U.S. patent application number 11/115208 was filed with the patent office on 2005-08-25 for needle bearing and method for grinding bearing parts thereof.
This patent application is currently assigned to NSK LTD.. Invention is credited to Fujinami, Makoto, Yoshiba, Takeyuki.
Application Number | 20050185876 11/115208 |
Document ID | / |
Family ID | 27347595 |
Filed Date | 2005-08-25 |
United States Patent
Application |
20050185876 |
Kind Code |
A1 |
Yoshiba, Takeyuki ; et
al. |
August 25, 2005 |
Needle bearing and method for grinding bearing parts thereof
Abstract
It is an object of the invention to provide a needle bearing
which can prevent occurrence of flake and seizure in the bearing
parts even under such severe lubricating condition as provided by a
compressor for a car air conditioner or a planetary unit for an
automatic transmission. The needle bearing is structured by barrel
grinding the raceway surface of a ring and the surface of a rolling
body without using a ceramic-related abrasive such as alumina or
silicon carbide.
Inventors: |
Yoshiba, Takeyuki;
(Kanagawa, JP) ; Fujinami, Makoto; (Kanagawa,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
NSK LTD.
|
Family ID: |
27347595 |
Appl. No.: |
11/115208 |
Filed: |
April 27, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11115208 |
Apr 27, 2005 |
|
|
|
10232570 |
Sep 3, 2002 |
|
|
|
6910948 |
|
|
|
|
Current U.S.
Class: |
384/618 |
Current CPC
Class: |
F16C 19/46 20130101;
F16C 19/30 20130101; F16C 33/64 20130101; F16C 33/547 20130101 |
Class at
Publication: |
384/618 |
International
Class: |
F16C 019/30; F16C
033/62; F16C 033/32 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2001 |
JP |
P. 2001-298524 |
Sep 27, 2001 |
JP |
P.2001-298525 |
Apr 22, 2002 |
JP |
P.2002-119451 |
Claims
1. A needle bearing comprising: a retainer having a plurality of
pockets; rings; and a plurality of rolling bodies rollably
incorporated in the respective pockets of the retainer and rolling
on raceway surfaces of the rings, wherein at least one of the
retainer, the rolling bodies and the rings is free from a foreign
substance having hardness equal to or higher than the hardness of
the base material of the rolling bodies.
2. (canceled)
3. A needle bearing comprising: a retainer having a plurality of
pockets; rings; and a plurality of rolling bodies rollably
incorporated in the respective pockets of the retainer and rolling
on raceway surfaces of the rings, wherein at least one of the
retainer, the rolling bodies and the rings is free from, on the
surface thereof, a foreign substance having a mean diameter of
larger than 30 .mu.m.
4. A needle bearing comprising: a retainer having a plurality of
pockets; rings; and a plurality of rolling bodies rollably
incorporated in the respective pockets of the retainer and rolling
on raceway surfaces of the rings, wherein, in case where 0.01
mm.sup.2 of the surface of at least one of the bearing parts, that
is, the retainer, the rolling bodies and the ring is set as a unit
area, the rate per unit area of existence of hard foreign
substances having hardness equal to or higher than the hardness of
the base material of the rolling bodies and sticking to the
surfaces of the bearing parts is set equal to or less than 10%.
5. A needle bearing comprising: a retainer having a plurality of
pockets; rings; and a plurality of rolling bodies rollably
incorporated in the respective pockets of the retainer and rolling
on raceway surfaces of the rings, wherein, in case where 0.01
mm.sup.2 of the surface of at least one of the bearing parts, that
is, the retainer, the rolling bodies and the ring is set as a unit
area, the number per unit area of hard foreign substances having
hardness equal to or higher than the hardness of the base material
of the rolling bodies and sticking to the surfaces of the bearing
parts is set equal to or less than 300.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a needle bearing which is
used in a car air conditioner or in a planetary unit for an
automatic transmission.
[0002] In a compressor for a car air conditioner or in a planetary
unit for an automatic transmission, as a bearing for supporting a
thrust load applied to a rotary part, there is used a thrust needle
bearing. However, in the compressor for a car air conditioner,
since HFC134a (Hydro Fluoro Carbon 134a) or PAG (Polyalkylene
glycol) is used as a refrigerant or operating oil, the lubricating
condition of the bearing is under a very severe environment. And,
the rotation condition of the bearing also ranges widely from high
speeds to low speeds, and further the load to be applied to the
bearing ranges from a condition of almost no load to a condition of
about 5000 N; and, depending on the operating conditions of the
compressor, these conditions are combined together at random.
[0003] Therefore, under the environment requiring such severe
lubricating condition, there is required a thrust needle bearing
which can provide better lubricating performance and, to satisfy
such requirement, conventionally, for example, the surface
roughness of a ring or a rolling body is enhanced or, as shown in
FIGS. 19A and 19B, in a thrust ring 1, there are formed notches 2
which are used to secure an oil passage. Also, as shown in FIG. 20,
in order to secure the passing oil amount of lubricating oil, the
collar portions 4 of an outer ring 3 are turned over to thereby
increase the opening height h.
[0004] However, in the compressor for a car air conditioner or in
the planetary unit for an automatic transmission (A/T), originally,
since the lubricating condition is very severe, the above-mentioned
measures can provide little effect. Also, because the lubricating
condition is very severe, for example, there occurs metal contact
between the ring and rolling body. Therefore, in case where foreign
substances higher in hardness than the rolling body are sticking to
the raceway surface of the ring and the pocket inner surface of the
retainer to be contacted with the rolling body, the rolling body is
worn due to the influence of the foreign substances, thereby
raising a fear that the bearing can be flaked or seized.
SUMMARY OF THE INVENTION
[0005] The present invention aims at eliminating the
above-mentioned drawbacks found in the conventional needle bearing.
Accordingly, it is an object of the invention to provide a needle
bearing which can prevent the occurrence of the flaking and seizure
even under such severe lubricating condition environment as
provided by a compressor for a car air conditioner or a planetary
unit for an automatic transmission.
[0006] In attaining the above object, according to a first aspect
of the invention, there is provided a needle bearing comprising: a
retainer having a plurality of pockets; rings; and a plurality of
rolling bodies rollably incorporated in the respective pockets of
the retainer and rolling on raceway surfaces of the rings, wherein
at least one of the retainer, the rolling bodies and the rings is
free from a foreign substance having hardness equal to or higher
than the hardness of the base material of the rolling bodies.
[0007] According to a second aspect of the invention, there is
provided a method for grinding bearing parts, wherein, when
grinding surfaces of the bearing parts made of metal using
abrasives, the abrasives have hardness lower than hardness of base
material of the bearing parts, and the surfaces of the bearing
parts are grinded using the abrasives by at least one of barrel
grinding, shot blasting, and shot peening.
[0008] Also, according to a third aspect of the invention, there is
provided a needle bearing comprising: a retainer having a plurality
of pockets; rings; and a plurality of rolling bodies rollably
incorporated in the respective pockets of the retainer and rolling
on raceway surfaces of the rings, wherein at least one of the
retainer, the rolling bodies and the rings is free from, on the
surface thereof, a foreign substance having a mean diameter of
larger than 30 .mu.m.
[0009] In the first to third aspects of the invention, as specific
means for preventing a foreign substance having hardness equal to
or higher than the hardness of the base material of the rolling
bodies or a foreign substance having a mean diameter larger than 30
.mu.m from being present on the surface of the ring, there can be
employed a method for barrel working the raceway surface without
using a ceramic-related abrasive such as alumina (hardness Hv of
1800 to 2200) or silicon carbide (hardness Hv of 2500 to 3000),
that is, a method for barrel working the raceway surface using an
abrasive lower in hardness than the base material of the rolling
bodies and ring of the bearing. And, in the case of the method
using a ceramic-related abrasive, as a post-working step, there is
used a barrel polishing method for polishing the needle bearing
using plastic material, wall nut material and corn material (coat
of corn), or a method for removing the ceramic-related abrasive
through a washing operation. By the way, the mean diameter of the
foreign substance here means the mean of the major minor diameters
of one particle.
[0010] According to a fourth aspect of the invention, there is
provided a needle bearing comprising: a retainer having a plurality
of pockets; rings; and a plurality of rolling bodies rollably
incorporated in the respective pockets of the retainer and rolling
on raceway surfaces of the rings, wherein, in case where 0.01
mm.sup.2 of the surface of at least one of the bearing parts, that
is, the retainer, the rolling bodies and the ring is set as a unit
area, the rate per unit area of existence of hard foreign
substances having hardness equal to or higher than the hardness of
the base material of the rolling bodies and sticking to the
surfaces of the bearing parts is set equal to or less than 10%.
According to a fifth aspect of the invention, there is provided a
needle bearing comprising: a retainer having a plurality of
pockets; rings; and a plurality of rolling bodies rollably
incorporated in the respective pockets of the retainer and rolling
on raceway surfaces of the rings, wherein, in case where 0.01
mm.sup.2 of the surface of at least one of the bearing parts, that
is, the retainer, the rolling bodies and the ring is set as a unit
area, the number per unit area of hard foreign substances having
hardness equal to or higher than the hardness of the base material
of the rolling bodies and sticking to the surfaces of the bearing
parts is set equal to or less than 300.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a section view of the structure of a needle
bearing according to an embodiment of the invention;
[0012] FIG. 2 is a graphical representation of the bus shape of the
surface of a rolling body obtained when glass beads are used as
abrasives;
[0013] FIG. 3 is a graphical representation of the bus shape of the
surface of a rolling body obtained when alumina oxide is used as
abrasives;
[0014] FIG. 4 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 1, shown in Table 1 before and after a
wear test is conducted;
[0015] FIG. 5 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 4, shown in Table 1 before and after a
wear test is conducted;
[0016] FIG. 6 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 5, shown in Table 1 before and after a
wear test is conducted;
[0017] FIG. 7 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 9, shown in Table 1 before and after a
wear test is conducted;
[0018] FIG. 8 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 8, shown in Table 1 before and after a
wear test is conducted;
[0019] FIG. 9 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 11, shown in Table 2 before and after a
wear test is conducted;
[0020] FIG. 10 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 13, shown in Table 2 before and after a
wear test is conducted;
[0021] FIG. 11 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 18, shown in Table 2 before and after a
wear test is conducted;
[0022] FIG. 12 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 22, shown in Table 2 before and after a
wear test is conducted;
[0023] FIG. 13 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 15, shown in Table 2 before and after a
wear test is conducted;
[0024] FIG. 14 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 31, shown in Table 3 before and after a
wear test is conducted;
[0025] FIG. 15 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 32, shown in Table 3 before and after a
wear test is conducted;
[0026] FIG. 16 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 37, shown in Table 3 before and after a
wear test is conducted;
[0027] FIG. 17 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 42, shown in Table 3 before and after a
wear test is conducted;
[0028] FIG. 18 shows the shape of a bus of a rolling body used in a
sample bearing, sample No. 39, shown in Table 3 before and after a
wear test is conducted;
[0029] FIGS. 19A and 19B are a perspective view of a thrust ring
used in a conventional thrust needle bearing; and,
[0030] FIG. 20 is a section view of the structure of a conventional
radial needle bearing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Now, description will be given below of the preferred
embodiments of a needle bearing according to the invention with
reference to the accompanying drawings.
[0032] FIG. 1 is a section view of the structure of a needle
bearing according to an embodiment of the invention. As shown in
FIG. 1, a needle bearing according to the present embodiment of the
invention comprises a ring 11, a plurality of rolling bodies
(needle-like rollers) 12, and a retainer 13.
[0033] The ring (hardness Hv of 650 to 800) 11, rolling bodies
(hardness Hv of 700 to 800) 12 and retainer (hardness Hv of 650 to
800) 13 are respectively made of metal such as SUJ2. In the
retainer 13, there are opened up a plurality of pockets (not shown)
for holding the rolling bodies 12 in a rollable manner, while the
pockets are disposed at regular intervals in the circumferential
direction of the ring 11. Also, the rolling bodies 12 as well as
the raceway surface 11a of the ring 11 and the pocket inner
surfaces 13a of the retainer 13 to be contacted with the rolling
bodies 12 are worked by barrel grinding using an abrasive (such as
a glass bead (hardness Hv of 400 to 500) and a metal ball (hardness
Hv of 400 to 600)) lower in hardness than the base material of
bearing parts such as the rolling bodies 12 and ring 11 in order to
remove scales and burrs produced when the present needle bearing is
heat treated.
[0034] When barrel grinding the bearing parts of the thrust needle
bearing, in case where the surfaces of the bearing parts are ground
using an abrasive lower in hardness than the base material of the
bearing parts, there can be obtained the following effect. That is,
even in case where the abrasives are not removed perfectly in a
washing step after a grinding operation but the abrasives are left
on the surfaces of the bearing parts, when the thrust needle
bearing is in actual use, the remaining abrasives are bitten into
and crushed in, for example, between the thrust ring 11 and rolling
bodies 12. Therefore, even in case where the abrasives are left on
the surfaces of the bearing parts, they exist no longer as foreign
substances which are higher in hardness than the base material of
the bearing parts, thereby being able to reduce the influence of
the abrasives remaining on the surfaces of the bearing parts.
[0035] To confirm the above effect, the present inventors, using a
thrust needle bearing having an inside diameter of 40 mm, an
outside diameter of 60 mm and a thickness of 5 mm (rated dynamic
load: 24000 N) as a test bearing, have conducted a rolling body
wear resistance test under the following test conditions: that is,
the axial load: 2000 N, the radial load: 0 N, the rotation speed:
2000 min.sup.-1, lubricating oil: kerosene (PAG=9:1), and test
time: 48 hrs. And, after completion of the test, the present
inventors have observed the rolling body surfaces of the respective
test bearings. FIGS. 2 and 3 show the results of our
observation.
[0036] Specifically, FIG. 2 shows the bus shape of the rolling body
surface when glass beads (#120, diameter of the order of 0.1 to 0.2
mm) were used as the abrasives, whereas FIG. 3 shows the bus shape
of the rolling body when aluminum oxide was used as the
abrasives.
[0037] As can be seen from the observation results shown in FIGS. 2
and 3, when aluminum oxide was used as the abrasives, in 48 hrs.
after start of the test, the rolling body 12 wore down to a
position shown by a solid line in FIG. 3. On the other hand, in
case where glass beads were used as the abrasives, when compared
with the case using aluminum oxide as the abrasives, the wear of
the rolling body 12 was improved greatly.
[0038] The above observation results show the following facts. That
is, when barrel grinding bearing parts made of metal, preferably,
the surfaces of the bearing parts may be ground using abrasives
having lower hardness than the base material of the bearing parts.
Specifically, because the hardness of the abrasives is lower than
that of the base material of the bearing parts, even in case where
the abrasives are not removed perfectly in a washing step after a
grinding operation but the abrasives are left on the surfaces of
the bearing parts, when the thrust needle bearing is in actual use,
the remaining abrasives are bitten into and crushed in, for
example, between the thrust ring 11 and rolling body 12. Therefore,
even in case where the abrasives are left on the surfaces of the
bearing parts, they exist no longer as foreign substances which are
higher in hardness than the base material of the bearing parts,
thereby being able to reduce the influence of the abrasives
remaining on the surfaces of the bearing parts.
[0039] By the way, the invention is not limited to the
above-mentioned embodiment. For example, in the above embodiment,
as the abrasives for grinding the surfaces of the bearing parts,
there are used glass beads; however, as the abrasives, there can
also be used a metal ball (diameter of about 1 mm) lower in
hardness than the base material of the bearing parts. Also, in the
above embodiment, the surfaces of the bearing parts are worked by
barrel grinding. However, they may also be worked by shot blasting
or by shot peening.
[0040] By the way, the inventors observed the bearing as to the
wear conditions generated therein and found, in the raceway surface
and rolling bodies, not only bitten traces caused by foreign
substances such as worn metal powder but also worn states caused by
microscopic foreign substances. When observing these bitten traces
and worn states in more detail, it has been confirmed that the same
bitten traces and worn states are repeatedly left in the raceway
surface and rolling bodies of the bearing.
[0041] The above observation results suggest that the bearing is
worn due to mixture of the foreign substances into the raceway
surface and rolling bodies: that is, it is assumed that the foreign
substances are fixed to the raceway surface and rolling body (the
foreign substances are buried into one of the raceway surface and
rolling body which is lower in hardness), the thus buried foreign
substances repeatedly damage the rolling body to thereby cause the
rolling body to wear.
[0042] Thus, the present inventors also observed the raceway
surface and rolling body of the bearing as to their initial states
before they are worn due to the foreign substances. According to
the results of this observation, it has been confirmed that, in the
initial states as well, there are repeatedly caused similar bitten
traces to the above case. Further, on the raceway surface of the
bearing in the initial state, the presence of the foreign substance
was also confirmed and, when the foreign substance was checked for
the component thereof, the component was found a ceramic component
such as aluminum oxide which is a non-metal component.
[0043] Further, when the raceway surface of a bearing, which had
not been used, was observed, such ceramic-related foreign substance
as mentioned above, such as alumina, was found. This shows a
possibility that the foreign substance has been already stuck to
the bearing when assembly of the bearing is completed. It is
believed that a media (an abrasive) and a compound used when the
bearing is worked by barrel grinding are left on the raceway
surface of the bearing to provide such foreign substance.
[0044] The above observations and assumptions show a possibility
that a small amount of media remaining on the raceway surface of
the bearing can cause the bearing to wear and thus can shorten the
life of the bearing greatly.
[0045] To confirm the above possibility, the present inventors,
using a thrust needle bearing having an inside diameter of 40 mm,
an outside diameter of 60 mm and a thickness of 5 mm (rated dynamic
load: 24000 N) as a test bearing, have conducted a rolling body
wear resistance test under the following test conditions: that is,
the axial load: 2000 N, the radial load: 0 N, the rotation speed:
2000 min.sup.-1, lubricating oil: kerosene (PAG=9:1), and test
time: 48 hrs. And, the number of foreign substances per unit area
existing on the bearing raceway surface and the maximum diameter of
the foreign substances were confirmed through an electronic
microscope before start of the test; and, after completion of the
test, the rolling body wear amounts of the respective test bearings
were measured. Table 1 shows the results of the measurement.
1TABLE 1 Maximum diameter Abrasive used Number of of foreign
Bearing wear Sample in barrel foreign substance Amounts Nos.
grinding substances (.mu.m) (.mu.m) 1 No abrasive 3 5 0 2 No
abrasive 5 11 0 3 No abrasive 9 32 0 4 No abrasive 5 43 10 5
Alumina 7 7 0 6 Alumina 18 26 0 7 Alumina 20 32 1 8 Alumina 17 52
10 9 Silicon carbide 14 33 1 10 Silicon carbide 23 53 15
[0046] In Table 1, sample numbers 1 to 4 show sample bearings which
are assembled using rings on which barrel working (grinding
operation) is not enforced, whereas sample numbers 5 to 8 show
sample bearings on which alumina is used as a media or as an
abrasive when they are worked by barrel grinding. Also, sample
numbers 9 and 10 show sample bearings on which silicon carbide is
used as an abrasive when they are worked by barrel grinding. By the
way, in Table 1, the maximum diameter of a foreign substance means
the greatest one of the means of the major diameter and minor
diameter of one particle.
[0047] Also, the present inventors have observed the surfaces of
the rolling bodies of the respective sample bearings after
completion of the above test. FIGS. 4 to 8 show the results of this
observation. Here, FIG. 4 shows the bus shape of the rolling body
in the sample bearing which is designated by the sample No. 1, FIG.
5 shows the bus shape of the rolling body in the sample bearing
designated by the sample No. 4, FIG. 6 shows the bus shape of the
rolling body in the sample bearing designated by the sample No. 5,
FIG. 7 shows the bus shape of the rolling body in the sample
bearing designated by the sample No. 9, and FIG. 8 shows the bus
shape of the rolling body in the sample bearing designated by the
sample No. 8, respectively. Also, in each of these figures, a
broken line shows the bus shape of the rolling body before start of
the test, whereas a solid line shows the bus shape of the rolling
body after completion of the test.
[0048] From the bus shapes of the rolling bodies shown in FIGS. 4
to 8, there can be confirmed the following facts: that is, in the
case of the sample bearing No. 1, since no abnormal condition is
found in the shape of the rolling body, it is confirmed that the
sample bearing No. 1 has not been worn. Also, in the case of the
sample bearing No. 4, the shape of the bus of the rolling body of
the sample bearing provides such shape as shown by a broken line
before the test, whereas it provides such shape as shown by a solid
line after the test; and, therefore, it is confirmed that the
sample No. 4 has been worn. Further, in the case of the sample
bearings Nos. 5 and 9, the media was removed from them by a washing
treatment after completion of barrel grinding and thus the
ceramic-related media having a mean diameter of 30 .mu.m was not
found on the raceway surfaces of these sample bearings; and
therefore, it is confirmed that the rolling bodies have not been
worn by foreign substances. In addition, in the case of the sample
bearing No. 8, it is confirmed that the rolling body thereof has
been worn up to such a position as shown by a solid line due to the
ceramic-related media remaining on the raceway surface of the
sample bearing.
[0049] From the above test, we can reach the following conclusion.
That is, in case where a needle bearing is structured such that at
least one of the ring, rolling body and retainer of the needle
bearing does not include on the surface thereof a foreign substance
equal to or higher in hardness than the base material of the needle
bearing, or a substance having a mean diameter larger 30 .mu.m, the
ring and rolling body can be prevented from wearing. Therefore,
even under such severe lubricating conditions as provided by a
compressor for a car air conditioner and a planetary unit for
automatic transmission, the bearing parts can be prevented from
being flaked or seized.
[0050] Next, the present inventors, in order to check the remaining
abrasives for the influence thereof, conducted a bearing wear test
under the following test conditions I employing not only needle
bearings which had been worked by barrel grinding using an
alumina-related abrasive (media) but also needle bearings worked by
barrel grinding using a silicon-carbide-related abrasive. And,
before the test, the rate per unit area (which is 0.01 mm.sup.2 of
the ringway surface of a bearing) of the remaining abrasive was
measured; and, after the test, the wear amounts of the rolling
bodies of the respective needle bearings were measured. Table 2
shows the results of these measurements.
[0051] Test Conditions I
[0052] (1) Sample bearing: Thrust needle bearing having: Inside
diameter: 40 mm, outside diameter: 60 mm, Thickness: 5 mm, Rated
dynamic load: 24000 N,
[0053] (2) Axial load: 3000 N
[0054] (3) Radial load: 0 N
[0055] (4) Rotation speed: 1800 min.sup.-1
[0056] (5) Lubricating oil: Kerosene (PAG=9:1)
[0057] (6) Test time: 48 hrs.
2TABLE 2 Bearing Abrasive Area occupied wear Sample used in by
foreign Amounts Nos. barrel grinding substance (%) (.mu.m) Judgment
FIG. 11 No abrasive 3% or 0 Good 7 less 12 No abrasive 7 2 Good --
13 No abrasive 21 7 No good 8 14 No abrasive 13 3 Good -- 15
Alumina 22 15 No good 11 16 Alumina 5 5 Good -- 17 Alumina 7 4 Good
-- 18 Alumina 12 1 Good 9 19 Alumina 9 0 Good -- 20 Silicon carbide
13 5 Good -- 21 Silicon carbide 4 3 Good -- 22 Silicon carbide 11 1
Good 10
[0058] In Table 2, sample Nos. 11 to 13 designate thrust needle
bearings in which, after they were worked by barrel grinding, the
raceway surfaces of the bearings were washed and the media was
removed therefrom; sample Nos. 15 to 19 designate thrust needle
bearings in which, as an abrasive in barrel working, there was used
alumina; and, sample Nos. 20 to 22 designate thrust needle bearings
in which, as an abrasive in barrel working, there was used silicon
carbide.
[0059] As can be clearly understood from the measurement results
shown in Table 2, the thrust needle bearings designated by the
sample Nos. 11, 12, 14, 16 to 22 are smaller in the bearing wear
amount than the thrust needle bearings designated by the sample
Nos. 13 and 15. The reason for this is believed that, in the case
of the thrust needle bearings, sample Nos. 13 and 15, the rate per
unit area of the remaining abrasive exceeds 10%, whereas in the
case of the thrust needle bearings, sample Nos. 11, 12, 14, 16 to
22, the rate per unit area of the remaining abrasive is equal to or
less than 10%.
[0060] Also, the inventors observed the rolling body bus shapes of
the respective bearings after completion of the above test. FIGS. 9
to 13 show the results of this observation. Here, FIG. 9 shows the
rolling body bus shape of the bearing, sample No. 11; FIG. 10 shows
the rolling body bus shape of the bearing, sample No. 13; FIG. 11
shows the rolling body bus shape of the bearing, sample No. 18;
FIG. 12 shows the rolling body bus shape of the bearing, sample No.
22; FIG. 13 shows the rolling body bus shape of the bearing, sample
No. 15, respectively. Also, in each of these figures, a broken line
shows the bus shape of the rolling body before the test was
started, whereas a solid line shows the bus shape of the rolling
body before the test was ended.
[0061] As can also be clearly seen from the rolling body bus shapes
shown in FIGS. 9 to 13, in the case of the needle bearings, sample
Nos. 11, 18, 22, no abnormal condition is found in the bus shapes
of the rolling bodies thereof and thus it is confirmed that the
rolling bodies have been little worn. On the other hand, in the
case of the needle bearings, sample Nos. 13 and 15, an abnormal
condition is found in the bus shapes of the rolling bodies thereof
and thus it is confirmed that the rolling bodies have been
worn.
[0062] From the above test results, the inventors can reach the
following conclusion. That is, when 0.01 mm.sup.2 of the raceway
surface is used as a unit area, in case where the rate per unit
area of a hard foreign substance such as the remaining abrasive is
set equal to or less than 10%, the amount of wear of the bearing
parts due to the foreign substance such as the remaining abrasive
can be reduced, which makes it possible to prevent occurrence of
flaking and seizure in the bearing parts.
[0063] Next, the inventors, in order to check the remaining
abrasive for the influence thereof, conducted a bearing wear test
under the following test conditions II using not only needle
bearings which had been respectively worked by barrel grinding with
an alumina-related abrasive (media) but also needle bearings
respectively worked by barrel grinding with a
silicon-carbide-related abrasive. And, before the test, the number
per unit area (which is 0.01 mm.sup.2 of the raceway surface of a
bearing) of the remaining abrasive was measured; and, after the
test, the wear amounts of the rolling bodies of the respective
needle bearings were measured. Table 3 shows the results of these
measurements.
[0064] Test Conditions II
[0065] (1) Sample bearing: Thrust needle bearing having: Inside
diameter: 40 mm, Outside diameter: 60 mm, Thickness: 5 mm, Rated
dynamic load: 24000 N,
[0066] (2) Axial load: 2000 N
[0067] (3) Radial load: 0 N
[0068] (4) Rotation speed: 2000 min.sup.-1
[0069] (5) Lubricating oil: Kerosene (PAG=9:1)
[0070] (6) Test time: 48 hrs.
3TABLE 3 Abrasive Number of Bearing wear Sample used in foreign
Amounts Nos. barrel grinding substances (.mu.m) Judgment FIG. 31 No
abrasive 3 0 Good 12 32 No abrasive 280 2 Good 13 33 No abrasive
340 6 No good -- 34 No abrasive 320 3 Good -- 35 No abrasive 300 3
Good -- 36 Alumina 320 2 Good -- 37 Alumina 285 3 Good 14 38
Alumina 135 1 Good -- 39 Alumina 390 10 No good 16 40 Alumina 320 7
No good -- 41 Silicon carbide 250 4 Good -- 42 Silicon carbide 280
4 Good 15 43 Silicon carbide 330 5 Good --
[0071] In Table 3, sample Nos. 31 to 35 designate thrust needle
bearings in which, after they were worked by barrel grinding, the
raceway surfaces of the bearings were washed and the media was
removed therefrom; sample Nos. 36 to 40 designate thrust needle
bearings in which, as an abrasive in barrel working, there was used
alumina; and, sample Nos. 41 to 43 designate thrust needle bearings
in which, as an abrasive in barrel working, there was used silicon
carbide.
[0072] As can be clearly seen from the measurement results shown in
Table 3, the thrust needle bearings respectively designated by the
sample Nos. 31, 32, 34 to 38, and 41 to 43 are smaller in the
bearing wear amount than the thrust needle bearings respectively
designated by the sample Nos. 33, 39, and 40. The reason for this
is believed that, in the case of the thrust needle bearings, sample
Nos. 33, 39, and 40, the number per unit area of the remaining
abrasives exceeds 300, whereas in the case of the thrust needle
bearings, sample Nos. 31, 32, 34 to 38, and 41 to 43, the number
per unit area of the remaining abrasives is equal to or less than
300.
[0073] Also, the inventors observed the rolling body bus shapes of
the respective bearings after completion of the above test. FIGS.
14 to 18 show the results of this observation. Here, FIG. 14 shows
the rolling body bus shape of the bearing, sample No. 31; FIG. 15
shows the rolling body bus shape of the bearing, sample No. 32;
FIG. 16 shows the rolling body bus shape of the bearing, sample No.
37; FIG. 17 shows the rolling body bus shape of the bearing, sample
No. 42; and, FIG. 18 shows the rolling body bus shape of the
bearing, sample No. 39, respectively. Also, in each of these
figures, a broken line shows the bus shape of the rolling body
before the test was started, whereas a solid line shows the bus
shape of the rolling body before the test was ended.
[0074] As can also be clearly seen from the rolling body bus shapes
shown in FIGS. 14 to 18, in the case of the needle bearings, sample
Nos. 31, 32, 37 and 42, no abnormal condition is found in the bus
shapes of the rolling bodies thereof and thus it is confirmed that
the rolling bodies have been little worn. On the other hand, in the
case of the needle bearing, sample No. 39, an abnormal condition is
found in the bus shape of the rolling body thereof and thus it is
confirmed that the rolling body has been worn.
[0075] From the above test results, the inventors can reach the
following conclusion. That is, when 0.01 mm.sup.2 of the raceway
surface is used as a unit area, in case where the number per unit
area of hard foreign substances such as the remaining abrasives is
set equal to or less than 300, the amount of wear of the bearing
parts due to the foreign substances such as the remaining abrasives
can be reduced, which makes it possible to prevent occurrence of
flaking and seizure in the bearing parts.
[0076] By the way, the invention is not limited to the above
illustrated embodiments. For example, in the above illustrated
embodiments, the invention is applied to a thrust needle bearing
but, of course, the invention can also be applied to a radial
needle bearing. In the case of the radial needle bearing, there can
also be employed specifications in which a cage and rollers (a
retainer and rolling bodies) are employed, and the rolling bodies
thereof are all composed of rollers.
[0077] As has been described heretofore, according to the first to
third aspects of the invention, since foreign substances higher in
hardness than the base material of rolling bodies exist no longer
on the surface of the ring, the surface of the rolling body and the
inner surface of the retainer, even under such severe lubricating
conditions as provided by a compressor for a car air conditioner
and a planetary unit for automatic transmission, the bearing parts
can be prevented from being flaked or seized.
[0078] And, according to the fourth and fifth aspects of the
invention, because the wear amounts of the bearing parts due to the
foreign substances such as the remaining abrasives can be reduced,
the bearing parts can be prevented from being flaked or seized.
* * * * *