U.S. patent application number 09/170324 was filed with the patent office on 2001-11-15 for an actuator for converting rotary motion into rectilinear motion.
This patent application is currently assigned to OBLON, SPIVAK, McCLELLAND, MAIER & NEUSTADT, P.C.. Invention is credited to MIYAHARA, MASAKI, NAGAI, SHIGEKAZU.
Application Number | 20010039846 09/170324 |
Document ID | / |
Family ID | 17715484 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010039846 |
Kind Code |
A1 |
NAGAI, SHIGEKAZU ; et
al. |
November 15, 2001 |
AN ACTUATOR FOR CONVERTING ROTARY MOTION INTO RECTILINEAR
MOTION
Abstract
Rotary motion of a ball screw is converted by a feed nut into
rectilinear motion to allow a displacement mechanism to make
rectilinear motion. When the ball screw involves axial deviation,
then an engagement member slides in a direction of the arrow C with
respect to a nut holder by the aid of a first guide mechanism, and
a second sliding guide slides in a direction of the arrow B with
respect to the engagement member by the aid of a second guide
mechanism. Accordingly, even when the ball screw involves axial
deviation with respect to the second sliding guide, the sliding
resistance is not increased between the second sliding guide and a
frame of an actuator. Therefore, even when there is any axial
deviation between the ball screw and the frame, there is no fear of
obstructing the displacement action of a displacement member.
Inventors: |
NAGAI, SHIGEKAZU; (TOKYO,
JP) ; MIYAHARA, MASAKI; (IBARAKI-KEN, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
OBLON, SPIVAK, McCLELLAND, MAIER
& NEUSTADT, P.C.
|
Family ID: |
17715484 |
Appl. No.: |
09/170324 |
Filed: |
October 13, 1998 |
Current U.S.
Class: |
74/89.36 ;
74/89.32 |
Current CPC
Class: |
Y10T 74/18656 20150115;
F16H 2025/2445 20130101; F16D 3/04 20130101; Y10T 74/18648
20150115; F16H 25/24 20130101; Y10T 74/1868 20150115; F16H
2025/2034 20130101 |
Class at
Publication: |
74/89.36 ;
74/89.32 |
International
Class: |
H02K 007/06; F16H
025/20 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 20, 1997 |
JP |
9-287290 |
Claims
What is claimed is:
1. An actuator comprising: a feed screw for being rotated by a
rotary driving source; a feed nut for engaging with said feed screw
and converting rotary motion of said feed screw into rectilinear
motion; a displacement member for making displacement along a frame
which accommodates said feed screw and said feed nut, in accordance
with a displacement action of said feed nut; and an axial
eccentricity-absorbing mechanism for engaging with said
displacement member and said feed nut in a state capable of
displacement in a direction perpendicular to a displacement
direction of said displacement member.
2. The actuator according to claim 1, wherein said axial
eccentricity-absorbing mechanism is provided with an engagement
member for connecting said feed nut and said displacement member, a
first guide mechanism which is linearly displaceable in a direction
perpendicular to said displacement direction of said displacement
member is provided at a connecting portion between said feed nut
and said engagement member, and a second guide mechanism which is
linearly displaceable in a direction perpendicular to said
displacement direction of said displacement member but in said
direction different from said displacement direction of said first
guide mechanism is provided at a connecting portion between said
engagement member and said displacement member.
3. The actuator according to claim 2, wherein each of said first
guide mechanism and said second guide mechanism comprises a guide
section which is formed to have a linear configuration, and a guide
groove which is slidably engaged with said guide section.
4. The actuator according to claim 2, wherein said second guide
mechanism is capable of linear displacement in a direction
perpendicular to said displacement direction of said first guide
mechanism.
5. The actuator according to claim 2, wherein said engagement
member is formed with a hole into which said feed screw is
inserted, and a wall for constructing said hole is separated from
said feed screw by a predetermined spacing distance.
6. The actuator according to claim 1, wherein said displacement
member is formed with a projection which protrudes to the outside
through a slit formed through said frame, and displacement motion
of said displacement member is transmitted to the outside of said
frame via said projection.
7. The actuator according to claim 1, wherein a cylindrical member,
which is arranged in said frame to surround said feed screw, has
its one end secured to said displacement member, and said
cylindrical member is displaceable in directions to make forward
and backward movement with respect to said frame.
8. The actuator according to claim 1, wherein said rotary driving
source is arranged coaxially with said feed screw, and rotary
motion of said rotary driving source is transmitted to said feed
screw via a coupling.
9. The actuator according to claim 1, wherein said rotary driving
source is arranged in parallel to said feed screw, and rotary
driving force of said rotary driving source is transmitted to said
feed screw via a rotary driving force-transmitting means.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an actuator for converting
rotary motion of a feed screw into rectilinear motion by using a
feed nut to allow a displacement member to perform rectilinear
motion.
[0003] 2. Description of the Related Art
[0004] An actuator, which is based on the use of a feed screw, has
been hitherto used as a driving source for transporting a workpiece
or the like. For example, as shown in FIG. 8, such an actuator 10
comprises a ball screw 16 with its one end which is connected to a
rotary shaft 14 of a motor 12. The other end of the ball screw 16
is rotatably supported by a shaft support member 18. A feed nut 20
meshes with the ball screw 16. The feed nut 20 is surrounded by a
displacement member 22. The displacement member 22 is formed with
an attachment section 24 which protrudes at an upper portion of the
displacement member 22 and which extends along its displacement
direction. The attachment section 24 protrudes upwardly through a
slit 28 which is formed at an upper portion of a frame 26 of the
actuator 10.
[0005] When the motor 12 is operated, the rotary motion of the ball
screw 16 is converted into rectilinear motion by the aid of the
feed nut 20. The rectilinear motion is transmitted to the
displacement member 22. Thus, the displacement member 22 makes
displacement along the longitudinal direction of the actuator
10.
[0006] However, if the conventional actuator 10 as described above
involves any axial deviation between the frame 26 and the ball
screw 16, then the sliding resistance with respect to the inner
wall of the frame 26 is increased when the displacement member 22
makes displacement, and the displacement action of the displacement
member 22 is obstructed when the displacement member 22 makes
displacement in the frame 26. For this reason, when the ball screw
16 is assembled to the frame 26, then it is necessary that the both
ends of the ball screw 16 are subjected to centering adjustment
with respect to the rotary shaft 14 and the shaft support member
18, and it is also necessary that the ball screw 16 is subjected to
centering adjustment with respect to the feed nut 20. Therefore, a
problem arises in that the assembling operation is complicated.
[0007] Further, if the central portion of the ball screw 16 is
warped, for example, when the actuator 10 has a lengthy size, or
when a load of a workpiece or the like is exerted on the
displacement member 22, then the sliding resistance between the
displacement member 22 and the frame 26 is increased in the same
manner as described above, and the displacement member 22
occasionally fails to make displacement. For this reason, it has
been impossible to allow the actuator 10 to have a fairly long
size, and it has been also necessary to restrict the load of the
workpiece.
SUMMARY OF THE INVENTION
[0008] A general object of the present invention is to provide an
actuator which is free from any fear of obstructing the
displacement action of a displacement member even when the actuator
involves axial deviation between a feed screw and a frame.
[0009] A principal object of the present invention is to provide an
actuator which prevents the displacement action of a displacement
member from being affected by positional deviation of a feed screw
and warpage of the feed screw by absorbing axial eccentricity of
the feed screw by using an axial eccentricity-absorbing mechanism
which is displaceable in a direction perpendicular to a direction
of displacement of the displacement member, making it possible to
permit the positional deviation and the warpage of the feed
screw.
[0010] Another object of the present invention is to provide an
actuator comprising an axial eccentricity-absorbing mechanism which
is composed of a first guide mechanism designed to be linearly
displaceable in a direction perpendicular to a direction of
displacement of a displacement member and a second guide mechanism
designed to be linearly displaceable in a direction perpendicular
to the direction of displacement of the displacement member but in
the direction different from the direction of displacement of the
first guide mechanism, thereby making it possible to absorb axial
eccentricity of a feed screw by using the relatively simple
mechanism.
[0011] The above and other objects, features, and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings in which a preferred embodiment of the present invention
is shown by way of illustrative example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 shows a perspective view illustrating an actuator
according to a first embodiment of the present invention;
[0013] FIG. 2 shows a longitudinal sectional view illustrating the
actuator shown in FIG. 1;
[0014] FIG. 3 shows a perspective view illustrating a displacement
mechanism used for the actuator shown in FIG.
[0015] FIG. 4 shows an exploded perspective view illustrating the
displacement mechanism shown in FIG. 3;
[0016] FIG. 5 shows a sectional view taken along a line V-V
illustrating the actuator shown in FIG. 1;
[0017] FIG. 6 shows a sectional view taken along a line VI-VI
illustrating the actuator shown in FIG. 1;
[0018] FIG. 7 shows a longitudinal sectional view illustrating an
actuator according to a second embodiment of the present invention;
and
[0019] FIG. 8 shows a longitudinal sectional view illustrating an
actuator concerning the conventional technique.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] The actuator according to the present invention will be
described in detail below with reference to the accompanying
drawings, referring to preferred embodiments.
[0021] With reference to FIGS. 1 and 2, reference numeral 30
indicates an actuator according to a first embodiment of the
present invention. The actuator 30 basically comprises a frame 32
formed to have a lengthy size, a motor 34 provided at one end of
the frame 32, a ball screw 36 rotatably supported in the frame 32,
and a displacement mechanism 38 for slidably contacting with the
inner circumference of the frame 32 to make displacement by the aid
of the ball screw 36.
[0022] A plurality of extending attachment grooves 40a to 40d,
which are used to attach the actuator 30 to another member by the
aid of unillustrated attachment means such as bolts, are formed
along the longitudinal direction on side surfaces of the frame 32.
Sensor grooves 42a, 42b, to which an unillustrated position sensor
is attached, are formed between the extending attachment grooves
40a, 40b, 40c, 40d to extend along the longitudinal direction.
[0023] One end of a spacer 44 is secured to one end of the frame
32. The motor 34 is secured to the other end of the spacer 44. The
ball screw 36 is connected via a coupling 48 to a rotary shaft 46
of the motor 34. Both ends of the ball screw 36 are rotatably
supported via bearings 52a to 52c by shaft support members 50a, 50b
installed inside at both ends of the frame 32.
[0024] The ball screw 36 is inserted into the displacement
mechanism 38 (see FIG. 3). As shown in FIG. 4, a first sliding
guide 54 is provided at one end of the displacement mechanism 38.
The first sliding guide 54 has its inner wall which is separated
from the ball screw 36 by a predetermined spacing distance. A
diametrally expanded section 56 is formed at one end of the first
sliding guide 54. The diametrally expanded section 56 is slidable
on the inner wall of the frame 32. A ring-shaped permanent magnet
57 is installed to the diametrally expanded section 56. In this
embodiment, a sensor (not shown), which is installed at a
predetermined position of the sensor groove 42a, 42b of the frame
32, detects the magnetic force of the permanent magnet 57 which is
displaced together with the displacement mechanism 38. Thus, for
example, the displacement amount of the displacement mechanism 38
can be detected.
[0025] A feed nut 60, which is formed to have a substantially
cylindrical configuration, abuts against an end of the first
sliding guide 54. The feed nut 60 is engaged with the ball screw 36
by the aid of ball members 62. One end of a nut holder 64, which
constitutes an axial eccentricity-absorbing mechanism 58, is
secured to one end of the feed nut 60. The nut holder 64 has its
inner wall which is separated from the ball screw 36 by a
predetermined spacing distance. As shown in FIG. 4, a first guide
groove 66, which extends in a direction (direction indicated by the
arrow C) perpendicular to the ball screw 36, is formed at the other
end of the nut holder 64. An engagement member 68, which is formed
to have a substantially ring-shaped configuration for constructing
the axial eccentricity-absorbing mechanism 58, has a first guide
section 70 which is slidably engaged with the first guide groove
66. A first guide mechanism 72 is constructed by the first guide
groove 66 and the first guide section 70. An inner wall for forming
a hole 73 of the engagement member 68 is separated from the ball
screw 36 by a predetermined spacing distance.
[0026] A second guide section 74 is formed to protrude on a surface
of the engagement member 68 opposite to the first guide section 70,
the second guide section 74 extending in a direction (direction
indicated by the arrow B) perpendicular to the axial direction of
the ball screw 36 and the displacement direction of the first guide
section 70 respectively. The axial eccentricity-absorbing mechanism
58 includes a second sliding guide 76. A second guide groove 78,
which is formed on the second sliding guide 76, is slidably engaged
with the second guide section 74. A second guide mechanism 80 is
constructed by the second guide section 74 and the second guide
groove 78. The second sliding guide 76 has its inner wall which is
separated from the ball screw 36 by a predetermined spacing
distance. A diametrally expanded section 82 is formed at one end of
the second sliding guide 76. The diametrally expanded section 82 is
slidable on the inner wall of the frame 32.
[0027] The first sliding guide 54 and the second sliding guide 76
are screwed into both ends of a substantially cylindrical
displacement member 84. The feed nut 60, the nut holder 64, and the
engagement member 68 are inserted into the displacement member 84.
A projection 86, which extends along the longitudinal direction of
the actuator 30, is formed to protrude at an upper portion of the
displacement member 84. The projection 86 is inserted into a slit
88 defined at an upper portion of the frame 32. Guide members 90a,
90b, each of which is formed to have a substantially angular
U-shaped configuration, are secured to both ends of the projection
86. The guide members 90a, 90b are slidable on walls which form the
slit 88. An unillustrated table or the like can be installed to the
projection 86.
[0028] The actuator 30 according to the first embodiment is
basically constructed as described above. Next, its operation will
be explained.
[0029] When the motor 34 is operated to rotate the rotary shaft 46,
the ball screw 36 is rotated via the coupling 48. The rotary motion
is transmitted via the ball members 62 to the feed nut 60. During
this process, the displacement mechanism 38 is prevented from
rotation, because the guide members 90a, 90b of the projection 86
are engaged with the walls of the slit 88. Accordingly, the rotary
motion is converted by the feed nut 60 into the rectilinear motion.
Thus, the displacement mechanism 38 is displaced in the direction
of the arrow A.
[0030] Next, explanation will be made for a case in which the ball
screw 36 suffers from axial deviation with respect to the frame 32
as shown in FIGS. 5 and 6.
[0031] When the ball screw 36 involves axial deviation in an amount
of b in the direction of the arrow B with respect to the frame 32,
as shown in FIG. 5, the second guide section 74 of the engagement
member 68 is displaced by the amount of b with respect to the
second guide groove 78 of the second sliding guide 76 which
constitutes the second guide mechanism 80. When the ball screw 36
involves axial deviation in an amount of c in the direction of the
arrow C with respect to the frame 32, as shown in FIG. 6, the first
guide section 70 of the engagement member 68 is displaced in the
amount of c with respect to the first guide groove 66 of the nut
holder 64 which constitutes the first guide mechanism 72. On the
other hand, the first sliding guide 54 and the second sliding guide
76 are not displaced in the directions of the arrows B, C with
respect to the frame 32. Therefore, when the ball screw 36 is
rotated in a state of involving axial deviation with respect to the
frame 32, the nut holder 64 is displaced in the depth direction in
FIGS. 5 and 6. However, there is no increase in sliding resistance
between the diametrally expanded sections 56, 82 of the first
sliding guide 54 and the second sliding guide 76 and the inner wall
of the frame 32. Thus, there is no fear of obstructing the
displacement action of the displacement mechanism 38 (see FIG.
2).
[0032] Accordingly, when the actuator 30 is assembled, it is
sufficient that the both ends of the ball screw 36 are subjected to
centering adjustment with respect to the shaft support members 50a,
50b. It is unnecessary to provide any step for performing strict
centering adjustment for the ball screw 36 and the feed nut 60 with
respect to the frame 32. Therefore, the assembling operation for
the actuator 30 is simplified, and the operation efficiency is
improved.
[0033] The displacement mechanism 38 is capable of making
appropriate displacement as well even when the actuator 30 has a
lengthy size with the ball screw 36 formed to be long, and the ball
screw 36 is warped due to its own weight, or even when the ball
screw 36 is warped by a load of a workpiece or the like exerted on
the displacement mechanism 38. Therefore, it is possible to obtain
the actuator 30 having a long displacement range. It is possible to
increase the load of the workpiece which can be transported by the
actuator 30.
[0034] Next, an actuator 100 according to a second embodiment will
be explained with reference to FIG. 7. The same components or parts
as those described in the first embodiment are designated by the
same reference numerals, detailed explanation of which will be
omitted.
[0035] A casing 104 is secured to one end of a frame 102 of the
actuator 100. The casing 104 is provided with a motor 106 which is
disposed in parallel to the frame 102. A pulley 110 is provided on
a rotary shaft 108 of the motor 106. On the other hand, a pulley
112 is provided at one end of a ball screw 111 which is rotatably
supported by a shaft support member 103 of the frame 102. A belt
113 is wound around the pulleys 110, 112.
[0036] The feed nut 60 is engaged via the ball members 62 with the
ball screw 111 in the same manner as in the actuator 30 according
to the first embodiment. The nut holder 64 is secured to the feed
nut 60. As shown in FIG. 4, the first guide section 70 of the
engagement member 68 is slidably engaged with the first guide
groove 66 of the nut holder 64. The second guide section 74 of the
engagement member 68 is slidably engaged with the second guide
groove 78 formed on a sliding guide 114.
[0037] A cylindrical displacement member 116, which surrounds the
feed nut 60, the nut holder 64, and the engagement member 68, is
provided at one end of the sliding guide 114. One end of a
cylindrical member 118 is secured to the other end of the sliding
guide 114. The other end of the cylindrical member 118 protrudes
through the end of the frame 102, and it is slidably supported on
the frame 102 by a support member 120. The end of the ball screw
111 is rotatably supported by a shaft support member 122 in the
cylindrical member 118. The cylindrical member 118 is closed by a
cover member 124. Accordingly, the actuator 100 is prevented from
dust or the like which would be otherwise cause invasion from the
outside of the actuator 100 into the inside of the frame 102. The
actuator 100 is completely free from the fear of adhesion of dust
or the like to the ball screw 111.
[0038] The actuator 100 according to the second embodiment is
constructed as described above. Next, its operation will be
explained.
[0039] When the motor 106 is operated, the pulley 110 is rotated
via the rotary shaft 108. The rotary motion is transmitted to the
ball screw 111 by the aid of the belt 113 and the pulley 112. The
rotary motion of the ball screw 111 is converted by the feed nut 60
into the rectilinear motion, and the sliding guide 114 is displaced
in the direction of the arrow D. Accordingly, the cylindrical
member 118 is displaced in directions to make forward and backward
movement with respect to the frame 102.
[0040] When the ball screw 111 involves axial deviation with
respect to the frame 102, the following action is made in the same
manner as in the actuator 30 according to the first embodiment.
That is, the second guide section 74 makes sliding movement with
respect to the second guide groove 78, and thus the engagement
member 68 is displaced with respect to the sliding guide 114.
Further, the first guide section 70 makes sliding movement on the
first guide groove 66, and thus the nut holder 64 is displaced with
respect to the engagement member 68 (see FIG. 4). Accordingly, even
when the ball screw 111 is rotated in a state of axial deviation
with respect to the frame 102, the sliding resistance is not
increased between the sliding guide 114 and the inner wall of the
frame 102. Thus, there is no fear of obstructing the displacement
action of the cylindrical member 118 (see FIG. 7).
[0041] Therefore, when the actuator 100 is assembled, it is
sufficient that the both ends of the ball screw 111 are subjected
to centering adjustment with respect to the support member 120, the
shaft support member 122, and the shaft support member 103. It is
unnecessary to provide any step for performing strict centering
adjustment for the ball screw 111 and the feed nut 60 with respect
to the frame 102. Therefore, the assembling operation for the
actuator 100 is simplified, and the operation efficiency is
improved.
[0042] The cylindrical member 118 is capable of making appropriate
displacement as well even when the ball screw 111 is warped by its
own load, or even when the ball screw 111 is warped by a load
exerted on the cylindrical member 118. Accordingly, it is possible
to obtain the actuator 100 having a long displacement range. It is
possible to increase the load of the workpiece.
[0043] As described above, in the actuators 30, 100 according to
the first and second embodiments, the ball screws 36, 111 have been
used as the feed screw. However, it is also preferable to use a
slide screw.
[0044] A flexible member such as those made of rubber may be used
in place of the engagement member 68 to connect the nut holder 64
to the second sliding guide 76 or the sliding guide 114 so that the
axial eccentricity-absorbing mechanism 58 is constructed.
* * * * *