JP2003193875A - Egr control device for engine with turbocharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the exhaustion of black smoke from an engine by determining the stable condition of the engine. <P>SOLUTION: A change of a target fuel injection amount corresponding to a change in load of the engine is set in a first map of a memory 44a, a change of a first stability limiting value for a fuel deviation between the target fuel injection amount and an actual fuel injection amount is set in a second map, a change in a target engine speed corresponding to a change of an engine speed is set in a third map, and a change of a second stability limiting value for a speed deviation between the target engine speed and an actual engine speed is set in a fourth map. A controller 44 determines a temporarily stable condition when the first deviation between the target fuel injection amount and the actual fuel injection amount in the first map is not larger than the first stability limiting value in the second map and the second deviation between the target engine speed and the actual engine speed in the third map is not larger than the second stability limiting value in the fourth map in the state that an EGR valve 13b is closed during the transient operation of the engine, and it determines a stable condition when the temporarily stable condition is continued for a preset time and opens the EGR valve. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a turbocharger and an E
The present invention relates to a device for controlling the opening degree of an EGR valve in an engine having a GR device.

[0002]

2. Description of the Related Art Conventionally, the supercharging efficiency for a cylinder of a supercharger that compresses intake air by the energy of exhaust gas and supplies the compressed air to a cylinder is variable, and the operating state of the engine including the acceleration state and the intake air amount is changed. There is disclosed an engine including a supercharger which is detected by a detecting means and is configured such that a controller changes a supercharging efficiency of the supercharger based on a detection output of the detecting means (Japanese Patent Laid-Open No. 2000-28287).
No. 9). In this engine, the controller is configured to calculate the basic fuel injection amount and the basic control amount of the supercharger based on the operating state of the engine, and to calculate the excess air ratio from the intake amount and the basic fuel injection amount. .

In the engine provided with the supercharger configured as described above, when the operating state of the engine is in an accelerating state, the controller corrects the basic control amount of the supercharger according to the magnitude of the excess air ratio. The final control amount is obtained, and the supercharging efficiency of the supercharger is controlled by this final control amount. As a result, since the supercharging control is performed based on the excess air ratio without immediately controlling the fuel injection amount by the excess air ratio, it is possible to prevent the occurrence of smoke without deteriorating the responsiveness to the load. .

[0004]

However, in the engine provided with the supercharger disclosed in the above-mentioned Japanese Patent Laid-Open No. 2000-282879, when the engine gradually shifts from the transient operating state to the steady operating state. Even if the basic control amount of the supercharger is corrected according to the magnitude of the excess air ratio to obtain the final control amount, and the supercharging efficiency of the supercharger is controlled by this final control amount,
When the engine is equipped with an EGR device, the exhaust gas is recirculated to the intake air, which makes it difficult to inject the optimum fuel for the actual intake air amount. An object of the present invention is to provide an EGR control device for a turbocharged engine that can reduce black smoke emission during transient operation of the engine by appropriately determining the stable state of the engine.

[0005]

The invention according to claim 1 is
As shown in FIG. 1, a fuel injection pump 46 for injecting fuel into the engine 11 having the turbocharger 12, and an EGR valve 13b configured to recirculate exhaust gas to the engine 11 and capable of adjusting the recirculation amount of exhaust gas are provided. EGR device 13 having
And the fuel injection amount of the fuel injection pump 46 and the EGR valve 1 according to the rotation speed of the engine 11 and the load of the engine 11.
It is an improvement of the EGR control device for a turbocharged engine equipped with a controller 44 for controlling the opening degree of each of 3b. The characteristic configuration is that the controller 44 sets the first map in which the change in the target fuel injection amount corresponding to the change in the load of the engine 11 is set, and the fuel deviation amount between the target fuel injection amount and the actual fuel injection amount. A second map in which a change in the first stability limit value is set, a third map in which a change in the target rotation speed of the engine 11 corresponding to a change in the rotation speed of the engine 11 is set, a target rotation speed and an actual rotation The controller 44 has a memory 44a for storing a fourth map in which a change in the second stability limit value of the rotation deviation amount from the speed is set.
However, while the EGR valve 13b is closed during the transient operation of the engine 11, the first deviation amount between the target fuel injection amount calculated based on the first map and the actual fuel injection amount is obtained, and based on the third map. The second deviation amount between the calculated target rotation speed and the actual rotation speed is obtained, the first deviation amount is less than or equal to the first stability limit value calculated based on the second map, and the second deviation amount is the fourth map. When it is less than or equal to the second stability limit value calculated based on, the temporary stable state is determined, and when the temporary stable state continues for a predetermined time, the stable state is determined, and the EGR valve 13b is opened. It has been configured to.

In the EGR controller for the turbocharged engine according to the first aspect, the controller 44 is
When the EGR valve 13b is closed during the transient operation of the engine 11, the first deviation amount between the target fuel injection amount calculated based on the first map and the actual fuel injection amount is calculated based on the second map. It is less than or equal to the stability limit value, and the second of the target rotation speed calculated based on the third map and the actual rotation speed.
When the deviation amount is less than or equal to the second stability limit value calculated based on the fourth map, it is determined that the engine 11 is in the temporary stable state. Next, the controller 44 determines that the engine 11 is in the stable state when the temporary stable state of the engine 11 continues for a predetermined time, and opens the EGR valve 13b. As a result, the stable state of the engine 11 can be appropriately determined, and thus the emission of black smoke during transient operation of the engine 11 can be reduced.

The turbocharger is preferably a variable capacity turbocharger or a wastegate turbocharger. Further, as shown in FIG. 1, the EGR device 13
Is the exhaust passage 1 connected to the exhaust port of the engine 11.
8 and the intake passage 3 connected to the intake port of the engine 11
9 and the EGR passage 13a that connects and communicates with the EGR passage 1
It is preferable to have an EGR valve 13b provided in 3a and capable of adjusting the flow rate of the exhaust gas recirculated from the exhaust passage 18 to the intake passage 39 through the EGR passage 13a.

The EGR device is connected to an EGR master piston, which is operated by an intake rocker arm that opens an intake valve of an engine cylinder in an intake stroke, and an oil passage that is connected to the EGR master piston via an oil passage. May have a slave piston for opening the exhaust valve provided in the same cylinder as the intake valve when pressure is generated by the operation of the EGR master piston, and an EGR valve for switching between holding and releasing the oil pressure in the oil passage. preferable. Further E
The GR device is an EG operated by an exhaust rocker arm that opens an exhaust valve of an engine cylinder during an exhaust stroke.
The R master piston is connected to the EGR master piston through an oil passage, and the intake valve provided in the same cylinder as the exhaust valve is opened when pressure is generated in the oil passage by the operation of the EGR master piston. It is possible to have a slave piston that operates and an EGR valve that switches between holding and releasing the oil pressure in the oil passage.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the diesel engine 11 includes a turbocharger 12 that compresses intake air with energy of exhaust gas discharged from the engine 11,
An EGR device 13 that recirculates exhaust gas is provided to the engine 11. As shown in detail in FIGS. 2 to 4, the turbocharger 12 is connected to the turbine wheel 14 that rotates by the energy of the exhaust gas discharged from the engine 11 and the turbine wheel 14 via a connecting shaft 16 to compress intake air. And a compressor wheel (not shown) for supplying the engine 11 to the engine 11. The turbine wheel 14 is an exhaust pipe 18
It is rotatably accommodated in a turbine housing 19 provided in the turbine housing 19, and a multi-stage air cylinder 21 is attached to the outer surface of the turbine housing 19 (FIG. 2). The piston rod 21a of the air cylinder 21 is connected to the stationary blade 26 via the link mechanism 22, the swing lever 23, and the rotating ring 24 (FIGS. 2 to 4). The vane 26 is the turbine wheel 1
4 is provided at the exhaust gas inlet of the turbine wheel 14, and the area of the nozzle 27 of the exhaust gas inlet of the turbine wheel 14 can be changed (FIGS. 3 and 4).

In this embodiment, the air cylinder 21 is a 12-stage air cylinder having six ports 21b to 21g, and each of the ports 21b to 21g is a cylinder conduit 28a to 28f and nozzle adjustment. It is connected to an air tank 31 via a valve 29 (Fig. 2). The nozzle adjusting valve 29 is composed of six electromagnetic valves 29a to 29f, and these electromagnetic valves 29a to 29f are turned on and off, respectively, and the pipe lines 28a to 28f for cylinders are communicated with or cut off from the air cylinder 21. The supply / discharge of compressed air in the air tank 31 can be switched to change the protruding length of the piston rod 21a.

The link mechanism 22 has a first link 22a whose one end is attached to the tip of the piston rod 21a,
A second link 22b having one end pivotally attached to the other end of the first link 22a, and a third link 2 having one end pivotally attached to the other end of the second link 22b and the other end pivotally attached to the turbine housing 19.
2c (FIGS. 2 to 4). Turbine housing 1
The support shaft 32 is rotatably attached to the third link 9
The other end of 2c is fixed to this support shaft 32 (FIG. 2). A stopper lever 33 is provided at the other end of the third link 22c so that the turbine housing 19 has a pair of stopper blocks 34, 3 for restricting the rotation of the stopper lever 33.
4 are provided. These stopper blocks 34, 34
Adjustment bolts 36, 36 capable of adjusting the rotation range of the stopper lever 33 are respectively screwed to the. A base end of the swing lever 23 is fixed to a portion of the support shaft 32 inserted into the turbine housing 19, and a first notch 23 is provided at a tip thereof.
a is formed (FIGS. 3 and 4).

The rotating ring 24 is the turbine wheel 1.
4 has an inner diameter greater than the outer diameter of 4, and the turbine wheel 14
It is rotatably mounted in the turbine housing 19 coaxially therewith (FIGS. 3 and 4). The rotating ring 24 is provided with a single first pin 24a that can be engaged with the first notch 23a of the swing lever 23, and project at equal intervals on the same circumference around the connecting shaft 16. The plurality of formed second pins 24b are provided so as to project. The turbine housing 19 has a rotating ring 2
4 and the turbine wheel 14 and connecting shaft 1
A plurality of stator vane holding pins 19a are provided at equal intervals on the same circumference centered at 6. The center of the vane 26 is rotatably fitted into each of the vane holding pins 19a. At the base end of the stationary vane 26, there is provided a second pin which can be engaged with the second pin 24b.
The notch 26a is formed, and the vane 26 is tapered from the center to the tip. Nozzle adjustment valve 29
Adjusts the area of the nozzle 27 between the stationary vanes 26 via the multi-stage air cylinder 21 so that the area of the nozzle 27 at the exhaust gas inlet of the turbine wheel 14 can be adjusted (FIGS. 2 to 4).

Returning to FIG. 1, the EGR device 13 includes an exhaust pipe 18 connected to an exhaust port of the engine 11 via an exhaust manifold 37 and an intake pipe connected to an intake port of the engine 11 via an intake manifold 38. It has an EGR passage 13a which connects and communicates with 39, and an EGR valve 13b provided in this EGR passage 13a. EGR passage 13a
Is connected to the exhaust pipe 18 on the exhaust gas downstream side of the turbine housing 19, and the other end is connected to the intake pipe 39 on the intake upstream side of the compressor housing 40 that rotatably houses the compressor wheel. The EGR valve 13 is a flow rate adjusting valve capable of adjusting the flow rate of the exhaust gas recirculated from the exhaust pipe 18 to the intake pipe 39 through the EGR passage 13a. The rotation speed of the engine 11 is detected by the rotation sensor 42, and the load of the engine 11 (the depression amount of the accelerator pedal) is detected by the load sensor 43. Further, the boost pressure (intake pressure) of the intake pipe 39 of the engine 11 is the intake pipe 39.
It is detected by the pressure sensor 45 provided in the.

As shown in detail in FIG. 5, the engine 11 is provided with a fuel injection pump 46 for injecting fuel into the engine 11. The fuel injection pump 46 is a control rack 4 that adjusts the amount of fuel injected into the engine 11.
A pump main body 47 in which 7a is slidably inserted, an electronic governor 48 for driving the control rack 47a, and a boost compensator 49 for adjusting the full rack position of the control rack 47a are provided. One end of the control rack 47a is connected to the electronic governor 48, and the other end is provided so as to project from the pump body 47. The boost compensator 49 is a case 49 attached to the pump body 47.
It has a rack stopper 49b housed in a for regulating the full rack position of the control rack 47a, and an actuator 49d housed in a case 49a for driving the rack stopper 49b via a transmission mechanism 49c. The actuator 49d is a stepping motor in this embodiment, and has both a function as an actuator for driving the rack stopper 49b and a function as a position sensor for detecting the position of the rack stopper 49b. The transmission mechanism 49c includes a stopper rack 49e fixed to a rack stopper 49b and an output shaft 49 of an actuator 49d.
and a drive gear 49g which is fitted to the stopper f and meshes with the stopper rack 49e. As the actuator, a linear solenoid or the like may be used instead of the stepping motor.

Returning to FIG. 1, the detection outputs of the rotation sensor 42, the load sensor 43, and the pressure sensor 45 are connected to the control inputs of the controller 44, and the control outputs of the controller 44 are the six electromagnetic valves of the nozzle adjusting valve 29. Valves 29a-29
f, the EGR valve 13b and the fuel injection pump 46, respectively. The controller 44 includes the first to fourth maps,
It has a memory 44a in which a map for steady operation and a map for transient operation are stored. On the first map, the engine 11
Change of the target fuel injection amount corresponding to the change of the load is set, and the change of the first stability limit value of the fuel deviation amount between the target fuel injection amount and the actual fuel injection amount is set in the second map. . Further, the change of the target rotation speed of the engine 11 corresponding to the change of the rotation speed of the engine 11 is set in the third map, and the fourth map shows the change of the rotation deviation amount between the target rotation speed and the actual rotation speed. 2 Change in stability limit is set.

Further, the EGR valve 13 is included in the map for steady operation.
When b is opened (the opening degree of the EGR valve 13b is used as a parameter), the change in the optimum fuel injection amount corresponding to the changes in the boost pressure, the rotation speed of the engine 11, and the load of the engine 11 (in this embodiment, , The optimum rack stopper 49
(change in position b) is set, and the map for transient operation is
Boost pressure when the EGR valve 13b is closed, engine 1
The optimum change of the fuel injection amount (in this embodiment, the optimum change of the position of the rack stopper 49b) corresponding to the change of the rotation speed of 1 and the load of the engine 11 is set.

The EG of the engine 11 constructed as described above
The operation of the R control device will be described with reference to FIGS. When the engine 11 is in a steady operation state, for example, when it is in an idling state such as waiting for a signal, the controller 44 compares each detection output of the pressure sensor 45, the rotation sensor 42, and the load sensor 43 with the first map of the memory 44a, EG
The R valve 13b is opened at a predetermined opening. Controller 4 at the same time
Since 4 sends a predetermined pulse signal to the actuator 49d, the actuator 49d rotates by a predetermined step angle based on this signal to move the rack stopper 49b to a predetermined position. As a result, since the control rack 47a can move in the direction of increasing or decreasing the fuel, the controller 44 controls the electronic governor 48 to move the control rack 47a in the direction of increasing or decreasing. Therefore, the optimum amount of fuel that is suitable for the operating state of the engine 11 is injected, that is, the fuel injection amount to the engine 11 matches the target fuel injection amount of the steady operation map, and therefore the optimum amount of fuel is selected according to the operating state. The engine output can be obtained.

When the engine 11 is in the transient operation state, for example, when the driver abruptly depresses the accelerator pedal to accelerate the engine 11, the controller 44 instantly closes the EGR valve 13b. At the same time, the controller 44 compares the detection outputs of the pressure sensor 45, the rotation sensor 42, and the load sensor 43 with the transient operation map of the memory 44a,
Since a predetermined pulse signal is sent to the actuator 49d, the actuator 49d rotates based on this signal by a predetermined step angle and moves the rack stopper 49b to a predetermined position, for example, the position shown by the solid line in FIG. As a result, the control rack 47a becomes movable in the fuel increasing direction, and the controller 44 controls the electronic governor 48 to move the control rack 47a in the fuel increasing direction. Therefore, the amount of fuel commensurate with the increase in the intake air amount due to the closing of the EGR valve 13b is supplied to the engine 11, that is, the fuel injection amount to the engine 11 can be increased to the target fuel injection amount of the transient operation map. The output of the engine 11 does not decrease.

When the engine 11 shifts from the transient operation state to the steady operation state, the controller 44 outputs the detection signals of the rotation sensor 42 and the load sensor 43 at every predetermined short time (0.010 to 0.020 seconds). The sensors 42, 43 and the first and third memory 44a of the memory 44a.
The map is compared to obtain a first deviation amount between the target fuel injection amount calculated based on the first map and the actual fuel injection amount, and the target rotation speed and the actual rotation speed calculated based on the third map. And a first deviation amount from Next, when the first deviation amount is equal to or less than the first stability limit value calculated based on the second map and the second deviation amount is equal to or less than the second stability limit value calculated based on the fourth map,
It is determined that the engine 11 is in the temporarily stable state. Further, when the temporary stable state of the engine 11 continues for a predetermined time (0.5 to 2 seconds), the controller 44 determines that the engine 11 is in the stable state and opens the EGR valve 13b. As a result, the stable state of the engine 11 can be appropriately determined, and thus the emission of black smoke during transient operation of the engine 11 can be reduced.

In the above embodiment, the EGR device is an external EGR device having an EGR passage and an EGR valve, but an internal EGR device may be used. This internal EGR device is operated by an intake rocker arm that opens an intake valve of a cylinder of an engine during an intake stroke.
The GR master piston is connected to the EGR master piston via an oil passage, and the exhaust valve provided in the same cylinder as the intake valve is opened when pressure is generated in the oil passage by the operation of the EGR master piston. Slave piston and EGR that switches between holding and releasing the oil pressure in the oil passage
And a valve.

The internal EGR device includes an EGR master piston which is operated by an exhaust rocker arm that opens an exhaust valve of an engine cylinder during an exhaust stroke, and an EG.
A slave piston that is connected to the R master piston through an oil passage and that opens an intake valve provided in the same cylinder as the exhaust valve when pressure is generated in the oil passage by the operation of the EGR master piston; It may have an EGR valve that switches between holding and releasing the hydraulic pressure in the passage.

In the above embodiment, the diesel engine is used as the engine, but a gasoline engine may be used. Further, in the above-described embodiment, the variable capacity turbocharger is used as the turbocharger, but the rotational speed of the turbine wheel can be increased by bypassing a part of the exhaust gas flowing into the turbine housing. It may be a waste gate type turbocharger that is controlled to prevent the boost pressure (intake pressure) of the intake pipe from exceeding the set pressure. Further, in the above embodiment, the multi-stage air cylinder is used as the multi-stage cylinder that drives the vanes provided at the exhaust gas inlet of the turbine wheel, but a multi-stage hydraulic cylinder may be used.

[0023]

As described above, according to the present invention, the change of the target fuel injection amount corresponding to the change of the engine load is set in the first map, and the target fuel injection amount and the actual change are set in the second map. The change of the first stability limit value of the fuel deviation amount from the fuel injection amount is set, the change of the target rotation speed of the engine corresponding to the change of the rotation speed of the engine is set in the third map, and the target is set in the fourth map. Since the change in the second stability limit value of the rotation deviation amount between the rotation speed and the actual rotation speed is set, the controller causes the target fuel injection calculated from the first map with the EGR valve closed during the transient operation of the engine. The first deviation amount between the fuel injection amount and the actual fuel injection amount is less than or equal to the first stability limit value calculated from the second map, and the second deviation amount between the target rotation speed calculated from the third map and the actual rotation speed is the fourth deviation amount. Second stability limit calculated from the map When it is less, it is determined that the engine is in temporary stable state. Next, the controller determines that the engine is in a stable state when the temporary stable state of the engine continues for a predetermined time, and opens the EGR valve. As a result, the stable state of the engine can be appropriately determined, so that the emission of black smoke during transient operation of the engine can be reduced.

[Brief description of drawings]

FIG. 1 is an E of a turbocharged engine according to an embodiment of the present invention.
The block diagram which shows a GR control apparatus.

FIG. 2 is an enlarged view of an essential part of the turbocharger.

FIG. 3 is a cross-sectional view of essential parts showing a state in which a nozzle area of an exhaust gas inlet of a turbine wheel of the turbocharger is narrowed by a multistage air cylinder.

FIG. 4 is a cross-sectional view of essential parts showing a state in which a nozzle area of an exhaust gas inlet of a turbine wheel of the turbocharger is expanded by a multistage air cylinder.

FIG. 5 is a fragmentary enlarged view of the fuel injection pump.

FIG. 6 is a flowchart showing a control procedure of the opening degree of the EGR valve by the controller according to the operating condition of the engine.

[Explanation of symbols]

11 engine 12 turbocharger 13 EGR device 13a EGR passage 13b EGR valve 18 Exhaust pipe (exhaust passage) 39 Intake pipe (intake passage) 44 controller 44a memory 46 Fuel injection pump

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 45/00 301 F02D 45/00 376B F02M 25/07 510B 376 550C F02M 25/07 510 550M 550 550R 570P 580A 570 580B 580 580C 580F F02B 37/12 301Q 301A F term (reference) 3G005 DA02 EA15 FA04 FA35 GA02 GA04 GB25 GB28 GC04 GD01 GE08 HA05 HA12 JA02 JA24 JA39 JA43 JB02 FA02 CA02 BA02 CA02 BA04 CA02 CA04 BA02 CA04 CA02 FA14 FA24 GA02 GA04 GA06 3G084 AA01 BA08 BA20 CA01 CA04 CA05 CA06 DA04 DA10 DA27 EB08 EB12 FA10 FA11 FA12 FA13 FA33 3G092 AA01 AA02 AA17 AA18 AB03 AB04 BB01 DA01 DA02 DA06 DB03 DC08 DC10 DG05 EA11 FA01 FA14 EC03 FA18 FA15 FA18 FA01 FA14 FA03 A11 HA05Z HA16Z HB01Z HE01Z

Claims (5)

[Claims] 1. An engine (11) having a turbocharger (12)
A fuel injection pump (46) for injecting fuel into the
(11) an EGR device (13) configured to recirculate the exhaust gas and having an EGR valve (13b) capable of adjusting the recirculation amount of the exhaust gas, a rotation speed of the engine (11), and the engine (11) An EGR control device for a turbocharged engine equipped with a controller (44) for controlling the fuel injection amount of the fuel injection pump (46) and the opening degree of the EGR valve (13b) according to the load of The controller (44) includes a first map in which a change in the target fuel injection amount corresponding to a change in the load of the engine (11) is set, and a fuel deviation amount between the target fuel injection amount and the actual fuel injection amount. 2nd map in which the change of the first stability limit value is set, and the 3rd set in which the change of the target rotation speed of the engine (11) corresponding to the change of the rotation speed of the engine (11) is set.
The controller (44) has a memory (44a) for storing a map and a fourth map in which a change in the second stability limit value of the rotation deviation amount between the target rotation speed and the actual rotation speed is set. While the EGR valve (13b) is closed during the transient operation of the engine (11), the first deviation amount between the target fuel injection amount calculated based on the first map and the actual fuel injection amount is obtained. The second deviation amount between the target rotation speed calculated based on the third map and the actual rotation speed is obtained, and the first deviation amount is equal to or less than the first stability limit value calculated based on the second map. And the second
When the deviation amount is less than or equal to the second stability limit value calculated based on the fourth map, it is determined that the temporary stable state is present, and when the temporary stable state continues for a predetermined time, it is determined that the temporary stable state is stable. EGR of the engine with a turbocharger, characterized in that the EGR valve (13b) is opened.
Control device. 2. The EGR control device for an engine with a turbocharger according to claim 1, wherein the turbocharger is a variable capacity type turbocharger or a wastegate type turbocharger. 3. An EGR device (13) communicatively connects an exhaust passage (18) connected to an exhaust port of an engine (11) and an intake passage (39) connected to an intake port of the engine (11). EGR passage (13a), and an EGR that is provided in the EGR passage (13a) and is capable of adjusting the flow rate of exhaust gas recirculated from the exhaust passage (18) to the intake passage (39) through the EGR passage (13a).
An EGR control device for a turbocharged engine according to claim 1, further comprising a valve (13b). 4. An EGR device is connected to an EGR master piston, which is operated by an intake rocker arm that opens an intake valve of an engine cylinder in an intake stroke, and an oil passage to the EGR master piston. A slave piston that opens an exhaust valve provided in the same cylinder as the intake valve when pressure is generated in the oil passage by the operation of the EGR master piston, and an EGR that switches between holding and releasing the oil pressure in the oil passage. An EGR control device for a turbocharged engine according to claim 1, further comprising a valve. 5. An EGR device is connected to an EGR master piston, which is operated by an exhaust rocker arm that opens an exhaust valve of an engine cylinder in an exhaust stroke, and an oil passage to the EGR master piston. A slave piston that opens an intake valve provided in the same cylinder as the exhaust valve when pressure is generated in the oil passage by the operation of the EGR master piston, and an EGR that switches between holding and releasing the hydraulic pressure in the oil passage. An EGR control device for a turbocharged engine according to claim 1, further comprising a valve.