JP2000064912A - Egr device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR device matching with each other the opening/ closing timing of a plurality of exhaust gas recirculation(EGR) valves, preventing occurrence of high concentration black smoke easily produced at EGR transient times, and besides, manufactured by a simple structure and at low cost by reducing the number of solenoid valves. SOLUTION: In this EGR device in which a plurality of exhaust manifolds 2a, 2b is formed by being matched with the air cylinder group of an engine E and EGR valves 5a, 5b performing a valve opening/closing operation by air pressure are respectively arranged in EGR passages 4a, 4b communicating the exhaust manifolds 2a, 2b with an intake passage 1, a solenoid valve 11 controlled by an engine controller 31 is arranged in an air piping 13 from an air pressure supply source 21, and air is supplied to the EGR valves 5a, 5b by being branched on a side further downstream from the solenoid valve 11, and also flowing resistance of branch passages 12a, 12b to the EGR valves 5a, 5b is formed approximately equal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbocharged diesel engine or the like, which has a plurality of EGR passages respectively connected to a plurality of exhaust manifolds formed corresponding to cylinder groups of the engine and to intake passages. The present invention relates to an EGR device that opens and closes an EGR valve provided in each EGR passage by air pressure.

[0002]

2. Description of the Related Art In measures against exhaust gas from engines such as diesel engines, in order to reduce the amount of NOx emitted from exhaust gas, a part of the exhaust gas, which is an inert gas, is recirculated to intake air to reduce the combustion temperature. It is known that EGR (exhaust gas recirculation), which suppresses NOx generation by keeping it low, is effective
It is widely used.

In a turbocharged diesel engine, EGR must be performed even in a high-load region where the amount of NOx emission is large in order to increase the NOx reduction effect. As shown, in a region A indicated by oblique lines at low and medium engine speeds and medium and high loads, the boost pressure (intake pressure) Pbm becomes higher than the exhaust pressure Pem. This makes it difficult to recirculate the portion as the EGR gas to the intake side.

[0004] The present inventors have studied the use of the pulsation phenomenon of the exhaust pressure in order to enable the EGR to be performed even in the region A where the EGR is difficult. In this region A, the average pressure is equal to the boost pressure Pbm.
> Even with the exhaust pressure Pem, as shown in FIG. 6, there is a portion X indicated by the hatched line where the boost pressure Pb <the exhaust pressure Pe due to pulsation, as shown in FIG. 6, so that the reed valve 7a as shown in FIG. , 7b are provided in the EGR passages 4a, 4b so that the combustion of the engine E does not deteriorate,
I decided to do GR.

The arrangement of the reed valves 7a and 7b prevents a reverse flow from the air supply side to the exhaust side when the boost pressure Pb> the exhaust pressure Pe to prevent the deterioration of the engine performance.
Reed valve 7 only when boost pressure Pb <exhaust pressure Pe
a and 7b are opened to perform EGR to reduce NOx.

In this case, only the cylinders having the same phase of the exhaust pulsation (or the phase of the intake pulsation) are aggregated so that the exhaust pulsation (or the intake pulsation) between the cylinders does not cancel each other. Cylinders whose phases of exhaust pulsation (or phases of intake pulsation) are close to each other are separated so that the respective pulsation effects can be used to the maximum.

More specifically, in the case of an in-line six-cylinder engine, as shown in FIG. 7, the exhaust manifold 2 is divided into three front cylinders and three rear cylinders to divide the exhaust manifold 2 into a plurality of exhaust manifolds 2a, 2b, EG.
R valves 5a, 5b, EGR coolers 6a, 6b, and reed valves 7a, 7b are provided, respectively, to provide two systems of EGR passages 4a,
4b, the air cylinders 9a, 9b of the EGR valves 5a, 5b are operated to open and close the EGR valves 5a, 5b.
Air is supplied to b from an air pressure supply source 31 such as an air tank.

With this EGR system, E
In the region A in FIG. 5 where the GR could not be performed, an EGR rate of 10% or more can be obtained, and the NOx can be significantly reduced.

[0009]

However, as shown in FIG. 7, the air supply to the EGR valves 5a and 5b is turned ON / OFF.
In order to perform the OFF control, the electromagnetic valves 51a and 51b are set to the respective EGR valves 5
a, 5b, the response speeds of the EGR valves 5a, 5b differ from each other due to variations in the response speeds of the solenoid valves 51a, 51b and lengths of the air pipes 42a, 43a, 42b, 43b. Even if the output timing of the on-off valve operation signal of the engine controller 31 is the same, the EGR valves 5a, 5
There is a problem that the timing of the opening and closing operation of b differs.

Therefore, the EGR valves 5a and 5b of each system cannot be controlled at the same timing, and the EGR cannot be smoothly performed at an appropriate timing. Particularly, in a transitional period in which the EGR is turned off at the time of acceleration of an increase in the engine load, even if the timing of one system is good, the timing of the other system is deteriorated. There is a problem that the engine cannot be stopped, the EGR amount becomes excessive, the combustion deteriorates, and black smoke of high concentration is generated.

In addition, if the solenoid valves 51a and 51b are provided for each of the EGR valves 5a and 5b, the number of solenoid valves increases. In particular, as shown in FIG.
When the valves 5Aa and 5Ab are used, each multi-stage EGR
Since the number of air cylinders provided in the valves 5Aa and 5Ab increases, a large number of solenoid valves 51Aa, 51Ab and 51 are obtained by multiplying the number of EGR valves 5Aa and 5Ab by the number of air cylinders.
Ba and 51Bb are required. As a result, not only the initial cost rises, but also the EGR system becomes complicated, causing problems such as complicated maintenance and inspection work and an increase in the failure rate.

The present invention has been made in order to solve the above-mentioned problem, and an object of the present invention is to provide a plurality of EGRs.
The opening and closing timing of the valve can be matched, and EG
It is an object of the present invention to provide a structurally simple and low-cost EGR device which can prevent the generation of high-concentration black smoke which is likely to be generated in the transition period of R, and has a reduced number of solenoid valves.

[0013]

An EGR device for achieving the above object forms a plurality of exhaust manifolds corresponding to a group of cylinders of an engine, and communicates each exhaust manifold with an intake passage. An EGR device provided with an EGR valve for operating an on-off valve by an air pressure in an EGR passage, wherein an electromagnetic valve controlled by an engine controller is provided in an air pipe from an air pressure supply source, and a distribution valve is provided downstream of the electromagnetic valve. The air flow is supplied to each of the EGR valves, and the flow resistance of the branch passage to each of the EGR valves is formed substantially equal.

In the EGR system for performing the multi-stage EGR, a plurality of exhaust manifolds are formed in correspondence with the cylinder groups of the engine, and multi-stages are formed by an air pressure in an EGR passage which communicates each exhaust manifold with the intake passage. An EGR device provided with a multi-stage EGR valve for operating an on-off valve at each stage for operating the on-off valve of the multi-stage EGR valve from an air pressure supply source via an electromagnetic valve controlled by an engine controller. In addition, air passages branching downstream from the solenoid valve and supplying air to the multi-stage EGR valves via branch passages having substantially the same flow resistance are provided.

The substantially same flow resistance with respect to the flow passage means that a flow passage having the same response timing of the EGR valve is formed. Usually, air pipes having the same diameter and the same length are connected to each other. However, if it is difficult to use the same diameter, same length, and same shape air piping due to the layout around the engine, etc., change the diameter and length, provide an orifice, For example, an air pipe that can take the same response timing is formed to form each of the branch passages. This air pipe can be determined by experiments, calculations, and the like.

According to the above arrangement, the same solenoid valve operates the on-off valve via the branch passage having the same flow resistance.
Since the response of the GR valve, that is, the opening / closing timing coincides, and the EGR of each system is also performed at the same timing, a smooth EGR
Is performed, and the generation of black smoke is suppressed even in the transition period.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the EGR device according to the present invention has a phase of exhaust pulsation close to that of intake pulsation and a phase of intake pulsation so that EGR can be performed by maximizing the pulsation effect of each of exhaust and intake. Only the close cylinders are assembled, and the cylinders are divided into a plurality of cylinder groups by dividing the cylinders into three front cylinders and three rear cylinders, and a plurality of exhaust manifolds 2a and 2b are formed corresponding to the divided cylinder groups.

Each of the exhaust manifolds 2a, 2a
b and the intake passage 1 are connected by EGR passages 4a, 4b, and the EGR valves 5a, 5b, which are opened and closed by pressurized air Ac supplied from an air pressure supply source 21 such as an air tank, are connected to the EGR passages 4a, 4b. 5b and EGR coolers 6a, 6b
Are provided.

The EGR passages 4a and 4b are provided with reed valves 7a and 7b, respectively. When the EGR valves 5a and 5b are opened to perform EGR, the pulsating exhaust pressure P
e and the reed valves 7a, 7b in accordance with the differential pressure between the boost pressure Pb.
b opens and closes, and when the exhaust pressure Pe> the boost pressure Pb, the valve is opened to perform EGR, and conversely, the exhaust pressure Pe <the boost pressure Pb
In this case, the valve is closed to prevent backflow of fresh air Ai.

As shown in FIG. 1 and FIG. 2, an engine controller 31 that inputs an engine speed Ne, an accelerator opening Acc, and the like to an air pipe 13 from an air pressure supply source 21 such as an air tank is input. An electromagnetic valve 11 is provided. The EGR valves 5a, 5b are provided with branch paths 12a, 12b branched from a passage 12c downstream of the solenoid valve 11.
More specifically, the EGR valves 5a and 5b are connected to air cylinders 9a and 9b for opening and closing valves, respectively.

Further, the flow resistances of the branch passages 12a and 12b are formed to be substantially equal. Substantially the same flow resistance with respect to the diversion passages 12a and 12b means that diversion passages are formed so that the response timing of the EGR valves 5a and 5b is the same, and usually the same diameter and the same length of pipes are used. However, if it is difficult to use the same diameter, same length, and same shape air piping due to the layout around the engine, change the diameter and length, or install an orifice. Or by providing a bent portion so that the same response timing can be obtained. The dimensions, shape, and the like of the air pipes forming the respective branch passages 12a and 12b can be determined by experiments, calculations, and the like.

According to the EGR device having the above configuration, the EGR device
The supply of air for opening and closing the valves 5a and 5b is ON / OFF controlled by the same solenoid valve 11 and through the branch passages 12a and 12b having the same flow resistance. 5b can be controlled to open and close, and in the transition period of EGR,
In particular, it is possible to prevent the generation of high-concentration black smoke when the EGR is off.

As shown in FIGS. 3 and 4, the EGR device for performing the multi-stage EGR includes the EGR valve 5a,
Instead of 5b, multi-stage EGR valves 5Aa and 5Ab are provided, and the following air supply is performed to the cylinders 9Aa and 9Ab for opening and closing the multi-stage EGR valves 5Aa and 5Ab.

First, the engine controller 31 controls the air passages 14, 13A from the air pressure supply source 21 to the first air inlets 91a, 91b for opening and closing the cylinders 9Aa, 9Ab in the first stage. A first solenoid valve 11A is provided, and a first air passage 12 downstream of the first solenoid valve 11A is provided.
Ac is branched into first branch passages 12A having substantially the same flow resistance.
a, 12Ab, and the first air inlets 91a, 91b, respectively.
Connect to

The engine controller 31 controls the air passages 14 and 13B from the air pressure supply source 21 to the second air inlets 92a and 92b for performing the second-stage opening and closing operations of the cylinders 9Aa and 9Ab. And a second electromagnetic valve 11B provided downstream of the second electromagnetic valve 11B.
The air passage 12Bc is branched, and second branch passages 12Ba and 12Bb having substantially the same flow resistance are provided.
a, 92b.

An EGR that opens and closes in multiple stages
In the case of a valve, a similar solenoid valve and a similar branch passage having substantially the same flow resistance are further provided and connected to the air inlet of each air cylinder.

An EG having a multi-stage EGR valve having the above configuration
According to the R device, even when the multi-stage EGR valves 5Aa and 5Ab are used, the opening and closing of the multi-stage EGR valves 5Aa and 5Ab is performed at each stage by the same first solenoid valve 11A or second solenoid valve 11B. And a first branch passage 12Aa having the same flow resistance,
Since the control is performed via the 12Ab or the second branch passages 12Ba, 12Bb, the multi-stage EGR valves 5Aa, 5Ab
Can be controlled to open and close.

Therefore, according to the EGR device having these structures, the opening and closing of the EGR valve can be controlled at the same timing, the generation of black smoke can be suppressed, and the number of solenoid valves in the EGR device can be reduced. The structure of the device is simplified, and the cost can be reduced.

[0029]

As described above, according to the EGR device of the present invention, the supply of air for opening and closing the EGR valve is performed by the same solenoid valve and through the branch passage having the same flow resistance.
Since the N / OFF control is performed, the opening and closing of the EGR valve can be controlled at the same timing, and the generation of high-concentration black smoke during the EGR transition period, particularly when the EGR is OFF, can be prevented.

In the case where a multi-stage EGR valve is used, the opening and closing of the EGR valve at each stage is controlled to be ON / OFF by the same solenoid valve and through the branch passage having the same flow resistance.
Since the control is performed, the opening and closing of the EGR valve can be controlled at the same timing. In addition, since the number of solenoid valves can be reduced, the structure of the EGR device can be simplified, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an EGR device of the present invention.

FIG. 2 is a configuration diagram showing an air pipe portion of FIG. 1;

FIG. 3 shows an EGR using the multi-stage EGR valve of the present invention.
It is a block diagram of an apparatus.

FIG. 4 is a configuration diagram showing an air pipe portion of FIG. 3;

FIG. 5 is a diagram illustrating the relationship between boost pressure and exhaust pressure with respect to engine torque and engine speed for explaining the operation of a reed valve.

FIG. 6 is a diagram illustrating a pulsating state of a boost pressure and an exhaust pressure with respect to a crank angle for explaining an operation of a reed valve.

FIG. 7 is a configuration diagram of a prior art EGR device.

FIG. 8 shows an EG using a prior art multi-stage EGR valve.
It is a block diagram of an R apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Intake passage 2, 2a, 2b Exhaust manifold 3 Intake manifold 4a, 4b EGR passage 5a, 5b EGR valve 5Aa, 5Ab Multistage EGR valve 6a, 6b EGR cooler 7a, 7b Reed valve 8 Turbocharger 8a Turbine 9a, 9b Air Cylinder 9Aa, 9Ab Multi-stage air cylinder 11 Solenoid valve 11A First solenoid valve 11B Second solenoid valve 12a, 12b Dividing passage 12Aa, 12Ab First dividing passage 12Ba, 12Bb Second
Dividing passages 12c, 13, 13A, 13B Air passages 12Ac First air passage 12Bc Second air passage 21 Air pressure supply source (air tank) 31 Engine controllers 91a, 91b First air inlets 92a, 92b Second air inlets

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) F02D 21/08 F02D 21/08 LF Term (Reference) 3G062 AA01 AA03 AA05 CA04 CA06 DA04 EA07 EB15 EC00 ED08 ED12 FA08 GA04 GA06 3G092 AA02 AA13 AA17 AA18 AB03 DC08 DG06 DG09 EA22 EC01 FA06 FA15 FA17 FA50 GA03 GA11 GA12 HD07X HE01Z HF08Z

Claims (2)

[Claims] 1. An EGR device comprising: a plurality of exhaust manifolds corresponding to a group of cylinders of an engine; and an EGR valve for operating an on-off valve by pneumatic pressure in an EGR passage connecting the exhaust manifold to an intake passage. An electromagnetic valve controlled by an engine controller is provided in an air pipe from an air pressure supply source, and the air is supplied to each of the EGR valves by dividing the flow downstream of the electromagnetic valve and supplying air to each of the EGR valves. An EGR device characterized in that the flow resistance of the branch passage is substantially equal. 2. A multi-stage EGR valve which forms a plurality of exhaust manifolds corresponding to a group of cylinders of an engine, and which opens and closes valves in multiple stages by air pressure in an EGR passage which communicates each of the exhaust manifolds with an intake passage. EGR provided
An apparatus, wherein at each stage for operating the on-off valve of the multi-stage EGR valve, an air pressure supply source is branched via an electromagnetic valve controlled by an engine controller, and is branched downstream from the electromagnetic valve. An EGR device characterized in that air passages for supplying air to the respective multistage EGR valves via branch passages having the same flow resistance are provided and formed.