JP3917799B2 - Brake drum manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, the friction material of the brake drum molded with Al-based composite material relates to the friction material in the manufacture how the brake drum wrap cast in an Al alloy.
[0002]
[Prior art]
Some motorcycles and automobiles use a drum brake as a braking device. The drum brake presses a brake shoe against the inner periphery (friction surface) of a brake drum that rotates integrally with a wheel, and controls the rotation of the brake drum with the brake shoe.
Some brake drums are integrally cast from cast iron in order to maintain the strength of the friction surface, and the brake drums made of cast iron are relatively heavy, which hinders the weight reduction of motorcycles and automobiles.
[0003]
In order to reduce the weight of the brake drum, some of the brake drum uses a lightweight member such as an aluminum alloy (hereinafter referred to as “Al alloy”). That is, the friction surface that requires wear resistance is formed of cast iron, and other parts are formed of a lightweight member such as an Al alloy, thereby reducing the weight of the brake drum. For this reason, it is possible to reduce the fuel consumption by reducing the weight of the motorcycle or the automobile.
[0004]
[Problems to be solved by the invention]
However, in motorcycles and automobiles, there is still a great need for weight reduction for the purpose of reducing fuel consumption, and a lighter brake drum is required depending on the type of brake drum.
[0005]
Therefore, an object of the present invention is to provide a technique capable of making the brake drum lighter.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an annular friction material made of an Al-based composite material having a plurality of convex portions formed on the outer periphery at the same pitch and an outer periphery of the friction material by meshing with the convex portions. A brake drum manufacturing method comprising: a combined Al alloy drum main body; a height of the convex portion set to 0.5 to 3.0 mm; and a pitch angle of the convex portion set to 6 to 45 °. the reinforcing material of metal oxide contacted with the magnesium nitride, producing the Al-based composite material impregnated with Al alloy reinforcing material in a state that allowed expose at least a portion the metal reinforcement by the reducing action of the magnesium nitride A step of forming the Al-based composite material by extrusion molding on a cylindrical member having irregularities on the outer periphery and the same inner diameter as the brake drum, and a width corresponding to the brake drum. cut to The gold and step Ru obtain friction material of the annular, heating the annular friction member to a predetermined temperature higher temperature than the mold, the heated friction member is cooled after setting the mold, the friction material Te wherein the step of adhering to the mold, the steps of wrapping casting the Al alloy serving as backup material in the friction material which is adhered, after wrapped cast the friction material of Al alloy, the friction material with cast wrapped Al alloy wherein the step and Ru Tona removed from the mold.
[0007]
The surface of the reinforcing material is metallized by the reducing action of magnesium nitride to improve the wettability between the reinforcing material and the molten Al alloy. Thereby, the interface between the reinforcing material and the Al alloy is firmly bonded, and an Al-based composite material having excellent extensibility is obtained. A friction material is manufactured by extruding this Al-based composite material. This friction material is excellent in tensile strength and proof stress by extrusion molding, and sufficiently secures the strength as a friction material. In addition, the weight of the friction material is reduced by making the matrix of the Al-based composite material a lightweight Al alloy.
[0008]
Further, by forming irregularities on the outer periphery of the friction material, the irregularities of the friction material are meshed with the backup material. For this reason, the friction material is firmly coupled to the backup material to prevent the friction material from being separated from the backup material when the drum brake is braked.
Furthermore, by using an Al alloy as the friction material matrix, the thermal conductivity can be improved as compared with conventional cast iron, the heat generated during braking can be easily dissipated, and the fade resistance is improved.
[0011]
Further , the friction material matrix is made of an Al alloy, so that the coefficient of linear expansion of the friction material is the same as that of the backup material. For this reason, when a brake is applied, a difference in thermal expansion between the friction material and the backup material is prevented.
[0012]
In addition, the friction material was set in the mold while being heated to a temperature higher than the mold by a predetermined temperature. Since the friction material is formed of an Al-based composite material, the coefficient of linear expansion of the friction material is larger than that of the mold. By heating the friction material to a temperature higher than that of the mold, the friction material is easily set in the mold by increasing the inner diameter of the friction material.
Further, since the friction material can be fitted in a state of being in close contact with the mold, the friction material can be cast coaxially with the axis of the brake drum. Furthermore, it is possible to prevent the Al alloy from adhering to the inner periphery of the friction material, or to suppress the Al alloy to a small amount even if the Al alloy adheres to the inner periphery of the friction material.
[0013]
In claim 2 , when the value obtained by dividing the cross-sectional area of the Al-based composite material before extrusion molding by the cross-sectional area of the cylindrical member after extrusion molding is defined as the extrusion ratio, the extrusion ratio in the extrusion molding method is 10 to 10. It is characterized by being set to 40.
[0014]
If the extrusion ratio is 10 or less, the tensile strength and proof stress of the cylindrical member (friction material) are reduced, and the strength as a friction material cannot be maintained. Therefore, the strength as a friction material was maintained by setting the extrusion ratio to exceed 10.
On the other hand, when the extrusion ratio exceeds 40, the pushing force increases and the extrusion speed decreases. As a result, the cycle time decreases and the production cost increases, so the upper limit of the extrusion ratio was set to 40.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
FIG. 1 is a perspective view of a motorcycle rear wheel to which a brake drum according to the present invention is attached.
The brake drum 10 includes a boss 11 attached to a rear axle and a front axle (not shown), a flange 12 integrally formed on the right end of the boss 11, a drum body integrally formed on the outer periphery of the flange 12 and disposed coaxially with the boss 11 ( Backup material) 13, a pair of flanges 14 and 14 attached to the outer periphery of the drum body 13, and an annular friction material 16 attached to the inner periphery of the drum body 13.
[0020]
The boss 11, the flange 12, the drum body 13, and the pair of flanges 14, 14 constitute a hub 15 by integrally casting with an Al alloy. By making the hub 15 made of an Al alloy, the weight can be reduced.
The friction material 16 is a member formed of an aluminum-based composite material (hereinafter referred to as “Al-based composite material”). Weight reduction can be achieved by molding the friction material 16 with an Al-based composite material. Furthermore, since the Al-based composite material includes a reinforcing material inside, the wear resistance necessary as a friction material can be sufficiently ensured.
[0021]
By forming the friction material 16 from an Al-based composite material, the matrix of the friction material 16 can be made of an Al alloy in the same manner as the drum body 13. For this reason, since the heat conductivity of the friction material 16 can be made higher than that of conventional cast iron, heat generated during braking can be easily radiated, and fade resistance is improved.
[0022]
According to the brake drum 10, a plurality of mounting holes 14 a... (... indicates a plurality) are formed in the pair of flanges 14, 14, and the spokes 20 are attached to the mounting holes 14 a. A rim 21 is attached to the brake drum 10, a tire 22 is attached to the rim 21, and a pair of brake shoes 23 and a pair of compression springs 24 are housed inside the brake drum 10.
[0023]
Next, a method for manufacturing the brake drum 10 will be described.
FIG. 2 is a flowchart showing a method for manufacturing a brake drum according to the present invention, where STxx indicates a step number.
ST10: An Al-based composite material is manufactured.
ST11: An Al-based composite material is formed by extrusion molding on a cylindrical member having irregularities on the outer periphery and the same inner diameter as the brake drum.
ST12: Cut the cylindrical member into a width corresponding to the brake drum.
ST13: The cut member is heated to a temperature higher than the mold by a predetermined temperature.
ST14: The heated member is set in a mold, and the set member is cast with an Al alloy as a backup material.
Hereinafter, each process of ST10 to ST14 will be described in detail with reference to FIGS.
[0024]
3 (a) to 3 (c) are first explanatory views of the brake drum manufacturing method according to the present invention, and (a) to (c) show ST10.
In (a), a reinforcing material 32 (hereinafter referred to as “alumina (Al ₂ O ₃ )”) made of a metal oxide is placed in a first crucible 31 in the atmosphere furnace 30. The alumina 32 is a porous molded body made of an oxide ceramic and is formed into a billet (cylindrical body).
An Al alloy 33 is placed on the alumina 32. Further, magnesium (Mg) 35 is put into the second crucible 34 in the atmosphere furnace 30. The Al alloy 33 is, for example, A6061, and Mg35 may be an Mg alloy.
[0025]
Next, in order to remove the air in the atmosphere furnace 30, the vacuum pump 36 is evacuated and the vacuum pump 36 is stopped when a certain degree of vacuum is reached. Next, argon gas (Ar: indicated by “x”) 38 a is supplied from the argon gas cylinder 38 into the atmosphere furnace 30 as indicated by the arrow (1). The atmosphere furnace 30 becomes an atmosphere of the argon gas 38a, and the Al alloy 33 and the magnesium 35 are not oxidized.
[0026]
At the same time, the atmosphere furnace 30 is heated by the heating coil 40 to raise the alumina 32, the Al alloy 33, and the magnesium 35 to a predetermined temperature (for example, about 750 ° C. to about 900 ° C.). As a result, the Al alloy 33 is dissolved and the magnesium 35 (indicated by “open triangles”) is evaporated as indicated by the arrow (2).
Here, the temperature in the atmosphere furnace 30 is detected by the temperature sensor 41, and the temperature in the atmosphere furnace 30 is adjusted to a set value by the control unit 42 based on the detection signal from the temperature sensor 41.
[0027]
In (b), nitrogen gas (N ₂ : indicated by “black circle”) 43 a is supplied from the nitrogen gas cylinder 43 to the atmosphere furnace 30 as indicated by arrow (3). At the same time, the inside of the atmosphere furnace 30 is pressurized (for example, atmospheric pressure + about 0.5 kg / cm ² ) to replace the atmosphere in the atmosphere furnace 30 with nitrogen gas 43a.
When the atmosphere furnace 30 is in the atmosphere of the nitrogen gas 43a, the nitrogen gas 43a reacts with the magnesium 35 to generate magnesium nitride (Mg ₃ N ₂ : indicated by “black triangle”) 44.
[0028]
Since the magnesium nitride 44 has a reducing action, it functions to change at least a part of the alumina 32 into metal (aluminum). Therefore, at least a part of the alumina 32 is in a state where the aluminum is exposed. The wettability can be improved by generating aluminum.
A billet-shaped Al alloy-based composite material 45 is produced by infiltrating the molten aluminum alloy 33 into aluminum changed from the alumina 32 and solidifying the infiltrated Al alloy 33.
[0029]
The Al-based composite material 45 can be made excellent in extensibility by metallizing the alumina 32 by the reducing action of magnesium nitride to improve wettability. For this reason, the Al-based composite material 45 can be made into a composite material that is excellent in formability and easily deforms plastically.
[0030]
In addition, in the infiltration process, when the atmosphere furnace 30 is in a pressurized atmosphere, the infiltration becomes faster and the Al-based composite material 45 can be obtained in a short time. Further, the atmosphere furnace 30 can be depressurized by the vacuum pump 36 and can be permeated in a short time even in a reduced pressure nitrogen atmosphere.
Furthermore, it is possible to reduce the alumina 32 by previously containing an Al alloy containing Mg in the alumina 32 of the porous molded body, and then forming magnesium nitride.
Further, an Al alloy may be placed on a porous molded body of alumina particles containing magnesium powder, and a composite treatment may be performed.
[0031]
In (c), the outer periphery 45a of the Al-based composite material 45 is cut with a cutting blade 46 (so-called peeling processing). As a result, the Al-based composite material 45 is processed into a shape suitable for subsequent extrusion molding.
As described above, the Al-based composite material 45 is a material that is excellent in formability and easily undergoes plastic deformation. Therefore, the extrusion molding shown in the following figure becomes possible.
[0032]
4 (a) and 4 (b) are second explanatory views of the method for manufacturing a brake drum according to the present invention, wherein (a) shows ST11 and (b) shows ST12.
In (a), the Al-based composite material 45 is inserted into the container 50 and pressed by the ram 51. Thereby, the Al-based composite material 45 is pushed out between the die 52 and the mandrel 53. By extrusion molding the Al-based composite material 45 by this extrusion molding method, a cylinder having irregularities (shown in (b)) on the outer periphery 55 and an inner diameter D1 identical to that of the brake drum 10 (shown in FIG. 1). A shaped member 54 is formed.
[0033]
Here, it is said that an ordinary Al-based composite material is difficult to extrude because of its small elongation. Therefore, the Al-based composite material 45 of the present invention was made of magnesium nitride and chemically improved the wettability between the metal oxide and the molten Al alloy. For this reason, the interface state between the metal oxide and the Al alloy can be chemically and strongly bonded. Therefore, it exhibits excellent extensibility as compared with ordinary Al-based composite materials. For this reason, the Al-based composite material 45 can be extruded.
[0034]
Thus, since the Al-based composite material 45 has excellent extensibility, it is possible to extrude a cylindrical member from a solid billet (so-called horodice manufacturing method) during extrusion molding. That is, when extruding the Al-based composite material 45, the Al-based composite material 45 can be divided into a plurality of pieces with a holrodice, and the divided Al-based composite material 45 can be pressed while being extruded.
For this reason, since it is not necessary to prepare a hollow billet in order to extrude a cylindrical member, productivity can be improved.
[0035]
The cylindrical member 54 is used as the friction material 16 shown in FIG. 1, and it is desirable to ensure the tensile strength and the proof strength at predetermined values in order to maintain the strength of the friction material 16. Therefore, when the value obtained by dividing the cross-sectional area S1 of the Al-based composite material 45 before extrusion molding by the cross-sectional area S2 of the cylindrical member 54 after extrusion molding is the extrusion ratio R, the extrusion ratio R in the extrusion molding method is Set to 10-40.
By applying deformation to the Al-based composite material 45 with the extrusion ratio R10 to 40, the cylindrical member 54 is of high quality without any internal defects, and thus a complicated quality control process is not required. The reason why the extrusion ratio R is set to 10 to 40 will be described in detail with reference to FIG.
[0036]
In (b), the cylindrical member 54 is cut into a width W corresponding to the brake drum 10 (shown in FIG. 1). The cut member is the friction material 16 of the brake drum 10 shown in FIG. Since the friction material 16 has ensured the tensile strength and the proof stress at predetermined values as described above, the strength as the friction material 16 can be maintained.
By the way, since the Al-based composite material 45 shown in FIG. 3 (c) is composited by the surface active action with the reinforcing material, the thermal conductivity (heat sinkability) is very good. On the other hand, it has excellent heat dissipation. Therefore, the heat dissipation of the friction material 16 can be further improved.
[0037]
Further, by forming irregularities on the outer periphery 17 of the friction material 16, the friction material 16 can be securely fixed to the brake drum 10 (shown in FIG. 1).
By the way, the unevenness of the friction material 16 can be molded simultaneously with the extrusion molding, so that the yield is improved. Therefore, the cost can be reduced as compared with the case of forming irregularities by cutting.
The unevenness of the friction material 16 will be described in detail with reference to FIGS.
[0038]
FIG. 5 is a graph showing the relationship between the extrusion ratio and the tensile strength / proof strength when the brake drum according to the present invention is manufactured. The horizontal axis indicates the extrusion ratio R, and the vertical axis indicates the cylindrical member 54 (that is, the cylindrical member 54). , Shows the tensile strength (MPa) and proof stress (MPa) of the friction material 16). The proof stress is a stress when a permanent strain of 0.2% is generated.
When the extrusion ratio R is 10 or less, the tensile strength of the friction material 16 becomes smaller than a predetermined value (about 380 MPa), and the proof stress becomes smaller than a predetermined value (about 240 MPa). For this reason, the friction material 16 cannot maintain strength.
Further, when the extrusion ratio R is 10 or less, casting defects (such as shrinkage cavities) remain during the production of the Al-based composite material, and there is a possibility that blow holes occur after extrusion.
[0039]
When the extrusion ratio R exceeds 10, the tensile strength of the friction material 16 can ensure a predetermined value (about 380 MPa), and the proof stress can ensure a predetermined value (about 240 MPa). For this reason, the friction material 16 can maintain intensity | strength and can also ensure internal quality. Therefore, the lower limit of the extrusion ratio R is set to 10 from the viewpoint of the mechanical properties of the Al-based composite material.
However, when the extrusion ratio R exceeds 40, the pushing force increases and the extrusion speed decreases. For this reason, since the cycle time is reduced and the production cost is increased, the upper limit of the extrusion ratio R is set to 40.
[0040]
FIG. 6 is a third explanatory view of the brake drum manufacturing method according to the present invention, and shows ST13.
The friction material 16 manufactured in the previous process is heated to a predetermined temperature (for example, 100 ° C.) in the heating furnace 60, and the heated friction material 16 is conveyed by the conveying means 61 to the standby position P1 as indicated by an arrow. The friction material 16 that has reached the standby position P <b> 1 is stopped at a predetermined position by the stopper piece 62 a of the first stopper means 62.
When the friction material 16 is moved to the fitting position P2 of the fitting means 63, the cylinder rod 62b of the first stopper means 62 is moved backward to raise the stopper piece 62a, and at the same time, the second stopper of the fitting means 63 is moved. The cylinder rod 64b of the means 64 is moved backward to raise the stopper piece 64a.
[0041]
In this state, by driving the conveying means 61, the friction material 16 arranged at the standby position P1 is moved to the fitting position P2. After the friction material 16 is moved to the fitting position P2, the cylinder rods 62b and 64b of the first and second stopper means 62 and 64 are advanced, and the stopper pieces 62a and 64a are lowered. Thereby, the friction material 16 in the fitting position P2 is kept stationary.
[0042]
Next, by advancing the cylinder rod 65a of the fitting cylinder 65, the plate 66 attached to the tip of the cylinder rod 65a is pushed out. By extruding the plate 66, the friction material 16 is moved along the rails 67 and 67 toward the convex portion 72 of the movable die 71 (hereinafter referred to as “movable convex portion”) as indicated by the arrow (4). The movable mold 71 is a member constituting the mold 70.
The fitting means 63 is configured to be movable (in the direction indicated by the white arrow or in the horizontal direction), so that the fitting means 63 is retracted outside the mold of the movable projection 72.
[0043]
7 (a) and 7 (b) are fourth explanatory views of the brake drum manufacturing method according to the present invention and show the first half of ST14.
In (a), the cylinder rod 65a of the fitting cylinder 65 is advanced to move the friction material 16 as shown by the arrow (4), so that the friction material 16 is fitted to the movable convex portion 72.
[0044]
The movable convex portion 72 includes a cooling means 74, and supplies cooling water from a water supply hose 75a of the cooling means 74 to the copper pipe 75b as shown by an arrow a. The cooling water flows out from the tip of the copper pipe 75b into the cooling water channel 76a, turns back as shown by the arrow, flows through the cooling water channel 76a, and is discharged from the drain hose 76b as shown by the arrow b.
Thus, the cooling water circulates inside the movable convex portion 72 and cools the movable convex portion 72 to about 50 ° C. For this reason, the movable type convex part 72 can be contracted, and the outer diameter D2 of the movable type convex part 72 can be made small.
On the other hand, since the friction material 16 is heated to 100 ° C., the inner diameter D 1 of the friction material 16 can be expanded more than the outer diameter D 2 of the movable convex portion 72. Therefore, the friction material 16 can be easily fitted into the movable convex portion 72.
[0045]
As shown in (b), since the cooling means 74 sets four cooling water channels 76a along the outer periphery of the movable convex portion 72 at intervals of 90 °, the outer periphery of the movable convex portion 72 is set at a predetermined temperature (about 50 ° C.).
In addition, the cooling water channel 76a of the cooling means 74 is not limited to four, and can be arbitrarily set corresponding to the cooling state.
[0046]
FIG. 8 is a fifth explanatory view of the brake drum manufacturing method according to the present invention and shows the first half of ST14.
By fitting the friction material 16 into the movable convex portion 72, the friction material 16 (100 ° C.) comes into contact with the movable convex portion 72 (50 ° C.). At this time, since the heat capacity of the movable convex portion 72 is larger than that of the friction material 16, the friction material 16 is cooled to the same temperature as the temperature of the movable convex portion 72 after the contact.
For this reason, the temperature of the friction material 16 decreases from 100 ° C. to 50 ° C., and the friction material 16 contracts. Therefore, the inner diameter D1 of the friction material 16 is reduced.
[0047]
On the other hand, the temperature of the movable convex portion 72 is maintained at 50 ° C. Accordingly, a shrink-fit state is established, and the friction material 16 is brought into close contact with the movable convex portion 72, so that the clearance between the friction material 16 and the movable convex portion 72 can be eliminated.
After the friction material 16 is fitted into the movable projection 72, the movable material 71 is moved toward the fixed die 77 as indicated by the arrow (5), so that the friction material 16 is set in the metal mold 70.
[0048]
FIG. 9 is a graph showing the amount of heat change between the friction material and the mold of the brake drum according to the present invention, the horizontal axis shows the temperature, and the vertical axis shows the clearance between the friction material 16 and the movable projection 72. . The thick solid line is a straight line indicating the thermal expansion of the movable convex portion 72, and the thin solid line and the broken line are straight lines indicating the thermal expansion of the friction material 16.
[0049]
The dimension of the inner diameter D1 of the friction material 16 was set to be not more than a clearance (for example, 0.05 mm) that does not allow melting to enter when the temperature of the friction material 16 becomes the same as that of the movable convex portion 72. The minimum value of the inner diameter D1 of the friction material 16 is indicated by a thin solid line as d1, and the maximum value of the inner diameter D1 of the friction material is indicated by a broken line as D1.
The friction material 16 is made of an Al-based composite material as described above. On the other hand, the mold 70 (movable mold projection 72) is manufactured from a hot mold material (SKD) of alloy tool steel.
[0050]
The linear expansion coefficient (thermal expansion coefficient) of the movable convex portion 72 (SKD) is about 13.5 × 10 ⁻⁶ / ° C., and when the temperature of the movable convex portion 72 is heated from 0 ° C. to 50 ° C., the outer diameter D2 Increases by +0.05. Further, when the temperature of the movable convex portion 72 is heated to 75 ° C., the outer diameter D2 increases by +0.075, and when heated to 100 ° C., the outer diameter D2 increases by +0.10. Since the movable convex portion 72 has a small linear expansion coefficient, the outer diameter D2 increases relatively gradually.
[0051]
On the other hand, the friction material 16 (Al-based composite material) has a linear expansion coefficient (thermal expansion coefficient) of about 20 × 10 ⁻⁶ / ° C., which is larger than that of the movable convex portion 72. Therefore, when the temperature of the friction material 16 is heated from 0 ° C. to 50 ° C., the maximum inner diameter D1 increases by +0.10, and when heated to 75 ° C., it increases by +0.15. Furthermore, when the temperature of the friction material 16 is heated to 100 ° C., it increases by +0.20. Since the linear expansion coefficient of the friction material 16 is large, the inner diameter D1 increases rapidly.
Note that the minimum inner diameter d1 of the friction material 16 also increases abruptly in the same manner as the maximum inner diameter D1.
[0052]
Therefore, when the friction material 16 is heated to 100 ° C., and the movable convex portion 72 is heated to 50 ° C., (maximum inner diameter D1−outer diameter D2) becomes +0.15, and (minimum inner diameter d1−outer diameter). D2) is +0.05. Therefore, since the clearance of the friction material 16 with respect to the movable convex portion 72 can be secured large, the friction material 16 can be easily fitted into the movable convex portion 72.
[0053]
On the other hand, when the friction material 16 is fitted into the movable projection 72, the friction material 16 is cooled to the temperature of the movable projection 72 because the heat capacity thereof is smaller than that of the movable projection 72. At this time, (maximum inner diameter D1−outer diameter D2) is reduced from +0.15 to +0.05, and (minimum inner diameter d1−outer diameter D2) is calculated from +0.05 to −0.05. For this reason, the clearance of the friction material 16 with respect to the movable-type convex part 72 can be made small, or a clearance can be eliminated by a shrink fit effect.
Therefore, the friction material 16 can be arranged coaxially with respect to the movable projection 72 so as not to be displaced, and the molten metal can be prevented from entering the inner peripheral side during pouring.
[0054]
Further, since the linear expansion coefficient (about 20 × 10 ⁻⁶ / ° C.) of the friction material 16 is larger than the linear expansion coefficient (about 13.5 × 10 ⁻⁶ / ° C.) of the movable convex portion 72, The shrink-fit effect can be obtained without raising the heating temperature too high. For this reason, the installation cost of the heating furnace 60 can be suppressed.
[0055]
10 (a) and 10 (b) are fifth explanatory views of the method for manufacturing a brake drum according to the present invention, and show the latter half of ST14.
In (a), after the mold 70 is closed, a molten Al alloy is filled from the gate 70a of the fixed mold 77 into the cavity 70b as shown by the arrow (6). Thereby, the friction material 16 is cast with Al alloy. The Al alloy in which the friction material 16 is cast becomes the backup material 15 (that is, the hub 15 (shown in FIG. 1)).
[0056]
Here, since the molten temperature of the Al alloy is about 680 ° C., the friction material 16 and the movable convex portion 72 are heated by the molten metal by filling the cavity 70b with the molten metal, and the friction material 16 and the movable convex portion 72 are heated. A relatively large clearance may occur between the two.
However, since the cooling means 74 is provided inside the movable convex portion 72 and the cooling water is circulated, it is possible to prevent the temperature of the movable convex portion 72 and the friction material 16 from rising.
[0057]
In (b), after the Al alloy is solidified, the movable die 71 is moved as indicated by an arrow (7), and the slide die 78 is moved as indicated by an arrow (8). Next, the cast product 79 is taken out from the movable mold 71 as shown by the arrow (9).
Since the friction material 16 can be fitted in close contact with the movable projection 72, the friction material 16 can be cast coaxially with the axis 10a of the brake drum 10. Furthermore, it is possible to prevent the Al alloy from adhering to the inner periphery 18 of the friction material 16, or even if an Al alloy adheres to the inner periphery 18 of the friction material 16, it can be suppressed to a small amount.
If necessary, the brake drum 10 shown in FIG. 1 is obtained by grinding the inner periphery of the friction material 16 of the casting 79 to a desired dimension.
[0058]
In this state, after the mold 70 is closed, the molten metal (about 680 ° C.) is filled. At this time, cooling water can be circulated by the cooling means 74 inside the movable convex portion 72 to suppress the temperature rise of the movable convex portion 72 and the friction material 16 to about 50 ° C. For this reason, the clearance between the friction material 16 and the movable projection 72 can be suppressed substantially in the same manner as the range of FIG.
Accordingly, the molten metal can be prevented from entering between the movable projection 72 and the friction material 16 during pouring, and the friction material 16 can be cast coaxially in the drum body 13.
[0059]
In the comparative example, the temperature of the movable convex portion 72 when the friction material 16 is fitted into the movable convex portion 72 is 120 ° C. Since the temperature of the movable convex portion 72 is as high as 120 ° C., it is necessary to heat the friction material 16 to a temperature higher than 120 ° C. in order to increase the clearance between the movable convex portion 72 and the friction material 16. Therefore, in order to raise the heating temperature of the friction material 16, the installation cost of heating equipment increases.
By fitting the heated friction material 16 into the movable convex portion 72, the temperature of the movable convex portion 72 rises from 120 ° C.
[0060]
In this state, the mold 70 is closed and then filled with molten metal (about 680 ° C.), whereby the temperature of the movable convex portion 72 rises to about 230 ° C. For this reason, the friction material 16 is also heated to about 230 ° C., and a relatively large gap is generated between the friction material 16 and the movable projection 72. Therefore, it is conceivable that the friction material 16 shifts with respect to the movable convex portion 72 during pouring, and it is difficult to cast the friction material 16 coaxially with the movable convex portion 72.
[0061]
In the embodiment, the temperature of the movable convex portion 72 when the friction material 16 is fitted into the movable convex portion 72 is 50 ° C. Since the temperature of the movable convex portion 72 is as low as 50 ° C., it is only necessary to heat the temperature of the friction material 16 to 100 ° C. Therefore, by suppressing the heating temperature of the friction material 16, it is possible to prevent the equipment cost of the heating equipment from increasing.
[0062]
In this state, after the mold 70 is closed, the molten metal (about 680 ° C.) is filled. At this time, the cooling water 74 is circulated by the cooling means 74 inside the movable convex portion 72, so that the temperature rise of the movable convex portion 72 and the friction material 16 can be suppressed to about 150 ° C. For this reason, the clearance between the friction material 16 and the movable projection 72 can be suppressed substantially in the same manner as the range of FIG.
Therefore, the molten metal can be prevented from entering between the movable convex portion 72 and the friction material 16 during pouring, and the friction material 16 can be coaxially cast into the drum body 13.
[0063]
FIG. 12 is an explanatory view of the operation of the drum brake according to the present invention.
As the motorcycle travels, the brake drum 10 rotates counterclockwise as indicated by an arrow. In this state, the cam 26 is rotated as indicated by an arrow, so that the pair of brake shoes 23 and 23 are expanded outward as indicated by the white arrow against the spring force of the tension spring 24. Thereby, the pads 23a, 23a of the brake shoes 23, 23 are pressed against the inner periphery 18 of the friction material 16, and the rotation of the brake drum 10 is stopped.
[0064]
By the way, the rotational force is transmitted to the hub 15 from the wheel side, and the drum body 13 of the hub 15 tries to rotate separately from the friction material 16. Therefore, the outer periphery 17 is formed to be uneven by providing the outer periphery 17 of the friction material 16 with the protrusions 17a at a constant pitch angle θ. The unevenness of the outer periphery 17 is meshed with the inner periphery of the drum body 13, and the friction material 16 is firmly coupled to the drum body 13. Therefore, the drum body 13 is prevented from separating from the friction material 16.
[0065]
Here, the pitch angle θ is set in a range of 6 to 45 °, and preferably 6 to 30 °, but is not limited thereto. Moreover, although it is preferable to set the height h of the convex part 17a to 0.5-3 mm comparatively low with respect to the thickness t of the friction material 16, it is not restricted to this.
The reason why the pitch angle θ of the convex portion 17a is set to 6 to 45 ° and the height h of the convex portion 17a is set to 0.5 to 3 mm will be described in detail with reference to FIG.
[0066]
FIGS. 13A and 13B are explanatory views of the thermal expansion of the friction material according to the present invention, where FIG. 13A shows a comparative example and FIG. 13B shows an example.
In (a), frictional heat is generated by pressing a brake shoe pad (not shown) against the inner periphery 101 of the friction material 100, and the friction material 100 rises to about 400 ° C. Since the generated heat is not immediately transmitted to the drum body 105, the friction material 100 is thermally expanded by the frictional heat.
[0067]
Here, since the height h1 of the convex portion 102 of the friction material 100 is set to be sufficiently high, the convex portion 102 expands greatly. In addition, since the pitch angle θ1 of the convex portions 102 is increased, the convex portions 102 are separated too much. For this reason, the inner periphery 101 equivalent to the convex part 102 expand | swells inside, and the expansion | swelling part 103 will be made. Therefore, the brake shoe pad cannot be uniformly pressed against the inner periphery 101 of the friction material 100.
[0068]
In (b), frictional heat is generated by pressing the pad 23a (shown in FIG. 12) of the brake shoe 23 against the inner periphery 18 of the friction material 16, and the friction material 16 rises to about 400 ° C. Since the generated heat is not transmitted to the drum body 13 instantaneously, the friction material 16 is thermally expanded by the frictional heat.
[0069]
Here, by setting the height h of the convex portion 17a as low as 0.5 to 3 mm, the thermal expansion of the convex portion 17a is suppressed. In addition, by setting the pitch angle θ of the convex portions 17a in the range of 6 to 45 °, preferably 6 to 30 °, the adjacent convex portions 17a are brought close to each other, and the inner periphery 18 of the friction material 16 is heated substantially uniformly. Can be inflated. Therefore, the brake shoe 23 can be uniformly pressed against the inner periphery 18 of the friction material 16.
[0070]
In addition, when pitch angle (theta) is the range of 30-45 degrees, it is preferable to set the height h of the convex part 17a low in the range of 0.5-3 mm. This is because by setting the height h of the convex portion 17a to be low, the inner circumference 18 corresponding to the convex portion 17a is inflated inward to form an expanded portion.
[0071]
If the pitch angle θ of the protrusions 17a exceeds 45 °, the adjacent protrusions 17a are too far apart from each other, and when the friction material 16 is thermally expanded, a gentle unevenness may occur on the inner periphery 18 of the friction material 16. There is.
On the other hand, when the pitch angle θ of the convex portions 17a is less than 6 °, the adjacent convex portions 17a are too close to each other, and the width of the outer peripheral concave portion becomes too small. For this reason, the convex part of the drum main body 13 engaged with this concave part becomes small, and when the brake shoe is pressed against the friction material 16, the convex part of the drum main body 13 is damaged, and the friction material 16 becomes the drum main body. There is a risk of separation from 13.
In order to eliminate this problem, the pitch angle θ of the convex portion 17a was set to 6 to 45 °.
[0072]
If the height h of the convex portion 17a is lower than 0.5 mm, the amount of engagement between the friction material 16 and the drum body 13 becomes too small. For this reason, when the brake shoe is pressed against the friction material 16, the friction material 16 may be separated from the drum body 13.
On the other hand, when the height h of the convex portion 17a is higher than 3 mm, there is a possibility that a gentle unevenness is generated on the inner periphery 18 of the friction material 16 when the friction material 16 is thermally expanded.
In order to eliminate this problem, the height h of the convex portion 17a was set to 0.5 to 3 mm.
[0073]
In the above embodiment, an example in which alumina 32 is used as a reinforcing material made of a metal oxide has been described. However, other oxide ceramics may be used as a metal oxide.
In the above embodiment, the example in which the friction material 16 is used for a brake drum of a motorcycle has been described. However, the friction material 16 may be applied to a brake drum of an automobile or the like.
[0074]
【The invention's effect】
The present invention exhibits the following effects by the above configuration.
According to the first aspect, the surface of the reinforcing material can be metallized by the reducing action of magnesium nitride to improve the wettability between the reinforcing material and the molten Al alloy. For this reason, an Al-based composite material excellent in extensibility is obtained by firmly bonding the interface between the reinforcing material and the Al alloy. Accordingly, the Al-based composite material can be extruded into a friction material.
By extruding the friction material, the tensile strength and the proof stress can be further improved, and sufficient strength can be ensured. In addition, the friction material can be reduced in weight by making the matrix of the Al-based composite material a lightweight Al alloy. Therefore, the weight of the brake drum can be reduced.
[0075]
Moreover, the unevenness | corrugation of a friction material can be meshed | engaged with a backup material by having an unevenness | corrugation in the outer periphery of a friction material. For this reason, the friction material can be firmly bonded to the backup material. Accordingly, it is possible to prevent the friction material from being separated from the backup material during braking of the drum brake.
In addition, by using an Al alloy as the matrix of the friction material, the thermal conductivity can be improved as compared with conventional cast iron. Therefore, heat generated during braking is easily radiated, and fade resistance is improved.
[0077]
Furthermore , by making the friction material matrix an Al alloy, the coefficient of linear expansion of the friction material can be made the same as that of the backup material. Accordingly, since the difference in thermal expansion between the friction material and the backup material can be reduced when the brake is applied, the coupling between the friction material and the backup material can be maintained firmly.
[0078]
In addition , the friction material was set in the mold while being heated to a temperature higher than the mold by a predetermined temperature. Since the friction material is formed of an Al-based composite material, the coefficient of linear expansion of the friction material is larger than that of the mold. The inner diameter of the friction material can be increased by heating the friction material to a temperature higher than that of the mold. Therefore, the friction material can be easily set in the mold.
Further, since the friction material can be fitted in a state of being in close contact with the mold, the friction material can be cast coaxially with the axis of the brake drum. Furthermore, it is possible to prevent the Al alloy from adhering to the inner periphery of the friction material, or to suppress the Al alloy to a small amount even if the Al alloy adheres to the inner periphery of the friction material.
[0079]
According to a second aspect of the present invention, a cylindrical member that is a material of the friction material is extruded at an extrusion ratio of 10 to 40. By making the extrusion ratio exceed 10, the tensile strength and proof stress of the friction material can be increased and the strength of the friction material can be maintained. In addition, productivity can be increased by increasing the extrusion ratio to exceed 10.
However, if the extrusion ratio exceeds 40, the pushing force increases and the extrusion speed decreases. As a result, the cycle time was reduced and the production cost was increased, so the extrusion ratio was set to 40 or less.
[Brief description of the drawings]
FIG. 1 is a perspective view of a rear wheel for a motorcycle to which a brake drum according to the present invention is attached. FIG. 2 is a flowchart showing a method for manufacturing the brake drum according to the present invention. FIG. 4 is a second explanatory view of the method for manufacturing a brake drum according to the present invention. FIG. 5 is a graph showing the relationship between the extrusion ratio, tensile strength, and yield strength when manufacturing the brake drum according to the present invention. FIG. 6 is a third explanatory diagram of a method for manufacturing a brake drum according to the present invention. FIG. 7 is a fourth explanatory diagram of a method for manufacturing a brake drum according to the present invention. FIG. 9 is a graph showing the amount of heat change between the friction material and the mold of the brake drum according to the present invention. FIG. 10 is a fifth explanatory diagram of the method of manufacturing the brake drum according to the present invention. FIG. 11: Breaker according to the present invention Illustration of thermal expansion of the friction material according to the operation explanatory view [13] The present invention of a drum brake according to the graph 12 shows the present invention described the casting process of the drum [Description of symbols]
DESCRIPTION OF SYMBOLS 10 ... Brake drum , 13 ... Drum main body , 15 ... Backup material (hub), 16 ... Cut member (friction material), 17 ... Outer periphery of friction material, 17a ... Outer convex part, 32 ... Reinforcement material (alumina), 33 ... Al alloy, 44 ... magnesium nitride, 45 ... Al-based composite material, 54 ... cylindrical member, 55 ... periphery of cylindrical member, 60 ... heating furnace, 70 ... die, 71 ... movable type, 72 ... movable type Convex part, S1 ... Cross-sectional area of Al-based composite material before extrusion molding, S2 ... Cross-sectional area of cylindrical member after extrusion molding, R ... Extrusion ratio, h ... Height of convex part, θ ... Pitch angle of convex part .

Claims (2)

An annular friction material made of an Al-based composite material having a plurality of convex portions formed on the outer periphery at the same pitch, and an Al alloy drum body coupled to the outer periphery of the friction material by meshing with the convex portions, A method for manufacturing a brake drum, wherein the height of the convex portion is set to 0.5 to 3.0 mm, and the pitch angle of the convex portion is set to 6 to 45 °,
The reinforcing material made of a metal oxide contacted with the magnesium nitride, for producing the Al-based composite material impregnated with Al alloy reinforcing material in a state that allowed expose at least a portion the metal reinforcement by the reducing action of the magnesium nitride Process,
A step of forming this Al-based composite material by an extrusion method on a cylindrical member having irregularities on the outer periphery and having the same inner diameter as the brake drum;
The cylindrical member, a step Ru obtain friction material of the annular cut to a width corresponding to the brake drum,
Heating the annular friction material to a temperature higher than the mold by a predetermined temperature;
Cooling the heated friction material after setting it in the mold, and attaching the friction material to the mold;
A step of casting the Al alloy as a back-up material into the closely- fitted friction material ;
After wrapped friction material cast in an Al alloy, a manufacturing method of the brake drum, wherein the Ru step and Tona removing the friction material with cast wrapped Al alloy from the mold. When the value obtained by dividing the cross-sectional area of the Al-based composite material before extrusion molding by the cross-sectional area of the cylindrical member after extrusion molding is taken as the extrusion ratio, the extrusion ratio in the extrusion molding method is set to 10-40. the process according to claim 1 Symbol mounting of the brake drum, characterized in that.

Images