Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
2001-11-13
2004-03-23
Gimie, Mahmoud (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C123S568230
Reexamination Certificate
active
06708675
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust gas recirculation valve provided in an exhaust gas recirculation passage in an internal combustion engine such as a diesel engine or a gasoline engine.
2. Description of the Prior Art
FIG. 6
is a longitudinal sectional view showing the internal structure of a conventional exhaust gas recirculation valve. Referring to the figure, a valve housing
1
is disposed in connection with an exhaust gas recirculation passage (not shown) of an engine serving an internal combustion engine. The valve housing
1
has a concave portion
2
opened at the top end thereof, an exhaust gas inlet port
3
communicated with the engine exhaust system (not shown) in the lower portion of the bottom wall of the concave portion
2
, an exhaust gas outlet
4
communicated with the engine air intake system (not shown), an exhaust gas passage
5
communicated with the exhaust gas inlet port
3
and exhaust gas outlet
4
, and a part assembly opening
6
in the bottom portion thereof.
A valve seat
7
is press-fitted and set in the exhaust gas passage
5
, a bushing
8
serving as a bearing is press-fitted and set halfway in the exhaust gas passage
5
within the valve housing
1
, a valve rod
9
is slidably inserted in the bushing
8
, a valve
10
is attached on the bottom end of the valve rod
9
and operable to move for closing and opening in an abutting and moving-away direction to the valve seat
7
, a spring holder
11
is fixed on the top end of the valve rod
9
by caulking means, a coil spring
12
is installed between the spring holder
11
and the bottom wall of the concave portion
2
, and the coil spring
12
becomes a pushing means to push the valve
10
in a valve-closing direction to abut on the valve seat
7
.
A cooling water passage
13
is provided around the bottom wall of the concave portion
2
of the valve housing
1
, and the cooling water passage
13
is operable to be connected with a cooling water inlet side pipe (not shown) and a cooling water outlet side pipe (not shown) for being communicated with a cooling water passage in the engine system. A holder portion
14
is integrally formed in the bottom wall portion of the concave portion
2
for preventing a deposit from entering the bushing
8
and a blocking member
15
blocks the part assembly opening
6
.
A stepping motor
20
controls and drives the valve
10
in an opening and closing direction serving as a valve driving means, and a motor housing
21
houses the motor. The motor housing
21
has an opening portion on the bottom surface thereof, and a spacer
23
for water-proofing is previously clamped through a rubber seal ring
22
by a clamp screw
24
on the downward surface of the fringe in the opening portion. The motor housing
21
in which the seal ring
22
and spacer
23
are thus unitized is clamped through the spacer
23
by a mounting screw
25
on the top end portion of the valve housing
1
.
Two yokes
26
for forming a magnetic path are assembled and fixed within the inner circumference surface of the motor housing
21
, two coil bobbins
27
are incorporated within the yokes
26
, solenoid coils
28
serving as a motor coil are wound around each coil bobbin
27
, and the solenoid coils
28
are electrically connected with a terminal
29
serving as a connecter. The terminal
29
is electrically connected with the pulse-sending portion of a control unit (not shown).
A rotor
30
is rotatably held by bearings
31
and
32
inside the motor housing
21
, the bearing
31
existing on the top side of the rotor
30
is incorporated in the motor housing
21
, and the bearing
32
existing on the bottom side of the rotor
30
is incorporated in the spacer
23
. A magnet
33
is held on the outer circumference of the rotor
30
, and a motor shaft
34
is configured to threadedly penetrate the center of the rotor
30
. The motor shaft
34
is located on the extended axis of the valve rod
9
.
A motor bushing
36
is fit in the central opening of the spacer
23
, and the motor shaft
34
is fit slidably in the motor bushing
36
. A motor spring holder
37
is coupled with the bottom end portion of the motor shaft
34
and lies under motor bushing
36
. A motor coil spring
38
lies between the motor spring holder
37
and spacer
23
. The motor coil spring
38
becomes a pushing means of pushing the motor shaft
34
in the opening direction of the valve
10
.
The operation in the conventional exhaust gas recirculation valve will next be described.
First of all, when the valve
10
is opened from the fully closing state, the solenoid coil
28
of the stepping motor
20
is excited by a pulsed voltage fed from the control unit (not shown) to the terminal
29
. The rotor
30
including the magnet
33
thereby stepwise rotates in the direction of valve opening. At this stage, precise open-loop control is performed because the number of the sent pulse is coincident with the step number. This stepwise rotation is changed to a rectilinear motion by a screw feed action through the threaded engagement between the rotor
30
and motor shaft
34
, and thereby the motor shaft
34
travels in the direction of valve opening. At this stage, the travel of the motor shaft
34
is assisted by the pushing force of coil spring
38
. At the moment when the top end of the valve rod
9
abuts on the bottom end of the motor shaft
34
by such travel of the motor shaft
34
, the valve rod
9
moves down by the driving force of the motor shaft
34
against the upward pushing force of the coil spring
12
, and at the same time the valve
10
provided on the bottom end of the valve rod
9
also moves down toward the valve seat
7
, to thereby open the valve. Thereby, the exhaust gas inlet port
3
and exhaust gas outlet
4
are communicated with each other through the exhaust gas passage
5
.
When the valve
10
is closed, the above operation is reversed. That is, the rotor
30
containing the magnet
33
stepwise rotates in the direction of closing the valve by the pulsed voltage sent from the control unit to the terminal
29
, and thereby the motor shaft
34
moves up in the direction of the closing valve. Following the movements, the valve rod
9
also moves up assisted by the upward pushing force of the coil spring
12
, and thereby the valve
10
closes the opening of the valve seat
7
.
Since the conventional exhaust gas recirculation valve is constructed as mentioned above, there exists the following drawbacks. Since the cooling water is introduced into the cooling water passage
13
, the cooling of the system of the valve
10
containing the stepping motor
20
and valve housing
1
, that is, the cooling of so-called valve body can be performed by use of the cooling water. However, because the cooling water passage
13
is provided around the valve housing
1
, the size of the valve body should be large, and further piping for connecting the cooling water passage
13
to the cooling water passage of the engine system is required. Thus, this requires a dedicated water-cooling piping for the exhausted gas recirculation valve in which the number of components is large and the construction thereof is complicated, which results in high-cost.
SUMMARY OF THE INVENTION
The present invention has been accomplished to solve the above-mentioned drawback. An object of the invention is to provide an exhaust gas recirculation valve which may prevent the valve and valve-driving means in the exhaust gas recirculation system from being overheated at an elevated temperature, thereby resulting in cost-down, without a dedicated water-cooling piping for the exhaust gas recirculation valve.
Another object of the invention is to provide an exhaust gas recirculation valve in which the cooling water of the engine system can directly cool the valve housing of the exhaust gas recirculation system with efficiency.
Still another object of the invention is to provide an exhaust gas recirculation valve in which the taking-out passage of cooling water from the engine sys
Kato Yasuhiko
Numata Eiji
Okada Hidetoshi
Yokoyama Hisashi
Gimie Mahmoud
Mitsubishi Denki & Kabushiki Kaisha
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