JPH0275753A - Small snow mobile - Google Patents

Abstract

PURPOSE:To prevent the increase of the size of a crank case by a method wherein, in a crank case, an intake air passage is opened in a manner to be positioned further rearward from a rear cylinder and a carburetor is connected to the intake air passage, and a primary shaft is situated below the intake air passage. CONSTITUTION:A 2-cycle water-cooled type V-shape 4-cylinder engine 10 contained in an engine room 6 has a pair of protruding cylinders 12 positioned in the front of a crank case 10 and laid approximately horizontally toward the front, and provided on its upper surface with a pair of protruding rear cylinders 13 on both side standing approximately upright. In this case, An intake air passage 21, individually connected to four crank chambers 19, is formed to the rear part of an upper case 11a with which a crank case 11 is formed. The intake air passage 21 is extended rearwardly obliquely upwardly in a position further in the rear from the rear cylinder 13, and a carburetor 23 is connected to the rear end opening part of the intake air passage 21. An expansion part 30 protruded downwardly and situated further in a rear than a crank shaft 17 is integrally protruded from a lower case 11b of the crank case 11, and a primary shaft 32 is pivotally supported internally of the expansion part 30.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a small snowmobile equipped with a V-type two-stroke engine.

[Conventional technology]

The mainstream engines for small snowmobiles are two-stroke engines, which have a simple structure and are easy to start in cold weather. As this small snowmobile has extremely large changes in running resistance and requires continuous gear changes, engine power is transmitted to the truck via a belt-type automatic transmission. The machine's drive sheave was attached directly to the end of the engine's crankshaft.

However, with this configuration, the crankshaft is bent by the tension of the belt, which requires a crankshaft with high rigidity, and the load burden on the bearing that supports the crankshaft increases. was there. "Refer to Japanese Utility Model Application Publication No. 49-39124." Therefore, as an improvement measure, the present applicant arranged a primary shaft driven by the crankshaft inside the crankcase, and used this primary shaft to drive the belt-type automatic transmission. I'm considering installing a sheave.

On the other hand, recently there has been a desire to increase performance by increasing the number of cylinders in the engine in order to improve running performance in fresh or deep snow and to enable more comfortable driving. In this case, if a parallel multi-cylinder engine is used in which multiple cylinders are arranged in the axial direction of the crankshaft, the width of the cylinders will expand in the left-right direction of the vehicle body, and there is a risk that it will not be possible to accommodate them in the narrow engine room. It is being considered to adopt a ■-shaped multi-cylinder engine in which the cylinders are arranged in a V-shape along the longitudinal direction of the vehicle body.

[Problem to be solved by the invention]

However, in this V-type multi-cylinder engine, the pair of cylinders protrudes separately in the longitudinal direction of the vehicle body, so it is difficult to open the intake passages in one direction like in a parallel multi-cylinder engine. The series of carburetors would be placed independently in an open space around each cylinder. For this reason, the space around the cylinder is occupied by the carburetor and the air cleaner connected to it, which imposes various restrictions on the engine configuration and layout. , the primary shaft would have to be moved to a position far behind the crankshaft.

Therefore, the total length of the engine becomes longer,
This necessitates shifting the engine mounting position to the front, which poses a problem in that the front and rear weight distribution of the vehicle becomes unbalanced.

The present invention was made based on the above circumstances, and an object of the present invention is to provide a small snowmobile in which the primary shaft can be arranged without significantly shifting the mounting position of the engine, and which can maintain a good front-rear weight balance of the vehicle body. do.

[Means to solve the problem]

Therefore, in the present invention, a two-stroke engine with a front cylinder and a rear cylinder arranged in a V-shape with a predetermined included angle in the longitudinal direction of the car body is housed in the engine room at the front of the car body. , inside the crankcase of this engine,
A belt-type automatic transmission has a single crankshaft and a primary shaft driven by power transmitted from the crankshaft, which is placed horizontally along the left and right sides of the vehicle body, and transmits engine power to the truck through this primary shaft. Assuming a small snowmobile equipped with a drive sheave, an intake passage is opened in the crankcase of the engine, located behind the rear cylinder, and connected to the front cylinder and the rear cylinder individually, and these intake passages are The main shaft is characterized in that the carburetors are connected to each other, and the primary shaft is disposed below the intake passage.

[Effect]

According to this configuration, all the carburetors connected to the front cylinder and the rear cylinder can be arranged centrally behind the rear cylinder, so a large space can be secured below the intake passage connected to the carburetor. The primary axis can be placed here easily.

Therefore, since the primary shaft is located immediately after the crankshaft, it is possible to prevent the crankcase from increasing in size, and it is possible to mount the primary shaft without significantly shifting the engine mounting position forward.

〔Example〕

The present invention will be explained below based on an embodiment shown in the drawings.

Reference numeral I in FIG. 3 is a frame serving as a vehicle body, and this frame l includes a tunnel-shaped main body portion 3 that covers the truck 2;
It is comprised of a front bottom part 4 called a bottom taber that continues to the front end of this main body part 3. The front bottom portion 4 is covered with a shroud 5, and an engine room 6 is formed between the shroud 5 and the front bottom portion 4. As shown in FIG. 1, the engine room 6 has a tapered shape in which the vertical dimension gradually decreases as it moves forward.

A seat 7 is installed on the main body 3 of the frame 1, and strut-shaped suspension devices 9 for supporting steering skis 8 are provided on both left and right sides of the front bottom 4.

By the way, as shown in FIG. 1, a two-stroke water-cooled V-type four-cylinder engine IO is accommodated in the engine room 6. The crankcase 11 of this engine 10 is divided into two parts, an upper case lla and a lower case llb.
A pair of left and right front cylinders 12 extending forward and lying substantially horizontally are provided on the front surface of the crankcase IO. Furthermore, a pair of left and right rear cylinders 13 that stand up substantially vertically are protruded from the upper surface of the crankcase 11.
These front cylinder 12 and rear cylinder 13 are arranged in a substantially V shape with a predetermined included angle in the longitudinal direction of the vehicle body with respect to the crankcase 11.

Each cylinder 14 of the front cylinder 12 and the rear cylinder 13
Pistons 15 are housed inside, and these pistons 15 are connected to one crankshaft 17 via a connecting rod 1B.
is connected to. The crankshaft 17 is supported by bearings 18 on the base surfaces of the upper case Ila and the lower case Ilb, and is placed horizontally along the left-right direction of the vehicle body.

As shown in FIG. 2, the inside of the crankcase 11 is divided into four crank chambers 19 corresponding to the number of cylinders.

These crank chambers 19 are arranged in parallel in the axial direction of the crankshaft 17, and the crank web 17a of the crankshaft 17 is housed in each crank chamber 19, and these crank chambers 19 are connected to each cylinder via a scavenging passage 20. 14 combustion chambers 14a.

At the rear end of the upper case 1laO constituting the crankcase 11, intake passages 21 are provided which are connected to the four crank chambers 19 individually. The intake passages 21 extend rearward and diagonally upward behind the rear cylinder 13, and are arranged in parallel along the axial direction of the crankshaft 17. A vaporizer 23 is connected. For this reason,
The carburetors 23 are arranged in a row in the axial direction of the crankshaft 17 behind the rear cylinder 13, and are arranged in parallel in the axial direction of the crankshaft 17.
The air cleaner 24 is connected to a single air cleaner 24 located at the rear of the air cleaner 24.

Note that the intake passage 21 is connected to the crank chamber 1 from the carburetor 23 side.
A reed valve 25 is provided that allows intake air to flow only towards the air intake.

In addition, the upper surface of the front cylinder 12 and the rear cylinder 13
An exhaust passage 2B that is opened and closed by a piston 15 is opened at the front surface of the exhaust passage 2B. The exhaust pipe 27 connected to the exhaust passage 2B is led toward the front of the engine 1O, and a large diameter chamber part 27a in the middle is housed in a space at the front of the engine room 6. .

On the other hand, in the lower case llb of the crankcase 11, there is a bulge 3 that protrudes downward at the rear of the crankshaft 17.
0 is integrally provided in a protruding manner. The bulge 30 is located below the intake passage 21, and a primary shaft 32 is pivotally supported within the bulge 30 via a bearing 31. The primer shaft 32 is parallel to the crankshaft 17, and a driven gear 33 is rotatably supported on its outer periphery. The driven gear 3 meshes with a drive gear 34 that rotates integrally with the rank shaft 17, and is connected to the primary shaft 32 via a buffer mechanism 35. The buffer mechanism 35 includes a first sleeve 36 that is rotatable with respect to the primary shaft 32, and a second sleeve 37 that is spline-engaged to the outer periphery of the primary shaft 32. The driven gear 33 is spline engaged.

Cam surfaces 3 are provided on mutually opposing surfaces of both sleeves 38 and 37.
8 are formed, and these cam surfaces 38 are pressed against each other by a disc spring 39. Therefore, the first sleeve 36 and the second sleeve 37 are coupled by the pressure contact of the cam surface 38, and the rotation of the driven gear 33 is transmitted to the primary shaft 32, but conversely, a large impact is generated from the primary shaft 32 side. If the force is applied, slippage occurs between the cam surfaces 38 and the disc spring 39 is compressed, thereby absorbing the impact transmitted to the driven gear 33 and eventually to the crankshaft 17.

Note that the meshing portion between the driving gear 34 and the driven gear 33 is as follows:
It is covered by a crankcase cover 40.

Further, a first boss portion 42 projecting downward is integrally provided at the lower front end of the lower case llb of the crankcase 11, and this first boss portion 42 is connected to the engine provided in the front bottom portion 4. Anti-vibration rubber 43 on subframe 41 for mounting
Supported through. At the same time, a second boss part 44 that projects rearward is integrally provided on the bulge part 30 that supports the primary shaft 32, and an engine bracket 45 bolted to this second boss part 44 is provided. , is supported by the subframe 4I via a vibration isolating rubber 43.

Therefore, the engine 10 of this embodiment is supported in a floating state with vibration isolation with respect to the frame I at a plurality of locations in the front and rear of the crankcase 11.

The engine power taken out to the primary shaft 32 of the engine IO is transferred to the belt-type automatic transmission 50 and the secondary reduction gear 5.
1 to the drive sprocket 52 of the track 2. To explain this power transmission line,
A driven shaft 54 is disposed in the engine room 6 and is located behind the engine IO and parallel to the primary shaft 32. The driven shaft 54 and the primary shaft 32 are connected to each other via a belt type automatic transmission 50. It is linked. As is conventionally known, the belt type automatic transmission 50 includes a drive sheave 55 attached to one end of the primary shaft 32 and a driven shaft 5.
An endless V-belt 57 is wound between the driven sheave 56 attached to one end of the sheave 55, 56
By changing the diameter of the V-belt 57 that is wound around the V-belt 57, the speed ratio can be changed continuously and steplessly.

Further, the secondary reduction gear 51 is constructed by winding an endless chain 59 between sprockets 58 attached to the driven To 54 and the drive shaft 53, respectively.
Engine power is transmitted to the truck 2 via the belt type automatic transmission 50.

Incidentally, an alternating current generator 60 and a recoil starter 61 are provided on the crankshaft I7 on the opposite side from the drive sheave 55. The housing 62 of the alternator 60 includes:
A starting gear 64 driven by the starter motor 63 is provided, and in the case of this embodiment, the starter motor 63
is arranged below the crankcase 11.

According to such a configuration, the upper case lla of the crankcase 11 is located behind the rear cylinder 13,
Each cylinder 14 of the front cylinder 12 and the rear cylinder 13
Since the intake passage 21 connected to the front cylinder I3 is opened, all four carburetors 23 connected to the front cylinder 12 and the rear cylinder 13 can be arranged in a line behind the rear cylinder I3. For this reason, these intake passages 21
A wide space can be secured below the rear of the crankshaft 17, and the primary shaft 32 can be arranged easily using this space.

Therefore, the primary shaft 32 is located immediately after the crankshaft 17, and it is possible to prevent the crankcase 11 from increasing in size. Therefore, the primary shaft 32 can be mounted without shifting the mounting position of the engine IO forward, and the A good weight balance can be maintained.

Further, since a space is opened below the crankcase 11, this space can also be used as an installation space for the starter motor B3, and the limited space in the engine room 6 can be effectively utilized.

Further, at the lower rear end of the crankcase 11, a bulging portion 3o that supports the primary shaft 32 protrudes downward.
The boss portion 44 can be formed on the crankcase II, and the position of the boss portion 44 can be easily set.

In the above embodiment, the front cylinder is laid almost horizontally, but the present invention is not limited to this. For example, the front cylinder is made to have a small forward inclination angle to protrude obliquely upward, and the rear cylinder is may be arranged so as to be tilted backward with respect to the direction of travel.

〔Effect of the invention〕

According to the present invention described in detail above, a large space can be secured at the rear lower part of the crankshaft, so the primary shaft can be arranged easily using this space.

Therefore, the primary shaft can be installed without moving the engine mounting position forward, and a good front-rear weight balance of the vehicle body can be maintained.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a sectional view showing the position of the engine in the engine room, FIG. 2 is a sectional view of the engine, and FIG. 3 is a side view of a small snowmobile. ■...Vehicle body (frame), 2...Truck, 6...
・Engine room, 10... V-type 2-stroke engine, 12... Front cylinder, 13... Rear cylinder,
17... Crankshaft, 21... Intake passage, 23...
・Carburizer, 32...Primary tube, 50...Belt type automatic transmission, 55...Drive sheave. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Scope of Claims] A V-shaped two-stroke engine is housed in an engine room at the front of the vehicle, in which a front cylinder and a rear cylinder are arranged in a V-shape with a predetermined included angle in the longitudinal direction of the vehicle, Inside the crankcase of this engine, a single crankshaft and a primary shaft driven by power transmission from the crankshaft are placed horizontally along the left and right direction of the vehicle body, and the power of the engine is tracked to this primary shaft. A small snowmobile equipped with a drive sheave for a belt-type automatic transmission that transmits power to the engine, and in the crankcase of the engine, there is an intake passage located behind the rear cylinder and connected to the front cylinder and the rear cylinder separately. A small snowmobile characterized in that the intake passages are opened, a carburetor is connected to each of the intake passages, and the primary shaft is disposed below the intake passage.