JPH0541474B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear wheel suspension system for a motorcycle in which a rear wheel is held movably up and down by a rear arm whose front end is pivoted to a frame.

(Background of the invention) The rear arm is formed into a substantially triangular chevron shape when viewed from the side,
It is known that the apex of this chevron is elastically supported by a single cushion unit (for example, the
51-40336). According to this configuration, the rigidity of the rear arm can be increased, and the steering stability can be improved. In addition, unlike conventional systems, two cushion units are not used separately, so there is no runout of the rear wheel rotating surface due to uneven characteristics of the cushion units, and it is possible to improve steering stability as well. This is the result.

Here, in the conventional device described above, one tank rail (main tube) extending diagonally downward and rearward from the steering head pipe is shaped like a pipe, and the cushion unit is inserted into this tank rail from the rear. The front end of the syon unit was supported pivotably. For this reason, there were problems in that the maintainability of the cushion unit was deteriorated, and the cooling performance of the cushion unit was also deteriorated.

It is also possible to arrange the cushion unit below the tank rail, but in this case the cushion unit will be close to the engine, and due to the relationship with the engine located below, it is difficult to There was a problem with the degree of freedom being restricted.

Furthermore, a structure in which the front end of the cushioning unit is pivotally supported at the rear end of the tank rail is also considered, but in this case, a sufficiently long cushioning unit cannot be used, and there is a problem that the vertical stroke of the rear wheel is restricted. Yes.

On the other hand, in the case of a diamond-shaped frame that uses the engine as part of the frame's strength member,
Holds the engine cylinder head to the frame. In order to prevent the engine from swinging from side to side, tank rails were traditionally separated into left and right sides. This also posed the problem of increasing the width of the vehicle body.

(Objective of the Invention) The present invention has been made in view of the above circumstances, and provides extremely good maintainability of the cushion unit, good cooling performance of the cushion unit, and the adoption of a sufficiently long cushion unit. The object of the present invention is to provide a rear wheel suspension system for a motorcycle, which has fewer restrictions on the engine mounting layout, and which allows the vehicle body width to be reduced despite the diamond-shaped frame structure.

(Structure of the Invention) According to the present invention, the object is to hold the rear wheel at the rear end of the rear arm, while elastically urging the rear arm downward by a cushion unit. The suspension system has a monokotsukku structure that extends almost along the straight line connecting the steering head pipe and the rear end of the rear arm, and a diamond-shaped frame that is vertically wide and hollow, with the rear part branching out to the left and right. and a bracket extending downward to pivotally support the front end of the rear arm, and holding the cylinder head of the engine on the frame and the rear part of the engine on the bracket, respectively, and connecting the front part of the cushion unit between the branch parts. This is achieved by a rear wheel suspension system for a motorcycle, characterized in that the cushion unit is accommodated in an upper open recess and the front end of the cushion unit is pivotally supported within the recess.

(Example) Fig. 1 is a partially omitted side view of a motorcycle equipped with an engine according to the present invention, Figs. is a plan view of a motorcycle with some parts omitted,
Further, FIG. 5 is an arrow A in FIG. 1 for indicating the relative positions of the front and rear cylinders.

In these figures, numeral 1 is a frame,
This frame 1 is formed by welding the peripheral edges of a pair of left and right members in a monadic shape, and a steering head pipe 2 is welded to the front end of the frame 1. That is, this frame 1 has a monokotsuk structure with a hollow interior. Please note that engine 2 is mentioned later.
The upper parts of the cylinders 21 and 22 of the engine 2, that is, the cylinder heads, are held in the frame 1, and the engine 2
0 constitutes a known diamond-shaped structure which becomes part of the strength member of the frame 1. A front fork (not shown) that supports a front wheel is attached to the steering head pipe 2. frame 1
extends obliquely downward and rearward from the steering head pipe 2 substantially along a straight line passing near the rear end of the rear arm 5, which will be described later. As described above, this frame 1 is shaped like a monarch, and is wide vertically and hollow. The rear part of the frame 1 is branched into left and right parts, and a recess 9 (FIG. 4) is formed between the branch parts.

Also, the rear part of this frame 1 is bent downward,
An opening 3 is formed here. An air cleaner (not shown) is attached to the opening 3, and the atmosphere flows into the frame 1 through the air cleaner and the opening 3. That is, the inside of the frame 1 serves as an intake passage that guides air from the air cleaner to the carburetors 26 and 27 described later. A pair of left and right brackets 4 are fixed to the rear end of the frame 1 (only the left side is shown in FIG. 1), and the rear end of an engine 20, which will be described later, is fixed to the brackets 4. Reference numeral 5 denotes a rear arm having a substantially triangular shape in side view.The front end of this rear arm 5 is pivotally supported by the bracket 4, and the rear wheel 6 is pivotally supported at its rear end. Note that the left side bottom side 5a of this rear arm 5 is formed into a pipe shape, and its rear end is connected to the rear hub case 7. A speed reducer consisting of a bevel gear is housed within the hub case 7, while a propeller shaft is inserted through the bottom side 5a, forming a known shaft drive type rear wheel drive mechanism. rear arm 5
The rear end of the cushion unit 8 is pivoted to the apex 5b of the cushion unit 8, and the front end of the cushion unit 8 is
It is pivoted within a recess 9 (see FIG. 4) formed in the frame 1.

As a result, the cushion unit 8 is disposed almost directly from the steering head pipe 2 to the vicinity of the rear end of the rear arm 5, that is, the vicinity of the axle of the rear wheel 6. Since the recess 9 that accommodates the cushion unit 8 is wide open upward and rearward, the cushion unit 8 can be easily maintained through this opening, and the cushion unit 8 can be cooled well.

20 is an overhead camshaft type air-cooled two-cylinder engine, and each cylinder 21, 22 of this engine 20 is inclined in the front-rear direction. In this engine 20, the upper part of the front cylinder 21 is connected to the frame 1 by a bracket 23, and the upper part of the rear cylinder 22 is connected to the frame 1 by a bracket 24 via an elastic member (not shown).
The rear end of the crankcase 25 of this engine 20 is fixed to the bracket 4 as described above. Intake ports are formed on opposing surfaces of each cylinder 21 and 22, and carburetors 26 and 27 located in spaces sandwiched between each cylinder 21 and 22 are connected to these intake ports. , 27 is further upstream of the frame 1
It is connected to the. Therefore, the intake air entering the frame 1 through the opening 3 passes through the frame 1 and is guided to the carburetors 26 and 27 of the respective cylinders 21 and 22.
Reference numerals 28 and 29 are exhaust pipes connected to the front and rear sides of each cylinder 21 and 22.

In Fig. 2, 40 is the crankshaft, 41, 42
4 is a main shaft and a subshaft forming a transmission, 43 is a damper shaft, and 44 is an output shaft. The rotation of the crankshaft 40 is transmitted to the main shaft 41 via a known wet multi-disc clutch 45 attached to the right end of the main shaft 41, and the rotation of the main shaft 41 is transmitted to the main shaft 41 through a group of transmission gears provided on the main shaft 41 and the counter shaft 42. 46 and is transmitted to the subshaft 42. The rotation of the subshaft 42 is caused by the damper shaft 4
Damper shaft 43 via damper 47 disposed on 3
Further, the rotation of the damper shaft 43 is transmitted to the output shaft 4 disposed in the front-rear direction via a bevel gear 48.
4 can be conveyed. A rear end portion of the output shaft 44 projects toward the rear of the crankcase 25, and the propeller shaft (not shown) is connected to this projecting portion via a universal joint.

50a and 51a are the pistons and connecting rods of the front cylinder 21, 50b and 51b are the pistons and connecting rods of the rear cylinder 22, and as is clear from FIGS. 2 and 3, the large end of the connecting rod 51a of the front cylinder 21,
The large end of the connecting rod 51b of the rear cylinder 22 is both pivotally connected to the crank pin 52, and the connecting rod 51a is adjacent to the right side of the connecting rod 51b. As a result, the front cylinder 21 is offset to the right, and the rear cylinder 22 is offset to the left.

In FIG. 2, 53a and 54a are the front cylinders 21
An overhead camshaft 55a is laterally supported on the cylinder head 54a. A cylinder head 5 is provided on the right side of the front cylinder 21, that is, on the side in the offset direction.
4a, a chain passage 56a is formed to communicate within the cylinder block 53a. 57a
is a shaft attached to the crankcase 25 so as to be located between the crankshaft 40 and the overhead camshaft 55a, and a sprocket 58 is attached to this shaft 57a.
A gear 59a formed integrally with a is rotatably supported. This gear 59a is the crankshaft 40
It meshes with a gear 60a fixed to. The sprocket 58a is located at the lower part of the chain passage 56a, and the sprocket 6 located at the upper part of the chain passage 56a is located at the right end of the overhead camshaft 55a.
1a is fixed, and these sprockets 58a, 6
A timing chain 62a is routed around 1a. That is, this timing chain 62
A forms an overhead camshaft drive mechanism together with a gear 59a, sprockets 58a and 61a, and the like. Note that this overhead camshaft drive mechanism causes the overhead camshaft 55a to rotate at half the speed of the crankshaft 40,
The opening and closing of intake and exhaust valves (not shown) are controlled.

Reference numeral 65a indicates a spark plug, and reference numeral 66a indicates a cooling air passage that is formed below the overhead camshaft 55a and opens on the left side of the cylinder 21, that is, the side in the anti-offset direction.The spark plug 65a is an opening on the left side of this cooling air passage 66a. It is attached so as to protrude obliquely from the front cylinder 21 to the left slope of the front cylinder 21. This spark plug 65
A plug cord 68a is connected to a by a plug cap 67a. (See Figures 1, 4 and 5).

Reference numeral 70a denotes a ventilation passage provided in the cylinder block 53a. is formed.

The rear cylinder 22 is connected to the front cylinder 2 as shown in FIG.
Since it is formed symmetrically with 1, the front cylinder 21
A coefficient b is assigned to a portion corresponding to , and, for example, the overhead camshaft is expressed as 55b, and its description will not be repeated.

The front cylinder 21 is not only offset to the right as described above, but also has a timing chain 62a on its right side, while the rear cylinder 22 is not only offset to the left but also has a timing chain on its left side. 62b is provided.
As a result, the spark plug 65b and plug cap 68b of the rear cylinder 22 are hidden behind the front cylinder 21, as shown in FIG. Similarly, the spark plug 65a and plug cap 68a of the front cylinder 21
is also located inside the left side surface of the rear cylinder 22. Therefore, even if there is an obstacle when moving the vehicle forward, the obstacle will hit the right side of the front cylinder 21 before hitting the spark plug 65b of the rear cylinder 22, the spark plug 65b of the rear cylinder 22, the plug cap, etc. 67b,
and plug cord 68b are effectively protected.
Furthermore, since the front cylinder 21 is offset to the right, the position of the spark plug 65a of the front cylinder 21 will be closer to the frame 1 side (center side of the vehicle body) as is clear from FIG. Frame 1 of cap 67a and plug cord 68a
The amount of protrusion to the left decreases. Therefore, the spark plug 65a, plug cap 67a, and plug cord 68a of the front cylinder are also less likely to hit obstacles.

In addition, since the front cylinder 21 is provided with the ventilation passage 70a, the running wind passes through this ventilation passage 70a to the rear cylinder 21.
is guided toward the spark plug 65b. Therefore, the cooling performance of the rear cylinder 22 is improved.

Furthermore, in this embodiment, the rear cylinder 22 is also provided with a ventilation passage 7.
0b, the traveling wind also hits the vicinity of the exhaust pipe 29 of the rear cylinder 22, making it possible to further improve cooling performance.

In this embodiment, the overhead camshaft drive mechanism is constructed using a timing chain, but it may also be constructed using a toothed belt, a bevel gear, or a plurality of spur gears connected together.

(Effects of the Invention) As described above, the present invention provides a frame with a monocot structure extending almost along a straight line from the steering head pipe to the vicinity of the rear end of the rear arm,
The rear part of this frame is made into a vertically wide and hollow branch part, and a recessed part which is open at the top is formed between the branch parts. The front part of the cushion unit is accommodated in this recess, and the front end of the cushion unit is pivotally supported within this recess, so even if the frame is widened vertically, the cushion unit can be maintained, improving maintainability. This improves the cooling performance of the cushion unit. Furthermore, if the branching portion of the frame is made sufficiently long, it is possible to use a sufficiently long cushion unit, and the vertical stroke of the rear wheel is not limited by the length of the cushion unit.

The frame also has a monokotsukku structure, making it resistant to twisting. For this reason, if a diamond-shaped frame structure is used in which the cylinder head of the engine is held in this frame, and the rear part of the engine is held in a bracket that descends from the rear of the frame, and the engine itself is used as a strength member of the frame, the frame width may become too large. The engine can be mounted so as to sufficiently suppress left-right twisting of the engine without causing any twisting. Therefore, it is possible to reduce the width of the vehicle body and improve seating comfort when riding.

[Brief explanation of the drawing]

Fig. 1 is a partially omitted side view of a motorcycle equipped with an engine according to the present invention, Figs. 2 and 3 are cross-sectional views taken along the - line and - line, and Fig. 4 is a partially omitted side view of the motorcycle. An omitted plan view of a motorcycle,
Further, FIG. 5 is an arrow A in FIG. 1 for indicating the relative positions of the front and rear cylinders. 20... Engine, 21... Front cylinder, 22... Rear cylinder, 62a, 62b... Timing chain, 65
a, 65b... Spark plug, 70a, 70b... Ventilation path.

Claims (1)

[Scope of Claims] 1. A rear wheel suspension system for a motorcycle in which a rear wheel is held at the rear end of a rear arm, and the rear arm is elastically biased downward by a cushion unit, comprising: a steering head pipe; A vertically wide and hollow diamond-shaped frame with a monokotsukku structure that extends almost directly between the rear end of the frame and the rear end of the rear arm, and the front end of the rear arm that extends downward from the rear end of the frame. and a bracket for pivotally supporting the cylinder head of the engine to the frame and the rear part of the engine to the bracket, respectively, while the front part of the cushion unit is placed in a recess between the branch parts that is open at the top. A rear wheel suspension system for a motorcycle, characterized in that the front end of the cushion unit is accommodated in the recess and is pivotally supported within the recess.