Gas sensor

Abstract

Provided is a gas sensor in which breakage during assembly of a sensor element is suppressed. A gas sensor is provided with a sensor element (10), a main metal fitting (138), a cylindrical holder (151) having a first element hole, a sleeve (106) having a second element hole, and a filling powder (156) that fills a gap between the main metal fitting and the sensor element. On at least one of the holder and the sleeve, flat surfaces (106f, 151f) that come into contact with the filling powder and protrusions (106p, 151p) that protrude from the flat surfaces toward the filling powder and surround the first element hole or the second element hole are formed, and when viewed from a direction perpendicular to the main surface of the sensor element, the protrusions (106p, 151p) protrude from the flat surfaces toward the filling powder and surround the first element hole or the second element hole. A corner portion (10e), which becomes thinner toward the filling powder and is parallel to the axial direction of the sensor element, is located between the top portion (106t, 151t) and the base portion (106b, 151b) of the protrusion near a boundary portion (BR) of the protrusion.

Description

Technical Field

[0001] This invention relates to a gas sensor having a sensor element for detecting the concentration of the gas being detected. Background Technology

[0002] Gas sensors with plate-shaped sensor elements are known as gas sensors for detecting the concentration of oxygen and NOx in exhaust gases from automobiles and other sources. As such a gas sensor, the following structure is used: a cylindrical main body fitting is used to hold the sensor element around it, and an annular retainer and a sleeve with an element hole for the sensor element to be inserted are arranged in the inner hole of the main body fitting, and a talc ring or other filling powder is arranged between the retainer and the sleeve to fill the gap between the main body fitting and the sensor element (Patent Document 1). Here, by pressing the sleeve against the retainer, the filling powder is compressed and enters the gap between the main body and the sensor element, thus sealing it.

[0003] Patent document 1: Japanese Patent Application Publication No. 2019-138679. Summary of the Invention The problem that the invention aims to solve

[0004] However, in the case of conventional gas sensors, such as Figure 8 As shown, the area around the element hole 1100h of the retainer 1100 and sleeve 1200 is a flat surface. Therefore, when the filling powder 1300 is compressed via the sleeve 1200, the pressure is concentrated at the weak corner 1000e of the sensor element 1000, and the sensor element 1000 may be damaged. The reasoning is as follows. For example, if the area around the element hole 1100h of the retainer 1100 is a flat surface, then when the filling powder 1300 is compressed, the pressing force F of the filling powder 1300 is applied equally to the sensor element 1000 around the element hole 1100h. However, this results in the corner 1000e, which has low strength, also being subjected to the same pressing force F as other parts, leading to damage to the corner 1000e. On the other hand, the filling powder 1300 fills (seals) the gap between the main body fitting and the sensor element 1000, thus making it difficult to reduce the overall pressing force F.

[0005] Therefore, the object of the present invention is to provide a gas sensor that suppresses breakage during the assembly of sensor elements. Methods for solving problems

[0006] To address the aforementioned issues, the gas sensor of the present invention comprises: a plate-shaped sensor element extending along an axial direction, with a detection portion for detecting a gas being detected formed at its front end; a cylindrical body fitting surrounding and holding the sensor element radially around its periphery; a cylindrical retaining member held within the inner hole of the body fitting, having a rectangular first element hole through which the sensor element is inserted; a cylindrical sleeve held within the inner hole of the body fitting at a position further rearward than the retaining member, having a rectangular second element hole through which the sensor element is inserted; and a filling powder disposed between the retaining member and the sleeve within the inner hole of the body fitting, filling the body fitting. The gap between the fitting and the sensor element, wherein, in the retainer forming a flat surface that contacts the filling powder and a protrusion that protrudes from the flat surface toward the filling powder and surrounds the first element hole, and / or in the sleeve forming a flat surface that contacts the filling powder and a protrusion that protrudes from the flat surface toward the filling powder and surrounds the second element hole, when viewed from a direction perpendicular to the main surface of the sensor element, the protrusion tapers toward the filling powder, and the corner of the sensor element parallel to the axial direction is located between the top of the protrusion and the base of the protrusion connected to the flat surface.

[0007] According to the gas sensor, when the filling powder is compressed, the pressing pressure of the filling powder applied to the sensor element near the boundary becomes the highest pressing pressure on the side near the top, the lower pressing pressure at the boundary, and further decreases from the boundary towards the base, becoming the lowest pressing pressure at the base and flat surface. Furthermore, as a result, the pressing pressure of the filling powder gradually decreases along the axial direction of the corner, thus suppressing the application of high pressing pressure to the corner with low strength as in other parts (such as the part near the top of the sensor element), and suppressing damage during sensor element assembly. On the other hand, near the top, the distance between the sleeve and the retainer becomes closer, and the pressing pressure becomes higher, so that the gap between the main body fitting and the sensor element can be reliably filled (sealed) using filling powder.

[0008] In the gas sensor of the present invention, when viewed from a direction perpendicular to the main surface of the sensor element, the width c of the top of the protrusion, the width b of the base where the protrusion connects to the flat surface, and the width a of the sensor element satisfy the relationship c < a < b. According to this gas sensor, the boundary portion can be reliably positioned between the top and the base.

[0009] In the gas sensor of the present invention, the top of the protrusion may be flat. According to this gas sensor, compared to the case where the top is a steep mountain shape, the filling powder around the sensor element can be compressed as a surface. Therefore, the filling powder can be used to stably fill the area around the sensor element, and the gap between the main body fitting and the sensor element can be filled (sealed) more reliably.

[0010] In the gas sensor of the present invention, the protrusion may also reach the end of the flat surface. According to this gas sensor, the protrusion reaches the end of the flat surface, which correspondingly increases the area of ​​the filling powder around the sensor element that can be compressed with higher pressure. This allows for more reliable filling (sealing) of the gap between the main body fitting and the sensor element.

[0011] In the gas sensor of the present invention, the gas sensor may also be an oxygen sensor or a NOx sensor. Invention Effects

[0012] According to the present invention, a gas sensor that suppresses breakage during sensor element assembly can be obtained. Attached Figure Description

[0013] Figure 1 This is a cross-sectional view along the length of the gas sensor according to an embodiment of the present invention. Figure 2 This is a 3D view of the sensor element. Figure 3 It is a three-dimensional view of the retainer. Figure 4 It is a 3D diagram of the sleeve. Figure 5 It is a front view showing the positional relationship of the sensor element, the holder, and the sleeve when viewed from a direction perpendicular to the main surface of the sensor element. Figure 6 This is a diagram showing the protrusion and dimensions of the sensor element when viewed from a direction perpendicular to the main surface of the sensor element. Figure 7 This is a perspective view showing a modified example of the sleeve. Figure 8 This is a diagram showing the compression state of the filling powder in a conventional gas sensor. Detailed Implementation

[0014] The embodiments of the present invention will be described below. Figure 1 This is an overall cross-sectional view along the length of the gas sensor (oxygen sensor) 200 according to an embodiment of the present invention. Figure 2 This is a 3D view of sensor element 10. Figure 3 This is a three-dimensional view of retainer 151. Figure 4This is a 3D view of sleeve 106. The gas sensor 200 is an oxygen sensor that detects the oxygen concentration in the exhaust gas of automobiles and various internal combustion engines.

[0015] exist Figure 1 In the gas sensor 200, the following components are included: a cylindrical main body fitting 138 with a threaded portion 139 formed on its outer surface for fixing to an exhaust pipe; a sensor element 10, which is plate-shaped extending along the axial direction O (the length direction of the gas sensor 200: the vertical direction in the figure); a ceramic cylindrical sleeve 106 arranged to surround the radial periphery of the sensor element 10; a ceramic (alumina) cylindrical retainer 151; a ceramic cylindrical separator 166 arranged inside the front end side of the through hole 166h extending along the axial direction to surround the rear end of the sensor element 10; and four terminal fittings 21 (in Figure 1 (Only two are shown in the figure), which are arranged between sensor element 10 and separator 166. Furthermore, the detection section 10a at the front end of the sensor element 10 is covered by a porous protective layer 20 such as alumina (see reference). Figure 2 ).

[0016] The main body component 138 is made of stainless steel and has a through hole 154 extending along the axial direction. It is configured in a generally cylindrical shape with a bracket portion 152 protruding radially inward toward the through hole 154. The sensor element 10 is positioned in the through hole 154 such that the front end of the sensor element 10 protrudes beyond the front end of the through hole 154 itself. Furthermore, the bracket portion 152 is formed with an inwardly tapered surface inclined relative to a plane perpendicular to the axial direction.

[0017] Furthermore, inside the through hole 154 of the main body fitting 138, a retainer 151, a filling powder 156 (hereinafter also referred to as a talc ring), and the aforementioned sleeve 106 are sequentially stacked from the front end to the rear end in a radially surrounding manner around the sensor element 10. Additionally, a compression seal 157 is provided between the sleeve 106 and the rear end 140 of the main body fitting 138. Furthermore, the rear end 140 of the main body fitting 138 is pressed against the sleeve 106 towards the front end through the compression seal 157.

[0018] On the other hand, such as Figure 1 As shown, on the front end side of the main component 138 ( Figure 1 A metal (e.g., stainless steel) single-layer protector 142, which covers the protruding portion of the sensor element 10 and has multiple holes, is installed on the outer periphery of the sensor element 10 by welding or the like.

[0019] Furthermore, an outer cylinder 144 is fixed to the outer periphery of the rear end side of the main body component 138. Additionally, on the rear end side of the outer cylinder 144 ( Figure 1 The opening at the top of the sensor element 10 is provided with a rubber loop 170, which is formed with four terminal fittings 21 for connection to the sensor element 10. Figure 1 (Only two are indicated in the text) The four leads of the electrical connection 146 (in) Figure 1 (Only two) Through-holes for inserting leads (not shown). In addition, the grommets 170 are pressed from the outside of the outer cylinder 144 to keep the grommets 170 inside the outer cylinder 144.

[0020] Additionally, on the rear end side of the sensor element 10, which protrudes beyond the rear end 140 of the main component 138 ( Figure 1 A separator 166 is disposed above the sensor element 10. Furthermore, this separator 166 is disposed on a total of four electrode pads 11 formed on the main surface of the rear end side of the sensor element 10. Figure 1 (Only two are shown in the image) around it. The separator 166 is formed into a cylindrical shape with a through hole 166h extending along the axial direction, and has a flange 167 protruding radially outward from the outer surface. The separator 166 is held inside the outer cylinder 144 by abutting against the retaining member 169 through the flange 167.

[0021] like Figure 2 As shown, the sensor element 10 is plate-shaped, extending along the axis O. The front end 10s becomes the detection section 10a for detecting oxygen concentration, and the detection section 10a is covered by a porous protective layer 20. It should be noted that the sensor element 10 itself has a known structure, although not shown, it includes: a gas detection section, a solid electrolyte that is permeable to oxygen ions, and a pair of electrodes; and a heater section that heats the gas detection section to maintain it at a constant temperature. In addition, four corner portions 10e are formed parallel to the axis O of the sensor element 10.

[0022] Furthermore, on the rear end side of one main surface 10m1 of the sensor element 10, two electrode pads 11 are arranged in the width W direction, and the sensor output signal from the detection unit 10a is output from these electrode pads 11 via the lead portion (not shown). In addition, on the rear end side of another main surface 10m2, which is arranged facing the main surface, two electrode pads 11 are also arranged in the width W direction, and power is supplied to the heater unit via the lead portion (not shown). Each electrode pad 11 is a rectangle that is relatively long in the direction of axis O, and can be formed, for example, into a sintered body with Pt as the main body.

[0023] Figure 3 A perspective view of the retainer 151 is shown. The retainer 151 is cylindrical and has a rectangular first element hole 151h through which the sensor element 10 is inserted. The retainer 151 is formed with filling powder 156 ( Figure 3 The flat surface 151f in contact with the upper side) and from the flat surface 151f toward the filling powder 156 ( Figure 3 The protrusion 151p of the upper side of the first element hole 151h protrudes and surrounds it.

[0024] Furthermore, when viewed from a direction D perpendicular to the main surface 10m1 of the sensor element 10, the protrusion 151p faces toward the filling powder 156 ( Figure 3 It is roughly a trapezoid that tapers to a thinner shape (on the upper side). In addition, a flat surface 151f is formed on the radially outer side of the first element hole 151h, and a protrusion 151p is formed to surround the first element hole 151h from the flat surface 151f toward the radially inner side.

[0025] The protrusion 151p has a top 151t and a base 151b connected to the flat surface 151f. In this example, a sloping surface 151s is formed between the top 151t and the base 151b. However, the shape of the protrusion 151p between the top 151t and the base 151b is not limited; for example, it can also be stepped. Additionally, in this example, the top 151t is flat (surface).

[0026] In addition, the periphery 151hm where the first element hole 151h intersects with the protrusion 151p has the following profile: after extending parallel to the main surface 10m at the top 151t, it extends along the inclined plane 151s toward the front end side in the direction of axis O, and extends along direction D in the middle of the inclined plane 151s. Therefore, with the sensor element 10 inserted into the first element hole 151h, the four corners 10e of the sensor element 10 (in) Figure 3 (Only three are shown in the image) The boundary portion BR (BR is also the perimeter 151hm) adjacent to the protrusion 151p is located in the middle of the slope 151s, that is, between the top 151t and the base 151b. The reason for this will be explained later.

[0027] Figure 4 A perspective view of sleeve 106 is shown. Sleeve 106 also has the same structure as retainer 151, so the description is simplified. Specifically, the sleeve 106 is cylindrical and has a rectangular second element hole 106h through which the sensor element 10 is inserted. A filling powder 156 is formed in the sleeve 106. Figure 4The flat surface 106f in contact with the upper side and from the flat surface 106f toward the filling powder 156 ( Figure 4 The protrusion 106p of the second element hole 106h protrudes from the upper side and surrounds it.

[0028] Furthermore, when viewed from a direction D perpendicular to the main surface 10m1 of the sensor element 10, the protrusion 106p faces toward the filling powder 156 ( Figure 4 It is roughly a trapezoid that tapers to a thinner shape (on the upper side). In addition, a flat surface 106f is formed on the radially outer side of the second element hole 106h, and a protrusion 106p is formed to surround the second element hole 106h from the flat surface 106f toward the radially inner side.

[0029] The protrusion 106p has a top 106t and a base 106b that connects the protrusion 106p to the flat surface 106f. In addition, in this example, a sloping surface 106s is formed between the top 106t and the base 106b. The periphery 106hm where the second element hole 106h intersects with the protrusion 106p also has the same profile as the periphery 151hm of the retainer 151. Similarly, the four corners 10e (not shown) of the sensor element 10 are located in the middle of the slope 106s, between the top 106t and the base 106b, near the boundary BR of the protrusion 106p (BR is also the periphery 106hm).

[0030] Next, refer to Figure 5 The reason why the boundary part BR is located between the top 151t, 106t and the base 151b, 106b is explained. Figure 5 This is a front view showing the positional relationship of the sensor element 10, the retainer 151, and the sleeve 106 when viewed from a direction D perpendicular to the main surface 10m1 of the sensor element 10.

[0031] If we focus on the sensor element 10 and the retainer 151, the four corners 10e of the sensor element 10 are close to the protrusion 151p at the boundary portion BR (BR is also the perimeter 151hm). Moreover, the boundary portion BR is located in the middle of the slope 151s (between the top 151t and the base 151b). Therefore, when the filling powder 156 is compressed via the sleeve 106, the pressing pressure of the filling powder 156 applied to the sensor element 10 near the boundary BR becomes the highest pressing pressure F1 on the side near the top 151t, becomes a lower pressing pressure F2 at the boundary BR, further decreases from the boundary BR towards the base 151b, and becomes the lowest pressing pressure F3 at the base 151b and the flat surface 151f. This is because the top 151t is closest to the sleeve 106, so the compressive load of the filling powder 156 is the highest.

[0032] Furthermore, as a result, the pressing pressure of the filling powder 156 gradually decreases along the axis O direction of the corner 10e as F1 to F3, thus suppressing the application of high pressing pressure F to the corner 10e with low strength in the same way as other parts (such as the part of the sensor element 10 near the top 151t), and suppressing the breakage of the sensor element 10 during assembly. On the other hand, near the top 151t, the distance between it and the sleeve 106 is close, and the pressing pressure becomes higher, so the gap between the main body fitting 138 and the sensor element 10 can be reliably filled (sealed) by the filling powder 156. In addition, the sleeve 106 can also suppress damage during the assembly of the sensor element 10.

[0033] like Figure 6 As shown, in order to reliably position the boundary portion BR between the top 151t and the base 151b, when viewed from direction D, it is preferable that the width c of the top 151t, the width b of the base 151b, and the width a of the sensor element 10 satisfy the relationship c < a < b. Similarly, in order to ensure that the boundary portion BR is reliably located between the top 106t and the base 106b, when viewed from direction D, it is preferable that the width c2 of the top 106t, the width b2 of the base 106b, and the width a of the sensor element 10 satisfy the relationship c2 < a < b2.

[0034] like Figure 3 , Figure 4 As shown, in this example, the top 151t and 106t are flat (surfaces). In this way, compared to the case where the top 151t and 106t are steep mountain shapes, the filling powder 156 around the sensor element 10 can be compressed as a surface. As a result, the filling powder 156 can be used to stably fill the area around the sensor element 10, and the gap between the main body fitting 138 and the sensor element 10 can be filled (sealed) more reliably.

[0035] In addition, such as Figure 4 As shown, in this example, the protrusion 106p reaches the end 106G of the flat surface 106f. Here, in Figure 4 In the example, the flat surface 106f extends to the outer peripheral surface of the sleeve 106 (except for the chamfer of the corner of the sleeve 106), and the outer peripheral surface corresponds to the end 106G. On the other hand, for example, Figure 7 As shown in the modified example of sleeve 116, the protrusion 116p (end face 116e) of sleeve 116 can also be located radially inward than the end of flat surface 116f (outer peripheral surface of sleeve 116) 116G. However, the protrusion 106p reaches the end 106G of the flat surface 106f, which correspondingly increases the area of ​​the filling powder 156 around the sensor element 10 that can be compressed with higher pressing pressure. As a result, the gap between the body fitting 138 and the sensor element 10 can be filled (sealed) more reliably.

[0036] This invention is not limited to the above-described embodiments, but naturally encompasses various modifications and equivalents included within the spirit and scope of this invention. For example, the shape of the protrusion is not limited to the above-described embodiments. The boundary portion can be located anywhere between the top and base of the protrusion. The protrusion may be formed in at least one of the retainer and the sleeve, but is more preferably formed in both the retainer and the sleeve. In addition to oxygen sensors, other types of gas sensors include full-range air-fuel ratio sensors and NOx sensors. Explanation of reference numerals in the attached figures

[0037] 10 Sensor Components 10a Testing Department 10e corner Main surfaces of 10m1 and 10m2 sensor elements 106 and 116 sleeves 106h Second Component Hole 106f and 151f flat surfaces 106p, 151p protrusions 106b, 151b base 106t, 151t top The ends of the flat surfaces of 106G and 116G 138 main body accessories 151 retainer 151h First Component Hole 156 Filler Powder 200 gas sensor O-axis D is perpendicular to the main surface of the sensor element. BR boundary section.

Claims

1. A gas sensor, characterized in that, have: A plate-shaped sensor element extends along the axial direction and has a detection section for detecting the gas to be detected formed at the front end. A cylindrical main body component surrounds and holds the sensor element radially around it; A cylindrical retainer is held in the inner hole of the main body fitting and has a rectangular first element hole for the sensor element to be inserted. A cylindrical sleeve is held in the inner hole of the main body fitting at a position closer to the rear end than the retainer, and has a rectangular second element hole for the sensor element to be inserted. as well as Powder is filled into the inner hole of the main body component, positioned between the retainer and the sleeve, to fill the gap between the main body component and the sensor element. The retainer has a flat surface that contacts the filling powder and a protrusion that protrudes from the flat surface toward the filling powder and surrounds the first element hole; and / or the sleeve has a flat surface that contacts the filling powder and a protrusion that protrudes from the flat surface toward the filling powder and surrounds the second element hole. When viewed from a direction perpendicular to the main surface of the sensor element, the protrusion tapers towards the filling powder. The corner of the sensor element, parallel to the axial direction, is located near the boundary of the protrusion between the top of the protrusion and the base of the protrusion where it connects to the flat surface.

2. The gas sensor according to claim 1, characterized in that, When viewed from a direction perpendicular to the main surface of the sensor element, the width c of the top of the protrusion, the width b of the base where the protrusion connects to the flat surface, and the width a of the sensor element satisfy the relationship c < a < b.

3. The gas sensor according to claim 1 or 2, characterized in that, The top of the protrusion is flat.

4. The gas sensor according to claim 1 or 2, characterized in that, The protrusion reaches the end of the flat surface.

5. The gas sensor according to claim 1 or 2, characterized in that, The gas sensor is an oxygen sensor or a NOx sensor.

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