Sliding member and method for manufacturing sliding member

Abstract

To provide a sliding member capable of suppressing the deterioration of toughness in a mounting part while a sliding part has excellent wear resistance, and a method for manufacturing the sliding member.SOLUTION: The sliding member 1 includes an attachment part 3 attached to a first predetermined member, an extension part 5 extending from the attachment part 3 and having a tip end 5a, and a sliding part 7 provided on the tip end 5a and contacting a second predetermined member different from the first predetermined member. The primary-crystal Si particles are segregated in the sliding part 7, and the content ratio of the primary-crystal Si particles gradually decreases from the sliding part 7 to the mounting part 3.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a slide member and a method for manufacturing the slide member. [Background technology]

[0002] Shift forks made of aluminum alloys are known for use in vehicle transmissions. The shift forks include a main body and a sliding contact portion. The sliding contact portion is also called a sliding portion or a claw portion. The sliding contact portion is a portion that comes into sliding contact with a speed-changing sleeve of the transmission. In other words, the aluminum alloy shift fork is a sliding member that requires wear resistance in the sliding contact portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 178432 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional aluminum alloy shift forks used as sliding members are cast using a hypereutectic Al-Si alloy. Therefore, primary Si crystallizes in areas other than the claws (sliding portion) during the casting process. In other words, the toughness of the entire shift fork is inferior to that of hypoeutectic to eutectic Al-Si alloys commonly used in aluminum alloy castings due to the crystallized primary Si. Therefore, the boss portion (mounting portion) of the shift fork, which has an insertion hole for connecting to the shift shaft of the transmission, is prone to stress concentration due to impact, but the required impact strength may be reduced due to a decrease in toughness. Sliding members such as aluminum alloy shift forks require toughness in the mounting portion to prevent a decrease in impact strength, and wear resistance in the sliding portion that comes into contact with other components.

[0005] Therefore, the present invention provides a sliding member that has excellent wear resistance in the sliding portion while suppressing a decrease in toughness in the mounting portion, and a method for manufacturing the sliding member. [Means for solving the problem]

[0006] In order to solve the above problems, a sliding member according to an embodiment of the present invention is an aluminum alloy casting made of an Al-Si alloy, comprising: a mounting portion to be mounted on a first predetermined member; an extension portion extending from the mounting portion; and a sliding portion provided at a tip of the extension portion and contacting a second predetermined member different from the first predetermined member. Primary Si particles are segregated in the sliding portion, and the content of the primary Si particles gradually decreases from the sliding portion to the mounting portion.

[0007] Further, in order to solve the above-mentioned problems, a manufacturing method of a slide member according to an embodiment of the present invention is a manufacturing method of a slide member, the slide member being an aluminum alloy casting made of an Al-Si alloy, comprising: an attachment portion to be attached to a first predetermined member; an extension portion extending from the attachment portion; and a sliding portion provided at a tip of the extension portion and in contact with a second predetermined member different from the first predetermined member, the aluminum alloy casting being made of an Al-Si alloy, primary crystal Si particles segregating in the sliding portion, and a content ratio of the primary crystal Si particles gradually decreasing from the sliding portion to the attachment portion, the manufacturing method comprising the steps of: arranging the mold so that the attachment portion is located below the mold and the sliding portion is located above the mold; filling the mold with a molten Al-Si alloy; and cooling the mold filled with the molten Al-Si alloy.

[0008] Further, in order to solve the above-mentioned problems, there is provided a method for producing a slide member according to an embodiment of the present invention, which is an aluminum alloy casting made of an Al-Si alloy, comprising: an attachment part to be attached to a first predetermined member; an extension part extending from the attachment part; and a sliding part provided at a tip of the extension part and in contact with a second predetermined member different from the first predetermined member, the aluminum alloy casting being made of an Al-Si alloy, wherein primary crystal Si particles segregate in the sliding part, and the content of the primary crystal Si particles gradually decreases from the sliding part to the attachment part, the method for producing the slide member employing a centrifugal casting method in which a rotation center line of a mold is provided outside the mold, and the method includes: an arrangement step of arrangement of the mold such that the attachment part is located far from the rotation center line and the sliding part is located near the rotation center line; a filling step of filling the mold with a molten Al-Si alloy; and a cooling step of cooling the mold filled with the molten Al-Si alloy while rotating it about the rotation center line. [Effects of the Invention]

[0009] The present invention provides a sliding member that has excellent wear resistance in the sliding portion while suppressing a decrease in toughness in the mounting portion, and a method for manufacturing the sliding member. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic view showing an example of a sliding member according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram showing an example of a transmission including a shift fork as a sliding member according to an embodiment of the present invention; [Figure 3] 3 is a flowchart showing a method for manufacturing a slide member according to an embodiment of the present invention. [Figure 4] FIG. 1A is a front cross-sectional view showing an example of a mold for a slide member according to an embodiment of the present invention; FIG. 1B is a side cross-sectional view showing an example of a mold for a slide member according to an embodiment of the present invention. [Figure 5] (A) A diagram showing an example of a segregation model of primary Si crystals in the molten metal filled into the mold of FIG. 4(A). (B) A diagram showing an example of a segregation model of primary Si crystals in the molten metal filled into the mold of FIG. 4(B). [Figure 6] FIG. 1 is a cross-sectional photograph of a test piece made of a hypereutectic Al—Si alloy. [Figure 7] FIG. 7 is an enlarged cross-sectional photograph of a region R1 in FIG. 6. [Figure 8] 8(A) is a cross-sectional photograph showing an enlarged view of region R2 in FIG. 7, and FIG. 8(B) is a cross-sectional photograph showing an enlarged view of region R4 in FIG. 8(A). [Figure 9] 9(A) is a cross-sectional photograph showing an enlarged view of region R3 in FIG. 7, and FIG. 9(B) is a cross-sectional photograph showing an enlarged view of region R5 in FIG. 9(A). [Figure 10] FIG. 10 is a front cross-sectional view showing an example of a mold when centrifugal casting is used as a modified example of the method for manufacturing a slide member according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of a slide member and a method for manufacturing a slide member according to the present invention will be described with reference to FIGS.

[0012] Fig. 1 is a schematic view showing an example of a sliding member according to an embodiment of the present invention, and also shows a shift fork 10 as a sliding member 1 according to this embodiment.

[0013] The slide member 1 according to this embodiment shown in FIG. 1 is an aluminum alloy casting made of an Al-Si alloy. That is, the slide member 1 is manufactured by casting. More specifically, wear resistance is imparted by casting using a hypereutectic Al-Si alloy. Hypereutectic Al-Si alloys are used in parts that require wear resistance, taking advantage of the properties of hard primary crystal Si.

[0014] 1, the sliding member 1 according to this embodiment includes an attachment portion 3 that is attached to a first predetermined member, which is another member, an extension portion 5 that extends from the attachment portion 3, and a sliding portion 7 that is provided at a tip end portion 5a of the extension portion 5 and that is for contacting a second predetermined member that is different from the first predetermined member. Note that the attachment portion 3 may have, for example, a through hole 3a so that it can be attached to the first predetermined member.

[0015] The sliding member 1 is, for example, a shift fork of a vehicle. In a vehicle transmission, the shift fork moves a shift sleeve to select a gear and engage the appropriate gear. Specifically, when a driver operates a shift lever, the shift fork moves and switches gears. Below, a shift fork 10 will be taken as an example of the sliding member 1 of this embodiment. Note that the sliding member 1 of this embodiment is not limited to a shift fork as long as it includes an attachment portion 3, an extension portion 5, and a sliding portion 7, and can also be applied to sliding members other than a shift fork.

[0016] FIG. 2 is a schematic diagram showing an example of a transmission including a shift fork as a sliding member according to an embodiment of the present invention.

[0017] A transmission 50 including a shift fork 10 as the sliding member 1 according to this embodiment shown in FIG. 2 includes, for example, a shift shaft 51 to which the shift fork 10 is attached, a main shaft 53, a first gear 55, a second gear 57, a synchronizer hub 61, and a shift sleeve 63.

[0018] As shown in FIG. 2 in addition to FIG. 1, shift fork 10 includes a boss portion 13 having an insertion hole 13a into which shift shaft 51 of transmission 50 is inserted, an arm portion 15 extending from boss portion 13 and fitting with play in outer peripheral groove portion 65 of transmission sleeve 63, and claw portions 17 provided at tip end portion 15a of arm portion 15 and making slidable contact with one side wall 65a and the other side wall 65b of outer peripheral groove portion 65.

[0019] When the sliding member 1 is a shift fork 10, the corresponding relationships between the components of the sliding member 1 and the components of the shift fork 10 are as follows: the attachment portion 3 is a boss portion 13, the extension portion 5 is an arm portion 15, and the sliding portion 7 is a claw portion 17. The first predetermined member is a shift shaft 51, and the second predetermined member is a speed-changing sleeve 63.

[0020] The boss portion 13 is attached to the shift shaft 51 by inserting (fitting) the shift shaft 51 into the insertion hole 13a. In other words, the shift fork 10 is attached to the shift shaft 51 via the boss portion 13.

[0021] The arm portion 15 extends from the boss portion 13 and branches into two at some point. The arm portion 15 has a bifurcated shape, which allows it to fit into the outer circumferential groove portion 65 so as to sandwich the speed change sleeve 63 therebetween.

[0022] Claw portions 17 are provided on respective bifurcated tip portions 15a of arm portion 15. As shift fork 10 moves in the axial direction of shift shaft 51, claw portions 17 slide relative to transmission sleeve 63 via one side wall 65a and the other side wall 65b of outer circumferential groove portion 65, thereby pressing transmission sleeve 63.

[0023] Conventional aluminum alloy shift forks are cast using a hypereutectic Al-Si alloy by die casting, which results in primary Si crystallization in areas other than the claws. As a result, the overall toughness of the shift fork is inferior to that of Al-Si alloys with a hypoeutectic to eutectic composition that are commonly used in aluminum alloy castings. This could result in a decrease in impact strength in the vicinity of the boss portion of the shift fork that is used to attach it to the shift shaft.

[0024] Therefore, in the slide member 1 according to this embodiment, primary crystal Si particles are segregated in the slide portion 7, and the content ratio of the primary crystal Si particles gradually decreases from the slide portion 7 to the attachment portion 3. In other words, in the shift fork 10 as the slide member 1, primary crystal Si particles are segregated in the claw portion 17, and the content ratio of the primary crystal Si particles gradually decreases from the claw portion 17 to the boss portion 13.

[0025] Specifically, stress tends to concentrate on the boss portion 13 of the shift fork 10 when an impact is applied. Therefore, the content of primary crystal Si particles is reduced near the boss portion 13, and instead an Al-Si alloy with a hypoeutectic to eutectic composition is used to suppress the reduction in toughness due to the primary crystal Si particles. Meanwhile, primary crystal Si particles are segregated near the claw portions 17 to impart wear resistance. Whether or not primary crystal Si particles are segregated can be determined, for example, from the results of a test to evaluate the hardness of the claw portions 17 and the results of image analysis of cross-sectional images of the claw portions 17.

[0026] A method for manufacturing the slide member 1 that can cause primary crystal Si to segregate only in a specific portion such as the slide portion 7 will be described in detail below.

[0027] FIG. 3 is a flowchart showing a method for manufacturing a slide member according to an embodiment of the present invention.

[0028] FIG. 4(A) is a front cross-sectional view showing an example of a mold for a slide member according to an embodiment of the present invention, and FIG. 4(B) is a side cross-sectional view showing an example of a mold for a slide member according to an embodiment of the present invention.

[0029] 4(A) and 4(B), the mold 100 for the sliding member 1 is assumed to be used for casting a shift fork 10 as the sliding member 1. H indicates the up-down direction of the mold 100, and coincides with the height direction of the mold 100. W indicates the left-right direction of the mold 100, which coincides with the width direction of the mold 100. D corresponds to the depth direction of the mold 100. The same applies to the figures described hereinafter. Also, Fig. 4(A) is a cross-sectional view taken through the center of the depth direction of the mold 100 and parallel to the vertical direction of the mold 100. The same applies to Figs. 5(A) and 10. Furthermore, Fig. 4(B) is a cross-sectional view taken through the mold 100 along line AA in Fig. 4(A) and parallel to the vertical direction of the mold 100. The same applies to Fig. 5(B).

[0030] As shown in Fig. 1 , Fig. 3 , Fig. 4(A), and Fig. 4(B), the method for producing a slide member 1 according to this embodiment includes an arrangement step S1 in which a mold 100 is arranged so that the mounting portion 3 of the slide member 1 to be cast is located below the mold 100 and the sliding portion 7 of the slide member 1 is located above the mold 100; a filling step S2 in which a molten Al-Si alloy is filled into the mold 100; and a cooling step in which the mold 100 filled with the molten Al-Si alloy is cooled. Specifically, the molten Al-Si alloy is a molten metal of a hypereutectic Al-Si alloy. Hereinafter, the molten Al-Si alloy may be simply referred to as "molten metal." Each of steps S1 to S3 will be described in more detail below.

[0031] In the placement step S1, the mold 100 is placed in a casting machine (not shown) while maintaining the placement shown in Fig. 4(A) and Fig. 4(B). The mold 100 has a cavity 101 for casting the slide member 1 and a runner 103, which is a path for pouring molten Al-Si alloy into the cavity 101. For ease of explanation, in the front cross-sectional view of Fig. 4(A), a part of the runner 103 that does not actually exist is shown by a two-dot chain line, and the remaining part of the runner 103 that exists is shown by a solid line. The same applies to Fig. 5(A).

[0032] The cavity 101 has a shape that follows the outer shape of the sliding member 1. A portion 101a of the cavity 101, where the mounting portion 3 of the sliding member 1 will be cast, is located below the mold 100, and a portion 101b of the cavity 101, where the sliding portion 7 of the sliding member 1 will be cast, is located above the mold 100. Therefore, when the sliding member 1 is cast inside the cavity 101 in the future, the sliding portion 7 will be located above the mounting portion 3 in the mold 100.

[0033] Runner 103 is provided to connect the upper surface of mold 100 and the underside of cavity 101. Runner 103 also communicates with portion 101a of cavity 101 located on the underside of mold 100.

[0034] In the filling step S2 following the placing step S1, molten metal is poured from the gate 103a of the runner 103 to fill the interior of the cavity 101. Because the runner 103 is provided from the top surface of the mold 100 toward the bottom of the cavity 101, the molten metal poured from the gate 103a flows smoothly through the runner 103 by the action of gravity and easily reaches the interior of the cavity 101. At this time, the molten metal flowing through the runner 103 flows into the interior of the cavity 101 from the portion 101a of the cavity 101. The molten metal may be poured from the gate 103a while tilting the mold 100. This reduces turbulence of the molten metal during pouring, reduces air entrainment, and improves the quality of the sliding member 1.

[0035] FIG. 5(A) is a diagram showing an example of a segregation model of primary Si crystals in the molten metal filled into the mold of FIG. 4(A), and FIG. 5(B) is a diagram showing an example of a segregation model of primary Si crystals in the molten metal filled into the mold of FIG. 4(B).

[0036] In the cooling step S3 following the filling step S2, the mold 100 with the molten metal 110 filled in the cavity 101 is cooled as shown in FIGS. 5(A) and 5(B). At this time, the mold 100 maintains the state in which it was placed in the placing step S1. That is, the mold 100 is maintained so that the attachment portion 3 of the sliding member 1 is located below the mold 100 and the sliding portion 7 of the sliding member 1 is located above the mold 100. Cooling the mold 100 in this position makes it possible to segregate primary crystal Si in the sliding portion 7 of the sliding member 1, as will be described below.

[0037] Specifically, the specific gravity of aluminum (Al) is 2.7 g / cm 3 In contrast, the specific gravity of silicon (Si) is 2.3g / cm 35(A) and 5(B), primary crystal Si particles 201 crystallized in the molten metal 110 filled inside the cavity 101 gradually float to the upper side of the mold 100 due to the difference in specific gravity, and segregate in regions Q1 and Q2 of the cavity 101 enclosed by a circle indicated by a dashed dotted line. Regions Q1 and Q2 correspond to the vicinity of the sliding portion 7 of the slide member 1. After the cooling step S3, the cast slide member 1 is removed from the mold 100, and the slide member 1 in which the primary crystal Si particles 201 have segregated in the sliding portion 7 is obtained.

[0038] By including the above-described steps S1 to S3, the method for manufacturing the slide member 1 according to the present embodiment makes it possible to manufacture the slide member 1 in which primary crystal Si is segregated only in a specific portion such as the sliding portion 7.

[0039] FIG. 6 is a cross-sectional photograph of a test piece made of a hypereutectic Al—Si alloy.

[0040] The top side of the test specimen 200 shown in Fig. 6 means the top side of the test specimen 200 that faced the top surface of the mold when the test specimen 200 was cast. In other words, the top side of the test specimen 200 faced the top side of the mold when the test specimen 200 was cast. The bottom side of the test specimen 200 means the bottom side of the test specimen 200 that faced the bottom surface of the mold when the test specimen 200 was cast. The same applies to Fig. 7.

[0041] FIG. 7 is a cross-sectional photograph showing an enlarged view of region R1 in FIG.

[0042] 8(A) is a diagram showing a cross-sectional photograph in which a region R2 in FIG. 7 is enlarged, and FIG. 8(B) is a diagram showing a cross-sectional photograph in which a region R4 in FIG. 8(A) is enlarged.

[0043] 9(A) is a diagram showing a cross-sectional photograph in which a region R3 in FIG. 7 is enlarged, and FIG. 9(B) is a diagram showing a cross-sectional photograph in which a region R5 in FIG. 9(A) is enlarged.

[0044] In the process of finding a manufacturing method for the slide member 1 according to this embodiment, the inventors cast a test piece made of a hypereutectic Al-Si alloy in order to observe the segregation of primary crystal Si. Here, the segregation of primary crystal Si in the cast test piece 200 will be described with reference to Figs. 6 to 9 .

[0045] A test piece 200 having a substantially rectangular parallelepiped shape (substantially flat plate shape) as shown in Fig. 6 was cast, and the state of its cross section was confirmed at two locations, the top side and the bottom side of the test piece 200, as shown in Fig. 7. As a result, as shown in Figs. 8(A) and 8(B), segregation of primary crystal Si particles 201 was confirmed on the top side of the test piece 200. Furthermore, as shown in Figs. 9(A) and 9(B), segregation of eutectic Si particles 203 was confirmed on the bottom side of the test piece 200. In other words, it was confirmed that segregation of primary crystal Si particles 201 was suppressed on the bottom side of the test piece 200. Therefore, as is clear from the observation results regarding the segregation of the primary-crystal Si particles 201 in the cross section of the test piece 200, in the manufacturing method of the slide member 1 according to this embodiment, by designating the location where the primary-crystal Si particles 201 are desired to segregate as the top side (upper side), the primary-crystal Si particles 201 are segregated at the same location, thereby imparting excellent wear resistance, and by designating the location where the segregation of the primary-crystal Si particles 201 is desired to be suppressed as the bottom side (lower side), the segregation of the primary-crystal Si particles 201 at the same location is suppressed, thereby making it possible to impart excellent toughness.

[0046] Furthermore, the method for manufacturing the slide member 1 according to this embodiment preferably uses gravity casting. Generally, in low-pressure casting, molten metal is filled into the cavity of a mold (metal mold) through a sprue provided on the lower side of the mold. Then, the molten metal filled from the portion farthest from the sprue, i.e., the upper portion of the cavity, solidifies sequentially. On the other hand, in the method for manufacturing the slide member 1 according to this embodiment, in order to segregate the primary crystal Si particles 201 on the upper side (top side) in the cavity 101 of the mold 100, it is necessary to delay the solidification of the molten metal 110 on the upper side. Therefore, by using gravity casting instead of low-pressure casting, the solidification of the molten metal 110 on the upper side is delayed, making it easier to segregate the primary crystal Si particles 201.

[0047] Furthermore, sand casting is preferably used as a manufacturing method for the slide member 1 of this embodiment. Sand casting is a manufacturing method in which molten metal is poured into a mold made of sand. Types of molds that can be used in sand casting include, for example, green sand molds (green molds), self-hardening molds (furan molds), glass-hardening molds (water glass molds), and thermosetting molds (shell molds). When the mold 100 is a sand mold, sand casting extends the time required for the casting to cool compared to when the mold 100 is a metal mold. In other words, sand casting extends the time required for the molten metal 110 filled inside the cavity 101 of the mold 100 to solidify. Therefore, sufficient time can be ensured for the primary crystal Si particles 201 to float up in the molten metal 110 in the cooling step S3.

[0048] 4 and 5, the mold 100 preferably has a feeder 105 connected to the sliding portion 7 of the sliding member 1. The feeder 105 is the area P surrounded by a two-dot chain line in FIGS. 4(A) and 4(B). The feeder 105 is a basin for storing the molten metal 110 filled in the cavity 101. The feeder 105 communicates with a portion 101b in the cavity 101 where the sliding portion 7 of the sliding member 1 will be cast in the cooling step S3, and delays solidification of the molten metal 110 in this portion 101b. This allows more primary Si particles 201 to float around the portion 101b in the cavity 101 where the sliding portion 7 will be cast. In other words, the primary Si particles 201 can be more reliably segregated in the sliding portion 7.

[0049] Furthermore, after the filling step S2, it is preferable that the feeder head 105 is closed to the outside of the mold 100. By doing so, the molten metal 110 stored in the feeder head 105 is isolated from the atmosphere outside the mold 100, making it easier to maintain a high temperature. That is, in the cooling step S3, the feeder head 105 further delays the solidification of the molten metal 110 in the part 101b in the cavity 101 where the sliding part 7 of the sliding member 1 will be cast, and can more reliably segregate the primary crystal Si particles 201 in the sliding part 7.

[0050] In the cooling step S3, the temperature of the molten Al-Si alloy filled inside the cavity 101 is preferably maintained at 580°C or higher for at least four minutes or more. This more reliably ensures that the primary crystal Si particles 201 have enough time to float up in the molten metal 110.

[0051] In the manufacturing method of the slide member 1 according to the present embodiment, the slide member 1 may be a shift fork. In this case, the manufacturing method of the slide member 1 can segregate the primary crystal Si particles 201 in the claw portions 17 of the shift fork 10 to be cast.

[0052] FIG. 10 is a front cross-sectional view showing an example of a mold when centrifugal casting is used as a modified example of the method for manufacturing a slide member according to an embodiment of the present invention.

[0053] As shown in FIG. 10 , a modified manufacturing method for the slide member 1 according to this embodiment employs centrifugal casting. In this centrifugal casting, the rotation center line C of the mold 100A is located outside the mold 100A. The rotation center line C coincides with the rotation axis of a centrifugal casting machine (not shown). The modified manufacturing method for the slide member 1 includes an arrangement step of arranging the mold 100A so that the mounting portion 3 of the slide member 1 is located farther from the rotation center line C and the sliding portion 7 of the slide member 1 is located closer to the rotation center line C; a filling step of filling the mold 100A with a molten Al-Si alloy; and a cooling step of cooling the mold 100A filled with the molten Al-Si alloy while rotating it about the rotation center line C. The arrangement step and cooling step specific to the modified manufacturing method for the slide member 1 according to this embodiment will be described below. Hereinafter, the manufacturing method for the slide member 1 according to this embodiment, which is not a modified example, may be referred to as a first example of a manufacturing method for the slide member 1.

[0054] In the placement step, the mold 100A is placed in a centrifugal casting machine while maintaining the placement shown in Fig. 10. Specifically, a portion 101a of the cavity 101 where the mounting portion 3 of the sliding member 1 is to be cast is located farther from the rotation center line C of the mold 100A, and a portion 101b of the cavity 101 where the sliding portion 7 of the sliding member 1 is to be cast is located closer to the rotation center line C of the mold 100A. In other words, when the sliding member 1 is cast in the cavity 101 in the future, the sliding portion 7 will be located closer to the rotation center line C than the mounting portion 3 in the mold 100A placed in the centrifugal casting machine.

[0055] In the cooling step, the mold 100A, whose cavity 101 has been filled with the molten metal 110 in the filling step, is cooled while being rotated about a rotation center line C, as shown in Fig. 10. By cooling the mold 100A in this manner, it becomes possible to segregate primary crystal Si particles 201 in the sliding portion 7 by the action of centrifugal force.

[0056] As described above, the method for manufacturing the slide member 1 according to this embodiment includes the arrangement step S1 of arranging the mold 100 so that the attachment portion 3 of the slide member 1 is located below the mold 100 and the sliding portion 7 of the slide member 1 is located above the mold 100, the filling step S2 of filling the mold 100 with a molten Al-Si alloy, and the cooling step S3 of cooling the mold 100 filled with the molten Al-Si alloy. Therefore, the method for manufacturing the slide member 1 according to this embodiment segregates primary crystal Si particles 201 in the sliding portion 7 located above the attachment portion 3 in the mold 100, thereby making it possible to manufacture a slide member 1 having excellent wear resistance in the sliding portion 7 and having, as an entire part, toughness and processability equivalent to those of Al-Si alloys of hypoeutectic to eutectic compositions commonly used in aluminum alloy castings.

[0057] Furthermore, in order to improve the wear resistance of aluminum alloys, it is conceivable to perform surface treatments such as anodizing or plating with an Fe—Ni alloy. However, these surface treatments require special equipment and involve additional steps. Furthermore, plating treatments reduce the recyclability of Al-based alloys. On the other hand, the method for manufacturing the slide member 1 according to this embodiment does not cause these problems, and therefore has excellent manufacturability and can maintain the recyclability of the Al-based alloy for the manufactured slide member 1.

[0058] The manufacturing method of the slide member 1 according to this embodiment uses gravity casting. Therefore, in comparison with the case where low-pressure casting is used, the manufacturing method of the slide member 1 can easily cause the primary crystal Si particles 201 to float to the portion 101b of the cavity 101, which is located above the mold 100 and in which the sliding portion 7 of the slide member 1 is cast, in the cooling step S3, and can easily segregate the primary crystal Si particles 201 in the portion 101b.

[0059] The method for manufacturing the slide member 1 according to this embodiment uses sand casting. Therefore, in the method for manufacturing the slide member 1, when the mold 100 filled with the molten metal 110 is cooled in the cooling step S3, it is possible to ensure time for the primary crystal Si particles 201 to float up and segregate in the portion 101b of the cavity 101 where the sliding portion 7 of the slide member 1 is cast.

[0060] Moreover, in the manufacturing method of the sliding member 1 according to this embodiment, the mold 100 has a feeder portion 105 having a tundish communicating with the sliding portion 7 of the sliding member 1. Therefore, in the manufacturing method of the sliding member 1, the time until the molten metal 110 in the part 101b of the cavity 101 where the sliding portion 7 is cast is solidified can be extended in the cooling step S3, thereby ensuring the time until the primary crystal Si particles 201 are segregated in the sliding portion 7.

[0061] Furthermore, the manufacturing method for the slide member 1 according to this embodiment includes the feeder 105 that is closed to the outside of the mold 100 after the filling step S2. Therefore, the manufacturing method for the slide member 1 further delays solidification of the molten metal 110 in the part 101b of the cavity 101 that becomes the sliding part 7 of the slide member 1 in the cooling step S3, thereby more reliably segregating the primary crystal Si particles 201 in the sliding part 7.

[0062] Furthermore, the method for manufacturing the slide member 1 according to this embodiment includes a cooling step S3 in which the melting temperature of the Al-Si alloy molten metal is maintained at 580°C or higher for at least four minutes. Therefore, the method for manufacturing the slide member 1 can reliably ensure time for the primary crystal Si particles 201 to segregate at the sliding portion 7 of the slide member 1.

[0063] Moreover, in the manufacturing method of the slide member 1 according to the present embodiment, the shift fork 10 is cast as the slide member 1. Therefore, the manufacturing method of the slide member 1 can manufacture the shift fork 10 including the claw portion 17 having excellent wear resistance due to the segregation of the primary crystal Si particles 201, and the boss portion 13 having high toughness due to the reduced content of the primary crystal Si particles 201.

[0064] Furthermore, a modified example of the method for manufacturing the sliding member 1 according to the present embodiment uses a centrifugal casting method in which the rotation center line C of the mold 100A is located outside the mold 100A, and includes an arrangement step of arranging the mold 100A so that the attachment portion 3 of the sliding member 1 is located farther from the rotation center line C and the sliding portion 7 is located closer to the rotation center line C, a filling step of filling the inside of the mold 100A with a molten Al-Si-based alloy, and a cooling step of cooling the mold 100A filled with the molten Al-Si-based alloy while rotating it about the rotation center line C. Therefore, in the modified method for manufacturing the slide member 1, the primary crystal Si particles 201 can be segregated in a relatively short time in the vicinity of the portion 101b of the cavity 101, which is located closer to the rotation center line C and where the slide portion 7 is to be cast, in the molten Al-Si alloy filled inside the cavity 101 of the mold 100A, by the action of the centrifugal force generated by rotating the mold 100A about the rotation center line C. Therefore, the modified method for manufacturing the slide member 1 can achieve effects equal to or greater than those of the first example of the method for manufacturing the slide member 1.

[0065] Therefore, according to the sliding member 1 and the manufacturing method for the sliding member 1 according to this embodiment, it is possible to prevent a decrease in toughness in the mounting portion 3 while providing the sliding portion 7 with excellent wear resistance.

[0066] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0067] 1...sliding member, 3...mounting portion, 3a...through hole, 5...extension portion, 5a...tip portion, 7...sliding portion, 10...shift fork, 13...boss portion, 13a...insertion hole, 15...arm portion, 15a...tip portion, 17...claw portion, 50...transmission, 51...shift shaft, 53...main shaft, 55...first gear, 57...second gear, 61...synchronizer hub, 63...speed change sleeve, 65...outer peripheral groove portion, 65a...one side wall, 65b...other side wall, 100, 100A...mold, 101...cavity, 101a, 101b...part, 103...runner, 103a...gate, 105...feeder portion, 110...molten metal, 200...test piece, 201...primary silicon particles, 203...eutectic silicon particles.

Claims

1. an attachment portion attached to a first predetermined member; an extension portion extending from the attachment portion and having a tip portion; a sliding portion provided at the tip portion and contacting a second predetermined member different from the first predetermined member, It is an aluminum alloy casting made of an Al-Si alloy, A sliding member in which primary crystal Si particles are segregated in the sliding portion, and the content ratio of the primary crystal Si particles gradually decreases from the sliding portion to the mounting portion.

2. When the sliding member is a shift fork, the first predetermined member is a shift shaft, the second predetermined member is a speed-changing sleeve having an outer circumferential groove portion, the mounting portion is a boss portion having an insertion hole and being attached to the shift shaft by inserting the shift shaft into the insertion hole, the extension portion is an arm portion that fits into the outer circumferential groove portion with play, 2. The sliding member according to claim 1, wherein the sliding portion is a claw portion that contacts one side wall and the other side wall of the outer circumferential groove portion.

3. an attachment portion attached to a first predetermined member; an extension portion extending from the attachment portion and having a tip portion; a sliding portion provided at the tip portion and contacting a second predetermined member different from the first predetermined member, It is an aluminum alloy casting made of an Al-Si alloy, A method for manufacturing a slide member in which primary crystal Si particles are segregated in the sliding portion, and a content ratio of the primary crystal Si particles gradually decreases from the sliding portion to the mounting portion, an arrangement step of arranging the mold so that the mounting portion is located below the mold and the sliding portion is located above the mold; a filling step of filling the inside of the mold with a molten Al-Si alloy; and a cooling step of cooling the mold filled with the molten Al-Si alloy.

4. The method for manufacturing the slide member according to claim 3, wherein the method for manufacturing the slide member uses gravity casting.

5. The method for manufacturing the slide member according to claim 3, wherein the method for manufacturing the slide member uses a sand casting method.

6. The method for manufacturing a sliding member according to claim 3, wherein the mold has a riser portion connected to the sliding portion.

7. The method for manufacturing a sliding member according to claim 6, wherein the feeder portion is closed to the outside of the mold after the filling step.

8. 4. The method for producing a slide member according to claim 3, wherein in the cooling step, the temperature of the molten Al-Si alloy filled in the mold is maintained at 580 degrees Celsius or higher for at least four minutes.

9. The method for manufacturing a sliding member according to claim 3, wherein the sliding member is a shift fork.

10. an attachment portion attached to a first predetermined member; an extension portion extending from the attachment portion and having a tip portion; a sliding portion provided at the tip portion and contacting a second predetermined member different from the first predetermined member, It is an aluminum alloy casting made of an Al-Si alloy, A method for manufacturing a slide member in which primary crystal Si particles are segregated in the sliding portion, and a content ratio of the primary crystal Si particles gradually decreases from the sliding portion to the mounting portion, the manufacturing method of the sliding member uses a centrifugal casting method in which a rotation center line of a mold is provided outside the mold, an arrangement step of arranging the mold so that the mounting portion is located farther from the rotation center line and the sliding portion is located closer to the rotation center line; a filling step of filling the inside of the mold with a molten Al-Si alloy; and a cooling step of cooling the mold filled with the molten Al-Si alloy while rotating the mold about the rotation center line.

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