JP2804306B2 - Engine exhaust control valve device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust control valve device for an engine in which exhaust control valves are provided at downstream open ends of a plurality of exhaust pipes from an exhaust port of an engine to an expansion chamber. Things.

BACKGROUND OF THE INVENTION In a four-stroke engine, a two-stroke engine, and the like, it is known that exhaust gas is intermittently guided to an exhaust pipe by opening and closing an exhaust valve, and an inertia effect and a pulsating effect of the exhaust gas are generated in the exhaust pipe. . These effects (called dynamic effects) change depending on the engine speed. Therefore, if this dynamic effect is maximized at a certain rotational speed to increase the volumetric efficiency, at another rotational speed, the dynamic effect works in the opposite direction and the volumetric efficiency is significantly reduced. Therefore, when the exhaust system specifications (exhaust pipe length, exhaust pipe diameter, etc.) are set so that this dynamic effect is optimal in the high rotation range, the torque is significantly reduced in the medium speed range (torque valley). There was a problem that occurs.

Therefore, an exhaust control valve that changes the exhaust flow area is provided near the opening end of the exhaust pipe to the expansion chamber, and the flow area decreases in the rotational speed range where the volume efficiency decreases, and the flow area decreases in other rotational 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 gathering in the expansion chamber, and the opening of each branch pipe facing the valve body is formed in a rectangular cross section, and the sides of the rectangular cross section are brought into close contact with each other to form a line. (See, for example, Japanese Patent Application No. 62-228598). In this apparatus, the branch pipes are sandwiched between the flanges formed on the front edge of each half and between the protrusions formed by pressing on the facing surfaces of the front portions of the two halves, and the front edges of the flanges are sandwiched between the flanges. It is obtained by welding a branch pipe. However, when the projections are formed on each half in this way, the vertical dimension of the expansion chamber becomes large, and the entire exhaust control valve device becomes large. Therefore, when this is disposed below the engine of the motorcycle, there arises a problem that an oil pan capacity for accumulating the lubricating oil of the engine becomes small and a gap (road clearance) from a road surface becomes small. In addition, since each branch pipe is only sandwiched between two places of the narrow flange and the convex part of the half body, the bonding strength between the branch pipe and the expansion chamber is reduced, and particularly, the welding portion between the branch pipe and the flange is reduced. In this case, there is a problem that the stress is concentrated, cracks are formed, and the durability is reduced.

(Object of the Invention) The present invention has been made in view of such circumstances,
When the downstream portion of the exhaust pipe is formed by a branch pipe having an opening facing the valve body and having a rectangular cross section, and each branch pipe is tightly arranged in a line to be sandwiched between a pair of upper and lower halves forming an expansion chamber. In addition, when the upper and lower halves are reduced in vertical dimension and disposed below the engine of the motorcycle, the oil pan capacity can be increased and the load clearance can be increased. It is an object of the present invention to provide an exhaust control valve device capable of increasing the bonding strength and durability of the exhaust control valve.

(Constitution of the Invention) According to the present invention, it is an object of the present invention to collect a plurality of exhaust pipes in an expansion chamber and to accommodate a valve body having a variable exhaust passage area facing the opening of each exhaust pipe in the expansion chamber. In the exhaust control valve device for an engine described above, each of the exhaust pipes has an independent tubular shape, and an opening of a downstream portion directly opposed to the valve body is formed in a rectangular cross section, and the open ends of the exhaust pipes are in close contact with each other. While welding in a row, the expansion chamber is formed by a pair of upper and lower halves sandwiching the vicinity of the opening of these exhaust pipes from above and below, and each half is continuous from its front edge to the opening end of each exhaust pipe. And a front edge of each half is welded to the exhaust pipe by being in close contact with the exhaust pipe from above and below.

(Embodiment) 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 showing a part of the exhaust system, and FIG. 4 is a sectional view taken along the line IV-IV, and FIG.
The figure is an end view taken along the line VV, FIG. 6 is a perspective view of a branch pipe assembly,
FIG. 7 is a side view showing a welded portion, and FIG. 8 is a side view of a motorcycle using the exhaust system.

In FIG. 8, reference numeral 10 denotes a four-cycle four-cylinder engine, which is mounted near the center of the vehicle body. This engine 10
Is a cylinder 14 that extends diagonally upward and forward from the crankcase 12
Having. The exhaust system includes four exhaust pipes 16 (16a to 16d) extending from the front of the cylinder 14 below the crankcase 12.
An exhaust control valve device 18 is connected to the rear end of the exhaust pipe 16 and collects exhaust gas from each exhaust pipe 16, and a collecting pipe 22 that guides exhaust gas from the exhaust control valve device 18 to a muffler 20.

The exhaust control valve device 18 is, as shown in FIGS.
Four branch pipes 24 (24a to 24d) connected to the respective exhaust pipes 16 to form a part of the exhaust pipes 16; It comprises a pair of upper and lower sheet metal halves 22a, 22b sandwiching it, and a valve body 28 in the expansion chamber 26 formed between these halves 22a, 22b for controlling the area of the exhaust passage. The collecting pipe 22 is composed of these halves 22
a, 22b. As shown in FIG. 6, each of the branch pipes 24 is formed by welding upper and lower flanges of the left and right halves to each other to form a tube, and the opening at the downstream end thereof has a rectangular shape elongated in the vertical direction. The rectangular downstream end of each branch pipe 24 opens into the expansion chamber 26 as shown in FIG.

The valve body 28 includes a main body 30 having an arc-shaped cross section, a fan-shaped end plate 32 (32a, 32b) integrally formed at both ends of the main body 30 and extending toward the center of the arc of the main body 30, and an end plate 32. Fixed valve stem 3
4 (34a, 34b).

A bearing plate 36 is fixed to one side surface of the half bodies 22a and 22b,
On the other side, a ring member 38 is fixed so as to surround the circular window. A bearing plate 40 is detachably bolted to the ring member 38. The valve element 28 is inserted into the expansion chamber 26 from the window from which the bearing plate 40 has been removed, and holds the tip of the valve shaft 34b on the bearing plate 36, while attaching the other end of the valve shaft 34b to this window.
Hold at 0.

The valve shaft 34a protrudes from the bearing plate 40, and a pulley 44 is fixed to the protruding end. The pulley 44 is rotated by a servo motor 48 via a wire 46 in accordance with the rotation speed of the engine 10, and the valve body 28 is controlled so as to close in a low to medium speed range of the engine 10 and open in a high speed range.

In FIG. 8, reference numeral 50 denotes a rear arm, the front end of which is pivotally supported by the vehicle body frame 52, and the rear wheel 54 attached to the rear end.
The spring force of the shock absorber 56 is applied to the rear arm 50 by the link mechanism 5.
Granted downward through 8, 60.

In the exhaust system, the upper end of the exhaust pipe 16 is attached to the cylinder 14, and the muffler 20
Is fixed to the body frame 52 by a bracket 62, and a pipe 63 connecting the collecting pipe 22 and the silencer 20 is a bracket 64
(FIG. 8), the link 58 is hung on a shaft support of the body frame 52 side.

66 is a front wheel, 68 is a fuel tank, 70 is an operation seat, and 72 is a battery.

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

Here, the branch pipes 24a to 24d are welded to each other by high-energy beam welding to form a branch pipe assembly 24A shown in FIG. That is, the branch pipes 24a to 24d are in close contact with each other at the long sides of the quadrangular section on the downstream side, and the periphery of the contact surface is welded by high energy beam welding, for example, laser beam welding. Here, according to this beam welding, the distance between the irradiation unit 74 and the welded portion can be made large,
As shown in the figure, while moving the irradiation unit 74 toward the gap between the two branch pipes 24, the irradiation unit 74 extends to the depth of a V-shaped valley formed between the adjacent branch pipes 24, for example, in the range B in FIG. Welding can be performed efficiently and well.

As shown in FIG. 7B, the bead 76 formed by the laser beam is formed deeply between the branch pipes without protruding upward from between the two branch pipes 24, and the surface of the bead 76 has a depressed arc-shaped cross section. No back bead is generated.
Here, by gradually reducing the intensity of the laser beam toward the toe of the bead 76, the bead 76 can be smoothly reduced toward the toe. For this reason, a bead end where stress concentration occurs is not formed, and durability against vibration is improved. Further, since the range of temperature rise by beam irradiation is small, thermal deformation is small, dimensional accuracy is improved, and the heat input is small, so that the strength does not decrease due to the coarsening of crystal grains.

3 and 5, the rear end of each branch pipe 24 is sandwiched between the halves 22a and 22b forming the expansion chamber 26. The front ends of the halves 22a and 22b The branch pipes 24 and the halves 22a, 22b are in close contact with each other continuously to the open end, and the front edges of the halves 22a, 22b are welded to the branch pipe 24. For this reason, the coupling strength 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 above embodiment, each of the branch pipes 24 is formed by welding left and right split halves into a tubular shape, but may be formed into a rectangular pipe by drawing or the like, or the exhaust pipe 16 itself may be processed into a cross section. It may be a square. In this case, before connecting the pipe 63 to the rear end of the collecting pipe 22, it is possible to directly visually check the back side of this welded part through the expansion chamber 26 from the rear end before connecting the pipe 63 to the rear end of the collecting pipe 22 whether or not a back bead is formed at the welded part of the exhaust pipe 16. The presence or absence of a back bead can be easily confirmed.

(Effect of the Invention) As described above, in the present invention, each exhaust pipe is formed into an independent tubular shape, and the opening of the downstream portion directly facing the valve body is formed in a square cross section, and the opening end of each exhaust pipe is formed. Are welded in a row in close contact with each other, and the vicinity of the open ends that are in close contact with each other is sandwiched between a pair of upper and lower halves forming an expansion chamber, and each half is connected from its front edge to the open end of each exhaust pipe. The front edge of each half was welded to the exhaust pipe by being continuously brought into close contact with the exhaust pipe from above and below. Therefore, the vertical dimension of the expansion chamber can be reduced, and when the expansion chamber is mounted below the engine of the motorcycle, the volume of the oil pan of the engine can be increased, and the load clearance can be increased. In addition, the concentration of stress applied to the joint between the exhaust pipe and the expansion chamber is reduced, so that the bonding strength is increased and the durability is increased.

[Brief description of the drawings]

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 showing a part of the exhaust system, and FIG. Figure,
4 is a sectional view taken along the line IV-IV, also partially omitted, FIG. 5 is an end view taken along the line VV, FIG. 6 is a perspective view of a branch pipe assembly, and FIG.
The figure is a side view showing a welded portion, and FIG. 8 is a side view of a motorcycle using this exhaust system. 16 ... exhaust pipe, 18 ... exhaust control valve, 22 ... collecting pipe, 22a, 22b ... half, 24 ... branch pipe, 26 ... expansion chamber, 28 ... valve body.

Claims (1)

(57) [Claims] An exhaust control valve device for an engine in which a plurality of exhaust pipes are gathered in an expansion chamber, and a valve body having a variable exhaust passage area is provided in the expansion chamber so as to face an opening of each exhaust pipe. Each of the exhaust pipes has an independent tubular shape, and the openings of the downstream portions directly facing the valve bodies are formed in a rectangular cross section, and the open ends of the exhaust pipes are welded in a line in close contact with each other, while the The expansion chamber is formed by a pair of upper and lower halves that sandwich the vicinity of the opening of these exhaust pipes from above and below, and each half is closely contacted with the exhaust pipe from the front edge to the opening end of each exhaust pipe from above and below. An exhaust control valve device for an engine, wherein a front edge of each half is welded to an exhaust pipe.