JP2008008241A - Control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a supercharger from shifting to its surge generation domain at the time of vehicular deceleration. <P>SOLUTION: The control device includes a supercharger 21 driven by exhaust energy from an engine, an intake-throttle valve 18 disposed on the downstream side of a compressor 23 of the supercharger 21, a supercharging pressure control means 24 for controlling the supercharging pressure of the supercharger 21, and a throttle ratio control means 31 for controlling an opening of the intake throttle valve 18. The supercharging pressure control means 24 controls to decrease the supercharging pressure of the supercharger 21, and the throttle ratio control means 31 controls to reduce the opening of the intake throttle valve 18 with moderate-controlling the opening at the time of vehicular deceleration. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to control of an engine including a supercharger, and more particularly to control for preventing surcharge of a supercharger during transient operation such as deceleration.

  As a device for improving engine output, a turbocharger driven by a turbine provided in an exhaust passage is known.

  As is well known, the efficiency of a turbocharger compressor can be expressed by using a pressure ratio between the upstream and downstream of the compressor and a gas flow rate passing through the compressor as parameters. If the pressure ratio deviates from the appropriate pressure ratio range (normal operation range) corresponding to the gas flow rate and shifts to the abnormal operation range, undesirable phenomena such as surging, choking, or turbine over-rotation occur, so the abnormal operation range is not entered. The operating point of the compressor must be determined as follows.

  However, when a turbocharger is used in combination with an automobile engine, the operating point of the compressor may transition to an abnormal operating region transiently due to a sudden change in the accelerator pedal opening. Even so, abnormal compressor operation occurs.

  For example, when the accelerator pedal is returned during high-speed steady operation or after acceleration, the exhaust flow rate decreases rapidly. At this time, the operating point of the compressor may shift to an abnormal operating region where surging may occur.

As a technique for preventing the occurrence of such surging, Patent Document 1 provides a bypass passage that bypasses the upstream and downstream sides of the compressor, and in the surge generation region, a part of the intake air that has passed through the compressor is upstream of the compressor through the bypass passage. A technique is disclosed in which the pressure ratio upstream and downstream of the compressor is reduced by returning, increasing the pressure upstream of the compressor, and decreasing the downstream pressure.
Japanese Utility Model Publication No. 6-69331

  By the way, the turbine is provided with a variable nozzle, and the variable nozzle is opened and closed according to the operating state, so that the supercharging pressure is quickly increased during acceleration and the like, and a sufficient intake amount is provided during high load operation and the like. A so-called variable capacity turbocharger that pumps into an engine is known. In addition, an intake throttle valve that controls an excess air ratio of intake air introduced into an engine in accordance with an operating state in order to further improve the purification efficiency of the exhaust aftertreatment device is known.

  In the engine having these variable capacity turbochargers and intake throttle valves, the applicants do not provide a new device for preventing surging such as bypass piping as in Patent Document 1, and perform surging during transient operation. In order to prevent this, we are developing a variable nozzle and intake throttle valve opening control for a variable displacement turbocharger. In addition, a technology has been developed that controls the intake throttle valve in the closing direction and the variable nozzle in the opening direction during transient operation such as sudden deceleration. In the case of sudden deceleration, etc., fuel cut control is performed, so the intake air is unburned, that is, discharged from the engine at a low temperature and flows into the exhaust aftertreatment device, which reduces exhaust purification efficiency. By closing the valve, the amount of air flowing into the exhaust aftertreatment device can be reduced, and the temperature drop of the exhaust aftertreatment device can be suppressed. Also, if the intake throttle valve is closed, the pressure ratio increases due to an increase in the pressure in the intake pipe downstream of the compressor, and the operating point of the turbocharger may enter an abnormal operating region where surging occurs. By reducing the rotational speed of the turbine by opening, the pressure rise downstream of the compressor is suppressed, and the transition to the abnormal operation region where surging occurs can be prevented.

  However, when the intake throttle valve operates faster than the variable nozzle, for example, when the intake throttle valve is driven by an electric actuator and the variable nozzle is driven using intake pipe negative pressure, the rotation of the turbine Before the number decreases, the pressure downstream of the compressor increases and the pressure ratio increases, and there is a risk of shifting to an abnormal operation region where surging occurs.

  Therefore, an object of the present invention is to prevent transition to an abnormal operation region where surging occurs even when the operating speed of the intake throttle valve is faster than the operating speed of the variable nozzle.

  The engine control apparatus of the present invention includes a supercharger driven by engine exhaust energy, an intake throttle valve provided in an intake passage downstream of a compressor of the supercharger, and a supercharging pressure of the supercharger And a throttle ratio control means for controlling the opening degree of the intake throttle valve, and when the vehicle decelerates, the supercharging pressure control means reduces the supercharging pressure of the supercharger. And the throttle ratio control means controls to reduce the opening of the intake throttle valve while performing a smoothing process.

  According to the present invention, the smoothing process is performed when the opening degree of the intake throttle valve is decreased, so that the intake throttle valve can be operated even when the operating speed of the intake throttle valve is faster than the operating speed of the supercharging pressure control means. Since the supercharging pressure decreases until the valve is closed, it is possible to prevent the occurrence of surging by suppressing the increase in the pressure ratio.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a system to which the first embodiment of the present invention is applied.

  1 is an engine, 2 is an exhaust passage, 3 is an intake passage, 4 is an EGR passage that connects the exhaust passage 2 and the intake passage 3, and 5 is intake air that has been compressed by a turbocharger compressor, which will be described later, to a high temperature It is an intercooler for cooling.

  The EGR passage 4 includes a diaphragm type EGR valve 6 that responds to a control pressure from a pressure control valve (not shown). The pressure control valve is driven by a duty control signal from an engine controller 31 to be described later, thereby obtaining a predetermined EGR rate corresponding to operating conditions.

  The engine 1 includes a common rail fuel injection device 10 as a fuel supply means. The fuel injection device 10 mainly includes a fuel tank (not shown), a supply pump 14, a common rail (accumulation chamber) 16, and a nozzle 17 provided for each cylinder. The fuel pressurized by the supply pump 14 is accumulated in the accumulation chamber. Once stored in 16, the high-pressure fuel in the pressure accumulating chamber 16 is distributed to the nozzles 17 corresponding to the number of cylinders.

  The nozzle 17 (fuel injection valve) includes a needle valve, a nozzle chamber, a fuel supply passage to the nozzle chamber, a retainer, a hydraulic piston, a return spring, and the like, and is a three-way valve (see FIG. 5) interposed in the fuel supply passage to the hydraulic piston. Not shown). When the three-way valve (solenoid valve) is OFF, the needle valve is seated, but when the three-way valve is turned ON, the needle valve is raised and fuel is injected from the nozzle at the tip of the nozzle. That is, the fuel injection start timing is controlled by the switching timing of the three-way valve from OFF to ON, and the fuel injection amount is controlled by the time to turn it ON. For example, the earlier the switching timing from OFF to ON, the more advanced the fuel injection timing, and the longer the ON time, the greater the fuel injection amount.

  The exhaust passage 2 downstream of the opening of the EGR passage 4 is provided with a variable capacity turbocharger 21 in which a turbine 22 that converts the thermal energy of the exhaust into rotational energy and a compressor 23 that compresses the intake air are connected coaxially. A variable nozzle 24 (geometry variable mechanism, supercharging pressure control means) driven by an actuator 25 is provided at the scroll inlet of the turbine 22, and the variable nozzle 24 has a predetermined supercharging pressure from a low rotational speed range during normal operation. The nozzle opening (tilting state) increases the flow rate of the exhaust gas introduced into the turbine 22 on the low rotational speed side by the engine controller 31 and the nozzle that introduces the exhaust gas into the turbine 22 without resistance in the high rotational speed region. Control the opening (fully open).

  The actuator 25 includes a diaphragm actuator 26 that drives the variable nozzle 24 in response to the control pressure, and a pressure control valve (not shown) that adjusts the control pressure to the diaphragm actuator 26. A duty control signal is generated so that the actual opening becomes the target nozzle opening, and this duty control signal is output to the pressure control valve. As a control pressure to the diaphragm actuator 26, for example, a negative pressure in the intake pipe can be used.

  An intake throttle valve 18 driven by a diaphragm type actuator 19 that responds to a control pressure from a pressure control valve (not shown) is provided in the intake passage 3 immediately upstream of the collector 3a. The configuration of the actuator 19 is the same as that of the EGR valve 6, and the pressure control valve for the intake throttle valve 18 is also driven by a duty control signal from the engine controller 31. As will be described later, the intake throttle valve 18 is controlled to be opened and closed during fuel cut control or during operation in response to a request from the exhaust aftertreatment device.

  In the engine controller (aperture ratio control means) 31 to which signals from the accelerator sensor 32, the sensor 33 for detecting the engine rotation speed and the crank angle, the water temperature sensor 34, the air flow meter 35, and the supercharging pressure sensor 36 are input, these signals. The vehicle deceleration is detected (vehicle deceleration detection means), and the EGR control and the boost pressure control are performed in a coordinated manner so that the target EGR rate and the target boost pressure are obtained. Since a specific control method is not directly related to the present invention, a description thereof will be omitted. In addition, when a predetermined condition is satisfied during deceleration with the accelerator off, so-called fuel cut control is performed to reduce the fuel injection amount. When the engine speed or the vehicle speed has decreased to a predetermined value, the fuel cut control is terminated.

  On the other hand, the exhaust passage 2 downstream of the turbine 22 is provided with an exhaust aftertreatment device comprising a NOx trap catalyst 29 and a DPF (diesel particulate filter) 28 for collecting PM in the exhaust.

  Next, control of the EGR valve 6, the intake throttle valve 18, the variable nozzle 24, and the fuel injection amount at the time of deceleration accompanied by a decrease in the fuel injection amount will be described.

  When traveling with the accelerator pedal depressed, closing the accelerator pedal and shifting to a deceleration state satisfies the conditions such as exceeding the specified vehicle speed or exceeding the specified engine speed, A so-called fuel cut control is performed to stop fuel injection for the purpose of improvement. This fuel cut control is canceled when the fuel cut condition is not satisfied, such as when the engine speed is reduced to a predetermined speed or when the vehicle speed is reduced to a predetermined speed, and fuel injection is resumed. When the fuel cut control is finished, control is performed so that the engine is operated at the idling speed through recovery control for preventing a torque shock or the like when fuel injection is resumed.

  By the way, when the fuel cut control is started, the combustion is not performed in the cylinder, so that the exhaust pressure starts to decrease. On the other hand, the intake pressure starts to decrease later than the decrease in exhaust pressure because of the intake flow, the inertia of the compressor 23, and the like. As a result, a period during which the exhaust pressure becomes lower than the intake pressure during the fuel cut control (differential pressure reversal period) occurs. If the EGR valve 6 is opened during the differential pressure reversal period, the intake fresh air flows from the intake passage 3 to the exhaust passage 2 through the EGR passage 4, and the oxygen concentration supplied to the exhaust aftertreatment devices 28 and 29 is reduced. As a result, the catalytic reaction is excessively activated, and the temperature of the NOx trap catalyst 28 is excessively increased. Further, when the exhaust pressure becomes lower than the intake pressure, the EGR gas that has been flowing through the EGR passage 4 until then flows backward and flows into the turbine 22 to generate so-called surge noise. Therefore, the EGR valve 6 is closed until the differential pressure reversal period ends from the start of the fuel cut control. Further, if the EGR valve 6 is closed at the start of the fuel cut control, all exhaust gas flows into the turbine 22 without branching to the EGR passage 4, so that a rapid decrease in the rotational speed of the turbine 22 can be suppressed. It is possible to prevent surging caused by a rapid decrease in the gas flow rate passing through the compressor 23.

  The control of the intake throttle valve 18 will be described with reference to the block diagram of FIG. The target aperture ratio calculation unit 100 calculates a target aperture ratio that provides an excess air ratio that is determined according to a request from an exhaust aftertreatment device described later. The surge prevention target throttle ratio calculation unit 101 calculates an intake throttle ratio (surge prevention throttle ratio) for preventing surging of the compressor 23 based on the rotational speed of the engine 1. Specifically, the table shown in FIG. 3 is searched by the engine speed. In FIG. 3, the vertical axis represents the intake throttle ratio, and the horizontal axis represents the engine speed. The curve TQHO in the figure represents the target intake throttle ratio, and the hatched area represents the area where surging occurs.

  The switch unit 102 selects the surge prevention throttle ratio when the intake throttle operation request F_DEC_TVO is input, and otherwise selects the throttle ratio calculated by the target throttle ratio calculation unit 100. Then, the annealing processing unit 103 calculates an “annealing time” when switching from the aperture ratio calculated by the target aperture ratio calculation unit 100 to the surge prevention aperture ratio. The “annealing time” here is the time from the start of fuel cut control until the opening of the intake throttle valve 18 is controlled to the throttle ratio for surge prevention, and the pressure ratio (supercharging pressure) at the start of fuel cut control. This is done by searching the table shown in FIG. 4 using the ratio of the detected value of the sensor 36 to the atmospheric pressure). Note that the vertical axis in FIG. 4 is the annealing time, and the horizontal axis is the pressure ratio between the upstream and downstream of the compressor. The larger the pressure ratio, the longer the “annealing time”.

  The intake throttle valve control unit 104 controls the drive of the intake throttle valve 18 based on the throttle ratio selected by the switch unit 102 and the “annealing time” obtained by the annealing processing unit 103. Specifically, the intake throttle ratio changes as shown in FIG. FIG. 6 is a time chart in which the vertical axis represents the throttle ratio of the intake throttle valve 18 and the horizontal axis represents time. When an intake throttle operation request F_DEC_TVO is input during operation at the target throttle ratio calculated by the target throttle ratio calculation unit 100, the throttle ratio calculated by the surge prevention target throttle ratio calculation unit 101 is switched. At this time, a time indicated by T in the figure is required from when the intake throttle operation request F_DEC_TVO is input until the throttle ratio calculated by the surge prevention target throttle ratio calculation unit 101 is reached. This time T is the “annealing time” calculated by the annealing processing unit 103.

  Here, the “annealing time” will be described. When the control for opening the variable nozzle 24 is started at the start of fuel cut control, there is a response delay of the control start and an operation time until the target opening is reached. A period in which the turbine 22 and the compressor 23 are in a state of being easily rotated occurs. In addition, the intake air flow and the compressor 23 have inertia. Therefore, when the intake throttle valve 18 operates faster than the variable nozzle 24, the opening of the intake throttle valve 18 decreases before the rotational speed of the compressor 23 decreases, and the intake air that has passed through the compressor 23 is sucked into the intake throttle valve. 18 dams up, the pressure ratio of the upstream and downstream of the compressor 23 increases, and surging occurs. Therefore, by providing an “annealing time”, the intake throttle valve 18 is not throttled to the target opening until the variable nozzle 24 reaches the target opening, and the pressure increase in the intake passage 3 downstream of the compressor 23 is suppressed. Thus, the occurrence of surging is prevented.

  The effect of the above control will be described with reference to FIG. FIG. 8 is a supercharging efficiency characteristic map of the compressor 23 of the turbocharger 21. The vertical axis represents the pressure ratio, and the horizontal axis represents the intake air amount Q passing through the compressor 23.

  As is well known, when the compressor 23 that compresses intake air is operated in a region (abnormal operation region) outside a portion (normal operation region) surrounded by a line C in the figure, surging, choking, overrotation of the turbine 22 and the like. Since an undesirable phenomenon occurs, the operating point of the compressor 23 must be determined so as not to enter the abnormal operating range.

  For example, at the time of sudden deceleration accompanied by fuel cut control, the exhaust pressure rapidly decreases, so the rotational speed of the turbine 22, that is, the rotational speed of the compressor 23 decreases rapidly, and the intake air amount Q decreases. The pressure ratio decreases more slowly than the intake air amount Q due to the above-described intake air flow, inertia of the compressor 23, and the like. Therefore, the operating point may move to the left in FIG. 8 and shift to an abnormal operating area. In order to prevent this, generally, the opening degree of the variable nozzle 24 is controlled to be small so that the rotational speed of the compressor 23 is maintained even if the exhaust gas flow rate decreases.

  However, when the intake throttle valve 18 is closed as in this embodiment, if the rotational speed of the compressor 23 is maintained, the pressure downstream of the compressor 23 increases and the pressure ratio increases (the operating point is shown in FIG. 8). May move to an abnormal operating range.

  Therefore, by controlling the opening of the variable nozzle 24 so as to increase with the start of fuel cut control, the rotational speed of the compressor 23 is reduced to suppress the pressure increase downstream of the compressor 23, and the rotational speed of the compressor 23 decreases. In order to prevent the intake throttle valve 18 from closing, an “annealing time” is provided to prevent the pressure ratio from increasing. If the pressure ratio decreases as the intake air amount Q decreases in this way, the operating point moves in the lower right direction in FIG. 8, and the occurrence of surging can be prevented.

  A large pressure ratio means that the compressor 23 is operating at a high rotational speed, and the intake air flow and the inertia of the compressor 23 are also large. Therefore, even when the variable nozzle 24 is controlled to open, the time until the rotational speed of the compressor 23 decreases is longer than when the pressure ratio is small. Therefore, the “annealing time” is set longer as the pressure ratio is larger.

  The “annealing time” may be calculated using the intake air amount instead of the pressure ratio. In this case, a table as shown in FIG. 5 is used. The vertical axis in FIG. 5 is the annealing time, and the horizontal axis is the intake air amount. The longer the intake air amount, the longer the annealing time.

  As described above, in the present embodiment, when the vehicle is decelerated, the variable nozzle 24 is opened to reduce the supercharging pressure and the opening of the intake throttle valve 18 is decreased while performing the smoothing process. Even when the operating speed is faster than the operating speed of the variable nozzle 24, it is possible to prevent surging from occurring due to an increase in the pressure ratio before the variable nozzle 24 opens.

  The annealing time is set based on the pressure ratio at the start of deceleration or the intake air amount, and the longer the annealing time is set as the pressure ratio is larger or the intake air amount is larger, so before the variable nozzle 24 is opened. It is possible to reliably prevent the pressure ratio from increasing.

  A second embodiment will be described.

  The present embodiment relates to the opening degree control of the intake throttle valve 18 according to a request from the exhaust aftertreatment device such as the NOx trap catalyst 29 or the DPF 28. The schematic configuration of a system to which this embodiment is applied is as shown in FIG. 1 as in the first embodiment.

  The NOx trap catalyst 29 traps NOx (nitrogen oxides) in the exhaust during lean combustion, and reduces and purifies the trapped NOx using HC and CO in the exhaust as a reducing agent during stoichiometric combustion or rich combustion. Is. The trap amount of NOx can be obtained, for example, by integrating the NOx emission amount estimated from the engine speed and the engine load with the operation time.

  In the normal operation (lean combustion), when the trapped NOx reaches the limit of the allowable range, the engine controller (regeneration request detecting means) 31 is used to regenerate and purify the trapped NOx by reducing and purifying the trapped NOx. When the predetermined exhaust temperature can be ensured, the excess air ratio is controlled so that rich combustion occurs (rich spike).

  Further, since the NOx trap catalyst 29 is poisoned by SOx (sulfur oxide) contained in a trace amount in the exhaust gas, when the engine controller 31 determines that the SOx has accumulated to the limit of the allowable range, this SOx becomes a NOx trap. In order to raise the exhaust temperature to a temperature at which it can be desorbed from the catalyst, the excess air ratio is controlled so that the stoichiometric combustion is almost achieved (release of sulfur poisoning).

  The engine controller (regeneration request detecting means) 31 performs so-called DPF regeneration in which the trapped PM is combusted when it is determined that the PM in the exhaust has accumulated in the DPF 28 to the limit of the allowable range. In order to raise the exhaust gas temperature to around 300 degrees, which is the temperature at which the accumulated PM can burn, the excess air ratio is set so that the air-fuel ratio becomes slightly lean (temperature increase). The PM accumulation amount can be estimated based on the pressure difference between the upstream and downstream sides of the DPF 28. For example, when the pressure difference becomes a predetermined value or more, it can be determined that the allowable range has been reached. It can also be obtained by estimating the PM emission amount from the operating conditions such as the engine speed and the engine load, and integrating this with the operating time.

  As described above, reduction of NOx trapped in the NOx trap catalyst 29 (hereinafter simply referred to as “NOx reduction”) and release of poisoning of the NOx trap catalyst 29 by SOx (hereinafter simply referred to as “sulfur poisoning release”). For this reason, it is necessary to obtain rich combustion and switch from lean combustion to rich combustion or stoichiometric combustion according to demand. However, there is a case where rich combustion or stoichiometric combustion cannot be obtained by the supercharger 21 alone. The opening degree of the throttle valve 18 is controlled. The configuration of the actuator 19 is the same as that of the EGR valve 6, and the pressure control valve for the intake throttle valve 18 is also driven by a duty control signal from the engine controller 31.

  In addition to this, if a large amount of PM accumulates and the DPF regeneration starts with the DPF bed temperature being high, the PM burns rapidly and the DPF may overheat, resulting in performance degradation. In order to prevent this, there is a control (hereinafter simply referred to as “preventing performance degradation”) that moderately burns PM by appropriately controlling the oxygen supply amount. Control.

  Note that, in a method for controlling the opening of the variable nozzle 24 and the opening of the intake throttle valve 18 of the exhaust turbine 22 so that the target fresh air amount can be obtained, the target fresh air amount can be obtained depending on the supercharger 21. There are a method of controlling the intake throttle valve 18 only in a non-idle region (for example, a low load region near an idle) and a method of simultaneously controlling the variable nozzle opening and the intake throttle valve opening regardless of the operation region. You can use this method. The EGR device can also be used as intake air amount adjusting means.

  In addition, since the operation based on the exhaust aftertreatment request is performed only when a predetermined condition is satisfied, the operations for performing these operations are collectively set as the conditional operation, and the operation for performing the lean operation is performed. If it distinguishes as a normal driving | operation, the method of making the transfer from a normal driving | running to a conditional driving | operation and the reverse will become well-known, In this embodiment, it describes in Unexamined-Japanese-Patent No. 2003-336520, for example This is done in the same way as the control. In addition, “excess air ratio determined based on exhaust aftertreatment request”, which will be described later, is also determined in the same manner as in Japanese Patent Application Laid-Open No. 2003-336520.

  By the way, when switching to the conditional operation, if the opening degree of the intake throttle valve 18 is decreased in order to make the excess air ratio richer than the stoichiometric ratio, the pressure in the intake passage 3 downstream of the compressor 23 increases. The ratio may increase and surging may occur. Therefore, the opening degree of the variable nozzle 24 is increased to reduce the rotational speed of the compressor 23, thereby preventing the pressure ratio from increasing. At this time, if the operating speed of the intake throttle valve 18 is faster than the operating speed of the variable nozzle 24, the opening of the variable nozzle 24 increases and the rotational speed of the compressor 23 decreases, as in the first embodiment. In addition, the pressure ratio increases and surging may occur. Therefore, the intake throttle valve 18 is controlled as shown in the block diagram of FIG. 7 when switching from the normal operation to the conditional operation. Hereinafter, a description will be given with reference to the block diagram of FIG.

  The target aperture ratio calculation unit 200 calculates a target aperture ratio. Since the intake throttle valve 18 is fully opened in principle during normal operation, the target throttle ratio is always fully open here.

  The target aperture ratio calculation unit 201 based on the exhaust aftertreatment request calculates an aperture ratio that provides an excess air ratio determined based on the exhaust aftertreatment request. In the case of NOx reduction, sulfur poisoning release, DPF regeneration, and prevention of performance degradation, the target opening of the intake throttle valve 18 is set to a value smaller than full open, but in the case of temperature rise, the excess air ratio is stoichiometric. Therefore, the target opening of the intake throttle valve 18 is fully opened.

  The exhaust aftertreatment determination unit 202 determines whether the operation state is a normal operation or a conditional operation. Here, State 1 is a normal operation, State 2 is an operation that performs NOx reduction among the conditional operations, State 3 is an operation that raises temperature, State 4 is an operation that releases sulfur poisoning, State 5 is an operation that performs DPF regeneration, and prevents performance degradation Therefore, the state number of the current operation state is input as a post-processing request. When the input value is State 1, it is determined that the operation is a normal operation, and otherwise, the operation is a conditional operation, and the determination result is input to the switch unit 203.

  In the switch unit 203, when the determination result in the exhaust post-processing determination unit 202 is normal operation, the opening set by the target aperture ratio calculation unit 201, that is, fully open is selected, and in the case of conditional operation, from the exhaust post-processing request The aperture ratio calculated by the aperture ratio calculation unit 201 is selected.

  Then, the annealing processing unit 204 calculates an “annealing time” when switching to the aperture ratio calculated by the target aperture ratio calculation unit 201 from the exhaust post-processing request. The “annealing time” referred to here is the time from when the intake throttle valve 18 is fully opened until it is controlled to the target throttle ratio determined from the exhaust post-treatment request, and is determined using the pressure ratio at the start of the control. Similar to the first embodiment, it is performed by searching the table shown in FIG.

  The intake throttle valve control unit 205 controls the drive of the intake throttle valve 18 based on the throttle ratio selected by the switch unit 203 and the “annealing time” obtained by the annealing processing unit 204.

  By controlling in this way, the opening degree of the intake throttle valve 18 is decreased in order to perform the regeneration control of the NOx trap catalyst 29 or the DPF 28 and the opening degree of the variable nozzle 24 is increased. Even when the operating speed is higher than the operating speed of the variable nozzle 24, the intake throttle valve 18 is closed before the opening of the variable nozzle 24 increases and the rotational speed of the compressor 23 decreases, and the pressure ratio increases. Thus, surging can be prevented from occurring.

  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.

It is the schematic of the system which can apply embodiment of this invention. It is a block diagram for demonstrating control of 1st Embodiment. It is a table for the target aperture ratio calculation for surge prevention. It is a table for calculating annealing time. It is a table for calculating annealing time. It is a time chart showing the opening change of an intake throttle valve. It is a block diagram for demonstrating control of 2nd Embodiment. It is an efficiency map of a compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Exhaust passage 3 Intake passage 4 EGR passage 5 Intercooler 6 EGR valve 10 Common rail type fuel injection device 14 Supply pump 16 Common rail (pressure accumulation chamber)
17 Nozzle 18 Inlet throttle valve 21 Variable capacity turbocharger 22 Turbine 23 Compressor 24 Variable nozzle (geometry variable mechanism)
25 Actuator 28 NOx Trap Catalyst 29 DPF (Diesel Particulate Filter)
31 Engine controller 32 Accelerator sensor 34 Water temperature sensor 35 Air flow meter 36 Supercharging pressure sensor

Claims (8)

A turbocharger driven by engine exhaust energy;
An intake throttle valve provided in an intake passage on the downstream side of the compressor of the supercharger;
Supercharging pressure control means for controlling the supercharging pressure of the supercharger;
Throttle ratio control means for controlling the opening of the intake throttle valve;
With
When the vehicle decelerates, the supercharging pressure control means controls to reduce the supercharging pressure of the supercharger, and the throttle ratio control means reduces the opening of the intake throttle valve while performing the smoothing process. An engine control device that controls the engine.   The throttle ratio control means performs an annealing process by setting an annealing time so that the intake throttle valve does not close before the supercharging pressure decreases. Item 4. The engine control device according to Item 1.   The engine control apparatus according to claim 1 or 2, wherein the aperture ratio control means sets a smoothing time in accordance with a pressure ratio at the start of vehicle deceleration.   4. The engine control device according to claim 3, wherein the aperture ratio control means sets a longer annealing time as the pressure ratio at the start of vehicle deceleration increases.   The engine control apparatus according to claim 1 or 2, wherein the aperture ratio control means sets a smoothing time according to an intake air amount at the time of starting deceleration of the vehicle.   6. The engine control apparatus according to claim 5, wherein the aperture ratio control means sets a longer annealing time as the amount of intake air at the start of vehicle deceleration increases.   The engine control apparatus according to any one of claims 1 to 6, wherein the supercharging pressure control means is a geometry variable mechanism capable of changing a geometry of a turbine of the supercharger. A turbocharger driven by engine exhaust energy;
An intake throttle valve provided in an intake passage on the downstream side of the compressor of the supercharger;
Supercharging pressure control means for controlling the supercharging pressure of the supercharger;
Throttle ratio control means for controlling the opening of the intake throttle valve;
At least one of a NOx trap catalyst or a DPF interposed in the exhaust passage of the engine and purifying exhaust;
A regeneration request detecting means for detecting a regeneration request of the NOx trap catalyst or DPF;
With
When the regeneration request detecting means detects the regeneration request, the supercharging pressure control means controls to reduce the supercharging pressure of the supercharger, and the throttle ratio control means opens the intake throttle valve. A control apparatus for an engine, characterized in that control is performed so as to reduce the degree while performing an annealing process.