Printing device

Abstract

This invention relates to a printing apparatus for suppressing the adhesion of fog to a drive circuit. A printing apparatus is characterized by comprising: a liquid nozzle for ejecting printing liquid to form an image on a medium; a circuit board having a drive circuit for driving the liquid nozzle; and a storage mechanism for storing cooling liquid in a liquid storage space, wherein the storage mechanism stores the cooling liquid in such a way that the entire drive circuit and the circuit configuration portion of the circuit board having the drive circuit are immersed in the cooling liquid in the liquid storage space.

Description

Technical Field

[0001] This invention relates to printing apparatus. Background Technology

[0002] In printing apparatuses that eject printing liquids such as ink from a liquid nozzle and form an image on a medium, heat generated in the drive circuit for driving the liquid nozzle can cause malfunctions in the drive circuit. Additionally, dust adhering to the drive circuit can also cause malfunctions. Patent Document 1 proposes a technique for printing apparatuses that includes a frame for cooling the drive circuit, i.e., a frame that suppresses dust adhesion to the drive circuit, in order to suppress such malfunctions.

[0003] Patent Document 1: Japanese Patent Application Publication No. 06-112678

[0004] However, in the technology described in Patent Document 1, when the printing liquid ejected from the liquid nozzle becomes mist and floats inside the printing apparatus, it is impossible to prevent the mist from adhering to the drive circuit. Therefore, as the printing liquid is ejected, the resulting mist adhering to the drive circuit may cause malfunctions in the drive circuit. Summary of the Invention

[0005] To address the above-mentioned problems, the printing apparatus of the present invention is characterized by comprising: a liquid nozzle that ejects printing liquid to form an image on a medium; a circuit board having a drive circuit for driving the liquid nozzle; and a storage mechanism for storing cooling liquid in a liquid storage space, wherein the storage mechanism stores the cooling liquid in such a manner that the entire drive circuit and the circuit configuration portion of the circuit board having the drive circuit are immersed in the cooling liquid in the liquid storage space. Attached Figure Description

[0006] Figure 1 This is a block diagram illustrating an example of the configuration of an inkjet printer 1 according to an embodiment of the present invention.

[0007] Figure 2 This is a perspective view showing an example of the schematic internal structure of an inkjet printer 1.

[0008] Figure 3 This is a cross-sectional view illustrating an example of the structure of the ejector section D[m].

[0009] Figure 4 This is a block diagram illustrating an example of the structure of head unit 3.

[0010] Figure 5 This is a timing diagram illustrating an example of the signals supplied to head unit 3.

[0011] Figure 6 This is an explanatory diagram used to illustrate an example of a specific signal Sd[m].

[0012] Figure 7 This is a block diagram illustrating an example of the configuration of the drive signal generation unit 4.

[0013] Figure 8 This is a top view illustrating an example of the structure of the drive unit 6 and the storage unit 600.

[0014] Figure 9 This is a cross-sectional view illustrating an example of the structure of the drive unit 6 and the storage unit 600.

[0015] Explanation of reference numerals in the attached figures

[0016] 1: Inkjet printer; 2: Control unit; 3: Head unit; 4: Drive signal generation unit; 5: Power supply unit; 6: Drive unit; 7: Conveyor unit; 31: Supply circuit; 32: Recording head; 40: Integrated circuit; 42: Smoothing circuit; 60: Circuit board; 61: Cover; 62: Heat sink; 600: Storage unit; TrH: Transistor; TrL: Transistor. Detailed Implementation

[0017] Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. However, the dimensions and scales of the various parts in the drawings differ appropriately from the actual dimensions and scales. Furthermore, the embodiments described below are preferred examples of the present invention, and therefore various technically preferred limitations have been added. However, unless specifically limited in the following description, the scope of the present invention is not limited to these embodiments.

[0018] A. Implementation Method

[0019] In this embodiment, an inkjet printer that ejects ink to form an image on recording paper PP is used as an example to describe the printing apparatus.

[0020] 1. Overview of Inkjet Printers

[0021] The following is a reference. Figures 1 to 3 An example of the configuration of the inkjet printer 1 according to this embodiment will be described.

[0022] Figure 1 This is a functional block diagram illustrating an example of the configuration of an inkjet printer 1.

[0023] like Figure 1As shown, a host computer or digital camera supplies printing data Img, representing the image that the inkjet printer 1 should form, to the inkjet printer 1. The inkjet printer 1 performs a printing process to form the image represented by the printing data Img supplied from the host computer onto recording paper PP.

[0024] The inkjet printer 1 includes: a control unit 2 for controlling various parts of the inkjet printer 1; a head unit 3 for having an ink ejection section D; a drive signal generation unit 4 for generating a drive signal Com for driving the ink ejection section D; a power supply unit 5 for supplying power to the head unit 3 and the drive signal generation unit 4; and a transport unit 7 for changing the relative position of the recording paper PP with respect to the head unit 3.

[0025] Furthermore, ink is an example of a "printing liquid," and recording paper PP is an example of a "medium." Additionally, the inkjet printer 1 that ejects ink is an example of a "printing apparatus," the head unit 3 equipped with an ink ejection section D is an example of a "liquid printhead," and the drive signal generation unit 4 that generates the drive signal Com to drive the head unit 3 is, for example, configured to include one or more circuits, and is an example of a "drive signal generation circuit." The power supply unit 5 that supplies power to the head unit 3 and the drive signal generation unit 4 is, for example, configured to include one or more circuits, and is an example of a "power supply circuit." Furthermore, hereinafter, the drive signal generation unit 4 and the power supply unit 5 are sometimes referred to as the drive unit 6. The drive unit 6 is configured to include one or more circuits and is an example of a "drive circuit."

[0026] In this embodiment, it is assumed that the inkjet printer 1 has one or more head units 3 and one or more drive signal generation units 4 corresponding one-to-one with the one or more head units 3. Specifically, in this embodiment, it is assumed that the inkjet printer 1 has four head units 3 and four drive signal generation units 4 corresponding one-to-one with the four head units 3. However, for ease of explanation, the following is an example. Figure 1 As shown, sometimes the explanation focuses on one of the four head units 3 and one of the four drive signal generation units 4, which is set to correspond to one of the head units 3.

[0027] Control unit 2 is configured to include one or more CPUs. However, control unit 2 may replace a CPU or, based on a CPU, incorporate programmable logic devices such as FPGAs. Here, CPU is short for Central Processing Unit, and FPGA is short for field-programmable gate array. Additionally, control unit 2 includes memory. The memory is configured to include volatile memory such as RAM (Random Access Memory), and one or both of non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable Read-Only Memory).

[0028] Details will be described later. Control unit 2 generates signals such as printing signal SI and waveform specification signal dCom to control the operation of various parts of inkjet printer 1.

[0029] Here, the waveform specification signal dCom is a digital signal that specifies the waveform of the drive signal Com. The drive signal Com is an analog signal used to drive the ejector section D. The drive signal generation unit 4 includes a DA conversion circuit that generates the drive signal Com having the waveform specified by the waveform specification signal dCom. Furthermore, the printing signal SI is a digital signal that specifies the type of operation of the ejector section D. Specifically, the printing signal SI specifies the type of operation of the ejector section D by indicating whether or not the drive signal Com is supplied to the ejector section D.

[0030] like Figure 1 As shown, the head unit 3 includes a supply circuit 31 and a recording head 32.

[0031] The recording head 32 has M ejector sections D. Here, the value M is a natural number satisfying "M≥1". Furthermore, the m-th ejector section D among the M ejector sections D of the recording head 32 is sometimes referred to as ejector section D[m]. Here, the variable m is a natural number satisfying "1≤m≤M". Additionally, when a component or signal of the inkjet printer 1 corresponds to an ejector section D[m] among the M ejector sections D, a subscript [m] is sometimes added to the symbol used to represent that component or signal.

[0032] The supply circuit 31 switches whether to supply the drive signal Com to the ejector section D[m] based on the printing signal SI. Furthermore, the drive signal Com supplied to the ejector section D[m] is sometimes referred to as the supply drive signal Vin[m].

[0033] As described above, in this embodiment, the inkjet printer 1 performs printing processing. During printing processing, the control unit 2 generates a printing signal SI, etc., based on the printing data Img, to control the head unit 3. Additionally, during printing processing, the control unit 2 generates a waveform specification signal dCom, etc., to control the drive signal generation unit 4. Furthermore, during printing processing, the control unit 2 generates a signal to control the transport unit 7. Thus, during printing processing, the control unit 2 controls the transport unit 7 by changing the relative position of the recording paper PP with respect to the head unit 3, and adjusts the presence or absence of ink ejection from the ejection section D[m], the ink ejection amount, and the ink ejection timing, etc., to form an image corresponding to the printing data Img on the recording paper PP.

[0034] Figure 2 This is a perspective view showing an example of the schematic internal structure of an inkjet printer 1.

[0035] like Figure 2 As shown, in this embodiment, it is assumed that the inkjet printer 1 is a serial printer. Specifically, when the inkjet printer 1 performs the printing process, it ejects ink from the ejection section D[m] while feeding the recording paper PP in the X1 direction and reciprocating the head unit 3 in the Y1 direction (which intersects the X1 direction) and the opposite direction of the Y1 direction (Y2 direction), thereby forming a dot Dt on the recording paper PP corresponding to the printing data Img.

[0036] Hereinafter, the X1 direction and its opposite direction, the X2 direction, will be collectively referred to as the "X-axis direction," the Y1 direction, which intersects the X-axis direction, and its opposite direction, the Y2 direction, will be collectively referred to as the "Y-axis direction," and the Z1 direction, which intersects both the X-axis and Y-axis directions, and its opposite direction, the Z2 direction, will be collectively referred to as the "Z-axis direction." In this embodiment, as an example, it is assumed that the X-axis direction, the Y-axis direction, and the Z-axis direction are orthogonal to each other. However, the present invention is not limited to this arrangement. The X-axis direction, the Y-axis direction, and the Z-axis direction can simply intersect each other. Furthermore, in this embodiment, the Z1 direction is defined as the direction in which ink is ejected from the ejection section D[m].

[0037] like Figure 2As shown, the inkjet printer 1 according to this embodiment includes: a frame 100; and a carriage 110, which can reciprocate within the frame 100 in the Y-axis direction and is equipped with four head units 3.

[0038] In this embodiment, such as Figure 2 As shown, assume that the carriage 110 houses four ink cartridges 120, each corresponding to one of the four ink colors: cyan, magenta, yellow, and black. Furthermore, in this embodiment, as described above, assume that the inkjet printer 1 has four head units 3, each corresponding to one of the four ink cartridges 120. Each ejector section D[m] receives ink from the ink cartridge 120 corresponding to the head unit 3 where the ejector section D[m] is located. Thus, each ejector section D[m] can fill its interior with the supplied ink and eject the filled ink from the nozzle N. Alternatively, the ink cartridges 120 may be located outside the carriage 110.

[0039] Furthermore, as described above, the inkjet printer 1 according to this embodiment includes a transport unit 7. For example... Figure 2 As shown, the conveying unit 7 includes: a carriage conveying mechanism 71 for reciprocating the carriage 110 in the Y-axis direction; a carriage guide shaft 76 for supporting the carriage 110 to reciprocate freely in the Y-axis direction; a media conveying mechanism 73 for conveying recording paper PP; and a pressure plate 75 disposed in the Z1 direction of the carriage 110. Therefore, when performing printing processing, the conveying unit 7 causes the head unit 3 and the carriage 110 to reciprocate together along the carriage guide shaft 76 in the Y-axis direction via the carriage conveying mechanism 71, and conveys the recording paper PP on the pressure plate 75 in the X1 direction via the media conveying mechanism 73, thereby changing the relative position of the recording paper PP with respect to the head unit 3, enabling ink to be sprayed onto the entire recording paper PP.

[0040] Figure 3 This is a schematic partial cross-sectional view of the recording head 32, which is cut off in a manner including the ejection portion D[m].

[0041] like Figure 3As shown, the ejector section D[m] includes a piezoelectric element PZ[m], a chamber CV filled with ink, a nozzle N communicating with the chamber CV, and a vibrating plate 321. The ejector section D[m] drives the piezoelectric element PZ[m] by supplying a drive signal Vin[m], causing the ink in the chamber CV to be ejected from the nozzle N. The chamber CV is a space divided by a chamber plate 324, a nozzle plate 323 on which the nozzle N is formed, and a vibrating plate 321. The chamber CV is connected to a reservoir 325 via an ink supply port 326. The reservoir 325 is connected to an ink cartridge 120 corresponding to the ejector section D[m] via an ink inlet 327. The piezoelectric element PZ[m] has an upper electrode Zu[m], a lower electrode Zd[m], and a piezoelectric element Zm[m] disposed between the upper electrode Zu[m] and the lower electrode Zd[m]. The lower electrode Zd[m] is electrically connected to a power supply line LD set to a potential VBS. Furthermore, when a drive signal Vin[m] is supplied to the upper electrode Zu[m] and a voltage is applied between the upper electrode Zu[m] and the lower electrode Zd[m], the piezoelectric element PZ[m] displaces in the Z1 or Z2 direction in response to the applied voltage, resulting in vibration of the piezoelectric element PZ[m]. The lower electrode Zd[m] is attached to the vibrating plate 321. Therefore, when the piezoelectric element PZ[m] is driven to vibrate by the drive signal Vin[m], the vibrating plate 321 also vibrates. Moreover, due to the vibration of the vibrating plate 321, the volume of the chamber CV and the pressure within the chamber CV change, and the ink filled in the chamber CV is ejected from the nozzle N.

[0042] In addition, during the printing process, some of the ink ejected from nozzle N becomes mist before it falls onto the recording paper PP and floats inside the frame 100.

[0043] 2. Overview of the Head Unit

[0044] The following is a reference. Figures 4 to 6 The outline of head unit 3 will be explained.

[0045] Figure 4 This is a block diagram illustrating an example of the structure of head unit 3.

[0046] like Figure 4 As shown, the head unit 3 includes a supply circuit 31 and a recording head 32. Additionally, the head unit 3 includes wiring LC that receives a drive signal Com from the drive signal generation unit 4.

[0047] like Figure 4 As shown, the supply circuit 31 includes M switches WS[1] to WS[M] that correspond one-to-one with the M ejector sections D[1] to D[M], and a connection state specifying circuit 310 that specifies the connection state of each switch.

[0048] The connection status specifying circuit 310 indicates the connection status specifying signal QS[m] for the on / off state of the specified switch WS[m] based on at least a portion of the printed signal SI, latch signal LAT, and change signal CH supplied from the control unit 2.

[0049] The switch WS[m] switches the conduction and deconduction of the wiring LC and the upper electrode Zu[m] of the piezoelectric element PZ[m] located in the ejector section D[m] based on the connection state specification signal QS[m]. In this embodiment, the switch WS[m] is turned on when the connection state specification signal QS[m] is high and turned off when it is low. When the switch WS[m] is on, the drive signal Com supplied to the wiring LC is supplied to the upper electrode Zu[m] of the ejector section D[m] as the supply drive signal Vin[m].

[0050] In this embodiment, when the inkjet printer 1 performs printing processing, one or more unit periods TP are set as the operation period of the inkjet printer 1. The inkjet printer 1 according to this embodiment can drive each ejection section D[m] for printing processing in each unit period TP.

[0051] Figure 5 This is a timing diagram showing the various signals, such as the drive signal Com, supplied to head unit 3 during a unit period TP.

[0052] like Figure 5 As shown, control unit 2 outputs a latched signal LAT with a pulse PLL. Therefore, control unit 2 defines the unit period TP as the period from the rise of the pulse PLL to the rise of the next pulse PLL.

[0053] In addition, the control unit 2 outputs a change signal CH with a pulse PLC during the unit period TP. Furthermore, the control unit 2 divides the unit period TP into a drive period TQ1 from the rise of the pulse PLL to the rise of the pulse PLC, and a drive period TQ2 from the rise of the pulse PLC to the rise of the pulse PLL.

[0054] like Figure 5As shown, the printing signal SI includes M individual designation signals Sd[1] to Sd[M], each corresponding to one of the M ejector sections D[1] to D[M]. The individual designation signal Sd[m] specifies the driving mode of the ejector section D[m] in each unit period TP during the printing process performed by the inkjet printer 1. Before each unit period TP, the control unit 2 synchronizes the printing signal SI, including the M individual designation signals Sd[1] to Sd[M], with the clock signal CL and supplies it to the connection state designation circuit 310. Then, the connection state designation circuit 310 generates a connection state designation signal QS[m] based on the individual designation signals Sd[m] in that unit period TP.

[0055] Furthermore, in this embodiment, it is assumed that during a unit period TP of the printing process, the ejector part D[m] can form any one of the following points Dt: a large dot composed of ink with an ink amount of ξ1, a medium dot composed of ink with an ink amount of ξ2 less than ink amount of ξ1, and a small dot composed of ink with an ink amount of ξ3 less than ink amount of ξ2.

[0056] Figure 6 This is an explanatory diagram used to illustrate a specific signal Sd[m].

[0057] like Figure 6 As shown, in this embodiment, during the unit period TP of the printing process, the individual designated signal Sd[m] can take any one of the following four values: "1" for designating the ejector D[m] as the large dot forming ejector DP-1; "2" for designating the ejector D[m] as the midpoint forming ejector DP-2; "3" for designating the ejector D[m] as the small dot forming ejector DP-3; and "4" for designating the ejector D[m] as the dot-free forming ejector DP-N. Here, the large dot forming ejector DP-1 is the ejector D that forms large dots during the unit period TP. The midpoint forming ejector DP-2 is the ejector D that forms midpoints during the unit period TP. The small dot forming ejector DP-3 is the ejector D that forms small dots during the unit period TP. The dot-free forming ejector DP-N is the ejector D that does not form dots during the unit period TP.

[0058] return Figure 5 Please provide an explanation.

[0059] like Figure 5 As shown, in this embodiment, the drive signal Com has a waveform PA1 set during drive period TQ1 and a waveform PA2 set during drive period TQ2.

[0060] Here, waveform PA1 is the waveform that returns to reference potential V0 after passing through a potential VLA1 (lower than reference potential V0) and a potential VHA1 (higher than reference potential V0). When a supply drive signal Vin[m] with waveform PA1 is supplied to the ejection section D[m], waveform PA1 is determined such that ink equivalent to ink amount φ1 is ejected from the ejection section D[m].

[0061] Furthermore, waveform PA2 is a waveform that travels from reference potential V0 through a potential VLA2 (lower than reference potential V0) and a potential VHA2 (higher than reference potential V0) and returns to reference potential V0. When a supply drive signal Vin[m] with waveform PA2 is supplied to the ejection section D[m], waveform PA2 is determined such that ink equivalent to ink amount φ2 is ejected from the ejection section D[m].

[0062] Furthermore, in this embodiment, it is assumed that the ink quantity ξ1 is equivalent to the sum of ink quantities φ1 and φ2, the ink quantity ξ2 is equivalent to ink quantity φ1, and the ink quantity ξ3 is equivalent to ink quantity φ2.

[0063] Furthermore, in this embodiment, as an example, it is assumed that when the potential of the supply drive signal Vin[m] supplied to the ejection section D[m] is high, the volume of the chamber CV of the ejection section D[m] is smaller compared to the case of a low potential. Therefore, when the ejection section D[m] is driven by the supply drive signal Vin[m] having a waveform PA1, etc., the ink in the ejection section D[m] is ejected from the nozzle N by the change in the potential of the supply drive signal Vin[m] from low to high potential.

[0064] like Figure 6 As shown, when the individual specified signal Sd[m] indicates that the value "1" is set for the ejector section D[m] as the large dot forming ejector section DP-1 during the unit period TP, the connection state specifying circuit 310 sets the connection state specifying signal QS[m] to a high level during the driving period TQ1 and driving period TQ2. In this case, the switch WS[m] is turned on during the driving period TQ1 and driving period TQ2. Therefore, the ejector section D[m] is driven by the supply driving signal Vin[m] with waveforms PA1 and PA2 during the unit period TP, ejecting ink equivalent to the ink amount ξ1 of the large dot.

[0065] Furthermore, when the individual specified signal Sd[m] indicates a value "2" indicating that the ejector part D[m] is designated as the midpoint forming ejector part DP-2 during the unit period TP, the connection state specifying circuit 310 sets the connection state specifying signal QS[m] to a high level during the driving period TQ1. In this case, the switch WS[m] is turned on during the driving period TQ1. Therefore, the ejector part D[m] is driven by the supply driving signal Vin[m] with waveform PA1 during the unit period TP, ejecting ink equivalent to the ink amount ξ2 at the midpoint.

[0066] Furthermore, when the individual specified signal Sd[m] indicates that the value "3" of the dot-forming nozzle D[m] is specified as nozzle DP-3 during the unit period TP, the connection state specifying circuit 310 sets the connection state specifying signal QS[m] to a high level during the driving period TQ2. In this case, the switch WS[m] is turned on during the driving period TQ2. Therefore, the nozzle D[m] is driven by the supply driving signal Vin[m] with waveform PA2 during the unit period TP, and nozzles ink equivalent to the ink amount ξ3 of the dot.

[0067] Furthermore, when the individual specified signal Sd[m] indicates that the value "4" for the ejector section D[m] to be designated as the point-non-forming ejector section DP-N during the unit period TP, the connection state specifying circuit 310 sets the connection state specifying signal QS[m] to a low level throughout the entire unit period TP. In this case, the switch WS[m] is open throughout the entire unit period TP. Therefore, the ejector section D[m] is not driven by the supply drive signal Vin[m] during the unit period TP, and no ink is ejected.

[0068] 3. Drive signal generation unit

[0069] The following is a reference. Figure 7 Meanwhile, a summary of the drive signal generation unit 4 will be provided.

[0070] Figure 7 This is a diagram illustrating an example of the circuit configuration of the drive signal generation unit 4.

[0071] like Figure 7 As shown, the drive signal generation unit 4 includes an integrated circuit 40, an amplifier circuit 41, a smoothing circuit 42, a pull-up circuit 43, and a filter circuit 44, and generates a drive signal Com based on the waveform specified signal dCom.

[0072] Integrated circuit 40, for example, is an LSI (Large Scale Integration) that generates gate signals SGH and SGL based on the waveform-specified signal dCom. Integrated circuit 40 includes analog-to-analog converter 402, subtractor 404, adder 406, attenuator 408, integrator attenuator 412, comparator 420, and gate driver 430.

[0073] The analog-to-analog converter circuit 402 is a DAC (digital-to-analog converter) that converts the digital waveform specification signal dCom into an analog signal Aa. Furthermore, the voltage amplitude of signal Aa is, for example, approximately 0 to 2 volts. This voltage is amplified by about 20 times to become the drive signal Com. That is, signal Aa is the signal before amplification of the drive signal Com.

[0074] The integrator attenuator 412 attenuates the signal SN1 input to the terminal Tn1 (described later) and outputs the integrated signal Ax.

[0075] The output of subtractor 404 is signal Ab, which represents the potential obtained by subtracting the potential of signal Aa from the potential of signal Ax.

[0076] The output of attenuator 408 is the attenuated signal Ay, which is the high-frequency component of the signal SN2 input to terminal Tn2 described later.

[0077] The adder 406 outputs a signal As representing the potential obtained by adding the potentials of signal Ab and signal Ay.

[0078] Comparator 420 outputs a modulated signal Ms after pulse modulation of signal As. Specifically, comparator 420 outputs a modulated signal Ms as follows: if signal As is a rising voltage, it becomes a high level (H) when it is above the threshold voltage Vth1; if signal As is a falling voltage, it becomes a low level (L) when it is below the threshold voltage Vth2. Furthermore, the threshold voltages Vth1 and Vth2 are set to a relationship of "Vth1 > Vth2".

[0079] Furthermore, the power supply voltage of the circuit from analog converter 402 to comparator 420 is, for example, a low voltage such as 3.3 volts. In contrast, the drive signal Com has a large amplitude, for example, sometimes exceeding 40 volts. Therefore, in the integrator attenuator 812, the signal SN1, which has an amplitude corresponding to the drive signal Com, is attenuated, so that the amplitude range of the signal Ax is consistent with the amplitude range of the signal in the circuit from analog converter 402 to comparator 420.

[0080] Furthermore, in this embodiment, an example digital signal is described as the waveform specification signal dCom. However, the waveform specification signal dCom can be any signal that specifies the target value when generating the drive signal Com. For example, an analog signal Aa can also be used as the waveform specification signal dCom. When signal Aa is the waveform specification signal dCom, the integrated circuit 40 can also be configured without the analog-to-analog conversion circuit 402.

[0081] Gate driver 430 outputs a gate signal SGH to terminal TnH, which converts the modulated signal Ms into a gate signal with a specific amplitude. Additionally, gate driver 430 outputs a gate signal SGL to terminal TnL, which converts a signal with the logic level of the modulated signal Ms inverted into a signal with a specific amplitude.

[0082] The amplifier circuit 41 includes, for example, transistors TrH and TrL, and generates an amplified signal Az by amplifying the modulation signal Ms based on the gate signals SGH and SGL output from the integrated circuit 40. Furthermore, in this embodiment, as an example, it is assumed that transistors TrH and TrL are N-channel field-effect transistors, i.e., FETs.

[0083] The gate signal SGH, output from gate driver 430, is input to the gate electrode of transistor TrH via terminal TnH and resistor RGH. Similarly, the gate signal SGL, output from gate driver 430, is input to the gate electrode of transistor TrL via terminal TnL and resistor RGL. The logic levels of gate signals SGH and SGL are mutually exclusive. Here, "mutually exclusive" means that the signal levels of gate signal SGH supplied to the gate electrode of transistor TrH and gate signal SGL supplied to the gate electrode of transistor TrL will not simultaneously be high; in other words, transistors TrH and TrL will not be turned on simultaneously. Furthermore, transistor TrH is turned on when its gate electrode is high and turned off when its gate electrode is low. Likewise, transistor TrL is turned on when its gate electrode is high and turned off when its gate electrode is low.

[0084] The drain electrode of transistor TrH is electrically connected to the power supply line of power supply potential VH set to the high potential side, and the source electrode is electrically connected to node Nd.

[0085] Additionally, the source electrode of transistor TrL is grounded, and the drain electrode is electrically connected to node Nd. Furthermore, the source electrode of transistor TrL can also be electrically connected to the power supply line LD, which is set to the low-potential side, i.e., potential VBS.

[0086] As described above, transistor TrH is turned on when the gate signal SGH supplied to the gate electrode is high and turned off when it is low. Similarly, transistor TrL is turned on when the gate signal SGL supplied to the gate electrode is high and turned off when it is low. Therefore, the amplified signal Az, obtained by amplifying the modulation signal Ms, is output to node Nd, which electrically connects the source electrode of transistor TrH and the drain electrode of transistor TrL.

[0087] The smoothing circuit 42 is an LPF, or Low Pass Filter, which smooths the amplified signal Az to generate the drive signal Com. The smoothing circuit 42 includes an inductor L0 and a capacitor C0. One end of the inductor L0 is electrically connected to node Nd, and the other end is electrically connected to the output terminal Tn-out. One end of the capacitor C0 is electrically connected to the output terminal Tn-out, and the other end is grounded.

[0088] The pull-up circuit 43 feeds back the signal SN1, which is the result of pulling up the drive signal Com output to the output terminal Tn-out, to the terminal Tn1. The pull-up circuit 43 includes: a resistor R1, one end of which is electrically connected to the output terminal Tn-out and the other end of which is electrically connected to the terminal Tn1; and a resistor R2, one end of which is electrically connected to the terminal Tn1 and the other end of which is electrically connected to the power supply line set to the power supply potential VH.

[0089] The filter circuit 44 is a BPF (Band Pass Filter), which feeds back the signal SN2, after removing the DC component from the frequency components of the drive signal Com within a specified frequency band, to terminal Tn2. The filter circuit 44 includes: a resistor R3; a capacitor C1, one end of which is electrically connected to the output terminal Tn-out, and the other end of which is electrically connected to one end of resistor R3; a resistor R4, one end of which is electrically connected to one end of resistor R3, and the other end of which is grounded; a capacitor C2, one end of which is electrically connected to the other end of resistor R3, and the other end of which is grounded; and a capacitor C3, one end of which is electrically connected to the other end of resistor R3, and the other end of which is electrically connected to terminal Tn2. Capacitor C1 and resistor R4 function as an HPF (High Pass Filter) to allow high-frequency components above the cutoff frequency of the drive signal Com to pass. Resistor R3 and capacitor C2 function as an LPF (Low Pass Filter) to allow low-frequency components below the cutoff frequency of the drive signal Com to pass. In this embodiment, the cutoff frequency of the HPF in the filter circuit 44 is set lower than the cutoff frequency of the LPF. Therefore, the filter circuit 44 allows frequency components in the drive signal Com that fall within a specified frequency band above the cutoff frequency of the HPF and below the cutoff frequency of the LPF to pass through. Furthermore, since the filter circuit 44 includes a capacitor C3, the DC component is removed from the signal in the drive signal Com that has passed through the specified frequency bands of the HPF and LPF, and the signal is fed back to terminal Tn2.

[0090] Thus, the drive signal generation unit 4 smooths the amplified signal Az at node Nd using the smoothing circuit 42 to generate the drive signal Com. The drive signal Com is integrated and subtracted by the integrator attenuator 412 and then fed back to the subtractor 404. Therefore, self-oscillation occurs at a frequency determined by the delay in the smoothing circuit 42, the delay in the integrator attenuator 812, and the transfer function of the feedback. However, because the delay of the feedback path via terminal Tn1 is large, the frequency of the self-oscillation cannot be increased to a level sufficient to ensure the accuracy of the waveform of the drive signal Com solely through feedback via terminal Tn1. In contrast, in this embodiment, in addition to the path via terminal Tn1, a path is also provided to feed back the high-frequency component of the drive signal Com via terminal Tn2, thereby reducing the overall feedback delay in the drive signal generation unit 4. That is, in this embodiment, compared to the case where there is no path via terminal Tn2, the frequency of signal As, which is the high-frequency component of the drive signal Com, added to signal Ab, can be increased, thus ensuring the accuracy of the drive signal Com.

[0091] 3. Drive signal generation unit

[0092] The following is a reference. Figure 8 and Figure 9 The following describes the drive unit 6, which includes the drive signal generation unit 4 and the power supply unit 5, and the storage unit 600 that houses the drive unit 6.

[0093] Figure 8 This is a top view of the drive unit 6 and storage unit 600 viewed from the YE1 direction towards the YE2 direction, which is opposite to the YE1 direction. Figure 9 It is along Figure 8 Cross-sectional view of the Ee line cutting drive unit 6 and storage unit 600.

[0094] Furthermore, hereinafter, the YE1 direction and its opposite direction, YE2 direction, will be collectively referred to as the "YE axis direction," the XE1 direction intersecting the YE axis direction and its opposite direction, XE2 direction, will be collectively referred to as the "XE axis direction," and the ZE1 direction intersecting both the XE and YE axis directions and its opposite direction, ZE2 direction, will be collectively referred to as the "ZE axis direction." In this embodiment, as an example, it is assumed that the XE axis direction, YE axis direction, and ZE axis direction are orthogonal to each other. However, the present invention is not limited to this arrangement. The XE axis direction, YE axis direction, and ZE axis direction can simply intersect each other. In addition, in this embodiment, the ZE1 direction is assumed to be a direction approximately parallel to the gravitational acceleration. Furthermore, the ZE1 direction can be a direction approximately parallel to the Z1 direction. Here, "approximately parallel" includes not only the case of complete parallelism but also the case where it is considered parallel considering an error. In this embodiment, "approximately parallel" includes the case where it is considered parallel if an error of about 10% is considered.

[0095] like Figure 8 and Figure 9 As shown, the storage unit 600 includes a circuit board 60 and a cover 61.

[0096] A driving unit 6 is provided on the circuit forming surface PC of the circuit board 60. Here, the circuit forming surface PC is a surface of the circuit board 60, which is the surface facing the YE1 direction among two surfaces with the YE axis direction as the normal direction.

[0097] The cover 61 is formed of metal. Specifically, the cover 61 is formed of a metal such as iron or copper that has a thermal conductivity of at least a first thermal conductivity. Here, the first thermal conductivity is, for example, 10 [W / m·K], more preferably 50 [W / m·K].

[0098] Furthermore, the cover 61 is fixed to the circuit board 60 by screws 69 and adhesive in a manner that it is connected to the circuit forming surface PC of the circuit board 60. Additionally, the cover 61 has a shape that protrudes from near its center in the ZE axis direction toward the YE1 direction. Therefore, by fixing the cover 61 to the circuit board 60, a space SP is formed between the cover 61 and the circuit board 60.

[0099] In addition, the cover 61 includes a heat sink 62. Specifically, the heat sink 62 is installed in the portion of the cover 61 located in the ZE2 direction relative to the space SP.

[0100] Coolant LQ is stored in the space SP. In this embodiment, the coolant LQ is stored in the space SP such that its surface is positioned further in the Z2 direction than the ZE2 direction end of the drive unit 6 housed in the space SP. That is, in this embodiment, the coolant LQ is positioned in the space SP such that its surface is positioned further in the Z2 direction than the Z2 direction end of the circuit board 60 where the drive unit 6 is located, i.e., the circuit arrangement portion 601. Hereinafter, the space in the space SP in which the coolant LQ is stored is referred to as partial space SP-L. In addition, the space in the space SP located further in the ZE2 direction than the surface of the coolant LQ, i.e., the space from which partial space SP-L is removed, is referred to as partial space SP-G. Furthermore, in this embodiment, even when the posture of the inkjet printer 1 changes, the coolant LQ is sealed within the space SP in a manner that prevents the coolant LQ from leaking to the outside of the space SP.

[0101] Here, coolant LQ refers to the liquid used to cool drive unit 6. More specifically, coolant LQ is, for example, a liquid with a thermal conductivity of at least a second thermal conductivity and is an insulating liquid. Here, the second thermal conductivity is, for example, 0.09 [W / m·K], more preferably 0.13 [W / m·K].

[0102] Furthermore, the coolant LQ has the property of boiling or evaporating into gas GQ at a reference temperature Tb based on the operating temperature Td of the drive unit 6. In this embodiment, the gas GQ is also sealed within the space SP, just like the coolant LQ.

[0103] Here, the operating temperature Td refers to either the operating temperature Td1 of the drive signal generation unit 4 when it generates the drive signal Com, or the operating temperature Td2 of the power supply unit 5 when it supplies power to one or both of the head unit 3 and the drive signal generation unit 4, or a temperature determined based on these two operating temperatures Td1 and Td2. The temperature determined based on operating temperatures Td1 and Td2 can be the lower of Td1 and Td2, the higher of Td1 and Td2, or the average of Td1 and Td2.

[0104] In addition, the reference temperature Tb refers to, for example, the same temperature as the operating temperature Td, or the temperature between the ambient temperature of the inkjet printer 1 and the operating temperature Td.

[0105] Furthermore, the coolant LQ is a liquid with a viscosity of at least a specified viscosity. Here, the specified viscosity means, for example, a viscosity higher than that of water.

[0106] In this embodiment, when the drive unit 6 is driven, the coolant LQ boils or evaporates due to heat from the drive unit 6, thus becoming gas GQ. Then, the gas GQ is cooled and condensed by the radiator 62, returning to coolant LQ. That is, according to this embodiment, the drive unit 6 is cooled by repeatedly performing a cycle consisting of the process of coolant LQ becoming gas GQ due to heat from the drive unit 6 and the process of gas GQ becoming coolant LQ again due to cooling by the radiator 62. Therefore, according to this embodiment, since it is not necessary to provide a structure for circulating coolant LQ, compared to a structure that requires circulating coolant LQ, the drive unit 6 can be miniaturized, thereby enabling the inkjet printer 1 to be miniaturized.

[0107] Furthermore, according to this embodiment, the entire drive unit 6 and the circuit configuration portion 601 in the circuit board 60 are covered by coolant LQ. Therefore, according to this embodiment, the adhesion of dust to the drive unit 6 can be suppressed, and the adhesion of mist floating within the housing 100 to the drive unit 6 can be suppressed. Thus, according to this embodiment, compared to a drive unit 6 not being covered by coolant LQ, the possibility of short circuits or leakage caused by mist adhesion in the drive unit 6 can be reduced.

[0108] Furthermore, in this embodiment, coolant LQ is an example of "cooling liquid", space SP is an example of "liquid storage space", and cover 61 is an example of "storage mechanism".

[0109] 5. Summary of Implementation Methods

[0110] As described above, the inkjet printer 1 according to this embodiment includes: a head unit 3 that ejects ink to form an image on recording paper PP; a circuit board 60 that is provided with a drive unit 6 for driving the head unit 3; and a cover 61 for storing coolant LQ in a space SP. The cover 61 stores coolant LQ in the space SP in such a way that the entire drive unit 6 and the circuit configuration portion 601 of the circuit board 60 in which the drive unit 6 is provided are immersed in coolant LQ.

[0111] Therefore, according to this embodiment, the adhesion of ink floating in the inkjet printer 1 to the fogging drive unit 6 can be suppressed.

[0112] Alternatively, in this embodiment, the driving unit 6 may include a power supply unit 5 that supplies power to the head unit 3.

[0113] Therefore, according to this embodiment, it is possible to suppress the adhesion of ink floating in the inkjet printer 1 to the power supply unit 5.

[0114] Alternatively, in this embodiment, the driving unit 6 may include a driving signal generation unit 4 that generates the driving signal Com of the driving head unit 3.

[0115] Therefore, according to this embodiment, the adhesion of ink floating in the inkjet printer 1 to the fog direction drive signal generation unit 4 can be suppressed.

[0116] Alternatively, in this embodiment, the cover 61 may have a metal wall for storing coolant LQ.

[0117] Therefore, according to this embodiment, the drive unit 6 can be cooled effectively.

[0118] Alternatively, in this embodiment, the cover 61 may also have a heat sink 62 that releases heat from inside the space SP to the outside of the space SP.

[0119] Therefore, according to this embodiment, the drive unit 6 can be cooled effectively.

[0120] Alternatively, in this embodiment, the coolant LQ may be a liquid with a viscosity of a specified viscosity or higher.

[0121] Therefore, according to this embodiment, compared to the case where the coolant LQ has a viscosity lower than the specified viscosity, the possibility of coolant LQ leaking out of the space SP can be reduced.

[0122] B. Variations

[0123] The above methods can be varied. Specific variations are shown below. Two or more methods selected from the following examples can be appropriately combined without contradiction. Furthermore, for elements that function and perform the same purpose as the implementation method in the variations of the following examples, the symbols referenced in the above description are used, and their detailed descriptions are appropriately omitted.

[0124] Variation Example 1

[0125] In the above embodiments, the example illustrates a method in which the space SP formed by the cover 61 and the circuit board 60 is a closed space and the coolant LQ is sealed within the space SP, but the present invention is not limited to this method. For example, the cover 61 may also form a space SP for storing the coolant LQ between itself and the circuit board 60, so that the coolant LQ is not sealed. That is, the space SP may be a space connected to the outside of the storage unit 600.

[0126] Variation Example 2

[0127] In the above-described embodiments and variations 1, the case where the housing unit 600 includes the circuit board 60 is illustrated, but the present invention is not limited to this manner. For example, the circuit board 60 may also be disposed separately from the housing unit 600 and housed inside the housing unit 600. In this case, the space SP may also be the space inside the housing unit 600, which is the space for housing the drive signal generation unit 4, the power supply unit 5, and the circuit board 60.

[0128] Variation Example 3

[0129] In the above-described embodiments and variations 1 and 2, examples illustrate the case where the drive unit 6 housed in the space SP includes a drive signal generation unit 4 and a power supply unit 5, but the present invention is not limited to this arrangement. For example, the power supply unit 5 may be provided separately from the drive unit 6. In this case, the drive signal generation unit 4 may be housed in the space SP formed by the housing unit 600 for storing coolant LQ, without housing the power supply unit 5. Alternatively, for example, the drive signal generation unit 4 may be provided separately from the drive unit 6. In this case, the power supply unit 5 may be housed in the space SP formed by the housing unit 600 for storing coolant LQ, without housing the drive signal generation unit 4.

[0130] Furthermore, when the drive signal generation unit 4 is housed within the space SP, only the amplification circuit 41 and the smoothing circuit 42, which generate relatively more heat, can be immersed in the coolant LQ, leaving the rest of the drive signal generation unit 4 undiluted. Alternatively, when the drive signal generation unit 4 is housed within the space SP, only the amplification circuit 41, which generates relatively more heat, can be immersed in the coolant LQ, leaving the rest of the drive signal generation unit 4 undiluted. Alternatively, when the drive signal generation unit 4 is housed within the space SP, only the smoothing circuit 42, which generates relatively more heat, can be immersed in the coolant LQ, leaving the rest of the drive signal generation unit 4 undiluted.

[0131] Variation Example 4

[0132] In the above embodiments and variations 1 to 3, examples illustrate the case where the drive unit 6 housed in the space SP does not include the control unit 2, but the present invention is not limited to this manner. For example, the drive unit 6 may also include the control unit 2. In this case, the control unit 2 may be housed together with one or both of the drive signal generation unit 4 and the power supply unit 5 in the space SP formed by the housing unit 600 for storing coolant LQ.

[0133] Variation Example 5

[0134] In the above embodiments and variations 1 to 4, it is assumed that the inkjet printer 1 has four head units 3, but the present invention is not limited to this configuration. The inkjet printer 1 may have one or more but no more than three head units 3, and it may also have five or more head units 3.

[0135] Variation Example 6

[0136] In the above-described embodiments and variations 1 to 5, the inkjet printer 1 is exemplified as a serial printer, but the present invention is not limited to this configuration. The inkjet printer 1 may also be a so-called line printer in which a plurality of nozzles N are arranged in the head unit 3 in a manner that extends wider than the width of the recording paper PP.

Claims

1. A printing apparatus, characterized in that, The printing apparatus includes: A liquid nozzle ejects a printing liquid to form an image on a medium; A circuit board is provided with a drive circuit for driving the liquid nozzle; and Storage mechanism, used to store cooling liquid in liquid storage space. The storage mechanism stores the cooling liquid in the following manner: In the liquid storage space, the entire drive circuit and the circuit configuration portion of the drive circuit provided in the circuit board are immersed in the cooling liquid.

2. The printing apparatus according to claim 1, characterized in that, The drive circuit includes a power supply circuit that supplies power to the liquid nozzle.

3. The printing apparatus according to claim 1, characterized in that, The driving circuit includes a driving signal generation circuit that generates a driving signal to drive the liquid nozzle.

4. The printing apparatus according to claim 1, characterized in that, The storage mechanism has a metal wall for storing the cooling liquid.

5. The printing apparatus according to claim 1, characterized in that, The storage mechanism includes a radiator that releases heat from the liquid storage space to the outside of the liquid storage space.

6. The printing apparatus according to any one of claims 1 to 5, characterized in that, The cooling liquid is a liquid with a viscosity of at least a specified viscosity.

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