JPH0467048B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to friction materials such as clutch facings and brake linings used in power transmission of automobiles. (Conventional technology and its problems) Friction materials, especially clutch facings, have excellent friction properties (stable coefficient of friction), wear resistance, mechanical properties (high berth strength), anti-jadder properties, and anti-sticking properties. required. Recently, among the above properties, sticking resistance has become an important characteristic item. In most cases, friction materials contain a small amount of salt, and this salt promotes rusting of the mating material, iron. In particular, salt containing chloride ions (Cl ^- ) and sulfate radicals (SO ₄ ^2- ) significantly promotes rusting of iron. If industrial machinery, automobiles, etc. that use friction materials are left in storage for a long period of time, rust may develop between the iron and the friction material, causing the two to stick together. Particularly in areas with large temperature differences, dew condensation tends to form between the iron and the friction material, and this condensation causes rust between the iron and the friction material, which tends to cause sticking as described above. As a method to solve this problem, rust preventive agents such as sodium nitrite, phosphoric acid, phosphates, boric acid, and borates are added to the friction material composition. As disclosed, there is a method of thermally spraying a metal that can be used as a sacrificial iron anode onto the surface of a friction material. However, the former rust prevention method is effective when the relative humidity is high and the amount of moisture absorbed by the friction material is large;
Under conditions where the friction material repeatedly absorbs moisture and dries, the anti-corrosion agent will be unevenly distributed and will not be sufficiently effective. The climate in areas where rusting actually occurs is low temperature and high humidity at night, but high temperature and low humidity during the day, resulting in friction materials repeatedly absorbing moisture and drying out. The latter rust prevention method is more effective than adding rust inhibitors, but
When the amount of deposited metal that can serve as a sacrificial iron anode is small, particularly when it is less than 5 mg/cm ² , the rust prevention effect cannot be maintained for a long period of time. Furthermore, if there is a large amount of metal that can become a sacrificial iron anode attached, it becomes difficult for the salt (electrolyte) necessary for sacrificial anode action to be eluted from the friction material. For this reason, gaps are likely to form where the iron and the metal that can serve as a sacrificial anode do not come into close contact with each other.
When dew condensation occurs in this gap, the rust prevention effect due to sacrificial anode action becomes insufficient. The object of the present invention is to provide a friction material that does not suffer from the above-mentioned drawbacks. (Means for Solving the Problems) As a result of various studies on the above-mentioned drawbacks, the present inventors deposited 5 mg/cm ² to 30 mg/cm ² of a metal that can serve as a sacrificial iron anode on the surface of the friction material. In addition, when grooves and/or holes are provided in a layer of metal that can be used as a sacrificial iron anode, a gap is created between the iron (the other material) and the metal that can be used as a sacrificial iron anode, and dew condensation occurs in the gap. It was confirmed that no rust occurred even when the friction material was applied, and the problems caused by the adhesion of iron and friction material were resolved. In the present invention, 5 mg/cm ² to 30 mg/cm ² of a metal that can be used as a sacrificial iron anode is adhered to the surface of a friction material, and grooves and/or holes are provided in the metal layer that can be used as a sacrificial iron anode. Regarding friction materials. In the present invention, a metal that can serve as a sacrificial anode for iron refers to a metal that, when coexisting with iron, serves as an anode instead of iron in the electrochemical mechanism of rust, thereby preventing iron from rusting. Examples include zinc, aluminum, magnesium, etc., and these metals may be used singly or in a mixture of two or more without any particular limitation. In addition, these metals may be attached in the form of wire or powder by thermal spraying to the surface of the iron and/or friction material. It may be attached to the surface of the friction material by adhesive using a binder, or it may be crimped by heating and pressurizing a metal foil, but there is no particular restriction, but from the viewpoint of workability, it may be attached by thermal spraying to the surface of the friction material. Preferably. The metal that can be used as a sacrificial iron anode is applied to the surface of the friction material in an amount of 5 mg/cm ² to 30 mg/cm ² , preferably 10 mg/cm ² to 25
It is necessary to deposit mg/ ^cm2 , and 5mg/ ^cm2
If it is less than 30mg/cm2, the rust prevention effect cannot be maintained for a long time, and if it exceeds 30mg/ ^cm2 , the performance as a friction material will deteriorate.
In particular, there are drawbacks such as a decrease in the initial coefficient of friction. In addition, excessive adhesion may lead to increased costs. The holes provided in the metal layer that can serve as a sacrificial iron anode are preferably 3 mm or less in diameter, and more preferably 1 mm or less in diameter. Further, the width of the groove is preferably 3 mm or less, more preferably 1 mm or less. Note that there is no particular restriction on the number of grooves and/or holes. There are no particular restrictions on the method of forming holes and grooves, but for example, in the case of clutch facings, brake linings, etc., metal that can be used as a sacrificial anode is attached to the friction surface, and then a sword mount with many needle-like protrusions is used. A hole can be made by pushing an instrument like this into the friction surface. Alternatively, streak-like grooves may be formed using a sharp knife. Alternatively, holes or gaps may be provided in the metal foil in advance and then the metal foil may be pressed against the friction surface. Furthermore, irregularities such as grooves may be formed on the surface of the friction material, and then a metal that can be used as a sacrificial anode may be deposited by thermal spraying. Grooves and/or holes are essential for effective sacrificial anode action. Without grooves and/or holes, the salt necessary for sacrificial anode action will not be leached from the friction material. A void is easily formed between the metal and the metal that can serve as a sacrificial anode, and when dew condensation occurs within this void, the rust prevention effect due to the sacrificial anode action becomes insufficient. In order to make the sacrificial anode effect even more effective, the above salt should be added to the friction material in an amount of 0.01 to 1.0% by weight when absorbing moisture.
It is desirable that the salt content be at a certain level. (Example) The present invention will be explained below with reference to Examples. Example 1 85 parts by weight of 4K class asbestos (manufactured by Johns Manbuil) and 15 parts by weight of Sufu were mixed uniformly, then processed into a carding machine to form an asbestos web, and 82 parts by weight of this asbestos web was heat-cured with cashew shell oil. After dispersing 18 parts by weight of abrasion-resistant powder (manufactured by Tohoku Kako, trade name FF1800), it was applied to a condenser to obtain asbestos sliver containing abrasion-resistant powder, which was then twisted using a spinning machine to form a single yarn with a diameter of 1 mm. Next, twist these two single yarns and one Shinchiyu wire with a diameter of 0.16 mm for 2.5
g/m of asbestos yarn containing wear-resistant powder. This asbestos yarn containing wear-resistant powder was impregnated with melamine-modified phenolic resin (manufactured by Dainippon Ink) in an amount of 20% by weight based on the coated yarn to obtain a coated yarn. Next, the coated yarn was preformed into a tablet in the shape of a clutch facing and heated at 150±5°C.
Heat and pressure molding was performed for 8 minutes at a pressure of 300Kg/ ^cm2 ,
Thereafter, the surface was polished, and after heat treatment at 200°C for 8 hours, the surface was further polished to obtain a clutch facing in the shape specified in the drawing. Next, a zinc wire with a purity of 95% is melted using a thermal spraying machine manufactured by Kato Metallicon Industries, trade name KR-5, and the voltage is
10 mg/cm ² of zinc was thermally sprayed onto the surface of the clutch facing obtained above under the conditions of 15 V, 20 A current, and 5 Kg/cm ² air pressure. After this, an instrument with needle-like protrusions 0.5 mm in diameter was pushed into the clutch facing at 5 mm intervals to create holes in the thin zinc film layer. Next, the clutch facing, which has holes in the thin zinc film layer, was pressed against the mating material, gray cast iron (JIS G5011), with a surface pressure of 2 kg/ ^cm2 , and rusting and sticking force tests were conducted under the conditions shown in Table 1. Ivy. The results are shown in Table 1. The following Examples and Comparative Examples were also tested for rust development and adhesion strength in the same manner. The clutch facing obtained in Example 1 contained 0.3% by weight of salt (Ca ²⁺ , Na ⁺ , Mg ²⁺ , Cl ^- ,
SO ₄ ^2- etc.) were included. Example 2 75 parts by weight of 4K class asbestos (manufactured by Cary) and 5 parts by weight of Sufu were mixed uniformly, then processed into a carding machine to form an asbestos web. Wear-resistant powder (manufactured by Tohoku Kako, product name)
After dispersing 18 parts by weight of FF1800), it was applied to a condenser to obtain asbestos sliver containing wear-resistant powder.
Thereafter, a clutch facing was obtained using the same steps and materials as in Example 1. Next, 20 mg/cm ² of zinc was deposited on the surface of the clutch facing obtained above by thermal spraying in the same manner as in Example 1. Thereafter, in the same manner as in Example 1, a clutch facing in which holes were formed in the zinc thin film layer was obtained. Note that the clutch facing obtained in Example 2 contained 0.1% by weight of salt. Example 3 Cut grooves measuring 1 mm x 5 mm were provided at 7.5 mm intervals in a zinc foil having a thickness of 30 m (21.5 mg/cm ² ). Next, this was pressed onto the surface of the clutch facing obtained in Example 1 at a pressure of 100 kg/cm ² and a temperature of 150±5° C. to obtain a clutch facing with grooves formed in the zinc foil. Comparative Example 1 A clutch facing was prepared in which 4 mg/cm ² of zinc was thermally sprayed onto the surface of the clutch facing obtained in Example 1, and holes were formed in the zinc thin film layer in the same manner as in Example 1 except for the above. Got Thing. Comparative Example 2 On the surface of the clutch facing obtained in Example 2
A clutch facing with holes formed in the zinc thin film layer was obtained in the same manner as in Example 2 except that 33 mg/cm ² of zinc was deposited by thermal spraying. Comparative Example 3 On the surface of the clutch facing obtained in Example 1
12 mg/cm ² of bad lead was sprayed and adhered. However, no holes, grooves, etc. are provided in the zinc thin film layer.

[Table] (Effects of the invention) The friction material of the present invention maintains its anti-corrosion effect for a long period of time even in high temperature and high humidity environments, environments where moisture absorption and dryness are repeated, and it also maintains its anti-corrosion effect for a long period of time even in environments where moisture absorption and dryness are repeated. It is industrially extremely effective.

Claims (1)

[Claims] 1. 5 mg/cm ² to 30 mg/cm ² of a metal that can be used as a sacrificial iron anode is deposited on the surface of the friction material, and grooves and/or holes are formed in the metal layer that can be used as a sacrificial iron anode. A friction material that is provided with. 2. The friction material according to claim 1, wherein the friction material is a clutch facing.