TW201631255A - Air-cooled engine, cylinder body member for air-cooled engine, and vehicle equipped with air-cooled engine - Google Patents

Abstract

The present invention addresses the problem of providing an air-cooled engine capable of improving cooling efficiency, in particular cooling efficiency of a piston part during initial sliding. This air-cooled engine is provided with a piston part, and a cylinder body part having a sliding surface along which the piston part slides. The air-cooled engine is characterized in that: the cylinder body part is provided with heat-dissipation parts provided to the outer surface thereof, and comprises a metal including Al; an inner circumferential section of the cylinder body part, said inner circumferential section including at least the sliding surface, is formed from an Al alloy having an Si content of at least 16 mass%; in the sliding surface, a plurality of substantially parallel linear grooves are formed, and primary Si crystal grains having an average crystal grain size of 8-50 [mu]m inclusive are exposed so as to come into contact with the piston part; Al contact sections which are formed between the plurality of linear grooves, and in which the Al alloy base material comes into contact with the piston part, are respectively exposed in the sliding surface between two adjacent primary Si crystal grains; and Al in the cylinder body part is physically continuous from the Al contact sections to the heat-dissipation parts.

Description

Air-cooled engine, cylinder block member for air-cooled engine, and vehicle with air-cooled engine

The present invention relates to an air-cooled engine, a cylinder block member for an air-cooled engine, and a vehicle equipped with an air-cooled engine.

The air-cooled engine is an engine constructed by exhausting heat generated by an engine by using air to cool the engine. In general, an air-cooled engine has a relatively simple construction when compared to a water-cooled engine. Therefore, the air-cooled engine is stronger and easier to maintain. On the other hand, the cooling efficiency of the air-cooled engine is lower than the cooling efficiency of the water-cooled engine. The heat of the engine can cause strain in the cylinder body and so on. Therefore, in the case of an air-cooled engine, it is desirable to increase the cooling efficiency.

Generally, in an air-cooled engine, heat is dissipated by the engine by blowing air to an outer surface of the cylinder block (for example, a heat sink). Further, various studies have been conducted on the cooling of the air-cooled engine (see, for example, Patent Documents 1 to 3).

In the air-cooled engine of Patent Document 1, an oil passage is formed on the outer wall of the cam chain chamber, and the oil passage is connected to an oil pump for injecting lubricating oil. The lubricating oil is sprayed from the oil passage toward the outer wall of the cylinder. Further, the air-cooled engines of Patent Documents 2 and 3 are configured such that the lubricating oil lubricated by the valve operating device of the valve chamber provided in the cylinder head flows down along the wall portion of the cylinder block.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 8-260960

[Patent Document 2] Japanese Patent Laid-Open No. Hei 10-54296

[Patent Document 3] Japanese Patent Laid-Open No. Hei 11-101112

The present invention provides an air-cooled engine, a cylinder block member for an air-cooled engine, and a vehicle equipped with an air-cooled engine, which can improve the cooling efficiency, particularly the cooling efficiency at the initial sliding of the piston portion.

The present invention can adopt the following constitution.

(1) An air-cooled engine comprising a piston portion and a cylinder block portion having a sliding surface on which the piston portion slides, wherein the cylinder block portion includes a heat radiating portion provided on an outer surface of the cylinder block portion. Further, the metal body containing Al is formed, and at least the inner peripheral portion of the cylinder body portion including the sliding surface is formed of an Al alloy having a Si content of 16% by mass or more, and substantially parallel lines are formed on the sliding surface. a primary-shaped Si crystal grain having an average crystal grain size of 8 μm or more and 50 μm or less is exposed in contact with the piston portion, and is formed between the plurality of linear grooves and is an Al alloy base material and the piston The Al contact portion in contact with the portion is exposed to the sliding surface between two adjacent Si crystal grains adjacent to each other, and Al in the cylinder block portion is physically continuous from the Al contact portion to the heat dissipating portion.

In the configuration of (1), the cylinder block portion includes a metal containing Al, and the inner peripheral portion including at least the sliding surface of the cylinder block portion is formed of an Al alloy having a Si content of 16% by mass or more. The average crystal grain size of the primary Si crystal grains is 8 μm or more and 50 μm or less. In the sliding surface, a plurality of substantially parallel grooves are formed, and the primary Si crystal grains are exposed in contact with the piston portion. From the viewpoint of bearing the load of the piston portion, the primary Si crystal grains are appropriately large. Small and properly distributed on the sliding surface. In this case, the Al contact portion is exposed to the sliding surface so as to be in contact with the piston portion between the two primary Si crystal grains adjacent to each other. Therefore, the primary crystal Si crystal having a hardness higher than that of the Al contact portion receives the load of the piston portion. Therefore, it is easy to reduce the load that the Al contact portion receives from the piston portion. Further, since the sliding surface forms a plurality of substantially linear grooves, the lubricating oil can be uniformly held on the sliding surface, and the uniformity of dispersion of the lubricating oil on the sliding surface is improved. In this case, since the Al contact portion is formed between the plurality of linear grooves, the supply of the lubricating oil on the surface of the Al contact portion is facilitated. According to the above reason, according to the configuration of (1), the piston portion can be brought into contact with the Al contact portion while suppressing the occurrence of the drag caused by the sliding of the Al contact portion and the piston portion. Further, the Al in the cylinder body portion is physically continuous from the Al contact portion to the heat radiating portion (for example, a heat sink) provided on the outer surface of the cylinder block portion. That is, the cylinder body portion has a heat conduction path including Al from the Al contact portion to the heat dissipation portion. Therefore, the heat received by the Al contact portion from the piston portion is efficiently conducted from the Al contact portion to the heat radiating portion, and is radiated from the heat radiating portion. Therefore, the cooling efficiency of the air-cooled engine, particularly the cooling efficiency at the initial sliding of the piston portion, can be improved. Further, when the piston portion is initially slid, there is a case where the fusion of the lubricating oil to the sliding surface is insufficient. If the cooling efficiency is insufficient, the cylinder body strain or the sliding surface may be dragged due to the high temperature. Therefore, the cooling efficiency at the initial sliding of the piston portion is important for the air-cooled engine.

(2) An air-cooled engine comprising: a piston portion; and a cylinder block portion having a sliding surface on which the piston portion slides, wherein the cylinder block portion includes a heat radiating portion provided on an outer surface of the cylinder block portion, Further, the metal containing Al is formed, and at least the inner peripheral portion of the cylinder portion including the sliding surface is formed of a high-alloy die-casting alloy having an Si content of 16% by mass or more, and is substantially parallel to the sliding surface. a plurality of linear grooves, the primary Si crystal grains being exposed in contact with the piston portion, formed between the plurality of linear grooves and being an Al alloy base material and the piston portion The contacted Al contact portion is exposed to the sliding surface between the two primary Si crystal grains adjacent to each other, and the Al in the cylinder block portion is physically continuous from the Al contact portion to the heat radiating portion.

According to the configuration of (2), the cylinder block portion includes a metal containing Al, and the inner peripheral portion including at least the sliding surface of the cylinder block portion is formed of a high-altitude die-casting, and is formed of an Al alloy having a Si content of 16% by mass or more. In the sliding surface, a plurality of substantially parallel grooves are formed, and the primary Si crystal grains are exposed in contact with the piston portion. From the viewpoint of bearing the load of the piston portion, the primary Si crystal grains have an appropriate size and are appropriately distributed on the sliding surface. In this case, the Al contact portion is exposed to the sliding surface so as to be in contact with the piston portion between the two primary Si crystal grains adjacent to each other. Therefore, the primary crystal Si crystal having a hardness higher than that of the Al contact portion receives the load of the piston portion. Therefore, it is easy to reduce the load that the Al contact portion receives from the piston portion. Further, since the sliding surface forms a plurality of substantially linear grooves, the lubricating oil can be uniformly held on the sliding surface, and the uniformity of dispersion of the lubricating oil on the sliding surface is improved. In this case, since the Al contact portion is formed between the plurality of linear grooves, the supply of the lubricating oil on the surface of the Al contact portion is facilitated. According to the above reason, according to the configuration of (2), the piston portion can be brought into contact with the Al contact portion while suppressing the occurrence of the drag caused by the sliding of the Al contact portion and the piston portion. Further, the Al in the cylinder body portion is physically continuous from the Al contact portion to the heat radiating portion (for example, a heat sink) provided on the outer surface of the cylinder block portion. That is, the cylinder body portion has a heat conduction path including Al from the Al contact portion to the heat dissipation portion. Therefore, the heat received by the Al contact portion from the piston portion is efficiently conducted from the Al contact portion to the heat radiating portion, and is radiated from the heat radiating portion. Therefore, the cooling efficiency of the air-cooled engine, particularly the cooling efficiency at the initial sliding of the piston portion, can be improved.

(3) The air-cooled engine according to (1) or (2), wherein the portion other than the inner peripheral portion of the cylinder block portion includes the heat radiating portion, and is physically continuous with the inner peripheral portion, and includes An Al alloy having a Si content which is the same as or smaller than the Si content of the inner peripheral portion, and the Si content of the inner peripheral portion, The Al alloy base material in the cylinder block portion is physically continuous from the Al contact portion to the heat radiating portion.

According to the configuration of (3), the Al alloy base material is physically continuous from the Al contact portion to the heat radiating portion. That is, the cylinder body portion has a heat conduction path that is continuous from the Al contact portion to the heat dissipation portion and that includes the Al alloy base material. Therefore, the heat received by the Al contact portion from the piston portion is efficiently conducted from the Al contact portion to the heat radiating portion, and is radiated from the heat radiating portion. Therefore, the cooling efficiency of the air-cooled engine, particularly the cooling efficiency at the initial sliding of the piston portion, can be improved.

(4) The air-cooled engine according to any one of (1) to (3), wherein the Al contact portion is exposed between the two primary Si crystal grains adjacent to each other on the sliding surface, and the heat radiating portion One piece is formed.

According to the configuration of (4), the Al alloy base material is physically continuous from the Al contact portion to the heat radiating portion. That is, the cylinder body portion has a heat conduction path that is continuous from the Al contact portion to the heat dissipation portion and that includes the Al alloy base material. Therefore, the heat received by the Al contact portion from the piston portion is efficiently conducted from the Al contact portion to the heat radiating portion, and is radiated from the heat radiating portion. Therefore, the cooling efficiency of the air-cooled engine, particularly the cooling efficiency at the initial sliding of the piston portion, can be improved.

(5) The air-cooled engine of any one of (1) to (4), wherein the plurality of linear grooves are such that a plurality of linear grooves pass between the primary Si grains. form.

According to the configuration of (5), since a plurality of linear grooves are formed at a narrow interval, the lubricating oil can be uniformly maintained between the primary Si grains. Therefore, the uniformity of dispersion of the lubricating oil on the sliding surface can be improved, and the uniformity of the oil film formed on the sliding surface can be improved. Therefore, abrasion and the like of the Al contact portion can be effectively suppressed. The Al contact portion can be brought into contact with the piston portion while suppressing the occurrence of the drag. Therefore, the heat received by the Al contact portion from the piston portion is more efficiently conducted from the Al contact portion to the heat radiating portion, and is radiated from the heat radiating portion. As a result, the cooling efficiency of the air-cooled engine, particularly the cooling efficiency at the initial sliding of the piston portion, can be further improved.

(6) The air-cooled engine of (5), wherein the pitch is smaller than an average crystal grain size of the primary Si crystal grains.

According to the configuration of (6), a plurality of substantially linear grooves are formed in a narrower interval. The uniformity of dispersion of the lubricating oil can be further improved. As a result, the cooling efficiency of the air-cooled engine, particularly the cooling efficiency at the initial sliding of the piston portion, can be further improved.

(7) The air-cooled engine according to any one of (1) to (4), wherein the cylinder block portion further comprises the above-described primary Si in addition to the primary Si crystal grains and the Al alloy base material. a eutectic Si crystal grain having an average crystal grain size smaller than an average crystal grain size of the crystal grain, wherein the plurality of linear grooves have a range of the eutectic Si crystal grain size in a particle size distribution of Si crystal grains of the cylinder block portion a depth of 1/3 or more of the upper limit value, and at least 1/4 of the upper side of the sliding surface is formed to be wider than the average crystal grain size of the primary Si crystal grains, and has a passing distance A portion between the above primary Si grains.

According to the constitution of (7), the substantially parallel plurality of linear grooves are formed to be wider than the average crystal grain size of the primary Si crystal grains, whereby the uniformity of dispersion of the lubricating oil on the sliding surface can be improved. . Thereby, the uniformity of the oil film formed on the sliding surface can be improved. Further, 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 particle size distribution of the Si crystal grains of the cylinder block portion, so that a sufficient amount of lubrication can be provided. The oil remains in the tank. Therefore, the oil film crack on the sliding surface can be suppressed. Further, a plurality of linear grooves have portions passing between adjacent primary Si crystal grains. As a result, since the primary Si crystal grains are subjected to the load of the piston portion, abrasion of the sliding surface (Al alloy base material) adjacent to both sides of the groove can be suppressed, and the lubricating oil in the groove can be easily held. Thus, in the constitution of (7), the uniformity of the oil film formed on the sliding surface can be improved, and a sufficient amount of lubricating oil can be maintained. Therefore, abrasion and the like of the Al contact portion can be effectively suppressed. The Al contact portion can be brought into contact with the piston portion while suppressing the occurrence of the drag. Therefore, the heat received by the Al contact portion from the piston portion is more efficiently conducted from the Al contact portion to the heat radiating portion, and is radiated from the heat radiating portion. The result can be further The cooling efficiency of the air-cooled engine, especially the cooling efficiency of the initial sliding of the piston portion, is improved.

(8) The air-cooled engine of (7), wherein the plurality of linear grooves have an upper limit value of a range of the eutectic Si crystal grain size in a particle size distribution of Si crystal grains of the cylinder block portion. 1/3 or more and less than the depth of the upper limit of the range of the eutectic Si crystal grain size.

According to the configuration of (8), a sufficient and appropriate amount of lubricating oil can be held in a plurality of linear grooves. Therefore, the uniformity of the oil film is further improved. As a result, the cooling efficiency of the air-cooled engine, particularly the cooling efficiency at the initial sliding of the piston portion, can be further improved.

(9) The air-cooled engine of (7) or (8), wherein the piston portion includes: a piston body; and a piston ring portion including a plurality of piston rings disposed on an outer circumference of the piston body; the plurality of wires The groove is formed to be wider than the average crystal grain size of the primary Si crystal grains and smaller than the distance from the lower end of the piston ring portion to the upper end of the piston ring portion in the reciprocating direction of the piston portion.

According to the configuration of (9), a sufficient and appropriate amount of the lubricating oil can be held in a plurality of linear grooves. Therefore, the uniformity of the oil film is further improved. As a result, the cooling efficiency of the air-cooled engine, particularly the cooling efficiency at the initial sliding of the piston portion, can be further improved.

(10) The air-cooled engine according to any one of (1) to (9), wherein at least a part of the primary Si crystal grains exposed on the sliding surface is broken, and is formed in the primary Si crystal by being broken The surface is exposed on the sliding surface.

According to the configuration of (10), the surface formed on the primary Si crystal grains (hereinafter also referred to as a broken cross section) due to being broken functions as an oil reservoir. The fracture surface of the primary Si crystal has irregularities, so that the amount of lubricating oil that can be maintained in the oil reservoir is large. The opening area of the oil reservoir is, for example, the same as the sectional area of the primary Si crystal grains. The depth of the oil reservoir is, for example, smaller than the diameter of the primary Si crystal grains. Thus, the oil reservoir containing the fractured section of the primary Si crystal is substantially A plurality of parallel linear grooves are formed together on the sliding surface. Therefore, the amount of the lubricating oil can be increased while maintaining the uniformity of the dispersion of the lubricating oil. As a result, the cooling efficiency of the air-cooled engine, particularly the cooling efficiency at the initial sliding of the piston portion, can be further improved.

(11) A cylinder block member comprising the cylinder block portion included in the air-cooled engine according to any one of (1) to (10).

According to the configuration of (11), a cylinder block member capable of improving the cooling efficiency, particularly the cooling efficiency at the initial sliding of the piston portion, is provided.

(12) A vehicle comprising the air-cooled engine of any one of (1) to (10).

According to the configuration of (12), it is possible to provide a vehicle including an air-cooled engine that can improve the cooling efficiency, particularly the cooling efficiency at the initial sliding of the piston portion.

According to the present invention, it is possible to improve the cooling efficiency, particularly the cooling efficiency at the initial sliding of the piston portion.

1‧‧‧ primary crystal Si grain

2‧‧‧ Eutectic Si grains

3‧‧‧Al alloy base metal

4‧‧‧Line slot

4a‧‧‧first linear groove

4b‧‧‧Second linear groove

5a‧‧‧ broken section

5b‧‧‧Oil Accumulation Department

8‧‧‧Line slot

8a‧‧‧First linear groove

8b‧‧‧second linear groove

100‧‧‧Cylinder body (cylinder block)

101‧‧‧Sliding surface

102‧‧‧Cylinder bore

103‧‧‧ cylinder wall

103a‧‧‧Outer surface

106‧‧‧Al contact

107‧‧‧Dissipation Department

108‧‧‧Si contact

110‧‧‧ crankcase

111‧‧‧ crankshaft

112‧‧‧ crank pin

113‧‧‧ crank arm

114‧‧‧Roller bearings (rolling bearings)

122‧‧‧Piston Department

122a‧‧‧Piston body

122b‧‧‧Piston ring

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

Upper end of 122m‧‧‧ (of piston ring 122b)

122n‧‧‧ (lower piston ring portion 122b) lower end

123‧‧‧Piston pin

130‧‧‧Cylinder head

132‧‧‧Intake 埠

133‧‧‧Exhaust gas

134‧‧‧Intake valve

135‧‧‧Exhaust valve

140‧‧‧ Connecting rod

144‧‧‧ big end

150‧‧‧ engine

301‧‧‧ ontology framework

302‧‧‧ head tube

303‧‧‧ Front fork

304‧‧‧ front wheel

305‧‧‧Handle

306‧‧‧post frame

307‧‧‧fuel tank

308a‧‧‧Main seat

308b‧‧‧ rear seat

309‧‧‧ rear arm

310‧‧‧ Rear wheel

312‧‧‧Exhaust pipe

313‧‧‧Muffler

315‧‧ ‧transmission machine

316‧‧‧ Output shaft

317‧‧‧Drive sprocket

318‧‧‧Chain

319‧‧‧ Rear wheel sprocket

L‧‧‧down direction

P‧‧‧ gap

R‧‧‧Reciprocating direction of the piston

U‧‧‧Up direction

Fig. 1 is a cross-sectional view schematically showing an air-cooled engine 150 of the first embodiment.

Fig. 2 is a side view schematically showing the piston portion 122 of the air-cooled engine 150 of the first embodiment.

Fig. 3 is a partially enlarged plan view schematically showing the sliding surface 101 of the cylinder block 100 of the first embodiment.

Fig. 4 is a partially enlarged cross-sectional view schematically showing the sliding surface 101 of the cylinder block portion 100 of the first embodiment.

Fig. 5 is a graph showing an example of a preferable particle size distribution of Si crystal grains.

Fig. 6 is a partially enlarged plan view schematically showing the sliding surface 101 of the cylinder block portion 100 of the second embodiment.

Fig. 7 is a partially enlarged cross-sectional view schematically showing the sliding surface 101 of the cylinder block portion 100 of the second embodiment, in (a) and (b).

Fig. 8 is a side view schematically showing a locomotive having the air-cooled engine 150 shown in Fig. 1 .

The inventors of the present invention have made an effort to improve the cooling efficiency of the air-cooled engine, and have focused on the thermal conductivity of Al. Al has a high thermal conductivity, but there is a drag due to the contact of the piston portion when the piston portion reciprocates. Therefore, in the air-cooled engine having the cylinder body made of metal containing Al, the Al portion is prevented from coming into contact with the piston portion. For example, in the cylinder body made of an Al alloy which is produced by high-pressure die casting in a relatively high Si content, the sliding surface is processed so that the primary Si crystal grains are exposed in a floating island shape. In the sliding surface, the contact between the piston ring and the Al alloy base material is suppressed, and the recess between the Si crystal grains functions as an oil reservoir. Thereby, it is possible to suppress the drag.

However, the inventors of the present invention have diligently studied in order to improve the cooling efficiency of the air-cooled engine, thereby obtaining the following findings.

In the cylinder body portion made of an Al alloy which is relatively high in Si content and manufactured by high pressure die casting, the primary Si crystal grains have an appropriate size and are appropriately distributed on the sliding surface from the viewpoint of bearing the load of the piston portion. Therefore, by uniformly maintaining a sufficient amount of lubricating oil between the primary Si grains by the sliding surface, the uniformity of the oil film formed on the sliding surface is improved, and even if the Al alloy base material is in contact with the piston portion, it is not easy. Produce a drag. That is, the Al alloy base material can be allowed to come into contact with the piston portion. Therefore, the Al alloy base material can be brought into contact with the piston portion while suppressing the occurrence of the drag. Further, Al is physically continuous from the Al contact portion of the Al alloy base material in contact with the piston portion to the heat dissipating portion provided on the outer surface of the cylinder block portion, whereby the Al contact portion can receive heat from the piston portion from the Al portion. The contact portion is efficiently conducted to the heat radiating portion and radiated from the heat radiating portion. As a result, the cooling efficiency of the air-cooled engine, particularly the cooling efficiency at the initial sliding of the piston portion, can be improved.

The present invention has been made based on the above findings, that is, contrary to the previous design ideas. Specifically, the present invention suppresses the generation of the drag while making the Al contact The contact portion is in contact with the piston portion, whereby the radiation from the heat radiating portion can be realized, and the inner peripheral surface (sliding surface) from the piston portion to the outer peripheral surface (heat radiating portion) can be efficiently realized. Conductive heat transfer. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<<First embodiment>>

<Air-cooled engine>

Fig. 1 is a cross-sectional view schematically showing an air-cooled engine 150 according to a first embodiment of the present invention. R is a direction in which the piston portion 122 reciprocates. The U system indicates the upward direction, that is, the direction from the cylinder block 100 toward the cylinder head 130. L indicates the downward direction, that is, the direction from the cylinder block 100 toward the crankcase 110. The air-cooled engine 150 is a forced air cooling type and has a cooling fan (not shown). The cooling fan is configured to transmit the rotation of the crankshaft 111. The air-cooled engine of the present invention is not limited to the forced air cooling type, and may be a natural air cooling type. The air-cooled engine of the present embodiment is a single-cylinder engine. However, in the present invention, the number of cylinders of the air-cooled engine is not particularly limited. The air-cooled engine of the present embodiment is a four-stroke engine, but may be a two-stroke engine.

The air-cooled engine 150 has a crankcase 110, a cylinder block 100, and a cylinder head 130. In the present embodiment, the cylinder block portion 100 is separated from the crank case 110. However, in the present invention, the cylinder block portion 100 and the crank case 110 may be integrated.

A crankshaft 111 is housed in the crankcase 110. The crank shaft 111 has a crank pin 112 and a crank arm 113.

A cylinder block 100 is disposed above the crankcase 110. The cylinder block portion 100 includes a cylinder wall 103. The cylinder wall 103 is formed to define the cylinder bore 102. A heat radiating portion 107 (heat sink) is provided on the outer peripheral surface 103a of the cylinder wall 103. The heat radiating portion 107 is a projecting body formed on the outer peripheral surface 103a in order to increase the contact area with air. The heat radiating portion 107 is not limited to a plurality of plate-like bodies as shown in Fig. 1 . Examples of the heat radiating portion include a rod-shaped body and a needle-shaped body. Further, the outer circumferential surface 103a of the cylinder wall 103 is formed in a bellows shape or a wave shape, etc. Therefore, the outer peripheral surface 103a may have the heat radiating portion 107.

A piston portion 122 is inserted into the cylinder bore 102 of the cylinder block portion 100. The piston portion 122 slides in the cylinder bore 102 in a state of being in contact with the sliding surface 101 of the cylinder block 100 (see FIG. 2). The piston portion 122 is formed of, for example, an Al alloy (typically an Al alloy containing Si). The piston portion 122 is formed by forging as disclosed in the specification of U.S. Patent No. 6,205,836. The piston portion 122 can also be formed by casting.

A cylinder sleeve is not provided in the cylinder bore 102. The inner surface of the cylinder wall 103 of the cylinder block 100 is not plated. In the present embodiment, the cylinder sleeve is not required, so that the simplification of the manufacturing steps of the air-cooled engine 150, the weight reduction of the air-cooled engine 150, and the improvement of the cooling performance can be achieved. Further, since it is not necessary to plate the inner surface of the cylinder wall 103, it is also possible to reduce the manufacturing cost.

A cylinder head 130 is disposed above the cylinder block 100. The cylinder head 130 forms a combustion chamber 131 together with the piston portion 122 of the cylinder block 100. The cylinder head 130 has an intake port 132 and an exhaust port 133. An intake valve 134 for supplying a mixed gas to the combustion chamber 131 is provided in the intake port 132, and an exhaust valve 135 for exhausting the inside of the combustion chamber 131 is provided in the exhaust port 133.

The piston portion 122 and the crank shaft 111 are coupled by a link 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 link 140, and the crank pin 112 of the crank shaft 111 is inserted into the through hole of the large end portion 144, whereby the piston is inserted The portion 122 is coupled to the crank shaft 111. A roller bearing (rolling bearing) 114 is provided between the inner circumferential surface of the through hole of the large end portion 144 and the crank pin 112. Further, the air-cooled engine 150 does not have an oil pump that forcibly supplies the lubricating oil, but the air-cooled engine of the present invention may be provided with an oil pump.

FIG. 2 is a side view schematically showing the piston portion 122 of the air-cooled engine 150 shown in FIG. 1 .

The cylinder wall 103 included in the cylinder block portion 100 has a sliding surface 101 on the inner circumferential side of the cylinder wall 103, and has a peripheral surface on the outer circumferential side of the cylinder wall 103. 103a. The cylinder wall 103 is integrally formed with the heat radiating portion 107. A piston portion 122 is provided in the cylinder bore 102 defined by the cylinder wall 103. The piston portion 122 includes a piston main body 122a and a piston ring portion 122b. The piston body 122a has a piston pin 123 that is inserted into a through hole of the link 140. The piston ring portion 122b includes three (plurality) piston rings 122c, 122d, and 122e provided on the outer circumference of the piston body 122a.

The piston ring 122c is also referred to as a top ring and is embedded in a top ring groove 122f provided on the outer circumference of the piston body 122a. The piston ring 122d is also referred to as a second ring and is embedded in a second ring groove 122g provided on the outer circumference of the piston body 122a. The piston ring 122e is also referred to as an oil ring and is embedded in an oil ring groove 122h provided on the outer circumference of the piston body 122a. The top ring 122c, the second ring 122d, and the oil ring 122e are spaced apart from each other in the reciprocating direction R of the piston portion 122, and are sequentially disposed from the top to the bottom. That is, in the present embodiment, the upper end 122m of the piston ring portion 122b in the reciprocating direction R of the piston portion 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. In particular, the piston ring portion 122b (piston rings 122c, 122d, 122e) of the piston portion 122 is in contact with the sliding surface 101 of the cylinder wall 103. Further, in the present embodiment, the piston ring portion 122b includes three piston rings, but the number of the piston rings constituting the piston ring portion 122b is not particularly limited.

The cylinder block portion 100 is formed of an Al alloy containing Si. Specifically, it is formed of an Al alloy having a Si content of 16% by mass or more. The Al alloy preferably contains 73.4% by mass or more and 79.6% by mass or less of Al, 16% by mass or more and 24% by mass or less of Si, and 2.0% by mass or more and 5.0% by mass or less of copper. The wear resistance and strength of the cylinder block 100 can be improved. Further, the Si content is also preferably 18% by mass or more. The Si content is also preferably 22% by mass or less. The Al alloy preferably contains 50 ppm by mass or more and 200 ppm by mass or less of phosphorus, and 0.01% by mass or less of calcium. When the Al alloy contains 50 ppm by mass or more and 200 ppm by mass or less of phosphorus, the Si crystal grains can be suppressed from being coarsened, so that Si crystal grains can be uniformly dispersed in the alloy. In addition, by setting the calcium content of the Al alloy to 0.01% by mass or less, the effect of refining the Si crystal grains of phosphorus can be secured, and a metal structure excellent in abrasion resistance can be obtained.

The cylinder block portion 100 includes a sliding surface 101 to which the piston portion 122 (see FIG. 1) is in contact. The sliding surface 101 is a surface (i.e., an inner peripheral surface) of the cylinder bore 103 side of the cylinder wall 103. In other words, the sliding surface 101 is the innermost surface of the inner circumferential surface of the cylinder wall 103 located in the radial direction of the cylinder block 100. Further, in the present invention, the sliding surface 101 is in contact with the piston portion 122, and the sliding surface 101 is in contact with the piston portion 122 via an oil film formed of lubricating oil.

In the present embodiment, the following linear grooves 4 are formed over the entire sliding surface 101 (see Fig. 3). In the present invention, the region in which the linear groove 4 is formed on the sliding surface 101 is not particularly limited. The area where the linear groove 4 is formed on the sliding surface 101 may be, for example, at least 1/4 of the upper side of the sliding surface 101. The region in which the linear groove 4 is formed on the sliding surface 101 may be, for example, at least a region of 1/4 of the upper side of the sliding surface 101 and a region of 1/4 of the lower side. The area of the upper side of the sliding surface 101 is 1/4 of the area closest to the cylinder head when the entire sliding surface 101 is equally divided into four portions along the sliding direction of the piston (the central axis direction of the cylinder bore 102). . The portion 1/4 of the lower side of the sliding surface 101 refers to the region located on the side closest to the crankcase.

Fig. 3 is a plan view showing the sliding surface 101 of the cylinder block 100 of the first embodiment in an enlarged manner and schematically shown. R is a direction in which the piston portion 122 reciprocates. Fig. 4 is a cross-sectional view showing the sliding surface 101 of the cylinder block 100 of the first embodiment in an enlarged manner and schematically shown. Furthermore, Fig. 4 is a cross-sectional view along the direction R. In Fig. 4, only the first linear groove 4a in the linear groove 4 is shown for the sake of convenience. Further, the arrow of the two-dot chain line shown in Fig. 4 is an arrow for explaining the flow of heat.

On the sliding surface 101, a plurality of primary Si crystal grains 1, a plurality of eutectic Si crystal grains 2, and an Al alloy base material 3 are exposed. When the molten metal of the Al-Si-based alloy having a hypereutectic composition is cooled, the Si crystal grains which are initially precipitated are referred to as "primary Si crystal grains". The Si grains deposited next are referred to as "eutectic Si grains". The primary Si crystal grains 1 are relatively large, for example, have a granular shape. The eutectic Si grains 2 are relatively small, for example, have a needle shape. It is not necessary for all the eutectic Si grains 2 to have a needle shape. It is also possible that a part of the eutectic Si grains 2 have a granular shape. In this case, the acicular eutectic Si grains 2 in the plurality of eutectic Si grains 2 are the main crystal grains. Al alloy base material 3 contains solid solution of Al Matrix. The cylinder block portion 100 has a plurality of primary Si crystal grains 1, a plurality of eutectic Si crystal grains 2, and an Al alloy base material 3. A plurality of primary Si crystal grains 1 and a plurality of eutectic Si crystal grains 2 are dispersedly present in the Al alloy base material 3.

The average crystal grain size of the primary Si crystal grains 1 is, for example, 8 μm or more and 50 μm or less. Therefore, a sufficient number of primary Si grains 1 exist per unit area of the sliding surface 101. Therefore, the load applied to each of the primary Si grains 1 during the operation of the air-cooled engine 150 is relatively small. The destruction of the primary Si crystal 1 during operation of the air-cooled engine 150 can be suppressed. Further, since the portion of the primary Si crystal grains 1 buried in the Al alloy base material 3 is sufficiently large, the fall of the primary Si crystal grains 1 can be reduced. Therefore, the abrasion of the sliding surface 101 due to the falling primary Si crystal grains 1 can also be suppressed. On the other hand, when the average crystal grain size of the primary Si crystal grains 1 is less than 8 μm, the portion of the primary Si crystal grains 1 buried in the Al alloy base material 3 is small. Therefore, when the air-cooled engine 150 is operated, the falling of the primary Si crystal grains 1 easily occurs. Since the primary crystal Si crystals which have fallen off function as polishing particles, the sliding surface 101 is largely worn. Further, when the average crystal grain size of the primary Si crystal grains 1 exceeds 50 μm, the number of primary Si crystal grains 1 per unit area of the sliding surface 101 is small. Therefore, there is a case where a large load is applied to each of the primary Si crystal grains 1 when the air-cooled engine 150 is operated, and the primary Si crystal grains 1 are broken. The fragment of the primary crystal Si crystal 1 that has been destroyed functions as polishing particles, so that the sliding surface 101 is largely worn. Further, the average crystal grain size of the primary Si crystal grains 1 is preferably 12 μm or more.

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

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

Here, the particle size distribution of the Si crystal grains in the cylinder block portion 100 will be described.

Fig. 5 is a graph showing an example of a preferable particle size distribution of Si crystal grains.

In the graph shown in FIG. 5, Si crystal grains having a crystal grain size of 1 μm or more and 7.5 μm or less are eutectic Si crystal grains 2, and Si crystal grains having a crystal grain size of 8 μm or more and 50 μm or less are included. It is a primary Si grain 1. As described above, the Si crystal grains 1 and 2 of the cylinder block portion 100 preferably have a particle size distribution in which the crystal grain size is in the range of 1 μm or more and 7.5 μm or less and the crystal grain size is in the range of 8 μm or more and 50 μm or less. There are peaks respectively. The wear resistance and strength of the cylinder block 100 can be increased to a large extent.

Further, from the viewpoint of reinforcing the Al alloy base material 3 by the eutectic Si crystal grains 2, as shown in Fig. 7, it is preferable that the crystal grain size is in the range of 1 μm or more and 7.5 μm or less (source). The degree at the peak of the eutectic Si crystal grain 2 is 5 times or more the degree of the second peak (from the peak of the primary Si crystal grain 1) in the range of the crystal grain size of 8 μm or more and 50 μm or less.

In order to control the average crystal grain size of the primary Si crystal grains 1 and the eutectic Si crystal grains 2, the cooling rate of the portion to be the sliding surface 101 may be adjusted in the step of casting the molded body (step S1c described below). As a specific example, for example, by casting the portion to be the sliding surface 101 by cooling at a cooling rate of 4° C./sec or more and 50° C./sec or less, the average crystal grain of the primary Si crystal grains 1 can be obtained. When the diameter is 8 μm or more and 50 μm or less, and the average crystal grain size of the eutectic Si crystal grains 2 is 7.5 μm or less, the Si crystal grains 1 and 2 are precipitated.

Next, the linear groove 4 formed on the sliding surface 101 will be described.

As shown in FIGS. 3 and 4, a plurality of linear grooves 4 are formed on the sliding surface 101. In the present embodiment, the plurality of linear grooves 4 include a plurality of first linear grooves 4a and a plurality of second linear grooves 4b. The plurality of first linear grooves 4a have a side from the upper left toward the lower right in FIG. The shape of the extension is substantially parallel to each other. The plurality of first linear grooves 4a are formed in a stripe pattern on the sliding surface 101. The plurality of second linear grooves 4b have shapes extending in the direction from the upper right toward the lower left in FIG. 3, and are substantially parallel to each other. The plurality of second linear grooves 4b are formed in a stripe pattern on the sliding surface 101. The plurality of first linear grooves 4a and the plurality of second linear grooves 4b are not parallel to each other but intersect. Thereby, the plurality of linear grooves 4 are formed in a lattice pattern on the sliding surface 101.

At least two or more linear grooves 4 of the plurality of linear grooves 4 are substantially parallel to each other. One of the plurality of linear grooves 4 may be intersected with the remaining linear groove 4 (the second linear groove 4b). It is also possible that all of the plurality of linear grooves 4 are formed so as not to intersect each other, and are substantially parallel. By "substantially parallel" is meant that adjacent linear grooves 4 extend in a non-intersecting manner. That is, the meaning of "substantially parallel", for example, even if the linear grooves 4 are strictly not parallel due to errors or variations in the formation of the linear grooves 4, it can also be interpreted as phase in the present invention. The adjacent linear grooves 4 are substantially parallel. Further, the sliding surface 101 has a group of the first linear grooves 4a and the second linear grooves 4b as a group of mutually parallel linear grooves, but in the present invention, the number of the linear grooves which are parallel to each other is There is no special limit. The slots belonging to different groups cross each other. The pattern formed by the plurality of linear grooves 4 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 4 may be a stripe pattern formed by the first linear groove 4a or the second linear groove 4b, or may be a polygonal lattice pattern such as a triangular lattice pattern. An example of a square lattice pattern is a polygonal lattice pattern. Furthermore, the spacing between the grooves of the stripe pattern and the lattice pattern does not have to be fixed.

In the present embodiment, the plurality of linear grooves 4 are formed in a regular pattern (a stripe pattern or a polygonal lattice pattern). In the present embodiment, the Al alloy base material 3 is exposed to the sliding surface 101 together with the primary ring Si crystal 1 in contact with the piston ring portion 122b (the piston portion 122) in the regular pattern. The sliding surface 101 formed with the linear grooves 4 formed into a regular pattern is exposed to the irregular surface of the prior surface (the Si crystal grains are exposed in a floating island shape) The sliding surface) can further improve the uniformity of dispersion of the lubricating oil. As a result, in the present embodiment, the uniformity of the oil film formed on the sliding surface 101 is high. In the following, except for the case where the first linear groove 4a and the second linear groove 4b are distinguished, the description about the linear groove 4 is also about the first linear groove 4a and the second linear groove 4b. The description of both.

As shown in FIG. 3, the planar shape of the linear groove 4 has a linear shape in plan view. However, in the present invention, the planar shape of the linear groove 4 is not limited to a linear shape as long as it has a linear shape that does not extend so as to intersect the linear grooves 4 that are substantially parallel to each other. That is, the linear groove 4 may also have a curved shape. The linear groove 4 may have a curved portion and a linear portion. Further, the linear groove 4 may have a curved portion. Further, the planar shape of the plurality of linear grooves 4 may be different depending on the linear grooves 4. It is also possible that all of the linear grooves 4 have the same or substantially the same shape in plan view. Further, each of the plurality of linear grooves 4 is not necessarily formed so that the entire area of the sliding surface 101 is continuous. Each of the plurality of linear grooves 4 does not have to extend to the end edge of the sliding surface 101. Each of the plurality of linear grooves 4 may also have a portion interrupted on the sliding surface 101.

Regarding the width of the linear groove 4, the width of the linear groove 4 is not particularly limited. The width of the linear groove 4 is preferably equal to or less than the maximum value of the range of the particle diameter of the primary Si crystal grains 1 in the particle size distribution of the cylinder block portion 100. The width of the linear groove 4 is also preferably about 10 μm or less. Further, the width of the linear groove 4 is preferably equal to or larger than the minimum value of the range of the particle diameter of the eutectic Si crystal grain 2 in the particle size distribution of the cylinder block portion 100. The width of the linear groove 4 is also preferably about 5 μm or more. As shown in Fig. 3, the linear groove 4 has a fixed width, but the present invention is not limited to this example. The linear grooves 4 may also have different widths depending on the position. Further, the width of the plurality of linear grooves 4 may be different depending on the linear grooves 4. It is also possible for all of the linear grooves 4 to have the same width or substantially the same width.

Regarding the depth of the linear groove 4, in the present embodiment, the linear groove 4 has a depth of 0.1 μm or more and less than 2.0 μm. However, in the present invention, the depth of the linear groove 4 is not particularly limited. Further, in the present invention, the linear groove 4 has a thickness of 0.1 μm or more and less than 2.0 μm. In the case of the depth, in addition to the linear groove 4, a groove having a depth deeper than the depth of the linear groove 4 (for example, a depth of 2.0 μm or more) 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 (for example, the linear grooves 8 described below) may be formed on the sliding surface. Further, the depth of the linear groove 4 may be 1.5 μm or less. The depth of the linear groove 4 may be 0.5 μm or more.

The cross-sectional shape of the linear groove 4 is a shape in which the width of the linear groove 4 becomes smaller as the depth of the linear groove 4 becomes larger. The cross-sectional shape of the linear groove 4 is a cross-sectional shape of the linear groove 4 on a plane perpendicular to the direction in which the linear groove 4 extends. Further, in the present invention, the cross-sectional shape of the linear groove 4 is not particularly limited. The cross-sectional shape of the linear groove 4 may be, for example, a substantially V shape as shown in FIG. 4 or a substantially U shape. Further, the cross-sectional shapes of the linear grooves 4 need not be the same. The cross-sectional shape of the linear groove 4 may vary depending on the position, or may vary depending on the linear groove 4. Further, the portion (mountain) between the linear grooves 4 is not necessarily a flat surface as shown in Figs. 3 and 4 . The portion between the linear grooves 4 may be an inclined surface or a ridge line.

Regarding the distance between the first linear grooves 4a, a plurality of substantially linear first grooves 4a are formed such that a plurality of first linear grooves 4a are formed between the primary Si grains 1 by a distance therebetween. For example, as shown in FIG. 4, a plurality of first linear grooves 4a pass through the gap P between the primary Si crystal grains 1. Further, on the sliding surface 101, a portion between the plurality of first linear grooves 4a is exposed in contact with the piston portion 122 (see Figs. 1 and 2). The portion of the sliding surface 101 that is in contact with the piston portion 122 is adjacent to the first linear groove 4a in a plan view, so that the supply of the lubricating oil to the sliding surface 101 can be smoothly performed. The distance between the first linear grooves 4a is preferably in the range of the eutectic Si crystal grains 2 included in the particle size distribution of the Si crystal grains of the cylinder block portion 100. The distance between the first linear grooves 4a is preferably 5 μm or more. The distance between the first linear grooves 4a is preferably 10 μm or less. In Fig. 3, the distance between one of the adjacent first linear grooves 4a is fixed regardless of the position, but the present invention is not limited to this example. That is, the distance between one of the adjacent pairs of the first linear grooves 4a does not have to be fixed. For example, the first linear grooves 4a adjacent to each other are formed in a meandering manner, and the distance between the first linear grooves 4a may be different depending on the position. Furthermore, Although the above description has been made regarding the first linear groove 4a, the description of the second linear groove 4b is the same as that of the first linear groove 4a, and thus the description thereof will be omitted.

In the present embodiment, at least one of the linear grooves 4 is formed by passing the primary Si crystal grains 1 by breaking the primary Si crystal grains 1. That is, at least one of the linear grooves 4 is formed to pass through the exposed surface of the primary Si crystal grains 1. Thereby, the uniformity of dispersion of the lubricating oil on the sliding surface 101 can be further improved. The invention is not limited to this example.

In the present embodiment, as shown in FIG. 4, the primary Si crystal grains 1 having the fractured surface 5a are exposed on the sliding surface 101. That is, in the present embodiment, at least a part of the primary Si crystal grains 1 exposed on the sliding surface 101 is broken, and is destroyed, so that the surface formed on the primary Si crystal grains 1 (that is, the fractured surface 5a) is exposed. Sliding surface 101. Thereby, the oil reservoir portion 5b is formed on the sliding surface 101. Since the fractured section of the primary Si crystal 1 has irregularities, the amount of lubricating oil that can be maintained by the oil reservoir 5b is large. The opening area of the oil reservoir portion 5b is the same as the cross-sectional area of the primary Si crystal grain 1 (the area exposed by the sliding surface 101). The depth of the oil reservoir 5b is smaller than the diameter of the primary Si crystal 1. The oil reservoir 5b including the fractured portion 5a of the primary Si crystal 1 is formed on the sliding surface 101 together with a plurality of substantially linear first grooves 4a. Therefore, the amount of lubricating oil can be increased while maintaining the uniformity of dispersion of the lubricating oil. It can suppress the grinding more effectively. The broken section 5a is formed when the surface processing of the cylinder block 100 is performed after casting of the cylinder block 100. Specifically, the fractured section 5a is formed, for example, when the primary Si crystal grains 1 are ground by a grindstone.

As shown in FIG. 4, the Al contact portion 106 is a portion where the Al alloy base material 3 is in contact with the piston ring portion 122b (piston portion 122). The Si contact portion 108 is a portion where the primary Si crystal grain 1 is in contact with the piston ring portion 122b (piston portion 122).

The Al contact portion 106 is formed between the plurality of first linear grooves 4a. The Al contact portion 106 is exposed to the sliding surface 101 between the two primary Si crystal grains 1 (Si contact portions 108) adjacent to each other. The Al contact portion 106 is a portion of the cylinder wall 103, and the cylinder wall 103 is integrally formed with the heat dissipation portion 107. That is, the Al contact portion 106 is integrally formed with the heat dissipation portion 107. Therefore, Al alloy base material The 3 series is physically continuous from the Al contact portion 106 that is in contact with the piston ring portion 122b (the piston portion 122) to the heat radiating portion 107. Therefore, as shown by the arrow of the chain link of FIG. 4, one part of the heat of the piston ring portion 122b (the piston portion 122) is conducted to the Al contact portion 106, passes through the cylinder wall 103, reaches the heat dissipating portion 107, and the self-heating portion 107 released. Therefore, the cooling efficiency of the air-cooled engine 150, in particular, the cooling efficiency at the initial sliding of the piston ring portion 122b (the piston portion 122) is improved.

Further, in the present embodiment, as shown in FIG. 4, a plurality of linear grooves 4 (the first linear grooves 4a and the second linear grooves 4b) are formed between the primary Si crystal grains 1 The linear grooves 4 are formed by the distance between them. Therefore, the plurality of linear grooves 4 and the plurality of Al contact portions 106 are located between the two Si contact portions 108 adjacent to each other. Specifically, the plurality of linear grooves 4 and the plurality of Al contact portions 106 are alternately located between the two Si contact portions 108 adjacent to each other. Therefore, the uniformity of dispersion of the lubricating oil can be improved. Therefore, abrasion and the like of the Al contact portion 106 can be effectively suppressed. The Al contact portion 106 can be brought into contact with the piston ring portion 122b (the piston portion 122) while suppressing the occurrence of the drag.

The plurality of linear grooves 4 are formed at a distance smaller than the average crystal grain size of the primary Si crystal grains 1. A plurality of linear grooves 4 are formed at a narrow interval. Therefore, the uniformity of dispersion of the lubricating oil can be further improved. As a result, the cooling efficiency of the air-cooled engine 150, particularly the cooling efficiency at the initial sliding of the piston ring portion 122b (the piston portion 122) can be further improved.

<Manufacturing method>

A method of manufacturing the cylinder block 100 in the present embodiment will be described.

The cylinder block portion 100 is manufactured, for example, by sequentially performing the following steps S1 to S4.

Step S1 Preparing a shaped body

Step S2 Precision boring

Step S3 rough grinding

Step S4, finally pondering

In the manufacturing method of the cylinder block 100, first, an Al alloy shape containing Si is prepared. The formed body is formed (step S1). The formed body contains primary Si crystal grains and eutectic Si crystal grains in the vicinity of the surface. The step S1 of preparing the molded body includes, for example, steps S1a to S1e.

Step S1a Preparation of Al alloy containing niobium

Step S1b produces a melt

Step S1c High Pressure Die Casting

Step S1d heat treatment

Step S1e Machining

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

Next, the prepared Al alloy is heated and melted by a melting furnace to form a molten metal (step S1b). Preferably, about 100 ppm by mass of phosphorus is added in advance to the Al alloy or the melt before the melting. When the Al alloy contains 50 ppm by mass or more and 200 ppm by mass or less of phosphorus, the Si crystal grains can be suppressed from being coarsened, so that Si crystal grains can be uniformly dispersed in the alloy. In addition, by setting the calcium content of the Al alloy to 0.01% by mass or less, the effect of refining the Si crystal grains by phosphorus can be secured, and a metal structure excellent in abrasion resistance can be obtained. That is, the Al alloy preferably contains 50 ppm by mass or more and 200 ppm by mass or less of phosphorus, and 0.01% by mass or less of calcium.

Then, casting is performed by high pressure die casting using a molten alloy of an Al alloy (step S1c). That is, the melt is cooled in a mold to form a molded body. At this time, by cooling the portion of the cylinder wall 103 which becomes the sliding surface 101 at a relatively fast cooling rate (for example, 4 ° C / sec or more and 50 ° C / sec or less), it is possible to obtain a resistance near the surface. A molded body of an abrasive Si crystal. This casting step S1c can be carried out using, for example, a casting apparatus disclosed in the specification of International Publication No. 2004/002658.

Next, the molded bodies taken out from the mold are called "T5", "T6" and "T7". Any of the heat treatments (step S1d). The T5 treatment is a treatment in which the formed body is quenched by water cooling or the like immediately after being taken out from the mold, and then, in order to achieve improvement in mechanical properties or dimensional stabilization, artificial aging is performed at a specific temperature for a specific time, and thereafter, gas is produced. cold. The T6 treatment is a treatment in which the shaped body is subjected to a solution treatment at a specific temperature for a specific time after being taken out from the mold, followed by water cooling, and then subjected to artificial aging treatment at a specific temperature for a specific period of time, followed by air cooling. The T7 treatment system is over-aged compared to the T6 treatment, and although the size stabilization can be achieved more than the T6 treatment, the hardness is lower than the T6 treatment.

Then, the molded body is subjected to specific machining (step S1e). Specifically, grinding is performed on the joint surface with the cylinder head or the joint surface with the crankcase.

After preparing the molded body as described above, precision boring processing for adjusting the dimensional accuracy is performed on the surface of the molded body, specifically, the inner peripheral surface of the cylinder wall 103 (that is, the surface on which the sliding surface 101 is formed) (step S2) .

Next, the surface subjected to the precision boring processing is subjected to rough honing treatment (step S3). That is, the surface to be the sliding surface 101 is polished using a grindstone having a small number of grits (a grindstone having a large abrasive grain).

Then, final honing processing is performed (step S4). That is, a region of the surface of the molded body which becomes the sliding surface 101 is polished using a grindstone having a relatively large number of grits (a grindstone having a small amount of abrasive grains). Further, the rough honing treatment and the final honing treatment can be carried out using, for example, a honing device as disclosed in Japanese Laid-Open Patent Publication No. 2004-268179. Further, the specifications of the grindstone in the rough honing treatment and the final honing treatment (the type of the abrasive grains, the number of the crystal grains (the grinding particle diameter), the type of the bonding agent, and the like) may be based on the linear grooves 4 formed on the sliding surface 101. Set according to the specifications.

Through the above steps, the sliding surface 101 of the present embodiment is formed. On the sliding surface 101, a plurality of primary Si crystal grains 1 and an Al alloy base material 3 are exposed. When the piston portion 122 reciprocates along the cylinder bore 102, the plurality of primary Si crystal grains 1 and the Al alloy base material 3 are connected to the piston portion 122. touch. Further, the sliding surface 101 has a plurality of linear grooves 4. The plurality of linear grooves 4 include a plurality of first linear grooves 4a substantially parallel to each other, and a plurality of second linear grooves 4b substantially parallel to each other. In the present embodiment, the linear groove 4 is formed by the grindstone, but the present invention is not limited to this example. The linear groove 4 can also be formed by, for example, a laser. Further, the number of times of the rough honing treatment and the final honing treatment is not limited to one, and may be two or more.

<<Second embodiment>>

The air-cooled engine 150 of the second embodiment is the same as the air-cooled engine 150 of the first embodiment except that the linear groove 8 is formed instead of the linear groove 4. Therefore, the linear groove 8 will be mainly described below. The description of the same points as those of the first embodiment will be omitted.

Fig. 6 is a plan view showing the sliding surface 101 of the cylinder block 100 of the second embodiment in an enlarged manner and schematically shown. R is a direction in which the piston portion 122 reciprocates. 7(a) and 7(b) are enlarged cross-sectional views showing the sliding surface 101 of the cylinder block 100 of the second embodiment in an enlarged manner. Further, Fig. 7 (a) and (b) are cross-sectional views in the direction R. In Figs. 7(a) and 7(b), only the first linear groove 8a of the linear groove 8 is shown for the sake of convenience. Further, the arrow of the two-dot chain line shown in Fig. 7(a) is an arrow for explaining the flow of heat.

A plurality of linear grooves 8 are formed in 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 toward the lower right in Fig. 6, and are substantially parallel to each other. The plurality of first linear grooves 8a are formed in a stripe pattern on the sliding surface 101. The plurality of second linear grooves 8b have shapes extending in the direction from the upper right toward the lower left in Fig. 6, and are substantially parallel to each other. The plurality of second linear grooves 8b are formed in a stripe 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. Thereby, the plurality of linear grooves 8 are formed in a lattice pattern on the sliding surface 101. Further, in FIG. 5, the portion in which the primary Si crystal 1 and/or the eutectic Si crystal 2 and the linear groove 8 are repeated represents a linear groove 8 to pass through the primary Si crystal 1 and/or eutectic. The square of the exposed surface of the Si crystal 2 The part of the formation. At least a portion of the portion is formed with a fractured surface 5a as shown in Fig. 7(b).

At least two or more linear grooves 8 of the plurality of linear grooves 8 are substantially parallel to each other. One of the plurality of linear grooves 8 may be crossed by a portion of the linear grooves 8 (the first linear grooves 8a) and the remaining linear grooves 8 (the second linear grooves 8b). It is also possible that all of the plurality of linear grooves 8 are formed so as not to intersect each other, and are substantially parallel. By "substantially parallel" is meant that adjacent linear grooves 8 extend in a non-intersecting manner. That is, the meaning of "substantially parallel", for example, even if the linear grooves 8 are not strictly parallel due to errors or deviations in the formation of the linear grooves 8, it can also be interpreted as phase in the present invention. The adjacent linear grooves 8 are substantially parallel. Further, the sliding surface 101 has a group of the first linear grooves 8a and the second linear grooves 8b as a group of mutually parallel linear grooves, but in the present invention, the number of the linear grooves which are parallel to each other is There is no special limit. The slots belonging to different groups 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 stripe pattern formed by the first linear groove 8a or the second linear groove 8b, or may be a polygonal lattice pattern such as a triangular lattice pattern. An example of a square lattice pattern is a polygonal lattice pattern. Furthermore, the spacing between the grooves of the stripe pattern and the lattice pattern does not have to be fixed.

In the present embodiment, the plurality of linear grooves 8 are formed in a regular pattern (a stripe pattern or a polygonal lattice pattern). In the present embodiment, the Al alloy base material 3 is exposed to the sliding surface 101 together with the primary ring Si crystal 1 in contact with the piston ring portion 122b (the piston portion 122) in the regular pattern. The sliding surface 101 formed with the linear grooves 8 formed into a regular pattern is more uniform than the conventional irregular sliding surface (the sliding surface in which the Si crystal grains are exposed in the floating island shape), thereby further improving the uniformity of dispersion of the lubricating oil. As a result, in the present embodiment, the uniformity of the oil film formed on the sliding surface 101 is high. In addition, in the following, except for the case where the first linear groove 8a and the second linear groove 8b are distinguished, the description about the linear groove 8 is also about the first linear groove 8a and the second linear groove 8b. The description of both.

As for the planar shape of the linear groove 8, as shown in FIG. 6, the linear shape of the linear groove 8 is linear. However, in the present invention, the planar shape of the linear groove 8 is not limited to a linear shape as long as it has a linear shape that does not extend so as to intersect the linear grooves 8 that are substantially parallel to each other. That is, the linear groove 8 may also have a curved shape. The linear groove 8 may have a curved portion and a linear portion. Further, the linear groove 8 may have a curved portion. Further, the planar shape of the plurality of linear grooves 8 may be different depending on the linear grooves 8. It is also possible that all of the linear grooves 8 have the same or substantially the same shape in plan view. Further, each of the plurality of linear grooves 8 does not have to be formed so that the entire area of the sliding surface 101 is continuous. Each of the plurality of linear grooves 8 does not have to extend to the end edge of the sliding surface 101. Each of the plurality of linear grooves 8 may have a portion interrupted 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 equal to or less than the maximum value of the range of the particle diameter of the primary Si crystal grains 1 in the particle size distribution of the cylinder block portion 100. The width of the linear groove 8 is also preferably about 10 μm or less. Further, the width of the linear groove 8 is preferably equal to or larger than the minimum value of the range of the particle diameter of the eutectic Si crystal grain 2 in the particle size distribution of the cylinder block portion 100. The width of the linear groove 8 is also preferably about 5 μm or more. As shown in Fig. 6, the linear groove 8 has a fixed width, but the present invention is not limited to this example. The linear grooves 8 may also have different widths depending on the position. Further, the width of the plurality of linear grooves 8 may be different depending on the linear grooves 8. It is also possible for all of the linear grooves 8 to 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 has 1/1 of the upper limit of the range of the particle diameter of the eutectic Si crystal 2 in the particle size distribution of the Si crystal grains of the cylinder block 100. 3 or more depths. Here, the meaning of the depth of the linear groove 8 will be described. Patent Document 3 discloses a technique for more effectively suppressing the occurrence of drag around 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 except for the region of the Si crystal grains existing in the floating island shape. Therefore, in the technique of Patent Document 3, the etching treatment is preferably such that it is difficult for the Si crystal grains to fall off from the sliding surface or It does not fall off, and it is difficult to form a deep recess or groove. On the other hand, in the present embodiment, since the linear grooves 8 are formed to be wider than the average crystal grain size of the primary Si crystal grains, the Al alloy base material which can be removed is limited. Therefore, a linear groove 8 having a relatively large depth can be formed. Specifically, in the present embodiment, the linear groove 8 has a depth of 1/3 or more of the upper limit of the range of the particle diameter of the needle-shaped eutectic Si crystal 2, and the eutectic can be prevented or suppressed. The detachment of the Si crystal 2 is performed. The primary Si crystal grains 1 have an average crystal grain size larger than the average crystal grain size of the eutectic Si crystal grains 2, and also prevent or suppress the seizure of the primary Si crystal grains 1. Since a plurality of linear grooves having a relatively large depth and substantially parallel are formed on the sliding surface, a large amount of lubricating oil can be maintained, and the uniformity of dispersion of the lubricating oil is improved. Therefore, in the present embodiment, the fall of the 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 of the range of the particle diameter of the eutectic Si crystal grains 2 in the particle size distribution of the Si crystal grains of the cylinder block portion 100. Further, it may have a depth of 1/2 or more of the upper limit of the range of the particle diameter of the eutectic Si crystal grains 2 in the particle size distribution of the Si crystal grains of the cylinder block portion 100.

Further, the linear grooves 8 preferably have a depth smaller than the upper limit of the range of the particle diameter of the eutectic Si crystal grains 2. This is because the lubricating oil held in the linear groove 8 can be supplied to the sliding surface 101 appropriately and efficiently. Further, the linear groove 8 preferably has a depth of 6.0 μm or less. Further, in the present invention, when the depth limit value and the lower limit value of the linear groove 8 are defined, a groove having a depth smaller than the depth lower limit of the linear groove 8 may be formed on the sliding surface 101. And/or a groove having a depth greater than a limit above the depth of the linear groove 8. In other words, in the present invention, grooves other than the linear grooves defined in the present invention (for example, the above-described linear grooves 4) may be formed on the sliding surface.

The cross-sectional shape of the linear groove 8 is a shape in which the width of the linear groove 8 becomes smaller as the depth of the linear groove 8 becomes larger. The cross-sectional shape of the linear groove 8 is a sectional shape of the linear groove 8 on a plane perpendicular to the direction in which the linear groove 8 extends. Further, 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, substantially V-shaped as shown in Fig. 7(a). The shape may also be a substantially U shape. Further, the cross-sectional shapes of the linear grooves 8 need not be the same. The cross-sectional shape of the linear groove 8 may vary depending on the position, or may vary depending on the linear groove 8. Further, the portion (mountain) between the linear grooves 8 is not necessarily a flat surface as shown in Figs. 6 and 7(a) and (b). The portion between the linear grooves 8 may be an inclined surface or a ridge line, or may form one or a plurality of grooves having a depth smaller than that of the linear grooves 8.

Regarding the distance between the first linear grooves 8, a plurality of substantially linear first grooves 8a are formed to be wider than the average crystal grain size of the primary Si crystal grains 1. As a result, at least a part of the plurality of primary Si crystal grains 1 are located between the first linear grooves 8a adjacent to each other. In the present embodiment, both the primary Si crystal grains 1 and the Al alloy base material 3 are exposed to the sliding surface 101 in contact with the piston portion 122 in the region between the adjacent first linear grooves 8a. 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 a plan view, so that the supply of the lubricating oil to the sliding surface 101 can be smoothly performed. Further, the Al alloy base material 3 is exposed to the sliding surface 101 so as to be in contact with the piston portion 122, and the primary Si crystal grains 1 are also exposed to the sliding surface 101 so as to be in contact with the piston portion 122, so that the sliding can be more effectively suppressed. Wear of the surface 101 (Al alloy base material 3). In Fig. 6, the distance between one of the adjacent first linear grooves 8a is fixed regardless of the position, but the present invention is not limited to this example. That is, the distance between one of the adjacent pairs of the first linear grooves 8a does not have to be fixed. For example, the first linear grooves 8a adjacent to each other are respectively formed in a meandering manner, and the distance between the first linear grooves 8a may be different depending on the position. Incidentally, the above description has been made regarding the first linear groove 8a, but the description of the second linear groove 8b is the same as that of the first linear groove 8a, and thus the description thereof is omitted.

In the present embodiment, as shown in FIG. 6, at least one of the linear grooves 8 is formed by passing 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 to pass through the exposed surface of the primary Si crystal grains 1. Thereby, the uniformity of dispersion of the lubricating oil of the sliding surface 101 can be further improved. The invention is not limited to this example.

In the present embodiment, as shown in FIG. 7(b), the primary Si crystal 1 having the fractured surface 5a is formed. It is exposed on the sliding surface 101. That is, in the present embodiment, at least a part of the primary Si crystal grains 1 exposed on the sliding surface 101 is broken, and is destroyed, so that the surface formed on the primary Si crystal grains 1 (that is, the fractured surface 5a) is exposed. Sliding surface 101. Thereby, the oil reservoir portion 5b is formed on the sliding surface 101. Since the fractured section of the primary Si crystal 1 has irregularities, the amount of lubricating oil that can be maintained by the oil reservoir 5b is large. The opening area of the oil reservoir portion 5b is the same as the cross-sectional area of the primary Si crystal grain 1 (the area exposed by the sliding surface 101). The depth of the oil reservoir 5b is smaller than the diameter of the primary Si crystal 1. The oil reservoir 5b including the fractured portion 5a of the primary Si crystal 1 is formed on the sliding surface 101 together with a plurality of substantially linear first grooves 8a. Therefore, the amount of the lubricating oil can be increased while maintaining the uniformity of the dispersion of the lubricating oil. It can suppress the grinding more effectively. The broken section 5a is formed when the surface processing of the cylinder block 100 is performed after casting of the cylinder block 100. Specifically, the fractured section 5a is formed, for example, when the primary Si crystal grains 1 are ground by a grindstone.

As shown in FIG. 7(a), the Al contact portion 106 is formed between the plurality of first linear grooves 8a. The Al contact portion 106 is exposed to the sliding surface 101 between the two primary Si crystal grains 1 (Si contact portions 108) adjacent to each other. The Al contact portion 106 is a portion of the cylinder wall 103, and the cylinder wall 103 is integrally formed with the heat dissipation portion 107. That is, the Al contact portion 106 is integrally formed with the heat dissipation portion 107. Therefore, the Al alloy base material 3 is physically continuous from the Al contact portion 106 that is in contact with the piston ring portion 122b (the piston portion 122) to the heat radiating portion 107. Therefore, as shown by the arrow of the two-point chain line of FIG. 7, one part of the heat of the piston ring portion 122b (the piston portion 122) is conducted to the Al contact portion 106, passes through the cylinder wall 103, reaches the heat dissipating portion 107, and the self-heating portion 107 release. Therefore, the cooling efficiency of the air-cooled engine 150, in particular, the cooling efficiency at the initial sliding of the piston ring portion 122b (the piston portion 122) is improved.

Further, in the present embodiment, the plurality of linear grooves 8 (the first linear grooves 8a and the second linear grooves 8b) are formed to be wider than the average crystal grain size of the primary Si crystal grains 1. Therefore, one or a plurality of Si contact portions 108 are located between adjacent linear grooves 8. Further, the linear groove 8 (first linear groove 8a) has a portion passing between the adjacent primary Si crystal grains 1. Therefore, 1 or plural The Si contact portions 108 and one or a plurality of Al contact portions 106 are located between the two linear grooves 8a adjacent to each other. Thereby, the uniformity of the oil film formed on the sliding surface 101 can be improved. Further, the plurality of linear grooves 8 have a depth of 1/3 or more of the upper limit of the range of the particle diameter of the eutectic Si crystal grains 2 in the particle size distribution of the Si crystal grains of the cylinder block portion 100, so that a sufficient amount can be obtained. The lubricating oil is held in the linear groove 8. Therefore, the oil film crack on the sliding surface 101 can be suppressed. Further, a plurality of linear grooves 8 have a portion passing between adjacent primary Si crystal grains 1. Thereby, the primary crystal Si crystal 1 receives the load of the piston ring portion 122b (the piston portion 122), so that the abrasion of the sliding surface 101 (the Al alloy base material 3) adjacent to both sides of the linear groove 8 can be suppressed. It is easy to maintain the lubricating oil in the linear groove 8. Therefore, in the air-cooled engine 150 of the present embodiment, the Al contact portion 106 can be brought into contact with the piston ring portion 122b (the piston portion 122) while suppressing the occurrence of the drag. As a result, the cooling efficiency of the air-cooled engine 150, particularly the cooling efficiency at the initial sliding of the piston portion 122, is improved.

The plurality of linear grooves 8 have a depth equal to or more than 1/3 of the upper limit of the range of the particle diameter of the eutectic Si crystal grains 2 in the particle size distribution of the Si crystal grains of the cylinder block 100, and have a larger cylinder portion 100 The particle size distribution of the Si crystal grains has a depth smaller than the upper limit of the range of the particle diameter of the eutectic Si crystal grains 2. Therefore, a sufficient and appropriate amount of the lubricating oil can be held in the plurality of linear grooves 8. Therefore, the uniformity of the oil film is further improved. As a result, the cooling efficiency of the air-cooled engine 150, particularly the cooling efficiency at the initial sliding of the piston portion 122, can be further improved.

The plurality of linear grooves 8 are wider than the average crystal grain size of the primary Si crystal grains 1 and smaller than the distance from the lower end 122n of the piston ring portion 122b to the upper end 122m of the piston ring 122b in the reciprocating direction of the piston portion 122. The distance between them is formed. Therefore, a sufficient and appropriate amount of lubricating oil can be held in the plurality of linear grooves 8. Therefore, the uniformity of the oil film is improved. As a result, the cooling efficiency of the air-cooled engine 150, particularly the cooling efficiency at the initial sliding of the piston portion 122, can be further improved.

In the first embodiment and the second embodiment, the case where the entire cylinder block portion is formed of an Al alloy having a Si content of 16% by weight or more will be described. However, the present invention is not limited thereto. In this case. In the present invention, as long as the cylinder body portion contains a metal containing Al, at least the inner peripheral portion of the cylinder block portion may be formed of an Al alloy having a Si content of 16% by mass or more. In this case, the thickness of the inner peripheral portion in the radial direction of the cylinder block portion is not particularly limited. Furthermore, the inner peripheral portion includes a sliding surface. In the present invention, Al in the cylinder block portion is physically continuous from the Al contact portion to the heat radiating portion, whereby the cooling property of the air-cooled engine is improved.

The present invention can also adopt the following constitution.

The inner peripheral portion including the sliding surface in the cylinder block portion is formed of an Al alloy having a Si content of 16% by mass or more. The portion other than the inner peripheral portion includes a heat radiating portion and is physically continuous with the inner peripheral portion. The portion other than the inner peripheral portion includes an Al alloy having a Si content which is the same as or equal to the Si content of the inner peripheral portion. The Al alloy base material in the cylinder body portion is physically continuous from the Al contact portion to the heat radiating portion.

In this configuration, the Al alloy base material in the cylinder block portion is physically continuous from the Al contact portion to the heat radiating portion, whereby the cooling property of the air-cooled engine is improved.

The cylinder block portion of the air-cooled engine of the present invention is not limited to the above example, and may be configured as follows. The cylinder block portion includes a cylinder outer cylinder portion having a heat radiating portion on an outer surface, and a cylinder sleeve that is used by being disposed in the cylinder outer cylinder portion. In this case, the cylinder sleeve corresponds to the inner peripheral portion of the cylinder block. The cylinder outer cylinder portion corresponds to a portion other than the inner circumferential portion of the cylinder block portion. The method of installing the cylinder sleeve is not particularly limited, and examples thereof include embedding into the cylinder bore 102, insert molding, and the like. The cylinder sleeve has a sliding surface for sliding the piston portion, and has an Al contact portion in contact with the piston portion in the sliding surface. The sliding surface is as described in the first embodiment or the second embodiment, and thus the description thereof is omitted. The cylinder sleeve is formed of an Al alloy having a Si content of 16% by mass or more. The cylinder sleeve has, for example, the composition described in the first embodiment. The cylinder outer cylinder portion may be formed of an Al alloy having a Si content of 16% by mass or more, or may be formed of an Al alloy or an Al material having a Si content of less than 16% by mass. Further, the outer cylinder portion of the cylinder may be formed of an Al alloy having a Si content equal to that of the cylinder sleeve, or may be an Al alloy having a Si content smaller than that of the cylinder sleeve. Gold or Al material is formed. Both the cylinder outer cylinder portion and the cylinder sleeve are formed of a metal containing Al (Al alloy containing Al or Al material), and the difference in thermal expansion coefficient between the outer cylinder portion and the cylinder sleeve is small or absent, so that the cause can be suppressed. The temperature rises to separate the cylinder outer cylinder from the cylinder sleeve. That is, the cylinder sleeve and the cylinder outer cylinder portion maintain a state of direct physical contact. Further, the Al alloy base material existing on the outer surface of the cylinder sleeve is in direct physical contact with the Al alloy base material or the Al material existing on the inner surface of the cylinder outer cylinder portion. Thereby, the physical continuity of Al can be ensured. Therefore, in the cylinder body portion, Al is physically continuous from the Al contact portion to the heat radiating portion. In other words, the cylinder body portion has a heat conduction path including Al continuously from the Al contact portion to the heat dissipation portion, similarly to the first embodiment and the second embodiment. As described above, the cylinder block portion including the cylinder outer cylinder portion and the cylinder sleeve is an example of the cylinder block portion of the present invention.

<cylinder block member>

The cylinder block member in the present embodiment is the cylinder block portion 100 itself according to the first embodiment (see Fig. 1 and the like). The cylinder block 100 has a portion of the sliding surface 101. However, in the present invention, the cylinder block member is not limited to this example. The cylinder block member may be provided with the cylinder block portion 100 having the sliding surface 101. The cylinder block member in the present invention may be a member (so-called cylinder) formed by integrally molding the cylinder block 100 and the crank case 110. The cylinder block member has a heat dissipating portion 107 formed integrally with the Al contact portion 106 in contact with the piston portion between the plurality of linear grooves 4, so that the air-cooled engine can be improved by being applied to an air-cooled engine. Cooling efficiency. Further, as the cylinder block member in the present embodiment, the cylinder block portion of the second embodiment may be applied instead of the cylinder block portion 100 of the first embodiment. Further, the cylinder block member in the present invention may be the cylinder body portion itself including the cylinder outer cylinder portion and the cylinder sleeve as described above.

<vehicle>

The vehicle of the present invention includes various types of vehicles such as snowmobiles such as automobiles, locomotives, and snowmobiles, and the number of wheels is not particularly limited, and is four wheels, three wheels, and two wheels. Further, the vehicle of the present invention may be a box type vehicle in which an engine is disposed in a portion away from the seat such as an engine room. The straddle type vehicle in which at least a part of the engine and the engine are disposed below the seat and the driver rides over the seat. The straddle-type vehicle also includes a vehicle that can be used by the driver to ride the knees together.

Hereinafter, a locomotive will be described as an example of a vehicle.

Fig. 8 is a side view schematically showing a locomotive including the air-cooled engine 150 of the first embodiment.

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

The rear frame 306 is attached in such a manner as to extend rearward from the upper end portion of the rear end of the body frame 301. A fuel tank 307 is disposed on the body frame 301, and a main seat portion 308a and a tandem seat 308b are disposed on the rear frame 306.

Further, at the rear end of the body frame 301, an arm 309 extending rearward is attached. The rear wheel 310 is rotatably supported at the rear end of the rear arm 309.

At the central portion of the body frame 301, the air-cooled engine 150 shown in Fig. 1 is held. In the air-cooled engine 150, the cylinder block 100 of this embodiment is used. An exhaust pipe 312 is connected to the exhaust port of the air-cooled engine 150, and a muffler 313 is attached to the rear end of the exhaust pipe 312.

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

In the locomotive (vehicle) according to the present embodiment, the air-cooled engine 150 including the cylinder block portion 100 is mounted, so that the cooling efficiency of the air-cooled engine can be improved, and the cylinder block portion 100 is provided between the plurality of linear grooves 4 The Al contact portion 106 in contact with the piston portion 122 is integrally formed Heat sink 107. Further, the locomotive (vehicle) according to the present embodiment includes the air-cooled engine 150 of the first embodiment, but may be provided with the air-cooled engine 150 of the second embodiment.

The measurement of the average crystal grain size of the primary Si crystal grains and the eutectic Si crystal grains is performed by image processing using a portion of the cylinder body portion which is a sliding surface. Based on the area of the Si crystal grains in the image obtained by the image processing, the diameter (equivalent diameter) of each Si crystal grain in the case where the Si crystal grains in the assumed image are in a true circle is calculated. Further, fine crystals having a diameter of less than 1 μm are not counted in Si crystal grains (primary Si crystal grains or eutectic Si crystal grains). From the above, the number (degrees) and diameter of Si crystal grains are specified. Based on this, the particle size distribution of the Si crystal grains in the cylinder body portion is obtained. The particle size distribution is, for example, a histogram as shown in FIG. The particle size distribution contains 2 peaks. The particle size distribution is divided into two regions by setting the diameter of the portion forming the valley between the two peaks to a threshold value. The region corresponding to the larger diameter is set as the particle size distribution of the primary Si grains. The region corresponding to the smaller diameter is the particle size distribution of the eutectic Si grains. Further, the average crystal grain size of the primary Si crystal grains and the average crystal grain size of the eutectic Si crystal grains were calculated based on the respective particle size distributions.

The width of the linear groove means the distance between one pair of ridge lines adjacent to each other in a section (cross-sectional curve) crossing the linear groove. Further, the cross-section of the piston portion is parallel to the sliding direction of the sliding surface (the reciprocating direction R of the piston portion). Further, the cross section is also parallel to the radial direction of the cylinder block. The depth of the linear grooves is the depth from the higher ridge line of one of the ridge lines adjacent to the linear groove to the deepest portion of the linear groove. The distance between the linear grooves is the distance between one of the adjacent sections (section curves) and the deepest part of the groove. Further, when the sliding surface adjacent to the linear groove is substantially a 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 grooves, the average value of the linear grooves included in the cross-sectional curve of the distance of 3 to 5 mm is used. Further, in the present invention, a groove other than the linear groove having the depth defined in the present invention may be formed on the sliding surface. In this case, when the width and spacing of the specific linear grooves are used, the use is as defined in the present invention. a linear groove of depth.

The terms and expressions used herein are for the purpose of description and are not intended to be limiting. It is to be understood that the invention is not to be construed as being limited by the scope of the invention.

The present invention has been made in a variety of different forms. The present disclosure should be considered as an embodiment of the principles of the invention. The embodiments are not intended to limit the invention to the preferred embodiments described and/or illustrated herein, and various embodiments are described herein.

Several illustrative embodiments of the invention are described herein. The invention is not limited to the various preferred embodiments described herein. The present invention also includes all embodiments that include equivalent elements, modifications, deletions, combinations (e.g., combinations of features across various embodiments), improvements, and/or changes that can be discerned by the present disclosure. The limitation of the scope of the patent application should be construed broadly based on the terms used in the scope of the patent application, and should not be limited to the embodiments described in the specification or the litigation of the present invention. Such an embodiment should be construed as non-exclusive. For example, in the present disclosure, the term "preferred" is non-exclusive and means "preferably, but not limited to".

1‧‧‧ primary crystal Si grain

2‧‧‧ Eutectic Si grains

3‧‧‧Al alloy base metal

4a‧‧‧first linear groove

5a‧‧‧ broken section

5b‧‧‧Oil Accumulation Department

101‧‧‧Sliding surface

103‧‧‧ cylinder wall

103a‧‧‧Outer surface

106‧‧‧Al contact

107‧‧‧Dissipation Department

108‧‧‧Si contact

122b‧‧‧Piston ring

P‧‧‧ gap

Claims (12)

An air-cooled engine including a piston portion and a cylinder body portion having a sliding surface on which the piston portion slides, wherein the cylinder block portion includes a heat radiating portion provided on an outer surface of the cylinder block portion, and includes In the metal containing Al, at least the inner peripheral portion of the cylinder portion including the sliding surface is formed of an Al alloy having a Si content of 16% by mass or more, and a substantially parallel plurality of linear grooves are formed on the sliding surface. The primary Si crystal grains having an average crystal grain size of 8 μm or more and 50 μm or less are exposed in contact with the piston portion, and are formed between the plurality of linear grooves and in contact with the piston portion by the Al alloy base material. The Al contact portion is exposed to the sliding surface between the two primary Si crystal grains adjacent to each other, and the Al in the cylinder block portion is physically continuous from the Al contact portion to the heat radiating portion. An air-cooled engine including a piston portion and a cylinder body portion having a sliding surface on which the piston portion slides, wherein the cylinder block portion includes a heat radiating portion provided on an outer surface of the cylinder block portion, and includes In the metal containing Al, the inner peripheral portion including at least the sliding surface of the cylinder block portion is formed of an Al alloy having a Si content of 16% by mass or more by high pressure die casting, and substantially parallel to the sliding surface is formed. a linear groove, the primary Si crystal grains are exposed in contact with the piston portion, and the Al contact portions formed between the plurality of linear grooves and the Al alloy base material in contact with the piston portion are attached to each other The adjacent two primary Si crystal grains are exposed between the sliding surfaces, and the Al in the cylinder block is physically continuous from the Al contact portion to the heat radiating portion. The air-cooled engine of claim 1 or 2, wherein a portion of the cylinder block other than the inner peripheral portion includes the heat dissipating portion and is physically continuous with the inner peripheral portion, and includes a Si content and the inner circumference In the Al alloy having the same Si content or less than the Si content in the inner peripheral portion, the Al alloy base material in the cylinder block portion is physically continuous from the Al contact portion to the heat dissipating portion. The air-cooled engine according to any one of claims 1 to 3, wherein the Al contact portion is exposed between the two primary Si crystal grains adjacent to each other on the sliding surface, and is integrally formed with the heat dissipating portion. The air-cooled engine according to any one of claims 1 to 4, wherein the plurality of linear grooves are formed such that a plurality of linear grooves are formed by a distance between the primary Si grains. An air-cooled engine according to claim 5, wherein said pitch is smaller than an average crystal grain size of said primary Si crystal grains. The air-cooled engine according to any one of claims 1 to 4, wherein the cylinder block portion comprises, in addition to the primary crystal Si crystal grains and the Al alloy base material, an average crystal having a crystal grain size higher than that of the primary crystal Si particles. a eutectic Si crystal grain having an average crystal grain size of a small particle diameter, wherein the plurality of linear grooves have an upper limit value of a range of the eutectic Si crystal grain size in a particle size distribution of Si crystal grains of the cylinder block portion a depth of 1/3 or more and at least 1/4 of the upper side of the sliding surface is formed to be wider than an average crystal grain size of the primary Si crystal grains, and has a pass through the adjacent primary Si crystal grains The part between. The air-cooled engine of claim 7, wherein the plurality of linear grooves have a limit value of a range of a range of the eutectic Si crystal grain size in a particle size distribution of Si grains of the cylinder block portion Above and less than the above The depth of the upper limit of the range of the eutectic Si crystal grain size. The air-cooled engine of claim 7 or 8, wherein the piston portion is provided with: a piston body; and a piston ring portion including a plurality of piston rings disposed on an outer circumference of the piston body; the plurality of linear grooves are It is formed to be wider than the average crystal grain size of the primary Si crystal grains and smaller than the distance from the lower end of the piston ring portion to the upper end of the piston ring portion in the reciprocating direction of the piston portion. The air-cooled engine according to any one of claims 1 to 9, wherein at least a part of the primary Si crystal grains exposed on the sliding surface is broken, and the surface formed on the primary Si crystal grains is broken due to being broken. Sliding surface. A cylinder block member comprising the above-described cylinder block portion included in an air-cooled engine according to any one of claims 1 to 10. A vehicle having the air-cooled engine of any one of claims 1 to 10.