JP2013113275A - Cylinder block and method for machining the same - Google Patents

Abstract

[PROBLEMS] To provide a cylinder block and a machining method thereof capable of realizing a bore machining shape easily using existing equipment as well as realizing low friction.
A cross section of an inner surface 111A of a bore 111 has a substantially perfect circular shape and a symmetrical shape with respect to a central axis when a cylinder head 220 is not fastened. The constricted portion 112A of the bore 111 that deforms into a constricted shape when the cylinder head 220 is fastened is expanded in advance radially outward as compared to the minimum diameter portion 113A of the bore 111 in an unfastened state. Thereby, the diameter of the constricted scheduled portion 112A (minimum diameter portion 112B after fastening) after fastening can be set larger than in the case where the diameter is not expanded in advance radially outward.
[Selection] Figure 4

Description

  The present invention relates to a cylinder block having a cylinder bore and a processing method thereof, and more particularly to an improvement in the shape of a bore capable of suppressing interference with a piston sliding in the cylinder bore.

  The cylinder block of the internal combustion engine is formed with a cylinder bore (hereinafter referred to as a bore) that slides relative to the piston via an oil film, and a cylinder head is bolted to the cylinder block. FIG. 1 is a plan view showing a schematic configuration of a specific example of a cylinder block 210 used in a four-cylinder engine, and FIG. 2 is a side sectional view showing a state in which a cylinder head 220 is fastened to the cylinder block 210. In FIG. 1, only the bore 211 and the bolt hole 212 are shown. In the present application, a cross section perpendicular to the axial direction is referred to as a cross section, and a cross section parallel to the axial direction is referred to as a side cross section (axial cross section).

  The cylinder block 210 is made of, for example, an Al material, and four bores 211 are formed on the upper surface of the cylinder block 210, and ten bolt holes 212 are formed. The bolt 230 is fastened to the bolt hole 212 of the cylinder block 210 through the bolt hole 221 of the cylinder head 220, whereby the cylinder head 220 is fixed to the upper surface of the cylinder block 210. A gasket 240 is provided between the cylinder block 210 and the cylinder head 220.

  A water jacket 251 is formed between the bore 211 and the bolt hole 212. The bore 211 is configured by a sleeve 252 made of, for example, cast iron. A hatch shape is formed on the inner surface of the sleeve 252 by honing, and the inner surface serves as a sliding surface. The bore 211 may be constituted by the inner surface of the hole formed in the cylinder block 210 instead of providing the sleeve 252.

  The inner peripheral surface 211A of the bore 211 is formed in a cylindrical shape by performing boring processing and honing processing, as shown in FIG. The However, when the cylinder head 220 is bolted to the upper surface of the cylinder block 210, the inner surface 211A of the bore 211 is deformed to become the inner surface 211B, as shown in FIG. Specifically, the upper end portion 213 of the inner peripheral surface 211A of the bore 211 is expanded in diameter, and the intermediate portion 214 is reduced in diameter to cause constriction. For this reason, when the piston is slid on the bore 211, the friction at the intermediate portion 214 becomes large.

  Therefore, in order to realize low friction, it is conceivable to improve the cylindricity of the bore 211 when the cylinder head 220 is fastened. For example, it has been proposed to process the cross section of the bore 211 into a non-circular shape after allowing for deformation when the cylinder head 220 is fastened (for example, Patent Document 1). In the technique of Patent Document 1, the cross section of the bore of the cylinder block when the cylinder head is not fastened is secondarily formed into a non-circular shape. In this case, the processed shape after the secondary molding is designed such that the non-circular bore is deformed and approximates to a substantially circular shape when the cylinder head is fastened to the cylinder block after the secondary molding.

Japanese Patent No. 41930886

  However, in the technique of Patent Document 1, the cross section of the processed shape of the bore is a non-circular shape, and when the cylinder head is actually fastened to the cylinder block, the processed shape of the bore is deformed and approaches a substantially perfect circular shape. In order to achieve this, it is considered that the side cross section of the processed shape of the bore needs to have a complicated uneven shape. For this reason, boring with a cutting tool is not easy, and it becomes difficult to form a hatch shape on the inner surface of the bore by honing, and as a result, existing equipment cannot be used.

  Accordingly, an object of the present invention is to provide a cylinder block and a machining method for the same that can realize low-friction as well as a bore machining shape easily using existing equipment. And

  In order to solve the above problems, the applicant of the present invention, for example, as disclosed in PCT / JP2011 / 061424, has a bore machining shape that compensates for the deformation of the bore when the cylinder head is fastened (the cross section of the inner surface is substantially the same). In addition to proposing a circular shape that is symmetrical with respect to the central axis, and a method for setting the machined shape, it is proposed to obtain a machined shape of such a bore by honing. In PCT / JP2011 / 061424, as a cross-sectional shape in the axial direction of the bore, for example, a substantially truncated cone shape in which a cross section from one end portion to the other end portion extends in a taper shape has been proposed. As a result of intensive studies on the shape, for example, knowledge about a shape that can be further processed is obtained, and the present invention has been completed.

  The cylinder block of the present invention is a cylinder block in which a bore is formed on one surface and a cylinder head is fastened. The bore of the cylinder head in an unfastened state has a substantially perfect circle shape, and the substantially perfect circle The diameter of the shape changes along the central axis, and the bore has a constricted portion that deforms into a constricted shape when the cylinder head is fastened to the cylinder block, and the constricted portion is the maximum of the unfastened bore. Compared with the small-diameter portion, it is characterized by being expanded radially outward.

  In the cylinder block of the present invention, since the cross section of the inner surface of the bore forms a substantially circular shape and is symmetrical with respect to the central axis, the bore machining shape is the same as PCT / JP2011 / 061424 proposed by the applicant. It can be easily obtained by boring or honing, and the hatch shape can be easily formed by honing. As a result, existing facilities can be used.

  Here, in the processed shape of the bore, the constricted planned portion is reduced in diameter when the cylinder head is fastened, and is deformed into a constricted shape, and thus becomes the minimum diameter portion after the cylinder head is fastened. However, in the cylinder block of the present invention, the constricted portion of the bore that is deformed into a constricted shape when the cylinder head is fastened is expanded in advance radially outward compared to the minimum diameter portion of the bore in the unfastened state. Thereby, the diameter of the constricted scheduled part (minimum diameter part after fastening) after fastening can be set larger than the case where the diameter is not expanded beforehand in the radial direction. Therefore, by appropriately determining the diameter of the constricted part according to the conditions such as the type of cylinder block, interference between the constricted part (the minimum diameter part after fastening) and the piston sliding in the bore after fastening. Can be suppressed. As a result, low friction can be realized.

  In the honing process, the method of forming the inner surface into a tapered shape by changing the diameter of the bore cross-section is more controllable than the method of forming the inner surface into a straight shape while keeping the diameter of the bore cross-section constant. Is difficult. However, in the cylinder block of the present invention, for example, only a part of the inner surface of the bore can be processed to have a tapered shape, so that the processed shape of the bore can be obtained more easily.

  The cylinder block of the present invention can be obtained, for example, by the following cylinder block processing method of the present invention. The cylinder block machining method of the present invention is a cylinder block machining method in which a bore is formed on one surface, the cylinder head is fastened, and the bore has a constricted planned portion that deforms into a constricted shape when the cylinder head is fastened. The bore is machined so that the cross section of the bore has a substantially circular shape and the diameter of the substantially circular shape changes along the central axis, and the cylinder head is fastened to the cylinder block before the bore is machined. The amount of deformation of the bore for data acquisition at the time is acquired along the central axis, the position in the central axis direction of the portion deformed into the constricted shape in the bore for data acquisition is grasped, and the shape of the constriction in the bore for data acquisition is processed when machining the bore The bore of the bore is formed by forming a tapered portion at at least one of the position corresponding to the central axial direction position of the deformed portion and the position in the vicinity thereof. The scheduled portion, as compared to the minimum diameter portion of the non-fastening state bores, characterized in that to extend radially outward.

  The cylinder block processing method of the present invention can obtain the same effects as the cylinder block of the present invention.

  In the cylinder block or the processing method thereof according to the present invention, a mode in which the inner surface of the bore processing shape does not include a straight portion extending linearly along the central axis may be used. Further, in the bore processed shape, for example, in an unfastened state, an aspect in which the diameter on one surface side where the cylinder head is fastened is set smaller than the diameter on the one surface side of the data acquisition bore may be used. In this case, in the axial cross section, for example, the inner surface of the bore and the inner surface of the data acquisition bore can intersect, and in this case, for example, the intersection between the inner surfaces is the clearance between the inner surface of the bore after tightening and the piston. May be used as a reference point for determining the diameter, and the diameter at the intersection of the inner surfaces of the bores may be used as the reference diameter.

  According to the cylinder block or the machining method of the present invention, not only can low friction be realized, but also the effect that the bore machining shape can be easily obtained using existing equipment is obtained. be able to.

It is a top view showing the schematic structure of the specific example of the cylinder block used for a 4-cylinder engine. It is a sectional side view showing the state where the cylinder head was fastened to the cylinder block. It is a figure for demonstrating the shape of the bore | bore of a prior art, Comprising: (A) is a process shape of the bore before cylinder head fastening, (B) is a sectional side view showing the deformation | transformation shape of the bore after cylinder head fastening. . An example of the shape of the bore | bore of the cylinder block which concerns on one Embodiment of this invention is represented, (A) is the processing shape of the bore before cylinder head fastening, (B) is a side cross section showing the deformation | transformation shape of the bore after cylinder head fastening. FIG. The other example of the shape of the bore of the cylinder block concerning one embodiment of the present invention is shown, (A) is the processing shape of the bore before cylinder head fastening, and (B) is the side showing the deformation shape of the bore after cylinder head fastening. It is sectional drawing. The other example of the shape of the bore of the cylinder block concerning one embodiment of the present invention is shown, (A) is the processing shape of the bore before cylinder head fastening, and (B) is the side showing the deformation shape of the bore after cylinder head fastening. It is sectional drawing. The other example of the shape of the bore of the cylinder block concerning one embodiment of the present invention is shown, (A) is the processing shape of the bore before cylinder head fastening, and (B) is the side showing the deformation shape of the bore after cylinder head fastening. It is sectional drawing. The other example of the shape of the bore of the cylinder block concerning one embodiment of the present invention is shown, (A) is the processing shape of the bore before cylinder head fastening, and (B) is the side showing the deformation shape of the bore after cylinder head fastening. It is sectional drawing. The other example of the shape of the bore of the cylinder block concerning one embodiment of the present invention is shown, (A) is the processing shape of the bore before cylinder head fastening, and (B) is the side showing the deformation shape of the bore after cylinder head fastening. It is sectional drawing. The other example of the shape of the bore of the cylinder block concerning one embodiment of the present invention is shown, (A) is the processing shape of the bore before cylinder head fastening, and (B) is the side showing the deformation shape of the bore after cylinder head fastening. It is sectional drawing. It is data for representing the deformation shape of the data acquisition bore when the cylinder head is fastened, and for determining the machining shape of the bore. It is a figure for demonstrating the method of the honing process in the processing method of the cylinder block which concerns on this invention, Comprising: It is a sectional side view showing a part of state of a honing process.

(1) Processed shape of bore Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 4 to 10 show examples of various shapes of the bore 111 of the cylinder block 110 according to an embodiment of the present invention. FIG. 4A shows a processed shape of the bore 111 before the cylinder head 220 is fastened, and FIG. It is a figure showing the deformation | transformation shape of the bore 111 of this. 4 to 10, the X direction in (A) is the horizontal direction of the upper opening surface of the bore 111, and the Y direction is a direction perpendicular to the X direction on the upper opening surface of the bore 111. The Z direction is a direction perpendicular to the upper opening surface of the bore 111. The one-dot chain line in the figure is the central axis.

  The cylinder block 110 of the present embodiment is different from the cylinder block 210 shown in FIGS. 1 and 2 in the machining shape of the bore, and the other configuration is the same as that of the cylinder block 210 shown in FIGS. Constituent elements are denoted by the same reference numerals and description thereof is omitted.

  In all the bores 111 shown in FIGS. 4 to 10, when the cylinder head 220 is not fastened, the cross section has a substantially perfect circle shape, and the diameter of the substantially perfect circle shape changes along the central axis. In this case, the bore 111 has a constricted planned portion 112A that is reduced in diameter and deformed into a constricted shape when the cylinder head 220 is fastened, for example, in an intermediate portion or a vicinity thereof. The constricted portion 112 </ b> A is expanded outward in the radial direction as compared with the minimum diameter portion 113 </ b> A when the cylinder head 220 is not fastened. Specifically, the maximum diameter of the constricted portion 112A is set larger than the minimum diameter of the minimum diameter portion 113A in the unfastened state. For example, as shown in FIGS. 4 to 10B, the constricted portion 112 </ b> A is a portion where the amount of diameter reduction (the amount of constriction) is maximum when the cylinder head 220 is fastened, and the minimum diameter after the cylinder head 220 is fastened. Part 112B.

  In FIGS. 4 to 9B, for convenience of illustration, the deformed shape of the bore 111 is similarly represented. However, the deformed shape actually differs depending on the processed shape of the bore 111. 4 (B), for convenience of illustration, in order to emphasize the deformation state of the bore 111, the low friction effect, etc., there is a portion where the gap between the inner surface of the bore 111 and the piston 260 is large. is there.

  When the cylinder head 220 is fastened to the upper surface of the cylinder block 110, the constricted portion 112A is reduced in diameter and deformed into a constricted shape on the inner surface of the bore 111, resulting in a minimum diameter portion 112B in the fastened state. However, since the side cross section of the processed shape of the bore 111 has the above shape, the diameter of the constricted portion 112A (minimum diameter portion 112B after fastening) of the cylinder head after tightening is cylindrical (FIG. 3A). Compared with the case of the bore 211, it becomes larger. Thereby, when the piston 260 is slid on the inner surface 111B of the bore 111 after fastening, the friction at the minimum diameter portion 112B is reduced. Hereinafter, a specific shape of the bore 111 shown in FIGS.

  The bore 111 shown in FIG. 4A has a tapered portion that linearly inclines so as to increase in diameter from the upper surface side to the lower surface side. Here, in this embodiment, for example, the diameter on the upper surface side is set smaller than the diameter of the bore 211 in FIG. 3A where the machining shape is a cylindrical shape, and the diameter on the lower surface side is larger than the diameter of the bore 211. Can be set large. The intersection point P between the inner surface 111A of the bore 111 and the inner surface 211A of the bore 211 is used as a reference point for determining the clearance between the inner surface 111B and the piston 260 after fastening, for example, and the diameter at the intersection point P of the inner surface 111A is used as a reference diameter. Can be used. Such a method for determining the reference diameter may be used for the following processed shape of the bore 111. The distance from the upper surface to the intersection point P can be set to about 30 mm, for example.

  In the bore 111 shown in FIG. 4A, the constricted portion 112A is located at, for example, an intermediate portion, the minimum diameter portion 113A in an unfastened state is located at, for example, the upper end portion, and the constricted portion 112A is Compared with the minimum diameter portion 113A, the diameter is set larger by expanding outward in the radial direction. For example, as shown in FIG. 4B, there may be a portion where the diameter of the inner surface 111B (solid line) after fastening is set smaller than the diameter of the inner surface 211A (broken line). Since the piston is constituted by, for example, an elastic piston ring, even if there is a portion where the inner surface 111B is slightly reduced in diameter and may come into contact with the piston ring, it is possible to suppress the occurrence of a problem.

  The bore 111 shown in FIG. 5A has a tapered portion 121 and a straight portion 122 formed in order from the upper surface side, for example. The tapered portion 121 is linearly inclined so as to increase in diameter from the upper end portion of the bore 111 toward the intermediate portion, for example. The straight portion 122 is connected to the lower end of the tapered portion 121, for example, and extends linearly along the central axis to the lower end of the bore 111. The diameter of the straight part 122 is set to the same diameter as the lower end of the taper part 121, for example.

  In this case, the constricted portion 112A is located at the boundary between the tapered portion 121 and the straight portion 122, for example, and the minimum diameter portion 113A in the unfastened state is located at the upper end portion of the tapered portion 121, for example. The planned portion 112A is expanded radially outwardly and has a larger diameter than the minimum diameter portion 113A. In such a bore 111, only a part of the inner surface 111A is processed so as to become the tapered portion 121, so that the low friction can be realized as described above. Therefore, the processed shape of the bore 111 is easily obtained. be able to.

  A bore 111 shown in FIG. 6A has a straight portion 131 and a tapered portion 132 formed in order from the upper surface side, for example. The straight portion 131 extends linearly along the central axis from the upper end portion of the bore 111 toward the intermediate portion, for example. The diameter of the straight part 131 is set to the same diameter as the upper end of the taper part 132, for example. The taper portion 132 is connected to the lower end of the straight portion 131, for example, and is inclined linearly so as to increase in diameter toward the lower end portion of the bore 111 therefrom.

  In this case, the constricted portion 112 </ b> A is located on the lower surface side of the boundary portion between the straight portion 131 and the tapered portion 132, and is located in the middle portion of the tapered portion 132 or in the vicinity thereof. The minimum diameter portion 113A in the unfastened state is positioned on the straight portion 131, and the constricted portion 112A is expanded radially outward and set to have a larger diameter than the minimum diameter portion 113A. In such a bore 111, the same effect as that of the bore 111 shown in FIG. 5A can be obtained, and the boundary portion between the straight portion 131 and the tapered portion 132 is an upper surface than the constricted portion 112A. Since it is located on the side, the portion where the amount of diameter reduction becomes large when the cylinder head 220 is fastened can be expanded in advance radially outward. As a result, low friction can be effectively realized.

  The bore 111 shown in FIG. 7A has, for example, a straight portion 141, a tapered portion 142, and a straight portion 143 that are sequentially formed from the upper surface side. The straight portion 141 extends linearly along the central axis from the upper end portion of the bore 111 toward the intermediate portion, for example. The straight portion 143 extends linearly along the central axis from, for example, an intermediate portion of the bore 111 toward the lower end portion. The tapered portion 142 is formed between the straight portions 141 and 143, and is inclined linearly so as to increase in diameter from the lower end of the straight portion 141 to the upper end of the straight portion 143. For example, the diameter of the straight portion 141 is set to the same diameter as the upper end of the tapered portion 142, and the diameter of the straight portion 143 is set to the same diameter as the lower end of the tapered portion 142, for example. Thereby, the diameter of the straight part 141 is set smaller than the diameter of the straight part 143.

  In this case, the constricted portion 112A is located at the lower end of the tapered portion 142, the minimum diameter portion 113A in the unfastened state is located in the straight portion 141, and the constricted portion 112A is compared with the minimum diameter portion 113A. And the diameter is set large by expanding radially outward. In such a bore 111, the same effect as that of the bore 111 shown in FIG. 5A can be obtained, but only the vicinity of the constricted portion 112A is a tapered portion 142, and other portions are formed. Since the straight portions 141 and 143 can be formed, the processed shape of the bore 111 can be obtained more easily.

  The bore 111 shown in FIG. 8A has a tapered portion 151 and a tapered portion 152 formed in order from the upper surface side, for example. The taper portion 151 is linearly inclined so as to increase in diameter from the upper end portion of the bore 111 toward the intermediate portion, for example. The taper portion 152 is connected to, for example, the lower end of the taper portion 151 and is inclined linearly so as to decrease in diameter toward the lower end portion of the bore 111 therefrom. The diameter of the upper end portion of the tapered portion 151 is set smaller than the diameter of the lower end portion of the tapered portion 152 as shown in FIG. 8A, for example, but larger than the diameter of the lower end portion of the tapered portion 152. It may be set.

  In this case, the constricted portion 112A is located at the boundary between the tapered portions 151 and 152, the smallest diameter portion 113A in an unfastened state is located at the upper end portion of the tapered portion 151, and the constricted portion 112A is Compared with the small-diameter portion 113A, the diameter is set larger by expanding radially outward. In this case, for example, a straight portion may be provided on at least one of the upper end portion and the lower end portion of the bore 111. In such a bore 111, the constricted planned portion 112A and the vicinity thereof can be expanded most outward in the radial direction, so that low friction can be effectively realized.

  A bore 111 shown in FIG. 9A has a tapered portion that linearly inclines so as to reduce the diameter from the upper end portion to the lower end portion of the bore 111, for example. In this case, the constricted portion 112A is positioned, for example, in the middle portion of the bore 111, the minimum diameter portion 113A in the unfastened state is positioned at the lower end portion of the bore 111, and the constricted portion 112A is the minimum diameter portion. Compared with 113A, the diameter is set larger by expanding radially outward.

  In this case, you may provide a straight part similarly to FIG. 5 (A) -7 (A). That is, you may use what turned the up-down direction of the bore 111 shown to FIG. Specifically, the bore 111 shown in FIG. 10A has a straight portion 161 and a tapered portion 162 formed in order from the upper surface side, for example. The straight portion 161 extends linearly along the central axis from the upper end portion of the bore 111 toward the intermediate portion, for example. The tapered portion 162 is connected to, for example, the lower end of the straight portion 161, and is inclined linearly so as to decrease in diameter toward the lower end portion of the bore 111 therefrom.

  In this case, the constricted planned portion 112A is located at, for example, an intermediate portion of the bore 111, the minimum diameter portion 113A in an unfastened state is located at the lower end portion of the tapered portion 162, and the constricted planned portion 112A is disposed at the minimum diameter. Compared with the portion 113A, the diameter is set larger by expanding radially outward.

(2) Determining Method for Bore Machining Shape A method for determining the machining shape of the bore 111 will be described mainly with reference to FIG. FIG. 11 shows data on the deformed shape of the data acquisition bore in the engaged state of the cylinder head, and is data for determining the machining shape of the bore 111. The L direction in FIG. 11 is a direction parallel to the X direction and the Y direction in FIG. 3A, and the axis indicating the amount of deformation in FIG. The origin in the Z direction in FIG. 11 is the position of the upper opening surface of the bore, and the axis indicating the distance from the upper opening surface of the bore is the Z axis.

  In the method of determining the machining shape of the bore 111, before the machining of the bore 111, the deformation amount of the data acquisition bore at the time of fastening of the cylinder head 220 is acquired along the central axis, and is deformed into a constricted shape in the data acquisition bore. The position of the portion in the Z direction (center axis direction position) is grasped.

  Specifically, in acquiring the deformation amount of the data acquisition bore, first, the data acquisition bore is processed on the upper surface of the data acquisition cylinder block. The processing shape of the data acquisition bore is, for example, a cylindrical shape, and the side cross section of the inner surface is linear. In the following, the bore 211 shown in FIG. 3A is used as the data acquisition bore, and the same reference numerals as those of the bore 211 are used.

  Next, the cylinder head 220 is fastened to the upper surface of the cylinder block 210, and the deformed shape of the data acquisition bore 211 when the cylinder head 220 is fastened is obtained. Specifically, the change amount of the diameter in the X direction and the change amount of the diameter in the Y direction of the deformed shape of the data acquisition bore are measured at predetermined intervals from the upper opening surface of the data acquisition bore 211 to the lower side. . Next, an average value of the amount of change in the diameter of the deformed shape in the X direction and the Y direction is calculated as a representative diameter. Thereby, for example, as shown in FIG. 11, data of a deformed shape of the data acquisition bore 211 is obtained. Next, the position in the Z direction of the constricted portion in the data acquisition bore 211 is grasped. The method of calculating the representative diameter is not limited to this, and other appropriate methods can be used as necessary. For example, as a representative diameter, an actual measurement value (a change amount of the deformed shape in the X direction or the Y direction) may be used. In addition, for example, when the amount of change in the diameter in the Y direction is large and the amount of change in the diameter in the X direction is small, it is preferable to use the amount of change in the diameter in the Y direction as the representative diameter.

  Next, at the time of processing the bore 111, a tapered portion is formed at at least one of the position corresponding to the Z-direction position of the portion deformed into the constricted shape in the data acquisition bore 211 and the vicinity thereof. In this case, for determining the shape of the tapered portion, for example, the method proposed by the applicant (method using an approximate shape of the deformed shape of the data acquisition bore 211) shown in PCT / JP2011 / 061424 can be used.

  Accordingly, the constricted portion 112A of the bore 111 can be expanded radially outward as compared to the minimum diameter portion 113A of the unfastened bore 111. In this way, the processed shape of the bore 111 can be obtained. In addition to the deformation of the inner surface of the bore 111 due to the fastening of the cylinder head 220, the machining shape of the bore 111 may be set in consideration of the thermal deformation of the inner surface of the bore 111 during engine operation. Further, in the processed shape of the bore 111, the difference between the diameter of the diameter 112A of the constricted portion and the diameter of the portion (upper end portion) that deforms to the maximum in the radial direction when the cylinder head 220 is fastened is defined as a taper amount. It is preferable to manage the machining shape of the bore 111 using the taper amount. In this case, the taper amount is determined according to various conditions such as the type of the cylinder block 110, and the numerical value can be set to about 50 μm, for example.

(3) Bore processing method A method of processing the bore 111 will be described. For example, roughing is performed on the inner surface of the bore 111 of the cylinder block 110 by boring. In this case, the bore 111 is processed to have a cylindrical shape. Subsequently, a finishing process is performed by performing a honing process on the inner peripheral surface of the bore 111.

  A honing machine used in the honing process has a grindstone on the surface of a cylindrical head, for example, and the grindstone has a rectangular parallelepiped shape extending along the axial direction of the head. In the honing process, as shown in FIG. 12, when the head 302 supported by the holder 301 is rotated about the axis and reciprocated in the axial direction on the inner surface of the bore 111, the inner surface of the bore 111 is polished by the grindstone 303. The

  In the present embodiment, for example, as shown in PCT / JP2011 / 061424, the rotational speed is appropriately controlled according to the axial position on the inner surface of the bore 111, or the head 302 of the head 302 with respect to the axial center H on the inner surface of the bore 111 is used. The machining shape of the bore 111 can be obtained by appropriately setting the position of the center I of the reciprocating motion or by appropriately combining these methods. In this case, the rotation speed of the head 302, the surface pressure by the grindstone 303, the switching position of the rotation speed, the total rotation speed, and other parameters are appropriately combined and adjusted. When adjusting the surface pressure by the grindstone, for example, the number of grindstones and the cross-sectional area of the grindstone are changed. Various machining shapes of the bore 111 can be obtained by such a machining method.

  As described above, in the present embodiment, the cross section of the inner surface 111A of the bore 111 has a substantially perfect circular shape and is symmetric with respect to the central axis. Therefore, the machining shape of the bore 111 can be easily made using existing equipment. Can be formed.

  Here, the constricted portion 112A of the bore 111 that deforms into a constricted shape when the cylinder head 220 is fastened is expanded in advance radially outward compared to the minimum diameter portion 113A of the bore 111 in the unfastened state. Thereby, the diameter of the constricted scheduled portion 112A (minimum diameter portion 112B after fastening) after fastening can be set larger than in the case where the diameter is not expanded in advance radially outward. Accordingly, by appropriately determining the diameter of the constricted portion 112A according to the conditions such as the type of the cylinder block 110, the constricted constricted portion 112A (minimum diameter portion 112B after fastening) and the inside of the bore 111 slide. Interference with the piston 260 to be performed can be suppressed. As a result, low friction can be realized. In particular, for example, only a part of the inner surface 111A of the bore 111 can be processed to be a tapered portion, so that the processed shape of the bore 111 can be obtained more easily.

  DESCRIPTION OF SYMBOLS 110 ... Cylinder block, 111 ... Bore, 111A ... Inner surface before fastening, 111B ... Inner surface after fastening, 112A ... Constriction planned part, 112B ... Minimum diameter part after fastening (constriction planned part after fastening), 113A ... Before fastening 121, 132, 142, 151, 152, 162 ... taper part, 122, 131, 141, 143, 161 ... straight part, 220 ... cylinder head, 211 ... bore for data acquisition, 260 ... piston

Claims (2)

In the cylinder block in which the bore is formed on one side and the cylinder head is fastened,
The bore of the cylinder head in an unfastened state has a substantially perfect circular shape, and the diameter of the substantially perfect circular shape changes along the central axis.
The bore has a constricted planned portion that deforms into a constricted shape when the cylinder head is fastened to the cylinder block;
The constricted portion is expanded radially outward as compared to the minimum diameter portion of the unfastened bore. In a machining method of a cylinder block, in which a bore is formed on one surface, a cylinder head is fastened, and the bore has a constricted planned portion that deforms into a constricted shape when the cylinder head is fastened.
The bore has a substantially circular shape, and the bore is processed so that the diameter of the substantially perfect circle shape changes along the central axis.
Before processing the bore, the deformation amount of the data acquisition bore when the cylinder head is fastened to the cylinder block is acquired along the central axis, and the position in the central axis direction of the portion deformed into the constricted shape in the data acquisition bore Figure out
By forming a tapered portion at at least one of the position corresponding to the position in the central axis direction of the portion deformed into the constricted shape in the bore for data acquisition at the time of processing of the bore and the position in the vicinity thereof, the constricted planned portion of the bore Is expanded radially outward as compared with the minimum diameter portion of the bore in the unfastened state.

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