Inkjet recording device

Abstract

To detect air entrapment and liquid leakage in a cooling system with a simple configuration that does not require the use of a flow meter to detect the flow rate of the refrigerant liquid. [Solution] The inkjet recording device 10 comprises a cooling device 6, a current detection device 88, and a determination device 8c. The cooling device 6 comprises a centrifugal pump 64 and a motor 64a that drives the centrifugal pump 64. The current detection device 88 detects the current flowing through the motor 64a. The determination device 8c determines whether air entrapment and liquid leakage occur in the circulation path of the cooling device 6 by comparing the current detected by the current detection device 88 with a current reference range.

Description

Technical Field

[0001] The present invention relates to an inkjet recording apparatus including a cooling device for cooling an inkjet head.

Background Art

[0002] An inkjet recording apparatus includes an inkjet head that discharges ink onto a sheet. In the inkjet recording apparatus, when the continuous operation time of the inkjet head is long, the temperature of the inkjet head rises.

[0003] If the temperature of the inkjet head rises too much, it has an adverse effect on the quality of the printed image. Therefore, it is important to cool the inkjet head to an appropriate temperature.

[0004] For example, it is known that the inkjet head includes a heat pump that cools air for cooling the inkjet head (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in an inkjet recording apparatus, due to the acceleration of print processing, the temperature of the inkjet head is more likely to rise. Therefore, it is desirable that the inkjet head can be efficiently cooled by a liquid-cooling type cooling device.

[0007] On the other hand, when a liquid-cooled cooling system is used, there is a risk of air entrapment or leakage of the refrigerant liquid in the circulation path. Therefore, it is important to detect the occurrence of air entrapment and leakage and take appropriate measures such as stopping the printing process.

[0008] Generally, the aforementioned air lock and liquid leakage manifest as changes in the flow rate of the refrigerant liquid in the circulation path. However, employing a flow meter to detect the flow rate of the refrigerant liquid is undesirable as it leads to increased costs.

[0009] The object of the present invention is to provide an inkjet recording device that can detect air entrapment and liquid leakage in a liquid-cooled cooling device with a simple configuration without employing a flow meter to detect the flow rate of the refrigerant liquid. [Means for solving the problem]

[0010] An inkjet recording apparatus according to one aspect of the present invention comprises an inkjet head, a cooling device, a current detection device, and a determination device. The inkjet head forms an image on a sheet by ejecting ink. The cooling device comprises a centrifugal pump and a motor that drives the centrifugal pump, and cools the inkjet head by circulating a coolant liquid through a circulation path via the inkjet head using the centrifugal pump. The current detection device detects the current flowing through the motor. The determination device determines whether or not air is trapped and liquid is leaking in the circulation path of the cooling device by comparing the current detected by the current detection device with a current reference range. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an inkjet recording device that can detect air entrapment and liquid leakage in a liquid-cooled cooling device with a simple configuration without employing a flow meter to detect the flow rate of the refrigerant liquid. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a diagram showing the configuration of an inkjet recording apparatus according to an embodiment. [Figure 2] Figure 2 is a block diagram showing the configuration of the control device in the inkjet recording apparatus according to the embodiment. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. Note that the following embodiments are merely examples of the present invention and do not limit the technical scope of the present invention.

[0014] [Configuration of the inkjet recording device 10] The inkjet recording device 10 includes a sheet storage unit 12, a sheet transport device 2, a printing device 3, and an ink supply device 4.

[0015] Furthermore, the inkjet recording device 10 also includes an operating device 801, a display device 802, and a control device 8.

[0016] The sheet transport device 2, the printing device 3, the ink supply device 4, and the control device 8 are housed within the main body 11 of the inkjet recording device 10.

[0017] The sheet transport device 2 transports the sheets 9 stored in the sheet storage section 12 one by one along the sheet transport path 20. Furthermore, the sheet transport device 2 sends out the sheets 9 with images formed on them by the printing device 3 from the sheet transport path 20. For example, the sheet transport device 2 sends the sheets 9 from the sheet transport path 20 to an output tray or another downstream device.

[0018] The sheet conveying device 2 includes a sheet delivery unit 21, multiple sets of conveying roller pairs 22, a first belt conveying unit 23, a second belt conveying unit 24, and a set of delivery roller pairs 25. The sheet delivery unit 21 sends sheets 9 one by one from the sheet storage unit 12 to the sheet conveying path 20.

[0019] A plurality of pairs of conveying rollers 22 take over the conveyance of the sheet 9 from the sheet feeding unit 21 and convey the sheet 9 toward the first belt conveyance unit 23.

[0020] The first belt conveyance unit 23 takes over the conveyance of the sheet 9 from the plurality of pairs of conveying rollers 22 and conveys the sheet 9 below the printing device 3. Further, the first belt conveyance unit 23 sends out the sheet 9 to the second belt conveyance unit 24.

[0021] The second belt conveyance unit 24 takes over the conveyance of the sheet 9 from the first belt conveyance unit 23 and further sends out the sheet 9 to the delivery roller pair 25. Note that the inkjet recording device 10 may be provided with a drying device (not shown). The drying device dries the ink on the sheet 9 conveyed by the second belt conveyance unit 24.

[0022] The delivery roller pair 25 sends out the sheet 9 on which an image is formed to the outside of the main body 11.

[0023] The printing device 3 executes a printing process by discharging ink onto the sheet 9 conveyed by the first belt conveyance unit 23. The printing process is a process of forming an image on the sheet 9.

[0024] The printing device 3 includes a plurality of inkjet heads 31 corresponding to a plurality of ink colors. Each inkjet head 31 has an ink discharge portion 31A including a plurality of nozzles that discharge ink respectively. The ink supply device 4 supplies inks of different colors to the plurality of inkjet heads 31 respectively.

[0025] In the present embodiment, the printing device 3 includes four inkjet heads 31 corresponding to four colors of black, cyan, magenta, and yellow. Further, the ink supply device 4 supplies inks of the four colors to the corresponding four inkjet heads 31 respectively.

[0026] The operating device 801 is a device that accepts human input. For example, the operating device 801 includes operation buttons and a touch panel. The display device 802 is capable of displaying information. For example, the display device 802 includes a display panel such as a liquid crystal panel.

[0027] [Control device 8] The control device 8 performs various data processing and controls the equipment provided by the inkjet recording device 10.

[0028] As shown in Figure 2, the control device 8 includes a CPU (Central Processing Unit) 81, RAM (Random Access Memory) 82, a secondary storage device 83, a signal interface 84, and a communication device 85, among others.

[0029] CPU81 is an example of a processor that performs various data processing and control tasks by executing computer programs.

[0030] RAM82 is a volatile memory device that can be read by a computer. RAM82 temporarily stores the computer program executed by CPU81 and the data that CPU81 outputs and references during the process of performing various operations.

[0031] The secondary storage device 83 is a non-volatile storage device that can be read by a computer. The secondary storage device 83 is capable of storing and updating the computer program and various types of data. For example, some or all of flash memory, SSD (Solid State Drive), and hard disk drive may be used as the secondary storage device 83.

[0032] The signal interface 84 converts signals output by various sensors into digital data and transmits the converted digital data to the CPU 81. Furthermore, the signal interface 84 converts control commands output by the CPU 81 into control signals and transmits the control signals to the controlled device.

[0033] The communication device 85 is capable of communicating with a host device (not shown) and other devices. The host device is an information processing device such as a personal computer or smartphone operated by a user.

[0034] For example, the CPU 81 receives a print job from the host device via the communication device 85. The printing device 3 forms the image specified by the print job on the sheet 9.

[0035] The CPU 81 includes a plurality of processing modules that are realized by executing the computer program. The plurality of processing modules include a main control unit 8a and a print control unit 8b, etc.

[0036] The main control unit 8a performs control to initiate various processes in response to operations on the operating device 801, as well as control of the display device 802.

[0037] The print control unit 8b causes the sheet transport device 2 to perform the sheet transport process. Furthermore, the print control unit 8b causes the print device 3 to perform the print process in synchronization with the transport of the sheet 9 by the sheet transport device 2.

[0038] Incidentally, if the continuous operation time of each inkjet head 31 is long, the temperature of each inkjet head 31 will rise.

[0039] If the temperature of each inkjet head 31 rises too high, it will negatively affect the quality of the printed image. Therefore, it is important to cool each inkjet head 31 to an appropriate temperature.

[0040] In the inkjet recording device 10, the temperature of each inkjet head 31 tends to rise more easily due to the increased speed of the printing process. The inkjet recording device 10 is equipped with a liquid-cooled cooling device 6 to efficiently cool each inkjet head 31 (see Figure 1).

[0041] The cooling system 6 comprises a main tank 61, multiple heat exchange units 62, a radiator 63, a circulation pump 64, a circulation motor 64a, and multiple tubes 65 (see Figure 1). The multiple tubes 65 connect the main tank 61, the multiple heat exchange units 62, the radiator 63, and the circulation pump 64, forming a circulation path for the refrigerant liquid.

[0042] Multiple heat exchange units 62 are arranged in contact with multiple inkjet heads 31. The cooling device 6 cools the multiple inkjet heads 31 by circulating the refrigerant liquid through the circulation path via the multiple inkjet heads 31 using a circulation pump 64.

[0043] The main tank 61 stores the refrigerant liquid. For example, the refrigerant liquid is water. Each of the multiple heat exchange units 62 performs heat exchange between each of the multiple inkjet heads 31 and the refrigerant liquid. As a result, each of the heat exchange units 62 cools each of the inkjet heads 31 that are at a higher temperature than the refrigerant liquid.

[0044] The radiator 63 radiates the heat of the coolant. The circulation pump 64 circulates the refrigerant through the circulation path. That is, the circulation pump 64 circulates the refrigerant between the main tank 61, the multiple heat exchange units 62, and the radiator 63. The circulation motor 64a drives the circulation pump 64.

[0045] The cooling device 6 further comprises an air vent valve 66, a replenishment device 67, and a liquid level gauge 68. The air vent valve 66 is a valve that opens and closes an air vent opening formed in a part of the circulation path. The air vent opening is formed in the highest part of the plurality of tubes 65 that form the circulation path.

[0046] The normal state of the air vent valve 66 is the closed state. The air vent valve 66 switches from the closed state to the open state in response to an open command from the CPU 81.

[0047] The replenishment device 67 replenishes the refrigerant liquid to the main tank 61. The replenishment device 67 comprises an auxiliary tank 67a, a replenishment pump 67b, and a replenishment motor 67c.

[0048] The auxiliary tank 67a contains the refrigerant liquid. The replenishment pump 67b supplies the refrigerant liquid in the auxiliary tank 67a to the main tank 61. The replenishment motor 67c drives the replenishment pump 67b.

[0049] The liquid level gauge 68 detects whether the level of the refrigerant liquid in the main tank 61 is at or below a reference level. When the liquid level gauge 68 detects that the level of the refrigerant liquid in the main tank 61 is below the reference level, the replenishment motor 67c operates.

[0050] When the aforementioned liquid-cooled cooling device 6 is used, there is a risk of air entrapment or liquid leakage in the circulation path. Therefore, it is important to detect the occurrence of air entrapment and liquid leakage and take appropriate measures such as stopping the printing process.

[0051] Generally, the aforementioned air lock and liquid leakage manifest as changes in the flow rate of the refrigerant liquid in the circulation path. However, employing a flow meter to detect the flow rate of the refrigerant liquid is undesirable as it leads to increased costs.

[0052] The inkjet recording device 10 has a configuration for detecting air entrapment and liquid leakage in the cooling device 6 with a simple configuration without employing the flow meter.

[0053] The circulation pump 64 is a centrifugal pump. This centrifugal pump can circulate a large amount of the refrigerant liquid with relatively low power consumption.

[0054] In the control device 8, the plurality of processing modules of the CPU 81 further include a determination unit 8c. The printing device 3 is also equipped with a plurality of temperature sensors 31x that detect the temperature of each of the plurality of inkjet heads 31. For example, each of the temperature sensors 31x is a thermistor.

[0055] The determination unit 8c is an example of a determination device that determines the state of the cooling device 6. The print control unit 8b is an example of a control device that controls multiple inkjet heads 31 and the cooling device 6.

[0056] The control device 8 further includes a circulating motor drive circuit 86, a replenishment motor drive circuit 87, and a current detection circuit 88 (see Figure 2). The circulating motor drive circuit 86 supplies an amount of power to the circulating motor 64a according to the power supply command from the print control unit 8b. The replenishment motor drive circuit 87 supplies power to the replenishment motor 67c in response to the replenishment command from the print control unit 8b.

[0057] The print control unit 8b controls the power supplied to the circulation motor 64a by feedback control based on multiple detected temperatures detected by multiple temperature sensors 31x and a target temperature. The print control unit 8b controls the power supplied to the circulation motor 64a by controlling the circulation motor drive circuit 86.

[0058] For example, the print control unit 8b sets the power supply amount by feedback control based on the representative value of the plurality of detected temperatures and the target temperature, and outputs the power supply command representing the set power supply amount to the circulating motor drive circuit 86. The representative value is, for example, the maximum or average value of the plurality of detected temperatures.

[0059] Furthermore, when the liquid level gauge 68 detects that the level of the refrigerant liquid in the main tank 61 has fallen below the reference level, the print control unit 8b operates the replenishment pump 67b by outputting the replenishment command to the replenishment motor drive circuit 87.

[0060] On the other hand, when the level gauge 68 detects that the level of the refrigerant liquid in the main tank 61 meets the reference level, the print control unit 8b stops the replenishment pump 67b by stopping the replenishment command to the replenishment motor drive circuit 87.

[0061] Activating the replenishment motor 67c to operate the replenishment pump 67b is equivalent to activating the replenishment device 67. Conversely, stopping the replenishment motor 67c to stop the replenishment pump 67b is equivalent to stopping the replenishment device 67.

[0062] The current detection circuit 88 detects the current flowing from the circulating motor 64a to the circulating motor 64a. The current detection circuit 88 is an example of a current detection device.

[0063] The determination unit 8c determines whether or not air entrapment and liquid leakage have occurred in the circulation path of the cooling device 6 by comparing the detected current of the current detection circuit 88 with a preset current reference range.

[0064] When the aforementioned liquid leak occurs, the load on the centrifugal pump decreases, and the current flowing to the circulation motor 64a decreases. On the other hand, when the aforementioned air entrapment occurs, the load on the centrifugal pump increases, and the current flowing to the circulation motor 64a increases.

[0065] Here, the lower limit of the current reference range is the first reference value, and the upper limit of the current reference range is the second reference value. The determination unit 8c determines that liquid leakage has occurred when the detected current falls below the first reference value. On the other hand, the determination unit 8c determines that air entrapment has occurred when the detected current exceeds the second reference value.

[0066] For example, the determination unit 8c sets the first reference value and the second reference value according to the representative values ​​of the plurality of detected temperatures.

[0067] For example, the print control unit 8b executes emergency stop control when the detection unit 8c determines that liquid leakage has occurred. This emergency stop control is a process that stops the circulation motor 64a and the replenishment motor 67c and prohibits the print process.

[0068] Furthermore, in the emergency stop control, the print control unit 8b outputs an alarm indicating the occurrence of the liquid leak through either or both of the display device 802 and the communication device 85. The display device 802 and the communication device 85 are examples of output devices that output information, respectively.

[0069] On the other hand, the print control unit 8b executes air venting control when the determination unit 8c determines that air has entered the print chamber. The print control unit 8b executes the air venting control when the print process is not being performed.

[0070] The situation in which the printing process is not performed is a situation in which ink is not ejected by the multiple inkjet heads 31. The print control unit 8b may create a situation in which ink is not ejected by the multiple inkjet heads 31 by prohibiting the printing process.

[0071] In the aforementioned air bleeding control, the print control unit 8b operates the replenishment motor 67c of the replenishment device 67, intermittently operates the circulation motor 64a, and performs the process of opening the air bleeding valve 66. As a result, the air in the circulation path is released through the air bleeding valve 66.

[0072] For example, the print control unit 8b executes the air bleeding control for a predetermined time, and then terminates the air bleeding control.

[0073] The print control unit 8b may output an alarm indicating the occurrence of air lock during the air venting control through either or both of the display device 802 and the communication device 85.

[0074] By employing the inkjet recording device 10, it is possible to detect air entrapment and liquid leakage with a simple configuration without employing a flow meter to detect the flow rate of the refrigerant liquid.

[0075] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0076] <Note 1> An inkjet head that forms an image on a sheet by ejecting ink, A cooling device comprising a centrifugal pump and a motor that drives the centrifugal pump, which cools the inkjet head by circulating a refrigerant liquid through a circulation path via the inkjet head using the centrifugal pump, A current detection device for detecting the current flowing through the motor, An inkjet recording apparatus comprising: a determination device that determines whether or not air entrapment and liquid leakage occur in the circulation path of the cooling device by comparing the detected current of the current detection device with a current reference range.

[0077] <Note 2> The system includes a control device that controls the inkjet head and the cooling device, The cooling device comprises a tank for storing the refrigerant liquid, a supply device for supplying the refrigerant liquid to the tank, and an air vent valve for opening and closing an opening formed in a part of the circulation path. The inkjet recording apparatus according to Appendix 1, wherein, when the occurrence of air entrapment is determined by the determination device, the control device operates the supply device in a situation where the inkjet head does not eject the ink, intermittently operates the motor, and performs air venting control by opening the air vent valve. [Explanation of Symbols]

[0078] 3: Printing device 6: Cooling device 8: Control device 10: Inkjet recording device 31: Inkjet head 31A: Ink ejection unit 31x: Temperature sensor 61: Main tank 62:Heat exchange section 63: Radiator 64: Circulation pump 64a: Circulation motor 66: Air vent valve 67: Supply device 67a: Auxiliary tank 67b: Replenishment pump 67c: Refill motor 68:Liquid level gauge 88: Current detection circuit

Claims

1. An inkjet head that forms an image on a sheet by ejecting ink, A cooling device comprising a centrifugal pump and a motor that drives the centrifugal pump, which cools the inkjet head by circulating a refrigerant liquid through a circulation path via the inkjet head using the centrifugal pump, A current detection device for detecting the current flowing through the motor, An inkjet recording apparatus comprising: a determination device that determines whether or not air entrapment and liquid leakage occur in the circulation path of the cooling device by comparing the detected current of the current detection device with a current reference range.

2. The system includes a control device that controls the inkjet head and the cooling device, The cooling device comprises a tank for storing the refrigerant liquid, a supply device for supplying the refrigerant liquid to the tank, and an air vent valve for opening and closing an opening formed in a part of the circulation path. The inkjet recording apparatus according to claim 1, wherein, when the occurrence of air entrapment is determined by the determination device, the control device operates the supply device in a situation where the inkjet head does not eject the ink, intermittently operates the motor, and performs air venting control by opening the air vent valve.

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