JP5519142B2 - Friction member and brake device - Google Patents

Description

The present invention relates to a friction member used in a brake device of an automobile, and more particularly to a friction member that suppresses occurrence of heat cracks in a cast iron counterpart material.
The present invention also relates to a brake device using the friction member, particularly a drum brake device.

  Conventionally, a drum brake device and a disc brake device are used as a brake device of an automobile, and a drum brake shoe and a disc brake pad in which a friction material is bonded to a metal base member are used as the friction member. Yes.

As the performance of the brake equipment, it is required that the braking effectiveness level is high, and as an improvement of the friction material to improve the braking effectiveness level,
(1) A large amount of metal particles is added to the friction material.
(2) A large amount of glass fiber is added to the friction material (for example, 10% by volume or more based on the entire friction material composition).
(3) An abrasive is added to the friction material, the average particle diameter of the abrasive (abstractive) is increased, and the addition amount is adjusted.
Such a method is known.

In order to further improve the effectiveness level of the brake, a friction material to which an abrasive having a Mohs hardness significantly higher than that of cast iron as a counterpart material is added is used.
The present applicant previously formed a non-asbestos-based friction material obtained by molding and curing a non-asbestos-based friction material composition mainly composed of a fiber base material, an inorganic filler, an organic filler, and a binder. In the present invention, an inorganic filler having a 90% particle size of 0.1 to 8 μm and a Mohs hardness of 6 to 8 is added as the inorganic filler in an amount of 0.1 to 10% by volume based on the entire friction material composition. A non-asbestos-based friction material was proposed (Patent Document 1).

  Further, in Patent Document 2, in a friction material composition containing a fiber substrate, a binder, an organic filler, and inorganic powder, an inorganic powder having a Mohs hardness of 5 or more and less than 7 is 7-30 with respect to the total weight of the friction material composition. It contains 0.5 to 4% by weight of inorganic powder having a weight percentage of 7 or more and a Mohs hardness of 7 or more based on the total weight of the friction material composition and 2 to 10% by weight of tin sulfide based on the total weight of the friction material composition. A friction material composition is disclosed.

  However, such a friction material to which a grinding material whose Mohs hardness is significantly larger than the counterpart cast iron can obtain sufficient braking effect, but the counterpart brake drum or disc rotor There was a problem that heat cracks occurred on the sliding surface.

The braking of the vehicle is performed by pressing the friction material against the rotating counterpart material. Due to the heat generated during braking, the sliding surface of the mating member becomes very hot, and the sliding surface is cooled by idling of the mating material during non-braking. Due to the repetition of thermal stress at this time, a crack occurs on the sliding surface of the counterpart material.
This crack is called a heat crack. The higher the heat generated during braking, the larger the heat crack.

If a heat crack occurs on the sliding surface of the counterpart material, the strength of the counterpart material is lowered, which is not preferable.
As a technique for suppressing heat cracks, first, attempts have been made to improve the materials of brake drums and disk rotors, which are counterpart materials.

  Patent Document 3 discloses a material for an automobile brake drum characterized in that the amount of magnesium added for spheroidizing graphite of cast iron is 0.025 to 0.032% by weight, and patent In Document 4, by weight ratio, C: 3.75 to 3.95%, Si: 1.8 to 2.2%, Mn: 0.5 to 0.8%, P: ≦ 0.1%, S: 0.08 to 0.15%, Mo: 0.2 to 0.7%, V: 0.2 to 0.6%, Cu: ≦ 1.5%, Cr: ≦ 0.1%, balance A disc brake rotor material is disclosed which is made of gray cast iron containing a chemical component which is substantially iron.

  As described above, studies on suppressing heat cracking have been made on the material of the counterpart material, but the actual situation is that no investigation has been made on the friction material side.

  As an improved technique for friction materials for the purpose of reducing brake squeal, Patent Document 5 discloses that hard inorganic particles harder than brake rotor materials such as magnesium oxide and metal particles such as copper powder are used as SBR. There is disclosed a friction material that is surrounded by an elastic material, mixed with a fiber base material, an inorganic filler, an organic filler, and a lubricant and heat-molded.

  This is because the magnesium oxide and copper powder on the surface of the friction material in contact with the disk rotor are retracted into the friction material by elastic deformation of the SBR when the friction material and the disk rotor are in sliding contact with each other. The contact points with the magnesium oxide and the copper powder increase, and the force applied to the individual magnesium oxide and the copper powder at the time of sliding contact is dispersed and reduced, so that the frictional vibration hardly occurs.

According to this technique, a sufficient anti-squealing effect is obtained by suppressing the occurrence of vibration itself.
However, since magnesium oxide and copper powder are surrounded by an elastic material, there is a problem that the original function of magnesium oxide and copper powder is hindered by the elastic material, and the document considers heat crack resistance. It is not a thing.

Japanese Patent Laid-Open No. 2000-309641 JP 2008-174705 A Japanese Patent Laid-Open No. 07-243460 JP 2005-82869 A Japanese Patent Application Laid-Open No. 07-317819

  In view of the above problems, the present invention provides a friction member made of a friction material capable of suppressing the occurrence of heat cracks in a cast iron counterpart material while ensuring sufficient braking effectiveness, and a brake device including the friction member. The purpose is to do.

The cause of the occurrence of heat cracks in the counterpart material is as described above, but it is considered that the following phenomenon occurs as the cause of the heat during braking particularly high.
(1) When the abrasive added to the friction material is larger than the Mohs hardness 4.5 of the cast iron, which is the counterpart material, the abrasive grinds the sliding surface of the cast iron counterpart material.
(2) The ground cast iron scraps adhere to the surface of the friction material.
(3) Cast iron scraps adhering to the friction material surface adhere to the sliding surface of the mating material again, and the location where the cast iron scraps adhere rises.
(4) Since the raised part slides locally, the part becomes hotter than the other part (smooth part where the cast iron scraps are not adhered).
(5) Further, an organic film is concentrated on the high temperature portion.
(6) Then, the organic film inhibits heat diffusion, makes it difficult to dissipate heat, promotes a temperature rise, and increases the temperature.

In particular, when an abrasive having a Mohs hardness of 6 or more is used, heat cracks are likely to occur. In addition, it is a phenomenon that is likely to occur in a drum brake device that has a structure that does not easily dissipate heat.
In the present invention, a method for ensuring a sufficient effect of a brake without adding an abrasive having a Mohs hardness significantly higher than that of cast iron, which causes the above problem, was examined.

  The present invention relates to a friction member mainly characterized by adding predetermined amounts of metal particles having a large malleability and calcined magnesium oxide having a predetermined diameter, and a brake device using the friction member. The present invention is based on the following technology. And

(1) A friction member used for a cast iron counterpart material,
One or more kinds of metal particles selected from aluminum, copper and brass are 1% by volume or more and 5% by volume or less,
The calcined magnesium oxide particles having an average particle diameter of 1 μm or more and 5 μm or less are 2 vol% or more and 7 vol% or less,
A friction member comprising: a friction material comprising:

(2) The friction member according to (1), wherein an average particle diameter of the metal particles is 150 μm or more and 250 μm or less.

(3) The friction member according to (1) or (2), wherein the metal particles are aluminum particles.

(4) A brake device comprising the friction member according to any one of (1) to (3).

(5) The brake device according to (4), wherein the brake device is a drum brake device.
The invention described in the claims relates to the above (3).

  According to the present invention, a friction member capable of ensuring sufficient effect and suppressing the occurrence of heat cracks and the friction member without using a grinding material whose Mohs hardness is significantly larger than cast iron is used. A brake device can be obtained.

  Referring to FIG. 1, the friction member 1 of the present invention is formed by molding a friction material composition mainly composed of a fiber base material, an inorganic filler, an organic filler, and a binder, and curing the binder. The friction material 2 is obtained by sticking to the metal base member 3. The friction member of the present invention is used as a drum brake shoe or a disc brake pad, and the brake device of the present invention uses such a friction member.

  In the present invention, calcined magnesium oxide particles having a malleability of metal particles having a large malleability of 1 to 5% by volume and an average particle diameter of 1 to 5 μm (Mohs hardness 5.5) in the friction material composition. 2 vol% or more and 7 vol% or less is added.

The metal particles having high malleability are one or more metal particles selected from aluminum, copper, and brass, and are added to obtain a sufficient effect.
By sliding between the friction material and the counterpart material, the metal particles in the friction material are transferred to the counterpart material. Since the malleability is great, the metal extends by sliding, and a metal film can be uniformly formed on the sliding surface of the counterpart material. A sufficient effect can be obtained by adhesion friction between the metal film and the metal particles contained in the friction material.

  An effect can be acquired by the addition amount of a metal particle being 1 volume% or more and 5 volume% or less. If it is less than 1% by volume, the formation of a metal film becomes insufficient, and sufficient effects cannot be obtained. On the other hand, if it exceeds 5% by volume, the thickness of the metal film becomes non-uniform and the coefficient of friction becomes unstable.

  The average particle diameter of the metal particles is preferably 150 μm or more and 250 μm or less. If the thickness is less than 150 μm, the formation of a metal film becomes insufficient, and a sufficient effect cannot be obtained. When it exceeds 250 μm, the thickness of the metal film becomes non-uniform, and in this case, the coefficient of friction becomes unstable.

The Mohs hardness of the metal particles having high malleability used in the present invention is not larger than the cast iron (Mohs hardness: 4.5) which is the counterpart material. The Mohs hardness of aluminum is 2.75, copper is 4.0, and brass is 4.0.
As the metal particles, it is preferable to use aluminum having higher malleability alone.

The calcined magnesium oxide particles are added to stably form a metal film.
The Mohs hardness of the calcined magnesium oxide particles is 5.5, which is slightly larger than the Mohs hardness of 4.5 of the counterpart cast iron. In the initial stage of braking, the calcined magnesium oxide grinds the sliding surface of the counterpart material, Appropriate irregularities can be formed on the sliding surface of the material. Since the metal particles bite into the uneven portions, the metal particles can be reliably transferred to the mating material sliding surface.

  The Mohs hardness of the fired magnesium oxide particles is slightly larger than the Mohs hardness 4.5 of cast iron, but not so much as to grind the cast iron so that the cast iron scraps do not adhere to the friction material side. Since cast iron scraps do not adhere to the friction material side, generation of heat cracks can be suppressed.

  The fired magnesium oxide particles also have the effect of suppressing the formed metal film from becoming too thick. When the metal film becomes too thick, the effect becomes unstable, but the fired magnesium oxide particles grind the metal film and keep it at an appropriate thickness, so the effect becomes stable.

  The effect of the calcined magnesium oxide particles can be obtained by setting the average particle diameter to 1 μm or more and 5 μm or less and the addition amount to 2% by volume or more and 7% by volume or less.

If the average particle diameter is less than 1 μm, sufficient unevenness cannot be formed on the sliding surface of the counterpart material at the initial stage of braking, so that the metal film cannot be stably formed. Further, the grinding effect is weak against the formed metal film, the thickness of the metal film becomes non-uniform, and the effect becomes unstable.
When the average particle diameter exceeds 5 μm, the metal film is excessively ground and sufficient effect cannot be obtained.

Further, if the addition amount is less than 2% by volume, sufficient unevenness cannot be formed on the sliding surface of the mating member in the initial stage of braking, so that the metal film cannot be stably formed. Further, the grinding effect is weak against the formed metal film, the thickness of the metal film becomes non-uniform, and the friction coefficient becomes unstable.
If the added amount exceeds 7% by volume, the metal film is excessively ground, so that a sufficient effect cannot be obtained.

  The friction material constituting the friction member of the present invention can include, in addition to the above metal particles and calcined magnesium oxide, a fiber base material, a binder, an organic filler, and an inorganic filler that are normally used for the friction material. .

  As a fiber base material, a well-known thing normally used for a friction material can be used, steel fibers, copper fibers, brass fibers, bronze fibers and other metal fibers, glass fibers, ceramic fibers, potassium titanate fibers, carbon Examples thereof include inorganic fibers such as fibers, rock wool, wollastonite, sepiolite, and artificial mineral fibers, and organic fibers such as aramid fibers, cellulose pulp, aramid pulp, and acrylic fibers. A combination of the above can be used. This fiber base material is used in the form of short fibers, and the addition amount thereof is preferably 5 to 60% by volume, more preferably 10 to 50% by volume with respect to the entire friction material composition.

  As the binder, known materials generally used for friction materials can be used. Thermosetting resins such as phenol resins and epoxy resins, and thermosetting resins modified with cashew oil, silicone oil, various elastomers, etc. Examples thereof include thermosetting resins in which resins, various elastomers, fluoropolymers and the like are dispersed, and these can be used alone or in combination of two or more. The amount of binder added is preferably 10 to 30% by volume, and preferably 12 to 25% by volume, based on the total amount of the friction material composition, in order to ensure sufficient mechanical strength and wear resistance of the friction material. Is more preferable.

  As the organic filler, known materials generally used for friction materials can be used, and examples include cashew dust, rubber dust (tire ground powder), various unvulcanized rubber particles, and various vulcanized rubber particles. These 1 type can be used individually or in combination of 2 or more types.

As the inorganic filler, in addition to calcined magnesium oxide and aluminum particles, copper particles, brass particles, known materials generally used for friction materials can be used. Vermiculite, mica, iron trioxide, barium sulfate, water Calcium oxide, light calcium carbonate, heavy calcium carbonate, flake graphite, earthy graphite, coke, molybdenum disulfide, tin sulfide, iron sulfide, tungsten sulfide, bismuth sulfide, zinc sulfide and other metal sulfides, iron particles, zinc Examples thereof include metal particles other than the above metal particles such as particles, and these can be used alone or in combination of two or more.
The addition amount of these organic fillers and inorganic fillers other than calcined magnesium oxide, aluminum particles, copper particles, and brass particles is preferably 40 to 70% by volume with respect to the total amount of the friction material composition, and 50 to 70%. It is more preferable to set it as volume%.

The friction member of this invention can be manufactured by the well-known method normally used for manufacture of a friction member. An example is shown below.
(1) Drum brake shoe as a friction member for a drum brake device A predetermined amount of a friction material composition is mixed uniformly using a mixer such as a Redige mixer or an Eirich mixer, and then the obtained raw material mixture is mixed. It puts into a preforming die and pressurizes it to form a preform.
Then, the preform is put into a thermoforming mold, and is molded by heating and pressing at a molding temperature of 130 to 180 ° C. and a molding pressure of 15 to 49 MPa for 3 to 10 minutes, and the obtained molded product is heated to a temperature of 140 to 250 ° C. For 2-12 hours. Thereafter, the friction surface is subjected to polishing treatment, cut or drilled as necessary, and the brake lining finished to the required dimensions is fixed to a metal shoe rim with an adhesive or rivet.
(2) A disc brake pad as a friction member for a disc brake device is uniformly mixed with a friction material composition containing a predetermined amount using a mixer such as a Redige mixer or an Eirich mixer, and the resulting raw material mixture is mixed. It puts into a preforming die and pressurizes it to form a preform.
Then, the metal back plate, which has been washed and rust-prevented in advance and coated with an adhesive, and the pre-formed product are put into a thermoforming mold, and the molding temperature is 130 to 180 ° C. and the molding pressure is 15 The resulting molded product is heat treated (post-cured) for 2 to 12 hours at a temperature of 140 to 250 ° C. Thereafter, the friction surface is subjected to polishing treatment, and coating, paint baking, scorch treatment, and the like are appropriately performed.

[Examples 1 to 14 and Comparative Examples 1 to 7]
Friction material compositions having the compositions shown in Tables 1 to 3 were blended, mixed uniformly for 10 minutes using a Redige mixer, and pre-molded by pressing at 10 MPa for 20 seconds in a pressure mold. The preform was heat-pressed for 6 minutes under the conditions of a molding temperature of 160 ° C. and a molding pressure of 40 MPa, then heat-treated (post-cured) for 5 hours at a temperature of 200 ° C., and subjected to a polishing treatment. 14. Brake linings for drum brakes of Comparative Examples 1-7 were prepared.
The evaluation was performed on the effectiveness level (efficacy, stability of effectiveness) and heat crack when the friction member was applied to the drum brake device and used for the front brake. The results are shown at the end of each table.
The evaluation method is as follows.

(1) Efficacy JASO C407-2000 (truck / bus brake device dynamometer test method) compliant classification: N3 (type 3 truck) front drum brake
Inertia: 2000kgm ²
Brake air pressure: 0.5 MPa
Second efficacy test Brake initial speed: 60 km / h
Above deceleration average value ◎: 6 or more (m / s ² )
○: 5.5 or more and less than 6 (m / s ² )
Δ: 5 or more and less than 5.5 (m / s ² )
X: Less than 5 (m / s ² )

(2) Stability of effectiveness JASO C407-2000 (Test method for truck / bus brake system dynamometer) Compliant category: N3 (Type 3 truck) front drum brake
Inertia: 2000kgm ²
Brake air pressure: 0.5 MPa
Second efficacy test Brake initial speed: 60 km / h, 100 km / h
The average value of deceleration at the initial braking speed of 100 km / h was divided by the average value of deceleration at the initial braking speed of 60 km / h. The closer the ratio is to 100, the better the stability of effectiveness.
◎: 95 or more ○: 90 or more and less than 95 △: 85 or more and less than 90 ×: less than 85

(3) Heat crack classification: N3 (type 3 truck) front drum brake inertia: 2000 kgm ²
Deceleration: 2 (m / s ² )
Initial braking speed: 120km / h
Temperature before braking: 100 ° C
Number of brakings: Measure the crack length of the sliding surface of the brake drum after 2000 tests ◎: Less than 10 mm ○: 10 mm or more and less than 20 mm Δ: 20 mm or more and less than 40 mm ×: 40 mm or more

  As shown in the evaluation of Tables 1 to 3, the drum brake device provided with the friction member of the present invention has an effect of suppressing the occurrence of heat cracks while being excellent in brake effectiveness and stability of effectiveness. .

  INDUSTRIAL APPLICABILITY The present invention can obtain a friction member having a high heat crack resistance while ensuring a sufficient effect level, and is extremely useful in practice as a brake device, particularly a drum brake device.

It is a figure which shows the outline of the friction member of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Friction member 2 ... Friction material 3 ... Metal base member (brake shoe)

Claims (4)

A friction member used for a cast iron counterpart material,
1% to 5% by volume of aluminum particles ;
The calcined magnesium oxide particles having an average particle diameter of 1 μm or more and 5 μm or less are 2 vol% or more and 7 vol% or less,
A friction member comprising: a friction material comprising: The friction member according to claim 1, wherein an average particle diameter of the aluminum particles is 150 μm or more and 250 μm or less. Brake device characterized by comprising a friction member according to claim 1 or 2. The brake device according to claim 3 , wherein the brake device is a drum brake device.