Brake friction material and method for forming transfer film using brake friction material

Abstract

To form a sufficient transfer film immediately after delivery even in a vehicle using a regenerative cooperation brake.SOLUTION: This brake friction material has a friction base material laminated on a back plate, and a transfer film material laminated on the friction base material and opposed to an opposed member, and the transfer film material is formed of a composition formed by including an organic filler in an extremely low temperature melting point resin component.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a brake friction material and a method for producing a transfer film using the brake friction material. [Background technology]

[0002] Disc brakes and drum brakes are known as braking devices installed in vehicles such as automobiles. Friction material (brake friction material) is provided on the brake pads of disc brakes and the brake shoes of drum brakes. Braking force is generated by friction when this brake friction material is pressed against and slid against the opposing components, the disc rotor and brake drum.

[0003] In recent brake systems, when brake friction material is pressed against and slid against a counter component (disc rotor or brake drum), the components of the brake friction material form a thin transfer film on the friction surface of the counter component. This transfer film stabilizes braking performance at high temperatures and suppresses wear of the brake friction material.

[0004] This transfer film is generated using the heat generated at the friction interface during braking. Electric vehicles such as BEVs (Battery Electric Vehicles), PHEVs (Plug-in Hybrid Electric Vehicles), and HEVs (Hybrid Electric Vehicles) use regenerative braking to decelerate.

[0005] In vehicles using regenerative braking, the braking force exerted by the brake friction material is lighter than in vehicles without regenerative braking. Therefore, the amount of heat generated at the friction interface between the brake friction material and the opposing member is small, making it difficult for a transfer film to form.

[0006] For example, Patent Document 1 (JP 2023-47688 A) discloses a technology that improves the components of brake friction material, making it possible to stably generate a transfer film even when braking with a small amount of heat using regenerative braking. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2023-47688 Summary of the Invention [Problem to be solved by the invention]

[0008] However, when a vehicle is shipped, it has hardly been driven on roads. Therefore, almost no transfer film is formed on the friction surface of the opposing component (disc rotor or brake drum) that faces the brake friction material. The technology disclosed in the above-mentioned document is a technology for stably forming a transfer film during driving.

[0009] Therefore, even with the technology disclosed in the document, it takes a relatively long time to generate a sufficient transfer film on the opposing components of a brake device installed in a vehicle that uses regenerative cooperative braking immediately after delivery.

[0010] Until a sufficient transfer film is formed on the opposing components of a vehicle using regenerative braking, braking force is unstable and braking distance is relatively extended. This results in a sense of discomfort for the driver. Furthermore, the delay in the formation of the transfer film can lead to unstable friction and rusting, and can also cause brake squeal and judder.

[0011] The present invention aims to provide a brake friction material that can generate a sufficient transfer film immediately after delivery, even in vehicles that use regenerative braking, and a method for generating a transfer film using the brake friction material. [Means for solving the problem]

[0012] One aspect of the present invention is a brake friction material having a friction base material laminated on a back plate and a transfer film material laminated on the friction base material and facing a facing member, wherein the transfer film material is formed from a composition containing an organic filler in a cryogenic melting point resin component.

[0013] In one aspect of the present invention, a transfer film generating method involves placing the wheels of a vehicle equipped with a brake device having the brake friction material on rollers provided on a fixed stand for a real-vehicle running test, restraining the vehicle on the fixed stand and driving the vehicle, activating the brake device to press the transfer film material of the brake friction material against the opposing member that rotates integrally with the wheel, continuing low-load braking for a predetermined period of time, and transferring the transfer film material to the friction surface of the opposing member using the heat generated at the friction interface between the transfer film material and the opposing member, thereby generating a transfer film on the friction surface.

[0014] In one aspect of the present invention, a transfer film generating method involves placing the wheels of a vehicle equipped with a brake device having a brake friction material provided with a transfer film material having a structure of two or more layers on rollers provided on a fixed stand for a real-life running test, restraining the vehicle on the fixed stand and driving the vehicle, activating the brake device to press the transfer film material of the brake friction material against the opposing member that rotates integrally with the wheel, continuing low-load braking for a predetermined period of time, and using the heat generated at the friction interface between the transfer film material and the opposing member to transfer at least the outermost transfer film layer to the friction surface of the opposing member, thereby generating a transfer film on the friction surface. [Effects of the Invention]

[0015] According to the present invention, the transfer film material that is laminated on the friction base material on the back plate and faces the opposing member is formed from a composition containing an organic filler in an extremely low melting point resin component, so that even in vehicles that use regenerative cooperative braking, it is possible to generate a sufficient transfer film immediately after delivery. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view of a disc brake device according to a first embodiment; [Figure 2] Cross-sectional view of the brake pad [Figure 3] 10 is a cross-sectional view of a brake pad according to a second embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [First embodiment]

[0018] 1 and 2 show a first embodiment of the present invention. The brake device 1 shown in FIG. 1 is provided on four wheels or drive wheels of a vehicle. The vehicle used in this embodiment is an electric vehicle. This electric vehicle has a regenerative cooperative brake as its brake system.

[0019] The brake device 1 is of the opposed piston type. The brake device 1 has a disc rotor 2 as an opposed member. The disc rotor 2 is fixed to the hub H of each axle and rotates integrally with the axle (wheel). The brake device 1 also has a caliper 3. The caliper 3 is fixed to the body of the electric vehicle. The caliper 3 straddles the outer edge of the disc rotor and is formed with a generally groove-shaped cross section. A cylinder 3a is formed on each of the surfaces of the caliper 3 facing the disc rotor 2. A piston 3b is attached to this cylinder 3a.

[0020] Furthermore, a brake pad 4 is provided on the front surface of this piston 3b. The brake pad 4 has a back plate 5 and a brake friction material 6. The back surface of the back plate 5 is fixed to the piston 3b. The back surface of the brake friction material 6 is fixed to the front surface of the back plate 5. The front surfaces of the brake friction material 6 face the friction surfaces 2a provided on both sides of the disc rotor 2. A brake cylinder chamber 3c is formed, closed by the cylinder 3a and the piston 3b.

[0021] The brake device 1 also has a brake drive unit 11. The brake drive unit 11 supplies and discharges brake fluid pressure to and from the brake cylinder chamber 3c. When the brake drive unit 11 supplies brake fluid pressure to the brake cylinder chamber 3c, the piston 3b pushes the brake pad 4 toward the friction surface 2a. Then, the brake friction material 6 of the brake pad 4 presses and holds the friction surfaces 2a provided on both sides of the disc rotor 2. When the brake friction material 6 presses and holds the friction surfaces 2a, the friction surfaces 2a slide against the brake friction material 6, and the friction generated at that time generates a braking force on the electric vehicle.

[0022] Both brake pads 4 are constantly biased in directions separating from each other by a return spring 7. When the brake drive unit 11 releases the brake fluid pressure supplied to the brake cylinder chamber 3c, both brake pads 4 move backward in directions separating from each other due to the biasing force of the return spring 7. As a result, the brake friction material 6 faces the friction surface 2a of the disc rotor 2 with a predetermined brake clearance, and the braking force is released.

[0023] 2, the brake friction material 6 has a three-layer structure. That is, the brake friction material 6 has, from the back plate 5 side, a two-layer material (underlayer) 6a, a friction base material 6b, and a transfer film material 6c.

[0024] The two-layer material 6a is a vibration absorbing layer that connects the back plate 5 and the friction base material 6b. The two-layer material 6a suppresses brake squeal during braking. The friction base material 6b is pressed directly against the friction surface 2a of the disc rotor 2 during braking, sliding and generating braking force for the electric vehicle.

[0025] The transfer film material 6c is transferred to the friction surface 2a by utilizing the heat generated at the friction interface when pressed against the friction surface 2a, thereby forming a transfer film on the friction surface 2a.

[0026] The transfer film material 6c is made of a composition containing a low-melting-point resin component containing a film-forming organic filler. Examples of the low-melting-point resin component include a low-melting-point phenolic resin and cashew particles. The film-forming organic filler is, for example, titanate.

[0027] This transfer film material 6c is transferred to the friction surface 2a in an actual vehicle running test process set up on the production line. In the actual vehicle running test, the wheels of an electric vehicle are placed on multiple rollers provided on a fixed base, and the electric vehicle is driven (runs) in a restrained state to perform various measurements.

[0028] In the brake device 1 for an electric vehicle having such a configuration, a method for transferring and adhering the transfer film material 6c of the brake friction material 6 to the friction surface 2a of the disc rotor 2 to form a transfer film will be described.

[0029] The transfer film is produced on the production line before shipping. The production line incorporates an actual vehicle running test process. This actual vehicle running test process is equipped with an actual vehicle running test device. First, an operator places each wheel of an electric vehicle that has been assembled as specified on a plurality of rollers provided on a fixing table of the actual vehicle running test device. Next, the operator fixes the electric vehicle to the fixing table. After that, the operator drives (runs) the electric vehicle. This causes the wheels of the electric vehicle to rotate on the rollers.

[0030] The worker operates the control device or depresses the brake pedal to activate the brake drive unit 11, supplying brake fluid pressure sufficient to generate light-load braking to the cylinder 3a provided in the caliper 3 of the electric vehicle. This causes the transferred film material 6c of the brake friction material 6 to be pressed against the friction surface 2a of the disc rotor 2. As a result, the transferred film material 6c of the brake friction material 6 slides on the friction surface 2a of the disc rotor 2, generating light-load braking.

[0031] The electric vehicle continues a state in which light-load braking is applied by the brake device 1 for a predetermined time. This generates heat at the friction interface between the transfer film material 6c of the brake friction material 6 and the friction surface 2a of the disc rotor 2. The transfer film material 6 is a cryogenic melting point phenolic resin composition. Therefore, by continuing low-load braking for a predetermined time, the heat generated at the friction interface can be used to transfer the transfer film material 6 to the friction surface 2a of the disc rotor 2. This creates a transfer film on the friction surface 2a. The transfer of the transfer film material 6 is performed during the actual vehicle running test process, resulting in high work efficiency.

[0032] As a result, when the electric vehicle is shipped, a transfer film has already been formed on the friction surface 2a of the disc rotor 2. Therefore, even when the driver operates the electric vehicle immediately after delivery and activates the regenerative braking system, a stable braking force can be obtained. Because the braking force is stable, the electric vehicle can be stopped within the braking distance intended by the driver.

[0033] It should be noted that the generation of the transfer film by the friction base material 6b when the regenerative braking cooperative system is activated is the same as in the conventional system, and therefore a description thereof will be omitted. [Second embodiment]

[0034] 3 shows a second embodiment of the present invention. In this embodiment, the transfer film material 6c has a two-layer structure. Components that are common to the first embodiment are given the same reference numerals, and descriptions thereof will be omitted or simplified.

[0035] The transfer film material 6c is composed of a first transfer film layer 6d on the friction base material 6b side and a second transfer film layer 6e as the outermost layer. The second transfer film layer 6e contains a resin component with a lower melting point than the first transfer film layer 6d. Specifically, the first transfer film layer 6d is a cryogenic melting point phenolic resin composition. The cryogenic melting point phenolic resin composition contains a cryogenic melting point phenolic resin containing a film-forming organic filler. The film-forming organic filler is, for example, titanate.

[0036] The second transfer film layer 6e is a composition in which fine titanate particles are mixed with an organic filler, such as a rubber filler, that spreads at a lower temperature than the cryogenic melting point phenolic resin.

[0037] In this embodiment, similarly to the first embodiment, the brake device 1 is operated to generate light load braking while the electric vehicle is being driven (running) in the actual vehicle running test device. Then, the second transfer film layer 6e of the transfer film material 6c is pressed against the friction surface 2a of the disc rotor 2.

[0038] The second transfer film layer 6e is a composition of fine titanate containing an organic filler that spreads at a lower temperature than cryogenic melting point phenolic resin. Therefore, the heat generated at the friction interface during low load braking allows the second transfer film layer 6e to be quickly transferred to the friction surface 2a of the disc rotor 2.

[0039] This ensures that in the actual vehicle running test process, a transfer film is reliably formed by transferring all of the second transfer film layers 6e onto the friction surface 2a of the disc rotor 2. Then, in the actual vehicle running test process, after all of the second transfer film layers 6e have been transferred, the first transfer film layer 6e is transferred onto the friction surface 2a of the disc rotor 2.

[0040] When the electric vehicle is shipped, all of the second transfer film layers 6e have formed transfer films on the friction surface 2a of the disc rotor 2. Therefore, even if some of the first transfer film layer 6d remains on the brake friction material 6 when the electric vehicle is shipped, the braking performance of the brake device 1 will not become unstable.

[0041] The present invention is not limited to the above-described embodiment, and for example, the above-described embodiment can be applied to vehicles other than electric vehicles.

[0042] The transfer film material 6c may also have a three-layer or more structure. In this case, the melting points of the cryogenic melting point resin components are set lower as the transfer film layer moves from the friction base material 6b side to the outermost transfer film layer. This allows for more reliable formation of the transfer film on the friction surface 2a of the disc rotor 2 before shipping the vehicle.

[0043] The brake friction material 6 can be applied not only to the brake pads 4 of the brake device 1 but also to the brake shoes of drum brakes. In this case, the opposing member is the brake drum. Furthermore, the brake friction material 6 can also be applied to the brake pads 4 and brake shoes that are replacement parts. [Explanation of symbols]

[0044] 1...Brake device, 2...Disc rotor, 2a...Friction surface, 3...Caliper, 3a...cylinder, 3b...piston, 3c...Brake cylinder chamber, 4...Brake pads, 5...backplate, 6...Brake friction material, 6...Transfer film material, 6a...Two-layer material (underlayer), 6b...Friction base material, 6c...Transfer film material, 6d...first transfer film layer, 6e...second transfer film layer, 7...return spring, 11...Brake drive unit, H...hub

Claims

1. a friction base material laminated on a back plate; a transfer film material laminated on the friction base material and facing the opposing member; In a brake friction material having The transfer film material is formed from a composition containing an organic filler in a resin component with a very low melting point. A brake friction material characterized by:

2. The transfer film material is formed of two or more transfer film layers, The melting point of the extremely low melting point resin component is set lower as it moves from the transfer film layer on the friction base material side to the transfer film layer on the outermost surface.

2. The brake friction material according to claim 1.

3. the transfer film material has a two-layer structure consisting of a first transfer film layer on the friction base material side and a second transfer film layer as an outermost layer facing the facing member; The first transfer film layer is formed from a composition containing a cryogenic melting point resin component having a low melting point, The second transfer film layer is formed of a composition containing an organic filler that spreads at a temperature lower than that of the cryogenic melting point resin component of the first transfer film layer.

2. The brake friction material according to claim 1.

4. A vehicle wheel equipped with a brake device having the brake friction material according to claim 1 is placed on a roller provided on a fixed stand for an actual vehicle running test, driving the vehicle while restraining it on the fixed base; activating the brake device to press the transfer film material of the brake friction material against the opposing member that rotates integrally with the wheel, thereby continuing low-load braking for a predetermined period of time; The transfer film material is transferred to the friction surface of the opposing member by the amount of heat generated at the friction interface between the transfer film material and the opposing member, thereby forming a transfer film on the friction surface. A method for producing a transfer film using a brake friction material.

5. A wheel of a vehicle to which a brake device having the brake friction material according to claim 2 or 3 is attached is placed on a roller provided on a fixed stand for an actual vehicle running test, driving the vehicle while restraining it on the fixed base; activating the brake device to press the transfer film material of the brake friction material against the opposing member that rotates integrally with the wheel, thereby continuing low-load braking for a predetermined period of time; The heat generated at the friction interface between the transfer film material and the facing member transfers at least the outermost transfer film layer to the friction surface of the facing member, forming a transfer film on the friction surface. A method for producing a transfer film using a brake friction material.

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