JP3618922B2 - Cylinder head fastening structure for vehicle engine unit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylinder head fastening structure of an engine unit for a vehicle, and more particularly to a structure that can reduce a pitch between cylinders when a head bolt is disposed between cylinders.
[0002]
[Prior art]
When a cylinder block and a cylinder head are fastened in a multi-cylinder four-cycle engine, a head bolt installed so as to be positioned between the cylinders in the cylinder block The A structure is generally employed in which a head is inserted through a cylinder head, the head bolt head is projected onto a washer mounting surface formed on the cylinder head, and a nut is screwed onto the projecting portion. In this case, a washer having a diameter as large as possible is used in order to reduce the surface pressure of the washer mounting surface as much as possible.
[0003]
The washer mounting surface is generally arranged so as to overlap below the cam shaft. Therefore, when the cylinder head is fastened to the cylinder block after the cam shaft is mounted on the cylinder head, the cam shaft A tool hole is formed through the tool hole, a tool is inserted into the tool hole, and the nut is tightened.
[0004]
[Problems to be solved by the invention]
By the way, a lifter guide hole into which the valve lifter is inserted is located on both sides of the inter-cylinder head bolt, and the lifter guide hole needs to ensure a predetermined thickness (wall thickness) according to the required rigidity. is there. Therefore, if the pitch between cylinders is narrowed in order to make the engine more compact, it becomes difficult to secure a washer mounting surface having a required diameter and a nut insertion hole between the lifter guide holes.
[0005]
In addition, in the case of an engine equipped with a side cam chain type camshaft drive mechanism, the torsional torque generated on the camshaft increases toward the side cam chain, but the above-mentioned tool hole is formed on the camshaft side of the camshaft. If the through hole is formed, it becomes difficult to ensure the torsional rigidity necessary for the camshaft.
[0006]
The present invention has been made in view of the above-described conventional situation, and can secure a washer mounting surface having a required diameter while narrowing the pitch between cylinders, and can be provided with a side cam chain type camshaft drive mechanism. It is an object of the present invention to provide a cylinder head fastening structure for a vehicle engine unit that can suppress a reduction in torsional rigidity of a shaft.
[0007]
[Means for Solving the Problems]
The invention of claim 1 is a cylinder head fastening structure of a vehicle engine unit 15 in which the cylinder block 22 and the cylinder head 23 are fastened by a head bolt 55 arranged between adjacent cylinders. A washer rotation hole 60 having a diameter slightly larger than that of the washer 57 and capable of rotating the washer 57 is formed in a portion immediately above the washer placement surface 56. The bottom surface of the washer rotation hole 60 serves as the washer placement surface 56, and An insertion hole 61 having a diameter smaller than 57 and slightly larger than the outer diameter of the head bolt head or nut 58 is formed so as to communicate with the cam shaft arrangement chamber 39 from the washer rotation hole 60. And a washer insertion slit 63 having substantially the same radial length as the washer rotation hole 60 at a right angle to the cam shaft 40. A head bolt with a head may be inserted into the insertion hole 61 and screwed into the cylinder block.
[0008]
A second aspect of the present invention is the engine unit according to the first aspect, wherein the upper part of the valve sliding direction is inclined outwardly of the cylinder bore, and the axis of the head bolt is a cam shaft. From the axis of It is characterized by being deviated outward from the cylinder bore.
[0009]
According to a third aspect of the present invention, in the first aspect, the cylinder head fastening structure is employed in a head bolt 55 that fastens an inter-cylinder portion of the cylinder head 23, and a camshaft disposed above the head bolt 55. 40 is rotationally driven by a cam shaft drive mechanism disposed at the cam shaft direction end portion of the cylinder head 23, and the inter-cylinder head located at the cam shaft drive mechanism side end portion of the cam shaft 40. A thrust receiving portion 65 for restricting the axial movement of the cam shaft 40 is formed in an upper portion of the bolt 55, and a tool hole 64 is formed so as to penetrate the thrust receiving portion 65. The nut 58 can be tightened by the inserted tool.
[0011]
[Effects of the invention]
According to the cylinder head fastening structure according to the first aspect of the present invention, in order to fasten the cylinder head 23 to the cylinder block 22, the washer 56 is inserted vertically from the slit 63 and the washer 56 is inserted into the washer rotation hole 60. Then, the nut 58 is seated on the washer placement surface 56, and then the nut 58 is inserted from the insertion hole 61 and screwed to the upper end of the head bolt 55. A head bolt with a head may be inserted and screwed into the cylinder block.
[0012]
In this way, the washer 57 having a larger diameter can be inserted while setting the nut insertion hole 61 to have a small diameter, so that the rigidity of the lifter guide hole can be secured and the surface pressure due to the nut fastening can be maintained within an allowable range. That is, since a small-diameter nut insertion hole 61 corresponding to a small-diameter nut may be formed between the lifter guide holes, the required rigidity can be ensured by increasing the wall thickness of the lifter guide hole 23b. Since the slit 63 is formed in a direction substantially perpendicular to the cam shaft, a large-diameter washer can be inserted without reducing the wall thickness of the lifter guide hole. As a result, the pitch between the cylinders can be narrowed, and the size of the engine in the cam shaft direction can be reduced.
[0013]
In the invention of claim 2, since the head bolt is displaced outward from the axis of the cam shaft, interference with the lifter guide hole can be avoided more reliably, and the pitch between the cylinders can be reduced to reduce the size of the engine. be able to. The lifter guide hole wall thickness is the thinnest at the opening portion of the insertion hole on the cam shaft arrangement chamber side because the lifter guide hole is inclined. As long as the thickness is ensured, in the portion below the opening, the gap with the insertion hole is widened, the wall thickness is equal to or greater than the thickness of the opening, and the rigidity of the lifter guide hole can be ensured.
[0014]
Invention of Claim 3 Then, when the camshaft 40 disposed above the head bolt 55 is rotationally driven by the side chain type cam drive mechanism, the camshaft 40 is located at the upper portion of the inter-cylinder head bolt located at the side cam chain side end. Since the thrust receiving portion 65 is formed and the tool hole 64 is formed through the thrust receiving portion 65, there is an effect that necessary torsional rigidity can be ensured without increasing the diameter of the entire cam shaft.
[0015]
That is, when the cam shaft is rotationally driven by the side chain type cam shaft drive mechanism, the torsion torque acting on the cam shaft increases toward the side cam chain side. In the present invention, a wide and large-diameter thrust receiving portion is formed in the portion where the torsional torque is increased. Therefore, the necessary twisting is achieved by compensating the rigidity that is reduced by forming the tool hole by forming the thrust receiving portion. Rigidity can be secured.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIGS. 1 to 17 are views for explaining an engine unit of a motorcycle according to an embodiment of the present invention. FIG. 1 is a left side view of a motorcycle on which the engine unit is mounted, and FIGS. FIG. 5 is a sectional view showing a communication hole portion of the cylinder block, and FIGS. 6 to 8 are a plan view, a sectional side view, and a sectional side view of the cylinder head, respectively. 9 is a cross-sectional side view of the head bolt portion, FIG. 10 is a plan view of the camshaft, FIGS. 11 and 12 are left side views of the transmission, cross-sectional rear development views, and FIGS. 13 and 14 are cooling water and lubrication. FIG. 15 is a rear view of the starting device, and FIGS. 16 and 17 are a plan view and a schematic configuration diagram of the intake device. The front and rear and the left and right in the present embodiment refer to the front and rear and the left and right when viewed in a seated state.
[0017]
In FIG. 1, reference numeral 1 denotes a motorcycle, and a body frame 2 of the motorcycle has a structure in which a seat rail 4 extending rearward of the vehicle body is connected to the rear ends of a pair of left and right main frames 3 having a substantially inverted L shape in side view. The fuel tank 5 is mounted on the upper portion of the main frame 3, and the main seat 6 and the tandem seat 7 are mounted on the upper portion of the seat rail 4.
[0018]
A front fork 9 is pivotally supported at the front end of the main frame 3 by a head pipe 8, and a front wheel 10 is pivotally supported at the lower end of the front fork 9. A rear arm 11 is pivotally supported by a pivot shaft 12 on a rear arm bracket 3a below the rear end of the main frame 3, and a rear wheel 13 is pivotally supported on the rear end of the rear arm 11. .
[0019]
A rear cushion 14 is interposed between the rear arm 11 and the vehicle body frame 2. The lower end of the rear cushion 14 is erected on the rear side of the rear cushion 14 and connected to the lower end of the first link 14a pivotally supported by the rear arm 11, and the upper end is pivotally supported by the vehicle body frame. The upper end of the first link 14a is connected to the vehicle body frame via a second link 14b that is erected on the rear side of the rear cushion 14, and the second link 14b and the first link 14a are connected to the rear cushion 14. A triangle. As described above, the lower end of the rear cushion 14 is supported by the first and second links 14a and 14b which are arranged upright upward, so that a large space is secured below the rear cushion 14 while ensuring so-called progressive characteristics. ing.
[0020]
An engine unit 15 is suspended below the main frame 3, and a radiator 16 is disposed on the front side of the engine unit 15. The engine unit 15 is a water-cooled four-cycle parallel four-cylinder five-valve engine, and is mounted with the cylinder axis 20 inclined forward and the crankshaft 21 directed in the vehicle width direction.
[0021]
As shown in FIGS. 2 to 4, the engine unit 15 has a cylinder head 23 stacked on the upper joint surface of the cylinder block 22 and fastened with a head bolt, and a head cover 24 is mounted on the upper joint surface of the cylinder head 23. In addition, a unit case 25 in which a crankcase and a transmission case are integrated is formed below the cylinder block 22 so as to be connected.
[0022]
The unit case 25 is divided into upper and lower cases 26, 27. The upper case 26 is integrally formed with the cylinder block 22. The crankshaft 21 is supported by a plurality of boss portions 29 formed on the split surfaces of the upper and lower cases 26 and 27 via bearings 30. Further, the crank chamber 19 for each cylinder is independent by the boss portion 29. An oil pan 28 is connected to the lower joint surface of the lower case 27.
[0023]
Four cylinder bores 22a are formed in the cylinder block 22 in parallel, and pistons 31 are slidably inserted in the cylinder bores 22a. A small end portion of a connecting rod 32 is connected to the piston 31 via a piston pin 31b, and a large end portion of the connecting rod 32 is connected to the crank pin 21a of the crankshaft 21. The piston 31 is of a so-called slipper type in which a notch recess 31c is formed in the piston pin 31b shaft end portion of the piston skirt 31a.
[0024]
Three intake ports 33 and two exhaust ports 34 are opened in a combustion recess 23 a formed on the opposed surface of each piston 31 of the cylinder head 23, and each opening can be opened and closed by an intake valve 35 and an exhaust valve 36. It has become. Bottomed cylindrical valve lifters 37, 37 are mounted on the upper ends of the valves 35, 36, and the valve lifters 37 are slidably supported by lifter guide holes 23b formed in the cylinder head 23. A spring 38 is provided between the valves 35 and 36 and a spring seat 23c formed on the cylinder head 23 to constantly urge the valves in the closing direction.
[0025]
Above the intake valves 35 and the exhaust valves 36, cam shafts 40 and 41 for pressing the valves are arranged in parallel with each other and in parallel with the crankshaft 21, respectively. Each of the cam shafts 40 and 41 is accommodated in a cam shaft arrangement chamber 39 formed by the cylinder head 23 and the head cover 24, and is fixed to the cam bearing portion formed in the cylinder head 23 by bolting. The cam cap 48 is rotatably supported.
[0026]
Further, cam sprockets 40 a, 41 a attached to the right ends of the cam shafts 40, 41 in the axial direction and cam drive teeth 21 b formed integrally with the right end of the crankshaft 21 are connected by a timing chain 42. The cam sprockets 40a and 41a, the timing chain 42, and the cam drive teeth 21b of the cam shaft drive mechanism configured as described above are integrally formed on the right outer end surface of the cylinder block 22 and the cylinder head 23. (Shaft drive mechanism arrangement chamber) 43 is accommodated. A rotor 44 having outer peripheral teeth is mounted inside the cam drive teeth 21b of the crankshaft 21, and a pickup 45 for detecting a crank rotation angle is opposed to the rotor 44. Reference numeral 46 denotes an auto tensioner that automatically adjusts the tension of the timing chain 42, and reference numeral 47 denotes a chain guide.
[0027]
An opening 50 for assembling the camshaft drive mechanism is formed in a portion of the outer wall 22b of the cylinder block 22 constituting the chain arrangement chamber 43 facing the crankshaft 21, and a lid member 51 is formed in the opening 50. Is detachably bolted. When viewed in the crankshaft direction, a communication hole 52 that communicates between the adjacent crank chambers 19 is formed in the lower portion of the cylinder bore 22a located in the assembly opening 50 so as to form the same axis.
[0028]
Each of the communication holes 52 is formed by machining from the assembly opening 50 to reduce the pumping loss due to the reciprocating motion of the piston. The inner surface of each cylinder bore 22a is coated with a hard plating film a in order to improve wear resistance. The plating film a is formed by masking the communication hole portion before the formation of the communication hole 52 and performing a plating process in this state, thereby facilitating the plating process and the communication hole. 52 processing work is facilitated.
[0029]
That is, the plating process is performed by energizing the cylinder bore 22a with the upper and lower end openings closed and the plating space filled with the plating solution. However, the communication hole 52 is processed and formed first. And the above-mentioned occlusion becomes difficult. On the other hand, when machining is performed after the plating treatment, the hard plating film a makes the machining difficult. In the present embodiment, since the plating process is performed in a state where the communication hole 52 is masked, the above-described problem can be avoided.
[0030]
Further, as shown in FIG. 5, each boss portion 29 of the upper case 26 is formed with a lubricating oil passage 53 that connects the bearing 30 of the crankshaft 21 and the inner peripheral surface of the communication hole 52. A cooling nozzle 54 is inserted into the lubricating oil passage 53, and an injection port 54a of the nozzle 54 is directed from the notch recess 31c of the piston 31 located at the bottom dead center to the piston back surface. Further, the thickness in the crankshaft direction of the communication hole 52 is W2 on the crankshaft side and narrower on the piston side with W1. Therefore, the lubricating oil injected from the injection port 54a is reliably supplied to the piston back surface without being obstructed by the peripheral edge of the communication hole 52 or the piston skirt, so that the piston 31 can be reliably cooled.
[0031]
Next, the fastening structure of the cylinder head 23 will be described.
6 to 10, bolt insertion holes 23d are formed in the cylinder axial direction on the intake side and the exhaust side of the portions between the cylinders of the cylinder head 23, and are planted in the cylinder block 22 in the bolt insertion holes 23d. The upper end of the provided head bolt 55 is located.
[0032]
A washer placement surface 56 is formed on the upper edge of the bolt insertion hole 23 d of the cylinder head 23, and a washer 57 having a slightly smaller diameter than the washer placement surface 56 is placed on the placement surface 56. ing. The cylinder head 23 is fastened and fixed to the cylinder block 22 via the washer 57 by screwing nuts 58 and 59 to the head bolt 55. The intake-side nut 58 has a smaller diameter than the washer 57, while the exhaust-side nut 59 has the same diameter as the washer 57.
[0033]
Here, if the size between cylinders is reduced in order to make the engine compact, it is difficult to secure a space for mounting the nut of the head bolt 55. In particular, since three lifter guide holes 23b are required on the intake side, the wall thickness necessary for the rigidity of the guide holes 23b is ensured while the dimensions between the cylinders are reduced, and the area required for the washer placement surface 56 is secured. It is difficult to ensure.
[0034]
In the present embodiment, the following structure is adopted in order to secure wall rigidity while reducing the dimension between cylinders and to secure a necessary washer arrangement area. On the upper side of the intake side washer placement surface 56 of the cylinder head 23, a washer rotation hole 60 is formed in the shape of a bag, which is slightly larger in diameter than the washer 57 and can rotate the washer 57 following the placement surface. The washer arrangement surface 56 and the washer rotation hole 60 are located below the lower edge of the lifter guide hole 23b when viewed in the height direction.
[0035]
Further, a nut insertion hole 61 is formed on the upper side of the washer rotation hole 60 so as to be smaller in diameter than the washer rotation hole 60 and slightly larger in diameter than the nut 58. The nut insertion hole 61 is formed in the camshaft arrangement chamber. 39 is open. A slit 63 having a slightly larger diameter than the washer 57 is formed on the inner surface of the nut insertion hole 61. The slit 63 is formed so as to pass through the center of the nut insertion hole 61 and to be perpendicular to the cam shaft 40, and is set to have substantially the same radial length as the washer rotation hole 60.
[0036]
In this way, the washer 57 is inserted from the slit 63 in a state of being vertically oriented and perpendicular to the cam shaft, and is rotated in the washer rotation hole 60 and seated on the washer placement surface 56 (FIG. 8, (See FIG. 9). The nut insertion hole 62 on the exhaust side is formed to have a slightly larger diameter than the washer 57, and the nut 59 has a pressing surface having the same diameter as the washer 57.
[0037]
Here, in the head bolt 55, the axis of the intake-side and exhaust-side head bolts 55, 55 between the cylinders is separated from the axis of the intake-side and exhaust-side cam shafts 40, 41 when viewed from above. That is, it is slightly offset outward from the center of the cylinder bore.
[0038]
Thus, since the inter-cylinder head bolt 55 is offset outward from the cam shaft axis, the wall thickness of the lifter guide hole 23b can be ensured while narrowing the inter-cylinder dimension.
[0039]
On the other hand, the head bolt 55 located at the end on the chain arrangement chamber 43 side is arranged so as to coincide with the cam shaft. Unlike the head bolts between the cylinders, the head bolts 55 arranged at the end portions are not narrowed by the lifter guide holes 23b, 23b, and therefore can be arranged closer to the chain arrangement 43 side. The wall thickness of the lifter guide hole 23b ′ can be secured without being offset from the axis.
[0040]
Here, the torsional torque acting on the camshafts 40 and 41 is maximum at the end portion on the cam chain arrangement chamber 43 side and decreases as the distance from the arrangement chamber 43 increases. On the other hand, the head bolt between the cylinders is offset outward from the cam shaft axis as described above, whereas the head bolt at the end of the chain arrangement chamber 43 coincides with the cam shaft axis. 64 is offset outward from the camshaft axis, whereas the end tool hole 64 'coincides with the camshaft axis.
[0041]
As described above, since the tool hole 64 ′ provided at a position where the torsion torque is large is made to coincide with the cam shaft axis line, it is possible to suppress a decrease in torsional rigidity of the cam shaft due to the tool hole 64 ′. Further, among the tool holes for inter-cylinder head bolts, the tool hole close to the cam chain placement chamber 43 is offset from the cam shaft axis, which is disadvantageous in terms of torsional rigidity. However, as will be described later, a thrust receiving portion 65 is provided. Therefore, it is possible to cover the reduction in torsional rigidity. The remaining tool holes are not problematic because the twisting torque is small.
[0042]
A thrust receiving portion 65 for restricting the axial movement of the cam shafts 40 and 41 is integrally formed with a predetermined axial width. The thrust receiving portion 65 is formed to have a larger diameter than other portions excluding the cam nose. The thrust receiving portion 65 is formed vertically above the head bolt 55 between the first and second cylinders located at the outermost end portion of the cam shafts 40 and 41 on the chain arrangement chamber 43 side (FIG. 6). reference). A tool hole 64 is formed through the thrust receiving portion 65 in the diametrical direction, and the tool hole 64 is formed so as to be coaxial with the head bolt 55. A similar tool hole 64 is also formed through the portion facing each other head bolt 55 of each camshaft 40, 41. Further, a tool hole 48a is formed in a portion of the cam cap 48 facing each tool hole 64, and a plug (not shown) is provided in the tool hole 48a provided at a position corresponding to the bearing portion adjacent to the cam chain. Removably inserted.
[0043]
Here, the thrust receiving portion is normally formed in a flange shape with a thin axial width, but in this embodiment, the thrust receiving portion 65 is formed with a thick axial width, thereby forming a tool hole 64. This suppresses a decrease in the torsional rigidity of the camshaft.
[0044]
Here, when the cylinder head 23 is assembled to the cylinder block 22, the intake and exhaust valves 34 and 35, the spring 38 and the valve lifter 37 are first assembled to the cylinder head 23, and the washers 57 and nuts 58 and 59 are attached to the washer arrangement surface 56. The cylinder head 23 is so-called sub-assembled by inserting and arranging the cam shafts 40 and 41 and the cam cap 48.
[0045]
Then, the sub-assembled cylinder head 23 is placed on the cylinder block 22, a fastening tool is inserted from the tool hole 48 a and the tool hole 64, and the nuts 58 and 59 are fastened to the head bolt 55. Of course, the camshafts 40 and 41 may be assembled after the cylinder head 23 is fastened to the cylinder block 22.
[0046]
As shown in FIG. 6, the camshaft bearing portions 66 and 66 at the end of the cylinder head 23 on the side of the chain arrangement chamber 43 are formed wider in the axial direction than the bearing portions of the other portions. A nut insertion hole 67 is formed in the bearing portion 66. The nut insertion hole 67 is formed offset from the bearing center line E toward the lifter guide hole 23b in the cam shaft direction. The oil passage 128 that connects the oil passages 127 and 129 on the intake side and the exhaust side is offset to the opposite side of the lifter guide hole 23b ′ from the bearing center line E, that is, in the direction perpendicular to the cam shaft. It is formed to extend. Thereby, the durability of the bearing portion 66 to which a large radial load is applied can be ensured while the nut insertion hole 67 is formed, and the oil passage 127 that allows the intake side and the exhaust side to communicate can be formed without any trouble.
[0047]
Next, the transmission 70 of the engine unit 15 will be described.
As shown mainly in FIGS. 2, 4, 11, and 12, the transmission 70 includes a main shaft (input shaft) 72 having an input gear group 71 mounted above the rear portion of the crankshaft 21, and the main shaft 72. Drive shafts (output shafts) 74 each having an output gear group 73 that meshes with the input gear group 71 are arranged below the shaft 72 in parallel with the crankshaft 21.
[0048]
Similar to the crankshaft 21, the drive shaft 74 is supported via a bearing 75 on a boss formed on a split surface of the upper and lower cases 26 and 27. The main shaft 72 is disposed in the upper case 26, and the left end portion of the main shaft 72 is supported by a boss portion of the upper case 26 via a bearing 76. The right side portion is supported by the right side wall 26g of the upper case 26 via a bearing 77 and a flange 78, and the flange 78 is fixed to the right side wall 26g by bolting.
[0049]
The left end portion of the drive shaft 74 protrudes outward from the unit case 25, and a drive sprocket 79 attached to the protrusion is connected to the rear wheel sprocket 13a of the rear wheel 13 via a chain 80. A clutch mechanism 81 is attached to the right end portion of the main shaft 72. The clutch mechanism 81 meshes with the small reduction gear 82 of the crankshaft 21, and is connected to the reduction large gear 83 supported by the main shaft 72 via a damper, and is splined to the main shaft 72. In this structure, a large number of clutch plates 86 are interposed between the inner drum 85 and the inner drum 85. The clutch mechanism 81 is connected to and disconnected from the engine power by rotating a push lever 87 connected to the inner drum 85.
[0050]
A shift drum 90, an input-side fork shaft 91, and an output-side fork shaft 92 are disposed in parallel with the rear side of the main shaft 72 and the drive shaft 74, and the shift drum 90 and each fork shaft 91 are arranged. , 92 are supported by right and left boss portions 26e, 26f integrally formed with the upper case 26. A bearing 90c is interposed between the left end portion of the shift drum 90 and the left boss portion 26f. Reference numeral 90d denotes a retaining plate for the bearing 90c and the fork shafts 91 and 92. In FIG. 11, the retaining plate 90 is removed.
[0051]
One input-side shift fork 93 is mounted on the input-side fork shaft 91, and two output-side shift forks 94, 94 are mounted on the output-side fork shaft 92 so as to be movable in the axial direction. Bifurcated claw portions 93b, 94b of the shift forks 93, 94 are slidably engaged with slide grooves 71b, 73b formed in the gears of the input gear group 71 and the output gear group 73, and the shift forks are also provided. Engagement pins 93 a and 94 a formed integrally with the base portions of 93 and 94 are slidably engaged with guide grooves 90 a formed on the outer peripheral surface of the shift drum 90. By rotating the shift drum 90 by a change mechanism (not shown), the shift forks 93 and 94 slide in the axial direction to move the gears of the input gear group 71 and the output gear group 73. Switching is performed between the lowest speed stage and the highest speed stage.
[0052]
An assembly opening 26a is formed in a portion of the left side wall of the upper case 26 facing the left end portions of the shift drum 90, the input-side fork shaft 91, and the output-side fork shaft 92, and a cover plate is formed in the assembly opening 26a. 95 (see FIG. 1) is detachably mounted.
[0053]
An upper part of the upper case 26 is integrally formed with an oil breather chamber 96 for separating in advance the lubricating oil mixed in the air discharged from the crankcase to the outside for adjusting the pressure in the crankcase. Has been. The air from which the lubricating oil is separated is introduced into the intake system. The bottom wall 26c of the oil breather chamber 96 is located in the vicinity of the upper side of the input side fork shaft 91, and restricts the rotation angle of the fork 93 when the input side shift fork 93 is assembled as will be described later. It is a stopper part.
[0054]
Next, the assembly procedure of the transmission 70 will be described.
{Circle around (1)} First, the upper case 26 is turned upside down so that the splitting surface faces upward and placed on an assembly table or the like. The main shaft 72 into which the input gear group 71 is incorporated is inserted through the insertion hole in the right side wall 26g from the right side wall opening 26d of the upper case 26, and the left end portion is fitted into the bearing 76 and the flange 78 is provided. The right side wall 26g is bolted (see FIGS. 2, 4 and 12).
[0055]
(2) Next, the claw portion 93b of the input side shift fork 93 is engaged with the sliding groove 71b of one gear of the input gear group 71 from the split surface side, and the claw portion 93b is rotated around the claw portion 93b. The base 93 c is brought into contact with the bottom wall 26 c of the oil breather chamber 96. As a result, the input side shift fork 93 is held in the state indicated by the two-dot chain line in FIG. 11 without disengaging the claw portion 93b from the sliding groove 71b. At this time, the engaging pin 93a is located slightly outside the outer peripheral surface of the shift drum 90.
[0056]
(3) Subsequently, the shift drum 90 is inserted into the drum support hole of the left boss portion 26f from the assembly opening 26a of the left side wall, and the right end portion (tip portion) 90b is inserted into the support hole of the right boss portion 26e. The shift drum 90 is set by fitting the bearing 90c at the left end portion into the support hole of the left boss portion 26f. At this time, the base 93c of the input side shift fork 93 is held at such a rotational angular position that the engaging pin 93a does not interfere with the outer peripheral surface of the shift drum 90, so that the shift drum 90 can be inserted without any trouble. It is.
[0057]
(4) Then, the base 93c of the input shaft side shift fork 93 is rotated upward to engage the engaging pin 93a in the guide groove 90a of the shift drum 90. In this engaged state, the input side The fork shaft 91 is inserted into the shift fork 93 from the assembly opening 26a side, and both ends of the input fork shaft 91 are inserted into the support holes of the left and right boss portions 26f and 26e of the upper case 26. Thereby, the assembly of the main shaft 72 and the input side shift fork 93 is completed.
[0058]
(5) Next, the output shaft side shift is performed on the drive shaft 74 in which the output gear group 73 is incorporated and the claw portions 94b, 94b of the output shaft side shift forks 94, 94 are engaged with the sliding grooves 73b, 73b. The engaging pin 94a of the fork 94 is placed on the split surface of the upper case 26 while being engaged in the guide groove 90a of the shift drum 90. In this state, the output-side fork shaft 92 is inserted into the shift fork 94 from the assembly opening 26a, and both end portions of the fork shaft 92 are inserted into the support holes of the left and right boss portions 26f and 26e of the upper case 26. . Finally, a retaining plate 90 d is attached, and a link mechanism is connected to the left end portion of the shift drum 90. The drive shaft 74 may be mounted after the shift forks 94, 94 are set.
[0059]
Next, the positional relationship among the crankshaft 21, the main shaft 72, and the drive shaft 74 will be described mainly with reference to FIG. The main shaft 72 has a sharp first axis angle θ1 formed by the crankshaft / main shaft straight line A connecting the shaft core and the shaft shaft of the crankshaft 21 and the cylinder axis 20 on the cylinder head side and the main shaft side. In other words, it is disposed at a position closer to the cylinder head 23 than a straight line C passing through the axis of the crankshaft 21 and perpendicular to the cylinder axis 20.
[0060]
The drive shaft 74 includes a main shaft / drive shaft straight line B connecting the shaft core of the main shaft 72 and the crank shaft / main shaft straight line A on the drive shaft side and the crank shaft side. It arrange | positions so that 2nd axial angle (theta) 2 may become an acute angle. Thus, the main shaft 72 and the drive shaft 74 are arranged so as to be carried on the back surface of the cylinder block 22.
[0061]
The maximum outer peripheral surface (the outer peripheral surface of the large reduction gear) 81a of the clutch mechanism 81 is located closer to the cylinder head 23 than the straight line D passing through the top surface of the piston 31 'located at the bottom dead center and perpendicular to the cylinder axis 20. doing. The main shaft 72, the shift drum 90, the fork shafts 91 and 92, and the drive shaft 74 are located in the axial projection surface of the large reduction gear 83 of the clutch mechanism 81.
[0062]
Next, the arrangement structure of the cooling water pump and the lubricating oil pump will be described.
As shown mainly in FIGS. 2, 13, and 14, both the cooling water pump 100 and the lubricating oil pump 101 of this embodiment are accommodated in the lower case 27, and the pump shaft 102 common to both the pumps is The crankshaft 21 and the drive shaft 74 are disposed below and in parallel with the drive shaft 74. The pump shaft 102 is rotatably supported in the housing unit 103 via bearings 104 and 105, the rotor 106 of the lubricating oil pump 101 is provided at the right end of the pump shaft 102, and the cooling water is provided at the left end. The impeller 107 of the pump 100 is fixed. A driven sprocket 108 is bolted and fixed to the right end surface of the pump shaft 102 in the axial direction, and the sprocket 108 is connected to a drive sprocket 110 mounted on a portion outside the flange 78 of the main shaft 72 via a chain 109. Has been.
[0063]
The housing unit 103 has a three-part structure of a main body portion 103a located in the center in the axial direction, a cooling side housing portion 103b and a lubrication side housing portion 103c located on the left and right sides. 103c is fastened to the main body 103a by bolts 111 and 112 screwed in the axial direction. The maximum diameter portion 103d of the housing unit 103 is disposed at a position facing the highest speed gear 73a (see FIG. 4) having the minimum diameter of the output gear group 73 of the drive shaft 74 in the radial direction.
[0064]
When the housing unit 103 is disposed so as to be close to the main shaft 72, the maximum diameter portion 103d is disposed so as to face the minimum diameter gear of the input gear group 71 of the main shaft 72 in the radial direction. It is desirable to do.
[0065]
Here, the housing unit 103 is housed in the lower case 27, and the cooling side housing portion 103b is fitted and supported to a boss portion 27a formed on the left side wall of the lower case 27 via an O-ring 27b. The lubrication-side housing portion 103c is disposed and fixed in the lower case 27 by fastening it to the vertical wall of the lower case 27 with two bolts 113, 113 screwed from below. The vertical wall extends in the substantially vertical direction from the vicinity of the mating surface with the upper case, and functions as a rib for improving the case rigidity.
[0066]
A seal member 114 is disposed on the left side of the left bearing 104 of the pump shaft 102 in the axial direction, and a mechanical seal 115 is disposed on the left side of the seal member 114 with a gap. A drain hole 116 is formed between the seal member 114 at the bottom of the main body 103 a and the mechanical seal 115, and a drain pipe (drain pipe) 117 is inserted into the drain hole 116. The lower end of the drain pipe 117 communicates with the outside through a drain passage 28 a formed in the oil pan 28. Thereby, the water leaked from the cooling water pump 100 is discharged to the outside of the engine. The drain pipe 117 is interposed between the housing unit 103 supported by the lower case 27 and the oil pan 28 attached to the lower case from below via an O-ring 117a without using a special support member. It is pinched.
[0067]
A cooling water return hose 118 is connected to the suction port 103e of the cooling side housing portion 103b, and a cooling water supply pipe 119 is connected to the discharge port 103f. The cooling water supply pipe 119 is led out to the front of the engine and is connected to a cooling jacket inlet (not shown) on the front wall of the cylinder block 23 via a cooling hose 123a and a water supply pipe 123b. Therefore, the space between the lead-out portion of the supply pipe 119 from the pump to the engine front wall passes through the crankcase 25, and the portion exposed to the outside and the cooling hose 123a and the water supply pipe 123b are also short, so the engine appearance is improved. .
[0068]
Further, an oil strainer 120 disposed in the oil pan 28 is connected to the lubricating oil suction port 103g of the lubricating side housing portion 103c, and the lubricating oil discharge port 103h is connected to the front wall of the lower case 27. The oil filter 121 is connected in communication. The lubricating oil exiting the oil filter 121 passes through the main gallery 122 and is supplied to each engine lubricating portion such as the crankshaft 21, the main shaft 72, the drive shaft 74, and the camshafts 40 and 41.
[0069]
Here, the cam shaft path of the lubricating oil is the first oil that opens between the first cylinder intake side of the cylinder head 23 and the chain arrangement chamber 43 as shown in FIGS. 3, 6 to 8, and 16. The discharge port 126a of the passage 126 is connected to the first oil passage 127 extending along the intake side cam shaft 40, and is connected to the fourth oil passage 129 extending along the exhaust side cam shaft 41 by the third oil passage 128. The first and fourth oil passages 127 and 129 communicate with the camshaft bearing portion. The lubricating oil that has lubricated the camshafts 40 and 41 is collected in the oil pan 28 through an oil return passage 130 formed between the exhaust sides of the third and fourth cylinders of the cylinder head 23.
[0070]
In the above embodiment, the cooling water pump and the lubricating oil pump are integrated and arranged in the clan case, but only the cooling water pump may be arranged in the crankcase.
[0071]
Next, the starting device for the engine unit 15 will be described mainly with reference to FIGS. The starter motor 135 is disposed in parallel with the crankshaft 21 on the back surface of the cylinder bore of the upper case 26. The motor 135 is supported by bolting and fixing the rear end support portion 135 a to the upper case 26 and fitting the front end boss portion 135 b into the boss portion of the upper case 26.
[0072]
The output gear 136 of the starter motor 135 protrudes into the upper case 26, which meshes with the large-diameter gear 138a of the intermediate gear 138. The intermediate gear 138 is supported by an intermediate shaft 137 that is bolted and fixed above the main shaft 72 in the upper case 26, and the intermediate shaft 137 has a maximum diameter portion (reduction large gear 83) of the clutch mechanism 81. ) In the axial projection plane.
[0073]
A small-diameter gear 138b of the intermediate gear 138 meshes with a start gear 139, and the start gear 139 is connected to a boss portion of a large reduction gear 83 supported by the main shaft 72 through a one-way clutch 140. ing. The one-way clutch 140 is configured to transmit the rotational force from the starter motor 135 to the reduction large gear 83 and not to transmit the rotational force from the crankshaft 21 to the starter motor 135 side.
[0074]
The exhaust system of the engine unit 15 mainly includes an exhaust pipe 141 connected to each exhaust port 34 opened in the front wall of the cylinder head 23, between the engine unit 15 and the rear wheel 13 and below the rear cushion 14. The first muffler 142 is arranged, and the second muffler 143 is arranged on the upper right side of the rear wheel 13.
[0075]
Each exhaust pipe 141 is bent downward from the exhaust port 34 and extends rearward through the lower part of the oil pan 28. The first muffler 142 is disposed using a space generated by the rear cushion link mechanism between the oil pan 28 and the rear wheel 13 being erected upward. A sound deadening mechanism and a catalyst (not shown) are accommodated in the case.
[0076]
Next, the intake device of the engine unit 15 will be described mainly with reference to FIGS. A quadruple carburetor unit 151 is connected to each intake port 33 led to the rear wall of the cylinder head 23 via a joint 150. The carburetor unit 151 is obtained by unitizing the first to fourth carburetors 151a to 151d corresponding to the first to fourth cylinders from the right side. Each of the carburetors 151a to 151d is an automatic variable venturi type having a butterfly throttle valve 152 that opens and closes by a throttle operation and a piston valve (not shown) that automatically opens and closes by an intake negative pressure of the engine. The valve shafts 153 of the throttle valve 152 are connected to each other by a connecting member 154 so that rotational force can be transmitted.
[0077]
A throttle opening sensor 155 that detects the opening of the throttle valve 152 is connected to the right end of the carburetor unit 151 in the vehicle width direction. The opening sensor 155 is connected to the chain arrangement chamber 43 side of the cylinder head 23. That is, it is arranged so as to be located on the back surface of the rightward protruding portion of the chain arrangement chamber 43. In addition, a throttle pulley 156 is attached to a connecting member 154 between the first vaporizer 151a and the second vaporizer 151b, and the throttle pulley 156 is connected to a throttle grip (not connected) of a steering handle via a throttle cable 157. (Shown). The throttle valves 152 are opened and closed synchronously by the turning operation of the throttle grip.
[0078]
Here, in the carburetor unit 151, the dimension W1 from the vehicle body center line L to the right outer end of the throttle opening sensor 155 is the same as the dimension W2 from the vehicle body center line L to the left outer end of the carburetor unit 151. It is arranged to be. Thus, the vehicle body center line L and the center line in the vehicle width direction of the carburetor unit 151 coincide with each other.
[0079]
The axes X1 and X2 passing through the centers of the intake passages of the first and second carburetors 151a and 151b and parallel to the vehicle body center line L pass through the cylinder axis 20 of the first and second cylinders. Are slightly offset (specifically, about 2 mm) from the axes Y1 and Y2 parallel to the chain arrangement chamber 43 side. On the other hand, the axis lines X3 and X4 of the third and fourth carburetors 151c and 151d are closer to the chain arrangement chamber 43 than the corresponding axis lines Y3 and Y4 of the third and fourth cylinders. It is larger than the devices 151a and 15b. Specifically, the third vaporizer 15c is offset by about 7 mm, and the fourth vaporizer 15d is offset by about 14 mm. The throttle pulley 156 increases the pitch between the carburetors. In this embodiment, the throttle pulley 156 is disposed between the first and second carburetors whose pitch is increased by the offset. Yes.
[0080]
Next, the effect of this embodiment is demonstrated.
In the present embodiment, the communication hole 52 that allows the crank chambers 19 to communicate with each other is positioned within the assembly opening 50 of the camshaft drive mechanism provided in the outer wall 22b of the cylinder block 22 when viewed in the crankshaft direction. Therefore, the communication hole 52 can be drilled by machining using the assembly opening 50, and there is no need to perform extra processing such as forming a machining opening separately. Therefore, it is not necessary to close the processing opening with the dedicated lid member, and the manufacturing cost can be reduced.
[0081]
Further, when the hard plating film is formed on the inner surface of the cylinder bore 22a, the plating process is performed prior to the machining of the communication hole 52, so that the plating process can be facilitated and the process of the communication hole 52 can be performed. Work can be facilitated. That is, the plating process is performed by closing the upper and lower openings of the cylinder bore 22a and flowing a current in a state where the closed space is filled with the plating solution. However, the communication hole 52 is first formed by machining. As a result, the blocking becomes difficult. On the other hand, when machining is performed after the plating treatment, the hard plating film makes the machining difficult. In the present embodiment, since the plating process is performed in a state where the communication hole 52 is masked, the above-described problem can be avoided.
[0082]
Further, when the lubricating oil passage 53 is formed in each boss portion 29 of the upper case 26 so as to open to the inner peripheral surface of the communication hole 52, and the lubricating oil is injected to the back surface of the piston through the passage 53, Since the upper width W1 of the communication hole 52 is narrower than the lower width W2, the injected lubricating oil is reliably supplied to the back surface of the piston without being blocked by the upper edge of the communication hole 52. In addition, it is not necessary to cut out the injection passage in the crank chamber wall, and the piston 31 can be efficiently cooled without increasing the cost.
[0083]
Furthermore, in the present embodiment, a slipper type piston 31 formed by forming a notch recess 31c in the piston skirt 31a is adopted, and the notch recess of the piston 31 located at the bottom dead center of the injection port 54a of the lubricating oil passage 53. Since the piston is directed to the back surface of the piston through 31c, the injection flow of the lubricating oil is not blocked by the piston skirt 31a, and the cooling efficiency can be improved from this point. Further, since the notch recess 31c is provided, the problem that the effective area of the communication hole 52 is narrowed by the piston skirt 31a can be avoided. Alternatively, it is not necessary to lengthen the connecting rod in order to avoid the area reduction due to the skirt.
[0084]
According to the cylinder head fastening structure of the present embodiment, the washer placement surface 56 is formed below the lower edge of the lifter guide hole 23 b of the cylinder head 23, and the washer having a diameter larger than that of the washer 57 following the placement surface 56. A rotation hole 60 is formed, a nut insertion hole 61 into which a nut 58 can be inserted is formed following the washer insertion hole 60, and a slit having substantially the same radial dimension as the washer rotation hole 60 is formed in the nut insertion hole 61. Since 63 is formed, the washer 57 can be seated on the mounting surface 56 by being inserted from the slit 63 in a state of being vertically oriented and tilted by the washer rotation hole 60. This makes it possible to reduce the dimension between adjacent lifter guide holes 23b while ensuring the required wall thickness of the lifter guide portion and the area of the nut tightening seating surface, thereby reducing the cylinder pitch and thus making the engine width compact. it can.
[0085]
Further, in the present embodiment, when the tool shaft 64 for tightening the head bolt disposed between the cylinders is formed in the cam shafts 40 and 41 so as to penetrate therethrough, portions of the cam shafts 40 and 41 close to the chain arrangement chamber 43, that is, twisting. Since the tool hole 64 formed in the portion where the torque torque increases and the formation position of the wide thrust receiving portion 65 are matched, the torsional rigidity of the camshaft due to the formation of the tool hole 64 is widened and large. This can be suppressed by the thrust receiving portion 65 having a diameter.
[0086]
In the transmission according to the present embodiment, the bottom wall 26c of the oil breather chamber 96 formed in the upper case 26 is used as a stopper portion that restricts the rotational angle position of the input side shift fork 93. The assembling property of the input side shift fork 93 can be improved without increasing the complexity of the structure.
[0087]
That is, as described in the above assembly procedure, when the input side shift fork 93 is rotated downward with the claw portion 93b engaged with the sliding groove 71a of the main shaft 72, the base portion 93c is moved to the bottom. Since it abuts against the wall 26c and is temporarily held at a predetermined position, from the side of the assembly opening 26a on the side of the upper case 26 with the engagement pin 93a of the shift fork 93 engaged with the guide groove 90a of the shift drum 90. It can be assembled by inserting the input side fork shaft 91. Conventionally, an opening for assembly is formed in the top wall of the crankcase. However, in the present embodiment, such an opening can be made unnecessary, and the processing man-hours, the lid member, and the assembly man-hour of the opening are unnecessary. Thus, the cost can be reduced, and the formation of the assembly opening can prevent the rigidity of the crankcase ceiling from being lowered.
[0088]
Further, the height position of the bottom wall 26c of the oil breather chamber 96 functioning as the stopper portion is set to a position where the locking pin 93a of the input side shift fork 93 is disengaged from the guide groove 90a of the shift drum 90. The shift drum 90 can be inserted without any trouble from the assembly opening 26a side in a state where 93 is temporarily held, and the assembly work can be easily performed from this point.
[0089]
Further, since the stopper portion is constituted by the bottom wall 26c of the oil breather chamber 96 formed integrally with the upper case 26, it is not necessary to form the stopper portion specially, and cost increase and case enlargement can be avoided.
[0090]
According to the present embodiment, the crankshaft 21, the main shaft 72, and the drive shaft 74 are divided into the first shaft angle θ1 formed by the crankshaft / main shaft straight line A and the cylinder axis 20, and the shaft straight line A and the main shaft / Since the second shaft angles θ2 formed with the drive shaft straight line B are arranged so as to form acute angles, the distance between the crankshaft 21 and the drive shaft 74 can be reduced, and the longitudinal length of the engine unit 15 can be shortened accordingly. it can.
[0091]
Since the longitudinal length of the engine unit can be reduced, the rear arm pivot portion can be positioned forward, and when the wheel base is set as in the conventional case, the length of the rear arm 11 can be extended, and the vertical swing angle of the rear arm can be reduced accordingly. This can improve running stability. In addition, when the rear arm length is set to be the same as the conventional one, the wheel base can be shortened and the maneuverability can be improved.
[0092]
Further, since the length of the rear arm 11 can be set large, an empty space can be secured between the engine unit 15 and the rear wheel 13, and the first muffler 142 can be arranged by effectively using the space. Thereby, the noise reduction effect of the exhaust gas can be improved and the center of gravity can be lowered.
[0093]
In this embodiment, as shown in FIG. 1, the second muffler 143 is connected to the rear of the first muffler 142 via the exhaust pipe 144. However, the second muffler is omitted depending on the capacity of the first muffler. It is also possible.
[0094]
Further, since the main shaft 72 is disposed closer to the cylinder head 23 than the right-angled straight line C passing through the crankshaft 21, the main shaft 72 is disposed so as to be supported by the back of the cylinder block 22. The length can be further reduced. Further, since the clutch mechanism 81 is disposed such that the maximum outer peripheral surface 81a thereof is located on the cylinder head 23 side with respect to the straight line D passing through the top surface of the piston at the bottom dead center, the engine unit 15 can also be reduced in size from this point.
[0095]
Since the main shaft 72, the shift drum 90, the fork shafts 91 and 92, and the drive shaft 74 are arranged in the axial projection surface of the maximum diameter portion of the clutch mechanism 81, the arrangement of the shafts becomes compact, and the unit case 25 The protrusion can be made smaller, and the engine can be made smaller in this respect as well.
[0096]
In the present embodiment, both the cooling water pump 100 and the lubricating oil pump 101 are disposed in the common housing unit 103, and the housing unit 103 is accommodated in the unit case 25, so that the protrusion from the crankcase side wall is eliminated. The engine width can be reduced accordingly, and the bank angle can be set larger.
[0097]
Further, since the maximum diameter portion 103d of the housing unit 103 is opposed to the maximum speed gear 73a having the minimum diameter of the drive shaft 74 in the radial direction, the distance between the pump shaft 102 and the drive shaft 74 can be reduced. Can be downsized.
[0098]
Since the left end of the housing unit 103 in the axial direction is fitted to the boss 27a of the lower case 27 via an O-ring 27b, and the right end is bolted and fixed to the lower case 27, the O-ring is supported. On the other hand, it is possible to reduce the fixing bolts while ensuring both the mounting strength and the sealing performance without applying a radial offset load, thereby reducing the cost and simplifying the mounting structure.
[0099]
Further, since the drain pipe 117 is inserted and disposed between the cooling water pump 100 and the lubricating oil pump 101 of the housing unit 103 and the drain pipe 117 communicates with the outside, water leaked from the cooling water pump 100 can be drained. In addition, it is possible to reliably prevent water from being mixed into the lubricating oil while disposing the cooling water pump 100 in the crankcase.
[0100]
According to the starter of the present embodiment, the output gear 136 of the starter motor 135 is engaged with the starter gear 139 attached to the main shaft 72 via the intermediate gears 138a and 138b, and is engaged with the starter gear 139 and the crankshaft 21. Since the one-way clutch 140 is interposed between the large reduction gear 83 and the starting gear 139, the intermediate gears 138a and 138b, and the output gear 136 do not rotate after the engine is started, the loss horsepower can be reduced.
[0101]
In addition, since the start gear 139 and the one-way clutch 140 are disposed between the large reduction gear 83 of the main shaft 72 and the input gear group 71, the axial dead space of the main shaft 72 can be used effectively and compactly disposed. Further, the crankshaft can be shortened as compared with the one-way clutch provided on the crankshaft. Note that the axial length and arrangement position of the main shaft 72 are the vehicle width direction position of the reduction small gear 82 arranged at the end of the crankshaft 21, the vehicle width direction position of the drive sprocket 79 for the rear wheel 13, and the speed change. Since it is inevitably determined by the number of stages, the dead space often occurs in the clutch mechanism inner portion of the main shaft 72 if the engine has the same specifications as the present embodiment.
[0102]
Since the intermediate shaft 137 of the intermediate gears 138a and 138b is disposed in the axial projection surface of the large reduction gear 83, the layout of the starting device can be made compact and the engine can be downsized. Further, interference with the connecting rod of the starter gear 139 can be avoided while reducing the pitch between the crankshaft and the main shaft.
[0103]
According to the intake device of this embodiment, the throttle opening sensor 155 is disposed at the end of the carburetor unit 151 on the side of the chain arrangement chamber 43, the throttle pulley is disposed between the first and second carburetors, and the vehicle body center line Since the dimension W1 from L to the outer end of the opening sensor 155 and the dimension W2 from the vehicle body center line L to the outer end of the carburetor unit 151 on the opposite side of the opening sensor 155 are arranged to be substantially the same. The throttle opening sensor 155 can be arranged in an empty space at the end of the chain arrangement chamber 43, and without increasing the vehicle width dimension of the main frame 3, the axes X1 to X4 of the carburetors 151a to 151d and the cylinders The total amount of offset with the axes Y1 to Y4 can be minimized. As a result, it is possible to reduce the intake passage resistance while reducing the vehicle body width dimension and improving the riding position.
[0104]
Further, since the throttle pulley 156 is arranged on the connecting member 154 between the first and second carburetors 151a and 151b located on the chain arrangement chamber 43 side, the offset between the carburetor and the cylinder is avoided while avoiding the increase in the vehicle body width dimension. The total amount can be minimized, and the tuning accuracy of each vaporizer can be improved. That is, for example, when a pulley is arranged at the left end of the carburetor unit, it is necessary to increase the offset amount between the third and fourth cylinders and the carburetor in order to avoid an increase in the vehicle body width. The tuning accuracy of the vaporizer is reduced.
[Brief description of the drawings]
FIG. 1 is a left side view of a motorcycle equipped with an engine unit according to an embodiment of the present invention.
FIG. 2 is a right side view of the engine unit.
FIG. 3 is a right side view showing a structure around a chain arrangement chamber of the engine unit.
FIG. 4 is a developed sectional rear view of the engine unit.
FIG. 5 is a cross-sectional view showing a communication hole portion of the engine unit.
FIG. 6 is a plan view of a cylinder head of the engine unit.
7 is a sectional view of the cylinder head (sectional view taken along line VII-VII in FIG. 6).
8 is a cross-sectional view of the cylinder head (a cross-sectional view taken along line VIII-VIII in FIG. 6).
FIG. 9 is a cross-sectional view (cross-sectional view taken along line IX-IX in FIG. 8) of a fastening portion of the cylinder head.
FIG. 10 is a plan view of an intake camshaft of the engine unit.
FIG. 11 is a left side view of the upper case portion of the engine unit.
FIG. 12 is a sectional view of the transmission unit of the engine unit.
FIG. 13 is a sectional view of a cooling water pump and a lubricating oil pump of the engine unit.
FIG. 14 is a side view of a lubricating oil pump portion of the engine unit.
FIG. 15 is a rear development view of the engine unit starter.
FIG. 16 is a schematic plan view of the intake device of the engine unit.
FIG. 17 is a schematic configuration diagram of the intake device.
[Explanation of symbols]
15 Engine unit
22 Cylinder block
23 Cylinder head
23b Lifter guide hole
39 Camshaft placement chamber
40, 41 Camshaft
55 head bolt
56 Washer mounting surface
57 Washer
58 nuts
60 Washer rotation hole
61 Nut insertion hole
63 slits
64 Tool hole
65 Thrust receiving part

Claims (3)

In a cylinder head fastening structure of a vehicle engine unit in which a cylinder block and a cylinder head are fastened by a head bolt disposed between adjacent cylinders, the cylinder head is disposed at a position immediately above the head bolt fastening washer mounting surface. A washer rotation hole that can rotate the washer with a slightly larger diameter than the washer is formed, the bottom surface of the washer rotation hole is the washer placement surface, and is smaller in diameter than the washer and from the outer diameter of the head bolt head or nut. A slightly large-diameter insertion hole is formed so as to communicate with the cam shaft placement chamber from the washer rotation hole, and the insertion hole passes through the center of the insertion hole and is substantially perpendicular to the cam shaft. A cylinder head fastening structure for an engine unit for a vehicle, wherein a slit for inserting a washer having a length is formed. 2. The engine unit according to claim 1, wherein an upper portion of the valve in the sliding direction is inclined outwardly of the cylinder bore, and an axis of the head bolt is displaced outwardly of the cylinder bore from an axis of the cam shaft. A cylinder head fastening structure for an engine unit for a vehicle. 3. The cylinder head fastening structure according to claim 1, wherein the cylinder head is fastened to a head bolt that fastens an inter-cylinder portion of the cylinder head, and a cam shaft disposed above the head bolt is located at an end of the cylinder head in the cam shaft direction. The cam shaft is driven to rotate by a cam shaft drive mechanism arranged, and the cam shaft is moved in the axial direction above the inter-cylinder head bolt located at the cam shaft drive mechanism side end of the cam shaft. A thrust receiving portion is formed, a tool hole is formed so as to penetrate the thrust receiving portion, and the nut can be tightened by a tool inserted into the tool hole. Cylinder head fastening structure for vehicle engine unit.

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