JP2976663B2 - Series double plunger pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precision plunger pump used in a liquid chromatograph or the like.

[0002]

2. Description of the Related Art In a liquid chromatograph, a mobile phase must be delivered to a column at a constant speed. At this time, if there is a pulsating flow in the mobile phase, the result of the chromatographic measurement fluctuates, and therefore, a pump with a small pulsation is selected as the pump that sends out the mobile phase. For this reason, a series type double plunger pump is often used in a liquid chromatograph apparatus.

An in-line double plunger pump is composed of a main piston and a sub-piston connected in series between a liquid source and a supply destination, and a main piston provided with front and rear check valves intermittently supplies liquid from the liquid source. Perform the function of sending out
The sub-piston acts to smooth the pulsating flow of liquid delivered by the main piston. As described above, since both pistons need to work in synchronization, each plunger of both pistons is
The position is determined by the main cam and the sub-cam rotated by the two pump motors. The amount of delivery of each piston during one rotation of both cams is shown in the graph of FIG. In the graph of FIG. 4, the horizontal axis represents the rotation angle θ of the cam, and the vertical axis represents the angular differential value dR / dθ of the radius R of the cam, where dR / dθ is the delivery amount of each piston per unit time. Therefore, the following description will be made by equating dR / dθ with the delivery speed.

As described above, since there are check valves before and after the main piston, the dR of the main piston (solid line) in FIG.
The main piston sends out the liquid when / dθ is 0 or more, but does not send out the liquid when dR / dθ is 0 or less. on the other hand,
The sub-piston (dashed line) sends out its own amount of liquid (plus the amount sent from the main piston) when dR / dθ is 0 or more, and from the main piston when dR / dθ is 0 or less. Is absorbed by that amount. for that reason,
In the case of the cam profile shown in FIG. 4, the delivery amount (total delivery speed) of the entire double plunger pump including the main piston and the sub piston is always constant (dashed line).

[0005]

In FIG. 4, the delivery speed of the entire double plunger pump is always constant, but actually, a pulsating flow is generated for the following reasons. That is, at the time when the main piston starts sending liquid (immediately after dR / dθ> 0), the pressure in the main piston is equal to the liquid source and has a low value. Until the pressure differential of the check valve is overcome, the liquid in the main piston is only compressed (pre-compression) and is not delivered to the auxiliary piston.

Another problem with conventional double plunger pumps is that such a pulsating cycle is long. When the cycle of the pulsating flow is short, the pulsating flow is likely to be absorbed by the capacity of the liquid path after the double plunger pump, and noise caused by the pulsating flow is (for example, in an application device such as a liquid chromatograph). The effect of the pulsating flow can be ultimately easily suppressed, for example, by making it easier to electrically remove. However, if the cycle of the pulsating flow is long, such an effect is unlikely to occur, so that the influence of the pulsating flow remains as it is.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to shorten the cycle of a pulsating flow so that the influence of the pulsating flow is finally reduced. It is an object of the present invention to provide an in-line type double plunger pump that can be used.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises a main piston and a sub-piston driven by a main cam and a sub-cam rotated by one drive shaft. In the in-line double plunger pump which sends out a constant flow rate as a whole, the drive shaft is moved in the predetermined angular range within one rotation, in the vicinity of the angular position corresponding to the position where the plunger of the main piston discharges the liquid most. In the reversal section set in (1), there is provided a cam rotation control unit that performs forward rotation and reverse rotation at a speed according to the cam shapes of the main cam and the sub cam.

Here, the main piston is the piston provided on the liquid source side, and has check valves at the front and rear. The auxiliary piston is the piston provided on the delivery destination side,
Does not have a check valve.

[0010]

When the cam shape (radius) of the main cam is RA (θ) and the cam shape (radius) of the sub cam is RB (θ), dRA
The delivery amount F1 of the double plunger pump as a whole while the drive shaft is normally rotated at the speed k1 (θ) in the section of (θ) / dθ> 0 is: F1 = k1 (θ) × h × ｛dRA (θ) / Dθ + dRB (θ) / dθ｝ (1) In this section, when the drive shaft is reversed at the speed k2 (θ) (in this case, dRA (θ) / dθ <0, the main piston does not send out the liquid, and the check valve sends the liquid from the sub-piston. Of the double plunger pump as a whole, F2 = k2 (θ) × h × {−dRB (θ) / dθ} (2) Here, h is a constant determined by the compressibility of the liquid and the delivery pressure.

From the equations (1) and (2), the condition for the output amount F1 during forward rotation and the output amount F2 during reverse rotation to be equal is: k1 (θ) × h × dRA (θ) / dθ + dRB (Θ) /
dθ｝ = k2 (θ) × h × {−dRB (θ) / dθ}. That is, the rotation speed k2 (θ) during reverse rotation is equal to the rotation speed k1 (θ) during normal rotation, and k2 (θ) = k1 (θ) x [× dRA (θ) / dθ + dRB.
By controlling the rotation of the drive shaft by the cam rotation control unit so that (θ) / dθ｝ / ｛− dRB (θ) / dθ｝, it is possible to equalize the output amounts during forward rotation and reverse rotation. In the above description, the section in which the normal rotation and the reverse rotation are performed is the section of dRA (θ) / dθ> 0 (at the time of normal rotation), but the same applies to the section of dRA (θ) / dθ <0 (at the time of normal rotation). By the calculation of (1), the speed ratio can be determined such that the forward and reverse rotation delivery amounts are equal.

Here, when the rotation of the drive shaft is reversed from the reverse rotation to the normal rotation, the delivery of the liquid from the main piston starts.
Although pulsation occurs due to the pre-compression, in the present invention, since the section where the forward rotation and the reverse rotation are performed is smaller than one rotation, the period of the pulsation is reduced, and as described above, the influence can be easily removed. become.

In the section in which the forward rotation and the reverse rotation are performed (reversal section), in order to minimize the amplitude of the pulsation caused by the preliminary compression, the position where the radius RA of the main cam is the maximum (that is, the plunger of the main piston is the liquid (The position at which is most discharged). Further, the angles of the forward rotation and the reverse rotation do not necessarily have to be the same, but are desirably the same in order to effectively remove noise in the electric signal caused by the pulsation.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An in-line double plunger pump according to one embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the double plunger pump according to the present embodiment includes a main piston 10 having check valves 13 and 14 at the front and rear, a sub-piston 20 connected after a check valve 14 on the delivery side, and both pistons 10. , 20 are driven. The driving mechanism includes a main cam 12 and a sub-cam 22 for moving the plungers 11 and 21 of the main and sub-pistons 10 and 20, respectively, a driving shaft 15 common to both the cams 12 and 22, and a motor 16 for rotating the driving shaft 15. A rotation plate 18 for detecting the rotation angle of the drive shaft 15, a position detector 19, and a control device 17 for rotating the motor 16 forward and backward based on signals from the position detector 19.

FIG. 2 shows the cam shapes of the main cam 12 and the sub-cam 22 of the double plunger pump of this embodiment. 2, the cam shape is represented by dR / dθ as in FIG. 4 (hereinafter, the main cam 12 is referred to as dRA / dθ, and the sub cam 22 is referred to as dRB / dθ). In the present embodiment, both the main cam 12 and the sub-cam 22 have a constant speed sending section. Assuming that the rotation speed dθ / dt = v of the drive shaft 15 is constant, in FIG. Sends liquid at dRA / dθ = fA (constant), and the sub cam 22 absorbs liquid at dRB / dθ = fB (constant). Therefore, in this section a, the liquid is delivered at a constant flow rate of the following: f = fA−fB = dRA / dθ−dRB / dθ (3)

Here, the last short section b of the section a (FIG. 2)
In this case, the rotation direction of the drive shaft 15 is reversed in a section from 170 ° to 190 °), and the drive shaft 15 is reversely rotated at the same speed v. At this time, as shown in FIG. 3B, the main cam 12 (broken line) is d
Since RA / dθ <0, no liquid is sent out and the sub cam 22
Only (solid line) delivers liquid at dRB / dθ = fB. For this reason, by setting fB = (１ ／) × fA (4), the forward rotation of this section b is performed at a flow rate of f = fA−fA / 2 = fA / 2 according to Equation (3) (FIG. 3). (A)), at the time of reverse rotation, fB = fA / 2 according to equation (4).
At the flow rate of (= f) (FIG. 3 (b)), the liquid is sent out, and the same flow rate f (= f
A / 2). Therefore, FIG.
As shown in (1), by repeating the forward rotation and the reverse rotation in the reversal section b, the liquid can be delivered at a constant flow rate f and the pulsation cycle can be shortened (the delivery is performed only in the forward rotation). In this case, the pulsation cycle is 360 ° in the rotation angle of the drive shaft 15, but is 40 ° in the present method).

Moreover, the inversion section b is dRA / dθ>
0, that is, the position where the radius RA of the main cam 12 is the largest,
The amount of liquid inside is minimal. For this reason, preliminary compression when the drive shaft 15 reverses from reverse rotation to normal rotation (FIG. 3)
The amplitude of the pulsation caused by (c) also decreases.

In the double plunger pump of the present embodiment, of course, it is also possible to discharge a fixed amount f of liquid by performing normal operation in normal rotation without using such a reversal section b. it can. In this case, there are advantages such that air bubbles entering the piston are easily released and durability of the pump (particularly, the piston) is improved.

[0019]

According to the in-line double plunger pump of the present invention, the period of the normal pulsating flow for each rotation of the drive shaft can be made shorter. For this reason, it becomes easy to electrically remove the noise caused by the pulsating flow (for example, in an application device such as a liquid chromatograph), and finally, the influence of the pulsating flow can be suppressed to a small level. In addition, the amplitude of the pulsating flow can be minimized by setting the section in which the normal rotation and the reverse rotation are performed (reversal section) near the portion of the main piston where the plunger discharges the liquid most. In this case, the pulsating flow is easily absorbed by the capacity of the liquid path after the double plunger pump, and the influence of the pulsating flow of the pump on the measurement result in a liquid chromatograph or the like can be further reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an in-line double plunger pump according to one embodiment of the present invention.

FIG. 2 is a graph showing cam shapes of a main cam and a sub cam of the double plunger pump according to the embodiment.

FIG. 3 is an explanatory diagram showing the sending speeds of the main and sub pistons during forward rotation (a), reverse rotation (b), and continuous forward / reverse rotation operation (c) of the double plunger pump of the embodiment.

FIG. 4 shows a main part of a conventional series double plunger pump;
5 is a graph showing the delivery speed of each sub piston.

[Explanation of symbols]

10 Main piston 20 Sub piston 11, 21 Plunger 12, 22
Main and sub cams 13, 14 ... Check valve 15 ... Drive shaft 16 ... Motor 17 ... Control device

Claims (1)

(57) [Claims] An in-line type double plunger pump comprising a main piston and a sub-piston driven by a main cam and a sub-cam rotated by one drive shaft, respectively, and delivering a constant flow rate as a whole. Axis 1
Within a predetermined angular range within the rotation, within a reversal section set near an angular position corresponding to the position where the plunger of the main piston discharges liquid most, at a speed according to the cam shapes of the main cam and the sub-cam. An in-line type double plunger pump comprising a cam rotation control section that drives forward and reverse rotations.