JPH09271654A - Liquid mixing apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously perform the mixing/transfer treatment of a plurality of liquids while making an apparatus compact and to prevent the fluctuations of a mixing ratio to perform mixing/transfer with high accuracy. SOLUTION: This liquid mixing apparatus 1 is equipped with an internal gear pump 10 having two suction ports 3, 4 and one emitting port 6 and equipped with a regulation valve 8 altering the open areas of the suction ports 3, 4 to make a transfer ratio alterable, the flow rate detection means 18, 19 respectively arranged on the side of the suction ports 3 and on the side of the emitting port 6 and a control means 21 regulating the regulation valve 8 based on the detection signals of the flow rate detection means 18, 19 to alter the transfer ratio of a plurality of liquids to requlate the transfer/mixing/ transfer ratio of a plurality of the liquids.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid mixing apparatus and method for continuously mixing and transferring a plurality of liquids at a desired ratio in various industries such as the food industry, chemical industry, medical / agricultural cosmetics industry, petrochemical industry and the like. It is about.

[0002]

2. Description of the Related Art Conventionally, as a liquid mixing device for mixing and transferring a plurality of liquids, a stirring tank for stirring and mixing a fixed amount of liquids supplied at a predetermined ratio, and a mixed liquid treated in the stirring tank. Of a batch processing type that is combined with a transfer pump that transfers the liquid to the next process, or a line mixer that pressure-feeds the supplied liquid while stirring and mixing the liquid, and a predetermined ratio of the liquid to be mixed in the line mixer. Various types of continuous treatment type and the like, which are combined with a raw material supply pump for supplying in the above are used.

However, the batch processing type using the agitation tank described above is inconvenient in that the processing can be performed only by the volume unit of the agitation tank, and the processing amount cannot be adjusted to an arbitrary amount. Also, while the raw material is being supplied to the stirring tank,
There is also a problem that the processing takes time because the mixing / transfer processing is interrupted.

On the other hand, the continuous processing type utilizing a line mixer has an advantage that the processing amount can be adjusted to an arbitrary amount and the mixing / transfer processing can be executed without interruption. There is a problem that it is difficult to make the apparatus compact, because the liquid itself needs a certain length or more for stirring and mixing the liquids.
Further, since the mixing ratio of the liquids is set by the discharge amount of each pump that supplies the raw material to the line mixer, there is a problem that it is difficult to finely adjust the mixing ratio.

From this background, therefore, an internal gear having two suction ports and one discharge port and a control valve capable of changing the transfer ratio by changing the opening area of each suction port. A liquid mixing device using a pump was developed.
This liquid mixing device is one in which a raw material tank storing a raw material liquid is connected to each suction port of the internal gear pump, and the internal gear pump is continuously operated to continuously mix and mix. It can be transferred and can be made compact as compared with an apparatus using a line mixer. In addition, the mixing ratio of the raw material liquids supplied to the internal gear pump can be adjusted by the control valve equipped in the internal gear pump.

[0006]

However, in the conventional liquid mixing apparatus using the above-mentioned internal gear pump, the control valve is manually operated by an operation lever or the like externally attached to the internal gear pump. In order to obtain a predetermined mixing ratio in consideration of the viscosity of the suction head and each raw material liquid in each raw material tank, each of the internal gear pumps is operated by operating the control valve before operation. The inflow rate of the raw material liquid is adjusted. However, since the control valve is manually operated, for example, during operation, due to a change in the suction head due to a change in the liquid level in the raw material tank, a change in the viscosity of the raw material liquid due to the influence of temperature, etc. When the inflow ratio of the raw material liquid to each suction port changes and the mixing ratio fluctuates accordingly, the mixing ratio becomes unstable, and there is a possibility that problems such as deterioration of the mixing accuracy may occur.

Therefore, an object of the present invention is to solve the above-mentioned problems, and it is possible to continuously carry out the mixing / transferring process of a plurality of liquids, and at the same time, it is suitable for downsizing of the apparatus.
If the mixing ratio or viscosity of the raw material liquid fluctuates during operation, the position of the control valve can be automatically adjusted to correct the mixing ratio to the initial appropriate value, preventing fluctuations in the mixing ratio. It is an object of the present invention to provide a liquid mixing apparatus and method capable of highly accurate mixing / transferring.

[0008]

The above object of the present invention is to provide a control valve having two suction ports and one discharge port and capable of changing the transfer ratio by changing the opening area of each suction port. Internal gear pump, a flow rate detecting means disposed at at least two positions on each of the suction port side and the discharge port side, and the control valve is adjusted based on a detection signal of the flow rate detecting means, This is achieved by a liquid mixing apparatus that includes a control unit that changes the liquid transfer ratio and that controls the transfer / mixing / transfer ratio of a plurality of liquids.

Further, the above object of the present invention is to provide an inscribed type having two suction ports and one discharge port and having a control valve capable of changing the transfer ratio by changing the opening area of each suction port. A gear pump, a viscosity detecting means disposed on the discharge port side, and a control means for adjusting the adjusting valve based on a detection signal of the viscosity detecting means and changing a transfer ratio of a plurality of liquids, This can also be achieved by a liquid mixing device that performs liquid transfer / mixing / adjustment of the transfer ratio.

Further, the above-mentioned object of the present invention is an inscribed type having two suction ports and one discharge port, and equipped with a control valve capable of changing the transfer ratio by changing the opening area of each suction port. In a liquid mixing method of transferring, mixing, and adjusting a transfer ratio of a plurality of liquids by a gear pump, based on a detection signal of a flow rate detection unit arranged at least at two positions on each of the suction port side and the discharge port side. This is achieved by a liquid mixing method characterized by adjusting the control valve to adjust the transfer ratio of a plurality of liquids.

The above object of the present invention is an inscribed type having two suction ports and one discharge port, and equipped with a control valve capable of changing the transfer ratio by changing the opening area of each suction port. In a liquid mixing method in which a plurality of liquids are transferred, mixed, and the transfer ratio is adjusted by a gear pump, the control valve is adjusted based on a detection signal of a viscosity detection unit arranged on the discharge port side to adjust a predetermined viscosity. This can also be achieved by a liquid mixing method characterized by obtaining a mixed liquid.

According to the above configuration of the present invention, by continuously operating the internal gear pump by the system utilizing the internal gear pump, it is possible to continuously carry out the mixing / transferring process of a plurality of liquids. By controlling the operation of the internal gear pump, the processing amount can be adjusted to an arbitrary amount.

During operation, due to fluctuations in the suction head due to changes in the liquid level in the raw material tank and changes in the viscosity of the raw material liquid due to the effects of temperature, etc., the ratio of the inflow ratio of the raw material liquid to each suction port of the internal gear pump is increased. Is changed, the occurrence of a change in the suction head or a change in the inflow ratio of the raw material liquid due to a change in the viscosity of the raw material liquid is immediately detected by the flow rate detecting means or the viscosity detecting means. Then, the control means for operating the control valve of the internal gear pump based on the detection signals of these detection means automatically adjusts the position of the control valve so as to maintain the original proper mixing ratio.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows a schematic configuration of an embodiment of a liquid mixing apparatus according to the present invention. The liquid mixing apparatus 1 of the present embodiment has two suction ports 3 as shown in the drawing.
Internal gear pump 10 having four and one discharge port 6
And two raw material tanks 15 for storing the raw material liquids 12 and 13 and being connected to the suction ports 3 and 4 of the internal gear pump 10 to supply the raw material liquids 12 and 13 to the suction ports 3 and 4,
16, flow rate detecting means 18 and 19 disposed at two positions on the suction port 3 side and the discharge port 6 side, and the internal gear pump 10 based on the detection signals of the flow rate detecting means 18 and 19. The control means 2 for adjusting the position of the control valve 8 of the above and changing the liquid inflow rate (that is, the transfer rate) from the suction ports 3 and 4.
1 for adjusting the transfer / mixing / transfer ratio of the raw material liquids supplied to the suction ports 3 and 4.

Here, the internal gear pump 10 has a slit in which the raw material liquid can be inserted between the pump casing 23 having the suction ports 3 and 4 and the discharge port 6 and the tooth 25a provided in a ring shape. 25b is formed and is rotatably supported in the pump casing 23; an outer rotation gear 25;
3, a support plate 29 having a crescent-shaped cross section, which is fixedly mounted on the outer ring gear 25 to keep the pinion gear 27 in an eccentric position with respect to the outer ring gear 25, and is movably mounted along the outer periphery of the outer ring gear 25. A control valve 8 whose transfer ratio can be changed by changing the opening areas S ₁ and S ₂ of 3 and 4 and a motor (not shown) for rotationally driving the pinion gear 27 are provided. Utilizing the fact that the meshing amount of the pinion gear 27 and the outer gear 25 changes with the rotation of the pinion gear 27, the raw material liquids 12 and 13 supplied to the suction ports 3 and 4 are sucked, stirred and mixed, Transfer.

A pipeline 31 for guiding the raw material liquid 12 in the raw material tank 15 to the suction port 3 is equipped with an opening / closing valve 33 located upstream of the flow rate detecting means 18. Further, the pipeline 35 that guides the raw material liquid 13 in the raw material tank 16 to the suction port 4 is also equipped with an opening / closing valve 36 that opens and closes the pipeline 35. The mixed liquid discharge conduit 37 connected to the discharge port 6 is equipped with the flow rate detecting means 19 and an opening / closing valve 38 for opening and closing the mixed liquid discharge conduit 37. The mixed liquid discharge conduit 37 is connected to a next process device 39 that performs the next process treatment on the mixed liquid.

In the case of this embodiment, the flow rate detecting means 18 and 19 are both electromagnetic flow meters which detect the flow rate in each pipe line in a non-contact manner and output it to the control means 21. A pressure gauge may be used instead of the flow meter if it is proportional to the hydraulic pressure.

The control means 21 uses a motor, a solenoid, or the like as an actuator to move and adjust the control valve 8 steplessly, and controls the rotation speed of the pinion gear 27. Further, the control means 21 can initialize the position of the control valve 8 to an arbitrary position by an instruction from an input means (not shown) such as a keyboard connected to the control means 21. And the internal gear pump 1
When 0 is operated, the flow rate detecting means 18,
The detected value in 19 is stored, and during the subsequent operation, the detected value in the flow detecting means 18 and 19 is maintained at a constant value (constant range) so that the flow detecting means 18 and 19 are maintained.
The position of the control valve 8 is automatically adjusted on the basis of the detection signal of 1. and the rotation speed of the outer rotation gear 25 is controlled.

Specifically, as shown in FIG. 2, the control means 21 adjusts the position of the control valve 8 and the rotation of the outer rotation gear 25. Before the operation of the internal gear pump 10, the flow rates A and B (initial setting values) of the raw material liquids 12 and 13 and the flow rate Q (initial setting value) at the discharge port 6 are stored (step 101). Then, the above-mentioned flow rate detecting means 18,
Based on the detected value from 19, the actual inflow amount qa into the suction port 3 and the actual discharge amount q from the discharge port 6 are detected, and from these detected values, A / B and q / (q- qa) is compared (step 102), and if A / B is smaller than q / (q-qa) according to the determination result, the control valve 8 is moved to the suction port 3 side, By reducing the opening area of the suction port 3, the suction port 4 is relatively
The amount of inflow from is increased to correct the fluctuation of the flow rate ratio (steps 103 and 104). Similarly, A / B is q /
When it is larger than (q-qa), the control valve 8 is moved to the suction port 4 side to reduce the opening area of the suction port 4, thereby relatively reducing the inflow amount from the suction port 4. Then, the fluctuation of the flow rate is corrected (step 11
0,111). When A / B is equal to q / (q-qa), the position of the control valve 8 is kept as it is,
The current situation is maintained (step 120).

Next, the discharge amount Q by the initial setting,
The magnitude is compared with the actual discharge amount q detected by the flow rate detecting means 19 after the operation (step 130), and Q <q
If so, the increased flow rate is reduced by lowering the rotation of the outer rotation gear 25 (steps 131 and 132).
If Q> q, the rotation of the outer rotation gear 25 is increased to recover the reduced flow rate (steps 140, 14).
1) If Q = q, there is no change in the discharge amount, so the rotation of the outer rotation gear 25 is maintained as it is, and the current state is maintained (step 150).

When the correction of the flow rate ratio and the correction of the discharge amount are completed, the process returns to step 102 and the same processing is repeated again.

In the liquid mixing apparatus 1 described above, by continuously operating the internal gear pump 10 by the method of utilizing the internal gear pump 10, it is possible to continuously carry out the mixing / transferring process of a plurality of liquids. By controlling the operation of the internal gear pump 10, the processing amount can be adjusted to an arbitrary amount.
Further, since the system uses the internal gear pump 10, the device can be made compact as compared with the system using the conventional line mixer.

During operation, the raw material tanks 15 and 16
Due to the fluctuation of the suction head due to the change of the liquid level in the inside and the change of the viscosity of the raw material liquids 12 and 13 due to the influence of temperature and the like, the raw material liquids 12 and 1 to the respective suction ports 3 and 4 of the internal gear pump 10 are changed.
When the inflow ratio of No. 3 changes, those raw material liquids 12,
Immediately after the change of the inflow ratio of 13, the flow rate detecting means 18,
The control means 21 which operates the control valve 8 of the internal gear pump 10 based on the detection signals of the control means 8 and 19 detected by the control means 19 of the control valve 8 maintains the original proper mixing ratio. Adjust the position automatically. Therefore, it is possible to prevent fluctuations in the mixing ratio during operation and perform highly accurate mixing and transfer.

The equipment positions of the flow rate detecting means 18 and 19 are not limited to those in the above embodiment. If it is possible to detect the flow rate at least at two positions on the two suction ports 3, 4 side and the discharge port 6 side, it is possible to detect the variation of the mixing ratio, and the control valve 8 based on the detection signal can be detected. It is possible to return the mixing ratio and the discharge amount to the initial set values by control or control of the rotation speed of the outer gear 25. Therefore, as shown in FIG. 3A, the flow rate detecting means 41 may be provided at two locations on the suction port 4 side and the discharge port 6 side of the internal gear pump 10. As shown in (b), the flow rate detecting means 41 may be provided on each of the two suction ports 3, 4 of the internal gear pump 10, and as shown in FIG. 3 (c). The flow rate detecting means 41 may be provided on all of the two suction ports 3 and 4 and the discharge port 6 side.

Control means 2 in the case of the configuration of FIG.
4 shows the processing in FIG. 1, the processing in the control means 21 in the case of the configuration of FIG. 3B is shown in FIG. 5, the processing in the control means 21 in the case of the configuration of FIG. 3C is shown in FIG. Shown respectively.

When the flow rate detecting means 41 is provided on the suction port 4 side and the discharge port 6 side as shown in FIG. 3 (a), it is the same as in the above embodiment, but as shown in FIG. Before operation of the internal gear pump 10, the flow rates A and B (initial setting values) of the raw material liquids 12 and 13 and the flow rate Q (initial setting value) at the discharge port 6 are stored (step 201). .
Next, based on the detection values from the flow rate detecting means 41, 41, the actual inflow amount qb into the suction port 4 and the actual discharge amount q from the discharge port 6 are detected, and from these detection values, The magnitude relation between A / B and (q-qb) / q is compared (step 202), and if A / B is smaller than (q-qb) / q according to the judgment result, the control valve 8 Is moved toward the suction port 3 to reduce the opening area of the suction port 3, thereby relatively increasing the inflow amount from the suction port 4 and correcting the fluctuation of the flow rate ratio (step 20).
3,204). Similarly, when A / B is larger than (q-qb) / q, the control valve 8 is moved to the suction port 4 side to reduce the opening area of the suction port 4, thereby relatively The amount of inflow from the suction port 4 is reduced to correct the fluctuation of the flow rate ratio (steps 210 and 211). When A / B is equal to (q-qb) / q, the position of the control valve 8 is kept as it is, and the current state is maintained (step 220).

Next, the discharge amount Q by the initial setting,
The size is compared with the actual discharge amount q detected by the flow rate detecting means 41 on the discharge port 6 side after the operation (step 23).
0) and Q <q, the flow rate increased by reducing the rotation of the outer gear 25 is reduced (steps 231, 23).
2) On the other hand, if Q> q, the flow rate reduced by increasing the rotation of the outer gear 25 is restored (step 24).
0, 241) and Q = q, there is no change in the discharge amount, so that the rotation of the outer rotation gear 25 is kept as it is and the current state is maintained (step 250). When the correction of the flow rate and the correction of the discharge amount are completed, step 202
Then, the same processing is repeated again.

As shown in FIG. 3B, the two suction ports 3 and 4 are provided.
When the flow rate detection means 41 is provided in each of the above, as shown in FIG. 5, the flow rates A and B of the raw material liquids 12 and 13 (initial setting values) are set before the operation of the internal gear pump 10.
And the flow rate Q (initial setting value) at the discharge port 6 are stored (step 301). Next, based on the detection values from the above-mentioned flow rate detecting means 41, 41, the actual inflow amounts qa, qb and the discharge amount q into the two suction ports 3, 4 are detected, and from these detection values, A / B and qa / qb are compared in magnitude (step 302), and if A / B is smaller than qa / qb, the control valve 8 is moved to the suction port 3 side according to the result of the determination. By reducing the opening area of the suction port 3, the amount of inflow from the suction port 4 is relatively increased to correct the fluctuation of the flow rate ratio (steps 303 and 304). Similarly, when A / B is larger than qa / qb, the control valve 8 is moved to the suction port 4 side to reduce the opening area of the suction port 4,
Relatively, the amount of inflow from the suction port 4 is reduced to correct the fluctuation of the flow rate ratio (steps 310 and 311).
When A / B is equal to qa / qb, the position of the control valve 8 is kept as it is, and the current state is maintained (step 320).

Next, the discharge amount Q by the initial setting,
The size is compared with the actual discharge amount q detected by the flow rate detecting means 41 on the discharge port 6 side after the operation (step 33).
0), and if Q <q, the flow rate increased by reducing the rotation of the outer gear 25 is reduced (steps 331, 33).
2) On the other hand, if Q> q, the rotation of the outer rotation gear 25 is increased to recover the reduced flow rate (step 34).
0,341) and Q = q, there is no change in the discharge amount, so that the rotation of the outer rotation gear 25 is maintained as it is and the current state is maintained (step 350). When the correction of the flow rate ratio and the correction of the discharge amount are completed, step 302
Then, the same processing is repeated again.

As shown in FIG. 3C, the two suction ports 3 and 4 are provided.
When the flow rate detecting means 41 is provided in each of the discharge port 6 and the discharge port 6, the processing in the control means 21 is as shown in FIG.
It may be similar to the case of (b). However, since the discharge amount q from the discharge port 6 is directly detected by 41, the detected value qa of the flow rate detection unit 41 arranged on the suction port 3 side and the detection value qb of the flow rate detection unit 41 arranged on the suction port 4 side. It becomes unnecessary to obtain the discharge amount q by calculating the sum of

Further, the raw material liquids 12 and 13 to be mixed
However, in the case of liquids having different viscosities, when the mixing ratio changes, the viscosity of the mixed liquid discharged changes accordingly. Therefore, as shown in FIG. 6, instead of the above-described flow rate detecting means, a viscosity detecting means 43 is provided on the discharge port 6 side, and the control means 2 is based on the detection signal of the viscosity detecting means 43.
1 is configured to control the position of the control valve 8 and the rotation speed of the outer rotation gear 25, thereby preventing a change in the mixing ratio during operation,
High precision mixing and transfer can be performed. As the viscosity detecting unit 43, it is preferable to use an in-line viscometer that can directly measure the viscosity of the mixed liquid discharged from the discharge port 6.

When the viscosity detecting means 43 is provided on the discharge port 6 side of the internal gear pump 10 as shown in FIG. 6, the control processing by the control means 21 is as shown in FIG. . However, in this example, the raw material liquid 12 that flows into the suction port 3 is the raw material liquid 13 that flows into the suction port 4.
The viscosity is higher than that. Before the operation of the internal gear pump 10, the desired viscosity η of the mixed liquid is stored as an initial value (step 401). Next, the magnitude relationship between the viscosity ηc sequentially detected by the viscosity detecting means 43 after the operation and the initial value η is compared (step 402), and if η is smaller than ηc according to the determination result, the raw material having high viscosity is obtained. Since it means that the inflow rate of the liquid 12 has increased, the control valve 8 is moved to the suction port 3 side to reduce the opening area of the suction port 3 and thus the suction port 4 is relatively moved.
The amount of inflow from is corrected to correct the fluctuation of viscosity (steps 403 and 404). On the other hand, when η is larger than ηc, it means that the inflow amount on the suction port 4 side has increased. Therefore, the control valve 8 is moved to the suction port 4 side to change the suction port 4 side.
By reducing the opening area of No. 1, the amount of inflow from the suction port 4 is relatively decreased, and the fluctuation of viscosity is corrected (steps 410 and 411). Further, when η is equal to ηc, the position of the control valve 8 is kept as it is, and the current state is maintained (step 420).
Returning to 02, the above processing is repeated.

As described above, by automatically controlling the position of the control valve 8 of the internal gear pump 10, it is possible to prevent the fluctuation of the viscosity of the mixed liquid.

In each of the above-mentioned embodiments, the number of the internal gear pumps 10 is one and two raw material liquids are mixed, but the liquid mixing apparatus and method of the present invention are the same as those described above. The liquid mixing apparatus 1 of the embodiment may be connected in multiple stages to mix and transfer three or more raw material liquids at a desired ratio.

[0035]

According to the liquid mixing apparatus and method of the present invention,
By using the internal gear pump, by continuously operating the internal gear pump, it is possible to continuously carry out mixing and transfer processing of a plurality of liquids, and to control the operation of the internal gear pump. Thus, the processing amount can be adjusted to an arbitrary amount. Further, since the system uses the internal gear pump, the apparatus can be made compact as compared with the system using the conventional line mixer. Then, during operation, the inflow ratio of the raw material liquid to each suction port of the internal gear pump changed due to the fluctuation of the suction head due to the change of the liquid level in the raw material tank and the change of the viscosity of the raw material liquid due to the influence of temperature etc. In this case, the change in the suction head and the change in the inflow ratio of the raw material liquid due to the change in the viscosity of the raw material liquid are immediately detected by the flow rate detection means or the viscosity detection means, and based on the detection signals of these detection means. The control means for operating the control valve of the internal gear pump automatically adjusts the position of the control valve to maintain the original proper mixing ratio.
Therefore, it is possible to prevent fluctuations in the mixing ratio during operation and perform highly accurate mixing and transfer.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a liquid mixing apparatus according to an embodiment of the present invention.

FIG. 2 is an operation explanatory view of the liquid mixing apparatus shown in FIG.

FIG. 3 is an explanatory view of an example of the equipment position of the flow rate detecting means in the liquid mixing apparatus according to the present invention.

FIG. 4 is an operation explanatory diagram in the case of the configuration shown in FIG.

FIG. 5 is an operation explanatory diagram in the case of the configuration shown in FIG.

FIG. 6 is a schematic configuration diagram of a liquid mixing apparatus according to another embodiment of the present invention.

FIG. 7 is an operation explanatory diagram in the case of the configuration shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid mixing device 3,4 Suction port 6 Discharge port 8 Control valve 10 Internal gear pump 12,13 Raw material liquid 15,16 Raw material tank 18,19,41 Flow rate detection means 21 Control means 43 Viscosity detection means

Claims (4)

[Claims] 1. An internal gear pump having two suction ports and one discharge port and having a control valve capable of changing a transfer ratio by changing an opening area of each suction port, and each suction. A flow rate detecting means arranged at least at two positions on the mouth side and the discharge side, and a control means for adjusting the adjusting valve based on a detection signal of the flow rate detecting means and changing a transfer ratio of a plurality of liquids. A liquid mixing device that is equipped and that controls the transfer / mixing / transfer ratio of multiple liquids. 2. An internal gear pump having two suction ports and one discharge port and having a control valve capable of changing a transfer ratio by changing an opening area of each suction port, and the discharge port. And a control unit that adjusts the control valve based on a detection signal of the viscosity detection unit and changes the transfer ratio of a plurality of liquids. Liquid mixing device that adjusts the ratio. 3. An internal gear pump having two suction ports and one discharge port and having a control valve capable of changing a transfer ratio by changing an opening area of each suction port, In a liquid mixing method of adjusting transfer / mixing / transfer ratio, the control valve is adjusted based on a detection signal of a flow rate detection unit disposed at at least two positions on each of the suction port side and the discharge port side, A liquid mixing method comprising adjusting the transfer ratio of a plurality of liquids. 4. An internal gear pump having two suction ports and one discharge port and having a control valve capable of changing a transfer ratio by changing an opening area of each suction port, In a liquid mixing method of adjusting the transfer / mixing / transfer ratio, the adjusting valve is adjusted based on a detection signal of a viscosity detecting means arranged on the discharge port side to obtain a mixed liquid having a predetermined viscosity. And liquid mixing method.