JP2016028204A - Control unit of internal combustion engine with turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve filling efficiency by scavenging to increase engine output and prevent degradation of exhaust catalyst transformation efficiency due to an increase in scavenging gas, in an internal combustion engine including a variable valve gear mechanism and a turbocharger.SOLUTION: A control unit 12 of an internal combustion engine 1 with a turbo type supercharger 5 including a variable valve gear mechanism 14 in at least either an intake side or an exhaust side, comprises: scavenging-air-quantity setting means 12 setting an upper limit value of a quantity of scavenging air passing from an intake passage 2 through a cylinder and blown into an exhaust passage 3 during a valve overlap period for satisfying a performance request for the internal combustion engine 1; and variable valve gear control means 12 controlling a length of the valve overlap period according to the quantity of the scavenging air.SELECTED DRAWING: Figure 8

Description

  The present invention relates to control of an internal combustion engine including a variable valve mechanism and a turbocharger.

  A variable valve mechanism is controlled to provide a valve overlap period. During this valve overlap period, the residual gas in the cylinder is scavenged into the exhaust passage using the differential pressure between the intake pressure and the exhaust pressure. A technique for increasing the amount of fresh air is known.

  For example, Patent Document 1 discloses a technique for obtaining a scavenging effect by controlling the throttle valve opening so that the intake pressure becomes higher than the exhaust pressure during the valve overlap period.

JP 2006-283636 A

  Incidentally, the scavenging amount during the valve overlap period varies depending on the operating state of the internal combustion engine and the operating environment even if the valve overlap period is the same. In particular, when a turbocharger is provided, the exhaust pressure is different between the steady state where the rotation speed of the turbocharger is constant and the transient state where the rotation speed increases, so the engine rotation speed, load, etc. The scavenging amount is different even in the same operating state and the same overlap period length.

  Therefore, if the valve overlap period is controlled by searching a map in which the valve overlap period is assigned to the engine speed and load as in Patent Document 1, a scavenging amount suitable for the operating state and operating environment is not necessarily obtained. Not always.

  Therefore, an object of the present invention is to obtain a scavenging amount suitable for an operating state and an operating environment even in an internal combustion engine with a turbocharger.

  A control device according to the present invention is a control device for an internal combustion engine with a turbocharger that includes a variable valve mechanism on at least one of an intake side and an exhaust side. And a performance requirement detecting means for detecting a performance requirement for the internal combustion engine, and an upper limit value for satisfying the performance requirement of the scavenging amount that passes through the cylinder from the intake passage to the exhaust passage during the valve overlap period. Scavenging amount setting means to be determined, and variable valve control means for controlling the length of the valve overlap period according to the upper limit value of the scavenging amount.

  According to the present invention, the scavenging amount for satisfying the performance requirement is set, and the valve overlap period is controlled accordingly, so that the performance requirement can be met even in the case of an internal combustion engine with a turbocharger. A satisfactory scavenging amount can be obtained.

It is a block diagram of the system to which this embodiment is applied. It is a figure which shows the stroke order of an inline 4 cylinder internal combustion engine. It is a block diagram which shows the calculation content for setting the fuel injection quantity which a control unit performs. It is a block diagram of the control for determining whether or not to reduce the valve overlap period, which is executed by the control unit. It is a block diagram which shows the calculation content for calculating | requiring the scavenging rate which a control unit performs. It is a block diagram which shows the calculation content for calculating | requiring exhaust pressure which a control unit performs. It is a block diagram which shows the calculation content for calculating | requiring the transient exhaust pressure fluctuation | variation which a control unit performs. It is a block diagram which shows the calculation content for determining the conversion angle of a variable valve mechanism which a control unit performs. It is a block diagram for scavenging amount upper limit calculation based on catalyst temperature which a control unit performs. It is a block diagram for scavenging amount upper limit calculation based on NOx discharge amount which a control unit performs. It is a block diagram for scavenging amount upper limit calculation at the time of torque sudden change which a control unit performs.

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

(First embodiment)
FIG. 1 is a system configuration diagram of an internal combustion engine to which the present embodiment is applied.

  A throttle chamber 4 for adjusting the amount of air flowing into the internal combustion engine 1 is provided at the inlet of the intake manifold 2 of the internal combustion engine 1, and an intake passage 6 is connected upstream thereof. A compressor 5 a of the supercharger 5 is installed on the upstream side of the throttle chamber 4 in the intake passage 6, and an air flow meter 8 for detecting the intake air amount is installed further on the upstream side.

  Each cylinder of the internal combustion engine 1 is provided with a fuel injection valve 15 that directly injects fuel into the cylinder. A turbine 5 b of the supercharger 5 is installed in the exhaust passage 7.

  The supercharger 5 is a so-called turbocharger, and a compressor 5a and a turbine 5b are connected via a shaft 5c. For this reason, when the turbine 5b is rotated by the exhaust energy of the internal combustion engine 1, the compressor 5a is also rotated, and the intake air is pumped downstream.

  An exhaust gas purification catalyst 18 is disposed downstream of the turbine 5b. A three-way catalyst or the like is used as the exhaust catalyst 18.

  The recirculation passage 10 is a passage connecting the intake passage 6a and an intake passage downstream of the air flow meter 8 and upstream of the compressor 5a (hereinafter referred to as an intake passage 6b), and is provided in the middle. When the valve 9 is opened, the intake passages 6a and 6b are communicated, and when the valve 9 is closed, the communication is blocked.

  The recirculation valve 9 is opened when the differential pressure between the supercharging pressure and the pressure in the intake manifold 2 (hereinafter referred to as the intake pipe pressure) exceeds a predetermined value, as is generally known. To do. For example, the reaction force of the built-in spring is urged in the valve closing direction against the valve body provided inside, and the boost pressure acts in the valve opening direction of the valve body, while the intake pressure is applied in the valve closing direction. When the pipe pressure is applied and the differential pressure between the supercharging pressure and the intake pipe pressure exceeds the reaction force of the spring, the valve is opened. Thereby, when the throttle chamber 4 is fully closed during traveling in the supercharging state, it is possible to prevent the supercharging pressure from being excessively increased. The differential pressure between the supercharging pressure and the intake pipe pressure when the recirculation valve 9 is opened can be set to an arbitrary value depending on the spring constant of the spring.

  The variable valve mechanism 14 only needs to change the intake valve closing timing (IVC) so that an overlap period in which both the exhaust valve and the intake valve are opened occurs. For example, a generally known variable valve mechanism such as one that changes the rotational phase of the intake camshaft relative to the crankshaft or one that changes the operating angle of the intake valve can be used. A similar variable valve mechanism 14 may be provided on the exhaust valve side to variably control the valve timing of the intake valve and the exhaust valve.

  The control unit 12 reads parameters relating to the operating state such as the intake air amount detected by the air flow meter 8, the accelerator opening detected by the accelerator opening sensor 13, and the engine speed detected by a crank angle sensor (not shown). Based on this, the ignition timing, valve timing, air-fuel ratio, etc. are controlled.

  Next, valve timing control and air-fuel ratio control performed by the control unit 12 will be described.

  When the pressure in the intake manifold 2 is higher than the pressure in the exhaust manifold 3, the control unit 12 is a variable valve operation so that a valve overlap period during which the intake valve and the exhaust valve are open occurs. Actuate mechanism 14.

  This is because, during the valve overlap period, fresh air flowing from the intake manifold 2 is blown through the exhaust manifold 3 as scavenging gas as it is, so as to increase the rotational speed of the turbine 5b and fill the cylinder. This is to increase efficiency.

  This effect will be specifically described with reference to FIG. FIG. 2 shows the stroke order of an in-line four-cylinder internal combustion engine in which the ignition order is the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder. The hatched portion in the figure indicates the valve overlap period.

  When the valve overlap period is provided, in the exhaust manifold 3, the exhaust gas discharged from the cylinder in the exhaust stroke and the scavenging gas of the other cylinders in the intake stroke at that time merge. For example, the exhaust gas exhausted in the exhaust stroke # 3ex of the third cylinder in FIG. 2 and the scavenged gas scavenged in the valve overlap period # 1sc of the first cylinder that becomes the intake stroke at that time merge.

  For this reason, compared with the case where there is no valve overlap period, that is, the case where there is no scavenging, the amount of gas introduced into the turbine 5b increases. Thereby, the rotational speed of the turbine 5b increases and the supercharging pressure by the compressor 5a increases. Further, since the scavenging discharges the residual gas in the cylinder together with the fresh air gas, the efficiency of filling the fresh air in the cylinder is increased as a result.

  Further, in the present embodiment, the energy for rotating the turbine 5b is obtained by burning the mixture of the exhaust gas and the scavenging gas joined by the exhaust manifold 3 before flowing into the turbine 5b by air-fuel ratio control described later. Increase more.

  For this reason, before the gas mixture of the exhaust gas exhausted from a certain cylinder during the exhaust stroke and the scavenged gas scavenged from the cylinder that is in the intake stroke at the same time during the valve overlap period flows into the turbine 5b. The fuel injection amount is set so that the air-fuel ratio is easy to burn. That is, the air-fuel ratio in the cylinder is made richer than the stoichiometric air-fuel ratio, exhaust gas containing unburned hydrocarbons is exhausted, and this exhaust gas and scavenging gas are mixed to facilitate combustion. For example, the fuel injection amount is set so that the stoichiometric air-fuel ratio is obtained.

  For example, when setting the fuel injection amount with respect to the amount of air sucked in the intake stroke # 3 in of the third cylinder in FIG. 2, the exhaust gas discharged in the exhaust stroke # 3ex of the third cylinder and the valve overlap of the first cylinder A fuel injection amount is set such that the mixture of scavenging gas discharged in the period # 1sc has an air-fuel ratio at which it is easy to burn. That is, when focusing on the air-fuel ratio in the cylinder of the third cylinder, the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio, and exhaust gas including unburned fuel is discharged in the exhaust stroke.

  The fuel injection amount set as described above is all injected by one fuel injection per stroke. The fuel injection timing is after the valve overlap period during the intake stroke, that is, after the exhaust valve is closed, or during the compression stroke. Details of the air-fuel ratio control will be described later.

  When injected in this way, the fuel that becomes the unburned hydrocarbon in the exhaust gas changes from a higher hydrocarbon with a long carbon chain to a lower hydrocarbon with a short carbon chain by receiving the heat of combustion during the expansion stroke, It becomes more combustible. Further, since the air-fuel ratio in the cylinder becomes richer than the stoichiometric air-fuel ratio, it approaches the output air-fuel ratio, so that the output can be improved as compared with the case of operating at the stoichiometric air-fuel ratio. Furthermore, since the inside of the cylinder is cooled by the latent heat of vaporization when the fuel is vaporized in the cylinder, it contributes to the improvement of the charging efficiency.

  FIG. 3 is a block diagram showing the calculation contents for setting the fuel injection amount to be injected into the cylinder. This block diagram includes estimation of the air-fuel ratio in the cylinder and in the exhaust manifold 3, which is performed using the set fuel injection amount.

  The exhaust pipe air-fuel ratio target value setting unit 301 sets an exhaust pipe target air-fuel ratio that is the target air-fuel ratio in the exhaust manifold 3. The target air-fuel ratio is set to an air-fuel ratio at which the mixture of exhaust gas and scavenging gas is easy to burn, for example, the stoichiometric air-fuel ratio.

  Note that the air-fuel ratio is not limited to the stoichiometric air-fuel ratio, for example, so that the mixture of exhaust gas and scavenging gas satisfies the required value of exhaust performance, that is, an air-fuel ratio that does not decrease the conversion efficiency of the exhaust catalyst 18. It may be set. Even in this case, the charging efficiency in the cylinder is improved by the scavenging effect, the generated torque is increased, and the exhaust performance can be prevented from being lowered.

  The in-cylinder trap intake air amount estimation unit 302 is a cylinder that is confined in the cylinder at the end of the intake stroke of the intake air amount based on the intake air amount detected by the air flow meter 8 and the scavenging rate. Estimate the amount of intake air in the inner trap. The scavenging rate is a value obtained by dividing the amount of fresh air by the amount of gas in the cylinder. A method for calculating the scavenging rate will be described later.

  The cylinder scavenging gas amount estimation unit 303 is the amount of the intake air amount that flows out to the exhaust manifold 3 during the valve overlap period for the cylinder that is in the intake stroke when the cylinder whose trap trap intake air amount has been calculated is in the exhaust stroke. The cylinder scavenging gas amount is estimated based on the scavenging rate and the intake air amount.

  The in-cylinder fuel injection amount setting unit 304 determines the fuel injection amount into the cylinder based on the exhaust pipe target air-fuel ratio, the in-cylinder trap intake air amount, and the cylinder scavenging gas amount.

  When the exhaust gas is mixed with the scavenging gas in the exhaust manifold 3, the air-fuel ratio changes to the lean side by the amount diluted with the scavenging gas. For example, if the fuel injection amount is set so as to be the stoichiometric air-fuel ratio with respect to the in-cylinder trap intake air amount, the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio, and when mixed with the scavenging gas in the exhaust manifold 3, it becomes leaner than the stoichiometric air-fuel ratio. Become.

  Therefore, the amount of hydrocarbons required to reach the target air-fuel ratio in the exhaust pipe when diluted to the scavenging gas is determined based on the trap air intake amount in the cylinder and the cylinder scavenging gas amount, and this hydrocarbon amount is generated. The fuel injection amount necessary for the above is set based on the trap air intake amount in the cylinder.

  In-cylinder air-fuel ratio estimation unit 305 estimates the air-fuel ratio in the cylinder from the fuel injection amount and the trap trap air intake amount. The exhaust pipe air-fuel ratio estimation unit 306 estimates the air-fuel ratio in the exhaust manifold 3 from the cylinder air-fuel ratio and the cylinder scavenging gas amount. If the in-cylinder fuel injection amount is feedback controlled based on these estimated values and the exhaust pipe target air-fuel ratio, the air-fuel ratio in the exhaust manifold 3 can be controlled with higher accuracy.

  FIG. 4 is a block diagram of control for determining whether or not to reduce the valve overlap period based on the in-cylinder air-fuel ratio estimation value obtained by the in-cylinder air-fuel ratio estimation unit 305. As the scavenging amount increases, the amount of fuel necessary to bring the air-fuel ratio in the exhaust pipe to a desired air-fuel ratio also increases, and the air-fuel ratio in the cylinder becomes richer accordingly. Therefore, when the fuel injection amount obtained by the calculation of FIG. 3 is used and the air-fuel ratio in the cylinder exceeds the combustion limit, in order to shorten the valve overlap period and reduce the scavenging amount, FIG. 4 is performed.

  In-cylinder air-fuel ratio allowable value calculation unit 401 sets an in-cylinder air-fuel ratio allowable value obtained based on conditions such as a combustion limit. The cylinder air-fuel ratio estimation unit 402 reads the cylinder air-fuel ratio estimated by the cylinder air-fuel ratio estimation unit 305 of FIG.

  The determination unit 403 compares the in-cylinder air-fuel ratio allowable value and the in-cylinder air-fuel ratio estimated value, and if it is determined that the in-cylinder air-fuel ratio estimated value is richer, the VTC control that is the control unit of the variable valve mechanism 14 A request to reduce the valve overlap period is made to the unit 404. As a result, the valve overlap period is reduced and the scavenging amount is reduced. That is, the upper limit value of the scavenging amount for satisfying the performance requirement is determined.

  3 and 4 described above, it is possible to control the air-fuel ratio of the mixture of exhaust gas and scavenging gas in the exhaust manifold 3 to an easily combustible air-fuel ratio and to ensure combustion stability in the cylinder. it can.

  Next, the scavenging rate used for estimating the trap air intake amount and the cylinder scavenging gas amount in the cylinder will be described with reference to FIG.

  FIG. 5 is a block diagram showing the calculation contents for calculating the scavenging rate.

  The scavenging rate is determined based on the amount of heat generated from the engine speed and the intake air amount and the amount of gas passing through the exhaust manifold 3 during steady operation. However, since the increase in the rotational speed of the turbine 5b is delayed with respect to the increasing speed of the amount of gas flowing through the exhaust manifold 3 during transient operation, pressure loss occurs. As a result, the exhaust pressure during transient operation becomes higher than the exhaust pressure during steady operation with the same intake air amount and the same engine speed. Therefore, in the calculation of FIG. 5, the scavenging rate is calculated by correcting the exhaust pressure during steady operation by the increase / decrease of the exhaust pressure fluctuation amount during transient operation (hereinafter referred to as transient pressure fluctuation).

  The collector pressure reading unit 501 reads the pressure in the intake manifold 2 as the collector pressure. The exhaust pressure reading unit 502 reads the exhaust pressure obtained by calculation described later. A transient pressure fluctuation reading unit 503 reads a transient exhaust pressure fluctuation amount obtained by calculation described later.

  The exhaust valve front-rear differential pressure calculation unit 504 calculates the exhaust valve front-rear differential pressure by subtracting the exhaust pressure from the collector pressure and adding transient pressure fluctuations thereto. As a result, the differential pressure before and after the exhaust valve including the transient exhaust pressure fluctuation amount is calculated.

  On the other hand, the engine rotation speed reading unit 505 reads the engine rotation speed based on the detected value of the crank angle sensor, and the overlap amount reading unit 506 reads the valve overlap amount obtained by calculation described later.

  A scavenging rate calculation unit 507 obtains a scavenging rate using a map set in advance based on the engine speed, the valve overlap amount, and the exhaust valve front-rear differential pressure, and the scavenging rate setting unit 508 scavenges the calculation result. Read as a rate. As shown in FIG. 5, the map used here is the exhaust valve front-rear differential pressure and the horizontal axis is the valve overlap amount. The control unit 12 stores a plurality of maps for each engine speed. Yes.

  FIG. 6 is a block diagram showing the calculation contents for obtaining the exhaust pressure read by the exhaust pressure reading unit 502. Since the exhaust pressure is greatly affected by the atmospheric pressure and the exhaust temperature, correction based on these increases the accuracy of estimating the exhaust pressure, and consequently the accuracy of estimating the scavenging rate. Specifically, the following calculation is performed.

  The exhaust temperature reading unit 601 reads the detection value of the exhaust temperature sensor 17, and the intake air amount reading unit 602 reads the detection value of the air flow meter 8. A reference exhaust pressure calculation unit 603 calculates a reference exhaust pressure using a map prepared in advance based on these read values. Thus, the exhaust pressure corresponding to the intake air amount and the exhaust temperature can be set as the reference value.

  On the other hand, the reference atmospheric pressure reading unit 604 reads the detected value of the atmospheric pressure sensor 16 when the reference exhaust pressure is calculated. Further, the atmospheric pressure reading unit 605 reads the current detection value of the atmospheric pressure sensor 16. Then, the atmospheric pressure correction unit 606 calculates the sum of the value obtained by subtracting the reference atmospheric pressure from the reference exhaust pressure and the atmospheric pressure, and the exhaust pressure calculation unit 607 reads the calculation result as the exhaust pressure. Thereby, the exhaust pressure according to atmospheric pressure can be estimated.

  FIG. 7 is a block diagram for calculating the transient exhaust pressure fluctuation amount read by the transient pressure fluctuation reading unit.

  Here, the transient exhaust pressure fluctuation amount is calculated using the intake air amount and the change amount of the throttle valve opening as a trigger for determining whether or not the transient operation is performed.

  The intake air amount reading unit 701 reads the detection value of the air flow meter 8. A throttle valve opening reading unit 702 reads the throttle opening. The throttle valve opening may be detected by a throttle position sensor, or in the case of an electronically controlled throttle, an instruction value to an actuator that drives the throttle valve may be read.

  The intake air change rate calculation unit 703 calculates an intake air change rate ΔQA that is a change rate of the intake air amount based on the intake air amount read by the intake air amount reading unit 701. The intake air change rate correction value calculation unit 714 calculates a value obtained by adding a first-order lag to the intake air change rate ΔQA as the intake air change rate correction value QMv by the following equation (1).

QMv = ΔQA × k + (1−k) × QMvz (1)
Based on the intake change speed correction value QMv obtained as described above, a transient exhaust pressure change amount estimation unit 711 calculates a reference transient exhaust pressure from a previously created map, and inputs the calculation result to the switch unit 712. To do.

  A change amount of the intake air amount is calculated by the intake air amount change calculation unit 704, and the first transient determination criteria and the intake air amount change amount stored in advance in the first transient determination criteria setting unit 705 by the first determination unit 708. And compare.

  The throttle valve opening change amount calculation unit 706 calculates the change amount of the throttle valve opening, and the second determination unit 709 stores the second transient determination criterion and the throttle stored in the second transient determination criterion setting unit 707 in advance. Compare the amount of change in valve opening.

  The third determination unit 710 reads the determination results of the first determination unit 708 and the second determination unit 709. Then, at least one of the intake amount change amount larger than the first transient determination criteria in the first determination unit 708 or the throttle valve opening change amount larger than the first transient determination criteria in the second determination unit 709 is established. If it is, it is determined that the vehicle is in transient operation. This determination result is input to the switch unit 712, and the switch unit 712 switches to a side where a transient exhaust pressure fluctuation is added when in a transient operation, and switches to a side where a transient exhaust pressure fluctuation amount is not added when not in a transient operation. The The transient exhaust pressure fluctuation determining unit 713 sets the value output from the switch unit 712 as the transient exhaust pressure fluctuation amount.

  FIG. 8 is a flowchart showing a control routine for determining the conversion angle of the variable valve mechanism 14. During this control, the valve overlap period is calculated.

  In step S801, the operating state of the internal combustion engine 1, for example, the collector pressure, the engine speed, the intake air temperature, the atmospheric pressure, the basic injection pulse, and the like are read. The basic injection pulse is a value correlated with the output of the internal combustion engine 1.

  In step S802, the scavenging amount upper limit value obtained from the operating state is calculated. Here, an example of how to obtain the scavenging amount upper limit value will be described.

  FIG. 9 is a block diagram for calculating the scavenging amount upper limit value based on the catalyst temperature.

  When fuel is injected so that the air-fuel ratio in the exhaust manifold 3 including the scavenged gas becomes the stoichiometric air-fuel ratio, and the mixture of exhaust gas and scavenged gas is burned in the exhaust manifold 3, the combustion energy is large. The efficiency of the supercharger 5 increases. Moreover, the higher the scavenging rate, the higher the ratio of fresh air in the cylinder and the higher the filling efficiency. That is, in order to satisfy performance requirements such as output improvement for the internal combustion engine 1, the scavenging amount should be as large as possible. However, as shown in FIG. 4, since the valve overlap period is limited by conditions such as the combustion limit, the upper limit of the scavenging amount is also limited.

  On the other hand, as the scavenging amount increases, the exhaust catalyst 18 is heated to a higher temperature by combustion in the exhaust manifold 3. Since the exhaust gas purification performance deteriorates when the temperature of the exhaust catalyst 18 rises excessively, it is necessary to set an upper limit value of the scavenging amount in order to suppress the temperature rise of the exhaust catalyst 18.

  Therefore, the scavenging amount is limited to such an extent that the exhaust catalyst 18 is not deteriorated, and this is set as the scavenging amount upper limit value.

  Note that, as the operation state, the collector pressure Boost, the engine rotation speed NE, the basic injection pulse TP, the intake air temperature TAN, and the atmospheric pressure PAMB are read.

  The catalyst upper limit temperature calculation unit 901 calculates a catalyst upper limit temperature that is an upper limit temperature of the exhaust catalyst 18 determined according to the operating state.

  Similarly, the scavenged catalyst upper limit temperature calculation unit 902 calculates the estimated scavenging catalyst temperature that is the estimated temperature of the exhaust catalyst 18 in the normal operating state where there is no scavenging, that is, the operating state in which the mixture of scavenging gas and exhaust gas is not combusted. calculate.

  The scavenging catalyst temperature increase allowable value calculation unit 903 calculates a scavenging catalyst temperature increase allowable value that is the difference between the catalyst upper limit temperature and the non-scavenging estimated catalyst temperature. The temperature rise of the exhaust catalyst 18 during scavenging can be allowed by the permissible value for the catalyst temperature rise during scavenging.

  The catalyst temperature allowable scavenging amount calculation unit 905 uses a map created in advance based on the scavenging catalyst temperature increase allowable value and the air-fuel ratio in the cylinder of the internal combustion engine 1 calculated by the cylinder air-fuel ratio calculation unit 904. A catalyst temperature allowable scavenging amount that is a scavenging amount upper limit value determined from the temperature of 18 is calculated. The map used here shows the relationship between the scavenging amount and the catalyst temperature rise for each cylinder air-fuel ratio.

  Then, the calculated catalyst temperature allowable scavenging amount determination unit 906 sets the calculated temperature as the scavenging amount upper limit value.

  When the scavenging amount upper limit value is determined based on the operating state of the internal combustion engine 1 such as the engine speed as described above and the environment in which the internal combustion engine 1 operates such as the intake air temperature or atmospheric pressure, the scavenging upper limit catalyst temperature calculation is performed. The calculation result of the unit 902 varies depending on the driving state and the environment. As a result, the catalyst temperature allowable scavenging amount also becomes a value corresponding to the operating state and environment.

  Further, in the calculation of FIG. 9, the scavenging amount upper limit value in the next cycle can be obtained by using the estimated value of the state of the next cycle as the input engine speed or the like. Therefore, even in the case of control during transient operation where feedforward control is required, it is possible to cope by calculating the scavenging amount upper limit after a predetermined time.

  Returning to the description of FIG.

  In step S802 in FIG. 8, in addition to the catalyst temperature allowable scavenging amount, a scavenging amount upper limit value that satisfies the performance requirement determined by the calculation in FIG. 4 is also calculated. Then, the smaller one is set as the scavenging amount upper limit value. In step S803 in FIG. 8, the valve overlap period is determined based on the scavenging amount obtained in step S802. If the scavenging amount and the valve overlap period are obtained in advance according to the specifications of the internal combustion engine to be applied, the valve overlap period can be easily set based on the scavenging amount. Then, the overlap amount reading unit 506 in FIG. 5 reads this value.

  In step S804, the conversion angle of the variable valve mechanism 14 for realizing the valve overlap period determined in step S803 is determined. If the relationship between the valve overlap period and the conversion angle is obtained in advance in accordance with the profile of the intake cam and exhaust cam of the internal combustion engine 1 to be applied, the conversion angle can be easily determined in accordance with the valve overlap period. Can do.

  If the fuel injection amount is set by the calculation of FIG. 3 as described above, the mixture of scavenging gas and exhaust gas mixed in the exhaust manifold 3 can be controlled to an air-fuel ratio that is easy to burn.

  Although the present embodiment has been described with respect to the case where the internal combustion engine 1 is a direct injection type in-cylinder, the present invention is not limited to this, and a so-called port injection type internal combustion in which fuel is injected into an intake port communicating with each cylinder. Applicable to institutions. In the case of a port injection type internal combustion engine, if the fuel injection is performed after the valve overlap period ends, that is, after the exhaust valve is closed, the injected fuel may be discharged together with the scavenging gas to the exhaust manifold 3. Therefore, the fuel injection amount setting method described above can be applied as it is.

  In FIG. 3, the cylinder scavenging gas amount estimation unit 303 estimates the cylinder scavenging gas amount for the cylinder that is in the intake stroke when the cylinder whose trap trap intake air amount is calculated is in the exhaust stroke. This is to cope with a transient operation state. However, in the normal operation, the cylinder trap intake air amount and the cylinder scavenging gas amount are the same for each cylinder, so the cylinder scavenging gas amount of the same cylinder as the cylinder that calculated the cylinder trap intake air amount is used. Can also determine the fuel injection amount.

  As described above, in the present embodiment, the following effects can be obtained.

  (1) The control unit 12 sets a scavenging amount for satisfying the performance requirement for the internal combustion engine 1 and controls the length of the valve overlap period according to this scavenging amount. Ratio, that is, filling efficiency is improved.

  (2) Since the control unit 12 limits the scavenging amount upper limit value based on the estimated temperature of the exhaust catalyst 18, when the scavenging gas is mixed with the exhaust gas in the exhaust manifold 3 and burned, It is possible to prevent the temperature from rising excessively.

  (3) Since the control unit 12 limits the scavenging amount upper limit value based on the operating state of the internal combustion engine 1 and the placed environment, an appropriate scavenging amount upper limit value can be set. In other words, the intake air amount and the exhaust temperature differ depending on the operating state and the surrounding environment, and the catalyst temperature rise allowable scavenging amount calculated based on these also differs, but according to the control, an appropriate scavenging amount upper limit value is set. Can be set.

  For example, when the atmospheric pressure is low, the turbocharger 5 is likely to rotate. Therefore, compared with a state where the atmospheric pressure is high, the rotational speed is likely to increase even if the scavenging amount is the same, and there is a possibility of over-rotation. In this case, if a part of the exhaust gas is bypassed by a wastegate or the like, over-rotation can be suppressed and the supercharger 5 can be protected. However, in this case, energy from scavenging gas and exhaust gas combustion is wasted. Therefore, if the scavenging amount upper limit value is set based on the environment in which the internal combustion engine 1 is placed, the scavenging amount can be set so as not to overspeed, and the turbocharger 5 is protected without wasting energy. it can.

  (4) The control unit 12 sets the scavenging amount upper limit value based on the scavenging-unexecuted state estimated based on the operating state and the state after scavenging execution estimated based on the in-cylinder target air-fuel ratio. . That is, the catalyst temperature allowable scavenging amount is set based on the temperature in the exhaust manifold 3 determined by the operating state such as the intake air temperature, and the temperature rise caused by burning the mixed gas of the scavenging gas and the exhaust gas. A scavenging amount upper limit value can be set.

  (5) After the elapse of a predetermined time estimated based on the operation state estimated value, for example, after one cycle, the control unit 12 has not yet performed scavenging, and after scavenging performed based on the target air-fuel ratio in the cylinder. The upper limit value of the scavenging amount is set based on the state. That is, the scavenging amount upper limit value for the next cycle can be set by inputting a value that estimates the state of the next cycle as the engine speed, load, or the like. An appropriate scavenging amount upper limit value can be set even during transient operation that requires feedforward control, such as during acceleration.

  (6) When the control unit 12 calculates a plurality of scavenging amount upper limit values based on a plurality of conditions, the control unit 12 selects the smallest scavenging amount upper limit value, so that it is possible to reliably prevent the system performance from being deteriorated.

(Second Embodiment)
Next, a second embodiment will be described.

  The system to which this embodiment is applied is the same as that of the first embodiment. The control is basically the same, but differs in that the scavenging amount upper limit value is calculated based on the NOx generation amount. Therefore, a method for calculating the scavenging amount upper limit value will be described.

  In the case of an in-cylinder direct injection internal combustion engine, the scavenging gas blown from the intake passage to the exhaust passage does not contain fuel, so the air-fuel ratio of the gas flowing into the exhaust catalyst 18 becomes leaner as the scavenging amount increases. Sneak away. If the inside of the exhaust catalyst 18 becomes leaner than the stoichiometric air-fuel ratio, the NOx conversion efficiency deteriorates, and the inflowing NOx cannot be completely processed, and the exhaust performance may deteriorate.

  Therefore, the scavenging amount upper limit value is set so that NOx that cannot be processed by the exhaust catalyst 18 is not generated.

  FIG. 10 is a block diagram showing the contents of the calculation contents for setting the scavenging amount upper limit value based on the NOx generation amount, which is executed by the control unit 12 in the present embodiment.

  The NOx generation amount calculation unit 1001 reads the engine rotational speed NE and the basic injection pulse TP, and performs a map search based on them, thereby calculating an allowable NOx generation amount in the operating state. The amount of NOx produced here refers to the amount discharged from the internal combustion engine 1.

  The vertical axis of the map used in the NOx generation amount calculation unit 1001 is the collector pressure Boost. The basic injection pulse TP is determined according to the cylinder intake air mass and has a correlation with the collector pressure Boost. Therefore, when the map search is performed, the read basic injection pulse TP is converted into the collector pressure Boost based on the correlation. The collector pressure Boost may be directly read.

  A cylinder air-fuel ratio reading unit 1002 reads the cylinder air-fuel ratio estimated by the cylinder air-fuel ratio estimating unit 305 of FIG.

  The scavenging amount calculation unit 1003 searches for a map indicating the relationship between the scavenging amount and the NOx generation amount created in advance for each cylinder air-fuel ratio by the NOx generation amount calculated by the NOx generation amount calculation unit 1001. A scavenging amount allowable in the operation state is calculated. This scavenging amount is set as the NOx generation allowable scavenging amount.

  The NOx generation allowable scavenging amount setting unit 1004 sets the NOx generation allowable scavenging amount as the scavenging amount upper limit value.

  By setting the scavenging amount upper limit as described above, it is possible to prevent the NOx conversion efficiency of the exhaust catalyst 18 from deteriorating when the mixture of scavenging gas and exhaust gas is combusted in the exhaust manifold 3.

  Further, when the scavenging amount upper limit value is determined based on the operating state of the internal combustion engine 1 such as the engine rotational speed and the environment in which the internal combustion engine 1 operates such as the intake air temperature and the atmospheric pressure as described above, the NOx generation amount calculation unit 1001 The calculation results vary depending on the driving state and environment. As a result, the NOx generation allowable scavenging amount also becomes a value according to the operating state and environment.

  As described above, in the present embodiment, in addition to the same effects as those of the first embodiment, the following effects are further obtained.

  (7) Since the control unit 12 limits the scavenging amount upper limit value based on the estimated value of the NOx emission amount from the internal combustion engine 1 to the exhaust manifold 3, it prevents the NOx conversion efficiency of the exhaust catalyst 18 from being lowered due to scavenging. it can.

(Third embodiment)
Next, a third embodiment will be described.

  The present embodiment relates to control in the case where the torque demand increases rapidly as in acceleration in the same system as the first embodiment. Basic control is the same as in the first embodiment, but the scavenging amount upper limit value set in step S602 in FIG. 6 is different. Hereinafter, the setting of the scavenging amount upper limit value will be described.

  FIG. 11 is a block diagram showing the content of calculation for setting the scavenging amount upper limit value. Here, as a general rule, the scavenging amount with the smaller catalyst temperature allowable scavenging amount or NOx generation allowable scavenging amount is set as the scavenging amount upper limit value. However, when the torque request value for the internal combustion engine 1 suddenly increases as during sudden acceleration, the torque request is made within a range that does not adversely affect the system such as the internal combustion engine 1 and the supercharger 5 shown in FIG. Switch to a higher scavenging amount upper limit that prioritizes satisfaction.

  When the scavenging amount upper limit value is increased in this way, the energy when the mixture of scavenging gas and exhaust gas burns in the exhaust manifold 3 increases, and as a result, the speed of rotation increase of the turbine 5b increases. The torque response of is increased.

  The arithmetic blocks 1101-1104 and the arithmetic blocks 105-1108 in FIG. 11 are the same as those in FIGS.

  The minimum value selection unit 1109 selects the smaller of the catalyst temperature allowable scavenging amount or the NOx generation allowable scavenging amount and inputs the result to the switch 1113.

  The torque change rate determination unit 1110 determines whether or not the change rate of the torque request value for the internal combustion engine 1 exceeds a preset threshold value based on, for example, the accelerator opening change amount. The threshold value is a value for determining whether it is necessary to prioritize the torque response over the catalyst temperature or the NOx generation amount, and is set in advance for each vehicle model to which this control is applied.

  When the torque request value change speed exceeds the threshold value, the timer 1111 is operated, and the switch 1113 is switched to the torque pickup allowable scavenging amount side described later only during a preset timer operation period. Although the timer operation period can be set arbitrarily, in order to prevent adverse effects on the system, the timer operation period is set shorter as the torque pickup allowable scavenging amount described later increases.

  The torque pickup allowable scavenging amount setting unit 1112 sets a torque pickup allowable scavenging amount that is a scavenging amount upper limit value when torque response is prioritized based on the operating state and operating environment of the internal combustion engine 1.

  As long as the timer 1111 is operating, the torque pickup allowable scavenging amount is set to a value that does not cause performance degradation of the exhaust catalyst 18 or the supercharger 5 even if the scavenging amount is maintained. In other words, the upper limit value of the normal scavenging amount is a level that does not cause a decrease in performance even when the normal scavenging amount upper limit is operated, whereas the allowable torque scavenging amount of the torque pickup is a level that can be allowed temporarily.

  Specifically, since it varies depending on the specifications of the internal combustion engine 1 and the exhaust catalyst 18, the exhaust path length, etc., the torque pickup permissible scavenging amount for each operating state and operating environment is mapped in advance, etc. Search for. For example, it is set to a value that is larger than the catalyst temperature allowable scavenging amount and the NOx generation allowable scavenging amount and that can ensure the combustion stability.

  The scavenging amount upper limit setting unit 1114 sets the scavenging amount selected by the switch 1113 as the scavenging amount upper limit value.

  As described above, the control unit 12 calculates the scavenging amount upper limit value based on the performance requirements for the internal combustion engine 1 such as the torque requirement and the constraint conditions such as the catalyst temperature and the NOx generation amount. Then, when the torque request value change rate exceeds the threshold value, such as during rapid acceleration, the torque pickup allowable scavenging amount is selected from the plurality of scavenging amount upper limit values, otherwise, Select the smaller scavenging amount upper limit based on the constraint.

  In the steady operation state, the smaller scavenging amount upper limit value based on the constraint condition is selected, so the largest scavenging amount is set in a range that does not affect the system.

  On the other hand, when there is a sudden increase in torque demand as in acceleration, a scavenging amount upper limit value that is larger than the scavenging amount based on the constraint condition is set for a certain period. That is, the upper limit value of the scavenging amount is raised only for a certain period. As a result, the energy supplied to the turbine 5b increases, and as a result, the torque responsiveness increases.

  As described above, in the present embodiment, in addition to the same effects as those of the first embodiment, the following effects are further obtained.

  (8) When the torque demand increases rapidly, the control unit 12 increases the scavenging amount. As a result, the combustion energy in the exhaust manifold 3, that is, the energy supplied to the turbine 5b increases, so that the torque response of the internal combustion engine 1 is improved.

  (9) When the torque demand increases sharply, the control unit 12 relaxes the scavenging amount upper limit for a certain period of time, so that it is possible to improve the torque response and prevent system performance degradation.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake manifold 3 Exhaust manifold 4 Throttle chamber 5 Supercharger 6 Intake passage 7 Exhaust passage 8 Air flow meter 9 Recirculation valve 10 Recirculation passage 12 Control unit 13 Accelerator opening sensor 14 Variable valve mechanism 15 Fuel Injection valve 16 Atmospheric pressure sensor 17 Exhaust temperature sensor 18 Exhaust catalyst

A control device according to the present invention is a control device for an internal combustion engine with a turbocharger that includes a variable valve mechanism on at least one of an intake side and an exhaust side. An exhaust combustion means for increasing the energy for rotating the turbocharger turbine by burning the mixture of exhaust gas and scavenging gas upstream of the turbocharger, and provided in the exhaust passage It means for estimating the temperature of the exhaust catalyst, a scavenging amount setting means for setting a scavenging ratio based on the upper limit temperature of the exhaust catalyst and the estimated temperature of the exhaust catalyst, a long length of the valve overlap period greater the scavenging ratio Variable valve control means for controlling to become .

Claims (9)

In a control device for an internal combustion engine with a turbocharger that includes a variable valve mechanism on at least one of an intake side or an exhaust side,
A performance requirement detection means for detecting a performance requirement for the internal combustion engine;
A scavenging amount setting means for determining an upper limit value for satisfying the performance requirement of the scavenging amount passing through the cylinder from the intake passage to the exhaust passage during the valve overlap period;
Variable valve control means for controlling the length of the valve overlap period according to the upper limit value of the scavenging amount;
A control device for an internal combustion engine with a turbocharger, comprising: Means for estimating the temperature of the exhaust catalyst provided in the exhaust passage;
The control device for an internal combustion engine with a turbocharger according to claim 1, wherein the scavenging amount setting means limits an upper limit value of the scavenging amount based on an estimated temperature of the exhaust catalyst. Means for estimating the amount of NOx discharged from the internal combustion engine into the exhaust passage;
The control device for an internal combustion engine with a turbocharger according to claim 1 or 2, wherein the scavenging amount setting means limits an upper limit value of the scavenging amount based on an estimated value of the NOx emission amount.   The turbo scavenging apparatus according to any one of claims 1 to 3, wherein the scavenging amount setting means sets an upper limit value of the scavenging amount based on an operating state of the internal combustion engine and an environment in which the internal combustion engine is placed. Control device for an internal combustion engine with a feeder. An operating state detecting means for detecting an operating state of the internal combustion engine;
Target air-fuel ratio setting means for setting a target air-fuel ratio in the cylinder;
Further comprising
The scavenging amount setting means sets an upper limit value of the scavenging amount based on a state where scavenging has not been performed based on the operating state and a state after scavenging has been estimated based on the target air-fuel ratio. The control device for an internal combustion engine with a turbocharger according to any one of claims 1 to 4. An operating state estimating means for estimating an operating state of the internal combustion engine after elapse of a predetermined time;
The scavenging amount setting means is configured to perform the scavenging amount based on a state in which scavenging has not been performed after a predetermined time has elapsed, which is estimated based on an estimated operating state value, and a state after scavenging has been estimated based on the target air-fuel ratio. 6. The control apparatus for an internal combustion engine with a turbocharger according to claim 5, wherein an upper limit value is set.   The turbo-charging system according to any one of claims 1 to 6, wherein the scavenging amount setting means increases the scavenging amount when an increasing speed of a torque request for the internal combustion engine exceeds a preset threshold value. Control device for internal combustion engine with a machine.   The scavenging amount setting means relaxes the upper limit value of the scavenging amount for a certain period when the rate of increase in torque demand for the internal combustion engine exceeds a preset threshold value. A control device for an internal combustion engine with a turbocharger as described.   The turbo type according to any one of claims 1 to 8, wherein the scavenging amount setting means selects the smallest scavenging amount upper limit value when a plurality of scavenging amount upper limit values are calculated based on a plurality of conditions. Control device for an internal combustion engine with a supercharger.

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