RU2807160C2 - Friction pair disc/brake for railway rolling stock - Google Patents

Abstract

FIELD: railway rolling stock.

SUBSTANCE: disc/brake friction pair for railway rolling stock, containing at least one pad having at least one friction element and a disc. The friction element is made of sintered material containing copper, iron, graphite, from 0.02% to 1.5% by weight of molybdenum, from 1% to 3% by weight of chromium, porosity from 20% to 35%; and the disc is made of cast iron containing from 0.05% to 2% of chromium by weight, from 0.05% to 2% of molybdenum by weight, from 0.1% to 2% of nickel by weight.

EFFECT: technical result is increased braking efficiency, reduced noise during braking.

7 cl, 6 tbl

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to Italian Patent Application No. 102019000016835, filed September 20, 2019, the contents of which are incorporated by reference.

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The invention relates to a disc/brake friction pair for railway rolling stock. In particular, this invention finds advantageous application for medium-speed trains, that is, those trains which have a maximum speed of less than 220 km/h, in particular for vehicles with speeds between 140 and 220 km/h.

PREREQUISITES FOR THE CREATION OF THE INVENTION

As is known to one skilled in the art, the structure of the brake in terms of friction elements and disc depends on the type of train on which the brake is installed.

Discs are usually made of steel or cast iron. Steel wheels provide greater strength than cast iron wheels, and at the same time are significantly more expensive. For these reasons, the use of steel discs is usually only justified for those trains that have high speed (above 220 km/h) or braking mass per disc, which makes the use of cast iron discs impossible due to the high energy dissipation and reduced power. In fact, for energies that are too high, the stresses on the disc during braking will be such as to compromise the integrity of the cast iron discs.

As for friction elements, they are usually made of sintered or organic material. Due to the high temperatures encountered during braking, the only friction elements that can be used for trains at medium and high speeds (over 160 km/h) are elements made of sintered material rather than organic material. Friction elements made of organic material have the disadvantage that they have to be replaced very often due to their high consumption (especially when used in medium/high speed trains) and that their friction characteristics are reduced at high temperatures.

Regarding sintered friction elements, it has long been believed that they should not be used in combination with a cast iron disc as they may cause premature wear of the disc.

The above means that even for medium speed trains, from 160 to 220 km/h, a combination of sintered friction elements with a steel disc is often used. This choice is also driven by increasingly demanding vehicle configurations in terms of performance.

Although the use of sintered friction elements in combination with steel discs provides superior braking performance, it has the disadvantage that it is particularly expensive and produces an annoying squealing noise, especially at low speeds.

It should be noted that low noise levels are becoming an increasingly important determining factor when choosing disc brakes to use. It is easy to understand that the need to control noise during braking is most acute for those trains that must make a large number of stops in centers with high population concentrations, such as metropolitan trains.

Thus, the need arose for a friction disc/brake pair brake for trains, the specifications of which were such as to make it cheaper than brakes currently in use and less noisy during braking, thus reducing the annoying squealing noise that usually is produced.

The present inventors have satisfied the above requirement by providing a disc/brake friction pair in which the friction elements are made of a certain sintered material and the disc is made of a certain cast iron. The disc/brake friction pair which is the subject of the present invention not only satisfies the above requirements but, surprisingly, also provides significant advantages in terms of wear resistance of both the disc and the friction elements. The ability to replace steel discs with cast iron discs significantly reduces the cost of the entire disc/brake friction pair and, surprisingly, significantly reduces the noise produced during braking.

SUMMARY OF THE INVENTION

The present invention relates to a disc/brake friction pair for railway rolling stock, the main technical features of which are included in claim 1 of the claims, and the preferred and/or additional features of which are included in dependent claims 2-7 of the claims.

DETAILED DESCRIPTION OF THE INVENTION

In order to better understand the invention, a non-limiting embodiment is given below by way of example.

Friction elements were created whose sintered material corresponds to the composition indicated in percentage by weight in Table I.

TABLE I

Min. % by weight Max. % by weight copper 10 70 iron 5 40 graphite 5 20 molybdenum 0.02 1.5 chromium 1 3 Friction modifier 5 20

The sintered material also has a porosity, expressed as a percentage (void volume compared to total volume), of 20% to 35%.

Specifically, the sintered material has the composition shown in percentage by weight in Table II and has a porosity of 28%.

TABLE II

copper 50 iron thirty graphite 10 molybdenum 0.75 chromium 1.25 Friction modifier 8

The sintered material described above was tested as a friction element on a cast iron disc made according to this invention (this represents one example of the invention and is designated A), on a cast iron disc with a composition that does not meet the requirements of this invention (this represents the first example of comparison and is designated letter B), and on a steel disk (this represents the second example of comparison and is marked with the letter C).

The cast iron disk according to the present invention must correspond to the composition indicated in percentage by weight in Table III.

TABLE III

Min. % by weight Max. % by weight carbon 3 5 silicon 1 2 manganese 0.5 1 sulfur 0.01 1 phosphorus <0.05 nickel 0.1 2 chromium 0.05 2 molybdenum 0.05 2 copper 0.1 1 Tin, lead, aluminum, titanium <0.01 iron Rest

Specifically, the cast iron disc according to the present invention has the composition shown in percentage by weight in Table IV.

TABLE IV

% by weight carbon 3.3 silicon 1.7 manganese 0.8 sulfur 0.06 phosphorus 0.02 nickel 1 chromium 0.2 molybdenum 0.5 copper 0.5 Tin, lead, aluminum, titanium 0.005 iron Rest

Table V shows the percentage by weight of the composition of the cast iron disc, the composition of which does not meet the requirements of the present invention.

TABLE V

% by weight carbon 3.5 silicon 1.7 manganese 1.02 sulfur 0.06 phosphorus 0.023 nickel 0 chromium 0.46 molybdenum 0 copper 0.7 Tin, lead, aluminum, titanium 0.005 iron Rest

The steel disc used is approved and currently available on the market and has the following characteristics: 21CrMoV5-11 EN 10028-2 (2003), DIN 17755 (1983).

The sintered material elements described above were tested on the three types of disc brakes (Examples A-C) described above. Specifically, the tests were performed on a dynamometer and focused on friction, disc structural integrity, disc wear, friction element wear and noise.

The friction test was carried out according to the procedure specified in the UIC 541-3 edition 7 program 6A and 6B.

The wheel structural integrity test was carried out according to the procedure specified in the EN 14535-3 standard - class C2 (200 km/h - 10 t/wheel).

The wear test of the disc and friction element was carried out according to the procedure specified in the UNI EN 14535-3 standard and according to specific application tests.

The noise test was carried out according to the UNI EN ISO 3095: 2013 procedure.

Table VI shows the results of the above tests expressed in indexed form with respect to a disc/brake friction pair containing a steel disc (Example C). Thus, it will be extremely easy and immediately to recognize the advantages provided by the disc/brake friction pair according to the present invention (Example A).

TABLE VI

A B C friction 100 100 100 Structural integrity of the disk 100 70 100 Disc wear 120 40 100 Friction element wear 200 200 100 noise 400 400 100

From the data presented in Table VI, it can be seen that the disc/brake friction pair, which is the subject of the present invention (A), not only allows the replacement of a steel disc with a cast iron disc, but also guarantees a significant improvement in wear life and noise.

The above results show that the present invention can provide a much more economical disc/brake friction pair for railway vehicles than for vehicles with steel discs, and at the same time improve the wear performance of the disc and the friction element. In terms of cost-effectiveness benefits, it should be noted that a cast iron blade costs about one-third of a steel blade.

The inventors believe that the above-mentioned advantages of the disc/brake friction pair according to the invention arise from the formation on the surface of the disc of a uniformly distributed layer of oxides, consisting mainly of chromium and molybdenum oxides. This oxide layer is formed during the interaction between the friction elements and the disc and is extremely resistant and firmly adheres to the disc, thus creating a highly protective layer. Using an electron microscope, it was found that this layer is about 5 microns thick.

According to a preferred embodiment of the present invention, the pads contain multiple friction elements of reduced dimensions instead of one larger friction element. Each pad consists of a main base plate, and a number of friction elements attached to the base plate. Each of the friction elements is made of a metal sheet and a friction insert firmly attached to the metal sheet.

The solution associated with the use of multiple friction elements of reduced dimensions is advantageous both from the point of view of the efficiency of pressure on the disc and therefore braking, and from the point of view of low noise.

Again, according to a preferred embodiment of the present invention, the disk consists of at least three circular sectors separated from each other and secured together to form a disk of multiple transverse contacts. A disk thus constructed is described in patent application EP0758059 A1, incorporated herein by reference.

Claims (7)

1. A disc/brake friction pair for railway rolling stock, containing at least one pad having at least one friction element and a disk, characterized in that the friction element is made of a sintered material containing copper, iron, graphite, from 0. 02% to 1.5% by weight molybdenum, 1% to 3% by weight chromium, porosity from 20% to 35%; and the disk is made of cast iron containing from 0.05% to 2% by weight chromium, from 0.05% to 2% by weight molybdenum, from 0.1% to 2% by weight nickel. 2. A disc/brake friction pair according to claim 1, characterized in that the sintered material of the friction element contains from 0.05% to 1% by weight of molybdenum, from 1% to 1.5% by weight of chromium, porosity from 25% to thirty%. 3. A disc/brake friction pair according to claim 1 or 2, characterized in that the sintered material of the friction element contains from 10% to 70% by weight of copper, from 5% to 40% by weight of iron, from 5% to 20% by weight of iron weight of graphite, from 5% to 20% by weight of friction modifier. 4. A disc/brake friction pair according to one of the previous paragraphs, characterized in that the cast iron making up the disc contains from 0.1% to 2% by weight of chromium, from 0.1% to 2% by weight of molybdenum, from 0. 5% to 1.5% by weight nickel. 5. A disc/brake friction pair according to one of the previous paragraphs, characterized in that the cast iron composing the disc contains from 3% to 5% by weight of carbon, from 1% to 2% by weight of silicon, from 0.5% to 1 % by weight manganese, from 0.01% to 1% by weight sulfur. 6. A disc/brake friction pair according to one of the preceding paragraphs, characterized in that the pad contains a main base plate and a plurality of friction elements attached to the base plate. 7. A disc/brake friction pair according to one of the preceding paragraphs, characterized in that the cast iron disc consists of at least three circular sectors, which are separated from each other and held together to form the disc by means of connecting elements.