents a pressure curve when the above control for energy recovery is started when the engine speed is higher than that of the curve II. As described above, during the energy recovery, the higher the engine speed, the larger the opening of the EGR valve 50 is opened. Accordingly, the pressure increase rate of the inter-valve passage becomes slower and slower as the engine speed at the start of energy recovery is higher or the decrease in the engine speed is slower.

  In the above description, the initial opening is set to a fully opened position as an example. However, the initial opening may be fully closed, or may be an arbitrary opening between fully closed and fully opened. In the above description, the final opening is a fully closed opening, but the final opening may be any opening between fully closed and fully open.

  As described above, the opening degree of the EGR valve 50 is set to the initial opening degree in response to the exhaust throttle valve 56 being closed at the start of energy recovery, and thereafter the opening degree of the EGR valve is set to the engine speed and Since it is changed based on the vehicle speed, the pressure in the exhaust passage upstream of the exhaust throttle valve can be increased while preventing a deceleration shock. Accordingly, energy recovery can be performed by increasing the pressure in the exhaust passage upstream of the exhaust throttle valve while preventing a deceleration shock.

  As described above, since deceleration torque (deceleration) that does not cause deceleration shock is only generated by energy recovery, the occurrence of exhaust braking is suppressed. Therefore, the running performance of the vehicle is not impaired by energy recovery.

  As mentioned above, although the energy recovery apparatus which concerns on this invention was demonstrated based on the said embodiment, this invention is not limited to this. In the above embodiment, the EGR passage 46 communicates with the upstream side of the exhaust throttle valve 56, that is, the inter-valve passage P, in the exhaust passage 28, and the opening degree of the EGR valve 50 provided in the EGR passage 46 is controlled. The pressure in the intervalve passage P was adjusted. However, the pressure adjustment of the inter-valve passage P may be performed using another communication passage communicating with the inter-valve passage P and another pressure regulating valve provided in the communication passage. For example, by providing a bypass passage that communicates between the valve passage P and the exhaust passage on the downstream side of the exhaust throttle valve 56, and controlling the opening of the bypass valve provided in the bypass passage, the pressure of the valve passage P is controlled. Adjustments may be made. In this case, the communication portion between the downstream end of the bypass passage and the exhaust passage 28 is preferably upstream of the catalytic converter 34.

  In the above, the opening degree (recovery opening degree) of the EGR valve 50 during energy recovery is determined based on the engine speed and the vehicle speed, but is defined based on at least one of the engine speed and the vehicle speed. A derivation setting may be made based on this. When the opening degree of the EGR valve 50 is controlled based only on the engine speed, the opening degree of the EGR valve 50 may be made smaller as the engine speed becomes lower. Further, when the opening degree of the EGR valve 50 is controlled based only on the vehicle speed, the opening degree of the EGR valve 50 may be made smaller as the vehicle speed becomes slower.

  In the above embodiment, the opening degree of the EGR valve 50 is changed in the closing direction from the initial opening degree to the fully closed final opening degree. However, the opening degree of the EGR valve 50 may be changed to a final opening degree other than full closing. The final opening may be set based on the engine speed and vehicle speed at the start of energy recovery. For example, when the engine speed at the start of energy recovery is on the high speed side, the engine speed is on the low speed side. With respect to the final opening of 0% opening, the final opening of 50% opening is set. Thereby, it is possible to prevent a deceleration shock from occurring. Furthermore, when the final opening is changed in this way, the arrival time from the initial opening to the final opening may be made substantially the same. For example, when the engine speed at the start of energy recovery is low, the opening of the EGR valve 50 is closed by 20% every time the engine speed decreases by 200 rpm, whereas when the engine speed at the start of energy recovery is high, the engine The closing speed of the EGR valve 50 toward the closing side may be changed in accordance with the engine speed at the start of energy recovery so that the opening degree of the EGR valve 50 is closed by 10% every time the speed decreases by 200 rpm.

  The mapped data as shown in FIG. 4 is preferably provided for each gear stage of the transmission. Then, by searching the data corresponding to the gear position at that time based on the engine speed and the vehicle speed, the opening degree of the EGR valve 50 at that time may be derived when the energy is being recovered. . By doing so, it becomes possible to prevent a deceleration shock from occurring more appropriately. When the gear position is changed during one energy recovery, the data used for deriving the opening degree of the EGR valve 50 may be switched at the time of the change. Therefore, the opening degree of the EGR valve 50 during the energy recovery can be changed not only in the decreasing direction but also in the increasing direction.

  Moreover, although energy recovery was performed during the fuel cut in the above-described embodiment, it may be performed at other times. For example, energy recovery may be performed during an operation state in which fuel is injected.

  In the above embodiment, the pressure energy recovered in the pressure accumulating tank 64 is used for assisting the operation of the supercharger 40. However, this does not limit the application of the recovered pressure energy, and the recovered pressure energy can be used for operation assistance of various functional parts. The energy recovery passage connecting the exhaust passage 28 and the pressure accumulating tank 64 and the energy discharging passage connecting various functional parts and the pressure accumulating tank 64 may be separated.

  Further, in the above embodiment, the exhaust throttle valve 56 is a butterfly valve, but may be a valve of another type. The exhaust throttle valve 56 can be, for example, a poppet valve or a shutter valve. As the exhaust throttle valve 56, a valve provided for an exhaust brake may be used. Further, the EGR valve 50 and the flow rate control valve 66 may be a valve of a type other than the poppet type valve, and may be a butterfly type valve or a shutter type valve. When the energy recovery passage and the energy release passage are separated, the valve provided in the energy recovery passage may be a check valve.

  Moreover, in the said embodiment, although it decided to provide one pressure accumulation tank 64, it may be provided with two or more. When two or more accumulator tanks 64 are provided, the accumulator tanks 64 can be dispersed in the vehicle.

  In the above embodiment, the present invention is applied to a diesel engine. However, the present invention is not limited to this, and the present invention can be applied to various internal combustion engines such as a port injection type gasoline engine and a cylinder injection type gasoline engine. It is applicable to. The fuel used is not limited to light oil or gasoline, but may be alcohol fuel, LPG (liquefied natural gas), or the like. Further, the number of cylinders of the internal combustion engine to which the present invention is applied may be any number.

  Although the present invention has been described with a certain degree of specificity in the above-described embodiments and modifications thereof, various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention described in the claims. It must be understood that changes are possible. That is, the present invention includes modifications and changes that fall within the scope and spirit of the appended claims and their equivalents.

It is a conceptual diagram of the internal combustion engine system of the vehicle to which the energy recovery device of the embodiment is applied. This graph shows changes in vehicle speed, pressure in the exhaust passage upstream of the exhaust throttle valve, and engine speed on the same time axis when energy is recovered by closing the exhaust throttle valve and EGR valve from the beginning. is there. It is a control flowchart of an embodiment. 5 is a graph conceptually showing a relationship between an opening degree of an EGR valve, an engine speed, and a vehicle speed in energy recovery control. 6 is a graph conceptually showing changes in the opening of the exhaust throttle valve, the opening of the EGR valve, and the pressure of the exhaust passage on the upstream side of the exhaust throttle valve on the same time axis in accordance with the energy recovery control. It is a graph showing the relationship between engine speed and deceleration torque. It is the graph which represented typically the pressure change of the exhaust passage upstream of an exhaust throttle valve accompanying energy recovery.

Explanation of symbols

10 Internal combustion engine 28 Exhaust passage 46 EGR passage 50 EGR valve 56 Exhaust throttle valve 64 Accumulation tank

Claims (5)

An exhaust throttle valve provided in an exhaust passage of the internal combustion engine, a pressure accumulating vessel that can communicate with the exhaust passage upstream of the exhaust throttle valve via a valve, and energy from the exhaust passage upstream of the exhaust throttle valve to the pressure accumulating vessel In an energy recovery device comprising an exhaust throttle valve control means for controlling the exhaust throttle valve to perform recovery,
A communication passage communicating with the exhaust passage upstream of the exhaust throttle valve;
A pressure control valve provided in the communication path;
When the exhaust throttle valve is controlled to be closed by the exhaust throttle valve control means, the opening of the pressure control valve is set so that the pressure in the exhaust passage upstream of the exhaust throttle valve is a pressure at which a deceleration shock does not occur. Pressure control valve control means for controlling;
An energy recovery device comprising:   The energy recovery device according to claim 1, wherein the communication path is an EGR path that connects an exhaust path upstream of the exhaust throttle valve and an intake path, and the pressure control valve is an EGR valve.   The pressure control valve control means sets the opening of the pressure control valve to an initial opening determined based on at least one of the engine speed and the vehicle speed in synchronization with the closing of the exhaust throttle valve, and then the engine speed and The energy recovery device according to claim 1 or 2, wherein the opening degree of the pressure control valve is controlled so as to change the opening degree of the pressure control valve based on at least one of vehicle speeds.   The pressure control valve control means controls the opening of the pressure control valve so that the opening of the pressure control valve becomes smaller as the engine speed becomes lower. The energy recovery device described in 1.   The pressure control valve control means controls the opening of the pressure control valve so that the opening of the pressure control valve is reduced as the vehicle speed becomes slower. Energy recovery equipment.

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