JP4471357B2 - Liquid discharge head and liquid discharge apparatus - Google Patents

Description

  The present invention relates to a liquid discharge head and a liquid discharge apparatus having a switch circuit in a liquid discharge mechanism, and in particular, by injecting energy into an ink discharge mechanism to discharge ink and depositing ink droplets on a recording medium. The present invention relates to a liquid ejection head and apparatus applicable to an inkjet recording head and an inkjet recording apparatus for forming an image, or an apparatus used for manufacturing a DNA chip, an organic transistor, a color filter, and the like.

  A recording apparatus such as an ink jet printer will be described as an example of the liquid ejecting apparatus. As a structure of the ink discharge mechanism (liquid discharge mechanism), an electric current as an energy is supplied to the heater composed of the heating resistor, and the ink (liquid) is heated using the heat generated by the heater to generate bubbles. 2. Description of the Related Art Conventionally, an ink that presses and ejects ink by an expansion motion is known. An ink jet recording system that forms an image by adhering ink droplets ejected from the ink ejection mechanism onto a recording medium has the advantages of high recording quality and low noise. Further, the ink jet recording method has advantages that color recording is relatively easy, recording is possible on plain paper, and the apparatus is easily downsized. Further, the ink jet recording method can perform high-speed recording by arranging a large number of ejection ports from which ink is ejected. For these reasons, the ink jet recording method is widely used in information output devices such as printers and facsimiles.

  FIG. 8 shows a main circuit configuration of a conventional inkjet recording head (liquid ejection head). As shown in the figure, this circuit has a configuration in which an ink discharge mechanism 51 including a heater and a switch circuit 52 are connected in series between a power supply VH and a ground potential GNDH. An external control signal from the main body of the ink jet recording apparatus according to the image signal is input to the switch circuit 52, whereby ON / OFF control of the current flowing to the heater is performed.

  The heater is formed in a nozzle filled with ink through an ejection port for ejecting ink. A first protective film made of silicon nitride (SiN) and having insulating properties is usually formed on the heater, and a tantalum (Ta) film is formed as a second protective film. The second protective film (hereinafter referred to as a Ta protective film) functions to protect the heater from an impact generated by a chemical reaction of the ink or the growth or disappearance of the bubbles when the ink bubbles are generated.

  When the switch circuit 2 is turned on and a current flows through the heater, the heater generates heat, and the generated heat heats the ink through the first and second protective films. When the interface temperature between the protective film and the ink reaches a predetermined temperature, ink bubbles are generated, and the ink on the heater is ejected from the ejection port.

  FIG. 9 shows the temperature change of the heater portion of the conventional ink jet recording head during ink ejection. FIG. 9A is a graph showing a change in the temperature of the heater, that is, the heating resistor, as a solid line, and a change in the surface temperature of the second protective film (hereinafter referred to as a Ta protective film) as a dotted line. FIG. 9B is a graph showing the waveform of the pulse voltage input to the switch circuit at the time corresponding to FIG.

The heater temperature and the surface temperature of the Ta protective film are T ₀ which is the same as the room temperature immediately before the switch circuit is turned on (time t ₀ ). When the switch circuit is turned on and a current flows through the heater, the heater temperature and the surface temperature of the Ta protective film, which have been T ₀ which is the same as the room temperature, increase. At time t ₁ when the surface temperature of the Ta protective film reaches T ₁ (≈300 ° C.), bubbles are generated at the interface between the Ta protective film and the ink. At this time, the heater temperature has already reached the slightly higher T ₂ than T _1. Due to the generation of bubbles, heat does not propagate from the surface of the Ta protective film into the ink, so the surface temperature of the Ta protective film starts to increase rapidly. Similarly, the heater temperature rises rapidly. These temperatures, the switching circuit was turned OFF, the time t ₃ when interrupting the flow of current to the heater and an apex, i.e., the temperature at this time the heaters and Ta protective film becomes maximum temperature T _P1, T _P2. The switching circuit was turned OFF, after the time t ₃ when the interrupting the flow of current to the heater, since the heater does not generate heat, the surface temperature of the heater temperature and Ta protective film drops sharply, eventually returns to the original room temperature T _0.

In such an ink jet recording head, if the ink ejection is repeated beyond the endurance limit, the ink may be burned on the surface of the second protective film (Ta). It becomes a factor to reduce the sex. Further, when the ink is repeatedly ejected, the surface of the Ta protective film is shaved and gradually thinned, the ink passes through the Ta protective film, the ink penetrates into the first protective film, and further to the heater and the metal wiring Ink penetrates and eventually breaks. On the other hand, the time between the time t ₃ when the switch circuit is turned off and the current flowing to the heater is cut off and the time t ₁ when bubbles are generated are shortened, and the maximum temperature T _P1 and the Ta protective film of the heater are reduced. It has been experimentally shown that the durability of the ink jet recording head is remarkably improved as the maximum temperature T _P2 is lowered.

Conventionally, in order to lower the highest temperature T _P2 of maximum temperature T _P1 and Ta protective layer of the heater, it has been made various devices. As an example of this, Patent Document 1 discloses a control in which a temperature sensor is attached to an ink jet recording apparatus, the temperature of the ink jet recording head is sensed by the temperature sensor, and the current is supplied to the heater, that is, the switch circuit is turned on. A configuration is disclosed in which a printer body is provided with a mechanism for controlling the signal width. At this time, the temperature sensor measures the temperature of the entire inkjet recording head.

As another example, in Patent Document 2, when a plurality of heaters are driven at the same time and the number of drives changes sequentially, the control for controlling the time for driving the heaters according to the number of simultaneously driven heaters is performed. A configuration in which the apparatus is provided in a printer main body is disclosed.
JP 2001-129995 A JP 2001-341355 A

  However, since the inkjet recording head disclosed in Patent Document 1 described above senses the entire temperature of the inkjet recording head, it is difficult to accurately grasp the temperature near the heater and control the switch circuit. It is. Therefore, there is room for more effective switch circuit control to keep the maximum temperature in the vicinity of the heater low.

  Further, in consideration of variations in heater currents flowing through a large number of heaters, the time for which the switch circuit is turned on needs to be longer than the time necessary for ink ejection in order to eject ink reliably. There is a limit to improving the durability of the heater by setting the time. On the other hand, measures are taken to reduce the variation in the heater current, but it is difficult to completely eliminate the variation, and it is expensive to correct the variation.

  In addition, due to process variations in each mass-produced inkjet recording head, the ON time of the switch circuit required for ink foaming (ejection) is measured before factory shipment, and this time is stored in the memory. The pulse width is preferably adjusted to the time stored in this memory by the PWM circuit mounted on the printer body. For this purpose, a memory is required for each ink jet recording head. Thus, the need for measurement before shipment from the factory and the installation and setting of the memory contribute to an increase in the cost of the printer main body.

  The present invention uses a configuration capable of appropriately executing ON / OFF control in a liquid discharge head that performs ON / OFF of energy injection into the liquid discharge mechanism and discharges the liquid filled in the liquid discharge mechanism. An object of the present invention is to provide a liquid discharge head capable of improving durability and reducing the cost, and a liquid discharge apparatus including the same.

In order to achieve the above-described object, in the liquid discharge head according to the present invention, a liquid discharge mechanism and a switch circuit are electrically connected in series between a first power supply and a second power supply, and the liquid discharge is performed by the switch circuit. a liquid discharge head for controlling the liquids ejection unloading by turning oN / OFF the energy injection into the mechanism, a signal correlated with the volume containing the parasitic element connected to the connection point of the liquid ejection mechanism and the switching circuit And a capacitance detection circuit for outputting for controlling the operation of the switch circuit.

  According to this configuration, the fact that the liquid has been discharged can be detected by the change in the capacitance at the connection point between the liquid discharge mechanism and the switch circuit, and immediately after the liquid has been discharged, the energy injection into the liquid discharge mechanism can be turned off. it can.

  By using the present invention, it is possible to prevent excessive energy from being injected into the liquid discharge mechanism even after the liquid has been discharged, thereby improving the durability of the heater. In addition, the heater current variation correction as in the prior art, the ON time measurement of the switch circuit necessary for foaming before shipment from the factory, the installation of a memory circuit for storing this time, and further to the recording device main body The necessity of mounting the PWM circuit is eliminated, and the manufacturing cost of the recording apparatus can be greatly reduced.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a main circuit configuration diagram of a portion including an ink discharge mechanism (liquid discharge mechanism) 1 having a heater 20 and nozzles in an ink jet recording head (liquid discharge head) according to a first embodiment of the present invention. 2 shows a cross-sectional view of an ink discharge mechanism 1 of an ink jet recording head as an example to which this circuit configuration can be applied.

  In the ink ejection mechanism 1, a heater layer 11 made of a heating resistor and a metal wiring layer 12 are formed on the element substrate 10 in a predetermined pattern. In these methods, a heater layer 11 is deposited on a silicon substrate as the element substrate 10, a metal wiring layer 12 is further laminated thereon, and the metal wiring layer 12 and the heater layer 11 are simultaneously etched into a predetermined pattern. It can be formed by partially etching only the metal wiring layer 12 at a predetermined position to expose the heater layer 11. The portion where the heater layer 11 is exposed functions as a heater 20 that generates heat when a current flows through the metal wiring layer 12.

  On the exposed portions of the metal wiring layer 12 and the heater layer 11, a first protective film 13 having insulating characteristics is formed. As the first protective film 13, silicon nitride (SiN) is generally laminated by a plasma CVD method. A second protective film 14 is formed on the first protective film 13. The second protective film 14 functions to protect the heater from the impact generated by the chemical reaction of the ink and the growth and disappearance of the bubbles when the ink bubbles are generated. As the second protective film 14, a tantalum (Ta) film is generally laminated.

  On the second protective film 14, a discharge port 17 for discharging the ink 16 and a nozzle forming member 15 that communicates with the discharge port 17 and forms a flow path filled with the ink 16 are stacked. The discharge port 17 is formed immediately above the heater 20. One end of the flow path is an ink inlet 18 through which ink is supplied from an ink supply system (not shown).

  FIG. 2A shows a state in which the ink 16 is filled in the nozzles. From this state, when a current is passed through the heater 20, the heater 20 is heated, and the ink is foamed and discharged from the discharge port 17. FIG. 2B schematically shows a state immediately after the ink 16 is ejected. After the ink is ejected, the ink 16 is supplied from the ink inlet 18, the ink 16 is refilled into the nozzle, and the state returns to the state shown in FIG.

  Next, a circuit configuration of a portion including the ink ejection mechanism 1 according to the present embodiment will be described with reference to FIG.

  Between the first power supply VH and the second power supply GNDH, an ink discharge mechanism 1 and a switch circuit 2 for controlling energy injected into the ink discharge mechanism 1 are connected in series. In the present embodiment, the second power supply GNDH is set to the ground potential.

  A switch control circuit 4 that controls the switching operation is connected to the switch circuit 2. A capacitance detection circuit 3 that detects a capacitance 5 including a parasitic element connected to the connection point is connected to a connection point between the ink ejection mechanism 1 and the switch 2. The capacitance detection circuit 3 is connected to the switch control circuit 4, and a detection signal from the capacitance detection circuit 3 is input to the switch control circuit 4. The switch control circuit 4 also receives an external control signal from the main body of the ink jet recording apparatus (liquid ejecting apparatus) for ejecting ink in accordance with image data formed by the ink jet recording head.

  Next, the operation of the circuit of FIG. 1 will be described.

  When a control signal serving as an ink ejection command is input to the switch control circuit 4, the switch control circuit 4 shifts the switch 2 to an ON state, thereby starting energy injection into the ink ejection mechanism 1. That is, current starts to flow through the heater 20. When current starts to flow through the heater 20, the heater 20 starts to generate heat, and the ink is heated by the heat. When the interface temperature between the second protective film of the heater 20 and the ink 16 reaches a predetermined temperature, the ink 16 in the nozzle is ejected from the ejection port 17 toward the recording medium.

At this time, the capacitance C _{H at} the connection point between the ink ejection mechanism 1 and the switch 2 changes. This is because, as shown in FIG. 2A, the capacity _CH is different between when the ink 16 is present on the heater 20 and when there is no ink 16 on the heater 20 as shown in FIG. 2B. Because. If the capacity value when the ink is filled is C1, and the capacity value when the ink runs out is C2, the relationship C1> C2 is established.

After detecting the change in the capacitance C _H , the capacitance detection circuit 3 outputs a detection signal correlated with the completion of ejection to the switch control circuit 4. Here, “correlation” is a signal for setting a threshold value in advance, even when the ink is completely exhausted, and assuming that ejection is completed when the remaining amount of ink falls below a certain amount. . The switch control circuit 4 shifts the switch 2 to the OFF state by this detection signal, cuts off the energy injection to the ink discharge mechanism 1 and cuts off the current flowing through the heater 20.

According to the embodiment described above detects a change in capacitance C _H generated in correlation with the discharge of the ink, thereby promptly after ink has been ejected, stop energy input to the ink ejection mechanism 1 can do. Therefore, it is possible to suppress excessive injection of energy into the ink ejection mechanism 1 having the heater 20 until after the ink is ejected, and to improve the durability of the heater 20.

At this time, in this embodiment, unlike the conventional technique, the energy injection amount to the heater is not controlled by the injection time, and thus it is not necessary to correct the variation in the heater current in order to adjust the energy injection amount. Before shipping to the factory, measure the energization time of the heater necessary for foaming and store it in the memory, install this memory circuit, and install the PWM circuit in the main body of the inkjet recording device Is also unnecessary. For these reasons, according to this embodiment, the manufacturing cost of the ink jet recording apparatus can be significantly reduced.
(Second Embodiment)
FIG. 3 shows a main circuit configuration diagram of a portion including an ink discharge mechanism having a heater RH of the ink jet recording head according to the second embodiment of the present invention.

  One end of the heater RH is connected to the drain of the power transistor Tr constituting the switch circuit, the other end of the heater RH is connected to the first power supply VH, and the source of the power transistor is connected to the second power supply GNDH. . In the present embodiment, the second power supply GNDH is set to the ground potential. In FIG. 3, the back gate of the power transistor Tr is short-circuited with the source. However, this is not always necessary, and the back gate may be connected to a third power source different from the source.

A capacitance detection circuit DET is connected to a connection point A between the drain of the power transistor Tr and the heater RH. Capacitance detection circuit DET has an oscillating circuit OSC which is an inverter, the oscillation circuit OSC, the capacitance C _H of the connection point A is connected as a load capacity. The output F _out of the oscillation circuit OSC is input to the buffer circuit BUF through the low pass filter LPF. Capacity output S1 of the detection circuit DET is the output of the first exclusive OR circuit XOR1, which receives the output F _out and the output S0 of the buffer circuit BUF of the oscillation circuit OSC. The buffer circuit BUF is provided to shape the waveform of the output of the low-pass filter LPF, and may not be provided depending on the characteristics of the low-pass filter LPF.

Since the capacitor C _H at the connection point A, a state where the ink on the heater RH is present, in the absence, it is larger in the state where the ink on the heater RH is present as described previously. Therefore, the oscillation frequency of the output F _out of the oscillation circuit OSC is lower when ink is present on the heater RH than when no ink is present. The characteristic of the low-pass filter LPF is that the output F _out of the oscillation circuit OSC is passed at a relatively low output frequency when ink is present on the heater, and when the ink is ejected and no ink is present on the heater. It is set to cut off when the output frequency is relatively high.

  The output S1 of the capacitance detection circuit DET is input to the switch control circuit CNT and connected to the clock terminal of the first D flip-flop DFF1. Further, the switch control circuit CNT is provided with a second D flip-flop DFF2 in which the first external control signal HES is input to the clock terminal. The inputs D of the first D flip-flop DFF1 and the second D flip-flop DFF2 are both connected to the power supply voltage VDD of the logic circuit, both have a reset terminal, and both reset terminals have a second terminal. An external control signal HER is input. The output VG of the capacitance detection circuit DET is the output of the second exclusive OR circuit XOR2 that receives the output S2 of the first D flip-flop DFF1 and the output S3 of the second D flip-flop DFF2, It is connected to the gate of the power transistor Tr.

  Next, the operation of the present embodiment will be described with reference to FIG. FIG. 4 is a timing chart when the circuit of FIG. 3 is operated.

Prior to ink ejection, the first and second D flip-flops DFF1 and DFF2 are reset as will be described later. Since ink is present on the heater RH, the capacitance C _{H at} the connection point A is relatively large. Therefore, the output frequency of the output F _out of the oscillation circuit OSC having the capacitance C _H as a load is relatively low. , F _out pass through the low pass filter LPF. For this reason, both inputs of the first exclusive OR circuit XOR1 are the same, and therefore the output S1 is at a low level. At this time, although not shown in the drawing, when F _out passes through the low-pass filter LPF, the output delay time with respect to F _out of S0 is set so that the output of the first exclusive OR circuit XOR1 becomes low level. In order to cancel out, a delay circuit may be provided between the oscillation circuit OSC and the first exclusive OR XOR1 as necessary.

  Since S1 is at the low level, the outputs S2 and S3 of the first and second D flip-flops DFF1 and DFF2 are both set to the low level before the pulse signal is input as the external control signal HES as described later. It has become. Therefore, the output of the second exclusive OR circuit XOR2 having S2 and S3 as inputs, that is, the output VG of the switch control circuit CNT is at the low level, and the power transistor Tr is in the OFF state.

  At the time of ink ejection, first, as the first external control signal HES, a pulse signal which is an ink ejection command corresponding to image data formed by the recording head is input from the recording apparatus main body side. When a pulse signal is input as the first external control signal HES, the output S3 of the second D flip-flop DFF2 becomes high level at the rising edge. At this time, since the ink still exists on the heater, the output S2 of the first D flip-flop DFF1 remains at the low level, and therefore the second exclusive OR circuit XOR2 The low level S2 and the high level S3 are inputted, and the output VG thereof becomes the high level. As a result, the power transistor Tr is turned on, and the current starts to flow through the heater RH.

When current starts to flow through the heater RH, the heater RH generates heat, and the heat heats the ink through the protective film on the heater RH. When the ink reaches a predetermined temperature, it foams and is ejected from the ejection port. Thus, when the ink runs out from the RH heater, the value of the capacitance C _H of the connection point A becomes small, the oscillation frequency of the output signal F _out of the oscillation circuit OSC is high. At this time, the output F _out of the oscillation circuit OSC is blocked by the low-pass filter LPF and the output S0 of the buffer circuit BUF is fixed at the high level (or low level) from the above-described characteristics of the low-pass filter LPF. the output S1 of the OR circuit XOR1 is a pulse wave of the same frequency and F _out. At the first rising edge of the pulse signal of S1, the output S2 of the first D flip-flop DFF1 becomes high level. Accordingly, the output VG of the second XOR again becomes a low level, thereby turning off the power transistor Tr and stopping the current injection into the heater RH.

When ink is ejected from the nozzle, the ink is again filled in the nozzle during a certain time determined by the characteristics of the nozzle. Accordingly, the oscillation frequency of the output signal F _out of the oscillation circuit OSC is lowered again, S0 and S1 is returned to before foaming state. Thereafter, a pulse signal is input as an external control signal HER from the recording apparatus at an appropriate timing, whereby the first and second D flip-flops DFF1 and DFF2 are reset, and their outputs S2 and S3 are at low level. The circuit returns to the state before ink ejection. At this time, since the outputs S2 and S3 are simultaneously returned to the low level, the output VG of the switch control circuit CNT remains low.

The configuration of the embodiment as described above, was used capacitance detection circuit DET which outputs a signal in response to a change in the capacitance C _H of the connecting point of the heater and the switch circuit, ON / OFF of the power transistor Tr as a switching circuit Control can be realized. Therefore, according to the present embodiment, as described in the first embodiment, it is possible to improve the durability of the heater RH and to obtain the effect that the manufacturing cost of the ink jet recording head can be reduced.

  In FIG. 3 of the present embodiment, a MOS transistor is described as the power transistor Tr. However, the switch circuit in the present invention is not limited to the MOS transistor, and may be a DMOS transistor, an offset MOS transistor, a bipolar transistor, or the like. Various transistors having switch characteristics capable of ON / OFF operation can be used.

Further, the configuration of the present invention described in these embodiments can also be applied to detecting ink discharge failure. Here, there are three main causes for ink discharge failure.
Cause 1: The ink inflow path is clogged with dust and the heater resistance RH is not filled with ink, so that ink is not ejected.
Cause 2: Ink is not ejected because the heater resistance RH does not function as a heating element due to its life or the like (when disconnected).
Cause 3: The nozzle outlet is clogged with dust, etc., and ink is not discharged.

  In the configuration of the present embodiment, it is possible to detect ink discharge failure in the case of cause 1 and cause 2 among the above three causes.

  In these cases, the ink does not fill the heater resistor RH or is not discharged after being filled, so that the capacitance value does not change. Therefore, if it is detected whether the capacity has changed even after a predetermined time has elapsed since the voltage was applied to the heater resistor RH, ink ejection failure can be detected.

Thus, according to the configuration of the present invention, the detection circuit 3 is means for detecting a change in the parasitic capacitance C _H of the connecting point of the heater resistor RH and the switch circuit 2, the switching circuit in response to the presence or absence of the detection Overheating of the heater resistor RH can be prevented by the switch control circuit 4 that controls the above.
(Liquid discharge device)
Next, the configuration of an example of a liquid ejection apparatus that mounts the liquid ejection heads of the first and second embodiments described above will be described.

  The liquid discharge head according to the present invention is a nozzle forming member made of a molded resin or a film that forms a discharge port and a flow path communicating therewith on the insulating layer of the semiconductor device having the circuit described in each of the above-described embodiments. Can be combined. Then, this liquid discharge head is connected to an ink tank that contains ink, and is mounted on a main body of an ink jet recording apparatus as a liquid discharge apparatus. If supplied to the ejection head, it can be operated as an inkjet recording head.

  FIG. 5 is a perspective view of a part of the liquid discharge head for explaining one configuration example of such a liquid discharge head. In the figure, in order to make the configuration easy to understand, a part of the liquid ejection head is shown broken away.

  The element base 152 is an electrothermal conversion element for generating heat by flowing an electric current in accordance with an electric signal from the main body side and discharging ink from the discharge port 153 by bubbles generated by the heat. The heaters 141 are arranged in a plurality of rows. Each of the heaters 141 is connected to a wiring electrode 154 that supplies a current for driving the heater 141, and the above-described switch element (not shown) is electrically connected to one end of the wiring electrode 154. ing. Further, although not shown, the above-described capacitance detection circuit, switch control circuit, and the like are formed on the element base 152, and the circuits shown in the above-described embodiments are configured by these.

  A nozzle forming member 156 is connected on the element base 152. As a result, the discharge ports 153 disposed at positions facing the respective heaters 141, the flow paths 155 for supplying ink to the respective discharge ports 153 and the plurality of flow paths 155 provided corresponding to the respective discharge ports 153. A common liquid chamber 157 for supplying ink is formed.

  FIG. 6 shows an overall structure of an example of a liquid discharge head in which the element substrate 152 is incorporated. The element base 152 connected to the nozzle forming member 156 is incorporated in the frame body 158. The element substrate 152 is connected to a flexible printed wiring board 160 provided with a contact pad 159 at one end for receiving an electrical signal from the recording apparatus main body side. Various electric signals such as drive signals are supplied to the element base 152 via the flexible printed wiring board 160 from the controller of the recording apparatus main body.

  FIG. 7 shows an ink jet recording apparatus IJRA which is an example of a liquid discharge apparatus equipped with the liquid discharge head of the present invention.

  The liquid ejection head is mounted on the carriage HC as an ink jet recording cartridge IJC together with the ink tank IT. The carriage HC is supported by a guide rail 5003 and a lead screw 5005 and has a pin (not shown) that engages with a helical groove 5004 of the lead screw 5005. The lead screw 5005 is rotated in conjunction with forward / reverse rotation of the drive motor 9011 via the drive force transmission gears 5011 and 5009, whereby the carriage HC is reciprocated in the directions of arrows a and b.

  The ink jet recording apparatus IJRA is provided with a recording medium transport mechanism for transporting the recording paper P that is a recording medium. The recording medium transport mechanism is provided with a platen at a position facing the ink ejection surface of the liquid ejection head mounted on the carriage HC and reciprocally moved. The recording paper P is conveyed by the paper pressing plate 5002 to the carriage. It is pressed toward the platen over the moving direction of HC.

  Photocouplers 5007 and 5008 are provided at one end of the reciprocating path of the carriage HC. The photocouplers 5007 and 5008 function as a home position detecting mechanism that confirms the presence of the lever 5006 of the carriage HC in this region and transmits a signal used for switching the rotation direction of the drive motor 9011.

  A cap member for capping the ink discharge surface is supported by a support member 5013 at a position facing the ink discharge surface of the liquid discharge head with the carriage HC positioned at the home position. An in-cap opening 5023 connected to a suction means (not shown) is formed in the member. The liquid discharge head is appropriately covered with the cap member when not in use, and is protected from drying and dust adhesion, and suction recovery is performed in which a part of ink in the liquid discharge head is sucked out by the suction means. A cleaning blade 5017 for cleaning the discharge port surface of the liquid discharge head is provided alongside the cap member. The cleaning blade 5017 is supported by the main body support plate 5018 via the support member 5019 so as to be movable in the front-rear direction toward the liquid ejection head. Needless to say, the cleaning blade 5017 is not limited to this form, and a known cleaning blade can be applied. These operations include a lever 5012 for starting suction for suction recovery, a cam 5020 engaged with the carriage HC, a clutch switching mechanism that moves with the movement of the cam 5020, and switches the driving force from the drive motor 9011. It is controlled by a known transmission mechanism.

  In the capping, cleaning, and suction recovery, when the carriage HC comes to the home position side region, it is possible to perform a desired process at a corresponding position for performing each process using the action of the lead screw 5005. It is configured as follows. These processing units can be configured to perform a predetermined operation at a known timing.

  Each configuration of the ink jet recording apparatus IJRA as the liquid ejecting apparatus described above is excellent both independently and in combination, and is a preferable configuration example for the present invention. Although not described in detail, the ink jet recording apparatus IJRA has a controller drive signal supply mechanism (not shown) including an electric circuit for supplying a drive control signal corresponding to a power supply voltage and an image signal to the element base 152. have.

  The present invention has been described with reference to various preferred embodiments. However, the present invention is not limited to the details of these embodiments, and each component in each embodiment can be substituted within the scope of the present invention. Obviously, it can be replaced with the equivalent.

FIG. 2 is a schematic diagram illustrating a main circuit configuration of the ink jet recording head according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a configuration example of an ink discharge mechanism portion using a heater of the ink jet recording head of FIG. 1. It is a schematic diagram which shows the main circuit structures of the inkjet recording head of the 2nd Embodiment of this invention. 4 is a timing chart when the circuit of FIG. 3 is operated. FIG. 3 is a perspective view showing a main part of an example of an ink jet recording head to which the first and second embodiments can be applied, with a part thereof broken. FIG. 6 is a perspective view showing an overall configuration of the ink jet recording head of FIG. 5. FIG. 6 is a perspective view of an example inkjet recording apparatus on which the inkjet recording head of FIG. 5 is mounted. It is a schematic diagram which shows the main circuit structures of the conventional inkjet recording head. It is a graph which shows the change of heater temperature and protective film surface temperature when ink is discharged using the conventional inkjet recording head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ink discharge mechanism 2, CNT switch circuit 3, DET capacity detection circuit 4Switch control circuit OSC oscillation circuit LPF Low pass filter BUF Buffer circuit

Claims (3)

A liquid discharge mechanism and a switch circuit are electrically connected in series between the first power supply and the second power supply, and the liquid discharge is controlled by controlling the energy injection to the liquid discharge mechanism by the switch circuit. In the discharge head,
Have a capacitance detection circuit for detecting a signal correlated with the capacity of the connection point of the switching circuit and the liquid ejection mechanism,
The liquid ejection head , wherein the capacitance detection circuit includes an oscillation circuit using the capacitance as a load . 2. The liquid according to claim 1 , wherein the capacitance detection circuit outputs a signal obtained by processing an output signal of the oscillation circuit and a signal obtained by passing the output signal of the oscillation circuit through a low-pass filter by an exclusive OR circuit. Discharge head. The low-pass filter passes an output signal having a frequency determined by the capacitance value of the oscillation circuit when the liquid exists in the liquid ejection mechanism, and the liquid exists in the liquid ejection mechanism of the oscillation circuit. The liquid discharge head according to claim 2 , wherein an output signal having a frequency determined by a value of the capacitance when not performing has a characteristic of blocking.

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