Patent Description:
The present disclosure relates to a print head drive circuit for controlling a stable drive of a print head provided with multiple piezoelectric elements, and a printing apparatus.

As a printing apparatus such as an ink jet printer, there is known a so-called piezoelectric printing apparatus that forms characters and images on a medium by driving a drive element including a piezoelectric element provided in a print head by a drive signal and ejecting a liquid such as an ink filled in a cavity from a nozzle by driving the drive element. An example of an ink jet printer is described in <CIT>.

In addition, as such a piezoelectric printing apparatus, there is known a printing method provided with a unimorph type drive element capable of forming a high-density ejection portion by sandwiching the piezoelectric element between two electrodes, and a printing method capable of increasing the drive amount of the drive element as compared with the printing method including the unimorph type drive element by providing a laminated drive element formed by stacking a piezoelectric element and an electrode in multiple layers as illustrated in <CIT>, and capable of increasing the amount of liquid ejected per unit drive of a drive element.

In addition, in <CIT>, a piezoelectric printing apparatus capable of producing a multi-gradation printed matter by arranging drive elements including a piezoelectric element at a high density, and a format of a data signal including information for producing a printed matter used in the printing apparatus are disclosed.

In recent years, there is an increasing market demand for increasing productivity in the piezoelectric printing apparatus as described in <CIT> and <CIT>. In response to such market demands, in the piezoelectric printing apparatus, it is required to increase the number of nozzles included in the print head and the number of drive elements including the piezoelectric element for driving the nozzles, and to increase the amount of liquid ejected per unit drive of the drive elements.

In order to increase the amount of liquid ejected per unit drive of the drive element including the piezoelectric element, it is necessary to drive the drive element to a large extent, and therefore it is necessary to supply a larger amount of current to the drive element. However, when a large amount of current is supplied to the drive element including the piezoelectric element, the influence of noise generated by the current increases. When the noise is superimposed on the data signal including the information for producing the printed matter, there is a possibility that malfunction of the printing apparatus may be generated.

In particular, when one print head includes <NUM> or more nozzles and a piezoelectric element, the amount of current supplied to the print head increases, the amount of information included in the data signal for producing printed matter also increases, and there is a significant possibility that malfunction of the printing apparatus may be generated.

According to an aspect of the present disclosure, there is provided a print head drive circuit according to claim <NUM>.

According to another aspect of the present disclosure, there is provided a printing apparatus according to claim <NUM>.

Hereinafter, preferred embodiments of the present disclosure will be described with reference to the drawings. The drawings used are for convenience of description. The embodiments described below do not unreasonably limit the contents of the present disclosure described in the aspects. In addition, not all of the configurations described below are essential constituent requirements of the present disclosure.

<FIG> is a diagram illustrating a schematic configuration of a printing apparatus <NUM>. The printing apparatus <NUM> of the present embodiment is described by exemplifying a serial printing type ink jet printer that forms an image on a medium P by reciprocating a carriage <NUM> on which a print head <NUM> that ejects an ink as an example of a liquid is mounted and ejecting the ink onto a transported medium P. In the following description, a direction where the carriage <NUM> moves is described as an X direction, a direction where the medium P is transported is described as a Y direction, and a direction where the ink is ejected is described as a Z direction. Although the X direction, the Y direction, and the Z direction are described as being orthogonal to each other, the present disclosure is not limited to the various configurations constituting the printing apparatus <NUM> being provided orthogonally to each other. In addition, as the medium P, any printing target such as printing paper, resin film, or cloth can be used. In addition, the printing apparatus <NUM> may be a so-called line printing type ink jet printer that forms an image on a medium by ejecting the ink to a medium transported from the print head provided side by side above a width of the medium.

As illustrated in <FIG>, the printing apparatus <NUM> is provided with an ink container <NUM>, a control mechanism <NUM>, a carriage <NUM>, a movement mechanism <NUM>, and a transport mechanism <NUM>.

A plurality of types of ink to be ejected on the medium P are stored in the ink container <NUM>. Examples of the color of the ink stored in the ink container <NUM> include black, cyan, magenta, yellow, red, and gray. As the ink container <NUM> in which such ink is stored, an ink cartridge, a bag-shaped ink pack made of a flexible film, an ink tank capable of replenishing ink, and the like can be used.

The control mechanism <NUM> includes, for example, a processing circuit such as a central processing unit (CPU) or a field programmable gate array (FPGA), and a storage circuit such as a semiconductor memory, and controls each element of the printing apparatus <NUM>.

The print head <NUM> is mounted on the carriage <NUM>. In addition, the carriage <NUM> is fixed to an endless belt <NUM> included in the movement mechanism <NUM>. The ink container <NUM> may be mounted on the carriage <NUM>.

A control signal Ctrl-H for controlling the print head <NUM> output by the control mechanism <NUM> and one or a plurality of drive signals COM for driving the print head <NUM> are input to the print head <NUM>. The print head <NUM> ejects the ink supplied from the ink container <NUM> based on the control signal Ctrl-H and the drive signal COM.

The movement mechanism <NUM> includes a carriage motor <NUM> and an endless belt <NUM>. The carriage motor <NUM> operates based on a control signal Ctrl-C input from the control mechanism <NUM>. The endless belt <NUM> rotates according to the operation of the carriage motor <NUM>. As a result, the carriage <NUM> fixed to the endless belt <NUM> reciprocates in the X direction.

The transport mechanism <NUM> includes a transport motor <NUM> and a transport roller <NUM>. The transport motor <NUM> operates based on a control signal Ctrl-T input from the control mechanism <NUM>. The transport roller <NUM> rotates according to the operation of the transport motor <NUM>. The medium P is transported in the Y direction as the transport roller <NUM> rotates.

As described above, the printing apparatus <NUM> ejects the ink from the print head <NUM> mounted on the carriage <NUM> in conjunction with the transport of the medium P by the transport mechanism <NUM> and the reciprocating movement of the carriage <NUM> by the movement mechanism <NUM> to land the ink at any position on the surface of the medium P and to form a desired image on the medium P.

Next, a functional configuration of the printing apparatus <NUM> will be described. <FIG> is a diagram illustrating a functional configuration of the printing apparatus <NUM>. The printing apparatus <NUM> is provided with a control mechanism <NUM>, a print head <NUM>, a carriage motor <NUM>, a transport motor <NUM>, and a linear encoder <NUM>.

The control mechanism <NUM> includes a drive circuit <NUM>, a control circuit <NUM>, and a power supply circuit <NUM>. The control circuit <NUM> includes a processor such as a microcontroller, for example. The control circuit <NUM> generates various data for controlling the printing apparatus <NUM> and signals based on the data based on various signals such as image data input from the host computer, and outputs the signals to the corresponding configurations.

A specific example of the operation of the control circuit <NUM> will be described. The control circuit <NUM> grasps a scanning position of the print head <NUM> based on a detection signal input from the linear encoder <NUM>. The control circuit <NUM> generates and outputs various signals according to the scanning position of the print head <NUM>. Specifically, the control circuit <NUM> generates a control signal Ctrl-C for controlling the reciprocating movement of the print head <NUM> and outputs the control signal Ctrl-C to the carriage motor <NUM>. In addition, the control circuit <NUM> generates a control signal Ctrl-T for controlling the transport of the medium P, and outputs the control signal Ctrl-T to the transport motor <NUM>. The control signal Ctrl-C may be input to the carriage motor <NUM> after being signal-converted via a driver circuit (not illustrated). Similarly, the control signal Ctrl-T may be input to the transport motor <NUM> after being signal-converted via a driver circuit (not illustrated).

In addition, the control circuit <NUM> generates ejection control signals DATA1 to DATAn, a change signal CH, a latch signal LAT, and a clock signal SCK as control signals Ctrl-H for controlling the print head <NUM> based on various signals such as image data input from the host computer and the scanning position of the print head <NUM>, and outputs these signals to the print head <NUM>.

In addition, the control circuit <NUM> outputs a drive control signal dA, which is a digital signal, to the drive circuit <NUM>.

The drive circuit <NUM> includes a drive signal output circuit <NUM> and a reference voltage signal output circuit <NUM>. The drive control signal dA is input to the drive signal output circuit <NUM>. The drive signal output circuit <NUM> converts the drive control signal dA into a digital or analog signal, and then amplifies the converted analog signal in class D to generate a drive signal COM. That is, the drive control signal dA is a digital signal that defines the waveform of the drive signal COM, and the drive signal output circuit <NUM> generates and outputs the drive signal COM by amplifying the waveform defined by the drive control signal dA in class D. Therefore, the drive control signal dA may be any signal that can define the waveform of the drive signal COM, and for example, the drive control signal dA may be an analog signal. Furthermore, the drive signal output circuit <NUM> may be able to amplify the waveform defined by the drive control signal dA, and may be, for example, an amplifier circuit in class A, an amplifier circuit in class B, an amplifier circuit in class AB, or the like.

The reference voltage signal output circuit <NUM> outputs a reference voltage signal VBS indicating the reference potential of the drive signal COM. The reference voltage signal VBS may be, for example, a signal having a ground potential having a voltage value of <NUM> V, or a signal having a DC voltage having a voltage value of <NUM>. <NUM> V or <NUM> V.

The drive signal COM and the reference voltage signal VBS are branched by the control mechanism <NUM> and then output to the print head <NUM>. Specifically, the drive signal COM is branched into n drive signals COM1 to COMn corresponding to each of the n drive signal selection circuits <NUM> included in the print head <NUM> described later in the control mechanism <NUM>, and then output to the print head <NUM>. Similarly, the reference voltage signal VBS is branched into n reference voltage signals VBS1 to VBSn included in the print head <NUM> in the control mechanism <NUM> and then output to the print head <NUM>. The drive signal COM and the drive signals COM1 to COMn to which the drive signal COM is branched are examples of the drive signal.

The power supply circuit <NUM> generates and outputs voltages VHV and VDD. The voltage VHV is a signal having a DC voltage having a voltage value of, for example, <NUM> V, and is used as a voltage for amplification in the drive signal output circuit <NUM> or the like. In addition, the voltage VDD is a signal having a DC voltage having a voltage value of, for example, <NUM> V, and is used as a power supply voltage, a control voltage, or the like of various configurations in the control mechanism <NUM>. In addition, the voltages VHV and VDD are also output to the print head <NUM>. The voltage values of the voltages VHV and VDD are not limited to the above-described 42V and <NUM>. In addition, the power supply circuit <NUM> may generate and output signals having a plurality of voltage values other than the voltages VHV and VDD.

As described above, the control circuit <NUM> generates various signals for controlling the operation of the print head <NUM> and outputs these signals to the print head <NUM>. An example of the control signal output circuit is a control circuit <NUM> that outputs a plurality of signals including the ejection control signals DATA1 to DATAn, the change signal CH, the latch signal LAT, and the clock signal SCK.

The print head <NUM> includes drive signal selection circuits <NUM>-<NUM> to <NUM>-n and a plurality of ejection portions <NUM>.

Each of the drive signal selection circuits <NUM>-<NUM> to <NUM>-n is configured as, for example, an integrated circuit device. The voltages VHV and VDD, the corresponding drive signals COM1 to COMn, the corresponding ejection control signals DATA1 to DATAn, the clock signal SCK, the latch signal LAT, and the change signal CH are input to each of the drive signal selection circuits <NUM>-<NUM> to <NUM>-n. The voltages VHV and VDD function as power supply voltages and control voltages of the drive signal selection circuits <NUM>-<NUM> to <NUM>-n, respectively. Each of the drive signal selection circuits <NUM>-<NUM> to <NUM>-n generates drive signals VOUT1 to VOUTn by selecting or not selecting the drive signals COM1 to COMn based on the input ejection control signals DATA1 to DATAn, the clock signal SCK, the latch signal LAT, and the change signal CH.

The drive signals VOUT1 to VOUTn generated by each of the drive signal selection circuits <NUM>-<NUM> to <NUM>-n are supplied to the piezoelectric element <NUM> included in the corresponding ejection portion <NUM>. The piezoelectric element <NUM> is driven by being supplied with the drive signals VOUT1 to VOUTn. An amount of ink corresponding to the displacement of the piezoelectric element <NUM> generated by driving the piezoelectric element <NUM> is ejected from the ejection portion <NUM>.

Specifically, the drive signal COM1, the ejection control signal DATA1, the latch signal LAT, the change signal CH, and the clock signal SCK are input to the drive signal selection circuit <NUM>-<NUM>. The drive signal selection circuit <NUM>-<NUM> generates a drive signal VOUT1 by selecting or not selecting the waveform of the drive signal COM1 based on the ejection control signal DATA1, the latch signal LAT, the change signal CH, and the clock signal SCK, and outputs the drive signal VOUT1 to one end of the piezoelectric element <NUM> included in the corresponding ejection portion <NUM>. In addition, a reference voltage signal VBS1 is supplied to the other end of the piezoelectric element <NUM>. The piezoelectric element <NUM> is displaced by the potential difference between the drive signal VOUT1 and the reference voltage signal VBS1.

Similarly, the drive signal COMi, the ejection control signal DATAi, the latch signal LAT, the change signal CH, and the clock signal SCK are input to the drive signal selection circuit <NUM>-i (i is any one of <NUM> to n). The drive signal selection circuit <NUM>-i generates a drive signal VOUTi by selecting or not selecting the waveform of the drive signal COMi based on the ejection control signal DATAi, the latch signal LAT, the change signal CH, and the clock signal SCK, and outputs the drive signal VOUTi to one end of the piezoelectric element <NUM> included in the corresponding ejection portion <NUM>. In addition, a reference voltage signal VBSi is supplied to the other end of the piezoelectric element <NUM>. The piezoelectric element <NUM> is displaced by the potential difference between the drive signal VOUTi and the reference voltage signal VBSi.

Here, each of the drive signal selection circuits <NUM>-<NUM> to <NUM>-n has a similar circuit configuration. Therefore, when it is not necessary to distinguish the drive signal selection circuits <NUM>-<NUM> to <NUM>-n in the following description, the drive signal selection circuits <NUM>-<NUM> to <NUM>-n may be referred to as a drive signal selection circuit <NUM>. The drive signals COM1 to COMn input to the drive signal selection circuit <NUM> are referred to as a drive signal COM, the ejection control signals DATA1 to DATAn are referred to as an ejection control signal DATA, and the drive signals VOUT1 to VOUTn output from the drive signal selection circuit <NUM> are referred to as a drive signal VOUT.

In addition, the print head <NUM> in the present embodiment will be described as including <NUM> drive signal selection circuits <NUM>. That is, in the following description, the print head <NUM> will be described as including the drive signal selection circuits <NUM>-<NUM> to <NUM>-<NUM>. The number of drive signal selection circuits <NUM> included in the print head <NUM> is not limited to <NUM>. In addition, the details of the operation of the drive signal selection circuit <NUM> will be described later.

Next, a configuration of the ejection portion <NUM> will be described with reference to <FIG> and <FIG>. <FIG> is a diagram illustrating a schematic configuration of the ejection portion <NUM>. As illustrated in <FIG>, the ejection portion <NUM> includes a piezoelectric element <NUM>, a diaphragm <NUM>, a cavity <NUM>, and a nozzle <NUM>.

The piezoelectric element <NUM> is a laminated piezoelectric vibrator in which a piezoelectric body <NUM> is sandwiched between electrodes <NUM> and <NUM> and laminated, and cut into elongated comb-teeth shapes. The drive signal VOUT is supplied to the electrode <NUM>, and the reference voltage signal VBS is supplied to the electrode <NUM>. Such a piezoelectric element <NUM> functions as a longitudinal vibration type piezoelectric vibrator that is displaced in the vertical direction in <FIG>, which is the longitudinal direction of the piezoelectric element <NUM>, depending on the potential difference between the drive signal VOUT supplied to the electrode <NUM> and the reference voltage signal VBS supplied to the electrode <NUM>. In addition, a fixed end portion of the piezoelectric element <NUM> is joined to a fixed portion <NUM>, and a free end portion of the piezoelectric element <NUM> projects outward from a tip end edge of the fixed portion <NUM>. That is, the piezoelectric element <NUM> is provided in a so-called cantilever state in the ejection portion <NUM>. In addition, a tip end surface of the free end portion of the piezoelectric element <NUM> is joined to an island portion <NUM> provided above the diaphragm <NUM>.

The diaphragm <NUM> is deformed with the displacement of the piezoelectric element <NUM> provided via the island portion <NUM> provided above in <FIG>. In addition, the cavity <NUM> is provided below the diaphragm <NUM> in <FIG>. That is, the diaphragm <NUM> functions as a diaphragm that expands or reduces the internal volume of the cavity <NUM> by deforming with the displacement of the piezoelectric element <NUM>. The inside of the cavity <NUM> is filled with ink supplied through an ink supply port <NUM> and a reservoir <NUM>. The cavity <NUM> functions as a pressure chamber whose internal volume changes due to the displacement of the piezoelectric element <NUM>. The nozzle <NUM> is formed in a nozzle plate <NUM> and is an opening portion communicating with the cavity <NUM>. The ink stored inside the cavity <NUM> is ejected from the nozzle <NUM> depending on the change in the internal volume of the cavity <NUM>.

In the ejection portion <NUM> configured as described above, when the voltage of the drive signal VOUT increases, the piezoelectric element <NUM> is displaced upward. The piezoelectric element <NUM> is displaced upward, so that the internal volume of the cavity <NUM> is expanded. Therefore, the ink is drawn from the reservoir <NUM>. On the other hand, when the voltage of the drive signal VOUT decreases, the piezoelectric element <NUM> is displaced downward. The piezoelectric element <NUM> is displaced downward, so that the internal volume of the cavity <NUM> is reduced. Therefore, an amount of ink corresponding to the degree of reduction in the internal volume of the cavity <NUM> is ejected from the nozzle <NUM>. That is, the ejection portion <NUM> includes the piezoelectric element <NUM> driven by supplying the drive signal VOUT based on the drive signal COM, and ejects the ink as a liquid on the medium P as the piezoelectric element <NUM> is driven. The piezoelectric element <NUM> may be configured to be displaced downward when the voltage of the drive signal VOUT increases, and to be displaced upward when the voltage of the drive signal VOUT decreases.

A plurality of nozzles <NUM> included in the ejection portion <NUM> configured as described above are provided side by side on the nozzle plate <NUM>.

<FIG> is a diagram illustrating an example of an arrangement of the nozzles <NUM> provided on the nozzle plate <NUM>. As illustrated in <FIG>, nozzle rows L in which m nozzles <NUM> are provided side by side along the Y direction are located in <NUM> rows along the X direction on the nozzle plate <NUM>. Here, the ten nozzle rows L provided on the nozzle plate <NUM> may be referred to as nozzle rows L1 to L10 in order in the direction along the X direction. In addition, <FIG> illustrates a case where the nozzles <NUM> are provided side by side in one row in the Y direction in each of the nozzle rows L1 to L10, and the nozzles <NUM> may be provided side by side in two or more rows along the Y direction in each of the nozzle rows L1 to L10.

Each of the nozzle rows L1 to L10 provided on the nozzle plate <NUM> is provided corresponding to each of the drive signal selection circuits <NUM>-<NUM> to <NUM>-<NUM>. Specifically, the drive signal VOUT1 output by the drive signal selection circuit <NUM>-<NUM> is supplied to one end of the m piezoelectric elements <NUM> included in the m ejection portions <NUM> provided in the nozzle row L1, and the reference voltage signal VBS1 is supplied to the other end of the piezoelectric element <NUM>. Similarly, the drive signals VOUT2 to VOUT10 output by each of the drive signal selection circuits <NUM>-<NUM> to <NUM>-<NUM> are supplied to one end of the m piezoelectric elements <NUM> included in the m ejection portions <NUM> provided in each of the nozzle rows L2 to L10, and each of the reference voltage signals VBS2 to VBS10 are supplied to the other end of the corresponding piezoelectric element <NUM>.

Here, each of the nozzle rows L1 to L10 in the present embodiment includes <NUM> or more nozzles <NUM> and the ejection portion <NUM>. That is, the print head <NUM> includes <NUM> or more ejection portions <NUM>. The ejection control signal DATA1 output by the control circuit <NUM> includes information corresponding to <NUM> or more ejection portions <NUM>, and the drive signal selection circuit <NUM>-<NUM> outputs the drive signal VOUT1 corresponding to each of the <NUM> or more ejection portions <NUM> defined by the ejection control signal DATA1. Similarly, each of the ejection control signals DATA2 to DATA10 output by the control circuit <NUM> includes information corresponding to <NUM> or more ejection portions <NUM>, and each of the drive signal selection circuits <NUM>-<NUM> to <NUM>-<NUM> outputs the drive signals VOUT2 to VOUT10 defined by the ejection control signals DATA2 to DATA10 to each of the corresponding ejection portions <NUM>.

As described above, the print head <NUM> in the present embodiment includes the ejection portion <NUM> including <NUM> or more piezoelectric elements <NUM> and the nozzles <NUM>. In other words, the print head <NUM> includes the <NUM> or more piezoelectric elements <NUM> and the nozzles <NUM>. The control circuit <NUM> outputs the ejection control signals DATA1 to DATA10 including information corresponding to each of the <NUM> or more ejection portions <NUM> of the print head <NUM>.

Next, an example of the waveform of the drive signal COM generated by the drive signal output circuit <NUM> and input to the drive signal selection circuit <NUM>, and an example of the waveform of the drive signal VOUT generated by the drive signal selection circuit <NUM> will be described with reference to <FIG> and <FIG>.

<FIG> is a graph illustrating an example of a waveform of the drive signal COM. As illustrated in <FIG>, the drive signal COM is a signal having a continuous waveform of trapezoidal waveforms Adp, Bdp, and Cdp arranged in a cycle T from the rise of the latch signal LAT at time t0 to the rise of the next latch signal LAT at time t6. In addition, the voltage values at the start timing and end timing of the trapezoidal waveforms Adp, Bdp, and Cdp are all common to the voltage Vc. That is, each of the trapezoidal waveforms Adp, Bdp, and Cdp is a waveform that starts at the voltage Vc and ends at the voltage Vc.

In addition, the control circuit <NUM> raises the change signal CH at time t2 between the period when the drive signal output circuit <NUM> outputs the trapezoidal waveform Adp and the period when the drive signal output circuit <NUM> outputs the trapezoidal waveform Bdp, and lowers the change signal CH at time t3 between the period for outputting the trapezoidal waveform Adp and the period for outputting the trapezoidal waveform Bdp. Similarly, the control circuit <NUM> raises the change signal CH at time t4 between the period when the drive signal output circuit <NUM> outputs the trapezoidal waveform Bdp and the period when the drive signal output circuit <NUM> outputs the trapezoidal waveform Cdp, and lowers the change signal CH at time t5 between the period for outputting the trapezoidal waveform Bdp and the period for outputting the trapezoidal waveform Cdp. That is, the trapezoidal waveform Adp is arranged at a period Ta between the time t1 when the latch signal LAT falls after the latch signal LAT rises at time t0 and the time t2 when the change signal CH rises. The trapezoidal waveform Bdp is arranged at a period Tb between the time t3 when the change signal CH falls and the time t4 when the change signal CH rises next. The trapezoidal waveform Cdp is arranged at a period Tc between the time t5 when the change signal CH falls and the time t6 when the latch signal LAT rises. Here, the time t6 corresponds to the above-described time t0. That is, the drive signal COM is a waveform that repeatedly includes the trapezoidal waveforms Adp, Bdp, and Cdp in the cycle T defined by the latch signal LAT.

When the trapezoidal waveform Adp is supplied to the electrode <NUM>, which is one end of the piezoelectric element <NUM>, a medium amount of ink is ejected from the ejection portion <NUM> corresponding to the piezoelectric element <NUM>. In addition, when the trapezoidal waveform Bdp is supplied to the electrode <NUM>, which is one end of the piezoelectric element <NUM>, a small amount of ink less than a medium amount is ejected from the ejection portion <NUM> corresponding to the piezoelectric element <NUM>. In addition, when the trapezoidal waveform Cdp is supplied to the electrode <NUM>, which is one end of the piezoelectric element <NUM>, the ink is not ejected from the ejection portion <NUM> corresponding to the piezoelectric element <NUM>, and the ink in the vicinity of the nozzle opening portion of the ejection portion <NUM> is slightly vibrated to prevent an increase in ink viscosity. That is, the trapezoidal waveform Cdp is a waveform for slightly vibrating the ejection portion <NUM>.

As described above, the drive signal COM includes the trapezoidal waveforms Adp and Bdp that drive the piezoelectric element <NUM> so as to eject the ink from the ejection portion <NUM>, and the trapezoidal waveform Cdp that drives the piezoelectric element <NUM> so that the ink is not ejected from the ejection portion <NUM>. Here, the trapezoidal waveform Adp is an example of a first drive waveform, and the trapezoidal waveform Cdp is an example of a second drive waveform.

<FIG> is a graph illustrating an example of the waveform of the drive signal VOUT corresponding to the case where each of "large dot", "medium dot", "small dot", and "non-recording" is formed on the medium P by the ink ejected from the ejection portion <NUM>.

As illustrated in <FIG>, the drive signal VOUT corresponding to the "large dot" is a waveform in which a trapezoidal waveform Adp arranged in the period Ta, a trapezoidal waveform Bdp arranged in the period Tb, and a constant waveform at a voltage Vc arranged in the period Tc are continuous in the cycle T. That is, when the drive signal selection circuit <NUM> selects the trapezoidal waveform Adp arranged in the period Ta, selects the trapezoidal waveform Bdp arranged in the period Tb, and does not select the trapezoidal waveform Cdp arranged in the period Tc in the cycle T, the drive signal selection circuit <NUM> outputs the drive signal VOUT corresponding to the "large dot" to the corresponding ejection portion <NUM>. When the drive signal VOUT corresponding to the "large dot" is supplied to one end of the piezoelectric element <NUM>, a medium amount of ink is ejected from the ejection portion <NUM> corresponding to the piezoelectric element <NUM> in the period Ta, a small amount of ink is ejected in the period Tb, and the ink is not ejected in the period Tc. Therefore, a medium amount of ink and a small amount of ink land, and the inks coalesce on the medium P in the cycle T. As a result, large dots are formed on the medium P.

In addition, the drive signal VOUT corresponding to the "medium dot" is a waveform in which a trapezoidal waveform Adp arranged in the period Ta, a constant waveform at a voltage Vc arranged in the period Tb, and a constant waveform at a voltage Vc arranged in the period Tc are continuous in the cycle T. That is, when the drive signal selection circuit <NUM> selects the trapezoidal waveform Adp arranged in the period Ta, does not select the trapezoidal waveform Bdp arranged in the period Tb, and does not select the trapezoidal waveform Cdp arranged in the period Tc in the cycle T, the drive signal selection circuit <NUM> outputs the drive signal VOUT corresponding to the "medium dot" to the corresponding ejection portion <NUM>. When the drive signal VOUT corresponding to the "medium dot" is supplied to one end of the piezoelectric element <NUM>, a medium amount of ink is ejected from the ejection portion <NUM> corresponding to the piezoelectric element <NUM> in the period Ta, the ink is not ejected in the period Tb, and the ink is not ejected in the period Tc. Therefore, a medium amount of ink lands on the medium P in the cycle T. As a result, medium dots are formed on the medium P.

In addition, the drive signal VOUT corresponding to the "small dot" is a waveform in which a constant waveform at a voltage Vc arranged in the period Ta, a trapezoidal waveform Bdp arranged in the period Tb, and a constant waveform at a voltage Vc arranged in the period Tc are continuous in the cycle T. That is, when the drive signal selection circuit <NUM> does not select the trapezoidal waveform Adp arranged in the period Ta, selects the trapezoidal waveform Bdp arranged in the period Tb, and does not select the trapezoidal waveform Cdp arranged in the period Tc in the cycle T, the drive signal selection circuit <NUM> outputs the drive signal VOUT corresponding to the "small dot" to the corresponding ejection portion <NUM>. When the drive signal VOUT corresponding to the "small dot" is supplied to one end of the piezoelectric element <NUM>, the ink is not ejected from the ejection portion <NUM> corresponding to the piezoelectric element <NUM> in the period Ta, a small amount of ink is ejected in the period Tb, and the ink is not ejected in the period Tc. Therefore, a small amount of ink lands on the medium P in the cycle T, and as a result, small dots are formed on the medium P.

In addition, the drive signal VOUT corresponding to "non-recording" is a waveform in which a constant waveform at a voltage Vc arranged in the period Ta, a constant waveform at a voltage Vc arranged in the period Tb, and a trapezoidal waveform Cdp arranged in the period Tc are continuous in the cycle T. That is, when the drive signal selection circuit <NUM> does not select the trapezoidal waveform Adp arranged in the period Ta, does not select the trapezoidal waveform Bdp arranged in the period Tb, and selects the trapezoidal waveform Cdp arranged in the period Tc in the cycle T, the drive signal selection circuit <NUM> outputs the drive signal VOUT corresponding to "non-recording". When the drive signal VOUT corresponding to this "non-recording" is supplied to one end of the piezoelectric element <NUM>, only the ink in the vicinity of the nozzle opening portion of the ejection portion <NUM> corresponding to the piezoelectric element <NUM> vibrates slightly, and the ink is not ejected from the ejection portion <NUM> corresponding to the piezoelectric element <NUM>. Therefore, the ink does not land on the medium P in the cycle T. As a result, dots are not formed on the medium P.

Here, the constant waveform at the voltage Vc supplied to the electrode <NUM> of the piezoelectric element <NUM> is also a waveform including a voltage at which the immediately preceding voltage Vc is held by the capacitance component of the piezoelectric element <NUM> when none of the trapezoidal waveforms Adp, Bdp, and Cdp is selected as the drive signal VOUT. Therefore, when none of the trapezoidal waveforms Adp, Bdp, and Cdp is selected as the drive signal VOUT, the voltage Vc is supplied to the piezoelectric element <NUM> as the drive signal VOUT.

Here, the cycle T from the rise of the latch signal LAT illustrated in <FIG> and <FIG> to the rise of the next latch signal LAT corresponds to the printing cycle of forming new dots on the medium P. The drive signal COM and the drive signal VOUT illustrated in <FIG> and <FIG> are merely examples, and various combinations of waveforms may be used depending on the moving speed of the carriage <NUM> on which the print head <NUM> is mounted, the physical properties of the ink supplied to the print head <NUM>, and the material of the medium P, and the like.

As described above, the drive signal selection circuit <NUM> selects or does not select the trapezoidal waveforms Adp, Bdp, and Cdp included in the drive signal COM, so that the drive signal VOUT is generated and output according to the size of the dots formed on the medium P. Here, the configuration and operation of the drive signal selection circuit <NUM> that outputs the drive signal VOUT will be described.

<FIG> is a diagram illustrating a configuration of the drive signal selection circuit <NUM>. As illustrated in <FIG>, the drive signal selection circuit <NUM> includes a control logic circuit <NUM> and m selection control circuits <NUM> provided corresponding to the m ejection portions <NUM>. That is, the drive signal selection circuit <NUM> includes the m selection control circuits <NUM> as many as the total number of ejection portions <NUM> that output the drive signal VOUT.

The ejection control signal DATA, the latch signal LAT, the change signal CH, the clock signal SCK, and the drive signal COM are input to the drive signal selection circuit <NUM>. The drive signal selection circuit <NUM> generates a drive signal VOUT by selecting or not selecting the trapezoidal waveforms Adp, Bdp, and Cdp included in the drive signal COM based on the ejection control signal DATA, the latch signal LAT, the change signal CH, and the clock signal SCK, and outputs the drive signal VOUT to the corresponding ejection portion <NUM>.

The control logic circuit <NUM> includes an SP shift register (S/R) group <NUM> and a selection control signal generation group <NUM>. The SP shift register group <NUM> holds program data q0 to q3 included in a setting data signal SP described later in the ejection control signal DATA input in synchronization with the clock signal SCK. The selection control signal generation group <NUM> latches the program data q0 to q3 held in the SP shift register group <NUM> and outputs the latched program data q0 to q3 as the selection control signals Q0 to Q3 to a decoder <NUM>.

The selection control circuit <NUM> includes a first shift register 222a, a second shift register 222b, a first latch circuit 224a, a second latch circuit 224b, a decoder <NUM>, and a selection circuit <NUM>. Here, in the following description, the m selection control circuits <NUM> included in the drive signal selection circuit <NUM> may be referred to as a first stage, second stage,. , and m-th stage in order from the upstream where the ejection control signal DATA is input. Similarly, each of the first shift register 222a, the second shift register 222b, the first latch circuit 224a, the second latch circuit 224b, the decoder <NUM>, and the selection circuits <NUM> included in the selection control circuit <NUM> of the first stage, second stage,. , and m-th stage may be referred to as a first stage, second stage,. , and m-th stage.

Among the ejection control signals DATA input in synchronization with the clock signal SCK, higher print data SIH and lower print data SIL included in a print data signal SI described later are held in the first shift register 222a and the second shift register 222b. Although the details will be described later, the ejection control signal DATA includes the higher print data SIH and the lower print data SIL corresponding to each of the plurality of ejection portions <NUM> as the print data signal SI. Among the print data signal SI propagated in synchronization with the clock signal SCK, the higher print data SIH is held in the first shift register 222a, and the lower print data SIL is held in the second shift register 222b.

Here, in the following description, the higher print data SIH and the lower print data SIL corresponding to the ejection portion <NUM> may be referred to as print data [SIH, SIL]. In addition, the print data [SIH, SIL] corresponding to each of the ejection portions <NUM> of the first stage to m-th stage may be referred to as print data [SIH1, SIL1], print data [SIH2, SIL2],. , and print data [SIHm, SILm].

Here, as illustrated in <FIG>, the SP shift register group <NUM>, the first shift register 222a, and the second shift register 222b are connected to each other in series in the drive signal selection circuit <NUM>. Specifically, the SP shift register group <NUM>, the first shift register 222a, and the second shift register 222b are connected to each other in series in the order of the SP shift register group <NUM>, the second shift register 222b corresponding to each of the first stage to m-th stage, and the first shift register 222a corresponding to each of the first stage to m-th stage in the drive signal selection circuit <NUM>. Therefore, the ejection control signal DATA is transferred in the order of the SP shift register group <NUM>, the second shift register 222b corresponding to each of the first stage to m-th stage, and the first shift register 222a corresponding to each of the first stage to m-th stage according to the clock signal SCK. That is, the clock signal SCK sequentially propagates the ejection control signal DATA to the shift register in the subsequent stage. In other words, the clock signal SCK is a signal that defines a propagation timing of the ejection control signal DATA.

Here, an example of a data format of the ejection control signal DATA will be described. The ejection control signal DATA is a signal that serially includes the setting data signal SP held in the SP shift register group <NUM>, the higher print data SIH held in the first shift register 222a, and the lower print data SIL held in the second shift register 222b in the order of the higher print data SIH corresponding to each of the ejection portions <NUM> of the m-th stage to first stage, the lower print data SIL corresponding to each of the ejection portions <NUM> of the m-th stage to first stage, and the program data q0 to q3. <FIG> is a table illustrating an example of the data format of the ejection control signal DATA. As illustrated in <FIG>, the ejection control signal DATA includes the setting data signal SP and the print data signal SI. In addition, the print data signal SI includes the higher print data SIH and the lower print data SIL.

The print data signal SI is a serial signal including data of a total of <NUM> bits including data of two bits of the higher print data SIH and the lower print data SIL for controlling the drive of piezoelectric element <NUM> included in the ejection portion <NUM> corresponding to each of m ejection portions <NUM>. The setting data signal SP is a serial signal including data for defining the drive pattern of the piezoelectric element <NUM>. Specifically, the setting data signal SP serially includes four program data q0 to q3 indicating the drive pattern of the piezoelectric element <NUM> determined by the combination of the higher print data SIH and the lower print data SIL included in the print data signal SI. Each of the program data q0 to q3 included in the setting data signal SP may include data of a plurality of bits for defining the drive pattern of the piezoelectric element <NUM>.

Returning to <FIG>, in the drive signal selection circuit <NUM>, the ejection control signal DATA as illustrated in <FIG> is sequentially transferred by the SP shift register group <NUM>, the second shift register 222b, and the first shift register 222a in synchronization with the clock signal SCK. As a result, the program data q0 to q3 included in the setting data signal SP are held in the SP shift register group <NUM>. The lower print data SIL corresponding to each of the ejection portions <NUM> of the first stage to m-th stage is held in the second shift register 222b. The higher print data SIH corresponding to each of the ejection portions <NUM> of the first stage to m-th stage is held in the first shift register 222a.

The higher print data SIH corresponding to each of the ejection portions <NUM> of the first stage to m-th stage held in the first shift register 222a is latched by the first latch circuit 224a corresponding to each of the ejection portions <NUM> of the first stage to m-th stage at the rising of the latch signal LAT. In addition, the lower print data SIL corresponding to each of the ejection portions <NUM> of the first stage to m-th stage held in the second shift register 222b is latched by the second latch circuit 224b corresponding to each of the ejection portions <NUM> of the first stage to m-th stage at the rising of the latch signal LAT.

The first latch circuit 224a outputs the latched higher print data SIH as latch data LTa to the decoder <NUM>, and the second latch circuit 224b outputs the latched lower print data SIL as latch data LTb to the decoder <NUM>.

In the following description, the latch data LTa output by the first latch circuit 224a corresponding to each of the ejection portions <NUM> of the first stage, second stage,. , and m-th stage may be referred to as latch data LTa1, LTa2,. , and LTam. The latch data LTb output by the second latch circuit 224b corresponding to each of the ejection portions <NUM> of the first stage, second stage,. , and m-th stage may be referred to as latch data LTb1, LTb2,. , and LTbm. In addition, in the following description, the latch data LTa and LTb may be referred to as latch data [LTa, LTb], and the latch data [LTa, LTb] corresponding to each of the ejection portions <NUM> of the first stage, second stage,. , and m-th stage may be referred to as latch data [LTa1, LTb1], latch data [LTa2, LTb2],. , and latch data [LTam, LTbm].

The selection control signals Q0 to Q3 corresponding to the program data q0 to q3 and the latch data [LTa, LTb] corresponding to the print data [SIH, SIL] are input to the decoder <NUM>. The decoder <NUM> generates a TG control signal S based on the selection control signals Q0 to Q3 and the latch data [LTa, LTb], and outputs the TG control signal S to the corresponding selection circuit <NUM>. Here, the selection control signals Q0 to Q3 corresponding to the program data q0 to q3 are data defining the drive pattern of the piezoelectric element <NUM>, and specifically, define a logic level of the TG control signal S to be output in each of the periods Ta, Tb, and Tc illustrated in <FIG> and <FIG>. In addition, the latch data [LTa, LTb] corresponding to the print data [SIH, SIL] is data for controlling the drive of piezoelectric element <NUM>, and specifically, is a signal for selecting a drive pattern defined by the selection control signals Q0 to Q3 corresponding to the program data q0 to q3.

That is, the decoder <NUM> decodes the selection control signals Q0 to Q3 corresponding to the program data q0 to q3 based on the latch data [LTa, LTb] corresponding to the print data [SIH, SIL], and outputs the TG control signal S having a predetermined logic level in each of the periods Ta, Tb, and Tc. The TG control signal S output from the decoder <NUM> may be converted into a high-amplitude logic signal based on the voltage VHV by a level shifter (not illustrated).

<FIG> is a table illustrating the decoding contents of the decoder <NUM>. As illustrated in <FIG>, the selection control signal Q0 corresponding to the program data q0 defines the logic level of the TG control signal S as the H, H, and L level in each of the periods Ta, Tb, and Tc. The selection control signal Q1 corresponding to the program data q1 defines the logic level of the TG control signal S as the H, L, and L level in each of the periods Ta, Tb, and Tc. The selection control signal Q2 corresponding to the program data q2 defines the logic level of the TG control signal S as the L, H, and L level in each of the periods Ta, Tb, and Tc. The selection control signal Q3 corresponding to the program data q3 defines the logic level of the TG control signal S as the L, L, and H level in each of the periods Ta, Tb, and Tc.

The decoder <NUM> selects the selection control signals Q0 to Q3 based on the latch data [LTa, LTb] corresponding to the print data [SIH, SIL] latched by the first latch circuit 224a and the second latch circuit 224b, and outputs the TG control signal S having a corresponding logic level. For example, when the latch data [LTa, LTb] input to the decoder <NUM> is [<NUM>,<NUM>], the decoder <NUM> outputs the TG control signals S having H, L, and L level at each of the periods Ta, Tb, and Tc defined by the selection control signal Q1.

The TG control signal S output from the decoder <NUM> is input to the selection circuit <NUM>. <FIG> is a diagram illustrating a configuration of the selection circuit <NUM> corresponding to one ejection portion <NUM>. As illustrated in <FIG>, the selection circuit <NUM> includes an inverter <NUM> which is a NOT circuit and a transfer gate <NUM>. While the TG control signal S is input to a positive control end not marked with a circle at the transfer gate <NUM>, the TG control signal S is logically inverted by the inverter <NUM> and input to a negative control end marked with a circle at the transfer gate <NUM>. In addition, the drive signal COM is supplied to an input terminal of the transfer gate <NUM>. Specifically, when the TG control signal S is at the H level, the transfer gate <NUM> makes the input terminal and an output terminal conductive, and when the TG control signal S is at the L level, the transfer gate <NUM> makes the input terminal and the output terminal non-conductive. The drive signal VOUT is output from the output terminal of the transfer gate <NUM>. That is, the transfer gate <NUM> switches whether or not to supply the drive signal COM to the piezoelectric element <NUM> as the drive signal VOUT. In the following description, controlling to be conductive between the input terminal and the output terminal may be simply referred to as "turning on", and controlling to be non-conductive between the input terminal and the output terminal is simply referred to as "turning off".

As described above, the ejection control signal DATA, the latch signal LAT, the change signal CH, the clock signal SCK, and the drive signal COM are input to the drive signal selection circuit <NUM>. By selecting or not selecting the drive signal COM based on the ejection control signal DATA, the latch signal LAT, the change signal CH, and the clock signal SCK, the drive signal VOUT as illustrated in <FIG> and <FIG> is generated and output to the corresponding ejection portion <NUM>.

Here, as described above, the drive signal selection circuit <NUM> is provided with m selection control circuits <NUM> corresponding to m ejection portions <NUM>. Each of the m selection control circuits <NUM> includes the first shift register 222a, the second shift register 222b, the first latch circuit 224a, the second latch circuit 224b, the decoder <NUM>, and the selection circuit <NUM>. That is, the drive signal selection circuit <NUM> includes m first shift registers 222a, m second shift registers 222b, m first latch circuits 224a, m second latch circuits 224b, m decoders <NUM>, and m selection circuits <NUM>.

In addition, as illustrated in <FIG>, the print head <NUM> is provided with n selection control circuits <NUM>. That is, the print head <NUM> includes m × n first shift registers 222a, m × n second shift registers 222b, m × n first latch circuits 224a, and m × n second latch circuits 224b, m × n decoders <NUM>, m × n selection circuits <NUM>, and m × n ejection portions <NUM>. Here, as described above, in the printing apparatus <NUM> of the present embodiment, the print head <NUM> includes <NUM> selection control circuits <NUM>, and the drive signal selection circuit <NUM> outputs the drive signal VOUT to <NUM> or more ejection portions <NUM>. That is, the print head <NUM> in the present embodiment includes <NUM> or more first shift registers 222a, <NUM> or more second shift registers 222b, <NUM> or more first latch circuits 224a, <NUM> or more second latch circuits 224b, <NUM> or more decoders <NUM>, <NUM> or more selection circuits <NUM>, and <NUM> or more ejection portions <NUM>.

In the print head <NUM> configured as described above, the transfer gate <NUM> included in the selection circuit <NUM> for switching whether or not to supply the drive signal COM to the piezoelectric element <NUM> is an example of a changeover switch. The configuration including the selection circuit <NUM> including the transfer gate <NUM> and the ejection portion <NUM> corresponds to an ejection module <NUM>. That is, the print head <NUM> includes <NUM> or more ejection modules <NUM> including the selection circuit <NUM> including the transfer gate <NUM> and the ejection portion <NUM> corresponding to each of the <NUM> or more ejection portions <NUM>. The ejection control signal DATA, the latch signal LAT, the change signal CH, the clock signal SCK, and the drive signal COM for driving the <NUM> or more ejection modules <NUM> are output from the control mechanism <NUM>. This control mechanism <NUM> is an example of a print head drive circuit.

The ejection control signal DATA for controlling the drive of <NUM> or more piezoelectric elements <NUM> of the print head <NUM> is an example of the selection signal. The higher print data SIH included in the print data signal SI in the ejection control signal DATA is an example of drive data. The program data q0 to q3 included in the setting data signal SP in the ejection control signal DATA are examples of drive pattern data. In addition, as illustrated in <FIG>, the drive signal selection circuit <NUM> switches whether or not to select the trapezoidal waveforms Adp, Bdp, and Cdp included in the drive signal COM in each of the periods Ta, Tb, and Tc defined by the latch signal LAT and the change signal CH, so that the drive signal VOUT supplied to the piezoelectric element <NUM> is generated. That is, each of the transfer gates <NUM> included in the m selection circuits <NUM> corresponding to each of the m ejection portions <NUM> switches from conductive to non-conductive or from non-conductive to conductive at the timing when the change signal CH and the latch signal LAT switch from the L level to the H level. In other words, the change signal CH and the latch signal LAT control each of the switching timings of the transfer gate <NUM>. Of the change signal CH and the latch signal LAT, the change signal CH is an example of the switching timing signal, and the latch signal LAT is another example of the switching timing signal.

In the printing apparatus <NUM> of the present embodiment configured as described above, since the print head <NUM> includes the <NUM> or more ejection portions <NUM>, when the transfer gate <NUM> included in the selection circuit <NUM> corresponding to each of the <NUM> or more ejection portions <NUM> is driven, a large current flows through the print head <NUM> as the transfer gate <NUM> is driven. Since a large current is generated when the transfer gate <NUM> is driven, there is a high possibility that noise due to the large current supplied to the print head <NUM>, such as switching noise due to the drive of transfer gate <NUM>, is generated. When the noise component due to the large current generated by driving the transfer gate <NUM> is superimposed on the print data [SIH, SIL] included in the ejection control signal DATA and the program data q0 to q3, there is a possibility that malfunction of the drive signal selection circuit <NUM> into which the ejection control signal DATA is input may be generated. As a result, the accuracy of the drive signal VOUT output from the drive signal selection circuit <NUM> is lowered. That is, in the printing apparatus <NUM> provided with the print head <NUM> having the <NUM> or more ejection portions <NUM> as illustrated in the present embodiment, a large current is generated by driving the transfer gate <NUM> provided corresponding to the ejection portions <NUM>. Therefore, there is a high possibility that the noise component due to the large current is superimposed on the ejection control signal DATA. As a result, there is a possibility that malfunction of the printing apparatus <NUM> may be generated and the printing quality of the printing apparatus <NUM> may be deteriorated.

In response to such a problem, the control circuit <NUM> included in the control mechanism <NUM> included in the printing apparatus <NUM> in the present embodiment stops the output of the ejection control signal DATA in the period of outputting the change signal CH for controlling the switching of the transfer gate <NUM>. Therefore, the possibility is reduced that noise generated by switching the transfer gate <NUM> is superimposed on the ejection control signal DATA. In other words, the control circuit <NUM> included in the control mechanism <NUM> exclusively outputs a change signal CH for controlling the switching of the transfer gate <NUM>, and an ejection control signal DATA for controlling the drive of <NUM> or more piezoelectric elements <NUM>. As a result, the possibility is reduced that the noise component based on a large current generated by driving the transfer gate <NUM> is superimposed on the ejection control signal DATA. As a result, the possibility is reduced that malfunction of the drive signal selection circuit <NUM> is generated, and the possibility is reduced that the accuracy of the drive signal VOUT output from the drive signal selection circuit <NUM> is deteriorated. Therefore, the possibility of malfunction of the printing apparatus <NUM> is reduced, and the possibility of deterioration of the printing quality of the printing apparatus <NUM> is reduced.

Here, a specific example of the timing at which the control circuit <NUM> included in the control mechanism <NUM> in the present embodiment outputs the ejection control signal DATA, the latch signal LAT, and the change signal CH to the drive signal selection circuit <NUM>, and the operation of the drive signal selection circuit <NUM> will be described with reference to <FIG> and <FIG>.

<FIG> and <FIG> are a graph for describing the operation of the drive signal selection circuit <NUM>. As illustrated in <FIG> and <FIG>, in the period Ta between the time t1 at which the latch signal LAT falls and the time t2 at which the change signal CH rises, the control circuit <NUM> serially outputs the higher print data SIH included in the print data signal SI in the ejection control signal DATA in synchronization with the clock signal SCK. Therefore, in the period Ta between the time t1 and the time t2, the higher print data SIH included in the print data signal SI in the ejection control signal DATA is input to the drive signal selection circuit <NUM>. In this case, the control circuit <NUM> continues to output the change signal CH having L level. Therefore, the transfer gate <NUM> continues to be an on or off state. That is, the control circuit <NUM> outputs the higher print data SIH included in the print data signal SI in the ejection control signal DATA and the constant change signal CH at the L level that controls the transfer gate <NUM> so as not to be switched in the period Ta. In other words, the control circuit <NUM> outputs the higher print data SIH included in the print data signal SI in which the logic level of the ejection control signal DATA changes without changing the logic level of the change signal CH in the period Ta.

In addition, as described above, the drive signal output circuit <NUM> outputs the trapezoidal waveform Adp included in the drive signal COM in the period Ta. In other words, at least a portion of the trapezoidal waveform Adp included in the drive signal COM output by the drive signal output circuit <NUM> is disposed in the period Ta.

In the period between the time t2 and the time t3 after the period Ta, the control circuit <NUM> stops the output of the clock signal SCK and also stops the output of the ejection control signal DATA. In this case, the control circuit <NUM> changes the logic level of the change signal CH from the L level to the H level. Therefore, the transfer gate <NUM> is switched to an on or off state according to the latch data [LTa, LTb] corresponding to the print data [SIH, SIL] input to the decoder <NUM>. That is, the control circuit <NUM> outputs a change signal CH having an H level different from the L level that controls the transfer gate <NUM> to be switched in the period between the time t2 and the time t3 after the period Ta. In other words, the control circuit <NUM> changes the logic level of the change signal CH and does not change the logic level of the ejection control signal DATA in the period between the time t2 and the time t3 after the period Ta.

In the period Tb between the time t3 at which the change signal CH falls and the time t4 at which the change signal CH rises, the control circuit <NUM> serially outputs the lower print data SIL included in the print data signal SI in the ejection control signal DATA in synchronization with the clock signal SCK. Therefore, in the period Tb between the time t3 and the time t4, the lower print data SIL included in the print data signal SI in the ejection control signal DATA is input to the drive signal selection circuit <NUM>. In this case, the control circuit <NUM> continues to output the change signal CH having L level. Therefore, the transfer gate <NUM> continues to be an on or off state. That is, the control circuit <NUM> outputs the lower print data SIL included in the print data signal SI in the ejection control signal DATA and the constant change signal CH at the L level that controls the transfer gate <NUM> so as not to be switched in the period Tb. In other words, the control circuit <NUM> outputs the lower print data SIL included in the print data signal SI in which the logic level of the ejection control signal DATA changes without changing the logic level of the change signal CH in the period Tb.

In addition, as described above, the drive signal output circuit <NUM> outputs the trapezoidal waveform Bdp included in the drive signal COM in the period Tb. In other words, at least a portion of the trapezoidal waveform Bdp included in the drive signal COM output by the drive signal output circuit <NUM> is disposed in the period Tb.

In the period between the time t4 and the time t5 after the period Tb, the control circuit <NUM> stops the output of the clock signal SCK and also stops the output of the ejection control signal DATA. In this case, the control circuit <NUM> changes the logic level of the change signal CH from the L level to the H level. Therefore, the transfer gate <NUM> is switched to an on or off state according to the latch data [LTa, LTb] corresponding to the print data [SIH, SIL] input to the decoder <NUM>. That is, the control circuit <NUM> outputs a change signal CH having an H level different from the L level that controls the transfer gate <NUM> to be switched in the period between the time t4 and the time t5 after the period Tb. In other words, the control circuit <NUM> changes the logic level of the change signal CH and does not change the logic level of the ejection control signal DATA in the period between the time t4 and the time t5 after the period Tb.

In the period Tc between the time t5 at which the change signal CH falls and the time t6 at which the latch signal LAT rises, the control circuit <NUM> serially outputs the program data q0 to q3 included in the setting data signal SP in the ejection control signal DATA in synchronization with the clock signal SCK. Therefore, in the period Tc between the time t5 and the time t6, the program data q0 to q3 included in the setting data signal SP in the ejection control signal DATA are input to the drive signal selection circuit <NUM>. In this case, the control circuit <NUM> continues to output the change signal CH having L level. Therefore, the transfer gate <NUM> continues to be an on or off state. That is, the control circuit <NUM> outputs the program data q0 to q3 included in the setting data signal SP in the ejection control signal DATA and the constant change signal CH at the L level that controls the transfer gate <NUM> so as not to be switched in the period Tc. In other words, the control circuit <NUM> outputs the program data q0 to q3 included in the setting data signal SP in which the logic level of the ejection control signal DATA changes without changing the logic level of the change signal CH in the period Tc.

In addition, as described above, the drive signal output circuit <NUM> outputs the trapezoidal waveform Cdp included in the drive signal COM in the period Tc. In other words, at least a portion of the trapezoidal waveform Cdp included in the drive signal COM output by the drive signal output circuit <NUM> is disposed in the period Tc.

When the latch signal LAT rises at time t6, the selection control signal generation group <NUM> latches the program data q0 to q3 held in the SP shift register group <NUM>, generates the selection control signals Q0 to Q3 according to the latched program data q0 to q3, and outputs the selection control signals Q0 to Q3 to the decoder <NUM>. In addition, when the latch signal LAT rises at time t6, each of the first latch circuits 224a latches the higher print data SIH held in the first shift register 222a all at once, and outputs the latched higher print data SIH as latch data LTa to the decoder <NUM>. Each of the second latch circuits 224b latches the lower print data SIL held in the second shift register 222b all at once, and outputs the latched lower print data SIL as latch data LTb to the decoder <NUM>.

The decoder <NUM> outputs a TG control signal S of the logic level defined by the selection control signals Q0 to Q3 according to the size of the dots defined by the latch data [LTa, LTb] corresponding to the print data [SIH, SIL].

Specifically, the decoder <NUM> selects the selection control signal Q0 when the print data [SIH, SIL] is [<NUM>, <NUM>]. Therefore, the decoder <NUM> outputs the TG control signals S having the H, H, and L level in the periods Ta, Tb, and Tc. In this case, the selection circuit <NUM> selects the trapezoidal waveform Adp in the period Ta, selects the trapezoidal waveform Bdp in the period Tb, and does not select the trapezoidal waveform Cdp in the period Tc. As a result, the drive signal selection circuit <NUM> generates and outputs a drive signal VOUT corresponding to the "large dot" illustrated in <FIG>.

In addition, the decoder <NUM> selects the selection control signal Q1 when the print data [SIH, SIL] is [<NUM>, <NUM>]. Therefore, the decoder <NUM> outputs the TG control signals S having the H, L, and L level in the periods Ta, Tb, and Tc. In this case, the selection circuit <NUM> selects the trapezoidal waveform Adp in the period Ta, does not select the trapezoidal waveform Bdp in the period Tb, and does not select the trapezoidal waveform Cdp in the period Tc. As a result, the drive signal selection circuit <NUM> generates and outputs a drive signal VOUT corresponding to the "medium dot" illustrated in <FIG>.

In addition, the decoder <NUM> selects the selection control signal Q2 when the print data [SIH, SIL] is [<NUM>, <NUM>]. Therefore, the decoder <NUM> outputs the TG control signals S having the L, H, and L level in the periods Ta, Tb, and Tc. In this case, the selection circuit <NUM> does not select the trapezoidal waveform Adp in the period Ta, selects the trapezoidal waveform Bdp in the period Tb, and does not select the trapezoidal waveform Cdp in the period Tc. As a result, the drive signal selection circuit <NUM> generates and outputs a drive signal VOUT corresponding to the "small dot" illustrated in <FIG>.

In addition, the decoder <NUM> selects the selection control signal Q3 when the print data [SIH, SIL] is [<NUM>, <NUM>]. Therefore, the decoder <NUM> outputs the TG control signals S having the L, L, and H level in the periods Ta, Tb, and Tc. In this case, the selection circuit <NUM> does not select the trapezoidal waveform Adp in the period Ta, does not select the trapezoidal waveform Bdp in the period Tb, and selects the trapezoidal waveform Cdp in the period Tc. As a result, the drive signal selection circuit <NUM> generates and outputs a drive signal VOUT corresponding to the "non-recording" illustrated in <FIG>.

Here, among the ejection control signal DATA output by the control circuit <NUM> included in the control mechanism <NUM>, the higher print data SIH included in the print data signal SI in the ejection control signal DATA for controlling the drive of piezoelectric element <NUM>, which is output by the control circuit <NUM> in the period Ta, is an example of a first information block. Among the ejection control signal DATA output by the control circuit <NUM> included in the control mechanism <NUM>, the lower print data SIL included in the print data signal SI in the ejection control signal DATA for controlling the drive of piezoelectric element <NUM>, which is output by the control circuit <NUM> in the period Tb, is an example of a third information block. Among the ejection control signal DATA output by the control circuit <NUM> included in the control mechanism <NUM>, the program data q0 to q3 included in the setting data signal SP in the ejection control signal DATA for defining the drive pattern of the piezoelectric element <NUM>, which is output by the control circuit <NUM> in the period Tb, is an example of a second information block. That is, the ejection control signal DATA includes a block that propagates the higher print data SIH included in the print data signal SI, a block that propagates the lower print data SIL included in the print data signal SI, and a block that propagates the program data q0 to q3 included in the setting data signal SP.

An example of the first period is the period Ta at which the control circuit <NUM> outputs the higher print data SIH included in the print data signal SI in the ejection control signal DATA and the constant change signal CH at the L level that controls the transfer gate <NUM> so as not to be switched. An example of the second period is a period after the period Ta and a period between the time t2 and the time t3 at which the control circuit <NUM> outputs the change signal CH in which the logic level for controlling the transfer gate <NUM> to be switched changes from the L level to the H level. An example of the third period is a period after a period between the time t2 and the time t3 and the period Tc at which the control circuit <NUM> outputs the lower print data SIL included in the print data signal SI in the ejection control signal DATA and the constant change signal CH at the L level that controls the transfer gate <NUM> so as not to be switched. An example of the fourth period is a period between the period between the time t2 and the time t3 and the period Tc, and the period Tb at which the control circuit <NUM> outputs the lower print data SIL included in the print data signal SI in the ejection control signal DATA and the constant change signal CH at the L level that controls the transfer gate <NUM> so as not to be switched. An example of the fifth period is a period between the period Tb and the period Tc, and a period between the time t4 and the time t5 at which the control circuit <NUM> outputs the change signal CH in which the logic level for controlling the transfer gate <NUM> to be switched changes from the L level to the H level.

In the printing apparatus <NUM> and the control mechanism <NUM> configured as described above, the ejection control signal DATA is transmitted separately in a block including the higher print data SIH, a block including the lower print data SIL, and a block including the program data q0 to q3. The control mechanism <NUM> outputs a block including the higher print data SIH in the ejection control signal DATA and a change signal CH having the L level for controlling the transfer gate <NUM> so as not to be switched in the period Ta. The control mechanism <NUM> outputs a change signal CH in which the logic level for controlling the transfer gate <NUM> to be switched changes from the L level to the H level in the period between the time t2 and the time t3 after the period Ta. The control mechanism <NUM> outputs a block including the higher print data SIH in the ejection control signal DATA and a change signal CH having the L level for controlling the transfer gate <NUM> so as not to be switched in the period Tc after the period between time t2 and time t3. That is, the control mechanism <NUM> outputs the ejection control signal DATA at the timing when the transfer gate <NUM> does not switch, and stops the output of the ejection control signal DATA at the timing when the transfer gate <NUM> switches. As a result, the possibility is reduced that the noise component generated when the transfer gate <NUM> is switched from on to off is superimposed on the ejection control signal DATA. Therefore, the possibility is reduced that the malfunction of the printing apparatus <NUM> is generated.

Furthermore, since the print head <NUM> includes the <NUM> or more ejection portions <NUM>, when the print head <NUM> includes <NUM> or more transfer gates <NUM> corresponding to the ejection portions <NUM>, a large current is generated when the transfer gate <NUM> is switched, and therefore, there is a possibility that the noise component generated when the transfer gate <NUM> is switched from on to off may increase. Even in such a case, the printing apparatus <NUM> and the control mechanism <NUM> in the present embodiment output the ejection control signal DATA at the timing when the transfer gate <NUM> does not switch, and stop the output of the ejection control signal DATA at the timing when the transfer gate <NUM> switches. Therefore, it is possible to reduce the possibility that the noise component generated when the transfer gate <NUM> is switched from on to off is superimposed on the ejection control signal DATA. Therefore, the possibility is reduced that malfunction of the printing apparatus <NUM> is generated.

In addition, in the printing apparatus <NUM> and the control mechanism <NUM> in the present embodiment, the block including the higher print data SIH in the ejection control signal DATA is output in the drive signal COM in the period Ta at which the trapezoidal waveform Adp for ejecting ink from the nozzle <NUM> is arranged. The block including the lower print data SIL in the ejection control signal DATA is output in the drive signal COM in the period Tb at which the trapezoidal waveform Bdp for ejecting ink from the nozzle <NUM> is arranged. The block including the program data q0 to q3 in the ejection control signal DATA is output in the drive signal COM in the period Tc at which the trapezoidal waveform Cdp vibrating slightly without ejecting ink from the nozzle <NUM> is arranged.

Among the trapezoidal waveforms Adp, Bdp, and Cdp included in the drive signal COM, the trapezoidal waveform Cdp that does not eject ink has a smaller maximum voltage value than that of the trapezoidal waveforms Adp, Bdp because the trapezoidal waveform Cdp does not eject ink. Therefore, the time during which the trapezoidal waveform Cdp is output in the drive signal COM is shorter than the time during which the trapezoidal waveforms Adp and Bdp are output. In addition, the amount of data included in the higher print data SIH and the lower print data SIL in the ejection control signal DATA increases as the number of nozzles <NUM> and piezoelectric element <NUM> of the print head <NUM> increases, whereas the program data q0 to q3 in the ejection control signal DATA are constant while increasing as the number of nozzles <NUM> and piezoelectric element <NUM> of the print head <NUM> increases, and furthermore, are smaller than the amount of data included in the higher print data SIH and the lower print data SIL in the ejection control signal DATA. Therefore, the time required to propagate the program data q0 to q3 in the ejection control signal DATA is shorter than the time required to propagate the higher print data SIH and the lower print data SIL in the ejection control signal DATA. At the timing when the trapezoidal waveform Cdp is output, which is shorter than the time when the trapezoidal waveforms Adp and Bdp are output in the drive signal COM, in the ejection control signal DATA, the program data q0 to q3 are propagated, which is shorter than the propagation time of the higher print data SIH and the lower print data SIL. Therefore, the possibility is reduced that the cycle T for ejecting ink on the medium P is inadvertently lengthened. That is, the time required to form an image on the medium P can be shortened, and the productivity of the printing apparatus <NUM> can be increased.

In the printing apparatus <NUM> and the control mechanism <NUM> in the above-described embodiment, it is described that the control circuit <NUM> included in the control mechanism <NUM> outputs the higher print data SIH in the ejection control signal DATA in the period Ta, outputs the lower print data SIL in the ejection control signal DATA in the period Tb, and outputs the program data q0 to q3 in the ejection control signal DATA in the period Tc. The higher print data SIH in the ejection control signal DATA and at least a portion of the lower print data SIL in the ejection control signal DATA may be output in the period Ta, a portion of the remaining part of the lower print data SIL in the ejection control signal DATA may be output in the period Tb, and the program data q0 to q3 in the ejection control signal DATA may be output in the period Tc. The higher print data SIH in the ejection control signal DATA and the lower print data SIL in the ejection control signal DATA may be output in the period Ta, the ejection control signal DATA may not be output in the period Tb, and the program data q0 to q3 in the ejection control signal DATA may be output in the period Tc. That is, the output of the ejection control signal DATA may be stopped at the timing when the control circuit <NUM> included in the control mechanism <NUM> outputs the change signal CH for switching the transfer gate <NUM>. Even in such a case, the same action effects as those of the above-described embodiment can be exhibited.

Hereinbefore, although the embodiments and modification examples have been described, the present disclosure is not limited to these embodiments, and can be implemented in a range of various embodiments. For example, the above embodiments can be combined as appropriate.

Claim 1:
A print head drive circuit (<NUM>) configured to drive a print head (<NUM>) including <NUM> or more ejection modules (<NUM>) each having an ejection portion (<NUM>) having a piezoelectric element (<NUM>) configured to be driven by a drive signal (COM) and configured to eject a liquid on a medium (P); and
a changeover switch (<NUM>) for switching whether or not to supply the drive signal (COM) to the piezoelectric element (<NUM>), with a selection signal (DATA) including a first information block (SIH) and a second information block (SIL) for selecting whether or not to drive the piezoelectric element (<NUM>), and a switching timing signal (CH) for changing a logic level to control a switching timing of the changeover switch (<NUM>), wherein
the print head drive circuit (<NUM>) is configured to output
the first information block (SIH) in which a logic level of the selection signal (DATA) changes without changing a logic level of the switching timing signal (CH), in a first period (Ta),
change the logic level of the switching timing signal (CH), and not change the logic level of the selection signal (DATA) in a second period after the first period (Ta), and
output the second information block (SIL) in which the logic level of the selection signal (DATA) changes without changing the logic level of the switching timing signal (CH) in a third period (Tb) after the second period; and
characterized in that
the first information block (SIH) and the second information block (SIL) consists of data for one printing cycle.