JPH0232462B2 - ENJINNOSHIRINDASOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylinder device for an engine used in a vehicle or the like.

As a conventional cylinder device of this kind, for example, the first
There is one shown in the figure. In the figure, 1 is a cylinder formed in a cylinder block 2, and a piston 6 with a top ring 3, a second ring 4, and an oil ring 5 attached to three ring grooves is slidably accommodated in the cylinder 1. ing. 7 is a piston pin, 8 is a connecting rod whose one end is pivotally supported by the piston pin 7, 9 is a crankshaft, and 10 is a main bearing cap. In addition, the top spring 3
The cross-sectional shape of the tip is formed into an arc shape.

By the way, it is known that the thickness of the oil film between the cylinder 1 and the piston ring, such as the top ring 3, changes as shown in FIG. 2 ("Internal Combustion Engine Engineering" Industrial Book P233). According to this, the oil film thickness h changes depending on the viscosity η of the lubricating oil, the piston speed U, and the load W applied to the top ring 3, and the oil film thickness h reaches its maximum in the middle of the stroke where the piston speed is high, and the oil film thickness h becomes vertical dead. At the point, the piston 6 temporarily stops and the piston speed U becomes zero, so the oil film thickness h approaches zero. However, when the lubricating oil present between the cylinder 1 and the top ring 3 is pushed out, the oil film thickness h does not become zero due to the squeezing action generated by the hydraulic pressure.

However, in such conventional cylinder devices, as shown in FIG. 3, from the viewpoint of seizure resistance and oil consumption, the cylinder 1 is honed to a surface roughness Ra of about 0.4a, so that the squeezing effect is reduced. Before this occurs, there is a solid contact between the piston ring such as the top ring 3 and the cylinder 1, and the gas pressure is high near the top dead center, so there is a problem that the frictional force of the top ring 3 with respect to the cylinder 1 becomes particularly large. That is, at the top dead center, the piston 6 stops and the force of forming an oil film between the top ring 3 and the cylinder 1 disappears, and the top ring 3 moves toward the cylinder 1 due to the gas pressure applied to the back surface of the top ring 3 in the ring groove. The lubricating oil between them is squeezed out (squeeze effect). It is known that the load capacity due to this squeeze action, that is, the force resisting the gas pressure, is proportional to 1/h ³ when the gap h is ("Bearing" Iwanami Shoten p.91), and as the gap h becomes smaller, the force that resists the gas pressure increases rapidly. The load capacity increases and a large squeezing effect can be obtained. On the other hand, when the surface roughness of the cylinder 1 and the top ring 3 is small, the oil film thickness is calculated in advance by taking into account the squeeze effect ("Internal Combustion Engine Engineering" Sangyo Tosho P233, published in 1976). According to this, the oil film thickness may be less than 1 micron.

On the other hand, when the surface roughness is about 0.4a, the so-called maximum roughness height Rmax is equivalent to 1.6a, so the squeezing effect cannot be obtained, and as a result, the cylinder 1 and the top ring 3 come into solid contact as described above. There was a problem that a boundary lubrication state was created, and the frictional force was greater than when an oil film was present.

The present invention was made by focusing on such conventional problems, and by smoothing the cylinder surface near the position where the top ring stops at top dead center where the piston speed becomes zero, the top spring An object of the present invention is to provide an engine cylinder device that promotes the squeezing action between the cylinder and the cylinder and reduces the frictional force between them.

Embodiments of the cylinder device of the present invention will be described below with reference to the drawings.

Figure 4 shows an example of this, and the surface roughness Ra of the cylinder 1 is finished to be 0.16a or less from the top dead center area where the top ring 3 stops to the top deck, and 0.25 to 0.63a below that to the lower deck. .

As a result, in areas where the surface roughness is 0.16 or less, the maximum height Rmax of the unevenness on the surface of the cylinder 1 is 0.6s or less, so even if the gas pressure on the back side of the top ring 3 is high, the squeezing effect top spring 3
There is no solid contact between the cylinder 1 and the cylinder 1, and a sufficient oil film is interposed between the cylinder 1 and the cylinder 1, so that the frictional force can be greatly reduced compared to the conventional one.

On the other hand, since the surface of the cylinder 1 other than the vicinity of the top dead center is finished with a surface roughness of about 0.4 as before, the lubricating oil holding power is increased and lubricating oil consumption is reduced.
Burn-in can be suppressed.

By the way, it is known that the actual minimum value of the oil film thickness h is not at top dead center, but at a crank angle of 15° to 20° after top dead center due to the dynamic effect of the squeeze action and gas pressure. (“Internal Combustion Engine Engineering” Industrial Book P233).

This is 2 to 3% of the stroke of piston 6.
corresponds to the lowered position (continuation ratio λ=l/r
≒3). Therefore, considering the thickness of the top ring 3, the boundary point 11 where the surface roughness of the cylinder 1 changes should be set at a position lower than the top dead center position of the top ring 3 by about 3 to 5% of the total stroke of the piston. good. Note that similar effects can be obtained when this cylinder shape is applied to a liner type cylinder block.

FIG. 5 shows another embodiment. This is cylinder 1
The smooth part (the part with a surface roughness of 0.16a or less) is between the position 11a where the top ring 3 stops and the position 11b where the piston has dropped by 3 to 5% of the total stroke, and the other parts are smooth. Roughness 0.25~0.63
It is based on the degree. According to this, the lubricating oil retention force in the upper part 1a is improved than in the vicinity 11a of the cylinder upper part, and the seizure resistance of the cylinder upper part 1a and the top land 12 of the piston 6 can be improved.

FIG. 6 shows still another embodiment, in which the upper part of the cylinder 1
In order to prevent seizure of the toppland 12 of the piston 6 and the piston 6, the upper part of the cylinder 1a is provided with a slight relief X so that the diameter of the upper part of the cylinder 1a is large.
Since the roughness of the cylinder 1 can be arbitrarily selected, processing of the cylinder 1 becomes easy.

FIG. 7 shows another embodiment. By changing the material of the inner surface of the cylinder 1 and machining it with the same honing stone, the roughness of the surface of the cylinder 1 can be varied depending on the position. For example, in the cylinder 1 of the cylinder block 2 made of high-silicon aluminum, there is cast iron between the vicinity of the position 11a where the top ring 3 stops and the vicinity of the position 11b below which the top ring 3 is lowered by 3 to 5% of the total stroke of the piston. After casting the ring 13 and machining, the aluminum surface is polished to a surface roughness of 0.25a or more using a honing stone.
It is honed to 0.63a,
Since cast iron is harder than aluminum, the surface roughness of the cast iron ring 13 is finer than that of aluminum. In this case, in order to prevent step wear due to the difference in hardness of the materials at the boundary between the aluminum cylinder 1 and the cast iron ring 13, the boundary between the aluminum cylinder 1 and the cast iron ring 13 is formed into a sawtooth shape 14. In addition, when the cylinder block 2 is made of cast iron, the ring 13
Ceramic can be used as a. In addition, apply wear-resistant powder such as silicon carbide only to the parts to be honed smoothly.
By honing, smoothness can be obtained quickly and with high precision.

As described in detail above, according to the present invention, the surface roughness of the cylinder is made finer near the top dead center where the top ring of the piston stops than in other parts, so that lubricating oil is applied between the top ring and the cylinder. Since the lubricating oil film can be sufficiently retained, the frictional force between them can be reduced, the mechanical efficiency of the engine can be improved, and the engine output and fuel efficiency can be improved.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional cylinder device, Fig. 2 is an explanatory diagram of the oil film thickness between the cylinder and piston ring, Fig. 3 is an enlarged sectional view of the main part of the cylinder device, and Fig. 4 5, 6 and 7 are enlarged sectional views of the main parts of the cylinder device of the present invention.
The figure is an enlarged sectional view showing the main parts of another embodiment. 1...Cylinder, 3...Piston ring (top ring), 3...Piston.

Claims (1)

[Scope of Claims] 1. A cylinder device for an engine, characterized in that the surface roughness of the cylinder is made smaller in the vicinity of the top dead center where the top ring of the piston stops than in other parts. 2. The surface roughness Ra of the cylinder should be 0.16a or less near the top dead center where the top ring of the piston stops.
The engine cylinder device according to claim 1, wherein the other portion is 0.25a to 0.63a.