JP3065118B2 - Trunk piston for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention comprises a plurality of compression rings and an oil ring disposed immediately below these compression rings. The oil ring has a pressure release hole communicating from a groove of the oil ring to the inside of the piston. The present invention relates to a trunk piston for an internal combustion engine, having an oil outlet hole disposed below each oil ring in each of the two quadrants in front of the piston pin end face and communicating with the inside of the piston.

[0002]

2. Description of the Related Art A piston of this kind is known from DE 927 544 A1. In this piston, one oil collecting groove is provided in each quadrant in front of both piston pin end faces below the oil ring. Before the lubricating oil reaches the combustion chamber, an attempt is made to derive an excessive amount of lubricating oil in this range by the oil collecting groove. However the piston pin longitudinal when the piston is subjected to a high load
It was found that a quadrant located in front of the axis would be short of oil. In the case of this piston, oil supply with excess oil in the quadrant in front of the piston pin end face due to the oil ring is caused by oil collecting grooves with a circumferential boundary and large diameter oil outlet holes at both ends. Is hindered by having

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to improve a piston of the above-mentioned kind such that sufficient lubrication of the piston ring and the outer surface of the piston is achieved over the entire circumference of the piston.

[0004]

According to the present invention, a pressure release hole is located in front of a longitudinal axis of a piston pin .
That both quarter provided in the central region of the circle only extends enclose oil collection groove of the piston, part of the smaller diameter in each pressure relief hole is provided, even at least one oil outlet and at least one pressure release hole The holes are solved by merging into a common outlet hole extending in the longitudinal direction of the piston and leading to free space below the piston.

[0005]

An advantage achieved by the present invention is that the gas pressure in the quadrant located in front of the longitudinal axis of the piston pin is appropriately reduced. Thus, in this region, on the one hand, the lateral movement of the oil in the direction towards the quadrant located in front of the longitudinal axis of the piston pin is prevented and, on the other hand, the oil adhering to the cylinder wall is displaced downwards. No pressurized combustion gas is generated that could lead to it. In this case, the annular collecting groove allows a lateral movement of the excess oil in front of the piston pin end face. Therefore, a portion of this oil can be unhindered through the annular oil collecting groove to the quadrant located in front of the longitudinal axis of the piston pin. On the other hand, another part of the excess oil is led out into the piston. Therefore, this oil does not cause such a large dynamic pressure that the oil ring floats from the lower surface of the ring groove or deforms the oil ring so that the oil leaks between the oil ring and the cylinder liner wall. . If these phenomena occur, the oil can reach the combustion chamber and burn there.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings showing a plurality of embodiments of a trunk piston according to the present invention.

FIG. 1 is a horizontal sectional view of one embodiment of a trunk piston according to the present invention, FIG. 2 is a sectional view taken along section line II-II of FIG. 1, and FIG. 3 is a sectional view taken along section line III-III of FIG. It is. The piston shown in FIGS. 1 to 3 has a plurality of grooves 2 for accommodating each compression ring 3. The upper part 1 is firmly connected to the lower part 4 in a manner known per se but not shown in detail. The lower part 4 is provided with another groove 5 for accommodating an oil ring. The groove 5 can basically be provided on the upper part of the piston. Similarly, the invention is not limited to a two-part piston. The lower part 4 further houses a piston pin, the longitudinal axis of which is indicated by the reference A-A.

[0008] A plurality of pressure release holes 7 branch off from the rear wall of the groove 5. Each pressure relief hole 7 leads to a vertical outlet hole 8. A sleeve is further fitted into each pressure relief hole 7, which forms a small diameter section 9. The pressure release holes 7 respectively join the grooves 5 in the respective central regions of the two quadrants a located in front of the piston pin longitudinal axis .

Immediately below the groove 5 for the oil ring 6,
An oil collecting groove 10 extending around the outer periphery of the piston is arranged. It is expedient for the oil collecting groove 10 to cut out the groove 5. In the central region of each quadrant b in front of the piston pin end face, oil outlet holes 11 branch off from the oil collecting groove 10, and these oil outlet holes also merge into the vertical outlet hole 8. In the case of the illustrated embodiment, one pressure release hole 7 and one oil outlet hole 11 respectively join the common outlet hole 8.

For example, when the piston moves downward during the expansion stroke, the piston performs a tilting movement about the axis AA of the piston pin. This tilting movement results in that the gap between the cylinder liner and the piston is reduced first in the area of one quadrant a and then later in the other quadrant a due to tilting. Therefore, in these ranges, the oil adhering to the cylinder liner is pushed out in the lateral direction toward the quadrant b. This effect occurs when the piston has an elliptical cross section, i.e., the piston diameter measured at the center of the quadrant a, as is usually the case with a piston under heavy load of a large diesel engine. It is further enhanced when it is larger than the diameter measured through the center of quadrant b.

Due to the tilting movement of the piston, a relatively large gap space is formed between the cylinder liner and the piston ring in two parts within the range of a quadrant a, and the gap space alternately closes the piston ring. There is a possibility that the combustion gas leaks through. This leads to a downward gas flow in quadrant a. However, by arranging the pressure release holes 7 in the central region of the quadrant a, the combustion gas that attempts to guide oil downward along the cylinder liner,
It is prevented from flowing out below the lowermost compression ring 3 and thus below the oil ring 6. This creates an area of low pressure here.

Due to the annular oil collecting groove 10, the oil that has accumulated near the oil ring 6 under pressure in the quadrant b fills the oil collecting groove 10 of the quadrant b, and Flow in the direction is further assured. Retarding the flow is in the quadrant a
This is promoted by the absence of backing gas pressure. The oil pressure in the quadrant b below the oil ring 6 is prevented from rising to a value that may cause the oil ring to float from the cylinder wall by providing the oil outlet hole 11 here. The diameter of this hole can be selected so that there is no possibility of generating an oil pressure for floating the oil ring 6 from the cylinder liner.

By leading the oil outlet hole 11 and the pressure release hole 7 to the common outlet hole 8 collectively, the oil is led to the lower side of the piston. This is because the exhaust gas flow is directed in the same direction as the desired oil discharge direction regardless of the piston movement. In this case, the small-diameter portion 9 of each pressure release hole 7 is provided with oil contained in the pressure release hole 7 during the expansion stroke of the piston by the combustion gas having a relatively high pressure.
To ensure that there is no danger of being returned to the outer surface of the piston.

In the case of the apparatus shown in FIG. 4, different from the above-described embodiment, one pressure release hole 12 is provided only at the center of each quadrant a. Each pressure release hole is an outlet hole 13
To join. Each of the outlet holes 13 has two oil outlet holes 1.
4 merge, and these oil outlet holes also branch off from the oil collecting groove 15 in the central region of the quadrant b.

In the above-described embodiment, the oil outlet hole and the pressure release hole are orthogonal to each other in the projection view, but the oil outlet hole 17 and the pressure release hole 16 are larger in angle in the projection view. FIG. 5 shows that they can also be arranged at an angle to each other. This is important, for example, when holes in the bolts connecting the upper and lower parts of the piston have to be avoided. In the case of this device, it is also expedient here that a common outlet hole 18 is provided for each one oil outlet hole 17 and pressure release hole 16.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of a trunk piston according to the present invention.

FIG. 2 is a sectional view of the piston shown in FIG. 1 taken along section line II-II.

FIG. 3 is a cross-sectional view of the piston shown in FIG. 1 taken along section line III-III.

FIG. 4 is a cross-sectional view of another embodiment of the piston.

FIG. 5 is a cross-sectional view of yet another embodiment of the piston.

[Explanation of symbols]

 Reference Signs List 5 groove 6 oil ring 7, 12, 16 pressure release hole 8, 13, 18 outlet hole 9 small diameter portion (sleeve) 10, 15 oil collecting groove 11, 14, 17 oil outlet hole a quadrant

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Sho 58-189338 (JP, U) Japanese Utility Model Sho 56-25040 (JP, U) German Patent Application Publication 3428007 (DE, A1) German Patent Application Publication 3005720 (DE, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02F 3/00 F01M 1/06 F16J 1/08

Claims (2)

(57) [Claims] 1. A plurality of compression rings (3), an oil ring (6) disposed immediately below these compression rings, and an oil collecting groove located below the oil ring and extending so as to surround the outer periphery of the piston. (10), and a pressure release hole (7,
12 and 16), oil outlet holes (11, 14, 17) are opened in the oil collecting groove (10), and both holes extend in the longitudinal direction of the piston and communicate with the free space below the piston. In the piston adapted to merge into the outlet holes (8, 13, 18), the cross section of the piston is divided into two quadrants (a) located in front of the longitudinal axis of the piston pin and front ends of both end faces of the piston pin. 4 with two quadrants (b) respectively located at
When considered as two quadrants, the oil outlet holes (11, 14, 17) are located at the ends of the piston pins.
Opening in the oil collecting groove (10) in the central region of the quadrant (b) located in front of the surface, the pressure release holes (7, 12, 16) being the length of the piston pin.
In the central area of the quadrant (a) located in front of the wrist , it opens into the groove (5) for accommodating the oil ring and has a small diameter in the pressure release holes (7, 12, 16). A trunk piston for an internal combustion engine, characterized by comprising a portion (9). 2. Trunk piston according to claim 1, characterized in that the oil collecting groove (10) extends in the axial direction of the piston to a groove (5) for accommodating an oil ring (6).