JP2008224366A - Temperature sensor for automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein a seizure occurs on a contact face between a nipple 106 and a boss 201 exposed to a high temperature after a temperature sensor 100 for an automobile is attached to an exhaust pipe 200, wherein the nipple 106 becomes thereby difficult to be removed from the boss 201, and wherein easiness of removing work may be impaired in the temperature sensor 100 for the automobile. <P>SOLUTION: An iron-aluminum intermetallic compound layer 2a or 2b having 5-100 μm of layer thickness is provided by executing fused aluminum plating treatment in at least one of the nipple 106 and the boss 201 made of steel. A material layer 1 of the nipple 106 is avoided thereby from contacting directly with a material layer 1 of the boss 201, and the seizure between the nipple 106 and the boss 201 is prevented thereby to facilitate the removing work for the temperature sensor 100. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an automotive temperature sensor used in a high temperature environment.

  The automobile temperature sensor is attached to the exhaust pipe in order to detect the temperature of the exhaust gas in the exhaust pipe of the vehicle.

  In order to attach the temperature sensor to the exhaust pipe, the exhaust pipe is provided with a boss for screwing the temperature sensor. This boss is provided with a female screw portion in which a female screw is formed, and an insertion portion in which an insertion hole is formed, which is located closer to the exhaust pipe than the female screw portion and has a diameter smaller than the minimum diameter of the female screw portion. ing. The temperature sensor is provided with a rib that can contact the inner wall of the insertion hole, and a nipple that is disposed on the opposite side of the exhaust pipe from the rib and has a male screw threadedly engaged with the female screw. Yes.

  Then, the male screw of this nipple is screwed into the female screw of the boss and tightened so that the tip of the rib is pressed against the inner wall of the insertion hole of the boss, and the airtightness in the exhaust gas pipe is secured, and the automobile An industrial temperature sensor is attached to the boss.

Such a temperature sensor for automobiles is disclosed in, for example, Japanese Patent Laid-Open No. 7-109933.
JP 7-109933 A

  In the above-mentioned Patent Document 1, the boss is not affected by the high temperature by making a hole having a size that allows the tip of the automotive temperature sensor to pass through the exhaust pipe and providing the boss outside the exhaust pipe. I have to.

  However, seizure is apt to occur at the fastening portion between the nipple and the boss, which fixes the automobile temperature sensor to the exhaust pipe, due to adhesion.

  Therefore, in order to prevent seizure, it may not be sufficient to attach the boss to the outside of the exhaust pipe as in Patent Document 1 described above. This is because the boss directly attached to the exhaust pipe through which high-temperature exhaust gas such as 300 to 700 ° C. flows cannot be avoided due to heat conduction from the exhaust pipe.

  When the automotive temperature sensor is exposed to such a high temperature and seizure occurs between the nipple and the boss, it becomes difficult to remove the nipple and the boss, and the automotive temperature sensor can be easily removed. There is a risk of damage.

  In view of such circumstances, an object of the present invention is to provide an automotive temperature sensor that can be easily removed.

  In order to solve the above-described problems, the present invention is characterized in that the invention according to claim 1 projects into an exhaust pipe through which exhaust gas discharged from an internal combustion engine flows, and detects a temperature of the exhaust gas; A sheath member in which an electrode wire for taking out an electrical signal of the temperature sensing portion is insulated and held inside, and a flange-shaped seal that is fixed to the outer periphery of the sheath member and has a seating portion on the end surface on the temperature sensing portion side A member, and a mounting seat formed of a steel material and attached to the outer periphery of the exhaust pipe, and having an internal thread portion and an abutting portion that abuts against the seating portion. The external thread provided on the outer periphery and the external thread provided on the outer side and the internal thread are screwed together to press the end surface of the sealing member opposite to the seat, thereby the seat The seal is brought into contact with the contact portion. In an automotive temperature sensor comprising a fixing member for fixing a member to the mounting seat, an iron-aluminum intermetallic compound layer is formed by subjecting at least one surface of the mounting seat and the fixing member to a molten aluminum plating process. An automotive temperature sensor provided.

  In other words, in order to avoid direct contact between steel materials (which is a mounting seat and a fixing member) in a high temperature environment that is one of the causes of seizure, either the mounting seat or the fixing member, or its Both surfaces are subjected to hot-dip aluminum plating to provide an iron-aluminum intermetallic compound layer. By this iron-aluminum intermetallic compound layer, when the fixing member is screwed to the mounting seat, direct contact between the bases of both members is avoided, and seizure can be prevented.

  According to a second aspect of the present invention, the average layer thickness of the iron-aluminum intermetallic compound layer is 5 to 100 μm. By setting the average layer thickness of the iron-aluminum intermetallic compound layer to 5 to 100 μm, it is possible to more significantly exhibit the effect of preventing seizure by the intermetallic compound layer.

  Hereinafter, an embodiment according to an automotive temperature sensor 100 embodying the present invention will be described with reference to the drawings. This automobile temperature sensor 100 is applied as a sensor for detecting the temperature of exhaust gas discharged from a vehicle engine, and is attached to an exhaust pipe of an automobile.

  As shown in FIGS. 1 to 3, the automotive temperature sensor 100 includes a temperature sensing unit 10 and a case unit 20. The temperature sensor 100 is fixed to the exhaust pipe 200 with the attachment portion 30.

  The temperature sensing unit 10 described above is a part that senses the exhaust temperature when exposed to exhaust gas, and mainly connects the temperature sensing element 101 such as a thermistor that senses the exhaust temperature, and the temperature sensing element 101 electrically. It consists of a sheath pin core 102 and a temperature sensing part cover 103 that protects the temperature sensing element 101.

  The temperature sensing part cover 103 is a metal bottomed cylindrical member, and is fitted to the outer periphery of the tip of the cylindrical sheath pin 104. The sheath pin 104 accommodates the sheath pin core wire 102 therein and protects the sheath pin core wire 102.

  Further, the temperature sensing unit 10 described above is connected to the case unit 20 via a sheath pin 104. The sheath pin 104 corresponds to a sheath member.

  Next, the case portion 20 accommodates the sheath pin 104, the connector 108 to which the sheath pin core wire 102 is connected, and the like, and includes a protection tube 107 and ribs 105 that accommodate these. Hereinafter, the upper side as viewed in FIG. 1 is defined as the base end side, and the lower side as the distal end side.

  The rib 105 is a dish-like member having a through hole in the center, and a stepped portion 105a is formed on the base end side. A cylindrical metal protection tube 107 is fitted into the stepped portion 105a and joined by welding or brazing. Further, the sheath pin 104 is inserted into the through hole of the rib 105, and the rib 105 is fixed to the sheath pin 104 by welding or brazing. At the tip end side of the rib 105, there is a seating portion 105b having a taper. The rib 105 corresponds to a sealing member.

  The connector 108 is connected to the sheath pin core 102 on the distal end side and connected to the lead wire 109 on the proximal end side. The lead wire 109 has flexibility to be attached to the end of the protection tube 107 and is accommodated in a protective tube 112 that can be bent flexibly.

  The attachment portion 30 includes a nipple 106 corresponding to a fixing member and a boss 201 corresponding to an attachment seat. The boss 201 and the exhaust pipe 200 are provided with a communication hole 202, and the temperature sensing unit 10 and the sheath pin 104 project into the exhaust pipe 200 through the communication hole 202.

  As shown in FIG. 2, the seating portion 105 b has a structure that abuts on a tapered portion 201 b on the inner peripheral tip side of the boss 201. Then, the male screw portion 106 a and the female screw portion 201 a provided on the nipple 106 and the boss 201 are screwed together, whereby the end surface on the distal end side of the nipple 106 presses the end surface on the proximal end side of the rib 105.

  That is, the taper portion 201b is pressed toward the distal end side by the seating portion 105b, so that the case portion 20 is attached to the exhaust pipe 200 while ensuring airtightness against the exhaust gas. Here, the tapered portion 201b corresponds to a contact portion.

  The nipple 106 is a substantially cylindrical member having a hole through which the outer periphery of the protection tube 107 and the protection tube 112 can be inserted, and is provided so as to surround the outer periphery of the protection tube 107. As for the diameter of the hole of the nipple 106, a gap 114 having a predetermined dimension is provided between the outer periphery of the protection tube 107 and the inner periphery of the nipple 106 so that the outer periphery of the protection tube 107 can be smoothly inserted.

  The exhaust temperature sensor 100 described above measures the temperature of the exhaust gas flowing through the exhaust pipe 200 and sends an exhaust temperature signal based on the exhaust temperature to a control device (not shown) via the lead wire 109.

  In the present embodiment, the nipple 106 and the boss 201 of stainless steel (SUS304 or SUS430), which is a steel material, are used.

  Then, an iron-aluminum intermetallic compound layer 2 a shown in FIG. 4, which is an enlarged view of a portion A in FIG. 2, was formed on the surface of the base layer 1 of the nipple 106 by a molten aluminum plating process in which the nipple 106 was immersed in an aluminum bath. . Here, the base layer 1 is an alloy layer mainly composed of iron.

  The above-mentioned molten aluminum plating was applied based on JISH8642, and three or more (99%) types of aluminum ingots were used. In the processing step of the molten aluminum plating process, first, as a pretreatment, the nipple 106 is degreased, pickled, and dried. Then, the nipple 106 is immersed in the dissolved aluminum bath for a predetermined time. By this dipping treatment, first, an iron-aluminum intermetallic compound layer 2a is formed on the surface of the base layer 1 which is the surface layer of the male thread portion 106a of the nipple 106, and an aluminum layer triple layer is formed on the surface. Thereafter, a low-temperature thermal diffusion treatment at around 700 ° C. is performed for about 30 minutes, and all the formed outermost aluminum layers are diffused and removed. Thereby, a substantially uniform iron-aluminum intermetallic compound layer 2a having an average thickness of 50 μm is formed. As post-processing, the nipple 106 in which the iron-aluminum intermetallic compound layer 2a is formed on the base layer 1 on the surface of the nipple 106 is pickled, washed with hot water, finished, and completed through an inspection process. The above series of steps corresponds to the hot dip aluminum plating treatment of the present invention.

  The low-temperature thermal diffusion treatment time can sufficiently form the iron-aluminum intermetallic compound layer 2a by the complete reaction of the aluminum layer inevitably formed by the molten aluminum plating treatment with the base layer 1. Set the time. However, even in the case where the aluminum layer is not completely formed into an intermetallic compound layer in the low-temperature thermal diffusion treatment, the aluminum layer is sufficiently smaller than the volume ratio of the iron-aluminum intermetallic compound layer 2a, and the male screw portion The aluminum layer may remain slightly as long as the axial force (screw tightening torque) at the time of screwing between 106a and the female screw portion 201a is guaranteed.

  Here, with respect to the thickness of the iron-aluminum intermetallic compound layer 2a, if the thickness of the iron-aluminum intermetallic compound layer 2a is less than 5 μm, the seizure prevention effect by the iron-aluminum intermetallic compound layer 2a does not appear. This was confirmed by experiments. For this reason, the layer thickness of the iron-aluminum intermetallic compound layer 2a is preferably 5 μm or more.

  Further, when an iron-aluminum intermetallic compound layer 2a having a layer thickness exceeding 100 μm is to be formed, the diffusion of the aluminum layer by the low-temperature thermal diffusion treatment becomes insufficient, and the attachment portion is formed by the remaining relatively low strength aluminum layer. The axial force at 30 may not be ensured. Therefore, the layer thickness is preferably 100 μm or less.

  Since iron and aluminum are metals that easily form a passive state, as shown in FIG. 4, an oxide film 3 is formed on the surface layer of the iron-aluminum intermetallic compound layer 2a. Incidentally, while the thickness of the iron-aluminum intermetallic compound layer 2a is 50 μm, the oxide film 3 is only a thickness of several nanometers.

  In the above-described embodiment, the low-temperature thermal diffusion treatment time is set to 30 minutes. However, based on the thickness of the iron-aluminum intermetallic compound layer 2a to be formed, the time during which the aluminum layer can sufficiently diffuse (for example, 5 minutes) (~ 2 hours) may be ensured.

  Note that the iron-aluminum intermetallic compound layer 2b may be formed on the surface of the base layer 1 of the female screw portion 201a by subjecting the boss 201 to the boss 201 instead of the nipple 106.

  Moreover, instead of the example of FIG. 4, as shown in FIG. 5 as an enlarged view of a portion A of FIG. 2, both the male screw portion 106a and the female screw portion 201a are subjected to hot dip aluminum plating treatment, An iron-aluminum intermetallic compound layer (2a and 2b) may be provided. That is, the iron-aluminum intermetallic compound layer 2a is formed on the surface of the base layer 1 of the male screw portion 106a, and the iron-aluminum intermetallic compound layer 2b is formed on the surface of the base layer 1 of the female screw portion 201a. You may do it. Thereby, the seizure prevention effect is further improved.

  By the way, in the above-mentioned embodiment, the oxide film 3 may be peeled off by vibration or the like. In that case, the peeling residue of the oxide film 3 is formed between the flank of the male screw portion 106a (the surface connecting the peak and the valley bottom) and the flank of the female screw portion 201a shown in FIGS. Will be accumulated in the gap 113. As a result, when the nipple 106 is removed from the boss 201, clogging is caused by the residue, and it may be difficult to remove the automotive temperature sensor 100.

  Therefore, even when an iron-aluminum intermetallic compound layer (2a or 2b) is formed on one or both of the surface of the base layer 1 of the male screw portion 106a and the surface of the base layer 1 of the female screw portion 201a, If the gap 113 can secure a capacity capable of sufficiently accumulating the debris from the oxide film 3, the temperature sensor 100 for an automobile can be removed satisfactorily.

  Specifically, the gap 113 formed when the male screw portion 106a and the female screw portion 201a that have been subjected to hot-dip aluminum plating are screwed together is formed as a gap that is formed when screwed without being hot-dip aluminum plated. The fitting configuration of the male screw portion 106a and the female screw portion 201a is changed so that a capacity of 113 or more can be secured.

  Here, regarding the tolerance position, as specified in JIS standard B0209-1, there are two types of G and H for the female screw, and a total of 4 for e, f, g, and h for the male screw. There are types. In the case of a female thread, the effective diameter is defined to increase when the tolerance position changes from H to G. On the other hand, in the case of a male thread, the tolerance position is g, f, e in order from h. It is specified that the effective diameter becomes smaller as it becomes. By adopting the male screw and the female screw in which these tolerance positions are appropriately selected, the size of the gap between the flank between the male screw and the female screw and the area where the male screw and the female screw are engaged with each other change.

  Therefore, in this embodiment, a tolerance position based on this JIS is appropriately selected. For example, it has been confirmed by this experiment that a sufficient axial force at the time of screwing is ensured, and the male thread portion 106a at the tolerance position e. And the internal thread part 201a of the tolerance position H is employ | adopted. In this way, the capacity of the gap 113 between the flank is increased as compared with the combination of the male screw portion 106a at the tolerance position g and the female screw portion 201a at the tolerance position H, which is used in the conventional nipple 106 and the boss 201. Can do.

  That is, by changing the tolerance position of the male screw portion 106a from g to e and reducing the effective diameter of the male screw portion 106a, the capacity of the gap 113 is increased as compared with the conventional case.

  As a result, even if the oxide film 3 is peeled off due to vibration or the like, the peeled debris accumulates in the gap 113 having a sufficient capacity. Therefore, when the nipple 106 is removed from the boss 201, it is clogged with the debris. This can effectively prevent the temperature sensor 100 for automobiles from becoming difficult to be removed.

  The female screw portion 201a may be changed from the tolerance position H to G. Then, since the effective diameter of the female screw portion 201a is increased, the capacity of the gap 113 between the flank can be further increased, and the effect of preventing clogging due to peeling off of the oxide film 3 can be further ensured.

  In addition, the iron-aluminum intermetallic compound layer (2a or 2b) formed by hot dip aluminum plating improves the corrosion resistance, wear resistance, and heat resistance of the male screw portion 106a and the female screw portion 201a. It is not always necessary to use stainless steel having the nipple 106 and the boss 201, and a cheaper steel material such as carbon steel can be used instead.

It is a general view of the temperature sensor for motor vehicles. It is the attachment figure to the exhaust pipe of the temperature sensor for motor vehicles. It is sectional drawing of an exhaust pipe and a boss | hub. It is the A section enlarged view in FIG. It is the A section enlarged view in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base layer 2a ... Iron-aluminum intermetallic compound layer 2b ... Iron-aluminum intermetallic compound layer 3 ... Oxide film 100 ... Automotive temperature sensor 101 ... Temperature sensing element 102 ... Seaspin core wire 103 ... Temperature sensing part cover 104 ... Seaspin (Sheath member)
105 ... Rib (sealing member)
105a ... Stepped portion 105b ... Sitting portion 106 ... Nipple (fixing member)
106a ... male screw portion 107 ... protection tube 108 ... connector 109 ... lead wire 112 ... protective tube 113 ... gap 114 ... gap 200 ... exhaust pipe 201 ... boss (mounting seat)
201a ... Female thread part 201b ... Tapered part (contact part)
202 ... Communication hole

Claims (2)

A temperature sensing part that projects into an exhaust pipe through which exhaust gas discharged from the internal combustion engine flows, and detects the temperature of the exhaust gas;
A sheath member formed by insulatively holding an electrode wire for taking out an electrical signal of the temperature sensing portion;
A flange-shaped sealing member fixed to the outer periphery of the sheath member, and having a seating portion on an end surface on the temperature-sensitive portion side;
An attachment seat formed of steel and attached to the outer periphery of the exhaust pipe, and having an internal thread portion and an abutting portion in contact with the seating portion on the inside;
The end surface on the opposite side of the seating portion of the sealing member is formed by a steel material and provided on the outer periphery of the sheath member, and the male screw portion and the female screw portion provided on the outer side are screwed together. An automotive temperature sensor comprising: a fixing member that presses the seating portion against the contact portion to fix the sealing member to the mounting seat.
A temperature sensor for an automobile, wherein an iron-aluminum intermetallic compound layer is provided on at least one surface of the mounting seat and the fixing member by performing a molten aluminum plating process.   The automotive temperature sensor according to claim 1, wherein an average layer thickness of the iron-aluminum intermetallic compound layer is 5 to 100 μm.

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