JP2761089B2 - Image forming apparatus and method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and method for recording an image on a recording medium such as paper or film according to an image signal.

2. Description of the Related Art Conventionally, as an image forming apparatus such as a copying machine or a printer, an image forming apparatus based on an ink jet system or the like is configured as shown in FIG. 3, for example.

The recording medium is conveyed (paper feed) during the recording operation of the image forming apparatus by, for example, nipping and conveying the recording medium (hereinafter, also referred to as recording paper) between a pair of upper and lower paper feed rollers and a paper discharge roller. . Here, the feed amount of the recording paper is equal to the line pitch (for example, 8 mm). Here, in order to always apply a constant tension to the recording paper, the feed amount of the paper discharge roller is set to be larger than that of the paper feed roller by, for example, 1%. For this reason, when recording on recording paper, if the distance from the paper feed roller to the rear end of the paper is 8 mm or more as shown in FIG. 5A, the recording paper is fed by 8 mm.

However, when the distance from the paper feed roller to the trailing edge of the paper is less than 8 mm as shown in FIG. 5B, the trailing edge of the recording paper is fed during the paper feeding as shown in FIG. 5C. The paper will fall out of the roller, and then the paper will be fed only by the paper discharge roller, so the paper feed amount will be 8 mm + α. Therefore, there is a possibility that the recording position is shifted due to a change in the paper feed amount.

[Problems to be Solved by the Invention] An object of the present invention is to solve the above-mentioned technical problems, and to provide an image forming apparatus and a method capable of recording a high-quality image as widely as possible on a surface of a recording medium. Is to do.

[Means for Solving the Problems] The image forming apparatus of the present invention repeats formation of a recording area having a predetermined width by scanning a recording head,
In an image forming apparatus that completes image recording on a recording medium, the image forming apparatus is provided on the upstream and downstream sides of a transport path for transporting the recording medium, and cooperates with the recording medium when transporting the recording medium by the predetermined width. The transport means in which the transport amount on the downstream side alone is set larger than that on the upstream side to apply tension, and whether or not the next transport of the recording medium includes a step in which the downstream transport means alone is performed. A determination unit for determining, and when the determination unit determines that the next transport of the recording medium includes the above-described process, the next recording start position in the transport direction of the recording medium is set to a position where recording can be performed by the recording head. Recording on a recording medium conveyed by a conveyance amount different from the predetermined width, according to a difference between the conveyance amount of the predetermined width and the different conveyance amount, the recording area of the recording head in the conveyance direction. Shift And having a recording control means for performing.

In the image forming method of the present invention, the recording medium is conveyed in the image forming method in which the recording head is scanned to form a recording area of a predetermined width repeatedly to complete image recording on the recording medium. A first transport that is provided on the upstream side and the downstream side of the transport path, and that transports the recording medium by the predetermined width in cooperation with transport means in which the transport amount of the downstream side alone is set larger than that of the upstream side; And a second transporting step of transporting the recording medium by a transporting amount different from the predetermined width, and a transporting step of the recording medium by the first or second transporting. A recording step for determining which one of the steps is to be performed, and when the determining step determines that the transporting step has been transported in the first transporting step, the recording on the transported recording medium is performed by the recording head. Of width A first recording step performed in the recording area, and a recording start position in the transport direction of the recording medium when the transport step is determined to have been transported in the second transport step by the determination step is a position where the recording head can record. According to the difference between the transport amount of the predetermined width and the different transport amount, the recording area of the print head is changed according to the difference between the transport amount of the predetermined width and the different transport amount. And a second recording step performed by shifting in the transport direction.

Hereinafter, an embodiment of the image forming apparatus of the present invention will be described with reference to the drawings. In this embodiment, a case will be described in which the present invention is applied to a serial type ink jet printer corresponding to a copying machine as an image forming apparatus.

FIG. 2 is a plan view of the printer, FIG. 3 is a cross-sectional explanatory view showing a schematic configuration thereof, FIG. 3 is a block diagram of a control unit of the printer, and FIG. 1 is a flowchart showing a control operation thereof.

First, a schematic configuration of the printer will be described with reference to FIGS.

In the figure, reference numeral 1 denotes an ink cartridge which constitutes a recording unit for recording an image on a recording medium 2 according to recording information. In the ink cartridge 1, the recording head 1a and the ink tank 1b are integrated, and can be replaced by disposable. The recording head 1a is provided with a plurality of liquid paths filled with liquid (ink). In the ink filled in these liquid paths, the surface tension and the external pressure are balanced at the orifice surface in a steady state. Electrothermal transducers are arranged in the plurality of liquid paths, respectively, and by applying at least one drive signal to these electrothermal transducers that provides a rapid temperature rise beyond nucleate boiling. It generates thermal energy and vaporizes adjacent ink to cause film boiling. Thereby, a bubble corresponding to the drive signal is formed in the ink, and the ink is ejected from the orifice surface to the recording medium 2 by the growth of the bubble. The bubbles are cooled by the ink and contract, and the ink is sequentially supplied from the ink tank 1b into the liquid path by capillary action.

As described above, by growing or contracting bubbles in the liquid path filled with ink, the ink can be ejected from the orifice surface to form one droplet. Therefore, when a drive signal is applied in a pulse shape to the electrothermal transducer in accordance with image information, the growth and contraction of bubbles are instantaneously performed, and ink is ejected from the orifice surface of the recording head 1a onto the recording medium 2. Recording. Incidentally, reference numeral 3 in the drawing denotes a platen for supporting the recording medium 2 conveyed to the recording section.

The ink cartridge 1 is mounted on a carriage 4 that can reciprocate in a main scanning direction (the width direction of the recording medium 2) along a guide shaft 4a. This carriage 4
Can move by transmitting the driving force supplied from the main scanning motor 5 shown in FIG.

Reference numeral 7 in the figure denotes a cassette capable of loading and storing the recording medium 2. Plain paper or OHP loaded in this cassette 7
The recording medium 2 such as a sheet is sequentially fed downstream by a paper feed roller 8. The recording medium 2 fed by the feed roller 8 is guided by guide members 8a and 8b provided above and below, and is guided to a pair of transport rollers 10a and 10b. As shown in FIG. 2, the conveying roller pair 10a, 10b is rotated by receiving a driving force from a sub-scanning motor 9. A discharge roller pair for discharging the recording medium 2 after recording via the above-described recording means is provided downstream of the pair of transport rollers 10a and 10b.
11a and 11b are provided. This discharge roller pair 11a, 11b
As shown in FIG. 2, the driving force supplied from the sub-scanning motor 9 is transmitted via a belt 12 to rotate.

A paper feed sensor 13 is provided downstream of the transport roller pair 10a, 10b, as shown in FIG. The paper feed sensor 13 detects that the recording medium 2 is being fed from the cassette 7.

Further, the carriage 4 is provided with a paper width sensor 14 which is a detecting means for determining the type of the recording medium 2 and its paper width.

Further, in the vicinity of the discharge roller pair 11a, 11b, a paper discharge sensor 1 is provided.
5 are provided. The paper discharge sensor 15 detects that the recording medium 2 after recording has been discharged, and detects the recording medium 2 at the time of manual sheet feeding. In addition, as each of the above sensors, a reflection type sensor is used.

In FIG. 3, reference numeral 16 denotes a discharge tray for stacking the recording medium 2 discharged from the discharge roller pair 11a, 11b.
Reference numeral 17 denotes a discharge port for the recording medium 2 and also serves as a paper feed port for manual paper feed.

Next, the configuration of the control unit of the printer configured as described above will be described with reference to the block diagram shown in FIG.

In the figure, reference numeral 18 denotes a control unit, which is a CPU 18a that executes the processing of the flowchart shown below, a ROM 18b that stores fixed data such as a program corresponding to the processing procedure, and a work R
It has AM18c and so on.

The control unit 18 receives detection signals from the paper feed sensor 13 and the paper discharge sensor 15, and sends signals to the recording head 1a, the main scanning motor 5, the sub-scanning motor 9, and the head control integrated circuit 19, respectively. Is output.

Next, the control operation of the control unit 18 will be described with reference to the flowchart shown in FIG.

First, in step S1, as shown in FIG. 3, the recording medium 2 is loaded and stored in the cassette 7, and is set in a state of waiting for input of a recording start key.

Next, in step S2, it is determined whether or not there is a recording start input.If there is a recording start input, the process proceeds to step S3 to start a recording operation, and if the recording start input has not been made, Remains in the recording start standby state.

When the recording operation is started, the process proceeds to step S3, where the recording medium 2 is fed from the cassette 7. At this time, manual paper feeding can also be performed from the paper feeding port 17. The recording medium 2 is transported by driving the sub-scanning motor 9 to rotate the transport roller pairs 10a and 10b and the discharge roller pairs 11a and 11b.

 Next, the process proceeds to step S4 to start recording the first line.

Here, the recording operation for plain paper shown in steps S4 to S10 will be described.

The ink cartridge 1 containing the recording head 1a moves in the main scanning direction of the carriage 4, and ink is ejected from the ejection openings of the recording head 1a onto the recording medium 2 according to the recording information, so that the recording of the first line is performed. (Step S
Four). When the recording for one line is completed, the conveying rollers 10a and 10b are rotated to convey the recording medium 2 by one line in the sub-scanning direction (the conveying direction of the recording medium 2). At the same time, the leading end side of the recording medium 2 is
It is held and transported by b (step S5).

 Hereinafter, the recording of the second line is performed in the same manner.

Here, for example, when A4 size recording paper is used as the recording medium, the paper feed amount for one line is equivalent to 48 pulses in the number of pulses of the sub-scanning motor 9. With this apparatus, in the case of A4 recording paper, recording for a total of 34 lines can be performed.

 In step S6, recording of the 33rd line is performed.

In step S7, the number of pulses of the sub-scanning motor 9 is set to 47 as the paper feed for one line from the 33rd line to the 34th line.
The pulsed paper is fed.

Here, the reason why the paper is fed by 47 pulses will be described with reference to FIGS. 5 (c), 6 (a), (b) and (c). If the distance from the paper feed rollers 10a, 10b to the rear end of the recording paper 2 is shorter than the line pitch (8 mm in this example), the recording is performed as shown in FIG. The paper 2 comes off the paper feed rollers 10a and 10b, and the recording paper 2 is fed only by the paper discharge rollers 11a and 11b. In order to apply a certain tension to the recording paper 2, the paper feed amount of the paper discharge rollers 11a, 11b is adjusted by the paper feed rollers 10a, 10b.
Therefore, if the paper is fed by 48 pulses in step S7 as shown in FIG. 6B, the paper is excessively fed. Therefore, in this example, one line of paper is fed by 47 pulses as shown in FIG. 6C so that the paper is not over fed.

However, strictly speaking, the 47-pulse feed does not achieve the desired feed amount, and the paper is slightly insufficient. It is assumed that the shortage of feed corresponds to, for example, approximately two pixels. If the storage is performed as it is in the insufficient feeding state, the row pitch between the 33rd line and the next 34th line is slightly shortened. Therefore, in this embodiment, the correction for the two pixels is performed by controlling the nozzles of the recording head.

That is, in step S8, the last line (line 34)
At the same time, the above-mentioned correction of the shortage of the feed is performed by controlling the nozzles of the print head. At the time of normal recording up to the 33rd line, as shown in FIG.
Inks corresponding to data 1 to data 128 are ejected from the nozzles up to the eighth. However, at the time of recording of the 34th line (for the last line), as shown in FIG.
No ink is ejected from nozzles No. 2 and No. 3, nozzle No. 3 is ink corresponding to data 1, nozzle No. 4 is ink corresponding to data 2, nozzle No. 128 is data 126
Are controlled so as to eject inks corresponding to.

In step S9, a paper discharging motion is performed, and in step S10, it is determined whether or not to perform continuous copying.

In this embodiment, the recording paper 2 is pulled out of the paper feed rollers 10a and 10b, is nipped and conveyed only by the paper discharge rollers 11a and 11b, and the distance from the paper discharge rollers 11a and 11b to the rear end of the recording paper 2 is equal to the line pitch. , The sub-scanning motor 9
Of the number of pulses and the inkjet recording head 1a
By controlling the nozzles, the last line (the 34th line in this example) that can be printed on the recording paper 2 can be printed without positional deviation. Further, in the present embodiment, the recording position of only the last line is controlled so as not to be shifted, but for example, the distance between the paper feed rollers 10a, 10b and the paper discharge rollers 11a, 11b may be several lines pitch. If there is enough information, it is possible to control not only the printing of the last line but also the printing of several lines before the last line while the recording paper 2 is being conveyed only by the paper discharge rollers 11a and 11b without displacement.

In the above embodiment, the case where the main body and the ink jet head are controlled has been described. However, instead of the ink jet head, a recording head in another dot printer, for example, a recording head such as a wire dot printer or a thermal dot printer, or a beam jet head is used. Is similarly controlled, the recording for the last line can be performed without positional deviation. For example, in the case of a recording head of a wire dot printer as shown in FIG. 8, it is possible to finely adjust the recording position of the last line, for example, by controlling the emergence of a wire at a specific position. That is, at the time of normal recording, recording corresponding to data 1 to data 5 is performed by the first to fifth wires, but at the time of recording the last line, recording by the first and second wires is not performed. , 3
The control is performed such that the recording corresponding to the data No. 1 corresponds to the data 1, the recording corresponding to the data No. 4 to the data 2 and the recording corresponding to the data No. 5 to the data 3. With such control, correction for the pixels corresponding to the shortage amount can be performed, and printing of the last line can be performed without positional displacement as described above.

Further, in the above-described embodiment, the case where the recording paper is A4 size is described. However, even when other document sizes such as B5 and A6 are used, the recording of the last line can be performed without displacement.

In these cases, if the recording paper is of a standard size, the information relating to the size of the recording paper is stored in advance in the first form.
If the setting is performed prior to the illustrated processing, the recording time of the last line can be recognized from the designated line pitch and size information. The mode of inputting the size information may be automatic or manual, as used in known copiers and recording devices.

Further, for example, if an appropriate means for measuring the distance from the paper feed roller to the trailing edge of the paper is provided, it is not necessary to input such size information. Can also be handled.

In addition, the row pitch and the number of motor steps are not limited to those described in the above-described example, but may be any appropriate values. Needless to say, the number of pulses to be reduced at the rear end of the paper can be appropriately selected.

Further, in the above-described embodiment, the number of pulses of the sub-scanning motor 9 is changed from 48 pulses to 47 pulses to change the paper feed amount immediately before recording the last line.
This may be performed by mechanical means. For example, the second
In the figure, several types of sub-gears having different gear ratios are connected to the gear connected to the sub-scanning motor 9, and by switching to these sub-gears, it is possible to change the paper feed amount of the transport roller and the discharge roller. It is.

In addition, in the above-described example, the recording medium conveying means is a roller pair, but may be in another form.

(Others) The present invention can be applied to a recording apparatus other than the ink jet recording apparatus as described above. However, when the present invention is applied to an ink jet recording method, the bubble jet proposed by Canon Inc. This provides excellent effects in a recording head and a recording apparatus of a system. According to such a method, it is possible to achieve a higher density and a higher definition of the recording, and it is easy to finely adjust the pixel unit.

As for the representative configuration and principle, it is preferable to use the basic principle disclosed in, for example, US Pat. Nos. 4,723,129 and 4,740,796. This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to a sheet or a liquid path holding a liquid (ink). By applying at least one drive signal to the electrothermal transducer, which corresponds to the recorded information and provides a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal transducer, and the recording is performed. This is effective because film boiling occurs on the heat-acting surface of the head, and consequently bubbles in the liquid (ink) can be formed corresponding to this drive signal on a one-to-one basis. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. U.S. Pat. No. 44
Those described in JP-A-63359 and JP-A-4345262 are suitable. Further, when the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As a configuration of the recording head, in addition to a combination configuration (a linear liquid flow path or a right-angled liquid flow path) of a discharge port, a liquid path, and an electrothermal converter as disclosed in the above-mentioned specifications, A configuration using U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600, which disclose a configuration in which is disposed in a bending region, is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge section of an electrothermal transducer for a plurality of electrical transducers, and an aperture for absorbing a pressure wave of thermal energy is discharged. The effect of the present invention is effective even if the configuration is based on JP-A-59-138461, which discloses a configuration corresponding to each part. That is, according to the present invention, recording can be reliably and efficiently performed regardless of the form of the recording head.

In addition, even with the serial type printer as in the above example, the recording head fixed to the main unit or attached to the main unit enables electrical connection with the main unit and supply of ink from the main unit. The present invention is also effective when a replaceable chip type print head or a cartridge type print head in which an ink tank is provided integrally with the print head itself is used.

Further, it is preferable to add recovery means for the print head, preliminary auxiliary means, and the like provided as a configuration of the printing apparatus in the present invention since the effects of the present invention can be further stabilized. To be more specific, capping means for the recording head, cleaning means, pressurizing or suctioning means, preheating means using an electrothermal transducer or another heating element or a combination thereof. Performing a preliminary ejection mode in which ejection is performed separately from printing is also effective for performing stable printing.

Regarding the type or number of storage heads to be mounted, for example, in addition to the one provided corresponding to a single color ink, a plurality provided corresponding to a plurality of inks having different recording colors and densities. May be used. That is, for example, the recording mode of the storage device is not limited to the recording mode of only the mainstream color such as black, but may be any of a recording head integrally formed or a combination of a plurality of recording heads. The present invention is also extremely effective for an apparatus provided with at least one of full colors by color mixture.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, an ink that solidifies at or below room temperature and softens or liquefies at room temperature, or the ink itself in an inkjet method. In general, the temperature is controlled within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. I just need. In addition, it is possible to positively prevent the temperature rise due to thermal energy by using the energy of the state change of the ink from the solid state to the liquid state,
Alternatively, an ink that solidifies in a standing state for the purpose of preventing evaporation of the ink is used, and in any case, the ink is liquefied by applying heat energy according to the recording signal, and the liquid ink is ejected, or a recording medium is used. The present invention is also applicable to a case where an ink having a property of being liquefied for the first time by thermal energy, such as an ink which starts to solidify when it reaches the ink, is used. The ink in such a case is disclosed in
No. -56847 or JP-A-60-71260, while being held as a liquid or solid substance in a porous sheet recess or through hole, facing the electrothermal converter. It is good also as a form. In the present invention,
The most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, the form of the ink jet recording apparatus of the present invention may be a form used for an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, or a facsimile apparatus having a transmission / reception function. Or the like.

[Effects of the Invention] As described above, according to the present invention, even when the distance from the discharge roller to the trailing edge of the recording paper is less than the line pitch, for example, the recording of the last line is performed without displacement. Therefore, it is possible to perform good image recording over a wide range on a recording sheet.

[Brief description of the drawings]

1 is an explanatory diagram of an operation sequence of an example of an image forming apparatus according to the present invention, FIG. 2 is a plan view of an example of an image forming apparatus according to the present invention, and FIG. 3 is an image forming apparatus shown in FIG. FIG. 4 is a block diagram showing a control unit of the image forming apparatus shown in FIG. 2, and FIGS. 5 (a), (b) and (c) are views of the image forming apparatus shown in FIG. 6A, 6B, and 6C are schematic diagrams for explaining recording of the last line using the image forming apparatus shown in FIG. 2; 7 (a) and 7 (b) are schematic diagrams showing a state of nozzle control of an ink jet recording head used in the image forming apparatus shown in FIG. 2, and FIG. 8 is an image forming apparatus according to the present invention. FIG. 3 is a schematic diagram showing a state of nozzle control of a wire dot type recording head used in the embodiment. 1a Printhead, 1b Ink tank, 2 Print medium, 3 Platen, 4 Carriage, 4a Guide shaft, 5 Main scanning motor, 6 Belt, 7 Cassette 8 feeding roller 8a and 8b guide member 9 sub-scanning motor 10a and 10b transport roller pair 11a and 11b discharge roller pair 12 belt 13 feeding Paper sensor, 14… Paper width sensor, 15… Discharge sensor, 16… Discharge tray, 17… Paper feed port, 18… Control unit, 18a… CPU, 18b… ROM, 18c… RAM, 19 ... Integrated circuit for head control.

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Claims (8)

(57) [Claims] An image forming apparatus that completes image recording on a recording medium by repeating formation of a recording area of a predetermined width formed by scanning a recording head, wherein an upstream side of a conveyance path for conveying the recording medium. Transport means provided on the downstream side, and the transport amount of the downstream side alone is set to be larger than that of the upstream side so as to apply tension to the recording medium when the recording medium is transported by the predetermined width in cooperation. Determining means for determining whether or not the next transport of the recording medium includes a step in which the downstream transport means alone is performed, and determining that the next transport of the recording medium includes the above step by the determining means When recording on the recording medium conveyed by a conveyance amount different from the predetermined width is performed so that the next recording start position in the conveyance direction of the recording medium becomes a position where recording can be performed by the recording head, In accordance with the difference between said different carry amount and Okuryou, image forming apparatus, comprising a recording control means for performing by shifting the recording area of the recording head in the conveying direction. 2. An image forming apparatus according to claim 1, wherein said recording control means changes said recording area in units of recording elements of said recording head. 3. The method according to claim 1, wherein the determining unit determines whether or not the next transport of the recording medium includes the step based on the size information of the recording medium and the transport amount of the predetermined width. The image forming apparatus as described in the above. 4. An image forming apparatus according to claim 1, wherein said recording head is arranged so as to be able to scan between said upstream and downstream conveying means. 5. The image forming apparatus according to claim 1, wherein said recording head forms an image by discharging ink onto a recording medium. 6. The image forming apparatus according to claim 5, wherein said recording head ejects ink by heat. 7. An image forming method which completes image recording on a recording medium by repeating formation of a recording area having a predetermined width by scanning a recording head, wherein an upstream side of a transport path for transporting the recording medium is provided. A first transporting step of transporting the recording medium by the predetermined width in cooperation with transporting means provided on the downstream side, wherein the transporting amount of the downstream side alone is set larger than that of the upstream side; A second conveying step of conveying the recording medium by a conveying amount different from the predetermined width, and a conveying step of the recording medium is any of the first and second conveying steps. A determining step of determining whether or not the transporting step has been transported in the first transporting step by the determining step, the recording on the transported recording medium is performed in the recording area of the predetermined width of the recording head. First 1
A recording step, and when it is determined in the determination step that the transport step has been transported in the second transport step, the recording start position in the transport direction of the recording medium is a position at which recording can be performed by the recording head. The recording on the recording medium conveyed by a conveyance amount different from the predetermined width is performed by shifting a recording area of the recording head in the conveyance direction according to a difference between the conveyance amount of the predetermined width and the different conveyance amount. And a second recording step to be performed. 8. The method according to claim 1, wherein the determining step determines whether the transporting step is the first or second transporting step based on the size information of the recording medium and the transporting amount of the predetermined width. Item 7. The image forming method according to Item 7.