Disc brake for a railway vehicle

Abstract

The invention relates to a disc brake for a rail vehicle, comprising a brake pad (1) and a brake disc (D) on which the brake pad (1) acts; said brake pad (1) comprising a base plate (2) and a plurality of friction elements (4) fixed to said base plate (2); said friction elements (4) comprising first friction elements (4b) made of a first material and second friction elements (4a) made of a second material; said disc brake being characterized in that the compression modulus (pressure required to compress the material by 1 mm) of said second material is less than the compression modulus of said first material by a value of more than 5 MPa; the number of said first friction elements (4b) being greater than the number of said second friction elements (4a).

Description

[0001] Cross-references to related applications

[0002] This patent application claims priority to Italian Patent Application No. 102020000028781, filed on November 27, 2020, which is incorporated herein by reference in its entirety. Technical Field

[0003] This invention relates to a disc brake for rail vehicles. In particular, the invention has advantages in low- and medium-speed rail vehicles, but its application is not exclusive. Background Technology

[0004] As is well known, disc brakes are subjected to a lot of pressure. In order to achieve the best braking effect, the braking force must be well transmitted from the brake pads to the brake disc.

[0005] For some time, the field has been working to replace the larger, single friction element with multiple smaller friction elements in brake pads. One solution in this regard requires each brake pad to consist primarily of a main base plate and multiple friction elements fixed to the base plate. Typically, each friction element consists of a metal plate and friction inserts permanently fixed to the metal plate.

[0006] Solutions involving the use of multiple smaller friction elements are advantageous in terms of pressure on the brake disc and thus braking effectiveness, as well as in terms of low noise. In this regard, it should be emphasized that low noise is becoming an increasingly important criterion when selecting which disc brake to use.

[0007] It's easy to imagine that for trains that require a large number of stops, such as subways, regional trains, or intercity trains, the most important thing is to control the noise during braking.

[0008] Many solutions that reduce braking noise suffer from the following drawback: lower braking force transmission from the brake pads to the brake discs, thus reducing the efficiency of the braking itself. In fact, it is clear that trains that make frequent stops (low- and medium-speed trains), even if they are not traveling at very high speeds, must be able to maintain high braking efficiency under all circumstances.

[0009] Herein and below, the term "medium-low speed train" refers to a train with a maximum speed of 220 km / h.

[0010] Another particularly important requirement related to brakes used on trains that make multiple stops is reducing pollution from fine dust generated during braking. In fact, the trains considered above repeatedly pass through and stop in densely populated areas, such as residential areas.

[0011] Typically, solutions that reduce braking noise have the drawback of requiring the release of large amounts of fine powder. Summary of the Invention

[0012] Therefore, there is a need for a disc brake for medium and low speed trains, whose technical feature is to ensure low noise during braking without causing disadvantages in braking efficiency and fine powder generation.

[0013] The inventors of this invention provide a solution for brake pads in disc brakes for medium- and low-speed trains, wherein the simultaneous presence of friction elements made of materials with different compression moduli, depending on specific conditions, ensures that the above requirements are met in a surprising way.

[0014] Subject matter of the invention

[0015] The subject of this invention is a disc brake for rail vehicles, comprising brake pads and a brake disc on which the brake pads act. The brake pads include a base plate and a plurality of friction elements fixed to the base plate; the friction elements include a first friction element made of a first material and a second friction element made of a second material; the disc brake is characterized in that the compressive modulus of the second material (the pressure required to compress the material by 1 mm) is at least 5 MPa less than the compressive modulus of the first material, preferably at least 10 MPa less; and the number of the first friction elements is greater than the number of the second friction elements.

[0016] It has been confirmed that a 5 MPa difference in compressive modulus already results in a significant reduction in noise. The noise reduction becomes even more pronounced when the compressive modulus exceeds 10 MPa.

[0017] Preferably, the friction elements are arranged in arched rows and overlap with the corresponding concentric lines of the brake disc on which the brake pads act during use; each arched row includes the first friction element and the second friction element.

[0018] Preferably, in each arched row, the number of the first friction elements is equal to or greater than the number of the second friction elements.

[0019] Preferably, the first material has a compressive modulus between 20 MPa and 40 MPa, and the second material has a compressive modulus between 2 MPa and 15 MPa.

[0020] Preferably, the first material is a sintered material and the second material is an organic material.

[0021] Preferably, the sintering material is composed of: 10% to 70% copper, 5% to 40% iron, 5% to 20% graphite, and 1% to 10% friction modifier.

[0022] Preferably, the organic material comprises: 5% to 30% by weight of rubber and resin, 10% to 50% by weight of filler, 5% to 20% by weight of graphite, and 5% to 20% by weight of friction modifier. Attached Figure Description

[0023] To better understand the invention with the aid of the accompanying drawings, the following describes one embodiment by way of non-limiting example only, wherein:

[0024] Figure 1 This is a top view of the brake pad, which is the subject of this invention, with transparent parts for clarity;

[0025] Figure 2 This is a top view comparing brake pads; for clarity, transparent parts are included.

[0026] Figure 3 Is the recording of noise results as Figure 1 A graph showing the speed changes related to the pads in the circuit.

[0027] Figure 4 The recorded noise results are subject to change. Figure 2 A graph showing the speed changes related to the brake pads;

[0028] Figure 5 It was recorded Figure 1 and Figure 2 A graph showing the results of friction on the brake pads. Detailed Implementation

[0029] exist Figure 3 In the figure, reference numeral 1 as a whole denotes a brake pad for a disc brake according to the present invention.

[0030] Brake pad 1 includes: a base plate 2; a dovetail connector 3 attached to the rear surface of the base plate 2 and responsible for attaching the brake pad 1 itself to the disc brake structure; and a plurality of friction elements 4 attached to the base plate 2 and arranged to apply pressure to the brake disc to perform braking action.

[0031] For the purposes of this invention, it is irrelevant whether the friction element 4 is temporarily or permanently attached to the plate 2.

[0032] The friction element 4 is arranged along an arched row shown in dashed lines and indicated by reference numeral 5. In use, it substantially overlaps with the concentric line of the brake disc D on which the brake pad 1 acts. For simplicity, the brake disc D is shown in dashed lines and only partially.

[0033] The friction element 4 is divided into five friction elements 4b made of sintered material and three friction elements 4a made of organic material. For clarity, the friction element made of organic material 4a is represented by a dashed surface.

[0034] The organic material of the friction element 4a has a composition that satisfies the following conditions: 5% to 30% by weight of rubber and resin, 10% to 50% by weight of filler, 5% to 20% by weight of graphite, and 5% to 20% by weight of friction modifier.

[0035] The organic material has a compressive modulus of 7 MPa.

[0036] The sintering material of friction element 4b has a composition that satisfies the following conditions: 10% to 70% copper, 5% to 40% iron, 5% to 20% graphite, and 1% to 10% friction modifier.

[0037] The sintered material has a compressive modulus of 27 MPa.

[0038] To measure the compressive modulus, a cylindrical specimen with a diameter of 11.3 mm and a height of 10 mm was taken perpendicular to the friction surface. In this way, the obtained cylinder has a diameter of 100 mm. 2 The sample was placed under the test head of a (Galdabini QUASAR 100) traction / compressor, and a gradually increasing force was applied at a rate of 7.45 daN / s. The compression modulus was calculated in MPa by normalizing the compression curves detected based on several key points of the curves themselves. The resulting value related to compression per 1 mm was then divided by the area of ​​the cylindrical sample (100 mm²). 2 Conversely, both the first and second materials can be sintered materials or organic materials, provided that they meet the compression modulus requirements included in the scope of the claim.

[0039] Not only can materials with different compressive moduli be obtained from materials with different chemical properties, but materials with different compressive moduli can also be obtained from materials of the same chemical type through different preparation processes.

[0040] For example, by changing the porosity of the resulting material, its compressibility can be altered.

[0041] exist Figure 2 In the figure, reference numeral 11 generally indicates a brake pad for a disc brake according to a comparative example.

[0042] The parts of the second brake pad 11 that are the same as those of the first brake pad 1 will be indicated by the same number and will not be described again.

[0043] Since all friction elements 4 are friction elements 4b made of sintered material, the second brake pad 11 is different from the first brake pad 1.

[0044] Noise measurements of the first brake pad 1 and the second brake pad 11 during braking were performed according to the procedures specified in UIC 541-3 No. 5B (7th edition), and friction tests were performed according to the procedures specified in UIC 541-3 No. 5B (7th edition).

[0045] Figure 3 and Figure 4 Includes graphs related to noise tests performed on brake pad 1 and brake pad 11, respectively.

[0046] Each graph contains different curves, which are related to different operating conditions and the force (pressure) exerted by the brake pads on the brake disc.

[0047] Of course, in Figure 3 and Figure 4 In the graphs, curves represented in the same way are produced under the same applied force conditions.

[0048] In each graph, there is a permissible line, which indicates that braking noise of up to 100 decibels is allowed at speeds of 80 km / h, while braking noise of up to 90 decibels is allowed below 60 km / h (where the train may be inside a station).

[0049] from Figure 3 and Figure 4 It can be clearly seen that the brake pads (which are the subject of this invention) Figure 3 The graph in the image shows how noise consistently falls below the permissible limit. In contrast, under most operating conditions, the brake pads ( Figure 4 The noise generated by the graphic is higher than the noise indicated by the permissible line for speeds below 60 km / h.

[0050] Figure 5 The graph contains records of different operating conditions (force and velocity of the brake pads on the disc). Figure 1 The brake pads (INV.) of the present invention and Figure 2 The friction values ​​on the brake pads (CONF.) are compared.

[0051] from Figure 5 The graphs clearly show that, despite some friction elements having lower compressive moduli, the brake pads of this invention surprisingly ensure the same performance in terms of friction as the comparative brake pads. This result allows for noise reduction without compromising braking performance.

[0052] Furthermore, the presence of most friction elements made of materials with higher compressive modulus ensures less fine powder generated due to friction applied during braking.

[0053] In summary, the present invention relates to a brake pad for a disc brake, wherein the presence of friction elements made of materials with different compression moduli can surprisingly reduce noise generated during braking. Figure 3 and Figure 4 (Comparison between), without therefore having the same braking efficiency as ( Figure 5 The disadvantages associated with high fine powder production are...

Claims

1. A disc brake for a rail vehicle, comprising a brake pad (1) and a brake disc (D), the brake pad (1) acting on the brake disc (D); the brake pad (1) comprising a base plate (2) and a plurality of friction elements (4) fixed on the base plate (2); the friction elements (4) comprising a first friction element (4b) made of a first material and a second friction element (4a) made of a second material; the disc brake is characterized in that the compressive modulus of the second material is at least 5 MPa less than the compressive modulus of the first material, wherein, The compression modulus is the pressure required to compress the material by 1 mm; the number of the first friction element (4b) is greater than the number of the second friction element (4a).

2. The disc brake for rail vehicles according to claim 1, characterized in that, The compressive modulus of the second material is more than 10 MPa smaller than that of the first material.

3. The disc brake for rail vehicles according to claim 1, characterized in that, The friction elements (4) are arranged in arched rows (5) and, in use, overlap with the respective concentric lines of the brake disc (D) to which the brake pads (1) act; each arched row (5) includes the first friction element (4b) and the second friction element (4a).

4. The disc brake for rail vehicles according to claim 3, characterized in that, In each arched row (5), the number of the first friction element (4b) is equal to or greater than the number of the second friction element (4a).

5. The disc brake for rail vehicles according to claim 1, characterized in that, The first material has a compressive modulus between 20 MPa and 40 MPa, and the second material has a compressive modulus between 2 MPa and 15 MPa.

6. The disc brake for rail vehicles according to claim 1, characterized in that, The first material is a sintered material, and the second material is an organic material.

7. The disc brake for rail vehicles according to claim 6, characterized in that, The sintering material is composed of: 10% to 70% copper, 5% to 40% iron, 5% to 20% graphite, and 1% to 10% friction modifier.

8. The disc brake for rail vehicles according to claim 6, characterized in that, The organic material is composed of: 5% to 30% by weight of rubber and resin, 10% to 50% by weight of filler, 5% to 20% by weight of graphite, and 5% to 20% by weight of friction modifier.

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