U.S. patent application number 13/881090 was filed with the patent office on 2013-11-14 for hermetic compressor.
This patent application is currently assigned to LG Electronics Inc.. The applicant listed for this patent is Jin Kook Kim, Kyoung Jun Park. Invention is credited to Jin Kook Kim, Kyoung Jun Park.
Application Number | 20130302149 13/881090 |
Document ID | / |
Family ID | 45994530 |
Filed Date | 2013-11-14 |
United States Patent
Application |
20130302149 |
Kind Code |
A1 |
Park; Kyoung Jun ; et
al. |
November 14, 2013 |
HERMETIC COMPRESSOR
Abstract
A hermetic compressor includes: a crank shaft rotated by using
an axial direction as a rotational axis; a stator rotating the
crank shaft; a first bearing penetrated by the crank shaft and
rotatably coupled to one side of the crank shaft based on the
stator to support one side of the crank shaft when the crank shaft
is rotated; a support part having one side provided at the stator
and the other side disposed to be adjacent to the other side of the
crank shaft, based on the stator; and a second bearing coupled to
the other side of the support part and supporting the other side of
the crank shaft.
Inventors: |
Park; Kyoung Jun; (Seoul,
KR) ; Kim; Jin Kook; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Park; Kyoung Jun
Kim; Jin Kook |
Seoul
Seoul |
|
KR
KR |
|
|
Assignee: |
LG Electronics Inc.
Seoul
KR
|
Family ID: |
45994530 |
Appl. No.: |
13/881090 |
Filed: |
October 25, 2011 |
PCT Filed: |
October 25, 2011 |
PCT NO: |
PCT/KR11/07952 |
371 Date: |
July 29, 2013 |
Current U.S.
Class: |
415/170.1 |
Current CPC
Class: |
F04D 29/056 20130101;
F04B 39/0094 20130101 |
Class at
Publication: |
415/170.1 |
International
Class: |
F04D 29/056 20060101
F04D029/056 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 25, 2010 |
KR |
10 2010 0104207 |
Claims
1. A hermetic compressor comprising: a crank shaft rotated by using
an axial direction as a rotational axis; a stator rotating the
crank shaft; a first bearing penetrated by the crank shaft and
rotatably coupled to one side of the crank shaft based on the
stator; a support part having one side provided at the stator and
the other side disposed to be adjacent to the other side of the
crank shaft, based on the stator; and a second bearing coupled to
the support part and supporting the other side of the crank
shaft.
2. The hermetic compressor of claim 1, further comprising: a frame
in which the crank shaft penetrates, wherein the first bearing is
provided between the frame and the crank shaft.
3. The hermetic compressor of claim 2, wherein the first bearing
support one side of the crank shaft when the crank shaft is
rotated.
4. The hermetic compressor of claim 1, wherein the second bearing
supports the other side of the crank shaft when the crank shaft is
rotated.
5. The hermetic compressor of claim 1, wherein the support part
fixes the second bearing to the stator.
6. The hermetic compressor of claim 1, wherein one side of the
support part is fixed to the stator by a fastening unit penetrating
one side of the support part.
7. The hermetic compressor of claim 1, wherein the support part is
integrally formed with the stator.
8. The hermetic compressor of claim 1, wherein a moment center of
the crank shaft is positioned at a support portion of the first
bearing supporting the crank shaft in an axial direction of the
crank shaft, and a compression part for compressing a refrigerant
upon receiving rotary force of the crank shaft is provided at one
end portion of the crank shaft based on the moment center of the
crank shaft.
9. The hermetic compressor of claim 8, wherein the second bearing
is disposed at the other side based on the moment center of the
crank shaft.
10. The hermetic compressor of claim 1, wherein the second bearing
is penetrated by the crank shaft.
11. The hermetic compressor of claim 1, wherein the second bearing
is a rolling bearing.
12. The hermetic compressor of claim 1, wherein the support part
supports an outer side of the second bearing.
13. The hermetic compressor of claim 1, wherein the second bearing
is provided at the other side of the support part.
14. The hermetic compressor of claim 1, wherein the second bearing
is press-fit to a space formed by the other side of the support
part and the other side of the crank shaft.
15. A hermetic compressor comprising: a crank shaft rotated by
using an axial direction as a rotational axis; a stator rotating
the crank shaft; a first bearing penetrated by the crank shaft and
supporting one side of the crank shaft when the crank shaft is
rotated; a second bearing penetrated by the crank shaft and
supporting the other side of the crank shaft when the crank shaft
is rotated; and a support part provided at the stator to fix the
second bearing.
16. The hermetic compressor of claim 15, wherein the first bearing
is rotatably coupled to one side of the crank shaft based on the
stator.
17. The hermetic compressor of claim 16, further comprising: a
frame in which the crank shaft penetrates, wherein the first
bearing is provided between the frame and the crank shaft.
18. The hermetic compressor of claim 16, wherein the support part
having one side provided at the stator and the other side disposed
to be adjacent to the other side of the crank shaft based on the
stator.
19. The hermetic compressor of claim 18, wherein the second bearing
is penetrated by the crank shaft and has one side coupled to the
other side of the support part, so as to be rotatably coupled to
the other side of the crank shaft.
20. The hermetic compressor of claim 18, wherein one side of the
support part is fixed to the stator by a fastening unit penetrating
one side of the support part.
Description
TECHNICAL FIELD
[0001] The present invention relates to hermetic compressor and,
more particularly, to a hermetic compressor capable of reducing a
friction loss of a crank shaft and lengthening a life span of a
bearing supporting the crank shaft.
BACKGROUND ART
[0002] A general hermetic compressor includes a motor part provided
in a hermetic container and generating power and a compression part
operating upon receiving power from the motor part. The hermetic
compressor may be classified into reciprocating, rotary, vane, and
scroll type compressors, or the like, according to how a
refrigerant, a compressible fluid, is compressed.
[0003] In the hermetic compressor, a crank shaft coupled to a rotor
of the motor part transfers power while rotating together with the
rotor, and an interworking member coupled to the crank shaft,
receiving power from the motor part, forms a compression chamber to
compress a refrigerant.
[0004] In the hermetic compressor, oil is filled at a lower portion
of a hermetic container, an oil flow path is formed in a
penetrative manner in the crank shaft in an axial direction of the
crank shaft, and an oil feeder is installed to be immersed in the
oil at a lower end of the oil flow path.
[0005] Accordingly, when compressor operates, the crank shaft
rotates to generate centrifugal force to pump oil, and the pumped
oil is sucked to be supplied between the crank shaft and the
bearing to thus prevent a friction loss generated when the crank
shaft is rotated.
[0006] Here, the compression part transfers reaction force
according to a reaction to the crank shaft in one direction, and a
plurality of bearings penetrated by the crank shaft transfer
reaction force in different directions according to their
penetrated positions. Here, the crank shaft is bent due to
resultant force of the reaction forces.
[0007] Also, when a plurality of bearings are installed to be
adjacent to prevent the crank shaft from being bent, the behavior
of the crank shaft may be stabilized, but a friction loss is
increased due to an increase in the area of the bearings according
to the increase in the number of bearings, and a life span of the
bearings is shortened according to the positions of the
bearings.
[0008] The increase in the friction loss and the shortened life
span of the bearings will result in reduction in the efficiency of
the compressor and reduction in the duration of replacement of the
bearings.
TECHNICAL PROBLEM
[0009] It is, therefore, a hermetic compressor according to the
present invention has one or more effects as follows.
TECHNICAL SOLUTION
[0010] First, when the crank shaft rotates, the second bearing
supports the other side of the crank shaft, making forces acting on
the crank shaft balanced.
[0011] Second, since the second bearing is coupled to the other
side of the crank shaft, force applied to the crank shaft is
reduced in a state in which moment balance and force equilibrium of
the crank shaft are maintained, the friction loss between the crank
shaft and the second bearing is reduced owing to the reduced force,
thus increasing compression efficiency and lengthening a life span
of the first and second bearings.
[0012] Third, since the second bearing is disposed at the other
side based on the moment center of the crank shaft to make a moment
balance, force of the first bearing supporting the crank shaft is
reduced, and accordingly, friction loss between the first bearing
and one side of the crank shaft is reduced.
[0013] Fourth, since the first bearing is provided at the crank
shaft, it supports one side of the crank shaft when the crank shaft
is rotated, preventing the crank shaft penetrating the frame from
being approached to either side of the frame.
[0014] Fifth, since one side of the support portion and the other
side of the stator are detachably coupled by a fastening unit, the
second bearing can be detachably attached along with the support
portion at the other side of the crank shaft.
ADVANTAGEOUS EFFECTS
[0015] The effects of the present invention are not limited to the
foregoing effects and any other unmentioned effects could be
clearly understood by a skilled person in the art from the
description of claims.
DESCRIPTION OF DRAWINGS
[0016] The above and other objects and features of the present
invention will become apparent from the following description of
preferred embodiments given in conjunction with the accompanying
drawings, in which:
[0017] FIG. 1 is a sectional view of a hermetic compressor
according to an embodiment of the present invention:
[0018] FIG. 2 is a view showing only major components of FIG.
1:
[0019] FIG. 3 is a view schematically showing forces acting on a
crank shaft according to one embodiment of the present invention:
and
[0020] FIG. 4 is a view schematically showing forces acting on a
crank shaft according to another embodiment of the present
invention.
BEST MODE
[0021] Advantages and features of the present invention, and
implementation methods thereof will be clarified through following
embodiments described with reference to the accompanying drawings.
The present invention may, however, be embodied in different forms
and should not be construed as limited to the embodiments set forth
herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the present invention to those skilled in the art.
Further, the present invention is only defined by scopes of claims.
Like reference numerals refer to like elements throughout.
[0022] The hermetic compressor according to embodiments of the
present invention will now be described with reference to the
accompanying drawings. In the following description, usage of
suffixes such as `module`, `part` or `unit` used for referring to
elements is given merely to facilitate explanation of the present
invention, without having any significant meaning by itself.
[0023] FIG. 1 is a sectional view of a hermetic compressor
according to an embodiment of the present invention.
[0024] With reference to FIG. 1, the hermetic compressor according
to an embodiment of the present invention includes a hermetic
container 1, a motor part 10 rotated in one direction or in both
directions, and a compression part 20 installed at an upper side of
the of the motor part 10 and compressing a refrigerant upon
receiving rotary force from the motor part 10.
[0025] The motor part 10 may be configured as a motor that makes a
constant velocity rotation in one direction. Also, a regular speed
motor or an inverter motor available for a forward rotation and a
reverse rotation may be applied as the motor part.
[0026] The motor part 10 includes a stator 11 supported by a frame
30 within the hermetic container 1, a rotor 12 rotatably installed
at an inner side of the stator 11, and a crank shaft 133 coupled to
the center of the rotor 12 to transfer rotary force to the
compression part 20.
[0027] A sleeve 24 (to be described) is coupled to an upper end of
the crank shaft 13 to make a piston 22 reciprocally move. A pin
part 13a is formed to be eccentric to have a certain eccentric
amount at the center of the shaft.
[0028] An oil flow passage 13b is formed to penetrate in an axial
direction from a lower end of the crank shaft 13 to an upper end of
the pin part 13a. An oil feeder 13c for pumping oil of the hermetic
container 1 is installed at a lower end of the foil flow path 13b
such that it is immersed in oil of the hermetic container 1. An
eccentric mass part 13d having a fan-like shape is formed at a
portion where the pin part 13a, which corresponds to an upper
portion thereof, starts, to cancel out an eccentric load while
forming a plane of the axial directional bearing 50 with an upper
face of the frame 30 (to be described).
[0029] The frame 30 is provided between the compression part 20 and
the motor part 10. The crank shaft 13 penetrates the frame 30. A
through tunnel is formed at the center of the frame 30 to allow the
crank shaft 13 to penetrate therein, and the crank shaft 13
penetrates through the through tunnel. A cylinder 21 (to be
described) is provided at one side of the frame 30.
[0030] A thrust bearing (not shown) may be provided between the
frame 30 and the eccentric mass part 131d according to an
embodiment of the present invention. The thrust bearing supports
the eccentric mass part to make the crank shaft 13 and the
eccentric mass part 13d rotate smoothly. Oil sucked through the oil
flow path 13b is supplied as a lubricant to the thrust bearing to
allow the thrust bearing to rotate smoothly.
[0031] A first bearing 40 is provided at one side of the crank
shaft 13, supporting one side of the crank shaft 13. The first
bearing 40 may be provided between the crank shaft 13 and the frame
30. The first bearing 40 is disposed in the through tunnel and
penetrated by the crank shaft 13, and supports the crank shaft 13
to ensure a smooth rotation between the frame 30 and the crank
shaft 13. Oil sucked from the oil feeder 13c may be supplied to the
first bearing 40. The supplied oil lubricates the first bearing
40.
[0032] A second bearing 60 is disposed at a lower end, i.e., the
other side of the crank, and allowing the crank shaft 13 to
penetrate therein. The second bearing 60 may be coupled to a
support 60 supportedly coupled to the stator 11. These components
will be described in detail with reference to FIG. 2 later.
[0033] The compression part 20 includes a cylinder 21 forming a
certain compression space V1, a piston 22 making a reciprocal
movement in a radius direction within the compression space V1 of
the cylinder 21 to compress a refrigerant, a connecting rod 23
having one end rotatably coupled to the piston 22 and the other end
rotatably coupled to the pin part 13 of the crank shaft 13 to
convert a rotational movement of the motor part 10 into a linear
movement of the piston 22, a sleeve 24 inserted between the pin
part 13a of the crank shaft 13 and the connecting rod 23 and
serving as a friction reduction member, a valve assembly 25 coupled
to a front end of the cylinder 21 and having a suction valve and a
discharge valve, a suction muffler 26 coupled to a suction side of
the valve assembly 25, a discharge cover 27 coupled to accommodate
a discharge side of the valve assembly 25, and a discharge muffler
communicating with the discharge cover 25 and damping discharge
noise of a discharged refrigerant.
[0034] The operation of the hermetic compressor having the
foregoing configuration according to an embodiment of the present
invention will now be described. First, when power is applied to
the stator 11 of the motor part 10, the rotor 12 is rotated
together with the crank shaft 13 according to interaction force of
the stator 11 and the rotor 12.
[0035] When the crank shaft 13 is rotated, the connecting rod 23
connected to the pin part 13 of the crank shaft 13 with the sleeve
24 interposed therebetween makes a rotating movement, and the
piston 22 coupled to the connecting rod 23 makes a reciprocal
movement linearly in the compression space V1 of the cylinder 21 to
compress the refrigerant, and this sequential process is repeatedly
performed.
[0036] At this time, the oil feeder 13c installed at the lower end
of the oil flow path 13b of the crank shaft 13 pumps oil of the
hermetic container 1, and the pumped oil is sucked through the oil
flow path 13b, so that one portion of the pumped oil is supplied to
a sliding portion of the compression part 20 and another portion of
the pumped oil is supplied between the frame 30 and the crank shaft
13 to lubricate them.
[0037] FIG. 2 is a view showing only major components of FIG. 1,
and FIG. 3 is a view schematically showing forces acting on the
crank shaft 13.
[0038] With reference to FIGS. 2 and 3, the hermetic compressor
according to an embodiment of the present invention includes the
crank shaft 13 rotated by using an axial direction as a rotational
axis, the stator 11 installed within the hermetic container and
rotating the crank shaft 13, the first bearing 40 penetrated by the
crank shaft 13 and rotatably coupled to one side of the crank shaft
13 based on the stator 11 to support one side of the crank shaft 13
when the crank shaft 13 is rotated, a support part 50 having one
side provided at the stator 11 and the other side disposed to be
adjacent to the other side of the crank shaft 13 based on the
stator 11, and a second bearing 60 penetrated by the crank shaft 13
and having one side coupled to the other side of the support part
50 and the other side rotatably coupled to the other side of the
crank shaft 13 to support the other side of the crank shaft 13 when
the crank shaft 13 is rotated.
[0039] The crank shaft 13 is rotated by using an axial direction as
a rotational axis. The crank shaft 13 is rotated by using an axial
direction of X-X' line of FIG. 2 connecting the upper and lower
ends, as a rotational axis.
[0040] The first bearing 40 is disposed between the crank shaft 13
and the frame 30. The first bearing 40 is penetrated by the crank
shaft 13 and supports the crank shaft 13 to ensure a smooth
rotation between the through tunnel of the frame 30 and the crank
shaft 13. The oil sucked from the oil feeder 13 may be supplied to
the first bearing 40, and the supplied oil is supplied to the first
bearing 40 to lubricate it.
[0041] In this case, the first bearing 40 is rotatably coupled to
one side of the crank shaft 13, i.e., an upper side of the crank
shaft 13, based on the stator 11. Namely, the compression part 20
is disposed at an upper side based on the stator 11, and the oil is
disposed at a lower side of the stator 11. Based on the stator 11,
the side where the compression part 200 is disposed at one side of
the crank shaft 13, and the side where the oil is disposed is the
other side of the crank shaft 13. Here, the first bearing 40 is
disposed at one side of the cranks shaft 13.
[0042] Reaction force according to action and reaction acting on
the compression part 20 acts on the crank shaft 13, the first
bearing 40 supports one side of the crank shaft 13. The first
bearing 40 supports one side of the crank shaft 13 when the crank
shaft 13 is rotated, so that the crank shaft 13 may not be inclined
to either side of the frame 30 in its rotation.
[0043] The stator 11 is disposed at a lower side of the first
bearing 40. As described above, the stator 11 rotates the crank
shaft 13 along with the rotor 12 upon receiving power.
[0044] The support part 50 is disposed at a lower side of the
stator 11, i.e., the other side of the stator 11, based on the
stator 11. The support part 50 is disposed between the other side
of the crank shaft 13 and the other side of the stator 11, such
that the second bearing 60 (to be described) is fixed to the stator
11.
[0045] One side of the support part 50 is provided at the stator
11. One side of the support part 50 may be integrally formed with
the stator 11 according to an embodiment. Also, the support part 50
may be fixed to the stator 11 by a fastening unit 51 penetrating
one side of the support part 50 according to a different
embodiment. Also, the support part 50 may be coupled to the stator
11 through welding, or the like.
[0046] Hereinafter, it is described that the support part 50 is
fixed to the stator 11 by the fastening unit 51 penetrating one
side of the support part 50, but the configuration of the support
part 50 and the stator 11 is not limited thereto. The fastening
unit 51 fastened to the stator 11 may be implemented by a general
long bolt.
[0047] Since one side of the support part 50 and the other side of
the stator 11 are detachably coupled by the fastening unit 51, the
second bearing 60 (to be described) can be detachably attached
along with the support part 50 at the other side of the crank shaft
13.
[0048] The other side of the support part 50 is disposed to be
adjacent to the other side of the crank shaft 13. Namely, the other
side of the support part 50 is disposed to be adjacent to the other
side of the crank shaft 13, i.e., the lower side of the crank shaft
13, based on the stator 11. The other side of the support part 50
may be disposed to be spaced apart from the other side of the crank
shaft 13 such that the second bearing 60 (to be described) can be
coupled.
[0049] The crank shaft 13 penetrates the second bearing 600. The
second bearing 60 is rotatably coupled to the other side of the
crank shaft 13. The second bearing 60 may be press-fit in a space
formed by the other side of the support part 50 and the other side
of the crank shaft 13 so as to be coupled. In this case, the crank
shaft 13 penetrates the center of the second bearing 60.
[0050] The support part 50 supports an outer side of the second
bearing 60 coupled to the other side of the crank shaft 13, and the
second bearing 60 fixed to the support part 50 supports the other
side of the crank shaft 133 when the crank shaft 13 is rotated.
[0051] The second bearing 60 may be implemented by various bearings
such as a rolling bearing, a sliding bearing, and the like.
Hereinafter, the second bearing 60 is implemented by a ball
bearing, a type of a rolling bearing, but the embodiment of the
second bearing 60 is not limited thereto.
[0052] The second bearing 60 supports the other side of the crank
shaft 13. The second bearing 60 supports the other side of the
crank shaft 13 when the crank shaft 13 is rotated, to making forces
acting on the crank shaft 133 balanced.
[0053] The second bearing 60 makes force acting on the crank shaft
13 balanced in the compression part in which a refrigerant is
compressed, upon receiving force of the first bearing acting on the
crank shaft 13 and rotary force of the crank shaft 13 at an end
portion of one side, i.e., an upper side of the crank shaft 13. In
this case, the respective forces acting on the crank shaft 13 must
be balanced, and these forces will now be described with reference
to FIG. 3.
[0054] With reference to FIG. 3, vector R1 represents a force of
the first bearing 40 supporting the crank shaft 13, among the
forces acting on the crank shaft 13.
[0055] Meanwhile, the compression part 20 applies a reaction force
F to one end portion of the crank shaft 13. The reaction force F
acts on the crank shaft 13 in a direction opposite to the direction
of the vector R1.
[0056] The second bearing 60 provides a force supporting the crank
shaft 133 to the other side of the crank shaft 13, and a vector
thereof is R2, which has the same direction as that of F and acts
in a direction opposite to the direction of R1.
[0057] Here, in order to make the forces balanced to prevent the
crank shaft 13 from moving in both directions, the sum of all of
the forces must be .SIGMA.F=0. Namely, when the direction of R1 is
determined to be a positive (+) direction, R1+(-R2)+(-F)=0.
[0058] Here, R1=F+R2 and the average F of the forces acting on one
end portion of the crank shaft 13 in the compression part 20 is
constant, so when R2 is reduced, R1 will be reduced, reducing the
force supported by the first bearing 40. As the force supported by
the first bearing 40 is reduced, a friction loss between the first
bearing 40 and one side of the crank shaft 13 is reduced, enhancing
compression efficiency.
[0059] Thus, it is required to be designed such that R2 is small,
and in order to reduce R2, a moment balance must be considered. In
moment balance, the center (O) of moment is positioned on the crank
shaft 13 in an axial direction. The center (O) of moment positioned
on the crank shaft 13 in the axial direction is positioned at an
upper side of the support part 50.
[0060] The center (O) of moment of the crank shaft 13 is positioned
as one point at one side of the crank shaft 13 supported by the
first bearing 40, and the crank shaft 133 makes a seasaw movement
based on the center (O) of moment.
[0061] Namely, the crank shaft 13 may be rotated in a clockwise
direction or counterclockwise direction based on the moment center
(O) to generate vibration. In this case, another rotational shaft
may be formed to be perpendicular to the rotational shaft X-X' of
the crank shaft 13 penetrating the movement center (O). The crank
shaft 13 may be rotated in a clockwise direction or
counterclockwise direction based on the another rotational
shaft.
[0062] Here, in order for the crank shaft 13 to make a moment
balance, rather than making a seasaw movement, the sum of all the
moments must be .SIGMA.M=0. Namely, in order for the crank shaft 13
to be stopped, rather than making a seasaw movement, according to
the moment by the force applied to one side of the crank shaft 13
and the force applied to the other side of the crank shaft 13, the
sum of all the moments must be 0.
[0063] Here, the point supporting the crank shaft 13 by the first
bearing 40 is the moment center (O) making a seasaw movement. Here,
the vector R1 acting on the first bearing 40 makes a force acting
on the moment center (O) , and the moment is R1*0=0.
[0064] The reaction force F applied by the compression part 20 to
one end portion of the crank shaft 13 is applied to one side, i.e.,
an upper side, based on the moment center (O), and the moment from
the moment center (O) to an operational point on which the reaction
force F acts is L1*F and the direction is a positive (+) direction
in a counterclockwise direction.
[0065] The force provided by the second bearing 60 to the other
side, i.e., a lower side, of the moment center (O), is R2, and R2
forms a moment-(L2*R2) in the clockwise direction.
[0066] Accordingly, the equilibrium equation with respect to the
sum of the moments is +(L1*F)-(L2*R2)=0. Here, R2=(L1/L2)*F, and
since F has a certain size as an average force provided to the
crank shaft 13 in the compression part 20, and as a result, when L2
is increased, R2 is reduced.
[0067] Thus, in order to reduce R2, L2 must be increased, and it is
to be disposed at a point farthest from the moment center (O) to
the maximum, and in this case, the second bearing 60 must be
disposed at the other side of the crank shaft 13.
[0068] Namely, the second bearing 60 must be disposed at the
opposite side of one end portion on which F acts based on the
moment center (O). In this case, the second bearing 60 is disposed
at the other side of the crank shaft 13 farthest from F based on
the moment center (O) of the crank shaft 13.
[0069] Since the second bearing 60 is coupled to the other side of
the crank shaft 13, force applied to the other side of the crank
shaft 13 is reduced in a state in which the crank shaft 13 is
maintained in the moment balance and force equilibrium, and a
friction loss between the crank shaft 13 and the second bearing 60
is reduced, thus increasing the compression efficiency and
lengthening a life span of the first bearing 40 and the second
bearing 60.
[0070] FIG. 4 is a view schematically showing forces acting on a
crank shaft according to another embodiment of the present
invention.
[0071] With reference to FIG. 4, a formation of a moment center
(O') of the crank shaft 13 at an upper side of the first bearing
40, rather than at a support portion of the first baring 40, due to
a change in the design of the crank shaft 13 or a change in other
components will be described, but such a description may also be
applicable to a case in which the moment center (O') is formed at a
lower side of the first bearing 40.
[0072] As shown in FIG. 4, the first bearing 40 is disposed at one
side, i.e., an upper side, of the crank shaft 13 based on the
stator 11, and the second bearing 60 is disposed at the other side,
i.e., a lower side, of the crank shaft 13 based on the stator
11.
[0073] Namely, in spite of the configuration illustrated in FIG. 4,
the respective forces acting on the crank shaft 13 must be balanced
likewise as in the foregoing embodiment. Among the forces acting on
the crank shaft 13, the vector of force supporting the crank shaft
13 by the first bearing 40 is R1.
[0074] Meanwhile, the compression part 20 applies reaction force F
to one end portion of the crank shaft 13. The reaction force F is
the same vector as that of R1, which acts on the crank shaft 13 in
a direction opposite to the direction of R1.
[0075] The FIG. 4 is a view schematically showing forces acting on
a crank shaft according to another embodiment of the present
invention.
[0076] The second bearing 60 provides a force supporting the crank
shaft 13 to the other side, i.e., the lower side, of the crank
shaft 13, and the vector is R2 which has the same direction as that
of F2 and acts in a direction opposite to that of R1. Here, in
order for the crank shaft 13 to make the force balanced, rather
than being moved in both directions, the sum of all the forces must
be .SIGMA.F=0. Namely, when the direction of R1 is determined to be
a positive (+) direction, R1+(-R2)+(-F)=0.
[0077] Here, likewise as in the embodiment described above with
reference to FIG. 3, R1=F+R2 and the average force F acting on one
end portion of the crank shaft 13 in the compression part 20 is
constant. Thus, when R2 is reduced, R1 will be reduced, reducing
the force supported by the first bearing 400.
[0078] Referring to the moment sum, the size of moment formed by
the first bearing 40 is R1*A, the product of the support force R1
of the first bearing 40 and the distance A between the support
point of the first bearing 40 and the moment center (O'), and its
direction is a positive (+) direction in a counterclockwise
direction.
[0079] The reaction force F applied by the compression part 20 to
one end portion of the crank shaft 13 is applied to one side, i.e.,
an upper side, based on the moment center (O'), and the moment from
the moment center (O') to an operational point on which the
reaction force F acts is L1*F and the direction is a positive (+)
direction in a counterclockwise direction.
[0080] The force R2 provided by the second bearing 60 to the other
side, i.e., a lower side, of the moment center (O') forms a
moment-(B*R2) in the clockwise direction.
[0081] Accordingly, the equilibrium equation with respect to the
sum of the moments is +(R1*A)+(L*F)-(B*R2)=0. Here,
R2*B=(L*F)+(R1*A), and since L*F is constant in a state in which O'
is not changed, it is determined by (R1*A) and (R2*B).
[0082] Here, R1=F+R2, and when it is applied to the above equation,
R2*(B-A)=F(L+A)
[0083] Here, F and L are constant, so if R2 is to be reduced, A
must be reduced in a state in which B is constant, or B must be
increased in a state in which A is constant. In this case, A is a
support point of the first bearing 40, which is restrained by the
coupling of the first bearing 40 to the frame 30, having a small
change width in size in terms of design, so increasing B is free in
terms of design.
[0084] Thus, in order to reduce R2, B must be increased, and here,
the second bearing 600 is disposed at the other side of the crank
shaft 13 farthest from the moment center (O') to the maximum in
order to increase B. This case is the same as the embodiment
described above with reference to FIG. 3.
[0085] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention.
Thus, it is intended that the present invention covers the
modifications and variations of this invention provided they come
within the scope of the appended claims and their equivalents.
* * * * *