JPH07197880A - Plunger type liquid supply pump - Google Patents

Abstract

PURPOSE:To accurately supply liquid without exerting an unreasonable force between a plunger and a seal. CONSTITUTION:Surfaces 46 approximately vertical to the movement direction of a plunger 29 are respectively formed on a plunger holder 28 and the plunger 29. A permanent magnet 44 is embedded at least in one of the surfaces and the other is formed of a magnetic material and in this way, the plunger holder 28 and the plunger 29 are intercoupled at the surfaces 46 by means of a magnetic force. This constitution causes comparatively free movement in a lateral direction of the plunger 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plunger type liquid feed pump used when a precise liquid feed such as a liquid chromatograph is required.

[0002]

2. Description of the Related Art As shown in FIG. 2, a plunger type liquid feed pump has a plunger holder 28 with a cam 14 having a predetermined profile with respect to a rotary shaft (camshaft) 13.
Is moved, and the plunger 29 held by the plunger holder 28 is pushed into the pump chamber 36, whereby liquid is sent. The plunger holder 28 has a return spring 33.
Since it is pressed against the surface of the cam 14 by the cam, even when the cam profile is on the suction side (that is, when the distance from the center of the rotating shaft 13 to the surface of the cam 14 decreases from the maximum point), The plunger holder 28 moves along the cam profile. In addition, pump room 3
Check valves (backflow prevention valves) 35 and 37 are provided on the inlet side and the outlet side of 6, respectively, and a seal (seal for pump chamber) 32 is provided between the plunger 29 and the pump chamber 36. . In FIG. 2, a cleaning chamber 34 for cleaning the surface of the plunger 29 is provided behind the pump chamber seal 32, and a seal (cleaning chamber seal) is also provided between the cleaning chamber 34 and the plunger 29. Three
0 is provided.

[0003]

Since the plunger type liquid feed pump is used when performing very precise liquid feed, the fitting error of each part is suppressed to a very small level, and the pump chamber seal is used. 32 is also a resin high pressure (about 400 kgf / c
m ² ) is used. Therefore, the plunger 29
Needs to reciprocate with extremely high precision, but a mechanism for driving the plunger 29 (pusher 27 described later) is used.
Etc.) is difficult to move with such high precision.

Therefore, in the plunger type liquid feed pump, conventionally, a plunger holder is provided between the plunger 29 and the drive mechanism to absorb an error in the movement of both. An example of a conventional plunger holder is shown in FIG.
It shows in (b). In FIG. 4A, the plunger 29 and the plunger holder 51 are freely connected with a slight play. That is, a large-diameter foot portion 55 is provided on the base side of the plunger 29, and the foot portion 55 is attached to the holder main body 52.
Also, the plunger 29 can be accommodated only in the space formed by the cap 53 (fixed to the holder body 52 with a screw).
And the plunger holder 51 are connected. However, in this type of plunger holder 51, there is a play p in the moving direction of the plunger 29 (if the play p is not provided, the plunger 29 and the plunger holder 28 will be rigidly connected, and the above problem will occur). Precise liquid transfer is not possible. For example, a parallel type double plunger pump, which will be described later in detail, is originally a pump A as shown in FIG.
And two pumps B and B are alternately discharged to discharge a liquid of a constant constant flow rate (A + B). However, if there is a play p as shown in FIG. 4 (a), Plunger 29 on both the suction side and the discharge side
Is delayed, and pulsation occurs in the total flow rate (A + B) as shown in the upper part of FIG. Further, in the case of low-pressure gradient liquid feeding in which plural types of liquids are sequentially switched and sucked and delivered within one cycle, as shown in FIG. 6, the ratio of each liquid (A liquid, B liquid, C liquid) changes. Resulting in.

In the plunger holder 61 shown in FIG. 4B, in order to eliminate such play p, the foot portion 65 of the plunger 29 is held by the pressing coil spring 67.
I am trying to press it against. However, as described above, since the pump chamber seal 32 clamps the plunger 29 with a very strong force, the frictional force between the plunger 29 and the seal 32 is very large. In the suction cycle, the plunger 29 moves against the holder body 62 against such a strong frictional force.
It is necessary to use a very strong coil spring 67 in order to keep it away from the user. However, since the coil spring 67 is not completely axisymmetric due to its structure, when a strong coil spring 67 is used, a force is applied to the plunger 29 in an oblique direction, which hinders the movement of the plunger 29 and shortens the life of the seal 32. Or

The present invention has been made to solve the above problems, and an object of the present invention is to perform accurate liquid feeding without applying an excessive force to the plunger and the seal. The object is to provide a plunger type liquid delivery pump that can be used.

[0007]

SUMMARY OF THE INVENTION In the present invention made to solve the above problems, a plunger connected to a plunger holder is moved by reciprocating the plunger holder along a cam profile by a cam and a return spring. In a plunger type liquid feeding pump that takes in and out of a pump chamber through a seal and sucks and discharges a liquid, the plunger holder and the plunger are provided with surfaces substantially perpendicular to the moving direction of the plunger, and the surface is It is characterized in that it is magnetically connected to the plunger.

[0008]

Since the plunger holder and the plunger are connected to each other by magnetic force on the above-mentioned surface, the plunger holder and the plunger are connected without play in the direction perpendicular to the surface (that is, the moving direction of the plunger), and the pump suction / No suction / discharge error occurs due to the delay of the plunger movement in the discharge stroke. On the other hand, since it can move relatively freely in the direction along the above-mentioned surface, an unreasonable force is not applied between the plunger and the seal.

The "substantially perpendicular to the moving direction of the plunger" provided on the plunger holder and the plunger may be a flat surface, or the plunger holder side may be a concave surface having a large radius of curvature (small curvature). Alternatively, the plunger side may be a combination with the same radius of curvature or a convex surface with a slightly smaller radius of curvature (a slightly larger radius of curvature).

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid chromatographic liquid sending apparatus according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 3, the liquid delivery device of this embodiment uses a so-called parallel type double plunger pump in which two plunger pumps (A) 16 and (B) 17 are arranged in parallel. The two plunger pumps 16 and 17 are respectively driven by two cams 14 and 15 fixed to one cam shaft 13, and alternately inhale the chromatographic mobile phase liquid 23,
It is discharged to a column (not shown) via the pressure sensor 20 and the damper 21. The cam profiles of both cams 14 and 15 are set so that the plunger pumps (A) 16 and (B) 17 inhale and discharge as shown in FIG. In addition,
The liquid delivery apparatus is provided with a CPU 11 that controls the entire operation. The CPU 11 receives a detection signal from a rotation sensor 18 that detects the rotational position of the camshaft 13 and a pressure sensor 20 that detects the pressure of the discharged liquid. Based on this, the rotation of the motor 12 that rotationally drives the camshaft 13 is controlled. Since both plunger pumps 16 and 17 have the same structure, only one plunger pump 16 will be described below.

The plunger pump 16 is composed of a movable portion that reciprocates according to the rotation angle of the cam 14, and a fixed portion that is fixed regardless of this. As shown in FIG.
The stationary part includes a case 25, check valves 35 and 37 on the suction and discharge sides, and the moving part includes the plunger 2
9, a plunger holder 28, a pusher 27 and the like. The moving part and the fixed part are connected by a return spring 33 in the case 25. Plunger 2
9 and the plunger holder 28 are magnetically coupled to each other as described later, and the plunger holder 28 is fixed to the pusher 27. The pusher 27 is slidable only in one direction inside the case 25, and is in contact with the cam 14 by a free roller 26 at one end thereof.

As described above, the pump chamber 36 is provided between the check valves 35 and 37 of the fixed portion, and the plunger 29 is configured to move in and out of the pump chamber 36. A pump chamber seal 32 is provided between the plunger 29 and the pump chamber 36, and a cleaning chamber seal 30 is provided between the plunger and the cleaning chamber 34.

A mechanism for connecting the plunger holder 28 and the plunger 29 will be described with reference to FIG. The plunger holder 28 is composed of a main body 42 and a cap 43 fixed to the main body with screws. A foot portion 45 having a diameter larger than that of the plunger 29 is provided on the base side of the plunger 29 (the side opposite to the pump chamber 36). The foot portion 45 of the plunger 29 is housed in the space provided between the main body portion 42 and the cap 43, and the root-side end portion of the foot portion 45 and the bottom portion of the space contacting the end portion are both the plunger 29. 4 which is perpendicular to the moving direction of the
It is supposed to be 6. A strong permanent magnet 44 (for example, a rare earth magnet or the like) is embedded in this surface 46 of the main body portion 42, while the foot portion 45 of the plunger 29 is made of a magnetic material (iron or the like). The legs 45 may be made of permanent magnets, and the body 42 may be made of a magnetic material, or both may be made of permanent magnets.

As described above, in the liquid delivery apparatus of this embodiment, since the plunger 29 and the plunger holder 28 are connected by a strong magnetic force, there is no play between the plunger holder 28 and the plunger 29 in the moving direction of the plunger 29. 5 and 6 in the combined suction and discharge strokes of the pump.
The suction / discharge error due to the delay of the movement of the plunger 29 as shown in FIG. On the other hand, since the plunger 29 can move relatively freely in the direction along the surface 46, an unreasonable force is not applied between the plunger 29 and the seal (particularly, the pump chamber seal 32), and the plunger 29 can be smoothly moved. Movement is guaranteed and a reduction in the life of the seals 30, 32 is prevented.

[0015]

In the liquid delivery device according to the present invention, since the plunger holder and the plunger are connected by the magnetic force on the surface substantially perpendicular to the moving direction of the plunger, the direction perpendicular to the surface (that is, the plunger). Moving direction)
With regard to (1), the plunger holder and the plunger are connected without any play, and the suction / discharge error due to the movement delay of the plunger does not occur in the suction / discharge stroke of the pump. On the other hand, since it can move relatively freely in the direction along the above-mentioned surface, no unreasonable force is applied between the plunger and the seal,
The smooth movement of the plunger is guaranteed and the reduction of seal life is prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an internal structure of a plunger holder used in a chromatographic liquid sending device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the internal structure of a plunger pump used in the liquid delivery device of the embodiment.

FIG. 3 is a block diagram of the entire liquid delivery device for a chromatograph that is an embodiment of the present invention.

FIG. 4 is a sectional view showing the internal structure of two types of conventional plunger holders.

FIG. 5 is a graph showing the suction / discharge characteristics of a parallel type double plunger pump.

FIG. 6 is a graph showing an example of an inhalation pattern at the time of low pressure gradient liquid transfer.

[Explanation of symbols]

11 ... CPU 12 ... Cam rotation motor 13 ... Cam shaft 14, 15 ... Cam 16, 17 ... Plunger pump 25 ... Case 26 ... Free roller 27 ... Pusher 28 ... Plunger holder 29 ... Plunger 30 ... Cleaning chamber seal 32 ... Pump Chamber seal 33 Return spring 34 Wash chamber 35, 37 Check valve 36 Pump chamber 42 Plunger holder body 43 Cap 44 Permanent magnet 45 Plunger foot

Claims (1)

[Claims] 1. A plunger type in which a plunger connected to the plunger holder is moved in and out of a pump chamber through a seal by reciprocally moving the plunger holder along a cam profile by a cam and a return spring, and sucking and discharging liquid. In the liquid feed pump, the plunger holder and the plunger are provided with respective surfaces substantially perpendicular to the moving direction of the plunger, and the plunger holder and the plunger are connected by magnetic force on the surfaces, and a plunger type liquid feed pump.