Double-headed swash type compressor and method for manufacturing cylinder block
TECHNICAL FIELD
[001] The present invention relates to a double-headed swash type compressor and a method for manufacturing a cylinder block, and more particularly, to a method for manufacturing a cylinder block and a journal bearing coming into contact with a shaft.
BACKGROUND ART
|002] A vehicle air conditioning system is a system which maintains the temperature inside a vehicle at a lower temperature than the external temperature using refrigerant. The vehicle air conditioning system includes a compressor, a condenser, and an evaporator in order to form a refrigerant circulation cycle. The compressor is a device which compresses and transfers refrigerant, and is operated by the power of an engine or [lie driving of a motor.
[0031 In a double-headed swash type compressor which is a type of reciprocating compressor, a disk-shaped swash plate is installed to a shaft to which the power of an engine is transferred. A plurality of pistons is installed around the swash plate with a shoe interposed therebetween. When the swash plate rotates, the pistons reciprocate in respective cylinder bores formed in a cylinder block, thereby allowing refrigerant to be introduced, compressed, and discharged. In this case, a valve plate to control the introduction and discharge of the refrigerant is installed between a housing and the cylinder block.
[004] In a conventional double-headed swash type compressor, a sliding bearing is installed between a shaft and a shaft bore in order to reduce wear and friction due to the

rotation of the shaft. However, the sliding bearing is made of a metal material coated with fluorine resin, and therefore, when a hole for movement of refrigerant is processed in the sliding bearing, the accuracy of the hole may be deteriorated and burrs may be generated due to the high elongation of the sliding bearing.
1005] In addition, in the initial stage where the double-headed swash type compressor is driven, the antiwear between the shaft and the sliding bearing is not stably performed, which may lead to an increase in friction due to the wear therebetween and thus leakage of refrigerant when the compressor is used for a long time.
DISCLOSURE TECHNICAL PROBLEM
[006] Accordingly, the present invention has been made in view of the above-mentioned problem, and an object thereof is to provide a double-headed swash type compressor and a method for manufacturing a cylinder block, in which a journal bearing coming into contact with a shaft of the double-headed swash type compressor is made of a sintered alloy and is formed with a pore such that oil contained in refrigerant is introduced and discharged through the pore.
TECHNICAL SOLUTION
[007] In accordance with an aspect of the present invention, a double-headed swash type compressor includes a cylinder block including a plurality of piston bores radially disposed, pistons reciprocating in the piston bores, and a shaft bore disposed between the piston bores, the shaft bore being formed with a plurality of refrigerant supply holes communicating with compression chambers defined by the respective piston bores and

pistons, front and rear housings-coupled to respective front and rear sides of the cylinder
block so as to define discharge chambers, a shaft inserted into the shaft bore, and having a
passage formed such that refrigerant moves therein, a refrigerant introduction hole
communicating with a suction space in the cylinder block to introduce refrigerant in the
suction space therethrough, and refrigerant discharge holes through which the refrigerant
introduced through the refrigerant introduction hole is discharged, a swash plate obliquely
installed to the shaft and connected to the pistons, and a journal bearing disposed between
an inner wall of the shaft bore and the shaft and made of a porous material, wherein a
distance between an outer peripheral surface of the shaft and an inner peripheral surface of
the shaft bore is greater than a distance between the outer peripheral surface of the shaft
and an inner peripheral surface of the journal bearing.
[008] The cylinder block may include a groove portion formed so as to be relatively
longer than a length of the journal bearing, for insertion of the journal bearing.
[009] The groove portion may be formed with a step disposed so as to face one surface
of the journal bearing and be spaced apart therefrom.
[0010] The journal bearing may have through-holes formed to be aligned with
refrigerant supply holes, and each of the through-holes and the refrigerant supply holes
may be obliquely disposed to the shaft bore in a longitudinal direction thereof.
[0011] The shaft may further include a coating layer formed on the outer peripheral
surface thereof facing the inner peripheral surface of the journal bearing.
[0012] The journal bearing may have an air porosity of 5 to 20% of overall volume
thereof.
[0013] The journal bearing may have an air porosity of 7% of overall volume thereof.
[0014] The journal bearing may be made of a sintered material.

[0015] The sintered material may include copper, tin, and graphite.
10016] The journal bearing may include a solid lubricant.
[0017] The solid lubricant may selectively use one of graphite, mica, talc, boric acid,
zinc oxide, plumbic oxide, sulfur, molybden disulphidc, polytctrafluoroethylenc (PTFH),
and hexagonal boric acid (hBN), or a combination thereof.
[0018] In the cylinder block, the outer peripheral surface of the shaft may be spaced
apart from the inner peripheral surface of the shaft bore by a first distance (a) in a state in
which the shaft is inserted into the shaft bore, and oil contained in refrigerant may be
introduced into or stored in the first distance (a) so that an oii film is formed on the shaft.
[0019] The journal bearing may be inserted into the shaft bore so as to be spaced apart
from an inner end of the shaft bore by a second distance (b), and oil contained in
refrigerant may be introduced into or stored in the second distance (b) so that an oi! film is
formed on the shaft.
[0020] The shaft may have a coating layer (21) formed on the outer peripheral surface
thereof, and the coating layer may be a Teflon coating layer.
[0021] The journal bearing may be made of a material composed of 89% copper, 10%
tin, and 1% graphite.
[0022] The journal bearing may be made of a material composed of 87% copper, 10%
tin, and 3% graphite.
[0023] In accordance with another aspect of the present invention, a double-headed
swash type compressor includes a cylinder block including a plurality of piston bores
radially disposed, pistons reciprocating in the piston bores, and a cylindrical shall bore
disposed between the piston bores, front and rear housings coupled to respective from and
rear sides of the cylinder block so as to define discharge chambers, a shaft having a

passage formed therein so as to communicate with a suction space disposed between the discharge chambers, so that refrigerant introduced into the suction space is transferred to the piston bores, a swash plate obliquely installed to the shaft and connected to the pistons, and a journal bearing disposed between an inner wall of the shaft bore and the shaft and made of a sintered material, wherein a space portion (S) is defined between an outer peripheral surface of the shaft and an inner peripheral surface of the shaft bore, and the space portion (S) communicates with the suction space.
[0024] The cylinder block may include a groove portion formed so as to be relatively longer than a length of the journal bearing, for insertion of the journal bearing, and the space portion (S) may extend to the groove portion.
|G025] The groove portion may be formed with a step disposed so as to face one surface of the journal bearing and be spaced apart therefrom, and a fluid introduced into the space portion may flow to the journal bearing via the step. [0026] The sintered material may include copper, tin, and graphite. [0027] In accordance with another aspect of the present invention, a double-headed swash type compressor includes a cylinder block including a plurality of piston bores radially disposed, pistons reciprocating in the piston bores, and a cylindrical shaft bore disposed between the piston bores, front and rear housings coupled to respective front and rear sides of the cylinder block so as to define discharge chambers, a shaft having a passage formed therein so as to communicate with a suction space disposed between the discharge chambers, so that refrigerant introduced into the suction space is transferred to the piston bores, a swash plate obliquely installed to the shaft and connected to the pistons, and a journal bearing disposed between an inner wall of the shaft bore and the shaft, made of a materia! composed of 89% copper, 10% tin, and 1% graphite, and having an air

porosity of 7% of overall volume thereof.
[0028] Alternatively, refrigerant may be moved when positions of the refrigerant
discharge holes coincide with positions of the through-holes formed in the journal bearing
during rotation of the shaft.
[0029] In accordance with a further aspect of the present invention, a method for
manufacturing a cylinder block includes preparing a cylinder block (ST100) including a
plurality of piston bores radially disposed, pistons reciprocating in the piston bores, and a
cylindrical shaft bore disposed between the piston bores, inserting a journal bearing made
o( a sintered material into each of both ends of the shaft bore (ST200), and processing
holes (ST300) so as to form through-holes in the journal bearing in a state in which the
journal bearing is inserted into the shaft bore while the shaft bore communicates with the
piston bores in the cylinder block.
[0030] The processing holes (ST300) may include moving forward a hole processing
tool in a direction inclined to a longitudinal direction of the shaft bore (ST310).
[0031] In the processing holes (ST300), the holes may be process at an angle of
inclination of 70El or 65 to 75D.
[0032] The method may further include impregnating the cylinder block (ST400) with
respect to the journal bearing.
[0033] The impregnating the cylinder block (ST400) may include immersing the
cylinder block in liquid resin and then taking out the same (ST410).
[0034] The preparing a cylinder block (ST100) may include processing the shaft bore so
as to have a first processing length in an inward longitudinal direction thereof (ST1 10).
[0035] The preparing a cylinder block (STI00) may include processing the shaft bore
such that a first inner diameter tolerance is maintained between an outer diameter of the

journal bearing and an inner diameter of the shaft bore (ST120).
[0036] The journal bearing may be made of a material composed of 89% copper, 10%
tin, and 1% graphite, and have an air porosity of 7% of overall volume thereof.
ADVANTAGEOUS EFFECTS
[0037] In accordance with the present invention, it is possible to realize stable lubrication of a journal bearing coming into close contact with a shaft of a double-headed swash type compressor and reduce generation of wear therein. Thus, the double-headed swash type compressor can be stably operated even when il is used for a Song lime. [0038] In the double-headed swash type compressor, the journal bearing is made of a sintered alloy and is formed with a pore such that oil contained in refrigerant is introduced
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in an unlubricated condition.
[0039] The accuracy of the journal bearing can be improved even when a hole for
movement of refrigerant is processed in the journal bearing. Therefore, it is possible to
simultaneously improve productivity and economic efficiency through an improvement in
workability and a reduction in defect rate by an operator.
[0040] Additional advantages, objects, and features of the invention will be set forth in
part in the description which follows and in part will become apparent to those having
ordinary skill in the art upon examination of the following or may be learned from practice
of the invention.
BRIEF DESCRIPTION OF DRAWINGS
[0041] The above and other objects, features and other advantages of the present

invention will be more clearly understood from the following detailed description taken in
conjunction with the accompanying drawings, in which:
[0042] Fig. 1 is an exploded perspective view illustrating a double-headed swash type
compressor according lo a first embodiment of the present invention;
[0043] Fig. 2 is an assembled perspective view illustrating the double-headed swash
type compressor according to the first embodiment of the present invention;
[0044] Fig. 3 is a perspective view illustrating a state in which a journal bearing is
inserted into a cylinder block, according to the first embodiment of the present invention;
[0045] Fig. 4A is a perspective view illustrating a state of operation of the journal
bearing and a shaft when the double-headed swash type compressor is initially operated in
an unlubricated state, according to the first embodiment of the present invention;
[0046] Fig. 4B is a view illustrating a state in which oil is discharged lo the shaft
through pores formed in the journal bearing, after the state of Fig. 4A;
[0047] Fig. 4C is a perspective view illustrating a state in which oil is introduced
through the pores in the journal bearing when the double-headed swash type compressor is
stopped, after the state of Fig. 4B;
{0048] Fig. 5 is a cross-sectional view illustrating a double-headed swash type
compressor according to a second embodiment of the present invention;
[0049] Fig. 6 is a perspective view illustrating a state in which a journal bearing is
inserted into a cylinder block, according to the second embodiment of the present
invention;
[0050] Fig. 7 is a cross-sectional view illustrating a double-headed swash type
compressor according to a third embodiment of the present invention;
[0051] Fig. 8 is a perspective view illustrating a stale in which a journal bearing is

inserted into a cylinder block, according to the third embodiment of the present invention; [0052] Fig. 9 is a flowchart illustrating a method for manufacturing a cylinder block according to another embodiment of the present invention; and
[0053] Fig. 10 is an enlarged view illustrating a cylinder block and pores formed in the cylinder block according to the present invention.
BEST MODE FOR INVENTION
[0054] Reference will now be made in detail to a double-headed swash type compressor according to a first embodiment of the present invention, examples of which arc illustrated in the accompanying drawings. Fig. 1 is an exploded perspective view illustrating a double-headed swash type compressor according to a first embodiment of the present invention. Fig. 2 is an assembled perspective view illustrating the double-headed swash type compressor according to the first embodiment of the present invention. Fig. 3 is a perspective view illustrating a state in which a journal bearing is inserted into a cylinder block, according to the first embodiment of the present invention. Fig. 4A is a perspective view illustrating a state of operation of the journal bearing and a shaft when the double-headed swash type compressor is initially operated in an unlubricated state, according to the first embodiment of the present invention.
[0055] Referring to Figs. 1 to 3, the double-headed swash type compressor, which is designated by reference numeral 1, includes a cylinder block 10 having a plurality of piston bores 12 formed around a shaft bore 11, front and rear housings 2 and 3 which are respectively coupled to the front and rear of the cylinder block 10, a shaft 20 installed through the front housing 2 and the cylinder block 10, and a compression unit 4 winch compresses a working fluid in the cylinder block 10 depending on the rotation of the shaft

[0056] The cylinder block 10 includes a front cylinder block 10a and a rear cylinder block 3 0b which are coupled so as to face each other. The shaft 20 is installed via the shaft bore 11 at the inner center of the front and rear cylinder blocks 10a and 10b. |0057] Specifically, the double-headed swash type compressor 1 includes a cylinder block 10, front and rear housings 2 and 3, a shaft 20, a swash plate 5, and a journal bearing 30. The cylinder block 10 includes a plurality of piston bores 12 which arc radially disposed, pistons 6 which reciprocate in the piston bores 12, and a shaft bore 11 which is disposed between the piston bores 12, and the shaft bore 11 is formed with a plurality of refrigerant supply holes 13 which communicate with compression chambers defined by the respective piston bores 12 and pistons 6. The front and rear housings 2 and 3 are respectively coupled to the front and rear of the cylinder block 10 so as to define discharge chambers. The shaft 20 is inserted into the shaft bore 1 1, and has a passage 22 formed such that refrigerant moves therein, a refrigerant introduction hole 23 communicating with the suction space in the cylinder block 10 to introduce refrigerant in the suction space therethrough, and refrigerant discharge holes 24 through which the refrigerant introduced through the refrigerant introduction hole 23 is discharged. The swash plate 5 is obliquely installed to the shaft 20 and is connected to the pistons 6. The journal bearing 30 is disposed between the inner wall of the shaft bore 11 and the shaft 20 and is made of a porous material. The distance between the outer peripheral surface of the shaft 20 and the inner peripheral surface of the shaft bore 13 is greater than the distance between the outer peripheral surface of the shaft 20 and the inner peripheral surface of the journal Dealing JU. [0058] In particular, the distance between the outer peripheral surface of the shaft 20

and the inner peripheral surface of the shaft bore 11 is greater than the distance between the outer peripheral surface of the shaft 20 and the inner peripheral surface of the journal bearing 30. This relationship is closely connected with the arrangement of the cylinder block 10 and the journal bearing. In the embodiment, the front and rear ends of the shaft 20 in the longitudinal direction thereof are in close contact with the journal bearing 30, and the outer peripheral surface of the shaft 20 is spaced apart from the inner peripheral surface of the shaft bore 11 in the cylinder block 10 by a first distance (a). [0059] On the other hand, since the outer peripheral surface of the shaft 20 is in close contact with the inner peripheral surface of the journal bearing 30, direct friction depending on the rotation of the shaft 20 is mainly generated between the shaft 20 and the journal bearing 30.
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shaft bore 11, as illustrated in the drawings.
[0061] In the cylinder block 10, the outer peripheral surface of the shaft 20 is spaced apart from the inner peripheral surface of the shaft bore 13 by a first distance (a) in the state in which the shaft 20 is inserted into the shaft bore 11. Accordingly, oil contained in refrigerant is introduced into or stored in the first distance (a), and thus an oil film is formed on the shaft 20. Therefore, when the shaft 20 rotates, friction due to the direct contact between the shaft 20 and the shaft bore 11 in the cylinder block 10 is reduced. |0062| That is, the direct friction with the shaft 20 is generated only at a position, in which the journal bearing 30 is inserted into the shaft bore 11, when the shaft 20 is supported and rotated at the position. Therefore, the friction is generated only at a specific position in the overall length of the shaft 20, and is not generated in the overall section of the shaft 20.

[0063] The first distance (a) is not limited to a specific distance, but the first distance (a) may be set to be about 2 mm through a simulation so as to form a stable oil film. [0064] The journal bearing 30 is inserted into the shaft bore 11 so as to be spaced apart from the inner end of the shaft bore 11 by a second distance (b), and oil contained in refrigerant is introduced into or stored in the second distance (b) so that an oil film is formed on the shaft 20. The second distance (b) refers to a distance between a step 15 to be described later and one surface of the journal bearing 30.
[0065] Since the oil contained in refrigerant is introduced into and stored in the second distance (b), the oil film may be stably formed regardless of the rotation of the shaft 20, and the leakage of refrigerant caused along the outer peripheral surface of the shaft 20 may be prevented or reduced. Thus, when the double-headed swash type compressor 1 is used for a long time, the matters relating to the leakage of refrigerant and the direct wear of the shaft 20 can be reduced.
[0066] In addition, since one end of the journal bearing 30 docs not come into direct contact with the step 15, the pressure generated by the insertion of the journal bearing 30 is not rapidly increased at a position adjacent to the step 15. Therefore, owing to the stable insertion of the journal bearing 30, the insertion stability of the journal bearing 30 can be improved and the damage and deformation of the journal bearing 30 can be reduced.
[0067] The second distance (b) is not necessarily limited to a distance illustrated in the drawings. The second distance (b) may not be formed so long as the journal bearing 30 is stably press-fitted into the shaft bore without the need of the second distance (b). [0068] Since the first distance (a) communicates with the second distance (b), oil contained in refrigerant may freely move between the first and second distances (a) and

(b). Therefore, the lubrication in the cylinder block 10 and the lubrication between the shaft 20 and the journal bearing 30 can be stably realized.
[0069] The refrigerant introduction hole 23 is disposed at the center of the shaft 20 in the longitudinal direction thereof or at a position spaced from the center of the shaft 20 in the longitudinal direction thereof. In this case, refrigerant may move to left and right sides at the shortest distance on the basis of the drawing in the passage 22 formed in the shaft 20. Thus, since the movement distance of refrigerant is short and the structure of the cylinder block is simplified, operation stability and processability can be improved. [0070] The cylinder block 10 includes the refrigerant supply holes 13 which are obliquely opened toward the respective piston bores 12 from the shaft bore 1 1 in order to move refrigerant therethrough. Since the holes for movement of refrigerant arc processed at one time from the piston bores 12 via through-holes 32 in the journal bearing 30 to the refrigerant supply holes 13 in the shaft bore 11, it is possible to improve workability by an operator, coincidence of opened holes, and process accuracy, and to reduce the generation of burrs. Therefore, the refrigerant supply holes 13 and the through-holes 32 may be processed at one time.
[0071] Each of the refrigerant supply holes 13 and the through-holes 32 is processed so as to be inclined toward the shaft 20 at a first angle of inclination. The first angle of inclination may be an angle of 70 D or an angle of about 65 to 75D.
[0072] The cylinder block 10 has a groove portion 14 which is relatively longer than the length of the journal bearing 30 for the insertion of the journal bearing 30. The step 15 is formed at a position, which faces one surface of the journal bearing 30 and is spaced by a predetermined distance, in the groove portion 14. The journal bearing 30 is inserted into the groove portion 14 formed over the first and second cylinder blocks 10a and 10b.

[0073] The groove portion 14 is formed for the insertion of the journal bearing 30, and the opened length of the groove portion 14 is relatively longer than the length of the journal bearing 30. For example, when the reference length of the groove portion 14 is "L", the groove portion 14 may further extend within a range of a tolerance of 1 to 2 mm or more. Therefore, the stable insertion of the journal bearing 30 can be performed. [0074] Since the step 15 has a length that extends by the same length as the thickness of the journal bearing 30, the journal bearing 30 does not protrude toward the inner center of the shaft bore 11 in the slate in which the journal bearing 30 is inserted thereinto. Therefore, it is possible to stably insert the shaft 20 and reduce friction due to the rotation thereof. [0075] In the embodiment, the shaft 20 rotates relative to the inner peripheral surface of
shaft 20 and reduce damage to the outer peripheral surface of the shaft 20, a coating layer 21 is formed on the shaft 20. The coating layer 21 may be formed on only the outer peripheral surface of the shaft 20 coming into contact with the inner peripheral surface of the journal bearing 30 or on the overall outer peripheral surface of the shaft 20, but the present invention is not limed thereto.
[0076] The coating layer 21 may be, for example, a Teflon coaling layer. The thickness of the coating layer 21 is not especially limited, but an optimal thickness is set through a simulation.
[0077] When the Teflon coating layer 21 is formed on the shaft 20, the wear and damage of the journal bearing 30 due to the rotation of the shaft 20 can be reduced, and the durability thereof can be improved. Therefore, even when the double-headed swash type compressor is used for a long time, refrigerant can be stably compressed.

[0078] The journal bearing 30 is forcibly press-fitted toward the front of the groove portion 14 from the rear thereof. To this end, the press-fitting of the journal bearing 30 is performed using a separate press unit.
|0079] In order to reduce the friction between the journal bearing 30 and the shaft 20, the journal bearing 30 is made of a sintered alloy obtained by compression-molding metal powder having a specific composition ratio at high pressure of several tons or more, and then sintering the same at high temperature, instead of using a separate lubricant or a lubrication component. In the embodiment, the journal bearing 30 may be made of, for example, a material composed of 89% copper, 10% tin, and 1% graphite. [0080] When the journal bearing 30 is made of the sintered alloy, the journal bearing 30 is manufactured by heating a material composed of copper, tin, and graphite at high temperature of the melting point thereof or more. Thus, the wear of the journal bearing 30 due to direct friction with the shaft 20 can be reduced and the tensile strength thereof can be improved. Therefore, even when the double-headed swash type compressor is used for a long time, the structural safety and strength of the journal bearing 30 can be uniformly maintained.
[0081] When the above material is heated at a temperature of 700 to 800DC in order to manufacture the journal bearing 30, tin is first melted and thus pores are formed in copper. In this case, the journal bearing 30 may have an air porosity of at least 7% of the overall volume thereof
|0082] The air porosity is a ratio of a vacant space to the overall volume of the journal bearing 30. The air porosity of at least 7% means that, when the overall volume of the journal bearing 30 is assumed to be 100%, the ratio of pore (vacant space) is at least 7%. The overall strength of the journal bearing 30 is changed according to air porosity. The

more the air porosity is increased, the more the strength of the journal bearing 30 is
decreased, and the more the air porosity is decreased, the more the strength of the journal
bearing 30 is increased.
[0083] When the journal bearing 30 has the air porosity of a specific percentage,
lubrication may be stably performed on the journal bearing 30 when the inner peripheral
surface of the journal bearing 30 coming into direct contact with the shaft 20 is not
lubricated in the initial stage where the double-headed swash type compressor is operated
in the stopped state.
|0084] The journal bearing 30 may be made of a material composed of 87% copper,
10% tin, and 3%> graphite. The strength of the journal bearing 30 may be slightly
changed according to the composition ratio of copper and graphite, but the same effect as
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[0085] As illustrated in the drawing, the shaft bore 11 into which the shaft 20 is inserted is formed at the center of the cylinder block 10, and the piston bores 12 arc arranged around the shaft bore 11.
[0086] The cylinder block 10 includes the refrigerant supply holes 13 which are opened toward the respective piston bores 12 from the shaft bore 11 in order to move refrigerant therethrough. All of the refrigerant supply holes 13 have the same diameter and are opened toward the respective piston bores 12.
[0087] The refrigerant supply holes 13 are opened in the state in which they are spaced at equal intervals. Accordingly, refrigerant is uniformly supplied to the piston bores 12, which are located at different positions, according to the rotation of the shaft 20. Mere, detailed uesenption mereol vvhi oe given togctner wiui the description of the shaft 20. [0088] Hereinafter, the lubrication relationship between the shaft and the journal bearing

according lo the present invention will be described in detail with reference to (he drawings.
[0089] Referring to Fig. 4A, in the initial stage where electric power is applied to the double-headed swash type compressor and the shaft 20 rotates at a specific rpm, the inner peripheral surface of the journal bearing 30 and the outer peripheral surface of the shaft 20 are maintained in an unlubricated state. However, lubrication is performed between the inner peripheral surface of the journal bearing 30 and the outer peripheral surface of the shaft 20 by the coating layer 21 formed on the outer peripheral surface of the shaft 20 in order to reduce the friction therebetween.
[0090] Referring to Fig. 4B, when the shaft 20 rotates at a specific rpm after the lapse of time tl, frictional heat is generated due to the friction between the inner peripheral surface of the 'on ma! bearing 30 and the outer Deri'^h era I surface of the sha ft 20 and thus the temperature of the contact portion therebetween is increased. As a result, oil contained in refrigerant, which is introduced into the pores formed in the journal bearing 30, flows out to the inner peripheral surface of the journal bearing 30.
[00911 In this case, since the oil film is formed between the inner peripheral surface of the journal bearing 30 and the shaft 20, the stable lubrication between the shaft 20 and the journal bearing 30 may be realized using oil contained in refrigerant without using a separate lubricant. Therefore, it is possible to prevent the contact surface between the shaft 20 and the journal bearing 30 from wearing due to the friction generated therebetween and to improve durability even when the double-headed swash type compressor is used for a long time.
[0092] For reference, on, wnicn is iiiirouuceu into or uiscnargcu irom hie pores ionncu in the journal bearing 30 according to a difference in pressure for each position between

the shaft 20 and the journal bearing 30 when the shaft 20 rotates, is consistently circulated. [0093] Referring to Fig. 4C, when the shaft 20 rotates and then stops, oil contained in refrigerant is introduced into the pores formed in the journal bearing 30 by capillarity. When the shaft 20 rotates again, the oil is discharged from the pores formed in the journal bearing 30 due to frictional heat, and is supplied to the outer peripheral surface of the shaft 20 in order to lubricate the outer peripheral surface of the shaft 20.
|0094] The journal bearing 30 preferably has an air porosity of 7% for stable lubrication with the shaft 20, as described above. Alternatively, the journal bearing 30 may have one of air porosities of 5% to 20% of the overall volume thereof, but the present invention is not limited thereto.
[0095] Referring to Fig. 2 or 3, the refrigerant discharge holes 24 arc disposed at front and rear positions spaced from the refrigerant introduction hole 23 which is disposed at one side of the center of the shaft 20 in the longitudinal direction thereof, and the journal bearing 30 is located in the state in which it is in surface contact with the outer peripheral surface of the shaft 20 formed with the refrigerant discharge holes 24. The journal bearing 30 is disposed at a position in which the refrigerant supply holes 13 arc formed in the shaft bore in order to supply refrigerant to the piston bores 12 along the passage 22 formed in the shaft 20 from among the movement paths of refrigerant into the double-headed swash type compressor. Therefore, the refrigerant may be stably moved to the shaft 20, the journal bearing 30, and the piston bores 12.
[0096] In particular, the refrigerant introduction hole 23 is located at the substantially center of the shaft 20 in the longitudinal direction thereof, and the refrigerant discharge holes 24 for discharge of supplied refrigerant arc spaced opart from ihc refrigerant introduction hole 23 by the substantially same distance. Accordingly, refrigerant and oil

may be uniformly supplied to the respective pistons disposed at both ends of the cylinder block. In addition, oil mixed in refrigerant is adhered to the inner wall surface of the shaft when the refrigerant flows in the shaft, and is separated from the refrigerant. [0097] If the distances between the respective refrigerant discharge holes and the refrigerant introduction hole differ from each other, the amount of oil mixed in refrigerant discharged from the refrigerant discharge holes may be significantly varied. However, since the distances between the respective refrigerant discharge holes and the refrigerant introduction hole are substantially equal to each other in the embodiment, the amount of separation of oil may be uniform. Through such a structure, working fluids may be uniformly compressed in the cylinders provided in the compressor. In addition, two journal bearings disposed at both ends of the cylinder block may have a uniform lubrication capability.
[0098] Oil is introduced into the cylinders only when the refrigerant supply holes J 3 overlap with the refrigerant discharge holes 24, and if not, the refrigerant discharge holes 24 face the inner surface of the journal bearing. In this case, the refrigerant and oil, which are previously supplied into the shaft, are discharged to the journal bearing through the refrigerant discharge holes, along with the rotation of the shaft. A portion of the oil mixed in the discharged refrigerant is introduced into the pores formed in the journal bearing or is applied to the journal bearing, and thus the lubrication capability of the journal bearing may be increased.
[0099] Even in this process, since the distances between the respective refrigerant discharge holes and the refrigerant introduction hole are substantially equal to each other. [he flow rate of oil supplied to the journal bearing may be uniform. Thereby, it is possible to prevent the shaft from having different lubrication capabilities at both ends

thereof.
[00100] The journal bearing 30 has the through-holes 32 opened at positions corresponding to the refrigerant supply holes 13. The through-holes 32 are opened at positions corresponding to the refrigerant supply holes 13 at the center of the journal bearing 30. The through-holes 32 are formed to move refrigerant thcrelhougru and arc processed in the state in which the cylinder block 10 is located on a separate jig (not shown).
[00101 ] Since the journal bearing 30 is made of a sintered alloy, as described above, the strength of the journal bearing 30 is stably maintained in itself. Accordingly, the generation of burrs can be reduced when the through-holes 32 arc processed, and the inner and outer peripheral surfaces of the through-holes 32 may be smooth even after the through-holes 32 arc processed. Therefore, it is possible to improve workability and processability by an operator and reduce defect rates.
{00102] The journal bearing 30 includes a solid lubricant, the solid lubricant selectively uses one of graphite, mica, talc, boric acid, zinc oxide, plumbic oxide, sulfur, moiybden disulphide, polytetrafluoroethylene (PTFE), and hexagonal boric acid (h.BN), or the combination thereof.
[00103] The lubrication between the journal bearing 30 and the shaft 20 may be stably realized using oil contained in refrigerant through the air porosity of the journal bearing 30. However, when the double-headed swash type compressor is operated in the slopped state, one of the above solid lubricants is selectively used in order to more stably operate the double-headed swash type compressor. In this case, the lubrication between the journal bearing 30 and the shaft 20 can be stably realized, without using a separate lubricant, in the initial stage where the shaft 20 is not lubricated.

[00104] In particular, since both the shaft 20 and the journal bearing 30 include a solid
lubricant in the embodiment, the lubrication between the journal bearing 30 and the shaft
20 may be stably realized for a certain time in an oil-free state. Accordingly, it is
possible to prevent the damage of the journal bearing 30 due to wear and friction until oil
contained in refrigerant is supplied to the journal bearing 30 through the pores thereof, and
to thereby improve the lubrication capability of the journal bearing 30.
[00105] The double-headed swash type compressor includes the front and rear housings 2
and 3 which are mounted to the front and rear of the cylinder block 10, and the
compression unit 4 which compresses refrigerant depending on the rotation of the shaft 20.
The compression unit 4 includes the swash plate 5 inserted into the shaft 20, and the
pistons 6 reciprocating in the piston bores 12 depending on the rotation of the swash plate 5
[00106] The swash plate 5 converts the rotational force of the shaft 20 into the reciprocating motion of the pistons 6. The swash plate 5 rotates along with the rotation of the shaft 20, and is obliquely disposed in one direction to the shaft 20, as illustrated in the drawings.
[00107] Hereinafter, a double-headed swash type compressor according to a second embodiment of the present invention will be described with reference to the drawings. [00108] Referring to Figs. 5 and 6, the double-headed swash type compressor, which is designated by reference numeral la, according to the embodiment includes a cylinder block 100, front and rear housings 2 and 3, a shaft 200, a swash plate 5, and a journal bearing 300. The cylinder block 100 includes a plurality of piston bores 120 which are radially disposed, pistons 6 which reciprocate in the piston bores 120, and a cylindrical shaft bore 110 which is disposed between the piston bores 120. The front and rear

housings 2 and 3 are respectively coupled to the front and rear of the cylinder block 100 so as to define discharge chambers. The shaft 200 has a passage 220 which is formed therein so as to communicate with a suction space disposed between the discharge chambers, and refrigerant introduced into the suction space is moved to the piston bores 120. The swash plate 5 is obliquely installed to the shaft 200 and is connected to the pistons 6. The journal bearing 300 is disposed between the inner wall of the shaft bore 110 and the shaft 200 and is made of a sintered material. A space portion S is defined between the outer peripheral surface of the shaft 200 and the inner peripheral surface of the shaft bore 110, and the space portion S communicates with the suction space. [00109] The configurations of the cylinder block and the shaft in the double-headed swash type compressor according to the present embodiment arc similar to those of the above-mentioned embodiment. The shaft is stably lubricated through the space portion S to reduce the wear and damage thereof, and the durability thereof can be improved when the double-headed swash type compressor is used for a long time.
[00110] To this end, the cylinder block 100 has a groove portion 140 which is relatively longer than the length of the journal bearing 300 for the insertion of the journal bearing 300. The space portion S extends to the groove portion 140.
[00111] The space portion S is a space defined between the outer peripheral surface of the shaft 200 and the inner peripheral surface of the shaft bore 110, and is spaced outward from the shaft 200 by a predetermined distance. Since oil contained in refrigerant introduced through the space portion S is moved to the groove portion 140, it is possible to stably lubricate the shaft 200 and prevent the wear of the shaft 200 during the rotation
, V, r-
t! iCi CUi.
[00112] In particular, the space portion communicates with the suction space through

which refrigerant to be compressed is introduced. The refrigerant introduced into the suction space contains oil, and the oil is separated from the refrigerant to be collected in the suction space. Since the space portion communicates with the suction space in which a large amount of oil is present, the oil may be smoothly and sufficiently supplied to the space portion so as to be transferred to the groove portion. Therefore, the journal bearing may be easily lubricated.
[00.1.13] A step 150 is formed in the groove portion 140 so as to face and be spaced apart from one surface of the journal bearing 300, and a fluid introduced into the space portion S Hows to the journal bearing 300 via the step 150. In this case, since oi! remains in a space defined between the step 150 and the journal bearing 300, lubrication can he stably performed even when the shaft 200 rotates in the state in which the double-headed swash type compressor la is stopped. Therefore, the durability of the shaft can be improved, [00114] The journal bearing 300 has through-holes 320 opened at positions corresponding to refrigerant supply holes 130. The through-holes 320 are opened at positions corresponding to the refrigerant supply holes 130 at the center o( the journal bearing 300. The through-holes 320 are formed to move refrigerant therethough, and are processed in the state in which the cylinder block 100 is located on a separate jig (not shown).
[00115] Since the journal bearing 300 is made of a sintered alloy, the strength of the journal bearing 300 is stably maintained in itself. Accordingly, the generation of burrs may be reduced when the through-holes 320 arc processed, and the inner and outer peripheral surfaces of the through-holes 320 may be smooth even after the through-holes jzO are processes. Inereiore, it is possiOic to improve vvorKaoiiil)' ano proccssaoiiii/v oy an operator and reduce defect rates.

|00116] Hereinafter, a double-headed swash type compressor according to a third embodiment of the present invention will be described with reference to the drawings. [00117] Referring to Figs. 7 and 8, the double-headed swash type compressor, which is designated by reference numeral lb, according to the embodiment includes a cylinder block 100a, front and rear housings 2 and 3, a shaft 200a, a swash plate 5, and a journal bearing 300a. The cylinder block 100a includes a plurality of piston bores 120a which are radially disposed, pistons 6 which reciprocate in the piston bores 120a, and a cylindrical shaft bore 110a which is disposed between the piston bores 120a. The front and rear housings 2 and 3 are respectively coupled to the front and rear of the cylinder block 100a so as to define discharge chambers. The shaft 200a has a passage 220a which is formed therein so as to communicate with a suction space disposed between the discharge chambers and refrigerant introduced into the suction space is transferred to the piston bores 120a. The swash plate 5 is obliquely installed to the shaft 200a and is connected to the pistons 6. The journal bearing 300a is disposed between the inner wall of the shaft bore 110a and the shaft 200a and is made of a material composed of 89% copper, 10% tin, and 1% graphite, and has an air porosity of at least 7% of the overall volume thereof.
[00118] The configurations of the cylinder block 100a and the shaft 200a in the double-headed swash type compressor according to the present embodiment arc similar to those of the above-mentioned embodiment. Tn the embodiment, the journal bearing 300a is made of a material composed of a specific ratio of copper, tin, and graphite, and has an air porosity of al least 7%, with the consequence that the journal bearing 300a may have a
journal bearing 300a is generated for a long time, the matters relating to the wear

therebetween can be reduced and the lubrication therebetween can be stably realized. [00119] Accordingly, since the wear and damage of the journal bearing 300a arc prevented, it is possible to improve the lubrication capability of the journal bearing 300a for reducing friction and stably rotate the shaft 200a.
[00120] The journal bearing 300a has through-holes 320a opened at positions corresponding to refrigerant supply holes 130a. The through-holes 320a are opened at positions corresponding to the refrigerant supply holes 130a at the center of the journal bearing 300a. The through-holes 320a are formed to move refrigerant thcrcthough, and are processed in the state in which the cylinder block 100a is located on a separate jig (not shown).
[00121] Since the journal bearing 300a is made of a sintered alloy, the strength of the journal bean nnri ,-,. IAA„ ,. i.,,.,.-, ,.,,.. .,...,.<- „r,.„r,.:..-,,-^,-f :-. ^.,I;_J ,„ .. ..,]..,.,,*:.,.
^pLi_U L'i iiiw Csiiuii i.vj, J-V/U, *Ji .i-UUti, tin, and 3%> graphite.
[00132] The journal bearing is manufactured by compression-molding metal powder
composed of copper, tin, and graphite at high pressure of several tons or more, and then
..:..,. „,.; oi iii auuiiiOii, Siiiee tne noies are SiuiuitaiieouSi)' proccssou m inc snail oorc and me piston bores when the through-holes are formed in the journal bearing, the holes for the

movement of refrigerant are formed at one time, instead of being formed individually.
Therefore, processability and workability can be improved and the dimension accuracy of
the holes communicating with each other can be improved, thereby reducing the
generation of foreign substances.
|00137] In addition, since the journal bearing is made of a sintered ahoy, the above
effects can be achieved, and the stable operation and durability of the double-headed
swash type compressor can be improved.
[00138] After the cylinder block processed through such a manner is moved by a forklift
or a separate transport means, the upper, lower, and side surfaces of the cylinder block arc
roughly processed. Subsequently, after front and rear cylinder blocks (not shown) arc
assembled to each other, the shaft bore and the piston bores are accurately processed.
'00139' After forei°n substances BTQ removed from the surface of the cylinder block bv
separate washing and drying processes, the surface of the cylinder block generated by die
casting is impregnated (ST400).
[00.140] The cylinder block is immersed in a reservoir ill led with liquid resin (ST410) and
is then taken out to the outside. In this case, since fine pores remaining on the surface of
the cylinder block are filled with resin, refrigerant is prevented from flowing out or
leaking.
[00141] Accordingly, even when the shaft is rotated for a long lime and refrigerant is
moved through the piston bores, the double-headed swash type compressor can be stably
used.
[00142] In the embodiment, the journal bearing is made of a material composed of 89%
„„„,..,„ -i AO/ J-:., „.- J 10/ ,T..„,-i ■,., „,„ .1 i.„„ „<„ , ■ ,,„,.„„:*,. ,., r .,. i ..„-- -70/ ~.r j, ., _... ,,._n vA.>ppv.i, 1 v /O tiii, UiiU i/O gidpilHC, UllU iiai til i clii jjUliJbilj w til icti^i .• / :l tji un_ uvtlilii
volume thereof. Since the effects thereof have been described above, detailed description

thereof will be omitted.
[00143] Hereinafter, the cylinder block and the pores formed in the cylinder block according to the present invention will be described with reference to the enlarged drawing.
[00144] Referring to Fig. 10, when the journal bearing 30, 300, or 300a according to the embodiment is made of a sintered material, it may be seen that pores having unspecific sizes and shapes are distributed in the journal bearing according to the result of checking the cross-section thereof using an electron microscope. Therefore, when oil contained in refrigerant remains in the pores or heat is transferred during the rotation of the shaft, the oil may be discharged to the shaft from the pores and thus the shaft may be stably lubricated. Various embodiments have been described in the best mode for carrying out the invention.
INDUSTRIAL APPLICABILITY
[00145] The present invention may be applied to a double-headed swash type compressor equipped with a journal bearing.
[00146] Although the present invention has been described with respect to the illustrative embodiments, it will be apparent to those skilled in the art that various variations and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

1. A double-headed swash type compressor comprising:
a cylinder block (10) comprising a plurality of piston bores (12) radially disposed, pistons (6) reciprocating in the piston bores (12), and a shaft bore (11) disposed between the piston bores (12), the shaft bore (11) being formed with a plurality of refrigerant supply holes (13) communicating with compression chambers defined by the respective piston bores (12) and pistons (6);
front and rear housings (2 and 3) coupled to respective front and rear sides of the cylinder block (10) so as to define at least a portion of discbarge chambers;
a shaft (20) inserted into the shaft bore (11), and having a passage (22) formed such thai refrigerant moves therein, a refrigerant introduction hole (23) communicating with a suction space in the cylinder block (10) to introduce refrigerant in the suction space therethrough, and refrigerant discharge holes (24) through which the refrigerant introduced through the refrigerant introduction hole (23) is discharged;
a swash plate (5) obliquely installed to the shaft (20) and connected to the pistons (6); and
a journal bearing (30) disposed between an inner wall of the shaft bore (11) and the shaft (20) and made of a porous material,
wherein a distance between an outer peripheral surface of the shaft (20) and an inner peripheral surface of the shaft bore (11) is greater than a distance between the outer peripheral surface of the shaft (20) and an inner peripheral surface of the journal bearing

2. The double-headed swash type compressor according to claim. 1, wherein the cylinder block (10) comprises a groove portion (14) formed so as to be relatively longer than a length of the journal bearing (30), for insertion of the journal bearing (30).
3. The double-headed swash type compressor according to claim 2, wherein the groove portion (14) is formed with a step (15) disposed so as to face one surface of the journal bearing (30) and be spaced apart therefrom.
4. The double-headed swash type compressor according to claim. 1, wherein the journal bearing (30) has through-holes (32) formed to be aligned with refrigerant supply holes (13), and each of the through-holes (32) and the refrigerant supply holes (13) is obliquely disposed to the shaft bore (11) in a longitudinal direction thereof.
5. The double-headed swash type compressor according to claim 1, wherein the shaft (20) further comprises a coating layer (21) formed on the outer peripheral surface thereof facing the inner peripheral surface of the journal bearing (30).
6. The double-headed swash type compressor according to claim 1, wherein the journal bearing (30) has an air porosity of 5 to 20% of overall volume thereof.
7. The double-headed swash type compressor according to claim I, wherein the journal bearing (30) has an air porosity of 7% of overall volume thereof.
8. The double-headed swash type compressor according to claim 1, wherein

the journal bearing (30) is made of a sintered material.
9. The double-headed swash type compressor according to claim 8, wherein the sintered material comprises copper, tin, and graphite.
10. The double-headed swash type compressor according to claim 8, wherein the journal bearing (30) comprises a solid lubricant.
11. The double-headed swash type compressor according to claim 9, wherein the solid lubricant selectively uses one of graphite, mica, talc, boric acid, zinc oxide, plumbic oxide, sulfur, molybden disulphide, polyteirafluorocthyiene (PTFE). and hexagonal boric acid (hBN), or a combination thereof.
12. The double-headed swash type compressor according to claim 1, wherein, in the cylinder block (10), the outer peripheral surface of the shaft (20) is spaced apart from the inner peripheral surface of the shaft bore (11) by a first distance (a) in a slate in which the shaft (20) is inserted into the shaft bore (1!), and oil contained in refrigerant is introduced into or stored in the first distance (a) so that an oil film is formed on the shaft (20).
13. The double-headed swash type compressor according to claim 1, wherein
the journal bearing (30) is inserted into the shaft bore (11) so as to be spaced apart from an
: ,,. i .-.riu.-, cu„rt u~--~, /i n U\- « r-.,-..-,^-) .-i:c<.-..,,-..-, su\ „.-.) .-.n .-..,.,(.,:.,.-,,-; :., ..,-,<■..: ,.,< :..
ii ii ii. i \-"-t JU Ui ii ii.- oiiu.il uUi V ^ i i J U V ti itwl iU. vi iC>Lwi iCi.' \'<-/ )y L i ni_ii i ii_ U i i i i^iii^.\.iniii. i t>
introduced into or stored in the second distance (b) so that an oil film is formed on the

shaft (20).
14. The double-headed swash type compressor according lo claim 1, wherein the shaft (20) has a coating layer (21) formed on the outer peripheral surface thereof, and the coating layer is a Teflon coating layer.
15. The double-headed swash type compressor according to claim 1, wherein the journal bearing is made of a material composed of 89% copper, 10% tin, and 1% graphite.
16. The double-headed swash type compressor according to claim 1, wherein the journal bearing (30) is made of a material composed of 87% copper. 10% tin. ?.p.d 3% graphite.
17. The double-headed swash type compressor according to claim 1, wherein the suction space is disposed between two discharge chambers defined by the front and rear housings, and the refrigerant introduction hole is disposed between the refrigerant discharge holes disposed adjacent to both ends of the shaft.
18. The double-headed swash type compressor according to claim 17, wherein distances between the refrigerant introduction hole and the respective refrigerant discharge holes are substantially equal to each other.
19. The double-headed swash type compressor according to claim 4, wherein,

when the through-holes do not overlap with the refrigerant discharge holes, the refrigerant discharge holes are disposed so as to face an inner wall surface of the journal bearing so that refrigerant in the shaft is discharged through the refrigerant discharge holes.
20. A double-headed swash type compressor comprising:
a cylinder block (100) comprising a plurality of piston bores (120) radially disposed, pistons (6) reciprocating in the piston bores (120), and a cylindrical shaft bore (110) disposed between the piston bores (120);
front and rear housings (2 and 3) coupled to respective front and rear sides of the cylinder block (100) so as to define discharge chambers;
a shaft (200) having a passage (220) formed therein so as to communicate with a suction space disposed between the discharge chambers, so that refrigerant introduced into the suction space is transferred to the piston bores (120);
a swash plate (5) obliquely installed to the shaft (200) and connected to the pistons (6); and
a journal bearing (300) disposed between an inner wall of the shaft bore (110) and the shaft (200) and made of a sintered material,
wherein a space portion (S) is defined between an outer peripheral surface of the shaft (200) and an inner peripheral surface of the shaft bore (110), and the space portion (S) communicates with the suction space.
21. The double-headed swash type compressor according to claim 20,
wherein the cylinder block (100) comprises a groove portion (M0) formed so as to be relatively longer than a length of the journal bearing (300), for insertion of the journal

bearing (300), and the space portion (S) extends to the groove portion (140).
22. The double-headed swash type compressor according to claim 21, wherein the groove portion (140) is formed with a step (150) disposed so as to lace one surface of the journal bearing (300) and be spaced apart therefrom, and a fluid introduced into the space portion (S) flows to the journal bearing (300) via the step (150).
23. The double-headed swash type compressor according to claim 20, wherein the sintered material comprises copper, tin, and graphite.
24. A double-headed swash type compressor comprising:
a cylinder block (100a) comprising a plurality of piston bores (120a) radially disposed, pistons (6) reciprocating in the piston bores (120a), and a cylindrical shaft bore (110a) disposed between the piston bores (120a);
front and rear housings (2 and 3) coupled to respective front and rear sides of the cylinder block (100a) so as to define discharge chambers;
a shaft (200a) having a passage (220a) formed therein so as to communicate with a suction space disposed between the discharge chambers, so that refrigerant introduced into the suction space is transferred to the piston bores (120a);
a swash plate (5) obliquely installed to the shaft (200a) and connected to the pistons (6); and
a journal bearing (300a) disposed between an inner wall of the shaft bore (110a)
graphite, and having an air porosity of at least 7% of overall volume thereof.

25. The double-headed swash type compressor according lo any one of claims 1 to 24, wherein refrigerant is moved when positions of the refrigerant discharge holes (24, 240, or 240a) coincide with positions of the through-holes (32, 320, or 320a) formed in the journal bearing (30, 300, or 300a) during rotation of the shaft (20, 200, or 200a).
26. A method for manufacturing a cylinder block, comprising:
preparing a cylinder block (ST100) comprising a plurality of piston bores radially disposed, pistons reciprocating in the piston bores, and a cylindrical shaft bore disposed between the piston bores;
inserting a journal bearing made of a sintered material into each of both ends of the shaft bore (ST200); and
processing holes (ST300) so as to form through-holes in the journal bearing in a stale in which the journal bearing is inserted into the shaft bore while the shaft bore communicates with the piston bores in the cylinder block.
27. The method according to claim 26, wherein the processing holes (ST300) comprises moving forward a hole processing tool in a direction inclined to a longitudinal direction of the shaft bore (ST310).
28. The method according to claim 26, wherein, in the processing holes
^.j i. 3\J\JJ, Li.v- iKji^S uiv piO^tSS at an augit- 01 iJ.ii_tiiiai.iGii Oi /\JL^ UI o~> iu /^\..:.

29. The method according to claim 26, further comprising impregnating llic cylinder block (ST400) with respect to the journal bearing.
30. The method according to claim 29, wherein the impregnating the cylinder block (ST400) comprises immersing the cylinder block in liquid resin and then taking out the same (ST410).
31. The method according to claim 26, wherein the preparing a cylinder block (SIT00) comprises processing the shaft bore so as to have a first processing length in an inward longitudinal direction thereof (ST110).
32. The method according to claim 26, wherein the preparing a cylinder block (S'lTOO) comprises processing the shaft bore such that a first inner diameter tolerance is maintained between an outer diameter of the journal bearing and an inner diameter ol' the shaft bore (ST120).
33. The method according to claim 26, wherein the journal bearing is made of a material composed of 89% copper, 10% tin, and 1% graphite, and has an air porosity of 7% of overall volume thereof.