Over-head cam type V-type engine

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an over-head cam type V-type engine, and more particularly to a V-twin engine comprising a lubricating oil feedback path from the head portion of a cylinder to an oil sump.

2. Description of the Related Art

FIG. 7

is a sectional view showing the structure of a conventional over-head cam type engine for an all terrain vehicle.

As shown in

FIG. 7

, the engine has a crank case

101

and a crank chamber

101

a

is formed in the crank case

101

. A cylinder

102

is provided to extend upward from the upper end of the crank case

101

such that an inner portion thereof communicates with the crank chamber

101

a

. Moreover, a crank shaft

103

is provided to penetrate through the crank chamber

101

a

in a horizontal direction and a piston

104

which reciprocates in the cylinder

102

is coupled through a connecting rod to a portion of the crank shaft

103

which is accommodated in the crank chamber

101

a

. On the other hand, a head portion

102

a

of the cylinder

102

is provided with a cam shaft

105

for driving an intake valve and an exhaust valve (not shown) through a cam (not shown). A cam chain

108

for transmitting the rotation of the crank shaft

103

to the cam shaft

105

and rotating the cam shaft

105

is co-wound on sprockets

107

and

106

provided on one end of the cam shaft

105

and a portion

103

a

of the crank shaft

103

which protrudes toward the outside of the crank chamber

101

a

, respectively. The cam chain

108

is accommodated in a cam chain tunnel

109

formed in the side portion of the cylinder

102

and a chain chamber

101

b

formed in the side portion of the crank case

101

to be connected to the cam chain tunnel

109

and separated from the crank chamber

101

a

through a wall. An oil chamber (not shown) is formed in the crank case

101

to communicate with the lower ends of the chain chamber

101

b

and the crank chamber

101

a

. An oil pump and an oil passage (not shown) are provided to supply a lubricating oil accumulated in the oil chamber to the cam shaft

105

provided in the head portion

102

a

of the cylinder

102

and the like. The reference numeral

110

denotes a belt converter provided on an end of the crank shaft

103

which penetrates through the chain chamber

101

b

and extends toward the outside thereof. The belt converter

110

serves to cause a driver to easily carry out a speed change operation of a vehicle.

In the over-head cam engine having such a structure, the cam shaft

105

or the like is lubricated by the lubricating oil supplied to the head portion

102

a

of the cylinder

102

and the lubricating oil which completes the lubrication is returned to the oil chamber through the chain tunnel

109

and the chain chamber

101

b

. Consequently, the cam shaft

105

or the like is forcibly lubricated.

If the cam shaft structure of the conventional over-head cam engine is to be applied to a engine having two cylinders inclined in opposite directions to each other, it is necessary to provide two sprockets for driving the cam shafts of the two cylinders on the crank shaft. Correspondingly, the length of the crank shaft is increased so that the width of the engine is made greater. There is a cam shaft driving structure in which the cam shafts of the two cylinders are driven through an intermediate shaft by a crank shaft. In such a cam shaft driving structure, the intermediate shaft is provided above the crank shaft to penetrate through the crank chamber and a sprocket for driving the cam shaft of each cylinder is provided in each of portions of the intermediate shaft which protrude toward outsides of the crank chamber, respectively, and only one sprocket for driving the intermediate shaft is provided on the crank shaft. As a result, one sprocket on the crank shaft is omitted, so that the width of the engine can be reduced.

In the cam shaft driving structure, however, if an oil passage extending from the chain chamber to the oil chamber is provided as in the conventional over-head cam type engine, the oil passage is to be formed in both side portions of the crank chamber. For this reason, the size of a crank case is increased, and furthermore, the size of an engine is increased. Moreover, a space in the crank case cannot be utilized effectively.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problems, it is an object of the present invention to provide an over-head cam type V-type engine which can be small-sized and can efficiently utilize a space in a crank case.

In order to attain the object, the present invention provides an over-head cam type V-type engine comprising a crank case having a crank chamber, a crank shaft provided to penetrate through the crank chamber, a first cylinder and a second cylinder provided in an upper portion of the crank chamber to be positioned on virtual lines extending like a V-shape upward from a center of the crank shaft as seen in an axial direction of the crank shaft, respectively, a cam shaft provided in a head portion of each of the first and second cylinders, an intermediate shaft provided above the crank shaft to penetrate through the crank chamber, a first transmitting means for transmitting a rotation of the crank shaft to the intermediate shaft through a chain at one of end sides of the intermediate shaft, a chain chamber formed adjacently to a side portion of the crank chamber and serving to accommodate the first transmitting means, a second transmitting means for transmitting a rotation of the intermediate shaft to the cam shaft of one of the first and second cylinders through a chain at the other end side of the intermediate shaft, a first chain tunnel for accommodating the second transmitting means, a third transmitting means for transmitting the rotation of the intermediate shaft to the cam shaft of the other cylinder through a chain at one of the end sides of the intermediate shaft, a second chain tunnel for accommodating the third transmitting means, an oil sump formed in a lower portion of the crank case and serving to accumulate a lubricating oil therein, a forcible oil supply means for supplying the lubricating oil from the oil sump to the head portion of each of the first and second cylinders such that each cam shaft is lubricated, a first lubricating oil feedback path formed such that the lubricating oil supplied to the head portion of one of the first and second cylinders flows down into the oil sump through the first chain tunnel and the crank chamber, and a second lubricating oil feedback path formed such that the lubricating oil supplied to the head portion of the other cylinder flows down into the oil sump through the second chain tunnel and the chain chamber.

In this specification, “above” also implies an obliquely upward direction as well as a just upward direction.

According to such a structure, the lubricating oil feedback path utilizes the inner space of the crank chamber, so that a space in the crank case can be saved. Consequently, the space of the crank case can be utilized efficiently. Moreover, the size of the engine can be reduced.

The cylinder may have a skirt portion, the skirt portion being provided to be inserted into the crank chamber, and an inlet hole for the lubricating oil flowing from the first chain tunnel into the crank chamber may be opened in a portion of an internal surface of the crank chamber which is opposed to a peripheral surface of the skirt portion of the cylinder.

According to such a structure, even if the lubricating oil vigorously flows into the crank chamber through the inlet hole, it hits against the skirt portion of the cylinder and is thereby prevented from advancing toward the inside of the crank chamber. Consequently, it is possible to prevent the lubricating oil from splashing on the crank shaft positioned in the crank chamber and its temperature from being raised.

A lubricating oil guide member may be provided on the internal surface of the crank chamber to guide the lubricating oil flowing into the crank chamber from the first chain tunnel through the inlet hole for the lubricating oil toward the oil sump avoiding a rotation region of the crank shaft accommodated in the crank chamber.

According to such a structure, the lubricating oil flowing from the inlet hole can be guided toward the oil sump so as not to splash on a crank web or a crank pin. As a result, it is possible to more effectively prevent the temperature of the lubricating oil from being raised.

The lubricating oil member may extend between an inner side surface of the crank chamber and an outer surface of the skirt portion of the cylinder circumferentially outside of rotation region of crank shaft from lower end of the inlet hole.

The first chain tunnel may be formed to extend from the head portion of one of the first and second cylinders and terminated in a portion of the crank case which includes the other end of the intermediate shaft, a belt converter for transmitting a power of the V-type engine to a transmission may be provided adjacently to the crank chamber in a portion of the crank shaft which protrudes from the crank chamber toward the other end side of the intermediate shaft, and an ambient air intake passage for cooling the belt converter may be formed adjacently to a terminating portion of the first chain tunnel.

According to such a structure, the size of the ambient air intake passage for cooling the belt converter can be reduced by effectively utilizing a space in the crank case. Furthermore, the amount of the protrusion of the belt converter toward the side can be decreased. Consequently, the width of the engine can be reduced.

The ambient air intake passage may be provided under the first chain tunnel and around a support boss which has a bearing supporting the crank shaft therein and protrudes from a side wall of the crank chamber.

These objects as well as other objects, features and advantages of the present invention will become more apparent to those skilled in the art from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a left side view typically showing the structure of an over-head cam type V-twin engine according to an embodiment of the present invention;

FIG. 2

is a sectional view taken along a line II—II in

FIG. 1

;

FIG. 3

is a view showing a right crank case as seen from leftward;

FIG. 4

is a left side view showing a mechanism for transmitting a rotation from a crank shaft to a cam shaft in the V-twin engine of

FIG. 1

;

FIG. 5

is a sectional view taken along a line V—V in

FIG. 4

;

FIG. 6

is a right side view showing the structure of a chain tunnel of a forward cylinder, a part of which is taken away; and

FIG. 7

is a sectional view showing the structure of a conventional over-head cam type V-twin engine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1

is a left side view typically showing the structure of an over-head cam type V-twin engine according to an embodiment of the present invention.

FIG. 2

is a sectional view taken along a line II—II in FIG.

1

.

FIG. 3

is a view showing a right crank case as seen from leftward.

FIG. 4

is a left side view showing a mechanism for transmitting a rotation from a crank shaft to a cam shaft in the V-twin engine of FIG.

1

.

FIG. 5

is a sectional view taken along a line V—V in FIG.

4

.

FIG. 6

is a right side view showing the structure of a chain tunnel of a forward cylinder, a part of which is taken away.

FIGS. 1 and 4

are perspective views for easily understanding the description. Moreover,

FIG. 4

shows a section of a chain tunnel which is cut in a plane where a cam chain extends. For easily understanding the description, furthermore,

FIG. 3

shows a state in which parts in a crank case are removed.

In the present embodiment, an over-head cam type V-twin engine (hereinafter referred to as a V-twin engine) is provided with a belt converter. The V-twin engine is mounted on a four-wheel straddle-type all terrain vehicle and a crank shaft is directed in the lateral direction of the vehicle in the present embodiment. Arrows X in

FIGS. 1 and 4

indicate the forward direction of the four-wheel straddle-type all terrain vehicle.

First of all, the schematic structure of a V-twin engine

11

will be described.

As shown in

FIG. 1

, a crank shaft

24

is provided to penetrate through a crank case

23

in a lateral direction (see

FIG. 2

) and a forward cylinder

21

and a rearward cylinder

22

are inclined forwardly and backwardly above the front part of the crank case

23

respectively in the V-twin engine

11

. The forward cylinder

21

and the rearward cylinder

22

are provided such that center lines

202

and

203

of cylinder liners

401

extend to have a V-shape upward from a shaft axis

201

of the crank shaft

24

as seen from a side. A crossing angle formed by the center lines

202

and

203

of the cylinder liners of the forward cylinder

21

and the rearward cylinder

22

seen from a side, that is, an angle a formed by the forward cylinder

21

and the rearward cylinder

22

is 90 degrees in the present embodiment. The reason is that the oscillation of the V-twin engine

11

should be reduced as much as possible.

A connecting rod

28

of a piston

27

of the forward cylinder

21

and a connecting rod

30

of a piston

29

of the rearward cylinder

22

are coupled to the crank shaft

24

, respectively. An input shaft

35

of a transmission is provided behind the crank shaft

24

in parallel with the crank shaft

24

, and a belt converter

31

is provided between the input shaft

35

of the transmission and the crank shaft

24

. More specifically, a drive pulley

32

is provided on one of the ends of the crank shaft

24

and a driven pulley

33

is provided on the input shaft

35

of the transmission, and a belt (not shown) is co-wound on the pulleys

32

and

33

. An output shaft

39

is provided to extend in a longitudinal direction below the input shaft

35

of the transmission, and the output shaft

39

and the input shaft

35

of the transmission are connected to each other through a transmission

34

. In other words, an intermediate shaft

36

for speed change, an idle shaft

38

for reverse and a bevel gear shaft

37

are provided below the input shaft

35

of the transmission in parallel with the crank shaft

24

, respectively. The four shafts including the input shaft

35

are mutually coupled such that a transmission ratio and a rotating direction can be changed by a gear group

34

a

provided therein.

On the other hand, the forward cylinder

21

and the rearward cylinder

22

are provided with cam shafts

302

and

303

for driving an intake valve and an exhaust valve (not shown), respectively. Moreover, the internal spaces of the cylinder liners

401

in which the pistons

27

and

29

of the forward cylinder

21

and the rearward cylinder

22

reciprocate communicate with the internal space of the crank case

23

, and coupling portions of the connecting rods

28

and

30

and the crank shaft

24

are accommodated in the crank case

23

. Moreover, the transmission

34

is also accommodated in the crank case

23

. An oil sump

40

is formed in a bottom portion

23

c

of the crank case

23

and an oil pump

43

is provided on the left side surface of the crank case

23

(see FIG.

2

). An oil path

41

is provided such that an inlet is positioned in the oil sump

40

and an outlet communicates with an intake port

43

a

of the oil pump

43

. A primary filter

42

is provided in the inlet portion of the oil passage

41

. A first oil path

45

is connected to an exhaust port

43

b

of the oil pump

43

, a secondary filter

46

is connected to the first oil passage

45

, and a main gallery

47

is connected to the secondary filter

46

. A second oil path

49

is formed from the main gallery

47

to a second bearing

26

for supporting the left end of the crank shaft

24

. As will be described later, furthermore, a third oil path

69

(see

FIG. 2

) is formed from the second bearing

26

to the coupling portions of the connecting rods

28

and

30

and the crank shaft

24

. Moreover, an oil path (not shown) is formed from the main gallery

47

to the cam shafts

302

and

303

in head portions

21

a

and

22

a

of the forward cylinder

21

and the rearward cylinder

22

. Consequently, a lubricating oil in the oil sump

40

is sucked from the inlet of the oil passage

41

into the oil pump

43

and is discharged from the discharge port

43

b

of the oil pump

43

, and is supplied to each place to be lubricated through the secondary filter

46

. The oil passage

41

, the oil pump

43

, the filters

42

and

46

and the oil path to each place constitute forcible oil supply means.

The lubricating oil supplied to the head portions

21

a

and

22

a

of the forward cylinder

21

and the rearward cylinder

22

is fed back to the oil sump

40

through chain tunnels

319

and

320

(see

FIG. 4

) and the crank case

23

as will be described below in detail. Moreover, the lubricating oil supplied to other places is dropped into the crank case

23

and is accumulated in the oil sump

40

. As described above, the forcible circulating structure of the lubricating oil is constructed.

Next, the structure of each portion will be described.

As shown in

FIG. 2

, the crank case

23

is divided into left and right crank cases

23

a

,

23

b

, which are joined to be formed into one crank case

23

.

As shown in

FIGS. 3 and 1

, a crank chamber

351

for accommodating the crank shaft

24

, and a transmission chamber

352

for accommodating the transmission

34

and an oil chamber

353

for forming the oil sump

40

are divided by a partition wall

358

in the crank case

23

. The crank chamber

351

, the transmission chamber

352

and the oil chamber

353

are formed in the front part of an upper portion, the rear part of the upper portion, and a lower portion in the crank case

23

respectively and communicate with each other through communicating portions

358

a

,

358

b

,

358

c

and

358

d

provided in the partition wall

358

. The reference numerals

354

,

356

,

357

and

359

denote through holes of the crank shaft

24

, the input shaft

35

, the intermediate shaft

36

for speed change and the idle shaft

38

for reverse (accurately, bearing fitting holes thereof), respectively. Thus, the crank case and the transmission case are integrated in the V-twin engine

11

. The reference numeral

355

denotes a through hole for supporting an intermediate shaft

301

(see

FIG. 4

) of a mechanism for transmitting a rotation to the cam shaft which will be described later.

The transmission

34

is accommodated in the transmission chamber

352

in such a manner that the input shaft, the intermediate shaft for speed change and the idle shaft for reverse are fitted in the through holes

356

,

357

and

359

together with bearings, respectively.

As shown in

FIGS. 2 and 3

, the oil passage

41

is formed in bottom portion of the oil chamber

353

and has an inlet provided with the primary filter

42

and an output communicating with the intake port

43

a

of the oil pump

43

. Moreover, the oil sump

40

is formed in the oil chamber

353

. An oil level

402

of the oil sump

40

is set such that the accumulated lubricating oil does not splash on the crank shaft

24

(a crank web

53

or the like) in the crank chamber

351

even if a vehicle body is inclined so that the V-twin engine

11

is tilted.

As shown in

FIGS. 1 and 2

, the crank shaft

24

is provided to penetrate through the crank chamber

351

of the crank case

23

in a lateral direction. A first bearing

25

and a second bearing

26

are provided in portions of the right and left side walls of the crank case

23

through which the crank shaft

24

penetrate, respectively. The crank shaft

24

is rotatably held in the crank case

23

by means of the first bearing

25

and the second bearing

26

. The first bearing

25

is constituted by a double row ball bearing and the second bearing

26

is constituted by a plain bearing.

The crank web

53

, the crank pin

52

, large ends

23

a

and

30

a

of the connecting rods and the like are accommodated in the crank chamber

351

, and the large end

28

a

of the connecting rod

28

of the piston in the forward cylinder

21

and the large end

30

a

of the connecting rod

30

of the piston

29

in the rearward cylinder

22

are coupled to the crank pin

52

through bearings

54

and

55

, respectively.

The belt converter

31

is provided on a right end

24

a

of the crank shaft

24

. In detail, the belt converter

31

is separated (sealed) from the inside of the crank case

23

through the right side wall of the crank chamber

351

. A main shaft

56

of the belt converter

31

is integrally connected to a portion of the crank shaft

24

which protrudes rightwards from the first bearing

25

, and the drive pulley

32

is provided on the main shaft

56

. A belt

71

is co-wounded on the drive pulley

32

and the driven pulley

33

. The belt converter

31

is covered with a belt converter cover

50

provided on the right side surface of the crank case

23

.

The drive pulley

32

has a fixed sheave

32

a

fixed to the main shaft

56

adjacently to the crank case

23

and a movable sheave

32

b

positioned on the outside (right) of the fixed sheave

32

a

. The movable sheave

32

a

is attached to the main shaft

56

integrally rotatably and movably in an axial direction thereof. A rear surface

32

a

′ of the fixed sheave

32

a

has such a shape as to form a fan. On the other hand, a space

323

is formed to surround a support boss

23

d

which is provided in right side wall of crank chamber

351

to protrude outward and holds the first bearing

25

therein. An outside (right) of the space

323

is partitioned by a plate

322

so that an ambient air intake passage

323

to the fan is formed. Consequently, an ambient air (an air which exists outside of V-twin engine

11

) is sucked from the ambient air intake passage

323

through the fan, so that the belt converter

31

is cooled. Moreover, a seal

72

for preventing the lubricating oil from entering the belt converter

31

is provided on the support boss

23

d

adjacent to and outside the first bearing

25

of the crank case

23

through which the crank shaft

24

penetrates.

On the other hand, a first sprocket

57

, a sprocket

59

for a pump drive shaft, a generator

51

and a recoil starter

61

are attached to a left end portion

24

b

of the crank shaft

24

in order from the inside. As will be described below, the first sprocket

57

serves to drive the cam shafts

302

and

303

of the forward cylinder

21

and the rearward cylinder

22

through an intermediate shaft chain

58

and an intermediate shaft

301

(see

FIG. 4

) and the like.

The oil pump

43

is provided in a lower portion of the left side surface of the crank case

23

and is driven by a pump drive shaft

44

. The exhaust port

43

b

of the oil pump

43

communicates with the first oil path

45

(see FIG.

1

). A sprocket

64

is provided on the pump drive shaft

44

and a chain

65

is co-wound on the sprocket

64

and the sprocket

59

for a pump drive shaft of the crank shaft

24

. Consequently, the pump drive shaft

44

is driven by the crank shaft

24

. The reference numeral

67

denotes a water pump which is coaxially attached to the pump drive shaft

44

. Moreover, the reference numeral

62

denotes a generator cover provided on the left side surface of the crank case

23

and serving to cover the sprocket

57

for an intermediate shaft, the sprocket

59

for a pump drive shaft, the generator

51

and the oil pump

43

, and the reference numeral

63

denotes a recoil starter cover provided integrally with the generator cover

62

and serving to cover the recoil starter

61

. A space covered with the generator cover

62

constitutes an auxiliary machinery room

360

including a chain chamber

360

a.

As shown in

FIG. 2

, the second bearing

26

is provided in a portion (hereinafter referred to as the second bearing support portion)

23

c

of the left side wall of the crank case

23

through which the crank shaft

24

penetrates and the second oil path

49

(see

FIG. 1

) is opened in the second bearing support portion

23

c

. The third oil path

69

is formed from the second bearing support portion

23

c

to bearings

54

and

55

of a coupling portion

80

of the large ends of the connecting rods

28

and

30

in the forward cylinder and the rearward cylinder through the inside of the second bearing

26

and the inside of the crank shaft

24

. Moreover, an oil path is formed from the second bearing support portion

23

c

to the head portions

21

a

and

22

a

of the forward cylinder

21

and the rearward cylinder

22

in order to forcibly supply an oil to the cam shaft provided in the head portion of each cylinder, which is not shown.

Next, detailed description will be given to a feedback path for the lubricating oil to be supplied to the head portions

21

a

and

22

a

of the forward cylinder

21

and the rearward cylinder

22

.

First of all, description will be given to a mechanism for transmitting a rotation from the crank shaft to the cam shaft.

As shown in

FIGS. 3

,

4

and

5

, the first sprocket

58

is provided in the portion

24

b

of the crank shaft

24

which protrudes leftwards from the crank chamber

351

adjacently to the second bearing

26

. The intermediate shaft

301

is provided in upper portion of the crank chamber

351

to penetrate through the crank chamber

351

. The intermediate shaft

301

is provided in parallel with the crank shaft

24

such that a shaft axis

204

is positioned above the crank shaft

24

and on a center plane

205

of the angle a formed by the forward cylinder

21

and the rearward cylinder

22

, and is rotatably supported on a pair of bearings

321

fixed to both side walls of the crank chamber

351

. A fifth sprocket

304

a

is provided in a portion of the intermediate shaft

301

which protrudes rightwards from the crank chamber

351

. Moreover, a sixth sprocket

304

b

and a second sprocket

305

are provided integrally side by side in a portion of the intermediate shaft

301

which protrudes leftwards from the crank chamber

351

. The fifth and sixth sprockets

304

a

and

304

b

are formed to have smaller outside diameters than the outside diameter of the second sprocket

305

. The intermediate shaft chain

58

is co-wounded on the first sprocket

57

of the crank shaft

24

and the second sprocket

305

of the intermediate shaft

301

. The first sprocket

57

, the second sprocket

305

and the intermediate shaft chain

58

are accommodated in the chain chamber

306

a

(the auxiliary machinery room

360

).

On the other hand, the forward cylinder cam shaft

302

is provided in the head portion

21

a

of the forward cylinder

21

and the rearward cylinder cam shaft

303

is provided in the head portion

22

a

of the rearward cylinder

22

. The cam shafts

302

and

303

are provided in parallel with the crank shaft

24

, respectively. As shown in

FIGS. 4

to

6

, a third sprocket

306

is provided on the forward cylinder cam shaft

302

and a fourth sprocket

307

is provided on the rearward cylinder cam shaft

303

. The third sprocket

306

is provided on the right end of the forward cylinder cam shaft

302

. The first chain tunnel

319

is formed to extend from a portion of the crank case

23

, in which the fifth sprocket

304

a

is provided, to a portion of the head portion

21

in which the third sprocket

306

is provided, through the right side portion of the forward cylinder

21

. The first cam chain

308

is co-wound on the fifth sprocket

304

a

of the intermediate shaft

301

and the third sprocket

306

of the forward cylinder cam shaft

302

through the first chain tunnel

319

. As is apparent from

FIGS. 5 and 6

, the first chain tunnel

319

is formed such that the support boss

23

d

of the first bearing

25

and the ambient air intake passage

323

are positioned below a termination part thereof.

Moreover, the fourth sprocket

307

of the rearward cylinder

22

is provided on the left end of the rearward cylinder cam shaft

303

and a second chain tunnel

320

is formed to extend from a portion of the chain chamber

360

a

in which the sixth sprocket

304

b

is provided to a portion of the head portion

22

a

in which the fourth sprocket

307

is provided through the left side portion of the rearward cylinder

22

, which is not shown. A second cam chain

309

is co-wound on the sixth sprocket

304

b

and the fourth sprocket

307

of the rearward cylinder cam shaft

30

through the second chain tunnel

320

. Consequently, the rotation of the crank shaft

24

is transmitted to the forward cylinder cam shaft

302

and the rearward cylinder cam shaft

303

through the intermediate shaft

301

, thereby the cam shafts

302

and

303

are rotated, so that the intake valve and the exhaust valve are opened or closed in the cylinders

21

and

22

. The reference numerals

310

to

315

denote chain guides for guiding a chain and the reference numerals

316

to

318

denote tensioners for giving a tension to the chain.

Next, description will be given to the feedback path for the lubricating oil which utilizes the chain tunnel of the rotation transmitting mechanism having such a structure.

As shown in

FIGS. 2 and 3

, the crank chamber

351

is constituted by a body portion

351

a

for accommodating the crank web

53

and the crank pin

52

and first and second skirt accommodating portions

351

b

and

351

c

for accommodating skirt portions

401

a

,

401

a

being lower portions of the forward cylinder and the rearward cylinder. The body portion

351

a

has a size required for accommodating the crank web

53

and the crank pin

52

turning around the shaft axis

201

of the crank shaft

24

, the large ends

28

a

and

30

a

of the connecting rods and the like. In order to reduce the size of the crank chamber

351

as much as possible in the present embodiment, the body portion

351

a

is generally formed cylindrically to have a slightly greater length (width) than the total width of the crank web

53

and the crank pin

52

and to have a slightly larger diameter than the diameters of the turning regions of the crank web

53

and the crank pin

52

(the rotation region of the crank shaft).

FIG. 3

shows a trajectory (turning diameter)

206

of the crank web

52

. The first and second skirt accommodating portions

351

b

and

351

c

having a short cylindrical shape are formed to extend forward and obliquely upward and rearward and obliquely upward from the upper surface of the body portion

351

a

and to be opened on the upper surface of the crank case

23

, respectively. The forward cylinder

21

is attached to the crank case

23

such that the skirt portion

401

a

of the cylinder liner

401

is fitted into the first skirt accommodating portion

351

b

of the crank chamber

351

. The skirt portion

401

a of the forward cylinder is provided such that a lower end thereof extends near the trajectory

206

of the crank web as seen from a side and has a clearance with respect to the internal surface of the first skirt accommodating portion

351

b

of the crank chamber

351

. The forward cylinder

21

is positioned with respect to the crank case

23

by means of a knock pin

405

. While the cylinder liner

401

is formed separately from the body of the forward cylinder

21

in the present embodiment, it may be formed integrally with the body of the forward cylinder

21

. The above-mentioned respects are the same as in the rearward cylinder.

On the other hand, as shown in

FIG. 6

, the first chain tunnel

319

is formed to extend obliquely upward from the upper part of the crank case

23

toward the head portion

21

a

of the forward cylinder

21

, and an oil hole (inlet hole)

341

is formed on the side wall of the crank chamber to be situate near the lower wall of the first chain tunnel

319

which is located in the crank case

23

and is the lowest portion of the first chain tunnel

319

. Accordingly, the first chain tunnel

319

communicates with the crank case

23

through the oil hole

341

(see FIG.

2

). As shown in

FIGS. 2 and 3

, the oil hole

341

is formed in a position of the internal surface of the first skirt accommodating portion

351

b

in the crank chamber

351

which is opposed to the outer peripheral surface of the skirt portion

401

a

of the forward cylinder. With such a structure, the lubricating oil flowing into the crank chamber

351

through the oil hole

341

hits against the outer periphery of the skirt portion

401

a

of the forward cylinder. An arcuate lubricating oil guide rib

361

is formed on the internal surface of the side wall of the crank chamber

351

to extend forward and downward from the lower part of the rear edge portion

341

a

of the opening of the oil hole

341

along the trajectory

206

of the crank web by a predetermined length. The lubricating oil guide rib

361

is positioned to have a clearance with the trajectory

206

of the crank web as seen from a side and protrudes from the internal surface of the crank chamber

23

to a position which is close to the outer periphery of the skirt portion

401

a

of the forward cylinder

21

as seen in a longitudinal direction. Consequently, the lubricating oil guide rib

361

can downward guide the lubricating oil flowing into the crank chamber

351

through the oil hole

341

, hitting against the outer periphery of the skirt portion

401

a

of the forward cylinder

21

and thus dropped so as not to spill the lubricating oil as much as possible without coming in contact with the turning crank web

53

. Moreover, communicating portions

358

d

and

358

e

are formed between the internal surface of the front wall of the crank case

23

and the partition wall

358

configuring the crank chamber

351

and the oil chamber

353

. Consequently, a lubricating oil flow-down path is formed from the oil hole

341

to the oil passage

41

of the oil chamber

353

. Referring to the rearward cylinder, a lubricating oil flow-down path (a second lubricating oil feedback path) is formed to reach the oil chamber

353

from the second chain tunnel

320

through the chain chamber

360

a

, which is not shown. In the present embodiment, thus, a lubricating oil feedback path (a first lubricating oil feedback path) is formed to enter the crank chamber

351

through the first chain tunnel

319

, so that the first chain tunnel

319

is formed to be terminated in a position including the intermediate shaft

301

. Therefore, a section of the side wall of the crank chamber

351

which surrounds the crank shaft

24

can be utilized for other purposes. More specifically, in the present embodiment, the double row ball bearing (the first bearing)

25

is provided in the same section, the belt converter

31

is provided close to the crank chamber

351

, and the ambient air intake passage

323

for cooling the belt converter

31

is formed in a space provided around the support boss

23

d

of the double row ball bearing

25

. Consequently, the width of the V-twin engine

11

can be reduced.

Next, description will be given to a forcible lubricating operation for the cylinder head portion of the V-twin engine having the above-mentioned structure.

In

FIGS. 1

to

6

, when the V-twin engine

11

is started, the crank shaft

24

is rotated so that the oil pump

43

is driven to supply the lubricating oil in the oil sump

40

to the head portions

21

a

and

22

a

of the forward cylinder

21

and the rearward cylinder

22

. The lubricating oil thus supplied lubricates the cam shafts

302

and

303

, then passes through the first and second chain tunnels

319

and

320

and flows down into the oil sump

40

of the oil chamber

353

. Consequently, the forcible lubricating operation for the cylinder head portion is carried out. In this case, the lubricating oil flowing down through the first chain tunnel

319

enters the crank chamber

351

through the oil hole

341

, and hits against the outer periphery of the cylinder skirt portion

401

a

of the forward cylinder and is thus dropped at that time. Thus, it is possible to effectively prevent the lubricating oil flowing in through the oil hole

341

from splashing on the connecting rod

28

, the crank pin

52

and the crank web

53

and its temperature from being raised. Most of the lubricating oil thus dropped is received by the lubricating oil guide rib

361

and is guided downward. Consequently, it is possible to prevent the dropped lubricating oil from splashing on the crank web

53

or the like and its temperature from being raised. As shown in an arrow

407

, the lubricating oil guided downward flows down along the internal surface of the front wall of the crank case

23

through the communicating portions

358

d

and

358

e

in the middle and reaches the oil passage

41

(see FIG.

3

).

The present invention is not restricted to the above described embodiment.

For example, the engine does not need to be always provided with the belt converter.

Moreover, the portion from the cylinder head portion to the crank case in the lubricating oil feedback path reaching the oil sump from the cylinder head portion may be constituted by a chain tunnel and-a dedicated oil path.

As the present invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.

Number	Name	Date	Kind
4729349	Sonoda et al.	Mar 1988	A
4915066	Koshimoto et al.	Apr 1990	A
5010859	Ogami et al.	Apr 1991	A
5014655	Ampferer	May 1991	A
5857441	Yonezawa et al.	Jan 1999	A
6374789	Kawamoto	Apr 2002	B2

Over-head cam type V-type engine

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (1)

US Referenced Citations (6)