JPH0392537A - Exhaust control valve device for engine - Google Patents

Abstract

PURPOSE:To reduce a vertical size and increase connecting strength by closely welding branch pipes with a square cross section in a line, and pinching the closely stuck openings of branch pipes between a pair of the upper and lower half bodies forming an expansion chamber. CONSTITUTION:The exhaust system of an engine is constituted of an exhaust control valve device 18 connected to rear ends of exhaust pipes to collect the exhaust and a collecting pipe 22 guiding the exhaust into a muffler. The exhaust control valve device 18 is constituted of many branch pipes 24 (24a-14d) forming part of exhaust pipes, a pair of half bodies 22 (22a and 22b) merged in the lateral direction of branch pipes 24 to pinch them vertically, and a valve body 28 located in an expansion chamber 26 formed between half bodies 22 to control the exhaust passage area. Downstream side opening ends of branch pipes 24 are formed into a square cross section and arranged in close contact with each other. Front edges of half bodies 22 are closely welded to opening ends of branch pipes 24.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine exhaust control device in which an exhaust control valve is provided at the downstream opening end of a plurality of exhaust pipes extending from an engine exhaust port to an expansion chamber. It is.

(Background of the Invention) It is known that in 4-stroke engines, 2-stroke engines, etc., exhaust gas is intermittently guided into the exhaust pipe by opening and closing the exhaust valve, causing an inertial effect and a pulsation effect of the exhaust gas in the exhaust pipe. . These effects (referred to as dynamic effects) vary depending on engine speed. Therefore, if this dynamic effect is maximized at a certain rotational speed to increase volumetric efficiency, at other rotational speeds the dynamic effect acts in the opposite manner and the volumetric efficiency is significantly reduced. Therefore, if the exhaust system specifications (exhaust pipe length, exhaust pipe diameter, etc.) are set so that this dynamic effect is optimal in the high speed range, the torque will significantly decrease (torque trough) in the medium speed range. There was a problem that occurred.

Therefore, an exhaust control valve that changes the exhaust flow area is installed near the opening end of the exhaust pipe to the expansion chamber, reducing the flow passage area in the rotation speed range where volumetric efficiency decreases, and reducing the flow passage area in other rotation speed ranges. It has been proposed to increase it (Japanese Patent Application No. 60-263752).

Here, the downstream part of the exhaust pipe is formed by branch pipes that meet in the expansion chamber, and the opening of each branch pipe that opens facing the valve body has a square cross section. A welded structure has already been proposed (see, for example, Japanese Patent Application No. 62-228598). This product supports each branch pipe between the flanges formed on the front edge of each half body and between the convex parts press-formed on the opposing surfaces of the front parts of both halves, and supports the branch pipes between the front edge of the flange and each other. The branch pipes are welded together. However, if the convex portion is formed in each half in this way, the vertical dimension of the expansion bow length chamber becomes large, and the entire exhaust control valve device becomes large. Therefore, when this is disposed below the engine of a motorcycle, problems arise in that the capacity of the oil pan for storing lubricating oil for the engine becomes small and the gap with the road surface (road clearance) becomes small. In addition, since each branch pipe is supported only at two places, the narrow flange and the convex part of the half body, the strength of the connection between the branch pipe and the expansion chamber is low.
In particular, stress concentration occurs at the welded portion between the branch pipe and the flange, causing cracks and other problems, resulting in reduced durability.

(Object of the Invention) The present invention was made in view of the above circumstances, and the downstream part of the exhaust pipe is formed by a branch pipe whose opening facing the valve body has a square cross section, and each branch pipe is connected to each other. When supporting between a pair of upper and lower halves that are brought into close contact with each other in a row to form an expansion chamber, the vertical dimensions of both halves are made smaller, and when the halves are disposed below the engine of a motorcycle, the capacity of the oil pan is reduced. It is an object of the present invention to provide an exhaust control valve device that can increase the load clearance, and increase the joint strength and durability between a branch pipe and an expansion chamber.

(Structure of the Invention) According to the present invention, this purpose is to collect a plurality of exhaust pipes in an expansion chamber, and to house a valve body in the expansion chamber opposite to the opening of each exhaust pipe to vary the area of the exhaust flow path. In the exhaust control valve device for an engine, the openings of the downstream portions of the exhaust pipes facing the valve body are formed to have a rectangular cross section, and the open ends of the exhaust pipes are arranged side by side in close contact with each other. An engine exhaust system characterized in that the chamber is formed by a pair of upper and lower halves supporting the vicinity of the openings of these exhaust pipes from above and below, and each half is closely welded from the front line to the opening end of each exhaust pipe. This is accomplished by a control valve system.

(Example) Fig. 1 is an exploded perspective view showing an exhaust system of a motorcycle engine according to an embodiment of the present invention, Fig. 2 is an enlarged sectional view of a part of the exhaust system, and Fig. 3 is an enlarged cross-sectional view of a part of the exhaust system. -III
The line cross-sectional view and FIG. 4 are IV-IV with some parts omitted as well.
5 is an end view taken along line V-V, 6 is a perspective view of the branch pipe assembly, 7 is a side view showing a welded part, and 8 is a motorcycle using this exhaust system. FIG.

In FIG. 8, reference numeral 10 is a 4-stroke, 4-cylinder engine, which is mounted near the center of the vehicle body.

This engine 10 has a sill 14 extending obliquely upward and forward from the crankcase l2. The exhaust system is cylinder l
four exhaust pipes 16 (16a to 16d) extending downward from the front of the crankcase 12, an exhaust control valve device 18 that is connected to the rear end of the exhaust pipe 16 and collects the exhaust gas from each exhaust pipe 16; Exhaust from the exhaust control valve device 18 to the muffler 2
0.

As shown in FIGS. 1, 2, and 6, the exhaust control valve device 18 includes:
The four branch pipes 24 (24a to 24d) that are connected to each of the exhaust pipes 16 and form a part of the exhaust pipe 16, and the downstream ends of these branch pipes 24 are collected side by side and viewed from above and below. A pair of upper and lower sheet metal halves 22a and 22b sandwiching each other, and an expansion chamber 2 formed between these halves 22a and 22b.
6 and a valve body 28 for controlling the exhaust flow path area. The collecting pipe 22 is formed by these halves 22a and 22b. As is clear from FIG. 6, each branch pipe 24 is formed into a tubular shape by welding the upper and lower flanges of the left and right halves to each other, and the opening at the downstream end thereof is a rectangle that is elongated in the vertical direction. The rectangular downstream end of each branch pipe 24 opens into an expansion chamber 26 as shown in FIG.

The valve body 28 includes a main body 30 having an arcuate cross section, and a main body 30 having an arcuate cross section.
A sector-shaped end plate portion 32 (32a, 32b) integrally molded on both ends of the body portion 30 and extending toward the arc center of the main body portion 30;
The valve shaft 34 (34a, 34b) is fixed to the valve shaft 2. A bearing plate 36 is fixed to one side of the half bodies 22a, 22b, and a ring member 38 is attached to the other side so as to surround a circular window.
is fixed. This ring member 38 has a bearing plate 40.
is removably bolted. The valve body 28 is a bearing plate 40
It is inserted into the expansion chamber 26 through the removed window, and the valve shaft 34b is inserted into the expansion chamber 26.
The tip of the valve shaft 34b is held on a bearing plate 36, while the other end of the valve shaft 34b is held on a bearing plate 40 attached to this window.

The valve shaft 34a projects from the bearing plate 40, and a boob 44 is fixed to the projecting end. The boob 44 is rotated by a servo moke 48 via a wire 46 in accordance with the rotational speed of the engine 10, and the valve body 28 is controlled to close in the low and medium speed range of the engine 10 and open in the high speed range.

In FIG. 8, 50 is a rear arm, the front end of which is pivotally supported by the vehicle body frame 52, and the rear wheel 54 is attached to the rear end. The spring force of a shock absorber 56 is applied downward to this rear arm 50 via link mechanisms 58 and 60.

In the exhaust system, the upper end of the exhaust pipe 16 is fixed to the sill 14, the muffler 20 is fixed to the vehicle body frame 52 by a bracket 62, and a pipe 63 connects the collecting pipe 22 and the muffler 20.
is suspended from the shaft support of the link 58 on the side of the vehicle frame 52 by a bracket 64 (FIG. 8).

66 is the front wheel, 68 is the fuel tank, 70 is the driver's seat, 7
2 is a battery.

Here, the exhaust control valve device 18 is driven by a servo motor 48 so as to close in a medium speed range and open in a high speed range, for example. As a result, a negative pressure wave is generated by the opening of the branch pipe 24 and returns upstream in the exhaust pipe 16, and a positive pressure wave is reflected by the valve body 28 and propagates upstream in the exhaust pipe 16. act on the exhaust valve, cancel each other out in a certain speed range, and the sum becomes zero. At this time, the pulsation effect is canceled out, and a decrease in volumetric efficiency (occurrence of torque valley) in this speed range can be suppressed.

The branch pipes 24a-d are now welded together by high energy beam welding to form the branch pipe assembly 24A shown in FIG.
is made. That is, the long sides of the downstream rectangular cross sections of the branch pipes 24a to 24d are brought into close contact with each other, and the periphery of this contact surface is welded by high energy beam welding, such as laser beam welding. According to this beam welding, the distance between the irradiation unit 74 and the welding part can be increased, so as shown in FIG. 7A, while moving the irradiation unit 74 toward the gap between the two branch pipes 24, 2
4, to the depths of the V-shaped valley formed between B and B in the same figure.
It is possible to weld efficiently and well over a range of .

Furthermore, as shown in FIG. 7B, the bead 76 created by the laser beam is formed deep between the branch pipes 24 without protruding upward from between the two branch pipes 24, and the surface of the bead 76 has a depressed circular arc cross section. , no back bead occurs. By gradually weakening the intensity of the laser beam toward the toe of the bead 76, the bead 76 can be smoothly reduced toward the toe. This eliminates the formation of bead edges where stress concentration occurs, improving durability against vibrations. In addition, since the range in which the temperature rises due to beam irradiation is small, thermal deformation is reduced and dimensional accuracy is improved, and since the amount of human heat is small, there is no possibility of a decrease in strength due to coarsening of crystal grains.

Further, the rear end of each branch pipe 24 is sandwiched between halves 22a and 22b forming an expansion chamber 26, as shown in FIGS. Each branch pipe 24 and each half body 22a, 22b are in close contact with each other continuously up to the open end, and the front edges of each half body 22a, 22b are welded to the branch pipe 24. Therefore, the strength of the connection between the branch pipe 24 and the collecting pipe 22 is increased, and the vertical dimension of the expansion chamber 26 is reduced, so that the volume of the oil pan 10a of the engine 10 can be increased, and the load clearance can be increased.

In the embodiments described above, each branch pipe 24 is made into a tubular shape by welding the left and right halves, but it can be made into a rectangular pipe by drawing or the like, or the exhaust pipe 16 itself can be processed to have a cross-sectional shape. It may be square and chino. In this case, before connecting the pipe 63 to the rear end of the collecting pipe 22, it is possible to directly visually inspect the back side of this weld through the expansion chamber 26 from the rear end to see if a back bead has formed at the weld of the exhaust pipe 16. , the presence or absence of the back bead can be easily confirmed.

(Effects of the Invention) As described above, the present invention welds branch pipes with a rectangular cross section in close contact in a line, and the openings of these branch pipes in close contact with each other are
Since it is sandwiched between a pair of upper and lower halves that form an expansion chamber, and each half is brought into close contact with the exhaust pipe from its front edge to the opening end of the branch pipe, it is possible to reduce the vertical dimensions of the collecting pipe. Therefore, when this is mounted below the engine of a motorcycle, the volume of the oil pan of the engine can be increased, and the road clearance can be increased. In addition, the concentration of stress at the joint between the branch pipe and the collecting pipe is reduced, and the joint strength is increased to 4. The strength increases and the durability increases.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view showing the exhaust system of a motorcycle engine according to an embodiment of the present invention, Fig. 2 is an enlarged cross-sectional view of a part of the exhaust system, and Fig. 3 is an exploded perspective view of the exhaust system of a motorcycle engine according to an embodiment of the present invention.
The line cross-sectional view and FIG. 4 are IV-I with some parts omitted as well.
Figure 5 is a cross-sectional view taken along line V, Figure 5 is an end view taken along line V-V, Figure 6 is a perspective view of the branch pipe assembly, Figure 7 is a side view showing the welded part, and Figure 8 is an automatic exhaust system using this exhaust system. It is a side view of a two-wheeled vehicle. 16...Exhaust pipe, 18...Exhaust control valve, 2
2...Collecting pipe, 22a, 22b--half body, 24...branch pipe, 26...expansion chamber, 28...
・Valve body.

Claims (1)

[Scope of Claims] An exhaust control valve device for an engine in which a plurality of exhaust pipes are gathered together in an expansion chamber, and a valve body for making the exhaust flow path area variable is housed in the expansion chamber, facing the opening of each exhaust pipe. , the openings of the downstream portions of the exhaust pipes facing the valve body are formed to have a rectangular cross section, and the opening ends of these exhaust pipes are arranged side by side in close contact with each other, while the expansion chamber is formed in the openings of these exhaust pipes. Formed by a pair of upper and lower halves that sandwich the vicinity from above and below,
An exhaust control valve device for an engine, characterized in that each half is closely welded from its leading edge to the opening end of each exhaust pipe.