Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
2002-10-28
2004-07-20
Gimie, Mahmoud (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C310S239000, C251S129130
Reexamination Certificate
active
06763813
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a current passing device of an EGR (exhaust gas recirculation) valve apparatus for constituting a recirculation system of, for example, an exhaust gas.
BACKGROUND ART
This kind of EGR valve apparatus in the prior art used a stepping motor as a valve opening/closing unit, but it has become to use a DC motor in place of the stepping motor in order to comply with increasing resolution, response and output power at the time of adjusting the opening of a valve.
FIG. 1
is a cross sectional view to show the current passing device of an EGR valve apparatus in the prior art.
FIG. 2
is an enlarged cross sectional view of a relevant part of the device in FIG.
1
. FIG.
3
(
a
) is a perspective view to partially show a brush holding pipe portion in FIG.
2
. FIG.
3
(
b
) is an end view of FIG.
3
(
a
).
In
FIG. 1
, a reference numeral
1
denotes a DC motor that is a driving unit (torque generating unit) of a valve for opening and closing an exhaust gas passage; a reference numeral
2
denotes a motor case thereof; a reference numeral
3
denotes a rotor rotatably supported in the motor case
2
via bearings
4
,
5
and the rotor
3
has a screw hole
3
a
which is made to penetrate through at its axial center portion; a reference numeral
6
denotes a magnet mounted on the outer periphery of the rotor
3
; and a reference numeral
7
denotes a stator core which is surrounding the outer periphery of the magnet
6
and a predetermined gap is formed between the stator core
7
and the magnet
6
.
A reference numeral
8
denotes a coil that is arranged on both sides in the axial direction of the stator core
7
and constitutes a stator; a reference numeral
9
denotes a motor shaft that is a valve driving shaft and the motor shaft
9
is formed of a screw shaft and is screwed into the screw hole
3
a
of the above described rotor
3
, thereby being moved in the axial direction by the rotation of the rotor
3
.
A reference numeral
10
denotes a valve shaft abutting member that is integrally formed with the motor shaft
9
and a protruding end (right end in
FIG. 1
) of the valve shaft abutting member
10
abuts an end portion of a valve shaft (not shown) having the above mentioned valve at the tip thereof to make the valve shaft follow the movement in the axial direction of the above mentioned motor shaft
9
to thereby open and close the above described valve.
A reference numeral
11
denotes a cover member which is mounted on an end surface of the motor case
2
in a side of the valve shaft abutting member
10
; a reference numeral
12
denotes a spring retaining member mounted on the protruding end side of the valve shaft abutting member
10
; a reference numeral
13
denotes a valve urging spring which is mounted between the spring retaining member
12
and the above mentioned cover member
11
and the spring
13
urges the valve at the tip of the valve shaft via the valve shaft abutting member
10
in the direction to which the valve opens.
A reference numeral
14
denotes a commutator that rotates integrally with the rotor
3
and has an axial hole
14
a
at the center thereof.
A reference numeral
15
denotes a power source side case which is mounted on an opening end portion on a side of the commutator
14
of the motor case
2
, and the power source side case
15
is made of one piece molded synthetic resin to constitute a main body of the current passing device of the DC motor
1
and is integral with a sensor built in portion
16
in which a position sensor (not shown) for detecting a degree of opening of the above mentioned valve is built and an input/output connector portion
17
in which a connector terminal is built.
In FIG.
1
and
FIG. 2
, a reference numeral
18
denotes a brush holding pipe portion integrally molded with a wall portion opposite to the commutator
14
of the power source side case
15
; reference numerals
19
denote a plurality of axial slits which are made at the brush holding pipe portion
18
; reference numerals
20
denote a plurality of brushes for passing current that are slidably inserted into the above mentioned brush holding pipe portion
18
and the brushes
20
are made of carbon particles and copper particles; reference numerals
21
denote a plurality of lead wires for passing current that are connected to the above mentioned brushes
20
and the lead wires
21
are extended from the slit
19
of the above mentioned brush holding pipe portion
18
and are connected to the connector terminal of the above mentioned input/output connector portion
17
; reference numerals
22
denote a plurality of brush pressing springs which are received in the above mentioned brush holding pipe portion
18
and an urging force of the spring
22
puts the tip of the brush
20
into sliding contact with the above mentioned commutator
14
. Herein, reference symbols
20
a
in
FIG. 2
denote the worn particles of the brush
20
.
Hereinafter, mounting the above mentioned brush
20
and mounting the power source side case
15
on the motor case
2
will be described.
First, when the brush
20
is mounted, in the first place the spring
22
is inserted into and received in the brush holding pipe portion
18
and then the brush
20
is inserted into the brush holding pipe portion
18
and when the brush
20
is inserted the lead wire
21
is slidably fitted in the slit
19
, thereby mounting the brush
20
is finished. After the brush
20
is mounted, the power source side case
15
is fitted in and fixed to the opening end portion of the motor case
2
while the tip of the brush
20
is pressed onto the commutator
14
, thereby mounting the power source side case
15
is finished.
Next, the operation of the device will be described.
When a direct current is supplied to the brush
20
, the direct current is passed through the coil
8
after rectification by the commutator
14
, so that an interaction between a magnetic field generated by the coil
8
and the magnetic field of the magnet
6
generates a rotational torque to the rotor
3
. When the rotor
3
is rotated by the rotational torque, the motor shaft
9
screwed in the screw hole
3
a
of the rotor
3
is forced by the screws thereby to be moved linearly in the axial direction.
Herein, in the case where the motor shaft
9
is moved in the right direction in
FIG. 1
, the valve shaft abutting member
10
is pushed in a direction against the urging force of the spring
13
by the motor shaft
9
to open the valve via the valve shaft connected to the valve shaft abutting member
10
. On the other hand, in the case where the motor shaft
9
is moved in the left direction in
FIG. 1
, the valve shaft abutting member
10
is made to follow the motor shaft
9
by the urging force of the spring
13
to close the valve via the valve shaft connected to the valve shaft abutting member
10
.
Since the current passing device of the EGR valve apparatus in the prior art is constituted in the manner described above, it presents the following problems: the self-heating of the brush
20
, which is caused when current is passed through the brush
20
, and frictional heat, which is generated when the brush
20
is pressed onto the commutator
14
, increase the ambient temperature of the brush holding pipe portion
18
to thermally deform the brush holding pipe portion
18
in the direction sandwiching the brush
20
as shown by a broken line in FIG.
3
(
b
), to impair the sliding ability of the brush
20
by the thermal deformation, which results in poor contact between the brush
20
and the commutator
14
. Thus, it is thought that a clearance between the brush holding pipe portion
18
and the brush
20
is increased in anticipation of the thermal deformation of the brush holding pipe portion
18
, but in this case, there is presented another problem that the brush
20
has a too much allowance and hence causes noises.
Further, there is presented the following problem: since the above mentioned brush holding pipe portion
18
has a simple constitution in which it has t
Fujita Youichi
Hasegawa Satoru
Miyoshi Sotsuo
Takai Katsunori
Castro Arnold
Gimie Mahmoud
Mitsubishi Denki & Kabushiki Kaisha
Sughrue & Mion, PLLC
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