JPS5996426A - Joint for suction or exhaust device in engine - Google Patents

Abstract

PURPOSE:To simplify the shape and facilitate the production by curving a whole length of a gas passage of a joint made by die casting connecting between an engine and a suction or an exhaust device at a fixed curvature. CONSTITUTION:In a joint 18 made by die casting to connect between a cylinder head of an engine and a suction or an exhaust device, a gas passage 22 inside a joint metal fitting 20 is continuously curved at a fixed curvature (r) in its whole length. Therefore, when a mold inside the gas passage 22 is removed after die casting, it is only necessary to draw out the mold along the curved direction of the gas passage 22. This construction permits to facilitate the work and improve the productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a die-cast joint that connects an engine to a carburetor, an exhaust pipe, or a muffler.

For example, scooter-type motorcycles use an engine unit that integrates the engine and a transmission case that houses the power transmission mechanism, but if 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 case on the rear side of the cylinder, and the carburetor and cylinder are connected with a joint. The layout can be considered. Considering productivity, it is preferable for this joint to be a die-cast molded product, which has good precision and hardly requires mechanical finishing.
Since the intake passage in the joint has a bent shape due to the mutual positional relationship between the cylinder and the carburetor, this shape causes problems such as a complicated mold structure and increased costs.

The present invention was made based on these circumstances, and
The purpose is to obtain a joint for intake and exhaust equipment in an engine that can reduce costs and improve productivity without complicating the mold structure even though the gas passage of the joint has a bent shape. .

That is, the joint according to the present invention is characterized in that the internal gas passage is continuously curved with a constant curvature over the entire length.

An embodiment of the present invention will be described below based on 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. The front end of an engine unit 7 is pivotally supported on the upright portion 6 at the rear of the frame 1, and the rear end of the engine unit 2 is suspended from the frame 1 by a shock absorber 8.

This engine unit 7 is shown in FIGS. 2 and 3. The engine 9 is a four-stroke single-cylinder engine, and is provided with an upright cylinder block 11 and a cylinder head 12 on the upper surface of a crankcase 10. A transmission case 13 is integrally provided on the left side of the crankcase 10 and extends rearward.
The rear wheel 14 supported at the rear end is driven by a V-belt continuously variable transmission (not shown) within the transmission case 13.

Note that the cylinder block 11 and cylinder head 12
is covered with an air shroud 15, into which outside air drawn in by a fan 16 is forcibly blown.

An intake port I7 is formed on the rear surface of the cylinder head 12, and a carburetor 19 as an intake device is connected to the intake port 17 via a joint 18 according to the present invention. As shown in FIG. 3, the carburetor 19 is offset to the left side of the cylinder head 12 and disposed on the transmission case 13, so that the joint 18 is curved in a substantially arc shape. As shown in detail in FIG. 4, this joint 18 is composed of a joint metal fitting 20 and a joint rubber 21, both of which are fixed to each other by burning. The joint fitting 20 is a die-cast molded product of aluminum, zinc alloy, etc., 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. Such a joint 18 has a flange portion 2 at one end of the joint fitting 2θ.
3 to the intake port 17, and joint rubber 2
The carburetor 19 and the intake port 17 are connected by connecting the open end of the carburetor 1 to the intake downstream end of the carburetor 19 via a flang fitting 24 .

Note that the intake upstream end of the carburetor 19 is connected to an air cleaner 25, and this air cleaner 25 is also connected to the transmission case 13.
placed above.

According to this configuration, since the joint fitting 20 is a die-cast molded product of aluminum or the like, the dimensional accuracy of each part is high, post-processing such as mechanical finishing is hardly required, and it is suitable for mass production. Moreover, in this case, the intake passage 22 inside the joint fitting 20 has a constant curvature r over the entire length.
Since the mold is continuously curved, when removing the mold inside the intake passage 22 after die-casting, simply pull out this mold and the joint fitting 20 relatively along the curved direction of the intake passage 22. 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 complex split mold structure, and productivity can be improved and costs can be reduced, and the benefits of die-casting can be fully utilized. I can make use of it.

In addition, with the intake passage 22 having the above-described shape, there is no stepped portion that would obstruct the flow of the intake air where the flow direction suddenly changes, so there is an advantage that the intake resistance is extremely small and the intake efficiency is improved. .

Note that the joint according to the present invention is not limited to a joint that connects the carburetor and the engine, but may be a joint that connects the exhaust pipe 26 and the engine 9 in FIG. 3, for example.

According to the present invention described in detail above, when the joint is made into a die-cast molded product, the gas passage in the joint is continuously curved with a constant curvature over the entire length, so that after the die-cast molding, the branch passage is formed. To remove the inner mold, it is only necessary to pull out the mold and the joint relatively along the curved direction of the passage, and the two can be easily separated. Therefore, although the intake passage is curved, there is no need for the mold structure to be a complicated split type, and there is an advantage that productivity can be improved and costs can be reduced.

[Brief explanation of drawings]

The drawings show an 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 sectional view of a joint. FIG. 5 is a sectional view taken along line V-V in FIG. 4. 9...Engine, 18...Joint, 19...
Intake device (vaporizer), 22... gas passage (intake passage)
, 26...exhaust device (exhaust pipe).

Claims (1)

[Claims] A die-cast joint that connects the engine and the intake system or exhaust system, and this joint has a curved gas passage inside, and this gas passage is continuously curved with a constant curvature over the entire length. A joint for an intake and exhaust system in an engine, which is characterized by: