JP2832896B2 - Motorcycle engine unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention is mounted on the lower center of a vehicle body of an underbone type, and a cylinder portion is nearly horizontal in order to adapt to the underbone type. The present invention relates to an engine unit of a motorcycle that leans forward.

(Prior Art) FIG. 6 shows an example of a small motorcycle, in which a gap between a steering wheel a and a seat b is low and a leg shield d is disposed behind a front wheel c. An engine unit e having a cylinder f inclined forward substantially horizontally is mounted on both sides of the engine unit e. g is a rear wheel, and h is a chain case.

 FIG. 7 shows a single unit of the engine unit e.

The engine type is 4 cycles. In this case, a valve operating mechanism is arranged on the front surface of the cylinder head i, an intake passage j is connected on the upper surface, and an exhaust passage k is connected on the lower surface. Installed. For this reason, a ventilation hole that opens in the front of the cylinder head i and passes around the combustion chamber and the ignition plug 1 is provided in the cylinder head i.

On the other hand, the cylinder f is fastened to the crankcase k by the stud bolt n together with the cylinder head i. Some of the stud bolts n cross the air guide holes due to layout. In this case, moisture and sand enter the gap between the stud bolt and the bolt insertion hole, causing an obstacle due to rust.

For this reason, a method of covering the stud bolt with a collar to close the gap between the bolt insertion hole and prevent intrusion of moisture or the like (Japanese Utility Model Publication No. 63-25324) or a bolt insertion hole in the mating surface between the cylinder f and the crankcase k Method of forming a groove reaching the surface and draining water that has entered (Japanese Utility Model Application Laid-Open No. 57-103335)
Is conventionally performed.

However, the former has a lot of man-hours and costs for the assembly, and the latter has the following problems.

That is, as described above, when the cylinder f is inclined forward substantially horizontally, the drainage hole formed by the concave groove is formed by the circle E in FIG.
6, the muddy water from which the front wheel c jumps up on a bad road or the like hits directly, as shown by the arrow D in FIG. High in nature. In this case, it is as if there is no drain hole, and the stud bolt is rusted by the accumulated water, and may be broken if the rust progresses. If the earth and sand that have penetrated into the bolt insertion holes are present as accumulated, they may enter the engine at the time of disassembly and damage the mating surface and the inner surface of the cylinder f.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-described problem, and has a stud bolt crossing an ignition plug cooling air guide hole when the cylinder is inclined substantially horizontally forward. To provide an engine unit for a motorcycle in which drain holes are not blocked by splashing muddy water from the front wheel or accumulation of intruded earth and sand, and rust damage of the stud bolts is reliably prevented. With the goal.

[Configuration of the invention]

(Means for Solving the Problems) In accordance with the above object, an engine unit for a motorcycle according to the present invention is configured such that a cylinder and a cylinder head which are inclined substantially horizontally forward are fastened to a crankcase by several stud bolts. The stud bolt at a low position among the engine units of a motorcycle intersects with the air guide hole formed in the cylinder head for introducing the traveling wind around the ignition plug, and intersects with the air guide hole. Below the mating surface between the cylinder and the crankcase where the stud bolt passes, an enlarged portion where the mating surface on the cylinder side protrudes below the mating surface on the crankcase side is integrally extended from the cylinder, and this mating surface on the cylinder side The protruding portion has a configuration in which a concave groove leading to the stud bolt insertion hole is formed as a drain hole.

(Function) With this configuration, since the drainage hole is located at a position hidden from the front wheel at the rear surface of the enlarged part, the muddy water jumped up by the front wheel is received at the front of the enlarged part. ,
Does not block openings.

Therefore, the drain hole always functions normally, does not collect water around the stud bolt, and effectively prevents the generation of rust.

Further, since the width of the concave groove is set to be large at the lower part, the drainage is good, and the opening is not blocked by accumulation of earth and sand mixed in the flowing water.

(Embodiment) A description will be given below with reference to the drawings showing an embodiment of the present invention.

FIG. 1 is a left side view of an engine unit according to an embodiment of the present invention, and FIG. 2 is a front view as viewed in the direction of arrow A in FIG.

The cylinder 2 and the cylinder head 3 are inclined substantially horizontally forward with respect to the crankcase 1, and the intake passage 4 and the exhaust passage 5 are opened on the upper and lower surfaces of the cylinder head 3. A mechanism is arranged. For this reason, the ignition plug 6 is attached to the side surface (the left side surface in the figure) of the cylinder head 3.

The leg shield 7 covers both sides of the cylinder 2, and the traveling wind (arrow C) guided between them flows from the front surface of the cylinder head 3 and flows backward. Therefore, the cooling fins 8 are formed parallel to the axis of the cylinder.

However, in such a form, the ignition plug 6 and the vicinity of the combustion chamber become insufficiently cooled. Therefore, the ignition plug 6 and the vicinity of the combustion chamber inside the cylinder head 3 pass through the forward opening 9 projecting to the lower right of the cylinder head 3. An air guide hole 10 is provided from both sides of the ignition plug 6 to the left side, and the cooling air is supplemented by the passing wind.

On the other hand, the cylinder 2 and the cylinder head 3 are assembled to the crankcase 1 by four stud bolts 12 and fastening nuts 13 planted in the crankcase 1. The lower right stud bolt 12a of the four crosses the air guide hole 10, and the stud bolt 12a and the bolt insertion hole 1
A gap with 4 leads to the air guide hole 10.

Next, as shown in FIG. 3, the stud bolts 12 are provided on the mating surface where the crankcase 1 and the cylinder 2 are joined.
Below the portion through which a passes, an enlarged portion 17 extends from the cylinder 2 so that the mating surface 16 on the cylinder side protrudes below the mating surface 15 on the crankcase side. 1a shows the profile of the lower edge of the crankcase 1.

The protruding part is provided on the cylinder side mating surface 16.
A concave groove 18 is formed from the lower edge of 16a to the bolt insertion hole 14 of the stud bolt 12a. The concave groove 18 is set so that the groove width is small near the bolt insertion hole 14 and is large at the protruding portion 16a.

As described above, the stud bolt 12a and the bolt insertion hole 1
Since the inside of the gap with 4 is communicated with the atmosphere by the air guide hole 10, moisture in the air enters and dew forms, and water droplets are generated.
Water droplets flow backward due to slight inclination, and
Is discharged through.

The lower edge of the mating surface between the crankcase 1 and the cylinder 2 in which the concave groove 18 is provided is located at a position where muddy water (arrow D) whose front wheels have jumped up on rough roads can easily fly. As shown, the mud 19 is blocked by the front of the bulge 17,
It does not adhere to the protruding portion 16a on the back. Therefore the groove 18
Is open all the time, continues the above-mentioned drainage without hindrance, prevents water from accumulating in the bolt insertion hole 14, and prevents the occurrence of rust.

In addition, sand and dust are blown from the air guide holes 10 through the bolt insertion holes 14
, Which is also mixed with water and discharged from the groove 18. In this case, since the concave groove 18 is formed so as to spread downward, it easily flows out and does not accumulate. Therefore,
When the engine is disassembled, the sand particles do not adhere to the mating surface or the inner surface of the cylinder, thereby damaging the surface and deteriorating the sealing performance, thereby preventing engine trouble.

The shape of the downwardly extending concave groove 18 makes it easy to wash out the drainage afterward even if mud may adhere.

FIG. 5 shows another embodiment, in which a concave groove 18a is formed in the protruding portion 16a so that a downward opening cannot be made. This further prevents the muddy water from flying into the concave groove 18a.

In this way, the drain holes of the stud bolts that intersect with the air guide holes always function normally without being blocked by mud, etc., even on rough roads, reducing the risk of rusting the stud bolts and causing damage due to the progress of rust. Eliminates the possibility of

In addition, the grooves forming the drain holes can be implemented without increasing the man-hour by simply setting an enormous part, and are compatible with those already on the market. , Does not impair productivity.

〔The invention's effect〕

As described above, in the engine unit of the motorcycle according to the present invention, the cylinder and the cylinder head, which are inclined substantially horizontally forward, are fastened to the crankcase by the several stud bolts, and the traveling wind is introduced around the ignition plug. In a motorcycle engine unit provided in a cylinder head with a ventilation hole intersecting with a stud bolt at a low position, a drain hole of the stud bolt intersecting with the ventilation hole is formed on a mating surface of a crankcase. It is formed by the concave groove on the cylinder side mating surface that protrudes downward, and the drainage hole functions normally without being blocked by muddy water splashing on the front wheel or the accumulation of intruded earth and sand, This has the effect of reliably preventing stud bolts from being rusted due to the accumulation of water in the insertion holes.

[Brief description of the drawings]

FIG. 1 is a right side view of an engine unit showing an embodiment of the present invention, FIG. 2 is a front view of the engine unit in FIG. 1 as viewed in the direction of arrow A, and FIG. FIG. 4 is a cross-sectional view for explaining the operation of the drain hole of FIG. 1, FIG. 5 is a rear view of a part of a cylinder showing another embodiment of the present invention, and FIG. 6 is a motorcycle. FIG. 7 is an enlarged left side view showing details of the engine unit. DESCRIPTION OF SYMBOLS 1 ... Crank case, 2 ... Cylinder, 3 ... Cylinder head, 6 ... Ignition plug, 10 ... Wind hole, 12,12a ... Stud bolt, 14 ... Bolt insertion hole, 15 ... Crank case Side mating surface, 16 …… Cylinder side mating surface, 16a ……
Overhanging part, 17 ... bulging part, 18, 18a ... Groove, 19 ... Mud.

Claims (2)

(57) [Claims] 1. A cylinder and a cylinder head which are tilted substantially horizontally forward are fastened to a crankcase by several stud bolts, and a wind guide hole for introducing running wind around an ignition plug is provided with a stud bolt at a low position. In a motorcycle engine unit provided in a cylinder head so as to intersect, a cylinder-side mating surface is provided at a lower portion of a cylinder-crankcase mating surface where a stud bolt intersects with a wind guide hole passes. The enlarged part that protrudes below the mating surface of the side is integrally extended from the cylinder,
An engine unit for a motorcycle, wherein a recessed groove reaching a through hole for the stud bolt is formed as a drain hole in a protruding portion of the cylinder side mating surface. 2. The groove width of the groove exposed at the protruding portion is:
2. The motorcycle engine unit according to claim 1, wherein the groove width is set to be larger than a groove width of a portion communicating with the stud bolt insertion hole.