JPH07103136A - Liquid discharger and operational control method thereof - Google Patents

Abstract

PURPOSE:To provide a liquid discharger and its operational control method, capable of preventing a hindrance attending on any stagnation in a transfer route and of performing the expected liquid discahrge without fail. CONSTITUTION:A three-way valve 40 is made into a suction state, operating a pump 30 for suction, and a liquid 13 in a tank 20 is drawn in up to a common tube 50 from an inlet tube 51, while the three-way valve 40 is selected to a discharge state, operating the pump 30 for discharge, then the liquid 13 in the common tube 50 is discharged out of a discharge tube 52, whereby the pump 30 is made into suction operation in leaving the three-way valve 40 in a state of being discharged intact, and air is inhaled from the discharge tube 52. In succession, the three-way valve 40 is selected to the suction state, operating the pump 30 for discharging, and the air is also discharged, thereby returning the liquid 13 in the inlet tube 51 to the inside of the tank 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid ejecting apparatus and a method of controlling the operation thereof, and in particular, it can be used for quantitative ejection of a liquid or the like mixed with fine powder which is hardened or separated and settles easily with the passage of time.

[0002]

BACKGROUND ART Conventionally, various types of liquid ejecting apparatuses have been used for transferring liquid. For example, a screw type or piston type pump is used for ordinary liquid transfer, and a tube type roller pump or the like is used for injecting a chemical that causes a problem of involvement of a sliding mechanism. Further, for the liquid application work, an apparatus in which an application nozzle, a spray nozzle or the like is combined with these ejection devices is used.

By the way, in the case of liquids such as adhesives and synthetic resin paints, which have the property of hardening with the passage of time, if the residence time in the transfer path becomes longer, the hardening will proceed and the quality will change before application. This will cause hardening and sticking, which will cause clogging of the conduit. Further, in a liquid or the like in which fine powder or the like is mixed, the fine powder or the like in the liquid is easily separated and settled with the passage of time, and if the residence time in the transfer route becomes long, the deterioration or clogging is similarly caused. Cause. Therefore, when transferring the curable or separable liquid as described above,
When the liquid is stored inside a tank, etc., the liquid is constantly stirred, and the transfer route such as piping is shortened, and the liquid is sucked in immediately before coating and discharged in a short time. Is required.

[0004]

However, when a plurality of objects to be coated are sequentially coated, a predetermined amount of liquid is ejected from the tip of the ejection side of the transfer path, and the liquid is moved to another object to be coated while the ejection is stopped. Such intermittent discharge operations are repeated, and temporary retention of the coating liquid in the transfer path is unavoidable in the stopped state between the discharge operations. Therefore, even if the transfer path from the storage tank or the like to the discharge end is shortened, retention in the transfer path is unavoidable, and the retained liquid may be altered in a short time. Therefore, there is a problem in that the quality of the discharged liquid cannot be completely avoided, and the desired liquid discharge cannot be performed sufficiently. An object of the present invention is to provide a liquid ejecting apparatus and an operation control method therefor capable of preventing an obstacle caused by staying in a transfer path and reliably ejecting a desired liquid.

[0005]

According to the present invention, the liquid remaining in the transfer path is returned to the tank or the like each time the liquid is discharged, thereby avoiding the retention of the liquid in the path and achieving the above object. Is what you are trying to do. The device of the present invention is
A tank that stores the liquid to be discharged, a suction tube whose proximal end communicates with a liquid phase portion in the tank, a common tube whose lower end is connected to the tip end of the suction tube, and an upper end of this common tube Connected to the pump capable of suction and discharge, a discharge tube having a proximal end side connected to a lower end side of the common tube, a common tube and a suction tube, and a communication between the common tube and the discharge tube. The present invention is characterized by further comprising switching means capable of alternately switching between an inhalation state in which it is blocked or a discharge state in which the common tube and the discharge tube are communicated with each other and the communication between the common tube and the suction tube is blocked.

Further, in the apparatus, the pump has a suction volume and a discharge volume which are larger than both the sum of the internal volumes of the suction tube and the common tube and the sum of the internal volumes of the discharge tube and the common tube. To do.
Further, in the above apparatus, the internal volume of the common tube is sufficiently large with respect to the amount of liquid to be discharged. Further, in the above apparatus, the switching unit is a three-way valve that connects the common tube to the suction tube in the suction state and connects the common tube to the discharge tube in the discharge state.

Further, in the above apparatus, the switching means is composed of a suction side pinch valve for clamping and closing the tip side of the suction tube, and a discharge side pinch valve for clamping and closing the base end side of the discharge tube. It is characterized by being Further, in the above apparatus, the pump is a cylinder type pump, and the piston that is in sliding contact with the inner surface of the cylinder is provided with a liquid seal for the entire circumference. Further, in the above apparatus, the pump is a cylinder type pump having a piston having an outer diameter larger than a common tube inner diameter, and the pump includes a compensating cylinder that relatively moves in synchronization with a relative movement of the cylinder and the piston of the pump. There is provided a volume compensating means having a compensating piston and a central hole formed in a tip end surface of the compensating piston and communicating with the inside of the cylinder through a compensating tube, and an outer diameter of the compensating piston is equal to that of the piston. The inner diameter of the central hole is equal to the inner diameter of the common tube.

On the other hand, the operation control method of the present invention is the operation control method of the above-mentioned apparatus, wherein the switching means is put into an inhalation state and the pump is inhaled to bring the liquid in the tank to at least the common tube. Inhaling, switching the switching means to the discharging state, operating the pump to discharge the liquid in the common tube from the discharging tube, and operating the pump while keeping the switching means in the discharging state. Sucking outside air from the discharge tube, switching the switching means to the suction state, operating the pump to discharge the outside air from the suction tube, and returning the liquid in the suction tube to the tank. Is characterized by.

In the above method, the suction position in which the pump sucks a predetermined amount, the amount of liquid to be discharged from the suction position, and the internal volume from the proximal side of the suction tube to the switching means are set in advance. A standby position for discharging a volume corresponding to the sum, and a discharging position for discharging a volume equal to or more than the sum of the liquid amount to be discharged from the suction position and the internal volume from the tip side of the discharge tube to the switching unit. When the liquid is sucked, the pump is sucked from the standby position to the suction position, when the liquid is discharged, the pump is discharged from the suction position to the discharge position, and when the outside air is sucked. The pump is sucked from the discharge position to the suction position, and when the outside air is discharged, the pump is discharged from the suction position to the standby position. Characterized in that to.

[0010]

[Operation] In the present invention as described above, by performing the operation based on the method described above by the apparatus described above, the liquid is discharged in a predetermined amount, and the liquid in the path due to the outside air is discharged from the tank each time the discharging operation is performed. Returned to. That is,
The liquid in the tank is sucked into the common tube from the suction tube by the pump, and the liquid on the pump side is measured by switching the switching means, and a predetermined amount is discharged from the discharge tube to the outside. Subsequently, the outside air is introduced from the discharge tube into the common tube, and the liquid in the suction tube is returned to the tank by switching the switching means and discharging the suction tube. For this reason, the liquid remains in each tube only for a short time during ejection, and the liquid does not stay in the tube for a long time. Therefore, the problem due to the retention in the path as in the above-described conventional discharge device is solved.

Here, if the internal volume of the common tube is made sufficiently larger than the amount of liquid to be discharged, the liquid will be weighed in the common tube and enter the pump even when handling corrosive liquids. Therefore, it is possible to avoid the possibility of impairing the operating performance of the pump. Further, if the switching means is a three-way valve, existing parts can be used and the operation can be simplified.
Furthermore, if the switching means is two pinch valves,
Since the contact between the mechanical portion and the liquid is avoided, the corrosion resistance can be ensured.

If the pump is of the cylinder type, the volume can be controlled accurately, and the volume accuracy can be increased by the liquid seal, so that the accuracy of the discharged liquid amount of the liquid can be increased. And, even when the pump is a cylinder type having a piston having an outer diameter larger than the common tube inner diameter, by providing the volume compensating means as described above,
It is possible to compensate for the volume change associated with the advance / retreat of the piston due to the difference between the piston tip area and the common tube cross-sectional area, and it is possible to improve the accuracy of the discharge suction operation by miniaturizing the liquid movement state in the common tube. Furthermore, in operation, the suction position, the standby position, and the discharge position are made to correspond to the internal volumes of the tubes, respectively, so that accurate metering or discharge is possible, and at the time of returning to the tank, depending on the discharge amount. By introducing a large volume of outside air into the tank, it is possible to compensate for the reduced volume due to discharge, and avoid inconveniences such as component volatilization due to pressure reduction in the tank and increase in suction resistance.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, the liquid ejection device 10 of the present embodiment.
A tank 20, a pump 30, and a three-way valve 40 as a switching means are provided inside and outside the main body case 11. Also, the three-way valve 40
A common tube 50 is connected between the pump 30 and the pump 30, and a suction tube 51 is connected between the three-way valve 40 and the tank 20.
A discharge tube 52 having a nozzle 12 at the lower end is connected to the three-way valve 40.

The common tube 50 is set so that its internal volume is larger than the volume V0 of the liquid to be discharged at one time. The internal volumes of the suction tube 51 and the discharge tube 52 are V1 and V2, respectively. In this embodiment, each tube 50-
The inner diameter d0 to d2 of 52 is the same, but the length is 5
1, the common tube 50, the discharge tube 52 are longer in this order. Therefore, the internal volume V1 of the suction tube 51 is smaller than the discharge volume V0, and the internal volume V2 of the discharge tube 52 is larger than the discharge volume V0 (see FIG. 3 (A)). The main body case 11 is supported by a robot arm (not shown) so that the nozzle 12 can be brought close to, in contact with, or inserted into any discharge target.

The tank 20 is a cup-shaped container supported by a support member 21 that extends laterally from the lower portion of the main body case 11, is made of a corrosion-resistant synthetic resin material, etc., and stores the liquid 13 to be discharged. Quantitative storage is possible. The base end side of the suction tube 51 described above is introduced into the tank 20 and
It communicates with the liquid phase portion of the liquid 13 inside.

The pump 30 is a syringe type pump having a cylinder 32 mounted on a clamp device 31 on the surface of the main body case 11 and a piston 33 which is advanced and retracted in the cylinder 32. On the tip side (lower side in the figure) of the cylinder 32, the common tube described above
50 connected. The piston 33 has a base end side (upper side in the figure) connected to a moving member 36, and the moving member 36 is movable back and forth along a guide rail 37 in the main body case 11 and a motor 35 via a feed screw mechanism 34. It is designed to be driven by. As a result, the rotation of the motor 35 is controlled by the feed screw mechanism 34.
Is used to drive the piston 33 forward and backward, and by accurately controlling the rotation of the motor 35, the amount of forward and backward movement of the piston 33 is accurately controlled, and the suction and discharge of the pump 30 are performed accurately. It is supposed to be.

The pump 30 is equipped with a liquid seal 60 around the base end side opening portion of the cylinder 32 in order to keep the internal space on the tip end side of the piston 33 airtight. Liquid seal 60
Has a seal space 62 formed by bulging outward around the base end side opening of the cylinder 32, and the inside thereof is filled with a seal liquid. The seal space 62 communicates with the outside via a pair of nipples 63 on the surface of the cylinder 32. A circulation device (not shown) is connected to each nipple 63 via a tube 64 so that the seal liquid in the seal space 62 is circulated. In addition to ensuring the sealing property, cleaning the surface of the piston 33 by cleaning. Is being pursued. A pair of O-rings (not shown) that are in sliding contact with the surface of the piston 33 are mounted on the inner circumferences of the cylinder 32 on the base end side and the tip end side of the seal space 62 to prevent leakage of the seal liquid.

The pump 30 is provided with a volume compensating means 70 on the upper surface of the main body case 11 for making the amount of operating liquid accurate. The volume compensating means 70 has a compensating cylinder 71 and a compensating piston 72. The compensating cylinder 71 is fixed to the moving member 36 by a rod 73, and the compensating piston 72 has a base end portion as a main body case.
It is fixed to 11, and the same amount of relative movement is performed according to the relative movement of the cylinder 32 and the piston 33.
A central hole 74 is formed so as to pass through the center from the tip end surface of the compensating piston 72, and this base end side end is connected to a nipple 76 near the tip end side of the cylinder 32 via a compensating pipe 75, and the piston inside the cylinder 32 is formed. 33 It communicates with the space on the tip side.

The outer diameter D3 of the compensating piston 72 is equal to the outer diameter D0 of the piston 33, and the inner diameter d3 of the central hole 74 is equal to the inner diameter d0 of the common tube 50. Thus, the volume change of the piston 33 and the cylinder 32 and the distance Ms only the relative movement the cylinder 32 when is ^{V0 = Ms × π × D0 2} /4, is as it moves the distance of the liquid or the like in the common tube 50 Is Mt =
^{V0 / (π × d0 2/} 4) = is a Ms × D0 ² / d0 ^2, the piston 33
The compensating cylinder 71 and compensating piston 72 move by the distance Ms due to the movement of, and the volume change at that time V3 = Ms × π × (D3 ² -d
Since 3 ² ) / 4 = Ms × π × (D0 ² -d0 ² ) / 4 is transmitted to the cylinder 32 through the compensation pipe 75, the actual volume change in the cylinder 32 is V0 '= Ms × π × D0. ^{2/4 -Ms × π × (} D0 2 -d0 2) /
^{4 = Ms × π × d0 2} /4 , and the thus actual travel distance of the liquid or the like in the common tube 50 Mt '= V0' / (π × d0 2/4) = Ms
And becomes equal to the moving amount of the piston 33. In other words, as it is, the large-diameter piston 33 makes the liquid movement amount in the common tube 50 roughly, while the volume compensating means 70 makes the liquid movement amount in the common tube 50 fine so that the liquid movement amount is compensated. The volumetric accuracy at the time of inhaling and exhaling is improved.

The three-way valve 40 has a rotor inside a casing 41.
(Not shown)
By rotating the rotor by the motor 43 installed in the lower extension portion of 11, it is possible to select between two positions of the suction state and the discharge state. A passage is formed inside the rotor, and this passage communicates the port to which the common tube 50 is connected with the port to which the suction tube 51 is connected in the suction state, and the port to which the common tube 50 is connected in the discharge state. And the discharge tube 52 is connected to the connected port. These three way valves 40 and pumps
The reference numeral 30 is connected to a control means (not shown) using a personal computer or the like, and the control means performs cooperative control based on a predetermined operation program to perform a series of operations described later.

In this embodiment thus constructed, the liquid discharge operation is performed in the following procedure. First, as shown in FIG. 3 (A), the relative position between the cylinder 32 and the piston 33 of the pump 30, the suction position S0, the standby position S1, the discharge position S2.
Is set. The suction position S0 is set at or near the mechanical suction limit of the pump 30. The standby position S1 is set to a position where the sum of the volume V0 to be discharged from the suction position S0 and the internal volume V1 of the suction tube 51 is discharged. Discharge position S2
Is set at a position where only the sum of the volume V0 to be discharged and the internal volume V2 of the discharge tube 52 is discharged. In operation,
The tank 20 is filled with the liquid 13, the pump 30 is set to the standby position S1, and the three-way valve 40 is set to the suction state. At this time, the inside of each of the tubes 50 to 52 is left empty (filled with air 14).

Next, as shown in FIG. 3 (B), the pump 30 is operated from the standby position S1 to the suction position S0 (suction volume V0 + V
1). As a result, 1 volume of liquid V0 + V1 from the tank 20
3 is sucked from the suction tube 51 through the three-way valve 40 into the common tube 50 (liquid suction operation M1). Subsequently, as shown in FIG. 3C, the three-way valve 40 is switched to the discharge state, and only the common tube 50 and the liquid 13 (volume V0) in the three-way valve 40 are communicated with the discharge tube 52. As a result, the liquid 13 is measured. Then, as shown in FIG. 3D, the pump 30 is operated from the suction position S0 to the discharge position S2 (the discharge volume V0 +
V2). As a result, the liquid 13 (volume V0) in the common tube 50 and the three-way valve 40 flows from the common tube 50 to the discharge tube.
It is ejected to the outside from the nozzle 12 at the tip through the path of volume V0 + V2 reaching 52 (liquid ejection operation M2).

Next, as shown in FIG. 3 (E), the pump 30 is moved from the discharge position S2 to the suction position while the three-way valve 40 is in the discharge state TO.
Operate up to S0 (suction volume V0 + V2). As a result, the external air 14 is sucked from the nozzle 12 at the tip into the path of the volume V0 + V2 from the discharge tube 52 to the common tube 50 (outside air suction operation M3). Then, as shown in FIG. 3 (F), the three-way valve 40 is switched to the suction state, the common tube 50 and the air 14 (volume V0) in the three-way valve 40 are communicated with the suction tube 51, and the pump 30 is moved to the suction position S0. To the standby position S1 (discharging volume V0 + V1). As a result, the air 14 (volume V0) in the common tube 50 and the three-way valve 40 is discharged into the tank 20 through the suction tube 51, and all the liquid 13 filled in the suction tube 51 by the air 14 is stored in the tank 20. It is returned to the inside (outside air discharge operation M4).

Incidentally, FIG. 4 shows the above-described liquid suction operation M1,
6 is a graph showing changes in the position of the pump 30 during a liquid discharge operation M2, an outside air suction operation M3, and an outside air discharge operation M4. In this figure, S0 to S2 indicate the position of the pump 30, M1 to M4 indicate four operations such as liquid suction, and R1 and R2 indicate the suction state and discharge state of the three-way valve 40.

According to this embodiment, the liquid suction operation M1, the liquid discharge operation M2, the outside air suction operation M3, and the outside air discharge operation are performed.
By repeating the four operations of M4, the desired volume V0
The liquid 13 can be accurately discharged. At this time, liquid
Each of the tubes 50 to 52 is filled with 13 for a short period of four operations. In particular, all the liquid 13 remaining in the intake tube 52 by the outside air intake operation M3 and the outside air discharge operation M4 is also stored in the tank.
Since it can be returned to the inside of 20, it is possible to solve the problems such as separation and deterioration of the liquid 13 due to the retention in the path for a long time, unlike the conventional discharge device.

In operation, the suction position S0, the standby position S1, and the discharge position S2 are made to correspond to the internal volumes of the tubes 50 to 52, respectively, and the path 13 is switched by the three-way valve 40 to measure the liquid 13 having a volume V0. Because it was liquid
The discharge amount of 13 can be made accurate. further,
At the time of returning the liquid 13 to the tank 20, by introducing the air 14 of the volume V0 of the liquid 13 sucked for discharge into the tank 20, the volume of the liquid 13 reduced by the discharge is compensated. ,
It is possible to avoid inconveniences such as component volatilization due to depressurization in the tank 20 and increase in suction resistance.

Further, the internal volume of the common tube 50 is set to the liquid 13
Since the volume 13 is larger than the volume V0 to be discharged, the liquid 13 does not enter the pump 30 even when the volume V0 is measured.Therefore, even if the liquid 13 is corrosive, the operation performance of the pump 30 is impaired. It is possible to avoid exertion. Since the three-way valve 40 is used as the switching means, existing parts can be used, the structure can be simplified and the cost can be reduced, and the operation and control can be simplified.

Since the pump 30 is a syringe type,
Accurate volume control is possible with a simple structure, and since the liquid seal 60 is provided in the middle to improve the hermeticity, it is possible to improve the accuracy of the discharge amount of the liquid 13. Further, the pump 30 is provided with a volume compensating means 70 to compensate for the volume change due to the difference between the tip area of the piston 33 and the cross-sectional area of the common tube 50, so that the outer diameter of the piston 33 is the inner diameter of the common tube 50. Even if the piston 33 is thicker and slightly moved, it is possible to solve the problem that the liquid 13 in the common tube 50 is largely moved, and it is possible to improve the volume accuracy when the liquid 13 is discharged or sucked.

Next, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. The liquid ejecting apparatus 10 of this embodiment basically has the same configuration as that of the first embodiment, and the description of the common parts will be omitted for simplification. On the other hand, in the above-described first embodiment, the suction tube 51 is shorter than the discharge tube 52, and the relationship between the discharge volume V0, the internal volume V1 of the suction tube 51, and the internal volume V2 of the discharge tube 52 is V1 <V0 <V2. However, in the present embodiment, the suction tube 51 is longer than the discharge tube 52, and V2 <V0 <V1 (see FIG. 5). Further, in relation to V0 to V2 described above, the respective positions S0 to S2 in the pump 30 are the suction position S0, the standby position S1, and the discharge position S2 in this order from the suction side toward the discharge side in the first embodiment. However, in this embodiment, the suction position S0, the discharge position S2, and the standby position S1 are in this order.

In this embodiment, like the first embodiment described above, the liquid suction operation M1 and the liquid discharge operation M are performed.
2. By repeating the four operations of the outside air suction operation M3 and the outside air discharge operation M4, the desired volume V0 of the liquid 13 is accurately discharged, and the sucked air 14 sucks the suction tube.
The liquid 13 in 51 is returned to the tank 20. Therefore, according to this embodiment, the same effect as that of the above-described first embodiment can be obtained.

Further, in this embodiment, the length setting of each tube 50 to 52 is different from that of the first embodiment, the internal volume V1 of the suction tube 51 is larger than the discharge volume V0, and the same pump as in the first embodiment is used. Although the desired operation cannot be obtained with the operation setting of 30 (see FIG. 4), the suction position S0, the standby position S1, and the discharge position S2 of the pump 30 are changed according to each volume V0 to V2 (see FIG. 6). As a result, a desired operation including the return of the liquid 13 in the suction tube 51 can be surely executed. Therefore, even when the suction tube 51 or the discharge tube 52 requires a predetermined length, the desired operation can be reliably performed.

The present invention is not limited to the above-mentioned embodiments, and the following modifications and the like are also included in the present invention. That is, in each of the above embodiments, the pump
30 suction position S0, standby position S1, discharge position S2 each volume V0 ~
I set it according to V2, but these are basic settings,
It may be partially increased or decreased as appropriate.

For example, although the discharge position S2 in each of the above-described embodiments is a position where V0 + V2 is discharged from the suction position S0, it may be a position where a predetermined amount is discharged as in S2 'shown in FIG. 4 or FIG. Liquid to be ejected by setting
Since the air or the like in the pump 30 will be discharged even after the liquid has been completely discharged from the tip of the nozzle 12, it is possible to obtain the breakage of the liquid 13 and the momentum of the discharge.

Further, in each of the above embodiments, the outside air suction operation M3
Although the return position of is the intake position S0, if this is further taken as the outside air intake position S0'O, the volume of the air 14 discharged into the tank 20 in the subsequent outside air discharge operation M4 can be made larger than V0 + V1 After returning the liquid 13 in the tube 51 to the tank 20, the air 14 sent to the tank 20 is increased to increase the suction tube 51.
The dischargeability of the liquid 13 therein can be improved.

On the other hand, in each of the above-described embodiments, the pump 30 is provided with the liquid seal 60 and the volume compensating means 70 to improve the volumetric accuracy of the suction and discharge, but these can be provided with a desired accuracy by other means. It may be omitted if appropriate. Further, the types of the tank 20, the pump 30, the three-way valve 40, the materials of the tubes 50 to 52, and the like may be appropriately selected, and the cost can be reduced by using existing ones.

Further, although the rotor type three-way valve 40 is used as the switching means in each of the above-mentioned embodiments, the tubes 50 to 52 are used.
May be branched and connected in a T-shape or a Y-shape, and a pinch valve or the like may be provided in the vicinity of the branch of the suction tube 51 and the discharge tube 52, respectively, and the switching means may be configured by these. With such a configuration, the liquid 13 is completely maintained in the tubes 50 to 52 and contact with the mechanical portion is avoided, so that further corrosion resistance can be ensured.

The front end opening surface of the suction tube 51 communicating with the inside of the tank 20 is not limited to downward, and may be upward when connecting to the bottom surface of the tank 20. However, in the case of facing upward, if it is thin, the liquid 13 will not flow in except in the inhalation state, but if it is thick to some extent, the tip of the liquid will be folded back into a substantially J shape and the inside of the suction tube 51 will be filled with air 14. It is desirable to take care not to replace the liquid 13 in the tank 20 during the operation.

[0038]

As described above, according to the present invention,
By performing the operation of returning the liquid remaining in the transfer path to the tank etc. each time the liquid is discharged, it is possible to avoid the liquid from accumulating in the path and prevent the obstacles associated with this accumulation to discharge the desired liquid. Can be reliably performed.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing the configuration of a first embodiment of the present invention.

FIG. 2 is a partially cutaway side view showing the configuration of the first embodiment.

FIG. 3 is a schematic diagram showing each operation of the first embodiment.

FIG. 4 is a graph showing the operation relationship of the first embodiment.

FIG. 5 is a schematic diagram showing settings of the second embodiment.

FIG. 6 is a graph showing the operation relationship of the second embodiment.

[Explanation of symbols]

 10 Liquid discharge device 13 Liquid 14 Air 20 Tank 30 Pump 40 Three-way valve as switching means 50 Common tube 51 Suction tube 52 Discharge tube 60 Liquid seal 70 Volume compensation means V0 Volume to be discharged V1 Internal volume of suction tube V2 Discharge tube Internal volume of S0 Pump suction position S1 Pump standby position S2 Pump discharge position M1 Liquid suction operation M2 Liquid discharge operation M3 Outside air suction operation M4 Outside air discharge operation R1 Intake state of switching means R2 Discharge state of switching means

Claims (9)

[Claims] 1. A tank for storing a liquid to be discharged, a suction tube having a base end side communicating with a liquid phase portion in the tank, a common tube having a lower end side connected to a tip end side of the suction tube, A pump that is connected to the upper end side of the common tube to allow suction and discharge, a discharge tube whose base end side is connected to the lower end side of the common tube, and connects the common tube and the suction tube to each other and discharges the common tube. And a switching means capable of alternately switching between an inhalation state in which communication with the tube is blocked or a discharge state in which the common tube and the discharge tube are in communication with each other and the communication between the common tube and the suction tube is blocked. A liquid ejecting device. 2. The liquid discharge apparatus according to claim 1, wherein the pump has a suction volume and a discharge volume that are equal to the sum of the internal volumes of the suction tube and the common tube and the sum of the internal volumes of the discharge tube and the common tube. A liquid ejection device, which is larger than any of the above. 3. The liquid ejecting apparatus according to claim 1 or 2, wherein the internal volume of the common tube is sufficiently larger than the amount of liquid to be ejected. 4. The liquid ejecting apparatus according to claim 1, wherein the switching unit causes the common tube to communicate with the suction tube in a suction state and the common tube in a discharging state. A liquid ejecting device, which is a three-way valve that communicates with the liquid ejection device. 5. The liquid ejecting apparatus according to any one of claims 1 to 3, wherein the switching means includes a suction-side pinch valve that clamps and closes a tip side of the suction tube, and A liquid ejection device comprising a ejection side pinch valve for clamping and closing the base end side. 6. The liquid ejecting apparatus according to any one of claims 1 to 5, wherein the pump is a cylinder type pump, and the piston slidingly contacting the inner surface of the cylinder is provided with a liquid seal for the entire circumference. A liquid ejecting apparatus comprising: 7. The liquid ejecting apparatus according to claim 1, wherein the pump is a cylinder type pump having a piston having an outer diameter larger than a common tube inner diameter, and the pump is A compensating cylinder and a compensating piston that move relative to each other in synchronism with the relative movement of the cylinder and the piston of the pump, and a central hole formed on the tip end surface of the compensating piston and communicating with the cylinder via a compensating tube. Volume compensation means is provided, the outer diameter of the compensation piston is equal to the piston,
The inner diameter of the central hole is equal to the inner diameter of the common tube. 8. A method for controlling the operation of a liquid ejecting apparatus according to claim 1, wherein the switching means is set to an inhalation state, and the pump is operated to inhale. The liquid is sucked into at least the common tube, the switching unit is switched to the discharge state, the pump is operated to discharge the liquid in the common tube from the discharge tube, and the switching unit is set to the discharge state. As it is, the pump is sucked to suck the outside air from the discharge tube, the switching means is switched to the suction state, and the pump is discharged to discharge the outside air from the suction tube to discharge the outside air in the suction tube. A method of controlling the operation of a liquid ejecting apparatus, wherein the liquid is returned to the inside of the tank. 9. The operation control method for a liquid ejecting apparatus according to claim 8, wherein a suction position at which the pump has inhaled a predetermined amount, a liquid amount to be discharged from the suction position, and a base of the suction tube in advance. A standby position at which the volume corresponding to the sum of the internal volume from the end side to the switching means is discharged, the amount of liquid to be discharged from the suction position, and the internal volume from the tip side of the discharge tube to the switching means. And a discharge position for discharging a volume equal to or more than the sum of the above, the pump is sucked from the standby position to the suction position when the liquid is sucked, and the pump is moved from the suction position when the liquid is discharged. A discharge operation is performed to a discharge position, the pump is sucked from the discharge position to the suction position when the outside air is sucked, and the pump is sucked when the outside air is discharged. Operation control method of the liquid discharge apparatus characterized by for discharging operation from the suction position to the standby position.