JP5060459B2 - 2-cycle engine - Google Patents

Description

  The present invention relates to a two-cycle engine used in small work machines such as a chain saw, a brush cutter, and a blower.

  A two-cycle engine includes a piston slidably mounted in a cylinder, an exhaust passage communicating with a combustion chamber formed in an upper portion of the cylinder, two scavenging passages communicating the crank chamber and the combustion chamber, and a crank chamber And an intake passage leading to In such a two-cycle engine, the opening portions on the cylinder side of the two scavenging passages are formed at positions facing each other across the cylinder on both sides of the exhaust passage.

In the above-described two-cycle engine, the mixed gas of fuel and air that has flowed into the crank chamber through the suction passage flows into the combustion chamber through the scavenging passages on both sides, and the piston is generated by the expansion force when the mixed gas is burned in the combustion chamber. Is reciprocated in the cylinder.
Specifically, when the piston rises in the cylinder, the pressure in the crank chamber decreases, and the mixed gas flows into the crank chamber through the intake passage (intake stroke). When the piston reaches top dead center and the piston descends due to the expansion force when the mixed gas is burned in the combustion chamber, the exhaust passage opens to the upper combustion chamber side of the cylinder, and the combustion gas in the combustion chamber enters the exhaust passage. Exhaust (exhaust stroke). When the piston is further lowered after the exhaust stroke, the scavenging passages on both sides open to the upper combustion chamber side of the cylinder, and the mixed gas in the crank chamber flows into the combustion chamber through the scavenging passages on both sides (scavenging stroke).

  In the scavenging stroke of the two-cycle engine, the exhaust passage and the scavenging passages on both sides open to the upper combustion chamber side of the cylinder, so that the unburned mixed gas flowing into the cylinder through the scavenging passages on both sides is also present along with the combustion gas in the combustion chamber. There may be a case where "blow-through" is exhausted into the exhaust passage. When this blow-through occurs, the unburned gas contained in the exhaust gas discharged from the engine increases, and the amount of hydrocarbons contained in the exhaust gas increases.

  As shown in FIG. 7, in the two-cycle engine 100, the mixed gas flowing into the cylinder 60 from the openings 21, 31 of the scavenging passages 20, 30 on both sides is a region opposite to the opening of the exhaust passage 80. The opening direction of the scavenging passages 20, 30 on both sides is set so that the gas flows toward the cylinder, but the mixed gas flowing into the cylinder 60 from the scavenging passages 20, 30 on both sides is strongly in the center of the cylinder 60. When the collision occurs, a part of the mixed gas flows toward the exhaust passage 80. That is, the blow-through that occurs in the first half of the scavenging stroke is caused by a shortcut of the flow of the mixed gas that has flowed into the cylinder 60 toward the exhaust passage 80.

Therefore, in a conventional two-cycle engine, a part of the mixed gas flowing into the cylinder from the scavenging passages on both sides is caused to flow toward the upper part of the cylinder so as to form a vertical vortex of the mixed gas in the cylinder. Some are configured (for example, see Patent Document 1).
In this configuration, the collision of the mixed gas flowing into the cylinder from the scavenging passages on both sides is reduced, and the amount of the mixed gas flowing into the cylinder that is short-cut toward the exhaust passage is reduced. The blow-through generated in the first half can be reduced.

JP 2006-348785 A (paragraphs 0035 to 0036, FIG. 2)

  However, in a conventional two-cycle engine configured to flow a part of the mixed gas toward the upper part of the cylinder, in order to adjust the blowing direction of the mixed gas, a built-up portion is formed in the scavenging passage, Since the wall surface in the scavenging passage is cut, and the processing of the scavenging passage is complicated and difficult to fine-tune, there is a problem that the manufacturing cost of the two-cycle engine increases.

  In the conventional two-cycle engine, in the scavenging process, after the mixed gas flowing into the cylinder from the scavenging passages on both sides flows in a loop along the inner wall surface of the cylinder, before the opening of the exhaust passage is closed. In addition, there is a problem that blow-through occurs in the latter half of the scavenging stroke by reaching the opening of the exhaust passage.

  Therefore, in the present invention, the above-described problems are solved, and the blowout generated in the first half and the second half of the scavenging stroke can be reduced with a simple structure, and the unburned gas contained in the exhaust gas is greatly reduced. It is an object of the present invention to provide a two-cycle engine that can perform the above.

  In order to solve the above-described problems, the present invention provides a piston that is slidably mounted in a cylinder, an exhaust passage that communicates with a combustion chamber formed in the cylinder, a crank chamber, and the combustion chamber. A scavenging passage, a second scavenging passage, and a suction passage that communicates with the crank chamber, and a mixed gas of fuel and air containing oil flows into the crank chamber through the suction passage and fills the crank chamber. The mixed gas is introduced into the combustion chamber through the first scavenging passage and the second scavenging passage, and the mixed gas is combusted in the combustion chamber, so that the piston is reciprocated in the cylinder. In the two-cycle engine, each opening on the cylinder side of the first scavenging passage and the second scavenging passage is formed at a position facing the cylinder, A shielding member having a plurality of holes is attached to a part of each of the first scavenging passage and the second scavenging passage, and the first scavenging passage and the second scavenging passage Each said shielding part is arrange | positioned in the position which becomes a diagonal on both sides of the said cylinder.

In this configuration, in the scavenging passage, the mixed gas flowing into the cylinder from the portion where the shielding member is attached has a lower flow velocity than the mixed gas flowing into the cylinder from the portion where the shielding member is not attached. As a result, the mixed gas flowing into the cylinder from the scavenging passages on both sides collides at a position closer to the shielding member than the central portion in the cylinder. Therefore, the mixed gas collides with the scavenging passages on both sides at positions close to the respective shielding members arranged at diagonal positions.
In this way, when the mixed gas collides at a position shifted from the center of the cylinder, the collision of the mixed gas becomes weaker and the mixed gas collides than when the mixed gas collides at the center of the cylinder. Since the flow to the exhaust passage side that occurs sometimes is reduced, it is possible to reduce the blow-by that occurs in the first half of the scavenging stroke.

  In addition, the flow rate of the mixed gas flowing into the cylinder from the scavenging passages on both sides becomes slow, and the collision position of the mixed gas flowing into the cylinder shifts from the center of the cylinder. While being stirred, the mixed gas tends to stay in the upper part of the cylinder. Therefore, in the scavenging stroke, the amount of the mixed gas flowing in a loop along the inner wall surface of the cylinder reaches the opening of the exhaust passage before the opening of the exhaust passage is closed. The blow-by generated in the stage can be reduced.

  Further, by attaching the shielding member to a part of the passage of the scavenging passage, the flow rate of the mixed gas flowing into the cylinder can be reduced, and further, by adjusting the opening area of the hole of the shielding member, The flow rate of the mixed gas flowing into the cylinder can be adjusted.

  In the above-described two-cycle engine, the shielding member can be constituted by a plate-like member in which a plurality of holes are formed. In this configuration, since the shielding member can be formed using existing punching metal or the like, the processing cost of the two-cycle engine can be reduced.

  In the above-described two-cycle engine, the cylinder side openings of the first scavenging passage and the second scavenging passage are each divided by a partition portion, and the shielding members are formed on both sides of the cylinder, respectively. Of the plurality of openings, it can be attached corresponding to the openings arranged at diagonal positions across the cylinder. With this configuration, the shielding member can be easily and reliably attached.

  According to the two-cycle engine of the present invention, by attaching a shielding member to a part of the scavenging passage, the flow rate of the mixed gas flowing into the cylinder is adjusted, and the blow-through generated in the first and second stages of the scavenging stroke Can be reduced. Therefore, with a simple structure, the amount of unburned mixed gas exhausted into the exhaust passage can be greatly reduced, and the amount of hydrocarbons in the exhaust gas can be reduced.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
A two-cycle engine 1A of the present embodiment shown in FIG. 1 is used for a small work machine such as a chain saw, a brush cutter, or a blower.
The two-cycle engine 1A includes a piston 50 that is slidably mounted in a cylinder 60. A mixed gas of fuel and air containing oil flows into the crank chamber 10 from the intake passage 70, and the crank chamber 10 A mixed gas of fuel and air filled therein is caused to flow into the upper portion of the cylinder 60 through the first scavenging passage 20 and the second scavenging passage 30 (see FIG. 2), and the combustion chamber 40 formed in the upper portion of the cylinder 60. The piston 50 is reciprocated in the cylinder 60 by the expansion force when the mixed gas is combusted inside.
Note that various power mechanisms in the two-cycle engine 1A of the present embodiment have the same configuration as that of a known two-cycle engine, and thus detailed description thereof will be omitted except for the characteristic configuration constituting the present invention.

  The two-cycle engine 1A includes a piston 50 slidably mounted in a cylinder 60, an exhaust passage 80 communicating with the combustion chamber 40 formed in the cylinder 60, and a crank chamber 10 and a combustion chamber 40 communicating with each other. A scavenging passage 20 and a second scavenging passage 30 (see FIG. 2), a suction passage 70 communicating with the crank chamber 10, and a crankshaft 90 rotating in conjunction with the reciprocating motion of the piston 50 in the crank chamber 10. I have.

The suction passage 70 is formed in a side portion of the cylinder block 61, one end is opened at the lower portion of the cylinder 60, and the other end is connected to a fuel supply passage (not shown).
When the piston 50 is located at the bottom dead center in the cylinder 60 (the state shown in FIG. 1), the opening on the cylinder 60 side of the suction passage 70 is closed by the side surface of the piston 50. On the other hand, as shown in FIG. 3, when the piston 50 is located at the top dead center in the cylinder 60, the opening on the cylinder 60 side of the suction passage 70 opens to the lower part of the cylinder 60 and communicates with the crank chamber 10.

The exhaust passage 80 is formed on the side of the cylinder block 61 on the side opposite to the suction passage 70, one end opening at the top of the cylinder 60, and the other end connected to an exhaust pipe (not shown).
When the piston 50 is located at the bottom dead center in the cylinder 60 (the state shown in FIG. 1), the opening on the cylinder 60 side of the exhaust passage 80 opens to the upper combustion chamber side of the cylinder 60 and communicates with the combustion chamber 40. On the other hand, as shown in FIG. 3, when the piston 50 is located at the top dead center in the cylinder 60, the opening on the cylinder 60 side of the exhaust passage 80 is closed by the side surface of the piston 50.

The first scavenging passage 20 and the second scavenging passage 30 are formed in the cylinder block 61 on both the left and right sides of the cylinder 60 in FIG. That is, the scavenging passages 20 and 30 on both sides are formed at positions shifted by approximately 90 degrees in the circumferential direction of the cylinder 60 with respect to the exhaust passage 80 as shown in FIG. As shown in FIG. 2, one end of the scavenging passages 20, 30 on both sides is opened at the top of the cylinder 60 at substantially the same height as the exhaust passage 80, and the other end is opened in the crank chamber 10.
In the two-cycle engine 1A of the present embodiment, the first scavenging passage 20 is formed on the right side of the cylinder 60 and the second scavenging passage 30 is formed on the left side in FIG.

The openings 21a and 21b on the cylinder 60 side of the first scavenging passage 20 are formed above the cylinder 60 in FIG. 5, and the openings 31a and 31b on the cylinder 60 side of the second scavenging passage 30 are cylinders in FIG. 60 is formed on the lower side.
As described above, the openings 21a and 21b on the cylinder 60 side of the first scavenging passage 20 and the openings 31a and 31b on the second scavenging passage 30 are cylinders on both sides of the opening on the cylinder 60 side of the exhaust passage 80. It is formed in the position which opposes on both sides of 60 center part.

The openings 21a and 21b of the first scavenging passage 20 are divided into two by a partition portion 21c formed at the center in the width direction, and the opening 21a on the suction passage 70 side and the opening 21b on the exhaust passage 80 side. And are formed. Similarly, the openings 31a and 31b of the second scavenging passage 30 are divided into two by a partition portion 31c formed at the center in the width direction, and the opening 31a on the suction passage 70 side and the opening on the exhaust passage 80 side. A portion 31b is formed.
Note that the mixed gas flowing into the cylinder 60 from the scavenging passages 20 and 30 on both sides flows toward the region opposite to the opening of the exhaust passage 80 (region on the suction passage 70 side). The opening direction of the scavenging passages 20 and 30 is set.

Shield members 22 and 32 each having a plurality of holes are attached to a part of each of the first scavenging passage 20 and the second scavenging passage 30.
Specifically, the shielding members 22 and 32 are arranged at positions corresponding to the opening 21a on the suction passage 70 side of the first scavenging passage 20 and the opening 31b on the exhaust passage 80 side of the second scavenging passage 30, respectively. Has been. That is, the two shielding members 22 and 32 are diagonally arranged across the central portion of the cylinder 60 among the four openings 21a, 21b, 31a, and 31b of the first scavenging passage 20 and the second scavenging passage 30. It is attached corresponding to the two openings 21a and 31b arranged.
Thereby, in a pair of opening part 21a, 31a (21b, 31b) which opposes on both sides of the cylinder 60, the shielding member 22 (32) is provided in one opening part 21a (31b). In other words, in each of the adjacent openings 21a and 21b (31a and 31b), the shielding member 22 (32) is provided in one opening 21a (31b).

The shielding members 22 and 32 are steel plate-like members that block the entire areas of the openings 21a and 31b. In the present embodiment, the existing punching metal in which a plurality of circular holes are formed is used. Yes.
Further, as shown in FIG. 2, the shielding members 22 and 32 are arranged in the height direction of the first scavenging passage 20 and the second scavenging passage 30 in the first scavenging passage 20 and the second scavenging passage 30. It is attached to a position closer to each opening 21a, 31b on the cylinder 60 side than the center of the cylinder.
In the present embodiment, in the cylinder block 61, the part to which the shielding members 22 and 32 are attached is divided, and the shielding members 22 and 32 are sandwiched between the cylinder block 61 and the divided block 61a. . In this configuration, the shielding members 22 and 32 can be easily attached to the first scavenging passage 20 and the second scavenging passage 30 by detaching the divided block 61 a from the cylinder block 61. In addition, the shielding members 22 and 32 can be easily maintained.

  As shown in FIG. 2, when the piston 50 is positioned at the bottom dead center in the cylinder 60, the openings 21a, 21b, 31a, 31b (see FIG. 6) on the cylinder 60 side of the scavenging passages 20, 30 on both sides are Opening to the upper combustion chamber side of the cylinder 60 leads to the combustion chamber 40. On the other hand, as shown in FIG. 4, when the piston 50 is positioned at the top dead center in the cylinder 60, the openings 21a, 21b, 31a, 31b on the cylinder 60 side of the scavenging passages 20, 30 on both sides (see FIG. 5). Is closed by the side surface of the piston 50.

As shown in FIGS. 1 and 2, the piston 50 is a member that reciprocates in the vertical direction in the cylinder 60 and has a circular shape in plan view.
When the piston 50 is located at the bottom dead center in the cylinder 60 (the state shown in FIG. 1), the opening on the cylinder 60 side of the suction passage 70 is closed by the side surface of the piston 50, and the opening on the cylinder 60 side of the exhaust passage 80 is opened. The openings 21 a, 21 b, 31 a, 31 b (see FIG. 6) on the cylinder 60 side of the scavenging passages 20, 30 on both sides open to the upper combustion chamber side of the cylinder 60 and communicate with the combustion chamber 40.
On the other hand, as shown in FIG. 4, when the piston 50 is located at the top dead center in the cylinder 60, the opening on the cylinder 60 side of the exhaust passage 80 and the opening portion 21a on the cylinder 60 side of the scavenging passages 20, 30 on both sides. , 21b, 31a, 31b (see FIG. 5) are closed by the side surface of the piston 50, and the opening on the cylinder 60 side of the suction passage 70 opens into the lower portion of the cylinder 60 and communicates with the crank chamber 10.

  The crankshaft 90 includes a first crankshaft 91 disposed on the right side of FIG. 4 and a second crankshaft 92 disposed on the left side of FIG. The first crankshaft 91 and the second crankshaft 92 are formed with output shafts 91 a and 92 a that are rotatably supported by the crankcase 11, and the piston 50 is connected via a connecting rod 93. When the piston 50 reciprocates in the vertical direction in the cylinder 60, the connecting rod 93 moves up and down in conjunction with the reciprocating motion of the piston 50, and the reciprocating motion of the piston 50 is converted into the rotational motion of the crankshaft 90. The shafts 91a and 92a rotate around the axis.

The two-cycle engine 1A of the present embodiment configured as described above operates as follows and exhibits the effects of the present invention.
In the intake / compression stroke, when the inside of the crank chamber 10 is in a negative pressure state as the piston 50 moves up, a mixed gas of fuel and air generated by a carburetor or a fuel injection device provided in a fuel supply passage (not shown) Then, it flows into the crank chamber 10 through the suction passage 70.

  When the piston 50 reaches the top dead center in the cylinder 60, the mixed gas flowing into the cylinder 60 in the previous scavenging stroke is compressed in the combustion chamber 40 as shown in FIG. When the mixed gas is ignited in the combustion chamber 40 by the spark plug 41 protruding into the combustion chamber 40, the piston 50 is pushed down in the cylinder 60 by the expansion force.

  When the piston 50 descends in the cylinder 60, as shown in FIG. 1, the exhaust passage 80 opens to the top of the cylinder 60 and communicates with the combustion chamber 40, and the combustion gas generated by the combustion of the mixed gas is exhausted. 80 is exhausted (exhaust stroke). Moreover, the gas mixture in the crank chamber 10 is compressed by lowering the piston 50.

  When the piston 50 descends in the cylinder 60 and the exhaust passage 80 begins to open to the upper combustion chamber side of the cylinder 60 and then the piston 50 further descends, as shown in FIG. Opens to the upper combustion chamber side of the cylinder 60 and communicates with the combustion chamber 40. Then, the mixed gas compressed in the crank chamber 10 flows into the cylinder 60 through the scavenging passages 20 and 30 on both sides (scavenging stroke).

As shown in FIG. 6, in the scavenging stroke, in the openings 21a, 21b, 31a, 31b of the scavenging passages 20, 30 on both sides, the air flows into the cylinder 60 from the openings 21a, 31b to which the shielding members 22, 32 are attached. The flow rate of the mixed gas is slower than the flow rate of the mixed gas flowing into the cylinder 60 from the openings 21b and 31a to which the shielding members 22 and 32 are not attached.
As a result, the mixed gas that has flowed into the cylinder 60 from the scavenging passages 20 and 30 on both sides collides at a position closer to the shielding members 22 and 32 than the central portion in the cylinder 60. That is, the mixed gas collides at two positions close to the shielding members 22 and 32 arranged at diagonal positions across the center of the cylinder 60.

  As shown in FIG. 3, the piston 50 that has reached the bottom dead center in the cylinder 60 rises again in the cylinder 60 by the rotational force of the crankshaft 90, and the suction and compression strokes are repeated.

  In the two-cycle engine 1A of the present embodiment, as shown in FIG. 6, the mixed gas collides at positions close to the shielding members 22 and 32 arranged at diagonal positions across the center of the cylinder 60. . As described above, when the mixed gas collides at two positions shifted from the central portion of the cylinder 60, the mixed gas flowing into the cylinder 60 from the scavenging passages 20, 30 on both sides is collected at the central portion of the cylinder 60. Compared with the case of collision, the collision of the mixed gas is weakened, and the flow to the exhaust passage 80 side that occurs when the mixed gas collides is reduced, so that the blow-through that occurs in the first half of the scavenging stroke can be reduced. .

  In addition, the flow velocity of the mixed gas flowing into the cylinder 60 from the scavenging passages 20 and 30 on both sides is slow, and the collision position of the mixed gas flowing into the cylinder 60 is shifted from the center in the cylinder 60, so that the combustion chamber 40 Inside, the mixed gas is sufficiently stirred, and the mixed gas is likely to stay in the upper part of the cylinder 60. Accordingly, since the amount of the mixed gas that flows in a loop along the inner wall surface of the cylinder 60 reaches the opening of the exhaust passage 80 before the opening of the exhaust passage 80 is closed, the latter half of the scavenging stroke is performed. It is possible to reduce the blow-by generated in

  Further, by attaching the shielding members 22 and 32 corresponding to the two openings 21a and 31b among the four openings 21a, 21b, 31a and 31b formed in the scavenging passages 20 and 30 on both sides, the cylinder 60 is attached. The flow velocity of the mixed gas flowing into the cylinder 60 can be reduced, and the flow velocity of the mixed gas flowing into the cylinder 60 can be adjusted by adjusting the opening area of the holes of the shielding members 22 and 32. . In addition, when adjusting the opening area of a hole part, an opening area can be easily adjusted by adding a hole part or obstruct | occluding a part of hole part. This is easier than adjusting the opening area by increasing or decreasing the size of one hole, and makes it easier to adjust the flow rate of the mixed gas passing through the shielding members 22 and 32.

  Thus, according to the two-cycle engine 1A of the present embodiment, the four openings 21a, 21b, 31a, 31b formed in the scavenging passages 20, 30 on both sides correspond to the two openings 21a, 31b. By attaching the shielding members 22 and 32, the flow rate of the mixed gas flowing into the cylinder 60 can be adjusted, and the blow-through that occurs in the first half and the second half of the scavenging stroke can be reduced. Therefore, the amount of unburned mixed gas exhausted to the exhaust passage 80 can be greatly reduced with a simple structure, and the amount of hydrocarbons in the exhaust gas can be reduced.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention.
For example, in the two-cycle engine 1A of the present embodiment, as shown in FIG. 6, punching metal is used for the shielding members 22 and 32, but the shape is limited if a plurality of holes are formed. However, a net-like member can also be used.

  In the two-cycle engine 1A of the present embodiment, the inflow amount of the mixed gas from the scavenging passages 20 and 30 into the cylinder 60 is provided by attaching the shielding members 22 and 32 to the openings 21a and 31b of the scavenging passages 20 and 30. The output of the engine decreases, and the opening area of the shielding members 22 and 32 is set so that this decrease in output falls within an allowable range.

  Further, the two-cycle engine 1A of the present embodiment is a four-flow scavenging engine in which two openings 21a, 21b, 31a, 31b are formed in the scavenging passages 20, 30 on both sides, respectively. The number is not limited, and the present invention can be applied to various engines.

It is the figure which showed the 2-cycle engine of this embodiment, and is a sectional side view in a scavenging stroke. It is sectional drawing which looked at the 2-cycle engine of this embodiment from the AA direction of FIG. It is the figure which showed the 2-cycle engine of this embodiment, and is a sectional side view in an intake and compression stroke. It is sectional drawing which looked at the 2-cycle engine of this embodiment from the BB direction of FIG. It is sectional drawing which looked at the 2-cycle engine of this embodiment from CC direction of FIG. In the two-cycle engine of this embodiment, it is explanatory drawing which showed the flow of the mixed gas of a scavenging stroke. It is explanatory drawing which showed the flow of the mixed gas of the scavenging stroke in the conventional 2 cycle engine.

Explanation of symbols

1A 2 cycle engine 10 Crank chamber 20 First scavenging passage 21a Opening portion 21b Opening portion 21c Partitioning portion 22 Shielding member 30 Second scavenging passageway 31a Opening portion 31b Opening portion 31c Partitioning portion 40 Combustion chamber 50 Piston 60 Cylinder 70 Suction passage 80 Exhaust passage 90 Crankshaft 91 First crankshaft 92 Second crankshaft 93 Connecting rod

Claims (3)

A piston slidably mounted in the cylinder;
An exhaust passage leading to a combustion chamber formed in the cylinder;
A first scavenging passage and a second scavenging passage communicating the crank chamber and the combustion chamber;
A suction passage that leads to the crank chamber,
A mixed gas of fuel and air containing oil flows into the crank chamber through the intake passage, and the mixed gas filled in the crank chamber is converted into the combustion chamber through the first scavenging passage and the second scavenging passage. A two-cycle engine that reciprocates the piston in the cylinder by causing the mixed gas to burn in the combustion chamber,
Each opening on the cylinder side of the first scavenging passage and the second scavenging passage is formed at a position facing the cylinder,
A shielding member in which a plurality of holes are formed is attached to a part of each of the first scavenging passage and the second scavenging passage,
The two-stroke engine, wherein the shielding portions of the first scavenging passage and the second scavenging passage are arranged at diagonal positions with the cylinder interposed therebetween.   The two-stroke engine according to claim 1, wherein the shielding member is a plate-like member in which a plurality of holes are formed. The cylinder side openings of the first scavenging passage and the second scavenging passage are each divided into two by a partition portion,
The shielding member is arranged corresponding to two openings arranged at diagonal positions across the cylinder among the four openings formed on both sides of the cylinder. The two-cycle engine according to claim 1 or 2.

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