JP7537232B2 - Liquid ejection device and image forming device - Google Patents

Description

The present invention relates to a liquid ejection device and an image forming device.

One type of liquid ejection device known is an inkjet recording device that includes an ink cartridge that stores ink, an ejection head formed with nozzles that eject the ink, and a liquid delivery pump that delivers ink from the ink cartridge to the ejection head through a liquid delivery tube.

In addition, a sensor is known that detects when the amount of ink in an ink cartridge falls below a threshold amount (hereinafter referred to as "ink end") due to a change in the volume of a buffer chamber caused by a drop in pressure in the ink supply tube (see, for example, Patent Document 1).

In the inkjet recording device configured as described above, the inside of an ink cartridge that has run out of ink is under negative pressure. When an ink cartridge in a negative pressure state is removed from the inkjet recording device, air gets into the liquid supply tube. Air that gets into the liquid supply tube can cause the ink to deteriorate or cause ejection problems in the ejection head. As a result, some inkjet recording devices perform a process to eliminate the negative pressure in the ink cartridge (hereinafter referred to as the "negative pressure elimination process") by rotating the liquid supply pump in reverse prior to removing the ink cartridge.

However, when performing the negative pressure elimination process with an inkjet recording device equipped with the sensor described in Patent Document 1, if the amount of reverse rotation of the liquid supply pump is small, the ink that has returned from the ejection head side flows into the buffer chamber, increasing its volume, and does not flow into the ink cartridge. On the other hand, if an attempt is made to return enough ink to eliminate the negative pressure in the ink cartridge after returning the volume of the buffer chamber to its original state, a new problem arises in that air flows in from the nozzle.

The present invention has been made to solve these problems, and aims to provide a liquid ejection device that can eliminate negative pressure inside the cartridge while preventing air from flowing into the nozzle.

In order to solve the above technical problems, one aspect of the present invention includes a cartridge loading section in which a cartridge storing liquid is loaded, a supply flow path having one end connected to the cartridge loading section, an ejection head connected to the other end of the supply flow path and having a nozzle formed therein for ejecting liquid supplied from the cartridge loaded in the cartridge loading section through the supply flow path, a liquid delivery pump capable of forward rotation to deliver liquid in the supply flow path from the cartridge loading section side to the ejection head side and reverse rotation to deliver liquid from the ejection head side to the cartridge loading section side, a sensor disposed in the supply flow path between the cartridge loading section and the liquid delivery pump for detecting when the amount of liquid in the cartridge loaded in the cartridge loading section becomes equal to or less than a threshold amount due to a volume change accompanying a pressure fluctuation in the supply flow path, and a pressure sensor disposed between the sensor and the liquid delivery pump. The device includes a return flow path that branches off from the supply flow path at a branching position and joins the supply flow path at a joining position between the cartridge loading section and the sensor; a first one-way valve that is disposed in the supply flow path between the sensor and the branching position and allows liquid to flow from the sensor side to the branching position and blocks liquid from the branching position to the sensor side; a second one-way valve that is disposed in the return flow path and allows liquid to flow from the branching position to the joining position and blocks liquid from the joining position to the branching position; and a controller that controls the liquid delivery pump based on the detection result of the sensor, and the controller rotates the liquid delivery pump forward and rotates the liquid delivery pump in the reverse direction by a predetermined amount in response to the sensor detecting that the amount of liquid in the cartridge is equal to or less than the threshold amount.

The present invention makes it possible to eliminate negative pressure within the cartridge while preventing air from entering the nozzle.

FIG. 1 is a perspective view of an image forming apparatus according to an embodiment of the present invention, as viewed from the front. FIG. 2 is a side view showing an outline of a mechanism of the image forming apparatus. FIG. 2 is a plan view showing an outline of a main part of a mechanism of the image forming apparatus. FIG. 1 is a schematic diagram of an ink ejection device. FIG. 4 is a diagram showing a schematic configuration of an end detection sensor. FIG. 2 is a diagram showing the hardware configuration of the image forming apparatus. 4 is a flowchart of an image forming process. 4 is a flowchart of an ink circulation process.

Figure 1 is a perspective view of the image forming apparatus of this embodiment, as seen from the front. The image forming apparatus 100 comprises an apparatus main body 101, a paper feed tray 102 for loading paper (sheets) that are attached to the apparatus main body 101, and a paper discharge tray 103 for stocking paper that is detachably attached to the apparatus main body 101 and on which an image is recorded (formed). In addition, a cartridge loading section 104 is provided at one end of the front surface of the apparatus main body 101 (to the side of the paper feed/discharge tray section), which protrudes from the front surface to the front side of the apparatus main body 101 and is lower than the top surface, for loading an ink cartridge. Furthermore, an operation display device 105, such as operation buttons and a display, is provided on the top surface of the cartridge loading section 104.

The cartridge loading section 104 can load ink cartridges 110k, 110c, 110m, and 110y (referred to as "ink cartridges 110" when no distinction is made between colors) containing inks (liquids) of different colors, such as black (K) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink, from the front side to the rear side of the device body 101. A front cover 106 that opens when the ink cartridges 110 are attached or detached is provided on the front side of the cartridge loading section 104 and can be opened or closed.

The operation display device 105 has remaining ink amount display units 111k, 111c, 111m, 111y (referred to as "remaining ink amount display unit 111" when the colors are not differentiated) arranged at positions corresponding to the mounting positions of the ink cartridges 110k, 110c, 110m, 110y of each color, which display when the ink cartridges 110k, 110c, 110m, 110y of each color have run out or are insufficient. The operation display device 105 also has a display and a speaker that notify the user of the status of the image forming device 100 by text information, beeps, etc.

Next, the mechanical section of the image forming apparatus 100 will be described with reference to Figs. 2 and 3. Fig. 2 is a side view showing an overview of the mechanical section. Fig. 3 is a plan view of the main section. In the mechanical section of the image forming apparatus 100, a carriage 133 is held slidably in the main scanning direction by a guide rod 131 and a stay 132, which are guide members that are hung horizontally on the left and right side plates 121A and 121B that make up the frame 121. The carriage 133 is moved and scanned in the main scanning direction of Fig. 3 via a timing belt by a main scanning motor (not shown).

As described above, the carriage 133 has ejection heads 134k, 134c, 134m, and 134y (referred to as "ejection heads 134" when the colors are not differentiated) that are formed with nozzles that eject ink of each color: yellow (Y), cyan (C), magenta (M), and black (Bk). The ejection heads 134k, 134c, 134m, and 134y are arranged on the underside of the carriage 133 with the tips of the nozzles facing downward.

The inkjet head constituting the ejection head 134 may be equipped with a pressure generating means such as a piezoelectric actuator, such as a piezoelectric element; a thermal actuator that uses an electrothermal conversion element, such as a heating resistor, to utilize phase changes caused by film boiling of a liquid; a shape memory alloy actuator that uses metal phase changes caused by temperature changes; or an electrostatic actuator that uses electrostatic force.

This ejection head 134 is equipped with a driver IC, and is connected to the controller 200 via a harness (flexible print cable) 122. The carriage 133 also temporarily stores ink and is equipped with head tanks 135k, 135c, 135m, 135y (referred to as "head tanks 135" when no distinction is made between colors) for supplying ink of each color to the ejection head 134. As described above, ink of each color is replenished and supplied to the head tanks 135 of each color from the ink cartridges 110 of each color mounted in the cartridge loading section 104 via the supply tubes L1 of each color.

The image forming apparatus 100 also includes a conveying device 140 that conveys paper 142 from the paper stacking section 141 to a position facing the carriage 133 to the paper output tray 103. The conveying device 140 is composed of, for example, a paper feed section, a conveying section, and a paper output section.

As a paper feed section for feeding the paper 142 loaded on the paper loading section (pressure plate) 141 of the paper feed tray 102, a paper feed roller 143 is provided which separates and feeds the paper 142 one by one from the paper loading section 141, and a separation pad 144 which faces the paper feed roller 143 and is made of a material with a large coefficient of friction, and this separation pad 144 is biased towards the paper feed roller 143.

The conveying section that sends the paper 142 fed from this paper feed section to the lower side of the ejection head 134 includes a guide member 145 that guides the paper 142, a counter roller 146, a conveying guide member 147, a pressing member 148 having a tip pressure roller 149, and a conveying belt 151 that electrostatically adsorbs the fed paper 142 and conveys it to a position facing the ejection head 134.

The conveyor belt 151 is an endless belt that is stretched between a conveyor roller 152 and a tension roller 153 and rotates in the belt conveying direction (sub-scanning direction). It also includes a charging roller 156 that charges the surface of the conveyor belt 151. The charging roller 156 is arranged to contact the surface of the conveyor belt 151 and rotate in response to the rotation of the conveyor belt 151. Furthermore, a guide member 157 is arranged on the back side of the conveyor belt 151 in correspondence with the printing area by the ejection head 134. The conveyor belt 151 moves in the belt conveying direction in FIG. 3 by the conveyor roller 152 being rotated via timing by the sub-scanning motor.

Furthermore, as a paper discharge section for discharging the paper 142 recorded by the ejection head 134, a separation claw 161 for separating the paper 142 from the conveyor belt 151, a paper discharge roller 162, and a paper discharge roller 163 are provided. And, the paper discharge tray 103 is disposed below the paper discharge roller 162.

In the image forming device 100 configured in this manner, the sheets 142 are separated and fed one by one from the paper feed tray 102. The sheets 142 fed approximately vertically upward are guided by the guide member 145, sandwiched between the conveyor belt 151 and the counter roller 146, and conveyed. The leading edge is further guided by the conveyor guide member 147 and pressed against the conveyor belt 151 by the leading edge pressure roller 149, changing the conveying direction by approximately 90°.

At this time, the controller 200 applies a voltage to the charging roller 156 so that positive and negative outputs are alternately repeated, and the conveyor belt 151 is charged with a charging voltage pattern, i.e., is charged with alternating positive and negative charges in strips of a specified width in the sub-scanning direction, which is the rotation direction. When the paper 142 is fed onto the conveyor belt 151 that is alternately charged with positive and negative charges, the paper 142 is attracted to the conveyor belt 151, and the paper 142 is conveyed in the sub-scanning direction by the rotation of the conveyor belt 151.

Then, the carriage 133 is moved in the main scanning direction based on main scanning position information from the linear encoder 137 while the ejection head 134 is driven in response to an image signal, so that ink droplets are ejected onto the stationary paper 142 to record one line, and after the paper 142 is transported a predetermined distance, the next line is recorded. Upon receiving a recording end signal or a signal indicating that the rear end of the paper 142 has reached the recording area, the recording operation is terminated and the paper 142 is ejected onto the paper ejection tray 103.

Next, referring to FIG. 4, an ink ejection device (liquid ejection device) 170 that ejects ink stored in the ink cartridge 110 from the nozzles of the ejection head 134 will be described. FIG. 4 is a schematic diagram of the ink ejection device 170. Note that the image forming device 100 is equipped with a plurality of ink ejection devices 170 corresponding to each of the colors of ink that can be ejected (e.g., black, cyan, magenta, yellow).

As shown in FIG. 4, the ink ejection device 170 mainly comprises a supply tube (supply flow path) L1 shown by a solid line, a return tube (return flow path) L2 shown by a dashed line, a cartridge loading section 104, an ejection head 134, a head tank 135, a liquid delivery pump 171, an end detection sensor (sensor) 172, a first SOL (first solenoid valve) 173, a second SOL (second solenoid valve) 174, a first one-way valve 175, and a second one-way valve 176.

The supply tube L1 is a flow path that supplies ink from the ink cartridge loaded in the cartridge loading section 104 to the ejection head 134. That is, the supply tube L1 connects the cartridge loading section 104 and the ejection head 134 via the first SOL 173, the end detection sensor 172, the first one-way valve 175, the liquid feed pump 171, the second SOL 174, and the head tank 135. The supply tube L1 is composed of multiple tubes that connect adjacent components.

The return tube L2 is a flow path that branches off from the supply tube L1 at the branching position P1 and merges with the supply tube L1 at the merging position P2. More specifically, the return tube L2 is composed of a tube that connects the branching position P1 to the second one-way valve 176, and a tube that connects the second one-way valve 176 to the merging position P2. The supply tube L1 and the return tube L2 are connected, for example, by a three-way valve provided at the branching position P1 and the merging position P2.

The branch position P1 is a position in the supply tube L1 between the end detection sensor 172 and the liquid delivery pump 171 (more specifically, the first one-way valve 175 and the liquid delivery pump 171). The merge position P2 is a position in the supply tube L1 between the cartridge loading section 104 and the end detection sensor 172 (more specifically, the cartridge loading section 104 and the first SOL 173).

The liquid delivery pump 171 is disposed between the first one-way valve 175 and the second SOL 174 of the supply tube L1. The liquid delivery pump 171 is configured to be capable of forward and reverse rotation by transmitting the driving force of a motor driven by the controller 200. "Forward rotation" is the rotation direction in which ink in the supply tube L1 is delivered from the cartridge loading section 104 side to the ejection head 134 side. "Reverse rotation" is the rotation direction in which ink in the supply tube L1 is delivered from the ejection head 134 side to the cartridge loading section 104 side.

The end detection sensor 172 is disposed between the cartridge loading section 104 of the supply tube L1 and the liquid delivery pump 171 (more specifically, the first SOL 173 and the first one-way valve 175). The end detection sensor 172 is a sensor that detects when the amount of ink in the ink cartridge 110 loaded in the cartridge loading section 104 falls below a threshold amount (hereinafter referred to as "ink end").

Figure 5 is a diagram showing the schematic configuration of the end detection sensor 172. The end detection sensor 172 mainly comprises a buffer chamber 181, a pressing rod 182, a coil spring (biasing member) 183, a filler 184, and a detection unit 185. However, the specific configuration of the end detection sensor 172 is not particularly limited as long as it detects the end of the ink by a change in volume caused by pressure fluctuations in the supply tube L1.

The buffer chamber 181 has an internal space for storing ink. The buffer chamber 181 is connected to the first SOL 173 and the first one-way valve 175 through the supply tube L1. That is, the buffer chamber 181 temporarily stores ink supplied from the first SOL 173 side through the supply tube L1 in its internal space, and discharges the ink to the first one-way valve 175 side through the supply tube L1.

The buffer chamber 181 is composed of a fixed wall 186 and a movable wall 187. The fixed wall 186 is a wall that does not substantially deform even when the pressure in the supply tube L1 changes. The supply tube L1 is connected to the fixed wall 186. The movable wall 187 is a wall that deforms due to pressure changes in the supply tube L1. More specifically, as shown in FIG. 5(B), the movable wall 187 is configured to bend in a direction that reduces the volume of the buffer chamber 181 as the pressure in the supply tube L1 decreases. The movable wall 187 is composed of an elastic member such as rubber.

The push rod 182 is attached to the outer surface of the movable wall 187 and moves with the deformation of the movable wall 187. The coil spring 183 biases the push rod 182 in a direction that causes the movable wall 187 to bend (i.e., reduces the volume of the buffer chamber 181). The filler 184 is attached to the push rod 182 and moves together with the push rod 182.

The detection unit 185 is disposed facing a portion of the movement range of the feeler 184. The detection unit 185 is, for example, a transmissive optical sensor equipped with an irradiation unit (LED) that irradiates light and a light receiving unit (photodiode) that receives the light irradiated from the irradiation unit. The irradiation unit and the light receiving unit face each other across a portion of the movement range of the feeler 184. However, the specific configuration of the detection unit 185 is not limited to the above example, and may be a reflective optical sensor or a proximity sensor.

When ink remains in the ink cartridge 110, the buffer chamber 181 is filled with ink. When the liquid supply pump 171 rotates forward in this state, the ink in the buffer chamber 181 is discharged to the ejection head 134 side through the supply tube L1, and the ink in the ink cartridge 110 flows into the buffer chamber 181 through the supply tube L1. At this time, as shown in FIG. 5A, the movable wall 187, which receives the pressure in the buffer chamber 181, maintains an undepressed state against the biasing force of the coil spring 183. In addition, the filler 184 is positioned at a different position from the optical path between the irradiation unit and the light receiving unit. In other words, the light irradiated from the irradiation unit is not blocked by the filler 184 and is received by the light receiving unit.

Next, if the liquid supply pump 171 continues to rotate in the forward direction even after the ink in the ink cartridge 110 is depleted, the ink in the buffer chamber 181 gradually decreases. This reduces the pressure in the buffer chamber 181, the supply tube L1 on the cartridge loading section 104 side of the buffer chamber 181, and the ink cartridge 110. As a result, the movable wall 187 gradually dents due to the biasing force of the coil spring 183, and the volume of the buffer chamber 181 decreases.

When the volume of the buffer chamber 181 falls below the threshold volume, as shown in FIG. 5(B), the filler 184 blocks the optical path between the light emitting unit and the light receiving unit. That is, the light irradiated from the irradiation unit is blocked by the filler 184 and is not received by the light receiving unit. The detection unit 185 detects the ink end in response to the light irradiated from the irradiation unit not being received by the light receiving unit, and outputs an end signal indicating the detection result to the controller 200.

Returning to FIG. 4, the first SOL 173 and the second SOL 174 are opened and closed according to the control of the controller 200. More specifically, the first SOL 173 and the second SOL 174 are closed when a control voltage is applied from the controller 200, and are opened when the application of the control voltage from the controller 200 stops.

The first SOL 173 is disposed between the cartridge loading section 104 of the supply tube L1 and the end detection sensor 172 (more specifically, between the junction position P2 and the end detection sensor 172). That is, when the first SOL 173 is open, ink can flow through the supply tube L1 between the junction position P2 and the end detection sensor 172. On the other hand, when the first SOL 173 is closed, ink cannot flow through the supply tube L1 between the junction position P2 and the end detection sensor 172.

The second SOL 174 is disposed between the liquid feed pump 171 and the head tank 135 of the supply tube L1. That is, when the second SOL 174 is open, ink can flow through the supply tube L1 between the liquid feed pump 171 and the head tank 135. On the other hand, when the second SOL 174 is closed, ink cannot flow through the supply tube L1 between the liquid feed pump 171 and the head tank 135.

The first one-way valve 175 is disposed between the end detection sensor 172 and the branch position P1 of the supply tube L1. The first one-way valve 175 allows the flow of ink from the end detection sensor 172 side to the branch position P1 side, and blocks the flow of ink from the branch position P1 side to the end detection sensor 172 side. The second one-way valve 176 is disposed in the return tube L2. The second one-way valve 176 allows the flow of ink from the branch position P1 side to the junction position P2 side, and blocks the flow of ink from the junction position P2 side to the branch position P1 side.

FIG. 6 is a hardware configuration diagram of the image forming apparatus 100. As shown in FIG. 6, the image forming apparatus 100 includes a CPU (Central Processing Unit) 201 as a control means, a RAM (Random Access Memory) 202 as a storage means, a ROM (Read Only Memory) 203 as a storage means, a HDD (Hard Disk Drive) 204 as a storage means, and an I/F 205 as an interface, all of which are connected via a common bus 206 as a communication means. The CPU 201, RAM 202, ROM 203, and HDD 204 are examples of the controller 200.

The CPU 201 is a computing means and controls the operation of the entire image forming apparatus 100. The RAM 202 is a volatile storage medium capable of reading and writing information at high speed, and is used as a working area when the CPU 201 processes information. The ROM 203 is a read-only non-volatile storage medium in which programs such as firmware are stored. The HDD 204 is a non-volatile storage medium with a large storage capacity that can read and write information, and in which the OS (Operating System), various control programs, application programs, etc. are stored.

The image forming device 100 processes various programs loaded from the ROM 203 or HDD 204 to the RAM 202 using the calculation functions of the CPU 201. This processing constitutes a software control unit including various functional modules of the image forming device 100. The combination of the software control unit thus constituted and the hardware resources installed in the image forming device 100 constitutes a functional block that realizes the functions of the image forming device 100.

The I/F 205 is an interface that connects the operation display device 105, the transport device 140, and the ink ejection device 170 to the common bus 206. That is, the controller 200 controls the operation display device 105, the transport device 140, and the ink ejection device 170 through the I/F 205.

Figure 7 is a flowchart of the image formation process. The controller 200 executes the image formation process shown in Figure 7 in response to receiving an image formation instruction from, for example, the operation and display device 105 or an external device. Note that at the start of the image formation process, it is assumed that the ink cartridge 110 containing ink is loaded into the cartridge loading section 104, the end detection sensor 172 has not detected the end of the ink, and the first SOL 173 and the second SOL 174 are open.

First, the controller 200 starts the forward rotation of the liquid delivery pump 171 (S701). As a result, ink in the head tank 135 is supplied to the ejection head 134, ink in the buffer chamber 181 is supplied to the head tank 135, and ink in the ink cartridge 110 is supplied to the buffer chamber 181. The forward rotation of the liquid delivery pump 171 continues until either step S705 or S706, which will be described later, is executed.

Next, the controller 200 forms an image on the paper 142 according to the acquired image formation instructions (S702). That is, the controller 200 causes the transport device 140 to transport the paper 142, causes the carriage 133 to move back and forth in the main scanning direction, and causes the ejection head 134 to eject ink from the nozzles at a predetermined timing. In this way, an image is formed on the paper 142. Note that the process of step S702 is already well known, so a detailed description will be omitted.

The controller 200 waits to execute the following process until the end detection sensor 172 detects the end of the ink before the formation of the image is completed (S703: Yes & S704: No) or until the formation of the image is completed before the end detection sensor 172 detects the end of the ink (S703: No & S704: Yes). Then, if the formation of the image is completed before the end detection sensor 172 detects the end of the ink (S703: No & S704: Yes), the controller 200 stops the forward rotation of the liquid supply pump 171 (S705) and ends the image formation process without executing the process from step S706 onwards.

On the other hand, when the ink in the ink cartridge 110 runs out during the image formation process, the ink in the buffer chamber 181 is consumed and the volume of the buffer chamber 181 gradually decreases. Then, when the optical path of the detection unit 185 is blocked by the filler 184, the end detection sensor 172 outputs an end signal to the controller 200. Then, in response to the end detection sensor 172 detecting the end of ink before the image formation is completed (S703: Yes & S704: No), the controller 200 stops the forward rotation of the liquid supply pump 171 (S706) and temporarily suspends the image formation on the paper 142.

To resume image formation on the paper 142, the empty ink cartridge 110 must be removed from the cartridge loading section 104 and a new ink cartridge 110 containing ink must be attached to the cartridge loading section 104. However, when an ink cartridge 110 that has run out of ink and has a negative pressure inside is removed from the cartridge loading section 104, air will get into the supply tube L1 that runs from the cartridge loading section 104 to the end detection sensor 172. Therefore, the controller 200 executes the processes from step S707 onwards to prevent air from getting into the supply tube L1 when replacing the ink cartridge 110.

First, the controller 200 closes the first SOL 173 and opens the second SOL 174 (S707). Next, the controller 200 rotates the liquid supply pump 171 in reverse a predetermined amount (S708). As a result, the ink stored in the head tank 135 enters the return tube L2 from the supply tube L1 at the branch position P1, and then enters the supply tube L1 again from the return tube L2 at the junction position P2, and flows into the ink cartridge installed in the cartridge loading section 104.

On the other hand, the ink that has passed through the liquid feed pump 171 is blocked by the first one-way valve 175 and does not flow into the end detection sensor 172. Also, the ink that has entered the supply tube L1 at the junction position P2 is blocked by the blocked first SOL 173 and does not flow into the end detection sensor 172. In other words, even if the liquid feed pump 171 is rotated in reverse in step S708, the volume of the buffer chamber 181 does not increase.

The amount of reverse rotation of the liquid supply pump 171 in step S708 is set to an amount that causes only a portion of the ink stored in the head tank 135 to flow back to the cartridge loading section 104. In other words, the state in which ink is stored in the head tank 135 is maintained even after step S708 is executed.

Next, the controller 200 stops the liquid supply pump 171 that has rotated in the reverse direction a predetermined amount, and then notifies the user of the ink end through the operation and display device 105 (S709). As one example, the controller 200 may light up the remaining ink level display unit 111 that corresponds to the ink cartridge 110 that has run out of ink. As another example, the controller 200 may prompt the user to replace the ink cartridge 110 through a display or speaker. The remaining ink level display unit 111, the display, and the speaker are examples of notification devices.

Next, the controller 200 waits to execute subsequent processes until the ink cartridge 110 that has run out of ink is replaced (S710: No). As one example, the controller 200 may detect that the ink cartridge 110 has been replaced using a sensor provided in the cartridge loading section 104. As another example, the controller 200 may accept an operation indicating that the ink cartridge 110 has been replaced via the operation display device 105.

Next, in response to the ink cartridge 110 being replaced (S710: Yes), the controller 200 opens the first SOL 173 (S711). Then, the controller 200 returns to step S701 and resumes the formation of the interrupted image.

On the other hand, when the liquid supply pump 171 is rotating in the forward direction in step S702, the amount of ink moving from the supply tube L1 to the return tube L2 through the branch position P1, and the amount of ink moving from the return tube L2 to the supply tube L1 through the junction position P2 are extremely small. Therefore, when the liquid supply pump 171 is rotating in the forward direction or is stopped, ink remains in the return tube L2.

In addition, among the inks that can be used by the image forming device 100, inks (e.g., AR ink (registered trademark)) that contain granular components (e.g., pigments, titanium oxide, etc.) will settle if they remain in the return tube L2 for a long period of time. If these settled granular components reach the nozzles, they may cause ejection problems or clogging. Therefore, the controller 200 needs to circulate the ink in the supply tube L1 and return tube L2 between the branch position P1 and the junction position P2.

Figure 8 is a flowchart of the ink circulation process. The controller 200 executes the ink circulation process shown in Figure 8, for example, at a predetermined time interval. It is assumed that at the start of the ink circulation process, the ink cartridge 110 containing ink is loaded into the cartridge loading section 104, the end detection sensor 172 has not detected the end of the ink, and the first SOL 173 and the second SOL 174 are open.

First, the controller 200 starts a timer to detect the arrival of a predetermined time (S801). The controller 200 then waits to execute subsequent processes until the timer started in step S801 times out (S802: No). The "predetermined time" is set to, for example, a time shorter than the time it takes for granular components contained in the ink to settle to the extent that they cause ejection defects, etc.

Next, in response to the timer timing out (S802: Yes), the controller 200 opens the first SOL 173 and closes the second SOL 174 (S803). The controller 200 then rotates the liquid supply pump 171 in reverse a predetermined amount of rotation (S804). The "predetermined amount of rotation" is set to a value required for the granular components of the ink retained in the return tube L2 to dissolve again into the liquid components. The "predetermined amount of rotation" in steps S708 and S804 may be the same or different.

As a result, ink moves from the supply tube L1 to the return tube L2 through the branching position P1, and ink moves from the return tube L2 to the supply tube L1 through the merging position P2. That is, ink circulates in the supply tube L1 and the return tube L2 between the branching position P1 and the merging position P2. On the other hand, by blocking the second SOL 174, ink stored in the head tank 135 is not returned to the liquid feed pump 171 even if the liquid feed pump 171 is rotated in reverse.

Then, the controller 200 stops the liquid supply pump 171, which has rotated in the reverse direction by a predetermined amount, and opens the second SOL 154 (S805). Furthermore, the controller 200 executes the processes from step S801 onwards again. Note that if the timer times out while an image is being formed on the paper 142 (S702), the controller 200 waits for the execution of steps S803 to S805, and executes steps S803 to S805 after the image formation is completed (S704: Yes → S705).

The above embodiment provides the following advantages:

According to the above embodiment, the negative pressure in the ink cartridge 110 can be eliminated by rotating the liquid supply pump 171 in reverse after detecting the ink end. Here, by providing the first one-way valve 175 and rotating the liquid supply pump 171 in reverse with the first SOL 173 closed, it is possible to prevent ink returning from the head tank 135 from flowing into the end detection sensor 172. As a result, the amount of ink required to eliminate the negative pressure in the ink cartridge 110 is reduced, which also prevents air from entering the nozzles.

When the first SOL 173 is omitted, the ink that flows back from the return tube L2 to the supply tube L1 through the junction position P2 is distributed to the ink cartridge 110 and the end detection sensor 172. Therefore, the amount of ink required to eliminate the negative pressure in the ink cartridge 110 increases compared to when the first SOL 173 is provided, but is reduced by simply providing the first one-way valve 175.

In addition, according to the above embodiment, after the negative pressure in the ink cartridge 110 is eliminated, a notification is given to replace the ink cartridge 110, which further appropriately prevents air from entering the supply tube L1.

Furthermore, according to the above embodiment, the ink in the return tube L2 is circulated at predetermined time intervals, which can prevent the granular components of the ink from settling in the return tube L2. Note that the controller 200 may execute the ink circulation process for all ink ejection devices 170, or may execute the process only for a specific ink ejection device 170 (for example, an ink cartridge 110 containing white ink is installed). Furthermore, if the ink circulation process is not implemented, the second SOL 163 can be omitted.

The cartridge that can be attached to and detached from the liquid ejection device is not limited to an ink cartridge that stores ink (liquid) used to record an image, but may be a cartridge that stores pre-treatment liquid, post-treatment liquid, or other liquid. Furthermore, the specific configuration of the image forming device 100 that can mount the ink ejection device 170 according to this embodiment is not limited to the example shown in Figures 1 to 3, and may be, for example, one that forms an image on large-sized paper.

Furthermore, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the technical gist of the present invention. All technical matters included in the technical ideas described in the claims are the subject of the present invention. The above-described embodiment shows a preferred example, but a person skilled in the art can realize various modifications from the disclosed contents. Such modifications are also included in the technical scope described in the claims.

100: Image forming apparatus 104: Cartridge loading section 105: Operation display device 110: Ink cartridge (cartridge)
111: remaining amount display unit 133: carriage 134: ejection head 135: head tank 137: linear encoder 140: transport device 170: ink ejection device (liquid ejection device)
171: Liquid delivery pump 172: End detection sensor (sensor)
173: First SOL (first solenoid valve)
174: Second SOL (second solenoid valve)
175: First one-way valve 176: Second one-way valve 181: Buffer chamber 182: Pressing rod 183: Coil spring 184: Filler 185: Detecting portion 186: Fixed wall 187: Movable wall 200: Controller

JP 2010-208082 A

Claims (7)

a cartridge loading section into which a cartridge containing a liquid is loaded;
a supply flow path, one end of which is connected to the cartridge loading section;
an ejection head connected to the other end of the supply flow path and having a nozzle formed therein for ejecting liquid supplied through the supply flow path from the cartridge loaded in the cartridge loading section;
a liquid feed pump capable of rotating in a forward direction to feed the liquid in the supply flow path from the cartridge loading unit side to the ejection head side and rotating in a reverse direction to feed the liquid from the ejection head side to the cartridge loading unit side;
a sensor disposed between the cartridge loading section and the liquid feed pump in the supply flow path, the sensor detecting that an amount of liquid in the cartridge loaded in the cartridge loading section has become equal to or less than a threshold amount due to a volume change caused by a pressure fluctuation in the supply flow path;
a return flow path that branches off from the supply flow path at a branching position between the sensor and the liquid feed pump and merges with the supply flow path at a merging position between the cartridge loading unit and the sensor;
a first one-way valve disposed in the supply flow path between the sensor and the branching position, allowing liquid to flow from the sensor side to the branching position side and blocking liquid to flow from the branching position side to the sensor side;
a second one-way valve that is disposed in the return flow path and allows liquid to flow from the branching position side to the junction position side and blocks liquid from flowing from the junction position side to the branching position side;
a controller that controls the liquid delivery pump based on a detection result of the sensor;
The controller:
The liquid delivery pump is rotated forward,
a liquid ejection device which rotates the liquid feed pump in a reverse direction by a predetermined amount in response to the sensor detecting that the amount of liquid in the cartridge has fallen below the threshold amount; A notification device is provided for notifying information,
The liquid ejection device according to claim 1 , wherein the controller notifies through the notification device that the amount of liquid in the cartridge has fallen below the threshold amount after rotating the liquid delivery pump in reverse by the specified rotation amount. a first solenoid valve disposed between the cartridge loading section and a sensor in the supply flow path and opened and closed under the control of the controller;
The controller:
With the first solenoid valve open, the liquid delivery pump is rotated forward;
3. The liquid ejection device according to claim 1, wherein the liquid feed pump is rotated in the reverse direction by the predetermined rotation amount with the first solenoid valve being closed. The liquid ejection device according to claim 3, characterized in that the controller rotates the liquid delivery pump in reverse at predetermined time intervals while keeping the first solenoid valve open. a second solenoid valve that is disposed between the liquid delivery pump and the discharge head in the supply flow path and is opened and closed under the control of the controller;
5. The liquid ejection device according to claim 4, wherein the controller rotates the liquid feed pump in reverse at predetermined time intervals while opening the first solenoid valve and closing the second solenoid valve. The sensor includes:
a buffer chamber whose volume decreases as the pressure in the supply flow path decreases;
A liquid ejection device as described in any one of claims 1 to 5, characterized in that it is provided with a detection unit that detects that the amount of liquid in the cartridge has reached a threshold amount in response to the volume of the buffer chamber becoming equal to or less than a threshold volume. A conveying device that conveys a sheet;
The liquid ejection device according to any one of claims 1 to 6,
an image forming apparatus, comprising: an ejection head that ejects liquid toward a sheet conveyed by the conveying device, thereby forming an image on the sheet;