Ink jet recording apparatus

Abstract

To adjust the capability of cooling an ink jet head according to the out-apparatus temperature.SOLUTION: An ink jet recording apparatus comprises: a tank 43 which stores cooling liquid C; a pump 44 which delivers the cooling liquid C; an ink jet head 12; a radiator 45 which cools the cooling liquid C; a blower 46 which blows air to the radiator 45; a flow path 40 which circulates the cooling liquid C through the tank 43, the pump 44, the ink jet head 12, and the radiator 45; a head temperature measurement unit 51 which measures a temperature Th of the ink jet head 12; an out-apparatus temperature measurement unit 52 which measures an out-apparatus temperature To; and a control unit which controls a flow rate F of the pump 44 according to the temperature Th of the ink jet head 12 measured by the head temperature measurement unit 51 and the out-apparatus temperature To measured by the out-apparatus temperature measurement unit 52.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an inkjet recording apparatus.

Background Art

[0002] In order to obtain good image quality in an inkjet recording apparatus, it is necessary to keep the ink at an appropriate viscosity. However, since the viscosity of the ink changes depending on the temperature of the ink, an appropriate temperature range is determined for each product. However, due to the heat generation of the drive circuit that drives the inkjet head, the temperature of the ink may exceed the upper limit value of the appropriate temperature range. Therefore, conventionally, techniques for cooling the inkjet head have been studied. For example, Patent Document 1 discloses a configuration in which the temperature of the drive circuit that drives the inkjet head is measured and the drive circuit is cooled according to the measured temperature.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when using a liquid cooling type cooling device, a flow path for circulating the coolant via the inkjet head, a radiator for cooling the coolant, and a blower for blowing air to the radiator are provided. The cooling capacity of the radiator varies depending on the temperature of the air outside the inkjet recording apparatus. In the configuration disclosed in Patent Document 1, since the outside temperature is not considered, there is a possibility that the cooling capacity becomes excessive or insufficient due to the outside temperature, and the temperature of the ink may deviate from the appropriate temperature range.

[0005] In view of the above circumstances, an object of the present invention is to adjust the cooling capacity when cooling an inkjet head by a liquid cooling method according to the outside temperature.

Means for Solving the Problems

[0006] To solve the above problems, an inkjet recording apparatus according to the present invention includes a tank for storing a coolant, a pump for sending out the coolant, an inkjet head, a radiator for cooling the coolant, a blower for blowing air to the radiator, a flow path for circulating the coolant through the tank, the pump, the inkjet head, and the radiator, a head temperature measuring unit for measuring the temperature of the inkjet head, an external temperature measuring unit for measuring the external temperature, and a control unit for controlling the flow rate of the pump according to the temperature of the inkjet head measured by the head temperature measuring unit and the external temperature measured by the external temperature measuring unit.

[0007] The control unit may increase the flow rate of the pump as the external temperature is higher.

[0008] When the temperature of the inkjet head and the external temperature are equal to or higher than the upper limit temperature of the appropriate temperature range of the ink, the control unit may set the flow rate of the pump to the maximum flow rate.

[0009] When at least one of the temperature of the inkjet head and the external temperature is lower than the upper limit temperature of the appropriate temperature range, the control unit may set the flow rate of the pump to be less than the maximum flow rate.

[0010] When the temperature of the inkjet head is lower than the upper limit temperature of the appropriate temperature range, the control unit may increase the flow rate of the pump as the temperature of the inkjet head is lower.

[0011] When the temperature of the inkjet head and the external temperature are lower than the lower limit temperature of the appropriate temperature range of the ink, the control unit may stop the pump.

Advantages of the Invention

[0012] According to the present invention, the ability to cool the inkjet head can be adjusted according to the external temperature.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0014] Hereinafter, an inkjet recording apparatus 1 according to an embodiment of the present invention will be described with reference to the drawings.

[0015] FIG. 1 is a perspective view showing the appearance of an image forming system 100. FIG. 2 is a front view schematically showing the internal configuration of the inkjet recording apparatus 1. FIG. 3 is a cross-sectional view showing the inkjet head 12. Hereinafter, the front side (front side) of the inkjet recording apparatus 1 will be defined as the side closer to the viewer in FIG. 2, and the left and right directions will be described with reference to the direction when viewing the inkjet recording apparatus 1 from the front. In each figure, U, Lo, L, R, Fr, and Rr indicate up, down, left, right, front, and rear, respectively.

[0016] The image forming system 100 (see FIG. 1) includes a paper feeding device 110, an inkjet recording device 1, a drying device 120, and a post-processing device 130. The paper feeding device 110 stores thousands of sheets and supplies the sheets to the inkjet recording device 1. The inkjet recording device 1 forms an image on the sheet by an inkjet method. The drying device 120 heats the sheet conveyed from the inkjet recording device 1 to dry the ink. The post-processing device 130 performs post-processing such as punching, stapling, and folding on the sheet conveyed from the drying device 120.

[0017] The inkjet recording device 1 (see FIG. 2) includes a rectangular parallelepiped main body housing 3. A conveyance unit 7 that adsorbs the sheet and conveys it in the Y direction is provided at the central part inside the main body housing 3. An image forming unit 6 that discharges ink to form an image is provided above the conveyance unit 7. A paper feed port 8 for introducing the sheet from the paper feeding device 110 is provided on the right side surface of the main body housing 3. A discharge port 9 for discharging the sheet on which the image is formed to the drying device 120 is provided on the left side surface of the main body housing 3. A conveyance path 10 that reaches the discharge port 9 from the paper feed port 8 through the gap between the conveyance unit 7 and the image forming unit 6 is provided inside the main body housing 3. A registration roller 18 is provided on the upstream side in the conveyance direction Y from the conveyance unit 7.

[0018] The conveyance unit 7 includes an endless conveyance belt 21 and a suction unit 24. The conveyance belt 21 has a number of ventilation holes (not shown) and is wound around a driving roller 25 and a driven roller 22. The upper surface of the suction unit 24 has a number of ventilation holes (not shown) and is in contact with the inner surface of the conveyance belt 21. By the suction unit 24 sucking air through the ventilation holes of the conveyance belt 21 and the ventilation holes of the suction unit 24, the sheet is adsorbed to the conveyance belt 21. When the driving roller 25 is driven in the counterclockwise direction by a driving unit (not shown) including a motor and a reduction gear, the conveyance belt 21 rotates in the counterclockwise direction, and the sheet adsorbed to the conveyance belt 21 is conveyed in the Y direction.

[0019] The image forming unit 6 includes a plurality (four in this embodiment) of head units 11. Each head unit 11 includes one or more (three in this embodiment) inkjet heads 12. An ink container 20 filled with black, cyan, magenta, and yellow inks is connected to each head unit 11 respectively.

[0020] The inkjet head 12 (see FIG. 3) includes a rectangular parallelepiped-shaped housing 12H having the longitudinal direction in the front-rear direction, a nozzle plate 14 provided at the bottom of the housing 12H, and a socket 12S to which a pipe for supplying ink is connected. The nozzle plate 14 includes a large number of nozzles 14N arranged in the front-rear direction. The nozzle 14N includes a branch flow path 14B branched from the downstream side of the socket 12S and a discharge port 14A provided on a nozzle surface 14F which is the lower surface of the nozzle plate 14. The diaphragm 14V also serves as a part of the inner wall of the branch flow path 14B. A pressurizing element 14Z is provided on the diaphragm 14V. As the pressurizing element 14Z, a piezoelectric element, an electrostatic actuator, a heater, or the like is used. A drive circuit 12D for driving the pressurizing element 14Z is connected to the pressurizing element 14Z.

[0021] The control unit 2 (see FIG. 2) includes an arithmetic unit and a storage unit (not shown). The arithmetic unit is, for example, a CPU (Central Processing Unit). The storage unit includes storage media such as a ROM (Read Only Memory), a RAM (Random Access Memory), and an EEPROM (Electrically Erasable Programmable Read Only Memory). The arithmetic unit performs various processes by reading and executing a control program stored in the storage unit. Note that the control unit 2 may be realized by an integrated circuit without using software.

[0022] On the upper part of the main body housing 3, a display operation unit 19 is provided (see FIGS. 1 and 2). The display operation unit 19 includes a display panel, a touch panel laminated on the display panel, and a keypad (not shown). The control unit 2 causes the display panel to display a screen representing the operation menu, status, etc. of the inkjet recording apparatus 1, and controls each part of the inkjet recording apparatus 1 according to the operations detected by the touch panel and the keypad.

[0023] The basic image forming operation of the inkjet recording apparatus 1 is as follows. When an image forming job is input to the inkjet recording apparatus 1 from the display operation unit 19 or an external computer, etc., the paper feeding device 110 sends out a sheet onto the conveyance path 10 through the paper feeding port 8, and the registration roller 18 whose rotation has been stopped corrects the skew of the sheet. When the registration roller 18 sends out the sheet to the conveyance unit 7 at a predetermined timing, the conveyance unit 7 sucks the sheet onto the conveyance belt 21 and conveys it in the Y direction. Ink is ejected from the inkjet head 12 onto the sheet to form an image. The sheet on which the image has been formed is discharged to the drying device 120 through the discharge port 9.

[0024] [Cooling Device] FIG. 4 is a piping system diagram of the cooling device 15. FIG. 5 is a block diagram showing the electrical configuration of the cooling device 15. In FIG. 4, the cooling device 15 corresponding to one head unit 11 is shown, but actually, similar cooling devices 15 are provided for each head unit 11.

[0025] The inkjet recording apparatus 1 according to this embodiment includes a tank 43 that stores the coolant C, a pump 44 that sends out the coolant C, an inkjet head 12, a radiator 45 that cools the coolant C, a blower 46 that blows air to the radiator 45, a flow path 40 that circulates the coolant C through the tank 43, the pump 44, the inkjet head 12, and the radiator 45, a head temperature measurement unit 51 that measures the temperature Th of the inkjet head 12, an external temperature measurement unit 52 that measures the external temperature To, and a control unit 2 that controls the flow rate F of the pump 44 according to the temperature Th of the inkjet head 12 and the external temperature To. Specifically, it is as follows.

[0026] [Tank] Connected to the tank 43 via a replenishment flow path 63 are a replenishment tank 61 and a replenishment pump 62. The replenishment pump 62 is, for example, a turbo pump, a gear pump, or the like. The tank 43 is provided with a liquid level detection unit 43S. The liquid level detection unit 43S includes, for example, a floating body and a sensor that detects the vertical position of the floating body. The liquid level detection unit 43S detects the height of the liquid level of the coolant C in the tank 43 and outputs data indicating the height of the liquid level to the control unit 2. The control unit 2 operates the replenishment pump 62 to replenish the coolant C from the replenishment tank 61 to the tank 43 so that the height of the liquid level is maintained within a predetermined range.

[0027] [Pump] The pump 44 is, for example, a turbo pump, a gear pump, or the like. The pump 44 sends out the coolant C from the tank 43 to the inkjet head 12.

[0028] [Flow path, radiator] The flow path 40 includes a supply flow path 41 that supplies the coolant C from the tank 43 to the inkjet head 12, and a recovery flow path 42 that recovers the coolant C from the inkjet head 12 to the tank 43. The supply flow path 41 leads from the tank 43 via the pump 44 and branches into three downstream of the pump 44 to reach each inkjet head 12. The radiator 45 is provided for each inkjet head 12. The recovery flow path 42 leads from each inkjet head 12 via the radiator 45 to the tank 43. The blower 46 introduces air from outside the inkjet recording apparatus 1 and blows it onto the radiator 45. The coolant C whose temperature has risen due to the heat generation of the drive circuit 12D of the inkjet head 12 is cooled by the radiator 45.

[0029] [Head temperature measurement unit] The head temperature measurement unit 51 is, for example, a thermistor, a thermocouple, etc., and is provided on each inkjet head 12. The head temperature measurement unit 51 measures the temperature of the inkjet head 12 (hereinafter referred to as the head temperature Th), and outputs data indicating the head temperature Th to the control unit 2.

[0030] [External temperature measurement unit] The external temperature measurement unit 52 is, for example, a thermistor, a thermocouple, etc., and is provided on the main body housing 3 of the inkjet recording apparatus 1. The external temperature measurement unit 52 measures the temperature of the air outside the inkjet recording apparatus 1 (hereinafter referred to as the external temperature To), and outputs data indicating the external temperature To to the control unit 2.

[0031] Next, the operation of the cooling device 15 will be described. The control unit 2 controls the cooling device 15 according to a control program showing the control procedure of the cooling device 15. The control program describes an algorithm for determining the flow rate ratio of the pump 44 according to the head temperature Th and the external temperature To. The flow rate ratio is the ratio F / Fmax of the flow rate F to the maximum flow rate Fmax of the pump 44.

[0032] FIG. 6 is a diagram showing the relationship between the head temperature Th and the external temperature To and the flow rate ratio F / Fmax. Here, the upper limit temperature Tmax and the lower limit temperature Tmin of the appropriate temperature range are the temperatures at which the ink properties change. The change in the ink properties causes ejection unevenness of the inkjet head 12 and white streaks in the image. The target temperature Ti within the appropriate temperature range is, for example, half of the sum of the upper limit temperature Tmax and the lower limit temperature Tmin.

[0033] In this example, the head temperature Th and the external temperature To are divided into four categories. The four categories are above the upper limit temperature Tmax, above the target temperature Ti and below the upper limit temperature Tmax, above the lower limit temperature Tmin and below the target temperature Ti, and below the lower limit temperature Tmin. The head temperature Th and the external temperature To are classified into the first to eighth states according to which of the four categories they belong to.

[0034] In the first state, both the external temperature To and the head temperature Th are above the upper limit temperature Tmax. In the second state, the external temperature To is above the upper limit temperature Tmax, and the head temperature Th is above the target temperature Ti and below the upper limit temperature Tmax. In the third state, the external temperature To is above the target temperature Ti and below the upper limit temperature Tmax, and the head temperature Th is above the upper limit temperature Tmax. In the fourth state, both the external temperature To and the head temperature Th are above the target temperature Ti and below the upper limit temperature Tmax. In the fifth state, the external temperature To is above the lower limit temperature Tmin and below the target temperature Ti, and the head temperature Th is above the upper limit temperature Tmax. In the sixth state, the external temperature To is above the lower limit temperature Tmin and below the target temperature Ti, and the head temperature Th is above the target temperature Ti and below the upper limit temperature Tmax. In the seventh state, the external temperature To is above the target temperature Ti and below the upper limit temperature Tmax, and the head temperature Th is above the lower limit temperature Tmin and below the target temperature Ti. In the eighth state, both the external temperature To and the head temperature Th are below the lower limit temperature Tmin.

[0035] The flow rate ratio F / Fmax is determined for each of the above states. The flow rate ratio F / Fmax in the first state is 100%. The flow rate ratios F / Fmax in the second, fourth, fifth, and sixth states are represented by Equation (1). F / Fmax = (100 + (Ti / Th)×100) / 2 ··· Equation (1) The flow rate ratio F / Fmax in the third state is a constant value less than 100%. The flow rate ratio F / Fmax in the seventh state is represented by Equation (2). F / Fmax = (100 + (Ti / To)×100) / 2 ··· Equation (2) The flow rate ratio F / Fmax in the eighth state is 0%, and the pump 44 is stopped.

[0036] Figure 7 is a diagram showing the change over time of the head temperature Th. In the figure, as an example, the first to fourth states are shown. In the first and third states, since the flow rate ratio F / Fmax is a constant value, the head temperature Th decreases at a substantially constant rate. This is because priority is given to rapidly lowering the head temperature Th.

[0037] Also, in the third state, since the flow rate ratio F / Fmax is lower than that in the first state, the rate of decrease of the head temperature Th is slow. This is because in the third state, the outside temperature To is lower than that in the first state, and if the flow rate ratio F / Fmax is the same as that in the first state, the decrease in the head temperature Th may be too rapid and the image quality may become unstable.

[0038] On the other hand, in the second and fourth states, as shown by Equation (1), as the head temperature Th decreases, the flow rate ratio F / Fmax increases. Therefore, near the upper limit temperature Tmax, the decrease in the head temperature Th is gentle, but as the head temperature Th decreases, the rate of decrease increases. By gently reducing the initial decrease in the head temperature Th, a rapid temperature drop of the ink is suppressed, so that the image quality can be stabilized.

[0039] Note that the above description shows an example in which the transition from the first state to the second state and the transition from the third state to the fourth state are realized due to the progress of cooling. In contrast, when the head temperature Th is below the upper limit temperature Tmax in the initial state, Equation (1) is applied from the beginning, and the head temperature Th decreases as shown by the two-dot chain line in Figure 7.

[0040] In the fifth state, since the outside temperature To is lower than the head temperature Th, Equation (1) is applied. This is because, according to the specifications of the water cooling mechanism, when cooling, the temperature of the air blown to the radiator 45 is the outside temperature To, so the greater the deviation between the outside temperature To and the head temperature Th, the more likely it is that a rapid temperature change will occur in the ink. By using Equation (1), the flow rate ratio F / Fmax is set by referring to the ratio of the head temperature Th to the target temperature Ti, so a rapid temperature change in the ink can be prevented. In the sixth and seventh states, since the head temperature Th and the outside temperature To are close to the target temperature Ti, the temperature is equalized by increasing the flow rate ratio F / Fmax.

[0041] According to the inkjet recording apparatus 1 according to the present embodiment described above, there are provided a tank 43 for storing the coolant C, a pump 44 for sending out the coolant C, an inkjet head 12, a radiator 45 for cooling the coolant C, a blower 46 for blowing air to the radiator 45, a flow path 40 for circulating the coolant C through the tank 43, the pump 44, the inkjet head 12, and the radiator 45, a head temperature measuring unit 51 for measuring the temperature Th of the inkjet head 12, an outside temperature measuring unit 52 for measuring the outside temperature To, and a control unit 2 for controlling the flow rate F of the pump 44 according to the temperature Th of the inkjet head 12 measured by the head temperature measuring unit 51 and the outside temperature To measured by the outside temperature measuring unit 52.

[0042] Since the drive circuit 12D of the inkjet head 12 generates heat, it is necessary to cool the inkjet head 12 in order to maintain the temperature of the ink within an appropriate temperature range. However, since the amount of heat generated by the drive circuit 12D varies according to the image density, the head temperature Th also varies. Therefore, it is necessary to adjust the cooling capacity according to the head temperature Th. However, in the case of the water-cooled cooling device 15, since the cooling capacity of the radiator 45 varies depending on the outside temperature To, there is a risk that the cooling capacity becomes excessive or insufficient due to the outside temperature To, and the temperature of the ink deviates from the appropriate temperature range. According to the present embodiment, since the flow rate F of the pump 44 is controlled according to the outside temperature To, the cooling capacity when cooling the inkjet head 12 by liquid cooling can be adjusted according to the outside temperature To.

[0043] Further, according to the inkjet recording apparatus 1 according to the present embodiment, the control unit 2 increases the flow rate F of the pump 44 as the outside temperature To is higher. According to this configuration, it is possible to suppress a decrease in the cooling capacity of the radiator 45 when the outside temperature To increases.

[0044] Further, according to the inkjet recording apparatus 1 according to the present embodiment, the control unit 2 sets the flow rate F of the pump 44 to the maximum flow rate Fmax when the temperature Th of the inkjet head 12 and the outside temperature To are equal to or higher than the upper limit temperature of the appropriate temperature range of the ink. According to this configuration, when the temperature Th of the inkjet head 12 and the outside temperature To become equal to or higher than the upper limit temperature of the appropriate temperature range of the ink, the inkjet head 12 can be cooled with the maximum cooling capacity.

[0045] Further, according to the inkjet recording apparatus 1 according to the present embodiment, the control unit 2 sets the flow rate F of the pump 44 to less than the maximum flow rate Fmax when at least one of the temperature Th of the inkjet head 12 and the outside temperature To is less than the upper limit temperature of the appropriate temperature range. According to this configuration, since the cooling rate becomes gentler than when the flow rate F of the pump 44 is the maximum flow rate Fmax, a rapid temperature drop of the ink is suppressed, and the image quality can be stabilized.

[0046] Further, according to the inkjet recording apparatus 1 according to the present embodiment, when the temperature Th of the inkjet head 12 is less than the upper limit temperature of the appropriate temperature range, the control unit 2 increases the flow rate F of the pump 44 as the temperature Th of the inkjet head 12 is lower. According to this configuration, cooling proceeds gently at the initial stage of cooling, and the cooling rate increases as cooling proceeds. Therefore, a rapid temperature drop at the initial stage is suppressed, and the image quality can be stabilized.

[0047] Further, according to the inkjet recording apparatus 1 according to the present embodiment, when the temperature Th of the inkjet head 12 and the outside temperature To are less than the lower limit temperature of the appropriate temperature range of the ink, the control unit 2 stops the pump 44. According to this configuration, energy can be saved when cooling is not required.

[0048] The above embodiment may be modified as follows.

[0049] Equation (1) is merely an example of a calculation formula for increasing the flow rate F of the pump 44 as the temperature Th of the inkjet head 12 is lower, and a calculation formula including an exponential function, a quadratic function, or the like may be used. Equation (2) is merely an example of a calculation formula for increasing the flow rate F of the pump 44 as the outside temperature To is lower, and a calculation formula including an exponential function, a quadratic function, or the like may be used.

Explanation of symbols

[0050] 1 Inkjet recording apparatus 2 Control unit 12 Inkjet head 40 Flow path 43 Tank 44 Pump 45 Radiator 46 Blower 51 Head temperature measurement unit 52 Outside temperature measurement unit C Cooling liquid

Claims

1. A tank for storing coolant, a pump for delivering the coolant, an inkjet head, a radiator for cooling the coolant, a blower for blowing air to the radiator, a flow path for circulating the coolant through the tank, the pump, the inkjet head, and the radiator, a head temperature measurement unit for measuring the temperature of the inkjet head, an external temperature measurement unit for measuring the external temperature, and a control unit for controlling the flow rate of the pump according to the temperature of the inkjet head measured by the head temperature measurement unit and the external temperature measured by the external temperature measurement unit. An inkjet recording apparatus characterized by comprising these components.

2. The inkjet recording apparatus according to claim 1, wherein the control unit increases the flow rate of the pump as the external temperature is higher.

3. The inkjet recording apparatus according to claim 2, wherein the control unit sets the flow rate of the pump to the maximum flow rate when the temperature of the inkjet head and the external temperature are equal to or higher than the upper limit temperature of the appropriate temperature range of the ink.

4. The inkjet recording apparatus according to claim 2, wherein the control unit sets the flow rate of the pump to less than the maximum flow rate when at least one of the temperature of the inkjet head and the external temperature is less than the upper limit temperature of the appropriate temperature range.

5. The inkjet recording apparatus according to claim 4, wherein the control unit increases the flow rate of the pump as the temperature of the inkjet head is lower when the temperature of the inkjet head is less than the upper limit temperature of the appropriate temperature range.

6. The inkjet recording apparatus according to claim 2, wherein the control unit stops the pump when the temperature of the inkjet head and the external temperature are less than the lower limit temperature of the appropriate temperature range of the ink.

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