JP7552178B2 - Liquid ejection device - Google Patents

Description

The present invention relates to a liquid ejection device.

Conventionally, there are various devices that perform preheat control during printing. For example, in Patent Document 1, an image forming device capable of functioning as multiple image recording devices such as a copier, facsimile, and printer is provided with a means for detecting and controlling the temperature of a heating element, a means for changing the preheat temperature of the heating element, and a means for counting the number of image formations for each of the above functions in a predetermined time, and the preheat temperature of the heating element is controlled according to the counting results. Also disclosed is a device that provides two states, a power saving state and a standby state, as the control means for the heating element, and is configured to switch between these two states based on the counting results.

In Patent Document 1, the above configuration is used to quickly respond to user requests while saving on power consumption for heating, but when this configuration is used in a serial inkjet printing device, the preheat control is not necessarily sufficient, as described below.

In serial inkjet printers, when printing on non-permeable media or low-permeable media such as acrylic, polyester, PVC films, and coated paper, the ink is dried by hot air drying or IR (infrared) drying. In order to heat the media before and during printing, the printer is equipped with a post-heater, print heater (platen heater), and pre-heater in the sub-scanning direction, and the temperature sensors installed in each heater are independently controlled to ensure that the media temperature is optimal for each sub-scanning location depending on the type of media.
The principle of infrared heating is that infrared rays are a type of electromagnetic wave, a type of light energy with a certain wavelength. The big difference with hot air is that the light penetrates the coating film (the film that forms on the surface of the ink). Basically, hot air only acts on the surface. The heat is transferred by conduction from the surface. Because of this, drying inevitably begins from the surface of the coating, which can easily lead to problems such as skinning, and there is a natural limit to how quickly it can be dried. Also, a film (film formation) forms on the surface of the ink, making it difficult for moisture and solvents to escape from the inside.

In a conventional method of infrared heating in a serial inkjet printer, a cure heater with an infrared heating device is turned on when printing starts. Therefore, for the image at the beginning of printing, the temperature sensor that detects the surface temperature of the media does not detect that the infrared heating device has warmed up sufficiently, resulting in insufficient heat and prone to drying defects, making it difficult to obtain a good image.
On the other hand, in serial inkjet printers, the media is usually stopped before printing. This is because moving the media before printing is inefficient, considering paper waste. If the infrared heating device described above is turned on when the media is stopped, heat will concentrate in one place on the media, causing problems (damage) such as deformation or melting of the media. For this reason, the infrared heating device is turned off until the printing operation starts and the media starts to move. However, as mentioned above, in order for the infrared heating device to provide the desired output to the media, it needs to be warmed up to a certain extent before printing.

In conventional techniques, preheat control is not performed with consideration given to these issues in serial inkjet printing devices, namely, avoiding damage to the media and improving image quality.
An object of the present invention is to provide a liquid ejection apparatus capable of preheating control that takes into consideration avoiding damage to media and improving image quality.

The liquid ejection device of the present invention is configured as a liquid ejection device characterized by comprising: a first heating means for heating a medium; and a control unit which controls the first heating means to heat at a first output during preheating, and when the temperature inside the first heating means reaches a predetermined threshold, controls the first heating means to heat at a second output that is equal to or higher than the first output, and starts transporting the medium by a transport means .

The present invention makes it possible to perform preheating control that takes into account the avoidance of damage to the media and the improvement of image quality.

1 is a perspective view of an external appearance of an inkjet recording apparatus according to an embodiment of the present invention. 2 is a schematic plan view of a carriage scanning mechanism shown in FIG. 1 . FIG. 2 is a cross-sectional view of the drying unit shown in FIG. FIG. 2 is a block diagram showing an example of the configuration of a recording apparatus according to the present embodiment. 5A and 5B are explanatory diagrams of a preheating operation performed by the recording apparatus in the present embodiment.

The embodiment of the liquid ejection device will be described in detail below with reference to the attached drawings. The liquid ejection device in this embodiment is, for example, a serial type inkjet recording device using an infrared heating device, and has the following features. That is, when a print job is input, the infrared heating device is controlled to enter preheating operation before starting the printing operation. Therefore, the drying quality of the image at the start of printing can be satisfied. In addition, the control regarding the above preheating operation is lower than when actually printing, and outputs at a temperature that does not actually damage the recording medium. Therefore, damage such as deformation or melting of the recording medium can be prevented during the preheating operation. Then, when the internal temperature of the infrared heating device reaches a predetermined threshold value or higher through the preheating operation controlled in this way, it is determined that preheating is complete, and the printing operation is started. The above-mentioned features of the present invention will be described in detail with reference to the following drawings.

Fig. 1 is an external perspective view of an inkjet recording apparatus 100 according to the present embodiment. Fig. 2 is a schematic plan view of the carriage scanning mechanism shown in Fig. 1. As shown in these figures, inside the recording apparatus 100, a guide rod 1 and a sub-guide rail 2 are hung between both side plates, and a carriage 5 is supported by the guide rod 1 and the sub-guide rail 2 so as to be movable in the direction of arrow A (main scanning direction).
A timing belt 11 that is stretched between a drive pulley 7 and a pressure pulley 10 is connected to the carriage 5. The timing belt 11 is driven by a main scanning motor 9 via the drive pulley 7, causing the carriage 5 to reciprocate in a main scanning direction A. Tension is applied to the timing belt 11 by the pressure pulley 10, so that the carriage 5 can be driven without slack. The "HP (home position) position" P is set, for example, at the top of the maintenance mechanism 26.

The print medium 150 is intermittently transported in the direction of arrow B (sub-scanning direction) below the reciprocating carriage 5, and a predetermined image is formed by ejecting ink droplets from recording heads 6k, 6c, 6m, and 6y mounted on the carriage 5 onto the platen 16. That is, the recording heads 6k to 6y are provided with a plurality of nozzles (not shown), and ink is ejected from the nozzles to form an image.
The print medium 150 on which an image has been formed is dried by a drying unit 17, which is a drying heater, in the paper discharge guide 32 (FIG. 3). The recording device 100 also includes a cartridge 60 that supplies ink to the recording head 6 (FIG. 3) and a maintenance mechanism 26 that performs maintenance on the recording head 6 mounted on the carriage 5. An encoder sensor 13 is disposed within the carriage 5, and by continuously reading an encoder sheet 14 stretched across both side plates, the carriage 5 is driven between the two side plates while detecting the main scanning direction position.

A media detection sensor 20 is also attached to the carriage 5, for example a reflective sensor, which detects the reflected light emitted by an LED to detect the presence or absence of an object underneath. In this embodiment, the area directly below the carriage is identified as the area outside the platen, the area above the platen, and the area above the media, depending on the value of the reflected light.

Figure 3 is a cross-sectional view of the drying unit 17 shown in Figure 1. The left side of Figure 3 is the front of the recording device 100 shown in Figure 1. The recording paper is transported from the right side of the figure to the left in the transport direction D. Four heaters are arranged on the transport path: a pre-heater 17-1, a print heater 17-2, a post-heater 17-3, and an infrared heating device 17-4.

The preheater 17-1 is a heater that warms the recording medium. The preheater 17-1 heats the medium from the side where the ink is being conveyed, so that the ink evaporates easily when it lands on the recording medium (preheating).
The print heater 17-2 is a heater that evaporates the moisture in the ink, forming a film on the ink surface (ink setting). By forming a film, a film is formed on the ink surface, and the ink is dried to the point where it does not stick to your hands when you touch it. The spread and size of the ink droplets (dots) are determined by the film formation, so it is also called ink setting. It is the most important heater for creating images.
The post-heater 17-3 is a heater that further heats the recording medium, evaporates the water and solvent in the ink, and dries the ink.
The infrared heating device 17-4 is a heater that heats the surface of the ink from inside the ink with far infrared rays (IR) to cause a polymerization reaction of the resin inside the ink, thereby hardening the ink.

The pre-heater 17-1, print heater 17-2, and post-heater 17-3 are each provided with a temperature sensor (17-1a, 17-2a, 17-3a) which is a thermistor that measures the temperature of the transport surface heated by the heater. The heaters are controlled based on the measurement results of these temperature sensors, and the temperature of the transport surface is controlled. Thermistors are used as the temperature sensors and are attached to the back side of the transport surface.
Each heater is provided with a thermostat (17-1b, 17-2b, 17-3b) so that the thermostat will turn off if the heater becomes uncontrollable and the temperature rises abnormally. Each heater is connected in series with its corresponding thermostat, so that if the thermostat turns off, the power supply to the heater is also cut off to ensure safety.

The infrared heating device 17-4 at least comprises one or more infrared heaters 17-4a which are heat sources, a thermopile 17-4b which is a non-contact temperature sensor which measures the surface temperature of the recording medium, a thermistor 17-4c which measures the temperature inside the infrared heating device 17-4 by measuring the temperature of the reflector 17-4f, a thermostat 17-4d which ensures safety by disconnecting in the event of abnormal heating, a cure fan 17-4e which generates an airflow to suppress an increase in humidity near the medium, promote drying, and further suppress overheating of the infrared heating device, and a reflector 17-4f which reflects infrared rays emitted from the infrared heater 17-4a, promoting heating in the direction of the recording medium.
A thermopile 17-4b, which is a non-contact temperature sensor, is used to control the temperature of the infrared heating device 17-4. The thermopile 17-4b measures the temperature of the surface of the recording medium, and controls the output of the infrared heater 17-4a so that the surface temperature of the recording medium becomes the desired temperature. A thermistor 17-4c, which is a second temperature sensor, is installed on the reflector 17-4f and measures the temperature of the reflector 17-4f. The role of the thermistor 17-4c is to monitor whether the temperature inside the infrared heating device 17-4 is abnormally high, and to determine whether preheating is complete.

Fig. 4 is a block diagram showing an example of the configuration of a recording apparatus in this embodiment. As shown in Fig. 4, the recording apparatus 100 has a control unit 400 that performs control in this embodiment. The control unit 400 has a CPU 401, an FPGA 402, and a motor driver 403, and performs various controls performed by the recording apparatus, such as CPU control, memory control, ink ejection control, sensor control, and motor control.
As shown in Figures 1 and 2, the printing device 100 also has a main scanning motor 9, a carriage 5 driven by the main scanning motor 9, a printing head 6 mounted on the carriage 5, a main scanning encoder sensor 13, and a media detection sensor 20.
The recording apparatus 100 also has a sub-scanning motor 404 and a conveying unit 405 driven by the sub-scanning motor 404. The conveying unit 405 has a sub-scanning encoder sensor 4051 that detects the conveyance amount in the sub-scanning direction, and a conveying roller 4052 that conveys the recording medium in the sub-scanning direction.

In addition, it has various mechanisms that a normal recording device should have, such as a winding motor (not shown), a winding section having a winding roller and a winding encoder sensor, a paper feed motor, a paper feed roller and a paper feed encoder sensor.
The drying unit 17 includes a preheater 17-1 (M units: divided into M units in the sub-scanning direction), a print heater 17-2 (N units: divided into N units in the main scanning direction), a post heater 17-3 (K units: divided into K units in the main scanning direction and the sub-scanning direction), and an infrared heating device 17-4 (L units: divided into L units in the main scanning direction or L=1). Temperature sensors are provided to measure the temperature of each divided heater. For example, the preheater 17-1 is provided with a thermistor 17-1a which is a temperature sensor, the print heater 17-2 is provided with a thermistor 17-2a which is a temperature sensor, and the post heater 17-3 is provided with a thermistor 17-3a which is a temperature sensor. The infrared heating device 17-4 is provided with a thermistor 17-4c which is a temperature sensor (second temperature sensor) and a thermopile 17-4b which is a non-contact temperature sensor. The control unit 400 controls the output of the heater based on the value of the temperature sensor so that the heater reaches a target temperature.

Fig. 5 is an explanatory diagram of the preheating operation performed by the recording device in this embodiment. As shown in Fig. 5, when the control unit 400 determines that a print job has been input, each heater starts a preheating operation, and when preheating is completed, the recording medium begins to be conveyed and the printing operation begins. Since the preheater 17-1, print heater 17-2, and post heater 17-3 are heaters that heat the recording medium by heat transfer from the back side of the recording surface side by the guide plate, preheating is completed when the temperature of each guide plate monitored by each thermistor reaches a target temperature value.
Since the infrared heating device 17-4 is not in direct contact with the recording medium, it uses a thermopile 17-4b, which is a non-contact temperature sensor, to measure the surface temperature of the recording medium and monitor the temperature. The infrared heater 17-4a provided in the infrared heating device 17-4 has a good temperature response to the recording medium, and furthermore, when the recording medium is stopped, the temperature of the recording medium rises quickly even when the infrared heater 17-4a is not sufficiently warmed up. Therefore, if the printing operation is started even though the surface of the recording medium has reached the target temperature, the infrared heater 17-4a is not sufficiently warmed up, so the heat amount of the infrared heater 17-4a cannot keep up when the recording medium starts to move, and the temperature of the recording medium cannot be maintained.

For these reasons, the surface temperature of the recording medium measured by the thermopile 17-4b alone is insufficient as a condition for the completion of preheating by the infrared heating device 17-4. Therefore, the temperature of the thermistor 17-4c, which is a second temperature sensor that monitors the temperature of the reflector 17-4f inside the infrared heating device 17-4, is set as the condition for the completion of preheating. In other words, if the infrared heater 17-4a is sufficiently warm, it can be determined that the temperature of the thermistor 17-4c located near the infrared heater 17-4a is also above a predetermined threshold value, and therefore the preheating condition can be met by setting the threshold value appropriately.

The preheating operation of the infrared heating device 17-4 will be described below with reference to Fig. 5. When the control unit 400 determines that a print job has been input, it turns on the infrared heater 17-4a. When the infrared heater 17-4a is turned on, the temperature of the recording medium surface rises, and the control unit 400 controls the infrared heater 17-4a so that the detection temperature 501 of the thermopile 17-4b becomes B°C, which is the control temperature during preheating.
When the control unit 400 determines that the thermopile 17-4b has reached B°C, the detected temperature 502 of the thermistor 17-4c is lower than the preheating target temperature T, which is a predetermined threshold, but is gradually rising. The control unit 400 continues preheating while maintaining the thermopile 17-4b at B°C, until the temperature of thermistor 17-4c reaches the preheating target temperature T. The control unit 400 then determines that preheating is complete at the timing t when the detected temperature 502 of thermistor 17-4c exceeds the preheating target temperature T.

At this time, when the detection temperature 502 of the thermistor 17-4c, which indicates that preheating of the preheater 17-1, print heater 17-2, and post heater 17-3 has already been completed, reaches a predetermined threshold value, the control unit 400 enters printing operation P and conveys the recording medium. When printing operation P begins, the control unit 400 controls the thermopile 17-4b so that the control temperature during printing becomes A°C. The control temperature during printing is a temperature (A≧B) that is equal to or higher than the control temperature during preheating and is obtained by adding a predetermined difference temperature d. Note that if the control unit 400 determines that preheating of the preheater 17-1, print heater 17-2, and post heater 17-3 has not been completed, it controls the thermopile 17-4b so that the temperature is maintained at B°C until preheating is completed and even after preheating is completed.

The control unit 400 sets the temperature required to dry the ink on the recording medium to A°C, which is the control temperature during printing. This temperature needs to be somewhat high, so it is a temperature at which the recording medium may be damaged, such as by deformation or burning. However, as long as the recording medium is being transported, the time at which the temperature is applied is limited, so no damage will be caused. Therefore, if the recording medium is stopped while the same temperature is applied, there is a possibility that there will be an excess of heat on the recording medium, which will result in a risk of the recording medium being damaged, such as by deformation or burning. Therefore, the control unit 400 sets the thermopile 17-4b to B°C, which is the control temperature during preheating, at which there will be no damage to the recording medium even when the recording medium is stopped. In this embodiment, the control temperature during printing, A°C, and the control temperature during preheating, B°C, are controlled to be the difference temperature d, but if it is determined that the recording medium will not be damaged even if it stops at A°C (or the damage is less than a predetermined reference value), the control unit 400 may control the control temperature during printing, A°C, and the control temperature during preheating, B°C, to be the same temperature (d=0, A=B).

In addition, the values of A°C, which is the control temperature during printing, and B°C, which is the control temperature during preheating, change for each recording medium (e.g., for each type of recording medium). For example, when the recording device 100 prints on recording media with different permeabilities, it is necessary to set the control temperature during printing, A°C, to a higher temperature because a non-permeable medium requires more energy for drying than a permeable medium. In addition, when the heat resistance temperature of the recording medium is different, the value of the control temperature during preheating, B°C, also changes accordingly. Therefore, the value of the difference temperature d between the control temperature during printing, A°C, and the control temperature during preheating, B°C, also differs for each recording medium. Therefore, the control unit 400 stores unique values of the control temperature during printing, A°C, and the control temperature during preheating, B°C, for each recording medium in a storage medium such as a memory, and calls up these values according to the recording medium to be used to execute the above control. For example, when the type of recording medium is PVC and when the type of recording medium is PET, the control temperature during printing, A°C (control temperature A), and the control temperature during preheating, B°C (control temperature B), can be set to different values, as shown in Table 1 below.

In Table 1, the detected temperature 502 is a fixed value. However, the value of the detected temperature 502 may differ depending on the design layout and the difference between the position where the controlled temperature during preheating, B°C, and the detected temperature 502 of thermistor 17-4c are measured. In such cases, the value of the detected temperature 502 of thermistor 17-4c may be set to a value in the range of approximately 50 to 100% of the controlled temperature during preheating, B°C.

To speed up the preheating operation of the infrared heating device 17-4, as shown in FIG. 5, the control unit 400 may output a control signal 503 to stop (OFF) the cure fan 17-4e until it is determined that preheating is complete, and when it is determined that preheating is complete, output a control signal 504 to operate (ON) the cure fan 17-4e. By stopping the cure fan 17-4e, it is possible to prevent the infrared heater 17-4a and the reflector 17-4f from cooling down, and to quickly complete preheating. In addition, by operating the cure fan 17-4e after preheating is complete, it is possible to prevent overheating inside the infrared heating device 17-4.

Furthermore, when the control unit 400 determines that an operation panel of the recording device 100 or an operation terminal such as a smartphone having a communication unit and capable of communicating with the recording device 100 via wireless communication (neither of which is shown) has received an operation related to the preheating operation from a user (e.g., setting of the preheating time), the control unit 400 may execute the preheating operation of the recording device 100 according to the operation or the operation received by the communication unit via the wireless communication. With this type of control, the time for the preheating operation can be set, changed, or deleted at the user's discretion, and a balance between drying quality and damage to the recording medium can be obtained according to the individual requirements of each user.
Furthermore, when the control unit 400 is directed to the operation unit similar to the above, the control unit 400 may control the heating of the recording medium based on the preheating control temperature B° C. and the printing control temperature A° C. that are received from the user by the operation unit for each type of recording medium. This allows these values to be set according to the individual requirements of each user.

In this way, in this embodiment, for example, when drying control of media and ink is performed using an industrial serial type inkjet printing device, the device includes a heating means (e.g., infrared heating device 17-4) for heating the recording medium, and a control unit (e.g., control unit 400 having CPU 401, FPGA 402, and motor driver 403) that controls the heating means to heat the recording medium at a first output (e.g., B°C, which is the control temperature during preheating) during preheating before printing begins, and controls the heating means to heat the recording medium at a second output (e.g., A°C, which is the control temperature during printing) that is equal to or higher than the first output when the temperature of the heating means reaches a predetermined threshold value (e.g., preheat target temperature T), and starts conveying the recording medium by the conveying means (e.g., conveying unit 405). Therefore, preheating control can be performed with consideration given to avoiding damage to the media and improving image quality. Specifically, it is possible to mitigate sudden temperature changes on the media, suppress deformation of the media and cockling caused by it, and suppress the occurrence of jams.

The heating means includes an infrared heater 17-4a, a first temperature sensor (e.g., thermopile 17-4b) that detects the temperature of the surface of the recording medium, and a second temperature sensor (e.g., thermistor 17-4c) that detects the temperature inside the heating means. The control unit continues the first output until the first temperature sensor detects a first temperature that is the control temperature during preheating, and changes the output of the infrared heater from the first output to the second output when the second temperature sensor detects a temperature that is the predetermined threshold. Therefore, in a serial type inkjet recording device that uses a heating device that dries ink on a medium, it is possible to satisfy the drying quality even for the image at the start of printing and prevent problems such as deformation or dissolution of the medium.

The control unit performs heating with the first output and heating with the second output according to the type of the recording medium. Therefore, by providing a unique value according to the type of each medium, drying quality can be ensured regardless of the medium used, and damage to the medium can be suppressed.
The heating means further includes a fan (e.g., cure fan 17-4e) for suppressing heating of the heating means, and the control unit stops the fan until the temperature of the heating means reaches the predetermined threshold, and operates the fan after the temperature of the heating means reaches the predetermined threshold. This prevents the infrared heater and the second temperature sensor from being cooled, and allows preheating to be completed quickly.

100 Inkjet recording apparatus 17 Drying section 17-1 Preheater 17-2 Print heater 17-3 Post heater 17-4 Infrared heating device 17-1a, 2a, 3a Thermistor 17-4 Infrared heating device 17-4b Thermopile 17-4c Thermistor (second temperature sensor)
17-4d Thermostat 17-4e Cure fan 400 Control unit 401 CPU
402 FPGA
403 Motor driver 404 Sub-scanning motor 405 Conveying section 4051 Sub-scanning encoder sensor 4052 Conveying roller

Japanese Patent Application Publication No. 08-146840

Claims (10)

A first heating means for heating the medium;
a control unit that controls the first heating means to heat the medium at a first output during preheating, and when a temperature inside the first heating means reaches a predetermined threshold, controls the first heating means to heat the medium at a second output that is equal to or higher than the first output, and starts conveying the medium by a conveying means;
A liquid ejection device comprising: 2. The liquid ejection apparatus according to claim 1 , further comprising a second heating means for contacting and heating the medium during the preheating. 3. The liquid ejection apparatus according to claim 1 , wherein the first heating means heats the medium from the surface. the liquid ejection device further includes a second heating unit that contacts and heats the medium during the preheating process;
3. The liquid ejection apparatus according to claim 1 , wherein the second heating means heats the medium from a rear surface. 5. The liquid ejection apparatus according to claim 1, wherein the first heating means uses far infrared rays for heating. the liquid ejection device further includes a first temperature sensor that detects a temperature of the surface of the medium, and a second temperature sensor that detects a temperature inside the first heating means;
the control unit continues the first output until the first temperature sensor detects a preheating control temperature, which is a control temperature during preheating, and changes the output of the first heating means from the first output to the second output when the second temperature sensor detects a temperature equal to the predetermined threshold value.
6. The liquid ejection apparatus according to claim 1, 7. The liquid ejection apparatus according to claim 6 , wherein the predetermined threshold value is set within a range of approximately 50% to 100% of the preheat control temperature. The control unit performs heating at the first output and heating at the second output depending on the type of the medium.
8. The liquid ejection device according to claim 1 , wherein the liquid ejection device is a liquid ejection device. the first heating means includes a fan that suppresses heating of the first heating means;
the control unit stops the fan until the temperature of the first heating means reaches the predetermined threshold, and operates the fan after the temperature of the first heating means reaches the predetermined threshold.
9. The liquid ejection apparatus according to claim 1, the control unit, when an operation unit receives an operation related to a preheating operation from a user, controls the first heating means to perform the preheating operation in accordance with the operation.
10. The liquid ejection apparatus according to claim 1,

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