Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2003-05-16
2004-05-18
Lam, Thanh (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06800R, C318S254100
Reexamination Certificate
active
06737771
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a device for stabilizing torque of a brushless servo motor used as a driving source such as a throttle valve, an actuator, an exhaust gas recirculation (hereinafter referred to as EGR) valve and the like.
BACKGROUND ART
FIG. 1
is an explanatory diagram in which a valve
11
of the EGR valve arranged in an exhaust gas return passage (c) for making an exhaust gas passage (a) of an engine E communicate with an intake gas passage (b) thereof is an object to be controlled and in which a brushless servo motor
21
is driven by an output of a control section
100
to control an opening of the valve
11
.
FIG. 2
is a longitudinal cross sectional view to show a constitution of the EGR valve having the brushless servo motor
21
as a driving source to which a servo control device is applied. In
FIG. 2
, a reference numeral
1
denotes a valve body in which a passage communicating with the exhaust gas return passage (c) disposed in a recirculation system of an exhaust gas is formed. When the valve
11
is moved up as shown in the drawing, it is put into contact with a seat
12
to thereby close the exhaust gas return passage (c) and when the valve
11
is moved down, it is separated from the seat
12
to thereby open the exhaust gas return passage (c).
A reference numeral
21
denotes a brushless servo motor to be a driving means (torque generating source) of a valve for opening/closing the exhaust gas passage,
22
denotes a motor case mounted on the valve body
1
,
23
denotes a rotor rotatably supported in the motor case
22
via bearings
24
,
25
, and the rotor
23
has a screw hole
23
a
which is made through a central portion of a shaft. A reference numeral
26
denotes a magnet mounted on an outer peripheral portion of the rotor
3
,
27
denotes a stator core surrounding an outer periphery of the magnet
26
, and between this stator core
27
and the above mentioned magnet
26
is formed a predetermined gap.
A reference numeral
28
denotes a coil that is arranged on the stator core
27
and it constitutes a stator,
29
denotes a motor shaft to be a valve driving shaft, and this motor shaft
29
is made as a screw shaft and screwed into the screw hole
23
a
of the above mentioned rotor
23
and made to move in an axial direction by a rotation of the above mentioned rotor
23
.
A reference numeral
30
denotes a valve shaft abutting member integrally formed with the motor shaft
29
. By making a top end of a valve shaft
13
having the above mentioned valve
11
at its top end abut against the tip (bottom end in
FIG. 1
) of this valve shaft abutting member
30
, the valve shaft
13
is made to follow a movement in the axial direction of the above mentioned motor shaft
29
to thereby open/close the above mentioned valve
11
.
A reference numeral
31
denotes a covering member mounted on an end surface of the valve shaft abutting member
30
side in the motor case
22
,
32
denotes a spring retaining member mounted on a tip side of the valve shaft abutting member
30
,
33
denotes a spring for urging the valve, which is hung between the spring retaining member
32
and the above mentioned covering member
31
, and this spring
33
urges the valve
11
at the tip of the valve shaft
13
via the valve shaft abutting member
30
in a direction that opens the valve
11
. A reference numeral
14
denotes a spring receiver mounted on the top end of the valve shaft
13
and between the spring receiver
14
and the valve body
1
is provided a return spring
18
.
A reference numeral
35
denotes a power source side case mounted on an opening end portion of the motor case
22
. This power source side case
35
is an integrally molded part made of synthetic resin and constitutes a main device body for passing a current through the brushless servo motor
21
and is an integral combination of a board
37
for mounting hall devices
36
and an input/output connector part
38
having a connector terminal
38
a
. A reference numeral
39
denotes a magnet that is mounted on an end of the rotor so as to move opposite to the hall device
36
.
FIG. 3
is a control circuit diagram of the brushless servo motor
21
in the prior art. The control circuit has hall devices
36
U,
36
V,
36
W for detecting a position of the rotor
23
, a switching unit
40
that includes a group of transistors for receiving the signals of these hall devices and switching the passing of a current through coils
28
U,
28
V,
28
W, and passes the current through the coils
28
U,
28
V,
28
W sequentially to thereby rotate the rotor
23
in a given direction.
The above mentioned switching unit
40
has switching devices (hereinafter referred to as switch devices)
41
U,
41
V,
41
W that receive output signals of the hall devices
36
U,
36
V,
36
W to be brought into conduction; an interrupting section
42
that receives output signals of the switch devices
41
U,
41
V,
41
W to output an interrupting signal; a signal processing block
43
that receives and processes output signals of the above mentioned hall devices
36
U,
36
V,
36
W based on the output signal of the interrupting section
42
; switch devices
44
to
49
that receive the output signals of the signal processing block
43
to be brought into conduction; and pairs of switch devices
50
and
51
,
52
and
53
,
54
and
55
each pair of which are connected in series to each other, have one end of one of coils
28
U,
28
V,
28
W connected to their connection midpoint, and change a state of conduction based on the output signal of the switch devices
44
to
49
.
The above mentioned signal processing block
43
has a digital input port
61
for receiving the output signals of the hall devices
36
U,
36
V,
36
W; a counter
62
for reading in an output of the digital input port
61
; a PI control computing section
64
for performing a PI control computation based on an output signal of the counter
62
and an output signal of a target value determining section
63
; an excitation duty computing section for performing an excitation duty computation based on an output signal of the PI control computing section
64
; an excitation phase computing section
66
for computing an excitation phase based on an output signal of the excitation duty computing section
65
and an output signal of the digital input port
61
; a digital output port
67
for outputting an ON signal based on an output signal of the excitation phase computing section
66
; and a PWM output port
68
for outputting a PWM signal based on an output signal of the excitation phase computing section
66
and an output signal of the excitation duty computing section
65
.
Next, an operation will be described.
The target value determining section
63
determines a target value. When the output signal of the hall devices
36
U,
36
V,
36
W detecting the position of the rotor
23
brings any one of the switch devices
41
U,
41
V,
41
W into conduction, an output signal of the interrupting section
42
receiving the conduction signal makes the digital input port
61
and the counter
62
start receiving an input signal.
The PI control computing section
64
performs the PI control computation based on a present value inputted via the counter
62
and a target value from the target value determining section
63
, and the excitation duty computing section
65
performs an excitation duty computation based on a result of the PI control computation and outputs a result of the excitation duty computation to the excitation phase computing section
66
and the PWM output port
68
.
The excitation phase computing section
66
performs the excitation phase computation based on the given result of the excitation duty computation and the input signal received via the digital input port
61
, and outputs a result of the excitation phase computation to the digital output port
67
and the PWM output port
68
.
The digital output port
67
outputs an ON signal, for example, to a terminal U based on the output signal of the excitation phase computing se
Fujita Youichi
Kawamura Satoshi
Miyoshi Sotsuo
Lam Thanh
Mitsubishi Denki & Kabushiki Kaisha
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