JP2004060451A - Oil passage structure of crankshaft for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the oil passage structure of an assembled crankshaft for an engine which dispenses with alignment of an oil passage in assembling the crankshaft and boring after assembly and enables centrifugal separation of foreign matters from passing oil. <P>SOLUTION: A crankpin 5p is formed in hollow shape and provided with an oil feeding hole 38 bored to communicate a hollow part 36 with the outer peripheral surface of the crankpin 5p. One journal part 5b is provided with an oil hole 35 bored to communicate with an oil supply source and opened adjoining one end face of a crank part 5c. A delivery tray 37 for delivering oil to the hollow part 36 from the oil hole 35 is mounted to one end part of the crank part 5c, and a foreign matter sump 40 for holding the foreign matters centrifugally separated from the oil in the delivery tray 37 during the rotation of the crankshaft 5 is provided in the delivery tray 37. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an oil path structure for an engine-assembled crankshaft in which both ends of a crankpin are press-fitted into two crank arms integrally connected to a pair of first and second journal portions to form a crank portion.
[0002]
[Prior art]
Conventionally, in an assembled crankshaft of an engine, an oblique communication hole is formed from the journal to the crankpin to connect an axial oil hole provided in the journal to an oil supply hole opened on the outer peripheral surface of the crankpin. It is known. (See, for example, Japanese Utility Model Application Laid-Open No. 56-29204).
[0003]
[Problems to be solved by the invention]
In an engine-assembled crankshaft, needle bearings and connecting rods are incorporated into the crankpin before assembly. Therefore, before assembly, the upstream and downstream portions of the oblique communication holes must be connected to the journal and crankpin sides. If the holes are formed, it is necessary to align the upstream and downstream portions of the communication hole when the crank pin is pressed into the crank arm during assembly, which is troublesome. Further, if an oblique communication hole is formed from the journal portion to the crank pin after assembly, it is necessary to provide a troublesome means for preventing chips from adhering to the needle bearing.
[0004]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to supply oil from an oil hole in a journal portion to an oil supply hole of a crankpin without forming an oblique communication hole, and to provide a crankshaft. It is an object of the present invention to provide an oil path structure for an engine-assembled crankshaft, which eliminates the need for oil path alignment and drilling after assembly when assembling the engine, and allows centrifugal separation of foreign matter from passing oil. And
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an engine-assembled crank having a crank portion formed by press-fitting both ends of a crank pin into two crank arms integrally connected to a pair of first and second journal portions. On the axis,
The crankpin is made hollow, and an oil supply hole is formed to connect the hollow part to the outer peripheral surface of the crankpin. At least one of the first and second journal parts is connected to an oil supply source and is provided at one end face of the crank part. An oil hole is formed adjacent to the oil hole, and a transfer plate for transferring oil from the oil hole to the hollow portion is attached to one end of the crank portion. The transfer plate is provided in the transfer plate during rotation of the crankshaft. A first feature is that a foreign matter pool for holding foreign matter centrifugally separated from the oil in the inside is provided.
[0006]
According to the first feature, the oil can be transferred from the oil hole of the journal portion to the oil supply hole of the crankpin by using a dish, and therefore, a diagonal communication hole is formed from the journal portion to the crankpin as in the related art. Since there is no need to install them, there is no need to align the holes when assembling the crankshaft or drill holes after assembling. In the transfer tray, foreign substances are separated from the passing oil by centrifugation and purified. Oil can be supplied to the crankpin side, which can contribute to improving engine durability.
[0007]
According to the present invention, in addition to the first feature, the transfer plate is fitted with a large-diameter portion into an annular positioning recess formed on one end surface of the crank portion, and a small-diameter portion is formed on the one journal portion. The second feature is that the bearing is elastically contacted with the inner end face of the bearing that supports the bearing.
[0008]
According to the second feature, the transfer plate can be simply and accurately attached to one end of the crank portion without using a special fixing member.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below based on preferred embodiments of the present invention shown in the accompanying drawings.
[0010]
1 is a vertical sectional view of a four-stroke engine for a power working machine according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along line 2-2 of FIG. 1, and FIG. 3 is a sectional view taken along line 3-3 of FIG. 4A is a sectional view taken along line 4A-4A in FIG. 3, FIG. 4B is a sectional view taken along line 4B-4B in FIG. 3, FIG. 5 is a sectional view taken along line 5-5 in FIG. 3, and FIG. 7 is a sectional view taken along line 7-7 of FIG. 3, FIG. 8 is a view corresponding to FIG. 1, showing a second embodiment of the present invention, and FIG. 9 is a sectional view taken along line 9-9 of FIG. 10 is a sectional view taken along line 10-10 of FIG. 9, and FIG. 11 is a sectional view taken along line 11-11 of FIG.
[0011]
First, a first embodiment of the present invention shown in FIGS. 1 to 7 will be described.
[0012]
1 to 3, a four-cycle engine E mounted on an engine bed B of a power working machine includes a crankcase 1 and a cylinder block 2 coupled to a front end of the crankcase 1 in a forwardly inclined posture. And a cylinder head 3 is integrally formed on the head of the cylinder block 2.
[0013]
The crankcase 1 includes left and right first and second case halves 1a and 1b joined at a joint surface P orthogonal to an axis of a crankshaft 5 described later to define a crank chamber 4 therebetween. The crank portion 1c of the crankshaft 5 is accommodated in the chamber 4, and the first and second journal portions 5a and 5b at the left and right ends of the crankshaft 5 are formed by opposing side walls of the first and second case halves 1a and 1b. It is supported via first and second ball bearings 6a, 6b. An oil seal 7a is mounted on the side wall of the first case half 1a, adjacent to the outside of the first ball bearing 6a, and in close contact with the outer peripheral surface of the first journal portion 5a of the crankshaft 5. The second ball bearing 6b is configured with a seal.
[0014]
A side cover 8 is joined to the outer surface of the second case half 1b, and a first valve operating chamber 9a is defined between the second case half 1b and the side cover 8. One end of the crankshaft 5 penetrates the side cover 8 across the first valve chamber 9a and extends to the outside, and an oil seal 7b that is in close contact with the outer peripheral surface of the one end is attached to the side cover 8. Is done.
[0015]
A head cover 10 defining a second valve operating chamber 9b is joined to the front end of the cylinder head 3, and a pair of rod passages 5c communicating between the first and second valve operating chambers 9a and 9b. , 5c are provided in the cylinder block 2.
[0016]
The crank pin 5p of the crank portion 1c is connected to a piston 11 sliding in the cylinder bore 1a via a connecting rod 12, and a needle bearing 17 is interposed between the crank pin 5p and the large end of the connecting rod 12. Is done.
[0017]
The cylinder head 3 is formed with an intake port 14i and an exhaust port 14e that open to the combustion chamber 13 inside the cylinder head 3, and is provided with an intake valve 15i and an exhaust valve 15e that open and close these ports 14a and 14b. A valve operating mechanism 19 for opening and closing the exhaust valves 15e, 15e is provided from the first valve operating chamber 9a to the second valve operating chamber 9b.
[0018]
That is, in the first valve chamber 9a, a drive timing gear 20 formed on the crankshaft 5, a camshaft 22 rotatably supported at both ends by the second case half 1b and the side cover 8, and the camshaft A driven timing gear 21 formed on the shaft 22 and driven at a half reduction ratio from the drive timing gear 20, a cam follower shaft 23 supported at both ends by the first case half 1a and the side cover 8; A pair of cam followers 24i and 24e are swingably supported by the cam follower shaft 23 and slidably engage with the intake cam 22i and the exhaust cam 22e of the cam shaft 22. In the second valve chamber 9b, valve springs 25i and 25e for urging the intake valve 15i and the exhaust valve 15e in the valve closing direction are respectively supported. And a pair of rocker arms 26i and 26e that are in contact with the upper end of the exhaust valve 15e. A pair of push rods 27i, 27e connecting between the other ends of the rocker arms 26i, 26e and the cam followers 24i, 24e are provided in the rod passages 5c, 5c.
[0019]
Accordingly, when the crankshaft 5 rotates, the camshaft 22 is driven in a reduced speed via the drive timing gear 20 and the driven timing gear 21, and the intake cam 22i and the exhaust cam 22e of the camshaft 22 are pushed through the cam followers 24i, 24e. When the rods 27i and 27e are respectively pushed up, the intake valve 15i and the exhaust valve 15e are opened, respectively. When the intake cam 22i and the exhaust cam 22e allow the push rods 27i and 27e to descend, the intake valve 15i and the exhaust valve 15e The valve springs 25i and 25e are closed by the urging force.
[0020]
1 to 4A, the crankcase 4 in the crankcase 1 is formed in a cylindrical shape having a minimum volume that follows the rotation trajectory of the crankshaft 5 so as not to store lubricating oil. U-shaped recesses 28a and 28b are formed on the joint surfaces of the first and second case halves 1a and 1b, respectively, and the recesses 28a and 28b constitute a first oil reservoir 28. The recesses 28a and 28b are formed together with the crank chamber 4 when the first and second case halves 1a and 1b are cast.
[0021]
The first valve chamber 9a between the second case half 1b and the side cover 8 is also formed with a minimum necessary volume so as not to store lubricating oil, and recesses 29a, 29b surrounding the first valve chamber 9a are formed. A second oil reservoir 29 is formed on the joint surface between the second case half 1b and the side cover 8, and these recesses 29a and 29b are formed. The recesses 29a and 29b are formed together with the first valve chamber 9a when the second case half 1b and the side cover 8 are cast.
[0022]
A plurality of through holes 30 are provided in the second case half 1b so as to communicate the first and second oil reservoirs 28 and 29 with each other. Lubricating oil O is stored in both oil storage chambers 28 and 29 to a higher level than the first and second journal portions 5a and 5b of the crankshaft 5.
[0023]
As shown in FIGS. 3, 4B and 6, the side cover 8 has an annular oil passage 31 surrounding the second journal portion 5b of the crankshaft 5 inside the oil seal 7b. Communicates via a rising oil passage 34 with a supply small chamber 33 which communicates with the lower part of the first oil sump chamber 28 via an outlet hole 32. The outlet hole 32 is formed in the second case half 1b, and the supply small chamber 33 and the rising oil passage 34 are formed between the joining surfaces of the second case half 1b and the side cover 8.
[0024]
The crankshaft 5 is an assembly type in which both ends of a hollow crankpin 5p are press-fitted into both crank arms with balance weights integrally connected to the first and second journal portions 5a and 5b to form a crank portion 5c. An oil hole 35 is formed in the second journal portion 5b. One end of the oil hole 35 opens to the annular oil passage 31 and the other end opens to the inner end side of the inner race of the second ball bearing 6b. Oil is transferred from the oil hole 35 to the hollow portion 36 of the crank pin 5p. The transfer plate 37 is attached to one end of the crank portion 1c with the balance weight. That is, when the first and second case halves 1a and 1b are joined, the large-diameter portion of the transfer plate 37 fits into the shallow annular positioning recess 43 formed on one end surface of the crank portion 5c. The small-diameter portion is compressed and deformed in the axial direction so as to resiliently contact the inner end face of the inner race of the second ball bearing 5b, and is set. In this case, the transfer plate 37 can be easily and accurately attached to one end of the crank portion 5c without using a special fixing member.
[0025]
The crankpin 5p is provided with an oil supply hole 38 for supplying oil from the hollow portion 36 to the needle bearing 17 between the crankpin 5p and the connecting rod 12. The oil hole 35 is provided with a check valve 39 that allows the fluid to flow in one direction from the annular oil passage 31 to the delivery tray 37 side.
[0026]
Inside the transfer tray 37, there is provided an annular foreign matter pool 40 which extends radially outward from the hollow portion 36 of the crankpin 5p.
[0027]
As shown in FIGS. 3 and 4A, a groove 4a extending in the axial direction is formed in the bottom of the crank chamber 4, and this groove 4a is inserted into an extension 9a 'extending below the first valve chamber 9a. A communicating hole 41 is formed in the second case half 1b, and a reed valve 42 for allowing fluid to flow in one direction from the crank chamber 4 to the first valve chamber 9a is formed in the second hole half 1b. It is attached to the case half 1b.
[0028]
In FIGS. 1, 3 and 7, the cylinder block 2 is provided with a recovery hole 45 which is opened at the lower part of the second valve chamber 9b, and the first oil sump chamber 28 extends from the cylinder block 2 to the crankcase 1. A return hole 47 that opens is provided, and a bent oil passage 46 that connects between the recovery hole 45 and the return hole 47 is formed on the joint surface of the cylinder block 2 with the crankcase 1 so as to bypass the cylinder bore 1a. At this time, the return hole 47 is disposed behind the recovery hole 45 (the side opposite to the head cover 10) and above the recovery hole 45 and the oil surface of the first oil reservoir 28.
[0029]
Referring again to FIG. 1, the ceiling wall of the head cover 10 is formed as a double wall composed of an inner wall 10a and an outer wall 10b so as to define a breather chamber 48 at an intermediate portion, and the inner wall 10a has a second wall. A through hole 49 communicating between the valve operating chamber 9b and the breather chamber 48 is formed, and a lead through which the fluid flows in one direction from the second valve operating chamber 9b to the breather chamber 48 is provided. A valve 50 is mounted. Further, a small hole 51 is formed in the inner wall 10a to communicate the lower part of the breather chamber 48 with the second valve operating chamber 9b.
[0030]
A breather pipe 52 that connects the breather chamber 48 to an air cleaner (not shown) of an intake system of the engine E is connected to the outer wall 10b.
[0031]
Next, the operation of the first embodiment will be described.
[0032]
During the operation of the engine E, the pressure in the crank chamber 4 pulsates due to the vertical movement of the piston 11, and the pulsation of the pressure acts on the check valve 39 through the hollow portion 36 of the crank pin 5p to open and close it. The pressure pulsation also acts on the reed valve 42 through the through hole 30 to open and close the reed valve 42, and propagates to the first and second valve chambers 9a and 9b.
[0033]
According to the opening and closing of the check valve 39, the stored oil O in the first oil storage chamber 28 is discharged from the outlet hole 32, the supply chamber 33, the rising oil passage 34, the annular oil passage 31, the oil hole 35, and the transfer tray 37. The oil is intermittently sucked into the crank chamber 4 through the hollow portion 36 of the crank pin 5p to lubricate the ball bearings 6a and 6b facing the crank chamber 4, and a part of the oil passing through the hollow portion 36 of the rank pin 5p is supplied. The needle bearing 17 between the crank pin 5p and the connecting rod 12 is lubricated through the hole 38.
[0034]
During this time, in the transfer plate 37 rotating together with the crankshaft 5, the oil passing through the inside is rotated, and foreign matter such as cutting chips and abrasion powder contained therein is centrifuged, and the foreign matter is separated into the hollow portion 36 of the crankpin 5 p. It is held by a foreign substance pool 40 that spreads more radially outward. Therefore, the purified oil can be supplied to the crank pin 5p side, which can contribute to improvement of the durability of the engine E.
[0035]
Thus, when the oil intermittently sucked into the crank chamber 4 is separated from the rotating crankshaft 5, it is scattered by centrifugal force to become an oil mist, and the oil mist is discharged from the through hole 41 by opening and closing the reed valve 42. The pressure is intermittently fed to the first valve operating chamber 9a, and then moves to the second valve operating chamber 9b through the rod passages 5c, 5c to lubricate each part of the valve operating mechanism 19 therebetween.
[0036]
When the oil mist that has finished lubricating the valve train 19 is liquefied, for example, by adhering to the inner wall of the second valve train 9b, the oil is returned from the recovery hole 45 below the second valve train 9b to the bent oil passage 46 and returned. The pressure is returned to the first oil reservoir chamber 28 through the hole 47 by the pressure pulsation of the second valve chamber 9b.
[0037]
The pressure pulsation in the second valve chamber 9b also opens and closes the reed valve 50 in the breather chamber 48. Therefore, when the blow-by gas generated in the crank chamber 4 rises up to the second valve chamber 9b together with the oil mist, When the reed valve 50 opens and closes, it is intermittently carried to the breather chamber 48 together with some oil mist, and expands to perform gas-liquid separation. Then, the liquefied oil returns to the second valve chamber 9b through the small hole 51, and the blow-by gas from which the oil has been separated is sucked into the suction system (not shown) through the breather pipe 52 and is subjected to combustion processing.
[0038]
Thus, by utilizing the pumping action of the pulsation of the crank chamber 4, the stored oil O in the first and second oil storage chambers 28 and 29 can be circulated to various parts of the engine E without using a special oil pump. Thus, the lubrication device can be simplified, and the cost can be reduced.
[0039]
While the oil O in the first oil storage chamber 28 circulates from the crank chamber 4 → the first valve chamber 9a → the rod passages 5c, 5c → the second valve chamber 9b → the first oil storage chamber 28, When the oil O in the first oil storage chamber 28 decreases, the oil O in the second oil storage chamber 29 is supplied to the first oil storage chamber 28 through the through hole 30. Since the total volume of the oil storage chambers 28 and 29 is large and a large amount of oil O can be stored, the engine E can be operated for a long time.
[0040]
In addition, the first oil sump chamber 28 is formed in the first and second case halves 1a and 1b constituting the crankcase 1 so as to surround the crank chamber 4, and the second oil sump chamber 29 is provided with the first oil sump chamber 29. Since the second valve body 9b is formed in the two case half 1b and the side cover 8 so as to surround the second valve chamber 9b, the first and second oil sump chambers 29 are formed by slightly expanding the crankcase 1 and the side cover 8 in the radial direction. Can be formed, which can contribute to downsizing of the engine E.
[0041]
In particular, the oil drawn into the hollow portion 36 of the crankshaft 5 from the first oil storage chamber 28 is scattered by the rotation of the crankshaft 5 to create an oil mist, so that an oil slinger for generating the oil mist is not required, and the number of parts is reduced. Not only can the structure be simplified due to the reduction of the size, but also the first and second oil sump chambers 28 and 29 having no oil slinger increase the degree of freedom of the shape, and can reduce the size of the engine E as a whole. It can be aimed at. Moreover, the first oil sump chamber 28 is constituted by concave portions 28a and 28b formed on the joint surfaces of the first and second case halves 1a and 1b, respectively, and the second oil sump chamber 29 is constituted by the second case half. When the first and second case halves 1a and 1b and the side cover 8 are cast, the crankcase 4 and the first chamber half 1a and 1b are formed by the concave portions 29a and 29b respectively formed on the joint surfaces of the body 1b and the side cover 8. Since it can be formed at the same time as the valve operating chamber 9a, manufacture is easy and cost can be reduced.
[0042]
The recovery hole 45 opened in the second valve chamber 9b and the return hole 47 opened in the first oil storage chamber 28 are separated from each other in both the horizontal and vertical directions, and communicate with each other through the bent oil passage 46. Therefore, even if the engine E is tilted while the operation is stopped, as long as one of the recovery hole 45 and the return hole 47 is exposed above the oil level of the first oil storage chamber 28, the first oil storage chamber Oil can be prevented from flowing backward from the second valve chamber 9b to the second valve chamber 9b.
[0043]
When the operation of the engine E is stopped, the check valve 39 is closed to shut off the oil hole 35 in the crankshaft 5, so that the oil hole 35 in the crankshaft 5 Even when the engine E is disposed at a large angle, such as when the engine E is retracted, the oil O in the first oil storage chamber 28 flows into the crank chamber 4 without fail, despite being disposed at a lower position. Can also be prevented.
[0044]
The delivery of oil from the oil hole 35 of the second journal portion 5b to the oil supply hole 38 of the crank pin 5p is performed by the transfer plate 37 attached to one end of the crank portion 5c. In addition, the need for drilling after assembly can be eliminated, and the cost can be reduced.
[0045]
Next, a second embodiment of the present invention shown in FIGS. 8 to 11 will be described.
[0046]
In the second embodiment, the first and second ball bearings 6a and 6b supporting the first and second journal portions 5a and 5b of the crankshaft 5 are both provided with seals. An annular oil passage 31 surrounding one journal portion 5a is provided in the first case half 1a, and a transfer plate 37 is attached to the crank portion 1c on the first journal portion 5a side. The check valve 39 as in the previous embodiment is not provided in the oil hole 35 in the crankshaft 5 that communicates between the annular oil passage 31 and the transfer plate 37. Instead, the annular oil passage 31 includes an oil passage 61 that extends from the front of the annular oil passage 31 through the side wall of the first case half 1a and extends forward in parallel with the axis of the cylinder bore 1a. An oil passage 62 extending between the joint surfaces of the crankcase 1 and the cylinder block 2 so as to extend upward along the inner peripheral wall of the cylinder bore 1a from the front end of the cylinder passage 1a. An oil passage 63 penetrating to the cover 8 side, and the second case half 1b and the side cover 8 are formed so as to bypass the second oil reservoir 9b downward from the opening end of the oil passage 63 to the side cover 8 side. It communicates with a supply small chamber 33 connected to a lower part of the first oil storage chamber 28 via an oil passage 64 passing between the joining surfaces.
[0047]
Thus, the oil passages 61 to 64 communicating with the annular oil passage 31 surrounding the first journal portion 5a of the crankshaft 5 once extend above the oil levels of the first and second oil sump chambers 28 and 29, and Since it bends downward and reaches the supply small chamber 33 connected to the lower part of the first oil sump chamber 28, even when the engine E is stopped, this does not occur even if the check valve 39 in the crankshaft 5 is not provided as in the previous embodiment. In the case of a large inclination, oil can be prevented from flowing into the crank chamber 4 side from the first oil sump chamber 28 through the annular oil passage 31.
[0048]
Other configurations are the same as those of the previous embodiment. Therefore, in FIGS. 8 to 11, parts corresponding to those of the previous embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0049]
The present invention is not limited to the above embodiment, and various design changes can be made without departing from the gist of the present invention.
[0050]
【The invention's effect】
As described above, according to the first aspect of the present invention, the crank portion is formed by press-fitting both ends of the crankpin into both crank arms integrally connected to the paired first and second journal portions. In the assembly type crankshaft, the crankpin is hollow and an oil supply hole is formed to communicate the hollow portion with the outer peripheral surface of the crankpin. At least one of the first and second journals is connected to an oil supply source. An oil hole is formed adjacent to one end surface of the crank portion, and a delivery plate for delivering oil from the oil hole to the hollow portion is attached to one end of the crank portion. During the rotation of the cylinder, a foreign material pool is provided in the transfer tray to hold the foreign material centrifuged from the oil. This can be done by using a transfer plate attached to one end of the crankshaft, so that it is not necessary to form an oblique communication hole from the journal to the crankpin as in the conventional case. Drilling after assembly is unnecessary, and in the transfer tray, foreign matter can be centrifuged from the passing oil and purified oil can be supplied to the crankpin side, improving engine durability. Can contribute to
[0051]
According to a second feature of the present invention, in addition to the first feature, the transfer plate is fitted with a large-diameter portion into an annular positioning recess formed on one end surface of the crank portion and has a small diameter. Since the portion is elastically abutted against the inner end surface of the bearing that supports the one journal portion, the transfer plate can be simply and accurately attached to one end of the crank portion without using a special fixing member. .
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional plan view of an engine for a power working machine according to a first embodiment of the present invention; FIG. 2 is a sectional view taken along line 2-2 of FIG. 1; FIG. 3 is a sectional view taken along line 3-3 of FIG. 4A is a sectional view taken along line 4A-4A in FIG. 3 [FIG. 4B] A sectional view taken along line 4B-4B in FIG. 3 [FIG. 5] A sectional view taken along line 5-5 in FIG. 3 [FIG. 7 is a sectional view taken along line 7-7 of FIG. 3; FIG. 8 is a view corresponding to FIG. 1 showing a second embodiment of the present invention; FIG. 9 is a sectional view taken along line 9-9 of FIG. FIG. 11 is a sectional view taken along line 10-10 of FIG. 9; FIG. 11 is a sectional view taken along line 11-11 of FIG.
E ··· Engine 5 ···· Crankshaft 5a, 5b ··· Journal 35 ··· Oil hole 36 ··· Hollow portion 37 ··· Delivery tray 38 ··· Refueling Hole 40: foreign matter reservoir 43: positioning recess

Claims (2)

An assembling crankshaft for an engine, in which both ends of a crankpin (5p) are press-fitted into both crank arms integrally connected to a pair of first and second journal portions (5a, 5b) to form a crank portion (5c). At
The crank pin (5p) is made hollow, and an oil supply hole (38) communicating the hollow portion (36) with the outer peripheral surface of the crank pin (5p) is formed. The first and second journal portions (5a, 5b) are formed. An oil hole (35) connected to the oil supply source and opened adjacent to one end face of the crank portion (5c) is formed in at least one of the oil supply sources. A transfer plate (37) for delivering and receiving is attached to one end of the crank portion (5c). In the transfer plate (37), centrifugal separation from oil is performed in the transfer plate (37) during rotation of the crankshaft (5). An oil passage structure for an engine crankshaft, characterized by having a foreign matter reservoir (40) for holding the removed foreign matter. The oil passage structure for an engine crankshaft according to claim 1,
The transfer tray (37) has a large-diameter portion fitted into an annular positioning recess (43) formed on one end surface of the crank portion (5c), and a small-diameter portion fits into the one journal portion (5b). An oil passage structure for an engine crankshaft, characterized in that the inner end surface of a bearing (6b) to be supported is elastically contacted.

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