Composition for a sensor element, temperature sensor and method for manufacturing the temperature sensor

Abstract

Composition for a sensor element (10) comprising Y2O3, Al2O3, MnO2, NiO and Fe2O3 and further ZrO2, and intended to be used in a temperature sensor (1), wherein a molar concentration of Zr used in the composition for the sensor element (10) is 0.2-0.5, and wherein a molar concentration of the metallic elements yttrium, aluminium, manganese, nickel and iron used in the composition for the sensor element (10) is accordingly 0.2-0.5, 0.01-0.1, 0.1-0.3, 0.1-0.3 and 0.03-0.1.

Description

Cross-reference to a related registration

[0001] Pursuant to 35 USC § 119, the application claims priority from Korean patent application No. 10-2012-53210, which was filed with the Korean Patent Office on May 18, 2012, and to whose entire disclosure reference is hereby made in full. Background 1. Field of invention

[0002] The present invention relates to a composition for a sensor element, a temperature sensor, and a method for manufacturing the temperature sensor comprising the composition for the sensor element. More specifically, the present invention relates to a composition for a sensor element with improved accuracy and thermal stability when measuring temperature, and to a temperature sensor in which wires are inserted into a sensor element and which comprises the same composition and exhibits heat resistance, impact resistance, vibration resistance, durability, and the like, enabling temperature measurements at high temperatures and under vibration conditions, and to a method for manufacturing the temperature sensor. 2. Description of the state of the art

[0003] As restrictions on harmful gases from vehicles increase, exhaust emission control systems for vehicles have recently been developed. Nitrogen oxides (NOx) are emitted, particularly in diesel vehicles, during fuel combustion. x ) and the like. Diesel vehicles, for example, can emit particulate matter (PM) of less than 0.005 g per 1 km, and to regulate these emissions, a DPF (Diesel Particulate Filter) system can be used as an exhaust emission reduction device. Installed in the exhaust system, the DPF collects the particulate matter in the exhaust using a catalytic filter and controls a regeneration process that burns off the collected PM when certain conditions are met.

[0004] The regeneration process is carried out at a temperature optimized for maximum effectiveness (e.g., the temperature at which the particulate matter collected in the filter is burned). To perform this process, a precise and durable temperature sensor must be integrated into the DPF system. This temperature sensor is also incorporated into a combustion chamber and related components commonly used in vehicles to accurately monitor the temperature at any given ambient temperature, ensuring reliable and long-lasting vehicle operation.

[0005] A temperature sensor is a device designed to measure temperature based on changes in material density, resistance, electromotive force, and the like, as a function of temperature. Temperature sensors include thermocouples, resistance temperature detectors, thermistors (NTC thermometers), and similar devices. A thermocouple thermometer is a thermometer that utilizes the thermal electromotive force of a thermocouple. It measures temperature based on the value of the thermal electromotive force generated at one junction when the two ends of two metal wires are connected and the other junction is held at a specific, fixed temperature.A resistance liquid thermometer is a device that measures temperature based on its resistance, utilizing the change in electrical resistance of a metal or semiconductor as a function of temperature. A thermistor thermometer is generally manufactured by sintering metal oxides, and the thermistor is a device whose electrical resistance changes with temperature.

[0006] Thermistor thermometers are divided into PTC (Positive Temperature Coefficient) thermistors and NTC (Negative Temperature Coefficient) thermistors. A PTC thermistor increases its resistance in response to a temperature increase, while an NTC thermistor decreases its resistance in response to a temperature increase.

[0007] The temperature sensor used for the exhaust system of a vehicle should be operated at a temperature of approximately 500 °C or higher and should have thermal shock resistance, which is resistant to repeated temperature changes between a high temperature and room temperature, and vibration and impact resistance, which is resistant to extreme vibrations often generated while driving the vehicle.

[0008] Conventional temperature sensors generally comprise a sensing element and connecting wires, and the sensing element is usually made of metals or metal oxides. The metal oxides are typically insulators; however, when transition metal oxides are mixed with them and sintered, they exhibit the conductivity of semiconductors. In particular, a temperature sensor used at high temperatures and manufactured by a ceramic process involving mixing a sensing element composition containing transition metal oxides, such as Fe₂O₃, NiO, Cr₂O₃, MnO₂, and the like, calcining, and sintering the composition, may experience a reduction in temperature measurement accuracy due to errors caused by a decrease in thermal stability at 500 °C or above and by the low resistance of only a few ohms.

[0009] The conventional temperature sensor is also manufactured by printing or coating paste electrodes made of silver (Ag), gold (Au), platinum (Pt) and the like onto the surface of the sensor element and by attaching lead wires or terminals made of nickel (Ni), Pt, Au, copper (Cu) and the like to it, and, when the electrodes are used on the surface, the lead wires or terminals can easily be separated and cut off from the surface of the element at high temperature or extreme vibrations.

[0010] Prior art temperature sensors are described, for example, in DE 101 39 109 A1, DE 199 08 444 A1, US 2003 / 0 038 704 A1, US 4 891 158 A, EP 0 866 472 A2.

[0011] The above description given as prior art relating to the present invention is intended only to help understand the background of the present invention and is not to be interpreted as part of the prior art as already known to a person skilled in the art. Summary of the invention

[0012] The present invention was made in an effort to solve the problems described above, which are associated with the prior art. The present invention provides a composition for a sensor element that exhibits improved thermal stability and accuracy, wherein the composition comprises Y₂O₃, Al₂O₃, MnO₂, NiO, and Fe₂O₃ as metal oxides and further ZrO₂.

[0013] The present invention further provides a temperature sensor exhibiting improved resistance to temperature cycling, impact resistance, vibration resistance, and the like, by incorporating lead wires into the sensor element, which comprises the sensor element composition; and a method for manufacturing the temperature sensor. The sensor element composition of the present invention comprises Y₂O₃, Al₂O₃, MnO₂, NiO, and Fe₂O₃, and furthermore ZrO₂. In one embodiment of the present invention, the molar concentration of zirconium (Zr) used in the sensor element composition is also approximately 0.2–0.5.In addition, in a further embodiment of the present invention, the molar concentration of the metallic elements yttrium (Y), aluminium (Al), manganese (Mn), nickel (Ni) and iron (Fe) used in the composition for a sensor element is approximately 0.2-0.5, 0.01-0.1, 0.1-0.3, 0.1-0.3 and 0.03-0.1.

[0014] The temperature sensor of the present invention comprises: a sensor element comprising the composition for a sensor element; and two connecting wires which are inserted into the sensor element parallel to each other.

[0015] Furthermore, the method for manufacturing the temperature sensor of the present invention comprises: weighing the composition for a sensor element; mixing the composition; calcining the mixture at approximately 1,000 °C to 1,400 °C for 30 minutes to 5 hours; pulverizing the calcined mixture to obtain a powder; placing the powdered mixture into a mold; inserting two connecting wires parallel to each other into the powdered mixture placed in the mold; compressing the powdered mixture; and sintering the compressed material at approximately 1,300 °C to 1,500 °C for approximately 30 minutes to 5 hours. Alternatively, the calcination can be carried out at approximately 1,200 °C for 2 hours and the sintering can be carried out at approximately 1,400 °C for 1 hour. Brief description of the characters

[0016] The features of the present invention, as well as those specified above, are described below with reference to exemplary embodiments thereof, which are illustrated in the accompanying figures. These figures are included here solely for illustrative purposes and are not intended to limit the present invention in any way. The following applies to the figures: Fig. Figure 1 shows an example temperature-resistance graph of a composition with Y 0,44 Al 0,04 Mn 0,108 Fe 0,064 Ni 0,108 0 1,14 for a sensor element to which no ZrO2 was added, according to a conventional composition for a sensor element. Fig. Figure 2 shows an example temperature-resistance graph of a composition with Zr 0,24 Y 0,44 Al 0,04 Mn 0‚108 Fe 0,064 Ni 0,108 O 1,62for a sensor element, wherein ZrO2 was added to the conventional composition for a sensor element, according to an exemplary embodiment of the present invention. Fig. Figure 3 shows an example XRD graph of a composition with Zr 0,24 Y 0,44 Al 0,04 Mn 0‚108 Fe 0,064 Ni 0,108 O 1,62 for a sensor element according to an exemplary embodiment of the present invention. Fig. Figure 4 shows an exemplary view of a temperature sensor comprising the composition for a sensor element, according to an exemplary embodiment of the present invention. Fig. Figure 5 shows an example of a sectional view of the temperature sensor from the Fig. 4, which was cut along AA', according to an exemplary embodiment of the present invention.

[0017] It should be understood that the accompanying figures are not necessarily to scale, but rather show a somewhat simplified representation of various preferred features that illustrate the underlying principles of the invention. Specific features of the embodiment of the present invention as disclosed herein, including, for example, specific dimensions, orientations, positions, and shapes, will be partly determined by the conditions and circumstances of the specific intended application and use.

[0018] In all figures, the reference numerals denote identical or equivalent parts of the present invention. Detailed description of the embodiments

[0019] The terminology used herein serves solely to describe certain embodiments and is therefore not intended to limit the invention in any way. As used herein, the singular forms "a" and "the" shall also include the plural forms unless the context clearly indicates otherwise. Furthermore, it should be understood that the terms "includes" and / or "comprehensive," when used in this description, indicate the presence of the aforementioned features, numbers, steps, operations, elements, and / or components / parts, but do not exclude the presence or addition of one or more further features, numbers, steps, operations, elements, components / parts, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the related items listed.

[0020] Unless explicitly stated or evident from the context, the term "approximately," as used herein, should be understood as lying within a range of normal scientific tolerances, for example, within 2 standard deviations from the mean. "Approximately" may be understood as lying within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clearly indicated by the context, all numerical values ​​stated herein are to be understood as including the term "approximately."

[0021] It should be understood that the term "vehicle" or "vehicle-" or any other similar term as used herein includes motor vehicles in general, such as passenger cars, including sports utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft, including a variety of boats and ships, aircraft and the like, as well as hybrid vehicles, electric vehicles, internal combustion engine vehicles, convertible hybrid electric vehicles, hydrogen-powered vehicles and other vehicles powered by alternative fuels (e.g., fuels derived from a source other than petroleum).

[0022] The present invention will now be described in detail with reference to the accompanying figures.

[0023] In one embodiment, the present invention provides a composition for a sensor element with improved accuracy and thermal stability, wherein the composition comprises Y₂O₃, Al₂O₃, MnO₂, and NiO as transition metal oxides, as well as an iron oxide selected from the group consisting of FeO, FeO₂, Fe₂O₃, and Fe₃O₄. The composition may further comprise ZrO₂, which exhibits high stability and high resistance at high temperatures.

[0024] A sensor element composed of transition metal oxides may exhibit a resistance that changes with temperature. This composition can be used in a temperature sensor by employing a principle that measures a random resistance value and detects the corresponding temperature. To accurately measure high temperatures, the resistance must be measurable at those high temperatures. A sensor element composed of transition metal oxides, such as Fe₂O₃, NiO, Cr₂O₃, MnO₂, and similar materials, which exhibits a low resistance of only a few ohms at high temperatures of 500 °C or more, cannot accurately measure the resistance and therefore cannot accurately detect the corresponding temperature.Furthermore, when using transition metal oxides, the thermal stability of the composition for a sensor element at high temperatures cannot be guaranteed, making it necessary to control the ratio of the proportions in the composition or to add a new material to ensure thermal stability.

[0025] The composition for a sensor element of the present invention can therefore comprise Y2O3, Al2O3, MnO2, NiO and Fe2O3 as metal oxides and further ZrO2, which has stability and a high resistance value, especially at high temperatures.

[0026] Furthermore, reagents used in the present invention can be oxides, such as Y₂O₃, Al₂O₃, MnO₂, NiO, Fe₂O₃, and ZrO₂, and it can be assumed that their chemical composition has a constant molar ratio before and after heat treatment. In addition, metal components for use in the composition can be oxidized, and the molar fraction of transition metal oxides can be changed.

[0027] The molar concentration of Zr used in the composition for a sensor element can be approximately 0.2–0.5. Furthermore, the molar concentrations of the metallic elements Y, Al, Mn, Ni, and Fe used in the composition for a sensor element can be approximately 0.2–0.5, 0.01–0.1, 0.1–0.3, 0.1–0.3, and 0.03–0.1, respectively. The thermal stability and the accuracy for measuring temperature at high temperatures can be adjusted according to the proportions of the components in the composition. Various experiments have shown that the composition for a sensor element has an optimal effect when it includes the components and proportions described herein.

[0028] In particular, in one embodiment of the present invention, the composition for a sensor element comprising Y2O3, Al2O3, MnO2, NiO and Fe2O3 as metal oxides and further ZrO2 was weighed and mixed to determine a ratio of the proportions of Zr 0,24 Y 0,44 Al 0,04 Mn 0‚108 Fe 0,064 Ni 0,108 O 1,62 to obtain the mixture. The mixture was calcined at approximately 1,200 °C for 2 hours, calcination being a heat treatment process that removes some or all of the volatile components when any material is heated to a high temperature for uniform mixing.

[0029] In addition, the calcined mixture was pulverized to obtain a powder. This powder was placed in a mold, and two lead wires were inserted parallel to each other into the molded powder. The mixture was then compressed to approximately 2 x 2 x 2 mm. Subsequently, the compressed material was sintered at approximately 1400 °C for one hour to obtain a sample for a sensor element. Sintering is a heat treatment process for solidifying a material produced by compressing the powder into a specific shape.

[0030] Furthermore, the ratio of the proportions for the composition, the size of the sample, the temperature of the heat treatment, the duration of the heat treatment and the like, which were used in the embodiment described above, can be changed according to the required properties of the sensor.

[0031] The Fig. Figure 1 shows an example temperature-resistance graph of a composition with Y 0,44 Al 0,04 Mn 0,108 Fe 0,064 Ni 0,108 O 1,14 for a sensor element 10 to which no ZrO2 was added, according to a conventional composition for a sensor element 10 and the Fig. Figure 2 shows an example temperature-resistance graph of a composition with Zr 0,24 Y 0,44 Al 0,04 Mn 0,108 Fe 0,064 Ni 0,108 O 1,62 for a sensor element 10 in which ZrO2 was added to the conventional composition for a sensor element 10, according to an exemplary embodiment of the present invention.

[0032] An equation for calculating the slope B, which is a linear slope, for the temperature-resistance graph is B = ln(R1 / R2) / (1 / T1-1 / T2), where R1 is the resistance value at absolute temperature T1 and R2 is the resistance value at absolute temperature T2.

[0033] As in the Fig. As shown in 1, the composition can be calculated using Y 0,44 Al 0,04 Mn 0,108 Fe 0,064 Ni 0,108 0 1,14 For a sensor element 10, to which no ZrO2 has been added, exhibit a resistance value of approximately 100 k Ohm at 0 °C, a resistance value of approximately 5 Ohm at 900 °C and a slope B of approximately 3,550, and the problem is that errors are generated due to the insufficient resistance value at 900 °C when measuring using a conventional measuring method.

[0034] As in the Fig. As shown in section 2, it was observed that the composition with Zr 0,24 Y 0,44 Al 0,04 Mn 0‚108 Fe 0,064 Ni 0,108 O 1,62For a sensor element 10, in which—as an example of the present invention—ZrO2 has been added to the composition for the sensor element 10, exhibiting a resistance of approximately 1.7 M ohms at 0 °C, a resistance of approximately 40 ohms at 900 °C, and a slope B of approximately 3,800. Due to the linearity of the composition and a very high resistance of approximately 40 ohms at 900 °C, the temperature of the composition can be easily measured using a general measuring method without additional amplification or correction.

[0035] The Fig. Figure 3 shows an exemplary graph of an X-ray diffraction (XRD) of the composition with Zr 0,24 Y 0,44 Al 0,04 Mn 0,108 FC 0,064 Ni 0,108 O 1,62 for a sensor element 10. As in the Fig. As shown in Figure 3, the appearance of the ZrO2 peak in the XRD graph indicates that the ZrO2 is present in the composition as an independent phase. Therefore, a composition for a sensor element 10 with improved accuracy and thermal stability can be provided because the ZrO2, added to the conventional composition for a sensor element 10 with stability and high resistance at high temperatures, is present as an independent phase.

[0036] The Fig. Figure 4 shows an exemplary view of a temperature sensor in which a sensor element 10 is used, comprising the composition for a sensor element 10 of the present invention, and the Fig. Figure 5 shows an example of a sectional view of the temperature sensor. Fig. 4, which was cut along AA'.

[0037] As in the Fig.As shown in Figure 4, the temperature sensor 1 can comprise a sensor element 10 and two connecting wires 20, which are inserted into the sensor element 10 and separated from each other by a distance L and each have a diameter d. A connecting wire 20 made of pure platinum (Pt) can be used; however, to increase the mechanical strength, a connecting wire made of Pt with 13% rhodium (Rh), to which 13% Rh has been added to the Pt, can be used.

[0038] After sintering to generate a higher resistance value, the distance L between the two lead wires 20 also increases. However, the distance L must be adjusted because, as the distance increases, the lead wires 20 move closer to the two sides of the sensor element 10, resulting in a decrease in powder fixation and a decrease in durability.

[0039] In particular, in one embodiment of the present invention, the composition for a sensor element 10, comprising Y2O3, Al2O3, MnO2, NiO and Fe2O3 as metal oxides and further ZrO2, was weighed and mixed to obtain a ratio of the proportions of Zr 0,24 Y 0,44 Al 0,04 Mn 0‚108 Fe 0,064 Ni 0,108 O 1,62 To obtain the mixture, calcination was carried out at approximately 1200 °C for 2 hours. The calcined mixture was pulverized to obtain a powder, the powdered mixture was placed in a mold, and the two lead wires 20 were inserted parallel to each other and at a distance of 0.6 mm into the powdered mixture. The mixture was then pressed into a 2 x 2 x 2 mm shape.

[0040] If the pressure is applied perpendicular to the lead wires 20, the lead wires 20 can also be deformed by an anomalous distribution of the powder filling, unevenly distributed pressure, and the like. Therefore, the pressure can be applied parallel to the direction in which the lead wires 20 are inserted. Furthermore, if the two lead wires 20 are inserted through the sensor element 10 to its base, a malfunction can occur during this process due to contact between the metal and the lead wires 20 when they are inserted into a metal tube.

[0041] The molded material can further be sintered at approximately 1400 °C for 1 hour to obtain a sample for a temperature sensor 1. In this experiment, the sensor element 10 shrank by about 10% due to a physicochemical reaction of the metal oxides contained in the sensor element 10 during the sintering process, and consequently, the sensor element 10 and the two inserted connecting wires 20 were even more firmly attached. Separation of the connecting wires 20 from the sensor element 10 can be prevented to provide a temperature sensor 1 with improved vibration resistance, impact resistance, durability, and the like.In addition, the ratio of the proportions in the composition, the size of the sample, the distance L between the two lead wires, the diameters d of the two lead wires, the temperature of the heat treatment, the duration of the heat treatment and the like, which are used in the embodiment described above, can be changed according to the required properties of a sensor.

[0042] In the present invention, the resistance value can be easily measured using an ordinary measuring instrument, and therefore a temperature corresponding to the resistance value can be accurately measured using a composition for a sensor element 10 which has thermal stability and a very high resistance of several M ohms at room temperature and a few ohms at high temperatures, wherein the composition comprises Y2O3, Al2O3, MnO2, NiO and Fe2O3 as transition metal oxides and further ZrO2, which has stability and a high resistance at high temperatures.

[0043] When the two connecting wires 20 are inserted into the sensor element 10 and subsequently molded, and the resulting formed material is sintered at a high temperature, the connecting wires 20 can be firmly attached to the sensor element 10 by the shrinkage of the sensor element 10 during the sintering process. This prevents the connecting wires 20 from separating from the sensor element 10, thereby increasing the vibration resistance, impact resistance, durability, and similar properties of the temperature sensor according to the present invention.

[0044] The invention has been described in detail with reference to exemplary embodiments thereof. However, those skilled in the art will recognize that changes and modifications can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

[1] Composition for a sensor element (10) comprising Y2O3, Al2O3, MnO2, NiO and Fe2O3 and further ZrO2, and intended to be used in a temperature sensor (1), wherein a molar concentration of Zr used in the composition for the sensor element (10) is 0.2-0.5, and wherein a molar concentration of the metallic elements yttrium, aluminium, manganese, nickel and iron used in the composition for the sensor element (10) is accordingly 0.2-0.5, 0.01-0.1, 0.1-0.3, 0.1-0.3 and 0.03-0.

1. [2] Temperature sensor (1), comprising: a sensor element (10) comprising a composition for a sensor element (10) of Y2O3, Al2O3, MnO2, NiO and Fe2O3 and ZrO2; and a multitude of supply wires (20) which are inserted in parallel into the sensor element (10), wherein a molar concentration of Zr used in the composition for the sensor element (10) is 0.2-0.5, wherein a molar concentration of the metallic elements yttrium, aluminium, manganese, nickel and iron used in the composition for the sensor element (10) is accordingly 0.2-0.5, 0.01-0.1, 0.1-0.3, 0.1-0.3 and 0.03-0.

1. [3] Method for manufacturing a temperature sensor (1), comprising: Weighing a composition of Y2O3, Al2O3, MnO2, NiO, Fe2O3 and ZrO2 for a sensor element (10); Mixing the composition; Calcine the mixture at approximately 1,000 °C to 1,400 °C for 30 minutes to 5 hours; Pulverizing the calcined mixture to obtain a powder; Pouring the powdery mixture into a mold; parallel insertion of a plurality of lead wires (20) into the powdery mixture; Compression molding of the powdery mixture; and Sintering of the molded material at approximately 1,300 °C to 1,500 °C for 30 minutes to 5 hours, wherein a molar concentration of Zr used in the composition for the sensor element (10) is 0.2-0.5, and wherein a molar concentration of the metallic elements yttrium, aluminium, manganese, nickel and iron used in the composition for the sensor element (10) is accordingly 0.2-0.5, 0.01-0.1, 0.1-0.3, 0.1-0.3 and 0.03-0.

1. [4] Method for producing a temperature sensor (1) according to claim 3, wherein the calcination is carried out at 1,200 °C for 2 hours. [5] Method for manufacturing a temperature sensor (1) according to claim 3, wherein the sintering is carried out at 1400 °C for one hour.

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