JPH0465230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motorcycle equipped with a swing-type engine unit, and particularly to the structure of an intake system for the engine.

For example, scooter-type motorcycles use an engine unit that integrates the engine and a transmission case that houses the power transmission mechanism, but when the engine cylinder is upright and intake is from the rear, the carburetor It becomes necessary to place it immediately after the cylinder. However, if the carburetor is placed on the centerline of the car body, interference with the rear wheels becomes a problem, so the carburetor is placed on the transmission casing on the rear side of the cylinder, and the carburetor and cylinder are connected at a joint. A possible layout is to connect the two. Considering productivity, it is preferable for this joint to be a die-cast molded product, which has high precision and requires almost no mechanical finishing, but the intake passage inside the joint has a bent shape due to the mutual positional relationship between the cylinder and carburetor. Therefore, depending on this shape, the mold structure becomes complicated, leading to inconveniences such as increased costs.

The present invention was made based on these circumstances, and although the intake passage in the joint is curved, the mold structure for molding the joint does not become complicated, and it reduces costs and improves productivity. An object of the present invention is to provide an air intake device for a motorcycle, which can realize an improvement in the air quality and also secure a sufficient capacity of an air cleaner on a case.

In order to achieve the above object, the present invention includes an engine, a crankcase of the engine that extends rearward from one side, supports a rear wheel at its rear end, and transmits the power of the engine to the rear wheel. In a motorcycle in which an engine unit is constructed by integrating a case housing a power transmission means, and the front end of the engine unit is pivotally supported on a frame, the engine has a cylinder block extending upward from the upper surface of the crankcase. an intake port is provided on the rear surface of the cylinder head connected to the upper end of the cylinder block, and a carburetor connected to the intake port and an air cleaner connected to the carburetor are disposed on the case of the engine unit, The intake port and the carburetor are connected by a die-cast joint curved in an arc shape in plan view, and this joint has an intake passage curved in an arc shape inside, and this intake passage extends over the entire length. It is characterized by being continuously curved with a constant curvature.

An embodiment of the present invention will be described below with reference to the drawings in which the present invention is applied to a scooter type motorcycle.

In FIG. 1, 1 is a frame, 2 is a front fork, 3 is a leg shield, 4 is a seat, and 5 is a cover that covers the bottom of the seat 4, respectively. Above frame 1
The front end of an engine unit 7 is pivotally supported on the rear rising portion 6, and the rear end of the engine unit 7 is suspended from the frame 1 by a shock absorber 8.

This engine unit 7 is shown in FIGS. 2 and 3. That is, 9 is a four-stroke, single-cylinder engine, which is provided with an upright cylinder block 11 and a cylinder head 12 on the upper surface of a crankcase 10. crank case 1
A transmission case 13 is integrally extended rearward on the left side of the transmission case 13, and a rear wheel 14 supported by the rear end of the transmission case 13 is connected to a V-belt continuously variable transmission ( (not shown). The cylinder block 11 and the cylinder head 12 are covered with an air shroud 15, into which outside air drawn by a fan 16 is forcibly blown.

An intake port 17 is provided on the rear surface of the cylinder head 12.
is formed. The intake port 17 is opened just in front of the rear wheel 14, and a carburetor 19 is connected to the intake port 17 via a joint 18. The carburetor 19 is arranged above the transmission case 13, which is offset to the left of the cylinder head 12, as shown in FIG. Therefore, the joint 18 is curved in a substantially arc shape when viewed from above, and connects the carburetor 19 and the intake port 17 at the same height position. This joint 18 is connected to a joint metal fitting 20 and a joint rubber 21 as shown in detail in FIG.
and are fixed to each other by baking. The joint fitting 20 is a die-cast molded product made of aluminum, zinc alloy, or the like, and has an intake passage 22 that is curved in an arc shape and has a circular cross section. This intake passage 22 is continuously curved with a constant curvature r over its entire length, and the cross-sectional shape of this passage 22 is also formed smoothly with a constant draft angle. In such a joint 18, the flange portion 23 of one end of the joint fitting 20 is bolted to the intake port 17, and the open end of the joint rubber 21 is connected to the intake downstream end of the carburetor 19 via a clamp fitting 24. The carburetor 19 and the intake port 17 are connected by this. Further, an upstream end of the intake air of the carburetor 19 is connected to an air cleaner 25 . Air cleaner 25
The air cleaner 25 is arranged above the transmission case 13 together with the carburetor 19, and since the carburetor 19 is located at a high position corresponding to the cylinder head 12, the air cleaner 25 extends vertically above the transmission case 13. There is.

According to such a configuration, the joint fitting 20
Since it is a die-cast molded product of aluminum or the like, the dimensional accuracy of each part is high, and post-processing such as mechanical finishing is almost unnecessary, making it suitable for mass production.
Moreover, in this case, the intake passage 22 inside the joint fitting 20 is continuously curved with a constant curvature r over the entire length, so when the mold inside the intake passage 22 is removed after die-casting, this mold It is only necessary to relatively pull out the mold and the joint fitting 20 along the curved direction of the intake passage 22, and the mold and the joint fitting 20 can be separated with a simple operation. Therefore, even though the intake passage 22 is curved, there is no need to use a complicated split mold structure, and it is possible to improve productivity and reduce costs, and to fully enjoy the benefits of die-casting. It can be used for

Further, if the intake passage 22 has the shape as described above,
Since there is no stepped portion that would cause a sudden change in the flow direction of the intake air or impede the flow, there is an advantage that the intake resistance is extremely small and the intake efficiency is improved.

Further, according to the above configuration, the cylinder head 12
The joint 18 connected to the intake port 17 of the carburetor 19 is curved in an arc shape when viewed from above.
is provided at a high position away from the upper surface of the transmission case 13. Therefore, the distance from the connecting part of the carburetor 19 and the air cleaner 25 to the top surface of the transmission case 13 becomes longer, so the air cleaner 25 can be made into a vertically elongated shape, which saves space in the limited space around the engine unit 7. Inside, sufficient capacity can be secured.

At the same time, by arranging the carburetor 19 and the air cleaner 25 on the transmission case 13 by bending the joint 18 into an arc shape, these carburetors 19 and 25 are arranged on the transmission case 13.
Also, the air cleaner 25 does not interfere with the rear wheel 14. Therefore, the rear wheels 14 can be placed closer to the engine 9, and the wheelbase can be shortened accordingly.

According to the present invention described in detail above, when the mold in the intake passage is taken out after molding the joint, it is sufficient to simply shift the mold and the joint relative to each other along the curved direction of the intake passage. can be easily separated. Therefore, even though the intake passage is curved, there is no need for a complicated mold structure, and productivity can be improved and costs can be reduced.

In addition, since the joint connected to the intake port of the cylinder head is curved in an arc shape when viewed from above, the carburetor is installed at a high position relative to the engine unit case, and the carburetor and air cleaner are connected to each other. The distance from the connection part to the top surface of the case becomes longer. Therefore, the air cleaner can be made vertically long, which has the advantage of ensuring a sufficient capacity of the air cleaner within the limited space around the engine unit.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1 is a side view of a motorcycle, Fig. 2 is a side view of an engine unit, Fig. 3 is a plan view of the engine unit, and Fig. 4 is a side view of a motorcycle.
The figure is a cross-sectional view of the joint, and Figure 5 is V- in Figure 4.
It is a sectional view along the V line. 1... Frame, 7... Engine unit, 9
...Engine, 10...Crankcase, 11...
...Cylinder block, 12...Cylinder head,
13... Case (transmission case), 14... Rear wheel,
17...Intake port, 19...Carburetor, 22...Intake passage, 25...Air cleaner.

Claims (1)

[Scope of Claims] 1. An engine, which extends rearward from one side of the engine's crankcase, supports a rear wheel at its rear end, and houses a power transmission means for transmitting the power of the engine to the rear wheel. In a motorcycle in which the case is integrated to form an engine unit, and the front end of the engine unit is pivoted to the frame, the engine has a cylinder block extending upward from the upper surface of the crankcase, and the engine unit has a cylinder block extending upward from the upper surface of the crankcase. An intake port is provided on the rear surface of the cylinder head connected to the upper end, and a carburetor connected to this intake port and an air cleaner connected to this carburetor are arranged on the case of the engine unit, and the intake port and carburetor are connected to each other. The joints are connected by a die-cast joint curved in an arc shape in plan view, and this joint has an intake passage curved in an arc shape inside, and this intake passage is continuous at a constant curvature over the entire length. An intake device for a motorcycle characterized by being curved.