JP3962276B2 - Brake drum manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a brake drum used in a drum brake.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a drum type brake is known in which a friction member (shoe) is pressed against an inner peripheral surface of a bottomed cylindrical member (brake drum) that rotates integrally with a wheel and brakes. Initially, the brake drum was made of cast iron alone, but in order to reduce the weight of the entire drum, aluminum die-cast molding was performed by casting a short cylindrical cast iron liner (sliding part component) into aluminum. It is generalized as a method for manufacturing a brake drum (for example, see Japanese Patent Application Laid-Open No. 58-217833).
[0003]
[Problems to be solved by the invention]
However, the conventional method for manufacturing a brake drum has some drawbacks. First, in order to cast a cast iron liner, it is necessary to position the cast iron liner in advance in the molding space (constructed by combining the concave mold and the convex mold) of the die casting apparatus before the molten aluminum is press-fitted. In this case, the positioning is performed by bringing the inner peripheral surface of the short cylindrical liner into direct contact with the outer peripheral surface of the convex columnar convex portion for forming the inner shape of the bottomed cylinder. The liner was fitted (or covered) on the columnar convex portion. In order to smoothly fit the cast iron liner to the convex shape, a slight gap is required between the two. However, if the gap is large, the radial positioning of the cast iron liner becomes unstable, and the molding space There is a possibility that the deviation (eccentricity) of the axis of the cast iron liner with respect to the axis will increase. If the eccentricity of the cast iron liner exceeds the allowable limit, the weight balance of the liner cast aluminum drum obtained by die casting will be lost, and the braking performance will be adversely affected.
[0004]
In addition, when molten aluminum is pressed into the molding space with a slight gap (that is, an air layer) left between the convex cylindrical convex surface and the cast iron liner, the outer peripheral surface side and inner peripheral surface of the liner The pressure difference between the two sides becomes excessive. The excessive differential pressure causes the liner to be deformed in a direction that eliminates the gap, or causes the crack to occur in the liner itself, thereby increasing the incidence of defective products. The present invention has been made in view of such circumstances.
[0005]
The object of the present invention is to allow the sliding member constituting material to be cast with a foreign metal in a state where the short cylindrical sliding member constituting material is accurately positioned in the molding space, and to be used at the time of manufacture. An object of the present invention is to provide a method of manufacturing a brake drum capable of greatly reducing the occurrence rate of non-defective products.
[0006]
[Means for Solving the Problems]
The invention of claim 1 is a step of disposing a short cylindrical sliding member constituting material in a molding space constructed between the concave portion of the first mold and the substantially cylindrical convex portion of the second mold, A bottomed cylindrical brake drum in which a short cylindrical sliding part constituent material is cast with metal through a step of press-fitting a molten metal of a different material from the sliding part constituent material into the molding space. It is a manufacturing method, Comprising: On the outer peripheral surface of the substantially cylindrical convex part of the said 2nd type | mold, the some holding protrusion which each extends in the direction parallel to the axial center (x) of the said substantially cylindrical convex part. provided, in the disposing step, the Ri by the second mold plurality of retaining projections provided on the outer peripheral surface of a substantially cylindrical projecting part of the each of these holding protrusions short cylindrical sliding by holding by line contact short cylindrical sliding portion constituent elements of the relative motion portion constituent elements, concave inner and outer peripheral surfaces of the first type of the sliding portion constituent elements Is the manufacturing method of the brake drum, characterized in that for positioning the sliding portion constituent elements in the molding space in a state that from the inner surface and between away from the outer peripheral surface of a substantially cylindrical projecting part of the second type .
[0007]
According to this method, the short cylindrical slide portion is held by the plurality of holding protrusions provided on the outer peripheral surface of the substantially cylindrical convex portion of the second mold. The sliding part component can be positioned in the molding space so that the axis of the component coincides with the axis of the molding space (that is, the axis of the final product), and the processing accuracy (particularly the weight balance) of the final product can be increased. Can be improved.
[0008]
Also, the holding mode of the short cylindrical sliding part constituent material by the plurality of holding protrusions is such that the inner and outer peripheral surfaces of the short cylindrical sliding part constituent material do not contact the inner wall of the molding space other than the holding protrusions. in the outer peripheral surface of the sliding portion constituent elements together is between an inner surface or et away of the recess of the first type, between even away from the outer peripheral surface of the projection of the inner circumferential surface of the second type of sliding portion constituent elements It is something to be made. For this reason, when the molten metal is pressed into the forming space, the space between the outer peripheral surface of the sliding member constituting material and the inner surface of the concave portion of the first mold also has an inner peripheral surface of the sliding member constituting material. The molten metal equally enters the space (gap) between the outer peripheral surface of the convex part of the second mold. In other words, the force that the molten metal that fills the molding space pushes the inner and outer peripheral surfaces of the sliding part component cancels each other, and there is no pressure difference between the inside and outside of the sliding part component. The positional displacement of the component member in the radial direction is prevented, and the sliding member component is prevented from being deformed or cracked by the molten metal press-fitting. Although the molten metal will solidify and shrink after the molten metal is pressed in, the molten metal has entered both the inner and outer peripheral surfaces of the sliding component. Deformation and cracking of the material are less likely to occur.
[0009]
Furthermore, according to this method, the first mold and the second mold are moved closer to and away from each other in the direction of the axis of the substantially cylindrical convex portion of the second mold, and the mold joining and the mold opening are performed. After the mold is opened, the product is removed from the second mold along the same direction. Each of the plurality of holding protrusions provided on the outer peripheral surface of the substantially cylindrical convex portion of the second mold extends in a direction parallel to the axis of the substantially cylindrical convex portion, so that the product from the second mold Removal is facilitated. In other words, each of said retaining projection from that contacting relationship with pairs and line short cylindrical sliding portion constituent elements of, after mold opening the first and second mold after solidification of the molten metal, the It is possible to reduce the punching resistance when the product in the bitten state with respect to the substantially cylindrical convex part of the second mold is removed from the second mold, and the product can be easily removed from the mold.
[0010]
In this specification, “short cylindrical shape” refers to a cylindrical shape having an axial length shorter than the diameter, and includes a ring shape. Moreover, it is preferable that the number of holding | maintenance protrusions provided in the outer peripheral surface of a substantially cylindrical convex part of a 2nd type | mold is at least three. If there are three or more holding protrusions, the holding of the short cylindrical sliding part constituting material with respect to the substantially cylindrical convex part of the second mold is stable, and there is no fear of causing a displacement when the molten metal is press-fitted.
[0011]
The invention of claim 2 is the method for manufacturing a brake drum according to claim 1, wherein the distal end portion of the first mold side of each retaining projection is characterized in that the rounding has been granted.
[0012]
According to this method, the configuration of the sliding portion having a short cylindrical shape with respect to the substantially cylindrical convex portion of the second die from the first die side in a state where the first die and the second die are separated from each other. Fit the material. By imparting roundness to the first mold side tip of each holding ridge, it becomes easier to externally attach the sliding member to the substantially cylindrical convex part of the second mold, improving workability. To do.
[0013]
The invention of claim 3 is a method of manufacturing a brake drum according to claim 1 or 2, in the disposing step, the short cylinder by a plurality of retaining projections provided on the convex outer circumferential face of the second mold holds the Jo sliding portion constituent elements of, and performing the axial positioning of the sliding portion constituting member by the engaging portion which projects into the recess of the first type.
[0014]
According to this method, when arranging the short cylindrical sliding member constituting material in the molding space, the radial positioning by the plurality of holding protrusions provided on the outer peripheral surface of the convex portion of the second mold, Positioning in the axial direction is simultaneously achieved by the engaging convex portion protruding in the concave portion of the first mold. For this reason, the positioning of the sliding member constituting material in the molding space can be accurately performed, and the processing accuracy of the product can be improved.
[0015]
The invention of claim 4 is a method of manufacturing a brake drum according to any one of claims 1 to 3, after the solution water from through the melt stuffing step has solidified, from the first and second type The method further comprises a step of grinding the inner peripheral surface of the removed cast-off product to expose the inner peripheral surface of the sliding member constituting material.
[0016]
According to this method, after positioning the sliding member constituting material in the molding space, the molten metal is press-fitted and then solidified, so that not only the outer peripheral surface side but also the inner peripheral surface side of the sliding member constituting material. A cast-in-place molded product (intermediate product) with a metal attached to the inside is obtained. By subjecting the inner peripheral surface of this cast-in-molded product to grinding to expose the inner peripheral surface of the sliding member constituent material, the sliding member constituent material comes into contact with its original function (that is, in contact with the friction member). The brake drum as the final product is completed.
[0017]
In addition, in Claims 1-4 , "the said sliding part constituent material is made from cast iron or a metal matrix composite material (MMC)" or "the metal different from the said sliding part constituent material is aluminum or "It is an alloy" is preferable.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment relating to a method of manufacturing a brake drum (final product) having a cross-sectional structure as shown in FIG. 3B will be described with reference to the drawings. Note that the brake drum 30 as the final product is formed by casting a cast iron liner 31 as a short cylindrical sliding member constituting member with an aluminum alloy flesh portion 32 and has a substantially bottomed cylindrical shape. The brake drum 30 includes a die-cast molding process for obtaining an intermediate product having a cross-sectional structure as shown in FIG. 3A, and a final product as shown in FIG. It is manufactured through a grinding process.
[0019]
As shown in FIG. 2, a molding die apparatus used for die casting includes a fixed mold 10 as a first mold and a movable mold 20 as a second mold, and is movable by a drive mechanism (not shown). 20 is moved closer to and away from the fixed mold 10. The fixed mold 10 has a concave portion 11 shaped like a hollow cylinder on the side facing the movable mold 20. On the other hand, the movable mold 20 has a substantially cylindrical convex portion 21 on the side facing the fixed mold 10 (see FIG. 1). The diameter of the substantially cylindrical convex portion 21 is set smaller than the diameter of the concave portion 11 of the fixed mold. By joining the fixed mold 10 and the movable mold 20 as shown in FIG. A single molding space S having an inner shape corresponding to the outer shape of the intermediate product) is secured in the mold apparatus.
[0020]
On the fixed mold 10 side, a press-fitting mechanism 12 for press-fitting a molten aluminum alloy as a molding material into the molding space S is provided. On the other hand, on the movable mold 20 side, there is provided an extrusion mechanism 22 (including an unillustrated extrusion pin) for removing an intermediate product from the movable mold 20 that is engaged with the movable mold 20 when the mold is opened. ing. Since the press-fitting mechanism 12 and the extrusion mechanism 22 are well-known mechanisms in the molding die apparatus, detailed description thereof is omitted. The fixed mold 10 and the movable mold 20 used in this embodiment have the following structural features.
[0021]
As shown in FIGS. 1 (A) and 1 (B), a plurality of outer peripheral surfaces 21a of the substantially cylindrical convex portion 21 of the movable mold 20 are used to externally hold a cast iron liner 31 around the convex portion 21. Ribs 23 (three in this embodiment) are formed as holding ridges. These ribs 23 are disposed so as to surround the axial center x of the substantially cylindrical convex portion 21 at equiangular intervals (in the present embodiment, at intervals of 120 degrees). Each rib 23 extends in a direction substantially parallel to the axis x. Needless to say, the direction in which the axis x extends is the direction in which the fixed mold 10 and the movable mold 20 are relatively close to each other. The height of each rib 23 is set such that the distance from the axis x to the apex of each rib 23 matches the inner radius of the cast iron liner 31, and the substantially cylindrical convex outer peripheral surface 21a from the axis x. (Ie, the radius of the convex portion 21) is less than the inner radius of the cast iron liner 31. Furthermore, the fixed mold side tip of each rib 23 is processed into an R shape, and each tip is rounded.
[0022]
On the other hand, as shown in FIG. 2, a plurality of pins 13 as protruding protrusions are provided on the bottom surface of the concave portion 11 of the fixed mold 10 (only two are shown in FIG. 2). The plurality of pins 13 are arranged so as to surround the axial center x (the axial center of the fixed concave portion 11 coincides with the axial center of the movable convex portion 21) at equal angular intervals. The distance from the axis x to the pin 13 is set to an intermediate value between the radius of the inner peripheral surface of the cast iron liner 31 and the radius of the outer peripheral surface. That is, each pin 13 is disposed at a position facing the end surface of the cast iron liner 31 held by the movable convex portion 21. The number of pins 13 is preferably the same as or more than the number of ribs 23.
[0023]
Next, the manufacturing procedure of the brake drum 30 of this embodiment will be described.
First, in a state where the movable die 20 is separated from the fixed die 10 (die opening state), a cast iron liner 31 is externally fitted to the substantially cylindrical convex portion 21 of the movable die (see FIG. 1). The cast iron liner 31 has a short cylindrical shape or a ring shape, and the liner 31 is inserted toward the movable mold 20 from a state in which the rear end portion of the liner 31 is opposed to the front surface of the substantially cylindrical convex portion 21. As a result, the cast iron liner 31 is fitted around the three ribs 23 protruding from the outer peripheral surface 21a of the substantially cylindrical convex portion. Since the end of each rib 23 is rounded as described above, the cast iron liner 31 can be smoothly fitted to the three ribs 23.
[0024]
The cast iron liner 31 is supported on the convex portion 21 in a state in which the inner peripheral surface of the liner 31 is separated from the convex outer peripheral surface 21a by supporting the inner peripheral surface side thereof with the three ribs 23. At this time, the liner 31 is accurately positioned with respect to the convex portion 21 by the cooperative positioning action of the three ribs 23 so that the axial center of the liner 31 coincides with the axial center x of the substantially cylindrical convex portion 21. The
[0025]
When the mounting of the cast iron liner 31 to the movable mold 20 is completed, the movable mold 20 is moved toward the fixed mold 10, and the molds 10 and 20 are clamped as shown in FIG. In the process of clamping, each pin 13 projecting from the recessed part 11 of the fixed mold comes into contact with the front end portion of the cast iron liner 31 fitted on the convex part 21 of the movable mold, and Each pin 13 pushes the liner 31 toward the main body of the movable mold 20 as it moves. As a result, when the clamping of both the molds 10 and 20 is completed, the cast iron liner 31 is sandwiched between the main body of the movable mold 20 and each pin 13, and the cast iron in the direction along the axis x is obtained. Positioning (axial positioning) of the liner 31 is achieved.
[0026]
When the molds 10 and 20 are clamped, a molding space S including the cast iron liner 31 is built in the molding die apparatus. As described above, the cast iron liner 31 is correctly positioned in the molding space S by the action of the ribs 23 and the pins 13. The holding aspect of the cast iron liner 31 in the molding space S, as shown in FIG. 2, with the outer peripheral surface of the liner 31 between the inner peripheral surface 11a or we release the fixed recess, the inner circumference of the liner 31 surface has become those between away from the outer peripheral surface 21a of the movable mold protrusion. That is, a predetermined space (or gap) is secured inside and outside the cast iron liner 31 except for the contact portion with the rib 23.
[0027]
Subsequently, the press-fitting mechanism 12 is operated to press-fit the molten aluminum alloy into the molding space S of the mold apparatus. Then, the molten aluminum spreads equally in the forming space S including the spaces (or gaps) secured inside and outside the cast iron liner 31 and fills the forming space S. Both molds 10 and 20 are opened when the molten metal is solidified after a lapse of a predetermined time from the injection of the molten metal. Due to the influence of solidification shrinkage of the aluminum alloy, the molded product bites into the substantially cylindrical convex portion 21 of the movable mold, and the molded product adheres to the movable mold 20 when the mold is opened. Thereafter, by operating the extrusion mechanism 22, the molded product (intermediate product) can be removed from the movable mold 20. At this time, since each rib 23 is in a line contact relationship with the short cylindrical liner 31, the removal resistance when the molded product is removed from the movable mold 20 is relatively small, and the molded product is removed from the mold by the extrusion mechanism 22. Is smooth.
[0028]
As shown in FIG. 3A, the intermediate product immediately after removal from the movable mold 20 is in a state in which an aluminum alloy meat portion 32 is also provided inside the cast iron liner 31. Therefore, in order to scrape off the meat portion 32 attached to the inner peripheral surface side of the liner 31, the inner peripheral surface of the intermediate product is subjected to grinding processing (and polishing processing following the grinding processing if necessary). . By this grinding process, as shown in FIG. 3B, the inner peripheral surface of the cast iron liner 31 (that is, the cast iron ground) is exposed, and the brake drum 30 as the final product is obtained. In addition, since the meat portion 32 on the inner peripheral surface side of the liner is completely scraped off by this grinding process, no trace of the ribs 23 is left in the final product.
[0029]
(Effect) According to this embodiment, the following effects can be obtained.
According to the present embodiment, cast iron liners are formed in the molding space S by the action of the three ribs 23 projecting from the movable substantially cylindrical projection 21 and the plurality of pins 13 projecting from the fixed recess 11. 31 can be accurately positioned both in the radial direction and in the axial direction. Therefore, the brake drum manufactured through such die-casting has an excellent weight balance especially around the axis and exhibits an ideal braking performance.
[0030]
In addition, since the molten metal spreads evenly in the space (or gap) inside and outside the short cylindrical liner 31 to be cast during die casting, the molten metal filling the forming space S is inside and outside the short cylindrical liner 31. The pressure exerted on the peripheral surface is canceled out. For this reason, there is no pressure difference (or non-uniform pressure distribution) that causes deformation or cracking of the liner 31 between the inner side and the outer side of the short cylindrical liner 31, and the shape and quality of the product after die casting. Can be kept good, and good products can be manufactured with high probability (that is, the incidence of defective products is low).
[0031]
(Modification) The embodiment of the present invention may be modified as follows.
The liner 31 as the short cylindrical sliding member constituent material is not limited to cast iron, and any material can be used as long as it can exhibit a desired braking ability in combination with a shoe. For example, a metal matrix composite material (MMC) such as an aluminum matrix composite material composed of aluminum as a metal base material or an alloy thereof and silicon carbide or alumina as a reinforcing material may be used. Further, the metal for casting the short cylindrical sliding part constituting material may be a metal other than an aluminum alloy. However, in order to reduce the weight of the brake drum as the final product, it is preferable to use a light metal typified by an aluminum alloy or a magnesium alloy.
[0032]
-The number of the said ribs 23 is not limited to three, Two or four or more may be sufficient. However, it is preferable that the number of the ribs 23 be three or more in order to ensure the stability and the unambiguous positioning when supporting the sliding member constituent material.
[0033]
【The invention's effect】
As described above in detail, according to the manufacturing method of the brake drum described in each claim, the sliding part constituent material is different in a state where the short cylindrical sliding part constituent material is accurately positioned in the molding space. Can be cast in metal. And it becomes possible to reduce significantly the incidence rate of inferior goods in the case of manufacture.
[Brief description of the drawings]
FIGS. 1A and 1B show a state in which a short cylindrical liner is externally fitted to a movable convex portion, FIG. 1A is a front view thereof, and FIG. 1B is a partial cross-sectional view taken along line AA in FIG. .
FIG. 2 is a cross-sectional view of a state where a movable space is joined to a fixed mold to form a molding space.
3A is a radial cross-sectional view of an intermediate product immediately after being punched from a mold apparatus, and FIG. 3B is a radial cross-sectional view of a final product obtained by grinding the intermediate product.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Fixed type | mold (1st type | mold), 11 ... Recessed part, 11a ... Inner peripheral surface of a recessed part, 13 ... Pin (engagement convex part), 20 ... Movable type | mold (2nd type | mold), 21 ... Substantially cylindrical convexity Part, 21a ... outer peripheral surface of substantially cylindrical convex part, 23 ... rib (holding ridge), 30 ... brake drum, 31 ... cast iron liner (short cylindrical sliding part constituting material), 32 ... meat part (material) ), S ... forming space, x ... axis.

Claims (4)

A step of disposing a short cylindrical sliding member in a molding space constructed between the concave portion of the first mold and the substantially cylindrical convex portion of the second mold; and the sliding in the molding space. A method of manufacturing a bottomed cylindrical brake drum in which a short cylindrical sliding part constituent material is cast with a metal through a process of press-fitting a molten metal of a different material and a moving part constituent material,
A plurality of holding protrusions each extending in a direction parallel to the axis (x) of the substantially cylindrical convex portion are provided on the outer peripheral surface of the substantially cylindrical convex portion of the second mold,
In the disposing step, the Ri by the second mold plurality of retaining projections provided on the outer peripheral surface of a substantially cylindrical projecting part of, each of these retaining projections said the short cylindrical sliding portion constituent elements of the by holding the short cylindrical sliding portion constituent elements of contacting against line, substantially circular of the second type from the inner surface of the recess inner and outer peripheral surfaces of the first type of the sliding portion constituent elements method for manufacturing a brake drum, characterized in that for positioning the sliding portion constituent elements in a state that was also between away from the outer peripheral surface of the columnar convex portions forming space. The method for manufacturing a brake drum according to claim 1, wherein a roundness is imparted to a tip end portion of each holding protrusion on the first mold side. In the arranging step, the short cylindrical sliding member constituting member is held by a plurality of holding protrusions provided on the outer peripheral surface of the convex portion of the second mold, and is projected into the concave portion of the first mold. The manufacturing method of the brake drum according to claim 1 or 2, wherein the sliding member constituting member is positioned in the axial direction by the engaging projection provided. After the molten metal solidifies after passing through the molten metal press-fitting step, the inner peripheral surface of the cast-in-molded product removed from the first and second molds is subjected to grinding to The method for manufacturing a brake drum according to any one of claims 1 to 3, further comprising a step of exposing the peripheral surface.

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