JP5371582B2 - Oil scraping ring for piston rod, manufacturing method thereof, and stuffing box provided with the oil scraping ring - Google Patents

Description

  The present invention relates to an oil scraping ring for a piston rod, and more particularly, an oil scraping ring for a piston rod used particularly in a large-sized two-cycle diesel engine for ships, a manufacturing method thereof, and a star equipped with the oil scraping ring. Regarding the fing box.

  In general, large two-cycle diesel engines for ships are provided with a partition plate between the scavenging chamber and the crank chamber of the engine, and the piston rod accommodates an airtight ring or an oil scraping ring provided immediately above the partition plate. Reciprocates through the stuffing box. For example, in a general stuffing box as shown in FIG. 3 disclosed in Patent Document 1, the airtight ring 100 is arranged on the scavenging chamber side of the stuffing box to maintain the airtightness of the scavenging chamber, and the oil scraping ring. 110 is disposed on the crank chamber side of the stuffing box and has a function of preventing the lubricant oil from flowing out from the crank chamber to the scavenging chamber side as the piston rod 300 reciprocates.

  The conventional oil scraping ring shown in FIG. 3 is composed of a combination of three divided ring bodies having two rail parts, and a coil spring 200 is arranged on the outer periphery and mounted on the ring groove in an overlapping manner. Is done. The inner surface of the piston rod is pressed and urged against the outer surface of the piston rod by the contraction force of the coil spring, and when the piston rod reciprocates, the lubricant that adheres to the piston rod surface and moves to the scavenging chamber is scraped off. Prevent excessive consumption of lubricants. In order to facilitate the removal and discharge of the lubricant oil that has been scraped off, an oil through hole 210 that penetrates the inner peripheral side and the outer peripheral side is generally provided between the two rail portions.

  Various improvements have been proposed for oil scraping rings used in stuffing boxes. For example, Patent Document 2 has an oil scraping ring made of synthetic resin, Patent Document 3 has an undivided steel ring, and Patent Document 4 has a conventional oil scraping ring divided into two in the axial direction. Then, it is proposed to insert a diamond-shaped spacing piece into the circumferentially divided part, Patent Document 5 proposes to apply a wear-resistant coating to the sliding part, and Patent Document 6 proposes a compact, lightweight and flexible structure. Has been.

  However, the conventional oil scraping ring in practical use generally has the following problems.

  The oil scraping ring is generally made of a metal such as cast iron or copper alloy or a resin material. However, when a resin material such as ethylene tetrafluoride resin is used as the material of the oil scraping ring, the rigidity is low and the piston rod outer periphery is made. The contact with the surface is good, so in the initial stage, good initial friction and good oil scraping performance can be expected, but during use, the lubricant is absorbed and softened, increasing wear, and conversely, There is a problem that the frequency of such component replacement becomes high. On the other hand, in the case of a metal oil scraping ring, the ring body is manufactured in the form of a split-type high-rigidity block. When the curvature of the inner periphery and the curvature of the piston rod outer periphery are different, there is a problem that sufficient oil scraping performance cannot be obtained. In order to solve the problem, various attempts have been made to develop a ring body with good followability as described in Patent Documents 3, 4 and 6, but the difference in curvature between the ring body inner periphery and the piston rod outer periphery is still different. It was necessary to manufacture as small as possible. Therefore, in order to match the curvature of the two, heat treatment for removing strain is performed in the manufacturing process, correction processing is further performed to remove distortion caused by internal stress after processing, or in-situ scraping is performed when the oil scraping ring is assembled. The current situation is that it is necessary to make the process complicated, and the cost increases due to an increase in man-hours.

JP 60-18664 A Japanese Patent No. 3083558 Japanese Patent Laid-Open No. 9-159028 Japanese Patent Laid-Open No. 10-148262 JP 2000-291807 A JP 2008-261364 A

  The present invention provides an oil scraping ring having a structure in which the concept of “improving the followability of the oil scraping ring to the piston rod as a small and lightweight flexible structure” attempted in Patent Document 6 is further improved. It is an object of the present invention to provide a method for manufacturing an oil scraping ring that suppresses the introduction of distortion or internal stress as much as possible in the manufacturing process as means for providing an accurate oil scraping ring. It is another object of the present invention to provide a stuffing box including an oil scraping ring having a structure that facilitates component replacement. In other words, ultimately, the oil scraping ring for piston rods that achieves reduction in oil consumption and long life, excellent maintainability, a manufacturing method thereof, and a stuffing box equipped with the oil scraping ring are provided. The task is to do.

The follow-up ability F of the oil scraping ring body to the piston rod is approximated by the following equation (1) by applying the equation of bending of the beam.
F = (3 ・ P ・ D ² ) / (E ・ h ₁・ a ₁ ³ ) ……………………………… (1)
P is the load of the coil spring, D is the nominal diameter of the ring body, E is the Young's modulus of the ring body, h ₁ is the axial width of the cross section of the ring body, and a ₁ is the radial thickness including the rail portion.
Here, h ₁ · a ₁ ³ is the amount of the moment of inertia when the cross section of the ring body is rectangular. Oil scraping rings usually have oil through holes, so strictly speaking, the moment of inertia of the cross section should be calculated in consideration of these oil through holes. Shall be.

According to the equation (1), variable according to the ring body of the design is h ₁ · a ₁ ³ according to the second moment. That is, the followability can be improved by reducing both the axial width and the radial thickness of the cross section.

In Patent Document 6, as a conventional oil scraping ring, for example, when the piston rod diameter is about 235 mm, the axial width h ₁ of the cross section is 20 mm and the radial thickness a ₁ is about 21.5 mm. The followability of the ring body was improved by reducing the size of the ring body to 14 mm with an axial width h ₁ of the cross section and 19 mm including a radial thickness a ₁ including a separate rail portion. 4A shows a conventional ring 410 of Patent Document 6 and FIG. 4B shows an improved ring 510.

As a result of diligent research in accordance with the basic concept described above, the inventors of the present invention divided the ring body, which conventionally has two rail portions, into two in the axial direction in terms of the axial width and radial thickness of the cross section. By using one rail, the axial width h ₁ of the ring body is reduced to 1/2 or less, and the radial thickness including the rail portion is 17 mm or more and 23 as in the case of Patent Document 6. Even if it is less than or equal to mm, the inventors have conceived to improve the follow-up F by reducing the thickness in the radial direction excluding the rail as much as possible. In addition, it was discovered that the number of divisions in the circumferential direction was reduced from the conventional 3 divisions to 2 divisions, which solved the difficulty of mounting the stuffing box in the case of a single rail, and made it possible to replace parts.

That is, the piston rod oil scraping ring of the present invention includes a ring body having a rail portion that is in sliding contact with the outer peripheral surface of the piston rod that reciprocates, and an annular shape that presses and biases the rail portion against the outer peripheral surface of the piston rod. In the oil scraping ring for a piston rod, the axial width of the cross section of the ring body is 5 mm or more and 10 mm or less, and the radial thickness excluding the rail portion is 10 mm or more and 20 mm or less. The ring body is divided into at least two in the circumferential direction, one rail portion at the inner circumferential axial center, the coil spring housing groove at the outer circumferential axial center, and one side of the upper and lower side surfaces Only a plurality of oil passage grooves are provided , and the oil passage groove is formed of a part of a bottom surface and a side surface of a cylinder parallel to the axial direction of the ring body . Here, the rail portion may be formed integrally with the ring body or attached to a groove on the inner peripheral side of the ring body. Moreover, it is preferable that the opening ratio with respect to the inner peripheral side and the outer peripheral side perimeter is 10 to 60%.

Moreover, the manufacturing method of the oil scraping ring for piston rods of this invention is characterized by forming an oil passage groove | channel by an end mill process . In the end mill processing of the oil passage groove, it is preferable that the processing axis and the processing direction are processed in parallel with the axis of the oil scraping ring. As a result, it is possible to provide a highly accurate oil scraping ring by suppressing the introduction of radial strain or internal stress that causes radial strain as much as possible.

  The oil scraping ring for piston rod of the present invention has a ring body width dimension of 1/2 or less by splitting the ring body, which has conventionally had two rail parts, into two parts in the axial direction. In addition, since the thickness in the radial direction excluding the rail portion is made as small as possible, the moment of inertia of the cross section is reduced and the followability is improved. Therefore, even with a small coil spring load, good oil scraping performance is exhibited from the beginning, contributing to a reduction in oil consumption and a longer life. Further, as one ring body, since the cross-sectional area is made smaller than that of the conventional ring body of Patent Document 6, the effect of reducing the inertial weight (mass) obtained in Patent Document 6 is also naturally obtained. It is further improved. That is, it contributes to the reduction of oil consumption and the extension of the life by improving the oil scraping performance by the ability to follow the lateral vibration of the piston rod and the reduction of struck wear due to the axial movement in the ring groove. In the case of a single rail, when the mounting to the piston rod of the stuffing box was divided into two in the circumferential direction, which was extremely difficult due to the coil spring load on the outer periphery of the ring falling in the circumferentially divided three ring Is preferable because it is easy. Furthermore, since the shape is simple compared to the shape of the conventional ring body shown in FIG. 3 and FIG. 4 and complicated processing is not required, the ring body can be easily manufactured. Eventually, the stuffing box itself can be reduced in size by reducing the axial width and radial thickness of the oil scraper ring. In the future, the size of a large two-cycle diesel engine for ships will be reduced. Have the potential to contribute.

  In the manufacturing method of the piston rod oil scraping ring of the present invention, the oil passage groove is processed by end milling so that the processing axis and the processing direction are parallel to the axis of the oil scraping ring. Compared to the case where the ring is processed or milled, no direct force in the radial direction of the ring is applied, so that the radial distortion, that is, the change in the curvature of the inner sliding surface of the ring body can be minimized. .

It is sectional drawing which shows typically the stuffing box equipped with the oil scraping ring for piston rods of this invention, The Fig.1 (a) is the oil of this invention according to the ring groove in which the conventional oil scraping ring was accommodated. Sectional view in which scraping rings are housed in three stages in each ring groove, and FIG. 1 (b) is an oil scraping ring according to the present invention in accordance with a ring groove in which a conventionally improved oil scraping ring that has been reduced in size and weight is accommodated. FIG. 6 is a cross-sectional view in which each ring groove is accommodated in two stages. It is a figure which shows the oil scraping ring for piston rods of this invention, The FIG. 2 (a) is the top view which looked at the oil scraping ring from the axial direction, The same FIG. 2 (b) is AA sectional drawing of the ring. is there. It is sectional drawing which shows typically the stuffing box equipped with the conventional oil scraping ring for piston rods. FIG. 4B is a cross-sectional view schematically showing a conventional stuffing box equipped with an oil scraping ring for a piston rod. FIG. 4B is an improved oil scraping ring that is smaller and lighter than FIG. 4A. It is sectional drawing accommodated.

FIG. 1 schematically shows a cross section of a stuffing box equipped with an oil scraping ring for a piston rod showing an embodiment of the present invention. (A) corresponds to a stuffing box 10 containing a conventional oil scraping ring, and the oil scraping ring 11 of the present invention is accommodated in three stages in each ring groove, and (b) is disclosed in Patent Document 6. The oil scraping ring 21 of the present invention is accommodated in two stages in each ring groove in accordance with the stuffing box 20 that accommodates a small and lightweight oil scraping ring. The oil scraping rings 11 and 21 have one rail portion 12 and 22 in sliding contact with the outer peripheral surface of the piston rod that reciprocates in the central portion in the axial direction on the inner peripheral side, and the rail portion on the outer peripheral surface of the piston rod. The annular coil springs 13 and 23 that press and urge the coil springs are provided in a coil spring housing groove formed in the central portion in the axial direction on the outer peripheral side. Oil passage grooves 14 and 24 are formed on one side (upper side surface in FIG. 1) of the upper and lower side surfaces of the oil scraping rings 11 and 21. The oil scraping rings 11 and 21 according to the present invention basically split the conventional two-rail oil scraping ring into two in the axial direction, thereby reducing the axial width h ₁ of the ring main body by using one rail. In addition, the radial thickness a ₁ is also reduced to such an extent that the ring body can maintain stable mounting in the ring groove of the stuffing box, thereby improving the follow-up performance. In FIG. 1 (b), the space 25 below the stuffing box 20 suggests that the stuffing box can be downsized in the axial direction, and the space 26 behind the oil scraping ring is the upper airtightness. This suggests that the entire stuffing box can be downsized if the ring size is taken into consideration. Conversely, it is possible to add a ring groove to the vacant space 25 in anticipation of a further oil consumption reduction effect.

  FIG. 2 (a) is a plan view of the oil scraping ring of the present invention as viewed from the axial direction, and FIG. 2 (b) shows an AA cross section. In FIG. 2, 11 oil passage grooves 14 or 24 are formed on one side of the upper and lower side surfaces of one ring body divided into two in the circumferential direction, and the groove depth is set so as not to be hung on the rail portion. The oil through groove is formed by end milling so that the machining axis and the machining direction are parallel to the axis of the oil scraping ring, and thus includes the bottom surface 31 and a part 32 of the side surface of the cylinder parallel to the ring axis direction. By this processing method, the introduction of strain due to processing in the ring radial direction is suppressed as much as possible. Moreover, the opening ratio with respect to the circumference of the ring inner peripheral side and the ring outer peripheral side of the oil passage groove is 10 to 60%. If the opening ratio is less than 10%, the oil will not be returned to the crank chamber sufficiently and the oil consumption will increase. Conversely, if the opening ratio exceeds 60%, the flat part on the side will decrease and the ring groove will decrease. Alternatively, it is not preferable because the contact with the side surfaces of the overlapping oil scraping rings becomes uneven and the side surface wear is promoted. The opening ratio is preferably 20 to 50%.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 and Comparative Example 1
For a 7-cylinder large two-cycle low-speed diesel engine with a bore diameter of 800 mm and a stroke of 2800 mm, the inner diameter is 310 mmφ, the outer diameter is 345 mmφ, the width is 6 mm, the thickness excluding the rail is 13 mm, the rail width is 1.5 mm, A cast iron oil scraping ring main body (Example 1) having a rail portion thickness of about 4.5 mm divided into two in the circumferential direction was produced. On one side of the ring body, 12 oil through grooves with a depth of 22 mm were dug with an end mill with a diameter of 22φ, and 24 whole rings were dug. As shown in Fig. 1 (a), this oil scraping ring was mounted in three stages on the stuffing box for two cylinders of the engine, and a 72-hour engine test was conducted to evaluate the initial conformability. For the remaining cylinders, the conventional oil scraping ring (Comparative Example 1) shown in FIG. 4A was used. The oil consumption was 0.23 and 0.19 in the cylinder using the oil scraping ring of the present invention, assuming that the average of the cylinder using the conventional oil scraping ring is 1. It can be seen that the oil consumption is reduced to 1/4 or less in the oil scraping ring of the present invention.

Example 2 and Comparative Example 2
For a 6-cylinder large two-cycle low-speed diesel engine with a bore diameter of 700 mm and a stroke of 2600 mm, the inner diameter is 270 mmφ, the outer diameter is 305 mmφ, the width is 6 mm, the thickness excluding the rail is 13 mm, the rail width is 1.5 mm, A cast iron oil scraping ring main body (Example 2) having a rail portion thickness of about 4.5 mm divided into two in the circumferential direction was produced. On one side of the ring body, 11 oil-groove grooves with a depth of 1.5 mm were dug with 22 mm diameter end mills, and 22 whole rings were dug. This oil scraping ring was mounted in two stages on a stuffing box for two cylinders of the engine as shown in FIG. 1 (b), and a 72-hour engine test was conducted. For the remaining cylinders, a conventional improved oil scraping ring (Comparative Example 2) disclosed in Patent Document 6 in FIG. 4B was used. The oil consumption was 0.64 and 0.57 for the cylinder using the oil scraping ring of the present invention, assuming that the average of the cylinders using the conventional oil scraping ring is 1. In the oil scraping ring of the present invention, it can be seen that the oil consumption is reduced by 30 to 40% compared to the conventional improved type.

Examples 3 to 8
Except for the number of oil passage grooves formed on one of the side surfaces of the ring body, the same cast iron oil scraping ring body (Examples 3 to 8) as in Example 2 was produced, and the same engine test as in Example 2 was performed. The results are shown in Table 1. Table 3 also shows the number of oil passage grooves, the inner peripheral side opening ratio, and the outer peripheral side opening ratio. When the opening ratio exceeded 20%, the reduction rate of oil consumption exceeded 30% with respect to the oil consumption of Comparative Example 2, and when the opening ratio exceeded 60%, side wear increased.

10, 20 Staffing box
11, 21 Oil scraping ring
12, 22 Rail section
13, 23 Coil spring
14, 24 Oil through groove
31 Bottom of cylinder parallel to ring axis direction
32 Cylindrical side parallel to the ring axis

Claims (5)

A ring body having a rail portion slidably contacting the outer peripheral surface of the piston rod that reciprocates; and an annular coil spring that presses and urges the rail portion against the outer peripheral surface of the piston rod. In oil scraping rings for piston rods with an axial width of 5 mm to 10 mm and a radial thickness excluding the rail of 10 mm to 20 mm, the ring body is divided into at least two in the circumferential direction. is equipped with one of the rail section on the inner circumferential side axial central portion, and a receiving groove of the coil spring on the outer peripheral side axial central portion, a plurality of oil through the grooves on only one side of the upper and lower sides, through the oil An oil scraping ring for a piston rod , wherein the groove is formed of a bottom surface and a part of a side surface of a cylinder parallel to the axial direction of the ring main body . 2. The oil scraping ring for piston rod according to claim 1 , wherein an opening ratio of the inner peripheral side and the outer peripheral side of the oil passage groove is 10 to 60%. The ring body is divided into at least two parts in the circumferential direction, with one rail part at the central part in the axial direction on the inner peripheral side, a receiving groove for the coil spring at the central part in the axial direction on the outer peripheral side, and only on one side of the upper and lower sides A method of manufacturing an oil scraping ring for a piston rod having a plurality of oil passage grooves, wherein the oil passage groove is formed by end milling. 4. The method of manufacturing an oil scraping ring for a piston rod according to claim 3 , wherein in the end mill processing of the oil passage groove, the end mill processing shaft and the processing direction are processed in parallel with the axis of the oil scraping ring. A stuffing box, wherein a plurality of piston rod oil scraping rings according to claim 1 or 2 are stacked in a single ring groove.

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