JP6127814B2 - Liquid ejection device - Google Patents

Description

  The present invention relates to a liquid ejection device that ejects liquid.

  Patent Document 1 discloses a line type recording apparatus (liquid ejection apparatus) including a full line recording head having a plurality of head units each having a predetermined number of nozzle groups and a head driver for driving the recording head. ing. In this recording apparatus, LVDS (Low Voltage Differential Signaling) technology is used for data transmission between the head driver and the recording head. The LVDS technology uses an LVDS line (differential transmission line pair) and a terminating resistor connected to the receiving end side of the LVDS line, and the differential current transmitted from the transmitting end side of the LVDS line is connected to both ends of the terminating resistor. This is a technique for transmitting data by generating a voltage.

  In the recording apparatus of Patent Document 1, each head unit of the recording head has an LVDS receiver connected in parallel to each other. The serial signal (differential signal) transmitted from the LVDS transceiver connected to the head driver can be received by the LVDS receiver of each head unit via the LVDS line.

  Patent Document 1 discloses a single termination configuration and a plurality of connections as an LVDS configuration. In the single termination configuration, an LVDS transceiver is installed at one end, an LVDS receiver is connected toward the other end, and a termination resistor is installed at the final end. The multiple connection is a configuration in which termination resistors are arranged at both ends, and an LVDS transceiver and an LVDS receiver are arranged therebetween.

JP 2008-1000048 A

  Here, a so-called serial type recording apparatus that performs recording while scanning one recording head in a direction intersecting the conveyance direction of the recording medium is known. Some of these serial recording apparatuses also use LVDS technology for data transfer between the recording head and the head driver. In this case, the above-described LVDS receiver and termination resistor are provided for this one recording head.

  By the way, from the viewpoint of reducing the manufacturing cost or the like, it is desired to divert the recording heads of a plurality of serial type recording apparatuses to the head units of the recording heads of the line type recording apparatus. However, if the recording heads of a plurality of serial type recording devices are diverted to the head unit of the recording head of the line type recording device, a termination resistor is provided for each head unit. A plurality of termination resistors are connected in parallel. As a result, problems such as a decrease in voltage level occurring at both ends of the termination resistor may occur, and the LVDS receiver of each head unit may not be able to receive differential signals normally.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid ejection apparatus that can normally receive differential signals in a plurality of head units having termination resistors.

  In order to solve the above problems, a liquid ejection apparatus according to the present invention includes a liquid ejection section for ejecting liquid and a differential including an ejection signal that is a signal for controlling ejection of liquid by the liquid ejection section. A plurality of head units each having a control circuit for receiving a signal; a transmission unit for transmitting the differential signal; and the transmission unit and the control circuits of each of the plurality of head units. A differential transmission line pair which is a pair of transmission lines for transmitting the differential signal transmitted from the transmission means to the control circuit of each of the plurality of head units, and transmitted from the transmission means. An amplification circuit for amplifying the differential signal, wherein the differential transmission line pair includes a common differential transmission line pair connected to the transmission means, the common differential transmission line pair, and the plurality of differential transmission line pairs. Head unit Each of the control circuits is connected to each other, and has a plurality of individual differential transmission line pairs connected in parallel to the common differential transmission line pair. The common differential transmission line pair is provided at a position closer to the transmission means than the position where the plurality of individual differential transmission line pairs are connected, and amplifies the differential signal transmitted from the transmission means. Each of the plurality of head units is supplied to the control circuit, and each of the plurality of head units has a termination resistor connected between the pair of individual differential transmission lines. The differential signal is received by detecting a voltage between the termination resistors.

  According to the present invention, since the differential signal is amplified by the amplifier circuit, the voltage level generated at both ends of the termination resistor can be increased. As a result, the differential signals can be normally received in the control circuits of the plurality of head units.

It is a schematic side view of an inkjet printer. It is a top view which shows the structure of an inkjet head. It is a fragmentary sectional view showing a channel of a head unit. It is an electrical block diagram of an inkjet printer. It is a circuit block diagram of driver IC. It is a figure which shows the connection structure of a control apparatus and driver IC. (A) is a figure which shows the waveform of the differential signal received by the driver IC when the amplifier circuit is not provided, and (b) is the differential signal received by the driver IC when the amplifier circuit is provided. It is a figure which shows a waveform. It is a circuit diagram of the LVDS driver of an amplifier circuit. It is a figure which shows the connection structure of the amplifier circuit and driver IC based on a modification. It is a figure which shows the waveform of the differential signal received with driver IC based on a modification.

  A schematic configuration of an inkjet printer 101 (hereinafter, printer 101) according to a preferred embodiment of the present invention will be described.

  As illustrated in FIG. 1, the printer 101 includes a rectangular parallelepiped housing 11. A paper discharge unit 15 is provided on the top plate of the housing 11. An ink jet head (hereinafter, head 1), a paper sensor 5, a platen 9, a paper feed tray 10, a transport mechanism 30, a control device 100, and the like are accommodated in the internal space of the housing 11. In the internal space of the housing 11, a conveyance path for conveying the paper P, which is a recording medium, is formed along the arrow shown in FIG. Further, a cartridge (not shown) is disposed in the housing 11 in a predetermined positional relationship with the head 1. The cartridge is connected to the head 1 via a tube (not shown) and a pump (not shown). This pump is driven when ink is forcibly sent to the head 1 (that is, when purging or initial introduction of liquid). Other than this, the pump is in a stopped state, and the pump does not disturb the ink supply to the head 1.

  As shown in FIG. 2, the head 1 includes two head substrates 4 elongated in the main scanning direction and six head units 3 that are adjacently disposed along the transport direction (sub-scanning direction). In the present embodiment, the six head units 3 are arranged in a staggered manner in the main scanning direction while being separated from each other. Specifically, the six head units 3 are divided into two groups, and the three head units 3 belonging to one group are provided on the head substrate 4 arranged on the upstream side in the transport direction, and the other group The three head units 3 belonging to are provided on a head substrate 4 arranged on the downstream side in the transport direction. The three head units 3 provided on the same head substrate 4 are arranged at the same position in the sub-scanning direction. The lower surface of each head unit 3 is a discharge surface 2 in which a plurality of discharge ports 8 are opened. The printer 101 is a line type that performs recording with the head 1 fixed. A specific configuration of the head 1 will be described in detail later.

  Returning to FIG. 1, the platen 9 is a flat plate-like member and faces the head 1 in the vertical direction. A predetermined gap suitable for image recording (image formation) is formed between the upper surface of the platen 9 and the ejection surface 2 of the head 1.

  The paper sensor 5 is disposed upstream of the head 1 in the transport direction of the paper P by the transport mechanism 30 (hereinafter simply referred to as “transport direction”). The paper sensor 5 detects the leading edge of the paper P and transmits a detection signal to the control device 100.

  The paper feed tray 10 is a box having an open top surface and is detachable from the housing 11. The paper feed tray 10 can accommodate a plurality of papers P.

  The transport mechanism 30 includes a pickup roller 31 and nip roller pairs 32 to 36. Under the control of the control device 100, the pickup roller 31 rotates by driving a paper feed motor 6 </ b> M (see FIG. 4), and sends out the uppermost paper P in the paper feed tray 10. The nip roller pairs 32 to 36 are arranged in this order from the upstream side in the transport direction along the transport path. One roller of each of the nip roller pairs 32 to 36 is a driving roller that is rotated by driving of the transport motor 7M (see FIG. 4) under the control of the control device 100. The other roller is a driven roller that rotates as the drive roller rotates.

  Under the control of the control device 100, the paper P sent out from the paper feed tray 10 by the pickup roller 31 is transported along the transport direction while being sandwiched between the nip roller pairs 32 to 36. When the paper P passes underneath each head unit 3 while being supported on the upper surface of the platen 9, black ink is discharged from the discharge port 8 (see FIG. 2) toward the surface of the paper P under the control of the control device 100. Is done. The ink ejection operation from the ejection port 8 is performed based on the detection signal transmitted from the paper sensor 5. The paper P on which the image is formed is discharged to the paper discharge unit 15 through the opening formed in the upper portion of the housing 11.

  Next, a specific configuration of the head 1 will be described with reference to FIGS. 2 and 3. FIG. 2 also shows a connection configuration between each head unit 3 and the control device 100.

  Each of the six head units 3 is an ink-jet head (recording head) used in a so-called serial-type ink-jet printer that performs recording while scanning in a direction crossing the transport direction of the paper P. The six head units 3 have the same configuration as each other. As shown in FIG. 3, the flow path unit 20, the actuator unit 24, the two driver ICs 25 (25a, 25b) (see FIG. 2), and A reservoir unit (not shown) is included. The reservoir unit is formed with a common liquid flow path including a reservoir for temporarily storing ink, and ink is supplied from the cartridge.

  The flow path unit 20 has a structure in which four metal plates 20a, 20b, 20c, and 20d are laminated, and an ink flow path is formed therein. The ink flow path includes one manifold flow path 21 and a plurality of individual flow paths 22 branched from the manifold flow path 21. The individual flow path 22 is provided for each discharge port 8, and reaches from the outlet of the manifold flow path 21 to the discharge port 8 via the pressure chamber 23. A plurality of discharge ports 8 are opened on the lower surface of the flow path unit 20. The plurality of ejection ports 8 constitute a plurality of ejection port arrays that extend in the main scanning direction and are arranged in the sub scanning direction. The plurality of pressure chambers 23 communicate with the plurality of discharge ports 8, respectively. The ink supplied from the reservoir unit to the manifold channel 21 is ejected from the ejection port 8 through the individual channel 22.

  The actuator unit 24 is disposed on the upper surface of the flow path unit 20 so as to cover the plurality of pressure chambers 23, and is disposed on the upper surface of the vibration plate 26 so as to face the plurality of pressure chambers 23. A piezoelectric layer 27 and a plurality of individual electrodes 28 disposed on the upper surface of the piezoelectric layer 27 are provided.

  The diaphragm 26 is a substantially rectangular metal plate in plan view. The diaphragm 26 is joined to the flow path unit 20 in a state of covering the plurality of pressure chambers 23. In addition, the upper surface of the conductive diaphragm 26 is disposed on the lower surface side of the piezoelectric layer 27, thereby generating an electric field in the thickness direction in the piezoelectric layer 27 between the plurality of individual electrodes 28 on the upper surface. Also serves as an electrode. The diaphragm 26 as the common electrode is connected to the ground of the driver IC 25 and is always held at the ground potential.

  The piezoelectric layer 27 is made of a piezoelectric material mainly composed of lead zirconate titanate (PZT), which is a solid solution of lead titanate and lead zirconate and is a ferroelectric substance. The piezoelectric layer 27 is continuously formed across the plurality of pressure chambers 23 on the upper surface of the diaphragm 26. The piezoelectric layer 27 is polarized in the thickness direction at least in a region facing the pressure chamber 23.

  A plurality of individual electrodes 28 are respectively disposed in regions on the upper surface of the piezoelectric layer 27 facing the plurality of pressure chambers 23. The plurality of individual electrodes 28 are fixed to the upper surface of the piezoelectric layer 27 and face each of the plurality of pressure chambers 23.

  The actuator unit 24 is connected to two driver ICs 25 (25a, 25b) mounted on a flexible printed circuit board (FPC). Further, the two driver ICs 25 are connected to the control device 100. As will be described in detail later, the two driver ICs 25 have pulse-shaped drive waveforms generated based on various signals (CLK, FIRE, and SIN: details of each signal will be described later) transmitted from the control device 100. A drive signal is supplied to each of the plurality of individual electrodes 28 of the actuator unit 24. That is, the potential of the individual electrode 28 is switched between a predetermined drive potential corresponding to the pulse height and the ground potential according to the drive waveform. Of course, the individual electrodes 28 to be driven are different between the two driver ICs 25. One driver IC 25a is connected to a part of the plurality of individual electrodes 28 of the actuator unit 24, and the other driver IC 25a. IC 25 b is connected to the remaining individual electrode 28.

  Next, the operation of the actuator unit 24 during ink ejection will be described. When a drive signal is supplied from a driver IC 25 to a certain individual electrode 28 and a driving potential is applied to the individual electrode 28, the individual electrode 28 is applied as a common electrode held at the ground potential. A potential difference is generated between the diaphragm 26 and an electric field in the thickness direction acts on the piezoelectric layer 27 sandwiched between the individual electrode 28 and the diaphragm 26. Since the direction of the electric field is parallel to the polarization direction of the piezoelectric layer 27, the active portion of the piezoelectric layer 27 contracts in the plane direction perpendicular to the thickness direction. Here, since the lower diaphragm 26 of the piezoelectric layer 27 is fixed to the upper surface of the flow path unit 20, as the piezoelectric layer 27 positioned on the upper surface of the diaphragm 26 contracts in the surface direction, The portion of the diaphragm 26 that covers the pressure chamber 23 is deformed so as to protrude toward the pressure chamber 23 (unimorph deformation). At this time, since the volume in the pressure chamber 23 decreases, the ink pressure in the pressure chamber 23 rises, and ink is ejected from the ejection port 8 communicating with the pressure chamber 23. In the present embodiment, the actuator unit 24 corresponds to the liquid discharge unit of the present invention, and the driver IC 25 corresponds to the control circuit of the present invention.

  Note that the printer 101 of the present embodiment has three types of droplet sizes (droplet volumes) ejected from each ejection port 8 in order to realize high-quality image recording by enabling multi-tone expression. You can choose from. That is, one discharge mode can be selectively selected from a total of four types of discharge modes, that is, a mode in which droplets are not discharged to one discharge port 8 and a mode in which three types of droplet volumes are different. Has been.

  Next, the electrical configuration of the printer 101 will be described with reference to FIGS.

  As shown in FIG. 4, the control device 100 includes a CPU (Central Processing Unit) 50, a ROM (Read Only Memory) 51, a RAM (Random Access Memory) 52, an ASIC (Application Specific Integrated Bus) 54, and the like. . The ROM 51 stores programs executed by the CPU 50, various fixed data, and the like. The RAM 52 temporarily stores data (such as image data) necessary for program execution. The ASIC 53 includes a head control circuit 55 and a transport control circuit 56. The ASIC 53 is connected to an external device 59 such as a PC (Personal Computer) via an input / output I / F (Interface) 58 so that data communication is possible. The head control circuit 55 controls the driver IC 25 based on a recording instruction (including image data) input from the external device 59. The transport control circuit 56 controls the paper feed motor 6M and the transport motor 7M based on the recording instruction input from the external device 59.

  The head control circuit 55 includes a control signal generation circuit 55a and a control signal output circuit 55b. The control signal generation circuit 55 a generates ejection signals such as FIRE, SIN, and CLK that are signals for controlling the actuator unit 24 based on the image data stored in the RAM 52. FIRE is a signal indicating four types of waveform data respectively corresponding to the four types of ejection modes described above. SIN is a control signal for controlling the operation of the head unit 3, and specifically, one type of waveform data is selected from the four types of FIRE waveform data for each discharge cycle of each discharge port 8. It is a waveform data selection signal for making it occur. CLK is a data transfer clock from the head control circuit 55 to the driver IC 25. The ejection cycle is the time required for the paper P to move relative to the head 1 by a unit distance corresponding to the resolution of the image recorded on the paper P.

  The control signal output circuit 55b outputs a variety of signals such as FIRE, SIN, and CLK generated by the control signal generation circuit 55a to each of the head units 3 and outputs them to a total of twelve driver ICs 25. It is a transmission circuit. Here, since FIRE and CLK are commonly used in each of the twelve driver ICs 25, these signals are commonly input to the twelve driver ICs 25 from the control signal output circuit 55b. Signal. In contrast, SIN is a signal that is individually input to the twelve driver ICs 25 from the control signal output circuit 55b. In the present embodiment, the control signal output circuit 55b corresponds to the transmission means of the present invention.

  The FIRE is output from the control signal output circuit 55b to each of the twelve driver ICs 25 via the FIRE signal line 40 (see FIG. 2). The FIRE signal line 40 is connected to the control signal output circuit 55b as a single signal line, but branches to 12 signal lines on the way to the 12 driver ICs 25, and these 12 signal lines. Are connected to each of the twelve driver ICs 25. CLK is output from the control signal output circuit 55b to each of the twelve driver ICs 25 via a CLK signal line 45 (see FIG. 5; not shown in FIG. 2) having substantially the same configuration as the FIRE signal line 40. .

  The SIN is output from the control signal output circuit 55b to each of the 12 driver ICs 25 via the SIN signal line 46 (see FIG. 2). The SIN signal line 46 individually connects the control signal output circuit 55b and each of the twelve driver ICs 25, and is connected to the control signal output circuit 55b as twelve signal lines. A signal line is connected to each of the 12 driver ICs 25.

  Note that FIRE, SIN, and CLK are output from the control signal output circuit 55b to each of the twelve driver ICs 25 as pulse-like differential signals via signal lines. That is, in FIG. 2, each signal line 40, 45, 46 is shown by one line, but each of these signal lines 40, 45, 46 is constituted by a pair of transmission lines. In FIG. 2, the FIRE differential signal is indicated as FIRE (+, −), the SIN differential signal is indicated as SIN (+, −), and the CLK differential signal is indicated as CLK (+, −). In the differential method, signals having opposite phases (H signal and L signal) are input to one and the other of the pair of transmission lines. The differential method is more resistant to noise than the single-ended method in which a signal is input with only one transmission line, and even a signal with a reference voltage (for example, 1.25 V) and a small amplitude (for example, a differential voltage of 300 mV). Can be transmitted.

  Next, the driver IC 25 will be described in detail with reference to FIG. The twelve driver ICs 25 provided in each of the six head units 3 have the same configuration, and as shown in FIG. 5, each of the receiving circuits 61a, 61b, 61c, the shift register 62, and the latch circuit, respectively. 63, a multiplexer 64, a drive buffer 65, a command detection unit 66, and a FIRE restoration circuit 67.

  Receiving circuits 61a, 61b, and 61c receive FIRE, SIN, and CLK differential signals, respectively, and convert them into serial data. The shift register 62 converts the serial data for each ejection port 8 related to the SIN input from the receiving circuit 61b into parallel data, and inputs the parallel data to the latch circuit 63 in synchronization with CLK. The latch circuit 63 is a so-called D-flip-flop, and inputs the parallel data input from the shift register 62 to the multiplexer 64 all at once in synchronization with an STRB signal described later. The multiplexer 64 selects a waveform pattern of the drive signal from a plurality of waveform patterns based on the data input from the latch circuit 63, generates a waveform signal, and inputs the waveform signal to the drive buffer 65. The drive buffer 65 amplifies the waveform signal input from the multiplexer 64 to generate a drive signal, and inputs the drive signal to each individual electrode 28 of the actuator unit 24.

  The command detection unit 66 includes a shift register 66a that converts serial data for each discharge port 8 related to SIN input from the reception circuit 61b into parallel data, and a logic circuit 66b that receives the parallel data from the shift register 66a. Including. Further, a special signal different from SIN is input to the logic circuit 66b. When the special signal is input, the logic circuit 66b outputs the STRB signal input to the latch circuit 63.

  The FIRE restoration circuit 67 converts the serial data related to FIRE input from the reception circuit 61 a into four parallel data that is the same as the number of waveform patterns of the drive signal in synchronization with the CLK, and sends the parallel data to the multiplexer 64. input.

  Next, a connection configuration between the control device 100 and the driver IC 25 will be described with reference to FIGS. 6 and 7. In FIG. 6, only the receiving circuit 61 a is illustrated as a component of the driver IC 25 for convenience of explanation. In the following, only the connection configuration between the control signal output circuit 55b and the twelve driver ICs 25 related to transmission / reception of FIRE will be described.

  As shown in FIG. 6, the FIRE signal line 40 connects the common differential transmission line pair 41 connected to the control signal output circuit 55b, and the common differential transmission line pair 41 and each of the twelve driver ICs 25. And 12 individual differential transmission line pairs 42. The twelve individual differential transmission line pairs 42 are connected in parallel to the common differential transmission line pair 41.

  The common differential transmission line pair 41 includes a first common differential transmission line pair 41a connected to the control signal output circuit 55b and the group of the head units 3 connected to the first common differential transmission line pair 41a. There are two second common differential transmission line pairs 41b corresponding to the number. Each of the two second common differential transmission line pairs 41b is connected to six individual differential transmission line pairs 42 connected to the driver IC 25 of the head unit 3 belonging to the same group. The six individual differential transmission line pairs 42 are sequentially connected (bus type connection) to the second common differential transmission line pair 41b. That is, the six individual differential transmission line pairs 42 are respectively connected to different positions (connection points) in the second common differential transmission line pair 41b.

  An amplification for amplifying the differential signal is provided at a position closer to the control signal output circuit 55b than a position where the individual differential transmission line pair 42 is connected in each of the two second common differential transmission line pairs 41b. A circuit 70 is provided. The amplifier circuit 70 is provided on each of the two head substrates 4. In the second common differential transmission line pair 41b, some transmission line pairs arranged between the connection position of the first common differential transmission line pair 41a and the position where the amplifier circuit 70 is provided are flexible. It is formed on a flat cable (FFC) 43. The amplifier circuit 70 will be described in detail later.

  The reception circuit 61 a of each driver IC 25 includes a termination resistor 75 connected between the individual differential transmission line pair 42 and an LVDS reception circuit 76. The LVDS reception circuit 76 detects the voltage difference between the termination resistors 75, thereby converting the differential signal output from the control signal output circuit 55b into serial data.

  By the way, the LVDS receiving circuit 76 is standardized so that it can receive a differential signal having an amplitude Vp centered on a predetermined reference voltage Vref. The control signal output circuit 55b is a differential signal having an amplitude Vp centered on the reference voltage Vref in the LVDS receiving circuit 76, assuming that only one termination resistor is connected to the FIRE signal line 40. The differential signal is output to the FIRE signal line 40 so as to be received.

  Here, as described above, in this embodiment, the termination resistor 75 is connected between each of the individual differential transmission line pairs 42 of the FIRE signal line 40. That is, a plurality of termination resistors 75 are connected in parallel to the control signal output circuit 55b. For this reason, the signal voltage of the differential signal output from the control signal output circuit 55b is divided by the plurality of termination resistors. Therefore, as shown in FIG. The voltage level of the center voltage Vc of the differential signal received at 1 is lower than the reference voltage Vref, and the amplitude Vn of the differential signal is also smaller than the amplitude Vp. For this reason, each LVDS receiving circuit 76 cannot normally receive the differential signal. In addition, the differential signal output from the control signal output circuit 55b is output to the driver IC 25 through the individual differential transmission line pair 42 after passing through the transmission line pair formed on the relatively long FFC 43. When the differential signal transmission path from the control signal output circuit 55b to the driver IC 25 is long as described above, the waveform of the differential signal may be disturbed by noise or the like as shown in FIG.

  Therefore, in the present embodiment, the amplifier circuit 70 is configured to amplify the differential signal output from the control signal output circuit 55b and supply it to the receiving circuits 61a of the plurality of head units 3. And the amplifier circuit 70 is provided in the connection position side with the separate differential transmission line pair 42 rather than the transmission line pair formed on FFC43 in each 2nd common differential transmission line pair 41b.

  As shown in FIG. 6, the amplifier circuit 70 is an LVDS buffer (differential amplifier circuit) including a termination resistor 71 connected between the second common differential transmission line pair 41b and an LVDS driver 72. As shown in FIG. 8, the LVDS driver 72 includes input terminals 72a and 72b, output terminals 72c and 72d, transistors M1 to M4, and bias circuits 73 and 74. A first signal Vin1 and a second signal Vin2 that are output from the control signal output circuit 55b and transmitted through one and the other transmission lines of the second common differential transmission line pair 41b are input to the input terminals 72a and 72b. . Each of the bias circuits 73 and 74 is a circuit for applying a bias voltage. The bias circuit 73 is disposed on the high potential side and generates a bias voltage Vbias_H. The bias circuit 74 is disposed on the low potential side and generates a bias voltage Vbias_L.

  Between the bias circuit 73 and the bias circuit 74, a series circuit composed of the transistors M1 and M2 and a series circuit composed of the transistors M3 and M4 are connected in parallel to each other. The transistors M1 and M3 are PMOS transistors, and the transistors M2 and M4 are NMOS transistors. The gates of the transistors M1 and M2 are connected to the input terminal 72a, and the gates of the transistors M3 and M4 are connected to the input terminal 72b. A connection point between the transistors M1 and M2 is connected to the output terminal 72c, and a connection point between the transistors M3 and M4 is connected to the output terminal 72c.

  In the above configuration, when the first signal Vin1 input to the input terminal 72a is at a high level (H signal) and the second signal Vin2 input to the input terminal 72b is at a low level (L signal), the transistor M2 Then, the transistor M3 is turned on, and a current flows in a direction returning from the output terminal 72d to the output terminal 72d through the terminating resistor 75 of the receiving circuit 61a of each driver IC 25. On the other hand, when the first signal Vin1 input to the input terminal 72a is at a low level and the second signal Vin2 input to the input terminal 72b is at a high level, the transistors M1 and M4 are turned on. A current flows in a direction returning from the output terminal 72c to the output terminal 72d through the terminating resistor 75 of the receiving circuit 61a of each driver IC 25. As a result, a differential signal is generated at both ends of the termination resistor 75.

  Next, optimization conditions for the bias voltage Vbias_H generated in the bias circuit 73 and the bias voltage Vbias_L generated in the bias circuit 74 will be described.

  As described above, the LVDS receiver circuit 76 is standardized so that it can receive a differential signal having an amplitude Vp centered on the reference voltage Vref. Therefore, the amplifier circuit 70 outputs the differential signal output from the control signal output circuit 55b so that the differential signal received by each LVDS receiver circuit 76 becomes a differential signal having an amplitude Vp centered on the reference voltage Vref. The signal may be amplified, that is, the reference voltage Vref_O and the amplitude Vp_O of the differential signal output from the output terminals 72c and 72d of the amplifier circuit 70 may be optimized. The optimization conditions for the reference voltage Vref_O and the amplitude Vp_O can be calculated by the following equations 1 and 2 based on the relationship between the output resistance of the amplifier circuit 70 and the combined resistance of the termination resistor 75.

Vref_O = Vref × (Rout + Rt / n) / (Rt / n) Equation 1
Vp_O = Vp × (Rout + Rt / n) / (Rt / n) Equation 2

Here, Rout is an output resistance of the amplifier circuit 70.
Rt is the resistance value of each termination resistor 75.
n is the number of driver ICs 25 of the head unit 3 belonging to the same group (the number of parallel termination resistors 75).

  The optimization conditions for the bias voltage Vbias_H and the bias voltage Vbias_L can be calculated by the following expressions 3 and 4 using the reference voltage Vref_O and the amplitude Vp_O calculated by the expressions 1 and 2.

Vbias_H = Vref_O + Vp_O / 2 Equation 3
Vbias_L = Vref_O-Vp_O / 2 Equation 4

  The bias voltage Vbias_H and the bias voltage Vbias_L calculated as described above are generated in the bias circuits 73 and 74, so that the voltage levels of the voltages generated at both ends of the termination resistor 75 of the driver IC 25 of each head unit 3 can be obtained. When the assumption is that only one termination resistor 75 is connected between the FIRE signal lines 40 for the plurality of head units 3, the voltage level of the voltage generated at both ends of the termination resistor 75 is the same. Can do. That is, as shown in FIG. 7B, the differential signal received by each LVDS receiving circuit 76 can be a differential signal having an amplitude Vp with the reference voltage Vref as the center. As a result, each LVDS receiving circuit 76 can normally receive the differential signal output from the control signal output circuit 55b. In addition, the amplifier circuit 70 is provided on the connection position side with the individual differential transmission line pair 42 rather than the transmission line pair formed on the FFC 43 in each second common differential transmission line pair 41b. Therefore, even if the waveform of the differential signal output from the control signal output circuit 55 b is disturbed when transmitted through the transmission line pair formed on the FFC 43, the waveform can be adjusted in the amplifier circuit 70. Thereby, it can suppress that the waveform of the differential signal received in the receiving circuit 61a of each driver IC25 is disturbed. In FIG. 7B, the solid line indicates the waveform of the differential signal received by the receiving circuit 61a of the driver IC 25 that is the closest to the amplifier circuit 70, and the dotted line is the driver IC 25 that is the farthest from the amplifier circuit 70. The waveform of the differential signal received in the receiving circuit 61a is shown.

  Here, when the differential signal is amplified by the amplifier circuit 70, the value of the current flowing through the second common differential transmission line pair 41b is also amplified, so that the noise generated during the differential signal transmission also increases. As a result, the waveform of the differential signal received by each driver IC 25 is disturbed. However, in the present embodiment, as described above, the six head units 3 are divided into two groups, and the amplifier circuit 70 is provided in each of the two second common differential transmission line pairs 41b corresponding to each group. Is provided. For this reason, since the amplification width for amplifying the differential signal in each amplifier circuit 70 can be reduced, it is possible to suppress the waveform of the differential signal received in each driver IC 25 from being disturbed.

  As described above, according to the present embodiment, since the differential signal output from the control signal output circuit 55b is amplified by the amplifier circuit 70, the voltage level generated at both ends of the termination resistor 75 of each driver IC 25 can be increased. As a result, the differential signals can be normally received in the driver ICs 25 of the plurality of head units 3.

  Next, a modified example of the present embodiment will be described with reference to FIG. 7B, FIG. 9 and FIG. In FIG. 9, for convenience of explanation, one transmission line of the FIRE signal line 40 is shown by a dotted line. In the above-described embodiment, each individual differential transmission line pair 42 is sequentially connected (bus type connection) to the second common differential transmission line pair 41b. That is, the distance between the driver IC 25 and the amplifier circuit 70 is different for each driver IC 25. In such a configuration, as shown in FIG. 7B, in the driver IC 25 having the shortest distance from the amplifier circuit 70, a part of the differential signal is reflected due to impedance mismatch or the like compared to the other driver ICs 25. Resulting in increased noise. In addition, as described above, when the differential signal is amplified by the amplifier circuit 70, noise generated during transmission of the differential signal also increases. Since the influence of this noise is particularly received by the driver IC 25 having the shortest distance from the amplifier circuit 70, there is a possibility that the driver IC 25 cannot normally receive the differential signal.

  Therefore, in this modified example, as shown in FIG. 9, a plurality of individual differential transmission line pairs 42 are connected to a certain connection point 44 in the second common differential transmission line pair 41b and the heads belonging to the same group. It is configured to connect the driver IC 25 of each unit 3. As a result, as shown in FIG. 10, the noise of the differential signal received by each driver IC 25 is converted into the differential signal received by the driver IC 25 having the closest distance from the amplifier circuit 70 when the bus connection is made. It can be made smaller than noise.

  In the present modification, the connection point 44 is arranged in the vicinity of the output terminals 72c and 72d of the amplifier circuit 70 in the second common differential transmission line pair 41b. As a result, the length of the transmission path between the amplifier circuit 70 and the connection point 44 through which a current having a current value obtained by adding the current values of the currents flowing through the individual differential transmission line pairs 42 can be shortened. Noise generated during transmission of differential signals can be reduced. Further, in this modification, the amplifier circuit 70 is arranged at the center of the head substrate 4 in the main scanning direction, and the connection point 44 is also arranged at the center of the head substrate 4 in the main scanning direction. Thereby, the lengths of the six individual differential transmission line pairs 42 can be made equal to each other and shortened. As a result, the influence of noise received by each driver IC 25 can be reduced.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. For example, in the above-described embodiment, the six head units 3 are divided into two groups, but may be divided into a group number smaller than the total number. For example, when each of the plurality of head units 3 is disposed at any of three or more different positions in the transport direction, the plurality of head units 3 may be grouped into three or more groups. . In this case, each of the plurality of head units 3 is disposed at the same position in the transport direction as the head units 3 belonging to the same group, and is disposed at a position different in the transport direction from the head units 3 belonging to different groups. Become. In addition, as many second common differential transmission line pairs 41b as the number of groups are provided, and each of the second common differential transmission line pairs 41b is connected to the driver IC 25 of a plurality of head units 3 belonging to the same group. The dynamic transmission line pair 42 is connected. And it is preferable to provide the amplifier circuit 70 in each 2nd common differential transmission line pair 41b.

  The plurality of head units 3 may not be grouped. That is, the common differential transmission line pair 41 does not include the second common differential transmission line pair 41b, and the twelve individual differential transmission line pairs 42 include one first common differential transmission line pair. It may be connected to 41a. In this case, one amplifier circuit 70 is provided for the first common differential transmission line pair 41a.

  In the above-described embodiment, each driver unit 3 is provided with two driver ICs 25. However, only one driver IC 25 may be provided, or three or more driver ICs 25 may be provided. .

  In the above-described embodiment, the number of head units 3 is six. However, the number of head units 3 is not limited to this and may be plural.

  In this embodiment, the present invention is applied to an ink jet printer that records an image or the like by ejecting ink onto a sheet. However, the application target of the present invention is to be used for such an application. Not limited. That is, the present invention can be applied to various droplet discharge devices that discharge various types of liquids other than ink to a target depending on the application.

24 Actuator unit (liquid discharge part)
25 Driver IC (control circuit)
40 FIRE signal line (differential transmission line pair)
41 Common differential transmission line pair 42 Individual differential transmission line pair 45 Signal line for CLK (differential transmission line pair)
70 Amplifying circuit 75 Termination resistor 101 Inkjet printer (liquid ejection device)

Claims (7)

A plurality of head units comprising: a liquid ejection unit for ejecting liquid; and a control circuit for receiving a differential signal including an ejection signal that is a signal for controlling ejection of the liquid by the liquid ejection unit;
Transmitting means for transmitting the differential signal;
The transmission unit is connected to the control circuit of each of the plurality of head units, and the differential signal transmitted from the transmission unit is transmitted to the control circuit of each of the plurality of head units. A differential transmission line pair, which is a pair of transmission lines;
An amplification circuit for amplifying the differential signal transmitted from the transmission means,
The differential transmission line pair is:
A common differential transmission line pair connected to the transmission means;
The common differential transmission line pair is connected to the control circuit of each of the plurality of head units, and a plurality of individual differential transmission line pairs connected in parallel to the common differential transmission line pair. And
The amplifying circuit is provided at a position closer to the transmitting means than the position where the plurality of individual differential transmission line pairs are connected in the common differential transmission line pair, and the differential circuit is transmitted from the transmitting means. For amplifying a signal and supplying it to the control circuit of each of the plurality of head units,
The control circuit of each of the plurality of head units is
A termination resistor connected between the individual differential transmission line pair;
The liquid ejection apparatus, wherein the differential signal is received by detecting a voltage between the terminal resistors.   In the amplifier circuit, the voltage level of the voltage generated at both ends of the termination resistor of the control circuit of each of the plurality of head units is such that only one termination resistor for the plurality of head units is the differential transmission line pair. 2. The liquid ejection according to claim 1, wherein the differential signal is amplified so as to be equal to a voltage level of a voltage generated at both ends of the terminal resistor when it is assumed that the terminal resistor is connected between the two. apparatus.   2. The plurality of individual differential transmission line pairs are respectively connected to a certain connection point in the common differential transmission line pair and the control circuit of each of the plurality of head units. Or the liquid discharge apparatus of 2.   The liquid ejection device according to claim 3, wherein the plurality of individual differential transmission line pairs have the same length. The plurality of head units are divided into groups having a smaller number of groups than the total number of the head units,
The common differential transmission line pair is:
A first common differential transmission line pair connected to the transmission means;
A second common differential transmission line pair for the number of groups connected to the first common differential transmission line pair;
Each of the second common differential transmission line pairs is connected to the individual differential transmission line pair connected to the control circuit of the head unit belonging to the same group,
The amplifier circuit has the number of the groups,
2. The amplifier circuit according to claim 1, wherein each of the second common differential transmission line pairs is provided at a position closer to the transmission means than a position where the individual differential transmission line pair is connected. The liquid discharge apparatus as described in any one of -4. A transport mechanism for transporting the recording medium along the transport direction;
The liquid ejecting apparatus according to claim 1, wherein each of the plurality of head units is arranged in a direction orthogonal to the transport direction. A transport mechanism for transporting the recording medium along the transport direction;
Each of the plurality of head units is disposed at the same position in the transport direction as the head units belonging to the same group, and is disposed at a position different in the transport direction from the head units belonging to different groups. The liquid discharge apparatus according to claim 1, wherein the liquid discharge apparatus is a liquid discharge apparatus.

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