JPH085490A - Pressure difference detector - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a pressure difference detector which has a simple structure and is applicable to ON-OFF operation or to some extent quantitative pressure difference detection. A pressure difference detector 1 of the present invention includes a cylinder 14 that receives a pressure medium, and a piston 17 that divides the inside of the cylinder 14 in a pressure-tight manner and that is slidably provided in the cylinder 14. , Two ports 13 and 19 capable of independently taking in and discharging a pressure medium, a piston support member 15 for elastically supporting the piston 17 with respect to the cylinder 14, and a piston for detecting displacement of the piston 17 in the cylinder 14. Displacement detection means 29 and 27 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure difference detector for detecting a pressure difference between two pressure medium systems and a change in the pressure difference. In particular, the present invention relates to a pressure difference detector having a simple structure and suitable for inspecting the airtightness of an airtight container.

[0002]

2. Description of the Related Art As a measuring instrument for detecting a pressure difference, a diaphragm type pressure difference detector has hitherto been representative. This pressure difference detector introduces two systems of fluid pressure to be compared on both sides of the diaphragm, measures the strain of the diaphragm with a strain gauge stretched on the surface of the diaphragm, and converts this strain into a pressure difference. .

Further, a plurality of pressure switches are used, and
It was also performed to detect the pressure difference stepwise by N-OFF.

[0004]

The above-mentioned conventional pressure difference detector has the following problems. 1. The structure was complicated and expensive. 2. Especially, when the pressure difference exceeds a certain threshold value, ON-O
There was no economical pressure difference detector suitable for FF operation and the function of outputting the signal.

The present invention has a simple structure and is an ON-OF.
An object of the present invention is to provide a pressure difference detector applicable to F operation or applicable to quantitative pressure difference detection to some extent. Another object of the present invention is to provide a pressure difference detector suitable for inspecting the airtightness of an airtight container.

[0006]

In order to solve the above-mentioned problems, a pressure difference detector of the present invention comprises a cylinder for receiving a pressure medium and a piston for partitioning the inside of the cylinder in a pressure-tight manner, and sliding in the cylinder. A piston that can be installed,
Two ports provided at both ends of the cylinder that sandwich the piston and capable of independently taking in and discharging the pressure medium, a piston support member that elastically supports the piston with respect to the cylinder, and displacement of the piston in the cylinder And a piston displacement detecting means for detecting.

[0007]

In the cylinder of the pressure difference detector of the present invention,
A piston that slides inside the cylinder is provided. The piston divides the interior of the cylinder into two parts in a compact manner. Further, the piston receives the pressure of the pressure medium existing in each divided part of the cylinder on both sides thereof, and is driven by the resultant force of the pressures to slide in the cylinder.
On the other hand, both ends of the cylinder (there is a piston between them)
Is provided with two ports, which are the ports through which the pressure medium enters and leaves the cylinder. Note that "two" means at least two and does not mean that the existence of three or more ports is excluded. The two ports can independently take in and discharge the pressure medium. Further, the piston is elastically supported with respect to the cylinder, and has an action of returning the piston to the vicinity of the origin when the piston driving force due to the pressure difference of the pressure medium disappears.

The displacement of the piston is detected by the piston displacement detecting means. This detection may be stepwise detection (ON or OFF when the displacement exceeds a certain threshold value), or may be quantitative detection. There is a causal relationship between the pressure difference of the pressure medium on both sides of the piston and the displacement of the piston (both need not be linear). Therefore, the pressure difference can be quantitatively detected by detecting the displacement of the piston.

The pressure medium referred to in the present invention means gas, liquid,
It means a medium that transmits a pressure having a certain degree of fluidity, such as a viscous substance, sludge, and a fluid granular material. Cylinders and pistons are not limited to so-called hydro-pneumatic cylinders and such things as pistons moving in them. The shape is not limited to a cylinder or a disc. Examples of the piston support member include a coil, a spring, a leaf spring, rubber, and an air spring. The "elasticity" of the piston support member
The characteristic of does not necessarily have to be linear (there is a linear relationship between force and deformation).

In the pressure difference detector according to one aspect of the present invention, the piston displacement detecting means emits an ON or OFF electric signal when the displacement of the piston exceeds a certain threshold value.

Such a pressure difference detector can be made to have a particularly simple structure, and there are many applications in which it can be sufficiently used if only such an action is achieved. Conventionally, as described above, even in such an application, an over-spec pressure difference detector or pressure detection system had to be used.

In the above-mentioned pressure difference detector according to one aspect of the present invention, the piston displacement detecting means is provided with the cylinder side electrical contact provided inside the cylinder and the movement of the piston provided on the piston. A piston-side electric contact that can contact the cylinder-side electric contact and a piston displacement detection circuit that conducts when both contacts are in contact may be provided.

The piston displacement detecting means of such a pressure difference detector can have a particularly simple structure. In addition,
This type of pressure difference detector is generally not possible for use with electrically conductive pressure media. In addition to the method of obtaining a signal by the contact of an electric contact, various methods can be used.

In a pressure difference detector according to another aspect of the present invention, the piston displacement detecting means detects the displacement of the piston as an analog value, and means for converting the detected value into a transmittable signal. And, it is supposed to have.

Here, "to detect the displacement of the piston as an analog value" means ON-OFF when the threshold value is passed.
It does not mean recognition, but rather means that the displacement of the piston is grasped quantitatively to some extent. Examples of such means are:
A capacitance type displacement sensor, etc. can be mentioned.
Among these, the capacitance type displacement sensor is preferable because it is inexpensive and highly reliable.

In the pressure difference detector of the present invention, the above-mentioned 2
A port pressure equalizing means for equalizing the pressure of one port may be further provided.

"Equalize" means to make the pressure of both ports substantially the same, or to confirm that they are the same. Such port pressure equalizing means is useful for adjusting or recognizing the 0 point (point where the pressure difference is 0) of the pressure difference detector.

An example of such a port pressure equalizing means is one having a short-circuit pipe for short-circuiting the two ports through which the pressure medium can pass, and a valve for opening and closing the short-circuit pipe. .

When the valve is opened to allow the pressure medium to flow between the ports substantially freely, the pressure medium pressure difference between the ports becomes almost zero. By thus equalizing the pressure to adjust the zero point of the pressure difference detector, then closing the valve and measuring the change in the pressure difference, the pressure difference can be measured with high accuracy.

The pressure difference detector of the present invention may further comprise a storage means for receiving a signal indicating that the pressures at both ports are equal and storing the piston position signal at this time as a zero point.

Here, the "signal indicating that the pressures of both ports are equal" is, for example, when a person looks at the separate pressure gauges attached to both ports to confirm that the pressures are equal, and the pressure is manually applied. It may be generated by inputting to the difference detector (or its upper control system). Alternatively, the sensor may detect that the valve in the short-circuit pipe is opened, and such a signal may be automatically given to the pressure difference detector when a certain time has elapsed.

Further, in the pressure difference detector according to another aspect of the present invention, the relationship between the pre-measured output signal of the piston displacement detecting means and the pressure difference between the two ports is stored, and the stored data is stored. May be arbitrarily read, and determination means for determining the pressure difference between the two ports from the output signal of the piston displacement detection means and the storage data of the storage means.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a pressure difference detector according to an embodiment of the present invention and a state in which a leak inspection of an airtight container is performed using the pressure difference detector. In FIG. 1, reference numeral 3 at the upper part of the drawing indicates an airtight container to be leak-checked. Reference numeral 1 indicates a pressure difference detector. Reference numeral 5 indicates an inspection pressure supply means (gas cylinder or the like).

The pressure difference detector 1 shown in FIG. 1 is roughly composed of a detector body 11 and a piston displacement detecting means 21. The detector body 11 has a hollow cylindrical cylinder 14. On the upper and lower end surfaces of the cylinder 14,
An inlet / outlet (port A13, port B19) through which gas (pressure medium) enters and leaves the cylinder 14 is provided. Inside the cylinder 14, the longitudinal direction of the cylinder (axial direction)
A piston 17 that slides in the cylinder is incorporated in the cylinder. The piston has a disc shape whose outer diameter is slightly smaller than the inner diameter of the cylinder. A seal 18 (0 ring or the like) is attached to the outer diameter surface of the piston 17. Therefore, the inside of the cylinder 14 is divided into two chambers with the piston 17 as a boundary, and the gas in both chambers does not cross the piston 17 and go back and forth.

The piston 17 has a piston support spring 15
It is connected to one end by (piston support member).
The other end of the piston support spring 15 is connected to the upper portion of the cylinder 14. Therefore, the piston 17 is elastically supported by the cylinder 14. When the pressures applied to the upper and lower surfaces of the piston 17 are equal, the piston 17 exists in the neutral position of the piston support spring 15. If there is a difference in pressure applied to the upper and lower surfaces, the piston 17 moves to a position where the resultant force due to the pressure difference and the spring force of the piston support spring 15 are balanced.

A piston-side electric contact 29 is attached to the upper end of the piston 17. A cylinder-side electric contact 27 is attached to the inner surface of the cylinder 14 above the piston-side electric contact 29. When the piston 17 moves upward due to the pressure difference, the piston side electrical contact 29 and the cylinder side electrical contact 27 come into contact with each other. The piston-side electric contact 29 and the cylinder-side electric contact 27 are connected to each other via the external wirings 39a and 39b.
7 and 29 are connected to a piston displacement detection circuit 23 that constitutes a piston displacement detection means 21.

The piston displacement detection circuit 23 changes a so-called contact signal generated at the above-mentioned two electric contacts 27, 29 into an appropriate voltage signal, the output signal of which is connected to the controller 25 and responds to a pressure change. It is designed to be used for alarm generation and display. FIG. 2 shows a configuration example of the piston displacement detection circuit 23 and the controller 25. The configuration example of the piston displacement detection circuit 23 will be described with reference to FIG. It is configured to have a conversion circuit 23a and a comparator 23b.

The signal conversion circuit 23a includes two electric contacts 2
A circuit for converting a so-called contact signal generated at 7, 29 into an appropriate voltage signal, and having a waveform shaping function for removing noise caused by so-called chattering of the contact and a function for converting the contact signal into a voltage signal. It must be The comparator 23b determines whether or not a voltage signal corresponding to the contact between the piston side electric contact 29 and the cylinder side electric contact 27 is output from the signal conversion circuit 23a. When it is determined that the cylinder side electrical contact 27 is in contact, a signal of a constant level is output to the controller 25.

On the other hand, the controller 25 includes an alarm drive circuit 25a.
And a warning light (or a warning buzzer) 25b driven by the driving warning circuit 25a. When the voltage signal of a constant level is input from the comparator 23b described above to the warning driving circuit 25a, the warning light ( Alternatively, the alarm buzzer 25b is energized and the alarm lamp 25b is turned on (or the alarm buzzer sounds), so that the user can know that a predetermined pressure change has occurred.

The airtightness inspection of the airtight container 3 shown in FIG. 1 will be described. First, the upper end of the pressure difference detector 1 is connected to the airtight container 3 to be inspected. A port short-circuit pipe 31 is attached to the pressure difference detector 1. The port short-circuit conduit 31 is connected to the A port 13 and the B
It is a conduit connecting to the port 19. This port short circuit line 3
In the middle of 1, an eco-raising valve 33 is attached. When the Equalize Rising Valve 33 is opened,
The port A13 and the port B19 of the detector body 11 are connected with almost no resistance. When the eco-rising valve 33 is closed, there is no communication between both ports. On the other hand, the inspection pressure supply means 5 (gas cylinder or the like) is also connected to the lower end of the pressure difference detector 1.

In this way, the eco-raising valve 33 is opened and the inspection pressure is introduced into the airtight container 3 to be inspected. When the pressure introduction is completed, the equalizing rising valve 33 is closed, and then a certain inspection time elapses.
In the meantime, if there is a pressure leak in the airtight container 3 to be inspected, the pressure in the upper chamber of the cylinder 14 of the pressure difference detector 1 communicating therewith is lowered. Then, piston 1
7 moves upward, the electric contacts 29 and 27 come into contact with each other, and the pressure difference occurrence is detected. In such a case, the airtight container 3 to be inspected fails the airtight inspection.

According to the inspection method described here, it is possible to automatically perform the airtight inspection of a large number of airtight containers to be inspected without measuring and recording the pressure. Therefore, the labor required for the inspection can be significantly reduced.

Next, the embodiment shown in FIG. 2 will be described. FIG. 2 is a diagram showing an embodiment of a pressure difference detector of the type capable of detecting piston displacement as an analog quantity. In addition,
The same components as those of the embodiment shown in FIG. 1 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described below.

In this embodiment, a capacitance type non-contact displacement sensor is used as the piston displacement detecting means. That is, the capacitance-type non-contact displacement sensor 35 in the present embodiment is fixed to the piston-side electrode 36 provided on the upper end of the piston 17 and the supporting piece 38 protruding from the inner peripheral surface of the cylinder 14. The fixed-side electrode 37 and the fixed-side electrode 37 are formed. Both the piston-side electrode 36 and the fixed-side electrode 37 are formed as flat plate electrodes, and electrostatic charges are generated according to the distance between the piston-side electrode 36 and the fixed-side electrode 37. The capacity is designed to change.

The piston side electrode 36 is connected to an external wiring 39a via a connection line (not shown), and is connected to the piston displacement detection circuit 40 via this external wiring 39a, while the cylinder side electrode 37 is connected to the other side. External wiring 39b
It is connected to the piston displacement detection circuit 40 via.
The piston displacement detection circuit 40 converts a change in capacitance of the capacitance-type non-contact displacement sensor 35 into a change in voltage signal. For example, as shown in FIG. It has a commonly used circuit configuration.

To briefly explain the circuit example shown in FIG. 3, the piston displacement detection circuit 40 of this embodiment is a so-called ring circuit constructed by using the diodes D1 to D4 and the oscillator 41. The output level can be changed by adjusting the adjusting capacitor C2 connected in series with the capacitance type non-contact displacement sensor 35.

As a concrete adjustment method, first, as already described, the ecological valve 33 is adjusted so that the pressures of the airtight container 3 and the inspection pressure supply means 5 become equal. At the same time, the adjusting capacitor C2 is adjusted so that the output level of the piston displacement detection circuit 40 becomes zero. After that, if a pressure leak occurs in the airtight container 3 to be inspected and the piston 17 moves according to the degree of the pressure leak, the output level of the piston displacement detection circuit 40 changes from zero. The amount of displacement of the piston 17, that is, the amount of change in pressure of the airtight container 3 to be inspected can be known by the magnitude of the level.

FIG. 4 shows an example of the controller 42 in this embodiment, and the controller 42 will be described below with reference to the figure. This controller 42 converts the output signal of the piston displacement detection circuit 40 into a signal format and level suitable for processing in the circuit at the subsequent stage.
And a comparator 44 that compares the output level of the voltage conversion circuit 43 with a preset threshold value, and drives a warning lamp (or a warning buzzer) 46 when a constant output signal is output from the comparator 44. Alarm driving circuit 45 and an analog / digital converter for analog-digital converting the output signal of the voltage conversion circuit 43 (in FIG. 4, "A /
It is abbreviated as "D" and hereinafter referred to as "A / D converter". ) 47 and a storage circuit 48 in which the relationship between the pressure change in the airtight container 3 to be inspected and the output change of the piston displacement detection circuit 40 via the A / D converter 47 is stored.
And a determination circuit 49 that determines the amount of change in pressure based on the output data of the A / D converter 47 and the data of the storage circuit 48 and outputs a signal corresponding to each amount of change. Display drive circuit 5 for numerically displaying the pressure change amount determined by the determination circuit 49 according to the output data.
0 is provided.

The threshold value set in the comparator 44 is used when the pressure change amount of the inspected hermetic container 3 detected by the piston displacement detection circuit 40 via the voltage conversion circuit 43 exceeds the allowable amount. Is set, and when the output voltage of the voltage conversion circuit 43 exceeds this threshold value, the comparator 44
Is, for example, one that outputs a one-shot trigger signal. And the alarm drive circuit 45
When a one-shot trigger signal is input from the comparator 44, the drive current required to turn on the alarm lamp 46 (or sound the alarm buzzer) is supplied.

The storage circuit 48 as storage means is, for example,
It is composed of a memory element represented by RAM or EEPROM, and as outlined above, changes in the output of the piston displacement detection circuit 40 when the pressure of the airtight container 3 to be inspected changes are detected by the A / D converter 47. The data corresponding to the output data of the A / D converter 47 and the pressure change amount are associated with each other and stored in advance.

The judging circuit 49 as a judging means reads the data stored in the memory circuit 48 and outputs the data to the A / D converter 4
By comparing the output data of No. 7 with the output data of No. 7, it is determined which of the pressure change amounts stored in the storage circuit 48 the pressure change amount of the inspected hermetic container 3 corresponds to. A voltage signal (or a digital signal) is output. Then, the display drive circuit 50 is configured to numerically display the pressure change amount on a liquid crystal display element (not shown) based on the signal output from the determination circuit 49.

In the above embodiment, the output level in the piston displacement detection circuit 40 is adjusted to zero by adjusting the adjusting capacitor C2, while there is no pressure change in the airtight container 3 to be inspected. Of course, it is not always necessary to set the reference level to zero, and it goes without saying that a constant value other than zero may be set as the reference level. It must be.

[0043]

As is apparent from the above description, the present invention exhibits the following effects. 1. The pressure difference detector of the present invention has a simple structure and can be manufactured at low cost. 2. It is possible to provide a pressure difference detector applicable for ON-OFF operation or to some extent quantitative pressure difference detection. 3. A pressure difference detector suitable for checking the airtightness of an airtight container can be provided. 4. In the pressure difference detector equipped with the port pressure equalizing means, it becomes easy to adjust or recognize the zero point.

[Brief description of drawings]

FIG. 1 is a diagram showing a pressure difference detector according to an embodiment of the present invention and a state in which a leak inspection of an airtight container is performed using the pressure difference detector.

FIG. 2 is a configuration diagram showing a configuration example of a piston displacement detection circuit and a controller in FIG.

FIG. 3 is a diagram showing an embodiment of a pressure difference detector of a type capable of detecting piston displacement as an analog amount.

FIG. 4 is a circuit diagram showing a circuit example of a piston displacement detection circuit in FIG.

5 is a configuration diagram showing a configuration example of a controller in FIG.

[Explanation of symbols]

1 Pressure Difference Detector 31 Port Short Circuit Pipe 3 Confidential Container to be Inspected 33 Equalizing Rising Valve 5 Inspection Pressure Supply Means 35 Capacitance Non-Contact Displacement Sensor 11 Detector Main Body 36 Piston Side Electrode 13 A Port 37 Cylinder Side Electrode 14 Cylinder 40 Piston displacement detection circuit 15 Piston support spring (Example of FIG. 3) 17 Piston 42 Controller 18 Seal (Example of FIG. 3) 19 B port 43 Voltage conversion circuit 21 Piston displacement detection means 44 Comparator 23 Piston displacement detection Circuit 45 Alarm drive circuit 25 Controller 48 Memory circuit 27 Cylinder side electrical contact 49 Judgment circuit 29 Piston side electrical contact

Claims (8)

[Claims] 1. A cylinder for receiving a pressure medium, a piston for partitioning the interior of the cylinder in a pressure-tight manner, the piston being slidably provided in the cylinder, and the pistons provided at both ends sandwiching the piston of the cylinder. , Two ports capable of independently taking in and discharging the pressure medium, a piston support member for elastically supporting the piston with respect to the cylinder, and a piston displacement detection means for detecting displacement of the piston in the cylinder A pressure difference detector characterized in that 2. The piston displacement detection means is ON or OF when the piston displacement exceeds a certain threshold value.
The pressure difference detector according to claim 1, which emits an electric signal of F. 3. A piston side electrical contact, wherein the piston displacement detecting means is provided inside the cylinder, and a piston side electrical contact provided on the piston and capable of contacting the cylinder side electrical contact as the piston moves. 2. The pressure difference detector according to claim 1, further comprising: a piston displacement detection circuit that outputs a signal of a constant level when both contacts are in contact. 4. The pressure according to claim 1, wherein the piston displacement detecting means includes means for detecting the displacement of the piston as an analog value and means for converting the detected value into a transmittable signal. Difference detector. 5. The pressure difference detector according to claim 1, further comprising port pressure equalizing means for equalizing the pressures of the two ports. 6. The port pressure equalizing means has a short circuit conduit for short-circuiting the two ports through which the pressure medium can pass, and a valve for opening and closing the short circuit conduit. The pressure difference detector described. 7. The pressure difference detector according to claim 1, further comprising storage means for receiving a signal indicating that the pressures of both ports are equal and storing the piston position signal at this time as a zero point. 8. A relationship between a pre-measured output signal of the piston displacement detecting means and a pressure difference between the two ports is stored,
A storage means capable of arbitrarily reading the stored data, and a determination means for determining a pressure difference between two ports from an output signal of the piston displacement detection means and the storage data of the storage means. Item 1. The pressure difference detector according to item 1.