JPH0468473B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic injection volume control system in a differential reciprocating injection pump.

Differential reciprocating injection pumps are economical and excellent injection pumps because the discharge amount of the left and right strokes is always constant, the discharge pressure ratio is always constant, and only one suction valve and one discharge valve are required. .

As an example, a hydraulically driven differential reciprocating injection pump will now be described with reference to FIG. 1.

1 is an electric motor, and when this electric motor 1 is rotated,
The variable discharge oil pump 4 rotates through the connecting shaft 2 and the coupling ring 3, and the hydraulic oil in the oil tank 5 is sucked into the variable discharge oil pump 4 through the suction filter 6 and the suction pipe 7, and is pressurized to become pressurized oil. , a pressure oil pipe 8, a flow meter 9, and a pressure oil pipe 10, and are supplied to the chamber A of the hydraulic cylinder 11, which is the drive side of the injection pump. 12 is a piston, which is located in chamber B of the hydraulic cylinder 11.
The hydraulic oil inside passes through the pipe 13 and is connected to the mechanical four-way valve 1.
4 and returns to the oil tank 5 from the return pipe 15.

16 is a pressure gauge connected to the pressure oil pipe 8 through a gauge pipe 17; 18 is a relief valve;
8 is connected to the pressure oil pipe 8 and the return pipe 15 through a pipe 19 and a return pipe 20, respectively. 21 is pressure oil pipe 1
a branch pipe connecting 0 and the mechanical four-way valve 14;
22 is a piston rod of the piston 12, 23 is a cam ring integrated with the piston rod 22, 24,
25 is a cam portion provided on both sides of the connecting rod 26, and 27 is a connecting rod that is integrated with the mechanical four-way valve 14 and the connecting rod 26.

Further, 28 is the injection side cylinder of the injection pump, 29 is its piston, and 30 is the piston rod of the piston. This piston rod 30 is integrated with the cam ring 23, so the piston 29 moves together with the piston 12. It's becoming like that. 31 is a suction valve, 32 is a hopper containing a solution to be injected, 33 is a suction pipe connecting the hopper 32 and the suction valve 31, 34 is a discharge valve, and 35 is a discharge pipe. When the piston 29 moves to the right, the hopper 32
The solution in the chamber is sucked into the chamber C of the cylinder 28 through the suction pipe 33 and the suction valve 31, and the solution in the chamber D is sent through the discharge pipe 35 to the point where it is to be injected. When the solution is moved to the left, half of the solution in the chamber C passes through the discharge valve 34 and the discharge pipe 35 to the point to be injected, while the other half is sucked into the chamber D of the cylinder 28. There is.

An example of a differential reciprocating injection pump is constructed as described above, and the cross-sectional area of the piston 12 is E.
If cm ² , the cross-sectional area of the piston rod 22 is 1/2
The diameter of each piston rod is determined so that if the cross-sectional area of the piston ²⁹ is ^Fcm2 , then the cross-sectional area of the piston rod 30 is 1/ ^2Fcm2 . In this way, when the hydraulic cylinder 11 side moves in the stroke direction of the solid line arrow, the hydraulic pressure loss in the pipe 13, mechanical four-way valve 14, and return pipe 15 is made zero, and the hydraulic pressure in the chamber A section is reduced to PKg/cm. ² , piston 12
The force WR applied to move the chamber to the right is WR=P×E/2.Similarly, in the case of left stroke, as is clear from Figure 1, the hydraulic oil pressure in both chambers A and B is PKg/cm. ² comes into play. Therefore, as mentioned above, the piston 12
The force WL acting on the piston 12 becomes WL=(E-E/2)P=P×E/2, and since WR=WL, the forces acting on the left and right strokes of the piston 12 are exactly the same.
Similarly, the required oil amount VL for left and right strokes,
Looking at VR, if the stroke length is Lcm, then for the right stroke, VR=(E-E/2)L=(E×L)/2cm ³ For the left stroke, VL=(E×L)/2cm ³ The amount of oil required for the left and right strokes is exactly the same.

From the above, it is clear that the reciprocating stroke on the hydraulic cylinder 11 side is performed continuously with the same force and at the same speed.

Similarly, regarding the cylinder 28 on the injection side, the cross-sectional area of the piston rod 30 is 1/2 that of the piston 29, so when the piston 29 moves to the right, the solution in the chamber D flows through the discharge pipe 35. The solution in the hopper 32 is injected into the inlet via an injection hose connected to its tip, but in this case, the volume of the chamber C increases, resulting in low pressure, the discharge valve 34 is closed, the suction valve 31 is opened, and the solution in the hopper 32 is injected into the inlet. is suction pipe 3
3. It passes through the suction valve 31 and is sucked into the chamber C.

In addition, in the left stroke, the pressure in the chamber C increases, the suction valve 31 closes and the discharge valve 34 opens, and the solution is discharged into the discharge pipe 35. On the other hand, the volume of the chamber D increases, so the discharge pipe 35 Half of the solution is returned to chamber D, and the other half is sent from the discharge pipe 35 to the point where it is to be injected.

As mentioned above, since the cross-sectional area of the piston rod 30 is 1/2 of the cross-sectional area of the piston 29, the discharge amount in the left and right strokes and the working discharge pressure per unit area are exactly the same, as on the hydraulic cylinder 11 side. Therefore, the discharge amount is the same for the left and right strokes,
This makes it possible to maintain the discharge pressure.

When pressure oil is supplied to the chamber A, the piston 12 and the cam ring 23 move in the direction of the solid arrow, and the piston 12 moves toward the hydraulic cylinder 11.
Immediately before reaching the end of the stroke, it collides with the cam portion 24, the mechanical four-way valve 14 is switched, and the pressure oil is also supplied to the chamber B through the branch pipe 21, the mechanical four-way valve 14, and the pipe 13. Since the area of pressure oil acting on the piston 12 on the chamber A side is smaller by the cross-sectional area of the piston rod 22, the piston 12 and the cam ring 23 move in the direction of the dotted arrow, and the hydraulic cylinder 1
Immediately before the first piston 12 reaches the stroke end, the cam ring 23 reaches the cam portion 25, the mechanical four-way valve 14 returns to the illustrated position, and the piston 12 moves again in the direction of the solid line arrow. That is, the piston 1 is moved by the pressure oil supplied from the variable discharge amount oil pump 4.
2 and 29 continuously reciprocate.

Therefore, although theoretically the reciprocating movement of the pistons 12 and 29 would send a fixed amount of solution from the discharge pipe 35 to the location where it is to be injected, in reality this does not work as theoretically.

[Problem to be solved by the invention] That is, the cross-sectional area of the piston 12 is Ecm ² , and the piston 2 is
The cross-sectional area of 9 is Fcm ² , and the discharge amount of the oil pump is Q ₀ /
min, and the discharge amount on the injection pump side is Q/min, then Q=Q ₀ ×F/E, and if the specific gravity of the solution is γ and the weight change of the injected solution per minute is XmKg, then Xm=Qγ = (Q ₀ × F/E) γ Therefore, if the specific gravity of the solution is constant, the measured value of the oil pump discharge amount Q ₀ can be taken into the controller as appropriate, and the measured value Q ₀ will always be a constant value. It may be possible to achieve good control if the oil pump is controlled so that the following conditions occur; however, this method is unfavorable in the following respects.

That is, first, on the hydraulic cylinder side, there are detection errors of the flow meter 9 and changes in the amount of leakage from small gaps due to pressure changes in the hydraulic oil of the piston 12, mechanical four-way valve 14, etc. , due to changes in efficiency due to wear of the suction valve 31, discharge valve 34, piston 29, etc., and changes in efficiency with respect to the suction speed of the injection cylinder, the relationship Xm = (Q ₀ × F / E) γ is always accurately maintained. This is because it is impossible to maintain

Furthermore, looking at the injection cylinder side, in the right stroke of the piston 29, the solution is sucked into the chamber C, but in the left stroke, the solution in the hopper 32 is not sucked at all.

The state of the suction stroke on the injection cylinder side is as shown in FIG _. The time required for one reciprocating stroke of the piston in , X ₀ is the change in weight of the hopper 33 during this one reciprocating stroke, that is, the suction amount and injection amount of the injection pump in one reciprocating stroke time t ₀ by the cylinder.

As is clear from this figure, in one reciprocating stroke t ₀ , suction is not performed in the first half t ₀ /2 hours, so there is no change in the hopper weight X, and in the second half
Although the hopper weight changes by X ₀ only in t ₀ /2 hours, the injection by the injection cylinder continues without interruption.

Generally, the sampling period of the controller is 0.2
Therefore, if the time t ₀ required for one reciprocating stroke of the piston in the injection cylinder is extremely long, for example, several _tens of seconds, even if the change in In controlling the drive cylinder, the speed at which the drive cylinder follows the control must be extremely slow, making it difficult to perform good automatic control.

[Means for Solving the Problems] The present invention has been made for the purpose of solving the problems of the prior art as described above, and has a configuration in which the suction side of the injection cylinder is A hopper containing a solution to be injected into the injection pump is provided so that its weight can be detected, and a flow rate detector or a speed detector is provided on the drive side of the pump by the hydraulic cylinder. A controller is provided that allows the time of the reciprocating stroke and the injection amount at that time to be set as a reference time and the reference injection amount, respectively, and the controller allows the time of the reciprocating stroke and the injection amount at the reference time to be set by the controller. The amount of change in the weight of the hopper and the flow rate of pressure oil in the hydraulic cylinder or the stroke length of the hydraulic cylinder are detected, and the proportional ratio between the two is determined from the detected flow rate or stroke length and the amount of change in the weight of the hopper. The flow rate or stroke length of the pressure oil of the hydraulic cylinder per unit time, which is determined as a weight change with respect to the oil flow rate or stroke length, and is detected and calculated at the time point when the reference time of the next reciprocating stroke of the injection pump has elapsed; The expected injection amount of the injection pump is calculated by multiplying by the proportional ratio, and this calculated value is compared with the injection amount preset in the controller.The flow rate or oil pressure of the pressure oil on the drive side of the injection pump is determined by the control signal obtained. This system is characterized in that the injection amount of the injection pump is controlled by controlling the stroke speed of the cylinder.

[Function] That is, the present invention provides a differential reciprocating injection pump with a hopper capable of detecting weight on the suction side of the injection cylinder, and a flow rate detector or speed detector on the drive side of the hydraulic cylinder or the like that drives the pump. In addition, a controller is provided that can set the reference time for one reciprocating stroke of the infusion pump and the reference injection amount during that time, and when the cylinder of the infusion pump actually makes one reciprocating stroke, the reference time elapses in this stroke. At the same time, the change in the weight of the hopper during this reference time and the flow rate of the pressure oil of the hydraulic cylinder or the average speed of the piston rod during the reciprocating stroke during this period are detected, and the change in weight of the hopper during the reference time during the one reciprocating stroke is detected. and the hydraulic cylinder flow rate or average speed, and assuming that the next reciprocating stroke takes the same time as the above one reciprocating stroke, the oil pump flow rate or The pressure oil side of the current hydraulic cylinder is calculated based on the average speed of the piston, the value obtained by multiplying this value by the proportional ratio (estimated injection amount), and the standard injection amount that is set in advance as a target value in the controller. This control is then performed for each stroke in order to make the injection amount constant in each stroke of the infusion pump.

[Example] Next, an example of the implementation of the present invention will be described with respect to the above-mentioned hydraulically driven differential reciprocating injection pump.

In FIG. 1, 36 is a variable discharge amount oil pump 4.
37 is a detection end of the flow meter 9; 38 is a load cell for measuring the weight of the hopper 32; 39 is a detection end of the load cell 38;
0 is connected to the connecting rod 27, and the mechanical four-way valve 1
A switch 41 is turned on and off by switching left and right at 4. A controller 41 has a built-in microcomputer, a timer, etc. The signal from the detection end 37 of the flowmeter 9 is sent from the detection end 39 of the load cell 38 via a signal cable 42. The signal is signal cable 43
In addition, the ON and OFF signals of the switch 40 are input to the controller 41 through a signal cable 44, while the output signal output from the controller 41 is input to the electro-hydraulic servo device through a signal cable 45. 36.

As mentioned above, the controller 41 has a built-in microcomputer, a timer, etc., and the timer uses the ON/OFF state of the switch 40 by switching the mechanical four-way valve 14 to turn the switch 40 ON or OFF. The time from the moment when it is turned OFF until it is turned ON again, that is, the time required for one actual reciprocating stroke of the piston 12 of the hydraulic cylinder 11 on the driving side, can be measured as the measurement time t.

Further, in the microcomputer, the reference time t ₀ set for measuring the time of one reciprocating stroke of the piston 12 and the target injection amount of the injection pump during that period are set in advance as the reference injection amount X ₀ . and,
Round trip time t measured in actual round trip
is larger than the set reference time _t0 , the measurement time is set to _t0 , and the amount of weight change _ΔX0 of the hopper ₃₂ during this time t0 is transmitted from the detection end 39 of the load cell 38 via the signal cable 43. The input is integrated and calculated, and at the same time, the detection end 37 of the flowmeter 9
The flow rate ΔQ ₀ of the oil pump 4 at the above measured time t ₀ is calculated by integrating the inputs coming through the signal cable 42 from the above, and the amount of weight change ΔX ₀ of the hopper 32 measured at the above measured time t ₀ is calculated. From the flow rate ΔQ ₀ of the oil pump 4 and the proportional ratio between the two as a constant K, the constant K=ΔX ₀ /ΔQ ₀ in this stroke is obtained. The constant K indicates the change in weight of the hopper with respect to the flow rate of the oil pump at time t ₀ measured in the above-mentioned one stroke.

Therefore, during the current reciprocating stroke, the outflow amount Δq of the oil pump 4 at the time when the stroke time t ₀ has elapsed is determined by calculating the input of the signal cable 42 from the detection end 37 of the flow meter 9 in the controller 41, The flow rate Δq of this oil pump is multiplied by the proportional constant K to calculate the injection amount ΔX expected at the current level as the expected injection amount, and this value ΔX is the reference injection amount of the controller 41 set in advance as a target value.
A comparison calculation is made with X ₀ , and a control output formed from the calculation result is applied to the electro-hydraulic servo device 36 via a signal cable 45 to automatically control the flow rate of the variable discharge oil pump 4 .

That is, in the present invention, during the current reciprocating stroke, the flow rate of the oil pump 4 until time t ₀ elapses is determined,
This value is multiplied by the proportionality constant K obtained from the weight change of the hopper 32 and the flow rate of the oil pump 4 determined in the previous reciprocating stroke to calculate the expected injection amount of the injection pump in the current reciprocating stroke. The calculated expected injection amount is compared with a reference injection amount set as a target value in the controller to control the injection amount of the infusion pump during the current reciprocating stroke.

In other words, in the present invention, assuming that the operating state of the previous reciprocating stroke is maintained even in the current reciprocating stroke, the current flow rate of the oil pump 4 when the stroke time t ₀ has elapsed during the current reciprocating stroke is Calculate the estimated amount of injection that will be injected by the injection pump at that time, and if the calculated expected amount does not match the preset standard injection amount, adjust the flow rate of the oil pump 4. It is designed to be automatically controlled during the current round trip.

In particular, the present invention solves the problem that when one reciprocating stroke is long, if the injection amount is controlled each time after waiting for the end of that stroke, the follow-up speed will be delayed, and the weight of the hopper 32 on the injection cylinder side will be reduced during one reciprocating stroke. The point that does not change in half of the strokes, i.e., the suction of solution by the injection cylinder 28 does not occur in the left stroke of the injection cylinder 28 in FIG. This solves the problem that it is difficult to calculate only from the weight change amount of 32.

Note that even if the measured time t of one reciprocating stroke of the piston 12 is smaller than the set time t ₀ , it can be controlled by the above method, but here, the weight change amount ΔX ₀ of the hopper 32 in the one reciprocating stroke time t of the piston 12 , that is, the injection amount calculated from the input signal from the detection end 39 of the load cell 38 and the controller 41
The control output is directly compared with the set injection amount X ₀ set to X 0, and the control output is sent to the electro-hydraulic servo device 36 via a signal cable 45 to control the oil discharge amount of the variable discharge oil pump 4 so that the injection amount is always the set value. can be controlled to match.

The reason for this is that when the speed of one reciprocating stroke is fast, for example within 10 seconds, control is performed by calculating the difference between the injection amount between the previous stroke and the current stroke while comparing it with the injection amount set in the controller 41. This is because the following speed is sufficient and smooth control is possible. but,
If the stroke speed is slow, comparing the injection amount set in the controller 41 with the injection amount of the previous step after the current process is completed, and controlling based on the difference, the follow-up speed will also become slower. It also becomes difficult to do it smoothly.

In the above embodiment, the hydraulic cylinder driven by the oil pump 4 is used as the drive source, and the proportionality constant K is calculated using the discharge amount detected by the flowmeter as K=ΔX ₀ /ΔQ ₀ . However, apart from this, for example, the average velocity ΔV ₀ of the left and right strokes of the piston rods 22 and 30 of the hydraulic cylinder or injection cylinder is detected, and this and the above variation ΔX ₀ are detected.
A proportionality constant K' indicating the injection amount per unit stroke length obtained from the above may be used in the calculation.
In addition, even in a variable displacement differential piston pump that uses an electric motor to vary the rotational speed of a crank reciprocating piston differential pump rather than a hydraulic drive system, the average rotational speed of the crank during one reciprocating stroke of the injection cylinder It is also possible to calculate the proportionality constant K'' that indicates the injection amount per unit rotational speed (angle) from the change in hopper weight and use it as described above.In other words, the reciprocating differential piston of each drive method It goes without saying that this method is effective for automatically controlling the injection amount using the suction side weight measurement method when the one-stroke speed is slow.

[Effects of the Invention] By adopting the automatic control method as described above, regardless of the length of one round trip time, the previous one is always adjusted based on the weight change amount of the hopper 32.
Calculate the proportional constant K in the reciprocating stroke, calculate the flow rate of pressure oil detected during the current stroke, and multiply the total flow rate of the oil pump in the current stroke by the proportional constant K. The injection amount of the injection pump is compared with the reference injection amount that is set in advance as a target value in the controller, and the oil pump is controlled based on the comparison result. , it is possible to control the injection amount very accurately and with very fast follow-up speed. Therefore, it is possible to control the amount of pressure oil leakage depending on the pressure change on the drive side, the amount of leakage depending on the oil temperature, or the injection amount. Even if a factor that changes the injection amount occurs, such as a change in the volumetric efficiency of the pump, or the factor fluctuates, it is possible to always accurately respond and control a predetermined injection amount by the injection pump.

Therefore, the method of the present invention is suitable as an automatic control method for the injection amount in a differential reciprocating infusion pump.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an example of the method of the present invention, and FIG. 2 is a diagram showing a suction stroke state on the injection pump side. 1...Electric motor, 4...Variable discharge amount oil pump, 5
... Oil tank, 7 ... Suction pipe, 8 ... Pressure oil pipe, 9 ...
Flowmeter, 11... Hydraulic cylinder, 12... Piston, 14... Mechanical four-way valve, 16... Pressure gauge, 22... Piston rod, 23... Cam ring, 24, 25... Cam portion, 26, 27... Connecting rod, 28... Injection side cylinder, 29... Piston, 30... Piston rod, 31... Suction valve,
32...Hopper, 33...Suction pipe, 34...Suction valve, 35...Discharge pipe, 36...Electrohydraulic servo device, 37...Detection end of flow meter, 38...Load cell, 39...Load cell Detection end, 40... Switch, 41... Controller, 42, 43, 4
4,45...signal cable.

Claims (1)

[Claims] 1. In a differential reciprocating injection pump, a hopper containing a solution to be injected is provided on the suction side of the injection cylinder so that its weight can be detected, and a flow rate detector is provided on the drive side of the pump by the hydraulic cylinder,
A controller is installed which has a built-in microcomputer, timer, etc., and is capable of setting the time of one reciprocating stroke of the infusion pump and the injection amount in that time as the reference time and reference injection amount in the reference stroke, During the reciprocating stroke, the controller detects the amount of change in the weight of the hopper and the flow rate of pressure oil in the hydraulic cylinder at the time point when the reference time has elapsed, and calculates the proportional ratio of both from the detected flow rate and the amount of change in the weight of the hopper. The proportional ratio is determined as a weight change with respect to the flow rate of pressure oil in the cylinder at a reference time, and the proportional ratio is calculated to the flow rate of pressure oil in the hydraulic cylinder, which is detected and calculated at the time point when the reference time elapses in the next one reciprocating stroke of the injection pump. The expected injection amount of the injection pump is calculated by multiplying the injection amount, and this calculated value is compared with a reference injection amount set in advance in the controller, and the flow rate of the pressure oil on the drive side of the injection pump is controlled by the control signal obtained. An automatic injection volume control system in a differential reciprocating injection pump characterized by controlling the injection volume of the injection pump.