JP2013029482A - Temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature sensor that reduce the possibility that a screw becomes loose even in environment in which the temperature sensor is exposed.SOLUTION: A temperature sensor 1 is fixed to an exhaust pipe 100 by being tightened up to a female screw part 112 provided in a peripheral wall 101 of the exhaust pipe 100. The temperature sensor 1 measures the temperature of exhaust gas flowing in the exhaust pipe 100. The temperature sensor 1 includes a male screw part 81 to be tightened up to the female screw part 112 of the exhaust pipe 100. A slit 85 is formed in the screw thread 84 of the male screw part 81. The slit 85 is a grooved region recessed inward in a radial direction of the temperature slit 1 at the tip of the screw thread 84, and formed continuously in a direction in which the screw thread 84 extends. When the male screw part 81 is tightened up to the female screw part 112, the screw thread 84 of the male screw part 81 elastically deforms in a direction such that the slit 85 decreases in opening width.

Description

  The present invention relates to a temperature sensor that detects the temperature of a fluid to be measured such as exhaust gas and intake gas.

  2. Description of the Related Art Conventionally, a temperature sensor that detects the temperature of a measurement target fluid that flows inside an automobile exhaust pipe or the like is known. The temperature sensor includes a male screw portion. For example, when the fluid to be measured is exhaust gas, the temperature sensor is attached to the exhaust pipe by tightening the male thread part of the temperature sensor to the female thread part provided on the boss of the exhaust pipe. When the temperature of the exhaust gas becomes high, the screw may be loosened due to thermal expansion. Further, the screw may be loosened due to the vibration of the vehicle. When the screw is loosened, the airtightness in the exhaust pipe is lowered, and the temperature sensor may come off from the female screw part.

In the temperature sensor mounting structure disclosed in Patent Document 1, the linear thermal expansion coefficient of the flange contacting the inner wall of the insertion hole of the boss is 2.5 × than the linear thermal expansion coefficient of the boss through which the temperature sensor is inserted. 10 ⁻⁶ / ° C. or higher. Therefore, as the temperature of the boss and the flange rises, the force with which the flange is pressed against the inner wall of the insertion hole becomes stronger, and the loosening of the screw is prevented.

JP 2004-239716 A

  By the way, the exhaust system of the vehicle is heated to a high temperature during actual driving, and decreases to a room temperature or lower when stopped. Although the temperature sensor is affected by repeated heating and cooling (cooling cycle), in recent years, the temperature difference between heating and cooling has increased, and the cooling cycle experienced by the temperature sensor has become more severe. Yes. Therefore, it may not be possible to sufficiently prevent the screws from loosening simply by defining the linear thermal expansion coefficient of the material such as the boss. Even if the linear thermal expansion coefficients of the boss and male thread are equal, if the temperature difference between heating and cooling increases, the boss and male thread are separate members, so there is a slight deviation in the thermal expansion and contraction of both. Occurs. There may be a difference in temperature distribution within the same member, and a thermal expansion and contraction may occur in each part within the same member. As a result, there is a possibility of loosening of the screw.

  An object of this invention is to provide the temperature sensor which can reduce possibility that a screw will loosen irrespective of the environment to which a temperature sensor is exposed.

  The temperature sensor according to the present invention is attached to the pipe by being fastened to a female screw part formed inside a mounting boss part provided on a peripheral wall of the pipe through which the fluid to be measured flows. A male screw part fastened to the female screw part, wherein the screw thread of the male screw part is recessed inward in the radial direction at the tip and is continuous in the direction in which the screw thread extends. The thread of the male threaded portion is formed so as to be elastically deformable in a direction in which the opening width of the slit becomes narrower when the male threaded portion is fastened to the female threaded portion.

  In the temperature sensor according to the present invention, when the male screw portion is tightened to the female screw portion of the mounting boss portion, the thread of the male screw portion receives a force from the female screw portion and elastically deforms in the direction in which the slit opening width becomes narrower. Since elastic stress is generated by elastic deformation of the thread of the male screw part, the normal force generated at the contact surface between the male screw part and the female screw part increases. Therefore, the frictional force is increased as compared with the case of using a normal screw thread not provided with a slit, and the possibility that the screw is loosened when the temperature sensor is attached to the female screw portion of the pipe is reduced. Furthermore, even if the temperature of the female screw part becomes higher than the temperature of the male screw part and the female screw part expands and the interval between the valleys of the female screw part increases, the male screw part is deformed in the direction in which the slits are expanded by the elastic force. As a result, the contact state between the male screw portion and the female screw portion is maintained. That is, the rate at which the contact area between the male screw portion and the female screw portion is reduced is lower than that in the case of using a normal screw thread that is not provided with a slit. Therefore, according to the present invention, it is possible to reduce the possibility that the screw loosens regardless of the environment to which the temperature sensor is exposed.

  The temperature sensor includes a flange that contacts an inner peripheral surface of the mounting boss portion and prevents the fluid to be measured from leaking from the inside of the pipe to the outside, and the male screw portion on the outer periphery. A nut may be further provided that is provided in an independent state, and the male screw portion is clamped to the female screw portion so that the flange is sandwiched and fixed between the inner peripheral surface of the mounting boss portion.

  In this case, the operator can easily attach the temperature sensor to the female thread portion by rotating only the nut that is independent of the flange. When the mounting is completed, the flange is pressed toward the tip by the nut, and the gap between the inner peripheral surface of the mounting boss portion and the flange is closed. As a result, the flange contacts the inner peripheral surface of the mounting boss portion, and the fluid to be measured is prevented from leaking from the inside of the tube to the outside, so that airtightness is maintained. On the other hand, a temperature sensor including a flange and a nut as separate bodies is formed by many members. Therefore, a temperature sensor including a flange and a nut is likely to be affected by thermal expansion because a difference in coefficient of thermal expansion may occur for each member. However, according to the present invention, the screw can be prevented from loosening regardless of the environment to which the temperature sensor is exposed, so that the temperature sensor can be firmly attached to the pipe even if it is affected by thermal expansion. By preventing the screws from loosening, the airtightness of the temperature sensor with respect to the tube can be ensured over a long period of time.

2 is a longitudinal sectional view of the temperature sensor 1. FIG. It is a figure which shows the attachment structure of the temperature sensor 1 with respect to the exhaust pipe 100. FIG. FIG. 3 is an enlarged view of a region A in FIG. 2.

  Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings. The drawings to be referred to are used for explaining technical features that can be adopted by the present invention. The configuration and the like of the sensor described in the drawings are not intended to be limited to this, but are merely illustrative examples. The vertical direction of FIGS. 1 to 3 is parallel to the direction of the axis O of the temperature sensor 1. The lower side of FIGS. 1 to 3 will be described as the front end side of the temperature sensor 1, and the upper side of FIGS. 1 to 3 will be described as the rear end side of the temperature sensor 1.

  As shown in FIG. 1, the temperature sensor 1 uses a thermistor element 21 as a temperature sensitive element. In this embodiment, the temperature sensor 1 attached to the exhaust pipe 100 (refer FIG. 2) for discharging | emitting exhaust gas (measuring fluid) discharged | emitted from the engine of a motor vehicle outside is illustrated. The temperature sensor 1 detects the temperature of the exhaust gas flowing in the exhaust pipe 100 by disposing the distal end portion 13 of the metal tube 11 including the thermistor element 21 in the exhaust pipe 100. The temperature sensor 1 mainly includes a metal tube 11, a thermistor element 21, a flange 60, a cylindrical member 31, and a nut 80.

  The metal tube 11 is a bottomed cylindrical tube made of metal (for example, a stainless alloy) and extends in the direction of the axis O of the temperature sensor 1. The metal tube 11 is reduced in diameter at the distal end portion 13 and the distal end 10 is closed. The thermistor element 21 is disposed in the distal end portion 13 of the metal tube 11. The thermistor element 21 has a known thermistor sintered body in which a perovskite oxide is formed in a disk shape, and a pair of electrode wires 22 (for example, Pt / Rh alloy wire) having one end embedded in the thermistor sintered body. Consists of configuration. A cement 23 is filled around the thermistor element 21. As a result, the thermistor element 21 is fixed in the distal end portion 13 of the metal tube 11.

  The rear end portion 14 side of the metal tube 11 is open, and the rear end portion 14 is inserted inside a stainless steel flange 60. The flange 60 has a sheath portion 61 and an overhang portion 62. The sheath portion 61 is a cylindrical portion extending in the axis O direction. The sheath 61 is formed with a thin outer diameter on the rear end side, and has a two-stage shape. The projecting portion 62 is a portion projecting in a bowl shape over the entire circumference in the radially outward direction on the distal end side of the sheath portion 61. The overhang portion 62 has a seat surface 63 that is a circumferential surface formed so as to be reduced in diameter toward the distal end side. The seat surface 63 has a tapered shape corresponding to a later-described tapered portion 114 (see FIG. 2).

  The rear end portion 14 of the metal tube 11 is inserted from the distal end side of the overhang portion 62 and is press-fitted inside the sheath portion 61. Further, the sheath portion 61 is laser welded in the circumferential direction, and an overlapping portion between the outer peripheral surface of the rear end portion 14 of the metal tube 11 and the inner peripheral surface of the rear end portion (a portion having a small outer diameter) of the sheath portion 61 is formed. It is joined. Accordingly, the flange 60 is fixed to the rear end portion 14 side of the metal tube 11 with respect to the thermistor element 21 in a state of protruding outward in the radial direction of the metal tube 11. A cylindrical member 31 that is a cylindrical member extending along the axis O direction is disposed on the rear end side of the flange 60. The cylindrical member 31 is fitted on the outer periphery of the distal end portion (a portion having a large outer diameter) of the sheath portion 61. Further, the cylindrical member 31 is laser welded in the circumferential direction, and the overlapping portion of the outer peripheral surface of the distal end portion of the sheath portion 61 and the inner peripheral surface of the distal end portion 32 of the cylindrical member 31 is joined. Thereby, the cylindrical member 31 is fixed to the flange 60.

A sheath member 41 extending in the direction of the axis O is disposed inside the metal tube 11, the flange 60, and the cylindrical member 31. The sheath member 41 has an outer cylinder 42 made of a stainless alloy (for example, SUS310S). A pair of sheath core wires 35 are inserted into the outer cylinder 42. The sheath core wire 35 is made of a stainless alloy (for example, SUS310S) and has a substantially circular cross section. The outer cylinder 42 is filled with insulating powder (not shown) mainly composed of MgO or SiO ₂ . Filling the insulating powder insulates the outer cylinder 42 from each sheath core wire 35 and holds the sheath core wire 35 in the outer cylinder 42.

  The distal end side of the sheath member 41 is disposed in the metal tube 11. The distal ends of the pair of sheath core wires 35 protrude from the distal end of the outer cylinder 42. Within the distal end portion 13 of the metal tube 11, the distal end portion of the sheath core wire 35 is connected to the pair of electrode wires 22 of the thermistor element 21 by laser welding or resistance welding. On the other hand, the rear end side of the sheath member 41 is disposed in the cylindrical member 31. The rear end portions of the pair of sheath core wires 35 protrude from the rear end of the outer cylinder 42. The rear end portion of the sheath core wire 35 is electrically connected to the two lead wires 51. Specifically, each of the two lead wires is formed by coating a metal stranded wire with an insulating coating material. A stranded wire is exposed at the tip of each lead wire 51, and a relay terminal 52 is attached to each of the exposed stranded wire by caulking. The relay terminal 52 is a plate-like member made of, for example, SUS304, and the end 53 on the tip side of the portion crimped to the lead wire 51 protrudes in a plate shape in the extending direction of the lead wire 51. The end portion 36 of the sheath core wire 35 is joined to the end portion 53 of the relay terminal 52 by resistance welding.

  The pair of sheath core wires 35, the lead wires 51, and the relay terminals 52 are insulated from each other by an insulating tube 75. Further, the sheath core wire 35, the lead wire 51, and the relay terminal 52 are also insulated from the cylindrical member 31 by the insulating tube 75. A grommet 71 made of heat-resistant rubber is disposed in the opening of the rear end portion 33 of the cylindrical member 31. The lead wire 51 is inserted through the grommet 71. The rear end portion 33 of the cylindrical member 31 is circularly or polygonally crimped toward the inside in the radial direction, so that the grommet 71 and the cylindrical member 31 are fixed to each other while maintaining airtightness.

  Each lead wire 51 is drawn out of the temperature sensor 1 from the rear end portion 33 of the cylindrical member 31, and is connected to a terminal member (not shown) of a connector for connecting to an external circuit (for example, an engine control unit). . The output of the thermistor element 21 is taken out from the sheath core wire 35 of the sheath member 41 to the external circuit through the lead wire 51.

  A cylindrical nut 80 is provided at the distal end portion 32 of the cylindrical member 31 (in other words, the rear end side of the projecting portion 62 of the flange 60) so as to surround the outer periphery of the cylindrical member 31. The nut 80 has a male screw part 81, a head part 82, and a shaft hole 83. The male screw portion 81 includes a screw thread 84 (see FIGS. 2 and 3) on the outer peripheral surface. Details of the structure of the thread 84 will be described later. The diameter of the male screw portion 81 is slightly larger than the diameter of the protruding portion 62 in the flange 60. The head portion 82 is a hexagonal nut having a size larger than that of the male screw portion 81 and is provided on the rear end side of the male screw portion 81. The shaft hole 83 is a hole formed through the male screw portion 81 and the head portion 82 in the axis O direction. The cylindrical member 31 is inserted into the shaft hole 83.

  In a state where the cylindrical member 31 is inserted into the shaft hole 83, the nut 80 can move in the direction of the axis O along the cylindrical member 31 and can rotate independently of the cylindrical member 31 and the flange 60. When the nut 80 moves to the distal end portion 32 of the cylindrical member 31, the distal end surface of the male screw portion 81 comes into contact with the rear end surface of the projecting portion 62, and movement of the nut 80 toward the distal end side is restricted. A position where the front end surface of the male screw portion 81 contacts the rear end surface of the overhang portion 62 is an appropriate mounting position of the nut 80.

  With reference to FIG. 2, the attachment structure of the temperature sensor 1 is demonstrated. A boss 110 for attaching the temperature sensor 1 is welded to the peripheral wall 101 of the exhaust pipe 100. The boss 110 includes a female screw portion 112 and an insertion hole 113. The female screw portion 112 is formed from the outer end (upper side in FIG. 2) of the boss 110 to the vicinity of the center portion, and is screwed with the male screw portion 81 of the nut 80. The insertion hole 113 is formed on the inner side of the exhaust pipe 100 (lower side in FIG. 2) than the position where the female screw portion 112 is provided. The insertion hole 113 inserts the distal end portion 13 (see FIG. 1) of the metal tube 11 in the temperature sensor 1 from the outside to the inside of the exhaust pipe 100. The insertion hole 113 includes a tapered portion 114 and a small diameter portion 115. The tapered portion 114 is a portion that decreases in diameter as it approaches the inner side of the exhaust pipe 100. Therefore, the inner wall of the tapered portion 114 faces the outside of the exhaust pipe 100 (upward in FIG. 2). The small diameter portion 115 penetrates from the inner side end portion of the tapered portion 114 to the inside of the exhaust pipe 100. The diameter of the small diameter portion 115 (the minimum diameter of the insertion hole 113) is smaller than the minimum inner diameter of the female screw portion 112 and the outer diameter of the overhang portion 62, and larger than the diameter of the metal tube 11. The boss 110 corresponds to the “mounting boss portion” of the present invention.

  When attaching the temperature sensor 1 to the exhaust pipe 100, the operator inserts the metal tube 11 into the insertion hole 113 of the boss 110. Along with this, the flange 60 passes through the female screw portion 112, and the nut 80 moves to the inlet of the female screw portion 112. When the operator rotates the head portion 82 of the nut 80 in the tightening direction, the male screw portion 81 is screwed (tightened) to the female screw portion 112. Since the nut 80 rotates independently of the cylindrical member 31, even if the nut 80 rotates, the lead wire 51 (see FIG. 1) cannot be twisted. Therefore, the operator can easily tighten the nut 80 to the female screw portion 112.

  When the operator continues to rotate the nut 80, the seat surface 63 of the overhanging portion 62 comes into contact with (in close contact with) the inner wall of the tapered portion 114 in the insertion hole 113 while being strongly pressed toward the tip side (the lower side in FIG. 2). ) In other words, when the nut 80 is fastened to the female threaded portion 112 of the boss 110, the protruding portion 62 of the flange 60 is sandwiched and fixed between the inner wall of the tapered portion 114 in the insertion hole 113 and the tip of the nut 80. Since the flange 60 is in contact with (in close contact with) the inner peripheral surface of the boss 110 (more specifically, the seat surface 63 of the overhanging portion 62 is in close contact with the inner wall of the tapered portion 114), the exhaust gas that flows through the exhaust pipe 100 is exhausted. Gas is prevented from leaking out of the exhaust pipe 100 through the insertion hole 113.

  The structure of the screw thread 84 will be described with reference to FIGS. As shown in FIG. 2, a slit 85 is formed in the thread 84 of the male screw portion 81. The slit 85 is a groove-like portion that is recessed radially inward at the tip of the screw thread 84. The slit 85 is continuously formed along the direction in which the thread 84 extends.

  When the nut 80 is fastened to the female threaded portion 112 of the boss 110, the screw thread 84 receives a force from the female threaded portion 112 and elastically deforms in a direction in which the width (opening width) of the slit 85 becomes narrower. As shown in FIG. 3, elastic stress is generated by elastic deformation of the thread 84 provided with the slit 85. As a result, the normal force generated at the contact surface between the screw thread 84 (the male screw portion 81) and the female screw portion 112 increases. Therefore, the frictional force is increased as compared with the case of using a normal screw thread not provided with the slit 85, and the possibility that the screw is loosened when the temperature sensor 1 is attached to the female screw portion 112 is reduced. Further, even if the female screw portion 112 expands larger than the male screw portion 81 and the interval between the valleys of the female screw portion 112 increases, the male screw portion 81 is deformed in the direction in which the slit 85 is expanded by the elastic force. As a result, the contact state between the male screw portion 81 and the female screw portion 112 is maintained. That is, the rate at which the contact area between the male screw portion 81 and the female screw portion 112 decreases is lower than when a normal screw thread that does not include the slit 85 is used. Therefore, even if the temperature sensor 1 is placed in a severe cooling / heating cycle environment where the temperature difference between heating and cooling is large, problems such as falling off due to loosening of the screws and deterioration of airtightness are unlikely to occur.

  In the temperature sensor 1 of the present embodiment, the flange 60 and the nut 80 are separate members, and the nut 80 can freely rotate independently of the cylindrical member 31 and the like. When the nut 80 is fastened to the female thread portion 112, the flange 60 is fixed in a state where it is pressed to the tip side by the nut 80. Therefore, the temperature sensor 1 can be easily attached to the boss 110 and airtightness can be secured. On the other hand, since the temperature sensor 1 having the flange 60 and the nut 80 as separate members is formed by many members, it is more easily affected by thermal expansion. Even if the linear thermal expansion coefficients of the flange 60, the nut 80, and the boss 110 are made equal, these are separate members, so that there is a possibility that the thermal expansion / contraction is displaced and the screw is loosened. The temperature sensor 1 of this embodiment can reduce the possibility that the screw is loosened by forming the slit 85 in the male screw portion 81. Therefore, the temperature sensor 1 of the present embodiment can prevent the occurrence of malfunctions due to loosening of screws (for example, a decrease in airtightness) while maintaining the advantage of using the flange 60 and the nut 80 as separate members.

[Evaluation test]
An evaluation test was conducted to confirm that the screws are less likely to loosen even under severe cooling and cycling conditions. Specifically, two temperature sensors that are not provided with the slit 85 in the male screw portion and three temperature sensors 1 (see FIGS. 1 to 3) that are provided with the slit 85 in the male screw portion 81 are prepared. An evaluation test was conducted in the following steps. The structures of the two types of temperature sensors differ only in whether or not the slits 85 are provided, and the other structures and dimensions are the same.

  (1) Each temperature sensor is mounted on the boss 110 provided at the bottom of the water tank. Record the tightening torque when mounting each temperature sensor. The material of the boss 110 is SUS304. (2) Start heating the bottom of the water tank with a burner. (3) When the temperature of the boss 110 reaches 400 ° C., water injection into the water tank is started. The amount of water injection was such that the temperature sensor body was completely submerged within 30 seconds. (4) After keeping the temperature sensor submerged for 1 minute, the water inside the water tank is drained. (5) The above (3) and (4) are carried out for 100 cycles. (6) Measure the removal torque of each temperature sensor. The results of this evaluation test are shown in Table 1.

  As shown in Table 1, in this evaluation test, all temperature sensors were mounted on the boss 110 with substantially the same tightening torque. However, the removal torque of the temperature sensor without the slit 85 was 0 Nm, whereas the removal torque of the temperature sensor 1 with the slit 85 was 4.9 Nm, 13.0 Nm, and 5.3 Nm. That is, the value of the removal torque is higher in all three temperature sensors 1 including the slit 85 than in the temperature sensor not including the slit 85. As described above, it was confirmed by this evaluation test that the screw 84 is less likely to loosen even in a severe heat cycle environment by providing the slits 85 in the thread 84 of the male screw portion 81.

  The present invention is not limited to the embodiments described in detail above, and various modifications may be made without departing from the scope of the present invention. In the temperature sensor 1 of the above embodiment, the flange 60 and the nut 80 are separate members, and the nut 80 can rotate independently of the cylindrical member 31 and the like. However, the present invention can also be applied to a temperature sensor in which the flange 60 and the nut 80 are not separate members, a temperature sensor in which the cylindrical member 31 rotates together with the nut 80, and the like.

  The flange 60 of the temperature sensor 1 in the above embodiment is pressed against the inner wall of the tapered portion 114 whose diameter decreases as it approaches the inner side of the exhaust pipe 100 in the insertion hole 113 (see FIG. 2). As a result, the gap is closed and airtightness is ensured. However, the portion of the insertion hole 113 that contacts the flange 60 may not be the tapered portion 114. For example, the insertion hole 113 may include a rear end facing surface that is perpendicular to the rear end side (upper side in FIG. 2) of the temperature sensor 1. The flange 60 may close the gap by contacting the surface facing the rear end of the insertion hole 113.

  The shape of the slit 85 may be changed. In the above embodiment, as shown in FIG. 3, the shape of the slit 85 in the cross section perpendicular to the extending direction of the slit 85 is V-shaped. However, the slit 85 may have a U-shaped cross section or a shape having a bottom surface and a side surface. The slit 85 may not be formed over the entire circumference of the screw thread 84. For example, the slit 85 may be formed only in the rear end side portion of the screw thread 84 with respect to the center portion.

DESCRIPTION OF SYMBOLS 1 Temperature sensor 60 Flange 80 Nut 81 Male thread part 84 Screw thread 85 Slit 100 Exhaust pipe 101 Perimeter wall 110 Boss 112 Female thread part 113 Insertion hole

Claims (2)

A temperature sensor that measures the temperature of the fluid to be measured by being fastened to a female screw portion formed inside a mounting boss provided on a peripheral wall of the tube through which the fluid to be measured flows, and being attached to the tube. ,
A male screw part fastened to the female screw part;
The thread of the male screw part includes a slit formed in a groove shape that is recessed radially inward at the tip and continuous along the direction in which the thread extends.
The temperature sensor characterized in that the thread of the male screw part is formed so as to be elastically deformable in a direction in which the opening width of the slit becomes narrow when the male screw part is fastened to the female screw part. A flange that contacts the inner peripheral surface of the mounting boss portion and prevents the fluid to be measured from leaking out of the tube to the outside;
The male screw part is provided on the outer periphery and provided in a state independent of the flange, and the male screw part is fastened to the female screw part so that the flange is sandwiched between the inner peripheral surface of the mounting boss part and fixed. The temperature sensor according to claim 1, further comprising:

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