JP2018059404A - Engine, cylinder body member, and vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine capable of more effectively suppressing occurrence of scuffing near a top dead center.SOLUTION: In an engine including a piston portion, and a cylinder body portion having a sliding face on which the piston portion is slid, the cylinder body portion is composed of Al alloy having a Si content of 16 mass % or more, and includes primary-crystal grains having an average crystal grain diameter of 8 μm or more and 50 μm or less, eutectic Si crystal grains having an average crystal grain diameter smaller than the average crystal grain diameter of the primary-crystal grains, and an Al alloy base material. At least on an upper 1/4 region of the sliding face, the primary-crystal Si crystal grains and the Al alloy base material are exposed to be kept into contact with the piston portion, and a plurality of substantially parallel linear grooves having a depth of 1/3 or more of an upper limit value of a range of the eutectic Si crystal grain diameter in a distribution of grain size of the Si crystal grain of the cylinder body portion, are formed at pitches wider than the average crystal grain diameter of the primary-crystal Si crystal grains, and have parts passing between the adjacent primary-crystal grains.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an engine, a cylinder body member, and a vehicle.

  In recent years, Al alloying of a cylinder body part is progressing for the purpose of weight reduction of an engine. The cylinder body portion is required to have high strength and high wear resistance. Therefore, as one of the Al alloys for the cylinder body, an Al alloy containing a large amount of Si, that is, an Al-Si alloy having a hypereutectic composition can be cited.

  Patent document 1 is disclosing the following techniques regarding the engine provided with the cylinder block made from Al alloy with comparatively high Si content.

  Si crystal grains and Al alloy base material are exposed on the sliding surface of the cylinder block with the piston ring. The sliding surface is mechanically processed so that Si crystal grains are raised. The exposed surface of the Si crystal grains is located inside the cylinder with respect to the exposed surface of the Al alloy base material. Therefore, the piston ring comes into contact with the Si crystal grains. Contact with the Al alloy base material of the piston ring is avoided. The cylinder block is made of an Al alloy having a relatively high Si content, and is manufactured by high pressure die casting. Therefore, primary Si crystal grains having an appropriate size are appropriately distributed on the sliding surface. Since the load applied to each primary crystal Si crystal grain becomes small during engine operation, destruction of the primary crystal Si crystal grain is suppressed. Moreover, since the primary crystal grains have an appropriate size, the primary crystal grains are prevented from dropping off from the sliding surface. Thereby, contact with the Al alloy base material of the piston ring is effectively avoided. Therefore, the occurrence of scuffing due to the contact between the Al alloy base material and the piston ring is suppressed. Moreover, lubricating oil is hold | maintained between the Si crystal grains which floated on the sliding surface, and the hollow between Si crystal grains functions as an oil reservoir. Thereby, the lubricity when the piston slides in the cylinder is improved, and the scuff resistance of the cylinder body portion is improved.

  As described above, in the cylinder block of Patent Document 1, primary crystal Si crystal grains having an appropriate size are exposed in a floating island shape so as to be distributed at an appropriate density on the sliding surface. Thereby, contact with Al alloy base material and a piston ring is avoided, and the hollow between Si crystal grains functions as an oil reservoir. As a result, the occurrence of scuffing is suppressed.

  Patent Documents 2 and 3 relate to an engine including a cylinder block made of an Al alloy having a relatively high Si content, as in Patent Document 1.

  In the cylinder block of Patent Document 2, the sliding surface is etched so that Si crystal grains are raised. By etching, irregularities are formed on the surface of the Al alloy base material located in the depressions between the Si crystal grains. As a result, the amount of lubricating oil retained by the depressions between the Si crystal grains is greater than that of the cylinder block of Patent Document 1. Therefore, the occurrence of scuffing is more effectively suppressed.

  In the cylinder block of Patent Document 3, the sliding surface is etched so that the unevenness formed on the surface of the Al alloy base material located in the depression between the Si crystal grains near the top dead center becomes deeper. As a result, the amount of lubricating oil retained by the depressions between the Si crystal grains located near the top dead center increases. Scuffing near the top dead center is more effectively suppressed.

  In the vicinity of the top dead center, lubrication between the sliding surface and the piston portion is mainly boundary lubrication. The top dead center is close to the combustion chamber of the engine. Therefore, the lubrication conditions near the top dead center are severe. Scuffing tends to occur near top dead center. Therefore, as in Patent Document 3, a technique for suppressing scuffing near the top dead center has been proposed.

Thus, conventionally, the cylinder block made of Al alloy having a relatively high Si content and manufactured by high pressure die casting has been upgraded on the assumption that the Si crystal grains are exposed in a floating island shape. In other words, there is a premise that scuffing can be suppressed by realizing the following two points at the root of the technical flow of cylinder blocks made of Al alloy that are relatively high in Si content and manufactured by high pressure die casting. It was.
Suppressing the contact between the piston ring and the Al alloy base material Making the recess between the Si crystal grains function as an oil reservoir

JP 2005-273654 A JP 2008-180218 A JP 2010-31840 A

  The present invention is to provide an engine, a cylinder body member, and a vehicle that can more effectively suppress the occurrence of scuffing near the top dead center.

  The present invention can employ the following configurations.

(1) An engine comprising a piston part and a cylinder body part having a sliding surface on which the piston part slides,
The cylinder body portion is formed of an Al alloy having a Si content of 16% by mass or more, and has primary crystal grains having an average crystal grain size of 8 μm or more and 50 μm or less, and an average crystal grain of the primary crystal grains Eutectic Si crystal grains having an average crystal grain size smaller than the diameter, and an Al alloy base material,
Among the sliding surfaces, at least in the upper quarter region of the sliding surface, the primary crystal Si crystal grains and the Al alloy base material are exposed so as to come into contact with the piston portion, and A plurality of substantially parallel linear grooves having a depth of 1/3 or more of the upper limit of the range of the eutectic Si crystal grain size in the Si crystal grain size distribution of the cylinder body part are the primary crystal Si. Formed with a pitch wider than the average crystal grain size of the crystal grains, and having a portion passing between the adjacent primary crystal grains of Si,
An engine characterized by that.

  In the configuration of (1), the cylinder body portion is formed from an Al alloy having a Si content of 16% by mass or more. The average crystal grain size of the primary crystal Si grains exposed in the upper 1/4 region of the sliding surface is 8 μm or more and 50 μm or less. From the viewpoint of receiving the load of the piston part, the primary crystal Si crystal grains have an appropriate size and are appropriately distributed on the sliding surface. Under this condition, the primary crystal Si crystal grains and the Al alloy base material are exposed so as to be in contact with the piston portion, and the range of the eutectic Si crystal grain size in the grain size distribution of the Si crystal grains in the cylinder body portion. A plurality of substantially parallel linear grooves having a depth equal to or more than 1/3 of the upper limit value are formed at a pitch wider than the average crystal grain size of the primary crystal grains. By forming a plurality of substantially parallel linear grooves at a pitch wider than the average crystal grain size of the primary crystal grains, it is possible to improve the uniformity of lubricating oil dispersion on the sliding surface. . Thereby, the uniformity of the oil film formed on a sliding surface can be improved. Further, since the plurality of linear grooves have a depth of 1/3 or more of the upper limit of the range of the eutectic Si crystal grain size in the grain size distribution of the Si crystal grains in the cylinder body portion, sufficient A sufficient amount of lubricating oil is retained in the groove. Therefore, the oil film breakage on the sliding surface can be suppressed. Further, the plurality of linear grooves have a portion that passes between adjacent primary crystal grains. As a result, since the primary Si crystal grains receive the load of the piston portion, wear of the sliding surfaces (Al alloy base material) adjacent to both sides of the groove is suppressed, and the lubricating oil in the groove is easily retained.

  The Al alloy base material is exposed on the sliding surface so as to come into contact with the piston portion. Conventionally, the contact between the Al alloy base material and the piston portion has been considered undesirable from the viewpoint of suppressing scuffing. However, in the configuration of (1), the Al alloy base material is exposed to the sliding surface together with primary crystal Si grains having an appropriate size and appropriately distributed on the sliding surface. Furthermore, as described above, in the configuration (1), the uniformity of the oil film formed on the sliding surface is improved and a sufficient amount of lubricating oil is retained. Therefore, the influence by the contact with the piston part of the Al alloy base material is suppressed to an acceptable level, and the effect of suppressing the scuffing by improving the uniformity of the oil film is obtained. As a result, the occurrence of scuffing can be suppressed more effectively.

(2) An engine comprising a piston part and a cylinder body part having a sliding surface on which the piston part slides,
The cylinder body portion is formed of an Al alloy having a Si content of 16% by mass or more by high pressure die casting, and has an initial crystal grain and an average crystal grain smaller than an average crystal grain size of the primary Si crystal grain. Including eutectic Si crystal grains having a diameter, and an Al alloy base material,
Among the sliding surfaces, at least in the upper quarter region of the sliding surface, the primary crystal Si crystal grains and the Al alloy base material are exposed so as to come into contact with the piston portion, and A plurality of substantially parallel linear grooves having a depth of 1/3 or more of the upper limit of the range of the eutectic Si crystal grain size in the Si crystal grain size distribution of the cylinder body part are the primary crystal Si. Formed with a pitch wider than the average crystal grain size of the crystal grains, and having a portion passing between the adjacent primary crystal grains of Si,
An engine characterized by that.

  According to the structure of (2), a cylinder body part is formed from Al alloy whose Si content is 16 mass% or more by high pressure die casting. From the viewpoint of receiving the load of the piston part, the primary crystal Si crystal grains have an appropriate size and are appropriately distributed on the sliding surface. Under this condition, the primary crystal Si crystal grains and the Al alloy base material are exposed so as to be in contact with the piston portion, and the range of the eutectic Si crystal grain size in the grain size distribution of the Si crystal grains in the cylinder body portion. A plurality of substantially parallel linear grooves having a depth equal to or more than 1/3 of the upper limit value are formed at a pitch wider than the average crystal grain size of the primary crystal grains. By forming a plurality of substantially parallel linear grooves at a pitch wider than the average crystal grain size of the primary crystal grains, it is possible to improve the uniformity of lubricating oil dispersion on the sliding surface. . Thereby, the uniformity of the oil film formed on a sliding surface can be improved. Further, since the plurality of linear grooves have a depth of 1/3 or more of the upper limit of the range of the eutectic Si crystal grain size in the grain size distribution of the Si crystal grains in the cylinder body portion, sufficient A sufficient amount of lubricating oil is retained in the groove. Therefore, the oil film breakage on the sliding surface can be suppressed. Further, the plurality of linear grooves have a portion that passes between adjacent primary crystal grains. As a result, since the primary Si crystal grains receive the load of the piston portion, wear of the sliding surfaces (Al alloy base material) adjacent to both sides of the groove is suppressed, and the lubricating oil in the groove is easily retained.

  The Al alloy base material is exposed on the sliding surface so as to come into contact with the piston portion. Conventionally, the contact between the Al alloy base material and the piston portion has been considered undesirable from the viewpoint of suppressing scuffing. However, in the configuration (2), the Al alloy base material is exposed to the sliding surface together with the primary crystal Si grains having an appropriate size and appropriately distributed on the sliding surface. Furthermore, as described above, in the configuration (2), the uniformity of the oil film formed on the sliding surface is improved and a sufficient amount of lubricating oil is retained. Therefore, the influence by the contact with the piston part of the Al alloy base material is suppressed to an acceptable level, and the effect of suppressing the scuffing by improving the uniformity of the oil film is obtained. As a result, the occurrence of scuffing can be suppressed more effectively.

(3) The engine according to (1) or (2),
The plurality of linear grooves are equal to or more than 1/3 of the upper limit of the range of the eutectic Si crystal grain size in the grain size distribution of the Si crystal grains of the cylinder body portion, and the range of the eutectic Si crystal grain size The depth is smaller than the upper limit value.

  According to the configuration of (3), a sufficient and appropriate amount of lubricating oil is held in the plurality of linear grooves. Therefore, the effect of suppressing scuffing by improving the uniformity of the oil film is enhanced. As a result, the occurrence of scuffing can be more effectively suppressed.

(4) The engine according to any one of (1) to (3),
The plurality of linear grooves have a depth of 2.0 μm or more and 6.0 μm or less.

  According to the configuration of (4), a sufficient and appropriate amount of lubricating oil is held in the plurality of linear grooves. Therefore, the effect of suppressing scuffing by improving the uniformity of the oil film is enhanced. As a result, the occurrence of scuffing can be more effectively suppressed.

(5) The engine according to any one of (1) to (4),
Between the adjacent linear grooves, both the primary crystal Si crystal grains and the Al alloy base material are exposed on the sliding surface so as to be in contact with the piston portion.

  According to the configuration of (5), the Al alloy base material is exposed to the sliding surface so as to come into contact with the piston portion together with the primary crystal Si crystal grains between the adjacent linear grooves. Therefore, wear of the sliding surface (Al alloy base material) is more effectively suppressed. Lubricating oil in the groove is more easily retained. Therefore, the occurrence of scuffing can be suppressed more effectively.

(6) The engine according to any one of (1) to (5),
The piston portion includes a piston body, and a piston ring portion including a plurality of piston rings provided on an outer periphery of the piston body,
The plurality of linear grooves are wider than the average crystal grain size of the primary Si crystal grains, and more than the distance from the lower end of the piston ring part to the upper end of the piston ring part in the reciprocating direction of the piston part. It is formed with a small pitch.

  According to the configuration of (6), a sufficient and appropriate amount of lubricating oil is held in the plurality of linear grooves. Therefore, the effect of suppressing scuffing by improving the uniformity of the oil film is enhanced. As a result, the occurrence of scuffing can be more effectively suppressed.

(7) The engine according to any one of (1) to (6),
The piston portion includes a piston body and a piston ring provided on an outer periphery of the piston body,
The plurality of linear grooves have a width smaller than the thickness of the piston ring.

  According to the structure of (7), when a piston ring slides on a sliding surface, it can suppress that a piston ring enters into a groove | channel or is caught. As a result, the reciprocating motion of the piston portion can be performed more smoothly, and the occurrence of scuffing can be suppressed more effectively.

(8) The engine according to any one of (1) to (7),
At least a part of the primary crystal Si crystal grains exposed on the sliding surface is destroyed, and the surface formed in the primary crystal Si crystal grains by the destruction is exposed on the sliding surface.

  According to the configuration of (8), the surface (hereinafter also referred to as a fracture surface) formed in the primary crystal grains by being broken functions as an oil reservoir. Since the fracture surface of the primary crystal grains has irregularities, the amount of lubricating oil that can be retained by the oil sump is large. The opening area of the oil sump is, for example, about the same as the cross-sectional area of the primary crystal grains. For example, the depth of the oil sump is smaller than the diameter of the primary crystal grains. In this way, an oil sump including a fracture surface of primary Si crystal grains is formed on the sliding surface together with a plurality of substantially parallel linear grooves. Accordingly, it is possible to increase the amount of the lubricating oil retained while maintaining the uniformity of the lubricating oil dispersion. Scuffing can be suppressed more effectively.

  (9) A cylinder body member including the cylinder body portion included in the engine according to any one of (1) to (8).

  According to the configuration of (9), it is possible to provide a cylinder body member that can more effectively suppress the occurrence of scuffing in the vicinity of the top dead center.

  (10) A vehicle including the engine according to any one of (1) to (8).

  According to the structure of (10), the vehicle provided with the engine which can suppress more effectively the generation | occurrence | production of the scuff near top dead center can be provided.

  According to the present invention, the occurrence of scuffing near the top dead center can be more effectively suppressed.

It is sectional drawing which shows typically the engine 150 which concerns on one Embodiment of this invention. FIG. 2 is a side view schematically showing a piston part 122 provided in the engine 150 shown in FIG. 1. It is a perspective view which shows typically the cylinder body part 100 with which the engine 150 shown in FIG. 1 is provided. It is sectional drawing which shows typically the cylinder body part 100 shown in FIG. FIG. 4 is a partially enlarged plan view schematically showing a sliding surface 101 of a cylinder body part 100 shown in FIG. 3. (A), (b) is a partial expanded sectional view which shows typically the sliding face 101 of the cylinder body part 100 shown in FIG. It is a graph which shows the example of the preferable particle size distribution of Si crystal grain. Fig. 2 is a side view schematically showing a motorcycle including the engine 150 shown in Fig. 1.

  Conventionally, in a cylinder body portion made of Al alloy having a relatively high Si content and manufactured by high pressure die casting, the sliding surface has been processed so that primary crystal Si crystal grains are exposed in a floating island shape. On the sliding surface, contact between the piston ring and the Al alloy base material is suppressed, and a recess between Si crystal grains functions as an oil reservoir. As a result, scuffing was suppressed.

  With respect to such a conventional design philosophy, the present inventors conducted intensive studies to more effectively suppress the occurrence of scuffing near the top dead center, and obtained the following knowledge.

  In the cylinder body part made of Al alloy having a relatively high Si content and manufactured by high pressure die casting, from the viewpoint of receiving the load of the piston part, the primary crystal Si grains have an appropriate size and are slid. It is distributed moderately on the moving surface. Therefore, if the uniformity of the oil film formed on the sliding surface is improved by maintaining a sufficient amount of lubricating oil in good balance between the primary Si crystal grains in the vicinity of the top dead center, the Al alloy mother will be improved. Even when the material comes into contact with the piston portion, it is difficult to cause scuffing. That is, the contact between the Al alloy base material and the piston portion is allowed. And since the merit by the improvement of the uniformity of an oil film can be enjoyed, generation | occurrence | production of the scuff near top dead center can be suppressed more effectively.

  The present invention has been completed based on the above-described knowledge, that is, knowledge that conflicts with the conventional design concept. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Engine>
FIG. 1 is a cross-sectional view schematically showing an engine 150 according to an embodiment of the present invention. In the present embodiment, R indicates the reciprocating direction of the piston part 122. U indicates the upward direction, that is, the direction from the cylinder body portion 100 toward the cylinder head 130. L indicates a downward direction, that is, a direction from the cylinder body portion 100 toward the crankcase 110. In the following, a water-cooled engine will be described as an example, but the present invention is not limited to this, and an air-cooled engine may be used. The engine of this embodiment is a single cylinder engine, but in the present invention, the number of cylinders of the engine is not particularly limited. The engine of the present embodiment is a 4-stroke engine, but may be a 2-stroke engine.

  The engine 150 includes a crankcase 110, a cylinder body portion 100, and a cylinder head 130. In the present embodiment, the cylinder body portion 100 and the crankcase 110 are separate, but in the present invention, the cylinder body portion 100 and the crankcase 110 may be integrated.

  A crankshaft 111 is accommodated in the crankcase 110. The crankshaft 111 has a crankpin 112 and a crank web 113.

  A cylinder body 100 is provided on the crankcase 110. The cylinder body portion 100 includes a cylinder wall 103 and an outer wall 104. The cylinder wall 103 has a substantially cylindrical shape. The cylinder wall 103 is formed so as to define the cylinder bore 102. The outer wall 104 surrounds the cylinder wall 103 and constitutes an outer shell of the cylinder body portion 100. A water jacket 105 is provided between the cylinder wall 103 and the outer wall 104.

  A piston portion 122 is inserted into the cylinder bore 102 of the cylinder body portion 100. The piston part 122 slides in the cylinder bore 102 in contact with the sliding surface 101 of the cylinder body part 100 (see FIG. 2). The piston part 122 is made of, for example, an Al alloy (typically an Al alloy containing Si). The piston portion 122 is formed by forging as disclosed in, for example, US Pat. No. 6,205,836. In addition, the manufacturing method of the piston part 122 is not specifically limited. The piston part 122 may be formed by casting, for example.

  A cylinder sleeve is not provided in the cylinder bore 102. The inner surface of the cylinder wall 103 of the cylinder body 100 is not plated. In the present embodiment, since a cylinder sleeve is not required, it is possible to simplify the manufacturing process of the engine 150, reduce the weight of the engine 150, and improve the cooling performance. Further, since it is not necessary to plate the inner surface of the cylinder wall 103, the manufacturing cost can be reduced. The present invention is not limited to the present embodiment. For example, a cylinder sleeve may be provided in the cylinder bore 102, and the cylinder sleeve may include the cylinder body portion 100 according to the present embodiment. The method for installing the cylinder sleeve is not particularly limited, and examples thereof include fitting into the cylinder bore 102 and casting. In this case, the cylinder sleeve has the sliding surface 101 according to the present embodiment. Further, the inner surface of the cylinder body portion 100 provided in the cylinder sleeve is not plated.

  A cylinder head 130 is provided on the cylinder body 100. The cylinder head 130 forms a combustion chamber 131 together with the piston part 122 of the cylinder body part 100. The cylinder head 130 has an intake port 132 and an exhaust port 133. An intake valve 134 for supplying air-fuel mixture into the combustion chamber 131 is provided in the intake port 132, and an exhaust valve 135 for exhausting the combustion chamber 131 is provided in the exhaust port 133. Yes.

  The piston part 122 and the crankshaft 111 are connected by a connecting rod 140. Specifically, the piston pin 123 of the piston portion 122 is inserted into the through hole of the small end portion 142 of the connecting rod 140, and the crank pin 112 of the crankshaft 111 is inserted into the through hole of the large end portion 144. Thereby, the piston part 122 and the crankshaft 111 are connected. A roller bearing (rolling bearing) 114 is provided between the inner peripheral surface of the through hole of the large end portion 144 and the crank pin 112. The engine 150 does not include an oil pump that forcibly supplies lubricating oil, but the engine of the present invention may include an oil pump.

  FIG. 2 is a side view schematically showing a piston portion 122 included in the engine 150 shown in FIG.

  The piston part 122 is provided in the cylinder bore 102. The piston part 122 includes a piston main body 122a and a piston ring part 122b. The piston body 122 a includes a piston pin 123 that is inserted into the through hole of the connecting rod 140. The piston ring portion 122b includes three (plural) piston rings 122c, 122d, and 122e provided on the outer periphery of the piston main body 122a.

  The piston ring 122c is also referred to as a top ring, and is fitted in a top ring groove 122f provided on the outer periphery of the piston main body 122a. The piston ring 122d is also called a second ring, and is fitted in a second ring groove 122g provided on the outer periphery of the piston main body 122a. The piston ring 122e is also referred to as an oil ring, and is fitted in an oil ring groove 122h provided on the outer periphery of the piston main body 122a. The top ring 122c, the second ring 122d, and the oil ring 122e are provided in this order from the top to the bottom with a space therebetween in the reciprocating direction R of the piston portion 122. That is, in the present embodiment, the upper end 122m of the piston ring part 122b in the reciprocating direction R of the piston part 122 corresponds to the upper surface of the top ring 122c. The lower end 122n of the piston ring portion 122b corresponds to the lower surface of the oil ring 122e. Of the piston part 122, in particular, the piston ring part 122 b (piston rings 122 c, 122 d, 122 e) is in contact with the sliding surface 101 of the cylinder wall 103. In the present embodiment, the piston ring part 122b is constituted by three piston rings, but the number of piston rings constituting the piston ring part 122b is not particularly limited.

  FIG. 3 is a perspective view schematically showing the cylinder body portion 100 provided in the engine 150 shown in FIG. FIG. 4 is a cross-sectional view schematically showing the cylinder body portion 100 shown in FIG.

  The cylinder body portion 100 has a sliding surface 101 and is made of an Al alloy containing Si. Specifically, it is formed from an Al alloy having a Si content of 16% by mass or more. The Al alloy preferably contains 73.4% to 79.6% by weight of Al, 16% to 24% by weight of Si, and 2.0% to 5.0% by weight of copper. . The wear resistance and strength of the cylinder body 100 can be increased. Moreover, it is also preferable that Si content is 18 mass% or more. The Si content is preferably 22% by mass or less. The Al alloy preferably contains 50 mass ppm or more and 200 mass ppm or less of phosphorus and 0.01 mass% or less of calcium. If the Al alloy contains 50 mass ppm or more and 200 mass ppm or less of phosphorus, it is possible to suppress the coarsening of the Si crystal grains, so that the Si crystal grains can be uniformly dispersed in the alloy. Moreover, by making the calcium content of the Al alloy 0.01% by mass or less, it is possible to secure the effect of refining Si crystal grains by phosphorus and to obtain a metal structure having excellent wear resistance.

  As shown in FIGS. 3 and 4, the cylinder body portion 100 includes a cylinder wall 103 on which a sliding surface 101 is formed, and an outer wall 104 having a surface exposed to the outer periphery. A water jacket 105 is provided between the cylinder wall 103 and the outer wall 104. The water jacket 105 is configured to hold a coolant.

  The cylinder body unit 100 includes a sliding surface 101 with which the piston unit 122 (see FIG. 1) contacts. The sliding surface 101 is a surface (that is, an inner peripheral surface) of the cylinder wall 103 on the cylinder bore 102 side. In other words, the sliding surface 101 is a surface located on the innermost surface of the cylinder wall 103 in the radial direction of the cylinder body portion 100. In the present invention, the contact of the sliding surface 101 with the piston portion 122 includes the contact of the sliding surface 101 with the piston portion 122 through an oil film formed of lubricating oil.

  In the present specification, the “upper side” of the sliding surface 101 is the cylinder head side (that is, the top dead center side). The “lower side” of the sliding surface 101 is the crankcase side (that is, the bottom dead center side). The upper quarter region 101a of the sliding surface 101 means that the entire sliding surface 101 is evenly divided into four along the sliding direction of the piston (the central axis direction of the cylinder bore 102). Refers to the area where it is located. The lower quarter region 101b of the sliding surface 101 refers to a region located closest to the crankcase.

  In the present embodiment, a linear groove 8 (see FIG. 5) described later is formed over the entire sliding surface 101. However, the present invention is not limited to this example. In the present invention, the portion where the linear groove 8 is formed may be at least the region 101 a on the upper quarter of the sliding surface 101. The portion where the linear groove 8 is formed may be only the upper quarter region 101a of the sliding surface 101, and the upper quarter region 101a and the lower quarter region of the sliding surface 101. 101b may be used.

  FIG. 5 is an enlarged plan view schematically showing the sliding surface of the cylinder body 100 shown in FIG. R indicates the reciprocating direction of the piston part 122. 6A and 6B are cross-sectional views schematically showing an enlarged sliding surface of the cylinder body 100 shown in FIG. FIG. 6 is a cross-sectional view along the direction R. 6A and 6B, only the first linear groove 8a among the linear grooves 8 is illustrated for convenience of explanation.

  A plurality of primary crystal Si crystal grains 1, a plurality of eutectic Si crystal grains 2, and an Al alloy base material 3 are exposed on the sliding surface 101. When the molten Al-Si alloy having a hypereutectic composition is cooled, the Si crystal grains that precipitate first are called "primary Si crystal grains". The precipitated Si crystal grains are called “eutectic Si crystal grains”. The primary crystal Si crystal grain 1 is relatively large and has, for example, a granular shape. The eutectic Si crystal grain 2 is relatively small, for example, has a needle shape. All the eutectic Si crystal grains 2 do not necessarily have a needle shape. Some eutectic Si crystal grains 2 may have a granular shape. In this case, among the plurality of eutectic Si crystal grains 2, the needle-like eutectic Si crystal grains 2 are main crystal grains. The Al alloy base material 3 is a solid solution matrix containing Al. The cylinder body 100 has a plurality of primary crystal Si grains 1, a plurality of eutectic Si crystal grains 2, and an Al alloy base material 3. The plurality of primary crystal Si grains 1 and the plurality of eutectic Si crystal grains 2 are dispersed in the Al alloy base material 3.

  The average crystal grain size of the primary crystal Si crystal grain 1 is, for example, not less than 8 μm and not more than 50 μm. Accordingly, a sufficient number of primary Si crystal grains 1 exist per unit area of the sliding surface 101. Therefore, the load applied to each primary crystal Si crystal grain 1 during operation of engine 150 is relatively small. The destruction of the primary crystal Si crystal grains 1 during operation of the engine 150 is suppressed. In addition, since the portion of the primary crystal Si crystal grain 1 embedded in the Al alloy base material 3 is sufficiently large, dropping of the primary crystal Si crystal grain 1 is reduced. Therefore, the wear of the sliding surface 101 due to the dropped primary crystal Si crystal grains 1 is also suppressed. On the other hand, when the average crystal grain size of the primary crystal grains 1 is less than 8 μm, the portion of the primary crystal grains 1 embedded in the Al alloy base material 3 is small. Therefore, when the engine 150 is operated, the primary crystal Si crystal grains 1 are likely to fall off. Since the dropped primary crystal Si crystal grains 1 act as abrasive particles, the sliding surface 101 may be greatly worn. When the average crystal grain size of the primary crystal grains 1 exceeds 50 μm, the number of primary crystal grains 1 per unit area of the sliding surface 101 is small. Therefore, a large load is applied to each of the primary Si crystal grains 1 during operation of the engine 150, and the primary Si crystal grains 1 may be destroyed. Since the broken pieces of the primary Si crystal grains 1 that have been destroyed act as abrasive particles, the sliding surface 101 may be worn significantly. Note that the average crystal grain size of the primary crystal Si crystal grains 1 is preferably 12 μm or more.

  In the present embodiment, the cylinder body portion 100 is formed of an Al alloy having a Si content of 16% by mass or more by high pressure die casting (HPDC). High pressure die casting is a casting method in which molten metal is supplied into a mold at a pressure exceeding atmospheric pressure by applying pressure to the molten metal. According to the high pressure die casting, the portion that becomes the sliding surface 101 can be cooled at a high cooling rate (for example, 4 ° C./second or more and 50 ° C./second or less). Thereby, for example, the average crystal grain size of the primary crystal Si crystal grains 1 can be controlled to 8 μm or more and 50 μm or less.

  The average crystal grain size of the eutectic Si crystal grain 2 is smaller than the average crystal grain size of the primary crystal Si crystal grain 1. The average crystal grain size of the eutectic Si crystal grains 2 is preferably 7.5 μm or less. The eutectic Si crystal grains 2 serve to reinforce the Al alloy base material 3. Therefore, by reducing the eutectic Si crystal grain 2, the wear resistance and strength of the cylinder body 100 can be improved.

Here, the particle size distribution of the Si crystal grains in the cylinder body 100 will be described.
FIG. 7 is a graph showing an example of a preferable particle size distribution of Si crystal grains.
In the graph shown in FIG. 7, the Si crystal grains having a crystal grain size in the range of 1 μm to 7.5 μm are eutectic Si crystal grains 2, and the Si crystal grains having a crystal grain size in the range of 8 μm to 50 μm. The crystal grains are primary crystal Si crystal grains 1. As described above, the Si crystal grains 1 and 2 of the cylinder body 100 have a grain size in which peaks exist in the range where the crystal grain size is 1 μm or more and 7.5 μm or less and the crystal grain size is 8 μm or more and 50 μm or less. It is preferable to have a distribution. The wear resistance and strength of the cylinder body 100 can be greatly improved.

  Further, from the viewpoint of reinforcing the Al alloy base material 3 with the eutectic Si crystal grains 2, as shown in FIG. 7, the first peak (eutectic crystal) in the range of the crystal grain size of 1 μm to 7.5 μm. The frequency in the peak derived from the Si crystal grain 2) is 5 times or more the frequency in the second peak (peak derived from the primary crystal Si crystal grain 1) in the range of the crystal grain size of 8 μm to 50 μm. preferable.

  In order to control the average crystal grain size of the primary crystal grains 1 and the eutectic crystal grains 2, the cooling rate of the portion that becomes the sliding surface 101 is adjusted in the step of casting the molded body (step S1c described later). do it. As a specific example, for example, by casting so that the portion that becomes the sliding surface 101 is cooled at a cooling rate of 4 ° C./second or more and 50 ° C./second or less, the average crystal of the primary crystal grains 1 is obtained. The Si crystal grains 1 and 2 can be precipitated so that the particle diameter is 8 μm or more and 50 μm or less and the average crystal grain diameter of the eutectic Si crystal grains 2 is 7.5 μm or less.

Next, the linear groove 8 formed on the sliding surface 101 will be described.
As shown in FIG. 5 and FIGS. 6A and 6B, a plurality of linear grooves 8 are formed on the sliding surface 101. In the present embodiment, the plurality of linear grooves 8 include a plurality of first linear grooves 8a and a plurality of second linear grooves 8b. The plurality of first linear grooves 8a have a shape extending in a direction from the upper left to the lower right in FIG. 5 and are substantially parallel to each other. The plurality of first linear grooves 8 a form a striped pattern on the sliding surface 101. The plurality of second linear grooves 8b have a shape extending in a direction from the upper right to the lower left in FIG. 5 and are substantially parallel to each other. The plurality of second linear grooves 8 b form a striped pattern on the sliding surface 101. The plurality of first linear grooves 8a and the plurality of second linear grooves 8b are not parallel to each other but intersect each other. Thereby, the plurality of linear grooves 8 form a lattice pattern on the sliding surface 101. In FIG. 5, the portion where the primary Si crystal grain 1 and / or the eutectic Si crystal grain 2 and the linear groove 8 overlap each other is shown in FIG. The part formed so that it may pass on the exposed surface of the crystal grain 2 is shown. In at least a part of the portion, a fracture surface 5a as shown in FIG. 6B is formed.

  Among the plurality of linear grooves 8, at least two or more linear grooves 8 are substantially parallel to each other. Among the plurality of linear grooves 8, some of the linear grooves 8 (first linear grooves 8a) and the remaining linear grooves 8 (second linear grooves 8b) may intersect each other. All of the plurality of linear grooves 8 may be formed so as not to cross each other, and may be substantially parallel. “Substantially parallel” means that adjacent linear grooves 8 extend so as not to intersect. In other words, regarding the meaning of “substantially parallel”, even if the adjacent linear grooves 8 are not strictly parallel when viewed due to errors or deviations in the formation of the linear grooves 8, the present invention. Can be interpreted as the adjacent linear grooves 8 being substantially parallel. The sliding surface 101 includes a set of first linear grooves 8a and a set of second linear grooves 8b as sets of linear grooves parallel to each other. In the present invention, the sliding surfaces 101 are parallel to each other. There is no particular limitation on the number of linear groove groups. The grooves belonging to different sets cross each other. The pattern formed by the plurality of linear grooves 8 formed on the sliding surface 101 is not limited to the square lattice pattern as shown in FIG. The pattern formed by the plurality of linear grooves 8 may be a striped pattern formed by the first linear grooves 8a or the second linear grooves 8b, or may be a polygonal lattice pattern such as a triangular lattice pattern. A square lattice pattern is an example of a polygonal lattice pattern. Note that the pitch between the grooves in the striped pattern and the lattice pattern is not necessarily constant.

  In the present embodiment, the plurality of linear grooves 8 form a regular pattern (such as a striped pattern or a polygonal lattice pattern). In the present embodiment, the Al alloy base material 3 is exposed to the sliding surface 101 so as to come into contact with the piston ring portion 122b (piston portion 122) together with the primary crystal Si crystal grains 1 in a pattern having regularity. The sliding surface 101 on which the linear grooves 8 having a regular pattern are formed is more dispersed in lubricating oil than the conventional irregular sliding surface (sliding surface in which Si crystal grains are exposed in a floating island shape). Can improve the uniformity. As a result, in this embodiment, the uniformity of the oil film formed on the sliding surface 101 is high. In the following description, except for the case where the first linear groove 8a and the second linear groove 8b are distinguished from each other, the description of the linear groove 8 is the first linear groove 8a and the second linear groove. It is also an explanation for both of them.

  Regarding the planar view shape of the linear groove 8, as shown in FIG. 5, the planar view shape of the linear groove 8 is linear. However, in the present invention, the shape of the linear groove 8 in plan view is limited to a linear shape as long as it has a linear shape extending so as not to intersect the adjacent linear groove 8 so as to be substantially parallel. Not. That is, the linear groove 8 may be curved. The linear groove 8 may have a curved portion and a straight portion. Further, the linear groove 8 may have a bent portion. Further, the planar view shape of the plurality of linear grooves 8 may differ depending on the linear grooves 8. The planar view shapes of all the linear grooves 8 may be the same or substantially the same. Further, each of the plurality of linear grooves 8 is not necessarily formed so as to be continuous over the entire sliding surface 101. Each of the plurality of linear grooves 8 does not necessarily extend to the edge of the sliding surface 101. Each of the plurality of linear grooves 8 may have an interrupted portion on the sliding surface 101.

  Regarding the width of the linear groove 8, the width of the linear groove 8 is not particularly limited. The width of the linear groove 8 is preferably smaller than the thickness of the smallest piston ring among the piston rings 122c, 122d, and 122e. Further, the width of the linear groove 8 is preferably equal to or greater than the average crystal grain size of the primary Si crystal grains 1. The width of the linear groove 8 is preferably equal to or greater than the maximum value in the range of the grain size of the primary crystal grains 1 in the grain size distribution of the cylinder body 100. As shown in FIG. 5, the linear groove 8 has a certain width, but the present invention is not limited to this example. The linear groove 8 may have a different width depending on the location. Further, the width of the plurality of linear grooves 8 may be different depending on the linear grooves 8. All the linear grooves 8 may have the same width or substantially the same width.

  Regarding the depth of the linear groove 8, in the present embodiment, the linear groove 8 is 1/3 of the upper limit value of the range of the grain size of the eutectic Si crystal grains 2 in the grain size distribution of the Si crystal grains of the cylinder body 100. It has the above depth. Here, the significance of the depth of the linear groove 8 will be described. Patent Document 3 discloses a technique for more effectively suppressing the occurrence of scuffing near the top dead center. In Patent Document 3, the sliding surface is etched, and the Al alloy base material is eluted substantially uniformly in the depth direction over the entire sliding surface excluding the Si crystal grain region existing in a floating island shape. Therefore, in the technique of Patent Document 3, it is preferable that the etching process is performed so that the Si crystal grains do not easily fall off from the sliding surface or do not fall off, and it is difficult to form deep recesses or grooves. On the other hand, in the present embodiment, the linear grooves 8 are formed at a pitch wider than the average crystal grain size of the primary Si crystal grains, so that the Al alloy base material to be removed is limited. Accordingly, the linear groove 8 having a relatively large depth can be formed. Specifically, in this embodiment, the linear groove 8 has a depth of 1/3 or more of the upper limit value of the range of the grain size of the eutectic Si crystal grains 2 mainly having a needle shape. Omission of Si crystal grains 2 is prevented or suppressed. The primary Si crystal grains 1 have an average crystal grain size larger than the average crystal grain diameter of the eutectic Si crystal grains 2, and the primary crystal Si crystal grains 1 are prevented or prevented from falling off. Since a plurality of substantially parallel linear grooves having a relatively large depth are formed on the sliding surface, a large amount of lubricating oil can be retained and uniformity of the lubricating oil is improved. Therefore, in the present embodiment, the drop of Si crystal grains can be prevented or suppressed, and the uniformity of the oil film can be improved. The linear groove 8 preferably has a depth of 2.0 μm or more. Further, the linear groove 8 may have a depth of 40% or more of the upper limit value of the particle size range of the eutectic Si crystal grains 2 in the particle size distribution of the Si crystal grains of the cylinder body portion 100. Moreover, you may have the depth of 1/2 or more of the upper limit of the range of the particle size of the eutectic Si crystal grain 2 in the particle size distribution of the Si crystal grain of the cylinder body part 100.

  Furthermore, it is preferable that the linear groove 8 has a depth smaller than the upper limit value of the grain size range of the eutectic Si crystal grains 2. This is because the lubricating oil held in the linear groove 8 is supplied to the sliding surface 101 appropriately and efficiently. Moreover, it is preferable that the linear groove | channel 8 has a depth of 6.0 micrometers or less. In the present invention, when the upper limit value and the lower limit value of the depth of the linear groove 8 are determined, the groove having a depth smaller than the lower limit value of the depth of the linear groove 8 and / or the line A groove having a depth larger than the upper limit value of the depth of the groove 8 may be formed on the sliding surface 101. In other words, in the present invention, grooves other than the linear grooves defined in the present invention may be formed on the sliding surface.

  The cross-sectional shape of the linear groove 8 is such that the width of the linear groove 8 decreases as the depth of the linear groove 8 increases. The cross-sectional shape of the linear groove 8 is the cross-sectional shape of the linear groove 8 in a plane perpendicular to the direction in which the linear groove 8 extends. In the present invention, the cross-sectional shape of the linear groove 8 is not particularly limited. The cross-sectional shape of the linear groove 8 may be, for example, a substantially V shape as shown in FIG. 6A or a substantially U shape. Further, the cross-sectional shapes of the linear grooves 8 do not have to be the same. The cross-sectional shape of the linear groove 8 may differ depending on the location, and may differ depending on the linear groove 8. Further, the portion (mountain) between the linear grooves 8 does not necessarily need to be a flat surface as shown in FIGS. 5 and 6A and 6B. The portion between the linear grooves 8 may be an inclined surface, may form a ridge line, and one or more grooves having a depth smaller than the depth of the linear groove 8 are formed. Also good.

  Regarding the pitch of the first linear grooves 8, the plurality of substantially parallel first linear grooves 8 a are formed at a pitch wider than the average crystal grain size of the primary crystal Si crystal grains 1. As a result, at least a part of the plurality of primary crystal Si crystal grains 1 is located between the first linear grooves 8a adjacent to each other. In the present embodiment, in the region between the adjacent first linear grooves 8 a, both the primary crystal Si crystal grains 1 and the Al alloy base material 3 are exposed to the sliding surface 101 so as to come into contact with the piston part 122. doing. Since the portion of the sliding surface 101 that is in contact with the piston portion 122 is adjacent to the first linear groove 8a in plan view, the lubricating oil is smoothly supplied to the sliding surface 101. Further, the Al alloy base material 3 is exposed on the sliding surface 101 so as to be in contact with the piston portion 122, but the primary crystal Si crystal grain 1 is also exposed on the sliding surface 101 so as to be in contact with the piston portion 122. Therefore, the wear of the sliding surface 101 (Al alloy base material 3) is more effectively suppressed. In FIG. 5, the pitch of the pair of first linear grooves 8a adjacent to each other is constant regardless of the location, but the present invention is not limited to this example. That is, the pitch between the pair of first linear grooves 8a adjacent to each other is not necessarily constant. For example, the first linear grooves 8a adjacent to each other may be formed to meander, and the pitch of the first linear grooves 8a may be different depending on the location. In addition, although the above-mentioned description is description regarding the 1st linear groove 8a, since the description about the 2nd linear groove 8b is the same as the description about the 1st linear groove 8a, description here is carried out. Omitted.

  In the present embodiment, as shown in FIG. 5, at least one of the linear grooves 8 is formed so as to pass through the primary Si crystal grains 1 by breaking the primary Si crystal grains 1. That is, at least one of the linear grooves 8 is formed so as to pass over the exposed surface of the primary crystal grain 1. Thereby, the uniformity of the dispersion | distribution of the lubricating oil in the sliding surface 101 is improved more. The present invention is not limited to this example.

  In the present embodiment, as shown in FIG. 6B, the primary crystal Si crystal grains 1 having the fracture surface 5 a are exposed on the sliding surface 101. That is, in this embodiment, at least a part of the primary crystal Si crystal grains 1 exposed on the sliding surface 101 is destroyed, and the surface formed on the primary crystal Si grains 1 by the destruction (that is, The fracture surface 5 a) is exposed on the sliding surface 101. As a result, an oil sump 5 b is formed on the sliding surface 101. Since the fracture surface of the primary crystal grain 1 has irregularities, the amount of lubricating oil that can be held by the oil sump 5b is large. The opening area of the oil sump 5b is approximately the same as the cross-sectional area of the primary crystal Si crystal grains 1 (the area of the portion exposed on the sliding surface 101). The depth of the oil sump 5 b is smaller than the diameter of the primary crystal Si crystal grain 1. An oil sump 5b including a fracture surface 5a of the primary crystal grain 1 is formed on the sliding surface 101 together with a plurality of substantially parallel first linear grooves 8a. Accordingly, it is possible to increase the amount of the lubricating oil retained while maintaining the uniformity of the lubricating oil dispersion. Scuffing can be suppressed more effectively. The fracture surface 5a is formed when surface processing of the cylinder body part 100 is performed after the casting of the cylinder body part 100. Specifically, the fracture surface 5a is formed, for example, when the primary Si crystal grains 1 are shaved with a grindstone.

  In the present embodiment, the cylinder body portion 100 is formed from an Al alloy having a Si content of 16% by mass or more. The average crystal grain size of the primary crystal Si crystal grains 1 exposed in the upper quarter region 101a of the sliding surface 101 is 8 μm or more and 50 μm or less. From the viewpoint of receiving the load of the piston portion 122, the primary crystal grains 1 have an appropriate size and are appropriately distributed on the sliding surface. Under this condition, the primary crystal Si crystal grain 1 and the Al alloy base material 3 are exposed so as to come into contact with the piston part 122, and the eutectic Si crystal grain 2 in the grain size distribution of the Si crystal grain of the cylinder body part 100 is obtained. A plurality of substantially parallel linear grooves 8 (first linear grooves 8a and second linear grooves 8b) having a depth of 1/3 or more of the upper limit value of the grain size range of the primary crystal Si crystal The pitch is wider than the average crystal grain size of the grains 1. A plurality of substantially parallel linear grooves 8 are formed at a pitch wider than the average crystal grain size of the primary crystal grains 1, thereby improving the dispersion uniformity of the lubricating oil on the sliding surface 101. Can do. Thereby, the uniformity of the oil film formed on a sliding surface can be improved. In addition, since the plurality of linear grooves 8 have a depth of 1/3 or more of the upper limit of the range of the grain size of the eutectic Si crystal grains 2 in the grain size distribution of the Si crystal grains of the cylinder body portion 100. A sufficient amount of lubricating oil is retained in the linear groove 8. Therefore, the oil film breakage on the sliding surface can be suppressed. Further, the plurality of linear grooves 8 have portions that pass between adjacent primary crystal grains 1. Thereby, since the primary crystal Si crystal grain 1 receives the load of the piston part 122, wear of the sliding surfaces 101 (Al alloy base material 3) adjacent to both sides of the linear groove 8 is suppressed, and the linear groove 8 The lubricating oil is easily retained.

  The Al alloy base material 3 is exposed on the sliding surface 101 so as to be in contact with the piston portion 122. Conventionally, the contact between the Al alloy base material 3 and the piston portion 122 has been considered undesirable from the viewpoint of suppressing scuffing. However, in the present embodiment, the Al alloy base material 3 is exposed to the sliding surface 101 together with the primary crystal Si grains 1 having an appropriate size and appropriately distributed on the sliding surface 101. Furthermore, as described above, the uniformity of the oil film formed on the sliding surface 101 is improved, and a sufficient amount of lubricating oil is retained. Therefore, the influence by the contact with the piston part 122 of the Al alloy base material 3 is suppressed to an acceptable level, and the effect of suppressing the scuffing by improving the uniformity of the oil film is obtained. As a result, the occurrence of scuffing can be suppressed more effectively.

<Manufacturing method>
The manufacturing method of the cylinder body part 100 in this embodiment is demonstrated.

The cylinder body 100 is manufactured, for example, by performing the following steps S1 to S4 in order.
Process S1 Prepared body Process S2 Fine boring Process S3 Coarse honing Process S4 Finish honing

In the manufacturing method of the cylinder body part 100, first, a molded body formed from an Al alloy containing Si is prepared (step S1). This compact includes primary crystal Si grains and eutectic Si crystal grains in the vicinity of the surface. Process S1 which prepares a molded object includes process S1a-S1e, for example.
Process S1a Preparation of silicon-containing Al alloy Process S1b Melt generation Process S1c High pressure die casting Process S1d Heat treatment Process S1e Machining

  First, an Al alloy containing Si is prepared (Step S1a). In order to sufficiently increase the wear resistance and strength of the cylinder body 100, as the Al alloy, 73.4% by mass to 79.6% by mass Al, 16% by mass to 24% by mass Si, and It is preferable to use an Al alloy containing 2.0% by mass or more and 5.0% by mass or less of copper.

  Next, the prepared Al alloy is heated and melted in a melting furnace to form a molten metal (step S1b). It is preferable to add about 100 ppm by weight of phosphorus to the Al alloy or molten metal before melting. If the Al alloy contains 50 mass ppm or more and 200 mass ppm or less of phosphorus, it is possible to suppress the coarsening of the Si crystal grains, so that the Si crystal grains can be uniformly dispersed in the alloy. Moreover, by making the calcium content of the Al alloy 0.01% by mass or less, it is possible to secure the effect of refining Si crystal grains by phosphorus and to obtain a metal structure having excellent wear resistance. That is, the Al alloy preferably contains 50 mass ppm or more and 200 mass ppm or less of phosphorus and 0.01 mass% or less of calcium.

  Subsequently, casting is performed by high-pressure die casting using a molten Al alloy (step S1c). That is, the molten metal is cooled in a mold to form a molded body. At this time, the portion of the cylinder wall 103 that becomes the sliding surface 101 is cooled at a high cooling rate (for example, 4 ° C./second or more and 50 ° C./second or less), so that Si crystal grains that contribute to wear resistance are brought close to the surface. A formed body is obtained. This casting process S1c can be performed using the casting apparatus currently disclosed by the international publication 2004/002658 pamphlet, for example.

  Next, any one of heat treatments called “T5”, “T6”, and “T7” is performed on the molded body taken out from the mold (step S1d). The T5 process is a process in which the molded body is rapidly cooled by water cooling or the like immediately after being taken out of the mold, and then artificially aged for a predetermined time at a predetermined temperature for improvement of mechanical properties and dimensional stabilization, and then air cooling. . The T6 treatment is a treatment in which after the molded body is taken out from the mold, it is subjected to a solution treatment at a predetermined temperature for a predetermined time, followed by water cooling, and then an artificial aging treatment at a predetermined temperature for a predetermined time, and then air cooling. The T7 process is an overaging process compared to the T6 process, and dimensional stabilization can be achieved compared to the T6 process, but the hardness is lower than that of the T6 process.

  Subsequently, predetermined machining is performed on the molded body (step S1e). Specifically, the mating surface with the cylinder head and the mating surface with the crankcase are ground.

  After preparing the molded body as described above, fines for adjusting the dimensional accuracy with respect to the surface of the molded body, specifically, the inner peripheral surface of the cylinder wall 103 (that is, the surface that becomes the sliding surface 101). Boring is performed (step S2).

  Next, a rough honing process is performed on the surface subjected to fine boring (step S3). That is, the surface to be the sliding surface 101 is polished using a grindstone having a relatively small count (a grindstone having large abrasive grains). In the present embodiment, the rough honing process is performed on the entire surface of the surface of the molded body, which becomes the sliding surface 101, but the present invention is not limited to this example. In the present invention, the rough honing process may be performed at least on the upper 1/4 region of the sliding surface 101.

  Subsequently, a finishing honing process is performed (step S4). That is, the region to be the sliding surface 101 in the surface of the molded body is polished using a grindstone having a relatively large count (a grindstone having small abrasive grains). The rough honing process and the finish honing process can be performed using a honing apparatus as disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-268179. In addition, the specifications of the grindstone in the rough honing process and the finishing honing process (type of abrasive grains, count (type of abrasive grain size), type of bond agent, etc.) depend on the specifications of the linear grooves 8 formed on the sliding surface 101. Can be set.

  Through the steps described above, the sliding surface 101 according to the present embodiment is formed. A plurality of primary crystal Si crystal grains 1 and an Al alloy base material 3 are exposed on the sliding surface 101. When the piston part 122 reciprocates in the cylinder bore 102, the plurality of primary crystal Si crystal grains 1 and the Al alloy base material 3 come into contact with the piston part 122. Further, the sliding surface 101 has a plurality of linear grooves 8 at least in the upper 1/4 region of the sliding surface 101. The plurality of linear grooves 8 include a plurality of first linear grooves 8a that are substantially parallel to each other and a plurality of second linear grooves 8b that are substantially parallel to each other. In the present embodiment, the linear groove 8 is formed by a grindstone, but the present invention is not limited to this example. The linear groove 8 may be formed by a laser, for example. Moreover, the number of times of the rough honing process and the finishing honing process is not limited to one, and may be two or more.

<Cylinder body member>
The cylinder body member in the present embodiment is the cylinder body portion 100 itself (see FIG. 1 and the like). The cylinder body part 100 is a part having a sliding surface 101. However, in the present invention, the cylinder body member is not limited to this example. The cylinder body member only needs to include the cylinder body portion 100 having the sliding surface 101. The cylinder body member in the present invention may be a member (so-called cylinder block) formed by integrally molding the cylinder body portion 100 and the crankcase 110. The cylinder body member in the present invention may be a cylinder sleeve used by being provided in the cylinder bore 102. Since the cylinder body member has the sliding surface 101 described above, it is possible to more effectively suppress the occurrence of scuffing in the engine (particularly near the top dead center) when applied to the engine.

<Vehicle>
The vehicle according to the present invention includes various types of vehicles such as automobiles, motorcycles, and snowmobiles such as snowmobiles, and the number of wheels is not particularly limited, such as four wheels, three wheels, and two wheels. Further, the vehicle according to the present invention is a box-type vehicle in which the engine is disposed at a location away from the seat such as an engine room, and at least a part of the engine is disposed below the seat, and the driver straddles the seat. It may be a straddle-type vehicle to board. The saddle riding type vehicle includes a scooter type vehicle that allows the driver to board with the knees aligned.

Hereinafter, a motorcycle will be described as an example of a vehicle.
FIG. 8 is a side view schematically showing a motorcycle including the engine 150 shown in FIG.

  In the motorcycle shown in FIG. 8, a head pipe 302 is provided at the front end of the main body frame 301. A front fork 303 is attached to the head pipe 302 so as to be able to swing in the left-right direction of the vehicle. A front wheel 304 is rotatably supported at the lower end of the front fork 303. A handle 305 is provided at the upper end of the front fork 303.

A rear frame 306 is attached so as to extend rearward from the upper rear end of the main body frame 301. A fuel tank 307 is provided on the main body frame 301, and a main seat 308 a and a tandem seat 308 b are provided on the rear frame 306.

  A rear arm 309 extending rearward is attached to the rear end of the main body frame 301. A rear wheel 310 is rotatably supported at the rear end of the rear arm 309.

  The engine 150 shown in FIG. 1 is held at the center of the main body frame 301. The engine 150 uses the cylinder body 100 in the present embodiment. A radiator 311 is provided in front of the engine 150. An exhaust pipe 312 is connected to the exhaust port of the engine 150, and a muffler 313 is attached to the rear end of the exhaust pipe 312.

  A transmission 315 is connected to the engine 150. A drive sprocket 317 is attached to the output shaft 316 of the transmission 315. The drive sprocket 317 is connected to the rear wheel sprocket 319 of the rear wheel 310 via a chain 318. The transmission 315 and the chain 318 function as a transmission mechanism that transmits the power generated by the engine 150 to the drive wheels.

  Since the motorcycle (vehicle) in the present embodiment is equipped with the engine 150 including the cylinder body portion 100 having the sliding surface 101 described above, it is possible to more effectively suppress the occurrence of scuffing particularly near the top dead center. .

  Measurement of the average crystal grain size of the primary crystal grains and the eutectic Si crystal grains is performed using image processing for a portion that becomes a sliding surface of the cylinder body. Based on the area of the Si crystal grain in the image obtained by the image processing, the diameter (equivalent diameter) of each Si crystal grain when the Si crystal grain in the image is assumed to be a perfect circle is calculated. Note that fine crystals having a diameter of less than 1 μm are not counted as Si crystal grains (primary Si crystal grains or eutectic Si crystal grains). As described above, the number (frequency) and diameter of the Si crystal grains are specified. Based on this, a particle size distribution of Si crystal grains in the cylinder body is obtained. The particle size distribution is, for example, a histogram as shown in FIG. The particle size distribution includes two peaks. The particle size distribution is divided into two regions with a diameter of a portion forming a valley between two peaks as a threshold value. It is assumed that the region corresponding to the large diameter is the particle size distribution of the primary Si crystal grains. The region corresponding to the small diameter is assumed to be the particle size distribution of the eutectic Si crystal grains. Then, based on each particle size distribution, the average crystal grain size of the primary crystal Si crystal grains and the average crystal grain size of the eutectic Si crystal grains are calculated.

  The width of the linear groove is a distance between a pair of ridge lines adjacent to each other in a cross section (cross-sectional curve) intersecting the linear groove. The cross section is parallel to the sliding direction of the piston portion and the sliding surface (reciprocating direction R of the piston portion). The cross section is also parallel to the radial direction of the cylinder body. The depth of the linear groove is a depth from a higher ridge line of a pair of ridge lines adjacent to the linear groove to a deepest portion of the linear groove. The pitch of the linear grooves is the distance between the deepest portions of a pair of adjacent grooves in the cross section (cross section curve). When the sliding surface adjacent to the linear groove is a substantially flat surface, the width of the linear groove is the distance between the edges of the pair of sliding surfaces (flat surfaces).

  In the present invention, as the width, depth, and pitch of the linear groove, the average value of the linear groove included in the cross-sectional curve having a distance of 3 to 5 mm is used. In the present invention, grooves other than linear grooves having a depth defined in the present invention may be formed on the sliding surface. In that case, when specifying the width and pitch of the linear groove, the linear groove having the depth defined in the present invention is used.

  The terms and expressions used herein are used for explanation and are not used for limited interpretation. It should be recognized that any equivalents of the features shown and described herein are not excluded and that various modifications within the claimed scope of the invention are permitted.

  The present invention can be embodied in many different forms. This disclosure should be considered as providing an example of the principles of the invention. Many illustrated embodiments are described herein with the understanding that these examples are not intended to limit the invention to the preferred embodiments described and / or illustrated herein.

  Several illustrative embodiments of the invention have been described herein. The present invention is not limited to the various preferred embodiments described herein. The present invention includes all embodiments including equivalent elements, modifications, deletions, combinations (eg, combinations of features across the various embodiments), improvements, and / or changes that can be recognized by those skilled in the art based on this disclosure. Include. Claim limitations should be construed broadly based on the terms used in the claims and should not be limited to the embodiments described herein or in the process of the book. Such embodiments should be construed as non-exclusive. For example, in this disclosure, the term “preferably” is non-exclusive and means “preferably but not limited to”.

DESCRIPTION OF SYMBOLS 1 Primary crystal Si grain 2 Eutectic Si crystal grain 3 Al alloy base material 5a Fracture surface 5b Oil reservoir 8 Linear groove 8a First linear groove 8b Second linear groove 100 Cylinder body part (cylinder body member)
101 Sliding surface 101a Upper quarter of sliding surface 101b Lower quarter of sliding surface 102 Cylinder bore 103 Cylinder wall 104 Outer wall 105 Water jacket 122 Piston part 122a Piston body 122b Piston ring part 122c Top ring (piston ring)
122d Second ring (piston ring)
122e Oil ring (piston ring)
122f Top ring groove 122g Second ring groove 122h Oil ring groove 122m Upper end of piston ring portion 122b 122n Lower end of piston ring portion 122b Piston pin 140 Connecting rod 150 Engine

Claims (10)

An engine comprising a piston part and a cylinder body part having a sliding surface on which the piston part slides,
The cylinder body portion is formed of an Al alloy having a Si content of 16% by mass or more, and has primary crystal grains having an average crystal grain size of 8 μm or more and 50 μm or less, and an average crystal grain of the primary crystal grains Eutectic Si crystal grains having an average crystal grain size smaller than the diameter, and an Al alloy base material,
Among the sliding surfaces, at least in the upper quarter region of the sliding surface, the primary crystal Si crystal grains and the Al alloy base material are exposed so as to come into contact with the piston portion, and A plurality of substantially parallel linear grooves having a depth of 1/3 or more of the upper limit of the range of the eutectic Si crystal grain size in the Si crystal grain size distribution of the cylinder body part are the primary crystal Si. Formed with a pitch wider than the average crystal grain size of the crystal grains, and having a portion passing between the adjacent primary crystal grains of Si,
An engine characterized by that. An engine comprising a piston part and a cylinder body part having a sliding surface on which the piston part slides,
The cylinder body portion is formed of an Al alloy having a Si content of 16% by mass or more by high pressure die casting, and has an initial crystal grain and an average crystal grain smaller than an average crystal grain size of the primary Si crystal grain. Including eutectic Si crystal grains having a diameter, and an Al alloy base material,
Among the sliding surfaces, at least in the upper quarter region of the sliding surface, the primary crystal Si crystal grains and the Al alloy base material are exposed so as to come into contact with the piston portion, and A plurality of substantially parallel linear grooves having a depth of 1/3 or more of the upper limit of the range of the eutectic Si crystal grain size in the Si crystal grain size distribution of the cylinder body part are the primary crystal Si. Formed with a pitch wider than the average crystal grain size of the crystal grains, and having a portion passing between the adjacent primary crystal grains of Si,
An engine characterized by that. The engine according to claim 1 or 2,
The plurality of linear grooves are equal to or more than 1/3 of the upper limit of the range of the eutectic Si crystal grain size in the grain size distribution of the Si crystal grains of the cylinder body portion, and the range of the eutectic Si crystal grain size The depth is smaller than the upper limit value. The engine according to any one of claims 1 to 3,
The plurality of linear grooves have a depth of 2.0 μm or more and 6.0 μm or less. The engine according to any one of claims 1 to 4,
Between the adjacent linear grooves, both the primary crystal Si crystal grains and the Al alloy base material are exposed on the sliding surface so as to be in contact with the piston portion. The engine according to any one of claims 1 to 5,
The piston portion includes a piston body, and a piston ring portion including a plurality of piston rings provided on an outer periphery of the piston body,
The plurality of linear grooves are wider than the average crystal grain size of the primary Si crystal grains, and more than the distance from the lower end of the piston ring part to the upper end of the piston ring part in the reciprocating direction of the piston part. It is formed with a small pitch. The engine according to any one of claims 1 to 6,
The piston portion includes a piston body and a piston ring provided on an outer periphery of the piston body,
The plurality of linear grooves have a width smaller than the thickness of the piston ring. The engine according to any one of claims 1 to 7,
At least a part of the primary crystal Si crystal grains exposed on the sliding surface is destroyed, and the surface formed in the primary crystal Si crystal grains by the destruction is exposed on the sliding surface.   A cylinder body member comprising the cylinder body portion included in the engine according to claim 1.   A vehicle comprising the engine according to claim 1.

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