JPH0118813Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a two-stroke engine, especially a cylinder,
Regarding the structure of crankcases, etc.

FIG. 1 shows a conventional engine, in which the cylinder 1 and the crankcase 2 are divided by the plane A-A, and the crankcase 2 itself is also divided by the plane B-B, which is perpendicular to the crankshaft 4. It is divided into four parts, left, right, top and bottom, by the C-C plane passing on the center line of the plane. In the conventional example shown in FIG. 1, the cylinder 1 and crankcase 2 have many machined surfaces (separated surfaces), and assembly work is time-consuming. It is also difficult to maintain assembly accuracy.

The conventional engine shown in FIG. 2 is an example in which the cylinder 1 and the upper part 2a of the crankcase 2 are integrally molded in order to reduce the processing surface (dividing surface). However, in the structure shown in FIG. 2, the axial width L' inside the crankcase 2 is too wide than the cylinder inner diameter D (see FIG. 3) due to the mold cutting of the scavenging passage 5. That is, the distance between the main bearings 6 becomes wider, causing problems in terms of strength and life of the crankshaft 4 and the main bearings 6. Furthermore, due to mold cutting reasons, it was not possible to form the scavenging passage inner wall 5a (imaginary line) between the scavenging passage 5 and the combustion chamber 8 as shown in FIG. 4, and the cylinder 1 was deformed in the direction of arrow E in FIG. Easy to do.

In the conventional engine shown in FIG. 5, the scavenging passage 5 is formed in a part of the cylinder 1 perpendicular to the crankshaft 4, thereby narrowing the axial width L' in the crankcase 2, and This solves the strength problem of the bearing 6. However, since the intake passage 9 and the exhaust passage 10 are located directly above the crankshaft 4, the intake pipe 11 may obstruct the flow of cooling air F, and the exhaust pipe 12 may interfere with attachment of the work equipment to the crankshaft output section 4a. A problem arises in that it interferes with work.
Further, the cylinder 1 is easily deformed as in the case described in FIG. 4.

This invention solves all the problems of the three types of conventional engines mentioned above.The cylinder and the upper part of the crankcase are integrally molded, and an adapter separate from the cylinder is attached to the cylinder on the side roughly perpendicular to the crankshaft. By fixing it to the adapter, a scavenging passage is formed by the inner wall of the scavenging passage of the cylinder and the adapter. The present invention will be explained below based on the drawings.

In FIG. 6 showing the first embodiment of the present invention, a cylinder head 21, a cylinder 22, and a crankcase upper part 23 are integrally molded by aluminum die-casting, and a crankcase lower part 20 is located below the crankcase upper part 23. It is fixed. 2
4 is a crankshaft, 25 is a connecting rod, and 26 is a piston.

A scavenging passage 27 is formed in the cylinder 22 at one end in a direction perpendicular to the crankshaft 24, and an adapter mounting hole 28, an adapter mounting seat 29, and an inner wall 30 of the scavenging passage are formed at the other end. The circumferential surface constitutes a part of the cylinder inner circumferential surface. An adapter 31 separate from the cylinder 22 is fixed to the mounting hole 28 and the mounting seat 29.

An intake passage 32 is formed in the adapter 31, and a wall surface 33 for forming a scavenging passage is formed, and a reed valve 3 is provided at the outlet of the intake passage 32.
5 is provided. The adapter 31 is inserted into the mounting hole 28 from the arrow Y side (right side in FIG. 6) in the reverse arrow Y direction, and the flange portion 31a is fastened to the mounting seat 29 with a plurality of bolts. The scavenging passage forming wall surface 33 forms a scavenging passage 36 with the scavenging passage inner wall 30 of the cylinder 22 . Scavenging passage 3
The lower end of the cylinder 6 opens into the crank chamber 37, and the other upper end (scavenging port) opens into the cylinder 22. The intake passage 32 communicates with the crank chamber 37 via the reed valve 35.

FIG. 7 is a view taken in the direction of the arrow in FIG. 6 with the adapter 31 removed, making the shapes of the mounting hole 28 and the mounting seat 29 clear.

In FIG. 8, which is a cross-sectional view of FIG. 6,
The axial width L of the crank chamber 37 is approximately as narrow as the cylinder inner diameter D. 40 is a main bearing.

Cylinder head 21 and cylinder 2 shown in FIG.
2 and the crankcase upper part 23 are integrally molded by aluminum die casting, for example, a first core 42 whose extraction direction is in the direction of arrow Y, a second core 43 whose extraction direction is in the direction of arrow Z, and a sixth core 42 whose extraction direction is in the direction of arrow Z. Casting is performed using molds 44 and 45 on the left and right sides of the figure. The arrow Y is perpendicular to the cylinder center line and is aligned with the crankshaft 24.
The direction is also perpendicular to . Arrow Z is parallel to the cylinder centerline and perpendicular to the crankshaft 24. The first core 42 is used to form the mounting hole 28, and the second core 43 is used to form the mounting hole 28.
2 and the inner peripheral surface of the crankcase upper part 23. Both molds 44, 45
The pulling direction (opening direction) is in the arrow X direction, respectively.
This is in the direction of arrow Y. Note that the first core 42 can also be formed integrally with the mold 45 on the right side of FIG.

FIG. 9 shows a second embodiment, in which the intake passage 3
A reed valve holder 47 is provided at the outlet portion of the valve 2, and the reed valve holder 47 is used as a part of the scavenging passage forming wall surface 33. Note that parts corresponding to those in FIG. 6 are given the same numbers as in FIG. 6. Further, the section '-' in FIG. 9 is substantially the same as the section shown in FIG.

FIG. 10 shows a third embodiment, in which a cylinder liner 49 is cast into the inner peripheral surface of the cylinder 22. The cylinder liner 49 is die-cast from high-silicon aluminum alloy. In FIG. 10, parts corresponding to those in FIG. 6 or 9 are given the same numbers as in FIG. 6 or 9. Further, the ``-'' cross section in FIG. 10 is substantially the same as the cross section in FIG. 8. According to the structure in Figure 10,
It is easier and cheaper to manufacture than traditional cast iron liner cylinders, which are manufactured in sand molds.

As explained above, the present invention provides an adapter 31 having a scavenging passage forming wall surface 33 and an intake passage 32.
is formed separately from the cylinder 22, and the cylinder 22
and the crankcase upper part 23 are integrally molded by casting, for example, aluminum die-casting, and the cylinder 2
An adapter attachment part (attachment hole 28) having an inner wall 30 of the scavenging passage is formed in the side part in the direction approximately perpendicular to the crankshaft 24 of No. 2, and an adapter 31 is formed in the adapter attachment part.
Since the scavenging passage 36 is formed by fixing the air to the air, there are the following advantages.

(1) Since the cylinder 22 and the crankcase upper part 23 are integrally molded, the number of gas leakage points and machined surfaces (divided surfaces) is reduced, which simplifies processing and assembly work and improves assembly accuracy. . Also, the cylinder 22 and the crankcase upper part 2
If 3 is integrally molded by die-casting, the manufacturing cost will also be significantly reduced.

(2) Adapter 3 having a scavenging passage forming wall surface 33
1 is formed separately from the cylinder 22, the cylinder 22 and the crankcase upper part 23 are integrated, so that the axial width L of the crank chamber 37 can be narrowed to approximately the same extent as the cylinder inner diameter D. can. Therefore, the distance between the main bearings 40 (FIG. 8) that support the crankshaft 24 is also narrowed, and the crankshaft 24 can be firmly supported. That is, the life of the main bearing 40 and the crankshaft 24 is extended.

(3) By narrowing the axial width L of the crank chamber 37, the volume of the crank chamber 37 can be reduced, thereby making it possible to reduce the volume of the crank chamber 37, resulting in a crank chamber precompression type two-stroke engine (Figs. 6, 9, and 10).
This improves the preload ratio and improves engine performance.

(4) Since the intake passage 32 and the exhaust passage 27 are located approximately perpendicular to the crankshaft 24, the intake pipe and exhaust pipe connected to both passages 32 and 27 do not obstruct the flow of cooling air. Moreover, it does not get in the way of the installation work of the working machine on the output side portion of the crankshaft 24.

(5) Since the scavenging passage inner wall 30 is formed in the cylinder 22, the strength of the cylinder 22 is increased.
There is little possibility that distortion etc. will occur.

(6) Since the intake passage outlet communicating with the crank chamber is integrally formed in the adapter and the reed valve is attached to this intake passage outlet, if the reed valve 35 is assembled to the adapter 31 in advance at the time of assembly, It becomes easy to attach to the engine body.

To explain again the important advantages of the present invention, the intake passage, its outlet, and the wall surface for forming the scavenging passage are formed in one member called the adapter, while the cylinder that is integrated with the upper part of the crankcase has one adapter mounting part. The entire intake passage and the scavenging passage can be formed by simply attaching the one adapter to one mounting portion.

Therefore, compared to a structure in which, for example, a member for forming an intake passage and a member for forming a scavenging passage are separately attached, the cylinder etc. can be easily formed, the structure is simplified, and the adapter can be easily assembled and maintained.

Although the two-stroke engines shown in FIGS. 6, 9, and 10 are of the crank chamber precompression type, the present invention can also be applied to two-stroke engines in which precompression is performed outside the crankcase.

[Brief explanation of drawings]

1, 2, and 5 are longitudinal sectional views of the conventional example, FIG. 3 is a cross-sectional view of FIG. 2, FIG. 4 is a partial cross-sectional view of FIG. Fig. 7 is a vertical cross-sectional view of the applied crank chamber precompression type two-stroke engine, and Fig. 6 is shown with the adapter removed.
8 is a cross-sectional view of FIG. 6,
9 and 10 are longitudinal sectional views of the second and third embodiments, respectively. 22...Cylinder, 23...Crankcase upper part, 24...Crankshaft, 28...Adapter mounting hole (adapter mounting part), 30...Inner wall of scavenging passage,
31...Adapter, 32...Intake passage, 33...
Wall surface for forming scavenging passage.

Claims (1)

[Scope of utility model registration request] One adapter 31 having a wall surface 33 for forming a scavenging passage and an intake passage 32 is formed separately from the cylinder 22, and the adapter 31 is further integrally formed with an intake passage outlet communicating with the crank chamber 37. Attach a reed valve 35 to the outlet of the passage,
The cylinder 22 and the crankcase upper part 23 are integrally cast, and the crankshaft 24 of the cylinder 22
An adapter mounting portion 28 having an inner wall 30 of the scavenging passage is formed at one location on a side approximately perpendicular to the scavenging passage 3 , and an adapter 31 is fixed to the adapter mounting portion 28 .
A 2-stroke engine characterized by the formation of 6.