JP2656930B2 - Liquid ejection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid ejection apparatus.

[Conventional technology]

2. Description of the Related Art In general, there is a liquid discharge device in which a single spool having a groove formed in a circumferential direction is provided in a hollow casing having a plurality of ports formed therein. In this liquid ejection device, the valve can be switched by moving the spool forward and backward along the axial direction.

By the way, in the liquid discharge device, when the liquid flowing through the valve is exchanged, it is necessary to clean the inside of the valve. In a conventional liquid discharge device, cleaning is performed in a state where the liquid discharge device is disassembled, or a cleaning liquid is injected into a valve from one port, and the cleaning liquid is discharged from another port while moving a spool forward and backward. There is a need. Further, in a conventional liquid ejection apparatus, a port is opened / closed and a flow path is simply switched.

[Problems to be solved by the invention]

However, when the liquid ejecting apparatus is disassembled for cleaning, there is a problem in that the cleaning operation is complicated.In the case of injecting the cleaning liquid from one port, the flow is caused by moving the spool forward and backward. There is a problem that the road is switched and sufficient cleaning cannot be performed.
Further, it is extremely difficult to discharge an accurate amount of liquid with the liquid discharge device alone.

Here, an object of the present invention is to provide a liquid ejection device that can automatically perform cleaning.

[Means for solving the problem]

According to a first aspect of the present invention, there is provided a liquid ejecting apparatus, comprising: a hollow casing; a liquid suction port and a liquid discharge port formed in the casing; a tank communicating with the liquid suction port; A first spool and a second spool which are slidably provided on the same axis and whose end faces are opposed to each other, a first drive mechanism for moving the first spool back and forth in the axial direction, and a second spool. A second drive mechanism for moving the spool back and forth in the axial direction; and control means for controlling the drive of the first drive mechanism and the second drive mechanism. The data of the spool moving operation at the time of washing is input, and the spool moving operation at the time of the switching valve switching operation is performed by first separating the first spool from the second spool. Thereby opening the liquid suction side port flows the liquid in the casing from the tank,
Thereafter, the second spool is moved forward together with the first spool to transport the liquid and open the liquid discharge side port. Further, the second spool is brought close to the first spool so that the liquid discharge side port is closed. And discharges the liquid remaining at the liquid discharge side port with a negative pressure generated between the two spools by separating the second spool from the first spool by a predetermined amount after the discharge of the liquid is completed. And further retracts the first spool and the second spool to close the liquid discharge side port and open the liquid suction side port. Thereafter, the first spool is brought closer to the second spool. And returning the liquid in the casing to the tank via the liquid suction side port, and the spool moving operation during the valve cleaning. The first spool is separated from the second spool, the liquid suction side port is opened, and the cleaning liquid flows into the casing from the tank, and then the first spool is moved closer to the second spool. The washing liquid in the casing is returned to the tank via the liquid suction side port.

Further, a second invention according to the liquid ejection device of the present application includes a hollow casing, a liquid suction side port and a liquid discharge side port respectively formed in the casing, and a tank communicating with the liquid suction side port. A first spool and a second spool, each of which is slidably provided on the same shaft in the casing and whose end faces are opposed to each other; a first drive mechanism for moving the first spool forward and backward in the axial direction; A second drive mechanism for moving the second spool forward and backward in the axial direction; and control means for controlling the drive of the first drive mechanism and the second drive mechanism. And data of a spool moving operation at the time of valve cleaning is input, and the spool moving operation at the time of the precise weighing operation is performed by first separating the first spool from the second spool. The liquid suction side port and the liquid discharge side port are simultaneously opened and the liquid flows out of the tank through the casing through the casing, and a predetermined amount of liquid flows out of the liquid discharge side port. The spool is advanced by a predetermined amount to close the liquid suction side port, and further, the second spool is advanced to cause the liquid in the casing to flow out of the liquid discharge side port by a predetermined amount, and then the first spool And the second spool is retracted. The spool moving operation at the time of the valve cleaning is performed by separating the first spool from the second spool and moving the liquid from the tank through the liquid suction side port into the casing. Cleaning fluid flows into the casing, and then moves the first spool close to the second spool to draw the cleaning fluid in the casing into the liquid. Via port is intended to return to the tank, characterized in that.

[Action]

Thus, according to the present invention, when the valve is switched, the flow paths of the first and second spools are switched by the first and second drive mechanisms according to the spool movement operation data for the valve switching operation of the control means. When the valve is moved forward and backward, and the valve is washed, the first and second spools are moved forward and backward by the first and second drive mechanisms according to the data of the spool moving operation at the time of pump washing of the control means, for example, one spool is fixed. In the state
When the other spool is moved forward and backward to allow the cleaning liquid to flow through the inside and outside of the casing through one port, and when performing the precise weighing operation, according to the data of the spool moving operation for the precise weighing operation of the control means, the first and the second are performed. After the 2 spool is moved forward and backward by the first and second drive mechanisms so that the flow path is switched, furthermore, the spool is moved forward and backward by the first and second drive mechanisms to perform precision weighing, thereby achieving the above object. It is assumed that.

〔Example〕

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. Here, in each embodiment, the same or similar components are denoted by the same reference numerals, and description thereof will be omitted or simplified.

1 and 2 showing the entire structure, a hollow casing 2 made of a material such as ceramics is provided on a frame 1, and an upper part of the casing 2 is located at a predetermined distance from each other. A first port 21 and a second port 22 are formed. The first port 21 is a port on the liquid suction side and communicates with a pressurized or non-pressurized tank 23 in which the liquid is stored. The second port 22 is a port on the liquid discharge side and receives the liquid. Discharge nozzle
Connected to 24. In the casing 2, a first spool 31 and a second spool 32, which are formed of a material such as ceramics so as to be able to advance and retreat on the same axis, are provided, respectively.
One end surfaces of the first and second spools 31 and 32 are arranged to face each other. Here, the time when the one end surfaces of the spools 31 and 32 are on the axis of the first port 21 is defined as the origin.

A first drive mechanism 41 is connected to the first spool 31 and a second drive mechanism 42 is connected to the second spool 32. The first and second drive mechanisms 41 , 32 advance and retreat, respectively. The first drive mechanism 41 includes a mounting member 43A mounted on the other end of the first spool 31, and two front and rear rods connected to the mounting member 43 and arranged in parallel with the first spool 31. 44A (see FIG. 2), a nut member 45A connected to these rods 44A, a ball screw shaft 46A screwed to the nut member 45A and arranged in parallel with the first spool 31;
A first stepping motor 47A is connected to the ball screw shaft 46A. Similarly to the first drive mechanism, the second drive mechanism 42 includes a mounting member 43B, a rod 44B, a nut member 45B, a ball screw shaft 46B, and a second stepping motor 47B. I have. Here, when the first and second stepping motors 47A and 47B rotate clockwise, the first and second spools 31 and 32 move in directions approaching each other, that is, moving away from the driven motors 47A and 47B, respectively. On the other hand, when the first and second stepping motors 47A and 47B rotate counterclockwise, the first and second spools 31 and 32 are separated from each other, that is, the motor 47 is rotated.
A and 47B are moved in directions approaching each other.

The first and second drive mechanisms 41 and 42 are connected to a control unit 50. The control means 50 controls the stepping motor 47
A control device 60 connected to A and 47B, and first to fourth control devices connected to the control device 60 and detecting the positions of the first and second spools 31 and 32 via the positions of the nut members 45A and 45B. It comprises limit switches 51, 52, 53, 54 and a personal computer (personal computer) 55 connected to the control device 60. Here, the first limit switch 51
Detects the position where the first spool 31 is located at the end of the first stepping motor, and the second limit switch 52 detects the position where the one end surface of the first spool 31 is on the axis of the first port 21 (the origin). ), And the third limit switch 53
When a position (origin) where one end surface of the second spool 32 is on the axis of the first port 21 is detected, the fourth limit switch 54
The position where the second spool 32 is located at the second stepping motor side end is detected. The personal computer 55 and the control device 60 are connected in parallel with the first and second drive mechanisms 41 and 42.
And various signals such as a start signal.

As shown in FIG. 3, an operation panel 60A of the control device 60 includes an electric lamp 61, an EXT lamp 62 for detecting that input from a personal computer 55 is possible, and one-cycle operation of the spools 31, 32. Completion lamp 63 for detecting the completion of
2Origin lamp 64, power switch 65, start switch 66, stop switch 67, reset switch 68, discharge amount setting digital switch 69, LSPD setting digital switch 70, HSPD setting digital for detecting that spools 31 and 32 are at the origin position It has a switch 71, a RATE setting digital switch 72, a negative pressure setting digital switch 73, and a mode switching channel (not shown). Here, as shown in FIG. 4, the LSPD setting digital switch 70 sets the frequency (PPS) at the time of starting and stopping the motor, the HSPD setting digital switch 71 sets the frequency (PPS) at the time of driving the motor, and RATE. The setting digital switch 72 sets the time constant (ms / 100
0PPS), the discharge amount setting digital switch 69 inputs the number of output pulses (INDEX PUSE), and the negative pressure setting digital switch 73 outputs the first and second pulses.
The amount of negative pressure between the spools generated when the spools 31 and 32 relatively move apart is input. By operating these switches 69 to 73, data on the movement of the first and second spools 31 and 32, that is, a time chart in a valve switching mode (see FIG. 6) described later and a time chart in a valve cleaning mode (FIG. 7) ) And a time chart of the origin return mode (see FIG. 8).

A control block diagram of the control device 60 is shown in FIG. In FIG. 5, a ROM circuit 83 is connected to a CPU 80 (model number Z80) via a data bus 81 and an address bus 82.
(2732), RAM circuit 84 (6116), ROM circuit 85 each
A, 86A (the R01-A) and two stepping motor controllers 85, 86 (the MCC-01), a first interface circuit 87 (8255), and a second interface circuit 88
(8255) and the third interface circuit 89 (8251)
Is connected to The ROM of the address bus 82
A decoder 90 is connected between the circuit 83 and the first interface circuit 87. Further, a clock oscillation circuit 92 and a baud rate switching circuit 93 are connected between the CPU 80 and the third interface circuit 89 via a timing signal line 91. Further, an oscillation device 95 is connected between the two stepping motor controllers 85 and 86 via an inverter 94. The first interface circuit 87 exchanges signals for the mode switching and the like with the RAM circuit 84 via the CPU 80, and the second interface circuit 88 exchanges the LSPD with the RAM circuit 84. The data necessary for the operation of each of the motors 47A and 47B input by the setting digital switch 70 and the like, in other words, the data and the like necessary for creating the time chart are exchanged via the CPU 80, and the third
The interface circuit 89 transmits data necessary for the operation of each of the motors 47A and 47B to and from the RAM circuit 84 in the same manner as the second interface circuit 88 from the personal computer 55 via external communication means called RS232C or the like. It is designed to be replaced via the CPU 80. Further, the one stepping motor controller 85 includes the first stepping motor 47A.
When the rotation of the motor 47A is rotated clockwise or counterclockwise according to the operation program corresponding to the time chart, and the program of the home position return mode is executed, specifically, ,
Upon receiving the detection signal of the first limit switch 51, the rotation of the first stepping motor 47A is reversed, and the second limit switch 5 is rotated when the motor 47A moves clockwise.
The rotation of the first stepping motor 47A is stopped in response to the second detection signal. On the other hand, the other stepping motor controller 86 is also a second stepping motor controller.
The rotation, stop, and rotation direction of the motor 47B are reversed. Specifically, when the motor 47B is rotated in a predetermined direction according to the operation program corresponding to the time chart and the program in the home position return mode is executed, Receiving the detection signal from the limit switch 53, stops the rotation of the second stepping motor 47B, receives the detection signal from the fourth limit switch 54, stops the rotation of the second stepping motor 47B, and Upon receiving the detection signal of the limit switch 52, the rotation of the second stepping motor 47B is reversed.

Next, the operation of the first embodiment having such a configuration will be described.

First, when switching the valve,
Data is previously input to the operation panel 60A of the control device 60 or the personal computer 55, and an operation program corresponding to, for example, the time chart shown in FIG. 6 is created. Thereafter, the valve switching code is selected by a mode switching channel (not shown), and the start switch 66 of the operation panel 60A or the start switch (not shown) of the personal computer 55 is pressed to start the second operation.
Operate the 1,2 spools 31,32.

The operating state of these spools 31, 32 is shown in FIG. That is, for example, as shown in FIG.
When the first stepping motor 47A rotates counterclockwise in response to a start signal from a start switch 66 disposed at 60A, the first spool 31 moves leftward in the drawing, that is, the origin position shown in FIG. 9 (A). Then, as shown in FIG. 9 (B), it moves to a predetermined position between the first and second ports 21 and 22. Thereby, the liquid flows into the casing 2 from the first port 21. Thereafter, after a lapse of a predetermined time t, when the first stepping motor 47A rotates counterclockwise and the second stepping motor 47B rotates clockwise at the same speed, as shown in FIG. 1,2
The spools 31 and 32 move at the same speed to the left
Move until one end surface of the first port 21 is positioned on the axis of the first port 21. Further, the second stepping motor 47B is rotated in the same direction as described above, and as shown in FIG.
The spool 32 is moved to the left in the figure until it comes into contact with the first spool 31. As a result, the liquid is discharged from the second port 22, and the valve is switched. Immediately thereafter, the second stepping motor 47B is slightly reversed, that is, rotated counterclockwise to move the second spool 32 a predetermined distance away from the first spool 31 as shown in FIG. When it moves, a negative pressure is generated between the first and second spools, and the liquid remaining in the second port 22 is drawn back into the casing 2. Further, when the first stepping motor 47A rotates clockwise and the second stepping motor 47B rotates counterclockwise at the same speed, as shown in FIG.
1 and 2 spools 31 and 32 are at the same speed.
32 returns until one end face is located on the axis of the second port 22. Thereafter, the second spool 32 is fixed around the driving of the second stepping motor 47B, and the first stepping motor 47A is further rotated clockwise to rotate the first spool 32.
The spool 31 is brought into contact with the second spool 31 and the casing 2
The liquid in the tank is returned to the tank 23. As a result, the first and second spools 31, 32 have returned to the state before operation, that is, returned to the origin. The above series of operations is performed only once or a plurality of times, and the valve switching operation is completed.

Next, when a valve cleaning operation is performed, data is input in advance by a switch on the operation panel 60A of the control device 60, and an operation program corresponding to the time chart shown in FIG. 6 is created. Then, after the cleaning liquid is stored in the tank 23, or the tank 23 storing the cleaning liquid is attached to the first port 21, the mode of the valve cleaning operation is set by the mode changeover switch, and the start switch of the operation panel 60A is set. Press 66 etc.

Then, as shown in FIG. 7, a start signal is input, and the rotation of the first stepping motor 47A in the counterclockwise and clockwise directions is repeated. Then, as shown in FIGS. 10 (A) to 10 (F), in a state where the second spool 22 is fixed, the first spool 21 repeatedly separates from and approaches the first spool 21 to the tank 23, and The cleaning liquid is reciprocated between the casing 2 and the casing 2, whereby the valve is cleaned.

Further, when returning the first and second spools 21 and 22 to the origin, data is input in advance by a switch of the operation panel 60A, and an operation program corresponding to the time chart shown in FIG. 8 is created. After that, set the homing mode using the mode switching channel and
Press the start switch 66 of 60A.

Then, both the first and second stepping motors 47A and 47B rotate counterclockwise, and the first and second spools 31 and 32 move in a direction to be separated from each other. Thereafter, the fourth limit switch 54 detects that the second spool 32 is located at the second stepping motor side end, and the second stepping motor 47A
Center of rotation. Further, a first stepping motor
The first limit switch 51 detects that 47A rotates and the first spool 31 is located at the end of the first stepping motor, and the first and second stepping motors 47A and 47B rotate clockwise. Is done. As a result, the first and second spools 3
When the end faces of the first and second spools 31 and 32 are located on the axis of the first port 21, the second and third lit switches 52 , 53 detect and stop the rotation of the stepping motors 47A, 47B.

According to the first embodiment, the control device 60 including the control device 60, the limit switches 51 to 54, etc.
Since the movement of the spools 31 and 32 can be controlled to perform not only valve switching but also cleaning and the like, cleaning of the valve can be performed automatically and sufficiently without disassembling the valve. In the present embodiment, the first and second drive mechanisms 41 and 42
Since the stepping motors 47A and 47B are easy to control, the handling of the valves becomes easy. Further, in this embodiment, when the valve is switched, the first spool 31 is connected to the second spool 32 because the liquid flows from the first port 21.
After moving a predetermined distance in the direction away from the object, a time t is set until the next operation, so that even if the liquid is highly viscous, the liquid can sufficiently flow. Furthermore, at the time of the valve switching operation, after the liquid is discharged from the second port 22, the second spool 32 is separated from the first spool 31, and the two spools 31, 3
Since a negative pressure is generated between the two, no liquid remains at the tip of the nozzle connected to the second port 22.
When the liquids 31, 32 move to the first port side, the liquid is excessively discharged from the tip of the nozzle 24, that is, the accuracy of the discharging operation is not lacking. Further, the one port 22 (21)
When the liquid is discharged from the casing, one end face of one spool 31 (32) is fixed on the axis and the other spool 32 (31) is brought into contact with the one spool 32 (32). The dead space in 2 and the remaining liquid can be eliminated.

Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment is different from the first embodiment in that data of the spool moving operation at the time of the precise weighing operation is input to the control means 50 instead of the data at the time of the pulse switching operation. This is substantially the same as the embodiment.

In the second embodiment, as shown in FIG. 14, the first port 21 is provided at the upper right portion of the casing 2 and the second port 21 is provided at the lower left portion thereof.
A port 22 is formed, and a container 100 provided on the balance 16 is disposed below the second port 22.

In the second embodiment, each of the switches 69 to 73 of the control device 60 constituting the control means 50 or these switches of the personal computer 55
By operating the same switches as in 69 to 73, the time chart of the precise weighing operation mode (see FIG. 12), the valve cleaning mode (see FIG. 7), and the time chart of the spool return to origin mode (see FIG. 8) Is to be entered.

In the second embodiment having such a configuration, in the case of performing a precise weighing operation, data is input in advance to the operation panel 60A of the control device 60 or the personal computer 55 to correspond to the time chart shown in FIG. Create a working program Thereafter, the precise weighing operation mode is selected by a mode switching channel (not shown), and the first and second spools 31, 32 are operated by pressing the start switch 66 of the operation panel 60A or the start switch of the personal computer. The operating states of these spools 31, 32 are shown in FIG. That is, the twelfth
As shown in the figure, a first stepping motor 47A is supplied by a start signal from a start switch 66 or the like.
When (see FIG. 1) rotates counterclockwise, the first spool 31 moves leftward in the drawing, that is, as shown in FIG. 13 (B) from the origin position shown in FIG. 13 (A). The second spool 22 moves to the position located on the left edge side, in other words, the valve is opened, and the liquid α in the tank 23 is supplied from the port 21 by the preliminary suction force of the first spool 31 to the casing 2.
Inside, it is in a state of being discharged from the port 22 into the container 100. Here, a feedback control in combination with a timer element or an electronic balance or the like as shown in FIG. 14 is performed to discharge a roughly measured discharge amount β of a preset discharge amount (for example, 90% of the target discharge amount). Thereafter, as shown in FIG. 13 (C), the second stepping motor 47B (first
When the second spool 32 rotates clockwise, the second spool 32 moves leftward in the figure by a distance h, and the valve is closed. In that state, measure the discharge amount β in the container 100,
Thereafter, as shown in FIG. 13 (D), the second spool 32 is further moved to the left in the drawing, that is, the distance of S, to perform the target precise weighing operation up to the necessary discharge amount (eg, β + γ). The discharge amount γ at that time (for example, 10% of the target discharge amount)
Is given by γ = π (φ, where φ _d is the diameter of spools 31 and 32.
_d ) Represented by ² × S / 4. Further, as shown in FIG. 13 (E) for improving the drainage by the liquid, a negative pressure operation is sometimes performed. Then, FIG. 13 (F)
As shown in (1), both the first and second spool valves 31 and 32 move rightward in the figure, return to the origin position, and one cycle of the precision weighing operation ends.

When performing the valve cleaning operation and the home position return operation, the same operation as in the first embodiment is performed.

According to the second embodiment, similarly to the first embodiment, in addition to the automatic cleaning of the valve, there is an effect that the measurement can be corrected after the valve is switched and the liquid can be precisely measured.

In the present invention, the valve of the above embodiment can be used also as an on-off valve by controlling the movement of the two spools 31, 32. That is, FIG. 11 (A),
As shown in (B), one of the spools (for example, the first spool 31) is fixed in a state where the second port 22 is open, and the other spool (the second spool 32) is If it is advanced and retracted so that one port 21 is opened and closed, it can also be used as an on-off valve. Further, in the above embodiment, two ports 21 and 22 are formed in the casing 2 constituting the valve. However, the casing 2 used in the present invention has three or more ports formed therein. Is also good. Further, in the present invention, a normal servo motor may be used instead of the first and second stepping motors 47A and 47B. Further, the first and second drive mechanisms 41 and 42 include a nut member 45A,
It is not always necessary to provide the 45B, the ball screw shafts 46A, 46B, and the like, and a gear mechanism or other connecting means such as a combination of a timing belt and a sprocket may be used.
Further, when cleaning the inside of the valve, in the above embodiment, the second
With the spool 32 fixed, the first stepping motor
Although the first spool 31 is moved forward and backward by 47A, the reverse may be applied in the present invention. If one-way flow is allowed, cleaning may be performed in the valve switching mode of the first embodiment.

〔The invention's effect〕

According to the present invention as described above, in addition to the switching of the valves, the cleaning of the valves can be performed automatically, and further, there is an effect that the precise measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a first embodiment according to the present invention, FIG. 2 is a plan view showing a part of the embodiment, and FIG. 3 is a front view showing an operation panel of a control device constituting control means. FIG. 4 is an explanatory diagram for inputting data necessary for creating an operation program corresponding to a time chart, FIG. 5 is a control block diagram of a control device, and FIG. 6 is data for valve switching operation. FIG. 7 is a time chart as data at the time of valve cleaning, FIG. 8 is a time chart as data at the time of return of the spool to the home position, and FIGS.
(G) is an explanatory diagram of the operation at the time of valve switching, FIGS. 10 (A) to (E) are operational explanatory diagrams at the time of valve cleaning, and FIG. 11 is an operation of using the valve of the present invention as an on-off valve. FIG. 12 is a time chart as precision weighing operation data used in the second embodiment of the present invention, and FIGS.
(F) is an explanatory diagram of the operation at the time of precision weighing, and FIG. 14 is a schematic configuration diagram showing a main part of the second embodiment. 2. Casing, 21, 22 Port, 31 First spool, 32 Second spool, 41 First drive mechanism, 42
... Second driving mechanism 47A First stepping motor 47B Second stepping motor 50 Control means 51-54 Limit switch 55 Personal computer 60
...... Control devices.

Claims (2)

(57) [Claims] 1. A hollow casing, a liquid suction side port and a liquid discharge side port respectively formed in the casing, a tank communicating with the liquid suction side port, and sliding on the same axis in the casing. A first spool and a second spool which are movably provided and whose end faces are opposed to each other, a first drive mechanism which advances and retreats the first spool in the axial direction, and which advances and retreats the second spool in the axial direction A second drive mechanism; and control means for controlling the drive of the first drive mechanism and the second drive mechanism. The control means includes data of a spool movement operation at the time of a valve switching operation and a valve cleaning operation. In the spool moving operation at the time of the valve switching operation, first, the first spool is separated from the second spool to open the liquid suction side port. And flowing the liquid from the tank into the casing, and then moving the second spool forward with the first spool to transport the liquid and opening the liquid discharge side port.
The liquid is discharged from the liquid discharge side port by bringing the second spool close to the first spool, and after the discharge of the liquid is completed, the second spool is separated from the first spool by a predetermined amount, and the two spools are separated. The liquid remaining in the liquid discharge side port is drawn back into the casing by the negative pressure generated between them, and further, the first spool and the second spool are retracted to close the liquid discharge side port and the liquid suction side. Opening the port, and then returning the liquid in the casing to the tank via the liquid suction side port by bringing the first spool close to the second spool. In the moving operation, the first spool is separated from the second spool, the liquid suction side port is opened, and the cleaning liquid is supplied from the tank into the casing. Liquid, and thereafter, the first spool is brought close to the second spool, and the cleaning liquid in the casing is returned into the tank via the liquid suction side port. Discharge device. 2. A hollow casing, a liquid suction side port and a liquid discharge side port respectively formed in the casing, a tank communicating with the liquid suction side port, and sliding on the same axis in the casing. A first spool and a second spool which are movably provided and whose end faces are opposed to each other, a first drive mechanism which advances and retreats the first spool in the axial direction, and which advances and retreats the second spool in the axial direction A second drive mechanism; and control means for controlling the drive of the first drive mechanism and the second drive mechanism, wherein the control means includes data of a spool movement operation at the time of precision weighing operation and at the time of valve cleaning. The spool movement operation at the time of the precision weighing operation is as follows. First, the first spool is advanced in a direction away from the second spool, and the liquid suction side port is moved. And the liquid discharge side port are simultaneously opened, and the liquid flows out of the tank through the casing through a predetermined amount from the liquid discharge side port, and then the second spool is advanced by a predetermined amount. The liquid suction side port is closed, and further, the second spool is advanced to allow the liquid in the casing to flow out of the liquid discharge side port by a predetermined amount, and then the first spool and the second spool are retracted. Wherein the spool moving operation at the time of valve cleaning is performed by flowing the cleaning liquid from the tank into the casing via the liquid suction side port while separating the first spool from the second spool, The first spool is brought close to the second spool, and the cleaning liquid in the casing is passed through the liquid suction side port into the tank. A liquid ejecting apparatus, wherein: