JP2804305B2 - Exhaust pipe joining method for exhaust control valve device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust pipe of an exhaust control valve device provided with an exhaust control valve at a downstream opening end of a plurality of exhaust pipes from an exhaust port of an engine to an expansion chamber. It relates to a joining method.

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 area of the exhaust flow path is provided near the opening end of the exhaust pipe to the expansion chamber. The area of the flow path is reduced in the rotational speed range where volume efficiency is reduced, and the flow area is reduced 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 that each branch pipe opens facing the valve body has a square cross section, and the sides of this square cross section are closely adhered to each other and welded. Have already been proposed (for example,
62-228597, etc.). In this device, the opening of the branch pipe is formed in an arc shape in a side view so as to be close to the outer peripheral rotation trajectory of the valve element having an arc cross section, so that the gap between the opening edge of the branch pipe and the valve element is strictly determined. Need to be managed. Conventionally, however, the opening edge of the branch pipe that is in close contact is TIG welded (tungsten inert gas welding), so that the bead becomes larger and protrudes toward the exhaust passage, reducing the exhaust passage area and causing a decrease in performance or heat. The dimensional accuracy is deteriorated due to the deformation, and it is necessary to secure the gap accuracy with the valve body by cutting a bead projecting from the opening edge after welding. In particular, when cutting is performed after welding, there has been a problem that the amount of deformation during use increases due to residual stress.

(Object of the Invention) The present invention has been made in view of such circumstances,
The downstream part of the exhaust pipe is formed by a branch pipe having an opening facing the valve body with a rectangular cross section, and when the branch pipes are welded to each other in close contact with each other, a bead generated at the opening edge of each branch pipe in close contact with each other. It is an object of the present invention to provide an exhaust pipe joining method for an exhaust control valve device, which does not project toward the exhaust passage side or the valve body side, does not require machining after welding, and improves dimensional accuracy.

(Constitution of the Invention) According to the present invention, it is an object of the present invention to arrange the downstream portions of a plurality of exhaust pipes in a line so as to open them in an expansion chamber, and to open the exhaust flow in the expansion chamber in close proximity to the openings of the exhaust pipes. In an exhaust pipe joining method for an exhaust control valve device accommodating a rotatable valve element having a circular cross-section and a variable path area, a downstream portion of each of the exhaust pipes which is open to face the valve element has a rectangular cross section. And forming these openings in a final shape of a circular arc in a side view substantially along the circular arc shape of the valve element when viewed from the rotation axis direction of the valve element. The openings are brought into close contact with each other in the axial direction, and a high-energy beam is irradiated from the valve body side toward the gap between the openings that come into close contact with each other so that these openings have a thickness within the range of their wall thickness and their arc-like shapes. Melt without changing the final shape The exhaust pipe joining method of the exhaust control valve device is characterized by being in contact with each other.

(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. 7A is a side view showing a welded portion, and FIG. 7B is a VII B-VII thereof.
FIG. 8 is a side view of a motorcycle using this 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.

As shown in FIGS. 1, 2, and 6, the exhaust control valve 18 includes four branch pipes 24 (24a to 24d) connected to each of the exhaust pipes 16 to form a part of the exhaust pipe 16, and A pair of upper and lower sheet metal halves 22a and 22b sandwiching the downstream ends of the branch pipes 24 side by side and sandwiching them from above and below, and an expansion chamber 26 formed between the halves 22a and 22b. And a valve element 28 for controlling the area of the exhaust passage. The collecting pipe 22 includes these halves 22a, 2a.
2b is formed. 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 is the third
It opens into the expansion chamber 26 as shown in the figure.

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. And a valve shaft 34 (34a, 34b) integrally formed.

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.

According to this embodiment, the negative pressure wave generated by the opening of the branch pipe 24 and returned upstream in the exhaust pipe 16 and the valve body
The positive pressure wave reflected by 28 and transmitted upstream in the exhaust pipe 16 acts on the exhaust valve, cancels out in a certain speed range, and the sum becomes zero. At this time, the pulsation effect is negated, and the volume efficiency in this speed range decreases (torque valleys occur).
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 increased,
As shown in FIG. 7 and FIG. 7A, while moving the irradiation unit 74 toward the gaps A and B between the two branch pipes 24, the gap A between the opening edges of the adjacent branch pipes 24 and the adjacent branch pipes
The depth of the V-shaped valley formed between 24 (range B in FIG. 7A)
The bead 76 can be formed efficiently and well by welding.

Also, if the irradiation unit 74 is moved toward the opening edge,
Welding can be performed without projecting the bead 76A at the opening edge from the opening edge. Bead 76A by this laser beam
As shown in FIG. B, it is formed deep between the branch pipes without projecting upward from between the two branch pipes 24, so that the beads do not protrude into the exhaust passage. Moreover, the surface of the bead 76A has a depressed arc-shaped cross section. That is, the open edges that are in close contact with each other are welded within their wall thickness and without changing their arcuate final shape. Also, since the range of temperature rise by beam irradiation is small, thermal deformation is small,
The dimensional accuracy is improved. This eliminates the need for machining such as cutting after welding in order to maintain the accuracy of the press-formed arc, and does not cause a decrease in accuracy due to residual stress caused by machining, and is caused by release of stress due to exhaust heat during use. Deformation is reduced.

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.

The high energy beam welding may use other beams such as electron beam welding in addition to laser beam welding.

(Effects of the Invention) As described above, in the present invention, when the downstream portion of the exhaust pipe having a square cross section is closely welded, the opening edges of these exhaust pipes that are in close contact with each other are welded by high energy beam welding using a laser beam or the like. Therefore, the bead at the opening edge can be reduced, and the bead does not reduce the exhaust passage area to reduce the engine performance, and the bead does not protrude toward the valve body, so that it is removed by machining. There is no need. Therefore, the gap accuracy between the opening edge and the valve body can be kept high.

[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 cross-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 the branch pipe assembly, and FIG.
FIG. 7B is a side view showing a welded portion, FIG. 7B is a sectional view taken along the line VIIB-VIIB, and FIG. 8 is a side view of a motorcycle using the exhaust system. 16 ... exhaust pipe, 18 ... exhaust control valve, 24 ... branch pipe, 26 ... expansion chamber, 28 ... valve body, 74 ... laser irradiation unit, 76A ... bead.

Claims (1)

(57) [Claims] A plurality of exhaust pipes are arranged in a row in a row, and each of the exhaust pipes is opened in an expansion chamber. A cross section of the exhaust pipe is formed in the expansion chamber so as to be in close proximity to the opening of each exhaust pipe and to have a variable exhaust passage area. In an exhaust pipe joining method for an exhaust control valve device accommodating an arcuate and rotatable valve body, a downstream portion of each of the exhaust pipes that opens to face the valve body is formed in a rectangular cross section, and these openings are formed. The valve body is formed in a final shape of an arc shape in a side view substantially along the arc shape of the valve body as viewed from the rotation axis direction of the valve body, and the downstream portions of these exhaust pipes are brought into close contact with each other in the rotation axis direction. By welding a high-energy beam from the valve body side toward the gap between the opening edges that adhere to each other, these opening edges are welded within their wall thickness and without changing their arc-shaped final shape. , Characterized in that An exhaust pipe joining method for a pneumatic control valve device.