Exhaust gas re-circulation valve

Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture

Reexamination Certificate

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Details

C123S568290

Reexamination Certificate

active

06279552

ABSTRACT:

FIELD OF THE INVENTION
The present invention is related to a exhaust gas re-circulation valve disposed in exhaust gas re-circulation passages of internal combustion gasoline or diesel engines for the purpose of returning engine exhaust gas back to the combustion chamber of the engine.
BACKGROUND ART
FIG. 1
is a cross section showing the layout of an EGR valve (exhaust gas re-circulation valve) as disclosed for example in JP-A-6/147025. In the figure, reference numeral
1
represents the valve housing (valve body),
1
a
is a first port allowing inflow of engine exhaust gas, lb is a second port allowing inflow of said exhaust gas,
1
c
is a third port allowing the outflow of exhaust gas inflowing from the first and second ports
1
a
and
1
b
,
2
is a valve shaft,
3
and
4
are two valves formed as a unit and secured to the valve shaft
2
,
5
is a diaphragm connected to the valve shaft
2
,
6
is a set spring tensioning the diaphragm
5
on the valve shaft side
2
(the direction of closure of the valve
3
),
7
is a source of negative pressure,
19
is a diaphragm chamber conducting negative pressure from the source of negative pressure
7
,
20
a
is a valve seat secured to the housing
1
by press-fitting or the like and in abutment with one of the valves
3
,
20
b
is a valve seat secured to the housing
1
by press-fitting or the like and in abutment with the other valve
4
.
The operation of the invention will now be explained.
Two valves
3
,
4
are fixed to respective valve seats
20
a
,
20
b
and are in the closed position. When negative pressure is applied to the diaphragm
5
, the valve shaft
2
together with the two valves
3
,
4
move upwards and put the first and second ports
1
a
,
1
b
in the open position and in communication with the third port
1
c
. When in the open position, engine exhaust gases flow into the valve housing
1
from the first and second ports
1
a
,
1
b
and outflow via the third port
1
c
. The gases may reenter the engine combustion chamber via the intake passage. As a result, it is possible to control increases in engine temperature and combustion of excess oxygen by controlling combustion by the amount of inflammable exhaust gas mixed in the engine combustion chamber even when the engine is on lean burn mode which uses a low mix ratio of air to fuel. It is also possible to control increases in nitrogen oxides (NO
x
) which accompany increases in engine temperature and combustion gases which are problems associated with lean burn mode.
However, the following problems are associated with conventional exhaust gas re-circulation valves constructed as above. Although the valve seats
20
a
,
20
b
are secured to the valve housing body
1
by press fitting or the like, irregularities easily occur in the process accuracy of the seats or in measurements when the seats are affixed. Such irregularities result in the formation of gaps leading to gas leaks between the valve and the seat when the valve is closed. Furthermore, the high temperature and pressure exhaust gases create overheating and thermal expansion in the valve housing
1
, the valve shaft
2
and the valves
3
,
4
. If the rate of the thermal expansion of these respective elements differs, a gap is created between the valve and valve seat and an exhaust gas leak results. Such exhaust gas leaks lead to the problem that, for example, when the engine is idling, extreme decreases in engine revolutions may occur, thus making idling unstable.
It is a purpose of the present invention to solve the above problems by the provision of an exhaust gas re-circulation valve without gaps between the valve and valve seat when the valve is closed, such gaps being caused by irregularities in the process and assembly accuracy of parts such as the valve and the valve seat.
It is a further purpose of the present invention to provide an exhaust gas re-circulation valve which minimizes irregularities in the process and assembly accuracy of parts such as the valve and valve seat as well as prevents the formation of gaps between the valve and valve seat when the valve is closed which are caused by the above irregularities. The exhaust gas re-circulation valve therefore does not allow valve opening when the valve is in the closed position due to the thermal expansion of parts as a result of high temperature exhaust gases.
It is a further purpose of the present invention to provide an exhaust gas re-circulation valve which allows for the simple elimination of gaps formed between the valve and valve seat in the closed valve position due to irregularities in processing or assembling accuracy of parts when the exhaust gas re-circulation valve is assembled.
It is a further purpose of the present invention to provide an exhaust gas re-circulation valve in which the valve seat alone can absorb gaps formed between the valve and the valve seat when in the closed position due to irregularities in the process and assembly accuracy of the parts.
It is a further purpose of the present invention to provide an exhaust gas re-circulation valve in which the valve itself can absorb gaps formed between the valve and valve seat when in the closed position due to irregularities in process or assembly accuracy.
It is a further purpose of the present invention to provide an exhaust re-circulation valve which does not open when in the closed position due to thermal expansion of the valve housing and the valve shaft as a result of high temperature exhaust gas even if for example the rate of thermal expansion of the valve housing and the valve shaft is different.
DISCLOSURE OF THE INVENTION
The exhaust re-circulation valve of the invention consists of a valve housing having an exhaust gas inlet and outlet connectable to the engine exhaust gas re-circulation passage as well as a first side passage from the inlet side and a second side passage branching from the first side passage, a first and second passage aperture formed in the branching communicating part of the first and second side passages, first and second valve seats provided in the first and second passage apertures, a valve shaft movably mounted in the axial direction of the valve housing and first and second valves which are mounted on the valve shaft and which close in abutment with the first and second valve seats when the valve shaft moves in one direction. In the exhaust gas re-circulation valve, either the valve seat or the valve or both have an adjusting mechanism allowing for the closing abutment of both the first valve with the first valve seat and the second valve with the second valve seat by a change in position or shape, when the valve shaft is mounted on the valve housing.
The exhaust gas re-circulation valve allows for the closing abutment of both the first valve with the first valve seat and the second valve with the second valve seat by providing for a change in shape or position of at least one of the valve or valve seat when the valve shaft is mounted on the valve housing. Hence even if there is an irregularity in the processing or assembling of the components of the exhaust gas re-circulation valve, the formation of any gaps between the valve and valve seat as a result of the irregularities can be prevented.
In the exhaust gas re-circulation valve according to the present invention, at least one of the first and second valves is movably mounted in the axial direction with respect to the valve shaft.
In this way, even in the event of a gap trying to form, the exhaust gas re-circulation valve provides for the elimination of gaps between the valve and the valve seat by pressure being exerted in the direction of closing abutment of the valve with the valve seat due to the elasticity of the elastic member. Therefore irregularities in the assembly or processing of the component parts of the exhaust gas re-circulation valve can be absorbed by the displacement of the valve due to the elasticity of the elastic member. As a result gaps do not form between the valve and the valve seat. Furthermore even if the valve shaft or the valve housing undergo t

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