Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2002-01-28
2003-05-27
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S07500D
Reexamination Certificate
active
06570282
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a cylinder servo motor having integrated therein a controller, a detector, a servo motor, a ball screw nut, and a ball screw shaft.
BACKGROUND OF THE INVENTION
FIG. 14
shows a related-art cylinder servo motor. As shown in the drawing, reference numeral
63
designates a motor serving as a drive source;
64
designates a rotational speed detector for detecting the rotational speed of the motor
63
;
68
designates a ball screw shaft;
67
designates a ball screw nut engaged with the ball screw shaft
68
; and
65
designates a hollow cylinder rod. A load is connected to a load-side end
65
a
, and an opposite end
65
b
of the cylinder rod
65
is fastened to the ball screw nut
67
. A rotary shaft bearing
82
is fitted around an end
68
a
of the ball screw shaft
68
. A motor shaft
63
a
and the end
68
a
of the ball screw shaft
68
are coupled together by means of a flexible coupling
70
. Reference numeral
77
designates an inner ring fastening nut. The inner ring fastening nut
77
, along with an outer ring fastening nut
76
screw-engaged with an inner peripheral wall of a cylinder case
66
, fixes the rotary shaft bearing
82
. The cylinder rod
65
is supported by a sleeve shaft bearing
83
which is fastened to a load-side end
66
a
of the cylinder case
66
and has an oil seal
84
. A slide block
69
is fastened to the cylinder rod
65
and is clearance-fitted to a keyway
66
b
formed in the cylinder case
66
. Reference numeral
71
designates a case, which secures the cylinder case
66
and a motor case
72
that houses and supports the motor
63
. Reference numeral
78
designates a hole formed in the case
71
; and
79
designates a blank cap. Reference numeral
73
designates a cover of the rotational speed detector
64
; and
74
designates a cable of the rotational speed detector
64
. Reference numeral
80
designates a power line of the motor
63
;
75
designates an amplifier serving as a controller; and
81
designates a higher-level controller.
In the related-art cylinder servo motor having the foregoing construction, power is fed to the motor
63
by way of the amplifier
75
in accordance with an instruction output from the higher-level controller
81
, thereby rotating the motor shaft
63
and the ball screw shaft
68
. Rotation of the cylinder rod
65
fastened to the ball screw nut
67
is stopped. Hence, the cylinder rod
65
does not rotate in conjunction with rotation of the ball screw shaft
68
and rotates directly along with the ball screw nut
67
, thus acting as a cylinder servo motor.
The related-art cylinder servo requires the cable
74
for connecting the rotational speed detector
64
and the amplifier
75
, and the power line
80
for connecting the motor
63
with the amplifier
75
. The cable
74
and the power line
80
are wired by a machinery manufacturer or an end user. Hence, there sometimes arise problems, such as an operation failure or a failure of the rotational speed detector
64
due to incorrect wiring.
The motor shaft
63
a
of the motor
63
and the end
68
a
of the ball screw shaft
68
are coupled together by means of the flexible coupling
70
. The coupling
70
requires the case
71
, and there must be ensured a space in the axis of ball screw shaft
68
, thereby increasing the overall length of the cylinder servo motor.
Since the ball screw shaft
68
is inserted into the cylinder rod
65
, only a ball screw shaft which is smaller in diameter than the cylinder rod
65
can be used as the ball screw shaft
68
. Hence, if an attempt is made to increase allowable thrust, the cylinder servo motor becomes bulky.
Since the cylinder rod
65
is supported by the sleeve shaft bearing
83
, wear arises in the slide section as a result of sliding friction. Particularly, at the time of high-speed operation, the life span of the cylinder serve becomes shorter.
Further, the rotation of the cylinder rod
65
is stopped by means of the slide block
69
clearance-fitted to the keyway
66
b
. Hence, a contact surface of the cylinder rod
65
is abraded by means of sliding friction, thereby resulting in an increase in backlash.
Contact between the slide block
69
and the keyway
66
b
arises in the form of sliding friction. Hence, at the time of operation, excessive thrust corresponding to a friction loss in the contact surface is required, thus deteriorating efficiency.
Further, at the time of assembly of a cylinder servo motor, the motor shaft
63
a
and the end
68
a
of the ball screw shaft
68
are coupled together by the flexible coupling
70
. A set screw (not shown) is fastened to the flexible coupling
70
, by use of a hexagonal wrench and by way of a hole
78
. To this end, the cylinder rod
65
must be moved along the axis of the ball screw shaft
68
, thereby finding a hole for the set screw. This results in an increase in the number of assembly steps, thereby adding to costs.
The present invention has been conceived to solve the drawback of the invention and is aimed at providing a cylinder servo motor capable of eliminating a necessity of wiring operation.
The present invention provides a compact cylinder servo motor which can produce large thrust and a long linear stroke.
The present invention is also aimed at providing an efficient cylinder servo motor having a long life span.
The present invention is also aimed at providing a cylinder servo motor which is superior in ease of assembly.
SUMMARY OF THE INVENTION
A cylinder servo motor according to the present invention comprises:
a servo motor having a rotor and a stator;
a cylinder servo motor main unit which is connected to a rotary shaft of the rotor of the servo motor by way of a ball screw nut and which has a ball screw shaft, the ball screw shaft moving in an axial direction;
a rotation sensor for detecting a rotary position of the servo motor; and
control means for controlling the rotation sensor and the servo motor, wherein
the cylinder servo motor main unit, the rotation sensor, and the control means are mechanically integrated;
the rotor of the servo motor is constituted of the rotary shaft and a permanent magnet, the rotary shaft being rotatably supported by a load-side bearing supported by a load-side bracket and by a non-load-side bearing supported by a non-load-side bracket, at least the load-side end of the rotary shaft being released, a through hole being formed in the rotary shaft so as to extend in an axial direction, and the permanent magnet being disposed opposite the stator fixed to the rotary shaft with a predetermined clearance therebetween;
the ball screw nut is constituted of a ball circulation mechanism and is mounted on a load-side shaft end of the rotary shaft;
the ball screw shaft is screw-engaged with the ball screw nut so as to become movable in only the axial direction such that a non-load-side shaft end of the ball screw shaft is housed in the through hole of the rotary shaft and such that a load-side end of the ball screw shaft protrudes from the load-side bracket;
a rotation portion of the rotation sensor is coupled to a non-load-side portion of the rotary shaft protruding from the hole formed in the non-load-side bracket and is covered with a rotation sensor cover;
the control means is disposed on a part of the non-load-side bracket distant from the stator; and
the control means and the rotation sensor cover are covered with a chassis to be fastened to the non-load-side bracket.
A necessity of wiring a line between the servo motor, the rotation sensor, and the control device section at a location to which the cylinder servo motor is to be shipped is obviated, thereby improving workability. As a result, a wiring failure, which otherwise is apt to arise at a location to which a cylinder servo motor is shipped, is prevented. Further, the wiring operation is obviated, thereby improving workability.
Since there is obviated use of any coupling for coupling a rotary shaft with a ball screw shaft, which would have hitherto been employed, the cylinder servo motor becomes compact
Ito Hidenobu
Mizutani Takao
Takamune Kouichi
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Tran
LandOfFree
Cylinder servomotor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cylinder servomotor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cylinder servomotor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3035587