JP4626270B2 - Liquid feeding device - Google Patents

Description

  The present invention relates to a plunger reciprocating liquid feeding device in which a plurality of plungers reciprocate to feed liquid, for example, a relatively small liquid feeding device, so-called small plunger reciprocating liquid feeding device.

  The plunger reciprocating liquid feeding device includes a driving motor, a plurality of plungers that respectively drive, for example, two pump heads, and a conversion mechanism that converts the rotational motion of the driving motor into the reciprocating motion of the plunger.

FIG. 2 shows the plunger speed characteristics with respect to the cam rotation angle θ in an ideal liquid feeding device having two pump heads.
Reference numeral 1 denotes a plunger speed characteristic of the first pump head. A cam is used as a conversion mechanism for converting the rotation of the drive motor into the reciprocating motion of the plunger. R is the distance from the rotation center of the cam, and dr / dθ on the vertical axis is the constant speed of the drive motor. This is the plunger speed when rotating. The upper side from the horizontal axis is the discharge side, and the lower side is the suction side.

The cam is formed so that dr / dθ is trapezoidal.
In the case of an ideal liquid in which the discharge flow rate of the supplied liquid is proportional to the discharge-side plunger speed, the liquid supply amount, which is the sum of the discharge flow rates of the two pump heads, rotates the drive motor at a constant speed. When this is done, it becomes constant throughout the cam angle as shown by symbol 3 in FIG.

However, in practice, in the first part (discharge start section) where the trapezoidal liquid feeding is performed, the liquid cannot be fed due to the high pressure due to the compressibility of the liquid or the response delay of the check valve, as shown in FIG. Deficient portions 4 and 5 occur in the discharge flow rate and pressure. This becomes a periodically generated pulsating flow, which deteriorates the liquid feeding accuracy.
In order to reduce this pulsating flow, the rotation speed of the drive motor is rotated faster than usual during the discharge start interval.

FIG. 4A shows correction of pulsating flow when liquid is supplied at a high pressure, and FIG. 4B shows correction of pulsating flow when liquid is supplied at a low pressure. a is a pulsating flow when the rotational speed of the cam is constant, b is a rotational speed of the cam for correcting the pulsating flow, and c is a corrected pulsating flow.
Since liquid loss at a higher pressure has a greater pressure deficit, it is necessary to increase the rotational speed of the drive motor as the pressure increases. Therefore, the higher the pressure, the greater the load on the drive motor, and a drive motor with a higher output is required.

  Therefore, as a method for solving the problem, in the case where the drive motor is rotated at a constant speed, the liquid supply amount in the discharge start section of the plunger is more excessive than the liquid supply amount in the other sections. No. 5 is used (see Patent Document 1).

  FIG. 6 shows the conventional pulsating flow correction when the cam shape of FIG. 5 is used, and FIG. 6A shows the pulsating flow correction when liquid is fed with almost no pressure. If the drive motor is rotated at a constant speed, as shown by a, an excessive amount A is generated in the liquid supply amount in the discharge start section. Therefore, when the drive motor is decelerated so that the rotational speed of the cam is decelerated in the discharge start section as shown in b, the liquid supply amount becomes constant as shown in c.

  (B) shows pulsating flow correction when the liquid is fed at a low pressure. When the drive motor is rotated at a constant speed, as shown in a, an excess liquid supply amount A ′ appears in a portion later in time in a section where the cam is corrected so as to supply excessive liquid. Therefore, in order to correct the interval, when the motor rotation speed is reduced as shown in b, the liquid feeding amount becomes constant as shown in c.

(C) shows pulsating flow correction when liquid is fed at a high pressure. In this case, the liquid supply deficit due to the high pressure and the liquid supply excess due to the cam correction are offset, and the liquid supply amount a when the drive motor rotates at a constant speed becomes constant. There is no need to correct the rotational speed b.
Japanese Patent No. 2745526

  The method of making the cam shape so that the amount of liquid delivered in the discharge start section of the plunger is more than the amount of liquid delivered in other sections, and correcting by slowing down the rotational speed of the drive motor is a heavy load on the drive motor. As a result, there is an advantage that a drive motor having a large output is not required.

The present invention relates to an improvement of a cam-shaped liquid feeding device in which the liquid feeding amount in the discharge start section of the plunger becomes excessive from the liquid feeding amount in other sections, and the excess liquid feeding amount due to the cam shape is determined from an ideal curve. It is an object of the present invention to provide a liquid feeding device capable of performing ideal pulsating flow correction at a high pressure and a low pressure without greatly removing it and without applying a load to a driving motor.

The present invention is a liquid feeding device including a driving motor, a plunger for driving a plurality of pump heads, and a conversion mechanism for converting the rotational motion of the driving motor into the reciprocating motion of the plunger, and the cam shape of the conversion mechanism is In any of the plunger discharge start sections, the liquid supply amount at the constant speed rotation of the drive motor is set to a shape that is more than the liquid supply amount in the other sections . In the present invention, the relationship between the liquid supply pressure and the compression completion angle is obtained in advance, and the excess liquid supply in the excessive liquid supply section becomes larger than the compression capacity of the liquid, and the liquid supply amount during constant speed rotation is obtained. When liquid is fed under low pressure where an excess amount appears, the drive motor is operated at a constant speed until the compression completion angle determined in advance under the liquid feed pressure, and after completion of compression, the drive motor is driven according to the excess amount. After decelerating the number of rotations of the motor from that at the time of constant speed rotation, the motor is returned to constant speed rotation again , and the excess liquid supply in the excessive liquid supply section becomes smaller than the compression capacity of the liquid, so When liquid is fed under high pressure where defects appear, the drive motor is driven at a constant speed until the compression completion angle determined in advance under the liquid feeding pressure, and after completion of compression , it is driven according to the missing parts. after accelerated than when constant velocity rotating the rotating speed of use the motor, back to a constant speed rotation again It was a liquid delivery device.

  In addition, when the liquid is fed under pressure where the excess liquid supply in the excess liquid delivery section is close to the compression capacity of the liquid and both the shortage and excess are present in the liquid delivery volume during constant speed rotation, the shortage Accordingly, the rotational speed of the driving motor may be accelerated more than at the time of constant speed rotation, and then the rotational speed of the driving motor may be decelerated from that at the time of constant speed rotation in accordance with an excess amount thereafter.

(Function)
The liquid has compressibility, and the discharge start section of the plunger is not fed until the liquid is compressed to the liquid feeding pressure, so that the liquid feeding amount is lost. The missing portion is compensated with an excess amount based on the cam shape.

When liquid is supplied at a low pressure, if the drive motor is rotated at a constant speed, excess liquid due to the cam shape appears as it is, resulting in excessive liquid supply. Decelerate so that the liquid delivery amount is constant.
In the case where the liquid supply defect is supplied at a high pressure that cannot be compensated for by the excessive amount due to the cam shape, the rotational speed of the cam is accelerated in a section where the defect appears, so that the liquid supply amount becomes constant.
When the liquid supply deficit due to pressure is close to the excess due to the cam shape, a large pulsating flow does not occur even if the drive motor is rotated at a constant speed, but the rotation speed of the drive motor is accelerated according to the cam shape. By subsequently decelerating, the pulsating flow can be removed more precisely.

  In the present invention, the cam shape for reciprocating the plunger is set so that the liquid supply amount at the constant speed rotation of the drive motor in the discharge start section is excessive compared to the liquid supply amount in the other sections, and the low pressure With a low-speed motor, it is ideal for both high and low pressure without greatly deviating the cam shape from the ideal curve. Pulsating flow can be corrected.

FIG. 7 shows an example of a small plunger reciprocating liquid feed pump to which the present invention is applied.
Reference numeral 10 denotes a driving stepping motor, and 11 denotes a cam shaft. The rotation of the stepping motor 10 is transmitted to the cam shaft 11 through the small pulley 12, the belt 13 and the large pulley 14 of the cam shaft 11.

  Two cams 15 and 16 are fixed to the cam shaft 11 to drive two pump heads. A disc 17 is also attached to the cam shaft 11, and a hole 18 is formed in the disc 17. By detecting the hole 18 by a photocoupler 19, the home position of the rotation angle of the cams 15 and 16 is detected. .

The base end of the cross head 20 is in contact with the cam 15, and the cross head 20 reciprocates as the cam 15 rotates. A plunger 21 of the first pump head 24 is attached to the other end of the cross head 20. The base end of the cross head 22 is also in contact with the other cam 16, and the cross head 22 reciprocates as the cam 16 rotates. A plunger 23 of a second pump head 25 is attached to the cross head 22.
The cams 15 and 16 are designed to have an angle-plunger speed characteristic as described later and shown in FIG.

  In the first pump head 24, the liquid 26 is sent to the flow path of the pressure sensor 28 through the suction filter 29 and the inlet block 27 by the reciprocating motion of the plunger 21. Also in the second pump head 25, the liquid 26 is sent to the flow path of the pressure sensor 28 through the suction filter 29 and the inlet block 27 by the reciprocating motion of the plunger 23. In the pump heads 24 and 25, a is an inlet check valve, b is an outlet check valve, and c is a seal member.

The liquid sent out from the first pump head 24 in the flow path of the pressure sensor 28 and the liquid sent out from the second pump head 25 merge and are sent out to the flow path connected to the pump outlet 30. 31 is a drain cleaning, 32 is a waste liquid bottle.
Reference numeral 33 denotes a CPU. A pressure signal from the pressure sensor 28 and a home position detection signal from the photocoupler 19 are sent to the CPU 33, and the CPU 33 controls the rotation speed of the stepping motor 10.

  The shapes of the cams 15 and 16 are determined so that the dr / dθ (plunger speed during constant speed rotation) characteristics with respect to the cam rotation angle θ are as shown in FIG. In FIG. 5, 1a relates to the first pump head and 2a relates to the second pump head.

The cam shape of the dr / dθ characteristic in FIG. 5 is shown below.
0 < θ ≦ 10… r = 15.5 + 0.075 θ ² /294.14062
10 < θ ≦ 25… r = 15.5 + (1.5 θ -7.5) /294.14062
25 < θ ≦ 70… r = 15.5 + (7 θ ² / 180-4 θ /9+605/36)/294.14062
70 < θ ≦ 205… r = 15.5 + (5 θ -173.75) /294.14062
205 <θ ≦ 220 ... r = 15.5 + (- 8 θ 2/90 + 373 θ /9-140735/36)/294.14062
220 <θ ≦ 250 ... r = 15.5 + (- 7 θ 2/180 + 175 θ /9-53615/36)/294.14062
250 < θ ≤300… r = 15.5 + (-0.1255 θ ² +62.75 θ -6902.5) /294.14062
300 < θ ≤340 ... r = 15.5 + (-12.55 θ +4392.5) /294.14062
340 < θ ≤ 360 ... r = 15.5 + (0.31375 θ ² -225.9 θ +4066.2) /294.14062

As shown in FIG. 5, in the section where one plunger starts discharging, if the drive motor is rotated at a constant speed, the sum of the speeds of both plungers becomes larger than the other section, and the liquid is discharged on the discharge side. If the plunger speed is accurately followed, the liquid feed amount 3a becomes excessive as indicated by symbol A in the discharge start section. However, the liquid has a compression coefficient k, and the volume change rate Vp necessary for increasing the pressure of the liquid of volume V by P is:
Vp = k · P · V (1) Typical numerical values of the compression coefficient k include k = 0.45 [GPa ⁻¹ ] for water and k = 1.25 [GPa ⁻¹ ] for methanol.

  FIG. 1 shows the relationship between the rotation angle and the rotation speed of the drive motor at each liquid supply pressure in this embodiment. The discharge starts from the angle A, the liquid is compressed in each pump head, and the liquid feeding amount is lost. Angles C and D are inflection points.

  (1) is a method for correcting the motor speed when the liquid feeding pressure is not so high and the portion up to the angle B is missing. The motor is rotated at a constant speed until the angle B, and after the angle B at which the compression of the liquid is completed, the liquid is fed from both plungers. Therefore, the speed is reduced in accordance with the excess amount, and after the angle D, the rotation returns to the constant speed. .

  (2) is a case where the liquid feeding pressure becomes higher than (1) and the amount of rotation necessary for compressing the liquid requires an angle C or more. In this case, after rotating the motor at a constant speed up to the angle C, the motor speed is accelerated to compensate for the missing portion. After completion of the compression, the liquid is fed from both plungers, so the speed is reduced in accordance with the excess amount, and after the angle D, the rotation returns to a constant speed.

  (3) is a case where the liquid feeding pressure is further increased and the amount of rotation necessary for compressing the liquid requires an angle D or more. In this case, after rotating the motor at a constant speed up to the angle C, the motor speed is accelerated to compensate for the missing portion. In the design of this embodiment, the motor rotation speed at the angle D is twice the rotation speed at the constant speed. After the angle D, when the correction is strictly performed, the acceleration is further accelerated. However, since the section angle is small, especially when the flow velocity is high, the time is very short, so even if the double speed is continued, there is almost no effect on the liquid supply of the defect amount. After the compression is completed, liquid is fed from both plungers, and since there is already no excessive angle due to the cam shape, it returns to constant speed rotation.

  The relationship between the liquid supply pressure and the compression completion angle can be estimated from the compression volume derived from equation (1) based on the volume of the pump head, and there are mechanical factors (check valve response delay and airtightness). It can be obtained by experimentally correcting the mechanical strain due to high pressure. Although the compression coefficient varies depending on the liquid to be fed, correction may be performed using a preset condition or may be automatically obtained by feedback control while monitoring the pressure.

  In this embodiment, it is a parallel-connected plunger type liquid feeding device in which pump heads are connected in parallel, and the acceleration / deceleration pattern of the drive motor is generated twice per one rotation of the motor. As another embodiment, it can also be implemented with a series-connected plunger type liquid feeding device. As a feature of the series connection type, the second pump head is always subjected to liquid feeding pressure, and the liquid feeding liquid is compressed only by the first pump head. Therefore, the acceleration / deceleration pattern of the driving motor is only required once per motor rotation.

  The liquid feeding device of the present invention can be used in an analyzer that requires liquid feeding at a constant flow rate, such as a liquid chromatograph that feeds a mobile phase at a constant flow rate.

It is a figure which shows the pulsating flow correction | amendment under the different pressure in the liquid feeding apparatus of an Example using the cam shown in FIG. It is a figure which shows the relationship between the plunger speed characteristic of an ideal liquid feeding apparatus, and the liquid feeding amount at the time of constant speed rotation. It is a figure which shows the relationship between the discharge flow volume and pressure in an actual liquid feeding apparatus. It is a figure which shows the pulsating flow correction | amendment under a different pressure in the conventional liquid feeding apparatus using the cam shown in FIG. It is a figure which shows the relationship between the plunger speed characteristic of the liquid feeding apparatus which gave the excess part to the cam shape in one Example, and the liquid feeding amount at the time of constant speed rotation. It is a figure which shows the pulsating flow correction | amendment under the different pressure in the conventional liquid sending apparatus using the cam shown in FIG. It is a block diagram of the mechanism part of one Example.

Explanation of symbols

10 Stepping motor 15, 16 Cam 21, 23 Plunger 24, 25 Pump head 33 CPU

Claims (2)

In a liquid feeding device including a driving motor, a plunger that drives each of a plurality of pump heads, and a conversion mechanism that converts a rotational motion of the driving motor into a reciprocating motion of the plunger.
The cam shape of the conversion mechanism is set to a shape in which the liquid feeding amount at the constant speed rotation of the driving motor in any of the discharge start sections of any plunger is more than the liquid feeding amount in the other sections,
The relationship between the liquid supply pressure and the compression completion angle is obtained in advance,
The excess liquid transfer feeding excess in the section is larger than the compression volume of the liquid, wherein the liquid feed when under low pressure that excess appears on feed rate at the time of constant speed rotation, the under the liquid feed pressure previously obtained until completion of compression angle by operating the drive motor at the constant speed rotation, after the rotational speed of the drive motor in accordance with the excess after completion of compression was decelerated than when the constant speed, again Return to the constant speed rotation ,
The excess feed feeding excess with liquid segment is smaller than the compression volume of the liquid, wherein the liquid feed when under high pressure defect content appears on feed rate at the time of constant speed rotation, the under the liquid feed pressure after up to previously obtained compression complete angle and the driving motor is operated at the constant speed rotation, the rotational speed of the drive motor in accordance with the defect content after completion of compression to accelerate than during the constant speed, again Returning to said constant speed rotation, The liquid feeding apparatus characterized by the above-mentioned .   When the liquid is fed under a pressure where the excess of the liquid in the excess liquid feeding section is close to the compression capacity of the liquid and both the shortage and the excess appear in the amount of liquid delivered at constant speed rotation, the shortage The liquid feeding according to claim 1, wherein the number of revolutions of the drive motor is accelerated from that at the time of constant speed rotation and then the number of revolutions of the drive motor is decelerated from that at the time of constant speed rotation in accordance with an excess amount thereafter. apparatus.

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