JP5513945B2 - Cylinder - Google Patents

Description

  The present invention relates to a cylinder in which a piston slides on an inner wall surface thereof, and more particularly to a cylinder capable of reducing reciprocating friction with a piston and maintaining the reduction effect over a long period of time.

Environmental issues such as global warming have been greatly highlighted on a global scale, and the development of fuel efficiency improvement technology for internal combustion engines to reduce CO _{2 in} the atmosphere has become a major issue. Reduction of the friction loss of the sliding member is required. In view of this, in recent years, the development of sliding member materials, surface treatment, and modification technologies that are excellent in wear resistance and seizure resistance and that can maximize the effect of reducing frictional force have been developed. It is being advanced.

  In order to improve the energy efficiency of a device using a cylinder, such as an improvement in fuel consumption of an internal combustion engine, reduction of friction loss is effective. In particular, friction reduction is effective between the piston ring that reciprocates and the inner wall surface of the cylinder. In order to reduce the reciprocating friction, it is said that reducing the surface roughness of the inner wall surface of the cylinder is an effective means. However, if the surface roughness is too small, the lubricating oil retained on the inner wall surface will be reduced. Since it almost disappeared, there was a problem that seizure resistance was lowered. In order to improve seizure resistance, in Patent Document 1, the cylinder liner is formed such that the surface roughness of the inner wall surface thereof becomes rougher from the top dead center side to the bottom dead center side of the piston. However, in Patent Document 1, since the surface roughness is large in the vicinity of the bottom dead center and the center of the stroke, there arises a disadvantage that the reciprocating friction increases.

  Patent Document 2 discloses a technique for reducing the reciprocating friction between the piston ring and the cylinder liner by forming a recess in the inner wall surface of the cylinder liner. In Patent Document 2, the cylinder liner is divided into a plurality of regions in the axial direction of the cylinder depending on the difference in sliding speed, and the shape of the indentation is different for each region, thereby enhancing the effect of reducing the reciprocating friction. . However, in Patent Document 2, the inner peripheral surface of the dent is not treated at all, and soot impurities generated during the combustion stroke and impurities of lubricating oil containing unburned fuel tend to adhere to the inner peripheral surface of the dent. In addition, when no treatment is performed on the inner peripheral surface of the recess, the fluidity of the lubricating oil in the recess is reduced, and soot generated by acid deterioration of the lubricating oil adheres to the inner peripheral surface of the recess. It becomes easy. Thus, when impurities and soot adhere to and accumulate on the inner peripheral surface of the dent, the volume in the dent decreases, resulting in a clogging state and an increase in reciprocating friction. There is a case.

JP-A-8-200135 JP 2007-46660 A

  The present invention has been made in view of the above problems, and has as its main object to provide a cylinder capable of reducing the reciprocating friction between the piston ring and the inner wall surface of the cylinder and maintaining the effect over a long period of time. To do.

The present invention for solving the above-mentioned problems is a cylinder in which a piston slides on an inner wall surface, and the lower surface position of the ring groove of the lowest piston ring at the top dead center of the piston among the inner wall surfaces of the cylinder A plurality of recesses having one or a plurality of surfaces are formed in the center region of the stroke which is a region between the bottom dead center of the piston and the upper surface position of the ring groove of the uppermost piston ring. the Ri one or at least a portion of the maximum height Ry of der least 30μm or less 0.1μm plurality of faces, the stroke center region, when the area of the stroke center region is 100%, The total area of all recesses is in the range of 1% to 80%, and the recesses are not formed in regions other than the stroke center region of the inner wall surface of the cylinder .

  The cylinder may include a cylinder body and a cylinder liner fixed to the inside of the cylinder body, and a plurality of the recesses may be formed on an inner wall surface of the cylinder liner.

  Further, the plurality of surfaces may be two side surfaces and one bottom surface.

  The maximum height Ry of the bottom surface may be not less than 0.1 μm and not more than 30 μm.

  Furthermore, the cylinder may be used for an internal combustion engine.

  According to the present invention, since the plurality of recesses are formed on the inner wall surface of the cylinder, the reciprocating friction between the piston ring and the cylinder inner wall surface can be reduced. In addition, by setting the maximum height Ry of at least a part of one or more surfaces forming the recess within a predetermined range, clogging in the recess due to accumulation of impurities and soot can be prevented. The effect of reducing the reciprocating friction between the piston ring and the cylinder inner wall surface can be maintained. The maximum height Ry is defined in JIS B0601-1994.

  In the cylinder of the present invention, the total area of all the recesses is in the range of 1% to 80% when the stroke center area is 100% of the area of the stroke center area. The same effect can be obtained even when the concave portion is not formed in a region other than the central region of the stroke.

  In addition, the cylinder of the present invention can obtain the same effect regardless of whether it is a type in which the inner wall surface of the cylinder and the piston slide or a type in which the cylinder liner fixed to the inside of the cylinder and the piston slide. Can do.

  Further, the same effect can be obtained even if the recess formed on the inner wall surface of the cylinder of the present invention is a recess formed from two side surfaces and one bottom surface.

Further, in the cylinder of the present invention, the effect of reducing the reciprocating friction between the piston ring and the cylinder inner wall surface can be maintained higher by setting the maximum height of the bottom surface within a predetermined range. By using this cylinder liner in an internal combustion engine, which is a field in which improvement in energy efficiency is particularly required, a high effect can be obtained.

It is a schematic sectional drawing which shows an example of the recessed part formed in the cylinder of this invention. It is a general | schematic expanded view which shows the example of the front shape of the recessed part formed in the cylinder of this invention. It is a schematic cross section which shows the example of the lubricating oil which remains on the internal peripheral surface of the recessed part formed in the cylinder of this invention. It is a schematic sectional drawing which shows the example of the impurity adhering to the internal peripheral surface of the recessed part formed in the cylinder of this invention. It is a schematic sectional drawing which shows an example of the adjustment method of the internal peripheral surface of a recessed part formed in the cylinder of this invention. It is explanatory drawing which shows an example of the formation position of the recessed part of the inner wall face of the cylinder liner which comprises the cylinder of this invention. It is explanatory drawing which shows an example of the range of a stroke center part area | region in the cylinder of this invention. It is a general | schematic expanded view which shows an example of arrangement | positioning of a recessed part in the cylinder of this invention. It is the general | schematic expanded view and schematic sectional drawing explaining the dimension position of the recessed part formed in the cylinder of this invention. It is a general | schematic expanded view which shows another example of arrangement | positioning of a recessed part in the cylinder of this invention. It is the schematic sectional drawing and schematic expansion | deployment figure explaining the area ratio in the cylinder of this invention. It is explanatory drawing which shows the measuring method of the maximum height Ry of a recessed part internal peripheral surface in the cylinder of this invention. It is the schematic which shows the dimension of the cylinder liner used in the Example of this invention. In the Example of this invention, it is a schematic sectional drawing which shows the state at the time of formation of a recessed part. It is a graph which shows the measurement result of the soot deposition rate in the Example of this invention. It is a schematic sectional drawing which shows the structure of the apparatus used in order to measure the reciprocating friction in the Example of this invention. It is a graph which shows the measurement result in the Example of this invention. It is a graph which shows the measurement result in the Example of this invention.

  The cylinder of the present invention is a cylinder in which a piston slides on an inner wall surface, and from the lower surface position of the ring groove of the lowest piston ring at the top dead center of the piston among the inner wall surfaces of the cylinder, A plurality of recesses formed of one or a plurality of surfaces are formed in the center region of the stroke, which is a region between the top dead center and the top surface of the ring groove of the uppermost piston ring. The maximum height Ry of at least a part of the surface to be processed is not less than 0.1 μm and not more than 30 μm.

  The cylinder of the present invention is not particularly limited as long as it has this requirement. Specifically, the cylinder of the present invention reduces the reciprocating friction with the piston ring by maintaining the maximum height Ry of the inner peripheral surface of the recess in the above range, and maintains the effect of reducing the reciprocating friction. Therefore, if it is used in combination with a piston and the piston slides on the inner wall surface of the cylinder, the same effect can be obtained regardless of the use, type, material, etc. of the cylinder. Therefore, the cylinder of the present invention can be used as a cylinder other than a heat engine, such as a compressor, in addition to an internal combustion engine such as an automobile or airplane engine or an external combustion engine such as a Stirling engine.

  The cylinder is composed of a cylinder body and a cylinder liner fixed to the inside of the cylinder. A piston slides on the inner wall surface of the cylinder liner. Although there is a “linerless type” that slides directly on the wall surface, the present invention can be applied regardless of the presence or absence of a cylinder liner.

  Hereinafter, each aspect (cylinder liner type and linerless type) of the present invention will be described.

A. First aspect (cylinder liner type)
The cylinder according to the first aspect of the present invention includes a cylinder body and a cylinder liner fixed to the inside of the cylinder body, and the plurality of recesses are formed on the inner wall surface of the cylinder liner. In this aspect, the inner wall surface of the cylinder body and the outer wall surface of the cylinder liner are fixed, and the piston slides on the inner wall surface of the cylinder liner. Therefore, the cylinder to which the cylinder liner is fixed The inner wall surface of the main body need not be provided with a recess.

  Hereinafter, the cylinder of this aspect will be described with reference to the drawings.

  First, the recessed part formed in the inner wall face of the cylinder liner which comprises the cylinder of this aspect is demonstrated. FIG. 1 is a schematic cross-sectional view showing an example of a recess formed in the cylinder of the present invention.

  In order to improve the energy efficiency of the device in which the cylinder is used, for example, to improve the fuel efficiency of the engine, it is effective to reduce the friction loss between the piston ring and the inner wall surface of the cylinder (in this embodiment, the inner wall surface of the cylinder liner). It is. Therefore, in the cylinder liner constituting the cylinder of this aspect, as shown in FIG. 1, a plurality of recesses 3 formed of one or a plurality of surfaces are formed on the inner wall surface. By forming the plurality of recesses 3 in the inner wall surface 2 of the cylinder liner, the contact area between the piston ring and the inner wall surface 2 of the cylinder liner can be reduced, and the frictional force can be reduced.

  The recess 3 formed in the cylinder liner inner wall surface 2 in this embodiment has a plurality of surfaces (in the case shown in FIG. 1A, two side surfaces 3a and 1) as illustrated in FIG. One bottom surface 3b), and as illustrated in FIG. 1B, a surface that can be formed by one surface (in the case shown in FIG. 1B, curved surface 3c) and that forms the recess 3. There is no particular limitation on the. Hereinafter, a surface forming a recess (for example, in the case shown in FIG. 1, two side surfaces 3 a and one bottom surface 3 b or curved surface 3 c) is referred to as a recess inner peripheral surface.

  Moreover, in this aspect, the front shape (surface developed in the cylinder circumferential direction) of the recess formed on the inner wall surface of the cylinder liner is not particularly limited, and can be appropriately adjusted according to the arrangement of the recess. . For example, as illustrated in FIGS. 2A to 2J, it is possible to form a concave portion formed of a straight line and / or a curved line. The recesses may be horizontally long as shown in FIGS. 2A to 2C, vertically long as shown in FIGS. 2D to 2G, or vertically as shown in FIGS. 2H to 2J. A shape with a substantially equal ratio of width to width may be used.

  Further, when the recess 3 is formed on the inner wall surface of the cylinder liner, part of the lubricating oil held by the inner wall surface of the cylinder liner flows into the recess when the piston slides. As shown in FIGS. 3 and 4, the inner peripheral surface of the recess has fine uneven portions, and when the maximum height Ry of the inner peripheral surface of the recess is larger than 30 μm, that is, when the inner peripheral surface of the recess is rough. The fluidity of the lubricating oil on the inner peripheral surface (fine uneven portion) of the concave portion is reduced, and the lubricating oil flowing into the concave portion 3 is not released from the concave portion as shown in FIG. Many remain on the surface. Residual lubricating oil 12 is oxidized and deteriorated to generate soot. The generated soot adheres to the inner peripheral surface of the recess, and then gradually accumulates in the recess starting from the soot adhering to the inner peripheral surface of the recess. I will do it. In the case where the recess 3 is clogged due to accumulation of soot, the contact area between the piston ring and the cylinder liner increases, and the effect of reducing the reciprocating friction exerted by forming the recess 3 is maintained. I can't do that.

  In addition, the lubricating oil contains impurities 11 such as soot and unburned fuel generated during the combustion stroke, and when the maximum height Ry of the inner peripheral surface of the recess is larger than 30 μm, FIG. As shown in FIG. 2, impurities 11 such as soot and unburned fuel are gradually deposited on the inner peripheral surface of the recess, and the effect of reducing the reciprocating friction cannot be maintained as described above. On the other hand, when the maximum height Ry is smaller than 0.1 μm, the processing cost increases and the quality becomes excessive.

  Therefore, in the cylinder liner of this aspect, the maximum height Ry of at least a part of the inner peripheral surface of the recess formed on the inner wall surface of the cylinder liner is defined in the range of 0.1 μm to 30 μm. By setting the maximum height of a part of the inner peripheral surface of the concave portion within the range, that is, by smoothing the inner peripheral surface of the concave portion, the fluidity of the lubricating oil in the vicinity of the inner peripheral surface of the concave portion can be improved. As shown in (a), the amount of lubricating oil 12 remaining on the inner peripheral surface of the recess can be reduced, and the amount of lubricating oil that is acid-deteriorated in the recess can be reduced. Further, by setting the maximum height Ry within the above range, the fluidity of the lubricating oil containing impurities on the inner peripheral surface of the recess is improved, and the impurity 11 is deposited in the recess as shown in FIG. Can be suppressed.

  The maximum height Ry is defined in JIS B0601-1994, and as shown in FIG. 12, the reference length L is extracted from the roughness curve in the direction of the average line, and the average of the extracted portions It is represented by the sum of the height Yp from the line to the highest peak and the depth Yv to the lowest valley bottom.

  Further, in this aspect, the portion having the maximum height Ry in the above range on the inner peripheral surface of the recess is not particularly limited, and the portion where the lubricating oil that has flowed in the inner peripheral surface of the recess tends to remain, impurities, etc. are likely to adhere. The maximum height Ry of the portion may be 0.1 μm or more and 30 μm or less, and it is not always necessary to smooth the entire inner surface of the recess. In addition, in a recess composed of a plurality of surfaces, for example, a recess composed of two side surfaces and one bottom surface illustrated in FIG. Therefore, the maximum height Ry of the bottom surface (the bottom surface and the surface in the vicinity of the bottom surface) is preferably in the above range. Moreover, in the concave part which consists of 1 curved surface illustrated in FIG.1 (b), it is preferable that the maximum height Ry near the lowest point (valley bottom) of a curved surface is the said range. The bottom surface refers to a surface that is located farthest from the cylinder inner wall surface 2 among the surfaces that form the inner peripheral surface of the recess.

(Method for forming recesses)
The method for forming the plurality of recesses 3 in the cylinder according to this aspect is not particularly limited, and any method can be adopted as long as the recesses 3 satisfying the above-described conditions can be formed.

  For example, after masking, a blasting method for forming recesses by spraying abrasive grains (adopted in the examples described later), a method for forming recesses by masking and then immersion in a corrosive solution, and letterpress printing , A corrosive processing method using a corrosive liquid instead of ink can be employed.

  Further, in the cylinder of this aspect, it is only necessary that the recess is finally formed, and it is not always necessary to form the recess in removing the cylinder surface in the manufacturing process, and conversely, the protrusion is formed on the cylinder surface. As a result, a portion where the convex portion is not formed as a result may be a concave portion.

  In this case, specifically, after predetermined masking, a method of forming a PVD film as a convex portion by various PVD methods can be used. In addition to PVD films, plating films such as chromium, copper, tin, zinc, nickel, nickel-phosphorous, etc., other films such as iron trioxide, manganese phosphate, fluororesin, fluororesin and graphite, fluororesin A film made of graphite, molybdenum disulfide, or the like can be used.

(Method for adjusting the maximum height Ry of the inner peripheral surface of the recess)
Next, a method for adjusting the inner peripheral surface of the recess formed in the cylinder of this aspect (a method for smoothing the inner peripheral surface of the recess) will be described with reference to FIG. 5A is a schematic cross-sectional view showing an example of a method for adjusting the maximum height Ry of the inner peripheral surface of the concave portion by covering, and FIG. 5B is a diagram showing the maximum of the inner peripheral surface of the concave portion by machining. It is a schematic sectional drawing which shows an example of the method of adjusting height Ry.

  The method for smoothing the inner peripheral surface of the recess formed in the cylinder of this aspect is not particularly limited, and a conventionally known method can be appropriately selected and adjusted. For example, as illustrated in FIG. 5A, the inner peripheral surface of the recess can be smoothed by covering the fine uneven portion on the inner peripheral surface of the recess with the surface film 21. Specifically, a fine coating on the inner peripheral surface of the recess is covered with a surface coating 21 formed by a plating method, a phosphate coating treatment method, a vapor deposition method, or the like, or a surface coating made of a predetermined material By coating the coating liquid for forming 21 with a conventionally known coating method such as spray coating, the surface can be smoothed so that the maximum height Ry is 0.1 μm or more and 30 μm or less. .

  Examples of the surface film formed by the plating method include a surface film containing a copper-based metal that is formed by immersing a cylinder liner in which a recess is processed into a copper sulfate solution and performing electrolytic plating.

  Examples of the surface film formed by the phosphate film treatment method include a phosphate film chemically generated on the inner peripheral surface of the recess using a phosphate treatment solution. For example, iron phosphate film formed using iron phosphate treatment liquid, manganese phosphate film formed using manganese phosphate treatment liquid, phosphoric acid formed using zinc phosphate treatment liquid Examples thereof include a zinc coating and a calcium phosphate coating formed using a calcium phosphate treatment solution. In particular, the phosphate film treatment method is a treatment method suitable for depth management, and is easy by covering fine irregularities on the inner peripheral surface of the recess with the surface film 21 formed by the phosphate film treatment method. The surface can be smoothed so that the maximum height Ry is 0.1 μm or more and 30 μm or less. The phosphate film treatment method refers to a chemical conversion treatment that chemically generates a phosphate film on the surface of a metal using a phosphate treatment solution, and is a surface formed by the phosphate film treatment method. The film 21 means a phosphate film.

  Here, in the case where abrasive grains are used for forming recesses in the manufacturing stage (for example, when recesses are formed by a blasting method), a pretreatment for pickling the inner peripheral surface of the recesses in advance is performed during the phosphate coating process. It is preferable. By this pretreatment, the inner peripheral surface of the concave portion can be activated, and the abrasive grains existing on the inner peripheral surface of the concave portion are removed even when the abrasive particles are present on the inner peripheral surface of the concave portion in the manufacturing stage. can do. Further, in the subsequent chemical conversion treatment, the surface grows while etching the inner peripheral surface of the recess, so that abrasive grains do not remain. Thereby, it is possible to prevent the abrasive grains from falling off during operation, and it is possible to prevent oil consumption due to excessive wear and vertical flaws on the inner wall surface of the cylinder.

  Furthermore, even if the abrasive grains cannot be completely removed in the pretreatment, the abrasive grains enter the inside of the phosphate film during the chemical conversion treatment and do not exist on the surface of the phosphate film. The abrasive grains do not fall off during operation.

  Examples of the surface film formed by vapor deposition (sputtering, plasma CVD, etc.) include a hard carbon film (for example, a diamond-like carbon film).

  Examples of the surface film formed by a conventionally known coating method include a surface film made of molybdenum disulfide, graphite, and resin. As a method of forming a surface film composed of molybdenum disulfide, graphite, and resin, a coating liquid in which molybdenum disulfide, graphite, resin, and a solvent that is added as necessary is prepared and applied. It can be formed by working and firing. Examples of the resin mixed with molybdenum disulfide and graphite include epoxy resin, polyimide resin, polyamideimide resin, acrylic resin, and polybenzimidazole resin.

  Further, as illustrated in FIG. 5B, by removing or reducing the fine irregularities on the inner peripheral surface of the recess by machining such as shot peening or brushing, the surface has a maximum height Ry of 30 μm or less. Can be smoothed. In addition, the broken line part in a figure shows the recessed part internal peripheral surface before adjustment of the maximum height Ry, 21 shows the area | region covered, 22 shows the area | region removed.

(Position of recess)
Next, an example of the formation position of the recessed part in the cylinder liner of this aspect is demonstrated concretely with reference to FIG. 6, FIG. FIG. 6 is an explanatory view showing an example of the formation position of the concave portion of the inner wall surface of the cylinder liner constituting the cylinder of the present invention, and FIG. 7 is a diagram of the cylinder liner fixed to the inside of the cylinder body of the present embodiment. It is a schematic sectional drawing which shows an example of the range of the said process center part area | region 4. FIG.

  The following description will focus on the case where the recess is formed only in the center area of the stroke. However, in the cylinder of the present invention, a plurality of recesses are formed on the inner wall surface of the cylinder (cylinder liner), and a part of the inner peripheral surface of the recess is formed. The maximum height Ry is 0.1 μm or more and 30 μm or less, and the formation position of the recess formed on the inner wall surface of the cylinder liner is not limited to the following example, and the piston ring and the cylinder liner It is sufficient to form a recess at a position where it is desired to reduce the contact area and reduce the frictional force.

  As illustrated in FIG. 6, a plurality of recesses 3 are formed on the inner wall surface 2 of the cylinder liner 1 in this embodiment. The recess 3 is formed only in the stroke center region 4 of the inner wall surface 2 of the cylinder liner 1 and is not formed in any region other than the region 4. The stroke center region 4 extends from the lower surface position of the ring groove of the lowest piston ring at the top dead center of the piston over the entire circumference of the inner wall surface 2 of the cylinder liner 1 to the uppermost piston ring at the bottom dead center of the piston. This is a region between the upper surface of the ring groove.

  FIG. 7 shows the piston 21a at the top dead center stop position and the piston 21b at the bottom dead center stop position in the same cross-sectional view when the piston reciprocates. The stroke center region 4 is formed on the inner wall surface 2 of the cylinder liner 1 from the lower surface 24 position of the ring groove 23 of the lowest piston ring 22 of the piston 21a at the top dead center stop position, to the piston at the bottom dead center stop position. This is a region between the top surface 27 of the ring groove 25 of the uppermost piston ring 26 at 21b. FIG. 7 shows a piston in which three piston rings (a first pressure ring, a second pressure ring, and an oil control ring) are used, and the lowest piston ring 22 is an oil control ring. The piston ring 26 is a first pressure ring.

  As described above, by forming a plurality of recesses on the inner wall surface of the cylinder liner, the contact area between the piston ring and the cylinder liner can be reduced and the frictional force can be reduced, but the moving speed of the piston is relatively low. In the vicinity of the top dead center and the bottom dead center, it is possible to reduce the reciprocating friction by reducing the surface roughness of the inner wall surface of the cylinder liner without forming a recess in the inner wall surface of the cylinder liner. On the other hand, in the stroke center region 4 which is a region where the sliding speed between the inner wall surface of the cylinder liner and the piston ring is high, the influence of the shear resistance of the lubricating oil becomes large. Considering such points, it is preferable that the recess is formed only in the stroke center region 4 of the inner wall surface of the cylinder liner. By forming the recess only in the stroke center region 4, the contact area between the piston ring and the inner wall surface of the cylinder liner can be reduced, and the influence of the shear resistance of the lubricating oil can be reduced.

  In addition, when a recess is formed in the entire area where the piston ring slides, that is, when a recess is formed in an area other than the center area of the stroke, the contact surface pressure increases due to a decrease in the contact area, and top dead Since boundary lubrication occurs near the point and bottom dead center, the frictional force increases. In addition, if there is a recess in such a portion, it becomes an unnecessary oil pool, which may burn and increase the amount of oil consumed.

  Here, when a plurality of recesses are formed randomly in the stroke center region 4, the contact area between the piston ring and the inner wall surface of the cylinder liner is small in the stroke center region 4 as a whole. The width of the sliding piston ring (the length in the axial direction of the cylinder) is very short compared to the stroke center region 4, so there may be a portion where no recess is formed depending on the location. In this portion, the piston ring sliding surface and the inner wall surface of the cylinder liner are in contact with each other by 100%, and the above effect may not be sufficiently exhibited. Considering such points, it is preferable that at least one of the plurality of recesses is present in all cross sections in the cylinder circumferential direction.

  As described above, the “stroke center region” means the ring groove of the uppermost piston ring at the bottom dead center of the piston from the lower surface position of the ring groove of the lowest piston ring at the top dead center of the piston. It is an area | region between the upper surface position. For example, as illustrated in FIG. 7, when three piston rings are arranged in the order of the first pressure ring, the second pressure ring, and the oil control ring from above the piston, the upper end of the stroke center region is the oil The lower surface 24 is the position of the lower surface 24 of the ring groove 23 of the control ring 22, and the lower end is the position of the upper surface 27 of the ring groove 25 of the first pressure ring 26 which is the uppermost piston ring. Note that, as described above, this aspect is not limited to the configuration in which three piston rings are used, but has two piston rings (one pressure ring and one oil control ring each), or a piston. The present invention can be similarly applied to a structure having one ring (a piston ring having both a gas seal and an oil control).

  As described above, when considering a cross section in the circumferential direction, if no recess is formed in a certain cross section, when the piston ring passes through the cross section, it passes through the cross section in which a plurality of recesses are formed. Compared to the case, the contact area between the piston ring and the inner wall surface of the cylinder liner is increased. Therefore, the influence of the shear resistance of the lubricating oil is increased, and as a result, the reciprocating friction is also increased.

  On the other hand, by forming at least one recess in all cross sections in the cylinder circumferential direction in the stroke center region, the contact area can be obtained even if the piston ring passes through any circumferential cross section in the stroke center region. Therefore, the reciprocating friction can be surely reduced.

  In addition, examples of the state in which “at least one of the plurality of recesses is formed in all cross sections in the circumferential direction of the cylinder” include the cases of FIGS. 8A and 8B. it can.

  FIG. 8A is a schematic development view showing an example of the arrangement of the recesses 3 in the stroke center region 4 of FIG. 1 described above. In FIG. 8A, the vertical direction in the drawing is the axial direction of the cylinder, and the horizontal direction in the drawing is the circumferential direction of the cylinder. As illustrated in FIG. 8A, in the line X drawn in the cylinder circumferential direction, the lowermost point 5a of the recess 3a is located below the uppermost point 6b of the recess 3b closest to the lower part thereof. In the line Y drawn in the cylinder circumferential direction, the lowest point 5b of the recess 3b is positioned below the uppermost point 6c of the recess 3c closest to the lower part. In this way, by arranging the recesses close to each other in the vertical direction so as to overlap with each other in the cylinder axial direction, at least one of the plurality of recesses can be formed in all cross sections in the cylinder circumferential direction. From the above, when the piston reciprocates, the piston ring that slides in the central region of the stroke can reduce the contact area with the cylinder inner wall surface at any position in the cylinder axial direction, reducing reciprocating friction. There is an effect.

  Here, FIG. 8B is also a schematic development view showing an example of the arrangement of the recesses 3 in the stroke center region 4 of FIG. 1 described above, similarly to FIG. 8A. Also in FIG. 8B, the vertical direction in the drawing is the axial direction of the cylinder, and the horizontal direction in the drawing is the circumferential direction of the cylinder. In FIG. 8A, the recess 3 is formed with a uniform area over the cylinder axis direction, but is not limited to this mode, and as shown in FIG. 8B, the cylinder axis direction The area of the recess 3 may be reduced in the vicinity of the end of the stroke center area 4, and the area of the recess may be increased in the vicinity of the center of the stroke center area 4.

  In this embodiment, the size of the recess is not particularly limited, and can be appropriately adjusted according to the size of the cylinder and the piston ring used together. The concave portion may be formed so as to penetrate the center region of the stroke in the cylinder axial direction, but from the viewpoint of maintaining the airtightness of the cylinder, the average length of the concave portion in the cylinder axial direction is the piston ring used. The length of the uppermost piston ring is preferably equal to or less than the length in the cylinder axial direction. More specifically, it is preferable that the uppermost piston ring of the used piston rings is about 5 to 100% of the length in the cylinder axial direction.

  The average length of the recesses in the cylinder circumferential direction is preferably within a range of 0.1 mm to 15 mm, and particularly preferably within a range of 0.3 mm to 5 mm. When the cylinder circumferential direction average length is less than this range, the effect of forming the concave portion may not be sufficiently obtained. On the other hand, if the circumferential average length exceeds this range, a part of the piston ring may enter the recess and a problem such as deformation of the piston ring may occur.

  The cylinder radial direction average length of the recesses is preferably in the range of 0.5 μm to 1000 μm, more preferably in the range of 0.5 μm to 500 μm, and particularly preferably in the range of 0.5 μm to 50 μm. When the average length in the cylinder radial direction of the recess is less than this range, the effect of forming the recess may not be sufficiently obtained. On the other hand, if the radial average length exceeds this range, processing is difficult, and problems such as the need to increase the radial average length of the cylinder liner (increase the wall thickness) occur. There is a case. In addition, the cylinder radial direction average length of a recessed part needs to be set suitably so that a recessed part inner peripheral surface may not protrude from a cylinder inner wall surface.

  In this aspect, the cylinder circumferential direction average length (interval) between adjacent recesses is preferably in the range of 0.1 to 15 mm, and particularly preferably in the range of 0.3 mm to 5 mm. If the cylinder circumferential average length (interval) between adjacent recesses is less than this range, the inner wall surface of the cylinder liner on which the piston ring slides is too small, and the inner wall surface of the piston ring and the cylinder liner May not be able to slide stably. On the other hand, when it exceeds this range, the effect of forming the recess may not be sufficiently obtained.

  In addition, each average length of the recessed part mentioned in this aspect shall mean the average length of each location illustrated in FIG. FIG. 9A is a schematic development view showing the cylinder axial direction of the inner wall surface of the cylinder liner in the vertical direction of the drawing. FIG. 9B is a schematic cross-sectional view of the cylinder liner in the circumferential direction. The axial average length of the concave portion is an average length of the concave portion 3 in the cylinder axial direction as illustrated in FIG. 9A.

  Moreover, the circumferential direction average length of the said recessed part 3 is an average of the length of the recessed part 3 in a cylinder circumferential direction so that it may illustrate in Fig.9 (a). As illustrated in FIG. 9B, the average length in the circumferential direction of the concave portion 3 means the average length in the surface including the inner wall surface 2, and the same applies to the area of the concave portion.

  Moreover, the radial direction average length of the said recessed part 3 is the average of the length from the bottom face of the recessed part 3 to the inner wall surface 2 of the cylinder liner 1 so that it may illustrate in FIG.9 (b). Moreover, the cylinder circumferential direction average length (interval) between the said recessed parts is the average of the space | interval of the adjacent recessed part 3, so that it may illustrate to Fig.9 (a) and (b).

  In this embodiment, the arrangement of the recesses is not particularly limited as described above. For example, FIG. 10 shows a developed view in which the inner periphery of the cylinder liner is opened in the circumferential direction. As illustrated in FIG. 10A, the recess is formed so as to penetrate the center area of the stroke in the cylinder axial direction. Alternatively, as illustrated in FIG. 10B, it may be formed in a spiral shape on the inner wall surface of the cylinder liner. In addition, as illustrated in FIGS. 10C and 10D, concave portions having a specific length in the cylinder axis direction may be arranged at regular intervals. Furthermore, the recesses may be arranged irregularly (randomly). In addition, the shapes and dimensions of the plurality of recesses formed on the inner wall surface of one cylinder liner may be different or the same.

  In this aspect, when a plurality of recesses are formed only in the stroke center region, the total area of all the recesses is within a range of 1 to 80% when the area of the stroke center region is 100%. It is preferable that the number of recesses formed per cross section in the cylinder circumferential direction is at least one. In addition, when the number of recesses formed in one cross section in the circumferential direction of the cylinder is too small, there is a possibility that the effect of reducing the reciprocating frictional force obtained by forming the recesses and reducing the contact area cannot be sufficiently obtained. is there. Therefore, it is preferable to form a recess that can sufficiently exhibit the effect for each cross section in the cylinder circumferential direction.

  The concave portion to the extent that the effect of reducing the reciprocating frictional force is different depending on the reciprocating speed of the piston used together, but in this aspect, when the concave portion is formed only in the central region of the stroke, The total area of all the recesses is preferably 1 to 80%, more preferably 10 to 60%, and particularly preferably 20 to 50% when the area of the stroke center region is 100%. If the area ratio is less than this range, the effect of forming the recess may not be sufficiently obtained. On the other hand, if the area ratio exceeds this range, the contact area is too small, and the piston ring is in a cylinder liner. Inconveniences such as being unable to slide stably on the inner wall surface may occur. From the viewpoint of the effect of reducing the reciprocating frictional force, there is a preferable range of the size of the recess. Therefore, the number of recesses and the number of recesses are determined so that the area ratio is within the above range and at least one recess is formed in all cylinder circumferential cross-sections while taking into account the size of each recess. It is necessary to adjust the arrangement.

In this embodiment, “the total area of all the recesses when the area of the stroke center region is 100%” means that the area of the recesses 3 is A as illustrated in FIGS. 11A and 11B. _{1, a 2,} a 3, when the _{··· a n, a 1, a} 2, a 3 to the area of the stroke center region is intended to mean the ratio of the sum of the · · · _{a n} . The total area ratio, the area _A 1 of the recesses 3 in the stroke center _region, A _2, A 3, total ··· _{A n A total} and, the area of the inner wall 2 other than the recess 3 in the stroke center region B Using B _total, it is expressed by the following formula. In addition, as illustrated in FIG. 11A, the area of the recess 3 here means not the area of the bottom surface of the recess 3 but the area in the cross section including the inner wall surface 2.

本態様においては、上述した凹部の形状、寸法、配置、面積率等は、行程中央部領域の全てにおいて同じでもよいし、領域によって異なっていてもよい。例えば、行程中央部領域において、シリンダ軸方向の各領域で上記面積率が異なっていてもよく、行程中央部領域の上方部分および下方部分においては凹部面積が小さく、行程中央部領域の中央部分においては凹部面積が大きくなっていてもよい。上記面積率等は段階的に変化しても、連続的に変化してもよい。

In this aspect, the shape, size, arrangement, area ratio, and the like of the recesses described above may be the same in all of the stroke center region, or may be different depending on the region. For example, in the stroke center region, the area ratio may be different in each region in the cylinder axis direction, the recessed area is small in the upper part and the lower part of the stroke center region, and May have a large recessed area. The area ratio or the like may be changed stepwise or continuously.

  The cylinder liner in this embodiment is used by being fixed inside the cylinder body, and a piston ring mounted on the piston slides on the inner wall surface. The dimensions, materials, and the like of the cylinder liner of this aspect can be appropriately designed in consideration of the dimensions and materials of the cylinder body, compatibility with the piston rings used together, and the operating temperature.

  In this aspect, from the viewpoint of reducing the reciprocating frictional force between the piston ring and the inner wall surface of the cylinder liner, when the recess is formed only in the stroke center region, the recess in the stroke center region is The ten-point average roughness Rz of the portion not formed is preferably 4 μm or less, more preferably 2 μm or less, and particularly preferably 1 μm or less. Further, in this aspect, all the areas where the piston slides have the above-mentioned surface roughness, such as the area near the top dead center, the area near the bottom dead center, and the stroke center area on the inner wall surface of the cylinder liner. It is preferable. The ten-point average roughness Rz is defined in JIS B0601-1994.

(Cylinder body)
The cylinder body used in this embodiment is only required to be able to fix the cylinder liner to the inside thereof, and its material, dimensions, etc. can be appropriately designed according to the application, operating temperature and the like.

(Piston ring used in combination with a cylinder)
The piston ring used in combination with the cylinder of this aspect is not particularly limited, and various piston rings that are currently known can be selected as appropriate.

  In particular, the outer peripheral sliding surface of the piston ring has various shapes depending on its purpose and application, but the cylinder of this aspect can be combined with all piston rings having different outer peripheral sliding surfaces. is there.

  For example, in the case of a piston ring with a three-ring configuration (two pressure rings and one oil ring), the outer peripheral sliding surface of the first pressure ring has a barrel shape, an eccentric barrel shape, a tapered shape, etc. The outer peripheral sliding surface of the second pressure ring is preferably a taper shape, an undercut shape, an underhook shape, etc., and the abutment shape is preferably an interrupted undercut shape. For an oil ring, a coil expander and an oil A two-piece oil ring consisting of a ring body and a three-piece oil ring consisting of two side rails and a spacer expander can be used. Especially, the outer peripheral sliding surface shape of the two-piece oil ring is a straight shape, Double bevel shape or barrel shape, the upper surface of the upper rail of the oil ring body and the lower surface of the lower rail It is preferable that a shape can be expected improvement of significant LOC by such combinations.

(Piston used in combination with cylinder)
The piston used in combination with the cylinder of this embodiment is not particularly limited, and various pistons that are currently known can be appropriately selected.

  Since the cylinder of this aspect has a plurality of recesses on its inner wall surface, the recesses function as an oil reservoir, and the amount of oil increases compared to a conventional cylinder (without recesses). There is concern over deterioration of the LOC due to oil left behind, and the oil left in the recesses flowing out to the sliding surface and being lifted up by the rising piston ring, or the remaining oil evaporates. . Therefore, in the piston used in combination with the cylinder of this aspect, in order to quickly discharge the oil, the oil drain holes (holes for discharging the oil to the crankcase) are 2-6 respectively in the thrust direction and the anti-thrust direction. You may devise such as forming a part and enlarging the diameter of an oil drain hole. Furthermore, it is preferable that the number and size of the oil drain holes in the thrust direction be larger than the oil drain holes formed in the anti-thrust direction.

B. Second aspect (linerless type)
The cylinder according to the second aspect of the present embodiment does not use the cylinder liner as in the first aspect, and the recess is formed directly on the inner wall surface of the cylinder body, and the piston is on the inner wall surface of the cylinder. It slides directly.

  The cylinder main body used in this aspect may be any one in which a recess having a maximum height Ry of at least part of the inner peripheral surface in the range of 0.1 μm or more and 30 μm or less is formed directly on the inner wall surface, There are no particular limitations on dimensions and materials.

  The cylinder of this embodiment is the same as the cylinder liner type cylinder of the above “A. First embodiment” except that no cylinder liner is used and a recess is formed directly on the inner wall surface of the cylinder body. Therefore, the description here is omitted. That is, the recess of “A. First aspect” can be applied to the linerless type of this aspect as it is, and the cylinder of this aspect is provided with a predetermined recess in the stroke center region of the inner wall surface. Thus, the same effects as those of the “first aspect” are achieved.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention. For example, as the material for the cylinder inner wall surface of the present invention, various conventionally used materials such as aluminum, aluminum-based alloys, cast iron, cast steel, and steel can be used.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

(Experiment 1)
The cylinder liner was processed by the following method, and the soot deposition rate in the concave portion of the cylinder liner was measured.

<Cylinder liner processing>
A masking plate is used in the central region of the stroke of the cylinder liner (material: FC250) having the dimensions (mm) shown in FIGS. 13A and 13B, and a recess is formed by the following procedure. The Ry was adjusted. The recess was formed in the shape and arrangement shown in FIG.

In addition, the used masking board is a product made from SUS420, and thickness is 0.5 mm.
(1) The masking plate was fixed to the inner wall surface of the cylinder liner.
(2) As shown in FIG. 14, the cylinder liner 90 was fixed to the turntable 91 of the blast processing machine.
(3) As shown in FIG. 14, the abrasive grain outlet 92 of the blasting machine is inserted inside the cylinder liner 90, the turntable 91 is rotated, and the abrasive grain outlet 92 is moved up and down while polishing. The particles are discharged onto the inner wall surface of the cylinder liner 90 (the abrasive particles are discharged only when the abrasive nozzle 92 is raised), and the recess is formed so that the area ratio is 50% of the central region of the stroke. Went. As the abrasive material, alumina was used, and the abrasive particle size was 53 to 74 μm. The abrasive spray pressure was about 2 MPa, and the rotation speed of the turntable 91 was 4 rpm. The vertical movement time of the abrasive grain ejection port 92 was 5 min × 2 times.
(4) The maximum height Ry was adjusted by appropriately adjusting the conditions of the blasting machine and polishing the bottom surface of the recess with an abrasive. Note that alumina was used as the abrasive, and an abrasive particle size of 10 to 200 μm was used. The abrasive jet pressure was 0.4 MPa, and the rotation speed of the turntable 91 was 8 rpm. Moreover, the vertical movement time of the abrasive grain jet nozzle 92 was 63.5 mm / min × 4 times.
(5) The cylinder liner 90 was removed from the turntable 91, and then the masking plate was removed from the cylinder liner.
(6) Honing was performed on the inner wall surface of the cylinder liner 90. The honing process is for removing wrinkles that may occur at the ends of the formed recesses.
(7) The shape of the formed recess was a rhombus as shown in FIG. 9A, and both the average length in the axial direction and the average length in the circumferential direction were 1.4 mm. Moreover, the cylinder radial direction average length of the recessed part was 10 micrometers.

<Measurement of soot deposition rate>
The soot deposition rate in the concave portion of the cylinder liner shown in FIG. 13A processed by the above procedure was measured. The soot deposition rate is within an arbitrary range of 50 mm × 50 mm, and the number of recesses where 50% or more of soot is deposited in the recesses is visually counted, and the counted number of recesses is set to an arbitrary 50 mm. It measured by dividing | segmenting by the number of the recessed parts which exist in the range of * 50mm. The engine used is a diesel engine with a displacement of 9000 cc, number of cylinders: 6, cylinder diameter, 112 mm, stroke: 150 mm, the speed of the diesel engine is 2700 rpm, the load is full load, and the water temperature is 90 ° C. I drove in.
<Evaluation>
FIG. 15 shows the measurement results of the soot deposition rate of the cylinder liner in which the maximum height Ry of the bottom surface of the recess is in the following range.
Comparative Example 1: Bottom height Ry is 40 μm
Example 1: The maximum height Ry of the bottom surface is 30 μm
Example 2: Maximum bottom surface height Ry is 10 μm
Example 3: Maximum bottom surface height Ry is 7 μm
Example 4: The maximum height Ry of the bottom surface is 2 μm
Example 5: Bottom maximum height Ry is 1 μm
Example 6: The maximum height Ry of the bottom surface is 0.1 μm
From FIG. 15, when the maximum height Ry of the bottom surface of the inner peripheral surface of the recess is 40 μm, the soot deposition rate is 40%, whereas the maximum height Ry is in the range of 0.1 μm to 30 μm. It can be seen that the soot deposition rate is significantly reduced to 1-18%.

  Needless to say, the present invention is not limited to the above embodiments. For example, in the above embodiment, the blasting method is used to adjust the maximum height Ry of the bottom surface of the recess, but the present invention is not limited to this. The maximum height Ry may be adjusted using a method or spray coating. Moreover, although the masking board was used in the said Example, it is not limited to this, You may use the masking sheet etc. which consist of resin.

(Experiment 2)
<Measurement of reciprocating friction force>
The reciprocating frictional force (N) of the cylinder liner shown in FIG. 13B processed by the above procedure was measured using the apparatus shown in FIG. The ten-point average roughness Rz of the portion of the inner wall surface of the cylinder liner where the concave portion is not formed is 2 μm, the average length in the cylinder radial direction of the concave portion is 10 μm, the maximum height Ry of the bottom surface of the concave portion is 1 μm to 5 μm, and the rotational speed FIG. 17 shows the measurement results of the reciprocating frictional force when the above-mentioned area ratio is 0%, 1%, 10%, 30%, 50%, 60%, and 80% when is 750 rpm. FIG. 17 shows the friction force ratio when the friction force of a conventional product in which the concave portion is not formed (the area ratio is 0%) is 1.00. The axial length h1 of the test piece piston ring used at this time was 1.2 mm, the radial length a1 was 3.2 mm, and the tangential tension Ft of the piston ring was 9.8 N. Moreover, the rotation speed at the time of measurement of a reciprocating frictional force was 50-750 rpm, the piston ring ambient temperature was 80 degreeC, and the supply oil used SAE viscosity 10W-30.

<Evaluation>
FIG. 17 shows that the friction force is effectively reduced when the area ratio is in the range of 1% to 80%, and the friction force is minimized when the area ratio is 50%. As the area ratio is increased, the frictional force is reduced by the contact area reduction effect up to 50%, and when the area ratio exceeds 50%, the contact area is reduced, thereby reducing the surface of the sliding portion. It is considered that the pressure is excessively high and the frictional force is increased.

(Experiment 3)
<Measuring mechanical loss>
Mechanical loss (FMEP) due to frictional force was determined using the apparatus shown in FIG. In this test method, a test piece piston ring was set on the piston, and after a familiar operation, the rotational speed corresponding to the engine speed was changed at an oil temperature of 80 ° C., and the frictional force was measured. In this embodiment, a cylinder liner (Example 7) in which a recess is formed only in the central region of the stroke, a cylinder liner (Comparative Example 2-1) in which no recess is formed, and a recess is formed only in the sliding end. Friction force was measured for the cylinder liner (Comparative Example 2-2) and the cylinder liner (Comparative Example 2-3) in which a concave portion was formed in the sliding end and stroke center region. In addition, when forming a recessed part in the said process center part area | region, when the area of the said process center part area | region was 100%, it formed so that the sum total of the area of all the recessed parts might be 50%. Further, the sliding end refers to a region (upper side sliding) of the cylinder liner of the apparatus illustrated in FIG. 16 from the upper end of the cylinder liner to the lower surface position of the ring groove of the piston ring of the test piece at the top dead center of the piston. End), and the region (lower sliding end) from the upper surface position of the ring groove of the test piece piston ring at the bottom dead center of the piston to the lower end of the cylinder liner. The measurement results are shown in FIG. FIG. 18 shows the mechanical loss ratio of other cylinder liners when the mechanical loss of the cylinder liner of Comparative Example 2-1 in which no recess is formed is 1.

<Evaluation>
From FIG. 18, the cylinder liner of Example 7 in which the recess is formed only in the center region of the stroke has the cylinder liner of Comparative Example 2-1 in which the recess is not formed, and the recess is formed in the sliding end. It can be seen that there is less mechanical loss than Comparative Examples 2-2 and 2-3.

DESCRIPTION OF SYMBOLS 1 ... Cylinder liner 2 ... Inner wall surface 3 ... Concave part 4 ... Stroke center part area | region

Claims (5)

A cylinder in which a piston slides on an inner wall surface,
Of the inner wall surface of the cylinder, between the lower surface position of the ring groove of the lowest piston ring at the top dead center of the piston and the upper surface position of the ring groove of the uppermost piston ring at the bottom dead center of the piston A plurality of recesses formed of one or a plurality of surfaces are formed in the central region of the stroke which is a region,
Wherein Ri one or at least a portion of the maximum height Ry of Der least 30μm or less 0.1μm multiple surfaces,
The stroke center region has a total area of all recesses in a range of 1% to 80% when the area of the stroke center region is 100%, and the stroke center portion of the inner wall surface of the cylinder A cylinder, wherein the recess is not formed in a region other than the region .   The cylinder according to claim 1, wherein the cylinder includes a cylinder body and a cylinder liner fixed to the inside of the cylinder body, and a plurality of the recesses are formed on an inner wall surface of the cylinder liner. .   The cylinder according to claim 1, wherein the plurality of surfaces are two side surfaces and one bottom surface.   The cylinder according to claim 3, wherein the maximum height Ry of the bottom surface is 0.1 μm or more and 30 μm or less.   The cylinder according to any one of claims 1 to 4, wherein the cylinder is used in an internal combustion engine.

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