JP6209943B2 - Supercharging assistance system for internal combustion engine and supercharging assistance method for internal combustion engine - Google Patents

Description

    The present invention is an internal combustion engine that uses a pressure-accumulation supercharging system that assists supercharging with an air-fuel mixture accumulated in a pressure accumulator vessel, while preventing overboost and maintaining the maximum combustion pressure of the internal combustion engine below an allowable maximum combustion pressure. The present invention relates to a supercharging assistance system for an internal combustion engine and a supercharging assistance method for an internal combustion engine that can secure an intake air amount and an EGR gas amount required during transient operation of the internal combustion engine.

  A turbocharger mounted on an internal combustion engine operates the turbine using the energy of the exhaust gas from the engine, and drives the compressor blades directly connected to the shaft of the turbine to take in the intake air. The compressed air is supplied to the cylinder according to the engine load.

  However, in this turbo-type supercharger, in a transient operation state where the load of the internal combustion engine increases rapidly, the required supercharge amount due to the turbo lag that delays the boost pressure from rising to the pressure set during steady operation. As a countermeasure, the EGR amount is reduced, so that the target EGR amount set in the steady operation condition cannot be secured, and soot is generated due to air shortage. There is a smoke limit problem that can be suppressed. Due to the problem caused by the turbo lag of this turbo-type supercharging system, the amount of EGR gas is limited and NOx increases, and the required acceleration performance at the time of start and overtaking cannot be obtained due to the suppression of the amount of supplied fuel. It has become the most important issue in relation to recent downsizing trends of internal combustion engines.

  In order to avoid the problem of the turbo lag, a mechanical supercharger that drives the compressor with the power of the crankshaft of the internal combustion engine may be used. When the engine speed is determined, the required fuel per cycle is determined. Since a certain amount of air is supercharged regardless of the injection amount, the compressor performs useless driving work when the fuel injection amount is small. Moreover, since a positive displacement supercharger is used for a mechanical supercharger, the driving work is large. Therefore, in general, the fuel efficiency is deteriorated in this mechanical supercharging system.

  Therefore, as a countermeasure against NOx increase and acceleration performance decrease due to shortage of air amount and EGR gas amount due to turbo lag in turbo type turbocharger and fuel consumption deterioration due to mechanical supercharger, internal combustion at the time of start or acceleration of vehicle etc. In a transient operation state of the engine, a pressure accumulation supercharging system that releases a mixture of air and exhaust gas pressurized in the pressure accumulation container into the intake passage may be employed. In this system, the boost pressure can be raised and both the intake air amount and the EGR amount can be secured, so that the fuel injection amount can be increased by increasing the air amount, and the acceleration performance can be improved. , NOx and soot emissions can be reduced.

  As this accumulator supercharging system, for example, in an internal combustion engine that uses gas accumulated in a gas accumulator for supercharging assistance, the pressure in the intake manifold or the pressure at the compressor outlet is detected to detect the accumulated gas. A supercharging assistance method and an internal combustion engine for an internal combustion engine that reduce the consumption of gas in a gas storage container used for supercharging assistance by starting supercharging assistance control for supercharging immediately before the smoke limit is applied. It has been proposed (see, for example, Patent Document 1).

  In general, in an accumulator supercharging system, even if the internal pressure in an accumulator vessel that accumulates a mixture of air and exhaust gas is constant, the internal pressure of the accumulator vessel is higher in the initial stage of releasing the mixture from the accumulator vessel. As it is consumed, the internal pressure of the pressure accumulating container decreases. Therefore, since the change of the supercharging pressure and the supercharging amount differs depending on the volume of the pressure accumulating container, the maximum combustion pressure (Pmax) of the engine greatly varies. In particular, in the low rotation speed range where only a small amount of air per unit time is required, the internal pressure of the accumulator vessel is high at the start of operation of the accumulator supercharging system. There is a problem that the combustion pressure increases.

  In order to suppress this maximum combustion pressure, if the internal pressure of the pressure accumulator vessel is lowered or the volume of the accumulator vessel is reduced, the amount of air-fuel mixture stored in the pressure accumulator vessel will be insufficient in the middle and high engine speed ranges. Or the number of supercharging assists that can be performed with a single charge of air is reduced, resulting in a problem that the amount of air required in the transient operation state of the engine cannot be obtained. Therefore, a large-capacity pressure storage container is required even at a low pressure.

JP 2012-251489 A

  The present invention has been made in view of the above, and an object of the present invention is to provide a supercharging assistance system for an internal combustion engine that uses a mixture of air and exhaust gas accumulated in a pressure accumulator for supercharging assistance, and an overcharge of the internal combustion engine. In the feed assist method, during transient operation of the internal combustion engine, when starting and accelerating from a low speed, over boost is prevented and the maximum combustion pressure of the internal combustion engine is maintained below the allowable maximum combustion pressure, while wasteful air-fuel mixture is reduced. To provide a supercharging assistance system for an internal combustion engine and a supercharging assistance method for an internal combustion engine that can suppress consumption and can secure a necessary intake air amount and EGR gas amount at the time of acceleration at a medium speed or higher. .

In order to achieve the above object, a supercharging assist system for an internal combustion engine according to the present invention pressurizes a mixture of a part of exhaust gas and air of an internal combustion engine and accumulates the pressure in a pressure accumulating vessel, thereby transiently operating the internal combustion engine. In the supercharging assistance system for an internal combustion engine that assists supercharging by discharging the air-fuel mixture accumulated in the pressure accumulating container to the intake passage of the internal combustion engine, a plurality of the pressure accumulating containers are provided in parallel. A control valve for controlling the release of the air-fuel mixture into the intake passage is provided for each pressure storage container, and the first pressure storage container of the plurality of pressure storage containers is used as a pressure storage container for a low rotation speed region. An accumulator other than the first accumulator is used as a pressure accumulator for the middle / high rotation speed region, and a volume of the first accumulator for the low rotation speed region is the volume of the accumulator for the medium / high rotation speed region. Smaller than before and before Set the container pressure of the first accumulator vessel for low rotational speed region lower than the pressure in the container accumulating container for the medium and high speed range, when the supercharging assisting the operating state of the internal combustion engine And a control device that controls the control valve so as to assist supercharging by selecting one or a plurality of pressure accumulators that discharge the air-fuel mixture from the plurality of pressure accumulators , When the operation state of the internal combustion engine is in a low rotational speed region at the time of supercharging assistance, the control device opens the control valve of the first pressure accumulating vessel and discharges the air-fuel mixture to the intake passage. When supercharging assistance is performed and the operation state of the internal combustion engine is in the middle / high rotational speed region during supercharging assistance, the control valve of one pressure accumulating vessel for the middle / high rotational speed region is opened and mixed While discharging the air into the intake passage to assist supercharging Depending on the required amount of air-fuel mixture released, the control valve of the other accumulator for the middle / high rotational speed region is also opened to release the air-fuel mixture into the intake passage and perform supercharging assist control. Configured as follows .

  According to this configuration, the required air amount per unit time required in the transient operation state of the internal combustion engine, which is determined according to the operation state of the internal combustion engine, for example, the engine rotation speed and the fuel injection amount (or load). In response to this, since one or a plurality of pressure accumulating containers are selected and supercharging assistance is provided, the supercharging assistance can be performed with the necessary and sufficient amount of the air-fuel mixture released in the transient operation state.

  As a result, in the low rotational speed region where the required air amount per unit time is small, it is possible to suppress the amount of air-fuel mixture in the entire pressure accumulator vessel by suppressing wasteful air consumption and to reduce the maximum combustion pressure of the engine. Abnormal increase can be suppressed, and the required air amount per unit time required for combustion in the internal combustion engine can be ensured in the middle and high rotation speed regions where the required air amount per unit time is large.

In this case, since the first pressure accumulating vessel is used for the low speed operation region and the second pressure accumulating vessel is used for the medium / high speed operation region, the discharge pressure is also a pressure suitable for each supercharging state. It is preferable to set the value to “1”, and this makes it possible to perform supercharging assistance more suitable for the transient operation state at that time.

  Further, in the above-described supercharging assist system for an internal combustion engine, the control device is a supercharging pressure calculation map showing a preset target supercharging pressure based on the engine rotational speed and the fuel injection amount of the internal combustion engine. And at the time of supercharging assistance, a target supercharging pressure is calculated from the actual engine speed and the actual fuel injection amount using the supercharging pressure calculation map, and the actual supercharging pressure is calculated based on the calculated target supercharging pressure. If one or a plurality of the pressure accumulating vessels is selected and control is performed to assist supercharging of the air-fuel mixture, supercharging assistance suitable for the transient operation state at that time is achieved with relatively simple control. can do.

And the supercharging assistance method of the internal combustion engine of this invention for achieving said objective pressurizes a part of exhaust gas and air mixture of an internal combustion engine, and accumulates in an accumulator, and the transient of the said internal combustion engine In a supercharging assistance method for an internal combustion engine that assists supercharging by releasing the air-fuel mixture accumulated in the pressure accumulating vessel into an intake passage of the internal combustion engine when in an operating state, the operating state of the internal combustion engine during supercharging assistance Accordingly, one or a plurality of pressure accumulating containers that discharge the air-fuel mixture are selected from a plurality of the pressure accumulating containers in parallel to assist supercharging of the air-fuel mixture , and at the time of supercharging assistance, the internal combustion engine When the operating state is in the low rotation speed region, a first pressure storage container for the low rotation speed region is selected from the plurality of pressure storage vessels, and the air-fuel mixture is supplied from the first pressure storage vessel to the intake passage. To the supercharging assist, and when supercharging assistance When the operating state of the internal combustion engine is in the middle / high rotational speed region, the internal combustion engine is for the middle / high rotational speed region in which the volume is larger than the first pressure accumulating container and the internal pressure of the container is set higher. The air-fuel mixture is discharged from one pressure accumulating container to the intake passage to assist supercharging, and depending on the required amount of air-fuel mixture released, the other air pressure accumulating containers for the medium and high rotation speed regions also In this method, the air-fuel mixture is discharged into the intake passage to assist supercharging .

  Further, in the above-described supercharging assistance method for an internal combustion engine, at the time of supercharging assistance, a target supercharge that is set in advance based on the engine rotation speed and the fuel injection amount of the internal combustion engine is determined from the actual engine rotation speed and the actual fuel injection amount. A target boost pressure is calculated using a boost pressure calculation map indicating the boost pressure, and one or a plurality of the pressure accumulating containers are selected so that the actual boost pressure becomes the calculated target boost pressure. Supercharge assistance.

  According to these methods, the same effects as those of the supercharging assist system for the internal combustion engine can be obtained.

  According to the supercharging assist system for an internal combustion engine and the supercharging assist method for an internal combustion engine of the present invention, the internal combustion engine is determined in accordance with the operating state of the internal combustion engine, for example, the engine speed and the fuel injection amount (or load). Depending on the required amount of air per unit time required in the transient operation state, one or more pressure accumulators are selected to assist supercharging, so the air-fuel mixture required in the transient operation state is released. The amount can be supercharged with a necessary and sufficient amount.

  As a result, in the low rotational speed region where the required air amount per unit time is small, it is possible to suppress the air-fuel mixture consumption by suppressing the wasteful air consumption and to increase the maximum combustion pressure of the engine abnormally. Further, the required air amount per unit time required for combustion in the internal combustion engine can be ensured in the middle and high rotation speed regions where the required air amount per unit time is large.

  Therefore, by suppressing the phenomenon of excessive use of the air-fuel mixture in the low rotation speed region and the shortage of the air-fuel mixture in the middle and high rotation speed regions, the necessary engine performance is maintained by providing necessary and sufficient supercharging assistance. At the same time, an abnormal increase in the maximum combustion pressure of the engine can be suppressed, and the maximum combustion pressure can be prevented from exceeding the allowable maximum combustion pressure.

It is a figure which shows the structure of the supercharging assistance system of the internal combustion engine of embodiment which concerns on this invention. It is a figure which shows an example of the control flow of the supercharging assistance method of the internal combustion engine of a reference form . 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.

  Hereinafter, a supercharging assistance system and a supercharging assistance method for an internal combustion engine according to embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, an internal combustion engine supercharging assist system 1 according to an embodiment of the present invention is provided in an engine (internal combustion engine) 10. In FIG. 1, the turbo-type supercharger is not particularly shown, but the application target of the present invention is that the accumulator supercharger system and the turbo-type supercharger system are applied even to an engine equipped only with the accumulator supercharger system. An engine equipped with both in combination may be used.

  In this supercharging assist system 1 for an internal combustion engine, a displacement type mechanical compressor is used to mix an air-fuel mixture M, which is a mixture of a part of exhaust gas passing through an exhaust passage (not shown) of the engine 10 and air (fresh air). And pressurized by a compressor (compressor) 20 such as an electric compressor or the like, and accumulated in a plurality (three in FIG. 1) of accumulators 21a, 21b, and 21c.

  The compressor 20 is connected to an intake passage 11 and an exhaust passage of the engine 10 via control valves (not shown), respectively, and sucks and compresses and pressurizes a part of air and exhaust gas. This pressurized air-fuel mixture M is a pressure regulating valve (regulator) 23a, 23b, 23c having a check valve function of the branch passages 22a, 22b, 22c of the air-fuel mixture supply passage 22 and a secondary side pressure regulating function. Are respectively stored in the pressure accumulating containers 21a, 21b, and 21c. Regarding the pressure regulating valves 23a, 23b, and 23c, when a check valve is separately provided, a regulator that does not have a check valve function may be used.

  When the accumulated air-fuel mixture M is discharged, the branch passages 22a and 22b are respectively routed through the control valves (solenoid valves with check valves) 24a, 24b and 24c of the branch passage of the mixture supply passage 22. , 22 c enters the mixture supply passage 22, is supplied to the intake passage 11, and enters each cylinder of the engine 10.

  The pressure accumulating containers 21a, 21b, and 21c are provided with oxygen concentration sensors 31a, 31b, and 31c that detect the oxygen concentration of the air-fuel mixture M and container internal pressure sensors 32a, 32b, and 32c that detect the internal pressures Pia, Pib, and Pic. .

  And during this pressure accumulation, using the detected values of the oxygen concentration sensors 31a, 31b, 31c provided in the pressure accumulating vessels 21a, 21b, 21c, etc., so that EGR can be performed at an appropriate EGR rate (oxygen concentration) during EGR. Knowing the oxygen concentration of the air-fuel mixture M and the amount of exhaust gas in the air-fuel mixture M in the pressure accumulating vessels 21a, 21b, and 21c so that the oxygen concentration of the air-fuel mixture M becomes a concentration suitable for EGR control The pressure is accumulated so that the amount of air becomes an appropriate ratio set in advance. Further, the air-fuel mixture M is appropriately accumulated so that the container internal pressures Pia, Pib, and Pic detected by the container internal pressure sensors 32a, 32b, and 32c do not become lower than the lower limit pressure Pod that allows supercharging assistance.

  The air-fuel mixture M accumulated in the pressure accumulating vessels 21a, 21b, 21c is branched from the pressure accumulating vessels 21a, 21b, 21c to the branch passages 22a, 22b, 22c when the engine 10 is in a transient operation state such as when the vehicle starts or accelerates. And is supplied to the intake passage 11 of the engine 10 via the air-fuel mixture supply passage 22 and used for supercharging assistance.

  The in-vessel pressures Pia, Pib, and Pic of the pressure accumulating vessels 21a, 21b, and 21c may be set to the same pressure, but the low rotation speed region R1 and the middle / high rotation speed region in the operation state in the transient operation state of the engine 10 If the discharge pressure Po is set to an optimum pressure value corresponding to each in accordance with R2, finer control can be performed. For example, for the low rotation speed region R1, a relatively low pressure is set so as not to cause an overboost, and for the medium / high rotation speed region R2, the pressure is set to a relatively high pressure so that the discharge amount of the mixture M is not insufficient. Set. In this case, although not shown in FIG. 1, regulators (pressure adjusting devices) for setting the in-vessel pressures Pia, Pib, and Pic of the pressure accumulating vessels 21a, 21b, and 21c to preset discharge pressures Poa, Pob, and Poc. May be provided, and the set pressures of the return valve and the relief valve that determine the upper limit of the internal pressure of the pressure accumulating containers 21a, 21b, and 21c may be changed in correspondence with each other.

  The accumulator vessels 21a, 21b, and 21c may have the same volume Vma, Vmb, and Vmc, but the low rotation speed region R1 and the middle / high rotation speed region R2 in the operation state in the transient operation state of the engine 10 may be used. Accordingly, finer control can be performed if the discharge amount of the air-fuel mixture M is set to an optimum discharge amount corresponding to each. For example, for the low rotation speed region R1, the container volume is relatively small so as not to uselessly assist supercharging, and for the medium / high rotation speed region R2, the discharge amount of the air-fuel mixture M is relatively large so as not to be insufficient. The container capacity.

  In addition, it is configured to include a control device 41 that controls the control valves 24a, 24b, and 24c during supercharging assistance. The control device 41 also performs an on / off operation of the compressor 20, but is usually configured to be incorporated in an overall system control device 40 that performs overall control of the engine 10 and overall control of the vehicle on which the engine 10 is mounted.

  The control device 41 performs supercharging by selecting one or a plurality of pressure accumulating containers for releasing the air-fuel mixture M from the plurality of pressure accumulating containers 21a, 21b, and 21c according to the operating state of the engine 10 during supercharging assistance. The control valves 24a, 24b, and 24c are controlled so as to assist.

In the reference mode, when the operating state of the engine 10 is in the low rotation speed region R1 in the supercharging assistance, the control device 41 selects one pressure storage container 21a from among the plurality of pressure storage containers 21a, 21b, 21c. When selected, the control valve 24a of the pressure accumulating vessel 21a is opened to assist the supercharging of the air-fuel mixture M, and when the operating state of the engine 10 is in the middle / high rotational speed region R2 at the time of supercharging assist, While selecting one accumulator vessel 21a (or 21b) from the vessels 21a, 21b, 21c and opening the control valve 24a (or 24b) of the accumulator vessel 21a (or 21b), supercharging assistance of the air-fuel mixture M is performed. Depending on the required amount of release of the air-fuel mixture M, the control valve 24b (or 24c) of another pressure accumulating vessel 21b (or 21c) is also opened to perform supercharging assist control. Configured.

  With this configuration, in the low rotational speed region R1 where the required air amount per unit time is small, it is possible to suppress the consumption amount of the air-fuel mixture M in the pressure accumulating vessels 21a, 21b, and 21c by suppressing unnecessary air consumption amount. At the same time, an abnormal increase in the maximum combustion pressure Pmax of the engine 10 can be suppressed, and the demand per unit time required for combustion in the engine 10 in the middle / high rotational speed region R2 where the required air amount per unit time is large. The amount of air can be secured.

  That is, at the time of supercharging assistance, when the operating state of the engine 10 is in the low rotational speed region R1, that is, in the case of starting the vehicle or accelerating from a low speed, the unit necessary for combustion in the engine 10 Since the required amount of air per hour is small, by supercharging assistance by reducing the volume (capacity) by reducing the number of pressure accumulating vessels 21a, 21b, 21c that discharge the mixture M to the intake passage 11 to one, Since the pressure drop of the pressure accumulating vessel 21a can be accelerated as the air-fuel mixture M is released, the consumption of the air-fuel mixture M more than necessary can be suppressed while ensuring the required amount of air per unit time. In addition, since the discharge pressure Poa of the air-fuel mixture M is lowered early, it is possible to avoid overboost and prevent the maximum combustion pressure Pmax of the engine 10 from exceeding the allowable maximum combustion pressure Pmc.

  Further, when the operating state of the engine 10 is in the middle / high rotational speed region R2, the air-fuel mixture M is released from the actual supercharging pressure Pim or the excess air ratio λ measured in advance or during supercharging assistance. When it is determined whether the amount is sufficient and the fuel injection amount q is small and the required amount of air is small, for example, when supercharging assistance from one pressure accumulating vessel 21a (or 21b) is sufficient, Supercharging assistance is performed only from one pressure accumulating container 21a, and the consumption of the air-fuel mixture M in the entire pressure accumulating containers 21a, 21b, 21c is suppressed.

  In addition, when it is determined that the amount of air required for the fuel injection amount q is large and the amount of air-fuel mixture M required for the supercharging assistance from one pressure accumulating vessel 21a (or 21b) is insufficient. Since supercharging assistance is performed not only from one pressure accumulating vessel 21a (or 21b) but also from another pressure accumulating vessel 21b (or 21c), increasing the total volume of the pressure accumulating vessels 21a, 21b (or 21b, 21c) Thus, the pressure drop can be delayed, and the time required to cover the required air amount can be extended to ensure the required air amount per unit time and the required air amount in the transient operation state as a whole.

Further, in the embodiment according to the present invention, the plurality of pressure accumulating containers 21a and 21b are configured by changing their volumes. Here, the volume of the second accumulation container 21b is made larger than the volume of the first accumulation container 21a. At the same time, the control device 41 selects the first pressure accumulating vessel 21a from among the plurality of pressure accumulating vessels 21a, 21b, and 21c when the operating state of the engine 10 is in the low rotation speed region R1 during supercharging assistance. Then, the control valve 24a of the first pressure accumulating vessel 21a is opened to assist the supercharging of the air-fuel mixture M, and when the operating state of the engine 10 is in the middle / high rotation speed region R2 during the supercharging assist, The control valve 24b of the second pressure accumulating vessel 21b having a volume larger than that of the first pressure accumulating vessel 21a is opened to assist the supercharging of the air-fuel mixture M, and in accordance with the required discharge amount of the air-fuel mixture M, the second The control valve 24c of the additional pressure accumulating vessel 21c different from the pressure accumulating vessel 21b is also opened to perform control for assisting supercharging of the air-fuel mixture M.

In this case, as in the reference embodiment, instead of increasing the volume for discharging the mixer M with the plurality of pressure accumulating vessels 21a, 21b (or 21b, 21c) and assisting the supercharging of the air-fuel mixture M, the second large volume Although the supercharging assistance of the air-fuel mixture M is performed by the pressure accumulating container 21b, the same effect as in the reference embodiment can be obtained.

  In this case, since the first pressure accumulating vessel 21a is used for the low rotation speed region R1 and the second pressure accumulating vessel 21b is used for the medium / high rotation speed region R2, the discharge pressures Poa, Pob, and Poc are also distinguished. It is preferable to set the pressure suitable for each supercharging state, and this makes it possible to assist supercharging more suitable for the transient operation state at that time.

In the supercharging assist system 1 for an internal combustion engine according to the above-described embodiment of the present invention , the control device 41 uses the target engine speed Ne and the fuel injection amount q of the engine 10 as a base to set a target overcharge that is set in advance. A supercharging pressure calculation map M1 showing the charging pressure Pit is provided, and at the time of supercharging assistance, the target supercharging pressure Pit is calculated from the actual engine speed Nem and the actual fuel injection amount qm using the supercharging pressure calculation map M1. Then, the control for assisting the supercharging of the air-fuel mixture M by selecting one or more of the pressure accumulating vessels 21a, 21b, 21c so that the actual supercharging pressure Pim becomes the calculated target supercharging pressure pit is performed. Configure to do. Thereby, the supercharging assistance suitable for the transient operation state at that time can be performed with relatively simple control.

  Further, when the container internal pressures Pia, Pib, and Pic in the respective pressure storage containers 21a, 21b, and 21c measured by the container internal pressure sensors 32a, 32b, and 32c are equal to or lower than a preset lower limit value Pid, the pressure storage container 21a. The pressure regulating valve 23a (or 23b, 23c) of (or 21b, 21c) is opened, the control valve 24a (or 24b, 24c) is closed, the compressor 20 is operated as necessary, and the mixture M is supplied. The pressure is accumulated in the pressure accumulating vessel 21a (or 21b, 21c).

Next, the supercharging assistance method for the internal combustion engine of the reference form in the supercharging assistance system 1 for the internal combustion engine of the above reference form will be described with reference to the control flow of FIG. The control flow of FIG. 2 is called and started from an advanced control flow when the vehicle including the engine 10 is in a transient operation state such as when starting or accelerating, that is, when the engine 10 is in a transient operation state. When the control flow is controlled, the control flow returns to the advanced control flow, and is called as the advanced control flow, and is shown to be repeatedly executed during the transient state of the engine 10.

  Then, when the vehicle equipped with the engine 10 shifts from the transient operation state to the steady operation state, that is, when the engine 10 shifts from the transient operation state to the steady operation state, the control is performed to return to the advanced control flow. Shown as a flow. Note that when the engine 10 stops in the middle of the control, an interrupt is generated and a return is made to return to the advanced control flow, and when the operation of the engine 10 is stopped, the operation ends with the end of the advanced control flow.

  When the control flow of FIG. 2 is called from the advanced control flow and started, it is determined in step S11 whether or not the operating state of the engine 10 is a transient operating state. This determination is made based on whether or not the torque generated by the engine 10 satisfies the required torque calculated from the accelerator opening. If it is not in the transient operation state in the determination of step S11 (NO), the process goes back to the advanced control flow and waits to be called in the next transient operation state.

  If it is determined in step S11 that the engine is in a transient operation state (YES), the process goes to step S12 to input data of the actual engine speed Nem, the actual fuel injection amount qm, and the actual boost pressure Pim. A value detected by the engine speed sensor 33 of the engine 10 is used for the actual engine speed Nem, and an in-cylinder fuel injection control command value or a fuel flow sensor (not shown) is used for the actual fuel injection quantity qm. Can be used. Further, as the actual supercharging pressure Pim, a value detected by the supercharging pressure sensor 34 can be used.

  Of the three input values (Nem, qm, Pim), the target boost pressure Pit is calculated from the actual engine speed Nem and the actual injected fuel quantity qm with reference to the boost pressure calculation map M1. To do.

  In the next step S13, it is determined whether the operating state of the engine 10 is in the low rotation speed region R1 or the middle / high rotation speed region R2. In this determination, if the actual engine rotational speed Nem is equal to or lower than the region determination rotational speed Nec set in advance through experiments or the like, it is determined that the operating state of the engine 10 is in the low rotational speed region R1 (YES), and the actual engine rotational speed Nem. Is greater than the region determination rotational speed Nec, it is determined that the operating state of the engine 10 is in the middle / high rotational speed region R2 (NO).

  If it is determined in step S13 that the operating state of the engine 10 is in the low rotational speed region R1 (YES), the process proceeds to step S14, where the in-vessel pressure Pia of the first pressure accumulating vessel 21a selected in advance is equal to or higher than the lower limit discharge pressure Pod. If it is above, the control valve 24a of the first pressure accumulating vessel 21a is opened to assist supercharging.

  When the container pressure Pia of the first pressure accumulating container 21a is lower than the lower limit discharge pressure Pod, whether or not the container pressure Pib of the second pressure storage container 21b selected in advance is equal to or higher than the lower limit discharge pressure Pod. If it is above, the control valve 24b of the second pressure accumulating vessel 21b is opened to assist supercharging. When the internal pressure Pib of the second pressure storage container 21b is also lower than the lower limit discharge pressure Pod, the internal pressure Pic of the other pressure storage container 21c is sequentially checked, and the pressure of the pressure storage container 21c higher than the lower limit discharge pressure Pod is checked. The control valve 24c is opened to assist supercharging, and the process goes to step S18.

  In this low rotational speed region R1, the target boost pressure Pit is such that the maximum combustion pressure Pmax in the cylinder (cylinder) does not exceed the allowable maximum combustion pressure Pmc, and the minimum excess pressure commensurate with the fuel injection amount q. The supply pressure Pmin is set. Supercharging assistance is performed at a discharge pressure Poa corresponding to the minimum supercharging pressure Pmin.

  In step S13, when the operating state of the engine 10 is in the middle / high rotation speed region R2 (NO), the process goes to step S15, and one of the pressure accumulating vessels 21a, 21b, 21c is replaced with one pressure accumulating vessel 21a (or 21b). When selected, the control valve 24a (or 24b) of the pressure accumulating vessel 21a (or 21b) is opened to supercharge the air-fuel mixture M.

  In the next step S16, it is determined whether or not the air-fuel mixture M is insufficient with only the supercharging assistance from one pressure accumulating vessel 21a (or 21b) with respect to the required discharge amount of the air-fuel mixture M. This determination is made by calculating in advance or by determining whether or not the discharge amount of the air-fuel mixture M is insufficient from the actual supercharging pressure Pim or the excess air ratio λ measured during supercharging assistance, and the fuel injection amount q If the supercharging assistance from one pressure accumulating vessel 21a (or 21b) is sufficient and not insufficient (NO), supercharging assistance is performed as it is, and the process goes to step S18.

  On the other hand, when the fuel injection amount q is large and the required amount of air is large, the supercharging assistance from one pressure accumulating vessel 21a (or 21b) is insufficient for the required amount of discharge of the air-fuel mixture M ( YES), go to step S17, assist supercharging from another accumulator 21b (or 21c), and return to step S16. Then, the number of pressure accumulating containers 21c used for supercharging assistance is increased until the discharge amount of the air-fuel mixture M becomes sufficient in step S16. Then, when the discharge amount of the air-fuel mixture M becomes sufficient, the process goes to step S18.

  In addition, in the pressure accumulating containers 21a, 21b, and 21c used for supercharging assistance, the pressures Pia, Pib, and Pic in the container are checked, and only the pressure accumulating containers 21a, 21b, and 21c higher than the lower limit discharge pressure Pod are selected. Then, the control valves 24a, 24b, 24c are opened to assist supercharging.

  In step S18, the control valve 24a (or 24b, 24c) turns on / off and releases the air-fuel mixture M so that the actual boost pressure Pim detected by the boost pressure sensor 34 becomes the target boost pressure Pit. Control to assist supercharging. This supercharging assist control is performed, and after a preset control time has elapsed, the process returns to step S11. Thereafter, Steps S11 to S18 are repeatedly performed. If it is determined in Step S11 that the vehicle is not in the transient operation state (NO), the process returns to the advanced control flow. Further, when the operation of the engine 10 is stopped in the middle of the control, an interrupt is generated, the return is made and the control flow returns to the advanced control flow, and this control flow is ended at the end of the advanced control flow.

  According to the control according to the control flow of FIG. 2, the pressure accumulating container 21 a that releases the air-fuel mixture M from the plurality of pressure accumulating containers 21 a, 21 b, 21 c according to the operating state of the engine 10 during supercharging assistance. One or more can be selected to assist the supercharging of the air-fuel mixture M.

  Further, at the time of supercharging assistance, when the operating state of the engine 10 is in the low rotation speed region R1, one accumulator vessel 21a is selected from the plural accumulator vessels 21a, 21b, 21c and the accumulator vessel 21a is selected. When supercharging assistance is performed and the operation state of the engine 10 is in the middle / high rotation speed region R2 during supercharging assistance, one accumulator vessel 21a (or 21b) is selected from the plurality of accumulator vessels 21a, 21b, 21c. Is selected to assist supercharging from this accumulator vessel 21a (or 21b), and supercharging assistance from another accumulator vessel 21b (or 21c) may be made according to the required amount of air-fuel mixture M released. it can.

  Further, at the time of supercharging assistance, a supercharging pressure indicating a target supercharging pressure Pit set in advance based on the engine rotational speed Ne and the fuel injection amount q of the engine 10 from the actual engine rotational speed Nem and the actual fuel injection amount qm. The target supercharging pressure Pit is calculated using the calculation map M1, and one or a plurality of pressure accumulating vessels 21a, 21b, 21c are selected so that the actual supercharging pressure Pim becomes the calculated target supercharging pressure Pit. Can be supercharged.

And the supercharging assistance method of the internal combustion engine of the embodiment according to the present invention in the supercharging assistance system 1 of the internal combustion engine of the above embodiment of the present invention is a diagram of the supercharging assistance method of the internal combustion engine of the reference mode . Step S15 of the control flow 2 can be implemented with a control flow replaced with S15A as in the control flow of FIG. In S15A, supercharging assistance is provided from the second pressure accumulating vessel 21b having a larger volume than the first pressure accumulating vessel 21a. Others are the same as the supercharging assistance method of the internal combustion engine of the reference form .

According to the control according to the control flow of FIG. 3, when the operating state of the engine 10 is in the low rotation speed region R1 during supercharging assistance, the first of the plurality of pressure accumulating vessels 21a, 21b, 21c is used. Pressure accumulating vessel 21a is selected and supercharging assistance is provided from the first accumulating vessel 21a. When the operating state of the engine 10 is in the middle / high rotational speed region R2 during supercharging assistance, the first accumulating vessel 21a while supercharging assisting the second accumulator vessel 21b is larger volume than 21a, in accordance with the discharge amount of the mixture M which are required, over from the second different additional pressure accumulator 21c is a pressure accumulator 21b You can subsidize.

  According to the supercharging assistance system 1 for an internal combustion engine and the supercharging assistance method for an internal combustion engine of the present invention, it is determined according to the operating state of the engine 10, for example, the engine speed Ne and the fuel injection amount q (or load Q). Since one or a plurality of pressure accumulating vessels 21a, 21b, 21c are selected to support the supercharging according to the required air amount per unit time required in the transient operation state of the engine 10, the transient operation state Thus, the supercharging assistance can be provided with a necessary and sufficient amount of the air-fuel mixture M released in the above-described manner.

  As a result, in the low rotational speed region R1 where the required air amount per unit time is small, the consumption amount of the air-fuel mixture M can be suppressed by suppressing the wasteful air consumption amount, and the maximum combustion pressure Pmax of the engine 10 can be reduced. An abnormal increase can be suppressed, and the required air amount per unit time required for combustion in the engine 10 can be ensured in the middle / high rotational speed region R2 where the required air amount per unit time is large.

  Therefore, the phenomenon that the air-fuel mixture is excessively used in the low rotation speed region R1 and the air-fuel mixture M becomes insufficient in the medium / high rotation speed region R2 is suppressed, and the necessary engine performance is obtained by providing necessary and sufficient supercharging assistance. At the same time, an abnormal increase in the maximum combustion pressure Pmax of the engine 10 can be suppressed, and the maximum combustion pressure Pmax can be prevented from exceeding the allowable maximum combustion pressure Pmc.

1 Supercharging assistance system 10 Engine (internal combustion engine)
11 Intake passage 20 Compressor (compressor)
21a, 21b, 21c Pressure accumulating container 22 Mixture supply passage 23a, 23b, 23c Pressure regulating valve (pressure regulating device)
24a, 24b, 24c Control valves 31a, 31b, 31c Oxygen concentration sensors 32a, 32b, 32c Container internal pressure sensor 33 Engine rotational speed sensor 34 Supercharging pressure sensor 40 Overall system controller 41 Controller Ne Engine rotational speed Nec Region determination rotational speed Nem actual engine speed M mixture M1 supercharging pressure calculation map Pim actual supercharging pressure Pit target supercharging pressure Pmax maximum combustion pressure Pmc allowable maximum combustion pressure Po discharge pressure Pod dischargeable lower limit pressure Pr residual pressure q fuel injection amount qc Calculated fuel injection amount qm Actual fuel injection amount R1 Low rotation speed region R2 Medium / high rotation speed region

Claims (4)

A part of the exhaust gas of the internal combustion engine and air mixture is pressurized and stored in a pressure accumulating vessel, and the air-fuel mixture accumulated in the pressure accumulating vessel is stored in the pressure accumulating vessel in a transient operation state of the internal combustion engine. In the supercharging assist system of the internal combustion engine that discharges to the supercharging assist system,
A plurality of the pressure accumulating containers are provided in parallel, and a control valve for controlling the discharge of the air-fuel mixture from each pressure accumulating container to the intake passage is provided for each pressure accumulating container,
Among the plurality of pressure accumulating containers, a first pressure accumulating container is used as a pressure accumulating container for a low rotational speed region, and a pressure accumulating container other than the first pressure accumulating container is used as a pressure accumulating container for a medium / high rotational speed region, The volume of the first pressure accumulating container for the speed region is formed smaller than the volume of the pressure accumulating container for the medium / high rotation speed region, and the internal pressure of the first pressure accumulating container for the low rotation speed region is Set to a state lower than the internal pressure of the pressure accumulating container for the medium / high rotational speed region,
Control of the control valve so as to assist supercharging by selecting one or a plurality of pressure accumulating containers for releasing the air-fuel mixture from the plurality of pressure accumulating containers according to the operating state of the internal combustion engine during supercharging assistance. together they constitute a control apparatus for performing,
The control device is
At the time of supercharging assistance, when the operating state of the internal combustion engine is in a low rotational speed region, the control valve of the first pressure accumulating container is opened to release the air-fuel mixture into the intake passage to assist supercharging,
At the time of supercharging assistance, when the operating state of the internal combustion engine is in the middle / high rotational speed region, the control valve of one pressure accumulating container for the middle / high rotational speed region is opened to allow the air-fuel mixture to flow into the intake passage In addition to assisting supercharging by releasing the air-fuel mixture, the control valve of the other accumulator for the middle / high rotational speed region is also opened according to the required amount of air-fuel mixture released, and the air-fuel mixture is supplied to the intake passage. A supercharging assistance system for an internal combustion engine, characterized in that it is configured to perform control for discharging and supercharging assistance. The control device is
Based on the engine rotation speed and fuel injection amount of the internal combustion engine, a boost pressure calculation map showing a preset target boost pressure is provided,
At the time of supercharging assistance, a target supercharging pressure is calculated from the actual engine speed and the actual fuel injection amount using the supercharging pressure calculation map so that the actual supercharging pressure becomes the calculated target supercharging pressure. 2. The supercharging assist system for an internal combustion engine according to claim 1, wherein control is performed to assist supercharging of the air-fuel mixture by selecting one or a plurality of the pressure accumulating containers. A part of the exhaust gas of the internal combustion engine and air mixture is pressurized and stored in a pressure accumulating vessel, and the air-fuel mixture accumulated in the pressure accumulating vessel is stored in the pressure accumulating vessel in a transient operation state of the internal combustion engine. In the supercharging assistance method of the internal combustion engine that discharges to the
At the time of supercharging assistance, according to the operating state of the internal combustion engine, one or a plurality of pressure accumulating containers that discharge the air-fuel mixture are selected from a plurality of the pressure accumulating containers in parallel to perform supercharging assistance of the air-fuel mixture With
At the time of supercharging assistance, when the operating state of the internal combustion engine is in the low rotation speed region, the first pressure accumulation is selected by selecting a first pressure accumulation vessel for the low rotation speed region from the plurality of pressure accumulation vessels. Discharging the air-fuel mixture from the container to the intake passage to assist supercharging,
During supercharging assistance, when the operating state of the internal combustion engine is in the middle / high rotational speed region, the medium / high rotational speed is set to have a larger volume and a higher internal pressure than the first pressure accumulating container. The air-fuel mixture is discharged from one pressure accumulator for the region into the intake passage to assist supercharging, and another pressure accumulator for the medium / high rotational speed region is used depending on the required amount of air-fuel mixture released. A supercharging assist method for an internal combustion engine, wherein supercharging assistance is performed by discharging the air-fuel mixture also from a container into the intake passage . At the time of supercharging assistance, using a supercharging pressure calculation map indicating a target supercharging pressure preset based on the engine rotational speed and the fuel injection amount of the internal combustion engine from the actual engine rotation speed and the actual fuel injection amount calculating a target boost pressure, so that the actual supercharging pressure becomes the calculated target boost pressure, to claim 3, characterized in that the supercharging assisting with one or more select said pressure accumulator The supercharging assistance method of the internal combustion engine of description .

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