JPH1030495A - Cylinder liner structure of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylinder liner structure being lighter in weight and excellent in working properties, which is able to prevent any possible damage to a cylinder liner, and simultaneously has facilitated those of insertional assembly and dismantlement of this cylinder liner, in this structure of inserting this dry cylinder liner into a cylinder body. SOLUTION: In this cylinder liner structure, inserting a dry cylinder liner 1 into a cylinder body 2 of an engine, this cylinder liner 1 is provided with a flange part 3 in the upper end of a liner tubular part 4, and fitting between the liner tubular part 4 and the cylinder body 2 is carried out, while an upper part of the liner tubular part 4 is made into a press fitting zone T and simultaneously the lower part is formed into a loose fitting zone L, and a lower end of the press fitting zone T is situated at the more lower side than a top ring 7 of a piston 6, and also, at the more upper side than an oil ring 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry liner system in which a cylinder liner is inserted into a cylinder body of an engine to cool indirectly from the outer periphery of the cylinder.

[0002]

2. Description of the Related Art In a cylinder liner for a cylinder of a small engine such as an automobile, a dry liner system is often used in which the cylinder liner is indirectly cooled from the outer periphery of the cylinder without directly cooling the outer periphery of the cylinder liner with cooling water. Have been. This dry liner type cylinder liner and cylinder body are fitted by a full-length press-fitting method in which the entire outer diameter of the cylinder liner is almost equal to the inner diameter of the cylinder body and press-fitted with "tightening fit". -651
16, the flange of the cylinder liner and the lower part of the liner cylinder are press-fitted, and the difference between the cylinder body inner diameter and the cylinder outer diameter in the middle part near the top dead center of the piston is slightly provided. The middle part is loosely fitted by inserting the `` clearance fit '', and the flange part on the upper part of the cylinder liner, which is proposed in Japanese Utility Model Application Laid-Open No. There is a lower loose fitting method in which a small-diameter liner cylinder part is loosely inserted.

[0003]

However, when the entire length of the cylinder liner is press-fitted as in the full-length press-fitting method, a large press-fit is required because the press-fitting band is long. Installation of the cylinder liner,
When removing, use a special tool or press machine, or after press-fitting, it is necessary to ensure the roundness by boring or honing the inner peripheral surface of the cylinder liner that is out of contact pressure at the time of press-fitting There is a problem that the properties are remarkably deteriorated.

In the intermediate loose fitting method,
Although the press-fitting band becomes shorter and the press-fitting becomes smaller, since the lower end of the cylinder liner remains press-fitted,
It was necessary to press-fit from the start of insertion to the end of insertion, and a significant improvement in work could not be expected. In addition, when the upper part of the liner cylinder portion of the cylinder liner is loosely fitted, such as in the middle loose fitting method or the lower loose fitting method, a flange portion is provided as described below. There is a problem in strength that a crack is generated in the connection step portion of the liner cylinder portion and the cylinder liner is damaged.

[0005] The occurrence of cracks at the connection between the flange portion of the cylinder liner and the liner cylinder portion is considered to occur by the following mechanism. First, if the upper part of the liner cylinder is loosely fitted, as shown in FIG. 3, the gap S between the liner cylinder 4 and the cylinder body 2 is very small under the flange 3. When the cylinder head is tightened by the force F from above, when the cylinder head is tightened,
Since the connection step 5 is statically deformed with the connection step 5 as a fulcrum as shown by a dashed line, a static stress is generated in the connection step 5.

Next, during operation of the engine, the combustion pressure (explosion pressure) in the cylinder and the side pressure generated by the piston are applied as internal pressure P to the inside of the cylinder liner, so that a small gap S is formed between the cylinder liner and the cylinder body. Then, a bending moment in the radially expanding direction as shown in FIG. 4 acts on that portion, and this bending moment generates elastic deformation. In addition to the above-mentioned static stress, a dynamic stress is generated by an internal pressure. In addition to shear stress, it is applied as tensile stress or compressive stress due to bending moment.

[0007] The magnitude of the combustion pressure is maximized when the piston in the stroke from compression to the combustion stroke reaches near the top dead center in the case of a general diesel engine, depending on the engine. It can be several tens of atmospheres.
The number of repetitions is a number corresponding to the number of revolutions of the engine, and is an enormous number. In addition, this gap S
At the upper end portion A, that is, at the connection step 5 between the flange 3 and the liner cylinder 4, even if it is elastically deformed, it cannot contact the cylinder body 2, and always has a thin wall thickness of the liner cylinder 4 of the cylinder liner 1. In addition to having to withstand these stresses only in the portion, the connecting step 5 serves as a fulcrum when elastically deforming repeatedly and is exposed to a very severe condition. Crack C will occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. An object of the present invention is to provide a cylinder liner in which a large combustion pressure is repeatedly applied during operation of an engine in a structure in which a dry cylinder liner is inserted into a cylinder body. The cylinder liner can be prevented from being damaged by making the upper part a press-fitting zone, and the cylinder liner structure is made easier by assembling and removing the cylinder liner by making the lower part of the cylinder liner a loose fitting zone. It is to be.

[0009]

In order to achieve the above object, in a cylinder liner structure in which a dry cylinder liner is inserted into a cylinder body of an engine, the cylinder liner is provided with a flange at an upper end of a liner cylinder. The fit between the liner cylinder and the cylinder body is formed such that the upper part of the liner cylinder is a press-fitting band and the lower part is a loose fitting band, and the lower end of the press-fitting band is Provided is a cylinder liner structure of an engine positioned below a top ring of a piston and above an oil ring at a piston top dead center position.

The press-fitting zone is set so as to include a range where a large combustion pressure acts. That is, the range of the large combustion pressure is from the upper end of the cylinder liner to the position of the top ring called the pressure ring of the piston which plays a role of maintaining the airtightness in the cylinder. This large combustion pressure does not reach because the propagation is interrupted. Therefore, it is sufficient to set the pressure fitting zone up to the position of the oil ring below the top ring for scraping off the oil.

Also, since the loose fitting zone is provided at the lower portion of the liner cylinder, the liner cylinder can be easily inserted into the liner fitting hole and set at the time of assembling. Since it is formed short around the chamber and press-fitted in the last step of fitting the cylinder liner into the liner fitting hole, the press-fitting is reduced. In addition, when the cylinder liner is removed, if the press-fitting band is first removed, the band becomes a loose fitting band thereafter and can be easily removed, so that the workability of assembling and removing is remarkably improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. A cylinder liner 1 of an engine E is formed by a flange 3 formed by expanding an upper part outward and a cylindrical liner cylinder 4 extending downward from an inner diameter of the flange 3. The cylinder liner 1 is fitted into the fitting hole 9.

The liner fitting hole 9 is provided with a flange receiving portion 9c and a liner cylinder housing 9d for fitting the flange 3 and the liner cylinder 4 of the cylinder liner 1 respectively. When fitting the liner tube portion 4 of the cylinder liner 1 to the liner tube housing portion 9d, a tight fitting press-fitting band T is provided above the liner tube portion 4, and a loose fitting loose fitting band L is provided below. And the position B of the lower end of the press-fitting zone T is lower than the top ring 7 of the piston 6 at the time of the piston top dead center and higher than the oil ring 8 of the piston 6. The lower part of the press-fitting band T from the position B at the lower end is defined as a loose fitting band L.

The press-fitting band T is formed by a "tight fit" in which the outer diameter D1 of the liner cylinder 4 is substantially the same as or slightly larger than the inner diameter H1 of the liner cylinder housing 9d of the cylinder body 2. Also, the loose fitting band L is equal to the outer diameter D of the liner cylinder 4.
2 is the inner diameter H1 of the liner cylinder housing 9d of the cylinder body 2.
It is formed with a smaller "clearance fit". Specifically, the loose fitting band L is the inner diameter H of the liner cylinder housing 9d.
1 is 0.006 mm to 0.1 mm from the outer diameter D2 of the liner cylinder 4.
It is preferable to set so as to be 025 mm larger.

In this case, the outer diameter of the liner cylinder portion 4 of the cylinder liner 1 is changed to form the press-fit fitting band T and the loose fitting band L. The press-fitting band T and the loose fitting band L may be formed by changing both the outer diameter of the liner tube 4 and the inner diameter of the liner tube housing 9d. The outer diameter D3 of the flange portion 3 of the cylinder liner 1 is substantially the same as or slightly larger than the inner diameter H2 of the flange receiving portion 9c of the cylinder body 2, so that "tight fit" is possible.

With the above structure, the upper part of the liner cylinder portion 4 of the cylinder liner 1 is formed in the press-fitting zone T. Therefore, when the cylinder head is stacked on the cylinder body 2 and tightened with bolts, Since the outer periphery of the upper part of the cylindrical portion 4 can be tightly supported by the cylinder body 2, the cylinder liner 1 can be prevented from being deformed as shown by a dashed line in FIG. Can be very small.

A press-fitting zone T is provided so as to cover a portion to which a large combustion pressure is applied when the engine is operating, and the cylinder liner 1 is provided with a flange 3 sandwiched between a cylinder head and a cylinder body 2 and a pressure fitting zone. A large combustion that is firmly fixed to the cylinder body 2 with the liner cylinder portion 4 of T, and is repeatedly applied to the inner wall of the cylinder liner 1 in the pressure fitting zone T of the cylinder liner 1 supported integrally with the cylinder body 2. Since the pressure can be received by both the cylinder liner 1 and the cylinder body 2,
Damage such as cracks due to fatigue failure of the cylinder liner 1 can be avoided.

Since the loose fitting zone L is provided at the lower part of the cylinder liner 1, when the cylinder liner 1 is inserted into the liner fitting hole 9 of the cylinder body 2 and assembled, the liner cylinder portion 4 is accommodated in the liner cylinder housing. It can be easily set in the part 9d,
Further, the press-fit fitting band T is shortened, and the liner cylinder 4
The cylinder liner 1 can be press-fitted with a small press-fit, and the press-fitting is only the last part of the assembly and the first part of the disassembly. The properties are significantly improved.

In addition, since the upper portion (neck portion) of the liner cylinder portion 4 is defined as a pressure fitting band T, the pressure fitting band between the portion of the flange 3 sandwiched between the cylinder head and the cylinder body 2 and the liner cylinder portion 4. The cylinder liner 1 can be firmly fixed to the neck of the T. Therefore, the thickness of the flange 3 in the vertical direction can be reduced, and the weight of the cylinder liner 1 can be reduced. When the thickness of the flange portion 3 can be reduced, a thick portion where the thermal stress due to the temperature difference between the cylinder liner 1 and the cylinder body 2 and the difference in thermal expansion between the two materials tends to be large, that is, Since the portion of the flange 3 is reduced, the amount of generated thermal stress can be reduced, and the stress load on the cylinder liner 1 and the cylinder body 2 can be reduced.

Therefore, only the upper part of the liner cylinder part 4 of the cylinder liner 1 which receives a large combustion pressure of the engine is set to the press-fitting zone T, and the lower part is set to the loose fitting zone L. Thus, it is possible to prevent the damage by reducing the stress to be applied, and to improve the workability of attachment and detachment. In addition, the length of the flange 3 of the cylinder liner 1 can be reduced, so that the weight can be reduced.

[0021]

As described above, according to the present invention,
In the structure in which the dry cylinder liner is inserted into the cylinder body, the upper part of the cylinder liner where the large combustion pressure is repeatedly applied during operation of the engine is used as a press-fitting band, and a flange portion that holds the cylinder liner between the cylinder head and the cylinder body The cylinder liner is firmly fixed to the cylinder body with the liner cylinder in the pressure fitting zone, and a large combustion pressure is applied to the upper part of the cylinder liner where the cylinder body is in close contact. In addition, the lower part of the cylinder liner where the large combustion pressure does not act is made a loose fitting zone to facilitate the insertion and assembly and removal of the cylinder liner, so that a cylinder liner structure with good workability can be obtained. it can.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a cylinder showing an embodiment of the present invention.

FIG. 2 is a partial sectional view of a cylinder showing the embodiment of the present invention.

FIG. 3 is a partial sectional view of a cylinder for explaining static deformation of the cylinder liner.

FIG. 4 is a partial cross-sectional view of a cylinder for explaining damage to the cylinder liner.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder liner 2 ... Cylinder body 3 ... Flange 4 ... Liner cylinder 5 ... Connection step 6 ... Piston 7 ... Top ring 8 ... Oil ring 9 ... Liner fitting hole T ... Press fit fitting band L ... Loose fitting Band

Claims (1)

[Claims] In a cylinder liner structure in which a dry cylinder liner (1) is inserted into a cylinder body (2) of an engine, the cylinder liner (1) has a flange (3) at an upper end of a liner cylinder (4). The upper part of the liner cylinder part (4) is made to be a press-fitting part (T) and the lower part is made to be a loose fitting part when fitting the liner cylinder part (4) and the cylinder body (2). (L), the lower end of the press-fitting zone (T) is below the top ring (7) of the piston (6) at the piston top dead center position and above the oil ring (8). Engine cylinder liner structure located in