KR100401748B1 - A PTC ceramic pre-heater and the preparing method thereof - Google Patents

Abstract

The present invention relates to a PTC ceramic heater for an auxiliary heating device and a method of manufacturing the same, and more particularly, a barium titanate (BaTiO ₃ ), which is a ferroelectric, as a main component, and includes Si, Ti, Fe, V, Cu, Pb, and It has low specific resistance at room temperature, including Sn component, and has high specific resistance above transition temperature of ferroelectric material. It has good low temperature characteristics, and it has good calorific value and fast heating performance of cooling water, which increases winter defrosting and heating effect. The present invention relates to a PTC ceramic heater for auxiliary heating device, which is a positive resistance temperature coefficient (PTC) thermistor capable of improving the quality of a vehicle, and a manufacturing method thereof.

Description

PTC ceramic heater for auxiliary heating device and its manufacturing method {A PTC ceramic pre-heater and the preparing method

The present invention relates to a PTC ceramic heater for auxiliary heating device and a method of manufacturing the same, and more particularly, based on the ferroelectric barium titanate (BaTiO ₃ ), and includes Si, Ti, Fe, V, Cu, Pb, and It has low specific resistance at room temperature, including Sn component, and has high specific resistance above transition temperature of ferroelectric material. It has good low temperature characteristics, and it has good calorific value and fast heating performance of cooling water to increase defrosting and heating effect in winter. The present invention relates to a ceramic heater for an auxiliary heating device which is a positive temperature coefficient of electrical resistivity (PTC ') thermistor capable of improving the quality of a vehicle, and a manufacturing method thereof.

Vehicles using direct injection engines adopt the method of heating and using the coolant by heating the engine after starting for winter heating and defrosting.

In the case of DI diesel engine, about 30 to 40% of heat source is degraded, so it takes about 40 minutes for heating and defrosting. In order to solve this problem, an auxiliary heater system capable of heating the cooling water is imported and used. The heater material is made of metal, so that the performance of the heater does not meet the specifications or is a factor in the cost increase.

Currently, medium and large vehicles use an auxiliary heater to heat the coolant, and the heat source is a metal glow plug. The metal glow plug has a low heat generation temperature and has a problem of reducing the service life due to surface cavitation caused by cooling water, and the total amount of the metal glow plug depends on imports, which is a major factor in the cost increase. have. In addition, the glow plug generates heat in the standby state when the power is not fully charged in the cooling water. At this time, a phenomenon such as surface oxidation and surface corrosion, such as red brittleness, occurs, which greatly shortens the life of the heater. .

As described above, the present invention has been made to solve the problems as described above. As a result, in developing a ceramic (PTC) heater element capable of exhibiting the same performance or higher, the main component is barium titanate (BaTiO ₃ ), which is a ferroelectric material, and Si, Ti, Fe, V, Cu, Pb, and Sn components. Including a low specific resistance at room temperature, and a high specific resistance above the transition temperature of ferroelectric material, it has good low temperature characteristics, excellent heat generation, and can quickly heat the cooling water. The present invention was completed by developing a ceramic heater.

1 shows a manufacturing process of the PTC ceramic heater according to the present invention.

In the present invention, 0.005% to 0.02% by weight of Si, 0.005% to 0.02% of Ti, 0.001% to 0.002% of Fe, 0.001% to 0.002% of V, 0.023% to 0.1% of Cu, 0.015% to 0.20% of Pb, and 0.1% to 0.25% of Sn. %, And BaTiO ₃ 95 to 99.75% by weight PTC ceramic heater for auxiliary heating device is characterized by.

In addition, the present invention

a) 0.005 to 0.02 weight percent Si, 0.005 to 0.02 weight percent Ti, 0.001 to 0.002 weight percent Fe, 0.001 to 0.002 weight percent V, 0.023 to 0.1 weight percent Cu, 0.015 to 0.20 weight percent Pb, 0.1 to 0.25 weight percent Sn , And BaTiO ₃ 95 to 99.75% by weight of a component, and then ball milling the raw powder with an alumina ball to a diameter of 0.5 μm or less,

b) the powder is dried in a hot air dryer for 40 to 50 minutes, calcined and pulverized,

c) mixing the raw material powder and the organic binder obtained in step b) in a weight ratio of 90:10, and

d) a method of manufacturing a PTC ceramic heater for an auxiliary heating device, comprising the step of forming, dewaxing and sintering the mixture of step c).

Hereinafter, the present invention will be described in more detail.

In the present invention, in manufacturing a ceramic heater for auxiliary heating device, by adding a specific chemical component to the ferroelectric barium titanate to make the barium titanate semi-conductive to reduce the resistance and increase the calorific value (PTC ceramic) and It provides a manufacturing method.

PTC is a ceramic material, which has a specific resistance as low as several tens of Ω-cm at a temperature near room temperature, so that current flows well.However, the transition of ferroelectrics due to Joule heat or ambient temperature change caused by its resistance When it is maintained above the temperature (transformation or Curie temperature), it has a high specific resistance of several MΩ-cm or more, and it is a unique electrical property of a material that blocks current. Various devices using these electrical characteristics have been developed, and various applications have been applied to automobile devices.

In PTC ceramics, the resistance change of a material with temperature can be divided into two types.

First, in the case of an insulator and a semiconductor having a relatively high electric resistance, when the temperature increases, the electron excitation (transition) increases, and the number of electrons that can contribute to the electric conduction increases and the electric resistance decreases. This change in resistance with temperature is called the Negative Temperature Coefficient (NTC).

In contrast, in the case of an electric conductor, as the temperature increases, the phonon of the electron lattice increases, and thus, the movement speed of the electron decreases, thereby increasing the resistance. This change in resistance with temperature is referred to as the positive temperature coefficient (PTC) described above.

In general, ceramics are ion-bonded or covalently bonded, so electrons are in close contact with the ions, so the energy band gap is large, which serves as a relatively insulator, and the resistance change with temperature also shows NTC characteristics. Because of the NTC characteristics of ceramics, ceramics can be used extensively in temperature sensors. However, when the appropriate elements are added to the ferroelectric polycrystalline ceramics, the ceramic exhibits PTC characteristics.

General properties of the PTC ceramic is as follows.

BaTiO ₃ used in the present invention is a component most frequently used as a main component of PTC ceramics. As a ferroelectric material, a large band gap is generally known as a material having high electric resistance. Since the electrical conductor as described above has to increase the number of free electrons in order to have a low resistance at low temperatures, which is a characteristic of PTC, a method of adding an electron-producing element to the material is used.

In the case of BaTiO ₃ PTC, impurity levels in the band gap are added by adding Sb ⁺⁵ , Nb ⁺⁵ , Ta ⁺⁵ and La ⁺³ , Pr ⁺³ , Na ⁺ , Gd ⁺³ , Y ^+3, etc. level) to make free electrons and to make electric resistance less. The transition metal ion is + 5 in the horizontal charge will decrease the resistance and the n- type semiconductive significantly the BaTiO ³ by substituting Ti ⁺⁴ and emit free electrons in order to maintain overall electroneutrality of the material in the BaTiO ₃ Let's do it. The rare earth metal ions charged with +3 replace Ba ⁺⁴ and release free electrons, thereby reducing the resistance by making BaTiO ³ n-type semiconducting. PTC ceramics lower the electrical resistance of the material by doping other valence ions.

As known in the art, a single crystal BaTiO ₃ cannot produce a PTC phenomenon, and thus a polycrystal of ferroelectric material must be used to produce a PTC phenomenon. The main reason why the PTC phenomenon is observed only in polycrystals is the same as the reason why PTC has high resistance above Curie temperature.

The general manufacturing process of polycrystalline ceramics consists of molding and sintering the powder to create a dense structure. That is, after sintering at high temperature, the cooling process is performed, and during cooling, the material is moved by diffusion. Diffusion takes time and therefore the material at the particle interface and inside the particle can vary depending on the cooling rate. The difference in material causes the electronic structure to be different, resulting in different electronic structures inside the particle interface and inside the particle. PTC ceramics create a grain boundary electron blocking layer by changing the electronic structure at the particle interface different from the inside of the particle. The interfacial electron blocking layer serves to increase the overall resistance of the material. Many agree that the main reason for PTC's high resistance above Curie temperature is due to the grain boundary depletion layer.

The fact that PTC properties only occur in ferroelectrics such as BaTiO ₃ makes the prediction that PTC phenomena will be closely related to ferroelectric phenomena. Ferroelectrics lose ferroelectricity and exhibit ferroelectric properties above Curie temperature, and ferroelectricity is preserved only below Curie temperature.

There are two main characteristics of ferroelectricity: spontaneous polarization and hysteresis.

Spontaneous polarization is a phenomenon in which polarization occurs under the Curie temperature without applying an electric field due to lattice anisotropy of ferroelectric materials. If the ferroelectric is kept below the Curie temperature, spontaneous polarization is considered to exist in the form of storing charge like a battery, but in reality it is not. In other words, when the charge is not stored, the energy of the entire system when the charge is stored is divided so that minute parts of the material are divided into an electric domain having the same crystal arrangement, and the electric field is applied to the entire material. Since they are arranged irregularly, the charges of the whole material cancel each other out.

When a ferroelectric is applied to an electric field, the electric field stores electric charges and is relocated in the direction of the electric field, thereby showing hysteretic characteristics between the electric field and polarization, which is another important characteristic of the electric field structure of the ferroelectric. PTC ceramics have n-type semiconductivity due to the addition of other valence ions, but they have high resistance due to the grain boundary layer, but below the Curie temperature, the electric charges cancel the grain boundary layer to lower the resistance. Being explained. Therefore, only ferroelectrics that can have an electric field structure in the material can be PTC ceramics.

Therefore, in the present invention, in order to manufacture a PTC ceramic heater having the above characteristics, it is preferable to add the barium titanate as a main component and an element having a heterogeneous valence, an element having the same valence, a grain boundary aid, a sintering agent, and the like. desirable.

Heterogeneous electrons used in the present invention include Y, La, Sb, Ce, Nb, etc., which changes the defect structure and adjusts the resistance change and the particle size. It is preferable to add the usage-amount in 0 to 0.008 weight%.

Homogenous valence elements used in the present invention include Sr, Pb, Ca, Sn and the like, which acts as a substituted solid solution to control the Curie temperature. It is good to use the usage-amount in 0 to 0.002 weight%.

In addition, the grain boundary preparation used in the present invention is to control the interfering insects of the grain boundary and to control the width of the resistance change. Specifically, Mn, Fe, V and Cu components are preferably added. It is preferable to use the usage-amount in 0 to 0.002 weight%.

As the sintering agent used in the present invention serves to lower the sintering temperature and to control the particle size, it is preferable to add, for example, Si, Ti and Ge components. desirable.

At this time, when the harmful content is contained in the component content of 0.0002 to 0.005% by weight deteriorates the PTC characteristic, if not adjusted to the minimum level, the PTC characteristic is reduced. Such harmful components include Na, K, Al, P and Mg.

Preferably, the PTC ceramic heater of the present invention is Si 0.005 to 0.02 wt%, Ti 0.005 to 0.02 wt%, Fe 0.001 to 0.002 wt%, V 0.001 to 0.002 wt%, Cu 0.023 to 0.1 wt%, Pb 0.015 to 0.20 wt %, 0.1 to 0.25 wt% Sn, and 95 to 99.75 wt% BaTiO ₃ is preferable.

On the other hand, the PTC ceramic heater of the present invention, after combining the components of the above composition, ball milling with alumina balls to a diameter of 0.5 μm or less, and drying the slurry in a hot air dryer at 120 ° C. for 40 to 50 minutes (temperature rise 5 ° C.). / min), followed by firing and pulverization, binder mixing, molding, dewaxing and sintering.

The firing is preferably performed by calcination (pre-sintering) (temperature rise 15 ° C./min) for 60 minutes in a furnace at 480 ° C. under an argon gas atmosphere in a conventional electric furnace. The pulverization is preferably pulverized to a calcination powder diameter of 0.5 ㎛ or less for 4 hours using an alumina ball.

In addition, in the binder mixing, the raw material powder and the organic binder (for example, PVA205) may be mixed at a weight ratio of 90:10.

The molding was pressed under a pressure of 3.4 kg · f / mm 2, de-waxed for 120 minutes (heating and cooling rate: 10 ° C./min) in an electric furnace maintaining 460 ° C., and then 2 hours in an atmosphere furnace at 1350 ° C. Sintering.

At this time, the temperature increase rate is 20 ℃ / min, the cooling conditions are maintained for 2 hours in the state of maintaining the 1000 ℃ and then cooled to the condition of 20 ℃ / min.

Then, the PTC ceramic heater can be manufactured by electrode printing by conventional electrode printing and electrode baking by conventional electrode baking.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited thereto.

EXAMPLE

Next, after combining the components of the composition of Table 1, ball milling with alumina balls to a diameter of 0.5 μm or less, and drying the slurry (temperature rise 5 ° C./min) at 120 ° C. for 40 to 50 minutes in a hot air dryer. After calcination (pre-sintering) (temperature rise 15 ° C./min) for 60 minutes at 480 ° C. in an argon gas atmosphere in an electric furnace, it was pulverized to an calcination powder diameter of 0.5 μm or less for 4 hours using an alumina ball. Thereafter, 90 wt% of the raw material mixture of the above composition and the remaining 10 wt% of the organic binder (PVA205) were mixed and binder mixed, and molded at 3.4 kg · f / mm 2, followed by degreasing at 460 ° C. for 120 minutes in a general electric furnace. (Warming and cooling rate: 10 ° C / min) was dewaxed, and the temperature rising rate 20 ° C / min for 2 hours at 1350 ° C, and maintained for 2 hours at 1000 ° C cooling conditions and then sintered for 20 ° C / min. Then, the electrode was printed by conventional electrode printing and the electrode was baked by a conventional electrode baking operation to prepare a PTC ceramic heater.

Physical properties of the PTC ceramic heater manufactured by the above embodiment are as follows.

① Dimension: L25.0 x W14.5 x T0.85

② Resistance: 0.17 Ω (Supplied voltage: 12.5 Vdc)

③ Tc: 200 ℃

As described above, the PTC ceramic heater according to the present invention has a low specific resistance at room temperature and a high specific resistance above the transition temperature of the ferroelectric material, and thus has a low temperature characteristic, excellent heat generation, and rapid heating performance of cooling water to remove winter defrost and heating effect. It can increase the vehicle quality by extending the service life.

Claims (2)

Si 0.005-0.02 wt%, Ti 0.005-0.02 wt%, Fe 0.001-0.002 wt%, V 0.001-0.002 wt%, Cu 0.023-0.1 wt%, Pb 0.015-0.20 wt%, Sn 0.2-0.025 wt%, and BaTiO ₃ PTC ceramic heater for auxiliary heating device characterized in that consisting of 95 to 99.75% by weight. a) 0.005 to 0.02 weight percent Si, 0.005 to 0.02 weight percent Ti, 0.001 to 0.002 weight percent Fe, 0.001 to 0.002 weight percent V, 0.023 to 0.1 weight percent Cu, 0.015 to 0.20 weight percent Pb, 0.1 to 0.25 weight percent Sn , And BaTiO ₃ 95 to 99.75% by weight of the components, and then ball milling to a raw material powder diameter of 0.5 ㎛ or less with an alumina ball, b) firing and pulverizing the slurry after drying the slurry for 40 to 50 minutes in a hot air dryer maintaining the powder at 120 ° C; c) mixing the raw material powder and the organic binder obtained in step b) in a weight ratio of 90:10, and and d) molding, dewaxing and sintering the mixture of step c).