JP4149831B2 - Multi-component mixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-component mixing apparatus that mixes a large number of liquids at a constant mixing ratio, such as a two-component coating apparatus that mixes and sprays a main agent and a curing agent.
[0002]
[Problems to be solved by the invention]
For example, in a two-component coating apparatus that mixes and sprays a main agent and a curing agent at a predetermined ratio, there is one that uses a plunger pump as a main agent pump and a curing agent pump. FIG. 6 shows a configuration of a plunger pump. The plunger pump 1 includes a cylinder 4 including a pump body 2 and a cylinder body 3 screwed into a lower portion of the pump body 2. A discharge port 5 is provided at a side portion of the pump body 2, and a suction port 6 is provided at a lower portion of the cylinder body 3.
[0003]
A piston rod 7 is inserted into the pump body 3 through a packing 8 so as to be airtight and slidable. A piston 9 that is inserted in the cylinder body 4 in an airtight and slidable manner is provided below the piston rod 7. A first check valve 10 is provided between the piston 9 and the piston rod 7. The suction port 6 is provided with a second check valve 11.
[0004]
In the plunger pump 1 configured as described above, when the piston rod 7 is pushed into the cylinder 4 and the piston 9 is lowered, the second check valve 11 is closed and the first check valve 10 is opened. As the liquid in the cylinder 4 is discharged from the discharge port 5, a part of the liquid is stored in the space above the piston 9 in the cylinder 4. On the other hand, when the piston rod 7 is retracted and the piston 9 is raised, the second check valve 11 is opened, and the liquid is sucked into the cylinder 4 from the suction port 6 and the first check valve 10 is closed. Thus, the liquid stored in the upper part of the piston 9 is discharged from the discharge port 5. That is, the plunger pump 1 is configured to discharge liquid in both steps of lowering and rising of the piston 9.
[0005]
In a two-component coating device, the check valve of one or both of the plunger pump for the main agent and the hardener is clogged with foreign matter, or the valve ball or valve seat constituting the check valve is damaged, resulting in poor seating. When it occurs, there is a problem that the discharge pressure is lowered and the mixing ratio of the main agent and the curing agent is lost.
[0006]
Therefore, a pressure sensor is provided in each supply path for supplying the main agent and curing agent discharged from both pumps to the mixer, and the discharge pressure of each pump is monitored, thereby detecting the occurrence of a sheet defect. Is considered.
[0007]
However, due to the structure of the plunger pump, the discharge pressure pulsates as the piston reciprocates. Moreover, when a sheet failure occurs, the minimum value of the discharge pressure decreases, or the time until the minimum value does not change but the minimum value changes to the maximum value becomes longer (in other words, the decreased discharge pressure The rise is delayed). For this reason, it is difficult to detect a sheet defect only by comparing the absolute value of the discharge pressure with a standard value.
[0008]
This invention is made | formed in view of the said situation, The objective is to provide the multi-liquid mixing apparatus which can detect generation | occurrence | production of the sheet | seat defect in a plunger pump reliably.
[0009]
[Means for Solving the Problems]
A multi-liquid mixing apparatus according to a first aspect of the present invention includes a piston rod that is connected to an output shaft of an air motor and can reciprocate in a cylinder, and a check valve that is opened and closed as the piston rod reciprocates. A plurality of plunger pumps for pumping liquid from the pump, a mixer for mixing the liquid by independently supplying the liquid pumped from the plurality of plunger pumps, and detecting the discharge pressure of each plunger pump A plurality of pressure sensors, and a seat for judging the seat failure of the check valve by integrating the detected pressure of the pressure sensor during one reciprocation of the piston rod and comparing the integrated value with a judgment value When the seat failure occurs in the check valve of the plunger pump, the piston rod is top dead. And the discharge pressure when it reaches the bottom dead center Dari depressed greater than usual, the rise in the delay of the discharge pressure or cause the fell. According to the above configuration, the sheet defect determination means compares the integral value of the discharge pressure of the plunger pump during one reciprocation of the piston rod with the determination value. Therefore, any change in the discharge pressure of the plunger pump accompanying the occurrence of the above-described sheet failure can be detected.
[0010]
According to a second aspect of the present invention, there is provided a multi-liquid mixing device comprising an operation signal output means for outputting a signal corresponding to the reciprocating motion of the piston rod, and the sheet defect determining means is configured such that the piston rod is positioned near the bottom dead center. The pressure sensor output is integrated, and the integrated value is compared with the bottom dead center determination value to determine the seat failure of the check valve, and the piston rod is top dead. From the second sheet defect determination means for integrating the pressure sensor output when located near the point and comparing the integral value with the top dead center determination value to determine the sheet defect of the check valve It is characterized by comprising.
[0011]
According to a third aspect of the present invention, there is provided a multi-liquid mixing apparatus comprising trigger pressure setting means for setting a trigger pressure, wherein the sheet defect determining means is configured to measure the pressure in a predetermined period from when the pressure sensor output becomes equal to or lower than the trigger pressure. The sensor output is integrated, and the integrated value is compared with a determination value to determine a seat failure of the check valve.
[0012]
According to a fourth aspect of the present invention, there is provided a multi-liquid mixing apparatus comprising: an operation signal output means for outputting a signal corresponding to a reciprocating motion of a piston rod; and a trigger pressure setting means for setting a trigger pressure; Integrating a difference between the pressure sensor output and the trigger pressure in a period from when the pressure sensor output becomes equal to or lower than the trigger pressure when the piston rod is located near top dead center until the trigger pressure is exceeded Processing, and comparing the integrated value and the top dead center determination value to determine the seat failure of the check valve, and when the piston rod is located near the bottom dead center The pressure sensor output and the trigger pressure in a period from the time when the pressure sensor output becomes equal to or lower than the trigger pressure to the time when the pressure exceeds the trigger pressure. The difference integrated process, characterized by being composed of a second sheet failure determining means for determining sheet failure of the check valve by comparing the integral value and the bottom dead center determination value.
[0013]
According to the second to fourth aspects of the present invention, the occurrence of a sheet failure is detected based on the integral value of the discharge pressure or the integral value of the pulsation of the discharge pressure when the piston rod is located near the top dead center or the bottom dead center. To do. Therefore, the occurrence of sheet failure can be detected at an early stage. It is also possible to detect whether a seat failure has occurred in the check valve that is closed during the piston rod ascending or descending process, and the location where the seat failure has occurred can be identified.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment in which the present invention is applied to a two-component coating apparatus as a multi-component mixing apparatus will be described with reference to FIGS. First, the whole structure of the two-component coating apparatus 21 is demonstrated, referring FIG. In FIG. 1, a solid line indicates a liquid system path, a broken line indicates an air system path, and a two-dot chain line indicates an electric control system path.
[0015]
The two-component coating apparatus 21 includes two plunger pumps 24 and 25 that pump up and pump the main agent and the curing agent from the main agent tank 22 and the curing agent tank 23 as liquid supply sources.
[0016]
The plunger pumps 24 and 25 both have the same configuration as the plunger pump 1 shown in FIG. Therefore, the same reference numerals are used for the same parts as the plunger pump 1 below.
[0017]
The discharge ports 5 of the plunger pumps 24 and 25 are connected to a static mixer 28 (corresponding to a mixer) through a main agent passage 26 and a hardener passage 27, respectively. An opening / closing valve 30 is connected to the discharge port of the static mixer 28 via a mixed solution hose 29. A discharge nozzle 31 is connected to the outlet of the on-off valve 30. The on-off valve 30 is, for example, pneumatically driven, and pressurized air is supplied from a pressurized air supply source (not shown) via an air supply hose 32.
[0018]
A filter device 33 and a pressure sensor 34 are provided in the middle of the main agent passage 26. A filter device 35 and a pressure sensor 36 are provided in the middle of the curing agent passage 27. The filter devices 33 and 35 are for removing dust generated due to wear of packing parts and O-rings (not shown) of the plunger pumps 24 and 25 provided in the course of the route of the main agent and the curing agent, A filter 37, an analog output pressure gauge 38, and a ball cock 39 are provided.
[0019]
The piston rods 7 of the plunger pumps 24 and 25 are both connected to a piston rod 41 that is an output shaft of the air motor 40, and move up and down together with the piston rod 41. That is, in this embodiment, the piston rods 7 of both plunger pumps 24 and 25 are driven and interlocked by the common air motor 40.
[0020]
The air motor 40 is configured such that the piston rod 41 moves up and down by pressurized air supplied from a pressurized air supply source (not shown) via an air supply hose 42. The air supply hose 42 is provided with a safety valve 43, a pressure gauge 44, an electropneumatic regulator 45, and a ball cock 46. Further, the air motor 40 is provided with first and second limit switches 47 and 48 for detecting that the piston rod 41 is located near the bottom dead center and the top dead center.
[0021]
The first limit switch 47 outputs an ON signal when the piston rod 41 is located on the bottom dead center side from a predetermined position near the bottom dead center, and outputs an OFF signal otherwise. The second limit switch 47 outputs an ON signal when the piston rod 41 is located on the top dead center side with respect to a predetermined position near the top dead center, and outputs an OFF signal otherwise.
[0022]
In the present embodiment, the piston rods 7 of the plunger pumps 24 and 25 are configured to move up and down in conjunction with the piston rod 41, so that the limit switches 47 and 48 function as operation signal output means.
[0023]
The controller 50 is mainly composed of a microcomputer, and includes a RAM as a volatile memory, an EEPROM (not shown) as a rewritable nonvolatile memory, etc. as storage means. The EEPROM stores a control program executed by the microcomputer, a determination value used for sheet defect determination processing described later, and the like. Accordingly, in this embodiment, the controller 50 functions as a sheet defect determination unit and a determination value setting unit.
[0024]
The controller 50 is supplied with output signals from limit switches 47 and 48 and pressure sensors 34 and 36. The controller 50 controls the electropneumatic regulator 45 to adjust the pressure of the driving air supplied to the air motor 40. Further, although not shown, the controller 40 is connected with various operation switches and indicators.
[0025]
The operation switch and the display are provided on an operation panel (not shown) provided in the two-component coating apparatus 21. The operation switch includes an ON / OFF switch for operating and stopping the plunger pumps 24 and 25, a switch for performing various settings, a switch for switching an operation mode, and the like. The indicator is composed of a liquid crystal display (LCD), an indicator lamp (LED), and the like for displaying the setting contents and operation status of the two-component coating apparatus 21 and notifying abnormality.
[0026]
Next, the operation of this embodiment will be described with reference to FIGS. When the start of the painting operation is instructed after the pressure of the driving air (primary air pressure) of the air motor 40 is set by operating the operation switch, the driving air is supplied to the air motor 40 from the pressurized air supply source. Is done.
[0027]
When the operator opens the on-off valve 30, the piston rod 7 of the plunger pumps 24, 25 together with the piston rod 41 is repeatedly raised and lowered. As a result, the main agent and the hardener are pumped up from the main agent tank 22 and the hardener tank 23 by the plunger pumps 24 and 25, and supplied to the static mixer 28 through the main agent passage 26 and the hardener passage 27. Then, the main agent and the curing agent mixed by the static mixer 28 are discharged from the discharge nozzle 31 through the mixed solution hose 29. In the coating apparatus 21, the ratio of the cylinder capacities of the plunger pumps 24 and 25 corresponds to the mixing ratio of the main agent and the curing agent.
[0028]
At this time, the controller 50 controls the electropneumatic regulator 45 so that the primary air pressure is set several seconds after the start of work is instructed. Thereby, damage to the filter 37 due to sudden pressurization is prevented.
[0029]
Further, the plunger pumps 24 and 25 discharge the main agent and the curing agent at a discharge pressure pressurized in proportion to the primary air pressure. At this time, the controller 50 reads the output signals of the pressure sensors 34 and 36 every predetermined time (for example, 1 ms), and detects the hydraulic pressure in the main agent passage 26 and the hardener passage 27. The hydraulic pressures in the main agent passage 26 and the hardener passage 27 correspond to the discharge pressures of the plunger pumps 24 and 25, respectively.
[0030]
Based on the output signals of the limit switches 47 and 48, the controller 50 determines that the piston rod 41 is near bottom dead center and top dead center, that is, the piston 9 (piston rod 7) of the plunger pumps 24 and 25 is bottom dead center and top. The presence or absence of occurrence of a sheet failure in the plunger pumps 24 and 25 is determined by comparing the integral value of the hydraulic pressure when located near the dead center with a predetermined determination value.
[0031]
Hereinafter, the sheet defect determination process will be described.
[0032]
FIG. 2 is a diagram for explaining the relationship between the hydraulic pressure in the main agent passage 26 or the hardener passage 27 and the output signals of the limit switches 47 and 48. (a) is an example of the hydraulic pressure, and (b) and ( c) shows output signals of the limit switches 47 and 48. In both the main agent and the hardener plunger pumps 24 and 25, the change in the discharge pressure caused by the vertical movement of the piston 9 and the change in the discharge pressure when a sheet failure occurs are substantially the same. Explain without distinction.
[0033]
In FIG. 2A, BP and UP indicate hydraulic pressures when the piston 9 is located at the bottom dead center and the top dead center. On the other hand, as shown in FIGS. 2B and 2C, the limit switches 47 and 48 output ON signals when the piston rod 41 of the air motor 40 is located near the bottom dead center and near the top dead center. As shown in FIG. 2, the bottom dead center and top dead center timing of the piston 9 of the plunger pumps 24, 25 is the bottom dead center or top dead center timing detected by the limit switches 47, 48. Slightly behind.
[0034]
Due to the structure of the plunger pumps 24 and 25 configured as described above, the discharge pressure pulsates as the piston 9 reciprocates, and when the piston 9 is located near the top dead center and the bottom dead center, it greatly decreases. . Further, the hydraulic pressure is lower when the piston 9 is located at the bottom dead center than when the piston 9 is located at the top dead center.
[0035]
According to the inventor's experiment, it was found that when a seat failure occurs in the plunger pumps 24 and 25, the hydraulic pressure near the top dead center and the bottom dead center of the piston 9 changes as shown in FIG. That is, a decrease in hydraulic pressure (broken line A) and a delay in rising of the lowered hydraulic pressure (broken line B) occur. Although FIG. 3 shows a state in which the hydraulic pressure decreases at the bottom dead center and the rise delay occurs at the top dead center, the opposite case may be present.
[0036]
Therefore, the controller 50 integrates the hydraulic pressure in the predetermined period T1 from the ON signal edge of the bottom dead center detection limit switch 47. Then, the integrated value is compared with the bottom dead center determination value, and when the integrated value falls below the bottom dead center determination value, it is determined that a seat failure has occurred in the second check valve 11. Further, the controller 50 integrates the hydraulic pressure in the predetermined period T2 from the ON signal edge of the top dead center detection limit switch 48. Then, the integrated value is compared with the top dead center determination value, and when the integrated value falls below the top dead center determination value, it is determined that a seat failure has occurred in the first check valve 10.
[0037]
If the controller 50 determines that any of the first and second check valves 10 and 11 has a defective sheet, the controller 50 indicates the type of plunger pump in which the defective sheet has occurred (for the main agent, for curing). Notification).
[0038]
In this case, the controller 50 calculates standard integrated values in the vicinity of the bottom dead center and the top dead center of the piston rod 7 based on detection outputs of the pressure sensors 34 and 35 in a steady state in advance. Then, a bottom dead center and a top dead center determination value are set by adding an allowable error to the standard integrated value. The predetermined periods T1 and T2 are appropriately set based on the ascending process time and the descending process time of the piston rod 7.
[0039]
As described above, according to the present embodiment, whether or not a sheet defect has occurred is determined based on the integral value of the hydraulic pressure (discharge pressure) when the piston rod 7 is located near the top dead center or the bottom dead center. Accordingly, it is possible to detect a phenomenon in which the absolute value of the fluid pressure dropped at the top dead center or the bottom dead center does not change, but the rise is delayed. For this reason, generation | occurrence | production of a sheet | seat defect can be detected reliably.
[0040]
Further, since the determination value when the piston rod 7 is located near the top dead center is different from the determination value when the piston rod 7 is located at the bottom dead center, the sheet defect can be detected with high accuracy.
[0041]
Further, the controller 50 is configured to set the determination value based on the detected hydraulic pressure of the pressure sensors 34 and 35. That is, every time a painting operation is performed by the two-component coating apparatus 21, the controller 50 updates the determination value. Therefore, it is possible to set an appropriate determination value that reflects various conditions such as the type of main agent and curing agent used and the operating environment of the two-component coating apparatus 21.
[0042]
Furthermore, in this embodiment, the plunger pumps 24 and 25 for the main agent and the curing agent are driven by a common air motor 40 so that the piston rods 7 of both plunger pumps 24 and 25 are interlocked. Therefore, the limit switches 47 and 48 for detecting the bottom dead center and the top dead center of the piston rod 7 can be shared, and the configuration can be simplified.
[0043]
4 and 5 show a second embodiment of the present invention, and different points from the first embodiment will be described. The same parts as those in the first embodiment are denoted by the same reference numerals. That is, in this embodiment, a pneumatic switch 51 is provided instead of the limit switch. The pneumatic switch 51 outputs a signal corresponding to the reciprocating motion of the piston rod 41 of the air motor 40. For example, the pneumatic switch 51 is turned on when the piston rod 41 is lowered and turned off when the piston rod 41 is raised.
[0044]
The output signal of the pneumatic switch 51 is supplied to the controller 50. Based on the output signal of the pneumatic switch 51, the controller 50 can detect that the piston rod 41 is in the ascending process or the descending process, in other words, that the piston rod 7 of the plunger pumps 24, 25 is in the ascending process or the descending process. it can.
[0045]
In the two-component coating apparatus 21, the controller 50 sets and stores the trigger pressure based on the fluid pressure detected by the pressure sensors 34 and 35 when a predetermined time has elapsed since the start of work was instructed. For example, the controller 50 sets the average value of the detected hydraulic pressures of the pressure sensors 34 and 35 during the single reciprocation of the air motor 41 as the trigger pressure.
[0046]
Subsequently, the controller 50 compares the detected fluid pressure with the trigger pressure. Then, the difference between the trigger pressure and the hydraulic pressure in the period from when the hydraulic pressure becomes equal to or lower than the trigger pressure to the trigger pressure is integrated.
[0047]
FIG. 5 is a diagram for explaining the relationship between the hydraulic pressure in the main agent passage 26 or the hardener passage 27 and the output signal of the pneumatic switch 51, and FIG. 5 (a) is a view corresponding to FIG. 2 (a). FIG. 5B shows an output signal of the pneumatic switch 51. In FIG. 5A, a straight line T indicates the trigger pressure.
[0048]
In the present embodiment, the integrated value of the difference between the trigger pressure and the hydraulic pressure calculated by the controller 50 corresponds to the areas S1 to S4 of the regions indicated by hatching in FIG. When the integrated value of the difference between the trigger pressure and the hydraulic pressure is calculated, the controller 50 then compares the integrated value with the bottom dead center determination value or the top dead center determination value. In this case, if the ON signal edge of the pneumatic switch is detected during the period from when the hydraulic pressure becomes equal to or lower than the trigger pressure until the trigger pressure is reached (integration processing period), it is compared with the top dead center judgment value and the OFF signal edge When is detected, it is compared with the bottom dead center discriminant value. When the integral value is larger than the discriminant value, it is determined that a sheet defect has occurred, and the fact that a sheet defect has occurred is notified together with the type of plunger pump (for main agent and curing agent).
[0049]
Even in such a configuration, it is possible to accurately detect the occurrence of a sheet defect as in the first embodiment.
The controller 50 is configured to set the trigger pressure based on the detected hydraulic pressure of the pressure sensors 34 and 35. Accordingly, it is possible to set an appropriate trigger pressure that reflects various conditions such as the type of main agent and curing agent used and the operating environment of the two-component coating apparatus 21.
[0050]
The present invention is not limited to the above-described embodiments, and for example, the following modifications are possible.
You may comprise so that generation | occurrence | production of a sheet | seat defect may be detected based on the integral value of the discharge pressure in the whole while the piston rod 7 reciprocates once.
[0051]
You may comprise so that generation | occurrence | production of a sheet | seat defect may be detected based on the integral value of the discharge pressure while the limit switches 47 and 48 are outputting the ON signal.
It is also possible to detect the occurrence of sheet failure based on the integrated value of the discharge pressure in a predetermined period from the time when the discharge pressure becomes equal to or lower than the trigger pressure.
[0052]
You may make it alert | report also whether the check valve in which the sheet | seat defect generate | occur | produced is a 1st check valve or a 2nd check valve.
The plurality of plunger pumps may be configured to be driven by different air motors.
[0053]
Instead of the limit switch, the top dead center and the bottom dead center may be detected by a proximity switch, an optical sensor, a magnetic sensor, or the like.
The determination value and the trigger pressure may be configured to be manually set by an operator.
The present invention can be applied not only to a coating apparatus but also to other multi-liquid mixing apparatuses such as an adhesive application apparatus.
[0054]
【The invention's effect】
As is clear from the above description, the multi-liquid mixing device of the present invention compares the integral value of the discharge pressure during one reciprocation of the piston rod of the plunger pump with the judgment value, so that the discharge associated with the occurrence of sheet failure Various changes in pressure can be reliably detected.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a two-component coating apparatus showing a first embodiment of the present invention. FIG. 2 is a diagram for explaining the relationship between fluid pressure and an output signal of a limit switch. FIG. 4 is a diagram for explaining a change in hydraulic pressure when a defect occurs. FIG. 4 is a diagram corresponding to FIG. 1 showing a second embodiment of the present invention. FIG. [Figure 6] Diagram showing the overall configuration of the plunger pump [Explanation of symbols]
4 is a cylinder, 7 is a piston rod, 10 and 11 are check valves, 21 is a two-component coating device (multi-component mixing device), 22 is a main agent tank (liquid supply source), 23 is a curing agent tank (liquid supply) Source), 24 and 25 are plunger pumps, 28 is a static mixer (mixer), 34 and 36 are pressure sensors, 40 is an air motor, 47 and 48 are limit switches (operation signal output means), and 50 is a controller (sheet failure judgment) Means, determination value setting means, trigger pressure setting means), 51 denotes a pneumatic switch (operation signal output means).

Claims (7)

A plurality of plunger pumps connected to an output shaft of an air motor and capable of reciprocating in a cylinder; a plurality of plunger pumps having a check valve that opens and closes in accordance with the reciprocating movement of the piston rod;
A mixer for mixing the liquid by independently supplying the liquid pumped from the plurality of plunger pumps;
A plurality of pressure sensors for detecting the discharge pressure of each plunger pump;
A sheet failure determination unit that integrates the detected pressure of the pressure sensor during one reciprocation of the piston rod and compares the integrated value with a determination value to determine a seat failure of the check valve. A multi-liquid mixing device characterized by. Comprising an operation signal output means for outputting a signal corresponding to the reciprocating motion of the piston rod;
The seat failure determining means integrates the pressure sensor output when the piston rod is located near the bottom dead center, and compares the integrated value with the bottom dead center determination value to determine the seat failure of the check valve. First sheet defect determination means for performing,
The pressure sensor output when the piston rod is located near the top dead center is integrated, and the integrated value is compared with the top dead center determination value to determine the seat failure of the check valve. 2. The multi-liquid mixing apparatus according to claim 1, wherein the multi-liquid mixing apparatus comprises a sheet defect judging means. Equipped with trigger pressure setting means for setting the trigger pressure,
The seat failure determination means integrates the pressure sensor output in a predetermined period from the time when the pressure sensor output becomes equal to or lower than the trigger pressure, and compares the integrated value with the determination value to determine the seat failure of the check valve. The multi-liquid mixing apparatus according to claim 1, wherein the determination is performed. An operation signal output means for outputting a signal corresponding to the reciprocation of the piston rod;
Trigger pressure setting means for setting the trigger pressure,
The seat defect determining means is configured to determine whether the pressure sensor output and the trigger pressure in a period from when the pressure sensor output becomes equal to or lower than the trigger pressure when the piston rod is located near top dead center until the trigger pressure is exceeded. A first sheet failure determination means for determining a seat failure of the check valve by comparing the difference between the integrated value and the top dead center determination value;
Integral processing of the difference between the pressure sensor output and the trigger pressure in the period from when the pressure sensor output becomes equal to or lower than the trigger pressure when the piston rod is located near the bottom dead center until the trigger pressure is exceeded 2. The apparatus according to claim 1, further comprising: a second sheet defect determination unit that determines a sheet defect of the check valve by comparing the integral value with a bottom dead center determination value. Multi-liquid mixing device. The multi-liquid mixing apparatus according to any one of claims 1 to 4, further comprising determination value setting means for setting a determination value based on a detection output of the pressure sensor. 5. The multi-liquid mixing apparatus according to claim 3, further comprising trigger pressure setting means for setting a trigger pressure based on a detection output of the pressure sensor. 7. The multi-liquid mixing apparatus according to claim 1, wherein the piston rods of the plurality of plunger pumps are connected to and interlocked with an output shaft of a common air motor.

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