JPH037559Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a cylinder liner support structure for an engine.

The so-called wet liner system, in which a cylinder liner is supported by a cylinder formed in the engine crankcase or cylinder block, and the outer periphery of the cylinder liner is used as a jacket for cooling water, is widely used in automotive diesel engines. .
Furthermore, in this type of wet liner type engine,
The lower part of the cylinder liner is supported by an annular deck provided on the crankcase, the upper end part of the cylinder liner contacts the cylinder head via the cylinder head gasket, and the cylinder head is tightened to the crankcase with a head bolt. In particular, types have already been proposed in which the cylinder liner is fixed to the crankcase.

Now, an example of its typical structure will be explained with reference to FIG. 2. Reference numeral 10 denotes a cylinder liner, the upper end of which has a stepped portion 10a for receiving the cylinder head gasket 12 and a corresponding top deck 14a of the crankcase 14. An upper flange 10b supported in the radial direction is provided, and a lower flange 10c is formed in the lower portion to rest on an annular lower deck 14b formed in the crankcase 14.
A thin cylindrical extension portion 10d is formed below c. The wall thickness t of the liner central portion 10e between the upper flange 10b and the lower flange 10c, and hence the outer diameter of the same portion, is the same as that of the upper and lower flanges 10c.
It is usually formed smaller than that of b and 10c. 16 is a cylinder head fastened to the upper surface of the crankcase 14 by a head bolt (not shown); 18 is a cooling water jacket formed between the cylinder liner 10 and the crankcase surrounding the central portion 10e; and 20 is a groove into which a watertight O-ring (not shown) is inserted between the contact surface of the cylinder liner 10 and the crankcase.

In the above structure, when the cylinder head 16 is fastened to the crankcase 14 with a head bolt via the gasket 12, the cylinder liner 10
is compressed in the axial direction by the tightening force F acting on the upper step portion 10a and the lower flange 10c, but the line of action of the force F and the center wall thickness of the central portion 10e of the cylinder liner and in the upper and lower parts of the same liner, respectively, as shown in the figure.
Since the cylinder liner 10 is deviated by l ₁ and l ₂ , a bending moment M ₁ =F×l ₁ acts on the cylinder liner 10 in addition to the compressive force F at the upper flange 10b, and also at the lower flange 10c. Similarly, compressive force F
In addition, a bending moment M ₂ =F×l ₂ acts. For this reason, the inner diameter of the cylinder liner 10 is smaller than the normal inner diameter at the upper and lower flange portions, and an extremely complicated bore deformation mode occurs in which the inner diameter is larger than the normal inner diameter at the thinner central portion 10e. Such a complicated deformation mode naturally causes a large radial change in the piston ring (pressure ring and oil ring) fitted on the piston that slides up and down inside the cylinder liner 10 at high speed. It is forced to repeatedly contract and expand,
This has the disadvantage of accelerating piston ring wear and increasing oil consumption.

The present invention was devised to improve the drawbacks of the above-mentioned known structure, in which the lower part of the cylinder liner is supported by an annular deck provided in the crankcase, and the upper end part of the cylinder liner is supported by the cylinder head gas. In a cylinder liner which is pressed into contact with a cylinder head via a butt, a first stage part of a small diameter supported by the deck is provided in the lower part of the cylinder liner, and a first stage part of a small diameter is provided adjacent to the first stage part. a second step portion formed so as not to come into contact with the deck and whose outer diameter is approximately equal to the outer diameter of the liner central portion; and a load point of the first step portion supported by the deck is located at the liner center portion. The gist of this invention is to provide a cylinder liner support structure for an engine, which is characterized in that it is configured to substantially coincide with the central wall thickness plane of the engine.

An embodiment of the present invention will be described in detail below with reference to FIG. (Members and portions that are substantially the same as those in the structure shown in FIG.
The lower part of the cylinder liner supported by the lower deck 14b of No. 4 has a first stepped part 10c' having an outer diameter smaller than the outer diameter of the liner center part 10e, and a first stepped part 10c' adjacent to and above the first stepped part 10c'. A second stepped portion 10c'' is formed in the liner central portion 10e and has an outer diameter equal to or approximately equal to the outer diameter of the liner central portion 10e.
c″ and the outer diameter of the liner central portion 10e are formed to be equal.) Then, the first step portion 10
c' is supported in contact with the lower deck 14b, and the second
The step portion 10c'' is formed so as not to come into contact with the lower deck 14b. Therefore, when the same tightening force F as in the conventional structure shown in FIG. 2 is applied, the first step portion 10c''
The load point c' approximately coincides with the thickness center plane of the center portion of the liner, and in the case shown, the deviation l' ₂ is much smaller than that of the conventional liner. Therefore, the bending moment of the stepped portion 10c' is M2 _' = F x _l2 ', and the moment arm _l2 ' is sufficiently smaller than _l2 , so the bore deformation mode of the lower part of the cylinder liner is determined by the structure shown in Fig. 2. The deformation also becomes significantly gentler, and the absolute value of the deformation also becomes smaller. Furthermore, in this embodiment, the upper part of the cylinder liner 10 is approximately the same in shape as the structure shown in FIG. 2, but the liner central part 10e
Since sufficient wall thickness t′ (>t) is given to
Since the wall thickness center plane is approaching the tightening force F side, the bending moment at this part is M ₁ ′=F×l ₁ ′,
Since l ₁ ′ < l ₁ , the bore deformation mode of the same part is also
The structure is gentler than the structure shown in FIG. 2, and the absolute value of the deformation is also smaller. As a result of these, the contraction of piston rings during engine operation,
The expansion is significantly less severe than in FIG. 2, resulting in less wear and oil consumption. Needless to say, it is preferable that the amount of overhang of the upper flange 10b of the cylinder liner 10 from the liner central portion 10e is as small as possible.

As mentioned above, in the engine cylinder liner support structure according to the present invention, the lower part of the cylinder liner is supported by the annular deck provided in the crankcase, and the upper end part of the cylinder liner supports the cylinder head gasket. In the cylinder liner, the lower part of the cylinder liner has a small-diameter first stage part supported by the deck, and a first stage part adjacent to the first stage part and attached to the deck. A second stage part is formed so as not to come into contact with each other and has an outer diameter approximately equal to the outer diameter of the liner central part, and is supported by the deck so that the load point of the first stage part corresponds to the wall thickness of the liner central part. To make the inner diameter deformation mode of the cylinder liner gentle in a type of engine in which the cylinder liner is supported on the crankcase at its lower part and is characterized by being configured to substantially coincide with the center plane. At the same time, it is possible to reduce the absolute value of deformation and reduce piston ring wear and oil consumption, which is extremely useful in practice.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing one embodiment of the present invention;
The figure is a conceptual cross-sectional view showing a conventional cylinder liner support structure. 10... Cylinder liner, 14... Crank case, 10c'... Lower step, 14b... Lower deck, 12... Cylinder head gasket.

Claims (1)

[Scope of utility model registration request] The lower part of the cylinder liner is supported by an annular deck provided in the crankcase, and the upper end part of the cylinder liner is pressed against the cylinder head via the cylinder head gasket. In the lower part there is a small diameter first support supported by the deck.
a step part, and a second step part that is formed adjacent to the first step part so as not to come into contact with the deck and whose outer diameter is approximately equal to the outer diameter of the center portion of the liner, and is supported by the deck. 1. A cylinder liner support structure for an engine, characterized in that a load point of a first stage portion substantially coincides with a center wall thickness plane of a central portion of the liner.