JP3443748B2 - EGR device for supercharged diesel engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR device for a supercharged diesel engine, and more particularly to an EGR device for a supercharged diesel engine applied to large vehicles such as trucks and buses.

[0002]

BACKGROUND OF THE INVENTION supercharged engine equipped with a turbocharger and currently numerous popular, NO _X in the exhaust gas
EGR (Exhaust Gas Recirculati
on: Exhaust gas recirculation) Fitting equipment is well known.

There are various types of such EGR devices. In any case, when performing EGR, it is necessary to provide a pressure difference between the exhaust side and the intake side, that is, the exhaust side pressure is set to the intake side. Must be higher than pressure. In the case of a supercharged engine, there is a region where the intake side pressure becomes higher than the exhaust side pressure due to supercharging, so EGR cannot be performed in that region unless these pressure differences are reversed by some method.

Generally, there are two types of EGR devices: one that performs intake throttling to lower the pressure on the intake side and one that closes the exhaust passage to increase the pressure on the exhaust side. Regarding the former, for example, JP-A-60-237153,
Japanese Unexamined Patent Publication (Kokai) No. 2-11858 and the like are disclosed. On the other hand, the latter is disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 5-71428. First, regarding the former, the one disclosed in Japanese Patent Laid-Open No. 60-237153 is applied to a relatively small supercharged gasoline engine mounted on a passenger car, etc., and in the case of a gasoline engine, exhaust pressure is high, and Since the intake throttle valve, that is, the throttle valve is naturally provided, EGR can be performed relatively easily. Further, the one disclosed in Japanese Patent Laid-Open No. 2-11858 is applied to a non-supercharged diesel engine,
In this case, an intake throttle valve for reducing the intake side pressure is equipped. Generally, in the case of a diesel engine, the exhaust pressure is relatively low, and in many cases the intake throttle is easy to handle because of problems such as exhaust gas temperature and soot in the exhaust. Regarding the latter, the one disclosed in JP-A-5-71428 is applied to a stationary supercharged diesel engine, which is provided with a variable back pressure control valve downstream of the turbine in the exhaust passage. The valve increases the pressure in the exhaust passage to control the EGR flow rate. Exhaust gas taken out from the exhaust passage, that is, EGR gas is sent to the intake passage after being processed by a soot trap, an EGR gas cooler, or the like. E that connects the exhaust passage and the intake passage
A valve is provided in the GR passage to finely adjust the EGR flow rate.

[0005]

In the case of the device disclosed in Japanese Unexamined Patent Publication (Kokai) No. 5-71428, which raises the pressure on the exhaust side, EG
The outlet of the R passage is connected to the intake passage upstream of the compressor of the turbocharger. E directly to this position
When the GR gas is returned, the soot and sulfate contained in the gas and the high temperature of the gas cause corrosion and deterioration of the compressor and the intercooler on the downstream side of the compressor. Therefore, in the above apparatus, the soot trap, the EGR gas cooler, and the like clean the EGR gas, cool it, and then send the gas to the intake passage.

However, when considering an EGR device for a supercharged diesel engine for vehicles, a soot trap and an EG
It is desirable to omit auxiliary equipment such as an R gas cooler as much as possible from the viewpoint of space, structure, cost, and the like.

Further, in the device for performing intake throttle as disclosed in Japanese Patent Laid-Open No. 2-11858, an intake throttle valve which is originally not particularly required for a diesel engine must be additionally provided, which is also disadvantageous. turn into. Further, the intake throttle valve becomes intake resistance, which deteriorates fuel efficiency.

Further, in the case of a supercharged diesel engine having a relatively large displacement applied to a large vehicle such as a truck or a bus, a valve for an exhaust brake is required in the exhaust passage, and this valve is used as an EGR device. Conventionally, the idea of making it a component part of was not found.

Therefore, an object of the present invention, which was devised in view of the above-mentioned viewpoint, is a simple structure, which prevents corrosion and deterioration of the compressor and the like to improve durability, and also has a function as an exhaust brake. Another object is to provide an EGR device for a supercharged diesel engine.

[0010]

In order to achieve the above object, the present invention provides an EGR passage which connects an exhaust passage in which a turbine of a turbocharger is provided and an intake passage in which a compressor of the turbocharger is provided. In an EGR device for a supercharged diesel engine having
The inlet of the GR passage is connected to the exhaust passage on the upstream side of the turbine, the outlet of the EGR passage is connected to the intake passage on the downstream side of the compressor, and the EGR is connected to the downstream side of the turbine on the EGR side. An exhaust pressure control valve that is controlled to an intermediate opening degree so that the inlet pressure of the EGR passage is increased by a predetermined pressure above the outlet pressure of the EGR passage when performing, and is controlled to be substantially fully closed when performing exhaust braking, The EGR passage is controlled so that the EGR flow rate is optimally controlled when performing EGR, and is fully closed when performing exhaust braking.
An R flow rate control valve is provided, a connection portion of the exhaust passage with the engine is formed by an exhaust manifold, and a plurality of the exhaust manifolds are provided so that the engine is a multi-cylinder and the predetermined cylinders are shared by each of the exhaust manifolds. An outlet is provided and these outlets are joined together.
Connect the inlet of the EGR passage to the confluence connection unit, to the confluence connection portion, provided with a partition valve body simultaneously open and close the takeout each above constitute the EGR flow rate control valve, the partition valve body
Is moved in and out along the guide groove provided in the merge connection.
When the valve is fully closed, the tip of the gate valve element is pressed by the pressing means.
It is pressed to the opposite side in the gas flow direction .

[0011]

According to the above construction, since the outlet of the EGR passage is connected to the intake passage on the downstream side of the compressor, the EGR gas is not sent to the compressor, so corrosion and deterioration are prevented and durability is improved. Can be improved. Further, the exhaust pressure control valve is set to an intermediate opening degree to increase the inlet pressure of the EGR passage above the outlet pressure, and the EGR flow rate control valve is adjusted, so that an optimum amount of EGR can be performed. Further, by making the exhaust pressure control valve substantially fully closed and the EGR flow rate control valve fully closed, exhaust brake becomes possible, and an EGR device having an exhaust brake function can be provided.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an EGR device for a supercharged diesel engine according to the present invention. Engine 1
It has a relatively large displacement applied to large vehicles such as trucks and buses, and has an intake passage 2 and an exhaust passage 3. An air filter 4 is provided at the air inlet of the intake passage 2, and a turbocharger 5 is provided at the upstream side in the intake passage 2.
The compressor 6 is installed, and the intercooler 7 is installed downstream of the compressor 6 (the intercooler 7 may not be provided). The connecting portion of the intake passage 2 to the engine 1, that is, the end portion on the most downstream side is formed by the intake manifold 8. The exhaust passage 3 includes an exhaust manifold 9 forming a connection portion with the engine 1, and an exhaust pipe 10 leading to the outside.
The turbine 11 of the turbocharger 5 is provided between the exhaust manifold 9 and the exhaust pipe 10.

The exhaust passage 3 and the intake passage 2 are the EGR passage 1
In this embodiment, the inlet 12a of the EGR passage 12 is connected to the exhaust manifold 9,
The outlet 12b of the EGR passage 12 is connected to the intake manifold 8. Further, the EGR passage 12 has an EGR flow control valve 1 for controlling a flow amount of EGR gas flowing therein.
3 is installed. The EGR flow rate control valve 13 ensures that when high pressure (about 8 kg / cm ² ) is applied during exhaust braking, E
In order to close the inside of the GR passage 12, a poppet valve that opens when the valve body is moved to the inlet 12a side is adopted. Further, the EGR flow control valve 13 has a pneumatic actuator 14 connected thereto, and the pneumatic actuator 14 substantially opens and closes the valve 13. Usually for large vehicles,
An air tank filled with compressed air is provided, and the pneumatic actuator 14 is substantially operated using the compressed air in the air tank (not shown) as a working medium. The EGR flow rate control valve 13 also needs to be controlled to an intermediate opening degree, and this is performed by air pressure control of an actuator 14 of a DSV (Duty Solenoid Valve) not shown.

An exhaust pressure control valve 15 is provided downstream of the turbine 11 in the exhaust passage 3, that is, in the exhaust pipe 10, to increase the exhaust gas pressure in the exhaust passage 3 by controlling the opening to a predetermined degree. As shown in FIG. 2, the exhaust pressure control valve 15 is composed of one sluice valve 15a and an air pressure actuator 16 that adjusts the opening of the sluice valve 15a in eight stages by the air input of three circuits. Eight degrees of opening up to the fully closed position can be obtained stepwise.

EGR flow control valve 13 and exhaust pressure control valve 15
Opening / closing control with respect to, that is, operation control of the actuators 14 and 16 is performed by the control means 17 connected thereto. Here, the control means 17 is specifically an ECU (Engine Control Unit) 1 that controls the fuel injection amount of the engine 1 and the like.
8 and the ECU 18 includes a circuit for controlling the valves 13 and 15. Signals such as the engine speed, engine load, supercharging pressure, exhaust pressure, water temperature, intake air temperature, and atmospheric pressure are constantly input to the ECU 18, and the ECU 18 is based on these signals. The open control is performed by the pre-stored opening amounts of the valves 13 and 15 that provide the optimum EGR flow rate. Optimal EGR
The flow rate or EGR rate is given in the form of a map mainly corresponding to the engine speed and the engine load. This flow rate value, that is, the EGR rate map is optimally obtained by a bench test or the like, and the opening degrees of the valves 13 and 15 are determined based on this,
In this embodiment, the opening degree is stored in the ECU 18. Of course, a flow rate sensor or the like may be provided in the EGR passage 12, the EGR flow rate may be directly measured, and the valves 13 and 15 may be comparatively controlled by comparing the measured flow rate value with the flow rate value map. In addition, the intake air amount is measured with an air flow sensor or the like, the EGR flow rate is calculated from the difference between the engine speed and the flow rate obtained from the boost pressure and the intake air temperature, and feedback control is performed for the target value. You may The ECU 18
Also determines the necessity of EGR depending on the operating state of the engine 1.

Further, the ECU 18 is also adapted to receive an exhaust brake signal 19 which is an on / off signal. The exhaust brake signal 19 is turned on / off by a manual switch provided in the cab of the vehicle.

Next, the operation of the embodiment will be described.

During operation of the engine 1, EGR is performed in the supercharging region.
When performing, the actuator 16 is operated by a signal from the ECU 18, and the exhaust pressure control valve 15 is controlled to have an intermediate opening degree (semi-closed state). Then, as shown in FIG. 3, the inlet 12a pressure P of the EGR passage 12 becomes E
The pressure P becomes slightly higher than the pressure Q at the outlet 12b of the GR passage 12, and this pressure difference enables EGR. Furthermore E
The actuator 14 is operated by a signal from the CU 18, and the EGR flow control valve 13 is controlled to a predetermined optimum opening. As a result, the optimum EGR for the engine 1
The flow rate is given, and NO _X can be reduced. here,
Since the outlet 12b of the EGR passage 12 is connected to the intake passage 2 on the downstream side of the intercooler 7, the EGR gas is not sent to the compressor 6 and the intercooler 7, and therefore corrosion and deterioration of them are prevented in advance. The durability can be improved. Further, since it is not necessary to provide the above-mentioned accessories and intake throttle valve, and the EGR passage 12 has the shortest distance,
GR device can be configured simply, cost,
It is also advantageous in terms of space.

When the exhaust brake is further applied, the exhaust brake signal 19 is input to the ECU 18, whereby the actuators 16 and 14 are actuated, the exhaust pressure control valve 15 is substantially fully closed, and at the same time the EGR flow control valve 13 is turned on. It is completely closed. As a result, the pressure in the exhaust passage 3 is significantly increased, and exhaust braking becomes possible.

In the past, valves for exhaust brakes were simply turned on / off to a near fully closed or fully open position. In the present invention, since the exhaust pressure control valve 15 also has an intermediate opening degree between the substantially fully closed position and the fully open position, it becomes possible to optimally increase the pressure in the exhaust passage 3 to perform EGR. . Further, at this time, the pressure in the exhaust passage 3 is not excessively increased, so that the deterioration of fuel efficiency due to the increase in exhaust pressure can be prevented.

Further, when the EGR is not performed during the operation of the engine 1, the exhaust pressure control valve 15 is fully opened, thereby preventing deterioration of fuel consumption. At this time, the EGR flow control valve 13 is fully closed to prevent the EGR gas from flowing.

FIG. 4 schematically shows an EGR rate map obtained by the test, in which the horizontal axis represents the engine speed and the vertical axis represents the engine load or generated torque. The EGR region shown by the diagonal lines is determined mainly in relation to exhaust gas regulations. The maximum value of the EGR rate is about 20%, and the EGR rate decreases as the engine load increases. If EGR is performed on the high load side, smoke becomes worse, and EGR is not performed or is reduced on the high load side. The optimum EGR flow rate is determined based on this map, and the opening degrees of the valves 13 and 15 are determined by the flow rate value.

FIG. 5 shows a modification of the exhaust pressure control valve 15. As shown in the figure, the exhaust pressure control valve 15 is mainly composed of one butterfly valve 20, two air cylinders 21, and a link device 22 connecting them. Air is independently input to the two air cylinders 21,
By this and the function of the link device 22, the butterfly valve 2
For 0, the opening is adjusted in four steps. In addition to this, a plurality of sluice valves having different strokes may be arranged in a row along the flow direction.

Further, FIG. 6 shows a modification of the EGR flow control valve 13. Generally, a supercharged diesel engine applied to a truck or the like has multiple cylinders. For example, in the case of 6 cylinders, two exhaust manifolds sharing three cylinders are provided, and these two exhaust manifolds are assembled and connected to a turbine. May be done. Considering the EGR, it is known that it is more efficient to send two separately than to send them together. In the example shown in FIG. 5, such a configuration is extremely simple. Two exhaust manifolds (not shown)
The outlets 23a and 23b are provided in each of the outlets 23a and 23b, and the outlets 23a and 23b are joined and connected to each other. The inlet 12a of the EGR passage 12 is connected to the connecting portion 24, and the connecting portion 24 is provided with a gate valve body 25 for simultaneously opening and closing the outlets 23a and 23b. Gate valve body 25
Moves in and out along a guide groove 26 provided in the connecting portion 24, and is substantially operated by the pneumatic actuator 14 or the air cylinder 27. When fully closed, the tip of the gate valve body 25 is pressed by the pressing means 28 to the opposite side in the gas flow direction, so that the EGR is included even when the exhaust brake is under high pressure.
The passage 12 and the outlets 23a and 23b are surely closed. In this way, the two outlets 23a, 2
3b can be opened and closed reliably and simultaneously with one gate valve body 25,
EGR flow control valve 1 that can withstand high pressure during exhaust braking
It can be 3. Note that such a configuration is possible even when the number of exhaust manifolds is further increased.

Besides, various modifications can be made, for example, by making the actuators 14 and 16 electrically driven by servomotors and the like.

[0027]

The present invention exhibits the following excellent effects.

(1) Corrosion and deterioration of the compressor and the like can be prevented and the durability can be improved.

(2) E having the function of an exhaust brake
It can be a GR device.

[Brief description of drawings]

FIG. 1 is an EGR of a supercharged diesel engine according to the present invention.
It is a block diagram which shows an apparatus and which shows one example.

FIG. 2 is a side sectional view showing an exhaust pressure control valve.

FIG. 3 is a graph showing an inlet pressure and an outlet pressure of an EGR passage.

FIG. 4 is a graph showing an EGR rate map.

FIG. 5 is a side sectional view showing a modified example of the exhaust pressure control valve.

FIG. 6 is a view showing a modified example of the EGR flow control valve, (a)
Is a front sectional view, and (b) is a side sectional view.

[Explanation of symbols]

1 engine 2 Intake passage 3 exhaust passage 5 turbocharger 6 compressor 11 turbine 12 EGR passage 12a entrance 12b exit 13 EGR flow control valve 15 Exhaust pressure control valve 17 Control means 19 Exhaust brake signal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification code FI F02D 9/06 F02D 9/06 A (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 25/07 570 F02M 25 / 07 550 F02M 25/07 580 F02B 37/00 302 F02D 9/06

Claims (2)

(57) [Claims] 1. An EGR device for a supercharged diesel engine having an EGR passage communicating between an exhaust passage in which a turbine of a turbocharger is provided and an intake passage in which a compressor of the turbocharger is provided. When the inlet is connected to the exhaust passage on the upstream side of the turbine, the outlet of the EGR passage is connected to the intake passage on the downstream side of the compressor, and EGR is performed on the exhaust passage downstream of the turbine. The inlet opening pressure of the EGR passage is controlled to an intermediate opening so as to be higher than the outlet pressure of the EGR passage by a predetermined pressure,
An exhaust pressure control valve that is controlled to be substantially fully closed when exhaust braking is provided is provided in the EGR passage so that the EGR flow rate is controlled to an optimum opening when EGR is performed, and fully closed when exhaust braking is performed. E controlled to be
A GR flow control valve is provided, a connection portion of the exhaust passage with the engine is formed by an exhaust manifold, and a plurality of the exhaust manifolds are provided so that the engine is a multi-cylinder and each predetermined cylinder is shared. An outlet is provided and each of these outlets is joined and connected, and the inlet of the EGR passage is connected to the joined connection.
A sluice valve element that constitutes the EGR flow control valve and opens and closes each of the outlets at the same time is provided in the merging connection portion.
The body appears and disappears along the guide groove provided at the confluence connection.
When the valve is moved and the valve is fully closed, the tip of the gate valve element is
An EGR device for a supercharged diesel engine, which is pressed to the opposite side in the direction of gas flow . 2. The exhaust according to the operating state of the engine
The optimum opening between the air pressure control valve and the EGR flow rate control valve is preset.
Is stored in memory, and the opening and exhaust brake signal are input.
Controls the exhaust pressure control valve and the EGR flow rate control valve.
Is provided, and the exhaust pressure control valve is fully opened.
The EGR device for a supercharged diesel engine according to claim 1, wherein the EGR device is variable stepwise from a stationary position to a substantially fully closed position .