Friction layer design structure and application using friction materials of various formulations

Abstract

The present invention discloses a friction layer design structure, which belongs to the field of friction layer design in mechanical equipment, and is used to achieve multiple material properties in a single friction layer. The friction layer and corresponding brake pad designed by the present invention can overcome the problems of NAO material being easy to wear out at high temperature and causing danger after exhaustion, semi-metallic material making loud noise in daily use, and no warning and easy danger before the friction layer is exhausted at a relatively low cost, and is particularly suitable for electric vehicles with high dead weight, high performance and kinetic energy recovery function. The present invention uses different friction materials to form a friction layer in layers (as shown in Figure 1), the outer layer M1 is NAO friction material, and the inner layer M2 is semi-metallic friction material. Initially, only the outer layer NAO material participates in friction, and the noise is small. When the outer layer is exhausted, the semi-metallic material participates in friction, which is wear-resistant and can still provide sufficient friction. At this time, the friction noise is loud, reminding the user to replace the brake pad. In addition, the present invention can also achieve the functions of reducing the cost of the friction layer, detecting brake wear by circuit, and reducing the preheating wear of the track car brake.

Description

Technical Field

[0001] The invention relates to the field of friction layer design of power machinery, in particular to a friction layer design structure comprising more than two formula friction materials and mechanical parts such as brake pads using the structure. Background Art

[0002] The friction layer is a component used in power machinery that relies on friction to perform braking and transmission functions. It mainly includes brake linings (brake pads) and clutch facings (clutch plates). Brake pads are used for braking, and clutch plates are used for transmission. Any mechanical equipment and various moving vehicles must have braking or transmission devices. The friction layer is a key component for the safe and reliable operation of mechanical equipment and various motor vehicles. The friction layer relies on the mechanism of friction to work, which causes the component to be in a state of high temperature and high pressure frequently, and continues to wear and change its state at any time. Once the friction layer is exhausted during the operation of the equipment or vehicle, braking or transmission failure will occur, which is very likely to cause accidents and requires regular inspection and maintenance; at the same time, high-speed friction will also generate a lot of noise and interfere with the environment. The ideal friction material should have several characteristics such as high friction coefficient, high temperature resistance, wear resistance, low noise, and low cost.

[0003] The friction materials and related characteristics commonly used in making friction layers are as follows:

[0004] 1. Semi-metal friction materials are used in disc brake pads. The material formula usually contains about 30% to 50% of iron metal (such as steel fiber, reduced iron powder, foamed iron powder). Semi-metal friction materials are named for this reason. Its characteristics: good heat resistance, high absorption power per unit area, high thermal conductivity, and can be applied to the braking conditions of automobiles running at high speed and heavy load. However, it has disadvantages such as high friction noise and brittle cracks at corners.

[0005] 2. NAO friction material. In a broad sense, it refers to non-asbestos-non-steel fiber friction materials, but the current discs also contain a small amount of steel fibers. Usually the brake pads are short-cut fiber friction blocks, and the clutch plates are continuous fiber friction plates. The advantages are low noise during operation, low operating temperature requirements, and sufficient braking force without warming up the car. The disadvantage is that the friction performance and wear resistance are greatly attenuated at high temperatures.

[0006] 3. Powder metallurgy friction material. Also known as sintered friction material, it is made by mixing, pressing, and sintering iron-based and copper-based powder materials at high temperatures. It is suitable for braking and transmission conditions at higher temperatures. For example: braking and transmission of aircraft, trucks, and heavy engineering machinery. Advantages: long service life; Disadvantages: high product price, loud braking noise, heavy and brittle, and large dual wear.

[0007] 4. Carbon fiber friction material. It is a type of friction material made of carbon fiber as a reinforcement material. Carbon fiber has the characteristics of high modulus, good thermal conductivity, and heat resistance. Carbon fiber friction material is the best performance among various types of friction materials. Carbon fiber friction pads have high power absorption per unit area and light specific gravity. They are particularly suitable for the production of aircraft brake pads. They are also used in brake pads of some high-end cars abroad. Because of its high price, its application range is limited and its output is relatively small.

[0008] The above materials each have their own characteristics and are suitable for different scenarios and equipment. At present, due to the high prices of 3 and 4, they are not suitable for general civilian vehicles. The friction materials used in civilian vehicles are generally selected from 1 and 2, and are suitable for different fields according to the characteristics of 1 and 2. Track vehicles generally use semi-metallic friction materials (material 1) or more advanced carbon fiber friction materials (material 4) because of the high frequency, high temperature and high pressure environment. Family cars with low frequency of use, pursuit of low noise and cost control now mostly use NAO friction materials (material 2).

[0009] However, with the advent of pure electric vehicles, the applicability of the above friction materials in braking systems is gradually decreasing, and there are mainly three problems.

[0010] First, NAO friction material, as a brake material for pure electric vehicles, has the risk of friction failure after easy wear and exhaustion at high temperatures. In order to achieve longer battery life, pure electric vehicles are generally equipped with large-capacity batteries, which are relatively heavy, reaching 2 tons to 2.5 tons, basically reaching the level of small trucks. At the same time, the high torque of the motor gives electric vehicles an acceleration capability that is almost like a racing car (some can accelerate to 100 kilometers in less than 3 seconds). The greater dead weight and faster speed determine that electric vehicles need a stronger braking system. Judging from the fact that electric vehicles such as Xiaomi SU7 have repeatedly worn out the brake pads in a short period of time on the track and caused brake failure, the performance of NAO material alone as a brake pad friction material is slightly insufficient, and there will be certain risks under high temperature and high pressure conditions such as intense driving or mountain running and long downhill. With the development of electric vehicles, their battery capacity (affecting the vehicle's dead weight) and motor performance (affecting the vehicle's acceleration performance) will continue to improve, and the insufficient performance of NAO materials will be further highlighted.

[0011] Second, the semi-metallic friction material has obvious braking noise. Although the high-performance semi-metallic formula friction material, especially the friction material of the racing brake pad, can meet the performance requirements of the braking system, its high braking noise will seriously affect the feeling of the vehicle occupants, especially the quiet driving characteristics of electric vehicles will further highlight the impact of braking noise.

[0012] Third, the existing brake wear alarm settings are still insufficient. The existing brake wear alarm methods are: first, the alarm iron sheet rubs against the brake disc to issue a noise warning, but the sound is similar to the friction of foreign objects, which is sometimes ignored or misjudged. The alarm iron sheet also occasionally falls off, and if it is not replaced in time, the alarm iron sheet will also wear the brake disc; second, it is detected by the brake sensor line, but if the brake pad has unilateral wear and other phenomena, it is easy to detect inaccurately, and its replacement steps and use costs are relatively higher; third, the driver judges the braking state by the brake foot feel, but the fully decoupled brake control system required by the L3 and L4 level autonomous driving systems will interfere with the brake foot feel, which can easily cause the driver to misjudge the vehicle's brake system; fourth, the driving computer estimates the life of the brake pad based on usage, which is undoubtedly inaccurate.

[0013] At the same time, new energy electric vehicles on the market now generally have kinetic energy recovery technology and use brakes relatively less. The service life and maintenance cycle of their brake pads are longer than those of ordinary vehicles, and the wear and tear is less likely to attract the driver's attention. However, they wear faster when used heavily, and the wear and tear is more difficult to estimate. It is easy for daily driving to be normal, but the brake pads are found to be exhausted only when the brake system needs to play a role in special situations such as high speed, downhill, and intense driving. Dangerous situation.

[0014] From the current perspective, the existing mainstream friction materials for household cars cannot perfectly meet the braking needs of new energy electric vehicles, and the silent and wear-resistant carbon fiber friction materials are difficult to be used as brake pad materials for general household cars due to their high prices.

[0015] In this regard, the present invention proposes a friction layer design structure using two or more friction materials with different formulations to improve the performance of the existing friction layer to meet the needs of different usage scenarios. Summary of the invention

[0016] The purpose of the present invention is to provide a friction layer design structure using two or more friction materials with different formulations to improve the performance of the existing friction layer to meet the needs of different usage scenarios. In particular, it can solve the problems of pure NAO materials being easily worn out at high temperatures and becoming frictionally disabled, semi-metallic materials making loud noises during daily use, and no warning before the friction layer is exhausted, which can easily lead to dangers, at a relatively low cost.

[0017] To achieve this object, the present invention provides a friction layer structure design comprising an inner and outer two-layer structure, wherein the outer layer (initially involved in friction) is a friction material formula with low friction noise to meet the quiet requirements of daily use, and the inner layer (starts to participate in friction after the outer layer material is exhausted) is a friction material formula with strong wear resistance and high friction noise.

[0018] The effect is that the initial state of the friction layer uses a friction material with less noise as the outer layer to participate in friction, and daily use is comfortable with low friction noise. When encountering special situations such as intense driving or after long-term use, the outer friction material is exhausted, and the inner friction material begins to participate in friction. At this time, a large friction noise will appear to remind the user that the friction layer is about to be exhausted, and it is necessary to drive carefully and replace related parts as soon as possible. At this time, the inner layer, as a more wear-resistant friction material, can still provide power or braking force to the relevant system for a certain period of time under high temperature and high speed conditions to ensure the safe operation of the equipment. This can not only provide a silent effect in daily use, but also ensure the safe operation in special situations such as the exhaustion of friction materials.

[0019] The present invention is particularly suitable for new energy electric vehicles with kinetic energy recovery function. For electric vehicles with kinetic energy recovery function, the daily deceleration is mainly based on kinetic energy recovery, and the loss of brake pads is very small; when encountering special circumstances and intense driving, the high weight and high speed will cause the brake pads to wear quickly. The traditional method of estimating the wear of brake pads by mileage is no longer applicable. It is difficult for drivers to make an accurate estimate of the life of the brake pads and replace them in time. The present invention can emit a friction noise reminder when the brake pads are about to run out, and can continue to provide braking force for a period of time while emitting friction noise, which can avoid accidents to a large extent.

[0020] Furthermore, in order to enhance the warning effect of the noise in the inner layer of the friction layer, when designing the silencer, chamfering, drilling and other silencer structures of the brake pad, it should be avoided to eliminate or enhance the friction noise generated by the inner layer of the friction layer.

[0021] Furthermore, the outer layer of the brake pad friction layer can be designed as an insulating material, while the inner layer is designed as a conductive material, and the brake detection system is connected to the brake disc and the inner layer of the brake pad friction layer. When the outer layer of the friction layer is exhausted and the inner layer begins to contact the brake disc, the brake detection circuit is connected, prompting the driver that the brake pad is about to be exhausted and needs to be replaced as soon as possible.

[0022] Furthermore, according to design requirements, the thickness ratio of the inner and outer layers of the friction layer can be changed. The thicker the inner layer, the longer it provides high-performance braking capabilities at high temperatures, but at the same time, the shorter the time it can be used silently.

[0023] Furthermore, when materials of different formulations are required to participate in friction at the same time, one or more layers of the friction layer can be set to friction materials of two or more formulations at the same time, and the proportions of friction materials of different formulations can be determined according to demand.

[0024] In addition to the purpose of daily silent use or brake wear detection, the brake system can also change the outer layer to low-cost general performance friction material and the inner layer to high-cost high-performance friction material, thereby reducing the overall cost of use while ensuring safety with the use of high-performance materials.

[0025] For racing cars or performance cars that are often driven aggressively, the brake pads can have a thinner outer layer made of low-temperature or room-temperature high-performance friction material, and an inner layer made of high-temperature high-performance friction material. This can reduce the time and wear of preheating the brake system during racing, and can also be compatible with street driving to a certain extent.

[0026] Furthermore, any brake system that requires friction materials with different performances at different use stages can use the friction layer designed by the present invention to achieve the purpose.

[0027] Furthermore, in addition to brake systems, the present invention can also be used in other equipment or situations that require friction materials with different properties at different use stages.

[0028] Furthermore, in order to adapt to more complex usage scenarios, the friction layer can be set to a structure of 3 or more layers.

[0029] Furthermore, the friction layer can be designed to be reinstallable or recyclable to further reduce the user's cost of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Attached Figure 1 The figure shows a schematic diagram of the structure of a brake pad having two friction layers made of different friction materials, wherein the dotted shaded portion is an oblique section of the brake pad. DETAILED DESCRIPTION

[0031] The core of this application is to provide a friction layer structure design with 2 or more friction materials of different formulations, to provide friction performance of different friction materials for different use stages, or to use multiple friction materials to participate in friction at the same stage, and to reflect the performance of multiple friction materials at the same time, so as to improve the performance of the existing friction layer and adapt to the use needs of different use scenarios. The main features of this structure are: it can make the friction layer show the performance characteristics of two friction materials of different formulations. If the design needs to reflect the performance of friction materials of different formulations at different use stages of the friction layer, the friction materials of different formulations can be layered in a manner parallel to the friction surface; if the design needs to make the friction layer show the performance of friction materials of different formulations at the same time, the friction materials of different formulations can be layered in a manner perpendicular to the friction surface, so that the friction materials of different formulations participate in friction at the same time; in addition, the friction material layering method can also be designed in a manner inclined to the friction surface, so that the proportions of friction materials participating in friction at different stages are different, or the friction materials of different formulations are combined into a friction layer in other ways.

[0032] In order to make the purpose, technical solution and effect of the present application clearer, the following will be combined with the accompanying drawings to fully and clearly describe the design of a brake pad friction layer of the present invention. Obviously, the brake pad embodiment described below is only one embodiment of the present application, not all embodiments. The present invention is not only applicable to brake pads, but any equipment that requires a friction layer can be applied to this patent. The friction layer of the present invention can be more than two layers. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0033] The attached figure shows a schematic diagram of a brake pad structure designed using the structure of the present invention. The main purpose of the brake pad is to solve the problems of pure NAO materials being easily worn out at high temperatures, semi-metallic materials making loud noises during daily use, and friction layers being exhausted without warning and prone to danger. The dotted shaded part in the figure is an oblique section of the brake pad, which is used to show the internal structure of the brake pad. Among them, M1 is the outer layer of the friction layer, and M2 is the inner layer of the friction layer. M1 and M2 are friction materials of different formulations, and together constitute the friction layer of the brake pad. D is the base layer of the brake pad, which mainly refers to the traditional structure of the brake pad such as the adhesive layer, heat insulation layer, steel plate, and silencer.

[0034] The difference between this embodiment and the traditional brake pad structure design is that although the traditional brake pad is layered, its friction layer has only one formula, and the remaining adhesive layer, steel plate and other layers basically cannot participate in friction and cannot provide braking force. The brake pad needs to be replaced before the friction layer is exhausted, otherwise it will endanger driving safety, and the thickness of the brake pad needs to be checked regularly to ensure braking performance. In the structure of this embodiment, the friction layer has two layers, the inner and outer layers, and the two layers use friction materials with different formulas. After the outer friction material is exhausted, the inner friction material can still participate in friction and provide braking force. At the same time, according to needs, the inner friction material can also be set as a friction material that will emit a large friction noise, so that it will emit a large friction noise when participating in friction, so as to remind the driver to replace the brake pad and avoid brake failure after the brake pad is exhausted due to untimely inspection.

[0035] As shown in the figure, the friction layer of the brake pad consists of two layers, M1 (outer layer) and M2 (inner layer). M1 is a NAO friction material with a thickness of about 10 mm, which is quiet and has a good texture for daily use but slightly poor high-temperature wear resistance. M2 is a track-grade semi-metal friction material with a thickness of about 3 mm, which has a loud noise, good braking performance and high-temperature wear resistance. When installed on the vehicle, the M1 layer first contacts the brake disc to provide braking force. At this time, the brake pad behaves like a NAO material brake pad, that is, low friction noise, good low-temperature performance, and slightly poor high-temperature wear resistance. When subjected to special circumstances such as intense driving or after long-term use, the friction material of the M1 layer is exhausted, and the friction material of the M2 layer begins to participate in friction. At this time, the brake pad behaves like a racing semi-metal brake pad, that is, loud braking noise, good braking performance and wear resistance at high temperatures. At this time, the brake disc can still provide reliable, even better braking performance than when using the M1 layer for friction. At the same time, the larger braking noise of the M2 layer can remind the driver that the friction layer is about to be exhausted, and the driver needs to drive carefully and replace the relevant parts as soon as possible. This solves the problems of pure NAO materials being easily worn out at high temperatures, semi-metallic materials being noisy during daily use, and friction layers being exhausted without warning and prone to danger. 3mm thick brake pads have reached the critical thickness for replacement, avoiding the waste of frequent brake pad replacements and the trouble of regular brake pad inspections.

[0036] This structure can also realize the function of using circuits to detect the exhaustion of brake pads. Set the M1 layer to an insulating material, set M2 to a conductive or low-resistance material, and connect the brake detection circuit to M2 and the brake disc at the same time. In the initial state, M2 is not in direct contact with the brake disc because M1 is an insulating material, and the brake pad detection circuit is open. When M1 is exhausted, M2 contacts the brake disc, and the brake pad detection circuit is connected, indicating that the brake pad is about to be exhausted.

[0037] Taking into account the poor low-temperature performance of some racing semi-metallic friction materials, different friction materials can be used in the same layer numbered 1 and 2 in the attached figure. For example, the M2 layer numbered 1 can still use NAO friction material, and the M2 layer numbered 2 can use semi-metallic material. In this way, both low-temperature performance and high-temperature performance can be taken into account while emitting friction noise, which not only provides a reminder but also ensures safety.

[0038] This brake pad is designed to take into account both quietness in daily use and braking performance under sudden and intense driving, as well as timely reminders for drivers to replace brake pads. If there are other needs, the formula and thickness of M1, M2 or 1, 2 can be adjusted to achieve different design purposes.

Claims

1. A design structure of a friction layer, characterized in that: The friction layer is composed of two or more friction materials with different formulations. The friction materials are layered parallel to the friction surface or layered perpendicular to the friction surface or in other forms according to actual needs.

2. The friction layer design structure designed according to the method of claim 1 is characterized in that: Two or more friction materials with different formulations are layered in parallel to the friction surface, and different friction materials do not participate in friction at the same time. Initially, only the outermost layer of material participates in friction, and the friction layer exhibits the performance of the outermost layer of friction material. After the outermost layer of friction material is worn out, the second outermost layer of material begins to participate in friction, and the friction layer exhibits the performance of the second outermost layer of friction material. The remaining layers of friction materials participate in friction layer by layer.

3. The friction layer designed using the method of claim 2 is characterized in that: The friction layer is mainly divided into two layers. The outer layer of the friction layer uses relatively silent friction materials, and the inner layer of the friction layer uses friction materials with larger friction noise. The thickness of the inner layer of the friction layer is set to be slightly larger than the critical value at which the friction equipment needs to be replaced. When the friction equipment is initially used, only the outer layer of the friction layer participates in friction, and the noise is small. When the outer layer of the friction layer is worn out, the friction layer is close to the critical thickness that needs to be replaced, and the inner layer of the friction layer begins to participate in friction, making a larger noise, reminding the equipment user to replace the friction equipment. At this time, the inner layer of the friction layer can still provide effective friction performance to ensure safety.

4. A brake pad equipped with a friction layer designed using the method of claim 3, characterized in that: The outer friction layer uses relatively quiet friction materials, such as NAO materials, and the inner friction layer uses noisy friction materials, such as racing semi-metallic friction materials. The thickness of the inner friction layer is set to 3-5mm. During initial use, only the outer friction layer participates in the brake friction, and the brake pads make less noise. When the outer friction layer is worn out, the brake pads are close to the critical thickness that needs to be replaced, and the inner friction layer begins to participate in the brake friction, making a loud noise to remind the driver to replace the brake pads. At this time, the inner friction layer can still provide effective braking performance to ensure safety.

5. The brake pad designed using the method of claim 4, characterized in that: According to different usage requirements in different scenarios such as use purpose, safety redundancy and noise requirements, different friction layer stratification formulas, different stratification thicknesses and different stratification layer numbers are set.

6. The brake pad designed according to the method of claims 4 and 5, characterized in that: Reasonable design of the brake pad's silencer structures such as silencers, holes, chamfers, etc. can effectively reduce the friction noise of the silent friction layer, while amplifying the friction noise of the noisy friction layer to achieve a better sound reminder effect.

7. The friction layer designed using the method of claim 2 is characterized in that: The outer layer of the friction layer uses general wear-resistant and cheap friction materials, and the inner layer of the friction layer uses expensive, highly wear-resistant and high-performance friction materials, which reduces the cost of use while ensuring safety of use.

8. The friction layer and corresponding wear detection circuit designed according to the method of claim 2 are characterized in that: The outer layer of the friction layer uses insulating friction materials, and the inner layer of the friction layer uses conductive or low-resistance friction materials. The wear detection circuit is connected to the inner layer of the friction layer and the friction surface (such as the brake disc) at the same time. When the outer layer material of the friction layer is exhausted, the inner layer of the friction layer will contact the friction surface during friction, the detection circuit will be turned on, and the friction detection system will issue a reminder to replace the friction layer. At this time, the friction layer can still operate effectively to ensure safety.

9. The brake pad designed according to the method of claim 3, characterized in that: The outer layer of the friction layer is a thinner low-temperature or room-temperature high-performance friction material, and the inner layer is a high-temperature high-performance friction material. It can be used on high-performance vehicles such as track cars to reduce brake warm-up time and wear, and is compatible with street driving to a certain extent.

10. The friction layer designed according to the method of claim 1, characterized in that: Two or more friction materials of different formulations are layered in a manner perpendicular to the friction surface. The friction materials of different formulations participate in the friction at the same time, and the performance of the friction materials of different formulations is reflected at the same time.

11. A friction layer designed in combination with the method described in claim 2 and claim 10, characterized in that: Friction materials of different formulations are layered in parallel to the friction plate and in a direction perpendicular to the friction surface, that is, a certain layer or several layers parallel to the friction surface contain friction materials of several different formulations at the same time.

12. The friction layer designed according to the method of claim 1, characterized in that: Two or more friction materials with different formulations are layered or combined in a manner inclined to the friction surface or in other ways to form a friction layer to meet different needs.

13. The friction layer or brake pad designed according to the method of claims 1-12, characterized in that: The friction layer or one or more layers of the friction layer are designed to be reinstallable or recyclable to further reduce the use cost.

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