Tube-Type Oxygen Sensor Pt Inner Electrode Coating Process and Equipment Used in Its Processing

Abstract

The present invention relates to the technical field of oxygen sensor production, in particular to a Pt inner electrode coating process for a tubular oxygen sensor and the equipment used in its processing. It includes the following steps: Step 1, mixing Pt powder with a binder to make a slurry; Step 2, atomizing the slurry with compressed air at 0.2 - 50 MPa for 10 - 50 s, and spraying the atomized slurry inside the zirconia tube blank to form a ring-shaped inner electrode; Step 3, placing the zirconia tube blank on the centrifuge disk of a centrifuge and rotating it at a speed of 500 - 5000 revolutions per minute to form a lead wire with a vertical line on the outermost side of the inner wall of the zirconia tube; Step 4, sintering the zirconia tube blank in a furnace, and naturally cooling it in the air after sintering to obtain the finished product. This Pt inner electrode coating process for a tubular oxygen sensor has the following advantages: ensuring the consistency of the thickness and width of the Pt electrode of the product; controlling the weight of Pt slurry used; reducing the learning cost of personnel during the preparation of this process; and improving production efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of oxygen sensor production, and in particular to a Pt inner electrode coating process for a tubular oxygen sensor and the equipment used in its processing. Background Art

[0002] The vehicle oxygen sensor uses zirconia electrolyte as the key material to measure the voltage or current generated by the difference in oxygen content between the exhaust gas and the air, so as to determine the oxygen content in the exhaust gas; and then control the fuel combustion situation. In a tubular oxygen sensor, it is necessary to coat Pt paste on the inner wall and the outer wall of the zirconia tube respectively and sinter it to serve as the catalytic electrode. At present, the existing coating process generally coats the platinum paste on the inner embryo of the zirconia ceramic tube by the way of manual dipping and stirring loop coating, and then conducts high-temperature sintering to form the Pt inner electrode. This method faces the problems that the thickness and width of the coating layer are uneven, and the weight of the platinum electrode paste cannot be accurately controlled, so the product performance cannot be effectively controlled. At the same time, manual coating also faces the problems of long learning time and low production efficiency. Summary of the Invention

[0003] In order to overcome the deficiencies in the existing oxygen sensor production process, the present invention provides a Pt inner electrode coating process for a tubular oxygen sensor and the equipment used in its processing.

[0004] The technical solution adopted by the present invention to solve its technical problems is: a Pt inner electrode coating process for a tubular oxygen sensor, including the following steps:

[0005] Step 1: Mix Pt powder with a binder to make a paste;

[0006] Step 2: Atomize the paste with compressed air of 0.2 - 50 MPa for 10 - 50 s, and spray the atomized paste inside the zirconia tube embryo to form an annular inner electrode;

[0007] Step 3: Place the zirconia tube embryo on the centrifugal disk of a centrifuge and rotate it at a speed of 500 - 5000 revolutions per minute to form a lead with a vertical line on the outermost side of the inner wall of the zirconia tube embryo;

[0008] Step 4: Sinter the zirconia tube embryo in a furnace, and after the sintering is completed, let it cool naturally in the air to obtain the finished product.

[0009] According to another embodiment of the present invention, further including, in Step 1, the particle size of the Pt powder is 0.05 - 0.5 μm, and the solid content of the paste is 40 - 80%.

[0010] According to another embodiment of the present invention, it further includes that in step one, the binder is composed of a mixture of alcohol, terpineol, and PVB. According to the mass parts, the slurry contains the following components: Pt powder, 20 - 100 parts, alcohol, 1 - 8 parts, terpineol, 5 - 20 parts, and PVB, 5 - 20 parts.

[0011] According to another embodiment of the present invention, it further includes that in step three, the width of the lead wire is 1 - 5 mm, and the thickness is 2 - 30 μm.

[0012] According to another embodiment of the present invention, it further includes that in step four, the sintering temperature is 1300 - 1550 °C, and the time is 12 - 72 H.

[0013] A device used in the Pt inner electrode coating process of a tubular oxygen sensor includes a tabletop. There is a hole at the center position of the tabletop. A motor is fixed to the reverse side directly below the hole by bolts. The output shaft of the motor passes through the hole and is installed with a centrifugal turntable. At least two cylinder brackets are evenly arranged on the outer side of the centrifugal turntable. A cylinder is fixed to the inner side of the cylinder bracket by bolts. An atomizing valve is installed at the end of the cylinder. The feed port of the atomizing valve is connected to a cartridge installed on the inner side of the cylinder bracket through a clamp. There is a pneumatic valve on the outer side of the cylinder bracket. The pneumatic valve is connected to the gas pipe joints of the cartridge and the atomizing valve through a pipeline. The air inlets of the pneumatic valve and the cylinder are connected to the gas source through pipelines. Clamps are evenly arranged on the outer ring of the centrifugal disk.

[0014] According to another embodiment of the present invention, it further includes that the number of clamps is an integer multiple of the number of cylinder brackets.

[0015] The beneficial effect of the present invention is that this Pt inner electrode coating process for tubular oxygen sensors has the following advantages:

[0016] 1. Ensure the consistency of the thickness and width of the Pt electrode of the product;

[0017] 2. Control the weight of Pt slurry used;

[0018] 3. Reduce the learning cost of personnel during the preparation of this process;

[0019] 4. Improve production efficiency. Description of the Drawings

[0020] The present invention will be further described below in conjunction with the drawings and embodiments.

[0021] Figure 1 is the structural schematic diagram of the present invention;

[0022] Figure 2 is the front view of the present invention;

[0023] Figure 3 is the top view of the present invention;

[0024] Figure 4 is a schematic structural view of the cylinder bracket of the present invention;

[0025] In the figure, 1 is the tabletop, 2 is the pneumatic valve, 3 is the centrifugal turntable, 4 is the cylinder bracket, 5 is the atomizing valve, 6 is the cartridge, 7 is the fixture, 8 is the cylinder, 9 is the air source, and 10 is the motor. Specific embodiments

[0026] A coating process for the Pt inner electrode of a tubular oxygen sensor includes the following steps:

[0027] Step 1: Mix Pt powder with a binder to form a slurry;

[0028] Step 2: Atomize the slurry with compressed air at 0.2 - 50 MPa for 10 - 50 s, and spray the atomized slurry inside the zirconia tube blank to form a ring-shaped inner electrode;

[0029] Step 3: Place the zirconia tube blank on the centrifugal disk of a centrifuge and rotate it at a speed of 500 - 5000 revolutions per minute to form a lead wire with a vertical line on the outermost side of the inner wall of the zirconia tube blank;

[0030] Step 4: Sinter the zirconia tube blank in a furnace, and after the sintering is completed, naturally cool it in the air to obtain the finished product.

[0031] According to another embodiment of the present invention, further including, in Step 1, the particle size of the Pt powder is 0.05 - 0.5 μm, and the solid content of the slurry is 40 - 80%.

[0032] According to another embodiment of the present invention, further including, in Step 1, the binder is composed of alcohol, terpineol, and PVB mixed together, and according to the mass fraction, the slurry contains the following components: Pt powder, 20 - 100 parts, alcohol, 1 - 8 parts, terpineol 5 - 20 parts, PVB, 5 - 20 parts.

[0033] According to another embodiment of the present invention, further including, in Step 3, the width of the lead wire is 1 - 5 mm, and the thickness is 2 - 30 μm.

[0034] According to another embodiment of the present invention, further including, in Step 4, the sintering temperature is 1300 - 1550 °C, and the time is 12 - 72 h.

[0035] A device used in the Pt inner electrode coating process of a tubular oxygen sensor, including a table 1. There is a hole at the center of the table 1. A motor 10 is fixed to the reverse side directly below the hole by bolts. The output shaft of the motor 10 passes through the hole and is equipped with a centrifugal turntable 3. At least two cylinder brackets 4 are evenly arranged on the outer side of the centrifugal turntable 3. A cylinder 8 is fixed to the inner side of the cylinder bracket 4 by bolts. An atomizing valve 5 is installed at the end of the cylinder 8. The feed port of the atomizing valve 5 is connected to a cartridge 6 installed on the inner side of the cylinder bracket 4 by a clamp. There is a pneumatic valve 2 on the outer side of the cylinder bracket 4. The pneumatic valve 2 is connected to the gas pipe joints of the cartridge 6 and the atomizing valve 5 through a pipeline. The air inlets of the pneumatic valve 2 and the cylinder 8 are connected to a gas source 9 through pipelines. Clamps 7 are evenly arranged on the outer ring of the centrifugal disk 3.

[0036] According to another embodiment of the present invention, it further includes that the number of the clamps 7 is an integer multiple of the number of the cylinder brackets 4.

[0037] The slurry after mixing Pt powder and binder is placed in the cartridge 6. The pneumatic valve 2 is a valve with one inlet and two outlets. After the gas source 9 passes through the pneumatic valve 2, it provides pressure for the cylinder 8 and the atomizing valve 5, so that the atomizing valve 5 installed on the cylinder 8 can move up and down. After being driven by the gas source 9, the atomizing valve 5 atomizes the slurry in the cartridge 6 and sprays it inside the zirconia tube blank to form a ring-shaped inner electrode. Subsequently, the gas source 9 drives the cylinder 8 to reset. After the motor 10 is powered on, it starts to rotate, driving the centrifugal turntable 3 to rotate at a high speed of 500 - 5000 revolutions per minute, so that the slurry atomized and coated inside the zirconia tube blank accumulates on the vertical line of its inner wall under the action of centrifugal force, forming a lead with a vertical line width of 1 - 5 mm and a thickness of 2 - 30 μm. Subsequently, the zirconia tube blank is taken off and placed in a sintering furnace, sintered at a temperature of 1300 - 1550 °C for 12 - 72 h, and then naturally cooled to obtain the finished product.

[0038] Both the pneumatic valve 2 and the motor 10 are connected to the PLC through communication lines. The opening and closing of the pneumatic valve 2 and the motor 10 are controlled through the control panel externally connected to the PLC, thereby realizing the control of the operation trajectory of the entire device.

[0039] The clamp 7 on the centrifugal turntable 3 is a groove corresponding to the outer wall of the zirconia tube blank, which is convenient for placing the zirconia tube blank. Since the number of the clamps 7 corresponding to the cylinder brackets 4 is an integer multiple, and its number is also an integer multiple of the atomizing valve 5. After atomizing a group of zirconia tube blanks, the motor 10 can be rotated manually or controlled by the PLC to rotate the centrifugal turntable 3, so that the next group of unatomized zirconia tube blanks is located below the atomizing valve 5, facilitating continuous operation.

[0040] The PLC synchronization has the control ability to open and close the air source 9, the pneumatic valve 2, and the atomizing valve 5. By controlling the opening duration of the atomizing valve 5, the amount of the sprayed slurry on the inner wall of the zirconium tube blanks of the same batch is controlled, thereby controlling the gram weight of the Pt slurry used and avoiding the waste of the slurry.

[0041] As Figure 4 , a set of devices is taken out separately for illustration of the connection mode between the air source 9, the pneumatic valve 2, and the cylinder 8, and the connection mode between the pneumatic valve 2, the atomizing valve 5, and the cartridge 6.

[0042] The air source 9 directly provides power for the pneumatic valve 2 and the cylinder 8, and can drive the cylinder 8 to move up and down. After the pneumatic valve 2 is split into two, it provides pressure for the cartridge 6 to transport the slurry in the cartridge to the position of the atomizing valve 5. At the same time, the atomizing valve 5 performs opening and closing operations under the guidance of the pneumatic valve 2.

[0043] When using the original process to coat the inner wall of the zirconium tube blanks with slurry, a single worker can operate 50 - 150 in one hour. When using this process and device to coat the inner wall of the zirconium tube blanks with slurry, a single worker can complete 200 - 500 products in one hour, greatly improving the production efficiency.

[0044] The above description is illustrative rather than restrictive to the present invention. Those of ordinary skill in the art understand that many modifications, variations, or equivalents can be made without departing from the spirit and scope defined by the appended claims, and all of them will fall within the protection scope of the present invention.

Claims

1. A coating process for the Pt inner electrode of a tubular oxygen sensor, characterized in that It includes the following steps: Step 1: Mix Pt powder with a binder to form a slurry; Step 2: Atomize the slurry with compressed air at 0.2 - 50 MPa for 10 - 50 s, and spray the atomized slurry inside the zirconium tube blank to form a ring-shaped inner electrode; Step 3: Place the zirconium tube blank on the centrifugal turntable of a centrifuge, rotate it at a speed of 500 - 5000 revolutions per minute, and form leads perpendicular to the circuit on the outermost side of the inner wall of the zirconium tube; Step 4: Sinter the zirconium tube blank in a furnace, and after sintering, cool it naturally in the air to obtain the finished product.

2. The tubular oxygen sensor Pt inner electrode coating process according to claim 1, characterized in that, In Step 1, the particle size of the Pt powder is 0.05 - 0.5 μm, and the solid content of the slurry is 40 - 80%.

3. The tubular oxygen sensor Pt inner electrode coating process according to claim 1, characterized in that, In Step 1, the binder is composed of alcohol, terpineol, and PVB. According to the mass fraction, the slurry contains the following components: Pt powder, 20 - 100 parts; alcohol, 1 - 8 parts; terpineol, 5 - 20 parts; PVB, 5 - 20 parts.

4. The tubular oxygen sensor Pt inner electrode coating process according to claim 1, characterized in that, In Step 3, the width of the lead is 1 - 5 mm, and the thickness is 2 - 30 μm.

5. The tubular oxygen sensor Pt inner electrode coating process according to claim 1, characterized in that, In Step 4, the sintering temperature is 1300 - 1550 °C, and the time is 12 - 72 h.

6. An apparatus used in the Pt inner electrode coating process of the tubular oxygen sensor according to any one of claims 1-5, comprising a tabletop (1), characterized in that, There is a hole at the center position of the tabletop (1). A motor (10) is fixed to the reverse side directly below the hole by bolts. The output shaft of the motor (10) passes through the hole and is equipped with a centrifugal turntable (3). At least two cylinder brackets (4) are evenly arranged on the outside of the centrifugal turntable (3). A cylinder (8) is fixed to the inner side of the cylinder bracket (4) by bolts. An atomizing valve (5) is installed at the end of the cylinder (8). The feed port of the atomizing valve (5) is connected to a cartridge (6) installed on the inner side of the cylinder bracket (4) by a clamp. There is a pressure valve (2) on the outside of the cylinder bracket (4). The pressure valve (2) is connected to the gas pipe joints of the cartridge (6) and the atomizing valve (5) by a pipeline. The air inlets of the pressure valve (2) and the cylinder (8) are connected to a gas source (9) by a pipeline. Clamps (7) are evenly arranged on the outer ring of the centrifugal turntable (3).

7. The device used in the Pt inner electrode coating process of the tubular oxygen sensor according to claim 6, characterized in that, The number of the clamps (7) is an integer multiple of the number of the cylinder brackets (4).

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