JPH10300607A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pressure sensor which is difficult to generate measurement errors even if screwed to a pusher, etc. SOLUTION: A support flange 37 on which a diaphragm 5 is fitted is fixed to the leading end of a fitting cylinder 35. A pressure introducing pipe 3 is inserted into this fitting cylinder 35 and is coupled and fixed to the support flange 37. A push rod 7 is inserted into the support flange 37 and the pressure introducing pipe 3 and this leading end is coupled to a push rod 39 and this is brought into contact with the diaphragm 5. A distortion causing body 13 is fixed to a pedestal 15, which is fixed to the pressure introducing pipe 3 on the opposing side of a diaphragm 5 side, while the push rod 7 is brought into contact with the distortion causing body 13 via a solid ball 11. An outer cylinder 25 covering the distortion causing body 13 and pedestal 15 is mounted to the fitting cylinder 35, and an external fitting screw part 35b is provided therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor,
In particular, the present invention relates to an improvement of a push rod type pressure sensor suitable for a pressure sensor mounted on a tip barrel of an extruder in order to detect and control a molding state by detecting a pressure amount of a molten resin.

[0002]

2. Description of the Related Art Conventionally, as a pressure sensor of this type, the present applicant has already filed Japanese Patent Application No. 2-295366 (Japanese Unexamined Patent Publication No. Hei.
No. 69829).

That is, as shown in FIG. 4, the pressure sensor 1 closes a hollow portion 3c of a pressure guiding tube 3 having a small diameter portion 3b following a screw portion 3a at one end side (lower side in the figure). , A push rod 7 for guiding the displacement of the diaphragm 5 is inserted into the hollow portion 3 c, and a first hard ball 9 is interposed between one end of the push rod 7 and the diaphragm 5 to make contact with the push. The other end of the rod 7 is brought into contact with the flexure element 13 via the second hard sphere 11, and the pedestal 15 is screwed and fixed to the outer periphery of the pressure guiding tube 3 on the flexure element 13 side to cover the flexure element 13. At the same time, the holding member 19 is screwed into the outer periphery of the pedestal 15 via the washer 17 to support the flexure element 13 and to be pressed against the second hard sphere 11 to have the support plate 23 supporting the connector receptacle 21 for external connection. Remove tube 25 It had fixed structure on a pedestal 15. Reference numeral 5a in FIG. 4 denotes a support ring for fixing the diaphragm 5 to the distal end of the pressure guiding tube 3, and reference numeral 27 denotes an O-ring for sealing.

The pressure sensor 1 is provided with a diaphragm 5 of a pressure guiding tube 3 in a mounting hole 31 provided in a barrel 29 of an extruder, for example.
Then, the small diameter portion 3b of the pressure guiding tube 3 is brought into contact with the step portion 31a in the mounting hole 31 and the screw portion 3a is tightened, and the pressure guiding tube 3 and the barrel 29 are pressed and sealed. Of the first hard ball 9, the push rod 7 and the second hard ball 1 via the displacement of the diaphragm 5.
When transmitted from 1 to the flexure element 13, an electric signal corresponding to the pressure is output from the flexure element 13 to the outside via the connector receptacle 21. In addition, in such a pressure sensor 1, pressure is applied between the diaphragm 5 and the strain generating element 13 by line or point contact, so that the pressure conversion loss from the diaphragm 5 to the push rod 7 is reduced, and the diaphragm 5 is hardly worn. In addition, the push rod 7 is hardly affected by the hysteresis of the diaphragm 5.

[0005]

However, in the above-described pressure sensor 1, the pressure guiding tube 3 and the screw portion 3a are integrally formed, and the push rod 7 is surrounded by the pressure guiding tube 3, the diaphragm 5, and the strain body 13. When the screw portion 3a of the pressure guiding tube 3 is strongly tightened in order to reliably pressurize the seal between the barrel 29 and the pressure guiding tube 3, the screw portion 3a is compressed and receives pressure compression. 3 becomes short, and the strain body 13 easily presses the push rod 7.

As a result, a state appears as if a measurement pressure was applied to the strain body 13, and a zero as a measurement reference fluctuates before and after the pressure sensor 1 is mounted, and a measurement error easily occurs. Moreover, even if the zero point is adjusted after the pressure sensor 1 is mounted, if the ambient temperature changes or the mounting state of the pressure sensor is adjusted, the compression state received by the threaded portion 3d of the pressure guiding tube 3 changes, causing a zero point fluctuation. Also, the zero adjustment did not eliminate the measurement error.

On the other hand, since the pressure and the temperature are mutually related parameters, it is preferable to arrange the temperature sensor together in an environment in which the pressure sensor 1 is used. Special ingenuity was required.

The present invention has been made to solve such a conventional disadvantage, and an object of the present invention is to provide a pressure sensor in which a measurement error hardly occurs even when the pressure sensor is fixed to an apparatus such as an extruder. Another object of the present invention is to provide a pressure sensor that can also incorporate a temperature sensor while ensuring accurate pressure measurement.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a pressure guiding tube having a hollow portion and a pressure guiding tube which is fixed so as to close the hollow portion of the pressure guiding tube and responds to the pressure of an object to be measured. A diaphragm that is displaced in the axial direction, a push rod that is inserted into the hollow part, and guides the displacement of the diaphragm, and an indirect or direct support that is indirectly or directly supported by the pressure guiding tube, and that generates electricity corresponding to the axial displacement of the push rod. It comprises a flexure element for outputting a signal, and a mounting tube which has an external mounting member on the outer circumference and is fitted on the outer circumference of the pressure guiding tube and partially fixed thereto. In the present invention, it is preferable that the mounting cylinder is fixed to the pressure guiding tube on the diaphragm side.

Further, according to the present invention, the pressure guiding tube and the push rod are formed of the same material, and an auxiliary push rod having a smaller coefficient of thermal expansion is connected to the tip of the push rod. It is good to face the above-mentioned diaphragm. Still further, in the present invention, the push rod and the auxiliary push rod are formed in a cylindrical shape, and a temperature sensing portion of a temperature sensor is inserted into the hollow portions of the push rod and the auxiliary push rod from the strain generating element side to the vicinity of the diaphragm. Is also possible.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Note that the same reference numerals are given to portions common to the conventional example.

FIG. 1 is a longitudinal sectional view showing one embodiment of a pressure sensor 1 according to the present invention. In FIG. 1, a support plate 23 to which a connector receptacle 21 for outputting a measurement signal to the outside is fixed is provided at one end (upper end in the figure) of a cylindrical outer cylinder 25.
The outer circumference of a large-diameter portion 35a of a mounting cylinder 35 described later is fitted and fixed to the other end (the lower side in the figure) of the outer cylinder 25. Reference numeral 27 denotes O for sealing.
It is a ring.

The mounting cylinder 35 is formed into a long and thin cylindrical shape with, for example, austenitic stainless steel (SUS304), and has one end (upper part in the figure) at one end as described above.
5a, which is expanded and fixed in the outer cylinder 25, and a screw portion 35b as an attachment member attached to, for example, a barrel 29 of an extruder is formed on the outer periphery of the other end (the lower side in the figure). The outer periphery of the mounting cylinder 35 between the large diameter portion 35a and the screw portion 35b is a loose nut portion 35c for rotating the mounting cylinder 35 itself, so that the mounting cylinder 35, that is, the pressure sensor itself can be rotated by a jig (not shown). Has become.

At the lower end of the mounting cylinder 35, an austenitic stainless steel (SUS
304), a support flange 37 formed in a ring shape is disposed, and the outer periphery of the lower end of the mounting cylinder 35 and the support flange 3 are formed.
7 and the outer periphery are fixed by welding, for example. Support flange 3
The distal end of 7 has a small diameter and projects annularly, and a known diaphragm 5 made of, for example, stainless steel (SUS630) is fixed to the support flange 37 via the support ring 5a so as to cover the distal end.

A pressure guiding tube 3 formed into a cylindrical shape by rolling from, for example, austenitic stainless steel (SUS304) is inserted into the mounting cylinder 35, and a part of the pressure guiding tube 3, for example, a lower end portion thereof. The support flange 37 is connected and fixed in the mounting cylinder 35 by, for example, welding.
The pressure guiding tube 3 protrudes from the large diameter portion 35a of the mounting cylinder 35, and a threaded portion 3d is formed on the outer periphery of the protruding portion.

In the hollow portion 3c formed by the pressure guiding tube 3, for example, austenitic stainless steel (SUS30)
4), a push rod 7 formed in an elongated rod shape is inserted and extends to the hollow portion 37a of the support flange 37. In the hollow portion 37a, the short auxiliary push rod 3 is shorted.
9 is fixedly connected. This auxiliary push rod 39
Is made of, for example, martensitic stainless steel (SUS403) having a smaller coefficient of thermal expansion than that of the push rod 7, is in contact with the inner surface of the diaphragm 5, and receives a pressure-receiving displacement of the diaphragm 5.

The push rod 7 protrudes from a threaded portion 3d formed on the upper side of the pressure guiding tube 3, and a hard ball 11 corresponding to the second hard ball in FIG. If the end face of the push rod 7 is made larger in diameter than the hollow portion 3c of the pressure guiding tube 3, it is possible to prevent the push rod 7 and the auxiliary push rod 39 from excessively pressing the diaphragm 5.

A ring-shaped pedestal 15 is fixed to the outer periphery of the screw portion 3d of the pressure guiding tube 3. As shown in FIG. 2, the pedestal 15 is provided with a plurality of circularly shaped screw cylinders 15a protruding therefrom, and a screw groove 15b is formed inside and outside the screw cylinder 15a. Thread groove 15
b is screwed into the screw portion 3d of the pressure guiding tube 3, and the holder 41 is screwed into the outer screw groove 15b. In FIG. 2, the inner thread groove 15b formed in the screw cylinder 15a is not visible. The upper part of the screw cylinder 15a has a tapered surface (hidden and invisible in FIG. 2) that expands in the direction of the pedestal and has a large diameter. By screwing the holder 41 in the direction of the pedestal 15, the screw cylinder 15a has a small diameter. The screw portion 3d of the pressure guiding tube 3 is tightened. The screw cylinder 15a
The same effect can be obtained even if this is formed in a tapered shape so that the entire outer periphery becomes smaller in diameter toward the open front end side.

The pedestal 15 is in contact with the peripheral edge of the strain body 13, and a disc-shaped restraining member 19 is overlaid on the strain body 13. A plurality of bolts 43 are respectively inserted from the holding member 19 side into the through holes 19a and 13a provided, and screwed into the screw holes 15c of the pedestal 15, so that the strain generating body 13 is attached to the pedestal 15 so as to be held down by the holding member 19. Fixed and strain body 13
Are fixed to the pressure guiding tube 3 via the pedestal 15.

The strain body 13 is a load cell having a known structure, and a plate-shaped deformation portion 13c is provided inside the ring portion 13b.
The protruding portions 13d and 13e (hidden and invisible in FIG. 2) protrude in the axial direction from the central portions on both sides of the deformed portion 13c, and the inside of the protruding portions 13d and 13e is formed as a conical concave portion having an open end. , The deformation portion 13c has an electrode 13f. The flexure element 13 incorporates, for example, a four-sided adhesive strain gauge type Wheatstone bridge circuit (not shown) containing a temperature compensation strain gauge, and is capable of deforming the deformation portion 13c by pressing the protrusion 13e. A corresponding electric signal can be output from the electrode 13f.

The protruding portion 13d of the strain body 13 is
9, when the deforming portion 13c is not deformed.
It has a protruding length such that a slight gap of about 1 mm is formed, and the protruding portion 13e on the opposite side comes into contact with the above-mentioned hard sphere 11 and stably receives it. The assembling procedure of such a pressure sensor 1 is, for example, such that the support flange 37 to which the diaphragm 5 is attached is attached to the pressure guiding tube 3 by the hollow portions 37 of each other.
a, 3c are aligned and welded and fixed, and the push rod 7 having the tip connected to the auxiliary push rod 39 is inserted into the pressure guiding tube 3 and the support flange 37.

The screw cylinder 15a of the pedestal 15 to which the holding member 19 and the strain body 13 are fixed by the bolt 43 is screwed into the outer periphery of the upper screw portion 3d of the pressure guiding tube 3, and the hard ball 11 is moved between the push rod 7 and the strain body 13. And the pedestal 15
Of the pedestal 15, that is, the strain body 1, by tightening the holder 41 screwed into the screw cylinder 15 a
3 is fixed to the pressure guiding tube 3. Thereafter, the flexure element 13 and the connector receptacle 21 are electrically connected and the outer cylinder 2 is connected.
5 is fitted and fixed to the large diameter portion 35a of the mounting cylinder 35, and the pressure sensor 1 is completed.

In such a pressure sensor 1, for example, the mounting cylinder 35 is fitted into the mounting hole 31 provided in the barrel 29 of the extruder with the diaphragm 5 side first, and the support flange 37 is fitted to the step 31a in the mounting hole 31. The screw portion 35b is tightened by rotating the loose nut 35c with a jig (not shown), and the space between the support flange 37 and the mounting cylinder 35 and the barrel 29 is pressure-sealed. When stress is applied to the diaphragm 5 by the pressure of the molten resin 33 in the extruder and the diaphragm 5 is displaced in the axial direction, the pressure displacement is transmitted to the strain body 13 via the auxiliary push rod 39, the push rod 7, and the hard ball 11, and The electric signal corresponding to the amount is generated by the flexure element 13.
Is output to the outside through the connector receptacle 21.

In the pressure sensor 1 thus configured, the support flange 37 on which the diaphragm 5 is mounted is attached to the mounting cylinder 35.
, And the cylindrical pressure guiding tube 3 is inserted into the mounting cylinder 35 to be connected and fixed to the support flange 37, and the push rod 7 is inserted into the pressure guiding tube 3 to the inside of the support flange 37 and is assisted. The push rod 39 is connected, the auxiliary push rod 39 is brought into contact with the diaphragm 5,
The pedestal 15 to which the flexure element 13 is fixed is fixed to the pressure guiding tube 3 on the side opposite to the diaphragm 5 side, and the push rod 7 is brought into contact with the flexure element 13 via the hard ball 11. And a pressure guiding tube 3 and a push rod 7 are disposed inside the pressure generating tube 3. Further, the pressure guiding tube 3 has an open end on the side opposite to the diaphragm 5 side, and a pedestal 15 on which the flexure element 13 is fixed is located on the open end side. Is fixed.

Therefore, the barrel 29 of the extruder and the mounting cylinder 3
Even if the screw portion 35b is strongly tightened in order to ensure the pressure seal between the five portions, the influence of the compression hardly appears on the pressure guiding tube 3 supporting the strain generating element 13. As a result, even if the screw portion 35b is strongly tightened, a state in which the measurement pressure is applied to the strain element 13 apparently does not easily occur as in the related art, and the measurement accuracy is improved. In addition, even if the surrounding temperature changes or the mounting state of the pressure sensor is adjusted after the mounting of the pressure sensor, the influence of compression due to these changes is unlikely to appear on the pressure guiding tube 3.

Further, as described above, the outer mounting cylinder 35
3 in which a pressure guiding tube 3 and a push rod 7 are arranged inside
In the layer configuration, the pressure guiding tube 3 covered by the mounting tube 35 is shielded from heat, so that it is less likely to be affected by air cooling, and the heat conduction to the strain body 13 is suppressed as compared with the conventional configuration, and the temperature rise is reduced. And the accuracy of pressure measurement is improved. Furthermore, in the above-described pressure sensor 1, the mounting cylinder 35, the pressure guiding tube 3, the support flange 37, and the push rod 7 are formed of austenitic stainless steel (SUS304) having a lower thermal conductivity than martensitic stainless steel (SUS403). Accordingly, it is possible to reduce the heat conduction to the strain body 13 side, and the pressure measurement accuracy is improved from this point as well.

Even if the pressure guiding tube 3 and the push rod 7 are made of austenitic stainless steel (SUS304) having the same coefficient of thermal expansion, there may be a difference in thermal expansion between them. An auxiliary push rod 39 is connected to the rod 7, and the auxiliary push rod 39 is connected to a martensitic stainless steel (SUS) having a smaller coefficient of thermal expansion than austenitic stainless steel.
403), if the shape and dimensions of the auxiliary push rod 39 are appropriately selected, even if there is a temperature change in the barrel 29, the difference in thermal expansion inside the pressure sensor can be canceled, and the fluctuation of the zero point is suppressed to a small value. It becomes possible.

Next, an application example of the pressure sensor of the present invention, that is, a configuration incorporating a temperature sensor will be described with reference to FIG. The pressure sensor 1 having this configuration is basically the same as the configuration of FIG. 1 except that the austenite stainless steel (SU
The push rod 7 formed in step S304) is
Similarly, the auxiliary push rod 39 connected and fixed to the tip of the push rod 7 is formed into a cylindrical shape having a hollow portion 7a by rolling, and the hollow portion 39a communicating with the hollow portion 7a by, for example, cutting counterboring. have.

The wire portion (sheath portion) 45a of the K-type thermocouple 45 penetrates the holding member 19, the insertion holes 19b and 13g provided in the center of the strain body 13 and the hard sphere 11 (FIG. 2). ), Is inserted into the hollow portions 7a and 39a up to the vicinity of the diaphragm 5, and a lead wire 45b for outputting a temperature signal from the thermocouple 45 and the connector receptacle 21 extends from the support plate 23 to the outside. . In such a pressure sensor 1, it is possible to measure the temperature of the molten resin 33 by the diaphragm 5 as well as the temperature of the molten resin 33 by the thermocouple 45.

Moreover, in the pressure sensor 1 of the present invention, the pressure guiding tube 3 and the push rod 7 are formed of austenitic stainless steel (SUS304) and the hollow portions 3a and 7a are formed by rolling.
Also, the cylindrical processing of the push rod 7 is extremely easy, the processing accuracy and the mechanical strength are high, and even if the wire part (sheath part) 45 a of the thermocouple 45 is inserted into the hollow part 7 a of the push rod 7, mechanical Good temperature measurement is possible while maintaining high strength.

In the embodiment shown in FIG. 3, the temperature sensor is not limited to the K-type thermocouple 45, but may be a J-type or T-type thermocouple, or a known temperature sensor. What is necessary is just to penetrate the member 19, the flexure element 13 and the hard ball 11 through the temperature-sensitive part, and to insert it into the hollow parts 7a and 39a up to the vicinity of the diaphragm 5.

In the pressure sensor of the present invention, the pressure guiding tube 3
The fixing portion between the mounting tube 35 and the mounting tube 35 is not limited to the distal end portion of the mounting tube 35, and the object of the present invention can be achieved by a configuration in which the mounting tube 35 is partially fixed in the middle of the pressure guiding tube 3. Since the pressure guiding tube 3 is fixed to the distal end of the mounting cylinder 35 on the diaphragm 5 side, it is possible to suppress the influence of the compression applied to the mounting cylinder 35 to a negligible level.

In the pressure sensor 1 described above, the mounting cylinder 35, the pressure guiding tube 3, the support flange 37 and the push rod 7 are connected to an austenitic stainless steel (SUS30).
4) and the auxiliary push rod 39 was formed of martensitic stainless steel (SUS403), but the material in the present invention is not limited to these.

[0034]

As described above, according to the present invention, the hollow portion of the pressure guiding tube is closed by the diaphragm, and the push rod for guiding the displacement of the diaphragm is inserted into the hollow portion, and the displacement of the push rod in the axial direction is reduced. A structure in which a strain body that outputs a corresponding electric signal is indirectly or directly supported on the pressure guiding tube, and a mounting cylinder having an external mounting member on the outer periphery is fitted on the outer circumference of the pressure guiding tube and partially fixed thereto. , The inside of the mounting cylinder has a three-layer structure of a pressure guiding tube and a push rod, the pressure guiding tube and the external mounting member are separated, and an open end is formed on the pressure guiding tube on the side opposite to the diaphragm, and the strain is applied to this. The body is fixed. Therefore, even if the mounting cylinder is strongly screwed to the barrel or the like of the extruder, for example, the mounting cylinder is subjected to the tightening compression, but the effect of the compression does not easily appear on the pressure guiding tube, the zero point of the strain generating element is hard to fluctuate, and accurate. Pressure measurement becomes possible. In the configuration in which the mounting cylinder is fixed to the pressure guiding tube on the diaphragm side, particularly, the influence of the compression of the mounting cylinder hardly appears on the pressure guiding tube, and extremely high-precision pressure measurement can be performed. Further, in the configuration in which the pressure guiding tube and the push rod are formed of the same material, an auxiliary push rod having a smaller coefficient of thermal expansion is connected to a tip of the push rod, and the diaphragm is opposed to the diaphragm via the auxiliary push rod. In addition, heat conduction from the diaphragm side to the strain body can be reduced, and the measurement accuracy can be further improved. Further, in the configuration in which the push rod and the auxiliary push rod are formed in a cylindrical shape, and the temperature sensing portion of the temperature sensor is inserted into the hollow portion of the push rod and the auxiliary push rod from the strain body side to the vicinity of the diaphragm, accurate Temperature measurement can be performed while ensuring pressure measurement.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a pressure sensor according to the present invention.

FIG. 2 is an exploded perspective view showing a pedestal, a strain body, and a holding plate in FIG.

FIG. 3 is a longitudinal sectional view showing an application example of the pressure sensor of the present invention.

FIG. 4 is a longitudinal sectional view showing a pressure sensor serving as a reference of the present invention.

[Explanation of symbols]

 Reference Signs List 1 pressure sensor 3 pressure guiding tube 3a, 3d screw portion 3b small diameter portion 3c, 7a, 37a, 39a hollow portion 5 diaphragm 5a support ring 7 push rod 9 first hard ball 11 second hard ball (hard ball) 13 strain generating body 13a 19a Through hole 13b Ring portion 13c Deformation portion 13d, 13e Projection portion 13f Electrode 13g, 19b Insertion hole 15 Pedestal 15a Screw cylinder 15b Screw groove 15c Screw hole 17 Washer 19 Suppression member 21 Connector receptacle 23 Support plate 25 Outer cylinder 27 O-ring 29 Barrel 31 Mounting hole 31a Step portion 33 Molten resin 35 Mounting cylinder 35a Large diameter portion 35b Screw portion (external mounting member) 35c Loose nut 37 Support flange 39 Auxiliary push rod 41 Holder 43 Bolt 45 Temperature sensor (thermocouple) 45a Element wire portion (Sheath part: temperature sensing part) 45 b Lead wire

Claims (4)

[Claims] A pressure guiding tube having a hollow portion, a diaphragm fixed so as to close the hollow portion of the pressure guiding tube and displaced in an axial direction according to a pressure of an object to be measured, and a diaphragm inserted into the hollow portion. A push rod that guides the displacement of the push rod, a strain body that is indirectly or directly supported by the pressure guide tube and outputs an electric signal according to an axial displacement of the push rod, and an external mounting member on an outer periphery. A mounting tube fitted on the outer periphery of the pressure guiding tube and partially fixed to the pressure guiding tube. 2. The pressure sensor according to claim 1, wherein the mounting cylinder is fixed to the pressure guiding tube on the diaphragm side. 3. The pressure guiding tube and the push rod are formed of the same material, and the push rod has an auxiliary push rod having a smaller thermal expansion coefficient than that of the push rod connected to a distal end thereof. The pressure sensor according to claim 1, wherein the pressure sensor is opposed to the diaphragm. 4. The push rod and the auxiliary push rod are formed in a cylindrical shape, and a temperature sensing part of a temperature sensor is inserted into a hollow portion of the push rod and the auxiliary push rod from the strain body side to the vicinity of the diaphragm. The pressure sensor according to claim 3.