Image forming apparatus

Abstract

To provide an image forming apparatus capable of adjusting a recording head to an appropriate temperature.SOLUTION: An image forming apparatus includes: a recording head 21; a temperature sensor 55 that detects the temperature of the recording head 21; and a temperature adjustment mechanism 23. The temperature adjustment mechanism 23 includes: a heat exchange unit 31 that performs heat exchange with the recording head 21; a tank 33 that stores fluid; a circulating conduit 35 including a forward conduit 35a and a return conduit 35b; a conduit 39 for heating and a conduit 41 for cooling that are provided on the forward conduit 35a; a heating unit 43 that heats the fluid flowing through the conduit 30 for heating; a cooling unit 45 that cools the fluid flowing through the conduit 41 for cooling; and switching valves 47 and 49 that are provided on the forward conduit 35a. The image forming apparatus is configured to: switch the switching valves 47 and 49 on the basis of the temperature detected by the temperature sensor 55, and send the fluid to the heat exchange unit 31 through the conduit 39 for heating or the conduit 41 for cooling to perform heat exchange with the recording head 21.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an image forming apparatus that forms an image on a recording medium by an inkjet method.

Background Art

[0002] In an inkjet image forming apparatus, in order to guarantee image quality, it is necessary to maintain the temperature of the ink ejected from the recording head within an appropriate range. When the temperature of the ink is outside the appropriate range, the viscosity of the ink changes and a predetermined image quality cannot be guaranteed.

[0003] Therefore, in order to heat and cool the recording head, the recording head may be provided with a heating device and a cooling device. Then, there are problems such as an increase in the size of the structure around the recording head or an increase in power consumption when a heater is used as the heating device.

[0004] In the inkjet coating apparatus described in Patent Document 1, all inkjet heads (corresponding to the recording head) are cooled to a temperature below the set temperature by a cooling unit, and then heated to the set temperature by a heating adjustment unit, so that the head body parts of all inkjet heads are adjusted to a predetermined set temperature.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the inkjet coating apparatus described in Patent Document 1, it is necessary to first cool all the inkjet heads to a temperature below the set temperature until all the inkjet heads are heated to the set temperature. Therefore, there is a problem that it takes time to start coating (printing). In addition, an air cooling mechanism is used during cooling, and a heater unit is used during heating. Thus, since two temperature adjustment mechanisms are required, there are also problems such as increased power consumption and increased size of the apparatus.

[0007] Therefore, in view of the above circumstances, an object of the present invention is to provide an inkjet type image forming apparatus capable of adjusting a recording head to an appropriate temperature without increasing power consumption or increasing the size of the apparatus.

Means for Solving the Problems

[0008] To achieve the above object, an image forming apparatus of the present invention includes a recording head that discharges ink onto a recording medium, a temperature sensor that detects the temperature of the recording head, and a temperature adjustment mechanism that adjusts the temperature of the recording head based on the result of the temperature sensor. The temperature adjustment mechanism includes a heat exchanger that performs heat exchange with the recording head, a tank that houses a fluid flowing through the heat exchanger, an outgoing pipeline that leads from the tank to the heat exchanger, a return pipeline that returns from the heat exchanger to the tank, a circulation pipeline including the outgoing pipeline and the return pipeline, a heating pipeline and a cooling pipeline that branch off in the middle of the outgoing pipeline and then merge back into the outgoing pipeline, a heating unit that heats the fluid flowing through the heating pipeline, a cooling unit that cools the fluid flowing through the cooling pipeline, and switching valves provided at the branching portion and the merging portion of the outgoing pipeline, respectively. The switching valve is switched based on the temperature detected by the temperature sensor, and fluid is sent to the heat exchanger through the heating pipeline or the cooling pipeline to perform heat exchange with the recording head.

[0009] In the present invention, it may further include a drying unit including a heater that dries the ink discharged onto the recording medium, and the heating unit may be a heat exchanger that performs heat exchange with the heater.

Effects of the Invention

[0010] According to the present invention, according to the present invention, the temperature of the recording head, that is, the temperature of the ink can be maintained within the image quality compensation temperature range by one system (temperature adjustment mechanism). Therefore, it is possible to suppress a decrease in image quality due to fluctuations in the temperature (viscosity) of the ink while suppressing an increase in the size of the apparatus and power consumption.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0012] Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[0013] First, with reference to FIG. 1, the overall configuration of the image forming apparatus 1 will be described. FIG. 1 is a front view schematically showing the internal configuration of the image forming apparatus 1. The image forming apparatus 1 includes a conveyance unit 3, an image forming unit 5, a drying unit 7, and a conveyance plate 9.

[0014] The conveying unit 3 includes a feeding roller 11 that feeds out the recording medium M, and a winding roller 13 that winds up the recording medium M. The winding roller 13 is connected to a motor (not shown) and rotates. By rotating the winding roller 13 in a predetermined direction at a predetermined rotational speed by the motor, the recording medium M is sent out from the feeding roller 11 and conveyed along the conveying direction X toward the winding roller 13. A plurality of tension rollers 15 are provided between the feeding roller 11 and the winding roller 13. The recording medium M is, for example, continuous paper such as a plastic film.

[0015] The image forming unit 5 is disposed above the recording medium M fed out from the feeding roller 11. The image forming unit 5 includes four recording heads 21B, 21C, 21M, 21Y (collectively referred to as the recording head 21). The recording head 21 has a vertically long rectangular parallelepiped shape and has left and right, front and rear side surfaces, and upper and lower end faces. The recording head 21 includes a large number of nozzles (not shown). The discharge ports of the nozzles open on the lower end surface of the recording head 21. A temperature adjustment mechanism 23 is provided in the recording head 21. The temperature adjustment mechanism 23 will be described later.

[0016] The four recording heads 21B, 21C, 21M, 21Y are arranged in order along the conveying direction X, and black, cyan, magenta, and yellow inks are respectively supplied thereto. The supplied ink is discharged from the discharge ports of each recording head 21 onto the recording medium M below.

[0017] The drying unit 7 is disposed above the recording medium M fed out from the feeding roller 11 on the downstream side in the conveying direction X of the image forming unit 5. The drying unit 7 is a heater such as an infrared heater or a halogen heater, and dries the ink discharged onto the recording medium M.

[0018] The conveying plate 9 is disposed below the image forming unit 5 and the drying unit 7. The upper surface of the conveying plate 9 is formed flat, and the width of the conveying plate 9 is wider than the widths of the recording medium M and all the recording heads 21. A heat source (not shown) is provided below the conveying plate 9 to heat the conveying plate 9 to a predetermined temperature. The conveying plate 9 is made of, for example, metal. The recording medium M fed out from the feeding roller 11 is conveyed along the upper surface of the conveying plate 9 below the image forming unit 5 and the drying unit 7.

[0019] Next, the temperature adjustment mechanism 23 of the recording head 21 will be described with reference to FIG. 2. FIG. 2 is a system diagram showing the temperature adjustment mechanism 23. As described above, the temperature adjustment mechanism 23 is provided for each recording head 21.

[0020] The temperature adjustment mechanism 23 includes a heat exchanger 31 that performs heat exchange with the recording head 21, a tank 33 that stores a fluid (e.g., water) flowing through the heat exchanger 31, a forward pipe line 35a that leads from the tank 33 to the heat exchanger 31, and a return pipe line 35b that returns from the heat exchanger 31 to the tank 33, and a circulation pipe line 35 including the same. A pump 37 is provided in the forward pipe line 35a. When the pump 37 is driven, the fluid is pumped up from the tank 33, and the pumped-up fluid is sent into the heat exchanger 31 through the forward pipe line 35a and circulates back to the tank 33 through the return pipe line 35b (see the arrow in FIG. 2). The pump 37 is electrically connected to the control unit 71.

[0021] In the forward pipe line 35a, a heating pipe line 39 and a cooling pipe line 41 that branch downstream of the pump 37 and then merge into the forward pipe line 35a are provided. A heating unit 43 that heats the fluid flowing through the inner path of the pipe line is provided in the heating pipe line 39. A cooling unit 45 that cools the fluid flowing through the pipe line is provided in the cooling pipe line 41. A branch-side switching valve 47 and a merge-side switching valve 49 are provided at the branch portion and the merge portion of the forward pipe line 35a, respectively. By switching both valves 47 and 49, the fluid pumped up into the forward pipe line 35a is sent into the heat exchanger 31 through the heating pipe line 39 or the cooling pipe line 41. Both valves 47 and 49 are electrically connected to the control unit 71.

[0022] Next, referring to FIG. 3, the heat exchanger 31 will be described. FIG. 3 is a perspective view showing the recording head 21 to which the heat exchanger 31 is attached. The heat exchanger 31 includes left and right heat exchangers 51L and 51R that are respectively fixed in close contact with the left and right side surfaces of the recording head 21. Since the left and right side surfaces of the recording head 21 are larger in area than the front and rear side surfaces and the upper and lower end surfaces, by bringing the heat exchanger 31 into close contact with the left and right side surfaces, more efficient heat exchange can be performed with the recording head 21. The left and right heat exchangers 51L and 51R are connected by a connection pipe 53. Further, an outgoing pipe 35a is connected to one of the heat exchangers 51L, and a return pipe 35b is connected to the other heat exchanger 51R.

[0023] A temperature sensor 55 is provided on the right side surface of the recording head 21. The temperature sensor 55 is electrically connected to the control unit 71 (see FIG. 2).

[0024] Next, referring to FIG. 4, the heating unit 43 will be described. FIG. 4 is a diagram schematically showing the heating unit 43. The heating unit 43 is a heat exchanger that performs heat exchange with the drying unit 7 (heater). Specifically, the heating pipe 39 is arranged to meander along the side surface of the heater (for example, the side surface of the housing of the heater). When the drying unit 7 is driven and heated, heat exchange is performed between the fluid flowing through the heating pipe 39 and the drying unit 7.

[0025] Next, referring to FIG. 5, the cooling unit 45 will be described. FIG. 5 is a perspective view showing the cooling unit 45. The cooling unit 45 includes a radiator 61 and a fan 63. The radiator 61 is provided with an inlet 61a from the cooling pipe 41 and an outlet 61b to the cooling pipe 41. A heat dissipation fin 61c is provided on one side surface of the radiator 61. The fan 63 is attached to the other side surface of the radiator 61. The fan 63 sucks in outside air and blows it toward the radiator 61. Thereby, the fluid flowing through the radiator 61 is radiated.

[0026] Next, referring again to FIG. 2, the control unit 71 will be described. As described above, the detection result of the temperature sensor 55 is input to the control unit 71. The control unit 71 calculates the temperature of the recording head 21 or the temperature of the ink based on the detection result. Further, the control unit 71 is electrically connected to the branch-side switching valve 47 and the confluence-side switching valve 49. The control unit 71 switches both valves 47 and 49 so that the fluid pumped up in the forward pipe 35a is sent to the heat exchanger 31 through the heating pipe 39 or the cooling pipe 41 based on the detection result of the temperature sensor 55.

[0027] Further, the control unit 71 is electrically connected to the pump 37 and controls the driving and stopping of the pump 37.

[0028] The image forming operation of the image forming apparatus 1 having the above configuration will be mainly described with reference to FIG. 2. At the start of the image forming operation, first, the drying unit 7 (heater) of the image forming apparatus 1 is driven. The control unit 71 determines whether the temperature of the recording head 21 (or ink) obtained from the detection result of the temperature sensor 55 provided in the recording head 21 is within the ink image quality compensation temperature range Tmin to Tmax. When the control unit 71 determines that the temperature of the recording head 21 is lower than Tmin, it switches both valves 47 and 49 to branch the forward pipe 35a to the heating pipe 39.

[0029] Next, the control unit 71 drives the pump 37. As a result, the fluid is pumped up from the tank 33 by the pump 37, and the pumped-up fluid is sent from the forward pipe 35a to the heating pipe 39. Then, in the heating unit 43, heat exchange is performed between the fluid and the drying unit 7 (the side surface of the heater housing). At this time, since the temperature of the fluid is lower than the temperature of the drying unit 7, heat is taken from the drying unit 7 to the fluid and the fluid is heated.

[0030] The fluid heated in this way is sent to the heat exchanger 31, and heat exchange is performed between the fluid and the recording head 21. At this time, since the temperature of the fluid is higher than the temperature of the recording head 21, heat is taken from the fluid to the recording head 21 and the recording head 21 (ink) is heated.

[0031] On the other hand, when the control unit 71 determines that the temperature of the print head 21 exceeds Tmax, it switches both valves 47, 49 to branch the outgoing conduit 35a to the cooling conduit 41. As a result, the pumped fluid is sent from the outgoing conduit 35a to the cooling conduit 41. Then, in the cooling unit 45, heat exchange occurs between the fluid and the radiator 61. At this time, since the temperature of the radiator 61 is lower than the temperature of the fluid, heat is absorbed from the radiator 61 by the fluid, and the fluid is cooled.

[0032] The fluid cooled in this manner is sent to the heat exchanger 31, where heat is exchanged between the fluid and the print head 21. At this time, since the temperature of the fluid is lower than that of the print head 21, heat is absorbed from the print head 21 by the fluid, thereby cooling the print head.

[0033] The control unit 71 drives the pump 37 until the temperature of the print head 21 falls within the range of Tmin to Tmax, and stops driving the pump 37 when it determines that the temperature of the print head 21 falls within the range of Tmin to Tmax.

[0034] Thereafter, the motor is driven to rotate the take-up roller 13, and the recording medium M is sent from the delivery roller 11 to the image forming section 5. In the image forming section 5, the recording medium M is transported along the upper surface of the transport plate 9. When the recording medium M is transported below the recording heads 21, ink of a predetermined color is ejected from each recording head 21 based on image data, and an image is formed on the recording medium M. As described above, the temperature of the ink is included in the ink image quality compensation temperature range Tmin to Tmax. The ink is dried auxiliary by the heated transport plate 9. Thereafter, the recording medium M on which the image has been formed is transported to the drying section 7. In the drying section 7, the ink is completely dried. Thereafter, the recording medium M is taken up by the take-up roller 13.

[0035] During the image forming operation, the detection result is input from the temperature sensor 55 to the control unit 71. The control unit 71 determines whether the temperature of the recording head 21 obtained from the detection result is within the ink image quality compensation temperature range Tmin to Tmax. When the temperature of the recording head 21 falls below Tmin or exceeds Tmax, the control unit 71 switches the two valves 47 and 49 and drives the pump 37 based on the temperature of the recording head 21 as described above, sending the fluid to the heating pipe 39 or the cooling pipe 41 to heat or cool the recording head 21.

[0036] As described above, according to the present invention, the temperature of the recording head 21, that is, the temperature of the ink, can be maintained within the image quality compensation temperature range by one system (temperature adjustment mechanism 23). Therefore, it is possible to suppress a decrease in image quality due to fluctuations in the temperature (viscosity) of the ink while suppressing an increase in the size and power consumption of the apparatus.

[0037] In addition, since the drying unit 7 of the image forming apparatus 1 is used as the heating unit 43, there is no need to provide another heater for temperature adjustment.

[0038] In the above embodiment, an example in which the temperature adjustment mechanism 23 is provided for each recording head 21 has been described. In this case, since the temperature can be adjusted for each recording head 21, the temperature of each color ink can be adjusted more accurately. However, in the temperature adjustment mechanism 23 shown in FIG. 2, on the downstream side of the merging side switching valve 49, the forward pipe 35a may be branched into four heat exchangers 31 provided for the four recording heads 21 and merged into the return pipe 35b from the four heat exchangers 31. In this case, the configuration of the temperature adjustment mechanism 23 can be simplified.

[0039] In addition, in the above embodiment, an example in which one recording head 21 is provided for each color of ink has been described. However, it can also be applied to a line head system in which a plurality (for example, three) of recording heads 21 are provided for each color of ink and the plurality of recording heads 21 are arranged in a staggered manner along the width direction of the recording medium M (the direction intersecting the conveyance direction X). In this case, one temperature adjustment mechanism 23 is provided for one recording head 21.

[0040] Also, in this case as well, similar to the above, in the temperature adjustment mechanism 23, downstream of the confluence-side switching valve 49, the forward pipe line 35a may be branched to all the heat exchangers 31 provided in all the recording heads 21 and then merged into the return pipe line 35b from the heat exchangers 31. Alternatively, the temperature adjustment mechanism 23 may be provided for each color of ink. In this case, four temperature adjustment mechanisms 23 are provided for each color of ink. In each temperature adjustment mechanism 23, downstream of the confluence-side switching valve 49, the forward pipe line 35a is branched to three heat exchangers 31 provided in three recording heads 21 and then merged into the return pipe line 35b from the three heat exchangers 31.

[0041] Although the present invention has been described with respect to specific embodiments, the present invention is not limited to the above embodiments. Those skilled in the art can modify the above embodiments without departing from the scope and gist of the present invention.

Explanation of Reference Numerals

[0042] 1 Image forming apparatus 7 Drying unit 21 Recording head 23 Temperature adjustment mechanism 31 Heat exchanger 33 Tank 35 Circulation pipe line 35a Forward pipe line 35b Return pipe line 39 Heating pipe line 41 Cooling pipe line 43 Heating unit 45 Cooling unit 47, 49 Switching valve 55 Temperature sensor

Claims

1. A recording head that discharges ink onto a recording medium, a temperature sensor that detects the temperature of the recording head, and a temperature adjustment mechanism that adjusts the temperature of the recording head based on the result of the temperature sensor, comprising: The temperature adjustment mechanism includes: a heat exchanger that performs heat exchange with the recording head; a tank that houses a fluid flowing through the heat exchanger; a circulation pipe including an outgoing pipe that leads from the tank to the heat exchanger and a return pipe that returns from the heat exchanger to the tank; a heating pipe and a cooling pipe that branch off in the middle of the outgoing pipe and then merge into the outgoing pipe; a heating unit that heats the fluid flowing through the heating pipe; a cooling unit that cools the fluid flowing through the cooling pipe; and switching valves provided at the branching portion and the merging portion of the outgoing pipe, respectively, wherein the switching valve is switched based on the temperature detected by the temperature sensor, and the fluid is sent to the heat exchanger through the heating pipe or the cooling pipe to perform heat exchange with the recording head. An image forming apparatus characterized by this.

2. Further comprising a drying unit including a heater that dries the ink discharged onto the recording medium, wherein the heating unit is a heat exchanger that performs heat exchange with the heater. The image forming apparatus according to claim 1, characterized by this.

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