Metal working – Method of mechanical manufacture – Shaping one-piece blank by removing material
Reexamination Certificate
2000-12-18
2002-11-05
Bryant, David P. (Department: 3726)
Metal working
Method of mechanical manufacture
Shaping one-piece blank by removing material
C029S412000, C074S089340, C074S089370, C251S129110
Reexamination Certificate
active
06473958
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motor shaft for a rotational-to-direct motion converting motor which is, for example, used for a valve (EGR-V) of an exhaust gas re-circulation system and has a mechanism for converting a rotational motion of a valve motor into a reciprocating motion (or a direct driving motion). Also, the present invention relates to a method of manufacturing the motor shaft.
2. Description of Related Art
As is disclosed in the Published Unexamined Japanese Patent Application H7-27023 (1995), an apparatus for controlling an exhaust gas re-circulation control valve (EGR-V) has been known as a prior art. In this control apparatus, a rotational motion in a stepping motor (or a linear motor) is converted into a linear motion, the EGR-V is driven, a valve opening is adjusted, and a flow rate of a re-circulated exhaust gas is adjusted. Also, a pushing type control valve, in which a motor shaft pushes a valve shaft to open a valve, and a lifting type control valve, in which a motor shaft pulls a valve shaft to open a valve, are disclosed in the Application.
Also, in the Published Unexamined Japanese Patent Application H8-49782 (1996), a technique, in which a compression molding is performed while arranging a non-protruding end of a screw shaft between metal molds, is disclosed as a processing method in the Application. Also, in the disclosure of the Application, the use of another processing method is allowed on condition that no flash is produced on a surface of an engaging-protruding portion in the processing method. Also, a mechanism, in which a motor shaft and a valve-shaft are integrally formed with each other to fix a valve to an end portion of the motor shaft, is disclosed.
In addition, in the Published Unexamined Japanese Patent Application H10-215545 (1998), a technique, in which a round bar is formed into a motor shaft by grinding the round bar with a finishing machine, and a technique, in which a motor shaft is molded according to a metal injection molding method, are disclosed. Also, a technique, in which a screw portion is formed according to a form rolling method, a rotation regulating portion adapted to a phase (or lead and pitch) of the screw portion is formed according to a resin inserting molding or a metal injection molding and the rotation regulating portion and the screw portion are welded together to form a motor shaft, is disclosed.
Here, a structure of a general EGR-V is described.
FIG. 1
is an internal structural diagram of a stepper motor driving type exhaust gas re-circulation control valve which denotes a motor-driven control valve apparatus and in which a stepper motor is used as a motor.
In
FIG. 1
, a housing
1
has an input port
2
leading to an exhaust system of an engine, an output port
3
leading to an intake system of the engine, a pair of reflux passages
4
a
and
4
b
, and a water-cooling passage
14
for cooling the motor and a valve body. A valve seat
6
is inserted into the reflux passage
4
a
under pressure, and a roll pin
13
prevents the valve seat
6
from coming out from the reflux passage
4
a
.
9
indicates a bush functioning as a bearing.
8
indicates a holder which prevents deposits from penetrating into the bush
9
. The holder
8
is arranged with the valve seat
6
on the same axis and is placed between the housing
1
and the valve seat
6
.
5
indicates a valve which is arranged to come in contact with the valve seat
6
. The valve
5
is fixed to a valve shaft
7
at caulking structure. The valve shaft
7
penetrates through the bush
9
, a spring holder A
10
and a washer
13
are fixed to the valve shaft
7
at caulking structure on the opposite side to the valve
5
.
12
indicates a spring A which is arranged between the spring holder A
10
and the housing
1
at a contracted form so as to give a power to the valve
5
in a valve-close direction.
20
indicates a stepper motor. An attaching screw
46
attaches the stepper motor
20
to the housing
1
so as to make an axis center of the stepper motor
20
agree with that of the housing
1
.
22
indicates a pair of bobbins. A coil
23
is wound on each bobbin
22
. A yoke A
24
and a yoke B
25
functioning as a magnetic path are arranged on the outer periphery of each bobbin
22
.
29
indicates a terminal electrically connected with the coils
23
. A connector is formed of the terminal
29
and a motor housing
21
.
27
indicates a plate A magnetically shielding one coil portion from the other coil portion.
26
indicates a plate B which prevents resin from flowing into the inner peripheries of the coil portions when the motor housing
21
is formed.
31
indicates a magnet.
32
indicates a rotor having the magnet
31
. A screw portion
32
a
and a stopper portion
32
b
for stopping the movement of a motor shaft
70
in a longitudinal direction are arranged in the inner periphery of the rotor
32
. The screw portion
32
a
is screwed to a screw portion
70
a
of the motor shaft
70
.
30
indicates a pair of bearings attached to both ends of the rotor
32
.
28
indicates a plate spring generating a side pressure given to the bearings
30
.
70
indicates the motor shaft having the screw portion
70
a
. The screw portion
70
a
is screwed to the screw portion
32
a
so as to make the motor shaft
70
perform a reciprocating motion, so that a rotational motion performed in the rotor
32
is converted into a linear motion of the motor shaft
70
.
34
indicates a stopper pin inserted into the motor shaft
70
under pressure.
41
indicates a motor bush having a bearing function and a rotation preventing function for preventing the rotational motion of the motor shaft
70
. The rotation preventing function is generated by a hole of the motor bush
41
having a D form at cross section.
40
indicates a motor holder having the same center as that of the motor housing
21
. The motor holder
40
is arranged between the motor housing
21
and the housing
1
and holds the bearings
30
and the motor bush
41
.
In the motor having the above configuration, in a valve opening operation, the rotor
32
including the magnet
31
is rotated in a valve-open direction step by step according to a pulse-shaped voltage signal which is sent from a control unit (not shown) to the terminal
29
. In this case, the number of transmitted pulses agrees with the number of stepped motions of the rotor
32
, so that an open loop control can be correctly performed. This step-by-step rotation of the rotor
32
is transmitted to the motor shaft
70
through the screw portion
32
a
of the rotor
32
and the screw portion
70
a
of the motor shaft
70
. Because a rotational motion in the motor shaft
70
is prevented by both a D portion
70
b
of the motor shaft
70
having a semi-circular shape at cross section and a D hole of the bush
41
, the rotational motion of the rotor
32
is converted into a linear motion of the motor shaft
70
, and the motor shaft
70
is moved in a valve-open direction (that is, in the lower direction in FIG.
1
).
Because a conventional motor shaft for a rotational-to-direct motion converting motor has the above configuration, it is difficult to perform the positioning of the motor shaft
70
in the form rolling, and there is a case where the screw portion is not correctly positioned.
Also, a rotation stopping portion (that is, the D portion
70
b
) of the motor shaft
70
is made of a material other than that of the motor shaft
70
to adapt the phase of one screw portion
32
a
to that of the other screw portion
70
a
, and one screw portion
70
a
is fixed to the rotation stopping portion to make the phase of the screw portion
70
a
agree with that of the rotation stopping portion. Therefore, there is a problem that the number of parts of the motor shaft
70
is increased and the processing procedure for the motor shaft
70
is complicated.
In addition, in the manufacturing method of the conventional motor shaft
70
, because a round bar is formed into the conventional motor shaft
70
by
Miyoshi Sotsuo
Yokoyama Hisashi
Bryant David P.
Mitsubishi Denki & Kabushiki Kaisha
Sughrue & Mion, PLLC
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