JP2000179362A - Intake control device of engine having turbosupercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the reacceleration characteristics by reducing the turbo lag at the time of reacceleration after deceleration of an engine, and to stabilize and ensure the purifying performance by preventing a catalyst from being supercooled. SOLUTION: An intake control device A of an engine having a turbosupercharger comprises an intake throttle valve 14 and an exhaust turbosupercharger 25, and executes feedback control of the exhaust reflux rate so that the air-fuel ratio in a combustion chamber 4 becomes a desired value. When operation state judging means 35d judges that an engine 1 is in a decelerating operation state, intake throttle valve control means 35c closes the intake throttle valve 14 by a specific amount. When the engine 1 enters a low-load and low-rotation operation region, an open valve control part 35e keeps the intake throttle valve 14 in an almost full open state until a set time lapses thereafter. When catalyst temperature judging means 35h judges that the temperature of a catalyst 22 is lower than a set catalyst temperature, the intake throttle valve 14 is closed by a specific amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbocharged engine provided with an intake throttle valve and an exhaust gas recirculation passage for recirculating a part of exhaust gas to an intake passage downstream of the intake throttle valve. The present invention relates to an intake control device that performs feedback control of an exhaust gas recirculation amount so that an air-fuel ratio of an inner combustion chamber becomes a target value, and particularly to a technical field related to control of an intake throttle valve at the time of engine deceleration.

[0002]

2. Description of the Related Art Conventionally, as an intake control device for an engine with a turbocharger, for example, as disclosed in JP-A-63-50544, the amount of exhaust gas recirculated to an intake system of a diesel engine is adjusted. Thus, there is known an apparatus in which the air-fuel ratio (excess air ratio) of the combustion chamber is indirectly controlled. In this device, the pressure and temperature in the intake passage are detected by a sensor provided in the intake passage of the engine,
The cylinder filling ratio of the intake air is obtained based on the detection result, and an exhaust gas recirculation amount control valve (exhaust gas circulation adjusting device) operated by an actuator is provided in the exhaust gas recirculation passage communicating the intake and exhaust passages. The exhaust gas recirculation amount is adjusted according to the charge ratio so that the air-fuel ratio of the combustion chamber becomes a predetermined target value.

[0003] Further, in Japanese Patent Laid-Open No. 9-4519, the amount of intake air is detected based on the engine speed, and the combustion chamber is detected in the same manner as described above based on the amount of intake air and the amount of fuel injection. Is indirectly controlled. In this case, the amount of NOx emission can be reduced by increasing the amount of exhaust gas recirculation, but on the other hand, the air-fuel ratio of the combustion chamber gradually decreases as the amount of exhaust gas recirculation increases, and if the air-fuel ratio is too small, smoke is generated Considering the characteristics of the in-cylinder injection diesel engine that the amount increases rapidly,
By controlling the air-fuel ratio to a value as small as possible (a value on the rich side) within a range where the amount of smoke does not increase sharply, the N
Ox and smoke are reduced.

Further, in a diesel engine or a direct-injection gasoline engine in which an air-fuel mixture is stratified around a spark plug, an intake negative pressure is low because excessive intake air is obtained in a low-speed operation state such as an idling operation. Therefore, even if the exhaust gas recirculation amount control valve is fully opened, a sufficient amount of exhaust gas recirculation may not be obtained. In this regard, in the latter conventional example (Japanese Patent Laid-Open No. 9-4519), an intake throttle valve is provided in an intake passage of a small diesel engine which is not usually provided with a throttle valve or the like, and the above-described intake air is provided. In the operation state where the negative pressure is small, the exhaust gas can be sufficiently recirculated by reducing the opening degree of the intake throttle valve and increasing the differential pressure between the intake and exhaust systems.

[0005]

Generally, a turbocharger driven by the exhaust of an engine to supercharge the intake air has an excellent supercharging capacity in a middle or high speed range of an engine having a large exhaust flow rate. Is obtained, but sufficient supercharging ability cannot be exhibited in a low rotation range where the exhaust gas flow rate is small. In addition, since the engine equipped with this turbocharger usually has a smaller compression ratio of the cylinder than the non-supercharged engine, the intake charging efficiency in the low rotation region is considerably lower than that in the middle rotation region.

Further, when the engine is in the deceleration operation state, the fuel injection amount is reduced and the combustion is weakened, so that the exhaust energy given to the turbocharger is also reduced.
This also reduces the supercharging capacity. Therefore, for example, when the vehicle enters a low-speed operation range while the engine is in a decelerating state during deceleration, the supercharging capacity of the turbocharger becomes extremely low. However, there is a problem of a so-called turbo lag that the reacceleration of the vehicle is deteriorated without increasing the speed.

With respect to this point, in the case where the air-fuel ratio of the combustion chamber is indirectly controlled by adjusting the exhaust gas recirculation amount as in the conventional example, when the engine enters a low-speed operation range in a deceleration operation state, Since the amount of fuel injection is small, a large amount of exhaust gas is recirculated. In this state, when the accelerator is depressed, the exhaust gas recirculation amount cannot be immediately reduced to zero. Therefore, there is a problem that the above-mentioned problem of the turbo lag is promoted by preventing the intake of air.

Further, when the air-fuel ratio of the combustion chamber is larger than the stoichiometric air-fuel ratio and the exhaust gas recirculation amount is large, the exhaust gas temperature becomes relatively low because the thermal efficiency becomes high. for that reason,
If the fuel injection amount is reduced and the combustion is weakened as described above during the deceleration operation of the engine, the exhaust gas temperature becomes considerably low, and the exhaust gas purifying catalyst is excessively cooled, thereby causing a decrease in the purifying performance. There is a fear. In particular, diesel engines have a higher compression ratio than gasoline engines,
Since the thermal efficiency is higher, the purification performance is likely to decrease due to the supercooling of the catalyst.

The present invention has been made in view of the above points, and an object of the present invention is to reduce the deceleration by devising a control procedure of an intake throttle valve during a deceleration operation of a turbocharged engine. It is an object of the present invention to reduce turbo lag at the time of subsequent re-acceleration to improve re-acceleration performance, and also to prevent overcooling of the catalyst to ensure stable purification performance.

[0010]

According to a first aspect of the present invention, an intake throttle valve is closed by a predetermined amount when the engine is decelerated, and a differential pressure between the intake and exhaust systems is increased to reduce the exhaust pressure. While ensuring the recirculation amount, the engine is shifted to the low-load low-speed region while the engine is in the deceleration operation state, and when the supercharging capacity of the turbocharger becomes significantly low, a predetermined period is prepared for the subsequent re-acceleration operation. , The intake throttle valve was opened.

More specifically, in the first aspect of the present invention, as shown in FIG. 1, the intake air is supercharged by the intake throttle valve 14 disposed in the intake passage 10 of the engine 1 and the exhaust gas of the engine 1. A turbocharger 25, an exhaust gas recirculation passage 23 for recirculating a part of the exhaust gas to the intake passage 10 downstream of the intake throttle valve 14, and an exhaust gas recirculation amount adjusting the exhaust gas recirculation amount by the exhaust gas recirculation passage 23 State quantity detection means 1 for detecting a state quantity relating to the air-fuel ratio of the combustion chamber 4 of the engine 1 with the valve 24
1, and the intake control device A for the engine is configured such that the opening degree of the exhaust gas recirculation amount control valve 24 is feedback-controlled based on the value detected by the state amount detection means 11. An operating state determining means 35d for determining an operating state of the engine 1, and an intake throttle valve for closing the intake throttle valve 14 by a predetermined amount when the operating state determining means 35d determines that the engine 1 is in a deceleration operating state. Control means 35c, and the intake throttle valve control means 35c
When the operating state determination means 35d determines that the engine 1 is in the low-load low-speed operation range, the valve-opening control unit 35e that opens the intake throttle valve 14 for a predetermined period after the determination.
It was made to have. Note that the predetermined period corresponds to a period in which it is predicted that the engine 1 in the deceleration operation state will subsequently shift to the acceleration operation state.

According to the above configuration, when the driver reduces the accelerator operation amount while the vehicle is running, the fuel supply amount is reduced in accordance with the accelerator operation, and the engine 1 enters a deceleration operation state. The deceleration operation state of the engine 1 is determined by the operation state determination unit 35d, and the intake throttle valve 14 is closed by a predetermined amount by the intake throttle valve control unit 35c.
The closing operation of the intake throttle valve 14 narrows the intake passage 10 to reduce the amount of intake air, and also reduces the intake pressure to increase the pressure difference between the intake system and the exhaust system. Can be secured. That is, when the engine 1 is in the deceleration operation state, the amount of fresh intake air can be reduced in accordance with the decrease in the fuel supply amount, and the exhaust gas recirculation amount can be sufficiently ensured to suppress the generation of NOx. .

When the operating state determining means 35d determines that the engine speed is further reduced and the engine 1 is in the low-load low-speed operating range, the valve opening control unit 35e performs the predetermined period after the determination. The intake throttle valve 14 is opened. As a result, the amount of intake air to the engine 1 and, consequently, the flow rate of exhaust gas to the turbocharger 25 are increased, and a decrease in the supercharging capacity of the turbocharger 25 is suppressed. By supercharging, the intake air amount of fresh air can be rapidly increased. Therefore, the turbo lag can be reduced, and the re-acceleration of the engine after deceleration can be improved.

According to a second aspect of the present invention, the valve opening control unit according to the first aspect of the present invention provides a valve opening control unit that determines whether the engine is in the low-load low-speed operation range from when the set time elapses. The throttle valve is opened.

That is, it is generally considered that when the engine enters the low-load low-rotation operation range in the deceleration operation state, if the set time further elapses, the engine directly shifts to the stop state. On the other hand, the possibility of shifting to the acceleration operation state is extremely high until the set time elapses, and during that time, the intake throttle valve is opened to prepare for re-acceleration, whereby the operation of the invention according to claim 1 is performed. The effect can be sufficiently obtained.

According to a third aspect of the present invention, in the first aspect of the present invention, there is provided an accelerator return state determining means for determining that the accelerator is in the return state when the accelerator operation amount is equal to or less than the set amount. When the accelerator return state determination means determines that the accelerator is in the return state, the intake throttle valve is opened. The set amount is
What is necessary is just to set so as to correspond to a state where the accelerator operation amount is extremely small.

Thus, when the accelerator operation amount becomes equal to or less than the set amount during the deceleration operation of the engine, it is conceivable that the driver is performing a speed change operation of the manual transmission. In such a case, the intake throttle valve 14 is opened to prepare for re-acceleration.
The operation and effect of the described invention can be sufficiently obtained.

According to a fourth aspect of the present invention, in the first aspect of the invention, the opening degree of the exhaust gas recirculation amount control valve is adjusted so that the air-fuel ratio of the combustion chamber becomes a target value based on the value detected by the state quantity detecting means. , And target value correction means for increasing and correcting the target value of the air-fuel ratio in the exhaust gas recirculation control means when the engine is decelerated.

According to this configuration, normally, the state quantity relating to the air-fuel ratio of the combustion chamber is detected by the state quantity detection means, and the opening of the exhaust gas recirculation amount control valve is controlled based on the detected value. Is controlled with high accuracy so as to be a target value, thereby reducing NOx and smoke in the exhaust gas. On the other hand, when the engine is decelerated, the fuel supply amount becomes extremely small. Therefore, if the air-fuel ratio of the combustion chamber is controlled to a normal target value, the exhaust gas recirculation amount control valve must be fully opened. Therefore, even if an attempt is made to close the exhaust gas recirculation amount control valve at the time of re-acceleration of the engine after deceleration, it takes too much time until the exhaust gas recirculation amount control valve is fully closed. Problem arises.

Therefore, in the present invention, when the engine is decelerated, the target value of the air-fuel ratio is made larger than usual so that the exhaust gas recirculation amount control valve is not fully opened even if the fuel supply amount is small. When the engine is re-accelerated, the delay of the closing operation of the exhaust gas recirculation amount control valve can be reduced, and the amount of fresh intake air can be rapidly increased.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the catalyst for purifying the exhaust of the engine and the catalyst inactive state determination for determining that the temperature state of the catalyst is lower than the activation temperature. Means and valve opening control prohibiting means for prohibiting control by the valve opening control unit when the catalyst inactive state determining means determines that the temperature state of the catalyst is lower than the activation temperature.

That is, in general, when the engine is decelerated, the fuel supply amount is reduced, the combustion is weakened, and the exhaust gas temperature is lowered. If the exhaust gas flow rate is large at this time, the inactive catalyst may be further cooled. Therefore, in the present invention, when the catalyst inactive state determining means determines that the temperature state of the catalyst is lower than the activation temperature, the opening operation of the intake throttle valve is prohibited by the valve opening control prohibiting means. The active catalyst can be prevented from being further cooled.

According to a second solution of the present invention, the opening degree of the intake throttle valve is controlled in accordance with the temperature state of the exhaust gas purifying catalyst in consideration of the fact that the exhaust gas temperature decreases when the engine is decelerated. The supercooling is prevented to prevent the purification performance from being lowered.

Specifically, according to the present invention, as shown in FIG. 1, the intake air is supercharged by the intake throttle valve 14 disposed in the intake passage 10 of the engine 1 and the exhaust gas of the engine 1. A turbocharger 25, an exhaust gas recirculation passage 23 for recirculating a part of the exhaust gas to the intake passage 10 downstream of the intake throttle valve 14, and an exhaust gas recirculation amount adjusting the exhaust gas recirculation amount by the exhaust gas recirculation passage 23 State quantity detection means 1 for detecting a state quantity relating to the air-fuel ratio of the combustion chamber 4 of the engine 1 with the valve 24
1, and the intake control device A for the engine is configured such that the opening degree of the exhaust gas recirculation amount control valve 24 is feedback-controlled based on the value detected by the state amount detection means 11. Then, a catalyst 2 for purifying the exhaust gas of the engine 1
2 and a catalyst temperature determining means 3 for determining whether or not the temperature state of the catalyst 22 is equal to or higher than a set catalyst temperature at which the activation temperature is higher.
5h and the engine 1 at least according to the accelerator operation amount.
Supply control means 35a for controlling the fuel supply to the fuel supply
When the fuel supply amount is made zero by the fuel supply amount control means 35a and the temperature state of the catalyst 22 is determined to be lower than the set catalyst temperature by the catalyst temperature determination means 35h, An intake throttle valve control means 35c for closing the intake valve 14 by a predetermined amount is provided.

With the above configuration, when the driver significantly reduces the accelerator operation amount during the running of the vehicle, the fuel supply amount is reduced to zero by the fuel supply amount control means 35a in accordance with the accelerator operation, and the engine is operated. 1 is suddenly decelerated. At this time, the temperature of the exhaust gas is rapidly lowered due to the interruption of combustion, and the catalyst 2
2 is also rapidly cooled, but when the temperature of the catalyst 22 becomes lower than the set catalyst temperature, the intake throttle valve 14 is closed by a predetermined amount by the intake throttle valve control means 35c and the exhaust gas flow rate decreases. 22 can be prevented from being excessively cooled. Thus, the temperature state of the catalyst 22 can be maintained at the activation temperature or higher, and the purification performance can be stably ensured.

According to a seventh aspect of the present invention, based on the sixth aspect, the opening degree of the exhaust gas recirculation amount control valve is adjusted so that the air-fuel ratio of the combustion chamber becomes a target value based on the value detected by the state quantity detecting means. And an exhaust gas recirculation control means for controlling the exhaust gas recirculation amount control valve by the exhaust gas recirculation control means when the fuel supply amount is reduced to zero by the fuel supply amount control means. And

According to this configuration, normally, the state quantity relating to the air-fuel ratio of the combustion chamber is detected by the state quantity detection means, and the opening of the exhaust gas recirculation amount control valve is controlled based on the detected value. Is controlled with high accuracy so as to be a target value, thereby reducing NOx and smoke in the exhaust gas. On the other hand, if the fuel supply amount is reduced to zero during engine deceleration, the intake air amount must be made infinite to control the air-fuel ratio of the combustion chamber to the normal target value, leading to erroneous control. However, in the present invention, the above-described erroneous control can be prevented by prohibiting the control of the exhaust gas recirculation amount adjusting valve by the exhaust gas recirculation control means.

According to an eighth aspect of the present invention, the exhaust gas recirculation control restricting means according to the seventh aspect of the present invention forcibly holds the opening of the exhaust gas recirculation control valve at the set opening.

Thus, when the fuel supply amount is reduced to zero by the fuel supply amount control means during engine deceleration, the control of the exhaust gas recirculation amount control valve by the exhaust gas recirculation control means is prohibited, and the exhaust gas recirculation amount control valve is controlled. Is forcibly set to the set opening. That is, if the opening degree of the exhaust gas recirculation amount control valve is controlled to, for example, the fully closed state or the minimum opening degree, the intake air amount can be increased very quickly when the engine again shifts to the acceleration operation state. This can also improve the re-acceleration. Note that NOx is not emitted because combustion is not performed while the fuel supply amount is set to zero.

According to a ninth aspect of the present invention, in the sixth aspect of the present invention, there is provided an engine coolant temperature judging means for judging that the temperature state of the engine coolant is equal to or higher than a set coolant temperature.
The intake throttle valve control means includes a valve opening control unit that opens the intake throttle valve at the time of determination by the engine water temperature determination means. The set water temperature may be, for example, the engine water temperature when the entire engine is overheated and the temperature state of the intake passage is high.

Thus, when the engine coolant temperature determining means determines that the temperature state of the engine cooling water is equal to or higher than the set water temperature, the temperature state of the intake passage is high, and the intake charge efficiency is reduced due to the decrease in intake density. Therefore, there is a possibility that a sufficient output cannot be obtained at the time of re-acceleration of the engine after deceleration. Therefore, according to the present invention, the intake throttle valve is opened by the valve opening control unit, the intake flow rate is increased, and the intake passage is cooled, so that the adverse effect of the output decrease at the time of re-acceleration can be reduced. When the engine water temperature is high, the catalyst is considered to be in a high temperature state. Therefore, even if the exhaust gas flow rate increases with an increase in the intake air flow rate, the problem of supercooling of the catalyst does not occur.

According to a tenth aspect of the present invention, as shown in FIG. 1, an intake throttle valve 14 disposed in an intake passage 10 of an engine 1, and a turbocharger for supercharging intake air by exhaust of the engine 1. 25, an exhaust gas recirculation passage 2 for recirculating a part of the exhaust gas to the intake passage 10 downstream of the intake throttle valve 14.
3, an exhaust gas recirculation amount control valve 24 for adjusting the amount of exhaust gas recirculated by the exhaust gas recirculation passage 23, and a state quantity detecting means 11 for detecting a state quantity relating to the air-fuel ratio of the combustion chamber 4 of the engine 1. It is assumed that the intake control device A of the engine is configured to feedback-control the opening degree of the flow control valve 24 based on the value detected by the state quantity detecting means 11. An operating state determining means 35d for determining an operating state of the engine 1, and an intake throttle valve for closing the intake throttle valve 14 by a predetermined amount when the operating state determining means 35d determines that the engine 1 is in a deceleration operating state. Control means 35
c, and an engine coolant temperature determining means 35j for determining that the temperature state of the engine coolant is equal to or higher than the set coolant temperature,
The intake throttle valve control unit 35c has a valve opening control unit 35e that opens the intake throttle valve 14 at the time of determination by the engine coolant temperature determination unit 35j. The set water temperature may be, for example, the engine water temperature when the entire engine is overheated and the temperature state of the intake passage is high.

According to the above configuration, when the driver reduces the accelerator operation amount while the vehicle is running, the fuel supply amount is reduced in accordance with the accelerator operation, and the engine 1 enters a deceleration operation state. The deceleration operation state of the engine 1 is judged by the operation state judgment means 35d, the intake throttle valve 14 is closed by a predetermined amount by the intake throttle valve control means 35c, and the generation of NOx is suppressed in the same manner as in the first aspect of the present invention. . However, when the engine coolant temperature determining means 35j determines that the temperature state of the engine cooling water is equal to or higher than the set water temperature, the valve opening control unit 35e opens the intake throttle valve 14 to increase the intake flow rate and increase the intake passage 10 Is cooled.

That is, in general, when the engine coolant temperature judging means 35j judges that the temperature state of the engine coolant is equal to or higher than the set coolant temperature, the intake air density becomes low due to the overheating of the intake passage 10, and the intake charging efficiency decreases. Therefore, there is a possibility that a sufficient output cannot be obtained at the time of re-acceleration of the engine after deceleration. Therefore, in the present invention, the intake throttle valve 14 is opened as described above to promote cooling of the intake passage 10, so that the intake charging efficiency can be sufficiently increased, and therefore, the output reduction during the re-acceleration described above. Can be avoided.

According to an eleventh aspect of the present invention, in the tenth aspect of the present invention, an intercooler for cooling intake air compressed by a blower of the turbocharger is provided. As a result, the high-temperature, high-pressure intake air compressed by the blower of the turbocharger is cooled by the intercooler, and the intake air density is increased. As a result, the intake charging efficiency can be increased, and the engine output can be improved. Therefore, the engine re-acceleration after deceleration can be improved.

According to a twelfth aspect of the present invention, there is provided an intake throttle valve disposed in an intake passage of an engine, a turbocharger for supercharging intake air by exhaust of the engine, and an intake air downstream of the intake throttle valve. An exhaust gas recirculation passage for recirculating a part of exhaust gas to the passage, an exhaust gas recirculation amount adjusting valve for adjusting an amount of exhaust gas recirculated by the exhaust gas recirculation passage, and a state quantity detecting means for detecting a state quantity related to an air-fuel ratio of a combustion chamber of the engine. And an intake control device for an engine, wherein the opening degree of the exhaust gas recirculation amount control valve is feedback-controlled based on a value detected by the state quantity detection means. Operating state determining means for determining an operating state of the engine; intake throttle valve control means for closing the intake throttle valve by a predetermined amount when the operating state determining means determines that the engine is in a deceleration operating state; Intake temperature determination means for determining that the temperature state of the intake passage downstream of the connection with the exhaust gas recirculation passage is equal to or higher than a set intake air temperature, wherein the intake throttle valve control means is provided by the intake temperature determination means A valve opening control unit that opens the intake throttle valve at the time of determination is provided.

According to the above construction, when the intake air temperature determining means determines that the temperature state of the intake passage is higher than the set intake air temperature, the intake throttle valve is opened by the valve opening control unit. The same operation and effect as those of the described invention can be obtained.

According to the thirteenth aspect, the engine according to the sixth aspect is a diesel engine.
As a result, the thermal efficiency of the diesel engine is higher than that of the gasoline engine, and the purification performance tends to decrease due to the supercooling of the catalyst. The effect that the purification performance can be stably ensured by controlling the degree of supercooling of the catalyst by controlling the degree of supercooling becomes particularly effective.

[0039]

Embodiments of the present invention will be described below with reference to the drawings.

(Overall Structure) FIG. 1 shows an intake control device A for a turbocharged diesel engine according to an embodiment of the present invention.
1 is, for example, a four-cylinder diesel engine mounted on a vehicle equipped with a manual transmission. This engine 1 has four cylinders 2, 2, ...
A piston 3 is inserted into each cylinder 2 so as to be able to reciprocate, and a combustion chamber 4 is defined in each cylinder 2 by the piston 3. Also,
An injector 5 is disposed at a substantially central portion of an upper surface of the combustion chamber 4 with an injection hole at a tip end thereof facing the combustion chamber 4. The injector 5 is opened and closed at a predetermined injection timing for each cylinder. 4
The fuel is directly injected into the tank.

Each of the injectors 5 is connected to a common common rail (accumulator) 6 for storing high-pressure fuel.
The common rail 6 is provided with a pressure sensor 6 a for detecting an internal fuel pressure (common rail pressure), and is connected to a high-pressure supply pump 8 driven by a crankshaft 7. The high-pressure supply pump 8 operates so that the fuel pressure in the common rail 6 detected by the pressure sensor 6a is maintained at a predetermined value or more (for example, 40 MPa during idle operation and 80 MPa or more in other operation states). A crank angle sensor 9 for detecting the rotation angle is provided at one end of the crank shaft 7. The crank angle sensor 9 includes a plate to be detected (not shown) provided at an end of the crankshaft 7 and an electromagnetic pickup disposed so as to face the outer periphery thereof. A pulse signal is output in response to the passage of the projection formed over the entire outer periphery.

Reference numeral 10 denotes an intake passage for supplying intake air (air) filtered by an air cleaner (not shown) to the combustion chamber 4 of the engine 1. The downstream end of the intake passage 10 is connected to a surge tank (not shown). Each cylinder 2 is branched and connected to a combustion chamber 4 of each cylinder 2 by an intake port. Further, a supercharging pressure sensor 10a for detecting a supercharging pressure supplied to each cylinder 2 via the surge tank is provided. In the intake passage 10, an air flow sensor (intake amount sensor) 11 for detecting a flow rate of intake air taken into the engine 1 and a blower driven by a turbine 21 to compress the intake air in order from the upstream side to the downstream side. 12
And an intercooler 13 for cooling the intake air compressed by the blower 12 and an intake throttle valve 14 for reducing the cross-sectional area of the intake passage 10. The intake throttle valve 14 is a butterfly valve provided with a notch so that intake air can flow even in a fully closed state.
Similarly to the valve 24, the magnitude of the negative pressure acting on the diaphragm 15 is adjusted by the negative pressure control solenoid valve 16, so that
The opening of the valve is controlled.

The air flow sensor 11 is a constant temperature hot film air flow sensor capable of reliably detecting the air flow rate even if there is a variation in the flow velocity. , And hot films disposed upstream and downstream of the heater, and based on the temperature of the two hot films, the intake passage 10 is connected to the downstream side (each cylinder). 2) and a reverse flow toward the upstream side are respectively detected. Only the air flow in the forward direction can be measured based on the value measured by the air flow sensor 11, and it is possible to avoid an error due to a backflow in controlling the exhaust gas recirculation amount.

In FIG. 1, reference numeral 20 denotes an exhaust passage for discharging combustion gas from the combustion chamber 4 of each cylinder 2. The upstream end of the exhaust passage 20 is branched and the combustion port of each cylinder 2 is opened by an exhaust port (not shown). It is connected to room 4. The exhaust passage 20 includes, in order from the upstream side to the downstream side, a turbine 21 that is rotated by the exhaust flow, HC in the exhaust gas,
Catalytic converter (not shown) for reducing CO and NOx
An exhaust temperature sensor (temperature state detecting means) 2 for measuring the temperature of exhaust flowing into the catalyst is provided near the catalytic converter 22 for reducing the temperature.
2a is provided.

The catalytic converter 22 is a catalyst for purifying NOx in an oxygen-excess atmosphere. An upstream first catalyst 22b and a downstream second catalyst 22c are arranged in the axial direction (flow direction of exhaust gas). Have been. The two catalysts 22
Each of b and 22c has a catalyst layer formed on the wall surface of each through-hole of a honeycomb-structured cordierite carrier (not shown) having a large number of through-holes extending parallel to each other in the axial direction. The one catalyst 22b oxidizes NOx in the exhaust gas to NO2, and the second catalyst 22c on the downstream side reduces the NO2 in the exhaust gas to N2.

As the catalytic converter 22, for example, the first catalyst 22b on the upstream side is made of Ag / Al ₂ O _{3 in} which Ag is supported as a catalyst metal on alumina as a base material, and the second catalyst 22b on the downstream side is formed. The catalyst is composed of Pt ⁺ -MFI obtained by supporting Pt as a catalyst metal on MFI (synthetic zeolite ZSM-5) as a base material by ion exchange. A catalyst having such NOx purification performance is, for example, shown in FIG.
As shown in (a), it is known that the purification performance has a characteristic that it strongly depends on the temperature state. That is, the NOx purification rate of the catalyst shown in FIG.
Although the temperature becomes extremely high in a temperature range of about 30 ° C., it drops rapidly with a rise in temperature in a higher temperature state.

Here, as the catalytic converter 22,
Although an example of the NO purification catalyst suitable for a diesel engine having a large amount of excess oxygen has been described above, the present invention is not limited to this. For example, while the air-fuel ratio of the exhaust gas emits NOx in a rich state near the stoichiometric air-fuel ratio or less, A catalyst having a function as a so-called NOx absorption catalyst that absorbs NOx in a lean state with a larger air-fuel ratio may be used.

As such a NOx absorption catalyst, for example, alumina or ceria carrying platinum Pt and at least one of alkaline earth metals such as barium Ba, alkali metal or rare earth metal is carried on the wall surface of the carrier. An inner catalyst layer and a two-layer coat type in which an outer catalyst layer supporting a zeolite supporting a noble metal such as platinum Pt are known, but a catalyst having such a NOx absorption function is also known. For example, as shown in FIG. 22 (b), it has a characteristic that its purification performance strongly depends on the temperature state.
The NOx purification rate of the catalyst shown in FIG.
Although the temperature becomes extremely high in a temperature range of about ° C, it drops rapidly with a rise in temperature in a higher temperature state.

As shown in FIG. 2, the turbocharger 25 comprising the turbine 21 and the blower 12
A plurality of flaps 21b, 21b,... Are provided so as to surround the entire circumference of the turbine 21 in a turbine chamber 21a that accommodates the nozzles.
Is a VGT (Variable Geometry Turbo) that rotates so as to change. In the case of this VGT, FIG.
.. Are positioned so as to face the turbine 21 in the circumferential direction to reduce the nozzle cross-sectional area A, thereby increasing the supercharging capacity even in the low rotation speed region of the engine 1 having a small exhaust flow rate. be able to. On the other hand, as shown in FIG. 2B, if the flaps 21b, 21b,... Are positioned so that their tips face the center of the turbine 21 and the nozzle cross-sectional area A is increased, the height of the engine 1 with a large exhaust flow rate is increased. High supercharging capacity can be obtained even in the rotation range.

The exhaust passage 20 is a portion upstream of the turbine 21 and is branched and connected to an upstream end of an exhaust gas recirculation passage (hereinafter referred to as an EGR passage) 23 for recirculating a part of exhaust gas to the intake side. The downstream end of the EGR passage 23 is connected to the intake passage 10 on the downstream side of the intake throttle valve 14 with respect to the intake air. Exhaust gas recirculation amount control valve (hereinafter EG)
An EGR valve 24 recirculates a part of the exhaust gas from the exhaust passage 20 to the intake passage 10 while adjusting the flow rate.

The EGR valve 24 is, as shown in FIG.
A valve rod 24b is fixed to a diaphragm 24a that partitions the valve box, and a valve body 24c for linearly adjusting the opening degree of the EGR passage 23 and a lift sensor 26 are provided at both ends of the valve rod 24b. The valve body 24c has a spring 2
While being biased in the closing direction (downward in the figure) by 4d, a negative pressure passage 27 is connected to a negative pressure chamber (a chamber above the diaphragm 24a) of the valve box. The negative pressure passage 27 is connected to a vacuum pump (negative pressure source) 29 via a negative pressure control electromagnetic valve 28, and the electromagnetic valve 28 communicates with the negative pressure passage 27 according to a control signal from an ECU 35 described later. By shutting off, the negative pressure for driving the EGR valve in the negative pressure chamber is adjusted, whereby the opening of the EGR passage 23 is linearly adjusted by the valve body 24c.

In other words, as shown in FIG. 4A, the negative pressure for driving the EGR valve increases (the pressure decreases) as the current increases, and is proportional to the negative pressure for driving the EGR valve. As shown in (5), the lift amount of the EGR valve body 24c changes. However, hysteresis is observed in the change in the lift amount of the EGR valve main body 24c.

The flap 21 of the turbocharger 25
A diaphragm 30 is attached to each of b, 21b,... similarly to the EGR valve 24, and the negative pressure acting on the diaphragm 30 is adjusted by an electromagnetic valve 31 for negative pressure control, so that the flaps 21b, 21b,. The amount of operation of ... is adjusted.

Each of the injectors 5, high-pressure supply pump 8, intake throttle valve 14, EGR valve 24, turbocharger 25
Are the control unit (Electronic Control Unit: hereinafter referred to as ECU) 3
5 to be operated by a control signal from the control unit 5. On the other hand, the ECU 35 has an output signal from the pressure sensor 6a, an output signal from the crank angle sensor 9, an output signal from the air flow sensor 11, an output signal from the exhaust temperature sensor 22a, and an output signal from the EGR valve 24. An output signal from the lift sensor 26, an output signal from an accelerator opening sensor 32 for detecting an operation amount (accelerator opening) of an accelerator pedal (not shown) by a driver of the vehicle, and a cooling water temperature of the engine 1 (not shown). At least an output signal from the water temperature sensor to be detected is input.

(Overall Configuration of Control System) The ECU 3
FIG. 5 is a block diagram showing an outline of the basic processing of the engine control in FIG. 5, in which the basic fuel injection amount is determined based on the accelerator opening and the EGR valve 24 is determined.
The EGR rate is adjusted by the operation of (1) to control the air-fuel ratio of each cylinder uniformly and with high accuracy. The control of the common rail pressure by the operation of the high-pressure supply pump 8, the control of the opening of the intake throttle valve 14, and the operation control (VGT control) of the flaps 21b, 21b, ... of the turbocharger 25 are performed. .

The EGR rate is the ratio of the recirculated exhaust gas amount (EGR amount) to the total exhaust gas amount. That is, E
GR ratio = EGR amount / total exhaust amount Here, the distribution of the exhaust gas recirculated from the EGR passage 23 to the intake passage 10 to the cylinders 2 differs, and in addition, the air intake characteristics per cylinder also vary. EG in the EGR passage 23
Even if the opening of the R valve 24 is the same, the EG in each cylinder 2
The deviation in the R ratio and the intake air amount deviation varies, and the intake air amount is small in a cylinder with a high EGR ratio and large in a cylinder with a low EGR ratio. Therefore, a target air-fuel ratio common to all the cylinders 2 is basically determined, the intake air amount is detected for each cylinder, and the exhaust gas is returned to each cylinder so as to reach the target air-fuel ratio according to the intake air amount. The flow rate is controlled. That is, E to the intake air amount of each cylinder 2
Instead of making the GR amount ratio uniform, the exhaust gas recirculation amount is controlled for each cylinder with a predetermined air-fuel ratio as a target, whereby the air-fuel ratio of each cylinder 2 is controlled uniformly and with high accuracy. be able to.

More specifically, the ECU 35 stores a two-dimensional map 36 in which the optimum value of the target torque trqsol is experimentally determined and recorded with respect to changes in the accelerator opening Acc and the engine speed Ne. The target fuel injection amount Fsol with respect to changes in the number Ne, the target torque trqsol, and the fresh air amount (this is the intake air amount and does not include fuel. The same applies hereinafter) FAir
Three-dimensional map 37 in which the optimal value of is experimentally determined and recorded.
And a two-dimensional map 38 in which the optimum value of the target air-fuel ratio A / Fsol is experimentally determined and recorded with respect to changes in the engine speed Ne and the target torque trqsol, and are electronically stored in the memory. I have.

The target air-fuel ratio A / Fsol is a control target value for determining the exhaust gas recirculation amount so as to achieve both reduction of NOx and reduction of smoke. That is, as shown in FIG. 6, the relationship between the air-fuel ratio of the diesel engine and the amount of NOx in the exhaust gas is illustrated. As the air-fuel ratio increases (toward the lean side), the amount of NOx tends to increase. If the air-fuel ratio is reduced (toward the rich side), the generation of NOx can be reduced.

However, as exemplified in FIG. 7, according to the relationship between the air-fuel ratio of the same engine and the smoke value in the exhaust,
When the air-fuel ratio falls below the air-fuel ratio that has changed to the rich side,
It can be seen that the amount of smoke suddenly increases. That is, NO
There is a limit to increasing the amount of exhaust gas recirculation to reduce the amount of x. In the control device A of this embodiment, the target air amount is reduced in order to suppress a sudden increase in smoke while reducing NOx in the exhaust gas. The fuel ratio A / Fsol is set to a value as rich as possible before the smoke amount starts to increase rapidly.

Fuel Injection Control Specifically, first, the target torque calculating section 41 uses the accelerator opening Acc detected by the accelerator opening sensor 32 and the engine speed Ne detected by the crank angle sensor 9. The target torque trqsol is determined with reference to the two-dimensional map 36 on the memory. This target torque trqsol
And the fresh air amount FA measured by the air flow sensor 11
Using ir and the engine speed Ne, the target injection amount calculation unit 4
In step 2, the target injection amount Fsol is determined with reference to the three-dimensional map 37 in the memory. And this target injection amount Fs
Based on ol and the common rail pressure CRP controlled as described later, the excitation time of each injector 5 is determined and controlled.

However, when the engine is decelerated, the target torque trqsol and the engine speed
Ne and the three-dimensional map 37
The target injection amount Fsol is determined with reference to a map different from the above. The target torque calculation unit 41 and the target injection amount calculation unit 42 correspond to a fuel supply amount control unit 35a (see FIG. 1) that controls a fuel supply amount to the engine 1 according to at least the accelerator opening Acc.

Exhaust gas recirculation control On the other hand, using the target torque trqsol and the engine speed Ne obtained in the target torque calculation section 41, the target air-fuel ratio calculation section 43 refers to a two-dimensional map 38 in a memory. A target air-fuel ratio A / Fsol for achieving both NOx and smoke is determined. Then, using the target air-fuel ratio A / Fsol and the target injection amount Fsol obtained by the target injection amount calculation unit 42, the target new air amount FAsol is calculated by the target new air amount calculation unit 44 (FAsol = Fsol × A / Fso
l) With the target fresh air amount FAsol as a target, the fresh air amount control unit 45 performs fresh air amount control. This fresh air control does not directly adjust the fresh air supply amount itself, but changes the fresh air amount by adjusting the recirculation amount of exhaust gas.
That is, instead of determining the fresh air correction amount, the operation amount EGRso of the EGR valve 24 is determined based on the target fresh air amount FAsol.
l is determined, and EGR is set to correspond to the manipulated variable EGRsol.
Controls the opening of the valve. The target air-fuel ratio calculator 43, the target fresh air amount calculator 44, and the fresh air amount controller 45 correspond to the exhaust gas recirculation control means 35b (see FIG. 1).

Common Rail Pressure Control The ECU 35 electronically stores a two-dimensional map 50 in which an optimum experimentally determined common rail pressure CRPsol in response to changes in the target torque trqsol and the engine speed Ne is recorded in a memory. The common rail pressure calculation unit 4 is provided using the target torque trqsol obtained by the target torque calculation unit 41 and the engine speed Ne.
In step 6, the target common rail pressure CRPsol is calculated with reference to the map 50, and the calculated common rail pressure CRPsol is used to control the common rail pressure.

In the map 50, the target common rail pressure CRPsol is set to increase as the engine speed Ne increases. This is because the higher the engine speed Ne is, the shorter the time during which the injector 5 can be opened is relatively short. Therefore, it is necessary to increase the injection pressure to secure a sufficient injection amount. On the other hand, in the low rotation range of the engine 1, it is preferable to inject fuel over a certain period of time, and to spread the fuel greatly along with the air flow in the combustion chamber, so that the valve opening time of the injector 5 is lengthened and correspondingly, The injection pressure is reduced. Further, the target common rail pressure CRPsol is set to increase as the target torque trqsol increases, and this is
This is because the larger the value is, the more the fuel injection amount needs to be increased, so that it is necessary to increase the injection pressure to secure the injection amount.

The intake throttle valve control ECU 35 stores in the memory a two-dimensional map 51 storing an experimentally determined optimum target intake throttle amount THsol in response to changes in the target fuel injection amount Fsol and the engine speed Ne. Using the target injection amount Fsol obtained in the target injection amount calculation unit 42 and the engine speed Ne, the target intake throttle amount calculation unit 47 refers to the map 51 by using the target injection amount calculation unit 42. The target intake throttle amount THsol is calculated, and the opening degree of the intake throttle valve 14 is controlled using the target intake throttle amount THsol. The control of the intake throttle valve is also performed differently from the steady state when the engine is decelerated. As will be described in detail later, the opening degree of the intake throttle valve 14 is usually made smaller than the steady state when the engine is decelerated. The target intake throttle amount calculator 4
Reference numeral 7 corresponds to the intake throttle valve control means 35c (see FIG. 1).

VGT Control Further, the ECU 35 stores a two-dimensional map 52 in which an optimum target supercharging pressure Boostsol determined experimentally in response to changes in the target torque trqsol and the engine speed Ne is electronically stored in a memory. The target supercharging pressure is stored in the target supercharging pressure calculating section 48 using the target torque trqsol and the engine speed Ne obtained in the target torque calculating section 41 with reference to the map 52. Boostsol
Is calculated. Using the target boost pressure Boostsol and the intake pressure Boost of the intake passage 10 downstream of the intake throttle valve 14 detected by the boost pressure sensor 10a, the boost pressure control unit 49 sets the intake pressure Boost to the target boost pressure. Supply pressure Boost
flap 21b of the turbocharger 25 so as to be sol,
The opening degrees VGTsol of the flaps 21b,... Are calculated, and the flaps 21b, 21b,.

(Overall Flow of Exhaust Gas Recirculation Control and Fuel Injection Amount Control) Next, the overall flow of exhaust gas recirculation and fuel injection amount control by the ECU 35 will be described with reference to FIG.
This control is executed in synchronization with the rotation of the engine 1 in accordance with a control program stored electronically on a memory.

First, as shown in steps S1 to S3 in the figure, the intake air amount FAir is determined for each cylinder based on the intake air amount detected by the air flow sensor 11 and the crank angle detected by the crank angle sensor 9. Desired. Further, the engine speed Ne obtained by the output from the crank angle sensor 9, the accelerator opening Acc detected by the accelerator opening sensor 32, and the intake air amount FAi
The target fuel injection amount Fsol is determined based on r (steps S4 to S6).

Subsequently, based on the accelerator opening Acc, the engine speed Ne, etc., a transient determination is made as to whether the engine 1 is in a steady operation state with a low load or a medium load, or in an acceleration operation state (step). S7) At the time of steady operation, a basic target air-fuel ratio is set, a target intake air amount is obtained based thereon, basic control of the EGR valve is performed, and this basic control is performed based on the intake air amount FAir of each cylinder. It is corrected by the EGR valve control for each (step S8
To S11). On the other hand, during acceleration operation, the target air-fuel ratio during acceleration is set, and EGR valve control and injection amount control during acceleration are performed (steps S12 to S14). The control during the deceleration operation will be described later.

(Calculation of Intake Air Volume for Each Cylinder) The intake air flow rate detected by the air flow sensor 11 is, for example, as shown in FIG. It can be seen that the hatched portion in the drawing is the backflow of intake air, and the integrated value obtained by subtracting this backflow, that is, the amount of intake air actually drawn into each cylinder 2 slightly fluctuates. .

FIG. 10 shows a specific control procedure when calculating the intake air amount for each cylinder using the air flow sensor 11 (steps S1 to S3 in FIG. 8). That is,
First, the intake air flow rate detected by the air flow sensor 11 is integrated, and the elapsed time at that time is measured. Each time the crank angle changes by 180 ° CA, the integral value Q (180 ( = FAir) is the intake air amount Qi of the cylinder (i), and the required time (crank timer time T) is the crank interval Ti of the cylinder (i).
And Then, the average value of the obtained intake air amounts Qi of the four cylinders is obtained as a basic intake air amount Qav (step A1).
~ A7). For convenience, cylinder numbers "0, 1, 2, 3" are assigned to the four cylinders in the order of ignition.

The rate of change ΔQi = Qi / Qi-1 of the intake air amount of the cylinder (i) and the rate of change ΔTi = Ti / Ti of the crank interval.
Ti-1 is determined with reference to the cylinder (i-1) which is one stroke earlier than the cylinder (i) to be in the intake stroke, and subsequently, the change index ΔQti = ΔQi of the intake air amount in consideration of the intake stroke time. / ΔTi is determined (steps A8 to A10). Here, ΔTi is taken into consideration due to torque fluctuation (angular velocity fluctuation of crankshaft 7).
This process is particularly effective during idling operation with large torque fluctuations. Then, based on the change index ΔQti, an intake air amount characteristic ΔQt ′ (i) for each cylinder is obtained by the following equation (step A11).

ΔQt ′ (i) = ΔQti × r + ΔQti ′ × (1-r) where 0 <r ≦ 1 Here, ΔQti ′ is the previous value of the change index ΔQti, and the above-described calculation is repeatedly executed. The current value and the previous value of the change index ΔQti are respectively reflected at a predetermined ratio in the intake air amount characteristic ΔQt ′ (i) of the cylinder (i), and the individual difference between the cylinders with respect to the intake air amount gradually increases. It becomes clearer.

(Transient Determination) FIG. 11 shows a specific control procedure of the transient determination (steps S4 to S7 in FIG. 8). This transient determination is an acceleration determination, and a determination based on a change in the accelerator opening and a determination based on a change in the fuel injection amount are performed. That is, when the engine 1 shifts from the steady operation state to the acceleration operation state, it is necessary to increase the intake air amount in accordance with the increase in the fuel injection amount. The recirculation amount is reduced, and is a transient determination for executing such control of the EGR valve 24.

More specifically, first, as a determination procedure based on a change in the accelerator opening Acc, the fuel injection amount is calculated from the three-dimensional map 37 in FIG. 5 using the accelerator opening Acc, the engine speed Ne, and the intake air amount Qav. F (= target injection amount Fsol) is read, and a change amount ΔAcc = Acc−Acc ′ is obtained based on the current value Acc and the previous value Acc ′ of the accelerator opening (steps B1 to B3). On the other hand, the acceleration determination reference αcc is read from the two-dimensional map using the fuel injection amount F and the engine speed Ne (step B4).

The acceleration determination criterion αcc is used for making an acceleration determination based on the accelerator opening change amount ΔAcc. For example, the higher the engine speed Ne, the larger the acceleration becomes, and it becomes difficult to determine that the vehicle is accelerating. The fuel injection amount F and the engine speed Ne are set so as to correspond to the fuel injection amount F and the engine speed Ne such that the larger the injection amount F becomes, the easier it is to determine the acceleration, and the set map is electronically stored in the memory. ing. In addition, since the exhaust gas recirculation amount is originally large during low load operation, the exhaust gas recirculation amount must be promptly reduced when the increase in the accelerator opening (increase in fuel injection amount) is large. Therefore, αcc is set so as to decrease as the fuel injection amount increases.

When the acceleration coefficient α = ΔAcc / αcc is larger than 1, it is determined that the engine 1 is in the accelerating operation state, and the target air-fuel ratio TA / F (= A / A Fs
ol), the EGR valve operation amount KTegr (=
Read EGRsol from the map (Steps B5 to B)
7). That is, the larger the change in the accelerator opening, the more quickly the exhaust gas recirculation amount needs to be reduced. Therefore, the map of the EGR valve operation amount KTegr shows that the opening degree of the EGR valve 24 increases as the acceleration coefficient α increases. The operation amount is experimentally determined and set so that is smaller.

Subsequently, an acceleration determination based on a change in the fuel injection amount is performed. In the case of the acceleration determination based on the accelerator opening, the EGR valve operation amount is determined based on the determination, so to speak, but in the case of the acceleration determination based on the next fuel injection amount, the actual acceleration request is A check is performed based on the injection amount, and control is performed in accordance with the acceleration demand.

That is, the rate of change ΔF = F / F ′ is determined based on the current value F and the previous value F ′ of the fuel injection amount, and a two-dimensional map is obtained using the fuel injection amount F and the engine speed Ne. The acceleration criterion Fk is read (steps B8, B
9). This Fk is set in the same way as the αcc and is electronically stored in the memory. Then, the injection amount change coefficient β
When ΔF / Fk is greater than 1, it is determined that the vehicle is in the accelerated operation state, and the process proceeds to control during acceleration.
0, B11).

(Control at Steady State) The control at the steady state is shown in FIG. 12, and the target torque Ttrq is obtained from the two-dimensional map 36 of FIG. 5 using the engine speed Ne and the accelerator opening Acc.
(= Trqsol), the target air-fuel ratio TA / F (= A / Fsol) is read from the two-dimensional map 38 using Ttrq and Ne, and the target air-fuel ratio TA / F is multiplied by the fuel injection amount F. Then, the target intake air amount TQ (= FAsol) is calculated (steps C1 to C3).

The target air-fuel ratio TA / F is set to NO as described above.
The value is set so that both the x reduction and the smoke reduction can be achieved. The value is set in the operating range of the engine 1, that is, the engine speed Ne and the engine torque Ttrq (in other words,
It is slightly different depending on the fuel injection amount F). For example, in a middle rotation speed or a high rotation speed region where sufficient supercharging is performed by the turbocharger 25, the in-cylinder compression temperature increases due to a large amount of intake air, and the air flow in the combustion chamber 4 increases to increase the air flow. The mixing state of the fuel and the fuel is also good, and the generation of smoke is extremely reduced. Therefore, comparing the high rotation region (the region where the supercharging pressure is high) of the engine 1 with the low rotation region,
The former can set the target air-fuel ratio smaller (toward the rich side).

Following the calculation of the target intake air amount TQ, an intake air amount deviation Qerr = TQ-Qav is obtained, and the basic EGR valve operation amount Tegr (= EGRsol) is determined according to the PID control rule so that the deviation Qerr becomes zero. (Steps C4 and C5).
That is, for example, a proportional control term obtained by integrating the control gain (P gain) of the proportional control operation with the deviation Qerr, and an integral control term obtained by integrating the control gain (I gain) of the integral control operation with the integrated value of the deviation Qerr. The basic EGR valve operation amount Tegr is determined by adding the differential value of the deviation Qerr to the differential control term obtained by integrating the control gain (D gain) of the differential control operation. Here, the control gain of the proportional control operation is obtained by multiplying a basic value by a gain coefficient K, and the response or convergence of the control can be changed by reducing or increasing the gain coefficient K. .

Following the determination of the basic EGR valve operation amount Tegr, the absolute value of the accelerator opening change amount ΔAcc is changed to a predetermined threshold value Tha
A condition for confirming a steady operation state that a state smaller than cc continues for a predetermined number of n cycles and fuel injection is performed is checked (step C6). Then, when the steady state of operation is confirmed, (i = 0, 1,
2, 3), the intake air amount characteristic ΔQt '(i) obtained above and EG
An EGR valve correction operation amount ΔTegr (i) for each cylinder is calculated based on the R correction gain E (i) (step C7). That is, ΔTegr (i) = ΔQt ′ (i) × E (i) + ΔTegr (i) ′ where ΔTegr (i) ′ is the previous value of the EGR valve correction operation amount of the cylinder (i). Then, in this calculation, ΔQt '
The value of (i) itself is emphasized, but by repeating the calculation, the EGR valve correction operation amount gradually reaches an appropriate value corresponding to the individual difference between the cylinders.

In this way, for example, i = 0, 1,
After obtaining the EGR valve correction operation amounts of all four cylinders in the order of 2, 3 and then, when the cylinder number i = 3 (step C8), the average value ΔTegr-av of the EGR valve correction operation amounts for the four cylinders is calculated. Ask. Although this average value should originally be zero, when the calculation in step C7 is performed, the average value becomes negative or positive due to various factors, and the average value becomes negative or positive based on the basic EGR valve operation amount Tegr. The original purpose of correcting and controlling the EGR valve operation amount of the cylinder 2 is impaired.
Therefore, when the average value ΔTegr-av becomes negative, the absolute value is added to ΔTegr (i) of each of the cylinders 2, and when the average value ΔTegr-av becomes positive, the absolute value is subtracted, so that the average value ΔTegr-av becomes zero. Correct (step C9).

The ΔTegr thus obtained is
(i) is added to the basic EGR valve operation amount Tegr, and each cylinder 2
EGR valve operation amount Tegr (i) is obtained (step C10),
Proceed to step D1 in FIG.

(Control at Acceleration Determination Based on Acceleration Coefficient α)
On the other hand, when the acceleration is determined in step B6 in FIG. 11, the transient target EGR valve operation amount KTegr obtained in step B7 varies depending on the magnitude of the acceleration coefficient α and TA / F, and the acceleration coefficient α Is larger than a predetermined value, the opening of the EGR valve 24 is set to zero. That is, when the driver's request for acceleration is large, the exhaust gas is not recirculated, the intake air amount of each cylinder 2 is maximized to suppress the generation of smoke, and the fuel injection amount is increased to increase the engine output. To increase.

In this case, control for giving a preset to the EGR valve 24 is performed so that when the engine 1 shifts from the acceleration operation state to the steady operation state again, the recirculation of exhaust gas can be started immediately. I do. That is,
When the EGR passage 24 is closed by the EGR valve 24, a predetermined EGR valve driving negative pressure (so that the pressing force of the valve body 24c against the valve seat by the spring 24d becomes as small as possible and thus the pressing force becomes zero). The preset negative pressure is applied to the negative pressure chamber so that the pressing force in the closing direction by the spring 24d and the negative pressure for driving the EGR valve are balanced. The preset negative pressure is, as shown in FIG. 4B, the EGR valve driving negative pressure at the time when the EGR valve 24 is controlled to close and the EGR valve lift reaches zero.

Specifically, a control flow for applying a preset negative pressure to the EGR valve 24 is as shown in FIG. That is, first, the EGR valve operation amount Tegr is
If the lift amount of the valve 24 is an operation amount that becomes zero, the value EGRVliFt of the lift sensor 26 is read (step D1,
D2). When the value EGRVliFt is larger than the value EGRV0 corresponding to the lift amount of zero, the EGR valve control is performed until the value becomes equal to the value EGRV0 (steps D3 and D3).
4) The negative pressure for driving the EGR valve is reduced until it becomes the preset negative pressure EGRV0.

On the other hand, in step D1, the EGR
If the valve operation amount Tegr is not the operation amount corresponding to the lift amount zero, the normal EGR valve control is executed without performing the procedures of steps D2 and D3 (steps D1 → D
4) Then return.

(Control at Acceleration Determination Based on Injection Amount Change Coefficient β) When acceleration is determined in step B11 of FIG. 11, first, as shown in each step of FIG. Using the fuel injection amount F and the engine speed Ne, KTA / F is read from a three-dimensional map in which the optimum transient target air-fuel ratio KTA / F (= A / Fsol) in these changes is recorded (step G1). The transient target air-fuel ratio KTA / F is leaner than the steady-state target air-fuel ratio TA / F so that the engine output can be quickly increased while reducing the amount of exhaust gas recirculation and suppressing the generation of smoke. Is set to Although not shown, the three-dimensional map shows the change of each value such that the smaller the fuel injection amount F, the larger the injection amount change coefficient β, and the lower the engine speed Ne, the closer to the lean side. The optimal value of KTA / F with respect to is calculated experimentally, recorded, and electronically stored in the memory.

Subsequently, the transient target air-fuel ratio KTA / F
A target intake air amount TQ (= FAsol) during transition is calculated based on the fuel injection amount F and the fuel injection amount F (step G2). And
Based on this TQ, the EGR valve operation amount is determined in the same manner as in the above-mentioned steady operation, and the amount of exhaust gas is rapidly reduced to increase the amount of intake air (step G below).
Steps C4 to C6 in FIG. 12 following Step 5 and steps D1 to D4 in FIG. 13).

Even when the transient target air-fuel ratio KTA / F is set to a leaner side than the steady state, when the engine 1 shifts to the acceleration operation state, the transient air-fuel ratio KTA / F is temporarily stored in the combustion chamber 4 of each cylinder 2. Excess fuel may be injected. Therefore,
In this flow, a certain limit is set in order to suppress an excessive increase in fuel. That is, the limit air-fuel ratio LimitA / F is read from the map of the fuel injection amount F and the engine speed Ne (step G3). Then, a limit value FLimit of the fuel injection amount is calculated based on the obtained limit air-fuel ratio LimitA / F and the current intake air amount Q (i), and the basic injection amount F and the limit value FL are calculated.
The smallest value of imit and the maximum injection amount Fmax is set as the target injection amount TF, and the process proceeds to step C4 in FIG. 12 (steps G4 and G5).

The relationship between the limit air-fuel ratio LimitA / F, the target air-fuel ratio KTA / F during transition and the target air-fuel ratio TA / F during steady state is shown in FIG.
5, the transient target air-fuel ratio KTA / F is set to be leaner than the steady-state target air-fuel ratio TA / F, and conversely, richer than the steady-state target air-fuel ratio TA / F. The limit air-fuel ratio LimitA / F is set. This limit air-fuel ratio LimitA
The limit smoke amount corresponding to / F is slightly larger than the limit smoke amount in the steady state, and is, for example, about 2 BU. In addition, the limit air-fuel ratio LimitA / F can be basically set to the lean side as the fuel injection amount increases, and to the rich side as the engine speed increases, and the fuel injection amount F and the engine speed Ne can be set. The optimum value experimentally obtained for the change of is stored electronically in the memory.
The basic injection amount F is based on the engine speed Ne and the accelerator opening.
Acc is the fuel injection amount determined by Acc and the maximum injection amount Fm
ax is the upper limit of the fuel injection amount that does not cause the destruction of the engine 1.

(Control at the time of engine deceleration) The characteristic part of the present invention is that the air-fuel ratio is feedback-controlled indirectly by the control of the EGR valve 24 as described above during the engine deceleration of the turbocharged diesel engine. In control. That is, during the deceleration operation of the engine 1, the fuel injection amount F is reduced or set to zero according to the accelerator opening Acc and the like, and the control of the EGR valve 24 is restricted. At the same time, the intake throttle valve 14 is closed by a predetermined amount to increase the pressure difference between the intake and exhaust systems, while the engine 1 shifts to a low-load low-speed region while the engine 1 is in a deceleration operation state, and the supercharging capacity of the turbocharger 25 is increased. Is predicted to be significantly low, the intake throttle valve 14 is opened for a predetermined period in preparation for the subsequent re-acceleration operation.

Specifically, when the engine 1 is in the deceleration operation state, the target injection amount calculation unit 42 of the ECU 35 uses the target torque trqsol and the engine speed Ne to obtain a two-dimensional map as illustrated in FIG. With reference to 37 ', the target injection amount Fsol is determined. In this map 37 ', when the operation state of the engine 1 is in the operation region (I) where the target torque trqsol is larger than the no-load operation curve at the time of deceleration, the target injection amount Fsol is larger than the corresponding steady-state target injection amount. The engine speed Ne is set to be small, thereby gradually decreasing the engine speed Ne. On the other hand, in the operation region (II) where the target torque trqsol is smaller than the no-load operation curve, the target injection amount Fsol is set to zero, and the engine speed Ne is rapidly reduced by so-called fuel cut control. I have. In the operating range (III) on the low rotation speed side in the range (II), the fuel cut control is not performed, and the required amount of fuel is injected to maintain the engine 1 in the idling state.

Next, the procedure of the intake throttle valve control performed by the ECU 35 when the engine is decelerated will be described in detail with reference to flowcharts shown in FIGS. This control is executed in synchronization with an output signal from the crank angle sensor 9 according to a control program stored electronically on a memory.

First, steps H1 to H in the flow of FIG.
As shown in FIG. 3, the accelerator opening Acc and the engine speed N
After detecting the fuel injection amount F, the temperature state of the catalyst is detected based on the output signal from the exhaust temperature sensor 22a (step H4), and the engine water temperature is determined based on the output signal from the water temperature sensor. Detect (Step H5).
Subsequently, in step H6, it is determined whether or not the engine 1 is in a deceleration operation state based on the accelerator opening Acc. That is, if the accelerator opening Acc is larger than the reference criterion opening Acc0 for the deceleration determination, the engine 1 determines that the vehicle is not in the deceleration operation state and determines NO, and proceeds to step H10. If it is less than the above, it is determined that the engine is decelerated to be YES, and the process proceeds to step H7. The engine deceleration determination may be performed in consideration of not only the accelerator opening Acc but also the degree of change in the engine speed Ne. For example, the accelerator opening Acc
May be determined to be in the engine deceleration operation state when is less than or equal to the determination reference opening Acc0 and the degree of decrease in the engine speed Ne is greater than a predetermined value.

Subsequently, at step H7, the fuel injection amount F
And an intake throttle amount TH from a two-dimensional intake throttle map based on the engine speed Ne. This intake throttle map corresponds to the map 51 in FIG. 5, and has an optimal intake throttle amount TH (= THso) corresponding to the fuel injection amount F and the engine speed Ne.
Although l) is experimentally determined and recorded, the intake throttle amount TH is set to a large value over substantially the entire region as compared with the steady state used in step H10 described later. That is, at the time of engine deceleration, the opening degree of the intake throttle valve 14 is made smaller by a predetermined amount than at the time of steady operation of the engine.

In the intake throttle map, as shown in FIG. 20, the fuel injection amount F or the engine speed Ne is calculated.
Is larger, the intake throttle amount TH is reduced, and when the engine 1 is in a high load or high rotation range, the intake throttle amount TH becomes zero, and the intake throttle valve 14 is set to be fully opened. . On the other hand, since the intake throttle amount TH is set to increase as the engine speed Ne decreases, the differential pressure between intake and exhaust can be increased even in the low engine speed range to ensure the exhaust gas recirculation amount.

Subsequently, at step H8, the fuel injection amount F
Based on the engine speed Ne and the engine speed Ne, the current operating region of the engine 1 is determined from the operating region determination map as illustrated in FIG. That is, when the engine 1 is in the low-load low-speed operation region (a) shown by hatching in FIG.
YES is determined in the step H9, and the step H in FIG.
On the other hand, when the engine 1 is in the other high-load or high-speed operation range (B), the routine proceeds to step H9.
It is determined as O, and the process proceeds to Step H21 in FIG. On the other hand, in step H10, in which it is determined that the engine is not being decelerated in step H6 and the process proceeds to step H10, if the engine is in a steady operation state, the intake throttle amount TH is read from the same intake throttle map as used in step H7. Then, this intake throttle amount TH is set and the routine returns. When the engine is in an accelerating operation state, the intake throttle amount TH is set to zero, and the intake throttle valve 14 is promptly opened to the full open state.

When the determination in step H9 in FIG. 17 is YES, the process proceeds to steps H11 and H11 in FIG.
At 12, the temperature state of the catalyst 22 is determined.
That is, when the temperature state of the catalyst 22 is lower than the activation temperature (NO in Step H11), Step H1
The process proceeds to step H16 via step 7, and the opening degree control of the intake throttle valve 14 is executed based on the intake throttle amount TH set in step H7. Further, when the temperature state of the catalyst 22 is equal to or higher than the activation temperature and lower than the set catalyst temperature higher than the activation temperature (see FIGS. 22A and 22B) (YES in step H11, step H11). (NO in H12), the process proceeds to step H18 described later. On the other hand, when the temperature state of the catalyst 22 is equal to or higher than the set catalyst temperature (YE
In S), the process proceeds to Step H13.

In step H13, the timer value Tup of the count-up timer for measuring the elapsed time from when the engine 1 enters the operation region (A) is compared with a value Tup1 corresponding to the set time, and Tup = If YES at Tup1, the process proceeds to step H17, while Tup1
If the set time has not elapsed in Tup1, the process proceeds to step H14, where a predetermined value ΔT is added to the timer value Tup, and the process proceeds to step H15. In this step H15, in order to bring the intake throttle valve into a substantially fully opened state, the aforementioned FIG.
The intake throttle amount TH set in step H7 of step 7 is newly set to TH =
Reset as 0. Then, in the following step H16, a control signal is output from the ECU 35 to the solenoid valve 16 for negative pressure control, and the opening degree control of the intake throttle valve 14 is executed.

That is, if the temperature state of the catalyst 22 is equal to or higher than the set catalyst temperature, the period from when the engine 1 enters the low-load low-speed operation region (a) in the deceleration operation state until the set time elapses. In addition, the intake throttle valve 14 is made to be substantially fully opened.

On the other hand, in step H13, when it is determined that the set time has elapsed with the timer value Tup = Tup1 and the determination is YES, the process proceeds to step H17, where the count-up timer is cleared (Tup = 0), and the process proceeds to step H16. . That is, when the temperature state of the catalyst 22 is lower than the activation temperature, if the exhaust throttle valve 14 is fully opened to increase the exhaust gas flow rate, the inactive catalyst may be further cooled. The intake throttle valve 14 is prevented from being substantially fully opened. This can prevent the inactive catalyst from being further cooled.

On the other hand, in step H12, the temperature state of the catalyst 22 is equal to or higher than the activation temperature, but it is determined that NO is lower than the set catalyst temperature. Determine if this is done. When this determination is NO and the fuel cut control is not performed, that is, when the fuel injection amount is not zero,
On the other hand, if the determination is YES and the fuel cut control is being performed, and the fuel injection amount F is zero, the process proceeds to step H19, where the control calculation of the EGR valve control (see FIG. 12) is performed. In the following step H20, the operation amount of the EGR valve is set to a value corresponding to fully closed or less,
The EGR valve 24 is forcibly controlled to the fully closed state. Then, the process proceeds to step H16, where
Based on the intake throttle amount TH set in step H7, the opening degree control of the intake throttle valve 14 is executed, and thereafter, the routine returns.

That is, when the fuel cut control is being performed while the engine 1 is in the decelerating operation state, there is a possibility that the temperature of the exhaust gas is rapidly lowered due to the interruption of the combustion and the catalyst 22 is excessively cooled. Therefore, in consideration of this, the catalyst 2
When the temperature state 2 is lower than the set catalyst temperature, the intake throttle valve 14 is closed to reduce the exhaust flow rate, whereby the temperature state of the catalyst 22 is maintained at or above the activation temperature, and Purification performance can be secured stably.

At the same time, the EGR valve control is prohibited, and E
The GR valve 24 is forcibly brought into the fully closed state, whereby the intake air amount can be promptly increased when the engine again shifts to the acceleration operation state.

Further, in step H21 of FIG. 19, which has proceeded after the determination of NO in step H9 of FIG. 17 has been made, it is determined whether fuel cut control is being performed as in step H17. If the determination is YES and the fuel cut control is being performed, the process proceeds to steps H22 and H23, where the control calculation of the EGR valve control is prohibited as in steps H19 and H20, and the EGR valve 24 is forcibly fully closed. Then, the process proceeds to step H16 in FIG.

On the other hand, if it is determined in step H21 that the fuel cut control is not being performed, the process proceeds to step H2.
Proceeding to step 2, it is determined whether the engine water temperature is equal to or higher than the set water temperature. When the determination is NO and the engine water temperature is lower than the set temperature, the process proceeds to step H16. On the other hand, when the determination is YES and the engine water temperature is equal to or higher than the set water temperature, the opening of the EGR valve 24 is set to a predetermined opening (step H25). (For example, 40 to 60%) or less, and the process proceeds to steps H15 and H16 to bring the intake throttle valve 14 into a substantially fully opened state.

That is, when the engine coolant temperature is equal to or higher than the set coolant temperature, the engine 1 is considered to be overheated as a whole, and the temperature state of the intake passage 10 is considered to be high. Become,
At the time of re-acceleration of the engine after deceleration, there is a possibility that a sufficient output cannot be obtained. Therefore, in this case, as described above, the intake throttle valve 14 is substantially fully opened to increase the intake flow rate, thereby promoting the cooling of the intake passage 10.
At the same time, the opening of the EGR valve 24 is limited to a predetermined opening or less to prevent the cooling of the intake passage 10 from being hindered by the high-temperature recirculated exhaust gas. When the engine coolant temperature is equal to or higher than the set coolant temperature, the catalyst 22 is also considered to be in a high temperature state. No problem.

Step H6 of the flow shown in FIG.
Steps H8 and H9 correspond to the operating state determining means 35d (see FIG. 1) for determining the operating state of the engine 1. Steps H7 and H16 correspond to the intake throttle valve control unit 35c that closes the intake throttle valve 14 by a predetermined amount when the operating state determination unit 35d determines that the engine 1 is in the deceleration operation state. I have.

Further, step H of the flow shown in FIG.
Steps 13 to H15 correspond to the operation state determination means 3
5d corresponds to the valve-opening control unit 35e that opens the intake throttle valve 14 from when it is determined that the engine 1 is in the low-load low-speed operation region (A) until the set time elapses.

Step H11 corresponds to the catalyst inactive state judging means 35f for judging that the temperature state of the catalyst 22 is lower than the activation temperature.
The processing procedure from step 1 to step H16 via step H17 corresponds to valve opening control inhibiting means 35g which inhibits the control by the valve opening control unit 35e at the time of determination by the catalyst inactive state determining means 35f.

Step H12 corresponds to the catalyst temperature determining means 35h for determining whether or not the temperature state of the catalyst 22 is equal to or higher than a set catalyst temperature higher than its activation temperature. H18-H20
The processing procedure that proceeds to step H16 after the above is that the fuel cut control is performed and the catalyst temperature determination means 35h determines that the temperature state of the catalyst 22 is lower than the set catalyst temperature. This corresponds to the intake throttle valve control unit 35c that closes quantitatively.

Further, the steps H19 and H20 are:
This corresponds to an exhaust gas recirculation control restricting means 35i that prohibits the EGR control when the fuel cut control is performed and forcibly holds the EGR valve 24 in the fully closed state.

Further, step H24 in FIG.
Corresponds to the engine water temperature determination means 35j that determines that the engine water temperature is equal to or higher than the set water temperature. The control procedure from step H24 to step H15 and H16 in FIG. This corresponds to a valve opening control unit 35e that brings the intake throttle valve 14 into a substantially fully opened state when the temperature is equal to or higher than the water temperature.

Therefore, according to the intake control apparatus A for the turbocharged engine according to this embodiment, for example, the driver reduces the amount of stepping on the accelerator while the vehicle is running, and the injector is operated in accordance with the accelerator operation. 5 when the fuel injection amount is reduced and the engine 1 enters the deceleration operation state, first, the operation state determination means 35d outputs the engine 1
Is determined, the intake throttle valve control means 35c
As a result, the intake throttle valve 14 is operated to the closed side. The closing operation of the intake throttle valve 14 causes the intake passage 10 to close.
, The intake air amount is reduced, the intake pressure is reduced, and the differential pressure between the exhaust system and the exhaust system is increased. Therefore, the exhaust gas recirculation amount is sufficiently ensured, and the generation of NOx is suppressed.

At this time, when the operating state determining means 35d determines that the engine 1 is in the low load and low speed operation region (a), the intake air is maintained until the set time elapses from the determination. The closing operation of the throttle valve 14 is prohibited, and conversely, the intake throttle valve 14 is substantially fully opened by the valve opening control unit 35e. That is, when the engine 1 is in the operation region (a) in the deceleration operation state, it is considered that the engine 1 shifts to the stop state in the deceleration operation state. Until the passage of time, the possibility of shifting to the acceleration operation state is extremely high. During that time, the intake throttle valve 14 is almost fully opened as described above, and the amount of intake air to the engine 1 and, consequently, turbocharging. The exhaust gas flow to the machine 25 is maximized.

As a result, in the operating region (A) where the supercharging capacity of the turbocharger 25 is reduced, the engine 1
Is very likely to shift to an accelerated driving state,
By reducing the supercharging capacity as much as possible by maximizing the exhaust gas flow rate, it is possible to quickly increase the intake air amount of fresh air by supercharging at the time of a transition to an acceleration operation state thereafter. Therefore, the turbo lag can be reduced, and the re-acceleration after deceleration of the vehicle can be improved.

In addition, when the fuel cut control is performed while the engine 1 is in the deceleration operation state, the EGR valve control is prohibited, and the EGR valve 24 is forcibly closed. Thus, when the driver again depresses the accelerator and the engine 1 shifts to the acceleration operation state, the recirculated exhaust gas does not prevent the intake of fresh air. Can be re-accelerated.

In this embodiment, the exhaust gas temperature sensor 2
The temperature state of the catalyst 22 is detected based on the output signal from 2a, and the opening of the intake throttle valve 14 is controlled according to the detection result. That is, if the temperature state of the catalyst 22 is lower than the activation temperature, the opening operation of the intake throttle valve 14 is prohibited, so that the supercooling of the catalyst 22 can be prevented. On the other hand, if the temperature state of the catalyst 22 is equal to or higher than the activation temperature but lower than the set catalyst temperature, the intake throttle valve 14 is fully opened only when the fuel cut control is not performed. Thus, the temperature state of the catalyst 22 can be maintained at or above the activation temperature, and the NOx purification performance can be stably ensured.

Further, in this embodiment, an intercooler 13 for cooling the high-temperature and high-pressure intake air supercharged by the turbocharger 25 is provided, and when the engine water temperature is higher than the set water temperature, the intake throttle valve is provided. The intake air flow of the fresh air is positively increased by bringing the intake air intake 14 into a substantially fully opened state, and the cooling of the intake passage 10 of the engine 1 is promoted by the intake air flow. This allows the intake passage 1
Since the decrease in the intake air density caused by the overheating of 0 can be reduced and the intake air charging efficiency can be sufficiently increased, the intake air amount of fresh air can be promptly increased at the time of the subsequent shift to the acceleration operation state. Thus, the re-acceleration of the engine 1 can also be improved.

(Modification) FIG. 23 shows a modification of the above embodiment. The configuration of the intake control device A of the turbocharged engine according to this modification is the same as that of the above-described embodiment, and therefore, the same components are denoted by the same reference numerals and description thereof will be omitted.

In this modified example, the engine 1 is in the deceleration operation state and in the low-load low-speed operation region (A),
In addition, when the accelerator opening Acc is extremely small, the intake throttle valve 14 is opened.

Specifically, in the control flow of the intake throttle valve at the time of engine deceleration shown in FIG. 17, when it is determined that the engine 1 is in the deceleration operation state and is in the low-load low-speed operation region (A) (step H9). YES), and then FIG.
In steps H11 and H12, the temperature state of the catalyst 22 is determined in the same manner as in the above-described embodiment. When it is determined that the temperature state of the catalyst 22 is equal to or higher than the set catalyst temperature, the process proceeds to step H13 '. In this step H13 ', it is determined whether or not the accelerator opening Acc is less than or equal to the set opening Acc1 (Acc1 <Acc0). If this determination is NO, the process proceeds to step H16, where the opening of the intake throttle valve 14 is opened. While the degree control is executed, if the determination is YES and the accelerator opening Acc is extremely small, the routine proceeds to step H15, resets the intake throttle amount TH to TH = 0, and then proceeds to step H16.

That is, the engine 1 is in the low-load and low-speed operation range (A) in the deceleration operation state, and the accelerator opening Ac
When c becomes extremely small, it is possible that the driver has almost released the accelerator pedal to shift the speed of the manual transmission, and in this case, the engine is very likely to shift to re-acceleration operation. In order to prepare for this, the intake throttle valve 14 is almost fully opened,
The exhaust flow rate is increased.

The step H13 'is executed at the accelerator opening Ac
When c is equal to or less than the set opening Acc1, the accelerator-return-state determining unit 35k that determines that the vehicle is in the accelerator-returned state corresponds to the accelerator-returned-state determination unit 35k. Is determined, the valve opening control unit 35e that opens the intake throttle valve 14
It corresponds to.

Therefore, according to this modification, similarly to the above embodiment, when the possibility that the engine 1 in the deceleration operation state shifts to the acceleration operation state is particularly high, the exhaust gas flow rate is maximized and the turbo A reduction in the supercharging capacity of the supercharger 25 is suppressed as much as possible, whereby the turbo lag can be reduced as in the above-described embodiment, and the re-acceleration of the engine after deceleration is improved.

(Other Embodiments) The present invention is not limited to the above embodiments, but includes other various embodiments. That is, the valve opening control unit 35e in the first embodiment sets the intake throttle valve 14 to a substantially fully opened state, but is not limited thereto.
4 may be operated only on the opening side.

In the above-described embodiment, when the fuel cut control is performed when the engine is decelerated, the feedback control of the EGR valve 24 is prohibited, and the EGR valve 24 is forcibly brought into the fully closed state. However, the target value of the air-fuel ratio in the feedback control of the EGR valve 24 may be increased when the engine is decelerated.

Specifically, the processing of steps H19 'and H20' shown in FIG. 24 may be performed instead of steps H19 and H20 of the flow shown in FIG. 18 or FIG. That is, in step H19 ', based on the engine speed Ne, the target air-fuel ratio correction coefficient τ (τ> 1) is obtained from a map stored electronically in the memory of the ECU 35.
In the subsequent step H20 ', the target fresh air amount calculation unit 44 multiplies the target air-fuel ratio A / Fsol calculated by the target air-fuel ratio calculation unit 43 by the target air-fuel ratio correction coefficient τ to obtain the target air-fuel ratio. The target fresh air amount calculation unit 44 calculates the target fresh air amount FAsol using the corrected target air-fuel ratio.

In this way, when the engine decelerates, E
Since the target value of the air-fuel ratio in the GR valve control is made larger than usual, the EGR valve 24 is not fully opened even if the fuel injection amount F is small. 24 can be reduced, and the re-acceleration can be improved. Incidentally, the step H19 '
Step H20 'corresponds to target value correction means 35L for increasing and correcting the target value of the air-fuel ratio in the EGR valve control at the time of engine deceleration.

In the above-described embodiment, the exhaust temperature sensor 22a is provided near the catalytic converter 22 to detect the temperature state of the catalyst. However, the present invention is not limited to this. Alternatively, the temperature state of the catalyst may be estimated.

Further, in the above embodiment, the temperature state of the intake passage 10 of the engine 1 is determined based on the engine water temperature, but the present invention is not limited to this. That is, for example, an intake air temperature sensor is provided in the intake passage 10 downstream of the connection with the EGR passage 23, and it is determined whether the intake air temperature detected by the intake air temperature sensor is equal to or higher than a set intake air temperature. Specifically, in step H24 of the flow shown in FIG. 19, instead of determining whether the engine water temperature is equal to or higher than the set water temperature, the temperature state of the intake air detected by the intake air temperature sensor is changed to the set intake air temperature. What is necessary is just to determine whether it is above. In this case, that step constitutes intake air temperature determination means. The opening degree of the intake throttle valve 14 may be controlled in accordance with the temperature state of the intake air detected in this manner so as to prevent overheating of the intake passage 10 as in the previous embodiment.

Further, according to the EGR valve control in the above embodiment, by adjusting the exhaust gas recirculation amount for each cylinder of the engine 1, the air-fuel ratio in the combustion chamber 4 of each cylinder 2 can be made uniform and the target value can be obtained. However, the present invention is not limited to this, and all four cylinders 2 may be controlled collectively.

In the above-described embodiment, the present invention is applied to the diesel engine 1 equipped with the common rail fuel injection system. However, instead of the common rail fuel injection system, a unit injector is provided for each cylinder. It is also applicable to diesel engines.

Further, the present invention includes not only a diesel engine but also a spark plug, and stratifies and burns the fuel (gasoline) injected around the spark plug to burn it.
The present invention is also applicable to a direct-injection gasoline engine that can be operated while recirculating a large amount of exhaust gas in an excessive air intake state with a throttle valve largely opened.

[0138]

As described above, according to the intake control apparatus for a turbocharged engine according to the first aspect of the present invention, the intake throttle valve is closed by the intake throttle valve control means during the deceleration operation of the engine. Accordingly, the amount of fresh air can be reduced in response to the decrease in the fuel supply amount, and the exhaust gas recirculation amount can be sufficiently ensured to suppress the generation of NOx.
Further, when the engine is in the deceleration operation state and enters the low-load low-speed operation region, the intake throttle valve is opened by the valve-opening control unit for a predetermined period after the shift to the low-load low-speed operation region, and the engine is opened. By increasing the amount of intake air to the turbocharger and the flow rate of exhaust gas to the turbocharger, it is possible to suppress a decrease in the supercharging capacity of the turbocharger. As a result, the turbo lag can be reduced, and the re-acceleration of the engine after deceleration can be improved.

According to the second aspect of the present invention, the intake throttle valve is opened from the time when the engine is determined to be in the low-load low-speed operation range to the time when the set time elapses. When there is a very high possibility of shifting to (1), a decrease in the supercharging capacity of the turbocharger can be suppressed.

According to the third aspect of the present invention, by opening the intake throttle valve in the accelerator return state where the accelerator operation amount is equal to or less than the set amount, the shift operation by the driver can be performed.
When the possibility of shifting to the acceleration operation state is extremely high, it is possible to suppress a decrease in the supercharging capacity of the turbocharger.

According to the fourth aspect of the invention, normally, the air-fuel ratio of the combustion chamber can be controlled to a target value with high accuracy to reduce NOx and smoke in the exhaust gas, while the target value is reduced when the engine decelerates. Is larger than usual,
The delay in the closing operation of the exhaust gas recirculation amount control valve during subsequent reacceleration of the engine can be reduced, and the intake air amount of fresh air can be rapidly increased.

According to the fifth aspect of the invention, when the temperature of the catalyst is lower than the activation temperature, the opening of the intake throttle valve is prohibited, so that the inactive catalyst can be prevented from being further cooled.

According to the intake control device for a turbocharged engine according to the sixth aspect of the present invention, when the fuel supply amount is reduced to zero when the engine is suddenly decelerated, the temperature of the catalyst becomes lower than the set catalyst temperature. If it is also low, by closing the intake throttle valve by the intake throttle valve control means and reducing the exhaust flow rate,
It is possible to prevent the supercooling of the catalyst and to stably secure its purification performance.

According to the seventh aspect of the present invention, normally, the amount of exhaust gas is controlled by the exhaust gas recirculation amount control means to reduce NOx and smoke in the exhaust gas, while the fuel supply amount is reduced to zero when the engine is decelerated. In this case, the control by the exhaust gas recirculation amount control means is prohibited, and the erroneous control can be prevented.

According to the eighth aspect of the invention, the exhaust gas recirculation amount control valve can be forcibly set to, for example, a fully open state when the engine is decelerated, and the intake air amount is increased very quickly at the subsequent re-acceleration, so that the engine Can be reaccelerated.

According to the ninth aspect of the present invention, when the temperature state of the engine cooling water is equal to or higher than the set water temperature and there is a concern that the intake charging efficiency is reduced due to overheating of the intake passage,
By opening the intake throttle valve by the valve opening control unit to promote cooling of the intake passage, it is possible to avoid the adverse effect of a decrease in engine output during subsequent reacceleration.

According to the intake control device for a turbocharged engine according to the tenth aspect of the present invention, the generation of NOx can be suppressed when the engine is decelerated, similarly to the first aspect, and the NOx after the deceleration can be suppressed. At the time of re-acceleration, it is possible to avoid the adverse effect of a decrease in engine output as in the case of the tenth aspect.

According to the eleventh aspect, the engine output can be increased by cooling the intake air by the intercooler.

According to the intake control device for a turbocharged engine according to the twelfth aspect of the present invention, the same effects as those of the tenth aspect can be obtained.

According to the thirteenth aspect, the effect of the sixth aspect is particularly effective in a diesel engine.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an engine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a part of the turbocharger in a small A / R state (a) or a large A / R state (b).

FIG. 3 is a configuration diagram of an EGR valve and a drive system thereof.

FIG. 4 is a graph showing a relationship between a drive current of the EGR valve and a drive negative pressure (a) or a lift amount (b).

FIG. 5 is an overall configuration diagram of an engine control system.

FIG. 6 is a graph showing a relationship between an air-fuel ratio and a NOx emission amount.

FIG. 7 is a graph showing a relationship between an air-fuel ratio and a smoke value.

FIG. 8 is a diagram showing a basic flow of exhaust gas recirculation and fuel injection amount control.

FIG. 9 is a graph showing a time change of an intake air flow rate of the engine.

FIG. 10 is a flowchart illustrating a calculation procedure of an intake air amount.

FIG. 11 is a flowchart illustrating a procedure of a transient determination process.

FIG. 12 is a flowchart illustrating a procedure for calculating an EGR valve operation amount.

FIG. 13 is a flowchart illustrating a processing procedure of control for giving a preset.

FIG. 14 is a flowchart illustrating a processing procedure of fuel injection amount control during acceleration.

FIG. 15 is a graph showing a relationship between a target air-fuel ratio during steady state, a target air-fuel ratio during acceleration, and a limit air-fuel ratio during transition.

FIG. 16 is a diagram illustrating an example of a map in which a fuel injection amount during engine deceleration is set in association with a target torque and an engine speed.

FIG. 17 is a flowchart illustrating a first half of a procedure of intake throttle valve control at the time of engine deceleration.

FIG. 18 is a flowchart showing a processing procedure of the latter half of intake throttle valve control when the engine is in a high load or high rotation operation range.

FIG. 19 is a flowchart illustrating a processing procedure in the latter half of intake throttle valve control when the engine is in a low-load low-speed operation range.

FIG. 20 is a diagram showing an example of a map in which an intake throttle amount during engine deceleration is set in association with a fuel injection amount and an engine speed.

FIG. 21 is a diagram illustrating an example of an operation region determination map in which an operation region of an engine is set in association with a fuel injection amount and an engine speed.

FIG. 22 (a) shows a catalyst for purifying NOx in an oxygen-excess atmosphere, and FIG. 22 (b) shows a catalyst for absorbing NOx in a state larger than the stoichiometric air-fuel ratio.
It is a figure showing an example of a graph showing temperature dependency of an Ox purification rate.

FIG. 23 is a diagram corresponding to FIG. 18 according to a modification in which the intake throttle valve is opened in the accelerator return state.

FIG. 24 is a flowchart illustrating another embodiment of a processing procedure for restricting EGR valve control.

[Description of Signs] A Intake control device for engine with turbocharger 1 Diesel engine 4 Combustion chamber 10 Intake passage 11 Airflow sensor (state quantity detection means) 12 Blower 13 Intercooler 14 Intake throttle valve 22 Catalyst 23 EGR passage (exhaust (Recirculation passage) 24 EGR valve (exhaust gas recirculation amount control valve) 25 turbocharger 35a fuel supply amount control means 35b exhaust recirculation control means 35c intake throttle valve control means 35d operating state determination means 35e valve opening control section 35f catalyst inactive state Determining means 35g Valve opening control prohibiting means 35h Catalyst temperature determining means 35i Engine water temperature determining means 35j Exhaust gas recirculation control limiting means 35k Accelerator return state determining means 35L Target value correcting means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) F02D 43/00 301 F02D 43/00 301R 301N F02M 25/07 570 F02M 25/07 570P 570G F term (reference) 3G062 AA01 AA03 AA05 BA04 BA06 CA05 CA07 EA05 EB05 EB06 FA08 GA00 GA01 GA04 GA06 GA08 GA09 GA12 GA15 GA21 3G065 AA01 AA03 AA04 CA00 CA11 CA12 DA02 EA05 FA11 GA00 GA05 GA09 GA10 GA14 GA18 GA27 BA03 A08 BA03 A08 BA03 A08 BA09 BA13 BA20 BA24 BA32. HE01Z HE03Z HE08Z HF08Z HF12Z HF25Z

Claims (13)

[Claims] 1. An intake throttle valve disposed in an intake passage of an engine, a turbocharger for supercharging intake air by exhaust of the engine, and a part of exhaust in an intake passage downstream of the intake throttle valve. An exhaust gas recirculation passage for recirculating exhaust gas, an exhaust gas recirculation amount adjusting valve for adjusting the amount of exhaust gas recirculated by the exhaust gas recirculation passage, and a state quantity detecting means for detecting a state quantity related to an air-fuel ratio of a combustion chamber of an engine. An operating state determining unit for determining an operating state of the engine, wherein the operating state determining unit determines the opening degree of the flow rate control valve based on a value detected by the state amount detecting unit; When the engine is determined to be in the deceleration operation state, the intake throttle valve control means for closing the intake throttle valve by a predetermined amount is provided. A turbo-charger having a valve opening control unit that opens the intake throttle valve for a predetermined period after the determination is made by the determination means that the engine is in the low-load low-speed operation region. Intake control device for an engine. 2. The valve opening control section according to claim 1, wherein the valve opening control section controls the intake throttle valve from when the operating state determining means determines that the engine is in the low-load low-speed operation range until a set time has elapsed. An intake control device for a turbocharged engine, wherein the intake control device is configured to be opened. 3. An accelerator returning state determining means for determining that the accelerator is in an accelerator returning state when an accelerator operation amount is equal to or less than a set amount, wherein the valve opening control unit determines whether or not the accelerator has been released by the accelerator returning state determining means. An intake control device for an engine with a turbocharger, wherein an intake throttle valve is opened when it is determined to be in a return state. 4. An exhaust gas recirculation control means for controlling an opening degree of an exhaust gas recirculation amount control valve such that an air-fuel ratio of a combustion chamber becomes a target value based on a value detected by a state quantity detection means, An intake control device for an engine with a turbocharger, wherein target value correction means for increasing and correcting a target value of an air-fuel ratio in the exhaust gas recirculation control means when the engine is decelerated is provided. 5. The catalyst according to claim 1, wherein the catalyst purifies the exhaust gas of the engine, a catalyst inactive state determining unit that determines that a temperature state of the catalyst is lower than an activation temperature, and the catalyst inactive state determining unit. And a valve-opening control prohibiting means for prohibiting control by the valve-opening control unit when the determination is made. 6. An intake throttle valve disposed in an intake passage of an engine, a turbocharger for supercharging intake air by exhaust of the engine, and a part of exhaust gas in an intake passage downstream of the intake throttle valve. An exhaust gas recirculation passage for recirculating exhaust gas, an exhaust gas recirculation amount adjusting valve for adjusting the amount of exhaust gas recirculated by the exhaust gas recirculation passage, and a state quantity detecting means for detecting a state quantity related to an air-fuel ratio of a combustion chamber of an engine. In an intake control device for an engine, wherein an opening degree of a flow control valve is feedback-controlled based on a value detected by the state quantity detecting means, a catalyst for purifying exhaust gas of the engine, and a temperature state of the catalyst is activated. Catalyst temperature determining means for determining whether the temperature is equal to or higher than a set catalyst temperature higher than the temperature, and fuel supply amount controlling means for controlling a fuel supply amount to the engine at least according to an accelerator operation amount When the fuel supply amount is set to zero by the fuel supply amount control unit and the catalyst temperature determination unit determines that the temperature of the catalyst is lower than the set catalyst temperature, the intake throttle valve is set to a predetermined amount. An intake control device for a turbocharged engine, comprising: a closing intake throttle valve control means. 7. An exhaust gas recirculation control means for controlling an opening degree of an exhaust gas recirculation amount control valve based on a value detected by a state quantity detection means so that an air-fuel ratio of a combustion chamber becomes a target value, An exhaust gas recirculation control restricting means for prohibiting control by the exhaust gas recirculation control means when the fuel supply amount is reduced to zero by the fuel supply amount controlling means; Control device. 8. An engine with a turbocharger according to claim 7, wherein the exhaust gas recirculation control restricting means forcibly keeps the opening of the exhaust gas recirculation amount control valve at a set opening. Intake control device. 9. An engine coolant temperature judging means according to claim 6, further comprising: an engine coolant temperature judging means for judging that a temperature state of the engine coolant is equal to or higher than a set water temperature. An intake control device for a turbocharged engine, further comprising a valve opening control unit that opens a throttle valve. 10. An intake throttle valve disposed in an intake passage of an engine, a turbocharger for supercharging intake air by exhaust of the engine, and a part of exhaust gas in an intake passage downstream of the intake throttle valve. An exhaust gas recirculation passage for recirculating exhaust gas, an exhaust gas recirculation amount adjusting valve for adjusting the amount of exhaust gas recirculated by the exhaust gas recirculation passage, and a state quantity detecting means for detecting a state quantity related to an air-fuel ratio of a combustion chamber of an engine. An operating state determining unit for determining an operating state of the engine, wherein the operating state determining unit determines the opening degree of the flow rate control valve based on a value detected by the state amount detecting unit; When it is determined that the engine is in the decelerating operation state, the intake throttle valve control means for closing the intake throttle valve by a predetermined amount; An engine water temperature determining means for determining that the engine is in the air conditioner, wherein the intake throttle valve control means has a valve opening control unit for opening an intake throttle valve when the engine water temperature determining means makes a determination. An intake control device for a charged engine. 11. The intake control device for an engine with a turbocharger according to claim 10, further comprising an intercooler for cooling intake air compressed by a blower of the turbocharger. 12. An intake throttle valve disposed in an intake passage of an engine, a turbocharger for supercharging intake air by exhaust of the engine, and a part of exhaust gas in an intake passage downstream of the intake throttle valve. An exhaust gas recirculation passage for recirculating exhaust gas, an exhaust gas recirculation amount adjusting valve for adjusting the amount of exhaust gas recirculated by the exhaust gas recirculation passage, and a state quantity detecting means for detecting a state quantity related to an air-fuel ratio of a combustion chamber of an engine. An operating state determining unit for determining an operating state of the engine, wherein the operating state determining unit determines the opening degree of the flow rate control valve based on a value detected by the state amount detecting unit; When it is determined that the engine is in a decelerating operation state, intake throttle valve control means for closing the intake throttle valve by a predetermined amount, and a downstream side of a connection portion with the exhaust gas recirculation passage An intake air temperature determining means for determining that the temperature state of the intake passage is equal to or higher than a set intake air temperature is provided.The intake throttle valve control means includes a valve opening control unit that opens the intake throttle valve when the intake air temperature determining means makes a determination. An intake control device for an engine with a turbocharger, comprising: 13. The intake control device for a turbocharged engine according to claim 6, wherein the engine is a diesel engine.