WO2023112124A1

WO2023112124A1 - Internal combustion engine and transportation device

Info

Publication number: WO2023112124A1
Application number: PCT/JP2021/045975
Authority: WO
Inventors: 慧太渡邉; 洋敬栗田
Original assignee: ヤマハ発動機株式会社
Priority date: 2021-12-14
Filing date: 2021-12-14
Publication date: 2023-06-22
Also published as: EP4219928A4; EP4219928A1

Abstract

An internal combustion engine (100) comprises: an aluminum alloy piston (40) having a piston head (43) and a piston skirt (44) extending from an outer peripheral portion of the piston head; and an aluminum alloy cylinder block (10) having a cylinder wall (12) including a sliding surface (12a) along which the piston slides. The aluminum alloy is exposed from the sliding surface of the cylinder wall. The piston skirt comprises: a skirt base (bl) formed from an aluminum alloy and having an outer peripheral surface on which a plurality of streaks (sg) are formed; and a resin layer (rl) formed on at least a part of the outer peripheral surface of the skirt base. The outer peripheral surface of the skirt base has a ten-point average roughness Rz_JIS of 20 μm or more.

Description

Internal combustion engines and transportation equipment

The present disclosure relates to an internal combustion engine, and more particularly to an internal combustion engine including an aluminum alloy piston and an aluminum alloy cylinder block. The present disclosure also relates to vehicles equipped with such internal combustion engines.

In recent years, aluminum alloys have been widely used as materials for pistons and cylinder blocks for internal combustion engines. When using a combination of an aluminum alloy piston and an aluminum alloy cylinder block, place a cast iron sleeve (liner) in the cylinder bore or plate the surface of the cylinder wall to ensure wear resistance. It is being processed.

On the other hand, a technique is known in which streaks are formed on the surface of the piston skirt and a resin layer is formed thereon (for example, Patent Document 1). The formation of the streaks improves the adhesion between the base material of the skirt portion and the resin layer. Sliding of the piston scrapes the resin layer to reduce surface roughness, thereby reducing sliding loss and improving initial conformability.

The resin layer of the skirt wears out when the internal combustion engine is operated for a certain amount of time. If a cast iron sleeve is placed in the cylinder bore or if the cylinder wall surface is plated, the aluminum alloy of the piston and the aluminum alloy of the cylinder block will remain in contact even if the resin layer is worn away. Since there is no direct contact, problems such as seizing are less likely to occur.

Japanese Patent No. 6485952

It has been proposed to use a high-silicon-aluminum alloy containing a large amount of silicon (hypereutectic composition) as the material for the cylinder block. Forming the cylinder block from a high-silicon aluminum alloy eliminates the need for a cast iron sleeve and plating, thereby reducing weight and simplifying the manufacturing process. However, if the cast iron sleeve and plating are omitted, if the resin layer on the skirt of the piston wears away, the aluminum alloy of the piston and the aluminum alloy of the cylinder block will come into direct contact, which may cause seizure. .

An embodiment of the present invention has been made in view of the above problems, and an object thereof is to provide an internal combustion engine having an aluminum alloy cylinder block and an aluminum alloy piston, even if cast iron sleeves and plating are omitted. An object of the present invention is to realize a structure capable of suppressing seizure after the resin layer wears out.

This specification discloses the internal combustion engine and transportation equipment described in the following items.

[Item 1]
an aluminum alloy piston having a piston head and a piston skirt extending from the outer periphery of the piston head;
an aluminum alloy cylinder block having a cylinder wall including a sliding surface on which the piston slides;
with
An aluminum alloy is exposed on the sliding surface of the cylinder wall,
The piston skirt includes a skirt base material made of an aluminum alloy, a skirt base material having a plurality of striations formed on an outer peripheral surface, and a skirt base material formed on at least a part of the outer peripheral surface of the skirt base material. and a resin layer,
The internal combustion engine, wherein the outer peripheral surface of the skirt base material has a ten-point average roughness Rz _JIS of 20 μm or more.

In the internal combustion engine according to the embodiment of the present invention, the piston skirt includes a skirt base material made of an aluminum alloy and having a plurality of streaks formed on the outer peripheral surface thereof, and at least part of the outer peripheral surface of the skirt base material. and a resin layer. Since the resin layer is formed on the outer peripheral surface of the skirt base material, the sliding loss is reduced and the initial conformability of the piston to the cylinder block is improved. Further, in the internal combustion engine of the present invention, the outer peripheral surface of the skirt base material has a ten-point average roughness Rz _JIS of 20 μm or more, which is because the streaks formed on the outer peripheral surface of the skirt base material are relatively deep. means When the resin layer is formed on the outer peripheral surface of the skirt base material, the resin material inevitably enters into the streaks. A mixed state of the exposed portion and the portion where the resin material remains can be maintained for a long period of time. Therefore, even after the resin layer is worn out, it is possible to prevent seizure between the aluminum alloy piston and the aluminum alloy cylinder block.

[Item 2]
The internal combustion engine according to item 1, wherein the plurality of striations extend in a circumferential direction of the piston.

The streaks can be formed, for example, by turning using a bit (cutting tool). In that case, the striations extend in the circumferential direction of the piston.

[Item 3]
3. The internal combustion engine according to item 1 or 2, wherein an average unevenness interval Sm of the outer peripheral surface of the skirt base material is 100 μm or more and 500 μm or less.

The uneven average interval Sm (corresponding to the pitch of streaks) on the outer peripheral surface of the skirt base material is preferably 100 μm or more and 500 μm or less. If the average unevenness interval Sm is less than 100 μm, there is a possibility that the productivity will be lowered or that the manufacturing of the cutting tool will be difficult. If the average unevenness interval Sm exceeds 500 μm, the machining accuracy of the piston may deteriorate. In addition, since the exposed width of the aluminum alloy after the resin layer is worn out becomes large, there is a possibility that the seizure resistance will somewhat deteriorate.

[Item 4]
4. The internal combustion engine according to any one of items 1 to 3, wherein the resin layer has a thickness of 10 μm or more and 50 μm or less.

From the viewpoint of maintaining the resin layer for a long period of time, the thickness of the resin layer is preferably 10 μm or more. Moreover, from the viewpoint of ease of manufacture, the thickness of the resin layer is preferably 50 μm or less.

[Item 5]
5. The internal combustion engine according to any one of items 1 to 4, wherein the resin layer contains a solid lubricant and hard particles.

By including hard particles in the resin layer, it is possible to delay the wear of the resin layer.

[Item 6]
6. The internal combustion engine according to any one of items 1 to 5, wherein the skirt base material has an anodized coating formed on the outer peripheral surface by phosphoric acid alumite treatment.

If the skirt base material has an anodized film formed by phosphoric acid alumite treatment on the outer peripheral surface, the adhesion of the resin layer to the skirt base material can be improved.

[Item 7]
7. The internal combustion engine according to any one of items 1 to 6, wherein the cylinder block is made of an aluminum alloy containing silicon.

When an aluminum alloy containing silicon is used as the material for the cylinder block, seizure resistance and wear resistance can be improved by exposing crystallized silicon crystal grains on the sliding surface.

[Item 8]
Transportation equipment provided with the internal combustion engine according to any one of items 1 to 7.

　The internal combustion engine according to the embodiment of the present invention is suitable for use in various types of transportation equipment.

According to an embodiment of the present invention, in an internal combustion engine having an aluminum alloy cylinder block and an aluminum alloy piston, it is possible to realize a structure capable of suppressing seizure after the resin layer wears even if cast iron sleeves and plating are omitted. be able to.

1 is a cross-sectional view schematically showing an engine (internal combustion engine) 100 according to an embodiment of the present invention; FIG. 1 is a perspective view schematically showing a cylinder block 10 included in engine 100. FIG. 3 is an enlarged plan view showing a sliding surface 12a of the cylinder wall 12; FIG. FIG. 2 is a side view schematically showing a piston 40 included in engine 100. FIG. 4 is a side view schematically showing a piston 40; FIG. 4 is a cross-sectional view schematically showing a piston skirt 44 of the piston 40; FIG. FIG. 5 is a diagram showing how wear progresses in a piston skirt 44' of a comparative example. 4 is a diagram showing how wear progresses in the piston skirt 44. FIG. 4 is a graph in which the vertical axis represents the remaining ratio of the resin layer rl and the horizontal axis represents the total test time for Examples 1, 2 and 3 and Comparative Examples 1 and 2. FIG. FIG. 5 is a diagram showing photographs of the outer peripheral surface of a piston skirt 44 at a specific total test time for Comparative Example 1 and Example 3, which have been binarized. FIG. 4 is a cross-sectional view showing another example of the configuration of the piston skirt 44; 4 is a cross-sectional view schematically showing a piston ring 42 of the piston 40. FIG. 1 is a side view schematically showing a motorcycle 300 equipped with an engine 100; FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Although a water-cooled engine will be described below as an example, the engine according to the embodiment of the present invention is not limited to a water-cooled engine, and may be an air-cooled engine. In addition, although a single-cylinder engine will be described below as an example, the number of cylinders of the engine is not particularly limited.

[Engine configuration]
FIG. 1 shows an engine (internal combustion engine) 100 according to an embodiment of the invention. FIG. 1 is a cross-sectional view schematically showing engine 100. As shown in FIG.

The engine 100 includes a cylinder block 10, a cylinder head 20, and a crankcase 30, as shown in FIG. Engine 100 further includes a piston 40 , a crankshaft 50 and a connecting rod (connecting rod) 60 . Hereinafter, the direction from the cylinder block 10 to the cylinder head 20 is defined as the upward direction, and the direction from the cylinder block 10 to the crankcase 30 is defined as the downward direction.

A cylinder block (sometimes called a "cylinder body") 10 has a cylinder wall 12 and an outer wall 13. Cylinder wall 12 is formed to define cylinder bore 11 . The outer wall 13 surrounds the cylinder wall 12 and constitutes the outer shell of the cylinder block 10 . A water jacket 14 that retains coolant is provided between the cylinder wall 12 and the outer wall 13 .

The cylinder head 20 is provided on the cylinder block 10. Cylinder head 20 defines combustion chamber 70 with cylinder wall 12 and piston 40 . The cylinder head 20 has an intake port 21 for introducing fuel into the combustion chamber 70 and an exhaust port 22 for discharging exhaust gas from the combustion chamber 70 . An intake valve 23 is provided in the intake port 21 and an exhaust valve 24 is provided in the exhaust port 22 .

The crankcase 30 is provided under the cylinder block 10. That is, the crankcase 30 is provided so as to be located on the side opposite to the cylinder head 20 with respect to the cylinder block 10 . Crankcase 30 may be separate from cylinder block 10 or may be formed integrally with cylinder block 10 .

The piston 40 is housed inside the cylinder bore 11 . In this embodiment, no cylinder sleeve is fitted in the cylinder bore 11 . Therefore, the piston 40 reciprocates up and down in the cylinder bore 11 while being in contact with the inner peripheral surface 12a of the cylinder wall 12 (the surface on the cylinder bore 11 side). That is, the inner peripheral surface 12a of the cylinder wall 12 is a sliding surface on which the piston 40 slides.

The crankshaft 50 is housed inside the crankcase 30 . The crankshaft 50 has a crankpin 51 and a crank arm 52 .

The connecting rod 60 has a rod-shaped rod main body 61 , a small end 62 provided at one end of the rod main body 61 , and a large end 63 provided at the other end of the rod main body 61 . The connecting rod 60 connects the piston 40 and the crankshaft 50 . Specifically, the piston pin 48 of the piston 40 is inserted into the through hole (piston pin hole) of the small end 62 , and the crank pin of the crankshaft 50 is inserted into the through hole (crank pin hole) of the large end 63 . 51 is inserted, thereby connecting the piston 40 and the crankshaft 50 . A bearing 66 is provided between the inner peripheral surface of the big end 63 and the crank pin 51 .

FIG. 2 is a perspective view schematically showing the cylinder block 10 of the engine 100. FIG. As already explained, the cylinder block 10 has the cylinder wall 12 including the sliding surface 12a and the outer wall 13, and the water jacket 14 is provided between the cylinder wall 12 and the outer wall 13. . In this embodiment, the cylinder block 10 is made of an aluminum alloy containing silicon. More specifically, the cylinder block 10 is made of a hypereutectic aluminum-silicon alloy. In this embodiment, the inner peripheral surface 12a of the cylinder wall 12 is not plated. Therefore, the aluminum alloy is exposed on the inner peripheral surface (sliding surface) 12 a of the cylinder wall 12 .

FIG. 3 is a plan view showing an enlarged sliding surface 12a of the cylinder wall 12. FIG. The cylinder wall 12 of the cylinder block 10 includes a solid solution matrix (alloy base material) 1 containing aluminum and a plurality of primary crystal silicon grains 2 dispersed in the matrix 1, and a part of the primary crystal silicon grains 2 are exposed on the sliding surface 12a. That is, the cylinder block 10 has the primary crystal silicon grains 2 on the sliding surface 12a.

Although not shown here, the cylinder wall 12 further includes a plurality of eutectic silicon grains dispersed in the matrix 1. Therefore, the cylinder block 10 may further have eutectic silicon grains on the sliding surface 12a. When a molten aluminum-silicon alloy with a hypereutectic composition is cooled, the relatively large silicon crystal grains that first precipitate are "primary silicon grains", and the relatively small silicon crystal grains that precipitate next are "co-crystalline". crystalline silicon grains”.

4A and 4B are side views schematically showing the piston 40 of the engine 100. FIG. 4A is a view of the piston 40 viewed from the axial direction of the piston pin 48 (see FIG. 1) (hereinafter referred to as the "piston pin axial direction"), while FIG. 4B is a view of the piston 40. It is a figure when it sees from the direction orthogonal to a pin axial direction.

In this embodiment, the piston 40 (more specifically, the piston body 41 described later) is made of an aluminum alloy. The piston 40 may be formed by forging or by casting.

The piston 40 has a piston body 41 and a plurality of piston rings 42, as shown in FIGS. 4A and 4B. Piston body 41 includes a piston head 43 and a piston skirt 44 .

The piston head 43 is located at the upper end of the piston 40. A ring groove for holding the piston ring 42 is formed in the outer peripheral portion of the piston head 43 .

The piston skirt 44 extends downward from the outer peripheral portion of the piston head 43 . The piston skirt 44 has two

portions

44a and 44b (referred to as a "first skirt portion" and a "second skirt portion") located so as to sandwich the central axis (cylinder axis) of the cylinder bore 11 in the radial direction.

The piston body 41 also includes a pair of piston pin bosses 45 formed with piston pin holes 45a through which piston pins 48 (see FIG. 1) are inserted, and ribs 46 connecting the piston pin bosses 45 and the piston skirt 44 to each other. have.

The piston ring 42 is attached to the outer peripheral portion of the piston body 41 , more specifically to the outer peripheral portion of the piston head 43 . Here, a configuration in which the piston 40 has three piston rings 42 is illustrated, but the number of piston rings 42 is not limited to three. Of the three piston rings 42, for example, the upper and middle piston rings (top ring and second ring) 42a and 42b are compression rings for keeping the combustion chamber 70 airtight, and the lower piston ring (third 42 c is an oil ring for scraping off excess oil adhering to the cylinder wall 12 . The piston ring 42 is made of a metallic material (eg steel).

The piston skirt 44 has a resin layer rl formed on at least part of the outer peripheral surface. In the example shown in FIGS. 4A and 4B, the resin layer rl is formed over substantially the entire outer peripheral surface.

An example of the cross-sectional structure of the piston skirt 44 is shown in FIG. As shown in FIG. 5, the piston skirt 44 has a skirt base material bl made of an aluminum alloy and a resin layer rl formed on at least part of the outer peripheral surface of the skirt base material bl.

A plurality of streaks sg are formed on the outer peripheral surface of the skirt base material bl. The streak sg is a streaky groove. The streaks sg can be formed, for example, by turning using a cutting tool. In that case, the streak sg extends in the circumferential direction of the piston 40 . In the example shown in FIG. 5, the cross section of each streak sg perpendicular to the circumferential direction of the piston 40 has a substantially triangular shape, but is not limited to this, and may have, for example, a substantially arcuate shape. In addition, although FIG. 5 shows an example in which a plurality of streaks sg are arranged with almost no space between them, a flat portion may exist between adjacent streaks sg.

The resin layer rl includes, for example, a polymer matrix and solid lubricant particles (solid lubricant) dispersed in the polymer matrix. As a material for the polymer matrix, for example, thermosetting polyamideimide can be suitably used, but the material is of course not limited to this. As the solid lubricant particles, various known solid lubricant particles can be used. For example, graphite particles and molybdenum disulfide particles can be preferably used. The resin layer rl can be formed, for example, by applying a liquid resin material to the base material bl by a spray method or various printing methods (screen printing method, pad printing method, etc.).

In this embodiment, the piston 40 is formed so that the ten-point average roughness Rz _JIS of the outer peripheral surface of the skirt base material bl is within a predetermined range. Specifically, the ten-point average roughness Rz _JIS of the outer peripheral surface of the skirt base material bl is 20 μm or more over substantially the entire outer peripheral surface.

Ten-point average roughness Rz _JIS , as represented by the following formula, is the altitude of the highest to fifth peaks R1, R3, R5, R7 and R9 and the average values of the elevations R2, R4, R6, R8 and R10 of the five deepest valleys. The ten-point average roughness Rz _JIS can be measured using a surface roughness measuring machine (for example, Surfcom 1400D manufactured by Tokyo Seimitsu Co., Ltd.).

As described above, in the engine 100 of the present embodiment, the piston skirt 40 includes a skirt base material bl formed of an aluminum alloy and having a plurality of streaks sg formed on the outer peripheral surface, and at least the outer peripheral surface of the skirt base material bl. and a resin layer rl formed thereon. Since the resin layer rl is formed on the outer peripheral surface of the skirt base material bl, the sliding loss is reduced and the initial conformability of the piston 40 to the cylinder block 10 is improved.

Further, in the engine 100 of the present embodiment, the ten-point average roughness Rz _JIS of the outer peripheral surface of the skirt base material bl is 20 μm or more. It means relatively deep. When the resin layer rl is formed on the outer peripheral surface of the skirt base material bl, the resin material inevitably enters into the streaks sg. The state in which the portion where the aluminum alloy is exposed and the portion where the resin material remains are mixed on the surface of the can be maintained for a long period of time. Therefore, even after the resin layer rl is worn out, seizure between the aluminum alloy piston 40 and the aluminum alloy cylinder block 10 can be suppressed. The ten-point average roughness Rz _JIS of the outer peripheral surface of the skirt base material bl can be adjusted, for example, by changing the cutting tool used when turning the skirt base material bl.

Here, the reason why the effect of suppressing image sticking is obtained will be explained again with reference to FIGS. 6 and 7. FIG.

6 and 7 show a comparison of relatively shallow streaks sg formed on the outer peripheral surface of the skirt base material bl (for example, the ten-point average roughness Rz _JIS of the outer peripheral surface is about 1.6 to 3.2 μm). In the piston skirt 44' of the example and the piston skirt 44 of this embodiment, it is a figure which shows a state that abrasion progresses. state), and a state in which wear has further progressed thereafter.

As can be seen from FIG. 6, in the piston skirt 44' of the comparative example, as the abrasion progresses after the resin layer rl is worn out, the ratio of the exposed aluminum alloy on the outer peripheral surface increases rapidly, leading to immediate seizure. .

On the other hand, in the piston skirt 44 of the present embodiment, as can be seen from FIG. 7, even if the abrasion progresses after the resin layer rl is worn out, the proportion of exposed aluminum alloy on the outer peripheral surface increases slowly. , can delay the occurrence of burn-in.

Subsequently, prototype pistons 40 having a ten-point average roughness Rz _JIS of 20 μm or more on the outer peripheral surface of the skirt base material bl were produced (Examples 1, 2 and 3), and the occurrence of seizure was suppressed (delayed) by a sliding test. The result of verifying the effect will be explained. For verification, the pistons of Examples 1, 2 and 3 and Comparative Examples 1 and 2 were compared. The ten-point average roughness Rz _JIS of the outer peripheral surface of the skirt base material bl was 24.8 μm, 66.7 μm, and 67.8 μm in Examples 1, 2 and 3, respectively, and 1.9 μm in Comparative Examples 1 and 2, respectively. , 11.6 μm. In addition, the thickness of the resin layer bl was 3 to 5 μm in all of Examples 1, 2, and 3 and Comparative Examples 1 and 2 (as described later, the thickness of the resin layer bl can be 10 μm or more. However, here, the thickness of the resin layer bl was set relatively small in order to shorten the test time).

　Figures 8 and 9 show the results of the sliding test. The sliding test was performed under the conditions of a load of 980 N, a rotation speed of 600 rpm, and a temperature of 140°C. FIG. 8 shows the remaining ratio of the resin layer rl (resin layer rl remaining in the region where the resin layer rl is formed on the outer peripheral surface of the piston skirt 44) in Examples 1, 2, and 3 and Comparative Examples 1 and 2. Area ratio) is plotted on the vertical axis and the total test time is plotted on the horizontal axis. In addition, the upper and lower parts of FIG. 9 show photographs of the outer peripheral surface of the piston skirt 44 at a specific total test time for Comparative Example 1 and Example 3, respectively, which have undergone binarization processing. . In each photograph in FIG. 9, the black portion is the portion where the aluminum alloy of the skirt base material bl is exposed, and the gray portion is the portion where the resin layer rl remains. Each photograph in FIG. 9 also shows the remaining ratio of the resin layer rl.

As shown in FIG. 8, in Comparative Examples 1 and 2, the residual ratio of the resin layer rl decreased sharply as the total test time increased. In Comparative Examples 1 and 2, burn-in occurred at the total test time of 3060 seconds and 3600 seconds, respectively. On the other hand, in Examples 1, 2 and 3, the decrease in the residual ratio of the resin layer rl was slow with an increase in the total test time, and no seizure occurred even after the total test time exceeded 7000 seconds.

In addition, from the comparison between the upper and lower parts of FIG. 9, in Example 3, the decrease in the remaining ratio of the resin layer rl is slower than in Comparative Example 1, and no seizure occurs (a relatively large amount of the resin layer rl remains). state) can be maintained for a long period of time.

From the above-described verification results, it can be seen that seizure between the aluminum alloy piston 40 and the aluminum alloy cylinder block 10 is suppressed for a relatively long time by setting the ten-point average roughness Rz _JIS of the outer peripheral surface of the skirt base material bl to 20 μm or more. confirmed that it is possible.

There is no particular upper limit to the ten-point average roughness Rz _JIS of the outer peripheral surface of the skirt base material bl, but if the ten-point average roughness Rz _JIS is too large, there is concern that it will adversely affect the machining accuracy of the piston. Therefore, from the viewpoint of machining accuracy of the piston, the ten-point average roughness Rz _JIS of the outer peripheral surface of the skirt base material bl is preferably 50 μm or less.

The uneven average interval Sm (corresponding to the pitch of the streaks sg) on the outer peripheral surface of the skirt base material bl is preferably 100 μm or more and 500 μm or less. If the average unevenness interval Sm is less than 100 μm, there is a risk that productivity will decrease, or that it will be difficult to manufacture a cutting tool for turning the skirt base material bl. If the average unevenness interval Sm exceeds 500 μm, the machining accuracy of the piston 40 may deteriorate. In addition, since the exposed width of the aluminum alloy after the resin layer rl is worn out becomes large, there is a possibility that the seizure resistance may somewhat deteriorate. The unevenness average interval Sm can be measured using a surface roughness measuring machine, like the ten-point average roughness Rz _JIS .

Although FIGS. 4A and 4B show an example in which the resin layer rl is formed on substantially the entire outer peripheral surface of the piston skirt 44, the resin layer rl may be formed only on a part of the outer peripheral surface. good. However, from the viewpoint of enhancing effects such as reduction of sliding loss and improvement of initial familiarity, it is preferable that the resin layer rl is formed as wide as possible on the outer peripheral surface of the piston skirt 44 . For example, the ratio of the area occupied by the resin layer rl in the outer peripheral surface of the piston skirt 44 is preferably 50% or more, more preferably 70% or more, and 90% or more (that is, the outer circumference of the piston skirt 44 It is more preferable that the resin layer rl is formed on substantially the entire surface.

Also, in the above description, the resin layer rl contains solid lubricant particles, but the resin layer rl may contain hard particles in addition to the solid lubricant. By including the hard particles in the resin layer rl, the abrasion of the resin layer rl can be delayed. For example, metal oxide particles can be used as the hard particles. The amount of hard particles to be added, the particle size of the hard particles, and the like are appropriately adjusted according to the hard particles to be used.

The thickness t1 (see FIG. 5) of the resin layer rl is not particularly limited, but from the viewpoint of maintaining the resin layer rl for a long period of time, the thickness t1 of the resin layer rl is preferably 10 μm or more. Moreover, from the viewpoint of ease of manufacture, the thickness t1 of the resin layer rl is preferably 50 μm or less. As can be seen from FIG. 5, the thickness t1 of the resin layer rl does not include the thickness of the portion where the resin material enters the streaks sg. Further, "the resin layer rl wears out" means that there is no resin material other than the resin material that has entered the streaks sg, and even the resin material that has entered the streaks sg It doesn't even need to cease to exist.

Another example of the configuration of the piston skirt 44 is shown in FIG. In the example shown in FIG. 10, the skirt base material bl has an anodized film (phosphate alumite film) bla formed on the outer peripheral surface by phosphoric acid alumite treatment. When the skirt base material bl has the phosphoric acid alumite film bla on the outer peripheral surface, the adhesion of the resin layer rl to the skirt base material bl can be improved. The thickness t2 of the phosphoric acid alumite film bla is, for example, 30 nm or more and 200 nm or less.

FIG. 11 is a cross-sectional view showing an example configuration of the piston ring 42 of the piston 40. As shown in FIG. In the example shown in FIG. 11 , a diamond-like carbon layer (hereinafter referred to as “DLC layer”) 42D is formed on the outer peripheral portion (outer peripheral surface) of the piston ring 42 . An outer peripheral portion of the piston ring 42 is a portion that contacts the cylinder wall 12 . Although the piston rings 42 do not have to have the DLC layer 42D, each piston ring 42 has the DLC layer 42D on its outer peripheral surface, thereby more reliably preventing the piston rings 42 from scuffing the cylinder wall 12. can do.

The DLC layer 42D is preferably formed by a vapor deposition method (for example, CDV method or PVD method). There are no particular restrictions on the composition or thickness of the DLC layer 42D. The thickness of the DLC layer 42D is preferably 2 μm or more in order to more reliably prevent scuffing. In terms of adhesion, the thickness of the DLC layer 42D is preferably 20 μm or less.

If an aluminum alloy containing silicon, such as that exemplified in the present embodiment, is used as the material of the cylinder block 10, the crystallized silicon crystal grains (primary crystal silicon grains 2) are exposed on the sliding surface 12a. Seizure resistance and wear resistance can be improved.

From the viewpoint of sufficiently increasing the wear resistance and strength of the cylinder block 10, the silicon content of the aluminum alloy, which is the material of the cylinder block 10, is preferably 15% by mass or more and 25% by mass or less. When the silicon content is 15% by mass or more, a sufficiently large amount of primary crystal silicon grains 2 can be crystallized, and the wear resistance of the cylinder block 10 can be sufficiently improved. When the silicon content is 25% by mass or less, the strength of the cylinder block 10 can be maintained sufficiently high. The aluminum content of the aluminum alloy is, for example, 73.4% by mass or more and 79.6% by mass or less. Moreover, the aluminum alloy may contain copper, and in that case, the copper content is, for example, 2.0% by mass or more and 5.0% by mass or less.

The wear resistance of the cylinder block 10 can be further improved by setting the average crystal grain size of the primary crystal silicon grains 2 within the range of 8 μm or more and 50 μm or less. When the average crystal grain size of the primary crystal silicon grains 2 exceeds 50 μm, the number of primary crystal silicon grains 2 per unit area of the sliding surface 12a is small. Therefore, a large load is applied to each of the primary crystal silicon grains 2 during operation of the engine 100, and the primary crystal silicon grains 2 may be crushed. Fragments of the crushed primary-crystal silicon grains 2 act as abrasive particles, so there is a risk that the sliding surface 12a will be greatly worn. Further, when the average crystal grain size of the primary-crystal silicon grains 2 is less than 8 μm, the portion of the primary-crystal silicon grains 2 buried in the matrix 1 is small. Therefore, during operation of the engine 100, the primary crystal silicon grains 2 are likely to fall off. Since the dropped primary-crystal silicon grains 2 act as abrasive particles, the sliding surface 12a may be greatly worn.

On the other hand, when the average crystal grain size of the primary crystal silicon grains 2 is 8 μm or more and 50 μm or less (more preferably 12 μm or more and 50 μm or less), a sufficient number of primary crystal silicon grains 2 per unit area of the sliding surface 12a. exist. Therefore, the load applied to each primary-crystal silicon grain 2 during operation of the engine 100 is relatively small, so crushing of the primary-crystal silicon grains 2 is suppressed. In addition, since the portion of the primary-crystal silicon grains 2 embedded in the matrix 1 is sufficiently large, the drop-off of the primary-crystal silicon grains 2 is reduced, and wear of the sliding surface 12a due to the dropped-off primary-crystal silicon grains 2 is also suppressed. be done.

The average crystal grain size of the eutectic silicon grains is smaller than the average crystal grain size of the primary crystal silicon grains 2 . The average crystal grain size of the eutectic silicon grains is, for example, 7.5 μm or less.

The average crystal grain size of the primary crystal silicon grains 2 and the eutectic silicon grains can be measured as follows by performing image processing on the image of the sliding surface 12a. First, based on the area of the silicon crystal grain obtained by image processing, the diameter (equivalent diameter) of each silicon crystal grain is calculated assuming that the silicon crystal grain is a perfect circle. Specify the number (degrees) and diameter. Fine crystals with a diameter of less than 1 μm are not counted as silicon crystal grains. Based on the calculated number (frequency) and diameter of the silicon crystal grains, the grain size distribution of the silicon crystal grains is obtained. The resulting particle size distribution (histogram) contains two peaks. The grain size distribution is divided into two regions with the diameter of the portion forming the valley between the two peaks as the threshold, the region corresponding to the large diameter being the grain size distribution of the primary crystal silicon grains, and the region corresponding to the small diameter being the eutectic. Suppose it is the particle size distribution of silicon particles. Then, based on each particle size distribution, the average crystal grain size of the primary crystal silicon grains and the average crystal grain size of the eutectic silicon grains can be calculated.

[Transport equipment]
The engine 100 according to the embodiment of the present invention is suitable for use in various transportation equipment. FIG. 12 shows an example of a motorcycle with an engine 100 according to an embodiment of the invention.

A motorcycle 300 shown in FIG. 12 is provided with a head pipe 302 at the front end of a body frame 301 . A front fork 303 is attached to the head pipe 302 so as to swing in the lateral direction of the vehicle. A front wheel 304 is rotatably supported at the lower end of the front fork 303 .

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

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

The engine 100 is held in the central portion of the body frame 301 . A radiator 311 is provided in front of the engine 100 . An exhaust pipe 312 is connected to an exhaust port of the engine 100 and a muffler 313 is attached to the rear end of the exhaust pipe 312 .

A transmission 315 is connected to the engine 100 . A drive sprocket 317 is attached to the output shaft 316 of the transmission 315 . Drive sprocket 317 is connected to rear wheel sprocket 319 of rear wheel 310 via chain 318 . Transmission 315 and chain 318 function as a transmission mechanism that transmits the power generated by engine 100 to the drive wheels.

Although a motorcycle is illustrated here as an example of transportation equipment, the engine according to the embodiment of the present invention is not limited to motorcycles, and is also suitable for other transportation equipment such as four-wheeled motor vehicles, three-wheeled motor vehicles, and ships. used for

As described above, the internal combustion engine 100 according to the embodiment of the present invention includes an aluminum alloy piston 40 having a piston head 43 and a piston skirt 44 extending from the outer peripheral portion of the piston head 43, and a slide on which the piston 40 slides. and a cylinder block 10 made of an aluminum alloy having a cylinder wall 12 including a moving surface 12a. The aluminum alloy is exposed on the sliding surface 12a of the cylinder wall 12. As shown in FIG. The piston skirt 44 is a skirt base material bl made of an aluminum alloy. and a formed resin layer rl. The ten-point average roughness Rz _JIS of the outer peripheral surface of the skirt base material bl is 20 μm or more.

In the internal combustion engine 100 according to the embodiment of the present invention, the piston skirt 44 includes a skirt base material bl formed of an aluminum alloy and having a plurality of streaks sg formed on the outer peripheral surface thereof, and at least a portion of the outer peripheral surface of the skirt base material bl. and a resin layer rl formed thereon. Since the resin layer rl is formed on the outer peripheral surface of the skirt base material bl, the sliding loss is reduced and the initial conformability of the piston 40 to the cylinder block 10 is improved. Further, in the internal combustion engine 100 of the present invention, the ten-point average roughness Rz _JIS of the outer peripheral surface of the skirt base material bl is 20 μm or more. It means relatively deep. When the resin layer rl is formed on the outer peripheral surface of the skirt base material bl, the resin material inevitably enters into the streaks sg. The state in which the portion where the aluminum alloy is exposed and the portion where the resin material remains are mixed on the surface of the can be maintained for a long period of time. Therefore, even after the resin layer rl is worn out, seizure between the aluminum alloy piston 40 and the aluminum alloy cylinder block 10 can be suppressed.

In one embodiment, the plurality of streaks sg extend in the circumferential direction of the piston 40.

The streaks sg can be formed, for example, by turning using a cutting tool. In that case, the streak sg extends in the circumferential direction of the piston 40 .

In one embodiment, the uneven average interval Sm of the outer peripheral surface of the skirt base material bl is 100 μm or more and 500 μm or less.

The uneven average interval Sm (corresponding to the pitch of streaks) on the outer peripheral surface of the skirt base material is preferably 100 μm or more and 500 μm or less. If the average unevenness interval Sm is less than 100 μm, there is a possibility that the productivity will be lowered or that the manufacturing of the cutting tool will be difficult. If the average unevenness interval Sm exceeds 500 μm, the machining accuracy of the piston may deteriorate. In addition, since the exposed width of the aluminum alloy after the resin layer rl is worn out becomes large, there is a possibility that the seizure resistance may somewhat deteriorate.

In one embodiment, the thickness of the resin layer rl is 10 μm or more and 50 μm or less.

From the viewpoint of maintaining the resin layer rl for a long period of time, the thickness t1 of the resin layer rl is preferably 10 μm or more. Moreover, from the viewpoint of ease of manufacture, the thickness t1 of the resin layer rl is preferably 50 μm or less.

In one embodiment, the resin layer rl contains a solid lubricant and hard particles.

Abrasion of the resin layer rl can be delayed by including hard particles in the resin layer rl.

In one embodiment, the skirt base material bl has an anodized coating bla formed on the outer peripheral surface by phosphoric acid alumite treatment.

When the skirt base material bl has an anodized film bla formed on its outer peripheral surface by phosphoric acid alumite treatment, the adhesion of the resin layer rl to the skirt base material bl can be improved.

In one embodiment, the cylinder block 10 is made of an aluminum alloy containing silicon.

When an aluminum alloy containing silicon is used as the material of the cylinder block 10, seizure resistance and wear resistance are improved by exposing crystallized silicon crystal grains (primary crystal silicon grains 2) on the sliding surface 12a. can be made

A transportation device according to an embodiment of the present invention includes an internal combustion engine 100 having any of the configurations described above.

The internal combustion engine 100 according to the embodiment of the present invention is suitable for use in various types of transportation equipment.

According to an embodiment of the present invention, in an internal combustion engine having an aluminum alloy cylinder block and an aluminum alloy piston, it is possible to realize a structure capable of suppressing seizure after the resin layer wears even if cast iron sleeves and plating are omitted. be able to. INDUSTRIAL APPLICABILITY An internal combustion engine according to an embodiment of the present invention is suitable for use in various types of transportation equipment including motorcycles.

1: Matrix (alloy base material), 2: Primary silicon grains, 10: Cylinder block, 11: Cylinder bore, 12: Cylinder wall, 12a: Sliding surface (inner peripheral surface of cylinder wall), 13: Outer wall, 14: Water jacket 20: Cylinder head 21: Intake port 22: Exhaust port 23: Intake valve 24: Exhaust valve 30: Crankcase 40: Piston 41: Piston body 42: Piston ring 42a: Top Ring, 42b: Second ring, 42c: Third ring, 42D: Diamond-like carbon layer, 43: Piston head, 44: Piston skirt, 44a: First skirt portion, 44b: Second skirt portion, 45: Piston pin boss, 45a: Piston pin hole 46: Rib 48: Piston pin 50: Crankshaft 51: Crank pin 52: Crank arm 60: Connecting rod 61: Rod main body 62: Small end 63: Large end 70: combustion chamber, 100: engine (internal combustion engine), 300: motorcycle, bl: skirt base material, bla: anodized film (phosphate alumite film), rl: resin layer, sg: streak

Claims

an aluminum alloy piston having a piston head and a piston skirt extending from the outer periphery of the piston head;
an aluminum alloy cylinder block having a cylinder wall including a sliding surface on which the piston slides;
with
An aluminum alloy is exposed on the sliding surface of the cylinder wall,
The piston skirt includes a skirt base material made of an aluminum alloy, a skirt base material having a plurality of striations formed on an outer peripheral surface, and a skirt base material formed on at least a part of the outer peripheral surface of the skirt base material. and a resin layer,
The internal combustion engine, wherein the outer peripheral surface of the skirt base material has a ten-point average roughness Rz JIS of 20 μm or more.
The internal combustion engine according to claim 1, wherein said plurality of streaks extend in the circumferential direction of said piston.
The internal combustion engine according to claim 1 or 2, wherein the uneven average interval Sm of the outer peripheral surface of the skirt base material is 100 µm or more and 500 µm or less.
The internal combustion engine according to any one of claims 1 to 3, wherein the resin layer has a thickness of 10 µm or more and 50 µm or less.
The internal combustion engine according to any one of claims 1 to 4, wherein the resin layer contains solid lubricant and hard particles.
The internal combustion engine according to any one of claims 1 to 5, wherein the skirt base material has an anodized coating formed on the outer peripheral surface by phosphoric acid alumite treatment.
The internal combustion engine according to any one of claims 1 to 6, wherein said cylinder block is made of an aluminum alloy containing silicon.
A transportation device equipped with the internal combustion engine according to any one of claims 1 to 7.