JPH0639076Y2 - Cylinder liner for model engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to improvement of a cylinder liner in a model engine.

[Prior Art] In recent years, in a model engine, a piston ring is not used for the piston in order to maintain the airtightness of the combustion chamber to a higher degree and to improve the output and stabilize the idling, as shown in FIGS. 6 and 7. The inner wall of the cylinder liner 101 has a slight inclination toward the upper part, for example, a cylinder liner of a 10cc class engine with a gradient of about 1/1000 mm to narrow the inner diameter toward the top dead center, and slightly less than the narrowed inner diameter. A piston 103 having a large outer diameter is directly fitted to the cylinder liner and used in combination so as to obtain a higher degree of airtightness than an engine using a piston ring.

[Problems to be Solved by the Invention] Since the conventional cylinder liner is thicker toward the upper part and is a rigid body, the peripheral wall is not elastically deformed, and the piston cannot be forced against the cylinder liner having a narrow inner diameter. It will slide toward top dead center and it will take a considerable time for the cylinder liner and the piston to fit in, and long run-in operation is required, and moreover, until the piston has the same slope as the cylinder liner (No. (Shown in Figure 7)
In the vicinity of the top dead center where the inner diameter becomes narrower, the cylinder liner and piston are fitted together considerably, causing the oil to run out of oil and causing seizure of the high-speed rotating model engine. Otherwise, it may cause a large amount of dirty exhaust gas to be discharged. Furthermore, even after the piston wears as shown in Fig. 7 and adapts to the slope of the cylinder liner, the cylinder liner and piston are further worn due to the rigid body and the airtightness cannot be maintained gradually. Better, but still short-lived and problematic. Also, due to the difference in the coefficient of thermal expansion of the cylinder liner and piston due to the change in the cooling state of the engine, the state becomes too hard or too loose, mainly when the throttle is suddenly opened and accelerated during the lowest speed operation. The engine was easy to stop, which was a problem.

In order to solve the above problems, this invention reduces the thickness of the peripheral wall near the top dead center of the cylinder liner with the inner diameter narrowed toward the top to reduce the peripheral wall near the top dead center against the sliding of the piston. It can be expanded and contracted within the range of elastic deformation to reduce the sliding resistance of the piston, and it can be slid with a high degree of airtightness to shorten the run-in operation and wear of the piston etc. can be significantly reduced compared to the past. An object of the present invention is to provide a cylinder liner for a model engine that can be smoothly operated for a long period of time without running out of lubricating oil.

[Means for Solving the Problems] In order to achieve the above object, the cylinder liner of the present invention has an annular recess 2 formed in the upper outer periphery of a cylinder liner 1 having an inner diameter narrowed toward the upper part to form a ring near the top dead center. A thin wall 1a that is elastically deformable is provided on the peripheral wall to increase airtightness near the top dead center and reduce sliding resistance of the piston to prevent abrasion of sliding parts, improve output, and stabilize idling. Is intended.

[Operation] According to the model engine equipped with the cylinder liner of the present invention, the thin wall portion of the peripheral wall of the cylinder liner expands within the range of elastic deformation in the compression stroke and the explosion stroke near the top dead center to maintain airtightness. Slide.

[Embodiment] An embodiment of the present invention will be described with reference to the drawings.

In FIGS. 1 to 5, 1 is a cylinder liner of a model engine A whose inner diameter is narrowed upward, and 3 is a piston having an outer diameter slightly larger than the narrowed inner diameter of the upper portion of the cylinder liner. This cylinder liner is enlarged in the drawing and the slope is exaggerated. However, in the case of an actual model 2-cycle engine, the stroke of the cylinder liner 1 is 22 mm and the slope of the inner wall is about 1/1000 mm in the 10 cc class. It is a slight one. Therefore, as apparent from the figure, the cylinder liner 1 gradually becomes thicker toward the top dead center, and the piston becomes tighter against the inner wall as the piston approaches the top dead center.

In this invention, an annular concave portion 2 having a U-shaped cross section is formed on the outer periphery of the upper portion of the cylinder liner 1, and the wall thickness of the peripheral wall near the top dead center of the cylinder liner is made elastically deformable. Expandable in range. The recess has a length corresponding to a stroke in which the piston 3 is particularly tight against an inner wall having a narrow inner diameter near the top dead center, and the depth thereof is a depth capable of forming an elastically deformable thin portion 1a. .

For example, the wall thickness of the cylinder liner 1 of a 10 cc class two-cycle engine is about 2-3 mm. In the case of this cylinder liner 1, the length of the thin portion 1a on the upper peripheral wall is about
It is elastically deformable with a thickness of about 8 mm and a thickness of about 1.5 mm. The length and thickness of the thin-walled portion 1a of the cylinder liner are not limited to the above dimensions, and are designed in consideration of compression, elastic deformation with respect to pressure in the explosion stroke, strength, and air tightness with the piston.

Although the annular recess 2 has a U-shaped cross section, the lower portion of the annular recess 2 corresponding to the boundary between the thick wall portion and the thin wall portion 1a of the peripheral wall is inclined as shown in FIG. 3 and as shown in FIG. If the wall thickness is gently changed as the circular arc surface 2b, the thin peripheral wall can be gently expanded when the piston rises.

In FIG. 5, reference numeral 4 denotes a crankcase, the cylinder liner 1 is provided inside the crankcase, and the cylinder head 5 is fixedly provided on the crankcase and the cylinder liner. 6 is a piston rod of the piston 3, 7 is a crankshaft, 8 is a spark plug, 9 is a suction hole, and 10 is an exhaust hole.

According to the above configuration, when the piston 3 rises toward the top dead center during compression, the piston 3 moves toward the cylinder liner 1.
Just before changing from the thick part to the thin part 1a
After that, the thin portion 1a is elastically deformed and pushed in, and the piston rises to the top dead center while slightly expanding the thin portion 1a toward the space side of the recess 2 as shown in FIG. Even in the explosion stroke, the thin upper peripheral wall tends to be slightly expanded by the explosive force, and the piston is kept airtight and smoothly descends.

[Advantage of Invention] According to this invention, the peripheral wall near the top dead center of the cylinder liner is made thin so that it can be expanded within the range of elastic deformation, so that it does not take so long for the cylinder liner and the piston to fit in. Therefore, the run-in can be short, the sliding resistance of the piston can be reduced, the wear of the sliding part can be prevented, and the oil out of the lubricating oil does not occur between the cylinder liner and the piston. No image sticking occurs. Further, since the wear of the cylinder liner and the piston is small, it is possible to prevent the exhausted dust from being discharged. Further, even after the piston is fitted into the cylinder liner, the elasticity of the thin wall makes it possible to maintain high airtightness, and therefore the life of the piston and the cylinder liner can be considerably extended.

Furthermore, although there is a difference in the coefficient of thermal expansion due to the change in the cooling condition of the cylinder liner and piston, the thin peripheral wall does not become too hard or too loose, so that the sliding of the piston is not hindered and the minimum speed is maintained. Even if the throttle is suddenly opened during driving to accelerate, there are many practical benefits such as smooth acceleration without stopping the engine.

[Brief description of drawings]

FIG. 1 is an enlarged vertical sectional view showing an embodiment of a cylinder liner in a model engine of the present invention, and FIG. 2 is an enlarged vertical sectional view of the piston in a state of being raised to a top dead center, FIGS. FIG. 5 is an enlarged vertical sectional view of an essential part showing another embodiment of the concave portion of the peripheral wall at the top dead center, FIG. 5 is a sectional view showing a model engine equipped with the cylinder liner of the present invention, FIG. 6 and FIG. FIG. 4 is an enlarged vertical sectional view of a conventional cylinder liner. 1 ... Cylinder liner, 1a ... Thin part, 2 ... Annular recess, 3 ... Piston.

Claims (1)

[Scope of utility model registration request] 1. A cylinder liner (1) having an inner diameter narrowed toward an upper part is formed with an annular recessed part (2) on an outer periphery thereof, and an elastically deformable thin wall part (1a) is provided on a peripheral wall near a top dead center. Cylinder liner for model engines, which is characterized by that.