JPH075219Y2 - Engine exhaust muffler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an exhaust muffler for an engine mounted on a jet-propelled small boat, a motorcycle, and various other vehicles.

<Prior Art> For example, in a conventional jet-propelled small watercraft, in order to achieve the muffling effect of the exhaust gas, as is clear from the schematic diagram of FIG. 12, a water-cooled type watercraft installed in the hull (1). A long exhaust pipe (3) is led forward from an exhaust manifold (not shown) of the engine (2), while a water turbo box (exhaust muffler) functions as an expansion chamber at the bow of the boat body (1). ) (4) is stored and installed, and the front end opening of the exhaust pipe (3) is exposed to the water turbo box (4) so that the exhaust gas from the engine (2) becomes water after the engine is cooled. Together with this, the water is introduced into the water turbo box (4) and then discharged into the atmosphere from the face of the box (4) through the discharge pipe (5).

That is, the exhaust gas of the engine (2) and its cooling water are
By performing mixed flow / heat exchange inside the exhaust pipe (3), the back pressure of the exhaust gas is reduced, and further, by further expanding / depressurizing the exhaust gas in the water turbo box (4), It achieves the effects of heat absorption and noise reduction from the surroundings.

<Problems to be solved by the invention> However, according to such a configuration, the exhaust pipe (from the exhaust manifold to the water turbo box (4)) is provided with the intention of preventing the output of the engine (2) from decreasing. Since 3) forms a generally straight exhaust flow path, it is difficult to efficiently attenuate the exhaust sound unless the entire volume of the exhaust flow path is set to be large. Due to the large size and weight of the exhaust pipe (3), the hull (1) has a limited size.
When designing, the overall weight balance and other factors will limit the design.

In this respect, motorcycles and other land vehicles do not have the water turbo box (4) as in the above-mentioned watercraft, and the water after engine cooling is not used for muffling the exhaust gas. ), It is necessary to make the volume even larger, or to adopt an exhaust bypass structure with a complicated partition inside, which means that the vehicle body becomes large and heavy, and the output of the engine equipped with it decreases. Will be invited.

Further, in the above-mentioned configuration of FIG. 12, it is also difficult to completely discharge the cooling water from the water turbo box (4). If this is left in the interior as much as possible, or if the cooling water is intentionally stored in order to increase the heat gradient of the exhaust gas, the cooling water becomes steam due to exhaust heat.
Under the influence of back pressure and pulsation of exhaust gas, the water flows backward from the water turbo box (4) toward the engine (2) and penetrates into the cylinder, causing a start failure of the engine (2), or a crank or There is a risk of rusting the shaft bearings and other parts. The above-mentioned boat capsizes relatively easily, but the same problem will occur at that time.

As a countermeasure for such a problem, Japanese Patent Laid-Open No. 1-175597 is known. And, with this, water after engine cooling is not mixed with exhaust gas, and water jackets (23) (24) are provided around the exhaust pipe (17),
Insert the cooling water supply port (31) of the cooling water supply pipe (30) extended from the jacket (23) (24) into the jacket (2
3) It is connected to the outer case (28) of the expansion type muffler (18), which is separate from (24), so that the exhaust gas can be cooled from outside by cooling water.

However, in such a configuration of cooling from the outside, since a large amount of cooling water is required, the volume of the water jacket (23) (24) must be increased, and the machining cost becomes expensive, and High precision assembly is also difficult.
On top of that, in order to make it larger and heavier, it is also constrained by its design when mounted on a limited size hull (11), and it causes trouble even if it receives a slight vibration or impulse. It will be.

<Means for Solving the Problems> The present invention intends to improve such problems, and an exhaust muffler useful for this purpose is to construct an exhaust gas expansion chamber and an outer cylinder of a certain length, A pair of front and rear cover plates that cover both ends of the opening of the cylinder, an exhaust gas inlet tube and an outlet tube that integrally project from the center of the opening of each cover plate in opposite directions, and the inlet tube. An inner cylinder, which is fitted on the longitudinal center line of the outer cylinder so as to be directly connected to the outlet cylinder, is integrally formed, and has a large number of small holes scattered on its circumferential surface, and the outer circumference of the inner cylinder. A sound absorbing material filled in the inner and outer mutual gaps facing each other between the surface and the inner peripheral surface of the outer cylinder, and a lead groove for generating a vortex flow of exhaust gas on the inner peripheral surface of the inner cylinder,
Its main feature is that it is applied in a spiral state in which a large number of scattered points are twisted in one direction.

<Embodiment> The specific construction of the present invention will be described in detail below with reference to the illustrated embodiment. FIG. 1 shows an overall outline of a jet-propelled small boat, and (10) is a fiber-reinforced plastic (FRP). )
It is a generic name for a boat made of a material such as a hollow closed type float structure. The engine room (11) is partitioned in the first half of the hull, while the upper surface of the second half is also operated. It is formed as a floor deck (12) for people to stand on. However, on the upper surface of the rear half of the hull (10), a seat for the operator to sit may be installed instead of the floor deck (12).

In the engine room (11), a water-cooled two-cycle engine (13), a fuel tank (14), etc. are stored and installed, and the engine (13) drives the jet propulsion device via the propulsion shaft (15). (Water Jet Pump)
(16) is driven so that propulsive force is applied to the hull (10).

That is, the propulsion shaft (15) extends below the floor deck (12) along the center of travel of the boat (10), and the front end of the propulsion shaft (15) extends through the clutch (17) to the engine. An impeller (18) is integrally and rotatably attached to the rear end of the propulsion shaft (15) while being integrally connected to a crankshaft (13) (not shown). (1
Reference numeral 9) is a water absorption duct as a pump case for receiving the impeller (18), which is formed below the floor deck (12) and whose front portion is a hull (1
0) It has an opening on the bottom.

When the propulsion shaft (15) is rotationally driven by the engine (13), water is sucked into the water absorption duct (19) by the impeller (18), and the water is sucked backward in the water absorption duct (19). It is accelerated and pressure-fed to the hull (10) by the steering nozzle (20) opening at the tail of the hull (10).
Will move forward. Needless to say, the operator can remotely control the steering nozzle (20) and swing it to the left and right to steer the boat body (10).

(21) is an exhaust pipe led out from the cylinder block of the engine (13) to the lower front side through an exhaust manifold, and (M) is an exhaust muffler connected to the vicinity of its end, both of which are for the engine. The exhaust gas is stored in the room (11), and exhaust gas is emitted from the muffler (M) to the atmosphere via the emission pipe (22).

In this regard, in the figure, although the discharge pipe (22) is installed at the bow by pulling out the exhaust pipe (21) obliquely from the engine (13) toward the lower front, the exhaust pipe (21 ) Is extended from the engine (13) toward the rear lower side, so that the discharge pipe (22) is installed in the stern part of the boat and the exhaust gas is discharged from the rear part of the hull (10). Of course good.

In any case, piping (not shown) is provided so that the cooling water of the engine (13) can be taken in from the high pressure portion of the water absorption duct (19) of the jet propulsion device (16), and the engine (13 ) Is cooled with water, and the cooling water after the action is introduced into the exhaust pipe (21) and the muffler (M), and the discharge pipe (22) is discharged together with the exhaust gas.
It is supposed to be released from.

In the present invention, the exhaust muffler (M) is made of stainless steel or light alloy as shown in FIGS.

That is, reference numeral (23) in the figure is an outer cylinder of a constant length that forms an exhaust gas expansion chamber, and (24) and (25) are welded to the outer cylinder (23) to cover both ends of the opening. These are a pair of front and rear cover plates that are fixed and integrated via means such as, but the exhaust gas inlet tube (26) and the outlet gas tube (27) are in opposite directions at the center of each opening. In the overhang state, all are fixed and integrated by means such as welding. The exhaust pipe (21) is connected to the inlet pipe (26) and the discharge pipe (22) is connected to the outlet pipe (27) via a connecting pipe or a connecting hose (not shown). It will be connected for communication.

In that case, in FIGS. 2 to 6, both cover plates (24) and (25) are formed in a simple flat plate shape orthogonal to the longitudinal center line (O-O) of the outer cylinder (23). As suggested from the first modification of FIG. 7, such that both cover plates (24) (25) intersect the longitudinal center line (O-O) of the outer cylinder (23) at an acute angle of less than 90 degrees, It may be formed in a tapered frusto-conical shape that projects in the opposite direction. According to this, the exhaust gas can be made to flow more smoothly into the expansion chamber in the outer cylinder (23).

(28) is the exhaust gas inlet pipe (26) and outlet gas pipe (2)
An inner cylinder fitted and integrated on the longitudinal center line (O-O) of the outer cylinder (23) to connect 7) and
A large number of small holes (29) are formed on the circumferential surface of the punching metal so as to be opened in a scattered distribution. Reference numeral (30) denotes a sound absorbing material such as glass wool or rock wool that is filled in the inner and outer mutual gaps between the outer peripheral surface of the inner cylinder (28) and the inner peripheral surface of the outer cylinder (23).

In this respect, in FIG. 2 to FIG. 6, the inner cylinder (28) is formed in a cylindrical shape having a uniform diameter, but as shown in the second modified example of FIG. May be formed in a conical shape whose diameter becomes smaller as it approaches the exhaust gas outlet tube (27). By doing so, as will be described later, the exhaust gas can be gradually accelerated and led out, and the water after engine cooling that has penetrated into the sound absorbing material (30) also vigorously moves in the inner cylinder (28). Combined with the negative pressure effect of the exhaust flow that travels straight, it can be sucked out more and more effectively.

(31) has a constant working length (L) on the circumferential surface of the inner cylinder (28), and the longitudinal centerline (OO) of the outer cylinder (23).
It is a plurality of lead grooves that are given under a constant twist angle (α) that intersects with the exhaust gas. And can be swirled. The lead grooves (31) are, as it were, bulged from the inside to the outside of the inner cylinder (28), so that there is no risk of giving resistance to the exhaust gas flowing inside.

Further, (32) and (33) are in a relational state where they extend substantially parallel to the lead groove (31) of the inner cylinder (28), and the introduction port cylinder (2
6) and the lead-out groove (27) are provided on the inner peripheral surface of the lead-out tube (27), respectively, since their function is to assist the action of the lead groove (31) in the inner tube (28). When the lead groove (31) of the inner cylinder (28) extends as long as possible in the working length (L), the flow to the inlet cylinder (26) and / or the outlet cylinder (27). Road lead groove (32)
It is also possible to omit the addition of (33). Incidentally, (L1)
(L2) is the lead groove (3
2) The working length of (33), (β) and (γ) are the same as the outer cylinder (2
The twist angles intersecting with the longitudinal center line (OO) of 3) are shown respectively.

In particular, when mounted and used on a jet-propelled small boat, as shown in the third modification of FIG. 9, the outer cylinder (23)
Cooling water inlet pipe (3
4) Overhang the connecting hose (3
5) through the sound absorbing material (3
It is possible to introduce it in the state of permeation into 0), and to make its cooling water participate in achieving the sound deadening effect. However, the cooling water is sucked out by the negative pressure action of the exhaust gas flowing at high speed in the inner cylinder (28), and is discharged from the outlet cylinder (27) together with the exhaust gas.

<Operation> According to the above configuration, the exhaust gas from the engine (13) is indicated by the solid arrow (x) in FIG. 6, and the cooling water after engine cooling is indicated by the dotted arrow (y) in the figure. As described above, in a mixed flow state of the both, it is introduced from the exhaust pipe (21) to the exhaust muffler (M), and in the process, heat exchange between the exhaust gas and the cooling water is performed, so that the thermal gradient of the exhaust gas is increased. , As soon as it is introduced into the muffler (M), it first undergoes an expansion action in the outer cylinder (23), so that the first
The next silencing effect will be achieved.

At that time, since the lead grooves (31) (32) for generating the vortex are provided on the inner peripheral surfaces of the exhaust gas inlet tube (26) and the inner tube (28), the exhaust gas is transferred to the muffler (M). At the beginning of the introduction of exhaust gas, the exhaust gas and cooling water swirl together in a spiral direction in one direction, the cooling water heavier than the exhaust gas is shaken off, and the sound of the outer cylinder (23) is temporarily absorbed. As a result of permeating into the material (30), the permeated cooling water also contributes to the achievement of the sound deadening effect.

On the other hand, the exhaust gas blown off by the cooling water makes a swirling and swirling motion by the lead groove (31) along the inner cylinder (28) and vigorously goes straight backward toward the outlet cylinder (27). In that case, since the lead grooves (31) (32) (33) are recessed from the inner peripheral surface of the inner cylinder (28), the lead grooves (31) (32) (33) do not give any resistance to the exhaust gas during the flowing process, The output performance of the engine (13) can be remarkably improved in combination with the straight travel in the inner cylinder (28).

In addition, the cooling water that has previously penetrated into the sound absorbing material (30) of the outer cylinder (23) swirls in the inner cylinder (28) along the longitudinal center line (OO) and vigorously. Due to the negative pressure effect of the exhaust gas traveling straight, it is sucked into the inner cylinder (28) from the sound absorbing material (30) through the small hole (29) of the inner cylinder (28), and then atomized together with the exhaust gas. Outlet tube (27)
Is discharged into the atmosphere through the discharge pipe (22), and there is no risk of backflow toward the engine (13).

In particular, if the inner cylinder (28) is formed in a conical shape as in the second modified example, an even more effective negative pressure action can be generated in the exhaust gas, which makes it smoother and more reliable. The cooling water can be sucked out. The muffler (M) of the present invention can also be used to improve its sound deadening effect by connecting a plurality of them in series or in parallel as shown in FIGS.

<Effects of the Invention> As described above, the exhaust muffler (M) of the present invention has an outer cylinder (23) of a certain length that forms an expansion chamber for exhaust gas due to its configuration.
And a pair of front and rear cover plates (24) and (25) that cover both ends of the opening of the outer cylinder (23), and the cover plates (24) and (25) are integrally formed in the opposite direction from the center of the opening. The inlet pipe (26) and the outlet pipe (27) for the overhanging exhaust gas, and the outer pipe (23) are connected so that the inlet pipe (26) and the outlet pipe (27) are directly connected. An inner cylinder (28) fitted and integrated on the longitudinal centerline (O-O) and having a large number of small holes (29) scattered on its circumferential surface, and an outer peripheral surface of the inner cylinder (28). And a sound absorbing material (30) filled in the inner and outer mutual gaps facing each other with the inner peripheral surface of the outer cylinder (23), and the lead groove (31) for generating a vortex flow of exhaust gas is provided on the inner peripheral surface of the inner cylinder (28). ) Is applied to a large number of scattered spirals that spiral in one direction, and is applied to the engine (13) mounted on a jet-propelled small boat. In this case, although the problems of the prior art described in the opening paragraph based on Japanese Patent Application Laid-Open No. 1-175597 and FIG. 12 can be completely solved and the muffling effect of the exhaust gas can be improved, the output reduction of the engine (13) It is also effective in reliably preventing starting failures.

That is, the present invention allows the exhaust gas and the cooling water after engine cooling to flow together from the exhaust pipe (21) of the engine (13) to the exhaust muffler (M), so to speak, so that the exhaust gas is cooled by water in the exhaust passage. In particular, on the inner peripheral surface of the inner cylinder (28) fitted and integrated on the longitudinal centerline (OO) of the outer cylinder (23) forming the expansion chamber, the longitudinal centerline ( O-
A plurality of lead grooves (31) having a constant twist angle (α) and a constant working length (L) intersecting with (O) are provided in a spiral spiral shape in the overall one direction, Since the exhaust gas is swirled by this, the cooling water that has been shaken off by the swirling and swirling motion of the exhaust gas and permeated into the sound absorbing material (30) of the outer cylinder (23) is, so to speak, silenced the exhaust gas. It will function as a wall and can achieve an excellent silencing effect.

Moreover, the cooling water swirls and swirls in the inner cylinder (28), and the negative pressure action of the exhaust gas traveling straight toward the outlet cylinder (27) causes the cooling water to flow from the sound absorbing material (30) to the inner cylinder (28). ), And is discharged from the outlet cylinder (27) together with the exhaust gas, so there is no reverse flow toward the engine (13), and the various types of backflow associated with it. The problem can be reliably prevented.

Further, the exhaust gas is guided by the lead groove (31) and moves straight while swirling and swirling in the inner cylinder (28), and the lead groove (31) is in the form of a literal groove. Since it does not project inward from the cylinder (28), it does not act as a resistance to the exhaust gas flowing inside the cylinder (28), and therefore the output performance of the engine (13) can be significantly improved.

Further, particularly when the structure of claim 2 is adopted, the swirling and swirling motion of the exhaust gas can be more effectively generated over the entire exhaust muffler (M), and the suction negative pressure of the cooling water is generated. It also has the effect of allowing smooth and reliable operation.

Furthermore, if the construction of claim 3 is adopted, it is more effective as a jet-propelled small-sized watercraft, and the cooling water of the engine (13) can be effectively utilized for the effect of silencing the exhaust gas.

It is needless to say that the effects of silencing and improving the output performance of the engine can be achieved without modification even when the present invention is applied to motorcycles and other various land vehicles, except for the action related to the cooling water. Yes.

[Brief description of drawings]

FIG. 1 is an overall schematic cross-sectional view of a jet-propelled small watercraft to which the present invention is applied, FIGS. 2 and 3 are side and front views showing the exhaust muffler of the engine, and FIGS. Sectional views taken along lines 4-4 and 5-5 in FIG. 2, FIG. 6 is a sectional view taken along line 6-6 in FIG. 3, and FIGS. 7 and 8 are first and second modifications of the present invention. Each sectional schematic view, FIG. 9 is a side sectional view showing the same third modified example, FIGS. 10 and 11 are explanatory views showing two kinds of connection use states of the present invention, and FIG. 12 corresponds to FIG. It is a sectional side view of a conventional product. (23) …… Outer cylinder (24) (25) …… Cover plate (26) …… Inlet cylinder (27) …… Outlet cylinder (28) …… Inner cylinder (29) …… Small hole (30) …… Sound absorbing material (31) (32) (33) …… Lead groove (34) …… Cooling water inlet tube (OO) …… Longitudinal centerline

Claims (3)

[Scope of utility model registration request] 1. An outer cylinder (23) having a constant length for forming an exhaust gas expansion chamber, and a pair of front and rear cover plates (24) (25) for covering both ends of an opening of the outer cylinder (23). An exhaust gas inlet tube (26) and an outlet tube (27) that integrally project in opposite directions from the center of the opening of each cover plate (24) (25), and the inlet tube (26) and the inlet tube (26). In order to connect the outlet cylinder (27) in a direct communication state, the outer cylinder (23) is fitted and integrated on the longitudinal center line (OO), and a large number of small holes (29) are formed on the circumferential surface. An inner cylinder (28) which is interspersed and opened; and a sound absorbing material (30) filled in the inner and outer mutual gaps between the outer peripheral surface of the inner cylinder (28) and the inner peripheral surface of the outer cylinder (23), The inner cylinder (28) is characterized in that exhaust gas eddy current generation lead grooves (31) are provided on the inner peripheral surface of the inner cylinder (28) in a spiral spiral state of twisting in a large number of scattered points in one overall direction. You Exhaust muffler of the engine. 2. An inlet cylinder (26) and / or an outlet cylinder (27)
The lead groove (32) (33) substantially parallel to the lead groove (31) provided on the inner peripheral surface of the inner cylinder (28) is provided on the inner peripheral surface of the. Exhaust muffler for the engine. 3. The exhaust muffler for an engine according to claim 1, wherein a cooling water inlet pipe (34) after cooling the engine is communicatively connected to an upper portion of the inner peripheral surface of the outer casing (23).