JP2002332879A - Egr device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily recirculate exhaust gas from an exhaust manifold to an intake pipe, even in the high load region of an engine equipped with a turbocharger. SOLUTION: In an EGR device for recirculating exhaust gas 8, from the upstream side to a turbine 16 to the downstream side of a compressor 34, a variable geometry turbocharger 15 capable of steplessly adjusting the opening of the nozzle vane of the turbine 16 by an electric motor 18 is adopted, and a throttle valve 26 capable of continuously adjusting the opening by an electric motor 25 is installed in an intake passage on the upstream side of the merged position of the recirculated exhaust gas; and an EGR valve 12, capable of continuously adjusting the opening by an electric motor 27 is installed midway in an EGR pipe 11. These electric motors 18, 25, and 27 are controlled properly, according to the operating conditions of the engine 1 so that the appropriate amount of recirculation of the exhaust gas 8 can be assured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an EGR device.

[0002]

2. Description of the Related Art Conventionally, in an automobile engine or the like, a part of exhaust gas is extracted from an exhaust side and returned to an intake side.
Exhaust gas recirculation (EGR: Exhaust Gas Recircula) in which the combustion of fuel in the engine is suppressed by the exhaust gas returned to the intake side and the combustion temperature is reduced to reduce the generation of NOx.
) is being performed.

FIG. 4 shows an example of an EGR device for performing the above-described exhaust gas recirculation. In the figure, reference numeral 1 denotes an engine which is a diesel engine, and the engine 1 has a turbocharger 2; The intake air 4 guided from the air cleaner 3 is sent through an intake pipe 5 to a compressor 2a of the turbocharger 2, and the intake air 4 pressurized by the compressor 2a is sent to an intercooler 6 for cooling. The intake air 4 is guided to the intake manifold 7 and distributed to each cylinder of the engine 1.

Further, exhaust gas 8 discharged from each cylinder of the engine 1 is sent to a turbine 2b of the turbocharger 2 through an exhaust manifold 9, and the turbine 2b
The exhaust gas 8 driven by is driven out of the vehicle through an exhaust pipe 10.

The exhaust manifold 9 (turbine 2
b), one end of each cylinder in the direction in which the cylinders are arranged in the exhaust passage, and an intake pipe 5 connected to the intake manifold 7.
An EGR pipe 11 is connected to one end of the (intake passage downstream of the compressor 2a), and a part of the exhaust gas 8 is extracted from the exhaust manifold 9 and the intake pipe 5
To be able to lead to.

Here, the EGR pipe 11 has the E
An EGR valve 12 for appropriately opening and closing the GR pipe 11,
An EGR cooler 13 for cooling the recirculated exhaust gas 8 is provided. In the EGR cooler 13, the temperature of the exhaust gas 8 can be reduced by exchanging heat between the cooling water and the exhaust gas 8. Thus, the combustion temperature can be reduced by recirculating the water-cooled exhaust gas 8 to the engine 1.

[0007] In the figure, reference numeral 14 denotes a fuel injection device mounted on the upper portion of the engine 1 for injecting fuel into each cylinder.

[0008]

However, in such a conventional EGR device, as shown in FIG. 5, mainly in a high load region, the supercharging pressure by the turbocharger 2 becomes higher than the exhaust pressure (see FIG. 5). 5, there is a problem that the exhaust gas 8 cannot be recirculated from the exhaust manifold 9 toward the intake pipe 5.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and enables the exhaust gas to be satisfactorily recirculated from the exhaust manifold toward the intake pipe even in a high-load region of an engine equipped with a turbocharger. It is intended to provide an EGR device.

[0010]

According to the present invention, a part of exhaust gas is extracted from an exhaust passage upstream of a turbine via an EGR pipe in an engine equipped with a turbocharger, and is recirculated to an intake passage downstream of a compressor. EG
An R device, which employs a variable geometry turbocharger in which a nozzle vane opening of a turbine can be steplessly adjusted by a first electric motor as a turbocharger, and a junction of recirculated exhaust gas in an intake passage. A throttle valve is provided on the upstream side so that the opening can be adjusted steplessly by a second motor, and the opening can be adjusted steplessly by a third motor in the middle of the EGR pipe. The EGR valve described above is provided, and the first to third electric motors are appropriately controlled in accordance with the operation state of the engine so as to secure an appropriate recirculation amount of the exhaust gas.

Thus, when a part of the exhaust gas is extracted from the exhaust passage upstream of the turbine and recirculated to the intake passage downstream of the compressor, the supercharging pressure of the turbocharger generally increases the exhaust pressure. If the opening of the nozzle vane of the variable geometry turbocharger in the high-load region, which tends to be higher, becomes larger than usual, the rotational speed of the exhaust gas in the turbine decreases, and the rotational speed of the turbine decreases, whereby the compressor side Since the amount of intake air decreases, the efficiency as a turbocharger decreases, and the supercharging pressure on the compressor side decreases,
In addition, the exhaust gas ventilation resistance to the turbine whose rotation speed has decreased increases, and the exhaust pressure on the upstream side of the turbine is increased. As a result, the exhaust pressure is maintained higher than the supercharging pressure, and the exhaust passage is properly returned to the intake passage. Will be circulated.

However, with only pressure control using only such a variable geometry turbocharger, control delay during rapid acceleration / deceleration is inevitable due to a time lag peculiar to the turbocharger. On the other hand, the control delay may be compensated by using the throttle valve opening control together.

In addition, the nozzle vane opening of the turbine,
The opening of the throttle valve and the opening of the EGR valve
Since the first to third motors are adjusted in a stepless manner, the opening is controlled to an appropriate degree in response to a control signal from an engine control computer or the like,
It is possible to ensure an appropriate amount of exhaust gas recirculation according to the operating state of the engine.

[0014]

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

FIGS. 1 to 3 show an example of an embodiment of the present invention, in which the same reference numerals as in FIG. 4 denote the same parts.

As shown in FIG. 1, in this embodiment, a variable geometry turbocharger 15 is employed as a turbocharger, and the nozzle vanes 17 (see FIG. 2) of a turbine 16 of the variable geometry turbocharger 15 are opened. Degree of first motor 18
Can be adjusted steplessly.

That is, as shown in detail in FIG.
No. 6 nozzle vanes 17 are attached to nozzle ring plates 20 around the turbine wheel 19 via pins 21 so as to be tiltable, and the angle of each nozzle vane 17 is set such that the angle of the link plate 22 with respect to the nozzle ring plates 20 in the circumferential direction is increased. The link plate 22 is changed in conjunction with the relative displacement, and the link plate 22 is rotated through the link 24 by the tilting operation of the lever 23 by the first electric motor 18.

Here, the first motor 18 is designed so that the tilting position of the lever 23 can be positioned at an arbitrary angle by using a battery mounted on the vehicle as a power source. This type of motor is already known as a commercial product. It has become a technology.

As shown in FIG. 1, a second electric motor 2 similar to the first electric motor 18 described above is provided upstream of the junction of the recirculated exhaust gas 8 in the intake pipe 5.
5, the throttle valve 26 is provided so that the opening can be adjusted in a stepless manner. Further, the EGR valve 12 provided in the EGR pipe 11 is also provided with a throttle valve similar to the first electric motor 18 described above. The opening can be adjusted steplessly by the third motor 27.

That is, as shown in detail in FIG. 3, in the throttle valve 26 or the EGR valve 12, the butterfly type valve element 26a or 12a is connected to the tilt shaft 26b or 12b.
Is provided so as to be tiltable around the tilting shaft 26b or 1
The lever 25c or 12c externally and integrally connected to the second motor 2b is moved to the link 25 by tilting the lever 25a or 27a by the second electric motor 25 or the third electric motor 27.
b or 27b can be tilted.

In adjusting the opening of the nozzle vane 17 on the turbine 16 side and the opening of the EGR valve 12 in the conventional turbocharger 2, an air-actuated actuator is generally used. For air-actuated actuators, 3 to 4
Only the position can be adjusted stepwise, and responsiveness is lacking due to an operation delay with respect to a control signal.

Further, in the example shown here, on the downstream side of the throttle valve 26 in the intake pipe 5,
A pressure sensor 28 for detecting a supercharging pressure of the intake air 4 is provided, and a pressure sensor 29 for detecting an exhaust pressure is provided in the exhaust manifold 9. On the other hand, the engine 1 has an engine speed. Rotation speed sensor 30 to detect
The fuel injection device 14 on the upper part of the engine 1 is provided with a fuel injection amount sensor 31 for detecting an amount of injected fuel. A sensor 32 is provided.

The detection signals from the pressure sensors 28 and 29, the rotation speed sensor 30, the fuel injection amount sensor 31, and the accelerator sensor 32 are sent to an engine control computer (ECU: Electronic Control Unit) 33. The engine control computer 3
In 3, the exhaust pressure is maintained higher than the supercharging pressure in accordance with the operating state determined from the engine speed, the fuel injection amount, and the accelerator opening, so that an appropriate recirculation amount of the exhaust gas 8 is secured. In addition, a control signal can be output to the third electric motors 18, 25, 27.

Here, the accelerator opening determined by the accelerator sensor 32 can be used as a material for grasping the driver's intention such as rapid acceleration / deceleration by monitoring the rate of change. By outputting a control signal to the first to third electric motors 18, 25, 27 while considering the intention, the opening degree of the nozzle vane 17 of the turbine 16, the opening degree of the pressure sensors 28, 29, the throttle valve 2
The opening degree of each exhaust gas 6 is adjusted steplessly in a comprehensive manner so as to secure an appropriate recirculation amount of the exhaust gas 8.

In the figure, reference numeral 34 denotes a compressor in the variable geometry turbocharger 15.

Thus, if the EGR device is configured as described above, when a part of the exhaust gas 8 is extracted from the exhaust manifold 9 upstream of the turbine 16 and recirculated to the intake pipe 5 downstream of the compressor 34, generally, When the opening degree of the nozzle vane 17 on the turbine 16 side of the variable geometry turbocharger 15 is opened more than usual in a high load region where the supercharging pressure by the turbocharger tends to be higher than the exhaust pressure, the rotational speed of the exhaust gas 8 in the turbine 16 is increased. , The rotation speed of the turbine 16 decreases, and the amount of intake air on the compressor 34 side decreases. As a result, the efficiency of the turbocharger decreases, and the supercharging pressure on the compressor 34 side decreases. The resistance of the exhaust gas 8 to the reduced number of turbines 16 increases and the turbine 1
As a result, the exhaust pressure is maintained higher than the supercharging pressure, and the exhaust manifold 9 is satisfactorily recirculated from the exhaust manifold 9 to the intake pipe 5.

However, pressure control using only such a variable geometry turbocharger 15 only
Since a control delay at the time of rapid acceleration / deceleration is inevitable due to a time lag peculiar to the turbocharger, the control delay is compensated for by using the opening control of the throttle valve 26 in combination with such a sudden change in the operating state. You can do it.

More specifically, for example, when the accelerator is deeply depressed and rapid acceleration is performed, the turbine 1 of the variable geometry turbocharger 15
Even if the opening degree of the nozzle vane 17 on the sixth side is controlled to be open, the supercharging pressure does not immediately decrease.
If the control for reducing the opening of the throttle valve 26 is performed in parallel with the control for opening the opening of the nozzle vane 17 of No. 6, the amount of intake air is immediately reduced by reducing the opening of the throttle valve 26. The supercharging pressure is reduced, the exhaust pressure is maintained higher than the supercharging pressure, and the exhaust gas 8 is satisfactorily recirculated from the exhaust manifold to the intake pipe 5.

The nozzle vane 1 on the turbine 16 side
7, the opening of the throttle valve 26, and the opening of the EGR valve 12, the first to third motors 18, 2
Since the adjustment is performed steplessly by 5, 27, the opening is controlled to an appropriate degree in response to a control signal from the engine control computer 33.

Therefore, in the present embodiment, the exhaust efficiency can be reduced even in a high load region of the engine 1 by arbitrarily reducing the substantial efficiency of the variable geometry turbocharger 15 and arbitrarily reducing the intake air amount by the throttle valve 26. The pressure can be maintained higher than the supercharging pressure, and at the same time, the EGR valve 12 can be controlled to an appropriate opening to adjust the recirculation amount of the exhaust gas 8 arbitrarily. The exhaust gas 8 can be satisfactorily recirculated from the exhaust manifold 9 to the intake pipe 5 downstream of the compressor 34, and an appropriate recirculation amount of the exhaust gas 8 according to the current operating state of the engine 1 is ensured. Can be secured.

The EGR device of the present invention is not limited to the above-described embodiment, but may be configured to extract exhaust gas from an exhaust pipe upstream of a turbine of a turbocharger, or to extract the extracted exhaust gas to a turbocharger. It may be possible to return to the intake manifold downstream of the compressor of the charger, and in the case of a gasoline engine, a throttle valve for reducing the amount of intake air may be provided separately from the throttle valve linked to the accelerator. ,
Also, the type of the EGR valve or the throttle valve does not necessarily have to be a butterfly type, and for example, a wastegate type may be adopted, and various changes may be made without departing from the gist of the present invention. Of course.

[0032]

According to the EGR device of the present invention described above,
By arbitrarily reducing the substantial efficiency of the variable geometry turbocharger and arbitrarily reducing the intake air amount by the throttle valve, the exhaust pressure can be maintained higher than the supercharging pressure even in a high engine load region. At the same time, the EGR valve can be controlled to an appropriate opening to adjust the amount of exhaust gas recirculation arbitrarily, so that the exhaust gas can be satisfactorily recycled from the exhaust passage upstream of the turbine to the intake passage downstream of the compressor. It is possible to achieve an excellent effect that it is possible to circulate, and it is possible to reliably ensure an appropriate amount of exhaust gas recirculation according to the current operating state of the engine.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment for implementing the present invention.

FIG. 2 is a detailed view of a nozzle vane of the turbine of FIG.

FIG. 3 is a detailed view of a throttle valve and an EGR valve of FIG. 1;

FIG. 4 is a schematic diagram showing a conventional example.

FIG. 5 is a graph for explaining a region where a supercharging pressure is higher than an exhaust pressure.

[Explanation of symbols]

 Reference Signs List 1 engine 4 intake 5 intake pipe (intake passage) 7 intake manifold (intake passage) 8 exhaust gas 9 exhaust manifold (intake passage) 10 exhaust pipe (intake passage) 11 EGR pipe 12 EGR valve 15 variable geometry turbocharger 16 turbine 17 Nozzle vane 18 First electric motor 25 Second electric motor 26 Throttle valve 27 Third electric motor 33 Engine control computer 34 Compressor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 9/02 F02D 21/08 301B 3G301 21/08 301 41/02 310D 41/02 310 310E 43/00 301K 43/00 301 301N 301R F02M 25/07 550C F02M 25/07 550 550R 570J 570 570P 580F 580 F02B 37/12 301Q F term (reference) AA05 BA06 EA11 ED08 FA05 GA04 GA05 GA06 GA14 GA21 GA22 3G065 AA01 AA03 AA10 CA12 DA05 DA06 EA07 EA10 GA04 GA06 GA10 GA14 GA41 GA46 GA47 3G084 BA05 BA08 BA20 CA04 DA04 FA00 FA10 FA12 FA13 FA33 3G092AA17 A18ZA18A18A18A18AA17 HF08Z 3G301 HA11 HA13 JA03 KA09 LA00 LA01 PA11Z PA16Z PB03Z PD14Z PE01Z PF03Z

Claims (1)

[Claims] An EGR device for extracting a part of exhaust gas from an exhaust passage upstream of a turbine in an engine equipped with a turbocharger via an EGR pipe and recirculating the extracted exhaust gas to an intake passage downstream of a compressor. The first motor adopts a variable geometry turbocharger capable of adjusting the nozzle vane opening of the turbine in a stepless manner, and the second motor is provided upstream of the recirculated exhaust gas merging point in the intake passage. A throttle valve whose opening can be adjusted steplessly by an EGR pipe, and an EGR valve whose opening can be adjusted steplessly by a third electric motor is provided in the middle of the EGR pipe. The first to third electric motors are appropriately controlled in accordance with the operation state of the engine so that an appropriate recirculation amount of the exhaust gas is An EGR device characterized in that the EGR device is configured to be secured.