JP2009299605A - Two-stroke engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-stroke engine for suppressing a phenomenon in which scavenge gas is discharged as uncombusted gas, and cleaning the exhaust gas by enhancing combustion efficiency. <P>SOLUTION: In a two-stroke engine having a crankcase, and a cylinder, scavenging ports are provided at left and right sides on a line connecting a center point of an exhaust gas port opened in the cylinder and a center axis of the cylinder, respectively. A line connecting a center point of the scavenging port and the center axis of the cylinder is configured to be inclined with respect to a crank axis line. In the crankcase, a longitudinal passage connected to the scavenging ports is formed, and configured to be connected to a lateral passage one end of which is opened to a crank chamber. Here, a line connecting the exhaust gas port and the intake port is located facing a position apart from the crank axis line at about 45 degrees, and the scavenging port is formed at a position apart from the intake port and the exhaust gas port at about 90 degrees. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a two-cycle engine suitable for use in a small engine power machine such as a chain saw or a brush cutter, and more particularly to a two-cycle engine having an improved scavenging port shape.

  Conventionally, as a portable engine power machine, a mower for mowing, an engine chain saw, an engine hedge trimmer, an engine blower, and the like are known. In these engine-powered machines, portability and portability may be essential. In that case, it is important to make them as small and light as possible. Therefore, a two-cycle engine having a simple structure and a light weight is widely used as an internal combustion engine.

In a two-cycle engine, the intake port and the exhaust port are generally arranged in a direction that is approximately 180 degrees away from the central axis of the cylinder, and the scavenging port is provided at a position that is approximately 90 degrees away from the intake port and the exhaust port. As a two-cycle engine having such a structure, the technique described in Patent Document 1 is known. In this known example, a scavenging passage in the vertical direction (the same direction as the movement direction of the piston) is provided in the cylinder. Are connected to each other by a communicating portion that extends in the lateral direction from the crank chamber.
JP 2000-179346 A

  In the two-cycle engine in Patent Document 1, the air-fuel mixture in the crank chamber flows into the cylinder-side scavenging passage through the crankcase-side scavenging passage, so that the air-fuel mixture is prevented from abruptly flowing into the cylinder 3. The air-fuel mixture is gradually supplied, and the supply of the air-fuel mixture is maintained without decreasing until the second half of the scavenging time period. As a result, not only can the air-fuel mixture be supplied smoothly, but also the amount of unburned gas discharged together with the exhaust gas can be reduced to less than half of the conventional amount by suppressing the mixing of the exhaust gas. It has the effect.

  However, the technique of Patent Document 1 has a problem that it is difficult to form a scavenging passage on the crankcase side in a so-called four-flow scavenging method in which two independent scavenging passages are provided. Furthermore, in the structure realized from the demand for miniaturization, that is, in a two-cycle engine in which the intake port and the exhaust port are disposed in a direction approximately 90 degrees away from the center axis of the cylinder, the technique of Patent Document 1 is used as it is. Could not be applied.

  The present invention has been made in view of the above background, and an object of the present invention is to provide a two-cycle engine that suppresses a phenomenon in which scavenging gas is discharged as unburned gas and improves combustion efficiency to clean exhaust gas. It is to provide.

  Another object of the present invention is to enable a scavenging passage to be formed also on the crankcase side in a two-cycle engine in which an intake port and an exhaust port are disposed in a direction approximately 90 degrees away from the central axis of the cylinder. It is in.

  Of the inventions disclosed in the present application, typical features will be described as follows.

  According to one aspect of the present invention, in a two-cycle engine having a crankcase and a cylinder, scavenging ports are respectively provided on the left and right sides of the line passing through the center point of the exhaust port opened inside the cylinder and the cylinder central axis. The line passing through the center point of the scavenging port and the cylinder center axis is inclined with respect to the crank axis, and the crankcase is formed with a longitudinal passage connected to the scavenging port, with one end connected to the crank chamber. It was configured to be connected to an open lateral passage. Here, a line connecting the exhaust port and the intake port is opposed to a position approximately 45 degrees away from the crank axis, and the scavenging port is provided at a position approximately 90 degrees away from the intake port and the exhaust port. Furthermore, a protrusion that extends outward from the rotation area of the crankweight is formed near the inlet of the scavenging passage from the inner peripheral surface of the crankcase of the crankcase so that the inlet of the scavenging passage is formed in the protrusion. Configured. As described above, when the scavenging ports are offset and formed, it becomes difficult to form the scavenging passage. Therefore, any one of the scavenging passages has an inlet opening in the longitudinal direction (moving direction of the piston) from the crank chamber. The remaining scavenging passage has an inlet that opens laterally from the crank chamber (a direction perpendicular to the moving direction of the piston).

  According to another feature of the present invention, the scavenging port is provided with a first scavenging port and a second scavenging port on the left and right sides, and a scavenging passage is provided in the crankcase independently for each scavenging port. At this time, any one of the scavenging passages connected to the second scavenging port has an inlet opening in the vertical direction from the crank chamber, and the scavenging passage connected to the remaining second scavenging ports, and the first scavenging port It is preferable that the scavenging passage connected to the cylinder has an inlet that opens laterally from the crank chamber.

  According to still another aspect of the present invention, the crankcase is manufactured by being divided in a cross section perpendicular to the crankshaft, and the protrusion is formed at one place on each of the divided crankcases. At this time, the cross section of the opening of the crank chamber of the scavenging passage is made smaller than the cross section of the opening of the scavenging port into the cylinder. Further, it is preferable that the cross-sectional area of the scavenging passage cylinder and the crankcase mounting surface is larger than the cross-section of the opening of the crank chamber.

According to the first aspect of the present invention, the scavenging ports are respectively provided on the left and right sides of the line passing through the center point of the exhaust port and the cylinder center axis that are opened inside the cylinder, and the line passing through the center point of the scavenging port and the cylinder center axis. Is configured to be inclined with respect to the crank axis, and in the crankcase, a longitudinal passage connected to the scavenging port is formed, and one end is connected to a lateral passage that opens into the crank chamber. The scavenging passage can be formed so as to penetrate the crankcase at a position avoiding the crankshaft and the crankshaft bearing portion. Therefore, the length of the scavenging passage can be made sufficiently long, and the scavenging effect can be improved.
According to the invention of claim 2, the line connecting the exhaust port and the intake port is opposed to a position approximately 45 degrees away from the crank axis, and the scavenging port is approximately 90 degrees away from the intake port and the exhaust port. By providing at the position, the arrangement angle of the intake port and the exhaust port can be set to 90 degrees, that is, a small and compact engine in which the mounting position of the carburetor and the muffler is set to 90 degrees can be realized.
According to a third aspect of the present invention, the protrusion extending outward from the rotation area of the crank weight is formed in the vicinity of the inlet of the scavenging passage from the inner peripheral surface of the crank chamber of the crankcase, and the scavenging is formed in the protrusion. Since the inlet of the passage is formed, scavenging is performed symmetrically with respect to the point connecting the cylinder center axis and the exhaust port center point even if the arrangement angle of the intake port and the exhaust port is within 180 degrees, for example, about 90 degrees. Ports can be placed.

  According to the invention of claim 4, since any one of the scavenging passages has an inlet opening in the vertical direction from the crank chamber, and the remaining scavenging passages have an inlet opening in the lateral direction from the crank chamber, In the crankcase that is divided by the rotation surface, the scavenging port can be offset.

  According to the invention of claim 5, since the scavenging port is provided with the first scavenging port and the second scavenging port on the left and right sides, respectively, and the scavenging passage is provided in the crankcase independently for each of these scavenging ports. A scavenging port having a volume corresponding to the scavenging direction, the scavenging amount, and the like can be realized.

  According to the sixth aspect of the present invention, any one of the scavenging passages connected to the second scavenging port has an inlet opening in the vertical direction from the crank chamber, and the scavenging connected to the remaining second scavenging ports. Since both the passage and the scavenging passage connected to the first scavenging port have an inlet that opens laterally from the crank chamber, in the engine in which the scavenging port is offset, independent first and second scavenging passages are provided. It can be provided in the crankcase.

  According to the seventh aspect of the present invention, the crankcase is divided and manufactured in a cross section perpendicular to the crankshaft, and the protrusion is formed at one place on each of the divided crankcases, so that the protrusion is formed on the protrusion. Since the scavenging passage inlet can be opened in a region where the scavenging is performed, it is easy to form a scavenging passage inlet having a cross-sectional area corresponding to the cross-sectional area on the scavenging port side.

  According to the invention of claim 8, since the cross section of the opening of the crank chamber of the scavenging passage is smaller than the opening cross section of the scavenging port into the cylinder, the exhaust gas characteristics can be improved.

  According to the ninth aspect of the present invention, the cross-sectional area of the cylinder and the crankcase mounting surface of the scavenging passage is larger than the cross-section of the opening of the crank chamber, so that the capacity in the scavenging passage can be increased and the scavenging characteristics are improved. The exhaust gas characteristics can also be improved.

  The above and other objects and novel features of the present invention will become apparent from the following description and drawings.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, parts having the same function are denoted by the same reference numerals, and repeated description is omitted. 1 is a perspective view showing an appearance of a chain saw to which a two-cycle engine according to an embodiment of the present invention is applied, FIG. 2 is a perspective view showing an appearance of the chain saw from another angle, and FIG. 3 is a view from still another angle of the chain saw. It is a perspective view which shows the external appearance.

  In FIG. 1, a chain saw 1 is equipped with a two-cycle engine, and a guide bar 11 protrudes in front of the main body. A saw chain (not shown) is wound around the periphery of the guide bar 11, and a tree, a branch, or the like can be cut by rotating the saw chain at a high speed. A two-cycle engine described later is housed in the housing 2 in a horizontal position. The housing 2 not only houses the engine but also attaches a guide bar 11 and covers around the engine 2 and is a skeleton part of the chain saw 1. A main handle 3 is provided above the housing 2, and a front handle 6 is provided so as to extend laterally and downwardly from the vicinity of the front end of the main handle 3.

  The main handle 3 is a handle for the operator to hold with the right hand, and the front handle 6 is a handle for the operator to hold with the left hand. A safety trigger 7a is provided near the upper portion of the main handle 3, and an ignition switch 7b is provided near the front end. A hand guard 12 is provided on the front side of the main handle. The hand guard 12 serves to protect a worker's hand from being hit by a branch or a cut object. Furthermore, the role of a brake for stopping the rotation of the saw chain by tilting the hand guard 12 forward may also be used. A left cover 4 covers the left side of the housing 2 (hereinafter, the description will be made by defining front, rear, left and right as shown in FIG. 1 with reference to the case where the operator holds the chainsaw 1). A recoil starter (not shown) for starting the engine is accommodated inside the left cover 4, and a starter handle 13 is attached through the left cover 4. In front of the left cover 4, a fuel tank cap 14a and a chain oil tank cap 15a are provided.

  2, the guide bar 11 is fixed to the right side of the housing 2 by two bolts (not shown) extending from the housing 2 and nuts 17a and 17b. On the right side of the housing 2, a driving force transmission mechanism to a saw chain, which will be described later, is attached, and a light cover 5 is provided to cover it. A chain catcher 16 is provided in the vicinity of the attachment portion between the housing 2 and the guide bar 11.

  In FIG. 3, a muffler guard 8 provided with a mesh-shaped air vent on the most part of the surface is attached behind the light cover 5 in order to guard against the heat of the engine muffler 66. A rear cover 9 is provided at the rear end of the chainsaw 1. The rear cover 9 is detachably fixed to the housing 2 by a fixing screw 18. On the right side of the fixing screw 18, a pull-out hook 20 is provided. For example, when working on a tree, the hook 20 is used to hang a rope when the chainsaw 1 is pulled up to a high place with a rope. The state shown in FIG. 3 is a state in which the hook 20 is housed, and the hook 20 hardly protrudes to the outside of the rear cover 9 except for a necessary part to be pulled out by hand. For this reason, it is possible to prevent the hook 20 from hitting the worker's body or hitting the surroundings during storage.

  Next, the internal structure of the chainsaw 1 will be described using the cross-sectional view shown in FIG. Inside the housing 2 of the chainsaw 1, the engine 50 is accommodated almost horizontally. Here, horizontal installation means that the direction of movement of the piston is horizontal during operation. Strictly speaking, in this embodiment, the direction of movement of the piston is not completely horizontal, and the tip portion is slightly lowered. It is “almost horizontal”. This is because when the engine 50 is completely placed horizontally, the height of the rear end portion of the chainsaw 1 is increased due to the relationship between the carburetor 67 and the air filter 68 disposed on the upper side thereof, and the engine 50 is inclined downward. It is what I did. The engine 50 performs an intake-compression-combustion-exhaust stroke while a piston 62 attached to the crank 64 via a connecting rod 63 reciprocates. The engine 50 is fixed to the housing 2 by two bolts 31 (FIG. 5) and 32 from the upper side and two bolts 33 (FIG. 5) and 34 from the lower side. A fuel tank 14 for the engine 50 and a chain oil tank 15 for supplying oil to the saw chain are provided on the front side of the housing 2.

  FIG. 5 is a perspective view for explaining a mounting state of the housing 2 and the engine 50, and FIG. 6 is a perspective view from these different angles. The housing 2 is configured by, for example, plastic integral molding, and the engine 50 is inserted in a direction indicated by an arrow in FIG. 5 and is fixed by four bolts 31 to 34 from the vertical direction. The engine 50 is formed with four screw holes (only 31b and 32b are shown in FIG. 5) to be screwed with these bolts. In FIG. 6, a flat surface portion 2a is formed on the front side of the surface opposite to the side on which the engine is inserted (the right surface) of the housing 2, and two fixed to the housing 2 are formed outside the flat surface portion 2a. The guide bar 11 is attached to the bolts 19a and 19b, and is fixed by nuts 17a and 17b.

  Here, in the engine 50 according to the present embodiment, as can be understood from FIG. 6, the intake port 56 and the exhaust port 57 are arranged at an interval of about 90 degrees. Normally, in the two-cycle engine, the intake port 56 and the exhaust port 57 are arranged at an interval of about 180 degrees. Therefore, in this embodiment, the arrangement and shape of the scavenging ports are devised to arrange them at an interval of about 90 degrees. The arrangement and shape of the scavenging port will be described later.

  In order to accommodate an oil pump (not shown), a recessed portion 2b that is recessed in a substantially rectangular shape is formed on the inner side when viewed from outside. By forming the recess 2b, the rigidity of the housing 2 can be further increased. A hole 2c for penetrating the crankshaft 51 is formed in the recess 2b. A hole 66a is formed on the side of the hole 2c, and is screwed into the screw hole 69 of the engine 50 from the lateral direction by the lateral bolt 41. . Here, in this embodiment, in addition to the four bolts 31 to 34 that are fixed from the vertical direction of the engine 50, the crankcase portion of the engine 50 is fixed by the lateral bolt 41 that is the fifth bolt. In addition, the engine 50 can be fixed to the housing 2 with good vibration characteristics.

  The recess 2b is covered with an oil pump cover 40 after an unillustrated oil pump is accommodated. The oil pump cover 40 is fixed to the housing 2 with three screws 42 through the crankshaft 51 through the hole 40a. Here, the screw 42 is screwed into a screw hole formed in the housing and does not contact the engine 50.

  Next, the engine 50 will be described with reference to FIGS. FIG. 7 is a perspective view of the engine 50 as viewed from the upper left front side, and FIG. 8 is a perspective view of the engine 50 as viewed from the lower left rear side. The crankcase is a split type composed of a right crankcase 52 and a left crankcase 53, and the split surface is a surface perpendicular to the axis of the crankshaft 51. A crankshaft 51 as an output shaft protrudes from the right crankcase 52, and a flywheel 54 is attached to the tip of the crankshaft from the left crankcase 53. The right crankcase 52 and the left crankcase 53 are fixed by three bolts 65a, 65b, 65c via a gasket (not shown) between them. In order to threadably engage with these three bolts 65a, 65b, 65c, the right crankcase 52 is formed with a female thread portion. Furthermore, the crankcase is provided with two bolt holes 31 b and 32 b for fixing the engine 50 to the housing 2 on the upper side of the engine 50. The bolt hole 31 b is provided in the left crankcase 53, and the bolt hole 32 b is provided in the right crankcase 52. Similarly, two bolt holes 33 b and 33 b are provided on the lower side of the engine 50. The bolt hole 33 b is provided in the left crankcase 53, and the bolt hole 34 b is provided in the right crankcase 52. Further, the right crankcase 52 is provided with a bolt hole 69 screwed with the lateral bolt 41, and a female screw is formed on the inner peripheral side thereof.

  The flywheel 54 is configured integrally with the fins, and a permanent magnet for generating high voltage electricity for ignition by the ignition coil 59 is provided on a part of the outer peripheral side. A clutch pawl for connecting to the starter is provided on the inner peripheral side of the fin. High-voltage electricity generated by the ignition coil 59 is transmitted to the plug cap 60 by a high-voltage cord extending from the ignition coil 59, and is supplied to the ignition plug 61 (FIG. 4) via the plug cap 60.

Next, the detailed structure of the engine 50 according to the present embodiment will be described. In this embodiment, as can be understood from FIG. 6, when viewed from the axis of the cylindrical piston 62, the engine intake port 56 and the exhaust port 57 are arranged at positions separated by 90 degrees. In order to realize this structure, the arrangement and structure of the scavenging port were devised. FIG. 9A is a side view of the cylinder 55 viewed from the exhaust port 57 side, and FIG. 9B is a cross-sectional view taken along the line AA in FIG. The cylinder 55 is manufactured by die-casting aluminum including the head portion. As can be understood from (2), in the engine 50 of the present embodiment, the exhaust port 57 is within 180 degrees with respect to the intake port 56, that is, approximately 90 degrees in the outer peripheral part of the cylinder, and between the inner peripheral ports of the cylinder 55 It is arranged away from the crank center line. The exhaust port 57 is formed to connect to an exhaust port opened in the cylinder 55 along a line passing through the cylinder central axis, and the intake port 56 is also an intake port opened in the cylinder along a direction substantially perpendicular to the cylinder axis. Formed to connect to. Thus, the exhaust direction and the intake direction with respect to the cylinder are substantially orthogonal, and the carburetor 67 is disposed 90 degrees away from the upper portion of the engine 50 and the muffler 66 is disposed at the side portion of the engine 50. Compared with the configuration in which the muffler 66 is disposed, the vertical or horizontal dimension can be reduced. Further, when the carburetor 67 and the muffler 66 are disposed at 90 degrees while the exhaust port 57 and the intake port 56 are at the diagonal positions of the engine 50, the exhaust port 57 and the muffler 66 or the intake port 56 and the carburetor 67 are compared. However, in the present application, such a necessity is not required, and it is possible to improve the assemblability and suppress the increase in size of the engine due to the communication portion. In addition, because of this configuration, the arrangement of the two scavenging ports 72b and 73b and 74b and 75b is symmetrical in the axial direction of the crankshaft as compared with the conventional engine in which the exhaust port and the intake port are 180 degrees apart. Rather than being arranged in such a way, the plane of symmetry is inclined and arranged.
The line connecting the exhaust port and the intake port is opposed to a position approximately 45 degrees away from the crank axis, and the scavenging port is substantially the same as the intake port and the exhaust port with respect to the line connecting the exhaust port and the intake port. It is provided at a position 90 degrees apart.

  FIG. 10 is a cross-sectional view taken along the line BB in FIG. 9 (1). (1) shows a state in which the scavenging passage covers 58a and 58b are removed, and (2) shows a state in which the scavenging passage covers 58a and 58b are attached. Show. As can be understood from FIG. 10 (1), the line passing through the center point of the scavenging port and the cylinder central axis is inclined with respect to the axis of the crankshaft 51. FIG. 10 (2) shows a state in which the scavenging passage covers 58a and 58b are attached. Since the cylinder 55 of the present embodiment is formed by die casting including the head portion, the passage portion in the cylinder of the scavenging port. Is formed using scavenging passage covers 58a, 58b.

  FIG. 11 is a view of the entire engine 50 as viewed from the intake port 56 side, and the left side shows a cross-section of the CC section of FIG. 9 (2). As can be understood from this figure, the scavenging passage 75 extends in a lateral direction (a direction parallel to the crankshaft 51) from a scavenging passage inlet 75a that opens into the crankcase, and thereafter, in a longitudinal direction (a direction parallel to the moving direction of the piston 62). The scavenging port 75b opens into the cylinder. What is characteristic in the present embodiment is that the passage is also extended in the crankcase 52 when the scavenging passage 75 is formed. Thus, since the scavenging passage 75 is formed up to the crankcase 52, a sufficiently long scavenging passage 75 can be realized. In particular, the lines passing through the center points of the scavenging ports 72b and 73b and 74b and 75b and the cylinder shaft center on the inner periphery of the cylinder are inclined with respect to the crank axis, that is, the scavenging passages 72 and 73, and Since 74 and 75 are disposed through the crankcase 53 at positions avoiding directly above the bearings 76 and 77 provided on the crankshaft 51 and the crankcase 53, a longer scavenging passage is provided in the crankcase 53. Can be formed. Further, the flow passage section in the vicinity of the center of the scavenging passage 75 is made larger. For example, the scavenging passage inlet 75a is narrowed compared with the region near the connection surface between the cylinder 55 and the left crankcase 52, and the cross-sectional area thereof is increased. It is getting smaller. Thus, by taking a flow passage cross section near the center, a scavenging passage having a sufficient capacity can be realized, and further, the scavenging passage inlet 75a is narrowed, so that the exhaust gas characteristics can be improved.

  FIG. 12 is a cross-sectional view showing a cross section of the entire engine 50 at the position of the DD section in FIG. 9 (2). Here, the scavenging passage 73 has a scavenging passage inlet 73a in the vertical direction at the protruding portion of the crank chamber, and the cross section becomes wider near the center, for example, near the connection surface between the cylinder 55 and the right crankcase 52. It is bent in the direction of about 90 degrees and opens into the cylinder at the scavenging port 73b.

  Next, the relationship between the internal shape of the crankcase (52, 53) and the arrangement of the scavenging ports will be described with reference to FIGS. FIG. 13 (1) is a diagram showing the shape of the EE portion of FIG. 12, that is, the crankcase mounting surface. The crankcase is divided into a right crankcase 53 and a left crankcase 53 at the EE portion. As can be understood from this figure, the crankcase according to the present embodiment is characterized in that a path for scavenging is provided independently from the crank chamber. The scavenging as this route includes scavenging passages 72 and 74 for a so-called first scavenging port (scavenging port far from the exhaust port) and a so-called second scavenging port (second scavenging port counted from the far side from the exhaust port). Scavenging passages 73 and 75 are formed. Moreover, in the crankcase according to the present embodiment, as shown in FIG. 13B, the first scavenging port and the second scavenging port provided in plane symmetry with respect to the split surface 37 of the normal crankcase are provided on the split surface 37. On the other hand, it is provided in a state that is not plane-symmetric. That is, the first scavenging port and the second scavenging port are disposed symmetrically with respect to the offset surface 38 that is offset from the dividing surface 37 by the angle θ. From another viewpoint, the offset surface 38 is generally perpendicular to the axis of the crankshaft 51, but in this embodiment, the offset surface 38 is not vertical but inclined. This is because the normal intake direction and the exhaust direction are 180 degrees apart from each other, but in the engine 50 according to the present embodiment, the carburetor 67 and the muffler are located 90 degrees apart. The positions of the scavenging port and the second scavenging port must be offset.

  As a result of the offset arrangement, the position of the inlet of the scavenging passage on the crank chamber side is divided into a scavenging passage that enters the inside of the width W of the crank chamber and a scavenging passage that does not enter. That is, the scavenging ports 72 and 75 do not enter the width W. 74 hardly enters. 73 enters completely. For this reason, the shape in the vicinity of the inlet of the crank chamber side of these scavenging passages has been devised.

  FIG. 14A is a cross-sectional view of the FF portion in FIG. 13 and shows the shape of the left crankcase 53 on the crank chamber side. The left crankcase 53 is provided with a bearing 76 that rotatably holds the crankshaft, and the direction of rotation is indicated by an arrow. The inside of the crank chamber side has a shape along the rotation trajectory of the crank weight, but only the region 79 is formed with a projecting portion having a right-angle inner wall. As shown in FIG. 14 (2), scavenging passage inlets 72a and 73a are formed in this region. The scavenging passage inlet 73a is formed in the vertical direction (direction parallel to the moving direction of the piston 62), and the scavenging passage inlet 72a is formed in the lateral direction (direction perpendicular to the split surface of the crankcase). By forming in this way, the length of the scavenging passage can be configured to be equal in the cylinder in which the carburetor 67 and the muffler are formed at 90 degrees apart.

FIG. 15 is a diagram for explaining the protruding portion. FIG. 15 shows the left crankcase 53 shown in FIG. 14 with a dotted line 81 and an oblique line. However, in this drawing, the description of the inlet of the scavenging passage inlet 72a is omitted. A dotted line 81 indicates the vicinity of the outer peripheral portion where the crank weight rotates. In a normal crankcase, an inner wall is provided at this position as in the portion indicated by 82. However, in the present application, the shaded region 79 protrudes outward to form a step 80 having a substantially right inner wall. In this embodiment, the space indicated by the step 83 and the region 79 is referred to as a “projection”.
FIG. 16 is a cross-sectional view taken along the line GG in FIG. 13 and shows the shape of the right crankcase 52 on the crank chamber side. The right crankcase 52 is provided with a bearing 77 that rotatably holds the crankshaft, and the direction of rotation is indicated by an arrow. Although the inside of the crank chamber side has a shape along the rotation trajectory of the crank weight, a protruding portion is formed only in the region 80. And in this area | region, as shown in FIG. 16, the scavenging passage inlets 74a and 75a are formed in the horizontal direction (direction perpendicular | vertical with respect to the division | segmentation surface of a crankcase). Here, unlike FIG. 14, the two scavenging passage inlets are in the horizontal direction because neither of the scavenging passages can be formed in the vertical direction. The lateral opening is formed by connecting to the scavenging passages 74 and 75 by aluminum die casting.

  As described above, the two-cycle engine according to the present embodiment has been described based on an example of a so-called four-flow scavenging method in which there are two scavenging ports. However, the present invention is not limited to this, and the two-cycle engine has one or three or more scavenging ports. But it is equally applicable.

  Although the two-cycle engine applied to the chainsaw has been described in the above embodiment, the device to which the present invention is applied may be any device and can be widely applied to other power machines as well.

  As mentioned above, although demonstrated based on embodiment which shows this invention, this invention is not limited to the above-mentioned form, A various change is possible within the range which does not deviate from the meaning.

It is a perspective view which shows the external appearance of the chainsaw which concerns on embodiment of this invention. It is a perspective view which shows the external appearance from another angle of the chainsaw which concerns on embodiment of this invention. It is a perspective view which shows the external appearance from another angle of the chainsaw which concerns on embodiment of this invention. It is sectional drawing of the chainsaw which concerns on embodiment of this invention. It is a perspective view for demonstrating the attachment state of the chain saw housing 2 and the engine 50 which concerns on embodiment of this invention. It is a perspective view from another angle for demonstrating the attachment state of the housing 2 of the chainsaw which concerns on embodiment of this invention. It is a perspective view of the engine 50 of the chainsaw which concerns on embodiment of this invention. It is a perspective view from another angle of the engine 50 of the chainsaw which concerns on embodiment of this invention. (1) is the side view which looked at the cylinder 55 from the exhaust port 57 side, (2) is sectional drawing of the AA part of (1). It is sectional drawing of the BB part of FIG. 9 (1), (1) shows the state which removed scavenging passage cover 58a, 58b, (2) shows the state which attached scavenging passage cover 58a, 58b. It is the figure which looked at the engine 50 whole from the inlet-port 56 side, and the left side shows the cross section of CC section of FIG. 9 (2). It is sectional drawing which showed the cross section in the position of the DD section of FIG.9 (2) about the engine 50 whole. (1) is a figure which shows the shape in the EE part of FIG. 12, ie, a crankcase attachment surface, (1) is a figure for demonstrating the positional relationship of an offset surface and a 1st and 2nd scavenging port. It is. It is sectional drawing of the FF part of FIG. 13, and is a figure which shows the shape by the side of the crank chamber of the left crankcase 53. FIG. It is a figure for demonstrating the shape of a protrusion part. It is sectional drawing of the GG part of FIG. 13, and is a figure which shows the shape by the side of the crank chamber of the right crankcase 52. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chain saw 2 Housing 3 Main handle 3a (Main handle) attachment part 4 Left cover 5 Right cover 6 Front handle 7a Safety trigger 7b Ignition switch 8 Muffler guard 9 Rear cover 9a (Rear cover) slit 10 Saw chain 11 Guide bar 12 Hand guard 13 Starter handle 14 Fuel tank 14a Cap 15 Chain oil tank 15a Cap 16 Chain catcher 17a, 17b Nut 18 Fixing screw 19a, 19b Bolt 20 Hook 21 Holding plate 22 Screw 23 Damper 24 Screw 31, 32, 33, 34 (For engine fixing ) Bolts 31a, 32a, 33a, 34a (for engine fixing) Bolt hole 37 (Crankcase) split surface 38 Offset surface 4 Oil pump cover 40a (Oil pump cover) hole 41 Lateral bolt 42 (Oil pump cover fixing) screw 50 Engine 51 Crankshaft 52 Right crankcase 53 Left crankcase 54 Flywheel 55 Cylinder 56 Air inlet 57 Air outlet 58a, 58b Scavenging passage cover 59 Ignition coil unit 60 Plug cap 61 Spark plug 62 Piston 63 Connecting rod 64 Crank 65a, 65b, 65c Bolt 66 Muffler 67 Carburetor 68 Air filter 69 Fixing hole 70a, 70b Bolt 72, 73, 74, 75 Scavenging passage 72a 73a, 74a, 75a Scavenging passage inlets 72b, 73b, 74b, 75b Scavenging ports 76, 77 Bearings 79, 80 (projecting part) region 83 steps

Claims (9)

In a two-cycle engine with a crankcase and cylinder,
A scavenging port is provided on each side of the line passing through the center point of the exhaust port opened inside the cylinder and the center axis of the cylinder,
The line passing through the center point of the scavenging port and the cylinder central axis is inclined with respect to the crank axis line,
The two-cycle engine according to claim 1, wherein a longitudinal passage connected to the scavenging port is formed in the crankcase, and one end is connected to a lateral passage that opens into the crank chamber.   A line connecting the exhaust port and the intake port is opposed to a position approximately 45 degrees away from a crank axis, and the scavenging port is connected to the line connecting the exhaust port and the intake port. The two-stroke engine according to claim 1, wherein the two-stroke engine is provided at a position approximately 90 degrees away from the exhaust port.   A protrusion extending outward from the rotation area of the crank weight is formed in the vicinity of the inlet of the scavenging passage from the inner peripheral surface of the crankcase of the crankcase, and the inlet of the scavenging passage is formed in the protrusion. The two-cycle engine according to claim 1 or 2, wherein   Any one of the scavenging passages has an inlet that opens in a vertical direction from the crank chamber, and the remaining scavenging passages have an inlet that opens in a lateral direction from the crank chamber. The two-cycle engine according to any one of three.   The scavenging port is provided with a first scavenging port and a second scavenging port on the left and right sides, respectively, and a scavenging passage is provided in the crankcase independently for each scavenging port. The two-cycle engine according to any one of the above.   Any one of the scavenging passages connected to the second scavenging port has an inlet opening in the vertical direction from the crank chamber, and the scavenging passage connected to the remaining second scavenging ports, and the first scavenging port The two-stroke engine according to claim 5, wherein both of the scavenging passages connected to each other have inlets that open laterally from the crank chamber.   The crankcase is manufactured by being divided into sections perpendicular to a crankshaft, and the protruding portion is formed at one place in each of the divided crankcases. The two-cycle engine according to item.   The two-stroke engine according to claim 7, wherein a cross section of the opening of the crank chamber of the scavenging passage is smaller than an opening cross section of the scavenging port into the cylinder.   9. The two-stroke engine according to claim 8, wherein a cross-sectional area of the cylinder and the crankcase mounting surface of the scavenging passage is larger than a cross-section of the opening of the crank chamber.

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