JP2518742Y2 - Muffler for inline 2 cylinder engine - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin muffler suitable for an alternate explosion type two-cylinder engine in which two cylinders are arranged in series with a crankshaft.

[0002]

2. Description of the Related Art When reducing the size and weight of an engine, which is the power source of a portable work machine such as a brush cutter, a chain saw, a tea cutter, and a sprayer, work such as carrying and brush cutting becomes easy. . Further, in this type of working machine, engine vibration is transmitted to the operator's hand, causing various problems.

As a means for solving the vibration problem, for example, Japanese Utility Model Publication No. 63-11300 discloses an engine in which a two-cycle two-cylinder is horizontally opposed to a crank rotation shaft. However, in the horizontal facing method, the lateral width of the entire engine becomes large, so that the engine side hits a tree branch or the like and workability and transportability are deteriorated. In addition, the balance of the machine body is poor, and the machine body easily swings in the left-right direction, resulting in poor operability. Furthermore, since both engines are arranged on the left and right sides centering on the crank rotation shaft, the structure related to intake and exhaust becomes complicated, and restrictions are imposed on the miniaturization and weight reduction of the entire engine.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have designed a two-cycle one-cylinder engine having a two-cylinder cylinder having a two-cylinder displacement which is divided into two cylinders so that the engine can be made compact and lightweight. , Proposed to fix the crankcase in series, and filed a utility model registration application. By arranging a plurality of cylinders in series with the crankshaft, the entire device becomes compact and the operability, workability, transportability, etc. are improved as compared with the horizontally opposed type.

In an engine of a type in which a large capacity cylinder is divided into a plurality of cylinders, an ignition plug that causes each cylinder to explode is required. In the conventional engine design, a distributor is required because a voltage for generating a spark is sequentially applied to the spark plugs provided in each cylinder. Therefore, the wiring system becomes complicated and the weight of the entire device also increases.

As a design in which the distributor is omitted, it is conceivable that sparks are generated in each of the plurality of cylinders to cause explosion and misfire depending on the state of the air-fuel mixture in the cylinders. However, the frequency of electromotive force generation is doubled by the number of cylinders, and the temperature rise of the magneto and rotor becomes significant. As a result, in particular, the inner type magnet deteriorates in a short time and stable electromotive force cannot be obtained.

Therefore, the present inventors have developed an in-line two-cylinder engine which employs a method of air-cooling an outer type magnet by cooling air taken in for cooling the cylinder, and a part of the engine is disclosed in Japanese Patent Application No. 3-194802. Filed as. In this in-line two-cylinder engine, it is possible to suppress the temperature rise of the magneto and the rotor and to drive the engine under stable conditions for a long period of time, although the electromotive force generation frequency is high.

The in-line two-cylinder engine can have a common intake system, exhaust system, and the like. Further, when the suction and the explosion in the individual cylinders are alternately repeated by shifting the cycle, it becomes possible to use a muffler, an air cleaner, etc. having a capacity of approximately one cylinder. Therefore, a compact design around the engine becomes possible, which is suitable for brush cutting work and the like. The exhaust system of each cylinder is arranged in the same positional relationship with the crankshaft.

The present invention focuses on a structure peculiar to an alternating explosion type in-line two-cylinder engine in which cylinders are arranged in series, and theoretically adopts a flat muffler having an inner volume corresponding to half of the conventional one. The purpose is to improve the usability of a portable work machine by making the engine area compact.

[0010]

In order to achieve the object, a muffler for an in-line two-cylinder engine of the present invention is used for an alternating explosive two-cylinder engine in which two cylinders 2a and 2b are arranged in series with a crankshaft. The muffler 5 has a box shape that spreads in a plane orthogonal to the exhaust direction from the engine exhaust port, and a partition plate 40 having ventilation holes 42a and 42b is provided inside the muffler 5 in the front and rear chambers A and B in the exhaust direction. The partition plate 40 is provided with a recess 41 protruding toward the front chamber A, the exhaust port is exposed to the front chamber A, and the tail pipe 50 is inclined with respect to the rear chamber B from the exhaust direction. The tail pipe 50 is arranged so that the upstream end of the tail pipe 50 faces the recess 41.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a brush cutter will be described below with reference to the drawings. However, the present invention is not limited to this, and is similarly applied to other portable working machines such as chainsaws, tea mowers and sprayers.

The muffler of this embodiment is incorporated in an in-line two-cylinder engine in which two cylinders 2a and 2b are arranged in series along the longitudinal direction of the operating main rod 1 of the brush cutter as shown in FIG. There is. The cylinders 2a and 2b are provided with an intake system that passes through the air cleaner 3 and the carburetors 4a and 4b, and an exhaust system that passes through the muffler 5. In addition, number 6
Shows a recoil starter for starting the engine. The output of the engine is taken out from the crankshaft, appropriately transmitted by the clutch mechanism incorporated in the clutch housing 7, and then transmitted to the tip of the operating main rod 1 through the transmission shaft inserted in the operating main rod 1. It is transmitted to the attached cutting blade.

As shown in FIGS. 2 and 3, the muffler 5 is a split type of the muffler body 10 and the muffler lid 20, and the cylinder case of the engine is fitted with a bolt 31 inserted into a sleeve 30 penetrating both. Stuck to.
The muffler body 10 and the muffler lid 20 are formed in a box shape with double walls 12 and 22 filled with glass wool 11 and 21. Then, by caulking the double wall 12 to the other double wall 22 at the abutting portion of the muffler body 10 and the muffler lid body 20, the muffler body 10 and the muffler lid body 20 are integrated via the partition plate 40 therebetween. To be done.

The muffler body 10 is, as shown in FIG.
On the side surface on the engine side, there are two exhaust inlets 13a, 13 respectively corresponding to the exhaust outlets of each cylinder block of the engine.
A gasket 14 in which b is formed is provided. Further, a mounting bolt hole 15 used for mounting an engine cover or the like is formed in the side wall.

As shown in FIG. 5, a tail pipe 50 is attached to the muffler cover 20 in an inclined manner. Then, the tail pipe 50 facing the inside of the muffler lid 20.
A recess 41 is formed in the partition plate 40 at the end of the partition plate 40.
The depth in which the tail pipe 50 is inserted is made large by the depression 41, and the height of the tail pipe 50 protruding from the muffler cover 20 can be suppressed by that much.

As shown in FIG. 6, the partition plate 40 has a plurality of ventilation holes 42a and 42b on both sides of the recess 41. When the partition plate 40 is sandwiched between the muffler body 10 and the muffler lid 20, the internal space of the muffler is divided into a front chamber A and a rear chamber B. The front chamber A and the rear chamber B are communicated with each other through the ventilation holes 42a and 42b.

From the engine side, exhaust inlets 13a, 13b
The exhaust gas sent into the first chamber through the chamber expands / diffuses in the front chamber A and decreases in pressure. Next, the exhaust gas passes through the vent holes 4
It flows into the rear chamber B from 2a and 42b. At this time, since the exhaust inlets 13a, 13b and the ventilation holes 42a, 42b are in a positional relationship apart from each other in FIG. 2, the exhaust gas flows in the front chamber A as shown by the arrow. Therefore, the pulsation on the engine side can be avoided from being directly transmitted to the rear chamber B side.

When the exhaust gas flows into the rear chamber B through the ventilation holes 42a and 42b, the exhaust gas expands and diffuses and repeatedly drops in pressure. The exhaust gas then flows into the tail pipe 50 from the rear chamber B and is released to the atmosphere. At this time, since the volume of the rear chamber B is increased by the amount of forming the depression 41, the pressure reducing action is large, and the flow velocity of the exhaust gas is sufficiently suppressed,
A sufficient muffling effect can be obtained.

[0019]

As described above, in the present invention, the muffler 5 for the two-cylinder engine of alternating explosion type in which the two cylinders 2a and 2b are arranged in series with respect to the crankshaft,
A partition plate 40 having a box shape extending in a plane orthogonal to the exhaust direction from the engine exhaust port and having ventilation holes 42a and 42b.
The inside of the muffler 5 is divided into front and rear chambers A and B with respect to the exhaust direction by the partition plate 40 provided with a recess 41 projecting to the front chamber A side and the exhaust port being provided with the front chamber A.
The tail pipe 50 is connected to the rear chamber B with an inclination to the exhaust direction, and the upstream end of the tail pipe 50 is arranged so as to face the recess 41. Taking advantage of the advantages of the alternate explosion type two-cylinder engine in which the cylinders are arranged in series with the shaft, a thin and compact split muffler including a tail pipe can be adopted. Since the muffler has two cylinders which alternately inhale and explode alternately, the muffler can be theoretically halved in capacity as compared with a one-cylinder engine having the same displacement. Further, since the two cylinders are arranged in the crankshaft direction, the muffler including the tail pipe can be arranged long in the crankshaft direction. as a result,
A flat air cleaner that covers the required capacity over a wide area can be used, and a compact design around the engine is possible, resulting in a portable work machine that is easy to use.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an in-line two-cylinder engine for a brush cutter to which the present invention is applied.

FIG. 2 is a sectional view showing the internal structure of the muffler.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is an IV-IV arrow view of FIG.

5 is a view taken along the line VV of FIG.

6 is a VI-VI arrow view of FIG.

[Explanation of symbols]

1 Operation Main Rod 2a, 2b Cylinder 5 Muffler 40 Partition Plate 41 Recess 42
a, 42b Vent hole 50 Tail pipe A Front chamber B Rear chamber

Claims (1)

(57) [Scope of utility model registration request] 1. Two cylinders (2
a. A muffler (5) for two-cylinder engine of alternating explosion type in which 2b) are arranged in series, and has a box shape extending in a plane orthogonal to an exhaust direction from an engine exhaust port, and a vent hole (42).
a partition plate (40) having a, 42b) allows the interior of the muffler (5) to be separated into two chambers in front and rear with respect to the exhaust direction.
It is divided into (A, B) and the partition plate (40) has a front chamber
A recess (41) protruding toward the (A) side is provided, the exhaust port is exposed to the front chamber (A) , and the tail pipe (50) is connected to the rear chamber (B) with an inclination to the exhaust direction. Then
At the upstream end of the tail pipe (50), the recess (4
A muffler for an in-line two-cylinder engine, which is arranged so as to face 1) .