Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
2002-12-23
2004-09-14
Wolfe, Jr., Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
Reexamination Certificate
active
06789532
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a mounting device for mounting an exhaust gas recirculation valve located in a reflux passage of exhaust gas of an internal combustion engine and others.
BACKGROUND ART
FIG. 6
is a cross sectional view showing a conventional mounting device for mounting an exhaust gas recirculation valve. Referring to the drawing, a valve housing
1
includes an exhaust gas inlet
2
that communicates to an exhaust system (not shown) of an engine acting as an internal combustion engine, an outlet
3
that communicates to an air intake system (not shown) of the engine, and a passage
4
that is interposed between the outlet
3
and the mentioned inlet
2
. In the passage
4
, a valve seat
5
is press-fitted. Reference numeral
6
designates a valve rod that passes through a bush
7
. A valve
8
that comes in contact with or separates from the valve seat
5
is mounted at a lower end portion of the valve rod
6
. Numeral
9
designates a holder for preventing a deposit from entering the bush
7
. Numeral
10
designates a spring holder that is given an upward impetus by coil spring (in other words, return spring)
11
. A through-hole
12
is formed in a central portion of the spring holder
10
. A tip portion
6
a
of the mentioned valve rod
6
is caulked and fixed into the through-hole
12
. Due to this caulking, the valve
8
, which is mounted at the lower end portion of the valve rode
6
, is given an impetus at all times in the direction of closing the valve with respect to the valve seat
5
. Furthermore, numeral
13
designates a cooling water passage for cooling a valve body and a motor, as described later. Numeral
15
designates a cap for sealing in an airtight manner.
Numeral
20
designates a stepping motor body serving as a stator assembly including a rotor portion described later. A spacer
21
, which prevents water from entering the stepping motor body
20
, is secured by a clamp screw
23
via a rubber ring
22
at a lower portion of the stepping motor body
20
. A motor bush
25
for holding a motor shaft
24
is disposed in a central opening of the spacer
21
. A spring holder
26
is connected to a lower end portion of the motor shaft
24
. Numeral
28
designates a spring, that is, an assist spring that is disposed between the spacer
21
and the spring holder
26
, and gives an impetus to the motor shaft
24
in the direction of opening the valve
8
.
Numeral
30
designates a bobbin around which a coil
31
is wound, and a yoke
32
and a yoke
33
providing a magnetic passage are formed about an outer periphery of the bobbin
30
. Numeral
34
designates a terminal, which is electrically connected to the coil
31
and forms a connector section along with a motor housing
35
. Numeral
36
designates a plate for shielding two coil parts in terms of magnetism. Numeral
37
designates a plate for preventing resin from coming into an inner periphery of the coil part at the time when the motor housing
35
is molded exteriorly.
Numeral
40
designates a magnet. Numeral
41
designates a rotor, which holds the magnet
40
, and at an inner periphery portion of which a female-threaded part
41
a
engaging with a male-threaded part
24
a
of the motor shaft
24
, and a stopper
41
b
in an axial direction for the motor shaft
24
are formed. Numeral
42
designates a bearing mounted on both ends of the rotor
41
. Numeral
24
b
designates a stopper part provided at the motor shaft
24
.
The stepping motor body
20
as constructed above is mounted onto the mentioned valve housing so as to be coaxial by means of a fixing screw
44
.
In addition, relation between the rotor
41
and the motor shaft
24
is now described. A lower half of the motor shaft is a plate-like member
24
c
, which includes a shaft in the direction of the motor shaft
24
at the center part thereof. The plate-like member
24
c
is inserted through a substantially square through hole of the motor bush
25
to be prevented from rotation. Further, the plate-like member
24
c
is held so as to be capable of moving in an axial direction thereby enabling the motor shaft
24
to move in up and down direction. By the screw-engagement between the male-threaded part
41
a
of the rotor
41
and the female-threaded part
24
a
of the motor shaft
24
, the rotation of the rotor
41
causes the motor shaft
24
to move up and down. The axial stopper
41
b
is a protrusion provided in a recess at an inner periphery of the rotor
41
. The axial stopper
41
b
comes into contact with the plate-like member
24
c
of the axial stopper
41
b
at an upper dead point of the motor shaft
24
due to the rotation of the rotor
41
. The rotor
41
is prevented from further rotation in one direction beyond the upper dead point, thereby the rise of the motor shaft
24
being stopped. At this time, the rotor
41
can rotate in the other direction, and therefore the axial stopper
41
b
does not come in contact with the plate-like member
24
c
any more when the motor shaft
24
comes down by the rotation of the rotor
41
in the other direction. In this manner, the rotor can continue to rotate in the other direction, and the motor shaft can come down further.
Now operation is described. First, for starting from the state of the valve being fully closed, the coil
31
of the stepping motor
20
is energized in response to a pulsed voltage transmitted to the terminal
34
from a control unit (not shown) at the time of opening operation of the valve. Then the rotor
41
including the magnet
40
rotates stepwise in the direction of opening the valve. At this time, number of transmission pulses is coincident with that of steps, thereby enabling an accurate open-loop control. This stepwise rotation is converted into a liner movement by and with the female-threaded part
41
a
of the rotor
41
and the male-threaded part
24
a
of the motor shaft
24
, and the motor shaft
24
moves in the direction of opening the valve (downward). At this time, the motor shaft
24
is assisted by the force of the assist spring
28
in the movement thereof. When the movement goes on and a top end surface of a tip portion
6
a
of the valve rod
6
comes in contact with a lower end surface of the motor shaft
24
, the valve rod
6
comes down against an upward impetus exerted by the return spring
11
due to a drive force of the motor shaft
24
. Furthermore, the valve
8
, which is mounted on the lower end portion of the valve rod
6
, also comes down with respect to the valve seat
5
to open the valve. Thus, the inlet
2
and the outlet
3
of the exhaust gas communicate with each other via the passage
4
.
At the time of closing the valve, the operation reverse to the mentioned one is carried out. The rotor, which includes the magnet
40
, rotates stepwise in the direction of closing the valve in response to a pulsed voltage transmitted from the control unit (not shown) to the terminal
34
. This rotation causes the motor shaft
24
to move in the direction of closing the valve (upward). Following this movement, also the valve rod
6
rises by an upward impetus exerted by the coil spring
11
, and then the valve
8
closes the opening of the valve seat
5
.
The conventional mounting device for mounting the exhaust gas recirculation valve is constructed as described above, and therefore the stepping motor body and the valve body can be cooled with the cooling water introduced into the cooling water passage
13
. However, since the cooling water passage
13
is formed around the valve housing
1
, the valve body becomes large in size. Moreover, e.g., a piping for connecting the cooling water passage
13
to that of the engine system is required, which means that a water-cooling piping only for mounting the exhaust gas recirculation valve of complicated construction composed of a large number of parts is required. Hence, a problem exits in that the structure as described above brings about an increase in cost.
The present invention was made to solve the problems described above, and has an object of achieving
Kato Yasuhiko
Yokoyama Hisashi
Mitsubishi Denki & Kabushiki Kaisha
Wolfe, Jr. Willis R.
LandOfFree
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