阅读说明：本技术 用于铁路车辆的盘/制动器摩擦扭矩 (Disc/brake friction torque for railway vehicles ) 是由 维托里奥·德索乔 罗伯特·博费利 于 2020-09-18 设计创作，主要内容包括：用于铁路车辆的盘/制动器摩擦扭矩,该铁路车辆包括至少一个衬垫,该衬垫包括至少一个摩擦元件和盘。摩擦元件由包括铜、铁、石墨、0.02至1.5重量％的钼、1至3重量％的铬和20至35％之间的孔隙率的烧结材料制成,并且该盘由铸铁制成,铸铁包括0.05至2重量％的铬、0.05至2重量％的钼、0.1至2重量％的镍。(Disc/brake friction torque for a railway car comprising at least one pad comprising at least one friction element and a disc. The friction element is made of a sintered material comprising copper, iron, graphite, 0.02 to 1.5% by weight of molybdenum, 1 to 3% by weight of chromium and a porosity of between 20 and 35%, and the disc is made of cast iron comprising 0.05 to 2% by weight of chromium, 0.05 to 2% by weight of molybdenum, 0.1 to 2% by weight of nickel.)

1. A disc/brake friction torque for a railway car, the railway car comprising at least one pad comprising at least one friction element and a disc; the disc/brake friction torque is characterized in that the friction element is made of a sintered material comprising copper, iron, graphite, 0.02 to 1.5% by weight of molybdenum, 1 to 3% by weight of chromium and a porosity between 20 and 35%; and in that the disc is made of cast iron comprising 0.05 to 2% by weight of chromium, 0.05 to 2% by weight of molybdenum, 0.1 to 2% by weight of nickel.

2. Disc/brake friction torque according to claim 1, characterized in that the sintered material of the friction element comprises 0.05 to 1 wt% molybdenum, 1 to 1.5 wt% chromium and between 25 and 30% porosity.

3. Disc/brake friction torque according to claim 1 or 2, characterized in that the sintered material of the friction element comprises 10 to 70 wt% copper, 5 to 40 wt% iron, 5 to 20 wt% graphite, 5 to 20 wt% friction modifier.

4. Disc/brake friction torque according to claim 1, characterized in that the cast iron from which the disc is made comprises 0.1 to 2% by weight of chromium, 0.1 to 2% by weight of molybdenum, 0.5 to 1.5% by weight of nickel.

5. Disc/brake friction torque according to claim 1, characterized in that the cast iron from which the disc is made comprises 3 to 5% by weight of carbon, 1 to 2% by weight of silicon, 0.5 to 1% by weight of manganese, 0.01 to 1% by weight of sulphur.

6. The disc/brake friction torque of claim 1, wherein the pad includes a primary base plate and a plurality of friction elements fixed to the base plate.

7. Disc/brake friction torque, according to claim 1, characterized in that the cast iron disc comprises at least three circular sectors, which are separate from each other and are held together by means of connecting elements to form the disc.

Technical Field

The invention relates to a disc/brake friction torque for railway vehicles. In particular, the invention finds advantageous application to medium speed trains, i.e. those trains having a maximum speed of less than 220km/h, in particular those trains having a speed between 140km/h and 220 km/h.

Background

As known to those skilled in the art, the construction of the brake, in terms of friction elements and discs, depends on the type of train on which the brake is mounted.

The disc is typically made of steel or cast iron. Steel discs have a higher strength than discs made of cast iron, and at the same time are much more costly. For these reasons, it is generally only reasonable to use steel discs for trains with high speeds (above 220 km/h) or brake quality per disc which, due to high energy dissipation and relative power, makes it impossible to use cast iron discs. In fact, the stresses on the disc during braking will compromise the integrity of the cast iron disc, because of the excessively high energy.

For friction elements, they are typically made of sintered or organic materials. Only friction elements for medium-high speed (over 160km/h) trains are made of sintered material rather than organic material, due to the high temperatures that occur during braking. Friction elements made of organic materials have the following disadvantages: due to their high consumption (especially when applied to medium/high speed trains), they have to be replaced very frequently and their friction properties are reduced at high temperatures.

For friction elements made of sintered material, it has long been generally accepted that they cannot be used in combination with cast iron discs, since they cause premature wear of the discs.

The above means that even for medium speed trains between 160km/h and 220km/h, a combination of sintered material friction elements and steel discs is usually employed. This choice also stems from the increasingly demanding requirements of vehicle configurations in terms of capacity.

Although the use of sintered material friction elements in combination with steel discs provides excellent braking efficiency, it has the disadvantage of being particularly costly and producing harsh, sharp sounds, particularly at low speeds.

It should be noted that low noise has increasingly become an important determinant in selecting a disc brake to be used. As can be readily appreciated, it is most strongly felt that for those trains, such as urban trains, which should stop multiple times in a central area where there is a high population of residents, noise suppression is required during braking.

It is therefore felt the need to be able to have a brake with disc/brake friction torque for trains, which has the technical characteristics of making it both cheaper than the brakes currently used and less noisy during braking, thus reducing the overall production of harsh sounds.

The inventors of the present invention have met the above requirements by generating a disc/brake friction torque wherein the friction elements are made of a specific sintered material and the discs are made of a specific cast iron. The disc/brake friction torque as subject of the invention not only meets the above requirements, but also surprisingly ensures significant advantages in terms of wear resistance of both the disc and the friction element. The possibility of replacing the steel disc with a cast iron brake disc greatly reduces the overall cost of the disc/brake torque and surprisingly significantly reduces the noise generated during braking.

Disclosure of Invention

The present invention relates to a disc/brake friction torque for a railway vehicle comprising at least one pad comprising at least one friction element and a disc; the disc/brake friction torque is characterized in that the friction element is made of a sintered material comprising copper, iron, graphite, 0.02 to 1.5% by weight of molybdenum, 1 to 3% by weight of chromium and a porosity between 20 and 35%; and in that the disc is made of cast iron comprising 0.05 to 2% by weight of chromium, 0.05 to 2% by weight of molybdenum, 0.1 to 2% by weight of nickel.

Preferably, the sintered material of the friction element comprises 0.05 to 1% by weight of molybdenum, 1 to 1.5% by weight of chromium and between 25 and 30% of porosity.

Preferably, the sintered material of the friction element comprises 10 to 70 wt% copper, 5 to 40 wt% iron, 5 to 20 wt% graphite, 5 to 20 wt% friction modifier.

Preferably, the cast iron from which the disc is made comprises 0.1 to 2% by weight of chromium, 0.1 to 2% by weight of molybdenum, 0.5 to 1.5% by weight of nickel.

Preferably, the cast iron from which the disc is made comprises 3 to 5% by weight of carbon, 1 to 2% by weight of silicon, 0.5 to 1% by weight of manganese, 0.01 to 1% by weight of sulphur.

Preferably, the pad includes a main base plate and a plurality of friction elements fixed to the base plate.

Preferably, said cast iron disc consists of at least three circular sectors, which are separated from each other and held together by connecting elements to form a disc.

Detailed Description

For a better understanding of the present invention, the following non-limiting examples thereof are included by way of illustration.

A friction element has been formed with a sintered material that conforms to the composition shown in weight percent in table I.

TABLE I

	Minimum weight%	Maximum weight%
			Copper (Cu)	10	70
Iron	5	40
			Graphite (II)	5	20
Molybdenum (Mo)	0.02	1.5
			Chromium (III)	1	3
Friction modifiers	5	20

The sintered material also has a porosity expressed as a percentage (volume of voids compared to the total volume) between 20% and 35%.

In particular, the sintered material had the composition shown in weight percent in table II and had a porosity of 28%.

TABLE II

Copper (Cu)	50
		Iron	30
Graphite (II)	10
		Molybdenum (Mo)	0.75
Chromium (III)	1.25
		Friction modifiers	8

The above-described sintered materials have been tested as friction elements on cast iron disks produced according to the invention, which represent one embodiment of the invention and are denoted a, on cast iron disks having a composition which does not meet the requirements of the invention, which represent a first comparative example and are denoted B, and on steel disks, which represent a second comparative example and are denoted C.

The cast iron discs according to the invention must meet the composition shown in weight percent in table III.

TABLE III

In particular, the cast iron disks according to the invention have the composition shown in table IV in weight percent.

TABLE IV

	By weight%
		Carbon (C)	3.3
Silicon	1.7
		Manganese oxide	0.8
Sulfur	0.06
		Phosphorus (P)	0.02
Nickel (II)	1
		Chromium (III)	0.2
Molybdenum (Mo)	0.5
		Copper (Cu)	0.5
Tin, lead, aluminium, titanium	0.005
		Iron	Remainder of

Table V shows the composition of cast iron disks in% by weight, the composition of which does not meet the requirements of the invention.

TABLE V

The steel discs used, approved and currently marketed, have the following characteristics: 21CrMoV5-11 EN 10028-2(2003), DIN 17755 (1983).

The above-described sintered material elements have been tested on the above-described three types of disc brakes (examples a-C). In particular, these tests are performed on a chassis dynamometer and relate to friction, disk structural integrity, disk wear, friction element wear and noise tests.

The friction test was performed according to the procedure indicated in UIC 541-3ed.7prog 6A and 6B standards.

The tests concerning the structural integrity of the disks were carried out according to the procedures indicated in the EN 14535-3-C2-type (200km/h-10 t/disk) standard.

The tests concerning wear of the disc and of the friction element were carried out according to the procedures indicated in the UNI EN 14535-3 standard and the specific application tests.

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

Table VI shows the results of the above tests in indexed form for disc/brake friction torque including steel discs (example C). In this way, the advantages of the disc/brake friction torque of the present invention (example a) will be recognized very simply and directly.

TABLE VI

	A	B	C
				Friction of	100	100	100
Structural integrity of the disc	100	70	100
				Disc wear	120	40	100
Friction element wear	200	200	100
				Noise (F)	400	400	100

From the data shown in table VI, it can be seen that the disc/brake friction torque that is the subject of invention (a) not only allows the replacement of steel discs with cast iron discs, but also ensures a significant improvement in terms of wear and noise.

The above results show that thanks to the invention it is possible to provide railway vehicles with a disc/brake friction torque that is more economical than disc/brake friction torques with steel discs and at the same time it is possible to improve the performance in terms of wear of the discs and friction elements. With respect to the advantages in terms of cost-effectiveness, it is important to note that cast iron discs cost about one third of steel discs.

The inventors believe that the above-mentioned advantages of the disc/brake friction torque of the present invention result from the formation of a uniformly distributed oxide layer consisting essentially of chromium and molybdenum oxides on the surface of the disc. This oxide layer is formed during the interaction between the friction element and the disc and is very durably and firmly fixed to the disc, thus forming a high degree of protection. Using electron microscopy, it has been estimated that this layer is about 5 microns thick.

According to a preferred embodiment of the present invention, the pad includes a plurality of friction elements of reduced size rather than a single larger friction element. Each pad is composed of a main base plate and a plurality of friction elements fixed to the base plate. Each friction element consists of a metal sheet and a friction plug permanently fixed to the metal sheet.

The solution related to the use of friction elements of reduced size is advantageous both in terms of efficiency of the pressure on the disc and therefore of the braking, and in terms of low noise.

Again according to a preferred embodiment of the invention, the disc comprises at least three circular sectors, which are separated from each other and are held together by a plurality of transverse pins to form the disc. The discs thus produced are described in patent application EP0758059a1, incorporated herein by reference.