EP4214423A1 - Method to select an elastomeric material for making an underlayer of a braking pad and corresponding braking pad - Google Patents

Method to select an elastomeric material for making an underlayer of a braking pad and corresponding braking pad

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Publication number
EP4214423A1
EP4214423A1 EP21770316.4A EP21770316A EP4214423A1 EP 4214423 A1 EP4214423 A1 EP 4214423A1 EP 21770316 A EP21770316 A EP 21770316A EP 4214423 A1 EP4214423 A1 EP 4214423A1
Authority
EP
European Patent Office
Prior art keywords
underlayer
elastomeric material
braking pad
frequency
volume
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21770316.4A
Other languages
German (de)
French (fr)
Inventor
Agustin Sin Xicola
Simone BALESTRA
Valentina IODICE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ITT Italia SRL
Original Assignee
ITT Italia SRL
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ITT Italia SRL filed Critical ITT Italia SRL
Publication of EP4214423A1 publication Critical patent/EP4214423A1/en
Pending legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D65/00—Parts or details
    • F16D65/0006—Noise or vibration control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D65/00—Parts or details
    • F16D65/02—Braking members; Mounting thereof
    • F16D65/04—Bands, shoes or pads; Pivots or supporting members therefor
    • F16D65/092—Bands, shoes or pads; Pivots or supporting members therefor for axially-engaging brakes, e.g. disc brakes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D69/00—Friction linings; Attachment thereof; Selection of coacting friction substances or surfaces
    • F16D69/02—Composition of linings ; Methods of manufacturing
    • F16D69/025—Compositions based on an organic binder
    • F16D69/026—Compositions based on an organic binder containing fibres
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D69/00—Friction linings; Attachment thereof; Selection of coacting friction substances or surfaces
    • F16D2069/005—Friction linings; Attachment thereof; Selection of coacting friction substances or surfaces having a layered structure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D69/00—Friction linings; Attachment thereof; Selection of coacting friction substances or surfaces
    • F16D2069/005—Friction linings; Attachment thereof; Selection of coacting friction substances or surfaces having a layered structure
    • F16D2069/007—Friction linings; Attachment thereof; Selection of coacting friction substances or surfaces having a layered structure comprising a resilient layer

Definitions

  • This disclosure is relating to a method to select an elastomeric material for making an underlayer of a braking pad and to the corresponding braking pad.
  • the underlayer in this disclosure is specifically intended as a layer of a braking pad, in particular a vehicle brake pads or blocks, and/or friction discs.
  • An aim of the present invention is a method to select an elastomeric material or rubber for making an underlayer of a braking pad.
  • a further aim of this disclosure is to provide a braking pad comprising an underlayer and a corresponding underlayer capable to reduce the cold noise.
  • a further aim of the present invention is a low cold noise generating underlayer to be associated to a friction material to form a braking pad or element.
  • a braking pad is also obtained according to claim 9.
  • Figure 1 schematically illustrates the graph of pressure v number of brakes in a cold noise test
  • Figure 2 schematically illustrates the graph of initial temperature v number of braked in the same test of Fig. 1 ;
  • Figures 3 and 4 show a topography of tan ⁇ of an underlayer according to comparative example 1 and respectively of inventive example 2;
  • Figures 5 and 6 show a topography of tan ⁇ of an elastomeric material used in the underlayer of comparative example 1 and, respectively, inventive example 2;
  • Figures 7 and 8 show a graph of Amplitude (db) v Pad temperature measuring the global noise obtained with a standard underlayer (standard UL) from comparative example 1 at 12 Khz and at 9 Khz in Fig. 7 and, respectively, the global noise obtained with the inventive underlayer of example 2 at the same frequencies in Fig. 8.
  • a new method has been found to select an elastomeric material for an underlayer of a braking pad in order to reduce the cold noise.
  • elastomeric material is intended a natural or synthetic rubber or a polymer with viscoelasticity.
  • the method characterizes the viscoelastic properties of the elastomeric material that is part of a layer of a braking pad.
  • the layer is usually known and in the following referred to as underlayer.
  • the method to select an elastomeric material for making an underlayer of a braking pad to reduce the cold noise comprises the steps of characterizing the viscoelastic properties of said underlayer through the DMTA method by calculating the elastic modulus and the viscous modulus of a specimen of the underlayer through the following formulas:
  • L, h and b are the length, height and thickness of the specimen, respectively
  • ⁇ is the phase shift between the applied force F and the displacement D
  • damping tan ⁇ is calculated as the ratio between the viscous modulus and elastic modulus according to the following formula:
  • the method to select an elastomeric material for making an underlayer of a braking pad to reduce the cold noise comprises the steps of characterizing the viscoelastic properties of an elastomeric material through the DMTA method by calculating the elastic modulus and the viscous modulus of a specimen of the elastomeric material through the following formulas Elastic modulus
  • L, h and b are the length, height and thickness of the specimen, respectively
  • an underlayer comprising from 5 to 25% in Volume of said elastomeric material, said elastomeric material having a tan ⁇ ⁇ 0.6 between a temperature of -40°C and 0°C and with a frequency between 20 Hz and 20 kHz.
  • DMTA analysis acronym for Dynamic Mechanical Thermal Analysis. This known laboratory test is useful for studying the viscoelastic behavior of polymers, such as elastomers and elastomeric mixtures. As it is know how to apply the DMTA method to a specimen, it is not described here in further details.
  • L, h and b are the length, height and thickness of the specimen, respectively
  • ⁇ is the phase shift between the applied force F and the displacement D
  • the elastic modulus and the viscoelastic modulus are calculated with the DTMA method, they are used in a further step of the method in combination with the Maxwell model (see G.C. Papanicolaou, S.P. Zaoutsos, in Creep and Fatigue in Polymer Matrix Composites (Second Edition), 2019 chapter 1.7.3 and 1.15.3) to analyze the elastomeric materials.
  • the Maxwell model considers a spring (elastic element) and a dashpot or heat sink (viscous element) in series.
  • the total deformation of the material is given by the sum of the elastic part plus the viscous part, the same is true for the temporal derivative of the deformation, i.e. the speed of the deformation.
  • the elastic and viscous modulus depend on the stress frequency and the temperature.
  • the elastic and viscous response can be varied by changing the stress frequency and the temperature.
  • Tan ⁇ is therefore defined as the ratio between the viscous modulus and elastic modulus, this property is often described as the ability to lose energy as heat (damping) as according to Cit. Menard, K. P., & Menard, N. (1999). Dynamic mechanical analysis. Encyclopedia of Analytical Chemistry: Applications, Theory and Instrumentation, 14- 16.
  • the material responds completely elastically, decreasing the frequency, the material increases its viscous response properties until it reaches the glass transition. Following, decreasing the frequency, we have the elastomeric material plateau.
  • This principle connects the frequency and the temperature to the elastic and viscous properties of a material as calculated with the above DTMA method. Having high temperatures means having low stress frequencies and vice versa.
  • the elastic and viscous modulus are subsequently measured at different frequencies between 1 Hz and 200KHz and for different isotherms creating bi-dimensional topographies. Adjacent isotherms are subsequently compared to calculate the average translation factor between two isotherms in the overlap zone, i.e, in the area where the same elastic modules can be found, but at different frequencies and temperatures.
  • the overlap zone between adjacent isotherms (Ti and Ti + 1) is found.
  • the algorithm reads as input the elastic and viscous modulus data measured by the DMTA. It performs a polynomial regression of third order for each isotherm and then it finds the overlap zone between adjacent isotherms.
  • Exemplary topography of a comparative underlayer and of an underlayer according to the invention are given in Fig. 5 and 6 and corresponding topography of the elastomeric materials used in the underlayer are given in Fig. 7 and Fig. 8.
  • the braking pad comprises a friction material, an underlayer and a backplate, wherein preferably the underlayer comprises from 5 to 25% of elastomeric material in Volume over the total volume of the underlayer, more preferably from 15 to 20% in volume.
  • the underlayer comprises preferably from 10% to 15% in Volume of steel fiber.
  • the underlayer comprises from 15 to 25% of organic fiber.
  • the underlayer comprises from 10 to 20%, more preferably from 8 to 16% of a binder.
  • the underlayer comprises from 15 to 20 % of a Filler.
  • the elastomeric material is an elastomer having a saturated chain of the polyethylene type.
  • the elastomeric material having the best damping properties are preferably chosen in the group consisting of EPM (Ethylene propylene monomer rubber), EPDM ((ethylene propylene diene monomer rubber), EPR (Ethylene propylene rubber), CIIR (Chlorobutyl Rubber), TPES (Thermoplastic Elastomers), TPU (Thermoplastic Polyurethane), POE (Polyolefin elastomers), SEBS-mA (styrene-(ethylene-butylene)-styrene grafted with maleic anhydride) and their mixtures.
  • the filler is preferably barite.
  • the underlayer of the preferred embodiment achieves a very good damping in the cold range and there isn’t braking noise in the cold range.
  • the elastomeric material used in the standard underlayer is ACR.
  • the composition of the preferred underlayer is reported in the table 2 below:
  • the elastomeric material used in the inventive example 2 is EPDM.
  • the cold noise of the underlayer is measured according to the specific test “cold noise test” procedure on the dynamometer consisting of 2034 braking following the SAEJ 2521 section cold. Each braking block has different pressure and temperature conditions as depicted in Figures 1 and 2. The test is done in a climatic chamber because Cold noise appears well below the room temperature.
  • the climatic chamber is at room temperature, then the temperature is decreased at -20°C and then risen again in five degrees steps up to 25°C.
  • Braking must be spaced out in time so as not to overheat the braking system.
  • the brake application is controlled by the disc temperature, for instance the brake starts when the disc surface reach 50°C.
  • the temperature is measured inside the underlayer using a thermocouple. For each braking, the noise generated by the pad is recorded with a microphone.
  • the cold noise can be reduced from 37% of noisy braking down to only 0.5%.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Braking Arrangements (AREA)

Abstract

It is disclosed a method to select an elastomeric material for making an underlayer of a braking pad to reduce the cold noise, said underlayer comprising at least one elastomeric material and said method comprising the steps of characterizing the viscoelastic properties of the elastomeric material through the DMTA method by calculating the elastic modulus and the viscous modulus of a specimen of the underlayer through the following formulas Elastic modulus (I) Viscous modulus (II) wherein: F force applied by the mechanical probe D displacement of the probe Ω frequency of the probe stress frequency m the mass of the specimen L, h and b are the length, height and thickness of the specimen, respectively Δ is the phase shift between the applied force F and the displacement D - Calculating the damping tan δ as the ratio between the viscous modulus and elastic modulus according to the following formula: (III) - Selecting an underlayer having a tan δ ≥0.06 between a temperature of -40°C and 0°C and with a frequency of between 20 Hz and 20 kHz.

Description

METHOD TO SELECT AN ELASTOMERIC MATERIAL FOR MAKING AN
UNDERLAYER OF A BRAKING PAD AND CORRESPONDING BRAKING PAD
Cross-Reference To Related Applications
This patent application claims priority from Italian patent application no. 102020000021889 filed on 17/09/2020., the entire disclosure of which is incorporated herein by reference.
Technical Field
This disclosure is relating to a method to select an elastomeric material for making an underlayer of a braking pad and to the corresponding braking pad.
The underlayer in this disclosure is specifically intended as a layer of a braking pad, in particular a vehicle brake pads or blocks, and/or friction discs.
Summary of the Invention
An aim of the present invention is a method to select an elastomeric material or rubber for making an underlayer of a braking pad.
A further aim of this disclosure is to provide a braking pad comprising an underlayer and a corresponding underlayer capable to reduce the cold noise.
A further aim of the present invention is a low cold noise generating underlayer to be associated to a friction material to form a braking pad or element.
According to a preferred embodiment a method is obtained according to claim 1.
Moreover according to a preferred embodiment a braking pad is also obtained according to claim 9.
Brief Description of Drawings
Preferred, but not limiting embodiments will be now described in more detail with reference to a number of practical working examples of implementation thereof, which are solely intended to disclose in a non-exhaustive and not limiting manner the feature which are part of the content of the present disclosure, and with reference to figures 1 to 8 of the attached drawings, in which:
Figure 1 schematically illustrates the graph of pressure v number of brakes in a cold noise test;
Figure 2 schematically illustrates the graph of initial temperature v number of braked in the same test of Fig. 1 ;
Figures 3 and 4 show a topography of tan δ of an underlayer according to comparative example 1 and respectively of inventive example 2;
Figures 5 and 6 show a topography of tan δ of an elastomeric material used in the underlayer of comparative example 1 and, respectively, inventive example 2;
Figures 7 and 8 show a graph of Amplitude (db) v Pad temperature measuring the global noise obtained with a standard underlayer (standard UL) from comparative example 1 at 12 Khz and at 9 Khz in Fig. 7 and, respectively, the global noise obtained with the inventive underlayer of example 2 at the same frequencies in Fig. 8.
Detailed Disclosure
According to an aspect of the present invention a new method has been found to select an elastomeric material for an underlayer of a braking pad in order to reduce the cold noise. As elastomeric material is intended a natural or synthetic rubber or a polymer with viscoelasticity.
The method characterizes the viscoelastic properties of the elastomeric material that is part of a layer of a braking pad. In particular the layer is usually known and in the following referred to as underlayer.
In brief the method to select an elastomeric material for making an underlayer of a braking pad to reduce the cold noise comprises the steps of characterizing the viscoelastic properties of said underlayer through the DMTA method by calculating the elastic modulus and the viscous modulus of a specimen of the underlayer through the following formulas:
Elastic modulus
Viscous modulus wherein:
F force applied by the mechanical probe
D displacement of the probe
Ω frequency of the probe stress frequency m the mass of the specimen
L, h and b are the length, height and thickness of the specimen, respectively
Δ is the phase shift between the applied force F and the displacement D
In a further step the damping tan δ is calculated as the ratio between the viscous modulus and elastic modulus according to the following formula:
Selecting an underlayer having a tan δ ≥0.06 between a temperature of -40°C and 0°C and with a frequency between 20 Hz and 20 kHz.
Alternatively the method to select an elastomeric material for making an underlayer of a braking pad to reduce the cold noise comprises the steps of characterizing the viscoelastic properties of an elastomeric material through the DMTA method by calculating the elastic modulus and the viscous modulus of a specimen of the elastomeric material through the following formulas Elastic modulus
Viscous modulus wherein:
F force applied by the mechanical probe D displacement of the probe
Ω frequency of the probe stress frequency m the mass of the specimen
L, h and b are the length, height and thickness of the specimen, respectively
Δ is the phase shift between the applied force F and the displacement D Then the damping tan δ is calculated as the ratio between the viscous modulus and the elastic modulus according to the following formula:
Then an underlayer is selected comprising from 5 to 25% in Volume of said elastomeric material, said elastomeric material having a tan δ ≥0.6 between a temperature of -40°C and 0°C and with a frequency between 20 Hz and 20 kHz. More in details, in a first step of the method the viscoelastic properties of the elastomeric materials or of the layer or underlayer are characterized by using the DMTA analysis (acronym for Dynamic Mechanical Thermal Analysis). This known laboratory test is useful for studying the viscoelastic behavior of polymers, such as elastomers and elastomeric mixtures. As it is know how to apply the DMTA method to a specimen, it is not described here in further details.
With the DMTA analysis, the elastic and viscous modulus are calculated according to the following formulas wherein:
F force applied by the mechanical probe
D displacement of the probe
Ω frequency of the probe stress frequency m the mass of the specimen
L, h and b are the length, height and thickness of the specimen, respectively
Δ is the phase shift between the applied force F and the displacement D
Once the elastic modulus and the viscoelastic modulus are calculated with the DTMA method, they are used in a further step of the method in combination with the Maxwell model (see G.C. Papanicolaou, S.P. Zaoutsos, in Creep and Fatigue in Polymer Matrix Composites (Second Edition), 2019 chapter 1.7.3 and 1.15.3) to analyze the elastomeric materials.
The Maxwell model considers a spring (elastic element) and a dashpot or heat sink (viscous element) in series. The total deformation of the material is given by the sum of the elastic part plus the viscous part, the same is true for the temporal derivative of the deformation, i.e. the speed of the deformation. Under this model the elastic and viscous modulus depend on the stress frequency and the temperature.
Once a material or a formulation for the underlayer is chosen, the elastic and viscous response can be varied by changing the stress frequency and the temperature.
According to the Maxwell model the damping can be defined as where the tan δ maximum is if A=/ π /2 and under the Maxwell model
Tan δ is therefore defined as the ratio between the viscous modulus and elastic modulus, this property is often described as the ability to lose energy as heat (damping) as according to Cit. Menard, K. P., & Menard, N. (1999). Dynamic mechanical analysis. Encyclopedia of Analytical Chemistry: Applications, Theory and Instrumentation, 14- 16.
According to the time temperature superposition principle it has also been considered the following: 1. Fixed frequency, variable temperature:
At low temperatures a polymer is in the glassy state, characterized by high elastic modules, increasing the temperature, the viscous properties increase and therefore we have an increase in the damping. The maximum polymer damping value is obtained during the glass transition, defined by the peak of the viscous module. Increasing the temperature further results in an elastomeric materialy plateau followed by thermal degradation.
2. Variable frequency, fixed temperature:
The same phases and transitions can be obtained by varying the frequency keeping the temperature fixed.
At very high frequencies the material responds completely elastically, decreasing the frequency, the material increases its viscous response properties until it reaches the glass transition. Following, decreasing the frequency, we have the elastomeric material plateau.
This principle connects the frequency and the temperature to the elastic and viscous properties of a material as calculated with the above DTMA method. Having high temperatures means having low stress frequencies and vice versa.
Given an elastic modulus at a temperature TO and frequency coO, if a temperature T1 is considered, it is possible to find a frequency col such that the two elastic modules are equal. From the ratio of the two frequencies it is possible to define the translation factor as according to the below equations using the WLF theory (Williams, Malcolm L., Robert F. Landel, and John D. Ferry." Journal of the American Chemical society 77.14 (1955): 3701- 3707):
Using the DMTA method and the Maxwell model as above disclosed the elastic and viscous modulus are subsequently measured at different frequencies between 1 Hz and 200KHz and for different isotherms creating bi-dimensional topographies. Adjacent isotherms are subsequently compared to calculate the average translation factor between two isotherms in the overlap zone, i.e, in the area where the same elastic modules can be found, but at different frequencies and temperatures.
By reading as input the elastic and viscous modulus data measured by the DMTA, the overlap zone between adjacent isotherms (Ti and Ti + 1) is found. In particular, the algorithm reads as input the elastic and viscous modulus data measured by the DMTA. It performs a polynomial regression of third order for each isotherm and then it finds the overlap zone between adjacent isotherms. The overlap zone consists in satisfying the condition E ' (Ti, wj ) = E ' (Ti + 1, wk), where the index i indicates the isotherms and wj and wk two frequencies between the maximum and minimum measured frequency experimentally.
Once the translation value has been calculated for each isotherm, all the isotherms can be translated with respect to a fixed reference temperature.
This procedure is then repeated for each reference isotherm. This allows to obtain a topography of the elastic and viscous module, i.e. a graph of frequency v temperature illustrating the tan δ as in Figures 5 to 8.
Namely from the relationship between the elastic and viscous module the topography of the tan δ above i.e. the damping is calculated for each isotherm with varying frequency.
Exemplary topography of a comparative underlayer and of an underlayer according to the invention are given in Fig. 5 and 6 and corresponding topography of the elastomeric materials used in the underlayer are given in Fig. 7 and Fig. 8.
It has been surprisingly found that these topographies allow to obtain information on and can be associated to the behaviour at cold noise of an underlayer on the bench tests.
Namely thanks to the analytical methodology used with the DMTA together with the WLF Equation above described, it has been shown that there is a correlation between the damping behavior in Cold Noise conditions and the viscoelastic characteristics of an underlayer and in particular of the elastomeric material portion of the underlayer.
In particular it has been experimentally verified that the best performance in term of reduction of cold noise are achieved by selecting a layer or underlayer having a tan δ≥ 0.06 between a temperature of -40°C and 0°C and with a frequency of between 20 Hz and 20 kHz, where the tan δ is as above defined.
It has also been experimentally verified that if the elastomeric material used in the layer or underlayer has a tan δ≥0.6 in a range of temperature between -40°C and 0°C and with a frequency between 20 Hz and 20 Khz the performance of the corresponding underlayer in the term of low cold noise are greatly increased.
This is also evidenced by comparing the damping topographies obtained with the results obtained from the experimental tests on cold noise. The difference in the damping between the tested materials is clear and occurs in particular at low temperatures, i.e. temperatures below 15 ° C when the cold noise occurs. By comparing the results obtained with different materials, it results that in a preferred embodiment the braking pad comprises a friction material, an underlayer and a backplate, wherein preferably the underlayer comprises from 5 to 25% of elastomeric material in Volume over the total volume of the underlayer, more preferably from 15 to 20% in volume.
Moreover the underlayer comprises preferably from 10% to 15% in Volume of steel fiber. Preferably the underlayer comprises from 15 to 25% of organic fiber. Preferably the underlayer comprises from 10 to 20%, more preferably from 8 to 16% of a binder.
Preferably the underlayer comprises from 15 to 20 % of a Filler.
All the percentages are given in % in volume over the entire volume of the underlayer.
Preferably the elastomeric material is an elastomer having a saturated chain of the polyethylene type.
The elastomeric material having the best damping properties are preferably chosen in the group consisting of EPM (Ethylene propylene monomer rubber), EPDM ((ethylene propylene diene monomer rubber), EPR (Ethylene propylene rubber), CIIR (Chlorobutyl Rubber), TPES (Thermoplastic Elastomers), TPU (Thermoplastic Polyurethane), POE (Polyolefin elastomers), SEBS-mA (styrene-(ethylene-butylene)-styrene grafted with maleic anhydride) and their mixtures. The filler is preferably barite.
It has been verified that the underlayer of the preferred embodiment achieves a very good damping in the cold range and there isn’t braking noise in the cold range.
The invention will be described in the following also in term of examples and comparative examples but these are reported for purposes of illustration and are not intended to limit the disclosure.
Example 1 and 2 comparative example 2
The composition of the known or standard underlayer used as comparative example is reported below in table 1.
Table 1
The elastomeric material used in the standard underlayer is ACR. The composition of the preferred underlayer is reported in the table 2 below:
Table 2
The elastomeric material used in the inventive example 2 is EPDM.
The damping topographies of the standard underlayer according to the comparative example 1 and of the inventive underlayer according to inventive example 2 are reported respectively in Fig. 5 (comparison) and 6 (invention).
The damping topographies of the standard elastomeric material according to the comparative example 1 and of the inventive elastomeric material according to inventive example 2 are reported respectively in Fig. 7 (comparison) and 8 (invention).
Cold noise test
In order to verify the improved results in term of cold noise, the following bench test has been executed on the underlayer of comparative example 1 and of inventive example 2.
The cold noise of the underlayer is measured according to the specific test “cold noise test” procedure on the dynamometer consisting of 2034 braking following the SAEJ 2521 section cold. Each braking block has different pressure and temperature conditions as depicted in Figures 1 and 2. The test is done in a climatic chamber because Cold noise appears well below the room temperature.
In a first step the climatic chamber is at room temperature, then the temperature is decreased at -20°C and then risen again in five degrees steps up to 25°C.
Braking must be spaced out in time so as not to overheat the braking system. The brake application is controlled by the disc temperature, for instance the brake starts when the disc surface reach 50°C.
The temperature is measured inside the underlayer using a thermocouple. For each braking, the noise generated by the pad is recorded with a microphone.
By correctly selecting the materials of the underlayer the cold noise can be reduced from 37% of noisy braking down to only 0.5%.
In particular the results obtained are reported in the table below where the number of braking considered as noisy are reported:
Similar results may be obtained by measuring the global noise obtained with a standard underlayer (standard UL) from comparative example 1 at 12 Khz and at 9 Khz as illustrated in fig. 7 and comparing the result with the results obtained with the inventive underlayer of example 2 at the same frequencies and as illustrated in Fig. 8.
As it is evident from the figures the choice of the elastomeric material and the overall composition of the underlayer according to the inventive example 2 improves the results in term of reduction of cold noise.

Claims

1. Method to select an elastomeric material for making an underlayer of a braking pad to reduce the cold noise, said method comprising the steps of:
- characterizing the viscoelastic properties of said underlayer comprising said elastomeric material through the DMTA method by calculating the elastic modulus and the viscous modulus of a specimen of the underlayer through the following formulas: wherein:
F force applied by the mechanical probe
D displacement of the probe
Ω frequency of the probe stress frequency m the mass of the specimen
L, h and b are the length, height and thickness of the specimen, respectively Δ is the phase shift between the applied force F and the displacement D
Calculating the damping tan δ as the ratio between the viscous modulus and elastic modulus according to the following formula:
Selecting an underlayer having a tan δ ≥0.06 between a temperature of -40°C and 0°C and with a frequency between 20 Hz and 20 kHz.
2. Method to select an elastomeric material for making an underlayer of a braking pad to reduce the cold noise comprising the steps of:
- characterizing the viscoelastic properties of an elastomeric material through the DMTA method by calculating the elastic modulus and the viscous modulus of a specimen of the elastomeric material through the following formulas wherein:
F force applied by the mechanical probe D displacement of the probe
Ω frequency of the probe stress frequency m the mass of the specimen
L, h and b are the length, height and thickness of the specimen, respectively Δ is the phase shift between the applied force F and the displacement D - Calculating the damping tan δ as the ratio between the viscous modulus and the elastic modulus according to the following formula:
Selecting an underlayer comprising from 5 to 25% in Volume of said elastomeric material, said elastomeric material having a tan δ ≥0.6 between a temperature of -40°C and 0°C and with a frequency between 20 Hz and 20 kHz.
3. Method according to claims 1 or 2, characterized in that said underlayer comprises from 45% to 50% in Volume of steel and organic fibers.
4. Method according to any of the previous claims, characterized in that said underlayer comprises from 8 to 16 % in volume of a binder.
5. Method according to any of the previous claims, characterized in that said underlayer comprises from 15 to 20 % in volume of a filler.
6. Method according to claim 5, characterized in that said filler is barite.
7. Method according to any of the previous claims, characterized in that said elastomeric material is chosen in the group consisting of EPM (Ethylene propylene monomer rubber), EPDM ((ethylene propylene diene monomer rubber), EPR (Ethylene propylene rubber), CIIR (Chlorobutyl Rubber), TPES (Thermoplastic Elastomers), TPU (Thermoplastic Polyurethane), POE (Polyolefin elastomers), SEBS-mA (styrene- (ethylene-butylene)-styrene grafted with maleic anhydride) and their mixtures and their mixtures.
8. Method according to any of the previous claims, characterized in that said underlayer comprises between 15 and 20% of said elastomeric material.
9. Braking pad comprising a friction material, a backplate, and an underlayer interposed between said friction material and said backplate, characterized in that said underlayer comprises from 5 to 25% in Volume of an elastomeric material chosen in the group constituted by EPM (Ethylene propylene monomer rubber), EPDM ((ethylene propylene diene monomer rubber), EPR (Ethylene propylene rubber), CIIR (Chlorobutyl Rubber), TPES (Thermoplastic Elastomers), TPU (Thermoplastic Polyurethane), POE (Polyolefin elastomers), SEBS-mA (styrene-(ethylene-butylene)-styrene grafted with maleic anhydride) and their mixtures and their mixtures.
10. Braking pad according to claim 9, characterized in that the elastomeric material is an elastomer having a saturated chain of the polyethylene type.
11. Braking pad according to claims 8 or 9, characterized in that the elastomeric material is chosen in the group consisting of EPM (Ethylene propylene monomer rubber), EPDM ((ethylene propylene diene monomer rubber), EPR (Ethylene propylene rubber)and their mixtures.
12. Braking pad according to any of the claims from 9 to 11, characterized in that it comprises from 45% to 50% in Volume of steel and organic fibers, from 8 to 16 % in volume of a binder and from 15 to 20 % in Volume of a Filler.
13. Braking pad according to claim 11, characterized in that the filler is barite.
14. Braking pad according to any of the claims from 9 to 13, characterized in that said underlayer comprises from 15 to 20% in Volume of said elastomeric material.
15. Braking pad obtained with the method of any of claims 1 to 8.
EP21770316.4A 2020-09-17 2021-09-16 Method to select an elastomeric material for making an underlayer of a braking pad and corresponding braking pad Pending EP4214423A1 (en)

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PCT/IB2021/058461 WO2022058928A1 (en) 2020-09-17 2021-09-16 Method to select an elastomeric material for making an underlayer of a braking pad and corresponding braking pad

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Publication number Priority date Publication date Assignee Title
US5099962A (en) * 1990-09-17 1992-03-31 Kabushiki Kaisha Toyota Chuo Kenkyusho Backing plate for disc brake with different damping layers for brake squeal
FI20065364A0 (en) * 2006-05-30 2006-05-30 Valtion Teknillinen Vibration damping system
EP2370250A1 (en) * 2008-12-15 2011-10-05 3M Innovative Properties Company Composite article including viscoelastic layer with barrier layer
KR102106343B1 (en) * 2012-01-16 2020-05-04 니혼 브레이크 고오교 가부시키가이샤 Friction material and method for manufacturing the same
US10344817B2 (en) * 2015-11-30 2019-07-09 Hyundai Motor Company Vehicle brake pad

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