Patent Publication Number: US-11376846-B2

Title: Liquid discharging apparatus

Description:
The present application is based on, and claims priority from JP Application Serial Number 2019-214343, filed Nov. 27, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     Embodiments of the present disclosure relate to a liquid discharging apparatus. 
     2. Related Art 
     In an ink-jet printer as an example of a liquid discharging apparatus, control signals generated in control circuitry, etc. provided in the body of the ink-jet printer are sent to a print head (discharging head) that has nozzles for discharging ink, and the timing of discharging the ink is controlled based on the control signals so as to print an image and/or a text, etc. on a medium. 
     For example, the following liquid discharging apparatus is disclosed in JP-A-2018-158487. A control signal generation unit that is control circuitry generates control signals corresponding to image data supplied from an external host computer. The liquid discharging apparatus forms an image that includes characters, figures, etc. corresponding to the supplied image data on a medium by controlling, based on the control signals, the transportation of the medium such as paper and the driving of various components included in the liquid discharging apparatus, for example, a head that discharges ink. 
     However, in the liquid discharging apparatus disclosed in JP-A-2018-158487, the various components of the liquid discharging apparatus, which are driven by the control signals outputted from the control circuitry, are scattered here and there inside the liquid discharging apparatus. Because of the scattered layout, wiring via which the control signals propagate is inevitably long. Consequently, there is a risk of a decrease in the quality of an image formed on a medium because the propagation precision of the control signals will decrease due to the influence of wiring impedance, etc. 
     SUMMARY 
     A liquid discharging apparatus according to a certain aspect includes: a discharging head that discharges liquid onto a medium by being driven; first and second components that are operable for discharging the liquid onto the medium; first and second control circuits that control driving of the discharging head; a first control circuit board on which the first control circuit is provided; a second control circuit board on which the second control circuit is provided; wherein the first component is electrically coupled to the first control circuit, the second component is electrically coupled to the second control circuit, a minimum distance between the first control circuit board and the first component is shorter than a minimum distance between the first control circuit board and the second component, and a minimum distance between the second control circuit board and the second component is shorter than a minimum distance between the second control circuit board and the first component. 
     The liquid discharging apparatus according to the certain aspect may further include: a housing that houses the first component, the second component, the first control circuit board, and the second control circuit board; and a transportation section that transports the medium onto which the liquid is discharged from the discharging head; wherein the housing may have a first face and a second face, the first face and the second face may be located with at least a partial overlap in a width direction of the medium intersecting with a transportation direction in which the medium is transported by the transportation section, a minimum distance between the first control circuit board and the first face may be shorter than a minimum distance between the first control circuit board and the second face, and a minimum distance between the second control circuit board and the second face may be shorter than a minimum distance between the second control circuit board and the first face. 
     In the liquid discharging apparatus according to the certain aspect, the minimum distance between the first control circuit board and the first face may be shorter than a minimum distance between the transportation section and the first face, and the minimum distance between the second control circuit board and the second face may be shorter than a minimum distance between the transportation section and the second face. 
     The liquid discharging apparatus according to the certain aspect may further include: a drive signal output circuit that outputs a drive signal for driving the discharging head; and a drive circuit board on which the drive signal output circuit is provided; wherein the second component may include the drive circuit board. 
     In the liquid discharging apparatus according to the certain aspect, the second component may include an electric motor that converts electric energy into kinetic energy. 
     In the liquid discharging apparatus according to the certain aspect, the driving of the discharging head may be controlled based on an image signal inputted from an input terminal, and the first component may include the input terminal. 
     In the liquid discharging apparatus according to the certain aspect, there may be a first mode in which it is possible to discharge the liquid from the discharging head and a second mode in which power consumption is smaller than in the first mode and the liquid is not discharged from the discharging head, and operation of the second control circuit may be stopped in the second mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall perspective view illustrating the appearance and external structure of a liquid discharging apparatus. 
         FIG. 2  is a sectional view schematically illustrating a part of the internal structure of the liquid discharging apparatus. 
         FIG. 3  is an overall view schematically illustrating a part of the internal structure of the liquid discharging apparatus. 
         FIGS. 4A, 4B  is a set of diagrams that illustrates an electric configuration of the liquid discharging apparatus. 
         FIG. 5  is a diagram that illustrates an example of the waveforms of drive signals COMA and COMB. 
         FIG. 6  is a diagram that illustrates an example of the waveforms of a drive signal VOUT. 
         FIG. 7  is a diagram that illustrates a configuration of a drive signal selection circuit. 
         FIG. 8  is a table that shows the content of decoding by a decoder. 
         FIG. 9  is a diagram that illustrates a configuration of a selection circuit. 
         FIG. 10  is a diagram for explaining the operation of the drive signal selection circuit. 
         FIG. 11  is a diagram that illustrates a structure of a discharger. 
         FIG. 12  is a diagram for explaining the layout of circuit boards when the liquid discharging apparatus is viewed from the +Z side. 
         FIG. 13  is a diagram for explaining the layout of circuit boards when the liquid discharging apparatus is viewed from the +Y side. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     With reference to the accompanying drawings, a certain non-limiting advantageous embodiment of the present disclosure will now be explained. The drawings will be referred to in order to facilitate an explanation. The specific embodiment described below shall never be construed to unduly limit the scope of the present disclosure recited in the appended claims. Not all of components described below necessarily constitute indispensable parts of the present disclosure. 
     In the present embodiment, an ink-jet printer capable of performing printing on a large-sized medium having a shorter-side width of A3 (297 mm) or larger, a so-called large format printer, is taken as an example of a liquid discharging apparatus for the purpose of explanation. In addition, roll paper, which is formed by wrapping paper around a core into a shape of a roll, is taken as an example of a medium onto which the liquid discharging apparatus according to the present embodiment discharges ink. The type of a medium onto which the liquid discharging apparatus discharges ink is not limited to roll paper. For example, sheets of paper cut into a predetermined size may be used. A cloth or other materials may be used. 
     1. Structure of Liquid Discharging Apparatus 
     With reference to  FIGS. 1, 2, and 3 , the appearance and structure of a liquid discharging apparatus  1  according to the present embodiment will now be explained.  FIG. 1  is an overall perspective view illustrating the appearance and external structure of the liquid discharging apparatus  1 .  FIG. 2  is a sectional view schematically illustrating a part of the internal structure of the liquid discharging apparatus  1 .  FIG. 3  is an overall view schematically illustrating a part of the internal structure of the liquid discharging apparatus  1 . 
     As illustrated in  FIG. 1 , the liquid discharging apparatus  1  includes a body  2  and a plurality of foots  3 . The body  2  includes a housing  10  that has a shape of substantially rectangular parallelepiped. The housing  10  includes a front wall  11 , a rear wall  12 , a first sidewall  13 , a second sidewall  14 , and a top wall  15 . The housing  10  is connected to a base frame  20  supported by the foots  3 . 
     In the liquid discharging apparatus  1 , a direction in which the base frame  20  and the top wall  15  face each other is defined as a height direction of the liquid discharging apparatus  1 , a direction in which the first sidewall  13  and the second sidewall  14  face each other along a plane orthogonal to the height direction is defined as a width direction, and a direction in which the front wall  11  and the rear wall  12  face each other along a plane orthogonal to the height direction is defined as a depth direction. In the liquid discharging apparatus  1 , the height direction is parallel to the direction of gravity when the width direction and the depth direction are on a horizontal plane. In the explanation below, the width direction is depicted as the X direction, the depth direction is depicted as the Y direction, and the height direction is depicted as the Z direction. The directional side indicated by the head of an arrow in the illustrated X direction may be referred to as “+X side”, and the directional side indicated by the tail of the arrow in the illustrated X direction may be referred to as “−X side”. The directional side indicated by the head of an arrow in the illustrated Y direction may be referred to as “+Y side”, and the directional side indicated by the tail of the arrow in the illustrated Y direction may be referred to as “−Y side”. Similarly, the directional side indicated by the head of an arrow in the illustrated Z direction may be referred to as “+Z side”, and the directional side indicated by the tail of the arrow in the illustrated Z direction may be referred to as “−Z side”. 
     As illustrated in  FIGS. 1 and 2 , the body  2  has a container portion  21 . The container portion  21  houses a cylindrical roll  24  formed by wrapping, around a core member  23 , a medium  22  on which an image is to be formed by the body  2 . Specifically, the container portion  21  is capable of accommodating a pair of rolls  24  arranged next to each other in the Z direction of the liquid discharging apparatus  1 . The container portion  21  has an opening  25  through the front wall  11  of the housing  10  at a position closer to the base frame  20 , and is formed from the front wall  11  toward the rear wall  12 . 
     As illustrated in  FIGS. 1, 2, and 3 , each of the pair of rolls  24  housed in the container portion  21  is rotatably mounted in the body  2 , and a first holder portion  31 , which holds one end of the roll  24 , and a second holder portion  32 , which holds the other end of the roll  24 , are attached in such a way as to be detachable from the body  2  through the opening  25 . When the first holder portion  31  and the second holder portion  32  are attached to the body  2 , the first holder portion  31  and the second holder portion  32  are arranged linearly along the X direction inside the container portion  21 . Each roll  24  is set in place into the container portion  21 , with the first holder portion  31  fixed to one end of the roll  24 , and with the second holder portion  32  fixed to the other end of the roll  24 . By this means, the pair of rolls  24  is positioned stably, with the first holder portion  31  and the second holder portion  32  arranged linearly along the X direction. 
     The first holder portion  31  is attached to a first side frame  61  illustrated in  FIG. 3  rotatably around a rotation axis extending in the X direction, that is, the width direction. The second holder portion  32  is attached to a second side frame  62  illustrated in  FIG. 3  rotatably around a rotation axis extending in the X direction, that is, the width direction. In other words, the first holder portion  31  and the second holder portion  32  hold the roll  24  rotatably around the center axis of the core member  23 . 
     The roll  24  held by the first holder portion  31  and the second holder portion  32  is driven to rotate by a driver portion  33  illustrated in  FIG. 3 . The driver portion  33  is located closer to the first sidewall  13  than the first holder portion  31 . The driver portion  33  includes a drive motor that is not illustrated. By rotation of the drive motor in the forward direction, the driver portion  33  causes the first holder portion  31  and the second holder portion  32  to rotate in such a way as to unreel the medium  22  from the roll  24  inside the housing  10  toward the rear wall  12 . 
     As illustrated in  FIGS. 1, 2, and 3 , a recording portion  35  is provided inside the housing  10 . The recording portion  35  includes a platen  36 , a guide shaft  37 , a carriage  38 , and a head  39 . 
     The platen  36  is located closer to the top wall  15  than the container portion  21 . The platen  36  is a plate-shaped member extending in the X direction inside the housing  10 . The medium  22  unreeled from the roll  24  is transported to the platen  36  inside the housing  10  and is thereafter transported over the platen  36  in a direction from the rear wall  12  toward the front wall  11 . 
     The guide shaft  37  is located closer to the top wall  15  than the platen  36 . The guide shaft  37  is a rod-shaped member extending in the X direction. The guide shaft  37  supports the carriage  38 . In other words, the carriage  38  is supported in such a way as to be movable along the guide shaft  37 . The carriage  38  is driven by a carriage motor  40  that includes a drive motor that is not illustrated. The carriage  38 , when driven, reciprocates along the guide shaft  37 . The head  39  is mounted on the face of the carriage  38  facing toward the platen  36 . The head  39  discharges ink toward the medium  22  supported on the platen  36  at predetermined discharge timing. As a result, an image is formed on the medium  22 . 
     As illustrated in  FIG. 2 , the body  2  includes a transportation portion  45 . Cooperating with the first holder portion  31  and the second holder portion  32  and the driver portion  33  inside the housing  10 , the transportation portion  45  transports the medium  22  unreeled from the roll  24 . The transportation portion  45  includes a transportation path forming portion  46 , an intermediate roller  47 , and a transportation roller  48 . 
     The transportation path forming portion  46  is provided individually for each of the pair of rolls  24 . The transportation path forming portion  46  is located closer to the rear wall  12  than each of the pair of rolls  24  housed in the container portion  21 . The transportation path forming portion  46  forms a transportation path  49  for guiding, toward the rear wall  12  of the housing  10 , the medium  22  unreeled from the roll  24  by rotational drive operation of the first holder portion  31  and the second holder portion  32 . 
     The intermediate roller  47  and the transportation roller  48  transport the medium  22  having passed through the transportation path  49 . Each of the intermediate roller  47  and the transportation roller  48  includes a driving roller and a driven roller that constitute a pair of rollers supported rotatably around respective rotation axes extending in the X direction. Each of the intermediate roller  47  and the transportation roller  48  supports the medium  22  by nipping the medium  22  between the driving roller and the driven roller. 
     The transportation portion  45  includes a drive motor that is not illustrated. The intermediate roller  47  and the transportation roller  48  are driven to rotate due to rotation of the drive motor in the forward direction. As a result, the medium  22  is transported to the platen  36  along the transportation path  49  and is thereafter transported over the platen  36  in a direction from the rear wall  12  toward the front wall  11 . Although  FIG. 2  illustrates a state of unreeling the medium  22  from both of the pair of rolls  24 , the medium  22  may be unreeled from only one of the pair of rolls  24  when image forming operation is performed. 
     As illustrated in  FIG. 2 , a paper ejection port member  50  and a cutter portion  51  are provided inside the housing  10 . The paper ejection port member  50  is located closer to the front wall  11  than the platen  36 . The paper ejection port member  50  supports the medium  22  having passed through the platen  36  and transports the medium  22  to a paper ejection port  53  formed through the front wall  11 . The cutter portion  51  cuts the medium  22  into a predetermined size. The medium  22  cut by the cutter portion  51  is ejected to the outside through the paper ejection port  53 . 
     As illustrated in  FIG. 3 , the body  2  includes an attachment portion  57  to which cartridges containing ink to be supplied to the head  39  are attached. The attachment portion  57  is located closer to the second sidewall  14  than the first holder portion  31  and the second holder portion  32 , and is located closer to the top wall  15  than the first holder portion  31  and the second holder portion  32 . The cartridges are connected to the head  39  via tubes or the like that are not illustrated. Ink is supplied from the cartridges to the head  39  via the tubes when internal pressure in the head  39  decreases due to discharging ink. 
     The body  2  further includes a maintenance unit  58  for maintenance of the head  39 . The maintenance unit  58  is located closer to the second sidewall  14  and the top wall  15  than the first holder portion  31  and the second holder portion  32 , and is located closer to the base frame  20  than the head  39 . 
     As illustrated in  FIGS. 1 and 3 , the body  2  has an operation portion  59 . The operation portion  59  is provided on the top wall  15  of the housing  10 . The operation portion  59  may be, for example, a touch panel, and is used by a user for inputting various kinds of information. 
     As explained above, in the liquid discharging apparatus  1  according to the present embodiment, the drive operation of the drive motor of the driver portion  33  drives the first holder portion  31  and the second holder portion  32 , and the drive operation of the drive motor of the transportation portion  45  drives the intermediate roller  47  and the transportation roller  48 . This transports the medium  22  included in the cylindrical roll  24  to the platen  36  via the transportation path forming portion  46 . 
     Either one of the driver portion  33  and the transportation portion  45 , which unreel and transport the medium  22  onto which ink droplets are to be ejected from the head  39 , is, or both are, an example of a transportation section. The direction in which the medium  22  is transported by either one or both of the driver portion  33  and the transportation portion  45  along the Y direction is an example of a transportation direction. The direction along the X direction intersecting with the Y direction is an example of a width direction of the medium  22 . The housing  10  included in the liquid discharging apparatus  1  is an example of a housing. Among the front wall  11 , the rear wall  12 , the first sidewall  13 , the second sidewall  14 , and the top wall  15  of the housing  10 , the first sidewall  13  and the second sidewall  14  are located with at least a partial overlap as viewed along the X direction. The second sidewall  14  is an example of a first face of the housing  10 . The first sidewall  13  is an example of a second face of the housing  10 . 
     2. Electric Configuration of Liquid Discharging Apparatus 
     Next, with reference to  FIGS. 4A, 4B , an electric configuration of the liquid discharging apparatus  1  will now be explained.  FIGS. 4A, 4B  is a set of diagrams that illustrates an electric configuration of the liquid discharging apparatus  1 . As illustrated in  FIGS. 4A, 4B , the liquid discharging apparatus  1  includes a power supply circuit board  100 , a first control circuit board  110 , a second control circuit board  120 , a drive circuit board  130 , a discharge control circuit board  140 , and a plurality of heads  39 . 
     A power voltage output circuit  101  is mounted on the power supply circuit board  100 . A voltage VAC is inputted into the power voltage output circuit  101  from a commercial alternating-current power supply provided outside the liquid discharging apparatus  1 . The power voltage output circuit  101  converts the inputted voltage VAC into a plurality of direct-current voltages including a voltage VHV, which is a direct-current voltage of 42 V, and a voltage VDD, which is a direct-current voltage of 3.3 V. That is, the power voltage output circuit  101  is an AC/DC converter that converts an alternating-current voltage into a direct-current voltage and includes, for example, a flyback circuit, etc. The power voltage output circuit  101  may generate the voltage VDD by lowering the voltage VHV after generating the voltage VHV. The power voltage output circuit  101  may generate a plurality of direct-current voltages by raising or lowering the voltage VHV, VDD. The voltage VHV, VDD outputted from the power supply circuit board  100  is inputted into the first control circuit board  110  via a cable  151 . 
     A control circuit  111  is mounted on the first control circuit board  110 . The control circuit  111  operates by using, as its power, a direct-current voltage that is based on the voltage VHV, VDD. An image signal IMG is inputted into the control circuit  111  from a host computer provided outside the liquid discharging apparatus  1 . After performing image processing based on the image signal IMG, the control circuit  111  outputs the image-processed information as an image processing signal IP to the second control circuit board  120  via a cable  152 . Examples of the image processing performed by the control circuit  111  are: color conversion processing of converting the inputted image signal IMG into color information of red, green, and blue, abbreviated as RGB, and further converting the color information RGB into color information ICMY corresponding to the colors of ink contained in the cartridges, and halftone processing of rendering the color information ICMY into processed signals of halftones. 
     The control circuit  111  is electrically coupled to the operation portion  59  described above. An operation information signal CS including information inputted by a user by operating the operation portion  59  is inputted into the control circuit  111  via a cable  153 . The control circuit  111  generates a signal for performing control corresponding to the operation information signal CS and outputs the generated signal to the second control circuit board  120  in addition to the image processing signal IP or as a signal different from the image processing signal IP. 
     The control circuit  111  may output the image processing signal IP after conversion into a pair of differential signals to the second control circuit board  120 . The control circuit  111  may output the image processing signal IP after conversion into a light signal, etc. to the second control circuit board  120 . The image processing performed by the control circuit  111  is not limited to the color conversion processing and the halftone processing described above. The control circuit  111  may output, as the image processing signal IP, a signal(s) subjected to various kinds of image processing. 
     A control circuit  121 , a differential signal conversion circuit  122 , and a serial signal conversion circuit  123  are mounted on the second control circuit board  120 . The control circuit  121 , the differential signal conversion circuit  122 , and the serial signal conversion circuit  123  operates by using a direct-current voltage based on the voltage VHV, VDD as its power voltage. 
     The control circuit  121  outputs a control signal for controlling each component of the liquid discharging apparatus  1 , based on the image processing signal IP inputted from the first control circuit board  110 . Specifically, based on the image processing signal IP, the control circuit  121  generates an original clock signal oSCK and original print data signals oSI 1  to oSIn as control signals for controlling the discharging of ink from the head  39 , and outputs these signals to the differential signal conversion circuit  122 . 
     The differential signal conversion circuit  122  converts the inputted original clock signal oSCK into a pair of differential signals dSCK+ and dSCK−, and outputs them to the drive circuit board  130  via a cable  154 . In addition, the differential signal conversion circuit  122  converts each of the inputted original print data signals oSI 1  to oSIn into the corresponding one of pairs of differential signals dSI 1 + to dSIn+ and dSI 1 − to dSIn−, and outputs them to the drive circuit board  130  via the cable  154 . The differential signals dSCK+ and dSCK− and the differential signals dSI 1 + to dSIn+ and dSI 1 − to dSIn− after conversion by the differential signal conversion circuit  122  may be differential signals conforming to the LVDS (Low Voltage Differential Signaling) transfer scheme or may be any of various high-speed transfer schemes other than LVDS such as LVPECL (Low Voltage Positive Emitter Coupled Logic) or CML (Current Mode Logic). 
     Based on the image processing signal IP inputted from the first control circuit board  110 , the control circuit  121  generates a latch signal LAT and a change signal CH as control signals for controlling the timing of discharging ink from the head  39 , and outputs them to the drive circuit board  130  via the cable  154 . 
     Moreover, based on the image processing signal IP inputted from the first control circuit board  110 , the control circuit  121  generates base drive signals DA 1  to DAn and DB 1  to DBn, on which drive signals COMA and COMB for driving the head  39  are based, and outputs them to the serial signal conversion circuit  123 . 
     The serial signal conversion circuit  123  converts the base drive signals DA 1  to DAn and DB 1  to DBn, which are inputted as signals in a parallel format, into signals in a serial format. The serial signal conversion circuit  123  further converts the converted signals in the serial format into a pair of differential signals sDAB+ and sDAB−, and outputs them to the drive circuit board  130  via the cable  154 . In addition, the serial signal conversion circuit  123  generates a pair of differential signals sDCK+ and sDCK−, which contain clock cueing the timing of de-conversion when the pair of differential signals sDAB+ and sDAB− containing the base drive signals DA 1  to DAn and DB 1  to DBn serially is converted back into the signals in the parallel format, and outputs them to the drive circuit board  130  via the cable  154 . 
     The control circuit  121  generates a carriage control signal CMC for controlling the driving of the carriage motor  40  configured to control the movement of the carriage  38 . The control circuit  121  outputs the carriage control signal CMC to the carriage motor  40  via a cable  155 . By this means, the non-illustrated drive motor included in the carriage motor  40  operates. The control circuit  121  generates a drive control signal DC 1  for controlling the non-illustrated drive motor included in the driver portion  33  configured to control the transportation of the medium  22 , and outputs the drive control signal DC 1  to the driver portion  33  via a cable  156 . The control circuit  121  further generates a drive control signal DC 2  for controlling the non-illustrated drive motor included in the transportation portion  45  configured to control the transportation of the medium  22 , and outputs the drive control signal DC 2  to the transportation portion  45  via a cable  157 . That is, the control circuit  121  generates control signals for controlling the movement of the carriage  38  and controlling the transportation of the medium  22 , and outputs the control signals to the corresponding components. 
     A parallel signal de-conversion circuit  131  and a plurality n of drive circuits  132 - 1  to  132 - n  are mounted on the drive circuit board  130 . The pair of differential signals sDAB+ and sDAB− and the pair of differential signals sDCK+ and sDCK− outputted from the serial signal conversion circuit  123  of the second control circuit board  120  are inputted into the parallel signal de-conversion circuit  131 . The parallel signal de-conversion circuit  131  generates the base drive signals DA 1  to DAn and DB 1  to DBn in the parallel format by de-converting the pair of differential signals sDAB+ and sDAB− at the timing cued by the inputted pair of differential signals sDCK+ and sDCK−. Then, the parallel signal de-conversion circuit  131  outputs the generated base drive signals DA 1  to DAn and DB 1  to DBn to the drive circuits  132 - 1  to  132 - n  respectively. 
     The base drive signals DA 1  and DB 1  are inputted into the drive circuit  132 - 1 . The drive circuit  132 - 1  converts the inputted base drive signal DA 1  into an analog signal. After the conversion, the drive circuit  132 - 1  performs class-D amplification on the converted analog signal, thereby generating and outputting a drive signal COMA 1  to the discharge control circuit board  140  via a cable  158 . The drive circuit  132 - 1  converts the inputted base drive signal DB 1  into an analog signal. After the conversion, the drive circuit  132 - 1  performs class-D amplification on the converted analog signal, thereby generating and outputting a drive signal COMB 1  to the discharge control circuit board  140  via the cable  158 . The drive circuit  132 - 1  generates a reference voltage signal VBS 1 , which serves as a reference when the head  39  described later discharges ink, and outputs it to the discharge control circuit board  140  via the cable  158 . 
     Similarly, the base drive signals DA 1  and DB 1  are inputted into the drive circuit  132 - n . The drive circuit  132 - n  converts the inputted base drive signal DAn into an analog signal. After the conversion, the drive circuit  132 - n  performs class-D amplification on the converted analog signal, thereby generating and outputting a drive signal COMAn to the discharge control circuit board  140 . The drive circuit  132 - n  converts the inputted base drive signal DBn into an analog signal. After the conversion, the drive circuit  132 - n  performs class-D amplification on the converted analog signal, thereby generating and outputting a drive signal COMBn to the discharge control circuit board  140 . The drive circuit  132 - n  generates a reference voltage signal VBSn, which serves as a reference when the head  39  described later discharges ink, and outputs it to the discharge control circuit board  140 . 
     The differential signals dSCK+ and dSCK−, the differential signals dSI 1 + to dSIn+ and dSI 1 − to dSIn−, the latch signal LAT, the change signal CH, and the voltages VHV and VDD, which are inputted from the second control circuit board  120 , propagate through the drive circuit board  130 . After propagating through the drive circuit board  130 , the differential signals dSCK+ and dSCK−, the differential signals dSI 1 + to dSIn+ and dSI 1 − to dSIn−, the latch signal LAT, the change signal CH, and the voltages VHV and VDD are outputted to the discharge control circuit board  140 . That is, the drive circuit board  130  behaves also as a relay board that relays the signals outputted from the second control circuit board  120 . 
     Among the differential signals dSCK+ and dSCK−, the differential signals dSI 1 + to dSIn+ and dSI 1 − to dSIn−, the latch signal LAT, the change signal CH, and the voltages VHV and VDD, which are inputted into the drive circuit board  130 , the latch signal LAT, the change signal CH, and the voltages VHV and VDD may be inputted into each of the drive circuits  132 - 1  to  132 - n  described above. The drive circuits  132 - 1  to  132 - n  may be driven by the voltage VDD used as power voltage and may generate the drive signals COMA 1  to COMAn and COMB 1  to COMBn respectively by amplifying the base drive signals DA 1  to DAn and DB 1  to DBn to a voltage that is based on the voltage VHV at the timing cued by the latch signal LAT and the change signal CH. In this case, the drive circuits  132 - 1  to  132 - n  may generate the reference voltage signals VBS 1  to VBSn respectively by boosting the voltage VDD. 
     A differential signal de-conversion circuit  141 , drive signal selection circuits  200 - 1  to  200 - n , and a temperature abnormality detection circuit  142  are mounted on the discharge control circuit board  140 . 
     Each pair of differential signals dSI 1 + to dSIn+ and dSI 1 − to dSIn− and the pair of differential signals dSCK+ and dSCK− are inputted into the differential signal de-conversion circuit  141 . The differential signal de-conversion circuit  141  generates print data signals SI 1  to SIn by performing de-conversion from the differential signals dSI 1 + to dSIn+ and dSI 1 − to dSIn− into single-end signals, and outputs them to the drive signal selection circuits  200 - 1  to  200 - n  respectively. In addition, the differential signal de-conversion circuit  141  generates a clock signal SCK by performing de-conversion from the differential signals dSCK+ and dSCK− into a single-end signal, and outputs it to each of the drive signal selection circuits  200 - 1  to  200 - n.    
     The print data signal SI 1 , the clock signal SCK, the latch signal LAT, the change signal CH, and the drive signals COMA 1  and COMB 1  are inputted into the drive signal selection circuit  200 - 1 . The drive signal selection circuit  200 - 1  generates a drive signal VOUT 1  by selecting or not selecting the drive signal COMA 1 , COMB 1  at the timing cued by the latch signal LAT and the change signal CH, based on the print data signal SI 1 , and outputs it to a head  39 - 1 . Similarly, the print data signal SIn, the clock signal SCK, the latch signal LAT, the change signal CH, and the drive signals COMAn and COMBn are inputted into the drive signal selection circuit  200 - n . The drive signal selection circuit  200 - n  generates a drive signal VOUTn by selecting or not selecting the drive signal COMAn, COMBn at the timing cued by the latch signal LAT and the change signal CH, based on the print data signal Sin, and outputs it to a head  39 - n . The configuration of the drive signal selection circuits  200 - 1  to  200 - n , and the detailed operation thereof, will be described later. 
     The temperature abnormality detection circuit  142  detects the temperature of the discharge control circuit board  140  and the temperature of the drive signal selection circuits  200 - 1  to  200 - n  mounted on the discharge control circuit board  140 . Then, the temperature abnormality detection circuit  142  generates a temperature abnormality detection signal XHOT, which indicates whether the temperature of the discharge control circuit board  140  and/or the temperature of the drive signal selection circuits  200 - 1  to  200 - n  are/is abnormal or not, and outputs it to the control circuit  121  mounted on the second control circuit board  120  via the drive circuit board  130 . In addition, the temperature abnormality detection circuit  142  generates a temperature information signal TH, which indicates the detected temperature, and outputs it to the control circuit  121 . 
     The drive signal VOUT 1  outputted from the drive signal selection circuit  200 - 1  and the reference voltage signal VBS 1  are inputted into the head  39 - 1 . Driven in accordance with a level difference between the drive signal VOUT 1  and the reference voltage signal VBS 1 , the head  39 - 1  discharges ink an amount of which corresponds to the driving from its nozzles. Similarly, the drive signal VOUTn outputted from the drive signal selection circuit  200 - n  and the reference voltage signal VBSn are inputted into the head  39 - n . Driven in accordance with a level difference between the drive signal VOUTn and the reference voltage signal VBSn, the head  39 - n  discharges ink an amount of which corresponds to the driving from its nozzles. The structure of the head  39 , and the detailed operation thereof, will be described later. 
     The head  39  configured to discharge ink as an example of liquid by being driven based on a drive signal COM is an example of a discharging head. The liquid discharging apparatus  1  includes the control circuit  111 ,  121  configured to control the driving of the head  39 . The control circuit  111  is an example of a first control circuit. The control circuit  121  is an example of a second control circuit. The first control circuit board  110 , on which the control circuit  111  is provided, is an example of a first control circuit board. The second control circuit board  120 , on which the control circuit  121  is provided, is an example of a second control circuit board. The drive signal COMA, COMB is an example of a drive signal. At least any of the drive circuits  132 - 1  to  132 - n  configured to output the drive signal COMA, COMB is an example of a drive signal output circuit. The drive circuit board  130 , on which the drive circuits  132 - 1  to  132 - n  are provided, is an example of a drive circuit board. 
     Each of the cables  151  to  158  providing electric connection for the power supply circuit board  100 , the first control circuit board  110 , the second control circuit board  120 , the drive circuit board  130 , the discharge control circuit board  140 , the plurality of heads  39 , the carriage motor  40 , the driver portion  33 , the transportation portion  45 , and the operation portion  59  may include a plurality of cables. For each of the cables  151  to  158  providing the connection, depending on the form of a signal propagating therethrough, a flexible flat cable (FFC), a coaxial cable, an optical communication cable, or the like may be used. 
     3. Configuration and Operation of Drive Signal Selection Circuit 
     Next, the configuration and operation of the drive signal selection circuits  200 - 1  to  200 - n  will now be explained. The drive signal selection circuits  200 - 1  to  200 - n  have the same configuration as one another. Therefore, in the following explanation, the drive signal selection circuits  200 - 1  to  200 - n  will be collectively described as a drive signal selection circuit  200  without distinguishing them from one another. Moreover, the drive signal selection circuit  200  described below receives an input of a print data signal SI as a representative example of the print data signals SI 1  to Sin, an input of a drive signal COMA as a representative example of the drive signals COMA 1  to COMAn, and an input of a drive signal COMB as a representative example of the drive signals COMB 1  to COMBn. Moreover, the drive signal selection circuit  200  described below outputs a drive signal VOUT to a head  39  by selecting or not selecting the drive signal COMA, COMB. Furthermore, the head  39  to which the drive signal VOUT is supplied receives an input of a reference voltage signal VBS as a representative example of the reference voltage signals VBS 1  to VBSn. 
     Prior to giving a description of the configuration and operation of the drive signal selection circuit  200 , an example of the waveforms of the drive signals COMA and COMB inputted into the drive signal selection circuit  200 , and an example of the waveforms of the drive signal VOUT outputted from the drive signal selection circuit  200 , are explained first below. 
       FIG. 5  is a diagram that illustrates an example of the waveforms of the drive signals COMA and COMB. As illustrated in  FIG. 5 , the waveform of the drive signal COMA is a seamlessly-combined waveform made up of a trapezoidal waveform Adp 1  during a period T 1  from the rising of the latch signal LAT to the rising of the change signal CH and a trapezoidal waveform Adp 2  during a period T 2  from the rising of the change signal CH to the next rising of the latch signal LAT. When the trapezoidal waveform Adp 1  is supplied to the head  39 , a small amount of ink is discharged from the corresponding nozzle. When the trapezoidal waveform Adp 2  is supplied to the head  39 , a medium amount of ink, which is larger than the small amount, is discharged from the corresponding nozzle. 
     As illustrated in  FIG. 5 , the waveform of the drive signal COMB is a seamlessly-combined waveform made up of a trapezoidal waveform Bdp 1  during the period T 1  and a trapezoidal waveform Bdp 2  during the period T 2 . When the trapezoidal waveform Bdp 1  is supplied to the head  39 , no ink is discharged from the corresponding nozzle. The trapezoidal waveform Bdp 1  is a waveform for preventing the viscosity of ink from increasing, wherein the prevention is achieved by causing minute vibrations in ink near the orifice of the nozzle. When the trapezoidal waveform Bdp 2  is supplied to the head  39 , a small amount of ink is discharged from the corresponding nozzle, similarly to the case of supply of the trapezoidal waveform Adp 1 . 
     The voltage at the timing of the start and end of each of the trapezoidal waveforms Adp 1 , Adp 2 , Bdp 1 , and Bdp 2  is a voltage Vc, which is common to them. That is, each of the trapezoidal waveforms Adp 1 , Adp 2 , Bdp 1 , and Bdp 2  starts at the voltage Vc and ends at the voltage Vc. A cycle Ta, which is made up of the periods T 1  and T 2 , corresponds to a print cycle of forming a dot on the medium  22 . 
     In  FIG. 5 , the trapezoidal waveform Adp 1  and the trapezoidal waveform Bdp 2  are depicted to be the same as each other. However, the trapezoidal waveform Adp 1  and the trapezoidal waveform Bdp 2  may be different from each other. Although it is described that a small amount of ink is discharged from the nozzles both in a case where the trapezoidal waveform Adp 1  is supplied to the head  39  and a case where the trapezoidal waveform Bdp 2  is supplied to the head  39 , the scope of the present disclosure is not limited to this example. That is, the waveforms of the drive signals COMA and COMB are not limited to the example illustrated in  FIG. 5 . Depending on the movement speed of the carriage  38  on which the head  39  is mounted, the property of ink that is discharged, the material of the medium  22 , and/or other factors, signals based on combinations of various waveforms may be used. The waveforms of the drive signals COMA 1  to COMAn and COMB 1  to COMBn corresponding respectively to the heads  39 - 1  to  39 - n  may be different from one another. 
       FIG. 6  is a diagram that illustrates an example of the waveforms of the drive signal VOUT for cases where the size of the dot to be formed on the medium  22  is “large”, “medium”, “small” and a case of “non-printing”, respectively. 
     As illustrated in  FIG. 6 , the waveform of the drive signal VOUT for a case where a “large dot” is to be formed on the medium  22  is a seamlessly-combined waveform made up of the trapezoidal waveform Adp 1  during the period T 1  and the trapezoidal waveform Adp 2  during the period T 2 . When the drive signal VOUT having this waveform is supplied to the head  39 , a small amount of ink and a medium amount of ink are discharged from the corresponding nozzle within the cycle Ta. Therefore, due to the merging of the respective ink droplets on the medium  22  into one, a large dot is formed thereon. 
     The waveform of the drive signal VOUT for a case where a “medium-sized dot” is to be formed on the medium  22  is a seamlessly-combined waveform made up of the trapezoidal waveform Adp 1  during the period T 1  and the trapezoidal waveform Bdp 2  during the period T 2 . When the drive signal VOUT having this waveform is supplied to the head  39 , a small amount of ink is discharged twice from the corresponding nozzle within the cycle Ta. Therefore, due to the merging of the respective ink droplets on the medium  22  into one, a medium-sized dot is formed thereon. 
     The waveform of the drive signal VOUT for a case where a “small dot” is to be formed on the medium  22  is a seamlessly-combined waveform made up of the trapezoidal waveform Adp 1  during the period T 1  and a flat waveform that is constant at the voltage Vc during the period T 2 . When the drive signal VOUT having this waveform is supplied to the head  39 , a small amount of ink is discharged from the corresponding nozzle within the cycle Ta. Therefore, due to the landing of this ink droplet onto the medium  22 , a small dot is formed thereon. 
     The waveform of the drive signal VOUT corresponding to “non-printing”, in which no dot is to be formed on the medium  22 , is a seamlessly-combined waveform made up of the trapezoidal waveform Bdp 1  during the period T 1  and a flat waveform that is constant at the voltage Vc during the period T 2 . When the drive signal VOUT having this waveform is supplied to the head  39 , no ink is discharged within the cycle Ta, except that minute vibrations occur in ink near the orifice of the corresponding nozzle. Since no ink droplet is ejected onto the medium  22 , no dot is formed thereon. 
     The flat waveform that is constant at the voltage Vc is a waveform of retention of the immediately-preceding voltage Vc when none of the trapezoidal waveforms Adp 1 , Adp 2 , Bdp 1 , and Bdp 2  is selected for the drive signal VOUT. Therefore, it can be said that the voltage Vc is supplied as the drive signal VOUT to the head  39  when none of the trapezoidal waveforms Adp 1 , Adp 2 , Bdp 1 , and Bdp 2  is selected for the drive signal VOUT. 
     The drive signal selection circuit  200  generates the drive signal VOUT by selecting or not selecting the waveform of the drive signal COMA and the waveform of the drive signal COMB, and outputs it to the head  39 .  FIG. 7  is a diagram that illustrates a configuration of the drive signal selection circuit  200 . As illustrated in  FIG. 7 , the drive signal selection circuit  200  includes a selection control circuit  220  and a plurality of selection circuits  230 . The head  39  to which the drive signal VOUT outputted from the drive signal selection circuit  200  is supplied includes a plurality m of dischargers  600 . 
     The print data signal SI, the latch signal LAT, the change signal CH, and the clock signal SCK are inputted into the selection control circuit  220 . Groups each consisting of a shift register (S/R)  222 , a latch circuit  224 , and a decoder  226  are provided in the selection control circuit  220 , wherein the groups correspond respectively to the plurality m of dischargers  600  of the head  39 . Namely, the drive signal selection circuit  200  includes the groups each consisting of the shift register  222 , the latch circuit  224 , and the decoder  226 , wherein the number of the groups is equal to the number of the plurality, m, of dischargers  600  of the head  39 . 
     The print data signal SI is a signal synchronized with the clock signal SCK. The print data signal SI is a signal of 2 m bits in total, containing pieces of 2-bit print data [SIH, SIL] for selecting any one of “large dot”, “medium-sized dot”, “small dot”, and “non-printing” for the plurality m of dischargers  600  respectively. The pieces of 2-bit print data [SIH, SIL] contained in the inputted print data signal SI are stored into the shift registers  222  corresponding to the plurality m of dischargers  600  respectively. Specifically, in the selection control circuit  220 , m stages of shift registers  222  corresponding to the plurality m of dischargers  600  are connected in a cascade arrangement, and the print data signal SI inputted serially is sequentially transferred to the next stage in accordance with the clock signal SCK. In  FIG. 5 , for the purpose of distinguishing the shift registers  222  from one another, they are sequentially labeled with the first stage, the second stage, . . . , the m-th stage from upstream in the sequential flow of the input of the print data signal SI. 
     At the rising of the latch signal LAT, each of the plurality m of latch circuits  224  latches the 2-bit print data [SIH, SIL] stored by the corresponding one of the plurality m of shift registers  222 . 
       FIG. 8  is a table that shows the content of decoding by the decoder  226 . The decoder  226  outputs selection signals S 1  and S 2  in accordance with the latched 2-bit print data [SIH, SIL]. For example, if the 2-bit print data [SIH, SIL] is [1, 0], the decoder  226  outputs the logical level of the selection signal S 1  as the H level in the period T 1  and as the L level in the period T 2  to the selection circuit  230 , and outputs the logical level of the selection signal S 2  as the L level in the period T 1  and as the H level in the period T 2  to the selection circuit  230 . 
     Each of the selection circuits  230  is provided for the corresponding one of dischargers  600 . That is, the number of the plurality of selection circuits  230  of the drive signal selection circuit  200  is equal to the number of the plurality, m, of dischargers  600  corresponding thereto.  FIG. 9  is a diagram that illustrates a configuration of the selection circuit  230  corresponding to one of the dischargers  600 . As illustrated in  FIG. 9 , the selection circuit  230  includes inverters  232   a  and  232   b , which are NOT circuits, and transfer gates  234   a  and  234   b.    
     The selection signal S 1  is inputted into the positive control terminal without a circle mark of the transfer gate  234   a , and is, on the other side, inputted into the negative control terminal with a circle mark of the transfer gate  234   a  through logical inversion by the inverter  232   a . The drive signal COMA is supplied to the input terminal of the transfer gate  234   a . The selection signal S 2  is inputted into the positive control terminal without a circle mark of the transfer gate  234   b , and is, on the other side, inputted into the negative control terminal with a circle mark of the transfer gate  234   b  through logical inversion by the inverter  232   b . The drive signal COMB is supplied to the input terminal of the transfer gate  234   b . The output terminal of the transfer gate  234   a  and the output terminal of the transfer gate  234   b  are connected in common, and the drive signal VOUT is outputted. 
     Specifically, the transfer gate  234   a  provides an electrical continuity between the input terminal and the output terminal if the selection signal S 1  is in the H level, and provides no electrical continuity between the input terminal and the output terminal if the selection signal S 1  is in the L level. The transfer gate  234   b  provides an electrical continuity between the input terminal and the output terminal if the selection signal S 2  is in the H level, and provides no electrical continuity between the input terminal and the output terminal if the selection signal S 2  is in the L level. As explained above, based on the selection signal S 1  and the selection signal S 2 , the selection circuit  230  performs selection regarding the waveform of the drive signal COMA and the waveform of the drive signal COMB, and outputs the drive signal VOUT. 
     With reference to  FIG. 10 , the operation of the drive signal selection circuit  200  will now be explained.  FIG. 10  is a diagram for explaining the operation of the drive signal selection circuit  200 . The print data signal SI is inputted serially in sync with the clock signal SCK and is sequentially transferred through the shift registers  222  corresponding to the dischargers  600 . Upon the stopping of the input of the clock signal SCK, the pieces of 2-bit print data [SIH, SIL] corresponding respectively to the dischargers  600  are stored into the shift registers  222 . The pieces of 2-bit print data [SIH, SIL] contained in the print data signal SI are inputted in the order corresponding to the dischargers  600  for the m-th stage, . . . , the second stage, the first stage of the shift registers  222 . 
     The latch circuits  224  latch the pieces of 2-bit print data [SIH, SIL] stored in the shift registers  222  all at once when the latch signal LAT rises. In  FIG. 10 , LT 1 , LT 2 , . . . , LTm denote the pieces of 2-bit print data [SIH, SIL] latched by the latch circuits  224  corresponding to the first stage, the second stage, . . . , the m-th stage of the shift registers  222 . 
     The decoder  226  outputs the logical levels of the selection signals S 1  and S 2  in accordance with the content of the table in  FIG. 8  in the periods T 1  and T 2 , depending on the dot size specified by the latched 2-bit print data [SIH, SIL]. 
     Specifically, if the print data [SIH, SIL] is [1, 1], the decoder  226  outputs the logical level of the selection signal S 1  as the H level in the period T 1  and as the H level in the period T 2 , and outputs the logical level of the selection signal S 2  as the L level in the period T 1  and as the L level in the period T 2 . In this case, the selection circuit  230  selects the trapezoidal waveform Adp 1  in the period T 1  and the trapezoidal waveform Adp 2  in the period T 2 . As a result, the drive signal VOUT corresponding to a “large dot” shown in  FIG. 6  is generated. 
     If the print data [SIH, SIL] is [1, 0], the decoder  226  outputs the logical level of the selection signal S 1  as the H level in the period T 1  and as the L level in the period T 2 , and outputs the logical level of the selection signal S 2  as the L level in the period T 1  and as the H level in the period T 2 . In this case, the selection circuit  230  selects the trapezoidal waveform Adp 1  in the period T 1  and the trapezoidal waveform Bdp 2  in the period T 2 . As a result, the drive signal VOUT corresponding to a “medium-sized dot” shown in  FIG. 6  is generated. 
     If the print data [SIH, SIL] is [0, 1], the decoder  226  outputs the logical level of the selection signal S 1  as the H level in the period T 1  and as the L level in the period T 2 , and outputs the logical level of the selection signal S 2  as the L level in the period T 1  and as the L level in the period T 2 . In this case, the selection circuit  230  selects the trapezoidal waveform Adp 1  in the period T 1  and neither of the trapezoidal waveform Adp 2  and the trapezoidal waveform Bdp 2  in the period T 2 . As a result, the drive signal VOUT corresponding to a “small dot” shown in  FIG. 6  is generated. 
     If the print data [SIH, SIL] is [0, 0], the decoder  226  outputs the logical level of the selection signal S 1  as the L level in the period T 1  and as the L level in the period T 2 , and outputs the logical level of the selection signal S 2  as the H level in the period T 1  and as the L level in the period T 2 . In this case, the selection circuit  230  selects the trapezoidal waveform Bdp 1  in the period T 1  and neither of the trapezoidal waveform Adp 2  and the trapezoidal waveform Bdp 2  in the period T 2 . As a result, the drive signal VOUT corresponding to “non-printing” shown in  FIG. 6  is generated. 
     As explained above, based on the print data signal SI, the latch signal LAT, the change signal CH, and the clock signal SCK, the drive signal selection circuit  200  performs selection regarding the waveform of the drive signal COMA and the waveform of the drive signal COMB, and outputs the selection result as the drive signal VOUT. That is, in a broad sense, the drive signal VOUT, which is generated by performing selection regarding the waveform of the drive signal COMA and the waveform of the drive signal COMB, is also outputted from the drive circuit  132 - 1  to  132 - n . That is, in the present embodiment, the drive signal VOUT is also an example of a drive signal for driving the head  39 . 
     4. Structure of Discharging Head 
     Next, the structure of one of the plurality m of dischargers  600  included in the head  39  will now be explained.  FIG. 11  is a diagram that illustrates a structure of the discharger  600 . As illustrated in  FIG. 11 , the discharger  600  includes a piezoelectric element  60 , a vibrating plate  621 , a cavity  631 , and a nozzle  651 . The vibrating plate  621  moves when the piezoelectric element  60  provided on its upper surface in  FIG. 9  is driven. The vibrating plate  621  behaves as a diaphragm that increases/decreases the internal capacity of the cavity  631 . The inside of the cavity  631  is filled with ink. The cavity  631  behaves as a pressure compartment, the internal capacity of which changes due to deformative movement of the vibrating plate  621  caused by the driving of the piezoelectric element  60 . The nozzle  651  is an orifice portion that is formed though a nozzle plate  632  and is in communication with the cavity  631 . Due to a change in the internal capacity of the cavity  631 , ink contained inside the cavity  631  is discharged from the nozzle  651 . Ink supplied through an ink supply port  661  is supplied to the cavity  631  via a reservoir  641 . 
     The piezoelectric element  60  has a structure of sandwiching a piezoelectric body  601  between a pair of electrodes  611  and  612 . In accordance with a potential difference between the electrodes  611  and  612 , the piezoelectric body  601  in this structure at the center portion of the electrodes  611  and  612  and the vibrating plate  621  deforms in the vertical direction in  FIG. 11  with respect to both ends. Specifically, the drive signal VOUT is supplied to the electrode  611 , which is one terminal of the piezoelectric element  60 , and the reference voltage signal VBS is supplied to the electrode  612 , which is the opposite terminal of the piezoelectric element  60 . The center portion of the piezoelectric element  60  deforms upward when the voltage of the drive signal VOUT decreases. The center portion of the piezoelectric element  60  deforms downward when the voltage of the drive signal VOUT increases. The vibrating plate  621  moves upward due to the upward deformation of the piezoelectric element  60 , thereby increasing the internal capacity of the cavity  631 . Therefore, ink is sucked in from the reservoir  641 . The vibrating plate  621  moves downward due to the downward deformation of the piezoelectric element  60 , thereby decreasing the internal capacity of the cavity  631 . Therefore, ink whose amount corresponds to the degree of the decrease in the internal capacity of the cavity  631  is discharged from the nozzle  651 . 
     As explained above, the discharger  600  includes the piezoelectric element  60  and discharges ink onto the medium  22  by the driven operation of the piezoelectric element  60 . The structure of the piezoelectric element  60  is not limited to the illustrated structure. Any other structure may be adopted as long as it is possible to discharge ink by deformative action of the piezoelectric element  60 . The vibration mode of the piezoelectric element  60  is not limited to flexural vibration. Longitudinal vibration may be used instead. 
     5. Layout of Circuit Boards Provided in Liquid Discharging Apparatus 
     As explained above, the liquid discharging apparatus  1  according to the present embodiment includes the power supply circuit board  100 , the first control circuit board  110 , the second control circuit board  120 , the drive circuit board  130 , the discharge control circuit board  140 , and the plurality of heads  39 . The power supply circuit board  100  and the first control circuit board  110  are electrically coupled to each other via the cable  151 . The first control circuit board  110  and the second control circuit board  120  are electrically coupled to each other via the cable  152 . The second control circuit board  120  and the drive circuit board  130  are electrically coupled to each other via the cable  154 . The drive circuit board  130  and the discharge control circuit board  140  are electrically coupled to each other via the cable  158 . The drive signal VOUT outputted from the discharge control circuit board  140  is inputted into the corresponding head  39 . By this means, ink is discharged from the head  39 . Since the ink droplets ejected land onto the medium  22 , an image is formed on the medium  22  as demanded. 
     Next, with reference to  FIGS. 12 and 13 , a specific example of the layout of the power supply circuit board  100 , the first control circuit board  110 , the second control circuit board  120 , the drive circuit board  130 , and the discharge control circuit board  140  inside the housing  10  of the liquid discharging apparatus  1  will now be described.  FIG. 12  is a diagram for explaining the layout of circuit boards when the liquid discharging apparatus  1  is viewed from the +Z side.  FIG. 13  is a diagram for explaining the layout of circuit boards when the liquid discharging apparatus  1  is viewed from the +Y side. 
     The medium  22  is transported in a region that is between the first side frame  61  and the second side frame  62  in  FIG. 12  and that is enclosed by the first side frame  61 , the second side frame  62 , and a top frame  63  in  FIG. 13 , wherein the top frame  63  is connected to both of the first side frame  61  and the second side frame  62  and is located on the +Z side with respect to the first side frame  61  and the second side frame  62 . That is, the transportation path forming portion  46 , the intermediate roller  47 , and the transportation roller  48  of the transportation portion  45  configured to transport the medium  22  are provided in the region enclosed by the first side frame  61 , the second side frame  62 , and the top frame  63 . The region enclosed by the first side frame  61 , the second side frame  62 , and the top frame  63  may be referred to as a medium transportation region  41 . 
     As illustrated in  FIGS. 12 and 13 , the power supply circuit board  100  is located on the −X side with respect to the medium transportation region  41  and is fixed to the rear wall  12 . The power supply circuit board  100  is electrically coupled to a terminal  161  via a cable  150  and is electrically coupled to the first control circuit board  110  via the cable  151 . 
     The terminal  161  is located on the −X side with respect to the power supply circuit board  100  and is fixed to the second sidewall  14 . The terminal  161  is electrically coupled to the power supply circuit board  100  via the cable  150 . A voltage VAC is inputted to the terminal  161  from a commercial alternating-current power supply provided outside the liquid discharging apparatus  1 . For example, an inlet that is connectable to a cable through which the voltage VAC propagates is used as the terminal  161 . In the liquid discharging apparatus  1 , a socket plug that is integrally made up of a cable through which the voltage VAC propagates and the terminal  161  may be used. 
     The first control circuit board  110  is located on the −X side with respect to the medium transportation region  41  and on the +Z side with respect to the power supply circuit board  100 , and is fixed to the rear wall  12 . The first control circuit board  110  is electrically coupled to the power supply circuit board  100  via the cable  151 , is electrically coupled to the second control circuit board  120  via the cable  152 , is electrically coupled to the operation portion  59  via the cable  153 , and is electrically coupled to a terminal  162  via a cable  159 . 
     The operation portion  59  is located on the −X side with respect to the medium transportation region  41  and on the +Z side with respect to the first control circuit board  110 , and is fixed to the top wall  15 . The operation portion  59  is electrically coupled to the first control circuit board  110  via the cable  153 . 
     The terminal  162  is located on the −X side with respect to the first control circuit board  110  and on the +Z side with respect to the terminal  161 , and is fixed to the second sidewall  14 . The terminal  162  is electrically coupled to the first control circuit board  110  via the cable  159 . An image signal IMG is inputted to the terminal  162  from a host computer provided outside the liquid discharging apparatus  1 . For example, a USB terminal to be connected to the host computer via a USB cable such that communication can be performed therebetween is used as the terminal  161 . Any terminal to which a cable for communication with the host computer is connectable can be used as the terminal  161 . For example, the terminal  161  may be a printer port. The liquid discharging apparatus  1  may be connected to the host computer such that communication can be performed therebetween wirelessly. In such a case, a receiver antenna for receiving a signal based on the wireless communication corresponds to the terminal  162 . 
     The second control circuit board  120  is located on the +X side with respect to the medium transportation region  41  and is fixed to the rear wall  12 . The second control circuit board  120  is electrically coupled to the first control circuit board  110  via the cable  152 , is electrically coupled to the drive circuit board  130  via the cable  154 , is electrically coupled to the carriage motor  40  via the cable  155 , and is electrically coupled to the driver portion  33  via the cable  156 . 
     The driver portion  33  is located on the +X side with respect to the medium transportation region  41  and on the −Z side with respect to the second control circuit board  120 , and is fixed to the first side frame  61 . The driver portion  33  is electrically coupled to the second control circuit board  120  via the cable  156 . 
     The carriage motor  40  is located on the +X side with respect to the medium transportation region  41  and on the +Z side with respect to the second control circuit board  120 , and is fixed to the guide shaft  37 . The carriage motor  40  is electrically coupled to the second control circuit board  120  via the cable  155 . 
     The drive circuit board  130  is located on the +Z side with respect to the medium transportation region  41  and is fixed to the rear wall  12 . In other words, the drive circuit board  130  and the medium transportation region  41  partially overlap with each other when viewed along the Z direction. The drive circuit board  130  is electrically coupled to the second control circuit board  120  via the cable  154  and is electrically coupled to the discharge control circuit board  140  mounted in the carriage  38  via the cable  158 . 
     As explained above, in the present embodiment, the first control circuit board  110  and the second control circuit board  120  are electrically coupled to each other via the cable  152 . The first control circuit board  110  is located on the −X side with respect to the medium transportation region  41  and is located on the side where there is the second sidewall  14  of the housing  10 . In addition, on the −X side with respect to the medium transportation region  41 , the operation portion  59 , via which a user inputs information so as to cause the liquid discharging apparatus  1  to discharge ink onto the medium  22 , and the terminal  162 , to which the image signal IMG representing data of an image to be formed on the medium  22  is inputted, are located in the liquid discharging apparatus  1 . 
     The operation portion  59  inputs the operation information signal CS via the cable  153  into the control circuit  111  mounted on the first control circuit board  110 . The terminal  162  inputs the image signal IMG via the cable  159  into the control circuit  111  mounted on the first control circuit board  110 . That is, in the liquid discharging apparatus  1 , the operation portion  59  operable for discharging ink onto the medium  22  is electrically coupled to the control circuit  111  mounted on the first control circuit board  110 , and the terminal  162  operable for discharging ink onto the medium  22  is electrically coupled to the control circuit  111  mounted on the first control circuit board  110 . The operation portion  59 , the terminal  162 , and the first control circuit board  110  are located on the −X side with respect to the medium transportation region  41 . 
     The second control circuit board  120  is located on the +X side with respect to the medium transportation region  41  and is located on the side where there is the first sidewall  13  of the housing  10 . In addition, on the +X side with respect to the medium transportation region  41 , the carriage motor  40 , which controls the movement of the carriage  38  on which the plurality of heads  39  is mounted, and the driver portion  33 , which causes the first holder portion  31  and the second holder portion  32  to rotate for controlling the transportation of the medium  22 , are located in the liquid discharging apparatus  1 . The carriage control signal CMC is inputted into the carriage motor  40  via the cable  155 . The drive control signal DC 1  is inputted into the driver portion  33  via the cable  156 . That is, the carriage motor  40  operable for discharging ink onto the medium  22  is electrically coupled to the control circuit  121  mounted on the second control circuit board  120 , and the driver portion  33  operable for discharging ink onto the medium  22  is electrically coupled to the control circuit  121  mounted on the second control circuit board  120 . The carriage motor  40 , the driver portion  33 , and the second control circuit board  120  are located on the +X side with respect to the medium transportation region  41 . 
     As explained above, the liquid discharging apparatus  1  includes the housing  10  that houses the first control circuit board  110 , the second control circuit board  120 , the operation portion  59 , the terminal  162 , the carriage motor  40 , and the driver portion  33 . Inside the housing  10 , the first control circuit board  110  and the second control circuit board  120  are located such that a minimum distance between the first control circuit board  110  and the second sidewall  14  is shorter than a minimum distance between the first control circuit board  110  and the first sidewall  13  and such that a minimum distance between the second control circuit board  120  and the first sidewall  13  is shorter than a minimum distance between the second control circuit board  120  and the second sidewall  14 . 
     Moreover, in the liquid discharging apparatus  1 , the operation portion  59  and the terminal  162 , which are electrically coupled to the first control circuit board  110 , are provided closer to the first control circuit board  110  than the second control circuit board  120 , and the carriage motor  40  and the driver portion  33 , which are electrically coupled to the second control circuit board  120 , are provided closer to the second control circuit board  120  than the first control circuit board  110 . In other words, the operation portion  59 , the terminal  162 , the carriage motor  40 , and the driver portion  33  are located such that a minimum distance from the first control circuit board  110  to the operation portion  59  and to the terminal  162  is shorter than a minimum distance from the first control circuit board  110  to the carriage motor  40  and to the driver portion  33  and such that a minimum distance from the second control circuit board  120  to the carriage motor  40  and to the driver portion  33  is shorter than a minimum distance from the second control circuit board  120  to the operation portion  59  and to the terminal  162 . 
     This structure makes it possible to shorten the wire-routing length of the cable  153  for electrically coupling the first control circuit board  110  to the operation portion  59  operable for discharging ink onto the medium  22  and the wire-routing length of the cable  159  for electrically coupling the first control circuit board  110  to the terminal  162  operable for discharging ink onto the medium  22 . In addition, this structure makes it possible to shorten the wire-routing length of the cable  155  for electrically coupling the second control circuit board  120  to the carriage motor  40  operable for discharging ink onto the medium  22  and the wire-routing length of the cable  156  for electrically coupling the second control circuit board  120  to the driver portion  33  operable for discharging ink onto the medium  22 . Therefore, the risk of contamination of signals propagating via the cables  153 ,  159 ,  155 , and  156  respectively with noise is reduced. 
     In the liquid discharging apparatus  1  according to the present embodiment, the drive circuit board  130 , on which the drive circuits  132 - 1  to  132 - n  configured to output the drive signals COMA 1  to COMAn and COMB 1  to COMBn for driving the respective heads  39  and the reference voltage signals VBS 1  to VBSn respectively are provided, is provided on the +Z side with respect to the medium transportation region  41  and closer to the second control circuit board  120  than the first control circuit board  110 . The drive circuit board  130  is electrically coupled to the second control circuit board  120  via the cable  154 . In this example, the drive circuit board  130  is located such that a minimum distance from the first control circuit board  110  to the operation portion  59  and to the terminal  162  is shorter than a minimum distance from the first control circuit board  110  to the drive circuit board  130  and such that a minimum distance from the second control circuit board  120  to the drive circuit board  130  is shorter than a minimum distance from the second control circuit board  120  to the operation portion  59  and to the terminal  162 . 
     This structure makes it possible to shorten the wire-routing length of the cable  154  for electrically coupling the second control circuit board  120  to each of the drive circuits  132 - 1  to  132 - n  mounted on the drive circuit board  130  operable for discharging ink onto the medium  22 . Therefore, the risk of contamination of a signal propagating via the cable  154  with noise is reduced. 
     Among the operation portion  59 , the terminal  162 , the carriage motor  40 , the driver portion  33 , and the drive circuit board  130 , which are operable for discharging ink onto the medium  22 , at least one of the operation portion  59  and the terminal  162  is an example of a first component, and at least one of the carriage motor  40 , the driver portion  33 , and the drive circuit board  130  is an example of a second component. That is, the first component could include the terminal  162 , which is an input terminal for an input of the image signal IMG for driving the head  39 , and the second component could include at least either the drive circuit board  130 , on which at least any of the drive circuits  132 - 1  to  132 - n  configured to output the drive signals COMA and COMB for driving the head  39  is mounted, or the carriage motor  40 , which includes, as the drive motor, an electric motor that converts electric energy into kinetic energy. 
     The meaning of the phrase “operable for discharging ink onto the medium  22 ” is not limited to direct drive operation for discharging ink from the head  39  onto the medium  22  but includes incidental operation performed in the liquid discharging apparatus  1 , too, such as, for example, input drive operation of inputting signals for discharging ink from the head  39  onto the medium  22 , transportation drive operation of transporting the medium  22  onto which ink is discharged from the head  39 , and head movement drive operation of moving the head  39  that discharges ink. In other words, the meaning of the phrase “operable for discharging ink onto the medium  22 ” includes indirect drive operation for discharging ink from the head  39  onto the medium  22 , too. 
     In the liquid discharging apparatus  1  according to the present embodiment, the first control circuit board  110  drives the liquid discharging apparatus  1  by processing various control signals inputted for causing the liquid discharging apparatus  1  to discharge ink onto the medium  22 . On the other hand, the second control circuit board  120  outputs a signal for moving the carriage  38  on which the head  39  is provided so as to cause the liquid discharging apparatus  1  to discharge ink onto the medium  22 , a signal for transporting the medium  22 , and a signal for generating the drive signal COMA, COMB for discharging ink from the head  39 . That is, the first control circuit board  110  performs signal conversion processing for converting control signals inputted externally into signals for discharging ink onto the medium  22 , and, based on the signals inputted from the first control circuit board  110 , the second control circuit board  120  performs processing for causing various components to operate for discharging ink onto the medium  22 . 
     Since the first control circuit board  110  and the second control circuit board  120  are configured to perform processing different from each other as explained above, they are different from each other in terms of the voltage levels and frequencies of the signals processed. For this reason, it is advantageous to arrange the first control circuit board  110  and the second control circuit board  120  at a distance from each other so as to avoid interference between the signals generated by the first control circuit board  110  and the signals generated by the second control circuit board  120 . 
     Therefore, in the present embodiment, in order to arrange the first control circuit board  110  and the second control circuit board  120  at a distance from each other, the medium transportation region  41 , including the transportation portion  45 , where the medium  22  is transported is provided between the first control circuit board  110  and the second control circuit board  120 . Specifically, the first control circuit board  110  is located on the −X side with respect to the medium transportation region  41  where the medium  22  is transported, and the second control circuit board  120  is located on the +X side with respect to the medium transportation region  41  where the medium  22  is transported. In other words, the first control circuit board  110  and the second control circuit board  120  are provided such that a minimum distance between the first control circuit board  110  and the second sidewall  14  is shorter than a minimum distance between the medium transportation region  41 , including the transportation portion  45 , and the second sidewall  14  and such that a minimum distance between the second control circuit board  120  and the first sidewall  13  is shorter than a minimum distance between the medium transportation region  41 , including the transportation portion  45 , and the first sidewall  13 . 
     This structure makes it possible to arrange the first control circuit board  110  and the second control circuit board  120  configured to perform processing different from each other at a distance from each other inside the housing  10  of the liquid discharging apparatus  1 . As a consequence, the risk of interference between the signals generated by the first control circuit board  110  and the signals generated by the second control circuit board  120  is reduced. 
     Besides a printing state, in which a print-demanded image is formed on the medium  22  by discharging ink from the head  39  onto the medium  22 , the liquid discharging apparatus  1  has a standby state and a sleep state. In the standby state, in which power consumption is smaller than in the printing state, the image signal IMG is not inputted into the liquid discharging apparatus  1 , and ink is not discharged from the head  39  onto the medium  22 . In the sleep state, in which power consumption is smaller than in the standby state, the image signal IMG is not inputted into the liquid discharging apparatus  1 , and ink is not discharged from the head  39  onto the medium  22 . In other words, the liquid discharging apparatus  1  has the printing state, in which it is possible to discharge ink from the head  39 , and the standby state and the sleep state, in both of which power consumption is smaller than in the printing state and in neither of which ink is discharged from the head  39 . 
     In the liquid discharging apparatus  1  according to the present embodiment, as described earlier, the first control circuit board  110  performs signal conversion processing for converting control signals inputted externally into signals for discharging ink onto the medium  22 , and, based on the signals inputted from the first control circuit board  110 , the second control circuit board  120  performs processing for causing various components of the liquid discharging apparatus  1  to operate for discharging ink onto the medium  22 . That is, the control circuit  121  provided on the second control circuit board  120  does not generate signals when in the standby state and when in the sleep state. Therefore, in at least one of the standby state and the sleep state, it is possible to stop the operation of the second control circuit board  120 . For this reason, in the liquid discharging apparatus  1  according to the present embodiment equipped with the first control circuit board  110  and the second control circuit board  120 , it is possible to further reduce power consumption in the standby state and the sleep state, in neither of which ink is discharged from the head  39 , because the first control circuit board  110  and the second control circuit board  120  are configured to perform processing different from each other in the liquid discharging apparatus  1 . 
     The printing state is an example of a first mode. At least one of the standby state and the sleep state is an example of a second mode. 
     6. Operational Effects 
     As explained above, the liquid discharging apparatus  1  according to the present embodiment includes the first control circuit board  110 , on which the control circuit  111  is provided, and the second control circuit board  120 , on which the control circuit  121  is provided. The operation portion  59  and the terminal  162 , which are electrically coupled to the control circuit  111 , are provided closer to the first control circuit board  110  than the second control circuit board  120 , and the carriage motor  40  and the driver portion  33 , which are electrically coupled to the control circuit  121 , are provided closer to the second control circuit board  120  than the first control circuit board  110 . That is, the minimum distance from the first control circuit board  110  to the operation portion  59  and to the terminal  162  is shorter than the minimum distance from the first control circuit board  110  to the carriage motor  40  and to the driver portion  33 , and the minimum distance from the second control circuit board  120  to the carriage motor  40  and to the driver portion  33  is shorter than the minimum distance from the second control circuit board  120  to the operation portion  59  and to the terminal  162 . 
     This structure makes it possible to shorten the length of wiring for signal propagation to each of the operation portion  59 , the terminal  162 , the carriage motor  40 , the driver portion  33 , which are scattered here and there inside the liquid discharging apparatus  1 . The shorter wiring reduces the influence of wiring impedance between the operation portion  59 , the terminal  162 , the carriage motor  40 , the driver portion  33  and the first control circuit board  110 , the second control circuit board  120 , resulting in greater signal propagation precision. This improves the discharge precision of ink discharged from the head  39 . As a consequence, the risk of a decrease in the quality of an image formed on the medium  22  is reduced. 
     Although a certain exemplary embodiment is described above, the scope of the present disclosure is not limited thereto. The present disclosure can be modified in various ways within a scope of not departing from the gist thereof. For example, some examples in the foregoing embodiment may be combined as needed. 
     The scope of the present disclosure encompasses a structure that is substantially the same as the structure described in the embodiment (for example, a structure with the same function, method, and result, or a structure with the same object and effects). The scope of the present disclosure encompasses a structure that is obtained by replacing a non-essential part in the structure described in the embodiment with an alternative. The scope of the present disclosure encompasses a structure that produces the same operational effects as that of the structure described in the embodiment, or a structure that achieves the same object as that of the structure described in the embodiment. The scope of the present disclosure further encompasses a structure that is obtained by adding known art to the structure described in the embodiment.