JP2012251489A - Supercharge-assist method for internal combustion engine and the internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supercharge-assist method for an internal combustion engine capable of reducing a consumption amount of gas in an accumulated gas container for use in supercharge-assist, by detecting an intake pressure and by starting the control of supercharge-assist using the compressed gas for the supercharge, immediately before reaching a smoke limit, in the internal combustion engine using the gas stored in the accumulated gas container for the supercharge-assist, and to provide the internal combustion engine.SOLUTION: In a transient state of this internal combustion engine 1, 1A, the supercharge-assist for shutting off EGR gas Ge and intake A by an operation of an EGR valve 21 and a flow path switching operation of a flow path switching device 30 to supply gas C in an accumulated gas container to an intake passage 12 is performed, only when a pressure Pt in the accumulated gas container 27 is equal to or more than a preset lower limit pressure PL and when a supply target fuel amount Qt calculated on the basis of a measured engine rotation speed Ne and accelerator opening Ac exceeds a non-supercharge maximum fuel amount (zero boost) Q0 in which the supercharge for the same engine rotation speed Ne is not performed.

Description

  The present invention relates to a supercharging assist method for an internal combustion engine and an internal combustion engine that can increase the EGR rate by supplying gas stored in a gas storage container into a cylinder in a transient state of the internal combustion engine.

  In EGR (exhaust gas recirculation) for reducing NOx (nitrogen oxide) in exhaust gas of an internal combustion engine such as a diesel engine, there are a high pressure EGR method and a low pressure EGR method in an internal combustion engine equipped with a supercharging system. In this high pressure EGR system, for example, as shown in FIG. 9, in an internal combustion engine 1X equipped with a high pressure EGR system, an EGR passage 17 is provided closer to the engine body 11 than the turbocharger 14, and the engine body The EGR gas Ge is recirculated from the 11 exhaust manifolds 11 b to the intake manifold 11 a via the EGR passage 17. Further, in the low pressure EGR system, for example, as shown in FIG. 10, in the internal combustion engine 1Y provided with the low pressure EGR system, an EGR passage 17 is provided on the opposite side of the engine body 11 from the turbocharger 14. The EGR gas Ge is recirculated from the downstream side of the turbine 14b to the upstream side of the compressor 14a via the EGR passage 17.

  In any of these EGR systems, the MAF control system is generally used to control the amount of EGR gas. In this MAF control method, if the amount of fresh air (air amount) sucked into the cylinder of the engine without EGR is Mo and the amount of fresh air sucked into the cylinder by performing EGR is Me, it is recirculated. Since the EGR gas amount Megr is Megr = Mo−Me, the EGR gas amount Megr is controlled by controlling the fresh air amount Me based on the valve opening degree of the EGR valve 21 based on this.

  That is, based on the data map of the fresh air amount Me created by setting the fresh air amount Me for each engine operating state in advance using the engine rotational speed Ne and the fuel load Q as parameters, the actual engine operating time is determined. The target fresh air amount Met is calculated from the rotational speed Ne and the fuel load Q, and the actual fresh air amount Me is controlled to become the target fresh air amount Met, thereby controlling the EGR gas amount Megr. Yes.

  However, when a turbocharger is used, the exhaust gas energy (enthalpy) is used for supercharging, so it is impossible to eliminate the response delay (turbo lag) of the turbocharger. The MAF control method has the following problems due to the turbo lag. In a transient state in which the load suddenly increases due to the turbo lag, the boost pressure does not increase to the pressure set during steady operation, so the intake air amount of the engine decreases. In other words, even an engine with a turbo-type supercharger has the same intake air amount as a non-supercharged engine.

  Therefore, the target EGR amount set under the steady operation condition cannot be achieved, and as shown in FIG. 11, the NOx emission amount increases when performing a rapid transient operation. Further, in order to limit the amount of soot generated, smoke limit control is performed in which the amount of fuel input is suppressed in a region where the soot does not increase when the supercharging pressure does not rise above a certain level. As a result, as shown in FIGS. 12 and 13, both the fuel injection amount Q and the air amount (Mo, Me) are suppressed as indicated by the dotted lines, and there is a problem that the power during acceleration is suppressed. For this reason, in a transient state where the load suddenly increases during acceleration or the like, an increase in NOx emissions and a deterioration in fuel consumption occur.

  On the other hand, in the case of using a mechanical supercharger that performs supercharging by directly driving the supercharger by an engine crankshaft or the like, the delay in the supercharging response can be eliminated, but the engine speed is determined. However, there is a problem that fuel efficiency deteriorates because the amount of supercharging is determined regardless of the amount of fuel and the amount of work required for driving is large.

  As a countermeasure, in recent years, an internal combustion engine 1Z having a storage gas supply system as shown in FIG. 14 has been studied, and in this storage gas supply system, a part Gp of the exhaust gas G discharged from the internal combustion engine 1Z. The mixed gas C mixed with air Aa is compressed by a positive displacement compressor (exhaust compressor) 25 to increase the pressure, and the increased mixed gas C is stored in a gas storage container (pressure container) 27 to release electromagnetic waves in a transient state. The valve 36 is opened and the mixed gas C is discharged to the intake passage 12 downstream of the intake valve (intake throttle) 35 via the pressure regulating valve 29, whereby the amount of intake air into the cylinder of the internal combustion engine 1Z is supercharged. There has been proposed a supercharging control device that increases the same level as an attached engine, reduces NOx by the effect of EGR, and solves the problem of turbo lag (see, for example, Patent Document 1).

  When this storage gas supply system is adopted, the supercharging pressure is increased by releasing the gas mixture C pressurized during the transition into the intake passage 12 of the engine 1Z, thereby increasing the amount of air into the cylinder. Can increase the amount of fuel. As a result, acceleration performance is improved and soot discharge can be suppressed. Further, since the supercharging pressure is higher than the internal pressure of the exhaust manifold 11b, the pumping loss of the internal combustion engine 1Z is reduced, and the fuel efficiency can be improved.

  Regarding the determination of rapid acceleration, which is the timing of releasing the mixed gas C, the driver's intention of rapid acceleration is determined using the rate of change of the engine speed, the rate of change of the accelerator depression amount, the rate of change of the fuel flow rate, etc. There is a way to do it.

  However, in the method of judging based on the rate of change of the engine speed or the like, as shown in FIG. 3, it is generally called zero boost Q, up to a non-supercharged maximum fuel amount Q0 corresponding to the fuel amount in the non-supercharged engine. Even if there is a region where there is no problem even if a delay in supercharging occurs due to the time lag of the turbocharger, even if this region RA is below the maximum amount of unsupercharged fuel Q0, Supercharging assistance by supply will be performed.

  On the other hand, since the amount of gas stored in the gas storage container is limited, if a large amount of stored gas is consumed, it takes time to store the pressure again, and the frequency of use of the supercharging assist device is limited. There is a problem that the work for accumulating pressure increases and the effect of improving fuel efficiency decreases.

JP 2011-21558 A

  The present invention has been made in view of the above situation, and an object of the present invention is to store a part of exhaust gas of an internal combustion engine, air, and any of these mixed gases using a gas compression device. Detects intake pressure in an internal combustion engine that accumulates in a vessel and temporarily supplies the gas into the cylinder in a transient state where the load increases suddenly to suppress NOx emission in the transient state and improve acceleration performance Then, by starting the supercharging assistance control using the accumulated gas for supercharging immediately before the smoke limit is applied, it is possible to reduce the consumption of gas in the gas storage container used for supercharging assistance. An object of the present invention is to provide a supercharging assist method for an internal combustion engine and an internal combustion engine.

  In order to achieve the above object, a supercharging assist method for an internal combustion engine according to the present invention comprises an EGR passage for recirculating a part of exhaust gas of the internal combustion engine into a cylinder, a part of exhaust gas of the internal combustion engine, A gas compression device for compressing air and any of these mixed gases, a gas storage container for storing the gas compressed by the gas compression device, and a flow path switching device between the gas storage container and the intake system passage In the supercharging assist method for an internal combustion engine provided with a storage gas supply passage connected via the internal combustion engine, in a transient state of the internal combustion engine, and the pressure inside the storage gas container is equal to or higher than a preset lower limit pressure and measured The EGR valve is operated only when the supply target fuel amount calculated from the determined engine speed and accelerator opening is equal to or greater than the maximum non-supercharged fuel amount when supercharging is not performed for the same engine speed. And the channel of the channel switching device The replacement operation, a method characterized by performing supercharging assisting to supply the gas in the gas storage vessel into the intake passage by blocking air intake and EGR gas.

  According to this method, when the operating state of the internal combustion engine such as when suddenly accelerating or starting a vehicle equipped with the internal combustion engine is in a transient state, the deterioration of the acceleration performance due to the turbo lag is minimized, and the exhaust gas is prevented. In supercharging assistance with accumulated gas that can reduce particulate matter (PM) and nitrogen oxides (NOx), supercharging assistance is performed only when supercharging assistance is required. The consumption of the gas stored in the auxiliary gas storage container can be minimized. In addition, this makes it possible to reduce the restriction on supercharging assistance, reduce the time until the pressure is accumulated again, and the amount of work, thereby improving fuel efficiency.

  In the above-described supercharging assist method for an internal combustion engine, the intake pressure is lower than the unsupercharged maximum intake pressure that can supply the intake amount capable of burning the fuel of the unsupercharged maximum fuel amount, or lower than the unsupercharged maximum intake pressure. If the supercharging assistance is performed after the set supercharging assistance start intake pressure is reached, the intake pressure is higher than the maximum non-supercharging intake pressure even if the supply target fuel amount requires supercharging assistance. Supercharging by not starting supercharging assistance until the pressure is required, that is, by supercharging assistance when the fuel injection amount is about to be throttled at the smoke limit during acceleration or starting transition The consumption of gas in the auxiliary gas storage container can be minimized, and the stored gas can be saved.

  In addition, if this supercharging assistance method is adopted, even if the turbocharger breaks down and the intake pressure does not increase, that is, even if the intake pressure does not exceed the maximum non-supercharged intake pressure, Since the normal amount of fuel without supercharging does not affect EGR and the intake method within a range smaller than the maximum amount of unsupercharged fuel, the operation of the internal combustion engine can be continued as it is.

  In the above-described supercharging assistance method for an internal combustion engine, when the supercharging assistance is performed, the fuel supply amount is set to the non-supercharging maximum fuel amount until the intake pressure becomes the supercharging assistance start intake pressure, and the intake pressure is increased. If the fuel supply amount is the supply target fuel amount from when the air pressure exceeds the supercharging assist start intake pressure and the supercharging assist is started, excessive fuel supply in the air shortage until the supercharging assist starts Thus, the generation of smoke can be prevented, and unnecessary fuel consumption that does not generate torque can be avoided to improve fuel efficiency.

  An internal combustion engine for achieving the above object is an internal combustion engine capable of implementing the above-described supercharging assist method of the internal combustion engine, and an EGR passage for recirculating a part of the exhaust gas of the internal combustion engine into the cylinder. A gas compression device that compresses a part of the exhaust gas of the internal combustion engine, air, and any of these mixed gases, a gas storage container that stores the gas compressed by the gas compression device, and the storage An internal combustion engine comprising: a storage gas supply passage for connecting a gas container and an intake system passage through a flow passage switching device; an EGR valve provided in the EGR passage; and a control device for controlling the flow passage switching device. The apparatus is in a transient state of the internal combustion engine, the internal pressure of the gas storage container is equal to or higher than a preset lower limit pressure, and the supply target fuel amount calculated from the measured engine speed and accelerator opening is The same The EGR gas and the intake air are cut off by the operation of the EGR valve and the flow path switching operation of the flow path switching device only when the maximum amount of non-supercharged fuel when the supercharging with respect to the gin rotation speed is not performed. It is configured to perform supercharging assistance for supplying the gas in the gas storage container to the intake passage.

  According to this configuration, since supercharging assistance is performed only when supercharging assistance is necessary, consumption of gas stored in the supercharging assistance gas storage container can be minimized. In addition, this makes it possible to reduce the restriction on supercharging assistance, reduce the time until the pressure is accumulated again, and the amount of work, thereby improving fuel efficiency.

  In the above internal combustion engine, the control device is configured such that the intake pressure is lower than the maximum non-supercharged intake pressure capable of supplying an intake amount capable of combusting the fuel of the maximum non-supercharged fuel amount, or lower than the maximum non-supercharged intake pressure. The control is performed to perform the supercharging assistance after the set supercharging assistance start intake pressure is reached. With this configuration, even if the target fuel amount requires supercharging assistance, supercharging assistance is not started until the intake pressure reaches the limit where supercharging exceeding the maximum non-supercharging intake pressure is required. Consumption of gas in the auxiliary gas storage container can be minimized. Thereby, the saved gas can be saved.

  Moreover, according to this configuration, even if the turbocharger breaks down and the intake pressure does not rise, that is, even if the intake pressure does not exceed the maximum non-supercharged intake pressure, Since the fuel amount without supply does not affect the EGR and the intake method within the range smaller than the maximum fuel amount, the operation of the internal combustion engine can be continued as it is.

  In the internal combustion engine, when the supercharging assistance is performed, the control device sets the fuel supply amount to the non-supercharging maximum fuel amount until the intake pressure becomes the supercharging assistance start intake pressure, The control is performed so that the fuel supply amount is set as the supply target fuel amount from the time when the supercharging assistance is started when the intake pressure exceeds the supercharging assistance start intake pressure.

  According to this configuration, it is possible to avoid excessive fuel supply due to shortage of air until the start of supercharging assistance, to prevent the generation of smoke, and to avoid unnecessary fuel consumption that does not generate torque and to improve fuel efficiency. .

  According to the supercharging assistance method and the internal combustion engine of the internal combustion engine according to the present invention, a part of the exhaust gas of the internal combustion engine, air, and any one of these mixed gases are stored in the gas storage container using the gas compression device. In an internal combustion engine that suppresses transient NOx emission and improves acceleration performance by temporarily supplying the gas into the cylinder in a transient state where the load increases and the load suddenly increases, the intake pressure is detected. By starting the supercharging assistance control using the accumulated gas for supercharging immediately before the smoke limit is applied, the consumption of gas in the gas storage container used for supercharging assistance can be reduced.

It is a figure showing composition of an internal-combustion engine of a 1st embodiment concerning the present invention. It is a figure which shows the structure of the internal combustion engine of 2nd Embodiment which concerns on this invention. It is a figure which shows the fuel amount characteristic at the time of non-supercharging, and the fuel amount characteristic at the time of supercharging. It is a figure which shows an example of the control flow of the supercharging assistance method of the internal combustion engine of embodiment which concerns on this invention. It is a figure which shows the detail of step S30 of FIG. It is a figure for demonstrating the drive of the gas compression apparatus for stored gas. It is a figure which shows the structure of the flow-path switching apparatus comprised with the three-way switching valve in the state by which the intake line was connected. It is a figure which shows the structure of the flow-path switching apparatus comprised with the three-way switching valve in the state by which the stored gas supply line was connected. It is a figure which shows the structure of the internal combustion engine of a high pressure EGR system of a prior art. It is a figure which shows the structure of the low pressure EGR type internal combustion engine of a prior art. It is a figure which shows the relationship between the change of a vehicle speed, and instantaneous NOx discharge | emission amount. It is a figure which shows the characteristic of the fuel injection quantity in a full load, and the movement at the time of transition. It is a figure which shows the response delay of the turbo supercharger at the time of transition, and the relationship of EGR. It is a figure which shows the structure of the internal combustion engine of a prior art.

  Hereinafter, an internal combustion engine supercharging assist method and an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an engine (internal combustion engine) 1 according to a first embodiment of the present invention includes an intake passage 12 connected to an engine body 11, an intake manifold 11a, and an exhaust passage 13 connected to an exhaust manifold 11b. It is configured. The intake manifold 11a and the intake passage 12 form an intake system passage, and the exhaust manifold 11b and the exhaust passage 13 form an exhaust system passage.

  The intake passage 12 is provided with a compressor 14a of a turbocharger 14, and the exhaust passage 13 is provided with a turbine 14b of a turbocharger 14, a diesel particulate filter (DPF) device 15, and a NOx occlusion reduction type. A NOx purification catalyst 16 formed of a catalyst or the like is provided.

  Further, an EGR passage 17 is branched from the exhaust passage 13 on the upstream side of the turbine 14b, and merges with the intake passage 12 on the upstream side of the compressor 14a at the EGR merging portion 18. The EGR passage 17 is provided with a diesel particulate filter (DPF) device 19, an EGR cooler 20, and an EGR valve 21 from the upstream side.

  Further, an exhaust gas introduction passage 22 is provided so as to branch from the exhaust passage 13 on the downstream side of the NOx purification catalyst 16. The exhaust gas introduction passage 22 is provided with an EGR cooler 23 and a three-way valve 24, and the exhaust gas introduction passage 22 is formed by a mechanical positive displacement turbocharger (preferably a reciprocating type) or the like. It is connected to the. The gas compression device 25 is connected to a gas storage container 27 formed of a pressure container or the like by a compressed gas supply passage 26. The gas storage container 27 is connected to the intake passage 12 by a stored gas supply passage 28. The exhaust gas introduction passage 22, the compressed gas supply passage 26 and the stored gas supply passage 28 form a pressure accumulation gas system passage.

  As shown in FIG. 6, the gas compression device 25 transmits power from an axle 31 of a vehicle on which the engine 1 is mounted to a drive shaft of the gas compression device 25 via gears 32 and 33 and an electromagnetic clutch 34. When the electromagnetic clutch 34 is turned on and connected, the gas compressor 25 is driven, and part of the exhaust gas G Gp from the exhaust gas introduction passage 22, the air Aa, and any one of these mixed gases C Is compressed and pressurized to be supplied to the gas storage container 27 and stored.

  As shown in FIG. 1, a pressure regulating valve 29 is disposed in the stored gas supply passage 28 to adjust the pressure of the gas C supplied to the flow path switching device 30. At this time, the three-way valve 24 preferably adjusts the amount of part Gp of the exhaust gas G and the amount of air Aa to keep the oxygen concentration in the gas C stored in the gas storage container 27 substantially constant. Thus, the control when performing EGR can be simplified.

  In order to control the above devices, a control device 40 called an engine control unit (ECU) that controls the overall operation of the engine 1 is provided, and the control device 40 controls the pressure Pt in the gas storage container 27. The engine rotation speed Ne, the accelerator opening degree Ac, and the like are detected, and the electromagnetic clutch 34 and the three-way valve 24 are controlled based on the results, and the amount (pressure) of the gas C in the gas storage container 27 and the exhaust gas Gp The mixing ratio of air Aa is adjusted and controlled.

  As shown in FIG. 1, when the gas storage device 27 is provided with an adjustment valve 27a for adjusting the maximum pressure inside the gas storage container 27 and the gas compression device 25 is driven, work always occurs. The adjustment valve 27a is adjusted as follows. In FIG. 1, the adjustment valve 27 a is provided in the gas storage container 27, but the adjustment valve 27 a may be provided in the compressed gas supply passage 26 between the gas storage container 27 and the gas compression device 25.

  That is, the engine 1 has an EGR passage 17 for recirculating a part Ge of the exhaust gas G into the cylinder, a part Gp of the exhaust gas G of the engine 1, the air Aa, and any one of these mixed gases. A gas compression device 25 that compresses C, a gas storage container 27 that stores the gas C compressed by the gas compression device 25, and a gas storage supply passage 28 that connects the gas storage container 27 and the intake passage 12 are provided. Composed.

  The intake passage 12 and the stored gas supply passage 28 are connected via a flow path switching device 30. When the flow path switching device 30 is arranged downstream of the EGR merging portion 18, which is the merging portion of the EGR passage 17 and the intake passage 12, the EGR gas Ge is provided in two stages by the EGR valve 21 and the flow path switching device 30. It is preferable because it can be shut off with. The flow switching device 30 is configured to switch between the stored gas supply passage 28 side and the upstream passage side of the intake passage 12 while the downstream passage side of the intake passage 12 is open.

  The flow path switching device 30 can be constituted by a three-way switching valve as shown in FIGS. In addition, although not shown, the intake valve provided in the intake system passage 12 and the opening / closing valve provided in the stored gas supply passage 28 may be used. That is, in the case of a system in which the intake passage 12 is closed by an intake valve (intake throttle) or the like without using the flow path switching device 30 of the three-way switching valve, the EGR merging portion 18 is provided upstream of the intake valve (not shown). It is preferable that the EGR gas Ge is provided to be shut off in two stages by the EGR valve 21 and an intake valve (not shown).

  In the flow path switching device 30 shown in FIGS. 7 and 8, the shutter 30c is moved by moving the rod 30b of the cylinder 30a for high-speed driving by inserting the driving gas Ap and extracting the gas Ae on the back surface of the piston. 7, the gas storage passage 28 side is closed, as shown in FIG. 7, and the upstream side 12a and the downstream side 12b of the intake passage 12 are communicated. Further, as shown in FIG. The upstream side 12 a side is closed, and the stored gas supply passage 28 and the downstream side 12 b of the intake passage 12 are communicated.

  Next, an engine (internal combustion engine) 1A according to a second embodiment of the present invention will be described. As shown in FIG. 2, in the engine 1A of the second embodiment, the EGR passage 17 is branched from the exhaust passage 13 downstream of the NOx purification catalyst 16 downstream of the turbine 14b. 17 is different from the first embodiment in which the turbocharger 14 branches from the exhaust passage 13 on the upstream side of the turbine 14b. Other points are the same as in the first embodiment.

  That is, the exhaust gas Ge flowing into the EGR passage 17 is a part of the exhaust gas G before passing through the turbine 14b of the turbocharger 14 in the engine 1 of the first embodiment. On the other hand, in the engine 1A of the second embodiment, it becomes a part of the exhaust gas G after passing through the turbine 14b of the turbocharger 14. In other words, the engine 1 of the first embodiment employs the high pressure EGR method, and the engine 1A of the second embodiment employs the low pressure EGR method.

  Next, a supercharging assist method for the internal combustion engine performed by the control device 40 of the engine (internal combustion engine) 1 or 1A will be described. This supercharging assist method for an internal combustion engine is a method that can be implemented by the engine 1 or 1A having the above-described configuration. In this supercharging assist method for an internal combustion engine, a part of the exhaust gas G in the exhaust passage (exhaust system passage) 13 of the engines 1 and 1A, the air Aa, and any one of these mixed gases C are compressed and stored. To do.

  At the same time, in the supercharging assistance method, when the operating state of the engine 1, 1A is not a transient state, a part Ge of the exhaust gas G of the engine 1, 1A is recirculated into the cylinder via the EGR passage 17, When the engine 1, 1 </ b> A is in a transitional state, supercharging assistance for temporarily supplying the gas C stored in the gas storage container 27 to the intake passage (intake system passage) 12 is performed. In this supercharging assistance, the EGR gas Ge from the EGR passage 17 and the fresh air A from the intake passage 12 are blocked by the flow path switching device 30 and only the gas C is supplied to the downstream intake passage 12. .

  Further, in this supercharging assist method for an internal combustion engine, a flow path switching device 30 configured by a three-way switching valve as shown in FIGS. 7 and 8 for shutting off the EGR gas Ge and fresh air A and supplying the gas C. Or the EGR gas Ge and the fresh air A are shut off and the gas C is supplied to an intake valve (not shown) provided in the intake passage (intake system passage) 12 and to the stored gas supply passage 28. Open / close valve (not shown).

  In these controls, the control device 40 is based on detected values such as the engine speed Ne, the engine air amount (Mo, Me), the engine fuel amount (fuel injection amount) Q, the pressure Pt inside the gas storage container 27, and the like. Thus, the pressure regulating valve 29, the EGR valve 21, and the flow path switching device 30 are controlled.

  In this supercharging assistance method, the supercharging assistance is performed under the condition that the operating state of the engine 1, 1A such as when the vehicle equipped with the engine 1, 1A is accelerated or started is in a transient state, and the gas storage container 27 Is equal to or higher than a preset lower limit pressure PL (Pt ≧ PL), and the supply target fuel amount Qt based on the measured engine rotational speed Ne and the accelerator opening degree Ac is a non-supercharging maximum fuel amount (zero). Boost) Supercharge assistance is performed only when Q0 is exceeded.

  The determination of whether the operating state of the engine 1 or 1A is a transient state, which is one of the three conditions for starting supercharging assistance, is the change rate ΔNe of the engine rotational speed Ne, the accelerator opening (accelerator depression amount). ) Judgment is made based on the rate of change ΔAc of Ac and the rate of change ΔQin of the fuel supply amount Qin. This is because the turbo lag problem does not occur if it is not in a transient state, so supercharging assistance is unnecessary.

  Further, the detected value Pt of the pressure sensor 51 provided in the gas storage container 27 is compared with a preset lower limit pressure PL, and only when the internal pressure Pt of the gas storage container 27 is equal to or higher than the lower limit pressure PL (Pt ≧ PL). The reason why the supply is supplemented is that the supercharging assistance gas C is insufficient and sufficient supercharging assistance cannot be performed unless the pressure Pt in the gas storage container 27 is equal to or higher than the lower limit pressure PL.

  Furthermore, supercharging assistance is performed only when the supply target fuel amount Qt exceeds the non-supercharging maximum fuel amount (zero boost) Q0. That is, supercharging assistance is performed only in the case of the region RB shown in FIG. 3 (region between the Q characteristic at the time of non-supercharging and the Q characteristic at the time of supercharging). The supply target fuel amount Qt is a fuel amount for generating torque required by the engine speed Ne and the accelerator opening degree Ac during a transition, and is supplied from the measured engine speed Ne and the accelerator opening degree Ac. Calculation is based on map data (Ne, Ac → Qt) for fuel amount calculation.

  At the same time, the non-supercharged maximum fuel amount Q0 that can be burned without supercharging at the engine speed Ne is calculated from the map data (Ne → Q0) for the non-supercharged maximum fuel amount. This non-supercharging maximum fuel amount Q0 is obtained from the Q characteristic at the time of non-supercharging. Up to a non-supercharged maximum intake amount capable of burning the non-supercharged maximum fuel amount Q0, intake can be performed without supercharging by the turbo supercharger 14 and without supercharging assistance. By imposing these three conditions, supercharging assistance can be performed only when supercharging assistance is required.

  The supercharging assistance starts when the intake pressure P exceeds the supercharging assistance start intake pressure P1 (P ≧ P1). The supercharging assistance start intake pressure P1 is set to a non-supercharging maximum intake pressure (zero boost pressure) P0 that is an intake pressure necessary for supplying an air amount necessary for the non-supercharging maximum fuel amount Q0, Alternatively, it is set to a value slightly lower than this non-supercharging maximum intake pressure P0. This non-supercharging maximum intake pressure P0 is calculated by referring to the map data (Ne → P0) for non-supercharging maximum intake pressure P0 from the measured value of the engine speed Ne.

  When the intake pressure P is equal to or less than the non-supercharging maximum intake pressure P0 (P <P0), supercharging and supercharging assistance are not necessary. The supercharging assistance is not started until the intake pressure P exceeds (P ≧ P1). Since the turbocharger 14 is operating, there is a time delay due to the turbo lag, but the intake pressure P exceeds the supercharge assist start intake pressure P1 and the non-supercharge maximum intake pressure P0 (P ≧ P1). , P ≧ P0). In addition, the time T0 of the period during which supercharging assistance is performed is set in advance from the results of experiments and the like. This time T0 is set to about 1 second, for example.

  Even if it is the supply target fuel amount Qt that requires supercharging assistance, it is possible to save the accumulated gas C by not starting supercharging assistance until the limit (P ≧ P1) where supercharging is necessary. it can. Thereby, the consumption of the gas C in the supercharging assistance gas storage container (pressure vessel) 27 can be minimized.

  Further, even if the turbocharger 14 fails and the supercharging pressure P cannot be increased, that is, even if the intake pressure P does not exceed the non-supercharging maximum intake pressure P0 (P ≧ P0), Strictly speaking, even if the intake pressure P does not exceed the supercharging assist start intake pressure P1 (P ≧ P1), the normal supply target fuel amount Qt without supercharging is smaller than the maximum fuel amount Q0 (Qt < Since the Q0) range control is not affected, the internal combustion engine can be operated as it is. From this point of view, it is preferable that the maximum difference between the non-supercharging maximum intake pressure P0 and the supercharging assist start intake pressure P1 is the same or different even if they are different.

  The fuel supply at the time of supercharging assistance is fuel supply control when the supply target fuel amount Qt exceeds the non-supercharging maximum fuel amount Q0, although the supply target fuel amount Qt is larger than the non-supercharging maximum fuel amount Q0. Until the intake pressure P becomes the supercharging assistance start intake pressure P1, in other words, until the supercharging assistance is performed, the fuel supply amount Qin is limited to the non-supercharging maximum fuel amount Q0 or less. As a result, the fuel supply amount Qin is within the smoke limit (within the region RA in FIG. 3), so that smoke can be avoided. The generated torque at this time is lower than the required torque, but the intake pressure P is increased to save the gas C.

  The fuel supply amount Qin is set as the supply target fuel amount Qt from when the intake pressure P exceeds the supercharging assistance start pressure P1 and supercharging assistance by the gas C is started. Thus, after the supercharging assistance is started, it is possible to avoid the occurrence of smoke even if the fuel supply amount Qin becomes the supply target fuel amount Qt that is larger than the non-supercharging maximum fuel amount Q0. The generated torque at this time is the required torque.

  Note that after the supercharging assistance performed during the turbo lag is stopped and the turbo supercharger 14 is switched to supercharging, the turbo lag of the turbo supercharger 14 is eliminated and sufficient supercharging is performed. Therefore, the occurrence of smoke can be avoided even if the fuel supply amount Qin is set to the supply target fuel amount Qt. By setting the fuel supply amount Qin to the supply target fuel amount Qt, the generated torque becomes the required torque. As a result, smoke can be prevented, excessive fuel supply in an air shortage state, that is, useless fuel consumption without generating torque can be avoided, and fuel consumption can be improved.

  Next, control for performing the above-described supercharging assistance will be described based on the control flow illustrated in FIGS. 4 and 5. The control flow of FIGS. 4 and 5 is called from the upper control flow together with the start of operation of the engines 1 and 1A, starts, and repeatedly executes step S11 to step S20 or step S11 to step S30. An interruption is generated by stopping the operation of the engines 1 and 1A, the return is performed from the middle of the control flow, the control flow is returned to the upper control flow, and the execution of this control flow is stopped.

  When the control flow of FIG. 4 is called, in step S11, data necessary for this control is input and calculated. As these data, the engine rotation speed Ne measured by the engine rotation speed sensor, the accelerator opening Ac measured by the accelerator opening sensor, the measurement by the fuel flow rate sensor, or calculated from the engine rotation speed Ne and the accelerator opening Ac. There are a target fuel amount Qt to be supplied, an intake pressure P measured by a boost sensor (intake pressure gauge) usually mounted on the engine, an internal pressure (internal pressure) Pt of the gas storage container 27, and the like.

  In the next step S12, preset determination data is input, or each determination data is calculated based on the data input in step S11 and preset map data. As the determination data, a determination change rate ΔNe0 of the engine rotation speed Ne and a determination change rate ΔAc0 of the accelerator opening Ac for determining whether or not the operating state of the engines 1 and 1A is in a transient state. There are a change rate ΔQin0 for determination of the fuel supply amount Qin, a lower limit pressure PL for determining the internal pressure Pt of the gas storage container 27, and a non-supercharging maximum fuel amount (zero boost) Q0.

  In the next step S13, it is determined whether or not the operating state of the engines 1 and 1A is in a transient state. In this determination, for example, one or several combinations of a change rate ΔNe of the engine speed Ne, a change rate ΔAc of the accelerator opening (accelerator depression amount) Ac, and a change rate ΔQin of the fuel supply amount Qin are changed for each determination. Judgment is made based on whether or not the rates are ΔNe0, ΔAc0, and ΔQin0. If it is determined in this determination that there is no transient state (NO), the process goes to step S20, and normal control operation without supercharging assistance is performed. If it is determined that the state is a transient state (YES), the process goes to step S14.

  In step S14, the internal pressure Pt of the gas storage container 27 is determined. If the internal pressure Pt is smaller than the lower limit pressure PL (Pt <PL) (NO), the process goes to step S20 to perform normal control operation without supercharging assistance. Do. When the internal pressure Pt is equal to or higher than the lower limit pressure PL (Pt ≧ PL) (YES), the process goes to step S15.

  In step S15, the supply target fuel amount Qt is determined. If the supply target fuel amount Qt is equal to or less than the non-supercharging maximum fuel amount Q0 (NO), the process goes to step S20, and normal control operation without supercharging assistance is performed. I do. When the supply target fuel amount Qt exceeds the non-supercharging maximum fuel amount Q0 (NO), the process goes to step S30 to perform the supercharging assist operation.

  In the normal operation in step S20, the same control as that in the engine not provided with the supercharging assist system is performed for a predetermined time (a preset time related to the determination of the engine operating state in step S11). Return to step S11.

  In the supercharging assist operation in step S30, as shown in FIG. 5, the intake pressure P is input every moment in step S31, the intake pressure P is determined in step S32, and the intake pressure P is supercharged. If it is smaller than the starting intake pressure P1 (P <P1) (NO), go to step S33 and supply target fuel amount calculated from the engine rotation speed Ne and the accelerator opening degree Ac that are measured every moment of the fuel supply amount Qin. It is set not to Qt but to the non-supercharged maximum fuel amount Q0 calculated from the engine rotational speed Ne measured every moment, and fuel injection into the cylinder is performed for a predetermined period of time (in advance related to the intake pressure determination interval). For a set time), and the process returns to step S31. At this time, the supply of gas C from the gas storage container 27 is not yet performed.

  In step S32, when the intake pressure P is equal to or higher than the supercharging assist start intake pressure P1 (P ≧ P1) (YES), the EGR valve 21 is controlled to be closed and the flow path switching device 30 is allowed to flow in step S34. The passage switching control is performed so that the intake passage 12 and the EGR passage 17 are shut off, and the storage gas supply passage 28 and the downstream side of the intake passage 12 are communicated with each other, so that the gas C accumulated only during a preset time T0 is supplied. Supply and provide supercharging assistance. In this step S34, the restriction on the fuel supply amount Qin, which was limited to the maximum amount of unsupercharged fuel Q0 in step S33, is released, and the engine rotation speed Ne and the accelerator opening degree Ac that are measured every moment. Is set to the supply target fuel amount Qt calculated from the above, and fuel is injected into the cylinder.

  When the supply of the accumulated gas C in step S34 is stopped after the time T0 has elapsed, the process goes to step S35, and the fuel supply amount Qin is calculated from the engine speed Ne and the accelerator opening degree Ac that are measured every moment. In a state where the target fuel amount Qt is set, in other words, in a state where the state where the fuel supply amount Qin is limited to the non-supercharged maximum fuel amount Q0 is released, for a preset time, the turbocharger The operation in a state where supercharging by 14 is used as necessary, in other words, the operation without supercharging assistance by the accumulated gas C is set in advance for a predetermined time (related to the operation state determination interval in step S36). ) And go to step S36.

  In step S36, the operating state of the engine 1, 1A is determined. If the operating state remains in a transient state (YES), the process returns to step S35. If the operating state is no longer in a transient state (NO), step S30 is terminated. To do. This determination is performed based on the same determination criteria as the determination in step S13. When step S30 ends, the process returns to step S11.

  By repeating the steps S11 to S20 or the steps S11 to S30, it is possible to carry out the above-described supercharging assistance control. When the operation of the engine 1 or 1A is stopped, an interrupt is generated, the process goes to return from the middle of the flow, returns to the upper control flow, and the execution of this control flow is stopped.

  According to the supercharging assistance method for the internal combustion engine and the engines (internal combustion engines) 1 and 1A, the operating state of the engine 1 and 1A at the time of sudden acceleration or start of the vehicle equipped with the engine 1 and 1A is in a transient state. Sometimes, the reduction in acceleration performance due to the turbo lag of the turbocharger 14 can be prevented to a minimum, and particulate matter (PM) and nitrogen oxides (NOx) in the exhaust gas G can be reduced. In supercharging assistance using the accumulated gas C, supercharging assistance is performed only when supercharging assistance is necessary, so that the consumption of the gas C stored in the supercharging assistance gas storage container 27 is minimized. be able to. In addition, this makes it possible to reduce the limitation of supercharging assistance due to the shortage of gas C, to reduce the time and work amount until accumulating again, and to improve fuel efficiency.

  Also, after the intake pressure P becomes the supercharging assist start intake pressure P1 (the non-supercharged maximum intake pressure P0 that can supply the intake amount capable of burning the fuel of the non-supercharged maximum fuel amount Q0 or a value slightly smaller than this). By supercharging assistance, even if the target fuel amount Qt requires supercharging assistance, the supercharging is performed until the intake pressure P is close to the maximum non-supercharging maximum intake pressure P0 where supercharging is necessary. Since assistance is not started, that is, supercharging assistance is performed after the fuel supply amount Qin is likely to be throttled by the smoke limit in a transient state at the time of acceleration or starting, the gas storage container 27 for supercharging assistance. The consumption of the gas C can be minimized, and the accumulated gas C can be saved.

  In addition, by adopting this supercharging assistance method, even if the turbocharger 14 breaks down and the intake pressure P does not increase, that is, the intake pressure P becomes the maximum non-supercharged intake pressure. Even if the fuel supply amount Qin without normal supercharging is not greater than Q0, the above supercharging assistance method does not affect EGR and the intake method within the range where the normal fuel supply amount Qin without supercharging is smaller than the maximum non-supercharging fuel amount Q0. The operation of the engine 1, 1A can be continued as it is.

  Further, during the supercharging assistance, the fuel supply amount Qin is set to the nonsupercharging maximum fuel amount Q0 until the intake pressure P reaches the supercharging assistance start pressure P1 (≈unsupercharged maximum intake pressure P0). Supercharging assistance is achieved by setting the fuel supply amount Qin as the supply target fuel amount Qt from when the supercharging assistance is started when P exceeds the supercharging assistance start pressure P1 (≈unsupercharged maximum intake pressure P0). Since excessive fuel supply due to shortage of air before the start can be avoided, the generation of smoke can be prevented, and consumption of useless fuel that does not generate torque can be avoided and fuel efficiency can be improved.

  A supercharging assistance method and an internal combustion engine for an internal combustion engine according to the present invention are provided for supercharging assistance in an internal combustion engine that performs supercharging assistance using stored pressure gas in a transient state of the internal combustion engine such as during rapid acceleration or starting. The consumption of gas in the gas storage container can be minimized, the deterioration of acceleration performance due to the turbo lag can be prevented to a minimum, particulate matter and nitrogen oxides can be reduced, and fuel consumption can be improved.

  Therefore, a part of the exhaust gas, fresh air, and any of these mixed gases are stored in the gas storage container using a gas compression device, and the gas is stored in the cylinder in a transient state where the load increases rapidly. It can be used in a supercharging assist method for an internal combustion engine mounted on a truck, a bus, a passenger car, etc., and an internal combustion engine that can be temporarily supplied to the vehicle to suppress NOx emission in a transient state and improve acceleration performance.

1, 1A, 1X, 1Y, 1Z engine (internal combustion engine)
11 Engine body 11a Intake manifold (intake system passage)
11b Exhaust manifold (exhaust system passage)
12 Intake passage (intake system passage)
13 Exhaust passage (exhaust system passage)
14 Turbocharger 17 EGR passage 21 EGR valve 22 Exhaust gas introduction passage 25 Gas compression device 26 Compressed gas supply passage 27 Gas storage container 28 Gas storage supply passage 30 Flow path switching device 31 Vehicle axle 34 Electromagnetic clutch 35 Intake valve (Intake throttle)
40 Control Device 51 Pressure Sensor A Fresh Air Aa Air Ac Accelerator Opening C Gas G Exhaust Gas Ge EGR Gas Gp Exhaust Gas Part Ne Engine Speed P Intake Pressure P0 Unsupercharged Maximum Intake Pressure (Zero Boost Pressure)
P1 Supercharging assistance start intake pressure Pt Internal pressure PL of gas storage container Lower limit pressure Q0 Maximum fuel amount without supercharging (zero boost Q)
Qin Fuel supply amount Qt Supply target fuel amount T0 Time during which supercharging assistance is performed

Claims (6)

An EGR passage for recirculating a portion of the exhaust gas of the internal combustion engine into the cylinder;
A gas compression device for compressing a part of the exhaust gas of the internal combustion engine, air, and any of these mixed gases;
A gas storage container for storing the gas compressed by the gas compression device;
In the supercharging assist method for an internal combustion engine provided with a stored gas supply passage for connecting the gas storage container and the intake system passage through a flow switching device,
The engine is in a transient state of the internal combustion engine, the internal pressure of the gas storage container is equal to or higher than a preset lower limit pressure, and the supply target fuel amount calculated from the measured engine speed and accelerator opening is the same. The EGR gas and intake air are shut off and stored only by operating the EGR valve and the flow path switching operation of the flow path switching device only when the amount of fuel is equal to or greater than the maximum amount of unsupercharged fuel when supercharging is not performed for the rotational speed. A supercharging assistance method for an internal combustion engine, characterized by performing supercharging assistance for supplying the gas in a gas container to an intake passage.   The intake pressure becomes the non-supercharged maximum intake pressure that can supply the intake amount capable of burning the non-supercharged maximum fuel amount, or the supercharging assist start intake pressure that is set lower than the non-supercharged maximum intake pressure. 2. The supercharging assistance method for an internal combustion engine according to claim 1, wherein the supercharging assistance is performed after a while.   During the supercharging assistance, the fuel supply amount is set to the non-supercharging maximum fuel amount until the intake pressure becomes the supercharging assistance start intake pressure, and the intake pressure exceeds the supercharging assistance start intake pressure. 3. The supercharging assist method for an internal combustion engine according to claim 2, wherein the fuel supply amount is set to the supply target fuel amount after supercharging assistance is started. An EGR passage for recirculating a portion of the exhaust gas of the internal combustion engine into the cylinder;
A gas compression device for compressing a part of the exhaust gas of the internal combustion engine, air, and any of these mixed gases;
A gas storage container for storing the gas compressed by the gas compression device;
A storage gas supply passage connecting the gas storage container and the intake system passage through a flow switching device;
In an internal combustion engine including an EGR valve provided in the EGR passage and a control device for controlling the flow path switching device,
Supply target fuel calculated from the measured engine speed and accelerator opening when the control device is in a transient state of the internal combustion engine, and the pressure inside the gas storage container is equal to or higher than a preset lower limit pressure. Only when the amount is equal to or greater than the maximum amount of unsupercharged fuel when supercharging is not performed for the same engine speed, the EGR gas and the intake air are operated by the operation of the EGR valve and the channel switching operation of the channel switching device. An internal combustion engine that performs supercharging assistance that shuts off the gas and supplies the gas in the gas storage container to the intake passage.   The control device is configured to provide a non-supercharged maximum intake pressure capable of supplying an intake amount capable of burning the fuel of the non-supercharged maximum fuel amount, or a supercharging assist set to be lower than the non-supercharged maximum intake pressure. The internal combustion engine according to claim 4, wherein the supercharging assistance is controlled after the start intake pressure is reached.   When the supercharging assistance is performed, the control device sets the fuel supply amount to the non-supercharging maximum fuel amount until the intake pressure reaches the supercharging assistance start intake pressure, and the intake pressure serves as the supercharging assistance. 6. The internal combustion engine according to claim 5, wherein the control is performed so that the fuel supply amount is the supply target fuel amount from when the supercharging assistance is started beyond the start intake pressure.

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