JP2006083978A - Method and device of manufacturing frictional material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method and a manufacturing metal mold of a frictional material for dispensing with a large-scale press device, by reducing generation of polishing powder, by shortening grinding work, while reducing a brake squeak. <P>SOLUTION: This device has a process of manufacturing a spare mold 30 having inclined faces 30b and 30b by pressurizing and hardening a powdery raw material without heating in a preliminary molding metal mold 10, and a process of forming the spare mold into the frictional material 3 having inclined faces 3b and 3b of a desired angle in a position of the inclined faces 30b by heating and pressurizing the spare mold in a molding metal mold 20; and is characterized by setting an angle α of the inclined face of the spare mold 30 larger than an angle β of the inclined face of the frictional material 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to manufacturing of a friction material such as a brake, and more particularly to a method and an apparatus for manufacturing a friction material capable of preventing brake noise.

  Disc pads used for automobile disc brakes are usually made by attaching a friction material to a steel back plate. The friction material is formed by pressurizing and heating a powdery raw material in which a fiber material, a filler, a binder, and the like are mixed. The disc brake presses the disc pad against a metal disc rotor, and brakes the automobile by the frictional force at that time.

  In such a disc brake, there is a problem that when the brake is operated, a disc pad, a disc rotor, etc. vibrate and a brake noise is generated. Since such a brake squeal becomes unpleasant noise, various measures have been taken. As one of measures for preventing brake squeal, a method of forming inclined surfaces at both ends of a disk pad is known.

  FIG. 5 shows a conventional example of a disk pad having such an inclined surface, where (a) is a front view and (b) is a bottom view. The disk pad 1 shown in FIG. 5 is configured by attaching a friction material 3 to a steel back plate 2. The friction material 3 has a flat friction surface 3a at the center, and inclined surfaces 3b and 3b are formed on both sides. The boundary lines 5 and 5 between the friction surface 3a and the inclined surfaces 3b and 3b on both sides are parallel to each other. As a result, the length of the friction surface 3a in contact with the outer peripheral side of the disc rotor is made equal to the length of the friction surface 3a in contact with the inner peripheral side.

  Providing such an inclined surface 3b reduces the area of the friction surface 3a and reduces brake noise.

  FIG. 6 shows another conventional example of a disk pad having an inclined surface. In FIG. 6 (a), inclined surfaces 3d and 3d are formed at both ends so that the friction surface 3c expands toward the outside of the disk rotor. In FIG. 6 (b), the friction surface 3e has an inverted sector shape. The inclined surfaces 3f and 3f are formed so as to be. The boundary lines 6 and 6 in FIG. 6A and the boundary lines 7 and 7 in FIG. 6B are not parallel to each other. That is, in the disk pad 1 of FIG. 6A, the length of the friction surface 3c contacting on the outer peripheral side of the disk rotor is longer than the length of the friction surface 3c contacting on the inner peripheral side. In the disk pad 1 of b), the length of the friction surface 3e that contacts on the outer peripheral side of the disk rotor is shorter than the length of the friction surface 3e that contacts on the inner peripheral side.

  The brake squeal is considered to be caused by vibration generated in the disk pad 1 and the disk rotor when the brake is operated. On the other hand, when the boundary lines 5, 6, and 7 of the disk pad 1 are not parallel to each other. The effect of suppressing the vibration of the disk rotor is increased. For this reason, the friction surfaces 3c and 3e are also fan-shaped as shown in FIG.

  By the way, the disk pad 1 is formed by attaching the friction material 3 to the steel back plate 2 as described above. After the application, the friction surfaces 3a, 3c, 3e are finished to a plane having a desired accuracy. In order to form the inclined surfaces 3b, 3d, 3f, grinding is performed.

  This grinding process is usually performed by the rotating grindstone 4, but the process of grinding the friction surfaces 3a, 3c, 3e and the process of grinding the inclined surfaces 3b, 3d, 3f are separate processes. For example, for machining the inclined surfaces 3b, 3d, 3f, several types of grinding wheels having different angles are prepared for the types of inclined angles of the inclined surfaces to be machined, and the inclined surfaces 3b, 3b, After the formation of 3d and 3f, surface grinding of the friction surfaces 3a, 3c and 3e is performed. In addition, the inclined surfaces 3b, 3d, and 3f were not grounded on both sides at the same time, but were ground on each side.

  Therefore, in the above grinding process, the number of man-hours is increased, and the tool needs to be replaced every time the process of the inclined surface is changed to the process of the friction surface, thereby reducing the productivity.

  On the other hand, Patent Document 1 (Japanese Patent Laid-Open No. 9-136255) proposes a grinding method as shown in FIGS. 7A to 7D as a grinding method for the disk pad shown in FIG.

  First, the disk pad 1 is held as shown in FIG. The rotating grindstone 4 is arranged so that the rotating shaft 4a thereof is parallel to the friction surface 3a. In this state, the rotating grindstone 4 is rotated in the direction of arrow D, and grinding is started with the rotating grindstone 4 from the right end of the friction material 3. The disk pad 1 is moved in the right direction in the figure, and this direction is the circumferential direction of the disk rotor (not shown). Grinding is started from the state in which the disk pad 1 is brought close to the rotating grindstone 4 as indicated by the arrow C, and is moved away from the rotating grindstone 4 as it is sent to the right. Thus, one inclined surface 3b is formed as shown in FIG.

  Next, as shown in FIG. 7B, the disc pad 1 is moved while keeping the distance from the rotating grindstone 4 constant. Thereby, the plane of the friction surface 3a is ground.

  When the grinding of the friction surface 3a is completed, as shown in FIG. 7C, the disk pad 1 is moved to the right while approaching the rotating grindstone 4 so that the grinding amount gradually increases. Finally, as shown in FIG. 7D, the opposite inclined surface 3b is formed. According to this method, the length of the rotating grindstone 4 in the direction of the rotating shaft 4a is set so as to cover the size of the disk pad 1, whereby the inclined surfaces 3b and 3b and the friction surface 3a are ground in one pass. be able to.

  Further, in Patent Document 2 (Japanese Patent Laid-Open No. 6-33960), a manufacturing method in which an inclined surface is created when a friction material is manufactured, and the polishing step is omitted, or the polishing can be performed by light polishing only by finishing polishing. Has proposed.

The friction material is formed by putting a powdery raw material of the friction material into a mold and solidifying by heating and pressing. Therefore, in Patent Document 1, an inclined surface is formed on the mold, and an inclined surface having a desired gradient can be formed on the molded friction material. However, even if the inclined surface is simply formed on the mold, the molded friction material does not become homogeneous.Therefore, vibration is applied to the mold during molding, and the fluidity of the powdery raw material is increased to achieve homogenization. I am trying.
JP-A-9-136255 JP-A-6-33960

  However, the grinding method of Patent Document 1 cannot form the inclined surfaces 3d and 3f in which the boundary lines 6 and 6 and the boundary lines 7 and 7 are not parallel as shown in FIG. There is also a problem that one inclined surface 3d, 3f, friction surface 3c, 3e, and the other inclined surface 3d, 3f must be ground as separate processes. Furthermore, the grinding method is not preferable in terms of work hygiene because a large amount of polishing powder is discharged.

  In Patent Document 2, it is possible to form the inclined surfaces 3d and 3f which are not parallel like the boundary lines 6 and 6 and the boundary lines 7 and 7. However, there is a problem that a device for applying vibration to the mold is required at the time of molding, and the press device becomes large.

  The present invention solves such a problem, and there is less brake squealing, grinding work can be shortened, generation of abrasive powder can be reduced, and a friction material manufacturing method that does not require a large press device and The object is to provide a mold for manufacturing.

  In order to achieve the above object, the friction material manufacturing method according to claim 1 of the present application is a method of manufacturing a preform having an inclined surface by pressing and solidifying a powdery raw material without heating in a preforming mold. And a step of heating and pressurizing the preform in a molding die to obtain a friction material having an inclined surface with a desired angle at the position of the inclined surface, the angle of the inclined surface of the preform It is characterized in that β is made larger than the angle α of the inclined surface of the friction material.

  The method for manufacturing a friction material according to claim 2 is characterized in that the angle β is twice or more the angle α.

  In order to achieve the above object, the friction material manufacturing mold according to claim 3 of the present invention is composed of a plurality of molds and a preforming mold for forming a space for charging a powdery raw material by a plurality of molds, and a plurality of molds. A molding die for forming a space for feeding a preform molded by the preforming mold, and the preforming die and the molding die are provided with inclined surfaces at the same position, The angle β of the inclined surface of the preforming mold is larger than the angle α of the inclined surface of the forming mold.

The metal mold for manufacturing a friction material according to claim 4 is characterized in that the angle β is at least twice the angle α.
[Action]

  A powdery raw material used as a raw material for the friction material is put into a preforming mold. In the preforming mold, inclined surfaces are formed at both ends, and the powdery raw material in the mold is pressed without being heated by a press machine, and becomes a preformed product having inclined surfaces at both ends. . Such a preform is placed in a molding die and heated and pressurized with a press machine to form a friction material. When the inclined surface of the preform and the molding die have the same gradient, the entire inclined surface of the molding die is in close contact with the inclined surface of the preform from the beginning of the pressing step. When heat is applied to the preform in this state, the powdery raw material constituting the preform is melted but cannot flow, and a friction material having a high density in the inclined surface portion can be obtained. Thus, when the density of the inclined surface becomes larger than the density of the friction surface, when the portion of the inclined surface disappears due to wear, brake squeal is likely to occur.

  On the other hand, in the present invention, the inclined surface formed in the preform is steeper than the inclined surface to be formed in the friction material. Therefore, the inclined surface of the molding die is initially contacted only inside the inclined surface of the preform, and a wedge-shaped space is formed outside the contact portion. Although the powdery raw material is in a molten state by heating, it becomes easy to flow because there is a space between the mold and the preformed product, and becomes a friction material of uniform quality. In a state where the melting has progressed, the inclined surface of the molding die is in contact with the molten friction material without gaps, and the finally formed friction material has an inclined surface with the same gradient as the inclined surface of the molding die. become.

  Thus, if the density of the inclined surface becomes the same as the density of the friction surface, even if the friction material is used and the portion of the inclined surface disappears due to wear, the brake noise does not occur.

  According to the friction material manufacturing method and friction material manufacturing die of the present invention, the friction surface portion and the inclined surface portion have substantially the same density and porosity, or the inclined surface portion has a smaller density and a higher porosity. The material can be manufactured. Such a friction material does not cause a brake squeal even if the wear progresses and the inclined surface disappears. In addition, a grinding operation for cutting an inclined surface is not required, and only a final polishing is required, the manufacturing process of the friction material can be shortened, and polishing powder can be reduced to improve the working environment.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram of a preforming mold according to the present invention. The preforming mold 10 is composed of an upper mold 15, a frame mold 16, and a plunger 17. These are attached to the press machine, but the frame die 16 is fixed, and the upper die 15 and the plunger 17 are movable in the vertical direction in the figure. The hollow portion 16a of the frame mold 16 has the same cross-sectional shape as the shape seen from the front of the friction material 3 shown in FIG. 5 (a), and the hollow portion 16a is formed through the top and bottom of the frame mold 16. The plunger 17 can move up and down in the hollow portion 16a. The upper die 15 is formed with two recesses 15a and 15a in order to form a protrusion that enters the binding hole 2a of the back plate 2. A flat surface 17a is formed at the center of the upper surface of the plunger 17, and inclined surfaces 17b and 17b are formed at both ends thereof. The angle of the inclined surface 17b is β. Since the inclined surface 17b is formed on the plunger 17, the boundary line between the inclined surface and the plane is not limited to being parallel as shown by the boundary lines 5 and 5 in FIG. 5, but the boundary lines 6 and 6 in FIG. Alternatively, non-parallel ones such as the boundary lines 7 and 7 in FIG.

  The upper die 15 is retracted upward in the figure, and the powdered friction material material is put into the hollow portion 16a above the plunger 17 in the frame die 16, the plunger 17 is raised, and the upper die 15 is lowered and added. Press. At this time, heating is not performed. Although the temperature of the preforming mold 10 naturally rises due to the pressurization, it is within the limit that the thermosetting resin in the powdery raw material does not melt. The powdery raw material contains sticky substances such as unvulcanized NBR, and when this is applied with pressure, it becomes like soft clay and spreads between other substances, like an adhesive. Acts to solidify the powdery raw material. As a result, the preform is solidified only by pressurization.

  FIG. 2 is a side view of the preform 30 and is a state in which the preform 30 is hardened only by applying pressure without heating in the preforming mold 10. The shape seen from the front is the same as that of the finished product of FIG. 5A, but the density is rough, and the thickness T of the finished product is pressure-bonded to the back plate 2 and compressed to a predetermined density. It is almost twice the thickness. The preform 30 has a flat surface 30a serving as a friction surface at the center of the lower surface in the figure, inclined surfaces 30b and 30b at both ends thereof, and two raised portions that enter the binding holes 2a of the back plate 2 on the upper surface in the figure. 30c, 30c. The angle of the inclined surface 30b is β which is the same as the angle of the inclined surface 17b formed on the plunger 17 of the preforming mold 10. In the preform 30, the density of the portion Y of the inclined surface 30 b is higher when the density of the portion X of the flat surface 30 a and the density of the portion Y of the inclined surface 30 b are compared.

  The preform 30 thus formed is attached to the back plate 2 as follows. First, the preform 30 is placed in the molding die 20 shown in FIG. The molding die 20 has basically the same structure as the preforming die 10. That is, the upper mold 25 and the frame mold 26 and the plunger 27 that moves up and down in the space formed through the frame mold 26 are configured. The frame mold 26 is formed with an opening having the same shape and the same size as the temporarily molded frame mold 16. On both sides of the upper surface of the plunger 27, inclined surfaces 27b and 27b are formed. The length of the inclined surface 27b is equal to the length of the inclined surface 30b of the preform 30, and is a length L as shown in FIG. 2 and the angle of inclination is α.

  The plunger 27 is stopped at an appropriate position in the frame mold 26, and the preform 30 is placed in the space of the frame mold 26. At this time, the raised portions 30 c and 30 c of the preform 30 are prevented from protruding from the upper surface of the frame mold 26. Next, the back plate 2 is placed on the upper surface of the frame mold 26. The back plate 2 is placed at a predetermined position by a positioning member (not shown) formed on the frame mold 26.

  The upper die 25 is lowered, the plunger 27 is raised, and pressure and heat are applied to the preform 30 and attached to the back plate 2. In the binding holes 2a and 2a, the raised portions 30c and 30c enter from the bottom, and the protrusions 25a and 25a of the upper mold 25 enter from the top to solidify to an appropriate density, thereby increasing the bonding force. Yes.

  FIG. 4A is an enlarged view of one inclined surface portion of the plunger 27 and the preform 30. As shown in the figure, the horizontal length L of both inclined surfaces 27b and 30b is the same, the angle of the inclined surface 30b of the preform 30 is β, and the inclined surface 27b formed on the upper surface of the plunger 27 is The angle is α, and β> α. Therefore, the two inclined surfaces 30b and 27b come into contact with each other at the inner end A and are separated at the outer end, so that a wedge-shaped space B is formed between the two inclined surfaces.

  The upper mold 25 presses the back plate 2 against the frame mold 26, and the plunger 27 moves up in the frame mold 26, and pressure is applied to the preform 30. At the same time, heat is applied to the preform 30 from the surrounding mold, and the preform 30 begins to melt. By melting, the inclined surfaces 30b and 27b that were initially in contact only at point A gradually increase the contact area, and when the entire preform 30 is in a molten state, the state shown in FIG. B will disappear. Until the space B disappears, the melted portion of the inclined surface 30b can flow using the space B. When the friction material 3 is obtained, the density of the inclined surface 3b and the friction surface 3a is almost equal. Will be equal.

In the present invention, if the angle β is slightly larger than the angle α, the space B is formed, so that fluidity is generated. However, if the angle β is twice or more than the angle α, the fluidity is ensured, and the inclined surface 3b. It is desirable to make the density with the friction surface 3a equal. Also, the larger the space B, the better the fluidity, which is desirable, and there is no upper limit as long as it is twice or more. However, the maximum value β _max of the angle β is as follows.

FIG. 4B is an enlarged view of one of the preforms 30 in FIG. The preform 30 has the flat surface 3a and the inclined surface 3b as the friction surfaces described above, but there are an affixing surface 30d to be affixed to the back plate 2 and an outer surface 30e as the other surfaces. A boundary between the plane 30a and the inclined surface 30b is a point A, a boundary between the inclined surface 30b and the outer surface 30e is a point C, and a boundary between the outer surface 30e and the pasting surface 30d is a point D. When the angle β increases, the point C approaches the point D, and when the point C and the point D overlap as shown in FIG. 4C, the maximum value β _max of the angle β is reached. This β _max is determined by the thickness T of the preform 30 and the horizontal length L of the inclined surface 30b. Here, the thickness T of the preform 30 is approximately twice the thickness t of the friction material 3 shown in FIG. Further, the horizontal length L of the inclined surfaces 30b and 3b is the same between the preform 30 and the friction material 3, and is a value determined when the disk pad 1 is designed. From the above, the maximum value β _{max of the} angle β is determined.

  On the other hand, the value of α is such that α> 0 since the inclined surface 3b only needs to function as an inclined surface. When the boundary lines 6 and 7 are not parallel as shown in FIG. 6, since the value of L changes depending on the position on the boundary lines 6 and 7, the value of β / α also changes.

  FIGS. 5A and 5B are views of the disk pad 1 molded and taken out by the molding die 20, wherein FIG. 5A is a front view and FIG. 5B is a bottom view, which is the same in appearance as the conventional example. is there. The angle of the inclined surface 3b is the same α as the angle of the inclined surface 27b formed on the plunger 27 of the molding die 20. Thereafter, finish polishing is performed as necessary to obtain a finished product.

Next, Table 1 shows the results of a brake squeal test performed on the friction material manufactured using the mold in a new state and a state in which the inclined surface disappears due to use.

Examples 1 to 5 are friction materials manufactured by the manufacturing method of the present invention, and Comparative Examples 1 to 3 are conventional manufacturing methods. For comparison, all the same powdery raw materials were used, and the molding conditions (pressure, temperature, etc.) of the preform 30 and the friction material 3 were all the same. The friction material of Comparative Example 3 was not provided with an inclined surface in the mold, but in the other friction materials, the angle α of the inclined surface was set to 15 ° in Examples 1, 2, 3 and Comparative Examples 1, 2. In Examples 4 and 5, the angle was 5 °. In Examples 1 to 3, the angle β of the inclined surface of the preforming mold was changed to 2 times, 3 times, and 4 times α. In Examples 4 and 5, the angle β is 9 and 12 times α. In Comparative Example 1, β = α, and in Comparative Example 2, an inclined surface is formed on the molding die without forming an inclined surface on the preform. In Comparative Example 3, neither the preforming mold nor the molding die was provided with an inclined surface, and the inclined surface was formed by polishing after molding. Α at this time was set to 15 °.

  In the test, a test piece was cut out from the friction surface 3a and the inclined surface 3b in addition to the squeal of the brake, and the specific gravity and porosity of the friction surface 3a and the specific gravity and porosity of the inclined surface 3b were measured. The porosity is the volume percentage of the void portion present in the friction material occupying the apparent total volume of the friction material. The method of dividing the friction surface portion and the inclined surface portion was performed in accordance with X and Y in FIG. The specific gravity was measured according to JIS D 4417, and the porosity was measured according to JIS D 4418.

  The specific gravity of Examples 1, 2, and 3 has almost no difference between the friction surface portion and the inclined surface portion, but a considerable difference was observed in Comparative Examples 1 and 2. This is presumably because the inclined surface portion is greatly compressed in the comparative example. Further, looking at Examples 1, 2, and 3, as β increases, the specific gravity of the inclined surface portion decreases, and in Example 1, the specific gravity of the inclined surface portion is slightly larger than the specific gravity of the friction surface portion. On the contrary, it can be seen that the specific gravity of the friction surface portion is larger.

  The porosity has a property of increasing as the specific gravity decreases. In Examples 1 and 2, the friction surface portion is larger than the friction surface portion and the inclined surface portion. It ’s reversed. Also, the porosity increases as the β magnification increases. This is considered to be because the specific gravity is reduced because the compressive force is reduced due to the presence of the space B. In Comparative Examples 1 and 2, the difference in porosity between the friction surface portion and the inclined surface portion is large, but it is considered that the specific gravity of the inclined surface portion is large. In the comparative example 3, since it forms by grinding, without forming an inclined surface with a metal mold | die, it is substantially the same.

  In Table 1, the brake noise is shown in Table 1 where ◎ indicates a state where there is no noise at all, ○ indicates a state where there is a very small noise, Δ indicates a state where there is a minute noise, and × indicates a state where a distinct noise is produced. When any of Examples 1 to 5 and Comparative Examples 1, 2, and 3 were new, they did not occur at all and were good.

  However, in the state where it is used until the inclined surface disappears, in Examples 3, 4 and 5, ◎ is completely absent, and in Examples 1 and 2, only “very small squeal” that is considered to be a problem occurs. However, in Comparative Example 1, a “small squeal” occurred in Δ, and in Comparative Example 2, a “scream” occurred clearly. However, in Comparative Example 3, the squeal remained very fine with a circle.

  From the above results, it was found that the specific gravity of the friction surface portion and the inclined surface portion is preferably lighter in the inclined surface portion, and the porosity is preferably higher in the inclined surface portion. That is, when the relationship of β ≧ 2α is established, the specific gravity of the inclined surface portion is decreased, and thereby the porosity is increased, so that it is considered that the brake squeal is eliminated.

  In Comparative Example 3, since the friction material was formed without forming the inclined surface, and then the inclined surface was formed by polishing, the specific gravity and the porosity could not be different between the friction surface portion and the inclined surface portion. For this reason, the results are almost the same as those of the present invention, but the problem of polishing work and polishing powder remains unsolved.

It is a figure of the metal mold | die for preforming of this invention. It is a side view of a preforming product. It is a figure of the metal mold | die for shaping | molding of this invention, (a) is a figure which shows a shaping | molding start state, (b) is a figure which shows a molding completion state. (A) is the figure which expanded the part of the one inclined surface of a plunger and a preform, (b) is the figure which expanded one of the preform 30 of FIG. 2, (c) shows (beta) _max . FIG. In the conventional example of the disk pad which formed the inclined surface, (a) is a front view, (b) is a bottom view. In the figure of another prior art example of a disk pad, (a) is an example in which the friction surface expands toward the outside of the disk rotor, and (b) is an example in which the friction surface has an inverted fan shape. (A)-(d) is a figure explaining the grinding method of the conventional disc pad.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Disc pad 2 Back plate 2a Binding hole 3 Friction material 3a Friction surface 3b Inclined surface 5, 6, 7 Boundary line 10 Pre-molding die 15 Upper die 16 Frame die 17 Plunger 20 Molding die 25 Upper die 26 Frame Mold 27 Plunger 27b Inclined surface 30 Preliminary product 30b Inclined surface β Angle of inclined surface of preformed product α Angle of inclined surface of friction material

Claims (4)

  A process for producing a preform having an inclined surface by pressing and solidifying the powdery raw material without heating in a preforming mold, and the preform has the same opening shape as the preforming mold. A friction material having an inclined surface of a desired angle at the position of the inclined surface by heating and pressing in a molding die, and the angle β of the inclined surface of the preform is set to the inclined surface of the friction material. A method for producing a friction material, characterized in that it is larger than the angle α.   2. The method for manufacturing a friction material according to claim 1, wherein the angle [beta] is at least twice the angle [alpha].   A preforming mold for forming a space for feeding powdery raw material by a plurality of molds, and a molding for forming a space for feeding a preformed product molded by the preforming mold by a plurality of molds. The pre-molding die and the molding die have the same opening shape and are provided with an inclined surface at the same position, and the angle β of the inclined surface of the pre-molding die is the molding die. A mold for manufacturing a friction material, characterized by being larger than an angle α of the inclined surface of the mold.   4. The mold for manufacturing a friction material according to claim 3, wherein the angle [beta] is at least twice the angle [alpha].

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