PH12016501707B1

PH12016501707B1 - Engine lubrication structure

Info

Publication number: PH12016501707B1
Application number: PH12016501707A
Authority: PH
Inventors: Fuminori Mizutani
Original assignee: Honda Motor Co Ltd
Priority date: 2014-03-28
Filing date: 2016-08-30
Publication date: 2016-10-03
Also published as: MY177190A; JPWO2015146672A1; PH12016501707A1; CN106164425B; CN106164425A; JP6117990B2; WO2015146672A1

Abstract

An engine lubrication structure includes a crankcase formed by a pair of half-cases divided at a dividing surface, a cylinder block, and an oil supply path. The oil supply path includes a first oil passage, a second oil passage, a first bypass hole and a second bypass hole, the first bypass hole having a first end which communicates with the first oil passage and a second end which communicates with a portion of the dividing surface which is separated from the joining surface between the first half-case and the cylinder block, the second bypass hole having a first end which communicates with the second oil passage and a second end which communicates with a portion of the dividing surface which is separated from the joining surface between the second half-case and the cylinder block. The second end of the first bypass hole and the second end of the second bypass hole are connected to communicate with each other at the dividing surface.

Description

the power unit of the embodiment of the present invention along a portion XI1-XH in Fig. 11 from which a rotation sensor is omitted.

Fig. 13 is a perspective view showing the power unit of the embodiment of the present invention from which the rotation sensor is omitted.

Fig. 14 is a cross-sectional view corresponding to a cross section XIV-XIV in

Fig. 11 of the power unit of the embodiment of the present invention.

Fig. 15 is a cross-sectional view corresponding to a cross section XV-XV in Fig. 11 of the power unit of the embodiment of the present invention.

Description of Embodiments

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that an arrow FR indicating the front of a vehicle, an arrow LH indicating the left of the vehicle, and an arrow UP indicating an upper portion of the vehicle are represented at appropriate places in the drawings used in the following description.

Fig. 1 is a left side view of a motorcycle 1 on which a power unit PU configured to adopt an engine E related to this embodiment is mounted.

In Fig. 1, Wf and Wr are a front wheel supported by a vehicle body frame (not shown) via a front fork 2 and a rear wheel supported by the vehicle body frame via a swing arm 3, respectively. Also, H is a steering handlebar disposed above the front fork 2, S is a seat on which an occupant sits, and T is a fuel tank disposed in front of the seat

S. The power unit PU is mounted under the fuel tank T at a center of the vehicle body frame.

The power unit PU shifts drive rotation of the engine I using a transmission M, and transmits its output to the rear wheel Wr via a transmission mechanism. Note that directions such as the front, rear, left, and right in the following description of the power unit PU are assumed to be the same as those when the power unit PU is mounted on a vehicle unless specifically mentioned otherwise.

Fig. 2 is a view showing a right side of the power unit PU, and Fig. 3 is a view showing a left side of the power unit PU. Also, Fig. 4 is a view showing a top surface of the power unit PU. Fig. 5 is a cross-sectional view which substantially corresponds to across section V-V in Fig. 2 of the power unit PU. Fig. 6 is a cross-sectional view which substantially corresponds to a cross section VI-VI in Fig. 2 of the power unit PU.

The engine E of the power unit PU includes a crankcase 11 configured to rotatably support a crankshaft 10 and a cylinder portion 12 which obliquely protrudes upward from a front upper portion of the crankcase 11. The crankcase 11 is also used as a transmission case of the transmission M, the crankshaft 10 is disposed at the front side of the crankcase 11, and a main shaft 13 (a transmission shaft) and a counter shaft 14 of the transmission M are disposed at the rear side of the crankshaft 10, parallel to the crankshaft 10. The main shaft 13 and the counter shaft 14 are rotatably supported by the crankcase 11. As shown in Fig. 5, the counter shaft 14 passes through a left side wall of the crankcase 11 to the outside, and a sprocket 15 for acquiring power is attached to the passing end thereof. A chain 9 is wound around the sprocket 15, and power is transferred to the rear wheel through the chain 9.

In the embodiment, the counter shaft 14 and the sprocket 15 configures a power acquisition portion in the power unit PU.

The cylinder portion 12 includes a cylinder block 17, a cylinder head 18, and a head cover 19.

The cylinder block 17 includes a cylinder bore 17a configured to accommodate apiston 16 to freely advance or retreat. The cylinder head 18 is attached to an upper portion of the cylinder block 17, and a combustion chamber 7 is formed between the cylinder head 18 and a top surface of the piston 16. The head cover 19 is attached to an : upper portion of the cylinder head 18.

As shown in Fig. 6, the cylinder head 18 and the upper portion of the cylinder block 17 overlap each other, and the cylinder head 18 is fastened and fixed to an upper surface of the crankcase 11 using a plurality of (four) stud bolts 20 (fastening members) together with the cylinder block 17.

The piston 16 is connected to the crankshaft 10 via a connecting rod 23 to be able to be interlocked and transfers forward and backward movement of the piston 16 according to an explosion in the combustion chamber 7 to the crankshaft 10 as a rotating force. Reference numeral 8 in Fig. 5 is a spark plug provided to face the combustion chamber 7.

In the cylinder head 18, an inlet port and an exhaust port (which are not shown in the drawing) are formed, and an intake valve and an exhaust valve (which are not shown in the drawing) which open and close the inlet port and the exhaust port are attached. As shown in Figs. 2 and 3, an inlet pipe 6 which configures an intake system of the engine E is connected to the inlet port. An exhaust pipe (not shown) which configures an exhaust system of the engine E is connected to the exhaust port. Also, as shown in Fig. 6, a valve mechanism 21 which opens and closes the intake valve and the exhaust valve is provided between the cylinder head 18 and the head cover 19.

Reference numeral 22 in Fig. 6 is a camshafl for operating a valve operating cam of the valve mechanism 21. The camshaft 22 is connected to the crankshaft 10 via a timing chain 5 io be able to be interlocked.

The engine E in the embodiment is a water-cooled single cylinder engine, the cylinder block 17 is provided with the single cylinder bore 17a, and a water jacket 50 is formed in the region around the cylinder bore 17a. Reference numeral 51 in Figs. 2, 4, and 5 is a water pump for delivering cooling water cooled by a radiator (not shown) to the water jacket 50.

As shown in Figs. 5 and 6, the crankcase 11 is configured by a pair of half-cases 11L and 11R which are divided into the left and right portions using dividing surfaces 11Laand 11Ra perpendicular to the crankshaft 10 as a boundary. The left and right half-cases 11L and 11R are divided into the left and right portions at a plane passing through a cylinder central axis C1 of the cylinder block 17, and the divided half-cases 11L and 11R are fastened and fixed using a plurality of bolts (not shown). A crank cover 30 which forms a closed space with the half-case 11R is attached to a right side portion of the right half-case 11R.

As shown in Fig. 5, a right end of the crankshaft 10 passes through a side wall of the right half-case 11R, and a primary drive gear 24 for transferring power to the main shaft 13 of the transmission M is attached to the passing end thereof. Also, a left end of the crankshaft 10 passes through a side wall of the left half-case 11L, and a rotor 25a of a power generator 25 is attached to the passing end thereof. An end of the rotor 25a and the region around the end are covered by a cover 25¢ of the power generator 25 which holds a stator 25b.

A right end of the main shaft 13 of the transmission M passes through a side wall of the right half-case 11R. A primary driven gear 26 which meshes with the primary drive gear 24 at a side of the crankshaft 10 and a clutch 27 configured to perform connection and disconnection of power according to an operation from the outside are supported by the end of the main shaft 13 which passes through the right half-case 11R.

The primary driven gear 26 is rotatably supported by the main shaft 13, and the clutch 27 is surrounded by a power transmission path between the primary driven gear 26 and the main shaft 13. Therefore, the clutch 27 can appropriately switch transmission and cutoff of power between the primary driven gear 26 and the main shaft 13 according to an operation from the outside.

The main shaft 13 and the counter shaft 14 of the transmission M are provided with a main gear group m1 and a counter gear group m2 which are configured by a plurality of transmission gears. The transmission M selects one of the transmission gears of the main gear group m1 and the counter gear group m2 according to an operation of a change mechanism (not shown), and an arbitrary transmission gear step (a gear position) including neutral is thus set. Therefore, when rotation power of the crankshaft 10 is transferred to the main shaft 13 via the clutch 27 in a state in which the transmission gear step is set in this way, the transmission M shifts the rotation power to a set ratio and outputs the rotation power to the outside from the counter shaft 14.

Note that reference numeral 28 in Fig. 5 is a kick shaft for rotating the crankshaft 10 at the time of kick starting.

As shown in Figs. 2 to 4, a balancer shafl 29 which extends parallel to the crankshaft 10 is disposed above a space between the crankshaft 10 and the main shaft 13 inthe crankcase 11. The balancer shaft 29 is rotatably supported by the crankcase 11.

The balancer shaft 29 rotates to be synchronized with the crankshaft 10 via a gear (not shown) so that rotation fluctuation of the crankshaft 10 is cancelled and a rotational balance is maintained.

Also, as shown in Fig. 6, a bottom of the crankcase 11 is provided with an oil pan 31 for storing a lubricating oil. An oil pump 32 (an oil supply source) which suctions oil in the oil pan 31 and pumps the oil to a site which needs to be lubricated in the power unit PU is installed above the oil pan 31 of the right half-case 11R. The oil pump 32 in the embodiment operates in response to rotation power from the crankshaft 10.

An oil supply path 33 in the power unit PU connected to the oil pump 32 is divided into a crank system oil passage 33C which supplies oil to a site which needs to be lubricated, such as a crank pin or a journal portion, around the crankshaft 10 through an inside of the crankshaft 10 from a discharge portion of the oil pump 32, and a valve system oil passage 33B which supplies oil to a site which needs to be lubricated in the valve mechanism 21 through an inside of a wall of the cylinder portion 12 from an upper portion of the crankcase 11. Also, a branched oil passage 34 for supplying oil around shafts such as the main shaft 13 and the counter shaft 14 of the transmission M is connected in the middle of the valve system oil passage 33B.

Fig. 7 is a bottom view corresponding to an arrow VII in Fig. 2 of the cylinder block 17. Fig. 8 is a perspective view showing cross sections of the crankcase 11 and the cylinder block 17 along a cross-sectional portion VII1-VIII in Fig. 7. In addition,

Fig. 9 is a perspective view of the right half-case 11R of the crankcase 11 viewed obliquely from above at the rear side so that the dividing surface 11Ra substantially faces the front. Fig. 10 is a perspective view of the left half-case 11L of the crankcase 11 viewed obliquely from above at the front side so that the dividing surface 11La substantially faces the front.

As shown in Fig. 6, a portion of the valve system oil passage 33B of the oil supply path 33 is formed in spaces between upper end surfaces 11Ru and 11Lu (joining surfaces) of the crankcase 11 and a lower surface 17d (a joining surface) of the cylinder block 17. As shown in Fig. 6, in the oil passage between the joining surfaces of the crankcase 11 and the cylinder block 17, an oil inflow portion 35a connected to the oil pump 32 is provided near a corner of a front right side of the cylinder block 17, and an oil outflow portion 36a connected to a side of the valve mechanism 21 is provided at a ~ corner of a rear left side of the cylinder block 17. As shown in Fig. 7, the inflow portion 35a and the outflow portion 36a of the oil passage between the joining surfaces are disposed in a range in which they overlap a diagonal line L1 passing through the cylinder central axis C1.

The above-described oil passage between the joining surfaces between the crankcase 11 and the cylinder block 17 includes a first oil passage 35 formed between the end surface 11Ru of the right (first) half-case 11R and the lower surface 17d of the cylinder block 17 and a second oil passage 36 formed between the end surface 11Lu of the left (second) half-case 11L and the lower surface 17d of the cylinder block 17.

In the embodiment, the first oil passage 35 is formed to be surrounded by the flat end surface 11Ru of the right half-case 11R and a groove 35¢ formed substantially along an outer circumferential edge portion of the cylinder bore 17a at the lower surface 17d of the cylinder block 17. Also, a first end in an extension direction of the first oil passage 35 is provided with the inflow portion 35a connected to a side of the oil pump 32.

The second oil passage 36 is formed to be surrounded by the flat end surface 11Lu of the left half-case 11L and a groove 36¢ formed substantially along the outer circumferential edge portion of the cylinder bore 17a at the lower surface 17d of the cylinder block 17. A first end in an extension direction of the second oil passage 36 is provided with the outflow portion 36a connected to a side of the valve mechanism 21.

Note that, in Fig. 6, cross sections are adjusted such that the first oil passage 35 and the second oil passage 36 are shown in the drawing. [

The first oil passage 35 extends in an arc shape from the inflow portion 35a of the front right side of the cylinder block 17 to the vicinity of the rear center of the cylinder block 17 via the rear right side of the cylinder block 17. As shown in Figs. 6 and 9, the first end of a first bypass hole 37 formed in the right half-case 11R communicates with the second end of the first oil passage 35.

Also, the second oil passage 36 extends in an arc shape from the outflow portion 36a of the rear left side of the cylinder block 17 to the vicinity of the rear center of the cylinder block 17 and ends at the vicinity of the rear center thereof. As shown in Figs. 6 and 8, a first end of the second bypass hole 38 formed in the left half-case 11 communicates with a second end of the second oil passage 36.

The first bypass hole 37 is configured as a substantially L-shaped hole whose first end is opened to the upper end surface 11Ru of the right half-case 11R. A second end 37a of the first bypass hole 37 is opened at a position of the dividing surface 11Ra of the right half-case 11R which is separated from the upper end surface 11Ru.

The second bypass hole 38 is configured as a substantially L-shaped hole whose first end is opened to the upper end surface 11Lu of the left half-case 11L. A second end 38a of the second bypass hole 38 is opened at a position of the dividing surface 11La of the left half-case 11L which is separated from the upper end surface 11Lu. Also, the left and right half-cases 11L and 11R are coupled so that the second end of the first bypass hole 37 and the second end of the second bypass hole 38 abut and are connected to each other.

Therefore, the first oil passage 35 and the second oil passage 36 are connected to each other via the first bypass hole 37 and the second bypass hole 38. Thus, oil flowing into the inflow portion 35a from the oil pump 32 sequentially passes through the first oil passage 35, the first bypass hole 37, the second bypass hole 38, the second oil passage 36, and the outflow portion 36a to be supplied to the valve mechanism 21 of the cylinder portion 12.

Also, in the second bypass hole 38, a vertical hole portion which extends downward from the upper end surface 11Lu of the half-case 11L extends a predetermined length further downward beyond a horizontal hole portion connected to a side of the first bypass hole 37.

The branched oil passage 34 for supplying oil around the shafts such as the main shaft 13 and the counter shaft 14 of the transmission M is connected 10 a side surface separated from a bottom 40a of an extension portion 40.

As shown in Fig. 7, insertion holes 39 through which the above-described stud bolts 20 are inserted are formed at four corners of a circumferential edge surrounding the cylinder bore 17a of the cylinder block 17. The four insertion holes 39 are disposed on the same pitch circle P centering on the cylinder central axis C1. Also, portions of the inflow portion 35a of the first oil passage 35 and the outflow portion 36a of the second oil passage 36, which are described above, are disposed at positions which are regions closer to the outside than the pitch circle P and near the insertion holes 39. As described above, the inflow portion 35a and the outflow portion 36a are disposed in a range in which they overlap the diagonal line L1 passing through the cylinder central axis C1.

For this reason, the first oil passage 35 and the second oil passage 36 are formed over the length of substantially half of the circumference around the cylinder bore 17a to surround positions of the dividing surfaces 11La and 11Ra of the crankcase 11.

A portion of the branched oil passage 34 branching off from the second bypass hole 38 includes an orifice hole 41 connected to the extension portion 40 and a passage groove 49 formed along the dividing surface 11La of the left half-case 11L. The left and right half-cases 11L and 11R are fastened and fixed so that the passage groove 49 abuts the flat dividing surface 11Ra of the right half-case 11R, thereby configuring a portion of a passage in a direction of the transmission M.

" : . |] : ’

DESCRIPTION Ce = -

ENGINE LUBRICATION STRUCTURE ’

Technical Field

The present invention relates to an engine lubrication structure which supplies oil for lubrication to a site which needs to be lubricated in an engine.

Priority is claimed on Japanese Patent Application No. 2014-070275, filed ,

March 28, 2014, the contents of which are incorporated herein by reference. - : :

CE,

Background Art =I / ny 5

Many engines adopted for vehicles suction oil in oil pans using oil pumps provided in crankcases and supply the oil to sites which needs to be lubricated in the engines from the oil pumps through oil supply paths formed in the crankcases or cylinder blocks.

An engine lubrication structure in which a portion of an oil supply path is configured to be provided at a joining surface portion between a crankcase and a cylinder block is known as an engine lubrication structure (for example, refer to Patent Document 1).

In the engine lubrication structure disclosed in Patent Document 1, a passage groove of a predetermined length which is curved about a cylinder central axis is formed ina joining surface at a crankcase side among joining surfaces between the crankcase

The orifice hole 41 is formed to communicate from a bottom of the passage groove 49 to a side surface of the extension portion 40 through drilling or the like at a side of the dividing surface 11La of the left half-case 11L.

As shown in Fig. 10, the passage groove 49 extends in a circular arc toward the rear lower side at a region surrounding the outside of the balancer shaft 29 in a circumferential wall of the left half-case 11L. An end of a rear lower side of the passage groove 49 is connected to a left passage hole 42 (a crossing hole) and a right passage hole 43 (refer to Fig. 11) which are linearly formed in the left half-case 11L and the right half-case 11R in left and right directions. The left passage hole 42 configures a portion of a passage configured to supply oil to a site which needs to be lubricated around the main shaft 13 of the transmission M. Also, the right passage hole 43 configures a portion of a passage configured to supply oil to a site which needs to be lubricated around the counter shaft 14 of the transmission M.

As shown in Fig. 10, a capture groove 44 which extends to surround around from an outer region of the second bypass hole 38 and the passage groove 49 to the rear side of the left passage hole 42 is formed in a region which faces the dividing surface 11La of the circumferential wall of the left half-case 11L. An extension end of the capture groove 44 which extends to surround around to the rear side of the left passage hole 42 is opened to an inner space of the crankcase 11. When oil flowing through the passage groove 49 or the second bypass hole 38 is leaked to the outside of the passage groove 49 or the second bypass hole 38 along the dividing surfaces 11La and 11Ra, the capture groove 44 functions to capture the oil and return the oil into the crankcase 11.

Fig. 11 is a plan view centering on a portion directly above the main shaft 13 in the transmission M of the power unit PU. Fig. 12 is a perspective view of a cross section of the power unit PU along a portion corresponding to a cross section XII-XII in

Fig. 11 viewed from a front left upper side. Also, Fig. 13 is a perspective view of the power unit PU viewed from a rear left upper side. Fig. 14 is a cross-sectional view corresponding to a cross section XIV-XIV in Fig. 11. Fig. 15 is a cross-sectional view corresponding to a cross section XV-XV in Fig. 11.

As shown in Fig. 11, a rotation sensor 53 for detecting rotation of a rotational element on the main shaft 13 of the transmission M is attached to a site of an upper wall 11Le of the left half-case 11L which is close to the rear side of the left passage hole 42.

The rotation sensor 53 detects rotation of a detection target gear close to the left end in the axial direction on the main shaft 13. As shown in Figs. 12 to 14, a sensor attachment hole 54 passing through the upper wall 11Le is formed in the upper wall 11Le around the left end of the half-case 11L. The rotation sensor 53 is attached to the sensor attachment hole 54, and a detection unit 53a of a front end side is close to a tooth surface of the detection target gear on the main shaft 13 in the crankcase 11. Inthe embodiment, as shown in Fig. 14, an axis C2 of the sensor attachment hole 54 is formed to be slightly inclined forward toward a lower side. For this reason, the detection unit 53a of the rotation sensor 53 is directed in a direction of the main shaft 13 in a state in which it is slightly inclined forward.

A crossing bead 55 which crosses the front vicinity of the sensor attachment hole 54 in a direction parallel to the main shaft 13 is formed at the upper wall 11Le of the left half-case 11L to protrude outward when viewed in a direction along the axis C2 of the sensor attachment hole 54. The crossing bead 55 protrudes in upper and left sides with respect to the upper wall 11Le near the left end of the half-case 111. Also, a bent bead 56 which extends from an outer end of the crossing bead 55 toward the vicinity of a left end in an axial direction of the main shafl 13 is formed at a left end wall of the half-case 11L to protrude leftward.

The above-described left passage hole 42 (the crossing hole) which configures a portion of the oil supply path 33 is formed in the crossing bead 55. A bent hole 57 whose upper end communicates with the left passage hole 42 is formed in the bent bead 56. A lower end of the bent hole 57 is configured to communicate with the left end in the axial direction of the main shaft 13 and to supply oil introduced via the left passage hole 42 and the bent hole 57 to a site which needs to be lubricated around the main shaft 13 through a passage in the main shaft 13.

As shown in Figs. 14 and 15, the crossing bead 55 and the left passage hole 42 therein extend between the balancer shaft 29 and the rotation sensor 53 in left and right directions. Also, the bent bead 56 and the bent hole 57 therein are inclined rearward from an upper end toward a lower end at a position closer to a left end than the sensor attachment hole 54. The bent bead 56 is formed such that the bent bead 56 and the detection unit 53a of a distal end side of the rotation sensor 53 partially overlap each other when viewed from the side in a direction along the main shaft 13. Therefore, the bent bead 56 covers a portion of a left side of the rotation sensor 53 at the left end of the left half-case 11L.

As shown in Figs. 12 and 14, a thickness T1 of an upper wall of the left passage hole 42 of the crossing bead 55 is formed to have a thicker thickness than a wall of another region in the region around the sensor attachment hole 54 of the left half-case 11L.

A left end of the counter shaft 14 of the transmission M protrudes sideward from aside wall of the left half-case 11L, and the protrusion portion is covered by a cover wall 58. The cover wall 58 includes an eaves part 58a of a circular arc shape which protrudes from a left end side of the half-case 11L. The eaves part 58a is configured to cover the region around approximately the first half of a protrusion portion of the counter shaft 14 and the sprocket 15 (refer to Fig. 5) and to protect them from the outside. Also, the eaves part 58a is formed to surround the rear lower side of the detection unit 53a of the rotation sensor 53.

As shown in Fig. 15, a portion of the eaves part 58a obliquely extends to cross a left side of the detection unit 53a of the rotation sensor 53 from an upper side of the counter shaft 14 toward the front lower side.

For this reason, both of the eaves part 58a and the bent bead 56 are formed to have a V shape viewed from the side in the direction along the main shaft 13. Also, the rotation sensor 53 is disposed to be surrounded by the eaves part 58a and the bent bead 56 in the V shape when viewed from the side in the direction along the main shaft 13.

As shown in Fig. 14, an inward protruding portion 59 which is protruding (downward) toward the inside of the crankcase 11 is formed at a site in which the sensor ~ attachment hole 54 of the upper wall 11Le of the left half-case 11L is formed. The sensor attachment hole 54 is formed over a top of the inward protruding portion 59 from the upper surface of the upper wall 11Le, and a lower end of the sensor attachment hole

54 is opened to the top of the inward protruding portion 59. Therefore, the sensor attachment hole 54 which surrounds the region around the rotation sensor 53 is configured to have a sufficiently long axis length.

Next, a flow of oil in each portion in a unit of the power unit PU related to the embodiment will be described.

When the crankshaft 10 rotates according to driving of the engine E, the oil pump 32 operates in response to the rotation of the crankshaft 10. As shown in Fig. 6, the oil pump 32 suctions oil stored in the oil pan 31 and discharges the oil toward the oil supply path 33. The oil discharged from the oil pump 32 branches off into the crank system oil passage 33C and the valve system oil passage 33B at the upper portion of the right half-case 11R of the crankcase 11. The oil flowing into the crank system oil passage 33C passes through a passage in the crankshaft 10 from the right end of the crankshaft 10 and is supplied to a site which needs to be lubricated, such as the crank pin or the journal portion, around the crankshaft 10.

On the other hand, as shown in Figs. 6 and 7, the oil flowing into the valve system oil passage 33B passes through a passage which extends upward from the front right side of the right half-case 11R and flows into the first oil passage 35 formed between the upper end surface 11Ru of the right half-case 11R and the lower surface 17d of the cylinder block 17 via the inflow portion 35a.

The oil flowing into the first oil passage 35 flows in an arc shape around the cylinder bore 17a toward a rear central side along the first oil passage 35, and a flow thereof is changed downward at a portion directly before the dividing surface 11Ra of the right half-casce 11R so that the oil flows into the first bypass hole 37 of the half-case 11R.

A direction of the oil flowing into the first bypass hole 37 is changed at a lower end in a substantially L shape in a direction of the dividing surface 11La, and the oil flows into the second bypass hole 38 of the left half-case 11L to surround a junction of the dividing surfaces 11Ra and 11La of the right half-case 11R and the left half-case 11L.

A direction of some of the oil flowing into the second bypass hole 38 is changed upward in a substantially L shape, and the oil flows into the second oil passage 36 formed between the upper end surface 11Lu of the left half-case 11L and the lower surface 17d ofthe cylinder block 17. A direction of the remaining oil flowing into the second bypass hole 38 is changed downward, and the remaining oil flows into the extension portion 40 and flows into the branched oil passage 34 of the transmission M side through the orifice hole 41 provided at the side surface of the extension portion 40.

The oil flowing into the second oil passage 36 from the second bypass hole 38 flows toward the outflow portion 36a near a rear left corner around the cylinder bore 17a from a rear central side of the cylinder block 17 and is supplied to a site which needs to be lubricated of the valve mechanism 21 through a passage in the cylinder block 17 from the outflow portion 36a.

As shown in Figs. 10 and 11, the oil flowing into the orifice hole 41 through the extension portion 40 from the second bypass hole 38 branches off and flows into the left passage hole 42 and the right passage hole 43 of a rear side of the balancer shaft 29 through the passage groove 49 formed at the dividing surface 11La of the left half-case 11L.

The oil flowing into the left passage hole 42 flows into the bent hole 57 at a left end region in an axial direction of the left half=case 111, a direction of the oil is changed 10 a lower side in a rear inclination, and the oil passes through a passage in the main shaft 13 from an left end of the main shaft 13 of the transmission M and is supplied to a site which needs to be lubricated, such as a bearing or a transmission gear, around the main shaft 13. On the other hand, a direction of the oil flowing into the right passage hole 43 is changed rearward at a right end region in an axial direction of the right half-case 11K, and the oil is supplied to a site which needs to be lubricated around the counter shaft 14 through a passage in the counter shaft 14 from a right end of the counter shaft 14 of the transmission M.

As described above, in the power unit PU according to the embodiment, the first oil passage 35 formed between the cylinder block 17 and the right half-case 11R is connected to the second oil passage 36 formed between the cylinder block 17 and the left half-case 11L via the first bypass hole 37 and the second bypass hole 38 which are connected to each other at portions of the dividing surfaces 11Ra and 11La separated from the upper end surfaces 11Ru and 11Lu (the joining surfaces) of the half-cases 11R and 11L. For this reason, the oil supply path 33 portion formed between the cylinder block 17 and the crankcase 11 is not connected across a joining portion of three members.

Therefore, by adopting this structure of the power unit PU, it is possible to easily form the oil supply path 33 crossing a joining portion between the cylinder block 17 and the left and right half-cases 11L and 11R without requiring extremely high machining accuracy or sealing performance for preventing oil leakage. Thus, by adopting the structure of the power unit PU, it is possible to increase a degree of freedom for design of the oil supply path 33.

In the power unit PU in the embodiment, as shown in Fig. 7, the first oil passage 35 and the second oil passage 36 are formed between the joining surfaces between the cylinder block 17 and the half-cases 11R and 11L such that the inflow portion 35a and the outflow portion 36a overlap the diagonal line L1 passing through the cylinder central axis C1 of the cylinder block 17. In the power unit PU, the inflow portion 35a and the outflow portion 36a are disposed in a farthest diagonal position relationship around the cylinder central axis C1. However, since the first oil passage 35 and the second oil passage 36 are connected via the first bypass hole 37 and the second bypass hole 38 which abut each other at the dividing surfaces 11Ra and 11La, leakage of oil from the oil supply path 33 can be easily prevented while the oil supply path 33 is disposed to have a high degree of freedom.

In the power unit PU in the embodiment, portions of the inflow portion 35a of the first oil passage 35 and the outflow portion 36a of the second oil passage 36 are disposed at a region closer to a radial outside region than the pitch circle P in which the insertion holes 39 of the stud bolts 20 formed in the cylinder block 17 are disposed, but both of the inflow portion 35a and the outflow portion 36a are disposed at a position near the insertion holes 39 through which the stud bolts 20 are inserted. For this reason, when the cylinder block 17 is fastened and fixed to the crankcase 11 using the stud bolts 20, it is possible to make the vicinity of the inflow portion 35a and the outflow portion 36a in tight contact manner by the fastening of the stud bolts 20.

Therefore, as this structure is adopted, even if the inflow portion 35a and the outflow portion are disposed closer to a radial outside region than the pitch circle P,

leakage of oil from portions near the inflow portion 35a and the outflow portion 36a can be prevented.

In the power unit PU related to the embodiment, the second bypass hole 38 which connects the first oil passage 35 and the second oil passage 36 together with the first bypass hole 37 is provided with the branched oil passage 34 which branches off at the second bypass hole 38 and supplies oil to the transmission M side. For this reason, a portion of the branched oil passage 34 can also be used as a passage which supplies oil to a side of the cylinder block 17. Therefore, as this structure is adopted, an oil passage of the entire power unit PU can be simplified.

Also, in the embodiment, the second bypass hole 38 of the left half-case 11L is provided with the branched oil passage 34, but the first bypass hole 37 of the right half-case 11R may be provided with the branched oil passage 34. The branched oil passage 34 may be provided to communicate with the first bypass hole 37 and the second bypass hole 38.

In particular, in the power unit PU related to the embodiment, the branched oil passage 34 is provided to branch off from a side surface of the extension portion 40 which extends downward from a lower end of the second bypass hole 38. For this reason, foreign substances mixed in oil can be deposited at the bottom 40a of the extension portion 40 before the oil is fed to the branched oil passage 34. Therefore, as this structure is adopted, foreign substances can be removed from oil supplied to the transmission M side in advance.

The first bypass hole 37 may be similarly provided with the extension portion 40 when the first bypass hole 37 of the right half-case 11R is provided with the branched oil passage 34.

In the power unit PU related to the embodiment, a portion of the branched oil passage 34 is configured by the passage groove 49 formed to face the dividing surfaces 11Laand 11Ra of the half-cases 11L and 11R. A somewhat complicated passage shape of the passage groove 49 can be easily formed in the dividing surface 11La of one half-case 11L through cutting or the like. For this reason, as this structure is adopted, a portion of the branched oil passage 34 can be easily formed.

Also, in the embodiment, the capture groove 44 configured to capture oil leaking to the outside of the passage groove 49 and return the oil into the crankcase 11 is formed at a region of an outer wall of the half-case 11L which is outside of the passage groove 49. For this reason, even if oil flowing in the passage groove 49 leaks to the outside of the passage groove 49 through a space between the dividing surfaces 11La and 11Ra of the half-cases 11L and 11R, leakage of the oil to the outside of the crankcase 11 can be prevented in advance by efficiently capturing the leaked oil using the capture groove 44.

When the first bypass hole 37 is provided with the branched oil passage 34, the passage groove 49 and the capture groove 44 may be formed at the dividing surface 11Ra of the right half-case 11R.

In the power unit PU in the embodiment, an orifice portion disposed upstream from the passage groove 49 of the branched oil passage 34 is configured by the orifice hole 41 formed in the bottom of the passage groove 49. For this reason, the orifice hole 41 can be easily formed in the bottom of the passage groove 49 of the half-case 11L through drilling or the like, and the number of parts can be reduced compared with when and a cylinder block. When the crankcase and the cylinder block are joined, a portion of an oil supply path is formed to be configured between the joining surfaces between the crankcase and the cylinder block. Also, in the engine disclosed in Patent Document 1, the crankcase is formed such that a pair of half-cases divided at a dividing surface perpendicular to a crankshafl is coupled to each other, and the passage groove is formed only in a range of a joining surface between one of the half-cases and the cylinder block.

Prior Art Documents

Patent Documents

Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2007-170314

Summary of Invention

Problems to be Solved by the Invention

However, in an engine in which a crankcase is configured by coupling a pair of half-cases, when an oil supply path is attempted to be formed to cross spaces between joining surfaces between a cylinder block and the half-cases, the oil supply path passes through a place at which three members come into contact with each other. Thus, high processing accuracy and sealing performance are required to prevent leakage of oil from the oil supply path. For this reason, the oil supply path is formed only in the range of the joining surface between the cylinder block and one of the half-cases (a range which does not exceed dividing surfaces of the half-cases) in many cases as in the lubrication structure disclosed in Patent Document 1. However, in this case, the degree of freedom indesign of the oil supply path is limited.

the orifice portion is configured by assembling orifice parts.

Note that the present invention is not limited to the above-described embodiments, and various changes in design are possible without departing from the scope of the present invention. For example, in the above-described embodiments, the first oil passage 35 and the second oil passage 36 are configured in the spaces between the cylinder block 17 and the half-cases 11L and 11R by forming the grooves 35¢ and 36c¢ at sides of the end surfaces 11Lu and 11Ru of the half-cases 11L and 11R.

However, the first oil passage 35 and the second oil passage 36 may be configured in the spaces between the cylinder block 17 and the half-cases 11L and 11R by forming the end surfaces 11Lu and 11Ru of the half-cases 11L and 11R as flat surfaces and forming a groove at a side of the lower surface 17d of the cylinder block 17.

A vehicle which mounts the above-described power unit may be a three-wheel vehicle (which also includes a vehicle having one front wheel and two rear wheels as well as a vehicle having two front wheels and one rear wheel) or a four-wheel vehicle in addition to the motorcycle.

Reference Signs List 10 Crankshaft 11 Crankcase 11L, 11R Half-cases 11La, 11Ra Dividing surfaces 11Lu, 11Ru End surfaces (joining surfaces) 16 Piston

17 Cylinder block 17d Lower surface (joining surface) 20 Stud bolt (fastening member) 32 Oil pump (oil supply source) 33 Oil supply path 34 Branched oil passage 35 First oil passage 35a Inflow portion 36 Second oil passage 36a Outflow portion 37 First bypass hole 38 Second bypass hole 39 Insertion hole 40 Extension portion 41 Orifice hole 44 Capture groove 49 Passage groove

C1 Cylinder central axis

L1 Diagonal line

M Transmission

An aspect of the present invention is to provide an engine lubrication structure capable of increasing a degree of freedom in design of an oil supply path, in which the oil supply path configured to cross joining surfaces between a cylinder block and a pair of half-cases can be easily formed.

Means for Solving the Problems

In order to solve the above problems, the present invention adopts the following aspects. (1) An engine lubrication structure related to an aspect of the present invention includes: a crankcase configured to rotatably support a crankshaft and formed by joining a pair of half-cases divided at a dividing surface perpendicular to the crankshaft to each other; a cylinder block configured to accommodate a piston which reciprocates, and joined with the crankshaft by crossing an end surface intersecting the dividing surface of each of the half-cases of the crankcase; and an oil supply path formed to extend from the crankcase to the cylinder block and configured to supply oil delivered from an oil supply source at a crankcase side to a site which needs to be lubricated in an engine, wherein the oil supply path includes a first oil passage having an inflow portion into which oil from the oil supply source flows and formed between joining surfaces between the cylinder block and the first half-case of the crankcase, a second oil passage having an outflow portion out of which oil flows toward the cylinder block and formed between joining surfaces between the cylinder block and the second half-case of the crankcase, a first bypass hole formed in the first half-case such that a first end thereof communicates with the first oil passage and a second end thereof communicates with a portion of the dividing surface which is separated from the joining surface between the first half-case and the cylinder block, and a second bypass hole formed in the second half-case such that a first end thereof communicates with the second oil passage and a second end thereof communicates with a portion of the dividing surface which is separated from the joining surface between the second half-case and the cylinder block, and wherein the second end of the first bypass hole and the second end of the second bypass hole are connected to communicate with each other at a dividing surface.

Thus, the first oil passage and the second oil passage are connected via the first bypass hole and the second bypass hole which are connected to each other at a dividing surface portion separated from the joining surfaces between the cylinder block and the crankcase. For this reason, the oil supply path is not connected while crossing a joining portion of three members. Thus, an oil supply path crossing the joining surfaces between the cylinder block and the pair of half-cases can be easily formed. 2) In the aspect of (1), the first oil passage and the second oil passage may be formed such that the inflow portion and the outflow portion overlap a diagonal line passing through a cylinder central axis of the cylinder block.

Thus, even if the inflow portion and the outflow portion are disposed in a farthest diagonal position relationship around the cylinder central axis, leakage of oil can be easily prevented by connecting the first oil passage and the second oil passage via the first bypass hole and the second bypass hole. (3) In the aspect of (2), the cylinder block may be fastened and fixed to the crankcase using a plurality of fastening members, insertion holes for the fastening members formed in the cylinder block may be disposed on a same pitch circle which has the cylinder central axis as a center, and at least portions of the inflow portion and the outflow portion may be disposed at positions which are regions closer to a radial outside 5 than the pitch circle and are near the insertion holes.

In this case, even if the inflow portion of the first oil passage and the outflow portion of the second oil passage are disposed at a region closer to a radial outside region than the pitch circle in which the insertion holes formed in the cylinder block are disposed, the cylinder block and the crankcase come into firm close contact with each other by fastening near the inflow portion and the outflow portion using the fastening members. For this reason, leakage of oil from the sites can be efficiently prevented. (4) In the aspect of any one of (1) to (3), the crankcase may be provided with (1) a transmission accommodation portion integrally formed with the crankcase and configured to accommodate a transmission and (ii) a branched oil passage branched off from at least one of the first bypass hole and the second bypass hole and configured to supply oil to the transmission.

In this case, the branched oil passage configured to supply oil to the transmission branches off from at least one of the first bypass hole and the second bypass hole. For this reason, a portion of the branched oil passage can also be used as a passage which supplies oil to a side of the cylinder block. Therefore, a structure of the oil passage of the entire engine including a transmission portion as well can be simplified.

(5) In the aspect of (4), the branched oil passage may branch off from a side surface of an extension portion which extends downward from a lower end of at least one of the first bypass hole and the second bypass hole.

In this case, since the branched oil passage branches off from the side surface of the extension portion which extends downward, foreign substances mixed in oil are deposited at the bottom of the extension portion to be difficult for the foreign substances to enter a side of the branched oil passage. Therefore, foreign substances can be removed from oil supplied to a side of the transmission in advance. (6) In the aspect of (4) or (5), a portion of the branched oil passage may be configured as a passage groove formed in at least one of the pair of half-cases to face the dividing surface.

In this case, the passage groove is formed to face the dividing surface of the half-case. For this reason, a relatively complicated passage shape can also be easily formed from the dividing surface through cutting, or the like. (7) In the aspect of (6), a capture groove configured to capture oil leaking to outside of the passage groove and return the oil into the crankcase is preferably provided at an outer region of the passage groove within an outer wall of the crankcase.

In this case, even if oil leaks to the outside of the passage groove, the capture groove captures and returns the oil into the crankcase. For this reason, leakage of oil from the crankcase can be efficiently prevented. (8) In the aspect of (6) or (7), an orifice portion may be provided upstream from the passage groove of the branched oil passage, and the orifice portion may be configured by an orifice hole formed at a bottom of the passage groove.

In this case, the orifice hole can be easily formed in the bottom of the passage groove of the crankcase through drilling or the like, and the number of parts can be reduced compared with when the orifice portion is configured by assembling orifice parts.

Advantageous Effects of Invention

According to an aspect of the present invention, the first oil passage between the cylinder block and the first half-case and the second oil passage between the cylinder block and the second half-case are connected via the first bypass hole and the second bypass hole which are connected to each other at a dividing surface portion of each of the half-cases separated from joining surfaces between the half-cases and the cylinder block.

For this reason, an oil supply path configured to cross joining surfaces and the cylinder block and the pair of half-cases can be easily formed without requiring remarkably high processing accuracy and sealing performance for preventing oil leakage. Therefore, according to an aspect of the present invention, a degree of freedom in design of the oil supply path can be increased.

Brief Description of Drawings

Fig. 1 is a left side view of a motorcycle which adopts a power unit of an embodiment of the present invention.

Fig. 2 is a right side view of the power unit of the embodiment of the present invention.

Fig. 3 is a left side view of the power unit of the embodiment of the present invention.

Fig. 4 is a top view of the power unit of the embodiment of the present invention.

Fig. 5 is a cross-sectional view which substantially corresponds to a cross section V-V in Fig. 2 of the power unit of the embodiment of the present invention.

Fig. 6 is a cross-sectional view which substantially corresponds to a cross section VI-VI in Fig. 2 of the power unit of the embodiment of the present invention.

Fig. 7 is a bottom view corresponding to an arrow VII in Fig. 2 of a cylinder block of the embodiment of the present invention.

Fig. 8 is a partial cross-sectional perspective view showing a cross section of the power unit of the embodiment of the present invention along a portion VIII-VIII in Fig. 7.

Fig. 9 is a perspective view of a right half-case of a crankcase of the embodiment of the present invention.

Fig. 10 is a perspective view of a left half-case of the crankcase of the embodiment of the present invention.

Fig. 11 is a top view centering on a portion directly above a main shaft of the power unit of the embodiment of the present invention.

Fig. 12 is a partial cross-sectional perspective view showing a cross section of

Claims

‘ y, iil g So oo CLAIMS IY

1. An engine lubrication structure comprising: a crankcase configured to rotatably support a crankshaft and formed by joining a pair of half-cases divided at a dividing surface perpendicular to the crankshaft to each other; a cylinder block configured to accommodate a piston which reciprocates, and Joined with the crankshaft by crossing an end surface intersecting the dividing surface of each of the half-cases of the crankcase; and an oil supply path formed to extend from the crankcase to the cylinder block and configured to supply oil delivered from an oil supply source at a crankcase side to a site which needs to be lubricated in an engine, wherein the oil supply path includes a first oil passage having an inflow portion into which oil from the oil supply source flows and formed between joining surfaces between the cylinder block and the first half-case of the crankcase, a second oil passage having an outflow portion out of which oil flows toward the cylinder block and formed between joining surfaces between the cylinder block and the second half-case of the crankcase, a first bypass hole formed in the first half-case such that a first end thereof communicates with the first oil passage and a second end thereof communicates with a portion of the dividing surface which is separated from the joining surface between the first half-case and the cylinder block, and a second bypass hole formed in the second half-case such that a first end thereof communicates with the second oil passage and a second end thereof communicates with a portion of the dividing surface which is separated from the joining surface between the second half-case and the cylinder block, and wherein the second end of the first bypass hole and the second end of the second bypass hole are connected to communicate with each other at the dividing surface.

2. The engine lubrication structure according to claim 1, wherein the first oil passage and the second oil passage are formed such that the inflow portion and the outflow portion overlap a diagonal line passing through a cylinder central axis of the cylinder block.

3. The engine lubrication structure according to claim 2, wherein the cylinder block is fastened and fixed to the crankcase using a plurality of fastening members, insertion holes for the fastening members formed in the cylinder block are disposed on a same pitch circle which has the cylinder central axis as a center, and at least portions of the inflow portion and the outflow portion are disposed at positions which are regions closer to a radial outside than the pitch circle and are near the insertion holes.

4. The engine lubrication structure according to any one of claims 1 to 3, wherein the crankcase is provided with (i) a transmission accommodation portion integrally formed with the crankcase and configured to accommodate a transmission and (i1) a branched oil passage branched off from at least one of the first bypass hole and the second bypass hole and configured to supply oil to the transmission.

5. The engine lubrication structure according to claim 4, wherein the branched

La 1 33 oil passage branches off from a side surface of an extension portion which extends downward from a lower end of at least one of the first bypass hole and the second bypass hole.

6. The engine lubrication structure according to claim 4, wherein a portion of the branched oil passage is configured as a passage groove formed in at least one of the pair of half-cases to face the dividing surface.

7. The engine lubrication structure according to claim 5, wherein a portion of the branched oil passage is configured as a passage groove formed in at least one of the pair of half-cases to face the dividing surface.

8. The engine lubrication structure according to any one of claims 6 or 7, wherein a capture groove configured to capture oil leaking to outside of the passage groove and return the oil into the crankcase is provided at an outer region of the passage groove within an outer wall of the crankcase.

9. The engine lubrication structure according to any one of claims 6 or 7, wherein an orifice portion is provided upstream from the passage groove of the branched oil passage, and the orifice portion is configured by an orifice hole formed at a bottom of the passage groove.

10. The engine lubrication structure according to claim 8, wherein an orifice portion is provided upstream from the passage groove of the branched oil passage, and toe ’ 34 the orifice portion is configured by an orifice hole formed at a bottom of the passage groove.