JP2844970B2 - Sliding member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member having a sliding surface made of a sprayed material. This sliding member can be applied to, for example, a brake rotor that slides on a brake pad.

[0002]

2. Description of the Related Art Conventionally, as a sliding member, a base material is formed of an aluminum-based alloy or a magnesium-based alloy for the purpose of weight reduction, and an iron-based metal or a copper-based material is used for ensuring the wear resistance of the sliding surface. There is known a metal in which a coating layer is formed by means such as thermal spraying. (JP-A-62-70534, JP-A-6-70534)
0-89558, JP-B-53-30865, JP-B-53-30866, and JP-A-55-15.
8337, JP-A-49-61564, JP-A-49-90641, JP-A-59-56438, and the like.

Further, Japanese Patent Application Laid-Open No. 61-218841 discloses a disk type brake rotor coated with a nickel plating layer in which fine ceramic particles of 0.1 μm or more are dispersed.

[0004]

In the above-mentioned brake rotor disclosed in Japanese Patent Application Laid-Open No. 61-218841, the fine ceramic particles are dispersed, so that the initial compatibility with the mating material is improved. Shave the surface of a semi-metallic pad. The effect of scraping by the fine ceramic particles continues not only at the beginning of use but also over a long period of use, so that there is a problem that the slidability is rather deteriorated.

[0005] By the way, in a brake rotor, generally,
When the vehicle travel distance exceeds a predetermined distance, the friction (reduction in roughness) of the pad is a hit and the friction coefficient becomes the original friction coefficient, and the friction coefficient is stabilized. However, in the initial stage (when the rotor is new), that is, when the vehicle travel distance does not exceed a predetermined distance, for example, about 1000 km, the initial surface roughness of the mating brake pad is 100 μm.
Since the contact area between the pad and the rotor is small, the friction coefficient at the initial stage when the brake pad and the disk rotor slide is about 0.1 smaller than the original friction coefficient between the two. There is.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sliding member capable of obtaining a required coefficient of friction from an early stage.

[0007]

Means for Solving the Problems The inventor of the present invention has conducted intensive studies on the sliding member, laminated a base sliding layer having a required friction characteristic on the surface of the base material of the sliding member, and dispersed the hard particles. And a shear adhesion strength of 0.3 to 8 kgf / cm
If stacked eliminable sprayed layer to the underlying sliding layer to ^two and to base the sliding layer, by the hard particles cut the mating member in the initial, the required friction coefficient early increases the coefficient of friction It can be obtained from the beginning, and after that, if the sprayed layer separates from the underlying sliding layer, so that the underlying sliding layer with the required frictional properties slides with the mating material, stable from the beginning. It was found that the obtained friction coefficient was obtained. The present invention has been made based on this finding. The plating layer disclosed in Japanese Patent Application Laid-Open No. 61-218841 has a high adhesion strength to the base material and does not separate from the base material.

The sliding member of the present invention comprises a base material, a base sliding layer having required friction characteristics laminated on the base material surface, a sprayed material laminated on the base sliding layer by thermal spraying, and a sprayed material. With hard particles dispersed in the material and having a shear adhesion strength of 0.3 to 8 k
gf / cm ² and a sprayed layer that can be detached from the underlying sliding layer. The base material of the sliding member can be appropriately selected, and iron, steel, stainless steel, magnesium alloy, titanium alloy, aluminum alloy, and the like can be used. As the aluminum alloy system, for example, an aluminum-silicon system can be adopted. The base sliding layer has a required frictional property laminated on the surface of the base material. The thickness of the base sliding layer varies depending on the type of the sliding member.
It can be 500 μm. The material constituting the base sliding layer is, for example, iron-chromium-carbon, iron-chromium-carbon-copper, tungsten, molybdenum, nickel, nickel-chromium, nickel-chromium-aluminum, or the like. Can be adopted. The base sliding layer can be formed by a thermal spray layer, a plating layer, a permeation plating layer, or the like. At the time of thermal spraying, it is desirable to perform a pretreatment such as a degreasing treatment and a blasting treatment on the surface of the base material, and it is also possible to perform a post treatment such as a grinding wheel grinding and a honing process.

The thermal sprayed layer laminated on the base sliding layer by the thermal spraying process slides with the mating material at the initial stage. The thickness of the sprayed layer depends on the type of the sliding member.
m. The thermal spray layer is formed of a thermal spray material constituting a matrix and hard particles dispersed in the thermal spray material. The thermal spray layer can be formed by thermal spraying a thermal spray powder in which hard particles are dispersed with a thermal spray gun. In this case, when the hard particles themselves are partially or wholly melted or softened by the thermal spraying heat, the particles may collide with the underlying sliding layer during thermal spraying. It also has the effect of deforming the shape. As the thermal spray material, for example, an iron-chromium-carbon system, an iron-chromium-carbon-copper system, a tungsten system, a molybdenum system, a nickel system, a nickel-chromium system, and a nickel-chromium-aluminum system can be adopted. Although depending on the type of the sliding member, the porosity of the thermal sprayed layer obtained by spraying the base sliding layer can be, for example, about 10 to 30%. Hard particles are zirconia particles (ZrO ₂ ), alumina particles, magnesia particles, primary silicon particles, Fe ₂ O
_Three particles can be adopted. The average particle size of the hard particles depends on the type of the sliding member, the thickness of the sprayed layer, the required abrasive action, and the like, but can be, for example, 3 to 40 μm, particularly 5 to 30 μm.

When the thermal spray layer slides to some extent with the mating material, it separates from the underlying sliding layer. Shear adhesion strength between the sprayed layer and the underlying sliding layer varies depending on the kind of the sliding members but, 0. 3
８8 kgf / mm ² , especially 0.5 to ² kgf / mm ²
f / mm ² . Adjustment of shear adhesion strength includes changing spraying conditions such as current value, voltage value, gas flow rate, spraying distance, changing the type of sprayed powder, changing the thickness of the sprayed layer, changing the porosity of the sprayed layer, This can be performed by changing the shape or by interposing a desorption promoting layer between the sprayed layer and the underlying sliding layer. The desorption promoting layer can be formed of a solid lubricant or the like.

In the sliding member of the present invention, an intermediate layer may be interposed between the base material and the base sliding layer in order to secure the adhesion strength between the base material and the base sliding layer. The intermediate layer can be formed, for example, by spraying a thermal spray powder of a nickel-based alloy, in particular, a nickel-chromium alloy 94% by weight and aluminum 6% by weight. Alternatively, it can be formed by spraying a thermal spray powder of 95.5% nickel and 4.5% aluminum. The thickness of the intermediate layer can be, for example, about 50 to 100 μm.

As the mating material, for example, an organic friction material can be used. Organic friction materials include binders such as phenolic resins, metals, aramids, base materials such as inorganic fibers,
A configuration including a friction modifier such as cache dust, rubber, and calcium carbonate can be employed.

[0013]

In the sliding member of the present invention, the sprayed layer initially slides with the counterpart material. At this time, since the hard particles cut the mating material, a required coefficient of friction is secured. Then, after sliding to some extent, that is, after the initial stage, particularly the hard particles of the sprayed layer are detached from the sprayed layer. In the sliding member of the present invention,
Defines the lower and upper limits of the shear adhesion strength of the sprayed layer
As a result, the sprayed layer containing hard particles adheres excessively to the underlying sliding layer.
Not be removed properly as frictional sliding progresses
You. Therefore, the base sliding layer slides on the mating material.

[0014]

Embodiment 1 First, Embodiment 1 will be described. That is, Al-1
A 2% Si alloy was cast in a cavity of a molding die to produce a disk rotor 1 having a ring-shaped sliding surface 2 shown in FIG. The disk rotor 1 has a diameter of 300 mm and a disk thickness of 2
0 mm. Then, using a first mixed powder obtained by mixing 50% by weight of Fe-Cr-C alloy powder and 50% by weight of Cu powder, the spraying gun is opposed to the sliding surface 2 of the disk rotor 1, and the disk is formed by plasma spraying. Sliding surface 2 of rotor 1
A base sliding layer 3 was formed on the substrate. In this case, Fe-Cr-C
The alloy powder has a composition of Cr 55-65 wt%, C 3-
4 wt%, the balance being substantially Fe, with a particle size of 10 to 74
μm was used. The Cu powder used had a purity of 95% and a particle size of 10 to 74 μm. In this case, a METCO 7 MB type spraying apparatus was used, and the current was 450 A and the voltage was 65
V, the amount of gas Ar gas 40 l / min, H ₂ gas 7.5 l / min, under conditions of spraying distance 130 mm, was laminated to a thickness 300 [mu] m.

Then, using a second mixed powder obtained by mixing 50% by weight of the ZrO ₂ powder and 50% of the first mixed powder by weight, using the same thermal spraying apparatus, a current of 380 A, a voltage of 60 V,
Under the conditions of a gas amount of Ar gas 40 L / min, H ₂ gas 5 L / min, and a spraying distance of 130 mm, a thickness of 20 L
An abrasive layer 4 as a thermal spray layer was laminated to a thickness of μm, thereby forming a sliding layer 5. FIG. 1 schematically shows a cross section of the sliding layer 5. As shown in FIG. 3, an abrasive layer 4 in which ZrO ₂ particles 4c and pores 4d are mixed is laminated on the base sliding layer 3. ZrO ₂ powder has a particle size of 1
Those having a size of about 5 to 25 μm were used. The reason why the spraying conditions for spraying the abrasive layer 4 are set to the low current and low H ₂ gas amount side is that the abrasive layer 4 is made more porous and the unmelted portion of the ZrO ₂ particles 4c is secured. That's why. The thickness of the sprayed abrasive layer 4 was measured by a film thickness gauge.

Thereafter, the surface of the abrasive layer 4 is ground by a grinding wheel using a grinding wheel (diamond), whereby the total thickness of the base sliding layer 3 and the abrasive layer 4 is reduced to 30.
The thickness was set to 5 μm. At this time, the thickness of the abrasive layer 4 is about 5 μm. Further, the rotor of Comparative Example 1 was also formed. That is, the same type of Al-Si rotor as in Example 1
Using a first mixed powder in which the same Fe-Cr-C alloy powder and Cu powder as in Example 1 were mixed, the first mixed powder was sprayed on a rotor under the same conditions as in Example 1 to form a 320 μm-thick powder. A sliding layer was formed, and then the surface of the sliding layer was ground by grinding to a thickness of 305 μm. In Comparative Example 1, the abrasive layer 4 in which ZrO ₂ particles were dispersed was not formed.

The rotor of Example 1 and the rotor of Comparative Example 1 were used and mounted on both front sides of a vehicle of the same type.
The pad which is a sliding partner material does not contain steel, and its material composition is (by volume ratio, aramid fiber 10).
%, Glass fiber 5%, calcium silicate 10%, phenol resin 15%, cashew dust 20%, graphite 5%, barium sulfate 20%, and other fillers 15%). The initial surface roughness of the pad surface is 300 μm RZ. Then, the vehicle was driven at a constant speed of 50 km on the test course, the vehicle was stopped by applying a brake (a braking deceleration of 0.3 G) every 200 km, and the vehicle was repeatedly driven up to a running distance of 1600 km. In this test, mileage 2
Remove the rotor and pad every 00km, JASO C
According to 406-82 (passenger car brake device dynamometer test method), the average friction coefficient at the time of initial contact check (initial braking speed 50 km / hr, braking deceleration 0.3 G, braking interval 120 seconds, number of braking 10 times) is measured. did. This result is shown by the characteristic line in FIG. According to the test results shown in FIG. 4, in Comparative Example 1, the friction coefficient μ does not recover to the original value (μ = approximately 0.4) unless the vehicle travels over 1000 km. On the other hand, in the first embodiment, the friction coefficient sharply increases up to the traveling distance of 200 km, and at a traveling distance of 400 km, the friction coefficient μ approaches 0.4 and recovers. In this test, the state of the pad surface was observed every 200 km of travel distance. As a result, in Comparative Example 1, the initial surface roughness was 300
The pad surface having a μmRZ becomes 5 μmRZ to 10 μmRZ at a running distance of 1000 km or more, whereas the surface roughness becomes as large at a running distance of 200 km and 400 km in the first embodiment. This is presumed to be an effect that the pad surface is smoothed by the ZrO ₂ particles 4c because the abrasive layer 4 in which the ZrO ₂ particles 4c are dispersed is present on the surface of the rotor 1.

In Example 2, instead of ZrO ₂ particles, alumina particles (Al ₂ O ₃ ) and magnesia particles (M
gO) and a rotor in which the abrasive layer 4 in which Fe ₂ O ₃ particles are dispersed was laminated on the underlying sliding layer 3. Then, as in the case of the first embodiment, the vehicle is mounted on both front sides of a vehicle of the same model, the vehicle travels at a constant speed of 50 km on a test course, and the vehicle is stopped by applying a brake every 200 km. Remove the rotor and pad, JASO C
The average coefficient of friction was measured according to 406-82. Also in the second embodiment, the friction coefficient μ is the same as in the first embodiment.
At an early stage.

In Example 3, an abradable layer 4 having ZrO ₂ particles was used as the underlying sliding layer 3 by using an Fe—Cr—C—Cu alloy powder and a ZrO ₂ powder having compositions other than those of Example 1. A laminated rotor was formed. Then, as in the case of the first embodiment, a built-in test was performed on a vehicle, and as in the case of the first embodiment, the effect of quickly recovering the friction coefficient μ was exhibited. Further, a rotor in which the abrasive layer 4 was laminated on the underlying sliding layer 3 was formed using a mixed powder obtained by mixing Cu powder and ZrO ₂ powder. Then, a test was conducted in the same manner as in Example 1, and as a result, the effect of recovering the friction coefficient μ at an early stage was exhibited, as in Example 1.

Test Example 1 The rotors A to I were formed in the same manner as in Example 1 except that the ratio of the ZrO ₂ powder was changed as shown in Table 1. Then, as in the case of Example 1, the vehicle was mounted on both front sides of the vehicle, the vehicle was run on a test course, and the average friction coefficient was measured every 200 km according to JASOC 406-82. As a result,
In the rotors A and B containing a small amount of ZrO ₂ particles, the effect of restoring the friction coefficient μ was not obtained at all even at a running distance of about 1000 km. On the other hand, in rotors C to H in which a large amount of ZrO ₂ particles were dispersed, characteristic lines similar to those in Example 1 were obtained, and the effect of quickly recovering the friction coefficient μ was obtained. The rotor I was stopped because the adhesiveness of the abrasive layer 4 was poor and was not worthy of evaluation. From this result, it was found that the mixing ratio of the ZrO ₂ powder in the abrasive layer 4 was optimal at 30 to 80 vol%.

[0021]

[Table 1] <Test Example 2> The same as Example 1 except that the center value of the particle size distribution of ZrO ₂ powder (the value occupied by 50% or more of the median of the normal distribution) in Example 1 was changed as shown in Table 2. The rotors J to O were formed by a suitable method. Then, a similar test was performed.

As a result, in the rotor J having a central particle size of 3 μm, since the ZrO ₂ particles are small and there is almost no abrasive action, the effect of recovering the friction coefficient μ is 10 km.
It was hardly obtained at around 00 km. In the case of the rotor O having a grain size center value of 40 μm, the friction coefficient μ increased to near 0.35 in the initial stage, that is, at a running distance of about 200 km. However, it subsequently decreased to around 0.3. As a result of observation of the pad surface, at 200 km, the surface roughness of the pad surface is reduced and smoothed, and the contact area temporarily increases,
Then, it is considered that the ZrO ₂ particles having a large particle diameter increased the sliding scratches of the pad and the rotor, and rather reduced the contact area between the pad and the rotor. On the other hand, in the rotors K to N having the median particle size of 5 to 30 μm, as in the case of Example 1, a good initial friction coefficient recovery effect was exhibited. As a result, it was found that the center value of the particle size distribution of the ZrO ₂ powder is preferably 5 to 30 μm.

[0023]

[Table 2] <Test Example 3> The rotor P was manufactured in the same manner as in Example 1 except that only the thickness of the abrasive layer 4 in which ZrO ₂ particles were dispersed was changed as shown in Table 3 by grinding. ~ U was formed. Then, a similar test was performed.
As a result, in the rotor P having a thickness of 1 μm, as shown by the characteristic line in FIG. 4, the friction coefficient at 200 km has an effect of being recovered, but since the abrasive layer 4 is thin, the abrasive layer 4 disappears early. Thereafter, the effect of recovering the coefficient of friction was moderate. It is presumed that this is because the abrasive layer 4 is thin and the abrasive function is insufficient.

On the other hand, in the rotor U having a thickness of 15 μm, 1
Up to 000 km, the same effect as in Example 1 is exhibited, but thereafter, the friction coefficient μ tends to slightly decrease. In this case, as a result of surface observation and surface roughness measurement, at 1000 km, the pad roughness temporarily becomes 5 to 10 μm RZ, but when the traveling distance increases further, the pad roughness increases to 20 μm RZ or more. Slightly lower. This shows a better coefficient of friction recovery with the abrasive layer 4, but then
Due to the further abrasion of the remaining abrasive layer 4 and the pad,
It is assumed that the surface roughness of the pad increases. on the other hand,
With the rotors Q to T having a thickness of 2 to 10 μm, a good friction coefficient recovery effect as in Example 1 was obtained. In addition, it was found that the abrasive layer 4 was almost detached and disappeared around 1000 km where the friction coefficient μ was recovered. Than this,
The opposite effect is obtained even if the abrasive layer 4 is too thick, and it is found that the thickness of the abrasive layer is preferably about 2 to 10 μm.

[0025]

[Table 3] <Test Example 4> After the base sliding layer 3 was laminated in the same manner as in Example 1, spraying was performed by changing the spraying conditions as shown in Table 4, and the abrasive layer 4 and the base sliding layer 3 were sprayed. The rotors V to Z and the rotor & were formed in which the shear adhesion strength was changed. Then, the same test as in the case of Example 1 was performed. This result is shown by the characteristic line in FIG. Here, rotors W to Z having a shear adhesion strength of 0.5 to 2.0 kgf / mm ²
In FIG. 5, as shown in FIG. 5, the tendency of the friction coefficient was exactly the same as in Example 1, and the effect of recovering the friction coefficient in the initial stage was obtained. On the other hand, in the rotor V having a small shear adhesion strength, the abrasive layer 4 was detached in the initial stage, and there was no friction coefficient recovery effect, and the tendency was almost the same as that of Comparative Example 1 shown in FIG.

The shear adhesion strength is 2.5 kgf / m
With the rotor & of m ² , the friction coefficient μ temporarily increases in the initial period up to the travel distance of 100 km, but there is no effect of restoring the friction coefficient even if the travel distance increases, and the friction coefficient is lower than that of Comparative Example 1. showed that. This is because, as a result of surface observation, the adhesive strength of the abradable layer 4 is too large, and the abradable layer 4 does not fall off. It is assumed that the friction coefficient μ did not increase due to the introduction of wear powder. From the above, it can be seen that in the abrasive layer 4 in which the ZrO ₂ particles 4c are dispersed, the shear adhesion strength of the abrasive layer 4 is preferably 0.5 to 2.0 kgf / mm ² .

[0027]

[Table 4]

As described above, according to the sliding member of the present invention, initially, the sprayed layer in which the hard particles having the abrasive action are dispersed slides with the mating material, so that the hard particles are hardened by the mating material. , Which increases the coefficient of friction and recovers. Further, according to the sliding member of the present invention, after sliding to some extent, the thermal spray layer, in particular, the hard particles of the thermal spray layer are detached, and the underlying sliding layer having required friction characteristics slides with the mating material. Required friction coefficient can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part.

FIG. 2 is a front view of a brake rotor.

FIG. 3 is a sectional view of a brake rotor.

FIG. 4 is a graph showing a relationship between a friction coefficient and a traveling distance.

FIG. 5 is a graph showing a relationship between a friction coefficient and a traveling distance.

[Explanation of symbols]

In the figure, 1 is a rotor, 2 is a sliding surface, 3 is a base sliding layer, 4 is an abrasive layer, 4c is ZrO ₂ particles, and 4d is a pore.

Claims (1)

(57) [Claims] 1. A base material, a base sliding layer having required frictional properties laminated on the base material surface, a sprayed material laminated on the base sliding layer by thermal spraying, and dispersed in the sprayed material. and the hard particles have and shear adhesion strength in 0.3~8kgf / cm ²
A sliding member comprising a sprayed layer defined and detachable from the underlying sliding layer.