JP2520050B2 - Pressure sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pressure sensor, and in particular, it is attached to a tip end head of an extruder for detecting a pressure amount of a molten resin and grasping and controlling a molding state. Suitable for pressure sensor, using a metal diaphragm as a pressure partition, the displacement of the diaphragm due to the pressure from the object to be measured is transmitted to the strain element by a push rod, and the electric signal according to the pressure amount is transmitted from the strain element. The present invention relates to improvement of a push rod type pressure sensor that outputs.

[Prior Art] Conventionally, as a pressure sensor of this type, a configuration shown in FIG. 6 is known.

That is, the connector receptacle 5 for external connection is fixed to one end (upper end in the drawing) of the outer cylinder 1 by the connector pedestal 3, and the cylindrical shape is provided inside the other end (lower end in the drawing) of the outer cylinder 1. The pedestal 7 is fitted and the peripheral portion of the strain-flexing body 9 for outputting an electric signal according to the pressure amount is fixed to the bottom of the cup-shaped restraining member 11 and fixed to the pedestal 7 via the restraining member 11. . Reference numeral 13 in the drawing is an insulating cable for connecting the connector receptacle 5 and the flexure element 9, and reference numeral 15 is an O-ring.

Inside the pedestal 7, the outer periphery of the upper portion of an elongated pressure guiding tube 19 having a hollow portion 17 is screwed in.
An upper push rod 21 and a lower push rod 23 are movably inserted into the upper part of the pressure gauge, and a hard ball 25 is interposed between the upper and lower push rods 21 and 23 so as to come into contact with the upper push rod 21 and the lower push rod 23. A hard ball 27 abuts between the push rod 21 and the flexure element 9 so that the lower push rod
The pressure displacement from 23 is transmitted to the flexure element 9, and the coil spring 31 is interposed between the flange 29 formed on the outer periphery of the upper end portion of the upper push rod 21 and the upper end surface of the pressure guiding tube 19, The upper push rod 21 is urged toward the flexure element 9.

The lower push rod 23 projects from the lower end surface of the pressure guiding tube 19, and the metal diaphragm 33 is fixed to the lower outer circumference of the pressure guiding tube 19 via a support ring 33b so as to contact the lower end surface of the lower push rod 23. . Reference numeral 35 in the figure is a loose nut for attaching the pressure sensor to an extruder (not shown).

In such a pressure sensor, when stress is applied to the diaphragm 33 by the pressure of the molten resin in the extruder, the lower push rod 23 is displaced, and the pressure displacement is applied to the strain element 9 via the hard ball 25, the upper push rod 21, and the hard ball 27. The transmitted electric signal corresponding to the amount of pressure is output from the strain element 9 to the connector receptacle 5.

[Problems to be Solved by the Invention] However, in the above-described pressure sensor, since the diaphragm 33 is in surface contact with the tip surface of the lower push rod 23, it is caused by friction between the diaphragm 33 and the lower push rod 23. In some cases, the conversion loss between pressure and displacement cannot be ignored, and the diaphragm 33 may easily rub.

In addition, since the deformation of the diaphragm 33 is accompanied by hysteresis, the displacement of the lower push rod 23 may be easily influenced by the hysteresis, and it is necessary to devise it from the viewpoint of ensuring accurate pressure measurement.

Furthermore, the pressure sensor with the above-mentioned configuration has a rated pressure of 10
Although it has an allowable overload performance of 0 to 120%, further overload may occur under actual use conditions, so improvement in this point is also desired.

The present invention has been made in order to solve such a conventional drawback, and provides a pressure sensor in which the pressure conversion loss from the diaphragm to the push rod is small and the diaphragm is not easily worn, and is not easily affected by the hysteresis of the diaphragm. To aim.

It is another object of the present invention to provide a pressure sensor that is unlikely to be damaged by an overload that may actually occur and that can accurately measure the pressure when the rated pressure is restored.

[Means for Solving the Problem] In order to solve such a problem, the present invention provides a diaphragm that is displaced in the axial direction according to the pressure of an object to be measured so as to close the hollow portion of a pressure guiding tube having a hollow portion. The push rod that guides the displacement of the diaphragm in its hollow part, and the first hard ball that transmits the displacement to the push rod is interposed between the push rod and the diaphragm, and the axial displacement A strain-generating body that outputs an electric signal according to the above is indirectly or directly supported by the pressure guiding tube, and its displacement is caused between the push rod and the strain-generating body on the side opposite to the first hard ball. And a second hard ball which is transmitted to the contact member, is opposed to the central portion of the strain-generating body with a slight gap, and has a contact portion that is in contact with the displacement element to regulate the displacement. Strain element It has a structure in which the pressure guiding tube is suppressed.

Further, in the present invention, the diaphragm is fixed in the push rod direction with a slight gap between the push rod and the pressure guiding tube, and further, a flange for contacting the pressure guiding tube and restricting displacement in the diaphragm direction is provided to the push rod. Can be provided in the.

[Operation] In the present invention having such means, when the diaphragm is displaced according to the pressure of the object to be measured, the displacement is transmitted to the push rod via the first hard ball, and the push rod causes the second hard ball to move. The strain-generating body is pressed through and an electrical signal corresponding to the displacement is output.

At that time, the first and second hard spheres make point or line contact with the diaphragm, push rod, and flexure element, and the axis of force passes through the center, so displacement from the diaphragm is accurate, low loss, and low friction. It is transmitted to the rod, and the hysteresis of the diaphragm is unlikely to affect it.

Moreover, even if a large load is applied to the strain-generating body, the contact portion of the restraining member abuts the central portion of the strain-generating body to regulate the displacement, so that the strain-generating body is not significantly deformed.

Further, in the configuration in which the diaphragm is fixed with a slight gap between the push rod direction and the pressure guiding tube,
Even if the diaphragm is largely displaced, the pressure guiding tube restricts the displacement and does not largely deform.

Further, in the configuration in which the push rod is provided with the flange for restricting the displacement, the displacement is restricted even if the push rod tries to move largely in the diaphragm direction.

[Examples] Examples 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 vertical sectional view showing an embodiment of the pressure sensor according to the present invention.

In the figure, a connector pedestal 3 to which a connector receptacle 5 for external output is screwed and fixed is fixed to an upper end of an outer cylinder 1, and a cylindrical pedestal 7 is provided inside a lower end of the outer cylinder 1. It is fitted and fixed from the 3 side.

The edge of the pedestal 7 on the connector pedestal 3 side is in contact with the peripheral portion of the flexure element 9 via a corrugated washer 37, and the cup-shaped restraining member 39 covers the flexure element 9 so that the pedestal 7 can be supported. It is fixed by being screwed on the outer periphery of.

Therefore, the bottom portion 39a of the restraining member 39 restrains the peripheral edge portion of the strain-flexing body 9 by the corrugated washer 37 to support the strain-flexing body 9 on the pedestal 7. The flexure element 9 can be configured to be directly supported on the pedestal 7 rather than indirectly.

As shown in FIG. 2, an insulating cable 13 for connecting the connector receptacle 5 and the strain-flexing body 9 is provided on the bottom portion 39a of the restraining member 39.
A plurality of insertion holes 39b are formed so as to avoid the central portion.

The flexure element 9 is a load cell having a known structure. For example, as shown in FIG. 3, a plate-shaped deforming portion 9b is provided in the center of the inside of the ring portion 9a in the axial direction. Projecting portions 9c and 9d (which are hidden and not visible in FIG. 3) are respectively projected from the above, and the insides of these projecting portions 9c and 9d are formed as conical recessed portions 9e and 9f, respectively.

The flexure element 9 incorporates, for example, a four-sided adhesive strain gauge type Wheatstone bridge circuit (not shown) containing a temperature compensating strain gauge, and is capable of deforming the deforming portion 9b by pressing the protruding portion 9d. A corresponding electric signal can be output from the electrode 9g formed on the deforming portion 9b.

As shown in FIG. 2, among the protrusions 9c and 9d of the flexure element 9, the protrusion 9c facing the bottom 39a of the restraining member 39 is the deformable portion 9c.
When b is not deformed, it has a protrusion length such that a slight gap t1 is formed between it and the bottom 39a, for example, a gap of about 0.1 mm, and the protrusion 9d on the opposite side is a hard ball 27 made of a steel ball. A part of the abutment is brought into contact with the inner surface of the conical recess 9f to stably receive it.

In addition, it is possible to handle up to about 150% of the rated pressure with a gap of about 0.1 mm, and in case of overload more than that, it is possible to suppress to overload of 150 to 2000% of the rated pressure by the restraining member 39. Is.

Returning to FIG. 1, the upper outer circumference of an elongated pressure guiding tube 19 having a hollow portion 17 is screwed into the inside of the pedestal 7. This pressure guiding tube 19 is, for example, martensitic stainless steel (SUS403).
A push rod 41 made of stainless steel is movably inserted into the hollow portion 17 from the pedestal 7 side.

Push rod 41 is upper and lower push rod 41
The a and 41b are screwed together to be integrated, and as shown in FIG. 4, the center of the tip surface of the upper push rod 41a is a conical recess 41c that is conically recessed. A part of the hard ball 27 is abutted on the opposite side to receive it stably.

A flange 41d is formed on the outer periphery of the tip end of the upper push rod 41a, and normally, a small gap t2, for example, a gap of about 0.1 mm is provided between the flange 41d and the end face of the pressure guiding tube 19.

Although this flange 41d does not directly participate in the measurement, for example, when the pressure sensor itself receives an impact, the push rod 41d
To prevent it from popping out in the direction of the diaphragm 45 described later.

The tip of the push rod 41, that is, the tip of the lower push rod 41b extends a little before the tip of the pressure guiding tube 19,
As shown in FIG. 5, the center of the end face is a conical recess 41e that is recessed in a conical shape, and a part of a hard ball 43 made of a steel ball located inside the hollow portion 17 of the pressure guiding tube 19 and the conical recess 41e. Abut and receive this stably.

For example, precipitation hardening stainless steel (SUS630), which has good elasticity, mechanical strength and corrosion resistance, is formed on the tip surface of the pressure guiding tube 19.
A diaphragm 45 made of metal is placed.

A projecting portion 45a integrally projects from the diaphragm 45 into the hollow portion 17 of the pressure guiding tube 19, and a central end portion of the projecting portion 45a is conically recessed to form a conical recess 45b. A part of the hard ball 43 is stably abutted on the side of the lower push rod 41b opposite to the conical recess 41e.

The diaphragm 45 is supported by a support ring 45c fitted on the outer periphery of the tip of the pressure guiding tube 19, and is positioned so as to leave a slight gap t3, for example, a gap of about 0.1 mm from the end surface of the pressure guiding tube 19. With a space of about 0.1 mm, the rated pressure is about 150
%, And in the case of more overload,
With the end surface of the pressure guiding tube 19, it is possible to suppress overload of about 150 to 2000% of the rated pressure.

Reference numeral 15 in FIG. 1 is an O-ring, and reference numeral 35 is a loose nut for attaching the pressure sensor to an extruder (not shown).

In such a pressure sensor, when stress is applied to the diaphragm 45 by the molten resin pressure in the extruder and the diaphragm 45 is displaced in the axial direction, the pressure displacement is transmitted to the strain element 9 via the hard ball 43, the push rod 41, and the hard ball 27. An electric signal corresponding to the amount of pressure is output from the flexure element 9 to the connector receptacle 5.

Moreover, the hard ball 43 is in line contact with the conical recess 45b of the diaphragm 45 and the conical recess 41e of the lower push rod 41b, and the hard ball 27 is in contact with the conical recess 41c of the upper push rod 41b and the conical recess 9f of the flexure element 9. Since they are in line contact, the displacement from the diaphragm is transmitted accurately, with low loss and with low friction on each central axis.

In particular, since the diaphragm 45 is connected via the hard ball 41 between the conical recess 45b of the diaphragm 45 and the conical recess 41e of the lower push rod 41b, even if the displacement of the diaphragm 45 causes hysteresis, it is affected by the hysteresis. It will be difficult.

Further, in FIG. 2, the protrusion 9c at the center of the flexure element 9 is formed.
Faces the bottom portion 39a of the restraining member 39 with a slight gap t1. Therefore, by setting this gap t1 within the limit of elastic deformation of the strain-flexing body 9, a large pressure is applied to the diaphragm 45 to cause the strain-flexing body. Even if 9 is largely deformed, the projecting portion 9c functions as a deformation stop wall that comes into contact with the bottom portion 39a and regulates the displacement,
It becomes possible to suppress the deformation of within the limit of elastic deformation,
It is possible to suppress fluctuations in measurement characteristics even after receiving a large pressure.

Further, as shown in FIG. 5, since the diaphragm 45 is fixed so as to face the tip of the pressure guiding tube 19 with a slight gap t3, the gap t3 is slightly exceeded by the displacement of the diaphragm 45 due to the rated pressure. If the distance is set to a large value, the pressure guide tube 19 will regulate the displacement even if the diaphragm is displaced greatly, and will function as a displacement stop wall, and even if the pressure is released and returns to the rated pressure, the output characteristics will not change from before. Can be obtained.

Furthermore, as shown in FIG. 1, since the flange 41d is formed on the outer periphery of the tip of the push rod 41, even if the push rod 41 is largely displaced in the direction of the diaphragm 45 due to vibration or impact, the flange 41d is guided. Since the displacement is regulated by contacting the end surface of the pressure pipe 19, the diaphragm 45 is not damaged or the push rod 41 does not pierce the diaphragm 45 and project.

In the above-described embodiment of the present invention, the hard balls 27, 43 are conical recesses.
Although the structure received by 9e, 9f, 41c, 41e, 45b has been described, the hard balls 2 are not necessarily formed by these conical recesses 9e, 9f, 41c, 41e, 45b.
No need to receive 7, 43, strain element 9, push rod 4
A configuration is also possible in which the end faces of 1 and the diaphragm 45 and the hard balls 27 and 43 are brought into contact with each other to make point contact. However, it is more stable to provide the conical concave portions 9e, 9f, 41c, 41e, 45b.
7 and 43 can be held, which is preferable.

EFFECTS OF THE INVENTION As described above, according to the present invention, a push rod as a stress transmission rod for fixing a diaphragm so as to close the hollow portion of a pressure guiding tube and for guiding the displacement of the diaphragm to the strain generating body in the hollow portion. The first hard ball between the diaphragm and the push rod, and the second hard ball between the push rod and the strain-generating body. Since it suppresses the strain-generating body in the pressure guiding tube by a restraining member having an abutting portion facing each other and abutting by the displacement of the strain-generating body to regulate the displacement,
Pressure is transferred from the diaphragm to the strain-generating body by a line or point contact, pressure conversion loss from the diaphragm to the push rod is reduced, the diaphragm is less likely to wear, and the push rod is less susceptible to the hysteresis of the diaphragm. Become.

Moreover, since the contact portion of the restraining member faces the central portion of the strain-generating body with a slight gap, even if a large pressure is applied to the diaphragm and the strain-generating body is largely displaced, the strain is generated at the contact portion. Since the body is restricted and is not displaced further, in addition to the above-mentioned effect, it is possible to suppress deformation of the flexure element within elastic displacement, it is difficult to suppress damage to the flexure element, and reliability is improved.

Further, in the configuration in which the diaphragm is fixed with a slight gap between the pressure guide tube and the push rod direction, even if a large pressure is applied to the diaphragm and the diaphragm is largely displaced, it is restricted by the pressure guide tube and it is difficult to make a large displacement. , It is possible to keep the diaphragm within the plastic deformation, damage of the diaphragm is prevented, and accurate measurement can be secured when the pressure returns to the rated pressure.

Further, in the configuration in which the displacement regulating flange is provided on the push rod, even if the push rod pushes the diaphragm outward with a large pressure for some reason, the flange comes into contact with the pressure guiding tube and the push rod is pushed. Since the displacement is regulated, the diaphragm is not damaged and the shock resistance is high.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a pressure sensor according to the present invention, FIG. 2 is a partially enlarged cross-sectional view showing the vicinity of a strain body, a second hard ball and a restraining member in FIG. 1, and FIG. FIG. 4 is a perspective view showing the flexure element in the figure, FIG. 4 is a partially enlarged sectional view showing the relationship between the flange of the push rod and the pressure guiding tube in FIG. 1, and FIG.
FIG. 6 is a partially enlarged sectional view showing the relationship between the push rod, the first hard sphere and the diaphragm in the figure, and FIG. 6 is a longitudinal sectional view showing a conventional pressure sensor. 1 ... Outer cylinder 3, 7 ... Pedestal 5 ... Connector receptacle 9 ... Strain element 9e, 9f, 41c, 41e, 45b ... Conical recess 11, 39 ... Restraining member 13 ... Insulation cable 17 ... Hollow part 19 …… Pressure guide tube 21 …… Upper push rod 23 …… Lower push rod 25 …… Hard ball 27 …… Second hard ball (hard ball) 29,41d …… Flange 31 …… Coil spring 33,45 …… Diaphragm 33b, 45c …… Support ring 35 …… Loose nut 37 …… Corrugated washer 39a …… Abutment member (bottom of restraining member) 41 …… Push rod 43 …… First hard ball (hard ball) 45a …… Projection

Claims (3)

(57) [Claims] 1. 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 axially in accordance with the pressure of an object to be measured, and the diaphragm inserted into the hollow portion. And a first hard ball that is interposed between the push rod and the diaphragm to abut against them and transmits the displacement of the diaphragm to the push rod, and indirectly or directly to the pressure guiding tube. And a strain-generating body that outputs electrical signals according to the axial displacement, and is interposed between the push rod and the strain-generating body on the side opposite to the first hard sphere so as to abut against them. A second hard ball that transmits the displacement of the push rod to the strain-flexing body, and a suppressing member that suppresses the strain-flexing body with respect to the pressure guiding tube, and has a slight difference from the central portion of the strain-generating body. The pressure sensor characterized by comprising a pressing member having a contact portion to the displacement-regulating contact by displacement of the strain generating body with opposed in space. 2. The pressure sensor according to claim 1, wherein the diaphragm is fixed in the push rod direction with a slight gap between the diaphragm and the pressure guiding tube. 3. The pressure sensor according to claim 1, wherein the push rod has a flange that comes into contact with the pressure guiding tube and restricts displacement in the diaphragm direction.