Method for manufacturing sensor element and slurry deposition device

Abstract

To prevent the front end side outer periphery or the like of a porous protective layer that covers a predetermined region around the front end of an element body from becoming partially thin.SOLUTION: A method for manufacturing a sensor element 20 includes a first step of preparing an element body 60, and a second step of immersing a predetermined region of the element body 60 in a slurry reservoir 91, then lifting it up, and thereby depositing a slurry 77, which will become a porous protective layer 76 after firing, to the predetermined region. In the second step, the element body 60 is vibrated when and / or after the predetermined region is lifted up from the slurry reservoir 91.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a sensor element and a slurry deposition device. [Background technology]

[0002] A conventional method for manufacturing a sensor element is known, in which the front end of a substantially flat element body, specifically the portion exposed to the gas to be measured, is immersed in a slurry and then pulled up to form a porous protective layer (see, for example, Patent Document 1). In this method, the element body is immersed in the slurry and then pulled up, and the element body is moved not only up and down along the longitudinal axis direction but also in a direction perpendicular to the longitudinal axis direction. In this way, the shear stress generated when the element body moves through the slurry is increased, and the viscosity of the slurry is reduced, improving wettability, and the porous protective layer is formed on the surface of the element body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5533767 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described manufacturing method of the sensor element, the porous protective layer may easily become thin in parts such as the outer periphery on the front end side. Because the element body and the front end side of the porous protective layer are exposed to the measurement gas containing water, if the outer periphery on the front end side of the porous protective layer becomes thin in parts, there is a concern that the water resistance of that part may decrease.

[0005] The main object of the sensor element manufacturing method and slurry application device of the present invention is to prevent the outer periphery of the front end side of the porous protective layer covering a predetermined region around the front end of the element body from becoming thin in part. [Means for solving the problem]

[0006] The method for manufacturing a sensor element and the slurry deposition apparatus of the present invention employ the following means to achieve the above-mentioned main object.

[0007] [1] The method for manufacturing a sensor element of the present invention comprises: A method for manufacturing a sensor element comprising: an element body having a front end and a rear end which are both ends along a longitudinal direction and a side surface which is a surface along the longitudinal direction, the front end side being exposed to a gas to be measured; and a porous protective layer covering a predetermined region around the front end of the element body, a first step of preparing the element body before or after firing; a second step of immersing the predetermined region of the element body in a slurry reservoir and then lifting it out, thereby adhering the slurry, which will become the porous protective layer after firing, to the predetermined region; Including, In the second step, the element body is vibrated when and / or after the predetermined region is lifted from the slurry reservoir. The gist of this is as follows.

[0008] The method for manufacturing a sensor element of the present invention includes a first step of preparing an element body before or after firing, and a second step of immersing a predetermined region of the element body in a slurry reservoir and then lifting it up to deposit a slurry that will become a porous protective layer after firing on the predetermined region. In the second step, the element body is vibrated when and / or after the predetermined region is lifted up from the slurry reservoir. Vibrating the element body allows the slurry adhering to the element body to move toward its front end. As a result, it is possible to prevent the front end-side outer periphery of the slurry adhering to the element body, and thus the front end-side outer periphery of the porous protective layer, from becoming partially thin.

[0009] [2] In the manufacturing method of the sensor element described above (the manufacturing method of the sensor element described in [1]), the second step may involve vibrating the element body horizontally when and / or after the predetermined area is lifted from the slurry reservoir.

[0010] [3] In the above-described method for manufacturing a sensor element (the method for manufacturing a sensor element according to [1] or [2]), in the second step, after the predetermined region is lifted from the slurry reservoir, the element body may be vibrated with a smaller amplitude and / or a smaller frequency than when the predetermined region is lifted from the slurry reservoir. In this way, it is possible to prevent the slurry adhering to the element body from separating from the element body and falling after the predetermined region is lifted from the slurry reservoir.

[0011] [4] In the above-described method for manufacturing a sensor element (the method for manufacturing a sensor element according to any one of [1] to [3]), the second step may include vibrating the element body with a smaller amplitude and / or a smaller frequency as the thickness of the slurry film at the front end side increases after the predetermined region is lifted up from the slurry reservoir. This allows the thickness of the slurry film at the front end side to be more appropriately adjusted.

[0012] [5] In the above-described method for manufacturing a sensor element (the method for manufacturing a sensor element according to any one of [1] to [4]), the second step may vibrate the element body with a larger amplitude and / or a larger frequency as the viscosity of the slurry pool increases when and / or after the predetermined region is pulled up from the slurry pool. In this way, the slurry adhering to the element body can be more appropriately moved toward the front end thereof based on the viscosity of the slurry pool.

[0013] [6] In the above-described method for manufacturing a sensor element (the method for manufacturing a sensor element according to any one of [1] to [5]), the second step may include at least one of: decreasing the speed of the element body when immersing the predetermined area in the slurry pool; increasing the time for which the predetermined area is immersed in the slurry pool; and decreasing the speed of the element body when lifting the predetermined area out of the slurry pool, as the viscosity of the slurry pool increases. In this way, the slurry can be more appropriately attached to the predetermined area based on the viscosity of the slurry pool.

[0014] [7] In the above-described method for manufacturing a sensor element (the method for manufacturing a sensor element according to any one of [1] to [6]), the second step may involve moving the element body at a speed that increases as the viscosity of the slurry pool increases, thereby stirring the slurry pool. In this way, the slurry pool can be more appropriately stirred based on the viscosity of the slurry pool, thereby more appropriately reducing variations in the components in the slurry pool.

[0015] [8] In the above-described method for manufacturing a sensor element (the method for manufacturing a sensor element according to any one of [5] to [7]), the second step may estimate the viscosity of the slurry reservoir based on a load acting on the element body when the element body is moved within the slurry reservoir. In this way, the viscosity of the slurry reservoir can be estimated.

[0016] [9] In the above-described method for manufacturing a sensor element (the method for manufacturing a sensor element according to any one of [5] to [7]), the second step may estimate the viscosity of the slurry pool based on the components and temperature of the slurry pool. In this way, the viscosity of the slurry pool can be estimated.

[0017]

[10] In the above-described method for manufacturing a sensor element (the method for manufacturing a sensor element according to any one of [1] to [9]), the second step may involve, after the predetermined region is lifted up from the slurry reservoir, using a jig to shape the front end of the slurry while vibrating the element body. In this way, the shape of the front end of the slurry and, ultimately, the shape of the front end of the porous protective layer can be shaped.

[0018]

[11] The slurry deposition device of the present invention is A sensor element includes an element body having a front end and a rear end that are both ends along a longitudinal direction and a side surface that is a surface along the longitudinal direction, the front end side being exposed to a gas to be measured, and a porous protective layer that covers a predetermined area around the front end of the element body, the slurry being applied to the predetermined area of ​​the element body to form the porous protective layer after firing, a holding portion that holds the element body before or after firing; a drive unit that moves the holding unit; a control unit that controls the drive unit; Equipped with the control unit controls the drive unit to move the holding unit while the holding unit holds the element body before or after firing, to immerse the predetermined region of the element body in a slurry reservoir, and then lift the element body up; Furthermore, the control unit controls the drive unit to vibrate the element body by vibration of the holding unit when and / or after the predetermined region is lifted up from the slurry reservoir by movement of the holding unit. The gist of this is as follows.

[0019] In the slurry deposition device of the present invention, the control unit controls the drive unit to move the holding unit to immerse a predetermined region of the element body in a slurry reservoir and then lift it up while the holding unit holds the element body before or after firing. In this case, the control unit controls the drive unit to vibrate the element body by vibrating the holding unit when and / or after lifting the predetermined region from the slurry reservoir. By vibrating the element body, the slurry adhering to the element body can be moved toward its front end. As a result, partial thinning of the front end peripheral portion of the slurry adhering to the element body, and ultimately of the front end peripheral portion of the porous protective layer after drying and firing, can be suppressed. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. [Figure 2] FIG. 2 is a longitudinal cross-sectional view of the sensor element 20. [Figure 3] 3A to 3C are process diagrams of a method for manufacturing the sensor element 20. [Figure 4] 3A to 3C are explanatory diagrams illustrating the manufacturing process of the sensor element 20. [Figure 5] FIG. 2 is a schematic diagram of a slurry deposition device 80 and the like. [Figure 6] FIG. 10 is an explanatory diagram of step S110. [Figure 7] FIG. 10 is a schematic diagram of a modified example of a slurry deposition device 180. [Figure 8] FIG. 10 is an explanatory diagram of step S110 in a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0021] Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a sensor element 20 manufactured by a sensor element manufacturing method according to an embodiment of the present invention, as viewed from the upper right front. FIG. 2 is a longitudinal cross-sectional view schematically showing a longitudinal cross-section of the sensor element 20. Note that upper connector electrodes 71, lower connector electrodes 72, and outer lead portions 75 are not shown in FIG. 1. In this embodiment, as shown in FIGS. 1 and 2, the longitudinal direction of the element body 60 of the sensor element 20 is defined as the front-rear direction (length direction), the stacking direction (thickness direction) of the solid electrolyte layers of the element body 60 is defined as the up-down direction, and the direction perpendicular to the front-rear direction and the up-down direction is defined as the left-right direction (width direction).

[0022] The sensor element 20 is used as part of a gas sensor. In addition to the sensor element 20, the gas sensor includes a protective cover that protects the front end of the sensor element 20 and a sensor assembly that houses the sensor element. This gas sensor is attached to, for example, an exhaust gas pipe of an internal combustion engine of a vehicle, and is used to detect the concentration (specific gas concentration) of a specific gas such as NOx, O2, or ammonia in the exhaust gas from the internal combustion engine. Of the two ends (front and rear ends) along the longitudinal direction of the sensor element 20, the front end is exposed to the measurement gas.

[0023] As shown in FIGS. 1 and 2, the sensor element 20 includes an element body 60, a detection unit 63, a heater 69, a plurality of upper connector electrodes 71, a plurality of lower connector electrodes 72, and a porous protective layer 76. The element body 60 has a laminated body in which a plurality of (six in this embodiment) oxygen ion conductive solid electrolyte layers such as zirconia (ZrO) are stacked. The element body 60 has a rectangular parallelepiped shape with its longitudinal direction aligned with the front-rear direction, and has first to sixth faces 60a to 60f as outer surfaces on the top, bottom, left, right, front, and rear sides, respectively. The first to fourth faces 60a to 60d are surfaces aligned with the longitudinal direction of the element body 60 and correspond to the side faces (top, bottom, left, and right faces) of the element body 60. The fifth face 60e is the front end face of the element body 60, and the sixth face 60f is the rear end face of the element body 60. The dimensions of element body 60 may be, for example, a length in the front-rear direction of 25 mm to 100 mm, a width in the left-right direction of 2 mm to 10 mm, and a thickness in the up-down direction of 0.5 mm to 5 mm. Element body 60 is formed with a measurement gas inlet 61 that opens to fifth surface 60e and introduces a measurement gas into itself, and a reference gas inlet 62 that opens to sixth surface 60f and introduces a reference gas (here, air) that serves as a reference for detecting the concentration of a specific gas into itself.

[0024] The detection unit 63 is for detecting the concentration of a specific gas in the gas to be measured. The detection unit 63 has a plurality of electrodes 64 to 68 disposed on the front end side of the element body 60. In this embodiment, the detection unit 63 includes an outer electrode 64 disposed on the first surface 60a, and an inner main pump electrode 65, an inner auxiliary pump electrode 66, a measurement electrode 67, and a reference electrode 68 disposed inside the element body 60. The inner main pump electrode 65 and the inner auxiliary pump electrode 66 are disposed on the inner circumferential surface of the space inside the element body 60, and have a tunnel-like structure.

[0025] The principle by which the detection unit 63 detects the concentration of a specific gas in a measurement gas is well known, and therefore a detailed description thereof will be omitted. The detection unit 63 detects the concentration of a specific gas, for example, as follows. The detection unit 63 pumps oxygen from the measurement gas around the inner main pump electrode 65 to the outside based on the voltage applied between the outer electrode 64 and the inner main pump electrode 65. The detection unit 63 also pumps oxygen from the measurement gas around the inner auxiliary pump electrode 66 to the outside based on the voltage applied between the outer electrode 64 and the inner auxiliary pump electrode 66. As a result, the measurement gas, whose oxygen concentration has been adjusted to a predetermined concentration, reaches the vicinity of the measurement electrode 67. The measurement electrode 67 functions as a NOx reduction catalyst and reduces the specific gas (NOx) in the measurement gas that has reached it. The detection unit 63 then generates an electromotive force between the measurement electrode 67 and the reference electrode 68 in accordance with the oxygen concentration after reduction, or generates a current flowing between the measurement electrode 67 and the outer electrode 64 based on the electromotive force, as an electrical signal. The electrical signal generated by the detection unit 63 in this manner is a signal indicating a value corresponding to the concentration of a specific gas in the measured gas (a value from which the concentration of the specific gas can be derived), and corresponds to the detection value detected by the detection unit 63.

[0026] The heater 69 is an electric resistor disposed inside the element body 60. When power is supplied from the outside, the heater 69 generates heat to heat the element body 60. The heater 69 heats and keeps warm the solid electrolyte layer that forms the element body 60, and can adjust the temperature to a temperature (e.g., 800°C) at which the solid electrolyte layer is activated.

[0027] Each of the plurality of upper connector electrodes 71 and the plurality of lower connector electrodes 72 is disposed on the rear end side of the side surface of the element body 60 and serves as an electrode for electrical conduction with the outside. The plurality of upper connector electrodes 71 and the plurality of lower connector electrodes 72 are exposed without being covered by the porous protective layer 76. In this embodiment, the four upper connector electrodes 71 are disposed side by side in the left-right direction on the rear end side of the first surface 60a (upper surface). The four lower connector electrodes 72 are disposed side by side in the left-right direction on the rear end side of the second surface 60b (lower surface). Each of the four upper connector electrodes 71 and the four lower connector electrodes 72 is electrically connected to one of the plurality of electrodes 64 to 68 of the detection unit 63 and the heater 69. An upper connector electrode 71 and an outer electrode 64 are electrically connected to each other via an outer lead portion 75 disposed on the first surface 60a. The other connector electrodes are each electrically connected to a corresponding electrode or heater 69 via a lead wire or through hole disposed inside the element body 60 .

[0028] The porous protective layer 76 is a porous body that covers a predetermined region around the front end of the element body 60 (a region within a predetermined range from the front end to the rear end), specifically, a part of the first to fourth surfaces 60a and the entire fifth surface 60e of the element body 60. The porous protective layer 76 covers the portions of the element body 60 that are exposed to the measurement gas, including the measurement gas inlet 61 and the outer electrode 64. The porous protective layer 76 covers and protects a portion of the element body 60. Specifically, the porous protective layer 76 serves as a protective layer that prevents, for example, water in the measurement gas from adhering to the element body 60 and causing cracks in the element body 60.

[0029] The porous protective layer 76 is made of a ceramic porous body such as porous alumina, porous zirconia, porous spinel, porous cordierite, porous titania, or porous magnesia. The thickness of the porous protective layer 76 may be, for example, 40 μm or more and 800 μm or less. The porosity of the porous protective layer 76 may be 10% or more and 85% or less. The porous protective layer 76 covers the measurement gas inlet 61, but because it is porous, the measurement gas can flow through the porous protective layer 76 and reach the measurement gas inlet 61.

[0030] The porosity of the porous protective layer 76 is a value derived as follows using an image (SEM image) obtained by observation using a scanning electron microscope (SEM). First, the sensor element 20 is cut along the thickness direction of the porous protective layer 76 so that the cross section of the porous protective layer 76 serves as the observation surface. The cut surface is then filled with resin and polished to obtain an observation sample. Next, an SEM image of the porous protective layer 76 is obtained by photographing the observation surface of the observation sample with the SEM magnification set to 1000x to 10000x. The obtained image is then analyzed to determine a threshold value using discriminant analysis (Otsu's binarization) based on the brightness distribution of the brightness data of the pixels in the image. Next, each pixel in the image is binarized into an object portion and a pore portion based on the determined threshold value, and the area of ​​the object portion and the area of ​​the pore portion are calculated. The porosity (unit: %) is then derived as the ratio of the area of ​​the pore portion to the total area (the total area of ​​the object portion and the pore portion).

[0031] Next, a method for manufacturing the sensor element 20 will be described. FIG. 3 is a process chart showing an example of the steps in the method for manufacturing the sensor element 20. FIG. 4 is an explanatory diagram showing an example of the manufacturing process of the sensor element 20. As shown in FIG. 3, in the method for manufacturing the sensor element 20, first, a fired element body 60 is prepared (step S100, see FIG. 4(a)). Next, a slurry 77 is applied to a predetermined region of the element body 60 (step S110, see FIG. 4(b)). Then, the slurry 77 applied to the element body 60 is fired to form a porous protective layer 76 (step S120, see FIG. 4(c)), thereby obtaining the sensor element 20.

[0032] Step S100 will be described. In step S100, first, a plurality of unsintered ceramic green sheets (six in this embodiment) corresponding to the element body 60 are prepared. Next, notches, through-holes, grooves, etc. are formed in each green sheet by punching or the like, and wiring patterns such as electrodes 64-68 and outer lead portions 75 are formed by screen printing, as needed. Each green sheet is then dried, and thereafter, the plurality of green sheets are stacked to form a laminate. The laminate thus obtained includes a plurality of element bodies 60. The laminate is cut into pieces the size of the element bodies 60, and fired at a predetermined firing temperature to obtain the element bodies 60. Note that in step S100, instead of manufacturing and preparing the element bodies 60, a pre-manufactured, fired element body 60 may be prepared.

[0033] Step S110 will now be described. Fig. 5 is a schematic diagram of a slurry deposition device 80 used in step S110. In Fig. 5, the left-right direction is the X-axis direction, the front-to-back direction (the direction penetrating the paper surface) is the Y-axis direction, and the up-down direction is the Z-axis direction. In step S100, slurry 77 is deposited on a predetermined region of the element body 60 by dipping using the slurry deposition device 80.

[0034] The slurry deposition device 80 includes a holding unit 81 that holds a plurality of element bodies 60, a driving unit 82 that moves the holding unit 81, an imaging unit 88 that captures images of a predetermined imaging range, a control unit 92 that controls the driving unit 82 and the imaging unit 88, and a slurry tank 90 that stores the slurry as a slurry reservoir 91. Note that the holding unit 81 may be configured to hold only one element body 60.

[0035] The drive unit 82 includes an X-axis motor, an X-axis movement mechanism that moves the holder 81 in the X-axis direction (left and right in FIG. 5) as the X-axis motor rotates, a Y-axis motor, a Y-axis movement mechanism that moves the holder 81 in the Y-axis direction (front and back in FIG. 5) as the Y-axis motor rotates, and a Z-axis motor, and a Z-axis movement mechanism that moves the holder 81 in the Z-axis direction (up and down in FIG. 5) as the Z-axis motor rotates. The drive unit 82 also includes a holder position sensor that detects the position of the holder 81 in the X-axis, Y-axis, and Z-axis directions.

[0036] The photographing range of the photographing unit 88 is defined as the range around the slurry 77 adhering to the representative element body 60, which is one of the multiple element bodies 60 held by the holding unit 81, after a predetermined area of ​​the representative element body 60 is immersed in the slurry reservoir 91 and then pulled up.

[0037] The control unit 92 includes a microprocessor having a CPU, a memory unit, and the like. The control unit 92 receives input of the position of the holder 81 from the holder position sensor of the drive unit 82 and the captured image from the photographing unit 88. The control unit 92 controls the position and movement of the holder 81 by controlling the drive unit 82. The control unit 92 analyzes the captured image from the photographing unit 88 to estimate the film thickness around the front end of the slurry 77 adhering to the element body 60. For example, the control unit 92 calculates the horizontal length of the slurry 77 at a predetermined position in the Z-axis direction by image analysis, and estimates the film thickness of the slurry 77 at the predetermined position based on the calculated length of the slurry 77.

[0038] The slurry reservoir 91 contains the material of the porous protective layer 76, a solvent, a binder, a pore-forming material, and the like. Examples of the material of the porous protective layer 76 include at least some of alumina, zirconia, spinel, cordierite, titania, and magnesia. Examples of the solvent include organic solvents such as acetone and inorganic solvents such as water. Examples of the binder include inorganic binders such as alumina sol, silica sol, titania sol, and zirconia sol, or organic binders such as PVB and PVA. Examples of the pore-forming material include materials that disappear during sintering, such as theobromine and acrylic resin. The particle size and amount of the pore-forming material are determined based on, for example, the desired porosity of the porous protective layer 76. The viscosity of the slurry reservoir 91 is determined based on, for example, the desired film thickness of the porous protective layer 76.

[0039] FIG. 6 is an explanatory diagram showing an example of step S110. In step S110, first, as shown in FIG. 6(a), the element body 60 is held by the holder 81 so that the front end side of the element body 60 faces downward (the fifth surface 60e faces downward). Next, as shown in FIG. 6(b), the control unit 92 controls the drive unit 82 to move the holder 81 downward in the Z-axis direction, thereby lowering the element body 60 and immersing a predetermined region of the element body 60 in the slurry reservoir 91. Then, as shown in FIGS. 6(c) and 6(d), the control unit 92 controls the drive unit 82 to move the holder 81 upward in the Z-axis direction, thereby raising the element body 60 and lifting the predetermined region of the element body 60 out of the slurry reservoir 91. As a result, the slurry 77 adheres to the predetermined region of the element body 60. That is, the predetermined region of the element body 60 is covered with the slurry 77. 6(c) and 6(d), when a predetermined region of the element body 60 is being pulled out of the slurry reservoir 91 (when a portion of the slurry 77 is in the slurry reservoir 91) and after the predetermined region is pulled out (when the entire slurry 77 is separated from the slurry reservoir 91), the control unit 92 controls the drive unit 82 to vibrate the element body 60 in the horizontal direction (X-axis direction and / or Y-axis direction) of the holding unit 81. This allows the slurry 77 adhering to the element body 60 to be moved toward its front end (the lower side in FIGS. 6(c) and 6(d)). As a result, it is possible to prevent the outer periphery of the front end of the slurry 77 (see the dashed frame in FIG. 6(d)) from becoming partially thin. In this embodiment, the speed (first speed) of the element body 60 when lowering the element body 60 to immerse the predetermined region in the slurry reservoir 91, the immersion time of the predetermined region in the slurry reservoir 91, and the speed (second speed) of the element body 60 when raising the element body 60 to lift the predetermined region from the slurry reservoir 91 are all constant values ​​determined in advance through experiments, analyses, etc. Furthermore, the amplitude and frequency of vibration of the element body 60 when lifting the predetermined region of the element body 60 from the slurry reservoir 91 and after lifting it are all constant values ​​determined in advance through experiments, analyses, etc. The vibration frequency is, for example, about 1 Hz to 10 Hz.Furthermore, after the predetermined region of the element body 60 is lifted up from the slurry reservoir 91, the control unit 92 vibrates the element body 60 until the film thickness around the front end of the slurry 77 reaches the target film thickness. Note that the control unit 92 can estimate the film thickness around the front end of the slurry 77 by analyzing the image captured by the photographing unit 88, as described above. Furthermore, after the predetermined region of the element body 60 is lifted up from the slurry reservoir 91, the control unit 92 may vibrate the element body 60 for a predetermined time.

[0040] Step S120 will be described. In step S120, the slurry 77 attached to the element body 60 is fired at a predetermined firing temperature. As a result, the slurry 77 is sintered to form the porous protective layer 76, and the sensor element 20 is obtained. As described above, by preventing the front end side outer periphery and other portions of the slurry 77 from becoming partially thin, it is possible to prevent the front end side outer periphery and other portions of the porous protective layer 76 from becoming partially thin. As a result, it is possible to prevent a decrease in the water resistance of the front end side outer periphery and other portions of the porous protective layer 76. Note that, before step S120, it is preferable to dry the slurry 77 attached to the element body 60. At this time, it is preferable to dry the slurry 77 while positioning the element body 60 so that the front end side of the element body 60 is facing downward.

[0041] Here, the correspondence between the components of this embodiment and the components of the present invention will be clarified. In this embodiment, the element body 60 corresponds to the element body, the porous protective layer 76 corresponds to the porous protective layer, step S100 corresponds to the first step, step S110 corresponds to the second step, and step S120 corresponds to the third step. Furthermore, the slurry deposition device 80 corresponds to the slurry deposition device, the holding unit 81 corresponds to the holding unit, the driving unit 82 corresponds to the driving unit, and the control unit 92 corresponds to the control unit.

[0042] According to the manufacturing method of the sensor element 20 of this embodiment described above in detail, the fired element body 60 is prepared, and a predetermined region of the element body 60 is immersed in the slurry reservoir 91 and then pulled out, thereby adhering the slurry 77, which will become the porous protective layer after firing, to the predetermined region. The element body 60 is then vibrated when and after the predetermined region is pulled out of the slurry reservoir 91. This allows the slurry 77 adhering to the element body 60 to be moved toward its front end. As a result, it is possible to prevent the front end side outer periphery of the slurry 77 adhering to the element body 60, and ultimately the front end side outer periphery of the porous protective layer 76, from becoming partially thin.

[0043] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms as long as they fall within the technical scope of the present invention.

[0044] For example, in the above-described embodiment, the fired element body 60 is prepared in step S100, and the slurry 77 is fired in step S120 to obtain the sensor element 20. However, the present invention is not limited to this. For example, the unfired element body 60 may be prepared in step S100, and the element body 60 and the slurry 77 may be fired together in step S120 to obtain the sensor element 20.

[0045] In the embodiment described above, in step S110, the element body 60 is vibrated in the horizontal direction when and after the predetermined region of the element body 60 is pulled up from the slurry reservoir 91, but this is not limiting. For example, the element body 60 may be vibrated only when and only after the predetermined region of the element body 60 is pulled up from the slurry reservoir 91. Furthermore, the element body 60 may be vibrated in a direction different from the horizontal direction, such as the vertical direction, when and / or after the predetermined region of the element body 60 is pulled up from the slurry reservoir 91.

[0046] In the embodiment described above, in step S110, the element body 60 is vibrated at a constant amplitude and a constant frequency when and after the predetermined region of the element body 60 is lifted from the slurry reservoir 91. However, this is not limiting. For example, after the predetermined region of the element body 60 is lifted from the slurry reservoir 91, the element body 60 may be vibrated at a smaller amplitude and / or a smaller frequency than when the predetermined region of the element body 60 is lifted from the slurry reservoir 91. This makes it possible to prevent the slurry 77 from separating from the element body 60 and falling.

[0047] In the embodiment described above, after the predetermined region of the element body 60 is lifted from the slurry reservoir 91 in step S110, the element body 60 is vibrated at a constant amplitude and a constant frequency. However, this is not limiting. For example, the amplitude and frequency of the vibration of the element body 60 may be set based on the film thickness of the slurry 77 adhering to the element body 60 around the front end, and the element body 60 may be vibrated using the set amplitude and frequency. In this case, the amplitude and frequency of the vibration of the element body 60 may be set based on the film thickness of the slurry 77 around the front end and a first amplitude-frequency map. The first amplitude-frequency map is determined in advance through experiments, analysis, etc., as a relationship between the film thickness of the slurry 77 around the front end and the amplitude and frequency of the vibration of the element body 60. The first amplitude-frequency map is determined so that both the amplitude and frequency of the vibration of the element body 60 decrease as the film thickness of the slurry 77 around the front end increases (approaching the target film thickness). By setting the amplitude and frequency of the vibration of the element body 60 in this manner, the slurry 77 can be more appropriately moved toward the front end based on the film thickness of the slurry 77 around its front end. As a result, the film thickness of the slurry 77 around its front end can be more appropriately adjusted, that is, the deviation between the final film thickness and the target film thickness can be more effectively suppressed. Note that only either the amplitude or frequency of the vibration of the element body 60 may be variable based on the film thickness of the slurry 77 around its front end.

[0048] In this modification, the amplitude and frequency of the vibration of the element body 60 are set based on the film thickness around the front end of the slurry 77, but this is not limiting. For example, the amplitude and frequency of the vibration of the element body 60 may be set based on the elapsed time after a predetermined region of the element body 60 is lifted from the slurry reservoir 91. In this case, it is preferable to set the amplitude and frequency of the vibration of the element body 60 so that they each decrease as the elapsed time increases. Note that only either the amplitude or the frequency of the vibration of the element body 60 may be variable based on the elapsed time.

[0049] In the above-described embodiment, in step S110, the element body 60 is vibrated at a constant amplitude and a constant frequency when and after the predetermined region of the element body 60 is lifted from the slurry reservoir 91. However, this is not limiting. For example, when and / or after the predetermined region of the element body 60 is lifted from the slurry reservoir 91, the amplitude and frequency of the vibration of the element body 60 may be set based on the viscosity of the slurry reservoir 91 or the slurry 77, and the element body 60 may be vibrated using the set amplitude and frequency. In this case, for example, the amplitude and frequency of the vibration of the element body 60 may be set based on the viscosity of the slurry reservoir 91 or the slurry 77 and a second amplitude-frequency map. The second amplitude-frequency map is determined in advance through experiments, analysis, or the like as a relationship between the viscosity of the slurry reservoir 91 or the slurry 77 and the amplitude and frequency of the vibration of the element body 60. The second amplitude-frequency map is determined so that the higher the viscosity of the slurry reservoir 91 or the slurry 77, the greater the amplitude and frequency of the vibration of the element body 60. This is because the higher the viscosity of the slurry reservoir 91 or the slurry 77, the more difficult it is to move the slurry 77 adhering to the element body 60 toward the front end. By setting the amplitude and frequency of the vibration of the element body 60 in this manner, the slurry 77 can be more appropriately moved toward the front end based on the viscosity of the slurry reservoir 91 or the slurry 77. Note that only either the amplitude or frequency of the vibration of the element body 60 may be made variable based on the viscosity of the slurry reservoir 91 or the slurry 77.

[0050] The viscosity of the slurry reservoir 91 and the slurry 77 can be estimated by, for example, the following first or second method. In the first method, the control unit 92 moves the element body 60 horizontally (in the X-axis direction or the Y-axis direction) within the slurry reservoir 91, and estimates the viscosity of the slurry reservoir 91 and the slurry 77 based on the load acting on the element body 60 (holding unit 81) at that time and a first viscosity estimation map. The load acting on the element body 60 can be estimated by the control unit 92 based on the relationship between the drive current values ​​of the X-axis motor and the Y-axis motor and the movement amount (movement speed) of the element body 60, or can be detected by a sensor for detecting the load. The first viscosity estimation map is determined in advance by experiments, analysis, or the like as a relationship between the load on the element body 60 and the viscosity of the slurry reservoir 91 and the slurry 77. The first viscosity estimation map is determined so that the viscosity of the slurry reservoir 91 and the slurry 77 increases as the load on the element body 60 increases.

[0051] In the second method, an operator inputs the components and temperature of the slurry reservoir 91, and the control unit 92 estimates the viscosity of the slurry reservoir 91 and the slurry 77 based on the input components and temperature of the slurry reservoir 91 and the second viscosity estimation map. Here, the temperature of the slurry reservoir 91 may be detected by a temperature sensor and input. The second viscosity estimation map is determined in advance through experiments, analysis, etc. as a relationship between the components and temperature of the slurry reservoir 91 and the viscosity of the slurry reservoir 91 and the slurry 77. The second viscosity estimation map is determined so that, for each combination of components of the slurry reservoir 91, the viscosity of the slurry reservoir 91 and the slurry 77 increases as the temperature of the slurry reservoir 91 decreases.

[0052] In this modification, the amplitude and frequency of vibration of the element body 60 are set based on the viscosity of the slurry reservoir 91 and the slurry 77, but this is not limiting. For example, after a predetermined region of the element body 60 is lifted up from the slurry reservoir 91, the amplitude and frequency of vibration of the element body 60 may be set based on the viscosity of the slurry reservoir 91 and the slurry 77 and the film thickness around the front end of the slurry 77. Note that only either the amplitude or frequency of vibration of the element body 60 may be variable based on the viscosity of the slurry reservoir 91 and the slurry 77 and the film thickness around the front end of the slurry 77.

[0053] In the above-described embodiment, in step S110, the speed (first speed) of the element body 60 when lowering the element body 60 to immerse a predetermined region in the slurry reservoir 91, the immersion time of the predetermined region in the slurry reservoir 91, and the speed (second speed) of the element body 60 when raising the element body 60 to lift the predetermined region out of the slurry reservoir 91 are all constant, but this is not limiting. For example, the first speed, immersion time, and second speed may be set based on the viscosity of the slurry reservoir 91. In this case, the first speed, immersion time, and second speed may be set based on the viscosity of the slurry reservoir 91 and a speed-time map. The speed-time map is determined in advance by experimentation, analysis, or the like as a relationship between the viscosity of the slurry reservoir 91, the first speed, the immersion time, and the second speed. The speed-time map is determined so that the higher the viscosity of the slurry reservoir 91, the smaller the first speed, the longer the immersion time, and the smaller the second speed. This is because the higher the viscosity of the slurry pool 91, the more difficult it is for the slurry 77 to adhere to the predetermined region of the element body 60. By setting the first speed, immersion time, and second speed in this manner, the slurry 77 can be more appropriately adhered to the predetermined region of the element body 60 based on the viscosity of the slurry pool 91. Note that only some of the first speed, immersion time, and second speed may be variable based on the viscosity of the slurry pool 91.

[0054] Although not described in the above-described embodiment, in step S110, the control unit 92 may control the drive unit 82 to rotate (revolve) the holding unit 81 and the element body 60 about a central axis extending in the vertical direction at least when the predetermined region of the element body 60 is immersed in the slurry reservoir 91, while the predetermined region is immersed in the slurry reservoir 91, or when the predetermined region is lifted from the slurry reservoir 91. This agitates the slurry reservoir 91, reducing the variation in the components in the slurry reservoir 91 and improving the adhesion of the slurry 77 to the predetermined region of the element body 60. In this case, the higher the viscosity of the slurry reservoir 91, the faster the element body 60 is rotated about the central axis. This is because the higher the viscosity of the slurry reservoir 91, the more difficult it is to reduce the variation in the components in the slurry reservoir 91 and the lower the adhesion of the slurry 77 to the predetermined region. By such control, the slurry pool 91 can be more appropriately stirred based on the viscosity of the slurry pool 91, thereby more appropriately reducing the variation in the components in the slurry pool 91, and more appropriately improving the adhesion of the slurry 77 to specified areas of the element body 60.

[0055] In this modification, the slurry reservoir 91 is agitated by moving the element body 60, but this is not limiting. For example, the variation in the components in the slurry reservoir 91 may be reduced by circulating the slurry between the slurry tank 90 and the second slurry tank using a circulation pump.

[0056] In the embodiment described above, the slurry deposition apparatus 80 of Fig. 5 is used in step S110, but this is not limiting. For example, the slurry deposition apparatus 180 of Fig. 7 may be used. The slurry deposition apparatus 180 of Fig. 7 is the same as the slurry deposition apparatus 80 of Fig. 5 except that it additionally includes a plurality of receiving portions 83, a frame portion 84, and a pair of lifting devices 85. Therefore, the same hardware components of the slurry deposition apparatus 180 as those of the slurry deposition apparatus 80 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0057] Each receiving portion 83 is fixed to the frame portion 84 so as to face the fifth surface 60e of the element body 60 at a distance in the Z-axis direction when the holder 81 holds the element body 60 with the front end side of the corresponding element body 60 facing downward (the fifth surface 60e facing downward). The inner peripheral surface of each receiving portion 83 is formed into a smoothly curved surface that convex downward, specifically, a shape that corresponds to the desired shape of the front end side of the slurry 77. Each of the pair of lifting devices 85 includes a motor and a lifting mechanism that moves the frame portion 84 (the multiple receiving portions 83) relative to the holder 81 in the Z-axis direction as the motor rotates. The lifting device 85 also includes a lifting position sensor that detects the position of the frame portion 84 in the Z-axis direction. The control unit 92 receives the position of the frame portion 84 from the lifting position sensor. The control unit 92 controls the pair of lifting devices 85 to control the position of the frame portion 84 (the multiple receiving portions 83). Basically, the position of the frame portion 84 is adjusted so that the fifth surface 60e of the element body 60 and the receiving portion 83 face each other at a predetermined distance in the Z-axis direction when the holding portion 81 holds the element body 60. The predetermined distance is determined based on the desired shape (including the desired film thickness) of the front end side of the slurry 77.

[0058] FIG. 8 is an explanatory diagram showing an example of step S110 of this modified example. In step S110 of this modified example, first, as shown in FIG. 8(a), the element body 60 is held by the holder 81 so that the front end side of the element body 60 faces downward (the fifth surface 60e faces downward). Next, as shown in FIG. 8(b), the control unit 92 controls the drive unit 82 to move the holder 81 downward in the Z-axis direction, thereby lowering the element body 60 and immersing a predetermined region of the element body 60 into the slurry reservoir 91. Then, as shown in FIGS. 8(c) and 8(d), the control unit 92 controls the drive unit 82 to move the holder 81 upward in the Z-axis direction, thereby raising the element body 60 and lifting the predetermined region of the element body 60 out of the slurry reservoir 91. In this modification, as shown in FIG. 8(d), after the predetermined region of the element body 60 is lifted from the slurry reservoir 91, the control unit 92 controls the drive unit 82 to vibrate the element body 60 horizontally by vibrating the holder 81 in the horizontal direction (X-axis direction and / or Y-axis direction). This allows the slurry 77 adhering to the element body 60 to be concentrated toward its front end (the lower side in FIG. 8(d)). The receiving unit 83 prevents the slurry 77 from separating from the element body 60, and the front end side of the slurry 77 can be shaped into a desired shape. As a result, the front end side of the porous protective layer 76 can be shaped into a desired shape. Note that shaping the front end side of the slurry 77 into a predetermined shape includes preventing the outer periphery of the front end side of the slurry 77 (see the dashed-line frame in FIG. 8) from becoming partially thin. Thereafter, the control unit 92 controls the lifting device 85 so that the frame portion 84 (the plurality of receiving portions 83) moves downward in the Z-axis direction relative to the holding portion 81. This allows the receiving portions 83 to be separated from the slurry 77.

[0059] In the above-described embodiment, the element body 60 has a rectangular parallelepiped shape, but is not limited to this. For example, the element body 60 may have a cylindrical or columnar shape. In this case, the element body 60 has only one side surface. [Industrial Applicability]

[0060] The present invention can be used in the manufacturing industry of sensor elements for detecting the concentration of a specific gas such as NOx in a measurement gas such as exhaust gas from an internal combustion engine. [Explanation of symbols]

[0061] 20 sensor element, 60 element body, 60a first surface, 60b second surface, 60c third surface, 60d fourth surface, 60e fifth surface, 60f sixth surface, 61 measured gas inlet, 62 reference gas inlet, 63 detection unit, 64 outer electrode, 65 inner main pump electrode, 66 inner auxiliary pump electrode, 67 measurement electrode, 68 reference electrode, 69 heater, 71 upper connector electrode, 72 lower connector electrode, 75 outer lead portion, 76 porous protective layer, 77 slurry, 80, 180 slurry deposition device, 81 holding portion, 82 drive portion, 83 receiving portion, 84 frame portion, 85 lifting device, 88 photographing portion, 90 slurry tank, 91 slurry reservoir, 92 control portion.

Claims

1. A method for manufacturing a sensor element comprising: an element body having a front end and a rear end which are both ends along a longitudinal direction and a side surface which is a surface along the longitudinal direction, the front end side being exposed to a gas to be measured; and a porous protective layer covering a predetermined region around the front end of the element body, a first step of preparing the element body before or after firing; a second step of immersing the predetermined region of the element body in a slurry reservoir and then lifting it out, thereby adhering the slurry, which will become the porous protective layer after firing, to the predetermined region; Including, The second step includes vibrating the element body when and / or after the predetermined region is lifted from the slurry reservoir. A method for manufacturing a sensor element.

2. A method for manufacturing the sensor element according to claim 1, the second step includes vibrating the element body in a horizontal direction when and / or after the predetermined region is lifted from the slurry reservoir; A method for manufacturing a sensor element.

3. A method for manufacturing the sensor element according to claim 1, In the second step, after the predetermined region is pulled up from the slurry reservoir, the element body is vibrated with a smaller amplitude and / or a smaller frequency than when the predetermined region is pulled up from the slurry reservoir. A method for manufacturing a sensor element.

4. A method for manufacturing the sensor element according to claim 1, In the second step, after the predetermined region is lifted up from the slurry reservoir, the element body is vibrated with a smaller amplitude and / or a smaller frequency as the thickness of the slurry on the front end side increases. A method for manufacturing a sensor element.

5. A method for manufacturing the sensor element according to claim 1, In the second step, when and / or after the predetermined region is pulled up from the slurry reservoir, the element body is vibrated with a larger amplitude and / or a larger frequency as the viscosity of the slurry reservoir increases. A method for manufacturing a sensor element.

6. A method for manufacturing the sensor element according to claim 1, In the second step, as the viscosity of the slurry pool increases, at least one of the following is performed: decreasing the speed of the element body when immersing the predetermined region in the slurry pool; increasing the immersion time of the predetermined region in the slurry pool; and decreasing the speed of the element body when lifting the predetermined region out of the slurry pool. A method for manufacturing a sensor element.

7. A method for manufacturing the sensor element according to claim 1, In the second step, the higher the viscosity of the slurry pool, the faster the element body is moved to agitate the slurry pool. A method for manufacturing a sensor element.

8. A method for manufacturing a sensor element according to any one of claims 5 to 7, comprising: the second step includes estimating the viscosity of the slurry reservoir based on a load acting on the element body when the element body is moved within the slurry reservoir; A method for manufacturing a sensor element.

9. A method for manufacturing a sensor element according to any one of claims 5 to 7, comprising: The second step estimates the viscosity of the slurry pool based on the components and temperature of the slurry pool. A method for manufacturing a sensor element.

10. A method for manufacturing the sensor element according to claim 1, In the second step, after the predetermined region is lifted up from the slurry reservoir, the shape of the front end side of the slurry is adjusted using a jig while vibrating the element body. A method for manufacturing a sensor element.

11. A sensor element includes an element body having a front end and a rear end that are both ends along a longitudinal direction and a side surface that is a surface along the longitudinal direction, the front end side being exposed to a gas to be measured, and a porous protective layer that covers a predetermined area around the front end of the element body, the slurry being applied to the predetermined area of ​​the element body to form the porous protective layer after firing, a holding portion that holds the element body before or after firing; a drive unit that moves the holding unit; a control unit that controls the drive unit; Equipped with the control unit controls the drive unit to move the holding unit while the holding unit holds the element body before or after firing, to immerse the predetermined region of the element body in a slurry reservoir, and then lift the element body up; Furthermore, the control unit controls the drive unit to vibrate the element body by vibration of the holding unit when and / or after the predetermined region is lifted up from the slurry reservoir by movement of the holding unit. Slurry deposition device.

Images