Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
1999-11-15
2002-02-19
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C123S568110, C123S339100
Reexamination Certificate
active
06347620
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a control valve assembly for regulating the flow amount of exhaust gas or intake gas flowing through an internal combustion engine of an automobile, etc., by opening and closing a valve by linear motion.
BACKGROUND ART
With the operation of an internal combustion engine of an automobile, etc., exhaust gas or intake gas, which is a controlled fluid, flows and the flow amount of the controlled fluid is regulated by control valve assemblies. The flow amount of the controlled fluid may be regulated, for example, by an exhaust gas recirculation valve (hereinafter EGR valve) or by an idle speed control valve (hereinafter ISC valve), functioning as a control valve assembly.
FIG. 5
is a schematic structural diagram of a conventional EGR valve as shown in Japanese Utility Model Publication No. 6-14054, and
FIG. 6
is a cross-sectional view showing the construction of the EGR valve in FIG.
5
.
In
FIGS. 5 and 6
, exhaust gas conveyed from an exhaust pipe
3
connected to a combustion chamber
2
in an engine
1
is cooled by a cooler
4
, then conveyed to an EGR valve
5
for regulating the recirculation of the exhaust gas to an intake pipe (not shown) in the engine
1
. The flow amount of the exhaust gas is regulated by a regulating valve
6
disposed in the EGR valve
5
for regulating the opening of an exhaust gas passage in response to a negative-pressure signal from the intake pipe. This exhaust gas is resupplied to the intake pipe. In this manner, the exhaust gas is recombusted in the engine
1
, thus reducing toxic nitrogen oxides in the exhaust gas. Moreover, the regulating valve
6
is operated by the pressure difference in a negative-pressure chamber
8
formed above a diaphragm
7
.
A housing
10
is provided with an input port
11
connected to the exhaust pipe
3
of the engine
1
, an output port
12
connected to the intake pipe of the engine
1
, and a fluid passage
13
in which the exhaust gas which is the controlled fluid flows. Partway along the fluid passage
13
, the regulating valve
6
contacting a valve seat
14
formed within the housing
10
is connected to a valve shaft
15
and slides within a shaft-bush
16
secured to the housing
10
. A holder
17
disposed below the shaft-bush
16
in an upper portion of the fluid passage
13
prevents penetration by carbon or foreign matter contained in the exhaust gas.
Moreover, although not shown in the figures in some cases, penetration by carbon or foreign matter contained in the exhaust gas is prevented by disposing labyrinth packing, shielding, metal-fiber packing, and the like, inside the holder
17
.
The diaphragm
7
is sandwiched by keep plates
20
a
,
20
b
, and the upper end
21
of the valve shaft
15
is mounted on the central portion thereof by crimping. A lower negative-pressure case
22
is disposed in close contact with an upper portion of the shaft-bush
16
and is attached to the housing
10
by a screw
23
through packing
27
described below. The negative-pressure chamber
8
is formed between the diaphragm
7
and an upper negative-pressure case
24
and negative pressure is introduced thereto from a negative-pressure source (not shown) by means of a negative-pressure inlet pipe
25
passing through and mounted on the upper negative-pressure case
24
which cooperates with the lower negative-pressure case
22
to hold the perimeter of the diaphragm
7
therebetween. Moreover, the regulating valve
6
connected to the valve shaft
15
is pressed downwards by a spring
26
disposed inside the upper negative-pressure case
24
, but the diaphragm
7
may move upwards depending on the magnitude of the negative pressure conveyed to the negative-pressure chamber
8
, and for that reason the regulating valve
6
may be driven upwards, varying the opening of the regulating valve
6
. The packing
27
is interposed between the housing
10
and the lower negative-pressure case
22
and shuts out the heat from the housing
10
.
In a construction having a single shaft-bush such as that in
FIG. 6
, because the amount of fluid controlled by EGR valves has increased with the strengthening of exhaust gas regulations, or because the amount of exhaust from truck engines
1
is large and the recirculation of exhaust gas by EGR valves for trucks is great, the need for large bores has increased even in the case of single regulating valves, and therefore, there has been a tendency for the weight on the end of the valve shaft to be problematic.
FIG. 7
shows a control valve assembly in which both ends of a valve shaft having a regulating valve secured thereto are held by shaft-bushes or brace plates in order to improve linear-drive control valve assemblies in which stable retention against the vibrations, etc., of the internal combustion engine was difficult with only a single shaft-bush as above.
FIG. 7
is a cross-sectional view showing the construction of another conventional EGR valve such as that disclosed in Japanese Patent Application Laid-Open No. 58-37374, for example.
In the numbering used in
FIG. 7
, the same numbering as that used in
FIG. 6
represents identical or corresponding parts. The construction shown in
FIG. 7
has, in addition to the construction of
FIG. 6
, a valve shaft
15
connected to the regulating valve
6
extending beyond the regulating valve
6
, an end portion
15
a
thereof being guided by insertion into the central boss
30
a
of a brace plate
30
secured to the housing
10
.
Meanwhile, there may be large surges in the controlled fluid, and
FIG. 8
shows a control valve assembly in which two regulating valves are disposed coaxially, so that the pressure of the controlled fluid is applied to the two regulating valves in mutually opposite directions in order to cancel out these surges. In this construction, the valve shaft securing the regulating valves must be lengthened.
FIG. 8
is a cross-sectional view showing the construction of a conventional ISC valve such as that disclosed in Japanese Utility Model Application Laid-Open No. 58-4759, for example.
In the numbering used in
FIG. 8
, the same numbering as that used in
FIG. 6
or
7
represents identical or corresponding parts. The ISC valve shown in
FIG. 8
has a valve shaft
15
contacting a plunger rod
32
moved linearly by a solenoid coil
31
, and two regulating valves
6
connected thereto. Because the length of extension of the valve shaft
15
beyond the shaft-bush
16
secured to the housing
10
on the solenoid coil
31
side is particularly large and cannot be supported by the shaft-bush
16
alone, an end portion
15
a
of the valve shaft
15
at the opposite end from that contacting the solenoid coil
31
being the drive source for opening and closing the regulating valve
6
is guided by insertion into the central boss
30
a
of the brace plate
30
, in the same way as in
FIG. 7
, with the aim of stabilizing sliding. In addition, in order to avoid deterioration of sliding due to carbon or foreign matter contained in the controlled fluid penetrating the sliding portion between the valve shaft
15
and the shaft-bush
16
or the sliding portion between the central boss portion
30
a
and the end portion
15
a
, the central boss portion
30
a
of the brace plate
30
constructed in the fluid passage
13
is constructed such that a shielding material
33
capable of expanding and contracting freely relative to the linear motion so as not to affect the sliding covers the shaft-bush
16
on the side nearest to the fluid passage
13
, or the central boss portion
30
a
and the end portion
15
a.
However, because conventional EGR valves and ISC valves have had the above constructions, they have suffered from the problems described below.
In a control valve assembly in which both sides of the regulating valve secured to the valve shaft are held by bushes or brace plates in order to achieve linear motion stabilized against the vibrations of the internal combustion engine, etc., the shaft-bush holding the valve shaft connected to the diaphragm or the solenoid coil be
Gimie Mahmoud
Mitsubishi Denki Kabushik Kaisha
Sughrue & Mion, PLLC
Wolfe Willis R.
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