JPH10167156A - Engine arrangement structure for scooter type motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine arrangement structure for a scooter type motorcycle which can ensure motion performance and a bank angle. SOLUTION: This structure has a pair of right and left upper down tubes 20 extending back downward from a head pipe 11 and bending backward at the middle and extending near the front lower end 17a of a saddle seat 17, and a pair of right and left lower down tubes 21 spaced downward the upper down tubes 20 and extending downward from the head pipe 11 and bending backward at the middle and extending near the front support shaft 23 of a rear arm 22. Most part of an engine 33 and a start clutch 45 is received in a space surrounded by four down tubes and is positioned between the front end 1a of the seat 17 and the front end 26a of a low floor type tread 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scooter-type motorcycle having a low-floor tread plate at a lower front portion of a seat, and more particularly to an engine arrangement structure.

[0002]

2. Description of the Related Art The engine arrangement structure of a scooter type motorcycle mainly employs a unit swing system of a rear arrangement type as shown in FIG. 4, in which a power unit 3 in which an engine 1 and a transmission case 2 are integrated is provided with a front end. The power unit 3 and a rear wheel 5 mounted on the rear end of the power unit 3 are integrally and elastically supported by a rear cushion 6 via a support shaft 4.

[0005] As another type, there is a front lower arrangement type as shown in FIG. 5, in which an engine 1 and a transmission 10 such as a transmission rod are disposed below a down tube 8 and a tread plate 9.

Japanese Patent Application Laid-Open No. 61-81884 discloses a prior art in which the above prior arts are described. Scooter type motorcycles of the above types are described in FIGS. 1 and 3 of the publication. I have.

[0005]

In the rear swing type unit swing system shown in FIG. 4, the center of gravity of the vehicle is shifted toward the rear wheels, so that the ground contact load of the front wheels 7 is reduced and the unsprung load of the rear cushion 6 is reduced. Turning performance and high-speed running performance cannot be expected. Conventionally, scooters with small displacement that run in low and medium speed regions are the mainstream, and in these scooters, more importance is placed on cost and foot placement of the treads than on the above-described kinetic performance. However, in recent years, with the large displacement and high output of the scooter, various kinds of kinetic performance such as turning performance and high-speed running performance have been required, and it is difficult to sufficiently cope with the structure as shown in FIG. Situation.

On the other hand, in the front lower arrangement type shown in FIG. 5, the center of gravity is closer to the center than in the rear arrangement type, but the engine body is disposed below the lower down tube 8 and the tread plate 9. As a result, the center of gravity becomes closer to the front and is greatly shifted downward, so that a significant improvement in exercise performance cannot be expected. In addition, the minimum ground clearance is reduced, the bank angle is restricted, and the turning performance and the like are also reduced in this respect.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a scooter-type motorcycle engine arrangement structure which can ensure sufficient exercise performance and bank angle, and can sufficiently cope with large displacement and high output. .

[0008]

In order to achieve the above-mentioned object, the invention according to claim 1 of the present application is to extend rearward and downward from a head pipe and bend rearward on the way to near a front lower end portion of a seat-type seat. A pair of left and right upper down tubes extending, and a lower down tube arranged at a distance below the upper down tube, the lower down tube extending rearward and downward from the head pipe and being bent rearward on the way. In a scooter-type motorcycle having a pair of left and right lower down tubes extending to the vicinity of a front end support shaft of a rear arm, and a low floor type tread on both sides of the lower down tube, most of the engine and the starting clutch are as described above. It is stored in the space surrounded by the four down tubes and is located between the front end of the seat and the front end of the low floor tread in the front-rear direction. It is characterized in that.

According to a second aspect of the present invention, in the scooter type motorcycle engine arrangement structure according to the first aspect, a speed change drive side which is parallel to the engine crankshaft and operatively connected to the crankshaft via an appropriate transmission mechanism. The rotating shaft is disposed in a space surrounded by the four down tubes, and a driving clutch of a starting clutch and a V-belt type transmission is provided on the driving-side rotating shaft.

[0010]

FIG. 1 is a left side view of a scooter type motorcycle to which the present invention is applied. A front end head pipe 11 of a vehicle body frame is rotatable by a front fork 13 on which a front wheel 12 is suspended. The front fork 13 is supported and a handlebar 15 is fixed to an upper end of the front fork 13.

The body frame includes an upper down tube 20.
And a pair of lower down tubes 21 on the left and right sides.
The lower down tube 21 extends obliquely rearward and downward from the upper end portion of the seat 17, curves rearward on the way, and extends near the front lower end portion 17 a of the seat 17. Are arranged at an interval from each other, extend obliquely downward and rearward from the lower end of the head pipe 11, extend substantially horizontally rearward on the way, and extend to the vicinity of the front end support shaft 23 of the swing type rear arm 22. It extends rearward and upward.

The body frame has a main cover 25 covering the upper side and both left and right sides thereof and a front cover 29 covering the front side.
The main cover 2 is attached.
A pair of left and right low-floor treads 26 are provided on both left and right sides of 5 so as to substantially extend along the lower horizontal portion of the lower down tube 21. The tread plate 26 is provided with the swing type rear arm 2.
The support shaft 23 extends substantially horizontally forward from the vicinity of the second support shaft 23, and is slightly upwardly inclined from the middle thereof, and a front end 26 a thereof is connected to the front cover 29.

FIG. 3 is a left side view of a main part shown with a cover removed. The engine 33 includes upper and lower down tubes 20 and 21.
In order to fit in the narrow space formed by the above, the cylinder center line C is arranged in a forward tilting posture close to a substantially horizontal state,
A pair of left and right mounting brackets 32 are formed on the upper and lower portions of the rear portion of the engine and on the upper portion of the front portion, respectively, and each mounting bracket 32 is attached to an engine mount 28 formed on each cross member 27 of the frame via an elastic member or the like. Attached. The engine 33 integrally includes a cylinder head 35, a cylinder block 34, and a crankcase 36 in order from the front end, and the crankcase 36 integrally includes a shaft case portion 36a that projects rearward. 3
8 is a carburetor, 39 is a radiator, and 40 is an intake air box for intake.

The crankshaft 41 of the engine 33 is located above the lower down tube 21.
Except for the oil pan 42, the overall width in the vertical direction is set between the lower down tube 21 and the upper down tube 20, and the overall longitudinal width of the engine is the front end 17a of the seat 17 and the front end of the tread plate 26. It fits within the width in the front-rear direction with the portion 26a.

The support shaft 23 of the rear arm 22 is fixed between a pair of left and right brackets 54 welded to the lower down tube 21. The front end of the rear arm 22 is rotatably fitted to the support shaft 23. The rear end of the rear arm 22 supports the rear wheel 30 and is suspended by an upper frame via a rear cushion 31 so as to be vertically swingable.

FIG. 2 is a plan view of a main part shown with a cover removed. A pair of upper down tubes 20 on the left and right sides are rearwardly kept at a relatively narrow left and right distance until a position corresponding to the rear end of the engine. , Then spread out into a C shape,
On the other hand, the lower down tube 21 is widened right and left immediately after the head pipe 11 and extends rearward. A rotating shaft 44 parallel to the crankshaft 41 is rotatably supported in the shaft case portion 36a of the crankcase 36 so that the left and right width of the engine 33 is compactly accommodated in the space surrounded by the four down tubes 20 and 21. Then, the centrifugal start clutch 45 and the driving gear thrust generating mechanism 46 are mounted on the rotating shaft 44 in the case 36a, and the driving gear 48 of the V-belt type automatic transmission 51 is mounted outside the case. is there. The rotating shaft 44 and the crankshaft 41 are linked to each other by a primary deceleration transmission mechanism 47 including a pair of sprockets 49 and 50 and a chain 52.

A cylinder shaft 55 is rotatably fitted to the support shaft 23 of the rear arm 22. The cylinder shaft 55 is provided with a driven gear 57 of the V-belt type automatic transmission 51 and a secondary gear. The drive sprocket 58 of the deceleration transmission mechanism 60 is fixed. The driven sheave 57 is linked to the drive sheave 48 by a V-belt 53. Drive sprocket 5
8 is the chain 6 on the driven sprocket 62 of the rear wheel 30.
1 to form a secondary deceleration transmission mechanism 60.

The drive sheave 48 and the driven sheave 57 of the V-belt type automatic transmission 51 are well-known transmissions having variable diameter sheaves. The gear ratio is automatically changed by changing the distance between the sheaves.

[0019]

[Other embodiments]

(1) As a transmission mechanism between the rotary shaft 44 having the centrifugal clutch 45 and the like and the crankshaft 41, a gear transmission mechanism may be provided in addition to a winding transmission mechanism such as a chain.

[0020]

As described above, according to the present invention,
In a space formed between a pair of left and right upper down tubes 20 and a pair of left and right lower down tubes 21 spaced apart below the upper down tubes 20, the engine 33 and Most of the starting clutch 45 is housed and accommodated within the front-rear width between the front end 17a of the seat 17 and the front end 26a of the low-floor tread 26. It is located near the center of gravity substantially at the center, and the unsprung load of the rear cushion 31 can be reduced. In addition, the minimum ground clearance can be kept high, and a large bank angle can be secured. Therefore, the kinetic performance such as turning performance and high-speed running performance is improved, and the engine arrangement is particularly suitable for a scooter-type motorcycle having a large displacement and high output.

(2) Since the four down tubes 20 and 21 substantially surround the entire engine, the four down tubes 20 and 21 serve to cover the engine 33.

(3) According to the second aspect of the invention, a starting clutch or the like is not mounted on the crankshaft 41, but a rotating shaft 44 different from the crankshaft 41 is connected to the crankcase 36 in parallel with the crankshaft 41. Since the starter clutch 45 and the drive adjusting thrust generating mechanism 46 are mounted on the rotating shaft 44, the left and right width of the entire engine can be reduced. Therefore, while the engine is arranged between the four down tubes, the rider can run with his or her feet on the left and right treads without greatly expanding the crotch, and the foot placement can be maintained.

[Brief description of the drawings]

FIG. 1 is a left side view of a scooter type motorcycle to which the present invention is applied.

FIG. 2 is a plan view of a main part of FIG.

FIG. 3 is a left side view of a main part of the same motorcycle as FIG.

FIG. 4 is a side view of a conventional example.

FIG. 5 is a side view of another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Head pipe 17 Seat type seat 20 Upper down tube 21 Lower down tube 22 Swing type rear arm 26 Low floor type tread board 31 Rear cushion 33 Engine 45 Start clutch 48 Drive shedding 51 V belt type automatic transmission

Claims (2)

[Claims] 1. A pair of left and right upper down tubes that extend rearward and downward from a head pipe and bend rearward on the way to extend near a front lower end of a seat, and a space below the upper down tube. A pair of left and right lower down tubes that extend rearward and downward from the head pipe and are bent rearward on the way to extend near the front end support shaft of the rear arm. In a scooter type motorcycle having a low floor type tread on both sides of a lower down tube, an engine and a starting clutch are mostly stored in a space surrounded by the four down tubes, and a front end of a seat is provided. A scooter-type motorcycle engine arrangement structure located between the front and rear widths of the low-floor tread and the front end of the low-floor tread. 2. The engine disposition structure of a scooter type motorcycle according to claim 1, wherein the transmission drive-side rotating shaft parallel to the engine crankshaft and operatively connected to the crankshaft via an appropriate transmission mechanism is provided. An engine arrangement structure for a scooter-type motorcycle, wherein the engine is arranged in a space surrounded by a down tube, and a drive clutch of a start clutch and a V-belt type transmission is provided on a drive-side rotating shaft.