JP2002350277A - Leak measurement apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leak detector capable of accurately detecting a leak amount even when a measurement object A is gas and fluid fed to the pressurizing side is gas. SOLUTION: In this leak measurement apparatus, the inside of a cylinder C is divided into one pressure chamber 4 and the other pressure chamber 5 by means of a piston P arranged inside the cylinder C slidably, and one pressure chamber 4 is connected to a pressurizing machine, while the other pressure chamber is connected to a circuit and the like as the measurement object A. According to a shift amount of the piston P in pressurization of one pressure chamber 4, a leak amount in the circuit and the like as the measurement object is measured. A pressure receiving area of the piston P inside the pressure chamber 4 is equalized to that inside the pressure chamber 5. In the cylinder C, a flow passage 12 for leading liquid to a clearance between the cylinder C and the piston P is formed, and a liquid film is formed in the clearance between the piston P and the cylinder C by means of the liquid led via the flow passage 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leak measuring device for detecting a leak of a circuit or the like to be measured based on a movement amount of a piston in a cylinder.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional type of leak measuring device. In this conventional leak measuring device, a piston holding portion 1 is formed in a cylinder C, and the piston P is slidably held by the piston holding portion 1. Further, both ends of the cylinder C are closed by caps 2 and 3. Thereby, the inside of the cylinder C is partitioned into one pressure chamber 4 and the other pressure chamber 5.

The piston P has a detection hole 6 on its axis.
Is formed. The detection hole 6 is opened only on one pressure chamber 4 side. The pressure receiving area S1 of one pressure chamber 4 including the bottom of the detection hole 6 is equal to the pressure receiving area S2 of the other pressure chamber 5. Further, a sensor element 7 composed of a sensor element is provided at the opening of the detection hole 6.

Further, a detection rod 8 is fixed to the one pressure chamber 4 side. The detection rod 8 is made smaller than the inner diameter of the detection hole 6 so that both are in a non-contact state. I keep it. Since the non-contact state is maintained as described above, the pressure in one pressure chamber 4 also acts on the bottom of the detection hole 6. Therefore, as described above, the pressure receiving areas S1 and S2 in the two pressure chambers 4 and 5 become equal.

A core 9 is provided on the detection rod 8, and the core 9 and the sensor element 7 constitute a differential transformer as a non-contact stroke sensor. The detection rod 8 is electrically connected to a detector 10 provided outside the cylinder C. A differential transformer like this is
The induced voltage changes according to the relative position between the sensor element 7 and the core 9, and the detector 10 detects the change in the induced voltage to detect the amount of movement of the piston P.

Therefore, for example, if one pressure chamber 4 is connected to the pressurized side (not shown) and the other pressure chamber 5 is connected to the measurement object A, if there is no leakage on the measurement object A side, both pressure chambers are connected. The pressures in the pressure chambers 4 and 5 are equal, for the following reason. That is, when the pressure on one pressure chamber 4 side is increased, if there is no leak on the measurement object A side, the piston P cannot move. Thus, the piston P
Cannot move means that the acting force on the piston P on the one pressure chamber 4 side and the reaction force on the other pressure chamber 5 side are balanced. Moreover, since the pressure receiving areas S1 and S2 of the piston P are equal as described above, when the forces acting on the piston P are balanced as described above, the pressures in the two pressure chambers 4 and 5 are also equal. As described above, when the pressures of the two pressure chambers 4 and 5 are equal, it means that there is no leakage even on the measurement object A side.

[0007] When a leak occurs on the measurement object A side, the pressure in the other pressure chamber 5 decreases by the amount of the leak. As a result, the piston P moves rightward in the drawing. At this time, an induced voltage corresponding to the amount of movement of the piston P is generated in the differential transformer. This induced voltage is detected by detector 1
0, the movement amount of the piston P, that is, the measurement object A
Measure the amount of leakage on the side. The fluid of the measurement target A may be a liquid or a gas. The fluid supplied to the pressure chamber 4 on the pressurizing side may be a liquid or a gas.

[0008]

In the above-mentioned conventional leak measuring device, since there is a slight gap between the piston P and the piston holding portion 1, the object A to be measured is a gas and the fluid to be supplied to the pressurized side. When the gas is also a gas, an error may occur in the measured value due to the gas passing through the gap.

That is, if both pressure chambers 4 and 5 have the same pressure, the gas in both pressure chambers 4 and 5 does not move through the gap between piston P and piston holding portion 1, but the measurement is performed. When a leak occurs in the object A and the pressure in the pressure chamber 5 connected to the measurement object A decreases, the gas in the pressure chamber 4 on the high pressure side may flow into the pressure chamber 5 with the movement of the piston P. There is. When the gas in the high-pressure side pressure chamber 4 flows into the low-pressure side pressure chamber 5 as described above, an error occurs in the measured value, and there is a problem that an accurate leak amount on the measurement target A side cannot be detected. The object of the present invention is to measure
It is an object of the present invention to provide a leak detector capable of accurately detecting a leak amount even when the gas is a gas and the fluid supplied to the pressurizing side is also a gas.

[0010]

A first aspect of the present invention is a piston slidably provided in a cylinder, which divides the inside of the cylinder into one pressure chamber and the other pressure chamber, and the one pressure chamber. Is connected to a pressurizing machine, the other pressure chamber is connected to a circuit to be measured, etc., and the amount of leakage of the circuit to be measured is measured by the amount of movement of the piston when one of the pressure chambers is pressurized. On the other hand, in a leak measuring device in which the pressure receiving areas of the pistons in the two pressure chambers are equal, the cylinder has a flow passage that guides a liquid to a gap between the cylinder and the piston. A liquid film is formed in a gap between the piston and the cylinder by the introduced liquid.

According to a second aspect, in the first aspect,
A partial or circumferential concave portion is formed on the inner peripheral surface of the cylinder, and a liquid film is formed between the piston and the cylinder by the liquid stored in the concave portion.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment shown in FIG. 1, an annular concave portion 11 is formed on the inner periphery of a piston holding portion 1 of a cylinder C. The annular concave portion 11 is closed by the outer periphery of the piston P to form a liquid chamber B for storing liquid. The liquid chamber B stores liquid such as oil, grease, and water. Also, a part of the liquid chamber B is
It is opened to the outer periphery of the cylinder C via the flow path 12.
Then, the opening 13 is closed with a cap 14 and the liquid chamber 1 is closed.
The liquid in 1 is prevented from leaking outside. Since the configuration other than the above is the same as that of the conventional example, the same reference numerals are given to the same components as those of the conventional example, and the detailed description thereof will be omitted.

When the liquid stored in the liquid chamber B comes into contact with the sliding surface of the piston P, the liquid spreads over the entire inner peripheral surface of the piston holding portion 1 through a gap between the piston P and the piston holding portion 1. When the liquid spreads over the entire inner peripheral surface of the piston holding unit 1 in this manner, a liquid film is formed in a gap between the piston P and the piston holding unit 1. Piston P and piston holding part 1
When a liquid film is formed in the gap between the piston P and the piston holding portion 1, the sealing function of the liquid film enhances the sealing performance. Therefore, gas can be prevented from passing through the gap between the piston P and the piston holding portion 1.

As described above, according to this embodiment, since the liquid film is formed between the piston P and the piston holding portion 1, even if the fluid in the pressure chambers 4 and 5 is a gas. The gas in the pressure chambers 4 and 5 does not move through the gap between the piston P and the piston holding portion 1. Therefore, even if the measurement target A is a gas and the fluid supplied to the pressurized side is a gas, no error occurs in the detection value, and the leak amount of the measurement target can be accurately detected.

In this embodiment, the liquid film is formed by the liquid stored in the liquid chamber B. However, the liquid may not be stored. That is, only the flow path 12 for guiding the liquid to the sliding surface of the piston P is formed in the piston holding section 1, and the liquid guided through the flow path 12 causes the liquid to flow between the piston P and the piston holding section 1. A liquid film may be formed. However, storing the liquid in the liquid chamber B as in this embodiment can maintain the liquid film for a long time and can prevent the liquid film from being cut.

Further, in this embodiment, the liquid chamber B is constituted by the annular concave portion 11, but the concave portion 11 forming the liquid chamber B may not be annular. For example, a partial concave portion may be formed on the inner periphery of the piston holding portion 1, and the concave portion may constitute the liquid chamber B. However, when the liquid chamber 11 is provided in a part of the holding unit 1 as described above, the liquid in the liquid chamber B must be spread at least one time around the outer circumference of the piston P. This is because the sealing property cannot be obtained unless a liquid film that goes around the outer circumference of the piston P is formed.

Therefore, the liquid chamber B is formed by the partial recess.
When the piston P is assembled, the piston P is rotated to form a liquid film on the outer periphery of the piston P around the piston P. Further, if the viscosity of the fluid is low without rotating the piston P, the fluid can be naturally spread over the entire gap between the piston P and the piston holding portion 1. If the concave portion 11 is formed in an annular shape as in this embodiment, a liquid film surrounding the outer periphery of the piston P can be always formed, so that the sealing property by this liquid film can be reliably obtained.

Further, in this embodiment, the piston P is slidably held by the piston holding portion 1. However, the piston holding portion 1 is omitted, and the piston P is brought into direct contact with the inner wall of the cylinder C. It may be configured. In this case, the flow path 12 and the concave portion 11 may be formed in the cylinder C.

[0019]

According to the first aspect of the present invention, since a liquid film can be formed on the sliding surface of the piston, the object to be measured is a gas and the fluid supplied to the pressurizing side is also a gas. Also, the liquid film exerts a sealing function, and the gas in the high pressure side pressure chamber does not flow into the low pressure side pressure chamber. Therefore, there is no error in the measured value, and the leak amount can be accurately measured.

According to the second aspect, since the liquid film is formed by the liquid stored in the concave portion, the liquid film can be prevented from being cut.

[Brief description of the drawings]

FIG. 1 is a sectional view of a leak measuring device according to an embodiment.

FIG. 2 is a sectional view of a conventional leak measuring device.

[Explanation of symbols]

 A measurement target C cylinder P piston 4 one pressure chamber 5 the other pressure chamber 11 recess 12 flow path

Claims (2)

[Claims] 1. A piston slidably provided in a cylinder to partition the inside of the cylinder into one pressure chamber and the other pressure chamber, and connect one of the pressure chambers to a pressurizing machine and connect the other pressure chamber to the other. While the chamber is connected to the circuit to be measured, etc., the amount of movement of the piston when one of the pressure chambers is pressurized, while measuring the amount of leakage of the circuit to be measured,
In the leak measuring device in which the pressure receiving areas of the pistons in the two pressure chambers are equal, in the cylinder, a flow path for guiding liquid to a gap between the cylinder and the piston is formed. A leak measuring device characterized in that a liquid film is formed in a gap between a cylinder and a cylinder. 2. A partial or circumferential concave portion is formed on the inner peripheral surface of the cylinder, and a liquid film is formed between the piston and the cylinder by the liquid stored in the concave portion. Item 6. A leak measuring device according to Item 1.