JP5266012B2 - Non-pulsating pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To comply with a wide range of operating conditions, in a nonpulsation pump having a plurality of reciprocating pumps and keeping a combined discharge flow rate obtained by combining the discharge rates of the reciprocating pumps constant. <P>SOLUTION: A plunger 16 for each reciprocating pump 12 performs compensation movement reducing pump chamber volume before a delivery period in order to compensate a reduction in the discharge flow rate caused when delivery is started. If the pump chamber volume is not appropriately compensated by the compensation movement, pulsation is caused in a delivery pipe 34. The pulsation is detected with a pressure sensor 38. Based on the detected pressure, a pressure regulating valve 36 is regulated so that, when the delivery is started, the reduction in the discharge flow rate and the reduced amount of the pump chamber volume through the compensation movement become equal to each other, that is, the pulsation is not caused. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a non-pulsating pump that includes a plurality of reciprocating pumps and that keeps the combined discharge flow rate of each pump constant.

  The reciprocating pump alternately repeats suction and discharge of the handled fluid by reciprocating motion of a reciprocating motion element such as a plunger. Therefore, in the single reciprocating pump, the fluid is discharged with pulsation. In order to eliminate this pulsation, a non-pulsation pump is known in which a plurality of reciprocating pumps are used and the combined discharge flow rate is constant.

  The following Patent Document 1 shows a non-pulsation pump using a diaphragm pump that is two reciprocating pumps. This pump discharges fluid by repeating a period in which only one of the reciprocating pumps discharges the handled fluid and a period in which both the reciprocating pumps discharge simultaneously. In the discharge period of only one side, the reciprocating motion is controlled so that a constant flow rate is discharged. Also, during the discharge period by both reciprocating pumps, the reciprocating motion of both pumps is controlled so that the combined discharge flow rate is constant and equal to the flow rate at the time of only one of them. Is done.

  Further, the pump of Patent Document 1 is configured to compensate for a decrease in flow rate at the beginning of discharge of each reciprocating pump, and further, this compensation amount can be adjusted. The decrease in the flow rate at the beginning of discharge, that is, the decrease in volumetric efficiency, is caused by the air remaining in the fluid when the mechanical drive of the reciprocating motion is transmitted by the working fluid and the residual air in the handling fluid. This is caused by leakage due to the air vent valve, leakage of check valves provided on the suction side and discharge side of the pump, and the like. In the pump of Patent Document 1, the reciprocator is driven and controlled in the direction of discharging the handled fluid before the start of the discharge period. However, at this time, the handling fluid is not actually discharged. The reciprocator before this discharge period is set so as to have a higher discharge amount than the assumed compensation amount. The excess amount of the compensation amount is adjusted so that the working fluid is discharged from the air vent valve and the compensation amount becomes appropriate. The air vent valve is provided with a mechanism for adjusting the amount of the working fluid discharged together with the air, and the discharge amount is adjusted in accordance with the volumetric efficiency that changes according to the operating condition of the pump.

JP-A-8-114177

  The non-pulsating pump described in the above publication uses an air vent valve to adjust the compensation amount, and there is a limit to the adjustable range. There is a need for a compensation adjustment mechanism that can accommodate a wider range of operating conditions.

  The non-pulsating pump according to the present invention is a non-pulsating pump in which the combined discharge flow rate obtained by summing the discharge flow rates of a plurality of reciprocating pumps is constant, and a pressure adjusting mechanism for adjusting the pressure of this pipe is provided on the discharge pipe. It is provided. In each reciprocating pump, in order to compensate for the decrease in the discharge flow rate that occurs at the start of the discharge, a reciprocating motion such as a piston or plunger is performed to reduce the pump chamber volume before the discharge period. ing. The decrease in the discharge flow rate that occurs at the start of discharge mainly varies depending on the back pressure of the non-pulsating pump, that is, the pressure in the discharge pipe. On the contrary, if the pressure in the discharge pipe is constant, the amount of decrease in the discharge flow rate is also constant. Therefore, the compensation movement of the reciprocating motion is set so as to compensate for the decrease in the discharge flow rate under a predetermined pressure, and the decrease in the discharge flow rate is adjusted by adjusting the pressure in the discharge pipe to this predetermined pressure. And the amount of decrease in the pump chamber volume due to the compensating motion can be maintained in a consistent state. The adjustment to the predetermined pressure can be achieved by reducing the fluctuation of the discharge flow rate caused by the excess or deficiency of the reduction amount of the pump chamber volume due to the compensation motion.

  The pressure adjustment mechanism can include a pressure sensor that detects the pressure of the discharge pipe and a pressure adjustment valve that is provided in the discharge pipe and adjusts the opening degree based on the pressure detected by the pressure sensor. By adjusting the opening of the pressure regulating valve, the pressure on the primary side of the pressure regulating valve, that is, the back pressure of the non-pulsating pump is adjusted.

  The pressure adjusting mechanism continuously acquires the pressure of the discharge pipe detected by the pressure sensor for a predetermined period and stores it. From the stored pressure waveform, a control unit is provided for detecting pressure fluctuation corresponding to fluctuations in the discharge flow rate due to excess or deficiency in the reduction amount of the pump chamber volume.

  The pressure adjusting mechanism may have a back pressure valve provided in the discharge pipe. The back pressure valve keeps the pressure upstream of the position where the back pressure valve is attached at a predetermined value, thereby adjusting the back pressure of the non-pulsating pump.

  By adjusting the pressure of the discharge pipe of the non-pulsating pump, the amount of decrease in the discharge flow rate at the start of discharge in each reciprocating pump and the volume of the pump chamber due to the reciprocating motion compensation of the reciprocating element before the discharge period of each reciprocating pump It is possible to maintain such that the amount of decrease is offset. As a result, pulsation is reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of a pulsation pump 10 according to the present embodiment. The non-pulsating pump 10 includes two reciprocating pumps 12A and 12B. These reciprocating pumps 12A and 12B have the same structure, and in the following, when it is not necessary to distinguish between them, description will be made using “12” in which A or B is omitted as a reference. The reciprocating pump 12 includes a cylinder block 14 and a plunger 16 that reciprocates within the cylinder block 14, and further includes a cylinder head 20 that forms a pump chamber 18 that is a closed space together with the cylinder block 14 and the plunger 16. The plunger 16 reciprocates by a cam 24 driven by a motor 22. Due to this reciprocation, the volume of the pump chamber 18 changes, and the handling fluid is sucked and discharged.

  A suction pipe 26 and a discharge pipe 28 are connected to the pump chamber 18, and a suction side check valve 30 and a discharge side check valve 32 are provided in these pipes, respectively. As described above, the reciprocating motion of the plunger 16 controlled by the cam 24 causes a change in the volume of the pump chamber 18. When the volume of the pump chamber 18 increases, the suction-side check valve 30 allows the handled fluid to be sucked into the pump chamber 18, and the discharge-side check valve 32 prevents the reverse flow from the discharge pipe 28. Function. Conversely, when the volume of the pump chamber 18 decreases, the suction side check valve 30 prevents the backflow of the handling fluid to the suction pipe 26, and the discharge side check valve 32 causes the flow of the handling fluid to the discharge pipe 28. Acts to allow.

  The discharge pipes 28A and 28B of the two reciprocating pumps 12A and 12B merge to form one discharge pipe 34, which extends downstream. An injection point where the handling fluid sent out by the pulsating pump 10 is injected downstream is located. The joined discharge pipe 34 is provided with a pressure adjusting valve 36 that can adjust the throttle amount, and the upstream discharge pipe 34 is provided with a pressure sensor 38 that detects the pressure in the pipe. . The value detected by the pressure sensor 38 is sent to the control unit 40 as an output signal, and the control unit 40 adjusts the opening of the pressure regulating valve 36 based on the detected value. The operation of the pressure adjustment mechanism including the pressure adjustment valve 36, the pressure sensor 38, and the control unit 40 will be described in detail later.

  FIG. 2 is a diagram showing the time change of the speed v of the plungers 16A and 16B of the two reciprocating pumps 12A and 12B. The velocity waveforms of the two plungers 16A and 16B are indicated by solid lines and broken lines, respectively, and the shapes are the same except that the phases are shifted by 180 °. If there is no loss in fluid discharge, the plunger speed v is proportional to the discharge flow rate q.

  The movement of each reciprocating pump 12 is a period between a discharge period Pd in which the speed v is positive, a suction period Ps in which the speed v is negative, and a suction period Ps before the discharge period Pd starts. The compensation period Pc is repeated. The discharge period Pd is a period in which the plunger 16 moves into the pump chamber 18 and moves so as to reduce its volume, thereby discharging the handled fluid in the pump chamber 18. Further, the suction period Ps is a period in which the plunger 16 moves backward so as to expand the volume of the pump chamber 18, and the handling fluid is sucked into the pump chamber 18 from the suction pipe 26. The compensation period Pc is a period provided to cope with a decrease in the discharge amount at the initial stage of the discharge period Pd, and the speed of the plunger 16 is positive, but in a properly adjusted state, the handled fluid in this period There is no discharge. The compensation period Pc will be described in detail later.

  The discharge period Pd further includes a single discharge period Pd1 in which only one reciprocating pump 12 discharges the handled fluid and a combined discharge period Pd2 in which the discharges of both pumps 12 are combined. The combined discharge flow rate in the combined discharge period Pd2 matches the discharge flow rate in the single discharge period Pd1. As a result, the combined discharge flow rates of the two reciprocating pumps 12A and 12B are always constant.

  FIG. 3 is a diagram showing details of the speed v of the plunger 16 and the discharge flow rate q of the reciprocating pump 12 corresponding to the plunger 16. When the compensation period Pc is not provided, the speed v of the plunger 16 increases with the start of the discharge period Pd as shown by the solid line, but the actual discharge flow rate q is at the beginning of the discharge period Pd as shown by the broken line. , Including the case of no longer discharging. The decrease in the discharge amount at this time corresponds to the area Ss of the hatched portion in the figure. This decrease is caused by various losses, and may impair the pulsation-free property of the pulsation-free pump 10. Further, the amount of decrease in the discharge amount can be predicted to some extent, but it is difficult to accurately predict it from the operating conditions of the pump, individual pump differences, and the like.

  In order to compensate for the decrease in the discharge amount, the above-described compensation period Pc is provided. At this time, the plunger 16 moves in the advancing direction, and the air in the pump chamber 18, the check in the mechanical drive portion, Pressure is preliminarily applied to the handling fluid so as to fill the loss due to leakage of the valves 30 and 32.

  This movement of the plunger 16 for compensating for the loss (hereinafter referred to as compensation movement) is a movement in the direction of discharging the handled fluid, but at this time, no discharge is performed. The volume of the pump chamber 18 that is reduced by the compensating motion of the plunger 16 at this time corresponds to the area Sc of the trapezoidal portion shown in the drawing. The area Sc of the volume reduction of the pump chamber 18 due to the compensation movement of the plunger is ideally made equal to the area Ss of the reduction amount of the discharge amount due to the loss. However, although it is assumed in advance that the discharge amount is reduced due to loss, the amount (Ss) is actually difficult to estimate at the time of designing the pump, and also varies depending on operating conditions such as the operating pressure of the pump. . The pump chamber volume reduction amount (Sc) due to the compensation movement is given by the movement of the plunger 16, that is, the profile of the cam 24. However, it is troublesome to change this profile later, and it corresponds to the change of the operating condition. It is also difficult to change appropriately.

  Therefore, in the non-pulsating pump of the present embodiment, the operating conditions, in particular, the back pressure of the non-pulsating pump, that is, the pressure in the discharge pipe 34 is set to a predetermined value without changing the dimensions and specifications on the pump side such as the cam profile. Control to keep the value. That is, the pressure in the discharge pipe 34 is adjusted so that the discharge amount reduction amount (Ss) due to loss becomes equal to the pump chamber volume reduction amount (Sc).

  The pressure sensor 38 of the pressure adjustment mechanism detects the pressure in the discharge pipe 34. When the discharge flow rate in the discharge pipe 34 varies, the pressure also varies in the same manner, and the pressure sensor 38 detects this variation and outputs it to the control unit 40. If the amount of decrease in discharge amount due to loss (Ss) is equal to the amount of decrease in pump chamber volume due to compensation motion (Sc), the pressure does not fluctuate, but the pump volume decrease amount (Sc) is the amount of decrease in discharge amount (Ss ), A pulsation in which the pressure increases at the end of the compensation period occurs. FIG. 4 is a graph showing the passage of time of the plunger speed v, the flow rate q, and the pressure p in the discharge pipe 34 when the pump chamber volume reduction amount (Sc) exceeds the discharge amount reduction amount (Ss). In FIG. 4, in order to compare the area corresponding to the initial discharge amount reduction amount (Ss) of the discharge period Pd with the pump chamber volume reduction amount (Sc), a hatched area is shown in the compensation period Pc. . Since the pump chamber volume reduction amount (Sc) is larger than the discharge amount reduction amount (Ss), the fluid is actually discharged at the end of the compensation period Pc. At this time, the combined discharge flow rate q of the two reciprocating pumps has a waveform having a convex portion as shown by a thick solid line in FIG. Further, the pressure p in the discharge pipe 34 also has a pulsation waveform having a convex portion.

  The control unit 40 controls the pressure regulating valve 36 based on the pressure p waveform. That is, when the convex portion Δp which is a pulsation is detected with respect to the value p0 which is the base of the pressure p, the pressure regulating valve 36 is throttled to increase the pressure in the discharge pipe 34 upstream thereof. As the back pressure of the pump increases, the amount of decrease (Ss) in the discharge amount due to loss increases (the area Ss increases). In order to detect pulsation, the control unit 40 stores a pressure waveform for a predetermined period, and detects a base value p0 and a convex portion Δp that becomes pulsation from the stored waveform.

  On the contrary, if the pump volume reduction amount (Sc) is smaller than the discharge amount reduction amount (Ss), the discharge amount decreases at the initial stage of the discharge period Pd, and pulsation in which the pressure decreases in the discharge pipe 34 occurs. FIG. 5 shows this in the same manner as FIG. When the pump volume reduction amount (Sc) is insufficient with respect to the discharge amount reduction amount (Ss), the composite discharge flow rate q is reduced at the beginning of the discharge period Pd. This is a waveform having a recess indicated by a thick solid line in FIG. Similarly, the pressure p in the discharge pipe 34 also has a pulsation waveform having a recess.

  When the control unit 40 detects the pulsation waveform having the concave portion, the control unit 40 opens the pressure adjustment valve 36 and reduces the pressure in the discharge pipe 34. By reducing the back pressure of the pump, the reduction amount (Ss) of the discharge amount due to loss is reduced (the area Ss is reduced). As described above, the pressure in the discharge pipe 34 is adjusted so that the amount of decrease in discharge amount (Ss) due to loss is equal to the amount of decrease in pump chamber volume (Sc) due to compensation motion.

  When the reduction amount (Ss) of the discharge amount is substantially equal to the reduction amount (Sc) of the pump chamber, the reduction amount of the discharge amount for one of the pumps due to the individual difference between the two reciprocating pumps 12A and 12B. (Ss) is large, and the pump chamber volume reduction amount (Sc) may be large for the other pump. In this case, the output of the pressure sensor 38 has a waveform that repeats positive and negative pulsations. When such a waveform is sent out, the control unit 40 determines that the target value is almost controlled, and maintains the throttle amount of the pressure regulating valve 36.

  By providing the pressure adjusting valve 36, the pressure in the discharge pipe 34 on the upstream side, that is, the back pressure of the non-pulsating pump 10 can be set without being affected by the pressure at the downstream side, for example, the injection point. .

  In the above-described embodiment, the opening degree of the pressure adjustment valve 36 is adjusted based on the pressure fluctuation (pulsation) in the discharge pipe 34, but the adjustment is performed based on the average pressure in the discharge pipe 34. Is also possible. Specifically, the output signal of the pressure sensor 38 is sent to the control unit through a low-pass filter for removing pulsation, and the pressure adjustment valve 36 is adjusted so that this value is maintained at a predetermined value. The predetermined value may be, for example, a pressure that is obtained in advance by a test and eliminates pulsation. Further, the pressure in the discharge pipe where the pressure fluctuation becomes small may be obtained at the site and adjusted to this value.

  Further, instead of the above-described pressure adjusting mechanism, a back pressure valve (pressure regulating valve) that keeps the pressure on the primary side (upstream side) constant may be provided. In this case, the back pressure valve is adjusted at the site so that no pulsation occurs, and thereafter the operation is performed in this state.

  Moreover, in the above-described embodiment, the non-pulsating pump configured by two reciprocating pumps is illustrated, but the above-described pressure adjusting mechanism is also applied to the non-pulsating pump configured by three or more reciprocating pumps. It is possible to provide. The plunger or piston is not a reciprocating pump that directly contacts the fluid to be handled, but a diaphragm pump that drives the diaphragm via the working fluid by a plunger or the like, and discharges the fluid to be handled by the reciprocating motion (membrane motion) of the diaphragm. The above-described pressure adjusting mechanism can also be provided in the non-pulsating pump.

It is a figure showing a schematic structure of a pulsation pump of this embodiment. It is a figure which shows the speed of a plunger. It is explanatory drawing about the reduction | decrease of the discharge amount by loss, and compensation of this reduction amount. It is a figure which shows the plunger speed, the discharge flow rate, and the pressure in discharge piping when the reduction amount (Ss) of actual discharge amount is less than the reduction amount (Sc) of the pump chamber volume by compensation movement. It is a figure which shows the plunger speed, the discharge flow rate, and the pressure in discharge piping when the reduction amount (Ss) of actual discharge amount exceeds the reduction amount (Sc) of the pump chamber volume by compensation exercise | movement.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Non-pulsation pump, 12 Reciprocating pump, 14 Cylinder block, 16 Plunger, 18 Pump chamber, 20 Cylinder head, 26 Suction pipe, 28 Discharge pipe, 34 Discharge pipe, 36 Pressure adjustment valve, 38 Pressure sensor, 40 Control part.

Claims (2)

Equipped with multiple reciprocating pumps that draw and discharge fluid by increasing or decreasing the pump chamber volume due to the reciprocating movement, and move the reciprocating elements so that the combined discharge flow rate of each reciprocating pump totals is constant. A non-pulsating pump,
The reciprocating element performs a compensating motion to reduce the pump chamber volume before the discharge period in order to compensate for the decrease in the discharge flow rate that occurs at the start of discharge in each reciprocating pump,
Further, in order to reduce the pulsation of the combined discharge flow rate due to the excess or deficiency of the reduction amount of the pump chamber volume due to the compensation motion, the presence or absence of the pulsation of the combined discharge flow rate is detected, and the combined discharge flow rate temporarily increases. If a convex pulsation is detected, the pressure of the discharge pipe of the non-pulsation pump is raised and maintained.If a concave pulsation where the combined discharge flow rate is temporarily reduced is detected, the pressure of the discharge pipe is lowered. have a pressure adjusting mechanism for maintaining,
The pressure adjustment mechanism includes a pressure sensor that detects the pressure of the discharge pipe, and a pressure adjustment valve that is provided in the discharge pipe and adjusts an opening degree based on the detected pressure.
Non-pulsating pump. The pulsating pump according to claim 1 ,
The pressure adjusting mechanism acquires the detected pressure for a predetermined period, stores the detected pressure, and a pressure corresponding to fluctuations in the discharge flow rate due to excess or deficiency in the reduction amount of the pump chamber volume from the stored pressure waveform Having a control unit for detecting fluctuations,
Non-pulsating pump.

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