KR20030075972A - Brake rotor for minimizing brake judder and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A brake rotor is provided which is capable of suppressing generation of heat and easily emitting heat by maximizing size of graphite as satisfying mechanical strength and hardness values required in existing brake rotor, and a manufacturing method of the brake rotor is provided. CONSTITUTION: In a brake rotor formed of gray cast iron, the brake rotor is characterized in that the gray cast iron comprises 3.7 to 4.0 wt.% of carbon and 0.8 to 2.2 wt.% of silicon, carbon equivalent between carbon and silicon is 4.5 to 4.7, and cooling speed during casting of the brake rotor is 45 to 55 minutes, wherein the gray cast iron further comprises 0.7 to 0.8 wt.% of manganese, 0.05 to 0.1 wt.% of sulfur, 0.05 to 0.1 wt.% of phosphorus, 0.2 to 0.4 wt.% of chromium, 0.2 to 0.4 wt.% of copper and 0.01 to 0.05 wt.% of tin, and wherein melt pouring temperature is in the temperature range of 1,410 to 1,440 deg.C, and melting furnace tapping temperature is in the temperature range of 1,490 to 1,510 deg.C. In a method for manufacturing a brake rotor formed of gray cast iron, the manufacturing method of the brake rotor comprises a process in which the gray cast iron comprises 3.7 to 4.0 wt.% of carbon and 0.8 to 2.2 wt.% of silicon, and carbon equivalent between carbon and silicon is 4.5 to 4.7; and a process in which cooling speed during casting of the brake rotor is 45 to 55 minutes.

Description

Brake rotor with minimum brake judder and manufacturing method {BRAKE ROTOR FOR MINIMIZING BRAKE JUDDER AND MANUFACTURING METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake rotor, and more particularly, to a brake rotor which minimizes the phenomenon of brake judder.

The configuration and operation of a conventional caliper brake rotor are as follows. 1 is an exploded perspective view of a disc brake according to the prior art, and FIG. 2 is a schematic cross-sectional view of FIG.

A disc (hereinafter referred to as brake rotor) mounting plate 3 having a coupling rod 3a formed on the outer circumference of the rotating shaft 2 of the steering knuckle 1 is fixedly installed, and the brake rotor mounting plate 3 is provided with a coupling hole. The brake rotor 5 in which 5a is formed is fixedly installed, and the coupling rod 3a is coupled to the coupling hole 5a. The caliper assembly is provided in the fixture 4 formed in one side of the steering knuckle 1. The caliper assembly includes a caliper 10 including a cylindrical cylinder 12 having a pad settled portion 11, an opening 12a and a closing wall 12b, and which is mounted to the pad settled portion 11. Pads 13 and 14, and a piston 15 inserted into the cylinder 12. Both side portions of the brake rotor 5 are fitted between the pads 13 and 14. The brake hose 16 supplies fluid to the space S between the closing wall 12b of the cylinder 12 and the piston 15, and the bush 17 serves to return the piston to its original shape while serving as a packing. Do it. When braking the vehicle, when the brake pedal is pressed, fluid flows into the space S through the brake hose 16, and the hydraulic pressure acts on the piston 15 and the closing wall 12b of the cylinder 12, thereby providing a pad 13. 14 moves the brake rotor 5 toward the brake rotor to squeeze the brake rotor 5 and brake the vehicle by the mutual frictional force between the brake rotor 5 and the pads 13 and 14. As the material of the brake rotor, gray cast iron (flake graphite iron) having excellent thermal characteristics, heat dissipation, and vibration damping ability is usually employed.

The brake judder is a brake torque change BTV (Brake Torque Variation) is generated when the vehicle brakes in such a manner as the pads 13 and 14 come into contact with each other in a non-parallel state. It refers to the phenomenon of vibrating the body or steering wheel by moving and amplifying along the suspension and steering system. Among the causes of the brake judder, the most influential factor is DTV (Disc Thickness Variation) in which the thickness and shape of the brake rotor change due to thermal deformation, and the change in the thickness of the brake rotor caused by non-parallel contact between the friction material and the brake rotor. It is becoming.

Efforts have been made to develop brake rotors with low DTV values. To date, studies on brake rotors have been conducted mainly on the heat transfer characteristics of the rotors, and are intended to eliminate rotor thickness changes caused by frictional heat. The study of braking characteristics according to the microstructure of gray cast iron is insignificant.

There may be many causes of DTV, but the present inventors note that deformation due to thermal effects is the biggest factor. Therefore, in order to minimize such thermal deformation, it is important to find an optimum carbon equivalent and cooling rate. The fact that the composition and cooling rate of the molten metal affect the graphite shape of the gray cast iron, the microstructure of the ferrite and the pearlite, and thus the hardness, strength, thermal conductivity, coefficient of friction, vibration damping ability, etc. Because it will affect.

The present invention has been made to solve the above problems, it is an object of the present invention to provide a brake rotor with a minimum of the brake judder phenomenon when braking.

According to claim 1 of the present invention, in the brake rotor made of gray cast iron, the content of carbon and silicon in the gray cast iron is 3.7 to 4.0 wt% carbon, 0.8 to 2.2 wt% silicon, and the carbon equivalent between them is 4.5 to 4.7, Cooling speed during the casting of the brake rotor is provided a brake rotor, characterized in that 45 minutes ~ 55 minutes.

Further, according to claim 2 of the present invention, the content of the other components of the gray cast iron according to claim 1, manganese 0.7 ~ 0.8wt%, sulfur 0.05 ~ 0.1wt%, phosphorus 0.05 ~ 0.1wt%, chromium 0.2 ~ 0.4wt It is provided with a brake rotor, characterized in that the%, copper 0.2 ~ 0.4wt%, tin 0.01 ~ 0.05wt%.

According to claim 3 of the present invention, the brake rotor according to claim 2, wherein the carbon equivalent is 4.673 and the cooling rate is 55 minutes.

According to claim 4 of the present invention, the brake rotor according to any one of claims 1 to 3, wherein the molten metal injection temperature is 1410 ℃ ~ 1440 ℃, melting furnace tapping temperature is 1490 ℃ ~ 1510 ℃ Is provided.

1 is an exploded perspective view of a conventional disc brake;

2 is a schematic cross-sectional view of FIG. 1 of a conventional disc brake;

3A and 3B are tissue photographs of a conventional brake rotor.

4A to 12B are structure photographs of the brake rotor under respective conditions when the carbon equivalent and the cooling rate are changed in the brake rotor according to the present invention.

The present invention is based on the inventors' recognition that it is most important to find the conditions of carbon equivalent and cooling rate as a casting method for suppressing thermal deformation in a conventional brake rotor, and the mechanical performance is improved through the DTV test. In order to find the optimum carbon equivalent and cooling rate that can provide the rotor, in the manufacture of the brake rotor, a step cast casting method is used to produce gray cast iron having different chemical composition and cooling rate, and fine. A comparative experiment on the characteristics of DTV according to organizational change is conducted. The results of the comparative experiments showed that the change of microstructure with the change of carbon equivalent and the cooling rate causes a remarkable change in the characteristics of DTV.

In the comparative experiment, the material change according to the composition of the rotor and the cooling rate is analyzed, and then the frictional wear pattern of the rotor is derived by using a commercial friction material.

First, the chemical composition, hardness, tensile strength and microstructure of the conventional rotor, and the results of DTV (Disc Thickness Variance) measurement, which is the main cause of the shaking phenomenon, are as follows. FIG. The organization chart of the brake rotor is photographed using an image analyzer.

1) chemical composition

division C Si Mn P S Cu Cr Sn Bal. Conventional rotor 3.7 0.8-2.1 0.8 0.05 0.03 0.21 0.25 0.02 Remainder

(The above values are based on wt%)

2) Carbon equivalent (C.E): 4.3

3) hardness and tensile strength

HB 185 to 210 (measuring 5 points each at 4 locations), 22 kg / f / cm ²

4) Graphite tissue

Graphite Shape: ASTM A, B or D type

Graphite Size: 0.2 ~ 0.3mm

5) DTV amount after endurance test

Machining variation after casting: 22㎛ compared to specification (10㎛ or less)

Strain after 30,000 Km endurance: 18 ~ 22㎛ or less

Among the above components and compositions, the components basically employed in the present invention and their composition ranges are as follows.

C Si Mn S P Cr Cu Sn Bal. 3.7 ~ 4.0 0.8-2.2 0.7 to 0.8 0.05 ~ 0.1 0.05 ~ 0.1 0.2-0.4 0.2-0.4 0.01 ~ 0.05 0.012

(The above values are based on wt%)

Next, in manufacturing the gray cast iron rotor according to the present invention experimentally produced a total of nine different microstructure gray cast iron rotor by changing the carbon equivalent and the cooling rate in the above basic components and its composition range, The meaning of the numbers in the table indicates Experimental Examples 1 to 9 according to the present invention produced under conditions of different carbon equivalents and cooling rates.

Cooling rate 25 minutes 40 minutes 45 minutes-55 minutes 4.0 One 2 3 4.3 4 5 6 4.5 ~ 4.7 7 8 9

4A to 12B attached to the specification of the present invention is an organization chart of the rotor tissue of Experimental Examples 1 to 9 using an image analyzer. In measuring the results, 10 microstructures in the circumferential direction were analyzed for nine rotors manufactured under each casting condition. The analysis area of each point was 0.5mm x 0.5mm and the graphite, ferrite and ferrite structures were simultaneously analyzed. For this purpose, we analyzed the effect of microstructure distribution on the uneven wear pattern of the rotor caused by friction material by analyzing the respective tissues by using the image analyzer to remove the severely changed and unchanged regions of the rotor.

As described above, the friction materials to be used for the wear test on nine gray cast iron rotors having different microstructures according to the change in carbon equivalent and cooling rate were selected from the domestic friction materials in mass production. The resulting values such as the hardness value and the graphite length of each obtained brake rotor are as follows.

Hardness Test (Brinell Hardness Tester, 10mm Ball, 3000Kgf)

division Cooling rate (25 minutes) Cooling speed (40 minutes) Cooling speed (45 ~ 55 minutes) Carbon equivalent (4.0) 190-210 180-190 185-190 Carbon equivalent (4.3) 190-210 185-200 185-190 Carbon equivalent (4.5 ~ 4.7) 180-190 175-190 160-170

Graphite length (length in actual kitchen: mm)

division Cooling rate (25 minutes) Cooling speed (40 minutes) Cooling speed (45 ~ 55 minutes) Carbon equivalent (4.0) 0.09-0.22 0.1-0.25 0.26-0.33 Carbon equivalent (4.3) 0.22-0.3 0.2-0.3 0.32-0.37 Carbon equivalent (4.5 ~ 4.7) 0.28-0.34 0.31-0.42 0.44-0.57

Graphite Shape (ASTM A, B, C, D, E Type)

division Cooling rate (25 minutes) Cooling speed (40 minutes) Cooling speed (45 ~ 55 minutes) Carbon equivalent (4.0) A or D A or D A or B Carbon equivalent (4.3) A A A Carbon equivalent (4.5 ~ 4.7) A A A or C

DTV (face-to-face attack) test result (Dynamo Testing: ㎛)

division Cooling rate (25 minutes) Cooling speed (40 minutes) Cooling speed (45 ~ 55 minutes) Carbon equivalent (4.0) 25 21 17 Carbon equivalent (4.3) 28 19 20 Carbon equivalent (4.5 ~ 4.7) 21 18 12

As can be seen from the above experimental results, it can be seen that the graphite shape, the graphite length, in particular, the DTV changes as the carbon equivalent and the cooling rate of the components change in the casting of the brake rotor.

In the above experimental results, it can be seen that the result value of Experimental Example 5 exhibits a performance substantially similar to that of the conventional brake rotor. Particularly, Experimental Example 9 (carbon equivalent: 4.5 to 4.7, cooling rate: 45 to 55 minutes), while meeting the mechanical requirements of the conventional brake rotor, it can be seen that the graphite length is greatly increased while the DTV is significantly reduced.

Such facts are clearly understood even when observed in comparison with FIGS. 3A and 3B which are tissue photographing degrees of the conventional brake rotor and FIGS. 12A and 12B which are tissue photographing figures of Experimental Example 9 of the brake rotor according to the present invention. 12A and 12B, the width and length of the graphite of the rotor structure increased significantly, and it can be seen that the black portion representing the graphite increased significantly compared to FIGS. 3A and 3B.

In addition, the inventors of the present invention preferably the temperature range of the molten metal during the casting of the brake rotor 1414 ℃ ~ 1440 ℃, the tapping temperature of the melting furnace is 1490 ℃ ~ 1510 ℃, it is optimal when the following casting conditions are satisfied We can see that we can produce brake rotors.

C Si Mn S P Cr Cu Sn Bal. 3.95 2.17 0.713 0.076 0.1 or less 0.250 0.301 0.044 0.012

(The above values are based on wt%)

1) carbon equivalent: 4.673

2) Injection temperature: 1434 ℃

3) Melting furnace tap temperature: 1506 ℃

4) Dismantling time (cooling speed): 55 minutes

According to the brake rotor according to the present invention manufactured under the above conditions, the lubrication characteristics and friction characteristics of the brake rotor are improved, and heat generation is suppressed. It was further improved, and the brake judder was also improved.

As described above, according to the brake rotor of the present invention, while satisfying the mechanical strength and hardness values required in the conventional brake rotor, the brake is capable of maximizing the size of graphite to suppress heat generation and facilitate heat dissipation. The rotor can be provided.

In addition, according to the brake rotor of the present invention, the braking force is increased due to the improved braking property, and the pedal feeling is improved due to the reduction of the brake judder phenomenon.

Claims (7)

In a brake rotor made of gray cast iron, The content of carbon and silicon in the gray cast iron is from 3.7 to 4.0 wt% of carbon and 0.8 to 2.2 wt% of silicon, and the carbon equivalent between them is 4.5 to 4.7, and the cooling rate during casting of the brake rotor is 45 to 55 minutes. Brake rotor. The method of claim 1, The content of the other components of the gray iron is manganese 0.7 ~ 0.8wt%, sulfur 0.05 ~ 0.1wt%, phosphorus 0.05 ~ 0.1wt%, chromium 0.2 ~ 0.4wt%, copper 0.2 ~ 0.4wt%, tin 0.01 ~ 0.05 wt% Brake rotor, characterized in that. 3. The brake rotor according to claim 2, wherein the carbon equivalent is 4.673 and the cooling rate is 55 minutes. The method according to any one of claims 1 to 3, Melt injection temperature is 1410 ℃ ~ 1440 ℃, melting furnace tapping temperature is 1490 ℃ ~ 1510 ℃ brake rotor, characterized in that. In the method for manufacturing a brake rotor made of gray cast iron, The content of carbon and silicon in the gray cast iron is 3.7 to 4.0 wt% carbon, 0.8 to 2.2 wt% silicon, and the carbon equivalent between them is 4.5 to 4.7, and Cooling speed during the casting of the brake rotor is a manufacturing method of the brake rotor, characterized in that it comprises a step of 45 minutes to 55 minutes. The method of claim 5, The content of the other components of the gray iron is manganese 0.7 ~ 0.8wt%, sulfur 0.05 ~ 0.1wt%, phosphorus 0.05 ~ 0.1wt%, chromium 0.2 ~ 0.4wt%, copper 0.2 ~ 0.4wt%, tin 0.01 ~ 0.05 wt% Method for producing a brake rotor, characterized in that. The method according to claim 5 or 6, Melt injection temperature is 1410 ℃ ~ 1440 ℃, melting furnace tapping temperature is 1490 ℃ ~ 1510 ℃ manufacturing method of a brake rotor characterized in that it further comprises a step of.