JP2005169866A - Recording head and recording apparatus using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording head which can supply a stable electric current to a heater even if a fluctuation occurs in voltage drop value under a wiring resistance, and a recording apparatus which is equipped with the recording head. <P>SOLUTION: This recording head is equipped with a regulator circuit for limiting a value of the electric current capable of flowing through each of a plurality of recording elements. The condition of the passage of the electric current through the recording element serves as the condition that a current limit for a driving circuit functions. Thus, even if the fluctuation occurs in the voltage drop value under the wiring resistance, the stable electric current can flow through the recording element when the recording element is operated in a range wherein the current limit continues to function. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a recording head and a recording apparatus including the recording head, and in particular, for example, an electrothermal conversion element that generates thermal energy necessary for ejecting ink and a driving circuit for driving the same are provided on the same substrate. The present invention relates to an ink jet recording head formed above and a recording apparatus using the recording head.

  2. Description of the Related Art Conventionally, for example, as information output devices in word processors, personal computers, facsimiles, and the like, there are printers that record desired information such as characters and images on a sheet-like recording medium such as paper or film.

  There are various known recording methods for the printer. Among them, recording is possible on a recording medium such as paper in a non-contact manner, color recording is easy, and quietness is high. Inkjet systems have attracted particular attention in recent years. As a configuration of a recording apparatus that employs this method, a recording head that discharges ink according to input recording information is mounted, and the recording head is reciprocally scanned in a direction perpendicular to the conveyance direction of the recording medium. Serial recording devices that perform recording are widely used because they are inexpensive and easy to downsize.

  In particular, the thermal ink jet method that utilizes the ink bubbling phenomenon induced by the thermal energy generated by energizing the heater for several microseconds to eject ink droplets forms a large number of nozzles at a high density on the recording head. It is possible.

  In such a thermal ink jet recording head (hereinafter referred to as a recording head), a heater that heats ink on a silicon single crystal substrate or the like by a semiconductor integrated circuit process, a protective film thereof, a driver circuit for energizing the heater, and its A recording element substrate (hereinafter referred to as a heater board) integrally formed with a logic circuit for performing control is used.

  FIG. 5 is a diagram for explaining an example of driving a conventional heater board.

  In FIG. 5, only one heater RH on the heater board, the driver transistor M1 for energizing the heater RH, and its peripheral circuit are extracted for the sake of simplicity.

  The heater RH has a resistance value of about 50Ω to 300Ω and is connected to the heater power source VH. Here, the heater power supply VH is a voltage of about several tens of volts to several tens of volts. The driver transistor M1 is a high breakdown voltage MOS transistor having a breakdown voltage equal to or higher than the heater power supply VH, and a current flows through the heater RH only during the time when the MOS transistor M1 is turned on.

  In an actual heater board, the elements shown in this figure are arranged in a number corresponding to the number of nozzles of the recording head.

  In addition to these elements, the heater board has wiring for energizing the heater with current, a logic circuit for defining the heater to be energized and its energization time, and a signal to be applied to the logic circuit. An input circuit for inputting into the heater board, a sensor for detecting temperature information, and the like are arranged.

  Hereinafter, each element shown in FIG. 5 will be described in detail.

  The LVC is a booster circuit for increasing the amplitude of a heat pulse signal applied from a logic circuit (not shown). The amplitude of the heat pulse signal applied from the logic circuit is a pulse signal having a relatively low voltage amplitude such as 3.3V or 5V. This voltage is boosted and converted to a higher voltage such as 8V or 10V by the booster circuit LVC. Here, the voltage power supply subjected to boost conversion is VHA.

  By driving the power MOS transistor with the drive signal of the voltage converted to the boosted voltage VHA, it becomes possible to reduce the on-resistance of the power MOS transistor, thereby realizing efficient heater driving. In the example shown in FIG. 5, the LVC functions as an inverter, and an output that is further logically inverted by an inverter including the MOS transistors M3 and M4 in the next stage is applied to the gate of the power MOS transistor M1. .

  In this configuration, the output of the inverter composed of the MOS transistors M3 and M4 becomes true, the boosted voltage VHA is applied to the gate of the power MOS transistor M1, and when the MOS transistor M1 is turned on, a heater current flows through the heater RH, and heat is generated. Ink bubbling will occur.

  By the way, in the conventional heater board, the power supply wiring which connects a heater electric current from the power supply terminal on a heater board to a heater is required, and a some heater is connected to the wiring. Since such a wiring has an impedance, when the heater current flows, a voltage drop depending on the impedance value and the flowing current value occurs in the wiring portion.

  FIG. 6 is a circuit diagram schematically showing the impedance of the wiring.

  In FIG. 6, RH is a plurality of arranged heater arrays, SW is a switching element for controlling current to flow to each heater, VH is a power supply terminal for flowing current to each heater element, and GNDH is a power supply via each heater element. Power supply ground terminals R1 to R10 through which a current from the terminal VH flows are resistors parasitic to wiring for connecting the power supply terminal VH and the heater RH or the switching element SW.

  The switching element SW is realized by a power MOS transistor as shown in FIG. 5, a logic circuit, a booster circuit LVC, and the like.

  Here, the current flowing from the power supply terminal VH to each heater varies depending on the number of heaters that are driven simultaneously. Therefore, the voltage value applied to both ends of each heater also varies depending on the number of heaters that are driven simultaneously. That is, when the number of heaters that are driven simultaneously is small and the current flowing through the wiring portion is small, the voltage drop at the wiring portion is small. However, when the number of heaters that are driven is large and the current flowing through the wiring portion is large, the voltage drop at the wiring portion is large. It will be a thing. Therefore, the voltage actually applied to both ends of the heater changes depending on the number of heaters to be driven.

  Further, this voltage value varies depending on the heater position. This is because the heater arranged at a location closer to the power supply terminal VH has a small parasitic resistance in the current flow path, but the heater arranged at a location away from the power supply terminal VH has a large parasitic resistance.

  Conventionally, in order to reduce such a change in voltage drop due to the number of heaters that are driven simultaneously, a method has been employed in which power supply wiring in the heater board is divided and drawn to each heater and connected to a power supply terminal.

  Normally, the recording head does not drive adjacent heaters at the same time, but adopts a configuration in which time-division driving is performed in which each successive heater is sequentially driven.

  For example, assuming that 16 heaters arranged in succession are one segment for time-division driving, a plurality of heaters are not driven simultaneously in the segment of these heaters. In order to drive all of them, each heater is driven one by one at different timing, and all the heaters can be driven for the first time by repeating the driving 16 times.

  In this way, 16 continuous heaters that are time-division driven are pulled out to the power supply terminal by one independent wiring (divided wiring) so that current for driving a plurality of heaters does not flow through the wiring simultaneously. Become. With such a configuration, the influence of the voltage drop difference in the wiring due to the number of simultaneously driven heaters has been reduced.

  FIG. 7 is a schematic diagram showing a circuit configuration when the conventional wiring is divided.

  In FIG. 7, as in FIG. 6, RH is a plurality of heaters, SW is a switching element for controlling energization of current to each heater, VH is a power supply terminal for flowing current to each heater element, and GNDH is Power supply terminals R1 to R10 through which current flows from each heater element are resistors parasitic on the power supply terminal and wiring for energizing each heater and switching element. Further, S1 to S4 are broken lines indicating one section for time-division driving arranged continuously, and only one heater can be turned on at the same time in the section.

  The switching element SW is realized by a power MOS transistor as shown in FIG. 5, a logic circuit, a booster circuit LVC, and the like.

  Here, the wiring design is performed so that the wiring resistances R3 to R10 have the same resistance value.

  FIG. 8 is a diagram illustrating an example of a wiring pattern in which wiring design is performed so that the wiring resistances R3 to R10 have the same resistance value.

  As can be seen from FIG. 8, connection is made from the power supply terminal VH to one end of each heater by independent wiring for each division of time division drive. Although not shown, the other end of the heater is connected to a switching element provided at the lower part of the wiring, and the switching element is further connected to the GNDH wiring and connected to the GNDH terminal by an independent wiring.

Further, as suggested from FIG. 8, in order to make the resistance values of the independent wirings approximately the same, the wirings connected to the heaters close to the terminals are thin and the wirings far away have a thick pattern.
JP-A-11-129479

  However, the following problems still exist in the conventional configuration.

  That is, in order to supply current independently within a limited heater board area, it is necessary to make each wiring width narrow so that the sum of the wiring width and interval is equal to or less than the heater board width. . Therefore, as compared with the case where divided wiring is performed, the value of wiring resistance increases as the number of divisions increases.

  As a recent trend of recording heads, the number of heaters that are simultaneously driven tends to further increase for the purpose of improving the recording speed, and this increase in wiring resistance has become remarkable.

  In order to generate the amount of heat required for ink foaming with a heater having such a high wiring resistance, it is necessary to apply electric power that takes into account the loss in the wiring resistance.

  In order to reduce the value of such wiring resistance, it is conceivable to secure a larger width of each wiring.

  However, if the number of simultaneously driven heaters is increased to improve the recording speed, the increase in the wiring width directly leads to an increase in the heater board size, and the heater board size is increased only to secure the wiring width. It may become a cause of cost increase.

  Next, it is conceivable to set the power supply voltage high so that the necessary amount of heat can be generated by the heater even with high wiring resistance.

  However, in order to control the heater current at a high power supply voltage, a switching element having a sufficient withstand voltage with respect to the power supply voltage is required. Usually, the switching element tends to increase in size with the withstand voltage, and this method also increases the cost. In order to improve the breakdown voltage without increasing the size of the heater board, it is conceivable to form an element with a structure capable of realizing a higher breakdown voltage in the heater board. Usually, such an element is complicatedly manufactured. This is often formed using a process, resulting in an increase in manufacturing cost.

  It is also conceivable to reduce the wiring resistance by increasing the thickness of the wiring layer.

  In order to achieve the purpose of the recording head, the recording element used for the recording head is in direct contact with the ink. Therefore, a protective film that can ensure sufficient resistance to ink immersion must be formed on the thick wiring layer and the upper surface of the heater. When this wiring layer is formed of a thick film, the level difference at the end of the wiring pattern increases in accordance with the film pressure. In order to cover such a large step with a protective film, it is necessary to increase the thickness of the protective film. The existence of such a thick protective film causes new problems such as changing the heat transfer characteristic from the heater film to the ink and making the ink foaming characteristic and the ink ejection characteristic have low reproducibility.

  Further, as described above, the layout of the divided wiring needs to be designed so that the wiring resistance value from the power supply terminal to each heater is constant. This is because if the energy applied to each heater is not constant, the ink bubbling and ink ejection characteristics between the heaters will change, resulting in a decrease in recording quality.

  At that time, in order to make the wiring resistance value constant, as shown in FIG. 8, the wiring width is narrow in the wiring connected to the heater near the power supply terminal, and the wiring width is small in the wiring connected to the heater farther away. By increasing the thickness, the layout is such that the resistance value between the terminal and the heater becomes equal.

  These wirings are usually formed by etching (patterning) of a metal thin film. In this etching process, there is usually a process variation factor that is a manufacturing etching shift such as overetching or underetching with respect to a target pattern size.

  At this time, the narrow wiring (that is, close to the power supply terminal) is more sensitively affected by the process variation to the thick wiring (that is, far from the terminal).

  Such a difference in the degree of influence on the process variation causes a variation in the wiring resistance value, resulting in a problem that equal energy cannot be applied to the heater.

  By the way, when the same energy cannot be applied to the heater in this way, even with the heater connected to the wiring with high wiring resistance to which smaller energy will be applied, the electric power that can surely achieve the foaming and ejection of the ink, Design to apply equally to all heaters. By doing so, ink ejection can be reliably achieved in all heaters.

  This means that an excessive electric power is applied to the heater connected to the wiring having a low wiring resistance than is originally required. Such excessive application of power shortens the life of the heater, which is problematic from the viewpoint of the reliability of the recording head.

  The problems related to the wiring resistance inside the heater board have been described above.

  However, normally, the wiring of the heater board is gathered as a common wiring at the pad terminal of the heater board, and is connected to the wiring of another component such as a printed board. The common wiring is connected to the power supply of the recording apparatus main body.

  In addition, as shown in R1 and R2 of FIG. 7, even within the heater board, the divided wirings are combined into one wiring pattern as a common wiring in the vicinity of the pad terminal.

  Such effects of voltage drop in the common wiring cannot be avoided by countermeasures by dividing the power supply wiring inside the heater board. It has been sought.

  The present invention has been made in view of the above-described problems of the conventional example. A recording head capable of supplying a stable current to a heater even if the voltage drop value due to wiring resistance varies, and the recording head It is an object of the present invention to provide a recording apparatus including the above.

  In order to achieve the above object, the recording head of the present invention has the following configuration.

  That is, a recording head having a plurality of recording elements connected to a common power supply line, connected in series to each of the recording elements, for driving the recording elements, and for driving the driving elements And an adjustment circuit that adjusts an applied voltage to be applied so that a current flowing through the driving element is a predetermined value or less.

  The drive element is a MOS transistor, and the adjustment circuit includes a first resistor connected in series to the recording element and a second MOS transistor connected to the first resistor. desirable. The driving state of the recording element is detected by a potential difference generated at both ends of the first resistor.

  Furthermore, one end of the first resistor is connected to the gate of the second MOS transistor, the other end is connected to the source, and the drain of the second MOS transistor is connected to the gate of the MOS transistor of the driving element. It is desirable that

  Furthermore, a booster circuit that boosts the input voltage for driving the drive element, and a third circuit having a polarity different from each other, connected in series between the power supply voltage side and the power supply ground side at the subsequent stage of the voltage booster circuit. The third MOS transistor is preferably provided on the power supply voltage side, and the fourth MOS transistor is preferably provided on the power supply ground side.

  In such a configuration, the gate voltage of the MOS transistor as the drive element is a voltage obtained by dividing the output voltage from the booster circuit by the on-resistance of the second MOS transistor and the third MOS transistor. It is desirable to become.

  As yet another aspect, in the case of further comprising a second resistor connected in series between the third MOS transistor and the fourth transistor, the gate voltage of the MOS transistor as the drive element The output voltage from the booster circuit is preferably a voltage obtained by dividing the output voltage by the second MOS transistor and the on-resistance of the third MOS transistor and the second resistance value.

  The recording head is preferably an ink jet recording head that performs recording by discharging ink from each recording element. In this case, each recording element uses thermal energy to discharge ink. It is desirable to be an electrothermal converter for generating thermal energy applied to the ink.

  Furthermore, the first resistor may be formed of a film having the same quality as the electrothermal converter.

  According to another aspect of the invention, a recording apparatus that performs recording with the recording head having the above-described configuration is provided.

  In the recording head according to the present invention described above, the adjustment circuit for limiting the current value that can flow through each of the plurality of recording elements is provided, and the current limitation for the driving element functions under the condition that the current flows through the recording element. By setting the conditions, even when fluctuations occur in the value of the voltage drop in the wiring resistance, when operating the recording element within the range where the current limit continues to function, a stable current is allowed to flow through the recording element. Is possible.

  By energizing the recording element under such driving conditions, a current that is always applied with a limited current flows to the heater. Since the limited current is substantially equal to the limit value, a stable current that is hardly affected by a voltage drop difference due to wiring flows through the recording element. As a result, the plurality of recording elements generate heat stably, and the ink jet recording head achieves stable ink heat generation and foaming.

  Therefore, since the recording head according to the present invention suppresses the influence of the voltage drop difference due to the wiring, it is not necessary to have a configuration for avoiding the voltage drop difference due to the wiring division, which has been conventionally required.

  Therefore, according to the present invention, it is possible to suppress a change in current flowing in the recording element due to a variation in applied energy caused by a voltage drop variation in a power supply wiring or the like, which varies depending on the number of simultaneously driven recording elements.

  As a result, it is not necessary to divide the power supply wiring, which has been conventionally performed to reduce the applied energy fluctuation. This leads to lower wiring resistance, and suppresses the expansion of the chip area for securing the wiring width necessary when the resistance is strictly adjusted by adopting the configuration of the divided wiring. be able to. That is, a reduction in the chip area of the heater board is achieved.

  In addition, if the divided wiring is shared, the wiring resistance value is lowered, which means that there is no need for high voltage driving to compensate for the energy loss that was necessary when the wiring resistance value was high. ing.

  In other words, it is not necessary to use a high-breakdown-voltage heater board having a large chip area or manufactured by a complicated process. The effect, reduction of the chip area, and reduction of the chip production cost by a simple manufacturing process can be expected.

  In addition, since the need for thicker wiring resistance is reduced, it is not necessary to increase the thickness of the protective film to protect the thick-film wiring. There is also an advantage that such problems do not occur.

  Further, variations in the manufacturing process caused by the divided wiring do not appear as variations in resistance value, and it is not necessary to apply excessive energy in consideration of resistance variations. As a result, it is possible to reduce the possibility of heater deterioration due to excessive energy application.

  Furthermore, it is possible to reduce the influence of voltage drop fluctuations in the common wiring resistance outside the heater board, and correction control for changing the heater driving time in consideration of them is not required.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  In this specification, “recording” (sometimes referred to as “printing”) is not only for forming significant information such as characters and figures, but also for human beings visually perceived regardless of significance. Regardless of whether or not it has been manifested, it also represents a case where an image, a pattern, a pattern, or the like is widely formed on a recording medium or the medium is processed.

  “Recording medium” refers not only to paper used in general recording apparatuses but also widely to cloth, plastic film, metal plate, glass, ceramics, wood, leather, and the like that can accept ink. Shall.

  Furthermore, “ink” (sometimes referred to as “liquid”) is to be interpreted broadly in the same way as the definition of “recording (printing)” above. It represents a liquid that can be used for forming a pattern or the like, processing a recording medium, or processing an ink (for example, solidification or insolubilization of a colorant in ink applied to the recording medium).

  Furthermore, unless otherwise specified, the “nozzle” collectively refers to an ejection port or a liquid channel communicating with the ejection port and an element that generates energy used for ink ejection.

  The “element base” used below does not indicate a simple base made of a silicon semiconductor but a base provided with each element, wiring, and the like.

  Furthermore, “on the element substrate” not only indicates the element substrate, but also indicates the surface of the element substrate and the inside of the element substrate near the surface. In addition, the term “built-in” as used in the present invention is not a word indicating that each separate element is simply placed on the base, but each element is formed by a semiconductor circuit manufacturing process or the like. It shows that it is integrally formed and manufactured on a substrate.

<Description of Inkjet Recording Apparatus (FIG. 1)>
FIG. 1 is an external perspective view showing an outline of a configuration of an ink jet recording apparatus 1 which is a typical embodiment of the present invention.

  As shown in FIG. 1, an ink jet recording apparatus (hereinafter referred to as a recording apparatus) transmits a driving force generated by a carriage motor M1 to a carriage 2 on which a recording head 3 that performs recording by discharging ink according to an ink jet system is mounted. 4, the carriage 2 is reciprocated in the direction of arrow A, and for example, a recording medium P such as recording paper is fed through a paper feeding mechanism 5 and conveyed to a recording position. Recording is performed by ejecting ink onto the recording medium P.

  Further, in order to maintain the state of the recording head 3 satisfactorily, the carriage 2 is moved to the position of the recovery device 10 and the ejection recovery process of the recording head 3 is intermittently performed.

  In addition to mounting the recording head 3 on the carriage 2 of the recording apparatus 1, an ink cartridge 6 for storing ink to be supplied to the recording head 3 is mounted. The ink cartridge 6 is detachable from the carriage 2.

  The recording apparatus 1 shown in FIG. 1 can perform color recording. For this reason, the carriage 2 contains four inks containing magenta (M), cyan (C), yellow (Y), and black (K) inks, respectively. An ink cartridge is installed. These four ink cartridges are detachable independently.

  Now, the carriage 2 and the recording head 3 can achieve and maintain a required electrical connection by properly contacting the joint surfaces of both members. The recording head 3 applies energy according to a recording signal to selectively eject ink from a plurality of ejection ports for recording. In particular, the recording head 3 of this embodiment employs an ink jet system that ejects ink using thermal energy, and responds by applying a pulse voltage to a corresponding electrothermal transducer in accordance with a recording signal. Ink is ejected from the ejection port.

  Further, in FIG. 1, reference numeral 14 denotes a transport roller that is driven by a transport motor M2 to transport the recording medium P.

<Control Configuration of Inkjet Recording Apparatus (FIG. 2)>
FIG. 2 is a block diagram showing a control configuration of the recording apparatus shown in FIG.

  As shown in FIG. 2, the controller 600 includes an MPU 601, a program corresponding to a control sequence to be described later, a required table, a ROM 602 that stores other fixed data, a carriage motor M1, a conveyance motor M2, and a recording. A special purpose integrated circuit (ASIC) 603 that generates a control signal for controlling the head 3, and a RAM 604, an MPU 601, an ASIC 603, and a RAM 604, which are provided with image data development areas and program execution areas, are connected to each other. A system bus 605 for transferring data, and an A / D converter 606 for inputting analog signals from the sensor group described below, A / D converting them, and supplying digital signals to the MPU 601 and the like.

  In FIG. 2, reference numeral 610 denotes a computer (or a reader for image reading, a digital camera, etc.) serving as a supply source of image data, and is collectively referred to as a host device. Image data, commands, status signals, and the like are transmitted and received between the host apparatus 610 and the recording apparatus 1 via an interface (I / F) 611.

  Further, reference numeral 620 denotes a switch group, which instructs activation of a power switch 621, a print switch 622 for instructing printing start, and a process (recovery process) for maintaining the ink ejection performance of the recording head 3 in a good state. For example, a recovery switch 623 for receiving a command input from the operator. Reference numeral 630 denotes a position sensor 631 such as a photocoupler for detecting the home position h, a temperature sensor 632 provided at an appropriate location of the recording apparatus for detecting the environmental temperature, and the like. It is a sensor group.

  Further, 640 is a carriage motor driver that drives a carriage motor M1 for reciprocating scanning of the carriage 2 in the direction of arrow A, and 642 is a conveyance motor driver that drives a conveyance motor M2 for conveying the recording medium P.

  The ASIC 603 transfers drive data (DATA) of the recording element (heater) to the recording head while directly accessing the storage area of the RAM 602 during recording scanning by the recording head 3.

<Structure of ink flow path and ink discharge port of recording head (FIG. 9)>
FIG. 9 is a perspective view showing a three-dimensional structure of a portion of the recording head 3 that ejects black ink.

  From FIG. 9, the flow of ink supplied from the ink cartridge 6K containing black (K) ink becomes clear. As shown in FIG. 9, the recording head 3 has an ink supply channel 102 for supplying black (K) ink. From the ink cartridge 6K, black ink is supplied to the ink supply channel 102 from the back side of the substrate 100. A supply path (not shown) for supplying is provided.

  Through this ink channel, the black ink is guided to the electrothermal transducer (heater) 40 provided on the substrate by the ink flow path 30. When the electrothermal transducer (heater) 40 is energized through a circuit to be described later, heat is applied to the ink on the electrothermal transducer (heater) 40 and the ink is boiled. Ink droplets 90 are ejected from the ejection port 35 by the bubbles.

  In FIG. 9, reference numeral 100 denotes an electrothermal transducer to be described in detail later, various circuits that drive the memory, memory, various pads that form electrical contacts with the carriage 2, and recording in which various signal lines are formed. A head substrate (hereinafter referred to as a head substrate or a heater board).

  One electrothermal transducer (heater), a MOS-FET for driving the electrothermal transducer, and the electrothermal transducer (heater) are collectively referred to as a recording element, and a plurality of recording elements are collectively referred to as a recording element section.

  Although FIG. 9 shows a three-dimensional structure corresponding to the portion for ejecting black ink in the recording head 3, the corresponding portion of the recording head 3 used for ejecting the other three color inks also has the same structure. doing. However, the structure is three times that shown in FIG. That is, there are three ink channels, and the size of the head substrate is about three times as large.

<Configuration of head cartridge (FIG. 10)>
As described above, the ink cartridge and the recording head may be formed so as to be separable and replaceable. However, as the head cartridge in which the ink cartridge and the recording head are integrally configured, the ink is used up. Sometimes the entire head cartridge may be replaced.

  FIG. 10 is an external perspective view showing a configuration of a head cartridge IJC in which an ink cartridge and a recording head are integrated. In the head cartridge IJC, as shown in FIG. 10, the left side from the dotted line K is the ink cartridge part IT, and the right side is the recording head part IJH. Such a head cartridge IJC is provided with an electrode (not shown) for receiving an electric signal supplied from the carriage side when mounted on the carriage, and the recording head is driven by this electric signal. Ink is discharged.

  In FIG. 10, reference numeral 500 denotes an ink discharge port array. Further, the ink cartridge portion IT is provided with a fibrous or porous ink absorber for holding ink, and is filled with ink.

  Hereinafter, embodiments of the recording head according to the present invention mounted on the above-described ink jet recording apparatus will be described.

[First embodiment]
FIG. 3 shows an equivalent circuit of a structure built in (element substrate) on the heater board of the recording head 3 according to the first embodiment of the present invention. Here, one heater RH among a plurality of heaters is shown. FIG. 6 is a diagram illustrating only the peripheral circuit and the peripheral circuit. Note that the same reference symbols are used for parts common to the circuit configuration of FIG. 5 shown in the conventional example.

  Specifically, FIG. 3 shows an arbitrary heater RH on the heater board, a driver transistor M1 for energizing the heater, and its peripheral circuit.

  Here, the heater RH has a resistance value of about 50Ω to 1 kΩ and is connected to a heater power source VH having a voltage of about a dozen V to a few dozen V. The driver transistor M1 is a high breakdown voltage MOS transistor having a breakdown voltage equal to or higher than the heater voltage VH, and a current flows through the heater RH only during the time when the MOS transistor M1 is turned on.

  It should be noted that the actual heater board includes the elements shown in the figure corresponding to the number of nozzles of the recording head, and in addition to these elements, the heater to be energized and its heater Conventionally, a logic circuit for defining energization time, an input circuit for inputting a signal to be applied to the logic circuit into the heater board, a sensor for detecting temperature information, and the like have been built and arranged. Similar to the example.

  Hereinafter, each element of FIG. 3 will be described.

  The LVC is a booster circuit for increasing the amplitude of a heat pulse signal applied from a logic circuit (not shown). The amplitude of the heat pulse signal applied from the logic circuit is a pulse signal having a relatively low voltage amplitude such as 3.3 V or 5 V, and this voltage is boosted and converted to a higher voltage (VHA) such as 8 V or 10 V. In this way, by driving the power MOS transistor with a voltage higher than the logic voltage, the on-resistance of the transistor is reduced and efficient heater driving is possible. In this embodiment, the booster circuit LVC functions as an inverter and is configured to further invert the logic with an inverter composed of the MOS transistors M3 and M4 in the next stage.

  When the output of the inverter composed of the MOS transistors M3 and M4 is applied to the gate of the power MOS transistor M1 and the MOS transistor M1 is turned on, a heater current flows through the heater RH, and heat generation and ink bubbling occur.

  The MOS transistor M2 forms a feedback circuit together with the resistor R1.

  When the heater current flows, a constant voltage is generated across the resistor R1. When this voltage becomes equal to or higher than the threshold voltage Vth of the MOS transistor M2, the gate voltage of the power MOS transistor M1 decreases to a voltage obtained by dividing the output of the booster circuit LVC by the on resistances of the MOS transistors M2 and M3.

  In such a circuit configuration, if the resistance value of the resistor R1 and the on-resistance values of the MOS transistors M2 and M3 are set to optimum values, the current limitation is performed so that the heater current does not flow beyond a certain value due to the effect of the feedback circuit. Can be added. That is, when a desired heater current flows, the potential difference generated by the resistor R1 may be set to a value that is about the threshold voltage Vth at which the MOS transistor M2 is turned on.

  Therefore, according to the embodiment described above, the current flowing through each heater can be made constant by limiting the current by the feedback circuit.

[Second Embodiment]
FIG. 4 is a diagram showing only one heater RH and its peripheral circuit extracted from the plurality of heaters mounted on the heater board of the recording head 3 according to the second embodiment of the present invention. The same reference symbols are used for parts common to the circuit configuration of FIG. 5 shown in the conventional example and the circuit configuration of FIG. 3 shown in the first embodiment. Therefore, the description of the components already described is omitted.

  When the configuration shown in FIG. 4 is compared with the configuration shown in FIG. 3, in the second embodiment, the current is limited by providing a feedback circuit from the heater current to the gate voltage of the power MOS transistor, as in the first embodiment. However, the second embodiment is different in that a resistor R2 is added.

  Hereinafter, elements characteristic of the second embodiment will be described.

  In this embodiment, the booster circuit LVC functions as an inverter, and is configured to further invert the logic with an inverter comprising MOS transistors M3 and M4 and a resistor R2 in the next stage. Then, the output of the inverter composed of the MOS transistors M3 and M4 and the resistor R2 is applied to the gate of the power MOS transistor M1, and when M1 is turned on, a heater current flows through the heater RH to generate heat and cause ink bubbling.

  The resistor R2, which is also a feature of this embodiment, controls the voltage applied to the gate voltage of the power MOS transistor M1 by dividing the voltage with the ON resistance of the MOS transistor M2 constituting the feedback circuit described later. It is arranged.

  Similar to the first embodiment, the MOS transistor M2 forms a feedback circuit together with the resistor R1. Therefore, when the heater current flows through the heater RH, a constant voltage is generated across the resistor R1. When this voltage becomes equal to or higher than the threshold voltage Vth of the MOS transistor M2, a voltage obtained by dividing the output from the booster circuit LVC by the ON resistance of the MOS transistor M3, the resistor R2, and the MOS transistor M2 is used as the gate voltage of the power MOS transistor M1. What is lowered to is applied.

  Here, if the resistance values of the resistors R1 and R2 and the on-resistances of the MOS transistors M2 and M3 are set to optimum values, a current limit may be applied so that the heater current does not flow beyond a certain value due to the effect of the feedback circuit. it can. That is, when a desired heater current flows, the potential difference generated by the resistor R1 may be set to a value that is about the threshold value Vth at which the MOS transistor M2 is turned on.

  Therefore, according to this embodiment described above, the current flowing through each heater can be made constant by limiting the current by the feedback circuit.

  Compared with the configuration of the first embodiment, in this embodiment, the value of the heater current can be selected by adjusting the value of the resistor R2 in addition to the MOS transistors M2 and M3. Even when a relatively small size transistor is arranged in both of the transistors M2 and M3, it is further advantageous in that the degree of freedom of the gate voltage setting value of the power MOS transistor M1 can be expanded.

  In addition, by adding the resistor R2, there is an effect that the charge application to the gate of the power MOS transistor M1 gradually proceeds.

  When a charge is suddenly applied to the gate of the power MOS transistor, the on-resistance of the MOS transistor decreases in a short time, and the drain-source current flows rapidly. Such a steep current change may induce power supply noise in some cases and cause the recording head to malfunction, so there is an advantage in gently applying the charge to the gate of the power MOS transistor M1.

[Other embodiments]
Although the power transistor as a driving element used for driving the heater RH shown in FIGS. 3 to 4 is a MOS transistor, the present invention is not limited thereto. For example, as the driving element, Bipolar transistors may be used. In this case, the output voltage from the booster circuit is applied to the base voltage of the bipolar transistor, and the base voltage is caused by the on-resistance of a plurality of bipolar transistors having different polarities connected in series between the power supply voltage VH and the substrate potential GNDH. It becomes the divided value.

  Further, the base voltage of the bipolar transistor is such that the on-resistance of a plurality of bipolar transistors of different polarities connected in series between the power supply voltage VH and the substrate potential GNDH and the resistance element R2 connected as shown in FIG. The value is divided by.

  In the above-described embodiment, the ink jet recording head that rapidly heats and vaporizes the ink by the heating element (heater) and discharges ink droplets from the orifice by the pressure of the generated bubbles has been described as an example. It will be apparent that the present invention can also be applied to a recording head which performs recording by this method.

  In this case, instead of the heater resistance in each of the above-described embodiments, elements used in each system are provided.

  In the above embodiments, the liquid droplets ejected from the recording head have been described as ink, and the liquid stored in the ink tank has been described as ink. However, the storage is limited to ink. It is not a thing. For example, a treatment liquid discharged to the recording medium may be accommodated in the ink tank in order to improve the fixability and water resistance of the recorded image or to improve the image quality.

  The above embodiments include means (for example, an electrothermal converter) that generates thermal energy as energy used for ink ejection, particularly in the ink jet recording system, and changes the state of the ink by the thermal energy. High density and high definition of the recording can be achieved by using the generating method.

  As its typical configuration and principle, for example, those performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 are preferable. This method can be applied to both a so-called on-demand type and a continuous type. In particular, in the case of the on-demand type, a rapid temperature rise exceeding the film boiling corresponding to the recorded information is applied to the electrothermal transducer disposed corresponding to the liquid path holding the liquid (ink). By applying at least one drive signal that gives the heat, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head, resulting in a one-to-one correspondence to this drive signal. This is effective because bubbles in the liquid (ink) can be formed. By the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection opening to form at least one droplet. When the drive signal is pulse-shaped, the bubble growth and contraction is performed immediately and appropriately, and thus it is possible to achieve the discharge of the liquid (ink) with particularly excellent responsiveness, which is more preferable.

  As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by employing the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface.

  As the configuration of the recording head, in addition to the combination configuration (straight liquid flow path or right-angle liquid flow path) of the discharge port, the liquid path, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, the heat acting surface The configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose a configuration in which is disposed in a bending region, are also included in the present invention.

  Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length is satisfied by a combination of a plurality of recording heads as disclosed in the above specification. Either a configuration or a configuration as a single recording head formed integrally may be used.

  In addition, a cartridge type recording head cartridge in which an ink tank (container) is integrally provided in the recording head itself described in the above embodiment may be used. It is also possible to adopt a replaceable chip-type recording head that enables easy connection and supply of ink from the apparatus main body. The ink tank of the recording head cartridge may be filled or refilled with ink.

1 is an external perspective view showing an outline of a configuration of an ink jet recording apparatus that is a typical embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration of a control circuit of the ink jet recording apparatus of FIG. 1. FIG. 5 is a diagram showing only one heater RH and its peripheral circuit extracted from a plurality of heaters mounted on the heater board of the recording head 3 according to the first embodiment of the present invention. FIG. 6 is a diagram illustrating only one heater RH and its peripheral circuit extracted from a plurality of heaters mounted on the heater board of the recording head 3 according to the second embodiment of the present invention. FIG. 6 is a drive circuit diagram of a recording element mounted on a conventional recording head. FIG. 6 is a diagram schematically showing the impedance of wiring of a recording element mounted on a conventional recording head. FIG. 10 is a diagram schematically showing the impedance of the wiring of a recording element that is divided in a conventional recording head. It is a figure which shows an example of the wiring pattern which designed wiring so that wiring resistance R3-R10 shown in FIG. 7 might become equal resistance value. FIG. 3 is a perspective view showing a three-dimensional structure of a portion of the recording head 3 that ejects black ink. 2 is an external perspective view showing a configuration of a head cartridge IJC in which an ink cartridge and a recording head are integrated. FIG.

Explanation of symbols

GNDH Power supply ground terminal LVC Booster circuit M1 Power MOS transistor M2 NMOS transistor (feedback circuit)
M3 PMOS transistor M4 NMOS transistor RH Heater resistance R1 Resistance (feedback circuit)
R2 resistors R1 to R10 wiring parasitic resistance SW switching element VHA boosting power source VH heater power source

Claims (13)

A recording head having a plurality of recording elements connected to a common power line,
A first transistor connected in series to each of the recording elements for driving the recording element;
A first resistor connected in series to the recording element and connected to the first transistor;
A recording head comprising: a second transistor that receives a potential between the first transistor and the first resistor and adjusts an applied voltage applied to drive the first transistor.   The recording head according to claim 1, wherein the first and second transistors are MOS transistors.   The recording head according to claim 2, wherein the driving state of the recording element is detected from a potential difference generated in the first resistor. One end of the first resistor is connected to the gate of the second MOS transistor, the other end is connected to the source,
The recording head according to claim 2, wherein a drain of the second MOS transistor is connected to a gate of the first MOS transistor. A booster circuit for boosting an input voltage for driving the drive element;
A third MOS transistor and a fourth MOS transistor having different polarities, which are connected in series between the power supply voltage side and the power supply ground side, in the subsequent stage of the voltage booster circuit;
5. The recording head according to claim 2, wherein the third MOS transistor is provided on the power supply voltage side, and the fourth MOS transistor is provided on the power supply ground side.   The gate voltage of the first MOS transistor is a voltage obtained by dividing an output voltage from the booster circuit by an on-resistance of the second MOS transistor and the third MOS transistor. 5. The recording head according to 5. A second resistor connected in series between the third MOS transistor and the fourth transistor;
The gate voltage of the first MOS transistor is a voltage obtained by dividing the output voltage from the booster circuit by the on-resistance and the second resistance value of the second MOS transistor and the third MOS transistor. The recording head according to claim 5, wherein:   The recording head according to claim 1, wherein the recording head is an ink jet recording head that performs recording by discharging ink.   The recording head according to claim 1, wherein the recording element is a heating resistance element.   The recording head according to claim 8, wherein the recording element is an electrothermal transducer for generating thermal energy applied to the ink in order to eject the ink using thermal energy.   A recording head cartridge comprising: the recording head according to claim 10; and an ink container for holding ink supplied to the recording head.   The recording head cartridge according to claim 11, wherein the ink container is filled with ink. A recording apparatus that performs recording with the recording head according to claim 1 or the recording head cartridge according to claim 11 or 12.

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