Patent Publication Number: US-2023140366-A1

Title: Inkjet recording apparatus, method for controlling inkjet recording apparatus

Description:
INCORPORATION BY REFERENCE 
     This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2021-176124 filed on Oct. 28, 2021, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to an inkjet recording apparatus and a method for controlling an inkjet recording apparatus that are configured to reduce ink viscosity. 
     An inkjet recording apparatus includes a recording head that includes a plurality of nozzles and a plurality of piezoelectric elements. Each of the plurality of nozzles ejects ink onto a sheet to form an image on the sheet. 
     Each of the plurality of piezoelectric elements pressurizes ink that is to be supplied to a corresponding one of the plurality of nozzles. The plurality of piezoelectric elements are provided in correspondence with the plurality of nozzles. 
     When the temperature of the ink decreases, the viscosity of the ink becomes high. When the viscosity of the ink to be supplied to each of the nozzles is high, ejection performance of the ink ejected from the nozzles with the operation of the piezoelectric elements is deteriorated. 
     There is known an inkjet recording apparatus that includes: a temperature detecting portion configured to detect the temperature inside the apparatus; and a heater configured to heat the ink that is to be supplied to the recording head. In this case, when the temperature detected by the temperature detecting portion is lower than a reference temperature, the inkjet recording apparatus causes the heater to operate. 
     SUMMARY 
     An inkjet recording apparatus according to an aspect of the present disclosure includes a plurality of nozzles, a plurality of piezoelectric elements, a temperature sensor, and a control portion. The plurality of nozzles eject ink onto a sheet to form an image on the sheet. The plurality of piezoelectric elements pressurize the ink that is to be supplied to the plurality of nozzles respectively. The temperature sensor detects temperature of the ink to be supplied to the plurality of nozzles. The control portion controls the plurality of piezoelectric elements. When, upon receiving a print request, a detection temperature detected by the temperature sensor is lower than a reference temperature, the control portion executes a preliminary vibration control to cause an ink meniscus oscillation to occur in each of the plurality of nozzles by vibrating the plurality of piezoelectric elements, and after the detection temperature increases up to the reference temperature, executes an ink ejection control to cause the ink to be ejected from the plurality of nozzles by vibrating the plurality of piezoelectric elements in correspondence with an output target image of the print request. When, upon receiving the print request, the detection temperature is higher than the reference temperature, the control portion executes the ink ejection control without executing the preliminary vibration control. 
     A method for controlling an inkjet recording apparatus according to another aspect of the present disclosure controls the inkjet recording apparatus that includes the plurality of nozzles, the plurality of piezoelectric elements, and the temperature sensor. The method includes a processor, when, upon receiving a print request, a detection temperature detected by the temperature sensor is lower than a reference temperature, executing a preliminary vibration control to cause an ink meniscus oscillation to occur in each of the plurality of nozzles by vibrating the plurality of piezoelectric elements. The method further includes the processor, after the detection temperature increases up to the reference temperature, executing an ink ejection control to cause the ink to be ejected from the plurality of nozzles by vibrating the plurality of piezoelectric elements in correspondence with an output target image of the print request. The method further includes the processor, when, upon receiving the print request, the detection temperature is higher than the reference temperature, executing the ink ejection control without executing the preliminary vibration control. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description with reference where appropriate to the accompanying drawings. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a configuration diagram of an inkjet recording apparatus according to a first embodiment. 
         FIG.  2    is a cross section diagram of a nozzle unit in the inkjet recording apparatus according to the first embodiment. 
         FIG.  3    is a block diagram showing a configuration of a control device in the inkjet recording apparatus according to the first embodiment. 
         FIG.  4    is a flowchart showing an example of a procedure of a recording head control in the inkjet recording apparatus according to the first embodiment. 
         FIG.  5    is a flowchart showing an example of the procedure of the recording head control in an inkjet recording apparatus according to a second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following describes embodiments of the present disclosure with reference to the accompanying drawings. It should be noted that the following embodiments are examples of specific embodiments of the present disclosure and should not limit the technical scope of the present disclosure. 
     First Embodiment: Configuration of Inkjet Recording Apparatus  10   
     An inkjet recording apparatus  10  according to a first embodiment is a printer that is configured to execute a print process by an inkjet method. 
     In the print process, an image is formed on a sheet  9 . The sheet  9  is a sheet-like image formation medium such as a sheet of paper or a resin film. 
     It is noted that the inkjet recording apparatus  10  may be a facsimile apparatus, a copier, or a multifunction peripheral that is configured to execute the print process by the inkjet method. 
     As shown in  FIG.  1   , the inkjet recording apparatus  10  includes a sheet storage portion  1 , a sheet supply device  2 , a print portion  3 , a plurality of ink containers  4 , a sheet conveyance device  5 , a sheet discharge device  6 , and a control device  8 . Furthermore, the inkjet recording apparatus  10  includes an operation device  801  and a display device  802 . 
     The sheet supply device  2 , the print portion  3 , the plurality of ink containers  4 , the sheet conveyance device  5 , the sheet discharge device  6 , and the control device  8  are disposed in a main housing  11 . 
     The sheet storage portion  1  is configured to store a plurality of sheets  9 . The sheet supply device  2  feeds the sheets  9  stored in the sheet storage portion  1  one by one to the sheet conveyance device  5 . 
     The sheet conveyance device  5  conveys the sheet  9  in a predetermined conveyance direction D 0  in a state where a surface of the sheet  9  faces the print portion  3 . A direction orthogonal to the conveyance direction D 0  is a main scanning direction D 1 , and a direction opposite to the conveyance direction D 0  is a sub scanning direction D 2  (see  FIG.  1   ). 
     The print portion  3  forms an image on the sheet  9  by ejecting inks of a plurality of colors towards the sheet  9  conveyed by the sheet conveyance device  5 . 
     The sheet conveyance device  5  is disposed below the print portion  3 . The sheet conveyance device  5  includes a conveyance belt  51  and a plurality of stretching rollers  52 . 
     The plurality of stretching rollers  52  rotatably support the conveyance belt  51 . A motor (not shown) rotates one of the plurality of stretching rollers  52 , thereby rotating the conveyance belt  51 . As the conveyance belt  51  rotates, it conveys the sheet  9  on its surface in the conveyance direction DO. 
     The sheet discharge device  6  is disposed downstream of the sheet conveyance device  5  in the conveyance direction DO. The sheet discharge device  6  discharges the sheet  9  with an image formed thereon to a discharge tray  12  from inside the main housing  11 . 
     The plurality of ink containers  4  store inks of predetermined colors. In the present embodiment, the colors of the inks are black, cyan, magenta, and yellow. Thus, the inkjet recording apparatus  10  includes four ink containers  4 . 
     [Pint Portion  3 ] 
     The print portion  3  forms an image on the sheet  9  by ejecting the inks onto the sheet  9  conveyed by the sheet conveyance device  5 . The print portion  3  includes a plurality of recording heads  30  corresponding to the plurality of colors of ink. 
     In the present embodiment, the print portion  3  includes four recording heads  30  that respectively corresponding to inks of black, cyan, magenta, and yellow. 
     Each of the recording heads  30  includes a nozzle unit  31 . The nozzle units  31  are disposed to face an upper surface of the conveyance belt  51 . The inks are supplied to the plurality of recording heads  30  from the plurality of ink containers  4 . 
     Each of the nozzle units  31  includes a plurality of nozzles  32  (see  FIG.  2   ). Each of the plurality of nozzles  32  ejects ink onto the sheet  9  to form an image on the sheet  9 . 
     Each of the nozzle units  31  includes a plurality of piezoelectric elements  33 , a plurality of pressure chambers  35 , and a plurality of diaphragms  34 . The plurality of piezoelectric elements  33 , the plurality of pressure chambers  35 , and the plurality of diaphragms  34  respectively correspond to the plurality of nozzles  32 . 
     The plurality of pressure chambers  35  are respectively communicated with the plurality of nozzles  32 . The plurality of pressure chambers  35  form passages via which the inks are supplied to the plurality of nozzles  32 , respectively. The inks in the plurality of pressure chambers  35  are an example of inks supplied to the plurality of nozzles  32 . 
     The plurality of diaphragms  34  respectively form a part of partition walls of the plurality of pressure chambers  35 . Upon receiving a drive signal, each of the plurality of piezoelectric elements  33  pressurizes the ink inside the pressure chamber  35  via the diaphragm  34 . 
     The drive signal is a pulse-width-modulated continuous pulse signal. The drive signal is supplied from the control device  8  to each of the plurality of piezoelectric elements  33 . 
     That is, upon receiving the drive signal from the control device  8 , each piezoelectric element  33  pressurizes the ink that is to be supplied to a corresponding one of the plurality of nozzles  32 . 
     Upon receiving the drive signal, each piezoelectric element  33  vibrates with as much energy that causes the ink to be ejected from a corresponding nozzle  32 . That is, upon receiving the drive signal, each piezoelectric element  33  pressurizes the ink inside the pressure chamber  35  to a degree where the ink is ejected from the corresponding nozzle  32 . 
     The ink pressurized by the piezoelectric element  33  with the drive signal supplied thereto, flows from the pressure chamber  35  to a corresponding nozzle  32 , and is ejected from the nozzle  32 . 
     The operation device  801  is configured to receive human operations. For example, the operation device  801  includes operation buttons and a touch panel. 
     The display device  802  is configured to display information. For example, the display device  802  includes a panel display device such as a liquid crystal display panel. 
     [Control Device  8 ] 
     The control device  8  executes various types of data processing and controls of the devices included in the inkjet recording apparatus  10 . The control device  8  is an example of a control portion that controls the plurality of piezoelectric elements  33  and other devices. 
     As shown in  FIG.  3   , the control device  8  includes a CPU (Central Processing Unit)  81  and peripheral devices such as a RAM (Random Access Memory)  82 , a secondary storage device  83 , and a signal interface  84 . Furthermore, the control device  8  includes a communication device  85  and a drive circuit  86 . 
     The CPU  81  is a processor that executes various types of data processing and controls by executing computer programs. The CPU  81  is an example of a processor that controls the plurality of piezoelectric elements  33  and other devices. 
     The RAM  82  is a computer-readable volatile storage device. The RAM  82  primarily stores the computer programs that are executed by the CPU  81 , and data that is output and consulted by the CPU  81  during execution of the various types of processing. 
     The secondary storage device  83  is a computer-readable nonvolatile storage device. The secondary storage device  83  is configured to store and update the computer programs and various types of data. For example, either or both of a flash memory and a hard disk drive are adopted as the secondary storage device  83 . 
     The signal interface  84  is configured to convert signals output from various types of sensors to digital data, and transmit the digital data to the CPU  81 . Furthermore, the signal interface  84  is configured to convert a control command output from the CPU  81  to a control signal and transmit the control signal to a control-target device. 
     The communication device  85  is configured to communicate with a host apparatus (not shown) and other apparatuses. The host apparatus is an information processing apparatus such as a personal computer or a smartphone operated by a user. 
     For example, the CPU  81  receives a print job from the host apparatus via the communication device  85 . The print portion  3  forms on the sheet  9  an image identified by the print job. 
     The drive circuit  86  receives the control signal from the CPU  81  via the signal interface  84 . The drive circuit  86  outputs the drive signal to each of the plurality of piezoelectric elements  33  in accordance with the received control signal. 
     The drive circuit  86  performs a PWM (Pulse Width Modulation) control of the drive signal in accordance with the content of the control signal. The drive circuit  86  controls, by the PWM control, the amount of ink that is ejected from each of the plurality of nozzles  32 . 
     The CPU  81  includes a plurality of processing modules that are realized when the computer programs are executed. The plurality of processing modules include a main control portion  8   a , a conveyance control portion  8   b , and a print control portion  8   c.    
     The main control portion  8   a  performs a control to start any one of the various types of processing in accordance with an operation performed on the operation device  801 , and performs a control of the display device  802 . 
     The conveyance control portion  8   b  controls the sheet supply device  2 , the sheet conveyance device  5 , and the sheet discharge device  6 . That is, the conveyance control portion  8   b  controls: the supply of the sheet  9  from the sheet storage portion  1 ; the conveyance of the sheet  9  by the sheet conveyance device  5 ; and the discharge of the sheet  9  by the sheet discharge device  6 . 
     The print control portion  8   c  causes the print portion  3  to execute the print process in synchronization with the conveyance of the sheet  9  by the sheet conveyance device  5 . The print control portion  8   c  causes the print portion  3  to execute the print process by controlling the plurality of piezoelectric elements  33 . 
     The print control portion  8   c  outputs the control signal to the drive circuit  86  via the signal interface  84 . This allows the print control portion  8   c  to control the plurality of piezoelectric elements  33  via the drive circuit  86 . 
     When the temperature of the ink decreases, the viscosity of the ink becomes high. When the viscosity of the ink to be supplied to each of the nozzles  32  is high, ejection performance of the ink ejected from the nozzles  32  with the operation of the piezoelectric elements  33  is deteriorated. 
     Thus the inkjet recording apparatus  10  includes a heater  71  configured to heat the ink (see  FIG.  2   ). Furthermore, the control device  8  includes a heater power supply circuit  87  that supplies power to the heater  71  (see  FIG.  3   ). 
     Furthermore, the plurality of processing modules of the CPU  81  include a heater control portion  8   d  (see  FIG.  3   ). The heater control portion  8   d  controls the heater  71  via the heater power supply circuit  87 . 
     Meanwhile, when the heater control portion  8   d  causes the heater  71  to operate when the environmental temperature is low, a first print time is reduced. The first print time is a time taken for the inkjet recording apparatus  10  to start the print process after receiving a print request. 
     The CPU  81  receiving the print job via the communication device  85  is an example of receiving the print job. In addition, the CPU  81  detecting a print start operation performed on the operation device  801  is another example of receiving the print job. 
     The print start operation includes an operation to specify print-target data, and a predetermined start operation. 
     However, if the heater control portion  8   d  causes the heater  71  to operate before receiving the print request, the heater  71  may consume power uselessly. 
     In addition, the heater  71  heats the ink via a passage of the ink or via a member that forms a case of the ink. In the example shown in  FIG.  2   , the heater  71  heats the ink via the nozzle unit  31 . As a result, the thermal efficiency of heating the ink by the heater  71  is not high. 
     It is noted that the nozzle unit  31  is a member forming the plurality of pressure chambers  35  and the plurality of nozzles  32 . The nozzle unit  31  is an example of a member forming a passage of the ink. The heater  71  heats the inks that are to be supplied to the plurality of nozzles  32 . 
     In the inkjet recording apparatus  10 , the print control portion  8   c  and the heater control portion  8   d  execute a recording head control (see  FIG.  4   ) that is described below. With this configuration, the inkjet recording apparatus  10  reduces the viscosity of the ink while restricting power consumption. 
     The inkjet recording apparatus  10  includes a temperature sensor  72  for each of the nozzle units  31  (see  FIG.  2   ). The temperature sensor  72  detects the temperature of the inks to be supplied to the plurality of nozzles  32 . For example, the temperature sensor  72  is a thermistor. 
     In the present embodiment, the temperature sensor  72  detects the temperature of the nozzle unit  31 . With this configuration, the temperature sensor  72  detects, via the nozzle unit  31 , the temperature of the inks staying in the nozzle unit  31 . 
     [Recording Head Control] 
     The following describes an example of a procedure of the recording head control with reference to the flowchart shown in  FIG.  4   . The print control portion  8   c  starts the recording head control when the print request is received. 
     For example, the print control portion  8   c  starts the recording head control when the print request is received via the communication device  85 . In addition, the print control portion  8   c  also starts the recording head control when the print start operation performed on the operation device  801  is detected. 
     In the following description, S 101 , S 102 , . . . are identification signs representing a plurality of steps of the recording head control. The print control portion  8   c  starts the recording head control with the process of step S 101 . 
     &lt;Step S 101 &gt; 
     In step S 101 , the print control portion  8   c  determines whether or not a detection temperature T 1  detected by the temperature sensor  72  is lower than a predetermined reference temperature TS 1 . 
     Upon determining that the detection temperature T 1  is lower than the reference temperature TS 1 , the print control portion  8   c  moves the process to step S 102 . On the other hand, upon determining that the detection temperature T 1  is equal to or higher than the reference temperature TS 1 , the print control portion  8   c  moves the process to step S 105 . 
     &lt;Step S 102 &gt; 
     In step S 102 , the print control portion  8   c  starts a preliminary vibration control. In the preliminary vibration control, the print control portion  8   c  supplies a predetermined preliminary vibration signal to the plurality of piezoelectric elements  33  via the drive circuit  86 . 
     The print control portion  8   c  vibrates the plurality of piezoelectric elements  33  by supplying the preliminary vibration signal to the plurality of piezoelectric elements  33 . Upon receiving the preliminary vibration signal, the plurality of piezoelectric elements  33  vibrate, and thereby an ink meniscus oscillation occurs in each of the plurality of nozzles  32 . 
     The preliminary vibration signal vibrates the plurality of piezoelectric elements  33  with as much energy that causes the ink meniscus oscillation. Specifically, the preliminary vibration signal is a continuous pulse signal having a lower frequency and a lower duty ratio than the drive signal. 
     During the execution of the preliminary vibration control, the ink meniscus oscillation occurs in the pressure chambers  35  and the nozzles  32 , without the ink being ejected from the nozzles  32 . This increases the temperature of the ink in the pressure chambers  35  and the nozzles  32 . 
     In addition, during the execution of the preliminary vibration control, the vibration energy of the piezoelectric elements  33  is efficiently transmitted to the inks via the diaphragms  34 . This increases the temperature of the inks in the pressure chambers  35  and the nozzles  32  efficiently. 
     After starting the preliminary vibration control, the print control portion  8   c  moves the process to step S 103 . 
     &lt;Step S 103 &gt; 
     In step S 103 , the print control portion  8   c  determines whether or not the detection temperature T 1  has increased up to the reference temperature TS 1 . 
     The print control portion  8   c  continues the preliminary vibration control while executing the process of step S 103  until the detection temperature T 1  increases up to the reference temperature TS 1 . Upon determining that the detection temperature T 1  has increased up to the reference temperature TS 1 , the print control portion  8   c  moves the process to step S 104 . 
     &lt;Step S 104 &gt; 
     In step S 104 , the heater control portion  8   d  starts a heater control to control the operation of the heater  71  via the heater power supply circuit  87 . 
     In the present embodiment, the heater control is a feedback control of the heater  71  based on the detection temperature T 1 . 
     For example, when the detection temperature T 1  is lower than a first target temperature, the heater control portion  8   d  causes the heater power supply circuit  87  to supply power to the heater  71  until the detection temperature T 1  increases up to a second target temperature. The second target temperature is higher than the first target temperature. 
     Furthermore, when the detection temperature T 1  is higher than the second target temperature, the heater control portion  8   d  causes the heater power supply circuit  87  to stop the power supply to the heater  71  until the detection temperature T 1  decreases up to the first target temperature. 
     It is noted that the heater control may be a PID control based on the detection temperature T 1  and the first target temperature. 
     The heater control portion  8   d  continues the heater control until the print process corresponding to the print request is completed. After starting the heater control, the heater control portion  8   d  moves the process to step S 105 . 
     &lt;Step S 105 &gt; 
     When the process of step S 105  is executed, the conveyance control portion  8   b  causes the sheet supply device  2  and the sheet conveyance device  5  to perform the supply and the conveyance of the sheet  9 . 
     In step S 105 , the print control portion  8   c  executes an ink ejection control in synchronization with the conveyance of the sheet  9 . 
     When the process of step S 105  is executed through the process of step S 102 , the print control portion  8   c  executes the ink ejection control after the preliminary vibration control is completed. 
     In the ink ejection control, the print control portion  8   c  outputs, to the plurality of piezoelectric elements  33  via the drive circuit  86 , a drive signal that corresponds to an output target image of the print request. 
     That is, in the ink ejection control, the print control portion  8   c  vibrates the plurality of piezoelectric elements  33  with as much level of energy that causes the inks to be ejected from the plurality of nozzles  32 . In other words, the print control portion  8   c  causes the inks to be ejected from the plurality of nozzles  32  by vibrating the plurality of piezoelectric elements  33  in correspondence with the output target image. 
     With the process of step S 105 , the print process corresponding to the print request is executed. The print control portion  8   c  executes the ink ejection control until the print process corresponding to the print request is completed, and then ends the recording head control. 
     As described above, the print control portion  8   c  executes the preliminary vibration control when, upon receiving the print request, the detection temperature T 1  detected by the temperature sensor  72  is lower than the reference temperature TS 1  (see steps S 101  and S 102 ). 
     Furthermore, after the detection temperature T 1  is increased up to the reference temperature TS 1  by the preliminary vibration control, the print control portion  8   c  executes the ink ejection control in correspondence with the output target image of the print request (see steps S 103  and S 105 ). 
     On the other hand, the print control portion  8   c  executes the ink ejection control without executing the preliminary vibration control when, upon receiving the print request, the detection temperature T 1  is higher than the reference temperature TS 1  (see steps S 101  and S 105 ). 
     With the execution of the recording head control, the heater  71  does not operate before the print request occurs. As a result, it does not happen that the heater  71  consumes power uselessly. In addition, the temperature of the inks in the pressure chambers  35  and the nozzles  32  is efficiently increased by the occurrence of the ink meniscus oscillation. As a result, it is possible to reduce the viscosity of the ink while restricting the power consumption. 
     In addition, the heater control portion  8   d  executes the feedback control of the heater  71  based on the detection temperature T 1  when, upon receiving the print request, the detection temperature T 1  is lower than the reference temperature TS 1  (see steps S 101  and S 104 ). 
     In the present embodiment, when, upon receiving the print request, the detection temperature T 1  is lower than the reference temperature TS 1 , the heater control portion  8   d  executes the feedback control of the heater  71  after the detection temperature T 1  is increased up to the reference temperature TS 1  by the preliminary vibration control (see steps S 101  to S 104 ). 
     On the other hand, the heater control portion  8   d  does not execute the feedback control of the heater  71  when, upon receiving the print request, the detection temperature T 1  is higher than the reference temperature TS 1  (see step S 101 ). 
     The inks whose temperature is increased by the preliminary vibration control are only the inks that stay in the pressure chambers  35  and the nozzles  32  before the ink ejection control is executed. With the execution of the feedback control of the heater  71 , the viscosity of the inks that flow into the nozzles  32  is maintained appropriately even when the print process is executed to deal with a large number of sheets  9 . 
     Second Embodiment 
     Next, an inkjet recording apparatus according to a second embodiment is described with reference to  FIG.  5   . 
     The inkjet recording apparatus according to the present embodiment has the same configuration as the inkjet recording apparatus  10  according to the first embodiment. 
     In the present embodiment, the print control portion  8   c  and the heater control portion  8   d  execute the recording head control, for example, by the procedure shown in  FIG.  5   . 
     The following describes an example of the procedure of the recording head control of the present embodiment with reference to the flowchart shown in  FIG.  5   . In the present embodiment, too, the print control portion  8   c  starts the recording head control when the print request is received. 
     In the following description, S 201 , S 202 , . . . are identification signs representing a plurality of steps of the recording head control. In the present embodiment, the print control portion  8   c  starts the recording head control with the process of step S 201 . 
     &lt;Step S 201 &gt; 
     In step S 201 , the print control portion  8   c  determines whether or not the detection temperature T 1  detected by the temperature sensor  72  is lower than the predetermined reference temperature TS 1 . The process of step S 201  is the same as the process of step S 101  shown in  FIG.  4   . 
     Upon determining that the detection temperature T 1  is lower than the reference temperature TS 1 , the print control portion  8   c  moves the process to step S 202 . On the other hand, upon determining that the detection temperature T 1  is equal to or higher than the reference temperature TS 1 , the print control portion  8   c  moves the process to step S 206 . 
     &lt;Step S 202 &gt; 
     In step S 202 , the print control portion  8   c  starts the preliminary vibration control. The process of step S 202  is the same as the process of step S 102  shown in  FIG.  4   . 
     After starting the preliminary vibration control, the print control portion  8   c  moves the process to step S 203 . 
     &lt;Step S 203 &gt; 
     In step S 203 , the print control portion  8   c  determines whether or not the detection temperature T 1  has increased up to the reference temperature TS 1 . The process of step S 203  is the same as the process of step S 103  shown in  FIG.  4   . 
     Upon determining that the detection temperature T 1  has increased up to the reference temperature TS 1 , the print control portion  8   c  moves the process to step S 204 . 
     &lt;Step S 204 &gt; 
     In step S 204 , the print control portion  8   c  determines whether or not a number of prints N 1  specified in the print request is equal to or larger than a predetermined reference number of sheets NS 1 . 
     The reference number of sheets NS 1  indicates the number of sheets  9  that can be printed with the inks staying in the pressure chambers  35  and the nozzles  32 . 
     Upon determining that the number of prints N 1  is equal to or larger than the reference number of sheets NS 1 , the print control portion  8   c  moves the process to step S 205 . On the other hand, upon determining that the number of prints N 1  is smaller than the reference number of sheets NS 1 , the print control portion  8   c  moves the process to step S 206 . 
     &lt;Step S 205 &gt; 
     In step S 205 , the heater control portion  8   d  starts the heater control. As described above, the heater control is a feedback control of the heater  71  based on the detection temperature T 1 . The process of step S 205  is the same as the process of step S 104  shown in  FIG.  4   . 
     The heater control portion  8   d  continues the heater control until the print process corresponding to the print request is completed. After starting the heater control, the heater control portion  8   d  moves the process to step S 206 . 
     &lt;Step S 206 &gt; 
     When the process of step S 206  is executed, the conveyance control portion  8   b  causes the sheet supply device  2  and the sheet conveyance device  5  to perform the supply and the conveyance of the sheet  9 . 
     In step S 206 , the print control portion  8   c  executes the ink ejection control in synchronization with the conveyance of the sheet  9 . The process of step S 206  is the same as the process of step S 105  shown in  FIG.  4   . 
     When the process of step S 206  is executed through the process of step S 202 , the print control portion  8   c  executes the ink ejection control after the preliminary vibration control is completed. 
     With the process of step S 206 , the print process corresponding to the print request is executed. The print control portion  8   c  executes the ink ejection control until the print process corresponding to the print request is completed, and then ends the recording head control. 
     With the adoption of the inkjet recording apparatus according to the present embodiment, the same effect is produced as with the adoption of the inkjet recording apparatus  10 . 
     In the present embodiment, the print control portion  8   c  executes the feedback control of the heater  71  based on the detection temperature T 1  when, upon receiving the print request, a first predefined condition is satisfied (see steps S 201 , S 204 , and S 205 ). The first predefined condition is that the detection temperature T 1  is lower than the reference temperature TS 1 , and the number of prints N 1  specified in the print request is equal to or larger than the reference number of sheets NS 1 . 
     Furthermore, the heater control portion  8   d  does not execute the feedback control of the heater  71  when, upon receiving the print request, a second predefined condition or a third predefined condition is satisfied (see steps S 201  and S 204 ). 
     The second predefined condition is that the detection temperature T 1  is lower than the reference temperature TS 1 , and the number of prints N 1  is smaller than the reference number of sheets NS 1 . The third predefined condition is that the detection temperature T 1  is higher than the reference temperature TS 1 . 
     According to the present embodiment, when the number of prints N 1  is small, the power consumption of the heater  71  is further reduced. 
     It is to be understood that the embodiments herein are illustrative and not restrictive, since the scope of the disclosure is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.