Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
1999-09-16
2001-05-08
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
Reexamination Certificate
active
06227183
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a mounting device for an exhaust gas re-circulation valve provided in an exhaust gas recirculation pathway in an internal combustion engine.
BACKGROUND OF THE INVENTION
Diagram
1
is an internal layout diagram of a stepping motor driven exhaust gas re-circulation valve. The stepping motor is a device for controlling the valve by electrical motive force.
In the diagram, reference numeral
1
represents the housing (valve body), and comprises an inlet port
2
connected to the engine exhaust system (not shown), an outlet port
3
connected to the engine air intake system (not shown) and a re-circulation pathway
4
. The valve seat
6
is press-fitted into the re-circulation pathway and prevents the rollpin
13
from detaching.
9
is a bush acting as a bearing,
8
is a holder for preventing the build up of deposits on the bush
9
and is fitted on the same axis as the valve seat
6
between the housing
1
.
5
is a valve which is disposed in abutment with the valve seat
6
and is secured to the valve shaft
7
by caulking. The valve shaft
7
extends through the bush
9
and a spring holder
10
and washer
50
are fixed to its other end by caulking.
12
is a spring which is provided between the spring holder
10
and the housing
1
in a compressed state with the direction of force being in the direction of valve closure.
14
is a cooling passage for cooling the motor and the body of the valve.
20
is the body of the stepping motor and is mounted on the housing
1
by a mounting screw so that the axes correspond.
22
is a bobbin around which the coil
23
is entwined, and which is provided with a yoke
24
and yoke
25
providing a magnetic circuit around the outer circumference.
29
is a terminal which is electrically connected to the coil
23
and which forms the connector element with the motor housing
21
.
27
is a plate which shields magnetically the two coil sections.
26
is a plate preventing the seepage of resin into the inner part of the coil when the motor housing is armor molded.
31
is a magnet.
32
is a rotor which protects the magnet
31
and forms a stopper
32
b
in the axial direction of the motor shaft and the threaded section
32
a
which meshes with the threaded section
33
a
of the motor shaft in the inner section.
30
are bearings fitted to both ends of the rotor
32
.
28
is platespring which pressures the side of the bearing.
33
is a reciprocating motor shaft which converts the rotations of the rotor
32
to rectilinear motion by the threaded sections
32
a
,
33
a
.
34
is a stopper pin which is press fitted into the motor shaft
33
,
41
is a motor bush which functions as a bearing for the motor shaft
33
and prevents rotation around the D hole.
40
is a motor holder disposed between the housing
1
so as to be concentric with the motor housing
21
and which protects the bearing
30
and the motor bush
41
. The spring holder
42
and the joint
43
are fixed to the distal end of the motor shaft
33
by caulking.
44
is a spring which is compressed between the spring holder
42
and the motor holder
40
so that the direction of the force is in the direction of valve opening
5
.
The operation of the valve will be explained on the basis of the force corresponding to the position of the valve in diagram
2
.
With reference to diagrams
1
and
2
, when the valves are opened starting from a position of total valve closure, the rotor
32
, including the magnet
31
, rotates in the direction of valve opening in a step-wise fashion in response to electrical pulses sent from the control unit (not shown) in the terminal
29
. The number of steps correspond with the number of pulses and constitutes precise open loop control. The step-wise rotations are converted into rectilinear motion by the threaded section
32
a
of the rotor
32
and the threaded section
33
a
of the motor shaft
33
. The motor shaft moves in the direction of valve opening (shown in the lower part of the diagram). At this stage, the movement of the motor shaft
33
is assisted by the force of the spring
44
. At the moment when the joint
43
and the spring holder
10
are in abutment as a result of this motion, since the force of the springs is added, the necessary force to move the motor becomes the difference of the springs. Further movement entails increased load including the spring constant of the springs.
When the valves are closed, the above process is reversed. The rotor
32
including the magnet
31
rotates step-wise in the direction of valve closure in response to: electrical pulses sent from the control unit (not shown) in the terminal
29
. At the moment when the joint
43
and the spring holder
10
become detached as the closure process continues, the load of the spring
44
is added to the motor shaft
33
and the load of the spring
12
is added to the valve
5
as a closure force.
A numerical example of the above process will now be discussed. If the setting of the spring is set using the open valve position as a standard, then the spring
12
in the set position has a load of 2 Kg f, and a spring constant of 0.05 Kg f/mm. The spring
44
in the set position has a load of 1.2 Kg f and a spring constant of 0.05 Kg f/mm. If the stroke from motor shaft activation to valve opening is given as 1 mm, and from opened to totally opened as 4.5 mm, then as shown in Diagram
2
, the maximum load on the motor at point of activation and point of total opening is equal to 1.25 Kg f. In addition the force of closure of the valve is 2 Kg f and is equal to the load in the set position of the spring A
12
.
Now referring to the conventional organization of the device (without the spring
44
), since the load condition of the spring
12
is the same, in order to achieve the same closure force as in the second diagram, the force generated by the motor must reach a maximum of 2.225 Kg f ( when the valve is completely opened).
As conventional exhaust gas re-circulation valves are constructed in the above manner, although it is possible to cool the valve body and the stepping motor with coolant introduced into the cooling passage
14
, the valve body must be sufficiently large to form the cooling passage
14
around the housing
1
. Furthermore a pipe is necessary to connect the coolant passage
14
to the engine coolant system which increases the number of necessary parts. The separate coolant system increases the complexity of the layout, all of which increases the price.
The present invention is proposed to solve the above problems. It is a purpose of the present invention to provide, without the need for a separate cooling system, a mounting device for an exhaust gas re-circulation valve which prevents overheating of the valve body and the stepping motor, which controls the movement of the exhaust gas re-circulation valve, due to high temperature exhaust gas. The invention also involves both a reduction in the size of the exhaust gas re-circulation valve and in the costs involved.
It is a further object of the present invention to enable easy mounting of the exhaust gas re-circulation valve on the engine block and to prevent the high temperature of the exhaust gas from being transmitted to the stepping motor.
Further objects include reductions in costs and the use of the invention in conjunction with a seal in the mounting part which prevents the valve seat from dislodging.
DISCLOSURE OF THE INVENTION
The mounting device for an exhaust gas re-circulation valve of the present invention comprises a valve body disposed in connection with the engine exhaust gas re-circulation passage, a valve seat provided in the interior of the valve body, a valve shaft mounted movably in the axial direction of said valve body, a valve which is connected to the valve shaft and which moves in the proximal abutting direction of the valve seat when said valve shaft moves in one direction and which moves away from said valve seat when said valve shaft moves in the other direction and a stepping motor which controls the direction of ope
Kato Yasuhiko
Miyake Toshihiko
Miyoshi Sotsuo
Okada Hidetoshi
Yokoyama Hisashi
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
Wolfe Willis R.
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