Patent Description:
A typical multiple disc clutch device mounted in, for example, an automobile includes a clutch housing obtained by forming a metal material into a cylindrical shape. The clutch housing has splines to which clutch plates or clutch discs can be fitted on an inner peripheral surface or an outer peripheral surface thereof. The clutch housing having the splines is obtained by, for example, a forming step and a cutting step. In the forming step, an aluminum material is cast into an aluminum casting having projections that extend in an axial direction and that are continuously arranged in a circumferential direction. In the cutting step, projecting end portions of the projections formed in the forming step are cut (more specifically, processed with an NC lathe) along a processing line having a predetermined processing diameter to form splines of predetermined dimensions. Some examples of prior art can be found in <CIT>, <CIT>, <CIT>, <CIT> and in <CIT>.

Unfortunately, according to the above-described related art, when the splines of predetermined dimensions are formed by cutting the projecting end portions of the projections by using an NC lathe, there is a risk that portions of the projections will be chipped when a cutting tool passes. More specifically, referring to <FIG>, when a projecting end portion of a projection f is cut along a processing line having a predetermined processing diameter D with a cutting tool T, there is a risk that a portion (corner portion) of the projection f will fall off to leave a chipped portion d on the spline when the cutting tool T passes the projection f, as illustrated in <FIG>. The spline having the chipped portion d may cause a problem that satisfactory power transmission cannot be achieved when clutch plates or clutch discs are fitted to the spline to provide the function of a clutch.

The present invention has been made in view of the above-described circumstances, and provides an aluminum component and a method for manufacturing the aluminum component with which the occurrence of chipping of splines can be reduced.

According the invention of Claim <NUM>, a method for manufacturing an aluminum component includes a forming step of obtaining an aluminum casting having projections that extend in an axial direction and that are continuously arranged in a circumferential direction and a cutting step of cutting projecting end portions of the projections formed in the forming step along a processing line having a predetermined processing diameter, thereby obtaining splines of predetermined dimensions. Each projection is formed such that side surfaces thereof are inclined to be tapered in a direction from a base end to a projecting end, and such that a portion of each side surface that is adjacent to the projecting end and that is cut in the cutting step is either an inclined surface or a rounded portion, the inclined surface having an inclination angle less than an inclination angle of a portion of the side surface that is adjacent to the base end.

According to the invention of Claim <NUM>, in the method for manufacturing an aluminum component according to Claim <NUM>, the inclination angle of the inclined surface of each projection with respect to a projecting end surface of the projection is set in a range of approximately <NUM>° to approximately <NUM>°.

According to the invention of Claim <NUM>, in the method for manufacturing an aluminum component according to Claim <NUM> or <NUM>, each projection is formed such that a projecting end surface thereof is inclined with respect to the axial direction and that the inclined surface or the rounded portion has a width that is greater in a region where the projecting end surface is high than in a region where the projecting end surface is low.

According to the invention of Claim <NUM>, in the method for manufacturing an aluminum component according to any one of Claims <NUM> to <NUM>, the splines are configured to allow a plurality of clutch plates or clutch discs to be fitted and assembled thereto.

According to the invention of Claim <NUM>, an aluminum component is formed from an aluminum casting having projections that extend in an axial direction and that are continuously arranged in a circumferential direction, the projections including projecting end portions to be cut along a processing line having a predetermined processing diameter to obtain splines of predetermined dimensions. Each projection is formed such that side surfaces thereof are inclined to be tapered in a direction from a base end to a projecting end, and such that a portion of each side surface that is adjacent to the projecting end and that is cut in the cutting step is either an inclined surface or a rounded portion, the inclined surface having an inclination angle less than an inclination angle of a portion of the side surface that is adjacent to the base end, wherein each projection is formed such that a projecting end surface thereof is inclined with respect to the axial direction and that the inclined surface or the rounded portion has a width that is greater in a region where the projecting end surface is high than in a region where the projecting end surface is low.

According to the invention of Claim <NUM>, in the aluminum component according to Claim <NUM>, the inclination angle of the inclined surface of each projection with respect to a projecting end surface of the projection is set in a range of approximately <NUM>° to approximately <NUM>°.

According to the invention of Claim <NUM>, in the aluminum component according to any one of Claims <NUM> to <NUM>, the splines are configured to allow a plurality of clutch plates or clutch discs to be fitted and assembled thereto.

According to the invention of Claims <NUM> and <NUM>, each projection is formed such that the side surfaces thereof are inclined to be tapered in the direction from the base end to the projecting end and that the portion of each side surface that is adjacent to the projecting end and that is cut in the cutting step is either the inclined surface or the rounded portion, the inclined surface having an inclination angle less than that of the portion of the side surface that is adjacent to the base end. Therefore, the occurrence of chipping of the splines can be reduced.

According to the invention of Claims <NUM> and <NUM>, the inclination angle of the inclined surface of each projection is set in the range of approximately <NUM>° to approximately <NUM>° with respect to the projecting end surface of the projection. Therefore, the occurrence of chipping of the splines can be more effectively reduced.

According to the invention of Claims <NUM> and <NUM>, each projection is formed such that the projecting end surface thereof is inclined with respect to the axial direction and that the inclined surface or the rounded portion has a width that is greater in a region where the projecting end surface is high than in a region where the projecting end surface is low. Therefore, even when each projection has a draft angle, the width of the inclined surface or the rounded portion can be increased in accordance with how easily the chipping occurs depending on the draft angle. Accordingly, the occurrence of chipping of the splines can be more effectively reduced.

According to the invention of Claims <NUM> and <NUM>, the splines are configured to allow a plurality of clutch plates or clutch discs to be fitted and assembled thereto. Therefore, when the clutch plates or the clutch discs are reliably fitted to the splines to provide the function of a multiple disc clutch, force can be reliably transmitted or blocked.

An embodiment of the present invention will now be described with reference to the drawings.

An aluminum component according to the present embodiment is composed of a clutch housing of a multiple disc clutch device mounted in, for example, a vehicle. Referring to <FIG>, the aluminum component is obtained by cutting an aluminum casting <NUM> integrally formed with a first cylindrical portion 1a and a second cylindrical portion 1b. More specifically, as illustrated in <FIG>, the aluminum component (clutch housing) according to the present embodiment is obtained by a forming step S1 and a cutting step S2. In the forming step S1, the aluminum casting <NUM>, which has projections f that extend in an axial direction X and that are continuously arranged in a circumferential direction, is obtained. In the cutting step S2, projecting end portions of the projections f formed in the forming step S1 are cut (processed with a lathe) along a processing line having a predetermined processing diameter D to form splines S of predetermined dimensions.

The aluminum casting <NUM> obtained in the forming step S1 will now be described.

The aluminum casting <NUM> is obtained by introducing an aluminum material in a molten state into a cavity of a casting mold at high pressure and speed and then cooling and solidifying the material. In the present embodiment, the aluminum material is a molten metal of aluminum (Al) containing a predetermined amount of silicon (Si). The aluminum casting <NUM> is integrally formed with the first cylindrical portion 1a and the second cylindrical portion 1b.

The projections f that extend in the axial direction X are continuously arranged on each of outer and inner peripheral surfaces of the first cylindrical portion 1a and an inner peripheral surface of the second cylindrical portion 1b over the entire region thereof in the circumferential direction Y. As illustrated in <FIG>, the projections f each have a projecting shape that includes a pair of side surfaces fa and a projecting end surface fd and that projects in a height direction Z. Recesses g are formed between the projections f that are adjacent to each other so that a projecting and recessed pattern extends continuously in the circumferential direction Y.

As illustrated in <FIG>, each projection f is formed such that the side surfaces fa (base side surfaces fc and inclined surfaces fb) thereof are inclined to be tapered in a direction from a base end (end adjacent to the recesses g) to a projecting end (end adjacent to the projecting end surface fd). The projecting end portion (inclined surfaces fb in the present embodiment) of each projection f is cut along the processing line having the predetermined processing diameter D to form the splines S of predetermined dimensions (see, for example, <FIG>).

As illustrated in <FIG>, each projection f according to the present embodiment is formed such that each side surface fa thereof includes the base side surface fc adjacent to the base end and the inclined surface fb adjacent to the projecting end, and such that a portion of each side surface that is adjacent to the projecting end and that is cut in the cutting step (inclined surface fb) has an inclination angle less than that of a portion of the side surface that is adjacent to the base end (base side surface fc). More specifically, the inclined surface fb has an inclination angle α with respect to the projecting end surface fd of the projection f, the inclination angle α being less than an inclination angle β of the base side surface fc with respect to the projecting end surface fd. In particular, the inclination angle α of the inclined surface fb is preferably in the range of approximately <NUM>° to approximately <NUM>°.

In addition, as illustrated in <FIG> and <FIG>, each projection f according to the present embodiment is formed such that the projecting end surface fd thereof is inclined with respect to the axial direction X (inclined upward in the direction from top to bottom in <FIG> and <FIG>), and such that each inclined surface fb has a width that is greater in a region where the projecting end surface fd is high (lower region in <FIG> and <FIG>) than in a region where the projecting end surface fd is low (upper region in <FIG> and <FIG>). In other words, as illustrated in <FIG>, assuming that each inclined surface fb has a width of H1 at the side at which the dimension of the projections f in the height direction Z is large and a width of H2 at the side at which the dimension of the projections f in the height direction Z is small, H1 is greater than H2.

The above-described aluminum casting <NUM> is formed into the clutch housing <NUM> (aluminum component) by cutting the projections f in the cutting step S2. As illustrated in <FIG>, the clutch housing <NUM> is integrally formed with a first cylindrical portion 2a and a second cylindrical portion 2b. The splines S, which are obtained by cutting the projections f, are formed on outer and inner peripheral surfaces of the first cylindrical portion 2a and an inner peripheral surface of the second cylindrical portion 2b.

The splines S formed on the first cylindrical portion 2a and the second cylindrical portion 2b allow a plurality of clutch plates to be fitted and assembled thereto. The clutch plates assembled to the clutch housing <NUM> and clutch discs fitted to a clutch member (not shown) are alternately stacked to function as a clutch device (multiple disc clutch) mounted in, for example, a vehicle, such as an automobile. In this case, the clutch discs and the clutch plates are brought into press contact with each other to enable transmission of driving force of the vehicle, and released from the press-contact state to block the transmission of the driving force of the vehicle.

The outer and inner peripheral surfaces of the first cylindrical portion 2a and the inner peripheral surface of the second cylindrical portion 1b each have an attachment groove e that extends in the circumferential direction Y so as to cross the splines S. The attachment grooves e are formed near open ends of the first cylindrical portion 2a and the second cylindrical portion 2b, and circlips that prevent the clutch discs fitted to the splines S from being removed are attachable to the attachment grooves e. Although the splines S according to the present embodiment are configured to allow the clutch plates to be fitted and assembled thereto, the splines S may instead be configured to allow a plurality of clutch discs to be fitted thereto to provide a multiple disc clutch in which the clutch discs and clutch plates fitted to a clutch member (not shown) are alternately stacked.

In the cutting step S2 according to the present embodiment, as illustrated in <FIG>, the projecting end portion (inclined surfaces fb) of each of the projections f formed in the forming step S1 is cut (processed with a lathe) along the processing line having the predetermined processing diameter D by using a cutting tool T to form the splines S of predetermined dimensions (required dimensions of a finished component). More specifically, when the cutting tool T of the lathe rotates along the processing line having the predetermined processing diameter D (in practice, the aluminum casting <NUM> rotates with respect to the cutting tool T that moves in the axial direction), the cutting tool T comes into contact with the inclined surface fb of one of the side surfaces fa of each projection f, and then passes the inclined surface fb of the other side surface fa (see <FIG>).

Each projection f according to the present embodiment is formed such that a portion of each side surface fa that is adjacent to the projecting end and that is cut in the cutting step S2 is the inclined surface fb having an inclination angle less than that of a portion of the side surface that is adjacent to the base end (base side surface fc). Therefore, as illustrated in <FIG>, when the cutting tool T passes the inclined surface fb (when the cutting tool T leaves the projection f), a force b generated by a force a applied to the projection f by the cutting tool T and acts in a direction for removing a surface of the projection f can be reduced. Accordingly, the occurrence of chipping can be reduced when the projection f is cut.

As illustrated in <FIG> and <FIG>, the projecting distance of each spline S obtained by the cutting process in the height direction Z is defined by the processing diameter D over the entire region of the spline S in the axial direction X (entire region excluding the region in which the attachment groove e is formed). Each spline S includes side surfaces Sa and a projecting end surface Sd. The projecting end surface Sd is a surface formed as a result of the cutting process using the cutting tool T. The side surfaces Sa include base side surfaces Sc, which are the base side surfaces fc of the corresponding projection f that are left uncut, and inclined surfaces Sb, which are portions of the inclined surfaces fb (portions of the inclined surfaces fb that are connected to the base side surfaces fc and that have not been cut off). Thus, each spline S according to the present embodiment includes the inclined surfaces Sb, which are the portions of the inclined surfaces fb that have not been cut off, in a region adjacent to the projecting end surface Sd. Therefore, the clutch plates or the clutch discs can be smoothly fitted to the spline S by being guided by the inclined surface Sb.

Each projection f according to the present embodiment is formed such that the projecting end surface fd thereof is inclined with respect to the axial direction X and that each inclined surface fb has a width that is greater in a region where the projecting end surface fd is high than in a region where the projecting end surface fd is low. Therefore, even when the projections f formed in the forming step S1 each have a draft angle (surface inclined downward toward the open end), the occurrence of chipping in the cutting process S2 can be effectively reduced. More specifically, in the case where the projecting end surface fd is inclined, chipping more easily occurs in the region where the projecting end surface fd is high than in the region where the projecting end surface fd is low when the end portion of the projection f is cut by the cutting tool T. Therefore, by forming each inclined surface fb such that the width thereof is greater in a region where chipping easily occurs than in a region where chipping is less likely to occur, the occurrence of chipping of the splines S can be more effectively reduced.

As described above, each projection f according to the present embodiment is formed such that a portion of each side surface fa that is adjacent to the projecting end and that is cut in the cutting step S2 is the inclined surface fb having an inclination angle less than that of a portion of the side surface that is adjacent to the base end (base side surface fc). Alternatively, referring to <FIG>, projections h may instead be formed, each projection h being formed such that a portion of each side surface fa thereof that is adjacent to the projecting end and that is cut in the cutting step S2 is a rounded portion ha. In this case, similar to the above-described embodiment, preferably, each projection h has a projecting end surface hb that is inclined with respect to the axial direction X, and each rounded portion ha has a width that is greater in a region where the projecting end surface hb is high than in a region where the projecting end surface hb is low.

In the present embodiment, a portion of each side surface fa that is adjacent to the projecting end and that is cut in the cutting step S2 is the inclined surface fb having an inclination angle less than that of a portion of the side surface that is adjacent to the base end (base side surface fc). Alternatively, a portion of each side surface fa that is adjacent to the projecting end and that is cut in the cutting step S2 is the rounded portion ha. Therefore, a contact area between a die (casting mold) used in the forming step S1 and an aluminum material (molten metal) is reduced.

Accordingly, the cooling speed at which the molten metal is cooled in the casting process is reduced, and the hardness of a metal structure that is generated is uniform between the inner region and the surface layer of the casting, so that a chilled layer formed on the surface of the casting (microstructure formed when molten aluminum comes into contact with the die and is suddenly cooled) can be reduced. The chilled layer is harder than the inner structure of the casting, but is brittle and easily chipped in the cutting process. Therefore, the occurrence of chipping in the cutting step S2 can be reduced by reducing the formation of the chilled layer.

In particular, in the present embodiment, the aluminum material (molten metal) introduced into the casting mold contains <NUM> to <NUM> weight percent of silicon (Si). More specifically, the composition of the aluminum material (molten metal) used in the forming step S1 of the present embodiment is as follows: <NUM> to <NUM> weight percent of silicon (Si), <NUM> weight percent or less of iron (Fe), <NUM> to <NUM> weight percent of copper (Cu), <NUM> weight percent or less of manganese (Mn), <NUM> weight percent or less of magnesium (Mg), <NUM> weight percent or less of zinc (Zn), <NUM> weight percent or less of tin (Sn), <NUM> weight percent or less of impurities, and aluminum (Al) as the balance. The chilled layer can be effectively reduced by adjusting the content of silicon (Si).

Thus, not only can the chilled layer be reduced due to the shape of the inclined surfaces fb (or the rounded portions ha), but further reduction in the chilled layer can be achieved due to the material. Accordingly, when the molten metal having the above-described composition is cast, the chilled layer formed on each inclined surface fb (or on each rounded portion ha) can be reduced. In the present embodiment, the chilled layer is hardly formed. Therefore, the occurrence of chipping in the cutting step S2 can be reduced. Referring to <FIG>, a micrograph of a chilled layer on an aluminum casting having no inclined surface fb shows that the chilled layer has a substantially uniform thickness (around <NUM>). In contrast, referring to <FIG>, a micrograph of a chilled layer on an aluminum casting having the inclined surface fb as in the present embodiment shows that the chilled layer is hardly formed on the inclined surface fb.

When, for example, the aluminum casting including the chilled layer shown in <FIG> was cut (processed with a lathe), chipping occurred at a rate of <NUM>%. When the aluminum casting on which the chilled layer is hardly formed shown in <FIG> was cut (processed with a lathe) under the same processing conditions, such as the feed speed, rotational speed, and cutting depth, chipping occurred at a rate of less than or equal to <NUM>%.

According to the above-described embodiment, each projection f (h) is formed such that the side surfaces fa thereof are inclined to be tapered in the direction from the base end to the projecting end. In addition, a portion of each side surface fa that is adjacent to the projecting end and that is cut in the cutting step S2 is the inclined surface fb having an inclination angle less than that of a portion of the side surface that is adjacent to the base end (base side surface fc). Alternatively, the portion of each side surface fa that is adjacent to the projecting end and that is cut in the cutting step S2 is the rounded portion ha. Therefore, the occurrence of chipping of the splines S formed on the clutch housing <NUM> (aluminum component) can be reduced. In particular, the inclination angle α of each inclined surface fb of each projection f with respect to the projecting end surface fd of the projection f is set in the range of approximately <NUM>° to approximately <NUM>°. Therefore, the occurrence of chipping of the splines S can be more effectively reduced.

In addition, each projection f (h) according to the present embodiment is formed such that the projecting end surface fd (hb) thereof is inclined with respect to the axial direction and that each inclined surface fb or each rounded portion ha has a width that is greater in a region where the projecting end surface fd (hb) is high than in a region where the projecting end surface fd (hb) is low. Therefore, even when each projection f (h) has a draft angle, the width of each inclined surface fb or each rounded portion ha can be increased in accordance with how easily the chipping occurs depending on the draft angle. Accordingly, the occurrence of chipping of the splines S can be more effectively reduced.

In addition, the splines S according to the present embodiment are configured to allow a plurality of clutch plates or clutch discs to be fitted and assembled thereto. Therefore, when the clutch plates or the clutch discs are reliably fitted to the splines S to provide the function of a multiple disc clutch, force can be reliably transmitted or blocked.

Although the present embodiment has been described, the present invention is not limited to this. For example, the aluminum casting <NUM> or the clutch housing <NUM> which includes the first cylindrical portion (1a, 2a) and the second cylindrical portion (1b, 2b) may be replaced by an aluminum casting or a clutch housing which includes one or three or more cylindrical portions having the projections f (h) or the splines S. In addition, although the aluminum component is the clutch housing <NUM> in the present embodiment, the aluminum component may instead be another component (including components other than those of a clutch) as long as the splines S are arranged in the circumferential direction.

In addition, although the inclination angle α of each inclined surface fb of each projection f according to the present embodiment with respect to the projecting end surface fd of the projection f is set in the range of approximately <NUM>° to approximately <NUM>°, the inclined surface fb may have another inclination angle as long as the inclination angle is less than that of a portion of the side surface that is adjacent to the base end (base side surface fc). In addition, although each projection f (h) according to the present embodiment is formed such that the projecting end surface fd (hb) thereof is inclined with respect to the axial direction X, each projection f (h) may instead be formed such that the projecting end surface fd (hb) thereof is not inclined (such that the dimension of each projection f (h) in the height direction Z is constant in the axial direction X).

Claim 1:
A method for manufacturing an aluminum component, the method comprising:
a forming step (S1) of obtaining an aluminum casting (<NUM>) having projections (f) that extend in an axial direction (X) and that are continuously arranged in a circumferential direction (Y); and
a cutting step (S2) of cutting projecting end portions of the projections (f) formed in the forming step (S1) along a processing line having a predetermined processing diameter (D), thereby obtaining splines (S) of predetermined dimensions,
characterized in that
wherein each projection (f) is formed such that side surfaces (fa) thereof are inclined to be tapered in a direction from a base end to a projecting end,
a portion of each side surface (fa) that is adjacent to the projecting end and that is cut in the cutting step (S2) is either an inclined surface (fa) or a rounded portion (ha), the inclined surface having an inclination angle (α) less than an inclination angle (β) of a portion of the side surface that is adjacent to the base end.