JP5851718B2 - Piston internal combustion engine driving method and piston internal combustion engine piston - Google Patents

Description

  The present invention relates to a method for driving a piston internal combustion engine and to a piston for this kind of piston internal combustion engine, in particular for a two-cycle large diesel engine, which is arranged in an assigned cylinder liner as a defining part of the working space. In this piston, the gap between the piston and the cylinder liner is covered by a piston ring package comprising a plurality of piston rings arranged side by side, each of these piston rings being one piston ring of each piston It is arranged in the groove and can be exposed to gas coming from the working space.

  In a practically used device of this type, all piston rings are provided with gas leaks. For this purpose, slitted piston rings are often used, the ends of the piston rings being spaced apart from one another, forming slits that penetrate from top to bottom and form a flow path for leaking gases. However, the cross-section of this slit increases with increasing width of the associated piston ring, ie with increasing wear.

  From European Patent No. 0742875, a piston of the type mentioned at the outset, at least the uppermost piston ring being configured as an airtight piston ring, this piston ring being designed to allow leakage control A piston provided with a groove on the outer peripheral side is known. It is also mentioned that a plurality or all of the piston rings of the piston ring package can be configured as airtight piston rings with an outer circumferential groove to allow control of leakage. Therefore, in any case, leakage is possible in each piston ring of the piston ring package, so that a strong leakage flow of the gas leaked from the working space is generated to some extent, and as a result, an output loss resulting therefrom is generated. Empirically, it should be taken into account that the life of a device of the above-mentioned type is very different if the piston ring of the piston ring package is different, which means a high maintenance cost.

  Japanese Patent No. 2048737 is a piston in which all piston rings are configured as airtight piston rings, which are assigned to these piston rings, and the piston ring grooves arranged above and below allow control of the leakage For this purpose, pistons are disclosed which are provided on the piston side and connected to each other by flow passages configured as perforations or the like. In other words, the leakage flow is stopped here by the lowermost piston ring. However, the lowermost piston ring is relatively heavily loaded at each work step and is therefore subject to wear more rapidly empirically than the piston ring above it.

  It is clear that both known devices require a relatively large number of piston rings in the piston ring package. However, the friction generated during operation and the resulting power loss increases with the number of piston rings. Thus, the known devices do not allow an optimum mode of operation in that respect.

European Patent No. 0742875 Japanese Patent No. 2048737

  Therefore, starting from the above, the object of the present invention is to achieve a balanced service life as much as possible in all piston rings by simple and inexpensive means, and to reduce output loss. It is to improve so that it is minimized.

  This problem is related to the above type of piston, according to the invention, only the piston ring farthest from the working space is configured as an airtight piston ring with no possibility of leaking, closer to the working space. Each of the other piston rings arranged in the is equipped with means to control the leakage of gas coming from the working space, and additional incoming leakage gas is added between at least two piston rings arranged side by side At least one expansion space is provided for inflating, so that the volume of the expansion space exceeds the volume of the ring space defined by two piston rings arranged side by side without any additional expansion space It is solved by.

  This measure ensures that the disadvantages of the known devices are avoided. Due to the expansion space provided according to the invention, the degree to which incoming leakage gases are possible in a known device that expands beyond the usual degree, i.e. in the ring space defined by two piston rings each. And thus advantageously act as a damping and retarding mechanism, whereby the pressure load acting on the airtight piston ring is attenuated and delayed during each working stroke of the piston . This advantageously allows the combustion pressure to be absorbed by the piston ring package to be optimally distributed to all piston rings and to a relatively long stroke area, which is balanced for all piston rings. It is advantageous to achieve a good service life and a good utilization of the available energy is obtained. The measure according to the invention provides an advantageous means of reducing the number of piston rings in the piston ring package compared to known devices, which not only leads to a reduction in friction loss, but also reduces the dynamic force. This provides a significant output gain over known devices. A further advantage of the measures of the present invention is that the piston of the present invention is also easily identifiable on the basis of its expansion space, and that the expansion space provided on the piston side is easily in the region of the scavenging port of the cylinder liner, for example. It can also be inspected, which facilitates maintenance.

  Advantageous and useful developments of this superordinate strategy are described in the dependent claims.

  Advantageously, at least one expansion space is placed in front of at least the airtight piston ring. This measure is particularly advantageous because it is particularly important to damp and retard the generated load at the lowest airtight piston ring, since no further leakage occurs in this ring.

  A further advantageous measure consists in providing at least one piston-side notch as an expansion space. In this case, a great structural freedom is advantageously obtained with respect to the dimensioning of the volume of the expansion space. In addition, it should be assumed that the volume of the expansion space configured as a notch on the piston side remains substantially constant during driving. Therefore, in this case, there is no need to worry about the width of the gap between the piston and the cylinder liner and the limitation during operation resulting from the deformation of the cylinder liner.

  Conveniently, a notch on the piston side that functions as an expansion space can be configured to surround the periphery in a groove shape. This not only simplifies manufacturing, but also advantageously provides an equivalent effect on the entire piston circumference.

  In a further development of this superordinate strategy, the absorption volume of each expansion space provided between the two piston rings can correspond at least to the volume of the piston ring groove, preferably slightly higher. Based on the above measures, it is advantageous to provide for use a piston ring package with fewer piston rings than piston ring grooves, so that the piston ring grooves are not simply arranged in the piston ring. In that case, of course, this groove is typically a piston ring groove and does not require an armor plate to be provided, and therefore may be slightly offset from the cross section. In addition to the above advantages, a very compact device is obtained here. Reducing the piston ring results in a reduction in friction and thus a reduction in power loss due to this, as already mentioned above. The above-described air gap advantageously provides a relatively large spacing between adjacent piston rings, which contributes to the expansion of the volume of the expansion space.

  Further forms and useful developments of the means of the superordinate concept are described in the other dependent claims and can be obtained in more detail from the description by the following examples based on the drawings.

It is a longitudinal cross-sectional view of the upper area | region of the cylinder piston assembly of a piston internal combustion engine. It is a perspective view of an airtight piston ring. It is an expanded view of an airtight piston ring provided with a leak groove on the outer peripheral side. FIG. 4 is a cross-sectional view of the piston ring of the basic type of FIG. 3 in an assembled state, in which the outer circumferential groove of the piston ring extends vertically to simplify the figure. Is shown.

  The main field of application of the present invention is piston internal combustion engines configured as large engines, in particular two-cycle large diesel engines used for marine drive. The basic structure and mode of operation of this type of device are known per se and will therefore not be described in further detail.

  The underlying cylinder-piston assembly in Figure 1 is part of a two-cycle large diesel engine. The illustrated cylinder piston assembly includes one cylinder 1 and a piston 2 accommodated therein. The cylinder 1 includes a cylinder liner 3 surrounding the cylinder 1 and a cylinder cover 4 accommodated thereon. A working space 5 is provided in the cylinder 1, and a lower boundary thereof is formed by a piston 2 that can move up and down and is guided in the cylinder liner 3. In the working space 5, during operation, a gas filling body substantially made of air is inserted through an inlet slit (not shown in detail) provided in the lower region of the cylinder liner 3, and the details are the same. In general, the fuel is charged through an injection device provided in the area of the cylinder cover 4 (not shown). In a large engine of the type shown here, the piston 2 is connected to a crosshead via a piston rod not shown in detail here, and this crosshead cooperates with the crankshaft of the engine via a connecting rod. .

  In order to allow normal operation of the engine, i.e. to prevent the combustion gas from leaking strongly from the working space 5 into the scavenging gas box provided below the piston, the cylinder liner is accommodated on the piston 2 Piston rings 6, 7 and 8 are provided in contact with 3 and arranged side by side in the direction of movement of the piston. These piston rings together form a so-called piston ring package 9, which in the illustrated example comprises three piston rings 6, 7, 8 arranged side by side in the direction of movement of the piston 2. More or fewer, at least two piston rings are conceivable. Each piston ring 6, 7, 8 is accommodated in an assigned piston ring groove 10, 11, 12 of the piston 2. The piston has, in the illustrated example, surrounding piston ring grooves 10, 11, 12 assigned to three piston rings 6, 7, 8.

  The piston ring of the piston ring package 9 covers the gap 13 between the outer peripheral surface of the piston 2 and the inner peripheral surface of the cylinder liner 3 in the peripheral region on the radially outer side, and correspondingly moves downward in the working space 5. Form a seal.

  The piston rings 6, 7, 8 must be spread in order to be attached to the piston 2 and in order to ensure a radial contact with the cylinder liner 3. For this purpose, the surrounding piston rings have movable end portions. In doing so, these ends can be configured to define slits that penetrate from top to bottom where leakage of gas coming from the working space 5 can occur. Another form of the structure without a closed slit surrounding it is shown in FIG. The piston ring that forms the basis of FIG. 2 has end regions that engage each other in the form of grooves and springs. Here, the end region on the left side of FIG. 2 is provided with a chamber-shaped notch 14 that opens radially outward and downward. In the other end region on the right in FIG. 2, a finger 15 protruding in the circumferential direction is provided, and this finger has a cross section that matches the cross section of the notch 14, and engages with this. Here, the mutual engagement length of the notch 14 and the finger 15 is dimensioned so that even when the piston ring expands as a result of wear, the mutual engagement is never lost.

  The piston ring package 9 of FIG. 1 is configured such that the piston ring 8 at the bottom, that is, furthest away from the working space 5, closes the gap 13 in an airtight manner. Therefore, this lowermost piston ring 8 is formed as an airtight piston ring corresponding to the basic policy of the structure shown in FIG. On the other hand, a means for controlling leakage of gas coming from the working space 5 is arranged in the two piston rings 6 and 7 disposed in front. This means may be a gap of the type described above, or may be a flow channel in the form of a bore or the like provided on the piston side connecting the piston ring grooves 10, 11, 12 to each other, or a notch on the piston side, etc. But you can. In any case, a flow path is formed, and through this flow path, the piston rings 7 and 8 placed on the first piston ring 6, that is, the piston ring 6 disposed closest to the working space 5, It can be exposed to gas coming from the working space 5. It is appropriate that the piston rings 6, 7, 8 are slightly lower than the piston ring grooves 10, 11, 12 belonging to the piston rings 6, 7, 8 so that the flow from the gap 13 to the radially inner region of the piston ring grooves 10, 11, 12 A path is formed and the piston rings 6, 7, 8 are correspondingly exposed to the gas coming from the working space 5 in the region of the radially inner circumferential surface for expansion.

  In the example shown, the upper two piston rings 6, 7 where gas leaks occur are also configured in the form of airtight piston rings, but at least one, preferably to allow control of the leaks. A plurality of outer peripheral grooves 16 are provided. In the illustrated example, as can be discerned from FIG. 3, the piston rings 6, 7 have a plurality of, here four, circumferential grooves 16 distributed over the entire circumference. These grooves are suitably arranged at an angle to the ring surface, which is advantageous for the rotational movement of the assigned piston ring. The depth t of the outer circumferential groove 16 is larger than the width b of the gap 13 as best seen in FIG. In this case, the passage cross section of the groove 16 that is effective during operation corresponds to a groove area that is not covered by the piston 2, that is, a groove area that protrudes from the outer peripheral surface of the piston 2, so that the area is parallel to the gap width b × A flow cross section is formed which is obtained from the width c of the groove 16 shown in FIG. Since the depth t of the groove is larger than the gap width b, the cross section does not change even when the piston ring 6 or 7 is worn. The depth t is suitably larger than the gap width b, taking into account the allocated allocated piston ring wear thickness allowed during the life of the piston ring as perceived by the naked eye. A passage cross section will exist for the entire lifetime. The outer circumferential groove 16 makes it possible to suppress the controlled leakage in the piston rings 6 and 7 to a narrow range at a low level.

  Leakage gas that flows through the flow path formed by the groove 16 reaches the respective ring space defined by the two piston rings, where it can be pressure relieved. However, since the width of the gap 13 is relatively small, this pressure relaxation is very small without additional measures. Therefore, in order to reduce the load on the lower piston ring 8 which is airtight, there is an expansion space 17 in the area above this piston ring 8, i.e. a free section or an enlarged part of the volume, without this enlarged part. An enlarged portion that is wider than the free section or volume is provided. The expansion space 17 provides an additional pressure relief means for leaking gases. I.e. in a ring space between two piston rings arranged regularly, i.e. in the form of piston rings 6, 7, or in the known device mentioned at the outset, in the form of a piston shown at 18 It provides greater pressure relief than is possible in the ring space defined by the ring.

  In the example of FIG. 1, the expansion space 17 is placed in front of the airtight piston ring 8, so that a direct motion coupling is obtained. Since the incoming gas can be relieved in the expansion space 17, the gas pressure acting on the lower piston ring 8 is reduced, as well as its load is delayed, correspondingly this load is connected to the pre-piston ring 7. For the first time at a time interval. This allows good utilization of the available energy over a relatively long range of the piston stroke. In addition, when the maximum load of the lower airtight piston ring 8 is generated, it should be assumed that an oil film has already been formed in the contact area with the cylinder liner 3.

  The volume of the expansion space 17, as already mentioned above, is not provided with a ring space 18 between the upper two piston rings 6, 7, or an expansion space for additional expansion of the incoming gas It is larger than the volume of the ring space 18 between the piston rings of the known device.

  In the exemplary embodiment shown in FIG. 1, the expansion space 17 is formed by a notch on the piston side. This may be, for example, radial drilling. However, as in the illustrated example, it is advantageous if a groove surrounding the periphery is provided to form the expansion space 17. This groove can have a similar shape to the piston ring groove, as indicated by the solid line in FIG. However, other cross sections may be considered, as indicated by the dashed lines in FIG.

  In order to prevent the support capacity of the region of the piston 2 that supports the piston ring 7 disposed above the expansion space 17 from being threatened by the expansion space 17, the expansion space 17 is arranged on the lower piston ring 8 Piston rings arranged in the first and second piston rings 6, 7 are spaced apart from the piston ring groove 12 arranged in front and the adjacent piston ring groove 11 arranged in the second piston ring 7. It is larger than the normal groove interval between the grooves 10 and 11. This enlarges the ring space defined by the piston rigs 7, 8, thereby leading to an enlargement of the free section and consequently an expansion space 17. In many cases, in some situations, this type of enlarged ring space is already sufficient to form an expansion space for additional expansion, thus omitting an additional piston-side notch be able to. Typically, however, the desired additional expansion cannot be achieved as desired without a notch on the piston side.

  The required volume of the expansion space 17 is adapted to the expected leakage in the region of the piston ring in the front, here the piston ring 7. When the leak is weak, the volume of the expansion space 17 may be 1 to 2 times the volume of the normal piston ring groove. When the leakage is strong, for example, a volume that is two to three times larger than the volume of the piston ring groove is conceivable. The illustrated example is based on a case where leakage is weak. Therefore, the expansion space 17 can be formed in the shape of a piston ring groove. Here, it may be true for the combination of piston and piston ring package that there should be one more piston ring groove for a given number of piston rings. That is, in the illustrated example of the piston package 9 having only three piston rings (an airtight piston ring 8 and two piston rings 6, 7 for controlling leakage), the piston 2 having four piston ring grooves is Used, where one piston ring groove, ie the third from the top, remains empty and no piston ring is provided. Therefore, this piston ring groove does not require a conventional armor plate or the like. Of course, other numbers of piston rings are also conceivable. In a simple case, the piston ring package 9 is arranged between two piston rings, namely a lower piston ring that hermetically closes the gap 13 and an upper piston ring that allows leakage control. An expansion space 17 can be provided.

  The additional expansion of the incoming gas, as already indicated, possible in the expansion space 17 preceding the hermetic piston ring 8, significantly reduces the load on the lower hermetic piston ring 8. This has an advantageous effect on the service life of the piston ring 8. In this case, the piston rings 6 and 7 placed in front of the piston ring are allowed to control leakage, so that the load is reduced. These rings can be configured such that the life of all piston rings 6, 7, 8 of the piston ring package 9 is approximately the same. For this purpose, the control of the permissible leaks in the piston rings 6, 7 can be performed individually, for example by setting the number and / or width of the grooves 16 provided as flow paths for controlled leaks. Can be set. Thus, the total cross-sectional area of the grooves 16 in the upper piston rings 6, 7 may be different, for example, the first piston ring 6 being controlled more than the piston ring 7 placed in front of the airtight piston ring 8, for example. Decrease in steps to have a larger flow cross section for leakage. It would also be conceivable to provide means for additional expansion of the incoming gas in the region between the piston rings 6, 7 where leakage is controlled.

  The above configuration makes it recognized that the present invention is not limited to the illustrated exemplary embodiment.

Claims (16)

A piston for a piston internal combustion engine, in particular for a two-cycle large diesel engine, arranged in an assigned cylinder liner (3) as a defining part of the working space (5), said piston (2) And the cylinder liner (3) is covered by a piston ring package (9) comprising a plurality of piston rings (6, 7, 8) arranged side by side, and the piston ring ( 6, 7, 8) are arranged in each piston ring groove (10, 11, 12) of the piston ( 2) and can be exposed to gas coming from the working space,
Only the piston ring (8) farthest from the working space (5) is configured as an airtight piston ring without leakage means, and each other piston ring (closer to the working space (5)) ( 6 and 7) are provided with means for controlling the leakage of gas coming from the working space (5), and between the at least two piston rings arranged side by side in the piston ring package (9) Piston, characterized in that at least one expansion space (17) is provided for additionally expanding the leaking gas.   The accommodation volume of the expansion space (17) exceeds the volume of the ring space (18) defined by two piston rings (6, 7) arranged side by side without an additional expansion space. The piston according to 1.   3. Piston according to claim 1 or 2, characterized in that at least one expansion space (17) is placed in front of at least the airtight piston ring (8).   The piston according to any one of claims 1 to 3, wherein the expansion space (17) includes at least one notch portion on the piston side.   5. The piston according to claim 4, wherein the notch on the piston side belonging to the expansion space (17) is formed in a groove shape.   6. The piston according to claim 5, wherein the groove belonging to the expansion space (17) is configured in the form of a piston ring groove in which a piston ring is not disposed.   The accommodation volume of each expansion space (17) provided between two piston rings corresponds to the volume of at least one piston ring groove (10, 11, 12). The piston according to claim 1.   8. The piston according to claim 7, wherein an accommodation volume of the expansion space is in a range of 1 to 3 times a volume of one piston ring groove (10, 11, 12).   The piston ring package (9) forms at least one hermetic piston ring (8) and a side surface of the expansion space (17) together with the hermetic piston ring (8), and at least one other controlled leak. The piston according to any one of claims 1 to 8, characterized in that it has a piston ring (7).   Three piston ring grooves (10, 11, 12) suitable for accommodating one piston ring (6, 7, 8) each, used as expansion space (17), and second to last and last 10. The piston according to claim 1, further comprising another groove arranged between the piston ring grooves (11, 12).   The distance between the piston ring grooves (11, 12) forming the side surface of the expansion space (17) is larger than the distance between the other piston ring grooves (10, 11). The piston according to any one of the above.   12. Piston according to any one of the preceding claims, characterized in that the airtight piston ring (8) has ends that are in close contact with each other in the form of grooves and springs.   Similarly, each piston ring (6, 7) placed in front of the airtight piston ring (8) also has ends that are tightly engaged with each other in the form of grooves and springs to control leakage. The piston according to any one of claims 1 to 12, wherein a notch is additionally provided. Each piston ring (6, 7) placed in front of the airtight piston ring (8) is provided with a groove (16) on the outer peripheral side, and the depth (t) of the groove (16) The width of the clearance ( 13 ) between the piston (2) and the cylinder liner (3) is greater than the width (b), taking into account the wear of the piston ring thickness allowed for the piston.   The leakage cross-sectional area corresponding to the effective total flow cross-sectional area of the groove (16) on the outer peripheral side of the piston ring (6, 7) provided with the groove (16) is larger than the cross-sectional area between the ends of the piston ring with slits. 15. The piston according to claim 14, wherein the piston is small. A method for driving a piston internal combustion engine, particularly a two-cycle large diesel engine, wherein a working space (5) is defined by a piston (2) disposed in a cylinder liner (3), and the piston (2) A gap (13) between the cylinder liner (3) and a plurality of piston rings (6, 11, 2) arranged side by side and arranged in one piston ring groove (10, 11, 12) of the piston ( 2) . In a method that is covered by a piston ring package (9) with 7, 8) and can be exposed to gas coming from the working space (5),
A gap (13) between the piston (2) and the cylinder liner (3) is hermetically closed downward by a piston ring (8) farthest from the working space (5), and the working space In each piston ring (6, 7) placed in front of the piston ring (8) farthest from (5), leakage control is allowed, and the pressure of the leaked gas is farthest from the working space (5). Before reaching the piston ring (8), the method is characterized in that it is reduced by expansion in at least one expansion space (17) provided for it.

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