JP3333375B2 - Mold for cylinder body of engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a mold used in manufacturing a cylinder body of an engine.

[0002]

2. Description of the Related Art In general, in an engine, a convex and annular convex flange portion is formed on a periphery of an external connection opening of an exhaust port in order to prevent exhaust gas from leaking from a connection portion between an exhaust port and an exhaust pipe. A gasket is interposed between the convex flange portions so that the flange portions of the exhaust pipe are in contact with each other and are fixed by bolts. In addition, since the heat of the high-temperature exhaust gas easily accumulates in the exhaust port portion, the flange surface of the exhaust port is depressed toward the center of the cylinder bore to reduce the volume of the portion and transmit more heat to the exhaust pipe side. Thus, the amount of accumulated exhaust heat is reduced.

On the other hand, the lower mating surface of the cylinder body to which the crankcase is connected needs to have a certain area to form a boss for attachment to the upper surface of the crankcase of the cylinder body. Therefore, when viewed in the axial direction of the cylinder bore, the boss may project from the lower half of the convex flange on the crankcase side in a direction perpendicular to the cylinder bore axis, in other words, the convex flange may be recessed from the boss.

When a cylinder body having such a structure is manufactured using left and right split molds, the convex flange portion of the exhaust port is recessed inward from the boss portion of the lower mating surface as described above. The convex flange portion is undercut during casting, and the convex flange portion cannot be cast with the left and right mold cutting structures.

For this reason, conventionally, a core forming a convex flange portion and a core forming an exhaust port are formed separately, and a combined core in which both cores are bonded is used. Are die cut in the axial direction of the exhaust port.

[0006]

However, in the above-mentioned conventional mold for a cylinder body, a core for an exhaust port and a core for a convex flange portion are separately formed, and the two cores are connected. There is a problem that the child structure is complicated and the cost increases.

Further, in order to reduce the weight, there may be a case where a hollow portion is formed in the lower mating surface of the cylinder body on the crankcase side. The die for the hollow portion is cut out in the axial direction of the cylinder bore. Therefore, a mold different from the above-mentioned core is required, and from this point, there is a problem that the mold structure is complicated and the cost is increased.

The present invention has been made in view of the above-mentioned conventional circumstances, and has as its object to provide a mold for an engine cylinder body which has a simple structure and can be reduced in cost.

[0009]

According to the present invention, a convex and annular convex flange portion to which an exhaust pipe is hermetically connected to a peripheral edge of an external connection opening of an exhaust port communicating with a cylinder bore is connected to a crankcase. In the mold for an engine cylinder body having a lightened concave portion on the surface, the left and right mother dies for forming the main part of the cylinder body, and the exhaust port and the convex flange portion of the left and right mother dies. An exhaust core forming an upper half located on the cylinder head side of the cylinder bore; and a lightening die formed in the axial direction of the cylinder bore to form the lightening recess. It is characterized in that a lower half mold part forming a lower half located on the crankcase side of the convex flange with the core is integrally formed.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 16 are views for explaining a mold for a cylinder body of a two-stroke engine according to an embodiment of the present invention. FIG. 1 is a left side view of a motorcycle, and FIG. 2 is a left side view of a body frame. , FIG. 3 is a left side view of a section of the engine, and FIGS. 4 to 6 are a plan view, a sectional front view, a sectional side view of the cylinder head, and FIGS.
Is a sectional side view and bottom view of the cylinder body, and FIGS. 9 and 1
0 is a configuration diagram showing a mold of a cylinder body, FIG. 11 is a perspective view of the mold, FIGS. 12 and 13 are cross-sectional plan views and side views of an air cleaner device, and FIGS. 14 and 15 are cross-sectional rear views and side views of a kick starting device. FIGS. 16 and 17 are views showing a suction cover of the air cleaner device. FIGS. 16A, 16B, 16C, 16D, and 16E are a plan view, a left side view, a front view, and d, respectively. -D line sectional view, e
It is a -e line sectional drawing. Note that, in this embodiment,
The front and rear mean left and right and front and rear in a state of sitting on a seat.

In FIG. 1, a motorcycle 1 has a body frame 2 connected to a head pipe 3 at a front end of a main frame 4 extending obliquely downward and rearward of the vehicle body. A rail bracket 6 having a U-shaped cross section extending obliquely upward is connected to an end thereof, and a gusset having an inverted U-shaped cross section so as to surround the connection portion, that is, the upper portion of the rail bracket 6 and the rear end of the main frame 4. 7 (reinforcement plate), and a pair of left and right seat rails 5 extending diagonally upward and rearward of the vehicle body are connected to upper ends of the gussets 7 and the rail brackets 6.

A backstay 8 is provided between each of the seat rails 5 and the rail bracket 6.
A seat tube 9 is provided upright on the upper surface of the gusset 7. A support bracket 10 is connected to a substantially lower portion of the center of the main frame 4, and a suspension bracket 11 extending downward is connected to a rear end of the main frame 4.
The engine 12 is supported by 0 and 11.

The seat tube 9 includes a front seat 13.
a, a front end of a seat 13 integrally formed with a rear seat 13b is pivotally supported. An oil tank 14, a battery 15, and a fuel tank 16 are disposed below the seat 13, respectively.

A front fork 20 is pivotally supported on the head pipe 3. A front wheel 21 is mounted on a lower end of the front fork 20, and a steering handle 22 is mounted on an upper end. The suspension bracket 11 has a pivot shaft 2
A rear arm 24 is pivotally supported through the rear arm 3 so as to be able to swing up and down, and a rear wheel 25 is mounted on a rear end of the rear arm 24. A rear cushion 27 is provided between the rear arm 24 and the rail bracket 6.

A cowling 31 provided with a headlight 30 is provided at the front of the head pipe 3.
A steering handle 22 is provided above. The engine 12 extends downward on the left and right sides of the main frame 4.
And an under cover 33 surrounding the seat 13, and a side cover 34 on the lower surface of the seat 13.
A tail light 35 is attached to the rear end of the fourth light source 4.

The engine 12 is, as shown in FIG.
This is an air-cooled two-cycle engine mounted on the body frame 2 with the axis (cylinder axis) of the cylinder bore 37d inclined forward by about 35 degrees. A cylinder head 38 is stacked on the upper mating surface of the cylinder body 37 and fastened with a head bolt, and a piston 39 is slidably inserted into a cylinder bore (cylinder) 37d of the cylinder body 37, and the piston 39 is inserted into the cylinder bore 37d. In this structure, the connecting rod 40 is connected to a crankpin 42 of a crankshaft 41. The combustion recess 3 is provided on the lower surface of the cylinder head 38.
8a is provided with a recess, and the spark plug 4 is provided in the recess 38a.
Two electrodes are exposed.

The interior of the crankcase 36 is divided by a partition wall 36c into a crank chamber 36a for accommodating the crankshaft 41 and a transmission chamber 36b for accommodating the transmission mechanism 43. The transmission mechanism 43 transmits the rotation of the crankshaft 41 to the rear wheel 25 via a centrifugal auto clutch (not shown) mounted on the right end thereof, a main shaft 43a, a drive shaft 43b, and a sprocket and a chain not shown. It is designed to communicate. Incidentally, reference numeral 47 in FIG. 1 denotes a chain cover.

A balancer shaft 45 is disposed below and parallel to the crankshaft 41. A cell motor 46 is provided at a front portion of a front wall 36d of the crankcase 36 so that a drive shaft 46a is attached to the left side of the vehicle body. And in parallel with the crankshaft 41. Although not shown, a centrifugal auto clutch is mounted on the right end side of the crankshaft 41.

On the outer peripheral wall of the cylinder body 37, a plurality of cooling fins 50 for heat radiation standing upright in the direction perpendicular to the cylinder axis are integrally formed at intervals in the cylinder axis direction. The ribs 50a at the center in the width direction are integrally connected. A plurality of scavenging ports 51 are formed in the cylinder wall of the cylinder body 37 to communicate the crank chamber 36a and the inside of the cylinder bore 37d. Further, in the lower mating surface 37b of the cylinder body 37 connected to the crankcase 36, a lightening concave portion 37a for reducing the weight is formed as shown in FIGS.

Next, the cylinder head 3 according to the present embodiment will be described.
8 will be described. The above cylinder head 3
As shown in FIGS. 4 to 6, a number of cooling fins that stand in the cylinder axis direction and extend in the vehicle traveling direction are integrally formed on the upper wall 8 at intervals in the vehicle width direction. Of the cooling fins, the top surface height of the outermost fins 52a, 52a located on the left and right outermost sides in the thickness direction (vehicle width direction) is a portion excluding the front end 52b 'of each inner fin 52b located on the inner side. Is higher than the top height. The top surface of the front end 52b 'of each of the inner fins 52b is formed at the same height as the outer fin 52a. That is, each of the inner fins 52b is formed in a stepped shape. A head cover 54 made of a metal plate is provided on the top surface of the stepped portion of each inner fin 52b via an elastic sheet 53 made of a rubber plate.
Are arranged, and the upper surface of the head cover 54 is flush with the top surfaces of the outer fins 52a and the front end 52b '. The head cover 54 is provided with bolts 57 on bosses 38d integrally formed at four corners of the cylinder head 38.
Are screwed together and fixed together. Further, the stud bolt hole 38b and the spark plug hole 38c of the elastic sheet 53 are provided.
A hole 53a is formed in a portion corresponding to.

The left and right outer fins 52a and the fins 5
2a, both ends in the longitudinal direction with the inner fin 52b adjacent to
And the central portion are integrally connected by a rib 60. The rib 60 of the adjacent inner fin 52b is also provided.
A cutout 61 is formed in the portion where is connected.
The notch 61 is an opening that opens a space a formed by the fins 52a and 52b and the rib 60 outward at a low position in an on-vehicle state. Discharge passage is formed.

Each of the inner fins 52b, which is located at the center in the vehicle width direction, is formed with a semicircular relief recess 62 having a trailing edge cut out in plan view. The lower edge of the frame 4 is located. By forming the escape recess 62, the cylinder head 38 can be attached and detached with the engine mounted on the vehicle body without changing the size and shape of the main frame 4 and the inclination angle of the engine 12. That is, in order to make the cylinder head detachable while the engine is mounted on the vehicle, it is conceivable to increase the forward inclination angle of the engine or change the frame position upward. There is a problem that the degree of freedom of the frame shape is reduced. Further, since the concave portion 62 is on the opposite side of an exhaust port described later, there is almost no effect on cooling performance, and since only a part of the inner fin 52b is cut out, the contact area of the elastic sheet 53 is extremely reduced. No impact on anti-vibration measures can be avoided.

An exhaust port 65 communicating with the cylinder bore 37d is formed obliquely downward on the front wall of the cylinder body 37. An annular convex flange 66 is formed around the outer connection opening of the exhaust port 65.
The convex flange portion 66 is formed so as to be recessed in the direction of arrow a in FIG. 7 so as to approach the center of the cylinder bore. This reduces the volume around the exhaust port 65 and suppresses the amount of heat stored by the exhaust gas. Further, since the convex flange portion 66 is depressed, the bending radius of the exhaust pipe 67 can be increased, and the bending process of the exhaust pipe 67 can be easily performed. And the problem of interference with the front wheels is less likely to occur.
On the other hand, since the convex flange portion 66 is recessed, the lower half portion 66b of the flange portion 66 is separated from the bolt boss portion 37c for fixing the cylinder body 37 to the crankcase 36 as shown in FIG. Since it is located on the center side of the cylinder bore, the shape of the casting mold is restricted as described later.

A flange 67b of the exhaust pipe 67 is fixed to the convex flange 66 with a gasket (not shown) by bolts. The exhaust pipe 67 extends downward from the cylinder body 37 and is then led out to the right side of the vehicle body and extends rearward therefrom.
Is connected.

Next, the mold of the cylinder body 37 in this embodiment will be described. Cylinder body 37
Is manufactured using the mold 70 shown in FIGS. That is, the mold 70 is a pair of left and right mother dies 71, 72 for forming the main part of the cylinder body 37.
And the exhaust port 6 in cooperation with the two molds 71, 72.
The exhaust core 73 that forms the upper half 66a located on the cylinder head side of the fifth and convex flange portions 66, the lightening concave portion 37a of the lower mating surface 37b of the cylinder body 37, and the convex flange portion 66 And a lightening die 74 forming a lower half 66b located on the crankcase side.

The exhaust core 73 has a substantially conical port portion 73a forming the exhaust port 65, and a cylindrical portion 73 forming the peripheral edge of the port opening and the inner peripheral surface of the convex flange portion 66.
b, the cylindrical portion 73b and the left and right mother molds 71,
The upper half portion 66a of the convex flange portion 66 is formed by the arc-shaped notch concave portions 71a and 72a formed in 72. Further, the core 73 is formed at the tip end surface of the port portion 73a at the time of casting.
A support portion 73c for positioning and supporting the projection is formed to protrude.

The lightening die 74 is provided in the cylinder body 37.
The base portion 74a that forms a part of the lower mating surface 37b and the boss portion 37c and the support portion 74c that supports the columnar portion 73b of the core 73 are integrally formed. A pair of convex portions 74b forming the lightening concave portion 37a protrude above, and a lower half portion forming the lower half portion 66b of the convex flange portion 66 with the cylindrical portion 73b on the periphery of the support portion 74c. The mold 74d is recessed.

After casting the molten metal in the mold 70, the cylinder body 37 divides the left and right mother dies 71, 72 into right and left molds, and cuts the exhaust core 73 rearward in the port axial direction. It is manufactured by punching the punching die 74 downward in the axial direction of the cylinder bore.

An intake opening 36e communicating with the crank chamber 36a is formed in a rear upper wall of the crankcase 36, and a reed valve 75 is inserted into the opening 36e. The reed valve 75 is a single-opening type having only a valve plate that opens upward. When the piston 39 rises, the crank chamber 36a automatically opens when a negative pressure is applied and air is introduced. To prevent air from blowing back. In addition, the intake opening 3
A carburetor 76 is connected upstream of the 6d reed valve 75, and an air cleaner device 68 is connected upstream of the carburetor 76.

Next, the air cleaner 68 will be described. The air cleaner device 68 is shown in FIGS.
As shown in the figure, the air inlet chamber A is formed by the connecting portion of the above-mentioned main frame 4 and the rail bracket 6 and the gusset 7 surrounding the portion, and an air cleaner case 80 made of resin is provided on the left portion of the gusset 7. It is arranged and configured. At the time of welding between the main frame 4 and the gusset 7 at the bottom of the air introduction chamber A, a gap is provided by not intentionally welding a part to drain the water. If rainwater or the like invades the water, it falls down and drains from the drainage part.

The air cleaner case 80 is of a left and right split type consisting of a case body 81 and a case cover 82, and the case body 81 is formed through flange portions 81a and 81b formed on the outer wall of the case body 81. Body frame 2
Bolts.

An element 83 for dividing the case main body 81 and the case cover 82 is provided at a mating portion of the case main body 81 and the case cover 82. It is clamped and fixed by the projection 84. The case cover 82 is
The boss portion 82a integrally formed with the boss portion 81a is coaxially engaged with the boss portion 81c of the case body 81, and is detachably attached to the case body 81 by screwing a bolt 85. Thus, the element 83 can be replaced simply by removing the case cover 82.

A cylindrical intake duct 86 extending in the vehicle width direction is integrally formed in the case main body 81, and the upstream intake port 86a of the intake duct 86 is connected to the case main body 8.
1 protrudes outward. In addition, the above intake duct portion 86
The downstream-side intake port 86b of the is opened through the element 83 into the case cover 82. A discharge port 81d is formed in a front wall of the case body 81, and the discharge port 81d is formed.
The upstream end of the vaporizer 76 is connected to d through an intake pipe 87.

The gusset 7 has an intake port 7a at the left rear side and an air intake port 7b at the front right section. The upstream intake port 86a of the intake duct 86 is connected to the intake port 7a. Through the air introduction chamber A. The gusset 7 has a generally bowl-shaped suction cover 26 surrounding the opening 7b.
f and 26g, which are fastened and fixed by bolts inserted therein, thereby preventing rainwater or the like from entering the opening 7b. This suction cover 26 has suction ports 26a to 26a.
d is formed, thereby preventing the intrusion of the rainwater and sufficiently securing the suction port area to reduce the suction resistance. A cover mounting boss 26e is formed at the front end of the suction cover 26 in the vehicle width direction.
The side cover 34 is bolted and fixed to e.

In this way, the air sucked from the air opening 7b through the suction ports 26a to 26d of the suction cover 26 is introduced from the air introduction chamber A into the case cover 82 through the air intake duct 86, Element 8 from here
3 and is discharged into the case body 81 into the discharge port 81d.
Is supplied to the vaporizer 76 (see the mark → in FIG. 12).

Next, a neutral kick starting device according to the present embodiment will be described with reference to FIGS. In the neutral kick starter, when a kick arm 91 disposed on the right side of the engine 12 is depressed, the kick shaft 90 rotates, and with the rotation, the ratchet 92 moves rightward in the axial direction, and the kick gear 93 moves to the kick gear 93. The crankshaft 41 is configured to be engaged, and the crankshaft 41 is rotated via the first speed gear 94 by the rotation of the kick gear 93. Note that the first speed gear 94 is rotatable on the drive shaft 43b in a state where a gear dog (not shown) is not engaged.

The crankcase 36 is divided into left and right cases (first and second cases) 95a and 95b, and a case cover 95c is detachably mounted on the right case 95b. The left end of the kick shaft 90 is a left case 95
The center part is supported by the right case 95b, and the right end part is supported by the case cover 95c. A stopper 96 is fixed to the inside of the left case 95a of the kick shaft 90 by caulking. The stopper 96 abuts on a case-side stopper (not shown) to regulate the return position (position before rotation) before the kick shaft 90 is depressed. The kick gear 93 is mounted on the inside of the right case 95b of the kick shaft 90 so as to be relatively rotatable. The kick gear 93 is held immovable in the axial direction by a circlip 97a and a stopper plate 97b.

A return spring 98 is provided between the right case 95b and the case cover 95c of the kick shaft 90 to constantly urge the kick shaft 90 in the anti-stepping direction, that is, toward the return position. One end 98a of the return spring 98 is locked to the right case 95b, and the other end 98b is locked to the kick shaft 90. A collar 99 is provided between the right case 95b of the kick shaft 90 and the case cover 95c.

The ratchet 92 disposed between the stopper 96 of the kick shaft 90 and the kick gear 93 is engaged with a torsion spline 90a formed on the kick shaft 90. The ratchet 92 has a predetermined torque. The spring 100 is mounted so as to be unable to rotate until the end of the ratchet 92.
The other end is locked to the left case 95a.

The stopper 96 and the ratchet 9
2, the kick gear 93 may be arranged symmetrically with respect to FIG. 14, that is, the stopper 96, the ratchet 92, and the kick gear 93 may be arranged in order from right to left in the figure.

The operation of the ratchet 92 will now be described. With the rotation of the kick shaft 90, the ratchet 92
When a rotational force is applied to the ratchet 92, the ratchet 92
The kick spline 90a does not rotate because it is held at 00, so that the torsion spline 90a receives the driving force in the axial direction of the kick shaft 90 and moves to the kick gear 93 side. And ratchet 92
Is engaged with the dog 93b of the kick gear 93, the rotation of the kick shaft 90 is transmitted to the kick gear 93 via the ratchet 92, and the kick gear 93 rotates the crank shaft 41 via the first speed gear 94. Become.

Next, the operation and effect of this embodiment will be described. According to the cylinder head anti-vibration structure of the present embodiment,
The top surface height of the left and right outer fins 52a is adjusted to the inner fin 52b.
Of the inner fins 52b and the head cover 54 with the elastic sheet 53 interposed therebetween.
7, the fins can be prevented from squeaking due to the vibration of the fins. In this case, the end surfaces of the elastic sheet 53 and the head cover 54 are covered with the outer fins 52a and are not visible from the side, so that the appearance from the side can be improved. Also, the number of components can be reduced and the cost can be reduced as compared with the conventional case where an elastic member is pushed between fins or the like.

Since the left and right outer fins 52a and the adjacent inner fins 52b are integrally connected by the ribs 60, the rigidity of the left and right outer fins 52a can be increased, and Fin squeak due to vibration can be prevented. Further, since the elastic sheet 53 and the head cover 54 are brought into contact with the outer fins 52a, the vibration of the outer fins 52a can be prevented from this point as well.

Furthermore, since the upper surfaces of the outer fins 52a and the adjacent inner fins 52b are covered with the head cover 54 or the like, muddy water or the like enters the space a surrounded by the fins 52a and 52b and the rib 60. In addition, since the notch 61 is formed in the inner fin 52b, even if muddy water or the like enters the space a, the invaded muddy water or the like is discharged outward from the notch 61. Thus, clogging of water, mud and the like due to the formation of the ribs 60 can be prevented.

Since the notch 61 is formed not on the outer fin 52a but on the inner fin 52b, the notch is not seen in a side view, and the appearance of the notch can be prevented from being deteriorated by providing the notch. Further, since muddy water and the like flows out to the front side of the vehicle, the muddy water and the like are not stained with muddy water and the like when viewed from the side.

Here, as shown by a two-dot chain line in FIG. 5, for example, a leg 53a is integrally formed on the elastic sheet 53 so as to protrude.
The leg portion 53a may be pushed between the outer fin 52a and the inner fin 52b. In this case, the vibration of the outer fins 52a can be further suppressed without increasing the number of parts, and the number of ribs 60 can be reduced or omitted.

According to the cylinder body mold 70 of this embodiment, the upper half 66a of the convex flange 66 is
The left and right mother dies 71 and 72 and the exhaust core 73 are formed, and the lower half 66b is provided with the exhaust core 73 and the hollow mold 74.
And the lower half mold part 74d formed in the exhaust core 73, the exhaust core 73 is connected to the exhaust port port part 7.
A simple structure consisting of 3a and the cylindrical portion 73b for the inner peripheral surface of the convex flange 66 is sufficient, and the core structure can be simplified and the cost can be reduced as compared with a conventional case where separate cores are formed and then joined.

Further, the lightening concave portion 37 is formed only by the lightening die 74.
a and the lower half 66b of the convex flange 66 can be formed at the same time, so that a separate mold member is not required, and the cost can be reduced accordingly.

According to the air cleaner device 68 of the present embodiment, the air inlet chamber A is formed by the connecting portion of the main frame 4 and the rail bracket 6 and the gusset 7 surrounding the portion, and the air inlet chamber A of the gusset 7 is Since the intake duct 86 of the air cleaner 80 is inserted and opened in the air introduction chamber A, it is possible to reliably prevent water from entering. In addition, the intake port 7
Since a is located higher than the bottom surface of the air introduction chamber A, the water that has entered the air introduction chamber A does not enter the intake duct portion 8b, and the minimum position of the air introduction chamber A is conscious. Since the main frame 4 and the main frame 4, which are provided separately, are discharged to the outside through a non-welding point (drainage) between the set 7 and the set 7, it is possible to prevent intrusion of water from entering the air. As a result, it is possible to surely prevent rainwater or the like from being sucked in without requiring a special water entry prevention plate or the like.

The intake duct 86 is connected to the case body 8.
Since they are integrally formed with one another, the cost can be reduced as compared with a case where a separate duct is provided. Further, since the volume of the air introduction chamber A is larger than that of the other body parts, the intake amount does not decrease, and the inside of the gusset 7 having higher rigidity is used as the air introduction chamber A. It can be prevented from becoming a source. Further, since the intake duct 86 is provided and the inside of the air cleaner is inverted, and both the upstream intake port 86a and the discharge port 81d are formed on the case body 81 side, a communication portion as an intake passage is not required on the case cover 82 side. Since the structure is easily detachable, maintenance such as cleaning and replacement of the element is easy. Further, the element 83 is sandwiched between the case body 81 and the case cover 82,
Since the case cover 82 is detachable, the element 83 can be replaced simply by removing the case cover 82, and maintenance can be easily performed from this point as well.

According to the kick starting device of the present embodiment,
When the kick shaft 90 is supported on the left and right cases 95a and 95b, the left case 95a of the kick shaft 90 is supported.
Since the stopper 96 is fixed to the side and the ratchet 92 and the kick gear 93 are mounted, the assembling work can be easily performed. That is, when assembling the kick shaft 90 to the crankcase 36, the stopper 96, the ratchet 92, and the kick gear 93 are previously mounted on the kick shaft 90, and the left end is assembled to the shaft support hole of the left case 95a. After the case 95a and the right case 95b are joined, the kick shaft 90 is turned to the pre-rotation position so that the stopper 96 contacts the case-side stopper at the portion of the kick shaft 90 protruding outward from the right case 95b. The return spring 98 is mounted in the moving state, and the collar 99 is mounted. Then, the case cover 95c may be attached, and finally, the kick arm 91 may be attached. This eliminates the need for the mounting work while aligning the stopper and the ratchet as in the related art, thereby improving workability. Note that a slit is formed in the collar 99, and the collar 99 can be mounted after the spring 98 is mounted by locating the end of the return spring 98 in the slit.

Further, a spring and a guide for moving the conventional ratchet in the axial direction can be dispensed with.
Since only one circlip is required to hold the kick gear immovably, the number of parts and the number of working steps can be reduced, and the cost can be reduced.

In the above embodiment, the case where the kick arm is arranged on the right side of the engine has been described. However, the kick arm may be arranged on the left side. In this case, the arrangement positions of the components are symmetric with respect to FIG.

[0054]

According to the present invention, the upper half of the convex flange is formed by the left and right mother dies and the exhaust core, and the lower half is formed by the exhaust core and the hollow recess. And the lower half mold part formed in the lightening die, so that the structure of the core can be simplified, and there is no need to separately form the lightening die, and the cost can be reduced. effective.

[Brief description of the drawings]

FIG. 1 is a left side view of a motorcycle for explaining a mold for a cylinder body of a two-cycle engine according to an embodiment of the present invention.

FIG. 2 is a left side view of a body frame of the motorcycle.

FIG. 3 is a sectional left side view of the air-cooled engine.

FIG. 4 is a plan view of a cylinder head of the engine.

FIG. 5 is a sectional front view of the cylinder head (FIG. 4)
VV sectional view).

FIG. 6 is a left side sectional view of the cylinder head.

FIG. 7 is a left side sectional view of a cylinder body of the engine.

FIG. 8 is a bottom view of the cylinder body.

FIG. 9 is a right side view showing a mold of the cylinder body.

FIG. 10 is a front view showing the mold.

FIG. 11 is an exploded perspective view of the mold.

FIG. 12 is a sectional plan view of the air cleaner device of the engine.

FIG. 13 is a left side view of the air cleaner device with a case cover removed.

FIG. 14 is a sectional plan view of the kick starting device for the engine.

FIG. 15 is a right side view of the kick starting device with a case cover removed.

FIG. 16 is a view showing a suction cover of the air cleaner device.

[Explanation of symbols]

 12 Two-cycle engine 37 Cylinder body 37a Lightening recess 65 Exhaust port 66 Convex flange 66a, 66b Upper half, lower half 71, 72 Left, right mother die 73 Exhaust core 74 Lightening die 74d Half die Department

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B22C 9/24 F02F 1/00

Claims (1)

(57) [Claims] 1. A convex and annular convex flange portion to which an exhaust pipe is air-tightly connected is provided on a peripheral edge of an external connection opening of an exhaust port communicating with a cylinder bore, and a lightening concave portion is provided on a joint face with a crankcase. In a cylinder body mold for an engine, the left and right mother dies for forming the main parts of the cylinder body, and the left and right mother dies are located on the cylinder head side of the exhaust port and the convex flange portion. An exhaust core forming a half portion, and a lightening die cut out in the axial direction of the cylinder bore to form the lightening concave portion, wherein the lightening die is provided with the exhaust core and the convex flange portion. A mold for a cylinder body of an engine, wherein a mold portion for a lower half portion forming a lower half portion located on the crankcase side is formed integrally.