Method of manufacturing brake pad with improved back plate

Abstract

The invention relates to a method for manufacturing a brake pad comprising a backing plate (10) and a friction lining (12), comprising at least the following steps: a) preparing the backing plate (10) for attaching the friction lining (12) to the backing plate (10), with or without an intermediate layer between the backing plate (10) and the friction lining (12), b) roughening at least a portion of the surface area of the backing plate (10), and c) attaching the friction liner (12) to the roughened surface of the backing plate, where the surface of the backing plate is roughened using a pulsed high pressure water jet (4).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing brake pads, in particular disc brake pads, characterized in that, inter alia, the brake pad carrier plate (backplate) is pre-treated or improved. Background Art

[0002] Brake pads for motor vehicles generally consist of a backplate and a friction lining attached thereto. An additional intermediate layer can be installed between the friction lining and the backplate, which is usually used as a noise reduction layer. In this case, the intermediate layer is attached to the friction lining and the backplate. The friction lining or the intermediate damping layer is usually attached to the backplate with an adhesive. If the friction lining consists of sintered material or contains a sufficient amount of such materials, it can also be attached to the backplate by hot pressing instead of an adhesive. In addition, the friction lining can also be attached to the surface of the backplate using fasteners such as bolts, pins and rivets.

[0003] In order to improve the bonding between the friction lining or the intermediate layer and the backplate, the surface of the backplate is usually treated or prepared using the latest techniques. For this purpose, the backplate is mechanically treated, for example, to produce small roughness (crimping) on the surface of the backplate. For example, if the backplate is made of a casting material such as gray cast iron, during the casting process, the holding element can be directly attached to the surface or the edge of the backplate. Finally, the surface can also be constructed by using a laser beam or sandblasting to make the backplate better adhere to the friction lining.

[0004] For example, DE19712203A1 shows a method for manufacturing brake pads. If the backplate consists of a carrier plate made of rolled or unrolled steel, it is considered advantageous to treat the backplate, for example, by a chemical pickling process, sandblasting or water spraying or other surface removal or deformation processes to make it better adhere to the friction lining. Pickling in a phosphating device is preferred.

[0005] DE3232865A1 also shows a method for manufacturing brake pads. A water jet is used to clean the iron pressing plate, producing a surface roughness with an average roughness value (Ra) of 0.8 to 1.3 μm. However, the surface must be coated to ensure reliable bonding with the friction lining. A dry rough spraying process (such as sandblasting) can achieve a surface roughness with an average roughness value (Ra) of 7.7 to 8.7 μm.

[0006] US6269669B1 shows a wet sandblasting process using particles for the backplate. According to US6269669B1, the backplate is usually roughened to a surface roughness with an average roughness value (Ra) between 2 and 7 μm to improve the bonding with the friction material.

[0007] EP1178236A2 also shows a wet blasting process using particles for backing plates, wherein a primer is given a preferred surface roughness with an average roughness value (Ra) of 1.5 to 7 μm, and then the friction material is applied to the surface roughness. The preferred roughness depth (Rz) is 10 to 30 μm.

[0008] JP5328609B2 shows a steel ball blasting method for a backing plate. The surface roughness of the sandblasted backing plate is between 5 and 15 or 20 μm. After sandblasting, an adhesive for the friction material is applied to the backing plate.

[0009] DE 10 2019 213 464 A1 shows a method for manufacturing a friction brake body, wherein the backing plate consists of grey cast iron with embedded graphite. Before the friction lining is coated, a water jet is used to reduce or remove the graphite near the surface. Laser cladding is used to apply the coating to the friction lining.

[0010] Furthermore, surface treatment using water jet processes is well known. Ecoclean-Group / DE offers processes and equipment for preparing metal surfaces prior to thermal spraying processes for applying hard metals or carbides.

[0011] The above measures taken during the manufacture of brake pads to improve the bonding of the intermediate layer or friction lining to the backing plate surface are complex, time-consuming and costly and therefore need to be improved. They also have the problem of requiring additional cleaning steps to remove substances added during the preparation process (e.g. sand particles) or particles generated during the processing (e.g. swarf, metal particles). Summary of the invention

[0012] The basis of the present invention is therefore to provide a method for manufacturing a brake pad which avoids or minimizes as far as possible the disadvantages occurring in the prior art while ensuring a strong and permanent bond between the friction lining and the backing plate.

[0013] Furthermore, it aims to determine whether additional benefits can be achieved by improving the bond between the friction lining and the backing plate, such as increased safety in high-performance applications (e.g. racing), and improved comfort, such as reduced noise when braking.

[0014] According to the invention, when manufacturing brake pads, it is therefore proposed to prepare the backing plate by roughening the surface (totally or partially) to receive the adhesive and the intermediate layer, the adhesive and the friction lining, or preferably to receive the intermediate layer and / or the friction lining without the previous application of adhesive. According to the invention, the roughening process enables a good bond between the backing plate and the friction material or the intermediate layer to be achieved even without the use of adhesive.

[0015] According to the present invention, the backplate is prepared by roughening the surface to which the intermediate layer or friction lining is to be applied. For this purpose, an adhesive layer can first be applied to the roughened surface. Preferably, the intermediate layer or friction lining is directly hot-pressed onto the roughened surface. The parameters for this purpose, such as pressure and temperature, correspond to the values in the prior art and are well known to those skilled in the art.

[0016] The roughening process is carried out using a (high-pressure) water jet. Suitable equipment for such water jet treatment is commercially available, for example, provided by Ecoclean Group / DE.

[0017] The preferred design and parameters of the method according to the present invention are explained in more detail below.

[0018] The so-called pulsating medium-pressure water jet technology, such as the technology sold by Ecoclean, is the preferred method. The water jet nozzle, preferably in the form of a pulsed water jet nozzle, operates together with a so-called ultrasonic transducer at a constant working pressure. Preferably, the working pressure is up to 850 bar, and the pulsation range generated by the ultrasonic transducer is up to about 20,000 pulses per second (20 kHz). Preferably, the water flow rate is much higher than 50 m / s, especially up to 380 m / s. The water temperature usually corresponds to the pipeline temperature (the supplier provides the water temperature in the network), or within the range of the pipeline temperature and the ambient or room temperature. Usually, it is not necessary to heat the water above room temperature.

[0019] It has been shown that the use of pulsed water jets is generally necessary to achieve sufficient roughening of the backplate surface according to the present invention. This is especially applicable to metal surfaces. Pulsed water jets with a water pressure between 600 and 850 bar are preferably used. The pulsation is preferably between 10 and 25 kHz, and even more preferably between 10 and 20 kHz.

[0020] Surprisingly, it has been found that, compared to the same brake pads with the same untreated backplate, the brake pads with the backplate treated according to the present invention produce much less noise during braking. This is because the backplate treated according to the present invention exhibits an increased damping effect. In the tests carried out so far, the damping has increased by 6.4% to 23% compared to traditional brake pads. Depending on the type of backplate and friction material, it can increase to more than 30%. The increase in the damping effect during braking and the consequent significant noise reduction are due to the greatly increased surface roughness generated according to the present invention, which is much higher than the surface roughness conventionally used for backplates so far.

[0021] Therefore, the present invention also relates to a method for reducing the noise caused by brake pads during braking when driving using the brake pads according to the present invention, and a method for manufacturing brake pads for this purpose using the backplate according to the present invention.

[0022] According to the present invention, a surface roughness with a roughness depth (Rz) of 50 to 500 μm is preferred, and more preferably a surface roughness of 100 to 350 μm, particularly 150 to 300 μm. The preferred method for measuring the surface roughness is to use a microscope to determine the microscopic pattern of the surface treated according to the present invention. This type of microscopic pattern is as Figure 3 shown.

[0023] The prior art has introduced various methods for measuring the roughness depth (Rz). In particular, measuring devices from different suppliers known to those skilled in the art are described (for example, see the entry under the German Wikipedia keyword "Rauheitsmessung").

[0024] Depending on the type of backplate and friction material, an increase in the surface roughness with a roughness depth (Rz) of at least 100 μm can significantly reduce the noise level during the braking process of the brake pad, where the backplate has been treated according to the present invention. For example, when the surface roughness with a roughness depth (Rz) of 200 to 300 μm is achieved, particularly good damping and noise reduction effects can be realized.

[0025] For example, in the master's thesis of N. O'Neil ("Optimized Surface Roughening by Pulsed Waterjet for Suitable Adhesion Strengh of Plasma Transferred Wire Arc Coating"), Carleton University, Ottawa, Ontario, 2020; see pages 49, 53, 63, and 64 (https: / / repository.library.carleton.ca / downloads / z890rv29c), general and example information regarding metal surface treatment and the interaction of process parameters with these materials (taking aluminum alloy A380 and gray cast iron (GCI) as examples) can be found. It also contains information regarding measurement methods and instruments applicable to various process parameters.

[0026] The speed at which the water jet is guided through the surface of the backplate to be treated is generally between 1 and 10 mm / s, preferably 1 to 4 mm / s, particularly 2 to 3 mm / s. These specifications preferably refer to a steel backplate. According to the present invention, softer materials, such as aluminum or aluminum alloys, can also be roughened at a higher speed.

[0027] Preferably, the water jet nozzle is positioned perpendicular to the surface to be treated. However, treatment can also be carried out from different angles. This is advantageous for treating a back plate having a partially recessed surface for positioning a friction lining. Treatment at an inclined angle can even sufficiently roughen the inner edge of the back plate. The distance between the surface of the back plate and the nozzle is preferably in the range of 10 to 70 mm, particularly in the range of 15 to 50 mm.

[0028] To ensure that the friction material can penetrate the surface well or adhere to the surface as firmly as possible, the entire surface of the back plate is usually treated according to the present invention.

[0029] According to the present invention, it may be advantageous to add a substance to the water used, which can prevent corrosion of the surface of the back plate in the short term. This is preferably triethanolamine with a concentration of less than 3%. An example of a commercial product is Castrol Techniclean HP, which is preferably added to the water at a concentration of 1.5% to 3% (by weight).

[0030] By generating the microscopic pattern of the treated surface, the penetration of the friction material into the roughened surface can be shown and examined. These images show the differences (Hinterscheidungen) and anchoring of the friction material on the treated surface with good resolution.

[0031] The back plate for the purposes of the present invention is preferably made of steel, preferably made of low-carbon steel, metal alloys based on iron and / or titanium, metal alloys with carbon fibers, and glass fiber or carbon fiber-reinforced plastics (GFRP and / or CFRP). Corresponding lightweight back plates are known in the prior art and are described, for example, in US2017204920A1.

[0032] Therefore, according to the present invention, the advantages of the method of manufacturing a brake pad using a back plate having a surface roughened by a water jet process are obvious:

[0033] - Compared with the corresponding methods of processing back plates known at present, the proposed water jet treatment is more time-saving and cost-effective.

[0034] - The surface of the back plate does not leave unwanted residues like other particle jetting methods such as sandblasting.

[0035] - The roughened surface is cleaned simultaneously without the need for an additional cleaning step.

[0036] - The water jet treatment does not require the use of additional substances that increase the process cost, such as surfactants or cleaners, and

[0037] - The method according to the present invention is also particularly suitable for low-cost back plates made of casting materials, such as gray cast iron. Description of the Drawings

[0038] Figure 1 Shows the steel backplate (a) in the untreated state after delivery and the surface of the same backplate after water jet treatment according to the present invention (b). The water jet forms a clean backplate surface with undercuts.

[0039] Figure 2 Shows the structure of a preferred pulsed water jet nozzle according to the present invention.

[0040] Figure 3 Shows a schematic diagram of a microscope image of a cross-section or microscopic pattern of the surface of a backplate treated according to the present invention.

[0041] Figure 4 Shows a schematic diagram based on a SEM (scanning electron microscope) image of a cross-section of a brake pad manufactured according to the present invention.

[0042] Figure 5 Shows the water jet 4 flowing out from the pulsed water jet nozzle 1 as shown in Figure 2 . The water jet has a bubble shape, which corresponds to the pulse of the ultrasonic transducer 2 of the pulsed water jet nozzle 1. The pulsed water jet 4 can generate a cavitation effect on the metal surface.

[0043] Figure 6 Shows a cross-section of an aluminum sample roughened by a pulsed water jet at different water pressure levels. Figure 6 The water pressure of the water jet in [] can be 20 MPa, 30 MPa or 40 MPa.

[0044] Figure 7 Shows the measured damping coefficients of the roughened sheets and the conventional series of sheets according to the present invention. In all characteristic modes, the roughened sheets have a higher damping coefficient than the conventional series of sheets. The conventional series of sheets have brass pins as friction material retaining function members, and two chamfers, namely a top chamfer and a radial chamfer. The roughened sheets have the same backplate as the conventional series of sheets, but the brass pins are omitted. The roughened sheets have the same friction material but no chamfers. Detailed Description of the Invention

[0045] Except for the roughening of the backplate surface according to the present invention, the brake pads are manufactured by methods known in the prior art for applying friction material or friction linings to the backplates of various brake pads (with or without an intermediate layer provided between the friction lining and the backplate). This is usually done by pressing the backplate against the friction material / friction lining at increased pressure and temperature.

[0046] To further improve the stability of the brake pads according to the present invention, an adhesive can be applied to the surface of the backplate before connecting the friction lining.

[0047] Figure 1 The surface of the backplate shown in b is treated with a water jet at a speed of 3 mm / s. The treatment is carried out at room temperature. The pressure of the water jet is about 760 bar.

[0048] Figure 3 The roughness depth of the surface of the backplate shown is up to about 500 μm. This surface is treated with a water jet at a speed of 1 mm / s. The pressure of the water jet is about 760 bar. The surface of the backplate shown is made of steel.

[0049] Figure 4 The area to be roughened on the backplate 10 of the brake pad shown is treated with a water jet according to the Figure 1 parameters mentioned. The backplate 10 is made of steel. The roughness depth of the roughened surface of the backplate 10 is mainly between 150 and 300 μm. The friction material 12 is directly pressed on the roughened surface of the backplate 10. The roughened surface of the backplate 10 causes interlocking 14 with the friction material 12, improves the bonding, and significantly reduces noise.

[0050] List of reference numerals

[0051] 1: Pulse water jet nozzle

[0052] 2: Ultrasonic transducer

[0053] 3: High-pressure chamber

[0054] 4: Pulse high-pressure water jet

[0055] 5: Nozzle chamber

[0056] 6: Oscillating magnetic core

[0057] 7: High-pressure water inlet

[0058] 10: Backplate

[0059] 12: Friction lining

[0060] 14: Interlocking of friction lining and backplate

Claims

1. A method for manufacturing a brake pad comprising a backplate (10) and a friction lining (12), at least comprising the following steps: a) Prepare the backplate (10) for attaching the friction lining (12) thereto, with or without an intermediate layer provided between the backplate (10) and the friction lining (12), b) Roughen at least a part of the surface area of the backplate (10), and c) Attach the friction lining (12) to the roughened surface of the backplate, characterized in that a pulsed high-pressure water jet (4) is used to roughen the surface of the backplate.

2. The method according to claim 1, wherein The part of the surface area is roughened to a surface roughness with a roughness depth of 50 to 500 microns.

3. The method according to claim 1 or 2, characterized in that, The part of the surface area is roughened to a surface roughness with a roughness depth of 100 to 350 microns.

4. The method according to any one of claims 1 to 3, characterized in that, The surface of the backplate is not treated with any adhesive after roughening and before applying the friction lining (12) or the intermediate layer.

5. The method according to any one of claims 1 to 4, characterized in that If the backplate is composed of an aluminum-based metal alloy, the water pressure of the water jet is between 600 and 850 bar or between 200 and 400 bar.

6. The method according to any one of claims 1 to 5, characterized in that The pulsation range of the water jet is 10,000 to 20,000 pulses per second.

7. The method according to any one of claims 1 to 6, characterized in that, The speed of the water jet is 150 to 380 m / s.

8. The method according to any one of claims 1 to 7, characterized in that, The water jet traverses the surface of the backplate to be roughened at a speed of 1 to 10 mm / s, preferably 1 to 4 mm / s, especially 2 to 3 mm / s.

9. The method according to any one of claims 1 to 8, characterized in that, The outlet nozzle of the water jet moves at a distance of 15 mm to 50 mm from the surface of the backplate to be roughened.

10. The method according to any one of claims 1 to 9, characterized in that, The water jet impacts the surface of the backplate to be roughened at a perpendicular angle.

11. The method according to any one of claims 1 to 9, characterized in that, The water jet impacts the surface of the backplate to be roughened at an inclined angle.

12. The method according to any one of claims 1 to 11, characterized in that, A corrosion-inhibiting substance is added to the water jet.

13. The method according to any one of claims 1 to 12, characterized in that, The backplate (10) is made of an iron-based, titanium-based or aluminum-based metal alloy, a metal alloy with carbon fibers, or a glass fiber-reinforced or carbon fiber-reinforced plastic.

14. Use of a backplate (10) roughened by the method according to any one of claims 1 to 13 for manufacturing a brake pad.

15. A method for reducing braking noise caused by brake pads, characterized in that, Use of a brake pad produced by the method according to any one of claims 1 to 13 in a vehicle.

16. Use of a brake pad manufactured by the method according to any one of claims 1 to 13 for reducing brake noise caused by the brake pad.

17. A brake pad manufactured by the method according to any one of claims 1 to 13.

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