JP2511334Y2 - Cylinder liner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an improvement of a cylinder liner fitted in a hole provided in an engine block.

[Conventional technology]

In an engine, a cylinder liner is fitted in a cylinder bore provided in an engine block to form a cylinder. Conventionally, a small engine cylinder liner is manufactured by forming its inner and outer peripheral surfaces into a perfect circle, and then fitting this into the bore of the engine block, and after confirming that it is close to a perfect circle, It incorporates a piston fitted around the outer circumference.

As described above, the bore of the cylinder liner after being assembled into the engine is kept in a perfect circle at the time of manufacture at a low temperature when the engine is stopped. However, when the engine is operated, heat load acts on the cylinder liner, and in an actual operating state, the cross-sectional shape of the bore is considerably deformed from a true circle to an elliptical shape. The cross-sectional deformation of the cylinder liner deteriorates the followability of the piston ring whose outer circumference is formed in a perfect circle, and causes an increase in oil consumption.

The reason why the cylinder liner is deformed in cross section is that the gap 3 between the bores 2 linearly arranged in the longitudinal direction of the arrow AB in the engine block 1 as shown in FIG. This is considered to be because the amount of cooling water passing through these gaps 3 and 4 tends to be smaller in the former than in the latter because it is narrower than the gap 4 in the thrust / anti-thrust direction of -D.

Therefore, the temperature of the gap 3 in the front-rear direction (AB direction) of the cylinder liner becomes higher than that of the gap 4 in the thrust / anti-thrust direction (CD direction). By the way, if the temperature of the cylinder liner varies in the circumferential direction due to the amount of cooling water as described above, the bore of the cylinder liner that was a perfect circle before the operation of the engine becomes elliptical depending on the temperature difference during operation. It will be transformed into. As a result, the gap between the piston ring and the inner peripheral surface of the cylinder liner becomes large, the sealing performance deteriorates, and the oil consumption increases.

As a means for solving the problem caused by the deformation of the cylinder liner due to the heat load, Japanese Utility Model Laid-Open No. 56-11341 proposes a method in which the cylinder liner has an elliptical outer periphery.

Specifically, as shown in FIG. 3, the cylinder liner 6 has an outer peripheral surface 6a of an elliptical shape and is fitted into a hole 7 having a perfect circular inner peripheral surface provided in the engine block 1. If the outer peripheral surface 6a of the Linda liner 6 has an elliptical shape, when the engine is stopped and the temperature becomes low, the hole 7 and the outer peripheral surface are
A gap 8 is formed between this and 6a.

Therefore, the cooling water enters the gap 8, which causes fretting (erosion phenomenon) and reduces the durability of the engine.

The amount of deformation of the inner diameter of the cylinder liner 6 during operation of the engine is determined by the temperature distribution. Even if the outer peripheral surface 6a of the cylinder liner 6 has an elliptical shape as described above, if the temperature distribution is different from the calculated value. It is said that the inner peripheral surface 6b, which is processed into a perfect circle, undergoes elliptical deformation along with a change in temperature distribution, which makes it difficult to maintain a perfect circle during operation, resulting in an increase in oil consumption. The problem occurs.

In order to solve the problem of fretting caused by the formation of the gap 8 between the engine block 1 and the outer peripheral surface 6a of the cylinder liner 6 as shown in FIG.
Inner peripheral surface 7a of hole 7 provided in engine block 1 as shown
Is formed into an elliptical shape, and by fitting the cylinder liner 6 having an elliptical outer peripheral surface 6a that fits this, a gap is prevented from being formed between the engine block 1 and the cylinder liner 6, and the engine is stopped. A method has been proposed in which the hole 7 and the outer peripheral surface 6a of the cylinder liner 6 are brought into close contact with each other in the state (at low temperature).

Certainly, in the case of the cylinder liner 6 having the structure shown in FIG. 2, it is possible to prevent fretting at low temperature because the gap 8 is not formed between the outer peripheral surface 6a and the hole 7 as shown in FIG. Is. However, even in the case of this structure, when the engine is operating, the cylinder liner 6 is in the AB direction and the C direction.
Due to the temperature difference inevitably occurring in the −D direction, the inner peripheral surface 6b of the cylinder liner 6 does not become a perfect circle but deforms into an elliptical shape, similar to the case of the cylinder liner 6 shown in FIG. There is a problem that the consumption of oil cannot be reduced.

The present invention solves the above-mentioned problems of the prior art and prevents fretting by tightly attaching the cylinder liner to the hole provided on the engine block side when the engine is cold, and prevents the fretting from occurring when the engine is operating and the temperature is high. It is an object of the present invention to provide a cylinder liner whose peripheral surface can be expanded and deformed into a perfect circle or a nearly perfect circle.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a perfect circular hole formed in an engine block by forming a cylinder liner in which an outer peripheral surface is a perfect circle and an inner peripheral surface is an elliptical shape determined by a temperature rise during engine operation. It is a cylinder liner that is formed so as to be fitted with a minor axis in the direction of high temperature.

Regarding the shape of the bore provided in the cylinder liner 6, the diameter of the engine block 1 in the front-rear direction (AB direction) is the minor axis L, and the diameter in the thrust / anti-thrust direction (CD direction) is the major axis M. The relationship between the major axis and the minor axis is determined by setting a condition satisfying LM = L * (temperature difference) * (coefficient of thermal expansion) as a target value.

It has been confirmed by various experiments that the specific value of (LM) is preferably in the range of 0.05 to 0.15.

[Action]

When the engine is stopped and the temperature is low, the bore formed in the cylinder liner has an elliptical shape, but if the temperature of the engine block rises to a predetermined temperature during operation,
The bore becomes a perfect circle or a state close to a perfect circle, and the piston ring is accurately brought into contact with and guided by the inner peripheral surface thereof.

〔Example〕

The sectional view shown in FIG. 1 shows an embodiment of the present invention, in which a cylinder liner 6 having a flange portion formed at the upper end is fitted and fixed in a hole formed in the engine block 1.

The bore 10 provided in the cylinder liner 6 has a minor axis L arranged in the front-rear direction of the engine (AB direction) and a major axis M arranged in the thrust / anti-thrust direction (CD direction).

That is, when the engine is stopped and the temperature is low, the cylinder bore 10 is formed in an elliptical shape designed in consideration of the temperature distribution in the state where the engine is operating, and the direction of the bore 10 is as shown in FIG. As shown in.

[Effect of device]

According to the present invention, a cylinder liner having an outer peripheral surface formed in a perfect circle and an inner peripheral surface formed in an elliptical shape determined by a temperature rise during engine operation has a high temperature inside a perfect circular hole formed in an engine block. The cylinder liner is formed so as to be fitted with its minor axis oriented in the direction, and can exert the following effects.

That is, when the engine is stopped and in a low temperature state,
Although the cylinder bore has an elliptical shape, when the engine operates and the cylinder liner reaches a predetermined temperature, the elliptical bore gradually deforms into a true circle due to thermal expansion of the cylinder liner. Then, in this state, the surface of the piston ring accurately follows the cylinder bore, the sealability between the piston ring and the cylinder liner is improved, and the oil consumption can be reduced.

Also, since the cylinder liner formed on the outer peripheral surface of the perfect circle is fitted in the perfect circle mounting hole formed in the engine block, it is of course necessary to operate the engine between the engine block and the cylinder liner while the engine is stopped. Since no gap is formed inside, the fretting phenomenon that occurs between the engine block and the cylinder liner can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view showing a relationship between a cylinder liner according to the present invention and a mounting hole provided in an engine block into which the cylinder liner is fitted. 2 and 3 are sectional views showing a conventional cylinder liner and an engine block into which the cylinder liner is fitted, and FIG. 4 is a plan view of the engine block. 1 ... Engine block, 2 ... Cylinder bore 3 ... Gap (high temperature part), 4 ... Gap (low temperature part) 6 ... Cylinder liner, 6a ... Outer surface 6b ... Inner surface 7 ... Mounting hole, 7a …… Inner surface 8 …… Gap.

Claims (1)

(57) [Scope of utility model registration request] Claim: What is claimed is: 1. A cylinder liner having an outer peripheral surface formed in a perfect circle and an inner peripheral surface formed in an elliptical bore defined by a temperature rise during engine operation in a perfect circular hole formed in an engine block. A cylinder liner formed so as to be fitted with the minor axis of the bore oriented in the direction of high temperature.