JPH07311097A - Liquid temperature sensor - Google Patents

Abstract

PURPOSE:To increase the speed and accuracy of temperature detection using a liquid temperature sensor which uses a bottomed metallic pipe as a thermistor housing by enhancing the assemblage of a thermistor to the bottom of the metallic cylinder, and reducing the size and variation of the gap between the bottom of the metallic pipe and the surface of the thermistor. CONSTITUTION:In a liquid temperature sensor in which a thermistor 2 is inserted into the bottom of the end of a bottomed metallic pipe 1 with the open end of the metallic pipe 1 embedded in a body 7 made of a synthetic resin, a small- diameter portion 27, tapered steps 28, and a medium-diameter portion 26 are formed continuously in that order in the metallic pipe 1 from the end of the pipe, with the inner surface of the small-diameter portion 27 having the same form as the surface of the thermistor 2 which makes close contact with the inner surface of the small-diameter portion 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid temperature sensor for measuring the temperature of liquid such as cooling water of a water-cooled engine.

[0002]

2. Description of the Related Art FIG. 2 shows a first conventional example of a liquid temperature sensor, in which a tip (lower end in FIG. 2) of a cylindrical tube 1 (bottomed metal tube) made of metal such as corrosion resistant metal is airtight. The base end (upper end in FIG. 2) is opened so as to have a larger radius. A thermistor 2, which is a semiconductor heat-sensitive element, is inserted so as to contact the tip (bottom) and the inner peripheral surface of the tube 1 as a housing (holder), and two lead wires 3 are drawn out from the thermistor 2. , The lead wires 3 are coated for mutual insulation. The rear ends of the two lead wires 3 are near the opening of the tube 1 and are connected to the two rod-shaped terminals 4 by soldering or the like. The tube 1 is filled with an insulating synthetic resin. There is. The synthetic resin in the tube 1 is integral with the body 7 including the connector 5 and the flange 6, and when the body 7 made of synthetic resin is molded, the base end portion of the tube 1, the thermistor 2, the lead wire 3, the terminal 4, etc. The inserts are embedded and bonded. A plurality of screw holes 10 are formed in the flange 6, and a reinforcing pipe 11 is fitted into the screw holes 10 if desired.

An annular O-ring groove 17 is formed in the central portion of the flange surface 15 of the flange 6 so as to surround the tube 1.
An O-ring 18 is installed in the O-ring groove 17. For example, the tube 1 is inserted through the insertion hole of the cooling water container wall of the water-cooled engine, the flange 6 is brought into contact with the outer surface of the cooling water container wall, and the screw is inserted into the screw hole 10 (reinforcement pipe 11) to the cooling water container wall. The liquid temperature sensor is attached to the cooling water container by screwing. The tip of the tube 1 and the like come into contact with the cooling water, and the temperature of the cooling water is transmitted to the thermistor 2 via the tip of the metal tube 1 having a large heat transfer coefficient, and the output measured by the thermistor 2 is the lead wire 3 and the terminal. 4 is transmitted to the outside. A liquid temperature sensor mounting device similar to the conventional liquid temperature sensor mounting device shown in FIG.
It is described in Japanese Patent No. 635.

In the first conventional example of FIG. 2, the tube 1
In order to improve the thermal responsiveness of the tip of the tube and increase the speed and accuracy of temperature detection, there should be no gap between the metal tube 1 and the thermistor 2, and the tube 1 from the tip to the back end Inner diameter and outer diameter B of the circular section of thermistor 2
(See FIG. 2) and have substantially the same size. For this reason, when the thermistor 2 is inserted into the tube 1 and attached to the bottom portion of the tube 1, it takes a long time to assemble and the assemblability is poor. Moreover, as shown in FIG. 2, since the thermistor 2 has a substantially elliptical vertical cross section, the mounting angle varies when mounting the thermistor 2 on the bottom of the tube 1 (in FIG.
The angle of the mounting part between the lead wire and the lead wire 3),
The size of the gap between the bottom of the tube 1 and the surface of the thermistor 2 is different. Due to the difference in the size of the gap, the thermal response varies, and the temperature detection accuracy decreases.

FIG. 3 shows a second prior art example of a temperature sensor (Japanese Patent Laid-Open No. Hei 3 (1999) -311980).
No. 128426), the surface of the thermistor 2 is covered with glass, and the thermistor 2 is pulled out from the thermistor 2. An insulating pipe 20 made of plastic or ceramic covers the lead wire 3, and the thermistor 2 is in contact with the end of the insulating pipe 20 so as not to form a gap. Thermistor 2 and insulated pipe 20
A metal thin film 21 formed by means of vapor deposition or the like is covered on the outer periphery of. In the temperature sensor of the second conventional example, since the thermistor 2 is closely adhered and covered with the metal thin film 21, the thermal responsiveness is good and the thermal responsiveness does not vary. However, for example, like a through hole in the cooling water container wall of a water-cooled engine. The metal thin film 21 cannot be used in a place where water pressure acts on it because of insufficient strength.

[0006]

SUMMARY OF THE INVENTION In a liquid temperature sensor using a bottomed metal tube as a thermistor housing, the present invention aims to improve the assemblability of the thermistor to the bottom of the metal tube, and to improve the bottom of the metal tube. An object of the present invention is to reduce the amount and variation of the gap between the surface of the thermistor and the surface of the thermistor to improve the speed and accuracy of temperature detection.

[0007]

SUMMARY OF THE INVENTION The present invention is a bottomed metal tube.
Insert the thermistor (2) into the bottom of the tip of (1), and
In a liquid temperature sensor in which the open base end of (1) is embedded in a synthetic resin body (7), the metal tube (1) has a small diameter part (27) and a taper step (28) in order from the tip. And medium diameter part (2
6) are formed continuously, and the inner surface of the small diameter part (27) is the thermistor.
It is formed in the same shape as the surface of (2), and the surface of the thermistor (2) is in close contact with the inner surface of the small diameter portion (27). The bottomed metal tube (1) is formed by deep drawing to have pressure resistance, and the axial length of the small diameter portion (27) is 1/2 or more of the longitudinal length of the thermistor (2). Therefore, the inner diameter of the open end of the small diameter portion (27) can be made equal to the maximum cylindrical inner diameter of the small diameter portion (27). The inner shape and size of the entire small diameter portion (27) may be the same as the surface shape and size of 1/2 or more of the length of the thermistor (2) in the vertical direction, and may be a size that can be fitted. The term "pressure resistance" as used herein means that it can withstand being used by being inserted into an insertion hole in a wall of a cooling water container of a water-cooled engine. Also, a bottomed metal tube with pressure resistance
The thermistor (2) is inserted at the bottom of the tip of (1), the thermistor (2) is connected to the terminal (4) through the lead wire (3), and the opened base end of the metal tube (1), the thermistor (2). 2)
In a liquid temperature sensor in which the lead wire (3) and the terminal (4) are connected to a synthetic resin body (7), a small diameter part ( 27), taper step (28), medium diameter section (26), outer step (2
2) and the large-diameter portion (25) are continuously formed, and the O-ring (18) is mounted on the outer periphery of the medium-diameter portion (26) near the outer stepped portion (22),
The inner surface of the small diameter part (27) is formed in the same shape as the surface of the thermistor (2), and the axial length of the small diameter part (27) is 1/2 or more of the vertical length of the thermistor (2). Yes, small diameter section (27)
The inner diameter of the open end of is made equal to the maximum inner diameter of the small diameter part (27),
The surface of the thermistor (2) is in close contact with the inner surface of the small diameter portion (27).

[0008]

[Operation] The thermistor is attached to the bottom of the tip of the bottomed metal tube (1).
(2) is inserted, the liquid temperature is measured by the thermistor (2), and the measurement output is taken out from the terminal (4) through the lead wire (3). A small diameter portion (27), a taper step portion (28) and a medium diameter portion (26) are continuously formed on the metal pipe (1) from the tip, and the inner surface of the small diameter portion (27) is the surface of the thermistor (2). Is formed in the same shape as the thermistor (2) surface has a small diameter part (27)
Since it is in close contact with the inner surface of, it has good thermal response. Metal tube
In (1), the small diameter part (27), taper step (28), and
The middle diameter portion (26), the outer stepped portion (22) and the large diameter portion (25) are continuously formed, and the O-ring (18) is formed on the outer periphery of the middle diameter portion (26) near the outer stepped portion (22). Since the metal pipe (1) is inserted into the insertion hole of the cooling water container wall of the water-cooled engine,
The ring (18) seals between the insertion hole and the metal tube (1).

[0009]

1 shows an embodiment of a liquid temperature sensor of the present invention. In the description of the embodiment shown in FIG. 1, parts having the same configurations as those of the first conventional example shown in FIG. In the embodiment of the present invention, the bottomed tube 1 (bottomed metal tube) is formed by deep drawing a stainless steel plate material, and the tube 1 has a small diameter portion 27, a tapered step portion 28, and a medium diameter portion in order from the tip. 26, outer step 22
(Portion substantially perpendicular to the axis of tube 1) and large diameter portion
25 are continuously formed. When the tube 1 is joined to the body 7, the outer step portion 22 is located at a portion slightly apart from the flange surface 15, and the thermistor 2 is inserted in the small diameter portion 27. The tube 1 becomes a large-diameter portion 25 from the outer step portion 22 toward the base end, the diameter is enlarged at the base end portion, and the base end has a flange shape. The synthetic resin in the tube 1 is integral with the body 7 including the connector 5 and the flange 6, and when the body 7 is molded, half of the large diameter portion 25 of the tube 1, the thermistor 2, the lead wire 3, the insert of the terminal 4, etc. Are embedded and combined.

The thermistor 2 of the embodiment of the present invention has an outer diameter A
It has a shape with rounded corners.
As shown in FIG. 1, there is a cylindrical surface having an outer diameter A at the central portion in the vertical direction, and the front end portion and the rear end portion are substantially bowl-shaped curved surfaces. The axial length of the small diameter portion 27 of the tube 1 is 1/2 or more of the longitudinal length of the thermistor 2 (about 2/3 in FIG. 1),
The inner surface shape / dimension of the entire small diameter portion 27 at the tip of the tube 1 is made the same as the shape / dimension of the surface of the thermistor 2 (limited to the curved surface of the tip portion and the cylindrical surface) (fittable shape / dimension). The inner surface and the outer surface of the thermistor 2 have the same shape.
The dimensions are in close contact. And
The inner diameter of the opening end of the small diameter portion 27 (the boundary portion between the small diameter portion 27 and the taper step portion 28) is made equal to the maximum cylindrical inner diameter A of the small diameter portion 27. A portion of 1/2 or less (about 1/3 in FIG. 1) of the base end side outer surface of the thermistor 2 has a tapered step portion 28 and a middle diameter portion 26 of the tube 1 (both larger than the outer diameter A of the thermistor 2). And is in contact with the synthetic resin. The connecting portion between the medium diameter portion 26 and the small diameter portion 27 is a taper step portion 28, and the connecting portion between the taper step portion 28 and the small diameter portion 27 is a state in which the thermistor 2 is attached to the bottom portion of the tube 1, The thermistor 2 is located at a position that is at least ½ of the total length from the tip of the thermistor 2.

Since a drawn product having a small surface roughness is used for the tube 1, the resistance when the thermistor 2 is inserted into the tube 1 is smaller than that in the conventional example, and the thermistor 2 is used.
Was easily inserted into the bottom (tip) of the tube 1. When the thermistor 2 is attached to the small diameter portion 27 of the tube 1, the large diameter portion 25 of the tube 1 can be easily moved to the tapered step portion 28 through the outer step portion 22 and the intermediate diameter portion 26. Next, the direction of the mounting portion of the lead wire 3 is aligned with the axial direction of the medium diameter portion 26, and the rear end portion of the thermistor 2 is evenly pressed, so that the front end portion of the thermistor 2 passes through the opening end of the small diameter portion 27 and the small diameter portion. 27
Then, the cylindrical surface of the thermistor 2 and the cylindrical maximum inner diameter A (fittable size) of the small diameter portion 27 are fitted into each other, and then the bowl-shaped tip of the thermistor 2 becomes the bowl-shaped tip of the tube 1. The cylindrical surface of the thermistor 2 and the cylindrical maximum inner diameter of the small diameter portion 27 are in close contact with each other. When the cylindrical surface of the outer diameter A of the thermistor 2 is fitted with the cylindrical maximum inner diameter portion of the small diameter portion 27 of the tube 1, the vertical center line of the thermistor 2 coincides with the center line of the small diameter portion 27, 2 is positioned at a predetermined angle with respect to the tube 1. In this way, the mounting angle of the thermistor 2 with respect to the small diameter portion 27 of the tube 1 becomes constant, and variations in thermal response are reduced. Further, the axial length of the small diameter portion 27 of the tube 1 is 1/2 or more of the longitudinal length of the thermistor 2 (about 2/3 in FIG. 1).
Therefore, the heat transfer between the small diameter portion 27 of the tube 1 and the thermistor 2 is performed quickly, and the thermal response is good.

The O-ring 18 is attached from the tip of the tube 1 having pressure resistance and moved toward the base end of the tube 1,
The ring 18 is brought into contact with the outer step 22 of the tube 1 and the liquid temperature sensor is ready for use. When mounting the liquid temperature sensor on the cooling water container, the tube 1 is inserted from the tip into the insertion hole of the container wall, and the flange surface 15 of the liquid temperature sensor is brought into contact with the outer surface of the container wall. O-ring 18 is tube 1
The outer surface of the middle diameter portion 26 and the inner surface of the insertion hole of the container wall are sealed.

[0013]

In the liquid temperature sensor of the present invention, a small diameter portion, a tapered step portion, and a medium diameter portion are continuously formed on the metal tube in order from the tip, and the inner surface of the small diameter portion is formed in the same shape as the surface of the thermistor. The surface of the thermistor is in close contact with the inner surface of the small diameter portion. Thus, the length of the small diameter portion of the metal tube in the axial direction is short, and the inner diameters of the medium diameter portion and the tapered step portion of the metal tube are considerably larger than the outer diameter of the thermistor. Therefore,
When the thermistor with the lead wire is assembled to the small diameter portion of the metal tube, the thermistor can be easily and quickly inserted into the tapered step portion through the middle diameter portion of the metal tube. Since the distance that the thermistor moves to bring it into close contact with the small diameter portion is shorter than the axial distance of the thermistor, the thermistor can be attached to the bottom of the metal tube in a considerably shorter time than in the case of the first conventional example. Therefore, the assemblability of the thermistor can be improved. Also, since the inner surface of the small diameter part is formed in the same shape as the surface of the thermistor, and the surface of the thermistor is in close contact with the inner surface of the small diameter part, the amount of gap between the small diameter part of the metal tube and the thermistor is small, and the contact Since the area is large, the thermal response is good, and variations in thermal response are reduced. As described above, the speed and accuracy of temperature detection are high. Further, when the metal tube formed by the deep drawing method is used, the resistance when inserting the thermistor into the metal tube is smaller than that of the metal tube whose inner surface is cut, and the assemblability of the thermistor is further improved. When a cylindrical portion is formed on both the thermistor and the small diameter portion of the metal pipe, the assembly angle between the thermistor and the metal pipe becomes constant due to this cylindrical portion, and the space between the thermistor and the small diameter portion of the metal pipe is fixed. It is possible to achieve better adhesion, further improve thermal responsiveness, and further reduce variations in thermal responsiveness.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a liquid temperature sensor of the present invention.

FIG. 2 is a sectional view of a liquid temperature sensor of a first conventional example.

FIG. 3 is a sectional view of a liquid temperature sensor of a second conventional example.

[Explanation of symbols]

 1 tube 2 thermistor 3 lead wire 4 terminal 7 body 18 O-ring 22 outer step 25 large diameter 26 medium diameter 27 small diameter 28 taper step

Claims (4)

[Claims] 1. A liquid temperature sensor in which a thermistor is inserted into the bottom of the tip of a bottomed metal tube, and the open base end of the metal tube is embedded in a body made of synthetic resin. The small-diameter portion, the tapered step portion, and the medium-diameter portion are successively formed in this order, the inner surface of the small-diameter portion is formed in the same shape as the surface of the thermistor, and the surface of the thermistor is closely attached to the inner surface of the small-diameter portion. Liquid temperature sensor. 2. A bottomed metal tube having pressure resistance is formed by a deep drawing method, and the axial length of the small diameter portion is ½ or more of the longitudinal length of the thermistor, and the opening of the small diameter portion is formed. The liquid temperature sensor according to claim 1, wherein the inner diameter of the end is made equal to the maximum cylindrical inner diameter of the small diameter portion. 3. The liquid temperature according to claim 1 or 2, wherein the inner surface shape and dimensions of the entire small diameter portion are the same as the surface shape and dimensions which are ½ or more of the longitudinal length of the thermistor, and are of a size that can be fitted. Sensor. 4. A thermistor is inserted into the bottom of the tip of a bottomed metal tube having pressure resistance, the thermistor is connected to a terminal through a lead wire, and an open base end of the metal tube, a thermistor, a lead wire, and a terminal. In a liquid temperature sensor coupled to a synthetic resin body, a metal tube molded by a deep drawing method has a small diameter portion in order from the tip,
A tapered step, a middle diameter portion, an outer diameter step, and a large diameter portion are continuously formed, an O-ring is attached to the outer circumference of the middle diameter portion in the vicinity of the outer height difference portion, and the inner surface of the small diameter portion has the shape of the thermistor surface. Is formed in the same shape as that of the thermistor, and the axial length of the small diameter portion is 1/2 or more of the vertical length of the thermistor, and the inner diameter of the open end of the small diameter portion is made equal to the maximum inner diameter of the small diameter portion. Is closely attached to the inner surface of the small diameter portion.