JP2527980B2 - Exhaust control device for motorcycles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a downstream side open end of a plurality of exhaust pipes extending from an exhaust port of an engine mounted near the center of a vehicle body to an expansion chamber arranged below the engine. The present invention relates to a motorcycle exhaust control device provided with an exhaust control valve.

(Background of the Invention) In a 4-cycle engine, a 2-cycle engine, etc., it is known that exhaust gas is intermittently guided to an exhaust pipe by opening and closing an exhaust valve, and an inertial 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 the dynamic effect is maximized in the high speed rotation range to increase the volumetric efficiency, the dynamic effect is adversely affected in the low and medium speed rotation range, and the volumetric efficiency is significantly reduced. Therefore, there has been a problem that a remarkable decrease in torque (torque valley) occurs in the medium speed range.

Therefore, an exhaust control valve that changes the exhaust flow passage area is provided near the opening end of the exhaust pipe to the expansion chamber, and the flow passage area is reduced in the rotational speed range where the volume efficiency is reduced, and the flow passage area is reduced in other rotational speed regions. It has been proposed to increase the number (Japanese Patent Application No. 60-263752).

In this case, the wall surface forming the expansion chamber vibrates in the expansion chamber due to the exhaust pressure wave, and noise called a so-called shell is likely to be generated. Therefore, this expansion chamber is required to have high rigidity with respect to this pressure wave. Therefore, it is conceivable to mold the expansion chamber and the downstream side portion of the exhaust pipe collected in this expansion chamber by casting, but in this case, productivity is poor,
It also becomes heavy and costly.
Further, when the expansion chamber is formed separately from the exhaust pipe, there is a problem that the strength of the joint portion between the two tends to decrease.

(Object of the Invention) The present invention has been made in view of such circumstances,
A highly rigid expansion chamber can be made lightweight with good productivity,
Also, the strength of the joint with the exhaust pipe can be secured sufficiently large,
An object of the present invention is to provide an exhaust control device for a motorcycle, which is also suitable for cost reduction.

According to the present invention, the object is to provide a multi-cylinder engine mounted in the vicinity of the center of the vehicle body, an expansion chamber arranged below the engine, and a guide from the front of the engine to the lower side. In a motorcycle including a plurality of exhaust pipes assembled in an expansion chamber, the downstream ends of the exhaust pipes are arranged side by side in the vehicle width direction, while the expansion chamber is formed by a pair of upper and lower half bodies, While holding the downstream end of each exhaust pipe between the flanges formed at the front edges of both halves and between the convex portions that are press-formed on all the opposing surfaces of both halves and that are long in the vehicle width direction, and inside the expansion chamber. Is achieved by an exhaust control device for a motorcycle, which is provided with an exhaust control valve for advancing and retracting in the opening at the downstream end.

(Embodiment) FIG. 1 is a perspective view of an expansion chamber which is an embodiment of the present invention, FIG. 2 is a plan sectional view of the same, and FIG. 3 is III-I in FIG.
II sectional view, FIG. 4 is a sectional view taken along the line IV-IV, FIG. 5 is a perspective view showing the downstream end of a part of the branch pipe, and FIG. 6 is a side view of a motorcycle using this exhaust system. .

In FIG. 6, reference numeral 10 is a 4-cycle 4-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.
Have. The exhaust system includes four exhaust pipes 16 (16a to 16d) extending from the front surface of the cylinder 14 to the lower side of the crankcase 12.
An expansion chamber 18 that is connected to the rear end of the exhaust pipe 16 and collects the exhaust gas of each exhaust pipe 16, and a collecting pipe 22 that guides the exhaust gas from this 18 to a silencer 20.
With.

Reference numeral 24 denotes a rear arm, the front end of which is pivotally attached to the lower portion of the frame 26, and the rear wheel 28 is attached to the rear end thereof.
30 is a front fork with a steering handlebar on its upper end
A front wheel 34 is attached to the lower end 32. 36 is a fuel tank and 38 is a driving seat.

The expansion chamber 18 is composed of a pair of upper and lower sheet metal press-formed halves.
It is made by overlapping 40 and 42. That is, as shown in FIGS. 1 to 4, the two halves 40 and 42 are provided to project along the front edge and the left and right edges toward the flanges 40a, 40b, 42a and 42b, respectively, and the left and right flanges 40b and 42b are welded to each other. As a result, the expansion chamber 18 is formed.

Reference numerals 44 (44a to 44d) are branch pipes that form a part of the exhaust pipe together with the exhaust pipe 16. Each of the branch pipes 44 is formed into a tubular shape by welding a pair of left and right pressed halves to each other, and its front end is circular in cross section and is connected to the exhaust pipe 16. Further, the downstream end of the branch pipe 44, that is, the downstream end of the exhaust pipe is a quadrangle that is long in the vertical direction, as is apparent from FIGS. Each branch pipe 44 has flanges 44A, 44 on its upper and lower surfaces.
A is projectingly provided, and the flange 44A has a notch 44B formed by notching a part near the opening as shown in FIG. The cutout 44B and the flange 44A on the opening side of the cutout 44B are provided with a branch pipe 44 so that welding beads do not appear on the outside.
A weld bead 44C is formed on the inner surface of the.

These branch pipes 44 are welded to each other so that their openings are closely attached to the left and right. Therefore, the openings are arranged in the width direction of the vehicle body.

The row of branch pipes 44 arranged side by side in this way is sandwiched between the flanges 40a, 42a provided at the front edges of the halves 40, 42. At this time, the flanges 40a and 42a are engaged with the notches 44B of the flange 44A of the branch pipe 44 (Fig. 3). Also, on the opposite surfaces of the front parts of both halves 40 and 42, the convex portion 40 is parallel to the flanges 40a and 42a.
c and 42c are pressed. These convex portions 40a, 42c contact the flange 44A located on the opening side of each branch pipe 44, and firmly hold each branch pipe 44 between the upper and lower halves 40, 42. Similar protrusions 40d and 42d are formed in parallel with the protrusions 40c and 42c, and these protrusions contribute to increasing the rigidity of the halves 40 and 42.

A bearing plate 46 is fixed to the right side surface of the expansion chamber 18, and a ring member 48 is fixed to the left side surface. This ring member 48 has a bearing plate
50 is bolted.

Reference numeral 52 denotes an exhaust control valve, which has a valve shaft 54 held by the bearing plates 46 and 50 and a valve body 56 fixed to the valve shaft 54 and having a circular arc section in the circumference centered on the valve shaft 54. With. Valve shaft 54
The left end of the is projected from the bearing plate 50, and the pulley 58 is fixed thereto. The pulley 58 is controlled via a wire by a servo motor (both not shown) so as to close in the low and medium speed range of the engine 10 and open in the high speed range.

As is clear from FIGS. 3 and 5, the parallel opening rows of the branch pipes 44 are formed in an arc shape so as to be close to the outer peripheral surface of the valve body 56. As a result, leakage of exhaust gas from the gap between the opening and the valve body 56 is prevented. Each branch pipe 44
As shown in FIGS. 2 and 5, one of the adjacent opening edges of the valve body 56
It has retreated slightly from. Then, the retracted opening edge and the adjacent opening edge are welded to form a bead 44D shown in FIG. As a result, the bead 44D does not project to the valve body 56 side,
The gap between the opening and the valve body 56 can be maintained with high accuracy.

Next, the operation will be described. When the diameter and length of the exhaust pipe 16 are set so that the volumetric efficiency of the engine 10 is high in the high speed range, the exhaust control valve 52 is closed in the medium speed range and opened by the servo motor. Driven. The positive pressure wave due to the opening of the exhaust valve of the engine 10 propagates in the exhaust pipe 16 and the branch pipe 44 at the speed of sound, and the negative pressure wave generated by the rapid expansion at the opening to the expansion chamber 18 is the exhaust pipe 16. And propagates in the opposite direction through the branch pipe 44 at the speed of sound and returns to the exhaust valve of the engine 10. If the valve body 56 facing this opening closes the opening, the positive pressure wave due to the opening of the exhaust valve is reflected by this valve body 56 and returns to the exhaust valve as a positive pressure wave at the speed of sound. Therefore, if the valve body 56 is controlled so that the area of the exhaust flow passage is approximately halved in the medium speed range where the dynamic effect acts in reverse, the negative pressure wave generated by the opening and returned and the valve body 56 The sum of the reflected positive pressure wave is zero. At this time, the pulsating effect is canceled out, and a decrease in volume efficiency (occurrence of a torque valley) in the medium speed range can be suppressed.

Since the square opening row of the branch pipe 44 is sandwiched between the flanges 40a, 42a provided at the front edges of the halves 40, 42 forming the expansion chamber 18 and between the convex portions 40c, 42c, expansion with the branch pipe 44 occurs. The connection with the chamber 18 becomes strong. Further, the convex portions 40c and 42c have a great effect on increasing the rigidity of the half bodies 40 and 42.

In this embodiment, since the opening of the branch pipe 44 is a vertically long rectangle, the width of the expansion chamber 18 can be reduced to ensure a large bank angle of the vehicle body.

Further, in this embodiment, since the downstream end of each branch pipe 44 faces the radius of the valve body 56 with high accuracy, the end face of the branch pipe 44 is machined from the mounting hole of the bearing plate 50 by a drill or the like. At this time, since the downstream end is held by the convex portions of the respective halves 40 and 42 from above and below, the branch pipes 40 and 42 do not vibrate and the workability is good.

(Effect of the Invention) As described above, according to the present invention, the downstream ends of the exhaust pipes are arranged side by side in the width direction of the vehicle body, and the open ends thereof are a front edge flange between a pair of upper and lower sheet metal stamped halves, and this flange. Since it is sandwiched between the convex portions parallel to the above, the strength of the joint between the expansion chamber and the exhaust pipe can be sufficiently increased. Further, a flange and a convex portion for holding the exhaust pipe are pressed on each half body, and the half body is pressed by the branch pipe, so that the rigidity of the expansion chamber is increased and the vibration damping of the expansion chamber is performed. Greater effect. Further, it has good productivity, can be made lightweight, and is suitable for cost reduction.

[Brief description of drawings]

FIG. 1 is a perspective view of an expansion chamber which is an embodiment of the present invention, and FIG.
The figure is the same plane sectional view, and FIG. 3 is III-III in FIG.
A sectional view, FIG. 4 is a sectional view taken along the line IV-IV, FIG. 5 is a perspective view showing a downstream end of a part of a branch pipe, and FIG. 6 is a side view of a motorcycle using this exhaust system. 10 ... Engine, 18 ... Expansion chamber, 40, 42 ... Half body, 40a, 42a ... Front edge flange, 40c, 42c ... Convex part, 44 ... Branch pipe that is a part of exhaust pipe, 52 ... Exhaust control valve.

Claims (1)

(57) [Claims] 1. A multi-cylinder engine mounted near the center of a vehicle body, an expansion chamber disposed below the engine, and a plurality of exhaust pipes which are guided downward from the front of the engine and gather in the expansion chamber. In a motorcycle including and, while the downstream ends of the exhaust pipes are juxtaposed in the vehicle body width direction, the expansion chamber is formed by a pair of upper and lower half halves, and is formed at the front edges of both halves. The downstream end of each exhaust pipe is sandwiched between the flanges and between the long projections formed in the width direction of the vehicle body by press molding on all the opposing surfaces of both halves, and the expansion chamber moves back and forth to the openings of these downstream ends. An exhaust control device for a motorcycle, comprising an exhaust control valve for controlling the exhaust.