Crimp contact and power line assembly with a plurality of lead wire cores provided therein, a gas sensor comprising the assembly, and method for manufacturing the gas sensor

Abstract

Arrangement of crimp contact (51) and power line with a plurality of conductor wire cores (16) provided therein, wherein the crimp contact (51) a terminal section for electrical connection to another part; and a holding portion (57) for holding the plurality of conductive wire cores (16) of the power line therein to be electrically connected to the power line, the holding portion (57) having a pair of side portions (77b) for fixing the conductive wire cores (16) by bending its front end sides (77c) to the conductive wire cores (16) of the power line, and a lower portion (57a) connecting one side at the rear end of the pair of side portions (77b), wherein the conductor wire cores (16) of the power line, which are held by the holding section (57), are deformed, wherein an inner surface of the holding portion (57) is in direct contact with the lead wire cores (16), and wherein the holding portion (57) has a Vickers hardness of 350 HV or more, and a metal layer comprising Ag or Au as a main component covers at least a part of an outer surface of the front end sides (77c) of the pair of side portions, the metal layer having a thickness of 0.1 µm or more.

Description

[0001] The present invention relates to a crimp contact, a crimp contact with an electrical line, a gas sensor provided with the crimp contact, and a method for manufacturing the gas sensor with the crimp contact. In particular, the crimp contact has a holding portion that crimps wire cores of a power line.

[0002] A conventional type of crimp terminal is known to have a holding portion extending in the axial direction and holding the lead wire cores of a power line thereon (for example, Patent Document 1). This holding portion includes a pair of side portions for fixing the lead wire cores by bending its front end sides toward the lead wire cores of the power line, and a bottom portion connecting a rear end side of the pair of side portions.

[0003] This crimp terminal with a power line is manufactured as follows. First, a crimp terminal is prepared. The crimp terminal has a U-shaped holding portion including a bottom portion and a pair of side portions rising from both ends of the bottom portion. Then, lead wire cores of a power line are arranged to contact an inner surface of the U-shaped holding portion. Then, the side portions are bent toward the bottom portion side by a pair of metal dies, namely an anvil and a crimping die. At this time, the front end sides of the side portions of the U-shaped holding portion slide along a sliding surface of the crimping die, and the side portions are sharply bent into a bundle of the lead wire cores of the power line.Then, the front end sides of the side portion are in contact with each other, and the lead wire cores are held and squeezed by the lower portion and the side portions.

[0004] In the method for manufacturing the crimp terminal described above, a crimping process is continuously performed on the U-shaped holding portion. Therefore, as the metal dies are repeatedly used in a crimping process, the sliding performance between the outer surfaces of the side portions and the sliding surface of the crimping tool gradually decreases. As the sliding performance decreases, the leading end surfaces of the side portions insufficiently penetrate the lead wire cores, and a crimping height, namely the height of the holding portion, increases. Therefore, the lead wire cores are insecurely fixed in the holding portion. This may result in the electrical conductivity between the power line and the crimp terminal being impaired.In recent years, due to the need for durability of a crimp terminal and the like, there has been a trend to form the crimp terminal from a material with high Vickers hardness, such as INCONEL (a trademark of INCO). Therefore, the sliding performance between the crimp terminal and the crimping tool tends to deteriorate as the crimping tool wears. Furthermore, the holding portion of the crimp terminal tends to stick to the crimping tool. Therefore, as described in Patent Document 1, a lubricant is preliminarily applied to the sliding surface of the crimping tool so that the sliding performance can be maintained and the holding portion can be formed with an appropriate crimping height even though the crimping process is continuously performed. As a result, the electrical conductivity between the power lines and the crimp terminals can be improved.

[0005] Such a crimp contact is installed in a gas sensor, which includes, for example, a sensor element, a metal housing, and a protective cover. The sensor element extends axially and has a sensing section at its front end. The metal housing is a cylindrical member for holding the sensor element therein, such that at least the sensing section is exposed from a front end of the metal housing. The front end of the protective cover is connected to the rear end of the metal housing, and the protective cover houses the power lines that are electrically connected to an external device. The crimp contact electrically connects the sensor element to the power line and is used to output a signal from the sensing section to an external device.The gas sensor is mounted, for example, on an exhaust system of an internal combustion engine exhaust pipe or the like, and is used to measure a gas to be measured (for example, oxygen, nitrogen, etc.) in the exhaust gas.

[0006] Further relevant prior art is disclosed in the following documents: US 2005 / 0 040 039 A1, US 5 245 132 A, US 2001 / 0 054 552 A1 and US 5 129 143 A.

[0007] [Patent Document 1: Japanese Laid-Open Patent Application (Kokai) No. 64-41184]

[0008] However, in Patent Document 1, a lubricant must be applied to a sliding surface of the crimping die during each crimping operation, which complicates the manufacturing process of the crimp terminal. Furthermore, the lubricant tends to adhere to the outer surfaces of both side portions of a holding portion. This is because the lubricant is previously applied to a sliding surface of the crimping die. When a gas sensor having such a crimp terminal is used as an oxygen sensor mounted on, for example, an internal combustion engine exhaust pipe or the like, the temperature of the holding portion of the crimp terminal becomes relatively high. This causes the lubricant adhering to the outer surfaces of the side portions of the holding portion to decompose due to heat, generating a decomposition gas.The decomposition gas thus generated then causes a fluctuation in the source voltage of the gas sensor, resulting in a measurement error. Furthermore, Patent Document 1 states that it is preferable to select a lubricant (e.g., tetrafluoroethylene, carbon, or the like) that does not generate decomposition gas for a crimp terminal provided in an oxygen sensor and the like. However, it is laborious to select the type of lubricant depending on the environment in which the gas sensor is to be used.

[0009] The present invention has been developed in view of the above problems in the prior art, and an advantage of the invention is to provide a crimp contact, a crimp contact with a power line, a gas sensor having the crimp contact, and a method for manufacturing a gas sensor, in which the sliding property between an outer surface of a holding portion and a sliding surface of a crimping tool is ensured without applying a lubricant to the sliding surface of the crimping tool, and in which the crimp contact can be used under high temperature conditions.

[0010] To solve the above-described problem, an arrangement comprising a crimp contact and a power line is provided according to claim 1. Furthermore, a gas sensor comprising this arrangement is provided. The gas sensor has the features of claim 6. Furthermore, a method for producing the gas sensor is provided with the features of claim 7. Further advantageous embodiments are defined in the dependent claims.

[0011] In the crimp terminal having the above-described construction, since a metal layer is provided on the outer surfaces of the leading end sides of the side portions, the outer surfaces of a pair of side portions can contact a sliding surface of a metal mold via the metal layer when the side portions are bent by the metal mold. This metal layer contains Ag or Au as a main component (i.e., more than 50 wt%) and can maintain and improve the sliding performance between the outer surfaces of both side portions of the holding portion and the sliding surface of the metal mold when the side portions of the holding portion are bent by the metal mold. Therefore, the leading end sides of the pair of side portions can sufficiently penetrate into a bundle of the lead wire cores. This ensures electrical conductivity between the power line and the crimp terminal.Specifically, even though the holding portion has a Vickers hardness of 350 HV or more, the sliding performance between the outer surface of both side portions of the holding portion and the sliding surface of the metal mold can be fully maintained. Since the metal layer is provided on each holding portion, gradual deterioration of the sliding performance between the outer surface of the holding portion and the sliding surface of the metal mold can be prevented despite continuous crimping operations.

[0012] The sliding performance between the outer surface of the holding portion and the sliding surface of the metal mold can therefore be continuously maintained without applying a lubricant to the sliding surface of the metal mold. Furthermore, because the metal layer has relatively high heat resistance, it is unlikely to melt when exposed to heat during the crimping process or in a high-temperature environment. The Vickers hardness of the holding portion is preferably 600 HV or less. If the Vickers hardness of the holding portion is greater than 600 HV, the holding portion will be difficult to bend.

[0013] The metal layer can be provided either on the outer surfaces of the front end sides of the side sections or on the entire outer surface of the side sections. Furthermore, the metal layer can be provided not only on the side section but also on an outer surface of the bottom section.

[0014] The metal layer of the crimp contact preferably has a Vickers hardness of 100 HV or less.

[0015] In the crimp terminal having the above-described construction, since the metal layer itself is soft to the extent that it has a Vickers hardness of 100 HV or less, sliding performance can be more effectively ensured between the holding portion and the metal mold. Therefore, when the holding portion is crimped by the metal mold, sliding performance is maintained between the outer surface of the holding portion and the sliding surface of the metal mold. Furthermore, the Vickers hardness of the metal layer can be determined from the material hardness of the metal layer. Examples of materials having a Vickers hardness of 100 HV or less include pure Au, pure Ag, and the like. However, the Vickers hardness of the metal layer is preferably 10 HV or more.

[0016] In the crimp contact according to the invention, the metal layer has a thickness of 0.1 µm or more.

[0017] In the crimping contact with the above-described construction, the metal layer, due to its thickness of 0.1 μm or more, provides secure sliding performance between the metal layer and the sliding surface of the metal mold. Furthermore, the metal layer can protect the metal mold from wear, making it unlikely that the holding portion will stick to the metal mold. Therefore, the service life of the metal mold can be extended while maintaining sufficient sliding performance between the metal layer and the sliding surface of the metal mold. On the other hand, the thickness of the metal layer is preferably 2 μm or less. If the thickness of the metal layer is greater than 2 μm, the metal layer is more likely to separate from the holding portion at the time of bending the side portions toward the bottom portion side due to an anvil and a crimping tool.

[0018] In the crimp contact having the above-described construction, an adhesive coating layer containing Au as the main component (i.e., more than 50 wt%) is formed between the metal layer and the outer surfaces of the front end sides of the side portions to improve the adhesion of the metal layer to the outer surface. This results in the metal layer less easy to peel off.

[0019] In the crimp terminal having the above-described construction, one of the outer surfaces of the front end side of the side portion is in contact with the other outer surface of the front end side of the side portion, so that the holding portion can firmly crimp the lead wire cores.

[0020] According to the invention, the crimp contact and a power line are provided, comprising: a power line having lead wire cores and a cover member exposing the lead wire cores at one end thereof;and a crimp contact having a terminal portion for electrical connection with another part, and a holding portion that holds the lead wire cores of the power line therein for electrical connection with the power line, the holding portion having a pair of side portions for fixing the lead wire cores by bending its front end sides to the lead wire cores of the power line, and a bottom portion connecting a rear end side of the pair of side portions, the holding portion having a Vickers hardness of 350 HV or more, and a metal layer having Ag or Au as a main component covering at least part of an outer surface of the front end sides of the pair of side portions.

[0021] In the crimp terminal having the above-described construction, since the metal layer is provided at least on the outer surfaces of the leading end sides of the side portion, the outer surfaces of the pair of side portions can come into contact with the sliding surface of the metal mold via the metal layer when the side portions are bent by the metal molds. This metal layer contains Ag or Au as a main component (i.e., 50 wt% or more) and can maintain or improve the sliding performance between the outer surfaces of both side portions of the holding portion and the sliding surface of the metal mold when the side portions of the holding portion are bent by the metal molds. Therefore, the leading end sides of a pair of side portions can sufficiently penetrate into a bundle of the lead wire cores.This ensures electrical conductivity between the power line and the crimp contact. Specifically, even though the holding portion has a Vickers hardness of 350 HV or more, the sliding performance between the outer surface of the holding portion and the sliding surface of the metal mold can be fully maintained. Since the metal layer is provided on each holding portion, gradual deterioration of the sliding performance between the outer surface of the holding portion and the sliding surface of the metal mold can be prevented despite continuous crimping operations. Therefore, the sliding performance between the outer surface of the holding portion and the sliding surface of the metal mold can be continuously maintained without applying a lubricant to the sliding surface of the metal mold.In addition, the metal layer is unlikely to melt when exposed to heat during the crimping process or in a high temperature environment because the metal layer has high heat resistance.

[0022] According to the present invention, there is also provided a gas sensor comprising: a sensor element extending in the axial direction and having a sensing portion at its front end; a cylindrical metal casing supporting the sensor element such that at least the sensing portion is exposed from a front end of the metal casing; a protective cover having a front end connected to a rear end side of the metal casing, wherein at least one power line for electrical connection to an external device is housed in the protective cover; the power line having lead wire cores and a cover member exposing the lead wire cores at one end thereof;and a crimp contact that electrically connects the sensor element to the power line and is configured to output a signal from the measuring section to an external device, the crimp contact comprising: a terminal section for electrically connecting to the sensor element, and a holding section in which the lead wire cores of the power line are held so that they are electrically connected to the power line, the holding section having a pair of side sections for fixing the lead wire cores by bending its front end sides to the lead wire cores of the power line, and a bottom section connecting the rear end side of the pair of side sections, the holding section having a Vickers hardness of 350 HV or more, and a metal layer containing Ag or Au as a main component covering at least part of an outer surface of the front end sides of the pair of side sections.

[0023] Since the metal layer on the crimp terminal of a gas sensor with the above-described design has good heat resistance, the metal layer of the crimp terminal does not melt or generate decomposition gas when exposed to a high-temperature environment during use. This means that the metal layer does not cause fluctuations in the source voltage of the gas sensor.

[0024] Furthermore, a method for manufacturing a gas sensor is provided, the gas sensor comprising: a sensor element extending in the axial direction and having a sensing portion at its front end; a cylindrical metal housing supporting the sensor element such that at least the sensing portion is exposed on the front end side of the metal housing; a protective cover having a front end connected to the rear end side of the metal housing, wherein at least one power line for electrical connection to an electrical device is provided in the protective cover; a power line having lead wire cores and a cover member exposing the lead wire cores at its end; and a crimp contact electrically connecting the sensor element to the power line and configured to output a signal from the sensing portion to an external device.wherein the crimp contact comprises: a terminal portion for electrical connection to another part, and a holding portion that holds the conductive wire cores of the power line therein for electrical connection to the power line, wherein the holding portion has a pair of side portions for fixing the conductive wire cores by bending its front end sides to the conductive wire cores of the power line, and a bottom portion that connects a rear end side of the pair of side portions, the method comprising: a plating step comprising forming a metal layer covering at least a portion on a surface of a metal plate that is to form the front end sides of the side portions, the metal layer comprising Ag or Au as a main component; a press-forming step comprising pressing the metal plate to form a U-shaped holding portion,which has the pair of side portions and the bottom portion such that one surface of the metal plate is an outer surface; and a crimping step which includes arranging the lead wire cores in the U-shaped holding portion and bending the side portions by a pair of an anvil and a crimping tool so that the holding portion crimps the lead wire cores, wherein the metal plate has a Vickers hardness of 350 HV or more.

[0025] Since the above-described method performs a plating step before a press-forming step, the metal plating can be applied to a metal plate before press-forming a U-shaped holding portion. Therefore, the metal layer can be easily formed.

[0026] In the plating step, the metal plating is preferably applied only to one side of the metal plate that will serve as an outer surface of the U-shaped holding portion. This is because plating costs can be saved compared to the case where the metal plating is applied to both sides of the metal plate.

[0027] In the crimping step, a bundle of the lead wire cores arranged in the U-shaped holding portion is crimped by the holding portion using the anvil and the crimping die. At this time, the outer surfaces of the leading end sides of a pair of side portions slide smoothly along the sliding surface of the crimping die over the metal layer, and the leading end sides of the pair of side portions can firmly dig into and partially penetrate the bundle of lead wire cores. Furthermore, since the metal layer is present at least on the outer surfaces serving as the leading end sides of the side portions of the U-shaped holding portion, the outer surfaces serving as the leading end sides of the pair of side portions are prevented from adhering to the sliding surfaces of the anvil and the crimping die after the crimping step.Furthermore, the metal plating is ductile, ensuring smooth sliding between the outer surface of the U-shaped holding section and each sliding surface of the anvil and crimping tool. This extends the service life of the metal die, as it is not damaged by successive crimping operations. Therefore, a crimp contact with the correct crimp height can be consistently produced.

[0028] The metal plating can be applied not only to the portion serving as the front end sides of the side portions of the holding portion, but also to the portion forming the entire surfaces of the side portions of the holding portion. Furthermore, the metal plating can be applied not only to the portion serving as the side portions, but also to the portion serving as the bottom portion.

[0029] The method for manufacturing the gas sensor further includes an adhesive layer coating step in which Au impact plating is applied to cover at least a portion on a surface of the metal plate which is to form the front end sides of the side portions, the adhesive layer coating step being performed before the plating step.

[0030] In the above-described method, Au impact plating is applied to at least a portion on one side of a metal plate where the leading end sides of the side portions are to be formed, and the bonding layer coating step is performed before the plating step. Therefore, the adhesion between the metal layer and the metal plate can be improved via the Au bonding layer coating layer, thereby preventing the metal layer from separating from the holding portion.

[0031] Furthermore, a method for manufacturing a gas sensor is provided, the gas sensor comprising: a sensor element extending in the axial direction and having a sensing portion at its front end; a cylindrical metal casing supporting the sensor element such that at least the sensing portion is exposed from a front end of the metal casing; a protective cover having a front end connected to a rear end side of the metal casing, the protective cover accommodating at least one power line for electrical connection to an external device; the power line having lead wire cores and a cover member exposing the lead wire cores at one end thereof;and a crimp contact that electrically connects the sensor element to the power line and is configured to output a signal from the sensing section to an external device. Furthermore, the crimp contact has a terminal section for electrically connecting to another part, and a holding section in which lead wire cores of a power line are held to be electrically connected to the power line. The holding section has a pair of side sections for fixing the lead wire cores by bending its front end sides toward the lead wire cores of the power line, and a bottom section that connects a rear end side of the pair of side sections.The method comprises: a press-forming step of pressing a metal plate to form a U-shaped holding portion including the pair of side portions and the bottom portion, the metal plate having a Vickers hardness of 350 HV or more; a plating step of forming a metal layer covering at least a part of an outer surface of the front end sides of the side portions of the U-shaped holding portion; and a crimping step of arranging the conductive wire cores in the U-shaped holding portion and bending the pair of side portions by an anvil and a crimping tool so that the holding portion crimps the conductive wire cores.

[0032] In the above-described method, since the plating step is performed after the press-forming step, for example, a U-shaped holding portion formed in the press-forming step can be immersed in a plating bath, so that metal plating can be easily formed on the outer surface of the U-shaped holding portion. Furthermore, since the metal plating is performed after the formation of the U-shaped holding portion, excessive metal plating can be avoided, thus saving the cost of metal plating. In the crimping step, the lead wire cores are arranged so as to be in contact with an inner surface of the U-shaped holding portion, and then the thus-formed holding portion is crimped between the anvil and the crimping die.Here, the outer surfaces of the front end sides of the pair of side portions slide smoothly along the sliding surface of the crimping die over the metal layer, and the front end sides of the pair of side portions dig deeply into the conductor wire cores or partially penetrate them. Furthermore, since the metal layer is provided on the outer surface of the U-shaped holding portion, the outer surfaces of the front end sides of the pair of side portions are prevented from adhering to the sliding surfaces of the anvil and the crimping die after the crimping step. Furthermore, the metal plating is ductile, ensuring the sliding performance between the outer surface of the U-shaped holding portion and each sliding surface of the anvil and the crimping die.Therefore, a crimping operation can be performed for a plurality of U-shaped holding portions sequentially, and a crimp contact provided with the holding portion can be continuously formed, which always has a proper crimping height.

[0033] According to the fifth aspect of the invention, the method may further comprise an adhesive layer coating step of applying Au impact plating covering at least a portion on a surface of the metal plate which will become the front end sides of the side portions, the adhesive layer coating step being performed between the press-forming step and the plating step.

[0034] In the method employing the above-described process, Au impact plating is applied to at least a portion on one side of a metal plate where the leading end sides of the side portions are to be formed, and the adhesive layer coating step is performed before the plating step. Therefore, due to the adhesive layer coating layer, the adhesion between the metal layer and the metal plate can be improved, thereby preventing the metal layer from peeling off the holding portion.

[0035] A gas sensor 1 according to an embodiment of the present invention will be explained below with reference to the drawings. However, the present invention should not be construed as being limited thereto. In the figures: Fig. 1 is a sectional view of a gas sensor 1 according to the embodiment of the present invention; Fig. 2 a side view of a crimp contact 51b; Fig. 3 a perspective view of a running section 53; Fig. 4 is a flowchart showing steps in the manufacture of a crimp contact 51b; Fig. 5 is a plan view of a metal plate 80 to which an impact plating treatment is applied; Fig. 6 is a perspective view showing the state in which lead wire cores 16 of a power line 14b for one element are arranged in a U-shaped holding portion 77; Fig. 7 a sectional view of a U-shaped holding section 77; Fig. 8 is a sectional view showing the state in which a U-shaped holding portion 77 is disposed between an anvil 120 and a crimping tool 121; Fig. 9 is a sectional view showing the state in which a U-shaped holding portion 77 is squeezed between an anvil 120 and a crimping tool 121; Fig. 10 is a sectional view of a holding portion 57; Fig. 11 is a diagram showing the results of Experiment 1; Fig. 12 is a sectional view of a holding portion 97 produced after performing eleven consecutive crimping operations; Fig. 13 a diagram showing the results of experiment 2; Fig. 14 a diagram showing the results of experiment 3; Fig. 15 is a flowchart showing a modification of the steps for manufacturing the crimp contact 51b; Fig. 16 is a plan view of a metal plate 80 to which a partial plating treatment has been applied; and Fig. 17 is a plan view of a metal plate 80 to which a partial plating treatment has been applied.

[0036] The following reference symbols are used to identify various design features in the drawings.

[0037] 1: Gas sensor; 2: Metal shell; 3: Protective cover; 6: Sensor element; 14: Power line; 16: Lead wire core; 51: Crimping contact; 57: Holding portion; 57a: Bottom portion; 57b: Side portion; 57c: Front end; 67: Flat holding portion; 77: U-shaped holding portion; 77a: Bottom portion; 77b: Side portion; 77c: Front end; 80: Metal plate; 85: Plating layer; 120: Anvil; 121: Crimping tool.

[0038] Fig. Fig. 1 is a sectional view of a gas sensor 1 according to an embodiment of the present invention. The term "front end side" used here refers to a lower side of the gas sensor in Fig. 1, and the term “rear end side” refers to an upper side of the gas sensor 1 in Fig. 1.

[0039] The gas sensor 1 is designed to be used in a motor vehicle exhaust pipe as an oxygen sensor to detect the oxygen concentration in the exhaust gas flowing through the exhaust pipe.

[0040] First, the gas sensor 1 is described. As in Fig. 1, the gas sensor 1 essentially comprises a substantially cylindrical metal shell 2, a sensor element 6 which detects the concentration of a specific gas (for example, oxygen) in an exhaust gas, a ceramic heater 7 for heating the sensor element 6, a protector 4 which protects a front end side of the sensor element 6, a separator 18 which is made of aluminum oxide and which has four crimp contacts 51 (only three of which are shown in Fig. 1) which are attached to four power lines 14 (of which only three are shown in Fig. 1), and a substantially cylindrical protective cover 3, which surrounds the separating device 18 in order to protect it. The sensor element 6 and the ceramic heater 7 extend in the axial direction of the gas sensor 1. In addition, the Fig. 1 as a “metal casing”.

[0041] The sensor element 6 comprises a solid electrolyte element 6a, an inner electrode 6b made of Pt or a Pt alloy provided on an inner surface of the solid electrolyte element 6a, and an outer electrode 6c provided on an outer surface of the solid electrolyte element 6a.

[0042] The metal shell 2 is configured to accommodate the sensor element 6. A rear end of the metal shell 2 is crimped radially inward, and a sensing portion provided at a front end of the sensor element 6 is exposed from the front end of the metal shell 2, thereby being supported in an insulated manner. Furthermore, the metal shell 2 has a cylindrical boss portion 2b on its rear end side. Furthermore, the front end side of the metal protective cover 3 is fixed to the boss portion 2b.

[0043] On the other hand, the metal shell 2 has a cylindrical boss portion 2a on its front end side, and the metal protector 4 is connected to the boss portion 2a. The protector 4 includes an outer protector 4a disposed on the outside and an inner protector 4b fixed inside the outer protector 4a, with the rear end side of the outer protector 4a being fixed to the outer periphery of the boss portion 2a. Furthermore, gas holes 4c are provided in the protector 4 so that the gas whose oxygen concentration is measured can flow to the measuring section of the sensor element 6 through the gas holes 4c (the gas holes in the inner protector 4b are not shown).

[0044] The sensor element 6 is inserted into the metal shell 2 via a metal gasket 9a, a ceramic holder 10, a metal gasket 9b, a sealing powder material 11 made of talc or the like, a ceramic sleeve 12, and a metal ring 13. Further, the ceramic heater 7 is inserted into the sensor element 6 from the rear end side to the front end side. Moreover, a flange 2c projecting radially outward is provided on an outer surface of the rear end side of the metal shell 2. A male thread 2d for fixing the metal shell 2 to an exhaust pipe (not shown) is provided between the flange 2c and the boss portion 2a. Furthermore, a gasket G is fixedly disposed between the male thread 2d and the flange 2c.

[0045] On the other hand, a separator 18 is inserted into the protective cover 3. A flange 18a projecting radially outward is provided on an outer periphery of the separator 18, and a substantially cylindrical separator holder 17 is interposed between the protective cover 3 and the separator 18 on the front end side opposite the flange 18a. Therefore, when the separator holder 17 supports and accommodates the separator 18, the separator holder 17 is enclosed by the protective cover 3. Further, within the separator 18, four crimp contacts 51 are electrically connected to the front end side of a plurality of lead wire cores 16 accommodated in each power line 14.

[0046] Specifically, each power line 14 includes power lines for an element 14a, 14b and power lines for a heater 14c, 14d (not shown). The lead wire core 16 of the power line for an element 14a is mechanically connected to a crimp contact 51a fitted onto the outer surface of the sensor element 6, and the power line for an element 14a is electrically connected to the outer electrode 6c of the sensor element 6. Furthermore, the lead wire core 16 of the power line for an element 14b is mechanically connected to a crimp contact 51b press-fitted into the inner surface of the sensor element 6, and the power line for an element 14b is electrically connected to the inner electrode 6b of the sensor element 6. The lead wire cores 16 of the power lines for a heater 14c, 14d are each connected to one of two crimp contacts 51c, which are connected to a heat generating resistor of the ceramic heater 7.

[0047] Furthermore, a grommet 19 made of rubber is inserted into the rear end side of the protective cover 3 near the separator 18. Furthermore, four power lines 14 extend to the outside of the gas sensor 1 through the grommet 19. Moreover, a through hole 19a is provided at the center of the grommet 19, and a filter unit 20 is fitted into the through hole 19a. The filter unit 20 consists of a cylindrical metal filter holder 20a and a PTFE filter 20b, and is covered by a peripheral surface and an upper surface of the filter holder 20a (the rear end side of the gas sensor 1). Therefore, atmospheric air on the rear end side of the gas sensor 1 can communicate with the interior of the protective cover 3 through the through hole 19a and the filter 20b of the filter unit 20.

[0048] Next, the crimp contact 51b will be explained. Although the crimp contact 51a, the crimp contact 51b, and the crimp contact 51c each have a different shape, only the crimp contact 51b will be explained. A detailed description regarding the crimp contact 51a and the crimp contact 51c will be omitted because the holding portion of the crimp contact 51b, which is an essential element of the present invention, is formed in the same way as the holding portion of the other crimp contacts. As shown in Fig. 2, the entire crimp contact 51b extends parallel to the axial direction of the gas sensor 1 (compare Fig. 1), and has an element mounting portion 52 that fits into the side at the rear end of the sensor element 6 (compare Fig. 1) so that it is electrically connected to the inner electrode 6b, a running section 53 in which a plurality of lead wire cores 16 of the power line for an element 14b are held, and which is crimped so that it is electrically connected to the power line, a lead section 54 arranged between the element fixing section 52 and the running section 53, and a securing part 55 arranged on the outer surface of the lead section 54 in contact with an inner surface of the separating device 18 (cf. Fig. 1) is designed to elastically hold the crimp contact 51b.

[0049] Next, the running section 53 is described. As can be seen from Fig. As shown in Fig. 3, the running portion 53 has three holding portions 57. The holding portions 57 are arranged along the longitudinal direction of the running portion 53 with a predetermined distance between them. Therefore, the lead wire cores 16 of the power line for one element 14b are arranged in and enclosed by the three holding portions 57, so that they are electrically connected to the running portion 53 of the crimp contact 51b. Furthermore, a plating layer 85 made of Ag is provided on the entire outer surface of the running portion 53. The plating layer 85 constitutes one aspect of the present invention, and its effects will be explained below.

[0050] Next, a method for manufacturing the crimp contact 51b is described. As shown in Fig. 4, first, a plating step (S10) is performed in which Ag plating is applied to a predetermined portion on one side of a metal plate 80 (see Fig. 5) is applied, which is used as the base material of the crimp contact 51b. Then, a press-forming step (S11) is performed, in which the Ag-plated metal plate 80 formed in the plating step is press-formed into a crimp contact 71b having a U-shaped holding portion 77. Then, a crimping step (S12) is performed such that the lead wire cores 16 of the power line for an element 14b are arranged to come into contact with the inner surface of the U-shaped holding portion 77 of the press-formed crimp contact 71b. Then, the holding portion 57 is pressed onto the lead wire cores 16 using two metal molds, namely an anvil 120 and a crimping tool 121 (see Fig. 8) to form the crimp contact 51b with the holding portion 57. The above-described manufacturing steps (S9, S10, S11, S12) for the crimp contact 51b are described in detail below.

[0051] First, as in Fig. 5, the metal plate 80 used as the material for the crimp contact 51b is manufactured. The metal plate 80 is formed as a band-shaped member and is made of INCONEL (a trademark of INCO). Then, press-molding of a flat terminal 61 serving as a crimp contact 71b (explained below) is performed on one side of the metal plate 80. The flat terminal 61 is composed of a flat fixing portion 62, a flat running portion 63, and a flat conducting portion 64. The flat running portion 63 is composed of three pieces of flat holding portions 67. Then, a plurality of such flat terminals 61 are arranged toward the longitudinal direction of the metal plate 80. At this time, the adjacent flat terminals 61 are arranged in opposite directions. Therefore, the flat running portions 63 of the adjacent flat terminals 61 are arranged alternately. This serves to reduce portion residues of the metal plate 80 after the press-molding step.Furthermore, the in . Fig. 5, a “portion serving as a holding portion” within the scope of the present invention.

[0052] Then, an adhesive layer coating step (S9) is performed. A masking process is performed on the other side of the metal plate 80 (the opposite side in Fig. 5), one side of which undergoes press-molding layout of the flat clamp 61. Au impact plating is applied to the opposite side of the metal plate 80. The Au impact plating process is used to improve the adhesion between an Ag plating (which will be formed later) and the INCONEL, which forms a base material of the metal plate 80. The impact plating is performed in a stripe fashion so that the Au plating can be applied first to the flat running portion 63 (three pieces of the flat holding portions 67) in each flat clamp 61 on which the press-molding layout is performed.

[0053] Then, the plating step (S10) is performed. Specifically, Ag plating is applied to a side of the metal plate 80 on which Au impact plating has already been performed. This plating step is performed in a manner similar to the bond layer coating step, in which Ag plating is applied in a stripe shape and formed on the Au impact plating.

[0054] In this way, one side of the metal plate 80 has two strips of the plating layers 85 in plan view, which are provided on the flat running portion 63 of the flat clamp 61. The thickness of the plating layer 85 is set to 0.1 μm or more (1.0 μm in the present embodiment), thereby effectively improving the sliding property between the plating layer 85 provided on the outer surface of the U-shaped holding portion 77 and a sliding surface of a concave portion 121a of the crimping tool 121 (see the Fig. 8 and Fig. 9) as described below. Furthermore, although pure Ag plating is used as the material of the plating layer 85 in the present embodiment, any metal plating that is ductile and heat-resistant, such as pure Au plating, may be used. When pure Au plating is used, the adhesion of Au impact plating is stronger than that of pure Ag plating. Since the plating layer 85 is formed by the metal plating with heat resistance, the plating cannot melt or generate any decomposition gas when the crimp contact 51b is applied to the gas sensor 1 attached to an exhaust pipe of an automobile and the like and exposed to a high-temperature environment. As a result, fluctuation in the source voltage of the gas sensor 1 can be prevented.

[0055] Next, the press-forming step (S11) will be described. In this press-forming step, the metal plate 80, on which the plating step (S10) was performed, is press-formed by a press machine (not shown). Specifically, the flat clamp 61 is press-formed according to the press-forming layout provided on the metal plate 80. The flat clamp 61 is press-formed into a U-shape with the flat running portion 63 so that the plate side on which the plating layer 85 is provided faces outward. In this way, as shown in Fig. 6, the crimp contact 71b is formed, which has a U-shaped running portion 73. Each U-shaped holding portion 77 constituting the U-shaped running portion 73 is formed into a U-shape, as viewed in cross section perpendicular to the axial direction, by a lower portion 77a and a pair of side portions 77b rising from opposite ends of the lower portion 77a, as shown in the Fig. 6 and Fig. 7. Furthermore, both front end sides 77c of the side portions 77b, which are located on the opposite side with respect to the lower portion 77a, are arranged obliquely to each other. Furthermore, the front end sides 77c have a slightly smaller thickness than other portions of the side portions 77b. Furthermore, the plating layer 85 is provided on the outer surface of the U-shaped holding portion 77.

[0056] Next, the crimping step (S12) is described. As in Fig. As shown in Figure 8, a pair of metal dies, namely the anvil 120 and the crimping jig 121, are employed. The anvil 120 has a convex portion 120a protruding upward. On the other hand, the crimping tool 121 has a concave portion 121a opening downward. A sliding surface located at the bottom of the concave portion 121a is provided with a substantially M-shaped configuration that curves from the center toward both sides of the concave portion 121a. Moreover, the concave portion 121a and the convex portion 120a fit each other. In such a pair of metal molds, the crimping tool 121 moves downward toward the anvil 120 to crimp an object (the U-shaped holding portion 77 in the present embodiment) sandwiched between the convex portion 120a and the concave portion 121a.

[0057] First, the U-shaped holding portion 77 is placed on the upper portion of the convex portion 120a. At this time, the opening side of the U-shaped holding portion 77 is positioned to correspond to the concave portion 121a of the crimping tool 121. Then, the lead wire cores 16 of the power line for one element 14b are arranged to be in contact with the inner peripheral surface of the U-shaped holding portion 77 (see the Fig. 7 and Fig. 8). Therefore, the conductive wire cores 16 are enclosed by the lower portion 77a and the side portions 77b.

[0058] Then, the crimping die 121 is moved down toward the anvil 120. As described above, since the front end faces 77c of the U-shaped holding portion 77 are inclined to each other, the sliding surface of the concave portion 121a of the crimping die 121 first contacts the outer surface of the front end faces 77c. Then, the front end faces 77c slide along the sliding surface of the concave portion 121a of the crimping die 121 because the thickness of the front end faces 77c is thinner than that of other portions of the side portions 77b. Since the sliding surface of the concave portion 121a of the crimping die 121 is substantially in the shape of the letter M, which is curved toward the center of both sides of the concave portion 121a, the front end faces 77c are gradually guided to be inclined to each other.

[0059] Since the plating layer 85 is provided on the outer surface of the U-shaped holding portion 77, the sliding property between the sliding surface of the concave portion 121a of the crimping tool 121 and the outer surface of the U-shaped holding portion 77 is ensured. Therefore, the front end sides 77c are strongly bent in an arc shape toward the lower portion 77a side, and the lead wire cores 16 are tightly squeezed by the lower portion 77a and the side portions 77b, as shown in Fig. 9. Furthermore, since the sliding surface of the concave portion 121a of the crimping tool 121 ensures sliding along the outer surface of the U-shaped holding portion 77, the outer surface of the U-shaped holding portion 77 does not adhere to any of the sliding surfaces of the anvil 120 and the crimping tool 121. In this way, the holding portion 57 can be easily detached from any sliding surface, and the crimp contact 51b is unlikely to be deformed. In this way, as shown in Fig. 10, the holding section 57 is completed, which has a plurality of conductive wire cores 16.

[0060] As in Fig. As shown in FIG. 10, the holding portion 57 includes a lower portion 57a and a pair of side portions 57b extending upward from both ends of the lower portion 57a, as viewed in cross section perpendicular to the axial direction. Furthermore, the front end faces 57c of the side portions 57b, which are located opposite to the lower portion 57a, are largely bent toward the lower portion 57a side. Furthermore, one of the outer surfaces of the front end face 57c is in contact with the outer surface of the front end face 57c. Thus, the lead wire cores 16 of the power line for one element 14b are enclosed by the holding portion 57 of the crimp terminal 51b, and are pinched by the lower portion 57a and the side portions 57b.

[0061] The Vickers hardness of the holding section 57 is greater than 350 (HV). The Vickers hardness of the holding section 57 is measured at several locations in its lower section 57a, and the average of the measurements is taken. The Vickers hardness measurement conditions are as follows: load of 300 gf and loading time of 10 seconds.

[0062] As described above, in the present embodiment, the plating layer 85 provided on the outer surface of the U-shaped holding portion 77 contributes to ensuring the sliding performance between the sliding surface of the concave portion 121a of the crimping tool 121 and the outer surface of the U-shaped holding portion 77. For example, when a plurality of U-shaped holding portions 77 are crimped one after another, secure sliding performance is ensured between the outer surface of the U-shaped holding portion 77 and the sliding surface of the concave portion 121a of the crimping tool 121. As a result, a crimp terminal 51b can be manufactured that is free from failure in terms of performance and appearance.

[0063] Then, in order to confirm the effect of the sliding property provided by the plating layer 85, an evaluation test for successive crimping was conducted using the anvil 120 and the crimping tool 121 on the U-shaped holding portion 77. First, with respect to this evaluation test, a method for evaluating a holding portion 57 formed in the crimping step will be described. As shown in Fig. As shown in Figure 10, the lowest, lower portion of the holding portion 57 was set as point P. The distance (height of the holding portion 57) from point P to the uppermost portion of the holding portion 57 was set as CH (crimp height). Furthermore, the thickness of the rising part of the two side portions 57b of the holding portion 57 was designated as W1 and W2, respectively. The outer surface at which the lower portion 57a and the side portions 57b connect was designated as point K. Then, using the thus-set reference points as evaluation points, an evaluation of the holding portion 57 and the crimp contact 51b was performed, taking into account the following characteristics: first, variation of CH, second, width of W1 and W2, third, shape of point K, fourth, appearance of the crimp contact 51b, etc.

[0064] First, Experiment 1 is explained. In Experiment 1, several conventional crimp terminals were manufactured that did not have a plating layer on the outer surface of a U-shaped holding portion to conduct a successive crimping test on U-shaped holding portions. Each CH (mm) of crimped holding portions was measured each time crimping was performed. Furthermore, a change in CH from a standard value (0 mm) of the CH of the holding portion measured during the first crimping was converted into a change Δh. No lubricant was used in this evaluation.

[0065] Next, the result of Experiment 1 is explained. As in Fig. As shown in Figure 11, after performing three consecutive crimping operations, the result was Δh = 0.005 mm; after performing six consecutive crimping operations, the result was Δh = 0.013 mm; after performing nine consecutive crimping operations, the result was Δh = 0.021 mm; and after performing eleven consecutive crimping operations, the result was Δh = 0.025 mm. From these results, it can be seen that the greater the number of crimping operations, the larger the value of Δh. As shown in Fig. 12, when a holding portion 97 is observed which is formed after performing eleven consecutive crimping operations, the value of CH of the holding portion 97 is slightly higher than that of the holding portion 57 according to the method shown in Fig. 10. Furthermore, some gaps were observed between the conductive wire cores 16 enclosed by a bottom portion 97a and both side portions 97b of the holding portion 97. Furthermore, the thickness of W1 and W2 is larger. Furthermore, burrs projecting downward were observed at point K of each holding portion 97.

[0066] Then, the result of Experiment 1 was examined. Since the sliding performance between the sliding surface of the concave portion 121a of the crimping tool 121 and the outer surface of the U-shaped holding portion gradually deteriorates with the increasing number of crimping operations, the front end sides of the side portions of the U-shaped holding portion do not dig into or penetrate the plurality of conductor wire cores 16. Therefore, the height of the crimped holding portion was obviously somewhat too high. Furthermore, as shown in Fig. 12, the front end sides 97c of the side portions 97b insufficiently penetrated into the plurality of conductive wire cores 16 and became loose, so that the conductive wire cores 16 were not tightly fastened. Furthermore, the possible reason for an increase in the thickness of W1 and W2 was that the side portions 97b were pressed by the crimping tool 121 from a direction perpendicular to the thickness of the side portions 97b. This is because the front end portions 97c sufficiently penetrated into the conductive wire cores 16. Furthermore, the possible reason for the occurrence of the burrs that appeared at each point K is that the side portions 97b were pressed from a direction perpendicular to the thickness of the side portions 97b, causing a part of the side portions 97b to extend downward to the gap between the anvil 120 and the crimping tool 121.

[0067] Next, Experiment 2 will be explained. In Experiment 2, similar to Experiment 1, a plurality of crimp terminals 71b according to the embodiment in which an Ag plating layer was applied to their outer surface were manufactured to conduct an experiment regarding the sequential crimping of the U-shaped holding portions 77. The CH (mm) of the crimped holding portion was measured each time a crimping operation was performed. A deviation in CH from a standard value (0 mm) of the CH of the holding portion measured in the first crimping operation was converted into a deviation Δh. No lubricant was used in this evaluation.

[0068] Next, the result of Experiment 2 is explained. As in Fig. 13, after performing three consecutive crimping operations, the result was Δh = 0.001 mm; after six consecutive crimping operations, Δh = 0.002 mm; after eleven consecutive crimping operations, Δh = 0.002 mm; after fifteen consecutive crimping operations, Δh = 0.004 mm; after twenty consecutive crimping operations, Δh = 0.004 mm; and after twenty-five consecutive crimping operations, Δh = 0.005 mm. When considering the holding portion 57 formed after twenty-five consecutive crimping operations, CH of the holding portion 57 was lower than that of the holding portion 97 of Fig. 12. Furthermore, no gap was observed between the lead wire cores 16 enclosed by the lower portion 57a and the side portions 57b (compare Fig. 10). In addition, the thickness of W1 and W2 did not change, and no burr was generated at point K.

[0069] Next, the result of Experiment 2 is examined. Since the sliding property between the sliding surface of the crimping tool 121 and the outer surface of the U-shaped holding portion 77 was ensured by the Ag plating layer 85, despite the increase in the number of crimping operations, the leading end sides 77c of the side portions 77b of the U-shaped holding portion 77 penetrated into the plurality of lead wire cores 17. Therefore, the CH of the holding portion 57 did not change. Furthermore, it was clear that the holding portion 57 formed after performing 25 consecutive crimping operations could tightly fix the lead wire cores 16 because the side portions 57b sufficiently penetrated into the lead wire cores 16. Furthermore, the holding portion 57 did not become loose, and the appearance of the entire crimp contact 51b was normal.Therefore, even though the crimping process was performed sequentially, a holding portion 57 could be formed that held and tightly fixed the lead wire cores 16. As a result, a crimp terminal 51b could be produced without any failure in its appearance.

[0070] Next, Experiment 3 will be explained. In Experiment 3, a plurality of crimp contacts 71b were manufactured, in which a plating layer of Au was applied to their outer surface. Then, similar to Experiments 1 and 2, a successive crimping test was conducted on the U-shaped holding portions 77. The CH (mm) of the crimped holding portion was measured each time a crimping operation was performed. A deviation in CH from a standard value (0 mm) of the CH of the holding portion measured in the first crimping operation was converted into a deviation Δh. No lubricant was used in this evaluation.

[0071] Next, the result of Experiment 3 is explained. As in Fig. As shown in Figure 13, after performing three consecutive crimping operations, the result was Δh = 0.003 mm; after performing six consecutive crimping operations, the result was Δh = 0.002 mm; after performing eleven consecutive crimping operations, the result was Δh = 0.007 mm; after performing fifteen consecutive crimping operations, the result was Δh = 0.004 mm; after performing twenty consecutive crimping operations, the result was Δh = 0.009 mm; and after performing twenty-five consecutive crimping operations, the result was Δh = 0.007 mm.

[0072] Next, the result of Experiment 3 is examined. Although the material of the plating layer 85 was changed from Ag to Au, approximately the same result as Experiment 2 was obtained. Therefore, it can be seen that the sliding performance between the sliding surface of the crimping tool 121 and the outer surface of the U-shaped holding portion 77 can be ensured even with a plating layer 85 made of Au. Furthermore, no failure was observed in the holding portion 57 having the plating layer 85 made of Au, and no failure was observed in the appearance of the crimp contact 51b having the holding portion 57. Although Au plating was used as an example in this experiment, any metal that is ductile and heat-resistant can be used.

[0073] As explained above, the gas sensor 1 according to this embodiment includes the crimp terminal 51b used to output a signal from the sensing portion of the sensor element 6 to an external device. In order to electrically connect to the lead wire cores 16 of the power line for one element 16b connected to an external device, the crimp terminal 51b includes the barrel portion 53 crimped to secure the lead wire cores 16 of the power line for one element 16b. The barrel portion 53 includes three holding portions 57. Furthermore, the holding portion 57 is configured such that the lead wire cores 16 of the power line for one element 16b are arranged in the U-shaped holding portion 77 so as to be crimped between the anvil 120 and the crimping tool 121.Then, in this embodiment, the plating layer 85 is formed on the outer surface of the U-shaped holding portion 77, thereby ensuring the sliding performance between the sliding surface of the crimping tool 121 and the outer surface of the U-shaped holding portion 77. Therefore, during the crimping step of the U-shaped holding portion 77, the front end sides 77c can slide smoothly along the sliding surface of the crimping tool 121 via the plating layer 85. Therefore, the front end sides 77c are deeply bent as an arc toward the lower portion 77a side, so that the conductive wire cores 16 can be firmly fixed by the lower portion 77a and the side portions 77b.

[0074] Furthermore, since the sliding performance between the sliding surface of the crimping die 121 and the outer surface of the U-shaped holding portion 77 is ensured, the outer surface of the U-shaped holding portion 77 does not adhere to the sliding surfaces of the anvil 120 and the crimping die 121. Therefore, the holding portion 57 can be easily removed from each sliding surface, and the crimp terminal 51b is unlikely to be deformed. Moreover, when a plurality of U-shaped holding portions 77 are successively crimped, the holding portion 57 that firmly fixes the lead wire cores 16 therein can be formed, and a crimp terminal 51b that has no defect in its appearance can be manufactured. This is because the sliding performance between the sliding surface of the crimping die 121 and the outer surface of the U-shaped holding portion 77 is ensured.

[0075] Since the plating layer 85 provided on the outer surface of the crimp contact 51b is made of Ag or Au and is heat-resistant, the plating layer 85 does not melt or generate decomposition gas in a high-temperature environment when the gas sensor 1 is mounted on an exhaust pipe of a motor vehicle or the like. As a result, the source voltage of the gas sensor 1 is not adversely affected.

[0076] The gas sensor according to the present invention is not specifically limited to the above-described embodiments, but can be modified in various ways within the scope of the invention. For example, in the plating manufacturing process (S10), Ag plating is performed on one side of the metal plate 80 with a stripe pattern so that the Ag plating can be applied to the flat running portion 63 (three flat holding portions 67). However, as shown in Fig. 16, the Ag plating can also be applied only partially to the flat running portion 63. By using partial plating, the cost of plating can be reduced. Furthermore, as shown in Fig. 17, in the running portion 63, the plating can be applied only to a portion serving as the front end sides of the side portions of the U-shaped holding portion 57. As a result, the plating cost can be reduced while ensuring the sliding performance between the sliding surface of the crimping die 121 and the outer surface of the U-shaped holding portion 77.

[0077] Furthermore, in the plating process (S10), all the die layouts of the flat terminals 61 provided on the metal plate 80 may be arranged in the same direction. Furthermore, a strip of the plating layer 85 may be provided on the plurality of flat running portions 63 arranged on the same side.

[0078] As in Fig. 4, the manufacturing steps for the crimp contact 51b in the present embodiment proceed in the order of the adhesive layer coating step (S9), the plating step (S10), the press-forming step (S11), and the crimping step (S12). However, as in the modification according to Fig.15, the crimp contact 51b can be formed in such a sequence that, for example, a press-forming step (S20) may be performed before an adhesive layer coating step (S19), impact plating is applied only to the U-shaped running portion 73 of the crimp contact 71b thus produced by press-forming, and then a plating step (S21) and a crimping step (S22) are performed in this order. In these manufacturing steps, the metal plate 80 is deformed by press-forming in the press-forming step, and the crimp contact 71b having the U-shaped holding portion 77 is formed. Then, only the U-shaped running portion 73 of the crimp contact 71b is immersed in an Ag plating bath or an Au plating bath, with the plating location adjusted by a liquid level controller.

[0079] The present invention is applicable not only to a gas sensor, such as an oxygen sensor, but also to various other devices.

[0080] Furthermore, it should be apparent to those skilled in the art that various changes may be made in the nature and details of the invention as hereinbefore described and illustrated. However, the scope of protection is determined by the claims.

Claims

[1] Arrangement of crimp contact (51) and power line with a plurality of conductor wire cores (16) provided therein, wherein the crimp contact (51) a terminal section for electrical connection to another part; and a holding portion (57) for holding the plurality of conductive wire cores (16) of the power line therein to be electrically connected to the power line, the holding portion (57) having a pair of side portions (77b) for fixing the conductive wire cores (16) by bending its front end sides (77c) to the conductive wire cores (16) of the power line, and a lower portion (57a) connecting one side at the rear end of the pair of side portions (77b), wherein the conductor wire cores (16) of the power line, which are held by the holding section (57), are deformed, wherein an inner surface of the holding portion (57) is in direct contact with the lead wire cores (16), and wherein the holding portion (57) has a Vickers hardness of 350 HV or more, and a metal layer comprising Ag or Au as a main component covers at least a part of an outer surface of the front end sides (77c) of the pair of side portions, the metal layer having a thickness of 0.1 µm or more. [2] Arrangement according to claim 1, characterized by that the metal layer has a Vickers hardness of 100 HV or less. [3] Arrangement according to one of claims 1 or 2, characterized by that an adhesive coating layer having Au as a main component is provided between the metal layer and the outer surface of the front end sides of the pair of side portions (77b). [4] Arrangement according to one of claims 1 to 3, characterized bythat the metal layer provided on the outer surfaces of the front end sides (77c) of the pair of side portions (77b) is in mechanical contact with each other. [5] An assembly according to any one of claims 1 to 4, wherein the power line comprises the lead wire cores (16) and a cover member exposing the power line cores (16) at one end thereof. [6] Gas sensor (1), in which are provided: a sensor element (6) extending in the axial direction and having a measuring section at its front end side; a cylindrical metal housing supporting the sensor element such that at least the measuring section is exposed from a front end side of the metal housing; a protective cover (3) having a front end connected to the side of a rear end of the metal housing, and an arrangement of crimp contact (51) and power line according to one of claims 1 to 5, wherein the protective cover (3) accommodates at least the power line for electrical connection to an external device; the power line has the conducting wire cores and a cover member exposing the conducting wire cores at one end thereof. [7] A method for manufacturing a gas sensor (1) according to claim 6, wherein the gas sensor (1) comprises: a sensor element (6) extending in the axial direction and having a measuring section at its front end; a cylindrical metal housing supporting the sensor element such that at least the measuring section is exposed from a front end side of the metal housing; a protective cover (3) having a front end connected to a rear end side of the metal housing, the protective cover (3) having therein at least one power line for electrical connection to an external device; wherein the power line has conductive wire cores (16) and a cover member exposing the power line cores (16) at one end thereof; and a crimp contact (51) which electrically connects the sensor element to the power line, and is designed to output a signal from the measuring section to an external device, wherein the crimp contact (51) comprises: a terminal portion for electrical connection to another part; and a holding portion (57) which holds the lead wire cores (16) of the power line therein so that they are electrically connected to the power line, wherein the holding portion (57) has a pair of side portions (77b) for fixing the conductive wire cores (16) by bending its front end sides (77c) to the conductive wire cores (16) of the power line, and a lower portion (57a) connecting a rear end side of the pair of side portions (77b), the method comprising: Forming the metal plating layer covering at least a portion of a surface of a metal plate (80) to become the front end sides (57a) of the side portions (77b), the metal layer comprising Ag or Au as a main component; Press-forming the metal plate (80) to form a U-shaped holding portion (57) having the pair of side portions and the bottom portion, such that one surface of the metal plate (86) is an outer surface; and Arranging the lead wire cores (16) in the U-shaped holding portion (57), and bending the side portions (77b) by a pair of an anvil (120) and a crimping tool (121) so that the holding portion (57) squeezes the lead wire cores, and wherein the metal plate (80) has a Vickers hardness of 350 HV or more. [8] Method for producing a gas sensor (1) according to claim 7, characterized by : Applying an Au adhesion layer coating so as to cover at least a portion on a surface of the metal plate which is to form the front end sides of the side sections, wherein the bond coat coating step is performed before the plating step.

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