Patent Grant
10118385
The present invention relates to printing element substrates, printheads, and printing apparatuses.
A printing element substrate in an inkjet printing apparatus, which includes a semiconductor integrated circuit, receives a clock signal (CLK) and an image data signal (DATA) from the main body of the printing apparatus, and performs a printing operation on the basis of the image data. A recent increase in printing speed has been accompanied by clock signals and image data signals having a frequency of as high as several hundreds of megahertz. A phase difference occurs between a clock signal and an image data signal due to variations in a transmitter circuit and a receiver circuit. A clock signal and an image data signal that have a higher frequency are more likely to be significantly affected by the phase difference. Therefore, it is more difficult to synchronize such a clock signal and data signal with each other. Therefore, it is necessary to provide a means for correcting the phase difference between a clock signal and a data signal.
As a disclosed technique of correcting the phase difference between a clock signal and a data signal, a delay-locked loop (DLL) circuit or a phase-locked loop (PLL) circuit is provided in a receiver circuit, for example. International Publication No. 2012/102709 discloses an inkjet printing apparatus in which the phase difference between a clock signal and a data signal is corrected in a transmitter circuit. In the inkjet printing apparatus disclosed in International Publication No. 2012/102709, a control IC that is provided in the main body (including the transmitter circuit) of the printing apparatus repeatedly reads image data signals received by a printing element substrate (in a receiver circuit), and checks the reception results, to determine an optimum phase correction amount.
In conventional techniques employing a delay-locked loop (DLL) circuit or a phase-locked loop (PLL) circuit, a training period for stabilizing the operation of DLL or PLL is required. In the technique disclosed in International Publication No. 2012/102709, it is necessary to check the result of reception performed by the printing element substrate a plurality of times in order to perform phase correction one time, and therefore, it takes a long time to determine the phase correction amount. Therefore, it is difficult to perform phase correction on a regular basis, and it is difficult to follow changes in phase caused by changes in temperature or changes over time.
With the above problems in mind, the present invention has been made. It is an object of the present invention to provide a highly reliable printing apparatus that includes a phase correction unit capable of following phase changes caused by changes in temperature or changes over time, without the need of a training period for stabilizing the operation.
According to one aspect of the present invention, there is provided a printing element substrate comprising: a printing element; a driving circuit configured to drive the printing element; a receiver circuit configured to receive a first signal and a second signal; and a correction circuit configured to correct a phase difference between the first signal and the second signal received by the receiver circuit, and output the corrected first and second signals to the driving circuit, wherein the correction circuit includes a first delay circuit configured to generate a plurality of first delayed signals having different delay times with respect to the first signal, and a second delay circuit configured to generate a plurality of second delayed signals having different delay times with respect to the second signal, the correction circuit specifies a phase of the first signal to be output to the driving circuit, on the basis of comparison between the plurality of first delayed signals and the second signal, and the correction circuit specifies a phase of the second signal to be output to the driving circuit, on the basis of comparison between the plurality of second delayed signals and the first signal having the specified phase.
According to another aspect of the present invention, there is provided a printhead comprising: a plurality of printing element substrates, wherein each printing element substrate includes a printing element, a driving circuit configured to drive the printing element, a receiver circuit configured to receive a first signal and a second signal, and a correction circuit configured to correct a phase difference between the first signal and the second signal received by the receiver circuit, and output the corrected first and second signals to the driving circuit, the correction circuit includes a first delay circuit configured to generate a plurality of first delayed signals having different delay times with respect to the first signal, and a second delay circuit configured to generate a plurality of second delayed signals having different delay times with respect to the second signal, the correction circuit specifies a phase of the first signal to be output to the driving circuit, on the basis of comparison between the plurality of first delayed signals and the second signal, and the correction circuit specifies a phase of the second signal to be output to the driving circuit, on the basis of comparison between the plurality of second delayed signals and the first signal having the specified phase.
According to another aspect of the present invention, there is provided a printing apparatus comprising: a printhead including a plurality of printing element substrates, wherein each printing element substrate includes a printing element, a driving circuit configured to drive the printing element, a receiver circuit configured to receive a first signal and a second signal, and a correction circuit configured to correct a phase difference between the first signal and the second signal received by the receiver circuit, and output the corrected first and second signals to the driving circuit, the correction circuit includes a first delay circuit configured to generate a plurality of first delayed signals having different delay times with respect to the first signal, and a second delay circuit configured to generate a plurality of second delayed signals having different delay times with respect to the second signal, the correction circuit specifies a phase of the first signal to be output to the driving circuit, on the basis of comparison between the plurality of first delayed signals and the second signal, and the correction circuit specifies a phase of the second signal to be output to the driving circuit, on the basis of comparison between the plurality of second delayed signals and the first signal having the specified phase.
According to the present invention, a phase difference can be instantaneously corrected without the need of a training period. Therefore, a highly reliable printing apparatus can be provided in which phase changes caused by changes in temperature or changes over time can be followed.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Preferred embodiments of the present invention will be described more specifically and in greater detail with reference to the accompanying drawings. Note that the relative arrangements of components, etc., described in examples are not intended to limit the scope of the present invention unless otherwise specified.
As used herein, the term “print” refers to not only formation of information having a meaning such as characters, graphics, etc., but also formation of meaningless information. Furthermore, the term “print” refers to formation of an image, a picture, a pattern, etc., on a printing medium, or processing of a printing medium, in a broad sense, irrespective of whether such information may or may not be made manifest and recognizable to the human eye.
As used herein, the term “printing medium” refers to not only paper that is used for typical printing apparatuses, but also a wide variety of materials that can receive ink, such as cloth, plastic film, metal sheets, glass, ceramics, wood, leather, etc.
As used herein, the term “ink” (may be interchangeable with the term “liquid”) should be interpreted in a broad sense as with the term “print.” Therefore, as used herein, the term “ink” refers to liquid that when applied to a printing medium can form an image, a picture, a pattern, etc., process the printing medium, or process itself (e.g., coagulation or insolubilization of a colorant in the ink applied to the printing medium).
As used herein, the term “printing element” refers to a set of a discharge opening, a liquid path that is coupled to and in communication with the discharge opening, and an element for generating energy to be utilized for discharging ink, unless otherwise specified.
As used herein, the term “nozzle” refers to a set of a discharge opening, a liquid path that is coupled to and in communication with the discharge opening, and an element for generating energy to be utilized for discharging ink, unless otherwise specified.
As used herein, the term “element substrate (head substrate)” with respect to a printhead refers to a substrate on which elements, interconnects, etc., are provided, but not a merely substrate of silicon semiconductor.
As used herein, the term “on” with respect to a substrate refers to not only a situation that an element is above the element substrate, but also situations that an element touches a surface of the element substrate or is partially or entirely inside the element substrate in the vicinity of a surface thereof. As used herein, the term “built-in” refers to a situation that elements are integrally formed or manufactured on an element substrate by a semiconductor circuit manufacturing process, etc., but not a situation that separate elements are merely disposed on a surface of a separate substrate.
An inkjet printhead (hereinafter referred to as a “printhead”) that is a most important characteristic feature of the present invention includes an element substrate, and a plurality of printing elements and a driving circuit for driving these printing elements, which are each implemented on the element substrate. As can be seen from the description that follows, the printhead includes a plurality of element substrates, and has a structure in which these element substrates are connected together in cascade. Therefore, the printhead can achieve a relatively long print width. Therefore, the printhead is applicable to not only typical serial printing apparatuses, but also printing apparatuses equipped with a full-line printhead having a print width corresponding to the width of a printing medium. Of serial printing apparatuses, the printhead is especially applicable to large-format printers for printing media having a large size, such as A0, B0, etc.
Therefore, firstly, a printing apparatus in which the printhead of the present invention is used will be described.
(Overview of Printing Apparatus)
In the printing apparatus 100, printing paper 15 is supplied from a feeder unit 17 to respective printing positions of the printheads, and is conveyed by a conveyance unit 16 included in a housing 18 of the printing apparatus.
An image is printed onto the printing paper 15 as follows. When the printing paper 15 is conveyed, so that a reference position of the printing paper 15 arrives below the printhead 101K which discharges black (K) ink, the printhead 101K discharges black ink. Similarly, the printhead 101C which discharges cyan (C) ink, the printhead 101M which discharges magenta (M) ink, and the printhead 101Y which discharges yellow (Y) ink, discharge ink of respective colors in this order when the printing paper 15 arrives at the respective reference positions, so that a color image is formed. The printing paper 15, on which an image has thus been printed, is exited and stacked on a stacker tray 20.
The printing apparatus 100 further includes the conveyance unit 16, and ink cartridges (not shown) for supplying ink to the printheads 101K, 101C, 101M, and 101Y. The ink cartridges can each be separately replaced for the respective ink. The printing apparatus 100 also further includes pump units (not shown) for supplying ink to the respective printheads 101 and performing respective recovery operations, a control substrate (not shown) for controlling the entire printing apparatus 100, etc. A front door 19 is opened or closed when an ink cartridge is replaced.
(Control Configuration)
Next, a control configuration for executing print control performed by the printing apparatus described with reference to
Note that when the printing apparatus includes a full-line printhead as shown in
An operation of the control configuration will be described. When print data is input to the interface 40, the print data is converted into print signals for printing by the gate array 33 and the MPU 31. Thereafter, the motor drivers 60 and 80 are driven, and the printheads 101 are driven on the basis of print data sent to the head driver 50, to perform printing.
Although, in an example described below, a full-line printhead will be described as an example, the present invention is not limited to this. The present invention may be applied to a printhead included in a serial printing apparatus as described above. In this case, the printhead is mounted on a carriage, and performs reciprocal movements in the width direction of a printing medium to perform a printing operation.
Although, in the description that follows, attention is focused on a single printhead 101, the present invention is applicable to a printing apparatus including a plurality of printheads 101 as shown in FIG. 1.
The printing element substrates 103 each include a first receiver circuit 106 for receiving a first signal 111 (DATA), a second receiver circuit 107 for receiving a second signal 112 (CLK), and a third receiver circuit 108 for receiving a third signal 113. The printing element substrates 103 also each include a correction circuit 105, and a driving circuit 104. Note that a printing element (not shown) is provided, corresponding to the driving circuit 104. A head control IC 109 generates the first signal 111, the second signal 112, and the third signal 113. The first signal 111, the second signal 112, and the third signal 113 are supplied from the head control IC 109 provided on the main-body substrate 102 of the printing apparatus to each printing element substrate 103 through the transmission line path 110.
The first signal 111, the second signal 112, and the third signal 113 are input to the correction circuit 105. The correction circuit 105 corrects a phase difference between the first signal 111 (DATA) and the second signal 112 (CLK) for each period of the third signal 113, to output a fourth signal 114 (Dadj) and a fifth signal 115 (CKadj). The fourth signal 114 (Dadj) is the first signal 111 (DATA) that has a corrected phase. The fifth signal 115 (CKadj) is the second signal 112 (CLK) that has a corrected phase. The fourth signal 114 (Dadj) and the fifth signal 115 (CKadj), which are output from the correction circuit 105, are input to the driving circuit 104. The driving circuit 104 is driven on the basis of the fourth signal 114 (Dadj) and the fifth signal 115 (CKadj), which have a corrected phase difference, and therefore, can reliably synchronize an image data signal with a clock signal, and thereby receive accurate image data.
The printing apparatus 100 determines the amount of correction of a phase difference between an image data signal (DATA) and a clock signal (CLK) during a period of time that the test flag signal 200 is transmitted after the pause period 203, and corrects the phase difference on the basis of the determined correction amount. Specifically, a phase difference between the test flag signal 200 transmitted after the pause period 203, and a clock signal (CLK), is obtained, and an optimum phase correction amount is determined on the basis of a phase relationship between these signals. The phase correction amount thus determined is maintained during all the time that the image data signal 201 is transmitted, and is reset at the timing of a rising of a latch signal (LT). Such an operation is repeated for each latch time. As a result, the printing apparatus 100 according to the first embodiment can follow phase changes caused by changes in temperature or changes over time, and therefore, reliability is ensured.
An operation of the correction circuit 105 will now be described with reference to
The second delay circuit 306 generates (m+1) second delayed signals 311 (CK_0, CK_1, CK_2, . . . , and CK_m) by delaying the second signal 112 (CLK). The second determination circuit 307 compares the phases of the second delayed signals 311 with the phase of the fourth signal 114. The second determination circuit 307 determines which of the second delayed signals 311 (CK_0, CK_1, CK_2, . . . , and CK_m) has a rising edge that coincides with a falling edge of the fourth signal 114 (Dadj), and outputs a second determination signal 309. The second multiplexer 308 selects, from the second delayed signals 311, a delayed signal having a delay time that is half the delay time of the delayed signal having the coincidence edge determined by the second determination circuit 307, on the basis of the second determination signal 309 output from the second determination circuit 307. In other words, the second multiplexer 308 is a selection circuit for selecting a signal to be output from the second delayed signals 311. Note that the second multiplexer 308 may select, for example, a second delayed signal that has a delay time that is smaller than the delay time of the delayed signal having the coincidence edge determined by the second determination circuit 307. Thereafter, the second multiplexer 308 outputs the selected second delayed signal 311 as the fifth signal 115 (CKadj).
A detailed operation of the first signal correction circuit 300 will now be described with reference to
In
In the example of
Next, a detailed operation of the second signal correction circuit 301 will be described with reference to
In the example of
According to the above configuration, in the printing apparatus of this embodiment, a training period for stabilizing the operation of a circuit is not required, and the phase difference can be instantaneously corrected. In addition, by performing the phase correction on a regular basis (e.g., for each latch time), phase changes caused by changes in temperature or changes over time can be followed, and therefore, reliability can be ensured.
In addition, as described above, the correction circuit according to the present invention does not require a capacitor which is required in an analog circuit such as a DLL circuit or a PLL circuit. A considerably large area is required to provide a capacitor in a substrate. The correction circuit according to the present invention includes only digital circuits, as described above, and therefore, the area can be saved.
In addition, since the correction circuit according to the present invention can be implemented using only digital circuits, the correction circuit is highly resistant to noise, compared to conventional techniques that employ analog circuits such as DLL circuits, PLL circuits, etc. In particular, on printing element substrates, when a printing element is driven, a current of the order of amperes instantaneously flows, so that much electromagnetic noise occurs. Therefore, the correction circuit according to the present invention is suitable for printing element substrates.
In the first embodiment described above, as shown in
Variation 2 of the first embodiment is the same as Variation 1 of the first embodiment, except that the first delay circuit 302 generates a single first delayed signal 310. This configuration can reduce the circuit scale of the first signal correction circuit. In this configuration, the first determination circuit 303 checks a total of two signals, i.e., the first signal 111 (DATA) and the single first delayed signal 310. The first multiplexer 304 selects one of the two signals, and outputs the selected signal as the fourth signal 114 (Dadj). The other configuration is the same as that of Variation 1 of the first embodiment and therefore will not be described.
As in the first embodiment, the correction circuit 105 corrects the phase difference between the first signal 111 (DATA) and the second signal 112 (CLK), to output the fourth signal 114 (Dadj) and the fifth signal 115 (CKadj). The operation of the correction circuit 105 is similar to that of the first embodiment and therefore will not be described in detail.
It has been known that the amount of ink discharged by a printing element substrate increases with an increase in temperature. Despite this, inkjet printing apparatuses are required to achieve the reproducibility and color stability of a printed image even during continuous printing. Conventional techniques have been disclosed for precisely controlling a driving voltage and a driving pulse for a printhead even during continuous printing. According to such conventional techniques, conditions (a driving voltage and a driving pulse) for driving a printing element are adjusted by a signal processing circuit in a printing apparatus on the basis of temperature data detected by a temperature detection element included in a printing element substrate, to perform control so as to become the amount of discharged ink uniformly.
For example, a diode may be used as the temperature detection unit 504. In this case, it is necessary to detect a very small change in voltage depending on the temperature characteristics (−2 mV/° C.) of the forward bias of the p-n junction. However, in the printing element substrate 503, digital signals such as an image data signal, a clock signal, etc., are supplied adjacent to the temperature detection signal 505, and noise from the digital signals is superposed on the temperature detection signal 505, and therefore, an error occurs in detected temperature.
To address this, in the printing apparatus 500 of this embodiment, a pause period during which the logic of a digital signal does not transition is provided, and the temperature detection signal 505 free from superposed noise is read during the pause period. As a result, in this embodiment, the temperature of the printing element substrate 503 can be accurately detected.
During the pause period 203, the logic of a digital signal such as an image data signal (DATA), a clock signal (CLK), etc. does not transition, and therefore, the temperature detection signal 505 is not affected by crosstalk noise. Therefore, the head control IC 109 can find the correct temperature of the printing element substrate 503.
The phase difference between the first signal 111 (DATA) and the second signal 112 (CLK) is corrected after the pause period 203, and therefore, the temperature detection signal 505 is not affected by noise that is caused, through a power supply, by the correction circuit 105 operating at high speed.
According to the above configuration, the printing apparatus according to this embodiment does not require a training period, and can instantaneously correct the phase difference between an image data signal (DATA) and a clock signal (CLK). As a result, an image data signal and a clock signal can be paused on a regular basis. By reading the temperature detection signal during this pause period, a temperature state of a printing element substrate can be accurately found without being affected by crosstalk of a data signal or a clock signal, resulting in high reliability.
In the foregoing, the first and second embodiments have been described. The present invention is not limited to these embodiments. For example, although the correction circuit 105 is provided together with the driving circuit 104 on the printing element substrate 103, the correction circuit 105 may be provided on a different substrate provided in the printhead 101. For example, although the frequency of the phase correction in the above embodiments is once a latch time, the present invention is not limited to this. The frequency of the phase correction may be two a latch time, four a latch time, or once a line time.
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. 2016-189918, filed Sep. 28, 2016, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-189918 | Sep 2016 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 9073076 | Oshima | Jul 2015 | B2 |
| 9272508 | Umeda et al. | Mar 2016 | B2 |
| 9488501 | Ito | Nov 2016 | B2 |
| 9688067 | Umeda et al. | Jun 2017 | B2 |
| Number | Date | Country |
|---|---|---|
| 2012102709 | Aug 2012 | WO |
| Entry |
|---|
| U.S. Appl. No. 15/590,489, filed May 9, 2017. |
| Number | Date | Country | |
|---|---|---|---|
| 20180086057 A1 | Mar 2018 | US |
