JP7024268B2 - Liquid discharge device - Google Patents

Description

The present invention relates to a liquid discharge device including a head and a gas supply mechanism for supplying gas to the discharge space of the head.

In a liquid discharge device, a technique of blowing gas (humidified air) from a gas outlet formed in a head is known in order to both stabilize the air flow in the discharge space and prevent the liquid discharge port from drying out. (See paragraph 0040 of Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-159557

When the liquid discharge frequency from the liquid discharge port is high, the air flow associated with the liquid discharge (hereinafter referred to as "discharge flow") and the air flow associated with the relative movement of the recording medium with respect to the discharge surface (hereinafter referred to as "discharge flow") are compared with the case where the discharge frequency is low. Hereinafter, a vortex is formed by the collision with the “relative moving flow”), and the airflow in the discharge space is easily turbulent. In Patent Document 1, when the gas (humidified air) is blown out at a predetermined flow rate regardless of the discharge frequency, there is a problem that the gas is blown out at an unnecessarily large flow rate, and a large amount of humidifying liquid (based on the humidified air) is associated therewith. The problem of consuming the liquid) arises, and both the stabilization of the air flow in the discharge space and the prevention of drying of the liquid discharge port cannot be effectively realized.

An object of the present invention is to provide a liquid discharge device capable of effectively both stabilizing the air flow in the discharge space and preventing the liquid discharge port from drying out.

The liquid discharge device according to the present invention controls a head having a discharge surface on which a liquid discharge port is formed, a gas supply mechanism for supplying gas to a discharge space facing the discharge surface, the head, and the gas supply mechanism. The control unit is provided with a control unit for supplying the gas so that when the frequency of discharging the liquid from the liquid discharge port is less than the threshold value, the wet gas is supplied to the discharge space at the first flow rate. The mechanism is controlled, and when the discharge frequency is equal to or higher than the threshold value, the gas supply mechanism is controlled so that the gas is supplied to the discharge space at a second flow rate larger than the first flow rate.

According to the present invention, the flow rate of the gas supplied to the discharge space is changed according to the discharge frequency. Specifically, when the discharge frequency is less than the threshold value, the airflow in the discharge space is less likely to be turbulent due to the collision between the discharge flow and the relative moving flow, and the liquid discharge port is more concerned about drying than the turbulence in the airflow in the discharge space. Will be done. Therefore, in this case, the wet gas is supplied at a small flow rate (first flow rate). This prevents the liquid discharge port from drying out. On the other hand, when the discharge frequency is equal to or higher than the threshold value, a vortex is likely to be formed due to the collision between the discharge flow and the relative moving flow, and there is a concern that the air flow in the discharge space may be turbulent. Therefore, in this case, the gas is supplied at a large flow rate (second flow rate). As a result, the influence of the vortex is suppressed and the airflow in the discharge space is stabilized. As described above, according to the present invention, the problem of blowing out gas at an unnecessarily large flow rate and the problem of consuming a large amount of humidifying liquid (the liquid that is the basis of the wet gas) are unlikely to occur, and the airflow in the discharge space is stable. It is possible to effectively realize both the conversion and the prevention of drying of the liquid discharge port.

The control unit controls the head so that the liquid is discharged from the liquid discharge port toward the recording medium that moves relative to the discharge surface, and when the discharge frequency is less than the threshold value, the liquid discharge. The gas supply mechanism may be controlled so that the wet gas is supplied from the upstream side of the discharge surface in the direction of relative movement of the recording medium to the discharge surface. The gas tends to flow downstream in the relative movement direction. Therefore, according to the above configuration, the wet gas effectively reaches the liquid discharge port. This makes it possible to more reliably prevent the liquid discharge port from drying out.

A gas outlet is formed on the discharge surface, and the gas supply mechanism may supply the gas to the discharge space by ejecting the gas from the gas outlet. In this case, the size of the liquid discharge device can be reduced as compared with the case where a member having a gas ejection port is provided separately from the head.

The liquid discharge device according to the present invention further includes a gas recovery port for recovering the wet gas, and the control unit has the wet state recovered from the gas recovery port when the discharge frequency is less than the threshold value. The gas supply mechanism may be controlled so that the gas of the gas is ejected from the gas outlet. In this case, by recovering and reusing the wet gas, it is possible to suppress the new generation of the wet gas and suppress the consumption of the humidifying liquid (the liquid that is the basis of the wet gas).

When the discharge frequency is equal to or higher than the threshold value, the control unit may control the gas supply mechanism so that gas is ejected from both the gas outlet and the gas recovery port toward the discharge space. As a result, when the discharge frequency is high, the influence of the vortex formed by the collision between the discharge flow and the relative moving flow can be effectively suppressed, and the air flow in the discharge space can be stabilized.

The gas recovery port is formed on the discharge surface, and may be located at a position where the liquid discharge port is sandwiched between the gas ejection port and the gas outlet. As a result, when the discharge frequency is less than the threshold value, the wet gas can be efficiently recovered and reused from the gas recovery port. When the discharge frequency is equal to or higher than the threshold value, the gas is ejected from the gas outlet and the gas recovery port arranged across the liquid discharge port, thereby affecting the influence of the vortex formed in the vicinity of the liquid discharge port. It can be effectively suppressed.

The control unit controls the head so that the liquid is discharged from the liquid discharge port toward the recording medium that moves relative to the discharge surface, and the gas outlet is more than the liquid discharge port. The gas recovery port may be arranged upstream of the relative movement direction of the recording medium with respect to the discharge surface, and the gas recovery port may be arranged downstream of the liquid discharge port in the relative movement direction. In this case, when the wet gas is ejected from the gas outlet, the wet gas flows smoothly along the relative moving flow, surely reaches the liquid discharge port, is efficiently recovered from the gas recovery port, and is re-collected. It will be used. This makes it possible to prevent the liquid discharge port from drying out and to reuse the gas more reliably. Further, when the gas is ejected from the gas outlet and the gas recovery port, the influence of the vortex can be suppressed on both the upstream and downstream sides in the direction of relative movement with respect to the liquid discharge port.

When the discharge frequency is equal to or higher than the threshold value, the control unit may control the gas supply mechanism so that a gas having a lower degree of wetness than the wet gas is supplied. When the discharge frequency is high, the liquid discharge port is difficult to dry, and there is little need to supply a wet gas. Therefore, in this case, by supplying a gas having a low degree of wetness as described above, it is not necessary to unnecessarily generate a gas in a wet state. That is, both the stabilization of the air flow in the discharge space and the prevention of drying of the liquid discharge port can be realized more effectively.

According to the present invention, both the stabilization of the air flow in the discharge space and the prevention of drying of the liquid discharge port can be effectively realized.

It is a schematic plan view of the printer which concerns on one Embodiment of this invention. It is a block diagram which shows the electric structure of the printer which concerns on one Embodiment of this invention. It is a figure which shows the partial cross section along the line III-III shown in FIG. 1 of the head of the printer which concerns on one Embodiment of this invention, and the structure of the gas supply mechanism which concerns on one Embodiment of this invention, (a). Is a diagram showing a situation in which a wet gas is ejected from a gas outlet and a wet gas is recovered from a gas recovery port, and (b) is a dry gas from both a gas outlet and a gas recovery port. It is a figure which shows the situation which is ejected. It is a flow diagram which shows the control content of the gas supply mechanism by the control part of the printer which concerns on one Embodiment of this invention.

First, the overall configuration of the printer 100 according to the embodiment of the present invention will be described.

As shown in FIG. 1, the printer 100 includes a head 1, a transport mechanism 3, a platen 4, and a control unit 5.

The head 1 is a line type color head. The head 1 is fixed at a predetermined position of the printer 100. The lower surface of the head 1 is a ejection surface 1a, and a plurality of ink ejection ports 1n are formed. The plurality of ink ejection ports 1n are arranged in a direction (scanning direction) orthogonal to the conveying direction of the paper 9 to form an ejection port row. The head 1 has a scanning direction in the longitudinal direction and covers the entire width of the paper 9. At the time of printing (that is, recording an image on the paper 9), ink is ejected from the ink ejection port 1n in accordance with the transportation of the paper 9.

Although one ejection port row is shown on the ejection surface 1a in FIG. 1, in reality, there are a plurality of ejection port rows 1a (for example, when the head 1 ejects four colors of ink, 4). One) discharge port row is formed. A plurality of discharge port rows are arranged in the transport direction.

The transport mechanism 3 has an upstream roller 3a located upstream of the head 1 in the transport direction and a downstream roller 3b located downstream of the head 1 in the transport direction. The upstream roller 3a and the downstream roller 3b are rotated by being driven by the transport motor 3m. At this time, the paper 9 is conveyed toward the ejection space V (a space facing the ejection surface 1a and defined by the ejection surface 1a and the platen 4) along the conveying direction.

The platen 4 is arranged between the upstream roller 3a and the downstream roller 3b so as to face the discharge surface 1a, and supports the conveyed paper 9 from below. The platen 4 is a flat plate member, and is sandwiched between two rollers 3a and 3b in the transport direction together with the head 1. The paper 9 faces the ejection surface 1a in the ejection space V through a gap suitable for printing.

As shown in FIG. 2, the control unit 5 includes a head driver 1d for driving the head 1, a transfer motor 3 m for driving the transfer mechanism 3, and pumps 2p1 and 2p2 constituting the gas supply mechanism 2 described later. And each of the switching valves 2v1 to 2v4 is electrically connected. The control unit 5 controls the head driver 1d, the transfer motor 3m, the pumps 2p1, 2p2, and the switching valves 2v1 to 2v4 based on the recording command (including image data) input from an external device such as a PC.

When the transfer motor 3m is driven, the two rollers 3a and 3b rotate. The paper 9 crosses the ejection space V in the transport direction while being supported by the platen 4. The head driver 1d is driven in synchronization with the feeding of the paper 9. Ink is ejected from the ink ejection port 1n on the paper 9 supported by the platen 4 based on the image data.

Next, the gas supply mechanism 2 will be specifically described.

As shown in FIG. 1, a gas ejection port 2x and a gas recovery port 2y are formed on the ejection surface 1a in addition to the ink ejection port 1n. The gas outlet 2x and the gas recovery port 2y constitute the gas supply mechanism 2. As will be described in detail later with reference to FIG. 3, the gas outlet 2x ejects a gas (including a wet gas) into the discharge space V by the action of the pump 2p1. The gas recovery port 2y recovers the wet gas from the discharge space V or ejects the gas into the discharge space V by the action of the pump 2p2.

As shown in FIG. 1, the plurality of gas outlets 2x are arranged along the discharge port row to form one outlet row. The plurality of gas recovery ports 2y are arranged along the discharge port row to form one recovery port row. The spout row is arranged upstream of the ink ejection port 1n in the transport direction. The collection port row is arranged downstream of the ink ejection port 1n in the transport direction. Each of the plurality of discharge port rows is sandwiched between one spout row and one collection port row in the transport direction.

In the present embodiment, the transport direction corresponds to the "relative movement direction" according to the present invention.

In addition to the gas outlet 2x and the gas recovery port 2y, the gas supply mechanism 2 includes a gas tank 2g, a water tank 2w, a pump 2p1, 2p2, and a switching valve 2v1 to 2v4, as shown in FIGS. Have.

The gas tank 2g stores gas (for example, air) and communicates with the atmosphere through a filter (not shown).

The water tank 2w stores a wet gas in the upper space, and stores a humidifying liquid (a liquid that is a base of the wet gas. In this embodiment, water) in the lower space. According to the consumption of the humidifying liquid, the humidifying liquid is replenished to the lower space of the water tank 2w by the replenishment means (not shown). A predetermined amount of humidifying liquid is always stored in the lower space of the water tank 2w.

The upper space of the water tank 2w communicates with the gas outlet 2x via the communication passage 2r1. A switching valve 2v3 and a pump 2p1 are arranged in the communication passage 2r1. The upper space of the water tank 2w further communicates with the gas tank 2g via the communication passage 2r2. The communication passage 2r2 is a passage branched from the position between the switching valve 2v3 and the pump 2p1 in the communication passage 2r1.

The lower space of the water tank 2w communicates with the gas recovery port 2y via the communication passage 2r3. A switching valve 2v4 and a pump 2p2 are arranged in the communication passage 2r3. The lower space of the water tank 2w further communicates with the gas tank 2g via the communication passage 2r4. The communication passage 2r4 is a passage branched from the position between the switching valve 2v4 and the pump 2p2 in the communication passage 2r3.

The control unit 5 controls the gas supply mechanism 2 to switch between opening and closing of the four switching valves 2v1 to 2v4. As a result, the communication destinations of the gas outlet 2x and the gas recovery port 2y are switched between the gas tank 2g and the water tank 2w. When it is necessary to prevent the ink ejection port 1n from drying, the water tank 2w is selected as the communication destination. When it is necessary to stabilize the air flow in the discharge space V, the gas tank 2 g is selected as the communication destination. The pump 2p2 is, for example, a tube pump, and the flow of gas in the communication passage 2r3 can be switched between the forward direction and the reverse direction.

When it is necessary to prevent the ink ejection port 1n from drying, the gas supply mechanism 2 closes the switching valves 2v1 and 2v2 under the control of the control unit 5 to separate the gas tank 2g from the gas ejection port 2x and the gas recovery port 2y. At the same time, the gas supply mechanism 2 opens the switching valves 2v3 and 2v4 under the control of the control unit 5, communicates the water tank 2w with the gas outlet 2x and the gas recovery port 2y, and starts driving the pump 2p2. At this time, the pump 2p1 is stopped, but does not obstruct the flow of gas in the communication passages 2r1 and 2r3. By driving the pump 2p2, gas is sucked from the discharge space V into the gas recovery port 2y. The gas is supplied to the lower space of the water tank 2w via the communication passage 2r3, and is humidified in the lower space of the water tank 2w to become a wet gas. The wet gas is ejected from the gas outlet 2x via the communication passage 2r1 (see FIG. 3A). As a result, the wet gas is supplied to the discharge space V. The wet gas flows in the vicinity of the discharge surface 1a along the transport direction, and a part of the wet gas is recovered from the gas recovery port 2y. Moisture in the gas is supplied to the ink in the ink ejection port 1n while the wet gas ejected from the gas ejection port 2x flows along the transport direction toward the gas recovery port 2y. As a result, it is possible to eliminate the thickening of the ink in the ink ejection port 1n or prevent the progress of the thickening. The gas recovered from the gas recovery port 2y is returned to the water tank 2w and then ejected from the gas outlet 2x again.

In the above case, when it is necessary to positively prevent the ink ejection port 1n from drying, the pump 2p1 may be driven in addition to the pump 2p2. The drive of the pumps 2p1 and 2p2 and their strength are set by the degree of dryness of the ink ejection port 1n and the environmental humidity.

When it is necessary to stabilize the air flow in the discharge space V, the gas supply mechanism 2 closes the switching valves 2v3 and 2v4 under the control of the control unit 5, and causes the water tank 2w from the gas outlet 2x and the gas recovery port 2y. Separate. At the same time, the gas supply mechanism 2 opens the switching valves 2v1 and 2v2 under the control of the control unit 5, communicates the gas tank 2g with the gas outlet 2x and the gas recovery port 2y, and starts driving the pumps 2p1 and 2p2. .. At this time, the pump 2p2 is rotated in the direction opposite to that in the case of FIG. 3A. Gas (atmosphere) is ejected from the gas outlet 2x and the gas recovery port 2y via a filter (not shown) and a gas tank 2g (see FIG. 3B). As a result, the dry gas is supplied to the discharge space V. At this time, the gas ejected from the gas ejection port 2x and the gas recovery port 2y flows substantially along the flight path of the ink, and is discharged flow (air flow accompanying ink ejection) and relative moving flow (paper 9 with respect to the ejection surface 1a). In this embodiment, the generation of vortices formed by collision with the airflow accompanying the relative movement of the paper 9) is suppressed. Therefore, the air flow in the discharge space V is stabilized.

Next, with reference to FIG. 4, the content of control by the control unit 5 will be described.

The control unit 5 first determines whether or not the image data has been input from the external device (S1). When the image data is input (S1: YES), the control unit 5 starts conveying the paper 9 (S2). The paper 9 is sent out from the paper feed tray (not shown), moves in the transport direction, and reaches the discharge space V. After S2, until the paper 9 reaches the ejection space V, the control unit 5 calculates the ejection frequency corresponding to the paper 9 based on the image data (S3). After S3, the control unit 5 determines whether or not the discharge frequency is less than the threshold value (S4).

In the present embodiment, the ejection frequency is calculated (S3) and determined (S4) for each group of ink ejection ports 1n. The plurality of discharge port rows are equally divided into several groups in the scanning direction. The ejection frequency of the group is the total number of ejections obtained by adding up the "effective number of ejections" per unit time of each of the plurality of ink ejection ports 1n constituting the group, and the ink ejection port 1n constituting the group. It is the value divided by the number of. Since the following control is performed for each group, the switching valves 2v1 to 2v4 and the pumps 2p1 and 2p2 are provided for each group.

The above "effective number of ejections" is adjusted by various factors (for example, ink droplet size, driving frequency at the time of ejection, and ink ejection speed) with respect to the "actual number of ejections". It is an ink. The larger these factors are, the larger the adjustment amount is set. For example, the larger the size of the ink droplet, the larger the "effective number of ejections" than the "actual number of ejections".

When the paper 9 is a roll paper, the ejection frequency is calculated (S3) and determined (S4) for each print area corresponding to a predetermined length in the transport direction of the roll paper.

The control unit 5 controls the gas supply mechanism 2 to supply the gas to the discharge space V. The amount of gas supplied and the form of supply depend on the judgment result of the discharge frequency.

When it is determined that the discharge frequency is less than the threshold value (S4: YES), the wet gas is supplied at a small flow rate (S5). Specifically, the control unit 5 drives the pump 2p2 with the switching valves 2v1 and 2v2 closed and the switching valves 2v3 and 2v4 open. As a result, as shown in FIG. 3A, the gas in the vicinity of the discharge surface 1a is sucked from the gas recovery port 2y and becomes a wet gas in the water tank 2w. The wet gas is supplied to the discharge space V from the gas ejection port 2x, flows along the discharge surface 1a, and goes downstream in the transport direction. A part of the gas is recovered from the gas recovery port 2y and returned to the water tank 2w.

On the other hand, when it is determined that the discharge frequency is equal to or higher than the threshold value (S4: NO), the gas (atmosphere) is supplied at a large flow rate (S6). Specifically, the control unit 5 drives the pumps 2p1, 2p2 with the switching valves 2v1 and 2v2 open and the switching valves 2v3 and 2v4 closed. At this time, the pump 2p2 is rotated in the direction opposite to that in the case of S5. As a result, as shown in FIG. 3B, the gas stored in the gas tank 2g is supplied to the discharge space V from both the gas ejection port 2x and the gas recovery port 2y. The gas supplied at this time is the atmosphere and is in a naturally moist state (a dry state having a lower degree of humidity than the moist gas supplied in S5).

When the paper 9 reaches the ejection space V, the control unit 5 ejects ink based on the image data so that printing on the paper 9 is performed (S7). The ink is ejected in synchronization with the transfer of the paper 9. After that, the control unit 5 determines whether or not printing on the paper 9 is completed (S8). If printing on the paper 9 is not completed (S8: NO), the control unit 5 returns the process to S4. That is, if the ejection frequency is less than the threshold value during printing on the paper 9, water is supplied from the gas to the ink in the ink ejection port 1n. Further, when the ejection frequency is equal to or higher than the threshold value during printing on the paper 9, a vortex formed by the collision between the ejection flow and the relative moving flow on both the upstream and downstream sides in the transport direction with respect to the flying ink. Occurrence is suppressed. Both contribute to improving image quality.

When printing on the paper 9 is completed (S8: YES), the control unit 5 determines whether or not the paper 9 to be printed next is present (S9). If there is a paper 9 to be printed next (S9: YES), the control unit 5 returns the process to S2. If there is no paper 9 to be printed next (S9: NO), the control unit 5 returns the process to S1 and waits for the input of new image data.

In the present embodiment, the above operation (air flow control) is performed for each group of ink ejection ports 1n.

The paper 9 of the present embodiment is a sheet of paper, but even when the paper 9 is a roll paper, the processing by the control unit 5 as described above is performed. If the paper is roll paper, the paper is conveyed seamlessly. The ejection frequency is obtained for each image of a predetermined length in the transport direction based on the image data. Therefore, the above-mentioned airflow control is switched every predetermined length.

When the waiting time for inputting the image data reaches a predetermined time, the control unit 5 caps the discharge surface 1a and humidifies the discharge space V. Capping of the ejection surface 1a refers to an operation of sealing the ink ejection port 1n, the gas ejection port 2x, and the gas recovery port 2y with a cap (not shown). Humidification of the discharge space V refers to an operation of ejecting a wet gas from the gas outlet 2x and supplying the wet gas to the discharge space V. The wet gas is supplied for a predetermined time. As a result, the discharge surface 1a is ready for long-term storage.

As described above, according to the present embodiment, the flow rate of the gas supplied to the discharge space V is changed according to the discharge frequency (see S4 to S6 in FIG. 4). Specifically, when the discharge frequency is less than the threshold value) (S4: YES in FIG. 4), the airflow in the discharge space V is unlikely to be turbulent due to the collision between the discharge flow and the relative moving flow, and the airflow in the discharge space V is less likely to be disturbed. There is more concern about the drying of the ink ejection port 1n than the disturbance. Therefore, in this case, the wet gas is supplied at a small flow rate (first flow rate) (see S5 in FIG. 4 and FIG. 3A). This prevents the ink ejection port 1n from drying out. On the other hand, when the discharge frequency is equal to or higher than the threshold value (S4: NO), a vortex is likely to be formed due to the collision between the discharge flow and the relative moving flow, and there is a concern that the air flow in the discharge space V may be turbulent. Therefore, in this case, the gas is supplied at a large flow rate (second flow rate) (see S6 in FIG. 4 and FIG. 3 (b)). As a result, the influence of the vortex is suppressed, and the airflow in the discharge space V is stabilized. As described above, according to the present embodiment, the problem of blowing out gas at an unnecessarily large flow rate and the problem of consuming a large amount of humidifying liquid are unlikely to occur, and the air flow of the ejection space V is stabilized and the ink ejection port 1n is prevented from drying. Both can be effectively realized.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various design changes can be made as long as it is described in the claims.

-The gas outlet and / or the gas recovery port may not be evenly arranged in the longitudinal direction of the discharge surface.
-The gas outlet and / or the gas recovery port is not limited to being formed on the discharge surface. For example, the gas outlet and / or the gas recovery port may be formed in a portion other than the discharge surface of the head. For example, two pipe members different from the head are arranged so as to sandwich the discharge surface 1a in the transport direction. Of the two pipe members, the pipe member located upstream of the discharge surface 1a in the transport direction has a gas outlet 2x formed at the lower end thereof and communicates with the pump 2p1. Of the two pipe members, the pipe member located downstream of the discharge surface 1a in the transport direction has a gas recovery port formed at the lower end thereof and communicates with the pump 2p2.
-The gas outlet is not limited to being upstream of the liquid discharge port in the relative movement direction, but is at the same position as the liquid discharge port in the relative movement direction or downstream of the liquid discharge port in the relative movement direction. May be good. The gas outlet may be arranged downstream of the liquid discharge port in the relative movement direction, and the gas recovery port may be arranged upstream of the liquid discharge port in the relative movement direction. The gas recovery port may be located at a position where the liquid discharge port is sandwiched between the gas outlet and the gas outlet in a direction intersecting the relative movement direction. The gas recovery port is not limited to the position where the liquid discharge port is sandwiched between the gas outlet and the gas outlet, and may be at any position.
-However, when the gas outlet is upstream of the liquid discharge port in the relative movement direction as in the above-described embodiment (when the gas is supplied from the upstream of the liquid discharge port in the relative movement direction), the relative movement flow. It is possible to reduce the influence of the above, and it is more effective in terms of stabilizing the air flow in the discharge space.
-In the above-described embodiment, the gas ejection port ejects gas in a direction inclined with the ejection surface 1a toward the vicinity of the ink landing position, but the gas may be ejected in any direction. For example, the gas outlet may eject gas in a direction orthogonal to the discharge surface. The recovery direction of the gas from the gas recovery port is not particularly limited, and may be a direction orthogonal to the discharge surface.
-The gas supply mechanism may supply at least the gas and does not have to recover the gas.
-The gas supply mechanism is not limited to being composed of a gas outlet, a pump, or the like, and may be composed of, for example, a fan or the like provided with rotary blades.
-The type of gas supplied by the gas supply mechanism is not particularly limited.
-The determination of the discharge frequency may be performed for each liquid discharge port, or may be performed for the entire liquid discharge port formed on the discharge surface.
-When the discharge frequency is equal to or higher than the threshold value, in the above-described embodiment, the water tank is separated from the path and the dry gas is supplied to the discharge space. However, it is not limited to this. For example, in the path passing through the water tank (FIG. 3A), the speed of the pump 2p2 may be changed according to the discharge frequency. Specifically, when the discharge frequency is equal to or higher than the threshold value, the speed of the pump 2p2 is increased as compared with the case where the discharge frequency is less than the threshold value. At this time, the humidification of the gas supplied to the lower space of the water tank 2w through the communication passage 2r3 becomes insufficient, and the gas having a low humidity is discharged from the gas outlet 2x through the communication passage 2r1. Is supplied to.
-When the discharge frequency is equal to or higher than the threshold value, a wet gas may be supplied to the discharge space.
-The liquid discharged from the liquid ejection port is not limited to the ink, and may be any liquid (for example, a treatment liquid that aggregates or precipitates the components in the ink).
-The head is not limited to the line type and may be a serial type. When the head is a serial type that discharges liquid while moving in the scanning direction, the direction opposite to the moving direction of the head corresponds to the "relative moving direction" according to the present invention. When the head is a serial type and bidirectional printing (operation of discharging liquid in each of the outward and return paths in the scanning direction), if the discharge frequency is less than the threshold value, the gas outlet or gas located upstream in the relative movement direction. Wet gas may be ejected from the recovery port. In this case, the pumps 2p1 and 2p2, which are the communication destinations of the switching valves 2v3 and 2v4, may be alternately switched between the outward path and the return path in the scanning direction.
-The present invention is not limited to printers, but can be applied to facsimiles, copiers, multifunction devices, and the like.

1 Head 1a Discharge surface 1n Ink ejection port (liquid ejection port)
2 Gas supply mechanism 2x Gas outlet 2y Gas recovery port 5 Control unit 9 Paper (recording medium)
100 printer (liquid discharge device)
V discharge space

Claims (8)

A head having a discharge surface on which a liquid discharge port is formed,
A gas supply mechanism that supplies gas from the discharge surface toward the discharge space to the discharge space facing the discharge surface.
A transport mechanism that transports the recording medium along the transport path that passes through the discharge space,
The head , the gas supply mechanism, and a control unit for controlling the transfer mechanism are provided.
The control unit
The transport mechanism is controlled so that the recording medium is transported along the transport path.
When the recording medium is in the discharge space and the liquid discharge frequency from the liquid discharge port is less than the threshold value, the gas supply mechanism is provided so that the wet gas is supplied to the discharge space at the first flow rate. Control and
When the recording medium is in the discharge space and the discharge frequency is equal to or higher than the threshold value, the gas supply mechanism is controlled so that the gas is supplied to the discharge space at a second flow rate larger than the first flow rate. A liquid discharge device characterized by the fact that. The control unit
The head is controlled so that the liquid is discharged from the liquid discharge port toward the recording medium that moves relative to the discharge surface.
When the discharge frequency is less than the threshold value, the gas supply mechanism is controlled so that the wet gas is supplied from the upstream of the liquid discharge port in the direction of relative movement of the recording medium to the discharge surface. The liquid discharge device according to claim 1. A gas outlet is formed on the discharge surface.
The liquid discharge device according to claim 2, wherein the gas supply mechanism supplies a gas to the discharge space by ejecting a gas from the gas outlet. Further provided with a gas recovery port for recovering the wet gas,
The control unit is characterized in that when the discharge frequency is less than the threshold value, the gas supply mechanism is controlled so that the wet gas recovered from the gas recovery port is ejected from the gas outlet. The liquid discharge device according to claim 3. A head having a discharge surface on which a liquid discharge port is formed,
A gas supply mechanism that supplies gas to the discharge space facing the discharge surface,
A control unit for controlling the head and the gas supply mechanism is provided.
The gas supply mechanism has a gas outlet and a gas recovery port.
The control unit
The head is controlled so that the liquid is discharged from the liquid discharge port toward the recording medium that moves relative to the discharge surface.
When the frequency of liquid discharge from the liquid discharge port is less than the threshold value, the gas supply mechanism is controlled so that the wet gas is supplied to the discharge space at the first flow rate.
When the discharge frequency is equal to or higher than the threshold value, gas is ejected from both the gas outlet and the gas recovery port toward the discharge space, and the gas is discharged into the discharge space at a second flow rate larger than the first flow rate. A liquid discharge device, characterized in that the gas supply mechanism is controlled so as to be supplied to the gas supply mechanism. The liquid discharge device according to claim 4 or 5, wherein the gas recovery port is formed on the discharge surface and is located at a position sandwiching the liquid discharge port with the gas outlet. The gas outlet is arranged upstream of the liquid ejection port in the direction of relative movement of the recording medium with respect to the ejection surface.
The liquid discharge device according to claim 6, wherein the gas recovery port is arranged downstream of the liquid discharge port in the relative movement direction. Claims 1 to 7 are characterized in that, when the discharge frequency is equal to or higher than the threshold value, the control unit controls the gas supply mechanism so that a gas having a lower degree of wetness than the wet gas is supplied. The liquid discharge device according to any one of the above items.

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