EP0546838A2

EP0546838A2 - Ink jet recording apparatus

Info

Publication number: EP0546838A2
Application number: EP92311310A
Authority: EP
Inventors: Yoshinori c/o Brother Kogyo K. K. Endo
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 1991-12-10
Filing date: 1992-12-10
Publication date: 1993-06-16
Also published as: EP0546838A3; JPH05155041A

Abstract

An ink jet recording apparatus (1) comprising a black ink recording head (13, 314K, KN1-KN25) for spouting a black ink against a recording medium (2); a non-black ink recording head (13, 314C, CN1-CN25) for spouting a non-black color ink different from the black ink, against the recording medium; control means (32, 40) for commanding the black and non-black ink recording heads to spout the black and non-black inks, respectively, the control means including timer means (172; 176) for measuring a time lapse after the non-black ink recording head (CN1) has last spouted the non-black ink, and generating a request signal (R; R′) when the measured time lapse has exceeded a reference time, the control means further including special operation command means (173, 174; 177, 178, 179; S326) for commanding, when the request signal is generated by the timer means, the non-black ink recording head (CN1) to effect a special ink spouting operation by spouting the non-black ink at a position of recording of the black ink recording head (KN1) on the recording medium.

Description

The present invention relates to a recording apparatus, such as an ink jet printer, for recording a color image.
There has been known a recording apparatus as shown in Fig. 17. The recording apparatus, i.e., ink jet printer includes a recording head 213 which is displaceable on a pair of guide shafts 211a, 211b by being driven by a motor (not shown). The recording head 213 is displaceable within the following three regions; (a) a recording region, A", in which the recording head 213 is opposed to a sheet convey roller 205, for effecting recording on a recording sheet conveyed by the roller 205, (b) a first extreme region, B", which is located on the right-hand side of the recording region A" and in which the recording head 213 effects a special ink spouting operation, i.e, spouting ink for preventing ink from drying up and thus clogging the outlet of an ink jet nozzle of the head 213; and (c) a second extreme region, C", which is located on the right-hand side of the first extreme region B" and in which, while the ink jet printer is not in use, the recording head 213 is air-tightly covered by a covering device 206 for preventing the drying of the ink left in the ink jet nozzle of the head 213.
Fig. 18 shows an enlarged view of the recording head 213. The head 213 includes four groups of ink jet nozzles 314K, 314C, 314M, 314Y for spouting black, cyan magenta, and yellow inks, respectively. More specifically, the four groups of ink jet nozzles 314K, 314C, 314M, 314Y are arranged in respective arrays parallel to each other.
Hereunder, there will be described a series of steps carried out by the above described ink jet printer, by reference to the flow chart of Fig. 19. First, in Step S220, it is judged whether or not a recording start command signal is received. Before the recording start command signal is supplied, the recording head 213 is held stationary in the second extreme region C" in which the head 213 is air-tightly covered by the covering device 206. If the recording start command signal is supplied and therefore an affirmative judgement is made in Step S220, Step S221 is subsequently carried out to operate a drive motor 203 of the covering device 206 and thereby retract a sealing cap 202 away from the recording head 213. Step S221 is followed by Step S222 to move the recording head 213 on the guide shafts 211a, 211b from the second extreme region C" to the first extreme region B", and subsequently in Step S223 all the ink jet nozzles 314K, 314C, 314M, 314Y of the recording head 213 effect a special ink spouting operation, that is, spouting respective color inks against an ink absorbing member 201 provided in the region B". In Step S224, the recording head 213 is then moved to the recording region A" in which the head 213 records one character line according to recording data.
After one character line is recorded in Step S224, Step S225 is carried out to identify, with respect to each of the ink jet nozzles 314K, 314C, 314M, 314Y of the recording head 213, whether or not the each nozzle has issued a request for a special ink spouting operation. This request must be issued before the ink dries up in the each nozzle and thereby clogs the outlet thereof. Generally, each nozzle is equipped with a timer means for periodically issuing a request. The period of issuance of requests is empirically determined, because the time duration necessary for the drying of an ink largely depends upon the properties of the ink and the environment of the the nozzles.
If an affirmative judgement is made with respect to at least one of the nozzles 314K, 314C, 314M, 314Y, subsequently in Step S228 the recording head 213 is moved to the first extreme region B", and further in Step S229 each of the above indicated at least one nozzle effects a special ink spouting operation, that is, spouting ink toward the ink absorbing member 201.
On the other hand, if it is judged in Step S225 that there is no nozzle 314K, 314C, 314M, 314Y requesting a special ink spouting operation, that is, if a negative judgement is made in Step S225, Step S226 is carried out to identify whether or not a current one character line recording operation has been ended. If a negative judgement is made in Step S226, Step S227 is carried out to effect a line feeding operation, and subsequently Step S224 and the following steps are repeated. Thus, Steps S224 through S227 are repeated until an affirmative judgement is made in Step S226. Meanwhile, if an affirmative judgement is made in Step S226, Step S230 is performed to move the recording head 213 to the second extreme region C", and further in Step S231 the covering device 206 is operated to air-tightly cover the recording head 213. Thus, one cycle of the series of steps of Fig. 19 is ended.
However, in the event that a quick drying ink is used for recording with a recording apparatus such as the above indicated ink jet printer, the ink dries up quickly in an ink jet nozzle or nozzles of a recording head, so that the dried ink clogs the nozzle or nozzles. Meanwhile, in the event that a slow (or non-quick) drying ink is used in the ink jet printer, it needs a long time for the drying of the ink on a recording sheet, so that the ink bleeds from the position of recording and/or contaminates an operator's hand or the recording sheet because of possible unintentional contact of the hand with the sheet. Thus, the ink jet printer is essentially required to implement the special ink spouting operation, and therefore essentially needs an ink absorbing member for carrying out the operation. The higher the frequency of implementation of the special ink spouting operation is, the higher ink absorbing capacity the ink absorber is required to have. Even in an extreme case, it is necessary to so frequently replace the ink absorber with another. However, in the event that a larger ink absorber is used, the ink absorber occupies a larger space in the ink jet printer, resulting in increasing the size of the printer as a whole. Meanwhile, in the event that the ink absorber is adapted to frequently be replaced with another, it is very cumbersome for an operator to so frequently do the work of replacing the ink absorber. In the latter case, additionally, the operator's hand and/or the printer may be stained with ink when the ink absorber is replaced with another.
Furthermore, in the event that the frequency of use of the ink jet printer is very high, the ink absorber provided in the first extreme region B" will sooner or later become incapable of absorbing ink, even if the ink absorber is of a large size. Consequently, the printer will be contaminated with ink.
Moreover, the ink jet printer is required to move the recording head 213 to the first extreme region B" so as to carry out a special ink spouting operation, when a request for the operation is issued during one character line recording operation. This leads to lowering the rate or speed of recording of the printer.
It is therefore an object of the present invention to provide a recording apparatus which is free of the need to replace, or even use, an ink absorber, by minimizing the frequency of implementation of the special ink spouting operation using the ink absorber, and therefore is free of the problem of contamination with ink, and which apparatus enjoys a small size and a high speed recording operation.
According to the present invention there is provided an ink jet recording apparatus comprising:
a black ink recording head for spouting a black ink onto a recording medium;
a non-black ink recording head for spouting a non-black colour ink different from said black ink, against said recording medium;
control means for commanding said black and non-black ink recording heads to spout said black and non-black inks, respectively,
said control means including special ink spouting operation request means for generating a request signal under determinable circumstances said control means further including special operation command means for commanding, when said request signal is generated by said timer means, said non-black ink recording head to effect a special ink spouting operation by spouting said non-black ink at a position where said black ink has been or is to be recorded on said recording medium.
The request means may comprise a recording apparatus wherein said request means comprises timer means for measuring a time lapse after said non-black ink recording head has last spouted said non-black ink, and for generating the request signal when the measured time lapse has exceeded a reference time.
The recording apparatus in accordance with the present invention does not need replacement of an ink absorbing member, or even use of the ink absorber itself, by minimizing the frequency of implementation of the special ink spouting operation using the ink absorber, and therefore is free of the problem of contamination with ink. In addition, the ink absorber may be of a small size, resulting in reducing the size of the recording apparatus as a whole. Furthermore, since the frequency of implementation of the special ink spouting operation using the ink absorber is minimized, the present apparatus effects recording on a recording medium at a high rate or speed.
In a preferred embodiment of the present invention, the special operation command means of the control means commands, when the request signal is generated by the timer means, the non-black ink recording head to effect the special ink spouting operation at the position on the recording medium where the black ink recording head has effected the recording with the black ink before the special ink spouting operation.
According to a feature of the present invention, the recording apparatus may further comprises a platen on which the recording medium is retained, and a carriage for supporting the black and non-black ink recording heads such that the recording heads are apart from each other by a predetermined distance in a recording direction which is parallel to a longitudinal direction of the platen and in which the recording heads supported by the carriage are displaceable for effecting recording on the recording medium, and such that the black ink recording head precedes the non-black ink recording head when the carriage is moved in the recording direction.
In the above indicated first embodiment, the control means may comprise (a) a counter serving as the timer means, (b) a shift register for generating a shift signal which is shifted afterward by a shift time duration from a black ink jet command signal commanding the black ink recording head to spout the black ink, the shift time duration being equal to a time period necessary for the carriage to move by the predetermined distance between the black and non-black ink recording heads, and (c) an AND gate for generating, when concurrently receiving the request signal and the shift signal, a special ink jet command signal commanding the non-black ink recording head to effect the special ink spouting operation.
In the above indicated first embodiment, alternatively, the control means may comprise (a) means for periodically generating a timing signal, (b) a counter for counting the generated timing signals, the counter serving as the timer means, (c) a shift register for generating a first, a second, and a third shift signal which are respectively shifted afterward by a first, a second, and a third shift time duration from a black ink jet command signal commanding the black ink recording head to spout the black ink, the second and third shift signals being respectively shifted afterward from the first and second shift signals by a time duration corresponding to one timing signal, the second shift time duration being equal to a time period necessary for the carriage to move by the predetermined distance between the black and non-black ink recording heads, and (d) an AND gate for generating, when concurrently receiving the request signal and the first, second, and third shift signals, a special ink jet command signal commanding the non-black ink recording head to effect the special ink spouting operation.
In the above indicated two alternatives according to the first embodiment of the present invention, the counter of the control means may generate, when the shift register does not generate the shift signal, or does not concurrently generate the first, second, and third shift signals, within a permitted time duration after generation of the request signal, a second request signal different from the request signal as a first request signal, the control means further comprising second special operation command means different from the special operation command means as a first special operation command means, the second special operation command means commanding, when receiving the second request signal, the carriage to move from a recording region in which the carriage is opposed to the platen, to a first extreme region different from the recording region, and commanding the non-black ink recording head to spout the non-black ink in the first extreme region.
In a preferred form according to the first embodiment of the present invention, the second special operation command means commands, when receiving the second request signal, the carriage to move from the recording region to the first extreme region and commands the non-black ink recording head to spout the non-black ink in the first extreme region, after the black and non-black recording heads have effected recording of a current character line on the recording medium.
According to another feature of the first embodiment of the present invention, the control means further comprises search means for searching for, after the request signal is generated by the timer means, the position of recording of the black ink recording head on the recording medium, the special operation command means commanding the non-black ink recording head to effect the special ink spouting operation at the found position on the recording medium where the black ink jet recording head has effected the recording with the black ink before the special ink spouting operation. In this case, the search means of the control means may comprise memory means for storing recording data representative of a color image to be recorded on the recording medium, and scanner means for scanning the recording data for finding a black ink jet command data which commands the black ink recording head to spout the black ink after the request signal is generated by the timer means. In addition, the control means may further comprise second special operation command means different from the special operation command means as a first special operation command means, the second special operation command means commanding, when the search means does not find the position of recording of the black ink recording head on the recording medium within a permitted time duration after generation of the request signal, the carriage to move from a recording region in which the carriage is opposed to the platen, to an extreme region different from the recording region, and commanding the non-black ink recording head to spout the non-black ink in the extreme region.
In another embodiment of the present invention, the special operation command means of the control means commands, when the request signal is generated by the timer means, the non-black ink recording head to effect the special ink spouting operation at the position on the recording medium where the black ink recording head will effect the recording with the black ink after the special ink spouting operation.
According to a feature of the above indicated second embodiment of the present invention, the control means further comprises search means for searching for, after the request signal is generated by the timer means, the position of recording of the black ink recording head on the recording medium, the special operation command means commanding the non-black ink recording head to effect the special ink spouting operation at the found position on the recording medium where the black ink recording head will effect the recording with the black ink after the special ink spouting operation.
According to another feature of the second embodiment of the present invention, the search means of the control means comprises memory means for storing recording data representative of a color image to be recorded on the recording medium, and scanner means for scanning the recording data for finding a black ink jet command data which commands the black ink recording head to spout the black ink after the request signal is generated by the timer means.
According to yet another feature of the second embodiment of the present invention, the recording apparatus further comprises a platen on which the recording medium is retained, and a carriage for supporting the black and non-black ink recording heads such that the recording heads are apart from each other by a predetermined distance in a recording direction which is parallel to a longitudinal direction of the platen and in which the recording heads supported by the carriage are displaceable for effecting recording on the recording medium, and such that the black ink recording head follows the non-black ink recording head when the carriage is moved in the recording direction.
According to a further feature of the second embodiment of the present invention, the control means comprises (a) a counter serving as the timer means, (b) means for generating a precursor signal before generation of the black ink jet command data by a time duration, 2t, wherein t is a time period necessary for the carriage to move by the predetermined distance between the black and non-black recording heads, (c) a shift register for generating, when receiving the precursor signal, a shift signal which is shifted afterward by a shift time duration from the precursor signal, the shift time duration being equal to the time period t which is half the time duration 2t, and (d) an AND gate for generating, when concurrently receiving the request signal and the shift signal, a special ink jet command signal commanding the non-black ink recording head to effect the special ink spouting operation.
In the second embodiment of the present invention, alternatively, the control means may comprise (a) means for periodically generating a timing signal, (b) a counter for counting the generated timing signals, the counter serving as the timer means, (c) means for generating a precursor signal before generation of the black ink jet command data by a time duration, 2t, wherein t is a time period necessary for the carriage to move by the predetermined distance between the black and non-black recording heads, (d) a shift register for generating, when receiving the precursor signal, a first, a second, and a third shift signal which are respectively shifted afterward from the precursor signal by a first, second, and third shift time duration, the second and third shift signals being respectively shifted afterward from the first and second shift signals by a time duration corresponding to one timing signal, the second shift time duration being equal to the time period t which is half the time duration 2t, and (e) an AND gate for generating, when concurrently receiving the request signal and the first, second, and third shift signals, a special ink jet command signal commanding the non-black ink recording head to effect the special ink spouting operation.
In yet another embodiment of the present invention, the recording apparatus further comprises a platen on which the recording medium is retained, and a carriage for supporting the black and non-black ink recording heads such that the recording heads are apart from each other by a predetermined distance in a direction parallel to a longitudinal direction of the platen, the control means commanding the carriage to reciprocate along the platen, and commanding the black and non-black ink recording heads to effect recording on the medium when the carriage is moved in each of opposite directions along the platen, the special operation command means commanding the non-black ink recording head to effect the special ink spouting operation when the carriage is moved in the each of the opposite directions.
In a further embodiment of the present invention, the recording apparatus further comprises a platen on which the recording medium is retained, and a carriage for supporting the black and non-black ink recording heads, the black and non-black ink recording heads recording dots by spouting the black and non-black inks, respectively, according to bit pattern data representative of predetermined positions in a matrix corresponding to each of at least one character line, when the carriage is moved along the platen. In this case, the special operation command means of the control means commands, when the request signal is generated by the timer means, the non-black ink recording head to effect the special ink spouting operation on the recording medium at one of recording positions of at least three consecutive dots with the black ink except for the recording positions of the opposite end two black dots.
The above and optional aims, features and advantages of the present invention will be better understood by reading the following detailed description of exemplary embodiments of the invention when considered in conjunction with the accompanying drawings, in which:

Fig. 1 is a cross-sectional view of an ink jet printer in accordance with the present invention;
Fig. 2 is a cross-sectional view for explaining the three regions, A', B', C' of the ink jet printer of Fig. 1 in which a recording head unit thereof is displaceable;
Fig. 3 is an enlarged, perspective view of the recording head unit of Fig. 2;
Fig. 4 is a diagrammatic view of an electric circuit of the ink jet printer of Fig. 1;
Fig. 5 is a flow chart for explaining the steps which are normally carried out by the ink jet printer of Fig. 1;
Fig. 6 is a flow chart for explaining the steps carried out for feeding a recording sheet in the ink jet printer of Fig. 1;
Fig. 7 is a flow chart for explaining the steps carried out for recording one character line in the ink jet printer of 1;
Fig. 8 is a flow chart for explaining the steps which are carried out by the ink jet printer of Fig. 1 for effecting a special ink spouting operation characteristic of the present invention;
Fig. 9 is an enlarged view of four groups of ink jet nozzles of the recording head unit of the ink jet printer of Fig. 1;
Fig. 10 is a diagrammatic view of the electric construction of a recording head driver of the ink jet printer of Fig. 1;
Fig. 11 is a diagrammatic view of one of control circuits of the head driver of Fig. 10, which circuit is provided for a first black ink jet nozzle;
Fig. 12 is a diagrammatic view of another of the control circuits of the head driver of Fig. 10, which circuit is provided for a first cyan ink jet nozzle;
Fig. 13 is a view showing an example of recording or printing of the ink jet printer of Fig. 1;
Fig. 14 is a timing chart for explaining the control of a second cyan ink jet nozzle;
Fig. 15 is a view corresponding to Fig. 12, showing another embodiment of the control circuit for the first cyan ink jet nozzle;
Fig. 16 is a timing chart for explaining the operation of the control circuit of Fig. 15;
Fig. 17 is a cross-sectional view for explaining the recording operation of a known ink jet printer;
Fig. 18 is an enlarged, perspective view of a recording head unit of the ink jet printer of Fig. 17; and
Fig. 19 is a flow chart for explaining the steps which are carried out by the ink jet printer of Fig. 17.

Referring first to Fig. 1, there is shown an ink jet printer 1 to which the present invention is applied. The printer 1 includes, at a front bottom part thereof, i.e., left-hand bottom part thereof as viewed in the figure, a sheet cassette 3 which is detachable from the printer 1 at the front thereof. The sheet cassette 3 stores a plurality of recording sheets 2 stacked on one another.
A sheet feed roller 4 is located on the right-hand upper side of the sheet cassette 3 set in the printer 1. The sheet feed roller 4 has a generally semilunar cross section, and feeds the top one of the stacked recording sheets 2 out of the cassette 3 toward a sheet convey roller 5. A first and a second shoot 7a, 7b are disposed between the sheet feed roller 4 and the sheet convey roller 5, for guiding the recording sheet 2 toward the sheet convey roller 5. A third shoot 7c and a pair of pinch rollers 6a, 6b cooperate with the sheet convey roller 5 to convey the recording sheet 2 toward a platen 8. More specifically, first, the leading end of the recording sheet 2 is pinched between the sheet convey roller 5 and the first pinch roller 6a, subsequently the sheet 2 is guided by the third shoot 7c, and then the sheet 2 is pinched between the sheet convey roller 5 and the second pinch roller 6b. A sheet sensor 16 is attached to the third shoot 7c, for detecting the leading and trailing ends of the recording sheet 2 being conveyed by the sheet convey roller 5.
The platen 8 is located downstream of the sheet convey roller 5, i.e., on the left-hand side of the roller 5 as viewed in Fig. 1, and extends horizontally, i.e., in a direction perpendicular to the plane of the sheet of Fig. 1. A pair of sheet output rollers 9a, 9b are disposed downstream of the platen 8. An outlet tray 10 is disposed on the left-hand side of the sheet output rollers 9a, 9b, for receiving the recording sheet 2 outputted by the sheet output rollers 9a, 9b. A star wheel is used as the second sheet output roller 9b, so as to prevent ink from sticking to the outer surface thereof.
A carriage 12 is provided above the platen 8 such that the carriage 12 is reciprocatable on a pair of guide shafts 11a, 11b in opposite directions parallel to a longitudinal axis line of the platen 8. The carriage 12 supports a recording head unit 13 which is detachable from the carriage 12 and is opposed to the platen 8. The recording head unit 13 is mounted on the carriage 12 by using a well known lock mechanism including a lock lever 14 as shown in Fig. 1. By pivoting the lock lever 14 in a counterclockwise direction, A, as viewed in the figure, the head unit 13 is locked on the carriage 12. Meanwhile, by pivoting the lock lever 14 in a clockwise direction, the head unit 13 is unlocked so as to be detachable from the carriage 12. A timing fence 15 is disposed so as to be parallel to the second guide shaft 11b. The timing fence 15 precisely detects the position of the carriage 12 being moved along the platen 8.
Fig. 2 shows the ink jet printer 1 as viewed from the back thereof, i.e., as viewed from right to left in Fig. 1. The recording head unit 13 is reciprocatable along the sheet convey roller 5 when the carriage 12 is moved on the guide shafts 11a, 11b by being driven by a motor (not shown). The head unit 13 is movable in the following three regions; (a) a recording region, A', in which the head unit 13 is opposed to the sheet convey roller 5 (or platen 8) for effecting recording on the recording sheet 2 retained on the platen 8, (b) a first extreme region, B', which is provided on the right-hand side of the recording region A' and in which the head unit 13 effects a special ink spouting operation, i.e., spouting ink from one or more of ink jet nozzles thereof toward an ink absorbing member 151, for preventing the ink from drying up and thereby clogging the outlet of the nozzle or nozzles; and (c) a second extreme region, C', which is located on the right-hand side of the first extreme region B' and in which, while the ink jet printer 1 is not in use, the head unit 13 is air-tightly covered by a covering device 156 for preventing the ink from drying and clogging the outlets of the ink jet nozzles of the head unit 13.
The covering device 156 includes a sealing cap 152 which air-tightly covers the outlets of ink jet nozzles of the recording head unit 13 and thereby prevents the ink left in the nozzles from drying up while the head unit 13 is positioned in the second extreme region C'. The covering device 156 additionally includes a rack 155 formed integrally with the sealing cap 152, a pinion 154 in engagement with the rack 155, and a pinion drive motor 153 for rotating the pinion 154. When the pinion 154 is rotated by the drive motor 153, the rack 155 engaged with the pinion 154 is reciprocatable toward (indicated at arrow C in Fig. 2), and away from, the recording head unit 13 positioned in the second extreme region C'.
Fig. 3 shows the recording head unit 13. The head unit 13 includes a nozzle support 315 for supporting a plurality of ink jet nozzles for jetting or spouting black, cyan, magenta, and yellow inks. More specifically, a group of black ink jet nozzles 314K, a group of cyan ink jet nozzles 314C, a group of magenta ink jet nozzles 314M, and a group of yellow ink jet nozzles 314Y are arranged in respective arrays parallel to each other, and those arrays extend in a direction perpendicular to the longitudinal axis line of the platen 8. An arrow, B, indicates a recording direction in which the recording head unit 13 (or carriage 12) is moved for effecting recording on the recording sheet 2 held on the platen 8.
Hereunder, there will be described the operation of the ink jet printer 1 by reference to the block diagram of Fig. 4 and the flow charts of Figs. 5, 6, and 7. Fig. 4 shows the electric circuit of the ink jet printer 1. The electric circuit includes an operator panel 41 which is operable for selecting one of various operating modes such as recording mode and communication mode. The panel 41 includes a display for indicating a selected operating mode and describing an abnormal situation in which the ink jet printer 1 is currently placed.
Figs. 5-7 shows the flow charts representing the respective steps regularly carried out by the ink jet printer 1. Those steps are effected under the control of the CPU 32.
Initially in Step S101 of Fig. 5, an operator operates the panel 41 to place the ink jet printer 1 in THE communication or ON-LINE mode. Subsequently, in Step S102, a central processing unit (CPU) 32 of the electric circuit generates a READY signal indicating the ink jet printer 1 has been placed in the READY mode. The READY signal is supplied to an external terminal device (not shown) via an interface 31 and a communication line 30. Thus, the ink jet printer 1 is ready to receive recording data from the terminal device.
In Step S103, the terminal device transmits recording data such as document data representative of a document, to the ink jet printer 1 through the communication line 30, and the document data is transferred to the CPU 32 via the interface 31. The CPU 32 stores the transferred document data in a random access memory (RAM) 33 according to control programs stored in a read only memory (ROM) 34. In Step S104, the CPU 32 stores a predetermined amount of data in the RAM 33, and transmits a BUSY signal to the terminal device via the interface 31 and communication line 30, so as to command the terminal device to temporarily stop transmitting the document data to the printer 1.
Subsequently, in Step S105, the CPU 32 associates the document data stored in the RAM 33, with corresponding sets of bit pattern data stored in the ROM 34. Each set of bit pattern data is representative of predetermined positions in a matrix such that those predetermined positions represent an image such as alphabetic letters, numerals, and symbols. Thus, the CPU 32 prepares four batches of combined bit pattern data for the four groups of ink jet nozzles 314K, 314C, 314M, 314Y. The four batches of combined bit pattern data cooperate with each other to represent one or more character lines of the document. In Step S106, the four batches of combined bit pattern data are transmitted to a recording head driver 40 and stored in respective memories provided for the four groups of nozzles 314K, 314C, 314M, 314Y. One character line is recorded on the sheet 2 by reciprocating the carriage 12 one time forward (i.e., in the recording direction B) and backward (i.e., in the opposite direction) along the platen 8.
Next, in Step S107, the CPU 32 identifies, based on a detection signal from the sheet sensor 16, whether or not a recording sheet 2 has been fed to the platen 8. If a negative result is obtained in Step S107, the control of the CPU 32 proceeds with Step S108 to feed a recording sheet 2 to the platen 8.
There will be described the sheet feeding operation by reference to the flow chart of Fig. 6. First, in Step S121, the CPU 32 operates a sheet feed/convey driver 35 to drive a sheet feed/convey pulse motor 36. The rotation of the pulse motor 36 is transmitted to the sheet convey roller 5 and the first sheet output roller 9a via respective gears (not shown). At the same time, the rotation power is transmitted to a clutch 37 through which the pulse motor 36 is connectable with the sheet feed roller 4. In Step S122, the CPU 32 supplies a trigger signal to the clutch 37 for connecting the pulse motor 36 to the sheet feed roller 4 for a time duration necessary to rotate the roller 4 by just one full turn. Consequently, the top one of the recording sheets 2 stacked in the sheet cassette 3 is fed out of the cassette 3 so as to be guided by the first and second shoots 7a, 7b, subsequently nipped by the sheet convey roller 5 and the first pinch roller 6a, and further conveyed by rotation of the sheet convey roller 5.
In Step S123, it is judged whether or not the sheet sensor 16 located between the first and second pinch rollers 6a, 6b has detected the leading end of the recording sheet 2. If the sheet sensor 16 has detected the leading end of the sheet 2, the sheet sensor 16 supplies a detection signal to the CPU 32, and the control of the CPU 32 proceeds with Step S124 to command the sheet feed/convey driver 35 to rotate the sheet feed/convey pulse motor 35 by a predetermined amount and then stop the rotation of the same 35. Thus, the leading end of the recording sheet 2 is brought into position with respect to the platen 8. On the other hand, if a negative judgement is made in Step S123, the control of the CPU 32 goes to Step S125 to count clock signals. If the CPU 32 counts up a predetermined number of clock signals, the control goes to Step S126 to generate an alarm sound informing the operator that an error has occurred in the sheet feeding operation.
Meanwhile, if an affirmative result is obtained in Step S107, or if a recording sheet 2 has been fed to the platen 8 in Step S108, the control of the CPU 32 goes to Step S109 to effect a one character line recording operation on the recording sheet 2, as described below.
Hereunder, the one character line recording operation will be explained by reference to the flow chart of Fig. 7.
First, in Step S131, the CPU 32 operates a carriage driver 38 to drive a carriage drive pulse motor 39. The rotation of the pulse motor 39 is transmitted to the carriage 12 via a pulley and a belt (both not shown), so that the carriage 12 is moved forward, i.e., in the recording direction B along the longitudinal axis line of the platen 8.
In Step S132, the CPU 32 judges whether or not the CPU 32 has received a timing signal from the timing fence 15. If an affirmative judgement is made in Step S132, the control of the CPU 32 goes to Step S133 to increment the content of a counter by one, thereby counting the number of timing signals from the timing fence 15 up to a predetermined lower limit value corresponding to the beginning position of recording on the platen 8 where the recording head unit 13 begins the one character line recording operation.
For example, provided that the value corresponding to the recording beginning position is predetermined at 200, the CPU 32 continues to increment the content of the counter up to 200 in Step S134. In Step S135, it is judged whether or not the content of the counter has been counted up to the predetermined value (e.g., 200). If an affirmative judgement is made in Step S135, the control of the CPU 32 goes to Step S135 to transmit a trigger signal to the recording head driver 40. Upon reception of the trigger signal, the head driver 40 drives appropriate ones of the black ink jet nozzles 314K of the recording head unit 13 to jet or spout black ink against the recording sheet 2 retained on the platen 8. Thus, a single dot line perpendicular to the above indicated recording direction B is recorded on the sheet 2. Subsequently, each time the CPU 32 receives a timing signal from the timing fence 15 as the carriage 12 is moved in the recording direction B, the CPU 32 supplies a trigger signal to the head driver 40 to record a corresponding dot line. Thus, consecutive dot lines are recorded on the sheet 2.
In this connection, it is noted that, as shown in Fig. 3, the respective arrays of ink jet nozzle groups 314K, 314C, 314M, 314Y are provided on the carriage 12 at a predetermined interval of distance from each other in the recording direction B. Therefore, the CPU 32 determines the time to generate a trigger signal to each of the other ink jet nozzle groups 314C, 314M, 314Y, by counting a corresponding suitable number of timing signals in addition to the predetermined lower limit value (e.g., 200) for the black ink jet nozzle group 314K.
For example, provided that the predetermined interval of distance between the respective arrays of the ink jet nozzle groups 314K, 314C, 314M, 314Y correspond to 10 timing signals supplied from the timing fence 15, the CPU 32 does not supply a trigger signal to the cyan ink jet nozzle group 314C until the content of the counter is incremented up to not less than 200 + 10. These operations correspond to Steps S136 and S137. Similarly, the CPU 32 does not supply a trigger signal to the magenta and yellow ink jet nozzle groups 314C, 314Y until the content of the counter is incremented up to not less than 200 + 20 or 200 + 30, respectively. These operations correspond to Steps S138 and S139, or Steps S140 and S141. After the content of the counter has been incremented up to the value corresponding to each of the three ink jet nozzle groups 314C, 314M, 314Y, the CPU 32 supplies a trigger signal to the each ink jet nozzle group 314C, 314M, 314Y each time the CPU 32 receives a timing signal from the timing fence 15. These operations are repeated, so that one character line is recorded on the recording sheet 2 with the four groups of ink jet nozzles 314K, 314C, 314M, 314Y.
Meanwhile, in Step S142, it is judged whether or not the content of the counter has been incremented up to a predetermined upper limit value corresponding to the ending position of recording on the platen 8 where the black ink jet nozzle group 314K ends the one character line recording operation. If an affirmative judgement is made in Step S142, the control of the CPU 32 goes to Step S143 to additionally count the timing pulses by a value (e.g., 30) corresponding to the distance between the leading (black) ink jet nozzle group 313K and the trailing (yellow) nozzle group 313Y, and subsequently stop the operation of the carriage driver 38. Then, the control of the CPU 32 goes to Step S110 of Fig. 5.
In Step S110, the CPU 32 waits for a predetermined time duration for attenuation of vibrations of the frame members of the ink jet printer 1 due to the displacement of the carriage 12. Subsequently, the CPU 32 resumes the operation of the carriage driver 38 to rotate the carriage drive pulse motor 39 in the reverse or opposite direction thereof by an amount equal to that necessary to move the carriage 12 in the recording direction B for effecting the one character recording operation. Thus, the carriage 12 is moved backward along the platen 8. This is the carriage returning operation. While the carriage 12 is returned, no recording operation is effected in the present embodiment.
Step S110 is followed by Step S111 to operate the sheet feed/convey driver 35 for a predetermined time duration to drive the sheet feed/convey pulse motor 36 and thereby rotate each of the sheet convey roller 5 and first sheet output roller 9a by a predetermined amount or angle. Consequently, the recording sheet 2 is conveyed forward by a predetermined amount or length. This is so called "line feeding" operation. The predetermined length is equal to the distance between the center lines of adjacent two character lines of the document recorded on the recording sheet 2. This length is adjustable by the operator through the operator panel 41.
In Step S112, it is judged whether or not the sheet sensor 16 has detected the trailing end of the recording sheet 2 during the line feeding operation. If an affirmative judgement is made in Step S112, the CPU 32 identifies that the recording of one page of the document has ended, therefore the control of the CPU 32 goes to Step S113 to cease the ink jet printer 1 from effecting subsequent recording operation and operate the sheet feed/convey driver 35 to rotate the sheet convey roller 5 and the first outlet roller 9a by an amount sufficient to output the recorded sheet 2 into the outlet tray 10. If the document includes the next page, the CPU 32 operates the sheet feed/convey driver 35 and triggers the clutch 37 to rotate the sheet feed roller 4 to feed the top one of the stacked recording sheets 2 out of the sheet cassette 3.
On the other hand, if a negative judgement is made in Step S112, the control of the CPU 32 returns to Step S102 to transmit a READY signal to the external terminal device to command the terminal device to resume supplying additional document data to the ink jet printer 1. Subsequently, the above-described series of steps are repeated.
Next, there will be described the special ink spouting operation of each of the ink jet nozzles 314K, 314C, 314M, 314Y of the recording head unit 13, by reference to the flow chart of Fig. 8. It is noted that the flow chart of Fig. 8 includes the steps carried out under the control of the CPU 32 and the steps carried out under the recording head driver 40 and therefore that the flow chart of Fig. 8 does not represent a complete control program used by the CPU 32 for effecting the special ink spouting operation.
In Step S319, it is judged whether or not the CPU 32 has received a recording start command signal through operation of the operator panel 41. Before the recording start command signal is supplied to the CPU 32, the carriage 12 is held stationary in the second extreme region C' in which the recording head unit 13 is air-tightly covered by the covering device 156. If the recording start command signal is supplied to the CPU 32 (thus, the printer 1 is placed in the recording mode) and therefore an affirmative judgement is made in Step S319, the control of the CPU 32 goes to Step S320 to operate a pinion driver 157 (Fig. 4) to rotate the pinion drive motor 153 of the covering device 156, so that the rotation power of the pinion 154 is transmitted to the rack 155. Consequently, the rack 155 is moved in a direction opposite to the direction C (Fig. 2), so that the sealing cap 152 is retracted away from the head unit 13. Thus, the ink jet printer 1 is placed in a condition in which the printer 1 is ready to start the one character line recording operation on the recording sheet 2 retained on the platen 8. Step S320 is followed by Step S321 to move the carriage 12 on the guide shafts 11a, 11b from the second extreme region C' to the recording region A' in which the head unit 13 effects the one character line recording operation according to the bit pattern data stored in the recording head driver 40.
During the one character line recording operation in Step S321, Step S322 is carried out to identify, with respect to each one of the ink jet nozzles 314C, 314M, 314Y except for the black ink jet nozzles 314K, whether or not the each one nozzle 314C, 314M, 314Y requests a special ink spouting operation. If an affirmative judgement is made with respect to the each one nozzle 314C, 314M, 314Y, Step S325 is carried out to identify whether or not the each one nozzle 314C, 314M, 314Y can effect the special ink spouting operation at a position of recording of a corresponding one of the black ink jet nozzles 314K, within a permitted time duration within which the ink left in the each nozzle 314C, 314M, 314Y does not dry up. If an affirmative judgement is made with respect to the each one nozzle in Step S325, Step S326 is carried out to effect the special ink spouting operation by spouting a corresponding color ink at the position of recording of the corresponding black ink jet nozzle 314K, while continuing to perform the normal recording operation. Steps S322, S325, S326 are effected under the control of the recording head driver 40, as described later.
On the other hand, if a negative judgment is made with respect to the each one nozzle 314C, 314M, 314Y in Step S325, the control of the CPU 32 proceeds, after the one character line recording operation has ended in Step S321, to Step S327 to move the carriage 12 from the recording region A' to the first extreme region B', and further to Step S328 to cause the each one nozzle to effect the special ink spouting operation in the region B', i.e., spout a corresponding color ink toward the ink absorber 151. When a dot recorded with each one of the color inks (i.e., cyan, magenta, and yellow) different from the black ink overlies a dot recorded with the black ink, the each one color ink is not sensible to the eyes of an observer. Thus, even though the special ink spouting operation or operations is/are carried out at a position or positions of recording of one or more black ink jet nozzles 314K, the spouted color ink does not deteriorate the quality of recording of the ink jet printer 1.
After the special ink spouting operation or operations is/are effected in Step S326 or Step S328, or if it is judged in Step S322 that there is no nozzle 314C, 314M, 314Y requesting the special ink spouting operation, the control of the CPU 32 goes to Step S323 to identify whether or not the entire recording operation has ended. If a negative judgement is provided in Step S323, then the control goes to Step S324 to effect a line feeding operation, and subsequently returns to Step S321 and the following steps. Thus, Steps S321 through S328 are repeated until an affirmative judgement is made in Step S323. Meanwhile, if an affirmative judgement is made in Step S323, the control goes to Step S329 to move the carriage 12 (or head unit 13) to the second extreme region C', and further to Step S330 to operate the pinion driver 157 to rotate the pinion drive motor 153 of the covering device 156. The rotation power of the drive motor 153 is transmitted to the rack 155 via the pinion 154 connected to the output shaft of the motor 153. Consequently, the sealing cap 152 is moved in the direction C, so that the sealing cap 152 is brought into close contact with the head unit 13. Thus, the nozzle support 315 of the head unit 13 is air-tightly sealed by the sealing cap 152. Thus, one cycle of the series of steps of Fig. 8 is ended.
Fig. 9 shows the nozzle support 315 of the recording head unit 13. Each of the groups of black, cyan, magenta, and yellow ink jet nozzles 314K, 314C, 314M, 314Y consist of twenty five nozzles KN1-KN25, CN1-CN25, MN1-MN25, and YN1-YN25, respectively.
Fig. 10 shows in detail the electric circuits of the recording head driver 40 for driving the four groups of ink jet nozzles KN1-KN25, CN1-CN25, MN1-MN25, YN1-YN25 of the recording head unit 13. Hereunder, there will be described the flow of electric signals through the head driver 40, by reference to Fig. 10.
With respect to, for example, the first black ink jet nozzle KN1, a first black ink jet nozzle data signal KS1 is supplied to a first black ink jet nozzle control circuit KC1. Fig. 11 shows in detail the electric circuit of the first black ink jet nozzle control circuit KC1. On one hand, the supplied data signal KS1 is transmitted directly to a first black ink jet nozzle drive circuit KD1 (Fig. 10), so as to drive the first black ink jet nozzle KN1. On the other hand, the supplied data signal KS1 is inputted to a RESET terminal of a counter 170 of the control circuit KC1. Meanwhile, the content of the counter 170 is incremented by one each time an ink jet timing clock signal CLK is supplied to the counter 170. When an ink jet command or high-level data signal KS1 is inputted to the counter 170, the content of the counter 170 is reset to zero. Thus, the counter 170 continues to count the ink jet timing clock signals CLK for a time duration during which the ink jet nozzle KN1 does not spout the black ink. Stated differently, the counter 170 measures that time duration. If the counted timing signal number or the measured time duration exceeds a reference value, that is, if the first black ink jet nozzle KN1 continues not to spout the black ink for more than a reference time, the counter 170 generates a request signal RK1 requesting the first black ink jet nozzle KN1 to effect a special ink spouting operation. Based on this request signal RK1, the CPU 32 operates in Step S328 of Fig. 8 for commanding the first black ink jet nozzle KN1 to effect the special ink spouting operation by spouting the black ink against the ink absorber 151.
Similar to the first black ink jet nozzle control circuits KC1, each of the other black ink jet nozzle control circuits KC2 through KC25 generates a request signal RK2 through RK25. However, since the frequency of use of the black ink jet nozzles KN1-KN25 are much higher than those of the other groups of ink jet nozzles CN1-CN25, MN1-MN25, YN1-YN25, the frequency of generation of the request signals RK1 through RK25 is much lower than those of the request signals of the other ink jet nozzles CN1-CN25, MN1-MN25, YN1-YN25.
Next, with respect to, for example, a first cyan ink jet nozzle CN1, a first cyan ink jet nozzle data signal CS1 is supplied to a first cyan ink jet nozzle control circuit CC1. Fig. 12 shows in detail the electric circuit of the first cyan ink jet nozzle control circuit CC1. The supplied data signal CS1 is inputted to one of two input terminals of an OR gate 171. On one hand, an output signal of the OR gate 171 is transmitted to a first cyan ink jet nozzle drive circuit CD1 (Fig. 10), so as to drive the first cyan ink jet nozzle CN1. On the other hand, the output signal of the OR gate 171 is inputted to a RESET terminal of a counter 172 of the control circuit CC1. Meanwhile, the content of the counter 172 is incremented by one each time an ink jet timing clock signal CLK is supplied thereto. When an ink jet command or high-level data signal KS1 is inputted to the counter 172, the content of the counter 172 is reset to zero. Thus, the counter 172 continues to count the ink jet timing clock signals for a time duration during which the ink jet nozzle CN1 does not spout the cyan ink. Stated differently, the counter 170 measures that time duration. If the counted timing signal number or the measured time duration exceeds a reference value, that is, if the ink jet nozzle CN1 continues not to spout the cyan ink for more than a reference time, the counter 172 generates a first request signal R requesting the first cyan ink jet nozzle CN1 to effect a special ink spouting operation.
In addition, the control circuit CC1 includes a shift register 174 which, when receiving an ink jet command or high-level first black ink jet nozzle data signal KS1, generates a high-level shift signal Q which is shifted afterward by a predetermined number of ink jet timing signals CLK from the ink jet command high-level data signal KS1. The above indicated predetermined number of timing signals CLK corresponds to the distance between the two arrays of the black and cyan ink jet nozzles KN1-KN25, CN1-CN25 on the carriage 12. If the high-level shift signal Q and the above indicated first request signal R are concurrently inputted to an AND gate 173 of the control circuit CC1, the AND gate 173 generates a special ink jet command signal S. The command signal S is inputted to the other of the two input terminals of the OR gate 171, so as to drive the first cyan ink jet nozzle CN1. If, however, no "normal" or "special" ink jet command signal CS1 or S is inputted to the OR gate 171 (therefore, counter 172) for a permitted time duration after the signal R is generated by the counter 172, the counter 172 generates a second request signal RC1. Based on this second request signal RC1, the CPU 32 operates in Step S328 of Fig. 8 for commanding the first cyan ink jet nozzle CN1 to effect the special ink spouting operation by spouting the cyan ink against the ink absorber 151 in the first extreme region B'.
Each of other cyan ink jet nozzle control circuits CC2-CC25 and each of magenta and yellow ink jet nozzle control circuits MC1-MC25, YC1-YC25 has a construction similar to the first cyan ink jet nozzle control circuit CC1, and generates a second request signal RC2-RC25, RM1-RM25, RY1-RY25 under a similar condition.
In the event that at least one of the request signals RK1-RK25 and second request signals RC1-RC25, RM1-RM25, RY1-RY25 is generated during the one character line recording operation in Step S321 of Fig. 8, the recording head unit 13 (or carriage 12) is moved, in Step S327, to the first extreme region B' (Fig. 2) after the one character line recording operation has ended in Step S321, and the ink jet nozzle or nozzles corresponding to the above indicated at least one request signal spouts or spout ink against the ink absorber 151 in Step S328. Thus, the ink jet printer 1 effectively prevents the ink left in each of the cyan, magenta, and yellow ink jet nozzles CN1-CN25, MN1-MN25, YN1-YN25 from drying up and thereby prevents the each nozzle from being clogged with the dried ink.
Hereunder, there will be described in more detail the operation of the cyan, magenta, and yellow ink jet nozzle control circuits CC1-CC25, MC1-MC25, YC1-YC25, by reference to Figs. 13 and 14. Fig. 13 shows a letter "A" consisting of black dots recorded with the black ink in the event that a first request signal R is generated in each of the second and seventh cyan ink jet nozzle control circuits CC2, CC7. Fig. 14 shows a timing chart for explaining the flow of electric signals in the second cyan ink jet nozzle control circuit CC2. The second black ink jet nozzle data signal KS2 includes two ink jet command high-level signals corresponding to the third and fifth ink jet timing signals CLK3, CLK5 as counted from the beginning of the one character line recording operation. The shift signal Q includes two high-level signals which are shifted backward by a time duration corresponding to ten ink jet timing signals CLK from the third and fifth high-level signals KS2, respectively. The ten timing signals CLK correspond to a length on the recording sheet 2 in which ten dots can be recorded, and corresponds to the distance between the two arrays of black and cyan ink jet nozzles 314K, 314C on the carriage 12 or head unit 13 (Fig. 9).
When the thirteenth timing signal CLK13 is generated, both the shift signal Q and the first request signal R are held at a high level, so that a high-level second request signal S is generated. Thus, a special ink spouting operation is effected. This corresponds to Step S326 of Fig. 8. In addition, the first request signal R is changed to a low level. In this way, the second and seventh cyan ink jet nozzles CN2, CN7 effect a special ink spouting operation by spouting the cyan ink toward the recording sheet 2 at the positions of recording of the second and seventh black ink jet nozzles KN2, KN7 shown in Fig. 13, respectively. That is, the drying of the cyan ink in the two nozzles CN2, CN7 and the clogging of the same CN2, CN7 with the dried cyan ink are effectively prevented.
While the present invention has been described in its preferred embodiment, it is to be understood that the present invention is by no means limited to the detailed particulars of the illustrated embodiment.
For example, in the illustrated embodiment, when an initial high-level shift signal Q corresponding to an initial high-level black ink jet nozzle data signal KS1-KS25 is generated after a high-level first request signal R is generated in each of the cyan, magenta, and yellow ink jet nozzle control circuits CC1-CC25, MC1-MC25, YC1-YC25, a special ink spouting operation is carried out at the position of recording of the black ink jet nozzle KN1-KN25 in response to the above indicated initial high-level black ink jet nozzle data signal KS1-KS25. However, the ink jet printer 1 may be adapted to carry out a special ink spouting operation at any of positions of recording with the black ink. For preventing such an inappropriate special ink spouting operation which results in recording a dot at a position slightly offset from the position of recording of a dot with the black ink, and thereby preventing the cyan, magenta, or yellow ink dot from partially overlapping the black ink dot, it is possible to adapt the ink jet printer 1 to effect a special ink spouting operation only at the position of recording of an intermediate one of at least three consecutive black dots except for the opposite two end dots thereof. With this arrangement, the quality of recording of the printer 1 is not lowered. Hereunder, there will be described in detail the construction and operation of a modified first cyan ink jet nozzle control circuit CC1' for the above indicated adaptation of the ink jet printer 1, by reference to Figs. 15 and 16.
First, by reference to Fig. 15, is described the flow of electric signals in the modified first cyan ink jet nozzle control circuit CC1' for the first cyan ink jet nozzle CN1. In this control circuit CC1', a first cyan ink jet nozzle data signal CS1 is inputted to one of two input terminals of an OR gate 175. On one hand, an output signal of the OR gate 175 is transmitted to the first cyan ink jet nozzle drive circuit CD1, so as to drive the first cyan ink jet nozzle CN1. On the other hand, the output signal of the OR gate 175 is inputted to a RESET terminal of a counter 176 of the control circuit CC1'. Meanwhile, the content of the counter 176 is incremented by one each time an ink jet timing clock signal CLK is supplied to the counter 176. When a high-level first black ink jet nozzle data signal KS1 is inputted to the counter 176, the content of the counter 176 is reset to zero. Thus, the counter 176 continues to count the timing clock signals CLK for a time duration during which the ink jet nozzle CN1 does not spout the cyan ink. If the counted timing signal number exceeds a reference value, that is, if the first cyan ink jet nozzle CN1 continues not to spout the cyan ink for more than a reference time, the counter 176 generates a first request signal R' requesting the first cyan ink jet nozzle CN1 to effect a special ink spouting operation.
As shown in a timing chart of Fig. 16, a shift register 179 of the control circuit CC1' generates, upon reception of a high-level data signal KS1, a high-level first, a high-level second, and a high-level third shift signal Q1, Q2, Q3 which are shifted afterward by nine, ten, and eleven timing signals CLK from the high-level data signal KS1, respectively. The shift signals Q1, Q2, Q3 are supplied to three input terminals of a three-input AND gate 178, respectively. In the event that three high-level shift signals Q1, Q2, Q3 are concurrently supplied to the AND gate 178, the AND gate 178 generates an output signal Q'. If two high-level signals Q' and R' are concurrently supplied to two input terminals of an AND gate 177, the AND gate 177 generates a special ink jet command signal S'. The command signal S' is inputted to the other of the two input terminals of the OR gate 175, so as to drive the first cyan ink jet nozzle CN1. If, however, no "normal" or "special" ink jet command signal CS1 or S' is inputted to the OR gate 175 (therefore, counter 176) for a permitted time duration after the high-level first request signal R' is generated by the counter 176, the counter 176 generates a high-level second request signal RC1. In this case, each of other cyan ink jet nozzle control circuits CC2'-CC25' and each of magenta and yellow ink jet nozzle control circuits MC1'-MC25', YC1'-YC25' has a construction similar to the control circuit CC1', and generates a second request signal RC2-RC25, RM1-RM25, RY1-RY25 under a similar condition.
Further, the ink jet printer 1 may be adapted to effect a special ink spouting operation only at the position of recording of an intermediate one of at least three consecutive black dots except for the opposite end two dots in each of dot lines recorded in a direction perpendicular to the longitudinal direction of the platen 8. Furthermore, the ink jet printer 1 may be adapted to effect a special spouting operation only at the position of recording of an intermediate one of at least three consecutive black dots except for the opposite end two dots in each of the dot lines and, at the same time, at the position of recording of an intermediate one of at least three consecutive black dots except for the opposite end two dots recorded along the platen 8. Additionally, the ink jet printer 1 may be adapted to effect a special spouting operation only at the position of recording of a center one of more than nine adjacent black dots consisting of at least three consecutive dots in each of at least three consecutive dot lines in each of character lines recorded along the platen 8.
There will be described another embodiment of the present invention, by reference to Figs. 2, 4, and 8 which have been used for describing the preceding, first embodiment of the invention. While, in the first embodiment, Steps S322, S325, and S326 in the flow chart of Fig. 8 are carried out under the control of the control circuit CC1 or CC1' of Fig. 12 or Fig. 15, during the implementation of Step S321, that is, while the one character line recording operation is being performed. However, it is possible to effect Steps S322, S325, and S326 under the control of the CPU 32, as follows: First, in Step S321, the CPU 32 commands the recording head unit 13 to complete the one character line recording operation. In the situation after this operation, the carriage 12 is located at one of opposite ends of the recording region A' (Fig. 2). Subsequently, in Step S322, the CPU 32 identifies whether at least one of the second request signals RC1-RC25, RM1-RM25, RY1-RY25 has been generated. If an affirmative judgement is made in Step S322, the control of the CPU 32 goes to Step S325 to identify whether at least one color ink jet nozzle CN1-CN25, MN1-MN25, YN1-YN25 corresponding to the above indicated at least one second request signal RC1-RC25, RM1-RM25, RY1-RY25 can effect a special ink spouting operation at a position of recording of a corresponding one of the black ink jet nozzles KN1-KN25, within a permitted time duration during which the ink left in the at least one color ink jet nozzle does not dry up. More specifically, the CPU 32 operates as scanner means for scanning the batch of combined bit pattern data for the group of black ink jet nozzles KN1-KN25, stored in the RAM 33, for finding a black ink jet command data (i.e., high-level signal data) which commands the above indicated corresponding one black ink jet nozzle to spout the black ink after the at least one second request signal RC1-RC25, RM1-RM25, RY1-RY25 is generated. If an affirmative judgement is made with respect to all the at least one color ink jet nozzle in Step S325, the control of the CPU 32 goes to Step S326 to produce a special ink jet command data which commands the at least one color ink nozzle jet nozzle to effect the special ink spouting operation by spouting a corresponding color ink at the found position of recording of the corresponding one black ink jet nozzle. This special ink spouting operation will be effected in Step S321 in the next cycle of the routine of Fig. 8. On the other hand, if a negative judgement is made with respect to any of the at least one color ink jet nozzle in Step S325, the control of the CPU 32 goes to Step S327 to move the carriage 12 to the first extreme region B' and command all the at least one color ink jet nozzle to effect the special ink spouting operation by spouting a corresponding color ink toward the ink absorber 151 provided in the region B'. Thus, the routine of Fig. 8 is implemented fully under the control of the CPU 32. In this embodiment, the routine of Fig. 8 is pre-programmed, and is stored in the ROM 34.
There will be described yet another embodiment of the present invention, by reference to Figs. 2, 3, 4, 8, 12, and 15 which have been used for describing the first embodiment. In the first embodiment, the ink jet printer 1 performs the one character line recording operation only in the forward direction, i.e., recording direction B shown in Fig. 3. However, in this third embodiment, the printer 1 is modified to effect the recording operation when the carriage 12 or recording head unit 13 is moved both in opposite directions along the platen 8, that is, both in the forward direction B and in the backward direction opposite to the direction B. In the instant embodiment, it is possible to adapt each of the color ink jet nozzles CN1-CN25, MN1-MN25, YN1-YN25 of the modified printer 1 to effect a special ink spouting operation at a position of recording of a corresponding one of the black ink jet nozzles KN1-KN25, also when the carriage 12 is moved in the backward recording direction. In this case, the black ink jet nozzles KN1-KN25 follows the color ink jet nozzles CN1-CN25, MN1-MN25, YN1-YN25 when the carriage 12 is moved in the backward recording direction. Therefore, in contrast to the first embodiment wherein a special ink spouting operation is effected at a position on a recording sheet 2 where a black ink dot has been recorded, a special ink spouting operation is effected, in the instant embodiment, at a position on a recording sheet 2 where a black ink dot will be recorded within a permitted time duration after generation of a first request signal R, R' requesting a special ink spouting operation.
More specifically, first, in Step S321 of Fig. 8, the CPU 32 commands the recording head unit 13 to complete the one character line recording operation. In the situation after this operation, the carriage 12 is located at one of opposite ends of the recording region A' (Fig. 2). Then, in Step S322, the CPU 32 identifies whether at least one of the second request signals RC1-RC25, RM1-RM25, RY1-RY25 has been generated. If an affirmative judgement is made in Step S322, the control of the CPU 32 goes to Step S325 to identify whether at least one color ink jet nozzle CN1-CN25, MN1-MN25, YN1-YN25 corresponding to the above indicated at least one second request signal RC1-RC25, RM1-RM25, RY1-RY25 can effect a special ink spouting operation at a position of recording of a corresponding one of the black ink jet nozzles KN1-KN25, within a permitted time duration during which the ink left in the at least one color ink jet nozzle does not dry up. To this end, the CPU 32 of the modified printer 1 operates as scanner means for scanning the batch of combined bit pattern data for the group of black ink jet nozzles KN1-KN25, stored in the RAM 33, for finding a black ink jet command data (i.e., high-level signal data) which commands the above indicated corresponding one black ink jet nozzle to spout the black ink after the at least one second request signal RC1-RC25, RM1-RM25, RY1-RY25 is generated. If an affirmative judgement is made with respect to all the at least one color ink jet nozzle in Step S325, the control of the CPU 32 goes to Step S326 to produce a special ink jet command data which commands the at least one color ink nozzle jet nozzle to effect the special ink spouting operation by spouting a corresponding color ink at the found position of recording of the corresponding one black ink jet nozzle. This special ink spouting operation will be effected in Step S321 in the next cycle of the routine of Fig. 8.
Alternatively, in Step S326, the CPU 32 may operate as means for generating, for each of the cyan ink jet nozzles CN1-CN25, for example, a precursor signal before generation of the above indicated black ink jet command data by a time duration, 2t (e.g., time duration corresponding to twenty ink jet timing clock signals CLK), wherein t is a time period (e.g., time duration corresponding to ten timing clock signals CLK) necessary for the carriage 12 to move by the predetermined distance between the arrays 314K, 314C of the black and cyan ink jet nozzle groups KN1-KN25, CN1-CN25. For the other two ink jet nozzles 314M, 314Y, the CPU 32 may operate in a similar manner. In this case, the shift register 174 of the first cyan ink jet nozzle control circuit CC1 of Fig. 12, for example, generates, when receiving the precursor signal, a shift signal Q which is shifted afterward by a shift time duration from the precursor signal, such that the shift time duration is equal to the time period t which is half the time duration 2t, and the AND gate 173 generates, when concurrently receiving the request signal R and the shift signal Q, a special ink jet command signal S commanding the first cyan ink jet nozzle CN1 to effect the special ink spouting operation. In addition, the shift register 179 of the first cyan ink jet nozzle control circuit CC1' of Fig. 15 generates, when receiving the precursor signal, a first, a second, and a third shift signal Q1, Q2, Q3, which are respectively shifted afterward from the precursor signal by a first, second, and third shift time duration, such that the second and third shift signals Q2, Q3 are respectively shifted afterward from the first and second shift signals Q1, Q2 by a time duration corresponding to one ink jet timing clock signal CLK, and that the second shift time duration is equal to the time period t which is half the time duration 2t, and the AND gate 177 generates, when concurrently receiving the request signal R' and the first, second, and third shift signals Q1, Q2, Q3 (i.e., signal Q' from the AND gate 178), a special ink jet command signal S' commanding the first cyan ink jet nozzle CN1 to effect the special ink spouting operation.
On the other hand, if a negative judgement is made with respect to any of the at least one color ink jet nozzle in Step S325, the control of the CPU 32 goes to Step S327 to move the carriage 12 to the first extreme region B' and command all the at least one color ink nozzle jet nozzle to effect the special ink spouting operation by spouting a corresponding color ink toward the ink absorber 151 provided in the region B'. In this third embodiment, too, the routine of Fig. 8 is implemented fully under the control of the CPU 32. The routine of Fig. 8 is pre-programmed, and is stored in the ROM 34.
As is easily understood from the foregoing description, the principle of the present invention is applicable to the ink jet printer 1 which is modified to effect recording when the carriage 12 is moved only in the backward direction opposite to the forward direction B shown in Fig. 3, although, in such a case, the "backward" direction should be called the "forward" direction.
Although the ink jet printer 1 of Fig. 2 is provided with the first extreme region B' in which the special ink spouting operation is effected, it is possible to omit the region B' because the region B' is not very practically necessary. Provided that the frequency of use of the black ink jet nozzles 314K be very high, the region B' may not be necessary.
While the foregoing description relates to the ink jet printer 1 adapted to sequentially carry out the respective operations of receiving document data, associating the document data with corresponding sets of bit pattern data stored in the ROM 34, recording one character line, returning the carriage 12, and feeding the recording sheet 2 by an amount corresponding to one character line, it is not difficult to adapt the printer 1 to concurrently effect some of those operations, by modifying the electric circuit of the printer 1 and/or the control programs according to which the CPU 32 carries out those operations.
Although in the illustrated embodiments the recording sheet 2 is outputted from the printer 1 upon detection of the trailing end of the sheet 2 by the sheet sensor 16, the printer 1 may be adapted to continue the recording operation until a predetermined number of character lines are recorded after detection of the trailing end of the sheet 2. In this case, the above indicated predetermined number of character lines may correspond to the distance between the location of the sheet sensor 16 and the location of recording of the recording head unit 13 as viewed in the feeding direction of the sheet 2.

Claims

An ink jet recording apparatus (1) comprising:
a black ink recording head (13, 314K, KN1-KN25) for spouting a black ink onto a recording medium (2);
a non-black ink recording head (13, 314C, CN1-CN25) for spouting a non-black colour ink different from said black ink, against said recording medium;
control means (32, 40) for commanding said black and non-black ink recording heads to spout said black and non-black inks, respectively,
said control means including special ink spouting operation request means for generating a request signal (R; R') under determinable circumstances said control means further including special operation command means (173, 174; 177, 178, 179; S326) for commanding, when said request signal is generated by said timer means, said non-black ink recording head (CN1) to effect a special ink spouting operation by spouting said non-black ink at a position where said black ink has been or is to be recorded on said recording medium.
A recording apparatus according to claim 1, wherein said request means comprises timer means (172; 176) for measuring a time lapse after said non-black ink recording head (CN1) has last spouted said non-black ink, and for generating the request signal (R; R') when the measured time lapse has exceeded a reference time.
A recording apparatus according to claim 1 or 2, further comprising:
a platen (8) on which said recording medium (2) is retained; and
a carriage (12) for supporting said black and non-black ink recording heads (314K, 314C) such that said recording heads are apart from each other by a predetermined distance in a recording direction (B) which is parallel to a longitudinal direction of said platen and in which said recording heads supported by said carriage are displaceable for effecting recording on said recording medium,
each of said recording heads comprising a group of ink jet nozzles (KN1-KN25, CN1-CN25) arranged in an array extending in a direction intersecting said longitudinal direction of said platen, so that the arrays of the respective groups of ink jet nozzles of said recording heads are parallel to each other and are apart from each other by said predetermined distance in said recording direction.
A recording apparatus according to claim 1, 2 or 3, wherein said special operation command means (173, 174; 177, 178, 179) of said control means commands, when said request signal (R; R') is generated by said request means (172, 176), said non-black ink recording head (CN1) to effect said special ink spouting operation at said position on said recording medium (2) where said black ink recording head (KN1) has effected said recording with said black ink before said special ink spouting operation.
A recording apparatus according to claim 4, further comprising:
a platen (8) on which said recording medium (2) is retained; and
a carriage (12) for supporting said black and non-black ink recording heads (314K, 314C) such that said recording heads are apart from each other by a predetermined distance in a recording direction which is parallel to a longitudinal direction of said platen and in which said recording heads supported by said carriage are displaceable for effecting recording on said recording medium, and such that said black ink recording head (314K) precedes said non-black ink recording head (314C) when said carriage is moved in said recording direction.
A recording apparatus according to claim 5 when dependent on claim 2, wherein said control means (32, 40) comprises:
a counter (172) serving as said timer means;
a shift register (174) for generating a shift signal (Q) which is shifted afterward by a shift time duration from a black ink jet command signal (KS1) commanding said black ink recording head (KN1) to spout said black ink, said shift time duration being equal to a time period necessary for said carriage (12) to move by said predetermined distance between said black and non-black ink recording heads (314K, 314C); and
an AND gate (173) for generating, when concurrently receiving said request signal (R) and said shift signal (Q), a special ink jet command signal (S) commanding said non-black ink recording head (CN1) to effect said special ink spouting operation.
A recording apparatus according to claim 5 when dependent on claim 2, wherein said control means (32, 40) comprises:
means (32) for periodically generating a timing signal (CLK);
a counter (176) for counting the generated timing signals, said counter serving as said timer means;
a shift register (179) for generating a first, a second, and a third shift signal (Q1, Q2, Q3) which are respectively shifted afterward by a first, a second, and a third shift time duration from a black ink jet command signal (KS1) commanding said black ink recording head (KN1) to spout said black ink, said second and third shift signals (Q2, Q3) being respectively shifted afterward from said first and second shift signals (Q1, Q2) by a time duration corresponding to one said timing signal (CLK), said second shift time duration being equal to a time period necessary for said carriage (12) to move by said predetermined distance between said black and non-black ink recording heads (314K, 314C); and
an AND gate (177, 178) for generating, when concurrently receiving said request signal (R') and said first, second, and third shift signals (Q1, Q2, Q3), a special ink jet command signal (S') commanding said non-black ink recording head (CN1) to effect said special ink spouting operation.
A recording apparatus according to claim 6 or claim 7, wherein said counter (172; 176) generates, when said shift register (174; 178, 179) does not generate said shift signal (Q; Q') within a permitted time duration after generation of said request signal (R; R'), a second request signal (RC1) different from said request signal as a first request signal,
said control means (32, 40) further comprising second special operation command means (32, 38) different from said special operation command means (173, 174; 177, 178, 179) as a first special operation command means, said second special operation command means commanding, when receiving said second request signal (RC1), said carriage (12) to move from a recording region (A') in which said carriage is opposed to said platen (8), to a first extreme region (B') different from said recording region, and commanding said non-black ink recording head (CN1) to spout said non-black ink in said first extreme region.
A recording apparatus according to claim 8, wherein said second special operation command means (32, 38) commands, when receiving said second request signal (RC1), said carriage (12) to move from said recording region (A') to said first extreme region (B') and commands said non-black ink recording head (CN1) to spout said non-black ink in said first extreme region, after said black and non-black recording heads (314K, 314C) have effected recording of a current character line on said recording medium (2).
A recording apparatus according to claim 8 or claim 9, further comprising a covering device (156) for air-tightly covering said black and non-black ink recording heads (314K, 314C), said covering device being disposed in a second extreme region (C') different from said recording region (A') and said first extreme region (B').
A recording apparatus according to any one of claims 3 and claims 5-10, wherein said control means (32, 40) commands said black and non-black ink recording heads (314K, 314C) to effect recording on said recording medium (2) when said carriage (12) is moved in one of opposite two directions parallel to said longitudinal direction of said platen (8), said one direction serving as said recording direction, said non-black ink recording head (CN1) effecting said special ink spouting operation when said carriage is moved in said one direction.
A recording apparatus according to claim 5, wherein said control means (32, 40) further comprises search means (S325) for searching for, after said request signal (R; R') is generated by said timer means (172; 176), said position of recording of said black ink recording head (CN1) on said recording medium,
said special operation command means (S326) commanding said non-black ink recording head (CN1) to effect said special ink spouting operation at the found position on said recording medium (2) where said black ink jet recording head (KN1) has effected said recording with said black ink before said special ink spouting operation.
A recording apparatus according to claim 12, wherein said search means (S325) of said control means (32, 40) comprises:
memory means (33) for storing recording data representative of a color image to be recorded on said recording medium (2); and
scanner means (32) for scanning said recording data for finding a black ink jet command data which commands said black ink recording head (CN1) to spout said black ink after said request signal (R; R') is generated by said timer means (172, 176).
A recording apparatus according to claim 12 or claim 13, wherein said control means (32, 40) further comprises second special operation command means (S327) different from said special operation command means (S326) as a first special operation command means, said second special operation command means commanding, when said search means (S325) does not find said position of recording of said black ink recording head (KN1) on said recording medium within a permitted time duration after generation of said request signal, said carriage (12) to move from a recording region (A') in which said carriage is opposed to said platen (8), to an extreme region (B') different from said recording region, and commanding said non-black ink recording head (CN1) to spout said non-black ink in said extreme region.
A recording apparatus according to claim 1 or 2, wherein said special operation command means (173, 174; 177, 178, 179; S326) of said control means (32, 40) commands, when said request signal (R; R') is generated by said request means (172; 176), said non-black ink recording head (CN1) to effect said special ink spouting operation at said position on said recording medium (2) where said black ink recording head (KN1) will effect said recording with said black ink after said special ink spouting operation.
A recording apparatus according to claim 15, wherein said control means (32, 40) further comprises search means (S325, 33) for searching for, after said request signal (R; R') is generated by said request means (172; 176), said position of recording of said black ink recording head (KN1),
said special operation command means (173, 174; 177, 178, 179; S326) commanding said non-black ink recording head (CN1) to effect said special ink spouting operation at the found position on said recording medium (2) where said black ink recording head will effect said recording with said black ink after said special ink spouting operation.
A recording apparatus according to claim 16, wherein said search means (S325, 33) of said control means (32, 40) comprises:
memory means (33) for storing recording data representative of a color image to be recorded on said recording medium (2); and
scanner means (32) for scanning said recording data for finding a black ink jet command data which commands said black ink recording head (KN1) to spout said black ink after said request signal (R; R') is generated by said request means (172, 176).
A recording apparatus according to claim 17, further comprising:
a platen (8) on which said recording medium (2) is retained; and
a carriage (12) for supporting said black and non-black ink recording heads (314K, 314C) such that said recording heads are apart from each other by a predetermined distance in a recording direction which is parallel to a longitudinal direction of said platen and in which said recording heads supported by said carriage are displaceable for effecting recording on said recording medium, and such that said black ink recording head (314K) follows said non-black ink recording head (314C) when said carriage is moved in said recording direction.
A recording apparatus according to claim 18 when dependent on claim 2, wherein said control means (32, 40) comprises:
a counter (172) serving as said timer means;
means (32) for generating a precursor signal before generation of said black ink jet command data by a time duration, 2t, wherein t is a time period necessary for said carriage (12) to move by said predetermined distance between said black and non-black recording heads (314K, 314C);
a shift register (174) for generating, when receiving said precursor signal, a shift signal (Q) which is shifted afterward by a shift time duration from said precursor signal, said shift time duration being equal to said time period t which is half said time duration 2t; and
an AND gate (173) for generating, when concurrently receiving said request signal (R) and said shift signal (Q), a special ink jet command signal (S) commanding said non-black ink recording head (CN1) to effect said special ink spouting operation.
A recording apparatus according to claim 18 when dependent on claim 2, wherein said control means (32, 40) comprises:
means (32) for periodically generating a timing signal (CLK);
a counter (176) for counting the generated timing signals, said counter serving as said timer means;
means (32) for generating a precursor signal before generation of said black ink jet command data by a time duration, 2t, wherein t is a time period necessary for said carriage (12) to move by said predetermined distance between said black and non-black recording heads (314K, 314Y);
a shift register (179) for generating, when receiving said precursor signal, a first, a second, and a third shift signal (Q1, Q2, Q3) which are respectively shifted afterward from said precursor signal by a first, second, and third shift time duration, said second and third shift signals (Q2, Q3) being respectively shifted afterward from said first and second shift signals (Q1, Q2) by a time duration corresponding to one said timing signal (CLK), said second shift time duration being equal to said time period t which is half said time duration 2t; and
an AND gate (177, 178) for generating, when concurrently receiving said request signal (R') and said first, second, and third shift signals (Q1, Q2, Q3), a special ink jet command signal (S') commanding said non-black ink recording head (CN1) to effect said special ink spouting operation.
A recording apparatus according to any of claims 18-20, wherein said control means includes second special operation command means (S327) different from said special operation command means (S326) as a first special operation command means, said second special operation command means commanding, when said search means (S325, 33) does not find said position of recording of said black ink recording head (KN1) on said recording medium within a permitted time duration after generation of said request signal, said carriage (12) to move from a recording region (A') in which said carriage is opposed to said platen (8), to an extreme region (B') different said recording region, and commanding said non-black ink recording head (CN1) to spout said non-black ink in said extreme region.
A recording apparatus according to any of claims 18-21, wherein said control means (32, 40) commands said black ink and non-black ink recording heads (314K, 314C) to effect recording on said recording medium (2) when said carriage (12) is moved in one of opposite directions parallel to said longitudinal direction of said platen (8), said one direction serving as said recording direction, said special operation command means (S326) commanding said non-black ink recording head (CN1) to effect said special ink spouting operation when said carriage is moved in said one direction.
A recording apparatus according to any of claims 1-22, further comprising:
a platen (8) on which said recording medium (2) is retained; and
a carriage (12) for supporting said black and non-black ink recording heads (314K, 314C) such that said recording heads are apart from each other by a predetermined distance in a direction parallel to a longitudinal direction of said platen,
said control means (32, 40) commanding said carriage to reciprocate along said platen, and commanding said black and non-black ink recording heads to effect recording on said medium when said carriage is moved in each of opposite directions along said platen,
said special operation command means (S326) commanding said non-black ink recording head (CN1) to effect said special ink spouting operation when said carriage is moved in said each of said opposite directions.
A recording apparatus according to any one of claims 1-23, further comprising:
a platen (8) on which said recording medium (2) is retained; and
a carriage (12) for supporting said black and non-black ink recording heads (314K, 314C),
said black and non-black ink recording heads recording dots by spouting said black and non-black inks, respectively, according to bit pattern data representative of predetermined positions in a matrix corresponding to each of at least one character line, when said carriage is moved along said platen.
A recording apparatus according to claim 24, wherein said special operation command means (S326) of said control means (32, 40) commands, when said request signal (R; R') is generated by said request means (172; 176), said non-black ink recording head (CN1) to effect said special ink spouting operation on said recording medium (2) at one of recording positions of at least three consecutive dots with said black ink except for the recording positions of the opposite end two black dots.
A recording apparatus according to any of claims 1-25, further comprising:
a platen (8) on which said recording medium (2) is retained;
at least one second non-black ink recording head (314M, 314Y) for spouting a non-black color ink different from said non-black color ink spouted by said non-black ink recording head (314C) as a first non-black ink recording head; and
a carriage (12) for supporting said black ink recording head (314K), said first non-black ink recording head (314C), and said at least one second non-black ink recording head (314M, 314Y) equidistantly from each other in a direction which is parallel to a longitudinal direction of said platen and in which said recording heads supported by said carriage is displaceable for recording on said recording medium.