CS205703B1 - Chrome-plated piston for the cylinder of the hydraulic brake - Google Patents

Description

SUMMARY OF THE INVENTION The invention provides a piston for a brake fluid cylinder provided with a chrome layer on the functional surface with substantially increased corrosion and abrasion resistance, thereby providing increased durability and reliability of the entire brake fluid.

The piston for the brake fluid cylinder must withstand corrosion and abrasion during operation. When vehicles are operated in winter, velrpi pistons are usually subject to intense corrosion stress in the presence of salts and abrasive particles. Production of pistons from corrosion resistant materials is economically demanding. Therefore, the pistons for the brake fluid cylinders are manufactured in a more convenient, less demanding manner, and are galvanized on the functional surface. The chrome layer is then reground to the specified dimensions. Even the piston thus produced loses its functional capability and reliability after some time. This is because the dimensioned chrome layer is damaged by grinding, while the remaining chrome layer is not evenly distributed over the functional area. The chrome plating associated with subsequent grinding is relatively laborious and demanding. The other proposed methods of protecting the pistons in the brake fluid cylinders are not generally performed due to technological problems of a different nature.

According to the invention, these disadvantages are overcome by solving a chromed piston in a brake fluid cylinder which is coated on the outer functional surface with a dense, continuous, directly dimensioned chromium layer of exactly the same physicochemical properties and interlayer layers in a leveling level of 3 to 30 micrometers on the fuper cylindrical surface and passing in the same or in a reduced thickness of the chrome layer at the edges of this surface gradually and completely evenly into the bare surface, preferably beyond this edge.

The chrome-plated piston for the brake fluid cylinder of the invention has, under comparable conditions, a service life of about 1 order of magnitude higher than the service life of, for example, the vehicle for which the liquid brake is applied, compared to a chromed piston and regrinded. As a result, the chrome-plated piston can be formed with a chrome layer of a smaller thickness (generally as long as the vehicle life), without jeopardizing the long-term reliability and long-term performance of the piston. The reliability and performance of the piston is ensured by the porous chrome-free coating and its integrity over the entire functional surface of the piston. Under the conditions for dimensional chrome plating, the porosity of the coating is closed at approximately 2 micrometers thick chrome layer. The functional cylindrical surface of the piston into the brake fluid cylinder can be provided with a chrome layer whose thickness exceeds 100 microns, while maintaining the prescribed dimensions without the need for regrinding. However, this is not advantageous since the quality of the piston does not increase. With a chromium layer thickness of the wheels of 30 microns, such a lifetime is reached,

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that this corresponds to the most demanding applications. The chromium layer can be deposited from all the chromium baths under known conditions. Functionally, those layers which are initially deposited as smooth are suitable. Highly suitable are chromium layers which are deposited at lower current densities or deposited at wheel bath temperatures of 60 ° C. The chromium layer must be completely evenly distributed from the beginning and its physico-chemical properties must be uniformly uniform throughout the cross-section and in the layers in permanent equilibrium with each other. The chrome layer is made on both fronts by a gradual and absolutely uniform transition to a bare, ie non-chrome, surface. Advantageously, it is expedient to place the transition layer outside the functional part of the chrome cylindrical surface, for example on its faces.

Claims (1)

SUBJECT Chrome-plated piston for the brake fluid cylinder, characterized in that it is coated on the outer functional surface with a dense, continuous, directly to a specified size, a deposited chrome layer of completely, uniform thickness. 3 to 30 micro As an example, a chromed piston is introduced into a brake fluid cylinder, on which a completely uniform, dense, non-porous chrome layer of 15 microns is formed by dimensional chromium plating. The thickness of the chrome layer is the same along the circumference and the length of the functional cylindrical surface. The chrome layer is terminated by a completely uniform transition to the bare, non-chrome surface, beginning at the edge of the functional cylindrical surface and ending at the piston face. In such a piston, the abrasion resistance on the chromed surface is about 12χ higher than the abrasion resistance of the chrome-plated piston, ground to a dimension. Corrosion resistance is also about 8 times higher. The service life and reliability of this component in the fluid brake is increased several times. The service life of the rubber parts functionally adjacent to such a piston is also increased accordingly.