JP2020016579A - Plunger, pump and liquid analyzer - Google Patents

Abstract

To provide a plunger which is excellent in chemical resistance and unlikely to be deformed by pushing and pulling forces during use and provide a pump having the plunger and a liquid analyzer.SOLUTION: A plunger 1 includes: a first member 2 which is made of alumina and has an outer peripheral surface 2a of an outer diameter and roundness; and a second member 3 which is made of stainless steel and has an insertion hole 3c having an inner peripheral surface 3a of an inner diameter and roundness and a bottom surface 3b located at one end of the inner peripheral surface 3a. The outer peripheral surface 2a is in contact with the inner peripheral surface 3a, and the first member 2 and the second member 3 are fixed to each other.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a plunger used for a pump for a liquid analyzer, a pump having the plunger, and a liquid analyzer.

  2. Description of the Related Art In a liquid analyzer such as a liquid chromatograph, a plunger and a pump for pressurizing and supplying a liquid in which a sample is dissolved are used. The plunger is required to have chemical resistance because it comes into contact with various samples and solvents in the pump. Patent Literature 1 describes a plunger in which a first plunger member made of a material such as sapphire or ceramic and a plunger holder made of a material such as metal or ceramic are fixed.

  A pump used in a liquid analyzer or the like is configured such that when a plunger is deformed due to a deformation of each member constituting the plunger due to a pushing force or a pulling force at the time of use, or a displacement of the fixing of each member, a predetermined discharge is performed. The quantity and discharge pressure cannot be maintained.

  As a method of fixing a plunger member such as sapphire or ceramic to a holder such as a metal, there are methods such as shrink fitting, press fitting, welding, and bonding (Patent Documents 1 and 2), but chemical resistance such as an analysis device is high. In the required applications, adhesion by welding or adhesives raises concerns about chemical resistance or adhesion strength. The design of the ratio of the outer diameter of the convex portion to the inner diameter of the concave portion in shrink fitting and press fitting of the convex ceramic and the concave metal is described in, for example, Patent Documents 3 and 4. The present inventor considered that the insertion hole (recess) on the holder side was used as a bottom having a bottom so as to abut on one end of the plunger member in order to increase the pressing force of the plunger. It was also found that the air in the insertion hole did not easily escape during shrink fitting, and the plunger was easily deformed.

JP-A-10-2280 WO 2015/033398 JP-A-61-40879 JP-A-62-4528

  An object of the present disclosure is to provide a plunger that is excellent in chemical resistance and is not easily deformed by a pushing force or a pulling force during use, and a pump and a liquid analyzer including the plunger.

  The plunger of the present disclosure is made of alumina, has a first member having an outer diameter d1 and an outer peripheral surface having a roundness of c1, and stainless steel, and has an inner diameter d2 having an outer peripheral surface having a circularity of c2 and the inner peripheral surface having a circularity of c2. A second member having an insertion hole having a bottom surface located at one end, wherein the outer peripheral surface is in contact with the inner peripheral surface and the first member and the second member are fixed to each other with a plunger. Therefore, at room temperature and at the time of non-insertion, d1-d2 is 0.1 μm or more and 10.0 μm or less, and either c1 or c2 is 0.2 μm or more, or (d1-d2) / d1 is 0. It is 0.005% or more and 0.5% or less, and either c1 / d1 or c2 / d1 is 0.01% or more. A pump of the present disclosure includes the plunger. A liquid analyzer of the present disclosure includes the pump.

  According to the present disclosure, it is possible to provide a plunger which is excellent in chemical resistance and is not easily deformed by a pushing force or a pulling force during use, and a pump and a liquid analyzer provided with the plunger.

It is the schematic of a liquid chromatograph. It is a schematic sectional drawing of the plunger of this embodiment.

  The plunger 1, the pump 12, and the liquid analyzer 10 of the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic view of a liquid analyzer (liquid chromatograph) 10, FIG. 2A is a schematic sectional view of a plunger 1, FIG. 2B is a schematic sectional view of a first member 2, and FIG. (c) is a schematic sectional view of the second member 3.

  In liquid chromatography, a liquid in which a sample is dissolved (called a mobile phase) is passed through a solid or liquid medium (a column) called a stationary phase, and an analyte is interacted with the stationary phase and the mobile phase ( This is an analysis method in which separation and detection are performed using differences in adsorption, distribution, ion exchange, and size exclusion. An analyzer for performing liquid chromatography is called a liquid chromatograph.

  The liquid chromatograph 10 of the present disclosure includes a storage tank 11, a pump 12, an injector 13, a column 14, a column oven 15, a detector 16, a data processor 17, and a waste liquid tank 18. The mobile phase containing the sample is stored in the storage tank 11. The mobile phase pressurized by the pump 12 is supplied to a column 14 via an injector 13, and a detector 16 detects an analyte. The pump 12 includes a plunger 1, a cylinder (not shown), a check valve (not shown), and the like, and pressurizes and supplies the mobile phase sucked into the cylinder by sliding between the plunger 1 and the cylinder. In particular, in the high-speed, high-resolution liquid chromatograph 10, the pump 12 capable of sending liquid at a high pressure of 100 MPa or more may be used.

  The plunger 1 is made of alumina, has an outer diameter d1, an outer peripheral surface 2a having a roundness c1, a first member 2 having an end surface 2b, and stainless steel, and has an inner diameter d2 and an inner peripheral surface 3a having a circularity c2. And a second member 3 having an insertion hole 3c having a bottom surface 3b located at one end of the inner peripheral surface 3a. Then, the outer peripheral surface 2a is in contact with the inner peripheral surface 3a, and the first member 2 and the second member 3 are fixed to each other. Examples of the fixing method include shrink fitting and press fitting.

  The first member 2 is inserted into the cylinder and comes into direct contact with the mobile phase (solution containing the sample) to pressurize the mobile phase. The second member 3 holds the first member 2 and transmits a pressing force and a pulling force to the first member. Alumina is suitable as a material of the first member 2 that is in direct contact with the mobile phase because it has excellent chemical resistance and a large Young's modulus (that is, hardly deforms). In particular, if the first member 2 is sapphire (single crystal alumina), it is preferable because it is more excellent in chemical resistance and generates less particles.

  The metal is suitable for press-fitting with alumina and fixing by shrink fitting. Among them, stainless steel is excellent in strength and chemical resistance, and is suitable as a material of the second member 3. If the second member 3 is a surface-strengthened stainless steel, it is preferable because it has excellent chemical resistance and is hardly deformed or damaged. Examples of the surface strengthening treatment include, for example, a solid solution diffusion treatment in which solid solution strengthening elements such as carbon and nitrogen are dissolved and diffused, and a corrosion resistant film coating treatment such as a nickel gold plating treatment.

  The plunger 1 is manufactured by inserting the first member 2 into the second member 3 by a method such as press fitting or shrink fitting. In particular, shrink fitting has a large sticking force, and the insertion portion is unlikely to be displaced even by a large pushing force or pulling force.

  If the fixing surface between the first member 2 and the second member 3 is displaced by the pressing force and the pulling force during use (when the plunger 1 slides on the cylinder), the plunger 1 is deformed, and the discharge pressure of the pump and This is a problem because the discharge amount changes. In the plunger 1 of the present disclosure, when not inserted at room temperature, d1−d2 is 0.1 μm or more and 10.0 μm or less, and one of c1 and c2 is 0.2 μm or more. Further, (d1-d2) / d1 is 0.005% or more and 0.5% or less, and either c1 / d1 or c2 / d1 is 0.01% or more. With the above configuration, the fixing force at the time of shrink fitting and press-fitting is increased, and the deformation of the plunger 1 due to the displacement of the fixing surface due to the pressing force and the pulling force at the time of use is less likely to occur. Further, it is easy to insert the first member 2 into the second member 3 when the outer peripheral surface 2a and the inner peripheral surface 3a are brought into contact with each other by a method such as shrink fitting or press fitting. If any of c1 / d1 and c2 / d1 is 0.01% or more, or if any of c1 and c2 is 0.2 μm or more, shrink-fitting and press-fitting work is performed inside the insertion hole 3c. The air easily escapes. Therefore, shrink fitting and press fitting work are easy. That is, it is effective in improving workability and productivity in manufacturing the plunger 1.

  For example, when d1 is 2.00 mm, d2 may be 1.9999 mm to 1.99 mm, and either c1 or c2 may be 0.2 μm or more.

  The outer diameter d1 of the outer peripheral surface 2a is a general micrometer or laser outer diameter measuring machine, the inner diameter d2 of the inner peripheral surface 3a is a general precision pin gauge, and the roundness c1 and c2 are the roundness and cylindrical shape measurement. It can be measured by a machine (for example, RONDCOM54 manufactured by Tokyo Seimitsu Co., Ltd.).

  The first member 2 has an end face 2b on the second member 3 side. When the end surface 2b of the first member 2 is in contact with the bottom surface 3b of the second member 3, the fixing surface does not shift even with a large pressing force, and is suitable for the pump 2 having a large discharge pressure. The end face 2b may be in contact with the bottom face 3b via an adhesive layer made of an adhesive. This is because the end face 2b and the bottom face 3b are separated from the liquid contact part. As the adhesive layer, an anaerobic adhesive is suitable. If any of c1 / d1 and c2 / d1 is 0.01% or more, or if any of c1 and c2 is 0.2 μm or more, shrink-fitting and press-fitting work is performed inside the insertion hole 3c. The air easily escapes. Therefore, the end face 2b and the bottom face 3b are easily brought into contact with each other, and it is easy to secure a predetermined pressing force. Further, if the end face 2b is convex and the bottom face 3b is concave, a fitting effect is produced even with the unevenness of that portion, and a structure in which the adhesion between 2 and 3 is further increased can be obtained.

  It is particularly preferable that c1 is 3.0 μm or less and c2 is 7.0 μm or less. It is particularly preferable that c1 / d1 is 0.15% or less and c2 / d1 is 0.35% or less, because the above-mentioned effects can be more effectively obtained.

  For example, when d1 is 2.00 mm and c1 is 3.0 μm or less and c2 is 7.0 μm or less, c1 / d1 is 0.15% or less and c2 / d1 is 0.35% or less. When c1 is larger than 3 μm and c2 is larger than 7 μm (c1 / d1 is larger than 0.15% and c2 / d1 is larger than 0.35%), the outer peripheral surface 2a and the inner peripheral surface 3a are separated. The contact area decreases, and it is difficult to secure a predetermined pulling force.

  When the connecting portion between the outer peripheral surface 2a and the end surface 2b is chamfered, the first member 2 can be easily inserted into the second member. The chamfer may be, for example, a c-plane of 0.01 to 0.1 mm.

The arithmetic average roughness Ra1 of the outer peripheral surface 2a is preferably not more than 0.01 μm. If the arithmetic average roughness Ra1 of the outer peripheral surface 2a is larger than 0.01 μm, the slidability with the cylinder and the liquid holding property deteriorate, and the contact area between the first member 2 and the second member 3 decreases. (Adhesion is reduced), and the pushing force and the pulling force are easily reduced. The arithmetic average roughness Ra1 of the outer peripheral surface 2a can be measured using a surface roughness / contour shape measuring instrument (for example, SURFCOM 1500SD3, Tokyo Seimitsu Co., Ltd.).

  The arithmetic average roughness Ra2 of the inner peripheral surface 3a is preferably 0.1 μm or more. When the arithmetic average roughness Ra2 of the inner peripheral surface 3a is 0.1 μm or more, a frictional force can be effectively obtained, and a pushing force and a pulling force can be easily secured. The arithmetic average roughness Ra2 of the inner peripheral surface 3a is preferably not more than 1.6 μm. When the arithmetic average roughness Ra2 of the inner peripheral surface 3a is 1.6 μm or less, the contact area between the first member 2 and the second member 3 increases (adhesion increases), and the pushing force and the pulling force are secured. It's easy to do. The arithmetic average roughness Ra2 of the inner peripheral surface 3a can be measured using a surface roughness / contour shape measuring instrument (for example, SURFCOM1500SD3, Tokyo Seimitsu Co., Ltd.).

  Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various changes, improvements, combinations, and the like can be made without departing from the gist of the present disclosure. For example, the first member 2 may be a polycrystalline alumina such as a ceramic, or may include a minute amount of a crystal phase other than alumina. The second member 2 may be made of stainless steel other than SUS316 as long as it can be press-fitted or shrink-fit as described above.

  A plurality of sets of a first member 2 made of sapphire and a second member 3 made of SUS316 stainless steel treated with pionite (registered trademark of Air Water Company) are prepared, and the outer diameter d1 of the outer peripheral surface 2a, the roundness c1, The arithmetic average roughness Ra1, the inner diameter d2 of the inner peripheral surface 3a, the roundness c2, and the arithmetic average roughness Ra2 are processed so as to satisfy the values of the conditions 1 to 9 shown in Table 1, respectively. A plurality of plungers 1 were manufactured by inserting the first member 2 into the second member 3 and shrink-fitting the same while heating the same to a temperature of from 200C to 200C with a hot plate or the like.

  Then, for each of the plungers 1, a compressive stress of about 300 MPa and a tensile stress of about 30 MPaN were applied to measure the amount of deformation. The measurement results are shown in Table 1. As shown in Table 1, under the conditions 1 to 5 according to the embodiment of the present disclosure, the amount of deformation was 2 μm or less in both compression and tension, but in the conditions 7 to 9, the deformation was either compression or tension. The amount became 33 μm or more. In condition 6, the difference (d1-d2) between the diameters of the first member 2 and the second member 3 is large, and both the roundness c1 of the first member 2 and the roundness c2 of the second member 3 are large. Due to its small size, air hardly escaped from the insertion hole 3 at the time of shrink fitting, and press-fitting was not possible.

DESCRIPTION OF SYMBOLS 1 Plunger 2 1st member 2a Outer peripheral surface 2b End surface 3 2nd member 3a Inner peripheral surface 3b Bottom surface 3c Insertion hole 10 Liquid analyzer (liquid chromatograph)
DESCRIPTION OF SYMBOLS 11 Storage tank 12 Pump 13 Injector 14 Column 15 Column oven 16 Detector 17 Data processor 18 Waste liquid tank

Claims (12)

A first member made of alumina, having an outer diameter d1 and an outer peripheral surface having a roundness c1;
A second member made of stainless steel and having an insertion hole having an inner diameter d2, an inner peripheral surface having a circularity of c2, and a bottom surface located at one end of the inner peripheral surface;
A plunger in which the first member and the second member are fixed to each other while the outer peripheral surface is in contact with the inner peripheral surface,
A plunger, wherein (d1-d2) / d1 is 0.005% or more and 0.5% or less and one of c1 / d1 and c2 / d1 is 0.01% or more at normal temperature and when not inserted.   The plunger according to claim 1, wherein c1 / d1 is 0.15% or less and c2 / d1 is 0.35% or less. A first member made of alumina, having an outer diameter d1 and an outer peripheral surface having a roundness c1;
A second member made of stainless steel and having an insertion hole having an inner diameter d2, an inner peripheral surface having a roundness c2 and a bottom surface,
A plunger whose outer peripheral surface is fixed by contacting with the inner peripheral surface,
A plunger, wherein d1-d2 is 0.1 μm or more and 10.0 μm or less and one of c1 and c2 is 0.2 μm or more when not inserted at room temperature.   The plunger according to claim 3, wherein c1 is 3.0 µm or less and c2 is 7.0 µm or less.   The plunger according to claim 1, wherein the first member further has an end face abutting on the bottom surface.   The plunger according to claim 1, further comprising an adhesive layer between the end surface and the bottom surface.   The plunger according to claim 1, wherein the end face is convex, and the bottom face is concave.   The plunger according to any one of claims 1 to 7, wherein the arithmetic average roughness Ra1 of the outer peripheral surface is 0.01 μm or less, and the arithmetic average roughness Ra2 of the inner peripheral surface is 0.1 μm or more.   The plunger according to any one of claims 1 to 8, wherein the first member is made of sapphire.   The plunger according to claim 1, wherein the second member is made of surface-strengthened stainless steel.   A pump provided with the plunger according to claim 1.   A liquid analyzer comprising the pump according to claim 11.

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