Electricity: motive power systems – Plural – diverse or diversely controlled electric motors
Reexamination Certificate
2002-05-31
2004-07-06
Nappi, Robert (Department: 2837)
Electricity: motive power systems
Plural, diverse or diversely controlled electric motors
C318S005000, C318S008000, C318S039000
Reexamination Certificate
active
06759818
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromotive actuator for use in operating, for example, a movable nozzle of a rocket and to a method for controlling the same.
2. Description of Related Art
Conventionally, as such an electromotive actuator as mentioned above, there is, for example, an electromotive actuator
51
which, as shown in
FIG. 6
, includes: a first motor
55
and a second motor
56
accommodated in a parallel state to each other in a housing
54
which is pivotally connected to a fuselage R
1
; a ball screw
50
disposed in parallel to the first motor
55
and the second motor
56
; a third gear
58
attached to a lead
52
of this ball screw
50
and simultaneously engaged both with a first gear
57
and a second gear
59
which are attached to respective output shafts of the first motor
55
and the second motor
56
; and an arm
61
attached coaxially with the lead
52
to a housing
60
which is integrally structured with a nut
53
of the ball screw
50
.
This electromotive actuator
51
is so structured that, for example, when the first motor
55
is malfunction, the lead
52
of the ball screw
50
is driven only with the second motor
56
to move the arm
61
together with the housing
60
in an arrow X direction.
As another electromotive actuator different from this electromotive actuator
51
, there is an electromotive actuator
71
which, as shown in
FIG. 7
, includes: a first motor
75
and a second motor
76
accommodated in a coaxial state with each other in a housing
74
which is pivotally connected to a fuselage R
2
; a ball screw
70
disposed perpendicularly to the first motor
75
and the second motor
76
; a differential gear array
79
which connects respective output shafts of the first motor
75
and the second motor
76
to a lead
72
of this ball screw
70
; and an arm
81
attached coaxially with the lead
72
to a housing
80
which is integrally structured with a nut
73
of the ball screw
70
, and in the first motor
75
and the second motor
76
, a first brake
77
and a second brake
78
for restricting the rotations of the respective output shafts are provided.
This electromotive actuator
71
is so structured that, for example, when the first motor
75
is malfunction, the first brake
77
brakes the output shaft of the first motor
75
and the lead
72
of the ball screw
70
is driven only with the second motor
76
to move the arm
81
together with the housing
80
in an arrow X direction.
Furthermore, as another electromotive actuator different from the electromotive actuators
51
,
71
described above, there is an electromotive actuator
91
which, as shown in
FIG. 8
, includes: a motor
95
accommodated in a housing
94
which is pivotally connected to a fuselage R
3
; a lead
96
of a ball screw disposed coaxially with this motor
95
; a nut
98
of the ball screw integrally structured with a housing
97
which is coaxially disposed with the motor
95
; and an arm
99
which is positioned on a side of the housing
97
opposite the nut
98
and which is coaxial with the motor
95
, and this electromotive actuator
91
is so structured that the arm
99
is moved in an arrow X direction together with the housing
97
by rotating the motor
95
.
In this case, as a multiphase motor used in the above-described electromotive actuators
51
,
71
,
91
, there is, for example, a three-phase brushless motor
100
which is, as shown in
FIG. 10
, provided with totally two sets of windings
101
,
102
of an A system and a B system. The windings
101
,
102
of this three-phase brushless motor
100
are both connected to inverters C, C respectively and electric currents flowing through the two sets of the windings
101
,
102
are feedback to interface circuits
105
,
106
via these inverters C, C respectively to perform electric current control.
In the above-described electromotive actuators, however, the electromotive actuator
51
shown in
FIG. 6
has a problem that efficiency of the electromotive actuator
51
is lowered due to an inertia load of the first motor
55
when the first motor
55
is malfunction and only the second motor
56
is operated.
Moreover, in order to prevent the influence of the inertia load of the first motor
55
, a clutch mechanism becomes necessary, and there exists a problem that reliability of a power transmission system of the electromotive actuator
51
is lowered.
The electromotive actuator
71
shown in
FIG. 7
has a problem that, since its mechanism system is relatively complicated, reliability cannot be said to be high, and in addition, manufacturing cost may possibly be increased.
Furthermore, in the electromotive actuator
91
shown in
FIG. 8
, when the arm
99
is fixed in a predetermined position while the motor
95
is burdened with a load, the position is maintained by a positioning servo based on a feedback signal from a not-shown position sensor, so that electric currents are concentrated to a power transistor for fixing (for example, a transistor C
1
) of an inverter C, as shown in
FIG. 9
, to increase heat generation due to a resistance loss of this power transistor C
1
, and therefore, there exists a problem that it cannot be said that there is no possibility that the inverter C is damaged.
Meanwhile, in the conventional three-phase brushless motor
100
used in the above-described electromotive actuators
51
,
71
,
91
, when, for example, the set of the windings
101
or the inverter C of the A system has a trouble, the three-phase brushless motor
100
operates only with the remaining set of the windings
102
of the B system since the two sets of the windings
101
,
102
are independent from each other, but there exists a problem that its output power is reduced by half.
Moreover, there exists problems that, when even one phase out of three phases becomes out of order in the remaining set of the windings
102
of the B system, an inoperable state is caused, and in addition, the damage of one phase induces the damage of the other phases when the inverters C, C are out of order in a normal short-circuit mode. Therefore, solving these problems has been a conventional object.
The present invention is made in view of the above-described conventional problems, and an object of an invention according to claim
1
and claim
2
is to provide an electromotive actuator which can realize structure simplification and reduction in manufacturing cost without lowering power transmission efficiency and reliability; an object of an invention according to claim
3
and claim
4
is to provide an electromotive actuator and a method for controlling the electromotive actuator which can reduce a resistance loss of a power transistor, and in addition, can realize uniform thermal distribution, and as a result, can downsize an inverter and enhance reliability; and an object of an invention according to claim
5
and claim
6
is to provide a multiphase motor and a method for controlling the same which can not only prevent an inoperable state but also suppress decrease in output power even when an inverter is malfunction or one phase out of multi-phases of windings has a trouble, and in addition, which can almost eliminate the possibility that the damage of one phase induces the damage of the other phases when the inverter is out of order in a normal short-circuit mode.
SUMMARY OF THE INVENTION
An electromotive actuator according to claim
1
of the present invention comprises a first motor and a second motor, and is characterized in the structure that a lead of a ball screw is disposed coaxially with a motor rotary shaft on a side of one motor out of the first motor and the second motor and a nut of the ball screw is disposed coaxially with the motor rotary shaft on a side of the other motor out of the first motor and the second motor, thereby connecting the first motor and the second motor to each other via the ball screw. This structure of the electromotive actuator is adopted as means for solving the conventional problems described abov
Colon Santana Eduardo
IHI Aerospace Co., Ltd.
Nappi Robert
LandOfFree
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