JPH11303912A - Friction member for wet clutch and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction member for a wet clutch, having superior μ-v characteristics and a judder-resistance, and a manufacturing method therefor. SOLUTION: This friction member for a wet clutch has an uneven friction surface whose projecting part has a roughness of 0.1 to 2.0 μm Ra, and can be manufactured by sliding a metal (metallic) friction member in a non-aqueous solution blended with a metal cleaning agent having a perbasic group. This friction member has minute surface roughness on which the presence or absence of the generation of a judder depends, thereby forming the friction member for a wet clutch with a superior judder-resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a friction member for a wet clutch used for a wet clutch in an automatic transmission.

[0002]

2. Description of the Related Art Automatic transmissions use wet clutches as lock-up clutches and shift clutches. In such a wet clutch, it is important to prevent the occurrence of judder, a shift, and a shock at the time of engagement. As a method of preventing the occurrence of judder, shifting, and shock at the time of engagement, it is effective to increase the positive gradient of the μ (friction coefficient) -v (slip speed) characteristic in the wet clutch.

As a method for improving the μ-v characteristic of a wet clutch, there is a method using an ATF (Automatic Transmission Fluid) and a wet clutch sliding member that provide good μ-v characteristics. Japanese Patent Application Laid-Open No. 63-66299 discloses an ATF in which a reaction product of a fatty acid and a dialkanolamine, a fatty acid,
F is disclosed to be contained.

[0004] Further, for a sliding member, a friction modifier is previously adsorbed to the surface of a friction material.
No. 253122. In these disclosed technologies, the μ-v characteristics are improved by a technique of lowering the solid friction coefficient by an adsorption film of a friction modifier and lowering μ in a low slip velocity region. However, in the wet clutch, further improvement of the μ-v characteristic is desired in order to allow the slip control region of the lock-up clutch to be expanded. Further, as the capacity of the wet clutch increases, judder is likely to occur, and it is expected that existing ATFs and friction members will have insufficient anti-judder properties. Here, in the technique of improving the μ-v characteristic only by reducing the solid friction coefficient as in the related art, there is a limit, and therefore, a sufficient μ-v characteristic corresponding to the high capacity of the wet clutch cannot be obtained.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a friction member for a wet clutch having excellent μ-v characteristics and judder resistance, and a method of manufacturing the same. And

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present inventors have improved the μ-v characteristics and realized excellent judder resistance by suppressing the decrease in μ in a high slip velocity region. Was found. That is, μ in the wet clutch is determined by the sum of the solid friction at the true contact portion and the fluid friction due to the oil film. Generally, the ratio of solid friction decreases because the oil film becomes thicker as the sliding speed increases. Fluid friction is extremely small compared to solid friction, and μ
Is reduced. Such a phenomenon causes the μ-v characteristic to have a negative gradient, thereby facilitating the occurrence of judder.

[0007] Therefore, as a technique for improving the judder resistance, a reduction in the ratio of solid friction in a high sliding speed range can be mentioned. As a concrete method of this,
Increasing the surface roughness can be mentioned. Here, the surface roughness generally handled is formed by irregularities having a width of several tens to several hundreds μm and a height of the order of several μm formed by processing or abrasion. FIG. 1 shows the relationship between the surface roughness obtained by a stylus roughness meter, which is a general method for measuring surface roughness, and the occurrence and non-occurrence of judder. FIG. 1 shows the surface roughness of the front cover after performing a judder durability test with an actual machine using ATFs containing different amounts of overbased Ca sulfonate. ATF contains overbased C of Ca (100).
a The amount of sulfonate was 100%,
5%, 50%, 25%, and 0% were used. FIG.
As can be seen from the table, there was no correlation between the surface roughness obtained by the stylus type roughness meter and the presence or absence of judder.

The surface roughness (hereinafter referred to as surface roughness) obtained by a stylus roughness meter is several tens to several hundreds of μm in width and several μm in height.
m. Regarding the irregularities, it is considered that the convex surface is an actual contact surface. Therefore, using an electron beam type three-dimensional roughness measuring device capable of measuring finer roughness, the roughness of the front cover contact surface after the test using actual notes (hereinafter referred to as the contact surface roughness). It was measured. Regarding the contact surface roughness, of the unevenness of the surface roughness, the vicinity of the top of 10 convex portions was measured with a measurement width of 40 μm, and the average value was obtained. Figure 2 shows the relationship between the contact surface roughness and the occurrence and non-occurrence of judder
Shown in From FIG. 2, the contact surface roughness is 0.1 μm Ra (Rz
In a region of 0.25 μm or more in terms of conversion, the occurrence of judder is suppressed.

From these results, the occurrence and non-occurrence of judder are not caused by the relatively large surface roughness obtained by the stylus-type roughness meter, but by the minute surface on the surface of the convex portion which is the actual contact portion. It turned out that it depends on roughness (contact surface roughness). That is, in the friction member for a wet clutch of the present invention, the friction surface has irregularities and the convex portion is 0.1 to 2.0 μm.
It is characterized by mRa.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The friction member for a wet clutch of the present invention has irregularities on the friction surface having a width of several hundred μm and a height of several hundred μm, which are formed by machining or abrasion, and is convex. It also has a roughness of 0.1-2.0 μm Ra on the part. The roughness of the convex part of the friction surface is 0.1μmR
If it is smaller than a, the roughness is too small to have any meaning as roughness, and even if the roughness is greater than 2.0 μmRa, the judder resistance hardly improves. Further, when the roughness of the friction surface becomes excessively large, the friction surface enters the above-mentioned unevenness region of the friction surface and does not effectively work to improve the μ-v characteristic, and also causes aggression to the mating friction material.

[0011] This indicates that the frictional surface of the friction member of the wet clutch has a roughness of μ-μm when the frictional surface is modeled.
It can also be seen from the example shown in FIG. 3 where the relationship with the v-characteristic was obtained by calculation. From FIG. 3, it can be seen that the μ-v characteristic becomes a positive gradient with an increase in the roughness of the contact surface, and the judder resistance tends to be improved. Moreover, this tendency is 0.1 to 2.0 μm.
In the range of mRa, the positive gradient of the μ-v characteristic is substantially constant. Therefore, even if the roughness of the contact surface is increased more than necessary, the judder resistance is hardly improved.

Further, the friction member for a wet clutch according to the present invention is manufactured by sliding a metal (based) friction member in a non-aqueous solution containing a metal detergent having an overbased group. By sliding a metal (based) friction member in a non-aqueous solution containing a metal detergent having an overbased group, roughness can be formed on the convex portion of the friction surface. As the metal (system) friction member, a steel plate or the like is preferable. As the overbased group, calcium carbonate, magnesium carbonate, sodium carbonate, barium carbonate and the like are preferable. With a metal detergent having an overbased group and a base number of 0 mgKOH / g, an appropriate contact surface roughness is not formed, and no judder prevention effect can be obtained. As the ratio of the overbased group to the metal detergent, the base number of the metal detergent is 10 to 400 mgKOH / g.
Is preferable.

As the metal detergent, metal sulfonates, metal phenates, metal salicinates and the like are preferable. A containing Ca sulfonate as a metal detergent
FIG. 4 shows the relationship between the contact surface roughness and the amount of Ca sulfonate when slid using TF. To form a contact surface roughness of 0.1 μm or more effective for preventing judder,
It is understood that the compounding amount is required to increase the base number of the solution by 0.04 mgKOH / g or more. Therefore, the base value of the solution is 0.04 m
It is necessary to increase the amount by at least gKOH / g.

Examples of the solvent used for the non-aqueous solution include mineral oil and synthetic oil. The solution may contain additives other than metal detergents, such as tooth antioxidants and ashless dispersants.
This is because the iron-based sliding member of the friction member and a paper friction material as a mating member were slid in an ATF containing a metal detergent having an overbased group, as shown in FIG. Original roughness, SEM of friction surface shown in FIG.
This can be seen from the analysis results of the element distribution shown in the photograph and FIG. Note that the three-dimensional roughness shown in FIG. 5 is a diagram showing a convex portion of the unevenness of the friction member, and the roughness is formed mainly along the sliding direction of the friction material. FIG. 6 is an SEM photograph of the surface shown in FIG. 6 and 7
It can be seen from the result that the shape of the roughness of the contact surface and the existing positions of calcium, phosphorus and oxygen correspond well. XPS analysis confirms that these products are a mixture of calcium oxide, calcium carbonate, calcium phosphate, etc., and that these are overbased Ca incorporated into ATF.
It is a reaction product resulting from the sulfonate and the phosphate ester.

[0015]

The present invention will be described below with reference to examples. As an example of the friction member for a wet clutch of the present invention, a friction member was manufactured. The friction member of the embodiment has a thickness of 2
A friction member using a hot-rolled mild steel sheet of 1 mm (JIS) was slid in an ATF using a paper friction member as a mating member. Note that the sliding at this time was performed by using an actual automatic transmission at a sliding speed of 0.3 m / s, 0.6 m / s, 0.9 m / s at oil temperatures of 40 ° C. and 80 ° C.
s, 1.2 m / s, 1.8 m / s, 2.4 m / s, and the total time was about 3 hours. The roughness of the contact surface of the iron-based friction member was formed by a product resulting from the additive overbased Ca sulfonate incorporated in the ATF. Example 1 The friction member of Example 1 had a contact surface roughness of 0.19 μm Ra, and the compounded additive was 2.4 wt% of overbased Ca sulfonate and phosphoric acid as an ATF used. 0.22 wt% of ester, 6.5 wt% of viscosity index improver, 0.22 wt of friction modifier
%, Ashless dispersant 4.5 wt%, antioxidant 1.0 w
t%, and the antifoam was 0.042 wt% ATF. (Example 2) The friction member of Example 2 had a contact surface roughness of 0.17 µmRa, and the compounded additive was 1.8 wt% of overbased Ca sulfonate and phosphoric acid as an ATF used. 0.22 wt% of ester, 6.5 wt% of viscosity index improver, 0.22 wt of friction modifier
%, Ashless dispersant 4.5 wt%, antioxidant 1.0 w
t%, and the antifoam was 0.042 wt% ATF. Example 3 The friction member of Example 3 had a contact surface roughness of 0.13 μm Ra, and the compounded additive was 1.2 wt% of overbased Ca sulfonate and phosphoric acid 0.22 wt% of ester, 6.5 wt% of viscosity index improver, 0.22 wt of friction modifier
%, Ashless dispersant 4.5 wt%, antioxidant 1.0 w
t%, and the antifoam was 0.042 wt% ATF. Example 4 The friction member of Example 4 had a contact surface roughness of 0.53 μm Ra, and the compounded additive was 2.4 wt% of overbased Ca sulfonate and a viscosity index of ATF used. The ATF was 6.5 wt% of the improver, 0.22 wt% of the friction modifier, 4.5 wt% of the ashless dispersant, 1.0 wt% of the antioxidant, and 0.042 wt% of the defoamer. (Comparative Example 1) The friction member of Comparative Example 1 had a contact surface roughness of 0.06 μm Ra, and the compounded additive was 0.6 wt% of overbased Ca sulfonate and phosphoric acid as the ATF used. 0.22 wt% of ester, 6.5 wt% of viscosity index improver, 0.22 wt of friction modifier
%, Ashless dispersant 4.5 wt%, antioxidant 1.0 w
t%, and the antifoam was 0.042 wt% ATF. (Comparative Example 2) The friction member of Comparative Example 2 had a contact surface roughness of 0.03 μm Ra, and the compounded additive was 0.22 wt% of a phosphate ester as the ATF used.
%, The viscosity index improver is 6.5 wt%, and the friction modifier is 0.1%.
The ATF was 22 wt%, the ashless dispersant was 4.5 wt%, the antioxidant was 1.0 wt%, and the defoamer was 0.042 wt%. (Comparative Example 3) The friction member of Comparative Example 3 had a contact surface roughness of 0.07 μm Ra, and as an ATF used, the compounded additive was neutral Ca sulfonate.
17 wt%, phosphate ester 0.22 wt%, viscosity index improver 6.5 wt%, friction modifier 0.22 wt
%, Ashless dispersant 4.5 wt%, antioxidant 1.0 w
t%, and the antifoam was 0.042 wt% ATF.

[0016]

[Table 1]

From Table 1, it can be seen that as the amount of the overbased Ca sulfonate increases, the contact surface roughness of the iron-based friction member increases. In Comparative Example 3 in which neutral Ca sulfonate was blended as Ca sulfonate, the roughness of the contact surface was small. That is, it can be seen that calcium carbonate, which is an overbased group, contributes to the formation of the contact surface roughness.

Further, in Example 4 in which the phosphate ester was not blended, the roughness of the contact surface was larger. Therefore, it is determined that the phosphate ester is one of the sources for supplying the reaction product, but is not the main factor that determines the magnitude of the contact surface roughness. (Evaluation) As an evaluation of Examples and Comparative Examples, a judder generation test was performed. As for the test method, a test was conducted using an actual machine, and occurrence and non-generation of judder were examined. The results are shown in Table 1.

In the embodiment of the present invention having a friction surface roughness of 0.1 μm Ra or more, since the occurrence of judder is suppressed, it is understood that the judder resistance is high. In these embodiments, the contact surface roughness is formed by sliding in an actual automatic transmission using ATF as a solution. However, additives other than the metal detergent having an overbased group are not essential for forming the contact surface roughness. Therefore, in the case of sliding in a process prior to assembling into an automatic transmission, the presence, type, and amount of other additives are not limited as long as a metal detergent having an overbased group is blended as a solution to be used.

[0020]

The friction member of the present invention is a friction member for a wet clutch which has excellent judder resistance because it has a small contact surface roughness depending on the presence or absence of judder.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between surface roughness and occurrence of judder by a stylus roughness meter.

FIG. 2 shows the relationship between the roughness of the contact surface and the occurrence and non-occurrence of judder.

FIG. 3 is a modeled frictional surface roughness and μ-v
FIG. 3 is a diagram showing a relationship with characteristics.

FIG. 4 is a graph showing the relationship between the increase in base number due to the addition of a metal detergent and the roughness of the contact surface.

FIG. 5 is a view showing a three-dimensional roughness of a friction surface of the iron-based sliding member according to the present invention.

6 is an electron micrograph of the friction surface shown in FIG.

7 is a diagram showing an analysis result of element distribution on the friction surface shown in FIG.

Continued on the front page (72) Inventor Toshihide Omori 41-Cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central R & D Laboratories Co., Ltd. Inside the corporation

Claims (2)

[Claims] 1. A friction member for a wet clutch, wherein a friction surface has irregularities and a convex portion has a roughness of 0.1 to 2.0 μm Ra. 2. The method according to claim 1, wherein the convex portion of the friction surface has a thickness of 0.1 to 0.1.
A wet clutch for forming a roughness of 2.0 µm Ra by sliding a metal (system) friction member against a mating member in a non-aqueous solution containing a metal detergent having an overbased group. A method for manufacturing a friction member.