U.S. patent application number 09/985384 was filed with the patent office on 2002-02-28 for feed screw device.
This patent application is currently assigned to NSK LTD.. Invention is credited to Kato, Soichiro, Tsukada, Toru.
Application Number | 20020023512 09/985384 |
Document ID | / |
Family ID | 27320850 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020023512 |
Kind Code |
A1 |
Tsukada, Toru ; et
al. |
February 28, 2002 |
Feed screw device
Abstract
A ring-like lubricant supply device 6 is fitted into a recess 4
of a nut member 2. The lubricant supply device 6 contains a
lubricant and is formed in an outer peripheral surface with notches
7. Tubular members 8 each having an outer diameter larger than the
diameter of the notch 7 are inserted into the notches, pushing and
widening the notches 7 in a circumferential direction. One end of
the tubular member 8 is fitted into a recess 9b of a retaining ring
9 and the retaining ring 9 is fixed to a nut member 2.
Inventors: |
Tsukada, Toru; (Gunma,
JP) ; Kato, Soichiro; (Gunma, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 Pennsylvania Avenue, NW
Washington
DC
20037-3213
US
|
Assignee: |
NSK LTD.
|
Family ID: |
27320850 |
Appl. No.: |
09/985384 |
Filed: |
November 2, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09985384 |
Nov 2, 2001 |
|
|
|
08877518 |
Jun 17, 1997 |
|
|
|
Current U.S.
Class: |
74/424.81 ;
74/467; 74/89.44 |
Current CPC
Class: |
Y10T 74/18744 20150115;
Y10T 74/19991 20150115; F16H 25/2418 20130101; Y10T 74/19702
20150115; F16H 25/2204 20130101; Y10T 74/19744 20150115; Y10T
74/1527 20150115; Y10T 74/18712 20150115; F16H 57/0497 20130101;
F16H 57/0406 20130101 |
Class at
Publication: |
74/424.81 ;
74/89.44; 74/467 |
International
Class: |
F16H 025/20; F16H
057/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 17, 1996 |
JP |
HEI. 8-155545 |
Jun 17, 1996 |
JP |
HEI. 8-155546 |
Jul 18, 1996 |
JP |
HEI. 8-189148 |
Claims
What is claimed is:
1. A feed screw device comprising: a screw shaft; a nut member
threadably engaging an outer periphery of the screw shaft; a
lubricant supply device fixed to said nut member, said lubricant
supply device coming in contact with the outer peripheral surface
of said screw shaft and having a predetermined elasticity; and
means for deforming at least the outer periphery of said lubricant
supply device in the circumferential direction.
2. The feed screw device according to claim 1, in which at least
portion of said lubricant supply device facing the screw shaft is
made of rubber or synthetic resin containing a lubricant.
3. The feed screw device according to claim 1, in which said
pressing means comprising: a notch formed in the outer periphery
side of the lubricant supply device; and an expansion member
inserted into said notch for deforming said lubricant supply device
in the circumferential direction.
4. The feed screw device according to claim 1, in which said nut
member is provided with a recess portion for attaching said
lubricant supply device and a retaining ring for retaining said
lubricant supply device within said recess portion.
5. The feed screw device according to claim 4, in which said
retaining ring is provided with a recess into which a part of said
pushing and widening means are inserted.
6. The feed screw device according to claim 1, in which said
lubricant supply device has a cut part at a place in the
circumferential direction.
7. The feed screw device according to claim 1, in which said
lubricant supply device is provided on the inner peripheral surface
with a projection which is fitted into thread groove formed on the
outer peripheral surface of said screw shaft.
8. The feed screw device according to claim 1, in which said nut
member is provided with a cap-shaped retaining ring which has a
recessing portion for accommodating said lubricant supply
device.
9. The feed screw device according to claim 4, in which said
pressing means comprising: a notch formed in the outer periphery
side of the lubricant supply device; and an expansion member formed
on said retaining ring and inserted into said notch so as to deform
said lubricant supply device in the circumferential direction.
10. The feed screw device according to claim 9, in which said notch
comprises two insertion holes formed on said lubricant supply
device at a predetermined interval in the circumferentical
direction, and said expansion member comprises two projections
respectively inserted into said two insertion holes, in which said
predetermined interval between said two projections is set slightly
smaller than that between said two insertion holes.
11. The feed screw device according to claim 1, in which said
lubricant supply device is provided with a plurality of lip parts
projected along the circumferential direction toward the inner
peripheral surface of said lubricant supply device and come in
sliding contact with the outer peripheral surface of said screw
shaft.
12. A feed screw device comprising: a screw shaft; a screw nut
threadably engaging an outer periphery of said screw shaft; and a
lubricant supply device disposed at at least one end of said screw
nut in the axial direction of said screw shaft for sealing the gap
opening between the screw nut and the screw shaft, and said
lubricant supply member being made of a lubricant-containing
polymer member, in which said lubricant-containing polymer member
is formed with a lubricant reserve portion.
13. The feed screw device according to claim 12, in which sid
lubricant reserve portion comprises a plurality of lubricant
reserve holes at positions distant from each other in the
circumferential direction.
14. The feed screw device according to claim 13, in which said
lubricant supply device further comprises a communication hole for
flowing a lubricant reserved in said lubricant reserve holes out
directly into outflow opening opened and formed on the inner
peripheral surface of said lubricant supply device.
15. The feed screw device according to claim 12, in which said
lubricant reserve portion comprises a lubricant reserve groove
which is continuously extended in the circumferential
direction.
16. The feed screw device according to claim 15, in which said
lubricant supply device further comprises a communication hole for
flowing a lubricant reserved in said lubricant reserve groove out
directly into outflow opening opened and formed on the inner
peripheral surface of said lubricant supply device.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a feed screw device of a ball
screw, square thread, etc. Particularly, the invention relates to a
feed screw device that can automatically supply a lubricant over a
long term.
[0002] A conventional ball screw, a kind of feed screw device, is
described in Japanese Utility Model Unexamined Publication Nos. Hei
7-4952 and 6-47762, etc., for example.
[0003] This kind of ball screw comprises a spiral thread groove 50a
made in the outer peripheral surface of a screw shaft 50 threadably
engaging a spiral thread groove 51a made in the inner peripheral
surface of a nut member 51 via a plurality of balls 52, as shown in
FIG. 1, for converting relative rotation of the screw shaft 50 to
the nut member 51 into relative displacement in an axial direction
of the nut member 51 via the balls 52.
[0004] An annular recess 53 is formed in both end parts of the
inner diameter face of the nut member 51 (in FIG. 1, only the right
end is shown), and a sealing member 54 is mounted on the recess
53.
[0005] The sealing member 54 is made from plastic containing a
lubricant into a ring shape, and a projection 54a that can be
fitted into the thread groove 50a of the screw shaft 50 projects
from the inner peripheral surface of the sealing member.
[0006] A ring-like garter spring 55 is inserted in the
circumferential direction between the outer peripheral surface of
the sealing member 54 and the recess 53 of the nut member 51. The
garter spring 55 clamps down all the outer peripheral surface of
the sealing member 54 toward the outer peripheral surface of the
screw shaft 50, that is, the sealing member 54 is pressed in the
inner diameter direction.
[0007] Further, a tapped hole 56 radially penetrating the
circumferential wall of the nut member 51 is made in the position
of the recess 53 in the nut member 51 and a set screw 57 is fitted
into the tapped hole 56, thereby fixing the sealing member 54 to
the nut member 51.
[0008] The garter spring 55 sets the gap between the inner
peripheral surface of the sealing member 54 and the outer
peripheral surface of the screw shaft 50 to zero or less for
preventing the lubricant filled in the ball screw from leaking to
the outside and a foreign material from entering the ball screw
from the outside.
[0009] Further, the lubricant exuding from the sealing member 54
decreases frictional resistance of the slide portion between the
inner peripheral surface of the sealing member 54 and the outer
peripheral surface of the screw shaft 50, namely, slide torque and
at the same time, is supplied to the thread groove 50a of the screw
shaft 50, the balls 52, and the thread groove 51a of the nut member
51.
[0010] However, for the conventional feed screw device of the
structure as described above, the garter spring 55 needs to be
inserted between the outer periphery of the sealing member 54 and
the recess 53 of the screw shaft 50 so that a dimension error of
the sealing member 54 is absorbed and that the inner peripheral
surface of the sealing member 54 comes in sliding contact with the
outer peripheral surface of the screw shaft 50; it is feared that
the outer diameter of the feed screw device may grow as large as
the garter spring.
[0011] In the conventional structure, the sealing member 54 is
pressed diametrically, so that it is abutted against the outer
peripheral surface of the screw shaft 50, thus the spring needs to
be disposed on all the outer periphery of the sealing member 54 in
the circumferential direction.
[0012] The inner diameter portion on the opposite side (portion not
pressed by the garter sprint) to the side pressed by the garter
spring 55 of the sealing member 54 in the axial direction apts to
float-up with respect to the outer peripheral surface of the screw
shaft and it is feared that a sufficient lubricant will not be
supplied from the portion.
[0013] Some conventional feed screw devices comprise a spring
inserted between the tip of the set screw 57 and the sealing member
54 in place of the garter spring 55. However, the lubricant supply
section is also pressed only diametrically, thus it is feared that
the inner peripheral surface of the sealing member 54 may be placed
out of contact with the outer peripheral surface of the screw shaft
50 or that the portion pressed by the set screw in sliding contact
with the screw shaft may be worn on one side in portions shifted 90
degrees from the placement position of the set screw 57, etc., for
example.
[0014] Even if hardware for suppressing jump out of the sealing
member 54 from the recess 53 is attached to the nut member 51, the
tapped hole 56 needs to be made in the nut member 51 and fixed by
the set screw 57 to prevent accompanying rotation of the screw
shaft 50 of the sealing member 54 in addition to the hardware;
workability is poor.
[0015] Further, when the sealing member 54 has a part cut (for
example, the sealing member 54 is made into c-shaped) because of
attachment thereof, the inner peripheral surface of the sealing
member 54 does not come in sufficient contact with the screw shaft
50 and it is feared that a sufficient lubricant will not be
supplied from the sealing member 54 depending on the operating
condition.
[0016] Known as another ball screw, a kind of conventional feed
screw device, is a device wherein a space 204 between a screw shaft
201 and a ball screw nut 202 threadably engaged into the screw
shaft 201 via a large number of balls 203 is filled with grease or
lubricant, as shown in FIG. 2. The ball screw is of seal type
wherein an annular recess 205 is made in an end of the ball screw
nut 202 and a sealing member 206 is fitted into the annular recess
205 to prevent powder dust, etc., from entering into the ball screw
nut 202.
[0017] By the way, to lubricate such a conventional ball screw
device, normally grease or lubricant is supplied from a grease
nipple 207 attached to the ball screw nut 202 to a ball circulation
passage for lubricating a rolling element.
[0018] However, particularly when the ball screw device adopting
such a lubrication system directly using lubricant or grease is
used in a high-temperature environment or a environment wherein
wood chips, etc., easily absorbing lubricants are existed, the
filled lubricant or grease flows out to the outside, is exhausted
fast, and must be again supplied repeatedly for a short term.
Japanese Utility Model Unexamined Publication No. Hei 7-4952 is
known as application relating to an oil-containing polymer
lubrication ball screw to improve this point.
[0019] For the oil-containing polymer lubrication ball screw
disclosed here, a lubricant supply member mounted on a ball screw
nut is formed of lubricant-containing rubber or synthetic resin and
the lubricant continuously exuding from the lubricant supply member
is automatically supplied to a rolling element lubrication passage
of the ball screw nut.
[0020] However, with the ball screw, as the lubricant supply member
containing the lubricant runs with the ball screw nut while coming
in contact with the screw shaft, the lubricant exudes from the
contact part for lubrication; lubricant supplied to a guide rail is
easily absorbed particularly in an environment wherein foreign
materials such as wood chips easily absorbing lubricant are
existed, and the lubricant can also be absorbed from the
lubricant-containing polymer member; resultantly, it is feared that
a lubrication failure may be invited.
SUMMARY OF THE INVENTION
[0021] It is therefore an object of the invention to provide a feed
screw device for enabling a lubricant-containing member to come in
uniform contact with an outer peripheral surface of a screw shaft
without enlarging the outer diameter of the feed screw device and
in a simple structure.
[0022] According to the invention, there is provided a feed screw
device comprising a screw shaft, a nut member threadably engaging
an outer periphery of the screw shaft, and a lubricant supply
device being fixed to the nut member, coming in contact with the
outer peripheral surface of the screw shaft, and having a
predetermined elastic force, wherein at least the portion of the
lubricant supply device facing the screw shaft is rubber or
synthetic resin containing a lubricant, wherein a notch is made in
the outer periphery of the lubricant supply device, and wherein an
expansion member fitted at least with the notch pressed in the
circumferential direction of the lubricant supply device is
inserted into the notch.
[0023] In the structure, when the expansion member is inserted into
the notch of the lubricant supply device, it causes the notch to
push and widen at least the outer periphery of the lubricant supply
device in the circumferential direction.
[0024] Thus, a compression force along the circumferential
direction acts on the inside of the outer periphery of the
lubricant supply device, at least deforming all the inner
peripheral surface in the inner diameter direction. Resultantly,
the inner diameter of the lubricant supply device is reduced for
absorbing a dimension error of the lubricant supply device, and the
inner peripheral surface of the lubricant supply device comes in
contact with the outer peripheral surface of the screw member.
[0025] As the feed screw device is driven, a lubricant contained in
the lubricant supply device exudes gradually over time, whereby
slide resistance between the outer peripheral surface of the screw
member and the inner peripheral surface of the lubricant supply
device is decreased and as the feed screw device is driven, a
lubricant is supplied to the outer peripheral surface of the screw
member.
[0026] In the feed screw device according to the present invention,
all the inner peripheral surface of the lubricant supply device can
be brought into contact with the outer peripheral surface of the
screw shaft by only inserting the expansion member into a part of
the lubricant supply device (notch), so that any member, such as a
garter spring to be installed on all the outer peripheral surface
of the lubricant supply device which was needed by the conventional
lubricant supply device can be eliminated.
[0027] In the case where the expansion member is formed with a
projection which is projected from a part of the outer peripheral
surface of the lubricant supply device and is fitted into a part of
the nut member, etc., it is possible that the expansion member also
serves prevention of rotation of the lubricant supply device.
[0028] In addition, according to the invention, there is provided
in a screw transmission device comprising a screw shaft, a nut
member threadably engaging an outer periphery of the screw shaft,
and a ring-like lubricant supply device being disposed in the nut
member with one axial end face opposed axially to the nut member
and an inner peripheral surface opposed to an outer peripheral
surface of the screw shaft, wherein at least the portion of the
lubricant supply device facing the screw shaft is rubber or
synthetic resin containing a lubricant, the improvement which
comprises a press member having a portion opposed axially to an
axial opposed end face of the lubricant supply device and being
fixed to the nut member and a projection projecting from the press
member to the lubricant supply device and inserted into the
lubricant supply device.
[0029] Further, in the screw transmission device, at least two
projections can also be provided and inserted into the lubricant
supply device so that pilot pressure in the circumferential
direction is put on the lubricant supply device as load.
[0030] In the structure, the device is sandwiched between the press
member and the nut member, so that an axial movement of the
lubricant supply device relative to the nut member is restricted
and the projection projecting from the press member prevents the
lubricant supply device from rotating with the screw shaft.
[0031] That is, an axial movement and rotation of the lubricant
supply device can be prevented by only fitting the press member
having the projection.
[0032] As the screw transmission device is driven, a lubricant
contained in the lubricant supply device exudes gradually over
time, so that slide resistance between the outer peripheral surface
of the screw member and the inner peripheral surface of the
lubricant supply device is decreased and as the screw transmission
device is driven, a lubricant is supplied to the outer peripheral
surface of the screw member.
[0033] Here, a pair of the projections may be provided approaching
each other and the projection span may be set smaller than the span
between the paired projection insertion positions disposed in the
lubricant supply device. In doing so, by sandwiching between the
paired projections, pilot pressure in the circumferential direction
is put as load and such a force to hold down the screw shaft acts
on the inner peripheral surface of the lubricant supply device.
[0034] Further, it is another object of the invention to provide a
long-life feed screw device stable over a long term by
automatically replenishing a lubricant supply member with a
lubricant for suppressing occurrence of a lubrication failure.
[0035] To the end, according to a second aspect of the invention,
there is provided, in a feed screw device comprising a screw shaft,
a screw nut threadably engaging an outer periphery of the screw
shaft, and a lubricant supply device being disposed at both ends of
the screw nut for sealing the gap opening between the screw nut and
the screw shaft, the improvement wherein the lubricant supply
member is made of a lubricant-containing polymer member, the
lubricant-containing polymer member being formed with lubricant
reserve parts.
[0036] According to invention, the lubricant-containing polymer
member seals both the ends of the screw nut and shuts off the
inside of the screw nut from the external atmosphere, whereby even
if the feed screw device is used in the external atmosphere which
is of a bad environment wherein wood chips, etc., easily absorbing
lubricant are existed, the inside of the screw nut is protected
against the wood chips, etc., and the smooth lubrication effect can
be maintained over a long time.
[0037] As a lubricant exudes from the lubricant-containing polymer
member and is consumed, the lubricant-containing polymer member is
replenished with a new lubricant sealed in the lubricant reserve
parts, so that the lubricant exudes from the lubricant-containing
polymer member over a long time even in atmosphere wherein wood
chips, etc., easily absorb the lubricant supplied to a guide rail,
so that stable lubrication can be carried out for a long time.
[0038] If foreign materials such as wood chips are deposited on the
lubricant-containing polymer member and the lubricant is absorbed
from the portion, the lubricant-containing polymer member is
replenished with a lubricant from the lubricant reserve parts, thus
it is not feared that a lubrication failure will be invited.
[0039] Specifically, the lubricant reserve parts formed in the
lubricant supply device may be lubricant reserve holes made near
the sealed face of the screw shaft or a lubricant reserve
peripheral groove extending surrounding the screw shaft. If an
annular recess is made in the screw nut and the lubricant supply
member is fitted into the annular recess and the lubricant reserve
holes or the lubricant reserve peripheral groove is closed on the
inner peripheral surface or bottom face of the recess, a lubricant
filled in the lubricant reserve holes or the lubricant reserve
peripheral groove can be sealed by a simple structure.
[0040] If the lubricant reserve peripheral groove is formed, the
lubricant-containing polymer member is replenished uniformly with a
new lubricant sealed in the lubricant reserve peripheral groove,
thus stable lubrication can be carried out for a long time. If a
plurality of the lubricant reserve holes are made in the
circumferential direction surrounding the screw shaft, the
lubricant-containing polymer member is replenished uniformly with a
new lubricant in the lubricant reserve holes, thus stable
lubrication can be carried out for a long time.
[0041] If a reinforcing plate is disposed overlapping the
lubricant-containing polymer member so as to shut off the
lubricant-containing polymer member from the external atmosphere,
it prevents wood chips, dust, etc., from coming in contact with the
lubricant-containing polymer member, so that absorbing the
lubricant in wood chips, dust, etc., from the portion can be
prevented. If a reinforcing plate is disposed so that a compression
force acts on the lubricant-containing polymer member, the
lubricant-containing polymer member can be adjusted in hardness and
insufficient strength by the reinforcing plate, and breakage,
cracks, etc., of the lubricant-containing polymer member can be
prevented. Since the reinforcing plate is provided, a metal
reinforcing plate (mandrel) need not be used; a problem of adhesion
between the lubricant-containing polymer member containing a large
amount of lubricant and the metal reinforcing plate need not be
considered.
[0042] Further, if the lubricant-containing polymer member is
formed with communication holes from the lubricant reserve parts
(lubricant reserve holes, lubricant reserve peripheral groove) to
the face coming in contact with the screw shaft, the lubricant
sealed in the lubricant reserve parts flows out into the screw
shaft through the communication holes. Thus, an appropriate
lubricant-containing polymer member is provided for a device
requiring a large amount of lubricant.
[0043] For example, a lubricant-containing polymer member can be
adopted as the lubricant supply device containing a lubricant
according to the invention.
[0044] For example, the product manufactured in the following
manner can be used as the lubricant-containing polymer member: Any
of paraffin hydrocarbon oil such as polyolefin oil, naphthene
hydrocarbon oil, mineral oil, ether oil such as dialkyl diphenyl
ether oil, or ester oil such as phthalate ester or trimellitate is
mixed as a lubricant with a polymer selected from the group
consisting of polyolefin polymers basically having the same
chemical structure such as polyethylene, polypropylene, and
polymethylpentane and the mixture is fused, then poured into a
predetermined mold and cooled and fixed under pressure.
[0045] Various additive agents such as an antioxidant, a rust
preventive, a wear inhibitor, a defoaming agent, and an extreme
pressure agent may be previously added to the mixture.
[0046] The percentage composition of the lubricant-containing
polymer member may be set to 20%-80% by weight of polyolefin
polymer and 80%-20% by weight of lubricant with respect to all
weight, because if the polyolefin polymer is less than 20% by
weight, hardness, strength, etc., required as the lubricant supply
device cannot be provided and if the polyolefin polymer exceeds 80%
by weight (the lubricant is less than 20% by weight), lubricant
supply lessens and the slide torque reduction and lubricant supply
effects decrease.
[0047] The above-mentioned polymers have the same basic structure
and differ in average molecular weight, covering the range of
1.times.10.sup.3 to 5.times.10.sup.6. Among the polymers, those of
comparatively low molecular weight ranging from 1.times.10.sup.3 to
5.times.10.sup.5 and those of ultra high molecular weight ranging
from 1.times.10.sup.6 to 5.times.10.sup.6 are used solely or mixed
as required.
[0048] To improve the mechanical strength of the lubricant supply
device, the following thermoplastic resin and thermosetting resin
may be added to the polyolefin polymer:
[0049] Resin such as polyamide, polycarbonate, polybutylene
terephthalate, polyphenylene sulfide, polyether sulfone, polyether
ether ketone, polyamide imide, polystyrene, or ABS resin can be
used as the thermoplastic resin.
[0050] Resin such as unsaturated polyester resin, urea resin,
melamine resin, phenol resin, polyimide resin, or epoxy resin can
be used as the thermosetting resin.
[0051] The resins may be used solely or mixed.
[0052] Further, to disperse the polyolefin polymer and any other
resin in a more uniform state, a proper compatibilization agent may
be added as required.
[0053] In addition to the polyolefin polymer and lubricant
combinations as described above, polyurethane rubber cured in a
grease-containing condition can also be used as the
lubricant-containing polymer, as described below in detail:
[0054] Polyurethane rubber is a compound produced by reaction of
polyisocyanate with an activated hydrogen compound.
[0055] Tolylene diisocyanate (TDI), hexamethylene diisocyanate
(MDI), prepolymer (MW1000-MW2000) produced by reaction of TDI and
MDI with an activated hydrogen compound, such as castor oil, or the
like can be used as polyisocyanate.
[0056] A long chain activated hydrogen compound such as hydrocarbon
of polybutadiene, etc., polyether of polyoxypropylene, etc., caster
oil or caster oil series polyol, polyester, or polycarbonate, a
polyhydroxy compound such as water or ethylene glycol, or a short
chain activated hydrogen compound such as amino alcohol, or
polyamino compound can be used as the activated hydrogen
compound.
[0057] Normal grease such as mineral oil or lithium soap grease can
be used as the grease.
[0058] In this case, preferably the percentage composition of the
lubricant-containing polymer member may be set to 80%-40% by weight
of polyurethane rubber and 20%-60% by weight of grease with respect
to all weight. If polyurethane rubber is less than 40% by weight,
necessary hardness, strength, etc., cannot be provided.
[0059] If polyurethane rubber exceeds 80% by weight (grease is less
than 20% by weight), lubricant supply lessens and the slide torque
reduction effect decreases.
BRIEF DESCRIPTION OF THE DRAWING
[0060] In the accompanying drawings:
[0061] FIG. 1 is a fragmentary sectional view to show the main part
of a conventional ball screw;
[0062] FIG. 2 is a sectional view to show a conventional feed screw
device;
[0063] FIG. 3 is an exploded perspective view to show the main part
of a ball screw according to a first embodiment of the
invention;
[0064] FIG. 4 is a sectional view to show the main part of a ball
screw according to the first embodiment of the invention;
[0065] FIG. 5 is views to show a lubricant supply device according
to the first embodiment of the invention; 5(a) and 5(b) are a
sectional view and a front view of the lubricant supply device
respectively;
[0066] FIG. 6 is views to show a retaining ring according to the
first embodiment of the invention; 6(a) and 6(b) are a side view of
the retaining ring and a front view from the outside of the
retaining ring;
[0067] FIG. 7 is an illustration to explain the effects of notches
and expansion members according to the first embodiment of the
invention; 7(a) shows a state before the expansion members are
inserted and 7(b) show a state after the expansion members are
inserted;
[0068] FIG. 8 is a sectional view to show the main part of a ball
screw according to a second embodiment of the invention;
[0069] FIG. 9 is views to show a lubricant supply device according
to the second embodiment of the invention; 9(a) and 9(b) are a
sectional view and a front view of the lubricant supply device
respectively;
[0070] FIG. 10 is views to show an expansion member according to
the second embodiment of the invention; 10(a) and 10(b) are a
side-view and a front view of the expansion member
respectively;
[0071] FIG. 11 is views to show a retaining ring according to the
second embodiment of the invention; 11(a) and 11(b) are a side view
of the retaining ring and a front view from the outside of the
retaining ring;
[0072] FIG. 12 is an exploded perspective view to show the main
part of a ball screw according to a third embodiment of the
invention;
[0073] FIG. 13 is a fragmentary sectional view to show the main
part of the ball screw according to the third embodiment of the
invention;
[0074] FIG. 14 is an exploded perspective view to show the main
part of a ball screw according to a fourth embodiment of the
invention;
[0075] FIG. 15 is a sectional view to show the main part of the
ball screw according to the fourth embodiment of the invention;
[0076] FIG. 16 is an illustration to explain the functions of
projections and insertion holes according to the fourth embodiment
of the invention;
[0077] FIG. 17 is an exploded perspective view to show the main
part of a ball screw according to a fifth embodiment of the
invention;
[0078] FIG. 18 is a sectional view to show the main part of the
ball screw according to the fifth embodiment of the invention;
[0079] FIG. 19 is an exploded perspective view to show the main
part of a ball screw according to a sixth embodiment of the
invention;
[0080] FIG. 20 is a sectional view to show another example of
lubricant supply device;
[0081] FIG. 21 is a sectional view to show the main part of a ball
screw according to a seventh embodiment of the invention;
[0082] FIG. 22 is a sectional view to show an inner diameter part
of another example of lubricant supply device;
[0083] FIG. 23 is a sectional view to show the main part of a ball
screw according to an eighth embodiment of the invention;
[0084] FIG. 24 is a perspective view to show a lubricant-containing
polymer member used in the eighth embodiment of the invention;
[0085] FIG. 25 is a perspective view to show a modified example of
the lubricant-containing polymer member shown in FIG. 24;
[0086] FIG. 26 is a sectional view to show the main part of a ball
screw according to a ninth embodiment of the invention;
[0087] FIG. 27 is a perspective view to show a lubricant-containing
polymer member used in the ninth embodiment of the invention;
[0088] FIG. 28 is a perspective view to show a modified example of
the lubricant-containing polymer member shown in FIG. 27;
[0089] FIG. 29 is a sectional view to show the main part of a ball
screw according to a tenth embodiment of the invention;
[0090] FIG. 30 is a sectional view to show the main part of a ball
screw according to an eleventh embodiment of the invention;
[0091] FIG. 31 is an illustration to show a first modified example
of a lubricant-containing polymer member formed with communication
holes according to the invention;
[0092] FIG. 32 is an illustration to show a first modified example
of a lubricant-containing polymer member formed with communication
holes according to the invention;
[0093] FIG. 33 is an illustration to show a first modified example
of a lubricant-containing polymer member formed with communication
holes according to the invention;
[0094] FIG. 34 is a perspective view to show application of the
invention to a single axis actuator;
[0095] FIG. 35 is a front view to show a lubricant-containing
polymer member used with the single axis actuator in FIG. 34;
[0096] FIG. 36 is a sectional view taken on line C-C in FIG.
35;
[0097] FIG. 37 is a sectional view of the main part of a modified
example of lubricant-containing polymer member according to the
invention;
[0098] FIG. 38 is a sectional view of the main part of a modified
example of lubricant-containing polymer member according to the
invention;
[0099] FIG. 39 is a sectional view of the main part of a modified
example of lubricant-containing polymer member according to the
invention;
[0100] FIG. 40 is a sectional view of the main part of a modified
example of lubricant-containing polymer member according to the
invention; and
[0101] FIG. 41 is a sectional view of the main part of a modified
example of lubricant-containing polymer member according to the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0102] Referring now to the accompanying drawings, there are shown
preferred embodiments of the invention. In the embodiments, feed
screw devices will be discussed by taking ball screws as examples.
Of course, the description to follow goes for other feed screw
devices such as square threads.
[0103] FIG. 3 is an exploded perspective view to show the main part
of a ball screw according to a first embodiment of the invention
and FIG. 4 is a sectional view of the main part.
[0104] First, a general configuration of the first embodiment will
be discussed. The ball screw comprises a nut member 2 threadably
engaged into a screw shaft 1 having a spiral thread groove 1a on an
outer peripheral surface via a large number of balls 3. The nut
member 2 is formed in an inner peripheral surface with a thread
groove 2a corresponding to the thread groove 1a of the screw shaft
1 and has a ball circulation passage (not shown) for guiding and
circulating the balls 3 rolling in both the thread grooves 1a and
2a in a thick barrel portion.
[0105] An annular recess 4 for attaching a lubricant supply device
is formed in both end faces of the inner diameter side of the nut
member 2 coaxially with the nut member 2. Two tapped holes 5 are
made in each of both the end faces of the nut member 2 with the
axes parallel with the axis of the nut member 2. A lubricant supply
device 6 is fitted into the recess 4 of the nut member 2
coaxially.
[0106] The lubricant supply device 6 is a ring-like member having
an outer diameter that can be fitted into the recess 4, as shown in
FIG. 5; for example, it is made of a material such as rubber or
synthetic resin for producing a predetermined elastic force for
providing flexibility and contains a lubricant such as grease or
mineral oil.
[0107] The lubricant supply device 6 has an assembly cut part 6a at
a place in a circumferential direction of the lubricant supply
device 6 and is formed with notches 7 at outer peripheral positions
shifted by 90 degrees from the cut part 6a in the circumferential
direction, whereby the two notches 7 are formed at symmetrical
positions mutually shifted 180 degrees in the circumferential
direction. In the embodiment, the notches 7 are made circular in
cross section extending in a thickness direction of the lubricant
supply device 6.
[0108] Further, projections 6b that can be fitted into the thread
groove 1a of the screw shaft 1 project in the inner diameter
direction on the inner peripheral surface of the lubricant supply
device 6.
[0109] Tubular members 8 are included making up an expansion member
that can be fitted into the notches 7 of the lubricant supply
device 6. The tubular member 8 has an external diameter slightly
larger than the diameter of the notch 7 and is slightly longer than
the thickness of the lubricant supply device 6.
[0110] Further, a retaining ring 9 is included for attaching the
lubricant supply device 6 to the nut member 2.
[0111] This retaining ring 9 has an inner diameter which is the
same as the diameter of the nut member 2 and an inner diameter to
place the retaining ring 9 out of contact with the outer peripheral
surface of the screw shaft 1, as shown in FIG. 4. In addition, as
shown in FIG. 6, on the face of the retaining ring 9 opposed to the
nut member 2, through holes 9a are made at positions corresponding
to the tapped holes 5 made in the nut member 2 and recesses 9b into
which the tubular members 8 can be fitted are formed at positions
corresponding to the notches 7 of the lubricant supply device
6.
[0112] First, the lubricant supply device 6 is fitted into the
recess 4 and is inserted between the screw shaft 1 and the nut
member 2, then the tubular members 8 are fitted into the notches 7
of the lubricant supply device 6 in parallel with the axis of the
nut member 2. Alternatively, after the tubular members 8 are fitted
into the notches 7, the lubricant supply device 6 is fitted into
the recess 4. In the state, the ends of the tubular members 8
fitted into the notches 7 project outward.
[0113] Successively, the projecting ends of the tubular members 8
are fitted into the recesses 9b of the retaining ring 9 and the
retaining ring 9 is abutted against the end of the nut member 2,
then set screws 10 inserted into the through holes 9a of the
retaining ring 9 are threadably engaged into the tapped holes 5 of
the nut member 2. Thus, the lubricant supply device 6 is fixed to
the nut member 2, as shown in FIG. 4.
[0114] Here, the lubricant supply device 6 is formed only of a
lubricant-containing polymer, for example. To manufacture the
lubricant supply device 6, for example, a lubricant-containing
polymer is fused, then injected into a predetermined metal mold,
pressurized, cooled and hardened, and molded. In this case,
injection molding can be executed. For example, used as the
lubricant-containing polymer member is a mixture of polyethylene
consisting of 20% by weight of low molecular weight polyethylene
(molecular weight 1.times.10.sup.3 to 5.times.10.sup.5) and 10% by
weight of ultra-high molecular weight polyethylene (molecular
weight 1.times.10.sup.6 to 5.times.10.sup.6) and 70% by weight of
paraffin mineral oil as a lubricant.
[0115] Next, the operation and effects of the ball screw will be
discussed.
[0116] When the screw shaft 1 makes relative rotation to the nut
member 2, the balls 3 in the nut member 2 roll on a spiral space
formed by the relative thread grooves 1a and 2a in the rotation
direction of the screw shaft 1 and circulate through a ball
circulation passage (not shown). As the balls 3 roll, the nut
member 2 is fed in the linear direction along the screw shaft 1.
The projections 6b of the lubricant supply device 6 prevent the
lubricant filled in the ball screw from leaking to the outside and
also prevent a foreign material such as dust from entering the ball
screw from the outside; the lubricant supply device 6 also serves
as a seal member.
[0117] Since the lubricant supply device 6 has a dimension error,
it is feared that a microscopic gap may be formed between the inner
peripheral surface and the outer peripheral surface of the screw
shaft 1. In the embodiment, however, the tubular members 8 larger
than the notches 7 are inserted into the notches 7, whereby the
notches 7 push and widen the outer periphery of the lubricant
supply device 6 in the circumferential direction, as shown in FIG.
7.
[0118] That is, a compression force toward the circumferential
direction acts on the inside of the outer periphery of the
lubricant supply device 6 and causes the full inner peripheral
surface to be displaced to the inner diameter side. Resultantly,
even if a dimension error exists, the full inner peripheral surface
of the lubricant supply device 6 comes in reliable contact with the
outer peripheral surface of the screw shaft 1.
[0119] At this time, in the embodiment, the lubricant supply device
6 is not pressed diametrically for bringing the inner peripheral
surface into contact with the outer peripheral surface of the screw
shaft 1; instead, the compression force along the circumferential
direction causes the inner peripheral surface to come in contact
with the outer peripheral surface of the screw shaft 1, thus the
notches 7 need not be made in all the peripheral surface of the
lubricant supply device 6. Moreover, the tubular members 8 of
expansion members are only inserted into the lubricant supply
device 6, so that enlarging the diameter of the nut member 2,
namely, the outer diameter of the feed screw device is not required
either.
[0120] Since the lubricant supply device 6 contains a lubricant,
the lubricant exuding gradually from the inner peripheral surface
of the lubricant supply device 6 drastically reduces frictional
resistance at the sliding time between the inner peripheral surface
of the lubricant supply device 6 and the outer peripheral surface
of the screw shaft 1, so that slide torque lessens, preventing
disturbance of drive of the ball screw.
[0121] Further, when the ball screw is driven, a lubricant exudes
gradually from the inner peripheral surface of the lubricant supply
device 6 with relative rotation of the screw shaft 1, is supplied
to the thread groove 1a of the screw shaft 1, and uniformly covers
the balls 3 rolling in the thread groove 1a and the thread groove
2a of the nut member 2 for stable lubrication over a long term.
[0122] Therefore, even if a lubricant is not supplied to the inside
of the nut member 2 from the outside, the ball screw can continue
good running for a long time at low torque. Since a lubricant need
not be supplied to the inside of the nut member 2 from the outside,
the ball screw can be used as effective lubrication means in a
system that can use only an extremely small amount of lubricant,
such as a semiconductor manufacturing system.
[0123] Further, as described above, the tubular members 8 are
inserted into the notches 7, so that a compression force toward the
circumferential direction acts on the inside of the lubricant
supply device 6, also producing the effect of bringing the opposed
faces of the cut parts 6a made in the lubricant supply device 6
into contact with each other or lessening the gap therebetween.
[0124] The ends of the tubular members 8 for pressing the inner
peripheral surface of the lubricant supply device 6 against the
outer periphery of the screw shaft 1 are fitted only into the
recesses 9b of the retaining ring 9, so that when the ball screw is
driven, rotation of the lubricant supply device 6 can be prevented.
This means that the tubular members 8 of expansion members also
have a role in stopping rotation of the lubricant supply device
6.
[0125] Next, a second embodiment of the invention will be
discussed. Members identical with or similar to those previously
described in the first embodiment are denoted by the same reference
numerals in FIGS. 8 to 11.
[0126] The basic configuration of a ball screw of the second
embodiment is similar to that of the first embodiment, as shown in
FIG. 8.
[0127] That is, as shown in FIG. 9, a lubricant supply device 6 is
formed in an outer peripheral surface with three notches shifted by
90 degrees in the circumferential direction, but is not formed on
an inner peripheral surface with projections 6b fitted into thread
groove 1a of screw shaft 1.
[0128] Expansion members 12 inserted into the notches 7 are made of
spring members each having a slit 12a along the axial direction, as
shown in FIGS. 10(a) and 10(b), for easy assembling of the
expansion members 12.
[0129] As shown in FIGS. 11(a) and 11(b), a retaining ring 9 has an
outer diameter that can be fitted into a recess 4 made in a nut
member 2 and has tapped holes 9c, each with an axis directed
diametrically, made in the peripheral surface in place of through
holes 9a. Mounting holes 13 each extending in the radial direction
thereof so as to be coincided with the tapped holes 9c are also
made in the nut member 2. In FIG. 8, numeral 17 denotes a set screw
mounted in the tapped hole 9c and the mounting hole 13.
[0130] Other components are similar to those of the first
embodiment.
[0131] The second embodiment has the function and effects similar
to those of the first embodiment.
[0132] The lubricant supply device 6 is not formed on the inner
peripheral surface with projections 6b that can be fitted into the
thread groove 1a of the screw shaft 1. However, the inner diameter
of the lubricant supply device 6 is shrunk by the action of the
expansion members for pressing the inner peripheral surface of the
lubricant supply device 6 against the outer peripheral surface of
the screw shaft 1, thereby making contact.
[0133] Next, a third embodiment of the invention will be discussed.
Members identical with or similar to those previously described in
the first embodiment are denoted by the same reference numerals in
FIGS. 12 and 13.
[0134] The basic configuration of a ball screw of the third
embodiment is similar to that of the first embodiment, as shown in
FIGS. 12 and 13.
[0135] However, a lubricant supply device 6 is abutted against the
end face of a nut member 2 coaxially without forming the nut member
2 with a recess into which the lubricant supply device 6 is
fitted.
[0136] Tapped holes 15 are made at positions of the end face of the
nut member 2 corresponding to the positions of notches 7 made in
the lubricant supply device 6.
[0137] A retaining ring 9 is molded into a cap-shape that can store
the lubricant supply device 6. Small-diameter tapped holes 16
directed toward the outside from the bottom faces of recesses 9b
into which tubular members 8 are fitted are made in place of
through holes 9a.
[0138] The tips of set screws 10 penetrating the tapped holes 16,
the recesses 9b, and the tubular members 8 coaxially are threadably
engaged into the tapped holes 15 of the nut member 2 for fixing the
lubricant supply device 6.
[0139] Thus, without making recesses 4 in the nut member 2, the set
screws 10 for fixing the lubricant supply device 6 can be laid out
at the same positions as the placement positions of the tubular
members 8 of expansion members.
[0140] However, at least the portion of the lubricant supply device
6 coming in contact with the outer peripheral surface of a screw
shaft 1, namely, only the inner peripheral surface may be made of a
member containing a lubricant.
[0141] Further, the lubricant supply device 6 may have only the
inner diameter side softened. In doing so, the hardness for holding
the shape required as the lubricant supply device 6 can be provided
on the outer peripheral surface side and the displacement amount in
the inner diameter direction on the inner peripheral side produced
by a compression force along the circumferential direction can be
set large and press pressure against the outer peripheral surface
of the screw shaft 1 can be set small.
[0142] Further more, although in the embodiments two or three
notches 7 are provided, one notch 7 or four or more notches 7 may
be made. The notches 7 need not be of the same shape.
[0143] The shape is not limited to circular cross section and may
be angular cross section; the axis of the notch 7 need not
necessarily be set in parallel with the axis of the nut member
2.
[0144] In the embodiments, the notches 7 are opened to the outer
periphery of the lubricant supply device 6, but may be formed into
a hole with the outer periphery side closed. However, the notch
opened to the outer periphery produces a larger effect.
[0145] The hollow tubular members are adopted for the expansion
members as an example, but the expansion members are not limited to
them; they may be like a circular cylinder and the cross section is
not limited to being circular.
[0146] Further, in the embodiments, the ends of the expansion
members are projected to the side of the retaining ring 9, but may
be projected to the side of the nut member 2 and the corresponding
recesses may be made on the side of the number member 2. A portion
projecting toward the outer peripheral direction of the lubricant
supply device 6 may be made on the outer periphery of the expansion
member for use as a rotation stopper.
[0147] In the embodiments, the lubricant supply device 6 also
serves as a seal member, but a separate seal member may be
provided.
[0148] Next, a fourth embodiment of the invention will be
discussed. Members identical with or similar to those previously
described in the first embodiment are denoted by the same reference
numerals in FIGS. 14 to 16 and will not be discussed again.
[0149] A lubricant supply device 106 has a cut part 106a for
assembly in the circumferential direction and two insertion holes
107 made with the cut part 106a. The two insertion holes 107 are
paired and are made so as to extend in parallel with the axis of
the lubricant supply device 106. In FIGS. 14 and 15, the insertion
holes are shown as through holes, but may be holes each having the
bottom surface.
[0150] Further, a fixed ring 108 for attaching the lubricant supply
device 106 to a nut member 2 is included. It provides a press
member with one surface facing the axial opposed end face of the
lubricant supply device 106.
[0151] The fixed ring 108 is a disk-like member having an inner
diameter which is the same as the outer diameter of the nut member
2 and an inner diameter to place the fixed ring 108 out of contact
with the outer peripheral surface of the screw shaft 1. On the face
opposed to the nut member 2, through holes 109 are made at
positions corresponding to tapped holes 5 made in the nut member 2.
In addition, projections 110 projecting toward the lubricant supply
device 106 are formed at positions corresponding to the insertion
holes 107 of the lubricant supply device 106.
[0152] The span between the two projections 110 is set slightly
smaller than that between the paired insertion holes 107. In the
embodiment, the projection 110 is formed by cutting a part of the
fixed ring 108 and bending the part to the lubricant supply device
106. That is, the projections 110 can be made by press working,
etc.
[0153] Assembling process of the lubricant supply device according
to the fourth embodiment will be described hereinafter.
[0154] First, the lubricant supply device 106 is fitted into a
recess 4 of the nut member 2 and is inserted between the screw
shaft 1 and the nut member 2. In the state, one axial end face of
the lubricant supply device 6 is opposed axially to the bottom face
of the recess 4 of the nut member 2 and the inner peripheral
surface of the lubricant supply device 106 is opposed diametrically
to the outer peripheral surface of the screw shaft 1.
[0155] Successively, the projections 110 of the fixed ring 108 are
inserted into the insertion holes 107 of the lubricant supply
device 106 and set screws 111 inserted into the through holes 109
are threadably engaged into the tapped holes 5 with the outer
periphery of the fixed ring 108 abutted against the end of the nut
member 2 coaxially, so that the fixed ring 108 is fixed to the nut
member 2.
[0156] Here, the lubricant supply device 106 is formed only of a
lubricant-containing polymer, for example. To manufacture the
lubricant supply device 106, for example, a lubricant-containing
polymer is fused, then injected into a predetermined metal mold,
pressurized, cooled and hardened, and molded. In this case,
injection molding can be executed. For example, used as the
lubricant-containing polymer member is a mixture of polyethylene
consisting of 20% by weight of low molecular weight polyethylene
(molecular weight 1.times.10.sup.3 to 5.times.10.sup.5) and 10% by
weight of ultra-high molecular weight polyethylene (molecular
weight 1.times.10.sup.6 to 5.times.10.sup.6) and 70% by weight of
paraffin mineral oil as a lubricant.
[0157] Next, the operation and effects of the ball screw will be
discussed.
[0158] When the screw shaft 1 makes relative rotation to the nut
member 2, balls 3 in the nut member 2 roll on a spiral space formed
by the relative thread grooves 1a and 2a in the rotation direction
of the screw shaft 1 and circulate through a ball circulation
passage (not shown). As the balls 3 roll, the nut member 2 is fed
in the linear direction along the screw shaft 1. The inner
peripheral surface of the lubricant supply device 106 prevents the
lubricant filled in the ball screw from leaking to the outside and
also prevent a foreign material such as dust from entering into the
ball screw from the outside; the lubricant supply device 106 also
serves as a seal member.
[0159] When the screw shaft 1 makes relative rotation to the nut
member 2 and then the nut member 2 is moved in the axial direction,
rotation torque and an axially external force are applied to the
lubricant supply device 106 as load.
[0160] However, in the embodiment, the lubricant supply device 106
is sandwiched axially between the bottom face of the recess 4 of
the nut member 2 and the fixed ring 108, thus an axial movement of
the lubricant supply device 106 is blocked. Resultantly, jump out
of the lubricant supply device 106 from the nut member 2 can be
prevented.
[0161] In addition, the projections 110 projected from the fixed
ring 8 are inserted into the insertion holes 107 of the lubricant
supply device 106, so that rotation of the lubricant supply device
106 in the circumferential direction can be prevented. Resultantly,
when the screw shaft 1 rotates, the lubricant supply device 106
does not rotate with the screw shaft 1 and comes in sliding contact
with the outer peripheral surface of the screw shaft 1.
[0162] At this time, since the lubricant supply device 106 contains
a lubricant, the lubricant exuding gradually from the inner
peripheral surface of the lubricant supply device 106 drastically
reduces frictional resistance at the sliding time between the inner
peripheral surface of the lubricant supply device 106 and the outer
peripheral surface of the screw shaft 1, so that slide torque
lessens, preventing disturbance of drive of the ball screw and
lessening the rotation force input to the lubricant supply device
106.
[0163] Further, when the ball screw is driven, a lubricant exudes
gradually from the inner peripheral surface of the lubricant supply
device 106 with relative rotation of the screw shaft 1 as described
above, is supplied to the thread groove 1a of the screw shaft 1,
and uniformly covers the balls 3 rolling in the thread groove 1a
and the thread groove 2a of the nut member 2 for stable lubrication
over a long term.
[0164] Therefore, even if a lubricant is not supplied to the inside
of the nut member 2 from the outside, the ball screw can continue
good running for a long time at low torque. Since a lubricant need
not be supplied to the inside of the nut member 2 from the outside,
the ball screw can be used as effective lubrication means in a
system that can use only an extremely small amount of lubricant,
such as a semiconductor manufacturing system.
[0165] Since the span between the projections 110 is set slightly
smaller than that between the paired insertion holes 107 made in
the lubricant supply device 106, the projections 110 inserted into
the insertion holes 107 give such pilot pressure F to make the
opposed faces between the cut parts 106a approach each other or
press the opposed faces, as shown in FIG. 16. As a result of the
pilot pressure F, even if the lubricant supply device 106 contains
a dimension error, such a force to hold the screw shaft 1 acts,
causing the inner peripheral surface of the lubricant supply device
106 to come in reliable contact with the outer peripheral surface
of the screw shaft 1.
[0166] At this time, the lubricant supply device 106 is not pressed
diametrically for bringing the inner peripheral surface of the
lubricant supply device 106 into contact with the outer peripheral
surface of the screw shaft 1 and such a force to hold the screw
shaft 1 causes the inner peripheral surface of the lubricant supply
device 106 to come in contact with the outer peripheral surface of
the screw shaft 1. If the insertion holes 107 and the projections
110 are not made on all the periphery of the lubricant supply
device 106 in the circumferential direction, all the inner
peripheral surface of the lubricant supply device 106 can come in
reliable contact with the screw shaft 1. Moreover, the insertion
holes 110 are only inserted into the insertion holes 107 of the
lubricant supply device 106, so that it is not necessary to enlarge
the diameter of the nut member 2, namely, the outer diameter of the
screw device.
[0167] By only assembling the fixed ring 108 having the projections
110 of a simple structure, jump out of the lubricant supply device
106 from the nut member 2 can be prevented, the lubricant supply
device 106 can be prevented from rotating with the screw shaft 1,
and the inner peripheral surface of the lubricant supply device 106
can be brought into contact with the outer peripheral surface of
the screw shaft 1.
[0168] Note that a pipe-shaped spacer may be previously inserted
into the insertion hole 107 of the lubricant supply device 106 for
preventing distortion between the projection 110 and the insertion
hole 107 when rotation force is input.
[0169] In this embodiment, although a set of a pair of insertion
holes and a pair of projections is taken as an example, a set of
two or more pairs of insertion holes or three or more insertion
holes and two or more pairs of projections or three or more
projections can be provided.
[0170] Next, a fifth embodiment of the invention will be discussed.
Members identical with or similar to those previously described in
the fourth embodiment are denoted by the same reference numerals in
FIGS. 17 and 18.
[0171] The basic configuration of a ball screw of the fifth
embodiment is similar to that of the fourth embodiment, as shown in
FIGS. 17 and 18.
[0172] However, a plurality of lip parts 120 are projected along
the circumferential direction toward the inner peripheral surface
of a lubricant supply device 106 and come in sliding contact with
the outer peripheral surface of a screw shaft 1.
[0173] A fixed ring 108 providing a press member has an outer
diameter set slightly larger than the diameter of a recess 4 of a
nut member 2 and has a part cut in the circumferential direction
instead of a through hole 109 shown in the fourth embodiment. A
pair of mounting holes 108b are made in the proximity of the cut
part 108a.
[0174] A ring-like fit groove 121 into which the fixed ring 108 can
be fitted is formed in the inner peripheral surface of the recess 4
of the nut member 2.
[0175] After the lubricant supply device 106 is engaged into the
recess 4, the fixed ring 108 is fitted into the fit groove 121 in
the recess 4. To fit the fixed ring 108, the mounting holes 108b
are used to lessen the distance between the opposed faces of the
cut part 106a for reducing the diameter of the fixed ring 8. In
this state, the fixed ring 108 is inserted into the recess 4.
[0176] Also in this case, projections of the fixed ring 108 are
inserted into insertion holes 107 of the lubricant supply device
106.
[0177] Other components and the function and effects of the fifth
embodiment are similar to those of the fourth embodiment.
[0178] However, the portions of the lubricant supply device 106
coming in contact with the screw shaft 1 are formed as the lip
parts 120 so as to provide interference, so that the inner
periphery of the lubricant supply device 106 comes in reliable
contact with the outer peripheral surface of the screw shaft 1 even
if pilot pressure F, etc., is not given. Thus, it is possible to
eliminate the pilot pressure F.
[0179] Even if the interference state is set up, press pressure put
on the outer peripheral surface of the screw shaft 1 is small,
because the lip parts 120 can be warpped. No problem arises in this
state.
[0180] In the fifth embodiment, the lubricant supply device 106 is
engaged into the nut member 2, thus set screws are not
required.
[0181] Next, a sixth embodiment of the invention will be discussed.
Members identical with or similar to those previously described in
the fourth embodiment are denoted by the same reference numerals in
FIG. 19.
[0182] The basic configuration of a ball screw of the sixth
embodiment is similar to that of the fourth embodiment, as shown in
FIG. 19.
[0183] However, a plurality of lip parts 120 are provided along the
circumferential direction toward the inner peripheral surface of a
lubricant supply device 106, so that pilot pressure F need not be
given, reducing the number of projections 110 formed on a fixed
ring 108 to one.
[0184] Other components and the function and effects of the fifth
embodiment are similar to those of the above-described
embodiment.
[0185] However, in order to balance mounting, a set of insertion
hole 107 and projection 110 may also be made at points shifted 180
degrees in the circumferential direction.
[0186] The lubricant supply devices of these embodiments may have
no projections on the inner peripheral surface or may be provided
with a plurality of lip parts 20. However, the invention is not
limited to them. For example, a spiral projection 106b that can be
fitted into the thread groove 1 of the screw shaft 1 may be made on
the inner peripheral surface of the lubricant supply device, as
shown in FIG. 20.
[0187] Next, a seventh embodiment of the invention will be
discussed. Members identical with or similar to those previously
described in the fourth embodiment are denoted by the same
reference numerals in FIG. 21.
[0188] The basic configuration of a ball screw of the seventh
embodiment is similar to that of the above-mentioned embodiment, as
shown in FIG. 21.
[0189] However, without forming a nut member 2 with a recess 104, a
cap-shaped press member 125 is formed and a lubricant supply device
106 is housed in the cap-shaped press member 125. At this time, a
bottom 125a of the cap-shaped press member 125 is opposed axially
to the axial opposed end face of the lubricant supply device
106.
[0190] Other components and the function and effects of the seventh
embodiment are similar to those of the above-described embodiment.
However, in the seventh embodiment, the nut member need not be
formed with the recess 4.
[0191] Further, a projection 110 is made on the bottom 125a opposed
axially to the lubricant supply device 106 as in the
above-described embodiment, but the invention is not limited to it.
For example, the projection 110 may be made on a circumferential
wall portion 125b opposed to the lubricant supply device 106 in the
circumferential direction 6.
[0192] In the embodiments, a part of the press member of the fixed
ring, etc., is cut and the cut part is bent for forming the
projection. However, the invention is not limited to it. For
example, the projection may be formed by welding etc., on the face
opposed to the lubricant supply device or a hole may be made in the
press member and a bar-like member may be attached to the hole as a
projection. However, if the projection is formed by cutting a part
of the press member and bending the cut part as described above, it
can be manufactured by press working easily and at low costs.
[0193] In the embodiments, the insertion holes are made in the
lubricant supply device and the projections are inserted into the
insertion holes. However, the invention is not limited to it. For
example, without making the insertion holes in the lubricant supply
device, it is possible to make the tips of the projections sharpen,
in such a manner that the projections may be stuck into the
lubricant supply device for insertion. At this time, in the case
where pilot pressure in the circumferential direction is preferably
put as load, the projections may be stuck into the lubricant supply
device while the lubricant supply device is being warped in the
circumferential direction.
[0194] In the embodiment, the lubricant supply device also serves
as a seal member, but a separate seal member may be provided.
[0195] The lubricant supply device may be divided into parts along
the circumferential direction. That is, the lubricant supply device
may be like a ring as a whole. In this case, projections may be
provided so as to connect the divisions or so as to correspond with
the divisions.
[0196] Further, as shown in FIG. 22, the portion of the lubricant
supply device coming in contact with the screw shaft 1 may be
formed into a plurality of lip parts 30 axially arranged.
[0197] Next, an eighth embodiment of the invention will be
discussed.
[0198] FIG. 23 is a sectional view to show the main part of a ball
screw according to the eighth embodiment of the invention to show a
specific structure of a feed screw device; the embodiment is
applied particularly to a seal-type ball screw.
[0199] In the embodiment, a spiral thread groove 201b is formed in
an outer peripheral surface 201a of a screw shaft 201 and a ball
screw nut 202 is formed in an inner peripheral surface 202a with a
thread groove 202b corresponding to the thread groove 201b. The
ball screw nut 202 is threadably engaged into the screw shaft 201
with a large number of balls 203 disposed between the thread
grooves 201b and 202b. Although not shown, a ball circulation
section for guiding the balls 203 into the thread grooves 201b and
202b and rolling and circulating the balls is formed in the thick
barrel portion of the ball screw.
[0200] The ball screw nut 202 is formed in an end face with an
annular recess 205 into which a lubricant-containing polymer member
210 is fitted. The lubricant-containing polymer member 210 is an
elastic member formed into a cylindrical shape, is provided with a
cut part 210a along the substantially axial direction as shown in
FIG. 24, and contains a lubricant such as grease or mineral
oil.
[0201] The lubricant-containing polymer member 210 formed into a
cylindrical shape is provided on an inner peripheral surface with a
projection stripe 210b to be fitted into the thread groove 201b of
the screw shaft 201 and formed in one end face 210c with a
plurality of lubricant reserve holes 210d at positions distant from
each other in the circumferential direction.
[0202] The lubricant reserve holes 210d are filled with a
lubricant, an outer peripheral surface 210e of the
lubricant-containing polymer member 210 is abutted against an inner
peripheral surface 205a of the recess 205 made in an end face of
the ball screw nut 202, and one end face 10c of the
lubricant-containing polymer member 210 is abutted against a bottom
face 205b of the recess 205. In this state, the projection stripe
210b is fitted into the thread groove 201b of the screw shaft 201,
so that the lubricant-containing polymer member 210 is fitted into
the recess 205, as shown in FIG. 23. The ball screw nut 202 is
formed with a tapped hole extending diametrically inward from the
outer peripheral surface and opened at the recess 205. As shown in
FIG. 23, a set screw 211 is screwed into the tapped hole from the
outer peripheral surface side, so that the lubricant-containing
polymer member 210 is fixed to the ball screw nut 202.
[0203] Since the openings of the lubricant reserve holes 210d are
closed on the bottom face 205b of the recess 205, the lubricant in
the lubricant reserve holes 210d is sealed in the ball screw nut
202. The lubricant reserve holes 210d is one example of the
structures of lubricant reserve parts according to the present
invention.
[0204] According to the ball screw of the structure, when the screw
shaft 201 makes relative rotation to the ball screw nut 202, the
balls 203 in the ball screw nut 202 roll on a spiral space formed
by the relative thread grooves 201a and 202a in the rotation
direction of the screw shaft 201 and circulate through a ball
circulation passage (not shown). As the balls 203 roll, the ball
screw nut 202 is fed in the linear direction along the screw shaft
201. When the ball screw nut 202 and the screw shaft 201 make
relative rotation, a lubricant exudes from the lubricant-containing
polymer member 210 fitted into the recess 205, is supplied to the
thread groove 201b of the screw shaft 201, and uniformly covers the
balls 203 rolling in the thread groove 201b and the thread groove
202b of the ball screw nut for stable lubrication. Therefore, even
if a lubricant is not supplied to the ball screw nut 202 from the
outside, the ball screw can continue good running at low
torque.
[0205] The lubricant-containing polymer member 210 also functions
as a seal member for sealing the end of the ball screw nut 202 and
shuts off the inside of the ball screw nut 202 from the external
atmosphere. Thus, even if the feed screw device is used in the
external atmosphere which is of a bad environment wherein for
example wood chips, etc., easily absorbing lubricant are existed,
the inside of the ball screw nut 202 is protected against the wood
chips, etc., and the smooth lubrication effect can be maintained
over a long time.
[0206] As a lubricant exudes from the lubricant-containing polymer
member 210 and is consumed, the lubricant-containing polymer member
210 is replenished with the lubricant sealed in the lubricant
reserve holes 210d, so that the simple structure enables the
lubricant to be sealed in the lubricant-containing polymer member
210 and the lubricant exudes from the lubricant-containing polymer
member 210 over a long time. Thus, the balls 203 rolling in the
thread groove 201b and the thread groove 202b of the ball screw nut
can be stably lubricated for a long time.
[0207] In the lubricant-containing polymer member 210, even if
foreign materials such as wood chips are deposited on the
lubricant-containing polymer member 210 and absorb the lubricant,
the lubricant-containing polymer member 210 is replenished with a
lubricant from the lubricant reserve holes 210d. Accordingly, it is
not feared that a lubrication failure will be invited.
[0208] FIG. 25 shows a modified example of the lubricant-containing
polymer member 210 of the eighth embodiment shown in FIG. 24.
[0209] A modified example lubricant-containing polymer member 214
is also an elastic member formed like a cylindrical shape and
having a cut part 214a along the substantially axial direction, and
contains a lubricant such as grease or mineral oil by a molding
method similar to that of the lubricant-containing polymer member
210.
[0210] The lubricant-containing polymer member 214 is formed on an
inner peripheral surface with a projection stripe 214b to be fitted
into the thread groove 201b of the screw shaft 201, and the
lubricant-containing polymer member 214 is formed in one end face
214c with a lubricant reserve peripheral groove 214d continuously
extending in the circumferential direction.
[0211] The lubricant reserve peripheral groove 214d is filled with
a lubricant. An outer peripheral surface 214e of the
lubricant-containing polymer member 214 is abutted against an inner
peripheral surface 205a of the recess 205 made in an end face of
the ball screw nut 202. One end face 214c of the
lubricant-containing polymer member 214 is abutted against a bottom
face 205b of the recess 205. In this state, the projection stripe
214b is fitted into the thread groove 201b of the screw shaft 201,
so that the lubricant-containing polymer member 214 is fitted into
the recess 205. The lubricant-containing polymer member 214 is
fixed to the ball screw nut 202 by the set screw 211 shown in FIG.
23.
[0212] Since the groove opening of the lubricant reserve peripheral
groove 214d made in the one end face 214c is closed on the bottom
face 205b of the recess 205, the lubricant in the lubricant reserve
peripheral groove 214d is sealed in the ball screw nut 202. This
lubricant reserve peripheral groove 214d is one example of
structure of the lubricant reserve part according to the present
invention.
[0213] The lubricant-containing polymer member 214 also functions
as a seal member for sealing the end of the ball screw nut 202 and
shuts off the inside of the ball screw nut 202 from the external
atmosphere. Thus, even if the feed screw device is used in the
external atmosphere which is of a bad environment wherein wood
chips, etc., easily absorbing lubricant are existed, the inside of
the ball screw nut 202 is protected against such bad environment,
so that the smooth lubrication effect can be maintained over a long
time.
[0214] As a lubricant exudes from the lubricant-containing polymer
member 214 and is consumed, the lubricant-containing polymer member
214 is replenished with the lubricant sealed in the lubricant
reserve peripheral groove 214d, so that the lubricant exudes from
the lubricant-containing polymer member 214 over a long time. Thus,
the balls 203 rolling in the thread groove 201b and the thread
groove 202b of the ball screw nut can be stably lubricated for a
long time.
[0215] Even if foreign materials such as wood chips are deposited
on the lubricant-containing polymer member 214 and absorb the
lubricant, the lubricant-containing polymer member 214 is
replenished with a lubricant from the lubricant reserve peripheral
groove 214d, thus it is not feared that a lubrication failure will
be invited.
[0216] FIG. 26 is a sectional view to show the main part of a ball
screw according to a ninth embodiment of the invention. FIG. 27 is
a perspective view to show a lubricant-containing polymer member
used in the ninth embodiment. Components identical with those
previously described with reference to FIGS. 23 to 25 in the eighth
embodiment are denoted by the same reference numerals in FIGS. 26
and 27 and will not be discussed again.
[0217] In the ninth embodiment, a lubricant-containing polymer
member 216 fitted into an annular recess 205 is an elastic member
formed into a cylindrical shape and having a cut part 216a along
the substantially axial direction, as shown in FIG. 27, and
contains a lubricant such as grease or mineral oil as in the eighth
embodiment. The lubricant-containing polymer member 216 is formed
on an inner peripheral surface with a projection stripe 216b fitted
into a thread groove 201b of a screw shaft 201 and formed in an
outer peripheral surface 216e with a plurality of lubricant reserve
holes 216d at positions distant from each other in the
circumferential direction.
[0218] The lubricant reserve holes 216d are filled with a
lubricant, the outer peripheral surface 216e of the
lubricant-containing polymer member 216 is abutted against an inner
peripheral surface 205a of the recess 205 made in a ball screw nut
202, and one end face 216c of the lubricant-containing polymer
member 216 is abutted against a bottom face 205b of the recess 205.
In this state, the projection stripe 216b is fitted into the thread
groove 201b of the screw shaft 201, so that the
lubricant-containing polymer member 216 is fitted into the recess
205, as shown in FIG. 26. Set screws 211 are screwed into tapped
holes made toward the recess 205 of the ball screw nut 202, so that
the tips of the set screws 211 are engaged into the lubricant
reserve holes 216d for fixing the lubricant-containing polymer
member 216 to the ball screw nut 202.
[0219] Since the openings of the lubricant reserve holes 216d are
closed on the inner peripheral surface 205a of the recess 205, the
lubricant in the lubricant reserve holes 216d is sealed in the ball
screw nut 202. The lubricant reserve holes 216d is one example of
structure of the lubricant reserve part according to the present
invention.
[0220] According to the ball screw of the structure, when the screw
shaft 201 makes relative rotation to the ball screw nut 202, the
balls 203 in the ball screw nut 202 roll on a spiral space formed
by the relative thread grooves 201a and 202a in the rotation
direction of the screw shaft 201 and circulate through a ball
circulation passage (not shown). As the balls 203 roll, the ball
screw nut 202 is fed in the linear direction along the screw shaft
201. When the ball screw nut 202 rotates, a lubricant exudes from
the lubricant-containing polymer member 216 fitted into the recess
205, is supplied to the thread groove 201b of the screw shaft 201,
and uniformly covers the balls 203 rolling in the thread groove
201b and the thread groove 202b of the ball screw nut for stable
lubrication. Therefore, even if a lubricant is not supplied to the
ball screw nut 202 from the outside, the ball screw can continue
good running at low torque.
[0221] The lubricant-containing polymer 216 also functions as a
seal member for sealing the end of the ball screw nut 202 and shuts
off the inside of the ball screw nut 202 from the external
atmosphere. Thus, even if the feed screw device is used in the
external atmosphere which is of a bad environment wherein for
example wood chips, etc., easily absorbing lubricant are existed,
the inside of the ball screw nut 202 is protected against the wood
chips, etc., and the smooth lubrication effect can be maintained
over a long time.
[0222] As a lubricant exudes from the lubricant-containing polymer
member 216 and is consumed, the lubricant-containing polymer member
216 is replenished with the lubricant sealed in the lubricant
reserve holes 216d, so that the lubricant exudes from the
lubricant-containing polymer member 216 over a long time. Thus, the
balls 203 rolling in the thread groove 201b and the thread groove
202b of the ball screw nut can be stably lubricated for a long
time.
[0223] Even if foreign materials such as wood chips are deposited
on the lubricant-containing polymer member 216 and absorb the
lubricant, the lubricant-containing polymer member 216 is
replenished with a lubricant from the lubricant reserve holes 216d,
thus it is not feared that a lubrication failure will be
invited.
[0224] FIG. 28 shows a modified example of the lubricant-containing
polymer member 216 of the ninth embodiment shown in FIG. 27.
[0225] A modified example lubricant-containing polymer member 218
is also an elastic member formed into a cylindrical shape and
having a cut part 218a along the substantially axial direction, and
contains a lubricant such as grease or mineral oil by a molding
method similar to that of the lubricant-containing polymer member
216.
[0226] The lubricant-containing polymer member 218 is formed on an
inner peripheral surface with a projection stripe 218b fitted into
the thread groove 201b of the screw shaft 201 and formed in an
outer peripheral surface 218e with & lubricant reserve
peripheral groove 218d continuous in the circumferential
direction.
[0227] As similar to the lubricant reserve peripheral groove 216d
shown in FIG. 26, the lubricant reserve peripheral groove 218d is
filled with a lubricant, an outer peripheral surface 218e of the
lubricant-containing polymer member 218 is abutted against an inner
peripheral surface 205a of the recess 205 made in the ball screw
nut 202, and one end face 218c of the lubricant-containing polymer
member 218 is abutted against a bottom face 205b of the recess 205.
In this state, the projection stripe 218b is fitted into the thread
groove 201b of the screw shaft 201, so that the
lubricant-containing polymer member 218 is fitted into the recess
205. A set screw 211 is screwed into the lubricant reserve
peripheral groove 218d for fixing the lubricant-containing polymer
member 218 to the ball screw nut 202.
[0228] Since the groove opening of the lubricant reserve peripheral
groove 218d made in the outer peripheral surface 218e of the
lubricant-containing polymer member 218 is closed on the inner
peripheral surface 205a of the recess 205, the lubricant in the
lubricant reserve peripheral groove 218d is sealed in the ball
screw nut 202. The lubricant reserve peripheral groove 218d is one
example of the structures of lubricant reserve part according to
the present invention.
[0229] The lubricant-containing polymer member of the structure can
provide the function and effects similar to those of the
above-described embodiment.
[0230] Even if foreign materials such as wood chips are deposited
on the lubricant-containing polymer member 218 and absorb the
lubricant, the lubricant-containing polymer member 218 is
replenished with a lubricant from the lubricant reserve holes 218d,
thus it is not feared that a lubrication failure will be
invited.
[0231] FIG. 29 is a sectional view to show the main part of a ball
screw according to a tenth embodiment of the invention. Components
identical with those previously described with reference to FIGS.
23 to 25 in the eighth embodiment are denoted by the same reference
numerals in FIG. 29 and will not be discussed again.
[0232] In the tenth embodiment, a lubricant-containing polymer
member 220 is fitted into an annular recess 205. The
lubricant-containing polymer member 220 has the same structure as
the lubricant-containing polymer member 210 shown in FIG. 24 except
that it is formed with a plurality of lubricant reserve holes 220d
filled with a lubricant in the circumferential direction of an
opposed end face 220f. The right opening of the
lubricant-containing polymer member 220 (in FIG. 29) is sealed by a
reinforcing plate 222.
[0233] The reinforcing plate 222 is a disk member made of a
material of a steel plate, hard rubber, plastic plate, etc., and
formed with an insertion hole 222a for a screw shaft 201 at the
position of the center of axle. It has an:outer peripheral diameter
set slightly smaller than the outer peripheral diameter of the end
face of a ball screw nut 202, and the insertion hole 222a is set
slightly larger than the outer diameter of the screw shaft 201.
While pressing the lubricant-containing polymer member 220 against
a bottom face 205b of the recess 205, the reinforcing plate 222 is
fixed to the ball screw nut 202 by set screws 224 indicated by
alternate long and short dash lines in FIG. 29.
[0234] Since the openings of the lubricant reserve holes 222d are
closed on the reinforcing plate 222, the lubricant in the lubricant
reserve holes 222d is sealed in the reinforcing plate 222 integral
with the ball screw nut 202. The lubricant reserve holes 222d is
one example of the structures of lubricant reserve parts according
to the present invention.
[0235] The lubricant-containing polymer member of the structure can
provide the function and effects similar to those of the
above-described embodiment.
[0236] As the effect proper to the embodiment, the
lubricant-containing polymer member 220 is shut off from the
external atmosphere by the reinforcing plate 222, so that wood
chips, dust, etc., can be prevented from entering the
lubricant-containing polymer member 220; it is not feared that the
lubricant is absorbed into wood chips, dust, etc., from the
portion.
[0237] Since the lubricant-containing polymer member 220 is held
down by the reinforcing plate 222 from the opening of the recess
205 (right in FIG. 29), an adhesion problem need not be considered.
The lubricant-containing polymer member 220 can be adjusted in
hardness and insufficient strength by press pressure received from
the reinforcing plate 222, thus breakage, cracks, etc., can be
prevented from occurring.
[0238] Further, in the embodiment, if the lubricant sealed in the
lubricant reserve holes 222d becomes insufficient, the lubricant
reserve holes 222d can be easily replenished with a lubricant
simply by loosening the set screws 224 and removing the reinforcing
plate 222 from the ball screw nut 222.
[0239] The embodiment uses the lubricant-containing polymer member
220 formed in the opposed end face 220f with a plurality of
lubricant reserve holes 220d. However, if a lubricant-containing
polymer member 220 formed in the opposed end face 220f with a
lubricant reserve peripheral groove continuous in the
circumferential direction (member similar to the
lubricant-containing polymer member 214 shown in FIG. 25) is used,
the function and effects similar to those of the embodiment can be
provided.
[0240] FIG. 30 is a sectional view to show the main part of a ball
screw according to an eleventh embodiment of the invention.
[0241] In the embodiment, the lubricant-containing polymer member
216 formed in the outer peripheral surface 216e with a plurality of
lubricant reserve holes 216d shown in FIG. 27 is fitted into an
annular recess 205, and the right opening of the
lubricant-containing polymer member 216 (in FIG. 30) is sealed by a
reinforcing plate 222.
[0242] The lubricant-containing polymer member of the structure can
provide the function and effects similar to those of the
above-described embodiment.
[0243] The embodiment uses the lubricant-containing polymer member
216 formed in the outer peripheral surface 216e with a plurality of
lubricant reserve holes 216d. However, if the lubricant-containing
polymer member 218 shown in FIG. 28, namely, member formed in the
outer peripheral surface 218e with the lubricant reserve peripheral
groove 218d is used, the function and effects similar to those of
the embodiment can be provided.
[0244] Lubricant-containing polymer members 230A, 230B, and 230C
shown in FIGS. 31 to 33 are modified examples of the
lubricant-containing polymer members 210, 214, and 216 respectively
shown in FIGS. 24 and 25 to 27.
[0245] The lubricant-containing polymer member 230A, 230B, 230C is
formed with microscopic communication holes 230a, 230b, 230c for
communicating lubricant reserve holes 210d and a projection stripe
210b, a lubricant reserve peripheral groove 214d and a projection
stripe 214b, lubricant reserve holes 216d and a projection stripe
216b. Slit-like or small-hole-like outflow openings 230a1, 230b1,
230c1 are made in the projection stripe 210b, 214b, 216b.
[0246] With a ball screw using the lubricant-containing polymer
member 230A of the structure, a lubricant sealed in the lubricant
reserve holes 210d flows out directly into the outflow opening
230a1 through the communication hole 230a. Thus, if much lubricant
is required to provide stable lubrication, the lubricant-containing
polymer member 230A becomes an optimum member. With another
lubricant-containing polymer member 230B (230C), a lubricant sealed
in the lubricant reserve peripheral groove 214d (lubricant reserve
holes 216d) flows out directly into the outflow opening 230b1
(230c1) through the communication hole 230b (230c). Thus, similar
effects to those of the lubricant-containing polymer member 230A
can be provided.
[0247] FIG. 34 shows a single axis actuator comprising the ball
screws of the embodiments. The single axis actuator comprises a
ball screw nut (not shown) in a slider 34 disposed for relative
rotation via balls in a screw shaft 1 having both ends supported
for rotation. Reference numeral 36 is a ball circulation section
for guiding a large number of balls into thread grooves of the
screw shaft 1 and the ball screw nut and circulating the balls. A
lubricant-containing polymer member 40 to which a reinforcing plate
is attached, fixed by a set screw 38 is disposed at position A
outside the ball circulation section 36. A lubricant-containing
polymer member 40 to which a reinforcing plate is attached is also
disposed at position B facing position A with the slider 34.
[0248] FIGS. 35 and 36 show the lubricant-containing polymer member
40 used with the single axis actuator. The lubricant-containing
polymer member 40 is formed with a lubricant reserve peripheral
groove 40a similar to that of the member, for example, shown in
FIG. 25 and lubricant reserve holes 40b similar to those of the
member, for example, shown in FIG. 24 at positions distant from the
lubricant reserve peripheral groove 40a. The lubricant reserve
peripheral groove 40a and the lubricant reserve holes 40b are
filled with a lubricant. As the lubricant exudes from the
lubricant-containing polymer member 40 and is consumed, the
lubricant reserve peripheral groove 40a and the lubricant reserve
holes 40b are replenished with a lubricant.
[0249] If the lubricant-containing polymer member 40 comprises the
lubricant reserve peripheral groove 40a and the lubricant reserve
holes 40b as lubricant reserve parts as described above, the
invention can also produce the function and effects similar to
those of the embodiments.
[0250] In the embodiments, we have discussed the ball screws, but
the invention is not limited to them; if the invention is applied
to slide screws adopting angular screws, etc., similar function and
effects can be provided.
[0251] Next, a modified example of the lubricant-containing polymer
member 230C shown in FIG. 33 will be discussed with reference to
FIG. 37.
[0252] As shown in FIG. 37, a lubricant-containing polymer member
330C has the same structure as the lubricant-containing polymer
member 230C except that it is not formed with the projection stripe
216b. An inner peripheral surface 330a of the lubricant-containing
polymer member 330C comes in direct contact with the outer
peripheral surface 201a of the screw shaft 201, so that a lubricant
exudes onto the outer peripheral surface 201a gradually with
rotation of the screw shaft. The lubricant-containing polymer
member 330C is formed with a microscopic communication hole 330b
for communicating a lubricant reserve groove 316d and the inner
peripheral surface 330a. A lubricant is supplied from the lubricant
reserve groove 316d directly to the outer peripheral surface 201a
of the screw shaft 201 through the communication hole 330b. As the
lubricant is directly supplied, more stable lubrication is
provided.
[0253] Further, a modified example of the lubricant-containing
polymer member 230B shown in FIG. 32 will be discussed with
reference to FIG. 38.
[0254] As shown in FIG. 38, a lubricant-containing polymer member
330B has the same structure as the lubricant-containing polymer
member 230C except that it is not formed with the projection stripe
214b. An inner peripheral surface 331a of the lubricant-containing
polymer member 330B comes in direct contact with the outer
peripheral surface 201a of the screw shaft 201, so that a lubricant
exudes onto the outer peripheral surface 201a gradually with
rotation of the screw shaft. The lubricant-containing polymer
member 330B is formed with a microscopic communication hole 331b
for communicating a lubricant reserve peripheral groove 314d and
the inner peripheral surface 330a. A lubricant is supplied from the
lubricant reserve peripheral groove 314d directly to the outer
peripheral surface 201a of the screw shaft 201 through the
communication hole 330b. As the lubricant is directly supplied,
more stable lubrication is provided.
[0255] Further, a modified example of the lubricant-containing
polymer member 230B shown in FIG. 32 will be discussed with
reference to FIG. 39.
[0256] As shown in FIG. 39, a lubricant-containing polymer member
332B has the same structure as the lubricant-containing polymer
member 230C except that it comprises a seal member 333 fitted into
the opening of the lubricant reserve peripheral groove 214d for
sealing a lubricant. The seal member 333 is made of the same
material as the lubricant-containing polymer member 332B.
Alternatively, the seal member 333 may be made of a plastic or
metal.
[0257] Next, a modified example of the lubricant-containing polymer
member 230B shown in FIG. 32 will be discussed with reference to
FIG. 40.
[0258] As shown in FIG. 40, a lubricant-containing polymer member
334B has the same structure as the lubricant-containing polymer
member 230B except for the placement position of the lubricant
reserve peripheral groove 314d. The lubricant-containing polymer
member 334B has a lubricant reserve peripheral groove 314d pulled
to the side of the outer peripheral surface 201a of the screw shaft
201, that is, the lubricant-containing polymer member 334B has the
lubricant reserve peripheral groove 314d which is shifted to the
diametric inside as much as possible for increasing elasticity, so
that a lubricant easily exudes from the lubricant reserve
peripheral groove 314d and is easily supplied to the outer
peripheral surface 201a of the screw shaft 201.
[0259] Further, a modified example of the lubricant-containing
polymer member 330C shown in FIG. 37 will be discussed with
reference to FIG. 41.
[0260] As shown in FIG. 41, a lubricant-containing polymer member
335B has the same structure as the lubricant-containing polymer
member 330C except that a groove 336 extending in the
circumferential direction is made in an inner peripheral surface
330a. Since the groove 336 extending in the circumferential
direction is made in the inner peripheral surface 330a, the
lubricant-containing polymer member 335B has the inner peripheral
thinner than the outer periphery and a lubricant sealed in a
lubricant reserve peripheral groove 314d exudes to the inner
periphery more easily than to the outer periphery and thus is
easily supplied to the outer peripheral surface 201a of the screw
shaft 201.
[0261] As we have discussed, when the feed screw device of the
invention is driven, a lubricant in the lubricant supply device
exudes gradually with rotation of the screw shaft and is
automatically supplied to the feed screw device. Resultantly, even
if a lubricant is not supplied from-the outside, the feed screw
device can continue good running for a long time at low torque.
[0262] Particularly, since a lubricant need not be supplied from
the outside, the feed screw device can be used as effective
lubrication means in a system that can use only an extremely small
amount of lubricant, such as a semiconductor manufacturing
system.
[0263] Moreover, in the feed screw device of the invention, the
inner peripheral surface of the lubricant supply device can be
brought into reliable contact with the outer peripheral surface of
the screw shaft by simple means and the outer diameter of the feed
screw device is not made large.
[0264] Moreover, in the feed screw device of the invention, jump
out of the lubricant supply device from the nut member and rotation
with the screw shaft can be prevented.
[0265] In the screw transmission device of the invention, the inner
diameter of the lubricant supply device is reduced by simple means
for uniform contact with the screw shaft; a lubricant can be
supplied well and wear on one side can be prevented.
[0266] As we have discussed, according to the feed screw device of
the invention, the lubricant-containing polymer member seals both
the ends of the screw nut and shuts off the inside of the screw nut
from the external atmosphere, so that even if the feed screw device
is used in the external atmosphere which is of a bad environment
wherein for example, wood chips, etc., easily absorbing lubricant
are existed, the inside of the screw nut is protected against the
wood chips, etc., and the smooth lubrication effect can be
maintained over a long time.
[0267] As a lubricant exudes from the lubricant-containing polymer
member and is consumed, the lubricant-containing polymer member is
replenished with a new lubricant sealed in the lubricant reserve
parts, thus the lubricant exudes from the lubricant-containing
polymer member over a long time and stable lubrication can be
carried out for a long time.
[0268] Further, even if foreign materials such as wood chips are
deposited on the lubricant-containing polymer member and absorb the
lubricant, the lubricant-containing polymer member is replenished
with a lubricant from the lubricant reserve parts, thus it is not
feared that a lubrication failure will be invited.
* * * * *