JPH01196503A - Method and apparatus for inspecting bore of very fine diameter capillary - Google Patents

Abstract

PURPOSE:To obtain a method which enables inspection of the bore of a capillary with high accuracy, by feeding a fluid to a capillary at a fixed flow rate being compressed to inspect the bore thereof with a compression controlled to balance the pressure of a feed liquid. CONSTITUTION:A liquid having a known characteristic of viscosity is fed to a capillary 2 having a very fine diameter with a pump 1 or the like while being compressed. Then, a compression is controlled to balance the pressure of the feed liquid. Then, based on a feeding requirement as met when the pressure of the feed liquid is balanced, the bore of the capillary is inspected. This enables the confirmation of the degree of penetration and passage in a very fine diameter capillary made of ceramics or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method and apparatus for inspecting the inner diameter of an extremely small diameter capillary, such as a ceramic fired capillary.

[Conventional technology]

Resistance tubes commonly used in chromatography include stainless steel tubes with an inner diameter of about 100 μm wound to the required length, and stainless steel tubes with an inner diameter of IIm to 2n filled with fillers with particle sizes of 3 to 10 μm. There are tubes made of solid quartz or fused silica tubes of appropriate length. The inner diameter of the fused silica tube can be freely selected within the range of 50 .mu.m to 300 .mu.m, but the outer diameter is often 500 .mu.m or less.

Among the conventional resistance tubes mentioned above, stainless steel tubes have problems in that they have too large an inner diameter and are easy to get dirty when used for supercritical fluids with low viscosity or in the micro and semi-micro flow range. be.

Packed columns can be made with desired resistance depending on the purpose, but they are expensive and not easy to handle. Additionally, fused silica tubes have the problem of being fragile and difficult to connect with other fluid components.

By the way, if the fluid flowing inside the tube is a material with Newtonian viscosity, the pressure generated is equal to 1/4 of the inner diameter, the length,
Viscosity coefficient and proportional to flow rate.

For example, the length and inner diameter are each 010cm x 20μ.
Section, 010cm x 30 um, 010cm x
When ethyl alcohol is passed through a 40 μm resistance tube from one end, the pressure generated is as shown in the table below.

Therefore, appropriate pressure can be generated by selecting the pipe diameter and pipe length.

In particular, the development of supercritical fluid chromatography, micro and semi-micro chromatography, etc. requires resistance tubes that are extremely small in diameter and easy to use. However, with conventional resistance tubes, it is not possible to manufacture tubes with extremely small diameters as described above, and there are various problems. Therefore, a prototype capillary was created that could meet the requirements as a resistance tube for supercritical fluid chromatography and micro and semi-micro chromatography. This is a zirconia capillary using fine ceramics, and the outer diameter is 5LIS.
The same size as the chromato tube, 1716", and the inner diameter of 20μ.
made in several steps between m and 50 p-m,
The length is 10 cm or 5 cm, which can be selected depending on the flow rate range and required pressure range.

[Problem to be solved by the invention]

However, even if a resistance tube like the one described above can be manufactured, it is necessary to inspect whether the capillary is a good product in order to put it into practical use. Since it is not used, there are no effective testing methods yet.

If the inner diameter of the tube is 100 μm or more, it is possible to check the quality of the tube by inserting a fine wire, but if the inner diameter is 50 μm or less, there is no wire that can be used to confirm insertion over a length of 10 cm.

Therefore, it has been considered to check whether the pipe has penetrated, for example by using an ink bleed test, but even this method can only confirm whether the pipe has penetrated or not. The problem is that I don't understand. Furthermore, although it is possible to examine the diameter of the hole on both end faces using a microscope, it is not possible to confirm whether the diameter of the hole penetrates the entire length of 10 cI11.

The present invention is based on the above consideration, and an object of the present invention is to provide a method and apparatus for inspecting the inner diameter of an extremely small diameter capillary, which can confirm the penetration and flow rate of an extremely small diameter capillary with high accuracy. It is.

[Means to solve the problem]

To this end, the present invention provides a method for inspecting the inner diameter of an ultra-fine capillary by feeding a fluid with known viscosity characteristics into the capillary, in which a constant flow rate is fed to the capillary while compressing the fluid. , the compression amount is controlled until the liquid feeding pressure is balanced, and the inner diameter is inspected based on the liquid feeding conditions when the liquid feeding pressure is balanced, and the apparatus for this purpose includes a compression means for compressing the fluid. , a liquid feeding means for feeding the compressed fluid to the capillary at a constant rate, a pressure detection means for detecting the fluid pressure on the discharge side of the liquid feeding means, and a control parameter of the compression means so that the detected pressure is balanced. The present invention is characterized in that it includes a control inspection means for inspecting the inner diameter of the capillary based on the liquid feeding conditions when an equilibrium pressure is obtained.

[Effect]

In the method and apparatus for inspecting the inner diameter of a very small diameter capillary of the present invention, a constant flow rate is sent to the capillary while compressing the fluid, and the amount of compression is controlled until the liquid feeding pressure is balanced, so that when the liquid feeding pressure is balanced, , there is no compression of the fluid during the liquid delivery stage to the capillary. Therefore, from the liquid feeding conditions at that time, the equilibrium pressure P, the viscosity coefficient η of the liquid feeding fluid, the liquid feeding flow,
Between IU, capillary length, and inner diameter d, the following relationship is obtained: L・η・U P=K (K is a constant). From this relationship, the inner diameter d can be inspected.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the method and apparatus for inspecting the inner diameter of an extremely small diameter capillary according to the present invention, in which 1 is an intelligent cascade pump, 2 is a capillary, 3 is a liquid feeding tank, 4 is a medium pressure filter, and 5 6 indicates a push screw, and 6 indicates a waste liquid tank.

The intelligent cascade pump 1 is a pump that is designed to feed a fixed amount of liquid regardless of the type of fluid to be fed even if the load changes, and has already been proposed by the present inventor (
For example, it is possible to use a pump disclosed in Japanese Patent Laid-open No. 61-178582).The present invention provides this intelligent cascade pump l with a medium pressure filter 4 and a set screw 5.
The capillary 2 is connected through the capillary 2, and an intelligent cascade pump 1 is used to send liquid from the liquid sending tank 3 into the fine ceramic capillary 2 to be inspected.

FIG. 2 is a diagram showing an example of the intelligent cascade pump 1, in which 11 is a drain valve, 12 is a pressure sensor, 13 is a metering pump, 14 is a compression pump, 15 and 16 are stepping motors, 17 and 18 are motor drivers,
19 is an A/D converter, 20 is a microprocessor, 21
'@' indicates the source, and 22 indicates the display operation unit.

Both the metering pump 13 and the compression pump 14 have variable plunger stroke lengths, and the microprocessor 20 allows the optimum operating conditions of each pump to be selected depending on the compressibility of the fluid, the operating pressure, and the flow rate range. The basic operating mode of this pump system is such that the metering pump 13 is configured to slowly discharge and quickly suck, while the compression pump 14 slowly sucks and quickly discharges. The discharge process of the compression pump 14 consists of a compression process of the transfer liquid and an actual transfer process, and the suction process of the metering pump 13 is synchronized with the latter process, so that the suction side pressure and the discharge side pressure of the metering pump 13 are approximately equal to each other. Make equal. That is, the metering pump 13 does not include any "compression" process, and the amount of liquid sent is determined by the plunger volume and stroke period of the metering pump 13.

In this way, if the compensation amount of the compression pump 14 just compensates for the effect of volumetric contraction caused by pressure, the pressure will be constant at any point in the discharge process of the metering pump 13, whereas if there is a shortage, there will be an excess. In this case, the pressure value changes between the beginning and end of the discharge process. Therefore, the microprocessor 20 determines the deviation from the optimal value according to the magnitude and slope of this change, changes the control parameters, determines the stroke length of the compression pump, and converges to the optimal condition (pressure change is zero).

FIG. 3 is a diagram showing a display example of the operation monitor screen. ■
This monitor indicates the set flow rate, ■ indicates the generated pressure, ■ indicates the plunger volume of the metering pump, ■ indicates the plunger volume of the compression pump, ■ indicates the compression volume horizontally, and ■ indicates the amount of pressure change during the metering pump discharge process. In this case, the inner diameter inspection is determined after waiting until the pressure change amount (■) during the metering pump discharge process becomes less than a predetermined value, for example, less than 1, and the evaluation is made based on the generated pressure (2). Note that the compressed volume horizontal position (■) is precented.

When using an intelligent cascade pump as described above and flowing ethyl alcohol through a capillary 2 of, for example, 30 μm x 10 cm, the pressure increases with each repeated plunger stroke. At the same time, the pressure change ΔP in the liquid feeding process of the metering pump of the intelligent cascade pump 1 decreases, and when ΔP is 1 kg/- or less, an almost equilibrium state is reached. The pressure generated at this time becomes the criterion for inner diameter inspection. If the pressure is not constant and always shows an increasing tendency,
In addition, if ΔP exhibits a relatively large positive value, this is evidence that there is a portion with abnormally large fluid resistance inside the tube.

When 24 prototypes were actually inspected, 11 had a weight of less than 20 kg/cal and were judged to be acceptable. The other three are 100 kg/cj ~ 200 kg/clI
It shows a value between + and becomes equilibrium (ΔP ~ 0), and the other 10
The book generated a pressure of 200 kg/cd, and ΔP>0.

During this test, the fluid that passed through the capillary contained fine particles that were unknown, whether they were cutting powder or raw material zirconia. That is, the fine powder that was inside the capillary was pushed out during the process of this inspection.

Although the specimen was subjected to ultrasonic cleaning twice before testing, it became clear that ultrasonic cleaning could not remove the fine powder that had entered the inside of the specimen, which had an extremely small diameter of 30 μm.

In addition, during the inspection process, there were cases where the pressure generated was different when the fluid was flowed from one end and the other, but this was clearly evidence that there was a foreign object inside whose position changed depending on the flow pressure. This is an investigation. Three of the 11 specimens that passed the test initially failed, but the foreign objects were pushed out by the forced flow and they passed the test.

Therefore, in those that passed the test, the generated pressure was constant regardless of the flow direction.

Furthermore, if a piece that fails the above test is divided into two parts and the same test is performed on each piece, it is possible to judge whether the piece passes or fails, although the pressure will decrease due to the difference in length. 10 failures
When we conducted such an inspection on 3 of the books, it was found that only 1 of the 4 parts of 10 (J) were clogged.

In this way, even if it fails at 10am, 5clN divided into two
At least one of each will pass.

This method means that, where P is the pressure, the length of the capillary is η, the flow rate is U, the inner diameter is d, and the constant is K, L・η・U P=□. That is, d can be found by actually measuring the relationship between P and U using a fluid whose η is known.

This test method can be carried out using a common pump, pressure gauge, and flow meter. It is shown that.

However, it goes without saying that the use of intelligent cascade pumps as described above is particularly optimal. The reason for this is: - It is very difficult to measure the flow rate in the μm 7mm range, and even if it is possible, there will be large errors, especially in short-time measurements. - If the relationship between flow velocity and pressure is not measured in real time, it will take until the system reaches equilibrium. I have to wait. This takes a very long time when using a general constant flow pump.

■When flowing at a constant flow rate through a constant resistance, the plunger stroke length required only for pressure increase (compression volume)
Once the parameters are determined and such optimal conditions are obtained, the intelligent cascade pump described above can be used for 25 seconds to 3 seconds by setting this parameter from the beginning.
An equilibrium state can be achieved within a range of 0 sec or 2 to 3 times this time. Further, whether or not an equilibrium state has been reached can be immediately determined by displaying the measurement result of ΔP.

■The above intelligent cascade pump does not require a flow meter; it only needs to have a built-in pressure indicator.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, if an intelligent cascade pump is used that can deliver a fixed amount of liquid in the micro region, regardless of load resistance or fluid combustibility, it can be used to detect the quality of thin tubes with an inner diameter of 100 μm or less. This can be determined by the pressure generated. In particular, it is possible to judge the finishing condition of capillaries made of fine ceramics such as zirconia (whether there are any clogged parts inside or the average value of the diameter). Moreover, by cutting the material in the length direction and examining the cut pieces using the same method, it is possible to recover good products and identify defective parts. Furthermore, it is possible to determine the characteristics of the fluid as an iso-resistance fluid, such as how much pressure loss will result when a fluid of any viscosity is flowed and how much.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the method and apparatus for inspecting the inner diameter of an extremely small diameter capillary according to the present invention, Fig. 2 is a diagram showing an example of an intelligent cascade pump l, and Fig. 3 is a diagram showing an example of a display on an operation monitor screen. FIG. 1... Intelligent cascade pump, 2...
Capillary, 3...Liquid feeding tank, 4...Medium pressure filter, 5...Press screw, 6...Waste liquid tank. Applicant: Hiki Denshi Co., Ltd. Agent: Patent attorney Ryukichi Abe (4 others) Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A method for inspecting the inner diameter of a micro-diameter capillary by sending a fluid with known viscosity characteristics into the capillary, in which the fluid is compressed and a constant flow rate is sent to the capillary. A method for inspecting the inner diameter of an extremely small diameter capillary, characterized in that the amount of compression is controlled until the pressure is balanced, and the inner diameter is inspected based on the liquid feeding conditions when the liquid feeding pressure is balanced. (2) An apparatus for inspecting the inner diameter of a micro-diameter capillary, which tests the inner diameter by feeding a fluid with known viscosity characteristics into the micro-diameter capillary, which includes a compression means for compressing the fluid, and a compression means for compressing the fluid; A liquid feeding means for feeding the liquid at a flow rate, a pressure detection means for detecting the fluid pressure on the discharge side of the liquid feeding means, and a control parameter of the compression means so that the detected pressure is balanced, and when an equilibrium pressure is obtained. An apparatus for inspecting the inner diameter of a very small diameter capillary, characterized by comprising a control inspection means for inspecting the inner diameter of the capillary based on liquid feeding conditions.