Patent Grant
9415584
1. Field of the Invention
The present invention relates to a liquid discharge head substrate, a liquid discharge head, and a printing apparatus.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2010-155452 describes a liquid discharge head substrate that suppresses the influence of the voltage variation of a power supply line which supplies power to a discharge element for discharging a liquid. In this liquid discharge head substrate, transistors are connected to the two terminals of the discharge element. These transistors control a voltage and a current applied to the discharge element. This makes it possible to stably supply power to the discharge element.
The present inventors have found that the characteristics of transistors which drive discharge elements may vary, depending on the accuracy of the manufacturing process of a liquid discharge head substrate, among a plurality of liquid discharge head substrates obtained from different wafers or different chips. As a result, power supplied to the discharge elements may vary. Some embodiments of the present invention provide a technique of suppressing variations in the power supplied to the discharge elements among the liquid discharge head substrates.
According to some embodiments, a liquid discharge head substrate comprising a discharge unit including a discharge element configured to generate energy for discharging a liquid from an orifice and a discharge control circuit configured to control the discharge element; and a first voltage generation circuit configured to supply, to the discharge control circuit, a first driving voltage for driving the discharge control circuit, wherein the discharge unit includes a first node having a voltage correlated with a voltage to be supplied to the discharge element, and the first voltage generation circuit controls the first driving voltage based on a comparison result of the voltage of the first node and a first reference voltage supplied from outside of the liquid discharge head substrate, is provided.
According to some other embodiments, a liquid discharge head substrate comprising a discharge unit including a discharge element configured to generate energy for discharging a liquid from an orifice and a discharge control circuit configured to control the discharge element; and a first voltage generation circuit configured to supply, to the discharge control circuit, a first driving voltage for driving the discharge control circuit, wherein the first voltage generation circuit controls the first driving voltage based on a comparison result of a voltage of one terminal of the discharge element and a first reference voltage supplied from outside of the liquid discharge head substrate, is provided.
According to some other embodiments, a liquid discharge head comprising a liquid discharge head substrate and a liquid supply unit, wherein the liquid discharge head substrate comprises: a discharge unit including a discharge element configured to generate energy for discharging a liquid from an orifice and a discharge control circuit configured to control the discharge element; and a first voltage generation circuit configured to supply, to the discharge control circuit, a first driving voltage for driving the discharge control circuit, the discharge unit includes a first node having a voltage correlated with a voltage to be supplied to the discharge element, the first voltage generation circuit controls the first driving voltage based on a comparison result of the voltage of the first node and a first reference voltage supplied from outside of the liquid discharge head substrate; and the liquid supply unit is configured to supply a liquid to the liquid discharge head substrate, is provided.
According to some other embodiments, a printing apparatus comprising a liquid discharge head which comprising a liquid discharge head substrate and a liquid supply unit, and a driving unit, wherein the liquid discharge head substrate comprises a discharge unit including a discharge element configured to generate energy for discharging a liquid from an orifice and a discharge control circuit configured to control the discharge element; and a first voltage generation circuit configured to supply, to the discharge control circuit, a first driving voltage for driving the discharge control circuit, the discharge unit includes a first node having a voltage correlated with a voltage to be supplied to the discharge element, the first voltage generation circuit controls the first driving voltage based on a comparison result of the voltage of the first node and a first reference voltage supplied from outside of the liquid discharge head substrate; the liquid supply unit is configured to supply a liquid to the liquid discharge head substrate; and the driving unit is configured to drive the liquid discharge head, is provided.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
A liquid discharge head substrate according to some embodiments of the present invention will be described with reference to
The discharge control circuit 102 controls the operation of the discharge element 101 by changing a voltage applied to the discharge element 101. The discharge control circuit 102 receives a driving signal from outside of the discharge unit 105. When the driving signal is at high level, the discharge control circuit 102 applies a voltage to the discharge element 101. In response to this voltage, the discharge element 101 applies energy to the liquid. Meanwhile, when the driving signal is at low level (for example, 0V), the discharge control circuit 102 applies no voltage to the discharge element 101. In this case, the discharge element 101 applies no energy to the liquid.
The voltage generation circuit 106 receives a reference voltage Vref input from outside of the liquid discharge head substrate 100 and a monitoring node voltage Vm of the discharge control circuit 102. The monitoring node voltage Vm is correlated with the voltage applied to the discharge element 101. Therefore, the voltage generation circuit 106 can check the voltage applied to the discharge element 101 by monitoring the voltage Vm. The reference voltage Vref is supplied, for example, from a liquid discharge apparatus to the liquid discharge head substrate 100.
The voltage generation circuit 106 generates a driving voltage VFB of the discharge control circuit 102 and supplies it to the discharge control circuit 102. The discharge control circuit 102 uses the driving voltage VFB as a driving power supply voltage. The discharge control circuit 102 determines, based on the driving voltage VFB, the voltage to apply to the discharge element 101. Therefore, the voltage generation circuit 106 can control the amount of current flowing through the discharge element 101 by regulating the value of the driving voltage VFB. More specifically, the voltage generation circuit 106 controls, or regulates, the value of the driving voltage VFB such that the monitoring voltage Vm and the reference voltage Vref input from outside of the liquid discharge head substrate 100 become substantially equal to each other.
The voltage generation circuit 106 includes a comparison circuit 107 which compares the monitoring voltage Vm and the reference voltage Vref. The voltage generation circuit 106 controls, or regulates, the driving voltage VFB based on the comparison result of the comparison circuit 107 and supplies it to the discharge control circuit 102.
The effect of the liquid discharge head substrate 100 will now be described. When using a structure described in Japanese Patent Laid-Open No. 2010-155452, the characteristics of transistors in a circuit which drives a discharge element may vary, depending on the accuracy of a process when manufacturing a liquid discharge head substrate, among a plurality of liquid discharge head substrates obtained from different wafers or different chips. When the characteristics of these transistors vary, a voltage applied to the discharge element varies, and thus the amount of current flowing through the discharge element varies accordingly even if the same driving voltage is supplied to each transistor of the plurality of liquid discharge head substrates. As a result, a liquid discharge amount varies among the plurality of liquid discharge head substrates even if they are driven on the same condition.
To cope with this, the voltage generation circuit 106 of the liquid discharge head substrate 100 controls, or regulates, the value of the driving voltage VFB such that the monitoring voltage Vm and the reference voltage Vref input from outside of the liquid discharge head substrate 100 become substantially equal to each other. Therefore, if the reference voltage Vref having a predetermined value is supplied to the plurality of liquid discharge head substrates 100, the monitoring voltage Vm has a predetermined value among the plurality of liquid discharge head substrates 100 irrespective of the characteristics of the transistor in each liquid discharge head substrate 100. Since the monitoring voltage Vm is correlated with the voltage applied to the discharge element 101, the currents flowing through the discharge elements 101 also become equal to each other among the plurality of liquid discharge head substrates. As a result, a variation in the liquid discharge amount is suppressed among the plurality of liquid discharge head substrates, increasing a manufacturing yield.
A liquid discharge head substrate 200 including an example of a circuit arrangement which implements the function of the liquid discharge head substrate 100 will now be described with reference to
First, the arrangement and the operation common to each of the discharge units 105a to 105c will be described. The discharge element 101 which generates energy for discharging the liquid is the heating element and represented as a resistor in the circuit diagram. The piezoelectric element may be used in place of the heating element. The same also applies to other embodiments to be described below. One terminal of the discharge element 101 is connected to a power supply VH and the other terminal is connected to the discharge control circuit 102. The discharge control circuit 102 includes a driving transistor 103 and a control circuit 104. In this embodiment, the driving transistor 103 is formed by, for example, an NMOS transistor. One main electrode of the driving transistor 103 is connected to the discharge element 101, the other main electrode is connected to ground, and the gate electrode serving as a control electrode is connected to the control circuit 104.
The control circuit 104 of the discharge control circuit 102 receives a driving voltage VHTM as the driving power supply voltage from the voltage generation circuit 106. The driving voltage VHTM corresponds to the driving voltage VFB in
The arrangement unique to the discharge unit 105a will now be described. The discharge unit 105a outputs, as the monitoring voltage Vm, the voltage of a node 11 in the discharge control circuit 102 to the voltage generation circuit 106. The node 11 is a portion where the discharge element 101 and the driving transistor 103 are connected to each other. The voltage of the node 11 is correlated with the voltage applied to the discharge element 101.
In this embodiment, the comparison circuit 107 in the voltage generation circuit 106 is formed by, for example, an inverting amplifier circuit. The monitoring voltage Vm is input from the discharge unit 105a to the inverting input terminal of the comparison circuit 107 and the reference voltage Vref is input from outside of the liquid discharge head substrate 200 to the non-inverting input terminal of the comparison circuit 107. The output from the comparison circuit 107 is fed back, as the driving voltage VHTM, to each discharge unit 105 via the source follower circuit of the voltage generation circuit 106. One main electrode of this source follower circuit is connected to a power supply VET and the other main electrode is connected to ground via the resistor. Since the voltage generation circuit 106 is arranged as described above, the driving voltage VHTM is supplied to the control circuit 104 of each discharge unit 105 such that the monitoring voltage Vm becomes equal to the reference voltage Vref.
The operation of the liquid discharge head substrate 200 will now be described. The discharge unit 105a is used as a monitoring unit configured to control the driving voltage VHTM to be supplied to each discharge unit 105. Each of the discharge units 105b and 105c is used as a liquid discharge unit configured to discharge a liquid corresponding to image data. In this embodiment, the discharge unit 105a is used only as the monitoring unit and does not discharge the liquid corresponding to the image data. When operating the liquid discharge head substrate 200, a Hi signal is supplied to the monitoring unit as a driving signal and a pulse signal is supplied to each liquid discharge unit as a driving signal. The Hi signal is always at high level irrespective of the image data. The pulse signal switches between high level and low level in accordance with the image data. In accordance with the image data, the pulse signal changes to high level in a case in which each discharge unit 105 should discharge the liquid and changes to low level (for example, 0V) in other cases. The discharge element 101 of the discharge unit 105a is always driven when operating the liquid discharge head substrate 200.
If the driving transistor 103 of the discharge unit 105a is ON, a current i1 flows through the discharge element 101 of the discharge unit 105a, a current i2 flows through the driving transistor 103, and a current i3 flows from the discharge unit 105a to the comparison circuit 107. In this case, i1=i2+i3 holds. The current i3 flowing through the comparison circuit 107 is much smaller than the currents i1 and i2. Therefore, the currents i1 and i2 become substantially equal to each other. Meanwhile, in the liquid discharge unit (for example, the discharge unit 105b), the current flowing through the discharge element 101 and the current flowing through the driving transistor 103 become equal to each other if the driving transistor 103 is ON. Variations in the characteristics of the respective elements in the plurality of adjacent discharge units 105 are smaller than those between the wafers or the chips, and thus can be ignored. Therefore, if the common driving voltage VHTM is input to the respective discharge control circuits 102 of the discharge unit 105a and the discharge unit 105b, the currents flowing through the respective driving transistors 103 of the discharge unit 105a and the discharge unit 105b become equal to each other. Therefore, it can be regarded that the current flowing through the discharge element 101 of the discharge unit 105a and the current flowing through the discharge element 101 of the discharge unit 105b are equal to each other. Therefore, as in this embodiment, if the driving voltage VHTM based on the node 11 in the one discharge unit 105a is supplied to the plurality of discharge units 105a to 105c, variations in the currents flowing through the discharge elements 101 of the respective discharge units 105a to 105c can be ignored.
The discharge element 101 is operated by switching driving in the liquid discharge head substrate 200. However, an arrangement in which, for example, the driving transistor 103 is formed by a PMOS transistor and driven as a source follower circuit may be adopted. In this case, the driving voltage VHTM has a value decreased by a voltage between the gate and source of the driving transistor 103 from a voltage of the node which connects the discharge element 101 and the driving transistor 103 of the discharge unit 105a. Further, in this embodiment, the driving transistor 103 is arranged between the discharge element 101 and ground. However, the driving transistor 103 may be arranged between, for example, the discharge element 101 and the power supply VH.
Furthermore, the case in which the liquid discharge head substrate 200 includes one driving transistor of the discharge control circuit 102 which controls the discharge element 101 has been described. However, the discharge control circuit 102 may be formed by two driving transistors. In this embodiment,
The driving transistor of each discharge unit 305 is formed by two MOS transistors, namely, the driving transistor 103 using the NMOS transistor and a driving transistor 302 using the PMOS transistor. Each transistor forms a source follower circuit. One terminal of the discharge element 101 is connected to the source of the driving transistor 103. The other terminal of the discharge element 101 is connected to the source of the driving transistor 302. The drain of the driving transistor 103 is connected to the power supply VH. The drain of the driving transistor 302 is connected to ground.
The gate electrode of the driving transistor 302 receives a constant voltage Vcont. In this case, a voltage increased by a voltage between the gate and source of the driving transistor 302 from the constant voltage Vcont is applied to a node 14 between the discharge element 101 and the driving transistor 302. The control circuit 104 is connected to the gate electrode of the driving transistor 103. The control circuit 104 receives the driving voltage VHTM and the driving signal for controlling the driving transistor 103. In this case, a voltage decreased by the voltage between the gate and source of the driving transistor 103 from the driving voltage VHTM is applied to the node 11 between the discharge element 101 and the driving transistor 103.
The voltage generation circuit 106 of the liquid discharge head substrate 300 also controls, or regulates, the driving voltage VHTM such that the monitoring voltage Vm and the reference voltage Vref supplied from outside of the liquid discharge head substrate 300 become equal to each other. As a result, a voltage across the discharge element 101 of each discharge unit 305 is determined not by the characteristics of the transistors but by the reference voltage Vref and the constant voltage Vcont. Therefore, variations in the voltages applied to the discharge elements 101 among the plurality of liquid discharge head substrates 300 are suppressed. This makes it possible to obtain, in the liquid discharge head substrate 300 using the two driving transistors for the discharge control circuit 102, the same effect as in the liquid discharge head substrate 200.
In this embodiment, the liquid discharge head substrate 300 adopts the arrangement in which each driving transistor is operated by using the source follower circuit. However, the present invention is not limited to this. The liquid discharge head substrate 300 may adopt, for example, an arrangement in which the two driving transistors undergo switching driving or an arrangement in which driving by the source follower circuit and switching driving are combined.
Furthermore, in this embodiment, the monitoring voltage Vm monitors the voltage of the node 11 which connects the discharge elements 101 of the discharge units 105a and 305a, and the driving transistor 103. However, the present invention is not limited to this. For example, the voltage of a node 12 which connects the driving transistor 103 and the control circuit 104 or a node 13 which connects the voltage generation circuit 106 and the discharge control circuit 102 may be input, as the monitoring voltage Vm, to the comparison circuit 107 of the voltage generation circuit 106. Both the voltages of the node 12 and the node 13 are correlated with the voltage applied to the discharge element 101. In either case, the voltage generation circuit 106 controls, or regulates, the driving voltage VHTM such that the monitoring voltage Vm becomes equal to the reference voltage Vref. If each of the discharge units 105a and 305a only functions as the monitoring unit, the discharge unit may not include the control circuit 104. In this case, the driving voltage VHTM is directly input to the gate electrode of the driving transistor 103. Therefore, the driving transistor 103 is always driven when operating the liquid discharge head substrates 200 and 300 even if the monitoring unit does not receive the driving signal. In this embodiment, the comparison circuit 107 uses the inverting amplifier circuit. However, any circuit arrangement may be adopted as long as feedback of the voltage generation circuit 106 functions so as to equalize the monitoring voltage Vm and the reference voltage Vref with each other.
The arrangement and the operation of a liquid discharge head substrate 400 including another example of a circuit arrangement which implements the function of the liquid discharge head substrate 100 will be described with reference to
In the liquid discharge head substrate 400, a switch 451 and a buffer circuit 402 are connected in series between the inverting input terminal of a comparison circuit 107 and a node 11 of a discharge unit 105a. A node which connects the buffer circuit 402 and the switch 451 is connected to ground via a holding capacitor 401. The switch 452 is provided in order to switch between two signals, namely, a monitoring Hi signal and a pulse signal corresponding to the image data, and input the signal to a control circuit 104 of a discharge control circuit 102. The switch 452 connects the control circuit 104 to either a terminal φA or a terminal φB. A control block 403 is connected to the output portion of the comparison circuit 107. The control block 403 controls the switch 451 and the switch 452. Compared to the voltage generation circuit 106, a voltage generation circuit 406 further includes the holding capacitor 401, the buffer circuit 402, the control block 403, and the switch 451, and forms a sample-and-hold circuit.
The operation of the liquid discharge head substrate 400 according to this embodiment will now be described with reference to
A case in which the discharge unit 105a is used as a liquid discharge unit for discharging the liquid will now be described. When the monitoring voltage Vm becomes equal to the reference voltage Vref, the control block 403 turns off the switch 451. This opens between the discharge unit 105a, and the holding capacitor 401 and the buffer circuit 402. The control block 403 turns off the switch 451 and connects the switch 452 to the terminal φB. Consequently, the pulse signal corresponding to the image data is input, as the driving signal, to the control circuit 104 of the discharge unit 105a, and the discharge unit 105a functions as the liquid discharge unit which discharges the liquid corresponding to the image data. In this case, the monitoring voltage Vm equal to the reference voltage Vref and held in the holding capacitor 401 is input to the inverting input terminal of the comparison circuit 107 via the buffer circuit 402.
When using the discharge unit 105a as the liquid discharge unit, a current i3 does not flow from the discharge unit 105a to the comparison circuit 107 because the switch 451 is OFF. Therefore, a current i1 flowing through a discharge element 101 of the discharge unit 105a becomes equal to a current i2 flowing through the driving transistor 103. As a result, in each discharge unit 105, a voltage controlled by the reference voltage Vref is applied to the discharge element 101 when discharging the liquid, making the current i2 flow. This makes it possible to obtain, in the liquid discharge head substrate 400, the same effect as in the liquid discharge head substrate 200.
In this embodiment, the pulse signal is input to the terminal φB of the switch 452. However, an arrangement in which, for example, a 0V-signal is input and the discharge unit 105a only operates as the monitoring unit may be adopted. When the monitoring voltage Vm becomes equal to the reference voltage Vref, the control block 403 connects the switch 452 to the terminal φB. In this case, the 0V-signal is input, as the driving signal, to the control circuit 104 of the discharge unit 105a. This turns off the driving transistor 103, and the power consumption can be reduced because no current flows through the discharge element 101. While the switch 452 is connected to the terminal φB, the driving voltage VHTM obtained when the monitoring voltage Vm and the reference voltage Vref become equal to each other is supplied to the control circuit 104 of each discharge unit other than the discharge unit 105a.
For example, the switch 452 may have three states, and switch among three signals, namely, the pulse signal, the Hi signal, and the 0V-signal as needed to input the signal to the control circuit 104 of the discharge unit 105a. This allows the discharge unit 305a to function as the liquid discharge unit and the monitoring unit which reduces the power consumption, respectively.
In this embodiment, the monitoring voltage Vm monitors the voltage of the node 11. However, for example, the voltage of a node 12 or a node 13 may be input to the comparison circuit 107 as the monitoring voltage Vm, as described above.
The arrangement and the operation of a liquid discharge head substrate 600 having another example of a circuit arrangement which implements the function of the liquid discharge head substrate 100 will be described with reference to
A comparison circuit 107a of the voltage generation circuit 106a receives a monitoring voltage Vma which monitors a node 11 of a discharge control circuit 102 in a discharge unit 305a and a reference voltage Vrefa applied from outside of the liquid discharge head substrate 600. A comparison circuit 107b of the voltage generation circuit 106b receives a monitoring voltage Vmb which monitors a node 14 of the discharge unit 305a and a reference voltage Vrefb applied from outside of the liquid discharge head substrate 600.
The driving transistor in each discharge unit 305 is formed by two transistors, namely, a driving transistor 103 serving as an NMOS transistor and a driving transistor 302 serving as a PMOS transistor. Each transistor forms a source follower circuit. One terminal of a discharge element 101 is connected to the source of the driving transistor 103. The other terminal of the discharge element 101 is connected to the source of the driving transistor 302. The drain of the driving transistor 103 is connected to a power supply VH. The drain of the driving transistor 302 is connected to ground.
The operation of the liquid discharge head substrate 600 will now be described. The voltage generation circuit 106a controls, or regulates, a driving voltage VHTM_H such that the monitoring voltage Vma becomes equal to the reference voltage Vrefa, and then outputs the regulated voltage. The voltage generation circuit 106b controls, or regulates, a driving voltage VHTM_L such that the monitoring voltage Vmb becomes equal to the reference voltage Vrefb, and then outputs the regulated voltage.
A control circuit 104 is connected to the gate electrode of the driving transistor 103. The control circuit 104 receives the driving voltage VHTM_H and a driving signal for controlling the driving transistor 103 from outside of the liquid discharge head substrate 600. The driving voltage VHTM_H is input to the gate electrode of the driving transistor 302. The monitoring voltages Vma and Vmb, the reference voltages Vrefa and Vrefb, and the driving voltages VHTM H and VHTM_L, respectively, have different values. In this embodiment, assume that Vma>Vmb, Vrefa>Vrefb, and VHTM_H>VHTM_L are satisfied.
The voltage generation circuit 106a of the liquid discharge head substrate 600 also controls, or regulates, the driving voltage VHTM_H such that the monitoring voltage Vma and the reference voltage Vrefa supplied from outside of the liquid discharge head substrate 600 become equal to each other. The voltage generation circuit 106b of the liquid discharge head substrate 600 also controls, or regulates, the driving voltage VHTM_L such that the monitoring voltage Vmb and the reference voltage Vrefb supplied from outside of the liquid discharge head substrate 600 become equal to each other. As a result, a voltage across the discharge element 101 of each discharge unit 305 is determined by the reference voltage Vrefa and the reference voltage Vrefb. Therefore, variations in the voltages applied to the discharge elements 101 among the plurality of liquid discharge head substrates 600 are suppressed. This makes it possible to obtain, in the liquid discharge head substrate 600, the same effect as in the liquid discharge head substrate 300.
In the liquid discharge head substrate 600 according to this embodiment, the two driving transistors control the voltages of the nodes in the two terminals of the discharge element 101. Furthermore, both of the two driving transistors are controlled by a feedback circuit. This further stabilizes the voltages applied to the two terminals of the discharge element 101 as compared with a case in which only the voltage of the node in one terminal of the discharge element 101 is controlled. As a result, variations in the voltages applied to the discharge element 101 can further be suppressed.
In this embodiment, the voltage of the node 11 is used as the monitoring voltage Vma. However, for example, the voltage of a node 12 or a node 13 may be input to the comparison circuit 107a as the monitoring voltage Vma, as described above. Also, the voltage of a node 15 which connects, for example, the voltage generation circuit 106b and the discharge control circuit 102 may be input, as the monitoring voltage Vmb, to the comparison circuit 107b. The nodes which monitor the monitoring voltage Vma and the monitoring voltage Vmb may be in any combination. Furthermore, the voltages of the nodes in the two terminals of the discharge element 101 may be monitored.
The arrangement and the operation of a liquid discharge head substrate 700 including another example of a circuit arrangement which implements the function of the liquid discharge head substrate 100 will be described with reference to
In the liquid discharge head substrate 700, a switch 451a and a buffer circuit 402a are connected in series between the inverting input terminal of a comparison circuit 107a and a node 11 of a discharge unit 305a. A node which connects a buffer circuit 402a and the switch 451a is connected to ground via a holding capacitor 401a. A reference voltage Vrefa is input from outside of the liquid discharge head substrate 700 to the non-inverting input terminal of the comparison circuit 107a. A switch 451b and a buffer circuit 402b are connected in series between the inverting input terminal of a comparison circuit 107b and a node 14 of the discharge unit 305a. A node which connects the buffer circuit 402b and the switch 451b is connected to ground via a holding capacitor 401b. A reference voltage Vrefb is input from outside of the liquid discharge head substrate 700 to the non-inverting input terminal of the comparison circuit 107b.
A control block 403a of a voltage generation circuit 406a controls the switch 451a. A control block 403b of a voltage generation circuit 406b controls the switch 451b. The switch 452 is provided in order to switch between two driving signals, namely, a monitoring Hi signal and a pulse signal corresponding to the image data, and input the signal to a control circuit 104 of a discharge control circuit 102. The signals from the control blocks 403a and 403b are transmitted to this switch 452 via, for example, a NOR circuit.
The operation of the liquid discharge head substrate 700 will now be described. First, a case in which the discharge unit 305a is used as a monitoring unit configured to control the driving voltages VHTM_H and VHTM_L to be supplied to each discharge unit 105 will be described. The control blocks 403a and 403b turn on the switches 451a and 451b to electrically connect the discharge unit 305a with the holding capacitors 401a and 401b and the buffer circuits 402a and 402b. In this case, the monitoring voltages Vma and Vmb are input to the inverting input terminals of the comparison circuits 107a and 107b via the buffer circuits 402a and 402b. In this case, the monitoring voltage Vma is held in the holding capacitor 401a and the monitoring voltage Vmb is held in the holding capacitor 401b. Also, the switch 452 is connected to a terminal φA in this case. This inputs the Hi signal, as the driving signal, to the control circuit 104 of the discharge unit 305a. Therefore, the discharge unit 305a is turned on and operates as the monitoring unit configured to monitor the node. The voltage generation circuit 406a controls, or regulates, the driving voltage VHTM_H such that the monitoring voltage Vma becomes equal to the reference voltage Vrefa, and supplies it to the control circuit 104 of each discharge unit. The voltage generation circuit 406b controls, or regulates, the driving voltage VHTM_L such that the monitoring voltage Vmb becomes equal to the reference voltage Vrefb, and supplies it to the gate electrode of the driving transistor 302.
A case in which the discharge unit 105a is used as the liquid discharge unit for discharging the liquid corresponding to the image data will now be described. When the monitoring voltages Vma and Vmb become equal to the reference voltages Vrefa and Vrefb respectively, the control blocks 403a and 403b respectively turn off the switch 451a and the switch 451b. Control signals from the control blocks 403a and 403b turn off the switch 451a and the switch 451b, and connect the switch 452 to a terminal φB by a signal switching circuit using a NOR circuit. This inputs, as the driving signal, the pulse signal corresponding to the image data to the control circuit 104 of the discharge unit 305a, and the discharge unit 305a functions as the liquid discharge unit which discharges the liquid corresponding to the image data. In this case, the monitoring voltages Vma and Vmb equal to the reference voltages Vrefa and Vrefb and held in the holding capacitors 401a and 401b are input, via the buffer circuits 402a and 402b, to the inverting input terminals of the comparison circuits 107a and 107b. Since the control circuit 104 of the discharge unit 305a receives the pulse signal, the driving voltage VHTM_H is input to the gate electrode of the driving transistor 103 when the pulse signal changes to Hi. The driving voltage VHTM_L is input to the gate electrode of the driving transistor 302.
The voltage generation circuit 406a of the liquid discharge head substrate 700 also controls, or regulates, the driving voltage VHTM_H such that the monitoring voltage Vma and the reference voltage Vrefa supplied from outside of the liquid discharge head substrate 700 become equal to each other. The voltage generation circuit 406b of the liquid discharge head substrate 700 also controls, or regulates, the driving voltage VHTM_L such that the monitoring voltage Vmb and the reference voltage Vrefb supplied from outside of the liquid discharge head substrate 700 become equal to each other. Since the switch 451a and the switch 451b are OFF, a current i3 does not flow from the discharge unit 305a to the comparison circuits 107a and 107b. Therefore, a current i2 flowing through a discharge element 101 has a predetermined value among the respective discharge units 305. As a result, in the discharge element 101 of each discharge unit 305, a voltage across the discharge element 101 when discharging the liquid is determined by the reference voltage Vrefa and the reference voltage Vrefb. Therefore, variations in the voltages applied to the discharge elements 101 among the plurality of liquid discharge head substrates 700 are suppressed. This makes it possible to obtain, in the liquid discharge head substrate 700, an effect obtained by combining the liquid discharge head substrate 400 and the liquid discharge head substrate 600.
The four embodiments according to the present invention have been described above. However, the present invention is not limited to these embodiments. In the liquid discharge head substrate using, for example, two driving transistors, the voltage generation circuit 406 may be used as the voltage generation circuit and the voltage generation circuit 106 may be used as the voltage generation circuit. The respective embodiments described above can be changed and combined as needed.
An embodiment of a printing apparatus according to the present invention will be described. An inkjet printing apparatus will be described. A liquid discharge head serving as the printhead of the inkjet printing apparatus includes an inkjet printhead substrate and a liquid supply unit configured to supply ink to the inkjet printhead substrate. The liquid discharge head substrate described in the above-described embodiment can be used as the inkjet printhead substrate. The printing apparatus includes this printhead and a driving unit configured to control this printhead.
It is possible to provide the inkjet printing apparatus capable of achieving high-speed printing and high-resolution printing by attaching the printhead 810 shown in
Photocouplers 907 and 908 are home position detection units configured to confirm the existence of a lever 909 provided in the carriage 920 in a region where the photocouplers 907 and 908 are provided, and perform, for example, switching of the rotation direction of the driving motor 901. A support member 910 supports a cap member 911 which caps the entire surface of the printhead 810. A suction unit 912 sucks the inside of the cap member 911 and performs suction recovery of the printhead 810 via an intra-cap opening 913. A moving member 915 can move a cleaning blade 914 forward and backward. A main body support plate 916 supports the cleaning blade 914 and the moving member 915. Not only the cleaning blade 914 shown in
The inkjet printing apparatus 900 having the above-described arrangement performs printing on the printing sheet P conveyed onto the platen 906 by the printing medium feeding apparatus while the printhead 810 reciprocally moves over the full width of the printing sheet P. The printhead unit 800 of the printhead 810 uses the inkjet printhead substrate serving as the liquid discharge head substrate according to the above-described embodiments. Therefore, the printhead unit 800 is compact and can achieve high-speed printing.
The arrangement of a control circuit configured to perform printing control of the above-described apparatus will now be described.
The operation of the above-described control arrangement will be described. When the print signal is input to the interface 1000, it is converted into print data for printing between the gate array 1004 and the MPU 1001. Then, the motor drivers 1006 and 1007 are driven, and the printhead is also driven in accordance with the print data that has transmitted to the head driver 1005, thereby performing printing.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2014-161896, filed Aug. 7, 2014, which is hereby incorporated by reference wherein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-161896 | Aug 2014 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5422662 | Fukushima | Jun 1995 | A |
| 6068360 | Hiwada | May 2000 | A |
| 7350891 | Oomura | Apr 2008 | B2 |
| 20020033864 | Hopkins | Mar 2002 | A1 |
| Number | Date | Country |
|---|---|---|
| 2010-155452 | Jul 2010 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20160039200 A1 | Feb 2016 | US |
