Patent Description:
In an ink supply apparatus that supplies ink and the like, as typified by an inkjet, in order to convey a high-viscosity ink having a large amount of solid components and high settleability in a dispersed state, a technology that relates to an operation is known (which, hereinafter, may be referred to as flow-through) in which the ink is conveyed by being circulated by taking, as part of the flow path, a liquid chamber for the ink in the discharge head. In addition, as technology for discharging a high-viscosity ink (of about <NUM> mPa·s, for example) that cannot be discharged by a normal inkjet method, an airless spray is known for which a high pressure is applied to the ink and the ink is vigorously discharged from a spray gun tip hole to atomize and coat the ink.

Where the above-described inkjet technology is concerned, in the case of a technology using hydraulic head pressure, it is difficult to convey the high-viscosity ink by circulating same because the circulation structure is under a pressure close to atmospheric pressure. If the conveyance through circulation cannot be performed, there is advancement of ink separation and precipitation, an abnormal image caused by a drop in ink concentration and discharge failure due to nozzle clogging caused by ink solid precipitate occur, and there is a problem that the ink cannot be blown over a distance by using a fluctuating pressure under meniscus control. Furthermore, in the case of an airless spray, there is a problem that, although high-viscosity ink can be discharged over a distance, there is advancement of ink separation and precipitation due to a structure in which the high-viscosity ink cannot flow through the discharge head, and discharge failure occurs due to an abnormal image caused by a drop in ink concentration, nozzle clogging caused by ink solid precipitate, and the like.

As such inkjet technology, a configuration is disclosed that includes a degassing unit and wherein a differential pressure is provided between a filling tank upstream of a discharge head and a drain tank downstream thereof to produce flow-through, and in order to supply ink to both tanks so that the ink in the filling tank and the drain tank is not depleted even if large droplets are discharged, a configuration in which, in a case where the ink in the filling tank or the drain tank is depleted, a state where the ink constantly flows through in the discharge head is maintained while a flow path is switched by an electromagnetic valve or the like so that a main tank and the filling tank or the drain tank communicate with each other is implemented using one pump (for example, <CIT>).

However, in the technology disclosed in <CIT>, because the degassing unit is provided, it is assumed to be a normal discharge head, and hence there is a problem that it is difficult for a high-viscosity ink to circulate and the high-viscosity ink cannot be stably discharged over a distance.

<CIT> discloses an inkjet printer apparatus which includes a pressure-regulated tank having an inlet connected to an ink reservoir, and an outlet connected to a printhead including nozzles for discharging continuous streams of ink drops towards a substrate for printing thereon and gutters for intercepting the ink drops not to be printed. The apparatus further includes a bypass line between the tank outlet and the ink reservoir, a bypass control valve for controlling the flow rate via the bypass line enabling the flow rate to be preset during draining of the tank, and a pump controllable to enable pre-calibrating the pump during filling of the tank. Also described is a method of controlling an inkjet printer apparatus by determining a nominal flow rate of the pump during a non-printing operation while filling the tank to a predetermined level, and controlling the pump during a printing operation to produce a flow rate slightly below the nominal flow rate when the level of the ink in the tank is at or above the predetermined level, and a flow rate slightly above the nominal flow rate when the level of the ink in the tank is below the predetermined level.

In light of the above-described problem, an object of the present disclosure is to provide a liquid supply apparatus and a liquid application apparatus that can discharge a high-viscosity liquid stably and over a distance.

The invention is defined by the subject matter of claim <NUM>. The dependent claims relate to preferred embodiments of the invention.

The accompanying drawings are intended to depict embodiments of the present disclosure.

Hereinafter, embodiments of a liquid supply apparatus according to embodiments of the present invention will be described in detail with reference to the drawings. In addition, the present disclosure is not limited by the following embodiments, and constituent elements in the following embodiments include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those within a so-called equivalent range. Various omissions, substitutions, changes, and combinations of constituent elements can be made without departing from the scope of the appended claims.

Hereinafter, a liquid supply apparatus according to embodiments of the present disclosure will be described in detail with reference to the drawings. The present disclosure, however, is not limited to the following one or more embodiments, and the constituent elements of the following one or more embodiments include elements that may be easily conceived by those skilled in the art, those being substantially the same ones, and those being within equivalent ranges. Various omissions, substitutions, changes, and combinations of constituent elements can be made without departing from the scope of the appended claims.

<FIG> is a diagram illustrating a configuration of an ink supply apparatus according to a first embodiment of the present disclosure. <FIG> are diagrams each illustrating a structure of an accumulator of the ink supply apparatus according to the first embodiment. <FIG> are diagrams each illustrating a structure of a piston pressing mechanism that can be substituted for the accumulator of the ink supply apparatus according to the first embodiment. <FIG> are diagrams each illustrating a structure of a subtank that can be substituted for the accumulator of the ink supply apparatus according to the first embodiment. A configuration of an ink supply apparatus <NUM> according to the present embodiment will be described with reference to <FIG>.

The ink supply apparatus <NUM> (an example of a liquid supply apparatus) is an apparatus for forming an image on a print medium by discharging a high-viscosity ink (hereinafter, the ink is sometimes referred to as high-viscosity ink or simply ink) from a discharge head <NUM> while causing the high-viscosity ink, which is a non-Newtonian fluid having thixotropy, to flow through. Note that, in the present embodiment, the ink will be described as an example, but the present invention can be generally applied to a high-viscosity liquid which is a non-Newtonian fluid having thixotropy. As illustrated in <FIG>, the ink supply apparatus <NUM> includes a high-pressure air supply source <NUM> (compressed air supply source), a regulator <NUM>, a pressurizing tank <NUM>, a stirring device <NUM>, a pump <NUM> (an example of a feeder), a filter <NUM>, an accumulator <NUM> (an example of a first mitigation device), a pressure gauge <NUM>, a discharge head <NUM>, a nozzle open-close control device <NUM>, a pressure control device <NUM> (first control device), and a control device <NUM>.

The high-pressure air supply source <NUM> is coupled to the pressurizing tank <NUM> via an air supply path <NUM>, and is an air supply source for sending high-pressure air compressed by a compressor or the like to the pressurizing tank <NUM>. The high-pressure air supply source <NUM> sends, for example, air compressed to a pressure equal to or greater than atmospheric pressure to the pressurizing tank <NUM>.

The regulator <NUM> is a regulator device that is installed on the air supply path <NUM> and that reduces the pressure of the high-pressure air supplied from the high-pressure air supply source <NUM> to a given pressure. That is, the regulator <NUM> adjusts the pressure of the air supplied from the air supply path <NUM> to a given pressure greater than atmospheric pressure and lower than the pressure of the air compressed by the high-pressure air supply source <NUM>, and uses the air at that pressure to pressurize an ink IK1, which is the high-viscosity ink with which the pressurizing tank <NUM> is filled. Adjustment of the pressure reduction by the regulator <NUM> is performed manually, for example.

The pressurizing tank <NUM> is a tank filled with the ink IK1, which is a high-viscosity ink. The air supply path <NUM> is coupled to an upper portion of the pressurizing tank <NUM>. The compressed air that is sent from the high-pressure air supply source <NUM> and passes through the regulator <NUM> is supplied into the pressurizing tank <NUM> to pressurize the ink IK1 in the pressurizing tank <NUM>. Furthermore, an ink flow path <NUM> (an example of a liquid flow path) that enables the ink IK1 to flow out is coupled to a lower portion of the pressurizing tank <NUM>, and the ink flow path <NUM> is coupled to the discharge head <NUM>. That is, the ink flow path <NUM> which is a "liquid flow path" indicates a flow path through which the ink flowing out from the pressurizing tank <NUM> flows into the discharge head <NUM>.

Note that the pressurizing tank <NUM> may include, for example, a water level gauge for measuring the fill amount of the ink IK1, an ink temperature controller such as a heater or a cooler for managing the viscosity of the ink IK1, a thermometer for managing and controlling the temperature of the ink IK1, and the like.

The stirring device <NUM> is a device for stirring the ink IK1 with which the pressurizing tank <NUM> is filled. The stirring device <NUM> includes a stirring motor 103a and a stirrer 103b.

The stirring motor 103a is a motor device for stirring the ink IK1 by rotationally driving the stirrer 103b. The on/off operation of the rotation of the stirring motor 103a is controlled by the control device <NUM>.

The stirrer 103b is a stirring member that rotates under the rotation of the stirring motor 103a to stir the ink IK1.

The pump <NUM> is a pump device that is installed at a position downstream (on an ink outflow side) from the pressurizing tank <NUM> and upstream (on an ink inflow side) from the accumulator <NUM> on the ink flow path <NUM>, and pressure-feeds and conveys the ink IK1, which is accumulated in the pressurizing tank <NUM>, toward the accumulator <NUM> in the direction indicated by arrow A in <FIG> on the ink flow path <NUM>. The pump <NUM> is a diaphragm pump that has a film called a diaphragm, which is an elastic body for separating ink and a structure, and that pressure-feeds the ink through contraction of the diaphragm. The speed of rotation of the pump <NUM> is controlled by the pressure control device <NUM>.

The filter <NUM> is a device that is installed at a position downstream from the pump <NUM> on the ink flow path <NUM> and that removes foreign matter in the ink which is pressure-fed by the pump <NUM>.

The accumulator <NUM> is installed on the ink flow path <NUM> at a position downstream from the filter <NUM> and upstream from the discharge head <NUM>, and is a pressure accumulator that absorbs and compensates for the increase and decrease in the pressure of the ink flowing inside to mitigate the fluctuation in the pressure. That is, the accumulator <NUM> is installed on the ink flow path <NUM> at a position downstream from the pressurizing tank <NUM> and upstream from the discharge head <NUM>, and absorbs the fluctuation of the pressure of the ink flowing through the ink flow path <NUM>. The accumulator <NUM> has a function to convert the pressure energy of liquid ink into the pressure energy of gas and to store the pressure energy. Specifically, the accumulator <NUM> absorbs the pressure energy applied to the liquid ink by reducing the volume of the gas, and meanwhile functions to compensate for the pressure energy of the liquid by using the pressure energy of the gas when the pressure energy of the ink is lost. Therefore, a damper effect of absorbing and compensating for the increase/decrease in the pressure can be exhibited, and the fluctuation in the pressure is mitigated. In this case, because the inside of the ink flow path <NUM> is sealed, the increase/decrease in the pressure of the ink becomes approximately the increase/decrease of the flow rate of the ink as is, and thus the accumulator <NUM> also serves to mitigate the flow rate of the ink.

For example, as illustrated in <FIG>, the accumulator <NUM> includes a main body 131a and a film 131b. The film 131b is called a bladder, and a gas such as nitrogen gas is sealed therein. In order to efficiently exert the effect of mitigating the pressure fluctuation of the ink by means of the accumulator <NUM>, a gas such as a nitrogen gas is sealed inside the film 131b at a sealing pressure of about <NUM>% of the pressure of the ink. In a case where the pressure of the ink flowing through the ink flow path <NUM> is small, as illustrated in <FIG>, the gas enclosed in the film 131b expands, and the film 131b enters a state of being in close contact with the inner wall surface of the main body 131a. Then, when the pressure of the ink flowing through the ink flow path <NUM> increases, as illustrated in <FIG>, the film 131b in which the gas is enclosed is reduced and the gas is compressed, and thus the pressure energy of the ink is absorbed by the gas. On the other hand, when the pressure of the ink flowing through the ink flow path <NUM> drops, as illustrated in <FIG>, the film 131b filled with the gas expands, and pressure energy is applied from the gas to the ink. Through these operations, the accumulator <NUM> functions to maintain a constant pressure of the ink flowing through the ink flow path <NUM>, and, as a result, fluctuation in the pressure of the ink can be mitigated.

Note that, in the example illustrated in <FIG>, the accumulator <NUM> is used as a device that mitigates the pressure fluctuation of the ink flowing through the ink flow path <NUM>, but the invention is not limited thereto. Instead of the accumulator <NUM>, a piston pressing mechanism <NUM>-<NUM> (an example of a first mitigation device) illustrated in <FIG>, a subtank <NUM>-<NUM> illustrated in <FIG> (an example of a first mitigation device), or the like may be used as a device that mitigates the pressure fluctuation.

As illustrated in <FIG>, the piston pressing mechanism <NUM>-<NUM> includes a shock absorber <NUM>-2a, a cylinder <NUM>-2b, and a piston <NUM>-2c, for example. As illustrated in <FIG>, the shock absorber <NUM>-2a is a member that attenuates and absorbs the fluctuation in the pressure from the ink flowing through the ink flow path <NUM> applied to the coupled piston <NUM>-2c. The cylinder <NUM>-2b is a cylindrical member that enables the piston <NUM>-2c, to which the shock absorber <NUM>-2a is coupled, to move slidably along an inner wall surface of the cylinder. The piston <NUM>-2c is a member that is coupled to the shock absorber <NUM>-2a and that reciprocates slidably along the inner wall surface of the cylinder <NUM>-2b. The fluctuation in the pressure of the ink received from the bottom surface of the piston <NUM>-2c is absorbed by the action of the shock absorber <NUM>-2a coupled to the piston <NUM>-2c. Due to this operation, the piston pressing mechanism <NUM>-<NUM> functions so that the pressure of the ink flowing through the ink flow path <NUM> is kept constant, and as a result, enables the fluctuation in the ink pressure to be mitigated.

As illustrated in <FIG>, the subtank <NUM>-<NUM> is a tank member in which a high-pressure gas is sealed. When the pressure of the ink flowing through the ink flow path <NUM> increases, the enclosed gas is reduced and compressed, and the pressure energy of the ink is absorbed by the gas, as illustrated in <FIG>. On the other hand, when the pressure of the ink flowing through the ink flow path <NUM> drops, the enclosed gas expands, and pressure energy is applied from the gas to the ink, as illustrated in <FIG>. Through these operations, the subtank <NUM>-<NUM> functions so that the pressure of the ink flowing through the ink flow path <NUM> is kept constant, and as a result, the fluctuation in the pressure of the ink can be mitigated.

The pressure gauge <NUM> is a pressure gauge that measures the pressure of the ink flowing through the ink flow path <NUM>. In the example of <FIG>, the pressure gauge <NUM> is installed at a position downstream from the accumulator <NUM> and upstream from the discharge head <NUM> on the ink flow path <NUM>, and that measures the pressure obtained by adding the discharge pressure when discharging the ink of the pump <NUM> to the pressure applied to the ink IK1 in the pressurizing tank <NUM> by the high-pressure air supply source <NUM> and subtracting the pressure loss in each device arranged on the upstream side from the pressure gauge <NUM> on the ink flow path <NUM>. In order to achieve stable ink discharge from the nozzles of the discharge head <NUM>, the pressure of the ink flowing through the discharge head <NUM> is stable. Therefore, in order to measure the pressure of the ink flowing to the discharge head <NUM> as accurately as possible, it is desirable to install the pressure gauge <NUM> at a position upstream from the discharge head <NUM> and as close to the discharge head <NUM> as possible to reduce the pressure loss of the ink without arranging anything other than the ink flow path <NUM> between the pressure gauge <NUM> and the discharge head <NUM>. In this case, the pressure of the ink flowing through the discharge head <NUM> measured by the pressure gauge <NUM> is referred to as the discharge pressure. Data on the pressure of the ink measured by the pressure gauge <NUM> is transmitted to the pressure control device <NUM>.

The discharge head <NUM> is an inkjet head that includes one or a plurality of openable-closable nozzles and that discharges high-viscosity ink from the nozzles. The open-close control of the nozzles of the discharge head <NUM> is performed by the nozzle open-close control device <NUM>. Specifically, the discharge head <NUM> uses a system in which a needle is operated by an actuator to open and close a nozzle. This system is a system in which a needle with a lid (plug) on a nozzle is lifted by an actuator so that ink flows out to the outside through the nozzle. In this case, when the outflow of the ink is stopped by quickly pressing the needle against the nozzle so as to cover (plug) the nozzle, the ink that has flown out becomes a droplet and is vigorously discharged substantially in the direction of the center line of the nozzle, and lands on the print medium while maintaining the droplet state up to about <NUM> ahead. For example, the configuration disclosed in <CIT> can be adopted as the configuration of the discharge head <NUM>. Furthermore, the discharge head <NUM> includes an in-head flow path (internal flow path) communicating with one or a plurality of nozzles, and one end of the flow path serving as an input hole is coupled to an ink flow path <NUM>, while the other end serving as a discharge hole is coupled to an ink flow path <NUM> (an example of a liquid flow path). That is, the ink that is conveyed from the ink flow path <NUM> flows through the above-described in-head flow path (internal flow path), and the ink is discharged from the in-head flow path through the nozzles. The ink flow path <NUM> is coupled to an upper portion of the pressurizing tank <NUM>. That is, the ink flow path <NUM> which is a "liquid flow path" indicates a flow path through which the ink flowing out from the in-head flow path (internal flow path) of the discharge head <NUM> flows into the pressurizing tank <NUM>. Thus, a circulation path is formed in which the ink repeatedly circulates in the liquid flow path formed of the ink flow path <NUM> and the ink flow path <NUM> in the order of the pressurizing tank <NUM>, the accumulator <NUM>, the discharge head <NUM>, and the pressurizing tank <NUM>. When the pump <NUM> is driven, the ink is conveyed in the circulation path in the direction of arrow A, and as a result, the ink also passes through the discharge head <NUM>. In this manner, a state in which the ink circulates in the circulation path to cause the ink to flow into the discharge head <NUM> is referred to as flow-through. In addition, the state in which the pump <NUM> is driven to cause ink to continuously flow into the discharge head <NUM> (the state in which the pump <NUM> circulates ink in the circulation path) when the discharge head <NUM> is discharging ink or not discharging ink is referred to as a constant flow-through.

The nozzle open-close control device <NUM> is a device that performs open-close control of a nozzle by using an actuator to operate a needle of the discharge head <NUM>.

The pressure control device <NUM> is a device that receives the data on the pressure of the ink measured by the pressure gauge <NUM> and that freely controls the speed of rotation of the pump <NUM> so that the pressure be a given pressure (a predetermined value). Furthermore, the pressure control device <NUM> performs stable pressure control of the ink by controlling the speed of rotation of the pump <NUM> in conjunction with the nozzle open-close control device <NUM> on the basis of the data on the pressure (discharge pressure) of the ink measured by the pressure gauge <NUM> when the nozzle of the discharge head <NUM> is not open. In this case, the pressure control device <NUM> detects the open state of the nozzle of the nozzle open-close control device <NUM> via the control device <NUM>.

Further, the pressure control device <NUM> temporarily raises or lowers the discharge pressure by controlling the speed of rotation of the pump <NUM>. For example, a solid material is dispersed in the ink, and sometimes aggregated ink, foreign matter, or the like, is filtered and accumulated by the filter <NUM>. As a result, the fluid resistance in the filter <NUM> increases, and the pressure of the ink measured by the downstream pressure gauge <NUM>, that is, the discharge pressure drops. In this case, the pressure control device <NUM> stabilizes the discharge pressure to a constant value by raising or lowering (in this case, raising) the discharge pressure by the pump <NUM> on the basis of the pressure of the ink measured by the pressure gauge <NUM>. Furthermore, for example, in order to recover an abnormal state such as clogging of the nozzle of the discharge head <NUM> with ink, the pressure control device <NUM> also, as nozzle cleaning, temporarily increases the discharge amount of ink by the pump <NUM> (increases the discharge pressure) and increases the discharge pressure in accordance with an instruction from a host control device <NUM>, thereby discharging the ink clogged in the nozzle.

The control device <NUM> is a controller that controls the operation of the entire ink supply apparatus <NUM>. The control device <NUM> performs, for example, on/off control of the stirring operation of the stirring device <NUM>, control of the nozzle open-close control device <NUM>, and control of the pressure control device <NUM>.

Note that the ink supply apparatus <NUM> may include other constituent elements in addition to the constituent elements illustrated in <FIG>. For example, the ink supply apparatus <NUM> may include, for example, a flow path opening/sealing valve including an electromagnetic valve or the like that controls the start and stop of the ink flow, a safety valve for releasing the high pressure of the pressurizing tank <NUM> to the atmosphere, a discharge switching flow path for discharging the ink from the circulation path, and the like.

<FIG> is a diagram illustrating a configuration for measuring a pressure and a flow rate of ink flowing into a discharge head in the ink supply apparatus according to the first embodiment. <FIG> are diagrams illustrating examples of graphs illustrating comparison results of the pressure and the flow rate of the ink flowing into the discharge head according to the presence or absence of the accumulator in the ink supply apparatus according to the first embodiment. With reference to <FIG>, stabilization of the pressure (discharge pressure) and flow rate of the ink flowing to the discharge head <NUM> by the accumulator <NUM> of the ink supply apparatus <NUM> according to the present embodiment will be described.

As described above, because the pump <NUM> includes a diaphragm (film), the ink in the pump <NUM> and the internal structure do not come into contact with each other, and thus defects such as contamination hardly occur. However, periodic fluctuations (pulsation) in the pressure and the flow rate of the ink due to contraction of the diaphragm (film) occur, which becomes an obstacle for maintaining a stable discharge pressure. As described above, because the ink supply apparatus <NUM> according to the present embodiment includes the accumulator <NUM> installed at a position downstream from the filter <NUM> and upstream from the discharge head <NUM> on the ink flow path <NUM>, it is possible to suppress pulsations of the pressure and the flow rate of the ink due to the driving of the pump <NUM>.

Furthermore, when the ink is discharged from the discharge head <NUM>, the pressure of the ink flowing in the discharge head <NUM> is released to the atmosphere only for the opening period of the nozzle, and hence the discharge pressure drops. At the same time, when the ink is discharged from the nozzles of the discharge head <NUM>, variation in the flow rate of the ink flowing to the discharge head <NUM> occurs in an amount equivalent to the total amount of the increase in the flow rate corresponding to the discharge amount of the ink on the upstream side from the discharge head <NUM> and the decrease in the flow rate corresponding to the discharge amount on the downstream side from the discharge head <NUM>. That is, when the ink is discharged from the discharge head <NUM>, a steep fluctuation occurs in the pressure (discharge pressure) and the flow rate of the ink. When ink is intermittently and continuously discharged from a plurality of nozzles of the discharge head <NUM>, it is conceivable that the discharge pressure at a certain timing is not constant, depending on the state of discharge from the nozzles in the vicinity including the discharge head up to immediately before (crosstalk). As described above, because the ink supply apparatus <NUM> according to the present embodiment includes the accumulator <NUM> installed on the ink flow path <NUM> at a position downstream from the filter <NUM> and upstream from the discharge head <NUM>, it is possible to suppress the fluctuation in the pressure and the flow rate due to the discharge of the ink from the discharge head <NUM>.

Here, a specific example illustrating the advantageous effect, in the ink supply apparatus <NUM> according to the present embodiment, of the pressure (discharge pressure) and the flow rate of the ink flowing through the discharge head <NUM> being stabilized by the accumulator <NUM> will be described with reference to <FIG>. In the ink supply apparatus <NUM> illustrated in <FIG>, in order to measure the flow rate of the ink flowing into the discharge head <NUM>, a flow meter <NUM> is installed at a position downstream from the accumulator <NUM> and upstream from the pressure gauge <NUM> on the ink flow path <NUM> with respect to the ink supply apparatus <NUM> illustrated in <FIG>. In the ink supply apparatus <NUM> illustrated in <FIG>, the pump <NUM> circulates the ink in the circulation path. In such a case, <FIG> illustrate graphs relating to the pressure (pressure measured by the pressure gauge <NUM>) and the flow rate (flow rate measured by the flow meter <NUM>) of the ink flowing through the discharge head <NUM> in a case where the accumulator <NUM> is not installed and in a case where installation thereof is desired in the configuration of the ink supply apparatus <NUM> illustrated in <FIG>.

The graph illustrated in <FIG> illustrates, in chronological order, the pressure value and the flow rate value of the ink flowing through the discharge head <NUM> in a case where the accumulator <NUM> is not installed. On the other hand, the graph illustrated in <FIG> illustrates, in chronological order, the pressure value and the flow rate value of the ink flowing through the discharge head <NUM> in a case where the accumulator <NUM> is installed. Note that both graphs are raw data measured by the pressure gauge <NUM> and the flow meter <NUM>, and thus include fine noise. As becomes clear upon comparing both graphs, it is understood that the periodic ink pressure and flow rate fluctuations (amplitudes) appearing in the graph of <FIG> are significantly suppressed as illustrated in the graph of <FIG>.

The graph illustrated in <FIG> illustrates results obtained by analyzing, using an FFT (fast Fourier Transform), the pressure value of the ink flowing through the discharge head <NUM> in a case where the accumulator <NUM> is not installed. On the other hand, the graph illustrated in <FIG> illustrates a result of FFT analysis of the pressure value of the ink flowing through the discharge head <NUM> in a case where the accumulator <NUM> is installed. As becomes clear upon comparing both graphs, in a case where the accumulator <NUM> is not installed, peaks occur at two specific frequencies, and it is understood that a strong fluctuation in the pressure value occurs at these frequencies. It is known that the frequencies of these peaks are caused by the speed of rotation of the pump <NUM> because the frequency also increases when the discharge amount of the pump <NUM> is increased, that is, the speed of rotation of the pump <NUM> is increased. On the other hand, the peaks are not observed in the graph in a case where the accumulator <NUM> is installed, and it is understood that the fluctuation in the pressure value at said frequencies is suppressed.

The graph illustrated in <FIG> illustrates a result of FFT analysis of the flow rate value of the ink flowing through the discharge head <NUM> in a case where the accumulator <NUM> is not installed. On the other hand, the graph illustrated in <FIG> illustrates a result of FFT analysis of the flow rate value of the ink flowing through the discharge head <NUM> in a case where the accumulator <NUM> is installed. As becomes clear upon comparing both graphs, in a case where the accumulator <NUM> is not installed, peaks occur at two specific frequencies, and it is understood that a strong fluctuation in the flow rate value occurs at these frequencies. As described above, it is known that the frequencies of these peaks are caused by the speed of rotation of the pump <NUM> because the frequency also increases when the discharge amount of the pump <NUM> is increased, that is, the speed of rotation of the pump <NUM> is increased. On the other hand, the peaks are not recognized in the graph in a case where the accumulator <NUM> is installed, and it is understood that the fluctuation of the flow rate value at these frequencies is suppressed.

In light of the foregoing, as illustrated in <FIG>, it is understood that, by installing the accumulator <NUM> at a position downstream from the filter <NUM> (the downstream side from the pump <NUM>) and upstream from the discharge head <NUM> on the ink flow path <NUM>, the pulsation of the pressure and the flow rate of the ink due to the driving of the pump <NUM> is suppressed, and the pulsation is suppressed to such an extent that peaks are not detected even using FFT analysis.

As described above, in the ink supply apparatus <NUM> according to the present embodiment, the pressurizing tank <NUM> is supplied with the air compressed by the high-pressure air supply source <NUM> and accumulates the ink pressurized by the compressed air, the pump <NUM> is installed on the ink flow path <NUM> at a position downstream from the pressurizing tank <NUM> and upstream from the accumulator <NUM> and pressure-feeds the ink in the pressurizing tank <NUM> toward the accumulator <NUM> to the ink flow path <NUM>, the discharge head <NUM> includes an internal flow path through which the ink conveyed from the ink flow path <NUM> flows and discharges the ink from the internal flow path via the nozzles, the accumulator <NUM> is installed in the ink flow path <NUM> on the downstream side from the pressurizing tank <NUM> and on the upstream side from the discharge head <NUM> and absorbs the fluctuation in the pressure of the ink flowing through the ink flow path <NUM>, a circulation path is formed in which the ink circulates in the ink flow path in the order of the pressurizing tank <NUM>, the accumulator <NUM>, the discharge head <NUM>, and the pressurizing tank <NUM>, and the pump <NUM> circulates the ink in the circulation path. As a result, fluctuations in the pressure and the flow rate due to the discharge of the ink from the discharge head <NUM> can be suppressed, and hence the high-viscosity ink (an example of liquid) can be discharged stably and over a distance. Furthermore, the pulsation of the pressure and the flow rate of the ink due to the driving of the pump <NUM> can be suppressed.

An ink supply apparatus according to a second embodiment will be described by focusing on differences from the ink supply apparatus <NUM> according to the first embodiment. In the present embodiment, a configuration in which an accumulator is also installed at a position downstream from the discharge head <NUM> will be described.

<FIG> is a diagram illustrating a configuration of an ink supply apparatus according to the second embodiment. The configuration of the ink supply apparatus 100a according to the present embodiment will be described with reference to <FIG>.

As illustrated in <FIG>, the ink supply apparatus 100a includes a high-pressure air supply source <NUM> (compressed air supply source), a regulator <NUM>, a pressurizing tank <NUM>, a stirring device <NUM>, a pump <NUM> (an example of a feeder), a filter <NUM>, an accumulator <NUM> (an example of a first mitigation device), a pressure gauge <NUM>, a discharge head <NUM>, a nozzle open-close control device <NUM>, an accumulator <NUM> (an example of a second mitigation device), a pressure control device <NUM> (a first control device), and a control device <NUM>. That is, the configuration of the ink supply apparatus 100a is similar to the configuration of the ink supply apparatus <NUM> according to the above-described first embodiment except that the accumulator <NUM> is provided.

The accumulator <NUM> is installed at a position immediately downstream from the discharge head <NUM> on the ink flow path <NUM>, and is a pressure accumulator that absorbs and compensates for the increase/decrease in the pressure of the ink flowing inside to mitigate the fluctuation in the pressure. That is, the accumulator <NUM> is installed on the ink flow path <NUM> at a position downstream from the discharge head <NUM> and upstream from the pressurizing tank <NUM>, and absorbs the fluctuation of the pressure of the ink flowing through the ink flow path <NUM>. The configuration of the accumulator <NUM> is similar to the configuration of the accumulator <NUM>, and instead of the accumulator <NUM>, the piston pressing mechanism <NUM>-<NUM> (an example of the second mitigation device) illustrated in <FIG> described above or the subtank <NUM>-<NUM> (an example of the second mitigation device) illustrated in <FIG> may be used.

Between a nozzle located most upstream on the circulation flow path in the discharge head <NUM>, that is, the nozzle closest to the accumulator <NUM>, and a nozzle located most downstream on the circulation path, that is, the nozzle farthest from the accumulator <NUM>, the magnitude of the pressure loss varies depending on the shape, distance, and the like of the flow path in the discharge head <NUM> to the accumulator <NUM>, and hence the pressure of the ink may vary.

The discharge head <NUM> is freely movable in a printable region of the image forming apparatus on which the ink supply apparatus 100a is mounted, and a plurality of nozzles is arranged so as to be as narrow as possible between the nozzles in order to discharge ink at any place in the printable region. In order to uniformly impart a damper effect to all the nozzles, it is conceivable to dispose a damper member for each nozzle, but this is unrealistic in view of the size and configuration layout of the discharge head <NUM>. Therefore, in the present embodiment, as described above, the accumulator <NUM> is installed at a position immediately downstream from the discharge head <NUM> on the ink flow path <NUM>. As a result, the damper effect can be more uniformly exhibited for all the nozzles of the discharge head <NUM>, and fluctuations in the pressure and the flow rate due to the discharge of the ink from the discharge head <NUM> can be more effectively suppressed.

Note that the accumulator <NUM> is desirably installed at a position downstream from the discharge head <NUM> and as close possible to the discharge head <NUM> in order to reduce the pressure loss in the flow path.

An ink supply apparatus according to a third embodiment will be described by focusing on differences from the ink supply apparatus <NUM> according to the first embodiment. In the present embodiment, a configuration in which another pressurizing tank is provided in addition to the pressurizing tank <NUM> will be described.

<FIG> is a diagram illustrating a configuration of an ink supply apparatus according to a third embodiment of the present disclosure. A configuration of an ink supply apparatus 100b according to the present embodiment will be described with reference to <FIG>.

As illustrated in <FIG>, the ink supply apparatus 100b includes a high-pressure air supply source <NUM> (compressed air supply source), a regulator <NUM> (first regulator), a pressurizing tank <NUM> (first pressurizing tank), a stirring device <NUM>, a regulator <NUM> (second regulator), a pressurizing tank <NUM> (second pressurizing tank), a stirring device <NUM>, a pump <NUM>, a filter <NUM>, a flow meter <NUM>, an accumulator <NUM> (an example of a first mitigation device), a pressure gauge <NUM>, a discharge head <NUM>, a nozzle open-close control device <NUM>, a pressure flow rate control device <NUM> (second control device), and a control device 300b.

The regulator <NUM> is a regulator device that is installed on the air supply path <NUM> and that reduces the pressure of the high-pressure air supplied from the high-pressure air supply source <NUM> to a given pressure (first pressure). That is, the regulator <NUM> adjusts the pressure of the air supplied from the air supply path <NUM> to a given pressure greater than atmospheric pressure and lower than the pressure of the air compressed by the high-pressure air supply source <NUM>, and uses the air at that pressure to pressurize an ink IK1, which is the high-viscosity ink accumulated in the pressurizing tank <NUM>. Adjustment of the pressure reduction by the regulator <NUM> is controlled by a pressure flow rate control device <NUM> to be described below.

The regulator <NUM> is a regulator device that is installed on an air supply path <NUM> branched from the air supply path <NUM>, and reduces the pressure of the high-pressure air supplied from the high-pressure air supply source <NUM> and passing through the regulator <NUM> to a predetermined pressure (second pressure) that is lower than the first pressure. That is, the regulator <NUM> adjusts the pressure of the air supplied from the air supply path <NUM> and passing through the regulator <NUM> to a given pressure greater than the atmospheric pressure and lower than the pressure of the air decompressed by the regulator <NUM>, and pressurizes the ink IK2, which is the high-viscosity ink with which the pressurizing tank <NUM> is filled, by means of air at this pressure. Adjustment of the pressure reduction by the regulator <NUM> is controlled by a pressure flow rate control device <NUM> to be described below. The air supply path <NUM> on which the regulator <NUM> is installed is coupled to an upper portion of a pressurizing tank <NUM> described below.

The pressurizing tank <NUM> is a tank filled with the ink IK2, which is a high-viscosity ink. The air supply path <NUM> is coupled to an upper portion of the pressurizing tank <NUM>. The compressed air that is sent from the high-pressure air supply source <NUM> and passes through the regulator <NUM> and the regulator <NUM> is supplied into the pressurizing tank <NUM> to pressurize the ink IK2 in the pressurizing tank <NUM>. Furthermore, an ink flow path <NUM> (an example of a liquid flow path) that enables the ink IK2 to flow out is coupled to a lower portion of the pressurizing tank <NUM>, and the ink flow path <NUM> is coupled to an upper portion of the pressurizing tank <NUM>. That is, the ink flow path <NUM> which is a "liquid flow path" indicates a flow path through which the ink flowing out from the pressurizing tank <NUM> flows into the pressurizing tank <NUM>. The ink flow path <NUM> coupled to the discharge hole of the in-head flow path of the discharge head <NUM> is coupled to the upper portion of the pressurizing tank <NUM>. Thus, the ink flowing out from the in-head flow path of the discharge head <NUM> is conveyed to the pressurizing tank <NUM> through the ink flow path <NUM>. The ink accumulated in the pressurizing tank <NUM> is supplied (conveyed) to the pressurizing tank <NUM> by the pump <NUM>, and the ink accumulated in the pressurizing tank <NUM> is conveyed toward the accumulator <NUM> by the pump <NUM>.

The "feeder" according to the present embodiment corresponds to the pressurizing tank <NUM>, the pressurizing tank <NUM>, the regulator <NUM>, the regulator <NUM>, and the pump <NUM>.

Thus, a circulation path is formed in which ink repeatedly circulates in the liquid flow path formed of the ink flow path <NUM>, the ink flow path <NUM>, and the ink flow path <NUM> in the order of the pressurizing tank <NUM>, the accumulator <NUM>, the discharge head <NUM>, the pressurizing tank <NUM>, and the pressurizing tank <NUM>. Furthermore, a pressure difference is generated between the pressurizing tank <NUM> and the pressurizing tank <NUM> by the pressure reduction processing of the regulator <NUM> and the regulator <NUM>, and the ink is conveyed in the direction indicated by arrow A from the bottom of the pressurizing tank <NUM> by the pressure difference, the ink circulates in the circulation path, and the ink also passes through the discharge head <NUM>. As described above, also in the ink supply apparatus 100b according to the present embodiment, a flow-through state in which the ink flows through the discharge head <NUM> is implemented. In addition, the state in which ink continuously flows into the discharge head <NUM> (the state in which the pressurizing tank <NUM>, the pressurizing tank <NUM>, the regulator <NUM>, and the regulator <NUM> circulate ink in the circulation path) due to the above-described pressure difference when the discharge head <NUM> is discharging ink or not discharging ink is referred to as a constant flow-through.

Note that the pressurizing tank <NUM> may include, for example, a water level gauge for measuring the fill amount of the ink IK2, an ink temperature controller such as a heater or a cooler for managing the viscosity of the ink IK2, a thermometer for managing and controlling the temperature of the ink IK2, and the like.

The stirring device <NUM> is a device for stirring the ink IK2 with which the pressurizing tank <NUM> is filled. The stirring device <NUM> includes a stirring motor 104a and a stirrer 104b.

The stirring motor 104a is a motor device for stirring the ink IK2 by rotationally driving the stirrer 104b. The on/off operation of the rotation of the stirring motor 104a is controlled by the control device 300b.

The stirrer 104b is a stirring member that rotates under the rotation of the stirring motor 104a to stir the ink IK2.

The pump <NUM> is a pump device that is installed on the ink flow path <NUM> and that pressure-feeds the ink IK2 in the pressurizing tank <NUM> in the direction of arrow B of the ink flow path <NUM>. The pressurizing tank <NUM> has the ink in the pressurizing tank <NUM> continuously flowing therein via the circulation path. On the other hand, because the ink in the pressurizing tank <NUM> continues to flow out to the ink flow path <NUM> due to the air pressurized by the regulator <NUM>, the ink is eventually depleted. Therefore, due to the driving of the pump <NUM>, the ink in the pressurizing tank <NUM> is continuously or intermittently returned to the pressurizing tank <NUM> via the ink flow path <NUM>. The pump <NUM> contains a film called a diaphragm, which is an elastic body that separates the ink and the structure, and pressure-feeds the ink through contraction of the diaphragm. The speed of rotation of the pump <NUM> is controlled by the pressure flow rate control device <NUM>.

The flow meter <NUM> is a flowmeter which is installed on the downstream side from the filter <NUM> on the ink flow path <NUM>, and which measures the flow rate of the ink flowing through the ink flow path <NUM>. The accumulator <NUM> is installed on the downstream side from the flow meter <NUM> on the ink flow path <NUM>.

The pressure gauge <NUM> is a pressure gauge that measures the pressure of the ink flowing through the ink flow path <NUM>. In the example of <FIG>, the pressure gauge <NUM> is installed at a position downstream from the accumulator <NUM> and upstream from the discharge head <NUM> on the ink flow path <NUM>, and measures the pressure obtained by subtracting the pressure loss in each device arranged on the upstream side from the pressure gauge <NUM> on the ink flow path <NUM> from the pressure applied to the ink IK1 in the pressurizing tank <NUM> by the high-pressure air supply source <NUM>. Data on the pressure of the ink measured by the pressure gauge <NUM> is transmitted to the pressure flow rate control device <NUM>.

The pressure flow rate control device <NUM> is a device that receives data on the pressure of the ink measured by the pressure gauge <NUM> and that controls the pressure reduction operation by the regulator <NUM> and the regulator <NUM> so that the pressure becomes a given pressure (a predetermined value). Furthermore, the pressure flow rate control device <NUM> performs stable pressure control of the ink by controlling the pressure reduction operation by the regulator <NUM> and the regulator <NUM> on the basis of the data on the pressure (discharge pressure) of the ink measured by the pressure gauge <NUM> when the nozzle of the discharge head <NUM> is not open, in conjunction with the nozzle open-close control device <NUM>. In this case, the pressure flow rate control device <NUM> detects the open state of the nozzle of the nozzle open-close control device <NUM> via the control device 300b. Furthermore, the pressure flow rate control device <NUM> receives the data on the flow rate of the ink measured by the flow meter <NUM>, and controls the drive time and the speed of rotation of the pump <NUM> so that the ink IK1 in the pressurizing tank <NUM> is not depleted.

In addition, the pressure flow rate control device <NUM> controls the pressure difference between the pressurizing tank <NUM> and the pressurizing tank <NUM> by controlling the pressure reduction processing for the regulator <NUM> and the regulator <NUM>, thereby temporarily increasing or decreasing the discharge pressure. For example, a solid material is dispersed in the ink, and sometimes aggregated ink, foreign matter, or the like, is filtered and accumulated by the filter <NUM>. As a result, the fluid resistance in the filter <NUM> increases, and the pressure of the ink measured by the downstream pressure gauge <NUM>, that is, the discharge pressure, drops. In this case, the pressure flow rate control device <NUM> stabilizes the discharge pressure at a constant value by raising or lowering (in this case, raising) the pressure set value for the regulator <NUM> on the basis of the pressure of the ink measured by the pressure gauge <NUM>. Furthermore, because the flow rate of the ink increases when the pressure difference between the pressurizing tank <NUM> and the pressurizing tank <NUM> increases, the pressure flow rate control device <NUM> controls the pressure difference between the pressurizing tank <NUM> and the pressurizing tank <NUM> by increasing the discharge amount of the pump <NUM>, extending the operating time, or changing the pressure set value of the regulator <NUM>.

The control device 300b is a controller that controls the operation of the entire ink supply apparatus 100b. The control device 300b performs, for example, on/off control of the stirring operations of the stirring device <NUM> and the stirring device <NUM>, control of the nozzle open-close control device <NUM>, and control of the pressure flow rate control device <NUM>.

Note that the ink supply apparatus 100b may include other constituent elements in addition to the constituent elements illustrated in <FIG>. For example, the ink supply apparatus 100b may include, for example, a flow path opening/sealing valve including an electromagnetic valve or the like that controls the start and stop of the ink flow, a safety valve for releasing the high pressure of the pressurizing tank <NUM> and the pressurizing tank <NUM> to the atmosphere, a discharge switching flow path for discharging the ink from the circulation path, and the like.

<FIG> is a diagram illustrating a configuration for measuring the pressure and the flow rate of the ink upstream and downstream from the discharge head in the ink supply apparatus according to the third embodiment. <FIG> are diagrams illustrating examples of graphs illustrating a comparison result of the pressure and the flow rate of the ink upstream and downstream of the discharge head according to the presence or absence of the accumulator and the presence or absence of the constant flow-through in the ink supply apparatus according to the third embodiment. <FIG> are diagrams illustrating examples of graphs illustrating a comparison result of the pressure and the flow rate of the ink upstream and downstream of the discharge head according to the presence or absence of the accumulator and the presence or absence of the constant flow-through in the ink supply apparatus according to the third embodiment. <FIG> are diagrams illustrating examples of graphs illustrating a comparison result of the discharge amount of ink of the discharge head according to the presence or absence of the accumulator and the presence or absence of the constant flow-through in the ink supply apparatus according to the third embodiment. With reference to <FIG>, stabilization of the pressure (discharge pressure) and flow rate of the ink flowing to the discharge head <NUM> by the accumulator <NUM> of the ink supply apparatus 100b according to the present embodiment will be described.

In the present embodiment, as described above, the pump <NUM> is used to prevent the ink IK1 in the pressurizing tank <NUM> from being depleted by returning the ink in the pressurizing tank <NUM> to the pressurizing tank <NUM> via the ink flow path <NUM>. Due to the pressure difference between the pressurizing tank <NUM> and the pressurizing tank <NUM>, the ink IK1 is conveyed in the direction of arrow A from the bottom of the pressurizing tank <NUM>, and is circulated in the circulation path. Therefore, the pressure (discharge pressure) of the ink flowing through the discharge head <NUM> is not affected by the pulsation by the pump <NUM>.

On the other hand, as per the first embodiment described above, when the ink is discharged from the discharge head <NUM>, the pressure of the ink flowing in the discharge head <NUM> is released to the atmosphere only for the opening period of the nozzle, and hence the discharge pressure drops. At the same time, when the ink is discharged from the nozzles of the discharge head <NUM>, variation in the flow rate of the ink flowing to the discharge head <NUM> occurs in an amount equivalent to the total amount of the increase in the flow rate corresponding to the discharge amount of the ink on the upstream side from the discharge head <NUM> and the decrease in the flow rate corresponding to the discharge amount on the downstream side from the discharge head <NUM>. That is, when the ink is discharged from the discharge head <NUM>, a steep fluctuation occurs in the pressure (discharge pressure) and the flow rate of the ink. Because the ink supply apparatus 100b according to the present embodiment includes the accumulator <NUM> installed on the downstream side from the filter <NUM> on the ink flow path <NUM> and on the upstream side from the discharge head <NUM>, the fluctuation in the pressure and the flow rate due to the discharge of the ink from the discharge head <NUM> is suppressed.

Here, a specific example illustrating the advantageous effect, in the ink supply apparatus 100b according to the present embodiment, of the pressure (discharge pressure) and the flow rate of the ink being stabilized by the accumulator <NUM> in a case where the ink is discharged from the discharge head <NUM> will be described with reference to <FIG>. In the case of the ink supply apparatus 100b illustrated in <FIG>, in order to measure the pressure and the flow rate of the ink on the downstream side from the discharge head <NUM>, unlike the ink supply apparatus 100b illustrated in <FIG>, the flow meter <NUM> and the pressure gauge <NUM> are arranged at a position downstream from the discharge head <NUM> on the ink flow path <NUM>. Furthermore, in the case of ink supply apparatus 100b illustrated in <FIG>, in order to measure the pressure after the action of the damper effect by the accumulator <NUM> with respect to the pressure of the ink on the upstream side from the discharge head <NUM> in a case where the ink is discharged from the discharge head <NUM>, the arrangement of the pressure gauge <NUM> and the accumulator <NUM> is switched around in comparison with the ink supply apparatus 100b illustrated in <FIG>. In the ink supply apparatus 100b illustrated in <FIG>, the ink is circulated in the circulation path by the pressure difference between the pressurizing tank <NUM> and the pressurizing tank <NUM>.

First, <FIG> illustrate graphs of the pressure and the flow rate of the ink on the upstream side from the discharge head <NUM> and the pressure and the flow rate of the ink on the downstream side in cases where the accumulator <NUM> is installed and not installed, and in a case where the ink is discharged from the discharge head <NUM> under the conditions of the constant flow-through state and the non-constant flow-through state, respectively. Here, the state in which constant flow-through is not performed refers to a state where the ink is not circulated in the circulation path during the discharge period of the discharge head <NUM> and where the ink is circulated in the circulation path outside the discharge period (hereinafter, referred to as intermittent flow-through).

The graph illustrated in <FIG> illustrates, in chronological order, a pressure value (pressure value measured by the pressure gauge <NUM>) and a flow rate value (flow rate value measured by the flow meter <NUM>) of the ink on the upstream side from the discharge head <NUM>, and a pressure value (pressure value measured by the pressure gauge <NUM>) and a flow rate value (flow rate value measured by the flow meter <NUM>) of the ink on the downstream side in a case where the ink is discharged from the discharge head <NUM> under the condition that the accumulator <NUM> is installed and in the constant flow-through state. On the other hand, the graph illustrated in <FIG> illustrates, in chronological order, the pressure value (pressure value measured by the pressure gauge <NUM>) and the flow rate value (flow rate value measured by the flow meter <NUM>) of the ink on the upstream side from the discharge head <NUM>, and the pressure value (pressure value measured by the pressure gauge <NUM>) and the flow rate value (flow rate value measured by the flow meter <NUM>) of the ink on the downstream side in a case where the ink is discharged from the discharge head <NUM> under the condition that the accumulator <NUM> is not installed and in the constant flow-through state. Note that both graphs are raw data measured by the pressure gauges <NUM>, <NUM> and the flow meters <NUM>, <NUM>, and thus include fine noise. As becomes clear upon comparing both pressure values graphs, it is understood that the fluctuation in the pressure value of the ink on the upstream side and the downstream side from the discharge head <NUM> illustrated in <FIG> is smaller than the fluctuation illustrated in <FIG>, and the fluctuation in the pressure due to the discharge of the ink of the discharge head <NUM> is suppressed by the accumulator <NUM>. Further, as becomes clear upon comparing both flow rate value graphs, the fluctuation of the flow rate value of the ink on the downstream side from the discharge head <NUM> illustrated in <FIG> is smaller than the fluctuation illustrated in <FIG>, and it is understood that the fluctuation in the flow rate on the downstream side due to the discharge of the ink from the discharge head <NUM> is suppressed by the accumulator <NUM>. Meanwhile, as for the flow rate value of the ink on the upstream side from the discharge head <NUM>, as illustrated in <FIG>, fine amplitude is not observed, and it is understood that the flow rate value gradually increases, and after the timing at which the discharge ends, gradually decreases without immediately returning to the flow rate value at the time of non-discharge. As described above, it is confirmed to what extent the discharge amount of the ink by the discharge head <NUM> is affected by the fact that the flow rate value of the ink on the upstream side from the discharge head <NUM> gradually increases, and after the timing at which the discharge ends, gradually decreases without immediately returning to the flow rate value at the time of non-discharge. This will be described in detail in <FIG>.

The graph illustrated in <FIG> illustrates, in chronological order, the pressure value (pressure value measured by the pressure gauge <NUM>) and the flow rate value (flow rate value measured by the flow meter <NUM>) of the ink on the upstream side from the discharge head <NUM> in a case where the accumulator <NUM> is installed and the ink is discharged from the discharge head <NUM> under the condition of not being in the constant flow-through state (that is, in the intermittent flow state). In this case, because the ink does not flow to the downstream side from the discharge head <NUM> due to a valve installed on the ink flow path <NUM> on the downstream side from the discharge head <NUM>, the graph of the pressure value and the flow rate value on the downstream side from the discharge head <NUM> is not illustrated. On the other hand, the graph illustrated in <FIG> illustrates, in chronological order, the pressure value (pressure value measured by the pressure gauge <NUM>) and the flow rate value (flow rate value measured by the flow meter <NUM>) of the ink on the upstream side from the discharge head <NUM> in a case where the ink is discharged from the discharge head <NUM> under the condition where the accumulator <NUM> is not installed and the ink is not in the constant flow-through state (that is, in the intermittent flow state). As becomes clear upon comparing both pressure value graphs, it is understood that the fluctuation in the pressure value of the ink on the upstream side from the discharge head <NUM> illustrated in <FIG> is smaller than the fluctuation illustrated in <FIG>, and the fluctuation in the pressure on the upstream side due to the discharge of the ink of the discharge head <NUM> is suppressed by the accumulator <NUM>. Furthermore, as for the flow rate value of the ink on the upstream side from the discharge head <NUM>, fine amplitude is not observed, as illustrated in <FIG>, and it is understood that the flow rate value gradually increases, and after the timing at which the discharge ends, gradually decreases without immediately returning to the flow rate value at the time of non-discharge. As described above, similarly to the case of <FIG>, the flow rate value of the ink on the upstream side from the discharge head <NUM> gradually increases, and after the timing at which the discharge ends, gradually decreases without immediately returning to the flow rate value at the time of non-discharge, but it is confirmed to what extent the discharge amount of the ink by the discharge head <NUM> is affected. This will be described in detail in <FIG>.

Furthermore, as becomes clear upon comparing the pressure value and the flow rate value of the ink on the upstream side from the discharge head <NUM> illustrated in <FIG> with the pressure value and the flow rate value of the ink on the upstream side from the discharge head <NUM> illustrated in <FIG>, the fluctuation in the pressure value and the flow rate value of the ink on the upstream side from the discharge head <NUM> illustrated in <FIG> is smaller than the fluctuation illustrated in <FIG>, and it is understood that the fluctuation in the pressure and the flow rate on the upstream side due to the discharge of the ink of the discharge head <NUM> is suppressed in the constant flow-through state.

In the graph illustrated in <FIG>, as described above, in order to confirm the effect of the behavior of the flow rate of the ink on the upstream side from the discharge head <NUM> illustrated in <FIG> on the discharge amount of the ink of the discharge head <NUM>, the pressure value (pressure value measured by the pressure gauge <NUM>) and the flow rate value (flow rate value measured by the flow meter <NUM>) of the ink on the upstream side from the discharge head <NUM> and the pressure value (pressure value measured by the pressure gauge <NUM>) and the flow rate value (flow rate value measured by the flow meter <NUM>) of the ink on the downstream side in a case where ink discharged continuously nine times from the discharge head <NUM> is divided into a first half, a middle half, and a latter half on three occasions are illustrated in chronological order. In addition, in <FIG>, the conditions of the presence or absence of the accumulator <NUM> and the presence or absence of the constant flow-through are illustrated in correspondence with the conditions illustrated in <FIG>.

First, the fluctuation in the pressure value of the ink on the upstream side and the downstream side from the discharge head <NUM> illustrated in <FIG> is smaller than the fluctuation illustrated in <FIG>, and it is understood that the fluctuation in the pressure due to the discharge of the ink of the discharge head <NUM> is suppressed by the accumulator <NUM>. Furthermore, the fluctuation of the flow rate value of the ink on the downstream side from the discharge head <NUM> illustrated in <FIG> is smaller than the fluctuation illustrated in <FIG>, and it is understood that the fluctuation of the flow rate on the downstream side due to the discharge of the ink of the discharge head <NUM> is suppressed by the accumulator <NUM>.

The fluctuation in the pressure value of the ink on the upstream side from the discharge head <NUM> illustrated in <FIG> is smaller than the fluctuation illustrated in <FIG>, and it is understood that the fluctuation in the pressure on the upstream side due to the discharge of the ink of the discharge head <NUM> is suppressed by the accumulator <NUM>.

It is also understood that the fluctuation in the pressure value and the flow rate value of the ink on the upstream side from the discharge head <NUM> illustrated in <FIG> is smaller than the fluctuation illustrated in <FIG>, and the fluctuation in the pressure and the flow rate on the upstream side due to the discharge of the ink of the discharge head <NUM> is suppressed in the constant flow-through state.

Furthermore, in the light of the comparison between <FIG>, it is understood that, through the inclusion of the accumulator <NUM>, the discharge amount of the ink discharged from the discharge head <NUM> is stable even with respect to the steep pressure fluctuation due to the discharge of the ink from the discharge head <NUM>, and it can be estimated that the thixotropy of the ink, which is a non-Newtonian fluid, is exhibited, and that the low viscosity state is maintained. Furthermore, in the light of the comparison between <FIG>, it is understood that, by setting the state to the constant flow-through state, the discharge amount of the ink discharged from the discharge head <NUM> is stable even with respect to the steep pressure fluctuation due to the discharge of the ink from the discharge head <NUM>, and it can be estimated that the thixotropy of the ink, which is a non-Newtonian fluid, is exhibited, and that the low viscosity state is maintained.

Furthermore, in the light of the results illustrated in <FIG>, it is also determined that the ink used by the ink supply apparatus 100b according to the present embodiment absorbs the energy which becomes a factor in the changes in pressure and flow rate. This phenomenon is considered to be because the ink is a high-viscosity fluid, and thus acts similarly to a brake with respect to the changes in pressure and flow rate, and absorbs the energy of the fluctuations in pressure and flow rate upon receiving a shear force exhibiting thixotropy and thus likewise acts similarly to a brake.

Note that, because the accumulator <NUM> is provided and the ink is in the constant flow-through state, the effect of suppressing the fluctuations in the pressure and the flow rate of the ink and the stability of the discharge amount with respect to the steep pressure fluctuation due to the discharge of the ink from the discharge head <NUM> is exhibited not only in the ink supply apparatus 100b according to the present embodiment, but also in the ink supply apparatuses <NUM> and 100a according to the first embodiment and the second embodiment, respectively.

As described above, in the ink supply apparatus 100b according to the present embodiment, the pressurizing tank <NUM> has the air compressed by the high-pressure air supply source <NUM> supplied thereto and accumulates the ink pressurized by the compressed air, and the accumulated ink is conveyed to the accumulator <NUM> side, the pressurizing tank <NUM> supplies the accumulated ink to the pressurizing tank <NUM>, the regulator <NUM> decompresses the compressed air supplied from the high-pressure air supply source <NUM> to the pressurizing tank <NUM> to a first pressure, the regulator <NUM> decompresses the compressed air supplied from the high-pressure air supply source <NUM> to the pressurizing tank <NUM> to a second pressure smaller than the first pressure, the pump <NUM> conveys the ink accumulated in the pressurizing tank <NUM> to the pressurizing tank <NUM>, and the discharge head <NUM> includes an internal flow path through which the ink conveyed from the ink flow path <NUM> flows, discharges the ink from the internal flow path via nozzles, and the ink flowing out from the internal flow path of the discharge head <NUM> is conveyed to the pressurizing tank <NUM> via an ink flow path <NUM>, and the accumulator <NUM> is installed in the ink flow path <NUM> at a position downstream from the pressurizing tank <NUM> and upstream from the discharge head <NUM>, and absorbs the fluctuation in the pressure of the ink flowing through the ink flow path <NUM>, thus configuring a circulation path in which the ink circulates in the ink flow path in the order of the pressurizing tank <NUM>, the accumulator <NUM>, the discharge head <NUM>, the pressurizing tank <NUM>, and the pressurizing tank <NUM>. As a result, fluctuations in the pressure and the flow rate due to the discharge of the ink from the discharge head <NUM> can be suppressed, and hence the high-viscosity ink (an example of liquid) can be discharged stably and over a distance.

An ink supply apparatus according to a fourth embodiment will be described by focusing on differences from the ink supply apparatus 100b according to the third embodiment. In the present embodiment, a configuration in which an accumulator is also installed at a position downstream from the discharge head <NUM> will be described.

<FIG> is a diagram illustrating a configuration of an ink supply apparatus according to a fourth embodiment of the present disclosure. A configuration of an ink supply apparatus 100c according to the present embodiment will be described with reference to <FIG>.

As illustrated in <FIG>, the ink supply apparatus 100c includes a high-pressure air supply source <NUM> (compressed air supply source), a regulator <NUM> (first regulator), a pressurizing tank <NUM> (first pressurizing tank), a stirring device <NUM>, a regulator <NUM> (second regulator), a pressurizing tank <NUM> (second pressurizing tank), a stirring device <NUM>, a pump <NUM>, a filter <NUM>, a flow meter <NUM>, an accumulator <NUM> (an example of a first mitigation device), a pressure gauge <NUM>, a discharge head <NUM>, a nozzle open-close control device <NUM>, an accumulator <NUM> (an example of a second mitigation device), a pressure flow rate control device <NUM> (second control device), and a control device 300b. That is, the configuration of the ink supply apparatus 100c is similar to the configuration of the ink supply apparatus 100b according to the third embodiment described above except that the accumulator <NUM> is provided.

The accumulator <NUM> is installed at a position immediately downstream from the discharge head <NUM> on the ink flow path <NUM>, and is a pressure accumulator that absorbs and compensates for the increase/decrease in the pressure of the ink flowing inside to mitigate the fluctuation in the pressure. The configuration of the accumulator <NUM> is similar to the configuration of the accumulator <NUM>, and instead of the accumulator <NUM>, the piston pressing mechanism <NUM>-<NUM> (an example of the second mitigation device) illustrated in <FIG> described above or the subtank <NUM>-<NUM> (an example of the second mitigation device) illustrated in <FIG> may be used. As a result, similarly to the second embodiment described above, the damper effect can be more uniformly exhibited for all the nozzles of the discharge head <NUM>, and fluctuations in the pressure and the flow rate due to the discharge of the ink from the discharge head <NUM> can be more effectively suppressed.

An ink supply apparatus according to a fifth embodiment will be described by focusing on differences from the ink supply apparatus 100b according to the third embodiment. In the present embodiment, a configuration in which the flow rate control valve <NUM> is installed at a position downstream from the pressurizing tank <NUM> on the ink flow path <NUM> will be described.

<FIG> is a diagram illustrating a configuration of an ink supply apparatus according to a fifth embodiment of the present disclosure. A configuration of an ink supply apparatus 100d according to the present embodiment will be described with reference to <FIG>.

As illustrated in <FIG>, the ink supply apparatus 100d includes a high-pressure air supply source <NUM> (compressed air supply source), a regulator <NUM> (first regulator), a pressurizing tank <NUM> (first pressurizing tank), a stirring device <NUM>, a regulator <NUM> (second regulator), a pressurizing tank <NUM> (second pressurizing tank), a stirring device <NUM>, a pump <NUM>, a flow rate control valve <NUM>, a filter <NUM>, a flow meter <NUM>, an accumulator <NUM> (an example of a first mitigation device), a pressure gauge <NUM>, a discharge head <NUM>, a nozzle open-close control device <NUM>, a pressure flow rate control device <NUM> (second control device and third control device), and a control device 300d. That is, the configuration of the ink supply apparatus 100d is similar to the configuration of the ink supply apparatus 100b according to the third embodiment described above except that the flow rate control valve <NUM> is provided.

The flow rate control valve <NUM> is installed on the ink flow path <NUM> at a position downstream from the pressurizing tank <NUM> and upstream from the accumulator <NUM>, and is a valve device that controls the flow rate of the ink flowing out from the pressurizing tank <NUM> to the ink flow path <NUM>. The opening degree of the flow rate control valve <NUM> is controlled by the pressure flow rate control device <NUM>.

The pressure flow rate control device <NUM> is a device that receives data on the pressure of the ink measured by the pressure gauge <NUM> and that controls the pressure reduction operation by the regulator <NUM> and the regulator <NUM> so that the pressure becomes a given pressure. Furthermore, the pressure flow rate control device <NUM> performs stable pressure control of the ink by controlling the pressure reduction operation by the regulator <NUM> and the regulator <NUM> on the basis of the data on the pressure (discharge pressure) of the ink measured by the pressure gauge <NUM> when the nozzle of the discharge head <NUM> is not open, in conjunction with the nozzle open-close control device <NUM>. In this case, the pressure flow rate control device <NUM> detects the open state of the nozzles of the nozzle open-close control device <NUM> via the control device 300d. Furthermore, the pressure flow rate control device <NUM> is installed on the ink flow path <NUM> at a position downstream from the pressurizing tank <NUM> and upstream from the discharge head <NUM>, and receives data on the flow rate of the ink measured by the flow meter <NUM>, and, on the basis of the data, performs control of the drive time and the speed of rotation of the pump <NUM> and control of the opening degree of the flow rate control valve <NUM>.

The control device 300d is a controller that controls the operation of the whole ink supply apparatus 100d. The control device 300d performs, for example, on/off control of stirring operations of the stirring device <NUM> and the stirring device <NUM>, control of the nozzle open-close control device <NUM>, and control of the pressure flow rate control device <NUM>.

As described above, in the ink supply apparatus 100d according to the present embodiment, because the pressure flow rate control device <NUM> stably controls the discharge pressure due to the provision of the flow rate control valve <NUM>, the increase and decrease of the flow rate when the adjustment of the pressure reduction by the regulator <NUM> and the regulator <NUM> is freely variable are handled.

The ink supply apparatus according to a sixth embodiment will be described by focusing on differences from the ink supply apparatus 100d according to the fifth embodiment. In the present embodiment, a configuration in which an accumulator is also installed at a position downstream from the discharge head <NUM> will be described.

<FIG> is a diagram illustrating a configuration of an ink supply apparatus according to a sixth embodiment of the present disclosure. A configuration of an ink supply apparatus 100e according to the present embodiment will be described with reference to <FIG>.

As illustrated in <FIG>, the ink supply apparatus 100e includes a high-pressure air supply source <NUM> (compressed air supply source), a regulator <NUM> (first regulator), a pressurizing tank <NUM> (first pressurizing tank), a stirring device <NUM>, a regulator <NUM> (second regulator), a pressurizing tank <NUM> (second pressurizing tank), a stirring device <NUM>, a pump <NUM>, a flow rate control valve <NUM>, a filter <NUM>, a flow meter <NUM>, an accumulator <NUM> (an example of a first mitigation device), a pressure gauge <NUM>, a discharge head <NUM>, a nozzle open-close control device <NUM>, an accumulator <NUM> (an example of a second mitigation device), a pressure flow rate control device <NUM> (second control device and third control device), and a control device 300d. That is, the configuration of the ink supply apparatus 100e is similar to the configuration of the ink supply apparatus 100d according to the above-described fifth embodiment except that the accumulator <NUM> is provided.

In the present embodiment, a configuration of a liquid application apparatus in which the above-described ink supply apparatus <NUM> is mounted will be described.

<FIG> is an external view of a liquid application apparatus <NUM> according to a seventh embodiment of the present disclosure. <FIG> is an external view of the liquid application apparatus <NUM> according to the seventh embodiment with a carriage of a printing device placed at a maintenance position. <FIG> is a diagram illustrating a configuration of an ink supply apparatus <NUM> mounted to the liquid application apparatus <NUM> according to the seventh embodiment. The overall configuration of the liquid application apparatus <NUM> according to the present embodiment will be described with reference to <FIG>. In the present embodiment, the configuration in which the liquid application apparatus <NUM> includes the above-described ink supplying apparatus <NUM> will be described, but the configuration is not limited thereto. A liquid application apparatus according to an embodiment of the present disclosure may include any of the above-described ink supply apparatuses 100a to 100e.

The liquid application apparatus <NUM> illustrated in <FIG> is an apparatus that divides a wide liquid application region of an installation surface such as a road surface into a plurality of printing regions, sequentially moves to each printing region, divides printing data for printing on the liquid application region into a plurality of printing images, and prints the printing images. The term "printing" refers to an operation of forming an image by applying or spraying ink to the installation surface. In <FIG>, a panel on the front side of a housing <NUM> illustrated in <FIG> is drawn is removed to depict the internal structure of the housing <NUM>, which is described later. As illustrated in <FIG>, the liquid application apparatus <NUM> includes the ink supply apparatus <NUM>, the housing <NUM>, and a hand truck <NUM>.

In the present embodiment, as illustrated in <FIG> and <FIG>, the ink supply apparatus <NUM> includes an ink supply mechanism <NUM>, a control device <NUM>, a discharge head <NUM>, a nozzle open-close control device <NUM>, and a pressure gauge <NUM>. Specifically, as illustrated in <FIG>, the ink supply mechanism <NUM> includes the components other than the discharge head <NUM>, the pressure gauge <NUM>, the nozzle open-close control device <NUM>, and the control device <NUM>, among the components of the ink supply apparatus <NUM> illustrated in <FIG>. The ink supply mechanism <NUM> is installed on the upper surface of the housing <NUM> as illustrated in <FIG>.

The housing <NUM> is a device that can be carried by the hand truck <NUM> and performs printing on an installation surface by scanning of a carriage <NUM> on which the discharge head <NUM> is mounted. As illustrated in <FIG> and <FIG>, the housing <NUM> includes four stands <NUM>, the carriage <NUM>, and a maintenance system 16a. For example, the ink supply mechanism <NUM> and the control device <NUM> are installed on the upper surface of the housing <NUM>.

The stands <NUM> are support members that are installed at four corners of the bottom of the housing <NUM> having a rectangular parallelepiped shape as a whole and that support the housing <NUM> in contact with the installation surface. The number of stands <NUM> is not limited to four, and may be at least three or more.

As illustrated in <FIG>, the carriage <NUM> is a member on which the discharge head <NUM> that discharges ink, the pressure gauge <NUM>, and the nozzle open-close control device <NUM> are mounted, and which is scanned in the main scanning direction and the sub-scanning direction by a movement mechanism described later. The scanning of the carriage <NUM> is controlled by the control device <NUM>. At least one of the pressure gauge <NUM> and the nozzle open-close control device <NUM> may be included in the ink supply mechanism <NUM>.

The maintenance system 16a is a mechanism that performs a maintenance process such as cleaning of the nozzle surface of the discharge head <NUM> mounted on the carriage <NUM>. For example, as illustrated in <FIG>, the control device <NUM> causes the maintenance system 16a to perform the maintenance process in a state where the carriage <NUM> is moved to a maintenance position <NUM>.

The hand truck <NUM> is a carrying device that lifts up the housing <NUM> from the bottom to carry the housing <NUM> to a printing region. As illustrated in <FIG>, the hand truck <NUM> includes a truck frame <NUM>, a lifting device <NUM>, a lifting device <NUM>, front wheels <NUM>, rear wheels <NUM>, and a handle <NUM>.

The truck frame <NUM> is a frame member having a shape surrounding in a rectangular shape, and is a frame member that supports the housing <NUM> from the bottom when the housing <NUM> is raised and lowered.

The lifting device <NUM> is a device that supports a portion of the housing <NUM> on one end (rear end) close to the handle <NUM> and lifts the housing <NUM> up and down.

The lifting device <NUM> is a device that supports a portion of the housing <NUM> on the other end (front end) opposite the one end close to the handle <NUM> and lifts the housing <NUM> up and down.

The front wheels <NUM> and the rear wheels <NUM> are wheels for moving the hand truck <NUM> front, back, left, and right.

The handle <NUM> is a handle member that is attached to the rear end of the hand truck <NUM> and is gripped by a user (operator). The user can grip the handle <NUM> to freely move the hand truck <NUM> front, back, left, and right.

<FIG> is a diagram illustrating a configuration of a moving mechanism of the carriage <NUM> of the liquid application apparatus <NUM> according to the seventh embodiment. The configuration of the moving mechanism for scanning the carriage <NUM> of the liquid application apparatus <NUM> according to the present embodiment will be described with reference to <FIG>.

As illustrated in <FIG>, the housing <NUM> includes frames 11a, a main scanning guide <NUM>, a main scanning motor 17a, sub-scanning guides <NUM>, sub-scanning motors 18a, and timing belts 18b as a moving mechanism for scanning the carriage <NUM>. The moving mechanism is supported by four stands <NUM> installed on the frame 11a constituting a peripheral edge of the bottom of the housing <NUM>.

The frame 11a is a frame member that constitutes four sides of the bottom of the housing <NUM>.

The main scanning guide <NUM> is a guide member that extends in the main scanning direction illustrated in <FIG> and supports the carriage <NUM> to be slidable in the main scanning direction.

The main scanning motor 17a is a motor for reciprocating the carriage <NUM> in the main scanning direction along the main scanning guide <NUM>.

The sub-scanning guides <NUM> are guide members that are installed on the frames 11a each extending in the sub-scanning direction illustrated in <FIG> and support the main scanning guide <NUM> to be slidable in the sub-scanning direction. As illustrated in <FIG>, the sub-scanning guides <NUM> are disposed on two frames 11a each extending in the sub-scanning direction and facing each other such that the sub-scanning guides <NUM> support the vicinities of both ends of the main scanning guide <NUM> extending in the main scanning direction.

The sub-scanning motors 18a are motors for reciprocating the main scanning guide <NUM> in the sub-scanning direction along the sub-scanning guides <NUM>. In this case, the sub-scanning motors 18a are rotated to drive pulleys, which are rotated by the sub-scanning motors 18a, and the timing belts 18b wound around the pulleys rotated by the sub-scanning motors 18a. Thus, the main scanning guide <NUM> reciprocates in the sub-scanning direction.

In this way, the carriage <NUM> on which the discharge head <NUM> is mounted can freely move in the main scanning direction and the sub-scanning direction on the plane surrounded by the four frames 11a.

Claim 1:
A liquid supply apparatus (<NUM>) comprising:
a compressed air supply source (<NUM>) to compress air;
a pressurizing tank (<NUM>, <NUM>) to be supplied with the compressed air from the compressed air supply source (<NUM>) and accumulate liquid pressurized by the compressed air;
a feeder (<NUM>) to feed the liquid accumulated in the pressurizing tank (<NUM>, <NUM>) to a liquid flow path (<NUM>, <NUM>, <NUM>);
a discharge head (<NUM>) including an internal flow path through which the liquid fed from the liquid flow path (<NUM>, <NUM>, <NUM>) flows, the discharge head (<NUM>) having a nozzle to discharge the liquid from the internal flow path;
a mitigation device (<NUM>, <NUM>-<NUM>, <NUM>-<NUM>) installed on the liquid flow path (<NUM>, <NUM>, <NUM>) at a position downstream from the pressurizing tank (<NUM>, <NUM>) and upstream from the discharge head (<NUM>), the mitigation device (<NUM>, <NUM>-<NUM>, <NUM>-<NUM>) to absorb a fluctuation in pressure of the liquid flowing through the liquid flow path (<NUM>, <NUM>, <NUM>), wherein the mitigation device is a piston pressing mechanism which includes an accumulator, a subtank, or a shock absorber; and
a circulation path in which the feeder circulates the liquid in the liquid flow path (<NUM>, <NUM>, <NUM>) in an order of the pressurizing tank (<NUM>, <NUM>), the mitigation device, the discharge head (<NUM>), and the pressurizing tank (<NUM>, <NUM>),
characterized in that
the feeder is a pump (<NUM>) that is installed on the liquid flow path (<NUM>, <NUM>, <NUM>) at a position downstream from the pressurizing tank (<NUM>, <NUM>) and upstream from the mitigation device, to pressure-feed the liquid in the pressurizing tank (<NUM>, <NUM>) toward the mitigation device and to the liquid flow path (<NUM>, <NUM>, <NUM>).