JPH0821462A - Disc brake pad - Google Patents

Abstract

PURPOSE:To improve the squeak suppressing performance in brake application and improve the rustproofness of the joint surface between a back plate and a frictional member. CONSTITUTION:As for a frictional member 3 which consists of a back plate 1 which is made of metal and equipped with a mold hole 2 and consists of a fibrous basic member, resin joinning agent, and a charging material is constituted so as to be joined integrally with the surface on one side of a back plate 1 and permit a part to intrude into the mold hole 2 on the back plate 1 and change the mold hole 2 at least partially, the hardness of the part 3a over the mold hole 2 is lower than the hardness of the part 3b on the surface of the back plate 1, and a shim 4 for closing the mold hole 2 on the back plate 1 is provided. Since the frictional member 3 consists of a low hardness part 3a and a high hardness part 3b, the squeak characteristic is improved, and the intrusion of water, etc., from the mold hole 2 can be prevented by the shim 4 attached on the back plate 1, and the rustproofness can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc brake pad used for a disc brake of an automobile or the like.

[0002]

2. Description of the Related Art A disc brake pad used for a disc brake of an automobile or the like comprises a metal back plate and a friction material integrally bonded to one surface of the back plate. The friction material frictionally engages with its counterpart members, the disk rotor and the brake drum, and plays an important role of converting kinetic energy into heat energy. Therefore, the friction material always generates heat and becomes high temperature. Therefore, such a friction material is required to have heat resistance, wear resistance, and the like, as well as stable friction characteristics with a small change in friction coefficient due to temperature changes. Further, it is necessary that the mating member has low aggression and that judder does not occur, and thus the characteristics required of the friction material cover many items.

Therefore, in order to satisfy these various characteristics, the friction material is formed as a composite material. That is, the friction material is a fiber base material forming a skeleton such as aramid fiber or potassium titanate fiber, a resin binder such as a phenol resin for binding and holding the fiber base material, and a matrix of these fibers and the binder. It is generally formed from various fillers that are dispersed and filled in. Further, as the filler, a solid filler such as barium sulfate and calcium carbonate, a solid lubricant such as graphite and molybdenum disulfide, cashew dust, metal powder, an abrasive agent such as silica, or other friction adjusting agents. Additives are used.

The disc brake pad is prepared by uniformly mixing these raw materials of the friction material and then preforming the same, and then press-molding the preform together with the backing metal to which the adhesive has been previously applied to form the friction material. It is generally manufactured by thermoforming and integrally joining to one surface of the backing. Generally, a mold hole is formed in the back plate, and by filling a part of the friction material in the mold hole,
The joint strength between the friction material and the back metal is enhanced.

By the way, one of the more important characteristics required for the friction material is that no unpleasant noise (noise) is generated during braking, that is, no squeal is generated. And, in recent years, this demand has been increasing more and more along with the speeding up and the sophistication of automobiles.

Such squeaking during braking is caused by the friction material or the pad vibrating due to the friction between the friction material and the disk rotor. In order to prevent or reduce such squeaking. Conventionally, various means have been known and practiced.

The best known means is to incorporate rubber dust (rubber powder) as a filler in the friction material. However, compounding rubber dust can improve the squealing performance due to its vibration damping effect,
Since rubber dust has low heat resistance, it may deteriorate the fade performance of the friction material.

Further, it is a generally well-known means to chamfer the end portion of the pad where vibration easily occurs.
However, although this improves the squealing performance to some extent,
There is also a limit to that, and the chamfering process itself is a relatively simple process, but the number of man-hours is increased in manufacturing the pad.

Although the squealing performance of the friction material itself is not improved, a shim (anti-vibration plate) such as a stainless plate or a rubber coating plate is interposed between the back metal of the pad and the piston of the brake caliper. However, it is generally done. However, this also has some squeal prevention effect,
There are also limits.

Therefore, unlike these means, a disc brake pad having improved squealing performance is provided by providing a friction material with a hardness difference so that the friction material does not easily resonate with vibration during braking. It is disclosed in Japanese Patent Laid-Open No. 5-332378. Specifically, the disc brake pad includes a metal back plate (plate) having a mold hole (binding hole), and a friction material (lining material) integrally joined to one side of the back plate. A part of the friction material enters the mold hole of the back plate and at least partially fills the mold hole. The friction material is formed such that the hardness of the portion on the mold hole of the back plate is lower than the hardness of the portion on the surface of the back plate.

[0011]

[Patent Document 1] Japanese Patent Application Laid-Open No. 5-332
According to the disc brake pad disclosed in Japanese Patent No. 378, a hardness difference is provided between a portion on the mold hole of the friction material and a portion on the surface of the back plate, and the friction material resists vibration during braking. Since the structure is formed so as not to resonate easily, squeal (noise) during braking can be effectively prevented or reduced. Moreover, this pad can be easily manufactured by a conventional thermoforming method.

However, in this disc brake pad, although the squealing performance can be improved, since the friction material in the mold hole portion has a low hardness and a low density, water or the like flows from the mold hole to the inside of the pad. It was easy to penetrate, so that the joint surface of the back plate with the friction material tended to be easily rusted. Then, rust is generated on the joint surface of the back plate with the friction material, and when the rust progresses, the friction material may finally come off from the back plate and fall into an unexpected danger.

Therefore, an object of the present invention is to provide a disc brake pad having improved squealing performance and improved rustproof property of the joint surface of the back plate with the friction material.

[0014]

DISCLOSURE OF THE INVENTION A disc brake pad according to the present invention comprises a metal back plate having a mold hole, a fiber base material, a resin binder, and a filler.
A friction material that is integrally joined to one surface of the back plate and that partially enters the mold hole of the back plate and at least partially fills the mold hole. Is provided with a friction material having a hardness lower than that of a portion on the surface of the back plate, and a shim that is adhered to the other surface of the back plate and closes the mold hole of the back plate.

Here, in the friction material integrally joined to one surface of the back plate, the difference between the hardness on the mold hole of the back plate and the hardness on the surface of the back plate is arbitrarily set. Can be set. The greater the difference in hardness, the better the squealing performance during braking. However, if the difference in hardness is too large, the hardness of the friction material as a whole becomes insufficient. Therefore, it is practically preferable that the difference in hardness of the friction material is about 5 to 30 in Rockwell hardness. However, this is not a limitation, and a hardness difference outside this range can be appropriately set.

The friction material having such a hardness difference is, for example, a fiber base material forming the friction material, a resin binder,
Also, it can be formed by making the specific composition or composition of the filler different so as to cause a hardness difference.
It can be easily formed by a usual thermoforming method. That is, when the preform of the friction material preliminarily preformed is thermoformed together with the back plate, a space is provided in the mold hole portion of the back plate, and pressure heating molding is performed in a state where no drag acts on the preform. is there. When the preform is compressed by thermoforming in this way, the portion corresponding to the mold hole of the back plate is not supported on the back plate surface, so the compressive stress is low, so it is rough (at low density). ) A friction material is formed and has a hardness lower than that of the friction material formed on the surface of the back plate. Then, in this case, the larger the space of the mold hole portion, the more the friction material having a lower hardness in the portion on the mold hole can be formed.

The fibrous base material, the resin binder, and the filler forming the friction material are the same as the conventional ones. That is, as the fiber substrate, aramid fibers, polyamide fibers, nylon fibers, rayon fibers, novoloid fibers, organic fibers such as triacetate fibers, potassium titanate fibers, rock wool, slag wool, alumina fibers, silicate fibers, carbon fibers, Inorganic fibers such as glass fibers, metal fibers such as Shinchu fibers, steel fibers, stainless steel fibers, and copper fibers can be mentioned, and these can be used alone or in combination of two or more kinds.

As the resin binder, phenol resin, melamine resin, epoxy resin, polyimide resin, polyester resin, or rubber such as SBR can be used. However, among these, the phenol resin or its modified product is the most commonly used one and is preferable.

Examples of the filler include body fillers such as barium sulfate and calcium carbonate, solid lubricants such as graphite, molybdenum disulfide and antimony trisulfide, metal powders such as cashew dust, copper powder, zinc powder and brass powder. Abrasive agents such as silica, or other additives for adjusting friction can be used.

In the disc brake pad of the present invention, as the shim, any plate-like material such as a metal plate made of stainless steel or a metal plate obtained by coating the metal plate with rubber or the like can be used as long as it can prevent water from permeating. Things can be used.

The adhesion of the shim to the back plate can be performed as a separate step, for example, after the pad is completed, but it is preferably performed at the time of thermoforming the friction material. In this case, the preform of the friction material and the back plate are set in the thermoforming die, and a shim coated with an adhesive such as a phenol resin in advance is laid on the back plate to thermoform the friction material. . As a result, the friction material is thermoformed and the friction material and the back plate are joined together, and the back plate and the shim are bonded together. In this way, by bonding the shim and the back plate during thermoforming, the disc brake pad can be manufactured without increasing the number of steps.

[0022]

In the present invention, the hardness of the portion of the friction material on the mold hole is lower than the hardness of the portion on the surface of the back plate. Therefore, the friction material has a difference in hardness and resonates with the vibration during braking. Since the structure is difficult, the squealing performance during braking is improved. Further, since the shim is adhered to the surface of the back plate on the side opposite to the side where the friction material is joined, the mold hole of the back plate is closed, so that water or the like is prevented from entering through the mold hole. The rust resistance of the joint surface of the back plate with the friction material is improved.

[0023]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view showing a disc brake pad according to an embodiment of the present invention.

In FIG. 1, 1 is a back plate made of a metal material such as steel, and 2 is a mold hole formed in the back plate 1. The number, size, arrangement, etc. of the mold holes 2 are arbitrary, and two holes are provided in this example. 3 is a friction material composed of a fiber base material formed by thermoforming, a resin binder, and a filler. This friction material 3
Is integrally joined to the surface on one side of the back plate 1, and a part thereof enters the mold hole 2 to at least partially fill the mold hole 2. The hardness of the portion 3a of the friction material 3 on the mold hole 2 is lower than that of the other portion, that is, the thickness direction portion 3b on the surface of the back plate 1. Therefore, the friction material 3 has a composite structure including the low hardness portion 3a and the high hardness portion 3b.

Thus, the squealing performance is improved because the friction material 3 is not homogeneous and has a difference in hardness, but the friction material in the portion 3a of the mold hole 2 has a low hardness and a low density. Therefore, water or the like enters the inside of the pad through the mold hole 2, and the joint surface between the back plate 1 and the friction material 3 easily rusts. Then, the shim 4 is adhered to the other surface of the back plate 1 to close the opening of the mold hole 2. This shim 4 has a shape substantially corresponding to the back plate 1, and here,
A stainless steel plate is used.

Since the shim 4 is adhered to the other surface of the back plate 1 as described above, water or the like is prevented from entering through the mold hole 2 and the rust resistance of the back plate 1 is improved. To do. Further, the shim contacts the piston of the brake caliper as in the conventional case, and reduces the occurrence of squeal.

<Manufacture of Disc Brake Pad> This disc brake pad can be easily manufactured by a usual thermoforming method.

FIG. 2 is a sectional view of the thermoforming die showing the manufacturing state of the disc brake pad of FIG.

In FIG. 2, the thermoforming die, generally designated by reference numeral 10, comprises an upper die 11, a middle die 12 and a lower die 13. In addition, the upper and lower arrangement of these molds may be reversed,
In that case, the upper mold 11 becomes the lower mold and the lower mold 13 becomes the upper mold.
The thermoforming die 10 is equipped with an appropriate heating device (not shown) so that the friction material can be pressure-formed under heating.

Then, in such a thermoforming mold 10,
A friction material preform 5 in which a raw material mixture of the friction material consisting of a fiber base material, a resin binder, and a filler is preformed in advance;
The back plate 1 on which the adhesive such as a phenol resin is applied in advance on the surface to be joined with the friction material is set. In this case, the shim 4 is also preliminarily coated with an adhesive agent and set on the back surface of the back plate 1 in an overlapping manner. This state is shown in FIG.

After the preform 5 of the friction material, the back plate 1 and the shim 4 are set in the thermoforming die 10 as described above, they are placed between the upper die 11 and the lower die 13 under heating. Pressurize.
As a result, the friction material is thermoformed, and the friction material and the back plate 1 and the back plate 1 and the shim 4 are bonded and adhered to each other.
Be integrated. Then, this thermoformed friction material is then subjected to post-heating treatment, surface finishing treatment, etc., and the disc brake pad of FIG. 1 is manufactured.

Here, the back plate 1 is provided on the preform 5 of the friction material.
The convex portion 6 that fits into the mold hole 2 of
The height of the convex portion 6 is smaller than the depth of the mold hole 2. Therefore, during thermoforming of the friction material, the preform 5 is compressed between the back plate 1 and the lower mold 13,
Since no drag acts on the preformed body 5 in the part of the mold hole 2, the part is extruded into the mold hole 2 to fill the mold hole 2. Therefore, in the portion of the mold hole 2, the pressing force acting on the preform 5 is smaller than that of the other portions, so that the friction material in this portion is relatively rough (low in density).
It is molded and has low hardness.

In this way, when the preform 5 of the friction material is thermoformed, a space for releasing the compressive stress is provided in the mold hole 2, so that the friction material 3 can be formed as shown in FIG.
The hardness of the portion 3a on the mold hole 2 can be formed lower than that of the thickness direction portion 3b on the surface of the back plate 1. Then, the hardness difference between the low hardness portion 3a and the high hardness portion 3b can be adjusted by changing the width or size of the space. That is, the preform 5 of the friction material
The hardness difference can be adjusted by changing the height or the like of the convex portion 6.

FIG. 3 is a sectional view showing various shapes of the preform 5 of the friction material.

The preform 5 of the friction material shown in FIG. 3 (a) is provided with a convex portion 6 at a portion corresponding to the mold hole 2 of the back plate 1, and the height of the convex portion 6 is changed. By
The hardness difference of the friction material can be adjusted. Therefore,
When the height of the convex portion 6 is the depth of the mold hole 2, the friction material 3 having substantially no hardness difference is formed.

The preform 5 of FIG. 3B corresponds to the preform 5 of FIG. 3A in which the height of the convex portion 6 is zero, and the surface thereof is flat. In the case of such a preformed body 5, there are advantages that the preforming die can be easily manufactured, and the workability is good because the positioning when setting in the thermoforming die is unnecessary.

The preform 5 shown in FIG. 3 (c) has a recess 7 formed in a portion of the back plate 1 corresponding to the mold hole 2.
By thus forming the portion corresponding to the mold hole 2 as the recessed portion 7, the hardness of this portion can be further lowered, and the difference in hardness can be maximized in the friction material.

In this way, by changing the height or depth of the preform 5 of the friction material of the portion corresponding to the mold hole 2 of the back plate 1, it is possible to form a friction material having an arbitrary hardness difference. it can. Then, the maximum hardness difference is obtained when the friction material 3 that has entered the mold hole 2 is not completely filled. By adjusting the composition of the friction material raw material, the hardness of the friction material after molding can be similarly changed. This composition can be adjusted, for example, by adjusting the compounding ratio of the resin binder, and when forming the preform 5 of the friction material, the compounding ratio of the resin binder is adjusted to the portion corresponding to the mold hole 2. By forming it with a small amount of material, the hardness of that portion can be lowered.

In this thermoforming, the shim 4 is adhered at the time of thermoforming the friction material.
The adhesion of the shim 4 to the back plate 1 can be performed as a separate step, for example, after the pad is completed. However, as shown in FIG. 2, it is preferable that the friction material is heat-formed at the same time as the number of steps is not increased. In addition, in this case, since the shim 4 may be displaced when the mold is opened, degassing at the time of heat formation is performed by a close contact degassing method in which the mold (upper mold 11) is not opened and only the depressurization is performed. It is preferable to carry out. Further, the application of the adhesive to the shim 4 can be performed by utilizing the conventional pretreatment line for the back plate, whereby the equipment cost can be minimized.

<Examples 1 and 2, Comparative Examples 1 to 6> With respect to the disc brake pads of the present example, in order to confirm the effects, the disc brake pads of Examples 1 and 2 (for PD51 type caliper). Was produced.

The friction material has the composition shown in Table 1 below.

[0043]

[Table 1]

Then, the raw material mixture of the friction material having the above composition was pressed at a pressure of 200 kg / cm ² for 2 minutes at room temperature to carry out preforming to form a preformed body 5. Then, as shown in FIG. 2, the preform 5, the back plate 1 to which an adhesive agent made of a phenol resin has been applied in advance, and the shim 4 made of a stainless steel plate to which an adhesive agent also made of a phenol resin has been applied in advance. And are set in the thermoforming die 10 and 40
Thermoforming was performed at a pressure of 0 kg / cm ² and a temperature of 160 ° C. for 10 minutes. Then, this was heat-treated at 250 ° C. for 120 minutes and then subjected to a surface finishing treatment or the like to produce a disc brake pad.

Here, the preform 5 used in the production of the disc brake pad of Example 1 is the convex portion 6 of FIG. 3 (a).
By this, the difference between the hardness of the portion (low hardness portion) 3a on the mold hole 2 and the hardness of the portion (high hardness portion) 3b on the surface of the back plate 1 in FIG. The Rockwell hardness was 10.

The preform 5 used for producing the disc brake pad of Example 2 has a flat surface shape as shown in FIG. 3 (b).
The above hardness difference was 20.

For comparison with Examples 1 and 2, discs of Comparative Examples 1 to 5 were different from each other in that the difference in hardness of friction materials was the same as that of Example except that the shim 4 was not adhered to the back plate 1. A brake pad was produced.

In the disc brake pad of Comparative Example 1, the difference in hardness between the low hardness portion 3a and the high hardness portion 3b of the friction material 3 is substantially zero.
The height of the convex portion 6 in (a) is substantially the same as the depth of the mold hole 2 of the back plate 1. In addition, Comparative Example 2
Then, the hardness difference is 5, and as the preform 5, the height of the convex portion 6 in FIG. 3A is smaller than the depth of the mold hole 2 of the back plate 1, but more than the case of the first embodiment. I used a big one. Furthermore, in Comparative Example 4, the difference in hardness was 15, and as the preform 5, a preform having a small height of the convex portion 6 in FIG. 3A was used. In Comparative Example 3, the same preform 5 as in Example 1 was used, and in Comparative Example 5, Example 2 was used.
The same preform 5 is used, and the hardness difference between them is 10 and 20, respectively, as in Example 1 and Example 2.

Further, as a comparative example 6, a disc brake pad in which the friction material was chamfered in order to improve the squealing performance was prepared. The pad of Comparative Example 6 is obtained by further chamfering the friction material end surface of the pad of Comparative Example 1.

Regarding the disc brake pads of Examples 1 and 2 and Comparative Examples 1 to 6, the presence or absence of shims 4 bonded to the back plate 1 and the portion of the friction material 3 on the mold hole 2 (low hardness portion). FIG. 4 collectively shows the hardness of 3a, the hardness difference (Rockwell hardness) of the portion (high hardness portion) 3b on the surface of the back plate 1, and the presence or absence of chamfering.

<Evaluation Test> For the disc brake pads of Examples 1 and 2 and Comparative Examples 1 to 6, squealing performance,
The rust resistance was tested and evaluated by the following method.

Regarding the squealing performance, a PD51-18V type caliper brake was used and the vehicle speed was 10 to 50 km /
The generation of squeaking (noise) during braking at h, liquid pressure of ² to 40 kg / cm ² , and 40 to 200 ° C. was examined and evaluated according to the following criteria. ○: Almost no squeaking occurred. Δ: Squeaking slightly occurred. X: Squealing frequently occurred.

As for rust prevention, the brake pad is 5%
After immersing in salt solution for 1 hour and then leaving it at room temperature for 23 hours, a rust test was conducted for 20 cycles, and after removing the friction material from the back metal, observing the occurrence of rust on the back metal, It evaluated according to the standard. ◯: No rust was generated. Δ: Slight rusting occurred. X: Rust occurred.

The results of this evaluation test are also shown in FIG.

<Test Results> As shown in the test results of FIG. 4, as shown in FIG. 1, shims 4 are adhered to the back surface of the back plate 1 to close the mold holes 2, and the mold holes of the friction material 3 are closed. The disc brake pads of Examples 1 and 2 in which a hardness difference was provided between the upper portion 3a and the back metal surface portion 3b showed good results in both squealing performance and rust prevention.

On the other hand, in the disc brake pads of Comparative Examples 1 to 5, the squealing performance was improved as the hardness difference of the friction material was increased. However, on the contrary, the antirust property is reduced. Particularly, in Comparative Examples 3 and 5, the difference in hardness of the friction materials is the same as in Examples 1 and 2, and the squealing performance is good, but the rust preventive property is poor.

From this test result, therefore, if the friction material is provided with a hardness difference in order to improve the squealing performance, the rust-preventing property is deteriorated. It can be seen that it can be effectively prevented by closing the mold hole. It is also understood that the difference in hardness of the friction materials is preferably 15 (Rockwell hardness) or more in order to obtain the best result in squealing performance.

Further, in comparison with Comparative Example 6 in which the friction material is chamfered, it is possible to provide a hardness difference in the friction material and to bond a shim to the back plate so that the friction material is not chamfered. It can be seen that squealing performance and anticorrosiveness equivalent to or higher than that can be obtained.

[0059]

As described above, the disc brake pad of the present invention comprises a metal back plate having a mold hole, a fiber base material, a resin binder, and a filler, and is provided on one side of the back plate. It is a friction material that is integrally joined to the surface and partly enters the mold hole of the back plate and at least partially fills the mold hole. A friction material having a hardness lower than that of a portion on the surface of the plate and a shim that is adhered to the other surface of the back plate and closes the mold hole of the back plate are provided.

Therefore, the friction material is formed of the low hardness portion on the mold hole and the high hardness portion on the surface of the back plate, and has a structure that does not easily resonate with vibration during braking. The squealing performance of time improves. Further, since the shim is adhered to the back plate and the mold hole is closed, it is possible to prevent water and the like from entering through the mold hole, and improve the rustproof property of the joint surface of the back plate with the friction material. Furthermore, since the friction material consisting of the low hardness portion and the high hardness portion can be easily formed by a method of ordinary thermoforming, for example, as compared with the case where chamfering is performed to improve the squealing performance,
It is possible to manufacture a disc brake pad that is low cost and has good squealing performance. Also, since the shim is bonded to the back plate, it is not necessary to provide a mounting portion for the back plate on the shim or an engaging portion for preventing the shim from shifting as in the conventional case, and the shim and the back plate have a simple shape. Can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view showing a disc brake pad according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a thermoforming die showing a state in which the disc brake pad of FIG. 1 is manufactured.

FIG. 3 is a cross-sectional view showing a preform of a friction material.

FIG. 4 is a table showing the configurations of disc brake pads of Examples of the present invention and Comparative Examples, and the results of evaluation tests.

[Explanation of symbols]

 1 Back Plate 2 Mold Hole 3 Friction Material 3a Low Hardness Part 3b High Hardness Part 4 Shim 5 Preform 6 Protrusion 7 Recess 10 Thermoforming Die 11 Upper Die 12 Medium Die 13 Lower Die

Claims (1)

[Claims] 1. A metal back plate having a molding hole, and a fiber base material, a resin binder, and a filler, which are integrally bonded to one surface of the back plate and A part of the friction material enters the mold hole of the back plate and at least partially fills the mold hole, and the hardness of the part of the back plate on the mold hole is the hardness of the part of the back plate on the surface. A disc brake pad comprising: a lower friction material; and a shim that is adhered to the other surface of the back plate and closes a mold hole of the back plate.