JP2005298852A - Rotating body for brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotating body for a brake comprising an aluminum alloy base the frictional sliding surface of which is coated with a ceramic thermal spray layer, in which the bonding strength between the aluminum alloy base surface and the directly sprayed-ceramic thermal spray layer is increased to prevent peeling and to improve durability. <P>SOLUTION: The rotating body for a brake comprising an aluminum alloy (including aluminum MMC) base 1 the frictional sliding surface of which is coated with a ceramic thermal spray layer 3 is produced by subjecting the sliding surface of the aluminum alloy base 1 to anodizing treatment to form an anodized aluminum layer 2, and forming the ceramic thermal spray layer 3 on the anodized aluminum layer 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a brake rotating body such as a brake disk and a brake drum, and more particularly to a lightweight rotating body for a brake made of an aluminum alloy (including aluminum MMC). Aluminum alloy brake rotating body with improved wear resistance by forming a layer, which can strengthen the bonding of the ceramic sprayed layer to the aluminum alloy substrate surface and improve its durability In particular, it is extremely effective when used for a brake rotating body such as an automobile, a motorcycle, a mounting bike, and a railway vehicle.

For rotating bodies for brakes such as disc brakes and brake drums, cast iron (FC) is generally used because various characteristics such as strength, wear resistance, and thermal conductivity are required.
On the other hand, since the rotating body for braking of a vehicle brake device such as an automobile is an unsprung part, and it rotates at high speed and accelerates and decelerates rapidly, in recent years it has been further controlled for weight reduction. Aluminum alloy brake discs have been put into practical use to improve the performance. One of them is aluminum MMC (aluminum composite), that is, ceramics (Al ₂ O ₃ , SiC, MgO, SiO ₂ , ZrO _{2 in} aluminum alloy). , WC, etc.) to improve wear resistance. However, although aluminum alloys such as aluminum MMC have high thermal conductivity, their melting point is relatively low (660 ° C.), so there is a problem in wear resistance under high brake load and high temperature, and therefore there is a problem in durability. .

  Also, in order to improve the durability of brake discs made of aluminum alloy, there are those in which the sliding surface is thermally sprayed with carbon steel, stainless steel, etc. with high wear resistance, and the sliding surface is covered with a wear resistant sprayed layer. In this case, in order to improve adhesion and bondability between the aluminum alloy base material and the coating layer and prevent the metal sprayed layer from peeling off, there is one in which a thermal spray intermediate layer mainly composed of nickel is interposed. (JP-A-7-224868). Since the coating layer is a wear-resistant metal sprayed layer such as carbon steel or stainless steel, its durability is not always sufficient.

In addition, to improve the durability of aluminum alloy brake discs, there are those whose sliding surfaces are coated with a ceramic sprayed layer, which is made of carbon steel, stainless steel, etc. because the coating layer is a ceramic sprayed layer. Abrasion resistance is superior to those coated with a wear resistant metal sprayed layer. However, aluminum MMC (thermal expansion coefficient: 17 × 10 ^{- 6} ℃) the ceramic thermal sprayed layer (coefficient of thermal expansion: 9 × 10 ^-6 ℃) because the difference in thermal expansion coefficient is large, because of the temperature difference between the two The ceramic sprayed layer peels from the surface of the aluminum MMC disk substrate. In order to make this temperature difference as small as possible, the ceramic sprayed layer is 0.2 to 0.5 mm. However, since the ceramic sprayed layer is thin, there is a problem in durability.

In order to strengthen the bonding of the ceramic sprayed layer to the surface of the aluminum alloy disk substrate and reduce its peelability, there is one formed by spraying an intermediate layer containing nickel as a main component (Japanese Patent Laid-Open No. 5-44753). (Hereinafter referred to as “prior art”). This enhances the bonding of the ceramic sprayed layer to the aluminum MMC substrate by interposing a nickel-based intermediate layer having excellent bonding properties to both the aluminum MMC and the ceramic sprayed layer. Since the temperature difference between the aluminum MMC base material and the ceramic sprayed layer due to the intermediate layer of the main component increases, the thermal expansion difference between them increases, and the stress applied to the interface increases. Can not be done, therefore, durability issues remain.
JP-A-7-224868 JP-A-5-44753

  This invention relates to a rotating body for brake in which a friction sliding surface of an aluminum alloy (including aluminum MMC) base material is coated with a ceramic sprayed layer, and bonding with the ceramic sprayed layer directly sprayed onto the surface of the aluminum alloy base material. An object of the present invention is to increase the strength and prevent the peeling while improving the durability.

  Means for solving the above-mentioned problem is that an alumite layer (anodized coating) is formed by anodizing the sliding surface of the aluminum alloy base material of the brake rotor, and a ceramic sprayed layer is formed on the anodized layer. It is formed.

[Action]
The alumite layer formed by alumite treatment on the sliding surface of the aluminum alloy base material is a part of the surface layer of the base material (an oxide layer grown from the base material layer), and the interfacial strength therebetween is extremely high. In addition, since the above-mentioned anodized layer is the same alumina as the ceramic sprayed layer, the weldability is high and the surface of the anodized layer is a micro uneven surface, so that the ceramic sprayed layer and the anodized layer are mechanically combined and firmly Furthermore, since the anodized layer and the ceramic sprayed layer are both alumina, the thermal expansion coefficient is almost the same. Therefore, since the bonding strength between the aluminum alloy substrate surface layer and the ceramic sprayed layer is strong and the stress applied to the interface is small, the ceramic sprayed layer does not peel from the alumite layer due to the difference in thermal expansion.
Therefore, even if a relatively thick ceramic sprayed layer is formed on the aluminum alloy substrate surface layer, it does not peel off from the aluminum alloy substrate, so the ceramic sprayed layer can be made thicker and the ceramic sprayed layer thickened. The durability is improved as much as possible.

As described above, an alumite layer formed by anodizing is formed on the brake surface of the aluminum alloy rotor base material of the brake rotor, and a ceramic sprayed layer is formed on the anodized layer. By making the interface between the material surface layer and the alumite layer, it is possible to avoid applying the above stress to the interface with the ceramic sprayed layer, thereby reliably preventing the ceramic sprayed layer from peeling off due to thermal stress. As a result, since the ceramic sprayed layer can be formed thick, the durability of the brake rotating body can be remarkably improved.
In addition, since the alumite treatment described above is performed at a low cost, the manufacturing cost of the brake rotating body is remarkably low as compared with the conventional technique in which a nickel-based thermal spray layer is used as an intermediate layer in order to prevent the ceramic thermal spray layer from peeling off. .

[Embodiment 1]
Embodiment 1 is that the thickness of the alumite layer by the alumite treatment in the above solution is 0.01 to 0.1 mm.
[Action]
When the thickness of the alumite layer is 0.01 mm or less in the alumite treatment, the above-mentioned effect due to the presence of the alumite layer is not remarkable, whereas when it is 0.1 mm or more, the alumite layer having relatively poor toughness is too thick. Since the alumite layer is destroyed by impact or the like, the bonding strength of the ceramic sprayed layer to the aluminum alloy substrate may be impaired as a result.

[Embodiment 2]
Embodiment 2 is that the thickness of the ceramic sprayed layer in the above solution is 0.6 to 1.0 mm.
[Action]
By setting the thickness of the ceramic sprayed layer to 0.6 or more, durability is higher than that according to the above prior art. On the other hand, when the thickness of the ceramic sprayed layer is 1.0 mm or more, the cost for forming the ceramic sprayed layer is remarkably high.

[Embodiment 3]
Embodiment 3 is that the aluminum alloy base material of the brake rotor in the above solution is made of aluminum MMC, and the ceramic volume content of the aluminum MMC is 15 to 50%.
[Action]
When the ceramic volume content in aluminum MMC is 15% or less, the coefficient of thermal expansion is as large as 20 × 10 ⁻⁶ ° C. or more, the difference in thermal expansion from the sprayed layer (9 × 10 ⁻⁶ ° C.) is large, and the bond strength is high. Low and peels off.
On the other hand, when the ceramic volume content exceeds 50%, the coefficient of thermal expansion decreases and approaches the thermal sprayed layer of 9 × 10 ⁻⁶ ° C., but the machinability is poor and causes an increase in cost.

  Since the present invention is most effective when applied to a brake device that operates under harsh conditions such as railway vehicles and automobiles, the present invention is applied to a first embodiment in which the present invention is applied to an automobile disc brake and an automobile drum brake. Example 2 will be described with reference to the drawings.

The brake disk base material 1 having an outer diameter of 275 mm in Example 1 is made of aluminum MMC, and the ceramic volume content of this aluminum MMC is 40%. An alumite layer 2 having a thickness (depth) of 0.03 mm is formed by anodizing the sliding surface of the brake disc with the brake pad. At this time, the thermal expansion coefficient of the brake disk substrate 1 is 17 × 10 ⁻⁶ ° C., and the thermal expansion coefficient of the alumite layer 2 is 7 to 9 × 10 ⁻⁶ ° C.
Then, alumina (Al ₂ O ₃ ) is sprayed on the alumite layer 2 to form an alumina sprayed layer 3 having a thickness of 0.8 mm.
Since the surface of the alumite layer 2 is a micro uneven surface, the ceramic sprayed layer 3 and the alumite layer 2 are mechanically coupled and integrated to be firmly bonded. Furthermore, since the thermal expansion coefficient of the alumina sprayed layer 3 is 9 to 10 × 10 ⁻⁶ ° C. and is almost the same as the thermal expansion coefficient of the anodized layer 2, the stress due to the difference in thermal expansion at the bonding surface (interface) between the two. Is extremely small.
Although the thermal expansion difference between the brake disk base material 1 and the anodized layer 2 is large, the anodized layer 2 is an oxide layer grown from the base material, and therefore the interface strength of these interfaces 4 is extremely strong. 4 is not destroyed due to the difference in thermal expansion.

The brake drum base material 21 having an inner diameter of 228.6 mm in Example 2 is made of aluminum MMC and has a ceramic volume content of 40%. The brake surface of the brake drum is anodized to form an alumite layer 22 having a thickness (depth) of 0.05 mm. The thermal expansion coefficient of the brake drum base material 21 at this time is 17 × 10 ⁻⁶ ° C., and the thermal expansion coefficient of the alumite layer 22 is 7 to 9 × 10 ⁻⁶ ° C.
Then, alumina (Al ₂ O ₃ ) is sprayed on the alumite layer 22 to form an alumina sprayed layer 23 having a thickness of 0.6 mm.
Although the difference in thermal expansion between the brake drum base material 21 and the alumite layer 22 is large, as described above, the interface strength of these interfaces 24 is extremely strong, so that the interface 24 is destroyed due to the difference in thermal expansion. Absent.

[Modification]
FIG. 3 shows a modification of the second embodiment. The brake drum base 31 is made of an aluminum alloy, and a cylindrical body 30 made of aluminum MMC (ceramics volume content 40%) having a thickness of 5 mm is fitted thereto. Yes. The inner surface of the cylindrical body is preliminarily anodized to form an alumite layer 32 having a thickness (depth) of 0.05 mm, and alumina (Al ₂ O ₃ ) is sprayed on the inner surface of the anodized layer 32 to obtain a thickness. An alumina sprayed layer 33 having a thickness of 0.6 mm is formed.

〔Effect confirmation〕
The results of the durability comparison test between Example 1 and the prior art will be described.
In the comparative prior art, the nickel-based intermediate layer has a thickness of 0.2 mm and the alumina sprayed layer has a thickness of 0.3 mm.
The test conditions were a deceleration of 5.88 m / s ² (0.6 G), a speed of 100 km / h → 0 km / h, cooling after braking, and repeated braking at a braking start temperature of 100 ° C. The number of braking is 50 times.

Test results According to the prior art A minute crack was generated on the rotor sliding surface, and the friction coefficient was reduced to 0.2 μm.
Maximum braking surface temperature of 590 ° C.
Example 1: The rotor sliding surface was not significantly damaged and the friction coefficient was 0.25 μm.
Maximum braking surface temperature of 610 ° C.

(A) is sectional drawing of Example 1, (b) is the A section enlarged view of (b). (A) is sectional drawing of Example 2, (b) is the B section enlarged view of (a). (A) is sectional drawing of the modification of Example 2, (b) is the C section enlarged view of (b).

Explanation of symbols

1 ... Brake disc base material 2, 22, 32 ... Anodized layer (anodized coating)
3, 23, 33 ... Alumina sprayed layer 21 ... Brake drum base material 30 ... Cylindrical body

Claims (5)

In a brake rotating body in which a friction sliding surface of an aluminum alloy (including aluminum MMC) base material is coated with a ceramic sprayed layer,
A brake rotating body in which the sliding surface of the aluminum alloy base material is anodized to form an anodized layer, and the ceramic sprayed layer is formed on the anodized layer.   The brake rotating body according to claim 1, wherein a thickness of the alumite layer by the alumite treatment is 0.01 to 0.1 mm.   The brake rotating body according to claim 1, wherein the ceramic sprayed layer has a thickness of 0.6 to 1.0 mm.   The brake rotating body according to claim 1, wherein the ceramic is alumina.   5. The brake rotor according to claim 1, wherein an aluminum alloy base material of the brake rotor is made of aluminum MMC, and the ceramic volume content of the aluminum MMC is 15 to 50%.

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