GB2311494A

GB2311494A - A carriage mounted printed circuit assembly and control system for an inkjket printer

Info

Publication number: GB2311494A
Application number: GB9705162A
Authority: GB
Inventors: Huston W Rice
Original assignee: Hewlett Packard Co
Current assignee: HP Inc
Priority date: 1996-03-28
Filing date: 1997-03-13
Publication date: 1997-10-01
Anticipated expiration: 2017-03-13
Also published as: GB2311494B; DE19642565A1; GB9705162D0; JPH106505A; DE19642565C2

Description

2311494 TECIINICAL FLELD 2 This invention relates to ink-jet printers, and

more particularly, to pen 3 control systems for operating ink-jet pens used in ink-jet printers.

4 BACKGROUND OF THE U".NTION

6 An ink-jet printer is a type of non-impact printer which forms characters 7 and other images by controllably spraying drops of ink from a printhead. One g conventional type of ink-jet printhead consists of a replaceable cartridge or pen 9 which is removably mounted to a movable carriage. The pen controllably ejects io liquid ink through multiple nozzles in the form of drops which travel across a 11 small air gap and land on a recording media.

12 Ink droplets are ejected from individual nozzles by localized heating. A 13 small heating element, typically in the form of a thermal resistor, is disposed at 14 each nozzle. An electrical current is passed through the element to heat it up. The is heated element vaporizes a tiny volume of ink which is ejected through the nozzle.

16 The heating elements are commonly formed on a single silicon wa&r chip, which 17 make the replaceable pen easy to assemble and inexpensive to produce.

18 A pen driver circuit is coupled to the heating elements to supply the energy g pulses for controllably depositing the ink drops. The pen driver is responsive to a character generator or other image forming circuitry to energize. selected nozzles 21 for forming the desired image. Energy pulses of effective magnitude to cause 22 deposition of an ink drop from the pen are referred to as "firing pulses."

23 In early generation ink-jet printers, a carriage-mounted pen had 30-50 24 nozzles. The pen driver was located on a stationary printed circuit board (PCB) 2s beside the carriage path. A flexible conductor bundle was connected between the 1 PCB and pen to permit reciprocating movement of the carriage. The conductor 2 bundle consisted of a single conductor connected between the pen driver and a 3 corresponding nozzle heating element, and conductors for power and ground 4 signals. The pen driver transmitted firing pulses over the dedicated conductors to s fire the corresponding nozzle heating element.

6 The single conductor-per-nozzle implementation was effective for pens 7 having a small number of nozzles (e.g., 30-50 nozzles). However, as pens 8 evolved, the number of nozzles increased to enable higher quality printing of 300 9 600 dpi (dots per inch). For instance, some pens that are commercially available o today have as many as 300 nozzles. As the number of nozzles grew, the single 11 conductor-per-nozzle approach became increasingly unmanageable to coordinate 12 from a control perspective or to physically assemble the hundreds of conductors 13 within a printer housing.

14 To reduce the number of conductors, ink-jet printer manufacturers is developed pens with low level logic circuitry integrated into the resistor silicon 16- wafer. Firing signals in the form of row and column addresses were sent over a 17 smaller cable to the pen, and the logic circuitry used the addresses to select the 18 appropriate nozzles. A combination of 16 row and 14 column addresses could be g used to drive a 300-nozzle pen. A small ribbon cable with only 30-40 conductor wires was used to carry the addresses in parallel from the pen driven. to the pen, 21 thereby substantially reducing the cabling requirements for implementing a higher 22 resolution printer. The BP Deskjet 850 and 1200 printers from HewlettParkard 23 Company are example printers that incorporate such logic-based pens.

24 Logic-based pens are relatively inexpensive to produce as the logic circuitry is incorporated into the same silicon chip that is used to hold the heating resistors.

2 1 However, this implementation has a drawback in that the control and timing of the 2 firing pulses being carried from the pen driver over the ribbon conductor to the 3 moving pen becomes increasingly difficult as the firing frequency increases and as 4 the firing requirements demand more precise control of the firing pulse energy.

s Modem day printers continue to push the envelop for higher throughput, which 6 equates to higher firing rates and greater control over the energy pulses. As a 7 result additional control circuitry is incorporated onto the PCB to ensure that the 8 control and timing of the firing pulse signals are accurate.

9 To reduce the need for such control precision, some more recent pens have io been introduced which place more decoding intelligence onto the pen IC. The 11 print data is sent serially over a serial conductor from the pen driver on the 12 stationary PCB to the pen. Decoding circuitry incorporated at the pen decodes the 13 serial bit stream into the appropriate column and row addresses, which are then 14 supplied to the selection logic circuitry for firing the selected nozzles.

is While this pen simplifies operation and helps reduce delay and timing 16 problems in the firing signals, the resultant pen is expensive to manufacture 17 because of the more sophisticated ICs must be produced and implemented on the 18 pen. These pens are designed, however, to be replaceable and/or disposable to ig satisfy other manufacturing goals of providing an efficient way to replenish spent ink supplies.

21 Accordingly, there remains a need to simplify and improve the operation of 22 pens with large numbers of nozzles, without increasing the manufacturing cost of 23 replaceable pens.

24 3 1 SUNIY OF THE INVENTION 2 A pen control system for an ink-jet printer includes a stationary printed 3 circuit assembly (PCA) mounted to the irik-jet printer frame, and a carriage printed 4 circuit assembly (PCA) mounted to the movable carriage. A serial conductor interconnects the stationary PCA to the carriage PCA to serially transfer data, 6 power, and ground signals from the stationary PCA to the carriage PCA.

7 The carriage PCA has a pen driver coupled to receive the data signals from 8 the stationary PCA. The pen driver converts the data signals into nozzle select 9 signals which are effective to cause a pen to deposit ink from selected nozzles.

to The nozzle select signals are transferred to the pen via an electrical pen connector 11 which electrically couples to the logic circuitry on the pen when the pen is 12 installed in the carriage.

13 The carriage PCA also has power regulating circuitry and temperature 14 control circuitry. The power regulator circuitry regulates power signals received is from the stationary PCA to various voltage levels used internally by the carriage 16 PCA, and to select and fire the pen nozzles. The temperature control circuitry 17 affords localized control of the pen temperature.

Is By implementing the pen driver and power regulating circuitry on the 19 carriage-based PCA, the firing pulses are locally generated and transferred directly to the pen, as opposed to being communicated over a long conductor. This design 21 substantially eliminates the problems associated with high precision control of the 22 firing pulses as they are transmitted from a stationary PCB to a moving pen.

23 Moreover, the control system supports the use of inexpensive pens, thereby 24 avoiding the manufacturing costs associated with the production of highly integrated pens.

4 1 BRIEF DESCRIPTION OF THE DRAWINGS

2 Fig. 1 is a diagrammatic illustration of a portion of an ink-jet printer 3 showing a control system according to one aspect of this invention. 4 Fig. 2 is an electrical circuit representation of firing resistors employed in s an ink-jet pen. 6 Fig. 3 is a block diagram of the control system.

7 8 DETAILED DESCRI1MON OF THE PREFERRED EMBODUVIENT 9 Fig. 1 shows a printing mechanism portion of an ink-jet printer 10. The lo ink-jet printer includes a platen 12, a shuttle assembly 14, and a control system 16. 11 The platen 12 is a stationary or rotatable element that supports a recording media 12 during printing. The shuttle assembly 14 includes a carriage 20 slidably mounted 13 on a fixed, elongated rod 22 to move bi-directionally across the platen 12. The 14 shuttle assembly 14 also includes a drive subassembly (not shown), such as a is stepper or DC motor mechanically linked to the carriage, that mechanically 16 maneuvers the carriage 20 back and forth along the rod 22. 17 The shuttle assembly 14 has one or more ink-jet printheads mounted to the 18 carriage 20. Two printheads 30 and 32 are illustrated for explanation purposes.,g When mounted in the carriage 20, the printheads 30 and 32 are disposed adjacent to, but spaced slightly from, the platen 12. A media feed mechanism (not shown), 21 such as friction rollers or a tractor feed subassembly, is used to advance the 22 printing media through the printer and between the platen 12 and the printheads 23 30, 32. The carriage 20 carries the printheads 30, 32 in a reciprocating motion 24 over a printing surface. Each print sweep is called a "print swath."

1 According to one type of known construction, the printheads 30, 32 are 2 embodied as replaceable, disposable pens which are removably mounted to the 3 carriage 20. Such pens comprise a self-contained ink supply, a nozzle pattern 4 formed at the pen tip, and a pen integrated circuit (IC) with heating elements (i.e., resistors) and selection logic for those elements. In this configuration, each 6 replaceable pen essentially forms an entire printhead. As used herein, the terms 7 "pen" and "printhead" are substantially interchangeable.

8 The first pen 30 is used for monocolor printing, such as black. It is a high 9 resolution pen (e.g., 600 dpi), with an example nozzle pattern consisting of. 300 nozzles arranged in two vertical 150-nozzle arrays which are staggered relative to 11 one another by an offset equal to a one-half nozzleto-nozzle distance. The 12 second pen 32 is a multicolored pen that is capable of printing three different 13 colors, such as cyan, magenta, and yellow. The pen 32 has sixty-four nozzles for 14 each color, yielding a total of 192 nozzles. lle resolution of the colored pen 32 is is less than the black pen 30, with an example resolution being 300 dpi.

16 Fig. 2 shows an electrical representation of the firing resistors on each pen 17 IC 36. The firing resistors are arranged in an M x N matrix pattern. The columns is of resistors (also called "primitives") share a common power line COLI, COL2, 19., COLN and a common ground line GND 1, GND 2,., G. The rows of resistors (also called "addresses") share a common control or select line ROWL 21 ROW2,., ROWM. When one address line is selected (e.g., ROW1), and one 22 column line is energized (e.g., COL2), the nozzle resistor at the intersection of the 23 address line ROWI and column line COL2 is fired. The corresponding transistor 24 passes current through the resistor between the energized column line and ground 6 i to heat the resistor to an effective temperature causing vaporization and ejection of 2 an ink drop through the corresponding nozzle.

3 In the illustrated implementation having two pens 30, 32, the same address 4 lines ROW1, ROW2,., ROWM are shared by both pens (although one pen may s not use as many address lines as the other). Each pen is given its own unique 6 column signal lines. During firing, one address line is selected and potentially 7 every column line is energized to fire multiple nozzles simultaneously.

8 The control system 16 includes a stationary printed circuit assembly (PCA) 9 40 which is mounted to a stationary fixture of the ink-jet printer 10, such as the frame or housing. The control system 16 fluther includes a carriage printed circuit 11 assembly (PCA) 42 mounted to the carriage 20, and a conductor 44 12 interconnecting the stationary PCA 40 to the carriage PCA 42. The stationary 13 PCA 40 functions as the primary logic or motherboard and controls all non-pen 14 related aspects. The carriage PCA 42 controls all pen-related aspects.

is Generally, the stationary PCA 40 sends printing data, power, and ground 16 signals to the carriage PCA 42. The carriage PCA 42 has an input connector 17 which couples to the conductor cable 44 to receive the data, power, and ground is signals from the stationary PCA 40. The carriage PCA 42 also has a pair of pen g connectors in the form of conductive contacts which electrically couple to contact pads formed on the pens 30 and 32. The contact pads on the removable pens 21 engage the contacts of the carriage PCA 42 when the pens are installed on the 22 carnage 20.

23 Fig. 3 shows a block diagram of the control system 16. The stationary PCA 24 1 40 contains an VO circuit 10 to handle FO tasks with external devices, such as a 2s host computer. The stationary PCA 40 further includes a carriage control circuit 7 1 52 for managing the carriage position and movement rate, a media control circuit 2 54 for controlling the printer feed mechanism, and a panel FO circuit 56 for 3 accommodating user interface functions for the printer's key panel and display.

4 The stationary PCA 40 also has a data/control format circuit 58 which formats the s data received from the host via the FO circuit 50 into a serial bit stream that is sent 6 to the carriage PCA 42 over conductor 44.

7 A serial interface manages the communication between the stationary PCA s 40 and the carriage PCA 42. The serial interface is bi-directional and includes the 9 serial conductor 44. The serial interface communicates setup information, o row/column selection data, power signals, and a ground signal from the stationary 11 PCA 40 to the carriage PCA 42. The serial interface finther communicates 12 temperature data and status information from the carriage PCA 42 back to the 13 stationary PCA 40.

14 In one implementation, the bi-directional interface is accomplished using is five signals: DInI (Data Input 1), DIn2, DOut, DClk, and DLoad. All signals 16 except DOut are inputs to the stationary PCA 42. The serial input data is split and 17 communicated over two physical conductors to lower the clock rate and electro g magnetic radiation. The signals are controlled to minimize Elfi as they are 19transmitted over a long flex cable 44 (e.g., 40 cm) between the stationary PCA 40 and the carriage PCA 42.

21 The first bit of the serial input word is an address bit that defines what type 22 of data is being sent. A value ADIN=0 means that printing data is being sent and a 23 value ADIN=1 means that setup data is being sent. The two different input words 24 may be sent in any order. Data written by either of the input types is latched at the 8 carriage PCA 42 until overwritten or cleared. The following table 1 shows an 2 example set of input bit assignments in order of their transmission.

3 4 Table 1: Serial Input Bit Assignments DInl/DIn2 Bit ADIN = 0 ADIN=1 6 (Print Data) (Setup Data) 7 1 0 Value = 0 Value = 1 8 1 1 Row Select Bit 0 (LSB) O=Pen 30; 1=Pen 32 9 1 2 Row Select Bit 1 DA Value Bit (LSB) 1 3 Row Select Bit 2 DA Value Bit 1 11 1 4 Row Select Bit 3 DA Value Bit 2 12 1 5 Row Select Bit 4 (MSB) DA Value Bit 3 13 1 6 Fire Column 1 DA Value Bit 4 14 1 7 Fire Column 2 DA Value Bit 5 is 1 8 Fire Column 3 DA Value Bit 6 16 1 9 Fire Column 4 DA Value Bit 7 (MSB) 17 2 0 Fire Column 5 Column Driver Test Mode is 2 1 Fire Column 6 Turn On/OEVpen Regulator 19 2 2 Fire Column 7 Under-voltage shutdown 2 3 Fire Column 8 Vpen Trim Bit 0 (LSB) 21 2 4 Fire Column 9 Vpen Trim Bit 1 22 2 5 Fire Column 10 Vpen Trim Bit 2 23 2 6 Fire Column 11 Vpen Trim Bit 3 (MSB) 24 2 7 Fire Column 12 AID Channel Sel, Bit 0 (LSB) 2 8 Fire Column 13 A/D Channel Sel Bit 1 9 1 2 9 Fire Column 14 A/D Channel Sel Bit 2 (MSB) 2 3 The carriage PCA 42 has a serial digital circuit 60 which receives the serial 4 data stream from cable 44, latches the data, and converts the serial stream to a s parallel format for high speed use internal to the carriage PCA. The print data is 6 sent when ADIN=O, and includes the bits for selecting columns and rows of firing 7 resistors that are to be driven. The serial digital circuit 60 sends this print data to 8 row and column drivers 62, 64 which output the appropriate firing control signals 9 to select and fire resistors in the pen firing matrixes 36, 37, thereby causing ink deposition ink from corresponding nozzles 38, 39. The row and column drivers 11 62, 64 decode the five row select bits to activate the appropriate rows in the firing 12 matrixes 36, 37, according to the following decode table 2.

13 14 Table 2: Row Address Decoding is R4 R3 R2 R1 RO Select Address 16 00000 No Address Selected 17 00001 Row 1 is 00010 Row 2 19 - - - - - 10101 Row 21 21 10 1 10 Row 22 22 101 1 1 No Address Selected 23 - - - - - 24 1 1 1 1 1 No Address Selected 1 In this implementation, the row addresses for rows 23-31 are undefined 2 because the 300 pen nozzles can be adequately addressed using rows 1-22 and 3 columns 1-14. These additional address may be used for additional setup/control 4 data, or reserved for future use in an event pens are manufactured with more s nozzles.

6 Two power signals of 18 V and 5 V are supplied to the carriage PCA 42 7 over the conductor 44. The carriage PCA 42 has voltage regulator circuitry 66 8 which regulates the power signals to various voltage levels used within the 9 carriage PCA and to drive the pen 30. The voltage regulator circuit 66 comprises jo four voltage regulator circuits:

11 (1) A pen voltage regulator regulates the unregulated 18 V signal to a 12 voltage level Vpen of approximately 8 V to 12 V. Vpen is used as a 13 resistor firing source for the nozzles, and is applied at the column lines 14 COL I, COL2, COLN within the firing matrixes 36, 37. The Vpen is voltage is shared by both pens 30, 32 since one pen is fired at a time.

16 The Vpen voltage is also programmable. The stationary PCA 40 sends a 17 signal (e.g., four bits in the Setup Data format in Table 2) to the carriage 18 PCA 42 to set the voltage level Vpen.

19 (2) A row voltage regulator regulates the 18 V signal to a voltage level Vrow of approximately 12 V. Vrow is used to select row lines ROW1, 21 ROW2,., ROWM in the pen firing matrixes 3 6, 3 7.

22 (3) A gate voltage regulator regulates the 18 V power signal to a voltage 23 level Vgate which is approximately equal to Vpen plus 13 V. Vgate is 24 effective to power the row and column pen drivers 62, 64.

(4) A boost voltage regulator regulates the 18 V power signal to a higher 2 voltage level Vboost of approximately 36 V.

3 Placing the voltage regulator circuitry 66 on the carriage PCA 42 allows 4 more precise control of the firing pulses to the pen. Unlike prior art systems, the s firing pulses are no longer transmitted over a long cable to the pen. Instead, the 6 various voltage levels, and particularly the sensitive Vpen voltage, are produced at 7 the carriage PCA 42 and closely communicated to the pen. Problems associated 8 with delays or interference due to transmission over a cable, which makes precise 9 control more difficult, are substantially removed with this design.

The pens 30, 32 are designed to operate optimally at approximately constant 11 temperature. The carriage PCA 42 is equipped with temperature control circuitry 12 70 to maintain the pens at their desired operating temperature. The temperature 13 control circuitry 70 includes a pulse warming circuit 72, a digital-to- analog (D/A) 14 converter 74, and an analog-to-digital (A/D) converter 76. lle temperature is control circuitry 70 sets a threshold temperature value, and the D/A converter 74 16 generates the voltages applied to warm the pen to the target temperature.

17 The temperature control circuitry 70 receives feedback information from is each pen that is indicative of the pen temperature. In one implementation, thermal 19 sense resistors are integrated into the pen and used to measure the actual temperature of the pen. The thermal sense resistors exhibit an increase in 2, resistance as the pen heats up. This resistance change is manifest as a rising 22 analog voltage signal which is received as feedback information from the pen and 23 converted by the A/D converter 76 to a digital signal. The digital value is 24 measured against a threshold value. If the actual pen temperature is below the 12 desired minimum operating temperature, the pulse warming circuit 72 preheats 2 the pen to the minimum operating temperature.

3 The carriage PCA 42 has other monitor and control circuits 80 which 4 handle an assortment of operating conditions. For instance, the circuits 80 track s over/under voltage, row/column over current, and other control conditions.

6 The carriage PCA 42 outputs certain data and status information back to the 7 stationary PCA 40 over the bi-directional serial interface. Like the input data, the g output data from the carriage PCA 42 has an address bit ADOUT that 9 communicates what type of data is being transmitted. The value ADOUT=0 o indicates that status data is being sent and a value ADOUT=1 indicates that 11 temperature data is being sent. Table 3 shows an example set input bit 12 assignments in order of their transmission.

13 14 Table 3: Output Bit Assignments is Bit ADOUT=0 ADOUT=1 16 (Status Mode) (AID Word) 17 0 Value=l Value=1 18 1 Temperate Warning Flag AID Complete 19 2 Over Temperature A/D Result Bit 0 (LSB) 3 Column Open Detected A/D Result Bit 1 21 4 Column Short Detected A/D Result Bit 2 22 5 Row Short Detected A/D Result Bit 3 23 6 Vpen Under Voltage Detected AID Result Bit 4 24 7 Output of Pen 30 PW digital filter A/D Result Bit 5 8 Output of Pen 32 PW digital filter A/D Result Bit 6 13 1 9 ID Bit A/D Result Bit 7 (MSB) 2 3 In compliance with the statute, the invention has been described in language 4 more or less specific as to structure and method features. It is to be understood, however, that the invention is not limited to the specific features described, since 6 the means herein disclosed comprise exemplary forms of putting the invention into 7 effect. The invention is, therefore, claimed in any of its forms or modifications 8 within the proper scope of the appended claims appropriately interpreted in 9 accordance with the doctrine of equivalents and other applicable judicial doctrines.

11 12 13 14 is 16 17 is 19 21 22 23 24 14

Claims

i CLAIEMS

2 1. A carriage printed circuit assembly (42) for mounting on a print head 3 carriage (20) of an ink-jet printer (10), the print head carriage (20) supporting one 4 or more removable pens (30, 32), the carriage printed circuit assembly comprising:

an input connector to electrically connect to a conductor (44) carrying data, 6 power, and ground signals from one or more sources located remotely from the 7 print head carriage (20); 8 a pen connector to facilitate electrical connection to a pen (30, 32); and 9 a pen driver (62, 64) coupled to receive the data signals from the input io connector and to convert the data signals into nozzle select signals which are 11 effective to cause the pen to deposit ink from selected nozzles, the pen driver (62, 12 64) outputting the nozzle select signals via the pen connector to the pen. 13 14
2. A carriage printed circuit assembly as recited in claim 1, fir&er is comprising voltage regulator circuitry (66) coupled to receive the power from the 16 input connector and to regulate the power to at least one voltage level. 17 18
3. A carriage printed circuit assembly as recited in claim 1, fluther g comprising:

a pen voltage regulator circuit (66) to receive the power from the input 21 connector and to regulate the power to a voltage level that is output at the pen 22 connector for use as a firing source effective to cause ink deposition from the 23 selected nozzles; and 24 the pen voltage regulator circuit (66) being responsive to a control signal 2.5 received from the input connector to adjust said voltage level.

is 1 2
4. A carriage printed circuit assembly as recited in claim 1, further 3 compnsing temperature control circuitry (70) coupled to the pen connector to 4 receive feedback from the pen (30, 32) indicative of pen temperature and to control s the pen temperature based upon the feedback.

6 7
5. An ink-jet printer (10) comprising a carriage printed circuit assembly g (42) as recited in claim 1.

9
6. A control system (16) for an ink-jet printer (10), the ink-jet printer 11 having a movable carriage (20) which carries and positions at least one pen (30, 12 32) over a printing surface, the control system comprising:

13 a stationary printed circuit assembly (PCA) (40) adapted for mounting to 14 the ink-jet printer external to the carriage (20); Is a carriage printed circuit assembly (PCA) (42) adapted for mounting to the 16 movable carriage (20); 17 a conductor (44) interconnecting the stationary PCA (40) to the carriage 8 PCA (42) to transfer data, power, and ground signals between the stationary PCA 19 (40) and the carriage PCA (42); the carriage PCA (42) having a pen driver (62, 64) coupled to receive the 21 data signals from the stationary PCA (40) via the conductor (44) and to convert the 22 data signals into nozzle select signals which are effective to cause the pen (30, 32) 23 to deposit ink from selected nozzles; and 24 16 1 the carriage PCA (42) having an electrical pen connector to facilitate 2 electrical connection to the pen (30, 32) for transferring the nozzle select signals 3 from the pen driver (62, 64) to the pen (30, 32).

4
7. A control system as recited in claim 6, wherein the carriage PCA (42) 6 also has voltage regulator circuitry (66) coupled to receive the power from the 7 fixed PCA (40) and to regulate the power to at least one voltage level.

9
8. A control system as recited in claim 6, wherein:

the carriage PCA (42) also has a pen voltage regulator circuit (66) to 11 receive the power from the stationary PCA (40) and to regulate the power to a 12 voltage level that is output at the pen connector for use as a firing source effective 13 to cause ink deposition from the selected nozzles; and 14 the stationary PCA (40) sends data to the carriage PCA (42) to set said is voltage level generated by the pen voltage regulator circuit (66).

16 17
9. A control system as recited in claim 6, wherein the carriage PCA (42) is also has temperature control circuitry (70) coupled to the pen connector to receive g feedback from the pen (30, 32) indicative of pen temperature and to control the pen temperature based upon the feedback.

21 22
10.An ink-jet printer (10) comprising a control system (16) as recited in 23 claim 6.

24 17