KR102410956B1 - Carbon material rotor and vane for vehicle vacuum pump and manufacturing method thereof - Google Patents

Abstract

The present invention discloses a method of manufacturing a rotor and a vane for a vacuum pump of a vehicle using a carbon material. The rotor and vane of the present invention are wet mixed to form a mixed carbon material by putting 100 parts by weight of carbon powder, 10 to 20 parts by weight of minced pitch-based carbon fiber powder, and 20 to 40 parts by weight of a pitch-based binder together with a solvent in a mixer. Step, a drying step of drying the carbon material, a granulation step of granulating the carbon material, a molding step of manufacturing the rotor and vane molded using a press mold, and the rotor and vane sintered by heat treatment at high temperature It includes a sintering step to prepare, and an impregnation step of filling the pores generated in the sintered rotor and vane by putting 100 parts by weight of the mesophase pitch into the impregnation device. According to the present invention, it is possible to manufacture a rotor and a vane for a vacuum pump of a brake system of a vehicle having excellent average flexural strength and good durability from a carbon material.

Description

A rotor and vane for a vacuum pump for a vehicle using a carbon material and a manufacturing method thereof

The present invention relates to a method for manufacturing a rotor and a vane for a vacuum pump for a vehicle brake system using a carbon material, and more particularly, to a carbon material for a vehicle vacuum pump by powder-molding a rotor and a vane for an initial shape, then sintering at a high temperature and sintering in the sintering process Carbon material rotor for vehicle brake system vacuum pump with good durability by lowering mechanical properties, especially expansion coefficient, and improving wear resistance by repeating the process of filling the pores by impregnating the pitch several times as much as impurities, volatile matter and insoluble matter are removed and to a method of manufacturing the vanes.

The vacuum pump that controls the existing mechanical brake system was a wet pump that operates the brake system with hydraulic pressure generated by transferring engine oil. ) by suction and transfer, it is being replaced by a dry pump that operates the brake system only with the pressure of air generated by the rotation of the rotor and the frictional force of the vanes.

In the case of dry friction between metal (the plate in the stuffing box inside the pump) and the metal (the rotor that generates the internal rotational force) under high-speed rotation, the iron-based (Fe) products that were conventionally used in the past are caused by rapid metal abrasion, friction noise, and sparks. Since the material composition cannot be applied due to the inherent danger of explosion, it is essential to apply a carbon material capable of dry friction operation. After initial molding, high-temperature vacuum heat treatment and pitch impregnation to improve mechanical properties were used to improve durability.

In Registered Patent Publication No. 10-1996205 “Eco-friendly carbon bearing applied with carbon fiber for vehicle transport in automobile production line and its manufacturing method”, carbon powder, carbon fiber, and pitch binder are mixed to form a source material, After grinding the material and forming an intermediate material into grains or granules through dry ice, the intermediate material undergoes a pretreatment process, vacuum heat treatment, and carbonization process to finally manufacture a carbon bearing, which is environmentally friendly and has mechanical strength, etc. This conventional bearing has the same or similar effect, the impregnation process is excluded, and the friction coefficient is lowered by the pitch-based carbon fiber mixed with the carbon bearing, thereby improving wear resistance and increasing durability. are doing

Registered Patent Publication No. 10-1996205 “Eco-friendly carbon bearing applied with carbon fiber for vehicle transport in automobile production line and its manufacturing method” (registered on June 27, 2019)

An object of the present invention is to provide a rotor and a vane for a vacuum pump for a brake system of a vehicle having excellent durability, and a method for manufacturing the same.

Another object of the present invention is to provide an eco-friendly rotor and vane for a vacuum pump of a vehicle and a manufacturing method thereof.

Objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

According to one aspect for achieving the above object, in a method for manufacturing a rotor and a vane for a vacuum pump for a brake system of a vehicle using a carbon material, 100 parts by weight of carbon powder, pitch-based carbon fiber powder (0.1mm to 1.5mm) 10 ~ 20 parts by weight, wet mixing step of forming a mixed carbon material by adding 20-40 parts by weight of a pitch-based binder obtained by vacuum heat treatment at 300 ° C. to 350 ° C. to purify impurities and volatiles in a mixer together with a solvent; a drying step of drying the carbon material mixed in the wet mixing step; a granulation step of granulating the dried carbon material into 60 mesh; A molding step of manufacturing the granulated carbon material into press molds and press-molded rotors and vanes; a sintering step of sintering the molded rotor and vane by vacuum heat treatment at a high temperature; and 100 parts by weight of the mesophase pitch was put into the impregnation apparatus to fill the pores generated by the removal of volatiles, impurities and insolubles in the sintering process in the sintered rotor and vane, and melted in the softening point of 300 ° C. and an impregnation step of forcibly press-fitting (impregnating) the liquid pitch by inputting the sintered rotor and vanes.

In the wet mixing step, the solvent is any one selected from the group consisting of methyl alcohol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and toluene 10 to 30 Weight parts can be added.

In the granulation step, the dried carbon material is pulverized and filtered into a 60 mesh shape, and then the carbon material is granulated into grain-shaped granules having an average particle size of 1.0 to 2.0 mm using a spray drying method. can

Before the sintering step, a pretreatment step of heat-treating the molded rotor and vane at 400 to 800° C. for 6 to 10 hours; may further include.

In the sintering step, heat treatment may be performed at 2,300 to 2,800° C. for 8 hours in a nitrogen atmosphere.

In the impregnation step, the pitch and graphite injected into the impregnation device are melted at a temperature of 200 to 400° C., and the sintered vane is added, and then the impregnation may be performed at 1 to 3 bar for 3 to 7 hours. The impregnation step may be repeated 3 to 4 times to improve mechanical properties.

After the impregnation step, a post-treatment step of heat-treating the impregnated vane at 500 to 600° C. for 1 to 5 hours; may further include.

The rotor and vane for a vehicle vacuum pump and a method for manufacturing the same according to the present invention are materials that can be used in dry and high-speed rotation (about 8,000 rpm) by lowering the coefficient of thermal expansion, and can perform a stable function during brake operation and have excellent durability do.

The rotor and vane for a vacuum pump for a vehicle brake system according to the present invention and a method for manufacturing the same do not cause environmental problems as an environmentally friendly carbon material free of impurities and harmful heavy metals.

Effects of the present invention are not limited to the above-described effects, and effects not mentioned will be clearly understood by those skilled in the art from this specification and the accompanying drawings.

1 is a photograph showing a state in which a rotor and a vane according to an embodiment of the present invention are used in a vacuum pump for a vehicle.
2 is a flowchart illustrating a method of manufacturing a rotor and a vane used in a vehicle vacuum pump and a carbon material thereof according to an embodiment of the present invention.
3 is a cross-sectional view of a mold for powder molding for rotors and vanes used in a vacuum pump for a brake system of a vehicle according to an embodiment of the present invention.
4 is a graph showing the density change according to the impregnation time during the manufacturing process of the rotor and the vane according to an embodiment of the present invention, and a photograph showing the appearance before and after the impregnation.
5 is a graph comparing average flexural strengths before, after, and after heat treatment after impregnation of a rotor and a vane according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings and the content to be described later. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art. Like reference numerals refer to like elements throughout. Meanwhile, the terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular form also includes the plural form unless otherwise specified in the phrase. As used herein, "comprises." and/or "comprising" does not exclude the presence or addition of one or more other components, steps, acts and/or elements in which the recited elements, steps, acts and/or elements are.

Hereinafter, with reference to the drawings, a carbon material for a vehicle vacuum pump, a rotor, and a vane and a manufacturing method thereof according to an embodiment of the present invention will be described in detail.

1 is a photograph showing a state in which a rotor and a vane according to an embodiment of the present invention are used in a vacuum pump for a vehicle.

Figure 1 (a) shows a conventional mechanical vacuum pump, Figure 1 (b) shows an electric vacuum pump to which the present invention is applied.

Referring to FIG. 1( a ), a conventional mechanical vacuum pump includes a housing 110 having an inlet and an outlet through which air is input and discharged, a cam ring 130 installed in the housing, and a cam ring and eccentrically mounted inside the cam ring. It is composed of a rotor 150 to be used, a vane 170 inserted into the slot of the rotor, and a plate 190 covering the upper portion of the cam ring. When the rotor rotates, the vane 170 rotates in contact with the inner surface of the cam ring by centrifugal force, and the space between the cam ring and the rotor is blocked by the vane. Since the rotor rotates eccentrically with the cam ring, the size of the closed space is reduced by rotation, which creates a vacuum as the air is compressed. The mechanical vacuum pump has a structure in which the rotating shaft is connected to the engine's drive shaft and operates at all times regardless of brake operation.

Referring to FIG. 1B , the electric vacuum pump includes a housing 115 , a cam ring 135 , a rotor 155 , a vane 175 , and a plate 195 . The electric vacuum pump is configured independently of the engine and is driven from the vehicle's generator or battery to operate only when necessary, which is advantageous in terms of fuel efficiency and efficiency. With a separate vacuum pump separated from the engine, it has a structure that does not require engine oil, so it is possible to simplify and reduce the weight, which is advantageous for improving fuel efficiency. The electric vacuum pump is called a dry lubrication device because it does not have a separate lubricating oil supply line for its simple structure. When the rotor 155 rotates, the vane 175 protrudes by centrifugal force and rotates in contact with the inner surface of the cam ring 135 . Friction occurs between the vane and the cam ring due to high-speed rotation, and when the vane is worn by frictional heat, the vacuum performance deteriorates, and in severe cases, the brake operation may change abnormally.

To prevent this, the rotor 155 and the vane 175 are manufactured by using a high-density carbon material that can minimize physical properties and dimensional changes for frictional heat, filling the pores in the carbon molded body with pitch and improving mechanical properties, cam ring ( 135) is made of a metal such as stainless steel or aluminum, but the inner surface may be coated with a low friction material such as tungsten disulfide (WS ₂ ) or molybdenum disulfide (MoS ₂ ).

2 is a flowchart illustrating a method for manufacturing a rotor and a vane used in a vacuum pump for a brake system for a vehicle and a carbon material thereof according to an embodiment of the present invention.

The process of manufacturing the rotor 155 or the vane 175 used in the vehicle brake system vacuum pump includes the carbon material manufacturing step (S210) of manufacturing the carbon material, which is the material, and the form of the rotor or vane using the carbon material. In the powder press molding step (S250) of molding, the sintering step (S250) of heat-treating the molded material at high temperature to give mechanical strength, and applying high-temperature heat during sintering, the material inside the carbon material is volatile, impurities and It includes an impregnation step (S250) to fill the pores generated when the insoluble matter is removed.

The carbon material manufacturing step (S210) includes a wet mixing step (S220), a drying step (S230), and a granulation step (S240).

In the wet mixing step (S220), 100 parts by weight of carbon powder, 10 to 20 parts by weight of pitch-based carbon fiber powder, and 20 to 40 parts by weight of a refined pitch-based binder are mixed with a solvent to form a slurry.

Nodular graphite is used as the carbon powder, and in the case of carbon powder, an average particle size of 50 to 250 μm is used. In the case of carbon fibers, powdered ones with an average length of 0.1 to 1.5 mm can be used. The pitch-based binder may be used in which impurities and volatiles are purified by vacuum heat treatment at 300 to 350°C.

In the wet mixing step (S220), as the mixer, an air-rotation precision mixing device can be used, and 10 to 30 parts by weight of a solvent and a carbon material are put into the mixer, and the rotation speed is 60 to 100 rpm for 2 to 6 hours. Mix. The solvent may be selected from organic solvents such as methyl alcohol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and toluene that can disperse carbon powder and pitches. have.

In the drying step (S230), the mixture is dried at a temperature of 40 to 80° C. for 20 to 40 minutes to remove the solvent.

In the granulation step (S240), the dried sample is pulverized and selectively collected into 60 mesh, and then the carbon material is granulated into grain-shaped granules having an average particle size of 1.0 to 2.0 mm by using a spray drying method.

In order to manufacture a rotor or a vane using a carbon material in a particulate state, a powder press molding step (S250) of making a molded body having the shape of a rotor or a vane, a pretreatment process that can ensure dimensional stability, and bonding between particles It includes a sintering step (S270) to achieve, and an impregnating step (S290) to fill the internal pores.

In the press molding step (S250), a particulated carbon material is put into a press mold to manufacture a molded body having a shape of a rotor or a vane.

3 is a cross-sectional view of a press mold for a rotor and a vane used in a vacuum pump for a vehicle according to an embodiment of the present invention. Fig. 3 (a) is a view showing a surface cut through the center of the mold when viewed from the front, and Fig. 3 (b) is a view showing a surface cut from the center of the mold when viewed from the side.

The press mold includes a base 310 , an upper pad 330 , and a lower pad 350 . In a state in which the lower pad is fixed with respect to the base, the granulated carbon material is put into the space above the lower pad 350 . The upper pad 330 is lowered to apply pressure to the carbon material. The press pressure can be applied from 0.5 to 2.0 ton/cm ² .

When the upper pad moves by a set distance and stops, the base 310 , the lower pad 350 , and the upper pad 330 may form a molding space 370 suitable for the shape of the molded body. When the molding is completed, the lower pad 350 may be raised with respect to the base to discharge the molded carbon material.

The sintering step (S270) is a step of heat-treating the rotor or vane formed in the press forming step at a high temperature. Since the carbon material is strongly bonded by high-temperature heat treatment, the mechanical strength of the molded rotor or vane is improved during the sintering step. On the other hand, when some components inside the carbon material are volatilized by high-temperature heat treatment and pores are formed inside the carbon material, it may be a factor to reduce the durability of the rotor or vane. Therefore, it is preferable to divide the sintering step into two steps and proceed sequentially. That is, it can proceed by adding a pre-treatment step before the sintering step.

In the pre-treatment step, the molded rotor or vane is heat-treated at 400-800° C. for 6-10 hours. In the pre-treatment stage, it is carried out for the purpose of dimensional stabilization that can secure the dimensions of the final carbon molded body through the removal of impurities and the primary shrinkage process.

In the sintering step, heat treatment is performed at 2,300 to 2,800° C. for 6 to 10 hours. Through high-temperature heat treatment, mechanical properties such as hardness, strength, and density can be improved and a uniform structure can be obtained. The sintering step prevents oxidation or carbonization of the carbon compact by creating an atmosphere of an inert gas such as nitrogen or argon.

In the impregnation step (S290), when the volatile matter, impurities and insoluble matter inside the carbon molded body are removed in the sintering process, as many pores as the removed are generated, these voids are filled to achieve stable wear.

In the impregnation device, 100 parts by weight of the pitch is put into the impregnation device, melted at 200-400° C., which is a softening point of 300° C., and then the sintered product is put in, and the impregnation is performed at 1 to 3 bar for 3 to 7 hours. Conduct. The pitch is preferably mesophase, and if necessary, 10 to 20 parts by weight of graphite may be additionally added.

After impregnation, a post-treatment process of heat treatment at 500-600° C. for 1 to 5 hours may be added.

Hereinafter, with reference to the embodiment, a rotor and a vane, which are carbon materials for a vehicle vacuum pump, according to an embodiment of the present invention will be described in detail.

<Example - Carbon material manufacturing>

100 parts by weight of carbon powder, 15 parts by weight of chopped pitch-based carbon fiber powder (0.1mm to 1.5mm), and 30 parts by weight of a pitch-based binder were mixed with 20 parts by weight of methyl alcohol and put into a precision mixing device. The mixing device was rotated at 80 rpm to evenly mix for 4 hours.

After mixing, the sample was dried in a dryer at 60° C. for 30 minutes.

A granular carbon material with an average particle size of 1.5 mm was prepared through a spray-drying process by collecting 60 mesh carbon particles.

< Example - Rota and vane forming and sintering>

The manufactured carbon material was put into the hopper (automatic material feeding device) of the powder press, and the rotor and vane shapes were formed by operating the press device. The press device applied a pressure of 1.5 ton/cm ² to the sample to cold-form the rotor and the vane.

After heat treatment at 600° C. for 8 hours as a pretreatment process for sintering, the sintering process was performed at 2,300° C. for 8 hours in a nitrogen atmosphere.

< Example - Rota and vanes impregnation >

Pitch impregnation was performed on the sintered product. 100 parts by weight of mesophase pitch was put into the impregnation device, melted at 300° C., and then the sintered product was added, followed by impregnation at 2 bar (about 2 atm) for 5 hours. After impregnation, heat treatment was performed at 550° C. for about 3 hours.

4 is a graph showing the density change according to the impregnation time during the manufacturing process of the rotor and the vane according to an embodiment of the present invention, and a photograph showing the appearance before and after impregnation.

4 (a) shows the density change according to the impregnation time, it can be seen that the density gradually increases as the impregnation time increases. However, the density increase after 1 hour is limited. In subsequent experiments, the impregnation time was maintained at 5 hours.

Figure 4 (b) is a photograph showing the appearance before impregnation, Figure 4 (c) is a photograph showing the appearance after impregnation. In the photo before impregnation, a large number of pores 410 indicated by black dots are visible, but it can be seen that the pores are not visible after impregnation.

< Experimental example - Average flexural strength>

Table 1 summarizes the results of measurement of average flexural strength and Shore hardness before impregnation, after impregnation, and after heat treatment after impregnation.

5 is a graph comparing the average flexural strength of rotors and vanes according to an embodiment of the present invention before impregnation, after impregnation, and after heat treatment after impregnation.

Before impregnation, the average flexural strength did not reach the target value, but it can be seen that the average flexural strength after impregnation was significantly improved. In the case of Shore hardness, it decreased slightly, but it is not a problem because there is room compared to the target value.

average flexural strength
(kgf/cm ² ) Shore hardness evaluation target value 490.00 75 before impregnation 394.67 88 × after impregnation 658.29 84 ○ Heat treatment after impregnation 819.03 84 ◎

From the above results, it can be seen that the average flexural strength of the rotor and the vane for the brake system vacuum pump of a vehicle can be significantly improved by impregnation using mesophase pitch and heat treatment after impregnation.

115: housing 135: cam ring
155: Rota 175: Vane
195: plate 410: pore

Claims (5)

In the manufacturing method of a rotor or vane for a brake system vacuum pump of a vehicle using a carbon material,
100 parts by weight of carbon powder, 10 to 20 parts by weight of chopped pitch-based carbon fiber powder, and 20 to 40 parts by weight of a pitch-based binder together with a solvent are put into a mixer to form a mixed carbon material;
a drying step of drying the carbon material mixed in the wet mixing step;
a granulation step of granulating the dried carbon material;
A molding step of manufacturing a molded body having a shape of a rotor or a vane using the granulated carbon material using a press mold;
a sintering step of heat-treating the molded body at a high temperature to produce a sintered body; and
After the sintering step, in order to fill the pores generated in the sintered body, 100 parts by weight of the mesophase pitch is put into an impregnation device to melt it, and then the impregnation step of impregnating the sintered body by inputting the sintered body; includes,
Before the sintering step, a pretreatment step of heat-treating the molded body at 400 to 800° C. for 6 to 10 hours; further comprising,
In the sintering step, heat treatment is performed at 2,300 to 2,800 ° C. for 6 to 10 hours in a nitrogen atmosphere,
In the impregnation step, the impregnation pitch put into the impregnation device is melted at a temperature of 200 to 400° C., and after the sintered body is put in, the impregnation is performed at 1 to 3 bar for 3 to 7 hours,
After the impregnation step, a post-treatment step of heat-treating the impregnated rotor or vane at 500 to 600° C. for 1 to 5 hours; the method of manufacturing a rotor or vane for a vacuum pump for a brake system of a vehicle further comprising a further comprising. The method of claim 1,
In the wet mixing step, the solvent is 10 to 30 parts by weight of any one selected from methyl alcohol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and toluene. A method of manufacturing a rotor or vane for a vacuum pump for a brake system of a vehicle, characterized in that The method of claim 1,
In the granulation step, after pulverizing the dried carbon material and filtering it to 60 mesh, the carbon material is granulated into grain-shaped granules having an average particle size of 1.0 to 2.0 mm using a spray-drying method. A method of manufacturing a rotor or vane for a vacuum pump for a brake system of a vehicle, characterized in that. delete delete

Images